The Journal of Engineering
Volume 2019, Issue 18, July 2019
Volumes & issues:
Volume 2019, Issue 18
July 2019
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- Volume 2019, Issue 18,
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Considering the growing wind power penetration in power systems, using the flexible control ability of these turbines to enhance power system dynamic behaviour has been investigated. One of the major challenges regarding the stability problem of power systems is the low-frequency oscillations (LFOs) of synchronous generators in a power system. Usually, power system stability units are used to damp these oscillations, but using wind turbine systems for this purpose has been suggested in recent studies. In this regard, mostly a linear supplementary control loop has been employed in the control system of wind turbines. Applying a linear structure for the supplementary control loop does not result in optimum performance since the power system operating conditions and the wind turbine power generation change continuously. In this study, adaptive control is used to design the supplementary loop. Doubly-fed induction generator (DFIG)-based wind turbine systems are used for this study. Since adaptive control parameters tend to optimum values, applying this controller will provide better damping for power system (LFOs at different wind speeds, as shown in this study.
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This study presents the synergy between the electric vehicle (EV) fast charging station (FCS) and wind generation. A queuing analysis based 24-h FCS charging demand is presented in the study. The uncertainty in wind speed variation is represented with a Weibull distribution function. The impact on the distribution system is analysed for EV penetration up to 50% and wind generation penetration up to 30%. The excess wind energy, reverse power flow, reduction in network losses and voltage deviation are investigated for the IEEE 123 bus radial distribution system to quantify the interaction between FCS and wind generation. The results show that 30% of wind generation is sufficient to supply 50% EV penetration and reduction in active and reactive energy loss is observed by 10.08% and 10.94%, respectively.
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LCL filters are widely used in distributed power-generation systems to attenuate high-frequency harmonics caused by pulse-width modulation switching of grid-connected inverters. A resonance occurs due to the series-connected reactive components. In order to damp resonance effects, active and passive damping methods are used. Lower switching frequencies are typically preferred to decrease switching power losses with high-power applications. Thus, control bandwidth of the system is limited and implementation of active damping gets harder. As a result, passive damping methods are commonly used in high-power applications. In this study, performances of two most commonly used passive damping methods which are series R damped and shunt R-C damped are analysed and compared in terms of resonance damping, grid current attenuation at high frequencies, and power losses on damping circuits.
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In order to stabilise floating wind turbines, an innovative motion stabilisation measure is proposed and verified here through conducting a series of numerical researches with the aid of SESAM. In the research, the numerical model of a spar-supported 5 MW floating turbine was developed first to investigate its motion stability in different depths water and under different wave conditions. Then, a new concept of motion stabiliser is proposed, which consists of a number of heave plates that are connected to floating turbine foundation via structural arms. The influences of both the number of heave plates and their arm length on motion reduction are then investigated in order to explore an optimal design of the proposed stabiliser. Considering the dynamic motions of a floating turbine is mainly affected by sea waves, the motion stabilising capability of the proposed stabiliser is investigated over a wide range of wave period 4–36 s. It has been found that after using the proposed motion stabiliser, both the pitch and heave motions of the floating turbine are successfully limited within the most range of wave period, especially when the wave period exceeds 12 s.
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Dual active bridge (DAB) DC/DC converter is an ideal high-power bidirectional DC/DC converter with multiple control methods. In this paper, the working characteristics of the DAB converters are analysed by the example of medium power mode, in which the voltage transfer ratio is less than 1. For the situation that the DAB converter is difficult to achieve soft switching at light load, a triple phase shift (TPS) control method is used. Combining with RMS current optimisation, a control method to achieve soft switching for full-power range is proposed. The control strategy enables the converter to realise zero voltage switching (ZVS) of all the switching device, which not only improves the operating conditions of the switching device, but also improves the converter efficiency. Finally, a prototype of DAB was built. Compared with the traditional control method, the experimental results verify the effectiveness of the proposed control strategy.
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This paper investigates the integration of large offshore wind farms using parallel HVAC and diode-rectifier based HVDC (DR-HVDC) systems. Three different operation modes, i.e. HVAC operation mode, DR-HVDC operation mode and parallel operation mode are investigated. A wind turbine control scheme including distributed control and centralised control is proposed to ensure the stable operation of the offshore wind farms under different operation modes. The proposed control requires no switching of the distributed control strategy when the operation mode is changed. Moreover, power flow between the DR-HVDC link and HVAC link under parallel operation can be well controlled with the centralised control. Simulation results in PSCAD/EMTDC verify the proposed control during transition among the three operation modes.
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The fast growth of offshore all-DC wind farm will bring problems such as the weakening of grid frequency stability and the increase of equivalent grid impedance. To overcome this, a coordination control strategy for offshore all-DC wind farm is proposed in this study with two salient features: better performance under weak grid condition, and real-time frequency support from wind farm. This strategy consists of three parts: the inertia synchronising control of receiving end converter, the constant ratio control of DC transformer and the frequency response of wind farm. With the proposed strategy, the all-DC wind farm operates like a synchronous generator to onshore grid, which provides fast frequency support when the onshore grid frequency changes. The effectiveness of the proposed method is validated in PSCAD/EMTDC.
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High operation and maintenance costs for offshore wind turbines push up the LCOE of offshore wind energy. Unscheduled maintenance due to unanticipated failures is the most prominent driver of the maintenance cost which reinforces the drive towards condition-based maintenance. SCADA based condition monitoring is a cost-effective approach where power curve used to assess the performance of a wind turbine. Such power curves are useful in identification of wind turbine abnormal behaviour. IEC standard 61400-12-1 outlines the guidelines for power curve modelling based on binning. However, establishing such a power curve takes considerable time and is far too slow to reflect changes in performance to be used directly for condition monitoring. To address this, data-driven, nonparametric models being used instead. Gaussian Process models and regression trees are commonly used nonlinear, nonparametric models useful in forecasting and prediction applications. In this paper, two nonparametric methods are proposed for power curve modelling. The Gaussian Process treated as the benchmark model, and a comparative analysis was undertaken using a Regression tree model; the advantages and limitations of each model will be outlined. The performance of these regression models is validated using readily available SCADA datasets from a healthy wind turbine operating under normal conditions.
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Due to rising environmental concerns and desire to achieve energy independence, the government of many countries across the world keen on promoting plug-in electric vehicles (PEVs). Consequently, high penetration of PEVs is expected in the imminent future. This work aims to develop models with the vehicle-to-grid operation of PEVs under different scheduling strategies namely, load stabilising model, charging/discharging cost model, battery degradation model and mixed-objective model, respectively. Further maximum penetration of PEVs corresponding to each scheduling model is evaluated. The impact of PEVs scheduling models on distribution system operational parameters such as peak load, transformer loading, distribution line limits and losses is also investigated. And finally, a comparative analysis of charging models in terms of technical and economic benefits is presented. The proposed model is implemented on the 38-node distribution system and simulation results demonstrate the comprehensive evaluation of proposed charging models.
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During power system restoration following a blackout, it is necessary to quickly restore as many generator units as possible to accelerate the speed of the system restoration. Considering that wind power of large capacity has the advantages of fast start-up speed, flexible access method etc., its participation in power system restoration can speed up grid recovery. However, due to wind power fluctuations, the integration of wind power during system restoration may impact the frequency of the restored system. In severe cases, the frequency of the restored system will exceed the limit, which will threaten the safety of the restored system. Consequently, the power reference of the wind farm needs to be optimised during the system restoration. Therefore, an optimisation model of power reference of the wind farm in power restoration based on the fuzzy chance constraints model was proposed in this study. The model maximises the power support of a wind farm on the basis of the safety of the restored system. Simulation results show that this method can provide more power under the condition that the system safety is guaranteed.
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The use of battery energy storage systems (BESS) is one of the methods employed in solving the major challenge of overvoltage, experienced on low voltage (LV) distribution networks with high penetration of photovoltaics (PV). The overvoltage problem limits the penetration levels of PV into the LV network, and the benefits that could be gained. This paper presents a smart scheme for the coordination of multiple battery energy storage systems (BESS) in such networks. An approximate method was adopted for the evaluation of network voltage sensitivity, and the coordination algorithm was developed based upon this. Through the efficient selection, coordination and timing of charge and discharge operations of the BESS, the scheme maintains bus voltages within statutory ranges during both periods of high PV power generation and high network load demand. The scheme also prevents sudden voltage rise, which usually occurs in such networks immediately a BESS gets fully charged. Simulations were carried out on a real LV distribution network and results demonstrate the effectiveness of this approach.
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This article proposes the optimal coordination problem of protective relays within a hybrid optimisation framework which is presented based on integer coded genetic algorithm (ICGA) and non-linear programming (NLP). The optimal coordination problem of directional overcurrent relays (DOCRs) is implemented while aimed at finding the optimal plug setting multiplier (PSM) and time dial setting (TDS). In this respect, PSM is a function of the current transformer (CT) size and the tap of the relay which is discrete in nature. TDS is a function of the operating time of the relay for different short-circuit currents at different locations of the system. Here, the variables of the problem are decomposed into continuous and discrete variables. The first stage of the problem uses the ICGA to determine the size of CTs considering the permitted tap of relays while the second stage utilises the NLP method to evaluate the feasibility and optimality. The presented framework is then simulated on an 8-bus test system. The obtained results verify the effectiveness and the applicability of the optimisation technique to find the optimal settings of DOCRs.
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SylWin1 is a VSC HVDC link connecting 864 MW offshore wind power generation to Germany's high voltage network. This paper presents a harmonic performance analysis of the offshore network carried out during the design and commissioning phase with a focus on the distortions at the 155 kV and 33 kV offshore networks caused by the amplification of harmonics generated by the HVDC and wind turbine converters. Low frequency harmonic amplification problems are mitigated by introducing active damping in the HVDC converter controls in order to achieve a cost effective solution with the aim of reducing offshore harmonic current and voltage distortions. The analysis was carried out with the help of detailed frequency domain model offline simulations of the offshore network and on-site measurements.
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High-penetration renewable energy and AC/DC hybrid network are two main basic characteristics of future power systems. Evaluating different networks' structure adaptability is extremely important for the power system to keep economical, safe, reliable and flexible. Firstly, the basic characteristic and the definition of network structure adaptability are given under the background of strong randomness. On this basis, several probable indexes of structure adaptability are proposed. After that, a practical calculation method is put forward, in which the Monte Carlo simulation method and the optimal economic dispatch model are used. Case studies are carried out on the modified IEEE 30-bus system, and the simulation results show that the proposed indexes can effectively reflect the adaptability of different network structures with the integration of high-penetration renewable energy.
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Due to the environmental burden, natural hazard and energy dilemma in Japan, renewable energy integration has become a key technology in the development of power systems and there has been significant increase in the use of wind and solar power generation. With the development of technologies and free fuel source offering, renewable energy power has been widely used in power system all over the world. On the other hand, because of diversification of generation operating in power system, it becomes more and more important to ensure the security and stability of power system in terms of supply–demand balance with a proper frequency range, to this end, balancing market has been developed in some European countries and regions in order to purchase the balancing power capacity and energy efficiently. In Japan, with the feed-in tariff policy spreading from 2012, it becomes a possibility that renewable energy balancing power participating in balancing market which will be newly established in 2020.
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A proficient power management between proposed multiple battery units in an EV is entailed to achieve the prolonged lifespan of batteries and to impede these from overcharging and overburdening during operation. At first, system configuration with three batteries has been developed for BEV architecture. Based on availability of their state-of-charge (SoC), power-sharing among these battery units is realised by applying a droop control method on power converter system (PCS), which acts as interfacing between battery units and powertrain of EV. To get optimal use of these supplies, balancing of SoCs among these parallel modules is performed by gradual equalisation of power using droop control. Droop control is implemented for both charging and discharging modes of operation using a bi-directional converter. SoC-based droop control method is performed on MATLAB/Simulink model included three energy storage units (ESUs) with PCS and simulation results at the constant speed of EV are shown to demonstrate and verify the approach.
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Battery energy storage systems (BESS) have started to be part of the photovoltaic (PV) system design to allow the further penetration of PV into the grid. This study deals with the sizing (power and energy capacity) of a BESS for residential households which are represented by a typical load consumption profile, they have electrical air conditioning and electrical water heating (water boiler) resembling a common residential house in Cyprus. The BESS sizing is done considering the local energy consumption profile and the energy efficiency class of the house and the water boiler. The BESS is sized in order to achieve zero PV grid export and to increase self-consumption.
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Recent innovations in information and communication technologies (ICT) provide new opportunities and challenges for the integration of distributed energy resources (DERs) into the energy supply system as active market players. By increasing the integration of DERs, the novel market platform should be designed for these new market players to provide correct incentives for them to join the market and follow market rules. In this paper, a feeder-based market is proposed for local energy trading among prosumers and consumers in the distribution system to share energy with other players in the local market and with neighbourhood areas. A two-step market clearing (2SMC) mechanism is proposed for market clearing, in which in the first step, each local market is cleared independently to determine the market clearing price and in the second step, players can trade energy with neighbourhood areas. In comparison to a centralised market, the proposed method is scalable and reduces computation overheads, because instead of clearing market for a large number of players, the market is cleared for a fewer number of players. Case studies demonstrate the efficiency and effectiveness of the proposed market clearing method in increasing social welfare and reducing computation time.
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The coherency of generators in a multi-machine power system is identified by determining the instantaneous phase difference between their rotor angles using a complex wavelet transform. A new phase difference matrix is proposed that represents the relative phase difference between the dominant frequency components of each pair of oscillating rotor angles and maps it into a higher dimensional space where data points corresponding to coherent generators lie in proximity. Next, density-based spatial clustering of applications with noise (DBSCAN) algorithm is used for automated grouping of coherent generators. A new objective function is proposed for the determination of control parameters of the clustering algorithm. The proposed approach is tested on the New England (NE) 39-bus test system and IEEE 145-bus test system.
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The increase in microgrids and smart grid research comprising renewable generation sources with advanced grid control functionalities is driving the need for sophisticated simulation and hardware in the loop (HIL) test facilities using digital real time simulators (DRTS). Unlike traditional off line simulation tools, DRTS provides fast, continuous real time operation as well as hardware interfaces to test the operation of physical control, protection and power devices before they are installed in the smart/micro grid application. The available computation resources of the DRTS to achieve fast, continuous real time operation impose a limitation on the size and level of detail of the power system model for the simulation and HIL application. Reduced dynamic models that represent the power system and control dynamics with sufficient accuracy provide an acceptable trade-off between the required computation resources and size of the power system model for large simulation applications. This paper discusses the dynamic average modelling of renewable energy generation sources for real time simulation applications.
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The large PV medium-voltage (MV) DC power collection system is more efficient than the traditional AC collection system, which provides an alternative for future PV applications. As one of the core components of the PV MVDC power collection system, key techniques of DC transformer are presented here in detail, including the technical requirements, and fault operation analysis in the DC collection system. When part of the PV DC module in the low-voltage (LV) side of DC transformer fails and bypassed, the DC collection system continues working normally with only part of power lost. When the MV side of DC transformer is shorted, all the PV modules exist and the collection system splits without ride-through techniques. The fault operation principle of DC transformer in PV MVDC power collection system is verified by simulations.
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In 2017, 34.8% of total electricity consumption in Northern Ireland was generated from renewable sources located in Northern Ireland. Alongside other significant changes to the electricity sector this leads to an increasing need for reactive power. This paper provides an overview of NIE Networks' nodal controller project which aims to deliver reactive power support to the wider system through the utilisation of Distributed Energy Resources (DERs). The requirements and implementation of the nodal controller are outlined with future work proposed to provide additional reactive power support to the system.
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The addition of distributed PV sources to low voltage distribution networks instigate issues to various operational parameters of the network. With modern smart inverters having controllable settings for voltage and power injection these issues can be alleviated. An Intelligent method utilising smart inverter functionalities of a PV source in a distribution network is proposed in present work to minimise, the power import from the grid, reduce network losses and minimise the magnitude of voltage violation. The optimal settings depend on load and generation variables. In order to reduce computational complexity, a scenario-based method is used to handle these stochastic components in the system. A Non-Sorted Genetic Algorithm (NSGA) is used for optimising the smart inverters parameters. The proposed scheme is envisaged to be realised by a Distribution Management System (DMS) which measures and coordinates all the smart inverters within the distribution feeder.
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To integrate bulk wind power, using modular multilevel converter (MMC) based DC grids is an effective solution to improve the flexibility and reliability of the power grid. This paper analyses a bipolar four-terminal MMC based DC grid to integrate wind farms with overhead lines. Since the overhead lines are prone to DC faults, the hybrid MMC is adopted in the system to ride through DC faults. The fault ride-through control strategies are designed, which remain continuous operation of wind turbines under DC faults. Besides, an adaptive dissipation control strategy associated with chopper resistances is designed to absorb surplus energy. Finally, simulations based on PSCAD/EMTDC platform verify the fault ride through control of hybrid MMC based DC grid and proves the effectiveness of the energy dissipation strategies.
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Nowadays, energy storage systems, such as batteries, are spreading in many applications. Among the kinds of batteries, the lithium-ion technology is one of the most promising solutions. Considering the photovoltaic (PV) plants, it is very important to perform a correct sizing of the battery pack to both maximise the self-consumption and minimise the total costs. In general, PV plants need a dc–dc converter to maximise the electric power that can be extracted from PV panels and a dc–ac converter to connect them to the ac grid. The battery pack can be connected in three different ways: dc coupled and ac coupled using a dedicated converter or through a direct connection on the dc-link between the dc–dc and dc–ac converters. In the present study, the last solution, without any dedicated converters, is used and a simple control strategy to both maximise the power extracted from the PV panel and regulate the charging/discharging of the battery is proposed.
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This study designs a market platform for peer-to-peer (P2P) energy trading in transactive energy (TE) systems, where prosumers and consumers actively participate in the market as seller or buyer to trade energy. An auction-based approach is used for market clearing in the proposed platform and a review of different types of auctions is performed. The appropriate auction approach for market clearing in the proposed platform is designed. The proposed auction mechanism is implemented in three steps namely determination, allocation and payment. This study identifies important P2P market clearing performance indices, which are used to compare and contrast the designed auction with different types of auction mechanisms. Comparative studies demonstrate the efficacy of the proposed auction mechanism for market clearing in the P2P platform.
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This work aims to investigate the impact of electric vehicles (EVs) charging/discharging strategies on the optimal operation of islanded microgrid (MG). For this purpose, firstly, load model of EVs under four different charging/discharging strategies, namely, uncoordinated charging mode, maximum renewable mode, valley filling mode and charging discharging mode is established. Thereafter, impact of these strategies on the optimal operation of MG is investigated. A 2m point estimate method is used to study the impact of forecast errors associated with load demand and renewable energy sources on the MG total cost under different EV charging/discharging strategies. Finally, a sensitivity analysis of variations of battery parameters on the MG total cost is also presented.
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This study presents a method to predict a day-ahead solar irradiation curve, under extreme meteorological phenomena (Föhn, north and south winds), existing in the province of San Juan, Argentina. The proposed method is based on an artificial neuronal network (ANN) which is trained with a data set filtered by the environmental variables that characterise the mentioned phenomena. A previously calculated ideal solar irradiation curve is modified from the forecasts generated by the ANN. The proposed methodology merges statistical learning methods and numerical weather prediction (NWP) methods, typically used to improve upon the raw forecast of a NWP model. A reduction of the uncertainty in the power production of photovoltaic plants in San Juan can be achieved with the results of the proposed forecasting method.
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As electrical power operations tend to be smart grid with strong penetration of renewable energy resources, the evolution of operational technology brings on board another dimension of vulnerabilities with the participation of cyber-physical systems (CPSs). Thus, it becomes essential to perform technical risk assessment and CPS prognosis to envisage the integrity of the system's operational resilience. The communication network elements such as cyber signal transmission, wireless sensor networks (WSNs) and the internet of things (IoTs) converges as a superhighway hub. This seeks to improve on network operations for efficient power delivery of distributed energy resources (DERs) integration grid. It then demands system configuration to be firewalled to avoid operational intrusions and malfunctions. The paper examines the technical threats involved in the paradigm of schemes and mitigation strategies. The areas of study are the vulnerabilities of the DERs integration with CPS, WSNs and IoTs layers. The risk aversion strategies of DERs integration with CPS are also discussed. The study aims to ascertain the intrusion level and responses of the integrated DERs grid in terms of power management. The paper's objective is to present an overview of current developments in the integrated cyber-power systems evolution and the implementation strategies with DERs.
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With the anticipated growth in use of electric vehicles (EVs) due to their benefits in environmental conservation and their potential as an energy storage device, corresponding charging facilities will also observe a growth. EVs require a charging infrastructure that supports a scenario which is capable of handling a large number of scheduling requests. However, this may result in a greater load on the grid. To mitigate the impacts of the increased charging load on the grid, photovoltaic (PV)-assisted charging stations, or PVCS, are proposed here. The benefits of PVCS are evaluated from the point of view of aggregator profits and energy consumption from the grid for a greater number of scheduling requests. With the use of PV at charging stations, it is found that for the period in which PV and battery storage are active, a majority of the charging requests are scheduled through the PV/Battery assist. Thus, reducing the effect on the grid along with an improvement in the total profit of the aggregators.
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Recently, the emerging subsynchronous oscillation (SSO) issue caused by interactions between power electronic converters and weak grids has provoked serious stability concerns. Impedance modelling based method has been widely used to analyse the emerging SSO phenomenon. In this paper, a frequency coupled impedance model (FCIM) is proposed to analyse this interaction. The FCIMs at multiple frequencies are measured and then the transfer function model is identified. The modelling method is then applied to type-4 wind turbine based farms connected to a weak AC grid. The aggregated impedance of the whole system is obtained by combining the FCIMs of all components in the power system. The system stability is then investigated by varying the online number of wind turbines. Time-domain simulations using PSCAD/EMTDC are carried out to verify the proposed methods of impedance modelling and stability analysis.
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With increasing penetration of renewable energy resources, the uncertain nature of these intermittent resources can introduce power dispatch problems resulting in serious risks to power system operational performance and reliability. Wind generation forecasts are crucial for power system scheduling and operation. In this study, a probabilistic method is proposed to assess the effects that wind generation forecast errors have on the dispatched power flow following short-term wind generation forecasts. Case studies have been conducted using a 29-bus reduced order model of the Great Britain power system under different scenarios. It is shown that the translation of wind plant forecast errors to errors in dispatched wind forecasts is non-linear at high penetration levels.
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This paper proposes a PV and wind output power generation forecasting agent for a multi-agent-based energy management system (EMS) in a smart microgrid. The microgrid EMS requires both generation forecast and load forecast to provide effective dispatch strategies. The efficiency of the EMS significantly relies on its forecasting accuracy. Firstly, this paper develops an adaptive neuro-fuzzy inference system (ANFIS)-based forecasting model and then utilise it for the development of wind and PV generation forecasting agent for microgrid energy management. ANFIS adopt the self-learning capability from the neural network and linguistic expression function from fuzzy logic inference and stands at the top of both the technologies in performance. The proposed model has been tested using two data sets, i.e., PV historical data and historical wind data. The fuzzy c means clustering (FCM) with hybrid optimisation algorithm-based ANFIS model shows better forecasting accuracy with both PV and wind forecast, therefore, implemented as PV and wind forecasting agent for microgrid EMS.
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To improve transmission capacity and stability margin of the power system, the doubly fed induction generators (DFIGs) based wind farm is transmitted over lines equipped with series compensation (fixed capacitors). However, the utilisation of series compensation brings the potential risk of subsynchronous resonance (SSR) in the power system. In this study, the SSR issue in DFIGs based wind farm integrated to a series-compensated network is studied based on the eigenvalue analysis and equivalent impedance model. The linearised state-space model of DFIGs based wind farm integrated to a series-compensated network is built first. Participation factors, sensitivities of eigenvalues and root loci, obtained by linearised state-space model, are observed to investigate the mechanism and the key parameters of SSR. Then, a method that can mitigate SSR in DFIGs based wind farm integrated to a series-compensated network is proposed based on virtual series resistance of the rotor. At last, the eigenvalue analysis and simulation are conducted to verify the effectiveness of the proposed mitigation method.
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The parameter optimisation of designed controllers for power systems is always a big concern and needs a lot of effort of researchers especially when the electricity grid becomes larger and more complex. This study proposes a control parameterisation using genetic algorithms (GAs) for power oscillation damping (POD) incorporating synchronous condensers (SCs) via software-in-the-loop simulation to enhance the damping and frequency stability for low-inertia systems. A closed-loop interfaced setup among real-time digital simulator, MATLAB, and OLE for process communication running in real time is analysed and implemented to optimise the POD parameters of a SC. Furthermore, a Prony technique based on the system measurement is applied to find out the frequency and damping ratio of the dominant oscillation mode. The POD optimal parameters are determined by the GA objective function that maximises the damping ratio of the dominant oscillation mode. The effectiveness of the proposed method in damping power oscillations and frequency stability improvement is verified through simulation results of the future western Danish power system. Simulation results demonstrate that the proposed approach offers good performance for parameter optimisation of the POD.
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This study presents a methodology to improve the operation of the power system and to deal with technical issues caused by electric vehicles (EVs) fast charging load. Fast charging stations (FCSs) are indispensable for widespread use of EVs since they can fully charge EVs in a short period of time. The integration of battery energy storage (BES) within the FCSs is considered a smart option to avoid the power congestion during the peak hours as well as the grid reinforcement costs due to FCSs. In addition, the BES can be used as multifunctional equipment, which is able to provide services such as peak shaving and frequency regulation. This study proposes a method to determine an optimal size of BES considering a stochastic modelling approach of the EVs load demand based on the users’ behaviour and their probabilistic driving patterns. Finally, a case study is carried out using a real DC fast-charging infrastructure in Copenhagen.
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This paper studies the wind power regulation problem by controlling a population of thermostatically controlled loads (TCLs) in smart grids. A decentralised bi-level control approach is proposed, where the first-level controller achieves load following based on wind power forecast, while the second-level controller deals with the forecast error effectively using the frequency deviation information. Specifically, to realise the fair dispatch of wind power in a users’ comfort sense, the wind power following problem is formulated as a quadratic optimisation problem, which is solved by the first-level controller. The second-level adopts a local proportional controller to handle the frequency deviation caused by the forecast errors of wind power. The proposed algorithm converges fast and is decentralised in the sense that the TCLs conduct local computation and keep the parameters’ privacy from the aggregator. Simulations are given to show the performance of the proposed approach.
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Due to serious environmental issues in recent years, renewable energy has been focused on all over the world to solve the issues. However, because of indirect characteristics such as variations of solar radiation intensity or wind speeds, the output of power generation utilizing renewable energy becomes unstable. As a result, frequency and voltage in the power system can fluctuate. To solve this problem, various methods to control the frequency variations have been studied and reported until now, one of which is based on High voltage direct current (HVDC) transmission line. This paper proposes a novel control scheme to reduce the frequency variations due to large penetrations of wind power and photovoltaic (PV) power, which is introduced to power flow control of HVDC transmission line with utilizing a notch-band pass filter in its frequency control system.
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A three-immense configurations of boost converter for renewable energy application is presented here. The voltage lift switched inductor (VLSI) structure is pledged to extra high-voltage conversion. The proposed work represents the modified high-voltage conversion boost converter (MBC) and its three configuration with VLSI module namely, modified boost converter with XL configuration (MBCVLSI-XL), modified boost converter with LY configuration (MBCVLSI-LY), and modified boost converter with XY configuration (MBCVLSI-XY). The advantages of proposed converter configurations are (i) immense voltage conversion ratio for high-voltage and low-current renewable energy applications; (ii) single switch topologies; and (iii) input inductor to avoid reverse current flow from load to source. The detail mathematical analysis of proposed configurations is carried out with and without considering the internal voltage drop across the circuit components. The comparative investigation is carried out with existed high-voltage conversion ratio topologies. The Matlab simulation results validates the working of proposed MBC configurations.
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Wind energy conversion systems (WECSs) require a suitable control to maximise the power generated by wind turbines independently on the wind conditions. Variable-speed fixed-pitch wind turbines with doubly-fed induction generators (DGIG) are used in WECSs for their higher reliability and efficiency compared to variable-pitch wind turbine systems. This study proposes an effective control algorithm to maximise the efficiency of fixed-pitch wind turbines with DFIGs using particle swarm optimisation control to compensate for the errors in the estimation of the circuit parameters of the generator. The proposed control algorithm generates an optimal speed reference to optimise the mechanical power extracted from the wind and the optimal d-axis rotor current through stator reactive power management to minimise the electrical losses of the doubly-fed generator. The optimal speed reference is provided by a maximum power point tracking control below the rated wind speed and a soft-stalling control above the rated wind speed, while the optimal d-axis rotor current is searched by a particle swarm optimisation algorithm. The proposed control system has been verified by numerical simulations and it has been demonstrated that the energy generated for typical wind speed profiles is greater than that of a traditional control based on a model-based loss minimisation.
- Volume 2019, Issue 18,
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To ease the heavy burden of inverter control, including line current regulation, harmonic current suppression, filter resonance suppression, grid distortion suppression, phase locked loop etc., the study proposes a master–slave current regulation method for an LCL-filter-based grid-connected inverter operating under variable grid condition. The proposed system is composed of a grid-connected voltage-source inverter (GC-VSI) in series with a bidirectional voltage-source converter (B-VSC) at the inverter output. The GC-VSI is responsible for line current regulation, while the B-VSC takes charge of harmonic current suppression and grid impedance cancellation. Owing to low volt-ampere of the B-VSC, the efficiency of the inverter system is not sacrificed. To confirm its validity, a simulation platform with the proposed inverter system has been built. The simulation results demonstrate the performance enhancement of the proposed inverter system operating under different grid conditions.
- Volume 2019, Issue 18,
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Power quality and current limitation are the most important aspects of the grid-connected power converters under fault. Since the distributed energy resources are widely used, fault management strategy is important for micro-grids applications. This paper presents a new control strategy for low-voltage ride-through for 3-phase grid-connected photovoltaic systems. The proposed method, which is designed in a synchronous frame using positive and negative sequence components, can protect the inverter from overcurrent failure under both symmetrical and unsymmetrical faults and provides reactive power support. The method does not require a hard switch to switch from MPPT to a non-MPPT algorithm, which ensures a smooth transition.
- Volume 2019, Issue 18,
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In this study, the switching mode and working waveform of dual active bridge (DAB) converter under triple phase-shift modulation scheme is analysed, and an ALL-ZVS (zero voltage switching) control strategy of all devices for full-power range with voltage transfer ratio M > 1 is proposed. First, a feasible control domain of ALL-ZVS is derived by analysing the constraints of the control variables of ZVS for all switching devices under different operating modes. On this basis, an ALL-ZVS control strategy of current RMS quasi-optimisation under the condition of M > 1 is proposed with the existing inductor current RMS optimisation control algorithm. It can be concluded that the proposed control strategy not only eliminates the switching loss, but also reduces the conduction loss, greatly improves the efficiency of the DAB converter. Finally, an experimental platform is built, and the experimental results verify the correctness and effectiveness of the proposed control strategy.
- Volume 2019, Issue 18,
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This study describes the technical principles behind the Power Potential innovation project in Great Britain (GB). The project aims to enable distributed energy resources (DERs) connected to the distribution network to provide services to the transmission grid, in a coordinated manner. This study focuses on the dynamic voltage control and the provision of reactive services that can be exercised through these assets. The specific control principles to enable participation of different DER technologies (synchronously and non-synchronously connected) to provide transmission support are described here. Simulation studies are included to theoretically validate the proposed solution using a detailed dynamic model of the transmission–distribution network in GB. The value of this control approach as a new tool for the system operator is also highlighted and the next steps for the Power Potential project are finally summarised.
- Volume 2019, Issue 18,
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Doubly fed induction generator (DFIG) is the most popular machine for the wind power application that consists of the ability for variable speed operation and reactive power control with the help of power electronics converters. It is one of the prominent system that follows grid code requirement as it remains connected with the grid even during the fault occurrence. For making the DFIG continuity in the grid, low-voltage ride through or fault ride through (FRT) techniques are used. Fault current limiter is one of the major schemes used under the FRT. A saturated core fault current limiter (SCFCL) is used in DFIG system to enhance the FRT capability. The main property of SCFCL is the change in permeability between the saturated and unsaturated conditions of the magnetic core to concurrently provide low steady-state impedance and high transient fault impedance for limiting the fault current.
- Volume 2019, Issue 18,
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The rapid variation of irradiance due to cloud movements and occlusions is the main factor causing the fluctuation of photovoltaic (PV) power generation. Accurate recognition and classification of cloud is the prerequisite of improving the prediction accuracy of irradiance. Total-Sky-Images (TSIs) taken by ground-based cameras are a good solution to analyse the distribution of cloud in real-time and is suitable for ultra-short-term PV power prediction. Images are often processed by threshold-based segmentation algorithm, which is based on the brightness or greyscale value of pixels. However, the sunlight can change the brightness or greyscale distribution of those pixels which represent cloud and cause misclassification. This paper proposes a novel cloud classification method based on greyscale compensation values (GCVs) and Otsu algorithm to solve this problem and divides the total sky into three parts: clear sky, thin cloud and thick cloud. GCVs are greyscale values which extract from clear-sky TSIs. Experimental results show that this method can effectively improve the accuracy of cloud classification.
- Volume 2019, Issue 18,
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Significant growth in residential solar photovoltaic (PV) installations and the ongoing decline in battery costs have increased interest in household solar battery energy storage projects in Finland in recent years. Among various potential applications, considerable attention is drawn to the use of the battery energy storage system (BESS) for the purpose of the households’ self-consumption enhancement. This study presents the results of a techno-economic study of the LiFePO4-based battery storage added to residential roof-top PV installations in Finland to maximise self-utilisation of on-site solar energy generation. Using a comprehensive DC model of BESS, the battery charge and discharge levels under the typical household load and PV production conditions are simulated. The estimates of the average retail electricity prices are used to assess the value that the customer-sited solar battery storage can provide to the household end-users in Finland. The economic attractiveness of the battery storage projects is evaluated considering the present and forecasted BESS costs and the electricity tariff levels in Finland and the conditions for profitable operation of the solar energy storage systems are determined.
- Volume 2019, Issue 18,
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The AC-DC hybrid microgrid is a credible evolution path for the microgrid. State estimation in complex distribution network is a significant foundation for the safe operation. In AC-DC hybrid microgrid, centralised state estimation algorithms have quite a few deficiencies such as large communication capacity and privacy protection. In response to these obstacles, this paper proposed a novel distributed state estimation algorithm. First, a three-stage state estimation model was established for AC-DC hybrid microgrid, in which the second stage is a nonlinear transform for the linearisation of the nonlinear state estimation progress so that the first and third stage can solve the linear state estimation problem. Furthermore, the Lagrangian relaxation method was ultilised for the distributed problem solution. In the proposed algorithm, AC subsystems and DC subsystems respectively execute state estimation through local information, and the overall consistency of the system state estimation can be eventually achieved according to the transfer iteration of the boundary information. The computational efficiency and convergence of the proposed method was ensured owing to the combination of bilinear theory and Lagrangian relaxation. Simulation results indicate that the proposed method can achieve its goal and be superior to existing method in efficiency.
- Volume 2019, Issue 18,
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Active yaw system is a very important component of modern horizontal axis wind turbines to keep the nacelle aligning with the stochastic wind direction. However, in practice, it is hard to keep the rotor facing into the wind precisely, which will lead to not only the loss in power production but the increment in aerodynamic loads. This study presents a data-driven approach to estimate yaw error for remote terminal unit.
- Volume 2019, Issue 18,
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The increasing wind integration in present grids to generate clean energy escalates the problem of low-frequency oscillations (LFOs) in the system. Here, a wide area-based coordinated control strategy of power system stabilisers (PSSs) and doubly fed induction generator's (DFIGs) power oscillation dampers (PODs) is presented to improve the system damping. An improved eigenvalue-based objective function is employed to optimally tune the variables of the controller using whale optimisation algorithm (WOA). The impact of DFIG location and thus the suitable wind farm locations are also found out using eigenvalue analysis and dynamic sensitivity analysis. The results are investigated on IEEE 68 bus test system highlighting the effectiveness of proposed strategy for a wide range of operating scenarios.
- Volume 2019, Issue 18,
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The paper reports the latest practice in the field for solar PV integration in distribution grids in Denmark, where the communication capability of solar inverters is exploited for integrating the monitoring and control functions of solar inverters into the SCADA system of the grid operator. The project demonstrates that, by implementing the enabled communication protocols of solar PV inverters in the remote terminal unit (RTU), the operator can receive measurements from the PV inverter on a variety of quantities, as well as remotely regulate the active and reactive power production for procurement of grid services. The practice demonstrates the feasibility of using solar PV plants for grid support in critical situations, where the experience is repeatable for other distribution grid operators to integrate distributed generation resources into the grid management functions. The work is carried out in cooperation with the grid operator of Bornholm, which is one of the islands in Denmark having the highest penetration of renewable energy.
- Volume 2019, Issue 18,
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This paper proposes a coordinated frequency control method for variable speed wind turbines with permanent magnet synchronous generators (VSWT-PMSGs) based offshore wind farm (OWF), which is connected to the main onshore grid through voltage source converter (VSC) based high voltage DC (HVDC) transmission system. The purpose of the proposed system is to damp the frequency oscillations of the onshore grid due to the installation of large-scale fixed speed wind turbines with squirrel cage induction generators (FSWT-SCIGs) based wind farm (WF) and photovoltaic (PV) power station. A novel centralised droop controller with the dead band is designed for VSWT-PMSGs to decrease the frequency fluctuations of the onshore main power system. In the proposed system, primary frequency reserve is implemented by deloading operation of VSWT-PMSGs in the OWF. The effectiveness of the proposed centralised frequency controller is verified through simulation analysis on a modified IEEE nine-bus model system in PSCAD/EMTDC software.
- Volume 2019, Issue 18,
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This work consists in assessing a real islanded power system from a dynamic security point of view, to support the planned installation, in the near future, of a hydro power plant with pumped storage, aiming to increase the integration of renewable energy. The analysed hydro power plant will include a Pelton turbine as it is a high-head hydro facility. Due to economic reasons, the adopted water pumping technology consists in fixed speed pumps coupled to induction motors with direct grid connection. It was possible to verify through detailed simulations of this power system's time domain behaviour that, even though the expected installation of this new power plant will bring additional frequency stability constraints, a robust technical solution may be found dealing with the new constraints without increasing the complexity of operation in this islanded power system. The conclusions obtained from this specific case are also valid for similar isolated power systems, namely when hydro pumping stations are being considered to increase time-variable renewable generation penetration.
- Volume 2019, Issue 18,
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The large penetration of wind generators in existing electrical grids induces critical issues that are pushing the system operators to improve several critical operation functions, such as the security analysis and the spinning reserve assessment, with the purpose of mitigating the effects induced by the injected power profiles, which are ruled by the intermittent and not-programmable wind dynamics. Although numerous forecasting tools have been proposed in the literature to predict the generated power profiles in function of the estimated wind speed, further and more complex phenomena need to be investigated in order to take into account the effects of the forecasting uncertainty on power system operation. In order to deal with this issue, this paper proposes a probabilistic model based on Markov chains, which predicts the wind power profiles injected into the grid, considering the real generator model and the effects of the power curtailments imposed by the grid operator. Experimental results obtained on a real case study are presented and discussed in order to prove the effectiveness of the proposed method.
- Volume 2019, Issue 18,
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Innovations which help facilitate predictive maintenance strategies have the potential to greatly reduce costs associated with wind turbine O&M by driving efficiency and increasing wind turbine availability. This study uses multiple examples of the same generator bearing failure to provide insight into how condition monitoring systems can be used in to train machine learning algorithms with the ultimate goal of predicting failure and remaining useful life. Results show that by analysing high-frequency vibration data and extracting key features to train support vector machine algorithms, an accuracy of 67% can be achieved in successfully predicting failure 1–2 months before occurrence. This study reflects on the limitations surrounding a generalised training approach, taking advantage of all available data, showing that if too many different examples are considered of different wind turbines and operating conditions, the overall accuracy can be diminished.
- Volume 2019, Issue 18,
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Fluctuations of electricity prices in demand response schemes and intermittency of renewable energy supplies necessitate the adoption of energy storage in power systems. This paper considers the heterogeneous cloud energy storage (HCES) on cloud energy storage operator side. The goal of this approach is to lower the cost of energy storage by exploiting the different operating characteristics and economics of different battery energy storage technologies. The customers are screened from the type of storage facility that they have purchased and cloud energy storage (CES) operator can maximize the benefit if the complementarily of the storage technologies can be utilized. Distributed generation such as photo-voltaic (PV) generation has also been considered on both side consumer as well as CES operator side for supplying power to energy storage facilities to reduce the cost of charging power. Furthermore, the paper also presents an economic viability of heterogeneous storage system using investment analysis methods. Numerical simulations are carried out based on HCES technological characteristics such as self discharge, round trip charge-discharge cycle efficiency, depth of discharge (DOD) and cycles life time. There is significant changes in the economic performances using HCES when compared with single energy storage.
- Volume 2019, Issue 18,
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The wind industry is showing increasing awareness about the importance of long-term direct shaft mechanical torque measurements to fully understand wind turbine (WT) dynamics, adopt proactive solutions for extreme load mitigation and enhance condition monitoring (CM) capabilities. Although torsional effects are important, torque measurement on such large, inaccessible machines is practically and logistically difficult, mainly because of the costly and intrusive specialised equipment currently available. This study details an experimental set-up for the investigation of shaft dynamic transient load and speed measurements through a contactless, low-cost torque meter. Results are obtained over a range of applied loads and compared with reference measurements from an in-line, invasive torque transducer. Average torque and speed root-mean-square error values of 0.53 Nm and 0.35 rpm, respectively, indicate good accuracy of the proposed contactless torque meter. Its implementation in the field would allow direct, cheap, real-time measurements of WT drive train loads for performance monitoring, control and CM purposes.
- Volume 2019, Issue 18,
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Wind power is playing an increasingly significant role in daily life. However, wind farms are usually far away from cities especially for offshore wind farms, which brought inconvenience for maintenance. Two conventional maintenance strategies, namely corrective maintenance and preventive maintenance, cannot provide condition-based maintenance to identify potential anomalies and predicts turbines' future operation trend. In this study, a model based data-driven condition monitoring method is proposed for fault detection of the wind turbines (WTs) with SCADA data acquired from an operational wind farm. Due to the nature of the alarm signals, the alarm data can be used as an intermedium to link the normal data and fault data. First, KPCA is employed to select principal components (PCs) to retain the dominant information from the original dataset to reduce the computation load for further modelling. Then the selected PCs are processed for normal-abnormal condition classification to extract those abnormal condition data that are classified further into false alarms and true alarms related to the faults. This two-stage classification approach is implemented based on the KSVM algorithm. The results demonstrate that the two-stage fault detection method can identify the normal, alarm and fault conditions of the WTs accurately and effectively.
- Volume 2019, Issue 18,
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In recent years, the transition process towards clean energy has caused many challenges to power systems, especially in the field of operation and power system control. Conventional generators, which have been providing ancillary services to maintain stability and reliability to the system, are being replaced by intermittent renewable generators. Therefore, maintaining system quality and stability in terms of power system frequency control is one of the major challenges that require new resources and system integration. Battery energy storage systems (BESSs), as fast-acting energy storage systems, with the capability to act as a controllable source and sink of electricity are one of the prominent solutions for system services. This study investigates the primary frequency control provision from BESSs to the renewable energy sources dominated power system. The simulation results for various cases have shown that integration of BESSs has significantly improved power system frequency stability.
- Volume 2019, Issue 18,
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A method is proposed for the economic optimisation of offshore wind cable connections through utilising the thermal inertia of the cable system. Taking account of expected wind yields, turbine reliability, and the dynamic thermal environment, the method determines the economically optimal number of turbines for a given export cable system. Analysis has shown that, providing means to actively curtail generation output so as to thermally protect the cable are in place, it is possible to reduce the cost of energy delivered to shore by up to £1/MWhr through the use of ‘over-planting’, i.e. building a wind farm that is larger than the continuous rating of its export cables.
- Volume 2019, Issue 18,
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The inherent complementarity of wind and solar energy resources is beneficial to smooth aggregate power and reduce ramp reserve capacity. This article proposes a progressive approach to assess the wind-solar complementarities in Shandong province, China for the preliminary planning of hybrid energy systems. Based on the NASA database, the long-term wind speed and solar irradiation data are obtained and transformed into capacity factors by virtual energy system models. Then, the local assessment that focuses on temporal characteristics is carried out to measure the complementarities in different time scales and search the optimal scale. Progressively, the space scale is extended from a local site to the whole study region and the global assessment is conducted to extract the spatial complementary characteristics. The assessment results are useful to provide the optimal temporal scale and spatial combination of wind-solar complementarity and the proposed approach can be generalised to other regions.
- Volume 2019, Issue 18,
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In recent years, a new type SSO issue, which has occurred in direct-drive permanent magnetic synchronous generators (PMSGs) based wind farm, brings a new challenge to the stability of the power system. In this paper, the SSO issue in grid-connected PMSGs system is studied by the eigenvalue analysis. The linearised state-space model of this system is built firstly. The impacts on the SSO characteristics from short-circuit ratio (SCR), impedance-frequency characteristic, resonant frequency of AC network and control parameters of PMSGs are observed by the root loci analysis. After that, electromagnetic transient simulation is carried out to verify the eigenvalue analysis. Meanwhile, the participation factors of SSO mode are calculated to analyse the subsynchronous control interaction (SSCI) between AC network and PMSG. The result shows that there is a SSO mode which is greatly influenced by AC network and DC capacitor, grid side converter (GSC) control of PMSG. The characteristics of AC network will affect the SSCI between AC network and PMSG.
- Volume 2019, Issue 18,
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The share of photovoltaic (PV) systems in the distribution networks is rapidly growing, leading to the common issue of overvoltage at the end of distribution feeders during the periods when peak generation is surplus to consumption. In this study, a hierarchical control is proposed to mitigate overvoltage at the point of connection of PV systems in physical low-voltage microgrids. The proposed mechanism is comprised of primary and secondary control layers to tackle the overvoltage problems given the communication capability is available. This mechanism employs a multi-objective optimisation approach to effectively coordinate curtailed active power and absorbed reactive power of the PV inverters with the aim of minimising the active power curtailment. The feasibility of the proposed control approach is successfully verified through simulations on a simplified LV network.
- Volume 2019, Issue 18,
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Wave Energy Converters (WECs) generally use a Mechanical Power-Take-Off (MPTO) involving hydraulics or gearing to optimise the extraction of energy from the incoming waves before converting it into electrical energy via a high speed rotating generator. This simplifies the design of the Electrical Power Conversion System (EPCS). Further, it facilitates the use of mechanical energy storage such as hydraulic accumulators to reduce the peaky nature of the power flow and allows the WEC resonant frequency to be tuned for maximum energy capture. This work compares two power electronic converter topologies for an Electrical PTO (EPTO). This EPTO is intended to replace the aforementioned MPTO and generator with a Permanent Magnet Linear Machine (PMLM) directly coupled to the WEC. The compared topologies comprise either a Current Source Converter (CSC) or a Voltage Source Converter (VSC) as the generator interface working in combination with a DC-DC converter and an Energy Storage System (ESS). The principle differences between the two topologies are explored and losses are evaluated in a modular EPCS working with a WEC. Wide-bandgap power electronic switches are assumed for both topologies over a range of switching frequencies. The evaluation concludes that the CSC topology is advantageous at higher switching frequencies.
- Volume 2019, Issue 18,
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Wind power forecasting (WPF) is crucial in helping schedule and trade wind power generation at various spatial and temporal scales. With increasing number of wind farms over a region, research focus of WPF methods has been recently moved onto exploring spatial correlation among wind farms to benefit forecasting. In this study, a spatio-temporal Markov chain model is proposed for very-short-term WPF by extending the traditional discrete-time Markov chain and incorporating off-site reference information to improve forecasting accuracy of regional wind farms. Not only are the transitions between the power output states of the target wind farm itself considered in the forecasting model, but also the transitions from the output states of reference wind farms to that of the target wind farm are introduced. The forecasting results derived from multiple spatio-temporal Markov chains regarding different reference wind farms over the same region are optimally weighted using sparse optimisation to generate forecasts of the target wind farm. The proposed method is validated by comparing with both local and spatio-temporal WPF methods, using a real-world dataset.
- Volume 2019, Issue 18,
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This work analyses the impact of photovoltaic generation on voltage stability margin in an islanded microgrid. An indicator of voltage collapse proximity, based on the maximum deliverable power, is used to study the contribution of photovoltaic generation to the voltage stability margin. In this context, the well-known power–voltage curves, also known as ‘nose’ curves, are developed, taking into account different levels of photovoltaic penetration. Furthermore, the effect of the power factor at the photovoltaic generators as well as the influence of the adopted model for such generators are also investigated. The results have shown that the photovoltaic generation can significantly affect the voltage stability margin.
- Volume 2019, Issue 18,
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High penetrations of wind generation have intermittency and volatility issues in deregulated power system. With increasing penetration of wind power, independent system operator (ISO) faces an enormous challenge in secure operation with intermittency and uncertainty of renewable energy resources. To handle these issues, battery energy storage system (BESS) is a probable solution for enhancing the wind penetration in the electric grid. In this regard, this article proposes a stochastic security constrained unit commitment (SCUC) with BESS considering wind uncertainty. The proposed approach is formulated and solved by Benders decomposition (BD) method which reduces computational time. The goal is to detect the optimal amount of SCUC, locational marginal price (LMP), wind curtailment, and line contingency by performing DC optimal power flow (DCOPF). Numerical case studies are investigated in detail using IEEE Reliability test system (RTS) 24-bus network and simulation results are found to be inspiring.
- Volume 2019, Issue 18,
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This article investigates the feasibility of interconnecting LCC-HVDC and VSC-HVDC through an un-interrupted DC autotransformer (DC AUTO). The interconnected system aims at taking advantage of two HVDC technologies. To begin with, the system configuration and the potential benefits are illustrated. Then, the corresponding control strategies towards LCC-HVDC, VSC-HVDC, and the un-interrupted DC AUTO are proposed. The installed controllers enable the system stable operation during both normal time and faulted conditions. Finally, a four-terminal test system is built on PSCAD/EMTDC platform to validate the technical feasibility of the interconnected system and the effectiveness of the proposed control strategy.
- Volume 2019, Issue 18,
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This paper proposes a new approach to determine the optimal sizing and location of a vanadium redox flow battery (VRFB) that provides load frequency control services in a power system, with the lowest cost for the utility grid. To this aim, the optimization model takes into account the impact of the energy storage system on the electrical system. With a stochastic optimization, the developed methodology calculates the operating costs of the electricity grid and the investment costs of the VRFB. The methodology uses a primary-dual interior point algorithm integrated in a meta heuristic algorithm and nested in an exhaustive search method.
- Volume 2019, Issue 18,
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With the high-penetration distributed photovoltaic (PV) systems accessed to a distribution network, the peak active power output of PV systems is always greater than the total local load demands, which might lead to the issues of overvoltage and reverse power flow in a distribution system. In this paper, based on the reactive power output capability of distributed PV inverters, a distributed PV reactive power local control strategy is proposed. Three types of voltage reactive power local control modes of PV inverter are analysed, respectively; they are voltage-var control mode (Q(V) mode), adjustable power factor mode (PF(P) mode) and active power curtailment mode (APC mode). The applicable conditions of different control modes are analysed. A simulation example based on IEEE 33-node system is studied, where the method of determining the optimal control mode under different operating scenarios of distribution system with PV is given, and the validity of the three local control modes is verified.
- Volume 2019, Issue 18,
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In recent years, major power outages caused by extreme natural disasters have incurred large economic losses in distribution systems. This study proposes a transient simulation and verification method for resilience-enhancement strategies and proposed a graphics processing unit-based parallel simulation method. The proposed method can be used to verify the transient feasibility of the distribution system before a strategy is actually executed. Simulations are performed to verify the proposed method.
- Volume 2019, Issue 18,
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The increasing complexity of the distribution system makes the practical distribution network operation much difficult. This paper presents an ordinal optimisation (OO) approach to solve the distribution network reconfiguration, which is an NP- hard problem with discrete control variables. OO uses crude and computationally fast model to reduce the search space. The spirit of OO is to seek the good enough solution instead of the best with high probability. The proposed approach is validated with two practical distribution systems, TPC 84 node test system. The results are compared with Optimal Flow Pattern (OFP), Common Genetic Algorithm (CGA), Partheno Genetic Algorithm with Tree Structure Encoding technology (TSE-PGA) and Second-Order Cone Programming (SOCP).
- Volume 2019, Issue 18,
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This article presents the modelling and assessment of a pulsating torque mitigation control strategy by using a tidal turbine emulator in a laboratory environment. Sudden changes and variability of the tidal flow velocity have the effect of creating pulsations on tidal current turbines. These pulsations have an adverse effect on tidal turbine fatigue and ultimate loading as well as the operation of the drivetrain. For the above reasons, a pulsating torque mitigation control strategy has been developed and tested which is based on modifying the reference maximum power point speed of the generator. This article presents the assessment of this pulsating torque mitigation control strategy in a laboratory setup. A 7 kW tidal current turbine is modelled in MATLAB/Simulink. The tidal turbine is emulated in the laboratory setup by using a torque-controlled induction motor. Results show the effectiveness of the method in a laboratory environment, the ability of the generator to accelerate and decelerate based on the speed controller commands and the difference between the pulsating torque mitigation control strategy and maximum power point operation (MPPO). In addition, the experimental results are compared with a Simulink model which will show the accuracy of the modelling process.
- Volume 2019, Issue 18,
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As the amount of wind power in power systems has increased, it has become necessary to curtail wind power in some high-penetration situations. In order to assess the need for curtailment arising from voltage stability considerations the authors develop a security constrained optimal power flow (SCOPF) for minimising the expected curtailment. The authors find that with a very high wind penetration and wind farms operating at unity power factor curtailment becomes necessary to satisfy voltage limits. In this case, the optimal solution in the studied system is to curtail at a single bus rather than curtailing by a smaller amount at several buses. However, allowing for reactive power production from wind farms reduces the need for curtailments.
- Volume 2019, Issue 18,
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This work presents a new wave energy converter power take off (PTO) system that combines two recent developments in drive train technology, the consequent pole linear vernier hybrid permanent magnet machine and the linear magnetic gear. The combined system is fully realised in three-dimensional finite element method and compared to a similar direct drive machine. While the resulting system is lighter, reducing the active material mass by 30%, and more efficient, the system requires larger amounts of high cost permanent magnet material and increased PTO complexity. It is summarised that while such a system could be recommended in certain conditions, it is not viable for general application.
- Volume 2019, Issue 18,
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During the operation of the integrated energy system (IES), the dynamic behaviour of heat loads can affect the optimal operation strategy. This study proposes a novel optimal day-ahead operation method of user-level IES considering the dynamic behaviour of heat loads. Firstly, based on the energy hub, the model of heat loads with dynamic behaviour is added into IES. The dynamic behaviour is embodied by water temperature which can be represented by differential equations. Then, the optimal day-ahead operation model aimed at minimising the energy purchase cost is proposed. Piecewise linearisation is utilised to simplify the temperature constraints which can transform the initial non-convex and non-linear optimisation into a linear programming problem. Finally, case studies are carried out on a practical case, and the results indicate that with the consideration of dynamic behaviour of heat loads, the energy purchase cost can be reduced by 5.6%.
- Volume 2019, Issue 18,
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Public transport is very influential industry affecting our society due to its significant environmental and social impact. Policy makers have seen electric vehicle as a tool to reduce greenhouse gas emissions. Cleanliness of power from the electricity grid plays a vital role in environmental impact in the transition to electric vehicle. In countries like China, USA, India etc., majority of electricity generation is still dominated by fossil fuel fired generators. Thus, in some cases, the environmental impact of electric vehicle may be more adverse in comparison to conventional internal combustion engine vehicles (ICEV). This paper tries to study the environmental effect of incorporation of 100 Electric Vehicle taxies in Johannesburg (JNB), South Africa. Firstly, the current electricity generation scenario and vehicles standards of SA with its carbon emission is discussed. Secondly, it is shown that with the current generation mix the adoption of EV is not sustainable. Finally, penetration of Renewable Energy (RE) system at charging stations is proposed with Renewable Energy Fraction (REF) of 40% and 58% to make carbon mission from EV equivalent to Euro III and Euro V standards of petrol ICEV. The optimised size of RE system is found using the Electric System Cascade Analysis.
- Volume 2019, Issue 18,
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with the onboard diesel generators and energy storage system to meet the propulsion and service load, the all-electric ship (AES) can be viewed as a ‘mobile microgrid’. Nowadays, photovoltaic (PV) generation is gradually integrated into the AES for a ‘greener’ voyage. To fully utilise the PV energy, this paper proposes a joint generation and voyage scheduling method for the PV integrated AES. The overall model is formulated as a bi-level programming problem and solved by column-and-constraint generation method. The simulation results manifest that, the integration of PV into AES leads to reductions on both the fuel consumption and CO2 emission.
- Volume 2019, Issue 18,
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This paper has described the technical considerations that are necessary to ensure the cost-effective and reliable connection of battery energy storage systems co-located with existing generation plants. The connection requirements of typical battery energy storage systems have been described and the procedures required to meet operational constrictions for connection at an existing plant are explained.
- Volume 2019, Issue 18,
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Biogas, as the product of anaerobic fermentation, is one of the main routes to utilize bioenergy. The biogas production rate is determined by lots of factors, of which temperature determines most. However, when operating in the cold climate or cold areas, the low digesting temperature often results in a relatively low efficiency or even a suspension in the fermentation process. This paper proposes a self-excited heating method to increase the digesting temperature in cold weather. It utilizes the self-produced biogas as fuel to generate heat for heating the biogas digester. The influence of this method on biogas production rate and digesting temperature are verified in this study. The results show that the digesting temperature increases about 3%–9% with a self-excited heating method for both household-scaled biogas digester and industry-scaled digester.
- Volume 2019, Issue 18,
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DC microgrids (DC-MGs) are capable of integrating and coordinating distributed energy resources into power systems, along with providing services to the wider system, e.g. balancing, frequency support, demand response and so on. This study investigates the capability of DC-MGs providing grid frequency support, for the GB enhanced frequency response service. In this study, photovoltaic generation, energy storage, and load form the DC-MGs. The control strategy is a decentralised scheme, based on conventional droop control for active power sharing and grid frequency support. Droop control is also used within the DC-MG for power-sharing amongst generation and load. Scenarios are conducted to evaluate the effectiveness of the control strategy and verified by MATLAB/Simulink simulations.
- Volume 2019, Issue 18,
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Norway has implemented economic incentives over several years to encourage a transition from conventional vehicles to electric vehicles (EVs), and now has the largest share of EVs per capita in the world. In this study, the authors explore the impacts of increasing EV penetration levels in a Norwegian distribution grid, by using real power measurements obtained from household smart meters in load flow analyses. The implications of installing a fast charger in the grid have been assessed, and an optimal location for it is proposed, aiming at minimising both grid losses and voltage deviations. Moreover, the potential for reactive power injection to reduce the voltage deviations caused by fast chargers has been investigated. Results show that the EV hosting capacity of the grid is good for a majority of the end-users, but the weakest power cable in the system will be overloaded at a 20% EV penetration level. The network tolerated an EV penetration of 50% with regard to the voltage levels at all end-users. Injecting reactive power at the location of an installed fast charger proved to significantly reduce the largest voltage deviations otherwise imposed by the charger.
- Volume 2019, Issue 18,
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This study presents a smart power strategy coordination for optimal electricity supply. It aims to coordinate the energy flow on the electrical system for a residential application in the southern area of the African continent, in conjunction with an intelligent demand management control strategy. It has been observed that there is a potential for renewable energy resources that can enhance the energy and development of the African continent if used efficiently. In addition, the continent is suffering from several energy crises, which could be resolved by appropriate energy control approaches. It has been observed that incorporating an autonomous smart strategy that can coordinate a hybrid energy supply for a residential energy demand could improve the power grid performance of the Southern African region. In this paper, a smart strategy that develops a dynamic real-time energy structure control is proposed. This approach uses the ability of smart metering to create a flexible communication control strategy (FCCS), which will manage the demand and the supply of energy. It ensures the consumer's optimal power supply while ensuring stability and good performance on the utility side.
- Volume 2019, Issue 18,
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As wind penetration level into power systems increases, provision of frequency support from wind plant is anticipated to become a requirement in grid codes. In addition to the virtual inertial response, two different approaches to delivering droop response from wind plant are presented and compared in this paper. The combination of droop and inertial response from wind plant has been assessed for a frequency time series. Simulation results show that the proposed approaches to delivering combined droop and inertial response can provide superior performance to either inertial or droop response alone.
- Volume 2019, Issue 18,
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The next-future extensive diffusion of distributed generation and the increasing energy demands due to new components (e.g. electrical vehicles, energy storages) are changing the characteristics of the power grid at the distribution level, which makes it inevitable to introduce the synchrophasor measurement technology into the distribution network. This study analyses the power spectrum for the background noise of the field measured voltage signal of 0.4 kV in one electrical vehicle charging station. The coloured filter model is established using the autoregressive moving average process, which leads to the conclusion that the coloured noise spectrum is generally concave. The impact of background noise for the phasor estimation is evaluated in the steady state and dynamic state referring to IEEE Std C37.118.1™-2011.
- Volume 2019, Issue 18,
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Crack is one critical factor that degrades the performance of photovoltaic (PV) panels. To gain a better understanding of the impacts of cracks appeared on PVs and also to mitigate it, its failure mechanism, detrimental effects, criticality, and potential risks on independent PV panels are firstly reviewed in this study. An experimental study which investigates the degree of series connected and parallel connected PV strings which are affected by cracked cells are presented. A comparison of impacts of the partially shaded PV panel string and cracked cells happened to the PV panel string is given to evaluate their criticality levels. The experimental results show that the series connected PV panel string is strongly affected once the cell is seriously cracked, as the current generation capability is clamped. Partial shading, however, shows better performance. In addition, though the overall power the parallel connected PV string is reduced, it is less affected by the cracked cells compared to the series connected one. Lastly, a bypass diode is added to a series connected PV panel string with cracked cells, and the experimental results show that it can be an effective way to minimise the negative impacts of cracks.
- Volume 2019, Issue 18,
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DC microgrids are expected to play an important role in maximising the benefits of distributed energy resources in future low carbon smart power systems. One of the remaining complex challenges is the requirement for effective DC protection solutions. The advancement of DC protection is hindered by the lack of good understanding and development of reliable and effective earthing schemes which can enable safe and secure operation of DC microgrids in both on-grid and off-grid modes. Therefore, this study discusses different DC microgrid earthing opportunities, and comprehensively evaluates through detailed simulation studies the influence of different earthing methods on the fault behaviour of DC microgrid. A transient model of an active DC microgrid is developed in PSCAD/EMTDC and used for the paper studies.
- Volume 2019, Issue 18,
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With the solar power panels as integrated surface elements in new building constructions, solar power will be economic attractive in urban areas, close to the power consumption. In the new dense urban areas, the rooftop areas will be attractive for other purposes, like terraces and green roofs. The solar power panels may instead be placed at the facades of the buildings – this is especially relevant at high geographic latitudes, where the altitude of the sun is low. It may even make sense to mount panels at all facades, better distributing the generation over the day.
- Volume 2019, Issue 18,
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An energy storage system (ESS) sizing method is proposed to enable wind farm (WF) to be a black-start (BS) source. This method handles three challenges: firstly, ESS has enough power to help WF start up. Secondly, the WF together with ESS is modelled as a virtual synchronous generator (VSG), and its frequency regulation capability is considered when sizing ESS. Thirdly, the power and capacity of ESS are determined so that VSG can deliver the required power during black-start. Instead of using wind speed probability distribution, kernel density estimation is used in this paper to directly estimate the probability distribution characteristics of ESS sizing. Simulation results show that with minimum investment cost on ESS, WF is able to be BS source.
- Volume 2019, Issue 18,
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This article proposes a new control paradigm for the seamless operation of a permanent magnet synchronous generator (PMSG) based wind energy conversion system (WECS) in both islanded and grid-connected modes. Conventionally, grid-connected WECS are controlled to extract the maximum power from the wind, known as maximum power point tracking (MPPT). However, in islanded operation, the objective is to control the power generated from the WECS to match the load demand, which here is called load following power generation (LFPG). This article proposes a power management system (PMS) which integrates the MPPT and LFPG capabilities of the WECS into a single-control paradigm. This enables the WECS to seamlessly achieve MPPT in grid operation, LFPG in islanded mode and low-voltage ride-through (LVRT) during fault. The proposed scheme is validated using MATLAB/SIMULINK simulations.
- Volume 2019, Issue 18,
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This study presents a method of anomaly detection within a gearbox by way of standardising temperature data. Assessing measured parameters in isolation is not sufficient to detect faults within a wind turbine. This technique uses temperature, rotational speed, and generator torque to detect a bearing fault within the gearbox. Standardising data allows a parameter to be analysed which also takes into consideration the operating state of the wind turbine, therefore providing a more holistic view of the health of the wind turbine and component being monitored.
- Volume 2019, Issue 18,
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This study exploits the impact of different low voltage ride-through (LVRT) methods and equipment on both the wind energy elements and the grid including wind turbine/farm ability to provide reactive compensation and maintain controllability during faults. The potential of using SFCL as an alternative LVRT equipment is preliminary studied. The study also exploits some severe scenarios that could face a multi-terminal high-voltage DC (HVDC) network. The influences of AC faults and control errors are examined. Results show limited deviations between the adopted LVRT methods. The wind turbine has to contribute to the stability of the AC collection grid of the wind farm, but it does not influence the grid, as both are decoupled through the multi-terminal HVDC grid. The implemented test systems and the examined events are developed in Matlab/Simulink and DIgSILENT.
- Volume 2019, Issue 18,
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Decentralisation of electricity generation, and electrification of heating and transportation pose challenges for the distribution networks, such as possible network congestion. Network operators investigate alternatives for reinforcements. Flexibility through demand response (DR) is one of these alternatives. Four theoretical possibilities for flexibility as a solution for congestion management are presented, in relation to four pilot projects on congestion management in the Netherlands. This article evaluates these four pilot projects based on six evaluation criteria. The strengths and weaknesses of all pilots are addressed, and the results of the pilot projects are discussed.
- Volume 2019, Issue 18,
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Photovoltaic systems are the important part of the energy market in many countries around the world. Such systems contain several parts and one of them is the inverter to produce the AC signal. In this paper, an estimation method is used to obtain the value of frequency, amplitude and phase of the grid signal used to drive the inverter in a proper way. The method is based on the 3-point spectrum interpolation and I class Rife-Vincent time windows. The tested signal contains harmonics and AWGN noise to reflect real and practical measurement conditions. Additionally, simulations were performed for various values of measurement parameters to show broadly properties of the method. The estimation time is only up to two CiR (cycles of the signal in the measurement window). Harmonic components and noise negatively affect the accuracy but the method is so flexible that it can be adjusted to the needs of a current estimation. The estimation error for SNR = 50–60 dB and for two additional harmonics is in the order of approximately 10−3.
- Volume 2019, Issue 18,
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Recently, there has been significant interest in developing the modular multilevel converter (MMC) based DC grids in the power industry. However, the immature DC circuit breaker (DCCB) technology hampers the development of DC grids in overhead lines transmission field. The full controlled power electronic devices based hybrid DCCB has been proposed and researched substantially. But the hybrid type DCCB suffers from the drawback of high cost and low reliability, leading to high capital cost for DC grids that require numerous DCCBs. In this paper, a mechanical type DCCB, consisting of a mechanical switch, a circuit and an oscillation circuit, is proposed. Then, a four-terminal bipolar MMC-HVDC system implementing the mechanical DCCBs is studied. Extensive simulations have been conducted to analyse the transient performance under different fault conditions. The simulation results verify the technical feasibility of this mechanical DCCB in DC grid.
- Volume 2019, Issue 18,
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This paper formulates a two-stage stochastic programming model for energy and reserve joint dispatch considering wind power uncertainty and the participation of incentive-based demand response (IBDR). The model consists two stages, the first stage is to determine the day-ahead energy dispatch and the reserve capacity need, the second stage is to determine the deployment of reserves to accommodate the realisation of wind power uncertainty in real time. The IBDR program and the thermal power units provide reserve together to cope with the uncertainty of wind power. The IBDR model considers the maximum response times of a DR agent during a day to assure the reliability of using electricity for end users. To reduce the computation burden caused by wind power scenarios, the inactive constraints identification method is utilised to eliminate redundant transmission line constraints before solving the original model. Finally, the effectiveness of the proposed model and the solving method are tested on the modified IEEE 118-bus test system with 50 DR agents.
- Volume 2019, Issue 18,
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Due to the increasing penetration, intermittent renewable energy sources (RESs), such as wind power, have added additional uncertainties to AC–DC power system operation. The strong correlation between wind power will bring larger computational errors. It makes generation dispatching incompatible with the current single-period optimal power flow practice. This study presents an AC–DC affinely adjustable robust dynamic optimal power flow (AARDOPF) model. Ellipsoidal uncertainty set is adopted to well fit the spatial-temporal correlated wind power. Affine policies are utilised in the re-dispatch process. To apply AC–DC AARDOPF, the base-point generation is calculated and determined to match the power with forecasted RES output. And once the uncertainty is revealed, generators reschedule its output through participation factors responding to the uncertain fluctuation of RES output to ensure a feasible solution for all realisations of RES output. Then original non-linear models are transformed into SOCP models. Finally, GUROBI is used to solve this model. Numerical results are obtained on modified AC–DC IEEE 30-bus and 118-bus system to minimise the expected operational cost. Comparing with stochastic dynamic optimal power flow (DOPF), this model is proved to be more practical and effective.
- Volume 2019, Issue 18,
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This study presents an approach of biogas generation coupled with electricity trading under electricity spot market to maximise the biogas power profits. The aim of this study is to achieve a minimal generation cost for the biogas generation system while eliminating the dependence on batteries due to the storage and tunable properties of biogas digester. In terms of the electricity prices at different times in the spot market, the operating control strategy for biogas generation is established to perform the optimal generation scheduling, which give the two model comparison results. The practical case of biogas engineering in the ecological park in Hunan Province in China is carried out to validate the effectiveness and practicability of the proposed strategy.
- Volume 2019, Issue 18,
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In this study, a newly developed amalgam power flow controller (APFC) is used for better controllability and voltage stability enhancement of modern power system with deep renewable penetration. A new voltage stability index is proposed to determine the potential site of APFC and then Grey Wolf optimisation based on fuzzy logic is adopted to determine the optimal parameter settings of the APFC. A quarter cosine and exponential fuzzy membership function have been used to find out membership value of diverse objectives. The multi-objective problem is formulated considering three different objectives of conflicting nature. The proposed optimisation framework is implemented on an IEEE benchmark system of 30 buses for different cases. The comparison of simulation results reveals the effectiveness of the proposed model.
- Volume 2019, Issue 18,
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This study proposes a novel method for detecting faults in the stator of the doubly-fed wind turbines based on the combination of singular value decomposition (SVD) filtering and least-squares parameter invariant signal technique (TLS-ESPRIT). The stator current signal and rotor current signal are simulated in the form of stator inter-turn short-circuit fault, and TLS-ESPRIT performance test is carried out. The results show that TLS-ESPRIT still has a high-frequency resolution for a short-time signal with high-frequency resolution and can accurately estimate the frequency of each part of stator current. This method can effectively shorten the sampling signal's tempo, the performance of its parameter estimation is also superior.a
- Volume 2019, Issue 18,
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This study presents a method to solve the dynamic model of a grid-connected photovoltaic (PV) inverter with battery energy storage. A three-phase grid-connected solar-battery system is studied using small-signal state-space modelling in the synchronously rotating dq-reference frame. The combined effect of a PV generator and a bi-directional dc–dc battery charger (BC) on the inverter dynamic behaviour is analysed. It is shown that the characteristic right-half-plane pole in the PV inverter's dc-link voltage control dynamics shifts to a lower frequency when the BC is connected, which improves the stability of the system and allows a lower bandwidth for the dc-link voltage control.
- Volume 2019, Issue 18,
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Wind energy technology is developing more and more from recent decades in many countries. Therefore, addressing the latest wind turbine research issues, this study develops a dynamic model of a permanent magnet synchronous generator and an active rectifier—as part of a unified dynamic model of a wind turbine generator in MATLAB/Simulink. In addition, a novel technique for the verification of the open-loop and the closed-loop transfer functions in the frequency domain is presented. The technique develops by analysing the frequency responses of the transfer function at various frequencies. Furthermore, the cascaded control loops of the developed model are designed and the stability of the designed controllers is tested in response to step changes in reference values.
- Volume 2019, Issue 18,
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The power sector is experiencing a considerable transformation, shifting primary sources of energy production towards more sustainable alternatives. Despite the benefits, the increasing penetration of renewable raised concerns in terms of intermittency and unpredictability of electricity production, challenging the balance between demand and supply. To this end, the GRIDSOL project proposes Smart Renewable Hubs designed to provide a single and steady output of electricity combining different renewable and storage technologies such as concentrated solar power, photovoltaic, electrical and thermal batteries. This study investigates the technical application and economic feasibility of GRIDSOL for the case of Fuerteventura. Based on different technology configurations, the outcomes show a relevant role of the concentrated solar power plant, replacing diesel plants for electricity generation. In one configuration, GRIDSOL can provide up to 68% of the energy consumption, with a capacity factor of 67% for the concentrated solar power plant and a 24% CO2 emission reduction compared to 2016 levels. The economic assessment, performed over different scenarios, shows that the applicability of GRIDSOL in the Canary system requires support in terms of investments grants on the capital expenditure (58% of the costs) or as feed-in premiums on energy production (54–67 €/MWh) to break-even.
- Volume 2019, Issue 18,
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The increasing wind power penetration makes it necessary for wind power to participate in system restoration, while the maturing wind power control technology makes it possible. To characterise the security level of the system accommodating a certain amount of wind power during black start, the security margin evaluation indexes of wind power particpating in black start were put forward, based on the influence of wind power on the system recovery. Then, the law of wind speed prediction error was analysed, the representative sample set of future wind conditions was generated by historical simulation method, the worst future wind conditions were obtained at a certain level of confidence, and the solution method of the security margin based on time-domain simulation was given. Additionally, with a specific black-start scheme, general steps to solve the security margin were demonstrated, the ‘wind power integration capacity – security margin’ curves were obtained, and the influence of wind power on system restoration security was analysed from multi-views. At last, the impact of wind speed prediction accuracy on system security margin was explored, and other applications of the presented method were given.
- Volume 2019, Issue 18,
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Energy is usually used in the form of cool, heat and electricity power in industrial park and town. Different types of energy are often coupled in generation, convention, storage and usage sides, especially with the existence of energy storage devices. Under this background, considering coupling of cold, heat and power in a regional energy system, this paper researches on the day-ahead co-operation strategy of regional combined cool, heat and power (CCHP) system. Based on modelling of typical equipment in the regional integrated system, a day-ahead co-operation strategy is proposed with the objective function to minimize daily operation cost of the CCHP system. The established mixed-inter non-linear programming model is solved by CPLEX mathematical programming software. Case study results demonstrate the feasibility and effectiveness of the proposed co-operation strategy of regional CCHP system.
- Volume 2019, Issue 18,
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This article proposes a new topology of double-sided linear Vernier permanent magnet (LVPM) machine with segmented translator structure. A combination of a typical Halbach array consists of two horizontally magnetised permanent magnets (PMs) sandwiched between a salient iron tooth and adjacent vertically magnetised PM pole with the aim of improving its electromagnetic performance. The coreless partitioned translator contributes to a significant reduction in mass and the associated cost. With the aid of finite element analysis (FEA), two LVPM machines with the same PM, and stator volume have been investigated, analysed, and compared. The results imply that the proposed LVPM is capable of producing higher force density, while it exhibits lower cogging force and force ripple compared to its counterpart.
- Volume 2019, Issue 18,
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Design of direct drive power take off in renewable energy generators tends to focus on force density, naturally leading to the use of relatively expensive permanent magnet machines. Elsewhere in the industrial landscape, induction machines traditionally rule as they are low cost and robust. In this study, the design of a generator for use in an open centred tidal turbine is presented as a case study to directly compare induction and permanent magnet machines. Mechanical constraints in the turbine design enforce a large magnetic gap in the generator, which inherently limits the power density and power factor. A comparison between the permanent magnet design and the induction design in terms of performance and economy has been presented.
- Volume 2019, Issue 18,
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The variable hydrological conditions that are found in run-of-the river projects require operations over a wide range of water-level variations. This article develops a novel optimisation strategy for permanent magnet synchronous generator (PMSG) used in hydroelectric plant. The basis of this strategy is a simplified subdomain (SD) analytical model of the surface-mounted PM generator combined with an improved genetic algorithm, which searches the optimal generator parameters that maximise the operating efficiency of generators at different water-level conditions and minimise the material cost. The electromagnetic performances of the optimised generator are investigated and compared with conventional optimal design. It is found that the proposed method allows the emergence of higher performances in variable hydrological conditions.
- Volume 2019, Issue 18,
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This study addresses a demand response programme (DRP) model considering the price elasticity of demand to determine the peak scheduling for different categories of consumers with the possibility of load shifting. The main objective is to minimise daily energy loss and improvement in the node voltage profile of distribution system along with the economic benefits of different stakeholders. The proposed work helps in appropriate selection of DRP for different feeders/consumers. The investigations are performed on a benchmark 33-bus test distribution system and comprehensive analysis is illustrated through simulation results.
- Volume 2019, Issue 18,
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Coordinated control and power management of distributed energy resources, such as diesel generators (DGs), photovoltaics (PVs) and battery energy storage systems (BESSs), is vital for secure, reliable and economical operation of a stand-alone microgrid system. This paper proposes a coordinated control and power management approach for a hybrid stand-alone microgrid system containing DGs and PVs and also BESSs, which commonly servers as a power supply solution for remote areas such as islands. The proposed approach takes into account the maximum utilisation of PV power, economical operation condition of diesel generators, status of battery energy storage system and their operation constraints to share the load among them. Efficacy of the proposed approach is validated through a RTDS-based simulation test and an actual project practice.
- Volume 2019, Issue 18,
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Electricity generation is largely dominated by conventional generators powered by fossil fuels. However, current trends are shifting towards installing renewable energy generation sources, such as wind and solar. Modern wind generators employ a converter in order to feed the generated power into the grid at the fundamental grid frequency. A converter is also required for solar generation for the same reason, converting DC to AC. In a 100% converter interfaced generation (CIG) based grid the existing operational rules regarding network security and system stability need to be re-defined, whereby converter controls should be developed which replace the system services traditionally provided by synchronous machines. This paper highlights the challenges associated with operating a 100% CIG-based system and the associated network locational issues required to maintain a stable system.
- Volume 2019, Issue 18,
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The idea of ‘energy router’ (ER) is put forward as a critical application of the energy Internet (EI), especially in the new generation of electric power system to fulfil the power management and to deal with the integration of massive distributed generations. Furthermore, AC/DC hybrid network becomes a kind of development trend since it can improve the power quality and efficiency compared with adding converters for DC loads. This article proposes a decentralised control method for multi-port converter (MPC)-based ERs to achieve flexible power regulation and ‘plug and play’ operation. With the proposed schemes, DC bus voltage can be maintained together by multi-ER through appropriately adjusting their transmitted power according to the pre-set power-sharing ratio. Furthermore, the sharing ratio can be online changed for flexible power regulation. The stability of the system is ensured by Lyapunov method, detailed simulation results are presented to validate the feasibility of the proposed scheme under different operating conditions.
- Volume 2019, Issue 18,
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To achieve low cost and compactness, small dc capacitance in dc-link is preferred in the cascaded H-bridge (CHB) static synchronous compensator (STATCOM). However, small dc capacitance will definitely result in high dc-link ripples among three clusters, and thus cause severe third-order harmonic currents under the asymmetric grid. In this study, to mitigate the third-order harmonic currents, a selective component compensation approach for the CHB STATCOM is proposed. To study the effect of the dc-link ripples on the phase currents, sequence component decomposition is employed to derive the relationship between the dc-link ripples and the converter voltages. The relationship reveals that the converter voltages contain positive, negative, and zero sequence components in both fundamental and third-order under the asymmetric grid, while only the positive and negative sequence components in third-order converter voltages result in third-order harmonic currents due to the three-wire system. Therefore, the third-order harmonic currents suppression method is proposed by only compensating the positive and negative components in third-order converter voltages. A 380 V/15 kVA STATCOM prototype is built to verify the proposed control method.
- Volume 2019, Issue 18,
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The increasing wind capacity integration brings new challenges to power system planning and operation, due to the intermittency and uncertainty of its power generations. This paper determines the optimal allocation of wind capacity with considerations of the impact of uncertainty in wind generation using the zonotope-based method, for the sack of reducing the possible violations of operation limits caused by wind power fluctuations. The uncertain variations of wind power are bounded by a zonotope and then propagated through a linearised power flow to get another zonotope, which captures all possible values of the system state variables. The state-bounding zonotope is then added to the optimal model to quantify and assess the impact of generation uncertainty on system static performance. The proposed method is applied to IEEE 33-bus system, the results prove the validity of the method and show that the zonotope based set-theoretic method is more efficient than probabilistic methods when focusing on the operation limits with considerations of the uncertainty of multiple renewable energy sources.
- Volume 2019, Issue 18,
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Existing dispatch and infrastructure investment tools for modelling the Scottish energy system do not currently include solar photovoltaic resource. This study describes the development of three spatially and temporally explicit solar resource datasets for use in these models, for domestic, commercial roof-mounted and ground-mounted arrays. They include the whole of Great Britain (GB) and are based on empirical weather data for 2000–2015. They are expected to be a valuable resource for energy system modelling in GB.
- Volume 2019, Issue 18,
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This paper proposes local reactive power control to mitigate the voltage fluctuation in medium-voltage systems using DSTATCOMs and photovoltaic (PV) inverters. New expressions are developed to estimate voltage fluctuations and reactive power compensations by transforming line segment power-flow variables into nodal power injections. Using local measurements of voltages and solar powers, the method can provide a fast estimation of reactive power compensations to maintain the voltage at every bus. DSTATCOMs are also properly allocated to enhance the voltage controllability. Coordinated control of multiple reactive power resources is investigated as well. One-second solar irradiance along with one-minute home loads is used to demonstrate the effectiveness of the proposed method.
- Volume 2019, Issue 18,
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This work proposes a new multiobjective framework for the sizing of Battery Energy Storage (BES) for grid-connected microgrid. A combined Particle Swarm Optimization and Technique for Order of Preference by Similarity to Ideal Solution (PSO-TOPSIS) is explored to solve the formulated problem. A grid-connected microgrid consisting of various renewable sources and BES is considered as a test system. The results obtained are found to be promising. A trade-off between the formulated objectives is presented and analysed.
- Volume 2019, Issue 18,
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Digital signal processing (DSP) methods have been used by many researchers for detection and classification of transient disturbances because of their fast and powerful abilities to recognise waveform distortions. However, some DSP methods such as the wavelet transformation (WT) show less accuracy when applied to noisy real data. In this study, disturbance features are extracted in the wavelet domain based on the WT levels. Moreover, a new feature extraction algorithm namely normalised Renyi entropy with the signal energy is applied. This algorithm has been proven to be effective and robust for noisy signals. However, their application in power systems has not yet been tested. Using a laboratory setup of an islanded micro-grid, experimental results validate the efficacy of the wavelet-based normalised Renyi entropy in the detection and classification of four disturbance types (voltage sag, interruption, harmonics, mixture of harmonics and sag).
- Volume 2019, Issue 18,
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One of the smartest evolution in the electrical power system is the integration of various renewable sources. It is an effective way to cater consumers growing power demands. The intermittency issues in renewable sources may lead to generation and demand imbalance. This imbalance creates various issues like frequency fluctuations, voltage variation, power quality problem and so on. This study proposes a method to reduce the frequency deviation. More the electric vehicles (EVs) in this system, then more the mobile storage devices for vehicle to grid (V2G). The charging/discharging rates of EVs are controlled as per the regulation signal coming from the system operator. The proposed scheme has been simulated using the frequency regulation data acquired from PJM. The proposed algorithm controls the total charging/discharging power based on the regulation signal and this is used to modify the charging/discharging rates of EVs. The result shows a better performance during grid to vehicle (G2V), at time 20:00 the regulation signal is −650 kW and it fully met by EVs. However, during V2G the performance is quite good, at time 08:00 the regulation signal is 800 kW and EVs meet only 180 kW due to less number of EVs for discharging.
- Volume 2019, Issue 18,
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Considering the electromagnetic transient (EMT) simulation for a large power system is complicated and impractical, a feasible solution is to model the area not of interest (external system) as a frequency-dependent network equivalent circuit by vector fitting (VF)-based rational approximation methods. However, when the external system is wind power integrated, errors may be generated from the equivalent network by traditional approximation methods. A proposed algorithm in which the wind turbines or dynamic loads in the external system are reduced at its working points of steady-state firstly and the results from VF method are passivity enforced can improve the accuracy of network equivalent both in frequency and time domain. A case study is considered to evaluate the performance of the proposed algorithm and the simulation results prove the validity of the algorithm for the good accuracy and less time consuming in simulation.
- Volume 2019, Issue 18,
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In this work, a dual-loop control strategy is applied to a highly distributed architecture of photovoltaic (PV)/battery-based DC microgrid, suitable for swarm electrification of developing regions. Typically, in such schemes, resource sharing among the spatially dispersed PV generation and battery storage resources is enabled via communication-based control methodologies, which adds cost and complexity to the overall system. Alternately, a communication-less and decentralised control methodology is proposed which utilises inner loop current control and outer loop voltage droop (V–I droop) control for the coordinated resource sharing among the distributed resources. Various scenarios of power sharing among the contributing households are evaluated and the efficacy of the proposed control scheme is validated through simulations on MATLAB/Simulink. Results show that the proposed decentralised control strategy is capable of ensuring stable and coordinated operation without any dedicated layer of communication among the dispersed generation/storage resources.
- Volume 2019, Issue 18,
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Integration of large scale wind farms into the electrical grid poses challenges due to the variable nature of the source of energy and the fact that induction generators, used in the wind turbines, lacking the voltage regulation capability or even, in some types, requiring reactive power support during operation. To solve this problem, large reactive power support is normally required and is usually provided by Flexible AC Transmission systems (FACTS) devices such as Static Var Compensator (SVC) or Static Synchronous Compensator (STATCOM). Due to the high investment cost of those equipment, an alternative solution using the existing infrastructure of wind and solar farms is investigated and proposed in this paper. The feasibility of the solution is verified using the case studies on the benchmarking system IEEE 39 Bus system performed under DIgSILENT/Power Factory platform.
- Volume 2019, Issue 18,
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In order to meet the power prerequisites of their citizens, many countries are heavily dependent on the utilization of fossil fuels for power generation. This has reduced the natural reserve of fossil fuels and caused a large percentage of greenhouse gas emissions (GHGs). It is imperative to harness energy from renewable energy resources (RERs) as a measure to supplement the authors’ daily energy needs from the conventional units. The proposed microgrid system deals with the incorporation of the wind turbine generator (WTG), diesel generator, hydro turbine, photovoltaic and battery storage system for optimisation of net present cost (NPC), annualised cost of the system (ACS), GHG, fuel cost, operating costs and cost of energy (COE) by using hybrid optimisation model for electric renewables using HOMER software. The system is designed with the energy demand of 618 kWh/day at a peak load of 72.5 kW. The values of NPC, COE, ACS and fuel consumption obtained in the optimised configuration are $942,654/yr, $ 127,415, $0.327/kWh and 51,236 L/yr. The simulation results obtained from the optimised scenario reveal that the utilisation of RERs has been found to be a cost effective means to supply remote areas.
- Volume 2019, Issue 18,
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Islanded microgrids allow for a continuous supply of customers even when there is an outage in the bulk power system. The frequency control and stability in microgrids is an ongoing field of research. This work investigates the influence of synthetic inertia control of doubly-fed induction generator wind turbines on the dynamics of inverter dominated microgrids with droop control. A special focus is placed on the impact of the phase-locked loop dynamics.
- Volume 2019, Issue 18,
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State-of-Charge (SOC) estimation is one of the fundamental functions undertaken by Battery Management System (BMS) in an Electric Vehicle (EV) to assess the residual service time of the battery during operation. Thus, an accurate model of the battery that efficiently describes its dynamic characteristics is necessary for precise SOC estimation. The variation in temperature effects battery parameters, and consequently, the estimation of SOC is subject to change in temperature. In this paper, the identification of parameters of battery model is considered as an optimisation problem and solved using meta-heuristic Ageist Spider Monkey Algorithm (ASMO) under the influence of varying temperature. The developed model is used for SOC estimation using three Recursive Bayesian filtering based adaptive filter algorithms. Further, the efficiency of the implemented adaptive filter algorithms is compared in terms of solution quality and computation time required for evaluation of SOC.
- Volume 2019, Issue 18,
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In the modern renewable energy system, recent years have seen a rise in the share of power being generated through photovoltaic (PV) plants. In the Danish power system, PV plants are mostly integrated in the medium- and low-voltage networks which are usually operating under unbalanced conditions. Furthermore, the increasing number of power-electronic-based equipment affects the grid during faults through their contribution to the fault current. So far studies of PV plants in unbalanced conditions are based on computational simulations, which have limitations in representing reality. Therefore, this study investigated the performance of a three-phase PV inverter under unbalanced operation and fault conditions. The inverter is tested in stable power system operation and during grid support situations through frequency response and reactive power control. All experiments are carried out using an experimental laboratory platform in PowerLabDK. The key outcomes from this study includes the correlation between positive sequence component of voltage and reactive power, active power and current under unbalanced operation, the frequency response dependence on positive sequence voltage, and the fault current contribution from PV inverter during different fault conditions.
- Volume 2019, Issue 18,
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Providing additional damping for system electromechanical oscillations through doubly fed induction generator (DFIG)-based wind turbines is investigated in this study. In this regard, first an objective function is developed to tune the DFIG control gains, aim to maximise the wind farm (WF) contribution to system oscillation damping, but it is shown that it causes a decrease in the damping of DFIG stator mode. In other words, with the current DFIG control design, it is not possible to improve both the small signal stability of the power system and the dynamic stability of WF together. Afterwards, two high-pass filters are suggested to be employed in the control design of DFIG. It is shown that with the modified control design, it is possible to improve the system oscillation without spoiling the dynamic stability of the WF itself. Eigenvalue analysis is performed to validate the effectiveness of the modified control design.
- Volume 2019, Issue 18,
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This study details the development of a mathematical thermal model of a small wind turbine gearbox for use in condition monitoring. The model was optimised and partially validated using experimental data from a wind turbine drivetrain test rig. The model was then used to mimic bearing faults, by simulating additional heat losses at respective faulty components. The extent to which the thermal behaviour changed as a result of a fault was studied, with a view to use such an approach to detect and locate faults.
- Volume 2019, Issue 18,
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The curtailment of wind power has caused huge economic losses and needs to be considered on the stage of transmission expansion planning (TEP). Based on the superquantile theory, the authors use the buffered failure probability to handle the events of wind power curtailment. This new measurement offers several advantages including clear concept, simple calculation, and flexibility. Moreover, the authors form a novel convex relaxation model of the TEP problem. A tri-level approximation algorithm is developed to solve the proposed probability constrained model. The numerical study verifies the performance of the proposed algorithm and demonstrates the advantages of the proposed model over deterministic TEP. Sensitivity analysis is performed to identify the influence of different thresholds in probability constrained TEP problem.
- Volume 2019, Issue 18,
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The modern power system is becoming more complex and dynamic because of increasing penetration of renewable energy resources, operating closer to system capacity for economic benefits. In order to maintain the system stability, the system operator is required to initiate appropriate preventive control action under severe contingencies while satisfying the system operating constraints. Real time transient stability assessment (TSA) of power system is proposed in this paper by using wide area measurement system (WAMS) and phasor measurement units (PMUs). An architecture based on least square support vector machine (LS-SVM) has been developed to identify the system stability state in real time. Also, this paper proposes a coherency based selection method to identify the appropriate members for generation rescheduling as preventive operation in insecure operating contingency. Rotor angle trajectories based transient stability index (TSI) is employed to classify the generators as either critical or non-critical generators in a power network. Accordingly preventive control action in the form of generation rescheduling can be initiated to achieve stability. The method has been demonstrated on the IEEE 10-machines, 39-bus system. The proposed methodology is effective and capable of handling complex power system models with multiple contingencies.
- Volume 2019, Issue 18,
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In the DC microgrid system, the energy storage system must have both high power density and high energy density, and it is difficult for a single type of energy storage device to meet this requirement. The battery and the super capacitor are highly complementary in performance. Here, the battery and the super capacitor are, respectively, connected to the DC bus through a bidirectional DC–DC converter to form a hybrid energy storage system. For a 380V DC microgrid system, a new type of symmetrical circuit topology structure with two inductors and two capacitors (CLLC) resonant network is proposed. Since the symmetrical CLLC resonant network has the zero voltage switching capability of the main power switch and the soft commutation capability of the output rectifier, the converter can operate at high power conversion efficiency. Finally, the effectiveness of the system control strategy is verified through simulation and experiments.
Using adaptive control in DFIG-based wind turbine systems to inhibit power system low-frequency oscillations
Impact of EV fast charging station on distribution system embedded with wind generation
Performance comparison of passive series R and shunt R-C damped LCL filter for grid-connected inverters
Numerical research of an effective measure for stabilising floating wind turbines in shallow water
ZVS Control strategy of dual active bridge DC/DC converter with triple-phase-shift modulation considering RMS current optimization
Parallel operation of diode-rectifier based HVDC link and HVAC link for offshore wind power transmission
Voltage source control of offshore all-DC wind farm
SCADA based nonparametric models for condition monitoring of a wind turbine
Impact analysis of different charging models for optimal integration of plug-in electric vehicles in distribution system
Fuzzy chance constraints model based power reference optimisation of wind farm in system restoration
Smart coordination of battery energy storage systems for voltage control in distribution networks with high penetration of photovoltaics
Hybrid mixed-integer non-linear programming approach for directional over-current relay coordination
VSC HVDC active damping for the Sylwin 1 offshore wind power plants
Probabilistic indexes and evaluation method for network structure adaptability with high-penetration renewable energy
Impact of renewable energy balancing power in tertiary balancing market on Japanese power system based on automatic generation control standard model
Droop control method in power converter system for balancing state-of-charge of energy storage units in EV
Energy class dependent residential battery storage sizing for PV systems in Cyprus
Two-step market clearing for local energy trading in feeder-based markets
DBSCAN-based coherency identification of generators using complex wavelet transform
Dynamic average modelling of renewable generation sources for real time simulation
DC transformer requirements and fault operation analysis in PV medium voltage DC power collection system
Development of NIE networks' nodal controller project to deliver reactive power support to the wider electricity system
An intelligent methodology to improve distribution system operational parameters utilising smart inverter functionalities of PV sources
A DC fault ride-through and energy dissipation scheme for hybrid MMC-MTDC integrating wind farms with overhead lines
Simple control strategy for a PV-battery system
Design of auction-based approach for market clearing in peer-to-peer market platform
Impact of EV charging/discharging strategies on the optimal operation of islanded microgrid
Solar energy production forecasting through artificial neuronal networks, considering the Föhn, north and south winds in San Juan, Argentina
Technical risk synthesis and mitigation strategies of distributed energy resources integration with wireless sensor networks and internet of things – review
Electric vehicle charge scheduling (EVCS) with PV assistance for variable energy purchase in a multi-aggregator environment
Frequency-coupled impedance model based subsynchronous oscillation analysis for direct-drive wind turbines connected to a weak AC power system
Analysis of the impacts of wind power forecast error on power system operation
FCM Clustering-ANFIS-based PV and wind generation forecasting agent for energy management in a smart microgrid
Analysis of SSR characteristics in DFIGs based wind farm integrated to a series-compensated network
Control parameterisation for POD via software-in-the-loop simulation
Multifunctional applications of batteries within fast-charging stations based on EV demand-prediction of the users’ behaviour
A decentralised bi-level control approach to wind power regulation via thermostatically controlled loads
Frequency control of power system including PV and wind farms by using output frequency band control of HVDC interconnection line
Novel immense configurations of boost converter for renewable energy application
Particle swarm optimisation technique to improve energy efficiency of doubly-fed induction generators for wind turbines
Master–slave current regulation of an LCL-filter-based grid-connected inverter under variable grid condition
A new control strategy for low-voltage ride-through of three-phase grid-connected PV systems
Unified ZVS strategy for DAB with triple-phase-shift modulation in boost mode
Enhancing transmission and distribution system coordination and control in GB using power services from DERs
Enhancing the fault ride through capability of DFIG-based wind energy system using saturated core fault current limiter
An improved cloud recognition and classification method for photovoltaic power prediction based on total-sky-images
Assessment of economic benefits of battery energy storage application for the PV-equipped households in Finland
Novel distributed state estimation method for the AC-DC hybrid microgrid based on the Lagrangian relaxation method
Online data-driven approach of yaw error estimation and correction of horizontal axis wind turbine
Wide area coordinated control for low-frequency oscillations damping in a wind-integrated power system
Solar PV plant for supplying ancillary services in distribution systems
Primary frequency regulation of the hybrid power system by deloaded PMSG-based offshore wind farm using centralised droop controller
Dynamic security of islanded power systems with pumped storage power plants for high renewable integration – A study case
A Markov chain-based model for wind power prediction in congested electrical grids
Prediction of wind turbine generator bearing failure through analysis of high-frequency vibration data and the application of support vector machine algorithms
Feasibility analysis of heterogeneous energy storage technology for cloud energy storage with distributed generation
Investigating wind turbine dynamic transient loads using contactless shaft torque measurements
Alarms-related wind turbine fault detection based on kernel support vector machines
Primary frequency regulation supported by battery storage systems in power system dominated by renewable energy sources
Thermal and economic optimisation of windfarm export cable
Complementarity assessment of wind-solar energy sources in Shandong province based on NASA
Investigation of SSO characteristics in grid-connected PMSGs system
Coordinated active and reactive power control for overvoltage mitigation in physical LV microgrids
Power-take-off topology comparison for a wave energy converter
Spatio-temporal Markov chain model for very-short-term wind power forecasting
Impact of photovoltaic systems on voltage stability in islanded distribution networks
Stochastic scheduling of battery energy storage system for large-scale wind power penetration
Interconnection of VSC-HVDC and LCC-HVDC using DC–DC autotransformer
Optimal sizing and location of vanadium redox flow battery in a power system with high wind power generation
Research on local voltage control strategy based on high-penetration distributed PV systems
Transient feasibility assessment and enhancement of resilience-oriented distribution grid restoration using parallel simulations
Ordinal optimisation approach for complex distribution network reconfiguration
Assessment of pulsating torque mitigation control strategy through tidal turbine emulation
Minimising wind power curtailments using OPF considering voltage stability
Investigation into linear generators with integrated magnetic gear for wave energy power take off
Optimal day-ahead operation of user-level integrated energy system considering dynamic behaviour of heat loads
Environmental feasibility of incorporation of electric taxis in South Africa
Joint generation and voyage scheduling for photovoltaic integrated all-electric ships
Technical challenges in co-location of battery storage and generation plants
An optimal self-excited heating method for biogas production under cold climate
Investigation of a decentralised control strategy for grid frequency support from DC microgrids
Impact of large-scale EV integration and fast chargers in a Norwegian LV grid
Smart energy coordination of a hybrid wind/ PV with battery storage connected to grid
Delivering combined droop and inertial response from wind plant for power system frequency stability
Investigation of background noise in active distribution network and its impacts on synchrophasor estimation
Experimental study of PV strings affected by cracks
Investigation of different system earthing schemes for protection of low-voltage DC microgrids
Perspectives on solar power in dense urban areas – with Copenhagen International School as case study
Enabling wind farm to be black-start source by energy storage
New control paradigm for both islanded and grid-connected operation of PMSG-based wind turbine
Standardisation of wind turbine SCADA data for gearbox fault detection
Comprehensive study on fault-ride through and voltage support by wind power generation in AC and DC transmission systems
Evaluating flexibility values for congestion management in distribution networks within Dutch pilots
Fast and accurate estimation of multifrequency signals with noise and harmonics in control of photovoltaic systems
Operation and transient performance of a four-terminal MMC based DC grid implementing high power mechanical DC circuit breaker
Two-stage stochastic programming for the joint dispatch of energy and reserve considering demand response
Second-order cone robust AC–DC DOPF considering correlation of wind power
Optimal operating control strategy for biogas generation under electricity spot market
Voltage stability index and APFC for performance improvement of modern power systems with intense renewables
SVD filtering and TLS-ESPRIT algorithm based on stator fault characteristic detection of doubly-fed induction generator
Combined source-effect of photovoltaic generator and bi-directional dc–dc battery charger on inverter control dynamics
Dynamic modelling of grid-connected permanent magnet synchronous generator wind turbine: rectifier dynamics and control design
Feasibility analysis of GRIDSOL technology in Fuerteventura: A case study
Security margin analysis of wind power participating in black start
Study on the day-ahead co-operation strategy of regional integrated energy system including CCHP
Development of low translator mass linear Vernier machine for wave energy power take off
Large direct drive generators: the induction machine as an alternative to permanent magnet machines
Multi-objective optimisation of hydroelectric PMSG considering water-level variation
Multiple DRPs to maximise the techno-economic benefits of the distribution network
Coordinated control and power management of diesel-PV-battery in hybrid stand-alone microgrid system
Network studies for a 100% converter-based power system
Decentralised DC voltage control and flexible power regulation for multi-port converter-based energy router
Third-order harmonic currents suppression method based on selective component compensation for cascaded H-bridge STATCOM under asymmetric grid
Optimal allocation of wind capacity considering the impact of generation uncertainty based on zonotope limited security regions
Developing a spatially and temporally explicit solar resource dataset for Great Britain
Reducing voltage fluctuations using DSTATCOMs and reactive power of PV inverters in a medium voltage distribution system
Multiobjective optimal sizing of battery energy storage in grid-connected microgrid
Detection and classification of disturbances in the islanded micro-grid by using wavelet transformation and feature extraction algorithm
Supplementary frequency control in power systems via decentralised V2G/G2V support
Network equivalent by vector fitting-based rational approximation in wind power integrated power systems
Dual-loop control strategy applied to PV/battery-based islanded DC microgrids for swarm electrification of developing regions
Effective integration of large-scale wind power using PV-STATCOM
Application of renewable energy resources in a microgrid power system
Influence of PLL on synthetic inertia of DFIG wind turbine in droop controlled microgrids
State-of-Charge estimation of Li-ion battery at different temperatures using particle filter
Test of PV inverters under unbalanced operation
Modifying the control design of DFIG-based wind turbines in order to inhibit power system oscillations
Thermal modelling of a small wind turbine gearbox for condition monitoring
Probability constrained optimisation model for transmission expansion planning considering the curtailment of wind power
Transient stability-oriented assessment and application of preventive control action for power system
Research on characteristics of bidirectional CLLC DC–DC transformer used in DC microgrid
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