IET Generation, Transmission & Distribution
Volume 13, Issue 20, 22 October 2019
Volumes & issues:
Volume 13, Issue 20
22 October 2019
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- Author(s): Behnam Mahamedi and John Edward Fletcher
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4511 –4522
- DOI: 10.1049/iet-gtd.2019.0808
- Type: Article
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The study reviews the current trends in the protection of inverter-based microgrids. This topic is currently given significant attention, as the inverter-interfaced distributed generation is likely to become dominant in microgrids. Since low fault current is a well-known signature of microgrids, the emphasis is on the complicated fault characteristics in inverter-based microgrids, bearing in mind that low-magnitude fault current and complicated fault responses are inter-related. The fault characteristics are rooted in the inverter controllers that can control inverter voltages and currents during the fault period such that they are completely different from the conventional fault characteristics. Given that these differences could impact conventional protection schemes, challenges to different elements of fault identification, i.e. fault detection, fault polarisation, and faulted phase selection in microgrids are separately addressed in detail. The existing preliminary solutions that define the current trends are discussed and gaps are identified accordingly. The review classifies techniques into three categories: modified classical techniques, heuristic techniques, and differential-based techniques. The explanations are supported by simulation case studies to provide clarification. The purpose is to provide the current status of microgrid protection and assist in developing new effective solutions to protect these grids.
Trends in the protection of inverter-based microgrids
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- Author(s): Belkacem Mahdad and Srairi Kamel
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4523 –4540
- DOI: 10.1049/iet-gtd.2018.5772
- Type: Article
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Optimal reactive power planning is an important task for experts and industrials to ensure the reliability of modern power systems. Actually, the structure of practical power systems becomes dynamic and characterised by uncertainty in load and non-linear characteristic of various elements of power systems such as constraints associated to thermal units, constraints associated with FACTS devices and renewable sources. This study introduces an intelligent strategy based new metaheuristic named Salp swarm algorithm (SSA) to improve the solution of reactive power dispatch by optimising the total power loss, the total voltage deviation individually and simultaneously considering static VAR compensators (SVCs). To improve the efficiency of the original algorithm in solving large test systems, a sub SSA is formed to optimise the various objective functions based on a grouped control variable. In this study, four grouped swarms named SSA_PG for active power, SSA_VG for voltages, SSA_Ti for Tap transformers, and SSA_SVC for SVCs are formed to operate in a flexible structure to minimise a specified objective function. The proposed intelligent planning strategy validated on the IEEE 30 bus and to the large electrical test system 114 Bus of the Algerian network at normal condition and considering critical situations such as margin loading stability and contingency. Results found using the proposed strategy compared to those cited recently in the literature proves its particularity in terms of solution quality and convergence characteristics.
- Author(s): Congshan Li ; Yikai Li ; Ping He ; Jian Guo ; Yan Fang ; Tingyu Sheng
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4541 –4550
- DOI: 10.1049/iet-gtd.2019.0138
- Type: Article
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According to the characteristics of line-commutated converter high-voltage direct current (LCC-HVDC) and voltage source converter high-voltage direct current (VSC-HVDC), respective additional emergency DC power support (EDCPS) controllers are designed, and a coordinated control strategy based on a hybrid multi-infeed HVDC system for EDCPS is proposed. Considering the differences in system recovery performance between LCC-HVDC and VSC-HVDC in providing EDCPS, the emergency power support priority issues and power allocation schemes for LCC-HVDC and VSC-HVDC are discussed in detail. To maintain the stability of the receiving-end AC system during boosting power process and to ensure the active power is raised to the specified value, this study also designs an additional reactive power controller that can make full use of the ability of VSC-HVDC to support the reactive power of the AC system. Finally, a hybrid three-infeed HVDC system consists of two parallel LCC-HVDCs and one VSC-HVDC is built on PSCAD/EMTDC and simulated. The effectiveness of the proposed approach is verified based on this hybrid three-infeed HVDC system.
- Author(s): Vibhuti Nougain ; Manas Kumar Jena ; Bijaya Ketan Panigrahi
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4551 –4557
- DOI: 10.1049/iet-gtd.2018.6208
- Type: Article
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Here, a new decentralised approach-based wide-area back-up protection (WABP) scheme is proposed for faulted line identification (FLI). The scheme is divided into two sub-routines, i.e. possible faulted region (PFR) identification and FLI. Initially, the power system under study is divided into different coherent regions. The concept of centre of reactive power (CORP) is used to accomplish the task of PFR. Once the faulted region is identified, FLI is done by continuously monitoring the direction of reactive power flow (DORPF) of each line within the PFR. The proposed scheme is extensively tested on IEEE-39 bus test system for different types of faults. The performance of the scheme under stressed system conditions is also investigated. The obtained results show that the suggested algorithm is able to maintain the balance between dependability and security aspects of the protection logic.
- Author(s): Lei Wang ; Mengdi Li ; Xinchang Deng
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4558 –4565
- DOI: 10.1049/iet-gtd.2018.5819
- Type: Article
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Large-scale photovoltaic (PV) power plants connected to the grid leads to the complex calculations in the modelling and simulation of the power system, especially in the electromagnetic transient progress. Common averaging methods are studied for modelling a grid-connected converter to simplify the calculation and balance accuracy and efficiency in simulation. The piecewise technique, which combines the time segment with similar operating characteristic, is applied to different averaging models of converters. The advantages and disadvantages of different piecewise averaging models are compared. In addition, a new piecewise generalised state-space averaging (P-GSSA) model is derived and a multiple time scale modelling is achieved for the grid-connected converters in PV systems. The model error and accuracy of the P-GSSA model are analysed, the physical significance and the influence factors in the model error of P-GSSA model are discussed. The research shows that P-GSSA model is flexible to be used in a PVs system simulation, and it can accurately reflect the steady state and transient characteristics of a converter. The analysis of the P-GSSA model is verified by simulating a DC/AC converter and a PV system.
- Author(s): Ankit Uniyal and Saumendra Sarangi
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4566 –4578
- DOI: 10.1049/iet-gtd.2018.5174
- Type: Article
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The increased renewable-based sources penetration in the microgrid (MG) has given rise to issues related to the voltage (V) and frequency (f) surpassing their tolerance limits, especially during off-peak hours. The fluctuations in V and f could be handled by available real-time control schemes within a specified range. Owing to the wide generation-load mismatch in the high-penetration scenario, deviations in V and f cannot be sorted out using available real-time control schemes and seeks further developments. An electronic load controller (ELC) in the MG can consume excess generation to regulate V and f. Hence, this work presents an analytical study to understand the significance of ELC in highly penetrated MGs in V and f regulation at off-peak hours. The problem is formulated as single- and multiple-optimisation problems, which are solved using heuristic techniques viz. particle swarm optimisation and non-dominated sorted genetic algorithm-II. To incorporate the effect of P–f and Q–V droop characteristics as exhibited by distributed generations in the power flow, a special load flow method is used. The analysis is conducted on IEEE 33-and 69-bus test systems modified as autonomous MGs. The results show that proposed method is capable of minimising V and f deviation.
- Author(s): Mohamed Ebeed ; Salah Kamel ; Juan Yu ; Francisco Jurado
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4579 –4591
- DOI: 10.1049/iet-gtd.2018.5609
- Type: Article
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This study proposes a comprehensive modelling for a unified power flow controller (UPFC) into a Newton–Raphson load flow algorithm. The developed UPFC model is based on the power injection approach considering four control modes to control the voltage magnitude of a specific bus, the active and reactive powers flow in a transmission line concurrently or selectively. The developed model avoids the modifications of the main part of the load flow algorithm (Jacobian matrix). This can be achieved by transforming the voltage sources of UPFC equivalent circuit into two injected loads at its sending and receiving buses. The required control values can be achieved by updating these injected loads as a function of them. Consequently, the complexities of incorporating UPFC in load flow algorithm are significantly reduced. The operating constraints of the UPFC model are enforced using the developed approach based on modifying and updating the specified values as a function of their maximum limits. The developed model with constraints handling approach is validated using standard IEEE 14-bus, 30-bus, and 118-bus test systems. The obtained results demonstrate the effectiveness of the developed model and its superiority to other reported conventional methods.
- Author(s): Jiang Zeng ; Zhonglong Huang ; Yuchang Ling ; Lin Yang ; Zhihua Li ; Guobin Qiu ; Bo Yang ; Tao Yu
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4592 –4603
- DOI: 10.1049/iet-gtd.2019.0314
- Type: Article
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Traditional PV inverter is designed for power generation and reducing harmonic distortion without capability of actively participating in harmonic elimination of power grid. This study proposes a virtual resistance based PV inverter to suppress the voltage harmonics at point of common coupling (PCC), in which PV inverters could simultaneously deliver power for fundamental and behave as a series of virtual resistances to absorb power harmonics and then convert them into fundamental power; as a result, voltage distortion of each node of power grid is significantly reduced. No additional sensors are required to measure the non-linear load current, such that a more flexible installation location of PV inverter can be achieved. Furthermore, current harmonics are controlled by PI controller to track the voltage harmonics multiplied by harmonic conductance, i.e. K h, such that the PV inverter can be equivalent to a virtual resistance. In particular, the absorbed power harmonics are used to evaluate the harmonic suppression, while harmonic conductance K h is regulated automatically to maximise the absorbed power harmonics. Both the simulation and experiment results demonstrate that the effectiveness of the propose method.
- Author(s): Anil Bharadwaj Chivukula and Suman Maiti
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4604 –4616
- DOI: 10.1049/iet-gtd.2018.5928
- Type: Article
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High-level penetration of wind energy generating system shows a negative impact on the performance of the existing grid due to injection of fluctuating power generated by the wind farms. This study presents a configuration of E-STATCOM which is formed by integrating hybrid energy storage system (HESS) into a modular multilevel converter. The E-STATCOM absorbs the fluctuations of wind power and injects constant power into the grid. It also provides necessary reactive power support to maintain the voltage at point of common coupling within the specified limit. The HESS is formed by combining battery and supercapacitor, which gives high energy density, as well as, high power density features. A control methodology with the dynamically varying limits has been proposed to operate the E-STATCOM as per the requirements. Apart from this, the effect of HESS on the circulating current is analysed and the corresponding control algorithms are developed. The complete system is simulated in PSCAD/EMTDC and the results show its effectiveness.
- Author(s): Hamid Reza Massrur ; Taher Niknam ; Mahmud Fotuhi-Firuzabad
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4617 –4629
- DOI: 10.1049/iet-gtd.2019.0686
- Type: Article
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The integration of various energy supplying systems increases the energy efficiency and energy system reliability. Smart microgrids are an ideal area to use multi-carrier energy systems. In this context, this study presents a novel modelling framework for optimal day-ahead scheduling of a networked multi-carrier energy microgrid (NMCEMG) system. The NMCEMG system in this study is composed of heat, gas, and power supply networks. The presented framework has enhanced the multi-carrier microgrid modelling against the previous works that modelled the multi-carrier microgrid as an energy hub due to difficulties in the energy flow analysis of heat and gas networks. The proposed framework optimises the day-ahead operating cost of the NMCEMG system considering nodal and energy flow constraints of each network. The proposed microgrid includes various energy interdependent equipment such as combined heat and power units, gas-fired boilers, power to gas units, electrical and heat storages and electric heat pumps. This study presents a new optimisation algorithm named self-adaptive modified whale optimisation algorithm based on wavelet theory to solve the day-ahead optimal scheduling of the NMCEMG problem. The numerical results corroborate the proposed modelling framework as superior over conventional hub-based multi-carrier microgrid models in terms of energy system security.
- Author(s): Sasan Ghasemi ; Amin Khodabakhshian ; Rahmat-Allah Hooshmand
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4630 –4641
- DOI: 10.1049/iet-gtd.2019.0254
- Type: Article
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After occurring extreme events distribution systems might be disconnected from the main grid, and there will be a complete blackout in the distribution network. In such situations, the only way to re-energise loads is to use available microgrids (MGs). Since power outputs of MGs are limited, the major concern for system operators is to energise the maximum critical loads (CLs) during the time needed for fault isolation and maintenance. To solve this problem, this study provides a systematic restoration process by using MGs. First, after the fault clearance the shortest paths between MGs and CLs are identified by Dijkstra’s algorithm. Then, the best paths are determined by using a new modified analytic hierarchical process (AHP) algorithm and fuzzy logic to achieve four goals: increasing restored energy, reducing path preparing time, decreasing number of switching operations and reducing unavailability of path. In the modified AHP, the parameters are so tuned that the engineers’ personal preferences are eliminated for selecting the best restoration paths. Also, the uncertainty of available energy of MGs is considered. The IEEE 123-node distribution network with MGs and CLs is used for simulations. Results clearly show the benefits of using this method for CL restoration.
- Author(s): Hanwen Gu and Zaibin Jiao
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4642 –4649
- DOI: 10.1049/iet-gtd.2019.0642
- Type: Article
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DC distribution technology is emerging as a prospective form of future power system owing to its advantages such as high controllability and easy compatibility. In medium- or low-voltage DC distribution systems, the two-level voltage-source converter (VSC) has become one of the preferred topologies for grid-connected converters. A comprehensive small-signal model for VSC-based DC distribution systems, which takes into consideration the AC filter, DC distribution cables, and all the controllers in the VSC is presented in this study. Based on the ideal AC source, an absolutely stable synchronous rotating coordinate system is built to preclude the influence of the short circuit ratio of the AC system. The proposed model is verified using a detailed electromagnetic transient simulation carried out using power systems computer-aided design (PSCAD). To analyse the impact of neglecting the AC filter and phase-locked loop controller, two simplified models are established, and a detailed comparison of the three models is presented. The results indicate that when using the two simplified models, the time-domain responses are significantly different from those in the PSCAD simulation and the obtained feasible domains of the control parameters tend to be either more optimistic or conservative. Thus, to carry out a small-signal stability analysis, the use of the proposed comprehensive model is recommended to ensure the safety of the DC distribution system.
- Author(s): Yue Zhu ; Jovica V. Milanović ; Kazi N. Hasan
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4650 –4658
- DOI: 10.1049/iet-gtd.2019.0489
- Type: Article
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Power system loads have been proven to have a significant influence on power system stability, and their accurate modelling is essential for reliable assessment of dynamic system behaviour. This study first applies an efficient sensitivity analysis method, to rank power system load model parameters based on their influence on system voltage, frequency, and angular stability considering a range of load models, operating conditions, and parameter correlations. Following this, the required accuracy levels of identified critical parameters for different types of stability studies are determined. Finally, this study demonstrates the importance of modelling correlation between load model parameters on establishing the parameter accuracy requirements for different types of stability studies. The practical significance of the approach is in enabling power system operators to identify and focus on accurate (with specified accuracy) modelling of only a subset of loads while being confident that the accuracy of system stability studies will not be compromised.
- Author(s): Suraj Sawai and Ashok Kumar Pradhan
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4659 –4666
- DOI: 10.1049/iet-gtd.2018.6565
- Type: Article
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This study presents a travelling-wave-based protection method for a two-terminal line using single-end data. The method uses polarity of the voltage and current travelling waves to decide the direction of fault. The magnitude and the arrival time of first incident current travelling wave, its reflections returned from the fault point and the remote bus at the relay point is used for the protection purpose. It includes a technique to discriminate reflection returned from fault point or remote bus, based on reflection coefficient of current travelling wave to locate the exact location of fault. For the case, when reflections returned from fault point, and remote end are not discriminable, a relation is formed using arrival time of first incident current wave, its reflections returned from the fault point and the remote bus to identify the internal fault. Using location of fault and the relation formed, protection decision is derived. Results for different fault types, fault locations, fault resistances and fault inception angles in a power system demonstrate the accuracy of the proposed method. Comparative assessment with available method is also provided.
- Author(s): Eman K. Belal ; Doaa M. Yehia ; Ahmed M. Azmy
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4667 –4676
- DOI: 10.1049/iet-gtd.2018.6849
- Type: Article
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To guarantee efficient and stable operation of a microgrid, overcharging and unbalanced state of charge (SOC) of batteries have to be mitigated. An adaptive droop control scheme is proposed in this study to provide energy management between distributed batteries having unbalanced SOC and different capacities. The proposed approach suggests using a droop factor proportional to the nth order of SOC in the charging mode and inversely proportional to the nth order of SOC in the discharging mode. Moreover, a modification is proposed to adapt the performance taking into account the battery relative capacity. The relative capacity of an individual battery is defined as the ratio between the maximum capacity of all batteries and the battery capacity. The proposed adaptive droop control scheme is investigated and analysed based on an accurate model of dc microgrid incorporating lithium-ion battery, photovoltaic, permanent-magnet synchronous generator-based wind energy system and constant power loads. Several operating conditions were considered to validate the proposed control approach. The proposed control scheme has been succeeded in keeping the dc bus voltage within limits and equalising SOC of batteries, either having similar or having different capacities.
New strategy based modified Salp swarm algorithm for optimal reactive power planning: a case study of the Algerian electrical system (114 bus)
Considering reactive power coordinated control of hybrid multi-infeed HVDC system research into emergency DC power support
Decentralised wide-area back-up protection scheme based on the concept of centre of reactive power
Research on modelling and simulation of converters for electromagnetic transient simulation in photovoltaic power generation system
Optimal allocation of ELC in microgrid using droop controlled load flow
Development of UPFC operating constraints enforcement approach for power flow control
Analysis and hardware implementation of virtual resistance based PV inverters for harmonics suppression
Analysis and control of modular multilevel converter-based E-STATCOM to integrate large wind farms with the grid
Day-ahead energy management framework for a networked gas–heat–electricity microgrid
Decision-making method for critical load restoration by using MGs
Comprehensive small-signal model and stability analysis of VSC-based medium-voltage DC distribution system
Ranking and quantifying the effects of load model parameters on power system stability
Travelling-wave-based protection of transmission line using single-end data
Adaptive droop control for balancing SOC of distributed batteries in DC microgrids
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- Author(s): Arslan Habib ; Andrés Julián Aristizábal ; Adeel Arshad
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4677 –4684
- DOI: 10.1049/iet-gtd.2018.5679
- Type: Article
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The Publisher is retracting this article, ‘Effect of PI controllers’ parameters on machine-network interaction of grid-connected PMSG system’, IET Gener. Trams. Distrib., 2019, (13), 10, pp. 4677-4684, doi: 10.1049/iet-gtd.2018.5679. The paper has been retracted due to concerns over the authorship.
Retracted: Effect of PI controllers’ parameters on machine-network interaction of grid-connected PMSG system
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- Author(s): Dalu Liu ; Gregory J. Kish ; Sahar Pirooz Azad
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4685 –4693
- DOI: 10.1049/iet-gtd.2019.0653
- Type: Article
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High-voltage direct current (HVDC) is a proven technology for grid integration of renewable energy sources such as offshore wind farms and interconnecting distributed systems to main power grids. One economical solution for electrifying rural communities is to extract a small amount of power from existing HVDC transmission lines with power electronic converters, which is called tapping. This study analyses the feasibility and system performance of parallel tapping line-commutated converter (LCC)-HVDC systems with multiple full-bridge modular multilevel converters under various fault scenarios and operating conditions. Simulation results reveal that undesirable system disturbances such as DC-link voltage sags, DC-link current overshoots, and the transient reduction of inverter extinction angle are imposed on the LCC-HVDC system in the case of tap station AC side faults. Such disturbances would endanger the reliable operation of the entire LCC-HVDC system with the parallel taps. Furthermore, this study proposes two fault mitigating schemes, i.e. a tap station current modulation controller and three supplementary controller configurations, to reduce the impact of tap station AC side faults on the LCC-HVDC system. Both fault mitigating schemes are controller-based solutions, which are augmented to the existing controllers by utilising only local measurements. The proposed schemes are verified through simulations in PSCAD/EMTDC.
- Author(s): M. Talaat and Mohamed A. Essa
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4694 –4701
- DOI: 10.1049/iet-gtd.2018.6926
- Type: Article
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Pre-breakdown analysis of dielectric liquids is important in many power system applications. The electric field effect is important as well in pool boiling as it improves the boiling process. This physical phenomenon combined with the pre-breakdown condition in a dielectric liquid has been investigated using a single artificial air bubble immersed in the dielectric liquid and attached to a high voltage electrode. The Level Set coupled with Volume of Fluid numerical method is used to simulate the behaviour of the air bubble in the dielectric liquid. This approach combined with considering the electrical stresses accounts for both the electrical and mechanical (Electrohydrodynamic) stresses on the bubble-liquid interface. Laplace's equation is used to solve the electric field distribution, while the fluid is solved by using Navier–Stokes equations. The electric force effect on the fluid is considered as a source term in the momentum equation. The simulation results show good agreement with the experimental data. It is observed that high-velocity eddies in the order of 22.88 mm/ss are generated inside the air bubble. These eddies are caused by high-pressure gradients near the bubble boundaries caused by the electric field. This high velocity improves the heat and mass transfer between the two fluids.
- Author(s): Yongcan Wang ; Suhua Lou ; Yaowu Wu ; Mengxuan Lv ; Shaorong Wang
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4702 –4711
- DOI: 10.1049/iet-gtd.2018.5182
- Type: Article
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As one of the promising renewable energy technologies, wind power generation has developed rapidly over the last decade. However, the rapid growth of wind power resulted in significant wind curtailment due to transmission congestion and lack of flexible resources. Although energy storage is the most efficient way to increase the flexibility of the power system, large capacities of cost-effective energy storage are not yet available today. Considering that coal-fired power plants are still the dominant suppliers of electricity in many countries, it has a great potential to increase large amounts of flexibility by retrofitting the existing coal-fired power plants. In this study, the coordinated planning model for transmission expansion and coal-fired power plants flexibility retrofits is proposed to accommodate high penetration of wind power. Robust optimisation is employed to handle the uncertainties of peak load demand and wind power capacity, and the robust planning model is solved by nested column-and-constraint generation method. The validity of the proposed planning model is demonstrated using the modified IEEE 24-bus test system and modified IEEE 118-bus test system.
- Author(s): Farhad Kouhian ; Ali Zangeneh ; José Ramón Martí
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4712 –4723
- DOI: 10.1049/iet-gtd.2019.0594
- Type: Article
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In this study, an optimal scheduling model is proposed to perform energy management in a microgrid (MG) including distributed energy resources in both grid-connected and islanded modes. To this end, a tri-level optimization model has been presented, in which Benders method decomposes the original problem into the main problem (the first level), sub-problem (SP) (the second level) and optimal SP (the third level). The first and second levels model the MG operation in grid-connected and islanded modes, respectively. Finally, the third level directs the obtained feasible solution of the second level to an optimal solution in the islanded mode. In the proposed model, the effect of an adjacent MG is also considered, and a call-option contract is used to model the transaction power between networked MG. While it is assumed that they are connected to each other, they only exchange power in the islanded mode to prevent the arbitrage state. The aim of the proposed model is to present a flexible and integrated operation of the MG, which has the ability to work in both grid connected and island modes. Uncertainties of the problem are modelled using the two-point estimation method (2 m + 1).
- Author(s): Nikita V. Tomin ; Victor G. Kurbatsky ; Ivan S. Reutsky
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4724 –4732
- DOI: 10.1049/iet-gtd.2019.0214
- Type: Article
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Modern power systems are far from immune from voltage collapse, and examples abound over the past decade. This is due to the fact the current generation of automatic emergency and operational Volt/VAr control systems can be ineffective and unreliable for some cases. The artificial intelligence (AI) techniques allow developing new automatic intelligent Volt/VAr control systems, which will mitigate negative consequences caused by the human factor and the shortcomings of traditional control systems. This study presents a hybrid Volt/VAr control system using an AI-based technology. The system consists of two components: a centralised deep learning control system (DeepCS) for preventive security control and a decentralised multi-agent control system (MACS) for emergency control. The DeepCS includes two deep neural networks – a deep multilayer perceptron to recognise reactive power injections and a long short-term memory network to predict system state after control actions. The MACS is a decentralised automatic Volt/VAr control that involves determining the time of critical overload and switching to the load shedding procedure. The proposed approach is highly efficient for various scenarios of two (IEEE 6, IEEE 118) test systems and one real 33-bus Bodaibo subsystem.
- Author(s): Chanjuan Zhao ; Wei Sun ; Jianping Wang ; Qiyue Li ; Daoming Mu ; Xiaobing Xu
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4733 –4740
- DOI: 10.1049/iet-gtd.2019.0472
- Type: Article
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The hierarchical networked control has attracted many attentions in the field of the islanded microgrid (MG). However, how to reduce the effects caused by random packet loss of communication is still need to be studied. In this study, the authors proposed a fully distributed cooperative secondary networked optimal control for both frequency and voltage restoration. A distributed consensus Kalman filter based estimator (DCKF-estimator) is introduced to obtain the estimation of the output state with the communication packet loss. Then, by incorporating the DCKF-estimator into the output feedback-like controller, the optimal output feedback-like gain is obtained based on the linear quadratic Gaussian-like control scheme. In addition, they also deduced the stability condition of the islanded MG closed-loop system. The simulations in different scenarios were carried out to evaluate the control performance. The results show that the proposed approach achieves accurate regulations (on frequency, voltage) and fast transient response, and has better stability and robust performance over communication packet loss.
- Author(s): Amin Abedi ; Jesus Beyza ; Franco Romerio ; Jose A. Dominguez-Navarro ; Jose M. Yusta
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4741 –4746
- DOI: 10.1049/iet-gtd.2018.6693
- Type: Article
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Fault analysis of modern power systems cannot be only addressed on classical reliability techniques but also considering the impact of cascading failures. This study proposes an original integrated approach for the risk management of a power system subject to random contingencies by using vulnerability and reliability quantitative measures. Five different systems based on the IEEE-RTS have been studied from the vulnerability and reliability perspectives. According to the calculation carried out and the multi-criteria decision making (MCDM) method applied to better consider the integration of both concepts, the vulnerability and reliability perspectives are complementary viewpoints that can help to design a more robust critical infrastructure.
- Author(s): Seyed-Alireza Ahmadi ; Vahid Vahidinasab ; Mohammad Sadegh Ghazizadeh ; Kamyar Mehran ; Damian Giaouris ; Phil Taylor
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4747 –4755
- DOI: 10.1049/iet-gtd.2019.0824
- Type: Article
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With the evolution of smart grids, penetration of distributed energy resources (DERs) in the distribution networks has become ever-increasing problem. To improve network reliability, the complexity of the two important aspects of adequacy and security must be well assessed. There is a trade-off between adequacy of DERs, and the distribution network security, i.e. improving the adequacy can reduce the security. In this study, enhancement of the distribution network adequacy and security is proposed. In this regard, capacity of simultaneous reconfiguration and DERs sizing are utilised to improve the adequacy and security of an active distribution network. In the reconfiguration process, graph theory concept is adopted to implement a fast reconfiguration method. Since DERs are active, a combined bus and line security index is used to overcome security concerns of their existence. The IEEE 33-bus distribution network as a widely used standard test system in reconfiguration studies, and a practical 83-bus distribution network of Taiwan Power Company (TPC) which is a part of a real distribution network, are used to test the performance of the proposed method. The simulation results demonstrate the performance of the proposed framework.
- Author(s): Sami Ekici ; Fatih Unal ; Umit Ozleyen
- Source: IET Generation, Transmission & Distribution, Volume 13, Issue 20, p. 4756 –4765
- DOI: 10.1049/iet-gtd.2018.6213
- Type: Article
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Various pattern recognition methods have been suggested for estimating high-voltage alternating current transmission line fault location. However, insufficient studies have been conducted on the transmission lines connected to hybrid power generation systems such as wind and solar plants. In this study, the performance of different regression methods was investigated on a hybrid power system. Different faults with random distances on the transmission line were simulated and a fault database created by recording the current and voltage signals of these faults. After normalising this data in the pre-processing phase, it was passed to the digital signal processing stage. By repeating the experiments, 497 different faults were created. Fault types, fault resistances, and fault inception angles were changed randomly in order to obtain similar fault occurrence conditions as in real life by writing a Matlab code. In order to obtain distinctive features, the discrete wavelet transform was used. For training and validation of the dataset, Matlab Regression Learner App (RLA) was employed and the obtained results compared to select the best model. After significant fault simulation, Matern 5/2, a type of Gaussian progress regression model, showed more promising results compared to other RLA models.
Control strategies to improve stability of LCC-HVDC systems with multiple MMC taps
Effect of electrohydrodynamic stresses in dielectric liquid: simulation study with the aid of single artificial air bubble using level set-volume of fluid method
Coordinated planning of transmission expansion and coal-fired power plants flexibility retrofits to accommodate the high penetration of wind power
Three-based level model to determine optimal scheduling of the MG integrated operation using Benders decomposition
Hybrid intelligent technique for voltage/VAR control in power systems
Distributed cooperative secondary networked optimal control with packet loss for islanded microgrid
MCDM approach for the integrated assessment of vulnerability and reliability of power systems
Co-optimising distribution network adequacy and security by simultaneous utilisation of network reconfiguration and distributed energy resources
Comparison of different regression models to estimate fault location on hybrid power systems
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