This study analyse the impact of different distributed generation (DG) operating modes towards the system performance when network reconfiguration, DG generation and tap changer setting are simultaneously configure to optimal value. The main consideration in the optimal configuration process is to minimise daily power losses. For the purpose of optimisation, imperialist competitive algorithm is applied. Analysis is conducted based on safety margin of total DGs penetration, photovoltaic generation based on daily irradiance and daily load profile. The analysis of different DG mode of operations is conducted using IEEE 33 having five tie-switches and one on-load tap changer.

This study addresses the adequacy of a generating system considering the impact of operation strategies of storages and hydro energy resources. It is assumed that the installed storage capacity of a system can be assigned for two purposes: first, economical operation which adopts storage to shift electric energy and smooth the load curve; and the second, reliability-based operation, which deploys storage to avoid load curtailments. The economical operation strategy is represented by starting from time domain data and using the load curve modification method to synthesise the overall impact of storage. The reliability-based operation is modelled with a new method based on Markov chain model that considers the dynamic behaviour of storage during time. Moreover, a novel state reduction method is presented for decreasing the number of Markov states in applications to large systems. The effectiveness of the presented methods is evaluated by running several simulation scenarios with results presented on three test systems. The results demonstrate that evaluating the system reliability in the presence of energy storage by considering the frequency and duration of system states is more effective than using methods based on the Capacity Outage Probability Table (COPT).

This study presents fuzzy-proportional–integral (PI)-based sensorless frequency and voltage control strategy for doubly fed induction generator connected to a dc microgrid system. A significant reduction of the costs can be achieved by this topology because only a single dc/ac converter and a diode rectifier are required instead of the traditional back-to-back converter topology. To improve the performance of the rotor current controller, a fuzzy PI-based control algorithm is used. Furthermore, a simple sensorless control technique based on the detection of the stator frequency is employed to detect the rotor position. The sensorless control technique can operate without the knowledge of the machine parameters. The main aim of this study is to keep the stator frequency as well as the dc bus voltage at the desired value under different load and wind speed conditions without using position sensor. Simulation and experimental studies were performed to verify the dynamic and steady-state performances of the proposed control strategy The results show that the proposed strategy not only has an excellent steady state and dynamic performance, but also it is robust against the variation of system parameters such as wind speed and load.

To conduct power system simulations with high shares of wind energy, standard wind turbine models, which are aimed to be generic rms models for a wide range of wind turbine types, have been developed. As a common practice of rms simulations, the power electronic interface of wind turbines is assumed to be ideally synchronised, i.e. grid synchronisation (e.g. phase locked loop (PLL)) is not included in simplified wind turbine models. As will be shown in this study, this practice causes simulation convergence problems during severe voltage dips and when the loss of synchronism occurs. In order to provide the simulation convergence without adding complexity to the generic models, a first-order filtering approach is proposed as a phase angle calculation algorithm in the grid synchronisation of the rms type-4 wind turbine models. The proposed approach provides robustness for the simulation of large-scale power systems with high shares of wind energy.

This study describes and presents preliminary experimental results from a novel prototype energy scavenging system installed in a model 2 m cylindrical autonomous underwater vehicle (AUV). The system, which is based on control moment gyroscope principles, utilises the gyroscopic response of a gimballed flywheel mounted within an AUV body to generate energy from the wave induced rotational motions of the vehicle. This method, using the reaction of a spinning wheel under an input torque to provide an output torque of greater magnitude, orthogonal to the input torque axis and the spin axis provides a means to harvest energy in-situ, without external appendages and additional hydrodynamic drag. The system promises to extend AUV mission durations indefinitely and reduce support vessel time currently required for periodical recharging and redeployment. A description of the system operation, design and experimental results from a series of regular wave tests conducted at zero speed in a towing tank are presented in this study. The results show that the system can harvest energy, with the greatest power generation around resonance, tailing off as the frequency increases and typically non-linear in nature. The system could potentially be applied to any rotationally excited platform e.g. autonomous surface vessels, buoys or boats

A single-phase grid connected transformerless inverter for solar photovoltaic (PV) systems is presented in this study. This inverter has the capability to extract maximum power from two separate PV panels operating under equal as well as mismatched meteorological conditions. The proposed inverter is based on the buck–boost principle, and hence, can tolerate a wide variation of voltage in both the PV panels. Further, due to the neutral point clamped structure of the inverter the neutral/ground terminal of grid is directly connected at the midpoint of two PV panels. This eliminates the flow of leakage current through the parasitic capacitances existing between the PV panels and the ground. The proposed inverter requires six switches and is free from shoot-through fault. This inverter does not require sensing of grid current for its operation. The principle of operation of the inverter is presented. The control strategy devised for the inverter is provided. The theoretical analysis is supported through detailed simulation studies carried out on Matlab/Simulink platform. Exhaustive experimental results obtained from a scaled down laboratory prototype developed for the inverter are presented to confirm the validity of the scheme.

In this study, an adaptive noise cancellation technique is applied to eliminate harmonics in a grid integrated solar photovoltaic (PV) system under non-linear load. A neuron is used to extract a fundamental component from polluted load currents. The proposed system serves multiple functions, as improvement of power quality at point of common coupling including other connected non-linear loads, extraction of maximum power from a given PV array and feeding extracted solar power into the distribution system. The multiple functionality at a time helps in fast recovery of cost of power converters. The proposed control algorithm is based on adaptive detection of fundamental component. The proposed control algorithm presents an improved sensitivity for fast load changes. This proposed two-stage PV power generating system is designed, modelled and tested to provide the solutions of several power quality problems in three-phase four-wire distribution system.

In recent years, the battery energy storage system (BESS) has been considered as a promising solution for mitigating renewable power generation intermittencies. This study proposes a stochastic planning framework for the BESS in distribution networks with high wind power penetrations, aiming to maximise wind power utilisation while minimise the investment and operation costs. In the proposed framework, the uncertainties in wind power output and system load are modelled by the Monte–Carlo simulation, and a chance-constrained stochastic optimisation model is formulated to optimally determine the location and capacity of BESS while ensuring wind power utilisation level. Then, the Monte–Carlo simulation embedded differential evolution algorithm is used to solve the problem. Simulation studies performed on a 15-bus radial distribution system prove the efficiency of the proposed method.

Due to the latest grid codes, wind turbines (WTs) are required to remain connected to grid under grid faults and supply reactive power into the grid. So, this paper proposes an improved fault ride through (FRT) strategy for doubly fed induction generators (DFIGs) under both symmetrical and asymmetrical grid faults. The proposed strategy is realized through active and passive FRT compensators. The active compensator is performed through control of the rotor- and grid-side converters of DFIGs to limit the stator and rotor over currents and inject reactive power into the grid to support the grid voltage recovery, respectively. The passive compensator is based on a three-phase rotor current limiter (RCL) resistor located in series with the rotor windings. It considerably reduces the rotor and stator overcurrent at the instants of grid faults occurrence and clearance. The proposed strategy decreases the stator and rotor over currents, electromagnetic torque oscillations and DC-link over voltage and also support grid voltage by supplying reactive power into the grid. In this way, the DFIG can fulfill the FRT requirements of the latest grid codes. Simulation studies using MATLAB/SIMULINK are conducted on a 1.5 MW DFIG-based WT to validate the effectiveness of the proposed FRT strategy.

This article presents an example of application of a modern test facility conceived for experiments regarding the integration of renewable energy in the power system. The capabilities of the test facility are used to validate dynamic simulation models of wind power plants and their controllers. The models are based on standard and generic blocks. The successful validation of events related to the control of active power (control phenomena in <10 Hz range, including frequency control and power oscillation damping) is described, demonstrating the capabilities of the test facility and drawing the track for future work and improvements.

Power management of stand-alone photovoltaic (PV) systems with centralised dc bus is usually performed using centralised algorithms based on complex state machines. This study proposes an intuitive and modular solution using a price-based approach. The dc bus is considered a market environment where a fictitious energy price is defined according to energy scarcity. The converters that connect the PV generator, loads, and energy storages to the dc bus choose their operation modes in response to the price. The proposed approach was applied to a stand-alone PV system with energy storage. Advantages of the proposed technique are scalability and intuitive programming effort due to the market analogy, so it may be helpful to developers of off-grid PV systems. Experimental results have been carried out to validate the proposed approach, proved effective to manage this system.

In this study, the authors propose a novel non-linear mathematical model of a hydro-energy generation system in the load rejection transient considering the elastic water hammer-impact of the penstock and the non-linear characteristics of the generator. More specifically, six dynamic transfer coefficients of the hydro-turbine are introduced to the generation system. Furthermore, the dynamic behaviours of the system are investigated using bifurcation diagrams and time waveforms from the point of engineering. Finally, these methods and analytical results will supply some principles for designing and running a hydropower station.

Prompted by technical issues that have arisen due to the widespread deployment of distributed intermittent renewable generators, rapidly rising peak demand and reductions in battery price, the use of battery-based energy storage systems in power networks is on the rise. While battery-based energy storage has the potential to deliver technical benefits, the best possible sizing, location and usage govern the financial viability. The objective of this study is twofold. Firstly, a generalised approach is proposed to model network upgrade deferral as a function of load growth rate, renewable generation penetration and peak shave fraction. This model is then used for the formulation of an optimisation problem which benefits from multi-period power flow analysis to co-optimise battery size, location, charge/discharge profile for a pre-specified number of units to be deployed in a given distribution network. The proposed approach is implemented using the generic algebraic modelling system platform and validated on an Australian medium voltage distribution network under multiple practical and potential future scenarios.

The present study emphasises the application of dish-Stirling solar thermal system (DSTS) in automatic generation control (AGC) of an unequal two area thermal system. The thermal systems are equipped with single reheat turbine, generation rate constraint, and governor dead band. The system dynamics with and without DSTS are tested for integral, proportional integral, proportional integral derivative, and three degree of freedom proportional integral derivative (3DOF-PID) as secondary controllers. The simultaneous optimisation of the controller parameters for each controller is done with biogeography based optimisation (BBO) technique. The 3DOF-PID controllers for the system having DSTS outperform the other controllers in terms of magnitude of oscillation, peak deviation, and settling time in system dynamic responses. The same is validated with random load perturbation. Sensitivity analysis proves that BBO optimised 3DOF-PID controller parameters obtained at nominal conditions are healthy enough. These optimised 3DOF-PID controller parameters are not necessarily needed to optimise for wide changes in system loading, and inertia constant H; step load perturbation (SLP) in all areas and higher SLP in area1. Integration of DSTS for AGC of thermal system is safely attributed.

This study proposes optimal rating and location of static synchronous compensator (STATCOM) for enhancing transient voltage stability of a real distribution network with wind power generation. The test network consists of fixed and variable speed wind turbines connected to a rural load centre. To ensure reliable and secure operation of the grid, the wind farm (WF) has to comply with the grid code for its low-voltage ride through operation. Loads play significant role in voltage stability analysis. Induction motors and general loads are modelled according to real-time data available with the system operator. In this study, dynamic reactive power requirement of WFs is considered for determination of rating of the STATCOM. Reactive power margin (Q _margin) of load bus is used as an index to identify the location of the STATCOM. Extensive simulation has been carried out in DIgSILENT to show the validity of the proposed approach.

This study proposes a grid supportive control scheme for a single-phase photo-voltaic (PV)-based inverter to mimic the behaviour of a synchronous generator during grid voltage/frequency variations. The converter embedded with the proposed controller, termed as a ‘single-phase synchronverter’, transforms a large segment of rooftop PV, which is, in general, single phase, to an ancillary service provider in compliance with the grid code (i.e. if the grid code allows rooftop PV to provide inertial/primary frequency/voltage response). Owing to fluctuations in incident solar irradiation, a battery has been connected at the dc link to take care of the variability in PV output power. The challenges involved in extending the three-phase synchronverter philosophy to a single-phase converter have been discussed and the performance of the resultant single-phase synchronverter to different values of virtual inertia and droop/regulation has been analysed. An experimental setup is developed and the system behaviour for different operating conditions has also been studied.

Photovoltaic (PV) generation systems with two-stage topology are recently emerged due to its flexibility of installation. However, most studies on dynamic stability of the PV generation system are based either on the first DC/DC stage or the second DC/AC stage in previous literature. A system-level modelling and stability has not been reported significantly, which is a crucial issue for the design of the PV system controllers. In this study, an integrated small-signal model for a two-stage PV generation system is derived to investigate the system stability and sensitivity. The proposed model takes into account the dynamics of the DC-link capacitor that was generally regarded as an ideal constant voltage source in previous researches. A v ² feedback based DC-link voltage control scheme is presented to address the non-linear relationship between capacitor energy and its voltage and thus a high performance DC-link voltage regulation is achieved. Hardware-in-loop tests using real time digital simulator are presented to validate the feasibility of the proposed method.

To experimentally study how a wave energy converter (WEC) behaves when parameters such as weight on the translator and buoy volume are changing is of significant importance when trying to optimise the WEC system. This study presents results from a WEC deployed at the Baltic Sea near the island of Åland. Compared with earlier experiments, the weight on the translator has been significantly increased to suit the buoy volume. Experimental results show that the power output between the upward and the downward motions are comparable up to the maximum speed for the downward motion of the translator. To study the speed of the translator in downward direction a model has been derived. The model has also been used to study the impact of having a changing active area. Moreover, finite element (FE) simulations done on the generator have been compared with experimental data and show a good agreement, but at high speeds of the translator the FE simulations start to deviate from the experiments.

Transient operations are very crucial for high power insulated-gate bipolar transistor modules, because high current and voltage are applied during this period for several microseconds. Therefore, the ability for doubly fed induction generator (DFIG) variable speed wind turbine power converters to withstand abnormal conditions is strictly imperative in order to achieve its lifetime specifications and also fulfil the grid codes. This study presents a new control scheme for DFIG wind turbine having parallel interleaved converters (PIC) configuration and a series dynamic braking resistor (SDBR) connected at its stator side. Interleaving the wind turbine converters in parallel configuration could help to increase the current capability, while the SDBR helps in post fault recovery of the wind turbine. The coordinated control analysis of the scheme was implemented in power system computer aided design and electromagnetic transient including DC simulation environment for a severe three-phase to ground fault. Results obtained were compared with the conventional DC chopper and crowbar rotor circuit protection scheme for the wind turbine. A better performance of the wind turbine variables were achieved using the proposed control scheme of the PIC and SDBR because the space vector modulation of the PIC results in maximum value of the change in common mode voltage, leading to improved switched output voltage of the voltage source converter leg.

Output powers of wind turbines (WTs) with variable blade pitch over nominal wind speeds are controlled by means of blade pitch adjustment. While tuning the blade pitch, conventional proportional–integral–derivative (PID) controllers and some intelligent genetic algorithms (IGAs) are widely used in hot systems. Since IGAs are community-based optimisation methods, they have an ability to look for multi-point solutions. However, the PID parameter setting optimisation of the IGA controllers is important and quite difficult a step in WTs. To solve this problem, while the optimisation is carried out by regulating mutation rates in some IGA controllers, the optimisation is conducted by altering crossover point numbers in others. In this study, a new IGA algorithm approach has been suggested for the PID parameter setting optimisation of the blade pitch controller. The algorithm rearranging both the mutation rate and the crossover point number together according to the algorithm progress has been firstly used. The new IGA approach has also been tested and validated by using MATLAB/Simulink software. Then, its superiority has been proved by comparing the other genetic algorithm (GAs). Consequently, the new IGA approach has more successfully adjusted the blade pitch of a WT running at higher wind speeds than other GA methods.

With more photovoltaic (PV) systems being integrated into distribution networks, power utilities are facing many challenges in both planning and operation. Network operators are concerned with PV variability and associated necessity of voltage regulation, control coordination, reserve adequacy and dispatch constraints. While to address the obligatory connection agreement, it is vital for PV farm owners to accurately estimate PV variability and then provide the most cost-effective compensation method. In the literature, PV variability of different scales has been investigated over the last 20 years. However, little has focused on output fluctuations of PV systems with long-term and high-resolution recorded data at a low-voltage distribution feeder level where voltage regulation has become a serious issue. This is particularly true in Australia, where PV penetration is growing in many states and is expected to grow further in the near future. This study utilises the data of a distributed 1.2 MWp PV system in the University of Queensland recorded over the last three years with 1-min resolution to analyse the statistical characteristics of PV power variability. The results from this study will provide very useful information for both power utilities and solar farm owners regarding network operation and future PV system development.

This study addresses an optimisation problem faced by a network of green buildings (NGBs) connected to the main electrical grid. The problem is formulated as a cooperative internal power control among interacting residential buildings. The cooperation is reached through a communication infrastructure in the NGB, where the global central controller of the network is the responsible for the coordination of the local residential buildings' energy management systems by properly allowing the optimal management of the internal and external power flows in each building. The main advantage of the cooperation among residential buildings is to better match the load profile of each building internally (at the network level). In order to achieve this goal, components such as energy storage system, distributed generations and loads are included. The uncertainties characteristics of wind speed, solar irradiation, and loads are also considered for the control and operation of the whole system. A small network of five residential buildings has been simulated using the proposed model. Numerical results demonstrate the effectiveness of the proposed network.