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Energy consumption is increasing rapidly; hence, the energy demand cannot be fulfilled using traditional power resources only. Power systems based on renewable energy, including solar and wind, are effective and friendly for the environment. Islanded hybrid microgrid systems (IHMS) are relatively new in this industry and combine two or more sustainable sources, such as wind turbines, solar photovoltaic (PV), and other renewable alternatives, ocean, wave, and geothermal energy, etc. While sustainable, long-lasting power sources are the best choice to satisfy the growing energy demands, they are still not yet ready to be used on a large scale due to their stochastic characteristics. Furthermore, integrating these sources into the existing energy system can cause high technical difficulties, due to the stochastic nature of solar and wind in the conventional grid system and common stand-alone framework. A review of research and applications of the effective hybridization of renewable energy sources is therefore essential to address those technical and economic issues and ensure system stability, reliability, and cost-effectiveness. This article discusses the challenges that might arise when a PV plant and a wind power station are combined to produce power for the conventional main grid or in a stand-alone system. In addition, this analysis provides light on optimization approaches for improving power quality and cost-effectiveness in a solar and wind integrated IHMS. Voltage fluctuation, frequency deviation, and the uncertain nature of solar irradiation and wind sources are significant challenges for both grid-connected and standalone hybrid systems. This study then provides an overview of the control strategies which might help enhance the integration of the IHMS in producing electricity for distribution to the grid-connected load and the islanded load. In this study, the possible issues that can hinder the smooth integration of these renewable sources have been discussed. Finally, this study discusses the recent platforms being used in IHMS as well as the potential of dispatch strategies on solar and wind-integrated IHMS. [ABSTRACT FROM AUTHOR]

In this article, a community integrated energy system (CIES) coupled with electricity, gas and heat is investigated, which integrates with renewable energies such as photovoltaic and wind turbine. The main goal is to seek an optimal scheduling scheme, including reducing the operating costs and fully exploiting the demand response potential. Firstly, given the structure of CIES, the system equipment and loads are modeled and analyzed. Moreover, considering the user controllable degree, a comprehensive user satisfaction method is established based on the combination of subjective weight and objective weight method. This paper concerns the user controllable degree in the process of flexible load optimization so that some amounts of loads are transferred from peak periods to off‐peak periods to flatten the load curve. Three cases studies in the article show the influence of user controllable degree and satisfaction on CIES. Finally, the system model is solved using CPLEX solver in MATLAB optimization software. The results show that the operating costs and environmental costs are reduced by 9.31% and 3.24% due to the presence of user controllable degree and satisfaction. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

It is well known that pitch controller can maintain output power of wind generator at rated level when wind speed is above the rated speed. Moreover, it can also enhance the transient stability of wind generator when severe network disturbance occurs in power system. In this paper, another new feature of pitch controller is analyzed. As wind speed varies randomly the output power of wind generator fluctuates continuously. This fluctuation can be minimized significantly by changing the blade pitch angle of wind turbine. Our proposed pitch controller can do this well. The wind generator output power loss and smoothness level are analyzed when the proposed pitch controller is used with wind turbine. Comparative studies are carried on using three types of input command power of the controller. Some technical points of mechanical servo system of wind turbine are emphasized to reduce the load of wind turbine. Moreover, different types of wind speed patterns are used to validate the effectiveness of the proposed controller. Simulation results show that the wind power fluctuation can be reduced significantly by using the proposed fuzzy logic based pitch controller. [ABSTRACT FROM AUTHOR]

The significant penetration of renewable energy resources and ever-rising load demand has gradually aggravated the safe operation of the interconnected power system. A generalized extended state observer and fractional-order theory based integral sliding mode control strategy is introduced in the interconnected power system to minimize the frequency deviation by controlling the governor of the generation unit. The generalized extended state observer is designed to estimate the disturbance from system uncertainty, load demand, and wind power fluctuation to improve the robustness of the interconnected power system. The fractional-order integral sliding mode control relieves the chattering of frequency deviation and tie-line power deviation. Besides, the superconducting magnetic energy storage and the wind model, as the ancillary frequency regulation devices, are implemented in the interconnected power system. The novel sliding mode controller based on generalized extended state observer is designed for the interconnected power system with the addition of the superconducting magnetic energy storage and the wind model. Stability proof and simulation comparison with the integer-order sliding mode control and other three control schemes are carried out as well. [ABSTRACT FROM AUTHOR]

Summary: Modern‐day hybrid wind farm operation is fundamentally dependent on the accuracy of short‐term wind power forecasts. However, the inevitable error in wind power forecasting limits the power transfer capability to the utility grid, which calls for battery energy storage systems to furnish the deficit power. This manuscript addresses a wind forecasting based penalty cost minimization solution for hybrid wind‐battery farms. We choose six wind farm sites (three offshore and the other three onshore) to study machine intelligent forecasting based solutions and compare the performance of a wavelet‐Twin support vector regression (TSVR) based wind power forecasting model with ε‐Twin support vector regression, Random forest, and Gradient boosted machines, for penalty cost minimization. We access the penalties that arise as power imbalances along with the battery system's cost. We find that TSVR based wind power forecasting method results in a minimum global operational cost for all the wind farm sites under study. [ABSTRACT FROM AUTHOR]

Summary: With the recent proliferation and penetration of wind farms into existing power grids, it is paramount to conduct numerous studies to counter grid disturbances based on operational grid codes. One of the ways of generating electric power from wind energy is by employing the promising technology of the permanent magnet synchronous generator (PMSG) wind turbine. In order to solve the transient stability intricacies posed by the stochastic nature of wind energy during grid faults, this paper proposes a fault current limiter for a PMSG‐based wind turbine control. The fault current limiter used in this study is a series dynamic braking resistor (SDBR). The best location to place the SDBR on the machine‐side and grid‐side converters (GSCs) of the wind generator was investigated, considering the grid voltage as its switching signal during transient state. Efforts have been given to find a suitable sizing of the SDBR. The performance of the SDBR has been investigated at various network strengths in weak and strong grids. A severe three‐line‐to‐ground fault and asymmetrical faults were used to test the robustness and rigidity of the controllers of the wind generator. The system performance was evaluated using power system computer aided design and electromagnetic transient including DC (PSCAD/EMTDC) platform. The same conditions of operation were used in investigating the various scenarios considered in this study, for effective comparison. [ABSTRACT FROM AUTHOR]

Featured Application: The proposed innovation allows for a significant reduction of large drops in wind power by using only the self-regulating capabilities of a wind turbine or wind power plant, as well as upstream wind measurement instrumentation, which may already be present at the wind farm. As the penetration of renewable energy generation in electric grids becomes more substantial, its contribution to the variability of the net load becomes more noticeable. Particularly in small or weak grids, the rate at which the output power of a wind farm decreases may become a concern to grid operators. In the present work, a novel approach, called forecast-based curtailment (FBC), is shown to be able to self-mitigate downward ramps on short time scales at a very small energy penalty, compared to conventional mitigation schemes, such as flat curtailment or up-ramp limitations. FBC allows to achieve compliance with ramp limits imposed by system operators at a very small energy cost and modest additional upfront investments. [ABSTRACT FROM AUTHOR]

This article examines the dynamic and transient performances of a battery energy storage system (BESS) connected with the output of a wind energy conversion system to smoothen the short-term fluctuations in the output power. A low-power experimental real-time testbed, using battery storage and representative power converters, is interfaced with a real-time digital simulator for the reduced-scale power hardware-in-the-loop simulation. Different configurations, where the energy storage system is integrated on the ac side via static synchronous compensator and directly at the dc link of the frequency converter using back–to–back converters, are examined under both constant and variable references. For each case, the resulting error in the net power flow, the operation of the battery, and the conduction losses in the power conversion stage are examined. The performances using the constant and variable reference of the storage device with full and reduced-order hardware stage of a storage element are demonstrated. The low-voltage transient performance of the BESS is also tested and the results are presented. The novel approach of the real-time low-power BESS testbed opens the door for in-lab testing of the energy storage devices for large wind or solar photovoltaic farms to save time and money. [ABSTRACT FROM AUTHOR]

This study presents a novel adaptive control scheme for variable-speed wind turbine (VSWT) driven permanent magnet synchronous generator (PMSG) to ensure its operation under different operating conditions. The adaptive control scheme is based on the affine projection algorithm (APA) which provides a faster convergence and less computational complexity than the least-mean-square algorithm. The proposed adaptive controller is used to control both the generator-side converter and the grid-side inverter without giving additional tuning efforts. Each vector control scheme for the converter/inverter has four APA-based adaptive proportional-integral (PI) controllers. Detailed modelling and the control strategies of the system under study are demonstrated. Real wind speed data extracted from Hokkaido island, Japan is used in this study. The dynamic characteristics of a grid-connected VSWT-PMSG are investigated in details to ensure the proposed controller operation under different operating conditions. The effectiveness of the proposed adaptive controller is compared with that obtained using optimised PI controllers by Taguchi method. The validity of the adaptive vector control scheme is verified by the simulation results which are performed using PSCAD/EMTDC environment. [ABSTRACT FROM AUTHOR]

Throughout the past several years, the renewable energy contribution and particularly the contribution of wind energy to electrical grid systems increased significantly, along with the problem of keeping the systems stable. This article presents a new optimization technique entitled the Archimedes optimization algorithm (AOA) that enhances the wind energy conversion system's stability, integrated with a superconducting magnetic energy storage (SMES) system that uses a proportional integral (PI) controller. The AOA is a modern population technique based on Archimedes' law of physics. The SMES system has a big impact in integrating wind generators with the electrical grid by regulating the output of wind generators and strengthening the power system's performance. In this study, the AOA was employed to determine the optimum conditions of the PI controller that regulates the charging and discharging of the SMES system. The simulation outcomes of the AOA, the genetic algorithm (GA), and particle swarm optimization (PSO) were compared to ensure the efficacy of the introduced optimization algorithm. The simulation results showed the effectiveness of the optimally controlled SMES system, using the AOA in smoothing the output power variations and increasing the stability of the system under various operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents a system using an energy capacitor system (ECS) to smoothen the output power fluctuation of a variable-speed wind farm. The variable-speed wind turbine driving a permanent-magnet synchronous generator is considered to be connected to the ac network through a fully controlled frequency converter. The detailed modeling and control strategy of the frequency converter as well as variable-speed operation of a wind turbine generator system are demonstrated. Afterward, a suitable and economical topology of ECS composed of a current-controlled voltage-source inverter, dc-dc buck/boost converter, and an electric double layer capacitor (EDLC) bank is presented, including their control strategies. Exponential moving average is used to generate the real input power reference of ECS. Another novel feature of this paper is the incorporation of a fuzzy-logic-controlled reference signal adjuster in the control of the dc-dc buck/boost converter, in which the stored energy of the EDLC bank is utilized in an efficient way. Due to this controller, the energy storage capacity of the EDLC bank can be reduced in size, thus resulting in reduction of the overall cost of the ECS unit as well as decrease in irrepressible operations during high and low energy levels of the EDLC bank. Finally, extensive simulation results are presented that validate the effectiveness of the proposed system to smoothen the output power fluctuation of the variable-speed wind farm. [ABSTRACT FROM AUTHOR]

The present development of power electronic encourages to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG) for wind power generation. Among those, operation and stability analyses (both dynamic and transient) of DFIG type of VSWT have already been reported in many literatures. On the other hand, operation and stability analyses of synchronous generator type of VSWT are not sufficient enough. This paper focuses on various operations of variable speed wind turbine driving a PMSG (VSWT-PMSG), developing suitable control strategies for the frequency converter in the system. Dynamic characteristic of VSWT-PMSG is analyzed using real wind speed data measured in Hokkaido Island of Japan. Transient characteristic of VSWT-PMSG during network fault condition is also analyzed in detail for both symmetrical and unsymmetrical faults. Moreover, permanent fault due to unsuccessful reclosing is considered, which is one of the salient features of this study. Extensive simulation results are presented which verifies the effectiveness of the control strategy, of VSWT-PMSG at different operating regions. [ABSTRACT FROM AUTHOR]

This paper presents a new method to enhance the transient stability of multimachine power system including wind farms, when a severe network disturbance occurs in the power system. For this purpose, the energy capacitor system (ECS) composed of power electronic devices and electric double layer capacitor (EDLC) is proposed. The control scheme of ECS is based on a sinusoidal PWM voltage source converter (VSC) and fuzzy logic controlled dc-dc buck/boost converter using insulated gate bipolar transistors (IGBT). Two wind farms are considered to be connected to the power system. Two-mass drive train model of wind turbine generator system (WTGS) is used in the analyses as the drive train modeling has great influence on the dynamic characteristics of WTGS. Real wind speed data are used in the analyses to obtain realistic responses. Different types of symmetrical and unsymmetrical faults are considered as the network disturbance. Simulation results clearly show that the proposed ECS can enhance the transient stability of wind generators in multimachine power system as well as their low voltage ride through (LVRT) capability. [ABSTRACT FROM AUTHOR]

It is well known that pitch controller can maintain output power of wind generator at rated level when wind speed is above the rated speed. Moreover, it call also enhance the transient stability of wind generator when severe network disturbance occurs in power system. In this paper, another new feature of controller is analyzed As wind speed varies randomly the output power of wind generator fluctuates continuously. This fluctuation can be minimized significantly by changing the blade pitch angle of wind turbine. Our proposed pitch controller can do this well. The wind generator output power loss and smoothness level are analyzed when the proposed pitch controller is used with wind turbine. Comparative studies are carried on using three types of input command power of the controller. Some technical points of mechanical servo system of wind turbine are emphasized to reduce the load of wind turbine. A Moreover, different types of wind speed patterns are used to validate the effectiveness of the proposed controller. Simulation results show that the wind power fluctuation can be reduced significantly by using the proposed fuzzy logic based pitch controller. [ABSTRACT FROM AUTHOR]

The increasing use of intermittent, renewable energy sources (RESs) for electricity generation in microgrids (MGs) requires efficient strategies for reliable and economic operation. Complementarity between RESs provides good prospects for integrating several local energy sources and reducing the costs of MG setup and operations. This paper presents a framework for maximizing the economic benefits of a grid-tied MG by exploiting the spatial and temporal complementarity between solar and wind energies (solar-wind complementarity). The proposed framework considers the cost of energy production from different RESs and the cost of bi-directional energy exchange with the main grid. For a given RES mix, a minimum system power loss (SPL) threshold can also be determined. However, at this SPL threshold, MG energy exchange cost is not always minimized. The framework determines the optimized SPL value (above the threshold) at which MG energy exchange cost gets minimized. Through this framework, MG operator can decide appropriate RES mix and can achieve various tradeoffs according to the energy production cost, solar-wind complementarity of the site and its required economic objectives. [ABSTRACT FROM AUTHOR]