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Present of wind power is sporadically and cannot be utilized as the only fundamental load of energy sources. This paper proposes a wind-solar hybrid energy storage system (HESS) to ensure a stable supply grid for a longer period. A multi-objective genetic algorithm (MOGA) and state of charge (SOC) region division for the batteries are introduced to solve the objective function and configuration of the system capacity, respectively. MATLAB/Simulink was used for simulation test. The optimization results show that for a 0.5 MW wind power and 0.5 MW photovoltaic system, with a combination of a 300 Ah lithium battery, a 200 Ah lead-acid battery, and a water storage tank, the proposed strategy reduces the system construction cost by approximately 18,000 yuan. Additionally, the cycle count of the electrochemical energy storage system increases from 4515 to 4660, while the depth of discharge decreases from 55.37% to 53.65%, achieving shallow charging and discharging, thereby extending battery life and reducing grid voltage fluctuations significantly. The proposed strategy is a guide for stabilizing the grid connection of wind and solar power generation, capability allocation, and energy management of energy conservation systems. [ABSTRACT FROM AUTHOR]

Power quality improvements help guide and solve the problems of inefficient energy production and unstable power output in wind power systems. The purpose of this paper is mainly to explore the influence of different energy storage batteries on various power quality indicators by adding different energy storage devices to the simulated wind power system, and to explore the correlation between system entropy generation and various indicators, so as to provide a theoretical basis for directly improving power quality by reducing loss. A steady-state experiment was performed by replacing the wind wheel with an electric motor, and the output power qualities of the wind power system with and without energy storage were compared and analyzed. Moreover, the improvement effect of different energy storage devices on various indicators was obtained. Then, based on the entropy theory, the loss of the internal components of the wind power system generator is simulated and explored by Ansys software. Through the analysis of power quality evaluation indicators, such as current harmonic distortion rate, frequency deviation rate, and voltage fluctuation, the correlation between entropy production and each evaluation indicator was explored to investigate effective methods to improve power quality by reducing entropy production. The results showed that the current harmonic distortion rate, voltage fluctuation, voltage deviation, and system entropy production are positively correlated in the tests and that the power factor is negatively correlated with system entropy production. In the frequency range, the frequency deviation was not significantly correlated with the system entropy production. [ABSTRACT FROM AUTHOR]

This paper discusses the result of the exergy efficiency analysis of direct-drive wind turbines by obtaining the exergy loss and destruction characteristics as well as the law of influence of every original factor on the dynamic change in the exergy efficiency. After proposing an exergy balance equation for wind power systems, a mathematical model of exergy analysis is constructed. Based on this model, the exergy utilization rate was improved by considering unavoidable exergy destruction. At first, the exergy loss characteristics were obtained using particle image velocimetry technology and the exergy destruction characteristics were obtained using simulation of finite volume method. Then, by combining the result of experiment and simulation, it was found that the exergy loss rate reached the maximum value at a tip speed ratio of 4.5–5.0. The exergy destruction rate was weakened between 10 and 15 degrees. The maximum value of exergy efficiency rate was 0.38, corresponding to exergy loss and destruction rate of 0.58 and 0.06. Finally, five factors were analyzed to determine the exergy efficiency influence weights. These were as follows: slot type = 0.30813, air gap length = 0.28471, yaw angle = 0.13637, the tip speed ratio = 0.04116, and matching characteristic = 0.25250. [ABSTRACT FROM AUTHOR]