An PV power fluctuation smoothing control method for off-grid CH-PV-PS generation system

Due to the volatility and intermittent characteristics of photovoltaic (PV), a renewable energy source, makes the fluctuations of the its power generation negatively to affect the stability of the power system, seriously for off-grid systems. In this paper, a power control method is proposed to solve this problem in a combined cascade hydro- photovoltaic -pumped storage (CH-PV-PS) generation system. Based on the empirical wavelet transform (EWT) method, the decomposition of PV active power is realized, and the grey relation analysis (GRA) is used to reconstruct the PV power and separate the high-frequency signal to obtain the output signal of the variable-speed pumped storage station(VSPSS), from which the PV power reference signal is constructed to make a difference with the local load, and the output of the VSPSS and the cascade hydro stations can be obtained after filtering. Finally, the performance of the method is evaluated by the data of PV station in Xiaojin County, Sichuan Province, China, and the simulation results indicate that the method can effectively suppress the PV power fluctuation and improve the smoothing effect and energy efficiency.