A New Method and Comparative Study of HESS Power Distribution for Smoothing PV Output Fluctuations

The output power of Photovoltaic (PV) generation system is random and fluctuating, and its power volatility can be smoothed by using hybrid energy storage system (HESS). In the study of HESS power distribution, wavelet transform needs to select wavelet basis, which lacks adaptivity, while the empirical modal decomposition (EMD) needs to add improvement and correction, increasing algorithm complexity. For the above situation, this paper apply empirical wavelet transform (EWT) to the HESS power distribution. By establishing the topology and control strategy of PV-HESS, the key problems for smoothing fluctuations are pointed out. After analysising the principle of wavelet transform, EMD and EWT, the adaptiveness of EWT in handling fluctuating PV output power signals is summarized. Combined with PV field data from Laiwu, Shandong Province, the results in MATLAB/Simulink show that EWT can decompose signal with adaptive layers without choosing the decomposition basis, avoid the modal mixing problem, meet the grid-connected target power requirements as well as the battery and supercapacitor working characteristics.