Hybrid Energy Storage Strategy for Suppressing Power Grid Fluctuation of Photovoltaic Power Generation System

Aiming at the problem that the grid-connected power fluctuation of the PV power system affects the stability of power grid operation, a hybrid energy storage strategy based on supercapacitor-battery is proposed to suppress the grid-connected power fluctuation of a photovoltaic power system. The low-pass filtering method is used to determine the suppressed goal of the supercapacitor, the high-frequency power is stabilized by the supercapacitor, and the low-frequency power is stabilized by the battery. Thereby achieve the purpose of rational allocation power deviation between different energy storage mediums. Secondly, a small-signal model of Buck/Boost bidirectional converter based on complementary PWM control is established for the situation that the DC bus voltage has greatly fluctuated when the double closed-loop control is to suppress. The battery adopts layered control, and the supercapacitor adopts a combination between voltage and current double closed-loop control and power feedforward to suppress DC bus voltage fluctuation. Finally, the Simulink simulation verifies the effectiveness of the proposed control strategy to suppress grid- connected power fluctuations.