Pre-synchronization Strategy for Photovoltaic-Storage Converter Based on Virtual Synchronous Generator

Photovoltaic-storage converters utilize virtual synchronous generator (VSG) technology to provide virtual inertia and damping characteristics to the grid, thereby improving the operational stability of the photovoltaic-storage microgrid (PSM). However, VSG based on phase-locked loop (PLL) can cause frequency fluctuations due to phase angle jumps during the pre-synchronization process. Moreover, PLL have adverse effects under weak grid conditions like the PSMs, leading to VSG instability and even system collapse. To address this issue, a VSG pre-synchronization control strategy based on virtual impedance is proposed. Firstly, the mechanism of phase angle jump is analyzed to reveal its impact on VSG grid connection process. Then, the phase angle controller is improved based on virtual impedance to eliminate phase angle jumps and enhance the frequency stability of VSG, achieving PLL-free pre-synchronization. Finally, MATLAB/Simulink simulation is conducted to validate the effectiveness of the proposed strategy.