Research on Pre-Synchronization Control Strategy for Microgrid VSG Inverter

In the microgrid, the virtual synchronous generator (VSG) technology realizes the friendly access of the distributed power supply and improves the stability of the power system by simulating the operating mechanism of the synchronous generator (SG). However, the VSG inverter has a large impact current at the moment when it is switching from off-grid to on-grid mode. For this reason, this paper proposes a pre-synchronization control strategy to solve this problem. Firstly, the principle of VSG inverter is introduced, the switching process between off-grid and on-grid mode is analyzed, and the cause of the impact current when connected to the grid is also discussed. Then, the pre-synchronization control strategy based on PLL including frequency compensation and amplitude compensation is designed to realize the seamless and smooth switching of VSG inverter from off-grid to on-grid mode. Finally, simulation verification is conducted through MATLAB/Simulink.