The Integrated Switching Control Strategy for Grid-Connected and Islanding Operation of Micro-Grid Inverters Based on a Virtual Synchronous Generator

In allusion to the virtual synchronous generator (VSG)-based voltage source inverters in micro-grids, an integrated control method combining a quasi-synchronization algorithm and an islanding detection algorithm is proposed to improve the power supply reliability and quality, which can simultaneously meet the operational requirements of both grid-connected mode (GCM) and off-grid mode (OGM), and the smooth switching between them. The quasi-synchronization algorithm of the micro-grid inverter is designed to realize a flexible grid connection. Moreover, for quickly detecting islanding phenomena, a novel islanding detection algorithm based on the VSG's inherent characteristics is put forward. Finally, the validity and availability of the proposed models and control strategies are comprehensively verified by simulation results based on Matlab/Simulink.