Research on Seamless Switching Strategies of Photovoltaic-Storage Microgrids Between Off-Grid and Grid-Connected Modes

With the rapid development of distributed power sources and energy storage systems, the operational stability of distribution networks has put forward higher requirements for power supply reliability. Especially with the integration of distributed energy into the distribution network, frequent switching of off grid modes can easily lead to problems such as voltage surges and power discontinuities. In response to the above issues, this article proposes a reliability improvement strategy for microgrid power supply based on virtual synchronous generators (VSG). This strategy introduces virtual power and utilizes the voltage and frequency support characteristics of VSG to achieve fast phase tracking of microgrids during mode switching, avoiding the nonlinearity and phase jump problems of traditional phase-locked loops (PLL). Through MATLAB/SIMULINK simulation and experimental verification, the proposed strategy can smoothly transition in different modes, significantly reducing the transient impact during the switching process, and providing an efficient and feasible control scheme for distribution systems under distributed power access conditions.