Abstract: In order to solve the problems of voltage fluctuation and large switching impulse current in the off-grid to grid switching mode of micro-grid power converter system, a phase synchronization controller based on state following and off grid/grid switching control strategy is proposed. The output of the V/f controller follows the output of the P/Q controller, and the phase synchronization module is introduced to synchronize the phase angle of the off-grid and the grid-connected phase angle. Finally, the Matlab/Simulink simulation model of the storage grid converter is established. Simulation results show that the proposed method can effectively suppress voltage fluctuation and reduce switching impulse current during off grid/grid switching.