A Seamless Soft Transferring Method for Microgrid Energy Storage Converter

When the microgrid with energy storage is switched between grid and off-grid operation modes, the voltage and current of the AC bus will be shocked at the transfer moment between the two modes without properly control method. It may trigger the protection device of the AC system and cause the failure of the grid or off-grid transformation. A seamless soft transferring method for microgrid energy storage converter is proposed in this paper for the problem. The proposed method performs soft-start control on AC voltage and active power when mutual transferring between grid and off-grid modes, thereby effectively suppress the transient impact of AC bus voltage and current. In addition, the voltage and active power change rate of the soft-start process are controllable. Finally, a simulation model of the microgrid is built and the proposed method is verified through Matlab/Simulink. The simulation results show that the proposed method can effectively suppress the transient impact during the transfer process and realize the seamless transformation between grid and off-grid modes.