A Novel Control Strategy Based on Four-port DC Microgrid for Seamless Operating Modes Transition

Combining the centralized control with distributed control, a novel unified coordinated control strategy is proposed for a four-port DC microgrid. The centralized controller calculates energy storage and electric vehicle's charging current references based on microgrid power balance, while the distributed controller adds a current control link in the droop control to track the current reference given by the centralized controller. Hence, the converter can transmit any power within the allowable range of its capacity. With the proposed control strategy, the power transmitted between the converter and the DC bus can be quickly reduced to zero in the case of mode transition between operating modes, such as cutting off a converter or pitching in a converter, avoiding voltage shock and achieving seamless transition. Finally, the effectiveness of the proposed unified coordinated control strategy is verified by MATLAB simulation model.