State of Charge Balancing for Distributed Battery Units Based on Adaptive Virtual Power Rating in a DC Microgrid

This paper proposes an adaptive virtual power rating method for state of charge (SoC) balancing among distributed battery units (BUs) in a DC microgrid. The virtual power rating is flexibly determined according to the SoC to obtain the droop gain of BU, and the balanced SoC is achieved by means of the modified droop controller. Because an accurate power sharing among BUs is satisfied by using only virtual power rating, SoC balancing performance is consistently ensured regardless of the line resistance difference. Moreover, the voltage restoration to keep the grid voltage at a desired value is easily realized without PI controller, and the proposed control strategy is implemented based on the distributed control method with simple low-bandwidth communication. The system stability is investigated, and the performance of the control method is demonstrated through both simulations and experiments.