State-of-Charge Balancing Control for Modular Battery System With Output DC Bus Regulation

State-of-charge (SOC) balancing of battery cells is very crucial for the battery management system (BMS) to prolong the operational lifetime of the battery system. In this article, an adaptive control algorithm is proposed to balance the SOCs for a series-connected battery system. The control strategy achieves power balancing using the current-SOC droop concept while maintaining a stable dc bus voltage regulation at the battery pack. The proposed control algorithm achieves the control objectives without any communication necessity among the batteries. Moreover, the control design and the stability analysis are shown in detail using small-signal modeling. Furthermore, the simulation and experimental validation are provided to verify the effectiveness of the proposed control algorithm. In addition, the conventional centralized control method is compared with the proposed distributed control concept. The proposed approach shows higher reliability, flexibility, and scalability compared to the conventional centralized cell balancing structures.