A decentralized SOC balancing method in cascaded H-bridge based storage modules

Due to different initial state of charge (SOC) of energy storage system, the SOC of cascaded storage module is unbalanced in microgrid. Many conventional methods realize SOC balance of cascaded storage module based on centralized communication. In this paper, a decentralized SOC balancing method is proposed without any communication. In this scheme, the modified P-f curves are changed by the local SOC information in real-time, which can change the out-inputting power for balancing SOC. Moreover, regardless of charging mode or discharging mode, the unified SOC balancing is guaranteed without changing control structure. Compared with Centralized communication, this scheme has a higher reliability and fault tolerance. The stability of this scheme is verified through small signal analysis of the complete system. Finally, the effectiveness of SOC balancing and transient response are verified through simulations.