State-of-Charge Balancing Control in Grid-Connected Single-Phase Cascaded H-Bridge Multilevel Converter Based Battery Storage Systems

Battery state-of-charges (SOCs) in a cascaded H-bridge multilevel converter (CHB-MLC) based battery storage systems (BSSs) may vary since electrochemical characteristics of batteries may differ. Consequently, efficiency and capacity of BSS drops drastically. Hence, SOC balancing is needed in CHB-MLC based BSSs. In this paper, a phase-shifted pulse width modulation (PS-PWM) based battery SOC balancing control scheme is proposed for grid-tied single-phase CHB-MLC based BSS. Moreover, a synchronous reference frame based bidirectional power flow control is utilized and unity power factor operation is obtained. Effective performance of the suggested BSS is tested and evaluated under different types of loads along with SOC imbalances. It is observed that while SOC balancing is accomplished successfully, active power flow is controlled and unity power factor operation is sustained.