A novel compound balancing control strategy of state of charge(SOC)combining injection of zero sequence voltage and negative sequence voltage is proposed to address the issue of SOC unbalance between phases in battery energy storage system based on cascaded H-bridge converter

which is on the basis of detailed analysis of the power model of the system. The output performance of the device

interphase SOC balancing capability and power quality are all taken into account in this strategy. The process of SOC balancing can achieve smooth transition and has no disturbance to the system. The operation results of experimental prototype verify the validity and effectiveness of the proposed control strategy.