Power-matching based SOC balancing method for cascaded H-bridge multilevel inverter

A power-matching based balancing method is proposed to solve the unbalanced state of charge (SOC) of the DC-side batteries in cascaded H-bridge multilevel inverter (CHBMI). First, the essential reason for SOC imbalance in CHBMI with phase disposition (PD) pluse width modulation (PWM) is analyzed, and the disadvantages of the voltage-matching based SOC balancing method are pointed out. Then, from the perspective of power-matching, an SOC balancing method is proposed to achieve fast SOC balance under arbitrary load characteristics. In addition, a power-matching algorithm avoiding zero-crossing detection is presented, which brings about accuracy and simplicity of the proposed method. Finally, the parameter of the proposed method is tuned by taking the switching loss and balancing speed into consideration. The simulation and experimental results show that the proposed method is of lower switching loss and faster balancing rate under arbitrary load characteristics.