An improved phase-shifted PWM method for a three-phase cascaded H-bridge multi-level inverter

This paper proposes an improved phase-shifted pulse-width modulation (PS-PWM) method for a three-phase cascaded H-bridge (CBH) multi-level inverter. In the proposed PS-PWM method, the switches at one leg of H-bridge cell (HBC) only operate and the switches at other leg are clamped. Therefore, the number of the multi-carrier signals depending on the voltage level can be reduced in half compared to the conventional PS-PWM method. The proposed method generates the same output voltage level as that of the conventional PS-PWM. In addition, it achieves the efficiency improvement of the three-phase CBH multi-level inverter and mitigates high frequency components in the common mode voltage compared with that of the conventional PS-PWM method. The performance and effectiveness are verified by simulation results of the three-phase CHB 5-level inverter.