Fourth-Arm Common-Mode Voltage Mitigation

The adverse effect of common-mode voltage (CMV) in pulse-width modulation inverters is widely acknowledged. Various approaches for mitigating CMV effect in PWM inverters have been proposed in the literature but they either show limited effect or impair the utilization of the drive. This paper proposes an active method for eliminating CMV in multilevel inverters which is independent on the inverter topology or its modulation scheme. In particular, the proposed method does not restrict the modulation index range of the drive. A detailed analysis of the active filter circuitry and a closed-form feed-forward control law are provided. Finally, selected simulation and experimental results are presented to validate the theoretical part.