A Modified Discontinuous PWM for Common-mode Voltage Elimination in 3-level 4-leg PWM Converter System

This paper proposes a pulse width modulation (PWM) method to eliminate common-mode voltage (CMV) in three-level four-leg neutral-point-clamped (NPC) PWM converter system. For the purpose of CMV reduction, several papers have paid attention to the three-level four-leg NPC PWM converter system. However, the conventional methods are unable to totally eliminate the CMV or to use limited voltage vectors according to switching pattern. Therefore, this paper proposes the discontinuous PWM (DPWM) control strategy in each sector and region to eliminate the CMV in three-level four-leg NPC PWM converter system. The DPWM method are used to reduce CMV and the remaining CMV is removed using fourth-phase switching. The simulation results are presented to verify the validity of the proposed method.