A novel PWM scheme to eliminate common-mode voltages in cascaded multi-level inverters

In this paper, mechanism of common-mode voltage of voltage source inverter is discussed in details, and it is pointed out that among the pulse width modulation (PWM) strategies for cascaded multi-level inverters (CMLI), those who based on inphase modulation of power-cell can cause common-mode voltage. Also, a novel SPWM for reducing common-mode voltage of cascaded multi-level inverter is presented, the proposed SPWM strategy using non-inphase modulation signals and third harmonic injection can totally eliminate common-mode voltage without extra hardware, and maintain high utilizing ratio of DC-Link voltage simultaneously. Theoretical analysis, simulation results are presented to verify the proposed strategy.