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

Abstract

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 pmposed SPWM strategy using nun-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.Index Terms-Common-mode voltages, cascaded multi-level inverter, Nun-inphase modulation, PWM.

Research on eliminating common-mode voltage of cascaded medium-voltage variable frequency driver with phase-difference SVPWM

“…as shown in Fig. 6(a), t x , t y , t 0 are separately the dwelling time of two neighboring vectors, zero-vectors V 0 or V 7 . T s is the switching period.…”

“…Considering low voltage utilization of above improved SPWM, third-order harmonics are injected into modulation signals, and such modulation scheme has been applied in cascaded MV-VSD [7].…”