A new clew for research on PWM methods of multilevel inverters: principle and applications

A novel clew for the research on carrier-based PWM methods of multilevel inverters is proposed in the paper, which is based on the concept Of combination of the control freedom degrees (CFD). As a typical application of the clew, a novel phase shift switching frequency optimum PWM (PS-SFO PWM) method is presented. Furthermore, the correlation between multilevel carrier-based PWM methods and space vector PWM (SVPWM) methods is established by theoretical analysis, by which the research on multilevel PWM methods can be included in the clew of the combination of CFD. From the clew, a simplified algorithm of SKPWM method for five-level cascade multilevel inverters is presented, which is equivalent to PS-SFO-PWM method. The correctness and the guiding significance of the proposed research clew for the research on multilevel PWM techniques is verified by the corresponding simulation results.