The modulation techniques in 3L-NPC cascade converter

The multilevel converter has been quite popular for the high-voltage and large-power applications. And many modulation techniques have been applied to the multilevel converter topologies. All the modulation techniques are pursuing high-power quality and minimum switching frequency. In this paper, the modulation techniques are analyzed deeply in a three-phase to single-phase 3L-NPC cascade converter. The phase-disposition PWM (PD-PWM) and phase-shifted PWM (PS-PWM) are discussed in this system and compared with phase opposition disposition PWM (POD-PWM) and alternative phase opposition disposition PWM (APOD-PWM). Finally, the PD-SPWM and PS-SPWM can better meet the power quality requirements of system by simulation and experiment.