Common-mode voltage injection techniques for quasi-two-level PWM-operated modular multilevel converters

Abstract

This paper studies the application of common-mode voltage injection techniques typically used in two-level inverters (carrier-based space-vector modulation and flat-top modulation in particular) to quasi-two-level PWM-operated modular multilevel converters. Similar to two-level inverters, the available operating area is extended to higher modulation indices. The properties of the respective techniques are compared to each other and to the modular multilevel converter in the normal operation mode. The results are based on simulations and the model is partly experimentally validated on a downscaled converter prototype.