Neutral points voltage balancing control of a four-level π-type converter

Abstract

In this paper, a carrier-based modulation method with optimal zero-sequence signal injection has been introduced to modulate a four-level π-type converter as well as regulate its DC-link neutral points' voltages. The two neutral points' voltages can be well controlled with a back-to-back configuration even under high modulation index and high power factor. A back-to-back experimental system has been built and tests under 300V have validated this control strategy