A New Two-Phase Five-Level Converter for Three-Phase Isolated Grid-Tied Systems With Inherent Capacitor Balancing and Reduced Component Count

Abstract

This paper presents a single dc source fed five-level converter topology for medium-voltage high-power isolated grid-tied systems with reduced power switch count. The proposed converter generates two-phase systems of voltages that are further converted to three phases by using Scott-T transformer connection. Compared to existing topologies, the proposed converter requires fewer power switches, gate drivers, and power diodes. An added advantage is that only a single dc source is required. An important feature of this topology is that the dc-link capacitor voltages have an inherent ability to self-balance by themselves without the need for extra balance circuitry and special control algorithms. The voltage stress across the power devices of the proposed converter is equal to half of dc-link voltage. A level-shifted carrier-based pulsewidth modulation scheme is used to inject current into the grid at unity power factor. Analysis and simulation and experimental results are presented to validate the performance of the proposed converter under grid-tied operation.