Cascaded Transformer Symmetric Single-Phase Converters with Two DC Sources

Abstract

In this paper, three multilevel single-phase converters with two dc sources and two shared legs are proposed and applied as inverters. One configuration has five legs and the other has eight legs. The configurations utilize injection transformers and, when isolation is not required, one transformer can be removed of proposed and conventional configurations. The calculation of the transformers turns ratio that improve the system symmetry is provided. The proposed configurations are compared with cascaded h-bridge and a single-phase shared leg converter with one dc source in terms of several characteristics. Compared with the conventional configurations, the proposed ones have more levels per transformer when the configurations have the same number of legs. The proposed configurations are interesting in terms of semiconductor losses for high voltage and low current applications. Experimental results are shown to demonstrate the feasibility of the system.