A new transformerless cascaded multilevel converter topology

In this paper a novel cascaded multilevel converter is proposed. It's derived from the generalized multilevel inverter topology and consists of a number of cascaded basic cells. All the dc capacitors are floating and the separated dc sources are not needed, so the bulky transformer used in conventional cascaded H-bridge converter is not necessary here. Moreover, it can actively balance each dc voltage level by adopting appropriate redundant switching states without any assistant circuits. Also it can be easily extended to higher levels. By comparing it with exiting main multilevel topologies, it is concluded that the proposed new topology is highly suitable for converters with a high number of levels. Operating principle and voltage balancing method are presented. The validity of the proposed topology and control method is verified by simulation and experimental results.

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