A novel cascaded multilevel converter with a single nonisolated DC link

This paper proposes the use of inductors to interface the DC links in a cascaded multilevel converter. This interconnection enables bidirectional flow of current, hence power, from/to a single DC supply/load and ensures a well balanced DC link. This eliminates the need for separate DC links (normally implemented using multiple AC/DC converters supplied via isolation transformers). Therefore, it may facilitate the implementation of medium and high power converters that require the exchange of active power such as adjustable speed drives and FACTS controllers. In this paper, the principle of operation of this novel converter topology is explained in detail using a simplified converter model. The feasibility of the proposed topology and the performance of the converter are demonstrated both by simulation results, from a 7-level PSpice converter model, and experimental results from a 5-level low power prototype.