The Polyphase Cascaded-Cell DC/DC Converter

This paper describes a new type of unisolated dc/dc converter employing cascaded converter cells, and its operation is analyzed. The topology and the operation of the converter have similarities with the modular multilevel converter for polyphase ac/dc conversion, but the ac voltages and currents are in this case only employed for redistributing power within the converter. It is shown how the nominal modulation indices for ac and dc voltage influence the semiconductor expenditure for the converter. A methodology for optimizing the design of the converter with regard to the required silicon area is devised. It is found that at voltage conversion ratios close to unity it is preferable to use a combination of full-bridge cells and half-bridge cells. Under such circumstances the proposed converter can offer lower semiconductor expenditure than a conventional buck converter.