An Isolated Multicell Intercell Transformer Converter for Applications With a High Step-Up Ratio

This paper proposes a converter topology dedicated to the interconnection between low voltage and high voltage networks or power sources. This topology uses the interleaving principle whose advantages are well known at this point. Its originality stems from the implementation of an isolating intercell transformer (ICT) that provides isolation, filtering, and intercell coupling through a single magnetic stage. The first section of this paper presents two ways to build bidirectional multicell converters, based on classic buck (or boost) cells on one hand, and buck-boost cells on the other. From the nonisolated versions of these two families, the synthesis of isolated versions is achieved by introducing classic two-winding coupled-inductors or transformers. A nonbidirectional isolated ICT version derived from the buck-boost family, the multicell ICT flyback converter, has already been studied and tested. Therefore, the second section describes the isolated multicell ICT converter derived from the buck (or boost) family and constitutes the main contribution of this paper. Its very interesting features regarding high step-up ratio requirements are emphasized, particularly by considering some limitations of the ICT flyback converter. Finally, a 10-kW test bench is presented. This test bench includes eight cells and an ICT created with separated transformers, making it possible to validate converter operations under realistic power conditions.