A New Multilevel Converter with Multi-Winding Medium-Frequency Transformer

In this paper, a novel multi-level converter was proposed where an isolated DC-DC converter with a multi-winding medium frequency transformer is used to realize the energy equalization within different cells. A cascaded H-bridge rectifier is directly connected to the AC grid and the normal input transformer was not necessary. Several separate DC buses can be produced by the cascaded H-bridge rectifier which can be inverted to medium frequency AC voltages and feed the primary windings of the multi-winding medium frequency transformer. On the secondary windings, several isolated DC buses will be produced from the output by the transformer. In this paper, the stability of the proposed converter and the equalization of the DC bus were analyzed. The control strategy of the whole system was studied and verified by some simulation and experiments.