Control and Performance of Capacitively-Isolated Bidirectional DC-DC Converter with Auxiliary Converters for Electric Railways

This paper presents the operating principles and control methods of a capacitively-isolated bidirectional dc-dc converter with auxiliary converters, which is intended for high power applications. It consists of a main converter, two auxiliary converters, two inductors, and two isolation capacitors. The proposed converter is characterized by achieving galvanic insulation and isolation without using transformer. In addition, it can achieve robust bidirectional power-flow control using the auxiliary converters. Further, the proposed converter can eliminate dc circuit breakers from the circuit. The operating principles and control methods presented in this paper are verified by experiments using a 200-W, 75-V down-scaled model.