Inner Power Control of Capacitively-isolated Bidirectional DC-DC Converter with Auxiliary Converters

This paper verifies the operating principles of a capacitively isolated bidirectional DC-DC converter with auxiliary converters, which is designed for electric railway systems. The main converter includes four unidirectional power devices, two capacitors for galvanic isolation, two inductors, and two auxiliary converters. In addition, bidirectional power flow can be archived by controlling the auxiliary converters appropriately. Meanwhile, the power balance between the auxiliary converters should be achieved for the converter stable operation. To solve this issue, this paper proposes an inner power control method based on triangular inductor current. The operating principles of the inner power control based on triangular inductor current are validated experimentally using a 1.2-kW, 120-V down-scaled model.