Comparative Study of Soft-Switched Isolated DC-DC Converters for Auxiliary Railway Supply

In modern railways coaches, the electrical separation between the high voltage side and the auxiliary equipments on the consumer side is realized by means of heavy and bulky 50-Hz transformers. In order to reduce the weight and size of the devices, today new power supply systems are proposed that consist in soft-switched isolated dc-dc converters with a lightweight medium frequency transformer and diverse output modules supplied by a common 600-V dc intermediate circuit. This paper aims to investigate in detail two such solutions of isolated dc-dc converters for auxiliary railway supply where zero-current transitions are achieved for the primary inverter switches. A comparison based on several criteria (overall power rating, losses in power semiconductor devices, operation in the whole range of load, etc.) is presented.