A medium voltage bidirectional DC-DC converter combining resonant and dual active bridge converters

In this paper, an isolated bidirectional dc-dc converter for medium voltage application is proposed. It combines the resonant converter and dual active bridge converter (DAB). Under normal load condition, this isolated converter operates at resonant point to achieve zero voltage (ZVS) turn on at primary side and zero current (ZCS) turn off at secondary side. When over current happens, the voltage across the resonant capacitor will be clamped by paralleled diode and the converter will automatically switch to resonant and DAB mixed operation mode, therefore cycle-by-cycle over current protection is achieved with constant switching frequency. Different operation modes are analyzed for the proposed circuits using time domain waveform and state trajectory. Detailed theoretical analysis and design procedure for transformer, resonant tank and semiconductor devices are discussed. Performance of the proposed circuit is verified by a 3 kV to 200 V, 2.5 kW experimental prototype with high voltage SiC devices.