Analysis and Design for Medium Voltage Dual Active Bridge Converter Based on Series-Connected SiC MOSFETs

In this article, a series-connected SiC MOSFETs-based medium voltage (MV) dual active bridge (DAB) converter featuring a lowvoltage difference amongdevices and high efficiency is proposed. In the developed DAB converter, the zero voltage switching-on characteristic is used to redesign the voltage balancing snubber circuits of the series-connected SiC MOSFETs. The snubber resistance is greatly reduced, whereas the snubber capacitance is increased, which realizes good voltage sharing and low switching-off loss of SiC MOSFETs. Furthermore, the operating modes and the operating characteristics ofMVDABconverter with large snubber capacitors are derived in detail. Based on the above analysis, snubber capacitance and auxiliary inductance are optimized, taking into account the losses and voltage imbalance in the series-connected SiCMOSFETs. Finally, a 4 kV/1 kVexperimental prototype is built and tested, and an experiment with up to 100 kW transmission power has been carried out. The results show that a maximum efficiency of 98.7% has been reached and the maximum voltage difference among SiC MOSFETs does not exceed 4%.