A 10 kV DC transformer (DCX) based on current fed SRC and 15 kV SiC MOSFETs

In this paper, a two level 10 kV DC transformer (DCX) based on 15 kV SiC MOSFETs is presented for medium voltage application. Current fed series resonant converter is proposed as the main circuit for two purposes: 1) realize ZVS on MV MOSFETs and ZCS on LV MOSFETs across entire load range. 2) minimize total required system capacitance, allowing film capacitors to replace electrolytic capacitors for longer lifetime performance. 15 kV device is utilized to reach its full voltage, frequency and power potential of 10 kV, 100 kHz and 30 kW, respectively. Inherent cycle by cycle over load current limiting capability is achieved by paralleling diodes on LV resonant capacitors. The operation principle under normal load and short circuit conditions, as well as ZVS design are provided in this paper. An all film capacitor 20 kW DC-DC prototype that converts 10 kV to 340 V is built to verify the theoretical analysis, which achieves operation frequency of 37 kHz and peak efficiency over 98%. 10 kV constant operation is the highest reported voltage for a two-level structure based converter without devices in series. Short circuit is conducted at 3 kV with a peak current limited within 11 A, with expect peak current within in 35 A at 10 kV short circuit condition.