A Medium Voltage Dual Active Bridge Converter based on Gen-3 10 kV SiC MOSFETs

Wide bandgap based medium voltage power semiconductor devices have opened up a multitude of opportunities for medium-voltage converters in power transmission and distribution. In addition to low on-state resistance, compared to its silicon counterparts, the fast switching capability of these devices has made it possible for medium voltage converter operation at high frequencies. This helps in the reduction in the size and weight of the magnetic components. A Mobile Utility Support Equipment based three-phase Solid-State Transformer (MUSE-SST) system is developed at FREEDM Systems Center to interconnect a three-phase 4160 V grid to a three-phase 480 V grid. The MUSE-SST system consists of three power conversion stages, to establish isolated grid interconnection, namely MVac/MVdc stage (MV Active front end converter), MVdc/LVdc stage (Dual active bridge converter), and LVdc/LVac stage (LV Active front end converter). Galvanic isolation is introduced in the MVdc/LVdc stage using an MV-LV high-frequency transformer. This paper discusses the modeling of the parasitic elements and characterization of the high-frequency transformer. A SPICE model is developed to emulate the parasitic elements of the high-frequency transformer. Experimental results validating the operation of the high-frequency transformer are provided. The medium voltage dual active bridge converter, which forms the MVdc/LVdc stage of the MUSE-SST system, is also discussed and experimental results demonstrating the operation and feasibility of the medium voltage dual active bridge converter are shown.