Medium Voltage Bidirectional DC-DC Isolator using Series Connected 10kV SiC MOSFETs

This paper proposes a practical and economically viable MVDC bidirectional DC-DC isolator required for interface of grids to Microgrid (MG), MG to MG and integration of large scale renewable energy sources to the grid. The proposed MVDC bidirectional isolator can also be used in MVDC to HVDC series/parallel taps and other MV interconnections that need galvanic isolation. Dual active bridge (DAB) DC-DC converter based isolator is a suitable solution for achieving isolation and bidirectional power flow in medium voltage applications. Three level, three phase DC-DC converter topology with series connected Gen 3 10kV SiC MOSFETs is used to implement the proposed DAB converter to obtain a 24kV DC bus. The design specifications of proposed DAB converter is described in detail. Large signal modelling for the three level and three phase DAB converter with a non-linear transformer model is presented. Finally, experimental results for a single phase half bridge DAB and full Bridge DAB converter operating at 2.5kV DC bus is presented.