Asynchronous Microgrid Power Conditioning System Enabled by Series Connection of Gen-3 SiC 10 kV MOSFETs

Asynchronous interconnection of grids has advantage over synchronous interconnection in terms of fault clearance time, islanding operation and disturbance propagation. Presently, asynchronous interconnection of medium voltage microgrids is realized using AC-DC and DC-AC power converters with the galvanic isolation provided by the power frequency transformers connected to the grids. The converters are typically implemented using 3.3 kV-6.5 kV silicon IGBTs. In this paper, a novel topology is proposed for asynchronous interconnection of 13.8 kV grids enabled by series connection of latest Gen-3 10 kV, 15 A SiC MOSFETs. The asynchronous microgrid power conditioning system (AMPCS) uses three level neutral point clamped (3L-NPC) legs in AC-DC, DC-DC and DC-AC power stages. The DC-DC stage provides the galvanic isolation between the grids, and is realized by three phase dual active bridge (DAB). Simulation results are provided to validate the performance of the AMPCS in bidirectional power flow, low voltage ride through condition and interconnection of grids with different frequencies. The 3- L NPC leg is designed, fabricated and demonstrated experimentally at 2.5 kV dc bus and 10 kHz switching frequency in sine-triangle inverter mode.