6.5kV FREEDM-Pair: Ideal high power switch capitalizing on Si and SiC

6.5kV Si IGBTs have been used widely in median voltage drives, HVDC, FACTs and traction systems. However, the large switching losses of the Si IGBT limit its switching frequency to only 100Hz to 1kHz. On the other hand, wide bandgap (WBG)power devices such as Silicon Carbide (SiC) MOSFET or JFET have demonstrated their superior advantages over Si IGBT, especially in terms of significantly reduced switching losses. A major issue facing large scale adoption of SiC power devices is still the much higher cost. This paper proposes that the FREEDM-Pair, a Si/SiC hybrid switch, should be an ideal and cost effective switch for high power applications. In the proposed FREEDM-Pair, a SiC MOSFET is connected in parallel with Si IGBT to combine the advantages of IGBT and MOSFET. A 6.5kV FREEDM-Pair is developed as an example to demonstrate its superior cost/performance. Experimental results demonstrated 70% switching loss reduction and the FREEDM-Pair cost is estimated to be only 50% higher than 6.5kV Si IGBT.