Design and Characterization of a Neutral-Point-Clamped Inverter Using Medium-Voltage Silicon Carbide Power Modules

Many industries are transitioning towards medium-voltage (MV) power electronics to achieve increases in system-level power density. The development of MV-capable Silicon Carbide (SiC) technology allows these applications to be realized without the need for combining semiconductors in series, or with fewer levels in multi-level converter structures. In addition, due to the low switching losses of SiC MOSFETs, these voltage levels can be reached while significantly improving power density. However, one concern with SiC-based MV systems is electromagnetic interference (EMI), and especially common-mode (CM) behavior. The fast edge rates and higher switching frequencies of SiC-based systems are known to produce increased CM/EMI signatures. This paper describes the implementation and characterization of a SiC-based Neutral-Point-Clamped (NPC) inverter that is designed to support CM/EMI analysis at medium voltage. Experimental results are provided from a set of commissioning experiments performed at a bus voltage of 5 kV and with a peak output power of 28 kW. Both time-domain and frequency-domain plots are provided for the leakage current through the grounding network of this system. These results demonstrate that CM behavior scales linearly with dc bus voltage.