Improved Switching Model of 10 kV SiC MOSFET and Its Application to Medium Voltage Multilevel Converters

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Abstract
Emerging 10 kV silicon carbide (SiC) MOSFET based medium voltage (MV) converters have attracted increasing research interest due to their significantly improved performance compared with silicon (Si) IGBT based converters. The success of such MV converter design requires an accurate model of 10 kV SiC MOSFETs, which is proposed in this paper. The impact of high voltage on the transconductance and the dynamic gate charge characteristics of the 10 kV SiC MOSFET is first characterized. Based on these results, an improved switching model considering high voltage impact is proposed and experimentally verified. The developed model is then applied to aid the design of a 5-level MV flying capacitor converter (FCC). A low-cost decoupling capacitor solution for FCC switching cell is proposed. Challenges posed by high switching speed are examined using the developed model, with a gate resistances selection strategy proposed. Finally, a prototype of the 10 kV SiC device based MV 5L-FCC phase-leg is developed. Its reliable operation under high voltage (e.g., 23 kV) and very fast switching speed (e.g., >100 V/ns) are demonstrated.
Funding Information
  • AMMTO office
  • U.S. Department of Energy (DE-EE0009134)

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