An Experimental Study of Short Circuit Behavior and Protection of 15 kV SiC IGBTs

Abstract

15 kV SiC n-channel IGBTs have been successfully demonstrated earlier up to 10 kHz switching frequency in medium voltage (MV) power converters such as solid state transformer and transformerless intelligent power substation. Short circuit safe operating area (SC-SOA) of a power device is an essential requirement to assess the reliability of the converters. In this paper, for the first time, the short circuit (SC) behavior of the 15 kV SiC IGBT was investigated by a non-destructive experimental method under hard-switch fault (HSF) up to 8 kV dc bus. The high voltage output curve of the 15 kV SiC IGBT was obtained experimentally up to 8 kV in steps of 500 V. A TCAD model of the 15 kV IGBT was developed to understand the behavior of the IGBT in the current saturation region. The HV output characteristics was used in the estimation of the short circuit withstand time of the IGBT under HSF SC condition up to 12 kV dc bus. A desat diode based short circuit protection circuit was demonstrated successfully for the 15 kV IGBT. Performance of the desat protection circuit is compared with the 10 kV SiC MOSFETs. Behavior of the SiC IGBT in the saturation region was explained with the help of the TCAD model and the analytical equations.