Mitigation of the Performance Derating in SiC Motor Drive Inverters Operating at Low Output Current Frequency

SiC MOSFET inverters have become the preferred choice for high-end motor drive applications due to their superior performance compared to Si IGBT inverters. When designing a three-phase inverter for motor drive applications, consideration must be given to derating in current that occurs during low-frequency operations. Inverter manufacturers must limit the semiconductors' current capabilities in the low-frequency region due to potential junction temperature exceedance. This paper proposes a control strategy to mitigate the current derating of the inverter at low output current frequency operations. This is accomplished by better distributing the losses among the semiconductors through the injection of a common mode reference voltage where the junction temperature of the semiconductors used as feedback is computed in real-time using the conduction resistance of the MOSFETs as a temperature-sensitive electrical parameter.