An Online Junction Temperature Estimation Method for SiC Inverter Considering Surge Avoidance

Online estimation of junction temperature (T_j) utilising the on-state voltage/resistance as a temperature-sensitive electrical parameter (TSEP) and employing a clamp circuit to measure TSEP represents an emerging technique for SiC inverters. However, existing T_j estimation methods fail to account for surge interference caused by parasitic capacitance in heat sinks within inverter topologies, which affects the clamp circuit output. To address these challenges, the prevalence of surge phenomena in inverter topologies is investigated and the applicability of five existing clamp circuits is analysed under such conditions. Based on this analysis, a surge-avoidance T_j estimation method is proposed that uses PWM states to isolate valid sampling intervals unaffected by surges. Finally, the effectiveness of the proposed method is validated and it accurately estimates T_j under varying load conditions and different switching frequencies with a 300°V inverter.