A Novel Converter-level Online Junction Temperature Estimating Method for SiC MOSFETs Based on Bus Current Overshoot

Online junction temperature estimating method is important for SiC converter operational reliability. Conventional online junction temperature estimating methods focus on the device level, leading to many problems, such as high cost and the difficulty in the integration. To deal with these challenges, a converter level online junction temperature estimating for SiC MOSFETs is proposed. First, the DC bus current overshoot is used as a junction temperature indicator. DC bus current overshoot is corresponding to the drain source turn on current overshoot. Previously, the drain source turn on current overshoot has served as a high-sensitivity junction temperature indicator. The relationship between these two parameters is analyzed, based on the state switching of an inverter with SVPWM. Second, a converter level online junction temperature estimating strategy is proposed. In every commutating transient leaving zero states, junction temperature of the corresponding SiC MOSFET can be estimated. In one power frequency period, junction temperature of all the switching devices can be evaluated. Finally, the proposed method is verified by experiments. The estimating error is within two degrees, which is robust to the operating conditions. The cost and difficulty for integration are reduced. The proposed method is more feasible for industrial applications.