A Novel Converter-level Online Junction Temperature Estimating Method for SiC MOSFETs Based on the Current Oscillation of DC and AC sides in a Single Phase Inverter

SiC power devices have been increasingly used in industrial applications. Junction temperature estimating is the basis of high reliability operation for SiC devices, since thermal stress is one of the dominating failure inducing factors. Thermal sensitive electrical parameter (TSEP) methods have been widely used for junction temperature estimating for the advantage in low invasiveness and fast response speed. However, conventional TSEP methods merely focus on a single semiconductor device instead of a converter, which results in high cost and difficulty in integration. Low sensitivity is another limitation. To solve the problems, a high-sensitivity converter-level online junction temperature estimating method is proposed in this paper based on the current oscillation (ΔiOS) of DC and AC sides in a single-phase inverter. Theoretical analysis is provided to illustrate why ΔiOS can serve as a converter-level junction temperature (Tj) indicator. The relationship between ΔiOS and Tj is obtained by experiment for calibration based on a dual pulse test. Online experiment for Tj estimating based on a single-phase inverter is provided to verify the effectiveness of the proposed method.