With the wide application of SiC power devices in electric vehicles, highvoltage DC transmission and new energy generation, how to monitor their health status in real time has become an important issue to enhance system reliability. In this thesis, a non-intrusive online measurement method based on the gate drive-side measurement unit is proposed where the on-resistance (Rds−on) of SiC MOSFETs is used as a health assessment index. By injecting a high-frequency small-signal current during the on-state period of the device and combining differential voltage detection, the method achieves the estimation of the device Rds−on without current sampling, which effectively avoids the problems of sensor bandwidth and synchronisation error in the traditional method. In this thesis, the mathematical model of the measurement principle was firstly established, and the functional relationship between the measured voltage and Rds−on was deduced. Subsequently, the circle design is validated through LTSpice simulation analysis. The experimental part is based on the PCB for measurement verification, and the results show that the estimation error of the method is controlled within 7% in the measurement range of 2−10mΩ, and the measurement results are consistent with the simulation trend, which verifies the feasibility and accuracy of the method.
Chaoran Long (Wed,) studied this question.