Analysis, Design, and Implementation of Junction Temperature Fluctuation Tracking Suppression Strategy for SiC MOSFETs in Wireless High Power Transfer

In order to improve system reliability and reduce device thermal fatigue failure in multi-load wireless power transfer(WPT) systems for electric vehicles, the implementation of junction temperature fluctuations suppression strategy for SiC MOSFETs is necessary. However, current methods are relatively lacking, and active thermal management has not been used in WPT systems. In this paper the relationship between circuit parameters and junction temperature of SiC MOSFET is analyzed. In particular, a junction temperature fluctuation tracking suppression strategy for SiC MOSFETs is proposed, which consists of a coarse and a fine adjustment stage. As for the former, a shunt capacitor bank switching method is implemented. In order to compensate for the coarse adjustment defects in the small adjustment range and poor effect, in fine adjustment stage, a changing driving voltage method is proposed. Lastly, a 5kW multi-load WPT system is built for verification. Experimental results show that the proposed strategy has obvious effect on the suppression of junction temperature fluctuation and keeps temperature near the target temperature. Benefiting from this, the maximum 13.9°C junction temperature fluctuation is completely eliminated when the power fluctuations within 36.1% of the rated power, and the heat load of each SiC MOSFET can be independently adjusted.