Effects of modularity on the performance and reliability of SiC MOSFET-based active front-end rectifiers in EV charging application

This paper compares the overall performance and reliability of modular and non-modular active front-end (AFE) rectifiers in electric vehicle (EV) charging applications, based on the high-fidelity electro-thermal modellling of the AFE rectifiers. The model contains the output characteristics of the SiC MOSFETs and their body diodes, the switching and conducting losses, as well as the effect of junction temperature, operating voltage, and currents. The Foster thermal network is used to estimate the SiC MOSFET junction temperature variation for both cases. A physics-of-failure-based reliability assessment tool is used to evaluate the component level reliability of the SiC MOSFETs based on the junction temperature, and the reliability of the DC link capacitor based on its voltage and temperature. Then the reliability of the converter is evaluated using a series reliability network for the non-modular and modular cases. The efficiency and performance of the systems are evaluated during a five-hour EV charging profile. During this time, the modular system shows an increase in efficiency of 5.3% and a decrease in the total harmonic distortion(THD) of the grid side currents by 71%. The MOSFET losses are reduced by 32%, and the filter losses by 51%. Moreover, in the modular case, the MOSFET junction temperature swings are three times smaller, and the maximum junction temperature is lowered by 7 degrees. This results in a significant increase in the component-level and system-level reliability in the modular case.