Coordinated Online Junction Temperature Estimation of MOSFETs and Antiparallel Diodes in Three-Phase SiC Inverters

Abstract

SiC power MOSFETs guarantee high power density and high efficiency in new generation power converters. The precise measurement of the devices junction temperature is important in this context for guaranteeing the reliability of the converter and the full exploitation of power semiconductors. While the use of Temperature Sensitive Electrical Parameters (TSEPs) has proven effective and feasible, their application in realworld power converters remains limited. Besides SiC MOSFETs, the temperature of the antiparallel diode is often overlooked and considered non critical. However, monitoring the temperature of all power electronic devices, diodes included, offers augmented reliability, adaptive adjustment of the converter's peak current at no risk of failure and advanced diagnostics. This paper shows that the on-board measurement of the conduction voltage of the SiC MOSFETs and antiparallel diodes can be used for the direct estimate of the respective junction temperatures in a 3-phase voltage source inverter. The diode temperatures come with no hardware complication, with respect to what is already in place for SiC MOSFETs characterization and estimate. The proposed methodology is validated on a proof-of-concept 2-level 3-phase inverter designed for the Formula SAE student electric competitions, showing the temperature estimate of the six MOSFETs and diodes at overload current operation.