Self-calibration for IGBT junction temperature measurement in power converter

Junction temperature is an important condition variable for IGBT and can be indirectly measured by the Thermo-Sensitive Electrical Parameter (TSEP). However, it is difficult to find the relationship between TSEP and device junction temperature in a real power converter system, which is essential for accurate measurement. In this paper, a self-calibration method is proposed to solve this problem. During calibration, the TSEP (e.g. dv/dt during IGBT turn-off) is measured under different operation conditions (e.g. temperature and current) by a specially programmed self-heating and on-line double-pulse testing process. By taking use of the existing hardware and sensors in a converter system, the calibration test can be conducted on-site with no need of hardware modification. Experimental work was carried out in the 3-phase voltage source inverter (VSI) drive system test rigs and the results validate the feasibility and effectiveness of the method.