Practical application-focused online V-I curve monitoring system for power semiconductor devices

As reliability is growing critical in power electronics systems, preventive maintenance for power semiconductor devices is crucial for extending system lifespan and improving robustness. However, conventional time-based maintenance often increases operational costs and unexpected downtime due to significant variation and uncertainty in the power semiconductor device's lifetime. In contrast, condition-based maintenance offers an optimized supervision scheme based on real-time health monitoring, reducing unnecessary costs and increasing overall system reliability.This paper presents a practical, non-intrusive, online condition monitoring system for detecting degradations in power semiconductor devices. The developed V-I curve monitoring system accurately measures VCE(SAT)-IC curves for IGBT and VF-IF curves for power diode during the normal operation of a full-bridge inverter. A novel conduction current (IC) sensing method based on a low-cost, tiny PCB sensor and a two-stage integrator was proposed. On-state voltage (VON) is measured by a diode-based circuit, and case temperature (TC) is sensed by a thermocouple. Real-time VON-IC-TC samples are captured simultaneously with 16-bit ADCs of the microcontroller and stored in the SD card. Acquired V-I curve data is analyzed using two statistical approaches to detect bond wire and solder layer degradations. Both the residual-based fit model and the multivariate T2 outlier methods successfully detected abnormal conditions, and comparisons are made for these two approaches.