Aging Detection and State of Health Estimation of Live Power Semiconductor Devices Using SSTDR Embedded PWM Sequence

Power semiconductor switches undergo degradation due to environmental and electro-thermal stresses resulting in an impedance variation within the device. This impedance variation can be characterized using reflectometry, which is a well-known technique in electromagnetics. A condition monitoring algorithm for power devices in a live power converter using spread spectrum time domain reflectometry (SSTDR) method has been introduced in this article. SSTDR has been successfully used for locating transmission line faults and detecting device degradation in power converters while running at static condition. However, the rapid variation in impedance throughout the entire live converter circuit caused by fast switching makes condition monitoring more challenging while using SSTDR. This article addresses these shortcomings by proposing a novel solution that can be successfully used to identify the aging of the power devices in a live converter. SSTDR test signal was applied at various test nodes in three different circuits: a single-phase H-bridge photovoltaic inverter, a dc-dc buck converter, and a three-phase inverter. The experimental results demonstrate that the SSTDR test data are consistent with the aging of the power devices and do not affect the switching performance of the modulation process even the test signal is applied across the gate-source interface of the power mosfet. This implies that the SSTDR technique can be integrated with the gate driver module, thereby creating a new platform for an intelligent gate-driver architecture that enables real-time health monitoring of power devices while performing features offered by a commercially available driver.