A Non-Invasive Online Condition Monitoring Method for Both SiC MOSFET and DC-Link Capacitor in a Single-Phase Inverter

Silicon carbide (SiC) power MOSFETs and dc-link capacitors are the core component in a single-phase inverter that contribute to the efficiency, power density and failure rate, etc., and their degradation characteristics have a significant impact on system reliability. This paper presents a non-invasive online condition monitoring method for both SiC power MOSFET and dc-link capacitor in a single-phase inverter, simultaneously. The failure prediction of SiC MOSFET is realized by monitoring its junction temperature using the investigated indicators turn-on transient drain current rate ($d_{i\mathrm{D}}/dt$) and gate threshold voltage ($V_{\mathrm{th}}$), and the degradation of the dc-link capacitor can be identified by the capacitance (C) using the secondary ripple current through the capacitor and input de voltage. Note that, in this proposed method, only the interface current between switches and dc-link capacitor needs to be monitored except the input voltage, which reduces the cost and simplifies the monitoring circuit. The principle of the proposed monitoring method is analyzed and followed by simulation verification. The test results show that this method has a high accuracy for both components.