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In this article, an online condition monitoring (CM) method is proposed for the bond wire degradation of insulated-gate bipolar transistor (IGBT) modules in a single-phase or three-phase three-level neutral-point-clamped (3LNPC) dc–ac, ac–dc converter. The proposed method has the ability to detect the whole IGBTs in a 3LNPC converter, based on finding the idle on-state IGBTs under the specific load current direction and switching sequence of a leg. The detection time is short (0.2 ms) and the influence of online CM on load current can be completely neglected as long as the insertion areas for CM test are chosen reasonably. Meanwhile, an advanced bond wire CM module is designed to conduct the CM test. This module can generate and inject the current pulse trains into IGBT modules, with the high current for CM test and low current for temperature-sensitive electrical parameter measurement, and sample the collector–emitter on-state voltage (VCE ON) stably and precisely. Finally, the experimental work was carried out to verify the effectiveness of the proposed method and the practicality of the developed CM module. [ABSTRACT FROM AUTHOR]

Condition monitoring is a cost-effective means to reduce the unscheduled maintenance cost of insulated gate bipolar transistor (IGBT) modules. The junction to case thermal resistance $R_{\mathrm {thjc}}$ is considered as a critical health indicator of IGBT module solder layer. However, thermal interface materials’ (TIMs) deterioration will not only reduce the heat dissipation performance but also affects the accuracy of $R_{\mathrm {thjc}}$ monitoring of IGBT modules. This article investigates the effect of thermal grease deterioration on $R_{\mathrm {thjc}}$ monitoring of IGBT module. First, it is found that the thermal grease deterioration will lead to the decrease of monitored $R_{\mathrm {thjc}}$ of IGBT module under the same health status of IGBT solder layer, despite that the thermal resistance of TIM increasing as deterioration of the TIM takes place. That is, the same monitored increment ratio of $R_{\mathrm {thjc}}$ caused by the solder fatigue may correspond to different health status of the IGBT module, which cannot accurately reflect its actual health status. Then, a compensation strategy for thermal resistance monitoring based on the TIM aging rate is proposed, which uses the established mapping relationship to decouple the negative coupling part of TIM degradation. The compensated thermal resistance can better reflect the actual health status of the IGBT module and approximately eliminate the negative impact. Finally, the feasibility of the proposed compensation strategy is verified by finite element model (FEM) analysis and experiments. [ABSTRACT FROM AUTHOR]