A Multiply Open-Circuit Diagnosis Method for Inverters in PMSM Drives Considering Fault State Transition

Fault diagnosis is crucial to ensuring the reliability of permanent magnet synchronous motor (PMSM) drive systems. For PMSM drive systems using three-phase two-level inverters, power switch open-circuit (OC) faults are one of the most common failure modes. However, most existing switch OC diagnostic methods are limited to diagnose single-switch OCs, are unable to identify simultaneous double-switch OC fault, and necessitate extensive experimental calibration of their diagnostic thresholds. This article proposes a unified method capable of diagnosing single- or double-switch OC faults. This approach divides the postfault response into distinct states based on changes in current paths, where each state is identified by assessing whether the residue between the inverter’s expected voltage and the actual output voltage exceeds a specific threshold. Furthermore, the localization of single- or double-switch OC faults is achieved by tracking the transitions among these fault response states. To enhance robustness, adaptive thresholds are formulated using the median of the observer error and equivalent input derived from a current sliding mode observer (SMO). One threshold serves to detect fault occurrence, while the other facilitates OC localization. The proposed method requires no supplementary hardware and demonstrates robustness against variations in control parameters, diverse operating conditions, and sensor noises. The effectiveness of the proposed method is validated through extensive experiments.