An FCS-MPC-Based Threshold-Free Diagnosis Method for Open-Circuit Faults in Traction Inverters

Abstract

The open-circuit (OC) fault is one of the most prevalent failures in the two-level inverter used in traction systems. Reliable fault diagnosis method can improve the security of the inverter. During the fault diagnosis process, thresholds are very important and the accuracy of fault diagnosis depends on the thresholds. However, inaccurate thresholds may lead to false or missed alarms. To reduce the dependence of fault diagnosis on thresholds, a threshold-free OC fault diagnosis method is proposed in this article, which is based on the finite control set-model predictive control (FCS-MPC). According to the analysis of the two-level inverter, the estimated values of the cost function in normal and faulty conditions are obtained. Then, the residual sequence is achieved. Traverse the residual sequence and the minimum residual is found, and it is used for fault location. The residual change rates are introduced for secondary confirmation of the fault diagnosis result. In the fault diagnosis method, no threshold is necessary and no redundant hardware is required. Finally, the experimental platform is established. The experimental results show that the proposed method is robust to parameter mismatches and can successfully diagnose the OC faults within one-eighth period of the three-stator current. The feasibility and effectiveness of the proposed fault diagnosis method are also verified by the experimental results.