Fault Diagnosis and Tolerance With Low Torque Ripple for Open-Switch Fault of IM Drives

In this article, for insulated gate bipolar transistor (IGBT) open-switch faults in voltage-source inverter-based field-oriented control induction machine drives, both the diagnosis method and the fault-tolerant strategy are presented. In the fault diagnosis method, phase voltages are reconstructed from the variables of the control system. Thus, additional sensors can be avoided. Then, the voltages of healthy and faulty conditions are analyzed. Next, the residual behaviors for faulty conditions are derived based on a comprehensive switching function model that considers the health state of the power switch. On this basis, fault detection and localization criteria can be obtained. In the fault-tolerant strategy, the three-phase six-switch (TPSS) topology and three-phase four-switch (TPFS) topology are combined. TPSS topology can provide the zero state, which eliminates the torque ripple caused by the zero state synthesis. An analytical comparison of torque ripples of TPSS and TPFS is given. It shows that the TPFS topology has lower torque ripple at higher speed and lighter load, whereas TPSS topology has lower torque ripple at lower speed and heavier load. By combining them, the lower torque ripple can be achieved at both high and low speed and heavy and light load. Finally, hardware-in-the-loop tests are carried out to show the effectiveness of the proposed methods.