Diagnosis-Free Self-Tolerant Scheme for Four-Leg Inverter Fed PMSM Drives With Open-Circuit Faults

The three-phase four-leg (TPFL) inverter fed motor drive has an additional phase leg, which can provide the redundant current path under fault conditions. Therefore, the TPFL inverter fed motor drive has attracted wide attention for applications with high reliability. To minimize the adverse impacts of diagnosis, i.e., misdiagnosis and torque disturbance, a diagnosis-free self-tolerant scheme is proposed for TPFL fed permanent magnet synchronous motor (PMSM) drives with open-circuit faults. It is revealed that the conflicts between d/q-axis current controllers and zero-sequence current controller cause the torque ripple in TPFL inverter fed PMSM drives under faults. For addressing that issue, a notch filter at the characteristic frequency is designed in zero-sequence current control path, and proper periodic current controllers are dedicated to achieve compatibility between normal and faulty operating conditions. Thus, the self-tolerant operation can be realized without diagnosis or reconfiguration of current references. Experimental results are given to verify the effectiveness of the proposed diagnosis-free self-tolerant scheme for TPFL inverter fed PMSM drives with both open-phase and open-switch faults.