Predictive Control for Asymmetrical Six-Phase PMSM Motor under Open-Circuit Fault Based on Internal Model Disturbance Observer

The open-circuit fault will introduce large torque ripple and increase the copper loss due to the lost degree of control freedom. As a result, the parameter mismatch of the machine occurs more easily. This paper presents an internal model disturbance observer based model predictive fault tolerant control for a six-phase permanent magnet synchronous motor (PMSM) under single-phase open circuit fault. The reduced-order modelling of the machine under single-phase open-circuit fault is derived first. The torque ripple and the copper loss in the fault condition is analyzed in detail. The necessity to compensate the predictive error caused by the multi-parameter mismatch under fault condition is justified. Then, the internal model disturbance observer is constructed to estimate the disturbances and compensate the error in the feedforward manner. Its stability is proved by the Lyapunov theory. Through the proposed disturbance observer, the torque ripple in the postfault operation is reduced and parameter robustness is enhanced. Experimental results demonstrate the effectiveness of the proposed method.