A Robust Observer and Nonorthogonal PLL-Based Sensorless Control for Fault-Tolerant Permanent Magnet Motor With Guaranteed Postfault Performance

This article proposes a robust observer and nonorthogonal phase-locked loop (PLL)-based sensorless control for the fault-tolerant permanent magnet synchronous motor (FTPMSM) in medium- and high-speed ranges to improve the position estimation reliability of the system, which can be applied for the sensorless control of the FTPMSM system in both normal and fault conditions. Due to the unsymmetric state of the FTPMSM under fault condition, a new sensorless control scheme based on the back electromotive force (EMF) of nonfault two-phase windings is proposed, in which the reference frame transformation is not necessary. The robust observer is proposed to accurately estimate the back EMF of the nonfault two-phase windings, which can guarantee the uniform boundedness and uniform ultimate boundedness of the system regardless of various uncertainties, including external disturbance, parameter variation, and phase winding fault. The nonorthogonal PLL is proposed to calculate the rotor position and speed of the FTPMSM by using the estimated two-phase back EMFs. The simulation and experimental results show that the FTPMSM system with the proposed sensorless control has excellent speed control performance, accurate rotor position/speed estimation, and great system robustness in the presence of various uncertainties, which is able to guarantee the system performance both in normal condition and in fault condition.