Improved Sensorless Control for Permanent-Magnet Synchronous Motor with Self-Inductance Asymmetry

An improved sensorless control for Permanent-Magnet Synchronous Motors (PMSM) with inductance asymmetry is proposed in this paper. Inductance asymmetry can be caused by manufacture tolerance, winding fault, or single winding operation of dual three-phase PMSM, etc. When the inductance is asymmetric, it not only makes the current unsmooth, but also yields inaccurate position and speed estimation of sensorless control. In this paper, an improved phase-locked loop (PLL) in the sliding mode observer (SMO) is proposed to improve the sensorless control in the case of asymmetric inductance. The improved PLL is based on a PIR controller for smooth current control. The improved method uses an additional resonant controller to compensate the second harmonic error. Furthermore, the second harmonic error is used to identify the value of the asymmetric self-inductance and correct the inductance parameters in the SMO. This method can accurately estimate the speed and position and ensure the performance of sensorless control. The simulation and experimental results obtained from a 400W SPMSM verify the effectiveness of the proposed method.