Sensorless Control of SPMSM Based on High-Frequency Positive- and Negative-Sequence Current Dual-Demodulation

In surface-mounted permanent magnet synchronous motor (SPMSM) low-speed sensorless control, the high-frequency sinusoidal voltage injection method for rotor position estimation is affected by the low saturation salient rate of SPMSM and the system delay, resulting in estimation error. This article proposes a dual-demodulation method utilizing the high-frequency positive- and negative-sequence stator current of the motor. This method is based on the principle of maximizing the effect of the salient inductance component and minimizing the significant component of noise, which improves the utilization of the current containing angle information and increases the signal-to-noise ratio of the position angle error fed to the rotor position observer. The dc bias of the current caused by system delay is also eliminated so that the accuracy of position estimation is improved. The proposed method is verified by experiment, and the results show that the accuracy of the estimated rotor position and dynamic performance of the estimator is greatly improved compared to existing methods.