An Improved Position-Sensorless Control Method at Low Speed for PMSM Based on High-Frequency Signal Injection into a Rotating Reference Frame

In this paper, a novel sensorless control strategy with the injection of a high-frequency pulsating sinusoidal voltage into a rotating reference frame for a surface-mounted permanent magnet synchronous motor (SPMSM) is proposed. Conventional schemes may face the problems of applying to the motor with no obvious salient pole effect, and the effect of filter on the bandwidth of the system. Different from the conventional schemes, the new proposed strategy injects a high-frequency pulsating sinusoidal voltage signal is injected into the estimate d-q rotating reference frame, and the rotor position information is obtained from the response of injected high-frequency current signal in the α-β stationary reference frame other than the d-q rotating reference frame,which can avoid failure of applying to the SPMSM with no obvious salient pole effect. With this approach, band-pass filter, which is necessary in the conventional sensorless control, is removed to simplify the control structure and improve the system dynamic control performance. Therefore, this paper proposes a simple structure, which modulates the high-frequency current signal directly and only passes through the low-pass filter to obtain the estimated rotor position angle. Finally, the feasibility of the improved high-frequency pulsating sinusoidal voltage injection control method is verified by simulation and experiment.