Sensorless Control Strategy by Square-Waveform High-Frequency Pulsating Signal Injection Into Stationary Reference Frame

In this paper, a new sensorless control strategy based on the square-waveform high-frequency pulsating voltage signal injection into the stationary reference frame is proposed. Similar to the sinusoidal-waveform injection method, by injecting the high-frequency square-waveform pulsating voltage carrier voltage into the α- (or β-) axis of the stationary reference frame, the response carrier current will fluctuate with the position-dependent saliency, and then the rotor position information can be retrieved without any filtering. Furthermore, with higher frequency, the bandwidth of the position estimation can be significantly improved compared with all the sinusoidal-waveform injection strategies, and the influence of the winding resistance can also be fully eliminated. Meanwhile, the proposed new strategy injects a pulsating high-frequency carrier voltage into the stator stationary reference frame as stable as the rotating carrier signal injection method. Then, the rotor position information can be retrieved from the carrier current response, which is amplitude modulated by the machine saliency as simple as the pulsating carrier signal injection method. The experimental results validate that this strategy can achieve accurate rotor position estimation with good steady-state and dynamic performances by considering the cross-saturation effect even when there exhibits some noise in the estimated rotor position.