Online Identification of Intrinsic Load Current Dependent Position Estimation Error for Sensorless PMSM Drives

Low-speed sensorless control of Permanent Magnet Synchronous Machine (PMSM) faces an intrinsic problem of increased position estimation error with increased load. This phenomenon is due to changed magnetic saliency caused by the load current on the machine side. Therefore, such position estimation error, which deteriorates the drive performance, cannot be corrected by the sensorless algorithm itself; it has to be detected/compensated by other methods. In this paper, an on-line identification method is proposed to detect reliably this load current dependent position estimation error. The unique features of the proposed method are its easy implementation and plug-and-play capability, without the needs of machine detailed flux map or extra devices such as a rotor locker; the detection process is very fast, so even with the q-axis current present, it will not cause noticeable rotor position change. Various experimental results are presented to validate the effectiveness of the proposed method.