Simple and Effective Online Position Error Compensation Method for Sensorless SPMSM Drives

In low-speed sensorless control of surface-mounted permanent magnet synchronous machine (SPMSM), high-frequency (HF) signal injection methods are often used to estimate the rotor position by tracking the motor saliency characterized by the inductances. Cross-saturation effects caused by the load current will influence the inductances, and consequently the saliency, which will introduce position estimation error to the sensorless drive, degrading the drive performance. Such load-dependent position estimation error, which is inherent in HF signal injection sensorless methods, is difficult to be identified by the sensorless algorithm itself. This article proposes a new online method to detect and compensate the load-dependent position estimation error for SPMSM without additional devices or the knowledge of the load-dependent HF inductances. The proposed method can identify effectively the load-dependent position estimation error by simply varying the direction of the current vector. Experimental results are presented to validate the proposed solution.