Position-Estimation Deviation-Suppression Technology of PMSM Combining Phase Self-Compensation SMO and Feed-Forward PLL

The sensorless drive method of the permanent magnet synchronous motor (PMSM) has attracted wide attention for its low cost and high reliability. As a critical technology, a fast and high-precision rotor-position estimation is essential. This article addresses the position-estimation deviation issue of the sensorless drive method based on the sliding-mode observer (SMO) and the phase-locked loop (PLL). A nonlinear equivalent model of the SMO is established to analyze and compensate for the position-estimation deviation caused by the SMO, and a feed-forward PLL is employed to suppress the steady-state position tracking error under variable speed operation. First, the phase-frequency characteristic of the SMO is obtained by studying the SMO and the switching functions in detail. Then, the analysis of the conventional PLL is carried out in terms of the error-transfer function. In addition, the position-estimation performance of the feed-forward PLL is discussed with the dynamic error coefficient method. Theoretical analysis and experimental evaluation validated the effectiveness of the proposed position-estimation deviation-suppression technology of the PMSM, combining the phase self-compensation SMO and the feed-forward PLL.