Improved AVF-PLL-Based Position Estimation Scheme for SPMSM Sensorless Drives

The combination of a high-performance filter and phase-locked loop (PLL) has been presented as an effective alternative for the position estimation of a permanent magnet synchronous motor (PMSM) drive. However, the feedback delays existing in the practical implementation of the filter and PLL usually lead to position estimation deviation. To enhance the accuracy of position estimation, this paper proposes a sensorless control technology based on an improved adaptive vectorial filter (AVF) and PLL. First, the effect of feedback delay on the filtering performance of the AVF and the tracking performance of the PLL are analyzed. Then, corresponding delay compensation methods for the AVF and PLL are proposed. A compensation term based on the prediction of the filtered back electromotive force (EMF), which can repress the filtering performance degradation caused by feedback delays, is introduced and combined with the conventional AVF. As a result, the amplitude and phase shifts with the filtered back EMF can be effectively eliminated before applying it to the PLL. A differential calculation structure, which can ensure that the closed-loop transfer function of the equivalent ideal PLL is the same as the ideal PLL under the condition of feedback delay, is proposed to replace the cascade calculation structure of the conventional PLL. In addition, an open-loop deviation compensation method is integrated to eliminate the position estimation static deviation. The effectiveness of the proposed sensorless control technology is investigated by experimental tests.