An improved method of initial rotor position detection for PMSM by voltage pulse injection

Background Accurate acquisition of the initial rotor position is crucial for permanent magnet synchronous motor (PMSM) control systems. Starting the motor without initial position detection may lead to excessive current or unexpected reverse rotation. However, the traditional voltage pulse injection method often suffers from insufficient accuracy and magnetic pole misidentification, which reduces the reliability and practical applicability of the detection results. Objective To eliminate the magnetic pole misidentification inherent in the traditional voltage pulse injection method and further improve detection accuracy, an improved method based on voltage pulse injection is proposed. Methods Firstly, to eliminate the magnetic pole misidentification observed in the traditional method, a magnetic pole identification (MPI) strategy is introduced. The MPI strategy determines whether the detected initial rotor position is consistent with the rotor polarity. If a polarity reversal is identified, the detected position is corrected by adding 180°. Next, to reduce the influence of sampling errors on detection accuracy, the magnetization effect of the injected current is enhanced. The difference among the feedback current responses becomes more pronounced, thereby mitigating the influence of sampling errors. Finally, a curve-fitting method is employed to further improve the detection accuracy. By utilizing the acquired current and position information, the current response curve near the actual rotor position is fitted, and the position corresponding to the peak current is selected as the final detection result. Results The effectiveness of the improved method has been validated through experiments conducted on a PMSM drive platform. The experimental results demonstrate that the improved method reduces the position detection error by an average of 32% and eliminates magnetic pole misidentification in the traditional method. Conclusions Compared with the traditional voltage pulse injection method, the improved method effectively enhances the accuracy of initial position detection, providing a strong basis for the stable operation of PMSM.