Key Takeaways & Executive Findings
- •• An enhanced quadrature phase-locked loop (EQPLL) with polarity correction and feedforward compensation is proposed to eliminate the 180° convergence deviation during motor reversal and reduce angle estimation errors during acceleration/deceleration. • The improved phase discriminator in the stationary frame enables polarity correction without relying on Park transform, avoiding accumulated estimation errors. • The feedforward compensation signal, filtered by an enhanced generalized integrator, achieves low-delay and low-noise angle error compensation. • Experimental validation shows the proposed scheme reduces noise mean square error by 24.33% compared to existing feedforward compensation methods.
Abstract
The sensorless control of surface-mounted permanent magnet synchronous motor (SPMSM) usually uses quadrature phase-locked loop (QPLL) to extract the phase information of the back electromotive force to realize the rotor angle estimation. However, the traditional QPLL has a convergence deviation of 180° when the motor is reversed, and the angle estimation error is obvious when the motor is accelerated and decelerated. To solve these problems, an enhanced QPLL (EQPLL) with polarity correction and high precision angle feedforward compensation is proposed. Firstly, the traditional phase discriminator is improved based on the two-phase stationary coordinate system, and the polarity correction function is designed by the error component of the improved phase discriminator to realize the non-convergent deviation angle estimation under the forward and reverse switching conditions of the motor. In addition, the error component of the improved phase discriminator is used as the feedforward compensation signal, and the enhanced generalized integrator is used to filter it, so as to realize the angle error compensation with low delay and low noise. Finally, the proposed scheme is verified by experiment on the motor platform, and compared with the existing scheme. The experimental results show that the proposed scheme can realize the polarity correction and angle error elimination, and at the same time, the noise mean square error is reduced by 24.33% compared with the existing angle feedforward compensation scheme.
1. Introduction
The surface-mounted permanent magnet synchronous motor (SPMSM) is widely recognized for its compact structure, simplified construction, and high reliability. These characteristics have led to the extensive adoption of SPMSMs in applications such as automotive systems, industrial control, and other fields. Rotor angle detection in SPMSMs is typically achieved through the use of physical sensors, which enable precise control of the motor's operation. However, the integration of physical sensors introduces additional complexity to the system, increases the motor's overall size, and makes the system more susceptible to environmental influences, including temperature fluctuations and electromagnetic interference [1]. Consequently, sensorless estimation has emerged as a prominent research focus in the field of SPMSM control.
Currently, sensorless estimation methods for SPMSMs primarily include the open-loop method [2], signal injection method [3], back electromotive force (BEMF) method, and flux linkage method [4−6]. Among various approaches, the BEMF and flux-linkage methods, typically represented by the sliding mode observer (SMO), have been the most extensively studied and widely applied. After estimating the BEMF or rotor flux using these observers, the rotor position and speed of the motor are typically tracked employing a quadrature phase-locked loop (QPLL) [7, 8]. However, traditional QPLL systems exhibit a 180° angle estimation deviation during motor reversal [9−14] and suffer from weak slope signal tracking capabilities [13−17]. Such angle estimation errors directly impact the accuracy of current signals in coordinate transformations, ultimately degrading motor control performance.
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HAN Kun, YU Chen, LI Wei (2026). Sensorless estimation of surface-mounted permanent magnet synchronous motors based on polar-corrected feedforward quadrature phase-locked loop. Journal of Central South University. https://doi.org/10.1007/s11771-026-6226-1
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Frequently Asked Questions
What is the main problem with traditional QPLL in sensorless SPMSM control?
Traditional QPLL exhibits a 180° angle estimation deviation during motor reversal and has weak slope signal tracking capabilities, leading to angle estimation errors during acceleration and deceleration, which degrade motor control performance.
How does the proposed EQPLL solve the polarity issue?
The proposed EQPLL improves the phase discriminator in the two-phase stationary coordinate system and designs a polarity correction function based on the error component, eliminating the non-convergent deviation angle under forward and reverse switching conditions without relying on Park transform.
What is the role of the feedforward compensation in the proposed scheme?
The error component of the improved phase discriminator is used as a feedforward compensation signal, filtered by an enhanced generalized integrator, to achieve low-delay and low-noise angle error compensation during speed variations.
What are the experimental results of the proposed scheme?
Experimental results show that the proposed scheme realizes polarity correction and angle error elimination, and reduces the noise mean square error by 24.33% compared to the existing angle feedforward compensation scheme.
What is the significance of the proposed method for industrial applications?
The proposed method enhances the accuracy and reliability of sensorless control for SPMSMs, which is crucial for applications in automotive systems and industrial control, potentially reducing costs and improving performance by eliminating physical sensors.
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