A three-stage synchronous motor low-speed rotor position estimation method

By injecting single-phase AC current into a three-stage synchronous motor, and using a combination of a second-order generalized integrator and a third-order phase-locked loop with the heterodyne method to estimate the rotor position, the problems of high system complexity and insufficient accuracy in the prior art are solved, and high-precision rotor position estimation is achieved.

CN122137289APending Publication Date: 2026-06-02NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
Filing Date
2026-02-05
Publication Date
2026-06-02

AI Technical Summary

Technical Problem

Existing methods for rotor position estimation in three-stage synchronous motors under zero-low speed conditions suffer from high system complexity and insufficient accuracy, especially the static error of the PI phase-locked loop during acceleration, which affects position accuracy.

Method used

A single-phase AC current is injected into the main exciter of a three-stage synchronous motor. The second harmonic response signal and its orthogonal signal are extracted by a second-order generalized integrator. The unit circle sine and cosine signals are constructed by combining linear operations. The position is estimated by using a third-order phase-locked loop and the heterodyne method. Sector correction is performed by combining the stator current polarity to compensate for the filter phase shift error.

Benefits of technology

The filter structure was simplified, the system order was reduced, the accuracy of rotor position estimation and steady-state position estimation was improved, the problem of difficult-to-tune phase-locked loop parameters was avoided, and high-precision rotor position estimation was achieved.

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Abstract

This invention discloses a method for zero-low-speed rotor position estimation of a three-stage synchronous motor. By injecting single-phase AC current into the main exciter of the three-stage synchronous motor, the αβ-axis response voltage signal of the main generator stator is extracted. A single second-order generalized integrator is used to simultaneously extract the second harmonic response signal and its orthogonal components. Based on the orthogonal signals, a low-frequency sine and cosine signal containing rotor position information is directly constructed through linear operations. The amplitude is then normalized to obtain a unit circle sine and cosine signal, which is input into a third-order phase-locked loop to achieve rotor position estimation. This invention avoids the use of complex cascaded filtering structures, simplifies the signal chain, and achieves high-precision rotor position estimation and reliable starting of the three-stage synchronous motor under zero-low-speed conditions.
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