VP21-09 Improved Flux Observer Sensorless Control of Permanent Magnet Assisted Synchronous Reluctance Motor
Creators: Tao Tang
Meng Lu
Pingting Lin
Liu Xiao
Dongpei Lu
Qicheng Dai
Publisher: name: IEEE
Year: 2025

For the magnetic saturation and cross coupling effect, the dq axis inductance parameters of the PMaSynRM are unstable. In sensorless control of PMaSynRM, traditional EMF observers have low control accuracy due to low signal-to-noise ratio during low-speed operation. Unlike the electromagnetic field, the rotor flux remains constant during low-speed operation, so the flux observer has better performance during low-speed operation[1]. In [2], the author points out that there is a DC offset problem using the conventional flux observer method and proposes the use of a non-ideal PR controller in a flux observer based machine current model to suppress this problem and experimentally verifies the scheme. And unlike the traditional flux observer, the nonlinear flux observer makes a difference between the magnitude of the estimated flux and the actual flux as the compensation of the estimated flux component, which solves the problem of poor tracking accuracy from start to low-speed operation more efficiently, and the system reliability is improved. In [3], it combines the nonlinear flux observer with the gradient descent method to propose an improved nonlinear flux observer for PMSM, which greatly reduces the angular error. So in order to accommodate inductive instability and improve the performance of the system at start and low-speed operation, we propose a variable gain nonlinear flux observer by researching the relationship between observer gain and load. Meanwhile, in order to adapt to the influence of PMaSynRM dq-axis inductance variation on the observer, online parameter identification is introduced to improve the system reliability. In simulation, the maximum angular error when the PMaSynRM start is 0.138rad, and the angular error is stable at 0.054rad after the given speed is reached in 0.5s, which basically achieves effective and reliable tracking. The simulation results (Fig.1 and Fig.2) verify the effectiveness and feasibility of the method.References: [1] W. Xu, Y. Jiang, C. Mu and F. Blaabjerg, "Improved Nonlinear Flux Observer-Based Second-Order SOIFO for PMSM Sen-sorless Control," in IEEE Transactions on Power Electronics, vol. 34, no. 1, pp. 565-579, Jan. 2019. [2] D. Wang, K. Lu and P. O. Rasmussen, "Improved Closed-Loop Flux Observer Based Sensorless Control Against System Oscillation for Synchronous Reluctance Machine Drives," in IEEE Transactions on Power Electronics, vol. 34, no. 5, pp. 4593-4602, May 2019. [3] J. Liu and Y. Zhang, "Performance Improvement of Nonlinear Flux Observer for Sensorless Control of PMSM," in IEEE Transactions on Industrial Electronics, vol. 70, no. 12, pp. 12014-12023, Dec. 2023.
For the magnetic saturation and cross coupling effect, the dq axis inductance parameters of the PMaSynRM are unstable. In sensorless control of PMaSynRM, traditional EMF observers have low control accuracy due to low signal-to-noise ratio during low-speed operation. Unlike the electromagnetic field, the rotor flux remains constant during low-speed operation, so the flux observer has better performance during low-speed operation[1]. In [2], the author points out that there is a DC offset problem using the conventional flux observer method and proposes the use of a non-ideal PR controller in a flux observer based machine current model to suppress this problem and experimentally verifies the scheme. And unlike the traditional flux observer, the nonlinear flux observer makes a difference between the magnitude of the estimated flux and the actual flux as the compensation of the estimated flux component, which solves the problem of poor tracking accuracy from start to low-speed operation more efficiently, and the system reliability is improved. In [3], it combines the nonlinear flux observer with the gradient descent method to propose an improved nonlinear flux observer for PMSM, which greatly reduces the angular error. So in order to accommodate inductive instability and improve the performance of the system at start and low-speed operation, we propose a variable gain nonlinear flux observer by researching the relationship between observer gain and load. Meanwhile, in order to adapt to the influence of PMaSynRM dq-axis inductance variation on the observer, online parameter identification is introduced to improve the system reliability. In simulation, the maximum angular error when the PMaSynRM start is 0.138rad, and the angular error is stable at 0.054rad after the given speed is reached in 0.5s, which basically achieves effective and reliable tracking. The simulation results (Fig.1 and Fig.2) verify the effectiveness and feasibility of the method.References: [1] W. Xu, Y. Jiang, C. Mu and F. Blaabjerg, "Improved Nonlinear Flux Observer-Based Second-Order SOIFO for PMSM Sen-sorless Control," in IEEE Transactions on Power Electronics, vol. 34, no. 1, pp. 565-579, Jan. 2019. [2] D. Wang, K. Lu and P. O. Rasmussen, "Improved Closed-Loop Flux Observer Based Sensorless Control Against System Oscillation for Synchronous Reluctance Machine Drives," in IEEE Transactions on Power Electronics, vol. 34, no. 5, pp. 4593-4602, May 2019. [3] J. Liu and Y. Zhang, "Performance Improvement of Nonlinear Flux Observer for Sensorless Control of PMSM," in IEEE Transactions on Industrial Electronics, vol. 70, no. 12, pp. 12014-12023, Dec. 2023.