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Friday 5 March 2021

Flux Observer Model for Sensorless Control of PM BLDC Motor with a Damper Cage

ABSTRACT: 

Sensorless control methods are commonly employed to derive the rotor position and speed information indirectly in permanent magnet (PM) brushless motor drives. Thereinto, the simple yet effective flux observer method is extensively applied in a wide range of applications. However, damper cage is sometimes employed in the rotor of certain PM brushless motor. Normally, high order current harmonic components occur in such damper cage during operations. The introduction of these extra current contents can significantly hinder the performance of conventional flux observer. By applying Park transformation, the fundamental harmonic components of stator phase currents, flux linkages, and voltages during steady-state operation, become constants under rotor synchronous reference frame, while the currents in the rotor damper cage are still alternating. In this paper, an improved flux observer method is proposed to filter the harmonic contents under the rotor synchronous reference frame for PM brushless motor with rotor damper cage. The validity and performance of the proposed flux observer are verified by both numerical analysis and experimental results.

KEYWORDS:

1.      Flux observer

2.      Mathematical model

3.      PM BLD motor

4.      Damper cage

5.       Harmonic components

 

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The harmonic components of the stator currents of the PM BLDC motor affect the accuracy of the flux observer-based sensorless control method. Moreover, some BLDC motors employ a damper cage or similar structure (such as the shield outside magnets, or the metal retaining sleeve) in the rotor. Since the currents in the damper cage cannot be measured, the flux observer-based sensorless control method is not readily applicable to such BLDC motors. Considering that the damper cage makes the stator currents have more harmonic components, an improved flux observer model is proposed. It is under the d-q synchronous rotating reference frame, so that all the fundamentals of voltage, current and flux linkage become DC components, whilst the harmonics of the stator currents and rotor cage currents are still AC components and can be easily eliminated with low pass filters. Using the left DC components (i.e., the fundamental components), the rotor position can be estimated accurately. According to the numerical analysis and experiment results, it is verified that 1the improved flux observer method works well for the BLDC motor with a damper cage, and the error between the observed and actual rotor position is sufficiently small.

REFERENCES:

 

[1] Apoorva Athavale, Kensuke Sasaki, Brent S. Gagas, Takashi Kato, Robert Lorenz, Variable Flux Permanent Magnet Synchronous Motor (VF-PMSM) Design Methodologies to Meet Electric Vehicle Traction Requirements with Reduced Losses, IEEE Trans. Ind. Appl., Vol. PP, No. 99, pp. 1-1, 2017.

[2] Ramakrishnan Raja, Tomy Sebastian, Mengqi Wang, Abraham Gebregergis, Mohammad Islam, Effect of Position Sensor Error on the Performance of Permanent Magnet Motor Drives, IEEE Trans. Ind. Appl., Vol. PP, No. 99, pp. 1-1, 2017.

[3] Peng Li, Wei Sun, Jian-Xin Shen, Flux Observer Model for Sensorless Control of PM BLDC Motor with a Damper Cage, Twelfth International Conference on Ecological Vehicles and Renewable Energies, 2017, Monte Carlo, Monaco:1-6.

[4] P. Snary, B. Bhangu, C. M. Bingham, ET AL., Matrix converters for sensorless control of PMSMs and other auxiliaries on deep-sea ROVs, IEE Proc., Electr. Power Appl., Vol. 152, No. 2, pp. 382–392, 2005.

[5] A. Kulkarni, M. Ehsani, A novel position sensor elimination technique for the interior permanent magnet synchronous motor drive, IEEE Trans. Ind. Appl., Vol. 28, No. 1, pp. 144–150, 199