Enhanced Generalized Vector Control Strategy for Torque Ripple Mitigation of IPM-type Brushless DC Motors

ABSTRACT:

 Optimal currents with appropriate harmonic components injected into the motor windings can effectively mitigate torque ripple for interior permanent magnet (IPM) type brushless DC motors (BLDCMs). However, existing approaches may fail to accurately inject the optimal currents into motors due to the limited current loop bandwidth. This paper proposes a simple enhanced generalized vector control strategy to mitigate the torque ripple for IPM-type BLDCMs. With the proposed vector control strategy, the control block diagram for IPM-type BLDCMs is as simple as that with traditional vector control for sinusoidal permanent magnet synchronous motors. Firstly, an electromechanical energy conversion voltage (EECV), considering the effects of the non-sinusoidal back-EMF and the rotor salience property, is proposed in -axis. Then, a novel coordinate frame is constructed with the proposed EECV, which is based on the arbitrary reference frame theory. As a result, the currents of IPM-type BLDCMs can be decomposed into two constant components, one being linked to the torque and the other one to the flux linkage. Thus, the bandwidth of current loop with simple proportional integral regulator can be equivalently expanded in the proposed coordinate frame. Finally, comprehensive experiments are conducted in different operation conditions to validate the effectiveness of the proposed vector control strategy. 1

KEYWORDS:

1.      Brushless DC motors (BLDCMs)

2.      Vector control

3.      Optimal currents

4.      Torque ripple mitigation

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

An enhanced generalized vector control strategy based on the arbitrary reference frame theory is proposed. And a voltage component involving in electromechanical energy conversion, namely EECV, is utilized to establish the novel coordinate frame of the generalized vector control strategy. Therefore, the current components of BLDCMs mapped in the proposed coordinate frame are constant, surmounting the bandwidth limitations of PI current regulator thoroughly. With the proposed strategy, the torque ripple minimization and MTPA operation for BLDCMs can be achieved simultaneously, and the steady and dynamic performance have been verified by experimental results. In addition, the influence of permanent magnet flux and inductance term variations on the torque ripple mitigation has been investigated with experimental tests.

In conclusion, the proposed method has the following advantages:

1) Compared with two phase feeding mode, the proposed method eliminates the switching of control strategy between normal conducting period and commutation period, and between low speed and high speedarea. Thus, the executability of torque ripple mitigation is enhanced.

2) Compared with the traditional vector control with Park transformation [4] and the vector control with GSRF [11], the proposed method can simplify the mathematical model of IPM-type BLDCMs, being similar with that of the surface sinusoidal PMSMs. Then, with simple PI current regulator, the steady state and transient state performance of torque ripple mitigation are improved.

3) Compared with the vector control based on the conventional rotor orientation with the additional resonant controllers[15]-[20]or repetitive controllers[21], or the method based on multiple reference frames[22], all torque ripple harmonic componentscan be mitigatedtheoretically, not only the selective torque harmonic components.Thus, the torque ripple can be mitigated further with the proposed method.

REFERENCES:

 

[1] T. Shi, X. Niu, W. Chen, and C. Xia, “Commutation torque ripple reduction of brushless DC motor in braking operation,”. IEEE Trans. Power Electron., vol.33 no.2, pp.1463-1475, Dec, 2018.

[2] H.S. Seol, J. Lim, D.W. Kang, J. S. Park and J. Lee, “Optimal design strategy for improved operation of IPM BLDC motors with low-resolution hall sensors,” IEEE Trans. Ind. Electro., vol.64, no.12, pp.9758-9766, Dec, 2017.

[3] M. Bertoluzzo, G. Buja, R. K. Keshri, and R. Menis, “Sinusoidal versus square-wave current supply of PM brushless DC drives: a conven-ience analysis,” IEEE Trans. Ind. Electro., vol.62, no.12, pp.7339-7349, Dec, 2015.

[4] G. Buja, M. Bertoluzzo, and R. K. Keshri, “Torque ripple-free operation of PM BLDC drives with petal-wave current supply,” IEEE Trans. Ind. Electro., vol.19, no.2, pp.4034-4043, July, 2015.

[5] J.-H. Song, and I. Choy, “Commutation torque reduction in brushless dc motor drives using a single dc current sensor,” IEEE Trans. Power Electron., vol.33 no.2, pp.312-319, Mar, 2004.