Department of Electrical Engineering, Southern Taiwan University

Department of Electrical Engineering, Southern Taiwan University

1

Commutation Torque Ripple Reduction in a Position Sensorless Brushless DC Motor

Drive

Commutation Torque Ripple Reduction in a Position Sensorless Brushless DC Motor

Drive

Student: Hsin-Feng Tu Professor: Ming-Shyan WangDate : Dec,29,2010

Dae-Kyong Kim, Kwang-Woon Lee, and Byung-Il Kwon, Member, IEEE, IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 21, NO. 6, NOVEMBER

2006

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Outline

Abstract Introduction Sensorless BLDC Motor Control Commutation Torque Ripple Reduction Strategy

Analysis of Commutation Torque Ripple Voltage Disturbance Rejection Method Implementation of the Proposed Strategy

Experimental Results Conclusion References

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Abstract

Presents a novel method to reduce commutation torque ripple in a position sensorless brushless dc (BLDC) motor drive.

Measures commutation interval from the terminal voltage of a BLDC motor.

Calculates a pulsewidth modulation (PWM) duty ratio using the measured commutation interval to suppress the commutation torque ripple.

Implemented in an air conditioner compressor controller reduces not only the pulsating currents but also vibrations of a position-sensorless BLDC motor.

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Introduction

Permanent magnet brushless dc (BLDC) motors have used wide application due to their power density and ease of control.

Since the proposed method directly measures commutation interval from motor terminal voltage waveforms, it does not require a current sensor and current control loop.

The experimental results show that the proposed method considerably reduces not only current ripples but also the vibrations of the compressor.

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Sensorless BLDC Motor Control

Commutation points of the inverter can be obtained by knowing

the zero-cross-point (ZCP) of the back-EMF and a speed

dependent period of time delay.

The commutation points are estimated like this

( )zcpT k is the zero crossing time of the back-EMF

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Sensorless BLDC Motor Control

Fig. 1. (a) Configuration of a BLDC motor drive

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Sensorless BLDC Motor Control

Fig. 1.(b) switching pattern

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Sensorless BLDC Motor Control

Fig. 1.(c) terminal voltage sensing circuit

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Sensorless BLDC Motor Control

Fig. 1.(d) terminal voltage waveforms

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Analysis of Commutation Torque Ripple

Average voltage applied to a non-commutated phase before commutation is

1mV

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Analysis of Commutation Torque Ripple

Fig. 2. Current paths in out-going unipolar PWM scheme when the phase current is being transferred from phase A to phase B.

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Analysis of Commutation Torque Ripple

From Fig. 2, the phase voltage equation during commutation is given as

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Analysis of Commutation Torque Ripple

In case of an out-going phase unipolar PWM ,average voltage appliedto a non-commutated phase is

2mV

From (3) and (8), it is apparent that the average voltage of the noncommutationed phase is disturbed by commutation. voltage disturbance generates pulsating current, pulsating current causes undesirable torque ripple during the commutation.

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Voltage Disturbance Rejection MethodIn order to minimize the pulsating current, the PWM duty ratio during commutation must be modified as (9) in order that the average voltage of the non-commutated phase maintains constant value, that is 2m mV V

If the phase back-EMF assumes constant in the commutation period and rotational velocity of motor, the phase back-EMF is given as

Equation (9) is adjusted as in

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Implementation of the Proposed Strategy

Fig. 3. Synchronization of the gating signals.

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Implementation of the Proposed Strategy

Fig. 4. Configuration of the proposed controller

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Experiment Results

Fig. 5. Configuration of the experimental BLDC motor drive

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Experiment Results

Fig. 6. Single rotary compressor and air conditioner for experimental test

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Experiment Results

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Experiment Results

Fig. 7. Measured duration of commutation in the rotary compressor with a BLDC motor

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Experiment Results

Fig. 8. Simulation results at running frequency (50 Hz). (a) Conventional control. (b) Proposed control

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Experiment Results

Fig. 9. Terminal voltage and phase current at running frequency (30 Hz). (a) Conventional control. (b) Proposed control

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Experiment Results

Fig. 10. Terminal voltage and phase current at running frequency (75 Hz). (a) Conventional control. (b) Proposed control

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Experiment Results

Fig. 11. Total vibration measured at the center of the compressor body

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Conclusion

This paper has proposed a commutation torque ripple reduction method for a position sensorless BLDC motor drive for he air conditioner.

Since the proposed method uses terminal voltage for measuring the commutation interval, the method does not require current sensors and a current control loop so that it is suitable for a low cost BLDC motor drive.

Experimental results have proved that the proposed control method considerably reduces not only the pulsating currents but also up to 31% of the total vibrations for the BLDC motor.

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References

[1] Electric Power Research Institute, “Electric Motors; Markets, Trends, and Applications,” Tech. Rep. TR-100423, Jun. 1992.

[2] R. Calson, M. Lajoie-Mazenc, and J. Fagundes, “Analysis of torque ripple due to phase commutation in brushless dc machines,” IEEE Trans. Ind. Appl., vol. 28, no. 3, pp. 632–638, May/Jun. 1992.

[3] Y. Murai, Y. Kawase, K. Ohashi, K. Nagatake, and Okuyama, “Torque ripple improvements for brushless dc miniature motors,” IEEE Trans. Ind. Appl., vol. IA-25, no. 3, pp. 441–450, May/Jun. 1989.

[4] T. M. Jahns and W. L. Soong, “Pulsating torque minimization techniques for permanent magnet ac motor drives-a review,” IEEE Trans. Ind. Electron., vol. 43, no. 2, pp. 321–330, Apr. 1996.

[5] P. Pillay and R. Krishnan, “Modeling, simulation, and analysis of permanent-magnet motor drives, Part II: The permanent-magnet synchronous drive,” IEEE Trans. Ind. Appl., vol. IA-25, no. 2, pp. 265–273, Mar./Apr. 1989.

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References

[6] C. Berendsen, G. Champenois, and A. Bolopion, “Commutation strategies for brushless dc motors: Influence of instant torque,” IEEE Trans. Power Electron., vol. 8, no. 2, pp. 231–236, Apr. 1993.[7] K. W. Lee, “Current control algorithm to reduce torque ripple in brushles dc motors,” in Proc. ICPE’98, 1998, vol. 1, pp. 380–385.[8] X. Zhang, “A new method to minimize the commutation torque ripple in trapezoidal BLDC motor with sensorless drive,” in Proc. PIEMC’00, 2000, vol. 2, pp. 607–611.[9] T. Endo and F. Tajima, “Microcomputer controlled brushles motor without a shaft mounted position sensor,” in Proc. IPEC’83, Tokyo, Japan, 1983, pp. 1339–1345.[10] K. Iizuka, “Microcomputer control for sensorless brushless motor,” IEEE Trans. Ind. Appl., vol. IA-27, no. 3, pp. 595–601, May/Jun. 1985.[11] K. Rajashekara, A. Kawamaura, and K. Matsuse, Sensorless Control of AC Motor Drives. New York: IEEE Press, 1996.

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