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Commutation Torque Ripple Reduction in a
Position Sensorless Brushless DC Motor
Drive
Dae-Kyong Kim, Kwang-Woon Lee, and Byung-Il Kwon, Member, IEEE, IEEE TRA
NSACTIONS ON POWER ELECTRONICS, VOL. 21, NO. 6, NOVEMBER 2006
Student: Hsin-Feng Tu
Professor: Ming-Shyan Wang
Date : Dec,29,2010
Department of Electrical Engineering,
Southern Taiwan University
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Outline
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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
Tzcp ( 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 Vm1 applied to a non-commutated phase before
commutation is
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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 Vm 2 applied
to a non-commutated phase is
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 Method
In 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 Vm 2  Vm
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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Thanks for your attention!
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