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Friday, 17 January 2020

A Torque Ripple Compensation Technique for a Low Cost Brushless DC Motor Drive



ABSTRACT:
This paper presents a torque ripple compensation technique for a Brushless DC (BLDC) motor drive that is operated without a DC link capacitor. The motor drive, which uses a single switch control strategy, resembles that of a buck converter during operation at any switching state. A simple buck converter based model is therefore proposed to predict the behaviour of the BLDC motor drive at constant speed. Using the model, the impact of operation without the DC link capacitor on the torque produced by the BLDC motor drive is investigated in detail. Theoretical behaviour of the BLDC motor drive is compared with Matlab/Simulink based simulations to demonstrate the validity of the compensation technique and the analysis. Experimental results of a 250 W prototype motor drive are also presented to further validate the theoretical analysis as well as the effectiveness of the proposed technique. Results convincingly indicate that the BLDC motor drive with torque ripple compensation offers comparable performance.

KEYWORDS:
1.      Brushless machines
2.      Torque ripple compensation

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:


Fig. 1. (a) A typical BLDC motor drive; and (b) a BLDC motor drive without
a DC link capacitor.
 EXPERIMENTAL RESULTS:



Fig. 2. Case 1 with M1 for E = 95V: (a) vin(t) and E; (b) im(t) by theoretical
analysis; (c) im(t) by simulation; and (d) im(t) by experiment.



Fig. 3. Case 2 with M2 for E = 80V: (a) vin(t) and E; (b) im(t) by theoretical
analysis; (c) im(t) by simulation; and (d) im(t) by experiment.



Fig. 4. Case 3 with M1 for E = 65 V: (a) vin(t) and E; (b) im(t) by
theoretical analysis; (c) im(t) by simulation; and (d) im(t) by experiment.


Fig. 5. A comparison between the comprehensive model and the simple
model: (a) case 1 with M1; (b) case 2 with M2; and (c) case 3 with
M1.



Fig. 6. Proposed compensation for case 1: (a) simulated im(t) without a capacitor and with a 150 μF capacitor; (b) simulated im(t) with proposed compensation; (c) experimental im(t); and (d) DC link voltage with proposed compensation.





Fig. 7. Proposed compensation for case 3: (a) simulated im(t) without a capacitor and with a 150 μF capacitor; (b) simulated im(t) with proposed compensation; (c) experimental im(t); and (d) DC link voltage with proposed compensation.


CONCLUSION:
A simple mathematical model and a compensation technique for inherent torque ripples of a BLDC motor drive, operated without a DC link capacitor, have been proposed. The simplicity of the model permits the controller to be implemented on inexpensive microcontroller platforms with very low resources. With the proposed technique for compensating torque ripples, comparable performance to a conventional BLDC motor drive with a large DC link capacitor can be achieved. However, with the torque ripple compensation technique, the overall complexity of the motor drive has been increased, which is a major disadvantage. Based on the application, major augmentations in both hardware and firmware may be required. The good agreement between the theoretical results, simulated results and experimental results demonstrate the accuracy of the simple buck model and the effectiveness of the proposed compensation technique. The proposed compensation technique is expected to be useful for manufacturing low cost BLDC motor drives with comparable performance.
REFERENCES:
[1] R. Krishnan, Electric Motor Drives, Modeling, Analysis, and Control. Prentice Hall, 2001.
[2] R. Krishnan, Permanent Magnet Synchronous and Brushless DC Motor Drives. CRC Press, 2010.
[3] J. F. Gieras, Permanent Magnet Motor Technology - Design and Applications: CRC Press, 2010.
[4] V. Sankaran, F. Rees, and C. Avant, “Electrolytic capacitor life testing and prediction,” in Industry Applications Conference, 1997. Thirty- Second IAS Annual Meeting, IAS ’97., Conference Record of the 1997 IEEE, vol. 2, Oct. 1997, pp. 1058–1065.
[5] H. K. Samitha Ransara and U. K. Madawala, "A Low Cost Brushless DC Motor Drive," in 6th IEEE Conference on Industrial Electronics and Applications, (IEEE ICIEA), Jun. 2011, pp. 2723-2728.