Direct Torque Control of Brushless DC Drives With Reduced Torque Ripple

 ABSTRACT:

The application of direct torque control (DTC) to brushless ac drives has been investigated extensively. This paper describes its application to brushless dc drives, and highlights the essential differences in its implementation, as regards torque estimation and the representation of the inverter voltage space vectors. Simulated and experimental results are presented, and it is shown that, compared with conventional current control, DTC results in reduced torque ripple and a faster dynamic response.

KEYWORDS:

1.      Brushless dc (BLDC) drives

2.      Direct torque control (DTC)

3.      Permanent-magnet motor

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Schematic of DTC BLDC drive.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulated results for Motor 1 (1500 r/min). (a) Phase-to-ground voltage. (b) Phase voltage. (c) Phase current. (d) Locus of stator flux linkage. (e) Electromagnetic torque.

Fig. 3. Simulated results for Motor 2 (400 r/min). (a) Phase-to-ground voltage. (b) Phase voltage. (c) Phase current. (d) Locus of stator flux linkage. (e) Electromagnetic torque.

CONCLUSION:

DTC has been applied to a BLDC drive, and its utility has been validated by simulations and measurements on two BLDC motors which have very different back-EMF waveforms. The main difference between the implementation of DTC to BLAC and BLDC drives is in the estimation of torque and the representation of the inverter voltage vectors. It has been shown that DTC is capable of instantaneous torque control and, thereby, of reducing torque pulsations.

REFERENCES:

[1] J. R. Hendershort Jr and T. J. E. Miller, Design of Brushless Permanent- Magnet Motors. Oxford, U.K.: Magana Physics/Clarendon, 1994.

[2] T. Kenjo and S. Nagamori, Permanent-Magnet and Brushless DC Motors. Oxford, U.K.: Clarendon, 1985.

[3] P. J. Sung,W. P. Han, L. H. Man, and F. Harashima, “A new approach for minimum-torque-ripple maximum-efficiency control of BLDC motor,” IEEE Trans. Ind. Electron., vol. 47, no. 1, pp. 109–114, Feb. 2000.

[4] C. French and P. Acarnley, “Direct torque control of permanent magnet drives,” IEEE Trans. Ind. Appl., vol. 32, no. 5, pp. 1080–1088, Sep./Oct. 1996.

[5] T. S. Low, K. J. Tseng, K. S. Lock, and K.W. Lim, “Instantaneous torque control,” in Proc. Fourth Int. Conf. Electrical Machines and Drives, Sep. 13–15, 1989, pp. 100–105.

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