A Novel Direct Torque Control Scheme for Induction Machines With Space Vector Modulation

ABSTRACT:

In this paper a new method for Direct Torque Control (DTC) based on load angle control is developed. The use of simple equations to obtain the control algorithm makes it easy tu understand and implement. Fixed switching frequency and low torque ripple are obtained using space vector modulation. This control strategy overcomes the must important drawbacks of classic DTC. Results shows the feasibility of the proposed method, obtaining good speed control bandwidth while overcoming classic DTC drawbacks.

KEYWORDS:

1.      Electric Drives

2.      AC Machines

3.      Direct Torque Control

4.      Space Vector Modulation

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig.  1. Classic DTC control block diagram

EXPECTED SIMULATION RESULTS:

Fig. 2. Comparison of dynamic response klween DTC-SVM.F ield Oriented Control and Classic DTC. (a) Field Oriented Control. (b) Classic Direct Torque Control. (e) proposed Method.

Fig. 3. Torque response comparison between DTC-SVM and classic DTC. (a) Field Onenled Control, (h) Classic Direct Torque Control, (c) Proposed Method.

Fig. 4. Size of hysteresis band and sampling frequency effects on torque

ripple for clasic DTC.

Fig. 5. Torque spectral analJsis cornpanson. (a) DTC-SVM torque spectrum,

(b) Classic DTC torque spectrum.

Fig. 6. Stator Current during speed reversal.

.CONCLUSION:

The DTC-SVM strategy proposed in this work to control flux and torque is based on few induction machine fundamental equations. Consequently, the control method is simple and easy to implement. No coordinate rotation and less PI controllers than in field oriented control are needed. 0.1 (1.2 0.3 0.4 0.5 0.6 In addition, the proposed DTC strategy is well suited for use lime Is] in conjunction with space vector modulation resulting in a powerful alternative to overcome the well known drawbacks Fig. IO. Stator Current during speed reversal. of the original DTC solution: variable switching frequency and high torque ripple.

REFERENCES:

[1] F. Blaschke. “A New Method for the Estructural Decoupling of AC Induction Machines”. Cmj Rec. IFAC, Duessektorf. Genmny, pages 1-15, Oct. 1971.

[2] 1. Takahashi, Y. Ohmori. “High-Performance Direct Torque Control of an Induction Motor?. IEEE Trons. on Indu.~rriol Applicutions, 25(2):257- 262. MarcWApril 1989.

[3] M. Depenbmk. “Direct Self-Control (DSC) of Inverter-Fed Induction Machine”. IEEE Trans. on Power Elecrronicr. 3(4):42M29, October 1988.

[4] D. Casadei. G. Sera, A. Tani. “Implementation of a Direct Torque Control Algorithm for Induction Motors Based on Discrete Space Vector Modulation”. IEEE Trans. on Power Electronics. 15(4):769-777, July 2Mm.

[5] C. Manins, X. Roboarn. T.A. Meynard. A. Carvalho. “Switching frequency lmposition and Ripple Reduction in DTC Drives by Using a Multilevel Converer”. IEEE Trans. on Power Electmnicr. 17(2):28& 297, March 2002.