# Direct Torque Control and Sensor-Less Control of Induction Machine

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Part of the Power Systems book series (POWSYS,volume 0)

## Introduction

The application of vector control method for variable speed induction motor drives has been described in chapter 3. Generally, a closed loop vector control scheme results in a complex control structure as it consists of the following components;

1. 1

PID controller for motor flux and toque

2. 1

Current and/or voltage decoupling network

3. 1

Complex coordinate transformation

4. 1

Two axis to three axis transformation

5. 1

voltage or current modulator

6. 1

Flux and torque estimator

7. 1

PID speed controller

In a direct torque control system introduced by Takahashi and Depenbrock independently in 1986, the first five components are replaced by two hysteresis comparators and a selection table1 − 3. This method therefore, results in highly simplified control structure compared to vector control. In the vector control scheme, it is assumed that the controllable power source can force any desired wave shape and value of current into the stator winding. But in practical circuits an inverter can produce only seven discrete space vector values of the actuating variable. In most cases none of these values is exactly equal to the desired instantaneous value of the space vector. Although by using high switching frequency in a PWM inverter the desired curves of the actuating variable can be sufficiently approximated. However, for high power drives, the switching frequency can not be more than 200-300 Hz due to economic reasons. Thus, in high power drives, it is very difficult to apply a current wave shape of desired magnitude and shape. The vector control therefore, can not provide very fast control required in many drives.

In direct torque control instantaneous values of torque and flux are calculated from primary variables and controlled independently by using an optimum switching table. The controllers for a direct torque control drive do not require complex coordinate transformation essential in all vector controlled drives. Instead the decoupling of non-linear ac motor structure is obtained by the use of ‘on –off’ control of inverter switches. The voltage vector is selected from the inverter feeding the motor with the help of hysteresis controllers.

### Keywords

• Induction Motor
• Induction Machine
• Voltage Vector
• Direct Torque Control
• Induction Motor Drive

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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## References

1. Depenbrock, M.: Direct Self-control (DSC) of Inverter Fed Induction Machine. IEEE Transactions on Power Electronics 3(4), 420–429 (1988)

2. Takahashi, I., Ohmori, Y.: High Performance Direct Torque Control of an Induction Motor. IEEE Transactions on Industry Applications 25(2), 257–265 (1989)

3. Takahashi, I., Noguchi, T.: A new quick response and high efficient control strategy of an induction motor. IEEE Transaction Industry Application 22(5), 457–464 (1986)

4. Ludke, I., Jane, M.G.: A comparative study of high Performance speed Control strategies for voltage Source PWM Inverter fed Induction Motor Drives. In: Seventh International Conference on Electric Machines and Drives, UK (September 1995)

5. Baader, U., Depenbrock, M.: Direct Self Control (DSC) of inverter fed induction machine: A basis for Speed control without speed measurement. IEEE Transaction Industry Application 28, 581–588 (1992)

6. Nash, J.N.: Direct torque control, Induction motor vector control, without an encoder. IEEE Transaction Industry Application 33(2), 333–341 (1997)

7. Buja, G.S., Kazmierkowski, M.P.: Direct torque control of PWM Inverter -Fed AC motors- A survey. IEEE Transaction Industrial Electronics 51(4), 744–757 (2004)

8. Bose, B.K.: Modern Power Electronics and AC Drives. Pearson Education Inc., London (2002)

9. Buja, G.: A new control strategy of Induction Motor drives: The direct flux and torque control. IEEE Industrial Electronics Newsletter 45, 14–16 (1998)

10. Holtz, J.: Sensorless Speed and position control of Induction Motors: Tutorial. In: IEEE Industrial Electronics Annual Conference, IECON (November-December 2001)

11. Ohtami, T., Takada, N., Tanaka, K.: Vector Control of Induction Motor without Shaft encoder. IEEE Transactions on Industry Applications 28(1), 157–165 (1992)

12. Holz, J.: Sensorless Position Control of Induction Motors-an emerging technology. IEEE Transactions on Industrial Electronics 45(6), 840–852 (1998)

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14. Kim, Y.R., Sul, S.K., Park, M.H.: Speed sensorless vector control of induction motor using extended Kalman filter. IEEE Transaction Industry Applications 30(5), 1225–1233 (1994)

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### Cite this chapter

Ahmad, M. (2010). Direct Torque Control and Sensor-Less Control of Induction Machine. In: High Performance AC Drives. Power Systems, vol 0. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-13150-9_4