PV-Battery Powered Direct Torque ControlledSwitched Reluctance Motor Drive


 Categorized as one of the renewable energies, Photo- Voltaic system has a great potential compared to its counterparts of renewable energies. This paper deals with the design of a Photovoltaic (PV)-Battery fed Switched Reluctance Motor(SRM). The system mainly composed of a PV module, boost converter, rechargeable battery, bidirectional converter, asymmetric bridge converter, SRM and system controllers. The main problems of SRM are high torque ripple, acoustic noise and vibration problems. In order to reduce these problems, a new direct torque control of 3.5 kW 8/6 SRM is proposed, which is simple and can be implemented with low cost processor. It can be seen from the simulation results that this scheme has well regulated the torque output of the motor with in hysteresis band. The proposed system assures its suitability for solar applications like solar vehicles, solar water pumping system and floor mills in hilly and isolated areas.


  1. PV module
  2. Switched reluctance motor
  3. Direct torque control
  4. Battery energy storage system



Figure 1. (a)PV-Battery fed Induction Motor drive (b) PV-Battery Switched Reluctance Motor drive


Figure 2. Variation of PV output voltage and current due variation in solar Radiation

Figure 3. Control of flux vector with in hysteresis band

Figure 4. Flux trajectory in d-q plane


Figure 5. Current waveform of different phases

Figure 6. Control of torque in hysteresis band

Figure 7. Flux waveform of different phases


 The proposed scheme reduces dc link voltage there by reducing capacitor size and insulation level. A single stage conversion is also possible without the use of boost converter. The advantage of using asymmetric bridge converter is freedom to control individual phase independently and no shoot through fault. Torque ripple in the SRM can be eliminated by Direct Torque Control technique. The results indicate that DTC of SRM can directly regulate the torque output of the motor within a hysteresis band.


 [1] Jewell W.T and Ramkumar R “The history of utility –interactive photovoltaic generation”,IEEE/PES procedings ,Vol 30 pp1-5,Feb 1988.

[2] J. Applebaum J and Sarma M.S;“The operation of permanent magnet dc motors powered by a common source of solar cells,.” IEEE Trans. On EC., ,Vol. 4, pp.635-641, dec 1989 .

[3] Putta Swamy C L, Singh Bhim and Singh B P; “Dynamic performance of permanent magnet brushless DC powered by a PV array for water pumping,. ”Journel of Solar materials and Solar cells, ,Vol. 36, No.2 pp.187-200,1995

[4] Bhat S.R, Pittet A and Sonade B S; “Performance optimization ofinduction motor pump system using photovoltaic source,.”IEEE Transon Industrial Applications., ,Vol. 23, No 6 pp.955-1000, Nov/Dec 1987.

[5] Daud, and M. Mahmoud; “Solar Power Induction Motor Drive WaterPump Operating on a Desert Well, Simulation and Field Test”,,.” IEEE Trans.on Renewable Energy, ,Vol. 30, pp.701-714,2005.

Single Stage PV System based Direct Torque Controlled PMSM Drive for Pump Load Application


 This paper presents design and modelling of single stage standalone PV based PMSM (Permanent Magnet Synchronous Motor) drive. Standalone power supply system is more feasible and convenient option for water pumping applications in irrigation. Three phase DTC (Direct Torque Control) VSI (Voltage Source Inverter) is presented for supplying the PMSM for variation in solar irradiation to control the flow of water in pumping application. MATLAB/SIMULINK environment is used for modeled the proposed single stage standalone PV system based PMSM drive and performance is investigated under change in solar irradiation.


  1. Direct Torque Control
  2. PMSM Drive
  3. Solar PV
  4. Water Discharge System



Fig. 1 System configuration of Single stage sensor less standalone solar PV based PMSM drive.


Fig.2 Steady state performance for single stage standalone PV based permanent magnet synchronous motor drive

Fig.3 Transient performance under change in irradiation


 A single stage off-grid solar photo voltaic system has been modeled using the PMSM employed for centrifugal pump load application. The proposed single stage standalone PV system reduces component count, eliminates intermediate power conversion stage and achieves high conversion efficiency for pumping application. The proposed single stage system gives adequate control on PMSM speed under wide variation in solar irradiation and employing DTC control using three-phase VSl.


[1] A. Khaligh and O.C. Onar , Energy harvesting solar, wind, and ocean energy conversion systems, CRC Press, New York, 20 I O.

[2] R. Teodorescu, M. Liserre and P. Rodriguez, Grid Converters for Photovoltaic and Wind Power Systems, I st edition, John Wiley, United Kingdom, 2011.

[3] M. G Villalva, 1. R. Gazoli and E.R. Filho, “Comprehensive Approach to Modeling and Simulation of Photovoltaic Arrays,” IEEE Trans. Power Electronics, vol. 24, no. 5, pp. 1198-1208, Mar. 2009.

[4] M. Matsui, T. Kitano, D. H. Xu and Z. Q. Yang, “A new maximum photovoltaic power tracking control scheme based on power equilibrium at dc link,” Proc. IEEE Industry Application Con!, Oct. 1999, vol. 2, pp. 804-809.

[5].T. K. Mikihiko and M. De-H. Xu, “Power sensor-less MPPT control scheme utilizing power balance at dc link – system design to ensure stability and response,” Proc IEEE IECON Con!, Dec. 200 I, pp. 1309-1314.

Space Vector Pulse Width Modulation Fed Direct Torque Control Of Induction Motor Drive Using Matlab-Simulink


Now a day’s induction motor drives are highly demanding to design both mechanical and electrical drive system which is used widely in many industrial applications. Recent years many mathematical models for induction motor drive using Simulink models are employed. Scalar and Vector control method can be applied to induction motors in three phases symmetric as well as unsymmetrical two-phase form. The mathematical and Simulink operation of the induction motor drive can be studied and it is equivalent to a DC motor by the vector control method. With the combined performance of the numerical electronics and power electronics we are capable to smoothly control the variable speed and torque in low power industrial operations. With the help of technological achievements, several command and control techniques are developed by the technologists to control the time, flux and torque of the industrial electrical machine drives. The direct torque control (DTC) technique is one of the most advanced mechanisms in control operation of torque and speed. This technique with SVPWM gives fine regulation without rotational speed controlled feedback. The electromagnetic torque and stator flux are estimated in DTC technique only stator currents and voltage and it is independent of the parameters of the motor except for the Rs i.e. stator resistance [7].


  1. Controller
  2. DTC
  3. IDM
  4. SVPWM and switching table.




 Fig.1. DTC block diagram



Fig.2. Electromagnetic torque

Fig.3. Rotor speed

Fig.4. Stator current

Fig.5. d-axis stator flux

Fig.6. q-axis stator flux

Fig.7. Electromagnetic torque

Fig.8. Rotor speed

Fig.9. Trajectory of direct axis stator and quadrature axis

flux (stationary reference frame)

Fig.10. Electromagnetic torque

Fig.11. Rotor speed

Fig.12. Direct axis stator flux

Fig.13. Quadrature axis stator flux

Fig.14. Direct axis stator current

Fig.15. Quadrature axis stator current

Fig.16. Stator flux trajectory

Fig.17. Rotor flux trajectory


The proposed paper highlights to create a Simulink model of  DTC in induction motor drive. The DTC technique allows the decoupled control of torque and stator flux operate indipendently. The control process is simulated with the help of simpower system MATLAB Simulink block set and Sector determination with open-loop induction motor drive is obtained. In conventional DTC technique, high torque ripple is produced because the voltage space vector which are considered is applied for the whole switching period without considering the torque error value. This torque ripple can be minimized in order to achieve a smooth operation of the drive system and its performances, by changing the duty cycle ratio of the voltage vector which are selected during each switching cycle period, based on the stator flux position and torque error magnitude. This constitutes the basic of SVPWM technique. here simulate DTC scheme based on SVPWM technique and comparative study of conventional DTC-SVM scheme is derived and studied.


[1] Takahashi Isao, Noguchi Toshihiko, ,,’’A New Quick-Response IEEE Transactions on Industry Applications , Vol. IA-22No-5, Sept/Oct 1986.


Direct Torque Control of Brushless DC Drives With Reduced Torque Ripple


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.


  1. Brushless dc (BLDC) drives
  2. Direct torque control (DTC)
  3. Permanent-magnet motor




Fig. 1. Schematic of DTC BLDC drive.



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.


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.


[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.

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


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.


  1. Electric Drives
  2. AC Machines
  3. Direct Torque Control
  4. Space Vector Modulation




 Fig.  1. Classic DTC control block diagram


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.


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.


[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.

Review of Vector Control Strategies for Three Phase Induction Motor Drive



Induction motor drives are at the heart of modern industrial and commercial applications. With conventional control techniques, induction motor drives have shown less than expected dynamic performance. With vector control techniques emerging as potential replacement in induction motor drives, this paper aims at highlighting various vector control strategies. Direct and indirect vector controls along with sensorless vector control are presented. Various speed control techniques are presented through the use of conventional controllers and Intelligent Controllers. A critical analysis and comparison is made with other control strategies.


  1. Field oriented control
  2. Sensorless vector control
  3. Direct torque control
  4. Modulation
  5. Parameter estimation



Fig. 1. Block diagram of general vector control scheme


 The use of vector control has been presented for Induction motor drives. A number of vector control schemes have been presented with merits and demerits of each. Different controllers (conventional and intelligent controllers) have been used in various schemes of vector control strategy. Potentially DTC is proving to be superior to other vector control techniques. Contrast to field oriented controller, it is more robust, does not require any transformation, current controller, or rotor position measurement. However, an improvement in torque ripples is the demand of this scheme. Sensorless vector control offers low cost and more reliability, but operation of this scheme in low speed region is one of its biggest drawbacks.


[1] Bimal. K.Bose (2002) – “Modern Power Electronics & AC Drives”, Prentice Hall, ISBN 0-13-016743-6

[2] Rupprecht Gabriel. Werner Leonhard, and Craig J. Nordby, “Field- Oriented Control of a Standard AC Motor Using Microprocessors”, IEEE Transactions On Industrial Applications, Vol. IA-16, No. 2, pp. 186-192, March/April 1980.

[3] Masato Koyama, Masao Yano, Isao Kamiyama, And Sadanari Yano, “Microprocessor-Based Vector Control System For Induction Motor Drives With Rotor Time Constant Identification Function”, IEEE Transactions on Industry Applications, Vol. IA-22, No. 3, pp. 453-459, May/June 1986.

[4] Ramu Krishnan, and Aravind S. Bharadwaj, “A review of parameter sensitivity and adaptation in indirect vector controlled induction motor drive systems”, IEEE transactions on power electronics, Vol. 6, No. 1, pp.695-703, October 1991.

[5] Luis J. Garces, “Parameter Adaption for the Speed-Controlled Static AC Drive with a Squirrel-Cage Induction Motor”, IEEE Transactions on Industry Applications, Vol. IA-16, no. 2, pp. 173 -178, March/April 1980.




Direct torque control (DTC) is one method used in variable frequency drives to control the torque (and thus finally the speed) of three-phase AC electric motors. This involves calculating an estimate of the motor’s magnetic flux and torque based on the measured voltage and current of the motor.

Stator flux linkage is estimated by integrating the stator voltages. Torque is estimated as a cross product of estimated stator flux linkage vector and measured motor current vector. The estimated flux magnitude and torque are then compared with their reference values. If either the estimated flux or torque deviates too far from the reference tolerance, the transistors of the variable frequency drive are turned off and on in such a way that the flux and torque errors will return in their tolerant bands as fast as possible. Thus direct torque control is one form of the hysteresis or bang-bang control.

  1. Analysis and performance of the induction motor under hysteresis current controlled DTC
  2. Simplified SVPWM Algorithm for Neutral Point Clamped 3-level Inverter fed DTC-IM Drive
  3. A Constant Switching Frequency based Direct Torque Control Method for Interior Permanent Magnet Synchronous Motor Drives
  4. Transient and Steady States Analysis of Traction Motor Drive with Regenerative Braking and Using Modified Direct Torque Control (SVM-DTC)
  5. Improved Direct Torque Control of Induction Motor
  6. Direct torque control of squirrel cage induction motor for optimum current ripple using three level inverter
  7. Study of Induction Motor Drive with Direct Torque Control Scheme and Indirect Field Oriented Control Scheme Using Space Vector Modulation
  8. Direct Torque Control of Induction Motor Drive with Flux Optimization
  9. Direct Torque Control of Induction Motor With Constant Switching Frequency
  10. Direct Torque Control Based on Space Vector Modulation with Adaptive Stator Flux Observer for Induction Motors
  11. Novel Direct Torque Control Based On Space Vector Modulation With Adaptive Stator Flux Observer For Induction Motors
  12. Study On Speed Sensorless SVM-DTC System Of PMSM
  13. Direct Torque Control of Induction Motors with Fuzzy Minimization Torque Ripple
  14. PMSM Speed Sensor less Direct Torque Control Based On EKF
  15. Simulink Model of Direct Torque Control of Induction Machine
  16. High Performance of Space Vector Modulation Direct Torque Control SVM-DTC Based on Amplitude Voltage and Stator Flux Angle



Direct Torque Control of Induction Motors with Fuzzy Minimization Torque Ripple

Direct torque control (DTC) is a new method of induction motor control. The key issue of the DTC is the strategy of selecting proper stator voltage vectors to force stator flux and developed torque within a prescribed band. Due to the nature of hysteresis control adopted in DTC, there is no difference in control action between a larger torque error and a small one. It is better to divide the torque error into different intervals and give different control voltages for each of them. To deal with this issue a fuzzy controller has been introduced. But, because the number of rules is too high some problems arise and the speed of fuzzy reasoning will be affected. In this paper, a comparison between a new fuzzy direct-torque control (DTFC) with space vector modulation (SVM) is made. The principle and a tuning procedure of the fuzzy direct torque control scheme are discussed. The simulation results, which illustrate the performance of the proposed control scheme in comparison with the fuzzy hysteresis connected of DTC scheme are given.
1. Induction machine
2. Direct torque control
3. Fuzzy logic
4. Space vector modulation


Fig. 1. A novel direct torque control scheme for ac motor drives (DTC) with fuzzy hysteresis and space vector modulation


Fig.2. response of trajectory of flux, electromagnetic torque and stator current for scheme of simulation results of fuzzy-hysteresis regulators connected

Fig. 3. response of trajectory of flux, electromagnetic torque and stator current for scheme of DTC- fuzzy hysteresis with SVM

In this paper, a fuzzy direct torque control with space vector modulation is analyzed in comparison to fuzzy hysteresis connected of DTC. The results obtained by numerical simulation are given. In short, the advantages of proposed fuzzy direct torque control using space vector modulation technique in comparison with a fuzzy hysteresis of DTC are the following:
– Reduced torque and flux distortion;
– Constant switching frequency thanks to apply SVM;
– Fast torque response because of the use of fuzzy controller;
– Lower sampling time;
– No problems during Low-speed operation;
– No current and torque distortion caused by sector changes.
[1] Casadei, D., serra, G., Tani, A, «Performance analysis of a DTC control scheme for induction motor in the low speed range», in proceeding of EPE, (1997), p.3.700-3.704, Trondheim.
[2] Depenbrok. M, «Direct self-control (DSC) of inverter fed induction machine», In: IEEE Trans. On PE (1988), Vol. PE-3, No4, October 1988, p 420-429.
[3] A. Cataliotti, G. Poma: “A Fuzzy approach for easy and robust control of an induction motor”. EPE 97, pp 2.421-2.425, 1997.
[4] J. R G Schonfield,”Direct torque control-DTC”, ABB Industrial Systems Ltd.
[5] Ned Gulley, J.-S. Roger Jang: Fuzzy Logic Toolbox for Use With Matlab”. The Math Works inc, Natick, Mass, 1996.

Direct Torque Control Based on Space Vector Modulation with Adaptive Stator Flux Observer for Induction Motors

This paper describes a combination of direct torque control (DTC) and space vector modulation (SVM) for an adjustable speed sensor less induction motor (IM) drive. The motor drive is supplied by a two-level SVPWM inverter. Using the IM model in the stator – axes reference frame with stator current and flux vectors components as state variables. In this paper, a conventional PI controller is designed accordingly for DTC-SVM system. Moreover, a robust full-order adaptive stator flux observer is designed for a speed sensor less DTC-SVM system and a new speed adaptive law is given. By designing the observer gain matrix based on state feedback control theory, the stability and robustness of the observer systems is ensured. Finally, the effectiveness and validity of the proposed control approach is verified by simulation results.
1. DTC
2. Stator Flux Observer
3. Torque Ripple


Fig. 1 Block Diagram of DTC-SVM system

Fig. 2 Torque waveform

Fig. 3 Speed waveform

Fig. 4 Stator Flux waveforms

Fig. 5 Stator flux Trajectory
Case B: DTC with PI controller

Fig. 6 Torque waveform

Fig. 7 Speed waveform

Fig. 8 Stator Flux waveforms

Fig. 9 Stator flux Trajectory
Case C: DTC with Stator Flux observer

Fig. 10 Torque waveform

Fig. 11 Speed waveform

Fig. 12 Stator Flux waveforms

Fig. 13 Stator flux Trajectory

A novel DTC-SVM scheme has been developed for the IM drive system, In this control method, a SVPWM inverter is used to feed the motor, the stator voltage vector is obtained to fully compensate the stator flux and torque errors. Furthermore, a robust full-order adaptive flux observer is designed for a speed sensor-less DTC-SVM system. The stator flux and speed are estimated synchronously. By designing the constant observer gain matrix, the robustness and based on state feedback stability of the observer systems is ensured. Therefore, the proposed sensor-less drive system is capable of steadily working in very low speed, has much smaller torque ripple and exhibits good dynamic and steady-state performance.

[1] I. Takahashi and T. Noguchi, “A new quick-response and high efficiency control strategy of an induction motor,” IEEE Trans. Ind. Appl.,vol. IA-22, no. 5, pp. 820–827, 1986.
[2] Y. S. Lai and J. H. Chen, “A new approach to direct torque control ofinduction motor drives for constant inverter switching frequency andtorque ripple reduction,” IEEE Trans. Energy Convers., vol. 16, no. 3,pp. 220–227, 2001.
[3] S. Mir, M. E. Elbuluk, and D. S. Zinger, “PI and fuzzy estimators for tuning the stator resistance in direct torque control of induction machines,” IEEE Trans. Power Electron., vol. 13, no. 2, pp. 279–287,1998.
[4] F. Bacha, R. Dhifaoui, and H. Buyse, “Real-time implementation ofdirect torque control of an induction machine by fuzzy logic controller,” in Proc. ICEMS, 2001, vol. 2, pp. 1244–1249.
[5] A. Arias, J. L. Romeral, and E. Aldabas, “Fuzzy logic direct torquecontrol,” in Proc. IEEE ISIE, 2000, vol. 1, pp. 253–258.

Study of Induction Motor Drive with Direct Torque Control Scheme and Indirect Field Oriented Control Scheme Using Space Vector Modulation

Induction motors are the starting point to design an electrical drive system which is widely used in many industrial applications. In modern control theory, different mathematical models describe induction motor according to the employed control methods. Vector control strategy can be applied to this electrical motor type in symmetrical three phase version or in unsymmetrical two phase version. The operation of the induction motor can be analyzed similar to a DC motor through this control method. With the Joint progress of the power electronics and numerical electronics it is possible today to deal with the axis control with variable speed in low power applications. With these technological projections, various command approaches have been developed by the scientific community to master in real time, the flux and the torque of the electrical machines, the direct torque control (DTC) scheme being one of the most recent steps in this direction. This scheme provides excellent properties of regulation without rotational speed feedback. In this control scheme the electromagnetic torque and stator flux magnitude are estimated with only stator voltages and currents and this estimation does not depend on motor parameters except for the stator resistance. In this dissertation report conventional DTC scheme has been described. Induction motor has been simulated in stationary d-q reference frame and its free acceleration characteristics are drawn. Conventional DTC scheme has been simulated with a 50 HP, 460V, 60 Hz induction motor. Literature review has been done to study the recent improvements in DTC scheme which somehow is able to overcome the drawbacks of conventional one. The space vector modulation technique (SVPWM) is applied to 2 level inverter control in the vector control based induction motor drive system, thereby dramatically reducing the torque ripple. Later in this project space vector PWM technique will be applied to DTC drive system to reduce the torque ripple.


Fig.1 Block diagram of conventional DTC scheme for IM drives

Fig.2 Electromagnetic torque

Fig.3 Rotor speed

Fig.4 Stator current

Fig.5 d-axis stator flux

Fig.6 q-axis stator flux

Fig.7 Electromagnetic torque

Fig.8 Rotor speed

Fig.9 Trajectory of d axis and q axis stator flux in stationary reference frame

Fig.10 Electromagnetic torque

Fig.11 Rotor speed

Fig.12 d-axis stator flux

Fig.13 q-axis stator flux

Fig.14 d-axis stator current

Fig.15 q-axis stator current

Fig.16 Mean value of Phase voltage of inverter

Fig.17 Line voltage output of inverter

Fig.18 Electromagnetic torque

Fig.19 Rotor speed

Fig.20 q-axis stator flux

Fig.21 d-axis stator flux
For any IM drives, Direct torque control is one of the best controllers proposed so far. It allows decoupled control of motor stator flux and electromagnetic torque. From the analysis it is proved that, this strategy of IM control is simpler to implement than other vector control methods as it does not require pulse width modulator and co-ordinate transformations. But it introduces undesired torque and current ripple. DTC scheme uses stationary d-q reference frame with d-axis aligned with the stator axis. Stator voltage space vector defined in this reference frame control the torque and flux. The main inferences from this work are:
1. In transient state, by selecting the fastest accelerating voltage vector which produces maximum slip frequency, highest torque response can be obtained.
2. In steady state, the torque can be maintained constant with small switching frequency by the torque hysteresis comparator by selecting the accelerating vector and the zero voltage vector alternately.
3. In order to get the optimum efficiency in steady state and the highest torque response in transient state at the same time, the flux level can be automatically adjusted.
4. If the switching frequency is extremely low, the control circuit makes some drift which can be compensated easily to minimize the machine parameter variation. The estimation accuracy of stator flux is very much essential which mostly depends on stator resistance because an error in stator flux estimation will affect the behaviour of both torque and flux control loops. The torque and current ripple can be minimized by employing space vector modulation technique.

[1] B. K.Bose. 1997. Power Electronics and Variable Frequency Drives. IEEE Press, New York.
[2] Kazmierkowski, R.Krishnan, Blaabjerg, Control in Power Electronics, Selected Problems.
[3] Takahashi Isao, Noguc hi Tos hihiko, „ıA New Quick-Response and High-Efficiency Control Strategy of an Induction Motorıı, IEEE Transactions on Industry Applications, Vol. IA-22 No-5, Sept/Oct 1986.
[4] Thomas G.Habetler, Francesco Profumo, Michele Pastorelli and Leon M. Tolbert “Direct Torque Control of IM us ing Space Vector Modulation” IEEE Transactions on Industry Applications, Vol.28, No.5, Sept/Oct 1992.
[5] E.Bassi, P. Benzi, S. Buja, “A Field Orientation Scheme for Current-Fed Induction Motor Drives Based on the Torque Angle Closed-Loop Control” IEEE Transactions on Industry Applications, Vol. 28, No. 5, Sept./ Oct. 1992.