Direct torque control of squirrel cage induction motor for optimum current ripple using three level inverter

ABSTRACT:

Control of induction motor is most precisely required in many high performance applications. With the development in power electronic field various control methods for control of induction motor have been developed. Among these Direct torque control (DTC) seems to be particularly interesting, being independent of machine rotor parameters and requiring no speed or position sensors. In addition to the simple structure it also allows a good torque control in transient and steady state conditions. The disadvantage of using DTC is that it results in high torque and flux ripple and variable switching frequency of voltage source inverter, owing to the use of hysteresis controllers for torque and flux loop. In order to overcome these problems, various methods have been proposed by several researchers like variable hysteresis band comparators, space vector modulation, predictive control schemes and intelligent control techniques. However these methods have diminished the main feature of DTC that is simple control structure. This report presents constant switching frequency based torque and flux controllers to replace conventional hysteresis based controllers where almost fixed switching frequency with reduced torque and flux ripple is obtained by comparing the triangular waveforms with the compensated error signals

KEYWORDS:

1.3-phase VSI
2. Torque controller
3. Flux controller

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:


Fig.1. Block diagram of conventional DTC method


Fig.2. MATLAB/SIMULINK Model of the DTC Drive

Fig.3. Torque response (a) Conventional DTC scheme (b) Improved DTC Scheme


Fig.4. Speed and Torque response for (a) Conventional DTC scheme (b) Improved DTC scheme

Fig.5. Circular flux locus (a) conventional DTC scheme (b) Improved DTC scheme


Fig.6. 3-phase line-line voltages and currents (a) Conventional DTC scheme (b) Improved DTC scheme

CONCLUSION:

In this paper a detailed comparison between the conventional DTC and improved DTC scheme is made with help of some Matlab simulation results and hence it is shown that a significant reduction in torque and flux ripple can be achieved with the improved DTC scheme also with improved controllers the switching frequency which is constant can be varied by varying the frequency of the triangular carrier waveforms of the torque controller

REFERENCES:

  1. 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, Sep.–Oct. 1986. [2] J-K. Kang, D-W Chung, S. K. Sul, (2001) “Analysis and prediction of inverter switching frequency in direct torque control of induction machine based on hysteresis bands and machine parameters”, IEEE Transactions on Industrial Electronics, Vol. 48, No. 3, pp. 545-553.
  2. Casadei, G.Gandi,G.Serra,A.Tani,(1994)“Switching strategies in direct torque control of induction machines,in Proc. of ICEM’94, Paris (F), pp. 204-209.
  3. J-K. Kang, D-W Chung and S.K. Sul, (1999) “Direct torque control of induction machine with variable amplitude control of flux and torque hysteresis bands”, International Conference on electric Machines and Drives IEMD’99,pp.640-642.
  4. Vanja Ambrozic, Giuseppe S. Buja, and Roberto Menis, ”Band- Constrained Technique for Direct Torque Control of Induction Motor”, IEEE Trans. On industrial electronics , vol. 51, no. 4, august 2004, pp.776-784

Analysis of Performance of the Induction Motor under Hysteresis Current Controlled DTC

ABSTRACT:

The direct torque control method is a powerful control technique for specially induction motor drive due its fast dynamic torque response. It originates in the fact that torque and flux is directly controlled by instantaneous space voltage vector unlike. Field Oriented Control (FOC) and smooth control of drives are being utilized to perform real time simulation on the ac motor variables, such as electromagnetic torque, fluxes, mechanical speed, etc. For the reason, direct torque control gradually has been used in the field requiring fast response since its introduction in the mid-1980. Even though the direct torque control has several problems. These problems are: (I) low switching frequency and variation in speed; (2) the increase of the torque ripple in the low speed region; (3) the short control period (25 /ls) for the good performance. To solve the problems of Direct Torque Control, several studies were carried out. This paper improves one of the drawbacks of Direct Torque Control with the Hysteresis direct torque control. In some papers to avoid these problems 2 level inverter with induction motor has been used but it is very complicated and didn’t show large improvement. In this paper, Hysteresis direct torque control method with 3 level inverter has been implemented and its effectiveness is compared with conventional direct torque control with 2 level inverter by using Matlab/Simulink.

KEYWORDS:

  1. Direct Torque Control
  2. Hysteresis Direct Torque Control
  3. Two Level Inverter
  4. Three Level Inverter.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Basic DTC Scheme

Induction Motor Hysteresis Current Controlled DTC

SIMULINK BLOCK DIAGRAM:

Simulink model of the direct torque controlled induction motor with Conventional DTC.

Induction Motor Hysteresis Current Controlled DTC

Simulated two level phase voltage s of Inverter with Conventional DTC and Simulated output wave form of the Id, Iq currents Drawns from Induction motor with conventional DTC

Induction Motor Hysteresis Current Controlled DTC

Fig.5. Simulated output wave form of the Reference and Simulated output wave form of the and actual speeds of the Induction Reference and actual Torque of the motor with conventional DTC Induction motor with conventional DTC

Induction Motor Hysteresis Current Controlled DTC

Simulated XY plot wave form of .Simulated phase voltages of inverter with flux current with conventional DTC. Hysteresis current controlled DTC

Induction Motor Hysteresis Current Controlled DTC

Simulated XY plot wave form of flux current with Hysteresis current controlled DTC

Induction Motor Hysteresis Current Controlled DTC

CONCLUSION:

In the present work initially the modeling and simulation of a three phase three level synchronous link converter using hysteresis controller and adaptive hysteresis controller is presented. The hysteresis controller for the 3 level converters is designed and developed in the Simulink model. The modeling, simulation of a direct torque and direct flux control of an induction motor fed from a three phase three level inverter is presented in this paper. The effectiveness of the proposed 3 level inverter fed induction motor drive controlled with hysteresis current controlled DTC is compared with 2 level inverter fed induction motor drive with conventional DTC and it is observed in simulation results the improvement in low speed operation performance of induction motor for high power three level inverter applications.

REFERENCES:

[I] Rakesh Kantaria and S.K.Joshi “A review on power quality problems and solutions” Power electronics National Conference November 2008.

[2]IEEE Std. 1159 – 1995, “Recommended Practice for Monitoringn Electric Power Quality.

[3]Yan Li, Chengxiong Mao, Buhan Zhang, Jie Zeng, “Voltage Sag Study for a Practical Industrial Distribution Network”, 2006 International Conference on Power System Technology, pp.I-4, Oct., 2006.

[4]Understanding FACTS: Concepts and Technology of Flexible AC Transmission Systems. Narain G. Hingorani, Laszlo Gyugyi. Wiley IEEE press.

[5] J. G. Nielsen, M. Newman, H. Nielsen, and F. Blaabjerg, “Control and testing of a dynamic voltage restorer (DVR) at medium voltage level,”iEEE Trans. Power Electron., vol. 19, no. 3,p.806,May 2004

 

 

Direct Torque Control of Induction Motor With Constant Switching Frequency

ABSTRACT

Direct Torque Control (DTC) has become a popular technique for the control of induction motor drives as it provides a fast dynamic torque response and robustness to machine parameter variations. Hysteresis band control is the one of the simplest and most popular technique used in DTC of induction motor drives. However the conventional direct torque control has a variable switching frequency which causes serious problems in DTC. This paper presents the DTC of induction motor with a constant switching frequency torque controller. By this method constant switching frequency operation can be achieved for the inverter. Also the torque and flux ripple will get reduced by this technique. The feasibility of this method in minimizing the torque ripple is verified through some simulation results.

 

KEYWORDS

  1. Direct torque control(DTC)
  2. Constant switching frequency
  3. Induction motor
  4. Three phase inverter.

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

Fig. 1. Block diagram of conventional DTC

 

EXPECTED SIMULATION RESULTS

Fig. 2. Step response of torque (a) hysteresis based (b) modified torque controller

Fig. 3. Response of torque and speed for squre wave torque reference in (a) hysteresis based (b)modified torque controller

Fig. 4.(a) Hysteresis based controller (b) modified torque controller

Fig. 5. flux waveform for (a) hysteresis based (b)modified torque controller

Fig. 6. flux locus for (a) hysteresis based (b)modified torque controller

Fig. 7. Frequency spectrum of the switching pattern Sb for (a) hysteresis based (b) modified torque controller

 

CONCLUSION

This paper presents a constant switching frequency torque controller based DTC of induction motor drive. By using the modified torque controller the switching frequency of the inverter also becomes constant at 10 kHz. As a result, the harmonic contents in the phase currents are very much reduced. So the phase current distortion is reduced. The torque ripple is also reduced by replacing the torque hysteresis controller with the modified torque controller. Moreover, with the modified torque controller, an almost circular stator flux locus is obtained. Without sacrificing the dynamic performance of the hysteresis controller, the modified scheme gives constant switching frequency. This work can be implemented using DSP. The work can be extended by increasing the switching frequency above audible range, i.e. more or equal to 20 kHz. This is an effective way to shift the PWM harmonics out of human audible frequency range. With high switching frequency the harmonic content of stator current will be reduced significantly.

 

REFERENCES

  1. John R G Schofield, (1995) “Direct Torque Control – DTC”, IEE, Savoy Place, London WC2R 0BL, UK.
  2. Tang, L.Zhong, M.F.Rahman, Y.Hu,(2002)“An Investigation of a modified Direct Torque Control Strategy for flux and torque ripple reduction for Induction Machine drive system with fixed switching frequency”, 37th IAS Annual Meeting Ind. Appl. Conf. Rec., Vol. 1, pp. 104-111.
  3. J-K. Kang, D-W Chung, S. K. Sul, (2001) “Analysis and prediction of inverter switching frequency in direct torque control of induction machine based on hysteresis bands and machine parameters”, IEEE Transactions on Industrial Electronics, Vol. 48, No. 3, pp. 545-553.
  4. Casadei, G.Gandi,G.Serra,A.Tani,(1994)“Switching strategies in direct torque control of induction machines,in Proc. Of ICEM’94, Paris (F), pp. 204-209.
  5. J-K. Kang, D-W Chung and S.K. Sul, (1999) “Direct torque control of induction machine with variable amplitude control of flux and torque hysteresis bands”, International Conference on Electric Machines and Drives IEMD’99, pp. 640-642

Speed Control of Induction Motor Using New Sliding Mode Control Technique

ABSTRACT

Induction Motors have been used as the workhorse in the industry for a long time due to its easy build, high robustness, and generally satisfactory efficiency. However, they are significantly more difficult to control than DC motors. One of the problems which might cause unsuccessful attempts for designing a proper controller would be the time varying nature of parameters and variables which might be changed while working with the motion systems. One of the best suggested solutions to solve this problem would be the use of Sliding Mode Control (SMC). This paper presents the design of a new controller for a vector control induction motor drive that employs an outer loop speed controller using SMC. Several tests were performed to evaluate the performance of the new controller method, and two other sliding mode controller techniques. From the comparative simulation results, one can conclude that the new controller law provides high performance dynamic characteristics and is robust with regard to plant parameter variations.

 

KEYWORDS:

  1. Induction Motor
  2. Sliding Mode Control
  3. DC Motors
  4. PI Controller

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

Induction motor drive system with sliding mode controller

Fig. 1 Induction motor drive system with sliding mode controller

EXPECTED SIMULATION RESULTS:

                           Rotor speed tracking performance (b)Rotor speed tracking error (c)Control effort Rotor speed tracking performance (b)Rotor speed tracking error (c)Control effort Rotor speed tracking performance (b)Rotor speed tracking error (c)Control effort

Fig.2 (a)Rotor speed tracking performance  (b)Rotor speed tracking error   (c)Control effort

image005 image006 image007

Fig.3 (a)Rotor speed tracking performance  (b)Rotor speed tracking error   (c)Control effort

image008 image009 image010

Fig.4 (a)Rotor speed tracking performance  (b)Rotor speed tracking error   (c)Control effort

 

CONCLUSION

In this paper, new technique to reduced chattering for sliding mode control is submitted to design the rotor speed control of induction motor. To validate the performances of the new proposed control law, we provided a series of simulations and a comparative study between the performances of the new proposed sliding mode controller strategy and those of the Pseudo and Saturation sliding mode controller techniques. The sliding mode controller algorithms are capable of high precision rotor speed tracking. From the comparative simulation results, one can conclude that the three sliding mode controller techniques demonstrate nearly the same dynamic behavior under nominal condition. Also, from the simulation results, it can be seen obviously that the control performance of the new sliding mode controller strategy in the rotor speed tracking, robustness to parameter variations is superior to that of the other sliding mode controller techniques.

 

REFERENCES

  1. Wade, M.W.Dunnigan, B.W.Williams, X.Yu, ‘Position control of a vector controlled induction machine using slotine’s sliding mode control’, IEE Proceeding Electronics Power Application, Vol. 145, No.3, pp.231-238, 1998.
  2. I.Utkin, ‘Sliding mode control design principles and applications to electric drives’, IEEE Transactions on Industrial Electronics, Vol.40, No.1, pp. 23-36, February 1993.
  3. K.Namdam, P.C.Sen, ‘Accessible states based sliding mode control of a variable speed drive system’, IEEE Transactions Industry Application, Vol.30, August 1995, pp.373-381.
  4. Krishnan, ‘Electric motor drives: modelling, analysis, and control’, Prentice-Hall, New-Jersey, 2001.
  5. J.Wai, K.H.Su, C.Y.Tu, ‘Implementation of adaptive enhanced fuzzy sliding mode control for indirect field oriented induction motor drive’, IEEE International Conference on Fuzzy Systems, pp.1440-1445, 2003.

 

Analysis and Mathematical Modelling Of Space Vector Modulated Direct Controlled Matrix Converter

ABSTRACT:

Matrix converters as induction motor drivers have received considerable attention in recent years because of its good alternative to voltage source inverter pulse width modulation (VSI-PWM) converters. This paper presents the work carried out in developing a mathematical model for a space vector modulated (SVM) direct controlled matrix converter. The mathematical expressions relating the input and output of the three phase matrix converter are implemented by using MATLAB/SIMULINK. The duty cycles of the switches are modeled using space vector modulation for 0.5 and 0.866 voltage transfer ratios. Simulations of the matrix converter loaded by passive RL load and active induction motor are performed. A unique feature of the proposed model is that it requires very less computation time and less memory compared to the power circuit realized by using actual switches. In addition, it offers better spectral performances, full control of the input power factor, fully utilization of input voltages, improve modulation performance and output voltage close to sinusoidal.

KEYWORDS:

  1. Matrix Converter
  2. Space Vector Modulation
  3. Simulation Model
  4. Induction Motor

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

image001

Figure 1: Block diagram of simulation model for direct matrix converter

EXPECTED SIMULATION RESULTS:
image002

Figure 2: Result for sector identification

image003

Figure 3: Input and output voltage with passive load for q=0.5; R=135.95Ω, L=168.15mH, Vim=100 V, fo = 60Hz, fs = 2kHz

image004

Figure 4: Input and output voltage with passive load for q=0.866; R=135.95Ω, L=168.15mH, Vim=100 V, fo = 60Hz, fs = 2kHz

 image005

 Figure 5: Input and output voltage with loaded induction motor for q=0.5; 3hp, Rs =0.277Ω, Rr=0.183Ω, Nr=1766.9rpm, Lm=0.0538H, Lr=0.05606H, Ls=0.0533H,fo=60Hz, fs=2kHz

image006

Figure 6: Input and output voltage with loaded induction motor for q=0.866; 3hp, Rs =0.277Ω, Rr=0.183Ω, Nr=1766.9rpm, Lm=0.0538H, Lr=0.05606H, Ls=0.0533H, fo=60Hz, fs=2kHz
image007

Figure 7: Input current with passive load; R=135.95Ω, L=168.15mH, Vim=100 V, fo = 60Hz, fs = 2kHz (a) q=0.5, (b) q = 0.866
image008

 Figure 8: Input current with loaded induction motor for q=0.866; 3hp, Rs =0.277Ω, Rr=0.183Ω, Nr=1766.9rpm, Lm=0.0538H, Lr=0.05606H, Ls=0.0533H, fo=60Hz, fs=2kHz

 CONCLUSION:

The main constraint in the theoretical study of matrix converter control is the computation time it takes for the simulation. This constraint has been overcome by the mathematical model that resembles the operation of power conversion stage of matrix converter. This makes the future research on matrix converter easy and prosperous. The operation of direct control matrix converter was analysed using mathematical model with induction motor load for 0.866 voltage transfer ratio.

 REFERENCES:

[1]. A. Alesina, M.G.B.V., Analysis And Design Of Optimum-Amplitude Nine – Switch Direct AC-AC Converters. IEEE Trans. On Power. Electronic, 1989. 4.

[2]. D. Casadei, G.S., A. Tani, L. Zari, Matrix Converters Modulation Strategies : A New General Approach Based On Space-Vector Representation Of The Switch State. IEEE Trans. On Industrial Electronic, 2002. 49(2).

[3]. P. W. Wheeler, J.R., J. C. Claire, L. Empringham, A. Weinstein, Matrix Converters : A Technology Review. IEEE Trans. On Industrial Electronic, 2002. 49(2).

[4]. H. Hara, E.Y., M. Zenke, J.K. Kang, T. Kume. An Improvement Of Output Voltage Control Performance For Low Voltage Region Of Matrix Converter. In Proc 2004 Japan Industry Applications Society Conference, No. 1-48, 2004. (In Japanese). 2004

[5]. Ito J, S.I., Ohgushi H, Sato K, Odaka A, Eguchi N., A Control Method For Matrix Converter Based On Virtual Ac/Dc/Ac Conversion Using Carrier Comparison Method. Trans Iee Japan Ia 2004. 124-D: P. 457–463.

Indirect Vector Control of Induction Motor Using Sliding-Mode Controller

 

ABSTRACT:

The paper presents a sliding-mode speed control system for an indirect vector controlled induction motor drive for high performance. The analysis, design and simulation of the sliding-mode controller for indirect vector control induction motor are carried out. The proposed sliding-mode controller is compared with PI controller with no load and various load condition. The result demonstrates the robustness and effectiveness of the proposed sliding-mode control for high performance of induction motor drive system.

 KEYWORDS:

  1. Indirect vector control
  2. Sliding mode control
  3. PI controller
  4. Induction motor
  5. Speed control

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

image001

Figure 1: Indirect vector controlled induction motor drive

EXPECTED SIMULATION RESULTS:

 image002

Figure 2: Speed response of PI controller at no load

image003

Figure 3:Speed response of Sliding-mode controller at no load

image004

Figure 4: Speed response of PI controller at load

image005

Figure 5: Speed response of Sliding- mode controller at load

image006

Figure 6:X-Y plot of Rotor flux of PI controller

image007

Figure 7: x-v plot of Rotor flux of Sliding-mode controller

CONCLUSION:

In this paper sliding-mode controller for the control of an indirect vector-controlled induction motor was described. The drive system was simulated with sliding-mode controller and PI controller and their performance was compared. Here simulation results shows that the designed sliding-mode controller realises a good dynamic behaviour of the motor with a rapid settling time, no overshoot and has better performance than PI controller. Sliding-mode control has more robust during change in load condition.

.REFERENCES:

[1] B.K Bose “Modern power electronics and ac drives “Prentice-Hall OJ India, New Delhi, 2008.

[2] M.Masiala;B.Vafakhah,;A.Knght,;J.Salmon,;”Performa nce of PI and fuzzy logic speed control of field-oriented induction motor drive,” CCECE , jul. 2007, pp. 397-400.

[3] F.Barrero;A.Gonzalez;A.Torralba,E.Galvan,;L.G.Franqu elo; “Speed control of induction motors using a novel Fuzzy-sliding mode structure,”IEEE Transaction on Fuzzy system, vol. 10, no.3, pp. 375-383, Jun 2002.

[4] H.F.Ho,K.W.E.Cheng, “position control of induction motor using indirect adaptive fuzzy sliding mode control,” P ESA, , Sep. 2009, pp. 1-5.

[5] RKumar,R.A.Gupta,S.V.Bhangale, “indirect vector controlled induction motor drive with fuzzy logic based intelligent controller,” IETECH Journals of Electrical Analysis, vol. 2, no. 4, pp. 211-216, 2008.

 

 

 

Sensor Less Speed Control of permanent magnet synchronous motor (PMSM) using SVPWM Technique Based on MRAS Method for Various Speed and Load Variations

ABSTRACT:

The permanent magnet synchronous motor (PMSM) has emerged as an alternative to the induction motor because of the reduced size, high torque to current ratio, higher efficiency and power factor in many applications. Space Vector Pulse Width Modulation (SVPWM) technique is applied to the PMSM to obtain speed and current responses with the variation in load. This paper analysis the structure and equations of PMSM, SVPWM and voltage space vector process. The Model Reference Adaptive System (MRAS) is also studied. The PI controller uses from estimated speed feedback for the speed senseless control of PMSM based on SVPWM with MRAS. The control scheme is simulated in the MATLAB/Simulink software environment. The simulation result shows that the speed of rotor is estimated with high precision and response is considerable fast. The whole control system is effective, feasible and simple.

KEYWORDS:

  1. PMSM
  2. Space vector pulse width modulation
  3. Model reference adaptive system

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Schematic Block of MRAS scheme                      

Fig. 1. Schematic Block of MRAS scheme

Sensor less control block diagram with MRAS system

Fig. 2. Sensor less control block diagram with MRAS system

EXPECTED SIMULATION RESULTS:

Reference and real speed of PMSM

Fig. 3. Reference and real speed of PMSM

Electromagnetic torque of PMSM

Fig. 4. Electromagnetic torque of PMSM

Reference and real speed of PMS

Fig. 5. Reference and real speed of PMS

Electromagnetic torque of PMSM

Fig. 6. Electromagnetic torque of PMSM

 Reference and real speed of PMSM

Fig. 7. Reference and real speed of PMSM

Electromagnetic torque of PMSM

Fig. 8. Electromagnetic torque of PMSM

Reference and real speed of PMSM

Fig. 9. Reference and real speed of PMSM

Electromagnetic torque of PMSM

Fig. 10. Electromagnetic torque of PMSM

CONCLUSION:

A detailed Simulink model for a PMSM drive system with SVPWM based on model reference adaptive system has being developed. Mathematical model can be easily incorporated in the simulation and the presence of numerous toll boxes and support guides simplifies the simulation. The space vector pulse width modulation technique (SVPWM) control technique is used in PMSM drive which has its potential advantages, such as lower current waveform distortion, high utilization of DC voltage, low switching and noise losses, constant switching frequency and reduced torque pulsations provides a fast response and superior dynamic performance. Matlab/Simulink based computer simulation results shows that the adaptive algorithm improve dynamic response, reduces torque ripple, and extended speed range. Although this control algorithm does not require any integration of sensed variables.

REFERENCES:

[1] Young Sam Kim, Sang Kyoon Kim, Young Ahn Kwon, “MRAS Based Sensorless vontrol of permanent magnet synchronous motor”, SICE Annual conference in Fukui, August 4-6,2003.

[2] Xiao Xi, LI Yongdong, Zhang Meng, Liang Yan, “A Sensorless Control Based on MRAS Method in Interior Pernanent-Magnet Machine Drive”, pp734-738, PEDS 2005.

[3] Zhang Bingy, Cen Xiangjun et al. “A pposition sensor less vector control system based on MRAS for low speeds and high torque PMSM drive”, Railway technology avalanche, vol.1, no.1, pp.6, 2003.

[4] P. Vas, “Sensorless Vector and Direct Torque Control”, Oxford University Press, 1988.

[5] A. K. Gupta and A. M. Khambadkone, “A Space Vector PWM Scheme for Multilevel Inverters Based on Two-Level Space Vector PWM,” IEEE Transactions on Industrial Electronics, vol. 53, no 5, pp. 1631-1639, Oct. 2006.