Improved Direct Torque Controller of Dual Inverter Fed Double Star Induction Motor

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1 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) Improve Direct orque Controller of Dual Inverter Fe Double Star Inuction Motor Sayara Sultana * Poornima.S D.S.G.Krishna M.ech.Power Electronics Asst.professor Asst.professor EEE.Dept,VNRVJIE EEE.Dept,VNRVJIE EEE.Dept,VNRVJIE Abstract this paper escribes the improve irect torque controller of Double star inuction motor. Double star inuction motors are wiely use in inustrial applications where high reliability is require; there are many avantages of it compare to conventional metho. It minimizes & reuces the torque pulsations an the current stress of each semiconuctor power evice by one half compare with the 3-phase conventional inuction motor. he Concept of Direct torque control has opene up a new possibility that Inuction motor can be controlle to obtain high Performance torque control as goo as that of DC or brushless DC motors. A PID controller is use to avoi unwante oscillations after applying the reference loa. Finally, simulation results obtaine from MALAB/Simulink environment. Keywors Direct torque control, Double star inuction motor,space vector pulse wih moulation,three phase inverter,controller. I. INRODUCION Now-a-ays the inuction machine[7] is most wiely use in inustrial rive systems because of its simple esign, rugge, low-price, easy maintenance an its spee epens on number of poles an frequency of applie power supply. It is not easy to have variable spee control & requires a variable-frequency power-electronic rive for optimal spee control. In the inustrial applications where high reliability is require, multi-phase inuction machines are use instea of traitional three-phase machines. he ouble star inuction machine[] is also known as six-phase inuction machine or ouble stator inuction machine nees a ouble three phase supply an is base on the principle of a ouble stators isplace by α=3 an rotor at the same time. he stators are similar to the stator of a simple inuction machine an fe with a 3 phase alternating current an provie a rotating flux. Each star is compose by three ientical winings with their axes space by 2π/3. Compare to three phase machine ouble star inuction machine has many avantages such as it minimizes the torque pulsations, total rating of system is multiplie, the torque pulsations will be smoothe, the rotor harmonic losses as well as the harmonics content of the DC link current will be reuce an the loss of one or more phases oes not prevent the machine working, so improving the system reliability. High power rives employing multiphase machines are require in a lot of applications, such as traction, electric/hybri vehicles an ship propulsion etc. In the mile of 8s new strategies for the torque control of inuction motor was presente by I. akahashi an. Noguchi as Direct orque Control (DC) an by M.Depenbrock as Direct Self Control. Recently, from the classical DC methos new control techniques calle Direct orque Control Space Vector Moulate (DC-SVM) has been evelope. In this new metho isavantages of the classical DC are eliminate. Basically, the DC-SVM strategies are the methos, which operate with constant switching frequency. II. DOUBLE SAR INDUCION MOOR MODELLING he Double-star inuction motor consists of a stanar simple squirrel-cage rotor an two separate three phase stator winings. he following assumptions are mae: Motor winings are sinusoially istribute, he two star have same parameters, Flux path is linear. he mathematical moel is written in stationary reference frame. he machine is represente with two stars winings: As, Bs, Cs an As 2, Bs 2, Cs 2 which are isplace by α = 3 an thee rotor phases Ar, Br, an Cr as shown in Fg.. 24, IJIRAE- All Rights Reserve Page - 76

2 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) Fig..Phasor representation of Double star inuction motor he Voltage equations for stationary reference frame are expresse as Vs RSis qs () Vqs RSiqs s (2) Vs2 RS 2is2 qs2 (3) Vqs2 RS 2iqs2 s2 (4) = Rriqr qr r r (5) = Rrir r r qr (6) he orque equation is expresse as 3 P e * ( iqs iqs2 ) ir ( is is2 ) iqr 2 2 (7) he Spee equation is given as P m ( e L ) 2J (8) III. DIREC ORQUE CONROL he basic principle of DC [7] is to irectly select stator voltage vectors accoring to the torque an flux errors which are the ifferences between the references of torque an stator flux linkage an their actual values. he governing equation for torque for this scheme is ue to the interaction of stator an rotor fiels. orque an stator flux linkage are compute from measure motor terminal quantities i.e. stator voltages an current. An optimal voltage vector for the switching of VSI is selecte among the six nonzero voltage vectors an two zero voltage vectors by the hysteresis control of stator flux an torque. A three-phase VSI has eight possible combinations of six switching evices. he six switches have a well efine state: ON or OFF in each configuration. So all the possible configurations can be ientifie with three bits (Sa, Sb, Sc), one for each inverter leg. he bit is set to if the top switch is close an to when the bottom switch is close. In orer to prevent short circuit of the supply, the state of the upper switch is always opposite to that of the lower one. Block iagram of DC-SVM of Double Star IM is shown in Fig.2. 24, IJIRAE- All Rights Reserve Page - 77

3 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) Fig.2.Block iagram of DC-SVM of Double Star Inuction Motor he basic functional blocks use to implement the DC-SVM of Double star Inuction motor scheme is shown in the above figure. In the propose system, torque & flux estimators are use to etermine the actual values of the flux linkages & torque. he switching table & hysteresis controllers are use to etermine the uration time of voltage vectors, & prouces the Voltage comman vector, approximate space vector can be generate with SVM an fixe switching frequency can be achieve. he output of the switching table is elivere to SVM block. he SVM block performs the space vector moulation of Vs to obtain the gate rive pulses for the inverter circuit. A. orque an Flux Estimator he feeback flux an torque are calculate from the machine terminal voltages an currents. he components of stator flux is given as s ( Vs is Rs) (9) s2 ( Vs2 is2rs2 ) () qs ( Vqs iqs Rs) qs2 ( Vqs2 iqs2rs2 ) s s s 2 s s 2 s s2 ( qs qs2 ) By using the flux components, current components an IM number of poles, the electromagnetic torque can be calculate as (4) p( i i i i ) e s qs s2 qs2 qs s qs s B. orque an Flux Controller he instantaneous values of flux an torque are calculate from stator variables by using flux an torque estimator. he comman stator flux an torque magnitue are compare with their respective estimate values an the errors are processe by the hysteresis ban controllers. he flux loop controller has two levels of igital output accoring to the following equations Where 2 HB is the total hysteresis banwih of the controller H = for H = -for he actual stator flux is constraine within the hysteresis ban an tracks the comman flux. he torque controller loop has three levels of igital output accoring to the following equations () (2) (3) H = for E > + HB (7) H = -for E > - HB (8) H = for - E + E > - HB < HB (5) HB (6) E < + HB (9) 24, IJIRAE- All Rights Reserve Page - 78

4 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) IV. SPACE VECOR PULSE WIDH MODULAION SVPWM [] is a form of PWM propose in the mi-98s that is more efficient compare to natural an regularly-sample PWM. In the space-vector moulation, a three-phase two-level inverter can be riven to eight switching states where the inverter has six active states (-6) an two zero states ( an 7).Space Vector Moulation (SVM) [4] was originally evelope as vector approach to Pulse Wih Moulation (PWM) for three phase inverters. It is a more sophisticate technique for generating sine wave that provies a higher voltage to the motor with lower total harmonic istortion. he main aim of any moulation technique is to obtain variable output having a maximum funamental component with minimum harmonics. A. Mathematical Equivalent of SVPWM. Rea the sample amplitues of V AN, V BN an V CN for the current sampling interval. 2. Determine the reference space-vector amplitue V SR using relation j2 j24 V SR = V AN + V BN * e + V CN * e 3. Determine the time equivalents of phase voltages, that is as, bs an cs as follows: s as = V AN *, Vc ( n ) s bs = V BN * an Vc ( n ) s cs = V CN * Vc ( n ) Where n is the number of levels. 4. Fin out offset as offset = - ( max + min )/2, where max, min are the maximum an minimum of as, bs an cs. 5. Determine as, bs an cs as as = as + offset, bs = bs + offset an cs = cs + offset. Signals ( as, bs an cs ) are ae with time offset offset. o obtain moifie time equivalents of the reference voltages namely, ( as, bs an cs ). he aition of offset to the reference phase voltage ensures that the moifie reference voltages always remain within the carrier regions in the entire linear moulation range. xs = xs + offset, x = a, b, c where the magnitue of offset is given as offset = - ( max + min ) /2 [4]. V. SIMULAION RESULS A. Block iagram of Controller esign for DC-SVM of Double star inuction motor Fig.3. Controller esign for DC-SVM of Double star Inuction motor In the above controller esign the torque & flux estimators are use to etermine the actual values of the flux linkages & torque. he comman stator flux an torque magnitue are compare with their respective estimate values 24, IJIRAE- All Rights Reserve Page - 79

5 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) an the errors are processe by the hysteresis ban controllers. he ual Switching table prouces the Voltage comman vectors & the output is elivere to ual SVM block which performs the space vector moulation Vs to obtain gating signal of the inverter circuits. he PID controller is given as an input to the Double star inuction motor (DSIM) output torque measurement to avoi unwante oscillations when reference loa is applie. B. Inverter output waveforms with Filter Inverter output voltage contains high frequency switching harmonics which are to be filtere before feeing the loa. A typical secon orer low pass filter can be use to avoi harmonics of orer of switching frequency or multiples of it. A secon orer filter gives better attenuation than first orer at any given frequency. So, an LC filter is preferre over L filter. 5 Line Voltages Vs ime LineVoltages(volts) ime(secs) Fig.4 Line Voltage waveforms 25 Phase Voltages vs ime 2 5 Phase Voltages(volts) ime(secs) Fig.5. Phase Voltage waveforms Filter parameters: R L C f f f mh mf C. orque Response orque response is shown in Fig.6, an Fig.7.Initially the torque increases from zero to certain point an then ecreases, when loa of 3N-m is applie at.4secs the torque increases but still the oscillations can be seen from the Fig.6. o avoi such unwante oscillations a PID controller is use, the waveforms for with PID controller can be seen from Fig orque Vs ime orque N-m 5 5 Peak overshoot -5 - Rise time settling time ime in Secs Fig.6. orque response at t=.4secs without PID controller 24, IJIRAE- All Rights Reserve Page - 8

6 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) 5 orque Vs ime 5 peak overshoot orque in N-m -5 - Rise time -5 settling time ime in secs Fig.7. orque response at t=.4secs with PID controller D. Spee response A spee response is shown in Fig.8 & Fig.9.Initially the spee increases from zero to 3rpm, when loa is applie at.4secs spee slightly ecreases but still oscillations can be seen from the Fig.8. o avoi such oscillations a PID controller is use, the waveforms for PID controller can be seen from the Fig.9. 4 Spee Vs ime 35 3 Spee rpm ime in Secs Fig.8. Spee response at t=.4secs Without PID controller 8 Spee Vs ime Spee rpm ime in Secs Fig.9.Spee response at t=.4secs With PID controller E. Current Response Current waveforms are shown in Fig., Fig.. Initially current increases for certain perio an then ecreases when loa is applie at.4secs the currents of 5A rises, but still the oscillations can be seen from the Fig..o avoi such oscillations a PID controller is use. 6 Iabc Vs ime 4 Iabc Amps ime Secs Fig..Current waveforms without PID controller 24, IJIRAE- All Rights Reserve Page - 8

7 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) 4 Currents Vs ime 2 Currents(A) ime(secs) Fig..Current waveforms with PID controller F. Flux response Flux response for with & without PID controller is shown from Fig.2,Fig.3.Initially the Flux increases from zero to certain point an remains in a steay state conition, when reference loa 3Nm is applie at.4secs Flux.8wb slightly ecreases but still the oscillations can be seen from the Fig.2. o avoi such oscillations a PID controller is use. he waveforms for with PID controller are shown in Fig.3..6 Flux Vs ime.4.2 Flux in Wb ime in Secs Fig.2.Flux response at.4secs without PID controller.6 Flux Vs ime.4.2 Flux Wb ime in Secs Fig.3. Flux response at.4secs with PID controller VI. CONCLUSION In this work the improve irect torque controller of ual two inverter fe Double star Inuction motor is implemente an simulate in MALAB environment. he comparison for with an without PID controller is shown in the Simulation results. he ual two level inverter is filtere before feeing to the motor. he DC was introuce to give fast ynamic torque an flux. It is shown from the simulation results that the DC with a PID controller avois unwante oscillations when reference torque is applie & response is very quick. REFERENCES [] Naia Akkari, Abelaziz Chaghi an Rachi Abesseme, Spee Control of oubly Star Inuction Motor Using Direct orque DC Base to on Moel Reference Aaptive Control (MRAC). Int.J.of Hybri Inform. echnology Vol.7, No.2, pp.9-28, 24. [2] Lekhchine Salima, Bahi ahar, Soufi Youcef, Direct orque Control of Dual Star Inuction Motor Int. J. of Renewable Energy Research, Vol.3, No., 23. [3] Ziane Djamel azib Ahme Dr AIB Nabil Pr Rekiouaoufik Stuy an Design of the irect torque control of Double star inuction motor, J. of Elect. Syst., pg.no.4-24, 23. [4] Hanumanji Kantari, Direct orque Control of Inuction Motor Using Space Vector Moulation, Int. J. of Moern Eng. Research (IJMER), Vol. 2, Issue.5, pp , Sep-Oct. 22. [5] Alnasir Z.A., Almarhoon A.H., Design of Direct orque Controller of Inuction Motor (DC), Int. J. of Eng. an echnology (IJE), Vol. 4, No 2, Apr-May 22. [6] L.Benali,a.chaghianr.abesseme comparative stuy between a ouble fe inuction machine an ouble star inuction machine using irect torque control DC, J. of Electrical Eng.Vol. 28, pp , 2. [7] P.Sweety Jose, Jovitha Jerome an S. Sathya Bama. Performance Enhancement of Direct orque control of Inuction Motor using Fuzzy Logic, ICAC. J. on soft computing,vol. 2, July2. 24, IJIRAE- All Rights Reserve Page - 82

8 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) [8] V.Anantha Lakshmi,. Brahmanana Rey, Masuria Kalavathi an V.C.Veera Rey, Direct orque Control Algorithm for Inuction Motor Drives for the Reuction of Common Moe Voltage, Proc. of Icetect, 2. [9] P. Nagasekhara Rey, J. Amarnath, P. Linga Rey, Space Vector Base Hybri Ranom PWM Algorithm for DC-IM Drive to Achieve Superior Waveform Quality, Innovative Systems Design an Eng.,Vol. 2, No. 3, November 2. [] Vinoth Kumar, Prawin Angel Michael, Joseph P. John an Dr. S. Suresh Kumar Simulation an comparison of SPWM an SVPWM control for three phase inverter,arpn.j. of Eng. an Appl. Sci., Vol. 5, No. 7, July 2. [] N. Ravisankar Rey,. Brahmanana Rey, J. Amarnath an D.Subba Rayuu, Simplifie SVPWM Algorithm for Vector Controlle Inuction Motor Drive Using the Concept of Imaginary Switching imes, Int. J. of Recent rens in Eng., Vol.2, No. 5, November 29. [2] Narayanan, Harish K. Krishnamurthy, Rajapanian Ayyanar, an V.. Ranganathan., Space Vector Base Hybri PWM echniques for Reuce Current Ripple, IEEE rans. on In. Electron. Vol. 55, NO. 4, April 28. [3] KhouirMarouani, FariKhoucha, Lotfi Baghli2, DjafarHaiouche3, Abelaziz Kheloui Stuy an Harmonic Analysis of SVPWM echniques for VSI-Fe Double-Star Inuction Motor Drive, Athens Greece, Proc. of the 5 th Meiterranean conference on control & automation, July-27-29, 27. [4] R.S. Kanchan, K. Gopakumar an R. Kennel, Synchronise carrier-base SVPWM signal generation scheme for the entire moulation range extening up to six-step moe using the sample amplitues of reference phase voltages, IE Electr. Power Appl., Vol., No. 3, May 27. [5] Domenici Casaei, Giovanni Serra, an Angelo ani., Implementation of a Direct orque Control Algorithm for Inuction Motors Base on Discrete Space Vector Moulation, IEEE rans. on Power Electron, Vol. 5, No.4, July 2. [6] Muhamma H. Rashi, Power electronics circuits, evices, an applications, hir eition, 24. [7] B.K. Bose, Moern Power Electronics an AC Drives, Pearson Eucation, 2. 24, IJIRAE- All Rights Reserve Page - 83

9 International Journal of Innovative Research in Avance Engineering (IJIRAE) ISSN: Volume Issue (November 24) APPENDIX Parameters of three phase Inuction Motor Power (P N) Rate Voltage Rate current Frequency Nominal Stator flux Rate orque Reference orque Rate Spee 3.5Kw 23V 5A 5Hz.8Wb Nm 3Nm 3rpm Stator resistance (Rs).83Ω Stator resistance2 (Rs2).83 Ω Rotor resistance (Rr).277Ω Mutual Inuctance (Lm).538H Stator self Inuctance Ls).553H Stator self Inuctance (Ls2).553H Rotor self Inuctance (Lr).566H Moment of Inertia (J).667 kg-2 Number of poles (P) 4 24, IJIRAE- All Rights Reserve Page - 84