Aville online t www.sieneiret.om Proei Computer Siene 5 (20) 505 52 The 2n Interntionl Conferene on Amient Systems, Networks n Tehnologies Spe Vetor Moultion Diret Torque Spee Control Of Inution Motor Mohmme T. Lzim, Muthnn J. M. Al-khishli,*, Ahme Is. Al-Shwi, Assoite Professor, Eletril Eng. Dept., Fulty of Engineering, Philelphi University, Ammn - Jorn,* Assoite Professor, Lser n Optoeletronis Eng. Dept, Fulty of Engineering., Nhrin University Bgh - Irq, Engineer, Rio Network Plnning Supervisor, Korek teleom/ Bgh offie, Bgh - Irq Astrt Vrious spets relte to ontrolling inution motors re investigte. Different ontrol strtegies re explore. The iret torque ontrol (DTC) strtegy is stuie in etils n its reltion to spe vetor moultion (SVM) is emphsize. An SVM-se DTC strtegy is suggeste n ontroller esign se on this strtegy is presente. A Simulink moel representing the ontroller is evelope n verifie using MATLAB-7. The moel exhiits high moulrity whih mkes it suitle for use in ifferent inution motor ontrol systems simultion senrios. Eh lok in the moel is evelope from the very si pilities of Simulink whih mkes the moel very suitle for testing n eugging. A moulr moel for the inution motor se on Kruse s moel is evelope. This moel is use in the simultion inste of the uilt-in Simulink inution motor lok, in orer to enle testing of vrious prts of the inution motor moel n to gin eep insight in mhine s opertion. This moel is teste seprtely n showe to e working properly through simulting iret AC strtup in Simulink. The performne of ontrol is evlute through simulting the whole system in Simulink n the suggeste SVM-se DTC ontrolling system is shown to e superior to other ontrolling strtegies investigte in the literture. It lso shows tht the inution motor settles own fster when using the suggeste strtegy ompre to other previously stuie strtegies. Keywors: Diret Torque Control; Multilevel Drives; Spe Vetor Moultion; Inution Motor Control. Introution With the enormous vnes me in semionutor tehnology uring the lst 20 yers, the require onitions for eveloping proper inution motor rive re present. These onitions n e ivie minly into two groups: The eresing ost n improve performne in power eletroni swithing evies. The possiility of implementing omplex lgorithms in the new miroproessors. However, one preonition h to e me, whih ws the evelopment of suitle methos to ontrol the spee of inution motors, euse in ontrst to its mehnil simpliity their omplexity regring their mthemtil struture (multivrile n non-liner) is not trivil mtter. It is in this fiel, tht onsierle reserh effort is evote. The im is to fin even simpler methos of spee ontrol for inution mhines. One metho, whih is populr t the moment, is Diret Torque Control (DTC). It hs emerge over the lst ee to eome one possile lterntive to the well-known Vetor Control of Inution Mhines [, 2]. Its min hrteristi is the goo performne, otining results s goo s the lssil vetor ontrol ut with severl vntges se on its simpler struture n ontrol igrm. DTC is si to e one of the future methos of ontrolling the inution mhine in four qurnts [3, 4]. In DTC it is possile to ontrol iretly the 4 sttor flux n the torque y seleting the pproprite inverter stte. This metho still requires further reserh in orer to improve the motor's performne, s well s hieve etter ehviour regring environmentl omptiility (Eletro Mgneti Interferene n energy), tht is esire Corresponing uthor. Tel +964790228647, E-mil Aress: muthnj2005@yhoo.om 877 0509 20 Pulishe y Elsevier Lt. Open ess uner CC BY-NC-ND liense. Seletion n/or peer-review uner responsiility of Prof. Elhi Shkshuki n Prof. Muhmm Youns. oi:0.06/j.pros.20.07.065
506 Mohmme T. Lzim et l. / Proei Computer Siene 5 (20) 505 52 nowys for ll inustril pplitions. Its min fetures re s follows: Diret ontrol of flux n torque. Iniret ontrol of sttor urrents n voltges. Approximtely sinusoil sttor fluxes n sttor urrents. High ynmi performne even t stnstill The min vntges of DTC re: Asene of o-orinte trnsforms. Asene of voltge moultor lok, s well s other ontrollers suh s PID for motor flux n torque. Miniml torque response time, even etter thn the vetor ontrollers. However, some isvntges re lso present suh s: Possile prolems uring strting. It ws suggeste y [5] tht y ompensting the sttor resistne voltge rop so tht sttor flux n e onstrute quikly, whih mkes DTC e pplile for low spee region. Requirement of torque n flux estimtors, implying the onsequent prmeters ientifition. Inherent torque n sttor flux ripple, whih ws overome y [6] when suggesting unifie torque n flux ontrol metho using DTC-se inution motor rive. 2. Priniple of Diret Torque Control In the pst, AC rives were only use in smll emning pplitions, regrless of the vntges of AC motors s opposite to DC motors, sine the high swithing frequeny inverters ost ws rther ompetitive [7]. With the evelopments in the power eletronis re, the vetor ontrol methos, whih use fst miroproessors n igitl signl proessing (DSP), me possile the use of inution motors in typilly DC motors ominte res, sine the urrent omponents prouing torque n flux re eouple, hieving the system seprtely exite DC motor similr fetures. The Diret Torque Control (DTC) metho, evelope y Germn n Jpnese reserhers [8], llows iret n inepenent eletromgneti torque n flux ontrol, seleting n optiml swithing vetor, mking possile fst torque response, low inverter swithing frequeny n low hrmoni losses. Fig. shows the lok igrm of DTC ontroller. With DTC it is possile to otin iret flux n eletromgneti torque ontrol, iniret voltge n urrent ontrol, sinusoil urrent n flux, low torque ripple, superior torque ynmis n hysteresis n-epenent inverter swithing frequeny [8]. Among its min vntges re the sene of oorinte trnsformtion (whih re usully neessry in most vetor ontrol rives), the sene of moultion speifi lok, n the nee to solute position etermintion. However, there re some prolems uring strt up n t low spee vlues, like the iffiulty in strtup urrent ontrol n high influene of motor prmeters, s well s vrile swithing frequeny n the nee of flux n spee estimtors [9]. With the inlusion of spee estimtor in the system, it is possile to otin gins in hrwre omplexity reution n igger mehnil enurne, mking possile the opertion in hostile environment n eresing the mintenne nees. Simultneously the noise n motor-lo inerti immunity re inrese. Fig. : Blok igrm of si DTC ontrol system. 2. Using Spe Vetor Moultion in DTC
Mohmme T. Lzim et l. / Proei Computer Siene 5 (20) 505 52 507 DTC uses n inution motor moel to preit the voltge require to hieve esire output torque [0]. By using only urrent n voltge mesurements, it is possile to estimte the instntneous sttor flux n output torque. An inution motor moel is then use to preit the voltge require to rive the flux n torque to the emne vlues within fixe time perio. This lulte voltge is then synthesize using Spe Vetor Moultion (SVM). The sttor flux vetor, s, n the torque proue y the motor, T em, n e estimte using Equtions () n (2) respetively. These only require knowlege of the previously pplie voltge vetor, mesure sttor urrent, n sttor resistne. s = (V s r s I s )Δt () T em = s I s ) (2) One the urrent sttor flux mgnitue n output torque re known, the hnge require in orer to reh the emne vlues y the en of the urrent swithing perio n e etermine. As shown in Fig. 2, the voltge require riving the error in the torque n flux to zero is lulte iretly. The lulte voltge is then synthesize using Spe Vetor Moultion []. If the inverter is not ple of generting the require voltge then the voltge vetor whih will rive the torque n flux towrs the emn vlue is hosen n hel for the omplete yle. Fig. 2: DTC using SVM lok igrm. 2.2 Three-Level Spe Vetor Moultion A three-level inverter iffers from onventionl two-level inverter in tht it is ple of prouing three ifferent levels of output phse voltge [2]. The struture of three-level neutrl point lmpe inverter is shown in Fig. 3. When swithes n 2 re on the output is onnete to the positive supply ril. When swithes 3 n 4 re on, the output is onnete to the negtive supply ril. When swithes 2 n 3 re on, the output is onnete to the supply neutrl point vi one of the two lmping ioes. () Fig. 3: () Three-level inverter. () Three-level inverter voltge vetors. () With three possile output sttes for eh of the three phses, there re totl of 27 (3 3 ) possile swith omintions. The result of plotting eh of the output voltges in -q referene frme is shown in Fig. 3.
508 Mohmme T. Lzim et l. / Proei Computer Siene 5 (20) 505 52 Fig. 4 shows tht the 27 swith omintions result in totl of 9 unique voltge vetors sine some of the omintions proue the sme voltge vetor. These ifferent omintions relte to ifferent wys of onneting the lo to the DC us tht result in the sme voltge eing pplie to the motor. Spe Vetor Moultion (SVM) is the pproximtion of n ritrry vetor in the -q vetor spe using the nerest three voltge vetors tht the inverter n generte [3]. The nerest three vetors re hosen y etermining the tringle within the vetor spe in whih the esire voltge vetor resies. The require onurtion of eh of the vetors is etermine y Equtions (3) n (4). These speify tht the emn vetor, V *, is the geometri sum of the hosen three vetors (V, V 2, V 3 ) multiplie y their on-urtions (, 2, 3 ) n tht their on- urtions must fill the omplete yle. (3) + 2 + 3 = (4) Equtions (3) n (4) n e omine to proue Eqution (5). Eqution (5) n then e rerrnge to otin Eqution (6). This is n expression for the vetor uty yles in terms of the esire voltge vetor n the three nerest voltge vetors. (5) (6) 3. Simulink Moel for DTC Controller A Simulink moel for DTC ontroller exploiting SVM is evelope. The moel is se on the generl lok igrm shown in Fig. 2. The moel is lso evlute n moulr Simulink inution motor is lso presente. The moel onsists of four loks, whih esign etils re given in [4]; in ition to the inution motor lok; eh of whih orrespons to lok in Fig. 2. These loks re: DTC lok. SVM lok. 3-level inverter lok. Sttor flux n torque estimtion lok. The DTC lok is shown in Fig. 4. Re(A.B) 5 Im(A.B) Tqr Re(A/B) Tq Im(A/B) Re(K.A) Im(K.A) 6 Tr 2 Re(/A) Im(/A) - T Re(A+B) Im(A+B) 7 Lqr 3 Re(A.B) Im(A.B) Re(A/B) Re(-A) Im(-A) Complex Computer Lq Im(A/B) 9 Re(K.A) Ls 4/3 Im(K.A) 0 Re(A.B) 8 Lr Re(/A) Im(/A) p Im(A.B) Re(A/B) 4 L Re(A+B) Im(A+B) Im(A/B) Re(K.A) Re(-A) Im(K.A) Im(-A) Complex Computer2 Vq E Re(/A) Im(/A) Re(A+B) 0 2 Im(A+B) V Re(-A) Im(-A) Complex Computer3 Fig. 4 Detils of the DTC lok. The DTC lok esign is se on the following nlysis: From the equivlent iruit of n inution motor in -q referene frme, expression of hnge in torque n hnge in sttor flux n e represente s follows:
Mohmme T. Lzim et l. / Proei Computer Siene 5 (20) 505 52 509 Now, (7) or (8) ) (9) Rerrnging Eqution (9) to extrt, we hve: (0) To evlute Eqution (0), omplex omputer is neee. Fig. 5 shows the etils of the omplex omputer lok. The omplex omputer lok is uilt roun lok tht multiplies two omplex numers: A = + j & B = + j. 9 Re(A+B) re 2 Re(A.B) - Re(-A) 3 im 2 Im(A.B) - 2 Im(-A) 4 0 Im(A+B) 3 Re(A/B) 4 Im(A/B) re im - 7 Re(/A) 5 Re(K.A) 6 Im(K.A) re - 8 Im(/A) 0 im Fig. 5 Detils of the omplex omputer lok. 4. Testing the Simultion The first step in testing the simultion is to test the opertion of the inution motor lok. This lok is highly moulr moel, whih enles testing the moel t vrious stges n gining eep unerstning of the mhine opertion. To test the inution mhine lok moel, the following prmeters re ssume: R r =0.39, R s =0.9, L ls =0.2 0-3, L lr =0.6 0-3, L m =4 0-3, f =00, p=4 n J=0.0226. A three-phse 50Hz, 220 V voltges is pplie to the 4-KW inution mhine with just the inerti lo (iret strtup). Figs. 6, 7 n 8 show the three-phse urrents, the torque, n the spee of the mhine, respetively. As it n e seen from the figures, the mhine elertes n then gets to stey stte in out 0.4 seons. This shows tht the moel of the inution mhine is working properly. The smll slip oserve in the figures is ue to the inerti lo.
50 Mohmme T. Lzim et l. / Proei Computer Siene 5 (20) 505 52 Fig. 6: Three-phse urrents of the inution motor in iret strtup t stey stte. Fig. 7: Torque in iret strtup t stey stte. Fig. 8: Angulr spee in iret strtup. () Fig. 9: () Torque n () Sttor urrent wveform in stey-stte test. ()
Mohmme T. Lzim et l. / Proei Computer Siene 5 (20) 505 52 5 The seon step in testing the simultion is to test the SVM-DTC ontrolle inution motor s whole system. In DTC sheme, the yle perio hs een ssume equl to 40 μs. The mplitue of the hysteresis ns hs een juste in orer to hieve men inverter swithing frequeny prtilly resonle. The hrteristis of the motor uner test is stnr 3-phse, 4-kW, 4-pole, 220 V, 50 Hz inution motor with referene urrent of 6.6 A, referene torque of (26.5 Nm), n referene spee of 440 rpm. The stey-stte performne of the DTC sheme is epite elow. Fig. 9 n shows the torque n the sttor urrent wveform, respetively. The trnsient performne of the DTC sheme hs een nlyze n the response to step vrition of the torque ommn from 0 Nm to 26.5 Nm (referene torque), t ifferent rotor spees. Fig. 0 illustrtes the torque responses otine using DTC sheme, t 200, 600, n 00 rpm, respetively. Fig. 0: The torque responses otine using DTC sheme, t () 200, () 600, n () 00 rpm. The results ove show tht the SVM-DTC strtegy n e use to hieve etter torque response in terms of settling time n mximum overshoot. In DTC sheme iret ontrol of the sttor urrents is not present n this my etermine over urrents when step vritions of torque n flux re pplie to the input ommns. Fig. : Step response of the () sttor n rotor fluxes, n () sttor urrent mgnitue.
52 Mohmme T. Lzim et l. / Proei Computer Siene 5 (20) 505 52 With referene to the torque, n iniret urrent ontrol n e otine introuing limit to the mximum torque vlue. With referene to the sttor flux, it n e note tht even smll vrition of the sttor flux ommn uses lrge vrition of the sttor urrent. This ehvior is lerly represente in Fig. n, whih shows the trnsients use y step vrition of the sttor flux ommn. In this se, n iniret ontrol of the sttor urrent n e esily otine foring the flux ommn to hnge slowly, oring to prefixe rmp wveform. 5. Conlusions Aoring to the results otine, the following onlusions my e rwn:. DTC is preferre over other ontrolling shemes for high ynmi pplitions, ut, on the other hn, shows higher urrent n torque ripple. This rwk n e prtilly ompenste y using SVM in the DTC sheme. 2. The DTC-SVM ontrolling sheme hs the vntge of eing esy to implement, mking it possile to use hep DSP ors to implement sophistite ontrollers. However, the tehnique is lso lening itself to more moern n heper implementtions using fiel progrmmle gte rry (FPGA). 3. Controlling shemes se on DTC n hieve etter torque responses thn other shemes in terms of settling time n mximum overshoot. 4. Simulink is very suitle environment for stuying n simulting inution mhines pplitions. The reserher n uil quite sophistite systems from the very si onepts. This mke Simulink moels very suitle for stuying omplex engineering prolems. 5. The Kruse s moel of the inution motor is the ville mthemtil representtion of the inution motor for the purpose of eveloping Simulink moulr moel. 6. The moulr moel evelope in this work to simulte the inution motor, gives the user of the moel ess to ll internl vriles whih mkes for flexiility n eep insight in the mhine opertion. This moel n e use to simulte ny mhine ontrol lgorithm without using estimtors. It n e use to simulte inution motors, s well s genertors without moifition. This vntge of the presente moel mkes it ville for solving ny inution mhine simultion prolem. Referenes. R. Toufouti, S Mezine.n H Benll, Diret Torque Control for Inution Motor Using Fuzzy Logi, ACSE Journl, Vol. 6, Issue 2, June, ( 2006), 7. 2. Xu. Hungsheng, H. A. Toliyt n L.J. Petersen, Five-Phse Inution Motor Drives with DSP-Bse Control System, IEEE Trnstions on Power Eletronis Vol. 7, Issue 4, Jul. (2002), 524. 3. Nuno M. Silv, Mrtins, P. António n Arino S. Crvlho, Torque n Spee Moes Simultion of DTC- Controlle Inution Motor, Proeeings of the 0th Meiterrnen Conferene on Control n Automtion, Lison, Portugl, July 9-2, (2002). 4. J. Fiz, M. B. B. Shrifin, A. Keyhni n A. B. Pro, Sensorless Diret Torque Control of Inution Motors Use in Eletri Vehile, IEEE Trnstions on Energy Conversion, Vol. 8, No., Mrh (2003). 5. Shyu, Shng, Chen n Jwo, Flux Compenste Diret Torque Control of Inution Motor Drives for Low Spee Opertion, IEEE Trnstions on Power Eletronis, Vol. 9, Issue 6, Nov. (2004), 608. 6. J. H. Ryu, K. W. Lee n J. S. Lee, A Unifie Flux n Torque Control Metho for DTC-Bse Inution- Motor Drives, IEEE Trnstions on Power Eletronis, Vol. 2, Issue., (2006), 234. 7. E. Ohno, Introution to Power Eletronis, Ohm-sh, Tokyo, 984. 8. P. Vs, Sensorless Vetor n Diret Torque Control, Oxfor University Press, (998). 9. D. Csei, G. Serr n A. Tni, Improvement of Diret Torque Control Performne y Using Disrete Spe Vetor Moultion Tehnique, IEEE Trnstions on Power Eletronis, Vol. 3, No. 2, 997, (998). 0. G. Helter, F. Profumo, M. Pstorelli n L. Tolert, Diret Torque Control of Inution Mhines Using Spe Vetor Moultion, IEEE Trns. on Inustry Applitions, Vol. 28, No. 5, Sep./Ot. (992), 045.. C. Lsu, I. Bole n F. Bljerg, A Moifie Diret Torque Control For Inution Motor Sensorless Drive, IEEE Trns. on Inustry Applitions, Vol. 36, No., Jn./Fe. (2000), 22. 2. P. Vs, "Eletril Mhines n Drives: A Spe-Vetor Theory Approh" Oxfor University Press, (992). 3. J. Kng, n S. Sul, New Diret Torque Control of Inution Motor for Minimum Torque Ripple n Constnt Swithing Frequeny, IEEE Trns. on Inustry App., Vol. 35, No. 5, Sep./Ot. (999), 076. 4. Ahm I. N. Al-Shwi,,"Spe Vetor Moultion Diret Torque Spee Control of Inution Motor", Thesis, Nhrin University, De., (2007).