ENERGETICAL PERFORMANCES OF SINUSOIDAL PWM STRATEGY FOR THE INDUCTION MOTOR AND VOLTAGE INVERTER SYSTEM: SIMULATION AND EXPERIMENTAL APPROACH

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1 Annals of he Universiy of Craiova, Elecrical Engineering series, No. 35, ; ISSN ENERGEICAL PERFORMANCES OF SINUSOIDAL SRAEGY FOR HE INDUCION MOOR AND VOLAGE INVERER SYSEM: SIMULAION AND EXPERIMENAL APPROACH Mihăiţă LINCĂ, Ileana-Anamaria MIRAN Faculy of Elecromechanical, Environmenal and Indusrial Informaics Engineering Universiy of Craiova Bd. Decebal nr.7, RO-644 Craiova mlinca@em.ucv.ro, mi_ana_maria@yahoo.com Absrac he elecric drive is a main componen of indusrial equipmen designed for small or large complexiy, because he achievemen of finished goods implies he adjusable mechanical energy available a he oupu of he sysem. Because he saic converers are needfull in such a sysem, he evoluion of he converer s command sub-sysems was also needful, o improve heir performance. he aim of his paper is he energeical analysis of he drive sysem and i had been performed on an experimenal sand and on i s equivalen SIMULINK model for differen saic operaion poins. I was considered feeding he asynchronous moor from an indirec volage source saic converer using he sinusoidal modulaion as command sraegy. wo cases had been aken ino consideraion: feeding he moor wih he same RMS volages and achieving he same mechanical shaf. he global model of he drive sysem, creaed in MALAB/SIMULINK environmen, provides all he needed informaion in order o calculae he parameer values for comparing he energeic performances, and highlighs he fac ha he load orque and frequency have heir influence on qualiy indicaors. he frequencies considered for he energeic analysis are Hz, H and 5Hz, and he load was adjused up o he nominal value. he inducion moor model implemens he equaions which considers he magneic resisance and main field sauraion wih he variaion of he saic magneizing inducance, depending on he magneizing curren. he following qualiy indicaors had been aken in o consideraion: efficiency, facor, elecrical losses. Keywords: elecric drive, saic converer, inducion moor, qualiy indicaors, sinusoidal modulaion Elecromechanical drive is an essenial componen of echnical equipmens for indusrial aciviies of high or low complexiy, because obaining he produc necessiae mechanical energy available he oupu drive sysem.. HEOREICAL ASPECS. he operaed equipmen o obain experimenal daa needed o deermine he energeical performances of each modulaion sinusoidal mehod, was used a sand ype Leybold [9]. his conains (Fig., Fig. ): mono phase full conrolled bridge recifier; DC link circui of he volage inverer; hree phase volage inverer wih IGB ransisors and is conrol modulus; asynchronous driving moor; he load (asynchronous moor of special consrucion and is orque conrol modulus); measuremen and recording equipmen (Fluke 4b analyzer and Merix OX 74 M oscilloscope). Power sysem componens have he nominal operaed daa indicaed below: Moor: P N =5W; U N = 3V; I N =.3A; cosφ =.79; n N = 35 ro/min. Inverer: U N = 3V; I N = A. Load: P N =5W; U N =3V; M N =Nm.. INRODUCION Saring from he square-wave modulaion he sinusoidal modulaion appeard and improved o minimize copper losses, orque ripple, ec. Pulse widh modulaion () echniques used oday o conrol he modern saic converers as par of high machine drives, srongly depend on swiching frequency of he semiconducors. Figure. : he drive sysem block diagram 39

2 Annals of he Universiy of Craiova, Elecrical Engineering series, No. 35, ; ISSN Figure. : he experimenal workbench o obain experimenal daa required o deermine he energeical performances of inducion moor feeding wih sinusoidal volage and frequency in he Hz-5Hz inerval, i was supplied by a synchronous generaor (6.kVA), in a plaforme whose srucure conains (Figure 3): one volage and frequency saic converer used o adjus he drive speed of he asynchronous auxiliary moor, respecively o adjus he given volage frequency; one inducion moor for driving he synchronous generaor; asynchronous generaor adjused by exciaion curren o deermine he acual value of he desired value; he load and he measuring and recording equipmen used in he previous sand. signal (u r mus have a maximum or a minimum in he middle of each u c alernance) you can use a single reference signal for he hree-phase. So, he harmonic specral of oupu volage conains only even harmonics. he volage frequency on load is equal wih command volage frequency and RMS volage value is proporional wih he command volage ampliude - [4],[8] Load volage approximaion wih a sinusoid is even beer, as he reference volage period is smaller in relaion wih command volage period, respecive as he frequency modulaion facor is bigger. hrough he command, beside solid wave command, HD facor becomes beer by reducing he low order harmonic ampliudes and increasing harmonics order of significan ampliude in relaion wih he fundamenal..3 Power qualiy indicaors In he compleed sudies, for compuing he acive and he reacive, he complex aparen heory [] (pq heory) has been used. In he pq heory, he insananeous complex aparen is defined as he produc of he volage phasor (u) and he complex conjugae of he curren phasor (i * ) - []: 3 * s = p + jq = u i = () 3 = [ ud id + uqiq + j( ud iq + uqid )] he real and he imaginary componens of complex aparen are: 3 p = ( udid + uqiq ) () ( u i u i ) 3 q = + d q q d (3) Is widely acceped ha he average value of he real par p, over one period of he volages and currens () gives exacly he acive P: Figure 3: he sand srucure for he energeical performances of inducion moor supplied by sinusoidal volage.. Sinusoidal modulaion According o he principle of pure sinusoidal modulaion, he easies ype of, he elemens + and - are found on he same phase of he inverer are ordered on he inervals on he one hand u c > u r and on he oher hand u c < u r. Considering he synchronous conrol, odd index modulaion and muliples of 3 and he opimal correlae beween reference signal and command P = pd (4) I s also widely acceped ha ha he average value of he imaginary par q, over one period of he volages and currens () gives he reacive Q: Q = qd (5) Saring from he insananeous complex aparen, he aparen can be defined [5], [7], keeping rue Bucholz s formula [3]. hus: 4

3 Annals of he Universiy of Craiova, Elecrical Engineering series, No. 35, ; ISSN S f U = s d (6) u Where U is he square RMS value of he volage phasor modulus, U = u d So, he aparen is given by: S f U 9 u i u 4 = 3 d = UI (7) (8) Considering he quadraure relaionship beween s, he disorsion is defined as D f f = S P Q (9) he qualiy analisys is based on he qualiy indicaors [6] specified below: he facor, he drive moor efficiency and he elecrical losses. 3. EXPERIMEN PROOCOL Before he real-ime experimens, a Malab / Simulink model was performed and several simulaion scenarios were considered. For he simulaion proocol i was considered feeding he asynchronous moor from an indirec volage source saic converer for he sinusoidal modulaion, and also from a hree-phase sinusoidal volage source, so he performances could be compared. he global model of he drive sysem was obained by inerconnecing he models corresponding o each componen of he drive sysem-[8]. hrough he experimenal proocol, he needed values o be measured in order o deermine he energeic performances of he asynchronous moor has been esablished: phase volage, line curren (he moor is in he dela connecion); acive a moor side and oal facor (all provided by he Fluke 4b analyzer), for feeding he moor a consan frequency (,, and 5 Hz) and differen values of he load orque (;. ;.4;.6;.8; ) N. he volage RMS values corresponding o each working poin has been esablished as follows: In case of feeding wih sinusoidal volage, for each working poin, feeding he moor wih a RMS volage value ha can ensure he same mechanical a he moor shaf as when feeding he moor wih volage. aking ino accoun he experimenal proocol and saring from measured daa for a saic operaing poin, he oher quaniies needed o deermine he energeic performances was calculaed and he comparaive analysis could be achieved. For each operaing poin he waveforms of volage and curren had been recorded, and also, he following quaniies: he RMS values of volage and curren, acive, roor speed, and orque, respecively. Recorded daa processing was done in Malab (Simulink). I should be noed ha qualiy compuing was made based on he recorded waveforms, orque and roor speed, using Malab Simulink models developed by he auhors -[8]. Figure 4 SIMULINK model of he drive sysem wih asynchronous moor and volage source inverer 4

4 Annals of he Universiy of Craiova, Elecrical Engineering series, No. 35, ; ISSN EXPERIMENAL RESULS 4.. Resuls based on he Malab Simulink model of he driving sysem Energeic performances were analyzed based on he model in figure 4, a he same frequency (, and 5 Hz) based on he graphical represenaions for he mos significan qualiy indices. A 5 Hz frequency (fig. 5) he efficiency corresponding o sinusoidal modulaion, for all values of he mechanical, equals he efficiency of sinusoidal volage feeding. he facor depends on he inverer command frequency and as well on he mechanical value. If for and 5Hz frequency, he evoluion is normal, for Hz i exiss a local minimum and maximum close he.9 value. Hz Hz 5 Hz f = Hz Figure 6: Power facor depending on he mechanical for an inverer wih sinusoidal modulaion and sinusoidal feeding 4.. Resuls based on he on-line experimenal daa f = Hz Energeic performances were analyzed a he same frequency (, and 5 Hz) based on he graphical represenaions for he mos significan qualiy indices. mechanical shaf, for he frequency of Hz, when feeding he moor from he volage inverer and from he corresponding sinusoidal volage are presened by fig. 7, fig. 8, fig f=hz..5. f = 5Hz Figure 5: Effeciency depending on he mechanical for an inverer wih sinusoidal modulaion and sinusoidal feeding for hree command frequencies Figure 7: Efficiencies versus mechanical he efficiency is increased for sinusoidal volage feeding (fig. 7), bu he difference o he big loads is very small. 4

5 Annals of he Universiy of Craiova, Elecrical Engineering series, No. 35, ; ISSN Hz wih volage which lead o he same mechanical performance, he equivalen circui has a sronger resisive characer f=hz Figure 8: he facor versus mechanical he facor (fig. 8) is significanly bigger for conrol up o approx. ½ of full load. Sill, he facor corresponding sinusoidal feeding becomes bigger, he difference decreases a high loads. he explanaion can be as he load small by feeding wih volage which leads o he same mechanical performance, he equivalen circui has a sronger resisive characer Figure : Efficiencies versus mechanical f=hz f=hz Figure : he facor versus mechanical Figure 9: he elecrical losses versus mechanical shaf he main elecrical losses are much higher for he conrol; hey decrease wih load increasing suggesing he moor operaion in supersauraing regime. mechanical shaf, for he frequency of Hz, when feeding he moor from he volage inverer and from he corresponding sinusoidal volage are presened by fig., fig., fig.. he efficiency is bigger for sinusoidal volage feeding, bu he difference o he big loads becomes smaller. he facor is significanly bigger for conrol up o approx. ½ of full load afer his once wih he load increasing i obain he same facor. he explanaion can be as he load small by feeding f=hz Figure : he elecrical losses versus mechanical he main elecrical losses, a operaion a zero load are double in conrol case and he difference decreases once wih he load increase, suggesing he moor operaion in supersauraing regime unil approx.½ of full load a he moor loading bigger of ½ of full load hey becomes equal. 43

6 Annals of he Universiy of Craiova, Elecrical Engineering series, No. 35, ; ISSN mechanical shaf, for he frequency of 5 Hz, when feeding he moor from he volage inverer and from he corresponding sinusoidal volage are presened by fig. 3, fig. 4, fig f=5hz. 5 5 Figure 3: Efficiencies versus mechanical.8.6 f=5hz Figure 4: he facor versus mechanical 5 f=5hz P Figure 5: he elecrical losses versus mechanical shaf he efficiency obained is beer han he sinusoidal feeding (fig. 3) decrease reducing by inerval ends. he facor (fig. 4) is significanly increased for he sinusoidal feeding han a he conrol, unil o approx 3/4 of full load hen once wih he load increasing obain he same facor. he main elecrical losses (fig. 5) are sensiive higher for feeding wih volage a load unil / of raed load, afer which hey are comparable. RMS volage value, for he frequency of Hz, when feeding he moor from he volage inverer and from he corresponding sinusoidal volage are presened by fig. 6, fig. 7, fig. 8. When feeding he moor wih he same RMS volage, he dependences beween he efficiency and he mechanical shaf are overlapped, suggesing he fac ha he wo regimes are equivalen f=hz Figure 6: Efficiency versus mechanical shaf I can be seen ha he facor is higher when feeding he moor wih sinusoidal volage, and his difference increases even more a high loads f=hz Figure 7: he facor versus mechanical shaf 44

7 Annals of he Universiy of Craiova, Elecrical Engineering series, No. 35, ; ISSN P 9 e 8 7 f=hz Figure 8: he elecrical losses versus mechanical shaf he difference beween he resuled elecrical losses for he wo cases is almos zero, making he wo cases equivalen. RMS volage value, for he frequency of Hz, when feeding he moor from he volage inverer and from he corresponding sinusoidal volage are presened by fig. 9, fig., fig f=hz Figure 9: Efficiency versus mechanical shaf f=hz Figure : he facor versus mechanical shaf I can be observed a slighly superior efficiency for he sinusoidal volage feeding han for he volage. When feeding wih sinusoidal volage, he facor is higher compared o he volage feeding, bu, a higher loads he wo facors are abou he same value. he oal elecrical losses are almos equal a low values of he load, and a higher load values, he losses are lower f=hz Figure : Elecrical losses versus mechanical RMS volage value, for he frequency of 5 Hz, when feeding he moor from he volage inverer and from he corresponding sinusoidal volage are presened by fig., fig. 3, fig. 4. In his siuaion, i can be seen ha he wo efficiencies are overlapped hroughou he load variaion inerval f=5hz. 5 5 Figure : Efficiency versus mechanical shaf he difference beween he sinusoidal volage feeding facor and he volage feeding facor (fig. 3) is also negligible over he enire load inerval. he oal losses for he sinusoidal volage feeding are approximaely equal o he oal losses corresponding o he volage feeding, observing sill a sligh superioriy of he modulaion over sinusoidal volage. 45

8 Annals of he Universiy of Craiova, Elecrical Engineering series, No. 35, ; ISSN f=5hz Figure 3: he facor versus mechanical shaf 5 5 f=5hz 5 5 Figure 4: Elecrical losses versus mechanical 5. CONCLUSIONS For he nominal frequency, i shows ha for feeding he moor wih he same RMS volages, he same efficiency is obained. When he same mechanical shaf is obained, he efficiency is smaller unil 8% of he raed. he efficiency dependence keeps he clasic shape, reaching he peak value a 73% of he nominal orque. When obaining he same mechanical, he efficiency difference is maximum (abou 5%) a % of he raed, while, when feeding he moor wih he same RMS values, he efficiency difference is minor. he qualiy indicaors revealed heir dependence of he load orque a consan frequency, and of frequency a consan orque, respecively. For all sudied frequencies, we remark he fac ha he efficiency is higher when feeding wih sinusoidal volage, bu a higher loads, he difference becomes very small. A low frequency, a good facor is achieved for he conrol unil 6% of full load. A 5 Hz a beer facor resuls for he sinusoidal volage feeding for all he load range. For all he hree cases, he elecrical losses are higher for he volage feeding, ye he difference decreases wih increasing load suggesing moor operaion in suprasauraion regime. he experimenal resuls confirm he simulaion resuls, for he case of he same RMS volage feeding, regarding he efficiency, bu his maching is less rue for he facor. References [] V.N. Nedelcu, Elecromechanical conversion heory, echnical Ed., Buchares, 978. (In Romanian) [] H. Akagi and A. Nabae, he p-q heory in hreephase sysems under non-sinusoidal condiions, European rans. on Elecrical Power, 3 (993), No., 7-3. [3] F. Buchholz, Die Drehsrom-Scheinleidung bei ungleichmäßiger Belasung der drei Zweige. Lich u. Kraf, Org. Elekroech. Ver München, No., 9. [4] A. Bioleanu, Mihaela Popescu, D. Mihai, C. Consaninescu, Saic converers and high performance conrol srucures,(in Romanian) Ed. SIECH, Craiova, pp [5] A. Bioleanu, Mihaela Popescu and V. Suru: P-Q Power heory: Some heoreical and Pracical Aspecs, Proceedings of h Inernaional School on Nonsinusoidal Currens and Compensaion (ISNCC ), pp. -5, June 5-8, Lagow, Poland, ISBN [6] Mihaela Popescu, A. Bioleanu, M. Dobriceanu, M. Linca, Energy-efficien inverer-fed inducion moor driving sysem, Proceedings of IEEE Inernaional Elecric Machines and Drives Conference, IEMDC 7, v, 7, p (INSPEC). [7] M. Lincă, Vlad Suru, Power qualiy in drive sysems based on space-vecor conroled saic converers and inducion moors, Annals of he Universiy of Craiova, Serie Elecrical engineering, No.34, Vol.II,, ISSN , pp.-5. [8] M. Lincă, Research on drive sysems wih asynchronous moor and volage and frequency saic converers, PhD hesis, Universiy of Craiova,. [9] G. F. v Schloheim, Frequency Converer echnology, Drives, Leybold Didacic GmbH. [] Wen-Chang sai, Esimaion of Core Losses in an Inducion Moor under Volage Exciaions Using Core Loss Curves esed by Epsein Specimens, Inernaional Forum on Sysems and Mecharonics, 7. 46