Estimation of electromagnetic compatibility and efficiency of the adjustable load systems of PMSG in wind turbines

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1 Ihor SHCHUR Naioal Uiversiy Lviv olyechic, Deparme of ower Egieerig ad Corol Sysems Esimaio of elecromageic compaibiliy ad efficiecy of he adjusable load sysems of MSG i wid urbies Absrac. I wid urbie (W) sysems wih variable agular speed of permae-mage sychroous geeraor (MSG), he harmoic compoes of geeraor curres i rasie ad seady sae have impac o eergy efficiecy. his paper ivesigaes he aure of harmoic disorios ad aalyses some promisig basic schemes of adjusable load sysems of MSG i W. Simulaio resuls are preseed o illusrae he performace of he proposed sysems. Sreszczeie. Geeraory sychroicze z magesami rwałymi (SMG), o zmieej prędkości obroowej, sosowae w elekrowiach wiarowych, wywarzają prądy, kórych składowe harmoicze w saach przejściowych i usaloych mają wpływ a sprawość eergeyczą akich geeraorów. W prezeowaym arykule przedsawioo wyiki badań ad właściwościami ziekszałceń harmoiczych oraz aalizę wybraych podsawowych schemaów układów do regulacji obciążeia SMG. W celu zilusrowaia właściwości propoowaych układów w arykule przedsawioo wyiki ich modelowaia. (Ocea kompaybilości elekromageyczej i sprawości sysemu regulacji obciążeia SMG w elekrowiach wiarowych) Keywords: wid urbie, elecromageic compaibiliy, efficiecy, rasie ad seady sae. Słowa kluczowe: elekrowia wiarowa, kompaybilość elekromageycza, sprawość eergeycza, say usaloe i przejściowe. Iroducio Eergy ad eviromeal crises i which makid foud iself a he ur of he s ceury ecessiae icreasig use of reewable eergy sources, icludig wid eergy [, ]. I low ad medium power wid urbies (W) hey are icreasigly usig permae-mage sychroous geeraors (MSG), which are simple o operae, quie easy o corol, are reliable, ad have high power efficiecy [, 4]. o receive he maximum power from W, MSG should work wih variable speed. Furher coversio of geeraed elecrical eergy may follow differe schemes, depedig o sysem cofiguraio ad is purpose wheher i is mea for sad-alog work or for he grid. However, i almos all cases he firs sep i he rasformaio of he variable speed MSG is recificaio of aleraig volage io direc volage. I usually occurs i cojucio wih power corol, for example, maximum power poi rackig (M) of W [, 4]. Corolled receivig of power from hree-phase MSG is implemeed accordig o wo schemes: ) MSG diode bridge (DB) DC-DC coverer, ) MSG acive recifier (AR) [5]. I he firs case, MSG load is o-liear, ad he cosumed geeraor curres are characerized by a wide rage of odd ad o-muliple of hree harmoics. I he secod case, due o WM, i is easy o provide he desired form of liear curres. Assumig ha he auomaic power corol is perfec, he facor ha limis eergy efficiecy of he sysem is oobservace of elecromageic compaibiliy (EMC) of subsysems power geeraio ad akig power from MSG i boh rasie ad seady sae, which is he subjec of his sudy [6]. Descripio of he research sysem o sudy eergy regulariy, we apply compuer simulaio i MaLab/Simulik of he W geeraio sysem wih omial power of 7.5 kw a wid speed V = m/s. Opios of W [7]: a washig area A = 4.7 m, depedecy of wid power coversio efficiecy facor o he ip speed raio of W λ is approximaed by polyomial () C , 4 5 r V, ω is he agular velociy of W, ad r is he radius of W. he compuer model of W is based o wo well-kow equaios for is power ad orque [, ]: W. 5 АС V () () W. 5 Р СР А r V For he bearless W, we used a muli-polar (umber of pairs of poles p = ) siusoidal surface mage MSG wih he followig parameers: R =. Ω, Ld Lq = mh, Ф =.4 Wb. oal mome of ieria of W ad MSG is J = kg m. o corol he AR oupu volage, we applied sraegy VOC (orieig he curre vecor alog he volage vecor) wih relay curres corol. M was provided by he corol of agular speed of he geeraor i proporio o wid speed o esure maximum value C [7]. Seady-sae of MSG loadig May desigers misakely hik ha DB receives ad recifies volage wih high efficiecy. However, his is o so, because we cao cosider DB aloe wihou he eergy source. I order o sudy eergy regulariies i he akig of power from MSG, we ivesigaed saioary codiios of wid geeraio pla s operaio i fudameally differe sysems of loadig MSG (Fig. ). All sysems were ivesigaed uder four differe wid speeds, ad for each of hem we were ryig o choose a opimal load such a value of resisace ha would allow us o achieve M. hese values are give i able ogeher wih he same (for all surveyed sysems) value of power of W W, is agular speed ω, he frequecy of MSG volage f, as well as he values of agle shif φ bewee he firs harmoics of phase emf ad curre. he research resuls are give i Figure as depedig o he wid speed of he geeraor efficiecy G ou W raio of acive oupu power of MSG o mechaical power of W. RZEGLĄD ELEKROECHNICZNY (Elecrical Review), ISSN -97, R. 87 NR / 85

2 S а) W MSG R disored oes (DB) icreases slighly haks o reducig of curres harmoic disorio, which is due o he iducace of geeraor widigs. N S b) W N S MSG DB С R dc + c) W V MSG AR С B Fig.. Efficiecy of MSG versus wid speed a differe loads N + i abc CS Fig.. Ivesigaed shemes of wid geeraio plas: a) symmeric loadig o hree resisors, b) loadig o he resisor hrough DB wih capacior filer (C = μf), ad c) loadig o volage AR wih siusoidal curres i phase wih geeraor emfs he differece bewee values G i he cases of loadig MSG o AR ad resisors R (verical shadig i Fig. ) is characerized oly by he value of cosφ because he cosumpio curres have a siusoidal shape. his differece becomes sigifica oly a high power (wid speeds), whe φ > o. able. arameers of simulaios V, W, ω, f, R, R dc, φ, m/s W rad/s Hz Ω Ω deg cosφ Reducio G i he case of he load o DB compared wih resisace load (horizoal shadig i Fig. ) is due o oly harmoic disorio because i boh cases φ is he same. he resuls of oal harmoic disorio facor HD ad major harmoic disorio facors HD (5, 7,, ) of oupu curre ad volage of MSG from wid speed are give i Figure. As i shows, a small wid speed (low power), here is a sigifica disorio of curre ad low volage disorio, as a high wid speed (high power), here is a sigifica disorio of volage ad low curre disorio, ad fially a medium speeds (5 m/s), here is roughly equal average disorio of boh curre ad volage. Wih icreasig of wid speed V, opimal agular velociy of W ad emfs of MSG icreases direcly i proporio o V, he maximum power - i proporio o V, ad curres - i proporio o V. However, he differece bewee o o-disored curres (R) ad o he G Fig.. Curre ad volage harmoic disorios of MSG, loadig o DB, a differe wid speeds rasie codiios of MSG loadig Because of sochasic aure of he wid speed ad he cosumpio of geeraed elecriciy, W sysems are almos always i a rasie codiio. ha is why, besides he possible harmoics associaed wih o-liear geeraor load, here are harmoics due o rasie volage ad curre of he geeraor. he purpose of his secio is o sudy he impac of hese harmoic disorios o he efficiecy of he W. A. heoreical sudy o assess he impac of oly harmoic disorio caused by rasies, we will assume ha he geeraor widigs have zero resisace ad iducace ad load o resisors. We will model he rasie mode by meas of he harmoic emporal depedece of MSG agular speed: (4) cosf m is he relaive chage of agular speed of he geeraor, m ad are ampliude ad average 86 RZEGLĄD ELEKROECHNICZNY (Elecrical Review), ISSN -97, R. 87 NR /

3 values of agular speed of he geeraor, ad f is oscillaio frequecy of MSG agular speed. ime depedece of he agle of he geeraor roor posiio is equal (4) F U I Subsiuig (6) - () io (4) fially yields d si f f (5) hase emf of MSG will vary accordig o he law (6) e E m sip (5) F si k r r p d si p si p d d (7) pk E m reflecs he relaioship bewee he peak value of phase emf of MSG ad is agular speed, ad k is a facor ha depeds o he pole mageic flux. Usig (), we ca express he value of opimum power load of he geeraor as a fucioal depedece o is opimal agular speed: (8) k r k is he coefficie ad r is he idex, which for W is equal o. Ampliude value of power of oe phase of MSG, geeraig power (8), equals (9) k m r he curre ha is cosumed from oe phase of MSG, equals () i I m sip () I E m m m Figure 4a shows ime depedeces of he agular speed of he geeraor ad phase volage ad curre for he cocree parameers of he mahemaical model (4) - (): = 6 rad/s, γ =.6, = s, p =, k =.5 Wb, k = 5 W s. Acive power ha is cosumed from oe phase of MSG over he period of agular speed oscillaio is. () e i d Effecive values of phase volage ad curre a he period are equal () U e d ; I i d ower facor [8] of he sysem MSG elecriciy cosumer is Fig.4. ime depedeces of agular speed ω of he geeraor ad i phase emf e ad curre i: a) radiioal approach, b) suggesed approach Numerical sudy of (5) cosiderig (4) ad (5) showed ha he value of F does o deped o he parameers, р, ad, which deermie he raio of oscillaio frequecies of agular speed of he geeraor ad emfs a is oupu. However, F depeds o r ad γ. For some ieger values of parameer r ad he rage of valid values γ =..., hese depedeces are give i Figure 5. heir aalysis shows ha decreasig he power facor caused by rasie mechaical ad elecrical processes ca be sigifica. Size ad characer of his decrease are mos depede o he relaioship bewee mechaical ad elecrical processes, which is defied by he parameer r. For W he reducio of F is o high ad has roughly.5% i he wide eough rage of γ =.4. B. Compesaio of losses caused by rasie harmoic disorio For r =, power facor (5) equals. his is due o proporioal relaio bewee emf ad curre rasies, which is equivale o resisive geeraor load. RZEGLĄD ELEKROECHNICZNY (Elecrical Review), ISSN -97, R. 87 NR / 87

4 his resul suggess a way ha ca provide F = for he mover wih ay value of parameer r o esure he chagig of he geeraor emf i rasie modes by law (6) E R m m R is he equivale load resisace. resposible for he compesaory fucio of agle shif φ, he is power mus be icreased o %. I schemes b) ad c) he firs ad he secod compesaory fucios are performed by he AR. Schemes a) ad b) provide he maximum efficiecy of he W i seady sae, bu i rasie codiios, as ivesigaed above, EMC is slighly worse due o various laws of chages i emfs ad curres a opimum load of he MSG. However, i schemes c) ad d), haks o he use of he HSG his disadvaage ca be elimiaed i he process of adjusig he geeraor exciaio, ha is, oe ca perform he hird compesaory fucio proporioal chage of he emfs ad curres i he rasie load of he geeraor. Fig.5. F a differe values of idex r versus relaive agular speed Accordig o (), ampliude value of curre will be I (7) m m Figure 4b shows he ime depedeces of he agular speed of he geeraor ad phase emf ad curre for he same parameers of he mahemaical model (4) - () as i Figure 4a, bu accordig o codiios (6) - (7). o impleme he corol law (6), oe mus be able o corol he geeraor exciaio. Recely, a umber of effecive hybrid sychroous geeraors (HSG) have bee developed. hese are geeraors wih permae-mage ad addiioal elecromageic exciaio, which is realized by placig o he saor he exciaio widig ha eables coacless desig of he geeraor ad is reliabiliy [9]. R Aalysis of he promisig sysems of RMSG adjusable load Our sudy shows ha he harmoic disorios i he curre of he geeraor, if i is loaded o he DB, lead o he loss of efficiecy from % a V =.5 m/s o 4% a V = m/s (Fig. ). hus, for he firs compesaory fucio providig EMC of he load wih siusoidal geeraor emf we have o esure he siusoidal form of he load curres. Furhermore, eve wih siusoidal curres a high wid speeds efficiecy begis o decrease rapidly because of he icrease i agle φ. Because of his, i is also advisable o perform he secod compesaory fucio o provide he liear curres i phase wih correspodig emfs. he load corol sysem wih such properies may be realized accordig o he fucioal schemes show i Figure 6a-d. I all schemes baery B is used as he load, ad o i oe may coec elecriciy cosumers or a iverer coeced o he grid. he mai fucio of auomaic corol he opimal load of he geeraor is performed by he corol sysem CS. I schemes a) ad d) he geeraor is loaded o he DB, which is why he fucio of providig he EMC is performed by he hree-phase curre acive filer AF. o compesae for he curre harmoic disorios, is power may be oly 5% of he W power. However, if we make he AF also Fig.6. Fucioal schemes of he promisig sysems of RMSG adjusable load o es he effeciveess of he proposed compesaio of rasie harmoic compoes, we did a compuer simulaio of he wid power geeraio pla described above, wih he HSG ad volage AR. For opimal corol of he geeraor load, oupu volage of speed regulaor, which is proporioal o he load power, forms a U RS geeraor exciaio accordig o (6): (8) k R k U p U RS k U is he coefficie of proporioaliy bewee volage ad power. 88 RZEGLĄD ELEKROECHNICZNY (Elecrical Review), ISSN -97, R. 87 NR /

5 Accordig o (7), he referece of direc curre compoe I i he roaig coordiae sysem wih field d agular speed (рω) is give I * (9) d U RS k Figure 7 shows he waveforms of phase emfs ad curres, which illusrae he work of he radiioal sysem wih MSG ad of he oe suggesed i he codiios of variable wid speed (ad correspodigly geeraor agular speed) accordig o he harmoic law V 7 si8. Waveforms show ha he proposed sysem, besides he o phase placig of emfs ad curres, esures heir proporioaliy, hereby compesaig for harmoic discoordiaio bewee hem. he value of equivale load resisace was chose R = Ω, which provides he rage of chagig of geeraor exciaio.65.. ha is why i he radiioal sysem he ampliude of emfs chages from 5 V o 85 V, as i he proposed sysem i chages from 5 V o 5 V. his also allows oe o reduce copper losses i he geeraor because of he reducio of curres a high wid speeds i correspodece o he growh exciaio of he HSG as compared o MSG. U R agular speed (Fig. 8). I he proposed sysem, haks o he regulaio of geeraor exciaio, ampliudes of emfs ad curres form simulaeously ad proporioally accordig o he power of elecrical load (Fig. 7b). Figure 8 shows he waveforms of wid urbie power ad oupu power of he wid geeraio sysem i radiioal ad suggesed sysems. oal losses i he geeraor for a period of chages of agular speed decreased i he proposed sysem by.4%, as compared wih he radiioal. Ulike scheme c) (see Fig. 6), which hrough wo chaels of regulaio AR ad DC-DC makes i possible o provide all hree compesaory fucios, i scheme d) he regulaio of geeraor exciaio performs he basic fucio of opimal geeraor load. hus, he hird compesaory fucio is o realized here. However, scheme d) has advaages over ohers i is simpliciy ad he smalles isalled power of he semicoducor coverer for he mai fucio of corollig he geeraor load. Fig.8. Simulaed waveforms of wid urbie power W, ad oupu power of wid geeraio sysem i he radiioal approach wih MSG ou ad suggesed approach wih HSG ou uder variable wid speed a) b) Fig.7. Simulaed waveforms of phase emfs e ad curres i of he geeraor uder variable wid speed: a) radiioal approach wih MSG, b) suggesed approach wih HSG Furhermore, i he radiioal sysem he ampliude of emfs chages accordig o he geeraor agular speed, while he ampliude of curres is moved i ime accordig o he power of elecrical load (Fig. 7a). he displaceme of he laer agais W power is associaed wih he accumulaio of kieic eergy durig he chages of W Coclusios I wid sysems he way i which he power is ake from he MSG has a sigifica impac o he eergy efficiecy of he sysem. Because of he limied power of he geeraor ad is grea ieral resisace i he oliear load such as a DB wih a capacior, he loss of eergy i he geeraor hrough harmoic disorio ca reach 5% of he omial losses. he bes way o avoid hese disorios is o use WM power elecroic coverers for akig power from he MSG, for example, AR, which eable siusoidal curres ad heir opimal phase shif i relaio o phase emfs wih miimal losses i he geeraor. I rasie codiios of W sysems, for isace whe here is variable agular speed or chage of he power load i he sysem, eve whe AR is used, here appear addiioal harmoic disorios of he isaaeous power, which have o do wih he differe characers of chage of he emf ad curre ampliudes. o improve he eergy efficiecy of elecriciy geeraio, his sudy suggess a mehod of compesaio for he eergy losses associaed wih he rasiioal modes because of he variable i ime flow of wid eergy. he mehod cosiss i he regulaio of boh he ampliudes of he geeraed emf ad he load curre accordig o he opimal power of he W. he goal is o esure ha he load of he geeraor is equivale o he resisive oe. he resuls of simulaio showed ha usig he proposed corol mehod makes i possible o reduce eergy loss i he sysem HSG AR of he wid pla RZEGLĄD ELEKROECHNICZNY (Elecrical Review), ISSN -97, R. 87 NR / 89

6 by more ha % for he es period of harmoic chage of he wid speed. REFERENCES [] B i achi F.D., B a isa H.D., M a z R.J., Wid urbie Corol Sysems: riciples, Modellig ad Gai Schedulig Desig, Spriger, Lodo, (7) [] H e lle L., Wid urbie sysems, Corol i ower Elecroics, Academic ress, (), 48-5 [] Marimoo S., Nakayama H., Saada M., ad a k eda Y., Sesorless oupu maximizaio corol for variable-speed wid geeraio sysem usig IMSG, IEEE ras. Id. Elecro., 4 (5), No., 6 67 [4] a K., ad I slam S., Opimum corol sraegies i eergy coversio of MSG wid urbie sysem wihou mechaical sesors, IEEE ras. Eergy Coversio, 9 (4), No., 9 99 [5] Blaabjerg F., Che Z., ad K j a e r S. B., ower elecroics as efficie ierface i dispersed power geeraio sysems, IEEE ras. ower Elecro., 9 (4), No. 5,84 94 [6] S h c hur I.Z., Impac of osiusoidaless o efficiecy of aleraive elecriciy geeraio sysems, roc. -h I. School o Nosiusoidal Curres ad Compesaio, Jue 5-8 (), [7] S h c hur I. Z., urleko O. R., Mulifucioal corol of he acive recifier i sad-alog wid geeraio sysem wih verical axis of roaio, Messeger of Naioal uiversiy Kharkiv polyechic isiue : roblems of auomaic drive. heory ad pracice, (8), 48-4 (i Ukraiia) [8] Garcia-Caseco E., Grio R., Orega R., Salichs M., ad S a kovic A. M., ower-facor compesaio of elecrical circuis, IEEE Corol Sysems Magazie, 7(7), [9] F a Y., C h a u K.., ad C h eg M., A ew hree-phase doubly salie permae mage machie for wid powergeeraio, IEEE ras. Id. Applica., 4 (6), No., 5 6 Auhor: prof. dr hab. iż. Ihor Shchur, Ukraia, oliechika Lwowska, Isyu Eergeyki i Układόw Serowaia, ul. Badery, 79 Lwόw, i_shchur@yahoo.co.i 9 RZEGLĄD ELEKROECHNICZNY (Elecrical Review), ISSN -97, R. 87 NR /