PRIMARY FREQUENCY CONTROL PARTICIPATION PROVIDED BY DOUBLY FED INDUCTION WIND GENERATORS

Transcription

1 RIMARY FREQUENCY CONTROL ARTICIATION ROIDED BY DOUBLY FED INDUCTION WIND GENERATORS Rogéro G. de Almeda INESC ORTO oro, orugal Abrac Th paper decrbe a conrol approach appled on doubly fed nducon generaor (DFIG) o provde a frequency regulaon capably. The conrol cheme propoed con n he negraon no acve power conrol loop of he roor conroller of an addonal conrol loop repondng proporonally o he yem frequency devaon provdng a prmary frequency regulaon capably. Th raegy wa exploed o allow wnd power peneraon n large olaed grd. Keyword Wnd generaon, frequency conrol, yem dynamc behavor INTRODUCTION J. A. eça Lope INESC ORTO FEU oro, orugal jpl@fe.up.p Wnd generaon end o play an mporan role n he oal generaon mx of he fuure power yem due he need o decreae CO emon reulng from elecrcy producon. Th wnd generaon can appear n large concenraon of wnd urbne (onhore and offhore), drecly conneced o he ranmon grd, or a dpered generaon (DG) un pread hrough drbuon grd. Snce wnd power uppled from a flucuang prmary energy ource he wnd he preence of uch a large amoun of generaon n he yem may have nfluence on he yem dynamc repone followng generaon mbalance and or grd durbance. Mo of hee concern are relaed wh he managemen and conrol of prmary and econdary reerve. Such fac are recevng laely conderable aenon from elecrc ule n everal counre leadng o he defnon of new Grd Code requremen for wnd farm, namely regardng rde hrough defaul capable and fa acve power frequency repone. Among he dfferen wnd energy converon (WEC) yem ued [], double fed nducon generaor (DFIG) are capable of provdng he requred capable whou he need of large co on he power elecronc hardware, provded ha adequae conrol raege are added. The conrol flexbly provded by he DFIG elecronc converer make poble o defne varou conrol raege for parcpaon n prmary frequency conrol. In prevou work, decrbed n [4], he capably of he DFIG n repondng o change n nework frequency decrbed, aumng a prevou deload regardng he maxmum orque exracon curve. In hee work a upplemenary conrol loop, ha ue a addonal npu varable he dervave of he yem frequency or he dervave of knec energy a any peed, wa aded provdng alo an nera repone mlar o ha of a ynchronou generaor. The feably of hee conrol raege wa demonraed hrough numercal mulaon performed n mple yem. In h work hee DFIG conrol concep are exploed and ued o provde addonal uppor o prmary frequency conrol allowng he ncreae of he level of wnd power peneraon n large olaed yem. The conrol approach aded con n he ue of an addonal frequency conrol loop ha negraed no he roorde acve power conroller of a DFIG. In h conrol cheme a mall deload regardng he maxmum power exracon curve of he wnd generaor mplemened o allow parcpaon n frequency conrol durng an evenual decreae of yem frequency. To complee he conrol approach, a pch conrol raegy alo ncluded and domnae he power conrol for hgh wnd peed. Dfferen ype of yem durbance lke horcrcu and load ncreae are appled n a medum ze olaed e yem, n order o evaluae he effecvene and he advanage of he ue of h frequency conrol cheme obaned from he DFIG. An evaluaon of he ue of h DFIG conrol approach o ncreae wnd power peneraon n h medum ze e grd dcued. STRUCTURE OF THE WEC SYSTEM. Doubly Fed Inducon Generaor Conrol Fgure depc he general cheme of he DFIG, converer and conroller exploed n h work. A full decrpon of he DFIG mahemacal model ued n h reearch gven n [5]. A dq volage regulaor aded for he conrol of he roorde converer, modeled a volage ource. To acheve acve / reacve power conrol capable he roorde converer operae n a aorflux dq reference frame, conrollng boh acve and reacve power oupu hrough v qr and v dr componen, obaned from wo eparae e of I conroller. More deal of h cheme are decrbed n [6]. The I conroller nvolve a cacade rucure, where he oude I block are ued o regulae he reference roor curren ( qref and dref ) and 5h SCC, Lege, 6 Augu 5 Seon, aper, age

2 he nner de I block are ued o regulae he v qr and v dr componen, repecvely [5,6]. β :6 Wr ch conrol a b c DFIG C Conroller ac bc cc Conroller 69/ C.69/ k Grd Fgure : General conrol cheme of he DFIG converer and conroller. Through he roorde acve power conrol loop he wnd urbne drven o operae wh maxmum power once he acve power reference npu of he conrol yem e from a wnd urbne operaonal mal power curve decrbed n econ.. Alhough he degree of complexy of he converer conroller large due o he large number of conrol parameer, he ype of rackng rajecory, durbance rejecon and paramerc robune may be mproved ung a cacade rucure of I conroller, a dcued n [5]. In h work he conrol parameer were fne uned ung a Genec Algorhm (GA) approach ha mze he DFIG repone regardng he condered durbance. The fne funcon ued o evaluae he qualy of a conrol parameer defned a f ( E EQ ) /, where E and E are he acve and Q reacve power error obaned a he oupu of he fr adder of he acve and reacve power conrol loop (ee Fgure 4). Th negral evaluaed for followng he durbance momen. The grdde converer C degned o conrol he DC lnk volage, akng no accoun he balance of he acve power beween he roor and he grd. The conrol algorhm mplemened o conrol converer C baed on concep of nananeou acve and reacve power heory a explaned n full deal n [7]. In h conrol raegy he hreephae aor volage are ranformed no αβ coordnae (Clark ranformaon hown n Annex) and aocaed wh a gven compenaon real power p c () and a gven compenaon magnary power q c (). Ung hee wo varable poble o oban he curren reference gnal o be modulaed by converer C, a follow: ca ( ) ( ) ( ) vα vβ pc cb= () ( ) ( ) ( ) vβ vα qc cc Where, ca cb, and cc are he compenaon curren n abc coordnae. v () and v () are he aor volage n coordnae, repecvely (beng v o ()= aumng a balanced power yem). By neglecng wchng loe and harmonc, he curren njeced by converer C ( ca, cb and cc ) o he grd uppoed equal o he curren reference gnal obaned from (). In h way, he oal acve and reacve power delvered o he grd n dq coordnae are defned a: = v v d g d d g q q g Q = v v q g q d g d q g = dg d dca = qg q qca ( ) ( ) (4) (5) Where dg and Q qg are repecvely he oal acve and reacve power delvered by he DFIG. arable v d, v q, d and q are he aor volage and curren n a dq reference; arable dca and qca are he compenaon curren from converer C n he dq reference. The full conrol rucure of he grdde converer depced n Fgure. k ωc ref r dc_ref dc kp k dc dc Mul pc() qc() Grd Sde In. ower Theory Eq. () vα() vβ() Inver. ark' Tran and Clark' Tran. vd, vq Generaor Roor Sde ca cb cc W M r dg j Qdg dg, qg ca cb cc Inver. ark' Tran. dc dca, qca C C dca j Qqca d, q d j Qq Fgure : Smplfed chemac conrol for converer C. Generaor Saor Sde. Opmal operang pon rackng of varablepeed wnd urbne. The mal mechancal power obaned from a gven wnd peed commonly expreed by he followng equaon: = ρc ( λ, θ ) AU (6) Beng Cp p w he mal power coeffcen of he wnd urbne for a gven wnd peed, A (m ) he effecve area covered by he urbne blade, U w (m/) he wnd peed and ρ (Kg/m ) ar deny. 5h SCC, Lege, 6 Augu 5 Seon, aper, age

3 C The calculaon of he mal power coeffcen,, can be obaned from he followng funcon a p uggeed n []: C p ( ).5 e λ 6 λ, θ =..4θ 5 λ (7).5 = λ λ.8θ θ (8) The mal p peed rao defned a ω R λ = U Where R (m) he blade radu and w ω (9) he mal wnd urbne roor peed (rad_mec/) for a gven wnd peed. From (6) and (9) an mum (maxmum) power value can be obaned a a funcon of he haf peed, referred o he generaor de of he gearbox, a follow: = kωr () Where, ( ) ( p ) 5 = ρ λ π, ωr ( p ) k C R = Gω, beng p number of pole and G he ranmon rao of gearbox. From () he wnd urbne predefned mal exracon power curve can be eablhed for a gven aocaed o a fxed blade angle whch hould be defned for an averaged hor erm wnd peed foreca. Such approach wa aded here becaue wa aumed ha he e where wnd urbne were nalled wa characerzed by ome rong wnd, whch requre an adjumen on he blade pch angle o exrac maxmum power n hoe condon. In h reearch wnd farm conued by and 5 wnd urbne were condered. Indvdual daa of hee generaor decrbed n he Annex. For boh wnd park k defned for a fxed blade angle equal o 6 degree, aumng ha a hor erm wnd peed foreca wa avalable. In Fgure he predefned maxmum exracon power curve aded for boh wnd park, a ued n he conrol procedure decrbed nex, are hown. k. rmary frequency conrol The prmary frequency conrol negraed no he roorde acve power conrol loop mlar o he one uually ued n ynchronou generaor. In h cae, he droop loop (characerzed by a regulaon R, expreed n p.u. n he yem bae) ued o produce a change n he acve power njeced by he DFIG when a yem frequency varaon occur. The acve power ncremen herefore proporonal o he yem frequency varaon and defned a: = R ω ( ω _ ) njeced ref y y ref ncremen () Th generaed acve power requre a new operang pon of he DFIG, characerzed by a new roaonal peed and mechancal power o be denfed n he power curve of a gven wnd peed (Fgure ). The npu reference acve power of he DFIG acve power loop nally obaned from a 5% deloaded maxmum power exracon curve, defned n Fgure, conderng he roaonal peed referred o he generaor de. For large deload combned operaon of he pch conrol and of he elecronc converer conrol hould be ued, a decrbed n [4]. Such approach allow an acve power njecon from he DFIG when he yem frequency decreae. Fgure 4 depc he full conrol approach aded for he roorde. (a) (b) Fgure : redefned power curve for: (a) wnd park wh 5 urbne; (b) wnd park wh urbne. rmary frequency conrol Wy Wy_ref /R Deloaded ower Curve Wr Meaured wnd ref mn max Q Qref DFIG Acve power conrol loop qr kpk kpk qref dr dref kpk kp4k4 vqr vdr Doubly Fed Inducon Generaor Model E'd E'q GRID Reacve power conrol loop Fgure 4: General chemac of he roorde I conroller and prmary frequency conrol. 5h SCC, Lege, 6 Augu 5 Seon, aper, age

4 .4 ch conrol For wnd peed below maxmum raed peed (accordng o he operaonal mal power curve) he npu reference acve power o he acve power loop n DFIG follow he eqn. () a dcued n a prevou econ. However, for wnd peed larger han maxmum raed peed, he blade pch regulaon domnae he conrol and lm he energy capured from he urbne. In h cae, he pch conrol (hown n deal n []) wll conrol he roor peed referred o he generaor de and wll operae unl he wnd cuoff peed lm reached. The npu peed reference for pch conrol defned accordng o [6]: max If mec max hen ωr ref = () T mec SIMULATION RESULTS Fgure 5 how he power yem ued o evaluae he performance of he general conrol approach decrbed prevouly. I nclude one large eam un, wo Deel and one hydro generaor and four wnd farm. Thee wnd farm are conued by or 5 DFIG, a decrbed n Fgure 5. Equvalen DFIG were ued o repreen each wnd park. The procedure ued o oban he elecromechancal equvalen of he wnd park are full decrbed n []. The parameer of each wnd generaor are preened n Annex. Two dnc operaon cenaro were condered: ) wnd generaor were aumed o be DFIG whou frequency regulaon conrol; ) he decrbed conrol approach wa uppoed o be ncluded n all he DFIG. The overall capacy of he wnd park repreen approxmaely abou 7 % of he oal nalled generaon. To perform he dynamc behavor analy of h yem a full mahemacal decrpon of he elecrcal and mechancal behavor of he ynchronou un conneced o bu,, and 9 wa alo ued. Synchronou generaor were repreened hrough a ffhorder ranen model ogeher wh an auomac volage regulaor (IEEE ype ) and a peed governor wh proporonal and negral frequency conrol. A ngle fr order model repreen he eam urbne and he equvalen of he wo Deel moor, a decrbed n [8]. A lnear model (whou ranen droop), decrbed n [9], wa ued o repreen he hydraulc un behavor. The mpedance marx model developed n [] ued o decrbe, n a compac form, he couplng beween he ranmon nework and he machne aor equaon. Convenonal ynchronou un ue a 5% droop value (n each machne bae). The nework daa and ynchronou un daa can be obaned from he auhor upon reque. Two ype of durbance were mulaed o evaluae he conrbuon from DFIG o ncreae yem robune. Seam Un 4 MW MAr Wnd ark wh machne of.66 MW MW.5 MAr MW 9 MAr 9 MW Hdrc Un. MAr 9 5 MW MAr MW.6 MAr Wnd ark wh machne of.66 MW Wnd ark wh 5 machne of.66 MW Equvalen Deel Un. 5 MW 8 MAr Wnd ark wh 5 machne of.66 MW Fgure 5: Sngle lne dagram of he e power yem Thee dubance were a follow: a) load ep ncreae a bubar 5; and b) ymmercal mpedan hreephae hor crcu a bubar. Due o pace lmaon, only he behavor of he wnd park conneced a bu bar (wh 5 wnd urbne) and bu bar 7 (wh wnd urbne) wll be preened. Wnd peed aumed o be conan (for cae a and b) and equal o 4 m/ and m/ for wnd park of bue and 7, repecvely.. Load ncreae A load ncreae wa mulaed hrough a udden ep ncreae of 5% of he load n bu bar 5, a = econd. Th correpond o a oal ncreae n he yem load of abou %. Inal cenaro An nal yem cenaro wa condered aumng ha all ynchronou un were n operaon and ha wnd power peneraon wa abou %. Reul: Fgure 6 llurae he yem frequency behavor wh and whou wnd farm parcpang n prmary frequency regulaon. Fgure 6: Syem frequency behavor for DFIG wh and whou parcpaon n prmary frequency conrol. 5h SCC, Lege, 6 Augu 5 Seon, aper, age 4

5 Dfferen droop (R) value were ued (5 % and %, n he machne bae). The frequency negral conrol of he ynchronou un brng frequency back o nomnal value. When frequency drop becaue of he load ncreae, wnd farm wh prmary frequency conrol are harng wh he convenonal un he frequency regulaon ak, mprovng n h way he overall yem repone. A droop of % ued by he DFIG ha already provded ome uppor o he yem durng he fr momen ha follow he durbance. A 5% droop lead o a larger njecon of acve power ncreang yem robune of operaon. In h cae, he DFIG prmary frequency conrol mpoe an acve power ncremen ha added o he reference npu, obaned from deloaded maxmum exracon power curve (ee Fgure ). A a reul, he roor peed fall, ranferrng knec energy no he grd and compenang he ncreae of acve power njeced by he DFIG. Snce he power ncremen gnal (defned n equaon ) become zero, followng he negral frequency conrol acuaon of he ynchronou un, he wnd urbne drven o operae agan nearer he reference mum mechancal power. If he negral frequency conrol of he ynchronou un wa no n operaon he DFIG would ncreae acve oupu power, harng he load ncreae wh he ynchronou un. If an addonal econdary frequency conrol gnal, defned by a wnd park conrol, repondng o an AGC reque, wa added o he fr adder of Fgure 4 would be poble o have alo wnd generaor parcpang n frequency conrol. Fgure 7 and 8 how he behavor of he njeced acve power and roor peed of wnd farm conneced o bu bar and 7, repecvely. (a) (b) Fgure 8: Roor peed n wnd farm conneced: (a) a bubar ; (b) a bubar 7. Increang wnd power generaon cenaro Convenonal ynchronou un upply he major poron of he acve power conumed by grd and are reponble for reeablh he overall yem frequency. So a reducon of he number of ynchronou un n operaon gnfcanly affec he overall frequency regulaon capably and can conrbue o reduce yem robune regardng durbance. In h mulaon cae wa aumed ha he Deel power aon ou of ervce, beng replaced by an ncreae from wnd power generaon, whch requre an ncreae n he number of wnd urbne nalled. Two cae were analyzed: ) he yem wh he Deel un and operang whou ncreae of new wnd generaon, correpondng o a wnd peneraon of,7%; and ) new wnd generaor are nalled n order o compenae he lack of he Deel un, ncreang wnd power peneraon o 8,%. In boh cae, DFIG wh or whou frequency prmary conrol are condered. The wnd farm characerc for boh mulaon cae are reumed n Table. Fgure 7: Acve power njeced by wnd farm conneced: (a) a bubar ; (b) a bubar 7. Bu bar SIMULATION CONDITIONS Fr cae Rang (MW) Wnd peed (m/) Bu bar Second cae Generaon (MW) Wnd peed (m/) Toal INCREASING OF DFIG (Second cae) Bu bar Wnd generaor added 8 and 7 and 8 8 Table : Daa concernng wnd farm for he condered mulaon cae. 5h SCC, Lege, 6 Augu 5 Seon, aper, age 5

6 Reul: A = econd, a load ncreae, a decrbed n he prevou econ, appled. The droop value ued by he DFIG n hee mulaon 5% (n he machne bae). The yem frequency behavor hown n Fgure 9. I can be oberved ha when wnd farm do parcpae n prmary frequency conrol an expreve enhancemen of yem repone clearly obaned. The replacemen of Deel generaon by wnd generaon doe no reduce yem robune of operaon, provded ha he requred wnd power avalable. ncremen ncreae he roor acve power alo ncreae and, conequenly, he roor peed end o fall a lle more afer faul elmnaon balancng he oal acve power ( aor roor ) njeced by DFIG a lluraed n Fgure Frequency (Hz) ,7% Wnd peneraon (DFIG w hou prmary conrol),7% Wnd peneraon (DFIG w h prmary conrol) 8,% Wnd peneraon (DFIG w hou prmary conrol) 8,% Wnd peneraon (DFIG w h prmary conrol) Tme () Fgure 9: Syem frequency behavor concernng Deel un urned off and wnd farm wh or whou ncreang of conneced DFIG.. Symmercal Impedan Three hae Shor Crcu. In order o evaluae he mpac of he DFIG prmary frequency conrol durng a hor crcu wa aumed ha he wnd generaor and her elecronc converer were able o whand h yem defaul (rde hrough defaul capably). A ypcal horcrcu clearng me equal o m wa aumed. Reul: A = econd a ymmercal mpedan hor crcu appled a bubar ung he nal cenaro defned n econ.. Fgure depc he yem frequency behavor, he acve power, and roor peed followng he hor crcu, repecvely. In h mulaon cae, oberved ha he prmary frequency conrol repond quckly and help o mprove lghly he yem frequency repone. Durng he hor crcu he overall yem repone more or le he ame wh and whou DFIG parcpang n prmary frequency conrol. A beer dampng performance obaned for he cae where DFIG ad he malle droop, a hown n Fgure, becaue afer faul elmnaon he DFIG parcpang n prmary frequency conrol lead o an ncreae n acve power njecon. In h cae a larger power ncremen added o he reference acve power npu when he yem frequency decreae a hown n Fgure. Th fac make poble for he convenonal ynchronou un o repond by njecng le acve power no he grd, hereby mprovng he yem frequency moohly. A dcued n he load ncreae cae, when he power Fgure : Frequency behavor durng a ymmercal mpedane faul. Acve power (MW) Acve power (MW) (a) (b) DFIG whou frequency prmary conrol DFIG wh droop R = % DFIG wh droop R = 5% Tme () Fgure : Acve power njeced durng ymmercal mpedane faul by wnd farm conneced: (a) a bubar ; (b) a bubar 7. Fgure : Roor peed durng ymmercal mpedane faul n wnd farm conneced: (a) a bubar ; (b) a bubar 7. 5h SCC, Lege, 6 Augu 5 Seon, aper, age 6

7 4 CONCLUSIONS In h work he mpac n an olaed yem of he ue of a prmary frequency conrol raegy, negraed no a DFIG acve power conrol loop and explong he yem frequency devaon a npu gnal, wa addreed. A dealed decrpon of he ued conrol approach wa provded and dcued. I wa hown ha he fac of havng wnd generaor parcpang n he frequency conrol may conrbue o ncreae yem robune, reducng frequency change followng durbance. Such a conrol approach allow ncreang wnd power peneraon n he yem (eher a drbued generaon or n large wnd park). Havng n mnd he ncreae n he peneraon of wnd generaon n power yem, namely ung DFIG echnology, uch a conrol approach can play a key role n provdng he neceary yem robune. ACKNOWLEDGMENT The auhor would lke o acknowledge Fundação para Cênca e Tecnologa of orugal (FCT) by uppor under he framework of he DITUNE OCTI7464/ESE/ projec. A. arameer: ANNEX Bae value for he perun yem converon. Bae ower: MA Bae olage:.69 k for lowvolage bubar, k for medumvolage bubar and 6 k for hgh volage bubar. B. Doubly Fed Inducon Generaor: n (kw) = 66, n (k) =.69, R (p.u.) =.67, X (p.u.) =., R r (p.u.) =.58, X r (p.u.) =.56, X m(p.u.) =.6, (r.p.m) = 5, No of pole = 4, raed lp generaor = %, DC olage = 6.6, Capacor = 84 µf, Roor ranformer reacance = 9.5%, C. Wnd Turbne: No. of blade =, Roor dameer = m, cun eed = 4 m/, cuoff peed = 5 m/, Am. deny =.5 Kg.m, Inera me conan = 4, Gear box rao : 6 D. Clark Tranformaon (abc) (αβ): And, a α = b β c a = b c α β Smlar expreon can be defned for he curren. REFERENCES []. Akhmaov, Analy of Dynamc Behavor of Elecrc ower Syem wh Large Amoun of Wnd ower, hd The, Aprl. [] J. G. Slooweg, S. W. H. de Haan, H. olnder and W. L. Klng, Modellng Wnd Turbne n ower Syem Dynamc Smulaon, IEEE ower Engneerng Socey Summer Meeng, ancouver, Canada, July 59,. [] J. Ekanayake and N. Jenkn, Comparon of he Repone of Doubly Fed and FxedSpeed Inducon Generaor Wnd Turbne o Change n Nework Frequency, IEEE Tranacon on Energy converon, vol. 9, No. 4, pp. 88, December 4. [4] J. Ekanayake, L. Holdworh and N. Jenkn, Conrol of DFIG Wnd Turbne, ower Engneerng Journal, vol. 7, No, pp. 8, February. [5] R. G de Almeda, J. A. eça Lope and J. A. L. Barrero, Improvng ower Syem Dynamc Behavor Through Doubly Fed Inducon Machne conrolled by Sac Converer Ung Fuzzy Conrol, IEEE Tranacon on ower Syem, vol. 9, No. 4, November 4. [6] R. ena, J. C. Clare and G. M. Aher, Doubly Fed Inducon Generaor Ung BackoBack WM Converer and Applcaon o arablespeed WndEnergy Generaon, IEE rocelecrc ower Applcaon, vol. 4, No, May 996. [7] H. Akag e al, Inananeou reacve power compenaor comprng wchng devce whou energy orage componen, IEEE Tran. Ind. Applcaon, vol. IA, pp. 656, May/June 984. [8]. Kundur, ower Syem Sably and Conrol, New York: McGrawHll, 994. [9] D. G. Ramey and J. W. Skooglund, Dealed Hydrogovernor Repreenaon for Syem Sably Sude, IEEE re Sably of Large Elecrc ower Syem, 974. []G.S. Savrakak and G. N. Karnoak, A General Smulaon Algorhm for he Accurae Aemen of Iolaed DeelWnd Turbne Syem Ineracon ar I: A General Mulmachne ower Syem Model, IEEE Tran. Energy Converon, vol., pp , Sepember h SCC, Lege, 6 Augu 5 Seon, aper, age 7