Maximum Power Control of DFIG Based Grid Connected Wind Turbine Generator System

Transcription

1 Intrnatonal Confrnc on Rnwabl Enrg and Powr Qualty (ICREPQ 18 Salamanca (Span, 1 th to th March, 018 Rnwabl Enrgy and Powr Qualty Journal (RE&PQJ ISSN X, No.16 Aprl 018 Maxmum Powr Control of DFIG Bad Grd Connctd Wnd Turbn Gnrator Sytm Muhammd Y. Worku 1*, M.A. Abdo, 1 Kng Fahd Unvrty of Ptrolum and Mnral Rarch Inttut, Cntr for Engnrng Rarch Dhahran, Saud Araba * Tl: , Fax: , mal: muhammdw@kfupm.du.a Kng Fahd Unvrty of Ptrolum and Mnral Dpartmnt of Elctrcal Engnrng Dhahran, Saud Araba Emal: mabdo@kfupm.du.a Abtract. Th papr prnt a mulaton modl of varabl pd wnd turbn wth a doubly fd nducton gnrator dvlopd n Matlab/mulnk. Vctor control of a doubly fd nducton gnrator (DFIG drv for varabl pd wnd powr gnraton dcrbd. A lp rng (wound rotor nducton gnrator wth back to back thr pha PWM convrtr btwn t rotor and th grd form th lctrcal ytm. A vctor control chm for th PWM convrtr rult n ndpndnt control of actv and ractv powr. Ln (upply voltag orntd rfrnc fram ha bn ud to ndpndntly control th actv and ractv powr. Rult ar provdd at th nd for ubynchronou and upr-ynchronou opraton of th DFIG. convrtr brdg. Snc th powr convrtr ha to convrt all th tator powr, th convrtr z dpnd on th tator powr ratng. Th advantag of th confguraton ar t ablty to mak th bt u of avalabl wnd powr and th fact that t lmnat th nd for a capactor bank nc t abl to draw t rqurd ractv powr from th grd. Howvr, th cot of th powr convrtr can b hgh du to t larg z []. Ky word Wnd nrgy convron ytm (WECS, wound rotor nducton machn, ub-ynchronou gnraton, uprynchronou gnraton, vctor control 1. Introducton Rnwabl nrgy ourc hav rcntly rcvd ncrad attnton du to concrn about th nvronmnt and th arch for altrnat nrgy ourc. Th man advantag of lctrcty gnraton from rnwabl ourc ar th abnc of harmful mon and th n prncpl nfnt avalablty of th prm movr that convrtd nto lctrcty. Wnd nrgy convron ytm (WECS ha provn to b a potntal ourc for gnraton of lctrcty wth mnmal nvronmntal mpact. A Worldwd ntalld capacty of wnd powr approxmatly 69,705 MW [1]. Squrrl cag and wound rotor Inducton gnrator ar th mot commonly ud gnrator for wnd powr applcaton. Squrrl cag bad WECS hown n Fg. 1. In th tup th tator of th qurrl cag nducton gnrator connctd to th grd by man of back-to-back connctd powr lctronc Fg.1 Varabl Spd WECS wth qurrl cag Inducton Gnrator Th powr convrtr z n th arlr ytm can b rducd by ung t on th rotor d of a wound rotor nducton gnrator to form a doubly fd nducton gnrator (DFIG a prntd n Fg.. Th powr convrtr now connctd btwn th rotor and grd. So t nd to carry only th lp powr, th magntud of whch wll b th machn lp tm th tator powr [- ] RE&PQJ, Vol.1, No.16, Aprl 018

2 Fg Varabl pd WECS wth wound rotor Inducton Gnrator Th opratng rgon of th DFIG n th torqu-pd plan hown n Fg.. Snc th rotor d control tratgy bcom advantagou wthn a lmtd lp rang, th opratng rgon prad out on both d of th ynchronou pd ω, mplyng both ub-ynchronou and upr-ynchronou mod of motorng and gnratng opraton [4-8]. Torqu 0 Mod I Mod III W Mod II Mod IV Spd Fg. Four Quadrant opratng rgon wth rotor d control. Sytm Modlng Fg. 4 C p v λ charactrtc for 0 ptch angl Bcau of th rlatonhp btwn C p and λ, a th turbn pd chang for a gvn wnd vlocty thr a turbn pd that gv a maxmum output powr. Th hown n Fg. 5 for varou wnd pd [14]. A n n th fgur th pak powr for ach wnd pd occur at th pont whr C p maxmzd. Th prm motvaton for varabl pd control of WECS to track th rotor pd wth changng wnd vlocty o that alway mantand at t maxmum C p valu. To maxmz th powr gnratd t thrfor drabl for th gnrator to hav a powr charactrtc that wll follow th maxmum C p ln. A. Wnd Turbn Modl A wnd turbn a machn for convrtng th kntc nrgy n wnd nto mchancal nrgy. Th workng prncpl of a wnd turbn ncompa two man convron proc. Th turbn cont of a rotor that xtract kntc nrgy from th wnd and convrt t nto a rotatng movmnt. Th thn convrtd nto lctrcty by a gnrator. Wnd powr gnraton ung prmannt magnt ynchronou gnrator prntd n [9-10]. For a horzontal ax wnd turbn, th amount of powr P m that a turbn capabl of producng gvn by [11-1]: P 1 m C pav (1 Whr P m th turbn mchancal powr, ρ th dnty of th ar n kg/m, A th xpod ara n m, V th vlocty n m/ and C p calld th powr coffcnt and gv th fracton of th kntc nrgy that convrtd nto mchancal nrgy by th wnd turbn. It a functon of th tp pd rato λ and dpnd on th blad ptch angl for ptch-controlld turbn. Th tp pd rato may b dfnd a th rato of turbn blad lnar pd and th wnd pd: W R t V ( Whr R th radu of th turbn and ω t th turbn rotatonal pd. A typcal rlatonhp btwn C p and λ (for maxmum ptch angl hown n Fg. 4 [11-1]. It clar from th fgur that thr a valu of λ for whch C p maxmzd thu maxmzng th powr for a gvn wnd pd. Fg.5 Typcal Turbn powr rlatonhp for varou wnd pd. Propod Controllr Varabl pd opraton of th wnd turbn can b ralzd by approprat adjutmnt of th rotor pd and ptch angl. For a varabl pd wnd turbn wth a doubly fd nducton machn, t pobl to control th load torqu at th gnrator drctly, o that th pd of th turbn rotor can b vard wthn crtan lmt. An advantag of th varabl pd wnd turbn that th rotor pd can b adjutd n proporton to th wnd pd n low to modrat wnd pd o that th optmal tp pd rato mantand. At th tp pd rato th arodynamc ffcncy, C p, at maxmum, whch man that th nrgy convron maxmzd. In gnral, varabl pd wnd turbn may hav two dffrnt control goal, dpndng on th wnd pd. In low to modrat wnd pd, th control goal mantanng a contant optmum tp pd rato for maxmum arodynamc ffcncy. In hgh wnd pd, th control goal to kp th ratd output powr fxd n ordr not to ovrload th ytm [15-19]. Vctor control chm for th DFIG dpctd n Fg RE&PQJ, Vol.1, No.16, Aprl 018

3 Fg.6 Vctor control chm for DFIG Two voltag-fd PWM convrtr ar nrtd n th rotor crcut, wth th upply-d PWM convrtr connctd to th tator/upply va thr ngl- pha chok. Th voltag-tranfr charactrtc of th ytm, ncludng th thr pha back-to-back PWM convrtr, ar gvn approxmatly by: E V m1 V E Vr m n nm m 1 ( Whr n th tator-rotor turn rato of th DFIG, th lp and m 1, m ar th PWM modulaton dpth of th tator-d and rotor d convrtr rpctvly. Eqn. ( dtrmn th pd rang of th gnrator. For wnd gnraton, a rtrctd pd rang accptabl on account of a mnmum wnd vlocty (th cut-n pd, blow whch vry lttl nrgy xtractabl. Th gnrator pd corrpondng to ratd wnd vlocty can b t at any pont by th choc of garbox rato. Of cour, to gt th maxmum bnft from th Schrbu chm, th pont hould b wll abov ynchronou pd whr powr xtractd from both th rotor and tator of th machn. Evntually, howvr, a th lp ncrad, th ytm ffcncy tart to dcra nc mor powr pa through th DC lnk convrtr and th rotor ron and frctonal lo ncra. A. Grd (Supply Sd Convrtr Control Th objctv of th vctor-control chm for th grdd PWM convrtr to kp th DC-lnk voltag contant rgardl of th magntud and drcton of th rotor powr, whl kpng nuodal grd currnt. Dcoupld control of actv and ractv powr flowng btwn rotor and grd don by ung upply voltag vctor orntd control (d -q. All voltag and currnt quantt ar tranformd to a pcal rfrnc fram that rotat at th am pd a th upply voltag pac phaor wth th ral ax (d-ax of th rfrnc fram algnd to th upply voltag vctor. At tady tat, th rfrnc fram pd qual th ynchronou pd. In uch a chm, currnt gd controlld to kp th dc lnk voltag contant and currnt gq ud to obtan th drd valu of ractv powr flow btwn th upply d convrtr and th upply. It may alo b rponbl for controllng ractv powr flow btwn th grd and th grd d convrtr by adjutng Q r,rf. Th chm mak u of th upply voltag angl dtrmnd dynamcally to map th upply voltag, th convrtr trmnal voltag and th pha currnt onto th nw rfrnc fram. Frt th upply voltag angl (ϴ ha to b dtrmnd. By dfnton, th upply voltag angl : tan 1 V V q d (4 Algnng th d-ax of th rfrnc fram along th upply-voltag poton,v q =0, and, nc th ampltud of th upply voltag contant V d contant. Th actv and ractv powr wll b: P Q gc gc V ( V d gd q gd V V q gq d gq ( V d ( V gd d gq (5 Th dc powr ha to b qual to th actv powr flowng btwn th grd and th grd d convrtr. Thu, E E C t o ( V d gd o or (6 Whr, o th currnt btwn th dc lnk and th tator and or th currnt btwn th dc lnk and th rotor. Thu, th dc lnk voltag can b controlld by controllng gd. Th control chm thu utlz currnt control loop for gd and gq wth th gd dmand bng drvd from th DC-lnk voltag rror through a tandard PI controllr a hown n Fg.7. Th currnt gq rfrnc wa forcd to zro o a to mak th dplacmnt qual to zro. Fg.7. Rfrnc currnt from DC lnk voltag rror B. Rotor-Sd Convrtr Control Th vctor-control chm for th rotor-d PWM convrtr nur dcouplng control of tator-d actv and ractv powr drawn from th grd. To xplot th advantag of varabl pd opraton, th trackng of optmum torqu-pd curv ntal. Spd can b adjutd to th drd valu by controllng torqu. So, an approach of ung actv powr t pont from th ntantanou valu of rotor pd and controllng th rotor currnt rd n ln voltag rfrnc fram to gt th drd actv powr wll rult n obtanng th drd valu of pd and torqu accordng to th optmum torqu pd curv. Th rfrnc valu of th tator-d actv powr obtand va a look-up tabl for a gvn gnrator rotor pd, whch nabl th optmal powr RE&PQJ, Vol.1, No.16, Aprl 018

4 trackng for maxmum nrgy captur from th wnd. Normally, th rfrnc valu of both tator-d and rotor d ractv powr, Q rf, Q rrf and ar all t to zro to nur unty powr factor opraton of th tudd wnd turbn. Ung th am approach lk th grd d convrtr, th tator and rotor currnt ar tranformd to th nw rfrnc fram ung th voltag angl calculatd n qn. (4. Stator flux lnkag xprd n th nw rfrnc fram: d q L L d q L L m rd m rq Whr, L = L 1 +L m Algnng th d-ax of rfrnc fram to b along th ln voltag wll rult n: λ d =0 and nglctng tator rtanc wll lad to V q =0. Subttutng for V q =0, th actv and ractv powr wll b mplfd a follow: P V Q ( V d d q d V V q q d q ( V d ( V d (7 d q (8 Thrfor, th abov quaton how that actv and ractv powr of th tator can b controlld ndpndntly. From Eqn. 7, d L d d L L L m m rd rd 0 (9 Subttutng for d nto th torqu and actv powr quaton wll rult n: P ( V d d Th tator magntzng currnt d j m Lm jq m Lm Thu, m From Eqn. 7, Q m q L L m ( V a contant valu. d rd (10 q Lmrq Lm q ( m rq L L (11 lm ( Vdq Vd ( m rq L (1 Thu, th varaton n rotor currnt wll alo rflct n th varaton of tator d currnt, d, q and hnc n th tator d ral and ractv powr alo. Th prncpl ha bn ud n th control of tator ral and ractv powr. Th control chm u a PI controllr to obtan th rfrnc valu for rd from ral powr rror that th dffrnc btwn drd and actual valu of ral powr. Smlarly, a PI controllr can b tund to gt th rfrnc valu for rq from th ractv powr rror. Thn, both rfrnc currnt wr tranformd to thr natural rfrnc fram that th rotor fram. Th rotor currnt rfrnc, aftr a dq-to-abc tranformaton, wr ud for mplmntng th tchnqu on th rotor d thr-pha convrtr. 4. Rult and Dcuon Th tudy mad wth mulaton on th Matlab/Smulnk and Powr Sytm Block St modul. Th nducton machn modlld on th tatonary rfrnc fram. Wth tatonary rfrnc fram, th pd of th rfrnc fram qual to zro. Stator and rotor voltag quaton, flux lnkag quaton and torqu quaton ar utlzd for modllng n trm of q componnt, d componnt and zro componnt. Stator and rotor crcut ar aumd to b tar connctd. In addton, all rotor paramtr ar tranformd to tator d va tator-rotor turn rato (n th tudy a turn rato of 1 aumd. Fg.8 Smulnk modl of Grd connctd DFIG Th trackng charactrtc obtand through a look up tabl for dffrnt turbn pd ω r by ntrpolatonxtrapolaton hown Fg. 9. Fg. 9. Trackng charactrtc A. Sub-ynchronou gnraton Fgur 10 to 17 how rpon of th ytm for uch applcaton. Fg. 10 how that th maurd actv RE&PQJ, Vol.1, No.16, Aprl 018

5 powr at th grd trmnal and th rfrnc actv powr from th optmal trackng ar th am at tady tat. Output Torqu (T m, from th wnd turbn and rfrnc actv powr (P rf, from optmal powr trackng dpctd n Fg. 11. Th ptch angl kpt contant at t maxmum valu (zro for ub-ynchronou gnraton whr th output powr blow th ratd valu a hown n Fg. 1. Th DC lnk voltag hld contant by th grd d convrtr controllr a prntd n Fg. 14. Th maurd ractv powr and th rfrnc ractv powr ar both zro at tady tat a n Fg. 15. Th tator voltag and currnt ar hown n Fg. 16. Fg. 14 DC lnk voltag Fg. 15 Actual ractv powr Q whn rfrnc ractv Powr (Q rf zro Fg. 10 Actual actv powr (P, uppr and rfrnc actv powr (P rf, lowr Fg.16. Stator voltag (uppr and currnt (lowr Fg. 11 Output Torqu (T m, uppr and rfrnc actv powr (P rf, lowr B. Supr-ynchronou gnraton Fgur 17 and 18 how th rpon of th ytm for upr-ynchronou gnraton. A dpctd n Fg. 17, th output torqu lmtd bcau th ptch angl calld n to acton nc from th trackng charactrtc (Fg.9 th output powr corrpondng to th wnd pd abov th ratd valu. Fg. 18 how that th ptch angl control calld n to acton whn th gnrator pd abov 1.1 p.u. Th ptch angl lmt th output powr and torqu. Fg. 1 Wnd pd (uppr V ptch angl (lowr RE&PQJ, Vol.1, No.16, Aprl 018

6 Fg. 17 Output torqu (T m, uppr and rfrnc actv powr (P rf, lowr Fg. 18 Wnd pd (uppr v ptch angl (lowr 5. Concluon It hown that a varabl pd ytm ung wound rotor nducton machn controlld from th rotor d upror bcau of hghr nrgy output, lowr ratng (hnc, lowr cot of convrtr, and bttr utlzaton of a gnrator whn compard to ytm ung a cag rotor nducton machn wth th am ratng. It ha bn hown from th mulaton rult that, ung vctor control, th rfrnc actv powr from th wnd and th maurd actv powr at th grd trmnal ar qual both at ubynchronou and upr-ynchronou pd opraton. In ordr to lmt th nrgy captur abov th ratd valu ptch control ha bn mplmntd to th ytm and Smulaton rult how that th controllr mantan th xtractd nrgy tll th ratd valu of th wnd turbn mchancal powr output. Acknowldgmnt Th author acknowldg th upport provdd by th Danhp of Scntfc Rarch, Kng Fahd Unvrty of Ptrolum & Mnral, through Elctrcal Powr and Enrgy Sytm Rarch Group fundd projct # RG140-1&. Rfrnc [1] [] Rajb Datta, V. T. Ranganathan Varabl-Spd Wnd Powr Gnraton Ung Doubly Fd Wound Rotor Inducton Machn A Comparon wth Altrnatv Schm IEEE Tranacton on Enrgy Convron, Vol. 17, No., Sptmbr 00 [] Alan Mullan, Mark O Mally Th Inrtal Rpon of Inducton- Machn- Bad Wnd Turbn IEEE Tranacton on Powr Sytm, Vol. 0, No., Augut 005 [4] L. Cadrc, M. Ermq Doubl-output nducton gnrator opratng at Sub ynchronou and upr ynchronou pd: tady-tat prformanc optmzaton and wndnrgy rcovry IEE Procdng-B, Vol. 19, No. 5, Sptmbr 199 [5] Dbpraad Panda l, Thoma.A.Lpo Doubl d control of wound rotor nducton machn for wnd nrgy applcaton mployng half controlld convrtr IEEE Tranacton on Enrgy Convron, 005 [6] Dbpraad Panda, Erc L. Bndct, Gr Vnkataramanan, Thoma A. Lpo A Novl Control Stratgy for th Rotor Sd Control of a Doubly-Fd Inducton Machn 001 IEEE [7] B. Rablo, W. Hofmann, Powr Flow Optmzaton and Grd Intgraton of Wnd Turbn wth th Doubly-Fd Inducton Gnrator IEEE Tranacton on Enrgy Convron, 005 [8] Mohammad Jafar Zandzadh, Abolfazl Vahd, Modlng and mprovmnt of drct powr control of DFIG undr unbalancd grd voltag condton, Elctrcal Powr and Enrgy Sytm, 59, 58 65, 014. [9] Muhammd Y. Worku, "Powr Smoothng Control of PMSG Bad Wnd Gnraton Ung Suprcapactor Enrgy Storag Sytm", Intrnatonal Journal of Emrgng Elctrc Powr Sytm. 017; [10] Muhammd Y. Worku, M. A. Abdo, and R. Iravan, " PMSG bad wnd ytm for ral-tm maxmum powr gnraton and low voltag rd through", Journal of Rnwabl Sutanabl Enrgy 9, 0104 (017; do: / [11] P.W. Carln, A.S. Laxon, E.B. Muljad, Th Htory and Stat of th Art of Varabl-Spd Wnd Turbn Tchnology Natonal Rnwabl Enrgy Laboratory, Fbruary 001 [1] Muhammd Ybr and M. A. Abdo, "Suprcapactor for wnd powr applcaton", Intrnatonal Confrnc on Rnwabl Enrgy Rarch and Applcaton, Madrd, Span, 0- Octobr 01. [1] Lhu Yang, Zhao Xu, Jacob otrgaard, Zhao Yang Dong, and Kt Po Wong, Advancd Control Stratgy of DFIG Wnd Turbn for Powr Sytm Fault Rd Through, IEEE TRANSACTIONS ON POWER SYSTEMS, Vol. 7, No., May 01. [14] Andrw Mllr, Edward Muljad, Donald S. Zngr A Varabl Spd Wnd Turbn Powr Control IEEE Tranacton on Enrgy Convron, Vol. 1, No., Jun 1997 [15] Muhammd H. Rahd Powr Elctronc Crcut, Dvc, and Applcaton Paron Educaton, Thrd dton 004 [16] E. Muljad, K. Prc, P. Mglor Control Stratgy for Varabl-Spd, Stall-Rgulatd Wnd Turbn Prntd at Amrcan Control Confrnc Phladlpha, PA Jun 4 6, 1998 [17] E. Muljad, C.P. Buttrfld Ptch-Controlld Varabl- Spd Wnd Turbn Gnrato Prntd at th 1999 IEEE Indutry Applcaton Socty Annual Mtng Phonx, Arzona Octobr -7, 1999 [18] Alxandr Hlmdag, Tmo Irmann, and Antonllo Mont, Fault Rd Through Crtfcaton of Wnd Turbn Bad on a Hardwar n th Loop Stup, IEEE Tranacton on Intrumntaton and Maurmnt, Vol. 6, No. 10, Octobr 014. [19] Tao Sun, Zh Chn, Frd Blaabjrg, Flckr Study on Varabl Spd Wnd Turbn wth Doubly Fd Inducton Gnrator IEEE Tranacton on Enrgy Convron, Vol. 0, No. 4, Dcmbr RE&PQJ, Vol.1, No.16, Aprl 018