Research on Wind Power System with Adaptive Speed Control of MPPT Algorithm

Transcription

1 Journl o Communiction nd Computr 12 (215) doi: / / D DAVID PUBLISHING Rsrch on Wind Powr Systm with Adptiv Spd Control o MPPT Algorithm Ai-mi Xio nd Yong-xin Ji 1. Dprtmnt o Computr Scinc nd Tchnology, Shndong Univrsity o Tchnology, Zibo 25549, Shndong Provinc, Chin Abstrct: MPPT (Mximum Powr Point Trcking) is on o th most importnt tchnologis in th wind powr systm. It nlyss th wind powr systm s modl. Bsd on proprtis o wind mchin s mchnicl nd lctricl, round th rotor dynmics nd th xcittion winding voltg, this ppr rsrchs th utomtic trcking lgorithm o rottionl spd. By dynmiclly chnging winding voltg it controls th gnrtor rction torqu, thn th rottionl spd is djustd nd it dvlops nw nonlinr dptiv trnsmission control modl or wind powr gnrtor. This control modl cn djust th xcittion winding o th ltrntor voltg dynmiclly nd mk wind turbins to chiv th mximum powr point trcking rpidly. Ky words: Adptiv grshit, mximum powr point trcking, xcittion voltg, rotor dynmics, spd trcking. 1. Introduction As pollution-r rnwbl rsourc, wind powr hs th dvntgs such s non-pollution, inxhustibl supply, tc. It plys n importnt position in th utur powr supply systm, nd it is lso n importnt symbol o dvlopmnt nd progrss o humn socity in th 21st cntury. But th problm xisting in th wind powr gnrtion systm is tht th ctul powr output is grtly inluncd by xtrnl ctors, nd thr is wid gp btwn th ctul powr output nd th prdictd powr output [1]. Most o th xisting wind turbins dopt th constnt spd oprtion mod, tht is, th spd o th wind turbin dos not chng long with th chng o wind spd, thror, th utiliztion icincy o wind nrgy is low. Th vribl spd wind turbin, with its dvntg o bing bl to trp mximum wind nrgy, hs gind ttntion rom th scholrs t hom nd brod, nd its instlld cpcity is incrsing vry dy. It cn mk th wind whl s rottionl spd rpidly trck th chng o wind spd, which mks th wind powr gnrtor lwys kp running t th optimum tip spd rtio, thrby Corrsponding uthor: Xio Ai-Mi, lcturr, rsrch ilds: lgorithm nd ntwork inormtion scurity. th wind nrgy is obtind to th mximum xtnt [2]. Sinc th wind powr gnrtion ws put into prcticl us, mny MPPT (mximum powr point trcking) lgorithms [3] hv bn dvlopd, nd thr hv bn lso som thorticl rsrchs bout convrsion icincy. To mk ull us o wind powr, strting rom nlyzing th chrctristics o th wind turbin, it nds to cptur th mximum powr point o th wind powr systm nd rliz utomtic trcking. Du to th rndomnss o th wind spd nd nonlinrity o th wind powr systm, it is quit diicult to control nd cptur th lrgst cpcity point, which is lso on o th hot issus o wind powr [4]. Th ppr is orgnizd s ollows: Sction 2 xplins modl introduction; Sction 3 discusss stblishmnt o th utomtic control modl; Sction 4 contins th study o simultion; Sction 5 is th conclusion. 2. Modl Introduction According Bz thory, th mchnicl powr output o wind turbin cn b writtn s [5]: Pm( Vw) Cp, R Vw (1) 2

2 312 Rsrch on Wind Powr Systm with Adptiv Spd Control o MPPT Algorithm is th ir dnsity, R is th rdius o th turbin sht, C P is th powr coicint (dimnsionlss), Vw is th wind vlocity. Undr crtin wind spd, th input mchnicl powr cquird by th gnrtor only dpnds on wind nrgy convrsion coicint [6], which in turn is th unction btwn tip spd rtio nd bld pitch ngl 4. Undr th condition tht th wind spd is dinit, input mchnicl cpcity th gnrtor obtind will b only dtrmind by wind nrgy convrsion coicint [7]. In Eq. (1), th powr which th gnrtor obtins rom wind is in dirct proportion to cpcity coicint nd th cubic o wind spd. Whn is dinit, th rltion btwn nd shows prbolic rltion [8]. Fig. 1 shows th rltion curv btwn thm. Th slint point corrsponds to th cptur point o th mximum wind nrgy, which is clld th optimum tip spd rtio hr. And it rchs th mximum or th tim bing. Bcus o th rndom vrition chrctristic o th wind spd, it otn cnnot work on th mximum point. Instd o it is in sttus o low convrsion icincy. I th mthod o djusting th bld pitch ngl to djust th running o th wind turbin is doptd, thn it blongs to th mchnicl djustmnt. In gnrl, or dopting th lctricl djustmnt, th bld pitch ngl is constnt. Thror, is just th unction o, nd th rltion curv btwn thm is lso on o th bsic chrctristics o th wind turbin. Th tip spd rtio is th unction o th rtio o th wind whl tip linr spd to th wind spd: wr (2) Vw Whr, w is th rotor spd (rd/s), V w is th wind vlocity (r/min). A typicl rltionship btwn C P nd is shown in Fig. 1 From Eqs. (1) nd (2), it cn b concludd tht P V k w 3, (3) m w w Whr: 5 1 R kw Cp. 3 2 Th block digrm o th wind turbin systm in Fig. 2 shows how th wind turbin works. Th wind nrgy convrsion systm includs wind turbin tht turns wind nrgy into mchnicl nrgy, nd gr box which cn grtly incrs th rotting spd o th gnrtor. Th gnrtor turns th mchnicl nrgy which is convrtd by wind nrgy into lctric nrgy. According to th mchnicl proprtis o th wind turbin, th ollowing qutions cn b sily obtind: Tm T Jmw (4) Tp T Jw (5) Tw p Tw (6) C PMPP opt Fig. 1 Typicl powr coicint curv.

3 Rsrch on Wind Powr Systm with Adptiv Spd Control o MPPT Algorithm 313 Fig. 2 Block digrm o th wind turbin systm. Tm is th wind torqu T is th trnsmission input torqu; Tp is th trnsmission output torqu; T is th sht torqu; w is th gnrtor ngulr vlocity; J m is th momnt o inrti o th turbin; J is th momnt o inrti o th gnrtor. W dind th gr rtio G G (7) w Using Eqs. (6) nd (7), intgrtd Eqs. (4) nd (5), it cn b concludd tht Jw T, m GT 2 Rrrnging J Jm G J rsults in Eq. (8) Pm P Jw G (8) w w P m is th wind powr, P w P is th lctric powr. K wc ( I) (9) Whr K is mchin-rltd constnt, ci ( ) is th lux in th gnrting systm, I is th ild currnt. Thn th xcitr dynmics o th systm is govrnd. LI IR u (1) Whr L is th inductnc o th circuit, R is th ild currnt, u is th ild voltg. 3. Estblishmnt o th Automtic Control Modl To chiv bttr control prormnc, both rotor dynmics Eq. (8) nd xcittion dynmics Eq. (1) must b tkn into considrtion. Th rotor spd o th wind turbin is controlld by djusting th xcittion winding voltg. In th lgorithm dsign, it chngs th winding voltg to control th rction torqu o th gnrtor, nd thn mks th rottion rt gt rlvnt djustmnt. Thror th control mthod o dptiv vribl spd control is concludd: A control voltg is dsignd to nbl th rotor spd o th wind turbin to trck th dsignd spd closly. Suppos thr is limit or, nd Eqs. (8) nd (1) r rwrittn to obtin: nd whr w A Bc I (11) I bu I (12) k GK w A, B, J J 2 w, R 1, b. L L

4 314 Rsrch on Wind Powr Systm with Adptiv Spd Control o MPPT Algorithm To dsign th trcking controllr, lt us din th rotor trcking rror s: w w. Dirntiting upon Eqs with rspct to nd rrrnging it rsults in: A Bc I w, (13) Now w considr tht th prmtrs such s k w, J nd A r unknown, w din b th stimt o nd b th stimt rror dind by thn w rwrit th rror dynmic qution s: kz A (14) whr * z Aˆ Bc I w k (15) k nd it is constnt. In th Eq. (15), i z is md to pproch zro s t, thn with t w cn gt tht. Thn wht w nd to do is to mking z. Now w tk drivtiv o th Eq. (15) nd substituting or w, nd I, thn w gt th Eq. (16) ˆ ˆ c z AA w B I w k w I ˆ ˆ c AA w B I w k w I Aˆ ( Aˆ k)( k z A ) w c c B bu ˆ B IA w w I I w F ( ˆ bu A k) A (16) w Whr ˆ ˆ F A ( A k)( k z) w c (17) B I ˆ A w w I w c b B b. (18) I Now i w dsign th control voltg so tht 1 u F kz. (19) b th Eq. (16) is rwritd s: ˆ z kz A k A. w (2) Considr th Lypunov unction cndidt V z A (21) Dirntiting V, thn V ˆ zz AA ( k z A ) z ( ˆ ˆ kz A k) A AA w (22) k kz z 2 2 A ( ˆ z ˆ A k) A w I th stimt prmtrs  r updtd vi ˆ A z Aˆ k w w cn gt th Eq. (23) 2 2 V k k z z ( ). k 1 z k z 2 2 k k z. min (23) (24) nd thn w hv L L2, z L L2 nd A L. From th Eq. (15) w s tht th bounddnss o z, nd  nsurs tht  is boundd. So L, thn A L, At lst w cn gt L. According to Brblt lmm, w cn conclud tht both nd z convrg to zro symptoticlly nd  rmin boundd. Thus th ollowing rsult is stblishd. Considr th wind powr gnrtion systm givn by Eq. (8) with th ild xcitr s shown in Eq. (1). I th ild voltg is djustd ccording to Eq. (19), whr is gnrtd by Eq. (15) nd  r updtd by Eq. (23), thn th rotor spd trcks th dsird spd symptoticlly.

5 Rsrch on Wind Powr Systm with Adptiv Spd Control o MPPT Algorithm Simultion Study To vriy th ct o th dptiv trcking control strtgy, th ollowing simultion work ws crrid out. Th slction o som control prmtrs ws s ollows: 45, k k In th simultion xprimnt, th idl trjctory to b trckd ws slctd s: w 3 2 sin( t). Fig. 3 shows comprison digrm btwn th ctul nd th idl rottion spd, nd th rd lin rprsnts th curv o th idl rottion spd, whil th yllow lin rprsnts th curv o th ctul rotor spd. Th igur shows tht th ctul rottion spd cn quickly trck th idl dsign curv nd cn lso kp highly ccurt trcking. Fig. 4 shows th trcking rror curv. In short rspons tim, it rlizs trcking with lmost zro rror. Obviously, th controllr dsignd mks us o th dptiv spd control mthod to complt rottionl spd trcking icintly nd smoothly. Th control voltg is dpictd in Figs. 5 nd Fig. 6 shows th stimt prmtrs. It is obsrvd tht th proposd mthod chivs th smooth nd ctiv trcking rotor ngulr spd/(rd/s) dsird rotor ngulr spd trcking rotor ngulr spd Fig. 3 Trcking o rotor ngulr spd tim(s) th rror o trcking rotor ngulr spd Fig. 4 Trcking rror tim(s)

6 316 Rsrch on Wind Powr Systm with Adptiv Spd Control o MPPT Algorithm.3.2 u control voltg Fig. 5 Control voltg tim(s) output A Unknown prmtr A1 Estimt prmtr Fig tim(s) Estimtion o unknown prmtr. 5. Conclusion With th mturing o wind powr tchnology, th continuous improvmnt o th qulity o wind powr products nd th grdul dcrs o th cost o wind powr, wind powr lrdy hs th potntil or lrg-scl dvlopmnt. Du to th nonlinrity o th wind powr systm, chngs o nvironmntl conditions, nd inlunc o othr ctors, th MPPT mthod hs bcom complx nd comprhnsiv problm. Aprt rom considring th intrinsic chrctristics o ch mthod, th slction o th MPPT mthod lso nds to considr svrl ctors o th controlling mthod, such s th diiculty, conomic costs, snsor typ, trcking spd nd ccurcy, ppliction rs. It dopts n intllignt wy to trck th lrgst cpcity point to rliz th mximum utiliztion o th wind nrgy. Th simultion rsult provs tht th doptd control strtgy cn complt th cptur o th lrgst cpcity undr dirnt spds o wind, which ors bttr comprhnsiv bnit. Rrncs [1] Abdullh, M. A., Ytim, A. H. M., Tn, C. W., nd Sidur, R A Rviw o Mximum Powr Point Trcking Algorithms or Wind Enrgy Systms. Rnwbl nd Sustinbl Enrgy Rviws 16 (5): [2] Frris, L. L Wind Enrgy Convrsion Systms. Englwood Clis, NJ: Prntic-Hll. [3] Bhrnikumr, R., Yzhini, A. C., nd Kumr, A. N. 25. Novl Mximum Powr Point Trcking Controllr or Wind Turbin Drivn Prmnnt Mgnt Gnrtor. IEEE Trnsction 2 (2).

7 Rsrch on Wind Powr Systm with Adptiv Spd Control o MPPT Algorithm 317 [4] Blbjrg, F., Chn, Z., nd Kjr, S. B. 24. Powr Elctronics s Eicint Intrc Indisprsd Powr Gnrtion Systms. IEEE Trns. Powr Elctron 19 (5): [5] Brkti, S. M., Kzrni, M., nd Chn, X. 25. A Nw Wind Turbin Egnrtion Systm Bsd on Mtrix Convrtr. In Proc. IEEE/PESGnrl Mting, [6] Nmmn, B., nd Krjngpn, K. 27. Mximum Pk Powr Trcking-Bsd Control Algorithms with Stll Rgultion or Optiml Wind Enrgy Cptur. In Powr Convrsion Conrnc, [7] Wng, Q., nd Chng, L. C. 24. An Intllignt Mximum Powr Extrction Algorithm or Invrtr-Bsd Vribl Spd Wind Turbin Systms. IEEE Trnsctions on Powr Elctronics 19 (5): [8] Jouko, N., Slvomir, S., nd Jri, P. M. 21. Low Voltg Rid through Tsting o Wind Turbin Drivs [EB/OL].http: / /