PSS Design of the Combined Cycle Power Station (CCPS)

Transcription

1 Procings of th Worl Congrss on Enginring an Computr Scinc 7 WCECS 7, Octobr 4-6, 7, San Francisco, USA PSS Dsign of th Combin Cycl Powr Station (CCPS) F. M. F. Souza, E. L. F. Danil, J. N. R. a Silva Jr, J. A. o Nascimnto, J. C. T. Campos M. Falcucci, an L. H. S. C. Barrto Abstract Th papr prsnts th projct to Powr Systm Stabilizr appli to th gnrators of th gas turbins of Combin Cycl Powr Station. Th projct vlop us MATLAB softwar for th stabilizr s paramtrs calculation. Th calculation was gottn from th linar mol bas on a machin connct on an infinit-bus. Th stabilizrs ha bn us to incras th machin ltromchanic oscillation amping. Th mol s valiation was givn for isturbancs simulation as loa stp an lins opn. Th calculat paramtrs wr compar with that ar implmnt in fil an th ons that ar suppli by th manufacturr. Th rsults show that it is possibl to improv th powr systm ynamic prformanc with this moling. Inx Trms Combin Cycl Plants, Dynamic Stability, Powr Systm Stabilizr. I. INTRODUCTION Th high financir, cologic an socials costs rsult of th big hyrolctric s construction an long transmission s lin hav stimulat th lctric nrgy istribut gnration, with th plant localiz clos to consumrs. For big urban cntrs, th most fficint altrnativ is a Combin Cycl Powr Station - CCPS, which utilizs gas turbins an stam turbin associat in th sam plant, both lctric nrgy gnration by natural gas. For that, th hat in th gas turbin s xhaustion gass is us to avantag, through of Hat Rcovry Stam Gnrator- HRSG, proucing th ncssary stam to th stam turbin s riv. Th natural gas is xmpt of sulphur an ashs, what it bcoms ispnsabl th xpnsiv installations of sulphurization an ashs limination that is man in coal an oil thrmal. Th aci rain problm is minimum in a natural gas thrmal, an th contribution for th global hating, for gnrat kw, is vry lssr that in th corrsponnts th coal an oil, for th bst thrmal fficincy. E. L. F. Danil (warlnnon@gmail.com), F. M. F. Souza (francismarry@yahoo.com.br), J. N. R. a Silva Jr (nilorjunior@yahoo.com.br), J. A. o Nascimnto (almia@.ufc.br), J. C. T. Campos (tls@ufc.br), L. H. S. C. Barrto (lbarrto@.ufc.br) ar with th Elctrical Enginring Dpartmnt, Fral Univrsity of Cará, Fortalza - CE, ZIP , Postal Co 6, BRA. M. Falcucci (-mail: mfalcucci@nsabr.com.br) is with th Fortalza Thrmolctric Cntral Gnration (CGTF-ENDESA), Caucaia CE, ZIP 66-, Postal Co 7, BRA. Th plant in stuy is compos for: two gas turbin, ach on with a nominal powr of,8mw; a stam turbin with nominal powr of 3,MW; two hat rcovry boilrs; a cooling towr; an lvating substation of 3MA; two gnrators with nominal powr of 33,8MA an a gnrator with nominal powr of 47MA. Th Combin Cycl Systm is a rlativly rcnt tchnology, it has chancs opn for improvmnt, ithr in a thrmal fficincy an th prformanc of th uipmnt. Th saf fficincy of a complx structur CCPS pns on thirs automatic controllrs, to guarant th opration s stability. In this papr ar prsnt mathmatical an computational mols vlopmnt of th control systms synchronous gnrators, consiring th spcific charactristics of this uipmnt typ an its us in thrmolctric. Th simulations rsults ar us for projct controllrs valiation. II. SYSTEM S STABILITY Th man for th nrgy gnration situat nxt to th consumption plac it coms growing stimulat, howvr, for th govrnmntal an public prssur for th nrgy matrix s ivrsification. Th Distribut Gnration not only aims at th gnration s cntralization as also th biggst trustworthinss in th lctric nrgy supply. Thrfor, th combin cycl thrmolctric plants ha start to gain gratr forc in Brazil, which ha mainly to th tchnological volution an th gas-lins msh s growth. Th majority of th nrgy companis aopt stablish computational moling bas in hyrolctric plants mols for th powr systm ynamics analysis. Howvr, this tchnology can b significantly iffrnt of us in combin cycl thrmal plants bcaus of th paramtrs tuning of th plants controllrs. Not consiring this iffrnc, th systm s amping is aning. Th powr systms stability rlats th capacity that th systms kps accptabl prmannt voltag in all th bus unr normal opration an aftr isturbanc occurs. A powr systm is totally pnnt of synchronous machins to lctric powr gnration. A ncssary conition for th satisfactory opration is that all th machins rmain in synchronism, or ISBN: WCECS 7

2 Procings of th Worl Congrss on Enginring an Computr Scinc 7 WCECS 7, Octobr 4-6, 7, San Francisco, USA ithr, that thy oprat with th sam sp. This aspct of th stability is conuct by th ynamics of th synchronous gnrators rotor angls an has bn rlat in litratur as rotor angl [7]. A soft variation in th systm loaing, consir as a small isturbanc can gnrat lctromchanical oscillations currnt of th lctromchanical toru unbalanc in th synchronous gnrators []. Th us of voltag rgulators provis th incras of th gnrators synchronism torus, howvr, rucs th liui systm amping, causing th ynamic instability. With th crating lctromchanical oscillations littl amping bcam ncssary to implmnt masur corrctiv to control ths situations. Th problm has bn solv through th introuction of PSSs - Powr Systm Stabilizrs [3], [5] an [8]. III. MODELING OF THE SYNCHRONOUS MACHINE AND ITS CONTROLLERS Turbin Excitation Systm Stator Rgulator Stabilizr Δ Δ δ Toru Fig.. Machin s rprsntation in block iagrams. Figur rprsnts th turbin, gnrator an its controllrs. Th gnrat voltag is controll by rgulating th systm xcitation. As soon as th magnitu of th systm xcitation incrass, th gnrat tnsion an th ractiv powr of xit incras. Th voltag rgulator vrifis th iffrnc btwn th machins output voltag an a rfrnc voltag. This iffrnc or voltag rror is compnsat through th xcitation systm control. Th us of fast xcitation systms can aftr bcom unsatisfactory th machins amping lvl whn th isturbanc occurs []. In stay stat, whn th shunting lin of th sp is zro or approximatly zro, th voltag rgulator pns only on th voltag rror. In transitory, th gnrator s sp is not constant an th rotor angl varis, causing oscillations in th rotor s movmnt. Th PSS s purpos is to us th gnrator s xcitation systm to rgulat th powr oscillations an consuntly to incras its stability. Th PSS oprats through th voltag rgulator, influncing its tuning point. Th machin s 3 r orr mol connct an infinit bus through an impanc uivalnt is prsnt in Fig.. Th mol s constants linariz for an opration point ar rprsnt by th uations to 6. In Fig., it is nclos th voltag rgulator, show for a gain an a tim constant T E. This mol is rlat in litratur for [4]. ΔT ct ΔT δ ct Δ i{ R x I[ R ( x x ) 3 ]} () () [ ( x x )( x x )] (3) 4 E f ct 3 i( x x i Δ (4) )[( x x ) snγ R cosγ ]} Δ t 5 ct t { x... snγ ]} ( x t i [ R cosγ ( x x ) cosγ R snγ [ ix ( x x )... x )] ixr t (5) (6) i [ R ( x x )( x x ] (7) Bing: infinit bus voltag. voltag that fins th axl position an that it supplis x th toru angl initial valu. δ initial toru angl. x irct axl ractanc. x irct axl transitory ractanc. x uaratur axl ractanc. x Rsn x x I { x[ δ ( )cos γ] I ( x x )[( x x ) snγ R cosγ]} Δ Δ t 6 ct δ uaratur axl transitory ractanc. ISBN: WCECS 7

3 Procings of th Worl Congrss on Enginring an Computr Scinc 7 WCECS 7, Octobr 4-6, 7, San Francisco, USA x circuit s propr ractanc of th rotor s iron. γ amittanc angl sris uivalnt lss th toru angl. currnt componnt in th uaratur axl. I trminal voltag s componnt of th gnrator in th uaratur axl in th machin s rfrnc. trminal voltag s componnt of th gnrator in th irct axl at machin s rfrnc. gnrator s trminal voltag in prmannt rgimn t (absolut valu). ΔT m - - Hs Δ s 5 Δ t insi of shown MATLAB softwar an as in Fig. 4, illustrat th scrns of th vlop program. w st st t st rf Fig. 3. PSS s blocks Diagram. st st E f 3 s 3To - 4 ΔE f Fig. 4. Systm Data. Fig.. Machin infinit bus blocks iagram. I. PSS PROJECT Th PSS is an lmnt that supplis an aitional input to th rgulator. It is projct to compnsat th lays that occur in th voltag control msh, whos purpos is to improv th powr systms ynamic prformanc. Th phas s compnsation is carri through by th us of la-lag functions, which supply phas avanc on th intrst fruncy scal. Th systm was shap through thr gnrating bus, which rprsnt two gnrators of th gas turbins an on gnrator of th stam turbin, an th infinit bus that was us as rfrnc bus. Th simulation, for loa flow s attainmnt, was ma in analysis of nts softwar (ANAREDE). Th ata gottn through th flow ar: voltag moul, voltag angl, activ an ractiv powr. Thy ha srv of input for th PSS paramtrs calculation, which was scrib Byon th loa flow ata it was inclu as input ata th gas turbin gnrator paramtrs, Fig. 5, all th paramtrs in pu an rfrnc bas of 3,8k an MA. Fig. 5. Machin s Data. Initially, a % voltag stp in th gas turbin was appli without th PSS, an through of th lctric powr s graph, ISBN: WCECS 7

4 Procings of th Worl Congrss on Enginring an Computr Scinc 7 WCECS 7, Octobr 4-6, 7, San Francisco, USA shown in Fig. 6, th systm s ominant fruncy was calculat. π ωosc 7,85ra / s (8) 9,38 8,58 Tabl. PSS Paramtrs. T T T 3 T 4 T Manufacturr 3,8,,4,,4 - ONS,,,4,,4 - Dsign 5,,64, ,5 Powr (MW) Fig. 6. Elctric Powr in Gas Turbin Gnrator. With th fruncy calculat in 8 an bing, s j(w osc ) th lay angl of xcitation systm s phas θ, calculat through 9, ual s to 39,5. A/ TTA s [( TA 3T) / 3TTA] s ( 6A/ TT A ) This lay will b compnsat by th la-lag phas avanc, avanc lay, whos projct paramtrs, ar th tim constants T an T ar ual to,64 an,554, rspctivly [6]. T T at ω osc a T snθ a snθ Tim (s), 5 ω c,67 s (9) () () Th PSS s gain, ual to 5, was ajust through simulation using softwar ANATEM (Transitory Analysis of Elctromchanical). As th oscillation fruncy is blow of 8 ra/s, it was opt to th washout projct that liminat fruncis blow of,67 ra/s, in accoranc with. Bing, w c th cut fruncy. () Tabl prsnts th PSS s paramtrs: (i) calculat by th manufacturr, (ii) us by th National Systm Oprator (ONS) an appli in fil an (iii) projct.. RESULTS AND DISCUSSION Th projct PSS s prformanc was compar with th on of th manufacturr an with th foun on in fil through simulation. Th paramtrs tuning was valiat using ANATEM softwar, for th systm s ynamic analysis bhavior. Th systm was simulat for th situations: (i) % loa stp using th configuration gnrating connct th infinit bus, (ii) national link systm with opning of th lin Cauip to Fortalza, (iii) national link systm with th Paulo Alfonso I plant turn off an (iv) opning of th lin Quixaá to Milagrs. Figur 7 illustrats th curv of lctric powr gnrat by th on of th gnrators of th gas Turbin. As it can b vrifi, th systm without PSS, whn submitt to a % loa stp, prsnt subsunt oscillations to th first on, what it can tak th loss of machin s synchronism. Howvr, with th nabl PSS, a amp rspons was gottn mor, guaranting th stability. -83, -9, -99, -37, -35, PSS - Turn off 9,5,8 4, 6,4 8,7, Tim (s) Fig. 7 Powr with PSS ONS an PSS turn off. In Figur 8, th projct PSS s prformanc is compar with th PSS implmnt in th thrmolctric an th calculat for th manufacturr. On it is obsrv that th projct PSS prsnts a smallr ovrshoot an on bttr tim of room for th systm, what bcoms viabl th practical implmntation of th projct paramtrs for us in fil. Th Figurs 9 an ar iffrntiat by th typ of simulat situation. In th first on, th systm is simulat with th opning of thr lins of 3k that connct Cauip to Fortalza. ISBN: WCECS 7

5 Procings of th Worl Congrss on Enginring an Computr Scinc 7 WCECS 7, Octobr 4-6, 7, San Francisco, USA -88, -9,3-96,5-3,8 PSS - Dsign PSS - Manufacturr -35, 9,5,,9,6,3 3, Tim (s) of th ajustmnts of PSS s paramtrs, confirming that th bst amping is gottn with th projct PSS. 6,86 6,34 59,98 59,93 PSS - Dsign PSS Turn off Fig. 8 Powr with PSS Dsign, ONS an Manufacturr s PSS. In scon on, th simulation was carri through rmoving th Paulo Alfonso I Hyrolctric. Both show to th bhavior of th gas turbins gnrators. As it can b vrifi, th rspons is sufficintly oscillatory without th PSS, in compnsation, th rspons bcoms sufficintly amp with th us of any PSS. Also it is possibl to vrify that th sign PSS maks possibl a amp rspons mor than th PSS aopt in fil ,878,, 3,99 5,99 7,99 9,98 Tim (s) 5,5 5,9 96,3 Fig. Fruncy oscillation in Paulo Alfonso I plant. 86,7 PSS - Turn off PSS - Dsign 77,,, 3,99 5,99 7,99 9,98 Tim (s) 55 Fig. Powr without Quixaa Milagrs lins transmission ,,3 9,5 73,8 55, PSS - Dsign PSS - Turn off,, 3,99 5,99 7,99 9,98 Tim (s) Fig. 9 Powr without Cauip Fortalza lins transmission. PSS - Dsign PSS - Turn off,, 3,99 5,99 7,99 9,98 Tim (s) Fig. Powr oscillation in Paulo Alfonso I plant. Th fruncy oscillation of th gnrators in stuy with th Paulo Alfonso I turn off is obsrv in Fig.. Through th graph, again, it provs fficincy of th projct mol in rlation to xcssivly. Figur illustrats th simulation th opning of th lin of 5 k that it bins Quixaá to Milagrs. Analogic to th occurrnc with th prvious situations, vrifis it importanc I. CONCLUSION In accoranc with th rsults wr vrifi th fficincy of th controllr through igital simulation. Th wav forms with th isabl PSS monstrat a littl amp rspons of th machin s toru angl. For th prsnt simulations, conclus that th PSS sign through th MATLAB, which us a mol simplifi for th systm of machin s xcitmnt, rval satisfactory. Through th computational moling, it is obtain to simulat ral systms an to gt paramtrs capabl to b insrt in normal conitions for th bst control of th gnrators in combin cycl powr station. ACNOWLEDGMENT Th authors thank th Fortalza Thrmolctric Powr plant - CGTF, company of th ENDESA group, to th National Avic Scintific an Tchnological Dvlopmnt CNP, th Suprior Lvl Prfction Coorination Staff - CAPES an th Rsarch Support Founation FUNCAP for th support tchnician an financing th rsarch. ISBN: WCECS 7

6 Procings of th Worl Congrss on Enginring an Computr Scinc 7 WCECS 7, Octobr 4-6, 7, San Francisco, USA REFERENCES [] P. M. Anrson A. A. Foua, (994) Powr Systm Control an Stability, IEEE, Nw York. [] P. unur, (994) Powr Systm Stability an Control, McGraw-Hill, Nw York. [3] O. M. Aw-Bab, (6) Damping of Elctromchanical Mos Using Powr Systm Stabilizrs (PSS) Cas: Elctrical Ymni Ntwork. Journal of Elctrical Enginring, ol. 57, N o. 5, 9 95, IEEE Trans. PWRS, pp [4] F. P, DMllo, (969) Concpts of Synchronous Machin stability as Affct by Excitation Control, IEEE Trans PWRS, pp [5] S. W. Mota, (6) Simulação Transitórios Eltromcânicos m Sistmas Potência, EPGRAF, Campina Gran - Brasil. [6]. Ogata, (997). Morn Control Enginring, Prntic Hall. [7] P. W. Saur, A. M. Pai, (998). Powr Systm Dynamics an Stability, Prntic Hall. [8] F. M. Souza, (6). Molagm Rgulaors Tnsão Estabilizaors Sistmas Potência Usinas Trmlétricas a Ciclo Combinao. Anais o IX Encontro Molagm Computacional, Blo Horizont - Brasil. ISBN: WCECS 7