Mitigating Balanced and Unbalanced Voltage Sag Via Shunt-Connected Voltage Source Convertor (VSC) by using Double Vector Controller

Transcription

1 sah Jounal of Appl Sns, Engnng an Thnology 6(3): , 03 ISSN: ; -ISSN: Maxwll Sntf Oganzaton, 03 Submtt: Dmb 7, 0 Apt: Mah 07, 03 Publsh: August 05, 03 Mtgatng Balan an Unbalan Voltag Sag Va Shunt-Connt Voltag Sou Convto (VSC) by usng Doubl Vto Contoll Abollah Sho, Hussan Shaf, Azah Moham an Shvn Sho Dpatmnt of Eltal, Elton an Systms Engnng, Unvst Kbangsaan, Malaysa Abstat: Ths stuy psnts a shunt-connt Voltag Sou Convto (VSC) to mtgat balan an unbalan voltag sag an gulat th g voltag at a fx lvl by nstng u atv pow at th Pont of Common Couplng (PCC). Moov, an nn Vto Cunt-Contoll (VCC) an out voltag ontoll (VVC) a appl togth to alulats th unt fns fo th VCC. Futhmo, an nuto/ apato/nuto (C) flt s pla wth th smpl -flt n btwn th VSC an th ntwo an t s onstut to u th voltag sag. ws, to ma up fo th unbalan ps, th postv an ngatv sun omponnts lat to th g voltag shoul b manag stntly. Th postv an ngatv sun omponnts lat to th g voltag shoul b manag stntly. Ths s ahv though th applaton of two npnnt ontolls fo th two suns wth an ntal asa stutu whh has bn xplat abov. Smulaton sults sgnat pop funtonng of th ontol systm whh has bn popos. Kywos: Pow ualty, atv pow ontoll, voltag an unt ontoll, voltag sag mtgaton, voltag sou onvto INTODUCTION In th nt as, pow ualty poblms spally voltag sag an hamon stoton a nown as on of th most sgnfant tops among pow systm ngns (Hngoan, 995; D Pna t al., 003; Wooly t al., 999; Jung t al., 00). Thfo, th oun of ths pow ualty vnts spally fo thos nusts whh a assoat wth nfomaton thnology systms an b vy hamful. ntly, stat-of-th-at pow lton bas ompnsatos all Custom Pow Dvs (CPD) hav bn vlop to mtgat th ngatv ffts of pow ualty poblms (Hngoan, 995). Th Ssonnt Voltag Sou Convtos (VSC), also all Stat Ss Compnsato (SSC) o Dynam Voltag sto (DV), an b atgoz as a typ of CPDs. Ths vs an b onnt n ss wth th stbuton f at th upstam s of th snstv loas to fftvly mtgat o lmnat th ffts of voltag sag, voltag mbalan an oth typs of pow ualty vnts (Hngoan, 995). Nvthlss, hgh nvstmnt an mantnan osts an omplx stutu a th man lmtatons to of Ss-onnt VSCs (Nwman an Holms, 00). Th Dstbuton Stat Synhonous Compnsato (D- STATCOM) s a typ of shunt-onnt CPDs whh s mostly bas on VSC an onnt n paalll wth snstv loas n stbuton ntwos to pott snstv loas aganst voltag sag, voltag vaaton an unt hamon stoton (Choma an Etza- Amol, 00; Esoba t al., 000). Th voltag sag ompnsaton statgy n D-STATCOM s bas on th atv pow njton at th onnton pont fo moat voltag sag, whl atv pow njton s manatoy to mtgat p voltag sags (Bolln, 999; Wang t al., 998). Thfo, a ps ontol statgy s nssay to mpov th ynam pfomans of D-STATCOMs. Suh ontolls shoul b abl to auatly ontol th voltag o unt fba loop an th swthng pattn of th nvts. Bas ontolls n D-STATCOM ontolls an b manly v nto voltag ontol an unt ontol, whh voltag ontol mo s manly ommon n Voltag ontol mo, th output AC voltag shoul ta th at fn voltag n DC uantts. Dpnng on th u ontol paamts, ths pou an b mplmnt usng (Cla an pa tansfom) fn to xtat atv atv pow an tuaat voltag omponnts as th tansfomaton valus an multplyng ths valus n th AC nstantanous voltag (Svnsson an ngn, 998). Th man lmtaton of ths thnu s th hgh snstvty of th tansfom valus to th mbalan voltag ontons, whh ma th ontol pou mo omplx. In ompason, th unt ontol mthos suh as hystss an avag unt ontolls a lss omplx an fast than voltag ontol mthos. In ths stuy, an mpov ontol mtho bas on voltag an unt gulaton s popos an usng Doubl Vto Contol (DVC) baus t has two Cosponng Autho: Abollah Sho, Dpatmnt of Eltal, Elton an Systms Engnng, Unvst Kbangsaan, Malaysa 379

2 s. J. Appl. S. Eng. Thnol., 6(3): , 03 vto-ontol loops. On of th loops s tan nto onsaton to gulat unt whl th oth loop gulats voltag at (PCC). Vto Cunt Contol (VCC) s appl fo ompnsato unt gulaton (Hngoan, 995) an Vto Voltag Contoll (VVC) wos as out ontol lop, whh tas th fn bus voltag to alz th voltag sag mtgaton. In th smulaton pogam PSCAD/EMTDC all th smulatons a a out an th lvant pfoman s manfst. wttn as Hanfos an N, 000; Wang t al., 998): u u ff pε ( u ) ff ε () (3) wh, an a th f-fowa tm an unt o at ah sampl, sptvly an:, ε ( n ) CONFIGUATION OF D-STATCOM WITH DUA VECTO CONTOE (DVC) u ω j [ ff g ] (4) DVC s manly a typ of asa ontoll sgn to ontol th u njt unt. DVC onssts of two vto ontolls namly Vto Cunt Contoll (VCC) an Vto Voltag Contoll (VVC). Vto unt ontoll: Th Vto Cunt Contoll (VCC) an b ons as a usful tool whh mas th ompnsato unt to ta th fn unt. Consng th shmat agam of th shunt-onnt VSC shown n Fg. an applyng Khhoff's voltag law to th VSC output flt by usng Cla an Pa tansfomaton un th fx two-oonat αβ fam, th voltag an unt at th Pont of Common Couplng (PCC) an b obtan as: u ( αβ ) ( t) ( αβ ) ( αβ ) αβ ) t ( g ( αβ ) ( αβ ) ( αβ ) ( αβ ) u ( t) g t () () wh, an a sstan an atan of th flt an u, g an a th VSC output voltag, PCC voltag an njt unt at th PCC, sptvly. By applyng th Synhonous fn Fam (SF),.., -oonat systm an Phas-o oop (P) n th VCC, th atv an atv unt an b spaatly ontoll. Thfo, E. () an b ε (5) Th popotonal gan, p, an th ntgal gan,, to attan th abat spons an also b fn as / T s / an K p, T s /T,, sptvly, wh, T, Th ntgato tm onstant s st to / Both atv an atv unts a ontoll npnntly wth hgh banwth, vn n ov moulaton gon usng th voltag lmtaton an Mnmum Ampltu Eo (MAE) tats (Ottstn an Svnsson, 00; Svnsson an ngn, 998). Th output voltag of VCC an b xpss n tms of SF by substtutng (4) an (5) n () as: ω u ( ) ( ) p, g u, ( )( ) ω ( ) ( ) ( ), p, g (6) (7) Vto Voltag-Contol (VVC): Th man tas of th VVC s to mantan an stablz th PCC voltag at ts Fg. : Sngl-ln agam of systm wth shunt-onnt VSC an -flt 380

3 s. J. Appl. S. Eng. Thnol., 6(3): , 03 Fg. : Blo shm of th wth ts lvant poss Fg. 3: G voltags ung 5% voltag sag. Wthout VSC at valu. In th psn of an njton tansfom wth wnng ato of : an assumng a nglgbl voltag op at th tansfom ato, th PCC voltag an b ons balan an ual to th flt apato voltag Fg. 6. Hn, th voltag at PCC an b ontoll an pt onstant. Consng Fg., th njt unt nto th g an b obtan as: ω j [ nj p, v, vε ( n ) (8) wh, ε () s th voltag o at sampl, s gvn by: ε ε AC-voltag ontoll: Th ampltu of th PCC voltag an b ontoll by njtng atv pow an also th voltag g an b hang by usng th ntwo mpan (Wooly t al., 999). Fgu shows` th omplt blo shm of th Vto Cunt-Contoll (VCC) wth ts lvant poss. Th voltag magntu o s tansmtt to th a-voltag ontoll, fom by a PI-gulato. In as of th stay-stat -voltag of wll b zo. s th g output fn atv unt, whh s f to th VCC an s th fn atv unt whh s au fom a slow -ln voltag ontoll that ompnsats fo VSC losss. Th apatv atv pow njt nto th ntwo by th VSC, has bn psnt as a blow: Thfo, ω nj nj ( ω ( ) wh, K p,v Th popotonal gan K,v Th ntgal gan ( p v ) (, v ), ) ( ) p, v (9) (0) If th ntgato tm onstant s ual to 30 ms an sttng of th unt an voltag ontoll a sptvly 70% an 5% of abat (Bongono t al., 005, Ptsson t al., 005)., v ( ) 38 Q g g () In vw of th fat that g s zo, whn th voltag of g s too low, apatv atv pow has bn njt an th unt wll b postv. Dst tm ampltu of th PI-gulato s gvn by: Tabl : Contol paamts g pamt G voltag E 400 V pu G Cunt I 40 A pu G funy f 50 HZ G nutan g. mh 0.4 pu G sstan g 0.05 Ω pu oa sstan l 0 Ω.73 pu oa nutan l 3.9 mh.3 pu DC-ln voltag u 600 V.5 pu Flt sstan 4.8 mω pu Flt nutan mh 0.09 pu g

4 Tabl : Systm paamt Cunt ontoll paamts Popotonal gan K P, 7.0(70% a bat) Intgato gan K, 0 AC- voltag ontoll paamts Popotonal gan K P,Q 0.97 Intgato tm onstant T,Q 0.0 P-ban wth α P 30 a/s Tabl 3: Injton tansfom paamts at pow S T 0 KVA.08 pu Shot-ut pow E T 30 V pu Shot-ut voltag P 4 W 0.05 pu aag nutan V 5.3 V 0.03 pu Ss sstan λ 0.3 mh 0.08 pu λ mω 0.04 [ pq g g g ] g [ TQ S s. J. Appl. S. Eng. Thnol., 6(3): , 03 ( n ) g g ( pq T )( 0.4 Q g () (3) wh, K PQ an T Q a th popotonal an ntgal gan of th gulato, sptvly. Pfoman spton: Tabls an a th ontoll an systm paamts sptvly (Wooly t al., 999). An by usng PSCAD/EMTDC, smulaton, ontol systm has bn nvstgat an tst. Fgu 3 has psnt th voltag at th PCC whn th VSC n l mo. As llustat, th voltag of PCC s un th nflun of a 5% voltag p an 9 phas-angl jump. Fgu 4 splay th VSC njt a hgh atv unt (los to 00A..) ung voltag sag to ma voltag at th PCC onstant 400V (Fg. 5). Aong to th smulaton sult t s possbl to ompnsat voltag sag wth nvstgat ontoll an by hangng -flt wth C-flt, VSC wll manag th amount of atv pow n. Systm pfoman by applyng ll-flt an atv ampng: In abov ston th VCC sb un stff g voltag, mpan of th g s appoxmatly ual to zo. If th PCC voltag stff s not nough, g wth th sam ynams of th njton unt wll hang, lang to th stablty poblm sb abov. It wll b ssntal to ovom ths poblms to shown th ynam of th g voltag at PCC. Consuntly, t shoul b mof onfguaton fo th SVC by ang a apato (C 60μμμμ) (Fg. 6). Paamts fo th njton tansfom a shown n Tabl 3. SIMUATION ANAYSIS ( n )] g g Th ontol systm, whh has bn off, has bn xamn un smla voltag p shown n n Fg. 0 an. 38 g Fg. 3. Th osllatons a vsbly snbl n Fg. 7. Instng a sst as a ampng tm n ss ( 0.5Ω) wth th flt apato wll la to th pvnton of ths phnomnon. Nonthlss, th ffowa tm n E. (4) s pt blow an Fg. 8 monstats that th PCC voltag s ajust to th pf valu whh appoxmats 0.0 pu osllatons an an b obsv n -voltag (Ptsson t al., 005,, 989): u ff [ ω j g ( ] (4) Dynam opaton ung unbalan voltag sag: Th popos ontol statgy by Smulaton sults has laf that t s only appopat fo mtgaton of balan voltag sag as you an s n Fg. 8, owng to th psn of th ngatv-sun n th masu uantts an to gan btt op wth unbalan voltag ps shoul mofy th onfguaton of th systm spaat to th ontol postv an ngatvsun of th njt unt. Mofatons of th ngatv-sun omponnts of th njt unt wll b llumnat n abov ston. Doubl vto otoll (v): To mpov th unbalan stuban ompnsaton two spaat ontols, Synhonous fn Fam (SF s ) an b us (Ptsson t al., 005, Snsama t al., 00), wh th postv an ngatv (SF) a synhonz to postv an ngatv sun omponnt of th ntwo voltag. Th sults an xplan by th blo shm of Dual Vto Contoll (DVC) (Wooly t al., 999). By Sun Spaaton Mtho (SSM) an sb sun omponnts of unt njton, voltag of apato an flt unt (Wooly t al., 999, Jung t al., 00). Euatons (3 an 3) a th sam fo th postv sun of VCC an VVC, sptvly. To ompnsat fo th unbalan stuban of th voltag, a ontol mtho s u to pou th sou fn unts of D-STATCOM n th as th ntwo voltag s unbalan. Ths fn unts nt th vto ontoll bas on whh onvto voltag a ma n phass a, b an. Th gnal tn s llustat n Fg. 9. In th Doubl Vto Contoll (DVC) (Wooly t al., 999), two ntal vto ontol blos xst whh a ffnt only n th sgn of oupl fatos btwn th an axs (Hngoan, 995). Th am s to tah th postv an ngatv omponnts of voltag an unt n th vnt of th unbalan voltag. Fou sgnals hang nto subsun omponnts. Dsptons of ths sgnals a pov )

5 s. J. Appl. S. Eng. Thnol., 6(3): , 03 Fg. 4: Injt unt of - an -omponnt as a sult of 5% voltag sag Fg. 5: Th-phas g voltags ompnsat at PCC.VSC an - flt a us Fg. 6: Shmat lat to th systm wth shunt-onnt VSC an C-output flt. Fg. 7: Th th-phas g voltags of th PCC ung th voltag sag.vsc n l mo Fg. 8: Th-phas g voltags of PCC. By applyng VSC, C-flt an atv ampng 383

6 s. J. Appl. S. Eng. Thnol., 6(3): , 03 Fg. 9: Shmat of systm (DVC) bas on oubl synhonous fn fams Fg. 0: Dsptons of ths sgnals Fg. : Dsptons of ths sgnals Fg. : Th-phas wav foms at PCC E g Ntwo voltag at PCC pont E Capato voltag of ompnsato flt I Cunt of VSC onvto I nj Injt unt to th ntwo Implmntng of ths fou sgnals s shown by E. (6, 7), (8, 9) an Fg. 0, : xx 0.5( (tt) (tt 0.005) (5) xx 0.5( (tt) (tt 0.005) (6) xx 0.5( (tt) (tt 0.005)) (7) xx 0.5( (tt) (tt 0.005)) (8) 384

7 s. J. Appl. S. Eng. Thnol., 6(3): , 03 To ompa th pfoman of th asa ontoll that w psnt n th pvous ston wth DVC un th sam unbalan voltag sag, llustat n Fg. 7, fo th-phas wavfoms an by usng Dual Vto Contoll, t wll b sussful mtgaton of th voltag sag an t s vntly vsbl n Fg.. CONCUSION Ths stuy sbs how to us VSC to mtgat voltag p. Moov, t susss an shows that VSC an ontol an mantan th ampltu of th ntwo s voltag wth ompnsatng voltag p by njtng atv pow. Nvthlss, ths n of ontol systm s ompltly snstv to th paamts vaatons of th systm. To gan at th hgh opaton an mo obust ontoll an stutu of shunt onnton, wth smpl -flt an C-flt has bn analyz. Invstgaton vals that by sltng a asa ontoll, wth VVC an VCC a mo powful ontoll an b ah. sult of th ontol systm has bn obtan n th postv an ngatv SF, n o to spaat ontol omponnts of postv an ngatv-sun of th ntwo voltag. Smulaton sults mantan that wth th popos ontol mtho, w an ahv hgh ynam pfoman by usng DVC. EFEENCES Bolln, M., 999. Unstanng Pow Qualty Poblms: Voltag Sags an Intuptons. IEEE Pss, Nw Yo. Bongono, M., J. Svnsson an A. Sannno, 005. An avan asa ontoll fo ss-onnt VSC fo voltag p mtgaton. Inusty Applatons Confn, Foutth IAS Annual Mtng Confn o of th 005, Gotbog, Swn, : Choma, K.N. an M. Etza-Amol, 00. Th applaton of a DSTATCOM to an nustal falty. IEEE Pow Engnng Soty Wnt Mtng, : D Pna, C., P. V, A. Sannno an M. Bolln, 003. Stat ss ompnsato fo voltag p mtgaton wth zo-sun njton apablty. IEEE Bologna Pow Th Confn Pongs, Italy, VO. 4. Esoba, G., A. Stanov an P. Mattavll, 000. atv Pow, mbalan an hamons ompnsaton usng -statom wth a sspatvtybas ontoll. IEEE Inusty Applatons Confn, Confn o of th 000, Boston, MA, USA, 4: Hanfos,. an H.P. N, 000. A gnal algothm fo sp an poston stmaton of AC motos. IEEE T. In. Elt., 47(): Hngoan, N.G., 995. Intoung ustom pow. IEEE Sptum, 3(6): Jung, S.Y., T.H. Km, S.I. Moon an B.M. Han, 00. Analyss an ontol of DSTATCOM fo a ln voltag gulaton. IEEE Pow Engnng Soty Wnt Mtng, South Koa, : , T.N., 989. Kompnssaton shnll vanlh blnstom ns shstomvbauhs. tzahv H. 8(B. ): Nwman, M.J. an D.G. Holms, 00. An ntgat appoah fo th potton of ss njton nvts. IEEE T. In. Appl., 38(3): Ottstn,. an J. Svnsson, 00. Vto unt ontoll voltag sou onvt-abat ontol an satuaton statgs. IEEE T. Pow Elt., 7(): Ptsson, A.,. Hanfos an T. Thng, 005. Evaluaton of unt ontol mthos fo wn tubns usng oubly-f nuton mahns. IEEE T. Pow Elt., 0(): Snsama, P., K. Paya an V. amanaayanan, 00. Analyssanpfomanvaluatonof a stbuton STATCOM fo ompnsatng voltag flutuatons. IEEE T. Pow Dlv., 6(): Svnsson, J. an M.B. ngn, 998. Vto unt ontoll g onnt voltag sou onvtnflun of nonlnats on th pfoman. 9th Annual IEEE Pow Eltons Spalsts Confn, PESC 98 o, 7- May, Gotbog, Swn, : Wang, P., N. Jnns an M. Bolln, 998. Expmntal nvstgaton of voltag sag mtgaton by an avan stat VA ompnsato. IEEE T. Pow Dlv., 3(4): Wooly, N.H.,. Mogan an A. Sunaam, 999. Expn wth an nvt-bas ynam voltag sto. IEEE T. Pow Dlv., 4(3):