Comparative Analysis for Extracting Compensation Current for Shunt Active Filter

Transcription

1 Ths work by IJARBEST s lcnsd undr Cratv Commons Attrbuton 4.0 Intrnatonal cns. Avalabl at Comparatv Analyss for Extractng Compnsaton Currnt for Shunt Actv Fltr Dhandayuthapan S 1, Sharmla C Rsarch scholar / EEE, SCSVMV Unvrsty, Kanchpuram 1 & Assstant Profssor / EEE, J Mathaaj Collg of Engnrng, Kanchpuram 1 Assstant Profssor / EEE, Collg of Engnrng, Gundy, Anna Unvrsty Abstract Th ncras of non-lnar loads n ndustral, commrcal and domstc faclts causs harmonc problms. Harmoncs caus malfunctons n snstv qupmnt, ncras hat n th conductors, ovrvoltag by rsonanc and affcts othr customr loads connctd at th Pont of Common Couplng (PCC). Shunt Actv Powr Fltr (APF) s dsgnd and mplmntd for powr qualty mprovmnts n trms of currnt harmoncs and ractv-powr compnsaton.. Th prformanc of th Shunt Actv Powr Fltr dpnds on th dsgn and charactrstcs of th controllr adoptd for APC. Ths papr s to fnd a sutabl control stratgy for rfrnc currnt ar utlzd for xtractng rfrnc currnt. Furthrmor, Hystrss Currnt Controllr (HCC) s appld to gnrat swtchng pulss of th PWM-nvrtr. Ths papr prsnts a comparatv study of two control stratgs to lmnatd harmoncs prsnt n th sourc currnt. Th systm s smulatd n MATAB-Smulnk for ffctvnss study. Indx Trms- p-q thory, Id-Q mthod, rfrnc currnt xtracton, and harmoncs I. INTRODUCTION Now days, th powr qualty n th dstrbuton systm s pollutd du to unbalancd load currnts. It gvs dstortd currnt at th pont of common couplng. In modrn powr systm th most mportant powr qualty ssus ar harmonc mtgaton and ractv powr compnsaton. Nonlnar loads rprsnt a larg prcntag of th total loads. Undr ths condtons, total harmonc dstorton (THD) may bcom vry hgh and dangrous for th systm. Th Powr qualty ndcs ar govrnd by varous standard rgulatons and rcommndatons such as IEEE-519. Passv fltrs ar achvd to mtgat harmoncs for th past two dcads.thy hav th dsadvantag of potntally ntractng advrsly wth th powr systm and t s mportant to chck all possbl systm ntractons whn thy ar dsgnd. Thy cannot oprat succssfully bcaus of paralll rsonanc problm at a slctd frquncy. SAF s an actv fltr whch s connctd to shunt wth th load and can work ndpndntly wth of th systm mpdanc charactrstcs. Actv fltrs can b ffcntly usd to corrct th powr factor, harmoncs mtgaton and ractv compnsaton, tc. Th basc prncpl of a shunt actv fltr s that t gnrats a currnt qual and oppost n polarty to th harmonc currnt drawn by th load and njcts t to th PCC. Th shunt actv fltr wth th systm confguraton s takn as thr phas brdg rctfr fds R load as non-lnar load as shown n Fg.1. 8

2 Fg.1.Systm confguraton wth SAF. Th ffcncy of harmonc compnsaton dpnds on th typ of control algorthm and to calculat th harmoncs load currnt. Th dffrnt control algorthms hav bn publshd for obtanng th APF rfrnc currnt. Ths control algorthms can oprat n tm doman or frquncy doman. In tm doman ths ar basd on nstantanous ractv powr algorthm (PQ), Synchronous dtcton mthod, Symmtrcal componnt thory (SC), Instantanous ractv and ractv powr currnt componnt thory (dq), constant powr factor Compnsaton thory, Prfct harmoncs cancllaton thory, tc. Ths papr compars th ffctv mthod of xtractng rfrnc currnt undr balancd snusodal voltag condtons. Th prformanc of pq thory, dq thory, ar compard. II. INSTANTANEOUS PQ THEORY H.Akag dvlopd an nstantanous p-q mthod [1].In ths thory actv fltr currnts ar obtand from th nstantanous actv and ractv powrs of th nonlnar load. Th thr phas voltags and currnts n a-b-c coordnats ar transformd nto α-β-0 co-ordnats usng Clark s transformaton as shown n quaton (1) and () = (1) = () = (3) p= (4) q= Th nstantanous actv powr (p), ractv powr (q) and zro squnc powr (p0) as shown n quaton (3).Th ac componnt of actv powr and ractv powr ar utlzd as th rfrnc powr. Th rfrnc currnts n α-β ar calculatd by usng quaton (5) = (5) 9

3 = (6) Th losss n VSI du to swtchng of smconductor dvcs so that addtonal avrag powr rqurd to compnsat for th losss. Th actual DC lnk capactor voltag (Vdc) s compard wth rfrnc valu and rror s procssd by PI controllr.ths nstantanous currnt rfrncs to th hystrss PWM currnt control ar dtrmnd. III. ID-IQ METHOD In ths mthod th compnsaton currnts ar obtand from nstantanous actv and ractv currnt componnts ld and lq of th nonlnar load [3]. Th mans voltags and load currnts ar to b transformd nto αβ coordnats as gvn by quatons blow. 1 1 u 1 / v w (7) 1 1 u 1 / 3 (8) v w p q p q (9) Howvr, th dq load currnt componnts ar drvd from a synchronous rfrnc fram Park s transformaton, whr θ rprsnts th nstantanous voltag vctor angl, gvn n q. (10) ld lq cos sn sn l cos l, 1 tan (10) Undr balancd and snusodal condtons angl θ s a unformly ncrasng functon of tm. Ths transformaton angl s snstv to voltag harmoncs and unbalanc, thrfor dθ/dt may not b constant ovr a mans prod. 10

4 Fg. Angular Rprsntaton ld lq 1 l l d (11) dq Th quadratur voltag componnt s always null, q =0, from quaton (10) bcoms nstantanous actv and ractv load currnts ld and lq dcomposd nto oscllatory and avrag trms. l d = - ~ ld+i d, lq = - ~ lq+i q (1) Th frst harmonc currnt of postv squnc s transformd to dc quantts. All hghr ordr currnt harmoncs ncludng th frst harmonc currnt of ngatv squnc, l+dqnh+l-dq1h, ar transformd to non-dc quantts and undrgo a frquncy shft n th spctra, and so, consttut th oscllatory currnt componnts. Ths assumptons ar vald undr balancd and snusodal mans voltag condtons. Elmnatng th avrag currnt componnts by HPF's th currnts that should b compnsatd ar obtand, cd = -~ld and cq = -~lq.fnally, th compnsatng currnts can b calculatd by th followng quatons c c 1 cd cq (13) c1 c c c / 3 (14) c T A Buttrworth fltr s chosn for th fltrng of harmoncs. Proportonal-ntgral (PI) controllr prforms th voltag rgulaton on th VSC dc sd. IV. SIMUATION RESUTS All th smulatons ar carrd out undr MATAB/Smulnk and smpowr toolbox for th dvlopmnt of SAF and ts control algorthm. Th rfrnc currnt xtracton n th tm doman for thr phas SAF undr nonlnar loads. Th prformanc of th algorthm s 11

5 obsrvd undr nonlnar loads. TABE I: CORRESPONDING PARAMETERS AND ITS VAUES Systm Sourc voltag 400V Systm frquncy 50Hz DC lnk capactor 35µF Sourc Rsstanc 0.1Ω Sourc Inductanc Rsstv oad(thr phas dod brdg rctfr) Srs Inductor oad 0.1mH 10Ω 1 mh a) Prformanc of Instantanous PQ Algorthm n voltag oad currnt n currnt Fltr currnt FFT Analyss 1

6 b) Prformanc of Id-Iq Mthod n voltag oad currnt n currnt Fltr currnt FFT Analyss V. CONCUSION In th prsnt papr two control algorthms ar dvlopd and vrfd wth thr phas thr wr systms. Both th mthods ar compnsat th currnt harmoncs n 3 phas 3wr systm. Th compnsaton prformanc of th two tchnqus s almost smlar undr dal balancd condtons and thy satsfy IEEE-519 standard t s obsrvd that Id-Iq mthod s mor snstv than Instantanous PQ algorthm undr balancd snusodal man voltag condtons. 13

7 REFERENCES [1] H. Akag, Y. Kanazawa, and A. Naba, Instantanous ractv powr compnsators comprsng swtchng dvcs wthout nrgy storag componnts, IEEE Trans. Ind. Appl., vol. IA-0, no.3, pp , May/Jun [] J. Afonso, C. Couto, and J. Martns, Actv fltrs wth control basd on th p q thory, IEEE Ind. Elctron. Soc. Nwsltt., pp. 5 11, Sp [3] V. Soars, P. Vrdlho, and G. D. Marqus, An nstantanous actv and ractv currnt componnt mthod for actv fltrs, IEEE Trans Powr Elctron., vol. 15, no. 4, pp , Jul [4].Rolm, D.Costa, and M.Ards Analysng and Softwar Implmntaton of a Robust Synchronzng P Crcut Basd on th pq Thory IEEE Trans on Ind lctroncs vol 53 N 6.pp Dcmbr 006 [5] A. Cavallan and G. C. Montaran, Compnsaton stratgs or shunt actv-fltr control, IEEE Trans. Powr Elctron., vol. 9, no. 6, pp , Nov [6] Molykutty Gorg and Karthk Prasad Basu, Thr Phas Shunt Actv Powr Fltr, Amrcan Journal of Appld Scncs, vol. 5, no. 8, pp , 008. [7] Gary W.Chang and Ta-Chang Sh, A Comparatv Study of Actv Powr Fltr Rfrnc Compnsaton Approachs, IEEE Trans. Powr Elctron, vol., pp ,