Adaptive Power System Stabilizer using Artificial Neural Network

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1 84 NAIONAL POWER SYSEMS CONFERENCE, NPSC Adaptv Pow Systm Stablz usng Atal Nual Ntwok P.C. Panda, A.. Panda and A. Routay Abstat-- An Atal Nual Ntwok (ANN) basd adaptv PSS and ts applaton to pow systm s psntd n ths pap. hs ANNPSS ombn s th advantags o mnmum vaan ontol statgy and th quk spons o ANN to yld to a nw typ o PSS. A popula typ o ANN, th multlay ppton wth o bak popagaton (EBP) tanng algothm s loyd n ths PSS. h ANN usd h has two hddn lays. h gnato spd was takn as nput and th stablzd voltag was th output. h ANN was tand by th tanng pas ospondng to dnt typs o dstubans and th pomans o th ANNPSS w oad wth th systm havng no-stablz and also wth CPSS. Rsult shows that th poposd ANNPSS an povd good dang o th pow systm ov a wd opatng ang and sgnantly ov th dynam poman o th syst y wods-- Adaptv Pow Systm Stablz, Atal Nual Ntwok. I. INRODUCION In ths modn ag du to ovgowng dmand o qualty o ltty, stablzng a pow systm und dstuban ondtons s on o th most otant qumnt o a pow. Pow Systm Stablzs hav bn wdly loyd o ths pupos. Untl now th onvntonal PSS and adaptv PSS hav bn wdly usd by pow ngns. Both onvntonal and adaptv PSS hav som poblm o th oth. ANN basd adaptv PSS s psntd n ths pap. h alzaton o PSS s basd on th da that th us o a supplmntay ontol sgnal n th xtaton and/o govno systm o th gnatng unt an povd xta dang o th systm and thus ov th unt s dynam poman []. h CPSS st poposd was basd upon a lna modl (lad-lag typ o popotonal ntgal typ) o pow systm at som opatng pont to da out th low quny osllatons on tansmsson lns. h CPSSs hav xd gan sttngs, whh a dtmnd und a patula opatng ondto But du to ts xd gan sttng a st o PSS paamts povdng good dynam pomans und a tan opatng ondton may no long ylds satsatoy sults whn th s a dast hang n opatng pont. o mantan a good dang haatst ov a wd opatng ang, adaptv PSS s a mo asonabl dsgn o th PSS as t taks nto onsdatons, nonlnaty and P.C. Panda s wth th Dpatmnt o Eltal Engnng, Na tonal Insttut o hnology, Roukla 7698, Inda. A.. Panda s wth th Dpatmnt o Eltal Engnng, Natonal Insttut o hnology, Roukla 7698, Inda. A.Routay s wth th Dpatmnt o Eltal Engnng, Indan Insttut o hnology, haagpu 73, Inda. stohast haatsts o th pow syst It an also solv th o-odnaton poblms among th stablzs. But th only daw bak s that t nds mo on ln outaton tm to alulat th ontol sgnal n ah salng pod. In th nt past Atal Nual Ntwok statd playng a vy otant ol n almost all lds o sah baus o ts ablty to moblz, apdty and obustnss. In th poposd ANNPSS a vy popula typ o ANN, th multlay ppton wth Eo Bak Popagaton tanng mthod has bn loyd. h ANN was tand to smulat th APSS s unton as los as possbl. A oason shows that th poman o ANNPSS s muh btt than that o CPSS and s losd to that o APSS. h poposd ANNPSS ombns th good poman o th APSS and quk spons o ANN makng th nw PSS wok muh btt than th al ons. II. ADAPIVE CONROL ALGORIHM o dsgn an adaptv PSS a sutabl modl must b hosn to psnt th ontolld syst h mnmum vaan ontol appoah poposd by Astom and Wttnmak (973) s usd n dvlopng th adaptv ontol algothm o ths wok. o apply mnmum vaan ontol appoah onsd a pow systm modl o th om 3 ( az a z a3 z ) y( t ) z ( b b z b z ) u( t ) ( t ) o A ( z ) y( B( z ) u( ( t )...(. A) wh ( s th unolatd andom squn o zo mans, whh dstubs th systm y( P() s ltal pow output om th gnato. u( s th stablz output njtd at th AVR summng pont. A(Z - ) and B(Z - ) a th polynomals o th lag opato Z - h adaptv ontol algothm s as ollows: () h auxlay output s outd om φ ( t ) y( t ) w( t ) λu ( t ).() H th pdtd valu o ø(t) s o th om () h valus o F,G,H a dntd usng th dntaton modl Φ ( t ) F( z H ( z ) y( G( z ) u(...() ) w(...(3)

2 INDIAN INSIUE OF ECHNOLOGY, HARAGPUR 73, DECEMBER 7-9, 85 Φ( X wh X ( { y( t ),..., y( t 3), u( t ), , u( t 3), w( t ),} and φ {, (3) h ontol u ( s ound aodng to th quaton y( g u( t ) g (4) h nxt sal s got and movd to stp (). III. ANNPSS RAINING o gt satsatoy poman om th ANNPSS, th onnton wghts must b dtmnd bo t s loyd to yld th dsd output. h poss o dtmnng th onnton wghts s usually d to as th tanng, whh plays a vy otant ol n dsgnng th ANNPSS. h ANN usd h was tand by mnmum vaan ontol APSS. h pupos o tanng h s to mak th ANNPSS unton as los to APSS as possbl. h tanng pa gnatd by th APSS onssts o spd s o th gnato as nput and stablzd voltag U as th tagt. Wth ths tanng pas at hand w pod to gu out a pop st o onnton wghts whh an bst t th nput-output pattns n th tanng st. In th psnt wok pap o bak popagaton (EBP) tanng algothm whh was dvlopd by Wbos [6] s loyd to tan th ntonntng wghts. A. Fowad Pass wh sum θ ( g g g h,,,,, y( t ) j a[ Σ W j All th wghts o th ntwok a ntalzd to small andom valus bo th stat o tanng. A outh od nput sgnal s usd o th ou nputs o th ANN.. s(), s(), s(3) and s(4) ospondng to w(, w(t-), w(t- ) and w(t-3) sptvly and th output o th ANN s th ontol sgnal U. Eah nuon gts th wghtd sum as th nput om th low lay. hs sum s altd by a nonlna atvaton unton (a tan hypbol unton h) to stablsh th output gvn by,}... y( t ) g u( t ) hw( j nput sgnal to nuon j output om pvous nuon j whh ( sum ( sum.( 4) u(...(5) θ )] b...( 6) θ ) s nput to th nuon W j onntng wght btwn nuon and nuon j and a (max mn)/, b (max mn)/ Wh max maxmum valu o th output mn mnmum valu o th output H Sum, n quaton (6) s ov all nods j n th pdng lay that onnts wth nuon though wghts W j. Analogously th output o th outh o nal lay s th output voltag U. B. Rvs Pass h voltag U got n th owad pass s oad wth th tagt and th wghts a thn adjustd to lmnat th total squad o. Wh m s th numb o output nods. At a M Ep ( )...(7) Σ t pm outpm m tanng pa p s psntd E p s outd and th wghts an b updatd to mnmz E p o th st o tanng data by mthod o gadnt dsnt. Wght updatng btwn hddn unt k and output unt m s don as p th ollowng quato η s th lanng at and α s th momntum ont. W mk wh ( p) η ( t ) ( nt, θ ( p )...( 8) )...( 9) W mk (p-) hang n wght ollowng th psntaton o th pvous nput-output pattn (p-). Smlaly wght updatng om any nput (o hddn) unt j to a hddn unt k s don by, W and kj ( p) η ( nt, θ ) Wh s a nod n th lay ollowng that o nod k. x F( x) a b...() x h non-lna atvaton unton takn n ths pap s h valus o η and α a takn. and.4 sptvly. o spd up th lanng poss th lanng s adaptv as th tanng poss gos on as p th law dsbd blow. Stp : h ntal valu o η. Stp : Lanng poss s statd by usng η. and α.4. h wghts a thn updatd as p th quatons (8) and () and ths s ontnud tll m jp α W p α W W k mk kj ( p )...( )......( )

3 86 NAIONAL POWER SYSEMS CONFERENCE, NPSC E( n) C all th tanng sts a psntd. It C s M t l. s l m l. s alld tato l. Stp 3: At th n th taton a nomalzd o unton s dnd as ollows: As th lanng gos on valus o E (n) gadually dass ndatng that th lanng s podng n th pop dto η( n ).99η ( n) E( n ) E( n ) ( ) ( ) < β E n E n Stp 4 : h valu o η s dasd whn th dn btwn two sussv tatons s dasng t... (3) A. h Phas Fault st o obsv th poman o th poposd stablzs und tansnt ondtons a th phas to gound ault s appld. H P.3 p.u., p...9 (lag), quvalnt atan o th doubl ut tansmsson ln s.4p.u. A th phas to gound shot ut ault was appld at th mddl o on tansmsson ln, whh s lad. s lat by dsonnton o th aultd ln and t was sussully losd at 4 s. Fg.- shows th vaaton o pow angl dvaton w..t. t Fom ths t s la that th CPSS ontols th pow angl dvaton o th gnato at th ault somwh btt than wth no-stablz. It also vals that th ANNPSS mnmzs th pow angl dvaton at th ault and qukly tuns to stablty by dang out th osllatons dastally....wh β s a postv onstant. H a valu o.8 o β gav satsatoy sults. h ANN s tand wth dnt typs o dstubans usually ad by a pow syst IV. SIMULAION SUDIES AND RESULS o study th pomans o th ANNPSS a thd od dst modl wth tm vayng onts s usd as a gnatng unt. Invstgatons a basd on a dtald modl o a gnatng unt onntd to a onstant voltag bus though two paalll tansmsson lns. A shmat dagam o th systm s shown n Fg. -. Fg-: 3-phas Fault st (Pow Angl Dvaton Vs m Chaatsts) B. CPSS Paamt unng In ths as th gnato s ntally opatng at P.7 p.u. p...85 (lag) upto s. At t s, a.5p.u. stp nas n pow n s appld whh ontnud upto 5 s, at t 5 s th systm tuns to ts ntal opatng ondto h paamts o CPSS a kpt th sam o all th smulaton studs and a tund aully. Fg.- 3 shows th sults o th study wth no stablz, CPSS and ANNPSS. It an b obsvd that th ANNPSS dam out th low quny osllatons vy qukly and thus stablshng ts supoty ov oth PSSs. Fg-: Systm Modl Usd n th Studs Studs hav bn pomd o dnt typs o majo aults whh quntly ou n th pow systm and pomans o ANNPSS s oad wth th systm wthout PSS and wth CPSS. Fg-3: Paamt unng st

4 INDIAN INSIUE OF ECHNOLOGY, HARAGPUR 73, DECEMBER 7-9, 87 C. Lght Load st In ths tst th gnato s opatng n a lght load ondto P. p.u., p...85 (lag). hs s th ondton upto s, at t s a.5p.u. stp nas n pow oud whh pval upto 5 s and at t 5 s th systm tuns to ntal opatng ondto h dstuban s lag nough to aus th systm to opat n a non-lna go h haatsts a as shown n Fg.-4. It an b asly obsvd that th ANNPSS gvs th bst sults. V. ANNPSS Vs APSS In th psnt wok th APSS s usd to tan th ANNPSS to at as ts ountpat. ypal oason uvs o th losd loop ontol systm spons wth ANNPSS and APSS a shown n Fg.- 6. Fg-4: L.L. st D. Ladng Pow Fato Opaton st It boms a dult stuaton o th ontoll whn th synhonous gnato s opatng at a ladng p.. hs s baus o th duton n stablty mag Howv und tan umstans, t boms ssntal to opat a gnato wth ladng p.. So a pow systm should b abl to opat satsatoly wth lad p.. Fo ths tst ntally P.3 p.u., p...9 (lad), at t s a. p.u. stp nas n pow n oud whh pvald upto 5 s and at ths th systm tuns to ts ntal opatng ondto Rsult s as shown n Fg.- 5 that shows th btt stablzng apaty o th ANNPSS. Fg-6: ANNPSS Vs APSS Fom ths uvs, t s sn that although th s not muh dn btwn th poman o ths two, dn ls spally n th st swng o th spons uvs. I th outaton had takn mo tm than th dn btwn ths two PSSs would bom mo sgnant. So t sgns that th ANNPSS has mo pomsng utu wth olatd systms lk multmahn pow systms. At pomng all ths tanng and tsts th ANNPSS s gvn a slghtly dnt ault as P.3 p.u., p...9 (lag). At t s.5 p.u. stp nas n pow n s gvn and at t 5 s th systm tuns to ts ntal ondto In ths as also th poman o th ANNPSS s th bst. VI. CONCLUSION An atal nual ntwok has bn usd to dvlop a nw gnaton PSS o a sl pow systm and pomsng sults a obtand om ths. A vy popula typ o ANN, th multlay ppton wth o bak popagaton tanng algothm s usd n ths ANNPSS. h ANN s tand by th mnmum vaan ontol APSS. In th tanng poss sval nput-output pattns a st old and stod n th tanng st and a usd to obtan th dsd wght subsquntly. o spd up th tanng poss, an adapton law s poposd to updat th lanng at. Fom th smulaton sults t s obsvd that th ANNPSS povds vy good dang o pow systms and mak t stabl vy qukly n oason to oth PSSs. Fg-5: Lad P.F. st

5 88 NAIONAL POWER SYSEMS CONFERENCE, NPSC p pω pe pu d VII. APPENDIX h gnatng unt s modld by svn st od ω ω ω ( Pm I ( V V U ) ( g pe U )......( 7) s d pω ω dntal quatons as gvn blow ( ) ( ) ( 3) ( 4) P g ) ( 5) x d ad ω...( 6) h dntal quatons o AVR-xt ombnaton a pe pu h govno usd s a thmal govno havng tans unton b g a s wh, & ω g h CPSS s o lad-lag typ havng tans unton V ( s) wh, w w s a Q s Q & s s d & s ( V V U ) ( g pe U ) s s d E E h paamts o th smulaton study a as gvn blow (all paamts a n p.u.) a.,x ad.6, X aq.66, d.89.3, X d.4, X q.743,.3 X d.33, X k.5, X k.65,h 3.46 X.6, R..,., g s -.4 s., V max 6., V mn -6. g.5, a -.38, b -.7, w.6 Q.5,.,.3 p.,., d., U max., U mn -. s., β.94, λ.99, Nu τ.5 Pd., P p 999., A k.5, τ.998, α.94 VIII. ACNOWLEDGEMEN D. P.C. Panda s thankul to MHRD, Govt. o Inda o gantng th R & D pojt on Ratv Pow Poblms and Managmnt n Pow and Poss Industy to ay out ths sah wok. VII. REFERENCES. Lppmann R.P., An ntoduton to outng wth nual nts, IEEE ASSP magazn, pp 4-, Apl Wassman P.D., Nual outng thoy and pat. 3. Hsu Yuan-yh and Chn Chao-Rong, unng o pow systm stablzs usng an atal nual ntwok, IEEE ans. on Engy Convson, Vol. 6, No 4, D Panda P.C., Ph.D. hss. 5. Sahu C.R., M.E. hss (994), supvsd by D. P.C. Panda, REC, Roukla. 6. Wdow B. and Lh Mhal A., 3 Yas o adaptv nual ntwoks: Pptons, Madaln and Bak popagaton, Po. IEEE, Vol. 78, No 9, pp 45-44, Spt Wbos P.J., Bak popagaton though tm, whn t dos and how to do t Po IEEE, Vol. 78, No, pp 35-36, Ot Pahalawathatha N.C., Hop G.S. and Malk O.P., An Ilt Sltunng Rgulato as a Pow Systm Stablz, Unv. o Calgay, Albta.

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