IEEE Transactions on Power Delivery, Vol. PWRD-1, No. 3, July 1986

A COMPUTER CONTROLLED VAR COMPENSATOR FOR DISTRIBUTION FEEDERS

G. Keene* A.Y. Chikhani*

wDept. of Eiectrical EngineeringRoyal Military CollegeKingston, Ontario, Canada

M.M.A. Salama** M.H. Rahman*

**Dept. of Electrical EngineeringUniversity of WindsorWindsor, Ontario, Canada

V.H. Quintana***Senior Member

R. Hackam**Senior Member

*** Dept. of Electrical EngineeringUniversity of WaterlooWaterloo, Ontario, Canada

Abstract - 'V/arious methods of rovJidi,VAR injectio ha--e been used to comprensatr i,-hindutiVe urrent i Dower disttri but nrfeeders. Some were based onr tne ortitmi-zatnof the l-cation and the ratino o1f thlcompensators cy minimizinc the re=ist i!elosses. However, these methods woere limiteCand their range and benef it reduced due to 4.heapproximatin fA the reactive load prof ieusinr. a sincle or a -limited multi-level moWdel.

This paper describes t:he design and thetestinz of a compensator that continuously.adAtapts to t'he inductive csurrent in the feeder,ensurin- a ma.ir.ium reduction o'f the resistivepower lo'sses at al levels of inductive loadfor a singly located compensator. The systemis based on a micproprocessor c tro edsusceptance onsistinpof a fi_xed inductor inseries with a t,hi yrist?or biased by a ixedcapacitor in parallel. By adjustinro thefiring ang-le cf; the thyristor in series withthe induct.or, a cont-.inuousl contro'lledcompensator is obtained. A detailed analysisof tihe harmonics and the means For theirsuppression are presented. The anal'sis haveteen verified exrperimenta11ly by desirnins andfabri -ain-i r. sa sui t ab1e system in which themodelLed feeder is tested iLn a laboratoryenvironment. Good agreement is obtainedbet-een the analysis anrd the ex.perimentalresuls-. The results of the arplication of asimpl ifI e-d versi on of the compensat.=1&or to. areal feed"er are also presented.

.INTRODbt.:TIoN

As the size of t;he power distributionsystem grows, a compensation for the reactivepower in. the systsem is needed to reduce thepower lJoss in the feeders. Fower eniineershave tackled the prob-lem f.or the last 4hirtyyears, usinc various techniques C l2. Nlea:rleand Samson : .;devel ped a scheme to minimizethe power loss in distribution feeders. TheydetWermined that, for a known uniformlydistrib;uted load, a maximum of 5k p:ower lossreductioin can be achieved by lacimna aspecific oapacitor at a specif;c ocation.Bae 3} presented a new approach to considerthe effect of chanrinc the reactive la,dlevels using a single-valued capac-itor. Hecalculat,ed the required rance of load level1s,provid,dina a maximum powjer loss reduction.

86 WM 179-6 A paper recommended and approvedby the IEEE Transmission and Distribution Committeeof the IEEE Power Engineering Society for presenta-tion at the IEEE/PES 1986 Winter Meeting, New York,New York, February 2 - 7, 1986. Manuscript submit-ted August 30, 1984; made available for printingNovember 14, 1985.

Amer e@;t al, 14 suggested that Neagle andSarson's Optimization formula for the powerloss reduction co.ld be applied to varyinQinduc-tive loads if the c_mpensatinc current isvaried to follow the change in the inductiveoad current.r This, they suggested, could be

done using thyristor-contXrolled react.ors withcapiacitor biasingi.

Eased on the analysis of Neagle and Samsonfor- the Deak load and applvino it at differentlevels, we propose a methlod of reactive powercompensation. 7n the proposed method, theopt-imal conditions for the maximum lossreduction are employed to ensure the mostefficient use of a capacitor-inductor bank.The reactive power generation (absorption) iscontro1lled by a microprocessor regulating thezate current ofL a thvyristor pair in serieswith the inductor. The capacitor currentacting as a permanent, constant bias ispartial.ly or completely neutralized leading tcoa var-iable and continuo_us c-ompensation based*On the actual value of. the complex currentflowing in the feeder.

The design of such a compensator, whichtracks the inductivre current level in thhefeeder and provides an adequate levelcompensation is described in this paper. Testesut.s which validate the proposed method are

also presented.

I.PROTLEM FORMULATO0N

Since in tlhis studv one of the mainobjectives is to describe the Concept ofap 'iat iOn of microDrocvessor for VARcompensation in a dist-ributioin system auniforml' loaded feeder which h=as no end loadand with -a neglig;l"r small voltare drop isassumed. The application to a distributionwsystem w-'ithn5lon-unf:orm loaci and non-uniformcross section feeder and end-loadliV'as recentlyreported . Trhe real component of thecurre.ncl is not affected, by the reactivecompensation hence only the reactive current

cons-iered. inc a per unit pu) sys=temf Ior the feeder lenth and source current asbase quantiies, the cumul-ative reacti.eCurrent as a funct rion fd istan.ce s rvLen by

J=I.. tl _

where i is the current-,frolm the source Anncomponent of -he course

at a distance - (pu!the indu,cive

curr.ent.

Figure I shows the current profile in t-hefeed-er.

The total rower lOss H due to the reactivJecurrent , is

TI= l 13! , R2

where R is the resistan-ce of t-he feeder.

If a Capacitive c!ompensator supplying a pu

0885-8977/86/0007-O337$O1.oo©1986 IEEE

337

338

,r -- I t_ ,ic | _ )._p'-A 4-

.,1 ) rf7 tze- so_ ,Ur-:e the o-,,' z-rent t e; --me5

V .gu-re 2 i Lustrates thecri-rf rrent;r;ofie du;e to t; prese:.ce of the ca7s-taito-Xr.'

:t ne read:v' _shcwn 2 t3.a fr a ma inumower l.oss reductionr the sonatin o the

Sub-

Uniformly distributed loads

. 0

Fc. :' Le.4a c-onnected thyristor contro&l'ledreactor iTLCR). Thh, thyc-istors in

parallel and oppcpite comb-ination.

I',

Fia. 1 C*urrent profile In the feeder.

rhen co-ntrolwled byr -R , thecurrent i it) irn the inductor Lof the source current.-,Tt ard

ir: 'nr a.-. e is c4ven ry

i.nstantanreousas a functionthe thyrivstor

capnacit-or a and' its ratino, are civen. b'-,

a =2/z3 (u) and I A13'- (t u ) ( 3

Sub- _Capacitor

-1 I

It s T {.o

wher-e = 7 /w L

' he fundamentalI Ccmonoonent of i(t) is

I = Im [l -2 -- sin 2a] (5)

and t,he indu+i-ve rec,tive power in the -C

V

L 2 wL a

iniformlr distributed loads1 . 0

K = (1 - - -nsin 2a)a Tr Tr

(7)

KU is t.e inductAive icmtensaon fact-,r. Thetoal reactive po.wer t. he i d.uct ive-

Caracitive bank is

3V 2

Q = 2m [C - ( -L x Ka )],Vars

Fic.2 Current. profile with one capacitor bank

lo-at.ed at distance 'a' (in u tr a

uniformlyLv distributed feeder.

3 . THYR._STC~-CONTiR-CLlED REACTOR

Bef ore presen-.t2ing th-h esin* f t e

comensa,tor systemt th.e -erformance of a

Thyristor-Controll.1ed Rea r JTCR si brrieiscusse

Ie ascuratiao of the TCR

is shown in Fic. 3. The controlling element is

pair of thvri-stors in parallel opposition.al conducting on alternate half cycles. If

the thvristors are fired after the peak of the

voit Age waveform, t,Dhe current through thereactor can be con\ltroI 1 ed .

(8)

T'he current, is not sinusoidal and containshicTher odd harmoni-cs. The macnitude of thefundamental-l and the hnarmonic components of the

current for different irinc anales are shown,in Fic.4. It will be observed that at .1cif irino: an 2 e_ the harmo. c comDonentsi.ncreases initia with increasing 'hefundamental component of the current. is

considered below. The higher harmonics are

dis=ussed in Set

4. C M.^JMPENSATOR MODC2El

A maximum power l3oss reduction Caan be

achieved in a uniformly loaded feeder if a

compensation is provided at a location two-

th.irds of the way along the lenath of the

Th1

C

f It11

feeder from the OLurce and t.he macnitude ofits current is two-thirds of the rea_tivec.urrent l . e.el a t the source '. This appliesat any load level as lonQ as tfhe nosition oftF.he compensator and the c-urreni thro;uh it

-4

r-

ciw

0

H

Reactive Current

F Funlamrntal3 Thi rd iarmonic

FiftihlEarmoiiic7 Sc,,,( nth llarmozi(

Ip

I 1p 31

I1

Fi7.5 Profile ofL un-.iformly distributedreactive lo'-ad in a feeder

. = 3I s i.in e.1 z

FIRING ANGLE (Radians)

From the measurements_ End the power facto,Jrto4n- 'a' he value ofusi no= e cu (,r 1 ) .

of the line currenton. t he oad s i de of

I1 dn be calculated

F g.4 Harmcnic comconents versus

ancl.eTCR firing

satisfy 's',e above criter a. 'f it is assumedth-at the location of. the co mpens tar is f i.e-dmhe:oe-sa--or reactive curren IT, shuld be

a4nu m^§ 2- follo.tw ecuation ( 3. u

:he netp react- _ive load,` current i induc iveand the current. thro--ugh the compensator iscaDacitive.

in order cal,ulate th%e requiredcompensator current, the feeder current andthe t.ower factor at the source must be

determiaied. From these quantities th,ereactive current at t"he source can be found1 o'

=- sin e

where i-s theP Induct.i1ve.currentpafter tzhe Point ofline curren,t after the point.:0 the phi-5ase angle between Ir

component of theinjectio,nIz theof. inje-ction, andand Vh

;;h;'e

The compensator current is a functionof the reactijve component of0 the current at

the source. A relationship between ,., and I

must be established since is not measured.Fror the case where the loads are uniformlvdistirCibuted and the compensator is optimall y

c da 'a' (F i:' * 5 } here a 2 13, it

foll'os1' that

i =i1 2,/ M) X.*= , / 3 T=J. If ' Q ?

andf%-rom equations (9) and (10)

Fic.6 Block diagram of the microprocessor-controlled compensator

5.HARDWARE IMPLEMENTATI ON

A schematic diacram oagff the compensatordesiLned and fabriated in 4.he rresent studyis sho.wn in Fi .b.6 he major components of

the compensator are:

I

4 .

C,,

the rower factor detector 4'PFD),the analog to digital converter (ADC!,the thyristor phase controlier (TP-t, deca_acitor and the TO"CR,t,he microcomputer,

Trthe FIJ,,^ is A phase detector. It measuresthe ancle between the lin voltage (VZ,) and

the li'Lne current It). he output of the PFDis an E-bit b`inary count whic-h is proportional

339

IS.S[ - 2/3 0.u- a

; cJli-fnrai crihlt -c f i-rli,--1. 0 p.u.

ACompensator

profile without compensation

11 )

-- ----- -l - ---- -

340

to te has a u n, e-rco:une i: is r_Ia t;e zer --rs:s =Ts t-the ._ine vol4tagean .d th e._un. The ___ntiis sto_.at t-he zT - sn of th e in e c-r-rent. Thezer- ave -e:eter b-y a ,ha e

co_nt.ro~er:m ~.^a,r, .nutacur-,ec b5'_ .rt.rI J_esr --tt e'

The A ii usedtC..atoneasure the inecurrentl: on the load si Ioref the comDennsatatr.The iurrer.is converted to a -;t.-a Usino acurren s-ensini- trafrmerasnd a smai1

resist.or. The actual outpu of the ADCcorrespDnr±ds to the -rms val.ue of the current.

The TPC rcnrlcIs the firinT angIe cft thethyristors in series with the inductor. Theheart cf the TPC is the ohase -ontroller(TCA7B',-E. "sing a ricital to Anal og Convertrer(DAC) thle mi--ro-omputer provides anr, inp ut,voltage to the phase control ler which ispro-ortional t-,he required fi.rincanrcle.

The microcomputer is desi_ned usinz aMotorola 68CZ2 microncrocessor . +t reads th-e.:ne current from the ADC_ and the angle fromthe FF,1D an.d conv.ert-s the lat ter to the pnaseangle. The microprocesscr then ca tulate thedesired firin angle And zprovides thenecessary control signal to t-hne TPC

E . 2.:.,F TWARE

The system s-ftware provides the orderedcontrol and the secuencin of events "that-occur w^?ithin the comiensa-tor ster. Thecomputer must c alcul te the firing anl'Je forthe thyris`r based on tne oaod crriren ndthe phase ancle. It reauires the calculatuionrof iz sin e. Va lues -f sin e for differe-tvalues of Z aree stored in a tab_Le . The pro utcis calul ted n a softt.ware rorcutine_. Theorocram-r reauires about, E, 00 bytes f memory.Figure sh7 _,7= h e software fl chart.

Ficu ,re il:srate the -rlaborato:,rv systemm C,t!t@i-,de f C=r +1 e~s.t ifh- -C r;hrw-=ymode_l for t-estinor trhe ocealDlti-onA of theco7pensat r A three onase adjustable R and

IJ load control~s the coer f=at-r an. the linecurrent _ . Ti;h A m,meter A' me=sure= therea;-ti e lSo crrerent aL 9 eTeamm-'ete-rAeMeasUre_ the tal 1ne aI-re,t r.urrentsensi,n transfol'armera-nd a tr e rms. m eter ar--connected t the T R to e 1- hrehe currenthrough tre reactorh It d notem tha

the tiaino caacitoir fedo r>ealidate theresul.ts a- the c-urrent throuzh it is const-ant.It s mei eis mo ele usini a const.aEnt capacitX kivebias in the software.

B .REEUItTB

Aft.er the system s-oftware is loaded intoth;e cop.muter and run the t,hree-phase lIomad isvaried to simulate varir.;ng load -levels. Ateach se lected load le.el the correspondingTCR firinq angle and t1he r'R phase current arerecorded. t is observed that at eachselected reactive load level, any increase ordecrease in the res-istive load does not affectthe r-R phase current siganificantly. Thelargest change observed is about 4%. Thismeans that the proper firing angle iscalculated correspoondino to the reactive loadcurrent and t,-he operations of the FF0, ADC and

t!he Firi-na ontrol circut for t,he reactor arechecked.

Fioure B illustrates the test result ofthe compensator . All curves are ,n pu ithth e s ,,=tem Ibe being the rated I-ranch

Fic. 7 Flov diagram of the- softare

compensat-or current I = ' 75A ecuals I ou.Frm Fil. t he fo1 inc obs-ervations --an besumrr.:ar.LZ.

I. The reactiv-e feeder culrrent I wnioh ismeasured using A. ireaies withinc.reasing the TPffiring anrgle a

Th.The required phase coDmpensat fisn currentIA to prori-. e a max,imum power Ios:reducti on also increases, wit+,h inoreasinQ.

3. The TOCR capacitive tias is constant, d; 1.ICpu th-hroug7hout the TPC'O firing. angle a .

4 . The requiired iTCRa max,imum powerwitsh increasino a.

phase cu-rrent to proi.deloss reduction de--rases

5. The fundamental t-heoretical vaIlue of t.heTCR current deCreases vith-. :ncreasnrig a .

6. The measured TCR rha=e current decreaseswi-th increasina a.

It will' be observed fLro-m Fig .q that the

341

0 3 FEEDER

LINE

120V 0 2 I 30

rr t r T t [ X {~~~~~~~~~~~~~cLOADl l l l l~~~~~~~~~~~~S RA Rct LA

RUE~~~~~~~~~~~~

RMS RMSL m ~~~~~~~~~TRANSMTI rP

THRISTORTRIGGERING MCOOPTRCIRCUIT TCR L PFD, ADC AND T

TCR CONTROLLER _

DUALFLOPPYDISK

Fig. 8. Microprocessor-controlled compensator test set-up

.1 1.1

1.0 + + 1.0

0.9 0.9

0.8 - 0.80 Fundamental (theor.)

0.7 0.7 A Sum of 1, 3, 5, 7 harmonicsz F- + Measured TCR phase current

zll 0.6 0 Reactive 'feder current S 0.6 -

A Req. comp. phase currontD { 4\ / / + TCI t'ncacitive bias

o 5 X Re/ _. TCR bhase curront0 Fnandamental (theor. j) 0.5v-

L-U V fleasuired TCR uhase currentL

0.4- >0.4-

uJ 0.3 < 0.3 -

cr_ cr0.2 0.2

0.1 0.1l+

0. 0. 0.0. 8 . 12 142.0.4 0.6 0.8 1.0 1.2 -1.4 1.6

TPC FIRING ANGLE (Radians) TPC FIRING ANGLE (radians)Fig. 9 Reactive current versus TPC firing angle Fig. 10 Sum of the fundamental and the harmonics

compared to measured TCR phase current

342

required TCR'F ha=-e -urrEtn s v ry c-lo-;se t,th e t e sreta..- 1L ct Va o thefunlda"mental co-nosen-c f the react ,currrent.F:7-r -anir xi n - rrent r the TP_.F -ri desthreoect ifri rfor the h'rito.s=ur, thati th.ne + z m er -a omponent of itscurrent 7_o. tL5_; _;'s__;*ua t e r s euu_r e fe thpiha-se rcurren-t.. T he rfeJr: e th e :ortrCller i st rackinc t he feeder rea -vIe uurrent, andcr:vi din: orcer lev"e -r zm;Densat i :n

t i-s als: aFparent from Fi that tcimere- a siCnifiant d; fference betvieen t1he

measured T_.R hase urrent and_ tphe requiredT xR hIase current This is shcwn in Flg.c .

3. HARMONQi CS

:ue to t.he des irabl;it,y of usino a

C.ntonuucsu= controw of the rea-tive -o,,-ver, thea=sociated harm,ni-c-s are ana-.lyze:d arn: measuresare t.aken to reduce theiLr e-Le:r-et onmthe sys-,temto an ac eptable omir. L,s

inaH.rmonrcii_ inr. a( c haract- rar e isstic Inarrmnonnc4ii s

cet--nethe thir hIarrm-cm ac dtit

tnyrJ. s vauc and th e re;--rs

¢~~c no.@_';i_r ;e_'_:t-5-i 'eve 2 ;in < i-l1tivand recomm-~_;,2end.ed ml'.e_ - o~- <re- r @ e - -t';'E _ a h z_2 E a t .1'~Hides 5 aiatt t:',3e associatd a r e

! ia-s p i - h e s=^_eii=t :w , _ v

Fic.l, _ - the charateri-sti- of the deiane -ion, it hi evident that a tihrouc1t-

anrl-s-ic f- -'e Inn eot,i:;n is- not necessary.

3

-alanc-ed System

These are generated by the non;R-inuaiuda-lrent,t end a...e LLd c racteri-t_-

harmonics. HEr on-cs,:- sove the th mmponentEre cener l" ne iil oer o-rd4er

ra-irt;e-rist ha;1-rmoics -an LC= eliminate: b"J

imzl.oef h'iich is t,ne s : uuse unit-iithdelt a connetd thvristcr Va ves to imiAnaehnar si-s ivisil b thr ee Thi is the

.icf i'cr hosen in th;e presente~p1 lc.t i ons . Telve ouLse inits ith tr:c-roie'-tor> sctoon con.snectd to deltas andtiJw'y sle:ondar.-'R.es cf the coUp'in transforemerare a- .s used 'eliminate harmno1s o-f tFer:f-.h and.the eventh order.

H-armonc ofevnrder

_en roer harmn-ic cenerated -b0 tln ce_:s:t:ve a urrent peai=s Ere

ocosoteoLni soon a i ace

POS A'

StC&342,AI MCrwiE e H, A t

2

F: 'LZ :el3t.-c nnection f

,,L.s' twl -^. qJ ;', .1.'+ ,\A

SECUNIIi> O ON.aR lFAN % A- 't ..

Fic . ll Cancellati on of evern harmonics

I rTh.hirld harmon is 2

d.-visible by three

haYrmcnics of an order

F rd harmonic on te t cn-eoe

o,rder

Th m-aximum valules of te :o:h a n d h

*ev m ar v : m'aoite' it5,h and

f the ra fundamental Current,

recpe t 'e The l m ri the ifth

har. rL occurs a - la irinri r.cpan-, 'eF or ntheonris-m n-c-n

or the chosen hs -p se onpensa r t ee

ha=rmonocs need oc- be eliminated u-ino f lters.

The desi suitabneu i ter is di=-usse. in

2p-coom-n .-

Th}e ma:Imun value of the third harmonic

is reac-ched' at 120' firinc ancle and amounts tc

ac,pr- , L ..mately 14 % of the rated fundamental

A morec,r ncfi- -ura ti.o n

e_iiminate troh

; -a n%~e .4 -'-- I +r

-e i .ned specif i-all.-

f- ift+ h and the ev nth order

I

s. I I

harmonri ! , -t . ++W-heelve pulse c ampe -n taorarrangeme-tent. ThIe comopensat--r bu is sri. inrow sect-ions which are connecteed - delta andw4ye secondar-v widin;<- of t;te c-,u jin:rtransformer. This is nos-t used in the res-ent

'- -?_~rkk The 'o rhase shift be t-een the twosectiorns results in a B 0 shi between t,h eharmonics.zenerated on the delta and the wvesect-isns and a cancellation of tU-he fif+t andthe seventh o;rder harmons-s n the rriJmrvside lor t".--'he feedlIer sEide.

. Non-chara teristics ha nrmcs-

In t-he present analysis a svmmetr" Snbalanc-ed cornd;Lit;ions in the systems areassumed. However, any asy.mmetry or imablancein the system results in .the seneration oifharmonics o.Lf all orders. The followi:nasymmetries and imbalances are important:

3-113-1 t 3RD HARMOrIC 1

Vol'tace imbalai ce

Reac-tor to.!lerances.Transformer tolerancesFiringz angle asymetrics between phases orbetw?een the positiLve and the necative halfcycles.

ArC7UL CURRENT

FUNAAMEI7TAI 1-L .:.2ND HARMONIC

"(POSITIVE HALFWAVE)

-4E 2ND HARONIC FCR 74E NEGAt4'.E NVA-':ICCPqE PNCRRESRON-,S TO THE AREAS EETWEE ACTUAL"' PPk''r V,40 T,HE l _ 1 J *

Fig. ,4 Secon-d harmonic c--eneration th-ro uQhasVmmetric positive an Id necative ha-Lwave areas

Fig. Ihird harmonic,voltaaes

unbalanced phase

asymmetrics. Th will be observed from Table Ithat the third harmonic com-onent is nots ian if iCant.

3.B Reductio-n- of 5tatic compeensator harmonics

The measure= taken to reduce the harmoniccurrents -n +the static compensator can bedivtided! into, t_hree types:

monensator configurationTI . Com- pe Insator des;ioanT7_ il terrs.

Csmnensat-r Confio-uration

The back to back thyrist_%ors o:'nfigurat ionin a comptensator valv*.e elimiinates the secondharmoni-cs and the delta -onne--ction eliminatesthe th1-ird harmonics and their mMultiples.Another option is to use a twelve pul secompensator in.stead Af a six-pu l-secompensat"or. This eliminates the fifth andthe seeenth harmonics and is recommended whent.he o-onditions for the harmosD.nios reduction arestringentn. However, this means i-creased costesp._eily a lower rat,inQs.

77 ICoensator!esicnThe resulting non-characteristic harmonic

currents are in the order of --oe percent ccthe ratIed fundamental curren t.

1.Seco.n and hird harmon-s-

Any asymmetry or imbalance nin the syvstemresults in a second order harmonic which doesnot cancel out. Figure 14 shows an imbala,nce'caused by asyrm.mmetri f-irinr andes a d theasso;ciated second order harmonics.

An asyvmme;trv caused by unbalanced phasevo.4ilacaes inegat.iv,e s-equence volta4es i sshownin Fiz. r with the as-socia-ted third harmonics.

The trans--Former tolerances have a .veryslight effect on harmonics ceneration Ibutvolta-e imbalance, reactor tolerance betweenphase reactors and firina angl"'e asvmmetricsa1l have some effect on the harmonics.

faAble I shows t-he non-characteristic, thirdharmonic component due to a combinatin of

using a lArr-e number of th vristsV'tohed _n ste s the harmcnic can bPereduced, oweVer, although. a large rnumber of

small st?eps indicatL'set_ vhe need for a

small er reactor-, the large nufmber of th rr istsrsw'tohesquic-kl'y negate's this advan+tace.

Anorsther aspect, in the desi.-In of thehardw.are is the tolerances in the eauipmenit-,.vhich c;an effect the non-c-haracteri tic

harmonics evaluaP tiLon. Tolerances ntransfrormer imped%,ances, reac .t-or toleranczes,capacitor banks tolerance and the accuracy i;nthe firi ng angle ±O.l deAJree) should be takenintoi cons,_5ideration in the ftilters design.

Folters

The; f-ifth and-_,Ithe seventh .narmonics are tobe eliminated in a E-Pu`se unit.

e tyt O-es,Lf rs are used to reduceharmoni.cs.

343

-1 .

2 .

B .

4.

344

. The hic as f_iter for i rcher orderrns o.-mrF : - ahn iMpedancf e

urve fr a thn an- 'e enfn ilter

Table 1 Levels of non-characteristic thirdharmonics

:_nrise a e3rh:r trD:edreact.-- ad a set -f C alaait- I ors anc -an ze

- r @ '_ 'w v '_ _is t UpA+ ,tG,ez_*'' ace s'i t*rect 2::n. e:e at system ":Ctaces u:,EOCO :r htruih a matchinQ rans orme eor

-hi:he-r 1- ':L,t-FaoTess Tne cz:mcensator is inended-mmrsvnne-ri-aI --nrilro :-nPtimizes the

ineotion : the reacte-4- '-I toe redu-ethereactive,,,,@ t,s_s_=es in vhe _.ys=te1m to-o ama nimum.

VOLTAGE IFIRING ANGLE

UNBALANCE ASYMMETRY IN

DIFFERENT PHASES

IN DEGREES

4

1

1

1

1

1

2.5

2.5

uf') TCR

The tnhyristo-r bridge is of therpe whiom inC.udes a oAncinareact-or is off the air c-;il tvpe.

HV BUS

selIf-cooledf an . T-he

-rder tuned filter

R.ecc.lating range uop 21c Ir~ AR.2. E'rSytne voltaes: _retly connected ur to

oDr t aat:ninc tranSt"Zrner fo_Ir

;_ e7i;e r- _ tS 4.tH z

4-

t; nt ;s a;+ | r. r e i @ 3 s ei a4I1a-,-n<_ hconven pev S;_ h A - rPen=ebr.

V~~~~~~

trec:en:'" p hreaker

s._t; ..le sCir reEty4ke-freSe swY'*4 -h;r A ................... set,riure -asnosfvr m e isceai :fteemead.

mtoents of the : nic e4sator,

I_ 4,-r-C }1C,Ytv W t-ur W ge@hast. be tlu:Ppe I :zi ttv ag.e: rceat' teahecacaip to-rs on. the lcw--E.'o tace sid2e and withsurge-arrester on the H.7. side, if necessary.

leotw vota;c e cnnec n-e itaument

Th; incomin r conmriseL a fast low-vcItaebreaker -1ofthw; it7L'hdrawabe type Itis inclu-;ed in t1he directiy-Connected versionas well as in the transformer version. Lhe_ow-vo ,tacge equ ipment als in:-cudes sets ofCiurent transformers fL .r protective andnMeasurIna1 :,urpcses.

AUX

Li 7I. LVL..~~~~_.

LW~~-.C F C

I ~~~TCR_

FI'L 1 Ma in oomponen ts of the dynami;c VARc mrena or

HV = ta-e connectino""ef:iMi pernt= ^ transformer

Lt s-aeii-tv_ace consnectin: ecai ment+

FC Fix ed pacitr

C-ontrol equimentlAX=.- Au.liiary power equipment

tt Fio, ed cavacitor

The capacitor battery Consists of three-phase units of non-PCB type formin- part of

the L.V. switchgear. The separate units are

built up of a large number of capac-torelements.

REACTOR

TOLERANCE

aI

MAXIMUM 3RD

HARMONIC

CURRENT

0.2

0.5

0.7

0.6

0.8

-2L10 102 103 10

Hz

Fic.I E 5tnh and 7thimpedance cu5.urve

(h Contarol equipment

Consists of a regulator control unit, 'herelk.ay prote-tive equipment and the aux;iliarycircuits.

11.CONCLUSION

TrI this taper, an accepted methoddeveloped by Neagle andd Samson for a singlelevel reactive current compensation, is

successful'ly appl7ied to dynamic, continuouslychancing reactive load conditions. Thereactive power compensator system designed forthis study performed well over the testedfeeder current range. The system successfullyextracts the reactive current component fromthe complex1 feeder current and adJusts thecurrent through the TCR to the appropriatele"el, su h that a maximum power lossreduction in the feeder is achieved.

The system hardware consis-ts ofine xtensive, lTo Tr and linear

C.i'-rciU s Theesoftware can be easily modifiedon sit-ie makina the operation of the systemsuff.ciently f Lex ib.le while the maint enanCeand t<he servicing can be easily performed btyrepl1acementorf card m-odu.les when nec-essary.

A detailed analysis of t,he harmonics anat.he means for their suppression are presen-ited.The analvsis have been verified experimentlallyby designing and fabricating a suitable systemin which. the modelled feeder is tested in a

345

laboratory environment. Gcod agreement isobtained Lbetw..een the analysis and thee,,xperimental results. The results of theieapplication of a simplified version of thecompensator to a real feeder are alsopressented.

REFEREN CES

El T.J.E. MiIler, "Reactive Power Contrrol inElectric Sy.stem' , John W,4iley and Sons,

[2 j1 N.M. Neacle and D.R. Samson,"LossReduction From ICapzacitors Inhstalled OnPrimary Feeders", AIEE Trans., Vol.7w,Part III, pP. 3'10-959, 1956.

3Z Y ac,5'BaL "Analytical Method Of CapacitorAllocation 0n Distribution PrimaryFeeders', PAS. lEEE Trans. Vol. PA--97,ppp.' 22-l-E,I 2 978.

C4 A.H. Amer, M. M. A. Salama and E.A.A.Manstur, "Optimum Value cf ReactW iveL'Ompensators With Controlled Rectifier f,orRadial Distr Ib uition Feeders", MEXIC.ON '81,.GuadalaJaraj Melico.-.co , Novembe r 1 q 8 1.

L'5 M.M.A. S'al mama, A.Y. Chikhani and R.Hackam, "Control o,f Reactive Power IT nDistributi ron Syrmstems With An End-load andFiixed L-ad Condition", Tran_s. IEEE PAS.Vol. PAS-104, 815 1MM 2128-2r 1 ,85.