7/25/2019 avr888

1/6

COMPUTATION OF RECLOSING TIME AND SUITABLEGAIN OF AUTOMATIC VOLTAGE REGULATOR

FOR ENHANCE SYSTEM STABILITY

L CAO QUYN v PHAN THTHANH BNH*

CNG TY TVN XY DNG IN 4 (PECC4)11 Hong Hoa Thm Nha Trang Khnh Ho , lecaoquyen@yahoo.com

* i hc Bch khoa, Tp. HCh Minh, Vit nam

BNG TM TT

Thi gian ng lp li cho ng dy nh hng rt nhiu n n nh h thng. Chn la thigian ng lp li kt hp vi chn la hskhuch i kch tph hp u nng cao khnng nnh. Bi bo ny a ra mt phng php tnh ton thi gian ng lp li ti u da trn tiu chunhm nng lng Lyapunov i vi hthng SMIB vi my pht c trang bkch t. Bi bo cng s

tin hnh kho st trn h thng thc (h thng 500/220kV Vit Nam nm 2010) bng chng trnhPSS/E-29 nhm nh gi tnh hiu quca cc nhn nh ny.ABSTRACT

The reclosing time of a transmission line has influenced on system stability. Selection of reclosingtime and suitable gain of automatic voltage regulator (AVR) would be enhanced and improved systemstability capacity. This paper presents a method computation of optimal reclosure based on criterion ofLyapunov Energy function of SMIB sytem with machine that equips excitation control. It will besimulated on real system (500/220kV transmission system of Viet Nam year 2010) by PSS/E-29

program for the purpose of effective appreciation of these verdicts.

1. GII THIU

Hu ht cc phng php ng lp li hinnay da vo trnh tci t thi gian ng lpli v sct li nu l scvnh cu. Nhnchung thi gian ng li c ci t cnh vngn nht (thi gian c tnh bao gm c thigian cn thit cc bung dp hquang trongmy ct ly li kh nng cch in ca mnh).i vi nhng s c c tnh cht thong quavic ng lp li ny cho php nng cao khnng truyn ti ng thi nng cao n nhh thng. Tuy nhin i vi cc s c l vnhcu vic chn thi gian ngn nht i khi li gy

ra mt n nh hthng bi chnh do scnygy ra. Qua qu trnh kho st ngi ta nhnthy rng, i vi ng lp li trong trng hpscduy tr (ng lp li ln sc), thi gianng lp li nhanh l khng cn thit [1]. Ccng dy truyn ti cp in p t220kV trxung, u ni trc tip vi my pht, thi giant lc c tn hiu ng lp li n khi my ctng thng dao ng trong khong 25 chu k

n 70 chu k. ng lp li sau 45 chu kl tt

nht, ng sau 25 chu ki khi gy ra huquxu v lm hthng mt ng b. Theo [1]thng thng sau s c u tin, tc rtomy pht, tng v gim. Nu s c duy tr, hthng c ng li trong qu trnh rto tng tcs dn n tc rto tip tc tng. Trongtrng hp ny tnh n nh ca hthng c thxu i. Nu trong qu trnh tng tc relay nglp li ng dy khng c ci t cho vicng li m schng li trong qu trnh rtogim tc sau giai on tng tc, qu trnh tngtc gy ra bi scth2 c thc b trdosgim tc ny.

Nhvy nu relay ng lp li c ci t theocch ny th thi gian ng lp li scn cdatrn thi gian rto ang giai on gim tc.Qua kho st vi nhiu chiu chnh AVRkhc nhau, ngi ta thy rng thi gian rtoi n qu trnh gim tc sau khi ct scphthuc nhiu vo hskhuch i KAca AVR.Vi hskhuch i nhthi gian ny ko di,trong khi vi hsln, thi gian li c rt

7/25/2019 avr888

2/6

ngn hn. Tuy nhin h s khuch i qu lnli lm cho bn thn AVR tpht sinh dao ngv gy mt ng b[5].Do c ththy rngsdao ng ca tc rto nh hng bi thigian ng li v vic chn la KAph hp.Hu ht cc sctrn ng dy u khng xc

nh c l sc tm thi hay vnh cu, victhc hin ng lp li vi thi gian c chnla ph hp u cho php ci thin iu kin nnh h thng. Nu s c l tm thi th vicng li ny slm tng cao khnng truyn ticng sut, nu l s c vnh cu th n cngkhng gy ra sdao ng mt ng bca my

pht.Bi bo ny trc ht sphn tch mi lin hca thi gian ng ti u da trn quan hgiahm th nng v bin dao ng gc rto,ng thi phn tch nh hng ca vic iuchnh KAn chu kdao ng rto sau scivi hmt my lm vic vi thanh ci v hn.M phng h SMIB (Single machine infinite

bus) c lp trn phn mm Matlab/Simulink.Cui cng s thc hin kho st cc nhn nhtrn cho h thng thc bng phn mm chuyndng PSS/E-29.

2. PHN TCH N NH HTHNG

Trong phn ny chng ta s xem xt cc biuthc ton hc lin quan n hmy pht kt nivi mt thanh ci v hn SMIB v s ccxt l s c 3 pha trn mch 2 ng dy gn

thanh ci IB c thhin nhhnh 1

Hnh 1: HSMIB

2.1Hphng trnh qu my pht

Theo [2], [3] cc phng trnh m tqu trnhqu trong my pht:

- Cc phng trnh m tqu trnh qu trongcun dy stato (n vtng i):

ud= - rsid + xqid+ Ed (1)uq= - rsiq - xdid+ Eq

- Cc phng trnh m tqu trnh qu trongcun dy rto (n vtng i):

fddddq

q

d EixxEdt

dET += )( ''

'

'0

(2)

qqqd

d

q ixxEdt

dET )( ''

''0 += (3)

- Phng trnh chuyn ng quay rto my pht

(n vtng i):

dt

dKPP

dt

dHDem

=

2

22 (4)

qdqdddqqe iixxiEiEP )('''' += (5)

Trong :+ ud, uq, id, iq,Ed , Eq : in p, dng in,

sc in ng dc trc v ngang trc.+ xd, xq, xd, xq: in khng v in khng

qu dc trc v ngang trc.+ Tdo,Tqo : Hng s qun tnh qu dc

trc v ngang trc.+ (t) : gc quay rto my pht+ : vn tc quay ng b.+ KD: hscn.+ Pm, Pe: cng sut cv in t+ rs: in trcun dy stato.

i vi hSMIB, hphng trnh m tin pdc v ngang trc stato c thm tng trngoire+jxe (bao gm ng dy v MBA u cc)trthnh:

ud= -(rs+re)id + (xq+xe)id+ Ed (6)

uq= -(rs+re)iq - (xq+xe)id+ Eq (7)

ddng cho cng vic tnh ton v kho st,in p v dng in ti thanh ci c chuynsang htrc toquay-dq bng php nhn vishn chuyn i trc toe-j.

uqr= uqi.cos- udi.sin (8)udr= uqi.sin- udi.cos (9)

Vi Vi= uqi+ judi= 1(pu) l in p ti thanhci v hn.

2.2

Thit bkch tv AVR

Thit bkch tloi IEEE type 1 v b tngiu khin in p - AVR c xem xt trong

bi bo ny vi skhi thhin hnh 2:

7/25/2019 avr888

3/6

Hnh 2.

Hm m tbo ho kch t ca my pht kchthch: Se(Efd) = Aex*e

Bex.Efd. Cc phng trnhm t hot ng ca thit b kch t v AVRtheo [3] l:

Te.dEfd/dt = -[Ke+ Se(Efd)]Efd+ Vr (10)Ta.dVr/dt = -Vr KaVso+ Ka(Vref Vt) (11)Tf.dVso/dt = -Vso Kf[Ke+ Se(Efd)]Efd/Te++ KfVr/Te (12)

T cc biu thc t (1) n (12) ta c th xydng c hSMIB bng cng cSimulink ca

phn mm Matlab [2].

3. IU KIN N NH I VI NGLP LI LN SC

Xt h thng SMIB, Theo [4] hm nng lngLyapunov qu sau khi sc(vi KD=0) cho

bi :

V(,) = M2-Pm(-S)-Pemax(cos-cosS)

Vi :M = 2H/: hng squn tnh ca my phtS: Gc ti vtr lm vic cn bng n nhPe

max: Cng sut in tcc iTha sthnht ca hm nng lngc gil ng nng tng ng vi sthay i vn tcgc my pht, phn cn li l th nng tngng vi s thay i gc my pht so vi imlm vic cn bng n nh. Hthng schu tcng nhiu khc nu vic thc hin ng lp lil ng ln s c. Nu my pht dao ng tt

dn, chu kdao ng u tin l chu km gcrto lch xa im cn bng n nh nht. Gclch n gi trcc tiu th thnng st gitr cc i ti thi im ny. Hnh 3 th hinng cong s dao ng gc rto v th nngi vi trng hp sc 3 pha v ct 1 mchng dy (tcl =0.22s) nhng khng thc hinng lp li.

Hnh 3: Dao ng gc v VPE

Qua cho thy ti thi im t = 1.28s gc lchc gi trnhnht tng ng vi thnng tgi trcc i. Nu chn thi gian ng lp lil thi im ny, khnng n nh h thng lln nht.

Hnh 4: Dao ng gc rto v thnng tngng vi trng hp KA=120 v 180, TA=0.01

Trn hnh 4 cho ta thy khi hskhuch i KAc chn ln hn dn n chu kdao ng utin din ra nhanh hn, thi gian thnng tgi trcc i qua cng rt ngn.

Hnh 5: Dao ng gc rto v thnng tngng vi trng hp KA=500 v 200

Hnh 5 cho ta thy thi gian thnng t gi trcc i trng hp AVR c h s KA=500 vKA=200 l 0.98s v 1.04sec, tc l thi gian chrt ngn xung 3 chu kkhi tng KAln gp 2.5

7/25/2019 avr888

4/6

ln. Qua qu trnh kho st c ththy rng giatng hskhuch i KA ln qu cao thi giantng ng thnng t n gi trcc i skhng gim theo hng t l v do nh hng

bi gii hn bo ha ca AVR v my pht kchthch. Mc khc chn KA ln gn lin vi hng

s qun tnh TA ln v iu ny dn n iukin n nh tnh xu i v TAnhl u im v

phng din iu khin nhanh nng cao chtlng qu trnh qu [5].

Nhvy chtiu chn thi gian ng lp liti u l cc i thnng vi chn la hng skhuch i ph hp.

Trnh ttnh ton theo cc bc sau:1. Gii bi ton phn bcng sut trng

hp vn hnh 2 mch v mt mchng dy. Tnh ton im cn bng nnh s

2.

Xc nh loi sc3 pha hay 1 pha, matrn tng dn khi cu trc hthng thayi v thi gian xo sctc.

3. Chn gi tr h s khuch i ban uKAcho AVR ca kch t.

4. Tnh ton tch phn s, xc nh gi trgc rto i ng vi tng thi im, tlc ct sc tcn tc+70chu k. Tnhth nng ng vi tng gi tr gc i,VPE(i).

5. Tm gi tr ln nht ca cc gi tr thnng thu c bc 4. Xc nh thi

im tj tng ng ca thnng cc iVPE() va tm c.6. Tng hskhuch i KAln mt bc

K (chn K ph thuc vo kh nngiu chnh ca AVR). Lp li tbc 4cho n khi tj tj+1 (chn trongkhong t 3 n 5 chu k) hoc KA=KAmax (gi trln nht c thiu chnhc ca AVR).

7. Thi im ng lp li ti u nht ngvi gi trt= tj+1.

i vi hthng nhiu my pht, do snhhng ca vic iu chnh KAn thi gian

gc t gi tr cc tiu khng ln lm (tjv tj+1 khng khc nhau nhiu i vi diiu chnh KA) do c thchn vi gitrnhhn (ph thuc vo di thi gian cthci t c ca rle ng lp li).

4. KHO ST M PHNG VI HSMIB

Xt hSMIB nhhnh 1 vi thng smy phtv kch tnhsau:

Pm=200MW, cos= 0.9, Vm= 13.8kVrs= 0.0048, xd=1.79, xq=1.66xd= 0.355, xq= 0.57Tdo= 7.9, Tqo= 0.41H = 3.77, KD=0f =50Hz, p = 4(scc)KA= 120, TA= 0.01, KE = 1, TE= 0.052KF= 0.2, TF=10Aex= 0.0012, Bex= 1.264.Si= 0.9+j0.4 (pu).

ng dy 2 mch c thng smi mch DZ:Zdz = 0.014+j0.0853.MBA u cc c Zmba = 0.00029 + j0.02925 ts13.8/220kV.Thi gian ct scti t=0.22sec, ng lp li ti25 chu k (t = 0.72s) ct ln 2 ti t2c= 0.94s.Xt 2 trng hp:KA= 120, TA=0.01 v KA= 500, TA=1.

Hnh 6: Dao ng gc ng vi t=0.72secKA= 120, TA=0.01

Hnh 7: Dao ng gc v VPEng vi

t=0.72sec, KA= 500, TA= 1Hnh 6, 7 th hin dao ng my pht mt nnh khi thc hin ng lp li sau 25 chu k.

7/25/2019 avr888

5/6

Hnh 8: Dao ng gc khi ng sau 53chu k

vi KA= 120, TA=0.01

Hnh 9: Dao ng gc v VPEkhi ng sau41chu kvi KA= 200, TA= 0.1

Hnh 8, 9 cho thy nu tng h s khuch iAVR t120 ln 200 th thi gian cho vic thchin ng lp li thnh cng srt ngn xung12 chu k.T kho st trn c th thy rng tiu ch chn thi gian ng lp li ti u da trn iukin cc i thnng kt hp vi iu chnh hskhuch i ca AVR l hp l.Phng php ng lp li vi thi gian trv c

xem xt la chn KAhp l c thm rng racho h nhiu my pht. kim chng nhnnh trn, tin hnh kho st n nh ng bichng trnh PSS/E-29 vi h thng thc500/220kV Vit Nam nm 2010.

5. KHO ST H THNG IN VITNAM NM 2010.

Mng truyn ti 500/220kV h thng Vit Namnm 2010 c 252 thanh ci v 102 my phtc a vo kho st v m phng.Hnh 10 di y trnh by s kt ni v

phn tch tro lu cng sut mt phn mng phang Bc Vit Nam, cm u ni NMNQung Ninh, Cm Ph. ng dy 220kV CmPh i Qung Ninh l ng dy mch kp

phn pha 2xACK300 di 30km cp in p220kV.

Hnh 10

y m phng tm thi gian ng li ti u 3pha cho scvnh cu 3 pha trn mch 2 onng dy 220kV ny, im scgn thanh ci

220kV Cm Phv thi gian ct scl 0.2sec.

Hnh 11

Bng 1: Cc thng skhuch i AVR, kch tKch tloi EXAC1A, Kc= 0.1, KD= 0KA TA KE TE Vmax/Vmin120 0.1 1 0.1 7180 0.1 1 0.1 7

Bphn kch tv AVR l loi EXAC1 c s hm truyn hnh 11. M phng cng skho st nh hng ca hskhuch i n nnh hthng vi 2 thng skhuch i KA khcnhau c trnh by bng 1.

Hnh 12 trnh by ng cong dao ng gcgia my pht Cm Phv Ho Bnh (nt swingbus) i vi trng hp ct s c 3 pha vkhng thc hin ng lp li.Hnh 13 cho thy nu thc hin ng lp lingay ti 25 chu k (t= 0.2+0.5 =0.7sec) my

pht smt ng b.

7/25/2019 avr888

6/6

Hnh 12: Dao ng gc rto trng hp sc

3 pha v khng thc hin ng lp li

Hnh 13: Dao ng gc rto trng hp sc3 pha v ng lp li sau 25 chu k

Hnh 14: Dao ng gc rto trng hp sc3 pha vnh cu, t= 0.792sec, KA=120

Hnh 14 biu din ng cong dao ng gcmy pht i vn nh, xt vi AVR c KA=120v thi gian ng lp li t= 0.792s c ci tng vi thi gian th nng t gi tr cc i.Vi KA=180, VPEt gi trcc i cng ti thiim t= 0.792s.

T cc kt qu trn c th thy rng chn thigian ng lp li trhn u c khnng nngcao n nh ca hthng.6. KT LUN

C th thy rng n nh h thng lin quan

nhiu n thi gian ng lp li v cch chnla KAthch hp. Nghin cu v kho st vi hSMIB, tuy da vo m hnh ton hc cin vkhng xt n s tc ng tng quan gia ccmy pht vi nhau, nhng y cng l csmrng cho vic nghin cu cho hthng phctp. i vi h thng phc tp kho st trn

phn mm PSS/E-29, vic thc hin thi gianng lp li ng vi gc rto cc tiu cng chothy tnh hiu quca phng php ny.Trong thc tcc scl thong qua hay vnhcu l khng th bit c v vic thc hinng lp li khi c sctrn ng dy l chcchn xy ra. Tuy nhin vi cch thc ci t thigian v iu chnh h s khuch i KAhp lca thit b AVR c xut bi bo ny,tnh n nh h thng c thc nng cao rtnhiu.

TI LIU THAM KHO1. Baohui H.Zhang, Senior Member, IEEE,

Yuchun C, Yuan, Zhe Chen, SeniorMember, IEEE, and Zhiqian Q Bo SeniorMember, IEEE, Computation of OptimalReclosure time for Transmission lines,IEEE Trans.power system , Vol.12(2002),

pp. 670.2. Chee-Mun Ong, Dynamic Simulation of

Electric Machinery School of Electrical &Computer Engineering Purdue UniversityWest Lafayette, Indiana, pp. 463-507.

3. Alvarado, Stability anylysis ofInterconnected power systems coupled withmarket dynamics IEEE Trans. on powersystem , Vol.16(2001), pp. 697.

4. M.A.Pai, University of Illinoist atChampaign/Urbana Energy functionanalysis for power system stability pp.14-18.

5.

Pgs, Pts L Vn t, Phn tch & iu khinn nh hthng in, NXB Khoa Hc vKThut, H Ni nm 2000, pp.140-145