Damping Measures Against Prospectiv Oscillations

8/13/2019 Damping Measures Against Prospectiv Oscillations

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correspo di g to the state variables "machi e speed a d"rotor a gle are calculated by D g LENT PowerFactoryso ware. The so ware is utilized to calculate o ly the selectedeige values by A old-La czos method arou d the poi t ieige space R AImg)=(O2*n*0.15)=(0 0.95) which

correspo ds to the poi t at the limit of stability for theexpected mode of i ter-area oscillatio s. t is also importa t to ote here that eige value a alysis is made by li earizi g thesystem arou d a operati g poi t (by the simulatio program) he ce it shows the performa ce of the system for small pe tu batio a ou d th op rati poi t he ce uch a alysiso ly give a rough idea o the te de cy of the system toi stability. i ce a y power system is a large o li ear systemcomprisi g of o li ear co trollers ge erators loads a dother switchi g devices o co clusio ca be draw regardi g the overall rotor a gle stabili of the system by such a alysis.He ce the o ly way to u dersta d a d illustrate the behaviorof the o li ear system is performi g time domaisimulatio s. Although a co clusio ca ot be draw regardi g stability by eige value a alysis the eque cy ra ge of possible u damped a d poorly damped modes ca besee .

. MULAT ON ESULTS

A. Base CaseThe Base Case correspo ds to mi imum loadi g of both the

Turkish Power ystem a d the ENT O-E ystem which caalso be amed as the worst case sce ario. The base case is theoperatio al sce ario where growi g oscillatio s have beeobserved i the system. Fig.I the eige value plot of thesystem is show . Table the most poorly dampedeige values correspo di g to the state variables machi espeed a d rotor a gle for Base Case are listed. Fig. 2 the tra sie t respo se of the system a er a 1200MW outage iENT O-E CE A regio is show . The modes illustrated iFig. 1 are listed i Table .

.

g na y a [ d) x .80

.60

Q. 0

2

the equilibrium poi t has some eige values o the right ha dside of the eige space. However this result does ot prove that the system is u stable due to the esse tially o li ear ature of power systems. He ce li ear a alysis tools ca ot be directly utilized i assessi g system o li ear stability.

Therefore the most co ve ie t way of assessi g the stabiliof a large i terco ected power system is to perform umericsimulatio s. The time domai simulatio s carried out with thesame model prove that the system is u stable as illustrated iFig. 2. The blue tre d illustrated i Fig. 2 correspo ds to the

eque y of Tu key whereas the d t d o re po ds to theeque cy of pai a er a outage. Possible reaso s of

u damped oscillatio s i this case are the mi imized dampi ge ect due to ge erators a d i dustrial loads such as i ductiomotors those are out of service i this period of the day.

ModeModeModeMode 4ModeSMode 6Mode 7

TABLE!THE MO T POO Y DAMPED MODE OF THE Y TEM

THE EXPE TED NTER AREA BAND

ImaginaryDamped

Real Part FrequencyPartHz)

-0,0874294 0,809913 0,12890170,2551103 0,7674463 0,1221429-0,2578936 0,7927783 0,1261746

-0,2 0,6 0,09549297-0,2980327 0,6632116 0,1055534-0,249159 0,6256811 0,09958024-0,0874294 0,6244366 0,09938218

DampingRatio

0,1073256-0,3154430,30934710,31622780,40989280,3699650,369716

Fr qu n y of urk y and Spa n A r a 1200 MOutag50 0 ', ' - - = q= f.

- Freque oISpa i n

50 ,49.99 L

49.98

i49 97

49 96

f f

.49 940 0, - 0 - f" O 0- L - 60 c 00

Time (Se


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for low eque cy i ter-area oscillatio s [15]. Howeveraccordi g to the feedback comi g om the excitatio s stemma ufacturers regardi g the applicability of the theoretIcallyoptimized setti gs a d due to some site speci c factors the

theoretically optimized setti gs are seldom applicable i

practice.The P retu i g study was made u it by u it i dividually by the co tributors of the Task 4 of the "Rehabilitatio offreque cy co trol performa ce of Turkish power system forsy chro ous operatio with UCTE project which was led bySwis g d rather tha p f i g a ystem- de glooptimizatio study regardi g suitable P setti gs so as todamp low eque cy i ter area modes. Therefore he keyst eof this approach was that si ce o e of the co sIderable sIzege erators would ampli the i ter-area power swi gs thesteady state stability of the overall system would be e ha ced.As stated before the applicability a d effective ess of theu it-wise proposed P setti gs were checked by site testsme tio ed i [8]-[14] which co ce the improveme t of atural dampi g of the machi e for both the local modes a d the i ter area modes.

the site tests i order to test the effective ess of the proposed P setti gs for local modes step respo se tests were co ducted by i jecti g2% (or 3%)step disturba ce oA VR voltage set poi t (or by cha gi g the voltage set poi t).The step tests were repeated for P o a d off casesseparately.

A gure of merit for the effective ess of P setti gs-orlocal mode dampi g is the exti ctio of ge erator actIve power oscillatio s withi two swi gs (i.e. o e period) whe the ge erator is loaded close to its ll rati g i the previouslyme tio ed step respo se tests. A importa t co sideratio for the applicability of the P setti gs those are successful idampi g local modes is that eve if the active poweroscillatio s are well damped o steady state oscillatio sshould be observed i the eld voltage thus the reactive powerfollowi g the disturba ces. Those steady state eld voltageoscillatio s arou d the operati g poi t are due to ampli catioof i here t oise i all practical systems by the large gai of the P which i dicates that the applied P gai isi applicable he ce should be reduced by certai amou t.

The step respo se test results of a sample power pla t areillustrated i Fig.3 a d Fig. 4 for the P off a d P ocases.

fp u u T [ i : 5 5 10 15 2 25 3 35 4 45 5. 50i i ! f I400 Ii3 t -: 1 < r T000 5 10 15 5 3 35 4 45 5

i :k - f - 0 70 5 10 1S 2 25 3 35 4 45 5J

:' + m r i e

ig. 3. S ep Response Tes Resul s wi h PSS O

3

: : i l1 5 W 25 30 5 50 sig. 4. S ep Response Tes Resul s wi h PSS On

By exami i g Fig.3 a d Fig. 4 it has bee co cluded that the P setti gs were suitable for dampi g local mode rotora gle oscillatio s co sideri g the previously me tio edapplicability criteria. . order to check the effective ess of the proposed sett gsfor e tire eque cy ra ge of i terest i additio to local modeswi gs eque cy respo se tests were co ducted by i jecti ga white oise sig al or pi k oise sig al om the AVRsummi g ju ctio i order to observe the effect of theP forcertai eque cy ra ge. This test was also performed for Poff case a dP o cases separately.

Fi l to va u te th que y t st r s lts FFT sis were applied o the recorded active power output sig al. t isexpected that whe the P is o the amplitude of active power oscillatio s will be less tha the P off case for thee tire eque cy ra ge om 0.1 Hz to 5 Hz.

t is importa t to ote here that it is better to perform theeque cy tests via i jecti g pure si usoids om the A VR

summi g ju ctio at speci c eque cies so as to cover thee tire eque cy ba d of i terest rather tha i jecti gli

type oise sig al. However this approach may ot be always possible due to equipme t a d time limitatio s.

The freque cy respo se test results of a sample power pla tare illustrated i Fig. 5 for theP off a d P o cases.

"

,,

r

1

r 3.5 4 5

ig. 5. Ampli ude Spec rum of Ac ive Power Varia ions for PSS O (Blue)and PSS On (Red) Cases


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is co cluded by exami i g Fig. 5 ha he re u ed Pse i gs are sui able for dampi g ro or a gle oscilla io s i hefreque cy ra ge om 0.1 Hz o3 Hz; i addi io o oexci i g he high eque cy orsio al modes.

System-Wide E ect of Retuning of PSSs of Major PowerPlants

This case is simula ed o show he ra sie respo se of hesame sys em i he Base Case wi h he applica io of osi eapplied P parame ers which were veri ed o damp (a leas o o dis urb) low eque cy i er-area oscilla io s by si e es s (i.e. he same e work opology a d he same dispa chsce ario wi h he modi ca io of he P se i gs of all major power pla s).

Fig. 6 a d Fig. 7 he eque cy of he coherege era ors i Turkey a d Europe a er a 1200 MW ou age iENT O-E CE A regio is show separa ely. ca be clearlysee ha he oscilla io s are well damped wi h respec o he base case illus ra ed i Fig. 2.

e me oma m a o of en erconnec ed em5O005

so

4 9 .9 9 5

49 .9 9

I I I r I I 1 1I I J II I I I1 1

I J J I1 %! I I I I49_97S

49.97 + 1 1II I I II 1 149 96 T 1 j 1

I49.95S O O 30 0 ( 0 ; 0 00

Time (5ec)

ig. 6. The Expec ed Transien Response of he Turkish Sys em a er a 1200MW Ou age in ENTSO E CESA a er Re uning of PSSs of All Major PowerPlan s in he Turkish Power Sys em

me oma mu a oo e e co ecy em5O 01' " = F. " C" = "=

- Frequ cyinSw a

0

I I I

49 98

r49 9749 96

49 .95

I I I

I I I49 .9 '

O O - - :0 0 0 -

ime ( ecl

ig. 7. The Expec ed Transien Response of he ENTSO-E CESA Sys ema er a 1200 Ou age in ENTSO-E CESA a er Re uning of PSSs of AllMajor Power Plan s in he Turkish Power Sys em

As s a ed before i his paper s udies are focused o heevalua io of rela ive effec of proposed precau io s o sys emdampi g. is impor a o o e here ha si ce he simula io

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model is represe a ive he simula io resul s will o show he exac si ua io a er i erco ec ed opera io . However he simula io model is reliable e ough o assess heeffec ive ess of re u ed P s a d o her dampi g measures he ce i ca be co cluded ha he basic behavior of he sys em

will be i his fashio .Fig. 7 is illus ra es ha he low freque cy i er-area modesare s ill prese i he sys em i his case al hough hey are o clear for some cohere ge era ors as he o e illus ra ed iFig. 6. The mai reaso is ha such oscilla io s are o

b e vable i h ge era o s i Turk y a e he re u g s udyofP s of major power pla s.

Therefore he mai reaso for he differe behavior be wee he ge era ors hroughou he sys em as illus ra ed iFig. 6 a d Fig. 7 is he differe ce i observabili y (commo ly referred o as he "mode shape ) of he poorly damped modesof he sys em (or combi a io of modes) for differe s a e variables (ro or a gle a d machi e speed for his case). isimpor a o o e here ha he "mode shape of he s a e variable is he e ry of he righ eige vec or of he speci cmode ha correspo ds o he speci c s a e variable i hes a e vec or (i.e. a vec or comprised of ge era or load a glesa d ro or speeds i his case).

Fig. 7 he eque cy re d illus ra ed wi h he blue li ecorrespo ds o he ge era or where he observabili of hemos poorly damped mode is fou d ou o be he grea es . Asexpec ed his ge era or wi h a cohere se of ge era orsswi g agai s he o her cohere ge era or se s i he sys em.

ca also be co cluded ha he ge era ors i Turke behave i a cohere ma er a er he re u ed P se i gs areapplied o all major power pla s. By care lly exami i g a dcompari g Fig. 6 a d Fig. 7 oge her wi h he o her simula io va iables i ca be co cluded ha he o si e applied Pse i gs are effec ive i improvi g sys em dampi g for low

eque cy i er-area oscilla io s.

D System-Wide E ect of Controller Mod cation of theSTATCOM

This case is simula ed o illus ra e he rela ive effec ofTATCOM ha is bei g pla ed o be modi ed o ac as a

dampi g measure [16]. The e work opology a d he dispa chsce ario are he same as he Base Case. addi io a 50MVAR TATCOM which is coupled o a busbar wi h a shorcircui MVA ra i g equal o 19170 MVA a mi imum loadi gco di io s is equipped wi h a w P -like co roller device

which provides a ex ra dampi g i pu o he TATCOMco roller providi g pure dampi g e ec for he eque cyosc a o s i expec ed er-area oscilla io ba dw d h asexplai ed i [1].

A impor a remark regardi g s a ic devices is ha due o he o li eari ies i he co roller s ruc ure of such devicesa d si ce hose devices are o ro a i g power sys emeleme s such as mo ors a d ge era ors eige value a alysis(li ear a alysis) regardi g he s a e vec or comprised of ro orspeed a d load a gle of he machi es do o give a clear ideaabou sys em s abili y i hose sce arios. Thereforeeige value a alysis is o illus ra ed for his simula io case.

A o her impor a co sidera io is ha he s a ic dampi gmeasures have o be i s alled i places where he powersys em is rela ively weak whereas he resis ive compo e of


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loadi g is high. i c th voltag o a stro g busbar will otcha g sig i ca tly with r activ pow r variatio s of limit dcapacity th ff ct of static dampi g m asur s is limit d icas th y ar i stall d i plac s wh r th tra smissio twork is stro g.

t should also b ot d that for all simulatio s r gardi g thmodi catio of static d vic s a d braki g r sistors thcorr spo di g busbar voltag was ch ck d ot to xc d th+/ 5%op ratio al p rforma c limits r gardi g voltagstability although ot illustrat d i a s parat gur .

Fi th tra si t r spo s of th syst to a 1 00outag i ENT O-E CE A r gio is show . From Fig. itca cl arly b s that th Turkish Pow r yst m oscillat sagai st th ENT O-E CE A syst m which m a s that thobs rvability of th poorly damp d low qu cy i t r-ar amod (or combi atio of mod s) is gr at r for th g rators thos ar l ctrically clos to East Europ a d Turk y.

T oin mu aio o e In e o nec e em5.01 - - - - "_ Oq== ' = - FrequencyofC p

I I I I I I 49 99 -

i 49 98J 49 97

I I I I I I Il

49 9 t J

499 ; , - , - - . 6 o ; O -

4 ,-35 + " . ' n r 1- - -: = ==-= ==== 1== =- ==11 5 f - - - - -

0 = = =F = 1:= == 0 0 1 0 50ime (Sec)--

ig. 11. The Expec ed Transien Response of he Turkish Sys em and hePower Drained by he Braking Resis or a er a 1200 MW Ou age in ENTSO-ECESA

H System-Wide E ect of Installation of a 5 MW BrakingResistor

t is ass med thro gho t the sim latio st dy that a5 MW braki g resistor at a 19170 MVA b sbar is eq ipped with itsspecial co troller i additio to the Base Case.

Fig. 12 the tra sie t respo se of the system to a1200MW o tage a d the power drai ed by the braki g resistoris show . As ca directly be see by a alyzi g Fig. 11 a dFig. 12 as the rati g of the braki g resistor i creases thedampi g performa ce of the system is e ha ced as expected.

5 .02 _ - ime

om : .m; on r _ e te r n ec

ed em_ _

' r T r 49.98

49.940

5 - -Ii 4 -- :-r -- -= = + =

0 0 0

,--

,n :- ,- -_ I-

-I- ,3 0 4 0

, ,- ,, ,I-

,5 0 60ime Sec)

,,Lr

I

-_

-

- _ -

6

ig. 12. The Expec ed Transien Response of he Turkish Sys em and hePower Drained by he Braking Resis or a er a 1200 MW Ou age in ENTSO-ECESA

The total e ergy drai ed by the braki g resistors as a ctioof time is ill strated i Fig. 13 together with the systemeq e cy.

4999r: -

49 49.9 5

T m m mh y m__ _____ _____ ____ _____ ____ __

- - -

49.9 0- : - - - , - - ; - 2

-

2oo , - - 175

150

1251; 75

j 500

0 00 20

ig. 12. The Expec ed Transien Response of he Turkish Sys em and heEnergy Drained by he Braking Resis or a er a 1200M Ou age in ENTSOE CESA

V. ONCLUS ONS this st dy accordi g to load ow a d tra sie t stability

sim latio s several tech ically feasible system operatio al

sce arios are sim lated a d the worst case system operatio alsce ario co sideri g small sig al rotor a gle stability isobserved to be the mi im m loadi g sce ario i s mmer d e to the mi imized dampi g effect of the i d strial loads a d thege erators.

Based o the sim latio st dies it has bee observed that ret i g of P s of the co siderable size power pla ts iT rkey which was a esse tial prelimi ary work to becompleted [16] is the most effective dampi g meas re regardi g the system stability a er sy chro o si terco ected operatio of the T rkish Power ystem a d

NT O- C A ystem. additio to the ret i g of P s of the co siderable size

power pla ts i T rkey modi catio of co trollers ofTATCOM a d VCs are also e ective as additio al


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dampi g measures. However the urge cy of these extra preve tive measures should be veri ed via W AMSmeasureme ts o ce the trial sy chro ous i terco ectio isestablished si ce satisfactory dampi g performa ce wasobserved with o site applied PSS setti gs.

stallatio of braki g resistors ca o ly be co sidered as alo g term i vestme t as a backup si ce the other cou termeasures together with the protectio system are expected to provide su cie t dampi g performa ce.

V EFERENCES[I] . Machowski, .W. Bialek, .R. Bumby,Power System Dynamics:

Stabili and Control New York: Wiley, 2008.[2] Union for the Coordination of Transmission of Electricity, UCTE

Operation Handbook,Union for the Coordination of T nsmission of Electrici June 2004. [Online]. Available:http://www.entsoe. eu/index. php?id=5 &no_cache= I &sword _ ist[]=handbook. [Accessed May 31, 2010].

[3] "Preventive Measures for Effective Damping of nter-area Oscillationsa er the Synchronous nterconnection of the Turkish Power System with

the UCTE Power System , UCTE, May 2009.[4] M. Klein, G. . Rogers, P. Kundur, "A Fundamental Study of nter-AreaOscillations in Power Systems, IEEE Transact ions on Power Systemsvol. 6, no. 3, pp. 914 921, Aug. 1991.

[5] H. Breulmann, E. Grebe, M. L sing, W Winter, R. Witzmann, P.Dupuis, M.P. Houry, T. Margotin, . Zerenyi, . Dudzik, . Machowski,L. Mar in, . M. Rodriguez, E. Urretavizcaya, "Analysis and Damping of

nter-Area Oscillations in the UCTE/CENTREL Power system , inCIGRE session 2000,2000, paper 38-113.[6] P. Kundur,Power System Stabili and Control New York: McGrawHill, 1994.

[ ] IEEE Recommended Practice for Excitation System Models for PowerSystem Stabili Studies, EEE Std. 421.5 2005.

[8] JTaborda, "Proposal for A VR and PSS Settings Karakaya HPS, ABB,Zurich, Switzerland, Jul. 2008.[9] F. Riegger, "Ataturk Unit I PSS Test Results, ABB, Zurich,

Switzerland, Nov. 2008.[10] J Taborda, "E bistan B AVR & PSS Settings Analysis, JT Systems,Nussbaumen, Switzerland, Dec. 2008.[II] J Taborda, "PSS Tuning and Testing Repor Oymapinar HPP, JTSystems, Nussbaumen, Switzerland, Jan. 2010.[12] . Taborda, "PSS Testing Repo : ENK CCPP UN TS 21X (GT) and

21A (ST), JT Systems, Nussbaumen, Switzerland, Apr. 2010.[13] CGencoglu, O.B. Tor, "PSS Retuning Site Tests for Gas Turbines ofAnkara (Baymina) NGCCPP: Observer Repor , TUB TAK UZA Y

Power Systems Depa ment Ankara, Turkey, Apr. 2010.[14] CGencoglu, O.B. Tor, "PSS Retuning Site Tests for Gas & SteamTurbines of zmir (Aliaga) NGCCPP: Observer Repor , TUB TAK

UZA Y Power Systems Depar ment Ankara, Turkey, May. 2010.[I ] "Complementary Studies for the Synchronization of the Turkish Power

System with the UCTE Power System , UCTE, May 200 .[16] "Preventive Measures for Effective Damping of nter Area Oscillations

a er the Synchronous nterconnection of the Turkish Power System with

the UCTE Power System , UCTE, May 2009.

V . OGRAPH ES

Osman Bulent Tor (S'04) received the B.S., M.S. andPh.D. degrees from Middle East Technical Universit(METU), Turkey, in 1998, 2001 and 2008, respectively. Heis working as a Chief Researcher at the Power Systems

Depar ment of Space Technologies Research nstitute of theScienti c and Technological Research Council of Turkey(TUB T AK). He is leading power system analysis group of

Power Systems Depa ment.

TE AS.

Cihangir Gencoglu (S'08) received the B.S. degree omMiddle East Technical University (METU) Turkey in 008He is studying towards the completion of his M. S. degree inMETU. He is working as a Researcher at the Power SystemsDepar ment of Space Technologies Research nstitute of theScienti c and Technological Research Council of Turkey(TUB TAK).

Oguz Yilmaz received B.S. and M.S. degrees om MiddleEast Technical University, Turkey, in 2002 and 2006.Between 2003-2006, he was with ntergen-ENKA zmirCCPP as a power plant engineer responsible from electricalequipment and turbine control systems. Currently he isworking as a Senior Researcher at the Power SystemsDepar ment of TUB TAK UZA Y being responsible omENTSO-E interconnection and ancillary services studies for

Mahmut Erkut Cebeci (S'02) received the B.S. and M.S.degrees om Middle East Technical Universit (METU),Turkey, in 2005 and 2008, respectively. He is working as aSenior Researcher at the Power Systems Depar ment ofSpace Technologies Research nstitute of the Scientific andTechnological Research Council of Turkey (TUB TAK).

Ali Nezih Guven (SM ) received the B.S. Degree omMiddle East Technical University (METU), Turkey, M.S.and Ph.D. degrees from the Ohio State University, USA, in19 9, 1981 and 1984, respectively. He is a professor in theDepar ment of Electrical and Electronics Engineering atMETU at present.

Damping Measures Against Prospectiv Oscillations

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