LOAD FLOW, CONTINGENCY ANALYSIS, STATE ESTIMATION AND OPTIMAL OPERATION FOR IEEE 14-BUS SYSTEM

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1 MLLIK D, et l, Interntionl Journl of Reserh Sienes nd dvned Engineering [IJRSE] TM Volume 2, Issue 15, PP: , SEPTEMER LOD FLOW, ONTINGENY NLYSIS, STTE ESTIMTION ND OPTIML OPERTION FOR IEEE 14-US SYSTEM Dr.M. LKSHMISWRUP 1*, Mr. D. RMESH 2* 1. Professor -Dept of EEE, Mll Reddy Engg. ollege (UTONOMOUS), Hyderd, Indi. 2. sst. Prof- Dept of EEE, Mll Reddy Engg. ollege (UTONOMOUS), Hyderd, Indi. strt In this pper the work is divided into two min prts. The first prt provides further improvements in power system stte estimtion nd the seond prt implements ontingeny onstrined Optiml Power Flow (OPF) in multiple ontingeny frmework. The demnd of the energy mngement systems (EMS) set forth y modern power systems requires fst energy mngement systems. ontingeny nlysis is mong the funtions in EMS whih is time onsuming. In order to hndle this limittion, this pper introdues gent sed tehnology in the ontingeny nlysis. The min funtion of gents is to speed up the performne. Negotitions proess in deision mking is explined nd the issue set forth is the minimiztion of the operting osts. The IEEE 14 us system nd its line outge hve een used in the reserh nd simultion results re presented. Index Terms model, negotition, optiml dispth, power systems. I. INTRODUTION It is well known tht power system is omplex network onsisting of numerous equipments like genertors, trnsformers, trnsmission lines, iruit rekers et. Filure of ny of these equipments during its opertion hrms the reliility of the system nd hene leding to outges. Whenever the pre speified operting limits of the power system gets violted the system is sid to e in emergeny ondition. These violtions of the limits result from ontingenies ourring in the system. Thus, n importnt prt of the seurity nlysis revolves round the power system to withstnd the effet of ontingenies. The ontingeny nlysis is time onsuming s it involves the omputtion of omplete lod flow lultions following every possile outge events like outges ourring t vrious genertors nd trnsmission lines. This mkes the list of vrious ontingeny ses very lengthy nd the proess very tedious. In order to mitigte the ove prolem, utomti ontingeny sreening pproh is eing dopted whih identifies nd rnks only those outges whih tully uses the limit violtion on power flow or voltges in the lines. The ontingenies re sreened ording to the severity index or performne index where higher vlue of these indies denotes higher degree of severity. The importne of power system seurity ssessment for predition of line flows nd us voltges following ontingeny hs een presented in [1-2]. The pper lso detils the hllenges fed for the prtil implementtion of seurity nlysis lgorithms. The pproximte hnges in the line flow due to n outge in genertor or trnsmission line is predited sed on distriution ftors [3-4]. The use of power flow solution in outge studies hs een delt in [5].ontingeny sreening or ontingeny seletion is n essentil tsk in ontingeny nlysis. This helps to redue the numerous omputtions; the ounding method [6] redues the numer of rnh flow omputtion y using ounding riterion tht helps in reduing the numer of uses for nlysis nd is sed on inrementl ngle riterion. The 1P-1Q method for ontingeny seletion hs een presented in [7]. In this method the solution proedure is interrupted fter n itertion of fst deoupled lod flow. Zorzky et l. introdued the onentri relxtion method for ontingeny evlution [8] utilizing the enefit of the ft tht n outge ourring on the power system hs limited geogrphil effet. The use of fst deoupled lod flow [9] proves to e very suitle for ontingeny nlysis. ontingeny seletion riterion sed on the lultion of performne indies hs een first introdued y Ejee nd Wollenerg [10] where the ontingenies re sorted in desending order of the vlues of performne index (PI) refleting their severity. The prtil implementtion of ontingeny sreening n e done y instlling the phsor mesurement units whih re eing used to pture the online vlues of us voltges nd ngles [11]. The fst estimtion of voltges in power system is essentil for ontingeny nlysis nd this ws proposed in [12]. prt from performne index other index like voltge stility riteri index n lso e hosen ontingeny rnking [13]. Multiple ontingeny n our in the power system t the sme time, hene its identifition nd nlysis is more omplited tsk, the multiple ontingeny sreening in power system hs een illustrted in [14]. The nlysis of power system ontingeny eomes more hllenging when the system is onneted to vrile genertion units like wind or solr systems, where the firm pity is vrile. In [15] the ontingeny nlysis y inorporting smpling of Injeted powers hs een done. In this pper, the vlues of tive power performne index (PIP) nd retive power performne index (PIV) hve een lulted for 5-us, IEEE-14 us nd IEEE-30 us systems using the lgorithm implemented in MTL softwre. sed on the vlues of PIV, ontingenies hve een rnked where trnsmission line ontingeny leding to high vlue of PIV hs een rnked 1 nd lest vlue of PIV hve een rnked lst. The lod flow nlysis following the most severe trnsmission line ontingeny hs een simulted nd the results of tive Interntionl Journl of Reserh Sienes nd dvned Engineering

2 MLLIK D, et l, Interntionl Journl of Reserh Sienes nd dvned Engineering [IJRSE] TM Volume 2, Issue 15, PP: , SEPTEMER power flow in vrious trnsmission lines nd the us voltges hs een nlyzed. II. ONTINGENY NLYSIS USING LOD FLOW SOLUTION Lod flow nlysis performs stti seurity nlysis for given system so tht the system is operted defensively. Due to ontingeny, the system my enter n emergeny stte, wherein the opertor hs to tle fst tions to restore the system k to norml. Here the sttus of ll the elements seleted s ontingeny sed under ontingeny nlysis setion re mde nd outge study is performed. The output of the progrm lrms the user of ny potentil overlods or out of limit voltges. ontingeny Seletion Sine ontingeny nlysis proess involves the predition of the effet of individul ontingeny ses, the ove proess eomes very tedious nd time onsuming when the power system network is lrge. In order to llevite the ove prolem ontingeny sreening or ontingeny seletion proess is used. Prtilly it is found tht ll the possile outges does not use the overlods or under voltge in the other power system equipments. The proess of identifying the ontingenies tht tully leds to the violtion of the opertionl limits is known s ontingeny seletion. The ontingenies re seleted y lulting kind of severity indies known s Performne Indies (PI) [1]. These indies re lulted using the onventionl power flow lgorithms for individul ontingenies in n off line mode. sed on the vlues otined the ontingenies re rnked in mnner where the highest vlue of PI is rnked first. The nlysis is then done strting from the ontingeny tht is rnked one nd is ontinued till no severe ontingenies re found. There re two kind of performne index whih re of gret use, these re tive power performne index (PIP) nd retive power performne index (PIV). PIP reflets the violtion of line tive power flow nd is given y (1) PIP = ( Pi Pimx ) L 2n i=1 (1) where, Pi = tive Power flow in line i, Pi mx = Mximum tive power flow in line i, n is the speified exponent, L is the totl numer of trnsmission lines in the system. If n is lrge numer, the PI will e smll numer if ll flows re within limit, nd it will e lrge if one or more lines re overloded, here the vlue of n hs een kept unity. The vlue of mximum power flow in eh line is lulted using the formul Pi mx = Vi Vj X (2) where, Vi= Voltge t us i otined from FDLF solution Vj= Voltge t us j otined from FDLF solution X = Retne of the line onneting us i nd us j nother performne index prmeter whih is used is retive power performne index orresponding to us voltge mgnitude violtions. It mthemtilly given y (3) PIV= [ 2(Vi Vinom) Vimx Vimin] 2 Npq i=1 (3) where, Vi= Voltge of us i, Vimx nd Vimin re mximum nd minimum voltge limits, Vinom is verge of Vimx nd Vimin, Npq is totl numer of lod uses in the system. ny power system opertes on stisfying the demnd from the genertion. nd lso on the ontingeny stte the power system should operte y giving lrm or to inform the inseurity to the opertor, lso to dignose the fulty us nd preventive mesures should e tken to hndle the ontingeny. There for ontingeny study is very importnt in the lod-flow nlysis. The performne index is lulted for every line outge for IEEE 14-us test system to implement the module for power system stti seurity ssessment. The seurity lssifition, ontingeny seletion nd rnking re done sed on the performne index whih is ple of urtely differentiting the seure nd non-seure ses. Here in this projet for IEEE-14 us nd lod flow nylsis nd performne index is done in MiPower softwre. Fig 1 Line Digrm of IEEE 14 us test system III. LOD FLOW METHODS The ojetive of power flow study is to determine the voltge nd its ngle t eh us, rel nd retive power flow in eh line nd line losses in the power system for speified us or terminl onditions. Power flow studies re onduted for the purpose of plnning (viz. short, medium nd long rnge plnning), opertion nd ontrol. The other purpose of the study is to ompute stedy stte operting point of the power system, tht is voltge mgnitudes nd phse ngles t the uses. y knowing these quntities, the other quntities like line flow (MW nd MVR) rel nd retive power supplied y the genertors nd loding of the trnsformers n lso e lulted. The onditions of over lods nd under or over voltges existing in the prts of the system n lso e deteted from this study. The different mthemtil tehniques used for lod flow study re 1. Guss Seidel method 2. Newton Rphson method 3. Fst Deoupled method 4. Stott s fst deoupled method III. Performne index. Voltge performne index: Interntionl Journl of Reserh Sienes nd dvned Engineering

3 Genertor1 us 1 us 8 us 8 us 1 us 2 Synhronous ompenstor Genertor us 2 us 9 us 9 us 3 us 10 Synhronous ompenstor us 3 us 10 us 11 us 4 us 11 us 4 us 5 us 12 us 5 us 12 us 6 Synhronous ompenstor us 6 us 13 us 13 us 7 Fourteen us system us 14 us 7 us 14 ontinuous powergui MLLIK D, et l, Interntionl Journl of Reserh Sienes nd dvned Engineering [IJRSE] TM Volume 2, Issue 15, PP: , SEPTEMER Where, n: Numer of uses, Wi: Weightge ftor for us i, V i new: post outge voltge mgnitude t us i, V i spe: Speified voltge mgnitude t us i (1.0 p.u.)vi mx: Mximum llowle voltge hnge,whih is omputed s the differene etween mximum voltge nd differene etween minimum voltge nd speified voltge, if the voltge mgnitude is less thn the speified voltge. The signifine of the weightge is to give lower rnking (higher severity) for poor voltge t speifi uses.. Lineflow performne index (2) Where, nl:totl numer of series equipment, Wi: Weightge ftor for series element I, Pi new: New rel powerflow in the line, Pi limit: Rel power flow limit of the line. The ontingeny n e rnked depending on the importne of line. If it is desired not to overlod prtiulr line, SE is very useful tool for the eonomi nd seure opertion of trnsmission networks. From erly dys of Sheweppe [3] [5], developments of SE re done s no tion of roust estimtion, hierrhil estimtion, with nd without the inlusion of urrent mesurements, et. The SE uses only volt- ge mgnitude, rel nd retive power injetions nd flows of SD mesurements. The inlusion of rnh urrents mesurements in SE deteriotes the performne of estimtors. It lso ledsto non uniquely oservle whih produes more thn one stte for the given one set of mesurements [6], [7]. Distriuted SE for very lrge power system hs een tken for study sine the very eginning. The omputtionl proedure involved in SE is n optimiztion funtion. The optimiztion funtion n e first order or seond order of the derivtive. The first order methods re the lssil weighted lest squres [8], the itertively reweighted lest squres [9] nd the liner progrmming sed on lest solute vlue estimtor. The seond order method involves the evlution of the Lgrngin Hessin mtrix. The priml-dul interior-point method nd Huer M estimtor re the solution metholodigies re ville in literture to solve the seond order method. The system sttes re evluted either y sttilly or dynmilly. The ove methods mentioned re stti stte estimtors. t the given point of time, the set of mesurements re used to estimte the system stte t tht instnt of time. The ommon method used to solve the stti SE is weighted lest squre nd weighted lest solute vlue methods. The heuristi methods re lso pplied to find the sttes. In the dynmi stte estimtion, the system sttes re ontinuously monitored t the regulr intervls. TheDSEusesthe Klmn filter,lepfroglgorithm, non-liner oserver tehnique nd invrint imedding method to estimte the system sttes dynmilly.. Weighted Lest Squre(WLS) Method In the WLS method, the ojetive is to minimize the sum of the squres of the weighted devitions of the estimted mesurements from the tul mesurements. The system sttes re estimted from the ville mesurements. The ojetive funtion is expressed s follows, (1) where fi(x) nd σ 2 is the system eqution nd the vrine of the i th mesurement respetively. J(x) is the weighted residuls. m is the numer of mesurements nd zi is the i th mesured quntity. If fi(x) is the liner funtion then the solution of eqn. (1) is losed form. Usully, the power flow nd power injetion equtions re desried y nonliner funtion. Hene the solution leds itertive proedure to determine the stte of the system. essed in WLS re (1) to find the grdient of J(x) nd (2) fore it into zero nd solved y Newton s method. The optiml stte estimte is found using eqn. (2). 12 (2) (3) where R Mesurement error ovrine mtrix x System stte vetor H Join mtrix z Mesurement vetor The ovrine mtrix R reflets the reltive reltion etween the mesurements. If there is no intertion etween the vrious mesurements then R will e digonl mtrix. The digonl elements re the vrines of the individul mesurements (ri =σ 2 ). Reently the SE with mesurement dependenies is solved with WLS tehnique [10]. V V I I V V I I V V I I I. V I V I Fig 1. SIMULTION MODEL FOR IEEE 14-US SYSTEM V V I I V I V I V I V I Interntionl Journl of Reserh Sienes nd dvned Engineering

4 MLLIK D, et l, Interntionl Journl of Reserh Sienes nd dvned Engineering [IJRSE] TM Volume 2, Issue 15, PP: , SEPTEMER Fig 4. LINE DT OF IEEE 14-US SYSTEM. Modl nlysis Fig 2. RESULTS OF US VOLTGES ROSS EH US (exmple 1,3,7 tken) Fig5 Eigen vlues of the redued Join mtrix ginst lod multiplition ftor, K. Fig 3. Yus formtion Interntionl Journl of Reserh Sienes nd dvned Engineering

5 MLLIK D, et l, Interntionl Journl of Reserh Sienes nd dvned Engineering [IJRSE] TM Volume 2, Issue 15, PP: , SEPTEMER Tle 1.4: se se lod dt (Pu on 100 MV se) for us P(MW) QMVR(pu) the 14-us test system Tle 1.5: se se genertor dt (Pu on 100 MV se) for the 14-us test system Fig 6 Line Digrm of IEEE 14 us test system Tle 1.1: Trnsmission lines dt (R, X nd in Pu on 100MV se) for the 14-us test system End uses R X / End uses MVR(pu) Tle 1.2: Trnsformer dt (R, X in pu on 100 MV se) for the 14-us test system End uses R X End uses R X Tp setting Tle 1.3: Shunt pitor(r, X in pu on 100 MV se) for the 14-us test system us V(pu) Tle 1.6: Eigen vlues of redued Join mtrix (Pu on 100 MV se) for the 14-us test system K E1 E2 E3 E Tle 1.7: Trnsformer dt for different lod levels (Pu on 100 MV se) for the 14-us test system Tle 1.8: Lod dt for different lod levels (Pu on 100 MV se) for the 14-us test system us P(pu) Q(pu) Lod level Interntionl Journl of Reserh Sienes nd dvned Engineering

6 MLLIK D, et l, Interntionl Journl of Reserh Sienes nd dvned Engineering [IJRSE] TM Volume 2, Issue 15, PP: , SEPTEMER Tle 1.9: Genertor dt for different lod levels (Pu on 100 MV se) for the 14-us test system us P(pu) Voltge(pu) Lod level Fig 7 Voltges in mgnitude nd ngle, Eigen vlues fter modl nlysis pplied Tle 1.10: Lod voltges nd retive power outputs of genertor 2 nd 3 t lod level 1 (Pu on 100 MV se) for the 14-us test system ontingeny V5 V6 QG3 QG2 Without outge, fixed tp Without outge, LT tive Line outge, fixed tp Line outge, LT tive Fig 9 Power Genertion versus us numer Tle 1.11: Lod voltges nd retive power outputs of genertor 2 nd 3 t lod level 2 (Pu on 100 MV se) for the 14-us test system ontingeny V5 V6 QG3 QG2 Without outge, fixed tp Without outge, LT tive Tle 1.12: Lod voltges nd retive power outputs of genertor 2 nd 3 t lod level 3 (Pu on 100 MV se) for the 14-us test system ontingeny V5 V6 QG3 QG2 Without outge, fixed tp Without outge, LT tive Fig 10 Power lod versus us numer Interntionl Journl of Reserh Sienes nd dvned Engineering

7 MLLIK D, et l, Interntionl Journl of Reserh Sienes nd dvned Engineering [IJRSE] TM Volume 2, Issue 15, PP: , SEPTEMER Fig 11 Retive power versus us numer REFERENES [1] Wood.J nd Wollenerg.F., Power genertion, opertion nd ontrol, John Wiley & Sons In., [2] Stott, ls O nd Montielli.J, Seurity nlysis nd Optimiztion, Pro. IEEE, vol. 75,No. 12, pp ,De [3] Lee.Y nd hen N, Distriution ftors nd retive power flow in trnsmission line nd trnsformer outge studies, IEEE Trnstions on Power systems, Vol. 7,No. 1,pp , Ferury [4] Singh S.N nd Srivstv S., Improved voltge nd retive distriution ftor for outge studies, IEEE Trnstions on Power systems, Vol. 12, No.3, pp , ugust 1997 [5] Peterson N.M, Tinney W.F nd ree D.W, Itertive liner power flow solution for fst pproximte outge studies, IEEE Trnstions on Power pprtus nd Systems, Vol. PS-91, No. 5, pp , Otoer [6] rndwjn V nd Luy M.G, omplete ounding method for. ontingeny sreening, IEEE Trnstions on Power systems, Vol. 4, No. 2, pp , My [7] luyeh F, ose nd Heth, Retive power onsidertion in utomti ontingeny seletion, IEEE Trnstions on Power systems, Vol. PS-101, No. 1, pp , Jnury [8] Zorzky J, Whng K.W nd Prsd K, Fst ontingeny evlution using onentri relxtion, IEEE Trnstions on Power systems, Vol. PS-99, No. 1, pp , Ferury [9] Stott nd ls O, Fst deoupled lod flow, IEEE Trnstions on Power pprtus nd Systems, Vol. PS-91, No. 5, pp , My [10] Ejee G. nd Wollenerg.F, utomti ontingeny Seletion, IEEE Trnstions on Power pprtus nd Systems, Vol. PS-98, No. 1, pp , Jnury [11] Innoent Kmw, Roert Grondin nd Lester Loud, Time- Vrying ontingeny Sreening for Dynmi Seurity ssessment Using Intelligent-Systems Tehniques, IEEE Trnstions on Power Systems, Vol. 16, No. 3, pp , ugust 2001 [12] T.Jin, L.Srivstv, S.N. Singh nd rvind Jin, Prllel Rdil sis Funtion Neurl Network sed Fst Voltge Estimtion for ontingeny nlysis, IEEE Interntionl onferene on Eletri Utility Deregultion, Restruturing nd Power Tehnologies, Hong Kong, pril [13] F. Ftehi, M.Rshidinejd nd. Ghrveisi, ontingeny Rnking sed on Voltge Stility riteri Index, IEEE Trnstions in Power System, 2007 [14] Vihv Donde, Vness Lopex, ernrd Lesieutre, li Pinr, ho Yng nd Jun Mez, Severe Multiple ontingeny Sreening in Eletri Power Systems, IEEE Trnstions on Power Systems, Vol.23, No.2, pp , My [15] Mgnus Perninge, Flip Linskog nd Lennrt Soder, Importne Smpling of Injeted Powers for Eletri Power System Seurity nlysis, IEEE Trnstions on Power Systems, Vol.27, No.1, Ferury Interntionl Journl of Reserh Sienes nd dvned Engineering