University of New Orlens SholrWorks@UNO University of New Orlens Theses nd Disserttions Disserttions nd Theses Fll 12-18-2014 Edutionl Modeling for Fult nlysis of Power Systems with STTOM ontrollers using Simulink Tetin rokhoeft University of New Orlens, trokho@uno.edu Follow this nd dditionl works t: https://sholrworks.uno.edu/td Prt of the Power nd Energy ommons Reommended ittion rokhoeft, Tetin, "Edutionl Modeling for Fult nlysis of Power Systems with STTOM ontrollers using Simulink" (2014). University of New Orlens Theses nd Disserttions. 1906. https://sholrworks.uno.edu/td/1906 This Thesis is rought to you for free nd open ess y the Disserttions nd Theses t SholrWorks@UNO. It hs een epted for inlusion in University of New Orlens Theses nd Disserttions y n uthorized dministrtor of SholrWorks@UNO. The uthor is solely responsile for ensuring ompline with opyright. For more informtion, plese ontt sholrworks@uno.edu.
Edutionl Modeling for Fult nlysis of Power Systems With STTOM ontrollers using Simulink Thesis Sumitted to the Grdute Fulty of the University of New Orlens in prtil fulfillment of the requirements for the degree of Mster of Siene in Eletril Engineering y Tetin rokhoeft.s. Zporizhzhy Ntionl Tehnil University, 2008 M.S. Zporizhzhy Ntionl Tehnil University, 2009 Deemer, 2014
Thnks Mom! To my Mother ii
KNOWLEDGMENTS This projet would not hve een possile without the support of mny people. Mny thnks to my dviser, Dr. Prviz Rstgoufrd, who red my numerous revisions nd helped me to mke some sense of the onfusion. lso thnks to my ommittee memers, Dr. Ittiphong Leevongwt nd Dr. Rsheed zzm, who offered guidne nd support. Thnks to the University of New Orlens for giving me the opportunity to get this degree nd opening the rod for me in life. nd finlly, thnks to my prents, nd friends who endured this long proess with me, pushed me, lwys offering support nd love. iii
FOREWORD This thesis is written s prt of the requirement for ompletion of Mster of Siene degree in Eletril Engineering t the University of New Orlens. The min prt of the thesis ws done during the time-period of Jnury 2013 until Deemer 2014 under supervision of my professor Dr. Prviz Rsrgoufrd. The simultions nd nlysis of results were performed in PERL lortory. The intent of the thesis is to develop methodology to model FTS devies in generl nd s n exmple STTOM in prtiulr for edutionl purposes. The thesis provides steps for developing STTOM model in Simulink nd provides the methodology for modeling, simulting, nd nlyzing five tegories of fults in test model with nd without presene of STTOM ontroller. The sujet is seleted in o-opertion with students nd fulty working in PERL nd I hve gined experiene during my study nd working on the sujet of the thesis. I hve een le to hieve the results tht I m stisfied with nd would like to thnk my supervisor from the University of New Orlens, Dr. Prviz Rstgoufrd. His vlule insights nd diretions gve me needful guidne to omplete the reserh nd write this thesis. iv
TLE OF ONTENTS Tle of ontents...v List of Figures... vii List of Tles... x strt... xi hpter 1...1 Introdution...1 1.1 Introdution to FTS Devies...2 1.2 Types of Fult...3 1.2.1 lned Three-Phse Fult nlysis...4 1.2.2 Unlned Fult nlysis...4 1.3 Review of Relevnt Studies...6 1.4 Ojetive of the Thesis...7 hpter 2 Model of the Power System...8 hpter 3 Model of the Power System with STTOM...22 3.1 STTOM Overview...22 3.2 STTOM Operting Priniple...23 3.3 Modeling of STTOM in Simulink...24 hpter 4 Test System...31 4.1 lned Three-Phse Fult...31 4.2 Three Phse-to-Ground Fult...37 4.3 Line-to-Ground Fult...42 4.4 Line-to-Line Fult...47 4.5 Doule Line-to-Ground Fult...52 hpter 5 Results nd nlysis...57 5.1 lned Three-Phse Fult...58 5.2 Three Phse-to-Ground Fult...61 5.3 Line-to-Ground Fult...62 5.4 Line-to-Line Fult...64 5.5 Doule Line-to-Ground Fult...66 hpter 6 onlusion nd Future Work...70 v
Referenes...72 ppendix...74 ppendix...75 ppendix...76 ppendix D...77 ppendix E...78 Vit...79 vi
LIST OF FIGURES Figure 1.1: Four ommon Types of Fult...4 Figure 1.2: () lned three phse fult, () lned three phse to ground fult...4 Figure 1.3: Line-to-ground fult on phse...5 Figure 1.4: Line-to-Line Fult on phses -...5 Figure 1.5: Doule Line-to-Ground Fult on phses -...5 Figure 2.1: () One-line Digrm of the 4-us System, () One-line Digrm of the Test Power System with desription in Tle 2.1...8 Figure 2.1): Sheme of the Test System...9 Figure 2.2: Voltge Soure Simulink lok...10 Figure 2.3: Lod Representtion in Simulink lok...11 Figure 2.4: Three-phse Trnsformer Simulink lok...12 Figure 2.5: Distriuted Trnsmission Line Simulink lok...16 Figure 2.6: Power System Model in Simulink...18 Figure 2.7 ): System Voltge Wveform Mesured fter Trnsformer...19 Figure 2.7 ): System urrent Wveform Mesured fter Trnsformer...20 Figure 3.1: Stti ompenstor (STTOM) System: Voltge Soure onverter (VS) onneted to the Network vi Shunt-onneted Trnsformer...22 Figure 3.2: Struture nd Equivlent iruit of STTOM...23 Figure 3.3: Stti ompenstor (STTOM) Equivlent iruit...24 Figure 3.4: STTOM ontroller System...24 Figure 3.5: Thyristor in Prllel with Series R iruit Susystem...25 Figure 3.6: Voltge Soure Inverter Model...26 Figure 3.7: One-line Digrm of the Power System with STTOM ontroller...26 Figure 3.8: Model of the Power System with STTOM in Simulink...27 Figure 3.9 ): System Voltge Wveforms Mesured fter Trnsformer...28 Figure 3.9 ): System urrent Wveforms Mesured fter Trnsformer...29 Figure 4.1: One-line digrm of the lned three-phse fult...32 Figure 4.2: Model without STTOM under lned Three-Phse Fult...33 vii
Figure 4.3: Model with STTOM under lned Three-Phse Fult...34 Figure 4.4: Voltge plot of the power system without STTOM Under three-phse fult...35 Figure 4.5: Voltge plot of the power system with STTOM Under three-phse fult...36 Figure 4.6: One-line digrm of the three-phse to-ground fult...37 Figure 4.7: Model without STTOM under Three-Phse to Ground Fult...38 Figure 4.8: Model with STTOM under Three-Phse to Ground Fult...39 Figure 4.9: Voltge plot of the power system without STTOM Under Three-Phse to Ground Fult...40 Figure 4.10: Voltge plot of the power system with STTOM Under Three-Phse to Ground Fult...41 Figure 4.11: One-line Digrm of the Power System with Line-to-Ground Fult...42 Figure 4.12: Model of the Power System without STTOM Under Line-to-Ground Fult...43 Figure 4.13: Model of the Power System with STTOM Under Line-to-Ground Fult...44 Figure 4.14: Voltge plot of the power system without STTOM Under Line-to-Ground Fult...45 Figure 4.15: Voltge plot of the power system with STTOM Under Line-to-Ground Fult...46 Figure 4.16: One-line Digrm of the us System with Phse-to-Phse Fult (-to-)...47 Figure 4.17: Model without STTOM under Line-to-Line Fult...48 Figure 4.18: Model with STTOM under Line-to-Line Fult...49 Figure 4.19: Voltge plot of the power system without STTOM Under Line-to-Line Fult...50 Figure 4.20: Voltge plot of the power system with STTOM Under Line-to-Line Fult...51 Figure 4.21: One-line Digrm of the Power System with Doule Line-to-Ground viii
Fult...52 Figure 4.22: Model of the power system without STTOM Under Line-to-Ground fult...53 Figure 4.23: Model of the power system with STTOM Under Line-to-Ground Fult...54 Figure 4.24: Voltge plot of the power system without STTOM Under Line-to-Ground Fult...55 Figure 4.25: Voltge plot of the power system with STTOM Under Line-to-Ground Fult...56 Figure 5.1 ): Voltge Peks fter the lned Three-Phse Fult lers In the System without STTOM...59 Figure 5.1 ): Voltge Peks fter the lned Three-Phse Fult lers In the System with STTOM...60 Figure 5.2 ): Voltge Peks fter the Three-Phse to Ground Fult lers In the System without STTOM...61 Figure 5.2 ): Voltge Peks fter the Three-Phse to Ground Fult lers In the System with STTOM...62 Figure 5.3 ): Voltge Peks fter the Line-to-Ground Fult lers In the System without STTOM...63 Figure 5.3 ): Voltge Peks fter the Line-to-Ground Fult lers In the System with STTOM...64 Figure 5.4 ): Voltge Peks fter the Line-to-Line Fult lers In the System without STTOM...65 Figure 5.4 ): Voltge Peks fter the Line-to-Line Fult lers In the System with STTOM...66 Figure 5.5 ): Voltge Peks fter the Doule Line-to-Ground Fult lers In the System without STTOM...67 Figure 5.5 ): Voltge Peks fter the Doule Line-to-Ground Fult lers In the System with STTOM...68 ix
LIST OF TLES Tle 2.1: Prmeters of the Power System...17 Tle 3.1: Thyristor in Prllel with Series R iruit Simulink lok Prmeters...25 Tle 5.1: omprison of Voltge Peks for the System Without nd With STTOM...69 x
STRT The nlysis of power systems under fult ondition represents one of the most importnt nd omplex tsks in power engineering. The study nd detetion of these fults re neessry to ensure tht the reliility nd stility of the power system do not suffer derement s result of ritil event suh s fult. The purpose of this thesis is to develop nd to present n edutionl tool for students to model FTS devies using Simulink. Furthermore, the development of this thesis provides the mens for students to model different types of fults. The development is sed on presenting power system the Test System - y its simplest form inluding genertion, trnsmission, trnsformers, lods nd STTOM devie s n exmple of the generl FTS devies. The thesis inludes modeling of the Test System using Simulink nd MTL progrm to produe the results for further nlysis. The findings nd development inluded in the thesis is intended to serve s n edutionl tool for students interested in the study of fults nd their impt on FTS devies. Students my use the thesis s the uilding lok for developing models of lrger nd more omplex power systems using Simulink nd MTL progrms for further study of impts of FTS devies in power systems. Simulink Fult nlysis, Power Systems, Types of Fult, STTOM, MTL, Modeling, xi
hpter 1 INTRODUTION There is rpid development in the field of eletril power systems in the reent yers where modeling nd simultion of genertion, trnsmission nd distriution susystems ply importnt roles in plnning nd opertion of power systems. Rpid growth of eletriity onsumption while mintining high level of system reliility hs used expnsion of power system grids during the pst few yers. The inrese in oth lod growth nd system reliility hs generted power system tht inludes lrger numer of lines, hene, requiring inresed fult nd ontingeny simultion of the system. Trnsmission lines re essentil prts of power system for power energy delivery from generting plnts to end ustomers where fults most likely our. Fults on the trnsmission system n led to severe eonomi losses. Trditionl updting of trnsmission system y onstruting new trnsmission lines eomes extremely diffiult euse of eonomi nd environmentl pressures [7]. High effiieny in terms of etter utiliztion of existing trnsmission lines, without ompromising the qulity nd reliility of eletril power supply hs thus to e found vi lterntive mens. In this respet, due to the reent dvnes in high power semiondutor tehnology, Flexile Trnsmission System (FTS) tehnology hs een proposed to solve this prolem [1, 2]. However, euse of the dded omplexity due to the intertion of FTS devies with the trnsmission system, the trnsients superimposed on the power frequeny voltge nd urrent wveforms (prtiulrly under fults) n e signifintly different from those systems not employing FTS devies. This differene will result in rpid hnges in system prmeters suh s line impedne nd power ngle. onsequently it is vitlly importnt to study the impt of the FTS devies when dded to the system model for simulting vrious fults on trnsmission lines in the system. To model FTS devies for trnsmission system fult nlysis, we need to explore modeling of vrious FTS devies nd trnsmission line fult tegories. In wht follows we riefly provide kground mteril on FTS devies nd trnsmission line fult tegories. 1
1.1. Introdution to FTS Devies The Thyristor ontrolled Series pitor (TS), the Universl Power Flow ontroller (UPF), the Stti Synhronous Series ompenstor (SSS), nd the Stti Synhronous ompenstor (STTOM) re some of the power ontrollers developed under the umrell nme of Flexile Trnsmission Systems (FTS). These devies ply key role in modern eletril networks euse they hve the pility of improving the opertion nd ontrol of power networks y inresing power trnsfer nd improving trnsient stility mong other hrteristis. ollterl to their mny strong points, the FTS ontrollers hve undesired impt on the protetion system tht should e tken into ount in modeling, simultion, nd design of future power systems. The FTS ontrollers, one instlled in the power grid, help to improve the power trnsfer pility of long trnsmission lines nd the system performne in generl. dditionlly FTS ontrollers re enefiilly used for fst voltge regultion, inresed power trnsfer over long lines, dmping of tive power osilltions, nd lod flow ontrol in meshed systems. Hingorni nd Gyugyi [3] provide useful nd thorough representtion of FTS devies in four tegories tht re used y reserhers in study nd design of power systems. The four tegories represented in [3] nd used in this thesis re: 1. Series ontroller. Series ontrollers re onneted to power line in series nd hve n impt on the power flow nd voltge profile. Exmples of these ontrollers re the SSS nd TS. 2. Shunt ontrollers. These ontrollers re shunt onneted to trnsmission lines nd re designed to injet urrent into the system t the point of onnetion. n exmple of these ontrollers is the Stti Synhronous ompenstor (STTOM). 3. Series-shunt ontrollers. These ontrollers re omintion of seril nd shunt ontrollers. This omintion is ple of injeting urrent nd voltge. n exmple of ontrollers is the Unified Power Flow ontroller (UPF). 4. Series-series ontrollers. These ontrollers n e omintion of seprte series ontrollers in multiline trnsmission system, or it n e single ontroller in single line. n exmple of suh devies is the Interline Power Flow ontroller (IPF). The STTOM, TS, 2
nd SS re three of the FTS ontrollers highlighted y their pity to provide wide rnge of solutions for oth norml nd norml onditions. The TS is mde of series pitor (TS) shunted y thyristor module in series with n indutor (LTS). n externl fixed pitor (FIXED) provides dditionl series ompensting. Normlly the TS opertes s vrile pitor, firing the thyristor etween 180 to 150. The SSS injets voltge in series with the trnsmission line in qudrture with the line urrent. The SSS inreses or dereses the voltge ross the line, nd therey, ontrolling the trnsmitted power. The STTOM is voltge-soure onverter (VS) sed ontroller whih mintins the us voltge y injeting n urrent through trnsformer. The STTOM n rpidly supply dynmi VRs required during system fults for voltge support. During fult in power system short iruit urrents flow, the mgnitude of these urrents n e of the order of tens of thousnds of mperes. So onsequently, the fult types hve to e determined nd nlyzed. With this rief kground mteril on FTS devies, we proeed to providing the neessry mteril on types of fults tht re importnt uilding loks in our study of fulted power systems tht inlude FTS devies [10]. 1.2 Types of Fults Grnger nd Stevenson [8] outlined lned three-phse fults, single line-to-ground fults, line-to-line fults, doule line-to-ground fults s four ommon types of fult ourrene on trnsmission lines. Figure 1.1 provides grphil view of the four types of fults. 3
Figure 1.1: Four ommon Types of Fult [8] 1.2.1 lned Three-Phse Fult lned three-phse fult is defined s the simultneous short iruit ross ll three phses of trnsmission line. three phse fult is ondition where either () ll three phses of the system re short iruited to eh other or () ll three phses of the system re grounded. Figure 1.2 provides pitoril view of lned three-phse fults. Figure 1.2: () lned three phse fult, () lned three phse to ground fult [8] lned three phse fult is lso lled s symmetri fult euse the power system remins in lne fter the fult ours. It is the most infrequent ut the most severe fult type, nd other fults, if not lered promptly, n esily develop into three-phse fult [8]. 1.2.2 Unlned Fults Single line-to-ground fults re fults in whih n overhed trnsmission line touhes the ground euse of wind, ie loding, or flling tree lim. mjority of trnsmission line fults re single line-to-ground fults. The single line to ground fult n our in ny of the three 4
phses. However, it is suffiient to nlyze only one of the phses [8]. Figure 1.3 depits line-toground fult on phse. Figure 1.3: Line-to-ground fult on phse [8] Line-to-line fults re usully the result of glloping lines euse of high winds or euse of line reking nd flling on line elow. Line-to- line fults my our in power system, with or without the erth, nd with or without fult impedne [8]. Figure 1.4 shows line-to-line fult on phses -. Figure 1.4: Line-to-line fult on phses - [8] Doule line-to-ground fult ours when two phses got shorted to the ground. This type of fult is ommon due to the storm dmge. Doule line-to-ground fult is presented on Figure 1.5. Figure 1.5: Doule line-to-ground fult on phses - [8] So fr we hve provided prolem sttement, FTS devies nd four ommon tegories tht re used y reserhers in their studies, nd four ommon types of fults experiened on 5
trnsmission lines. We next provide summry of the studies tht hve een onduted nd reported y investigtors using FTS devies. 1.3 Review of Relevnt Studies Vrieties of fult studies nd some reserh hve een done on the performne of distne relys for trnsmission systems inluding different FTS devies nd re reported in literture. The nlytil results sed on stedy-stte model of STTOM, nd the impt of STTOM on distne relys t different lod levels re presented in [18]. In [19], the voltgesoure model of FTS devies is used to study the impt of FTS on tripping oundries of distne relys. The work in [20] shows tht thyristor ontrolled series pitor (TS) hs ig influene on the mho hrteristi nd retne while the studies in [21], [15] nd [4] demonstrte tht the presene of FTS devies on trnsmission line will ffet the trip oundry of distne relys, nd oth the prmeters of the FTS devie nd its lotion hve impts on the trip oundry. Wvelet trnsform sed multi resolution nlysis pproh n e suessfully pplied for effetive detetion nd lssifition of fults in trnsmission lines. With STTOM ontroller, fult detetion, lssifition nd lotion n e omplished within hlf yle using detil oeffiients of urrents [13, 16]. Wvelet trnsform is n effetive tool in nlyzing trnsient voltge nd urrent signls ssoited with fults oth in frequeny nd time domin. The new wvelet-fuzzy omined pproh for digitl relying is highly used nowdys s well. The lgorithm for fult lssifition employs wvelet multi resolution nlysis (MR) to overome the diffiulties ssoited with onventionl voltge nd urrent sed mesurements due to effet of ftors suh s fult ineption ngle, fult impedne nd fult distne. The omined pproh employs wvelet trnsform together with fuzzy logi. The wvelet trnsform ptures the dynmi hrteristis of the non-sttionry trnsient fult signls using wvelet MR oeffiients. The fuzzy logi is employed to inorporte expert evlution through fuzzy inferene system (FIS) so s to extrt importnt fetures from wvelet MR oeffiients for otining oherent onlusions regrding fult lotion [16]. 6
ll the studies show tht when the FTS devie is in fult loop, its voltge nd urrent injetion will ffet oth the stedy nd trnsient omponents in voltge nd urrent nd hene the pprent impedne seen y onventionl distne rely is different from tht on system without FTS. When the types of fults desried in Setion 1.2 our, the mgnitude of us voltge nnot exist t its opertionl rnge, either voltge drops or inreses. To prevent this effet, STTOM FTS ontroller is the est solution to mintin us voltge mgnitude in suitle rnge [1]. There is lwys need to develop innovtive methods for trnsmission line protetion. 1.4 Ojetives of the Thesis The first ojetive of this thesis is to study in dynmis the ommon fult types tht our in the power system. Seondly is to perform the nlysis of influene tht FTS devies nd in prtiulr STTOM hs on power system under five tegories of fults desried in Setion 1.2. These ojetives re omplished y reting model of power system in Simulink MTL sed progrm. Simulink is the environment in MTL tht hs design tools to model nd simulte power system. Simulink hs een used to uild the STTOM [2,5,6,9] nd to study different types of influenes tht it hs on power system desried in Setion 1.3. We fous on studying the influene of STTOM on test power system during fult event. Moreover, we simulte, nlyze, nd ompre the results of five different types of fults on the test system without nd with STTOM model. The reminder of the thesis is orgnized to inlude the neessry prts in order to determine the effet of the STTOM on power system. So firstly the model of power system is developed in hpter 2. Seondly STTOM ontroller ws introdued into the system nd nlyzed in hpter 3. In hpter 4 five different types of fults were dded in the power system with STTOM. hpter 5 inludes the nlysis of STTOM influene on the power system nd onluding remrks nd future work re inluded in hpter 6. 7
hpter 2 MODEL OF THE POWER SYSTEM To stisfy the ojetives of the thesis desried in hpter 1 we need to develop suitle power system in Simulink. The simplest 4-us system with genertor, step-up trnsformer, trnsmission line, step-down trnsformer nd lod n e onsidered. Suh system is presented on Figure 2.1 ). Figure 2.1 ): One-line digrm of the 4-us power system However, s stted in hpter 1, this work is onentrted on studying the influene of the STTOM devies on the power system depending on its point of insertion. Tht is why the originl system n e simplified into test power system presented in Figure 2.1 ). Genertor, represented the rest of the system, is onneted to the prt of the test system where STTOM will e instlled to hieve ojetives of the thesis. The test power system onsists of voltge soure, trnsmission line, two lods nd trnsformer, whih prmeters n e found in Tle 2.1. Figure 2.1 ): One-line digrm of the test power system with desription in Tle 2.1 8
The test power system n e presented s sheme onsisting of prt where STTOM will e instlled nd the rest of the system. Depending on the point of STTOM insertion, test system n e modified for the future studies. Sheme of power system used in this work is presented in Figure 2.1 ). Figure 2.1 ): Sheme of the test system The genertor in the test system is modeled y voltge soure nd for nlysis of the results, the genertor is n idel voltge soure in Simulink. lthough in rel power systems genertors hrteristis re not idel, the hoie of power soure ws to simplify the nlysis using Simulink results. The voltge soure used to model the genertor of Figure 2.1 ) is represented y Figure 2.2. voltge soure model in Simulink ws presented y three-phse idel sinusoidl voltge soure with mplitude of 120 degrees. 735000 2 3 volts nd with three phses lgging eh other y 9
Figure 2.2: voltge soure Simulink lok The two lods in Figure 2.1 ) re represented s indutive insted of resistive lods. It is importnt to hve indutive nd not just resistive lods in order to hieve the similrity with rel world power system. Two lods were dded into two different ples of the power system: one on the genertion side nd one fter step-down trnsformer on the lod side. Simulink models of the lod re shown y Figure 2.3. 10
Figure 2.3: Lod representtion in Simulink lok Trnsformer is lso dded into the system to hieve the similrity with the rel world power system. It is step-down trnsformer from genertion side of the model to the lod side. Three-phse trnsformer lok of the Simulink power system model is presented in Figure 2.4. Three-phse trnsformer model in Simulink ws uilt y speifying prmeters for winding 1 nd winding 2, nd lso mgnetiztion hrteristis whih re the following: Winding 1 prmeters: [V1 Ph-Ph(Vrms), R1(pu), L1(pu)]= [735e3, 0.15/30/2, 0.15*0.7] Winding 2 prmeters: [V2 Ph-Ph(Vrms), R2(pu), L2(pu)]= [ 16e3, 0.15/30/2, 0.15*0.3] Mgnetiztion resistne: [Rm (pu); mgnetiztion indutne Lm (pu)]= [500, 500] 11
Figure 2.4: Three-phse trnsformer Simulink lok In order to simulte trnsmission line, distriuted model of the line with speifi R, L nd vlues tht re shown in Tle 2.1 were hosen. Trnsmission line is the model lok tht hs to e explined in more detils sine its vlues hnge depending on the length of the line. Thus, we will present the neessry theory for distriuted prmeter model of trnsmission lines in this setion. distriuted prmeter is prmeter whih is spred throughout struture nd is not onfined to lumped element suh s oil of wire. The generi line onsists of two ondutors with potentil differene V(x) etween them, nd urrent I(x) tht flows down one ondutor, nd returns vi the other. urrent flowing in wire gives rise to mgneti field, H. y the definition L, the indutne of iruit element, L ΦI, is Φ, the flux linking the iruit element, multiplied y I, the urrent flowing through it. ut the longer setion of wire is, the more Φ would e needed for the sme I. Thus, L s the distriuted indutne for the trnsmission line hs to e defined. It hs units of Henrys per unit length nd n e found s length of trnsmission line multiplied y distriuted indutne of L. The two ondutors would lso hve distriuted pitne whih hs units of Frds per unit length nd n e found s the length of trnsmission line multiplied y distriuted pitne. Thus, we see tht the trnsmission line hs oth distriuted indutne L nd distriuted pitne whih re tied up with eh other. There is relly no 12
wy in whih we n seprte one from the other hving only the pitne, or only the indutne; there will lwys e some of eh ssoited with eh setion of line no mtter how smll or how ig we mke it [12]. These elements of trnsmission line suh s pitne nd retne my e used in the per phse equivlent iruit of three-phse line operting under lned onditions. The Distriuted Prmeter Line lok, used in Simulink, implements n N-phse distriuted prmeter line model with lumped losses. The model is sed on the ergeron's trveling wve method [5]. In this model, the lossless distriuted L line is hrterized y two vlues (for single-phse line): the surge impedne l Z = nd the wve propgtion speed v= 1, l where l nd re the per-unit length indutne nd pitne [12]. For the test model used in the simultions, distriuted prmeters of the trnsmission line suh s resistne presented y resistne per unit length (Ohms/km) speified y positive nd zero-sequene resistnes [r1 r0]- [0.01273 0.3864]. Indutne presented y indutne per unit length (H/km) with positive nd zero-sequene indutnes [l1 l0]- [0.9337e-3 4.1264e-3]. pitne presented y pitne per unit length (F/km) speified y positive nd zero-sequene pitnes [1 0]- [12.74e-9 7.751e-9]. Positive, negtive nd zero-sequene omponents re used to resolve unlned three-phse systems into lned system of phsors. The symmetril omponents differ in the phse sequene, tht is, the order in whih the phse quntities go through mximum. The phse omponents re the ddition of the symmetril omponents nd n e written s follows: = 1 1 1 + = + 2 = + 2 2 + + 0 + In order to solve the system (2.1) it hs to e written in terms of one phse, for exmple phse, omponents nd the opertorα, whih hs mgnitude of unity nd, when operted on ny omplex numer, rottes it nti-lokwise y n ngle of 120 degrees. The opertorα, the squre of it nd (1+j0) phsor form lned symmetril system [12]. If Z, Z, nd Z re the impedne of the lod etween phses,, nd, then sequene impednes re given in (2.2): 0 0 (2.1) 13
14 ) ( 3 1 : ) ( 3 1 : ) ( 3 1 : 3 2 1 Z Z Z Z zero Z Z Z Z negtive Z Z Z Z positive + + = + + = + + = α α (2.2) Trnsmission lines re ssumed to hve positive nd negtive sequene to e equl [12], so only positive sequene ws mentioned in the test system. Tking into ount the numers from the test model for indutne speified y positive nd zero-sequene indutnes [l1 l0]- [0.9337e-3 4.1264e-3] nd pitne speified y positive nd zero-sequene pitnes [1 0]- [12.74e-9 7.751e-9], we n get the following equtions speified in (2.3): 9 7.751 ) ( 3 1 9 12.74 ) ( 3 1 9 12.74 ) ( 3 1 3 4.1264 ) ( 3 1 3 0.933 ) ( 3 1 3 0.933 ) ( 3 1 0 0 = + + = = + + = = + + = = + + = = + + = = + + = e e e e l l l l e l l l l e l l l l neg pos neg pos α α α α (2.3) Solving the ove system of equtions (2.3) in Mtl progrm the following solutions were found: ) 0.0432 0.0748 ( 007) (1 ) 0.0432 0.0748 ( 007) (1 ) 0.0864 (0.3822 007) (1 0.0028 0.0048 0.0028 0.0048 0.0055 0.0028 j e j e j e j l j l j l = = + = = = = (2.4) Trnsmission lines my e represented y single retne in the single line digrm s l nd re the per-unit length indutne nd pitne. For lossless line (r = 0), the quntity e + Z i, where e is the line voltge t one end nd i is the line urrent entering the sme end, must rrive unhnged t the other end fter trnsport dely τ. v d = τ (2.5) where d is the line length nd v is the propgtion speed [12]. Using the notion of propgtion speed nd surge impedne, the following n e estlished in (2.6):
15 l Z = (2.6) l = d τ The model equtions for lossless line re: ) ( ) ( ) ( ) ( τ τ + = t i Z t e t i Z t e S s r r (2.7) ) ( ) ( ) ( ) ( τ τ + = t i Z t e t i Z t e r r S S knowing tht, ) ( ) ( ) ( t I Z t e t i sh S S = (2.8) ) ( ) ( ) ( t I Z t e t i rh r r = In lossless line, I sh nd I rh, whih re two urrent soures of two-port model, re omputed in (2.9): ) ( ) ( 2 ) ( τ τ = t I t e Z t I rh r sh (2.9) ) ( ) ( 2 ) ( τ τ = t I t e Z t I sh S rh When losses re tken into ount, new equtions for I sh nd I rh (2.10) re otined y lumping R/4 t oth ends of the line nd R/2 in the middle of the line: R = totl resistne = r d The urrent soures I sh nd I rh re then omputed s follows [12]: )) ( ) ( 1 ( ) 2 1 ( )) ( ) ( 1 ( ) 2 1 ( ) ( τ τ τ τ + + + + = t I h t e Z h h t I h t e Z h h t I sh S rh r sh (2.10) )) ( ) ( 1 ( ) 2 1 ( )) ( ) ( 1 ( ) 2 1 ( ) ( τ τ τ τ + + + + = t I h t e Z h h t I h t e Z h h t I rh r sh S rh where 4 r Z Z + = 4 4 r Z r Z h + = (2.11)
For multiphse line models, modl trnsformtion is used to onvert line quntities from phse vlues (line urrents nd voltges) into modl vlues independent of eh other. s the test model is three-phse unlned system, it would hve to e solved y tking the vlues of phse omponents seprtely nd onverting them into modl quntities. This n e omplished y using trnsformtions like Krrenuer, lrke or like whih re ommonly used in EMPT-like progrms. These trnsformtions result in the sme modl impednes nd dmittnes s would result from pplying symmetril omponents trnsformtion in the 60 Hz phse domin [5]. These trnsformtions re utomtilly performed inside the Distriuted Prmeter Line lok of Simulink whih model is presented on Figure 2.5. Figure 2.5: Distriuted trnsmission line Simulink lok Numeril vlues for eh of the omponents of the power system re desried next. The system onsists of 600 km trnsmission line powered y 735 kv genertor. 735kV/16kV Delt/Y trnsformer onneted to the power system to step down the voltge. Two lods 330 nd 16
250 MW eh re instlled on the power system s well. The detils of the power system re presented in the Tle 2.1. Tle 2.1: Prmeters of the power system Genertor 735kV 3 phse voltge soure Lod 1 330MW/250 tive, 330MVr Retive Lod 2 250MW/250 tive, 250MVr Retive Trnsmission line Length=600km, R= 0.01273 Ohm/km, L= 0.9337e-3 H/km, = 12.74e-9 F/km Putting ll the omponents together into one model, we reeive grphil representtion of the power system uilt in Simulink whih is shown in Figure 2.6. fter simultions hd een performed the voltge nd urrent n e oserved t the vrious lotions of the system. This is done y inluding the grph loks for plotting voltge nd urrent wveforms (Figure 2.7). 17
ontinuous powergui Idel Voltge Soure 1 1 1 Trnsmission Line (600 km) Three-Phse V-I Mesurement1 V I 330 MVr Lod U1 I1 Three-phse Trnsformer 735/16kV U2 Three-Phse V-I Mesurement V I I2 + v - Voltge Mesurement U3 no sttom 250 MVr Lod Figure 2.6: Power system model in Simulink 18
Figure 2.7 ): System voltge wveform mesured fter trnsformer, where: pink xis phse, yellow xis phse, lue xis phse Figure 2.7 ) revels voltge wveform of the system t the us fter the step-down trnsformer of the one-line digrm of Figure 2.1. Figure 2.1 is onverted to Figure 2.6 using Simulink modeling omponents nd the mesuring devies instlled t terminls of step-down trnsformer of Figure 2.6. s seen in Figure 2.7 ) the three mesured voltges ppering s different three olors represent lned three phses of the voltge t the us with the sme 19
mgnitude nd 120 degrees phse ngle. Figure 2.7 ) is repli of 2.7 ) exept for the urrent phses t the us. Figure 2.7 ): System urrent wveform mesured fter trnsformer, where: pink xis phse, yellow xis phse, lue xis phse In hpter 3 we introdue model of STTOM in the Simulink model of hpter 2 for running wht if senrios while pplying different fults. The developed integrted Simulink model ould e used for studying ehvior of STTOM when the trnsmission system is 20
exposed to fults in hpter 4. The purpose of the developments of hpter 3 nd hpter 4 is to provide the edutionl tool for studying ehvior of power systems tht re pushed to their stility limit nd to study the improvements mde y dding FTS ontrol devies in generl nd STTOM in prtiulr. s stted in [14], STTOM llows n inrese in trnsfer of power while improving stility limits y djusting the power system prmeters suh s voltge, urrent, frequeny nd phse ngle. 21
hpter 3 MODEL OF THE TEST POWER SYSTEM INLUDING STTOM 3.1 STTOM Overview stti synhronous ompenstor (STTOM), lso known s "stti synhronous ondenser" ("STTON"), is regulting devie used on lternting urrent eletriity trnsmission networks [1]. STTOM is self ommutted swithing power onverter supplied from n eletri energy soure nd operted to produe set of djustle multiphse voltge, whih my e oupled to n power system for the purpose of exhnging independently ontrollle rel nd retive power. The ontrolled retive ompenstion in eletri power system is usully hieved with the vrint STTOM onfigurtions. The STTOM hs een defined with following three operting struturl omponents. First omponent is Stti: sed on solid stte swithing devies with no rotting omponents; seond omponent is Synhronous: nlogous to n idel synhronous mhine with three sinusoidl phse voltges t fundmentl frequeny nd the third omponent is ompenstor: provided with retive ompenstion. It is sed on power eletronis voltge-soure onverter nd n t s either soure or sink of retive power to n eletriity network. If onneted to soure of power it n lso provide tive power. It is memer of the FTS fmily of devies [3], [17]. Figure 3.1: Stti ompenstor (STTOM) system: voltge soure onverter (VS) onneted to the power system vi shunt-onneted trnsformer [3] Usefully STTOM is instlled to support eletriity networks tht hve poor power ftor nd often poor voltge regultion nd the most ommon use of it is for voltge stility. stti synhronous ompenstor is voltge soure onverter sed devie where the voltge soure is reted from D pitor nd therefore stti synhronous ompenstor hs very 22
little tive power pility. However, STTOM tive power pility n e inresed if suitle energy storge devie is onneted ross the d pitor. The retive power t the terminls of the stti synhronous ompenstor depends on the mplitude of the voltge soure. For exmple, if the terminl voltge of the voltge soure onverter (VS) is higher thn the voltge t the point of onnetion, the STTOM genertes retive urrent nd when the mplitude of the voltge soure is lower thn the voltge, it sors retive power. The response time of STTOM is shorter thn tht of stti vr ompenstor (SV), minly due to the fst swithing times provided y the Insulted Gte ypolr Trnsistor (IGTs) of the voltge soure onverter. The STTOM lso provides etter retive power support t low voltges thn n SV, sine the retive power from STTOM dereses linerly with the voltge (s the urrent n e mintined t the rted vlue even down to low voltge) [10]. 3.2 STTOM Operting Priniple STTOM onsists of oupling trnsformer, n inverter nd D pitor s shown in Figure 3.2. Figure 3.2: Struture nd equivlent iruit of STTOM [3] STTOM is usully used to ontrol trnsmission voltge y retive power shunt ompenstion. sed on the operting priniple of the STTOM [3] the equivlent iruit hs een derived, whih is displyed y Figure 3.3. 23
Figure 3.3: Stti ompenstor (STTOM) equivlent iruit [3] In the derivtion, it is ssumed tht the hrmonis generted y the STTOM re negleted nd the system s well s the STTOM is three phses lned. The STTOM is equivlently represented y ontrollle fundmentl frequeny positive sequene shunt voltge soure. In priniple of the STTOM output voltge n e regulted in suh wy tht the retive power of the STTOM n e hnged [11]. 3.3 Modeling of STTOM in Simulink In order to study improvement of trnsfer pility nd voltge ontrol of the power system 6-pulse STTOM ws instlled on the low side of the trnsformer of Figure 2.1 ). The ontrol model of STTOM tht is used in the test system is shown in Figure 3.4. 1 2 3 KP KP1 KP2 1 Ulin 2 lf u+90 is U_lin imp U Y DI4 signlrms lf DI2 I_rms U Y DI1 RMS Inverter 1 U Y Out1 i + Ikr Thyristor lok 1 imp_1 imp_4 U X x Thyristor lok 2 imp_1 imp_4 U X x Thyristor lok 3 imp_1 imp_4 U X x - i + - i + - Figure 3.4: STTOM ontroller system 24
The STTOM onsists of six IGT inverters nd three phse-shifting trnsformers. Eh inverter uses thyristor in prllel with series R iruit lok to generte lmost squrewve voltge. The prmeters of the STTOM ontrol system re presented in Tle 3.1. Tle 3.1: Thyristor in prllel with series R iruit Simulink lok prmeters Resistne Ron 0.001 Ohm Indutne Lon 1.13e-3 H Snuer resistne Rs 500 Ohm Snuer pitne s 250e-9 F The prmeters represent the Simulink internl resistne Ron nd internl indutne Lon of the thyristor model s well s snuer prmeters resistne Rs nd pitne s. The prmeters re true when thyristor is in the on-stte, nd hene, on for representing internl resistne nd indutne. This model is represented on Figure 3.5. 1 X g VT2 u,i,imp_1 VT1 g m k m k u,i,imp_4 2 x 3 U 1 imp_1 2 imp_4 Figure 3.5: thyristor in prllel with series R iruit susystem 25
The inverters of Figure 3.4 with speifitions of Figure 3.5 re fed to the seondry windings (L=18.7e-3 H) of phse-shifting trnsformers whose primry windings re onneted to produe n lmost sinusoidl voltge output. The voltge soure inverter in this reserh is represented with the help of synhronized 6-pulse genertor whih n e viewed in the Figure 3.6. 1 U_lin 2 lf lph_deg pulses lok 6-Pulse1 Step2 Prod 1 imp Figure 3.6: Voltge soure inverter model The susystems of Figure 3.4, 3.5, nd 3.6 omplete the STTOM model whih is used to injet or derese retive power to regulte the voltge to the test system. The STTOM model is dded to the low side of the trnsformer tht is onneted to the rest of the system t its high side voltge us. The rest of the system is represented y genertor, lod, trnsformer, nd trnsmission line with speifi numeril vlues for simultion purposes. The one-line digrm of the rest of the system onneted to the lod nd the STTOM model is shown y Figure 3.7. Figure 3.7: One-line digrm of the power system with STTOM ontroller Figure 3.8. The model of the power system with the STTOM ontroller in Simulink is shown in 26
ontinuous powergui Idel Voltge Soure 1 1 1,, Susystem4 Trnsmission Line (600 km) Three-Phse V-I Mesurement1 V I 330 MVr Lod U1 I1 Three-phse Trnsformer 735/16kV U2 Three-Phse V-I Mesurement V I I2 + v - Voltge Mesurement U3 Itir Out1 Ulin lf STTOM 250 MVr Lod 31 onstnt Figure 3.8: Model of the power system with STTOM ontroller in Simulink 27
Figure 3.9 shows voltge nd urrent wveforms fter performing simultions tht inlude model of the STTOM. The wveforms will lter e ompred with the wveforms of hpter 2 whih exludes STTOM model. Figure 3.9 ): System voltge wveforms mesured fter trnsformer 28
Figure 3.9 ): System urrent wveforms mesured fter trnsformer where: pink xis phse, yellow xis phse, lue xis phse We n see from the urrent grph of Figure 3.9 ) tht the STTOM injeted out 20% urrent into the system whih is neessry for inresing trnsfer pility nd improving voltge ontrol. In voltge stility nd ontrol prolems voltge dereses due to insuffiient power delivered to the lods. In order to prevent system from ollpsing, it is neessry to injet the dditionl retive power into the system. This is espeilly ruil for the trnsmission lines, sine they re generlly long nd trnsfer of retive power over these lines is very diffiult due 29
to signifint mount of retive power requirement. STTOM, y injeting retive power into the system, helps to prevent or lessen the prolems of trnsfer pility of the system. STTOM n e lso solution for voltge ontrol prolems. Voltge ontrol n e ttined y suffiient genertion nd trnsmission of energy. The min reson for voltge instility is the lk of suffiient retive power in the system, whih n e regulted y STTOM y injeting urrent into the system whih n e oservly seen on Figure 3.9 ). The performne of the power system is ffeted y mny ftors nd prtiulrly fults on trnsmission lines. The Simulink model nd simultions of the test system inluding STTOM nd fult models provide the mens to students for studying effetiveness of using FTS devies in generl nd STTOM ontroller s n exmple. hpter 4 inludes steps for modeling nd simultion of five different types of fult nd STTOM ontroller for nlysis of the Test System of hpter 3. 30
hpter 4 TEST SYSTEM To vlidte the ility of STTOM to stilize voltge in power system using Simulink s n edutionl tool, the most ommon types of fults desried in the hpter 1 re simulted in hpter 4 using different senrios nd models. Speifilly, we model nd simulte five types of fults: - lned three-phse fult; - three-phse fult to the ground; - line-to-ground fult; - line-to-line fult; - doule line-to-ground. Development of the edutionl methodology onsists of two steps: speifi type of fult is modeled nd integrted in the model of the test system without STTOM model while reording the results of simultion; nd inlusion of the model of STTOM ontroller in the test system while simulting different types of fults. The developed edutionl tool my then e used for simulting wht if senrios y pplying different fult types t different lotions in the test system with further modeling nd inlusion of other FTS devies thn STTOM. The simultions were performed for 2 seonds onsisting of 120 yles to etter oserve three time periods tht re present in the simultions: time efore the fult, time during the fult nd time fter the fult. Time period fter the fult n e divided into two su-periods: time immeditely fter the fult nd the time during whih the system goes into stedy stte. Results from oth experiments re summrized in Tle 4.1. 4.1 lned three-phse fult One-line digrm of the lned three-phse fult is presented on the Figure 4.1. 31
Figure 4.1: One-line digrm of the lned three-phse fult Figure 4.2 represents the model of the power system without STTOM under lned three-phse fult in Simulink. Wheres Figure 4.3 represents the model of the power system with STTOM under lned three-phse fult in Simulink. The prmeters of the three-phse reker re shown in ppendix. 32
ontinuous powergui 1 1 1 Idel Voltge Soure Trnsmission Line 1 (300 km) Three-Phse reker Trnsmission Line 1 (300 km)1 U3 no sttom Three-Phse V-I Mesurement1 V I 330 MVr Lod + - v Voltge Mesurement U1 I1 U2 Three-phse Trnsformer 735/16kV Three-Phse V-I Mesurement V I I2 250 MVr Lod Fig 4.2: Model without STTOM under lned three-phse fult 33
ontinuous powergui Idel Voltge Soure 1 1 1,, Susystem4 Trnsmission Line 1 (300 km) Trnsmissio Line 1 (300 km)1 U1 U2 with ST Three-Phse reker Three-Phse V-I Mesurement1 V I 330 MVr Lod I1 Three-phse Trnsformer 735/16kV Three-Phse V-I Mesurement V I I2 + - v Voltge Mesurement U3 Itir Out1 250MVr Lod Ulin lf STTOM 31 onstnt Fig 4.3: Model with STTOM under lned three-phse fult The voltge grph of the power system without STTOM under three-phse fult is shown on Figure 4.4. 34
Fig 4.4: Voltge plot of the power system without STTOM under three-phse fult on Figure 4.5. The voltge grph of the power system with STTOM under three-phse fult is shown 35
Figure 4.5: Voltge plot of the power system with STTOM under three-phse fult ompring the Figures 4.4 nd 4.5, we n onlude tht pek voltges of the system with STTOM re smller thn the system without one. The more detiled nlysis of the results will e presented in hpter 5. 36
4.2 Three-phse-to-ground fult One-line digrm of the three-phse to ground fult is presented on the Figure 4.6. Figure 4.6: One-line digrm of the three-phse to ground fult Figure 4.7 represents the model of the power system without STTOM under threephse to ground fult in Simulink. Wheres Figure 4.8 represents the model of the power system with STTOM under three-phse to ground fult in Simulink. The prmeters of the three-phse reker re shown in ppendix. 37
ontinuous powergui 1 1 1 Idel Voltge Soure Trnsmission Line 1 (300 km) Three-phse to ground reker Trnsmission Line 1 (300 km)1 Three-Phse V-I Mesurement1 V I 330 MVr Lod U1 U2 I1 Three-phse Trnsformer 735/16kV Three-Phse V-I Mesurement V I I2 + - v Voltge Mesurement U3 no sttom 250 MVr Lod Figure 4.7: Model without STTOM under three-phse to ground fult 38
ontinuous powergui 1 1 1 Idel Voltge Soure,, Susystem4 Trnsmission Line 1 (300 km) Three-phse to ground reker Trnsmission Line 1 (300 km)1 Three-Phse V-I Mesurement1 V I 330 MVr Lod U1 U2 I1 Three-phse Trnsformer 735/16 kv Three-Phse V-I Mesurement V I I2 + v - Voltge Mesurement U3 Itir Out1 Ulin lf STTOM 250 MVr Lod 31 onstnt Figure 4.8: Model with STTOM under three-phse to ground fult The voltge grph of the power system without STTOM under three-phse to ground fult is shown on Figure 4.9. 39
Figure 4.9: Voltge plot of the power system without STTOM under three-phse to ground fult The voltge grph of the power system with STTOM under three-phse to ground fult is shown on Figure 4.10. 40
Figure 4.10: Voltge plot of the power system with STTOM under three-phse to ground fult 41
nlyzing Figure 4.9 nd 4.10 nd the numeril vlues from the Tle 5.1 in hpter 5, we n mke the onlusion tht instlltion of the STTOM in the system with three-phse to ground fult ws the most effetive. More detiled results re presented in hpter 5. 4.3 Line-to-ground fult One-line digrm of the line-to-ground fult is presented on the figure 4.11. Figure 4.11: One-line digrm of the power system with line-to-ground fult The model of the power system without STTOM under line-to-ground fult in Simulink is presented in the Figure 4.12. Wheres Figure 4.13 represents the model of the power system with STTOM under line-to-ground fult in Simulink. The prmeters of the line-to-ground reker re shown in ppendix. 42
ontinuous powergui 1 1 1 Idel Voltge Soure Trnsmission Line 1 (300 km) Line-to-ground reker Trnsmission Line 1 (300 km)1 330 MVr Lod Three-Phse V-I Mesurement1 U1 U2 no sttom V I I1 Three-phse Trnsformer 735/16kV Three-Phse V-I Mesurement V I I2 + v - Voltge Mesurement U3 no sttom 250 MVr Lod Figure 4.12: Model of the power system without STTOM under line-to-ground fult 43
ontinuous powergui Idel Voltge Soure 1 1 1,, Susystem4 Trnsmission Line 1 (300 km) Line-to-ground reker Trnsmission Line 1 (300 km)1 Three-Phse V-I Mesurement1 V I 330 MVr Lod U1 with ST U2 with ST I1 Three-phse Trnsformer 735/16kV Three-Phse V-I Mesurement V I I2 + v - Voltge Mesurement U3 Itir Ulin Out1 lf STTOM 250 MVr Lod 31 onstnt Figure 4.13: Model with STTOM under line-to-ground fult The voltge grph of the power system without STTOM under line-to-ground fult is shown on Figure 4.14. 44
Figure 4.14: Voltge plot of the power system without STTOM under line-to-ground fult The voltge grph of the power system with STTOM under line-to-ground fult is shown on Figure 4.15. 45
Figure 4.15: Voltge plot of the power system with STTOM under line-to-ground fult Numeril vlues of the voltge peks from the Tle 5.1, whih onludes the results from Figures 4.14 nd 4.15, indite tht instlltion of the STTOM into the system with lineto-ground fult ws effetive s the voltge peks re smller when STTOM is in the system. 46
4.4 Line-to-line fult One-line digrm of the line-to-line fult is represented on the figure 4.16. Figure 4.16: One-line digrm of the us system with phse-to-phse fult (-to-) Line-to-line fult n our etween ny two phses. However, it is suffiient to nlyze only one se etween two phses. In this work -to- fult ws nlyzed. Figure 4.17 represents the model of the power system without STTOM under line-to-line fult in Simulink. Wheres Figure 4.18 represents the model of the power system with STTOM under line-to-line fult in Simulink. The prmeters of the line-to-line reker re shown in ppendix. 47
ontinuous powergui 1 1 1 Idel Voltge Soure Trnsmission Line 1 (300 km) Line-to-line reker Trnsmission Line 1 (300 km)1 U3 Three-Phse V-I Mesurement1 V I 330 MVr Lod + v - Voltge Mesurement U1 U2 I1 Three-phse Trnsformer 735/16 kv Three-Phse V-I Mesurement V I I2 250 MVr Lod Figure 4.17: Model without STTOM under line-to-line fult 48
ontinuous powergui 1 1 1 Idel Voltge Soure,, Susystem4 Trnsmission Line 1 (300 km) Trnsmission Line 1 (300 km)1 Line-to-line reker U3 Three-Phse V-I Mesurement1 V I 330 MVr Lod + - v Voltge Mesurement U1 U2 with ST I1 Three-phse Trnsformer 735/16 kv Three-Phse V-I Mesurement V I I2 Itir Ulin Out1 lf STTOM 250 MVr Lod 31 onstnt Figure 4.18: Model with STTOM under line-to-line fult The voltge grph of the power system without STTOM under line-to-line fult is shown on Figure 4.19. 49
Figure 4.19: Voltge plot of the power system without STTOM under line-to-line fult The voltge grph of the power system with STTOM under line-to-line fult is shown on Figure 4.20. 50
Figure 4.20: Voltge plot of the power system with STTOM under line-to-line fult Pling STTOM into the system with line-to-line fult ws the seond most effetive fter three-phse to ground fult s the results in Tle 5.1 indite. The voltge peks were muh smller in the system with STTOM thn in the one without it. 51
4.21. 4.5 Doule line-to-ground fult One-line digrm of the model with doule line-to-ground fult is presented on figure Figure 4.21: One-line digrm of the power system with doule line-to-ground fult Figure 4.22 represents the model of the power system without STTOM under doule line-to-ground fult in Simulink. Wheres Figure 4.23 represents the model of the power system with STTOM under doule line-to-ground fult in Simulink. The prmeters of the doule line-to-ground reker re presented in ppendix D. 52
ontinuous powergui 1 1 1 Idel Voltge Soure Trnsmission Line 1 (300 km) Doule Line-to-ground reker Trnsmission Line 1 (300 km)1 Three-Phse V-I Mesurement1 V I 330 MVr Lod U1 U2 I1 Three-phse Trnsformer 735/16 kv Three-Phse V-I Mesurement V I I2 + v - Voltge Mesurement U3 no sttom 250 MVr Figure 4.22: Model of the power system without STTOM under doule line-to-ground fult 53
ontinuous powergui Idel Voltge Soure 1 1 1,, Susystem4 Trnsmission Line 1 (300 km) Doule line-to-ground reker Trnsmission Line 1 (300 km)1 Three-Phse V-I Mesurement1 V I 330 MVr Lod U1 U2 with ST I1 Three-phse Trnsformer 735/16 kv Three-Phse V-I Mesurement V I I2 + - v Voltge Mesurement U3 Itir Out1 Ulin lf STTOM 250 MVr Lod 31 onstnt Figure 4.23: Model of the power system with STTOM under doule line-to-ground fult The voltge grph of the power system without STTOM under doule line-to-ground fult is shown on Figure 4.24. 54
Figure 4.24: Voltge plot of the power system without STTOM under doule line-toground fult The voltge grph of the power system with STTOM under doule line-to-ground fult is shown on Figure 4.25. 55
Figure 4.25: Voltge plot of the power system with STTOM under doule line-toground fult The result presented in Figure 4.25 ompletes the modeling nd simultion of five tegories of fults pplied to the test system with nd without model of STTOM. We nlyze the results reorded in hpter 4 in hpter 5. 56
hpter 5 RESULTS ND NLYSIS Using the models of STTOM, the test system onneting the lod us with STTOM injetion, nd the rest of the system nd the models of five tegories of fults in Simulink; the students my simulte different types of fult for studying the impt of STTOM on stedy stte nd dynmi performne of the test system. ll doumented studies of hpter 4 show tht when model of STTOM is inluded in the loop, its voltge nd urrent injetion will ffet oth the stedy nd trnsient response of voltge nd urrent, nd hene their vlues will e different from those on system without STTOM model. In wht follows, we present rief nlysis of the responses ompring the impt of STTOM model using Simulink for edutionl purposes. To ompre the effet of inlusion of STTOM in modeling the test system, we will use the index of Eqution 5.1 for Pek Voltge improvement. I 1 = [1- (Pek Voltge without STTOM )/(Pek Voltge with STTOM)] (5.1) The purpose of hpter 5 is to simulte the models developed in hpter 4 nd to ompre the lod us voltge profile with nd without inlusion of STTOM for interested students. To simulte lrger test system, the steps ppering in hpter 4 nd the simultion outomes of hpter 5 my e used y students s uilding loks of modeling nd simulting lrger systems. The edutionl tool presented in the thesis my e followed y students for modeling other FTS devies thn STTOM. Furthermore, for nlysis purpose nd for determining the usefulness of FTS devies in power system, students my use other metris thn the index of Eqution 5.1. We present other smple indies y Eqution 5.2 nd Eqution 5.3. I 2 = [1 (Osilltion without STTOM)/(Osilltions with STTOM)] (5.2) In Eqution 5.2, we ount the numer of osilltions efore rehing stedy stte voltge vlue with nd without inlusion of STTOM model in the test system. Use of STTOM my result in stle voltge profile with lesser numer of osilltions ppoint tht my e 57
investigted y students using the edutionl modeling tool development of using Simulink in hpter 4. s third index, we my use the settling time to stedy stte vlue of voltge with nd without inlusion of STTOM in the test system. Eqution 5.3 provides the settling time index. I 3 = [1-(Settling time without STTOM)/(Settling time with STTOM)] (5.3) In Eqution 3, the settling time is mesured etween the strt of the fult time nd up to the time of rehing stedy stte fter the fult is removed nd the system hs rehed its stedy stte opertion. While the proposed mesures in Eqution 5.2 nd Eqution 5.3 re not intended for use in this thesis, they my e used y students for nlyzing power systems tht inlude FTS devies nd the developments of the thesis in future. 5.1 lned three-phse fult Let us model lned three phse fult with nd without model of STTOM in the Simulink test system. Students my use modeling of the omponents of the system inluding fult model of hpter 4 to study the impt of inlusion of STTOM ontroller in lod us voltge nd urrent performne efore, during, nd fter the speifi simulted fult is lered. Figure 5.1 nd Figure 5.2 depit the performne of the test system t the lod us mesured y oserving the voltge profile of the us in the three time periods. 58
Figure 5.1 ): Voltge peks fter the lned three-phse fult lers in the system without STTOM 59
Figure 5.1 ): Voltge peks fter the lned three-phse fult lers in the system with STTOM The three olors in Figure 5.1 nd Figure 5.2 represent the three voltge phses on the vertil xis versus time on the horizontl xis. The peks of the voltge fter the fult lers re lmost the sme in the system with or without STTOM. Using the index of Eqution 5.1, students my ompre the impt of STTOM in three periods of time. It seems tht STTOM hs miniml or no impt on Pek Voltge during or fter the lned three-phse 60
fult is lered. The numeril vlue of pek voltge is inluded in the summry Tle 5.1. Tle 5.1 my e expnded to inlude indies proposed y Eqution 5.1, 5.2, nd 5.3. 5.2 Three-phse to ground fult For the power system under three-phse to ground fult STTOM ppered to e the most effetive. The pek voltge of the system with STTOM ws lower thn the one without STTOM. The stedy-stte vlue of the voltge ws rehed fster in the system with STTOM thn in the one without it. The omprison of the voltge peks is presented y Figure 5.2. The numeril vlues re presented in the Tle 5.1. Figure 5.2 ): Voltge peks fter the three-phse to ground fult lers in the system without STTOM 61
Figure 5.2 ): Voltge peks fter the three-phse to ground fult lers in the system with STTOM 5.3 Line-to-ground fult For the power system under line-to-ground fult STTOM ppered to e effetive. The pek voltge of the system with STTOM ws lower thn the one without STTOM. The stedy-stte vlue of the voltge ws rehed fster in the system with STTOM thn in 62
the one without it. The omprison of the voltge peks is presented on figure 5.3. The numeril vlues re presented in the Tle 5.1. Figure 5.3 ): Voltge peks fter the line-to-ground fult lers in the system without STTOM 63
Figure 5.3 ): Voltge peks fter the line-to-ground fult lers in the system with STTOM 5.4 Line-to-line fult For the power system under line-to-line fult STTOM ppered to e effetive. The pek voltge of the system with STTOM ws lower thn the one without STTOM. The stedy-stte vlue of the voltge ws rehed fster in the system with STTOM thn in the 64
one without it. The omprison of the voltge peks is presented on figure 5.4. The numeril vlues re presented in the Tle 5.1. Figure 5.4 ): Voltge peks fter the line-to-line fult lers in the system without STTOM 65
Figure 5.4 ): Voltge peks fter the line-to-line fult lers in the system with STTOM 5.5 Doule line-to-ground fult For the power system under doule line-to-ground fult STTOM ppered to e effetive. The pek voltge of the system with STTOM ws lower thn the one without STTOM. The stedy-stte vlue of the voltge ws rehed fster in the system with 66
STTOM thn in the one without it. The omprison of the voltge peks is presented on figure 5.5. The numeril vlues re presented in the Tle 5.1. Figure 5.5 ): Voltge peks fter the doule line-to-ground fult lers in the system without STTOM 67
Figure 5.5 ): Voltge peks fter the doule line-to-ground fult lers in the system with STTOM ll the numeril vlues hve een omined into the tle for etter omprison nd ese of understnding of the STTOM dvntges. 68
Tle 5.1: omprison of the voltge peks for the system without nd with STTOM Type of Fult Pek voltge without STTOM Pek voltge with STTOM lned three-phse 2.41e4 2.43e4 Three-phse to ground 2.72e4 2.52e4 Line-to-ground 2.68e4 2.58e4 Line-to-line 2.4e4 2.22e4 Doule line-to-ground 2.21e4 2.11e4 The modeling development using Simulink, modeling of different types of fults, modeling of STTOM, nd development of the simple test system serve s edutionl uilding loks for modeling nd simultion of lrger systems y students. Use of proposed indies of Eqution 5.1-5.3 nd summry tles similr to Tle 5.1 re intended to help students in lerning the impt of FTS devies in the system while the system experienes different types of fults. We will mke further onluding remrks in hpter 6. 69
hpter 6 ONLUSIONS ND FUTURE WORK STTOM is one of the most widely used FTS devies for effiient power system opertion. It is sed on voltge soure onverter nd n injet or sink n lmost sinusoidl urrent with vrile mgnitude to n eletriity network. If onneted to soure of power it n lso provide tive power. Usully STTOM is instlled to support eletriity networks tht hve poor power ftor nd often poor voltge regultion. There re however, other uses, the most ommon use is for voltge stility. It is widely used t the mid-point of trnsmission line or hevy lod re to mintin the onneting point voltge y supplying or deresing retive power into the power system. euse of the presene of STTOM devies in fult loop, the voltge nd urrent signls will e ffeted in oth stedy nd trnsient stte. This thesis inludes n edutionl methodology for modeling, simulting, nd then nlyzing ehvior of STTOM when exposed to different types of fults. power system is first represented y nd equivlent system onneted to lod y two trnsformers nd one trnsmission line. The system is further redued to model where the rest of the system is onneted to lod us y trnsmission line where STTOM is onneted to the high end of the step-down trnsformer with lod. The proposed test system is therefore equipped with the STTOM model with pproprite sensing devies mesuring three phse voltge nd urrent t the high nd the low end of the step-down trnsformer. The thesis inludes lssifition nd detil of fult types nd methodology for modeling fults using Simulink. Using MTL, simultion studies of the Test-System tht inludes models for fults nd STTOM were performed nd mesured y the voltge nd urrent sensors in three time periods; efore, during, nd post fult periods. To ensure pturing the trnsient nd stedy stte ehviors of the system inluding STTOM nd different fult types, the voltge nd urrent profiles t different lotions in the system where oserved nd reorded for 2 seonds more thn neessry time for the dynmis to settle t their stedy stte vlues. The oserved dt is used in MTL to nlyze the Test-System tht inludes STTOM nd fult types. 70
fter providing methodology for modeling fults nd STTOM using Simulink, we propose three indies in hpter 5 tht my provide edutionl insight to students for studying usefulness of STTOM in fulted power systems. Equtions 5.1-5.3 nd similr indies to pper in future works t PERL (Power & Energy Reserh Lortory) nd other FTS devies thn STTOM will e pursued further. Studying Voltge Pek my e performed using Eqution 5.1 while frequeny osilltion nd settling time my e studied y use of Eqution 5.2 nd 5.3. This work desries the model of STTOM in Simulink. MTL Simulink model ws used to simulte nd nlyze types of fults. In very preliminry nlysis nd edutionl purposes, the simultion results show the impt of STTOM on the system. In prtiulr STTOM devie dereses voltge peks nd dips during nd fter fult ondition tht improves rehing stle stte of the system with smller overshoots. This thesis my e extended to inlude lrger numer of uses y inluding smller in size equivlent of the rest of the system, inlusion of fults t different lotions thn t the us where the STTOM is onneted to, inlusion of models of other FTS devies thn STTOM, nd inlusion of genertor nd lod dynmis in the lrger test system. This thesis provides the edutionl uilding loks for students to study ehvior of FTS devies nd not s tool for nlysis of fulted power systems tht inlude FTS devies. The thesi therefore my e used s uilding loks for modeling nd simultion of lrger nd more relisti systems with the id of Simulink nd MTL. The proposed future works nd extensions will e performed y the student reserhers in the University of New Orlens Power nd Energy reserh Lortory. 71
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PPENDIX Three-phse reker lok tht is used in the model with lned three-phse fult s well s in the model with three-phse to ground fult hs next prmeters: Figure : Prmeters of the three-phse reker lok in Simulink used for three-phse fult 74
PPENDIX Three-phse reker lok tht is used in the model with line-to-ground fult (swithing only one phse phse to ground) hs next prmeters: Figure : Prmeters of the three-phse reker lok in Simulink used for line-to-ground fult 75
PPENDIX prmeters: The idel reker lok tht is used in the model with line-to-line fult hs next Figure : Prmeters of the idel reker lok in Simulink used for line-to-line fult 76