《电力系统暂态稳定与电磁暂态 Transient Stability and.pdf》由会员分享，可在线阅读，更多相关《电力系统暂态稳定与电磁暂态 Transient Stability and.pdf（11页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、IEEE TRANSACTIONS ON POWER DELIVERY,VOL.24,NO.4,OCTOBER 20092385Interfacing Techniques for Transient Stabilityand Electromagnetic Transient ProgramsIEEE Task Force on Interfacing Techniques for Simulation ToolsV.Jalili-Marandi,V.Dinavahi,K.Strunz,J.A.Martinez,and A.RamirezAbstractTransientstability(
2、TS)andelectromagnetictransient(EMT)programsarewidelyusedsimulationtoolsinpowersystems,with distinct applications but competing requirements.TS pro-grams are fast which makes them suitable for handling large-scalenetworks,however,the modeling is not sufficiently detailed.Onthe other hand,EMT simulato
3、rs are highly detailed,but limited inspeed;consequently,they are used to simulate only small portionsof the network.Integrating these two types of simulators generatesa hybrid simulator which inherits the merits of both programs.Ahybrid simulator can fulfill the modeling requirements of a largenetwo
4、rk by providing a fast as well as a detailed simulation.Es-tablishing a connection between two different programs brings upseveralimportantissueswhichhavebeenaddressed,classified,andexplained in this paper.An alternative integrated modeling of TSand EMT is also discussed using the concept of frequen
5、cy shifting.Index TermsElectromagnetic transient analysis,hybrid simu-lation,interfacing,power system transient stability.I.INTRODUCTIONTRANSIENT STABILITY(TS)and ElectromagneticTransient(EMT)studies are two important analyses inpower systems 1,2.Transient stability study is importantfor planning an
6、d design,operation and control,and post-dis-turbances analysis in power systems 3.Transient stabilitytype programs solve several thousands of differential-alge-braic equations for multi-machine power systems assumingsingle-phase fundamental frequency behavior.To handle suchlarge numbers of equations
7、 a time-step in the range of millisec-onds is chosen for the simulation.Applications such as insulation coordination,design of pro-tection schemes,and power electronic converter design requirethe computation of electromagnetic transients.EMT simula-tion must be done by considering all phases,over a
8、wide rangeof frequency,and with a time-step in the range of microsec-onds or even less.In the past,traditional EMT analysis wasbased on the Transient Network Analyzer(TNA),an analogManuscript received December 12,2007;revised March 27,2008.Currentversion published September 23,2009.This work was sup
9、ported by the Nat-ural Science and Engineering Research Council of Canada(NSERC).Paper no.TPWRD-00800-2007.Task Force members:U.Annakkage,V.Dinavahi(Task Force Chair),S.Fil-izadeh,A.M.Gole,R.Iravani,V.Jalili-Marandi,J.Jatskevich,A.J.Keri,P.Lehn,J.A.Martinez,B.A.Mork,A.Monti,L.Naredo,T.Noda,A.Ramirez
10、,M.Rioual,M.Steurer,and K.Strunz are with the Task Force on InterfacingTechniques for Simulation Tools,which is with the Working Group on Mod-eling and Analysis of System Transients Using Digital Programs,IEEE PowerEngineering Society Transmission and Distribution Committee.Color versions of one or
11、more of the figures in this paper are available onlineat http:/ieeexplore.ieee.org.Digital Object Identifier 10.1109/TPWRD.2008.2002889scaled-down representation of the study system.In the TNAlines were modeled as series PI-circuits made up of R,L,andC elements 2.The application of TNA has been rest
12、ricted dueto its high cost,large dimensions,and model simplification is-sues.The advent of digital computers offered an alternate ap-proach for EMT analysis that overcame some of the restrictionsof TNA.EMT-type programs allow low-cost,flexible,and ac-curate modeling of the EMT phenomenon;however,the
13、se sim-ulators are not without some limitations related to modeling ac-curacy and processing time 2,4,5.Several applications in large-scale power systems such assimulation of transient states of the network including powerelectronic apparatuses and control devices associated withFACTS and HVDC requi
14、re a simulator as fast as the TS andas detailed as the EMT simulator.Many attempts were madetowards that end,such as using parallel processing or simplifiedmodels in the form of equivalents 68,however,in mostcases they were found inadequate for dealing with the large sizeofrealisticpowersystems.Thei
15、deaofacombinedTSand EMTsimulator was first proposed and implemented by Heffernanet al.9,in 1981.Two separate and distinct simulators wereintegrated for transient analysis of a system which includes aHVDC link 10.Later several improvements were made indifferent steps of building the hybrid simulator.
16、The application of hybrid simulation is a relatively recenttopic.Our intent in this paper is to aggregate various terms,definitions,and methods which have been used in each step ofbuildingahybridsimulator.Thepaperisorganizedasfollows:inSection II,general terms and definitions which are related to th
17、eTSandEMTprogramswillbereviewed.Althoughtherearesev-eral documents concerning these topics,here we briefly presentthe latest definitions reported in IEEE Standards and Task Forcepublications.In Section III and Section IV,the properties andrestrictions of TS and EMT programs will be described.In Sec-
18、tion V the motivation for using a hybrid simulator is presented.Section VI presents an overview of all the requirements andprotocols used for hybrid simulation.In Section VII,an inte-grated EMT-TS frequency adaptive simulation method will bediscussed.The conclusion of this paper appears in Section V
19、III.II.GENERALTERMS ANDDEFINITIONSA.TransientIEEE Standard Dictionary defines a transient phenomena asfollows 11:Pertaining to or designating a phenomenon or a quantity thatvaries between two consecutive steady states during a time in-0885-8977/$26.00 2009 IEEE2386IEEE TRANSACTIONS ON POWER DELIVERY
20、,VOL.24,NO.4,OCTOBER 2009terval that is short compared to the time scale of interest.Atransient can be a unidirectional impulse of either polarity ora damped oscillatory wave with the first peak occurring in ei-ther polarity.Overvoltages due to lightning and capacitor energizationare examples of eve
21、nts that cause impulsive and oscillatorytransients,respectively.Some of the most common types oftransient phenomena in power systems include energizationof transmission lines,switching off of reactors and unloadedtransformers,linear resonance at fundamental or at a harmonicfrequency,series capacitor
22、 switching and sub-synchronousresonance,and load rejection 2.B.StabilityFrom a system point of view there exist several types of sta-bility definitions such as:Lyapunov stability,input-output sta-bility,stability of linear systems,and partial stability 1.Kim-bark has classically defined stability re
23、lated to power systemsin12,however,this definition was restricted to synchronous ma-chines,and their being“in step.”The IEEE/CIGRE Joint TaskForce on Stability Terms and Definitions 1 adopted the fol-lowing definition:Power system stability is the ability of an electric powersystem,for a given initi
24、al operating condition,to regain a stateof operating equilibrium after being subjected to a physicaldisturbance,with most system variables bounded so that prac-tically the entire system remains intact.Instability in power systems can be caused by either small orlarge disturbances.During a small dist
25、urbance the set of equa-tions which describe the perturbed power system can be lin-earized;however,during the large disturbance these equationscannotbelinearizedforthepurposeofanalysis13.Typicalex-amplesofsmalldisturbancesareasmallchangeinthescheduledgeneration of one machine,or a small load(say 1/1
26、00 of systemcapacity or less)disconnected or added to the network 14,15.Severeperturbationssuchasshort-circuitfaultsandlossofgenerationeventsarerepresentativeoflargedisturbances.Addi-tionally,phenomena which cause instability problems in powersystems have been sub-classified based on their duration
27、1.C.Transient StabilityPower system stability phenomena can be categorized intothree major classes:rotor angle stability,voltage stability,andfrequency stability.If an interconnected network has been sub-jected to a perturbation;the ability of this power system to keepits machines in synchronism,and
28、 to maintain voltages of allbuses as well as the frequency of the whole network around thesteady-state values is the basis for the above mentioned classifi-cation 3.Each form of stability phenomena may be caused bya small or large disturbance.Althoughintheliteraturethetermtransientstabilityhasbeenus
29、ed to refer to the large-disturbance rotor angle stability phe-nomenon 13,14,some authors have used this term as a gen-eral purpose stability study of the given network with a partic-ular disturbance sequence 16.The IEEE/CIGRE task force re-port has categorized both the small and large disturbance r
30、otorangle stability phenomena as short-term events.Furthermore,it recommends the term transient stability for large-disturbancerotor angle stability phenomenon,with a time frame of interestin the order of 3 s to 5 s following the disturbance.This timespan may increase up to 1020 s in the case of ver
31、y large net-works with dominant inter-area swings 1.D.Electromagnetic TransientAn electromagnetic transient can be defined as the responseof the power system elements to a perturbation caused by ex-ternal electromagnetic fields or to a change in the physical con-figuration of the network such as swi
32、tching and loading.Elec-tromagnetic transients in power systems result from a combina-tion of transient components in lumped-parameter elements andtraveling waves in distributed-parameter elements 17.Tran-sient over-voltage on a transmission line that is energized fromone end,while its other end is
33、still open,presents a typical caseof an electromagnetic transient.It consists in a very fast timevariation waveform superimposed on the fundamental(source)frequency waveform.According to transmission line theory,ifthe sending end is connected to a dc voltage source of 1 p.u.there exists a 2 p.u.over
34、-voltage at the open ended terminal.This doubling effectcan also be observed atthe motor terminalsof adjustable speed drives,in cases where the length of cablebetween the pulse-width modulated converter and the motor ismore than 20 m.Furthermore,the over-voltage can produce atransient phenomenon in
35、nearby transmission systems or elec-trical equipments without even being physically connected tothe energized line.Switching operations,faults,and direct orindirect lightning strikes are other sources for electromagnetictransients in inter-connected power networks 2.E.Parallel ProcessingThe method o
36、f Diakoptics,introduced in 1952 by Kron 18,is the earliest application of the network partitioning and par-allel processing in power systems.Several research areas inpowersystemssuch asload flow,transientstability,electromag-netictransients,securityassessment,andreliabilitystudieshavetaken advantage
37、 of parallel processing techniques to achievehighly efficient computations 1923.The IEEE Task Forcereport 20 has proposed the following definition of parallelprocessing:Parallel processing is a form of information processing inwhich two or more processors together with some form of inter-processor c
38、ommunications system,cooperate on the solution ofa problem.Two types of parallelization are available:parallel-in-spaceand parallel-in-time.A parallel-in-space approach is based ondecomposing the original system into smaller subsystems anddistributing their computations among several processors 24.A
39、s power systems are stiff systems(i.e.,a system in which timeconstants of the subsystems vary over a wide range 13),it ispractical to use multi-rate integration methods for different sub-systems to discretize differential-algebraic equations(DAEs)which describe the dynamic behavior of subsystems 25.
40、A parallel-in-time approach is based on using simultaneousmultiple time-step solution of nonlinear DAEs that describe thesystem 24.In this case,each processor is assigned to solveequations for only one iteration,and usually the number of pro-cessors should be equal or greater than the number of requ
41、iredJALILI-MARANDI et al.:INTERFACING TECHNIQUES FOR TRANSIENT STABILITY2387iterations.Experimental studies claim that partitioning a net-work into too many subsystems by using a large number ofprocessors which are parallel-in-space increases the inter-pro-cessorcommunicationtime,whileexcessiveexplo
42、itationofpar-allel-in-timeprocessorsincreasesthenumberofiterations.Nev-ertheless,apropercombinationofthesetwotypesofparalleliza-tion methods can be used to effectively accelerate the speed ofcomputation 24.III.PROPERTIES ANDRESTRICTIONS OFTRANSIENTSTABILITYSIMULATORSThecompletepowersystemmodelfortra
43、nsientstabilityanal-ysis can be mathematically described by a set of first-order dif-ferential equations and a set of algebraic equations.The dif-ferential equations model dynamics of the rotating machineswhilethealgebraicequationsrepresentthetransmissionsystem,loads,and the connecting network 26.Th
44、ese equations arenonlinear,and the typical solution approach is to use a dis-cretization method such as the Trapezoidal rule to convert thedifferential equations to a new set of nonlinear algebraic equa-tions,and then solving these two sets of nonlinear algebraicequations by a suitable iterative met
45、hod such as the Newton-Raphson.Section A in the Appendix provides the details on thegeneral solution of the transient stability problem.A complete description of the power network requires a verylarge number of equations.For instance,consider a realisticinter-connected power system which includes ov
46、er 3000 busesand about 400 power stations which are feeding 800 loads.As-suming that the transmission system and loads are modeled byalgebraic equations,and the generation stations are modeled bya set of 20 first-order differential equations each.The transientstabilityanalysisofthedescribednetworkne
47、edssolvingof8000differential equations and about 3500 algebraic equations 15,27.To make this solution as time-efficient as possible usuallya time-step in the range of milliseconds is chosen for the sim-ulation.In transient stability studies it is assumed that voltageand current waveforms more or les
48、s remain at power frequency(60 or 50 Hz).Thus,for modeling the electrical parts of thepower system steady-state voltage and current phasors can beused.Moreover,transient stability study is a positive-sequencesingle-phase type of analysis 2,28.Largeintegrationtime-stepofthetransientstabilityprogramsi
49、s the main restriction for the detailed representation of non-linear elements(such as power electronic apparatus)and dy-namicallyfastevents(suchaslineenergization).Forexample,toevaluatetransientresponsesofHVDClinksand FACTSdevicesatime-stepintheorderofafewmicrosecondsisneeded.Hence,in conventional t
50、ransient stability programs these devices canjust be represented as quasi-steady-state models,which are suit-able for normal working conditions or are developed for a spe-cific type of disturbance 28.IV.PROPERTIES ANDRESTRICTIONS OFELECTROMAGNETICTRANSIENTSIMULATORSThere are several cases in power s