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    ELEMENTS OFELEMENTS OF FACTS CONTROLLERS

    R ji K V PhDRajiv K. Varma, PhDAssociate Professor

    Hydro One Chair in Power Systems Engineering University of Western OntarioUniversity of Western Ontario

    London, ON, CANADArkvarma@uwo.ca

  • POWER SYSTEMS -Where are we heading?

    A historic change overtaking electrical power industrypower industry Large scale grid integration of renewable

    energy sourcesenergy sources Implementation of Smart Grids

    ULTIMATE AIM: to provide reliable, quality power at minimum cost

  • Overwhelming need forOverwhelming need for increased transmission capacity on lines

    control of power flow in specific corridors control of power flow in specific corridors assurance of system reliability in the event

    of faultsof faults

    P ibl h h Possible through: FLEXIBLE AC TRANSMISSION SYSTEMS (FACTS)

  • FACTS

    Flexibility of Electric Power Transmission Flexibility of Electric Power Transmission The ability to accommodate changes in the electric

    transmission system or operating conditions while y p gmaintaining sufficient steady state and transient margins

    Fl ibl AC T i i S (FACTS) Flexible AC Transmission Systems (FACTS) Alternating current transmission systems

    incorporating power-electronic based and other incorporating power electronic based and other static controllers to enhance controllability and increase power transfer capability

  • Comparison of different limits of power flow

  • ADVANTAGES OF FACTS DEVICES/CONTROLLERS

    Increase / control of power transmission capacity in a line capacity in a line prevent loop flows

    Improvement of system transient stability Improvement of system transient stability limitE h t f t d i Enhancement of system damping

    Mitigation of subsynchronous resonance

  • ADVANTAGES OF FACTS /DEVICES/CONTROLLERS (contd)

    Alleviation of voltage instability Limiting short circuit currents Limiting short circuit currents Improvement of HVDC converter terminal

    performanceperformance Load Compensation Grid Integration of Renewable Power

    Generation Systems

  • Compensatorsp

    Synchronous Condensers Synchronous Condensers FACTS

    THYRISTOR BASED FACTS THYRISTOR-BASED FACTS Static Var Compensator (SVC) - Shunt Thyristor Controlled Series Capacitor (TCSC) - SeriesThyristor Controlled Series Capacitor (TCSC) Series

    VOLTAGE SOURCE CONVERTER BASED FACTS Static Synchronous Compensator (STATCOM) - Shunt Static Synchronous Series Compensator (SSSC) - Series Unified Power Flow Controller (UPFC) Composite Unified Power Flow Controller (UPFC) - Composite

  • Concept of FACTSp

    V1 V20

    XLi21VVP

    ToincreasePowerTransferP12I V V

    sin2112LX

    P

    IncreaseV1,V2 DecreaseXL

    installparallelline provide midline shunt reactive compensation (Shunt FACTS) providemidlineshuntreactivecompensation(ShuntFACTS) insertseriescapacitor(SeriesFACTS) injectinthelineavoltageinphaseoppositiontotheinductivevoltagedrop(VSC

    FACTS)

    Controlangulardifferenceacrosstransmissionline

  • Thyristor Based FACTS

    CONTROLLERS

  • Static Var Compensator: A single-phase Static Var Compensator: A single-phase Thyristor Controlled Reactor (TCR)

  • Current and voltages for different firing angles in a TCR

  • Features of SVC OperationFeatures of SVC Operation

    SVCsaremeanttoprovidedynamicvoltagesupportnotp y g ppsteadystatevoltagesupport

    SVCsarefloatinginsteadystate(i.e.donotexchangereactiveith th t )powerwiththesystem)

    Fixed CapacitorTCR: High Steady state losses even when theFixedCapacitor TCR:HighSteadystatelossesevenwhentheSVCisfloating

    Capacitorsaremadeswitchable: MechanicallySwitchedCapacitors(MSCTCR) ThyristorSwitchedCapacitor(TSCTCR)

  • Basic elements of SVC

  • Concept of SVC Voltage Controlp g

    SVC Contribution depends on:

    -System strength Xs-SVC Rating

    SVC more effective in weak systems!

    SVC response slows down as systemdown as system becomes stronger.

  • SVC APPLICATIONSSVC APPLICATIONS

  • POWER TRANSFER IMPROVEMENT

    V1 V20

    LXVVP sin2112

    1 2

    XL

    L

    o

    XP

    andpuVVIf

    1

    901,

    max12

    21

    V1 V20

    XL/2 XL/2SVC

    Vm/2

    mVVP sin1 SVCo

    m

    L

    P

    andpuVVVIf

    XP

    2

    1801,

    2sin

    2

    21

    12

    LXP max12 Power Transfer Doubles

  • 18

    Variation in real and reactive power in SMIB systemVariation in real and reactive power in SMIB system

  • 19

    Real power of the SMIB system with varying compensationReal power of the SMIB system with varying compensation

  • POWER TRANSFER IMPROVEMENT

    V1 V20

    LXVVP sin2112

    1 2

    XL

    L

    o

    XP

    andpuVVIf

    1

    901,

    max12

    21

    V1 V20

    XL/2 XL/2SVC

    Vm/2

    mVVP sin112

    SVCo

    m

    L

    XP

    andpuVVVIf

    X

    2

    1801,

    22

    max12

    21

    12

    Power Transfer Doubles - with large SVCLX

    max12 Power Transfer Doubles - with large SVCPower Transfer Increases Substantially - with realistic SVC

  • TRANSIENT STABILITY ENHANCEMENT

    Power angle curve for improving transient t bilit istability margin

  • SYSTEM DAMPING AUGMENTATIONN U N N

    SVC

    G1P1, 1 Infinite bus

    Ifd(dtispositive,i.e.rotorisacceleratingduetobuiltupkineticenergy,theFACTSdeviceiscontrolledtoincreasegeneratorelectricalpoweroutput

    Ifd(dtisnegative,i.e.rotorisdeceleratingduetolossofkinetic energy the FACTS device is controlled to decreasekineticenergy,theFACTSdeviceiscontrolledtodecreasegeneratorelectricalpoweroutput

    SVCbusvoltagenotkeptconstantbutmodulatedinresponsetoauxiliarysignals

  • Choice of Auxiliary Signals For Damping Control

    L l Si l LocalSignals linecurrent real power flowrealpowerflow busfrequency busvoltage/angle

    RemoteSignals (Synthesized/Telecommunicated/PMU) rotorangle/speeddeviationofaremotegeneratorangle / frequency difference between remote voltages at the angle/frequencydifferencebetweenremotevoltagesatthetwoendsofthetransmissionline

    Signalsshouldbeeffectiveforpowerflowineitherdirection

  • Two Area System StudyTwoAreaSystemStudy

    G1 1 5 6 7 8 9 10 11 3110 km 110 km125 km 10 km

    7 9 11 3G3

    10 km 25 km110 km 110 km

    42

    L7 L 9SVC

    GG2G4

  • Simulation ResultsSimulationResults SystemResponsewithoutSVC

  • Simulation Results (Contd)SimulationResults(Cont d) SystemResponsecomparisonwithSVCdifferentauxiliarycontrolsignals

  • Mitigation ofMitigationofSub Synchronous Resonance (SSR)SubSynchronousResonance(SSR)

  • Subsynchronous Resonance (SSR)Subsynchronous Resonance (SSR)

    Simple radial system to study SSR:

    Fig. 1. Turbine-Generator feeding infinite bus through series compensated transmission network

  • Subsynchronous Resonance (SSR)Subsynchronous Resonance (SSR)

    S b h R (SSR) h i SubsynchronousResonance(SSR)phenomenonisusuallyassociatedwithsynchronousmachineconnectedtoseriescompensatedtransmissionnetwork.

    Definition of SSR by IEEE SSR Task Force: DefinitionofSSRbyIEEESSRTaskForce: Subsynchronousresonanceisanelectricpowersystemconditionwheretheelectricnetworkexchangesenergywith the turbine generator at one or more of the naturalwiththeturbinegenerator atoneormoreofthenaturalfrequenciesofthecombinedsystembelowthesynchronousfrequencyofthesystem.

  • Damping of torsional

    mode 3 with an SVC

  • PREVENTION OF VOLTAGE INSTABILITYN N N

    Voltageinstabilityiscausedduetotheinadequacyofg y q ypowersystemtosupplythereactivepowerdemandofcertainloadssuchasinductionmotors.

    Adropintheloadvoltageleadstoanincreaseddemandforreactivepowerinsuchcaseswhich,ifnotmetbythepower system, results in a further fall in bus voltage.powersystem,resultsinafurtherfallinbusvoltage.

    Thiseventuallyleadstoaprogressive,yetrapiddeclineofvoltage at that location which may have a cascadingvoltageatthatlocationwhichmayhaveacascadingeffectonneighbouringregionsresultinginsystemvoltagecollapse.

  • A case study system

  • S t t i t f i i itSystem transient response for opening one circuit

  • System transient response for opening one circuit with FC-TCR SVC

  • IMPROVEMENT OF HVDC LINK PERFORMANCE

    Voltage regulation Voltage regulation Support during recovery from large

    disturbancesdisturbances Suppression of temporary over voltages

  • The inverter ac bus voltage during a g gpermanent inverter block

  • SVC Application in Large Wind PowerSVC Application in Large Wind Power Integration:

    Dynamic Reactive Power SupportDynamic Reactive Power Support

  • System Descriptiony

    Study investigates several alternatives of integrating: Studyinvestigatesseveralalternativesofintegrating: 1000MWofpowergeneration includingconventionalinduction

    windgeneration.f k TotransmitpowerfromDakotastoTwinCities,Wisconsin,Iowa

    andIllinois.

    Onealternativecomprises500MWcoalgeneration atanew345KVstationnearHettinger.

    And5new100MWwindparks oneatHettingerandtheother4areatMarmarth,Bowman,BelfieldandNewEngland.

  • Issues (Contd.)ssues (Co td )

    Conventional induction generator exampleConventional induction generator example. 3-phase fault at the vicinity of wind farm.

  • Solution (Contd.)( )

    Conventional induction generation with SVCs

  • THYRISTOR CONTROLLED SERIES COMPENSATOR SERIES COMPENSATOR

    (TCSC)( )

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