Implementation Of IEC Standard Models For Power System .
Downloaded from orbit.dtu.dk on: May 23, 2021Implementation of IEC Standard Models for Power System Stability StudiesMargaris, Ioannis; Hansen, Anca Daniela; Bech, John ; Andresen, Björn ; Sørensen, Poul EjnarPublished in:Proceedings of 11th International Workshop on Large-Scale Integration of Wind Power into Power SystemsPublication date:2012Link back to DTU OrbitCitation (APA):Margaris, I., Hansen, A. D., Bech, J., Andresen, B., & Sørensen, P. E. (2012). Implementation of IEC StandardModels for Power System Stability Studies. In Proceedings of 11th International Workshop on Large-ScaleIntegration of Wind Power into Power SystemsGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyrightowners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portalIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.
Implementation of IEC Standard Models for PowerSystem Stability StudiesIoannis D. Margaris1, Anca D. Hansen1, John Bech2, Björn Andresen2, Poul Sørensen11Technical University of DenmarkDepartment of Wind EnergyRoskilde, s Wind Power A/SE W EN OEN DES ESG 2Denmarkjohn.bech@siemens.com, bjoern.andresen@siemens.comAbstract— This paper presents the implementation of thegeneric wind turbine generator (WTG) electrical simulationmodels proposed in the IEC 61400-27 standard which iscurrently in preparation. A general overview of the differentWTG types is given while the main focus is on Type 4B WTGstandard models, namely a model for a variable speed windturbine with full scale power converter WTG including a 2mass mechanical model. The generic models for fixed andvariable speed WTGs models are suitable for fundamentalfrequency positive sequence response simulations during shortevents in the power system such as voltage dips. The generalconfiguration of the models is presented and discussed; modelimplementation and results are provided in order to illustratethe range of applicability of the generic models underdiscussion.power system stability studies and the applicability of thesemodels in various cases have to be carefully assessed inorder to ensure reliable evaluation of the critical operatingscenarios of the power.Keywords- standard wind turbine models; power systemstability studies, Type 4 wind turbineThe Western Electricity Coordinating Council (WECC) Renewable energy Modeling Task Force (REMTF) has alsobeen working towards the development of generic models inpower system simulations for wind turbine generators.These models have been extensively described in [10].According to the definition given in [13] the term genericrefers to a model that is standard, public and not specific toany vendor. Therefore, for different parameters given themodels should be able to emulate the response of a widerange of equipment.I.INTRODUCTIONWind power generation represents significant amount ofpower system production capability in many largeinterconnected power systems and novel ancillary servicesare increasingly provided by wind turbine generators(WTGs) posing serious challenges in modeling andvalidation procedures of the models used in relevant powersystem studies. Development of generic models for modernwind power generation is becoming a necessity forTransmission System Operators (TSOs) and DistributionSystem Operators (DSOs) in order to perform reliabledynamic analysis of the power system. Dynamic windpower generation models are often available in commercialsimulation software platforms, e.g. Siemens PSS E,DigSILENT PowerFactory, Eurostag , GE PSLF etc. aswell as in user-defined applications in own-built orcommercially available softwares including PSCAD ,MATLAB-Simulink etc. The level of detail and the amountof input data required for such models is under continuousrevision due to changes in the relevant power systemtechnologies. The response of the generic models applied inThe International Electrotechnical Commission (IEC)specifies in Part 1 of the IEC 61400-27 series wind turbinemodels as well as validation procedures which can beapplied in power system stability studies i.e. largedisturbance short term voltage stability, rotor angle stability,frequency stability, small-disturbance voltage stabilityphenomena. Typical events in the power system which areoften simulated include, among others, short-circuits, loss ofgeneration or loads, system separation in two synchronousareas etc.The paper is organized as follows: Section II providesthe WTG model structure and implementation in thededicated power system commercial simulation softwareDIgSilent PowerFactory (PF). The dynamic response of theType 4B WTG model during fault events in the grid isdiscussed in Section III and conclusions regarding the IECstandard modeling approach are briefed in section IV.II.MODEL DESCRIPTIONA. General Structure of WTG modelsBased on the IEEE definition, there are four windturbine types which are commercially available:
-Type 1: Fixed speed wind turbine withasynchronous generators directly connected to thegrid, i.e. without power converter. Type 1A refers towind turbines without fault-ride through (FRT)capability while Type 1B wind turbines areequipped with blade angle FRT control.-Type 2: Partially variable speed wind turbine withwound rotor asynchronous generator, blade anglecontrol and variable rotor resistance (VRR).-Type 3: Variable speed wind turbine with woundrotor asynchronous generator, direct connection ofthe stator to the grid and connection of the rotorthrough a back-to-back power converter. This typeis usually referred to as doubly-fed asynchronousgenerator (DFAG) wind turbine.-Type 4: Variable speed wind turbines withsynchronous or asynchronous generator connectedto the grid through a full scale power converter.There are two different models of Type 4 WTGs,Type 4A where the aerodynamic and mechanicalparts are neglected and Type 4B which includes a 2mass mechanical model assuming constantaerodynamic torque.The general structure of the generic models for all typesof WTGs is given in Figure 1.Figure 1. General model structure of IEC 61400-27-1 electricalsimulation models for WTGs, [1]B. Structure and implementation of Type 4B WTG modelThe basic configuration of a Type 4B wind turbine isshown in Figure 2. The generator can be either synchronousor induction while the mechanical parts of the wind turbinecan be included or not, depending on the presence of achopper in the converter system or not. Type 4 windturbines without chopper typically induce power oscillationsafter the occurrence of a fault which are due to torsionalexcited in the drive train of the wind turbine.Figure 3. Runtime wind turbine Type 4 model structure, [1]Figure 3 shows the following blocks which are includedin the WTG model:-Aerodynamic, which is modeled through a constantaerodynamic torque model assuming short timeperiod of events under study e.g. voltage dips.-Mechanical, which is modeled via a 2-massequivalent. The two masses correspond to the highspeed mass of the turbine and the low speed rotor ofthe generator. The 2-mass equivalent is consideredsufficient for the scope of studies described in theIEC Part 1 document for standard models, [].-Generator system, which is modeled via the staticgenerator component in DIgSilent PowerFactorysoftware including a current limiter. The staticgenerator is typically used in any kind of static (norotating) generator modeling. In Type 4 WTGs theresponse, seen from the grid side, is determined bythe full converter attached to the generator allowingfor use of the static generator component.-Control system, which includes the active powerand reactive power control loop, see also Fig. 5 and6.-Protection system, which models the gridunder/over voltage and under/over frequencyprotection functions. The protection limits as well asthe time of disconnection are determined based onmeasurements of the voltage and frequency at theWTG terminal bus.The mechanical system illustrated in Figure 4 isrepresented through a 2-mass model in order to account forthe torsional shaft oscillations excited in the mechanicalsystem in case of a torque imbalance e.g. during a fault inthe grid – see Figure 4. The parameters required for themechanical system are given in Table I.UsFigure 2. Electrical and mechanical components of Type 4B WTGs, [1]Figure 4. Two mass model for the mechanical system as implemented inDIgSILENT PowerFactory software
TABLE I.PARAMETER LIST FOR TWO-MASS MODELThe LVRT detection blocks outputs the signal LVRTand the signal FpostFRT in one of the 3 following stages:SymbolUnitDescriptionSourceHWTRp.u.Inertia constant of windturbine rotorManufacturer 0: during normal operation (UWTT Udip) –LVRT 0Hgenp.u.Inertia constant ofgeneratorManufacturer 1: during fault (UWTT Udip) – LVRT 1kshp.u.Shaft stiffnessManufacturer cshp.u.Shaft dampingManufacturer2: post fault – the system stays in this stagewith UWTT Udip for t Tpost. In this stage onlyFpostFRT 1The active power control loop is illustrated in Figure 5and mainly consists of a 1st order filter with the timeconstant of the power lag and a rate limiter for the activepower reference of the wind turbine. Note that the generatorspeed is used as an input to the active power control loop inorder to account for the electromechanical oscillationsespecially during faults. These are thus present in the activecurrent output command signal iPcmd of the loop. TheLVRT signal is calculated in the reactive power controlblock, see Figure 6, and is used to freeze the state of thefilter when low voltage is detected.maxUWTTLimitsK/(1 sT)ωgenminPrate maxPrefRateLimiterPrate min1/ωinitPmax1st OrderFilteriPcmdFigure 6. Reactive power control loop implemented in DIgSILENTPowerFactory softwareLVRTPminFigure 5. Active power control loop implemented in DIgSILENTPowerFactory softwareThe reactive power control loop includes several optionsfor controlling the reactive power and/or voltage as well asthe LVRT capability function. As illustrated in Figure 6 andTable II further below, one can select different controlconfigurations for the reactive power, i.e. open / closed loopoperation, voltage / without voltage control, power factor /reactive power control operation mode. The externalreference signal XWTT,ref can be either voltage difference orreactive power command from a wind power plantcontroller if available.The reactive current control signal iQcmd is defined asthe combination of three components, namely the voltagedependent current Iqv, the frozen current Iqfrz and theconstant post fault current Iqpost. The industry currentlyoffers three different options regarding the reactive currentoutput both during normal and LVRT conditions. Theresults presented in this paper have been calculated based onthe following selection:TABLE II.REACTIVE POWER CONTROL LOOP OPERATION MODESSelectionFactorMode of operation in the Q control loopMPFPower FactorQ controlMUVoltage ControlWithout VoltageControlMOLOpen LoopClosed LoopValue: 1Value: 0The current outputs of the active and reactive powercontrol loops are inputs to a current limiter, see Figure 7,which includes the following components: Limitation of the maximum continuous currentduring normal operation at the wind turbineterminals, imax Limitation of the maximum current during avoltage dip at the wind turbine terminals,imax,dip The maximum current ramp rate the windturbine terminals, dimax‐During the fault the current output is defined asiQcmd iqfrz iqv Prioritization of active or reactive powerduring LVRT operation‐After the fault, for time duration Tpost, thecurrent output is defined as iQcmd iqfrz iqpost Voltage dependency of the active and reactivecurrent limits provided by lookup tables iP,VDLand iQ,VDL respectively
Terminal Voltage [pu]1.210.80.60.40.200CASE STUDYThe simulations in this section have been carried outusing the test system described in [13], see also Fig. 10.The test system includes a Thevenin equivalent model forthe external grid, two step-up transformers, the collectioncable, a circuit breaker and the wind turbine generator,which is represented by the built-in static generator modelin PowerFactory. The parameters of the electricalcomponents of the test system can be found in [13].Figure 8. Single line diagram of the test systemA typical 3-phase short circuit of 400 ms duration hasbeen simulated at the MV bus, as illustrated in Figure 8.Section III.A includes result when priority of the reactivecurrent component is applied in the current limitation blockduring the LVRT period while Section III.B illustrates acomparison between active and reactive powerprioritization. This feature provides with the capability torepresent a Type 4 WTG response during voltage dips fordifferent grid codes’ requirements regarding theactive/reactive current injection during the low voltageinstant.A. Results for Q priority in the current limiterIn this first set of results reactive power current isprioritized during the voltage dip. Figures 9-11 illustrate thevoltage, the reactive current components as well as theLVRT and FpostFRT detection signals. As soon as the shortcircuit is cleared the FpostFRT signal remains equal to onefor Tpost 1 sec.Reactive currentcomponents [pu]III.1,5Time [sec]22,530iQcmdiqfrziqviQref-0.5-1LVRT 0FpostFRT 1LVRT 1LVRT 0LVRT 0-1.5-200,511,5Time [sec]22,53Figure 10. Reactive current components during and short after the shortcircuitLVRT, FpostFRT signalsIt is noted here that the current limiter defines to a greatextent the response of the wind turbine model especiallyduring voltage dips and thus the limits for the currents needto be defined in a reliable and realistic way.1LVRT 0Figure 9. Voltage at the WT terminals during and short after the shortcircuit1.21FpostFRTLVRT0.80.60.4LVRT 0FpostFRT 1LVRT 1LVRT 0LVRT 00.2000.511.5Time [sec]22.53Figure 11. The LVRT and FpostFRT signals during and short after theshort circuitThe active and reactive power response of the WTG isgiven in Fig. 12 and 13 respectively. Due to the reactivepower prioritization, during the voltage dip reactive currentis injected as defined in the LVRT strategy applied – seealso Section II above –, forcing active power to zero as longas the voltage remains low. At the fault clearance, thesudden increase in the voltage at the WTG terminal leads toa surge of reactive power while in the post fault period, aslong as the FpostFRT signal remains equal to one, reactivepower is injected to the grid offering voltage support to thegrid. Before and after the fault, the Power Factor control hasbeen chosen, thus the WTG keeps unity power factor.1.4Active Power [pu]Figure 7. Active and reactive current limiter and prioritizationimplemented in DIgSILENT PowerFactory software0,5LVRT 0FpostFRT 1LVRT 1LVRT 01.210.80.60.40.200246Time [sec]81012Figure 12. Active power response during and short after the short circuit
Terminal Voltage [pu]1.210.80.60.40.20-0.20246Time [sec]810Figure 13. Reactive power response during and short after the short circuitAerodynamic,Airgap Power [pu]Fig. 14 shows the results for the aerodynamic and airgappower, which are inputs to the mechanical system of themodel. The airgap power is calculated at the static generator,thus is equal to the electrical power injected to the grid as nolosses are taken into account. The torsional oscillations,which were simulated using the 2-mass model for themechanical model, are visible in the rotor speed as well as inthe electrical power produced by the WTG, see Fig. 12 and15. At the fault instant, the low voltage leads to a suddendecrease of the electrical torque resulting in thecorresponding increase of the rotor speed as long as thevoltage remains low. The oscillation frequency modes ofthese oscillations can be calculated based on the parametersof the mechanical system, [10].1.21Q priorityP priority0.80.60.40.200120,5122,53Fig. 17 and 18 illustrate the active and reactive powerresponse when active or reactive power is prioritized in thecurrent limiter. In the first case, active power is injected tothe grid despite the low voltage during the fault. At the faultclearance, reactive power is provided equally for active orreactive power prioritization while active power isoscillating following the torsional modes described insection IIIA.1.411.210.8Q priorityP priority0.60.40.2000.8240.60.41,5Time [sec]Figure 16. Voltage at the WT terminals during and short after the shortcircuit when active or reactive power is prioritizedActive Power [pu]Reactive Power [pu]1.26Time [sec]81012Figure 17. Active power response during and short after the short circuitwhen active or reactive power is prioritized0.20246Time [sec]81012Figure 14. Aerodynamic and airgap power during and short after the shortcircuitGenerator speedRotor speedRotor, Generator Speed [pu]1.151.1Reactive Power [pu]0Q priorityP priority1.210.80.60.40.20-0.20241.0516Time [sec]81012Figure 18. Reactive power response during and short after the short circuitwhen active or reactive power is prioritized0.950.90.850.80IV.246Time [sec]81012Figure 15. Generator and rotor speed during and short after the shortcircuitB. Comparison between P and Q priority in the currentlimiterThis section includes results for the same short circuitpresented above when active power prioritization is selectedin the current limiter block described in section II. As shownin Fig. 16, when active power is prioritized, the reactivepower injection is almost zero during the low voltage instantleading to lower voltage minimum compared to the case ofreactive power prioritization.CONCLUSIONSIn this paper the implementation and performance of thestandard IEC proposed Type 4B model for WTGs has beendescribed and assessed through simulations in the dedicatedsimulation software platform DIgSilent PowerFactory. Thegeneral structure of the standard models defined in Part 1 ofthe IEC 61400-27 series has been presented.The standard Type 4B model for WTGs includes aconstant aerodynamic torque model, the active and reactivepower control loop, a 2-mass mechanical model, the staticgenerator system including the current limiter withprioritization of active or reactive power and the protectionfunction for under/over voltage and frequency. The reactivepower loop comprises a LVRT control strategy which
defines the reactive current output of the controller duringand short after a voltage dip at the wind turbine terminals.Results from a short circuit simulated were shown forthe main electrical variables of the system and a comparisonhas been presented to illustrate the prioritization function ofactive or reactive power, which is part of the current limiterblock. The performance of the model during and short afterthe voltage dip is considered realistic as compared to fieldmeasurements for voltage dips provided by manufacturers inrelevant publications. Validation of this standard Type 4Bmodel implemented in DIgSILENT PowerFactorysimulation platform against field measurements is furtherneeded to ensure the applicability of this model in powersystem studies. Following the validation proceduredescribed in Part 1 of the IEC 61400-27 series, the modelwill soon be tested against real measurements provided bymanufacturers and the parameterization of the model will bethus improved to match a real WTG performance duringtransient events in the power system e.g. voltage dips.ACKNOWLEDGEMENTThe authors would like to
The International Electrotechnical Commission (IEC) specifies in Part 1 of the IEC 61400-27 series wind turbine models as well as validation procedures which can be applied in power system stability studies i.e. large-disturbance short term voltage stability, rotor angle stability, frequency
IEC 61215 IEC 61730 PV Modules Manufacturer IEC 62941 IEC 62093 IEC 62109 Solar TrackerIEC 62817 PV Modules PV inverters IEC 62548 or IEC/TS 62738 Applicable Standard IEC 62446-1 IEC 61724-1 IEC 61724-2 IEC 62548 or IEC/TS 62738 IEC 62548 or IEC/TS 62738 IEC 62548 or IEC/TS 62738 IEC 62548 or IEC/
IEC has formed IECRE for Renewable Energy System verification - Component quality (IEC 61215, IEC 61730, IEC 62891, IEC 62109, IEC 62093, IEC 61439, IEC 60947, IEC 60269, new?) - System: - Design (IEC TS 62548, IEC 60364-7-712, IEC 61634-9-1, IEC 62738) - Installation (IEC 62548, IEC 60364-7-712)
IEC 61869-9, IEC 62351 (all parts), IEC 62439-1:2010, IEC 62439-3:2010, IEC 81346 (all parts), IEC TS 62351- 1, IEC TS 62351- 2, IEC TS 62351- 4, IEC TS 62351- 5, Cigre JWG 34./35.11, IEC 60044 (all parts), IEC 60050 (all parts), IEC 60270:2000, IEC 60654-4:1987, IEC 60694:1
The new IEC 61439 series is expected to have a similar structure to IEC 60439 with several new additions*: IEC 60439 IEC 61439 Series IEC 61439-1 General rules IEC 61439-2 Power switchgear and controlgear assemblies IEC 61439-6 Busbar trunking systems IEC 61439-3 Distribution boards IEC 61439-4 Assemblies for construction sites IEC 61439-5
The new IEC 61439 series is expected to have a similar structure to IEC 60439 with several new additions*: IEC 60439 IEC 61439 Series IEC 61439-1 General rules IEC 61439-2 Power switchgear and controlgear assemblies IEC 61439-6 Busbar trunking systems IEC 61439-3 Distribution boards IEC 61439-4 Assem
IEC 61968-4 IEC 61968- 6 IEC 61968-7 IEC 61968-8 IEC 61968-9 Applicable parts of IEC 61968 Series Network Operation (NO) IEC 61968-3 Operational Planning & Optimization (OP) IEC 61968-5 Bulk Energy Management (EMS) IEC 61970 & Applicable parts of IEC 61968 Series External Systems: Customer Account Management (ACT) Financial (FIN) Business .
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IEC 60034-7 IEC 60034-8 IEC 60034-9 IEC 60034-11 IEC 60034-12 IEC 60034-14 IEC 60034-30 IEC 60085 IEC 60038 IEC 60072 CEMER motors comply with the relevant European and International norms and regulations, in particular wi
