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FINAL PROJECT REPORT

WECC WIND GENERATOR DEVELOPMENT

Prepared for CIEE By:

National Renewable Energy Laboratory

Project Manager: Eduard Muljadi

Authors: Edward Muljadi, Abraham Ellis

Date: March, 2010

A CIEE Report

Acknowledgments

The support of the U.S. Department of Energy (DOE), the Western Electric Coordinating

Council (WECC), and the California Energy Commissionʹs PIER Program are gratefully

acknowledged.

The author expresses his gratitude to the members WECC Wind Generator Modeling Group

(WGMG) and Model Validation Working Group (MVWG), General Electric, Siemens PTI who



have beeninstrumentalinprovidingtechnicalsupportandreviews,and, guidance during the

developmentofthisproject.



DISCLAIMER

This draft report was prepared as the result of work sponsored by the California Energy Commission. It does not necessarily represent the views

of the Energy Commission, its employees or the State of California. The Energy Commission, the State of California, its employees, contractors

and subcontractors make no warrant, express or implied, and assume no legal liability for the information in this report; nor does any party

represent that the uses of this information will not infringe upon privately owned rights. This report has not been approved or disapproved by the

California Energy Commission nor has the California Energy Commission passed upon the accuracy or adequacy of the information in this report.

Preface ..

TheCaliforniaEnergyCommission’sPublicInterestEnergyResearch(PIER)Programsupports

public interest energy research and developme nt that will help improve the quality of life in

California by bringing environmentally safe, affordable, and reliable energy services and

productstothemarketplace.

ThePIERProgramconductspublicinterestresearch,development,anddemonstration

(RD&D)

projectstobenefitCalifornia.

The PIER Program strives to conduct the most promising public interest energy research by

partnering with RD&D entities, including individuals, businesses, utilities, and public or

privateresearchinstitutions.

 PIERfundingeffortsarefocusedonthefollowingRD&Dprogram areas:

 BuildingsEnd‐UseEnergy

Efficiency

 EnergyInnovationsSmallGrants

 Energy‐RelatedEnvironmentalResearch

 EnergySystemsIntegration

 EnvironmentallyPreferredAdvancedGeneration

 Industrial/Agricultural/WaterEnd‐UseEnergyEfficiency

 RenewableEnergyTechnologies

 Transportation

ThedraftfinalreportfortheWesternElectricityCoordinatingCouncil(WECC)WindGenerator

Developmentproject (contractnumber500‐02

‐004,workauthorizationnumber MR‐065),is the

summaryofactivitiesreportedinseparate interimreports:

WINDPOWERPLANTEQUIVALENCING

WINDPOWERPLANTDATACOLLECTION

MODELVALIDATIONOFWINDTURBINEGENERATOR

This project is sponsored by the WECC‐WGMG, California Energy Commission (Energy

Commission),and the National Renewable Energy Laboratory

(NREL).Theinformation from

thisprojectcontributestoPIER’sEnergySystemsIntegrationProgram.

FormoreinformationaboutthePIERProgram,pleasevisittheEnergyCommission’swebsiteat

www.energy.ca.gov/research/

orcontacttheEnergyCommissionat916‐654‐4878.



iii

Table of Contents

Preface...............................................................................................................................................ii

AbstractandKeywords.....................................................................................................................vi

ExecutiveSummary...........................................................................................................................1

1.0 IntroductionandScope...........................................................................................................3

2.0 DescriptionofWindTurbineGeneratorTechnologies.......................................................5

Type1–Fixed‐speed,inductiongenerator...............................................................................5

Type2–Variableslip,inductiongeneratorwithvariablerotorresistance..........................6

Type3–Variablespeed,doubly‐fedasynchronousgeneratorswithrotor‐sideconverter6

Type4–Variablespeedgeneratorswithfullconverterinterface.........................................7

3.0 WindPowerPlantandPowerFlowEquivalencing............................................................8

4.0 WindPowerPlantData...........................................................................................................10

4.1Dataforsteady‐staterepresentation....................................................................................11

PowerFlowNetworkData................................................................................................11

4.2Datafordynamicanalysis.....................................................................................................12

TheprocessofcreatingadynamicfileforaWTG.........................................................12

4.3DataforWTGModelValidation..........................................................................................13

Infinitebusrepresentation.................................................................................................13

FieldMeasurementforDynamicDataforModelValidation......................................14

Theperphasevoltagewaveforms....................................................................................14

ProcessingDataforPSLFSimulation–ModelValidationExercise............................14

5.0 ModelValidationofWindTurbineGenerator....................................................................16

5.1Validationagainstthefieldmeasurements.........................................................................16

5.2Validationagainstthedetailed(manufacturerspecific)models.....................................17

6.0 SummaryandDissemination.................................................................................................19

7.0 FuturePlan................................................................................................................................20

References...........................................................................................................................................21

Glossary.............................................................................................................................................22

AppendixI‐ListofPublications.....................................................................................................I

AppendixII‐ListofShortCoursesandWorkshops....................................................................II

AppendixIII‐WindPowerPlantEquivalencing..........................................................................III

AppendixIV‐WindPowerPlantDataCollection.......................................................................IV

AppendixV‐ModelValidationofWindTurbineGenerator.....................................................V

AppendixVI‐WECCWindPowerPlantPowerFlowModelingGuide..................................VI

AppendixVII‐WECCWindPowerPlantDynamicModelingGuide......................................VII

 



List of Figures

Figure1‐Fourdifferenttypesofwindturbinegenerator...................................................................5

Figure2‐PhysicaldiagramofatypicalWPP........................................................................................8

Figure3‐SingleturbinerepresentationforaWPP...............................................................................9

Figure4–Steadystateanddynamicdatagroupings.........................................................................11

Figure5‐Single‐machineequivalentimpedanceofNMEC‐WPP...................................................12

Figure6‐Dynamicmodelinputpreparation......................................................................................13

Figure7‐Theper‐phase‐voltagesvan,vbn,andvcnasrecorded........................................................14

Figure8‐Blockdiagramsindicatingtheflowprocesstoconvertthemonitoredvoltageintothe

inputdataforGENCLSmodule....................................................................................................15

Figure9‐InputdatatoGENCLStoperformthedynamicsimulation...........................................15

Figure 10‐Comparison between the generic model and the measured data for a Type 2 and

Type3WTG......................................................................................................................................16

Figure11‐ComparisonbetweenthegenericmodelandthedetailedmodelforaType1WTG.18

Figure12‐ComparisonbetweenthegenericmodelandthedetailedmodelforaType4WTG.18

Abstract and Keywords

Windenergycontinuestobeoneofthefastest‐growingpowergenerationsectors.Thistrendis

expectedtocontinuegloballyasweattempttomeetagrowingelectricalenergydemandinan

environmentally responsiblemanner.Asthe number of wind powerplants (WPPs) continues

togrowandthelevelofpenetration

becomeshighinsomeareas,thereisanincreasedinterest

on the part of power system planners in methodologies and techniques that can be used to

adequatelyrepresent WPPs in interconnectedpower systemstudies.This project ispartof an

overall industry effort to develop, validate  and implement generic positive‐

sequence stability

models forwind power plants (WPP).Although the modelsare designed specifically to meet

Western Electricity Coordinating Council (WECC) modeling requirements, the results also

benefittheindustryasawhole.Thesegoalsrepresentchallenges,someofwhich aredescribed

below:

 There are currently four major different types of

 wind generators, and all of them are 

fundamentallydifferent fromconventionalgenerators.It isnecessary tohavedifferent

typesofwindturbinegenerator(WTG)dynamicmodelstocloselyrepresenteachofthe

fourtypes.

 Wind turbine generators are a relatively new kind of technology where significant

technicalinnovationis

stilloccurring.Thus,planningmodelswerenotreadilyavailable

untilrecently.Fromanengineeringpointofview,representingWPPsasnegativeloads

or conventional generators is unacceptable.With the recent development and 

implementation of WECC generic models of WTGs, wind power plants can now be

representedmoreproperly.

 WPPsare

topologicallycomplex.Typicalplantshavehundredsofturbinesspreadover 

averylargearea,interconnectedbymilesofradialfeedercir cuits,andfinallyconnected 

to the utility grid at the point of interconnection (POI).In grid planning studies, it is

impracticaltorepresentthiscomplexsystemexplic itly.AlthougheachWPP

hasunique

characteristics(e.g.terminalvoltage,windcondition,lineimpedance,etc),itisnecessary

to find a reasonable equivalent representation that reproduces the important plant

behaviorasseenfromthePOI.

 Validation of dynamic models is needed to verify that the models closely match the 

dynamicbehaviorofactualequipment.

FieldmeasurementcanbeusedtovalidateWPP

models.Sincesuitablefielddataisdifficulttoobtain,modelverificationbycomparison

to manufacturer‐specific, higher‐order (more detailed), and validated dynamic models 

canbeused.

 Modelshavelimitedvalueunlesstheyarewelldocumentedandmadeavailabletogrid

plannersinthesimulationplatformsoftheirchoice.Forthisreason,thisprojectaimedat

implementing the models in simulation platforms that are typically used for grid

planning (GE PSLF and Siemens‐PTI PSSE).In addition, dissemination of the project

vii

results is accomplished via publications at the appropriate conferences, websites,

workshops,seminars,and,shortcourses.

In this report, we summarize the project which covers dynamic model development of four

typesofwindturbinegenerators,datacollectionneededformodelvalidation,powerflowwind

powerplantequivalencing,modelvalidation,andmodelingguidelines

developedforWECC.

Theinterimreportsareincludedasappendicesofthisfinalreport.Thegenericdynamicmodel

of four types of wind turbine generator has been implemented on two major power system

simulationplatforms:Siemens‐PTIPSSEandGeneralElectricPSLF.Theterm“generic”isused

toreferto

thedynamicmodelthatdoesnotcontainproprietaryinformationprotectedbywind

turbine manufacturers.These dynamic models  of WTG are now part of the standard model

libraryinPSSEandPSLF.ThemodelingguidesarepubliclyavailableattheWECCwebsite

.

Keywords:Dynamicmodel,equivalencing,modelvalidation,windpowerplant,wind

turbine,windintegration,andsystemintegration.

http://www.wecc.biz/library/WECC%20Documents/Documents%20for%20Generators/Generato

r%20Testing%20Program/Wind%20Generator%20Power%20Flow%20Modeling%20Guide.pdf

- 1 -

Executive Summary

It is expected that large amounts of wind capacity will continue to be added to the power

system.The size of individual turbines has increased dramatically from a mere several

hundred kilowatts to multi megawatt turbines.The size of individual wind power plants

(WPPs)hasalsoincreased significantly.Inthepast,

atypicalWPPconsistedofseveralturbines.

Today, typical WPP nameplate capacity is 100MW to 200MW. Total capacity in a region or

clustercan reach 1 GW ormore.By some projections, asmuch as 20 GW ofadditional wind

generation capacity may be added in the Western Electricity Coordinating

Council (WECC) 

footprintwithin thenext10–15years.Theincreaseinlevelofpenetration ofrenewableenergy

generation in the WECC region, and California in particular, poses significant challenges

concerningtheabilityofthepowersystemtomaintainreliableoperation.

For many years, lack of open access to adequate

 models has resulted in much of the wind

capacity being modeled as conventional induction machines or negative loads in regional

planning studies.The increased use of this energy source necessitates a more accurate

representation of installed wind capacity.Misrepresentation of a WPP in a dynamic model

reducesconfidenceinthe

transmissionplanningprocessandcanleadtoerroneousconclusions.

Manufacturer‐specific, proprietary models  are made available for interconnection studies;

however, their use is also challenging in practice.The overall goal of the generic modeling

effortistoaddressthesechallenges.

TheWindGeneratorModelingGroup(WGMG)hascompletedthefirstphase

developmentand

implementationof generic windturbine models.Fourgenericmodels produced bythis effort

represent the types of turbines that currently  hold the largest market share in the North

American region. WECC is interested in ensuring that accurate and validated models  of

standardwind turbines are readily available for

regionalstudies.This meansthat the models

should be suitable for inclusion in the WECC standard dynamic model database.The

availability of data sets for testing the models is critical to meet WECC’s model validation

requirements. WECC is also interested in guidelines discussing the methods of representinga

WPP in power

 system studies. These goals are reflected in the functional guidelines of the

WECC WGMG.The WECC models will be generic in nature,that is,they donot require nor

revealproprietarydatafromtheturbinemanufacturers.

These improved, standard (i.e., generic, non‐proprietary) dynamic models would enable

planners, operators, and

engineers to plan and operate the system taking into account the

characteristics capabilities of modern wind turbines (e.g., dynamic, variable, reactive power

compensation, dynamic generation shedding capability, and soft‐synchronization with  the

grid).Withtheappropriatedynamicmodelsavailableforwindturbines,plannerscouldmore

accuratelystudytransmissioncongestionorother

majorgridoperatingconstraints,eitherfrom

areal‐timegridoperationsortransmissionplanningperspective.Thesemodelscouldbeused

by transmission planners in expanding the capacity of existing transmission facilities to

accommodatewindenergydevelopmentinamannerthatbenefitselectricityconsumers.

- 2 -

This has become increasingly important as the penetration amounts of wind energy systems

have increased.The WECC‐WGMG efforts also provides opportunities for researchers at

universitiesandnationallaboratoriestomoreeasilyaccesstowindturbinemodelsandconduct

research.

This report is the final report for the WECC Wind Generator

 Development Project, contract

number #500‐02‐004, work authorization number MR‐065, a  project sponsored by the WECC‐

WGMG,CaliforniaEnergyCommission(EnergyCommission),andNationalRenewableEnergy

Laboratory(NREL).Thisreportsu mmarizestheactivitiesperformedinthisprojectasreported

intheinterimreports:

 WindPowerPlantEquivalencing

 WindPowerPlantDataCollection

 ModelValidationofWindTurbineGenerator

TwoWECCguideswerepublishedbyWECC‐WGMG:

 WECCWindPowerPlantPowerFlowModelingGuide

 WECC Wind Power Plant Dynamic Modeling Guide (currently posted for comment

throughtheWECCModelingandValidationWorkGroup)

The

genericmodelsofwindturbinegenerators(Type1 –Type4)havebeendevelopedandare

now included in the standard model library of the PSSE and PSLF software platforms.The

generic models are also being implemented in two other software platforms: Operation

TechnologyETAP,andPowertechLabsDSATools.

Resultsfromthisprojecthavebeenwidely

disseminatedthroughpresentationsatworkshopsandshortcoursesconductedatmeetingsand

conferences sponsored by WECC, IEEE, Utility Wind Integration Group (UWIG), and

universities.Duringtheprogressofthisproject,technicalreports,andconferencepaperswere

alsopublishedatdifferentconferences.

‐3‐

1.0 Introduction and Scope

This report summarizes the results accomplished at the time of project conclusion.Before

WECC‐WGMG embarked on working on dynamic models of wind turbine generators,

availabilityofappropriatemodels forrepresentationofWPPswerelimited.Forthemostpart,

onlymanufacturer‐specificuser‐writtenmodelswereavailableonalimitedbasis

(throughnon‐

disclosureagreements)forthe purposesofconductinginterconnection studies.Thesetypesof

dynamic models are developed in full detail, including information deemed to be proprietary

by the turbine manufacturers.Manufacturer‐specific models sometimes are not fully

integrated into the standard model library of simulation software, which leads to

model

maintenance and compatibility issues.Also, difficulties sometimes occur when we want to

study an area with several WPPs from multiple manufacturers.Compatibility issues, limited

accessto modelsand longtechnical supportiterations often results inlong delaysto complete

the studies.After projects are completed, the proprietary nature of the

 models prevents their

inclusion in the WECC standard dynamic database for the purposes of conducting regional

studies.

With funding from WECC, CEC and DOE, and support from several organizations including

DOE and Sandia, the WECC‐WGMG completed the first phase of the effort to develop and

implementwind turbine generator

(WTG)dyn amic models.The WECC dynamicmodels are

intended to be generic in nature and non‐proprietary, and thus are readily available for use.

Generic models allow for unique characteristics of WTGs from different manufacturers to be

represented by adjusting model parameters.These WECC dynamic models are currently

availableinthe

libraryofthePSLF(developedbyGE)andPSSSE(developedbySiemensPTI).

Default input data for each models is also provided.The generic models are also being

implemented in two other software platforms: Operation Technology ETAP, and Powertech

LabsDSATools.

Thisreportisorganizedasfollows:

 Section1–IntroductionandProjectScope

 Section2–Background

o Thissectionprovidesbackgroundofdifferenttasksconsideredinthisproject

 Section3–DescriptionofFourdifferenttypesofWindTurbineGeneratorTechnologies

 Section4–WindPowerPlantEquivalencing

o Thissectiondescribestheequivalencingmethodusedtorepresenthundredsof

turbinewithintheWPPasareducedmodelforbulksystemplanning.

 Section5–WindPowerPlantData

o ThissectiondescribesthedataneededtosimulateandvalidateWPP.

 Section6–ModelValidationofGenericModelsforWindTurbineGenerators

o ThissectiondescribesthemethodusedtovalidateWPP

 Section7–SummaryandDissemination

‐4‐

o Thissectiondescribesthesummaryanddisseminationtothepublic

 Section8–FuturePlans

o Thissectiondescribestheplantoexpandthemodelingeffort



‐5‐

2.0 Description of Wind Turbine Generator Technologies

Despitetheseeminglylargevarietyofutility‐sca leWTGsinthemarket,eachcanbeclassifiedin

one of four basic types, based on the generator topology and grid interface.The distinctive

topologicalcharacteristicsofeachtypeareshowninFigure1andarelistedbelow:

• Type1–Fixed

‐speed,inductiongenerator

• Type2–Variableslip,inductiongeneratorswithvariablerotorresistance

• Type3–Variablespeed,doubly‐fedasynchronousgeneratorswithrotor‐sideconverter

• Type4–Variablespeedgeneratorswithfullconverterinterface



Figure1‐Fourdifferenttypesofwindturbinegenerator

Type 1 – Fixed-speed, induction generator

The Type 1 WTG is an induction generator with minimal control.The torque speed

characteristic is very steep (about 1%slip at rated torque).There is no power semiconductor

switches used in this WTG in a normal running condition.The WTG absorbs reactive power

both in generating or motoring mode.The

 reactive power required by the WTG is

compensated by mechanically switched capacitor bank (MSC).With a slow varying wind

‐6‐

speed,the MSC is able tofollow thereactive  power variation andthe terminalvoltage is very

closelyregulated.Underfasttransients,theterminalvoltage maybela gginginresponseanda

wider voltage and output variation can be expected.Similarly, with sudden changes in

frequency, the output power may respond

 instantaneously without any output current

restrictions,thus,afrequencyresponsesimilartoasynchronousgeneratorcanbeexpected.

Type 2 – Variable slip, induction generator with variable rotor

resistance

TheType2WTGisawoundrotorinductiongeneratorwiththecapabilitytoadjusttheeffective

externalrotorresistance.Theeffective valueoftheexternalrotorresistance isadjustablevia a

simplethree‐phasediode rectifier,DC chopper,anda  parallelresistance.Thus effectively,the

WTGcanbecontrolledto

deliveraconstantratedpowerforwindspeedshigherthanratedby

adjustingthetotalrotorresistance.Belowratedwindspeeds(lowtomediumwindspeeds),the

operationof Type2 WTGsis verysimilar totheoperation ofType 1WTGs.In thehighwind

speed region, the WTG

generates constant output power, output currents, and output power

factor.Althoughtheexternalrotorresistanceiscapableof maintainingconstantoutputpowe r

at higher slips, the heat loss within the rotor resistance can be very high at higher slips.The

pitchcontrolleroftheWTGisusuallyadjustedtokeepthe

sliptobeascloseaspossibletothe

rated slip when the WTG operates in high wind speed.The WTG of this  type tends to react 

faster to sudden (transient) changes than WTG Type 1 because of its ability to maintain the

outputrealandreactive powerwiththe

adjustableexternalrotorresistanceandpitchcontroller.

Thus,asuddenwindgustdoesnotproducelargepowerandreactivepowersurges,norvoltage

dropslikewithType1WTGs.

Type 3 – Variable speed, doubly-fed asynchronous generators with

rotor-side converter

TheType3WTGisalsoknownasdoubly‐fedinductiongenerator(DFIG).Type3andType4

WTGs include a powerconverter to  control the WTG.In a Type 3  WTG the rotor winding is

connected to the power converter and the stator winding is connected to the grid. Under



normal conditions or small transients, the power converter controls the output power of the

generator, reactive power or bus voltage.It can control the real and reactive power

independently and instantaneously.The power converter controls the stator output via

electromagnetic coupling between stat or and rotor separated by the air gap.

Under severe

disturbance (i.e., fault transients), the stator winding is exposed to abnormal and unbalanced

voltagedue tothefaultsthat occurin the transmissionlines.Asaresult,thepower converter

maylose its abilityto controlthe output of realand reactivepower,anditmay have toapply



thecrowbarmechanismtoprotecttheDCbusfromanovervoltagecondition.Thecrowbarin

effectisshortingtherotorwinding,thus,makingtherotorwindingappearlikeasquirrel‐cage 

induction generator.The temporary imbalance between the aerodynamic power and the

electrical output power may accelerate the rotor

speed.To limit the rotor speed, the pitch

controlleradjuststhepitchangleofthebladestoavoidanoverspeedcondition.

‐7‐

Type 4 – Variable speed generators with full converter interface

For the Type 4 WTG, the power converter acts as a buffer between the grid and the electric

generator,thus,anytransientsoccurringinthegridarenottranslatedtotheelectricgenerator.

Undernormal or fault transients,the power convertercan be fullycontrolled.However, one

shouldrealizethat the

powerconverterhasa currentlimittoprotectth e outputcurrent ofthe

powersemiconductors(e.g.IGBTanddiodes),andwhenthegridvoltageislowduringafault

transient disturbance, the maximum output power that can be delivered to the grid is also

limited.Thus,thepitchcontrollerwill

limittherotorspeedfromover‐speedingavoidingarun‐

awaysituation.



‐8‐

3.0 Wind Power Plant and Power Flow Equivalencing

A typical modern WPP, as shown in Figure 2, consists of hundreds of turbines of the same

types.AWTGisusuall yratedatlowthreephasevoltageoutput(480–600V).Apadmounted

transformer at each turbine generator steps up the voltage to the medium voltage collector

system

(12 kV– 34.5kV).Several turbinesthat arephysically closetogetherare connectedto

laterallytoformagroup.Severalofthesegroupsareconnectedtoalargermainfeeder.Several

ofthese feeders areconnected tothesubstation wherethesubstation transformersteps  up the

voltage to a

desired transmission level (e.g., 230 kV).A very large WPP  can have several

substationtransformers.AnexampleofaWPPlayoutcanbeseeninFigure1.

POI or

connection

to the grid

Collector System

Station

Feeders and Laterals (overhead

and/or underground)

Individual WTGs

Interconnection

Transmission Line



Figure2‐PhysicaldiagramofatypicalWPP

Within a WPP, different turbines may operate under appreciably different conditions.Line

impedance connecting each wind turbine to the POI  differs from each other.At a  particular

instant in time, the wind speed experienced by one turbine can be significantly different from

anotherturbinelocatedatanotherpartoftheWPP.

ThediversityofaWPPisagoodattribute

inmanyways.Forexample,theoutputvariabilityoftheentireWPPisattenuatedwith respect

to the variability observed on a single wind turbine.The interaction  between a WPP and the

grid is dete rmined by the collective behavior of the

WPP.In contrast, a conventional power

plantinteractswiththegridasasinglelargegenerator.

‐9‐

WPP equi valencing describes methods of equivalencing collector system in a large WPP.We

simplifieda WPP withmany windturbines intoasimplified turbine representation,asshown

inFigure3.

The full system representation (FSR) is a representation of WPP where every turbine is

represented along with the interconnecting collector system

 connecting each turbine with

another,andconnectinggroupofturbinestothePOI.

Asingleturbinerepresentation(STR)isarepresentationofWPPwherea singleturbineisused 

torepresent theentireWPP.Thisrepresentationismorepracticalforbulksystemsimulations.

Alatersectionofthereportwill

providetechnicaljustificationfortheuseoftheSTRinpower

flowanddynamicstabilitysimulations.Forvariousreasons,someWPPsmaycontaindifferent

types of wind turbines.  Sometimes, a single WPP could have clusters that are very different

from the electrical connection point of view.For example, a portion of

 the plant may be

connectedthroughalongoverheadfeeder,whileanotherportionoftheplantmaybeconnected

throughshortundergroundfeeders.ThisdiversityofWPPs,ifdeemedsignificant,canalsobe

represented with a  model similar to the STR by defining distinct WTG groups, each of which

can

be modeled as an STR.Several methods of grouping considerations are also possible,

resulting in a multiple turbine re presentation (MTR) that can more accurately represent the

unique characteristics of a significantly diverse WPP.The interim report presented in

AppendixIIIdescribesmethodsusedtorepresentWPPsbyequivalenceinamore

lengthyand

detaileddescription.

Pad-mounted

Transformer

Equivalent

Wind Turbine

Generator

Equivalent

PF Correction

Shunt Capacitors

Collector

System

Equivalent

Interconnection

Transmission

Line

Plant-level

Reactive

Compensation

POI or Connection

to the Transmission

System

Station

Transformer(s)

1 2 3 4 5

Figure3‐SingleturbinerepresentationforaWPP

‐10‐



4.0 Wind Power Plant Data

The data required can be divided into two parts; the steady state data needed to solve the

powerflow portion ofdynamic simulation, andthe dynamic dataneeded tosolve the electro‐

mechanical interaction between the grid and the WTGs.A more detailed discussion about

windplantdatarequiredtosimulate

WPPandtovalidateaWTGdynamicmodelcanbefound

inAppendixIV.

The steady‐state data is mostly power system network data from the WPP and its reactive

power capability.This includes power factor correction capacitors at the WTG terminals or

reactivepowersupportequipment(e.g.,capacitors,STARCO M

orsimilar)locatedelsewherein

the WPP.Since a WPP consists of hundreds of turbines, the collector system is simplified by

equivalencingtheWPPintoasimplerepresentation(e.g.,singleturbinerepresentation).

The dynamic data consists of the generic model parameters for the specific WTG being

representedandplantlevelreactive

controls.

 The wind turbine model requires the use of several modules corresponding to the

turbine type used in the simulation.Some of the model parameters may need to be

adjustedtomatchthecharacteristicsofeachturbinemanufacturer.

 Specialflags andseveralparametervaluesoftheWTGmodulesneedtobesettoreflect

how the WTGs participate in the voltage/reactive power control strategy for the plant.

Some of the generic models require wind speed condition as an input to initialize the

pitchangle.

 Other dynamic elements  including reactive power support  equipment are modeled

explicitly,usingconventionalmodels.



Thepowersystemnetworknormallyoperateswithinanarrow voltageandfrequencyenvelope.

Inanormalsituation,thevoltageandfrequencyatthebusesareatorveryclosetoratedvalues

(voltage= 1.0 per

unit,and frequency  = 1.0 per unit).Equipment (i.e., loads)connected tothe

grid is designed to operate near rated frequency and voltage levels, with some tolerance to

allow for temporary excursions. The allowable voltage and frequency deviation is limited in

magnitude(range)andduration.Generallyandundernormalconditions,steady

‐statevoltage

is allowed to vary in a very limited range (max. 5% under normal conditions and 10% under

transientconditions).Steady‐statefrequencyvariationfollowsevenmorestrictlimits.During

transient events caused by faults or equipment switching, voltage  and frequency can deviate

more significantly. The characteristics of the

system, including the network, generators and

load, determine whether the system is stable during steady‐state and transient conditions.

Steady‐stateanddynamicanalysisareperformedtomeasurethemarginofstabilityandpower

systemperformanceundertransientevents.

The WECC‐WGMG recommends the use of the single‐machine equivalent model

 shown in

Figure 3 to represent WPPs in WECC base cases. This representation is recommended for

‐11‐

transient stability simulations and power flow studies.In Figure 4, the dashed line

circumscribes the power system elements that may requir e  dynamic models.The solid line

circumscribesthepowersystemnetworkofaWPPrepresentation.



Figure4–Steadystateanddynamicdatagroupings.

4.1 Data for steady-state representation

The term steady state analysis in this section  refers to the power flow or load flow analysis

commonlyperformedinpowersystemstudies.Thedatarepresentstheequivalentcircuitofthe

networktobeanalyzed,differenttypesofbusesi.e.,ageneratorbusorP‐Vbus,loadbusorP

‐Q

bus,andinfinitebusorswingbus.

Power Flow Network Data

Beforeproceedingwithmodelvalidation,itisnecessarytomodeltheWPPnetwork,andadjust

reactive power control strategy to reflect what is implemented in the field and match data 

recordings. As an example, the WPP equivalent circuit for the New Mexico Energy Center

(NMEC) WPP is shown in Figure 5.

This equivalent is a single turbine  representation.The

WPPconsistsof136turbineswithatotalcapacityof204MW.Eachwindturbineisratedat1.5

MW.Thewindturbineusedisavariable‐speedwindturbine(doubly‐fedinductiongenerator).

Mostof thecollecto r systems areunderground cables.

Themethod of equivalencing described

previously was used to find the equivalent impedances of the collector systems, the pad‐

mountedtransformer,andthestationtransformer.Thesystembaseusedis100MVA.

‐12‐

Pad-mounted

Transformer

Equivalent

Wind Turbine

Generator

Equivalent

Collector

System

Equivalent

Station

Transformer

WTG

Terminals

Transmission

Station

Req = 0.0135

Xes = j0.0497

0.1004

R = 0.0027

X = j0.0245

R = 0.014

X = j0.0828

Figure5‐Single‐machineequivalentimpedanceofNMEC‐WPP

Since the WPP is controlled to keep the voltage at the POI and the voltage at the generator

terminal constant, the dynamic model was set to VARFLG = VLTFLG = 1.The regulated

voltage(busC)settingwasnotrecorded.WecanusethereactivepoweroutputatthePOIbus



A to determine the setting of the regulated bus voltage.After trial and error, we adjust the

regulatedvoltageatbusCsothattheoutputreactivepoweratbusAis23MVAR.

4.2 Data for dynamic analysis

Power system stability is defined as the ability of the system to reach equilibrium after a

disturbance with most system variables bounded so that practically the entire system remains

intact.Power system stability  has been  an area of interest since the initial development of

interconnectedpowersystems,particularlyfollowingtheadvent

oflong‐distancetransmission.

The importance of the subject cannot be overstated.Loss of stability can result in severe

economic,technical,andsocialupsets.

To study power systemstability, dynamic analysis is usually performed for the system under

investigation.In general, the dynamic data required is the input data for

the WTG.The

dynamicdataisusuallycontainedinaninputfilewithextension.dyd.Theinputfilewillhave

the description of the wind turbine dynamic modules with the appropriate input data for the

correspondingwindturbinetobesimulated.

The process of creating a dynamic file for a WTG

Theprocessofcreatingadynamicfile(.dydor.dyr)foraWPPisillustratedintheflowchart

showninFigure6.Itconsistsofseveralsteps:

1) Choosethe typeofwindturbinethatmatchestheplantwhosemodelisbeingvalidated

2) Select thecorrespondinggenericmodeland

inputparametersrelatedtotheturbines

chosen.

3) Select anappropriatemodelforplant‐levelcontrolreactivepowerequipmentinthe

plant.

4) Inmanycases,reactivepowercontrollabilityisprovidedbytheWTGsthroughaplant‐

levelcontroller(forWTGType3andType4).Thegenericmodelsfor

Type3andType

‐13‐

4WTGshaveemulatorsforplant‐levelcontrolsoptionsthatallowsforseveralcontrol

options.

a) Select voltagecontrolorpowerfactorcontrolorreactivepowercontrol,accordingto

whatisimplementedintheproject.

b) Ifthereisvoltagecontrolcapability(terminalvoltageandremotebus),specifythe

remotebus

thatiscontrolled.

4.3 Data for WTG Model Validation

Infinite bus representation

Forthepurposeofvalidation,thenetwork isrepresentedasanidealgeneratorconnectedtothe

POI through an equivalent impedance.We are using a facility in PSLF whereby a classic 

generatormodel(GENCLSspecifically)canbeusedtoinjectameasuredvoltage andfrequency 

tracesasawaytosimulate

atransienteventandcomparethemodelresponse(specifically,real

and reactive power) to field measurements.This technique has limitations, including

unbalancedsituations,lackofcompleteknowledgeofnetworkconditions,andthefactthatwe

are using a STR instead of MTR or FSR.Referring to Figure 6b, the ideal

generator is

represented by a generator classic GENCLS. This module allows the voltage and frequency

profilesto bespecified.Theinputdatatothismoduleisaninputfilecontainingthreecolumns.

Thefirstoneisthetimeindicator.Thesecondcolumnisthetimeseriesofvoltage,andthethird



columnisthetimeseriesofthefrequency.



Figure6‐Dynamicmodelinputpreparation

a) WTG

b) idealgenerator/infinitebus(faultsimulator)

‐14‐

Field Measurement for Dynamic Data for Model Validation

Field‐datameasurementcanbeusedtoverifyorvalidateadynamicmodel.Thefielddataisa

set of data measured at the POI.The data can be recorded at high sampling rates and the

recordingistriggeredbyatransienteventandusedtorecordtheeventfrompre

‐faulttopost‐

fault.Ideally, 10 to 20 seconds post‐disturbance data at sufficient resolution (20 samples per

secondorhigherifthe dataisRMS;7200 samplespersecondorhigherifthe dataispoint‐on‐

wave) is needed for model validation exercise.Typical fault recorders only capture

2 – 4

secondsofper‐phasevoltageandcurrentdata,whichismarginallyusefulformodelvalidation.

The model validation example below uses an actual 4‐seecond fault recording for the New

Mexico WPP described above.The location of data monitoring equipment is usually at the

substation POI.The data

 measured is used to drive the simulation, and the response of the

windplantmodelsimulatediscomparedtotheactualmeasureddata.

The per phase voltage waveforms

It can be seen in Figure 7 that the three‐phase voltage currents van, vbn , and vcn recorded are

symmetricallybalancedvoltagesinthepre‐faultcondition.Thefaultoccursinthetransmission

lines in the vicinity of the WPP.It can be seen that the three‐phase  voltage becomes an

unbalancedvoltage  with phase B dropping significantly for a period offour cycles, before the

fault

iscleared.Thepost‐faultcondi t ion showsthatthethree‐phasevoltagesrecovertonormal

againandasmalloscillationisshownonthethree‐phasewaveforms.

0.9 0.92 0.94 0.96 0.98 1 1.02 1.04 1.06 1.08 1.1

-4

-3

-2

-1

x 10

Time (s)

Voltages (V) - Measured

Three Phase Voltages - 1

Figure7‐Theper‐phase‐voltagesvan,vbn,andvcnasrecorded

Processing Data for PSLF Simulation – Model Validation Exercise

ThegenericdynamicmodeltobevalidatedisavailableinPSSEandPSLFprograms. Touse

PSLFprogram,weneedtogettheinputdata todrivethesimulator.Theinputdatawillbethe

captured voltage waveform at the POI representing the fault and the outside power system

network.As

 described earlier, the model validation strategy is to use the gencls PSLF model,

which can take positive‐sequence voltage magnitude and frequency as a function of time to

imposeasboundaryconditionsinthesimulation.Thus,conversionfromthesinusoidalvoltage

waveform into the positive‐sequence voltage magnitude  and frequency

needs to take place.

‐15‐

The process of converting monitored voltage data into input data is ill ustrated  in Figure 8.

MoredetailinformationcanbefoundinAppendixII.

Figure8‐Blockdiagramsindicatingtheflowprocesstoconvertthemonitoredvoltageintotheinput

dataforGENCLSmodule

Then the dq axis quantities in stationary reference frame are converted into a synchronous

referenceframe.Tousethedqvoltagefortheinputtotheprogram,weconvertthevoltagein

thesynchronousreference‐framephasorquantitiesusingthefollowingequation:



Sincethemodulesimulatingthevoltagesource

GENCLSusesthevoltagemagnitudeandits

frequency,weneedtoconvertthephaseangleinformationtothecorrespondingfrequency

changes.Thefrequencychangescanbecomputedfromthephaseanglechangesdividedbythe

timestep.

f(t)

qdet)

Positive‐sequencesimulationmodelsarenotdesignedtoaccuratelyrep roduceresponsetohigh

frequency components of the transient event (typical integration time step is approximately 4

milliseconds).For this reason, it is prudent to filter out these high‐frequency components in

voltage,frequencyandpowershouldbefilteredappropriately.

Finally,theinputdata(voltage

andfrequency)arereadytobeusedinmoduleGENCLSasshowninFigure9.Anexample of

aninputfilecontainingvoltageandfrequencyfortheGENCLSisgiveninAppendix2.

V and f

0.2

0.4

0.6

0.8

1.2

00.511.52

Time (s)

Voltage (p.u.)

0.95

0.99

1.03

1.07

1.11

1.15

Frequency (p.u.)



Figure9‐InputdatatoGENCLStoperformthedynamicsimulation

atan

qde qe de qde

qde

VVV















‐16‐

5.0 Model Validation of Wind Turbine Generator

WTG needs to be validated to ensure that the behavior of the dynamic model reflects the 

behavioroftheactualWTG.Thewindturbinemanufacturerusuallydevelopsadetailedmodel

of their turbine.This model contains detailed information considered proprietary by the

turbine manufacturer.The detailed model or manufacturer’s specific dynamic

 model is not

releasedtothepublic,thus,theWECCgenericmodelsdevelopedinthisprojectaretheclosest

models to the detailed model without revealing the proprietary information embedded in the

detailed model.Thedetail model is usually validated rigorously by the turbine manufacturer

againstlaboratorymeasurementwithina

controlledenvironment,anditis consideredthebest

representation of the wind turbine.Ideally, the WECC generic dynamic models should be

validated by turbine manufacturers against field measurements.In addition, it is not always

easytogetfielddatameasurementfromtheWPPoperatororowner.Thus,asanalternativeto



using field measurement, you can compare the simulation of generic  dynamic models to the

detailed models.A more detailed discussion on WTG Model Validation is presented in the

AppendixVofthisreport.



Figure10‐ComparisonbetweenthegenericmodelandthemeasureddataforaType2andType3

WTG.

5.1 Validation against the field measurements

The goal of this validation effort is to match the output of the dynamic model against actual

measurements captured at the transmission  station, where disturbance recordings can be

‐17‐

obtainedrelativelyeasily.Thedisturbanceusedasanexampleinthisreportconsistsofaline‐

to‐groundfaultinthevicinityofthetransmissionstation,whichresultedinavoltagetransient

large enough to excite a significant dynamic response from the WPP, within the design

responsecapability of thegeneric

model (upto about 5Hz).Data before thefault occurred is

required to establish  the pre‐disturbance power flow conditions that are used to initialize the

model.Thedisturbancerecordshouldextendseveralsecondsafterthecontingency,consistent

withthetimeframeofinterestofpositive‐sequencetransientstability

analysis.

An example of validation using measured data is presented in Figure 10.The validation

requires measured data to be preprocessed.The measured three phase voltage recorded at

highspeedispreprocessedtogetthevoltagemagnitudeandthefrequencyvariationduringthe

fault.The voltage and frequency waveform are used

 to drive the simulation.The real and

reactive power outputs from the simulations are compared to the measured real and reactive

power.

5.2 Validation against the detailed (manufacturer specific) models

Inthissubsection,thevalidationofgenericdynamicmodelsagainstthedetailedmodelswillbe

presented.The generic dynamic models and the detailed models are simulated on the same

power system network, the same size of WPP, and using a prescribed fault event.The

simulation results from the two different dynamic

 models are then compared, and the

difference is used to tune the parameters of the genericmodelsuntil the two dynamic models

generatesthesameoutputcharacteristics.

The dynamic models developed in this project are validated against the detailed dynamic

models by the model developers (Siemens Power Technologies International, and

General

Electric).The model developers have signed a non‐disclosure agreement with the turbine

manufacturerstodevelopthedetaileddynamicmodels.InFigure11,aType1WTG(induction

generator)fromaspecificturbinemanufacturerissimulated.Theoutputofthegenericmodel

iscomparedtotheoutputsimulationofthe

Type1WTGdetailedmodel.

Thedashedlineistheoutputsimulationofthedetailedmodel,andthesolidlineistheoutput

simulationofthegenericmodel.ItisshownthattheterminalvoltageVTERM,therealpower

output PELEC, the reactive power QELEC and the rotor speed SPEED

are all in agreement 

betweenthegenericmodelandthedetailedmodel.

In Figure 12, the generic model of a Type 4 WTG is simulated and the simulation output  is

compared against the detailed model of a Type 4 WTG when it is subjected to the same fault

eventusing the

samepower system network.The solidline representsthegenericmodeland

the dashed line represents the detailed model.The real power PELEC and reactive power

QELEC traces are shown and the signals are almost identical.Note, that the Type 4 WTG is

modeledbasedonfullpowerconversionthat

excludesthemodelingofthemechanicaldynamic

ofthewindturbine.



‐18‐



Figure11‐ComparisonbetweenthegenericmodelandthedetailedmodelforaType1WTG.



Figure12‐ComparisonbetweenthegenericmodelandthedetailedmodelforaType4WTG.



SPEED

QELEC

PELEC VTERM

PELEC QELEC

‐19‐



This project concluded with major accomplishments, including the completion of dynamic

modelsoffourtypesofwindturbinegeneratorsontwomajorpowersystemsoftwareplatforms

(PSLFandPSSE),modelvalidation ofthefourtypes ofWTGdynamicmodels, andtheWECC

modelingguides.

Theresultofthisprojectis

disseminatedinmanydifferentways.Currently,theGenericWTG

dynamicmodels(Type1–Type4)developedbySiemensPTIandGeneralElectricarepresently

includedinthesoftwarelibraryofthePSSEandPSLF.Inthepastmanypowersystemplanners

didnothaveanyoptiontomodelWPPother

thanrepresentingtheWPPasnegativeloadsora

simpleinductiongenerator.TheavailabilityofthedynamicmodelsoffourtypesofWTGgives

thepowersystemplannersbetteroptionstorepresenttheWPPcorrectly.

TheWECCPowerFlowGuide(2009)andWECCDynamicModelingGuide(tobecompletedin

2010) is accessible via the WECC website.This guide  was developed by the Wind Generator

ModelingGroup(WGMG)oftheWECC.ThePowerFlowGuideiscurrentlyavailablefromthe 

WECC website.The Dynamic Modeling Guide is currently being reviewed by the WGMG –

WECCanditwillbemadeavailable

fromtheWECCwebsite.

Workshops/short‐courses/seminars on WTG dynamic modeling were presented at various

eventssponsoredbytheIEEE,WECC,UWIG,IEC,andvariousuniversities.

Technicalpapersgiven attheIEEE,WindPower, andotherconferencesonrelatedtopics:WPP

equivalencing, fault analysis of a wind plant, WTG dynamic model

validation methodology,

powersystemstability,andshortcircuitbehaviorofWPP.

ThelistoftechnicalpapersandpublicationsrelatedtothisprojectislistedinAppendixI.The

listofworkshops,andshortcoursesisgiveninAppendixII.Aninterimreport  describingthe

equivalencing is included in Appendix III, an

 interim report describing the data collection is

givenin theAppendixIV,and theinterim reporton dynamicmodel validationis givenin the

AppendixV.CopiesofWECCguidesaregivenintheAppendicesVIandVII.



6.0 Summary and Dissemination

‐20‐



Thetopic of dynamicmodeling ofWPP needsto be expanded.Thiscontinuation is necessary

becauseofthewindtechnologyischangingrapidly−itrequirescontinuesmodeladaptationto

reflectthelatestturbine implementation.Parametersensitivities,identification,andtuning of

WTG dynamic models for differe nt  manufacturers are needed to help

manufacturer derived

parametersforgenericdynamicmodelsrepresentingtheirturbines.

In the next phase, it is also necessary to revise/improve dynamic models to include droop,

ramp‐limit,reservemanagement,preprogrammedfrequency/inertialresponse,relayprotection.

Thesecapabilitieswillsoonbeimplementedbyturbinemanufacturersandtheexistingmodels

may have to be

 upgraded to reflect new capabilities.Some of new turbine concepts may be

designedandinstalledinthenearfuture.Thenewturbineconceptshouldalsoberepresented

especiallyiftheirpresenceinthepowergridandthesizearesignificant.

In order to facilitate  the adaptation of generic models by

other software vendors, we need to

support other software vendors (e.g., Powertech Lab, Inc., Operation Technology, Inc.) to

implementWTGdynamicmodelsontheirplatforms.

The availability and use of future PMU data collected by different agencies (WECC, BPA,

ERCOTetc) willbeaccessedtovalidatedynamicmodels,predictWPPstability,

designpossible

newWPPcontrolsandprotection.

Finally, we need to interact with the IEEE, the IEC, WECC, and UWIG for standard/guide

developmentandpublicdissemination.



7.0 Future Plan

‐21‐

References

[1] E.Muljadi,C.P.Butterfield,A.Ellis,J.Mechenbier,J.Hocheimer,R.Young,N.Miller,R.

Delmerico,R.Zavadil,J.C.Smith,”EquivalencingtheCollectorSystemofaLargeWind

PowerPlant”,presentedattheIEEEPowerEngineeringSociety,AnnualConference,

Montreal,Quebec,June12‐16,2006.

[2] E.Muljadi,B.Parsons,

ʺComparingSingleandMultipleTurbineRepresentationsina

WindFarmSimulation,ʺpresentedattheEuropeanWindEnergyConference(EWEC‐

2006),Athens,Greece,February27–March2,2006.

[3] N.W.Miller,J.J.Sanchez‐Gasca,W.W.Price,andR.W.Delmerico,“Dynamicmodeling

ofGE1.5and3.6

MWwindturbine‐generators forstabilitysimulations,”inProc.2003

IEEEPowerEngineeringSocietyGeneralMeeting,pp.1977–1983,June2003

[4] J.O.G.Tande,E.Muljadi,O.Carlson,J.Pierik,A.Estanqueiro,P.Sørensen,M.

O’Malley,A.Mullane,O.Anaya‐Lara,andB.Lemstrom.Dynamicmodelsofwindfarms

for

powersystemstudies–statusbyIEAWindR&DAnnex21,”EuropeanWindEnergy

Conference&Exhibition(EWEC),London,U.K.,Nov.22−25,2004.

[5] T.PetruandT.Thiringer,”Modelingofwindturbinesforpowersystemstudies,”IEEE

TransactionsonPowerSystems,Volume17,Issue4,Nov.2002,pp.1132–

1139.

[6] “GenericType‐3WindTurbine‐GeneratorModelforGridStudies”,Version1.1,

preparedbyWECCWindGeneratorModelingGroup,September14,2006

[7] “WECCWindPowerPlantPowerFlowModelingGuide”,preparedbyWECCWind

GeneratorModelingGroup,November2007

[8] P.C.Krause,AnalysisofElectricMachinery,McGrawHill

Co.NY,19862



‐ ‐

Glossary .

Thefollowingacronymsareusedinthisreport:

CEC CaliforniaEnergyCommission

CRPWM CurrentRegulatedPulseWidthModulation

DFAG DoublyFedAsynchronousGenerator

DFIG DoublyFedInductionGenerator

DOE DepartmentofEnergy

ERCOT ElectricReliabilityCouncilofTexas

FERC FederalElectricRegulatoryCommission

FOC FluxOrientedController

FPL FloridaPowerand

Light

FSR FullSystemRepresentation

IEC InternationalElectrotechnicalCommission

IEEE InstituteofElectricalandElectronicEngineers

LVRT LowVoltageRideThrough

NMEC NewMexicoEnergyCenter

NDA NonDisclosureAgreement

NEC NationalElectricalCode

NERC NorthAmericanElectricReliabilityCouncil 

NREL NationalRenewableEnergyLaboratory

PFC PowerFactorCorrection

PIER

PublicInterestEnergyResearch

PNM PublicServiceofNewMexico

POI PointofInterconnection

PSLF PositiveSequenceLoadFlow

PSSE PowerSystemSimulatorforEngineers

RAS RemedialActionScheme

‐ ‐

SVC

Static VAr Compensator

TSR TipSpeedRadio

VAr Volt‐AmpereReactive

WECC WesternElectricityCoordinatingCouncil

WGMG WindGeneratorModelingGroup

WTG WindTurbineGenerator

WF WindFarm

WPP WindPowerPlant



‐ ‐

Appendix I - List of Publications

1. R. Piwko, E. Camm, A. Ellis, E. Muljadi, R. Zavadil, R. Walling, M. O’Malley, G. Irwin,

and, S. Saylors, “A Whirl of Activity”, the IEEE Power and Energy Magazine,

November/December 2009

2. D. Burnham, S. Santoso, E. Muljadi, “Variable Rotor Resistance Control of Wind

Turbine Generators,” presented at the IEEE Power Engineering Society, General

Meeting, Calgary, Alberta, Canada, July 26-30, 2009.

3. M. Singh, K. Faria, S. Santoso, E. Muljadi “Validation and Analysis of Wind Power

Plant Models using Short-Circuit Field Measurement Data,” presented at the IEEE Power

Engineering Society, General Meeting, Calgary, Alberta, Canada, July 26-30, 2009.

4. E. Muljadi, T. Nguyen, M.A. Pai, “Transient Stability of the Grid with a Wind Power

Plant,” to be presented at the IEEE Power System Conference and Exposition, Seattle,

WA, Mar. 15-18, 2009.

5. E. Muljadi, T. Nguyen, M.A. Pai, “Impact of Wind Power Plants on Voltage and

Transient Stability of Power Systems,” presented at the IEEE Energy2030 conference,

Atlanta, Georgia, Nov. 17-18, 2008.

6. A. Ellis, E. Muljadi, ”Wind Power Plant Representation in Large-Scale Power Flow

Simulations in WECC,” presented at the IEEE Power Engineering Society, General

Meeting, Pittsburgh, PA, July 20-24, 2008.

7. E. Muljadi, A. Ellis,” Validation of Wind Power Plant Dynamic Models”, invited panel

discussion presented at the IEEE Power Engineering Society, General Meeting,

Pittsburgh, PA, July 20-24, 2008.

8. E. Muljadi, Z. Mills, R. Foster, J. Conto, A. Ellis, ” Fault Analysis at a Wind Power Plant

for a One Year of Observation”, presented at the IEEE Power Engineering Society,

General Meeting, Pittsburgh, PA, July 20-24, 2008.

9. E. Muljadi, S. Pasupulati, A. Ellis, D. Kosterov,” Method of Equivalencing for a Large

Wind Power Plant with Multiple Turbine Representation”, presented at the IEEE Power

Engineering Society, General Meeting, Pittsburgh, PA, July 20-24, 2008.

10. R. Zavadil, N. Miller, A. Ellis, E. Muljadi, E. Camm, and B. Kirby, “Queuing Up”, the

IEEE Power and Energy Magazine, November/December 2007

11. E. Muljadi, C.P. Butterfield, B. Parsons, A. Ellis, ”Characteristics of Variable Speed

Wind Turbines Under Normal and Fault Conditions”, presented at the IEEE Power

Engineering Society, Annual Conference, Tampa, Florida, June 24-28, 2007.

12. M. Behnke, A. Ellis, Y. Kazachkov, T. McCoy, E. Muljadi, W. Price, J. Sanchez-Gasca

“Development and Validation of WECC Variable Speed Wind Turbine Dynamic Models

for Grid Integration Studies” presented at the Windpower 2007, WINDPOWER 2007

Conference & Exhibition, Los Angeles, CA, June 24-28, 2007.

13. E. Muljadi, C.P. Butterfield, B. Parsons, A. Ellis, “Effect of Variable Speed Wind

Turbine Generator on Stability of a Weak Grid”, published in the IEEE Transactions on

Energy Conversion, Vol. 22, No. 1, March 2007.

14. E. Muljadi, C.P. Butterfield, A. Ellis, J. Mechenbier, J. Hocheimer, R. Young, N. Miller,

R. Delmerico, R. Zavadil, J.C. Smith, ”Equivalencing the Collector System of a Large

Wind Power Plant”, presented at the IEEE Power Engineering Society, Annual

Conference, Montreal, Quebec, June 12-16, 2006.

‐ ‐

Appendix II - List of Short Courses and Workshops

1) WECC – 2009 Generator Model Validation Workshop, held at Tristate Generator and

Transmission Association, Westminster, CO May 18-19, 2009

2) WECC - 2009 Modeling Workshop for Planning Engineers, held at PG&E, San

Francisco, CA, April 16-17 2009

3) IEEE Dynamic Performance of Wind Power Generation Task Force (DPWPGTF)

“Tutorial on Wind Generation Modeling and Controls,” IEEE PSCE Conference, Seattle,

WA, USA – March 2009

4) Tutorial “Wind Energy Boot Camp” organized by New Mexico State University, PNM,

and NREL at Albuquerque, NM, Nov 12-14, 2008

5) IEEE Dynamic Performance of Wind Power Generation Task Force (DPWPGTF)

“Tutorial on Wind Generation Modeling and Controls,” IEEE PES General Meeting,

Pittsburgh, PA, USA – July, 2008

6) “WECC Wind Generator Modeling Project “, Policy Advisory Committee, California

Energy Commission (CEC), Irwindale, CA, 8/20/2007 and Kick off meeting for the, Los

Angeles, CA, 8/21/2007

7) “Wind Generator Modeling”, CEC-PIER-TRP Technical Advisory Committee Meeting,

Sacramento, CA, October 3, 2006

8) “Equivalencing Large Wind Power Plant”, WECC 2006 Modeling Workshop, Las Vegas,

NV, June 14-15, 2006

