Wind-turbine-control-algorithms

ECN-C--03-111WindturbinecontrolalgorithmsDOWEC-F1W1-EH-03-094/0E.L.vanderHooft;P.Schaak;T.G.vanEngelenDecember2003ECN-C--03-1111WindturbinecontrolalgorithmsAbstractTheobjectiveofDOWECtask3ofworkpackage1hasbeendefinedas’researchanddevel-opmentofwindturbine(power)controlalgorithmstomaximizeenergyyieldandreductionofturbinefatigueload,anditsoptimisationforoffshoreoperation’.InaccordancewiththeDOWECbaselineturbineandtherelatedDOWECturbineallactivitieswerefocusedonactivepitchtovane,variablespeedconcept.Theresultsofthistaskcontributetothe:•set-upofamodularcontrolstructurebasedontheoreticalanalysisandindustrialneeds;•increaseofturbineperformance(powerproduction,loadreduction)byadditionalcontrolfeaturesandactions.ItcanbeconcludedthatthecontrolstructureissuperiortoordinaryPDfeedbackcontroloftherotorspeed.AnindependentcomparisonfortheDOWECturbineusinganaerodynamiccode,withastate-of-the-artcontrolstructure,hasresultedinimprovementsconcerning:•extremefore-afttowerbendingmoment(-40%);•fatiguefore-afttowerbottombendingequivalentmoment(-50%);•variationsinbladepitchrate(standarddev.-0.65dg/s);•tiltmoment(-10%).Themeanpowerproduction(10min)inaboveratedwindspeedswasover99%ofitsratedvalue.Oppositetotheimprovementsithasbroughtaboutlargervariationsingeneratorspeed(standarddev.+0.5rpm),increaseofyawmoment(12%)andradialbladeforces(14%).Theunderlyingapproachofthecontrolstructuredividesthemultivariablewindturbinesystemintodifferentindependentscalarsubsystemsbybandfil-tering.Asaconsequencetheresultingsetpoints,thepitchrateandelec-trictorque,consistofadditivecontributionsofthedifferentcontrolactions.Concerningpowercontrol,ordinaryrotorspeedfeedbackhasprovedtobearobustcore.However,valuableextensionsweredevelopedbywindspeedfeedforwardcon-trol(pitchcontrol)andoptimisationaroundratedcondition(electrictorquecontrol).Promisingresultshavebeenachievedonfore-afttowerdampingbypitchcontrol.Electrictorquecontrolhasenabledconsiderabledampingresultsof(collective)drivetrainresonancesandpossibilitiesforbadlydampedsidewardtowervibrations.Keywords:DOWEC,Windturbinecontrol,PitchControl,PowerControl,TorqueControl,Variablespeedcontrol2ECN-C--03-111AcknowledgmentThisreportisissuedwithintheframeworkoftheDOWECproject,supportedbytheEETprogrammeoftheDutchMinistryofEconomicAffairs.Unfortunately,onlyoneauthorcanbethefirstauthorofareport,inthiscasethreewouldhavebeenmuchbetter.Mycolleague,PieterSchaak,hascontributedtoalargeextendtotheresultsofthisreport,byperformingtheresearchanddevelopmentonpowerfuloptimisationaroundratedconditions(subsection3.4.2),reductionoftowerloading(section5.2and5.3)andafinalsimulationcase(chapter4).Myothercolleague,TimvanEngelen,hasbeeninvolvedintenselybydrivetraindamping(section5.1),andhiscontributionsonturbinemodelling,windandwavedynamics(chapter2)havebeenappearedtobeindispensible.AsataskleaderofDOWEC-WP1-task3,mycontributionswerefocussedonreporting,taskmanagement,supportingDOWECcontrolactivities[3]andthedevelopmentofwindspeedfeedforwardcontrol(subsection3.2.5).Finally,BenHendriksisacknowledgedforDOWECprojectmanagementandhiskindattitudetowardswindturbinecontrol.EricvanderHooft,Petten,December18th,2003ECN-C--03-1113Windturbinecontrolalgorithms.4ECN-C--03-111CONTENTS1Introduction72ModellingtheDOWECturbine92.1Systemdescription................................92.2Windturbinesubsystems.............................92.2.1Rotoraerodynamics...........................92.2.2Rotatingmechanicalsystem.......................122.2.3Towerdynamics.............................142.2.4Electricconversion............................152.2.5Pitchactuationsystem..........................162.3Externalphenomena...............................162.3.1Rotoreffectivewindspeed........................162.3.2Towertopeffectivewaveforces......................183Designofpowercontrolalgorithm233.1Powercontrolapproach..............................233.2Pitchcontrolalgorithmatfullloadoperation...................253.2.1Rotorspeedfeedbackcontrol.......................253.2.2Dynamicinflowcompensation......................353.2.3Inactivityzoneandlimitation......................353.2.4Forcedrotorspeedlimitation.......................373.2.5Estimatedwindspeedfeedforward...................383.3Pitchcontrolalgorithmatpartialloadoperation.................453.4Torquesetpointcontrol..............................453.4.1Stationarypowerproductioncurve....................463.4.2Poweroptimisationaroundratedwindspeed..............473.4.3Dynamicrotorspeedlimitation.....................554Powercontrolsimulationresults594.1Simulationconditions...............................594.1.1Turbinemodel..............................594.1.2Externalphenomena...........................604.1.3Powercontrolalgorithm.........................604.1.4Simulationruns..............................604.2Controlperformanceatratedwindspeed.....................634.3Controlperformanceaboveratedwindspeed..................644.4Controlperformanceathighwindspeed.....................654.5Controlperformanceatveryhighwindspeed..........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