建模和控制的太阳能热电站

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MODELLINGANDCONTROLOFASOLARTHERMALPOWERPLANT

EskoK.Juuso

ControlEngineeringLaboratory,DepartmentofProcessandEnvironmentalEngineering,P.O.Box4300,FIN-90014UniversityofOulu,Finland

Abstract:Model-basedcontroldesignisessentialinthecontrolofsolarpowerplants.Dynamiclinguisticequation(LE)modelsoperateaccuratelyinmostoper-atingconditions.Smoothtransitionsbetweensubmodelsarebasedonfuzzylogicandfuzzysetsystemsarealsousedforspecialsituations.Thehybridsimulatorhasbeentestedwithextensiveprocessdata,andtheadaptivecontrollertunedwiththesemodelsreducesconsiderablytemperaturedifferencesbetweencollectorloops.Efficientenergycollectionisachievedeveninvariableoperatingcondition.Distributedparametermodelsextendtheoperabilitytodrasticchanges,e.g.start-upandlargeloaddisturbances,andlocaldisturbancesandmalfunctioning.Copyrightc󰀁2005IFAC

Keywords:Solarpowerplant,dynamicmodelling,intelligentsimulationenvironments,non-linearmodels,linguisticequations,fuzzysetsystems

1.INTRODUCTIONSolarpowerplantsshouldcollectanyavailablethermalenergyisinausableformatthedesiredtemperaturerange,whichimprovestheoverallsystemefficiencyandreducesthedemandsplacedonauxiliaryequipments.Incloudyconditions,thecollectorfieldismaintainedinastateofreadinessfortheresumptionoffull-scaleoperationwhentheintensityofthesunlightrisesonceagain.Solarcollectorfieldisisgoodtestplatformforvariouscontrolmethodologies(Camachoetal.,1997;Juuso,1999).

Lumpedparametermodelstakingintoaccountthesunposition,thefieldgeometry,themirrorreflectivity,thesolarradiationandtheinletoiltemperaturehavebeendevelopedforasolarcol-lectorfield(Camachoetal.,1997).Feedforwardcontrollersbasedlumpedanddistributedenergybalancesextendedthesemodels(ValenzuelaandBalsa,1998;FarkasandVajk,2002).

Linguisticequationshavebeenusedinvariousin-dustrialapplications(Juuso,1999;Juuso,2004b).Therobustdynamicsimulatorbasedonlinguis-ticequationsisanessentialtoolinfine–tuningofthesecontrollers(Juuso,2003).Thisdata-drivendynamicLEmodellingapproachiscom-binedwithadynamicenergybalanceandex-tendedtodevelopingdistributedparametermod-els(Juuso,2004a).

Thispapersummarizesmodellingandcontrolac-tivitieswiththeLEmethodologyfromthefirstLEcontrollersimplementedin1996(Juusoetal.,1997)andthefirstdynamicLEmodelsde-velopedin1999(Juusoetal.,2000)tothemul-tilevelLEcontrollersandtherecentextensionstodistributedparametermodels.Thepaperalsopresentshowtheoverallsystemisusedincon-troldesign.AlltheexperimentshavebeencarriedoutintheAcurexSolarCollectorsFieldofthePlataformaSolardeAlmerialocatedinthedesertofTabernas(Almeria),inthesouthofSpain.Fig.1.LayoutoftheAcurexsolarcollectorfield.2.SOLARPOWERPLANTTheaimofsolarthermalpowerplantsistoprovidethermalenergyforuseinanindustrialprocesssuchasseawaterdesalinationorelectric-itygeneration.Inadditiontoseasonalanddailycyclicvariations,theintensitydependsalsoonat-mosphericconditionssuchascloudcover,humid-ity,andairtransparency.Unnecessaryshutdownsandstart-upsofthecollectorfieldarebothwaste-fulandtimeconsuming.Finallyifthecontrolisfastandwelldamped,theplantcanbeoperatedclosetothedesignlimitstherebyimprovingtheproductivityoftheplant(Juusoetal.,1998).

TheAcurexfieldsuppliesthermalenergy(1MW)informofhotoiltoanelectricitygenerationsystemoraMulti–EffectDesalinationPlant.Thesolarfieldconsistsofparabolic–troughcollectors(Juusoetal.,1997).Controlisachievedbymeansofvaryingtheflowpumpedthroughthepipesduringtheplantoperation.Inadditiontothis,thecollectorfieldstatusmustbemonitoredtopre-ventpotentiallyhazardssituations,e.g.oiltem-peraturesgreaterthan300oC.Thetemperature

increaseinthefieldmayriseupto110degrees.Inthebeginningofthedailyoperation,theoiliscirculatedinthefield,andthevalvetostoragesystem(Fig.1)isopenwhenanappropriateoutlettemperatureisachieved.

Anoverviewofpossiblecontrolstrategiespre-sentedin(Camachoetal.,1997)includebasicfeedforwardandPIDschemes,adaptivecontrol,model-basedpredictivecontrol,frequencydomainandrobustoptimalcontrolandfuzzylogiccontrol.Acomparisonofdifferentintelligentcontrollersispresentedin(Juuso,1999).Alinguisticequation(LE)controllerwasfirstimplementedonasolarcollectorsfield(Juusoetal.,1997).Lateradap-tivesetpointprocedureandfeedforwardfeatureshavebeenincludedforavoidingoverheating.Thepresentcontrollertakesalsocareoftheactualsetpointsofthetemperature(JuusoandValen-zuela,2003).

Modelshavebeenintegratedtovariouscontrolschemes.Feedforwardapproachesbaseddirectlyonthesteadystateenergybalancerelationshipscanusemeasurementsofsolarradiationandinlettemperature(Camachoetal.,1992).Afeedfor-wardcontrollerhasbeencombinedwithdifferentfeedbackcontrollers,evenPIDcontrollersoperateforthispurpose(ValenzuelaandBalsa,1998).Theclassicalinternalmodelcontrol(IMC)canoperateefficientlyinvaryingtimedelayconditions(FarkasandVajk,2002).TheadaptationschemeofLEcontrollersisextendedbyamodel-basedhandlingoftheoperatingconditions(JuusoandValenzuela,2003).