外文翻译-基于ControlLogix5550+PLC的锅炉水位控制系统

BoilerlevelcontrolsystembasedonControlLogix5550PLCAbstract-ThispaperisaresearchdesignbasedonEFPTprocesscontroldevice.Inthedesign,actualindustryfieldhasbeensimulatedandcorrespondingmodelinghasbeencarriedonfortheboilerlevelsystem.ThentheappropriatePIDparameterhasbeensortedoutandControlLogia5550PLChasbeenusedtocontroltheentireboilerlevelsystem.Atlast,acorrespondingcontrolinterfacehasbeenestablishedandtheboilerlevelhasbeenunderasafeandaccuratecontrolKeywords：EFPT，PID，Modeling，Boilerlevel;1IntroductionThetaskoftheindustrialboilerlevelcontrolistomaintainadynamicbalancebycontrollingthewaterflowandevaporation,sothatthedrumlevelcanbemaintainedinthetechnologicallevel,whichisanecessityforensuringsafeoperationandalsooneofthemainindicatorsoftheboiler'snormaloperation.Waterlevelwhichistoohighwillaffecttheeffectofthesteam-waterseparation,buttoolowitiswillbreakringcycleorevencauseboilerexplosion.Toensureasafeandefficientproduction,theboilerlevelmustbestrictlycontrolledinmaintainingconstantorchangingonlyaccordingtoacertainrule.UsingLogix5550PLCwithanalogyI/Omodules,launchedbyRockwellAutomationCompanyascontrollers,andEFPTprocesscontrolexperimentaldeviceascontrolobject,thissystemhavebroughttheboilerwaterlevelunderanaccuratecontrolinaminiboilersystemwithsensorsandactuatorsthatusedinindustrialproduction.Fig.1Boilerlevelsettingvalueadjustmentsystem2SystemOverviewThissystemiscomposedofanEFPTprocesscontroldevice,aninverter,aLogix5550PLCandacomputer.EFPTprocesscontroldeviceisasimulatedheatingandwatersupplyanddrainagesystemforamicro-smallboiler.Itrealizesprocesscontrolinaminiboilersystemwithsensorsandactuatorsusedinindustrialproduction.Theactuatorincludesnotonlymeasuringappliance,butalsoACinverter,heatingcontroller,heaterandsoon.Thesystemsimulatesindustryscenethroughamini-boilerheating,watersupplyanddrainagesystem,whichisreliableandvisual.Inthedesign,boilerLevelwasselectedasthecontrolledvariable.Thecontrolledobjectiscomposedofthewatertrough,theforcepump,theboilerandthepipe-linevalve.MicroMaster6SE9214-ODA40inverteristakenastheactuatorandtheboilerleveliscontrolledbyLogix5550.ConfigurationsoftwareRSView32andtouchscreenPanelView1000arecombinedtorealizethereal-timemonitoring.Inthedesign,asimpledesignofsingle-loopboilerliquidlevelvalueadjustmentisselectedforthestudy.ThecompositionofthesystemisshowninFig.1.Inthedesign,theinverterasanactuatordirectlyreceivesPLCanalogyI/Oportoutput,andconvertersintofrequencyofinvertersoastodrivethe3-phasemotorintheliftpump,changetheinlet,andadjusttheboilerleveltothedynamicbalanceatlast.Andtheconfigurationsoftwareisusedtodesignmonitoringpicturetorealizethecomputerandthetouchscreentotheboilerlevellong-distanceandthescenemonitoring.[1].Pumpstarted,pidcontrollerpressuretransmittertothecontrolpointtoprovidethepressuresignal,whenthepressurepointisnotequaltosetvalue,pidcontrollerbyadjustingtheinverteroutputfrequencytochangethepumpspeedtoregulatethepipelinepressureconstitutesaclosed-loopfeedbackcontrolsystem,waterpressureregulatorsothatuserstimely,smallfluctuationsinresults.Andintheprocesscontrolsystemdesignedtotakefullaccountoftheprincipleofloadbalancing,totake"first-in-firstout"strategyofliningup,thewaytheimplementationoftherotatingfrequencytoensurethatthebasicbalanceofthewaterusage.

1FrequencyControlConstantPressureWaterSupply

Principle

FrequencyControlConstantPressureWaterSupplySystembytheprogrammablelogiccontroller(plc),converter(built-pid),pressuretransmitter,low-voltageelectricalandpumpcomponents,suchasFigure

1.Mapm1~m3forwaterpumpmotors,p1~p3forpumps,km1~km6formotorstartingandstoppingeachoftheACcontactorswitch.Basicworkingprincipleofthesystem:bytheplcasignaltotheinvertertocontrolthewatercyclework,whenthelargevolumeofwaterconsumedbytheplccontrolofallwaterlineinstalledintheoutletpipeofthepressuretransmitter,pressurestandardsignalsintodc0v~10vintotheanalogsignalconverterwithpidregulator,pressuresettingsandpressurefeedbackvaluesaftertheimplementationofpidcalculatedvaluesoftheoutputofafrequencyconvertertosetthevalueforthepumpbytheinvertertoprovidevariablefrequencyelectricalpowertorealizesteplessspeedregulationofelectricpumpstoregulatetheexitofthewatersupplypipenetworkpressure,constantpressurewatersupplytoachievethepurpose.Pressurefeedbacksignalinordertoensureanaccuratevalue,yetthevalueoffeedbacksignaltosetthefiltertimeconstant.Thescopeofthepowerconverter,Figure1canincreasethenumberofthemotortoachieve"amulti-trailers,"Optimizationoftheprogram.3EstablishingMathematicsmodelforthechargedobjectOneofthemaintasksofestablishingcontrolsystemmathematicalmodelistodeterminethemathematicalmodelofthecontrolledobject.Generally,therearetwokindsofbasicmethodsforestablishingprocesscontrolmathematicalmodel:mechanismanalysisandexperimentalmethod.However,forcontrolledobjectwhosestructureandinternalprocessisverycomplex,itisverydifficulttodeterminetheobjectjustbyitsowninternalphysicalprocessandtosolveoutthedifferentialequationssystematically.Besides,consideringthenonlinearfactor,mechanismanalysisusedsomeapproximationandhypothesisformathematicaldeduction.Althoughtheseapproximationandassumptionshavepracticalbasis,butnotfullyreflectactualsituation,andevencauseincalculableeffects.Therefore,inthisdesign,theexperimentalmethodischosentoestablishamathematicalmodelforcontrolledobject.Thiskindofmodelingisbasedontheinputandoutputintheactualproductionprocess,thatistosay,establishingmathematicalmodelforthecontrolledobjectthroughprocessidentificationandparameterestimation.Inthisdesign,stepresponsecurvemethodisusedtoidentifymathematicalmodelsoftheprocess.A20Hzstepdisturbanceinputsignalisappliedtothechargedobject,andtheresponsecurveoftheoutputthatchangeswithtimecanbemapped.Aftertheanalysis,thetransferfunctionofthecontrolledobjectcanbedefined.Intheprocessofexperiment,theobjectwasconductedseveraltests.UsingRSLogix5000trendmonitoringfunctioncurve,morethan10chargedobjectstepresponsecurvehavebeenrecorded.Toalltheparametersforaverage,steadytime:ts≈821.525s,steadyvalue:h(∞)=58.5,peaktime:tp=394.4sovershoot:a%}29%.Accordingtothetheoreticalanalysis,thecontrolledobjectisthemostlikelysecond-orderobject.However,thedifferenceisveryapparentbetweentheidealsecond-ordercontrolledobjectstepresponsecurveandtheactualcurves.Sotheidealcurvecan'tresponsetoitsactualcharacteristics.Itisinferredthatthecontrolledobjectmaybethesecond-ordercontrolledobjectthatincludeszero.ThetryanderrormethodandMATLABsimulationtoolsareusedtogetacurvewhoseparametersareclosetotheaveragedynamicparametersofthecontrolledobject'sresponsecurve.ItisshowninFig.2.Someadjustmentscanbemadeaccordingtothefollowingrules:1)Whenthezeroisclosertotheimaginaryaxis,settlingtimewillbelongerandtheovershootwillbebiggerandpeaktimewillbesmaller.Withthezeroclosingtotheimaginaryaxis,theeffectismoreobvious.2)Theeffectwhichtheclosedloopdominantapiceshaveondynamicperformanceisincreasingthepeaktime,reducingtheovershootandadjustingtime.Nonparametricmodelisusedtodescribethecontrolledobject.Inotherwords,stepresponsecurvewhichapproximatelydescribethecontrolledobjectisusedbecauseofthecontrolledobject'scomplexityanduncertainty.Toaconstantwatersupply,landinginthewaterpressuretoincreasetheinverteroutputfrequency,whenthemaximumfrequencyconverterandaconstantpressurepumpcannotmeettherequirements,whilerunningthepumpfrequencytoswitchtotherunningfrequency,Atthesametimeneedtostartasecondfrequencyorthirdpumpuntilthewatersupplytomeettherequirements.Needtodeterminecriteriaforthelaunchofanewwaterpumpistheinverteroutputfrequencyissettoreachtheupperlimit.Inordertodeterminethefrequencyoftheinverterlimitstheaccuracyofleastsquaresbychanceshouldbethefrequencyofthefrequencyoffluctuationsintheceilingfromthesituation.Invertercontrolmotorpumpsareactivatedeachtimethesoft-start,andrequirestheuseofwaterpumpsmustturntoserveasacontinuousvariablefrequencypumpoperationshallnotexceed3h,eachtimewhentheneedtolaunchanewwaterpump,thepumpwillrunfromtheexistingremovaloftheinverter,andreplacethepower-frequencyoperation,resettheinverterandrunthepumpforanewstart.ThreepumpstocontrolthedutycycleistheuseofpumpNo.1waytoachieve(to3intheplus1equaltozero),orcombinedwiththetotalnumberofpumppumppumprotationtoachieveitswork.4Theinstallationofcontrollerparameter4.1TheselectionofcontrolalgorithmAfterestablishingtheapproximatemathematicalmodelofthecontrolledobject,acompletefeedbackcontrolsystemcanbeformedtoimprovetheperformanceoftheopen-loopcontrolsystem.PIDisanidealcontrollawinthatintegralisintroducedbasingontheproportion,whichcaneliminatetheresidualerror,plusthederivativeaction,whichcanalsoimprovethestabilityofthesystem.Accordingtothecharacteristicsofthecontrolledobjectandlaboratoryconditions,asingle-loopfeedbackcontrolloopforthecontrolledobjectisestablished,andPIDalgorithmisusedtorealizeboilerlevelcontrol.TheschematicdiagramoflevelcontrolisshowninFig.3.Opentheoutletvalvetoacertaindegree,andmakethehydraulicdischargeinvariable.Comparingtheprocessvariablesofthewaterlevelinfeedbackwiththegivenvolume,thedeviationcanbeobtained.PIDinstructiondoesPIDoperationonthedeviation,andtheresultsisacontrolvariable,sothefrequencyoftheinvertercanbechangedtocontroltherotatespeedofthepump.Iftheliquidlevelisonthehighside,theresultsmakethecontrolvariablesmaller,andreducetherateofinflow,makeliquidlevellower;ifthelevelisonthelowside,theresultsmakethecontrolvariablelarger,andincreasetherateofinflow,makeliquidlevelhigher.4.2TheParameterTuningofPIDBecausethetransferfunctionofthecontrolledobjectincludesazerosecond-orderlink,thecomputationworkloadisquitebigregardlessofusingtheroot-locusmethodorthefrequencycharacteristiclawamongtheorymethodswhentuningPIDparameter.Andtheprocessmathematicalmodelcanonlyreflectdynamicparameterapproximately,sothereliabilityoftheparametervaluewhichisobtainedbythetheoreticalcalculationisnotveryaccurateanditwillbeadjustedconstantlyinthescene.Therefore,engineeringparametertuningischosentoseekthePIDparameterinthedesign.Thecommonmethodofengineeringtuningaredynamiccharacteristicparameters,thestableboundarylaw,thedecaycurvelawandfieldexperiencesettingmethod,etc.IntheprocessofPIDparameters,the4:1decaycurvelawisadopted.Thestepsare:1)Intheclosedsystem,regulator'sintegraltimeissetthelargest(Ti≈∞)anddifferentialtimeTdissetzero(Td=0).Theproportionistakenthegreatvaluetoperformthegivenvalueperturbationexperimentrepeatedly,andtheproportionisreducedgraduallyuntiltherecordcurvepresentsupto4:1weaken.Thentheproportioniscalled4:1weakenproportionssandthedistancesbetweentwoneighboringwaveridge'sarecalled4:1dampedcycleTs.Intheexperiment,thelevelquantitativetestissetforthe200mm,andthenthesystemresponsecurveisobtainedandreorganized4:1decaycurve(thickredlineisshowninFig.4'Thusmeasuring:δs≈8，Ts≈2.2;2)Accordingtothefollowingformula,eachparameteroftheregulatorsisδ=0.8,δs≈6.4;Ti=0.3,Ts≈6.6;Td=0.1,Ts≈2.23)Accordingtotheseresults,regulatorparametersareset.Thenthedynamicprocessofsystemisobservedandtheparametersaremadeadjustmenttodeterminetheoptimumparameters.5MonitoringDesignFrequencyaccordingtotheprincipleofconstantpressurewatersupplysystemthedesignwaterlevelcontrolsystemofthewatertowerblockdiagramshowninFigure2,thecitywaternetworkeqwiththewaterlevelcontrollertocontroltheinjectionvalveyv1,aslongasthewaterlevelbelowthehighwatermark,thentothepoolwaterautomatically.Poolofhigh/lowwaterlevelsignaldirectlytotheplc,asahigh/lowlevelalarm.Inordertoensurecontinuityofsupply,thewaterlevelofthesmallerdistancebetweentheupperandlowerlimits.Domesticwaterandfirewaterpumpthreeshared[3],usuallyyv2solenoidvalveinastateofloss,theclosureofthefirepipenetwork,whenafireoccurs,thesolenoidvalvewasyv2electricity,waterdistributionnetworkwiththeclosureoflife,threewaterpumpsforfireuse,andmaintainhigh-pressurefirewatervalue.Aftertheliftingofthefire,threeusedomesticwaterpumpreplacedandthecycleofoperation,tomaintainconstantlowwatervalue.Eachpumpmotorcanrunfrequency,andfrequencycanberun.Whenthesmallvolumeofwaterconsumed,awaterpumpunderthecontroloftheconverterstableoperationoflargequantitiesofwatertothepumpwhenrunningatfullspeedthereisnoguaranteethatthepressureonnetworkstability,plcpressuregiventhelowerlimitoftheinvertersignalandhigh-speedsignalatthesametimeplcwasdetected,plcautomaticallyworkintheoriginalstateofthepumpfrequencyintofrequencyoperation,inordertomaintainthecontinuityofpressureatthesametimeusethenextpumpputintooperationafterstart-upconverterinordertoincreasethesupplypipenetworkpressureofwatertoensurestability;ifrunningtwopumpscannotmeettherequirementsofthepressure,thefrequencyofworkwillbefollowedbyastateintothepump-frequencyoperation,andthenpumpintoavariablefrequencyoperation;whenthewaterconsumptionreduction,thefirstperformanceinverterhasbeenworkingeffectivelyatthelowestspeedsignals,whenthepressuresignal,suchastheceilingisstillthere,plcwillbethefirstfirstrunofthepumpfrequencytoquitinordertoreducethevolumeofwatersupplied,whenthetwosignalswhentherearestill,plcandthenquitsecondfrequencyofthepumptorununtilaconstantpressurewatersupplypumpwithfrequencyconverter.Allpumpmotorsstartfromastoptoandfromthestarttostopbytheinvertertocontroltoachievesoft-startwithset,toavoidthestartofhigh-currentimpacttothepumpmotortoextendthelifeofthemotor.Atthesametime,theuseofvariablefrequencyoperationofthesystempumpswatercycleinorderto"firsttoopenthefirstgate"oftheorderofrelatedpumps,sothatboththewatersupplysystemtoensureback-upwaterpumps,waterpumpsandthesystemhavethesamerunningtimeaseffectiveinpreventingback-uppumpdeathoccurrednotlong-termphenomenonofrustandimprovethecomprehensiveutilizationrateofequipment,reducingmaintenancecosts.

ElectricalcontrolsystemmaincircuitseeFigure3.ACcontactorkm1,km3,km5werethreepumpmotorcontrolm1,m2,m3frequencyoperation;ACcontactorkm2,km4,km6respectivelycontrolm1,m2,m3ofFrequencyoperation;fr1,fr2,fr3thermalrelayforprotectionofthethreepumpmotoroverload;qs1,qs2,qs3,qs4respectively,andthreepumpmotorinvertermaincircuitisolationswitch;fu1~fu3mainlyThefusecircuit.Thesystemworksinmanualmode,plcalarmdetectiononlybytheartificialadoptionofpanelbuttonsandswitchesFromwaterpumpstostopandswitch;thesystemworksinautomaticmode,allcontrolledbytheplccompletedreporttothepolice.RSView32softwareandPanelBuilder32softwareofRockwellAutomationCompanyarerespectivelyusedtodesignmonitorscreentocompletesuchfunctionasanimatingdisplay,parametersetting,reportoutput,thecurrentcurvedisplayandhistorycurvedisplayandsoon.Andmakethecomputerandtouchscreenachievetheremoteandon-sitecontroltotheboilerliquidlevel.ThepicturescreenofsystemmonitorisshowninFig.5Themainworkofrealizingconfigurationistoestablishlevelcontrolobjectsandmakeanimatingdisplayscenes.Controlledobjectsincludeinlettingwaterflow,exportingwaterflowandthenumericalobjectoftheboilerlevel.Whenanimationconnectionisestablished,thebasicgraphicelementsandanimationcomponentlibraryarecalledintheuserwindowtoconstructconfigurationdiagram.Graphicobjectsanddataobjectsdefinedbythestatearesetinthestateofthecorrespondingattributeandanimationconnectionisdefined.Havingfinishedthedesignofthedevelopingsystem,youcanswitchtorunmodetocarryonthereal-timemonitoringtothecontrolsystemandtestconfiguration.6ConclusionsThispaperhasintroducedthecompositionandrunningofEFPTprocesscontrolsystembasedonControlLogix5550PLCcontrol,themathematicalmodelestablishingofcontrolledobjectandtheparametertuningofPID.Theuseofconfigurationsoftwareextendsthecommunicationfunction.Throughexperimentaltesting,thecontrolcurve'sovershootissmallandthetransitiontimeisshort,sothecontroleffectisquiteideal.Thisdevicebeingreliableandintuitiveissuitableforscientificresearchandteaching,andhasimportantapplicationvalueintheactualindustrialproduction.thedesignofthetowersthewaterlevelcontrolsystemusesaprogrammablelogiccontroller,inverterbasedonchangesinwaterpressuretransmitterthroughthepidtorealizesteplessspeedvariablefrequencydrivepumpmotorinthewaterchangestomaintainconstantwaterpressuremeetthewaterrequirements,soastoachievethepurposeofconstantpressurewatersupply.Intheprocesscontrolsystemdesignedtotakefullaccountoftheprincipleofloadbalancing,totake"first-in-firstout"strategyofliningup,thewaytheimplementationoftherotatingfrequencytoensurethatthebasicbalanceofthewaterusage.FrequencyConstantPressureWaterSupplytochangethesupplyofthepreviousquantitativemethodstoachieve"DAMA"principle,constantpressurewatersupplyfrequencymodethussavingenergy,easytooperate,highdegreeofautomation.基于ControlLogix5550PLC的锅炉水位控制系统摘要本文是基于EFPT过程控制设备的研究设计。实际工业领域的设计，已经模拟和相应的建模beencarried锅炉水位系统。然后适当的PID参数已整理出ControlLogix5550PLC已被用来控制整个锅炉水位系统。最后，相应的控制界面建立好了，锅炉水位也已在平安和精确控制下关键词：EFPT，PID控制，建模，锅炉水平;1引言工业锅炉水位控制的任务是维持一个动态的平衡，通过控制水的流量和蒸发，使汽包水位保持在技术水平，这是确保锅炉平安运行的必要条件和主要指标之一。锅炉水位太高会影响汽水别离的效果，但太低了，也会破坏循环周期，甚至导致锅炉爆炸。为了确保平安和高效的生产，必须严格控制锅炉水位，保持恒定或在一定的范围内变化。使用Logix5550PLC的I/O模块，控制器，把罗克韦尔自动化公司推出EFPT过程控制实验装置作为控制对象，该系统带来了在一个小型锅炉系统的精确控制，把传感器和执行器的锅炉水位用于工业生产。2系统概述该系统由EFPT过程控制设备，变频器，Logix5550PLC和一台电脑组成。EFPT过程控制设备是模拟加热和一个微型小锅炉的供水和排水系统。在工业生产中使用的传感器和驱动器在一个小型锅炉系统，实现过程控制。执行机构包括不仅仪表，还有AC逆变器，加热控制器，加热器等。该系统通过一个小型锅炉供热，供水和排水系统，是可靠和视觉模拟的工业现场。选定锅炉水位为控制变量。被控对象组成的水槽，磁力泵，锅炉和管道阀门。微硕士6SE9214-ODA40变频器作为执行机构采取Logix5550控制锅炉水位。组态软件RSView32和触摸屏PanelView1000相结合，实现实时监控。在设计上，设计简单的单回路锅炉液位值调整被选定为研究对象。该系统的组成如图1。图1锅炉水位设定值调节系统变频器作为执行机构的设计，直接接收PLC的类比I/O端口输出，并转换成使变频器频率带动扬程水泵三相电机，改变进气口，锅炉水位调整到在最后的动态平衡。和配置软件用于监控画面设计，以实现计算机和触摸屏的锅炉水位长途和现场监测。1

变频调速恒压供水系统的原理变频调速恒压供水系统主要由可编程控制器(plc)、变频器(内置pid)、压力变送器、低压电器及水泵等组成见图

1.图中m1~m3为水泵电机,p1~p3为水泵,km1~km6为电机起、停及互相切换的交流接触器。系统根本工作原理:由plc向变频器发出信号,控制水泵循环工作,当用水量大时,由plc控制全部水安装在出水管网上的压力变送器,将压力信号转换成标准的dc

0

v~10

v的模拟量信号送入变频器内的pid调节器,压力设定值与压力反响值进行比拟后,经pid计算输出一个执行值作为变频器的频率给定值,由变频器为水泵电机提供可变频率的电源,实现水泵电机的无级调速,调节管网出口处供水压力,到达恒压供水目的。为了保证水压反响信号值的准确、不失值,对反响信号设置滤波时间常数。在变频器功率范围内,图1中的电机数量可以增加,实现“一拖多机〞的优化方案。3建立被控对象的数学模型建立控制系统数学模型的主要任务之一是确定被控对象的数学模型。一般来说，建立过程控制的数学模型的根本方法有两种：机理分析与实验方法。然而，为控制对象，其结构和内部流程是非常复杂的，它是很难确定的对象，只是通过自身内部的物理过程，并解决了系统的微分方程。此外，考虑非线性因素，分析机制，用一些数学推导的近似和假设。虽然这些近似和假设有实践根底，但不能完全反映实际情况，甚至造成不可估量的影响。因此，在本设计中，选择实验方法建立被控对象的数学模型。这种造型的根底上，在实际生产过程中，也就是说，建立数学模型为控制对象，通过过程识别和参数估计的输入和输出。在这个设计中，阶跃响应曲线法用于识别过程的数学模型。20Hz的阶跃扰动输入信号施加到被控对象，并且，随着时间的变化可以映射输出的响应曲线。经过分析，控制对象的传递函数可以被定义。在实验的过程中，对象进行了屡次测试。使用RSLogix5000趋势的监测功能曲线，10多个被控对象的阶跃响应曲线已被记录。平均，稳定时间，所有的参数：TS≈821.525s，稳定值：H〔∞〕=58.5，顶峰时间：TP=394.4s超调量：σ≈29％。根据理论分析，控制对象是最有可能的二阶对象。然而，区别是非常明显的理想二阶被控对象的阶跃响应曲线和实际曲线之间。所以理想的曲线不能反响其实际的特点。据推断，控制的对象可能是第二阶控制对象，其中包括零。的尝试和错误的方法和MATLAB仿真工具，用于获取曲线的参数接近被控对象的响应曲线的平均动态参数。如图2所示可根据以下规那么做一些调整：1〕当零接近虚轴，稳定时间将更长，冲会更大，顶峰时间会更小。与零闭幕虚轴，效果更明显。2〕闭环主导根尖动态性能的影响是增加的顶峰时间，减少超调量和调整时间。非参数模型来描述受控对象。换句话说，其中约描述受控对象的阶跃响应曲线是由于控制对象的复杂性和不确定性。为了恒定供水,在水压降落时要升高变频器的输出频率,当变频器到达上限频率且一台水泵还不能满足恒压要求时,那么把变频运行的水泵切换到工频上运行,同时需要变频启动第二台或第三台水泵,直到满足供水要求。判断需不需要启动新水泵的标准就是变频器的输出频率是否到达设定的上限值。为了判断变频器工作频率达上限值的准确性,应滤去偶然的频率波动起的频率到达上限的情况。变频器控制水泵电机的每一次启动均为软启动,并规定各台水泵必须交替使用,任一台泵连续变频运行不得超过3

h,因此每次需启动新水泵时,将现行运行的水泵从变频器上切除,并换上工频电源运行,将变频器复位并用于新运行水泵的启动。三台水泵的工作循环控制是使用水泵号加1的方法实现(到3在加1时等于零),即用水泵的总数结合水泵号实现水泵的轮换工作。4安装控制器参数4.1控制算法的选择近似​​被控对象的数学模型建立后，形成一个完整的反响控制系统，可以提高开环控制系统的性能。PID是一个理想的控制律，