pscad学习5包笔记5switching and non linear elements开关和非线性元件是在仿真中根据特定的条件变化其状态这些

SwitchingandNon-LinearSimpleSelectionofSwitchingNon-LinearElementsSwitchingandnon-linearelementsarethosethatchangestateduringasimulation,accordingtocertainconditions. Thesedevicescanrangefromsimpleswitchingelements,suchaspowerelectronicdevices,(i.e.thyristors,diodes,etc.),breakersandfaults,tomorecomplexnon-linearelementsthatcanhavemanystates,suchasthearrestor.块，到更复杂的包含状态的非线性元件，比如arrestor.Inadditiontothosewithmanystates,non-lineardevicescanalsobemodeledwithanadditionalcompensatingcurrentsourcethatcanbeprogrammedtorepresentanynon-linearity.的方法可以代替任意的非线件。SimpleThereareseveraldifferentmethodsforrepresentingasimpleswitchingelementintimesimulationprograms[5]. Themostaccurateapproachistorepresentthemasideal. Thatis,possessingbothazerointheONstateandaninfiniteintheOFFstate.值为理想器件。也就是说，在ON状态时等值为0电阻，在OFF状态时等值为无Althoughthisapproachisveryaccurateandtheresultingequationseasiertosolve,thedrawbackisthatmanypossiblestatesarecreated,whichmusteachberepresentedbydifferentsystemEXAMPLE3-3-ConsiderthenetworkofFigure3-3andletthe representasimpleswitch. IfR12wereconsideredideal,thentwodifferentnetworkscouldresult,dependingonthestateofthe ThisisillustratedinFigure3-4:3-4Nowimagineforinstance,anetworkcontainingmanyswitches(asina48-pulseGraetz ),agreatnumberofdifferentnetworkconfigurationswouldresultifidealswitchingelementswere基于实际，考虑一个包含众多开关器件的网络（48Graetz），InEMTDC,simpleswitchingdevicesarerepresentedasavariableresistor,possessinganONandanOFF Althoughthistypeofrepresentationinvolvesanapproximationofboththezero(ON)andaninfinite(OFF)ofanidealswitch,itisadvantageousinthatthesamecircuitstructurecanbemaintained,andtheelectricnetworkwillnotneedtobesplitintomultiplenetworks,asaresultofeachswitchingevent.在EMTDC中，简单的开关装置被等值为变化的电阻，有开电阻和关断电阻两种状态。虽然这种等值近似于等值为0电阻和无穷大电阻，但每次开关发生SelectionofSwitchingInEMTDC,thereareprovisionstoallowforzeros(seeIdealBranches). However,whiletheidealbranchalgorithmisveryreliableandgivesthetheoreticalresult,itdoesinvolveextracomputationstoavoidadivisionbyzerowheninvertingtheconductancematrix. Thus,byinsertingareasonabletypicalofaclosedswitch,youcanimprovethesimulationspeed. non-zerovaluelargerthan0.0005shouldbeusedwhereverEMTDC，0G0值可以提真速度。任意的非零且大于0.0005欧姆的值在任何可能的情况下Selectionoftheswitchingsisimportant: Iftheistoosmall,itsvaluemaydominatetheconductancematrixandtheotherdiagonalelementscouldbeovershadowed Thiswillcauseitseffectiveconductancematrixinversiontobeinaccurate. ThedefaultON valueinPSCADis0.001. threshold,underwhichtheIdealBranchalgorithmwillbeinvoked,is0.0005.Branch算启动.TheseimportantfactorsshouldbekeptinmindwhenchoosingaswitchCircuitlossesshouldnotbesignificantlyCircuitdamshouldnotbereducedsignificantly: Duetothesolutionbeinginstepsofdiscretetimeintervals,numericalerrormaycreatelessdaminthecircuitthanexpectedinreality. Asmallamountofadditionalfromaclosedswitch,ifjudiciouslyselected,maycompensatethenegativedameffectinthesolutionmethod.实际电路更少的阻尼。明智地为关断的开关选择较少增加电阻，或以补偿Non-LinearTherearetwomethodsforrepresentingnon-linearelementsin ThePiecewiseLinear,andtheCompensatingCurrentSource Eachmethodpossessesitsownprosandcons,andtheselectionofeitherissimplyuptotheuser.ThePiecewiseLinearAlthoughanon-lineardevicemaypossessacharacteristicthatiscontinuous,controllingthedeviceascontinuousisnot Continuallychangingbranchconductancecanaconductancematrixinversioneverytimestep,resultinginasubstantiallylongerruntimeinlargenetworks.虽然非线件可能拥有续的特性曲线，但不推荐把它当做连续的来管Figure3-5-(a)Continuous (b)PiecewiselinearconductanceInordertominimizeruntime,aPiecewiseLinearapproximationmethodasillustratedinFigure3-5(a)and(b)isused. piecewiselinearcurvewillintroduceseveral'stateranges'intothenon-linearcharacteristic,dramaticallyreducingtheamountofmatrixinversionsperrun,yetmaintainingreasonableaccuracy.为了减小仿真时间，使用了图3-5说明的一种分段线性化的方法。分段线性化InEMTDC,non-lineardevices,suchastheArrestorcomponent,utilizethePiecewiseLineartechnique.EMTDCArrestorCompensatingCurrentSourceAnothermethodtomodelinganon-linearcharacteristicisthroughtheuseofacompensatingcurrentsource. ThistechniqueisplishedbyaddinganequivalentNortoncurrentsourceinparallelwiththedeviceitself,therebyallowingfortheadditionorsubtractionofextracurrentatthedevicebranchnodes.Figure3-6-CompensatingCurrentSourceMethodCaremustbetakenwhenusingthismethodtomodeldevicenon-asanopencircuittovoltagesinthepresenttimethereby Moreoftenthannot,thecompensatingsourceasanopencircuittovoltagesinthepresenttimethereby Thiscreatede-stabilizationproblemsinthesimulation[5]. circumventthisproblem,thecompensatingcurrentsourceshouldbeusedinconjunctionwithacorrectionsou