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时间:2019-07-16
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1、Fall2011:ECE4510LectureNote(VII):PerformanceIndicesforEstimatingLoadMargintoVoltageInstabilityProf.Hsiao-DongChiangSchoolofElectricalandComputerEngineeringCornellUniversity,Ithaca,NY14853WhilecontinuationpowerflowmethodscangenerateP-VandQ-Vcurvesinareliablemanner,theymaybe
2、tooslowforon-lineapplications.Toovercomethisdifficulty,anumberofperformanceindicesintendedtomeasuretheseverityofthe(static)voltagestabilityproblemhavebeenproposedinliterature.TheseindicesintendtoprovidesomemeasureofhowfarthesystemisawayfromthepointatwhichthesystemJacobianb
3、ecomessingular.Amongthem,thefollow-ingindicesreceiveconsiderableattentionofdifferentdegree:•minimumsingularvalue•conditionnumberofthesystemJacobian•angulardistancebetweenthecurrentstableequilibriumpointandtheclosestunstableequilibriumpointinaEuclideansense.•energydistanceb
4、etweenthecurrentstableequilibriumpointandtheclosestunstableequilibriumpointusinganenergyfunction.Theseperformanceindicescanbeviewedasprovidingsomemeasurerelativetothedis-tancebetweenthecurrentoperatingpointandthebifurcationpoint.Theseperformanceindices,however,aredefinedin
5、thestatespaceofpowersystemmodelsinsteadofintheparameterspace.Thus,theseperformanceindicescannotdirectlyanswerquestionssuchas:“Canthesystemwith-standa100MVarincreaseonbus11?”or:“Canthesystemwithstandasimultaneousincreaseof70MWonbus2and50Mvarsonbus6?".Onebasicrequirementforu
6、sefulperformanceindicesisfortheirfunctiontoreflectthedegreeofseverityofthedirectmechanismleadingtheunderlyingsystemtowardanundesiredstage.Inthecontextofvoltageinstabilityinpowersystems,ausefulperformanceindexmusthavetheabilitytomeasuretheamountofloadincreasethatthesystemca
7、ntoleratebeforeinsta-bility(whentheunderlyingmechanismofinstabilityisduetoloadvariations),orassesswhetherthesystemcansustainacontingencywithoutinstability(whentheunderlyingmechanismofinstabilityiscausedbyacontingency)andmeasuretheseverityofthecontingency.Inordertoprovidead
8、irectrelationshipbetweenitsvalueandtheamountofloadincreasesthatthesystemcanwithstandbefor
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