Page 25 - 2023年第54卷第8期
P. 25

NewunderstandingofThoma’sformulaforcriticalstablesectionof
                                           surgechamberinhydropowerstation

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                                  ZHANGJian ,YAOTianyu,WANGQinyi,QIUWeixin,
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                                                CHENLong,CHENSheng
                                (1.TheNationalKeyLaboratoryofWaterDisasterPrevention,Nanjing210098,China;
                           2.CollegeofWaterConservancyandHydropowerEngineeringHohaiUniversity,Nanjing210098,China)
                  Abstract:Thoma’sformulaforcriticalstablesectionisgenerallyregardedasasignificantbasisforjudgingtheop
                  erationalstabilityofthewaterconveyanceandpowergenerationsystem ofhydropowerstationwithsurgechamber.
                  Thispresentstudyfirstlytheoreticallydemonstratesthesystemcannotbestablewithboththerigidbodyassumption
                  andconstantoutputregulation.TheThoma ’sformulaforcriticalstablesectioncouldbeobtainedbecausethewater
                  inertiaofthepenstocksandthetailracetunnelisneglectedinthederivation,whichisthekeyfactortothesystem
                  instability.Furthermore ,itisprovedtheoreticallythatthehydraulicsystemmaynotrunstablyundertheconstant
                  outputregulationmodefortheactualelasticwater.Meanwhile ,thestabilityofthewaterconveyanceandpower
                  generationsystemofthehydropowerstationwithsurgechambermainlydependsonthewaterhammerreflectioncoef
                  ficientoftheupstreamanddownstreamsideoftheturbine.Thefrictionofthediversiontunnel,penstockandtail
                  racetunnelareallbeneficialtostability ,whilethesizeofthesurgechamberhasrelativelylittleeffectonstability.
                  Underconstantoutputregulationmode ,thewaterconveyanceandpowergenerationsystemofthehydropowerstation
                  withsurgechambermustbeunstablenomatteradoptingtherigidwaterhypothesisoractualelasticwater.Anunstable
                  systemcouldnotexiststablesection ,andThoma’sformulaforcriticalstablesectionisnotvalidintheory.
                  Keywords:hydropowerstation;surgechamber;stability;Thoma’sformula;waterhammerreflectioncoefficient

                                                                                    (责任编辑:李福田)




              (上接第 897页)
                      Probabilisticforecastingoffloodprocessesbasedonhybriddeeplearningmodels

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                            CUIZhen,GUOShenglian,WANGJun ,ZHANGJun,ZHOUYanlai
                    (1.StateKeyLaboratoryofWaterResourcesandHydropowerEngineeringScience,WuhanUniversity,Wuhan 430072,China;
                               2.HydrologyBureau,YangtzeRiverWaterResourcesCommission,Wuhan 430010,China)
                  Abstract:Thetraditionalartificialneuralnetworkmodelcannotquantifytheuncertaintyoffloodforecastingand
                  isunabletoconsiderthetemporalcorrelationoffloodprocessforecastinginmulti - timecontinuousforecasting.In
                  thispaper ,aXAJ - LSTM- EDE - MDNmodelisconstructedbyfusingtheXinanjiang(XAJ)model,thelong
                  short - termmemory(XAJ - LSTM- EDE)neuralnetworkbasedontheexogenousinputencoder - decoderstructure,
                  andthemixturedensitynetwork(MDN)toachieveprobabilisticforecastingofthefloodprocess.Themodeltrans
                  formsthepointestimatesgeneratedbythedecodingprocessintotheestimatesofconditionalprobabilitydistribu
                  tionswhileconsideringthetemporalcorrelationoftheforecastedflood.Thelossfunctionisfurtherestablishedu
                  singthemaximumlikelihoodestimationmethod ,andthemodelparametersaretrainedbyanadaptivemomentes
                  timationalgorithm.ThestudyresultsinthetworiverbasinsofLushuiandJianxishowthatthemodelcaneffective
                  lyreflecttheuncertaintyoftheforecastfloodwithoutreducingtheforecastaccuracyoftheXAJ - LSTM- EDEmod
                  el ,andobtainreasonableandreliableconfidenceintervalsandexcellentprobabilisticforecastperformance.It
                  providesmoreriskinformationfordecision - makingsuchasreservoirfloodcontrolandscheduling ,andalsopro
                  videsareferenceforstudyingtheapplicationofdeeplearninginprobabilisticfloodforecasting.
                  Keywords: probabilisticforecasting; uncertaintyanalysis; longand short -term memory neuralnetworks;
                  encoder - decoderstructure;mixturedensitynetworks

                                                                                    (责任编辑:耿庆斋)

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