文档名：网侧故障下光伏直流并网系统不平衡功率快速平抑方法
摘要：网侧故障下,光伏直流并网系统的并网变流器将根据电网电压变化实时控制输出功率,而直流侧光伏单元需接收系统功率指令后控制有功输出,两者间无法实现有功功率的快速平衡,导致直流电压持续偏移.传统方法通过投入耗能装置消耗盈余有功功率,以抑制直流电压抬升,但投资成本高.为此,该文提出一种网侧故障下系统不平衡功率快速平抑方法,在分析故障期间电网电压幅值变化趋势基础上,构建并网变流器内部计算电压变化轨迹算式.该方法利用故障初期内部计算电压数据,计算带权邻近度以求解电压变化轨迹算式关键项系数,进而求得所需系统功率指令.所提方法的优点在于有效地缩短了盈余功率持续时间,减少了对耗能装置的依赖,并且易于实现.仿真结果表明,所提方法可维持直流电压在安全范围内,为系统低电压穿越提供可靠保障.
Abstract：Inthecaseofgrid-sidefaults,thegrid-connectedconverter(GCC)ofthephotovoltaicDCgrid-connectedsystem(PV-DCGS)shouldreducetheoutputpowerinrealtimebasedonthevariationsofACgridvoltage.Atthesametime,thePVsarerequiredtoreduceactivepoweraccordingtothepowercommandissuedbythecentralcontroller.Duringthelowvoltageridethrough(LVRT)period,duetothedifferenceincontrolresponsespeedbetweenGCCandPVs,andthedelayinsystemcommandprocessing,theunbalancedpowerwithinPV-DCGSwilloccur,resultinginDCbusvoltagedeviation.Traditionally,energy-dissipatingdevicesareusedtoabsorbtheexcesspowertosuppresstherisingmagnitudeoftheDCbusvoltage.However,theinvestmentcostandmaintenancecomplexitywillincreaseaccordingly.Toaddresstheseissues,thispaperproposesafastmethodforreducingtheunbalancedpowerofPV-DCGSundergrid-sidefaults,whichcanlimitthedeviationofDCbusvoltagetoanacceptablerange.First,thestructureofPV-DCGSisintroducedandtheinfluenceofthevariationofthesystempowercommandontheDCbusvoltageisanalyzed.Second,thevariationcharacteristicoftheinternalcalculationvoltageofGCCduringLVRTisrevealed.Then,thevoltagevariationtrajectoryformulaisconstructedandthevariationcharacteristicsofthekeycoefficientsoftheconstructedformulaareanalyzed.Third,theweightedproximityisintroducedtocalculatethekeycoefficientsoftheconstructedformula.Theexactvoltagevariationtrajectoryformulacanbeobtainedbythecalculatedkeycoefficients.Finally,theexpectedpowercommandcanbeobtainedbyputtingappropriatelengthofvoltagedataintotheconstructedformula,andeffectiveDCbusvoltagesuppressioncanbeachieved.ThesimulationmodelofthePV-DCGSisbuiltonthePSCAD/EMTDCelectromagneticsimulationplatform,whichverifiesthefeasibilityandeffectivenessoftheproposedmethod.Simulationsondifferenttypesofshort-circuitfaultsareperformed.ThecomparisonofthevoltagevariationtrendbetweenthesimulationsystemandtheactualpowersystemshowsthatthevariationtrendoftheinternalcalculationvoltageofGCCinthesimulationsystemissimilartothatoftheactualpowersystem.Inordertoquicklycalculatethekeycoefficientsoftheconstructedvoltageformula,thedatawindowlengthshouldbeselectedappropriately.Thesimulationresultsshowthatwhenthedatawindowlengthisselectedbetween5～20ms,thecalculationerrorofkeycoefficientsislessthan5%.Consideringthereliabilityofcalculationresults,thedatawindowlengthofthispaperisselectedat20ms.Undertheselecteddatawindowlength,differenttransitionresistancesofACgridfaultsaretested.Theresultsshowthatthekeycoefficientsoftheconstructedvoltageformulacanbecalculatedreliably,andthecalculationerrorofthedominanttermissmallerthan10%.Tofurtherillustratetheeffectivenessoftheproposedcalculationmethodforkeycoefficients,thesimulationwaveformsofthree-phasesymmetricalfaultarecarriedout.Theresultsshowthatthenumericalresultsoftheconstructedvoltageformulaaresimilartothoseofthesimulationwaveform,thecalculationerroriswithin5%.Comparedwiththetraditionalcentralizedcontrolmethod,theproposedmethodcaneffectivelysuppressthepeakvalueoftheDCbusvoltagetotheacceptablerange(≤1.05(pu))duringLVRTperiod.Inconclusion,theproposedmethodcanquicklyandreliablycalculatethesystempowercommandrequiredforLVRTbyusingthevoltagedataoftheexternalACsystemattheinitialfaultstage,whichshortenstheexcesspoweranditsduration,resultinginthereductionofDCvoltagedeviation.Withtheproposedmethod,theGCCandPVsarefreefromoperatingatunexpectedDCovervoltagerange(＞1.05(pu)).Inaddition,theproposedmethodweakensthedependenceonadditionalenergy-dissipatingequipmentandreducestheinvestmentcost.
作者：李俊涛 贾科 董学正 毕天姝Author：LiJuntao JiaKe DongXuezheng BiTianshu
作者单位：新能源电力系统全国重点实验室(华北电力大学)北京102206
刊名：电工技术学报
Journal：TransactionsofChinaElectrotechnicalSociety
年，卷(期)：2024, 39(5)
分类号：TM615
关键词：光伏直流并网系统 低电压穿越 电压变化轨迹 功率指令 带权邻近度
Keywords：PhotovoltaicDCgrid-connectedsystem(PV-DCGS) lowvoltageridethrough(LVRT) voltagevariationtrajectory powercommand weightedproximity
机标分类号：TM712TM46TM614
在线出版日期：2024年3月19日
基金项目：国家自然科学基金网侧故障下光伏直流并网系统不平衡功率快速平抑方法[
期刊论文] 电工技术学报--2024, 39(5)李俊涛 贾科 董学正 毕天姝网侧故障下,光伏直流并网系统的并网变流器将根据电网电压变化实时控制输出功率,而直流侧光伏单元需接收系统功率指令后控制有功输出,两者间无法实现有功功率的快速平衡,导致直流电压持续偏移.传统方法通过投入耗能装置...参考文献和引证文献
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网侧故障下光伏直流并网系统不平衡功率快速平抑方法 A Fast Method for Suppressing Unbalanced Power in Photovoltaic DC Grid-Connected System under Grid-Side Faults
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