基于MMC的多端柔性直流输电系统改进下垂控制策略

基于MMC的多端柔性直流输电系统改进下垂控制策略一、本文概述Overviewofthisarticle随着可再生能源的大规模开发和利用，多端柔性直流输电系统（Multi-TerminalVoltageSourceConverterbasedHighVoltageDirectCurrent,MMC-MTDC）在电力系统中扮演着日益重要的角色。MMC-MTDC系统以其独特的优势，如电压源型换流器（VoltageSourceConverter,VSC）的灵活控制、易于扩展和集成多种可再生能源等，正逐渐成为连接电网和分布式能源的主要方式。然而，如何保证MMC-MTDC系统的稳定运行，特别是在系统受到扰动或故障时，仍能保持电压和功率的稳定，是当前研究的关键问题。Withthelarge-scaledevelopmentandutilizationofrenewableenergy,MultiTerminalVoltageSourceConverterbasedHighVoltageDirectCurrent(MMCMTDC)playsanincreasinglyimportantroleinthepowersystem.TheMMC-MTDCsystemisgraduallybecomingthemainwaytoconnectthepowergridanddistributedenergyduetoitsuniqueadvantages,suchasflexiblecontrolofVoltageSourceConverter(VSC),easyscalability,andintegrationofmultiplerenewableenergysources.However,howtoensurethestableoperationoftheMMC-MTDCsystem,especiallyintheeventofdisturbancesorfaults,whilestillmaintainingvoltageandpowerstability,isakeyissueincurrentresearch.下垂控制策略作为一种常用的分布式电源控制策略，因其具有简单、易实现和无需通信等优点，在MMC-MTDC系统中得到了广泛的应用。然而，传统的下垂控制策略在面对系统参数摄动、线路阻抗变化以及多换流器间的交互影响等问题时，其控制性能往往难以保证。因此，对下垂控制策略进行改进，以提高MMC-MTDC系统的稳定性和鲁棒性，具有重要的理论意义和实践价值。Thedroopcontrolstrategy,asacommonlyuseddistributedpowercontrolstrategy,hasbeenwidelyusedinMMC-MTDCsystemsduetoitsadvantagesofsimplicity,easeofimplementation,andnoneedforcommunication.However,traditionaldroopcontrolstrategiesoftenstruggletoensuretheircontrolperformancewhenfacedwithsystemparameterperturbations,lineimpedancechanges,andtheinteractioneffectsbetweenmultipleconverters.Therefore,improvingthedroopcontrolstrategytoenhancethestabilityandrobustnessoftheMMC-MTDCsystemhasimportanttheoreticalsignificanceandpracticalvalue.本文旨在研究基于MMC的多端柔性直流输电系统改进下垂控制策略。将深入分析传统下垂控制策略的原理及其在MMC-MTDC系统中存在的问题；将提出一种新型的下垂控制策略，通过引入自适应参数调整、虚拟阻抗等改进措施，以提高系统的动态响应能力和稳定性；将通过仿真和实验验证所提改进下垂控制策略的有效性和优越性。本文的研究结果将为MMC-MTDC系统的稳定控制和优化运行提供新的思路和方法。ThisarticleaimstostudytheimproveddroopcontrolstrategyformultiterminalflexibleDCtransmissionsystemsbasedonMMC.Wewillconductanin-depthanalysisoftheprinciplesoftraditionaldroopcontrolstrategiesandtheproblemstheyfaceintheMMC-MTDCsystem;Anewtypeofdroopcontrolstrategywillbeproposedtoimprovethedynamicresponseandstabilityofthesystembyintroducingadaptiveparameteradjustment,virtualimpedanceandotherimprovementmeasures;Theeffectivenessandsuperiorityoftheproposedimproveddroopcontrolstrategywillbeverifiedthroughsimulationandexperimentation.TheresearchresultsofthisarticlewillprovidenewideasandmethodsforthestablecontrolandoptimizedoperationoftheMMC-MTDCsystem.二、多端柔性直流输电系统概述OverviewofMultiterminalFlexibleDCTransmissionSystem多端柔性直流输电系统（Multi-TerminalVoltageSourceConverterbasedHighVoltageDirectCurrent，简称MMC-MTDC）是近年来在电力系统中兴起的一种新型输电技术。与传统的两端直流输电系统相比，多端直流输电系统具有更高的灵活性和可扩展性，能够更好地适应复杂的电网结构和多变的电力需求。MultiTerminalVoltageSourceConverterbasedHighVoltageDirectCurrent(MMCMTDC)isanewtransmissiontechnologythathasemergedinpowersystemsinrecentyears.ComparedwithtraditionaltwoterminalDCtransmissionsystems,multiterminalDCtransmissionsystemshavehigherflexibilityandscalability,andcanbetteradapttocomplexpowergridstructuresandchangingpowerdemands.多端柔性直流输电系统主要由多个电压源型换流器（VoltageSourceConverter，VSC）和直流输电线路组成。每个换流器都通过变压器与相应的交流系统相连，而各换流器之间则通过直流线路相互连接。在这种结构中，每个换流器都可以独立地控制其有功功率和无功功率的注入或吸收，从而实现对整个系统的灵活控制。ThemultiterminalflexibleDCtransmissionsystemmainlyconsistsofmultipleVoltageSourceConverters(VSCs)andDCtransmissionlines.EachconverterisconnectedtothecorrespondingACsystemthroughatransformer,andtheconvertersareconnectedtoeachotherthroughDClines.Inthisstructure,eachconvertercanindependentlycontroltheinjectionorabsorptionofitsactiveandreactivepower,therebyachievingflexiblecontroloftheentiresystem.多端柔性直流输电系统的核心优势在于其下垂控制策略。下垂控制是一种基于换流器输出电压和电流的控制方法，它通过调整换流器的输出电压和电流来平衡系统中的功率流动。在多端系统中，下垂控制策略需要考虑到多个换流器之间的相互作用和影响，因此需要进行相应的改进和优化。ThecoreadvantageofmultiterminalflexibleDCtransmissionsystemliesinitsdroopcontrolstrategy.Sagcontrolisacontrolmethodbasedontheoutputvoltageandcurrentoftheconverter,whichbalancesthepowerflowinthesystembyadjustingtheoutputvoltageandcurrentoftheconverter.Inmultiterminalsystems,thedroopcontrolstrategyneedstoconsidertheinteractionandinfluencebetweenmultipleinverters,socorrespondingimprovementsandoptimizationsareneeded.改进的下垂控制策略旨在提高多端柔性直流输电系统的稳定性、效率和可靠性。通过优化下垂曲线的形状和参数，可以更好地平衡系统中的功率分布，减少换流器之间的功率振荡和环流，从而提高系统的整体性能。改进的下垂控制策略还需要考虑到系统的动态特性和故障情况下的应对策略，以确保系统在各种运行条件下都能保持稳定和可靠。Theimproveddroopcontrolstrategyaimstoimprovethestability,efficiency,andreliabilityofmultiterminalflexibleDCtransmissionsystems.Byoptimizingtheshapeandparametersofthesagcurve,itispossibletobetterbalancethepowerdistributioninthesystem,reducepoweroscillationsandcirculatingcurrentsbetweenconverters,andthusimprovetheoverallperformanceofthesystem.Theimproveddroopcontrolstrategyalsoneedstoconsiderthedynamiccharacteristicsofthesystemandtheresponsestrategiesincaseoffaults,toensurethatthesystemcanmaintainstabilityandreliabilityundervariousoperatingconditions.多端柔性直流输电系统作为一种新型的输电技术，在电力系统中具有重要的应用前景。而改进的下垂控制策略则是实现其高性能运行的关键之一。未来随着技术的进步和研究的深入，多端柔性直流输电系统及其下垂控制策略将在电力系统中发挥更加重要的作用。MultiterminalflexibleDCtransmissionsystem,asanewtypeoftransmissiontechnology,hasimportantapplicationprospectsinpowersystems.Theimproveddroopcontrolstrategyisoneofthekeyfactorsinachievinghigh-performanceoperation.Inthefuture,withtheadvancementoftechnologyandthedeepeningofresearch,multiterminalflexibleDCtransmissionsystemsandtheirdroopcontrolstrategieswillplayamoreimportantroleinthepowersystem.三、传统下垂控制策略的局限性分析Analysisofthelimitationsoftraditionaldroopcontrolstrategies多端柔性直流输电系统（MMC-MTDC）在新能源接入、区域电网互联等领域具有广泛的应用前景。下垂控制策略作为该系统的一种基本控制方法，通过模拟同步发电机的下垂特性，实现各换流器之间的有功功率和无功功率的自动分配。然而，随着系统规模和复杂性的增加，传统下垂控制策略的一些局限性逐渐显现。Multiterminalflexibledirectcurrenttransmissionsystem(MMCMTDC)hasbroadapplicationprospectsinfieldssuchasnewenergyaccessandregionalpowergridinterconnection.Asabasiccontrolmethodofthesystem,thedroopcontrolstrategysimulatesthedroopcharacteristicsofthesynchronousgeneratortoachieveautomaticallocationofactiveandreactivepowerbetweenvariousconverters.However,asthescaleandcomplexityofthesystemincrease,somelimitationsoftraditionaldroopcontrolstrategiesgraduallybecomeapparent.传统下垂控制策略在参数整定方面存在困难。下垂系数的选择对系统的稳定性和功率分配精度有着直接影响。若下垂系数设置不当，可能导致系统振荡或功率分配不均。随着系统运行条件的变化，下垂系数也需要进行动态调整，这对控制系统的设计提出了更高的要求。Traditionaldroopcontrolstrategiesfacedifficultiesinparametertuning.Theselectionofdroopcoefficienthasadirectimpactonthestabilityandpowerallocationaccuracyofthesystem.Ifthedroopcoefficientisnotsetproperly,itmayleadtosystemoscillationorunevenpowerdistribution.Astheoperatingconditionsofthesystemchange,thedroopcoefficientalsoneedstobedynamicallyadjusted,whichputshigherrequirementsonthedesignofthecontrolsystem.传统下垂控制策略在应对故障和扰动方面表现不足。当系统发生故障或受到外部扰动时，下垂控制可能无法快速准确地调整功率分配，导致系统失稳或设备损坏。由于多端柔性直流输电系统具有多个换流站和复杂的拓扑结构，故障的传播和扩散速度较快，这对系统的保护和恢复提出了挑战。Thetraditionaldroopcontrolstrategyperformspoorlyindealingwithfaultsanddisturbances.Whenthesystemmalfunctionsorissubjectedtoexternaldisturbances,droopcontrolmaynotbeabletoquicklyandaccuratelyadjustpowerallocation,resultinginsysteminstabilityorequipmentdamage.DuetothemultipleconverterstationsandcomplextopologyofmultiterminalflexibleDCtransmissionsystems,thepropagationanddiffusionspeedoffaultsisfast,whichposeschallengestotheprotectionandrecoveryofthesystem.传统下垂控制策略在优化调度和节能降耗方面的潜力有限。在新能源接入和区域电网互联的背景下，多端柔性直流输电系统需要实现更加灵活和高效的功率调度。然而，传统下垂控制策略在优化调度方面缺乏有效手段，难以实现系统经济运行和节能降耗的目标。Thetraditionaldroopcontrolstrategyhaslimitedpotentialinoptimizingschedulingandreducingenergyconsumption.Inthecontextofnewenergyintegrationandregionalpowergridinterconnection,multiterminalflexibleDCtransmissionsystemsneedtoachievemoreflexibleandefficientpowerscheduling.However,traditionaldroopcontrolstrategieslackeffectivemeansinoptimizingscheduling,makingitdifficulttoachievethegoalsofsystemeconomicoperationandenergyconservationandconsumptionreduction.传统下垂控制策略在多端柔性直流输电系统中的应用存在一定的局限性。为了克服这些局限性，需要研究并开发更加先进和高效的控制策略，以满足系统规模扩大、复杂性增加以及新能源接入等需求。TheapplicationoftraditionaldroopcontrolstrategiesinmultiterminalflexibleDCtransmissionsystemshascertainlimitations.Toovercometheselimitations,itisnecessarytoresearchanddevelopmoreadvancedandefficientcontrolstrategiestomeettheneedsofsystemscaleexpansion,increasedcomplexity,andnewenergyintegration.四、改进下垂控制策略的设计与实施Designandimplementationofimproveddroopcontrolstrategy随着多端柔性直流输电系统（MMC-MTDC）在电网中的广泛应用，如何优化其控制策略以提高系统的稳定性、效率和响应速度成为了研究的热点。下垂控制策略作为其中的一种基本控制方法，虽然具有简单易行、无需通信等优点，但在面对多端系统时，其局限性也逐渐显现。因此，本文提出了一种改进的下垂控制策略，旨在提升MMC-MTDC系统的整体性能。WiththewidespreadapplicationofMultiTerminalFlexibleDirectCurrent(MMCMTDC)transmissionsystemsinpowergrids,howtooptimizetheircontrolstrategiestoimprovesystemstability,efficiency,andresponsespeedhasbecomeahotresearchtopic.Asoneofthebasiccontrolmethods,thedroopcontrolstrategyhastheadvantagesofsimplicityandnoneedforcommunication,butitslimitationsgraduallybecomeapparentwhenfacingmultiterminalsystems.Therefore,thisarticleproposesanimproveddroopcontrolstrategyaimedatimprovingtheoverallperformanceoftheMMC-MTDCsystem.我们对传统下垂控制策略进行了深入分析，明确了其在多端系统中的不足，如电压波动大、功率分配不均等问题。针对这些问题，我们设计了一种基于虚拟阻抗和电压下垂系数的改进下垂控制策略。Wehaveconductedanin-depthanalysisoftraditionaldroopcontrolstrategiesandidentifiedtheirshortcomingsinmultiterminalsystems,suchaslargevoltagefluctuationsandunevenpowerdistribution.Wehavedesignedanimproveddroopcontrolstrategybasedonvirtualimpedanceandvoltagedroopcoefficienttoaddresstheseissues.该策略的核心思想是通过引入虚拟阻抗来减小系统的电压波动，同时优化电压下垂系数，以实现更为精准的功率分配。虚拟阻抗的设计考虑了系统的动态特性和稳定性要求，通过合理设置阻抗值，可以在保证系统稳定运行的同时，有效减小电压波动。Thecoreideaofthisstrategyistoreducevoltagefluctuationsinthesystembyintroducingvirtualimpedance,whileoptimizingthevoltagesagcoefficienttoachievemoreaccuratepowerallocation.Thedesignofvirtualimpedancetakesintoaccountthedynamiccharacteristicsandstabilityrequirementsofthesystem.Bysettingimpedancevaluesreasonably,voltagefluctuationscanbeeffectivelyreducedwhileensuringstablesystemoperation.在实施阶段，我们首先将设计的改进下垂控制策略嵌入到MMC-MTDC系统的控制器中。通过调整控制器的参数，使得系统能够按照新的控制策略进行运行。Intheimplementationphase,wefirstembedthedesignedimproveddroopcontrolstrategyintothecontrolleroftheMMC-MTDCsystem.Byadjustingtheparametersofthecontroller,thesystemcanoperateaccordingtothenewcontrolstrategy.为了确保新策略的有效性，我们进行了大量的仿真实验和现场测试。仿真实验结果表明，改进后的下垂控制策略在减小电压波动、优化功率分配等方面均取得了显著的效果。现场测试也验证了新策略在实际应用中的可行性和优越性。Toensuretheeffectivenessofthenewstrategy,weconductedextensivesimulationexperimentsandon-sitetesting.Thesimulationexperimentresultsshowthattheimproveddroopcontrolstrategyhasachievedsignificanteffectsinreducingvoltagefluctuationsandoptimizingpowerallocation.Onsitetestingalsoverifiedthefeasibilityandsuperiorityofthenewstrategyinpracticalapplications.本文提出的基于虚拟阻抗和电压下垂系数的改进下垂控制策略，为MMC-MTDC系统提供了一种更为有效的控制方法。通过实施这一策略，不仅可以提高系统的稳定性和效率，还可以优化功率分配，实现更为均衡的能源利用。未来，我们将进一步深入研究该策略在其他类型直流输电系统中的应用，以期为我国电网的智能化和高效化提供更为强大的技术支持。TheimproveddroopcontrolstrategybasedonvirtualimpedanceandvoltagedroopcoefficientproposedinthisarticleprovidesamoreeffectivecontrolmethodforMMC-MTDCsystems.Byimplementingthisstrategy,notonlycanthestabilityandefficiencyofthesystembeimproved,butpowerallocationcanalsobeoptimizedtoachievemorebalancedenergyutilization.Inthefuture,wewillfurtherinvestigatetheapplicationofthisstrategyinothertypesofDCtransmissionsystems,inordertoprovidestrongertechnicalsupportfortheintelligenceandefficiencyofChina'spowergrid.五、实验结果与分析Experimentalresultsandanalysis为了验证提出的基于MMC的多端柔性直流输电系统改进下垂控制策略的有效性，我们进行了详细的仿真实验和实际运行测试。InordertoverifytheeffectivenessoftheproposedimproveddroopcontrolstrategyformultiterminalflexibleDCtransmissionsystemsbasedonMMC,weconducteddetailedsimulationexperimentsandactualoperationaltests.在仿真环境中，我们构建了一个多端柔性直流输电系统模型，并分别应用了传统的下垂控制策略和我们的改进下垂控制策略。仿真结果表明，在相同的运行条件下，采用改进下垂控制策略的系统在动态响应、电压波动抑制和功率分配等方面均表现出优越的性能。特别是在系统受到扰动时，改进策略能够更快地恢复稳定，并减少对其他端口的影响。Inthesimulationenvironment,weconstructedamultiterminalflexibleDCtransmissionsystemmodelandappliedbothtraditionaldroopcontrolstrategiesandourimproveddroopcontrolstrategies.Thesimulationresultsshowthatunderthesameoperatingconditions,thesystemusingtheimproveddroopcontrolstrategyexhibitssuperiorperformanceindynamicresponse,voltagefluctuationsuppression,andpowerallocation.Especiallywhenthesystemisdisturbed,theimprovementstrategycanrestorestabilityfasterandreducetheimpactonotherports.为了进一步验证改进下垂控制策略在实际应用中的效果，我们在一个实际运行的多端柔性直流输电系统上进行了测试。测试期间，系统经历了多种不同的工况和扰动，包括负载突变、线路故障等。实际运行数据显示，采用改进下垂控制策略的系统在应对这些工况和扰动时，能够保持更稳定的运行状态，同时提高了系统的效率和可靠性。Inordertofurtherverifytheeffectivenessoftheimproveddroopcontrolstrategyinpracticalapplications,weconductedtestsonamultiterminalflexibleDCtransmissionsysteminoperation.Duringthetestingperiod,thesystemexperiencedvariousoperatingconditionsanddisturbances,includingsuddenloadchanges,linefaults,etc.Actualoperatingdatashowsthatthesystemusingimproveddroopcontrolstrategycanmaintainamorestableoperatingstatewhendealingwiththeseworkingconditionsanddisturbances,whileimprovingtheefficiencyandreliabilityofthesystem.通过对比仿真实验和实际运行测试的结果，我们可以得出以下改进下垂控制策略在动态响应和电压波动抑制方面明显优于传统策略；改进策略能够更好地实现功率的均衡分配，减少系统内部的功率振荡；在实际应用中，改进策略表现出了更强的鲁棒性和适应性，能够应对各种复杂的工况和扰动。Bycomparingtheresultsofsimulationexperimentsandactualoperationaltests,wecanconcludethattheimproveddroopcontrolstrategyissignificantlybetterthantraditionalstrategiesintermsofdynamicresponseandvoltagefluctuationsuppression;Improvingstrategiescanbetterachievebalancedpowerallocationandreducepoweroscillationswithinthesystem;Inpracticalapplications,theimprovementstrategyexhibitsstrongerrobustnessandadaptability,andcancopewithvariouscomplexworkingconditionsanddisturbances.我们提出的基于MMC的多端柔性直流输电系统改进下垂控制策略在理论分析和实际应用中都取得了良好的效果。这为多端柔性直流输电系统的优化设计和稳定运行提供了新的思路和方法。TheimproveddroopcontrolstrategybasedonMMCformultiterminalflexibleDCtransmissionsystemproposedbyushasachievedgoodresultsinboththeoreticalanalysisandpracticalapplication.ThisprovidesnewideasandmethodsfortheoptimizationdesignandstableoperationofmultiterminalflexibleDCtransmissionsystems.六、结论与展望ConclusionandOutlook本文研究了基于MMC的多端柔性直流输电系统的改进下垂控制策略，通过理论分析和仿真验证，得出了一系列有益的结论。本文提出的改进下垂控制策略能够有效提升多端柔性直流输电系统的稳定性，降低了电压和电流的波动，提高了系统的传输效率和电能质量。该策略在应对系统参数变化和故障情况时也表现出良好的鲁棒性和自适应性，为实际工程应用提供了可靠的理论支持。ThisarticlestudiestheimproveddroopcontrolstrategyofamultiterminalflexibleDCtransmissionsystembasedonMMC.Throughtheoreticalanalysisandsimulationverification,aseriesofbeneficialconclusionshavebeendrawn.TheimproveddroopcontrolstrategyproposedinthisarticlecaneffectivelyenhancethestabilityofmultiterminalflexibleDCtransmissionsystems,reducevoltageandcurrentfluctuations,andimprovethetransmissionefficiencyandpowerqualityofthesystem.Thisstrategyalsodemonstratesgoodrobustnessandadaptabilityindealingwithsystemparameterchangesandfaultsituations,providing