双极柔性直流输电系统换流站交流三相接地故障分析及保护
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摘要
随着电压等级和传输容量的提高,基于对称双极接线的多端柔性直流输电技术被越来越多地应用到实际工程中。换流站交流接地故障会对双极柔性直流输电系统产生严重危害,因此换流站的快速保护技术尤为重要。为此,首先分析了基于双极结构的多端柔性直流电网换流站交流三相接地故障的暂态特性,推导了故障电流中各组成成分的解析表达式。其次,根据故障暂态特性提出了一种适用于双极拓扑结构和金属回线接地方式的多端柔性直流电网快速保护策略。该保护利用换流器桥臂电流识别故障,动作速度快,可靠性高,并具有一定抗过渡电阻能力。在PSCAD/EMTDC仿真平台上搭建四端直流电网模型,仿真结果验证了故障暂态特性分析及所提出的保护方法在不同故障情况下的正确性。
With the increase of voltage level and transmission capacity, the bipolar wiring mode has become popular in actual high voltage direct current(HVDC) projects. The AC grounding fault of converter will cause serious harm to bipolar HVDC systems. Therefore, the fast protection scheme of HVDC system converters comes to be particularly important. In this paper, three-phase grounding fault transient characteristics in a multi-terminal DC power grid, based on bipolar wiring mode, are analyzed firstly. And mathematic expressions of each component of fault current are derived. Then, a fast protection scheme is proposed for bipolar HVDC system with metallic return according to the fault transient characteristics. Moreover, the scheme utilizes arm current of converter for fault identification and is verified to have the advantages of fast action speed, high reliability and the ability to resist the transition resistance. A four-terminal DC power grid model is established in PSCAD/EMTDC, and the validity of the protection scheme under different fault conditions is verified by simulation results.
With the increase of voltage level and transmission capacity, the bipolar wiring mode has become popular in actual high voltage direct current(HVDC) projects. The AC grounding fault of converter will cause serious harm to bipolar HVDC systems. Therefore, the fast protection scheme of HVDC system converters comes to be particularly important. In this paper, three-phase grounding fault transient characteristics in a multi-terminal DC power grid, based on bipolar wiring mode, are analyzed firstly. And mathematic expressions of each component of fault current are derived. Then, a fast protection scheme is proposed for bipolar HVDC system with metallic return according to the fault transient characteristics. Moreover, the scheme utilizes arm current of converter for fault identification and is verified to have the advantages of fast action speed, high reliability and the ability to resist the transition resistance. A four-terminal DC power grid model is established in PSCAD/EMTDC, and the validity of the protection scheme under different fault conditions is verified by simulation results.
引文
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[16]LIBT,LIUYC,LIB,etal.Developmentprocessandanalytical methodofthepole-to-poleDCfaultintheMMC-MVDCsystem[J].IET Power Electronics, 2018, 10(15):2085-2091.
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[18]魏晓光,杨兵建,汤广福.高压直流断路器技术发展与工程实践[J].电网技术, 2017,41(10):3180-3188.WEIXiaoguang,YANGBingjian,TANGGuangfu.TechnicaldevelopmentandengineeringapplicationsofHVDCcircuitbreaker[J].Power System Technology, 2017, 41(10):3180-3188.
[2]LIU S, XU Z, HUA W, et al. Electromechanical transient modeling of modular multilevel converter based multi-terminal HVDC systems[J].IEEE Transactions on Power Systems, 2013, 29(1):72-83.
[3]XU J, GOLE A M, ZHAO C. The use of average-value model of modularmultilevelconverterinDCgrid[J].IEEETransactionsonPower Delivery, 2015, 30(2):519-528.
[4]TANG L, OOI B T. Locating and isolating DC faults in multi-terminal DCsystems[J].IEEETransactionsonPowerDelivery,2007,22(3):1877-1884.
[5]XUESM,LIUC.Line-to-linefaultanalysisandlocationina VSC-basedlow-voltageDCdistributionnetwork[J].Energies,2018,11(3):536.
[6]常非,杨中平,林飞.具备直流故障清除能力的MMC多电平子模块拓扑[J].高电压技术,2017,43(1):44-49.CHANGFei,YANGZhongping,LIN Fei.Multilevel sub-moduletopologyofMMCwithDCfaultclearancecapability[J].HighVoltage Engineering, 2017, 43(1):44-49.
[7]DEBNATHS,QINJ,BAHRANIB,etal.Operation,control,and applicationsofthemodularmultilevelconverter:areview[J].IEEE Transactions on Power Electronics, 2014, 30(1):37-53.
[8]XUES,LIANJ,QIJ,etal.Pole-to-groundfaultanalysisandfast protection scheme for HVDC based on overhead transmission lines[J].Energies, 2017, 10(7):1059.
[9]张文亮,汤涌,曾南超.多端高压直流输电技术及应用前景[J].电网技术,2010,34(9):1-6.ZHANGWenliang,TANGYong,ZENGNanchao.Multi-terminal HVDC transmission technologies and its application prospects in China[J]. Power System Technology, 2010, 34(9):1-6.
[10]何炎,李周,李亚州,等.基于真双极接线的VSC-MTDC系统功率转代策略[J].电力系统自动化,2017,41(19):95-101.HEYan,LIZhou,LIYazhou,etal.Powerconversionstrategyof VSC-MTDC system based on real bipolar wiring mode[J]. Automation of Electric Power Systems, 2017, 41(19):95-101.
[11]郭晓茜,崔翔,齐磊.架空线双极MMC-HVDC系统直流短路故障分析和保护[J].中国电机工程学报,2017,37(8):2177-2185.GUO Xiaoqian, CUI Xiang, QI Lei. DC short-circuit fault analysis and protection for the overhead line bipolar MMC-HVDC system[J]. Proceedings of the CSEE, 2017, 37(8):2177-2185.
[12]余修勇,肖立业,林良真,等.基于单端量的柔性直流电网故障识别方案[J].高电压技术,2018,44(2):440-447.YUXiuyong,XIAOLiye,LINLiangzhen,etal.Single-endedfast fault detection scheme for MMC-based HVDC[J]. High Voltage Engineering, 2018, 44(2):440-447.
[13]周杨,贺之渊,庞辉,等.双极柔性直流输电系统站内接地故障保护策略[J].中国电机工程学报,2015,35(16):4062-4069.ZHOUYang,HEZhiyuan,PANGHui,etal.Protectionofconverter groundingfaultonMMCbasedbipolarHVDCsystems[J].Proceedings of the CSEE, 2015, 35(16):4062-4069.
[14]CHEN J, LI B, DONG B, et al. Simulation and analysis of fault characteristicsoftheMMC-HVDCsystemunderbipolarconnection mode[C]∥PowerandEnergyEngineeringConference.[S.l.]:IEEE,2016:2534-2538.
[15]梅念,陈东,吴方劼,等.基于MMC的柔性直流系统接地方式研究[J].高电压技术,2018,44(4):1247-1253.MEINian,CHENDong,WUFangjie,etal.Studyongrounding methodsforMMC-basedVSC-HVDCsystems[J].HighVoltageEngineering, 2018, 44(4):1247-1253.
[16]LIBT,LIUYC,LIB,etal.Developmentprocessandanalytical methodofthepole-to-poleDCfaultintheMMC-MVDCsystem[J].IET Power Electronics, 2018, 10(15):2085-2091.
[17]徐政,刘高任,张哲任.柔性直流输电网的故障保护原理研究[J].高电压技术,2017,43(1):1-8.XUZheng,LIUGaoren,ZHANGZheren.Researchonfaultprotection principle of DC grids[J]. High Voltage Engineering, 2017, 43(1):1-8.
[18]魏晓光,杨兵建,汤广福.高压直流断路器技术发展与工程实践[J].电网技术, 2017,41(10):3180-3188.WEIXiaoguang,YANGBingjian,TANGGuangfu.TechnicaldevelopmentandengineeringapplicationsofHVDCcircuitbreaker[J].Power System Technology, 2017, 41(10):3180-3188.