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适用于柔性直流互联交流系统的无电压方向元件判据
引用本文:薛士敏,史哲,李蕴,徐绍军,杨静悦,李博通.适用于柔性直流互联交流系统的无电压方向元件判据[J].电力系统自动化,2017,41(4):143-149.
作者姓名:薛士敏  史哲  李蕴  徐绍军  杨静悦  李博通
作者单位:智能电网教育部重点实验室(天津大学), 天津市 300072,智能电网教育部重点实验室(天津大学), 天津市 300072,国网北京市电力公司, 北京市 100031,国网北京市电力公司, 北京市 100031,智能电网教育部重点实验室(天津大学), 天津市 300072,智能电网教育部重点实验室(天津大学), 天津市 300072
基金项目:国家高技术研究发展计划(863计划)资助项目(2015AA050102);国家自然科学基金资助项目(51577129);天津市自然科学基金资助项目(14JCYBJC21000)
摘    要:背靠背柔性环网控制装置的应用使配电网由单端电源供电的辐射状网络变为多端电源供电网络,三段式电流保护无法判断故障方向。为了既保证配电网保护动作可靠性又保留三段式电流保护,需要为保护安装方向元件。文中通过研究背靠背柔性环网控制装置接入的交流配电网发生不同位置相间故障时序电流间的相位规律,提出了基于流过保护的负序电流和同一母线上无源支路正序电流间相位关系的故障方向判别元件,并给出了正反方向故障时方向元件的动作区间。该方向元件适用于由传统电源、采用负序电流抑制的柔性环网控制装置或分布式电源构成的且母线含无源支路的多端供电网络。该元件受过渡电阻影响小,无需安装电压互感器,在三相对称故障时仍可保证保护的正确动作,不存在传统功率方向元件出口三相故障时的死区问题。经PSCAD仿真验证了该方向元件在系统不同位置发生各种相间故障时的正确性和有效性。

关 键 词:柔性直流输电  模块化多电平换流器  故障穿越  交流配电网  方向元件  负序电流
收稿时间:2016/4/9 0:00:00
修稿时间:2016/12/29 0:00:00

A Criterion for Non-voltage Directional Elements Applied in AC Networks Connected with VSC-based Interconnection Devices
XUE Shimin,SHI Zhe,LI Yun,XU Shaojun,YANG Jingyue and LI Botong.A Criterion for Non-voltage Directional Elements Applied in AC Networks Connected with VSC-based Interconnection Devices[J].Automation of Electric Power Systems,2017,41(4):143-149.
Authors:XUE Shimin  SHI Zhe  LI Yun  XU Shaojun  YANG Jingyue and LI Botong
Affiliation:Key Laboratory of Smart Grid of Ministry of Education(Tianjin University), Tianjin 300072, China,Key Laboratory of Smart Grid of Ministry of Education(Tianjin University), Tianjin 300072, China,State Grid Beijing Electric Power Company, Beijing 100031, China,State Grid Beijing Electric Power Company, Beijing 100031, China,Key Laboratory of Smart Grid of Ministry of Education(Tianjin University), Tianjin 300072, China and Key Laboratory of Smart Grid of Ministry of Education(Tianjin University), Tianjin 300072, China
Abstract:The application of voltage source converter(VSC)based interconnection devices in the AC system makes the distribution network change from a radial network with one-terminal power supply to a multi-terminal power supply network. However, the conventional three-section current protection applied in distribution network is not able to determine the direction of the fault. Therefore it is necessary to install directional elements to ensure the reliability of three-section current protection. The phase relationships between sequence currents under phase-to-phase faults that happen at different locations in the AC distribution network connected with the back-to-back VSC-based interconnection device is deduced. Then a novel criterion for fault direction recognition is proposed based on the phase relationship between the negative-sequence current flowing through the protected line and the positive-sequence current flowing through the passive branches emanating from the same bus. Through theoretical analysis, the action interval of direction element under forward faults and backward faults are derived. The proposed directional element is applicable to multi-terminal power supply networks containing VSC-based interconnection devices or VSC interfaced distributed generators(DGs), where there is passive branch emanating from each bus. The proposed directional element does not require potential transformers(PTs), and is scarcely affected by the transition resistance. Under a three-phase symmetrical fault, the correct operation of the protection can still be guaranteed, and the dead zone problem of conventional power directional elements when the fault happens at the outlet of the relay can be avoided. The criterion is verified by a large number of PSCAD simulation results of phase-to-phase faults that occur at different locations of the distribution network. This work is supported by National High Technology Research and Development Program of China(863 Program)(No. 2015AA050102), National Natural Science Foundation of China(No. 51577129)and Tianjin Natural Science Foundation(No. 14JCYBJC21000).
Keywords:voltage source converter based high voltage direct current(VSC-HVDC)transmission  modular multilevel converter(MMC)  fault ride-through(FRT)  AC distribution network  directional element  negative-sequence current
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