基于虚拟功率比的柔性直流输电系统短路故障检测方法  

Detection Method for Short-circuit Fault of Flexible DC Transmission System Based on Virtual Power Ratio

作　　者：李文博 汤晓君[1] 张泽宇 王浩[1] LI Wenbo;TANG Xiaojun;ZHANG Zeyu;WANG Hao(School of Electrical Engineering,Xi'an Jiaotong University,Xi'an 710049,China)

机构地区：[1]西安交通大学电气工程学院,西安710049

出　　处：《高电压技术》2024年第10期4703-4712,I0014-I0018,共15页High Voltage Engineering

基　　金：国家重点研发计划(2018YFB0904702)。

摘　　要：柔性直流输电具有潮流灵活、输送能力强的优点,快速、灵敏的故障检测技术对直流系统的安全稳定运行极其重要。由于过渡电阻和限流电抗器的存在以及测量噪声的影响,使得故障后的暂态特征微弱,进而使得多数故障检测方法的应用受限。为此,提出了一种基于虚拟功率比的柔性直流输电系统短路故障识别方案。首先,分析了多端直流输电系统的故障特性,利用虚拟接地点简化故障后的等效电路,明确了发生区内外故障的特征差异。在此基础上,提出虚拟功率比以增强故障发生后的特征差异,分析了不同工况下的虚拟功率比的特点,提出基于双端非同步虚拟功率比的故障保护策略。最后,在PSCAD/EMTDC中搭建了四端直流输电系统模型,对各种工况下的故障检测性能进行仿真验证。结果表明:所提保护策略能够实现对直流故障的准确识别,只需20 kHz的采样频率,即可在1 ms内完成故障检测,且对过渡电阻、噪声具有较强的耐受能力,相比于其他故障保护方法具有显著优势。Flexible DC transmission has advantages of flexible power conversion and high transmission capacity.Fast and sensitive fault detection technology is extremely important for the safe and stable operation of DC network.The presence of transition resistors,the configuration of current limiting reactors and the influence of measurement noise facilitate the transient characteristics after faults to be weak,which restricts the application of most fault detection methods.To this end,this paper proposes a short-circuit fault identification method for DC transmission systems based on virtual power ratio.Firstly,the fault characteristics of the multi-terminal DC transmission system are analyzed,and the equivalent circuit after failure is simplified by using virtual neutral point to clarify the differences between faults inside and outside the zone.On this basis,a virtual power ratio is proposed to enhance the characteristic differences after fault occurrence,the characteristics of the virtual power ratio under different fault conditions are analyzed,and the fault protection strategy based on double-ended non-synchronous virtual power ratios is proposed.Finally,a four-terminal HVDC model is built in PSCAD/EMTDC to verify the fault detection performance under various fault situations.The results show that the proposed method can be adopted to achieve accurate identification of fault types with a sampling frequency of 20 kHz and complete fault detection within 1 ms.Meanwhile,it has a strong tolerance to transition resistance and noise,and has significant advantages over other methods.

关 键 词：多端直流输电 虚拟接地点 故障识别 虚拟功率比 短路故障检测 

分 类 号：TM721.1[电气工程—电力系统及自动化]