【作者】 刘静；

【导师】 段建东；

【作者基本信息】 西安理工大学 ， 电力系统及其自动化， 2016， 硕士

【摘要】 随着智能电网的持续建设,高电压、大容量的直流输电在电网安全稳定运行中发挥着日益重要的作用。然而直流线路往往长达几十上千公里,途经复杂地形乃至恶劣环境,发生线路故障的风险极大,而且故障位置的查找异常不易,若不能及时清除故障还将严重影响整个电力系统的安全运行。因此,快速、准确地进行故障测距和保护一直是高压直流线路方面的研究热点,当前得以工程应用的主流方法是时域行波法,同时人们也在研究频域类的故障测距与保护算法。但是,现有的这些方法各有利弊,或受限于波头的识别,或受限于频率的混叠。为此,本文融合时域行波的特点,研究一种新型的高压直流输电线路故障测距与保护的方法及其算法。首先,在高压直流输电系统故障特征分析的基础上,利用故障电流暂态量的频谱与故障距离之间的数学关系,形成基于固有频率的故障测距与线路保护的总体思想。其次,为降低固有频率混叠可能的不利影响,充分利用双端行波故障测距法的粗测结果界定固有频率的真实范围,即预报范围;在此范围内,通过小波分解、多信号分类方法精确提取固有频率,即校正固有频率值;利用此固有频率值求取对应的故障距离,形成基于电流暂态量固有频率预报与校正的故障测距实用算法。接着,进一步分析直流线路上故障时与在换流站及其所连交流侧上故障时固有频率的区别,构建比较线路两端所测固有频率值的直流线路保护方法,即频差保护。最后,在电力系统电磁暂态仿真软件PSCAD/EMTDC上搭建了某直流输电系统,进行不同故障距离、过渡电阻情况下大量的故障仿真,测试了基于固有频率的高压直流输电线路故障测距与保护的Matlab算法程序,测试结果显示该测距方法具有较高的精度,所提线路保护是可行的。更多还原

【Abstract】 With the continuous construction of smart grid,HVDC of high voltage and large capacity plays a very important role in the safe and stable operation of power grids.But the DC line is generally long,and it always goes through complex terrain or harsh environment,as a result,the risk of faults is great and it’s difficult for fault location.So study of fast and accurate for DC line fault location and protection method and device has been a hot research in electric power engineering.At present,the mainly fault location method of HVDC transmission lines is traveling wave method in time domain.At the same time,fault location method in frequency domain is studied.But all the methods have their own advantages and disadvantages.For example,time domain method is limited to the recognition of wave head and frequency domain method is limited to aliasing of frequency.Therefore,a new fault location and protection method and its algorithm are put forward by fusion of the characteristics in time domain.Firstly,the fault characteristics of HVDC system is analyzed and on the basis the general ideology of fault location and protection based on natural frequency is proposed by using the relationship between the transient component of fault current and fault distance.Secondly,in order to decrease the influence of the aliasing of natural frequency,this paper makes full use of the rough fault location result by using two-terminal traveling wave fault location method.Through the method to define the real range of natural frequency,that is the natural frequency prediction.Then wave analysis and MUSIC algorithm are used to determine the natural frequency,that the correction of natural frequency.Use this natural frequency to calculate the fault distance,and that is the practical fault algorithm of location based on the natural frequency prediction correction of fault current transient component.Thirdly,natural frequency difference of faults of AC side and Converter Station and District external fault are analyzed,and based on the different characteristics of the natural frequency,the protection criterion is put forward in order to realize the judgment of the DC system area within the region or outside fault,that the frequency difference protection.At last,a HVDC system is established in electromagnetic transient simulation software PSCAD/EMTDC,and conditions of different fault distance,different transition resistance are simulated,then fault algorithm of location practical based on the natural frequency prediction correction of fault current transient component and its Matlab algorithm program are tested.Test results show that the fault location method has high accuracy and the proposed line protection is feasible.更多还原