基于时频分析的高压直流输电线路保护方法

发布时间：2018-02-01 12:48

本文关键词： 高压直流输电行波保护行波固有频率线路边界小波能量相对熵纵联保护雷击干扰小波能量矩　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：高压直流输电工程具有传输功率大、线路造价低的优点,相比交流输电线路更适合于远距离、大功率输电,中国的能源分布和电网结构决定了高压直流输电具有广阔的发展前景。但超长的送电距离、情况复杂的输电走廊、恶劣的工作条件使直流输电线路发生短路、雷击等事故的概率增加,统计表明线路故障占直流输电系统故障的一半,因此研究高压直流输电线路保护对保障系统的安全稳定运行具有至关重要的作用。为此,论文针对高压直流输电线路现有保护误动率高和高阻故障时保护可靠性差这两个关键问题开展研究,主要工作有:1)利用行波固有频率的高压直流输电线路纵联保护方法。通过总结现行行波保护存在的问题,进一步利用故障行波频域特征构建保护算法,利用行波固有频率与输电线路的故障距离和边界条件之间的数学关系,提出一种基于行波固有频率的高压直流输电线路纵联保护方法,可以起到行波保护后备保护的作用,动作于线路高阻故障。2)提出一种基于电压、电流突变量方向特征的高压直流输电线路纵联保护方法。在分析高压直流输电系统和故障叠加电路的基础上,利用小波能量相对熵有效地识别高压直流输电线路的故障暂态。给出一种基于小波能量相对熵的纵联保护方法可以准确动作于区内故障,保护性能不受故障类型、故障距离、过渡电阻和噪声的影响。3)将小波能量相对熵计算方法应用于高压直流输电线路单端保护。针对现有的高压直流输电线路单端保护存在可靠性差、耐过渡电阻能力差的问题,提出一种新的单端保护方法。首先,分析直流线路边界滤波环节的频率阻抗特性;然后计算滤波环节两侧电流之间的小波能量相对熵,进而描述电流各频段能量差异;最终构造直流线路单端保护判据,可实现区内、外故障的识别。该保护方法原理简单,能快速、可靠地识别直流线路区内、外故障,具有一定耐过渡电阻能力。4)为防止雷击干扰时保护误动,构建了一种高压直流输电线路雷击干扰识别元件。雷击时间会产生大量高频分量,对需要识别行波波头的行波保护和利用故障高频分量的保护影响比较大。论文从小波分析理论出发,利用小波能量矩分析故障性暂态和非故障性暂态情况下暂态信号能谱值在各个频段的分布,实现对雷击未故障、雷击故障以及普通短路故障的准确、快速识别。论文利用多种时频分析方法探讨了直流输电线路保护及雷击干扰识别的具体方案,解决了现有直流线路保护可靠性不高、耐受过渡电阻能力差的问题,可以为高压直流输电线路保护的相关研究提供支持。
[Abstract]:HVDC transmission project has the advantages of large transmission power and low line cost. Compared with AC transmission line, it is more suitable for long-distance and high-power transmission. China's energy distribution and power network structure determine that HVDC transmission has a broad development prospects, but long transmission distance, complex transmission corridor, poor working conditions make HVDC transmission lines short circuit. The probability of accidents such as lightning stroke increases, and the statistics show that the line faults account for half of the faults of HVDC transmission system. Therefore, it is very important to study the protection of HVDC transmission line to ensure the safe and stable operation of the system. This paper focuses on the two key problems of high misoperation rate and low reliability of protection for HVDC transmission lines. The main work is: (1) using the traveling wave natural frequency of HVDC transmission line longitudinal protection method. Through summing up the existing problems of traveling wave protection, further using the fault traveling wave frequency domain features to construct the protection algorithm. Based on the mathematical relationship between natural frequency of traveling wave and fault distance and boundary condition of transmission line, a longitudinal protection method for HVDC transmission line based on natural frequency of traveling wave is proposed. It can act as back-up protection of traveling wave protection, which is applied to line high resistance fault. 2) A voltage based method is proposed. Longitudinal protection method for HVDC transmission lines with directional characteristics of current abrupt changes. Based on the analysis of HVDC transmission system and fault superposition circuit. Using the relative entropy of wavelet energy to identify the fault transient of HVDC transmission line effectively, a longitudinal protection method based on relative entropy of wavelet energy is presented. Protection performance is not subject to fault type, fault distance. The effect of transition resistance and noise. 3) the wavelet energy relative entropy method is applied to the single-terminal protection of HVDC transmission line. The reliability of the existing single-terminal protection of HVDC transmission line is poor. A new single-terminal protection method is proposed for the problem of poor resistance resistance. Firstly, the frequency impedance characteristics of the boundary filtering link of DC line are analyzed. Then the relative entropy of wavelet energy between the two sides of the filter is calculated, and then the energy difference of each frequency band of the current is described. Finally, the single terminal protection criterion of DC line is constructed, which can realize the identification of fault in and out of the DC line. This protection method is simple in principle and can be used to identify the fault in and out of the DC line quickly and reliably. In order to prevent the maloperation of lightning interference, a lightning strike identification element for HVDC transmission line is constructed. The lightning strike time will produce a large number of high frequency components. It has great influence on the traveling wave protection which needs to identify the traveling wave head and the protection using the fault high frequency component. This paper is based on the theory of wave analysis. Wavelet energy moments are used to analyze the distribution of the energy spectrum of transient signals in the fault transient and non-fault transient conditions, so as to achieve the accuracy of lightning failure, lightning strike fault and common short-circuit fault. Rapid identification. This paper discusses the specific scheme of DC transmission line protection and lightning disturbance identification by using various time-frequency analysis methods, and solves the problem that the reliability of the existing DC line protection is not high. The problem of poor resistance resistance can support the research of HVDC transmission line protection.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM773

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