【作者】 徐威；

【导师】 张艳霞；

【作者基本信息】 天津大学 ， 电气工程， 2018， 硕士

【摘要】 高压直流输电技术(high voltage direct current,HVDC)自1954年出现以来,因其具有传输容量大、送电距离远、控制系统性能优越等特点,已在远距离大容量输电、城市电网扩容、异步电网互联、孤岛供电和新能源发电入网等领域得到了广泛应用,在电力系统中占据的地位越来越显著。输电线路传输距离长,工作条件恶劣,故障率高,研究高压直流输电线路的保护对保证电网的安全稳定运行具有重要意义。本文介绍了高压直流输电系统的基本结构、控制系统和控制策略,基于PSCAD/EMTDC搭建了高压直流输电系统的仿真模型,实现了对高压直流输电系统正常工况及故障的仿真。本文利用分布参数模型推导了输电线路的双曲函数传输方程,将各频率的电流和电压均分解为正向行波和反向行波两部分,并阐述了输电线路两端正向行波和反向行波之间的物理意义和彼此关系。在此基础上,基于直流分量的正向行波电流和反向行波电流,通过双曲函数传输方程利用本侧测量值计算得到对侧的计算值,再与对侧的测量值相减构成正向行波差动电流和反向行波差动电流,提出了基于正反向行波电流的高压直流输电线路的行波差动保护新原理。利用相模变换对双极输电线路的电气量进行解耦,将基于线模直流分量的正向行波差动电流和反向行波差动电流构成双极输电线路的实用选区判据。通过分析故障后保护装置安装处地模电流与故障点处地模电流之间的关系,将直流电流的地模分量用于构成故障选极判据。在此基础上,给出了保护选区判据和选极判据的整定计算原则。本文提出的保护从原理上解决了输电线路传输过程中因分布参数引起电流幅值衰减所造成的差动保护不平衡电流问题。仿真结果证明了行波差动保护能正确区分区内外故障,选极判据能实现正确选极,适合作为高压直流线路的后备保护。更多还原

【Abstract】 Since the advent of high voltage direct current(HVDC)transmission technology in 1954,due to its advantages of large transmission capacity,long transmission distance and excellent controlling performance.HVDC transmission technology has been widely applied to long-distance large-capacity transmission,urban power grid expansion,asynchronous power grid interconnection,isolated island power supply,new energy generation connection to grids and other fields.It plays an increasingly important role in the power system.However,HVDC transmission lines have the following characteristics: long transmission distance,poor working conditions and high failure rate.Therefore,it is of great significance to study the protection of HVDC transmission lines to ensure the safe and stable operation of the power grid.This paper introduces the basic structure,control system and control strategy of HVDC transmission system.Based on PSCAD/EMTDC,the simulation model of HVDC transmission system is built and the simulations of the normal working conditions and faults of HVDC transmission system are realized.In this paper,the distribution parameter model is used to derive the hyperbolic function transmission equation of the transmission lines.The current and voltage of each frequency are decomposed into two parts: the forward traveling wave and the backward traveling wave.The physical meaning and relationship of the forward and backward traveling waves at both ends of the transmission lines are described.Based on the forward traveling wave current and the backward traveling wave current of the direct current component,through the hyperbolic function transmission equation,the calculated value of the opposite side is obtained by using the measured value of this side.And then the calculated value of the opposite side is subtracted from the measured value of the opposite side to form the forward traveling wave differential current and the backward traveling wave differential currents.So,a new principle of traveling wave differential protection for HVDC transmission lines based on the forward and backward traveling wave currents is proposed.The phase-mode transformation is used to decouple the electric quantity of the bipolar HVDC transmission lines.The forward traveling wave differential current and the backward traveling wave differential current based on the line mode of direct current component constitute the selected-area criterion of the bipolar HVDC transmission lines.By analyzing the relationship between the ground mode current on the installation site of the protection device and the ground mode current at the fault point after fault,the ground mode component of direct current is used to constitute the selected-fault-pole criterion.On this basis,the principles of setting calculation for the selected-area criterion and the selected-fault-pole criterion of the protection are given.The protection proposed in this paper theoretically solves the unbalanced current problem of current amplitude attenuation caused by distributed parameter in the transmission lines transmission process.The simulation results show that the proposed traveling wave differential protection can correctly distinguish fault from inside or outside and select the fault pole,which is suitable for backup protection of HVDC transmission lines.更多还原