论文总字数：18717字

摘 要

我国国土面积广阔，能源消耗地和煤炭、石油等能源产地东西分布不均。直流输电网拥有输电线路网损小、输电可靠性高和输电传输容量大等优点，适合我国能源供需地跨度大、需远距离输电等国情。所以，伴随着未来电力系统输电网的扩建和社会经济、民生事业的高速发展，直流输电网将成为远距离大功率输电的首选。在直流电网的众多研究发展方向中，柔性直流输电技术是最受业界关注的。

当故障发生在多端柔性直流输电网中时，本次毕设主要考虑发在直流侧的双极短路故障和分为正极、负极接地的单极接地短路故障。对于柔性直流输电网而言，直流侧发生故障时产生的过电流、过电压将严重威胁输电网整体安全稳定工作。因此，直流线路故障保护是关系到柔性直流电网安全发展的重要技术。

本课题将利用PSCAD电气仿真软件搭建多端柔性直流输电网的结构模型，将主要针对MMC、MMC-HVDC输电系统以及双极短路故障、单极接地短路这两类常发生在柔性输电系统中的故障进行研究。同时将依据PSCAD仿真软件中搭建的三端MMC-HVDC输电模型进行故障仿真，验证单极接地故障发生后的电压、电流的仿真值与理论上故障发生后电压、电流变化规律的合理性和双极短路故障发生后的电压、电流的仿真值与理论上故障发生后电压、电流变化规律的合理性。根据MMC-HVDC输电系统直流侧线路故障的特点，从整个柔性直流输电系统所用的电力电子器件绝缘水平、直流断路器和直流系统控制策略等角度去分析研究柔性直流输电直流侧故障的保护策略。

关键词：多端柔性直流输电网；双极短路故障；单极接地故障；直流线路故障保护

ABSTRACT

China is a vast country with uneven distribution of energy consumption, coal, oil and other energy sources. DC transmission network has the advantages of small loss of transmission line network, high transmission reliability and large transmission capacity. It is suitable for China's energy supply and demand to span long distance transmission and other national conditions. Therefore, with the expansion of power transmission network in the future and the rapid development of social economy and people's livelihood, DC transmission network will become the first choice for long-distance high-power transmission. Among the many research and development directions of DC power grid,the flexible DC transmission technology is the most concerned in the industry.

When the fault occurs in the multi-terminal flexible DC transmission network, this project mainly considers the double-pole short-circuit fault on the DC side and the single-pole short-circuit fault which is divided into positive pole and negative pole grounding.For the flexible DC transmission network, the over current and over voltage generated by the DC side fault will seriously threaten the overall safety and stability of the transmission network.Therefore, DC line fault protection is an important technology related to the development of flexible DC power grid.

This topic will use PSCAD electrical simulation software to build the structural model of multi-terminal flexible DC transmission network, and mainly study the MMC, MMC-HVDC transmission system, bipolar short-circuit fault and single-pole grounding short-circuit, two common faults in the flexible transmission system.At the same time, the simulation value of voltage and current after the single-pole grounding fault is studied to see if it conforms to the theoretical variation rule of voltage and current after the fault.The same method will be used to study the bipolar short circuit fault.According to the characteristics of DC side line fault of MMC-HVDC transmission system, the protection strategy of DC side fault of multi-terminal flexible HVDC transmission system is analyzed from the perspectives of insulation level of power electronic devices, DC circuit breaker and control strategy of DC system used in the whole multi-terminal flexible HVDC transmission system.

KEY WORDS: Multi-terminal flexible DC transmission network; Bipolar short circuit fault; Single-pole grounding fault; DC line fault protection

目 录

摘 要 I

Abstract II

第一章 绪论 1

1.1 课题研究背景及意义 1

1.2 直流输电故障研究现状 1

1.2.1 柔性直流输电系统直流侧故障分析 1

1.2.2 多端柔性直流输电系统直流侧故障分析 2

1.3 论文主要工作 2

第二章 MMC-HVDC输电系统基本原理 3

2.1 MMC工作原理 3

2.2 MMC拓扑结构 4

2.3 MMC的调制方式 6

2.4 MMC运行控制系统 6

2.5 本章小结 7

第三章 MMC-HVDC输电系统故障分析 8

3.1 双极短路故障 8

3.1.1 双极短路故障介绍 8

3.1.2 双极短路故障机理分析 8

3.1.3 双极短路故障电流分析 10

3.2 单极接地故障 11

3.2.1 单极接地故障介绍 11

3.2.2 单极接地故障机理分析 11

3.2.3 单极接地故障电流分析 13

3.3 本章小结 13

第四章 MMC-HVDC故障仿真与保护策略 15

4.1 三端MMC-HVDC输电系统仿真模型 15

4.2 MMC-HVDC直流侧故障仿真 17

4.2.1 MMC-HVDC直流侧双极短路故障仿真 17

4.2.2 MMC-HVDC直流侧单极（正极）接地故障仿真 18

4.2.3 MMC-HVDC直流侧单极（负极）接地故障仿真 19

4.3 MMC-HVDC直流侧故障保护策略 20

4.3.1 单极接地故障保护策略 20

4.3.2 双极短路故障保护策略 20

4.4 本章小结 21

第五章 总结与展望 22

参考文献 23

致 谢 24

第一章 绪论

课题研究背景及意义

随着IGBT、GTO等全控型电力电子器件的不断深入研究和高速发展，其作为换流设备开始广泛应用于直流输电系统领域。这种需要通过全控型电力电子元件组成换流设备的直流输电系统在国内电气领域被称为“柔性直流输电”。

“两电平”、“三电平”和“模块化多电平”是现今“柔性直流输电”系统换流站的三大分类。但是，两电平和三电平换流器有以下三点技术发展瓶颈：

剩余内容已隐藏，请支付后下载全文，论文总字数：18717字