基于VSC的多端直流系统故障定位方法研究

With the development of renewable energy and electronic techniques, the VSC-based multi-terminal DC power networks, which cause less energy loss and easier network connection, have become more and more important in the research of smart grid. The complicated connections of multi-terminal DC networks produce some technical problems such as location of the DC faults. However, the research on the fault location with the terminal information of DC networks was rarely reported. This project aims to solve some critical issues of fault location in multi-terminal DC networks such as the simplification of DC network topology, the characterization of transient signals, and so on. Based on the analysis of DC network topology, DC faults and characteristics of transient fault signals, three algorithms: travelling wave based fault location, parameter calculation based fault location, and fault transient signal de-noising will be proposed. Finally, a fault location system of multi-terminal DC networks will be setup. Such system can help improving the techniques of fault isolation and system recovery of multi-terminal DC networks. The research of this project is helpful to the social development of Chinese smart grid and the industrial application of large-scale DC power transmission and distribution.

随着新能源的广泛应用和电力电子技术的飞速发展，基于VSC的多端直流输配电技术凭借其能量损失少、接入性好等优势，已成为未来智能电网中不可缺少的重要部分。多端直流系统网络结构的日渐复杂带来了诸如直流系统内部故障定位困难等方面的问题，而利用多端直流系统端口处暂态信息进行故障定位方面的研究较为匮乏。本项目围绕多端直流系统网络结构简化和等效、故障和干扰暂态信号时频特征提取等关键问题，在系统性研究多端直流系统网络拓扑结构、内部故障机理、暂态故障信号的传播和波形特性等主要因素的基础上，研究多端直流系统行波定位法、基于参数计算的多端系统故障定位法、以及故障暂态信号识别和去噪算法，建立多端直流系统故障定位算法体系，从而丰富多端直流系统故障隔离和系统恢复的手段。本项目立足社会经济发展中的重大问题，研究结果有望为大规模直流输配电网络的应用提供技术支撑，具有较强的理论价值和应用前景。

本项目围绕多端柔性直流故障定位开展相关研究，项目取得了一系列的研究成果和发现。主要包括三个方面：1、通过对多端网络拓扑中，故障暂态信号传播过程的衰减特性分析，发现利用最大行波波头来实现多端柔直故障定位，方法简单，易于工程实现，且从本质上避免了传统基于初始行波波头和最短路径的定位方法在部分特殊拓扑情况下，存在定位盲区的缺点。2、通过对故障后换流器等效故障回路的时域分析，改进了传统基于阻抗的线路定位方法，发现利用多端口故障暂态信息，联立电路约束方程，可以完全抵消过渡电阻对故障定位产生的影响，提高定位准确度。3、通过在多端直流系统故障定位和暂态扰动识别的模型中，引入基于无监督学习的人工智能算法，发现与传统基于特征提取的故障分析方法相比，基于深度无监督学习算法的方法可以更加可靠稳定的描述信号暂态特性，拟合非线性映射关系，在故障分析领域有很大的应用前景。