为了高效且可靠地利用分布式电源，微电网技术应运而生，但其多源且分散的网络结构及分布式电源的特点，导致传统配电网的线路故障检测方法与继电保护方案无法继续适用。因此，为满足微电网安全、可靠运行的要求，本文将基于分布式电源的暂态输出特性对其线路保护方法进行研究。

首先，对单个分布式电源的暂态输出特性进行理论研究及仿真分析。针对逆变型分布式电源不同的控制方式分别建立详细模型，考虑其电流输出的约束条件，并结合不同故障类型，分析得出各控制方式下分布式电源输出的暂态电流表达式及特征。通过仿真验证了不同控制方式下分布式电源暂态电流特征分析的准确性。

其次，对系统级微电网不同运行模式下发生故障时各区段两端电流特征的差异性进行分析推论及仿真验证。提出并建立单一模量可涵盖所有故障类型的微电网一模分量网络模型，进一步对系统级下分布式电源的暂态电流一模分量特征进行分析及推论，在考虑其运行模式、故障位置的情况下，得出检测点电流一模分量表达式及频率特征，提出仅在故障发生区段两端获取的电流一模分量频率特征存在差异性。仿真验证了其差异性分析结果的正确性，为后续所提微电网线路保护方法在理论上提供了支撑。

最后，提出了基于暂态电流一模分量的频率特征差异性的微网线路保护方法。以电流突变量作为保护启动量，提取了各保护监测点的电流一模分量，利用小波变换将时域一维信号转化为频域二维图像信号，根据差异哈希算法计算区段两侧的时频图汉明距离，通过判断差异性比较结果是否大于动作阈值，确定保护是否动作。通过在MATLAB软件中搭建仿真模型对该方法的有效性进行了验证，结果表明在不同运行条件、不同拓扑结构下，均能够实现保护的可靠动作，具有自适应性以及较高的灵敏性。

In order to efficiently and reliably utilize distributed power sources, micro-grid technology has emerged. However, its multi-source and decentralized network structure, as well as the characteristics of distributed power sources, make traditional power grid fault detection methods and relay protection schemes no longer applicable. Therefore, in order to meet the requirements for safe and reliable operation of micro-grids, this paper will study its line protection method based on the transient output characteristics of distributed power sources.

First, theoretical research and simulation analysis are conducted on the transient output characteristics of a single distributed power source. Detailed models are established for different control methods of inverter-type distributed power sources, taking into account the constraints on their current output, and combined with different types of faults, the transient current expressions and characteristics of distributed power source output under each control method are analyzed. The accuracy of the analysis of transient current characteristics of distributed power sources under different control methods is verified through simulation.

Secondly, the differences in the current characteristics at both ends of each section in the event of a fault in different operating modes of a system-level micro-grid are analyzed and verified through simulation. A single module network model that can cover all types of faults is proposed and established for the micro-grid system with transient current 1-mode components. Furthermore, the transient current 1-mode component characteristics of distributed power sources in the system-level are analyzed and deduced, and considering the operating mode and fault location of the micro-grid, the 1-mode component expression and frequency characteristics of the detection point current are obtained. It is suggested that the frequency characteristics of the 1-mode component current obtained at both ends of the fault zone differ. The accuracy of the difference analysis results is verified through simulation, providing theoretical support for the subsequent micro-grid line protection methods proposed.

Finally, a micro-grid line protection method based on the frequency characteristic differences of transient current 1-mode components is proposed. The protection start-up quantity is the current surge amount, and the 1-mode components of the current for each protection monitoring point are extracted. The wavelet transform is used to convert the one-dimensional signal in time domain into a two-dimensional image signal in frequency domain. The Hamming distance of the time-frequency spectrum on both sides of the zone is calculated based on difference hash algorithm. By comparing the difference comparison results with the action threshold, the protection action is determined. The effectiveness of this method is verified through a simulation model built in MATLAB software. The results show that under different operating conditions and different topologies, the protection can be reliably activated with adaptability and high sensitivity.

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