Unlike conventional synchronous generators, the fault characteristics of inverter-based distributed generators (IBDGs) are mainly determined by the inverter control strategies. Their limited fault current contributions make the protection design of islanded microgrids (MGs) become a major challenge. This article focuses on the fault characteristics and protection scheme design of islanded MGs. First, the phase differences between the positive-sequence current fault components (PSC-FCs) at both terminals of fault line are analyzed under different network topologies and fault severities. It points out the phase characteristic differences between internal and external faults. Then, on basis of this to overcome the problems of the phase measurement error and protection setting, a waveform difference feature-based protection scheme is proposed. The protection criteria are formulated using the first peak sign and time information of PSC-FCs between both terminals of line, which are extracted by the mathematical morphology (MM) technology. Only relatively low bandwidth communication is required to achieve accurate fault identification. Finally, the simulation results on a 10-kV islanded MG model demonstrate that the proposed scheme can identify internal faults reliably in both looped and radial islanded MGs under different fault resistances and measurement noises.

中文翻译：

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基于波形差异特征的孤岛微电网保护方案

与常规同步发电机不同，基于逆变器的分布式发电机（IBDG）的故障特性主要由逆变器控制策略决定。它们有限的故障电流贡献使孤岛微电网（MGs）的保护设计成为一项重大挑战。本文重点介绍了孤岛型微机的故障特征和保护方案设计。首先，分析了故障线路两端的正序电流故障分量（PSC-FC）之间在不同网络拓扑和故障严重性下的相位差。指出了内部故障和外部故障之间的相位特性差异。然后，在此基础上，克服了相位测量误差和保护设置的问题，提出了一种基于波形差异特征的保护方案。使用线路两端之间的PSC-FC的第一个峰值信号和时间信息来制定保护标准，这些信息是通过数学形态学（MM）技术提取的。仅需要相对较低带宽的通信即可实现准确的故障识别。最后，在10 kV孤岛MG模型上的仿真结果表明，该方案可以在不同的故障电阻和测量噪声下可靠地识别环形和径向孤岛MG中的内部故障。