This study reviewed existing conventional and nonconventional protection schemes for grid‐connected and islanded mode operations in North American microgrid projects. The microgrid projects investigated in this study used different types of distributed energy resources (DERs) and integrated hydropower/diesel generators, gas/steam/wind turbines, and photovoltaic systems with energy storage. In this work, conventional protection schemes were defined as those within the IEEE Standard C37.2‐2008, whereas nonconventional schemes were those not defined within this standard. The pros and cons of conventional and nonconventional protection schemes were discussed in detail. The overvoltage, undervoltage, and frequency elements were the most common conventional protection schemes applied in microgrid projects in North America. These protection elements were used to detect the islanded conditions and faults that could not be sensed by overcurrent relays because of small fault currents contributed by low‐inertia DERs and power‐electronic sources. Directional overcurrent elements were used to distinguish between external (grid) and internal (microgrid) faults. Adaptive protection was the most popular nonconventional protection scheme applied to the microgrid projects. In conclusion, different types of DERs and operational modes must be considered in order to address the protection and control challenges of each microgrid and to obtain the best technical and economical solution.

中文翻译：

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北美微电网中使用的保护方案

这项研究回顾了北美微电网项目中用于并网和孤岛模式运行的现有常规和非常规保护方案。在这项研究中研究的微电网项目使用了不同类型的分布式能源（DER）以及集成的水电/柴油发电机，燃气/蒸汽/风力涡轮机以及具有储能功能的光伏系统。在这项工作中，常规保护方案定义为IEEE标准C37.2-2008中的方案，而非常规方案则是未在本标准中定义的方案。详细讨论了常规和非常规保护方案的优缺点。过电压，欠电压和频率元素是北美微电网项目中最常用的常规保护方案。这些保护元件用于检测由于低惯性DER和电力电子源产生的较小故障电流而无法被过流继电器检测到的孤岛状态和故障。方向性过电流元件用于区分外部（电网）故障和内部（微电网）故障。自适应保护是应用于微电网项目的最受欢迎的非常规保护方案。总之，必须考虑不同类型的DER和操作模式，以解决每个微电网的保护和控制难题，并获得最佳的技术和经济解决方案。方向性过电流元件用于区分外部（电网）和内部（微电网）故障。自适应保护是应用于微电网项目的最受欢迎的非常规保护方案。总之，必须考虑不同类型的DER和操作模式，以解决每个微电网的保护和控制难题，并获得最佳的技术和经济解决方案。方向性过电流元件用于区分外部（电网）故障和内部（微电网）故障。自适应保护是应用于微电网项目的最受欢迎的非常规保护方案。总之，必须考虑不同类型的DER和操作模式，以解决每个微电网的保护和控制难题，并获得最佳的技术和经济解决方案。