Abstract—Microgrids usually operate in grid-connected or islanded mode. Due to substantial variation in fault current, same protection coordination scheme cannot be applied in both modes. Moreover, network topology keeps on changing due to momentary events. In this paper, an adaptive protection strategy is proposed to avoid any miscoordination between numerical directional overcurrent relays under a fault instance. Through this scheme, the relay settings can be updated online as per the operating mode and prevailing topology. The proposed tactic employs a central protection center with data storage and programming capability, smart electronic devices and communication channels to acquire and transfer real-time data. The relay coordination problem is formulated as a non-linear optimization function, with coordination time interval constraints. The optimal relay settings under both operating modes are obtained through non-linear programming and hybrid genetic algorithm non-linear programming method. To handle contingencies of communication channel failure, a novel inclusive mode settings are also introduced to protect the system in both modes even with line or DG outages. The proposed adaptive approach is tested on a nine bus radial distribution system with DGs. It has been found that the proposed scheme provides reliable system protection under different operating scenario.

中文翻译：

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不同运行模式下微电网中的自适应保护策略

摘要——微电网通常以并网或孤岛模式运行。由于故障电流的显着变化，不能在两种模式中应用相同的保护协调方案。此外，网络拓扑会因瞬时事件而不断变化。在本文中，提出了一种自适应保护策略，以避免故障情况下数值方向过流继电器之间的任何协调不当。通过该方案，继电器设置可以根据操作模式和当前拓扑进行在线更新。提议的策略采用具有数据存储和编程能力的中央保护中心、智能电子设备和通信通道来获取和传输实时数据。中继协调问题被表述为非线性优化函数，具有协调时间间隔约束。通过非线性规划和混合遗传算法非线性规划方法获得两种工作模式下的最佳继电器整定值。为了处理通信通道故障的意外情况，还引入了一种新颖的包容模式设置，即使在线路或 DG 中断的情况下，也可以在两种模式下保护系统。建议的自适应方法在带有 DG 的 9 总线径向配电系统上进行了测试。已经发现，所提出的方案在不同的操作场景下提供可靠的系统保护。还引入了一种新颖的包容模式设置，即使在线路或 DG 中断的情况下，也可以在两种模式下保护系统。建议的自适应方法在带有 DG 的 9 总线径向配电系统上进行了测试。已经发现，所提出的方案在不同的操作场景下提供可靠的系统保护。还引入了一种新颖的包容模式设置，即使在线路或 DG 中断的情况下，也可以在两种模式下保护系统。建议的自适应方法在带有 DG 的 9 总线径向配电系统上进行测试。已经发现，所提出的方案在不同的操作场景下提供可靠的系统保护。