Protection of Networked Microgrids Using Relays With Multiple Setting Groups

The protection of multiple interconnected microgrids is a challenging task because of changes in the topology of the system. A microgrid can operate in an islanded mode or get connected to another autonomous microgrid or grid-connected microgrid or directly to the utility grid. The short-circuit currents can change widely because of the connection status of a microgrid in the system of multiple or networked microgrids. In this article, a novel setting groups based scheme is presented for the protection of networked microgrids using directional overcurrent relays. The developed scheme can provide adequate protection to all microgrids under all possible interconnection among the microgrids and utility grid. A vector is generated for each possible interconnection of microgrids in the system to categorize them into four groups using
k
-means clustering. The optimum settings of relays considering all operational aspects of each group are calculated using a nonlinear programming based algorithm. Based on the topological interconnections of microgrids in the system, one of the setting groups can be enabled using a low-bandwidth communication link. The proposed protection approach has been validated on a benchmark test system for networked microgrids. The suitability and the effectiveness of the developed settings of the relays have been analyzed adequately.