Centralized adaptive directional overcurrent protection system for a microgrid with relay coordination

Modern society is highly concerned about eco-friendly technologies, including power generation. As a result of this, the microgrid concept has become a rapidly growing trend in this era. The introduction of microgrids offered distinct advantages such as reduced greenhouse gasses and pollutant emissions, high reliability, and minimization of overall energy consumption. Microgrids require dedicated attention for its protection solutions as the classic protection systems cannot be applied directly. These protection problems are mainly due to its drastic fault current level variation when it changes its operation mode from grid-connected mode to islanded mode. The conventional protection system has several issues, including selectivity and sensitivity between these operating modes. Adaptive protection can be used as a better solution for these issues. This paper demonstrates a centralized adaptive directional overcurrent protection system for a ring-type microgrid with a synchronous generator and three-phase inverter-based source. The test system and relay structure are modeled and simulated using MATLAB Simulink. Simulations have been done for three possible configurations considering both grid-connected and islanded modes. The results are obtained to observe the primary and backup relay behavior for different configurations.