Optimal Protective Coordination of Microgrids Considering N-1 Contingency Using Dual Characteristics Directional Overcurrent Relays

Abstract

Microgrids (MGs) could be operated in grid-connected and islanded modes. Although the ability of MGs to operate under various operation modes improve the system flexibility and reliability, the MGs' protection system might be adversely affected due to this matter. The adaptive protection schemes have been introduced for MGs and their different operation modes and network configurations. However, the adaptive protection schemes require communication and monitoring infrastructures. Hence, the communication-free protection schemes using local measurement considering different operation modes and network configurations have received much attention in the literature. The literature shows a research gap in developing a communication-free protection scheme considering different operation modes and network configurations due to the unavailability of upstream substations, distributed generations, and other MGs' elements like distribution lines. This paper tries to fill this research gap by proposing a new protection scheme using dual characteristic overcurrent relays based on N-1 contingency. The proposed method is applied to the IEEE 8-bus test system. The power flow and short circuit analyses are implemented in DIgSILENT, and the genetic algorithm (GA) solves the proposed optimization problem in the MATLAB environment. Test results illustrate the advantages of the proposed method compared to existing schemes only considering the limited operation modes and network configurations. Test results imply that the coordination constraint violation does not appear for N-1 contingency by applying the proposed method.