Adaptive protection scheme for microgrids based on SOM clustering technique

Abstract

Microgrids are penetrating into the power systems at an unprecedented rate. The reason is the mutual economic and environmental benefits of microgrids, both for power grid utility and the consumers. Some special features of microgrids such as, the two main operational conditions called, islanded and grid-connected modes, and being composed of various types of distributed energy resources along with different uncertainties cause some tough challenges to protection and control systems. From the protection aspect, the coordination of overcurrent relays protection will become a difficulty, due to the extensive changes in the fault current levels sensed by these devices. In this paper, a new adaptive protection coordination scheme based on Self-Organizing Map (SOM) clustering algorithm is proposed for digital overcurrent relays equipped with several setting groups. Considering the similarity of mis-coordinated relay pairs for the clustering purpose, the proposed protection scheme focuses on solving the mis-coordination between main/backup relay pairs. As a case study, a modified IEEE 33-bus test system is used as a microgrid. In the case study, a synchronous distributed generation and two electric vehicle charging stations are installed. The results suggest that not only the proposed method is fully capable and flexible to significantly improve the mis-coordination of overcurrent relay pairs, but it can also ameliorate the operating time of relay.