Intelligent Relay Coordination Method for Microgrid

Abstract

This chapter basically deals with the protection coordination of a typical microgrid with distributed energy sources. As we are aware that fault current changes its direction when microgrid switches from non-islanded condition to islanded condition, so the main challenge before the power engineer’s is to have a proper protection coordination in dual configuration of microgrid (islanded and non-islanded condition). In this chapter, a smart grid-based fault current limiter (FCL) has been proposed which suppresses the fault currents to the level such that the proper protection coordination is possible. One of the unique characteristics of the FCL is that it is ‘invisible’ during normal condition but becomes active during faulted or islanding condition. The important component in FCL is the reactance which has a major contribution in reducing the fault current of the microgrid. So in this chapter, investigation with reactance FCLs is discussed for proper coordination of directional overcurrent relay (DOCR) settings during symmetrical three-phase faults. Here, the microgrid model with distributed generation (DG) is considered for the investigation. The DG taken for the study is the conventional synchronous generator connected to medium voltage network. The proposed protection scheme is validated on radial distribution system (the benchmark Canadian distribution system model) of 9-bus which is adequately connected to DGs within the microgrid. Further in the present work, three configurations of the microgrid are considered, i.e. grid connected, islanded and dual. From the simulation results, it is concluded that the optimized FCL is able to co-ordinate properly the protective devices for different configurations of microgrid.