Short-Circuit Analysis of DER-Based Microgrids in Connected and Islanded Modes of Operation

Since microgrids should be able to smoothly operate in two distinct modes—grid-connected and islanded, their fault currents can widely fluctuate depending on the operational mode. When microgrid is connected grid, highest current, by far, supplied utility grid. In this mode, current contribution from distributed energy resources (DERs) less than 20%. However, when switches islanded grid lost DERs are sole sources. Thus, overall mode multiple times lower compared Moreover, most of inverter-based, with limited currents, which further reduces With rapid rise penetration around globe, phenomenon adversely influence relay protection, thus needs precisely analyzed. Therefore, main purpose paper thoroughly analyze differences operation modes a microgrid, consequently derive conclusions regarding required improvements calculations protection analysis emerging microgrids. A representative test bed developed modelled using in-house software as well state-of-the-art hardware-in-the-loop environment. Several different short-circuit faults were simulated analyzed both grid-connected modes. The results show that significantly differ operating highly system. calculation algorithms aimed at radial distribution grids, mostly used for available literature, need improved provide precise time-efficient considered. These valuable insight into state microgrids’ reveal several important directions future research.