Protection techniques in AC microgrids under DGER penetration : A comprehensive review and future directions

The rapid integration of renewable Distributed Generation (DG) is transforming traditional electrical networks into decentralized AC microgrids. While these systems offer enhanced flexibility, the high penetration of inverter-dominated resources introduces significant protection challenges. Conventional schemes, designed for unidirectional flow and high fault currents, often fail in microgrids due to bidirectional power flows, and the limited fault current capacity of power electronic interfaces in both grid-connected and islanded modes. Numerous strategies have been proposed in the literature to address these challenges. This paper provides a comprehensive review of recent AC microgrid protection techniques, including conventional, and adaptive-based methods. A comparative analysis highlights the strengths, limitations, and suitability of each approach under varying microgrid operating conditions. Based on this analysis, key insights and recommendations are presented to support future advancements in microgrid protection systems.