On Protection Schemes for AC Microgrids: Challenges and Opportunities

The integration of Distributed energy resources (DERs) into distribution networks has been increasing in recent years, causing concerns related to operation, control, stability, reliability, and protections. The traditional protection schemes based on overcurrent (OC) relays, which are commonly used in radial distribution networks, experience issues with fault current levels and tripping decision rules due to the wide variations in operating conditions of microgrids under Inverter based resources (IBR) under parallel operation. In this paper, the effects of Distributive Generation (DG) penetration on conventional protection schemes in microgrids are examined, and a thorough review of multiple approaches for addressing protection challenges in microgrids, based on existing literature and exhaustive studies, is presented. Potential adaptive and intelligent protection schemes are discussed which enhances the performance of traditional protection schemes in microgrids. This paper provides an insightful approach of the challenges associated with DER integration in distribution networks and presents a range of solutions for protecting and enhancing microgrids operation. This paper also delivers an exhaustive review of norms and standards, emphasizing the need for advanced protection schemes that can handle the dynamic and intermittent nature of DERs and the importance of integrating communication and control system architectures into microgrids ensuring reliability and resiliency.