Assessing the impact of distributed energy resources on overcurrent protection in microgrids for enhanced effectiveness
Abdelfattah A. Eladl, Ahmed N. Sheta, Mohammed A. Saeed, Vladimír Bureš, Bishoy E. Sedhom
Abstract
• Examining how distributed energy resource (DER) integration impacts fault current characteristics, addressing critical challenges such as bidirectional power flow, sympathetic tripping, protection blindness, system instability, and loss of coordination. • Analyzing the performance of overcurrent relays using a modified IEEE 33-bus system, highlighting the limitations in traditional protection methods, and emphasizing the need for adaptive and innovative relay settings. • Investigating the effects of DER-induced changes on microgrid stability through critical clearing times (CCTs) and relay response analyses to ensure reliable and stable operations. • Providing actionable guidelines for optimizing relay settings and coordination, contributing to the development of robust and sustainable protection strategies for DER-rich microgrids. The inevitable diminutions of fossil fuel, declined energy efficiency, and sustainability considerations have sparked concerns about centralized generating facilities in traditional grids. Therefore, integrating distributed energy resources (DERs) into system installations has emerged as a dependable option to meet growing energy requirements while maintaining acceptable quality and efficiency standards. Despite notable advancements in system characteristics post-DER integration, this decentralized layout has impacted the functioning patterns of the entire system, including protection schemes. Designing an effective protection strategy in DER-rich systems is challenging due to many hurdles, including variations in short-circuit values, sympathetic tripping, protection blindness, loss of coordination, and system instability post-faults. Thus, this paper evaluates the efficacy of overcurrent protection in addressing the challenges introduced by DERs in power grids. It investigates overcurrent relay coordination issues, clarifying relevant equations and formulations from literature. Moreover, it assesses overcurrent relay performance in various scenarios post-DER integration. This evaluation is performed on a modified IEEE 33-bus system, equipped with DERs. Simulation and analysis are conducted using DigSILENT and MATLAB to simulate the system, analyze network stability, and solve optimization problems.