Microgrid Harmonic-Restrained Dual Slope Differential Protection

Maintaining the reliability of distributed energy resources (DER) in a grid-connected system is challenging due to fluctuating fault currents and harmonics. Fixed over-current (OC) protection schemes often fall short, particularly sympathetic tripping and missing operation events. To address these issues and reduce the impact of harmonics on the power distribution system in the presence of wind power generation type-3, the paper introduces a novel solution named a harmonics-restrained dual-slope current differential relay setting methodology. This work has developed and implemented a mathematical model for harmonic-restrained dual slopes to enhance microgrid stability. Simulations involving line to ground (LG), line to line to ground (LLG), and line to line to line to ground (LLLG) faults validate the methodology, demonstrating its ability to eliminate sympathetic tripping, missing operation, and mitigating harmonic impact without relying on centralized communication. Comparing the proposed protection scheme to the conventional OC relay, the present approach proves superior in terms of reliability, speed, and overall effectiveness and does not require a communication facility and wide area measurement system (WAMS) structure. Improvements in relaying makes proposed protection algorithm a compelling choice for securing grid-connected DER systems, ensuring their reliable and robust performance.