Study of the Protection Improvements for a Weak Grid Area With High Inverter-Based Resources (IBRs)

Technical Report · Wed Feb 25 00:00:00 EST 2026

DOI:https://doi.org/10.2172/3021515· OSTI ID:3021515

Wang, Jing ^[1]; Hasan, Abu Shouaib ^[1]; Velaga, Yaswanth Nag ^[1]; Chen, Lang ^[2]; Dubeau, Joseph ^[2]; Arana, Andrew ^[2]

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1. National Laboratory of the Rockies (NLR), Golden, CO (United States)
2. Florida Power & Light, Miami, FL (United States)

This project designs enhanced protection scheme for the real-world weak grid area with a high penetration of IBRs. As the existing protection schemes are originally designed for traditional synchronous machines, we first evaluate if the protection scheme will continue to operate reliably in systems with high levels of IBRs. Hardware relays are tested using a controller-hardware-in-the-loop setup. PSCAD electromagnetic transient simulation with IBR original equipment manufacturer black-box models is used to perform fault studies and generate COMTRADE data, which are replayed by a real-time digital simulator (RTDS) to feed input to the hardware relays. Three scenarios are analyzed: normal operation, an N-1 contingency, and an IBR-only scenario. The evaluation results reveal the following: 1) the protection scheme remains reliable under normal conditions and N-1 contingencies and 2) in IBR-only scenarios, differential protection (87L) continues to operate reliably, whereas local protection elements, such as distance and directional elements, fail because of the lack of regulated negative sequence current contributed by IBRs. Enhanced protection is designed to address the challenge of lack of negative sequence current from IBRs, including increased restraining factors a2 and k2 to block 32Q or using V instead QV ORDER for ground faults, enhanced mho distance element with voltage and phase angle supervision for L-L faults. The efficacy of enhanced protection logic is validated and proven to work reliably. Additionally, IEEE Std. 2800-2022 negative sequence current compliant GFL and GFM IBRs from another vendor are tested and proven to work reliably without need for enhanced logic. Therefore, this work provides valuable decision-making for utilities facing protection system challenges due to IBRs, either designing enhanced protection scheme or requesting their IBRs being IEEE Std. 2800-2022 compliant to produce regulated negative sequence current for protection relay to make correct decision.

• Research Organization: National Laboratory of the Rockies (NLR), Golden, CO (United States)
• Sponsoring Organization: Florida Power and Light (FPL); USDOE Office of Critical Minerals and Energy Innovation (CMEI)
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 3021515
• Report Number(s): NLR/TP--5D00-98333
• Country of Publication: United States
• Language: English

Related Subjects

24 POWER TRANSMISSION AND DISTRIBUTION
97 MATHEMATICS AND COMPUTING
grid-following inverter
grid-forming inverter
IEEE Std. 2800-2022
negative sequence current
transmission line protection