NERC will have to issue its highest level of alert to address shortcomings revealed in a recent information request about inverter use, the ERO said in a report issued April 1.
A Level 3 alert indicates specific steps deemed essential for certain stakeholders to ensure reliable grid operation. The ERO has only used it once before, to set out “essential actions” for utilities to prepare for cold weather in 2023. (See NERC Board May Force Action on Cold Weather Standard.) Issuing a Level 3 alert requires approval from NERC’s Board of Trustees.
The Aggregated Report on NERC Level 2 Recommendation to Industry summarizes the findings from a Level 2 alert sent to stakeholders in June 2024, inspired by concerns over inverter-based resources and related modeling practices after a series of grid disturbances in recent years involving such generators. (See NERC Targets IBR Modeling Concerns in Level 2 Alert.)
NERC directed the alert at generator owners (GOs), transmission planners (TPs) and planning coordinators (PCs). GOs that own grid-connected IBRs were required to provide a range of information about them, including:
-
- manufacturers of inverters on their systems;
- model numbers for their inverters and their quantity;
- nameplate ratings for each model of inverter;
- inverter- and plant-level voltage and frequency protection settings;
- inverter- and plant-level reactive power capabilities and control information;
- model types used to represent facility model data to TPs and PCs; and
- dynamic and load-flow model files for each facility.
NERC also provided a series of questions for IBR owners, TPs and PCs including whether their organizations have publicly available model submission and quality requirements, what type of generator models are permitted during the interconnection process, and how the organizations verify accuracy of their models.
The ERO said stakeholder feedback “indicated that GOs do not keep the requested data and information readily available and up-to-date and are reliant on [original equipment manufacturer] and consultant support” to provide the information when requested. Not only does this make event analysis more difficult, it calls into question the quality of planning data submitted by GOs.
GOs’ responses to the question about generator models revealed that an overwhelming majority, 78%, submit only standard library models to their TPs and PCs. 15% submit manufacturer-specific models, and only 7% submit both — despite the fact that “NERC guidance and FERC Order 2023 indicate that both should be submitted.”
A majority of GOs indicated that they have publicly available model submission and quality requirements, and believe their requirements align with NERC’s dynamic modeling recommendations. But only 16% of GOs said they require equipment-specific, user-written positive sequence phasor domain generator models to be submitted for interconnection studies, while a slim majority — 97 out of 190 respondents — said they do not require submission of equipment- and site-specific electromagnetic transient (EMT) generator models during the interconnection process.
78% said they perform EMT model verification, and 70% indicated they do not integrate EMT models into generator interconnection studies. 81% said their organization lacks the tools and personnel to effectively perform EMT analysis.
The question about inverters’ origins revealed that five original equipment manufacturers account for about 74% of the inverter fleet by generation capacity, and 83.1% by number of inverters. Although the Level 2 alert did not mention cybersecurity concerns, the dominance of a small number of manufacturers has caused concern among the cybersecurity community because inverters produced by the same company may share common vulnerabilities that make infiltration and sabotage easier.
NERC has not said what would be in a potential Level 3 alert, but the ERO emphasized that it would contain “only voluntary essential actions, [with] the mitigation of risk … left up to individual stakeholders.”