On October 19, 2023, FERC issued a final rule directing the North American Reliability Corporation (“NERC”) to develop or modify reliability standards to address reliability concerns attributable to inverter-based resources (“IBRs”)—i.e., solar photovoltaic, wind, fuel cell, and battery storage resources. FERC explained that the current reliability standards were designed for a grid mostly comprised of synchronous resources, where all generators are operating at the same frequency across the grid. In recent years, there has been a substantial increase in renewable generation, such as wind and solar, which is largely nonsynchronous, meaning generators that do not operate at the same frequency as the synchronized grid. Nonsynchronous resources are often programmed to trip offline during system disturbances, resulting in the potential loss of significant amounts of generation at one time. FERC issued this order in response to the “unprecedented proportion of nonsynchronous resources” expected to connect to the grid in the coming years and the “material impact” of IBRs on the Bulk Power System, including at least 12 documented events where IBRs responded “unexpectedly and adversely” to normally cleared line faults and the largest IBR-related disturbance NERC has ever recorded. The rule directs NERC to submit the updated standards by November 4, 2026.
FERC’s directive aims to address four specific issues: IBR data sharing; IBR model validation; IBR planning and operational studies; and IBR performance requirements. Regarding data sharing, FERC found that the current reliability standards do not require generators and transmission and distribution providers to provide behavioral data of IBRs, “at a sufficient level of fidelity for Bulk-Power System planners and operators to accurately plan for, operate during, and analyze disturbances on the Bulk-Power System.” To address this issue, the new standards must: (1) require registered IBR owners and operators to provide modeling data and parameters “that accurately represent the registered IBRs” to planners, reliability coordinators, transmission operators, and balancing authorities; (2) require IBR owners to install disturbance monitoring equipment to be shared with system planners and operators to be used in validating IBRs’ models; and (3) require transmission owners and distribution providers to provide system planners and operators with modeling data of unregistered IBRs that individually or in aggregate materially affect the reliable operation of the Bulk-Power System.
Regarding model validation, FERC found the current reliability standards do not provide system planners and operators with accurate models to ensure reliable operation of the Bulk-Power System. To address this issue, the new standards must: (1) require the use of “approved industry generic library IBR models that accurately reflect the behavior of IBRs during steady state, short-circuit, and dynamic conditions;” (2) require registered IBR owners and transmission and distribution providers with unregistered IBRs on their systems to provide models representing the IBR’s dynamic behavior “at a sufficient level of fidelity” so that planners and operators can perform planning and operational studies “on a basis comparable to synchronous generation resources;” (3) require system planners and operators to timely validate and update system models by comparing verified IBR models to actual system operating behavior; and (4) require planners, reliability coordinators, transmission operators, and balancing authorities to develop a uniform framework of data exchange and modeling criteria for all interconnections to coordinate the creation of these system models. To address planning and operational studies issues, FERC is directing that the new reliability standards require planning coordinators and transmission planners to include evaluation of registered and unregistered IBR performance and behavior under normal and contingency conditions in their planning assessments.
Additionally, the order directs that the new reliability standards shall include performance requirements for IBRs. Specifically, IBR owners and operators must use appropriate settings to ride through frequency and voltage disturbances (i.e., maintain real power output and provide voltage and frequency support), allowing tripping to protect the IBR equipment only in situations similar to synchronous resources. Relatedly, the new standards may contemplate an exemption to the ride through requirement for currently operating IBRs unable to meet the requirement, but in such cases, the standards must also provide for the mitigation of the reliability impacts to the Bulk-Power System. Finally, the standards must prohibit the artificial interference with an IBR’s post-disturbance ramp rate to allow for a “quick and stable” return to pre-disturbance output while allowing for technical differences between IBR technologies.
A copy of FERC’s order can be found here.