FERC on July 24 approved two new reliability standards establishing frequency and voltage ride-through requirements for inverter-based resources, completing the second milestone in the commission’s Order 901 (RM25-3).
The standards will take effect the first day of the first calendar quarter 12 months after the effective date of the commission’s approval order.
In its order, the commission largely followed its December 2024 Notice of Proposed Rulemaking. (See FERC Approves NERC Assessment, Seeks Comment on IBR Standards.)
That NOPR proposed approving PRC-024-4 (Frequency and voltage protection settings for synchronous generators, type 1 and type 2 wind resources, and synchronous condensers) and PRC-029-1 (Frequency and voltage ride-through requirements for IBRs), while also requiring NERC to submit two informational filings on exemptions to ride-through requirements for legacy IBRs.
Most comments on the NOPR supported approving the two standards, along with NERC’s proposed definition of the term “ride-through.” However, some stakeholders expressed concern that PRC-029-1 could cause projects to be delayed or even canceled. Ørsted Wind Power asked FERC to remand the standard for further development because “developing projects may be abandoned, decreasing generation when reserve margins are already tight.”
The Louisiana Public Service Commission also drew attention to the standard’s proposed exemption period, which would give owners of legacy IBRs — resources that are already in operation when the standard goes into effect — 12 months after the effective date of the standard to request an exemption to the voltage and frequency ride-through requirements. The PSC said this measure “impermissibly favors legacy IBR owners at the expense of [grid] reliability.”
Several comments mentioned the exemption process, with both Ørsted and Dominion Energy saying the developers ignored “extensive comments during the standard development process” raising issue with a perceived lack of consideration for projects in active development that cannot satisfy the standard’s ride-through requirements.
However, NERC replied that it followed all its rules for soliciting industry feedback, even after the Board of Trustees invoked its authority to accelerate the development process. (See “Board Invokes Standards Authority to Meet IBR Deadline,” NERC Board of Trustees/MRC Briefs: Aug. 15, 2024.) The ERO said the “standard was narrowly developed to avoid undue negative effects on competition beyond what is necessary for reliability.”
Invenergy, Ørsted and two clean energy associations also asked FERC to have NERC update the standard to implement another exemption for HVDC-connected IBRs with choppers — used in offshore wind projects to protect converters by dissipating excess power during grid faults. The commenters said IBRs with choppers cannot meet a 10-second ride-through window mandated in PRC-029-1 because the “chopper’s thermal limit requires tripping the HVDC system to prevent overheating and thermal damage beyond two seconds.”
Additional Exemptions?
In its filing, FERC said there was not enough information for it to determine whether additional exemptions are needed. The commission therefore directed NERC to determine “whether and … how to account for” the ability of chopper-equipped IBRs to comply with the ride-though provisions of the standard, as well as whether the “lead time between adopting IBR design specifications and placing the IBR in service” merits an exemption as well. NERC must submit its determination, along with any proposed changes to PRC-029-1, within 12 months of the order’s effective date.
Also due in 12 months are modifications to the standard addressing commenters’ concerns that “owners of legacy IBRs may not be able to secure the necessary documentation from … manufacturers” to identify the specific component of the IBR causing limitations.
The ERO will also have to submit an informational filing 18 months after the conclusion of the exemption process — 30 months after the effective date of the standard — to “assess the reliability impacts of the exemptions.” In this the commission was persuaded by NERC’s response to the NOPR, which proposed requiring two filings, 12 and 24 months after the effective date. FERC said NERC would need “more than 12 months to compile the data requested in the first filing, and a filing at 24 months will not be timely and may include redundant information.”
The filing must assess the reliability impacts of the exemptions for each interconnection and each reliability coordinator area, for the following data:
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- Total number of IBRs for which generator owners are subject to compliance with the standard and their aggregated MW capacity;
- Total number of IBRs for which GOs requested exemptions and their MW capacity;
- Total number of IBRs, and MW capacity, for which GOs were granted exemptions;
- Total number of granted exemptions, and MW capacity, by exemption type (voltage and/or frequency); and
- Total number of granted exemptions, and MW capacity, by IBR type (wind, solar, battery energy storage system or fuel cell)
At the commission’s meeting, Commissioner David Rosner thanked NERC staff for their efforts developing the standards, calling them “critically important work for the commission.”
“There’s nothing more appropriate than solving tomorrow’s problems today, before they become problems tomorrow, and that’s what we’re doing here on these standards,” Rosner said. “I [also] want to encourage vigilance here. I think we’re making progress on frequency ride-through, but there’s more to do.”
“What’s the next thing? What’s this commission, 10 years from now, going to look back to and think, ‘Hey, that was a good idea’?” he continued. “I think one of those things, perhaps, [is] asking [IBRs] to do more on their grid-forming capabilities. So I look forward to them working with their stakeholders [and] finding the right engineering solutions to these problems as they think through standards going forward.”