ERO stakeholders expressed a range of opinions about NERC’s proposed ride-through requirements for inverter-based resources, with some asking for multiple changes before their acceptance by FERC (RM25-3).

NERC submitted 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) for FERC’s approval on Nov. 4, 2024, along with three others. (See NERC Submits IBR Standards to FERC.) The standards addressed the second milestone in FERC Order 901, covering performance requirements and post-event performance validation for registered IBRs.

Commissioners called for stakeholder comments on PRC-024-4 and PRC-029-1 in December 2024 in a notice of proposed rulemaking (NOPR) that suggested approving the standards, along with the definition of “ride-through,” and requiring NERC to submit informational filings 12 and 24 months after the close of the period for generator owners (GOs) to seek exemptions for existing IBRs permitted under PRC-029-1. (See FERC Approves NERC Assessment, Seeks Comment on IBR Standards.)

These filings would provide information on the number of legacy IBRs that would be subject to compliance, and on the number of exemptions requested and granted by NERC.

In its comments, NERC acknowledged the proposed information filings were based on concerns about the effect of generator exemptions on grid stability and the desire to avoid issuing too many. But the ERO urged FERC to change its directive to require a single filing 18 months after the close of the exemption period rather than at 12 and 24 months.

NERC said 12 months “may be too soon for NERC to review all exemption requests and determine which requests qualify for the exemption,” while 24 months “would result in FERC not receiving a comprehensive understanding of the exemptions’ impact on reliability as quickly and result in redundant information being provided.” An 18-month deadline would provide enough time to review all data and give the commission the information it needs, NERC said.

Comments also were submitted by a range of ERO participants. In one filing, a group of ISOs and RTOs comprising CAISO, MISO, PJM and SPP generally supported FERC’s NOPR with no issues. However, the writers did observe the exemption process provided in PRC-029-1 “does not contemplate the actual exemption requests also be submitted to … ISOs and RTOs.”

The ISOs and RTOs said they believe it’s reasonable “that generators seeking such exemptions provide copies … to ISOs and RTOs and other system operators,” but added that they could support the standard as written “based on the common understanding” that it would not prevent operators from seeking that information on their own.

Other comments sought more significant changes, particularly to PRC-029-1. In a joint filing, the American Clean Power Association (ACP) and the Solar Energy Industries Association (SEIA) urged FERC to direct the incorporation into PRC-029-1 of the following revisions:

• • Expand exemptions to include resources that have executed an interconnection and primary design, procurement and/or construction agreements by the effective date of the standard.
  • Clarify the evidence required to secure an exemption on the basis of equipment limitations.
  • State that existing equipment that receives an exemption due to hardware limitations will not lose it if new equipment is added separately to the plant.
  • Update the treatment of equipment at HVDC-connected IBRs.
  • Retain the ability of an exemption from frequency ride-through requirements.

ACP/SEIA said the changes would “maximize electric system reliability, ensure just and reasonable rates by avoiding excessive retrofit and replacement costs that do not improve reliability, and prevent undue discrimination.”

The Edison Electric Institute also supported revising PRC-029-1’s exemption eligibility, which “does not consider the impact on [GOs] who have projects under development.” EEI said the standard, as written, did not account for “long lead time projects,” which “require GOs and project developers to make engineering decisions based on equipment design well before resources can be secured [and] built.”

EEI asked FERC to have NERC modify the exemption process to include projects for which the equipment already has been contracted for, delivered or deployed. In addition, it expressed concern about the objectivity of the exemption process and urged FERC to direct modifications aimed at ensuring NERC carries out the process consistently across all regions.