MISO said Wednesday that it will postpone filing tariff revisions to implement four seasonal capacity auctions and impose a more rigorous accreditation process on participating resources.

Those filings are now slated for September rather than June, the RTO said.

“We are working on modifications, revisions, refinements,” MISO Director of Market Design Kevin Vannoy told stakeholders at a Resource Adequacy Subcommittee meeting April 14.

Vannoy said MISO still plans to hold four distinct seasonal auctions, but staff must refine the proposed resource accreditation. The RTO still expects the changes to be ready in time for the 2023/24 planning year.

Many MISO members still oppose the RTO’s proposal availability-based capacity accreditation, which measures a unit’s recent performance against predetermined periods of high risk on the system. Stakeholders last month voted against the design and voiced concern to MISO’s Board of Directors. (See MISO, Stakeholders Disagree on Post-storm Accreditation.)

Stakeholders have disparaged the availability-based accreditation for its reliance on a small set of hours throughout the year that contain historical reliability risks. They said the plan would introduce volatility and result in owners never confidently scheduling planned maintenance outages for their units.

“We understand we cannot introduce a proposal that introduces volatility,” Vannoy said, though he added that MISO hasn’t settled on a new accreditation design yet. He promised MISO would provide “substantial support” in the form of analysis for any new accreditation design it proposes.

Vannoy said the fact remains that MISO has resources that “chronically” underperform during times of need in both hot and cold weather.

RTO staff said they plan to return to the May RASC meeting with more proposal changes. The grid operator still plans to submit a single FERC filing reflecting a seasonal capacity auction proposal equipped with separate seasonal reserve requirement values and resource accreditation changes.

“We think the resource adequacy changes need to move forward as a package,” Executive Director of Market Strategy and Design Scott Wright said.

MISO is also planning to perform regional resource adequacy assessments to identify which areas in its footprint are short on supply. The assessment will differ from the Organization of MISO States’ and MISO’s annual resource adequacy survey that relies on responses from load-serving entities.

Wright said where the current capacity auction only looks out a year, the RA assessments will examine resource retirements and additions five to 10 years out. He said MISO has been discussing the concept internally for some time.