Voting will begin soon on NERC’s latest proposed reliability standard to address FERC’s directive to improve the reliability of inverter-based resources, the oldest of the ERO’s high-priority standards projects.

NERC’s Standards Committee approved posting MOD-026-2 (Verification and validation of dynamic models and data) for a 26-day comment period at its latest meeting May 21. (See NERC Standards Committee Rejects IBR Definitions Request.) The comment period began May 22; voting will begin June 9 and end the same day as the comment period on June 18.

Formation of ballot pools began May 22 and concluded at 8 p.m. ET on June 4. The implementation plan for MOD-026-2 will be up for a vote along with the standard.

According to the technical rationale provided by the standard development team, the project originally was suggested by NERC’s Inverter-based Resource Performance Task Force (IRPTF) in 2020. The IRPTF said MOD-026-1 and MOD-027-1 — which “require generator owners to provide verified dynamic models to their transmission [planners] for … power system planning studies” — needed updates to “clarify requirements related to IBRs and to require sufficient model verification to ensure accurate generator representation in dynamic simulations.”

When FERC issued Order 901 in 2023 directing NERC to develop standards to improve the reliability of IBRs, NERC tapped Project 2020-06 — begun in response to the IRPTF’s report — to address the third milestone in the order, along with two other ongoing projects. The standards for Milestone 3 must be filed with FERC by Nov. 4, with full implementation by Jan. 1, 2030.

To satisfy FERC’s directive, MOD-026-2 combines MOD-026-1 and MOD-027-1, with changes that include expanding requirement R1 of MOD-026-1 to cover electromagnetic transient models. These were not mentioned in the previous version because they are required only of IBRs, flexible AC transmission system devices and HVDC facilities. It adds requirements that transmission planners and planning coordinators develop processes for generator and transmission owners to submit documents on model verification.

A new requirement concerns verification of models’ relationship to in-service equipment at IBR facilities. The SDT said “transmission planners and planning coordinators are faced with challenges relying solely on positive sequence dynamic models to ensure reliable operation” of the grid.

For example, simulation platforms currently in use “are generally not suitable for capturing the dynamic response of” IBRs, meaning that some protection systems or controls cannot be accurately modeled and ride-through performance cannot be assessed. The models also do not include IBRs’ real code behavior, instead relying on “engineering judgment based on controller block diagrams.”

The implementation plan for MOD-026-2 envisions requirement R1 becoming effective on the first day of the first calendar quarter that is 12 months after the date of FERC’s approval, with MOD-026-1 and MOD-027-1 to be retired immediately prior. All other requirements of the new standard would become effective 24 months after the overall standard.