By Troy Dahlgren, NERC Reliability Specialist

FERC Order 901, issued on October 19, 2023, mandates the development of new and revised reliability standards to address the challenges posed by the increasing integration of inverter-based resources (IBRs) into the electric grid. This order represents a transformative regulatory initiative aimed at ensuring the stability and reliability of the U.S. electric grid as renewable energy sources become increasingly dominant. 

Key Provisions and Milestones

The order outlines four major milestones targeting various aspects of IBR management, including data sharing, model validation, and system performance monitoring.

Milestone 2 focuses on improving real-time monitoring and control capabilities for IBRs to enhance system reliability and operational transparency. 

The standards associated with Milestone 2 of FERC Order 901 have been developed and submitted for regulatory approval. NERC filed these new and revised Reliability Standards with FERC by the November 4, 2024, deadline, addressing key aspects such as ride-through performance requirements for IBRs. These standards are currently under review by FERC. On December 19, 2024, FERC proposed to approve the first of these standards but will be seeking more information on exemptions for certain IBRs. Comments are due 60 days after publication in the Federal Register.

The primary standards involved in this milestone include:

• PRC-028-1: This standard establishes monitoring requirements for both bulk electric system (BES) connected IBRs and non-BES connected IBRs that contribute to an aggregate nameplate capacity of 20 MVA or more and are interconnected at voltages of 60 kV or higher. The compliance timeline requires entities to implement Requirements R1 through R7 at 50% of their generating facilities within three years of the standard’s effective date, achieving full compliance by January 1, 2030. 
• PRC-029-1: This standard introduces performance-based ride-through requirements for IBRs, ensuring that these resources can maintain operation during voltage and frequency excursions, thereby enhancing grid stability. The standard is set to become effective six months after receiving approval from the applicable governmental authority. 
• PRC-030-1: Developed in response to multiple disturbance reports, this new standard addresses unexpected inverter-based resource event mitigation. It mandates that Generator Owners analyze any unexpected cessation of current injection and implement mitigation measures to prevent recurrence. 

Milestone 3 of this order focuses on enhancing data sharing and model validation for all IBRs, aiming to improve the accuracy and reliability of models used in local reliability studies, interconnection processes, and ongoing performance validation. 

The North American Electric Reliability Corporation (NERC) has outlined several key projects under Milestone 3:

1. Project 2020-06 – Verifications of Models and Data for Generators: This project addresses the verification and validation of models for registered IBRs, unregistered and aggregated IBRs, and aggregated distributed energy resources. It focuses on defining terms such as model verification and validation, developing processes for post-interconnection model validation based on performance data, and setting validation expectations using performance data. 
2. Project 2021-01 – System Model Validation with IBRs: This project focuses on system-level model verification and validation against actual behavior during disturbances, aligning steady-state and dynamic representations where appropriate. It aims to develop criteria for performing validation, determine minimum study conditions for validation studies, and establish processes to communicate system-wide model defects to Transmission Planners and other associated entities. 
3. Project 2022-02 – Uniform Model Framework for IBR: This project involves developing a NERC-maintained library of generic IBR model types and establishing a uniform framework for data sharing and model development. The goal is to ensure that other standards utilize performance data and the model library within this framework. 
4. Project 2022-04 – Electromagnetic Transient (EMT) Modeling: Expected to be added to Milestone 3 in December 2024, this project aims to establish EMT studies for IBRs during the interconnection process. It seeks to align with other modeling requirements developed by Milestone 3 project teams to ensure a streamlined process for model validation and data sharing. 

NERC has scheduled a Milestone 3 workshop for January 15–16, 2025, encouraging modeling subject matter experts to participate and contribute. 

All Milestone 3 projects must be filed with FERC by November 4, 2025, with full implementation required by January 1, 2030, to comply with Order No. 901. 

Industry stakeholders are encouraged to engage with these drafting teams early in 2025 to ensure a timely filing and to contribute to a consistent approach to modeling validation and data sharing.