Verification of Models and Data with an IBR Focus

MOD-026-1—which requires verification of generator excitation control systems and plan voltage/variance control models—plays a foundational role in ensuring reliable system studies. Although MOD-026-1 was designed for synchronous generators, its model verification principles are increasingly applied to inverter-based resources (IBRs) to ensure simulations reflect real-world behaviors. However, recent system events and analysis from the North American Electric Reliability Corporation (NERC) show that IBR models often fail to reflect the actual performance of the facilities they represent. This mismatch poses a serious reliability concern as IBR penetration continues to increase within the Bulk Power System (BPS).

IBRs respond to faults and frequency changes differently from synchronous generators. Unlike traditional units, IBRs can trip offline based on configuration settings, not just physical stress. When planning models fail to capture those behaviors, operational risk is introduced.

Modeling problems have caused real-world disturbances. NERC analyzed ten major instances where IBRs experienced unplanned power reductions during faults or voltage events in the Aggregated Report on NERC Level 2 Recommendation to Industry: Findings from Inverter-Based Resource Model Quality Deficiencies Alert. NERC’s analysis uncovered some systemic modeling issues including (but not limited to):

• Models submitted for system studies did not reflect plant behavior seen in the field
• 66 percent of Generator Owners (GOs) set protection settings that limit IBR ride-through, even though their equipment could handle more
• 20 percent of facilities artificially capped reactive power at 0.95 power factor, limiting grid support during disturbances
• Dynamic models showed frequent mismatches between reported “as-left” values and what was actually implemented; especially in key settings like frequency droop, voltage ride-through, and deadband parameters
• Many GOs didn’t have access to their own model data and relied entirely on third-party consultants or OEMs to retrieve basic information like control settings.

Recommendations: How to improve MOD-026-1 Outcomes for IBRs

Generator Owners

• Carefully review model accuracy and parameter alignment before submission
• Verify control software versions are current and compatible with submitted models
• Establish a formal, documented workflow for model verification and validation
• Maintain records of all validation reports, test data, and correspondence

Transmission Planners

• Set clear timelines for model submission and review processes
• Send formal acknowledgement requests when receiving models or updates from GOs
• Use calendar notifications or task reminders to ensure deadlines are met
• Retain all evidence of model verification steps and communications for audit purposes

By applying these internal controls, both Generator Owners and Transmission Planners can take immediate steps to reduce risk to the BPS and ensure future compliance. If you have any questions regarding MOD-026-1 or any other Reliability Standards, please contact information@texasre.org.

Resources:
Findings from Inverter-Based Resource Model Quality Deficiencies Alert
NERC Alert IBR Model Quality Deficiencies
NERC Alert: Inverter-Based Resource Performance and Modeling