Meeting Summary – 10/11/2024 IBRWG Meeting

1 – Antitrust Admonition – Julia Matevosyan

• Antitrust admonition was shared with meeting participants.

2 – SSR/SSFR Best Practices – Anuradha Dissanayaka, Andrew Isaacs – Electranix

• Introduction of Anuradha Dissanayaka, Electranix engineer leading SSO studies.
• Overview of Sub-Synchronous Oscillations (SSO) including historical events and impacts: Mojave generator SSR event in the 1970s and south Texas SSCI event in 2009.
• Importance of detailed studies for IBR plants near series capacitors before commissioning to prevent issues.
• Explanation of various sub-synchronous phenomena: SSR, SSTI, SSCI, SSFR.
• Description of study processes: Screening (passive and dynamic frequency scanning) and detailed EMT simulations.
• Challenge of modeling accurate systems and the back-and-forth required with OEMs to complete studies.
• Importance of accurately modeling transformer saturation to prevent SSFR (Sub-Synchronous Ferro Resonance).
• Discussion on the problems of adding new series capacitors in areas with high IBR penetration.
• Sensitivity studies and control tuning as solutions for various sub-synchronous issues.
• Potential of grid-forming battery energy storage systems (BESS) to improve damping and minimize risks.
• Application of SSR and SSFR detection relays to manage certain phenomena.
• Recent findings about grid-forming BESS providing positive damping over a wide frequency range.

3 – PFR from IBRs under “Deep” Curtailment – Scott Karpiel – SMA, All

ERCOT PFR sma11Oct2025

PV_Inverter_OEM_PFR_Capability_Under_Curtailment_20241011.pdf

• Discussion on the ability of inverter-based resources (IBR) to provide primary frequency response (PFR) under deep curtailment.
• SMA inverters can respond in less than 150 milliseconds, but are limited by the accuracy of measurement devices and plant controller processing time.
• Photovoltaic (PV) resources operate at maximum power points and may not increase AC power to respond to frequency events if curtailed to zero.
• IBR units are not ideal for frequency response compared to hybrid systems with battery energy storage systems (BESS).
• A question was raised about SMA inverters’ ability to respond when curtailed to zero with adequate irradiance.
• Scott emphasized the role of the plant controller in ensuring the inverter can increase active power quickly during low-frequency events.
• Discussion on the use of weather stations and algorithms to estimate the available power for frequency response, acknowledging it as challenging.
• Questions regarding the accuracy, model performance under low dispatch, and potential discrepancies in model behavior were addressed.
• The discussion included how curtailment affects the high sustained limit (HSL) reported to ERCOT and the estimation of available capacity.
• Clarification that plant controllers can perform ongoing measurements crucial for frequency response, with the role of the PPC in providing grid frequency data.

4 – NOGRR245 and NOGRR255 Updates – Stephen Solis – ERCOT

NOGRR245_255_Update_IBRWG_10112024.pdf

• NOGRR245 was recently approved, effective October 1, 2024; changes to guides and language in process details provided.
• Performance requirements from NOGRR245 become effective after entities enhance ride-through capabilities; coordination activities are ongoing.
• Model quality testing procedures updated in DWG procedure manual, approved by Reliability and Operations subcommittee.
• NOGRR245 includes specific steps for handling performance failures, such as investigation, reporting, and model validation.
• NOGRR255, effective August 1, 2024, aligns with PRC-028, focusing on disturbance monitoring equipment and data retention requirements.
• NOGRR255 introduces timelines for resource compliance and site selection for monitoring equipment installations.
• FAQs on NOGRR255 clarified language issues and requirements for disturbance monitoring at plant level versus individual inverters or turbines.
• Discussion on monitoring equipment emphasized root cause analysis importance and advisory on utilizing existing equipment.
• Future updates to NOGRR255 depend on outcomes from FERC directions and ongoing performance assessments.

5 – NERC Standards Update – PRC-029 – TRE

20241011_Update_to_IBRWG.pdf

• Rachel Coyne presented updates in place of Mark Henry.
• Activity around PRC-029 related to milestone two for FERC Order 901 was discussed.
• PRC-029 caused industry disagreements; NERC invoked rules of procedure, section 321.
• A technical conference was held in September to build consensus with OEM participation.
• Changes to PRC-029 include updating the ride-through definition and modifying requirements three and four.
• PRC-029 passed with 77.88% support; other standards in milestone two also passed.
• Standards to be filed with FERC by November 4.
• Update on regional standard bow one TRE version two project SAR-013 was given.
• Scope of SAR includes provisions on governor generator deadband, rules of GOBA and CEA roles, and PFR performance for battery energy storage.
• Project approved by Texas RE MRC on September 18, and standard drafting team solicitations concluded.
• Next step is for MRC to approve slate and start drafting the next revision of that standard
• Consensus reached, particularly on requirement three concerning the broad band of frequency operational range.
• Continued discussions on PFR response limitations, especially for IBR, beyond OEM capabilities.

6 – Other Industry Updates – Julia Matevosyan ESIG

ERCOT_IBRWG_NERC_and_Other_Updates_101024.pdf

• Series of grid forming seminars will include six sessions with various presenters from ISOs, utilities, NERC.
• Registration for the seminars will be available on the IBR working group’s presentation.
• The I2X meeting is scheduled for October 24 in Providence and will be a hybrid meeting.
• The meeting is sponsored by the Department of Energy and involves the I2X Interconnection Innovation Change.
• The I2X meeting will be combined with a workshop with numerous presentations over two days.
• Registration will be available online for the seminar series and the webinar in mid-October on grid funding projects.

6.1 – Lunch Break

• Meeting paused for a 30-minute lunch break.

7 – AGS ESR Model Quality Tests and Discussion – Poria Astero, Sun Wook Kang – ERCOT

ERCOT AGS-ESR Oct-11-2024 IBRWG

• Discussed ERCOT recommendations on advanced grid support inverter-based energy storage resource (AGS ESR) test requirements.
• Sun Wook Kang emphasized the importance of the effort due to the increasing presence of inverter-based resources (IBRs) and decreased availability of conventional units for maintaining grid reliability.
• Highlighted key efforts like synchronous condenser projects, PGRR109 improvement, and NOGRR245 approval for better IBR operating requirements.
• Electranix contracted in 2023 to support the development of functional specifications and test framework for AGS ESR.
• Presentation of interconnection requests showed a 93% IBR and 42% battery projects focus as of August 2024.
• Battery resources are seen as increasingly important for ERCOT and are capable of software updates for grid support (GFM capability).
• Expectation that AGS ESR will improve grid stability and system strengths, while reducing impact of disturbances.
• Plans to submit PGRR and NOGRR by year-end, involving stakeholder feedback on test requirements.
• Poria Astero outlined detailed AGS ESR test framework including site-specific model quality and unit model validation tests.
• Test Bench setups explained: Test Bench 1 with impedance to model grid stress, Test Bench 2 for islanded operation.
• Several test scenarios discussed involving stability under phase angle jumps, voltage disturbances, and frequency changes.
• Presentation emphasized reactive power following voltage changes, inertial response during frequency changes, and system SRF 
• AGS ESR test requirements considered grid-following and grid-forming characteristics.
• Existing large voltage disturbance test and a modified loss of synchronous machine test to ensure parallel operation capability.
• Acknowledged further test suggestions from Electranix, with a focus on necessary tests for AGS ESR adoption.
• Focus on ongoing collaboration with stakeholders, manufacturers for test validation and feedback.

8 – Other Business

• Not Discussed