In a major step toward strengthening grid reliability, the ERCOT Board of Directors unanimously approved NOGRR272 and PGRR121 on September 22, 2025, establishing new Advanced Grid Support (AGS), also known as grid-forming, requirements for inverter-based Energy Storage Resources (ESRs). These revisions now await final approval from the Public Utility Commission of Texas (PUCT).
What’s Changing?
NOGRR272 introduces AGS requirements for ESRs connected to the ERCOT Transmission Grid. These include the ability to maintain internal voltage phasors and synchronize with the grid during dynamic events. The requirements apply to ESRs with Standard Generation Interconnection Agreements (SGIA) executed on or after April 1, 2026, marking a key milestone in ERCOT’s transition to a more resilient, inverter-dominated grid.
PGRR121 complements this by updating the Model Quality Test (MQT) requirements defined by the Dynamics Working Group (DWG) to ensure that inverter-based ESRs are accurately modeled and validated for their dynamic performance under a range of system conditions.
New Additions to DWG Model Quality Tests
PGRR121 introduces two new AGS-related tests to the DWG MQT suite:
- Inertia Response Test: Evaluates the model’s ability to reflect the facility’s response to system frequency changes, supporting ERCOT’s need to assess dynamic behavior under low-inertia conditions.
- Loss of Synchronous Machine Test: Confirms the facility’s ability to maintain synchronism and voltage phasor following the loss of synchronous generation.
- This test focuses on validating stability while the facility remains grid-connected
- It is not intended to require standalone operation without ERCOT grid support
Why This Matters
ERCOT’s system is rapidly evolving, with projections exceeding 100 GW of new inverter-based capacity by 2026. Over 20 Generic Transmission Constraints (GTCs) have been implemented to manage reliability risks, many tied directly to IBR behavior. The new AGS requirements aim to:
- Improve voltage and frequency response during grid events
- Reduce the risk of resource tripping or instability
- Increase GTC limits, potentially reducing curtailments
ERCOT’s internal assessments, presented to the Inverter-Based Resource Working Group (IBRWG) in July 2024, demonstrated the technical feasibility and system benefits of grid-forming ESRs. These findings align with global practices in the UK and Australia.
EPE's Role
At EPE, we are ready to support developers and asset owners in meeting ERCOT’s evolving interconnection and modeling requirements through:
- Preparation and validation of PSS®E, TSAT and PSCAD dynamic models and MQTs
- Execution of DWG Model Quality Tests, including the new Inertia Response and Loss of Synchronous Machine tests
- Comprehensive interconnection application and model submission support
- Guidance on compliance timelines for projects affected by PGRR121
With deep expertise in modeling and interconnection processes, EPE remains a trusted partner in navigating ERCOT’s evolving regulatory landscape. Contact our team using the form below to find out how we can help you improve modeling accuracy, regulatory compliance, and long-term grid reliability.
