ERCOT is now raising the bar on dynamic modeling, highlighting two key drivers behind their proposed changes:
- The rapid growth of power-electronics-dominated loads, particularly data centers and other Large Electronic Loads (LELs)
- Observed system events where load tripping behavior created potential reliability concerns
ERCOT emphasized that accurate dynamic representation of large loads is essential for transmission stability studies, weak grid evaluations, and system operating assessments. The proposed Planning Guide Revision Request (PGRR) aims to formalize dynamic data expectations, introduce standardized quality testing, and align modeling practices across software platforms.
What Changes from the Current Process
Under today’s framework:
- PSS/E models are required for all large loads
- TSAT models are required when PSSE User Defined Models (UDMs) are used.
- PSCAD models are required only for subsynchronous oscillation (SSO) studies or certain co-located scenarios
- Model Quality Testing (MQT) is limited in scope and typically focused on generation resources with co-located load
The proposed PGRR would materially expand these requirements as follows:
- PSCAD Required for all large loads
- Model Quality Testing (PSSE, PSCAD, and TSAT) required for all large loads
The proposed MQT framework includes Converter Model Validation Test (CMV) for LELs only, which is Hardware-type validation for the Uninterruptible Power Supply (UPS) converter and associated computational load. This is designed to demonstrate accuracy of the PSCAD model of the converter type.
For LELs specifically, the purpose is to demonstrate compliance with ride-through expectations, including alignment with ongoing NOGRR282 voltage ride-through criteria. For non-LELs, MQT would still be required to improve understanding of dynamic behavior.
ERCOT also indicated that simplified composite load representations are no longer sufficient for LEL modeling. Instead, ERCOT recommends using EPRI UDM for the power electronic portion and CMLD for the cooling portion if it cannot be represented using EPRI UDM.
New Submission Milestones in the Interconnection Timeline
The proposed PGRR integrates dynamic data review into multiple checkpoints of the large load interconnection process. Before initiating the stability study in the Large Load Interconnection Study (LLIS), pre–Quarterly Stability Assessment (QSA), and prior to Initial Energization (LELs only), including confirmation that as-built settings match studied models.
Existing LELs and “Material Changes”
The proposed PGRR also introduces new requirements for material changes to existing LELs.
If an existing LEL undergoes a significant modification, such as conversion from crypto mining to data center operations, or changes to ride-through capability or control systems, for example, the facility may be required to re-enter the large load interconnection process.
What to Expect Next
ERCOT indicated it plans to formally submit the PGRR to the Reliability and Operations Subcommittee (ROS) in March. Stakeholder feedback is ongoing, and implementation details, including updates to the Dynamics Working Group (DWG) Procedure Manual, are still being refined. All information presented to date remains preliminary and subject to change as ERCOT workshops continue.
What This Means for Developers
For large load developers, particularly data center and other LEL projects, this proposal signals:
- Earlier and more rigorous dynamic modeling requirements
- Mandatory PSCAD modeling regardless of SSO applicability
- Formalized Model Quality Testing prior to stability studies and QSA
- Greater scrutiny of as-built alignment prior to energization
- Potential re-entry requirements for significant post-energization changes
Dynamic modeling is moving from a study input to a structured compliance framework embedded throughout the interconnection lifecycle.
How EPE can Support
EPE is actively engaged in Large Load Working Group (LLWG) discussions and closely tracking the development of this proposed PGRR. We support clients with:
- PSS/E, PSCAD, and TSAT model development
- Model Quality Testing preparation and execution
- Model alignment for LLIS and QSA
- Evaluation of material changes for existing LELs
- Strategic positioning under evolving ERCOT modeling standards
As ERCOT finalizes these requirements, early preparation will be critical to avoid delays in study progression or energization readiness. We will continue to monitor workshops and stakeholder updates and provide further analysis in upcoming Watt’s Current articles once the PGRR framework is finalized.
If you would like to discuss how these proposed modeling requirements could affect your project, contact our team of experts using the form below.
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