PJM's Model Verification Guidance and the Move to MOD-026-2

PJM tells Generator Owners how to prepare and submit model verification cases in PJM Guidance for NERC MOD-026-027: Generation Owner Preparation & Submittal, Revision 4, dated July 17, 2025. The guidance was written for MOD-026-1 and MOD-027-1. Under the MOD-026-2 implementation plan, both of those standards retired immediately before MOD-026-2 took effect on April 1, 2026. As of October 4, 2026, PJM's Planning Modeling Submissions page still links MOD-026-1, MOD-027-1 and this guidance. This post summarizes what the guidance asks for and how it lines up with MOD-026-2.

What PJM's Guidance Asks For

Models on PJM's Acceptable Model List

Excitation and governor models must be on the PJM Acceptable Model List (Appendix A-2), which draws on the historical NERC acceptable model list, NERC's unacceptable model list, the ERAG Acceptable Models Working Group and PJM experience. Each model is marked acceptable, not recommended or not accepted. PJM requires generic models with due diligence to match unit performance, and PJM decides whether a generic model is insufficient.

IBR-Specific Content

• Aggregate plants must model the plant Volt/Var control system, and aggregate inverter-based plants must model active power and frequency control functions.
• For IBRs, the guidance states that momentary cessation capability is mandatory in the model. Appendix A-4 lists what to get from the inverter manufacturer: low- and high-voltage momentary cessation thresholds or curves, recovery delay, active current recovery ramp rate and any reactive current recovery limits.
• All IBRs submit an EMT model, which PJM uses to benchmark the positive-sequence model. Revision 4 added this requirement. The EMT model must be validated through factory or field testing and reflect the as-built configuration, and it comes with setup instructions, a list of control functions and parameters, the software version, a site-specific sample case and a matching single-line diagram.

User-Defined Models

If a Generator Owner believes a generic model cannot represent the unit, PJM asks for a technical justification comparing the generic model with lab or field data; UDMs for both PSS/E and TSAT with model structure, data and closed-loop control logic (no black boxes); at least one generic model alongside the UDM; and a DLL compatible with PJM's current software, with an updated DLL within 30 days if PJM changes software versions.

The Submittal Package

Cases go through the PJM Planning Community, with separate cases for MOD-026 and MOD-027 submittals. Attach:

• .raw power flow file in PSS/E version 35 format, covering the local system up to the POI bus, with an aggregated model for renewable plants
• .dyr dynamics file in PSS/E version 35 format, with the control and limiter models that fit the unit type
• Laboratory test report signed by the preparer and reviewer, with manufacturer information, test procedures and results, machine MVA base, a unit ID consistent with EIA-860 and the model in PSS/E format; comparison plots of test and simulation are recommended
• EMT model and documentation for IBR facilities
• A single-line diagram is recommended but not mandatory; the .lis file is optional

PJM assigns a case number and processes the case within 90 calendar days.

Self-Review and PJM's Determination

PJM strongly recommends, but does not require, a self-review before submittal (Table 1): a no-disturbance run, a three-phase POI fault with trip, voltage and governor reference steps using PSS/E BAT commands, a voltage ride-through fault case and a frequency reference step for renewable plants, and an LVRT log check. PJM then finds the model usable or not usable and posts the result in the Planning Community. A not-usable finding closes the case; the guidance gives the Generator Owner 90 calendar days, citing MOD-026/027 R3, to open a new case with revised files and an explanation of the changes.

What Changes Under MOD-026-2

MOD-026-2 replaced MOD-026-1 and MOD-027-1 on April 1, 2026. Its implementation plan phases in compliance:

• April 1, 2027 (R1 and R7). Each Planning Coordinator and Transmission Planner must have jointly developed dynamic model requirements, including which legacy facilities need EMT models and what EMT models, formats and level of detail are acceptable. Transmission Planners must provide current in-use models within 90 calendar days of a written request from the facility owner.
• April 1, 2029 (R2 to R6). Generator Owners provide verified positive-sequence models (R2) and, for IBR, HVDC and FACTS facilities, EMT models (R3); provide updated models within 180 calendar days of a change that alters dynamic response (R4); and respond within 120 calendar days to a Transmission Planner notice that a model is not acceptable (R6). Transmission Planners review submittals within 120 calendar days (R5).

Three points for PJM Generator Owners:

• PJM's MOD-026-2 model requirements under R1 are due by April 1, 2027. Expect them to replace or revise the July 2025 guidance, and check PJM's Planning Modeling Submissions page for the current version before preparing a case.
• PJM's guidance already asks every IBR for an EMT model. MOD-026-2 R3 excludes legacy facilities (commercial operation before April 1, 2026) that the Transmission Planner does not identify under R1, and legacy facilities whose OEM no longer supports an EMT model. Whether PJM keeps an EMT model requirement for every existing IBR will be set in its R1 requirements.
• Response times differ. The current guidance gives 90 calendar days after a not-usable finding; MOD-026-2 R6 gives 120 calendar days from a notice of unacceptability, from April 1, 2029.

Interconnection Is a Separate Track

For new service requests, PJM sets model requirements in other documents: the PJM Dynamic Model Development Guidelines for Interconnection Analysis, Revision 2.1 (March 10, 2026), and the PJM EMT Model Development Guidelines for Inverter-Based Resources, Revision 0 (March 5, 2026). Under the Dynamic Model Development Guidelines, projects in Cycle 01 and later submit a PSCAD model at Decision Point II, and As Built Data models must reflect the settings after commissioning. These documents govern the interconnection study process, not MOD-026 verification of an operating plant.

Updating Your Internal Procedure

• Map each unit to a model on PJM's Acceptable Model List and record any UDM justification.
• For IBR plants, keep the EMT and positive-sequence models under version control together, with the benchmarking cases and plots.
• Record momentary cessation parameters by inverter make, model and site configuration, using the Appendix A-4 list.
• Standardize PSS/E v35 .raw and .dyr deliverables and lab report contents (signatures, MVA base, EIA-860 ID).
• Run PJM's Table 1 self-review cases before each submittal and archive the inputs and plots with the model version.
• Track the MOD-026-2 dates: PJM's R1 requirements by April 1, 2027; R2 to R6 from April 1, 2029, including the 180-day model update after any change that alters dynamic response.

Where GridStrong Fits

GridStrong's platform keeps model files, lab reports, DLLs and EMT and positive-sequence benchmark results under version control, and assembles the attachments a Planning Community case needs.

Sources: PJM Guidance for NERC MOD-026-027, Revision 4 (July 17, 2025); PJM Dynamic Model Development Guidelines for Interconnection Analysis, Revision 2.1 (March 10, 2026); PJM EMT Model Development Guidelines for Inverter-Based Resources, Revision 0 (March 5, 2026); NERC MOD-026-2 and its implementation plan (Project 2020-06, October 2025).