What Generator Owners and IBR Developers Must Do — A Planning Engineer’s Perspective
Executive Summary
PJM’s Dynamic Model Development Guidelines represent a fundamental shift in how generation—especially Inverter-Based Resources (IBRs)—must be modeled, validated, and governed throughout the interconnection lifecycle. These requirements go well beyond traditional PSS®E stability model submissions. They establish a model fidelity, benchmarking, and validation framework intended to ensure that increasing levels of solar, wind, and battery storage do not compromise bulk power system stability.
For Generator Owners (GOs) and IBR owners in particular, the message from PJM is unambiguous:
A dynamic model that merely runs is no longer acceptable. A model must be numerically stable, behaviorally accurate, benchmarked against PSCAD, and traceable to as-commissioned field settings.
This article explains what PJM is now requiring, why it matters, and what generator owners must do—practically and strategically—to remain compliant and avoid queue delays, deficiency findings, or unusable model determinations.
1. Why PJM Tightened Dynamic Modeling Requirements
PJM’s grid is undergoing rapid transformation:
- High penetration of solar PV, wind, and BESS
- Reduced system inertia
- Increased reliance on fast-acting inverter controls
- Greater exposure to weak-grid conditions (low SCR)
Traditional RMS-only dynamic modeling has proven insufficient to capture:
- Control-loop interactions
- Current limiting behavior
- Momentary cessation
- Plant-level voltage and frequency coordination
As a result, PJM now treats electromagnetic transient (EMT) modeling as the reference truth for inverter behavior and requires RMS models to be benchmarked against PSCAD.
2. Who Is Impacted
These requirements apply to:
- All new generator interconnection requests in PJM
- All IBR facilities (solar, wind, BESS, hybrids)
- Projects >20 MW, and smaller projects where requested by PJM
- As-Built submissions following commissioning
Synchronous generators are still subject to the guidelines, but the most significant changes apply to IBR Generator Owners.
3. PSCAD Is No Longer Optional for IBR Owners
What Changed
Historically, PSCAD was requested selectively. Under the 2024–2025 framework:
- PSCAD models are expected for IBR facilities
- PSCAD represents the authoritative behavior of inverter controls
- PSS®E / TSAT models must be benchmarked to PSCAD, not vice versa
What PJM Expects in PSCAD
The PSCAD model must represent:
- Inverter control loops (PLL, current control, voltage support)
- Plant controller logic
- Collector system equivalents
- Step-up transformers
- Ride-through behavior
- Frequency response logic
Vendor-proprietary logic may remain masked, but output behavior must match field performance.
4. Mandatory Plant-Level Control Modeling
PJM explicitly requires:
- Explicit plant controller (REPC / PLNTBU1) representation
- Correct coordination between inverter-level (REEC) and plant-level controls
- Accurate voltage control, frequency response, and reactive power prioritization
Single-machine equivalents without plant-level logic are no longer acceptable for most IBR projects.
5. Benchmarking: From Best Practice to Requirement
RMS vs EMT Alignment
PJM requires that:
- PSS®E / TSAT models reproduce PSCAD step responses
- Voltage, frequency, and power recovery behavior align
- Control limits and ramp rates match
Flat Start Test
All models must demonstrate:
- 20-second no-disturbance simulation
- Active and reactive power variation ≤ 0.1 MW / 0.1 MVAR
- No initialization errors or hidden control oscillations
Failure of the flat start test is an automatic red flag.
6. Ride-Through and Momentary Cessation Enforcement
PJM has adopted a firm position consistent with NERC guidance:
- Momentary cessation must be eliminated to the extent possible
- Inverters must inject reactive current during low-voltage conditions
- Active power must recover rapidly after fault clearing
If momentary cessation is unavoidable due to equipment limits:
- It must be explicitly documented
- It must be correctly modeled
- It must be disclosed during submittal
Undocumented cessation behavior is a common cause of model rejection.
7. MOD-026 / MOD-027 Philosophy Applied to IBRs
Although MOD-026 and MOD-027 historically applied to excitation and governor systems, PJM now applies the same validation philosophy to IBR controls:
- Model parameters must reflect as-commissioned settings
- Simulation results must align with recorded field data
- Factory Acceptance Test (FAT) reports are required for As-Built submissions
This effectively extends model validation obligations to inverter-based plants.
8. Simulation Time Step and Numerical Robustness
PJM requires a minimum simulation time step of 0.004167 seconds for dynamic testing.
Implications:
- Poorly written user-defined models may fail numerically
- Legacy DLLs often require updates
- Numerical stability is now evaluated explicitly
A model that only works at coarse time steps is considered deficient.
9. Deficiency Management and the 90-Day Clock
If PJM identifies deficiencies:
- Generator Owners have 90 days to cure
- Failure results in the model being deemed “not usable”
A non-usable model can:
- Delay interconnection studies
- Stall queue progress
- Force resubmission and revalidation
This is no longer an informal review cycle—it is a compliance deadline.
10. Practical Action Plan for Generator & IBR Owners
To remain compliant in PJM, Generator Owners should:
- Engage inverter and plant controller vendors early
- Secure PSCAD models aligned with expected field settings
- Ensure PSS®E models are benchmarked—not approximated
- Perform flat start, VRT, and frequency response testing internally
- Document every assumption and parameter source
- Treat dynamic modeling as a lifecycle obligation, not a one-time deliverable
Technical FAQ (Planning Engineer Perspective)
FAQ 1: Why does PJM require PSCAD when RMS tools have worked for decades?
RMS tools are insufficient to capture fast inverter control dynamics, current limits, and EMT-level interactions. PSCAD provides the ground-truth behavior that RMS models must now emulate.
FAQ 2: Is PSCAD required for all PJM projects?
Not universally, but IBR projects should assume PSCAD will be required, especially for larger or electrically weak interconnections.
FAQ 3: What happens if my PSCAD and PSS®E models don’t match?
The RMS model will be flagged as deficient and must be corrected. PJM considers PSCAD the reference.
FAQ 4: What does “flat start” really test?
It verifies numerical stability, control initialization, and absence of hidden oscillations before any disturbance is applied.
FAQ 5: Why is the 0.1 MW / 0.1 MVAR limit so strict?
Small deviations often indicate control conflicts, integrator wind-up, or initialization errors that worsen under disturbance.
FAQ 6: Can I disable momentary cessation in the model even if the inverter supports it?
Only if it reflects actual field settings. PJM expects modeling to match real behavior, not desired behavior.
FAQ 7: How does PJM define weak grid conditions?
Typically SCR ≈ 3 or lower at the POI, but effective grid strength can degrade over time as more IBRs interconnect.
FAQ 8: When should REGCBU1 be used instead of REGCA1?
REGCBU1 is preferred for weak-grid or low-SCR conditions due to superior numerical robustness.
FAQ 9: Are vendor “black box” models acceptable?
Yes, provided the behavior is transparent, documented, and validated against field or PSCAD results.
FAQ 10: What is PJM looking for in FAT reports?
Confirmation that transformer and control equipment were tested and commissioned consistent with modeled parameters.
FAQ 11: Do these requirements apply after COD?
Yes. As-Built submissions must reflect as-commissioned settings and validated behavior.
FAQ 12: Can poor dynamic models delay my queue position?
Yes. Non-usable models can stall studies and trigger resubmittal requirements.
FAQ 13: How detailed must collector system modeling be?
An equivalent impedance representation is acceptable, but it must accurately reflect losses and voltage behavior.
FAQ 14: Why does PJM care about numerical time step size?
Small time steps expose numerical instability that may be hidden at coarser resolutions.
FAQ 15: Is TSAT required for all IBRs?
TSAT is required where time-domain accuracy beyond PSS®E is necessary, especially for fast inverter dynamics.
FAQ 16: How does this affect hybrid PV + BESS plants?
Hybrids require coordinated modeling of shared inverters, charging logic, and plant-level controls.
FAQ 17: Are IEEE 1547 settings sufficient for PJM compliance?
IEEE 1547 applies primarily to distribution-connected DERs. Transmission-connected PJM resources face stricter requirements.
FAQ 18: What is the most common reason models are rejected?
Mismatch between modeled behavior and actual control logic—especially during faults.
FAQ 19: Can reactive capability be supplemented with switched shunts?
Yes, but automatic control and coordination with the plant controller must be demonstrated.
FAQ 20: Does PJM require frequency response from IBRs?
Yes. Primary frequency response with ≤5% droop and ±36 mHz deadband is mandatory.
FAQ 21: How often must models be updated?
Any time control settings change materially, models must be updated and resubmitted.
FAQ 22: What is PJM’s view on legacy projects?
Existing projects may be grandfathered, but modifications or uprates trigger current requirements.
FAQ 23: Who is responsible for model accuracy—the EPC or the Owner?
Ultimately, the Generator Owner is responsible, regardless of delegation.
FAQ 24: Can PJM request PSCAD after initial submission?
Yes. PSCAD may be requested later if system conditions warrant.
FAQ 25: What is the biggest mindset shift for Generator Owners?
Dynamic models are no longer static study artifacts—they are living representations of real assets.
Closing Thought
For Generator Owners in PJM, especially IBR owners, dynamic modeling is now a compliance discipline, not just a planning exercise. Those who treat it strategically—early, rigorously, and transparently—will move through the PJM process far more efficiently than those who do not.
