SPP and MISO IBR Modeling Compliance: How to Deliver Study-Grade UDMs Now and Validate to As-Built Later

Executive Summary

Southwest Power Pool (SPP) is proposing a modeling package that must be submitted at the time of interconnection request: standard-library dynamic models and user-defined models (UDMs) for PSS®E and TSAT, plus an EMT/PSCAD UDM and a Dynamic Model Quality & Performance Test (MQT) report, with later checkpoints for as-built evaluation and post-commissioning validation. In parallel, MISO has advanced a complementary program—tying IEEE 2800-aligned performance requirements to enhanced modeling, parameter verification, and a staged implementation plan across the interconnection process. Together, these trends mean developers should submit an early, technically defensible, plant-level model that (1) reflects the intended control philosophy, (2) passes a defined MQT battery including ride-through and weak-grid (SCR) stress, and (3) is formally re-validated once OEM equipment is selected and tested. This memo explains how to comply, compares SPP’s proposal with MISO’s plan, and provides a step-by-step technical playbook—down to control blocks, parameter ranges, testing menus, and documentation—to deliver “fit-for-study” models now and “as-built-accurate” models later (SPP) (MISO) (NERC) (FERC) (IEEE) (ERCOT).

1. Foundations

1.1 Why these modeling requirements exist

Since 2016, large grid disturbances have repeatedly revealed that many inverter-based resource (IBR) models in interconnection studies did not reflect actual plant behavior. NERC’s Level-2 Industry Recommendation documents model quality deficiencies (e.g., mis-tuned limits, missing protection logic, mis-initialized states) and links them to unexpected IBR tripping or output reduction during grid events—driving both planning and operations risk (NERC).

MISO’s own analysis shows that poor modeling and study practices are a key contributor to IBR performance issues on the bulk power system, motivating strengthened model content, quality tests, and parameter verification throughout the interconnection lifecycle (MISO).

FERC Order No. 2023 tightened interconnection data/model deliverables and explicitly requires models (including UDMs and EMT representations) that achieve an accuracy comparable to synchronous generator models, with validation evidence tying model behavior to equipment behavior (FERC).

Plain-language translation: the grid has seen too many surprises from IBRs during real events. The fix is to demand better, more realistic models up front, test those models against credible disturbances, and prove later—using site and OEM data—that the study models match the built plant.

Analogy: think of submitting architectural plans for a high-rise in a windy city. Regulators will accept a wind-tunnel-tested design first, but they’ll still require field measurements and as-built checks after construction to prove the building reacts to gusts as predicted.

1.2 What SPP is proposing (scope and timing)

SPP’s materials focus on plant-level dynamic response requirements during interconnection studies and a modeling package—PSS®E standard model, PSS®E UDM, TSAT standard model, TSAT UDM, PSCAD UDM—plus a Dynamic Model Quality & Performance Test report, with later as-built and post-commissioning validation (SPP). The proposal enumerates a model-quality test menu: initialization checks, balanced fault ride-through, small V/F disturbances, HVRT/LVRT, HFRT/LFRT, protection verification, and an SCR sweep (SPP).

Plain-language translation: SPP wants five models and a test report at request time to run the studies right away, and they expect you to prove those models behave reasonably across the usual stressors (faults, voltage/frequency dips/spikes, weak grid). Later, you must align the study model to the chosen equipment and field measurements.

1.3 What MISO is proposing (content and rollout)

MISO’s multi-year initiative links IEEE 2800 performance requirements to interconnection modeling, emphasizing dynamic model sufficiency (PSS®E/TSAT/EMT), parameter verification evidence, and conformance processes. The stakeholder record shows PAC/IPWG items proposing revised IBR modeling requirements (PAC-2024-2), requirements for parameter verification, feedback windows (e.g., August 5, 2025), and a target to finalize requirements by late 2025 (MISO).

Plain-language translation: MISO is standardizing how your models must look, what tests you have to pass, and what proof you must provide that the numbers in your model match the hardware you build—mapped to IEEE 2800 behavior (voltage/frequency support, ride-through, etc.). (IEEE)

Summary:

• Driver: real grid events exposed model deficiencies; authorities now require stronger models and proof they match reality (NERC) (FERC).
• SPP: five-model package + MQT at request; as-built and post-commissioning validation later (SPP).
• MISO: IEEE 2800-aligned performance and parameter verification embedded into interconnection modeling steps (MISO) (IEEE).

2. Core Concepts & Mechanics

2.1 Model types and why each matters

• PSS®E/TSAT standard-library models: generic inverter/plant control templates used for broad studies; they initialize quickly and integrate into regional databases.
• PSS®E/TSAT UDMs: custom block-diagram models that capture plant-specific control structures (PLL type, current limiter, voltage/reactive control, frequency-watt, protection timers).
• EMT/PSCAD UDM: physics-rich switching-level or average EMT representations to capture fast protection/control interactions (e.g., PLL loss of lock, current-limit dynamics, DC-link behavior) that RMS tools can’t (SPP).

Plain-language translation: use standard blocks for compatibility, UDMs for realism, and EMT for the really fast/complex stuff.

Analogy: think of weather models—global models for the big picture, regional models to capture local terrain, and high-resolution storm models for tornado formation.

2.2 IEEE 2800 performance envelope (what “reasonable performance” means)

IEEE 2800 establishes a unified envelope for IBR behavior on the bulk power system: voltage ride-through (consecutive deviations), frequency ride-through, reactive power capability and voltage support, active power/frequency response, and control stability considerations. Interconnection regions (including MISO) are proposing to implement these behaviors explicitly in modeling and conformance checks (IEEE) (MISO).

Plain-language translation: your model must stay online through specified voltage/frequency dips and supply the right voltage and frequency support—matching a standard rulebook.

Example: if bus voltage sags to 0.2 pu for 150 ms during a fault, your model shouldn’t trip unless permitted; it should provide reactive current support consistent with the defined curve.

2.3 The Model Quality & Performance Test (MQT) battery—what to run and why

SPP’s test menu and similar regional practices coalesce into a predictable battery:

• Initialization & sanity checks (state variables finite, limits feasible).
• Small-signal V/F steps to verify linearized responses and setpoint tracking.
• HVRT/LVRT and HFRT/LFRT to verify ride-through and current/voltage controllers.
• Protection verification (e.g., overcurrent, over/undervoltage, ROCOF, frequency rate logic, blocking/unblocking).
• Weak-grid stress via SCR sweep (e.g., 10 → 2) to test PLL stability, current limit windup, and Q-V/V-Q interactions (SPP) (ERCOT).

Plain-language translation: prove the model starts correctly, behaves sensibly for small nudges, stays online during the expected jolts, trips only when it should, and remains stable as the grid gets “softer” (weaker).

Analogy: a car maker tests a prototype by idling (initialization), gentle lane changes (small signals), potholes and emergency stops (ride-through), airbag logic (protection), and a slippery road (weak-grid SCR).

2.4 How to build a defensible plant-level UDM before selecting an OEM

The practical approaches you outlined are sound, with clarifications:

1. Functional/technology-class UDM. Implement the intended control architecture (grid-following vs. grid-forming), including:
   
   • PLL: SRF or DSOGI-PLL with configurable bandwidth (e.g., 3–10 Hz study-grade; lower for weak-grid).
   • Current limitation: priority logic (reactive-first vs. active-first), soft/hard limiting slopes, and decoupling.
   • Voltage/Reactive control: outer voltage loop, inner current loop, Q-V droop, AVR/STATCOM modes; coordinate with plant-level controls.
   • Frequency/Active control: droop/rate limits, deadbands, FFR/INFR (if declared). • Protection: time-coordinated OVR/UVR/OFR/UFR curves, ROCOF, phase jump, PLL loss-of-lock.
   • Parameter ranges bounded to basis-of-design and IEEE 2800 envelopes (IEEE).
2. Representative OEM-agnostic UDM. Use a vetted template derived from prior fleets; document what is assumed: PLL bandwidth, current-limit priority, crowbar or DC-chopper timing for WTGs/PV hubs, and plant-level control latencies. Note parameter ranges and which items are placeholders pending data sheets.
3. Parameter-space commitment plus milestone updates. In your transmittal, explicitly commit to update triggers (on equipment selection and after commissioning) and identify which parameters will tighten (e.g., PLL bandwidth ±20%, current limit slope ±10%, protection time constants ±25%). This aligns with Order 2023’s validation evidence concept and SPP/MISO phased verification (FERC) (SPP) (MISO).

2.5 “Model correctness” in practice—five technical guardrails

1. Unit/plant decomposition: represent unit-level controls and a separate plant controller (AGC/voltage coordinator/plant VAR controller), with proper summations and droops.
2. Limit realism: include anti-windup, rate limits, and saturation blocks in current regulators and plant controllers; document priorities.
3. Initialization discipline: initialize PLL, filters, and limiters consistently with the power flow; validate by a zero-disturbance run.
4. Event realism: emulate protection filtering and delays (e.g., 1–3 cycle filtering, 1–5 cycle logic delay) to avoid unrealistically fast trips.
5. Weak-grid hygiene: show stability across SCR ≥ 3 without retuning; if SCR < 3 is expected, document alternative tuning or grid-forming capabilities and re-test (SPP) (MISO).

Summary:

• Use the right model for the right study (standard vs. UDM vs. EMT).
• Map behavior to IEEE 2800, then prove it with an MQT battery and SCR sweep.
• Build “functional UDMs” now with bounded parameters; tighten later to OEM data.

3. Applications & Implications

3.1 How to assemble the SPP package at interconnection request

Deliverables (study-grade, plant-level):

• PSS®E: one standard library model plus a UDM of the same plant (match outputs/limits).
• TSAT: same structure as PSS®E (standard + UDM), cross-checked for consistent limits and ride-through.
• EMT/PSCAD UDM: an average-value EMT model that reproduces fast limit/protection dynamics for key events (e.g., three-phase faults with delayed clearing, line energization, phase jumps).
• MQT report: plots and pass/fail commentary for initialization, small V/F steps, all ride-through curves, protection demonstrations, and SCR sweep; include a parameter table with min/nominal/max commitments (SPP).

Plain-language translation: submit five harmonized models and a test report that proves they behave; make sure PSS®E and TSAT tell the same story and that EMT captures the fast stuff.

3.2 How to meet MISO’s evolving expectations in parallel

MISO’s record shows a formal path to adopt IEEE 2800 performance requirements, explicit modeling requirements (PSS®E/TSAT/EMT), and parameter verification evidence woven into the interconnection process and stakeholder checkpoints (MISO). Your deliverables should therefore include:

• IEEE 2800 traceability: a table mapping your ride-through and support features/parameters to the IEEE clauses MISO references.
• Parameter verification plan: what tests (factory/commissioning/disturbance) will produce the evidence that values in the UDM match measured behavior; how you’ll reconcile deviations.
• Conformance artifacts: a living spreadsheet linking studies ↔ site tests ↔ disturbance playback showing the same control responses within tolerances (MISO) (IEEE).

3.3 Case-type illustrations

• Weak-grid PV+STATCOM site: the SCR sweep reveals PLL instability at SCR ≈ 2.5 with default bandwidth. You retune to bandwidth ~3–5 Hz, adopt reactive-priority current limiting, and add a plant-level Q-V droop to improve damping; repeat tests show stable post-fault recovery (SPP) (ERCOT).
• Hybrid wind+storage: EMT playback of a phase jump event shows PLL loss-of-lock risk; adding a phase-jump detector to freeze the PLL angle during transients and smoothing active-power commands avoids spurious protection trips; the PSS®E/TSAT UDMs incorporate equivalent logic and pass MQT.
• Parameter verification: commissioning test ramps (±5% voltage, ±0.2 Hz frequency, step Q commands) are recorded; you overlay measurements with model outputs and sign an attestation of accuracy per Order 2023 guidance (FERC).

3.4 Why this matters

High-fidelity, validated models reduce re-study risk, prevent late-stage surprises, and shorten the path from request to energization. Regions are converging on common expectations—IEEE 2800 conformance, UDM transparency, EMT for fast phenomena, and verification evidence—so doing this once, properly, scales across SPP, MISO, and beyond (SPP) (MISO) (IEEE).

Summary: 

• SPP requires a five-model package plus MQT at request, with later validation.
• MISO adds explicit IEEE 2800 mapping and parameter verification.
• Robust early modeling reduces rework and aligns with Order 2023 validation.

4. Integration & Broader Context

4.1 How this connects to adjacent domains

• Protection engineering: UDMs must emulate relay/filter delays; EMT supports interactions with series compensation, STATCOMs, and remedial schemes.
• Grid operations: better models feed operational studies (TSAT) and outage planning, improving stability margins under high IBR dispatch (SPP).
• Standards & compliance: IEEE 2800 defines the behavioral envelope; Order 2023 defines modeling/validation obligations; NERC alerts set modeling quality expectations (IEEE) (FERC) (NERC).

4.2 From equations to practice—control blocks that matter most

• PLL: bandwidth (ωc), damping (ζ), and phase-jump handling determine stability in SCR sweeps. Rule of thumb: start with lower bandwidth for SCR < ~4 and verify phase-jump resilience in EMT.
• Current regulator: decoupled d-q loops with anti-windup and rate limits; reactive-priority during LVRT per IEEE 2800.
• Plant controller: Q-V droop (slope and deadband) to share reactive effort across units; coordinate with STATCOM. Plain-language translation: small settings in PLL and current limits change how the plant rides through faults and weak grid—tune them intentionally and prove your choices in MQT.

4.3 Open issues and active debates

• Grid-forming (GFM) adoption: how to standardize GFM features in PSS®E/TSAT UDMs and EMT models so that study and field behavior align remains active work (IEEE).
• Parameter verification tolerances: MISO and others are developing pragmatic error bands between model and measurement; expect evolving guidance as more field data accumulates (MISO).
• Disturbance playback libraries: regions are curating event libraries for standardized playback/validation; practices are still converging (NERC).

Summary:

• Controls and protection details drive success.
• GFM, tolerances, and disturbance playback methods are fast-moving frontiers.
• Cross-disciplinary alignment (standards, planning, operations) is the endgame.

5. Practical Compliance Playbook (SPP + MISO)

5.1 Model development (90–120 days before request)

• A. Define the basis-of-design (BOD): grid-following PV/WTG or grid-forming; intended PLL bandwidth range; current-limit priority; plant Q-V droop; protection logic timing; expected SCR at POI and collector buses.
• B. Build harmonized models: implement PSS®E and TSAT UDMs with identical control structure, limits, and protection; create an average-value EMT (PSCAD) with matching logic.
• C. Parameter ranges: tabulate min/nominal/max and identify placeholders tied to OEM datasheets (e.g., crowbar/ chopper delay, DC-link time constants).
• D. Internal MQT: run the full battery—initialization, small V/F steps, HVRT/LVRT, HFRT/LFRT, protection checks, SCR sweep; iterate tuning to pass. (SPP) (ERCOT).

5.2 Interconnection submittal package (at request)

• Five models: PSS®E standard + UDM; TSAT standard + UDM; PSCAD UDM.
• MQT report: include plots, pass/fail notes, and parameter-range commitments.
• Conformance statement: declare IEEE 2800 feature coverage and any deviations; map features/parameters to clauses used by MISO.
• Change control: state the update triggers—(1) at equipment selection, (2) after commissioning; acknowledge material-change governance if parameters fall outside committed ranges (SPP) (MISO) (IEEE).

5.3 Post-selection update (OEM chosen)

• Replace placeholders with datasheet/test values (PLL bandwidth, current limit slopes, protection delays).
• Re-run MQT; append a delta report comparing “study-grade” vs. “as-selected” results.
• Provide Order-2023 attestation that models reflect equipment behavior within agreed tolerances (FERC).

5.4 Commissioning & post-commissioning validation

• Conduct commissioning tests (voltage steps, frequency steps, reactive/active commands) and capture high-resolution PMU/SCADA.
• Run disturbance playback (e.g., staged faults where permitted or natural events) in EMT and RMS; overlay results with field data; document parameter verification per MISO’s section on parameter verification (MISO).
• Submit a final validation report and archive models in operations databases (TSAT) per regional processes (SPP) (MISO).

5.5 Common pitfalls (and fixes)

• Mis-matched PSS®E vs. TSAT limiters → maintain a single parameter source and cross-tool unit tests.
• Over-aggressive PLL bandwidth causing weak-grid oscillations → reduce bandwidth and add phase-jump handling; verify in EMT and SCR sweep.
• Missing protection filters → implement realistic measurement filtering and logic delays.
• Generic STATCOM models not coordinated with plant controller → include plant-STATCOM interaction and Q-sharing droop; test under LVRT.

5.6 Documentation checklist (embed in your submittal)

• BOD and control block diagrams (unit and plant).
• Parameter table with ranges and placeholders clearly labeled.
• IEEE 2800 feature mapping.
• Full MQT plots and a summary pass/fail matrix.
• Change-control milestones and attestation language aligned to Order 2023 (FERC) (IEEE).

Select Citations

• (SPP) Model Development Advisory Group (MDAG) materials on proposed IBR modeling requirements and model-quality tests
• (MISO) IBR performance, modeling, and conformance program; proposed IBR modeling requirements, parameter verification, and timelines (PAC-2024-2; IPWG/PAC records)
• (NERC) Level-2 Industry Recommendation on IBR Model Quality Deficiencies and aggregated analyses of modeling issues
• (FERC) Order No. 2023 (Final Rule) and guidance on modeling/validation and attestation
• (IEEE) IEEE 2800 overview and implementation context for IBR performance requirements
• (ERCOT) Model Quality Tests and Voltage Ride-Through testing practices informing regional MQTs