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  Inverter Fault Contribution Modeling Reference Database (v2.1)
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DEFINITION
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The Inverter Fault Contribution Modeling Reference Database (v2.1) is a standardized,
version-controlled repository of empirically validated and simulation-verified fault
current injection characteristics for grid-forming (GFM) and grid-following (GFL)
inverters under diverse fault conditions, network configurations, and control
settings. It provides structured, interoperable data to support protection
coordination, relay setting calculations, and short-circuit analysis in
inverter-dominated microgrids and distribution systems. Designed as a template
resource, it enables consistent modeling assumptions, traceable parameterization, and
reproducible fault contribution quantification across engineering tools and
stakeholders.

OVERVIEW
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Inverter-based resources (IBRs) exhibit fundamentally different fault response
behaviors compared to synchronous generators—lacking inherent inertia, exhibiting
current-limiting behavior, and responding to faults based on control architecture,
grid-support functions (e.g., reactive current injection), and DC-link dynamics. The
v2.1 database addresses the critical gap in standardized fault contribution data by
curating representative inverter models (e.g., IEEE 1547-2018 compliant GFL/GFM
units), their fault current waveforms (magnitude, duration, harmonic content, DC
offset), peak symmetrical/asymmetrical current values, and time-domain transient
profiles under phase-to-phase, phase-to-ground, and three-phase faults at varying
voltage sag depths and grid strength (SCR/XR ratios). Each entry includes metadata
specifying control mode (e.g., PQ, V/f, droop), active/reactive power setpoints,
fault impedance range, sampling resolution, and validation methodology (e.g.,
PSCAD/EMTDC, MATLAB/Simscape, hardware-in-the-loop). The database supports both
deterministic and probabilistic protection studies by enabling parametric sweeps over
inverter dispatch states, grid topology variants, and fault location uncertainty. Its
template structure facilitates integration with industry-standard protection software
(e.g., ETAP, DigSILENT PowerFactory, SKM) via standardized JSON/CSV schemas and
companion Python API bindings for automated relay coordination workflows.

KEY COMPONENTS
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1. Fault Current Waveform Library
2. Control-Mode-Specific Injection Profiles
3. Grid Strength & Fault Impedance Parameterization Matrix

APPLICATIONS
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  - Adaptive Overcurrent Relay Setting Optimization
  - Microgrid Protection Coordination Validation
  - Fault Ride-Through (FRT) Compliance Assessment

KEY FORMULAS
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Peak Asymmetrical Fault Current (GFL): I_{peak} = \sqrt{2} \cdot I_{rms} \cdot \left(1 + e^{-\frac{t}{\tau}}\right)
  -> Estimates peak asymmetrical current for grid-following inverters, where τ is the effective time constant derived from control bandwidth and filter dynamics
GFM Short-Circuit Ratio (SCR_sc): SCR_{sc} = \frac{S_{base}}{|V_{pref}| \cdot |I_{fault,max}|}
  -> Defines inverter short-circuit capability relative to its rated apparent power and prefault voltage; used to classify fault support level per IEEE 2800
Current Limiting Factor (CLF): CLF = \frac{I_{fault,actual}}{I_{fault,ideal}} = \min\left(1, \frac{I_{lim}}{|I_{ref}|}\right)
  -> Quantifies reduction in fault current due to inverter current limiting, where I_lim is the hardware/software current ceiling and I_ref is the commanded current magnitude

RELATED CONCEPTS
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  - Grid-Forming Control
  - Fault Ride-Through (FRT)
  - Short-Circuit Ratio (SCR)

REFERENCES
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IEEE Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces (https://standards.ieee.org/ieee/1547/1547.html)
IEEE Guide for Design, Operation, and Integration of Distributed Energy Resources with Associated Electric Power Systems Interfaces (https://standards.ieee.org/ieee/2800/2800.html)
Inverter Fault Contribution Modeling Reference Database (v2.1) — Technical Specification Document (https://microgrid-protection.org/resources/ifcmd-v2.1-spec)

TAGS
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microgrid, protection coordination, inverter modeling