DERify

DERify is a Python-based toolkit for performing Distributed Energy Resource (DER) interconnection studies and impact analysis on electric distribution networks. Built on top of the dss-python extension, DERify leverages multiple OpenDSS engine instances for fast, scalable scenario evaluation—making it ideal for utilities, consultants, and researchers.

Features

• Automated Loss and Fault Studies
  Evaluate how DERs, such as battery storage and PV systems, impact network losses and fault currents.

• Multi-Engine, Parallel Scenario Analysis
  Harness multiple OpenDSS engines in parallel to quickly evaluate large batches of scenarios or system configurations.

• Detailed Metrics for Interconnection
  Extract circuit-level electrical results and metrics to quantitatively support DER hosting capacity and interconnection decisions.

• GIS Circuit Visualization
  Integrate with geopandas and folium for interactive circuit mapping (compatible with shapefile-based network data).

• Object-Oriented Extensible Architecture
  Easily customize and extend analysis pipelines for DER and network modeling needs.

Why DERify?

OpenDSS (and thus its Python extensions) is the de facto open-source tool for distribution system simulation, widely used for DER impact studies. However, its built-in support for simulating dynamic (transient) faults involving inverter-interfaced DERs is limited:

• Dynamic Fault Limitations for Inverter-Based DERs:
  As of 2023, OpenDSS primarily models inverter-based DERs (PV systems, BESS, etc.) for steady-state studies. During dynamic fault analysis (SolveMode=Dynamic), the OpenDSS solver disables user-defined inverter models, as there is no detailed internal inverter control or ride-through implementation in the time-domain solution (see EPRI OpenDSS Manual, Section 12.18–12.22).

  "Note that elements such as PVSystem, Storage, and WindGen are turned OFF automatically when the Dynamic simulation starts. These components are steady‐state models and do not have dynamic models."
  — OpenDSS Manual

• Workaround Used in DERify:
  To evaluate worst-case network fault currents (e.g. for protection studies), DERify temporarily replaces inverter DERs with equivalent voltage-source Generator elements. These "dummy" generators mimic the capacity and topology of the DERs, ensuring correct short-circuit calculations. This approach, found in the host.py module, follows best practice workarounds in the literature and industry (EPRI, 2016; Quint et al., 2022).

Example Workflow

from derify import DERCircuit

# Setup circuit with DER config
ckt = DERCircuit(
    ckt_path="./CKT/CKT_Daily.dss",
    bess_attrs=[{'storage_id': "mv_battery", 'bus_id': "busMV3", ...}],
    pvsys_attrs=[...]
)
losses = ckt.calculate_losses()
ckt.fault_network()

For detailed usage and options, see docs/usage.md.

Installation

DERify depends on:

• dss-python (pip install dss-python)
• numpy, geopandas, folium, matplotlib

Install dependencies via requirements.txt.

Citation and References

• OpenDSS Manual: sourceforge.net/projects/electricdss/files/OpenDSSManual/
• Quint, R., et al. "Fault Current Contributions from Inverter-Based Resources: A Review." IEEE Trans. Power Delivery, 2022. doi:10.1109/TPWRD.2022.3146750
• EPRI, "Distribution Fault Current Contributions from Distributed Energy Resources, 2016." PDF

License

Distributed under the MIT License. See LICENSE.

Acknowledgements

DERify utilizes the dss-python engine and builds on OpenDSS concepts pioneered by EPRI.

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Note: For limitations and best practices regarding dynamic studies with inverters, see the FAQ.