DistOPF

DistOPF provides an open-source, multi-phase, unbalanced, optimal power flow (OPF) tool for distribution systems to aid students and researchers. The tool aids users by providing:

• Unbalanced multi-Phase OPF model generators usable with common Python solver packages such as CVXPY and SciPy;

• A platform for creating and benchmarking new algorithms on a set of standard test systems;

• An OpenDSS model importer allowing users to import power system models directly from the OpenDSS model format;

• Model validation with OpenDSS;

• Functions for visualizing results.

The tool is composed of four major parts, 1) model input system, 2) optimization model formulation, 3) OPF solver interface, and 4) solution output and visualization. Models are described using a set of CSV files that are read in as Pandas DataFrames. Buses are described in one CSV having columns for loads, base units, and voltage limits. Lines, switches, and transformers are described in a CSV having columns for each term in the upper diagonal impedance matrix. Regulators, capacitor banks, and generators each have their own CSV. To aid in model creation and validation, models can also be created using OpenDSS and converted to the tabular format. The tool provides classes and functions to make it easy to formulate and solve the power system for new users while being flexible for advanced users to create new models and algorithms. The tool has been used to solve a variety of problems including, conservation voltage reduction, power loss minimization, and generation curtailment minimization, where either generator real or reactive power injections are controlled.

Installation

pip install

pip install distopf

Optional Extras

Extra	Install command	Purpose
cim	pip install distopf[cim]	CIM XML file import support (requires pre-release packages cim-graph and gridappsd-python)

Note: The cim extra depends on pre-release packages. If you do not need CIM file support, a plain pip install distopf is sufficient. CIM functionality will raise an informative ImportError if those packages are not installed.

Developer Installation

To install the latest version from github:

1. From the directory you want to keep your DistOPF files, run:

git clone https://github.com/nathantgray/distopf.git

3. Create or activate the python environment you want to use.
4. From the directory where the DistOPF package is stored, run:

pip install -e .

To also install the optional CIM extra in editable mode:

pip install -e ".[cim]"

This installs your local DistOPF package the python environment you activated. The -e option enables editable mode, which allows you to directly edit the package and see changes immediately reflected in your environment without reinstalling.

Getting Started

Using provided cases:

Unconstrained Power Flow

import distopf as opf
case = opf.create_case(opf.CASES_DIR / "csv" / "ieee123")
result = case.run_pf()
result.plot_network().show(renderer="browser")

DER Curtailment Minimization

import distopf as opf
case = opf.create_case(opf.CASES_DIR / "csv" / "ieee123_30der")
result = case.run_opf(objective="curtail_min", control_variable="P", v_max=1.05, v_min=0.95, gen_mult=10)
result.plot_network().show(renderer="browser")

Optimization Wrappers

DistOPF supports multiple optimization wrappers for solving OPF problems:

Pyomo Wrapper — LinDistFlow (default)

The default Pyomo wrapper uses the LinDistFlow model (formulation="lindist").

• Model: Linear approximation of power flow equations
• Solver: Pyomo with linear solvers
• Speed: Fast, suitable for real-time applications
• Accuracy: Good for systems with small voltage deviations

import distopf as opf
case = opf.create_case(opf.CASES_DIR / "csv" / "ieee123_30der")
result = case.run_opf(wrapper="pyomo", objective="loss")  # formulation="lindist" is the default

Pyomo Wrapper — BranchFlow

The BranchFlow model type uses nonlinear power flow equations with IPOPT or MINLP solvers for higher accuracy. Use formulation="branchflow".

• Model: Nonlinear power flow equations (exact)
• Solver: IPOPT (continuous) or MINLP using Gurobi if installed (discrete controls)
• Speed: Slower than linear, but more accurate
• Accuracy: Nonlinear power flow representation

Continuous Optimization (IPOPT)

For continuous optimization without discrete controls:

import distopf as opf
case = opf.create_case(opf.CASES_DIR / "csv" / "ieee123_30der")
result = case.run_opf(
    formulation="branchflow",
    objective="loss",
    solver="ipopt",
)

Discrete Controls (MINLP)

Enable regulator tap optimization and capacitor switching with MINLP solvers:

import distopf as opf
case = opf.create_case(opf.CASES_DIR / "csv" / "ieee123")
result = case.run_opf(
    wrapper="pyomo",
    formulation="branchflow",
    objective="loss",
    control_regulators=True,      # Enable regulator tap control
    control_capacitors=True,       # Enable capacitor switching
    initialize="fbs",              # Recommended for discrete controls
    solver="gurobi",               # MINLP compatible solver 
)

Matrix BESS Wrapper (Multi-Period with Batteries)

The matrix_bess wrapper supports multi-period (time-series) optimization with battery energy storage.

import distopf as opf
case = opf.create_case(opf.CASES_DIR / "csv" / "ieee123_30der_bat")
result = case.run_opf(wrapper="matrix_bess", objective="loss")

Wrapper Comparison

Feature	Matrix/Matrix BESS	Pyomo
Model Type	LinDistFlow (linear)	LinDistFlow or Non-Linear BranchFlow
Formulation	Matrix-based	Algebraic equations
Solver API	Scipy or CVXPY	Pyomo
Prefered Solver	HiGHs or Clarabel	IPOPT, Gurobi, Knitro

Solver Requirements

• IPOPT: Install via conda install -c conda-forge ipopt. On Ubuntu, apt-get install coinor-libipopt-dev only installs headers and shared libraries; it does not provide the ipopt executable that Pyomo's SolverFactory("ipopt") expects.

Result Fields

PowerFlowResult uses descriptive field names. Short aliases are also accepted for backward compatibility.

Field Name	Alias
active_power_flows	p_flows
reactive_power_flows	q_flows
active_power_generation	p_gens
reactive_power_generation	q_gens
active_power_loads	p_loads
reactive_power_loads	q_loads
capacitor_reactive_power	q_caps
battery_active_power	p_bats
voltage_magnitudes	voltages

Dual Variables

When running with duals=True, dual variables are accessible on the result object:

result = case.run_opf(wrapper="pyomo", objective="loss", duals=True)
result.dual_power_balance_p
result.dual_power_balance_q
result.dual_voltage_drop
result.dual_voltage_limits

Using a custom model.

Create CSVs formatted as shown below and store them in a single folder. The csv names must match exactly as shown. Column order is not important.

-your_model_directory
   -branch_data.csv
   -bus_data.csv
   -gen_data.csv
   -cap_data.csv
   -reg_data.csv
   -bat_data.csv

import distopf as opf
case = opf.create_case(
    data_path="path/to/your_model_directory",
)

Or load them as dataframes

import distopf as opf
import pandas as pd
branch_data = pd.read_csv("path/to/your_model_directory/branch_data.csv", header=0)
bus_data = pd.read_csv("path/to/your_model_directory/bus_data.csv", header=0)
gen_data = pd.read_csv("path/to/your_model_directory/gen_data.csv", header=0)
cap_data = pd.read_csv("path/to/your_model_directory/cap_data.csv", header=0)
reg_data = pd.read_csv("path/to/your_model_directory/reg_data.csv", header=0)
bat_data = pd.read_csv("path/to/your_model_directory/bat_data.csv", header=0)
schedules = pd.read_csv("path/to/your_model_directory/schedules.csv", header=0)  # Optional for multi-period cases
case = opf.Case(
    branch_data=branch_data,
    bus_data=bus_data,
    gen_data=gen_data,
    cap_data=cap_data,
    reg_data=reg_data,
    bat_data=bat_data,
    schedules=schedules
)

Phase naming convention: Three-phase buses and lines use phases a, b, c. Triplex (North American split-phase residential secondary) buses and lines use phases s1 and s2, which are the two 120 V legs of a center-tapped single-phase transformer. s1s2 refers to the 240 V line-to-line connection across both legs.

branch_data.csv

• fb: From bus id number
• tb: To bus id number
• r_aa, r_ab, r_ac, r_bb, r_bc, r_cc: upper-diagonal resistance matrix elements (p.u.) for 3-phase lines
• x_aa, x_ab, x_ac, x_bb, x_bc, x_cc: upper-diagonal reactance matrix elements (p.u.) for 3-phase lines
• r_s1s1, r_s1s2, r_s2s2: resistance matrix elements (p.u.) for triplex (split-phase) lines
• x_s1s1, x_s1s2, x_s2s2: reactance matrix elements (p.u.) for triplex (split-phase) lines
• primary_phase: primary-side phase for center-tap transformer branches (e.g. "a", "b", "c")
• s_a_max, s_b_max, s_c_max: per-phase apparent power limits (VA)
• type: overhead_line, switch, transformer, center_tap_xfmr, etc.
• name: other name of line
• status: (for switches) OPEN or CLOSED
• s_base: base VA
• v_ln_base: base line-to-neutral voltage
• z_base: base impedance
• phases: phases present on the line (e.g. "abc", "s1s2", "a")

bus_data.csv

• id: unique id for each bus (integer starting at 1)
• name: bus name
• pl_a, ql_a, pl_b, ql_b, pl_c, ql_c: active and reactive loads p.u.
• bus_type: SWING or PQ. SWING bus is voltage source
• v_a, v_b, v_c: voltage magnitude p.u. (input parameter for SWING bus. Other not used as input)
• v_ln_base: base line-to-neutral voltage (V)
• s_base: base power (VA)
• v_min, v_max: voltage magnitude limits (p.u.)
• cvr_p, cvr_q: conservation voltage reduction parameters; alternative to ZIP model for voltage dependant loads. (set to 0 for no voltage dependence)
• pl_s1, ql_s1, pl_s2, ql_s2, pl_s1s2, ql_s1s2: active and reactive loads for triplex (split-phase) buses (p.u.)
• primary_phase: primary-side phase for triplex buses (e.g. "a", "b", "c")
• phases: phases at bus (e.g. "abc", "a", "ab", "s1s2", etc.)

gen_data.csv

• id: bus id
• name: generator name
• p_a, p_b, p_c: active power output (p.u.)
• q_a, q_b, q_c: reactive power output (p.u.)
• s_base: base power (VA)
• s_a_max, s_b_max, s_c_max: rated maximum apparent power output per 3-phase (VA)
• p_s1, p_s2: active power output for triplex (split-phase) generators (p.u.)
• q_s1, q_s2: reactive power output for triplex generators (p.u.)
• s_s1_max, s_s2_max: rated maximum apparent power for triplex phases (VA)
• phases: generator phases (e.g. "abc", "s1s2") (this IS implemented)
• q_a_max, q_b_max, q_c_max: (not implemented) maximum reactive power output (p.u.)
• q_a_min, q_b_min, q_c_min: (not implemented) minimum reactive power output (p.u.)

cap_data.csv

• id: bus id
• name: capacitor name
• q_a, q_b, q_c: nominal reactive power (p.u.)
• phases: capacitor phases (abc string)

reg_data.csv

• fb: From bus id number
• tb: To bus id number
• name: regulator name
• tap_a, tap_b, tap_c: tap position (p.u.) -16 to +16; 0 is no tap change

Case and run_opf Options

create_case() / Case.__init__() parameters

Parameter	Default	Description
data_path	required	Path to CSV directory, .dss file, or .xml CIM file
start_step	0	Starting time step for multi-period analysis
n_steps	1	Number of time steps (1 = single-period)
delta_t	1.0	Hours per time step (for battery energy calculations)
ignore_schedule	False	If True, ignore schedule data; use multiplier 1.0 everywhere
ignore_gen	False	If True, remove all generators
ignore_bat	False	If True, remove all batteries
ignore_cap	False	If True, remove all capacitors
ignore_reg	False	If True, remove all regulators

When constructing Case directly, pass DataFrames instead of data_path: branch_data, bus_data, gen_data, cap_data, reg_data, bat_data, schedules.

case.modify() parameters

Parameter	Description
v_swing	Override substation voltage (scalar or 3-element array, p.u.)
v_min	Override all bus voltage lower limits (p.u.)
v_max	Override all bus voltage upper limits (p.u.)
gen_mult	Scale all generator outputs and ratings
load_mult	Scale all loads
cvr_p	CVR factor for active power: cvr_p = (dP/P)/(dV/V). ZIP equivalent: 2kz + ki
cvr_q	CVR factor for reactive power: cvr_q = (dQ/Q)/(dV/V). ZIP equivalent: 2kz + ki

OpenDSS Interface

You may also run using an OpenDSS model file as input.

import distopf as opf
case = opf.create_case(
    data_path="path/to/your_model_directory/model.dss",
)

CIM XML Interface

To load a power system model from a CIM XML file, install the optional cim extra first:

pip install distopf[cim]

Then pass the path to your .xml file:

import distopf as opf
case = opf.create_case(data_path="path/to/model.xml")

If the cim extra is not installed, calling create_case with a .xml file will raise:

ImportError: CIM file support requires optional dependencies.
Install them with: pip install distopf[cim]

Citing this tool

Gray, Nathan T., Dubey, Anamika, Reiman, Andrew P., "DistOPF: Advanced Solutions for Distribution Optimal Power Flow Analysis - DistOPF v0.2 Documentation," (2025), https://doi.org/10.2172/2999990

@techreport{osti_2999990,
  author       = {Gray, Nathan T. and Dubey, Anamika and Reiman, Andrew P. and Sadnan, Rabayet},
  title        = {DistOPF: Advanced Solutions for Distribution Optimal Power Flow Analysis - DistOPF v0.2 Documentation},
  institution  = {Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)},
  doi          = {10.2172/2999990},
  url          = {https://www.osti.gov/biblio/2999990},
  place        = {United States},
  year         = {2025},
  month        = {03}}

R. Sadnan, N. Gray, A. Bose, A. Dubey and K. P. Schneider, "Scaling Distributed Optimal Renewable Energy Coordination in Unbalanced Distribution Systems," in IEEE Transactions on Sustainable Energy, vol. 17, no. 1, pp. 3-15, Jan. 2026, doi: 10.1109/TSTE.2024.3492976.

@ARTICLE{10745555,
  author={Sadnan, Rabayet and Gray, Nathan and Bose, Anjan and Dubey, Anamika and Schneider, Kevin P.},
  journal={IEEE Transactions on Sustainable Energy}, 
  title={Scaling Distributed Optimal Renewable Energy Coordination in Unbalanced Distribution Systems}, 
  year={2026},
  volume={17},
  number={1},
  pages={3-15},
  doi={10.1109/TSTE.2024.3492976}}