Load Flow (Power Flow)

pandapower OpenDSS

Load Flow (power flow) computes steady-state voltages, currents, and power flows on your diagram. Run this first; most other studies assume a network that already solves.

When to use

• Check that bus voltages stay inside a sensible band
• See line and transformer loading and system losses
• Test a dispatch or load change before running short-circuit or OPF

How to run

1. Build a connected network with a slack (External Grid or slack generator).
2. Click Simulate → Load Flow and pick an engine tab.
3. Keep the defaults for a first run, then click Run.
4. Read voltages and loadings on the diagram. The Network Health Dashboard opens after a successful solve.

What you will see

Bus voltage (pu and angle), line and transformer loading, and P/Q at generators, loads, and the external grid. You can then export a PDF report, compare two runs, or plot line current vs distance — those tools reuse this solve.

Dialog parameters (Pandapower)

Include controller (Pandapower)

The Load Flow dialog (Pandapower tab) and Grid Code Compliance (P-Q & U-Q) each have three independent checkboxes under Include controller. Tick only the families you want to move during that run. Grid Code Compliance (P-Q) does not use this block; it uses Transformer tap control and Shunt control instead.

• Two-winding transformer tap changer — pandapower DiscreteTapControl on two-winding transformers that have discrete tap control enabled in the transformer dialog.
• Three-winding transformer tap changer — the same, for three-winding transformers.
• Shunt reactor tap changer — pandapower DiscreteShuntController (voltage / target step) and Line P→shunt step lookup from the shunt Control tab. Both shunt modes require this checkbox; they no longer run from the shunt dialog alone.

Park Controller is a separate diagram element with its own enable toggle. It is not gated by these three checkboxes.

Discrete Tap Control (DiscreteTapControl)

For pandapower load flow only, you can model discrete OLTC/NLTC behaviour with pandapower’s DiscreteTapControl controller:

1. Open the Transformer or Three Winding Transformer dialog for each unit that should regulate voltage.
2. Enable discrete tap control, choose control side, and set vm_lower_pu / vm_upper_pu (deadband).
3. Run Load Flow, stay on the Pandapower tab, and tick the matching Include controller checkbox (two-winding and/or three-winding).

Electrisim sends discrete tap settings and the matching run_control_trafo2w / run_control_trafo3w flags to the backend; the solver may change tap_pos within tap_min…tap_max to keep the controlled bus inside the band.

Solver fallback (Pandapower)

If the requested algorithm does not converge, the backend retries a short sequence of more robust settings rather than failing after the first Newton-Raphson divergence. Typical later plans:

1. Same algorithm and initialisation, but without transformer/shunt controllers (setpoints restored to the values from the diagram).
2. More Newton iterations (e.g. 50).
3. Flat start with a higher iteration limit.
4. Iwamoto Newton-Raphson (step-size multiplier) with a flat start — intended for ill-conditioned, heavily compensated cases that plain Newton overshoots.

If a fallback plan succeeds, results are still shown on the diagram. When controllers were dropped to obtain a solution, Electrisim shows an alert with the plan that worked and the failed attempts. Treat those voltages and flows as a diagnostic solve, then either relax tap/shunt targets, check data, or run again with controllers off on purpose.

The JSON result may include controller_fallback_warning with the same text (see Advanced notes in exported results).

Dialog parameters (OpenDSS)

Output results

Values are written onto the diagram. The table below lists the quantities for export and for the health dashboard.

Post–load-flow results and tools

The features below are part of the Load Flow workflow. They do not run a separate simulation; they interpret, visualise, compare, or export the output of the most recent successful load flow solve (Pandapower or OpenDSS).

Network Health Dashboard

After a successful load flow run (Pandapower or OpenDSS), Electrisim opens the Network Health Dashboard: a floating, draggable summary panel computed entirely in the browser from the simulation JSON. It complements the usual on-diagram result boxes by aggregating KPIs at system level.

Line current vs distance along a path

After a successful pandapower or OpenDSS load flow, the Network Health Dashboard includes Line current vs km…. It builds a staircase chart of current (kA) against cumulative route length (km) for a simple path made only of AC Line segments: consecutive lines with no branching (every intermediate bus along the traced set must have degree two in terms of those selected edges). Branching paths, meshes, DC lines, and transformers in series are outside this tool's intended use; for mixed equipment, inspect per-element results on the diagram instead.

Engineering Report (PDF)

After a successful load flow (Pandapower or OpenDSS), you can download a multi-page PDF built in the browser from the same result data the Network Health Dashboard uses. The report is for handover: cover page with project fields, executive summary, single-line diagram pages (overview plus zoomed detail tiles on large schematics), voltage and loading sections, issues, and tables by element type.

Scenario Compare

After two load flow solves on the same project (same engine: Pandapower with Pandapower, or OpenDSS with OpenDSS), Electrisim can compare the current result against a pinned baseline without juggling two tabs or spreadsheets. Comparison is computed in your browser using the same KPI logic as the Network Health Dashboard.

Algorithm Details

Newton-Raphson Method (Default): This is the most widely used power flow algorithm, providing fast convergence for well-conditioned networks. It linearizes the power balance equations using the Jacobian matrix and iteratively solves for voltage corrections.

Other Algorithms:

• Iwamoto: Enhanced Newton-Raphson with improved convergence for ill-conditioned systems
• Backward Forward Sweep: Suitable for radial distribution networks
• Gauss-Seidel: Simpler iterative method, slower convergence but more robust for some cases
• FDBX/FDXB: Fast decoupled variants for transmission networks

Limitations and Considerations

Technical References

Based on: pandapower Power Flow Documentation and OpenDSS.

Algorithm Type: Iterative solution of power balance equations using various numerical methods.

Documentation References: 📘 pandapower Power Flow 📘 pandapower runpp() 📗 OpenDSS Power Flow

Controllers

pandapower OpenDSS

Discrete transformer tap and shunt step controls are exercised by running Load Flow:

• Pandapower: enable the matching Include controller checkbox (two-winding tap, three-winding tap, and/or shunt), together with the settings on each transformer or shunt.
• OpenDSS snapshot: discrete shunt voltage control and Line P→shunt step run from the same shunt dialog (no extra Include-controller tick). Transformer DiscreteTapControl remains pandapower-only.

For Grid Code Compliance (P-Q & U-Q), the same three pandapower Include-controller checkboxes apply when you enable them in that dialog. Grid Code Compliance (P-Q) uses its own Transformer tap control and Shunt control options instead.

Technical reference: pandapower Controller / run_control.

If you bookmarked this page previously as “Controller Simulation,” use Load Flow with “Include controller” instead.

Short Circuit

pandapower OpenDSS

Short Circuit calculates fault currents on the network so you can size breakers, check withstand, and feed protection studies. The two engine tabs are not interchangeable: pandapower follows IEC 60909; OpenDSS runs a native fault study.

When to use

• Breaker and fuse interrupting ratings
• Relay pickup and protection coordination
• Grid-code style IEC 60909 studies (pandapower tab)

How to run

1. Confirm the diagram already solves in Load Flow with the same engine you will use for faults.
2. Click Simulate → Short Circuit and choose the engine tab.
3. Set fault type (3-phase, 2-phase, or 1-phase) and run.
4. Read currents on the buses and branches. Use those values for Arc Flash if you need incident energy next.

Fault types

Electrisim supports three types of short circuit faults:

• Three-Phase Fault (3ph): Symmetrical fault affecting all three phases. Typically produces the highest fault current. Used for symmetrical interrupting capacity rating.
• Two-Phase Fault (2ph): Fault between two phases. Produces lower fault current than three-phase. Used for phase-to-phase protection.
• Single-Phase Fault (1ph): Fault between one phase and neutral/ground. Includes zero sequence impedance. Critical for ground fault protection and neutral sizing.

Input Parameters

Calculation Cases

According to DIN/IEC EN 60909, different calculation cases are used:

• Maximum Case (Ik"): Highest fault current (typically for breaker sizing). Assumes maximum generation, minimum impedances, voltage = 1.1 pu (c_max).
• Minimum Case (Ik'): Lowest fault current (typically for protection coordination). Assumes minimum generation, maximum impedances, voltage = 0.9 pu (c_min).

Output Results

The short circuit analysis provides detailed fault current information:

Algorithm Details

The short circuit calculation follows DIN/IEC EN 60909 standard:

• Voltage Factor (c): c_max = 1.1 for maximum case, c_min = 0.9 for minimum case (low voltage)
• Impedance Correction: Generator and transformer impedances are corrected according to the standard
• Far-from-Generator Approximation: Used when fault is far from generators (symmetrical current decays quickly)
• Near-to-Generator: Special handling when fault is close to generators (asynchronous contribution)
• Solution Method: Matrix inversion or LU factorization of network admittance matrix

Limitations and Considerations

Short Circuit based on OpenDSS

In addition to the Pandapower (IEC 60909) short circuit analysis, Electrisim offers short circuit calculation based on OpenDSS. In the Short Circuit dialog, select the OpenDSS tab to run a conventional fault study using the Open-Source Distribution System Simulator.

OpenDSS fault study (Solve Mode=FaultStudy) computes for every bus:

• Initial symmetrical short-circuit current (I''_k, ikss) in kA
• Peak short-circuit current (i_p, ip) in kA
• Thermal short-circuit current (I_th, ith) in kA
• Positive-sequence short-circuit resistance (R_k, rk_ohm) and reactance (X_k, xk_ohm) in ohms

Fault type (e.g. 3-phase) and frequency can be set in the OpenDSS tab. Results are shown on the diagram at each busbar. This option uses the same network model as OpenDSS load flow (buses, lines, loads, generators, external grid).

OpenDSS references: Fault Studies, Fault Study Mode, Bus.Isc().

Technical References

Based on: pandapower Short-Circuit and DIN/IEC EN 60909 (Pandapower); OpenDSS Fault Studies (OpenDSS).

Algorithm Type: Pandapower: symmetrical components method with impedance-based fault calculation following international standards. OpenDSS: conventional fault study with Thévenin equivalent and open-circuit voltage per bus.

Documentation References: 📘 pandapower Short-Circuit 📘 Running a Short-Circuit Calculation 📗 OpenDSS Fault Studies

Standards: IEC 60909: Short-circuit currents in three-phase a.c. systems (Pandapower).

Arc Flash Analysis (IEEE 1584)

pandapower

Arc Flash estimates thermal hazard at each bus: Electrisim runs a 3-phase maximum short-circuit (IEC 60909), then IEEE 1584-2018 for arcing current, incident energy, arc-flash boundary, and an NFPA 70E–style PPE category. Results are painted on the diagram.

When to use

• PPE selection from incident energy
• Arc-flash boundary for labelling and approach
• Comparing LV feeder hazard (for example MCC vs a remote panel)

How to run

1. Build the network and confirm short-circuit data (source impedances, transformer ratings) is filled in.
2. Click Simulate → Arc Flash (IEEE 1584).
3. Set working distance, electrode configuration, and clearing times, then run.
4. Read incident energy, AFB, and PPE category on each applicable bus.

How it is calculated

1. Short circuit: 3-phase max fault currents (I_kss) are calculated for all buses.
2. Arcing current (I_arc): IEEE 1584-2018 converts bolted fault current to arcing current using electrode configuration, gap, and voltage.
3. Reduced arcing current: I_arc-min is evaluated (variation factor); both clearing times are considered and the worst-case energy is kept.
4. Incident energy (IE): Energy at the working distance in cal/cm², including enclosure correction factor where applicable.
5. Arc-flash boundary (AFB): Distance where IE equals 1.2 cal/cm².
6. PPE category: Mapped from IE using NFPA 70E thresholds (Cat 0–4 / Dangerous).

Voltage range and methods

• 208 V – 15 kV: IEEE 1584-2018 empirical model (verified open-source coefficients via arcflash-calc).
• Above 15 kV: Ralph Lee method; the result box is tagged method: RalphLee so HV estimates are not confused with IEEE 1584 LV/MV results.
• Below 0.208 kV: Bus is skipped as outside the IEEE 1584 applicability range.

Input Parameters

Electrode configurations

• VCB — Vertical conductors in a metal box (typical switchgear / MCC)
• VCBB — Vertical conductors terminated in an insulating barrier inside a box
• HCB — Horizontal conductors in a metal box (often higher IE)
• VOA — Vertical conductors in open air
• HOA — Horizontal conductors in open air

Output Results

Each bus result box typically shows:

Demo model

Import the industrial example arc_flash_industrial_demo.py (File → Import) to see a clear LV gradient: short cables (MCC Near) show higher IE / PPE than long feeders (Panel Far). Buses at 20 kV are labeled with the Ralph Lee method.

Limitations and Considerations

Technical References

Based on: IEEE Std 1584-2018 (Guide for Performing Arc-Flash Hazard Calculations); short-circuit currents from pandapower short-circuit; calculation library arcflash-calc (IEEE 1584-2018 implementation).

Related: Short Circuit documentation · IEEE 1584 standard

Motor Starting Analysis

pandapower ANDES

Motor Starting checks voltage dip and loading when asynchronous motors start. Use the steady-state study for three snapshots (before / locked-rotor / after), or the dynamic study for a time-domain startup. Methods include DOL, soft-start, star-delta, autotransformer, and reactor.

When to use

• Voltage dip vs a limit (for example 10–15%) during DOL or soft-start
• Comparing starter methods in steady-state
• Start time and voltage recovery in dynamic mode

How to run

1. Place Motor elements and fill locked-rotor data.
2. Click Simulate → Motor Starting.
3. Choose steady-state or dynamic, the motors to start, and the starter method.
4. Run and review bus dip, branch loading, and (in dynamic mode) the time plots.

Input Parameters

Results

• SLD boxes: bus V before/during/after and dip % (green PASS / red FAIL); motor I_start and method
• Results dialog: tables for motors, buses, branches; CSV download; Chart.js plots for dynamic mode
• Summary: worst dip, voltage/thermal fail counts

Limitations and Considerations

Technical References

Based on: pandapower load flow and motor element (lrc_pu, rx); ANDES Motor3 + Toggle for time-domain startup. Typical study outputs include voltage drop before/during/after start, start time, and grid loading.

Related: Motor element · Short Circuit · Transient Stability (ANDES)

Transient Stability (ANDES Time-Domain Simulation)

ANDES

Transient Stability shows how the network responds over time to a bus fault or line trip: rotor swings, voltage recovery, and whether machines stay in synchronism.

When to use

• Synchronism after a fault (speed and angle swings)
• Comparing clearing times and fault locations
• Voltage recovery after a clear or line trip

How to run

1. Place a synchronous Generator and fill the Dynamics tab (defaults are applied if fields are empty).
2. Click Simulate → Transient Stability (ANDES).
3. Set end time, optional fault bus and clear times, and optional line outage.
4. Run and inspect generator speed/angle and bus voltage vs time.

Input Parameters

Results

• Multi-series charts: generator speed ω (pu), rotor angle δ (rad), bus voltage (pu), mean frequency (Hz)
• Summary: tf, point count, generator/bus counts, event settings
• List of applied dynamic defaults and mapping warnings (e.g. skipped DC lines, static generators)
• CSV export of the time series

Requirements & Limitations (MVP)

• At least one synchronous Generator; mark one generator as slack (or include an External Grid plus generators)
• Static generators are not modelled as SynGen in this MVP (warned in results)
• Three-winding transformers and DC lines are skipped
• Full ANDES model catalogue (100+ models) is not exposed — GENROU/GENCLS, EXDC2/SEXS, TGOV1 only

Technical References

Based on: ANDES PFlow + TDS. Demo model: transient_stability_two_machine_demo.py (File → Import).

Related: Eigenvalue Analysis · Generator Dynamics tab · Motor Starting (dynamic)

Eigenvalue Analysis (ANDES Small-Signal Stability)

ANDES

Eigenvalue analysis linearises the system around the current operating point and plots modes in the complex plane: damping and oscillation frequency. Negative real parts are stable; positive real parts grow.

When to use

• Small-signal stability at the current dispatch
• Poorly damped local or inter-area modes
• Effect of inertia, droop, or exciter gains (Generator Dynamics tab)

How to run

1. Use the same dynamic network as for transient stability (no fault is required).
2. Click Simulate → Eigenvalue Analysis (ANDES).
3. Run and inspect the s-plane plot, damping ratios, and optional participation factors.

Input Parameters

Results

• Stability verdict: stable, marginally_stable, or unstable
• Counts: positive / zero / negative eigenvalues
• s-plane scatter plot and table of σ, ω, f (Hz), damping ratio ζ
• Participation factors for highlighted modes (when available)

Technical References

Based on: ANDES eigenvalue tutorial.

Related: Transient Stability · Generator Dynamics tab

Protection Coordination Study

pandapower

Protection coordination checks whether devices operate in the right order for a chosen fault. Electrisim runs IEC 60909 short-circuit, then evaluates fuses and overcurrent (and related) devices. You get trip or melt times, I–t curves, and miscoordination warnings.

When to use

• Fuse melt and relay trip times for a fault at a bus or along a line
• Time-current grading between upstream and downstream devices
• A first miscoordination screen on a radial feeder

How to run

1. Place switches on lines, transformers, or bus connections in your diagram (switches are required for protection assignment).
2. Open each switch’s dialog → Protection tab. Choose Fuse (library or custom I–t curve) or OC relay (DTOC, IDMT, or IDTOC) and set pickup / grading parameters.
3. Click Simulate → Protection Coordination.
4. In the dialog, choose fault location (along a line or at a busbar), fault type (3ph / 2ph / 1ph), and case (max / min). Configure grading defaults on the Grading tab if switches leave fields empty.
5. Review the results dialog: short-circuit summary, tripping table (including melting time for fuses), I–t chart, and miscoordination list. Optionally export a .txt report.

Fault location modes

Dialog parameters

These fields are sent as ProtectionCoordinationPandaPower in the POST body together with network elements.

Switch protection settings

Per-switch parameters are configured on the Switch dialog Protection tab (see also Switch):

• Fuse — library type (e.g. Siemens NH-2 series) or custom JSON curve (t_min, t_total, x_min, x_total) plus rated current.
• OC relay — DTOC, IDMT, or IDTOC; IEC inverse curve; TMS, grading delay, instantaneous and backup trip times; automatic or manual pickup currents.

At least one switch with a fuse or OCR assigned is required; otherwise the study returns an error.

Outputs

• Short-circuit summary — e.g. Ikss at the fault bus (kA).
• Tripping table — per switch: device type, tripped/melted flag, activation current (activation_parameter_value, kA), trip/melt time (trip_melt_time_s, s).
• Time-current chart — log-log grading curves (Chart.js) when enabled.
• Miscoordination warnings — pairs of devices whose trip times are closer than the grading margin (t_diff).
• Export — optional .txt download with the same summary fields.

Prerequisites and tips

• Valid network topology with external grid (or slack) and in-service switches on protected branches.
• For results comparable to pandapower fuse examples, match fuse types per feeder, avoid duplicate fuses on both ends of the same line unless intended, and align external-grid short-circuit strength (s_sc_max_mva) with your reference case.
• OCR relays require matplotlib in the backend environment (pip install matplotlib).

Limitations

• Primary path is short-circuit based; overload (scenario=pp) is optional when enabled in the study dialog. For motor-start voltage dip studies, use Motor Starting Analysis.
• Differential (87) and distance (21) use Electrisim evaluators on SC results (not native pandapower device classes).
• Line-end duplicate switches report identical branch currents by design.
• Subscription required in the cloud app (same gating as other premium analyses).

Technical references

pandapower v3.3.2 — Protection · Short-circuit (IEC 60909)

DG Interconnection Screening (OpenDSS)

OpenDSS

Screens a proposed DER (PVSystem, Storage, or Generator) at the point of connection for voltage band, thermal loading, and reverse power. You can compare Volt-VAR inverter control and estimate hosting capacity.

When to use

• A first interconnection check before a full impact study
• Whether Volt-VAR or feeder controls would fix a voltage/thermal fail
• An estimate of hosting capacity at the POC

How to run

1. Place a DER on the feeder and note the POC bus.
2. Click Simulate → DG Interconnection Screening (OpenDSS).
3. Select POC bus, DER, proposed kW, voltage/thermal limits; optionally enable hosting-capacity search and InvControl compare.
4. Review pass/fail checks, mitigations, and hosting capacity kW.

Related studies: Battery Sizing for Busbar Requirements; Grid Code Compliance (P-Q & U-Q).

Monte Carlo Load Flow (OpenDSS)

OpenDSS

Monte Carlo load flow samples load variation over many trials and reports bus voltage and line loading statistics (min, mean, max, and percentiles).

When to use

• Voltage and loading risk when load is uncertain
• A distribution of results instead of a single snapshot

How to run

1. Build a network suitable for OpenDSS load flow (include loadshapes for Gaussian M1 where required by OpenDSS).
2. Open Simulate → OpenDSS Load Flow (or the OpenDSS tab of Load Flow).
3. Set Solution Mode to M1, M2, or M3; choose sample Number, Random (Uniform / Gaussian), and hour for M3.
4. Review the Monte Carlo results dialog: bus V percentiles, line loading stats, and summary convergence count.

Wind Turbines contribute with their curve-derived p_mw (and optional controller Pref) on each sampled solve the same way as in snapshot load flow.

Harmonic Analysis

OpenDSS

Harmonic Analysis computes voltage and current THD: how non-linear equipment injects harmonic currents and how they propagate. Assign spectra on the Harmonic tab of the relevant elements, then run this study.

Watch on YouTube

When to use

• Voltage and current THD at each bus
• Checks against power-quality limits (for example IEEE 519)
• Filter design and harmonic propagation from converters or VFDs

How to run

1. Build the fundamental model: buses with rated voltage, lines, transformers, shunts, and an External Grid.
2. On each non-linear element, open the Harmonic tab and set the spectrum.
3. Click Simulate → Harmonic Analysis. Set base frequency and the harmonic orders (for example 3, 5, 7, 11, 13).
4. Review bus VTHD, per-order voltages, line harmonic currents, and the spectrum chart.

Where harmonics are defined (Harmonic tab)

Parameters from these tabs are included in the payload sent to the solver so the backend can build matching OpenDSS commands.

Spectrum modes (UI)

Load harmonic impedance (OpenDSS)

For loads, %SeriesRL, conn, puXharm, and XRharm control how the load’s harmonic-frequency model splits between parallel and series R–L paths. This matches the EPRI discussion of harmonic load modelling. Always cross-check sensitivity (e.g. %SeriesRL 0 vs 100%) if results are borderline for compliance.

OpenDSS — Harmonics Load Modeling

Harmonic Analysis Results window

• Summary line — Base frequency, solved orders, NeglectLoadY flag.
• Voltage spectrum chart — Per selected bus: harmonic voltage magnitudes as percent of fundamental line-to-line voltage (useful for relative distortion at the bus).
• Table — Name (bus user name when set), VTHD [%], and columns V_h [kV] per order (line-to-line harmonic magnitudes in kV).

If VTHD or harmonic kV are near zero, check that at least one injection source has a non-None spectrum with content at the orders you are solving, and that the network is connected to the slack.

Standards and planning context

Voltage THD and harmonic levels are often compared to limits in IEEE Std 519, IEC 61000, or local grid codes. Limits depend on the agreed PCC, system strength, voltage level, and jurisdiction. Electrisim provides engineering quantities (THD, harmonic voltages and currents); compliance assessment remains your interpretation against the applicable standard and contract.

How it works (solver)

Electrisim drives OpenDSS harmonic flow: the circuit is solved in fundamental mode first, then mode=harmonics is applied with the requested order list. Monitors capture bus-related voltages and line currents per harmonic; results are aggregated into bus VTHD and per-order magnitudes for the JSON response and the UI.

Configuration checklist

Open Simulate, set Analysis type: Harmonic, enter orders (comma-separated), and confirm frequency. Configure each injecting element’s Harmonic tab. For filters, use shunt reactors/capacitors (and lines/transformers) as in the fundamental model. Export OpenDSS commands from the flow dialog if you need to reproduce the case outside Electrisim.

Based on: OpenDSS Harmonic Flow Analysis; OpenDSS Load (spectrum, %SeriesRL); OpenDSS Vsource (external equivalent).

Optimal Power Flow (OPF)

pandapower

Optimal Power Flow finds a least-cost generation dispatch that still respects voltage limits, thermal limits, and generator capability. Unlike load flow, the solver is allowed to change dispatch (within your costs and limits).

When to use

• Least-cost dispatch while serving load
• Checking whether a target dispatch is feasible with voltage and thermal limits
• Comparing AC OPF (more accurate) with DC OPF (faster, active power only)

How to run

1. Fill generator costs (or accept dialog defaults) and bus/line limits used by OPF.
2. Click Simulate → Optimal Power Flow.
3. Choose AC or DC OPF and run.
4. Read the new dispatch on generators and the flows that result.

Dialog parameters

Objective Function

The default objective function minimizes total generation cost, which is typically defined as:

Minimize: Σ (Cost_i × P_gen,i) for all generators i

Where Cost_i is the cost coefficient for generator i and P_gen,i is the active power output. Cost functions can be linear, quadratic, or piecewise linear.

Polynomial versus piecewise linear (Electrisim)

In the OPF dialog, Cost function type selects how generator operating costs are modeled before calling pandapower:

• Polynomial — Each synchronous generator gets a smooth cost in active power: by default a small positive quadratic term (convexity / curvature) plus a marginal linear rate that you set per machine (OPF run dialog and/or the generator’s OPF tab as marginal cost per MWh). This matches pandapower poly_cost (cp2_eur_per_mw2, cp1_eur_per_mw, cp0_eur). It is usually the most robust choice for AC OPF.
• Piecewise linear — Cost is linear on each power segment; Electrisim builds a single segment between each generator’s minimum and maximum OPF active power, with slope equal to your marginal rate (same interpretation as the linear term in the polynomial case). This matches pandapower pwl_cost. Use it when you think of marginal price as constant between min and max P; multi-segment tariffs would require additional segments (not exposed individually in the UI).
• No cost function — No polynomial/PWL costs are created for economic minimization; the OPF can still converge but economic dispatch is not driven by generator marginal costs.

Currency — The OPF dialog lets you choose a marginal cost currency for labels only. Numerical values are passed to the solver as-is; pandapower still names internal cost columns with eur for historical reasons. Interpret objective values (e.g. total_cost) in the same unit system you used when typing marginal costs.

Constraints

The OPF solution must satisfy:

• Power Balance: Total generation equals total load plus losses
• Generator Limits: P_min ≤ P_gen ≤ P_max, Q_min ≤ Q_gen ≤ Q_max
• Voltage Limits: V_min ≤ V ≤ V_max at each bus using net.bus.min_vm_pu / max_vm_pu from the diagram (see Bus)
• Thermal Limits: Branch loading respects element ratings; optional OPF caps — set max_loading_percent on lines, two-winding, or three-winding transformers. A value > 0 adds a pandapower OPF thermal limit for that element; 0 leaves the default unconstrained behaviour.
• Reactive Power Limits: Generator reactive power capability constraints

Output Results

The OPF results include optimized dispatch and system state:

Prerequisites

• OPF-capable network: slack/external grid, generator and storage models compatible with pandapower OPF.
• Bus voltage bounds (min_vm_pu, max_vm_pu) should bracket a feasible region.
• For meaningful objective values, define polynomial or piecewise costs—Electrisim can auto-create defaults from the dialog Cost function type when no costs exist.

Diagram-level inputs

• Generators: active/reactive limits and any OPF-specific fields exposed in element dialogs.
• Storage: optimisation-tab limits map into pandapower OPF constraints.
• Buses: voltage set-points and min/max magnitudes bound the OPF solution.

API response (successful OPF)

The route returns JSON with:

Failures respond with error: true, a descriptive message, exception text, and optional pandapower diagnostic payloads.

Note: PandaModels.jl / PowerModels.jl OPF paths referenced in pandapower docs are not wired through Electrisim; only PYPOWER-style runopp/rundcopp are available.

Algorithm Details

AC OPF: Solves the full nonlinear optimization problem using Interior Point Method (IPM) or Sequential Quadratic Programming (SQP). Provides accurate results but requires significant computation time for large networks.

DC OPF: Uses a linearized power flow model (ignoring losses and reactive power). Much faster than AC OPF but less accurate. Suitable for transmission planning where reactive power is less critical.

Solver: PYPOWER, which is based on MATPOWER and uses MATLAB optimization solvers (converted to Python).

Limitations and Considerations

Technical References

Based on: pandapower Optimal Power Flow and PYPOWER.

Algorithm Type: Nonlinear/Linear optimization with Interior Point Method or Sequential Quadratic Programming.

Documentation References: 📘 pandapower Optimal Power Flow 📘 PYPOWER OPF

Time Series Simulation

pandapower

Time Series runs one AC load flow per hour (or time step). At each step, load and generation follow the profiles you enter, so you can see voltages and loadings over a day or a year.

When to use

• Daily or yearly voltage and loading with varying load and generation
• Checking whether a snapshot load flow hides an overloaded hour

How to run

1. Build the network and confirm a single Load Flow converges.
2. Open Time Series Simulation.
3. Set the horizon (for example 24 hours) and a profile for each load and generator.
4. Run and review charts in the results dialog; export if you need a spreadsheet.

Dialog — simulation horizon

• time_steps — number of sequential power-flow solves. Each step represents one hour by default (e.g. 24 = one day, 8760 = one year).

Dialog — load & generation profiles (per element)

Every Load, Generator, and Static Generator on the diagram gets its own profile editor. Enter one numeric value per time step, separated by commas or spaces. You can also import a .csv or .txt file.

Quick fill (optional toolbar above the element cards) lets you apply a preset shape to all loads or all generators at once — this replaces the older “Global preset” mode, which applied one profile to every element and often failed to converge on meshed or transformer-heavy networks. Per-element control with absolute MW values is the recommended approach.

Preset shapes available for quick fill:

• Load: constant, daily (residential), industrial, variable
• Generation: constant, solar, wind, variable

The Random (tutorial) button fills absolute MW values between 0 and the element’s base P — matching the pandapower notebook example.

Dialog — advanced power flow settings

Collapsed under Advanced power flow settings in the dialog:

• frequency — system frequency (Hz).
• algorithm — nr (Newton-Raphson), iwamoto_nr, fastdecoupled, or dc.
• calculate_voltage_angles — auto, yes, or no.
• init — initialization method. Auto is recommended; after the first converged step the backend warm-starts from previous results.

Convergence tips

• Verify the network converges in a single Load Flow before running time series.
• Use Absolute P (MW) when values look like notebook MW numbers — do not mix absolute MW values with scale-factor mode.
• Keep initialization on Auto unless you have a specific reason to change it.
• Large simultaneous swings in load and generation can stress weak networks; try smoother profiles first.

Results dialog

After a successful run, the results dialog shows:

• Summary — convergence status, duration, element counts, and non-converged step numbers if any.
• Charts — input profiles, bus voltages, line loading, load P, static generator P.
• Statistics — min / max / average voltage and line loading across all hours.
• Detailed data — scrollable table of bus results for every hour.

Enable Download Excel report automatically in the setup dialog, or click Export to Excel in the results dialog. Sheets include Summary, res_bus, res_line, res_load, res_sgen, and profiles. If the Excel library cannot load, a CSV fallback is offered.

API payload

Posted as TimeSeriesSimulationPandaPower Parameters together with the diagram JSON:

• time_steps, profile_mode (always custom from the UI), element_profiles — per-element { element_type, mode, values, display_name }.
• load_profile, generation_profile — preset names used only for quick-fill reference.
• frequency, algorithm, calculate_voltage_angles, init.

Outputs (JSON)

Extraction tip: Filter busbars / lines by time_step to plot trajectories; use the statistics blocks for KPI cards.

pandapower alignment

Official reference: Time Series Simulation. Electrisim approximates the profile-driven loop using repeated runpp calls, which is appropriate when you need bus/line summaries and Excel export rather than registered OutputWriters.

Economic Analysis

pandapower

Economic Analysis totals CAPEX from element costs, power losses from a load flow, and optionally energy losses over a lifetime using load and generation profiles.

When to use

• Project CAPEX from lines, transformers, and other equipment
• Where the losses are (lines, transformers, impedances, DC lines)
• Energy-loss cost over a lifetime when you supply an energy price

How to run

1. Fill the Economic tab on the elements you want in the CAPEX total.
2. Click Simulate → Economic Analysis.
3. Optionally enable energy-loss profiles and a lifetime / energy price.
4. Run and compare CAPEX, power losses, and energy-loss cost.

How it is calculated

The economic analysis performs the following steps:

1. CAPEX: Sums costs from the Economic tab of each element (lines, transformers, etc.). For lines: cost × length_km × parallel. For transformers: cost × parallel.
2. Power Losses: Runs one AC load flow and extracts active power losses (pl_mw) from lines, transformers, three-winding transformers, impedance branches, DC lines / DC lines mapped through pandapower.
3. Energy Losses (optional): When profiles are enabled, Electrisim builds hourly scaling traces for loads and generators, evaluates losses on a compact grid of operating points with repeated runpp, then interpolates losses for each hour (SciPy RegularGridInterpolator when both load and generation vary). This estimates the sum of hourly loss energy, Σ P_loss(t)Δt, with Δt = 1 h.
4. Period vs lifetime MWh: The simulation-period integral is exposed as total_energy_losses_period_mwh. Multiplying by Lifetime (years) yields total_energy_losses_mwh, representing cumulative losses across the project horizon.
5. Energy Loss Cost: When an energy price is supplied, cost equals total_energy_losses_mwh (lifetime MWh) × price.

Formulas: Power Losses and Electrical Energy Losses

Power losses are computed by pandapower from the load flow results. The following formulas apply per element type:

Power Loss (P_loss) per Element

AC Line, Impedance, DC Line (line_dc):

P_loss = P_from + P_to

where P_from is active power flow into the element at the "from" bus, and P_to is active power flow into the element at the "to" bus (power flow convention: one direction is positive, the other negative, so the sum equals the power dissipated).

Transformer (2-winding and 3-winding):

P_loss = P_hv + P_lv

where P_hv is active power at the high-voltage side and P_lv at the low-voltage side. Equivalent to P_from + P_to in terms of power balance.

HV DC Link (dcline):

P_loss = P_from + P_to

with P_to = −P_from × (1 − loss_percent/100) − loss_mw. The loss is thus P_from × (loss_percent/100) + loss_mw.

Physical interpretation: For resistive elements (lines, impedance), P_loss ≈ I²R, where I is the current and R the resistance. For transformers, losses include copper (I²R) and iron (no-load) losses.

Total Power Losses

P_total,loss (MW) = Σ P_loss over all lines, transformers, impedance elements, and DC lines

Electrical Energy Losses

Hourly losses are reconstructed via interpolation from strategically sampled AC load flows (see workflow above—not full pandapower run_timeseries). Energy over the simulated horizon:

E_period (MWh) = Σ_t=1..N P_loss(t) × Δt

Lifetime cumulative energy:

E_lifetime (MWh) = E_period × lifetime_years

The JSON field total_energy_losses_period_mwh stores E_period; total_energy_losses_mwh stores E_lifetime.

Energy Loss Cost

Cost = E_lifetime (MWh) × energy_price_per_MWh

Economic analysis request payload

The frontend merges diagram cells with an object typ: "EconomicAnalysisPandaPower Parameters". Important keys mirrored by Flask (app.py):

• frequency, currency, algorithm, calculate_voltage_angles, init
• use_generation_profile — UI sets this true whenever profile widgets are shown.
• time_steps, lifetime_years, load_profile, generation_profile, energy_price_per_mwh, energy_price_currency, calculation_mode

Economic analysis JSON outputs

• total_capex, capex_breakdown: Aggregated CAPEX and per-element contribution pulled from diagram economics fields.
• total_power_losses_mw, power_losses_breakdown: Sum of pl_mw after the baseline load flow.
• total_energy_losses_period_mwh: Integrated losses over time_steps hours (Δt = 1 h).
• total_energy_losses_mwh: Lifetime cumulative (= period × lifetime_years).
• energy_loss_cost: Lifetime MWh × price when provided.
• load_profile_values, generation_profile_values: Hourly scaling vectors stored for auditing/charts.

Input Parameters

Results

• Total CAPEX: Sum of all element costs in the selected currency
• CAPEX Breakdown: Table of element type, name, and cost per element
• Total Power Losses (MW): Sum of active power losses from load flow
• Power Losses Breakdown: Table of element type, name, and power loss (MW) per element
• Total Energy Losses (period): total_energy_losses_period_mwh — integrated MWh over the simulated hour window.
• Total Energy Losses (lifetime): total_energy_losses_mwh — equals period energy × lifetime years.
• Energy Loss Cost: Lifetime MWh × energy price when specified.
• Profiles used: Load and generation profile names and hour count used for the calculation

Note: Set cost per unit in the Economic tab of each element dialog (lines, transformers, etc.) before running Economic Analysis. Element names in the breakdown match the names shown in the CAPEX and Power Losses tables.

Reactive Power Capability (PQ Diagram) App menu: Grid Code Compliance (P-Q & U-Q)

pandapower

This study builds a PQ diagram (and U-Q/Pmax) at the point of common coupling (PCC) for plants modelled with static generators and/or wind turbines. It sweeps plant P, runs load flow at each step and PCC voltage, and records the Q range the plant can deliver.

Video tutorials: Reactive Power Capability (PQ Diagram) — YouTube; offshore wind P-Q/Pmax worked example — 450 MW grid compliance (Part 1) (video card). U-Q/Pmax offshore tutorial planned separately.

How to run it

1. Model the plant and grid: define a bus as the PCC, an external grid at the PCC (voltage source), and one or more static generators and/or wind turbine generators for the plant.
2. In the Electrisim menu, choose Grid Code Compliance (P-Q & U-Q) (under Simulate; pandapower).
3. Select PCC bus, external grid, and the Static Generator or Wind Turbine Generator units that represent the plant.
4. Set P Max (MW), number of P steps, and voltage levels at PCC (pu) (comma-separated, e.g. 0.9, 0.95, 1.0, 1.05, 1.1).
5. Optionally enable limit Q to avoid branch overloads and set a maximum loading (%).
6. Optionally add grid code requirements: pick a P-Q template and P rated (MW), or use Apply to fill the table. A matching U-Q/Pmax template is selected automatically when U-Q is still “none”; you can override it. You can also edit P, Q_min, Q_max manually.
7. Run the calculation. While the backend works, a small progress panel can show each voltage level being processed (when streaming is supported).

Key parameters explained

Built-in grid code templates

Choose Custom (manual table) to type P, Q_min, and Q_max yourself, or pick a built-in envelope. Values are per-unit of P rated before scaling to MW and Mvar. These summaries support study and visualization only—always confirm against the official code text and your TSP or connection agreement.

• ENTSO-E RfG — PPM inner envelope (EU minimum); PPM outer envelope (maximum TSO range)
• VDE AR-N 4120 variant 2 (Germany HV, ≥110 kV); VDE AR-N 4110 (Germany MV)
• Polish IRiESP — Type D (≥110 kV); PPM / wind farms; PPM P-Q/Pmax Fig. 2 @ 400 kV (offshore Type D PPM)
• GB Grid Code (UK, National Grid ESO)
• Spanish P.O. 12.2 (REE)
• Danish Grid Code (Energinet TF 3.2.5)
• Italian Grid Code (Terna, Allegato A.68)
• Saudi Arabian Grid Code (SAGC, May 2024) — Connection Code §2.5.5.1, Fig. 2.1:
  • Power Park Module: at the connection point, for active output below 20% of rated power, Q within ±0.05·P_rated; for output above 20%, Q within ±0.33·P_rated (unless the TSP agrees a different threshold in the connection agreement).
  • Synchronous generating unit: at rated active power, capability between 85% power factor lagging and 95% leading at the unit terminals. For P below rated, the template uses a linear ramp toward (0, 0) so the chart has points to interpolate; the published text is explicit at rated output, so check with your TSP if you need a different partial-load shape.

U-Q/Pmax diagram and grid-code templates

NC RfG Art. 21(3)(b)(i) requires reactive power capability at maximum active power as a function of voltage at the PoC (U-Q/Pmax profile). Electrisim extracts Q_max and Q_min at P = Pmax from the same RPC sweep used for P-Q diagrams and displays them in a dedicated U-Q / Pmax results view.

1. In the RPC dialog, set P Max to rated output. You can leave voltage levels at a single value (e.g. 1.0 pu); the solver unions the U points from the U-Q template into the sweep so the U-Q chart is a curve.
2. Pick a P-Q Template (or set a U-Q Template under U-Q/Pmax Grid Code Requirements). If U-Q is still “none”, Electrisim applies the paired U-Q envelope for that P-Q template (Polish Type D / PPM, Polish PPM Fig. 2 @ 400 kV, ENTSO-E PPM inner, VDE AR-N 4110).
3. After the run, open results and switch from P-Q / Pmax to U-Q / Pmax: net Q at the PCC (Mvar) on the X-axis (positive = overexcited), voltage (p.u.) on the Y-axis. Red is simulated capability; blue is the PCC requirement envelope (overexcited solid, underexcited dashed) with a filled requirement area.
4. Review the COMPLIANT / NON-COMPLIANT badge and the per-voltage results table; export CSV includes U-Q sections.

If the U-Q curve still has only one or two voltage points, add more levels by hand (e.g. 0.875, 0.9, 0.925, 0.95, 1.0, 1.05, 1.075, 1.1 pu) and Calculate again.

Built-in U-Q templates: Polish IRiESP PPM U-Q/Pmax @ 400 kV (Fig. 1 tapered polygon) and @ 110 kV; ENTSO-E PPM U-Q inner envelope. Values are per-unit of P_rated before scaling to Mvar.

P-Q PPM template: Polish IRiESP – PPM P-Q/Pmax Fig. 2 @ 400 kV (Type D) matches NC RfG Figure 2: ±0.33 Q/Pmax at Pmax, −0.35 / +0.40 Q/Pmax from 10–90% P. Selecting it also applies the 400 kV U-Q template unless you already chose a different U-Q envelope.

What the results show

• PQ diagram per voltage tab: P (MW) vs Q (Mvar) at the PCC, with capability Q_max/Q_min curves and optional grid-code requirement curves.
• U-Q/Pmax diagram (results view toggle): Q_max/Q_min at P = Pmax vs PCC voltage (Q on X, U on Y), with optional U-Q grid-code overlay (blue requirement area) and compliance badge.
• Compliance badge when requirements are defined: whether interpolated capability meets the required Q band at check points (separate flags for P-Q per voltage tab and U-Q at Pmax).
• Warnings (e.g. power flow only converged at a reduced Q fraction, or Q limited due to overload constraints). See Warnings in the results dialog below.
• Download CSV for all voltage levels and curve points.

Warnings in the results dialog

The yellow Warnings list explains how certain points on the PQ curves were obtained. It does not mean the whole analysis failed; it flags individual (voltage, P) combinations where the solver had to relax assumptions.

“Q_max converged at X% capability” / “Q_min converged at X% capability”

For each sweep point, the backend sets static-generator reactive power toward the full theoretical limit from the selected Q capability mode (for example, from each generator’s S_n and its share of plant P). It runs AC power flow starting at 100% of that limit. If power flow does not converge, it retries with 90%, then 80%, 70%, and lower fractions until a case converges. The number in the message is that fraction of theoretical reactive capability at which load flow first succeeded—it is not a percentage of solver iterations or “partial convergence.”

• A value below 100% means the tool could not obtain a valid solution at full theoretical Q for that point; the chart shows the PCC Q from the reduced setpoint. Neighbouring P steps may use different fractions, which can make the capability curve look irregular or jagged compared to a smooth envelope.
• Typical causes include stressed or weak-grid conditions, PCC voltages far from nominal, heavy reactive exchange with the network, or model aspects (impedances, transformer taps, P sharing among generators). Improving data quality or simplifying extreme branches often reduces these warnings.

“Q_max limited due to overload” / “Q_min limited due to overload”

These appear only when limit Q to avoid branch overloads is turned on. Here, reactive capability was reduced so that the worst line or transformer loading stays within your maximum loading (%), even if a higher Q would otherwise have been numerically feasible.

Technical summary

For each PCC voltage level and each P in the sweep, the backend adjusts generator P and Q, runs AC power flow (with robust solver fallbacks), and reads Q at the PCC. Q_max and Q_min branches correspond to overexcited and underexcited plant operation relative to the network. This is a numerical envelope built from many load-flow solutions, not a single analytical formula for the whole grid.

Based on: pandapower AC power flow (runpp) executed repeatedly inside Electrisim’s RPC workflow.

Grid Code Compliance (P-Q) App menu: Grid Code Compliance (P-Q)

pandapower

This study is a P-Q diagram at the point of connection only — no U-Q view. The distinctive option is plant Q through a Park Controller, instead of setting Q on each machine locally.

How to run it

1. Model the plant: PCC bus, external grid at the point of connection, wind turbines and/or static generators, and optionally a Park Controller linked to those machines.
2. Simulate → Grid Code Compliance (P-Q) (pandapower only).
3. Select PCC, external grid, Park Controller, and plant units (auto-filled from the park Machines list when park control is on).
4. Set Pn, sweep start / step / end (% of Pn), voltage levels, Q capability mode, and optional grid-code P-Q template.
5. Optionally enable loading limit, voltage protection at LV terminals, worst-case transformer taps, shunt-first Q reduction, and Q with units not operating.

Key parameters

Procedure

For each voltage level and each P from sweep start to sweep end:

1. Set Q to the plant/unit capability (Qmax, then Qmin) and run a load flow.
2. If loading limits are violated and Shunt control plus Loading limit are on, reduce shunt compensation one step at a time before touching plant Q.
3. Then reduce Q by the Q reduction step (% of Pn) until the network is within limits or Q reaches 0 Mvar.
   • Park controller off: each unit’s Q setpoint is reduced as a function of its rating (local Q on the static generator / wind turbine).
   • Park controller on: the Park Controller constant-Q setpoint at the point of connection is reduced.
4. Transformer tap control: two load flows per P (lower vs upper tap voltage setpoint); keep the more restrictive Q envelope. Discrete taps only.

Park Controller Q applies to wind turbine and static generator elements only, not synchronous generators. OpenDSS is not supported.

Results show the red capability / blue requirement P-Q chart (click a red point to apply that load flow on the diagram), a MW/Mvar vs p.u. of Pn unit toggle, loading and voltage summary, optional 10% table, and CSV download. Grid-code templates are the same P-Q envelopes as in Grid Code Compliance (P-Q & U-Q).

Contingency Analysis

pandapower

Contingency analysis takes equipment out of service one piece at a time, runs AC load flow, and flags thermal or voltage violations. Today this is single-outage (N-1 style) only.

When to use

• N-1 screening for overloads and voltage excursions
• Ranking outages by violation count
• A worst-case snapshot for reinforcement discussions

How to run

1. Build and solve a normal Load Flow first so the network is connected and the base case converges.
2. Ensure each busbar has a numeric nominal voltage vn_kv (kV), not descriptive text from other equipment.
3. Click Simulate → Contingency Analysis (active subscription required).
4. In the Contingency Analysis Parameters dialog, set element type (lines, transformers, generators, or all), voltage and thermal limit checks, and thresholds (min/max voltage in p.u., maximum loading %).
5. Click Analyze. When the study completes, the Contingency Analysis Results dialog opens automatically.
6. Use filters and expandable rows to inspect violations; download CSV for a full audit trail or expand Worst-case network snapshot for bus/line/trafo values after the heaviest outage.

Results dialog

After a successful run, Electrisim shows an interactive results window (not only console output):

• Summary cards — cases analyzed, converged, failed, cases with violations, total violation count.
• Search and filters — find a case by name or outage text; show All, With violations, or Failed only.
• Case list — sorted by violation count (highest first). Each row shows status (Converged, Non-convergent, or Failed), a violation badge, and a short summary (e.g. voltage vs thermal counts).
• Expandable details — click a row to open grouped tables for voltage and thermal violations (up to 25 rows per group in the UI; use CSV for the full list).
• Worst-case snapshot — collapsible section with bus, line, and transformer results from the contingency with the most violations (same data used for optional diagram colouring).
• Download CSV — exports every case with status and violation summaries.

Non-convergent cases mean the AC power flow did not solve after that outage (often islanding or loss of slack). Failed indicates another backend error; the detail row shows the message.

Prerequisites

• Solvable base-case AC power flow (slack/external grid, connected topology).
• Reasonable voltage and thermal limits for meaningful violation detection.
• Valid bus vn_kv on every busbar (numeric kV).

Dialog parameters

These fields are sent as ContingencyAnalysisPandaPower Parameters in the POST body together with network elements (see development/API notes if you integrate programmatically).

Outputs and JSON shape

The HTTP response is JSON (often gzip-compressed). Top-level keys:

Extracting results: Use contingency_results for complete audit trails and CSV export; use summary.critical_contingencies for quick screening; use top-level bus/line/transformer only for the worst-case view on the canvas.

Relationship to pandapower documentation

pandapower documents contingency workflows under Contingency analysis, including run_contingency and limit helpers. Electrisim follows the same physical idea (sequential AC PF after outages) but uses its own loop so the UI can evolve independently. For deeper algorithm options, refer to the official docs.

Limitations

• Steady-state only—no transient or voltage stability assessment.
• Each case removes one element; double or common-mode outages are not generated.
• No automatic redispatch or load shedding after an outage.
• Islanded or non-convergent cases are reported with converged: false and an error or convergence violation entry.
• Large networks may produce many voltage violations per case when limits are tight; use the results dialog filters and CSV export rather than reading every violation in the UI.

Technical references

pandapower v3.3.2 — Contingency analysis · runpp

Battery (BESS) sizing — POC busbar P/Q targets App menu: Battery Sizing for Busbar Requirements

pandapower

This study sizes the electrical P/Q the BESS must provide so the point of coupling (POC) bus meets a target P (MW) and Q (Mvar). It answers “how hard must the battery work for this schedule?” — not switchgear ampacity.

When to use

• BESS P/Q needed to meet a POC schedule
• Comparing load-supply, export, and reactive-support targets

How to run

1. Model the POC bus, grid connection, and the BESS (Storage or BESS AC Block).
2. Click Simulate → Battery Sizing for Busbar Requirements.
3. Set the POC bus and target P/Q, then run.
4. Read the required BESS P and Q and whether the target was reached.

Dialog parameters

Multiple Scenarios Mode

When selecting "Multiple Scenarios" mode, you can evaluate five different operational scenarios simultaneously. Each scenario has editable target P and Q values:

All scenario values are editable before running the calculation. The results show the required BESS power for each scenario separately, allowing you to determine the maximum BESS capacity needed across all scenarios.

Output Results

For each scenario (or single target), the results include:

API payloads and result extraction

The browser POSTs the diagram JSON plus a sibling object bess_sizing_params with typ: "BessSizingPandaPower", carrying storageId, pocBusbarId, targets, tolerances, gains, frequency, algorithm, and optional scenarios when running multi-case mode.

Single target response (JSON): bess_p_mw, bess_q_mvar, bess_s_mva, achieved_p_mw, achieved_q_mvar, error_p_mw, error_q_mvar, converged, iterations, or an error string when sizing cannot proceed.

Multiple scenarios response: { "calculationMode": "multiple", "scenarios": [ ... ] } where each scenario echoes the input targets and the same numeric keys as the single-mode payload.

Visualization (Multiple Scenarios Only)

When running multiple scenarios, the results include two visualization plots:

1. POC P–Q (Target vs Achieved) Plot: Shows a scatter plot comparing target and achieved P/Q values at the Point of Coupling. Blue circles represent target values, green circles represent achieved values. Dashed lines connect target-achieved pairs for each scenario.
2. Required BESS P–Q Plot: Shows a scatter plot of the required BESS active and reactive power for each scenario. Green circles represent the calculated BESS requirements.

Both plots include grid lines, axis labels, and scenario name annotations for easy identification.

Algorithm Details

The sizing algorithm implements a proportional controller with the following characteristics:

• Initial Guess: initial_p = -target_p_mw × 1.05 and initial_q = -target_q_mvar × 1.05. The negative sign accounts for the fact that BESS must discharge (negative P from BESS perspective) to supply positive power at POC, and the 1.05 factor accounts for losses.
• Control Loop: Uses proportional control with damping factor of 0.5 to prevent oscillations:
  • delta_p = -kp_p × error_p × damping
  • delta_q = -kp_q × error_q × damping
• Sign Convention:
  • At POC: Positive P = consumption from grid, Negative P = generation to grid
  • For BESS: Negative P = discharging (generation), Positive P = charging (consumption)
• Convergence: Algorithm converges when |error_p| < tolerance AND |error_q| < tolerance

Limitations and Considerations

Technical References

Based on: pandapower control framework with custom BESS control controller implementation.

Algorithm Type: Iterative proportional control with Newton-Raphson power flow solver.

Documentation References: 📘 pandapower Control Documentation 📘 pandapower Storage Element

Bus

pandapower OpenDSS

A bus is a connection point (node / busbar). Every other element must attach to at least one bus. Load-flow results show voltage magnitude and angle here — so set rated voltage (vn_kv) correctly before you run anything.

Documentation References: 📘 pandapower Bus 📗 OpenDSS Documentation

Parameters:

OPF note: Bus min_vm_pu / max_vm_pu are sent to the pandapower backend with each study. If limits are missing or inconsistent (e.g. max ≤ min) on a bus, Electrisim substitutes a wide 0.8–1.2 p.u. band for that bus only so AC OPF can converge on stressed networks.

Line

pandapower OpenDSS

Draw a Line as an edge between two buses (it is not a palette shape). Enter length and impedance, or keep the defaults for a first test. Use this for cables and overhead lines; use Impedance when you only have R and X between two buses.

UI defaults on drop: length_km 1, type cs (cable), endtemp_degree 250 °C, zero-sequence r0_ohm_per_km/x0_ohm_per_km 0.1 Ω/km, parallel 1, df 1.

Documentation References: 📘 pandapower Line 📗 OpenDSS Line

Parameters:

Load

pandapower OpenDSS

A load is demand at a bus (P and Q). Use constant power unless you have a reason for constant current or impedance. This is the usual way to model customers, motors-as-PQ, and plant auxiliaries.

Documentation References: 📘 pandapower Load 📗 OpenDSS Load

Parameters:

Harmonic Parameters (OpenDSS):

These parameters are used when running harmonic analysis with the OpenDSS engine. They define how the load injects harmonic currents and how the harmonic-frequency impedance of the load is represented. See also the Harmonic Analysis section for spectrum modes and workflow.

Motor

pandapower OpenDSS

An asynchronous motor. Use it when you need locked-rotor inrush for Motor Starting or a motor contribution in short-circuit. In OpenDSS it is mapped through a Load equivalent, not a native motor object.

Documentation References: 📘 pandapower Motor 📗 OpenDSS Motor

Parameters:

Asymmetric Load

pandapower OpenDSS

Asymmetric loads allow modeling of unbalanced three-phase loads where each phase can have different power consumption. This is particularly useful for distribution network analysis.

Documentation References: 📘 pandapower Asymmetric Load 📗 OpenDSS Load

Parameters:

Static Generator

pandapower OpenDSS

Static generators represent generators with static (PQ) behavior — for example photovoltaic systems or small generation units. For wind turbines with an editable P–v power curve, prefer the dedicated Wind Turbine element. In OpenDSS, a static generator is a Generator with Model=1 (constant kW and kvar), not a voltage-controlled Model=3 bus. Both static generators and wind turbines can be selected in Grid Code Compliance (P-Q & U-Q).

Documentation References: 📘 pandapower Static Generator 📗 OpenDSS Generator

Parameters:

Wind Turbine

pandapower OpenDSS

A dedicated wind generation element based on the Static Generator model. Active power for load flow is always derived from a wind power curve P(v) and the configured wind speed — you do not set p_mw independently. Changing wind speed (in the element dialog or in Component Data) updates P [MW] immediately from the curve.

Palette: Sources (or Electrical abstract sources) → Wind Turbine. A worked example is File → New → offshore wind farm 1 GW (rev 6; 100 km export).

Documentation References: 📘 pandapower Static Generator 📗 OpenDSS Generator

Wind-specific parameters

In addition to the usual Static Generator fields, the Wind Turbine dialog provides:

Default dynamics plant kind is WIND for ANDES studies when renewable/IBR models are used.

Q capability (voltage-dependent, P and U)

The Wind Turbine Q capability tab defines reactive limits Q_min/Q_max as a function of both active power P and terminal voltage U (voltage-dependent Q limits). Enable Use Q capability curve so load flow applies the limits (pandapower enforce_q_lims and optional capacitive/inductive Q setpoint).

Built-in Q capability templates (stored in p.u. of S_n; confirm against OEM data):

• FRC WTG P–U (voltage-dependent) — typical Type IV fully rated converter: Q vs P and U. Default for new turbines (~2.5 MW class: about ±0.44 p.u. Q at U=1.0 and moderate P, tapering toward rated P and at high/low voltage).
• ±0.95 PF vs P (1D, U = 1.0 p.u.) — |Q| ≈ P·tan(arccos(0.95)) at each P; single voltage row. Same shape as the Static Generator 15 MW template, scaled to this turbine S_n.
• 15 MW offshore 1·Un chart (1D) — digitized manufacturer-style P–Q envelope at 1.0 p.u. voltage (asymmetric import/export).

Asymmetric Static Generator

pandapower OpenDSS

Asymmetric static generators allow modeling of unbalanced generation where each phase can produce different power levels.

Documentation References: 📘 pandapower Asymmetric Static Generator 📗 OpenDSS Generator

Parameters:

External Grid

pandapower OpenDSS

The external grid represents the connection to a higher voltage level or an infinite bus. It serves as the slack bus in power flow calculations and provides the voltage reference.

Documentation References: 📘 pandapower External Grid 📗 OpenDSS Vsource

Parameters:

Transformer

pandapower OpenDSS

Transformers connect different voltage levels in the network. They can be equipped with tap changers for voltage regulation.

Schematic Labels: Each transformer terminal can display a custom label on the canvas symbol (e.g. "HV", "LV"). These labels are purely cosmetic — they help identify which winding connects to which bus on the schematic, but do not affect simulation parameters or solver data. Edit them in the Schematic tab of the transformer dialog. Changes appear immediately on the canvas.

Documentation References: 📘 pandapower Transformer 📗 OpenDSS Transformer

Parameters:

Three Winding Transformer

pandapower OpenDSS

Three winding transformers have three separate windings, typically connecting three different voltage levels at one location.

Schematic Labels: Each of the three terminals can display a custom label on the canvas symbol (e.g. "HV", "MV", "LV"). These labels are purely cosmetic — they help identify which winding connects to which bus on the schematic, but do not affect simulation parameters or solver data. Edit them in the Schematic tab of the transformer dialog. Changes appear immediately on the canvas.

For the solver, Electrisim maps the three connected buses to HV / MV / LV by bus voltage (vn_kv): highest, middle, then lowest. If two buses share the same voltage, the original connection order is used as a tie-break so the mapping stays stable between runs.

Documentation References: 📘 pandapower Three Winding Transformer 📗 OpenDSS Transformer

Parameters:

Generator

pandapower OpenDSS

Generators represent synchronous generators with dynamic behavior. They are typically used for large power plants and have voltage control capabilities.

Documentation References: 📘 pandapower Generator 📗 OpenDSS Generator

Parameters:

Harmonic Parameters (OpenDSS):

Slack concept by framework

The slack parameter in Electrisim applies to Pandapower load flow only. OpenDSS handles the slack bus differently:

For OpenDSS load flow, the slack role is handled by Vsource elements (External Grid), not by the Generator object.

Capacitor & Shunt Reactor

pandapower OpenDSS

Electrisim provides two separate shunt elements for reactive power compensation: a Capacitor (capacitor bank for leading reactive power) and a Shunt Reactor (inductive shunt for lagging reactive power). Both appear as separate components in the element palette and have dedicated dialog forms. Internally, both map to the pandapower shunt element, while in OpenDSS they map to the Capacitor and Reactor elements respectively.

Documentation References: 📘 pandapower Shunt 📗 OpenDSS Capacitor 📗 OpenDSS Reactor

Capacitor Parameters:

Shunt Reactor Parameters:

How shunt reactor parameters work together

The dialog is organised in three tabs. The relationship between “static” shunt data and “control” is:

1. Power tab — base P and Q. Here you set p_mw and q_mvar as the reference shunt power at 1.0 p.u. If you do not use a step characteristic table, the network model uses this pair together with step and max_step (equivalent shunt scaling with the step number).
2. Electrical tab — vn_kv. Shunt equipment rating; it must be consistent with the bus you connect to. It does not, by itself, turn control on or off.
3. Control tab — steps and the optional table.
   • step and max_step define the discrete positions of the shunt. max_step is the top step index you model (e.g. if steps are 0, 1, …, N, set max_step = N).
   • If Shunt characteristic table (step-dependent P/Q) is off, P and Q at the operating point follow the base values on the Power tab, combined with step.
   • If that option is on, you must fill the table so each step has its own p_mw and q_mvar at 1.0 p.u. Pandapower stores this as shunt_characteristic_table; OpenDSS applies the same rows to the Reactor. The dialog’s Fill steps 0…max step uses max_step to create empty rows you can complete.
4. Control tab — discrete shunt (voltage) control. This is a different option from the characteristic table (you can enable either, both, or neither). The table defines what P and Q are at each step; Discrete shunt control changes step so the shunt bus voltage moves toward vm_set_pu. When both are on, the controller only updates step; the injections at that step still follow the table. For pandapower load flow and RPC, tick Shunt reactor tap changer under Include controller. OpenDSS snapshot load flow runs the same loop when the option is enabled on the shunt.
5. Control tab — Line P → shunt step. A separate lookup: the solver reads P on a reference line and sets step from the band table (typical VSR behaviour). This is also gated by Shunt reactor tap changer on pandapower / RPC; OpenDSS snapshot applies it after the solve.

Summary. Use the Power tab for a simple fixed or step-scaled shunt; add the characteristic table when each step has different P/Q at 1 p.u.; use discrete shunt control for a voltage target; use Line P → shunt step for flow-based VSR tap. If a table and a controller are both enabled, the table provides the per-step model and the controller selects the step. All of these are properties of the shunt on the single-line diagram; the pandapower load-flow or RPC dialog turns controller execution on or off for the run.

Impedance

pandapower OpenDSS

A branch between two buses defined only by R and X (not a physical line type). Use it for a coupling, a simplified equivalent, or a connection that is not a cable or overhead line.

Documentation References: 📘 pandapower Impedance 📗 OpenDSS Documentation

Parameters:

Ward

pandapower OpenDSS

A Ward equivalent stands in for a neighbouring network you do not want to draw in full: a constant-power plus constant-impedance injection at one bus. Prefer this over inventing dummy lines when you only have a reduced-network equivalent.

Documentation References: 📘 pandapower Ward 📗 OpenDSS Documentation

Parameters:

Extended Ward

pandapower OpenDSS

Like a Ward equivalent, plus an internal bus and impedance so the voltage response of the reduced network is more accurate. Use it when a plain Ward model is too crude at the boundary bus.

Documentation References: 📘 pandapower Extended Ward 📗 OpenDSS Documentation

Parameters:

Storage

pandapower OpenDSS

Storage elements represent battery energy storage systems (BESS) or other energy storage technologies that can both consume and generate power. Electrisim uses a unified Storage element that maps to both pandapower and OpenDSS. Parameters are organized in the dialog into five tabs: Power, Energy, Configuration, Optimization (OPF), and OpenDSS Parameters.

Documentation References: 📘 pandapower Storage 📗 OpenDSS Storage 📗 OpenDSS Storage Properties

Parameters (Power & Energy)

Parameters (Configuration)

Parameters (Optimization – pandapower OPF)

Parameters (OpenDSS-specific)

These parameters apply when using OpenDSS for load flow, harmonics, or time-series simulations. They control the built-in inverter model, dispatch logic, and losses.

OpenDSS Implementation Notes

The following implementation details ensure consistent results between Pandapower and OpenDSS for storage elements:

• Power dispatch: Both kWRated (inverter capacity) and kW (requested dispatch power) are set explicitly. The state (DISCHARGING/CHARGING/IDLING) is derived from the sign of p_mw.
• Reactive power convention: Pandapower uses load convention (positive = absorbing). OpenDSS Storage uses generator convention (positive = supplying). The conversion is applied automatically.
• Reserve handling: When min_e_mwh ≥ max_e_mwh, the OpenDSS %reserve parameter is not set. This prevents blocking discharge in snapshot power flow when the reserve would otherwise lock 100% of stored energy.
• Connection and phases: The conn (wye/delta) and phases (1–3) parameters are passed to OpenDSS for correct modeling of single-phase or delta-connected storage.
• Inverter model: OpenDSS Storage includes a built-in inverter model with efficiency, idling losses, and dispatch modes. Pandapower uses a simpler PQ-bus model; time-domain SOC updates require custom scripting.

BESS AC Block

pandapower OpenDSS

The BESS AC Block is a composite element available in the Storage palette (next to the Storage element). When you drag and drop it onto the canvas, it automatically creates and connects a complete Battery Energy Storage System (BESS) AC interconnection setup in a single step.

The block includes:

• BESS BUSBAR 1 — MV busbar rated at 33 kV (high-voltage side)
• Step-up Transformer — HV: 33 kV, LV: 690 V, connecting the MV and LV busbars
• BESS BUSBAR 2 — LV busbar rated at 0.69 kV (low-voltage side)
• Storage — Battery storage element (includes built-in inverter model) connected to the LV busbar

All four elements are pre-wired with correct connection points. Result placeholders for load flow and short-circuit analysis appear automatically for each busbar, the transformer, and the storage unit. You can connect the BESS AC block to your existing network by linking BESS BUSBAR 1 to your MV grid (e.g., 33 kV).

Documentation References: 📗 Storage 📗 OpenDSS Transformer 📗 Storage Properties

Note: The BESS AC Block is a composite palette template (MV bus, step-up transformer, LV bus, and Storage). It is not a separate backend element type — both pandapower and OpenDSS receive the four connected standard elements. Default drop values: MV bus 33 kV, LV bus 0.69 kV, transformer 33/0.69 kV, 1 MVA. You can modify all parameters to match your project.

Controls

The sidebar Controls palette groups plant and feeder controllers. It uses two analysis-oriented sub-tabs:

• Steady-state — controllers that affect snapshot / control-mode load flow:
  • OpenDSS: RegControl, CapControl, StorageController
  • Common (pandapower & OpenDSS): Wind Turbine Controller (steady-state) (power-curve Pref)
  • Pandapower: Park Controller (steady-state) (plant Q/V/PF/tanφ)
• Dynamic — time-domain controllers:
  • Common: Wind Turbine Controller (dynamic) (averaging & gradient limiting)

Double-click a control on the diagram to open its parameter dialog. OpenDSS controls are created as native OpenDSS objects when you run OpenDSS load flow. Wind Turbine Controllers are applied on the frontend (they do not create OpenDSS RegControl-style objects).

Pandapower-only elements

These palette elements are included only when the simulation engine is set to Pandapower. If you run load flow or short circuit with OpenDSS, they are excluded and Electrisim shows a warning listing any unsupported elements on the diagram.

• SVC, TCSC, SSC (STATCOM) — FACTS devices
• DC Line, DC Bus, Load DC, Source DC — DC network modeling
• Switch, VSC, B2B VSC — switching and converter elements

Static Var Compensator (SVC)

pandapower

Static Var Compensators are FACTS devices used for dynamic voltage support and reactive power control. They can rapidly adjust reactive power output.

Documentation References: 📘 pandapower SVC 📗 OpenDSS Documentation

Parameters:

Thyristor-Controlled Series Capacitor (TCSC)

pandapower

TCSCs are FACTS devices that provide controllable series compensation to regulate power flow and improve transmission capacity.

Documentation References: 📘 pandapower TCSC 📗 OpenDSS Documentation

Parameters:

Static Synchronous Compensator (SSC / STATCOM)

pandapower

Static Synchronous Compensators (STATCOM) are advanced FACTS devices that use voltage source converters to provide dynamic reactive power support. They offer superior voltage control compared to traditional SVCs. In the palette this element appears as SSC(STATCOM).

Documentation References: 📘 pandapower SSC 📗 OpenDSS Documentation

Parameters:

DC Line

pandapower

DC lines represent high-voltage direct current (HVDC) connections between AC systems. They provide controlled power transfer and can connect asynchronous networks.

Documentation References: 📘 pandapower DC Line OpenDSS: Not Available

Parameters:

DC Bus

pandapower

DC buses represent connection points in DC networks, similar to AC buses but for direct current systems. They serve as nodes where DC components like DC loads, DC sources, and DC lines can be connected.

Documentation References: 📘 pandapower DC Bus OpenDSS: Not Available

Parameters:

Load DC

pandapower

DC loads represent power consumption in DC networks. They consume active power from the DC system.

Documentation References: 📘 pandapower Load DC OpenDSS: Not Available

Parameters:

Source DC

pandapower

DC sources represent voltage sources in DC networks, similar to external grids in AC systems. They provide voltage reference and power injection into the DC network.

Documentation References: 📘 pandapower Source DC OpenDSS: Not Available

Parameters:

Switch

pandapower

Switches represent circuit breakers, load break switches, or disconnectors that can connect or disconnect network elements (lines, transformers, or buses). In pandapower, a switch connects a bus to a line, transformer, three-winding transformer, or another bus. In OpenDSS, open switches are modeled by opening the corresponding line or transformer element.

Documentation References: 📘 pandapower Switch 📗 OpenDSS Documentation

Parameters:

Protection tab (Protection Coordination Study)

When running the Protection Coordination Study, assign a device on the Switch dialog Protection tab. Key fields:

Voltage Source Converter (VSC)

pandapower

Voltage Source Converters are power electronic devices that connect AC and DC networks. They enable bidirectional power flow and provide voltage control capabilities, making them essential for HVDC systems and renewable energy integration.

Documentation References: 📘 pandapower VSC OpenDSS: Not Available

Parameters:

Back-to-Back Voltage Source Converter (B2B VSC)

pandapower

In Electrisim, the B2B VSC cell models a dual–DC–bus back-to-back converter: one AC connection plus two DC buses (plus and minus) for detailed DC grid or metallic-return style studies. In pandapower v3.3.2 this maps to the B2B VSC element (create_b2b_vsc, net.b2b_vsc).

Alternatively, a single–AC–to–single–DC connection uses the VSC element and DC Bus per side as needed.

Documentation References: 📘 pandapower B2B VSC OpenDSS: Not Available

Parameters (Load Flow / OPF; connections from the diagram):

OpenDSS-only elements

These palette elements are included only when the simulation engine is set to OpenDSS. They are not sent to Pandapower; if any are on the diagram during a Pandapower calculation, Electrisim warns that they will be skipped.

• PVSystem — photovoltaic array and inverter
• Load 1ph, Source 1ph, Generator 1ph, Line 1ph, Transformer 1ph — explicit single-phase (phases=1) distribution elements

Single-phase distribution modeling

Use the five 1ph elements to build radial feeders such as: Source 1ph → Transformer 1ph → Line 1ph → Load 1ph, with optional Generator 1ph for distributed generation. Each exposes Phase (1, 2, or 3) and Connection (wye L-N or delta L-L) so the correct OpenDSS bus terminal (bus.1, bus.1.2, etc.) is used.

Tip: On radial single-phase lines, prefer wye (L-N) for loads and generators. Delta connection requires two energized phase nodes on the bus; if only one node is energized (typical for Line 1ph with wye connection), delta-connected loads may draw little or no power. Electrisim automatically switches delta loads and generators to wye on radial feeders and reports a warning in the load-flow results.

PVSystem

OpenDSS

The PVSystem element combines the photovoltaic (PV) array and the PV inverter in a single model. It assumes that the inverter tracks the maximum power point (MPP) of the panel quickly, making it suitable for quasi-static time-series (QSTS) simulations with time steps of at least one second. This model is adequate for most interconnection impact studies.

Documentation References: 📗 OpenDSS PVSystem 📗 OpenDSS PVSystem Properties

Note: PVSystem is an OpenDSS-only element. Pandapower has no direct equivalent; it can be approximated using a static generator.

Parameters

Parameters are organized by analysis type in the Electrisim PVSystem dialog:

PV Array Properties

PV Inverter Properties