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. Overview: Harmonic analysis & IEEE 519 guide.

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Where to find it

Simulate → Harmonic Analysis (OpenDSS). Set spectra on each source or non-linear element first.

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.
OpenDSS modelling notes

OpenDSS harmonic studies in Electrisim follow the same logical steps as in standalone DSS: assign spectra, define which orders to solve, then run a harmonic power flow. Electrisim automates the command sequence.

  • The slack is an External Grid (Vsource in OpenDSS).
  • NeglectLoadY neglects load shunt admittance in the harmonic solution (common in OpenDSS tutorials).
  • Bus rows in results use the Name from the Bus dialog when you have set it.

Where harmonics are defined (Harmonic tab)

Element Typical use Key parameters
Load Nonlinear or equivalent harmonic current injection (drives, rectifiers, aggregated customer distortion) Spectrum (Default / Linear / Custom / None), spectrum_csv, pctSeriesRL, conn, puXharm, XRharm
External Grid Voltage distortion at the grid or stiff source (often small; use Default or Custom) Spectrum for Vsource (defaultvsource or Custom CSV)
Generator, Static Generator Synchronous machine or equivalent source with subtransient impedance for harmonic interaction Spectrum, spectrum_csv, Xdpp, XRdp
PVSystem Inverter-based resource harmonic current spectrum Spectrum, spectrum_csv; other PV properties as in OpenDSS
Storage Battery inverter spectrum (named spectrum for OpenDSS Storage) Spectrum name (e.g. default)

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

Spectrum modes (UI)

Mode Meaning for the engineer OpenDSS behaviour (summary)
Default Use the EPRI/OpenDSS built-in spectrum for that element class (e.g. defaultload, defaultvsource, defaultgen). Reference spectra with predefined harmonic content.
Linear Simple “decay with order” teaching or screening case: magnitudes scale roughly as 100/h % on odd harmonics 3, 5, 7, 11, 13 (angles 0°). Not a substitute for device-specific spectra. Electrisim creates an explicit Spectrum object so injection is non-zero; OpenDSS itself does not define a single global spectrum named “Linear” for all elements.
Custom Your measured or manufacturer spectrum (IEC-style table, field survey, or EMTP export). Backend issues New Spectrum.<name> from CSV then references it.
None This element does not inject harmonics for the study (still present at fundamental). No harmonic spectrum on that element.

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).

Last updated: October 2026

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