Consultancy · study

Control interaction studies

As converters cluster on the network, their fast inner controls can interact with each other and with the grid in ways no single project sees in isolation. A control-interaction study looks for these adverse interactions — poorly damped or unstable modes — and identifies what drives them.

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When it's needed

When this study is needed.

  • Several inverter-based or HVDC schemes connect electrically close together.
  • A connection sits on a weak part of the network where control margins are tight.
  • Equipment from different vendors must coexist and no one has assessed the combination.
  • Commissioning or operational experience has shown unexplained oscillations.
Method

How we approach it.

  1. Map the converters, their controls and the network in the region of interest.
  2. Screen with impedance-based methods to find frequencies and conditions where damping is marginal.
  3. Reproduce the suspect modes in time-domain EMT to confirm cause and severity.
  4. Test sensitivities: grid strength, number of units online, control settings and dispatch.
  5. Recommend mitigations — setting changes or supplementary damping — and verify them.
Software

Tools we use.

  • PSCAD / EMTDC for time-domain confirmation
  • Impedance-scan and frequency-domain analysis tooling
  • Vendor control models for each converter scheme
Scenarios

Scenarios & operating points.

  • Varying numbers of converters online and dispatch combinations
  • Range of grid strengths and network topologies / outages
  • Different vendor control modes and setting groups
  • Pre- and post-mitigation comparisons
Deliverables

What you receive.

  • Interaction assessment report with identified modes and drivers
  • Impedance / damping evidence and confirming EMT waveforms
  • Mitigation recommendations with verification results
  • Documented assumptions and model provenance
Quality & validation

Evidence that stands up to review.

Findings are corroborated across methods — impedance screening and time-domain confirmation — rather than relying on a single technique, and the governing conditions are stated explicitly so the operator can review them.

Selected work

Comparable experience.

Case-study write-ups for this service are in preparation. To discuss directly relevant project experience, brief us — we can talk it through, under NDA where appropriate.

FAQ

Questions engineers ask.

How is this different from a single-plant compliance study?
Compliance studies assess one plant against the code. Control-interaction studies look at how multiple controls and the network behave together, which can reveal problems that each project passes individually but that emerge in combination.
Do you need every vendor's model?
To be conclusive, the relevant converter control models for the region are needed. Where some are unavailable, we are explicit about what can and cannot be concluded.
What mitigations are typical?
Often control-setting adjustments, retuning of inner loops, or supplementary damping. The right answer depends on the mode; we verify any recommendation in the model before proposing it.
Next step

Brief us on a study.

Send a one-paragraph scope — the system, the codes that apply, and the question you need answered. We typically reply within two working days.

Brief us on a project→

Related: Consultancy hub · SSO / impedance studies · BESS & inverter compliance · HVDC & IBR integration

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consulting@velonenergy.com