Consultancy · study

Control interaction studies

As converters cluster on the grid, their fast controls can interact with each other and with the network in ways no single project sees. We look for those poorly damped or unstable modes and find what drives them.

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Power swing · dampingIllustrative

Power swing after a small disturbance, before and after retuning the controls.

When it's needed

When you need it.

Several converter plants or HVDC links connect close together electrically.
The connection sits on a weak part of the grid, where control margins are thin.
Equipment from different vendors has to work together, and nobody has checked the mix.
Unexplained oscillations appeared during commissioning or operation.

Method

How we run it.

01
Map
Map the converters, their controls and the network around them.
02
Screen
Use impedance methods to find where damping is marginal.
03
Reproduce
Recreate suspect modes in EMT to confirm cause and severity.
04
Stress
Test grid strength, units in service, settings and dispatch.
05
Fix
Recommend setting changes or added damping, and verify them.

Tools and scenarios

What we use and what we test.

Tools

PSCAD / EMTDCTime domain
Impedance scan toolsFrequency domain
Vendor control modelsEach converter

Scenarios we run

Different numbers of converters in service and dispatch mixes
A range of grid strengths, topologies and outages
Vendor control modes and setting groups
Before and after the fix

Deliverables

What you get.

ReportInteraction assessment with the modes found and what drives them
EvidenceImpedance and damping results with confirming EMT waveforms
FixesRecommended changes and the results that verify them
MethodAssumptions and model sources, written down

How we check it

Findings are checked with more than one method, impedance screening and time-domain runs, and the conditions that decide the result are stated so the operator can review them.

Selected work

Related case studies.

Case 03 · SSO and compliance40 MW battery: SSO screening and NESO complianceImpedance scan, Nyquist, voltage injection, FRT and FFCI from one model.Case 02 · EMT modellingGenerator EMT model checked against site measurementsA full PSCAD model with excitation, stabiliser and protection, validated on site.

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

Have a study like this coming up?

Discuss a project contracts@velonenergy.com