LCC
Line-commutated converter schemes: thyristor valves, commutation failure, reactive and filter design, AC system strength.
HVDC consultants · United Kingdom
HVDC consultants for converter station control, protection and scheme definition.
Unit Vector Solutions provides independent HVDC consultants to asset owners, developers and contractors — engineers who define what a converter station must do, hold the vendor’s design to it, and witness the tests that prove it. HVDC is where the company began, and it remains our deepest specialism.
LCC & VSC
Both converter technologies, including MMC
Point-to-point & multi-terminal
Onshore interconnectors and offshore export
Owner, developer, contractor
Whichever side of the contract you sit on
UK-based
Working UK-wide and internationally
Most of what goes wrong on a DC link was decided before the contract was signed: the main circuit parameters, the reactive compensation strategy, how the scheme starts, stops and rides through faults. Our HVDC consultants work at that stage, giving clients an engineering view that is independent of any converter vendor.
The team has worked on line-commutated and voltage-source converter schemes, point-to-point and multi-terminal, onshore interconnectors and HVDC export systems for offshore wind. Because the same firm designs AC substations and runs power system studies, a converter station and its AC yard can be engineered by one team — unusual among HVDC consultancies, and a real saving in interfaces.
We are UK-based and work UK-wide and internationally, embedded in client teams or on fixed-scope packages.
What our HVDC consultants deliver
Scheme definition
- Development and independent review of HVDC main scheme parameters
- Feasibility assessment, optioneering and value engineering
- Studies supporting option selection — AC/DC interaction, reactive compensation, harmonics
- FEED for converter station primary and secondary systems
Control & protection
- Functional specifications for HVDC control and protection
- Sequence design — start-up, shut-down, transitions and restart strategies
- Requirements capture for LCC and VSC control systems
- Review of vendor control philosophies and protection settings
Assurance & testing
- Owner-side engineering support through detailed design and factory testing
- Replica and real-time simulator (RTDS) test specification and witnessing
- Interoperability and interface review for multi-vendor and multi-terminal schemes
- Offshore wind export system engineering and grid compliance interfaces
Typical engagements
- Owner’s engineer for an interconnector developer through FEED and vendor selection
- Independent review of control and protection specifications on behalf of a transmission owner
- Embedded HVDC consultant within a contractor’s design team for an offshore export link
- RTDS and replica test witnessing and deviation close-out ahead of site commissioning
Common questions
What does an HVDC consultant do?
An HVDC consultant sits between the asset owner and the converter vendor. We define and review the main scheme parameters, write the control and protection functional specifications, design start-up, shut-down and transition sequences, and witness replica and real-time simulator testing so the owner knows the scheme will behave as specified.
When should HVDC consultants be involved?
Before vendor selection. The decisions that drive cost and risk on a DC link — converter topology, reactive compensation, ride-through strategy — are fixed at feasibility and FEED. Independent engineering at that stage is far cheaper than changing a contract later.
Do you work on both LCC and VSC schemes?
Yes. Our engineers have worked on line-commutated and voltage-source converter schemes, point-to-point and multi-terminal, including HVDC export systems for offshore wind.
Can you support factory, replica and RTDS testing?
Yes. We write test specifications, attend and witness tests on replica and real-time digital simulator platforms, and report against the functional specification so deviations are closed before site.
Do you provide HVDC consultants as owner’s engineer?
Yes. We act as owner’s engineer through feasibility, specification, vendor selection, design review, factory testing and commissioning, and we also embed individual HVDC consultants within client or contractor teams.
Where are your HVDC consultants based?
In the UK, in West Yorkshire. We work UK-wide and internationally, on site or remotely, in whatever mix the project needs.
Related capabilities
HVDC consultancy through the project lifecycle
Where HVDC consultants earn their fee.
Clients bring us in at whichever stage they have reached. The earlier the better: the decisions that fix cost and risk on a DC scheme are made long before the first valve is delivered.
01
Feasibility & optioneering
Technology selection (LCC or VSC), main scheme parameters, reactive compensation and the studies that separate options on cost and risk.
02
Specification & FEED
Functional specifications for control and protection, sequence design, requirements capture and the FEED primary and secondary design for the converter station.
03
Vendor engagement & design review
Tender evaluation, review of vendor control philosophies and protection settings, deviation handling and technical queries through detailed design.
04
Factory, replica & RTDS testing
Test specifications, witnessing on real-time simulator and replica platforms, and closure of deviations against the functional specification before site.
05
Commissioning & operations
Energisation and trial operation support, performance verification, as-built review and post-energisation investigations.
Technologies
HVDC consultants across every converter technology in service.
Line-commutated and voltage-source schemes behave differently, fail differently and are specified differently. We have worked on both, and on the multi-terminal and offshore systems that combine them.
VSC / MMC
Voltage-source and modular multilevel converters: grid-forming control, black start, weak-grid operation, harmonic stability.
Multi-terminal
Multi-vendor and multi-terminal DC systems: interoperability, DC protection philosophy, co-ordination between terminals.
Offshore export
HVDC export links for offshore wind: platform interfaces, wind-farm control interaction, grid compliance at the onshore point.
Why independent HVDC consultants
Engineering judgement that is not selling you a converter.
Vendors know their own equipment better than anyone. What they cannot give you is a view that is independent of it. That is the job of an HVDC consultant, and it is the whole of ours.
- Independent of vendorsOur HVDC consultants sell engineering judgement, not equipment. Recommendations are made on the owner’s behalf.
- Control and protection at the coreConverter control was the founding discipline of the company, not a service added later.
- AC and DC under one roofThe AC yard, the studies and the converter station are engineered by people who talk to each other daily.
- Assumptions on the recordEvery specification, review and study states its inputs and limits, so it can be challenged, reused and defended.
Talk to an HVDC consultant about your scheme.
Talk to an HVDC engineer about your scheme, at whatever stage it has reached.