Challenge
Project Details
Customer: Scottish and Southern Electricity Networks (SSEN) Transmission
Location: Scotland, UK
Scope: Three HVDC Light® converter stations in multi-terminal scheme, executed in two stages:
- Caithness-Moray link commissioned in 2018 and prepared for further expansion
- Shetland link operating since Aug ‘24
Client’s needs: To connect the Shetland to the UK transmission system whilst strengthening onshore network in Northern Scotland
Solution
Three HVDC Light® converter stations connected in multi-terminal scheme
Based on Hitachi Energy HVDC Light® VSC technology
Symmetric monopole ±320 kV DC
Blackhillock (1,200 MW) – stabilizes the DC grid through DC voltage control
Kergord (600 MW) – stabilizes Viking wind farm on Shetland through frequency and AC voltage control
Multi-purpose HVDC for up to five converter stations and two solutions for multi-terminal connection point
Spittal (800 MW) – stabilizes Caithness AC network through grid forming control
DC Grid Master Controller to coordinate all signals and sequences, already implemented at first stage
Detail multi-terminal studies for up to 5 stations. Off-line simulation studies using Virtual Control & Protection (vMACH) for efficiency and early risk mitigation
Impact
Multi-terminal HVDC interconnection provides flexibility to transfer power in multiple directions, based on supply and demand, with minimal power losses
Contribute to bringing all greenhouse gas emissions to net zero by 2050
Enhance grid performance and resilience through voltage and frequency control
Help to connect and transmit wind power generated on the islands to the UK
A future proof solution boosting the integration of renewable energy
