The future wind power development in the Nordic region will to a large extent be based on offshore wind power plants. At the same time, the increased need for balancing and reserve capacity in the future Nordic power systems with planned wind power development to 15-20 % of consumption calls for increased interconnection capacities, first of all to enable a more extensive and economically beneficial utilisation of the flexible Nordic hydro power.
Preliminary studies (e.g. the EU Tradewind and Kriegers Flak) have indicated that it is advantageous to combine the grid connection of offshore wind power plants with interconnections in large offshore grids. Such grids can also support other offshore power customers, e.g. wave power plants and oil platforms, possibly with gas power plants.
HVDC technology is already widely used for interconnection between power system areas, enabling power transmission over long distances without sub stations. The traditional line commutated HVDC technology works well with two terminals, and is therefore widely used for this purpose. The future large offshore grids will require more complex network topologies with multiple connection points to make it possible to combine grid connection of offshore wind power plants with increased interconnection capacities in large offshore grids.
The newer Voltage Source Converter (VSC) based HVDC grid technologies is the most promising technical solution for such grids. This technology is already widely used in two terminal applications such as interconnector between areas and as grid reinforcement. However, to use this technology for the multi terminal application with large scale wind power connections, there is a need to develop solutions for a stable and secure design and operation of the grid.
Objectives
The overall objective of the OffshoreDC project is to identify and pursue solutions to offshore HVDC grids and their functionality as means of integrating large amounts of offshore wind power. With voltage-source converter-based HVDC possibilities for integrating multiple wind plants with multi-terminal DC transmission promises benefits in power flow control and asset utilisation. DC network operation, multi-plant control and connection to land AC grids are among the challenges to be solved.
It is the purpose to develop consistent solutions that allow pre-standardisation by bringing together key industry stakeholders: wind power plant manufacturers, wind power plant developers and operators, HVDC sysem providers, offshore and onshore grid owners and operators. The industrial partners include ABB, Vestas, DONG Energy and Energinet.dk. The academic partners include Risø DTU, Chalmers, SINTEF, DTU Electro, VTT and Aalborg University. Thus, the purpose is to specify and develop the new technical and economical solutions in close cooperation between the relevant industry sectors.