Building an offshore grid in the North Sea has many advantages, the primary one being the increased penetration of renewable energy in Europe which will be essential to meeting its 2020 renewable energy targets. By using a meshed Grid, instead of connecting the wind farms radially, a level of redundancy and flexibility is introduced to the system. Additionally, through international interconnection, conventional power generation (gas, coal, hydro etc) can be distributed between countries using the offshore grid when there is little wind generation. There is also the opportunity to store excess wind generation by connecting to Norway, which has a significant amount of installed hydroelectric generation.

The greater distances from shore mean that much of this grid will be implemented using high voltage direct current (HVDC) technology, rather than the conventional AC transmission. A multi-terminal HVDC (MTDC) system will be required to allow interconnections between different wind farms and onshore locations. Thus the primary technology used will be voltage source converters as it is more suited to MTDC the conventional HVDC (Line commutated converters).

Nodes will be an important element of this offshore grid, as they will be used to join the paths of the grid together and control the distribution of power. They will also enable cables of different voltage levels to be interconnected, and could allow competing converter types to be connected together.

However the main constraint of how this grid will be implemented will be its cost. Thus, there will be an economic trade-off between the level of redundancy and flexibility in the system of the system with the cost of not having it. This research intends to investigate the use of DC nodes in the proposed offshore grid. Alternative node topologies, and the technology used to build them, will be assessed based on reliability, capital and running costs, and fault capability.

Benefits

The objective of this project is to better understand the considerations that are to be taken when considering further infrastructure with regard to offshore DC connections.