To launch the Energy Futures blog we have Caitríona Sheridan from the Control and Power Research Group in Imperial’s Department of Electrical and Electronic Engineering. Her work looks at electricity transmission and the creation of Europe wide electricity grid, a Super Grid. Caitríona also presented one of our weekly energy seminars in May 2016 and you can find a copy of her slides here [PDF].

A European Super Grid would bring many benefits which include greater renewable energy penetration, increased security of supply, and reduced dependency on fossil fuels. This grid is likely to be realised using High Voltage DC (HVDC) transmission. However, what this grid will look like and where it will be built is still not clear. My research looks at HVDC technologies to create a European Super Grid, using offshore UK wind farms as the initial stepping stones toward an electrically interconnected Europe.

I am a PhD student at Imperial College London, co-funded by National Grid and Arup. I am based in the Control and Power Research Group in the Electrical and Electronic Engineering Department. I graduated from University College Cork, in the southwest of Ireland in 2011 and began my PhD in January 2012. My undergraduate degree gave me an interest in power electronics and power systems. My PhD combines this interest in power electronics with challenging research questions about increasing the amount of renewable energy in the European transmission system.

A European Super Grid would enable international energy trading, increased penetration of renewable energy, and improved security of supply. This grid will evolve from interconnecting pre-existing point-to-point links. Some speculative illustrations are shown below. One common feature in each illustration is that several HVDC links connect at a single node, and it not known how these nodes will be configured.

The UK has a large resource of potential offshore wind generation, mostly in the North Sea. Up to 33 GW has been identified off the UK coast by the Crown Estate. To put that into context the peak UK electricity demand is approximately 60 GW. The significant distances of these wind farms from the shore imply that HVDC transmission is the economic choice to transmit the energy ashore.

The substantial distance of these wind farms from the UK shore could have another benefit, they could be used as a node to enable connections to other European countries. For example the Dogger Bank wind farm development is 290 km off the coast, at its furthest. This development could act as a stepping stone to a link to Norway, or Denmark. Interconnecting countries through a wind farm would allow surplus renewable energy to be traded directly rather than rerouting power over a longer distance.

The main barriers toward this European Super Grid are political, economic, and technical. The main technical obstacles which need to be overcome to realise this grid are in the areas of protection, DC voltage conversion and power flow control. This research looks at some of the enabling technologies for this grid which can be used to overcome these technical barriers.

DC/DC converters have been studied in detail and they are analogous to the AC transformer. However, unlike the transformer there is no one topology for all applications. I have explored different DC/DC converter topologies that could be used in an offshore HVDC grid. Another topic in my research is on AC/DC converters, which allows AC and DC transmission systems to interconnect. Typically a full scale AC/DC converter would have almost 4000 power electronic switches, and this computationally intensive to simulate. I have developed reduced order models (RDM) of these AC/DC converters which enable time efficient computer simulations of larger networks.

Using converter knowledge possible offshore scenarios can be examined and simulated for many different cases. These include testing new converter topologies in a HVDC grid, studying power flow within a large grid and determining suitable control algorithms, and studying how the grid responds to different fault conditions. This research hopes to aid the understanding of an offshore HVDC grid.