Coordinating research in energy networks

Mega Grid

Exploring technological, planning and control system innovations that will help to create European interconnections to exploit diverse sources of renewable energy and improve system security.

A trans-European grid

National transmission networks in European countries are currently interconnected, allowing limited inter-country energy trading. The current level of interconnection however is not sufficient to support the large flows of energy needed to balance a European electricity system that has very high penetrations of renewable energy.

There are a variety of abundant renewable energy sources across Europe, including:

  • Wind energy in the north and west;
  • Solar resources in the south (and indirectly from North Africa); and
  • Hydro energy in the Nordic and Alpine regions.

A diverse range of generation types can provide a more dependable supply when aggregated ? but a new, much larger transmission grid is required to access that diversity. This is the mega grid.

HVDC challenges

The unavailability of traditional overhead line routes will force many of the new mega grid connections underground or even underwater. The unmanageable reactive power requirements associated with AC operation of long cables means that DC interconnections will be required. There are a number of challenges associated with the deployment of High Voltage DC (HVDC) cables and networks, which work within HubNet seeks to address. These include:

  • Raising the operating voltage of transistors in AC/DC converter modules;
  • Reducing power losses in these transistors, using wide band-gap materials;
  • Investigating and developing thermal design and component choices to ensure fault current passage and short term overload do not erode component lifetime;
  • Investigating fault management and the use of DC circuit breakers;
  • Understanding how a DC mega grid can be designed and controlled to support the connected AC networks, both in steady state and transient operation;
  • Understanding options for contingency management and risk assessment in large scale AC/DC networks; and
  • Assessing the economic robustness of a ?case for a Mega-Grid? by balancing the associated risks and costs.

DC / AC Integrated Operation

The resulting mega grid is likely to consist of highly integrated AC and DC networks. Not only will the new HVDC grids be comparable in size and capacity with the underlying AC networks, but these DC systems will be expected to provide a greater range of services such as reserve and stability capabilities. Existing HVDC links are relatively small (e.g. compare the current GB 2 GW HVDC interconnector with France to the GB peak demand of 60 GW) and are used only for energy transfer.

The interactions between AC and DC networks are very complex. HubNet seeks to model these interactions, including the complex dynamics of the AC/DC converters in order to determine suitable system control strategies that ensure the secure operation of the future mega grid.

Theme leader: Prof Jovica Milanovic (Manchester).

The images above show a type test of an 800kV current-source thyristor valve (top) and an illustration of the trans-European grid (bottom).