Introduction: In July 2009, the three Great Britain Transmission Licence holders supported by a Project Working Group published their report to the Electricity Networks Strategy Group (ENSG) on the strategic reinforcements required to facilitate connection of the generation mix to the GB transmission networks by 2020. The report presents generation and demand scenarios consistent with the EU target for 15% of energy to be produced from renewable sources by 2020 and identifies and evaluates a range of potential electricity transmission network solutions that would be required to accommodate these scenarios.

Among the options currently under consideration is the use of a multi-terminal High Voltage Direct Current (HVDC) link to provide additional capacity across transmission boundaries in the onshore transmission system and potentially to be used in the connection of offshore generation. Such a multi-terminal High Voltage Direct Current (HVDC) link might prove to be the most overall economic and efficient solution available when wider developments are taken into account. National Grid has not previously implemented Voltage Source Converter (VSC) HVDC converters on the transmission system and no multi-terminal VSC HVDC system has been implemented anywhere in the world. The introduction of this technology onto the transmission system must be managed in a manner that takes due consideration of any potential technology risks.

Objectives: The key objective of the proposed work is to simulate a multi-terminal VSC HVDC link using a Real Time Digital Simulator (RTDS) in order to study its operation on the electricity transmission system. An RTDS is a powerful state of the art simulator that allows power system simulation of various power system components in real-time timescales. The use of an RTDS will allow for the technology to be modelled in significantly more detail and accuracy than available via software solutions such as PowerFactory, PSSE or PSCAD. RTDS systems are also capable of outputting analogue signals allow for the testing of equipment such as protection relays etc.

The simulation will fulfil the role of a phantom trial in accordance with National Grid's policy for the introduction of new technology. The work aims to demonstrate that a multi-terminal VSC HVDC system as proposed is feasible, to identify potential problems with application of the technology, areas of further research and to inform specifications.

The use of the RTDS will allow for the simulation and evaluation of any converter topologies or control strategies that have been made public by suppliers or proposed by other parties.

Further to the primary objective of this research is the added benefit of developing the UK research capability in the field of HVDC. It is the aim of industry and academia to establish significant expertise in HVDC in the UK in order to ensure that the rapid expansion of complex HVDC systems across the UK and Europe occurs as smoothly as possible. This project supports this aim and will be followed by further proposals in the future.