A multi-terminal HVDC transmission is an HVDC system with more than two converter stations.
A multi-terminal HVDC transmission is more complex than an ordinary point-to-point transmission. In particular, the control system is more elaborate and the telecommunication requirements between the stations become larger.
The first large-scale multi-terminal HVDC system in operation in the world is the 2,000 MW Hydro Québec - New England transmission built by ABB between 1987 and 1992. The operating experience of this transmission is very good and has proved that from a technical point of view there are no problems to connect several converter stations to the same HVDC transmission line.
The world’s first multi-terminal ±800 kV UHVDC transmission link will be the North East - Agra HVDC in India. The link comprises four terminals located at three converter stations with a 33% continuous overload rating and the power transmission system will thus have the possibility to convert 8,000 MW – which is the largest HVDC transmission ever built.
The HVDC Light technology makes multiterminal systems a lot easier since it is no need to balance the currents like in “conventional multi-terminal” HVDC.