A new concept for superconducting DC transmission from a wind farm Jacob Østergaard a, * , Ole Tønnesen b , Jørgen Kaas-Pedersen b , Arne Hejde Nielsen b , Chresten Træholt b a DEFU, P.O. Box 259, DTU/Building 325, DK-2800 Lyngby, Denmark b Department of Electrical Power Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark Abstract Projectswithlargeoffshorewindfarms(upto500MW)areinprogress.Connectingtheparkstothepowergridwith conventionalACtransmissiontechniqueisdifficultduetonon-controllablepowerflowandvoltagestabilityproblems. A new concept for connecting remotely located wind farms is suggested and described. The concept is based on combining superconducting DC power transmission and cooled power electronic. Ó 2002 Published by Elsevier Science B.V. Keywords: Superconducting power cables; Power electronics; Wind turbines 1. Introduction Several projects around the world target the developmentofhightemperaturesuperconducting (HTS) power cables and result in large-scale ap- plications outside the laboratories. In May 2001 the world’s first HTS power cable in a public utility network was installed in Denmark and taken into operation, and the year before a HTS cable supplying a cable manufacturing plant was installed in the US [1,2]. Projects with large offshore wind farms (up to 500 MW) are in progress in several countries in- cluding Denmark and The Netherlands. In Den- mark, a 150 MW park will be installed in the autumn of 2001, and the total installed offshore wind power in Denmark in 2030 is planned to be 4000 MW, corresponding to a production of 20% of the total Danish electricity consumption [3]. When connecting a large amount of wind tur- bine production to the grid by conventional AC technology,anumberofproblemsarise.Incaseof afaultinthegrid,whichcausesavoltagedrop,the present wind turbines with asynchronous genera- tors are disconnected. With a large amount of wind turbine production the disconnection cannot be accepted due to the loss of power production. On the other hand operating the turbines on the network during a voltage drop results in an in- creased reactive power consumption by the wind turbine generators. This will reinforce the voltage drop, and a voltage collapse (blackout) will hap- pen [4]. Furthermore, the large amount of con- ventionally connected wind turbines can cause Physica C 372–376 (2002) 1560–1563 www.elsevier.com/locate/physc * Corresponding author. Fax: +45-45-93-12-88. E-mail address: joe@defu.dk (J. Østergaard). 0921-4534/02/$ - see front matter Ó 2002 Published by Elsevier Science B.V. PII:S0921-4534(02)01063-8