The Gotland HVDC Light project-experiences from trial and commercial operation

The electrical system on Gotland, owned by Gotlands Energiverk AB (GEAB) has normally no production except for wind power. The power is provided from the mainland with a peak load of approximately 160 MW, and the frequency is regulated by the HVDC link. The HVDC Light installation on Gotland is the first application where a HVDC link is used as an integral part of an AC system. This combined with the environmental demands and the special conditions in the weak network on the Island of Gotland makes this project a very special one that applies high demands on the performance of both hardware and software. The demand for extensive modeling to evaluate the performance and to optimize the control functions has been met by use of the SIMPOW and EMTDC tools. The HVDC Light Cable design has been proven and the environmental advantages have been fully utilized. The controllability has been used for enhancing the power quality and stabilizing the voltage in fault situations, this ability has been proven by measurements and a staged fault test. Both RI and sound levels have been measured and shown to fulfil the stipulated demands. The HVDC Light link has been in operation since November 1999 and is functioning according to expectations. The project has left the building and construction stage. To further exploit the controllability of the VSC converters a follow up project is formed that studies the more sophisticated ways of enhancing performance and interaction with the complex environment of wind power production in the weak network of southern Gotland.