Siemens will supply 22 3.2MW turbines to the site, boosting installed capacity to 70.4MW from 21MW. The direct-drive turbines will be installed in 2015.
The Klim wind project, which was commissioned in 1996, has been using 35 Vestas V44 600KW turbines.
The Swedish power company said the existing 18-year-old turbines would be sold to an unnamed company to be renovated.
Vattenfall's head of Nordic wind power, Alberto Méndez Rebollo, said the process to upgrade the turbines had run smoothly thanks to close cooperation between politicians and land owners in the area.
