Boralex and Infinergy announced plans to extend the 21-turbine 90MW wind farm at Limekiln in Caithness on 11 November.
The extension proposal consists of seven turbines and will increase the installed capacity by about 20MW.
The extension plan is expected to be submitted to the Scottish Government in spring 2020. Full construction works are envisaged to start in 2021 and the site is expected to be fully operational before the end of 2022.