Griffin Wind Farm with 68 wind turbines, each with a capacity of up to 3MW will have a maximum peak output of 204MW. Plans were originally submitted to the Scottish Government in 2004.
The wind farm is projected to offset up to 461,000 tonnes of carbon dioxide per year during its operation, and will generate electricity equivalent to the annual demand of 114,000 average UK homes.
GreenPower's managing director Robert Forrest said: "Once fully operational, Griffin Wind Farm will make a significant contribution to both the UK and Scottish targets for reducing carbon emissions by 2010. This is also a major step forward for our business and will underpin major growth over the next three years."