A method of controlling a wind turbine, the wind turbine comprising a propeller arrangement, a synchronous machine, and coupling means for functionally coupling the synchronous machine to the propeller arrangement, the method comprising;
- selectively operating the wind turbine in a first mode in which the synchronous machine is functionally coupled to the propeller arrangement and acts as a synchronous generator to supply power to an electrical grid, and a second mode in which the synchronous machine is functionally decoupled from the propeller arrangement and acts as a synchronous condenser to adjust the power factor of the electrical grid.