A wind turbine of variable speed type comprising: - a wind turbine tower; - a nacelle provided on said wind turbine; - a wind turbine rotor hub rotatably mounted at said nacelle, said wind turbine rotor hub having at least one wind turbine blade mounted thereon; - a shaft coupled to said wind turbine rotor hub and to, optionally through a gear box, - a primary generator which via power lines has a primary stator electrically connected to a grid connection, and a primary rotor electrically connected to - a back-to-back converter at a generator side converter end and wherein the back-to-back converter at a grid side converter end is electrically connected to the grid connection; - a secondary generator coupled to the shaft (201, 204) via a mechanical coupling, characterised in that the secondary generator is electrically connected to the primary rotor of the primary generator and to the generator side converter end of the back-to-back converter; and said wind turbine further comprises: - a controller with controlling capacities and connection means to: - a first switch between the primary generator and the grid connection; - a second switch between generator side convertor end of the back-to-back converter and the secondary generator; - a third switch between the generator side converter end of the back-to-back converter and the primary generator; and which controller and switches (401, 402, 403) are configured to switch power on/off from said primary generator and said secondary generator to the back-to-back converter and a grid. - a wind turbine tower; - a nacelle provided on said wind turbine; - a wind turbine rotor hub rotatably mounted at said nacelle, said wind turbine rotor hub having at least one wind turbine blade mounted thereon; - a shaft coupled to said wind turbine rotor hub and to, optionally through a gear box, - a primary generator which via power lines has a primary stator electrically connected to a grid connection, and a primary rotor electrically connected to - a back-to-back converter at a generator side converter end and wherein the back-to-back converter at a grid side converter end is electrically connected to the grid connection; - a secondary generator coupled to the shaft (201, 204) via a mechanical coupling, characterised in that the secondary generator is electrically connected to the primary rotor of the primary generator and to the generator side converter end of the back-to-back converter; and said wind turbine further comprises: - a controller with controlling capacities and connection means to: - a first switch between the primary generator and the grid connection; - a second switch between generator side convertor end of the back-to-back converter and the secondary generator; - a third switch between the generator side converter end of the back-to-back converter and the primary generator; and which controller and switches (401, 402, 403) are configured to switch power on/off from said primary generator and said secondary generator to the back-to-back converter and a grid. - a controller with controlling capacities and connection means to: - a first switch between the primary generator and the grid connection; - a second switch between generator side convertor end of the back-to-back converter and the secondary generator; - a third switch between the generator side converter end of the back-to-back converter and the primary generator; - a first switch between the primary generator and the grid connection; - a second switch between generator side convertor end of the back-to-back converter and the secondary generator; - a third switch between the generator side converter end of the back-to-back converter and the primary generator;