This invention relates to 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 and a shaft coupled to said wind turbine rotor hub and to, optionally via 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 where the back-to-back converter at a grid side converter end is electrically connected to the grid connection. The wind turbine further comprises a secondary generator coupled to the shaft via a mechanical coupling and electrically connected to the primary rotor of the primary generator and the generator side converter end of the back-to-back converter.