WIND TURBINE

The Invention describes a wind turbine (2) comprising an active yaw System (1) realised to maintain an upwind Orientation (UW) of the wind turbine aerodynamic rotor (22) during safe operating conditions, which active yaw System (1) comprises a number of yaw drive units (10), and wherein a yaw drive unit (10) comprises a negative brake (103); a principal power supply (25) configured to supply power to the active yaw System (1) during normal Operation of the wind turbine (2); and a dedicated negative brake reserve power supply (11) configured to supply power to the negative brakes (103) in the event of a grid disconnect. The Invention further describes a method of operating such a wind turbine.