A method and an apparatus for yaw control of a wind turbine under a typhoon. The method for yaw control may include: determining, before or when the typhoon comes, whether there is a fault in a yaw system of the wind turbine; performing a normal yaw control over the wind turbine according to the wind direction, if determination is negative; and performing a yaw control corresponding to the fault on the wind turbine according to the wind direction, if determination is positive. The yaw control corresponding to the fault is performed before or when the typhoon comes, in case of one of a yaw drive mechanism fault, an electronic brake mechanism fault, or a hydraulic brake mechanism fault. The wind turbine is downwind oriented and yaw load reduction is achieved.

A wind turbine is provided. The turbine includes a support having an axis of rotation, a generator, a plurality of blades rotatably mounted on the support about the axis of rotation, the blades being moveable between a retracted position generally parallel with the axis of rotation and a fully deployed position generally perpendicular with the axis of rotation, the blades being connected to the generator such that rotation of the blades in a direction induced by wind causes the generator to produce electricity, and the provision of electricity to the generator rotates the blades, and a controller connected to the generator and configured to deliver a flow of current to the generator that is sufficient to move the blades from the retracted position toward the fully deployed position and insufficient to move the blades all the way to the fully deployed position. The flow of current induces rotation of the blades in the direction induced by wind, which creates a centrifugal force that moves the blades from the retracted position toward the fully deployed position. As the blades move from the retracted position, the blades have increasing exposure to ambient wind to receive additional rotational force from ambient wind, and the additional rotational force being sufficient to, either alone or in combination with the flow of current, move the blades into the fully deployed position.

A rotor lock system (20) for securing a main shaft assembly of a wind turbine (2) in a substantially stationary position, the main shaft assembly comprising a main rotor shaft (16) supported by a base frame (14), and the rotor lock system comprising: a locking disk (22), associated with the main rotor shaft (16), and provided with a plurality of locking apertures (26); and a locking unit (24) comprising a first end (28) arranged to engage with the locking disk (22), and a second end supported by a mounting feature (38) associated with the base frame (14), wherein the locking unit (24) is configured to be adjustable relative to the mounting feature (38) so that the first end (28) moves linearly with respect to the mounting feature.

The present disclosure is directed to a system and method for controlling a wind turbine during adverse wind conditions. In one embodiment, the method includes monitoring one or more wind conditions near the wind turbine. Another step includes detecting one or more adverse wind conditions near the wind turbine. In response to detecting one or more adverse wind conditions, the method also includes reducing a power output of the wind turbine by a predetermined percentage. Further, the predetermined percentage is a function of a number and a type of the detected adverse wind conditions occurring during a predetermined time period.

The present disclosure is directed to a system and method for reducing vortex-induced vibrations of a tower of a wind turbine. The wind turbine has a nacelle mounted atop the tower. The nacelle has a rotor with a rotatable hub having at least one rotor blade mounted thereto. The rotor blade has a first pitch position. Thus, the method includes measuring, via one or more sensors, an acceleration of the nacelle. The method also includes determining a rotor speed of the rotor. Further, the method includes determining a second pitch position for the rotor blade based on the acceleration of the nacelle and the rotor speed and pitching the rotor blade to the second pitch position if the rotor speed is below a speed threshold and the acceleration of the nacelle is above an acceleration threshold. As such, the second pitch position disturbs vortices caused by interactions between the tower and the rotor blade as the rotor blade passes in front of the tower so as to reduce vortex-induced vibrations of the tower.

A system and method for protecting a wind turbine from extreme wind gusts includes monitoring a wind speed and a wind direction at the wind turbine. The method also includes determining a wind gust threshold, wherein wind speeds and wind directions exceeding the wind gust threshold, respectively, are indicative of an extreme wind gust occurring at the wind turbine. In addition, the method includes comparing, via a controller, the monitored wind speed or a function thereof and the wind direction or function thereof to the wind gust threshold, respectively. Thus, the method includes implementing, via a controller, a corrective action when the monitored wind speed and the monitored wind direction exceed the wind gust threshold, respectively.

There is provided a method of avoiding edgewise vibrations during a non-operational period of a wind turbine. The method comprises defining a non-operational period for a wind turbine arranged at a specific site, determining expected wind conditions at the specific site during the non-operational period and defining a plurality of potential yaw orientations for the wind turbine. The method further comprises determining the relative probability of edgewise vibrations occurring during the non-operational period for each potential yaw orientation based upon the expected wind conditions during the non-operational period, determining one or more preferred yaw orientations, which are the yaw orientations in which the probability of edgewise vibrations occurring is lowest, and arranging the wind turbine in one of the preferred yaw orientations during the non-operational period.

A method for operating a plurality of wind energy installations configured for supplying electric power to an electrical supply system, that each have an aerodynamic rotor with rotor blades and an electrical generator and also operating equipment, is disclosed. The wind energy installations are operated while they are not connected to the electrical supply system, where at least one of the wind energy installations produces electric power and inputs the electric power into a local DC voltage system that connects the wind energy installations if the at least one of the wind energy installations currently produces more power than needed for supplying its own operating equipment. Additionally or alternatively, the operating equipment is supplied totally or in part with power from the local DC voltage system if the at least one of the wind energy installations currently produces less power than needed for supplying its operating equipment.

The invention provides a wind turbine having a system for positioning the rotor in an azimuthal reference position Az.sub.ref and for maintaining it therein for a predetermined period of time, the wind turbine being arranged in test mode. Said rotor positioning system comprises a first controller (31) configured to generate a generator speed reference .sub.ref from the difference between the rotor azimuthal reference position Az.sub.ref and the rotor azimuthal measured position Az.sub.meas and a second controller (35) configured to generate a generator torque reference T.sub.ref from the difference between said generator speed reference .sub.ref and the generator speed measured .sub.meas.

A locking system for a rotatable mounted unit of a wind turbine is provided, including at least one lock adapted to lock and unlock the rotatable mounted unit, wherein the locking system includes first and second devices to prevent rotation, wherein the lock is prevented from changing from the locked state if at least one of the devices to prevent rotation is in a secure state, wherein a control unit is adapted to generate a control command changing the first device to prevent rotation into the secure state if the lock currently locks the rotatable mounted unit, wherein the locking system automatically changes the second device to prevent rotation into the secure state if an access condition is fulfilled, wherein the access condition is fulfilled if a recorded access information indicates that a room with the rotatable mounted unit is currently accessed or going to be accessed.