Abstract: In a wind turbine, an open loop control algorithm for incrementally or positively adjusting the pitch angles of individual rotor blades may be used to increase spacing between the base of the turbine tower and an approaching blade tip. As each rotating blade passes in front of the tower base, a minimum clearance distance may be assured to avoid blade tip strikes of the base. In accordance with at least one embodiment of the control algorithm, as each blade approaches the tower base, it may be feathered to reduce its power loading, and to facilitate increased clearance beyond the normal unloading or feathering produced by the so-called tower shadow effect. To offset resultant loss of torque, the remaining blades may be correspondingly pitched toward power, i.e. into the wind, to balance and/or smooth out the overall rotor torque curve, and thus to avoid torque ripples.

Abstract: A method for mitigating loads on a wind turbine in yaw error events is disclosed. The method may include determining a yaw error and a speed of the wind turbine and determining a magnitude of de-rating of the wind turbine based upon magnitudes of the yaw error and the speed. The method may further include reducing power output of the wind turbine based upon the magnitude of de-rating.

Abstract: A method for locking a rotor of a wind turbine in a long term parking state is disclosed. The method may include applying rotor brakes, enabling a long term parking configuration of the rotor and providing an emergency feather response for protecting the wind turbine against faults.