Wind turbine yawing system with multiple mechanical braking levels

A method of controlling a wind turbine that includes a tower, a nacelle, a yaw drive, and a plurality of mechanical brakes, the method comprising:

• while the wind turbine is in a yawing state, activating the yaw drive to rotate the nacelle to a first orientation relative to the tower;
• in response to the nacelle reaching the first orientation, transitioning the wind turbine from the yawing state to a parked by brake state in which the yaw drive is inactive, each mechanical brake of a first subset of the plurality of mechanical brakes is in an open state, and each mechanical brake of a second subset of the plurality of mechanical brakes is in a closed state, wherein a first amount of braking torque is provided between the tower and the nacelle when each of the plurality of mechanical brakes is in the closed state, and a second amount of braking torque is provided between the tower and the nacelle that is less than the first amount of braking torque when only the second subset of the plurality mechanical brakes is in the closed state;
• in response to detecting a rotation of the nacelle while in the parked by brake state, transitioning the wind turbine from the parked by brake state to a parked by motor state in which the yaw drive is activated to provide a counter acting torque in opposition to the detected rotation of the nacelle;
• transitioning the wind turbine between the parked by brake state and the parked by motor state during a period of time, wherein transitioning the wind turbine from the parked by motor state to the parked by brake state occurs each instance an amount of the counter acting torque being provided in opposition to the detected rotation of the nacelle while in the parked by motor state drops below a torque threshold that is below the second amount of braking torque;
• and
• changing the torque threshold based on a number of times the wind turbine has transitioned between the parked by brake state and the parked by motor state during the period of time.

A computer program product for controlling a wind turbine that includes a tower, a nacelle, a yaw drive, and a plurality of mechanical brakes, the computer program product comprising:

• a non-transitory computer-readable storage medium;
• and
• program code stored on the non-transitory computer-readable storage medium that, when executed by one or more processors, causes the one or more processors to:
• while the wind turbine is in a yawing state, activate the yaw drive to rotate the nacelle to a first orientation relative to the tower;
• in response to the nacelle reaching the first orientation, transition the wind turbine from the yawing state to a parked by brake state in which the yaw drive is inactive, each mechanical brake of a first subset of the plurality of mechanical brakes is in an open state, and each mechanical brake of a second subset of the plurality of mechanical brakes is in a closed state, wherein a first amount of braking torque is provided between the tower and the nacelle when each of the plurality of mechanical brakes is in the closed state, and a second amount of braking torque is provided between the tower and the nacelle that is less than the first amount of braking torque when only the second subset of the plurality mechanical brakes is in the closed state;
• in response to detecting a rotation of the nacelle while in the parked by brake state, transition the wind turbine from the parked by brake state to a parked by motor state in which the yaw drive is activated to provide a counter acting torque in opposition to the detected rotation of the nacelle;
• and
• transition the wind turbine between the parked by brake state and the parked by motor state during a period of time;
• and
• change a number of mechanical brakes in the second subset of the plurality of mechanical brakes based on a number of times the wind turbine has transitioned between the parked by brake state and the parked by motor state during the period of time.