A device and a method of controlling an operation of a wind turbine is provided. The wind turbine includes a rotor having a plurality of rotor blades, the rotor being mounted to a nacelle to rotate about a rotation axis and the nacelle being mounted to a tower to rotate about a yaw axis so that the rotation axis is also rotatable about the yaw axis. The method includes the following steps: determining a wind direction, acquiring a yaw angle of the nacelle and the rotation axis, determining an angular misalignment between the wind direction and the yaw angle of the rotation axis, which angular misalignment is measured in a plane which is perpendicular to the yaw axis, and performing a stall operation in case the angular misalignment exceeds a predetermined threshold value.

A method for operating a wind turbine with hinged wind turbine blades is disclosed. The wind turbine comprises an adjustable biasing mechanism arranged to apply an adjustable biasing force to each wind turbine blade which biases the wind turbine blade towards a position defining a minimum pivot angle or towards a position defining maximum pivot angle. A biasing force is selected for each wind turbine blade and the selected biasing force is applied to the respective wind turbine blades. The wind turbine is operated while monitoring rotor unbalance of the wind turbine. In the case that the rotor unbalance exceeds a first threshold value at least one of the wind turbine blades is selected, and the biasing force applied to the selected wind turbine blade(s) is adjusted.

The present invention relates to control of a wind turbine in a stop process where a stop controller is used to pitch the blades at a number of pre-set pitch rates including a first pitch rate and a second pitch rate. The stop controller is arranged to access desired pitch angles of the stopping process and add an envelope band to the desired pitch angles. In the stop process, pitching at a selected pitch rate among the number of pre-set pitch rates is performed, and the pitch rate is changed according to criteria to keep the pitch value within the envelope band.

A wind turbine (1) comprising a tower (2), a nacelle (3) mounted on the tower (2) via a yaw system, a hub (4) mounted rotatably on the nacelle (3), the hub (4) comprising a blade carrying structure (5), and one or more wind turbine blades (6) connected to the blade carrying structure (5) via a hinge (7) is disclosed. Each wind turbine blade (6) is thereby arranged to perform pivot movements relative to the blade carrying structure (5) between a minimum pivot angle and a maximum pivot angle. The blade carrying structure (5) is provided with one or more elements (8) configured to improve aerodynamic properties of a surface of the blade carrying structure (5) by increasing a lift and/or decreasing a drag of the blade carrying structure. The increase in lift and/or decrease in drag varies as a function of angle of attack (AOA) between the blade carrying structure (5) and the incoming wind.

Provided is a wind turbine and to a method and a device for controlling aerodynamic properties of a blade of the wind turbine, the blade including a predetermined number of add-on members which are actuated by a corresponding trim actuator to alter the aerodynamic properties of the blade, wherein each trim actuator is configured to hold the add-on member in a predetermined first position and a predetermined second position. The control device is configured to determine a first number of add-on members which are to be held at the predetermined first position, and to determine a second number of add-on members which are to be held at the predetermined second position.

Provided is a wind turbine including a tower, a nacelle arranged at an upper end of the tower, a hub connected to the nacelle and a plurality of blades extending from the hub, wherein the wind turbine further includes a drag device for increasing the drag of the wind turbine) in air and/or for increasing the aerodynamic damping, the drag device including a planar surface configured to be directed perpendicular to an air flow.

A wind turbine system comprising a nacelle mounted on a tower, a rotor having a plurality of blades and a boundary layer control system configured to control airflow through blade surface openings in each of the blades. The wind turbine system includes a control system configured to perform at least one of the following: to monitor an operational speed parameter of the wind turbine, and to activate the boundary layer control system if it is determined that the 1 operational speed parameter exceeds a predetermined speed parameter threshold; to monitor tower motion and to activate the boundary layer control system based on a determination of excessive tower motion; to monitor for a wind turbine shutdown condition, and to activate the boundary layer control system if it is determined that a wind turbine shutdown condition has been identified; and to monitor the aerodynamic loads on the blades, and to activate the boundary layer control system also based on a determination of excessive blade loads. The system thereby provides an approach to activating and deactivating the boundary layer control system to reduce operational risk to the wind turbine.

Wind turbine blade comprising at least one deformable trailing edge section having a plurality of actuators consecutively arranged substantially downstream from one another and a control system for controlling the actuators, wherein a downstream end of one actuator is connected by a substantially rigid link with an upstream end of the next actuator and the plurality of actuators comprises an upper actuator being mounted above a chord line of the blade section and a lower actuator being mounted below a chord line of the blade section. Wind turbines comprising such a blade and methods of controlling loads on a wind turbine blade are also described.

A system and method for braking a wind turbine includes monitoring rotation of the wind turbine generator rotor. A braking torque is applied to reduce the rotational speed of the rotor at a first setpoint rotational speed. The braking torque is proportionally increased as the rotational speed of the rotor increases beyond the first detected setpoint rotational speed up to a maximum braking torque.

The invention provides a method of shutting down a wind turbine, the wind turbine comprising a rotor with a plurality of blades; and a generator system coupled to the rotor. The method comprises: operating the generator system to generate electrical power and apply a load torque to the rotor; controlling the electrical power generated with a power reference signal; determining that a shutdown of the wind turbine is required; in response to the determination that a shutdown of the wind turbine is required, changing the power reference signal so as to increase the electrical power generated thereby slowing the rotor; determining that a speed of the rotor has reduced below a threshold; and in response to the determination that the speed of the rotor has decreased below the threshold, changing a pitch of the blades to further slow the rotor.