Abstract: A wind turbine comprising one or more wind turbine blades arranged to perform pivot movements between a minimum pivot angle and a maximum pivot angle, each wind turbine blade extending between an outer tip and an inner tip, wherein each wind turbine blade has an outer portion extending between the hinge and the outer tip and having a first length, and inner portion extending between the hinge and the inner tip and having a second length, wherein a coning angle of the blade carrying structure is larger than zero and/or a tilt angle of the rotor axis is larger than zero, and wherein a horizontal distance from the tower at a vertical position defined by a position of the hinge at tower passage to a point of connection between the blade carrying structure and the hub is equal to or less than the second length.

Abstract: Embodiments herein describe in-plane vibration damping techniques for MR turbines. The MR turbines can include arms that extend from a common tower and support multiple rotors. Because the rotors are disposed laterally away from the tower, side-to-side motion of the tower causes the rotors to have an angled trajectory that includes both lateral and vertical displacement. In addition, a rotor disposed on one side of the tower in MR turbine can have a very different trajectory than a rotor disposed on the opposite side of the tower. To account for the vertical displacement and the different trajectories, in one embodiment, a controller can use different phase offsets for each rotor when calculating pitch offsets for performing in-plane vibration damping. In another embodiment, the controller can use both the lateral and vertical accelerations of the rotors to identify the pitch offsets for the rotors to perform in-plane vibration damping.

Abstract: A method and a device for dampening movement in a multiple rotor (MR) wind turbine located at sea and comprising a tower (2) extending in an upwards direction, a load carrying structure (3, 4) forming a first section (3) and a second section (4), the first and second sections extending in different directions away from the tower (2). To provide efficient dampening of the movement, the method comprises tethering a first body (20) to the first section (3), the first body being at least partly submerged into the sea.

Abstract: A first aspect of the invention provides a method of testing a yaw system (200) of a wind turbine, the wind turbine comprising a rotor; the yaw system (200) comprising a yaw gear (202) coupled to the rotor so that rotation of the yaw gear (202) causes yaw rotation of the rotor, and first and second sub-systems (204a, 204b), the first sub-system (204a) comprising a first pinion gear (206a) and a first drive motor (208a) coupled to the yaw gear (202) by the first pinion gear (206a), the second sub-system (204b) comprising a second pinion gear (206b) and a second drive motor (208b) coupled to the yaw gear (202) by the second pinion gear (206b).

Abstract: A method of operating a wind turbine during a service, wherein the wind turbine comprises at least one rotor-nacelle assembly, the or each rotor-nacelle assembly comprising a rotor; the method comprising: detecting that a service is to be or is being carried out on the wind turbine; and, on detecting that a service is to be or is being carried out on the wind turbine, reducing an operating level of the or each rotor-nacelle assembly.

Abstract: The present invention relates to a multirotor wind turbine comprising at least two rotor nacelle assemblies mounted to a support arrangement via respective yawing systems, and a toe angle control system for controlling the toe angles of the rotor nacelle assemblies with respect to the support arrangement; wherein the toe angle control system is configured to operate in a first mode in which the rotor nacelle assemblies are held at positive toe angles while the wind turbine is generating power in a main production mode; wherein the toe angle control system is further configured to monitor the operating mode of the wind turbine, and to switch to a second mode in which the yawing systems of the rotor nacelle assemblies are operated to reduce the toe angles of the rotor nacelle assemblies if an operating mode-based trigger condition has been met.

Abstract: A method for detecting and controlling whirling oscillations of the blades of a wind turbine is presented. The detection of the whirling oscillations is based on measurement signal indicative of blade oscillations, and a rotation transformation of the measurement signal from a measurement frame into at least one target frame based on the whirling oscillation frequency. The rotation-transformation comprises a backward or forward rotation transformation direction relative to a rotor rotation direction. The control is based on an oscillation component obtained from the rotation-transformed measurement signal where the oscillation component is indicative of the whirling oscillation in the backward and/or forward rotation direction.

Abstract: A method for controlling a multirotor wind turbine comprising two or more energy generating units is disclosed. At least one load carrying structure is connected to a foundation or to a tower via a yaw arrangement, and the load carrying structure carries the at least two energy generating units. A requirement to a change in operation of at least a first of the energy generating units is detected. Control commands for the first energy generating unit and for at least a second energy generating unit, mounted on the same load carrying structure, are generated. The control commands cause the required change in operation, and the control commands cause coordinated operation of at least the first energy generating unit and the second energy generating unit. The control commands are generated under the constraint that a yaw moment of the yaw arrangement is maintained below a predefined threshold level.

Abstract: Embodiments herein describe in-plane vibration damping techniques for MR turbines. The MR turbines can include arms that extend from a common tower and support multiple rotors. Because the rotors are disposed laterally away from the tower, side-to-side motion of the tower causes the rotors to have an angled trajectory that includes both lateral and vertical displacement. In addition, a rotor disposed on one side of the tower in MR turbine can have a very different trajectory than a rotor disposed on the opposite side of the tower. To account for the vertical displacement and the different trajectories, in one embodiment, a controller can use different phase offsets for each rotor when calculating pitch offsets for performing in-plane vibration damping. In another embodiment, the controller can use both the lateral and vertical accelerations of the rotors to identify the pitch offsets for the rotors to perform in-plane vibration damping.

Abstract: A method and a device for dampening movement in a multiple rotor (MR) wind turbine located at sea and comprising a tower (2) extending in an upwards direction, a load carrying structure (3, 4) forming a first section (3) and a second section (4), the first and second sections extending in different directions away from the tower (2). To provide efficient dampening of the movement, the method comprises tethering a first body (20) to the first section (3), the first body being at least partly submerged into the sea.

Abstract: A multiple rotor (MR) wind turbine comprising a tower (21) extending in an upwards direction, a load carrying structure (22) extending in an outwards direction and being fixed to the tower, and an energy generating unit (54) fixed to the load carrying structure, wherein the outwards direction is transverse to the upwards direction, the wind turbine further comprising a hoisting line (53) for communication of objects (52) to and from the energy generating unit (54), the hoisting line being windable from an attachment point (55) of the load carrying structure or from the energy generating unit. To allow positioning of hosted objects near the tower, or at selectable distance from the tower, the hoisting line extends from the attachment point via a suspension point (56) to a lifting point (57) where the object (52) can be attached, and the suspension point (56) is movable outside the load carrying structure.

Abstract: A first aspect of the invention provides a method of monitoring the condition of a yaw system of a wind turbine, the wind turbine comprising a rotor, the yaw system arranged to control a yaw rotation of the rotor, the method comprising: providing design data 5 representing an expected relationship between yaw moment and yaw rotation speed; measuring a pair of parameters, the pair of parameters comprising a yaw moment parameter indicative of a yaw moment applied to the yaw system, and a yaw rotation speed parameter indicative of a yaw rotation speed caused by the yaw moment; using the design data to evaluate whether the pair of parameters deviates from the expected 10 relationship; and determining a condition of the yaw system on the basis of the evaluation.

Abstract: The invention is about a method for controlling a wind turbine with a variable rotor area. The wind turbine comprises a rotor with one or more rotor blades which are arranged hinged at an adjustable pivot angle, where the variable rotor area depends on the pivot angle, and where the pivot angle is adjustable dependent on a variable pivot force provided by a pivot actuator. The method comprises determination of a maximal pivot force based on the input operational parameter which relate to an actual load or a predicted load of the wind turbine, determining a desired pivot force based on a desired operational performance of the wind turbine, and determining a pivot force set-point to be applied to the pivot actuator based on the desired pivot force so that the pivot force set-point is equal to or below the maximal pivot force.

Abstract: A wind turbine comprising one or more wind turbine blades arranged to perform pivot movements between a minimum pivot angle and a maximum pivot angle, each wind turbine blade extending between an outer tip and an inner tip, wherein each wind turbine blade has an outer portion extending between the hinge and the outer tip and having a first length, and inner portion extending between the hinge and the inner tip and having a second length, wherein a coning angle of the blade carrying structure is larger than zero and/or a tilt angle of the rotor axis is larger than zero, and wherein a horizontal distance from the tower at a vertical position defined by a position of the hinge at tower passage to a point of connection between the blade carrying structure and the hub is equal to or less than the second length.

Abstract: A method for controlling a multirotor wind turbine is disclosed. A first operational state of each of the energy generating units of the wind turbine is obtained. A difference in thrust acting on at least two of the energy generating units is detected. At least one constraint parameter of the set of operational constraints is adjusted in accordance with prevailing operating conditions and in accordance with the detected difference in thrust, and a new operational state for at least one of the energy generating units is derived, based on the at least one adjusted constraint parameter, the new operational state(s) counteracting the detected difference in thrust. Finally, the wind turbine is controlled in accordance with the new operational states for the energy generating units.

Abstract: A method for controlling a wind turbine is disclosed. During full load operation, a power reference value, Pref, representing a power level to be supplied to the power grid by the wind turbine, is received, and the wind turbine is controlled in order to produce an output power which is at or near the power reference value, Pref, while maintaining a constant torque on the generator. In the case that the produced output power of the wind turbine exceeds the power reference value, Pref, excess produced energy is stored in the energy storage system, and in the case that the produced output power of the wind turbine is below the power reference value, Pref, stored energy is retrieved from the energy storage system. A power level being equal to the power reference value, Pref, is supplied to the power grid.

Abstract: A first aspect of the invention provides a method of testing a yaw system (200) of a wind turbine, the wind turbine comprising a rotor; the yaw system (200) comprising a yaw gear (202) coupled to the rotor so that rotation of the yaw gear (202) causes yaw rotation of the rotor, and first and second sub-systems (204a, 204b), the first sub-system (204a) comprising a first pinion gear (206a) and a first drive motor (208a) coupled to the yaw gear (202) by the first pinion gear (206a), the second sub-system (204b) comprising a second pinion gear (206b) and a second drive motor (208b) coupled to the yaw gear (202) by the second pinion gear (206b).

Abstract: A method of charging an energy storage system, such as a battery, a capacitor, or a super capacitor, using a wind turbine is described. The method comprises establishing if turbine power production can be increased and establishing if the energy storage system is capable of taking a charge. If both conditions are met, the power generated by the wind turbine is increased above a rated power of the wind turbine and the additional power is used to charge the energy storage systems. A method of control is also disclosed.

Abstract: A first aspect of the invention provides a method of monitoring the condition of a yaw system of a wind turbine, the wind turbine comprising a rotor, the yaw system arranged to control a yaw rotation of the rotor, the method comprising: providing design data 5 representing an expected relationship between yaw moment and yaw rotation speed; measuring a pair of parameters, the pair of parameters comprising a yaw moment parameter indicative of a yaw moment applied to the yaw system, and a yaw rotation speed parameter indicative of a yaw rotation speed caused by the yaw moment; using the design data to evaluate whether the pair of parameters deviates from the expected 10 relationship; and determining a condition of the yaw system on the basis of the evaluation.

Abstract: A method of operating a wind turbine during a service, wherein the wind turbine comprises at least one rotor-nacelle assembly, the or each rotor-nacelle assembly comprising a rotor; the method comprising: detecting that a service is to be or is being carried out on the wind turbine; and, on detecting that a service is to be or is being carried out on the wind turbine, reducing an operating level of the or each rotor-nacelle assembly.