Abstract: Techniques for controlling loading on a wind turbine blade in the flap-wise direction. A system model has a description of flap loading on the blade and is used to predict flap loading on the blade over a prediction horizon using the system model. A dynamic flap loading limit is determined based on predicted flap loading and a measured flap loading, and a constraint is defined to limit flap loading on the blade based on the dynamic flap loading limit. The predicted flap loading is used in a cost or performance function, and the cost function is optimized subject to the constraint to determine pitch for the blade to control flap loading on the blade. Advantageously, the dynamic limit varies based on discrepancies between predicted and measured flap loading to allow for adaptive back-off from extreme loads prior to such loads building up or being exceeded.

Abstract: A wind turbine control unit includes an upsampling module that receives a first control signal that includes a current control sample value and a predicted control trajectory. The upsampling module also calculates a second control signal in dependence on the current control sample value and the predicted control trajectory. The second control signal has a higher frequency than the first control signal. The upsampling module further outputs the second control signal for controlling an actuator.

Abstract: Aspects of the present invention relate to a method of controlling a renewable power plant comprising a plurality of renewable power generators electrically connected by a local network and configured to supply active power to a main network. The method comprises: in response to receiving a signal requesting substantially zero active power supply to the main network: categorizing a generator as power-supplying, and the remaining generators as power-consuming; operating the power-consuming generators to generate no active power and to have their auxiliary systems draw power from the local network; and operating the power-supplying generator to supply active power to the local network such that the plant supplies substantially zero active power to the main network.

Abstract: Embodiments are generally directed to techniques for operating a wind turbine of a wind power plant. An associated method comprises determining, using one or more sensors of the wind turbine, a first power production level of the wind turbine; determining, during an unconstrained operation of the wind turbine, one or more available power correction factors using the first power production level; determining, using one or more wind power parameters applied to a predefined model for estimating an available power of the wind turbine, an estimated available power value; adjusting the estimated available power value using the one or more available power correction factors to produce the available power value; and controlling, using the available power value, the wind turbine to produce a second power production level.

Abstract: A wind turbine control unit includes an upsampling module that receives a first control signal that includes a current control sample value and a predicted control trajectory. The upsampling module also calculates a second control signal in dependence on the current control sample value and the predicted control trajectory. The second control signal has a higher frequency than the first control signal. The upsampling module further outputs the second control signal for controlling an actuator.

Abstract: A wind turbine control unit comprising a control module configured to control an actuator system by outputting a first control signal, wherein the first control signal includes a current control sample value and a predicted control trajectory; the control unit further comprising an upsampling module configured to receive the first control signal from the control module, and to output a second control signal for controlling the actuator system, the second control signal having a higher frequency that the first control signal. The upsampling module calculates the second control signal in dependence on the current control sample value and the predicted control trajectory. The embodiments provide a more accurately reproduced control signal at a higher frequency that is suitable for onward processing which does not suffer from the problems of aliasing and delay that exist with conventional upsampling techniques.

Abstract: A method of controlling a wind turbine is described. The method comprises calculating a current wear rate for each of the main bearing of a turbine rotor and the blade bearings of rotor blades mounted on the turbine rotor, and calculating a blade pitch adjustment of the rotor blades to achieved a desired ratio between main bearing wear and blade bearing wear in dependence on the calculated current wear rates of the main bearing and the blade bearings.

Abstract: There is provided a method for controlling a hydraulic pitch force system (220) so as to reduce or eliminate a decrease in hydraulic oil pressure (241) if a hydraulic system parameter value is outside a hydraulic system parameter range, the method comprising: Obtaining (690) the hydraulic system parameter value, and operating the hydraulic pitch force system (220) according to a reduced mode (692) if the hydraulic system parameter value is outside the hydraulic system parameter range, wherein in the reduced mode one or more pitch based activities are reduced (694) or suspended. An advantage thereof may be that it enables keeping the wind turbine in production in certain instances rather than shutting down the wind turbine. In aspects, there is furthermore presented a computer program product, a pitch control system (250) and a wind turbine (100).

Abstract: A method of operating a wind turbine having a rotor. Sensor data is received from one or more sensors of the wind turbine and maximum load values are obtained on the basis of the sensor data. The maximum load values are indicative of maximum loads acting on a component of the wind turbine such as a rotor blade. An estimated extreme load value, such as a 50-year return load, is obtained on the basis of the maximum load values and compared with a reference value. A maximum thrust limit is set on the basis of the comparison, and the wind turbine is operated in accordance with the maximum thrust limit so that a wind thrust force acting on the rotor does not exceed the maximum thrust limit.

Abstract: Techniques for controlling loading on a wind turbine blade in the flap-wise direction. A system model has a description of flap loading on the blade and is used to predict flap loading on the blade over a prediction horizon using the system model. A dynamic flap loading limit is determined based on predicted flap loading and a measured flap loading, and a constraint is defined to limit flap loading on the blade based on the dynamic flap loading limit. The predicted flap loading is used in a cost or performance function, and the cost function is optimized subject to the constraint to determine pitch for the blade to control flap loading on the blade. Advantageously, the dynamic limit varies based on discrepancies between predicted and measured flap loading to allow for adaptive back-off from extreme loads prior to such loads building up or being exceeded.

Abstract: A wind turbine control unit comprising a control module configured to control an actuator system by outputting a first control signal, wherein the first control signal includes a current control sample value and a predicted control trajectory; the control unit further comprising an upsampling module configured to receive the first control signal from the control module, and to output a second control signal for controlling the actuator system, the second control signal having a higher frequency that the first control signal. The upsampling module calculates the second control signal in dependence on the current control sample value and the predicted control trajectory. The embodiments provide a more accurately reproduced control signal at a higher frequency that is suitable for onward processing which does not suffer from the problems of aliasing and delay that exist with conventional upsampling techniques.

Abstract: A method of controlling a wind turbine comprising at least one rotor blade, and at least one accelerometer housed within a nacelle or a tower of the wind turbine. The method comprises: determining a whirling mode frequency for the wind turbine; measuring an acceleration signal that is indicative of the movement of the nacelle of the wind turbine; determining a frequency spectrum of the measured acceleration signal in the proximity of the determined whirling mode frequency; determining a characteristic value that is representative of the energy content of the measured acceleration signal having the determined frequency spectrum; and performing at least one control action if the characteristic value exceeds a predetermined threshold.

Abstract: A method of operating a wind turbine having a rotor. Sensor data is received from one or more sensors of the wind turbine and maximum load values are obtained on the basis of the sensor data. The maximum load values are indicative of maximum loads acting on a component of the wind turbine such as a rotor blade. An estimated extreme load value, such as a 50-year return load, is obtained on the basis of the maximum load values and compared with a reference value. A maximum thrust limit is set on the basis of the comparison, and the wind turbine is operated in accordance with the maximum thrust limit so that a wind thrust force acting on the rotor does not exceed the maximum thrust limit.

Abstract: Embodiments are generally directed to techniques for operating a wind turbine of a wind power plant. An associated method comprises determining, using one or more sensors of the wind turbine, a first power production level of the wind turbine; determining, during an unconstrained operation of the wind turbine, one or more available power correction factors using the first power production level; determining, using one or more wind power parameters applied to a predefined model for estimating an available power of the wind turbine, an estimated available power value; adjusting the estimated available power value using the one or more available power correction factors to produce the available power value; and controlling, using the available power value, the wind turbine to produce a second power production level.

Abstract: A method of calibrating load sensors of a wind turbine, and a wind turbine for such load sensor calibration, are disclosed. The wind turbine comprises a rotor, a plurality of rotor blades, and a plurality of load sensors associated with the rotor blades. While the rotor is rotating, at least one of the rotor blades is moved from a first calibration position to a second calibration position, and load values from the load sensors are measured. The number of rotor blades being moved is at least one fewer than the number of the plurality of rotor blades. The rotation of the rotor may be during idling of the wind turbine. The movement of the blade(s) may be to change the pitch angle of the blade(s). At least one of the rotor blades not being moved to a calibration position may also be moved, for example to control the rotational speed of the rotor.

Abstract: Embodiments of the present invention relate to control of a wind turbine during a recovery period after a grid fault. It is disclosed to operate a wind turbine during the recovery period to determine the actual pitch angle of the rotor blades and the actual wind speed, and based on that determining a desired pitch angle of the rotor blades, as well as a pitch ramp rate so that the actual pitch angle can be brought to match the desired pitch angle before the end of the recovery period. In embodiments, the steps performed in the recovery mode are repeated at intervals during the recovery period.

Abstract: There is provided a pitch control system (210) for controlling a pitch force system (220) for pitching a blade (103) of a wind turbine (100), the pitch control system (210) being arranged for activating (682) an auxiliary pitch force subsystem (224) at an initiation point in time where a main pitch force is sufficient to pitch the blade (103) into a target pitch value. An advantage thereof may be that tracking of a target pitch value may be improved and the impact on the pitch force system (220) may be reduced. In aspects, there is furthermore presented a hydraulic pitch system (206), a wind turbine (100), a method and a computer program product.

Abstract: A sensor system for a wind turbine blade, the system comprising: a blade load sensor providing a load measurement; a processing unit interfaced with the blade load sensor and configured to provide a corrected load parameter as an output. The processing unit includes: an axial force estimation module that determines an estimated axial force on the wind turbine blade in a direction along the length of the blade; and a load calculation module that 10 determines the corrected load parameter based on the estimated axial force and the load measurement of the blade load sensor.

Abstract: A method, a controller and a wind turbine with a controller for controlling the wind turbine in a cluster of wind turbines. Each wind turbine is controlled individually and each windturbine is configured to deliver power to the same utility grid. According to the method a delivery from a first wind turbine is reduced from a present power level to a reduced power level in response to an initial frequency of the utility grid exceeding a first threshold value; and the wind turbine is allowed to continue delivering power at the reduced power level.

Abstract: A method of controlling a wind turbine comprising at least one rotor blade, and at least one accelerometer housed within a nacelle or a tower of the wind turbine. The method comprises: determining a whirling mode frequency for the wind turbine; measuring an acceleration signal that is indicative of the movement of the nacelle of the wind turbine; determining a frequency spectrum of the measured acceleration signal in the proximity of the determined whirling mode frequency; determining a characteristic value that is representative of the energy content of the measured acceleration signal having the determined frequency spectrum; and performing at least one control action if the characteristic value exceeds a predetermined threshold.