A noise reduction element extends between a first end and a second end in a first direction. The noise reduction element extends between a third end and a fourth end in a second direction perpendicular to the first direction. The noise reduction element includes a base part configured to be attached to a trailing edge of a wind turbine blade. The base part has a first base part surface and a second base part surface. The base part extends between the first end and a first position in the first direction. The noise reduction element includes a first serration part having a serration pressure surface and a serration suction surface and extending in the first direction between the first position and the second end. The first serration part has a thickness in a third direction between the serration pressure surface and the serration suction surface.

A system and method are provided for reducing vibrations and loads in one or more rotor blades on a rotor hub of a wind turbine when the rotor hub is in a locked or idling condition. An electronically tunable mass damper is attached to a fixed location on one or more of the rotor blades. The mass damper is maintained on the rotor blades during the locked or idling condition of the rotor hub. The method includes sensing movement of a mass component of the mass damper from vibrations or oscillations induced in the rotor blade. The mass damper is automatically tuned based on the sensed movements of the mass component by automatically varying an electrical characteristic of the mass damper.

A horizontal axis wind turbine comprising a rotor having a plurality of blades, the rotor having a radius R of at least 80 meters, the blades comprising: a root end and a tip end, the blades extending in a spanwise direction from the root end to the tip end; a leading edge and a trailing edge, the blades extending in a chordwise direction along a chord from the leading edge to the trailing edge; a shoulder between the root end and the tip end where a chord length defined between the leading edge and the trailing edge is at a maximum; the blades being twisted between the root end and the tip end and the twist is defined by a twist distribution curve along the spanwise direction of the blades, each blade further comprising: an inboard region between the root end of the blade and the shoulder of the blade; an outboard region between a rotor radius 0.9R and the tip end of the blade; and a mid-board region located between the inboard region and the outboard region; a noise reduction feature in the mid-board region of the blade, the noise reduction feature projecting from the trailing edge and extending from a first radial position R1 toward the tip end; wherein the twist distribution curve comprises a first inflection point in the vicinity of the first radial position R1.

A method is provided for reducing the noise emission of a wind turbine rotor blade. The rotor blade has a leading edge, a trailing edge, a suction side, a pressure side and an attachment part at least partially on the pressure side. A pressure-side transition is present between the pressure side and the attachment part. The pressure-side transition is leveled by applying a leveling compound.

A radiating component of the wind turbine is modelled as a plurality of elements, wherein each element represents a physical portion of the radiating component and at least a portion of each of the elements are acoustically coupled to one or more of the other elements. A simulation of a vibrational source located within the wind turbine is applied at an interface of the modelled radiating component. A transfer function is used to determine the transmission of vibrations from an interface with the vibrational source to the elements. Tonal noise radiated from the elements to an environment external to the wind turbine is determined based upon the transmission of vibrations from the interface through the elements. The design of the radiating component, or of a component between the radiating component and the vibrational source, is modified to reduce the tonal noise radiated from the radiating component.

A method and an apparatus for controlling noise of multiple wind turbines. The method includes: determining a noise-influencing sector of each of the multiple wind turbines, based on positions of the multiple wind turbines and a position of a noise-influencing site; acquiring a current wind direction; determining whether there is at least one wind turbine of the multiple wind turbine under the current wind direction operating in the noise-influencing sector; and limiting output power of the at least one wind turbine, in a case that the determination is positive.

A shroud includes a first shroud that covers a first side face to which a muffler is adjacent among four side faces that an engine has, a second shroud that covers a second side face adjacent to the first side face and a third side face, and a third shroud that sections a muffler space for housing the muffler with the first shroud, the first shroud and the second shroud form an upstream side air guide path that makes cooling air flow around the engine, and the muffler space is connected to a downstream side of the upstream side air guide path.

A device and a method of controlling blade instabilities of a wind turbine is provided. The method including the following steps: defining at least one preliminary overspeed threshold value; defining a fluttering rotor speed at and above which a predetermined fluttering of at least one of the blades occurs, the fluttering rotor speed is defined as a function of the pitch angle and/or as a function of the wind speed; setting a final overspeed threshold value to be equal to or smaller than a minimum rotor speed of the at least one preliminary overspeed threshold value and the fluttering rotor speed at the actual pitch angle and/or at the actual wind speed; and controlling the rotor speed to not exceed the final overspeed threshold value.

A rotation speed avoidance control method for a wind turbine generator system. The method comprises: when a power-limited operation instruction is received, determining a power value upper limit required by the instruction: determining whether the required power value upper limit is in a power avoidance interval corresponding to a rotation speed avoidance interval; and when the required power value upper limit is in the power avoidance interval, setting the maximum allowable power value of a wind turbine generator system to be a lower boundary value of the power avoidance interval. An upper boundary value of the power avoidance interval is a power value determined on the basis of an upper boundary value of the rotation speed avoidance interval, and the lower boundary value of the power avoidance interval is a power value determined on the basis of a lower boundary value of the rotation speed avoidance interval, wherein the rotation speed avoidance interval and the power avoidance interval are open intervals. By means of the control method, an operation range of the rotation speed of a wind turbine generator system in a power-limited operation state can be prevented from overlapping with a rotation speed avoidance interval, thereby preventing resonance of the generator system, load increase or other safety problems. In addition, the present invention further relates to an apparatus for implementing the control method, and a wind turbine generator system.

A system and method are provided for controlling a wind turbine. Accordingly, a controller of the wind turbine detects a transient grid event and generates a torque command via a drive-train-damper control module. The torque command is configured to establish a default damping level of a torsional vibration resulting from the transient grid event. The controller also determines at least one oscillation parameter relating to the torsional vibration and determines a target generator torque level based thereon. The target generator torque level corresponds to an increased level of damping the torsional vibration relative to the default damping level.