Patent Description:
A wind turbine rotor blade may have installed a flow regulating device on its surface, which flows from the leading edge to the trailing edge of a rotor blade of a wind turbine. An example of such a flow regulating device is a vortex generator (VG) installed on the suction side of the wind turbine rotor blade. In general, a flow regulating device may be considered to comprise a device which is capable of enhancing the lift coefficient of the aerofoil section, for example by increasing the level of energy of the boundary layer of the rotor blade.

Other aerodynamic devices may act in concert with the vortex generator and may influence the effect of the vortex generator depending on the state of the spoiler. Examples of the latter aerodynamic device are typically spoilers, installed on the suction side of the blade, between the trailing edge and the vortex generator. Alternatively, spoilers may be present alone, i.e. not combined with vortex generators or other flow regulating devices. Spoilers may be configured such that its shape and/or orientation can be regulated, e.g. by a pneumatic or hydraulic or mechanical actuator.

The spoiler may act in concert with the vortex generator and may influence the effect of the vortex generator depending on the state of the spoiler, i.e. a protrusion height and/or tilt angle by which the spoiler extends from or is tilted relative to other surface portions of the rotor blade.

<CIT> discloses a wind turbine blade including adjustable lift-regulating means arranged on or at the surface of the wind turbine blade and extending in the longitudinal direction of the blade and an activation means by which the lift-regulating means can be adjusted and thus alter the aerodynamic properties of the blade. The lift-regulating means comprise one or more flexible flaps.

<CIT> discloses a wind turbine blade comprising a blade body and a device for modifying the aerodynamic surface or shape of the blade, wherein a pneumatic actuator controls the position and/or movement of the device, wherein a pressure chamber positioned within the blade body is present. The pressure chamber may be pressurized thereby changing the state of the device, thereby modifying the aerodynamic surface or shape of the blade.

<CIT> discloses a wind turbine wing comprising a pneumatically actuated spoiler movable perpendicular to an airstream.

<CIT> disclose a rotor blade comprising an aerodynamic device for influencing the airflow flowing from the leading edge section of the rotor blade to the trailing edge section of the rotor blade, wherein the aerodynamic device is mounted at a surface of the rotor blade and comprises a pneumatic or hydraulic actuator, such as a hose or a cavity of which the volume depends on the pressure of the fluid being present inside the pneumatic or hydraulic actuator.

It is desirable to monitor the performance of the spoilers or other flow regulating aerodynamic devices regulated by a pneumatic or hydraulic actuator and their influence on the wind turbine power production. In particular, there may be a need to identify when a flow regulating aerodynamic device of such type is faulty.

According to the present invention, it is provided a method for detecting the operative status of an aerodynamic device for influencing the airflow flowing from the leading edge of a rotor blade for a wind turbine to the trailing edge of the rotor blade, the aerodynamic device being movable by an actuator between a first protruded configuration and a second retracted configuration. The method comprises the steps of:.

The present invention permits to observe the transients of the aerodynamic devices to monitor them, so that failures are identified and consequently can be mitigated. Existing sensors in the turbine can be used making the detection method cost effective.

The monitoring may be performed continuously or periodically. In the latter case, the monitoring may be performed according for example to a predefined schedule.

According to embodiments of the invention, the operational value is any of:.

Any other signal, whose value is influenced by the presence and/or activation and/or deactivation of an aerodynamic device may be used.

According to embodiments of the invention, the desired temporal course of an operational value is registered during a non-faulty time interval of the aerodynamic device. Alternatively, the desired temporal course of an operational value is calculated.

According to embodiments of the invention, comparing the measured temporal course of the operational value with a desired temporal course of an operational value comprises calculating a difference between the measured temporal course of the operational value and the desired temporal course.

The drawings are in schematic form. Similar or identical elements are referenced by the same or different reference signs.

<FIG> shows a conventional wind turbine <NUM> for generating electricity. The wind turbine <NUM> comprises a tower <NUM> which is mounted on the ground <NUM> at one end. At the opposite end of the tower <NUM> there is mounted a nacelle <NUM>. The nacelle <NUM> is usually mounted rotatable with regard to the tower <NUM>, which is referred to as comprising a yaw axis substantially perpendicular to the ground <NUM>. The nacelle <NUM> usually accommodates the generator of the wind turbine and the gear box (if the wind turbine is a geared wind turbine). Furthermore, the wind turbine <NUM> comprises a hub <NUM> which is rotatable about a rotor axis Y. When not differently specified, the terms axial, radial and circumferential in the following are made with reference to the rotor axis Y.

The hub <NUM> is often described as being a part of a wind turbine rotor, wherein the wind turbine rotor is capable to rotate about the rotor axis Y and to transfer the rotational energy to an electrical generator (not shown).

The wind turbine <NUM> further comprises at least one blade <NUM> (in the embodiment of <FIG>, the wind rotor comprises three blades <NUM>, of which only two blades <NUM> are visible) mounted on the hub <NUM>. The blades <NUM> extend substantially radially with respect to the rotational axis Y.

Each rotor blade <NUM> is usually mounted pivotable to the hub <NUM>, in order to be pitched about respective pitch axes X. This improves the control of the wind turbine and in particular of the rotor blades by the possibility of modifying the direction at which the wind is hitting the rotor blades <NUM>. Each rotor blade <NUM> is mounted to the hub <NUM> at its root section <NUM>. The root section <NUM> is opposed to the tip section <NUM> of the rotor blade.

<FIG> illustrates the rotor blade <NUM> comprising an aerodynamic device <NUM> in the form of an actuated spoiler. Between the root section <NUM> and the tip section <NUM> the rotor blade <NUM> furthermore comprises a plurality of aerofoil sections for generating lift. Each aerofoil section comprises a suction side <NUM> and a pressure side <NUM>. The aerofoil shape of the aerofoil portion is symbolized by one aerofoil profile which is shown in <FIG> and which illustrates the cross-sectional shape of the rotor blade at this spanwise position. Also note that the suction side <NUM> is divided or separated from the pressure side <NUM> by a chord line <NUM> which connects a leading edge <NUM> with a trailing edge <NUM> of the rotor blade <NUM>.

The aerodynamic device <NUM> is arranged on the suction side <NUM> between the leading edge <NUM> and the trailing edge <NUM>.

The aerodynamic device <NUM> in <FIG> is movable by means of a pneumatic actuator, for example an inflatable cavity operated by a pressure line <NUM>, or by means of an hydraulic actuator or by means of a mechanical actuator.

The pressure line <NUM> is comprised in a pressure supply system <NUM> and controlled by a control unit <NUM>. The pressure supply system <NUM> provides a pressurized fluid, for example pressurized air or other pressurized gasses. In this context, the term "pressurized fluid" not only implies positive pressure but also negative pressure, wherein fluid is sucked (or "drawn") out of the pressure hose of the aerodynamic device <NUM>. The pressure line <NUM> could be in practice realized as tubes or pipes which do not significantly change their volume. Finally, the control unit <NUM> is responsible for setting a specific pressure at the pressure supply system <NUM> which subsequently leads to a certain predetermined pressure at the aerodynamic device <NUM>.

In the example shown in <FIG>, the control unit <NUM> and the pressure supply system <NUM> are located in the root section <NUM> of the rotor blade <NUM>. According to other embodiments of the present invention (not shown in the attached figures), these parts could also be placed elsewhere in the wind turbine, such as e.g. in the hub <NUM> of the wind turbine <NUM>.

The rotor blade <NUM> additionally comprises a flow regulating unit <NUM> comprising multiple pairs of vortex generators.

The flow regulating unit <NUM> are arranged on the suction side <NUM> of the blade <NUM> between the aerodynamic device <NUM> and the the trailing edge <NUM>.

According to other embodiments of the present invention (not shown in the attached figures), the flow regulating unit <NUM> are arranged on the suction side <NUM> of the blade <NUM> between the leading edge <NUM> and the aerodynamic device <NUM>.

According to other embodiments of the present invention (not shown in the attached figures), the flow regulating unit <NUM> are not present and only the aerodynamic device <NUM> is used to regulate the flow on the surface of the blade <NUM>.

According to other embodiments of the present invention (not shown in the attached figures), the blade <NUM> comprises a plurality of aerodynamic devices <NUM>.

<FIG> shows the aerodynamic device <NUM> in a first protruded configuration.

In the first configuration the aerodynamic device <NUM> deviates the airflow <NUM> which is flowing from the leading edge <NUM> to the trailing edge <NUM> of the rotor blade.

The aerodynamic device <NUM> in the first protruded configuration induces stall. This is visualized with relatively large vortices <NUM> downstream of the aerodynamic device <NUM>. A consequence of the induced stall is a decrease in lift of the rotor blade and, consequently, a reduced loading of the rotor blade and related components of the wind turbine.

<FIG> shows the aerodynamic device <NUM> in a second retracted configuration, i.e. moved downwards towards the surface of the rotor blade <NUM>.

In this second configuration, the airflow <NUM> flowing across the aerodynamic device <NUM> remains attached to the surface of the rotor blade <NUM>, thus that no flow separation, i.e. stall, occurs. As a consequence, the lift of the rotor blade increases. Re-energizing vortices <NUM> are generated in the boundary layer by the vortex generators <NUM>, which have the effect of helping increasing the lift. As a result, the highest lift values can be achieved.

By operating the actuator, i.e. the pressure line <NUM>, of the aerodynamic device <NUM>, the aerodynamic device <NUM> can be moved between the first protruded configuration and the second retracted configuration in order to vary the aerodynamic properties of the blade as desired and requested when operating the wind turbine <NUM>.

<FIG> the plot shows an activation signal <NUM> for the aerodynamic device <NUM>, which is being activated in the first protruded configuration at an activation time T1. The plots <NUM>, <NUM>, <NUM> show a desired normalized temporal course of three operational values of the wind turbine <NUM>, namely the turbine power production <NUM>, the rotor speed <NUM> and the rotor thrust <NUM>, respectively. The desired temporal courses of the operational values are registered during a non-faulty time interval of the aerodynamic device <NUM>. Alternatively, the desired temporal courses of the operational values are calculated offline, for example according to theoretical models.

The desired normalized temporal courses <NUM>, <NUM>, <NUM> may be therefore defined as expected values, when the aerodynamic device <NUM> is working correctly, without faults.

According to the present invention the actual temporal courses of at least one of the desired operational values <NUM>, <NUM>, <NUM> of the wind turbine <NUM> are measured when activating or deactivating of the actuator of the aerodynamic device <NUM>. The measured temporal courses are compared with the desired temporal courses of the operational values to derive an operative status of the aerodynamic device <NUM>.

According to embodiments of the present invention, the comparison involves calculating a difference between the measured temporal courses and the desired temporal courses. According to other embodiments of the present invention, the deviation between the measured temporal courses and the desired temporal courses involves the calculation of typical error function, e.g. the simple moving average error function or the mean squared error function or the exponential error function.

When the deviation between measured and desired operational values is excessive a faulty condition of the aerodynamic device <NUM> is identified and remedies can be taken, for example a maintenance intervention may be scheduled.

Claim 1:
Method for detecting the operative status of an aerodynamic device (<NUM>) for influencing the airflow (<NUM>) flowing from the leading edge (<NUM>) of a rotor blade (<NUM>) for a wind turbine (<NUM>) to the trailing edge (<NUM>) of the rotor blade (<NUM>), the aerodynamic device (<NUM>) being movable by an actuator between a first protruded configuration and a second retracted configuration, the method comprising the steps of:
- measuring a temporal course of an operational value of the wind turbine (<NUM>) during activation or deactivation of the actuator of the aerodynamic device (<NUM>), the operational value being influenced by the presence and/or activation and/or deactivation of the aerodynamic device (<NUM>),
- comparing the measured temporal course of the operational value with a desired temporal course (<NUM>, <NUM>, <NUM>) of an operational value,
- deriving an operative status of the aerodynamic device (<NUM>).