Patent Description:
In the above defined technical field, systems are known, which comprises a plurality of radar units operatively configured to emit and receive radar signals. The radar units are typically mounted on and around the wind turbine tower, the radar units being positioned so as to measure reflections of an emitted radar signal from the turbine blade. A processing unit is configured to receive measurement data from the radar unit and to determine, by analysis of Doppler shift, time of flight, phase and amplitude in received radar signals relative to transmitted signals due to movement of the blade towards or away from the turbine tower, the velocity of the blade in the direction towards or away from the turbine tower. This permits to calculate the trajectory and, in particular, the absolute speed and position of the blade.

Using radar units to measure blade position based on the Doppler Effect is for example described in <CIT> and permits to avoid the installation of other types of sensors on the blades or nacelle of the wind turbine. This reduces manufacturing and maintenance costs of the wind turbine, since sensors positioned on the tower are easier to replace in the field.

However such a solution is not yet optimal considering that for objects which are rotating, like the blades or nacelles, the installation of a plurality of radar units is required.

A single radar unit may be in fact used but only for detecting the passage of the blade at a single location. At least two radar units (horizontal mounted) are required for following the position of blade around the nacelle yawing. One radar unit is able to detect the revolution of the blade at a specific position. More than two single radar units may be used for improving redundancy, resolution and confidence of the detection, thus however further increasing costs and software resources. Each radar unit requires a dedicated processing unit for elaborating the signals and deriving the position and speed of the blade.

<CIT>, discloses a system for detecting intruders using coaxial leaky cables buried underground, designed to detect, classify, and locate individuals moving in proximity to the buried cables. The system focuses on perimeter security and aims to reduce false alarms by detecting intruders at ground level.

<CIT> discloses a detection system of flying objects around a wind turbine comprising radiating elements around the tower connected to emitters and receivers, and a signal processing unit aimed to deliver information regarding position and speed of said flying object.

Scope of the present invention is to provide a simple, efficient and cost effective object position and/or speed detection device for a wind turbine, by solving the inconveniences mentioned with reference to the above cited prior art.

A further scope is that of permitting to follow the trajectory of an object in surrounding of the wind turbine, in particular permitting to monitor the position and/or speed of a blade of a wind turbine.

This scope is met by the subject matter according to the independent claims.

According to a first aspect of the present invention a wind turbine including a tower, at least one rotatable blade and an object position and/or speed detection device is provided. The object position and/or speed detection device comprises:.

The target object may be at least one rotatable blade of the wind turbine.

According to a second aspect of the present invention a method for detecting the position and/or speed of a target object in an area comprising a wind turbine is provided, the method comprising the steps of:.

By using one or more leaky feeders the number or transmitters and receiver may be considerably reduced. In particular, according to the present invention only one transmitter and only one receiver may be advantageously used. The area where the position and/or speed of a target object can be detected is extendable by simply increasing the length of the leaky feeder, which is simpler and cheaper than increasing the number of transmitter and receivers. One single processing unit is also enough for analysing the signals from the transmitters and to the receiver and calculate the position and speed, direction and size of the target object.

According to possible embodiments of the invention, two leaky feeders are used respectively connected to one electromagnetic transmitter and to one electromagnetic receiver. This may simplify the implementation of control software with reference to a solution with only one leaky feeder.

According to other possible embodiments of the invention, a plurality of leaky feeders are used, said plurality of leaky feeders comprising a first and a second group of leaky feeders respectively connected to the at least one electromagnetic transmitter and to the at least one electromagnetic receiver. Advantageously, each of the plurality of leaky feeders may be conveniently geometrically configured for optimally following the trajectories of the target objects or of a plurality of target objects According to possible embodiments of the invention, the at least one leaky feeder is geometrically configured as an arc around the tower. In particular, the at least one leaky feeder may be geometrically configured as a loop (or part/segment of a loop) surrounding the tower of the wind turbine.

The at least one leaky feeder and/or the at least one electromagnetic transmitter and/or the least one electromagnetic receiver are installed on or inside the tower of the wind turbine.

According to the invention, the position and/or speed detection device is a component installed on the wind turbine.

In particular, the device of the present invention may be installed on one blade of the wind turbine or on the tower. More particularly, the position and/or speed detection device may be installed inside the tower as well for protecting it from environmental influences, and the direct and indirect effects of a lightning strike.

In wind turbine for offshore application the position and/or speed detection device may be installed on other components of the wind turbine, fixedly attached to the tower. According to other possible configurations, the position and/or speed detection device may be distanced from the tower of the wind turbine.

According to possible embodiments of the invention, the first and second electromagnetic signals may be radar or ultrasonic signals.

According to the invention, the at least one leaky feeder is conveniently chosen as a coaxial leaky cable. Alternatively, according to other possible non-claimed embodiments of the invention where the first and second electromagnetic signals have greater frequencies, the at least one leaky feeder is a leaky waveguide or leaky stripline.

<FIG> shows a partial cross-sectional view of a wind turbine <NUM> including an object position and speed detection device <NUM> according to the invention.

The wind turbine <NUM> comprises a tower <NUM>, which is mounted on a non-depicted fundament. A nacelle <NUM> is arranged on top of the tower <NUM>. In between the tower <NUM> and the nacelle <NUM> a yaw angle adjustment device (not shown) is provided, which is capable of rotating the nacelle around a vertical yaw axis Z.

The wind turbine <NUM> further comprises a wind rotor <NUM> having one or more rotational blades <NUM> (in the perspective of <FIG> only two blades <NUM> are visible). The wind rotor <NUM> is rotatable around a rotational axis Y. In general, when not differently specified, the terms axial, radial and circumferential in the following are made with reference to the rotational axis Y.

The blades <NUM> extend radially with respect to the rotational axis Y.

The wind turbine <NUM> comprises an electric generator <NUM> having a stator <NUM> and a rotor <NUM>. The rotor <NUM> is rotatable with respect to the stator <NUM> about the rotational axis Y to generate electrical power. The electric generator <NUM> and the generation of electrical power through the present invention is not a specific object of the present invention and therefore not described in further detail.

The object position detection device <NUM> according to the present invention comprises:.

The leaky feeder <NUM> is a communications elongated component, which leaks an electromagnetic wave which is transmitted along the component. The leaky feeder <NUM> may be constituted by a leaky coaxial cable or a leaky waveguide or a leaky stripline. The leaky feeder is connected to an electromagnetic transmitter <NUM> in order to transmit a first electromagnetic signal <NUM> along the leaky feeder <NUM> towards a target object, whose position is to be detected. The leaky feeder <NUM> comprises a plurality of slots to allow the first electromagnetic signal <NUM> to leak out of the leaky feeder <NUM> along its entire length towards the target object.

The slots may be, according to possible embodiments, regularly distributed along the length of the leaky feeder <NUM>. According to other possible embodiments of the present invention, the leaky feeder <NUM> is a normal coaxial cable with low optical coverage of the outside conductor (mesh or slots/apertures), which also leaks electromagnetic waves.

The leaky feeder <NUM> may be provided with a heating system (not shown) in case severe over icing conditions are possible. Heating may be provided by air flowing between in and outside conductor or by electrical current which runs in inner or outer conductor of leaky feeder.

The first electromagnetic signal <NUM> may be, according to possible embodiments, a radar signal or an ultrasonic signal. In cases where the first electromagnetic signal <NUM> is a radar signal or an ultrasonic signal the leaky feeder <NUM> is preferably configured as a coaxial leaky cable.

According to other embodiments, particularly where the first electromagnetic signal <NUM> is of higher frequency, the leaky feeder <NUM> is preferably configured as a leaky waveguide.

In general, according to the different embodiments of the present invention, the first electromagnetic signal <NUM> may be of any frequency, provided that it can be transmitted to the target object and be reflected by the target object. When the first electromagnetic signal <NUM> impinges the target object, a reflected second electromagnetic signal <NUM> is transmitted towards the leaky feeder.

The plurality of slots of the leaky feeder <NUM> allow the second electromagnetic signal <NUM> to leak into the leaky feeder <NUM> towards the electromagnetic receiver <NUM>.

The processing unit <NUM> analyses the first electromagnetic signal <NUM> and the second electromagnetic signal <NUM> for determining the position, speed, direction and size of the target object. According to the known (radar) principles of the amplitude, phase, Doppler effect and of ToF (Time of Flight), the processing unit <NUM> is able to compare the first electromagnetic signal <NUM> and the second electromagnetic signal <NUM> caused by a moving object and consequently to determine the speed and/or position and/or direction and/or size of such object. The position of such object may be an angle with respect to a rotational axis or the three-dimensional position with respect to a system of Cartesian axes.

As shown in <FIG>, a first embodiment of the object position and speed detection device <NUM> comprises only one leaky feeder <NUM>. The leaky feeder <NUM> extends between a first end <NUM> and a second end <NUM>. The first end <NUM> is connected to an electromagnetic transceiver <NUM> comprising one electromagnetic transmitter <NUM> and one electromagnetic receiver <NUM>. The second end <NUM> is connected to one final resistance <NUM>. The object position detection device <NUM> is used for detecting the position of a rotational blade <NUM> of the wind turbine <NUM>. According to the present invention, the positions of all the rotational blades <NUM> of the wind turbine <NUM> are detectable.

According to embodiments of the present invention, the electromagnetic transmitter <NUM> and the electromagnetic receiver <NUM> may be both connected to the first end <NUM> or to the second end <NUM> via a signal splitter or y-adapter. According to other embodiments of the present invention, the electromagnetic transmitter <NUM> is connected to the first end <NUM> and the electromagnetic receiver <NUM> is connected to the second end <NUM>.

The leaky feeder <NUM> must not connected directly to the electromagnetic transmitter <NUM> and to the electromagnetic receiver <NUM>, e.g. a non-leaky feeder cable (i.e. a normal coaxial cable) may be interposed between the leaky feeder <NUM> and the electromagnetic transmitter <NUM> and/or the electromagnetic receiver <NUM>. A normal coaxial cable may be connected directly to the electromagnetic transmitter <NUM> and to the electromagnetic receiver <NUM> or it may be used for interconnection.

According to embodiments of the present invention, the target object is the nacelle <NUM> for the detection of the position of the nacelle about the vertical yaw axis Z.

According to embodiments of the present invention, other target objects may be detected in an area comprising a wind turbine <NUM>, for example animals or intruders or changing waves (in offshore applications).

The leaky feeder <NUM> of <FIG> is geometrically configured as a rectilinear line.

According to other embodiments of the present invention, the leaky feeder <NUM> may be geometrically configured as an arc.

With reference to <FIG>, the leaky feeder <NUM> is geometrically configured as a circular loop surrounding the tower <NUM>.

According to other embodiments of the present invention, any other geometrical configuration is possible, provided that the first electromagnetic signal <NUM> can be transmitted towards the target object and the second electromagnetic signal <NUM> can be reflected by the target object towards the leaky feeder <NUM>.

The leaky feeder <NUM> the electromagnetic transmitter <NUM> and the electromagnetic receiver <NUM> are installed on the tower <NUM>. According to other embodiments of the present invention, the leaky feeder <NUM> the electromagnetic transmitter <NUM> and the electromagnetic receiver <NUM> may be not directly installed on the wind turbine <NUM>, i.e. distanced from the wind turbine <NUM>.

According to other embodiments of the present invention, a plurality of leaky feeders <NUM> may be used. As shown in <FIG>, a second embodiment of the object position and speed detection device <NUM> comprises two leaky feeders <NUM>, parallel to each other, and extending between respective first ends <NUM> and second ends <NUM>, respectively adjacent to each other. The two leaky feeders <NUM> are configured according to an antiparallel configuration, where a first leaky feeder <NUM> extends between:.

In such embodiment, one first leaky feeder <NUM>, connected to the electromagnetic transmitter <NUM>, is dedicated for the transmission of the first electromagnetic signal <NUM>, while another second leaky feeder <NUM>, connected to the electromagnetic receiver <NUM>, is dedicated for receiving the first electromagnetic signal <NUM>.

<FIG> shows a third embodiment of the object position and speed detection device <NUM>, which, similarly to the embodiment of <FIG>, comprises two leaky feeders <NUM>. The third embodiment differs from the second embodiment in that a first leaky feeder <NUM> extends between:.

According to other embodiments of the present invention (not shown, the object position and speed detection device <NUM> comprises a plurality of leaky feeders <NUM> with more than two leaky feeders <NUM>. Such plurality of leaky feeders <NUM> comprising a first and a second group of leaky feeders <NUM> respectively connected to one or more electromagnetic transmitters <NUM> and to one or more electromagnetic receivers <NUM>. Each of the plurality of leaky feeders <NUM> may be conveniently geometrically configured for optimally following the trajectories of the target objects or of a plurality of target objects.

Claim 1:
Wind turbine (<NUM>), including a tower (<NUM>), a nacelle (<NUM>), at least a rotatable blade (<NUM>), the wind turbine (<NUM>) comprising an object position and/or speed and/or size detection device (<NUM>) installed on said wind turbine (<NUM>) for detecting a target object in the surroundings of the tower (<NUM>) of the wind turbine (<NUM>), in particular the target object being the rotatable blade (<NUM>), characterized in that said detection device (<NUM>) comprises
- at least one coaxial leaky cable (<NUM>),
- at least one electromagnetic transmitter (<NUM>) connected to the least one coaxial leaky cable (<NUM>) for transmitting a first electromagnetic signal (<NUM>) along the at least one coaxial leaky cable (<NUM>) towards a target object, whose position and/or speed and/or size is to be detected,
- at least one electromagnetic receiver (<NUM>) connected to the at least one coaxial leaky cable (<NUM>) for receiving from the at least one coaxial leaky cable (<NUM>) a second electromagnetic signal (<NUM>), said second electromagnetic signal (<NUM>) being reflected from the target object when the first electromagnetic signal (<NUM>) hits the target object,
- a processing unit (<NUM>) connected to the electromagnetic transmitter (<NUM>) and the electromagnetic receiver (<NUM>) and configured to analyse said first electromagnetic signal (<NUM>) and said second electromagnetic signal (<NUM>) for determining the position and/or speed and/or direction and/or the size of the target object,
wherein any one of the coaxial leaky cables (<NUM>) and/or the at least one electromagnetic transmitter (<NUM>) and/or the least one electromagnetic receiver (<NUM>) are configured to be installed on or inside the tower (<NUM>) of the wind turbine (<NUM>).