Patent Description:
With the gradual depletion of energy sources such as coal and oil, people are paying more and more attention to the use of renewable energy sources. Wind energy, as a kind of clean and renewable energy source, is getting more and more attention from all over the world. For coastal islands, grassland pastoral areas, mountainous areas and plateau areas where water and fuel are scarce and transportation is poor, the use of wind power generation according to local conditions is very suitable and promising. Wind power generation refers to conversion of kinetic energy of wind into electrical energy by use of wind turbines.

During the operation of a wind turbine, due to damage to blades, sensor failures, control system failures, or encounter of extreme wind conditions, the vibration of the whole wind turbine may become unstable, and a clearance distance between a blade tip and a tower may decrease sharply, which eventually causes the blade to collide with the tower, resulting in fracture of the blade or the tower. This phenomenon is called "tower sweeping".

At present, a clearance of the blade is monitored mainly in the following manners. Attitude of the blade tip and the clearance distance are calculated based on reflected waves after collision of emitted electromagnetic or mechanical waves with a detected object, or an orientation of a deformed blade tip is detected by image recognition and then the clearance distance is obtained by cumbersome data post-processing or algorithms.

However, when wind turbine blades are subjected to uncertain loads, direction and attitude of the blade tip after deformation are uncertain, which may be waving, swinging or twisting. Using the above technical manners to detect the orientation of the blade tip and then process the data is cumbersome and complicated, and has an undesirable effect.

In addition, it is inconvenient to install and maintain a detection device on the tower. Moreover, measurement results of some laser devices are easily affected by dust, smog, and other environments. A prior art example can be found in <CIT>.

An objective of embodiments of the present invention is to provide an apparatus and method of monitoring a clearance of a blade of a wind turbine, and a wind turbine, which can simply, conveniently and effectively monitor the clearance between the blade and a tower to prevent tower sweeping.

In an aspect of the embodiments of the present invention, there is provided an apparatus for monitoring a clearance of a blade of a wind turbine. The apparatus includes: a signal transmitter provided on each blade of the wind turbine; a first signal receiver and a second signal receiver provided on a nacelle of the wind turbine; and a control system communicatively connected with the first signal receiver and the second signal receiver. The signal transmitter is installed at the top of a blade tip of the blade. The wind turbine has a safety clearance plane, the safety clearance plane being a plane which is located at a safety clearance position between the blade tip and a tower and is parallel to an axis of the tower, where the first signal receiver and the second signal receiver are arranged symmetrically with respect to the safety clearance plane. The control system determines whether there is a risk of tower sweeping, based on a sequence in which the first signal receiver and the second signal receiver receive a signal transmitted by the signal transmitter.

In another aspect of the embodiments of the present invention, there is provided a method of monitoring a clearance of a blade of a wind turbine. The method includes: transmitting, by a signal transmitter, a signal, in response to a blade of the wind turbine approaching a tower from above in a predetermined angle range, where the signal transmitter is installed at the top of a blade tip of each blade of the wind turbine; receiving, by a first signal receiver and a second signal receiver installed on a nacelle of the wind turbine, the signal transmitted by the signal transmitter, respectively, where the first signal receiver and the second signal receiver are arranged symmetrically with respect to a safety clearance plane of the wind turbine, the safety clearance plane being a plane which is located at a safety clearance position between the blade tip and the tower and is parallel to an axis of the tower; and determining, by a control system communicatively connected with the first signal receiver and the second signal receiver, whether there is a risk of tower sweeping, based on a sequence in which the first signal receiver and the second signal receiver receive the signal transmitted by the signal transmitter.

In still another aspect of the embodiments of the present invention, there is provided a wind turbine, including: a tower; a nacelle installed at the top of the tower; a hub installed at an end of the nacelle; and a plurality of blades installed on the hub. The wind turbine further includes the apparatus for monitoring the clearance of the blade of the wind turbine as described above.

In a particular embodiment, the first signal receiver is disposed close to the blade; the second signal receiver is disposed close to the tower; in response to the first signal receiver receiving the signal transmitted by the signal transmitter earlier than the second signal receiver, the control system determines that the blade is located outside of the safety clearance plane, and the tower is safe; and in response to the first signal receiver and the second signal receiver receiving the signal transmitted by the signal transmitter at the same time, or the first signal receiver receiving the signal transmitted by the signal transmitter later than the second signal receiver, the control system determines that the blade is located on or inside of the safety clearance plane, and there is the risk of tower sweeping.

In a particular embodiment, when it is determined that there is the risk of tower sweeping, the control system controls the wind turbine to perform a shutdown operation.

In a particular embodiment, the first signal receiver and the second signal receiver are installed at a bottom of the nacelle.

In a particular embodiment, the first signal receiver and the second signal receiver are located on a projection line of an axis of a drive train of the wind turbine on a bottom surface of the nacelle of the wind turbine.

In a particular embodiment, the first signal receiver and the second signal receiver are installed on a side of the nacelle.

In a particular embodiment, a signal receiving range of the first signal receiver and the second signal receiver is a predetermined angle range where the blade rotates close to the tower from above.

In a particular embodiment, the signal transmitter is powered by a solar cell.

With the apparatus for monitoring the clearance of the blade of the wind turbine according to the embodiments of the present invention, the clearance between the blade and the tower can be monitored effectively to prevent tower sweeping, without being affected by orientation and attitude of deformation of the blade tip, and without the need for a large amount of cumbersome data processing. The apparatus is easy to install and maintain, has an efficient and reliable performance, and is not easily affected by the environment.

Moreover, the apparatus for monitoring the clearance of the blade of the wind turbine according to the embodiments of the present invention is simple in structural design and is low in cost, and can be widely promoted.

Exemplary embodiments will be described herein in detail, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numerals in different drawings indicate the same or similar elements unless otherwise indicated. Embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses consistent with some aspects of the present invention as detailed in the appended claims.

Terms used in the embodiments of the present invention are merely for the purpose of describing particular embodiments, and are not intended to limit the present invention. Unless otherwise defined, technical terms or scientific terms used in the embodiments of the present invention shall have the ordinary meaning as understood by those ordinary skilled in the art to which the present invention belongs. Words "first", "second" and the like, as used in the description and claims of the present invention, do not indicate any order, number or importance, but are used only to distinguish between different components. Likewise, words "one" or "a" and the like do not indicate a limitation in number, but indicate the presence of at least one. The term "a plurality of" or "several" indicates two or more. Unless otherwise indicated, words "front", "rear", "lower" and/or "upper" and the like are used for illustrative purposes only, and are not limited to a position or a spatial orientation. Words such as "include" or "comprise" are intended to mean that an element or object that appears before "include" or "comprise" covers elements or objects listed after "include" or "comprise" and their equivalents, and does not exclude other elements or objects. Words "connect" or "couple" and the like are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Singular forms of "a", "said" and "the" as used in the description and appended claims of the present invention are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

<FIG> illustrates a schematic side view of a wind turbine <NUM> according to an embodiment of the present invention. As shown in <FIG>, the wind turbine <NUM> includes: a tower <NUM>; a nacelle <NUM> installed at the top of the tower <NUM>; a hub <NUM> installed at an end of the nacelle <NUM>; and a plurality of blades <NUM> installed on the hub <NUM>. The wind turbine <NUM> according to the embodiment of the present invention further includes an apparatus <NUM> for monitoring a clearance of the blade of the wind turbine. The apparatus <NUM> is configured to monitor a clearance of the blade of the wind turbine <NUM>.

The apparatus <NUM> for monitoring the clearance of the blade of the wind turbine according to the embodiment of the present invention includes a signal transmitter <NUM>, a first signal receiver <NUM>, a second signal receiver <NUM>, and a control system <NUM>. The signal transmitter <NUM> is provided on each of the blades <NUM> of the wind turbine <NUM>, and the signal transmitter <NUM> is installed at the top of a blade tip of the blade <NUM>. Signals transmitted by the signal transmitter <NUM> may include, but are not limited to, electromagnetic waves, sound waves or other signal waves, for example. Power for the signal transmitter <NUM> is provided by a battery or other power sources, for example, the signal transmitter <NUM> is powered by a solar cell, thereby saving energy.

The first signal receiver <NUM> and the second signal receiver <NUM> are provided on the nacelle <NUM> of the wind turbine <NUM>. The first signal receiver <NUM> and the second signal receiver <NUM> may be installed on the nacelle <NUM>, for example, by welding, bonding, screwing, riveting, snap-fitting, magnetic attraction, or other installation methods. The wind turbine <NUM> has a safety clearance plane S, and the safety clearance plane S is a plane which is located at a safety clearance position between the blade tip and the tower <NUM> and is parallel to an axis L of the tower <NUM>, where the first signal receiver <NUM> and the second signal receiver <NUM> are arranged symmetrically with respect to the safety clearance plane S.

<FIG> illustrates a schematic front view of the wind turbine <NUM> according to an embodiment of the present invention in operation. As shown in <FIG>, a signal receiving range of the first signal receiver <NUM> and the second signal receiver <NUM> is set to be a predetermined angle range β where the blade <NUM> rotates close to the tower <NUM> from above. The first signal receiver <NUM> and the second signal receiver <NUM> can receive the signals transmitted by the signal transmitter <NUM> when the blade <NUM> rotates close to the tower <NUM> from above in the predetermined angle range β. As the blade <NUM> continues to rotate upwards away from the tower <NUM> from the bottom, for example, as the blade <NUM> rotates upwards from the bottom shown in <FIG> to the left side shown in <FIG>, the first signal receiver <NUM> and the second signal receiver <NUM> can no longer receive the signals.

The predetermined angle range β where the blade <NUM> rotates close to the tower <NUM> from above can be determined based on the type of the wind turbine <NUM>. For example, in an embodiment, the predetermined angle range β where the blade <NUM> rotates close to the tower <NUM> from above can be set to about <NUM>°-<NUM>°.

In some embodiments, the first signal receiver <NUM> and the second signal receiver <NUM> are installed at the bottom of the nacelle <NUM>. For example, the first signal receiver <NUM> and the second signal receiver <NUM> are located on a projection line of an axis of a drive train of the wind turbine <NUM> on a bottom surface of the nacelle <NUM> of the wind turbine <NUM>.

In other embodiments, the first signal receiver <NUM> and the second signal receiver <NUM> can be installed on a side of the nacelle <NUM>. In this way, maintenance of the first signal receiver <NUM> and the second signal receiver <NUM> can be facilitated.

The control system <NUM> is communicatively connected with the first signal receiver <NUM> and the second signal receiver <NUM>, and the control system <NUM> can determine whether there is a risk of tower sweeping, based on a sequence in which the first signal receiver <NUM> and the second signal receiver <NUM> receive a signal transmitted by the signal transmitter <NUM>.

Referring to <FIG>, the first signal receiver <NUM> is disposed close to the blade <NUM>, and the second signal receiver <NUM> is disposed close to the tower <NUM>. If the first signal receiver <NUM> close to the blade <NUM> receives the signal transmitted by the signal transmitter <NUM> earlier than the second signal receiver <NUM> close to the tower <NUM>, it indicates that a distance d1 from the signal transmitter <NUM> to the first signal receiver <NUM> is less than a distance d2 from the signal transmitter <NUM> to the second signal receiver <NUM>. In this case, the control system <NUM> can determine that the blade <NUM> is located outside of the safety clearance plane S, that is, the blade <NUM> is farther away from the tower <NUM> than the safety clearance plane S, and the tower <NUM> is safe.

If the first signal receiver <NUM> and the second signal receiver <NUM> receive the signal transmitted by the signal transmitter <NUM> at the same time, or the first signal receiver <NUM> receives the signal transmitted by the signal transmitter <NUM> later than the second signal receiver <NUM>, it indicates that the distance d1 from the signal transmitter <NUM> to the first signal receiver <NUM> is equal to or greater than the distance d2 from the signal transmitter <NUM> to the second signal receiver <NUM>. In this case, the control system <NUM> can determine that the blade <NUM> is located on or inside of the safety clearance plane S, that is, the blade <NUM> is on the safety clearance plane S or the blade <NUM> is closer to the tower <NUM> than the safety clearance plane S, and there is a risk of tower sweeping.

In some embodiments, when it is determined that there is a risk of tower sweeping, the control system <NUM> can further control the wind turbine <NUM> to perform a shutdown operation so as to prevent tower sweeping, and the blades <NUM> stop rotating.

With the apparatus <NUM> for monitoring the clearance of the blade of the wind turbine according to the embodiments of the present invention, the clearance between the blade <NUM> and the tower <NUM> can be monitored effectively to prevent tower sweeping, without being affected by orientation and attitude of deformation of the blade tip, and without the need for a large amount of cumbersome data processing. The apparatus is easy to install and maintain, has an efficient and reliable performance, and is not easily affected by the environment.

Moreover, the apparatus <NUM> for monitoring the clearance of the blade of the wind turbine according to the embodiments of the present invention is simple in structural design and is low in cost, and can be widely promoted.

Embodiments of the present invention also provide a method of monitoring a clearance of a blade of a wind turbine. <FIG> illustrates a flowchart of a method of monitoring a clearance of a blade of a wind turbine according to an embodiment of the present invention. As shown in <FIG>, the method of monitoring the clearance of the blade of the wind turbine according to the embodiment of the present invention includes steps S11 to S13.

At step S11, a signal is transmitted by a signal transmitter <NUM>, in response to the blade <NUM> of the wind turbine <NUM> approaching a tower <NUM> from above in a predetermined angle range β, where the signal transmitter <NUM> is installed at the top of a blade tip of each blade <NUM> of the wind turbine <NUM>.

At step S12, the signal transmitted by the signal transmitter <NUM> is respectively received by a first signal receiver <NUM> and a second signal receiver <NUM> installed on a nacelle <NUM> of the wind turbine <NUM>, where the first signal receiver <NUM> and the second signal receiver <NUM> are arranged symmetrically with respect to a safety clearance plane S of the wind turbine <NUM>, the safety clearance plane S being a plane which is located at a safety clearance position between the blade tip and the tower <NUM> and is parallel to an axis L of the tower <NUM>.

At step S13, it is determined whether there is a risk of tower sweeping, based on a sequence in which the first signal receiver <NUM> and the second signal receiver <NUM> receive the signal transmitted by the signal transmitter <NUM>.

The first signal receiver <NUM> is disposed close to the blade <NUM>, and the second signal receiver <NUM> is disposed close to the tower <NUM>. If the first signal receiver <NUM> receives the signal transmitted by the signal transmitter <NUM> earlier than the second signal receiver <NUM>, it is determined that the blade <NUM> is located outside of the safety clearance plane S, and the tower <NUM> is safe. If the first signal receiver <NUM> and the second signal receiver <NUM> receive the signal transmitted by the signal transmitter <NUM> at the same time, or the first signal receiver <NUM> receives the signal transmitted by the signal transmitter <NUM> later than the second signal receiver <NUM>, it is determined that the blade <NUM> is located on or inside of the safety clearance plane S, and there is a risk of tower sweeping.

In some embodiments, the method of monitoring the clearance of the blade of the wind turbine according to the embodiment of the present invention further includes step S14. At step S14, when it is determined that there is a risk of tower sweeping, the wind turbine <NUM> is controlled to perform a shutdown operation so as to prevent tower sweeping.

The method of monitoring the clearance of the blade of the wind turbine according to the embodiment of the present invention has beneficial technical effects similar to those of the apparatus <NUM> for monitoring the clearance of the blade of the wind turbine as described above, which will not be repeated herein.

Claim 1:
An apparatus (<NUM>) for monitoring a clearance of a blade of a wind turbine comprising:
a signal transmitter (<NUM>) provided on each blade (<NUM>) of the wind turbine (<NUM>), the signal transmitter (<NUM>) being installed at a top of a blade tip of the blade (<NUM>);
a first signal receiver (<NUM>) and a second signal receiver (<NUM>) provided on a nacelle (<NUM>) of the wind turbine (<NUM>), the wind turbine (<NUM>) having a safety clearance plane (S), and the safety clearance plane (S) being a plane which is located at a safety clearance position between the blade tip and a tower (<NUM>) of the wind turbine (<NUM>) and is parallel to an axis (L) of the tower (<NUM>);
and
a control system (<NUM>) communicatively connected with the first signal receiver (<NUM>) and the second signal receiver (<NUM>), the control system (<NUM>) determining whether there is a risk of tower sweeping, based on a sequence in which the first signal receiver (<NUM>) and the second signal receiver (<NUM>) receive a signal transmitted by the signal transmitter (<NUM>), characterized in that the first signal receiver (<NUM>) and the second signal receiver (<NUM>) are arranged symmetrically with respect to the safety clearance plane (S).