DK201770693A1

DK201770693A1 - Control system for a wind turbine

Info

Publication number: DK201770693A1
Application number: DKPA201770693A
Authority: DK
Inventors: Nielsen Johnny; Deleuran Grunnet Jacob; Rasmussen Jes
Original assignee: Vestas Wind Systems A/S
Priority date: 2017-09-14
Filing date: 2017-09-14
Publication date: 2018-09-19

Abstract

The present invention relates to a control system for a wind turbine that is configured to: obtain 3-dimensional images of an exterior portion of the wind turbine and/or a ground region adjacent to a base of the wind turbine from a 3-dimensional scanning device associated with the wind turbine; and monitor the wind turbine and/or control operation of the wind turbine in dependence on the 3-dimensional images obtained from the 3-dimensional scanning device. The scanning device may be a LIDAR scanning device, and may be located on the underside of the nacelle of the wind turbine.

Description

(¹⁹) DANMARK (10)

DK 2017 70693 A1

(12)

PATENTANSØGNING

Patent- og Varemærkestyrelsen (51) lnt.CI.: F03D 7/04 (2006.01) F03D 17/00 (2016.01) G06K 9/20 (2006.01) (21) Ansøgningsnummer: PA 2017 70693 (22) Indleveringsdato: 2017-09-14 (24) Løbedag: 2017-09-14 (41) Aim. tilgængelig: 2018-09-13 (43) Publiceringsdato: 2018-09-19 (71) Ansøger:

VESTAS WIND SYSTEMS A/S, Hedeager 42, 8200 Århus N, Danmark (72) Opfinder:

Johnny Nielsen, Apotekervej 14, 9230 Svenstrup J, Danmark

Jacob Deleuran Grunnet, Augustenborggade 15,3. th., 8000 Århus C, Danmark

Jes Rasmussen, Nygårdsparken 10, 8464 Galten, Danmark (74) Fuldmægtig:

Vestas Wind Systems A/S Patents Department, Hedeager 42, 8200 Århus N, Danmark (54) Titel: CONTROL SYSTEM FORA WIND TURBINE (56) Fremdragne publikationer:

US 2012/0045330 A1

US 2011/0090110 A1

EP 2821639 A1

US 2013/0287567 A1

EP 2333329 A2 (57) Sammendrag:

The present invention relates to a control system for a wind turbine that is configured to: obtain 3dimensional images of an exterior portion of the wind turbine and/or a ground region adjacent to a base of the wind turbine from a 3-dimensional scanning device associated with the wind turbine; and monitor the wind turbine and/or control operation of the wind turbine in dependence on the 3-dimensional images obtained from the 3-dimensional scanning device. The scanning device may be a LIDAR scanning device, and may be located on the underside of the nacelle of the wind turbine.

Fortsættes...

DK 2017 70693 A1

Figure 2

DK 2017 70693 A1

CONTROL SYSTEM FOR A WIND TURBINE

TECHNICAL FIELD

The present disclosure relates to a control system for a wind turbine and particularly, but not exclusively, to a control system that is configured to monitor a wind turbine and/or control operation of a wind turbine in dependence on 3-dimensional images obtained from a 3-dimensional scanning device associated with the wind turbine.

BACKGROUND

Wind turbines are generally provided with a monitoring system for performing in use monitoring of various different operational parameters such as tower deflection, blade deflection, rotor speed and rotor acceleration. However, existing turbine monitoring systems are generally highly complex and rely on sensor data from a large number of individual point sensors such as strain sensors and accelerometers that are each configured to measure a specific quantity at their specific location. Installing a large number of point sensors in a wind turbine is time-consuming and expensive, and in some cases it may not be possible to install sensors at all locations for which a reading may be desired. In addition, turbine monitoring systems that rely on data from a large number of individual sensors may be impaired if one or more of the sensors stops functioning correctly, and sensors in certain locations may be difficult to repair or replace if damaged.

It is an aim of the present invention to address disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a control system for a wind turbine, wherein the control system is configured to:

obtain 3-dimensional images of an exterior portion of the wind turbine and/or a ground region adjacent to a base of the wind turbine from a 3-dimensional scanning device associated with the wind turbine; and

DK 2017 70693 A1 monitor the wind turbine and/or control operation of the wind turbine in dependence on the 3-dimensional images obtained from the 3-dimensional scanning device.

The 3-dimensional images may take the form of point cloud or point mesh measurements, and may include at least a portion of the tower of the wind turbine. Alternatively, or in addition, the 3-dimensional images may include at least a portion of a blade of the wind turbine (for example at least a portion of each blade as it passes the tower). In some cases the 3-dimensional images may further include at least a portion of a nacelle of the wind turbine, depending on the location and orientation of the 3-dimensional scanning device.

Monitoring of the wind turbine may comprise determining one or more operating parameters or component states related to the tower, the blades and/or the nacelle of the wind turbine.

The use of a 3-dimensional scanning device to generate images of the exterior of the wind turbine 1 and its surroundings allows a large number of different parameters to be monitored accurately based on data from a single sensor, and facilitates direct measurement of various parameters that cannot be measured directly using conventional sensors currently included in wind turbines. The use of a 3-dimensional scanning device also reduces the need to rely on knowledge of the exact dimensions of the wind turbine and the exact positions of sensors and markers because the control system is able to independently determine the 3-dimensional shape of the wind turbine and its surroundings, and to directly measure the 3-dimensional positions of recognisable features relative to the scanning device.

The control system may be configured to monitor one or more operating parameters related to the tower in dependence on the 3-dimensional images, for example tower deflection (including lateral deflection and/or twist), tower loading and/or tower oscillation. By using a 3-dimnesional scanning device to measure the current shape of the tower it is possible to determine the deflection state of the tower and measure tower oscillation along substantially the entire height of the tower, thereby providing a more complete and accurate determination of the deflection and oscillation states of the tower than can be achieved using conventional point sensors. In some

DK 2017 70693 A1 embodiments the control system may be configured to track movement of the tower relative to the ground in order to improve the accuracy of tower deflection monitoring, for example by monitoring the positions of one or more recognisable target features located on the ground, or by calculating the angle of the ground relative to the tower and/or relative to the 3-dimensional scanning device.

The control system may be configured to monitor one or more operating parameters related to the nacelle in dependence on the 3-dimensional images, for example nacelle yaw angle, nacelle yaw speed, nacelle yaw moment, yaw error angle, nacelle tilt angle and/or nacelle tilt moment.

The control system may be configured to monitor one or more operating parameters related to the rotor and/or blades in dependence on the 3-dimensional images, for example blade tip clearance (between the tip of the blade and the tower), rotor azimuth angle, rotor speed, rotor angular acceleration, blade tip speed, blade tip acceleration, blade pitch angle, blade deflection, blade twist, blade loading and/or blade vibration. The control system may also be configured to predict blade tip clearance distances for subsequent blade passages, for example in dependence on the measured blade tip clearance distances for previous blade passages, measured rotor speed or tip speed, and the measured deflection state of the tower. The ability to accurately measure blade tip clearance distances and predict the blade tip clearance distance for subsequent blade passages is particularly useful for optimising control of the wind turbine to maximise power output while ensuring safe operation, and also facilitates the use of longer and/or more flexible blades and lower tilt angles for the nacelle and rotor.

The control system may be configured to perform structural health monitoring for the wind turbine in dependence on the 3-dimensional images, for example by detecting damage to at least one of the tower, the nacelle, the rotor and the blades; and/or by monitoring the presence of ice and/or dirt on at least one of the tower, the nacelle, the rotor and the blades.

The control system may be configured to control operation of the wind turbine in order to limit one or more of: tower deflection (including lateral deflection and/or twist), tower loading, tower oscillation, tilt moment, yaw moment, yaw error angle, yaw speed, blade

DK 2017 70693 A1 tip clearance, rotor speed, blade tip speed, blade deflection, blade twist, blade loading and blade vibration in dependence on the 3-dimensional images. For example, the control system may be configured to output a control signal setting a torque or power output demand and/or a control signal setting a pitch angle or yaw angle demand in dependence on one or more parameters derived from the 3-dimensional images.

The control system may be configured to compare the 3-dimensional images with at least one reference model of at least a portion of the wind turbine, and to monitor at least one operating parameter in dependence on the comparison. For example, the control system may be configured to determine one or more operating parameters related to the tower in dependence on the error between a 3-dimensional image of at least a portion of the tower and a reference model of the tower. Alternatively, or in addition, the control system may be configured to modify the shape of a reference model of the tower to match the measured shape of the tower in a 3-dimensional image, and to determine one or more operating parameters related to the tower in dependence on the modified reference model. Alternatively, or in addition, the control system may be configured to select a reference model from a plurality of reference models having a shape that approximately matches the measured shape of the tower in a 3-dimensional image, and to determine one or more operating parameters related to the tower in dependence on the selected reference model. The shape, position and/or angle of a blade may also be assessed by comparison with at least one reference model in a similar manner (either using an integrated wind turbine reference model including the blades or alternatively using separate reference models of the blades).

The control system may be configured to identify one or more recognisable target features in the 3-dimensional images, and to monitor at least one operating parameter in dependence on the position(s) of the recognised target feature(s). The target features may be natural features (that is inherent features) of the wind turbine and/or its surroundings; and/or markers (that is devices added to the wind turbine and/or its surroundings specifically for the purpose of being identified in an image for monitoring purposes). The position(s) of the recognised target feature(s) (for example the locations and/or orientations of the recognised target features relative to each other and/or relative to the 3-dimensional scanning device) may be used to determine one or more operating parameters related to the tower, the nacelle, the rotor and/or the

DK 2017 70693 A1 blades directly. Alternatively, or in addition, the position(s) of the recognised target feature(s) may be used in comparing a 3-dimensional image with at least one reference model of at least a portion of the wind turbine.

The control system may further comprise at least one 3-dimensional scanning device configured to generate the 3-dimensional images. However, it will be appreciated that in some cases the scanning device(s) may be supplied separately to the control module(s) forming the control system of the present invention.

The scanning device may comprise a transmitter configured to emit a signal, and a receiver configured to receive the reflected signal. The transmitter and the receiver may be located together within a common housing, or alternatively may be provided separately, and optionally at separate locations. The transmitter may optionally be configured to emit a pulsed signal, and optionally a laser light signal.

The scanning device may be an electromagnetic radiation based scanning device, for example a visible light based scanning device, although other frequencies are also possible, including radio waves, microwaves, infrared light, UV light, X-rays and gamma rays. The scanning device may be, for example, a LIDAR scanning device (that is a Light Imaging Detection and Ranging scanning device). The LIDAR scanning device may be a micro-LIDAR device (that is a small form factor LIDAR device, which may have a width and/or height of less than 100mm or less than 60mm) and/or a solid state LIDAR device and/or a single chip LIDAR device.

The scanning device may be mounted to the nacelle of the wind turbine. In this case the scanning device may be configured to generate the 3-dimensional images including at least a portion of the tower, at least a portion of a blade and/or at least a portion of the ground region adjacent to the base of the wind turbine. The scanning device may be mounted to the underside of the nacelle, and may face downwardly from the nacelle, optionally in an at least substantially vertical direction (although it will be appreciated that the scanning device may have a wide field of view that enables it to generate the 3-dimensional images over a wide angle range).

Alternatively, the scanning device may be mounted to the tower of the wind turbine. In this case the scanning device may be configured to generate the 3-dimensional

DK 2017 70693 A1 images including at least a portion of the tower, at least a portion of a blade, at least a portion of the nacelle and/or at least a portion of the ground region adjacent to the base of the wind turbine. The scanning device may be located adjacent to a top end of the tower, and may face downwardly, optionally in an at least substantially vertical direction. Alternatively, the scanning device may be located adjacent to a base of the tower, and may face upwardly, optionally in an at least substantially vertical direction.

Alternatively, the scanning device may be mounted separately to the wind turbine, for example on the ground adjacent to the base of the wind turbine. In this case the scanning device may be configured to generate the 3-dimensional images including at least a portion of the tower, at least a portion of a blade and/or at least a portion of the nacelle. The scanning device may face upwardly from the ground, optionally in an at least substantially vertical direction.

Where the control system comprises a plurality of the scanning devices the scanning devices may be provided at a plurality of different locations. For example, the control system may include at least one scanning device mounted to the nacelle, at least one scanning device mounted to the tower and/or at least one scanning device mounted separately to the wind turbine. The multiple scanning devices may each generate separate 3-dimensional images, which may be used separately or in combination for monitoring the wind turbine and/or controlling operation of the wind turbine.

According to a second aspect of the present invention there is provided a control system for a wind turbine, wherein the control system is configured to: obtain 3dimensional images of an exterior portion of the wind turbine and/or a ground region adjacent to a base of the wind turbine from a 3-dimensional scanning device mounted to the nacelle of the wind turbine; and monitor the wind turbine and/or control operation of the wind turbine in dependence on the 3-dimensional images obtained from the 3dimensional scanning device. By mounting the scanning device to the nacelle it is possible to maximise the portions of the wind turbine and its surroundings that are visible to the scanning device, thereby maximising the monitoring capabilities of the control system. For example, the scanning device may be able to generate the 3dimensional images including substantially the entire height of the tower, as well as at least a portion of each blade as it passes the tower. The scanning device may be mounted to the underside of the nacelle, and may face downwardly.

DK 2017 70693 A1

According to a third aspect of the present invention there is provided a method of monitoring a wind turbine and/or controlling operation of a wind turbine, the method comprising steps of: obtaining at least one 3-dimensional image of an exterior portion of the wind turbine and/or a ground region adjacent to a base of the wind turbine from a 3-dimensional scanning device associated with the wind turbine; and monitoring the wind turbine and/or controlling operation of the wind turbine in dependence on the 3dimensional image(s) obtained from the 3-dimensional scanning device. The method may be used when operating a control system according to the first and/or second aspects of the present invention, and may generally include any step(s) associated with the normal operation of such a control system.

According to a further aspect of the present invention there is provided a non-transitory computer readable storage medium comprising computer readable instructions for a computer processor to carry out the method of the third aspect of the present invention.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figures 1 and 2 schematically illustrate a wind turbine comprising a control system in accordance with an embodiment of the present invention;

DK 2017 70693 A1

Figure 3 schematically illustrates a control system in accordance with an embodiment of the present invention;

Figure 4 schematically illustrates a 3-dimensional image generated by a LIDAR scanning device forming part of the control system illustrated in Figure 3, and

Figures 5a, 5b and 6 schematically illustrate methods of determining the deflection state of a wind turbine tower by comparison of a 3-dimensional image of the tower with one or more reference models in accordance with possible embodiments of the present invention.

DETAILED DESCRIPTION

Figures 1 and 2 schematically illustrate a wind turbine 1 provided with a control system in accordance with an embodiment of the present invention. In the present embodiment the wind turbine is an on-shore wind turbine, although it will be appreciated that the invention may equally be applied to an off-shore wind turbine. The wind turbine 1 comprises a tower 2 that extends upwardly from the ground G and a nacelle 3 that is mounted to the top of the tower 2 and configured for rotation relative to the tower 2 about a substantially vertical yaw axis. The nacelle 3 is provided with a rotor 4 including a central hub 5 and a plurality of blades 6 extending outwardly from the hub 5. The rotor 4 is configured to rotate relative to the nacelle 3 about a substantially horizontal axis of rotation, and is connected via a drivetrain to an electrical generator housed within the nacelle 3. The main structural features of wind turbines are well known to the skilled person and will not be described further.

The wind turbine 1 is provided with a control system 10 according to an embodiment of the present invention, as schematically illustrated in Figure 3. The control system 10 comprises a control module 11 that is configured to monitor operation of the wind turbine 1 and control operation of the wind turbine 1 in dependence on 3-dimensional images or measurements obtained from a LIDAR scanning device 12 (as described in more detail below). In the embodiment illustrated in Figure 1 the control module 11 is located at the base of the tower 2. However, it will be appreciated that the control module 11 could equally be provided at a different location (including at a location remote from the wind turbine 1). It will further be appreciated that the processors and

DK 2017 70693 A1 memory modules forming the control module 11 need not all be provided together at a single location, but may instead be split across a plurality of separate locations (including locations remote from the wind turbine 1).

The control system 10 further comprises a LIDAR scanning device 12 that is in electronic communication with the control module 11 and configured to be controlled by the control module 11, as schematically illustrated in Figure 3. The LIDAR device 12 may be, for example, a single chip, solid state, micro-LIDAR device, although other types of 3-dimension scanning device may equally be employed in other embodiments of the present invention. Suitable LIDAR devices are commercially available from, for example, Velodyne LiDAR and Quanergy Systems Inc.

The LIDAR device 12 includes a light emitting device 13 and a light receiving device 14 or camera. The light emitting device 13 is configured to emit pulses of visible laser light, and the light receiving device 14 is configured to receive light from the light emitting device 13 as reflected back towards the light receiving device 14. The control system 10 is configured to generate 3-dimensional images or measurements of the exterior of the wind turbine 1 and the ground region G adjacent to the base of the wind turbine 1 in dependence on the timing and intensity of the reflected light received at the light receiving device 14 in a manner conventional for LIDAR systems. The 3dimensional images may be generated with a refresh rate of, for example, 10 to 100Hz or 50 to 100Hz, although lower or higher frame rates are also possible. As with conventional LIDAR systems, the 3-dimensional images take the form of point cloud or point mesh measurements including a large number of data points each having a defined 3-dimensional location, with the distance to each point being determined based on the time taken for reflected light to be received back at the light receiving device 14. The processing of raw sensor data to generate the 3-dimensional images may be performed at the LIDAR device 12 and/or at the control module 11.

The LIDAR device 12 is mounted to the underside of the nacelle 3, as schematically illustrated in Figure 2, and generally faces downwardly towards the base of the tower 2 and the ground region G surrounding the base of the tower 2. The LIDAR device 12 has a field of view of, for example, 120 degrees, and the field of view of the LIDAR device 12 includes a portion of the tower 2, a portion of a blade 6 (depending on the angular position of the rotor 4), and a portion of the ground region G surrounding the

DK 2017 70693 A1 base of the tower 2. The control module 11 is therefore able to continuously obtain 3dimensional images in the form of point cloud or point mesh measurements including a portion of the tower 2, a portion of a blade 6, and a portion of the ground region G surrounding the base of the tower 2 substantially in real time during use of the wind turbine 1. Figure 4 schematically illustrates a simplified version of a 3-dimensional image generated by the control system 10 when one of the blades 6 is pointing directly towards the ground G.

The control module 11 is configured to process the 3-dimensional images obtained from the LIDAR device 12 and to extract recognisable features of the tower 2, the blades 6 and the ground region G adjacent to the base of the tower 2 from the 3dimensional images, for example using an object detection or feature extraction algorithm. The control module 11 is able to recognise both natural features and markers (natural features being inherent features of the tower 2, the blades 6 and the ground region G such as a tower door, the interface between the base of the tower 2 and the ground G, and paths, steps or buildings close to the base of the tower 2; and markers being devices such as reflective patches, strips of tape, printed patterns or signs that may be added to the tower 2, the blades 6 and/or the ground region G specifically for the purpose of being identified in an image for monitoring purposes). The positions of one or more recognisable features (for example the locations and/or orientations of the recognisable features relative to the LIDAR device 12 and/or relative to each other) are used in various turbine monitoring operations, as described below. The control module 11 may be configured to automatically and independently select suitable target features to be used in turbine monitoring, for example by extracting recognisable features from a reference measurement generated by the LIDAR device 12 during a calibration process. Alternatively, or in addition, one or more target features may be selected by an operator during calibration of the control module 11.

The control system 10 is configured to monitor various different operating parameters, component states and environmental conditions related to the wind turbine 1 and its surroundings in dependence on the 3-dimensional images obtained from the LIDAR device 12, including, for example, tower deflection, tower loading, tower oscillation, nacelle yaw angle, nacelle yaw speed, nacelle yaw moment, yaw error angle, nacelle tilt angle, nacelle tilt moment, blade tip clearance, rotor azimuth angle, rotor speed,

DK 2017 70693 A1 rotor acceleration, blade tip speed, blade tip acceleration, blade pitch angle, blade deflection, blade twist, blade loading, blade vibration, blade/tower damage, ice accumulation, dirt accumulation and ground activity. The control system 10 of the present invention provides a cost-effective monitoring system that can monitor a large number of different parameters in order to provide redundancy in combination with other known monitoring systems and/or to reduce the number of sensors required for monitoring the wind turbine 1. In particular, the use of a 3-dimensional scanning device to generate images of the exterior of the wind turbine 1 and its surroundings allows a large number of different parameters to be monitored accurately based on data from a single sensor, and facilitates direct measurement of various parameters that cannot be measured directly using conventional sensors currently included in wind turbines. The use of a 3-dimensional scanning device also reduces the need to rely on knowledge of the exact dimensions of the wind turbine and the exact positions of sensors and markers because the control system is able to independently determine the 3-dimensional shape of the wind turbine and its surroundings, and to directly measure the 3-dimensional positions of recognisable features relative to the scanning device. Various examples of monitoring functions that may be carried out in accordance with the present invention are described below.

During use of the wind turbine 1 the tower 2 undergoes deflection (including lateral deflection and twist) and oscillation, for example due to thrust forces acting on the rotor

4. The control module 11 is configured to determine the deflection state of the tower 2 (including lateral deflection and twist) and measure oscillation in dependence on the 3dimensional shape of the portion of the outer surface of the tower 2 that is visible to the LIDAR device 12, for example by exploiting knowledge of the tower’s undeflected shape. In this way the control module 11 is able to determine the deflection state and measure oscillation along substantially the entire height of the tower 2, thereby providing a more complete and accurate determination of the deflection and oscillation state of the tower than can be achieved using conventional point sensors.

In some embodiments the control module 11 may be configured to store one or more reference models of the tower 2, and to compare 3-dimensional images of the tower 2 obtained from the LIDAR device 12 with the reference model(s) in order to determine the deflection state of the tower 2. The reference model(s) may be saved in the control module 11 before installation of the control module 11 in the wind turbine 1, or

DK 2017 70693 A1 alternatively generated or modified by the control module 11 during a calibration process, for example based on measurements obtained by the LIDAR device 12. In some embodiments the control module 11 may be configured to modify the shape of a reference model to match the shape of the tower 2 as measured using the LIDAR device 12, or to select a reference model having a shape that approximately matches the shape of the tower 2 as measured using the LIDAR device 12, and to determine the deflection state of the tower in dependence on the modified or selected reference model, as described in more detail below.

According to one possible embodiment, the control module 11 stores a reference model 200 of the tower 2 in the form of a finite element mesh model or other CAD model, as schematically illustrated in Figure 5a. The reference model 200 includes the structural and dynamic properties of the tower 2, and has a variable shape that can be modified by controlling one or more variable model parameters. In use, the control module 11 obtains a 3-dimensional image 100 of the current shape of the tower 2 from the LIDAR device 12 and compares the 3-dimensional image 100 of the tower 2 with the reference model 200 by extracting a 3-dimensional point cloud 201 from the reference model 200 and comparing the 3-dimensional image 100 to the 3dimensional point cloud 201 extracted from the reference model 200, as schematically illustrated in Figure 5a (in which tower deflection has been exaggerated for the purposes of illustration). The control module 11 then modifies the variable parameters of the reference model 200 to change the shape of the reference model 200 in order to reduce the error between the 3-dimensional image 100 and the reference model 200. The 3-dimensional image 100 of the current shape of the tower 2 is then compared with the modified version of the reference model 200’ by a extracting a second 3dimensional point cloud 201’ from the modified version of the reference model 200’ and comparing the 3-dimensional image 100 to the second 3-dimensional point cloud 20T, as schematically illustrated in Figure 5b. These steps may be repeated in an iterative process until the shape of the reference model 200 at least substantially matches the shape of the tower 2 as measured using the LIDAR device 12, for example when the error between the 3-dimensional image 100 and the reference model 200 falls below a predetermined threshold. The deflection state of the tower 2 may then be determined from the reference model 200 as modified to match the current shape of the tower 2. Other operating parameters related to the tower 2 may

DK 2017 70693 A1 also be derived directly from the reference model, including, for example, forces acting on the tower 2 and local strain values.

According to another possible embodiment, the control module 11 stores a plurality of reference models 200a, 200b, 200c of the tower corresponding to a plurality of different deflection states, as schematically illustrated in Figure 6 (again with tower deflection exaggerated for the purposes of illustration). In use, the control module 11 obtains a 3-dimensional image 100 of the current shape of the tower 2 from the LIDAR device 12 and compares the 3-dimensional image 100 of the tower 2 with the reference models 200a, 200b, 200c, as schematically illustrated in Figure 6, for example by extracting 3-dimensional point clouds from the reference models 200a, 200b, 200c and comparing the 3-dimensional image 100 to the 3-dimensional point clouds. The control module 11 then selects the reference model 200b that is most similar in shape to the current shape of the tower 2 as measured using the LIDAR device 12. The deflection state of the tower 2 may then be derived from the selected reference model 200b and/or determined from a look up table associated with the selected reference model 200b.

According to another possible embodiment, the control module 11 stores a reference model of the tower in a substantially undeflected state. In use, the control module 11 obtains a 3-dimensional image 100 of the current shape of the tower 2 from the LIDAR device 12, compares the 3-dimensional image 100 of the tower 2 with the reference model, and determines the deflection state of the tower 2 in dependence on the error between the current shape of the tower 2 as measured using the LIDAR device 12 and the shape of the reference model. The deflection state of the tower 2 may, for example, be determined using one or more look up tables and/or one or more equations that indicate the tower deflection state based on a calculated difference between the measured shape of the tower 2 and the shape of the reference model. In this case it may not be necessary to modify the shape of any reference model or select a reference model from a plurality of standard reference models in order to determine the deflection state of the tower 2. The reference model may, for example, be a point cloud or point mesh measurement of the tower 2, which may be obtained by the LIDAR device 12 during a calibration process while the tower 2 is in a substantially undeflected state.

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Alternatively, or in addition to the tower deflection monitoring methods described above, the control module 11 may be configured to use the positions of one or more recognisable target features (including natural features and/or markers located on the tower 2 and/or the ground region G adjacent to the base of the tower 2) in determining the deflection state of the tower 2. In some embodiments the positions of one or more recognisable target features may be used to determine the tower deflection state directly (in which case it may not be necessary to compare the measured shape of the tower 2 with any reference model, as in the deflection monitoring methods described above). For example, the control module 11 may store reference positions for one or more target features (such as the tower door 2a, a path G1 leading to the wind turbine 1, and a building G2 close to the base of the wind turbine 1), which may be set based on a reference measurement obtained by the LIDAR device 12 during a calibration process while the tower 2 is in a substantially undeflected state. The deflection state of the tower 2 (including lateral deflection and twist) may then be determined by detecting changes in the absolute and/or relative positions of the target features 2a, G1, G2, for example in dependence on the error between the measured positions of the target features 2a, G1, G2 and the stored reference positions for the target features. In other embodiments the positions of one or more recognisable target features may be used in comparing a 3-dimensional image of the tower with a reference model of the tower 2. For example, the control module 11 may be configured to extract one or more target features from a 3-dimensional image obtained by the LIDAR device 12 during use of the wind turbine 1, and to associate the extracted target features with equivalent features on a reference model. In this case the control module 11 may be configured to use the positions of the extracted target features in aligning the 3-dimensional image with the reference model and/or in assessing the error between the 3-dimensional image and the reference model.

In other embodiments the control module 11 may also be configured to calculate the angle of the ground region G adjacent to the base of the tower 2 (for example the angle of the ground G relative to the tower 2 and/or relative to the LIDAR device 12) and to use the angle of the ground G in determining the deflection state of the tower 2.

Tower loading information may be derived in dependence on the measured deflection state of the tower 2, for example based on data in look up tables associated with different tower shapes.

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Tower oscillation may be measured by monitoring changes in the shape of the tower 2 as measured by the LIDAR device 12 over time.

Nacelle tilt angle may be measured by calculating the angle of the tower 2 relative to the LIDAR device 12 in the 3-dimensional images generated by the LIDAR device 12, and nacelle yaw moment may be calculated in dependence on the measured tilt angle.

As described above, the control module 11 is configured to extract recognisable features (including natural features and/or markers on the tower 2, the blades 6 and/or the ground region adjacent to the base of the tower 2) from the 3-dimnesional images obtained from the LIDAR device 12, and to use the positions of one or more recognisable target features (for example the locations and/or orientations of the recognisable target features relative to the LIDAR device 12 and/or relative to each other) in various turbine monitoring operations. In particular, the positions of recognisable target features are used in determining the yaw angle of the nacelle 3 with respect to the tower 2, thereby allowing a direct and reliable measurement of the nacelle yaw angle.

In the present embodiment, the control module 11 is configured to obtain a reference measurement of the tower 2 and the ground region G adjacent to the base of the tower 2 from the LIDAR device 12 during a calibration process while the nacelle 3 is at a known yaw angle with respect to the tower 2 and the tower 2 is in a substantially undeflected state. The control module 11 then applies an object detection or feature extraction algorithm to extract recognisable features from the reference image, and automatically selects a plurality of target features for use in monitoring the wind turbine 1, for example a tower door 2a, a path G1, and a building G2 as schematically illustrated in Figure 4. The positions of the selected target features 2a, G1, G2 in the reference image (for example the positions of the target features relative to each other and/or relative to the LIDAR device 12) are then recorded as reference positions for the target features and stored in a memory module. During subsequent use of the wind turbine 1, the control module 11 is then able to calculate the current yaw angle of the nacelle 3 in dependence on the change in the positions of the selected target features 2a, G1, G2 relative to the stored reference positions for the target features.

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Nacelle yaw speed, nacelle yaw moment and yaw error angle may also be calculated in dependence on the measured yaw angle.

If the orientation(s) of one or more recognisable features of the wind turbine and/or its surroundings are known (such as the orientation of a door 2a and a path G1 relative to north), the control module 11 is also able to recognise the orientation of those features and use the measured orientation of the recognised features to calibrate the north position for use in turbine monitoring and control processes.

As described above, the field of view of the LIDAR device 12 covers both the tower 2 and the blades 6 as they pass the tower 2. It is therefore possible to monitor various different operating parameters related to the blades 6 based on the 3-dimensional images obtained from the LIDAR device 12. In particular, the control module 11 is able to directly measure the blade tip clearance distance for each blade 6 (that is the minimum distance between the tip of each blade 6 and the nearest point of the tower 2 as it passes the tower 2) during operation of the wind turbine 1 from the 3-dimensional images. The control module 11 is also able to measure rotor speed and tip speed for each blade 6 based on the rate at which each blade 6 moves across the field of view of the LIDAR device 12, for example by differentiating the blade tip position. In addition, by recognising the individual blades 6 and the position of the blade 6 within the field of view of the LIDAR device 12, the control module 11 is also able to measure the azimuth angle of the rotor 4. The individual blades 6 may be automatically recognised using markers installed on the blades 6 specifically for the purpose of enabling blade identification and/or based on natural differences between the blades 6, which may be identified during a calibration process. The rotor speed may also be calculated by differentiation of the rotor azimuth angle, and blade tip speed may be calculated based on the calculated rotor speed. Rotor acceleration and blade tip acceleration may also be calculated by differentiating the rotor speed and blade tip speed.

The control module 11 may additionally be able to predict blade tip clearance distances for subsequent blade passages, for example in dependence on the measured blade tip clearance distances for previous blade passages, measured rotor speed or tip speed, and the measured deflection state of the tower 2. The ability to accurately measure blade tip clearance distances and predict the blade tip clearance

DK 2017 70693 A1 distance for subsequent blade passages is particularly useful for optimising control of the wind turbine to maximise power output while ensuring safe operation, and also facilitates the use of longer and/or more flexible blades 6 and lower tilt angles for the nacelle 3 and rotor 4.

The control module 11 is also able to calculate the pitch angle of each blade 6 as it passes the tower 2, for example by identifying the position and/or orientation of the cordline of a blade in a 3-dimensional image obtained from the LIDAR device 12. Other blade features may equally be used for monitoring the pitch angle, including natural features and/or markers located on the blades 6.

Blade deflection, blade twist, blade vibration and blade loading information may also be derived in dependence on the 3-dimensional images generated by the LIDAR device 12 using techniques similar to those described above in connection with tower monitoring.

The control module 11 is further configured to perform structural health monitoring in order to detect damage to the tower 2 and the blades 6 of the wind turbine 1 (including wear and missing/incorrectly installed components). For example, damage to the tower 2 may be detected by identifying abnormal tower shapes, sudden changes in the shape of the tower and abnormal tower oscillation states. Abnormal tower shapes may be identified by comparing the shape of the tower 2 as measured by the LIDAR device 12 with one or more reference shapes stored for the tower 2. Similarly, damage to a blade 6 may be detected by identifying abnormal blade shapes, sudden changes in blade shape and abnormal blade oscillation states; and abnormal blade shapes may be identified by comparing the shape of a blade 6 as measured by the LIDAR device 12 with one or more reference shapes stored for the blades 6. Missing or incorrectly installed components such as flaps, vortex generators and other aero add-ons may also be identified in dependence on the measured outline or contour of a blade 6.

Surface damage and wear to the tower 2 and the blades 6 may also be detected based on changes in the reflectivity of damaged or worn regions of the tower and blades. For example, the leading edge of each blade 6 is provided with a protective coating layer that is more reflective than the underlying surface of the blade 6,

DK 2017 70693 A1 resulting in a region of increased brightness in the 3-dimensional images generated by the LIDAR device 12. Damage and wear to the leading edge coating layers results in changes to the reflectivity of the leading edges of the blades 6. The control module 11 is therefore able to detect damage and wear to the leading edges of the blades 6 based on the 3-dimensional images generated by the LIDAR device 12 by identifying changes in the reflectivity of the leading edges over time and/or by detecting deviations from an expected reflectivity for a particular region of a leading edge. Damage and wear to other portions of the wind turbine 1 (including the tower 2) may also be detected in an equivalent manner.

The accumulation of ice and dirt on the tower 2 and blades 6 also result in changes to the contour and reflectivity of the tower 2 and blades 6, and the control module 11 is also able to detect the presence of ice and dirt in dependence on changes to the contour and/or reflectivity of the tower 2 and blades 6 as measured using the LIDAR device 12.

The control module 11 is configured to output a warning notification if damage or a significant build-up of ice or dirt is detected.

The various parameters monitored by the control module 11 as described above may be used in many different turbine monitoring and control functions. For example, the control module 11 may be configured to output a control signal setting a torque or power output demand or a pitch angle or yaw angle demand in dependence on one or more of the above-described parameters derived from the 3-dimensional images in order to limit tower deflection, tower loading, tower oscillation, tilt moment, yaw moment, yaw error angle, yaw speed, blade tip clearance, rotor speed, blade tip speed, blade deflection, blade twist, blade loading and/or blade vibration to within acceptable boundaries. In addition, the deflection and oscillation states of the tower 2 and the blades 6 may be used in structural health monitoring of the wind turbine 1, as described above.

In the above-described embodiment the control system 10 comprises a single 3dimensional scanning device 12 located on the underside of the nacelle 3 of the wind turbine 1 and facing towards the ground G. However, in other embodiments the 3dimensional scanning device may equally be in a different location. For example, a

DK 2017 70693 A1 control system according to the present invention may equally include a 3-dimension scanning device mounted to the tower, for example adjacent to the top end of the tower and facing downwardly towards the ground, or adjacent to the base of the tower and facing upwardly towards the nacelle. Alternatively, the 3-dimensional scanning device may be mounted separately to the wind turbine, for example adjacent to the base of the tower and facing upwardly towards the nacelle.

In other embodiments the control system may equally include a plurality of 3dimensional scanning devices associated with a single wind turbine, for example at least one scanning device mounted to the nacelle, at least one scanning device mounted to the tower and at least one scanning device mounted separately to the wind turbine. The multiple scanning devices may each generate separate 3-dimensional images, which may be used separately or in combination for monitoring operation of the wind turbine.

It will be appreciated that many other modifications may be made to the abovedescribed embodiments without departing from the scope of the present invention as defined in the accompanying claims.

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Claims

1) A control system for a wind turbine, wherein the control system is configured to:

a. obtain 3-dimensional images of an exterior portion of the wind turbine and/or a ground region adjacent to a base of the wind turbine from a 3dimensional scanning device associated with the wind turbine; and

b. monitor the wind turbine and/or control operation of the wind turbine in dependence on the 3-dimensional images obtained from the 3dimensional scanning device.

2) A control system according to claim 1, wherein the control system is configured to monitor one or more of: tower deflection, tower loading and tower oscillation in dependence on the 3-dimensional images.

3) A control system according to claim 1 or claim 2, wherein the control system is configured to monitor one or more of: nacelle yaw angle, nacelle yaw speed, nacelle yaw moment, yaw error angle, nacelle tilt angle and nacelle tilt moment in dependence on the 3-dimensional images.

4) A control system according to any preceding claim, wherein the control system is configured to monitor one or more of: blade tip clearance, rotor azimuth angle, rotor speed, rotor acceleration, blade tip speed, blade tip acceleration, blade pitch angle, blade deflection, blade twist, blade loading and blade vibration in dependence on the 3-dimensional images.

5) A control system according to any preceding claim, wherein the control system is configured to detect damage to at least one of the tower, the nacelle, the rotor and the blades in dependence on the 3-dimensional images.

6) A control system according to any preceding claim, wherein the control system is configured to monitor the presence of ice and/or dirt on at least one of the tower, the nacelle, the rotor and the blades in dependence on the 3dimensional images.

7) A control system according to any preceding claim, wherein the control system is configured to control operation of the wind turbine in order to limit one or more of: tower deflection, tower loading, tower oscillation, tilt moment, yaw

DK 2017 70693 A1 moment, yaw error angle, yaw speed, blade tip clearance, rotor speed, blade tip speed, blade deflection, blade twist, blade loading and blade vibration in dependence on the 3-dimensional images.

8) A control system according to any preceding claim, wherein the control system is configured to compare the 3-dimensional images with at least one reference model of at least a portion of the wind turbine, and to monitor at least one operating parameter in dependence on the comparison.

9) A control system according to any preceding claim, wherein the control system is configured to identify one or more recognisable target features in the 3dimensional images, and to monitor at least one operating parameter in dependence on the position(s) of the recognised target feature(s).

10) A control system according to any preceding claim, further comprising at least one 3-dimensional scanning device configured to generate the 3-dimensional images.

11) A control system according to claim 10, wherein the scanning device is a LIDAR scanning device.

12) A control system according to claim 10 or claim 11, wherein the scanning device is mounted to the nacelle of the wind turbine.

13) A control system according to claim 10 or claim 11, wherein the scanning device is mounted to the tower of the wind turbine.

14) A control system according to claim 10 or claim 11, wherein the scanning device is mounted separately to the wind turbine.

15) A control system for a wind turbine, wherein the control system is configured to:

a. obtain 3-dimensional images of an exterior portion of the wind turbine and/or a ground region adjacent to a base of the wind turbine from a 3dimensional scanning device mounted to the nacelle of the wind turbine; and

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16) A method of monitoring a wind turbine and/or controlling operation of a wind turbine, the method comprising steps of: obtaining at least one 3-dimensional image of an exterior portion of the wind turbine and/or a ground region adjacent 5 to a base of the wind turbine from a 3-dimensional scanning device associated with the wind turbine; and monitoring the wind turbine and/or controlling operation of the wind turbine in dependence on the 3-dimensional image(s) obtained from the 3-dimensional scanning device.

10 17) A non-transitory computer readable storage medium comprising computer readable instructions for a computer processor to carry out the method of claim 16.

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