DK179188B1

DK179188B1 - Wind turbine and a method of operating a wind turbine

Info

Publication number: DK179188B1
Application number: DKPA201670502A
Authority: DK
Inventors: Matthew Summers
Original assignee: Envision Energy (Jiangsu) Co Ltd
Priority date: 2016-07-06
Filing date: 2016-07-06
Publication date: 2018-01-22
Also published as: DK201670502A1; WO2018006849A1

Abstract

The present invention relates to a wind turbine, a wind turbine farm, and a method of operating a wind turbine. The wind turbine comprises a wind turbine tower and a nacelle with a rotor. A yaw control system is used to yaw the nacelle relative to the wind turbine tower in order to correct any yaw errors. A first parameter is measured on the wind turbine and used to determine a first yaw angle for maximum power production. A second parameter is measured on a unit positioned separately from the wind turbine which is then transmitted to the wind turbine. The second parameter is used to determine a second yaw angle for maximum power production. The yaw error is determined using the first and second yaw angles and a corrective yaw action is triggered if the yaw error exceeds a threshold.

Description

<¹θ> DANMARK (10)

<¹²> PATENTSKRIFT

Patent- og

Varemærkestyrelsen (51) Int.CI.: F03D 7/02(2006.01) (21) Ansøgningsnummer: PA 2016 70502 (22) Indleveringsdato: 2016-07-06 (24) Løbedag: 2016-07-06 (41) Aim. tilgængelig: 2018-01-08 (45) Patentets meddelelse bkg. den: 2018-01-22 (73) Patenthaver: Envision Energy (Jiangsu) Co. Ltd, No. 3 Shenzhuang Road, Shengang Street, Jiangyin 214443, Kina (72) Opfinder: Matthew Summers, 320 Jackson Hill St. Apt. 205, TX-77007 Houston, Texas, USA (74) Fuldmægtig: Patrade A/S, Fredens Torv 3A, 8000 Århus C, Danmark (54) Benævnelse: Wind turbine and a method of operating a wind turbine (56) Fremdragne publikationer:

EP 2213873 A1 US 2011/0101691 A1 US 2010/0066087 A1 (57) Sammendrag:

Fortsættes ...

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Wind turbine and a method of operating a wind turbine

Field of the Invention

The present invention relates to a wind turbine and a method of operating a wind turbine, comprising a wind turbine tower, a nacelle arranged on top of the wind turbine tower, and a rotor comprising a rotatable hub with at least two wind turbine blades arranged relative to the nacelle, the wind turbine further comprises a yaw bearing unit arranged between the nacelle and the wind turbine tower, a yaw mechanism configured to yaw the nacelle relative to the wind turbine tower, and a yaw control system configured to align the nacelle relative to a wind direction. The method and the yaw control system comprise the steps of: measuring at least one first parameter of said wind turbine, determining a first yaw angle based on said at least one first parameter, the first yaw angle being indicative of a maximum power production for the wind turbine, and determining a yaw error of the wind turbine.

The present invention further relates to a wind turbine farm comprising at least one unit and a first wind turbine, the first wind turbine comprises at least one first sensor configured to measure at least one first operating parameter, the at least one unit comprises at least one second sensor configured to measure at least one second parameter.

Background of the Invention

It is well known in the wind turbine industry to yaw the nacelle and, thus, the rotor relative to the wind direction using sensor data indicative of the wind direction, wind speed, air density and other relevant data. Conventional wind turbines comprise a wind vane or a similar sensor for measuring the wind direction and which is placed on top of the nacelle and, thus, downwind relative to the wind turbine blades of the rotor.

A known problem is that the wind turbine is often operated with a suboptimal yaw error due to issues with the calibration or the mounting of such wind direction sensors or due to the complexity of the airflow around the wind turbine. Another known problem with such wind direction sensors is that the sensor output tends to drift over time and, thus, regular tests are required to determine if recalibration is required. Secondly, the optimal position for maximum power production may not be to align the rotation axis of the rotor with the wind direction due to wind shears, wind veers or the wake effect from an upwind wind turbine. This means that the wind turbine is often not placed in an optimal position for producing a maximum power output, and thus power is lost due to this non-optimal position.

Thirdly, it is known to measure the wind speed with an anemometer placed on the nacelle, wherein the measured signal is frequently biased as function of the yaw error. Using this anemometer signal to calculate an optimal position will often result in an incorrect yaw angle, since the wind speed may appear smaller with larger yaw error while the estimated rotor efficiency may appear larger with larger yaw error when it is in fact smaller.

One way to solve this problem is to mount additional sensors to the wind turbine in order to detect and correct the position of the wind turbine. EP 2653722 A1 discloses a wind turbine wherein additional two sensors, each measuring a stagnation pressure or wind velocity, are placed at the opposite sides on the front of the hub. The difference between the two measurements, alternatively a yaw error is determined based on the measurements, is used by the controller to correct the yaw angle of the nacelle. EP 2182205 BI discloses a similar solution, but wherein the two sensors are mounted on opposite sides of the nacelle housing.

US 2014/0186176 A1 discloses a wind turbine with additional two pressure sensors mounted within the front end of the hub and connected to a very accurate pressure sensor, wherein a yaw error is determine based on the differential pressure. An existing yaw angle sensor provides a reference yaw angle which is used by the controller to yaw the nacelle in order to correct the yaw error.

All the above mentioned solutions require the use of additional sensors mounted to the wind turbine which adds to the total costs for each wind turbine in a wind turbine farm as well as the total installation costs. The above-mentioned solutions also introduce new risks for an error in the wind turbine operation due to the failure or malfunction of a sensor.

In the article “A novel intelligent approach for yaw position forecasting in wind energy systems”, Mehmet Yesilbudak, et al., a forecasting system for estimating the yaw angle of a 2 MW wind turbine within time intervals of 10 minutes is proposed. Six different parameters are used as input for the controller which uses a k-nearest neighbour classifier algorithm to analyse the historical data. The result of this knearest neighbour classifier algorithm is evaluated using a Euclidean distance metric algorithm, a Manhattan distance metric algorithm and a Minkowski metric algorithm in order to determine the combination of selected parameters and selected distance metric algorithm that provide the most accurate result.

It is suggested that this algorithm can be implemented in a real-time yaw control system, however, further details about how to implement the algorithm are not provided. It is not clear from the article which of the 2, 3, 4, 5 and 6 inputs combined with which distance metric algorithm provide the best result and, thus, should be implemented in the yaw control system. This article aims to improve the yaw control by attempting to forecast future yaw movements based on historical data measured solely on the wind turbine.

Patent application EP 2213873 Al describes a method of operating a wind turbine comprising a yaw control mechanism and discloses a method that relies on measuring a first parameter of the wind turbine, determining a first maximum rotor efficiency based on the first parameter and then determining a yaw error of the wind turbine.

Object of the Invention

An object of the invention is to provide a yaw control system and a method that does not require an installation of additional sensors and measurement thereof.

Another object of the invention is to provide a yaw control system and a method capable of improving the accuracy of the yaw control.

Yet another object of the invention is to provide a yaw control system and a method capable of determining the yaw angle which yields the maximum power output.

Another object of the invention is to provide a yaw control system and a method capable of verifying the alignment of the nacelle relative to the wind direction.

Description of the Invention

An object of the invention is achieved by a method of operating a wind turbine, comprising a wind turbine tower, a nacelle arranged on top of the wind turbine tower, a rotor comprising a rotatable hub with at least two wind turbine blades arranged relative to the nacelle, the wind turbine further comprises a yaw bearing unit arranged between the nacelle and the wind turbine tower, a yaw mechanism configured to yaw the nacelle relative to the wind turbine tower, and a yaw control system configured to align the nacelle relative to a wind direction, wherein the method comprises the steps of:

measuring at least one first parameter of said wind turbine, determining a first maximum rotor efficiency of the wind turbine based on said at least one first parameter, determining a yaw error of the wind turbine, characterised in that the method further comprises the steps of:

measuring at least one second parameter of at least one unit separate from the wind turbine, determining a second maximum rotor efficiency of the wind turbine based on said at least one second parameter, wherein the yaw error is determined based on the at least first maximum rotor efficiency and the at least second maximum rotor efficiency.

This provides a yaw control method that does not involve measurements using additional sensors mounted on the wind turbine. The present yaw control method provides an alternative solution for improving the accuracy of the yaw control compared to other conventional yaw control methods. This allows the wind turbine to be yawed relative to the wind direction so that it is properly aligned with a yaw angle for maximum power production. The present configuration can also be used to determine if a correction of the measured signal of the wind data sensor located on the wind turbine is required or not.

The present yaw control method can suitably be implemented as a control algorithm in any horizontal axis wind turbines, including variable speed wind turbines. The wind turbine communicates with at least one separate unit, i.e. one unit, in order to at least receive a measurement of at least a second parameter carried out on this separate unit. This allows the alignment of the wind turbine to be verified or corrected using measurements carried out separately from the wind turbine.

The present control algorithm can suitably be activated at any wind speed above a cutin wind speed and a cut-out wind speed. If the rotor in the event of an emergency situation, or for other reasons, is placed in a standstill, e.g. by using a rotor brake system, or otherwise idling, the present control algorithm should not be activated. The present yaw control method may use a common set of first and/or second parameters for wind speeds between the cut-in wind speed and a rated wind speed and for wind speeds between the rated wind speed and the cut-out wind speed. Alternatively, a first set of first and/or second parameters may be used for wind speeds between the cut-in wind speed and the rated wind speed while a second set of first and/or second parameters may be used for wind speeds between the rated wind speed and the cut-out wind speed. This allows the yaw control to be adapted to a particular wind turbine configuration in order to further improve the accuracy of the yaw control.

According to one embodiment, the at least one second parameter is measured within a wind turbine farm, wherein at least said wind turbine is arranged in the wind turbine farm.

One or more second parameters are suitably measured within or relative to a wind turbine farm in which the wind turbine is situated. The separate unit or units in question may be positioned inside the same wind turbine farm or positioned relative to the wind turbine farm.

Said second parameters may be measured on the same separate unit and then transmitted to a yaw control system in the wind turbine and/or a remote monitoring station. Alternatively, said one or more second parameters may be measured on two or more separate units each positioned relative to the wind turbine, wherein each set of measurements may be transmitted to the yaw control system in the wind turbine and/or the remote monitoring station. The yaw control system/remote monitoring station may subsequent process and analyse the individual sets of measurements in order to determine one or more yaw angles indicative of one or more nacelle orientations in which a maximum power production can be achieved. The alignment of a selected wind turbine or the measurement of a selected wind data sensor can thus be verified or corrected using any number of separate units.

The second parameter may in example, but not limited to, be an operating parameter or a meteorological parameter which is used to operate the wind turbine farm or a wind turbine thereof. The second parameter may be selected dependent on the particular configuration of the wind turbine, the particular configuration of the separate unit and/or the layout of the wind turbine farm. The present yaw control may thus be performed using existing measurements already available in the wind turbine farm.

According to one embodiment, the at least one second parameter is an operating parameter and the at least one unit is at least a second wind turbine.

The selected second parameter may be any operating parameter measured directly on the second wind turbine and which relates to the operation of that second wind turbine. The first parameter may also be an operating parameter, wherein said first and second operating parameters are the same or different operating parameters. This allows the second operating parameter to be selected according to the particular configuration of the second wind turbine.

In example, but not limited to, the first and/or second operating parameter may be a rotor speed, a rotor torque, a power output, the nacelle orientation (i.e. the yaw angle thereof), a wind direction, a wind speed, a turbulence metric, inflow angles, a wind shear metric, an ambient air temperature, an ambient air pressure, a pitch angle of a wind turbine blade, or other suitable operating data.

This allows the actual yaw angle, e.g. the first yaw angle, of a selected wind turbine to be verified or corrected using adjacent or nearby wind turbines. Optionally, the measurement of the adjacent or nearby wind turbines can be used to determine if the wind data sensor measurement is within acceptable limits or if a correction is required.

According to one embodiment, the at least one second parameter is a meteorological parameter and the at least one unit is at least a met mast, or the at least one second parameter is an operating parameter and the at least one unit is at least a substation.

The selected second parameter may be any meteorological parameter measured separately from the wind turbine and which indirectly relates to the operation of that wind turbine. This is suitable if the wind turbine farm comprises a met mast.

In example, but not limited to, the second meteorological parameter may be a wind direction, a wind speed, an air density, an ambient air temperature, an ambient air pressure, a humidity, a turbulence metric, a wind shear metric, wind gusts, inflow angles, or other suitable wind data.

The selected second parameter may also be another operating parameter measured separately from the wind turbine and which directly or indirectly relates to the operation of that wind turbine. This is suitable if the wind turbine farm comprises a substation.

In example, but not limited to, said another operating parameter may be a power output, a power efficiency, or other suitable power data.

This allows the actual yaw angle of a selected wind turbine to be verified or corrected using a nearby met mast or substation. The measurement of the adjacent or nearby met mast or substation can also be used to determine if the wind data sensor measurement is within acceptable limits or if a correction is required.

According to one embodiment, said at least one first parameter comprises wind data, the wind data being measured relative to said rotor.

One or more first parameters are suitably measured within or relative to the wind turbine, e.g. the selected wind turbine. Said one or more first parameters may be meteorological parameters, operating parameters, or a combination thereof

The selected first parameter may be a meteorological parameter, e.g. wind data, which relates to the operation of that wind turbine. The first and second meteorological parameters may be the same or different meteorological parameters. The wind data may be measured relative to the nacelle and, thus, downwind relative to a rotor plane. Alternatively, the wind data may be measured upwind relative to the rotor plane. This allows the desired wind direction in which a maximum power production can be achieved, e.g. the yaw angle thereof, to be estimated more accurately using measurements from the separate unit or units.

In example, but not limited to, the first meteorological parameter may be a wind direction, a wind speed, an air density, an ambient air temperature, an ambient air pressure, a humidity, a turbulence metric, a wind shear metric, wind gusts, inflow angles, or other suitable wind data.

This configuration is particularly suitable if the wind turbine comprises a wind data sensor in the form of an anemometer arranged on the nacelle, since the measured wind data is used to determine an operating set point, e.g. yaw angle, for operating the wind turbine.

In one embodiment, at least one of said at least one first parameter and said at least one second parameter comprises a combination of wind data and power data.

In a particular configuration of the present yaw control method, the first parameter may comprise a combination of wind data and power data, such as wind direction or yaw angle combined with rotational speed or power output. The second parameter may in this particular configuration comprise power data, such as power output or rotational speed, or wind data, such as wind speed. Other combination of power data and wind data can be used for the first and/or second parameter.

In example, the second parameter may comprise a combination of wind data and power data while the first parameter may comprise power data and, optionally, also wind data.

According to one embodiment, said at least second maximum rotor efficiency is determined by applying a regression algorithm to the at least one second parameter and evaluating the output of the regression algorithm.

The first parameters, e.g. the first operating or environmental parameter, may be initially processed and filtered before being further processed in the yaw control system. The yaw control system may use any suitable algorithm or techniques to determine a yaw angle, i.e. first yaw angle, indicative of a maximum power production for the wind turbine, i.e. the first wind turbine. In example, but not limited to, the first yaw angle may simply be determined as a mean or median distribution of the measured wind direction. Alternatively, the machine learning algorithm or regression algorithm described below, or a different machine learning algorithm or regression algorithm, may also be used to estimate the first rotor efficiency as function of the reference parameter. This first rotor efficiency may subsequently be used to determine the first yaw angle. This yaw angle may then be used as an operating set point for aligning the nacelle relative to the wind direction.

The second parameters, e.g. the second operating or environmental parameter, may be suitably processed and analysed in order to estimate the rotor efficiency, i.e. the second rotor efficiency, as function of the same or a different reference parameter. A regression algorithm may be applied to the measured second parameter or parameters. The regression algorithm may in example, but not limited to, be a nearest neighbour algorithm, a random forest, a neural network, or another suitable regression algorithm. Said nearest neighbour algorithm may be a k-nearest neighbour algorithm, a radius based nearest neighbour algorithm, or a combination thereof. The output of the regression algorithm may subsequently be evaluated in order to determine another yaw angle, i.e. second yaw angle, indicative of a maximum power production for the wind turbine, i.e. the first wind turbine. This second yaw angle and the first yaw angle may be used to determine or calculate a yaw error indicative of the angular difference between these two operating set points, as described later.

The above-mentioned machine learning algorithm may be used to generate at least one estimated output value for each data point in time, thus creating a set of output values for all the measured data points. This set of output values, e.g. the first and/or second rotor efficiency, may then be evaluated in order to determine the data point indicative of the maximum power production for the wind turbine, i.e. the first wind turbine, and thus the first and/or second yaw angle. The output of the regression algorithm may be evaluated by applying a distance metric algorithm, a decision tree, a neural network, or another suitable evaluation algorithm. This second yaw angle can thus be used to confirm or verify the current alignment of the nacelle relative to the wind direction and/or to determine if a correction of the wind data sensor is required.

The above-mentioned reference parameter used to estimate the first and/or second rotor efficiency may in example, but not limited to, be the wind direction, the wind speed, or another suitable reference parameter. The reference parameter may be measured in or on the wind turbine or separate from that wind turbine.

The first and/or second rotor efficiency may in example, but not limited to, be measured as a power output, a rotational speed of the rotor, or another suitable parameter indicative of the rotor efficiency. Optionally, the first and/or second rotor efficiency may be estimated as function of the power output, the rotational speed and/or the wind speed.

According to one embodiment, the method further comprises at least the step of:

comparing the yaw error to a threshold, and yawing the nacelle into alignment relative to the wind direction when said yaw error exceeds the threshold, or comparing the yaw error to said threshold, and transmitting an output signal to a wind turbine operator when said yaw error exceeds the threshold.

The yaw error may simply be determined as the angular difference between the first and second yaw angles, alternatively in relation to the wind direction. This yaw error may be compared to a threshold value in order to determine if an event should be triggered. The threshold value may define a range in both yaw directions in which no π

corrective yaw action is applied to the wind turbine. The threshold value may be selected between 1 degree and 10 degrees in either direction.

Alternatively, the yaw error may be determined by performing a suitable statistical analysis of the first and second yaw angles and, optionally, of the wind direction. In example, but not limited to, a confidence interval algorithm, a Bayesian interval algorithm, or another suitable interval estimation algorithm may be applied to the data points of the first and second yaw angles and e.g. the wind direction. Suitable lower and upper limit values, e.g. thresholds, may be applied to the output of this interval estimation algorithm, wherein said lower and upper limit values are indicative of the above-mentioned range. The lower and upper limit values may be defined as a confidence range between 90% and 99%.

The yaw control system may generate an output signal, e.g. a binary one, triggering an event if the yaw error exceeds the threshold value in one direction or falls outside the range defined by the lower and upper limit values. The output signal may further trigger the calculation of a corrective yaw angle as function of the determined yaw error.

The output signal may simply be transmitted to an operator of the wind turbine or the wind turbine farm. The output signal may trigger an alarm, e.g. a visual alarm and/or an acoustic alarm, notifying the operator that a corrective yaw action is required. Optionally, the corrective yaw angle may further be transmitted and displayed to the operator. The operator may thus manually determine the required corrective yaw action, e.g. transmit a suitable control signal to the yaw control system, so that the nacelle is brought into alignment again. The output signal may alternatively notify the operator that a correction of the wind data sensor on the wind turbine is required. The corrective yaw angle may indicate the amount of correction required to bias the measured signal of the wind data sensor. This allows the operator to determine the desired corrective action, wherein the operator may remotely correct the yaw angle or send a worker to fix the wind data sensor.

The output signal may alternatively trigger the activation of a yaw mechanism in the wind turbine, wherein the corrective yaw angle may be applied to the nacelle by operating the yaw mechanism accordingly. The operation of the yaw mechanism may be controlled by a controller, e.g. a microprocessor, a logic circuit, or another suitable controller in the yaw control system. This allows the yaw control system to automatically yaw the nacelle into alignment when a yaw error is detected.

An object of the invention is also achieved by a wind turbine comprising a wind turbine tower, a nacelle arranged on top of the wind turbine tower, a rotor comprising a rotatable hub with at least two wind turbine blades arranged relative to the nacelle, the wind turbine further comprises a yaw bearing unit arranged between the nacelle and the wind turbine tower, a yaw mechanism configured to yaw the nacelle relative to the wind turbine tower, and a yaw control system configured to align the nacelle relative to a wind direction, wherein the wind turbine further comprises at least one first sensor configured to measure at least one first parameter, the yaw control system is further configured to determine a first maximum rotor efficiency of the wind turbine based on said at least one first parameter, characterised in that the yaw control system is configured to receive a measurement of at least one second parameter from at least one unit positioned separately from the wind turbine, the yaw control system is configured to a second maximum rotor efficiency of the wind turbine based on said at least one second parameter, wherein the yaw control system is configured to determine a yaw error based on the first maximum rotor efficiency and the second maximum rotor efficiency.

This provides a wind turbine with an improved yaw control system which eliminates the need for installing additional sensors at the nacelle or at the hub. This provides an alternative solution for improving the accuracy of the yaw control which, in turn, allows for an increased power production. The present yaw control system enables an optimal yaw angle for maximum power production to be determined, even if this optimal yaw angle is not perpendicular to the wind direction. The nacelle and, thus, the rotor can subsequently be positioned and yawed to this yaw angle. The present yaw control system also allows the second yaw angle to be used to determine if a correction of the wind data sensor is required or not.

The wind turbine is a horizontal axis wind turbine, e.g. a variable speed wind turbine, with at least two, e.g. three, wind turbine blades. The wind turbine has a yaw system arranged relative to the wind turbine tower and the nacelle. The yaw system comprises a yaw bearing unit, such as a ball bearing, a roller bearing, or a friction bearing, connected to the wind turbine tower and the nacelle respectively. The yaw system further comprises a yaw mechanism, such as a yaw motor or another suitable yaw mechanism, positioned relative to the yaw bearing. The yaw system is connected to a yaw control system configured to control the yawing of the nacelle.

According to one embodiment, the at least one second parameter is an operating parameter or a meteorological parameter, wherein the yaw control system is configured to determine the second maximum rotor efficiency based on said operating parameter or meteorological parameter.

The wind turbine comprises at least one communications module configured to communicate with a corresponding communications module in one or more separate units and/or a corresponding communications module in a remote monitoring station. The communications module may be a SCADA link, a wired connection, or a wireless connection. This enables the wind turbine at least to receive the measurement of the second parameter from one or more separate units.

The wind turbine, i.e. the first wind turbine, may be communicating with at least a second wind turbine positioned relative to the first wind turbine. Alternatively, the first wind turbine may communicate with multiple second wind turbines and, thus, receive individual measurements of a second parameter from each of the second wind turbines. The individual measurements may subsequently be processed and analysed in order to determine a common rotor efficiency or individual rotor efficiencies. This common rotor efficiency or individual rotor efficiencies may be used to determine the second yaw angle indicative of a maximum power production as described above. The first and second wind turbines may have same capacity or same rotor size, alternatively different capacities or rotor sizes. This allows the first maximum rotor efficiency and, thus, the first yaw angle to be verified or corrected using one or more second wind turbines.

Alternatively, the separate unit may be a met mast (meteorological mast) or a substation arranged inside or relative to the wind turbine farm. The substation may be a collector substation, a transmission substation, a switching substation, a distribution substation, or another suitable substation. The separate unit may thus measure at least one meteorological parameter, e.g. wind data, or at least one operating parameter, e.g. power data, which is then used to determine the second maximum rotor efficiency and, thus, the second yaw angle. This also allows the first maximum rotor efficiency and, thus, the first yaw angle to be verified or corrected.

According to one embodiment, the at least one first sensor is a wind data sensor mounted on the nacelle, wherein said wind data sensor is configured to measure wind data.

One or more first and/or second sensors may suitably be used to directly measure the first and/or second operating parameter, alternatively the first and/or second parameter may be derived from the measured signal of said one or more first and/or second sensors. The first and/or second sensor may be an operation data sensor in example, but not limited to, a torque sensor, an angular sensor, an accelerometer, a pressure sensor, a strain gauge, a temperature sensor, a power sensor, a rotational speed sensor, or another suitable first sensor. This allows the first and/or second sensor to measure one or more selected operating parameters which, in turn, are used to estimate the first and/or second rotor efficiency. A maximum first and/or rotor efficiency is then determined based on this estimated first and/or second rotor efficiency.

The first and/or second wind turbine may in example comprise a wind data sensor, such as a wind vane, a LIDAR, an anemometer or another suitable wind data sensor, arranged inside the nacelle or positioned on exterior of the nacelle. This wind data sensor may be configured to measure wind data, e.g. at least one meteorological parameter, on the first and/or second wind turbine. This wind data may then be used to determine the first and/or second maximum rotor efficiency and, thus, the first and/or second yaw angle as described above.

The met mast, or the substation, may comprise a second sensor in the form of a LIDAR, a SODAR, an anemometer, or another suitable wind data sensor. The wind data sensor may be configured to measure wind data, e.g. at least one meteorological parameter, which may then be used to determine the second maximum rotor efficiency and, thus, the second yaw angle.

The first wind turbine may comprise at least one other sensor configured to measure a reference parameter which is used by the yaw control system to determine the first and/or second rotor efficiency as function of this reference parameter. The reference parameter may also be used as a selected first parameter for the present yaw control system. Alternatively, the reference parameter may differ from the selected first parameters used in the present yaw control system.

According to one embodiment, the yaw control system is configured to determine said second maximum rotor efficiency by applying a regression algorithm to at least one second parameter and evaluating the output of the regression algorithm.

The yaw control system may be configured to store the historical data of the first parameter and/or the second parameter in one or more local databases for subsequent analysis. Alternatively, the historical data may be stored in an external database. This historical data can be accessed by the yaw control system and/or by the remote monitoring system and then processed and analysed in order to determine the first and/or second yaw angle as described above.

The first and/or second parameter may be measured over a predetermined time period, preferably over a relatively long time period, e.g. one or more months, in order to establish a sufficient amount of data for use in the yaw control system.

The yaw control system may be configured to apply a regression algorithm to the historical data of at least the second parameter, wherein the output of the regression algorithm is evaluated in order to estimate the second rotor efficiency. A second maximum rotor efficiency may then be determined and, thus, a second yaw angle may be determined based on this second maximum rotor efficiency. This allows the alignment of the wind turbine to be verified or corrected by means of measurements carried out separately from the first wind turbine.

The machine learning algorithm, e.g. regression algorithm, implemented in the yaw control system may further be evaluated by applying a suitable evaluation algorithm in order to determine the yaw angle, e.g. second yaw angle, indicative of a nacelle orientation for maximum power production. This second yaw angle can thus be used to confirm or verify the current alignment of the nacelle relative to the wind direction and/or to determine if a correction of the wind data sensor is required.

The yaw control system may be configured to determine the first rotor efficiency based on the first parameter using any known techniques. Alternatively, the abovementioned machine learning algorithm or regression algorithm may also be used to estimate the first rotor efficiency. A first maximum rotor efficiency may then be determined based on this first rotor efficiency.

According to one embodiment, the yaw control system is configured to compare the yaw error to a threshold and generate an output signal when the yaw error exceeds the threshold.

One or more threshold values may be stored in the yaw control system and used to determine if a yaw correction action is needed. The yaw control system may simply calculate a yaw error as the difference between the first yaw angle and the second yaw angle, alternatively in relation to the wind direction. The yaw control system may further be configured to compare this yaw error to the threshold value. If the yaw error is below the threshold value, then no yaw correction action is initiated. If the yaw error is above the threshold value, then a yaw correction action is initiated.

Alternatively, the yaw control system may be configured to apply a suitable interval estimation algorithm to the data points of the first and second yaw angles. The yaw control system may further be configured to analyse the output of the interval estimation algorithm in order to determine the yaw error. Lower and upper limit values may be used as thresholds for determining when a yaw corrective action is required. If the yaw error is within the range defined by the lower and upper limit values, then no yaw correction action is initiated. If the yaw error is outside this range, then a yaw correction action is initiated.

The yaw control system may be configured to generate an output signal if the yaw error exceeds the threshold value in one direction or if the yaw error is outside the above-mentioned range. This output signal may be transmitted to the remote monitoring station via the communications modules. The output signal may activate a suitable alarm unit at the remote monitoring station, thus notifying the operator that a yaw action or a correction of the wind data sensor is required.

The yaw control system may further be configured to determine a corrective yaw angle based on the yaw error. This corrective yaw angle may be transmitted to the remote monitoring station, or be applied to the wind turbine by operating the yaw mechanism via the yaw control system.

An object of the invention is further achieved by a wind turbine farm comprising at least one unit and a first wind turbine, the first wind turbine comprises at least one first sensor configured to measure at least one first parameter, the at least one unit comprises at least one second sensor configured to measure at least one second parameter, characterised in that the first wind turbine is a wind turbine as described above and/or configured to be operated as described above.

The present wind turbine described above can suitably be arranged in a wind turbine farm along with other wind turbines. Said other wind turbines may also be configured to be operated as described above.

The wind turbine, i.e. the first wind turbine, is initially positioned in the first yaw angle by the yaw mechanism for producing a maximum power output. The maximum power output, i.e. the first maximum rotor efficiency, may be determined using conventional techniques, and will thus not be described in further details. The alignment of the first wind turbine may be verified by measurements carried out on one or more separate units positioned relative to the first wind turbine. This eliminates the need for additional sensors, such as a pair of pressure sensors arranged on the nacelle or the hub.

Conventional yaw control systems aim to align the nacelle so that the rotor plane is positioned perpendicularly to the wind direction. However, this position may not provide a maximum power production. This is achieved in conventional yaw control systems by only using operating parameters measured on that wind turbine. The present yaw control system enables the nacelle to be placed in any yaw angle providing a maximum power production, even if said yaw angle differs from the wind direction. This is achieved by using operating parameters measured on that wind turbine and another set of parameters measured on a separate unit.

According to one embodiment, said at least one unit is at least a second wind turbine, a met mast, or a substation, wherein said second wind turbine, met mast, or substation is positioned relative to said first wind turbine.

The measured second parameter may be analysed and evaluated in order to estimate the second maximum power output which, in turn, is used to determine the second yaw angle. This second yaw angle is then used to calculate a yaw error which, in turn, is used to determine if a corrective yaw action is needed as described above.

The present yaw control system allows operating parameters of an adjacent or nearby wind turbine to be used to verify that the first turbine is correctly aligned so that maximum power production is achieved. Also, this allows the wind data measured at the first wind turbine to be verified or corrected using wind data measured separately from the first wind turbine. This provides an alternative and less expensive solution compared to conventional yaw control systems.

The present yaw control system further enables the second yaw angle and, thus, the second estimated maximum power output to be determined using meteorological parameters measured on another wind turbine, met mast, or substation. This also allows the position and, thus, the wind data of the first turbine to be verified so that maximum power production is achieved. This also provides an alternative and less expensive solution compared to convention yaw control systems.

The present yaw control method may be implemented in all wind turbines in the wind turbine farm, wherein measurement of at least one adjacent or nearby wind turbine is used to verify the alignment of a selected wind turbine. The yaw control method described above may be repeated for each wind turbine in the wind turbine farm. This allows the total power output of the wind turbine farm to be increased.

An object of the invention is further achieved by a system comprising a remote monitoring station in communication with at least one wind turbine comprising a wind turbine tower, a nacelle arranged on top of the wind turbine tower, a rotor comprising a rotatable hub with at least two wind turbine blades arranged relative to the nacelle, the at least one wind turbine further comprises a yaw bearing unit arranged between the nacelle and the wind turbine tower, a yaw mechanism configured to yaw the nacelle relative to the wind turbine tower, and a yaw control system configured to align the nacelle relative to a wind direction, wherein the at least one wind turbine further comprises at least one first sensor configured to measure at least one first parameter, the remote monitoring station is configured to determine a first maximum rotor efficiency of the at least one wind turbine based on said at least one first parameter, characterised in that the remote monitoring station is further in communication with at least one unit positioned separately from the at least one wind turbine, wherein the at least one unit comprises at least one second sensor configured to measure at least one second parameter, the remote monitoring station is configured to determine a second maximum rotor efficiency of the at least one wind turbine based on said at least one second parameter, wherein the remote monitoring station is further configured to determine a yaw error based on the first maximum rotor efficiency and the second maximum rotor efficiency, and optionally to transmit a corrective action to the yaw control system of the at least one wind turbine if the yaw error exceeds a threshold.

Alternatively, the processing and the analysis of at least the second parameter may be performed in a control system in the remote monitoring station, wherein the separate unit may transmit the measurement of the second parameter to the control system. The control system may store and subsequently analyse the second parameter in order to determine a second maximum rotor efficiency and, thus, a second yaw angle as described above. The control system may also determine the yaw error and, optionally, the corrective yaw angle as described above.

The processing and the analysis of the first parameter may further be performed in the control system, wherein the wind turbine may transmit the measurement of the first parameter to the control system. The control system may store and subsequently analyse the first parameter in order to determine a first maximum rotor efficiency and, thus, a first yaw angle as described above. Alternatively, the first rotor efficiency may be measured on the wind turbine and then transmitted to the control system.

This allows the operator in the remote monitoring station to monitor and control the yaw movement of a selected wind turbine based on a yaw error calculated in the control system of the monitoring station. The operator is also able to determine if the measured signal of the wind data sensor of the selected wind turbine is within acceptable limits or not.

The invention is not limited to the embodiments described herein, and thus the described embodiments can be combined in any manner without deviating from the objections of the invention.

Description of the Drawing

The invention is described by example only and with reference to the drawings, wherein:

Fig. 1 shows a first embodiment of a wind turbine frame,

Fig. 2 shows a second embodiment of a wind turbine frame,

Fig. 3 shows an exemplary embodiment of a yaw control system according to the invention,

Fig. 4 shows an exemplary flowchart of a yaw control method according to the invention,

Fig. 5 shows a first exemplary graph of the first and second power outputs as function of the yaw angle, and

Fig. 6 shows a second exemplary graph of the first and second yaw angles.

In the following text, the figures will be described one by one and the different parts and positions seen in the figures will be numbered with the same numbers in the different figures. Not all parts and positions indicated in a specific figure will necessarily be discussed together with that figure.

Reference list

1. Wind turbine farm

2. First wind turbine

3. Second wind turbine

4. Wind turbine tower

5. Nacelle

6. Yaw bearing unit

7. Hub

8. Wind turbine blades

9. Remote monitoring station

10. Substation

11. Met mast

12. Yaw control system

13. Communications module

14. Corresponding communications module

15. Controller

16. First sensor

17. Second sensor

18. Database

19. Yaw mechanism

20. Measurement of first parameter

21. Estimation of first rotor efficiency

22. Measurement of second parameter

23. Estimation of second rotor efficiency

24. Measurement of reference parameter

25. Determination of maximum rotor efficiencies

26. Determination of a yaw error

27. Comparing yaw error with threshold

28. Calculation of corrective yaw angle

29. First rotor efficiency

30. Second rotor efficiency

31. Yaw angle

32. First yaw angle

33. Second yaw angle

34. Difference in performance

35. First solid lines, no corrective yaw action

36. Second solid lines, operating range

37. Yaw error

Detailed Description of the Invention

Fig. 1 shows a first embodiment of a wind turbine farm 1 or system comprising a first wind turbine 2 and at least a second wind turbine 3 according to the invention. Each wind turbine 2, 3 comprises a wind turbine tower 4, a nacelle 5 arranged on the wind turbine tower via a yaw bearing unit 6. A rotor comprising a hub 7 with at least two wind turbine blades 8 is rotatably connected to a drive train in the nacelle 5.

The first wind turbine 2 comprises a yaw control system (shown in fig. 3) with a communications module (shown in fig. 3) capable of communicating a corresponding communications module (not shown) in the second wind turbine 3. The yaw control system is configured to control the yaw movement of the nacelle 5 based on a yaw error. The first and second wind turbines 2, 3 are also able to communicate with a remote monitoring station 9 configured to monitor the performance of the wind turbine farm 1.

The second wind turbine 3 is positioned relative to at least the first wind turbine 2 and comprises at least one second sensor (shown in fig. 3) in the form of a wind data sensor or an operation data sensor. The second sensor is configured to measure at least one second parameter, such as a meteorological parameter, which is transmitted to the first wind turbine 2.

Fig. 2 shows a second embodiment of the wind turbine farm 1’ or system, wherein the wind turbine farm 1’ further comprises a substation 10 and/or a met mast 11. The substation 10 and/or the met mast 11 comprises a corresponding communications module (not shown) capable of communicating with at least the first wind turbine 2 via its communications module. The substation 10 and/or the met mast 11 may optionally also communicate with the remote monitoring station 9.

The substation 10 and/or the met mast 11 is positioned relative to at least the first wind turbine 2 and comprises at least one second sensor (shown in fig. 3) in the form of a wind data sensor. The second sensor is configured to measure at least one second parameter, such as a meteorological parameter, which is transmitted to the first wind turbine 2.

Fig. 3 shows an exemplary embodiment of a yaw control system 12 according to the invention arranged in the first wind turbine 2. The yaw control system 12 comprises a communications module 13 configured to communicate, e.g. via SCADA link, with a corresponding communications module 14 in the remote monitoring system 9, the second wind turbine 3, the met mast 11, and/or the substation 10.

The yaw control system 12 further comprises a controller 15 configured to control the yaw movement of the nacelle 5. The controller 15 is configured to process and analyse the measurement of the first sensor 16 and the measurement of the second sensor 17. The measurement of the second sensor 17 is transmitted to the yaw control system 12 via the respective communications modules 13, 14. The respective measurements are stored in a database 18.

The yaw control system 12, e.g. the controller 15, is configured to estimate a first rotor efficiency and a second rotor efficiency based on the measurements from the first and second sensors 16, 17. The yaw control system 12 is further configured to determine a first yaw angle and a second yaw angle for maximum power production of the first wind turbine 2 and determine a yaw error based on the first and second yaw angles as described in relation to fig 4.

The yaw control system 12 is configured to generate an output signal which triggers the activation of a yaw mechanism 19 in the first wind turbine 2. A corrective yaw angle is applied to the first wind turbine 2 via the yaw mechanism 19 if the yaw error exceeds a threshold.

Fig. 4 shows an exemplary flowchart of a yaw control method which is implemented in the yaw control system 12 of the first wind turbine 2. The yaw control method can also be implemented in a control system in the remote monitoring system 9.

A first parameter is measured 20 on the first wind turbine 2 via the first sensor 16. The first parameter is processed and analysed in the yaw control system 12 using a regression algorithm in order to estimate 21a first rotor efficiency.

A second parameter is measured 22 on a separate unit, e.g. the second wind turbine 3, the met mast 11, the substation 10, via the second sensor 17. The second parameter is processed and analysed in the yaw control system 12 by applying a regression algorithm to the signal of the second sensor 17. The output of the regression algorithm is evaluated in order to estimate 23 a second rotor efficiency.

A reference parameter, e.g. wind direction, is further measured 24 on the first wind turbine 2.

The reference parameter is used to estimate the first and second rotor efficiencies as function of this reference parameter. A first maximum rotor efficiency and a second maximum rotor efficiency is then determined 25 and a corresponding first yaw angle and a second yaw angle are determined as function of the first and second maximum rotor efficiencies.

A yaw error is then determined 26 based on the first yaw angle and the second yaw angle, e.g. using an interval estimation algorithm. The yaw error is afterwards compared 27 to a suitable threshold in order to determine if a corrective yaw action is required.

If the yaw error is below the threshold, then no corrective yaw action is initiated. If the yaw error is above the threshold, then a corrective yaw action is initiated and a corrective yaw angle is calculated 28 based on the yaw error.

The controller 15 may automatically apply the corrective yaw angle via the yaw mechanism 19. Alternatively, or additionally, an output signal may be sent to the remote monitoring and, thus, trigger an alarm. Optionally, the corrective yaw angle may further be sent to the remote monitoring station and thereby notifying the operator of the required corrective action.

Fig. 5 shows a first exemplary graph of the first rotor efficiency 29 and the second rotor efficiency 30 as function of the yaw angle 31. The x-axis shows the relative yaw angle measured in degrees and the y-axis shows the estimated performance and the air density indicative of the rotor efficiency of the first wind turbine 2.

As illustrated in fig. 5, the first yaw angle 32 is indicative of the first maximum rotor efficiency 29’ and the second yaw angle 33 is indicative of the second maximum rotor efficiency 30’. The difference between the first yaw angle 32 and the second yaw angle 33 indicates a yaw error.

The difference 34 indicates the difference in performance, e.g. power output, between the two yaw angles. This yaw error can be used to correct the alignment of the first wind turbine 2 relative to the wind direction so that it is yawed into an optimal yaw angle for maximum power production.

Fig. 6 shows a second exemplary graph of the first and second yaw angles 32, 33, wherein the first solid lines 35 indicate a range in which no corrective yaw action is applied. The second solid lines 36 indicate an operating range of the first wind turbine 2 relative to the first yaw angle 32. Here, the first yaw angle 32 is determined using known techniques, such as mean distribution of measured wind direction.

The dotted line indicates a predetermined accuracy of the yaw control used to correctly align the first wind turbine 2 relative to the wind direction in order to obtain maximum power production.

The yaw error 37 between the first yaw angle 32 and the second yaw angle 33 is used to correct the measurement of the first sensor 16.

Claims

claims

1.4. Wind turbine park (1) according to claim 13, characterized in that the at least one unit is at least one other wind turbine (3), a meteorological mast (111 or a substation go (10), wherein the second wind turbine (3), the meteorological mast (3)). 11) the eher substation (10) is positioned relative to the first wind turbine (2).

A system comprising a remote monitoring system (9) associated with at least one wind turbine (2, 3) comprising a wind turbine tower (4), a nacelle (5) arranged on top of the wind turbine tower (4), a rotor comprising one. rotatable hub with at least two wind turbine blades (8) arranged relative to the nacelle (5), the wind turbine (2,3) further comprising a bend bearing unit (6) arranged between the nacelle (5) and the wind turbine bar, a bending mechanism (19) configured to bend the nacelle (5) relative to the wind turbine barrel (4) and a bend guide system (12) configured to create the nacelle (5) relative to a wind direction, wherein the at least one wind turbine (2, 3) further comprises at least one first sensor (16) configured to measure at least one first parameter, wherein the remote monitoring station (9) is configured to determine a first maximum rotor efficiency of the at least one wind turbine based on the at least one first parameter, characterized by. that the iron monitoring station (9) is further connected with at least one unit separate from the at least one wind turbine (2, 3), wherein the at least one unit comprises at least one other sensor (17) configured to measure at least one other parameter, wherein the remote monitoring station (9) is further configured to determine a second maximum rotor efficiency of the at least one wind turbine based on the at least one other parameter wherein

The iron monitoring station (9) is further configured to determine a pitch error (37) on the basis of the first maximum rotor efficiency and the second maximum rotor efficiency and optionally transmit a corrective influence to the pitch control system (12) by the at least one wind turbine (2, 3), if the pitch error exceeds a threshold.

parameter

Measure 1 ^st parameter Estimate rotor effiency r

Determine maximum rotor efficiencies as a function of reference parameter s Measure

In 2 ^nd parameter

Calculate difference between maximum rotor efficiencies

1. A method for operating a wind turbine (2, 3). comprising a wind turbine tower (4), a nacelle (5) arranged on top of the wind turbine tower (4), a rotor comprising a rotatable hub (7) with at least two wind turbine levers (8) arranged relative to the nacelle (5), wherein the wind turbine (2.3 ) further comprises a bend bed (6) arranged between the nacelle (S) and the wind turbine tower (4), a bore mechanism rack (19) configured to bend the nacelle (5) relative to the wind turbine tower (4) and a bend control system (12) configured to set up the nacelle (5) relative to a wind direction wherein the method comprises the steps;

measuring at least one first parameter (20) of the wind turbine,

determining a first maximum rotor efficiency (21, 25) of the wind turbine based on the at least one first parameter,

determining a bending error (37) of the wind turbine, characterized in that the method further comprises the tunes;

measuring at least one other parameter (22) of at least one unit separated from the wind turbine,

determining a second maximum rotor efficiency (23, 25) of the wind turbine based on the at least one other parameter, wherein the pitch error (37) is determined on the basis of the first maximum rotor efficiency (21, 25) and the second maximum rotor efficiency (23, 25) ).

2?

meteorological mast (11), or the at least one other parameter is an operating parameter, and the at least one unit is at least one substation (10).

Method according to any one of claims 1 to 4, characterized in that the at least one first parameter comprises wind data, which wind data is measured relative to the rotor.

Method according to any of claims 1 to 5, characterized in that the second maximum rotational efficiency is determined by applying a regression algorithm to the at least one other parameter and evaluating the output of the regression algorithm.

Method according to any one of claims 1 to 6. characterized in that the method further comprises at least the step:

comparing the pitch error (.37) with a threshold value and the bending of the needle (5) for alignment with the wind direction when the pitch error (37) exceeds the threshold value; or

comparing the pitch error with the threshold (27) and sending an output signal to a wind turbine operator when the pitch error (38) exceeds the threshold.

A wind turbine (2, 3) comprising a wind turbine grid tower (4), a nacelle (5) arranged on top of the wind turbine axle nose (4), a rotor comprising a rotatable hub with at least two wind turbine blades (8) arranged relative to the needle (5). , wherein the wind turbine (2,3) further comprises a bend or unit (6) arranged between the nail (5) and the wind turbine bar (4), a bending mechanism (19) configured to bend the nail (5) relative to the wind turbine tower (4), and a bend control system (.12) configured to create the navel (5) relative to a wind direction, wherein the wind turbine (2, 3) further comprises at least one first sensor (16) configured file to paint at least one first parameter, said bend control system (12) is further configured to determine a first maximum roton efficiency of the wind turbine (2, 3} based on the at least one first parameter, characterized in that the bend system (12) is configured to receive a measurement of at least one second parameter from at least one unit located apart from the forward turbine, which bend control system (2) is configured for a second maximum rotor efficiency of the wind turbine based on the at least one other parameter, wherein the bend control system in 12) is configured to determine a bend error (37) on the basis of the first maximum rotomirkninøsgrad. and the second maximum rotor efficiency.

A wind turbine (2, 3) according to claim 8, characterized in that the at least one other parameter is an operating parameter or a meteorological parameter, wherein the tilt control system (12) is configured to determine the second tilt angle (33) based on the operating parameter or the meteorological parameter,

Wind turbine (2, 3) according to claim 8 or 9, characterized in that the at least one sensor is a wind data sensor mounted on the nacelle (S), in which the wind data sensor is configured to triage wind data.

A wind turbine (2, 3) according to any one of claims 8 to 10, characterized in that the bend control system (12) is configured to determine the second bend angle (33) by applying a regression algorithm to the at least one second parameter and evaluate the output of the regression algorithm.

Wind turbine (2, 3) according to any one of claims 8 to 11, characterized in that the pitch control system (12) is configured to compare the pitch error with a threshold value and generate an output signal when the pitch error exceeds the threshold value.

A wind turbine park (i) comprising at least one first unit and a first wind turbine (2), wherein the first wind turbine (2) comprises at least one first foil (lo) configured to measure at least one first parameter, wherein the at least one unit comprises at least one other sensor (17) configured to measure at least one other parameter, characterized in that the first wind turbine (2) is a wind turbine (2, 3) according to any one of claims

30 to 12 and / or configured to operate according to any one of claims 1 to 7.

Process according to claim S, characterized in. the at least one other parameter is measured inside a wind turbine park (1), wherein the least mentioned wind turbine (2) is arranged in the wind turbine park (].).

Method according to claim 1 or 2, characterized in that the at least one other parameter is an operating parameter and the at least one unit is at least one other wind turbine (3),

Method according to claim 1 or 2, characterized in that the at least one other parameter is a meteorological parameter and the at least one unit is at least one

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SEARCH REPORT - PATENT Application No. PA 2016 70502 1. 1 1 Certain claims were found unsearchable (See Box No. I). 2, 1 1 Unity of invention is lacking prior to search (See Box No. II). A. CLASSIFICATION OF SUBJECT MATTER F03D 7/02 (2006.01) According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) F03D Documentation searched other than minimum documentation to the extent that such documents are searched in the fields DK, NO, SE, FI: IPC classes as above. Electronic database consulted during the search (name of database and, where practicable, search terms used) EPODOC, WPI, FULL TEXT: ENGLISH C. DOCUMENTS CONSIDERED TO BE RELEVANT Category * Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim no. A A A EP 2213873 Al (SIEMENS AG), 2010-08-04. Couple. [0025], [0060], US 2011/0101691 AI (HASHIMOTO et al), 2011-05-05. The whole document. US 2010/0066087 A1 (HAYASHI et al.), 2010-03-18. The whole document. - 1 1 Further documents are listed in the continuation of Box C. * Special categories of cited documents: A Document defining the general state of the art which is not considered to be of particular relevance. D Document cited in the application. Έ Earlier application or patent but published on or after the filing date. L Document which may throw doubt on priority claim (s) or which is cited to establish the publication date of another citation or other special reason (as specified). O Document referring to an oral disclosure, use, exhibition or other betyder. P Document published prior to the filing date but later than the priority date claimed. T Document not in conflict with the application but cited to understand the principle or theory underlying the invention. X Document of particular relevance; the claimed invention cannot be considered novel or cannot be considered to involve an inventive step when the document is taken alone. Y Document of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the art. Document member of the same patent family. Danish Patent and Trademark Office Helgeshøj Allé 81 DK-2630 Taastrup Denmark Telephone No. +45 4350 8000 Facsimile No. +45 4350 8001 Date of completion of the search report 2 February 2017 Authorized officer Steffen Hostrup Larsen Telephone No. +45 4350 8555

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SEARCH REPORT - PATENT Application No. PA 2016 70502 C (Continuation). DOCUMENTS CONSIDERED TO BE RELEVANT Category * Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim no.

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SEARCH REPORT - PATENT Application No. PA 2016 70502 Box No. In Observations where certain claims were found unsearchable This search report has not been established in respect of certain claims for the following reasons: 1. 1 1 Claims Note: because they relate to subject matter not required to be searched, namely: 2. Claims Nos .: because they relate to parts of the patent application that do not comply with the prescribed requirements to such an extent that no meaningful search can be performed, specifically: 3. 1 1 Claims Note: because of other matters. Box No, II Observations where unity of invention is lacking prior to the search The Danish Patent and Trademark Office found multiple inventions in this patent application, as follows:

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SEARCH REPORT - PATENT Application No. PA 2016 70502 SUPPLEMENTAL BOX Continuation of Box [.]

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