System for determining a pressure distribution

Abstract

Disclosed is a system (100) for determining a pressure distribution, comprising a sensor assembly comprising a sensor configured to provide pressure data; a control module configured to receive position data indicating a spatial characteristic of the sensor assembly and to determine a pressure distribution based on the position data and the pressure data Also disclosed is a method for determining the pressure distribution comprising providing pressure data, receiving position data indicating a spatial characteristic of a sensor assembly, and determining a pressure distribution based on the position data and the pressure data.

Description

[0001] System for determining a pressure distribution

[0002] The invention relates to system for determining a pressure distribution. More specifically, the present invention includes a system and method for determining a flow vector component based on the pressure distribution to provide information relating to the alignment of a rotor with respect to a flow direction.

[0003] To enhance the efficiency of power generation and minimize the strain on a turbine, it is crucial to determine the precise orientation of the incoming wind relative to the turbine. Typically, a wind direction sensor like a wind vane is installed atop the nacelle to measure the wind direction, and the turbine rotor is then continually adjusted to face the wind. Even a slight deviation in the wind direction measurement, i.e., by a few degrees, can lead to misalignment of the turbine rotor. As a result, the turbine blades may experience different and increased loads than what was initially estimated, leading to higher wear and tear on the blades, blade root connections, bearings and overall decreased turbine efficiency.

[0004] In known wind turbines, the prevailing wind direction can be measured by means of wind vanes and the prevailing wind speed can be measured by rotating anemometers or hot-wire anemometers. Depending on corresponding measured values for wind direction and wind speed, a nacelle of the wind turbine can be aligned. In addition, an angle of attack of rotor blades can be changed. These measuring systems may require moving parts, in particular a wind vane or paddle wheels such that measuring results depend on the mobility of these parts which may vary depending on ambient parameters and wear of the measurement device. This can increase the measurement error and maintenance cost. Furthermore, a measuring system relying on a hot-wire or Doppler anemometers is sensitive to foreign bodies and requires additional data, i.e., ambient temperature and humidity, to yield correct wind characteristics.

[0005] Usually, these measuring systems are installed at the end of the nacelle of the wind turbine such that the wind speed is determined when the wind has already passed the rotor of the wind turbine. This position of the measuring systems causes that the measuring results to be influenced by the turbulence introduced by the blades which limits the accuracy of the alignment of the rotor, respectively nacelle. Specifically, as the wind turbine rotor spins it can produce turbulence, vortices and fluid flow shedding. These phenomena can produce a systematic error in a nacelle mounted wind measurement system, such that the turbine is not optimally aligned with the oncoming wind. This can result in decreased energy production efficiency, less optimal startup or storm shutdown operation and / or increase in mechanical stresses of components of the turbine. The disturbed wind signal can cause errors in the assessment of wind turbine performance.

[0006] WO 2005 / 093435 Al discloses an apparatus to determine the speed and direction of the wind experienced by a wind turbine comprising at least one sensor fixed to the rotor of said wind turbine, an angular sensor to measure the angular position of the rotor of said wind turbine, and a circuit which converts the relationship between the output of said at least one sensor and the output of the angular sensor into the speed and direction of the wind experienced by the wind turbine. The sensing apparatus can measure the wind speed and direction in three dimensions.

[0007] DE 20 2007 006 089 U1 discloses a wind measuring system for a wind turbine equipped with a rotor which can be adjusted to the wind direction comprising a wind sensor on the side of the rotor facing the wind. The wind sensor is mounted on an instrument carrier that is uncoupled from a rotational movement of a rotor head by a pivot bearing. The instrument carrier is held substantially in a predetermined position by a weight mounted eccentrically to the axis of rotation of the at least one rotor.

[0008] The accuracy of determining the wind vector in relation to a yaw-angle or pitch of the blades of a wind turbine directly relates to the precision of which a ratio of current power output to a maximum achievable power output can be determined. Power output of a wind turbine generator can be proportional to the wind speed, in particular until a rated power output is reached. The output is usually kept constant after reaching the rated power output even with an increase in wind speed. This can be achieved by controlling the pitching action of the blades in response to an increase in wind speed. The wind turbine could also be turned away from the wind, in particular by changing the yaw direction.

[0009] The wind direction can also be used to correct the yaw direction of the wind turbine. Ideally, the wind turbine should be facing into the wind, the rotor face perpendicular to the direction of wind for maximum power output. The yaw direction refers to the horizontal direction in which the wind turbine is facing.

[0010] In case of wind gusts, the turbine may be subjected to a substantial wind speed increase in a small time interval. Maintaining the power output of the wind turbine generator at a desired level may require rapid changes of the pitch angle of the blades or yaw angle of the rotor. However, common wind measurement systems may be subject to an increased delay due to the type of measurement, measuring frequency and / or the mounting position on the nacelle. As a result, generator speed, and hence power, may increase considerably during gusts, and may exceed a maximum power output level which may trigger a shutdown of the wind turbine. Moreover, depending on the orientation of the turbine, a gust may also significantly increase fore-aft and side-to- side bending moments of the tower due to increased wind shear.

[0011] Increasing the rotor size of turbines can also increase the error of nacelle mounted sensors. The error may be dynamic causing the turbine to yaw between two misalignments and not reach alignment with the actual unperturbed wind direction. In addition to the non-optimal controlling of the wind turbine this may increase wear on the yawing components.

[0012] It is therefore an object of embodiments of the present invention to overcome or at least reduce some or all of the above described disadvantages of the known wind direction measurements by providing a pressure distribution measurement system which can form the basis for an improved yawing control and increase the precision of an alignment of the wind turbine rotor with the actual wind direction.

[0013] According to an aspect the present invention relates to a measuring system for determining a pressure distribution, comprising a sensor assembly, wherein the sensor assembly can comprise a sensor configured to provide pressure data. The system can further comprise a control module configured to receive position data indicating a spatial characteristic of the sensor assembly and to determine the pressure distribution based on the position data and the pressure data. The sensor can be configured to perform a pressure measurement and the pressure data can correspond to the pressure measurement.

[0014] A pressure distribution can comprise a pressure along a trajectory, a pressure gradient field, pressure measurements over time and / or space, pressure values captured at spaced apart, in particular spatially fixed in relation to one another, measurement locations.

[0015] A pressure distribution can refer to the way that pressure is distributed across a surface or within a fluid. It can be a measure of the amount of force per unit area that is exerted on a particular surface, specifically the sensor. The captured pressure distribution can vary based on the shape of the surface, the velocity and viscosity of the fluid, and the presence of any external forces.

[0016] When a fluid flows over a surface, the pressure distribution can be used to determine an amount of drag that is being exerted on the surface. This can be used to modify a position and / or orientation of aerodynamic structures, in particular of a rotor, wing or blade.

[0017] The pressure distribution can also be used to analyse the behaviour of objects that are immersed in fluids, such as submarines, ships or aircrafts. Based on a pressure distribution, in particular around these objects, the form, position and / or orientation of can be controlled to modify the effective forces acting on the device.

[0018] The pressure distribution can be measured using a pressure sensor and / or by measuring a force exerted by a fluid on a surface. Based on the captured pressure data, pressure maps that show the distribution of pressure across a surface or within a fluid can be generated.

[0019] The sensor assembly can generally comprise all components necessary to capture the pressure data and provide the pressure data, in particular to the control module. Additionally the sensor assembly can be self-sufficient with regard to power requirements. Alternatively, the sensor assembly can be powered externally, in particular by the control module. Preferably, the measuring system can comprise a power source to enable processing of the pressure data and transmission of processed data and / or pressure data to a receiver. Additionally or alternatively, the measurement system can be powered by an external device, in particular a device the measurement system is mounted to.

[0020] The spatial characteristic can comprise location information, i.e., coordinates. The coordinates can be local coordinates such that a relative pressure distribution and / or relative wind vector can be determined. The control module can be configured to transform the relative pressure distribution and / or the relative wind vector into an absolute pressure distribution, respectively an absolute wind vector based on further position data indicating a relation of the relative coordinates to absolute coordinates of a reference system, in particular geographic coordinates with earth's surface as a reference. Additionally or alternatively, the absolute wind vector and / or absolute pressure distribution can relate to a coordinate system of a reference object. In particular the control module can determine the wind vector in reference to a local coordinate system based on an orientation of a rotor or turbine head. As such the measurement system can determine a difference vector between the orientation of the rotor and the wind vector. Preferably, the difference vector is two-dimensional, corresponding to an angle in a yaw-plane of a rotor, more preferably the difference vector is three-dimensional including an angle in a pitch-plane of the rotor in addition to the yaw-angle.

[0021] The measurement system, the sensor assembly or at least the sensor can be mounted on a blade of a wind turbine. Herein, the difference vector may also comprise a component relating to the pitch angle of a blade or a plurality of blades.

[0022] Capturing the output from the sensor at various intervals throughout a rotor's rotation and correlating these measurements to corresponding angular positions the control module can be configured to determine a pattern, in particular a sinusoidal pattern, which can serve as a basis to determine speed and direction of the wind. The control module can be configured to evaluate a plurality of measurements, in particular performing a statistical analysis to determine systematic variations in the wind speed and direction determination and to adjust the pressure distribution, respectively the wind vector according to the captured variations. Preferably, the control module can be configured to determine a mean wind speed and / or mean wind direction.

[0023] The control module can be configured to determine the wind vector based on the position data and the pressure data independent of a position and / or orientation of the sensor assembly, in particular the sensor in relation to a reference object, in particular the rotor or rotor head.

[0024] The present system achieves the distinct advantage that a single measuring device can be used to simultaneously measure the deviation of the orientation of the wind vector determination device from the prevailing wind direction as well as the wind speed. On the basis of the wind speed measurement, the respective optimum yaw angle and / or attack angle of the rotor blades against the wind can be determined. Thus, the output power yield extracted from the wind can be maximized. In contrast, on the basis of the simultaneous wind direction measurement, the alignment of the nacelle of the wind turbine in the wind direction can be carried out quickly and accurately.

[0025] The measurement system according to the invention is preferably used in front of the rotor of a wind turbine, so that adverse conditions, i.e., a stalling rotor, can be prevented, e.g., by applying appropriate yawing. This can also result in a reduction of blade and system loads and stresses. The measurement system according to the invention may not require any rotating parts for determining the pressure distribution.

[0026] Furthermore, it is of particular advantage that the measurement system can be disposed on existing wind turbines.

[0027] The speed of rotor rotation and the power output can be regulated by means of a control system for the angle of incidence of the rotor blade, i.e. tilting and / or yawing. This can achieve the advantage of protecting the rotor from rotating at above a rated maximum speed.

[0028] The sensor assembly may comprise a pressure buffer tube which comprises a first end and a second end. The sensor can be disposed at the second end or within the pressure buffer tube. The pressure buffer tube can comprise an inlet section wherein the inlet section can be disposed at the first end. Furthermore, the pressure buffer tube may comprise a main tube body configured to fluidly connect the sensor and the inlet section. The pressure buffer tube can form a conduit from the inlet opening to the sensor such that a pressure at the inlet opening can be transferred to the sensor. The shape and form of the pressure buffer tube can be arbitrary under the condition that the influence of the pressure buffer tube on the pressure value at the inlet opening in reference to the pressure value at the sensor is known. The control module can be configured to account for a contribution of the pressure buffer tube to the pressure value when processing the pressure data. The pressure buffer tube can achieve the advantage that the sensor can be positioned away from the inlet opening such that the sensor can be shielded from environmental effects, i.e., temperature fluctuations, debris, precipitation, etc.

[0029] The inlet section form part of the main tube body or can be formed as one piece with the main tube. The pressure buffer tube can be a hole, in particular a bore, in a solid main body.

[0030] The output of the sensor can indicate a surface pressure at a point of a reference object, in particular a rotor hub, spinner or turbine body. The surface pressure may relate to the speed of the air flowing over the surface and serve as a basis to determine a wind speed and direction.

[0031] The inlet section can be aligned with a position axis. The inlet section can determine a reference point, in particular a reference orientation, for determining the pressure distribution. The position axis can be a symmetry axis of the inlet section, in particular, when the inlet section forms a straight tube. Additionally or alternatively, the position axis can form a normal vector of an entrance plant of the inlet section, wherein the exit plane is disposed at an end of the inlet section in contact with the medium of which the pressure is to be determined. The inlet section in can intersect with a surface, in particular a curved surface, of a reference object in which the inlet section is disposed. Herein, the ridge line of the inlet section, i.e., the inlet opening, can be comprised in a flat intersection plane. Alternatively, the ridge line can follow the curved surface such that the ridge line is comprised in a curved plane, in particular spanned by the reference object. Herein, the position axis can be a normal vector of a flat median plane of the curved plane.

[0032] The sensor may be disposed in a sensor plane and a normal vector of the sensor plane may be aligned with the position axis. This achieves the advantage that the sensor plane can form a reference plane no which determining the wind vector can be based. In particular, the control module can be configured to determine a wind vector based on the position and / or orientation of the sensor in combination with position data indicating a position of a reference object on which the sensor can be disposed to determine the wind vector. The sensor may be aligned with the inlet section.

[0033] The spatial characteristic may be a position and / or an orientation of the sensor assembly, preferably a component of the sensor assembly, in particular the sensor. This achieves the advantage that the control module can determine the pressure distribution in local coordinates and by reference data in global coordinates.

[0034] The position data may indicate the spatial characteristic of the inlet section as the spatial characteristic of the sensor assembly. This achieves the advantage that the inlet section can form a reference characteristic, in particular a reference point on which the control module can base the calculation of the pressure distribution and / or wind vector.

[0035] The position data may indicate the spatial characteristic of the sensor as the spatial characteristic of the sensor assembly. This achieves the advantage that the sensor can form a reference characteristic, in particular a reference point on which the control module can base the calculation of the pressure distribution and / or wind vector.

[0036] The inlet section and / or the pressure buffer tube may comprise an inlet opening. The inlet section and / or the pressure buffer tube may be configured to fill with a medium, in particular through the inlet opening. This achieves the advantage that the pressure at the inlet opening can be transferred through the inlet section, respectively the pressure buffer tube to the sensor. Thus, the orientation or form of the inlet section, respectively pressure buffer tube can be independent from the sensor orientation.

[0037] The pressure buffer tube may be configured to transport a pressure signal to the second end, in particular from the inlet opening, preferably via the medium. Additionally, the medium inside the pressure buffer tube can be the same as the medium in contact with the inlet opening. Alternatively, the medium inside the pressure buffer tube and / or the inlet section can differ in aggregate state and / or density from the medium outside of the pressure buffer tube, respectively inlet section. The medium comprised within the inlet section and / or pressure buffer tube can be a liquid or a gel. This can increase the shielding of the sensor from ambient disturbances (debris, rain, ice, dust, etc.)

[0038] The control module may be configured to determine a first vector component, a second vector component, a third vector component and / or an absolute value of a wind vector based on the position data and the pressure data. The position data may comprise data on a rotation of the sensor assembly, specifically the sensor such that the sensor scans the wind as it rotates. Based on the relationship between the pressure data and the angular position at which the pressure data was captured the control module can be configured to calculate the wind speed and direction.

[0039] The wind vector may comprise two vector components spanning a two-dimensional wind plane. This can reduce the computational load, decreasing latency and / or increasing operational efficiency due to decreased power requirements. Limiting to two dimensions can further be beneficial when only a yaw-correction and not a tilt-correction is available. The wind vector may comprise three vector components spanning a three-dimensional wind space. This allows for a three-dimensional adjustment of the turbine, in particular the rotor based on the wind direction. Alternatively, if the adjustment is limited to yaw control, the additional load on the turbine due to a wind vector component in a third dimension is available such that a complete mechanical load on the turbine can be determined.

[0040] The position data may comprise spatial data configured to numerically represent a physical object in a coordinate system. This achieves the advantage that the control module may determine a wind vector based in the coordinate system of the physical object, i.e., the control module may be configured to transform a relative wind vector in a local coordinate system to a wind vector in relation to a part of the turbine, in particular the rotor.

[0041] The physical object may be one of or a combination of the following: the measuring device, the sensor assembly; the sensor; the pressure buffer tube; the inlet section; the inlet opening; and / or reference point or reference object in fixed spatial relation to one of the above. Thus, the control module can achieve the advantage of processing position data independent of the source object the position data corresponds to and convert the position data to correlate with the inlet section, inlet opening or sensor such that the pressure data can be related to a specific position and / or orientation at the time of capturing the pressure data. The position data can comprise a plurality of overlaying movements, i.e. a yawing turbine, pitching blades and / or spinning rotor. Preferably, the control module can be configured to determine the wind vector based on a subset of superimposed movements, i.e. remove effects based on yawing.

[0042] The coordinate system may be a geographic coordinate system; local coordinate system, in particular a spherical coordinate system; or a plurality of interlinked local coordinate systems. For example, a wind vector can be determined for each turbine of a plurality of turbines in a respective local coordinate system, wherein the local coordinate systems are linked by vectors indicating their relative location to one another in a reference coordinate system.

[0043] The position data comprises temporal data representing a point in time corresponding to the spatial data. This achieves the advantage that the control module can correlate a timed capture of the pressure data with the spatial data to determine an orientation and / or position of the sensor assembly, inlet opening, inlet section and / or sensor when the pressure measurement is recorded. Preferably, each spatial data entry is correlated with a temporal data in the position data.

[0044] Each local coordinate system of the plurality of local coordinate systems may be referenced by a reference coordinate to at least one other local coordinate system of the plurality of local coordinate systems such that the position of the physical object within the plurality of local coordinate systems is determined by its local coordinate system and the reference coordinate of its local coordinate system to another local coordinate system. For example, each turbine of a set of wind turbines can have a local coordinate system where the reference coordinates determine the relative positions of the wind turbines with respect to one another.

[0045] A relative position of a first local coordinate system, in particular its origin, may be referenced to a second local coordinate system, in particular its origin.

[0046] The pressure data may comprise at least two pressure measurements, in particular a first pressure measurement captured when the inlet section is at a first position and a second pressure measurement captured when the inlet section is at a second position. The at least two measurements can correspond to two angular positions of a rotation of the rotor. Preferably, the measurements are spaced apart by at least 1°, preferably at least 5°, more preferably the pressure measurements are spaced apart 45°, 90° or 180°. The control module can be configured to determine a divergence of the capture angle based on previous position data and pressure data. This achieves the advantage that each pressure measurement may not be recorded at a precise angle. The control module can be configured to determine an expected pressure value and adjust the correlated angular position based on the expected pressure value. This can be achieved for rotor rotation and other overlaying motions, such as vibration of the rotor, tilting of the rotor, swinging motion of the rotor and / or a precession of the rotor.

[0047] The control module can be configured to determine a relation between the position during the rotation of the rotor, in particular during multiple rotations of the rotor. Herein, the relation can be based an angular function, specifically sinusoidal.

[0048] The sensor may be configured to periodically determine a pressure and to periodically provide corresponding pressure data. The control module may be configured to link the pressure measurements to the position data to create a pressure profile indicating the pressure at specific time instances. The time instances may form a single period of the movement of the position axis, preferably the inlet section. The pressure profile, in particular a periodicity of the pressure profile, may correspond to an angular motion of the rotor. Preferably, the pressure profile can be matched a predetermined section of the angular motion or a complete period of the angular motion. Additionally, the pressure profile can correspond to a combined motion of a base rotation superimposed with fluctuations, in particular periodic fluctuations. These additional movements can be caused by a rotor wobble, i.e., precession, a rotor vibration, a rotor oscillation, a tower oscillation, i.e. swinging, The control module may be configured to relate the pressure profile to the position data. Preferably the control module may be configured to link an angular position of the position axis to a corresponding pressure measurement. Thereby, a correlation of the angular position and the pressure determined at that angular position can form the basis to determine a wind speed and wind vector. Specifically, the control module can determine a wind vector based on a plurality of pressure measurements at different positions. Herein, the measurements can be achieved by a single sensor that moves along a trajectory or by a plurality of sensors that are spaced apart and preferably perform synchronous pressure measurements.

[0049] The control module may be configured to periodically determine the pressure distribution and / or the wind vector based on the pressure profile and / or the position data. A high update frequency of the wind vector can increase the precision of a yaw alignment of the turbine. The measurement system may continuously determine a wind vector such that a yawing motion can be based on real time wind vector information. Preferably, the wind vector can also be evaluated during the yawing motion to confirm the yaw alignment.

[0050] The position data may comprise data relating to a full rotation of the physical object in a predetermined plane, preferably along a predetermined trajectory, in particular a predetermined closed-loop trajectory in the coordinate system. The control module can be configured to determine a periodicity of the pressure measurements and to determine deviations of the pressure measurements between subsequent periods. The periodic movement can be proportional to a movement of a rotor and / or blade of a turbine.

[0051] The control module may be configured to determine a pressure profile for at least part of a rotation, preferably a full rotation.

[0052] The position data may comprise one-dimensional rotational data, in particular angular data of the physical object.

[0053] The control module may be configured to adjust a sampling frequency of the sensor and / or to select a specific pressure measurement based on the position data, in particular based on an angular position of the physical object. This achieves the advantage that a minimal number of measurements, in particular measurements spaced apart by a predetermined distance or angle, or measurements at predetermined positions or angles can be captured. The sampling frequency can be proportional to a speed of the sensor assembly and / or a correlating angular speed. Hence, a pressure profile resolution can be kept constant. Additionally or alternatively, a spatial pressure resolution can be increased, in particular when high deviations between periods are detected, i.e., due to actual wind speed fluctuations, gusts, storms, turbine movement etc.

[0054] The control module may be configured to control capturing pressure measurements and / or configured to select a set of pressure measurements from a plurality of pressure measurements to match pressure measurements with corresponding angular positions of the physical object. This can achieve the advantage that a mismatch of the sampling frequency and the movement of the sensor assembly, respectively sensor or inlet section, can be compensated. Thereby, pressure measurements at fixed positions can be achieved. Additionally and / or alternatively, the control module may be configured to initiate capturing a pressure measurement at specific instances, in particular matching predetermined positions.

[0055] The control module may be configured to determine an orientation of the position axis, in particular with reference to the physical object, based on the pressure data and position data. This can achieve the advantage that the sensor assembly, inlet opening, inlet section and / or sensor can be mounted at an arbitrary position and / or at an arbitrary orientation with respect to the reference object. Preferably, the control module may be configured to determine a wind vector relative to a plane of rotation of the measurements system, specifically, the sensor assembly, the inlet opening, inlet section and / or sensor. For example, the measurement system may be disposed on any rotating component of a turbine and due to the rotational periodicity of the pressure profile the control module may determine the orientation of the rotation plane towards a wind vector. Thereby, the control module can determine a yaw angle offset of the turbine.

[0056] The trajectory of the position axis, preferably the inlet section, may comprise an additional movement, in particular a periodic movement, i.e., a precession, in particular in addition to a trajectory of a reference object according to the position data. The position data may represent a rotation of the turbine, specifically a rotation of the rotor or rotor cap and the inlet section may perform an additional precession. This can be due to additional forces causing an imperfect rotation. Alternatively, the position data may comprise the additional precession.

[0057] The control module may be configured to determine an orientation of the position axis based on the additional movement. The sensor assembly, specifically the inlet opening, inlet section and / or sensor can be aligned with a rotation axis of the turbine, preferably a rotation axis of the rotor hub. The alignment can be defined by a symmetry axis matching the rotation axis. An ideal rotation of the sensor assembly, specifically a single inlet opening, inlet section and / or sensor can lead to non-varying pressure measurements as the orientation of the inlet opening, inlet section and / or the sensor may not change with the rotation. However, a typical turbine rotation may comprise an additional movement component overlaying the base rotation, i.e., the rotor may perform a precession around its base rotation axis. This additional movement component may alter the orientation or position of the sensor assembly, specifically the inlet opening, the inlet section and / or the sensor towards the wind. This may achieve the advantage that the captured pressure may vary at different positions along the actual trajectory of the sensor assembly, which may be based on the base rotation of the rotor in combination with the additional movement component.

[0058] The control module may be configured to determine the contribution of the additional movement to the pressure measurement, in particular the pressure profile. This achieves the advantage that the additional movement can be used to determine the wind vector. Additionally and / or alternatively, the wind vector can be corrected to remove a contribution of the additional movement. Furthermore, the control module can be configured to determine the additional movement, i.e., an angular velocity and / or angular acceleration of the reference object, specifically the rotor based on the pressure data. Preferably, the control module is configured to determine a wind vector in a static configuration, i.e. the sensor assembly does not move relative to the wind vector. The control module may be configured to captured pressure data at a frequency substantially higher than the rotational speed of the hub such that an angular resolution of the pressure measurements is higher than 2°, preferably higher than 1°, more preferably higher than 0.1°. The control module may be configured to determine a yaw angle, roll angle and / or a pitch angle of the sensor assembly, inlet opening, inlet section and / or sensor.

[0059] The control module may be configured to determine a periodicity of the additional movement. The periodicity of the additional movement can be smaller or larger than a base rotation of the rotor. The control module may require a complete period to determine a pressure profile, respectively wind vector. The control module may determine the wind vector based on a complete period of the base rotation and / or a complete period of the additional movement.

[0060] The control module may be configured to determine the pressure distribution and / or the wind vector based on the additional movement. This achieves the advantage that the wind vector can be determined independent from a base rotation. In particular, a correlation of the base rotation and an alignment of the sensor assembly and / or a predetermined position and / or orientation in reference to a base rotation is not required.

[0061] The control module may be configured to adjust the pressure distribution and / or the wind vector based on the additional movement, in particular to remove a perturbation based on the additional movement from the pressure distribution and / or the wind vector. This achieves the advantage of increased precision of the wind vector. The control module may be configured to compare at least two instances of a pressure profile to determine a drift of the pressure sensor. This achieves the advantage that the pressure sensor can be calibrated during use. In particular, the pressure sensor can be adjusted for the drift to provide accurate absolute pressure values. This may achieve the advantage that the pressure sensor may not need to be calibrated prior to use. Alternatively, an additional calibration can be maintained by continuous adjustment of the calibration based on the pressure measurements. In particular, when a plurality of sensors is used, the sensors can be calibrated with reference to one another.

[0062] The control module can calibrate the sensor assembly, adjust to varying ambient parameters and / or account for sensor shifts in particular induced by wear and / or aging. Preferably, the control module is configured to adjust each subsequent pressure measurement based on a captured pressure drift or pressure abnormality.

[0063] The control module may be configured to adjust a pressure profile and / or a pressure distribution based on the drift, in particular to remove a drift-based contribution to the pressure distribution and / or the pressure profile. This can achieve the advantage that an initial calibration of the sensor can be maintained and accurate absolute pressure measurements can be captured. Additionally, the accuracy of the determined wind vector can be maintained respectively increased by removing drift based components.

[0064] The control module is configured to determine an angle between the position axis and the wind vector. This achieves the advantage that when an orientation and / or position of the sensor assembly, respectively the inlet opening, inlet section or sensor is known, the control module may determine an absolute direction of the wind vector, i.e. in reference to a ground based coordinate system. Herein the control module may receive a yaw position of the wind turbine to determine an absolute wind angle.

[0065] The control module may be configured to determine the position axis based on the position data and the pressure data, in particular when the position axis moves, along a periodic trajectory, preferably an elliptical trajectory, more preferably a circular trajectory, in particular based on a precession in reference to periodic angular motion of the reference object.

[0066] The inlet section may be disposed on a reference object.

[0067] The sensor may be disposed on a reference object.

[0068] The position axis may be aligned with a predetermined axis of the reference object and / or wherein the inlet section and / or the sensor is in a fixed spatial relation to the reference object. This achieves the advantage that any movement of the reference object can be transferred to the measurement system, specifically, the inlet opening, inlet section and / or sensor. Thus, the control module can determine a trajectory of the inlet opening, inlet section and / or sensor based on the motion of the reference object.

[0069] The position axis may be oriented relative to an orientation vector, in particular an orientation vector of the reference object, wherein an angle between the orientation vector and the position axis is less or equal to 160°, preferably less than 90°. For example, the inlet section and / or a normal vector of the inlet opening may point forward in reference to the rotor and / or the blades. An orientation vector can coincide with a rotation axis of the rotor. An angle between the orientation vector and a wind vector is preferably larger than 90°, i.e., the rotor is at least partially facing the oncoming wind. The position axis can be oriented relative to the orientation vector such that the inlet opening, inlet section and / or sensor are oriented at an angle with respect to the orientation vector. In particular, the sensor assembly, inlet opening and / or inlet section may be at least partially oriented along the orientation vector. For example, a rotor hub may comprise a hub surface having a rounded surface, wherein the sensor assembly is disposed on the hub surface. Herein, the inlet opening, inlet section and / or sensor may be disposed on the hub surface at an incline or directly perpendicular. When mounted at an incline, the orientation of the inlet opening, inlet section and / or sensor may partly coincide with the rotation axis of the rotor, preferably in a forward facing manner or at an angle of up to 70° facing backwards. The control module can be configured to determine the wind vector, at least the wind direction, independent of an orientation, specifically an incline of the sensor assembly, inlet opening, inlet section and / or sensor, relative to rotor hub. Specifically, the control module can be configured to determine a contribution of the orientation of the sensor assembly, inlet opening, inlet section and / or sensor to the pressure measurement, specifically the pressure profile.

[0070] The measuring system, the sensor assembly or the inlet section may perform a periodic movement with respect to a reference object. Herein, the reference object can in particular be the nacelle of the wind turbine. Preferably the periodic movement enables the measurement system to determine a wind vector, in particular when the sensor assembly comprises only one sensor. Based on the periodic movement, pressure measurements over time can be performed and evaluated at identical positions using only one sensor. Alternatively, a plurality of sensors can be used. Herein, measurements of the sensors for part of the periodic movement can be combined to determine a pressure profile for a complete period. For example, once a second sensor of the plurality of sensors reaches the position of a first sensor the pressure is determined for a complete period, i.e., a complete rotation. The periodic movement can by segmented by the number of sensors. Additionally and / or alternatively, a plurality of sensors can be used to calibrate and / or average the pressure data. For example, the pressure can be determined by a plurality of sensors at the same position for a single period of the periodic movement. The control module can be configured to determine outliers in the pressure data, i.e. a deviating sensor, and / or increase precision of the pressure measurement by averaging over a plurality of captured pressure values. The periodic movement can be congruent to a movement of an object the sensor assembly is mounted to, i.e. the rotor of a wind turbine. Alternatively, the periodic movement represents an additional movement in relation to the object the sensor assembly is mounted to. For example, the sensor assembly rotates around an axis independent of the rotation of the rotor. The sensor assembly may rotate counter to or following the rotation of the rotor. The angular velocity of the sensor assembly can differ from the angular velocity of the rotor.

[0071] The measuring system may be attached to a reference object.

[0072] The control module may be configured to be electrically powered by the reference object.

[0073] The control module may comprise a power source, in particular a replenishable or rechargeable power source, preferably a generator configured to generate electrical power based on a movement of the reference object, more preferably a solar-based and / or wind-based generator. The power module can be configured to provide power to the control module.

[0074] The reference object is one of the following: a blade, in particular of a turbine or rotor; a hub, in particular of a turbine or rotor; a spinner, in particular of a turbine; a part of a turbine affected by, in particular moving based on, a yaw control of a turbine, preferably a nacelle of a turbine; or a spatially fixed part of a turbine, in particular a tower of a turbine. The control module may be configured to receive positional or orientational reference data pertaining to the reference object. The positional reference data can indicate a relative position of the sensor assembly to the sensor assembly and / or a relative position of a reference point of the trajectory of the sensor assembly to the reference object. The orientational reference data can indicate an angle of a movement plane of the sensor assembly, inlet section, inlet opening and / or sensor in relation to the reference object. The orientation of each part of the measuring system may be defined by a normal vector of a corresponding orientation plane of the respective part.

[0075] The control module may be configured to receive orientation data indicating an orientation of the reference object and / or the measuring system, in particular indicating a pitch angle and / or a yaw angle in absolute or relative spatial coordinates and / or indicating a rotation angle, in particular a rotation angle in a plane perpendicular to a yaw plane. This enables the comparison of a determined wind vector in relation to the orientation of the reference object, in particular the rotor. The control module can determine a difference between the orientation of the rotor in relation to the wind vector, in particular a yaw misalignment, i.e., a difference angle between the wind direction and the rotor orientation.

[0076] The yaw angle may be determined in a plane parallel to a ground plane. A rotation angle may be determined in a plane perpendicular to the ground plane. Preferably, the rotation plane is perpendicular to the yaw plane.

[0077] The control module may be configured to determine a difference between the orientation data and the wind vector based on the pressure distribution, in particular to determine a deviation angle of the wind vector projected onto the yaw plane of the reference object and / or to determine a deviation angle of the wind vector projected onto the pitch plane of the reference object. Preferably, the control module can be configured to determine a pitch angle correction for a pitch angle of a blade of the rotor. Additionally or alternatively, a pitch angle correction for a pitch angle of the rotor relative the ground plane and / or yaw plane can be determined by the control module. This achieves the advantage that an adjustment in multiple axes can achieved, in particular to directly orient the rotor in line with the wind vector. The control module can provide continuous correction data, in particular to a turbine yaw control such that the time interval of misalignment can be advantageously reduced.

[0078] The control module may be configured to determine a yaw misalignment of the reference object based on the pressure distribution.

[0079] The control module may be configured to provide yaw adjustment data indicating a yaw adjustment to reduce the yaw misalignment based on the determined yaw misalignment.

[0080] The measurement system may comprise a communication interface configured to provide pressure data, a pressure distribution, a wind vector and / or yaw adjustment data to a data interface corresponding to the reference object. Preferably, a plurality of distributed, i.e., spaced apart, sensor assemblies, e.g., when mounted on a plurality of wind turbines, can provide a spatial pressure distribution. Thereby, a pressure field in arrangement of wind turbines can be determined. More specifically, in combination with position data of each turbine the influence of each turbine on the pressure distribution of turbines located downwind can be determined. The yaw adjustment data can be used for a plurality of turbines, in particular a locally clustered plurality of wind turbines. Thus, the yaw alignment precision of a wind park can be increased, in particular based on a single measurement system.

[0081] The inaccuracy of the determined yaw misalignment may be below 5°, preferably below 2°, more preferably below 1°. This can in particular be achieved by calibrating the sensor and removing orientation based contributions to the pressure profile, i.e., the pressure profile is captured over a complete period of a periodic movement of the sensor assembly, e.g., one rotor rotation. Also the pressure profile can be determined per each revolution of the rotor and the pressure distribution adjusted accordingly. Additionally, the position of the sensor assembly outside a shear layer of the flow at the rotor and preferably in a laminar flow, non-turbulent flow or at least weakly turbulent flow section can contribute to an increased accuracy.

[0082] The control module may be configured to determine an offset of the position axis to the predetermined axis and to adjust the pressure distribution based on the offset, in particular remove the offset-based contribution to the pressure distribution. In particular, any contribution to the pressure profile induced by the orientation of the sensor assembly, the inlet opening, inlet section and / or sensor may contribute symmetrically to the pressure profile such that the effect on determining a pressure distribution and therefrom a wind vector can be removed. This can achieve the advantage that the inlet opening, inlet section and / or sensor does not need to be precisely oriented and / or mounted on the rotor. Any orientation of the sensor assembly can be used to determine the pressure distribution.

[0083] The sensor may be configured to determine the pressure of a medium, in particular a dynamic pressure of a flow of a medium. The sensor can capture the pressure of a fluid, preferably air and / or water. The dynamic pressure can be a combination of a static pressure of the medium and a flow speed induced pressure contribution.

[0084] The measurement system may comprise a rotation sensor configured to provide rotation data, wherein the rotation data indicates at least one of the following: a rotation angle; an angular velocity, in particular with respect to a center of rotation of a reference object. The rotation sensor may determine a tangential velocity, in particular in relation to the position of the inlet section, inlet opening and / or sensor. The rotation angle and / or angular velocity can correspond to a rotation of a reference object, in particular the rotor of the turbine.

[0085] The control module can be configured to perform a self-orientation. Thus, an initial manual alignment is not needed. Specifically, the control module can comprise a feedback loop using inertial measurement units (IMU). This can also achieve the advantage to compensate for angular drift. The IMU can further be used to correct the wind vector, specifically the wind direction.

[0086] The control module may be configured to determine a pressure gradient based on the orientation data, the position data and / or the pressure data. The pressure gradient can be determined over an area and / or over time. For example sensor assemblies and / or sensors disposed on a set of turbines can determine a localized pressure field. This can achieve the advantage that the influence of each turbine with respect to the other turbines can be determined. The pressure gradient over time can indicate a change in wind direction and / or wind intensity and can form a basis for a turbine position adjustment, in particular a yaw adjustment.

[0087] The sensor assembly may comprise a plurality of sensors, preferably between 2 and 14 sensors, more preferably 5 sensors. The sensor assembly may comprise a plurality of pressure buffer tubes, preferably a matching number of pressure buffer tubes according to the number of sensors, wherein each pressure buffer tube is associated with a sensor. An increasing number of sensors can increase the accuracy of the determined pressure distribution and thereby also the wind vector. The control module can be configured to determine a wind vector, at least a wind direction based on the difference in pressure measurements of multiple sensors at the same location, the sensors, inlet openings and / or inlet sections preferably having the same orientation. This can further achieve the advantage that a rotation of the sensors relative to the wind direction is not required to determine the wind speed and / or wind direction.

[0088] The position data may indicate the spatial characteristic of the geometric center or a reference point at a fixed distance of the geometric center of the plurality of inlet sections and / or the plurality of sensors. Thus, the control module can be configured to convert a movement of a reference object into corresponding movement of the sensor assembly, i.e., the plurality of inlet openings, inlet sections and / or sensors. Thus, the control module can determine a trajectory relative to the wind vector based on the movement of the reference object. Based on the trajectory and the corresponding pressure measurements the control module can update the pressure distribution and thereby the wind vector.

[0089] The sensors of the plurality of sensors may be spaced apart in fixed positions with respect to one another. Additionally or alternatively, the pressure buffer tubes of the plurality of pressure buffer tubes may be spaced apart in fixed positions with respect to one another. Furthermore, the inlet sections of the plurality of inlet sections may be spaced apart in fixed positions with respect to one another. The spacing between the sensor openings can increase the precision of the measurement. Additionally and / or alternatively, the inlet sections and / or the inlet openings can be oriented at an angle with respect to one another. This can increase the sensitivity of the measurement system with respect to varying wind directions.

[0090] The space spanned by all inlet sections of the plurality of inlet sections is equal to or less than a hemisphere. For example, all inlet sections may be disposed on the same hemisphere. Preferably, the inlet sections and / or inlet openings are oriented parallel to one another. Preferably, at least one inlet opening is located at the center of the hemisphere. The hemisphere can also be a part-ellipsoid, where one inlet opening is disposed at the maximum curvature point, i.e., the tip, of the ellipsoid.

[0091] A first inlet section of the plurality of inlet sections may be aligned with the position axis and a second inlet section of the plurality of inlet sections may be aligned with a second axis. Herein the position axis and the second axis may be angled with respect to one another.

[0092] Each of the inlet sections of the plurality of inlet sections may be aligned with the position axis. This can achieve the advantage that each sensor may capture the pressure at the same angle in combination with

[0093] The control module may be configured to determine a speed vector based on the pressure data of the plurality of sensors, in particular a wind speed vector.

[0094] The sensor assembly may form a multi-hole probe and / or the control module may be configured to measure a magnitude and / or a direction of a flow velocity vector with respect to the sensor assembly and / or a static and / or a total pressure.

[0095] Based on the data captured via the multi-hole probe the control module can determine a velocity and a direction of wind, respectively air flow, in particular at the mounting point of the probe. The multi-hole probe can be considered as a type of anemometer. The probe can comprise a plurality of cylindrical tubes, i.e., pressure buffer tubes, specifically inlet sections, with multiple inlet openings at different angles. The probe can be inserted into the airflow, and a pressure difference between the holes can be measured to determine the wind velocity and direction.

[0096] The multiple holes on the probe are placed at different angles to capture the direction of the airflow. The pressure difference between the inlet openings can be measured using a differential pressure transducer or a manometer, which achieves the advantage of providing wind velocity and direction measurements with increased accuracy.

[0097] Based on the pressure data captured using the multi-hole probe, the control module can be configured to determine a fluid property, in particular turbulence intensity, Reynolds stress and / or other aerodynamic parameters.

[0098] The multi-hole probe achieves the advantage of providing measurements of the wind velocity and direction in three dimensions. Using a plurality of probes at different locations can yield a detailed map of the wind flow, in particular around an object or structure.

[0099] Preferably, the multi-hole probe can be a 5-hole-probe comprising a streamlined axisymmetric body that points into the flow and comprising five inlet openings, i.e., pressure sensing holes. The pitch and yaw planes orientation relative to the sensor assembly can be independent of a device used to position the probes, in particular for a calibration of the measurement system. The pressure distribution on the surface of the 5-hole-probe may depend on the angle of incidence of the mean flow vector relative to the axis of the probe. To determine the three-dimensional orientation and magnitude of the flow vector, the surface pressure can be sampled at five positions. For example, on an axis of the probe and at four equidistant locations of the probe.

[0100] The central inlet opening and corresponding sensor may provide a conventional stagnation pressure, in particular when the flow vector is perpendicular to that point on the surface. The pressure difference between the side sensing-holes can relate to an inflow velocity vector which can be used to determine the yaw direction.

[0101] The probe may comprise a body-length to tip-diameter ratio resulting in an elongated shape, preferably the ratio is at least 5: 1, preferably 10: 1, more preferably 20: 1.

[0102] The shape of the sensor assembly may be small enough to not disturb the flow. The velocity of the flow along the sensor assembly can be uniform and / or large enough to not cause laminar separation leading to self-induced turbulence.

[0103] The inlet opening of each inlet section of the plurality of inlet sections may be flush with an outer surface of the reference object.

[0104] The sensor assembly, the inlet sections or the pressure buffer tubes may protrude less than 20 cm, preferably less than 10 cm, more preferably less than 5 cm from an outer surface of the reference object.

[0105] Each inlet section of the plurality of inlet sections may be aligned with an orientation vector of the reference object within a tolerance of 20°, preferably 10°, more preferably 5°.

[0106] The measurement system may comprise a measurement head section and a stem section.

[0107] The head section may form the reference object.

[0108] The sensor assembly may be disposed on the head section. The stem section may be configured to attach the head section to the reference object. This can achieve the advantage of providing variable mounting options. The stem section can be removable attached to the reference object and / or the head section can be removably attached to the stem section. This allows a user configurable attachment, i.e., mechanical and / or electrical connection, of the system, specifically the sensor assembly to the reference object. The stem may be configured to dispose the inlet opening, inlet section and / or sensor above a boundary layer of the spinner, in the plane in which the sensors lie and in a direction which is tangential to the surface of the spherical spinner at the point where the sensors are mounted.

[0109] The stem section may have a tubular form and / or the head section may form one of the following shapes: a part ellipsoid, preferably a partial sphere; a cone; a pyramid, preferably a polygonal pyramid, preferably pentagonal pyramid; a poly-sided cone, preferably a five-sided cone; a pyramid stump, in particular having a polygonal base; a polygonal sphere-shape. The shape of the head section and correspondingly disposed inlet openings can determine the relative angle of a normal vector of the respective inlet opening with regard to the wind vector. The tubular form of the stem section can reduce drag and place the inlet openings outside of a boundary layer of the flow around the reference object.

[0110] The stem section may be oriented at a predetermined, preferably non-zero angle with respect to a rotation axis of the reference object. The predetermined angle can be known such that a relative orientation of the inlet section can be determined in combination with rotation and / or position data. Additionally and / or alternatively, an effect of the angled orientation can be removed from the pressure profile due to the effect cancelling out over a full rotation. The angle can be arbitrary, thereby reducing the requirements of exact placement of the measurement system onto the reference object.

[0111] A diameter of the head section may be less or equal to a diameter of the stem section. This can achieve the advantage that the stem section and head section form a smooth object, decreasing a perturbation of flow by the measurement system.

[0112] Every radial vector of the head section which intersects the stem section may enclose an angle of less than 20°, preferably an angle of less than or equal to 90°, with the symmetry axis of the stem section. For example, the head section may have an unobstructed surface that allows for a sensor or inlet section to be disposed such that it faces backwards up to 160° with reference to an orientation vector of the turbine. This achieves the advantage that a rotor facing surface of the head section can be minimally obstructed by the stem section. In particular, the intersection between the head section and the stem section can be defined by a radial cone having two radial vectors from the center of the head section each at 20°.

[0113] A base surface of the head section may match a cross section of the stem section such that the head section may form a tip of the stem section. This can reduce perturbations to the surrounding flow by providing a smooth surface with reduced drag. A cross-sectional area between the head section and the stem section may be larger or equal to 10%, preferably 20%, more preferably 50% of a largest cross-sectional area of the head section. Thereby, a cross section of the stem at the mounting point of the head section is smaller than a cross section of the head section. This can achieve the advantage that sensors, specifically inlet openings can be oriented at an angle larger than 90° at the head section. In other words, an inlet opening disposed on the top can at least partially face towards the rotor. Preferably, the stem section comprises a constant cross section and / or a constant cross sectional area. The head section can be a sphere mounted to a cylindrical stem section, wherein in part of the surface of the head section faces towards the rotor of a turbine. The inlet openings can be disposed such that essentially a 360° coverage regarding the wind direction can be realized.

[0114] The sensor assembly, preferably all sensors, may be disposed on the head section. This can achieve the advantage that the pressure measurements can be captured outside of a boundary layer of the reference object. In particular the corresponding inlet openings can be disposed on the head section. The head section and stem section can be removably connected. Preferably, all components relevant to capturing and processing pressure data, specifically the control module, are disposed in the head section to allow efficient servicing, in particular by dismounting the head section from the stem section.

[0115] Each inlet section may be oriented along a predetermined axis. The absolute value of a projection of each predetermined axis onto a rotation axis of the reference object may equal at least 5%, preferably 10% of the length of the inlet section. For example, the sensors may not be directly located in the plane of rotation. This can achieve the advantage that that pressure profiles at differing angles can be determined, increasing the accuracy of the determined wind direction and / or wind vector. The inlet section may be disposed in a fixed predetermined relation to one another. A projection can comprise backward and forward facing inlet openings when viewed in relation to a reference object, in particular a rotor. The normal vector of an inlet opening can be angled with respect to the rotation axis. The angle can be less than 90°.

[0116] The sensor assembly may comprise at least two spatially separated sensors and the control module may be configured to determine a degree of turbulence, density of the medium and / or temperature of the medium based on the pressure data from the at least two sensors and / or the position data. Each of the sensors can capture pressure date which may differ based on the relative orientation and position of the sensors, respectively their corresponding inlet openings. The control module can process the pressure data taking into account the spatial relation of the at least two sensors. With spatially separated inlet openings the system may not require an additional movement, i.e., a rotation of the reference object to determine the wind direction, respectively the wind vector. The control module can be configured to determine the wind vector based on the orientation and position of the inlet openings and the corresponding pressure data.

[0117] The measurement system may comprise a plurality of sensor assemblies. Each sensor assembly of the plurality of sensor assemblies may be disposed in a fixed position and / or orientation with respect to a corresponding individual reference object. The individual reference objects, i.e., individual turbines, may be spaced apart from one another. Each sensor assembly of the plurality of sensor assemblies may be configured to provide pressure data. This can achieve the advantage that a localized pressure distribution and / or wind vector field can be determined. Each turbine can be optimally angled with respect to their respective yaw angle to maximized energy output. The system can detect deviations of sensor assemblies from expected values, i.e., when pressure data deviates above a predetermined variance. Thereby, defects can be detected and / or drifts can be accounted for. A set of sensor assemblies can determine the wind vector and set yaw angles for a plurality of wind turbines. In particular also wind turbines not equipped with a sensor assembly.

[0118] The sensors may be disposed on individual surfaces of the head section. In particular the inlet openings can be disposed on the individual surfaces. Each surface can have a predetermined orientation such that a relative orientation of each inlet opening is known to the control module. The shape of the head section can thereby determine the orientation and / or position of the inlet opening.

[0119] The control module may be configured to receive position data indicating a spatial characteristic of the sensor assembly for each sensor assembly of the plurality of sensor assemblies and / or indicating a spatial characteristic of the respective individual reference object; receive pressure data from the plurality of sensor assemblies; and / or to determine a pressure distribution based on the position data and the pressure data. The position data can be a static position within a coordinate system and / or comprise a periodic movement, i.e., a specific rotation of the corresponding reference object, i.e., the rotor. Based on the received data the control module can interrelate pressure data from different positions to determine a wind vector field and / or average the wind vector respectively wind direction over a plurality of measurements, in particular a plurality of positions.

[0120] The control module may be configured to determine a pressure distribution and or a pressure gradient field based on the pressure data received from the plurality of sensor assemblies. This can achieve the advantage that local variations can be determined, in particular within a cluster of wind turbines. The system can be configured to adjust each turbine within the cluster to optimize the energy output over the complete cluster. Herein an optimal position of a single turbine with reference to the complete cluster may differ from an optimal position when considering the single turbine alone. The control module can determine an impact of a wind turbine on the wind vector field and adjust each turbine accordingly to optimize output.

[0121] The control module may be configured to provide a plurality of yaw adjustment data. Each yaw adjustment data may correspond to a specific reference object. This achieves the advantage that the control module can control the alignment of a plurality of turbines.

[0122] The measurement system may comprise a plurality of control modules. Each control module of the plurality of control modules may be assigned to a predetermined reference object and / or a predetermined sensor assembly of the plurality of sensor assemblies. This achieves the advantage that the system is scalable to control a plurality of turbines. A plurality of control modules can provide redundancy for a plurality of turbines. Each control module can perform individually and / or as a node of a control network.

[0123] The control modules may be configured to communicate pressure data, pressure distributions, wind vectors and / or yaw adjustment data between each other. This achieves the advantage that the locally captured pressure data can be related to the received data to verify the local measurement, adjust the local measurement based on the received data and / or to adjust a local yaw correction based on the received data.

[0124] The sensor may be disposed on a surface of a reference object, preferably wherein the sensor plane may be disposed on the surface of the reference object, more preferably the sensor plane may be arranged flush with the surface of the reference object. This can achieve the advantage that a pressure measurement can be determined without the use of a pressure buffer tube. The sensor can be directly exposed to the flow. The sensor can be embedded in the reference object or mounted onto the reference object.

[0125] The measurement system may comprise an off-phase removal device. The off-phase removal device may be configured to remove an off-phase medium from the pressure buffer tube, preferably the inlet section. An off-phase medium may be in a state of matter differing from the expected state matter for the medium inside the pressure buffer tube. For example, the expected medium can be a gas, in particular air, such that an off-phase medium can be a solid or a liquid. The expected medium can be a liquid such that a solid and / or gas can be an off-phase medium. This can achieve the advantage that liquid due to precipitation and / or ice buildup due to a temperature change or snow fall can be removed. Thereby consistency and precision of the pressure data measurements can be achieved. Also manual service of the system can be avoided. The off-phase removal device may comprise a heater, in particular a heating element, configured to heat at least part of the pressure buffer tube or to heat the medium inside the pressure buffer tube to alter the state of matter of the off-phase medium, in particular from solid to liquid and / or from liquid to gaseous. The heat may transform a liquid to a gas and / or a solid to a liquid and / or gas such that the medium can be removed from the pressure buffer tube.

[0126] The pressure buffer tube may comprise a drainage opening to remove off-phase medium from the pressure buffer tube. Preferably the drainage opening may be closed when performing a pressure measurement. The medium can flow out of the inlet opening and / or drain through the drainage opening in the pressure buffer tube.

[0127] The control module may be configured to determine the presence of off-phase medium in the pressure buffer tube based on the pressure data, preferably based on a deviation in the pressure data, more preferably a deviation in expected pressure data of one sensor in reference to a second sensor. This can achieve the advantage of continuous functioning of the system even in the event that one or more sensors are affected by off-phase medium or debris in the respective pressure buffer tube.

[0128] The heater may be configured to apply heat to the inlet section, preferably the inlet opening. Heat can be conducted via the pressure buffer tube to also apply heat to inner sections of the system, in particular the sensor. Ice or liquid may build up at the inlet opening due to the higher exposure and / or lower temperature at the surface. Positioning the heater close to the surface can increase efficiency.

[0129] The control module may comprise a temperature control configured to control a temperature of the pressure buffer tube, the inlet section, the inlet opening and / or the sensor. This can achieve the advantage that an effect of varying ambient temperatures on the pressure measurement can be reduced. The control module can account for a variation of the pressure data due to a temperature change and / or control the temperature to be within a predetermined interval to minimize a temperature related influence.

[0130] The off-phase removal device may comprise a blower configured to induce a counter flow in the pressure buffer tube to remove off-phase medium from the pressure buffer tube, preferably by blowing off-phase medium out of the pressure buffer tube through the inlet opening.

[0131] Below, system embodiments will be discussed. These embodiments are abbreviated by the letter "S" followed by a number. Whenever reference is herein made to "system embodiments", these embodiments are meant. Measuring system (100) for determining a pressure distribution, comprising a sensor assembly comprising a sensor configured to provide pressure data; a control module configured to receive position data indicating a spatial characteristic of the sensor assembly; and configured to determine a pressure distribution based on the position data and the pressure data. Measuring system according to the preceding embodiment wherein the sensor is configured to perform a pressure measurement and wherein the pressure data corresponds to the pressure measurement. Measuring system according to any of the preceding embodiments wherein the sensor assembly comprises a pressure buffer tube which comprises a first end and a second end, wherein the sensor is disposed at the second end or within the pressure buffer tube; and / or wherein the pressure buffer tube comprises an inlet section wherein the inlet section is disposed at the first end. Measuring system according to any of the preceding embodiments wherein the pressure buffer tube comprises a main tube body configured to fluidly connect the sensor and the inlet section. Measuring system according to any of the preceding embodiments with features of S3, wherein the inlet section is aligned with a position axis. Measuring system according to any of the preceding embodiments wherein the sensor is disposed in a sensor plane wherein a normal vector of the sensor plane is aligned with the position axis. Measuring system according to any of the preceding embodiments wherein the spatial characteristic is a position and / or an orientation of the sensor assembly, preferably a component of the sensor assembly, in particular the sensor. Measuring system according to any of the preceding embodiments with features of S3, wherein the position data indicates the spatial characteristic of the inlet section as the spatial characteristic of the sensor assembly. Measuring system according to any of the preceding embodiments wherein the position data indicates the spatial characteristic of the sensor as the spatial characteristic of the sensor assembly. 510. Measuring system according to any of the preceding embodiments wherein the inlet section and / or the pressure buffer tube comprises an inlet opening and is configured to fill with a medium, in particular through the inlet opening.

[0132] 511. Measuring system according to any of the preceding embodiments with features of S3, wherein the pressure buffer tube is configured to transport a pressure signal to the second end, in particular from the inlet opening, preferably via the medium wherein the medium inside the pressure buffer tube is the same as the medium in contact with the inlet opening.

[0133] 512. Measuring system according to any of the preceding embodiments wherein the control module is configured to determine a vector component, preferably a first vector component, a second vector component, a third vector component and / or an absolute value of a wind vector based on the position data and the pressure data.

[0134] 513. Measuring system according to any of the preceding embodiments wherein the wind vector comprises two vector components spanning a two-dimensional wind plane.

[0135] 514. Measuring system according to any of the preceding embodiments wherein the wind vector comprises three vector components spanning a three-dimensional wind space.

[0136] 515. Measuring system according to any of the preceding embodiments wherein the position data comprises spatial data configured to numerically represent a physical object in a coordinate system.

[0137] 516. Measuring system according to any of the preceding embodiments with features of S15, wherein the physical object is the measuring device; the sensor assembly; the sensor; the pressure buffer tube; the inlet section; the inlet opening; and / or a reference point or reference object in fixed spatial relation to one of the above.

[0138] 517. Measuring system according to any of the preceding embodiments with features of S15, wherein the coordinate system is a geographic coordinate system; a local coordinate system, in particular a spherical coordinate system; or a plurality of interlinked local coordinate systems. Measuring system according to any of the preceding embodiments with features of S15, wherein the position data comprises temporal data representing a point in time corresponding to the spatial data. Measuring system according to any of the preceding embodiments with features of S15, wherein each local coordinate system of the plurality of local coordinate systems is referenced by a reference coordinate to at least one other local coordinate system of the plurality of local coordinate systems such that the position of the physical object within the plurality of local coordinate systems is determined by its local coordinate system and the reference coordinate of its local coordinate system to another local coordinate system. Measuring system according to any of the preceding embodiments with features of S15, a relative position of a first local coordinate system, in particular its origin, is referenced to a second local coordinate system, in particular its origin. Measuring system according to any of the preceding embodiments wherein the pressure data comprises at least two pressure measurements, in particular a first pressure measurement captured when the inlet section is at a first position and a second pressure measurement captured when the inlet section is at a second position. Measuring system according to any of the preceding embodiments wherein the sensor is configured to periodically determine a pressure and to periodically provide corresponding pressure data, and wherein the control module is configured to link the pressure measurements to the position data to create a pressure profile indicating the pressure at specific time instances, preferably, wherein the time instances form a single period of the movement of the position axis, preferably the inlet section. Measuring system according to any of the preceding embodiments with features of S22, wherein the control module is configured to relate the pressure profile to the position data, preferably the control module is configured to link an angular position of the position axis to a corresponding pressure measurement. Measuring system according to any of the preceding embodiments with features of S22, wherein the control module is configured to periodically determine the pressure distribution and / or the wind vector based on the pressure profile and / or the position data. 525. Measuring system according to any of the preceding embodiments with features of S15, wherein the position data comprises data relating to a full rotation of the physical object in a predetermined plane, preferably along a predetermined trajectory, in particular a predetermined closed-loop trajectory in the coordinate system.

[0139] 526. Measuring system according to any of the preceding embodiments with features of S25, wherein the control module is configured to determine a pressure profile for at least part of a rotation, preferably a full rotation.

[0140] 527. Measuring system according to any of the preceding embodiments wherein the position data comprises one-dimensional rotational data, in particular angular data of the physical object.

[0141] 528. Measuring system according to any of the preceding embodiments wherein the control module is configured to adjust a sampling frequency of the sensor and / or to select a specific pressure measurement based on the position data, in particular based on an angular position of the physical object.

[0142] 529. Measuring system according to any of the preceding embodiments with features of S27, wherein the control module is configured to control capturing pressure measurements and / or select a set of pressure measurements from a plurality of pressure measurements to match pressure measurements with corresponding angular positions of the physical object.

[0143] 530. Measuring system according to any of the preceding embodiments wherein the control module is configured to determine an orientation of the position axis, in particular with reference to the physical object, based on the pressure data and position data.

[0144] 531. Measuring system according to any of the preceding embodiments wherein the trajectory of the position axis, preferably the inlet section, comprises an additional movement, in particular a periodic movement, i.e., a precession, in particular in addition to a trajectory of a reference object according to the position data.

[0145] 532. Measuring system according to any of the preceding embodiments with features of S31, wherein the control module is configured to determine an orientation of the position axis based on the additional movement.

[0146] 533. Measuring system according to any of the preceding embodiments with features of S31, wherein the control module is configured to determine the contribution of the additional movement to the pressure measurement, in particular the pressure profile. 534. Measuring system according to any of the preceding embodiments with features of S33, wherein the control module is configured to determine a periodicity of the additional movement.

[0147] 535. Measuring system according to any of the preceding embodiments with features of S33, wherein the control module is configured to determine the pressure distribution and / or the wind vector based on the additional movement.

[0148] 536. Measuring system according to any of the preceding embodiments with features of S33, wherein the control module is configured to adjust the pressure distribution and / or the wind vector based on the additional movement, in particular to remove a perturbation based on the additional movement from the pressure distribution and / or the wind vector.

[0149] 537. Measuring system according to any of the preceding embodiments wherein the control module is configured to compare at least two instances of a pressure profile to determine a drift of the pressure sensor.

[0150] 538. Measuring system according to any of the preceding embodiments with features of S37, wherein the control module is configured to adjust a pressure profile and / or a pressure distribution based on the drift, in particular to remove a driftbased contribution to the pressure distribution and / or the pressure profile.

[0151] 539. Measuring system according to any of the preceding embodiments with features of S3, wherein the control module is configured to determine an angle between the position axis and the wind vector.

[0152] 540. Measuring system according to any of the preceding embodiments wherein the control module is configured to determine the position axis based on the position data and the pressure data, in particular when the position axis moves, along a periodic trajectory, preferably an elliptical trajectory, more preferably a circular trajectory, in particular based on a precession in reference to periodic angular motion of the reference object.

[0153] 541. Measuring system according to any of the preceding embodiments with features of S3, wherein the inlet section is disposed on a reference object.

[0154] 542. Measuring system according to any of the preceding embodiments with features of S6, wherein the sensor is disposed on a reference object.

[0155] 543. Measuring system according to any of the preceding embodiments with features of S41, wherein the position axis is aligned with a predetermined axis of the reference object and / or wherein the inlet section and / or the sensor is in a fixed spatial relation to the reference object. Measuring system according to any of the preceding embodiments with features of S41, wherein the position axis is oriented relative to an orientation vector, in particular an orientation vector of the reference object, wherein an angle between the orientation vector and the position axis is less or equal to 160°, preferably less than 90°. Measuring system according to any of the preceding embodiments wherein the measuring system, the sensor assembly or the inlet section performs a periodic movement with respect to a reference object. Measuring system according to any of the preceding embodiments wherein the measuring system is attached to a reference object. Measuring system according to any of the preceding embodiments with features of S46, wherein the control module is configured to be electrically powered by the reference object. Measuring system according to any of the preceding embodiments wherein the control module comprises a power source, in particular a replenishable / rechargeable power source, preferably a generator configured to generate electrical power based on a movement of the reference object, more preferably a solar-based and / or wind-based generator. Measuring system according to any of the preceding embodiments with features of S41, wherein the reference object is one of the following: a blade, in particular of a turbine or rotor; a hub, in particular of a turbine or rotor; a spinner, in particular of a turbine; a part of a turbine affected by, in particular moving based on, a yawcontrol of a turbine, preferably a nacelle of a turbine; or a spatially fixed part of a turbine, in particular a tower of a turbine. Measuring system according to any of the preceding embodiments wherein the control module is configured to receive orientation data indicating an orientation of the physical object, in particular the reference object, and / or the measuring system, in particular indicating a pitch angle and / or a yaw angle in absolute or relative spatial coordinates and / or indicating a rotation angle, in particular a rotation angle in a plane perpendicular to a yaw plane. Measuring system according to any of the preceding embodiments with features of S50, wherein the yaw angle is determined in a plane parallel to a ground plane, and / or wherein a rotation angle is determined in a plane perpendicular to a ground plane. 552. Measuring system according to any of the preceding embodiments with features of S50, wherein the control module is configured to determine a difference between the orientation data and the wind vector based on the pressure distribution, in particular to determine a deviation angle of the wind vector projected onto the yaw plane of the reference object and / or to determine a deviation angle of the wind vector projected onto the pitch plane of the reference object.

[0156] 553. Measuring system according to any of the preceding embodiments wherein the control module is configured to determine a yaw misalignment of the reference object based on the pressure distribution.

[0157] 554. Measuring system according to any of the preceding embodiments with features of S53, wherein the control module is configured to provide yaw adjustment data indicating a yaw adjustment to reduce the yaw misalignment based on the determined yaw misalignment.

[0158] 555. Measuring system according to any of the preceding embodiments with features of S53, comprising a communication interface configured to provide pressure data, a pressure distribution, a wind vector and / or yaw adjustment data to a data interface corresponding to the reference object.

[0159] 556. Measuring system according to any of the preceding embodiments with features of S53, wherein the inaccuracy of the determined yaw misalignment is below 5°, preferably below 2°, more preferably below 1°.

[0160] 557. Measuring system according to any of the preceding embodiments with features of S41, wherein the control module is configured to determine an offset of the position axis to the predetermined axis and to adjust the pressure distribution based on the offset, in particular remove the offset-based contribution to the pressure distribution.

[0161] 558. Measuring system according to any of the preceding embodiments wherein the sensor is configured to determine the pressure of a medium, in particular a dynamic pressure of a flow of a medium.

[0162] 559. Measuring system according to any of the preceding embodiments comprising a rotation sensor configured to provide rotation data, wherein the rotation data indicates at least one of the following: a rotation angle according to embodiment S51; an angular velocity, in particular with respect to a center of rotation; and / or a tangential velocity; 560. Measuring system according to any of the preceding embodiments with features of S50, wherein the control module is configured to determine a pressure gradient based on the orientation data, the position data and / or the pressure data.

[0163] 561. Measuring system according to any of the preceding embodiments wherein the sensor assembly comprises a plurality of sensors, preferably between 2 and 14 sensors, more preferably 5 sensors, according to embodiment S2, and wherein the sensor assembly comprises a plurality of pressure buffer tubes, preferably 5 pressure buffer tubes, according to embodiment S3.

[0164] 562. Measuring system according to any of the preceding embodiments with features of S61, wherein the position data indicates the spatial characteristic of the geometric center or a reference point at a fixed distance of the geometric center of the plurality of inlet sections and / or the plurality of sensors.

[0165] 563. Measuring system according to any of the preceding embodiments with features of S61, wherein the sensors of the plurality of sensors are spaced apart in fixed positions with respect to one another and / or wherein the pressure buffer tubes of the plurality of pressure buffer tubes are spaced apart in fixed positions with respect to one another and / or wherein the inlet sections of the plurality of inlet sections are spaced apart in fixed positions with respect to one another.

[0166] 564. Measuring system according to any of the preceding embodiments with features of S57, wherein the space spanned by all inlet sections of the plurality of inlet sections is equal to or less than a hemisphere.

[0167] 565. Measuring system according to any of the preceding embodiments with features of S57, wherein at a first inlet section of the plurality of inlet sections is aligned with the position axis and a second inlet section of the plurality of inlet sections is aligned with a second axis, and wherein the position axis and the second axis are angled with respect to one another.

[0168] 566. Measuring system according to any of the preceding embodiments with features of S57, wherein each of the inlet sections of the plurality of inlet sections is aligned with the position axis.

[0169] 567. Measuring system according to any of the preceding embodiments with features of S61, wherein the control module is configured to determine a speed vector based on the pressure data of the plurality of sensors, in particular a wind speed vector.

[0170] 568. Measuring system according to any of the preceding embodiments wherein the sensor assembly forms a multi-hole probe and / or wherein the control module is configured to measure a magnitude and / or a direction of a flow velocity vector with respect to the sensor assembly and / or a static and / or a total pressure. Measuring system according to any of the preceding embodiments with features of S41 and S61, wherein the inlet opening of each inlet section of the plurality of inlet sections is flush with an outer surface of the reference object. Measuring system according to any of the preceding embodiments with features of S41 and S61, wherein the sensor assembly, the inlet sections or the pressure buffer tubes protrude less than 20 cm, preferably less than 10 cm, more preferably less than 5 cm from an outer surface of the reference object. Measuring system according to any of the preceding embodiments with features of S41 and S61, wherein each inlet section of the plurality of inlet sections is aligned with an orientation vector of the reference object within a tolerance of 20°, preferably 10°, more preferably 5°. Measuring system according to any of the preceding embodiments comprising a measurement head section and a stem section. Measuring system according to any of the preceding embodiments with features of S72, wherein the head section forms the reference object. Measuring system according to any of the preceding embodiments with features of S72, wherein the sensor assembly is disposed on the head section and / or wherein the stem section is configured to attach the head section to the reference object. Measuring system according to any of the preceding embodiments with features of S72, wherein the stem section has a tubular form and / or wherein the head section forms one of the following shapes: a part ellipsoid, preferably a partial sphere; a cone; a pyramid, preferably a polygonal pyramid, preferably pentagonal pyramid; a poly-sided cone, preferably a five-sided cone; a pyramid stump, in particular having a polygonal base; a polygonal sphere-shape. Measuring system according to any of the preceding embodiments with features of S72, wherein the stem section is oriented at a predetermined, preferably nonzero angle with respect to a rotation axis of the reference object. 577. Measuring system according to any of the preceding embodiments with features of S72, wherein a diameter of the head section is less or equal to a diameter of the stem section.

[0171] 578. Measuring system according to any of the preceding embodiments with features of S72, wherein every radial vector of the head section which intersects the stem section encloses an angle of less than 20°, preferably an angle of less than or equal to 90°, with the symmetry axis of the stem section.

[0172] 579. Measuring system according to any of the preceding embodiments with features of S72, wherein a base surface of the head section matches a cross section of the stem section such that the head section forms a tip of the stem section.

[0173] 580. Measuring system according to any of the preceding embodiments with features of S72, wherein a cross-sectional area between the head section and the stem section is larger or equal to 10%, preferably 20%, more preferably 50% of a largest cross-sectional area of the head section.

[0174] 581. Measuring system according to any of the preceding embodiments with features of S72, wherein the sensor assembly, preferably all sensors and / or all inlet sections, are disposed on the head section.

[0175] 582. Measuring system according to any of the preceding embodiments with features of S72, wherein each inlet section is oriented along a predetermined axis, wherein the absolute value of a projection of each predetermined axis onto a rotation axis of the reference object equals at least 5%, preferably 10% of the length of the inlet section (i.e., the sensors are not directly located in the plane of rotation.

[0176] 583. Measuring system according to any of the preceding embodiments with features of S72, wherein the sensor assembly comprises at least two spatially separated sensors and wherein the control module is configured to determine a degree of turbulence, density of the medium and / or temperature of the medium based on the pressure data from the at least two sensors and / or the position data.

[0177] 584. Measuring system according to any of the preceding embodiments comprising a plurality of sensor assemblies, wherein each sensor assembly of the plurality of sensor assemblies is disposed in a fixed position and / or orientation with respect to a corresponding individual reference object, wherein the individual reference objects (i.e., different turbines) are spaced apart from one another, wherein each sensor assembly of the plurality of sensor assemblies is configured to provide pressure data. 585. Measuring system according to any of the preceding embodiments with features of S72 and S83, wherein the sensors and / or inlet openings are disposed on individual surfaces of the head section.

[0178] 586. Measuring system according to any of the preceding embodiments with features of S84, wherein the control module is configured to receive position data indicating a spatial characteristic of the sensor assembly for each sensor assembly of the plurality of sensor assemblies and / or indicating a spatial characteristic of the respective individual reference object; receive pressure data from the plurality of sensor assemblies; and / or to determine a pressure distribution based on the position data and the pressure data.

[0179] 587. Measuring system according to any of the preceding embodiments with features of S84, wherein the control module is configured to determine a pressure distribution and or a pressure gradient field based on the pressure data received from the plurality of sensor assemblies.

[0180] 588. Measuring system according to any of the preceding embodiments wherein the control module is configured to provide a plurality of yaw adjustment data, in particular according to embodiment S54, wherein each yaw adjustment data corresponds to a specific reference object.

[0181] 589. Measuring system according to any of the preceding embodiments with features of S84, comprising a plurality of control modules, wherein each control module of the plurality of control modules is assigned to a predetermined reference object and / or a predetermined sensor assembly of the plurality of sensor assemblies.

[0182] 590. Measuring system according to any of the preceding embodiments with features of S89, wherein the control modules are configured to communicate pressure data, pressure distributions, wind vectors and / or yaw adjustment data between each other.

[0183] 591. Measuring system according to any of the preceding embodiments with features of S6, wherein the sensor is disposed on a surface of a reference object, preferably wherein the sensor plane is disposed on the surface of the reference object, more preferably wherein the sensor plane is arranged flush with the surface of the reference object.

[0184] 592. Measuring system according to any of the preceding embodiments comprising an off-phase removal device, wherein the off-phase removal device is configured to remove an off-phase medium from the pressure buffer tube, preferably the inlet section, wherein an off-phase medium is in a state of matter differing from the expected state matter for the medium inside the pressure buffer tube.

[0185] 593. Measuring system according to any of the preceding embodiments with features of S92, wherein the off-phase removal device comprises a heater, in particular a heating element, configured to heat at least part of the pressure buffer tube or to heat the medium inside the pressure buffer tube to alter the state of matter of the off-phase medium, in particular from solid to liquid and / or from liquid to gaseous.

[0186] 594. Measuring system according to any of the preceding embodiments wherein the pressure buffer tube comprises a drainage opening to remove off-phase medium from the pressure buffer tube, wherein preferably the drainage opening is closed when performing a pressure measurement.

[0187] 595. Measuring system according to any of the preceding embodiments wherein the control module is configured to determine the presence of off-phase medium in the pressure buffer tube based on the pressure data, preferably based on a deviation in the pressure data, more preferably a deviation in expected pressure data of one sensor in reference to a second sensor.

[0188] 596. Measuring system according to any of the preceding embodiments with features of S93, wherein the heater is configured to apply heat to the inlet section, preferably the inlet opening.

[0189] 597. Measuring system according to any of the preceding embodiments wherein the control module comprises a temperature control configured to control a temperature of the pressure buffer tube, the inlet section, the inlet opening and / or the sensor.

[0190] 598. Measuring system according to any of the preceding embodiments with features of S92, wherein the off-phase removal device comprises a blower configured to induce a counter flow in the pressure buffer tube to remove off-phase medium from the pressure buffer tube, preferably by blowing off-phase medium out of the pressure buffer tube through the inlet opening.

[0191] Below, method embodiments will be discussed. These embodiments are abbreviated by the letter "M" followed by a number. Whenever reference is herein made to "method embodiments", these embodiments are meant.

[0192] Ml. Method for determining a pressure distribution comprising the steps of providing pressure data; receiving position data indicating a spatial characteristic of a sensor assembly; and determining a pressure distribution based on the position data and the pressure data.

[0193] M2. Method according to the preceding embodiment comprising the step of transporting a pressure signal to the second end of a pressure buffer tube, in particular from the inlet opening, preferably via a medium comprised within the pressure buffer tube, preferably wherein the medium inside the pressure buffer tube is the same as the medium in contact with the inlet opening.

[0194] M3. Method according to any of the preceding embodiments comprising the step of determining a first vector component, a second vector component, a third vector component and / or an absolute value of a wind vector based on the position data and the pressure data.

[0195] M4. Method according to any of the preceding embodiments comprising the step of periodically determining a pressure and periodically providing corresponding pressure data, and linking the pressure measurements to the position data.

[0196] M5. Method according to any of the preceding embodiments with features of M4 comprising the step of creating a pressure profile indicating the pressure at specific time instances, preferably, wherein the time instances form a single period of movement of the position axis.

[0197] M6. Method according to any of the preceding embodiments comprising the step of relating the pressure profile to the position data, preferably comprising linking an angular position of the position axis to a corresponding pressure measurement.

[0198] M7. Method according to any of the preceding embodiments comprising the step of periodically determining the pressure distribution and / or the wind vector based on the pressure profile and / or the position data.

[0199] M8. Method according to any of the preceding embodiments comprising the step of determining a pressure profile for at least part of a rotation, preferably a full rotation.

[0200] M9. Method according to any of the preceding embodiments comprising the step of adjusting a sampling frequency of the sensor and / or to selecting a specific pressure measurement based on the position data, in particular based on an angular position of the physical object. MIO. Method according to any of the preceding embodiments comprising the step of controlling capturing pressure measurements and / or selecting a set of pressure measurements from a plurality of pressure measurements to match pressure measurements with corresponding angular positions of the physical object.

[0201] Mil. Method according to any of the preceding embodiments comprising the step of determining an orientation of the position axis, in particular with reference to the physical object, based on the pressure data and position data.

[0202] M12. Method according to any of the preceding embodiments comprising the step of determining an orientation of the position axis based on an additional movement.

[0203] M13. Method according to any of the preceding embodiments with features of M12 comprising the step of determining the contribution of the additional movement to the pressure measurement, in particular the pressure profile.

[0204] M14. Method according to any of the preceding embodiments with features of M12 comprising the step of determining a periodicity of the additional movement.

[0205] M15. Method according to any of the preceding embodiments with features of M12 comprising the step of determine the pressure distribution and / or the wind vector based on the additional movement.

[0206] M16. Method according to any of the preceding embodiments with features of M12 comprising the step of adjusting the pressure distribution and / or the wind vector based on the additional movement, in particular to remove a perturbation based on the additional movement from the pressure distribution and / or the wind vector.

[0207] M17. Method according to any of the preceding embodiments comprising the step of comparing at least two instances of a pressure profile to determine a drift of the pressure sensor.

[0208] M18. Method according to any of the preceding embodiments with features of M17 comprising the step of adjusting a pressure profile and / or a pressure distribution based on the drift, in particular to remove a drift-based contribution to the pressure distribution and / or the pressure profile.

[0209] M19. Method according to any of the preceding embodiments comprising the step of determining an angle between the position axis and the wind vector.

[0210] M20. Method according to any of the preceding embodiments comprising the step of determining the position axis based on the position data and the pressure data, in particular when the position axis moves, along a periodic trajectory, preferably an elliptical trajectory, more preferably a circular trajectory, in particular based on a precession in reference to periodic angular motion of the reference object.

[0211] M21. Method according to any of the preceding embodiments comprising the step of receiving orientation data indicating an orientation of the reference object and / or the measuring system, in particular indicating a pitch angle and / or a yaw angle in absolute or relative spatial coordinates and / or indicating a rotation angle, in particular a rotation angle in a plane perpendicular to a yaw plane.

[0212] M22. Method according to any of the preceding embodiments comprising the step of determining a difference between the orientation data and the wind vector based on the pressure distribution, in particular to determine a deviation angle of the wind vector projected onto the yaw plane of the reference object and / or to determine a deviation angle of the wind vector projected onto the pitch plane of the reference object.

[0213] M23. Method according to any of the preceding embodiments comprising the step of determining a yaw misalignment of the reference object based on the pressure distribution.

[0214] M24. Method according to any of the preceding embodiments comprising the step of providing yaw adjustment data indicating a yaw adjustment to reduce the yaw misalignment based on the determined yaw misalignment.

[0215] M25. Method according to any of the preceding embodiments comprising the step of providing pressure data, a pressure distribution, a wind vector and / or yaw adjustment data to a data interface corresponding to the reference object.

[0216] M26. Method according to any of the preceding embodiments comprising the step of determining an offset of the position axis to the predetermined axis and adjusting the pressure distribution based on the offset, in particular removing the offsetbased contribution to the pressure distribution.

[0217] M27. Method according to any of the preceding embodiments comprising the step of determining the pressure of a medium, in particular a dynamic pressure of a flow of a medium.

[0218] M28. Method according to any of the preceding embodiments comprising the step of providing rotation data, wherein the rotation data indicates at least one of the following: a rotation angle; an angular velocity, in particular with respect to a center of rotation; and / or a tangential velocity;

[0219] M29. Method according to any of the preceding embodiments comprising the step of determining a pressure gradient based on the orientation data, the position data and / or the pressure data.

[0220] M30. Method according to any of the preceding embodiments comprising the step of determining a speed vector based on the pressure data of the plurality of sensors, in particular a wind speed vector.

[0221] M31. Method according to any of the preceding embodiments comprising the step of measuring a magnitude and / or a direction of a flow velocity vector with respect to the sensor assembly and / or a static and / or a total pressure.

[0222] M32. Method according to any of the preceding embodiments comprising the step of receiving position data indicating a spatial characteristic of the sensor assembly for each sensor assembly of the plurality of sensor assemblies and / or indicating a spatial characteristic of the respective individual reference object; and receiving pressure data from the plurality of sensor assemblies; and / or determining a pressure distribution based on the position data and the pressure data.

[0223] M33. Method according to any of the preceding embodiments comprising the step of determining a pressure distribution and or a pressure gradient field based on the pressure data received from the plurality of sensor assemblies.

[0224] M34. Method according to any of the preceding embodiments comprising the step of providing a plurality of yaw adjustment data, wherein each yaw adjustment data corresponds to a specific reference object.

[0225] M35. Method according to any of the preceding embodiments comprising the step of communicating pressure data, pressure distributions, wind vectors and / or yaw adjustment data between control modules.

[0226] M36. Method according to any of the preceding embodiments comprising the step of removing an off-phase medium from the pressure buffer tube, preferably the inlet section, wherein an off-phase medium is in a state of matter differing from the expected state matter for the medium inside the pressure buffer tube.

[0227] M37. Method according to any of the preceding embodiments comprising the step of heating at least part of the pressure buffer tube or heating the medium inside the pressure buffer tube to alter the state of matter of the off-phase medium, in particular from solid to liquid and / or from liquid to gaseous.

[0228] M38. Method according to any of the preceding embodiments comprising the step of determining the presence of off-phase medium in the pressure buffer tube based on the pressure data, preferably based on a deviation in the pressure data, more preferably a deviation in expected pressure data of one sensor in reference to a second sensor.

[0229] M39. Method according to any of the preceding embodiments comprising the step of applying heat to the inlet section, preferably the inlet opening.

[0230] M40. Method according to any of the preceding embodiments comprising the step of controlling a temperature of the pressure buffer tube, the inlet section, the inlet opening and / or the sensor.

[0231] M41. Method according to any of the preceding embodiments comprising the step of inducing a counter flow in the pressure buffer tube to remove off-phase medium from the pressure buffer tube, preferably by blowing off-phase medium out of the pressure buffer tube through the inlet opening.

[0232] Brief description of figures

[0233] The present invention will now be described with reference to the accompanying drawings, which illustrate embodiments of the invention. These embodiments should only exemplify, but not limit, the present invention.

[0234] Fig. 1 schematically depicts an embodiment of the measurement system disposed on a hub of a turbine according to the present invention;

[0235] Fig. 2 schematically depicts an embodiment of the measurement system disposed on a reference object according to the present invention;

[0236] Fig. 3 schematically depicts an embodiment of the measurement system disposed on a reference object according to the present invention;

[0237] Fig. 4 schematically depicts an embodiment of a measurement system according to the present invention; and

[0238] Fig. 5 schematically depicts an orientation of a wind turbine with a measurement system according to the present invention. It is noted that not all the drawings carry all the reference signs. Instead, in some of the drawings, some of the reference signs have been omitted for sake of brevity and simplicity of illustration. Embodiments of the present invention will now be described with reference to the accompanying drawings.

[0239] Figure 1 shows a schematic representation of the measurement system according to the invention. The measuring system 100 can determine a pressure distribution and comprises a sensor assembly 101 that includes a sensor 102 for providing pressure data. A control module 103 receives position data, which indicates a spatial characteristic of the sensor assembly, and uses this information along with the pressure data to determine the pressure distribution.

[0240] In the sensor assembly can comprise a pressure buffer tube 104-1 with a first end 105 and a second end 106. The sensor is either located at the second end or within the pressure buffer tube. Additionally, the pressure buffer tube has an inlet section at its first end, which is aligned with a position axis x. The main tube body of the pressure buffer tube connects the sensor to the inlet section 107 allowing for the transmission of a pressure present at the inlet section to the sensor.

[0241] The sensor assembly can comprise a plurality of pressure buffer tubes 104-1, 104-2, 104-3, 104-4. Herein each pressure buffer tube can comprise the features according to the embodiment of the first pressure buffer tube 104-1. The control module can be configured to process pressure data captured by the plurality of sensors 102-1, 102-2, 102-3, 102-4. Preferably, all inlet sections, respectively inlet openings are aligned along the orientation axis x. The inlet openings can be disposed on the dome shaped section such that normal vectors of the inlet opening cross-sections are angled with respect to the orientation axis x. Preferably, each of the normal vectors encloses the same angle with the orientation axis x. Additionally or alternatively a normal vector of a center inlet opening can coincide with or be parallel to the orientation axis x.

[0242] The sensor assembly can represent a one-dimensional pressure sensor wherein the measurement system is configured to use the rotation and / or orientation of a reference object, e.g., a wind turbine to determine the wind direction, in particular in reference to an orientation axis of the measurement system and thereby an orientation of the wind turbine in reference to the wind direction. The control module may compensate an effect of a rotation of the reference object on the pressure measurement to provide an accurate measure of the pressure profile and based on the pressure profile the wind speed or wind vector.

[0243] The plurality of pressure buffer tubes can be disposed as a bundle at a tip of a rod which preferably can be a unibody. The inlet openings 108-1 to 108-4 can be evenly distributed, specifically symmetrically distributed on a front surface of the rod. Preferably, the inlet openings are disposed in a circular pattern. One inlet opening may be disposed at a center location of the rod.

[0244] When air flows past the measurement system, specifically past the inlet opening, it creates an angle with the centerline of the inlet section. If this angle is zero, the pressure sensors at the tube ends can measure the total pressure of the airflow. If the angle is not zero, the pressure detected by two sensors corresponding to two inlet openings which are offset with respect to one another differs. This difference is caused by the dynamic pressure resulting from the velocity of the airflow. The pressure variation between these sensors is a function of the flow angle.

[0245] To determine the specific function relating the pressure difference to the flow angle, the probe can be calibrated. A calibration curve can be embedded in the control module, representing the measured pressure difference as a function of the measured angle.

[0246] The inlet opening establishes a relationship between the flow angle and the angle of attack at the measurement system, and by reference at the reference object, e.g., the wind turbine. The flow angle can be related to a yaw angle of the wind turbine. The measurement system, in particular comprising 5 sensors, can provide yaw and / or pitch information simultaneously. In other words, a flow angularity in two perpendicular planes can be determined. This can also be achieved when a single sensor is rotated and the pressure is recorded for a full rotation.

[0247] Specifically, when the inlet opening is moved throughout the flow field a comprehensive map of flow angularity can be created.

[0248] The spatial characteristic of the sensor assembly, specifically the sensor, is determined by the position data which represents the position and / or orientation of the sensor assembly in a coordinate system.

[0249] The measuring system can also determine a wind vector based on the position data and pressure data. The wind vector can be two-dimensional or three-dimensional, depending on the application.

[0250] The measuring system is designed to capture pressure measurements at different positions of the inlet section. These pressure measurements can be linked to the position data, creating a pressure profile that indicates the pressure at specific time instances. The control module can adjust the sampling frequency of the sensor and select specific pressure measurements based on the angular position of the sensor assembly.

[0251] The control module can receive orientation data indicating the orientation of the reference object and the measuring system. This data helps determine the deviation angle between the wind vector and the reference object, as well as the yaw misalignment. The control module can provide yaw adjustment data to reduce the yaw misalignment.

[0252] To ensure accuracy, the control module compares pressure profiles to detect any drift in the pressure sensor and adjusts the pressure distribution accordingly. It can also determine the offset of the position axis and adjust the pressure distribution to remove the offset-based contribution.

[0253] A wind turbine 200, i.e., a horizontal axis wind turbine (HAWT) with a measurement system 100 according to the invention is illustrated in Figure 2.

[0254] The wind turbine may include a tubular tower supporting a nacelle, blades 201-1, 201- 2 and a hub 202 of the turbine. Typically, the wind turbine may comprise three blades, whereas the third blade is not shown. The nacelle may house the drive train, e.g., a gearbox, shafts, couplings, generator and yaw drive(s). Other items such as the control electronics may be housed within the nacelle as well.

[0255] The blades are connected to the hub, and the hub may comprise a pitch control mechanism to control the pitch angle of each blade. Three blades can be employed, however, one, two or four or more blades could be employed as well. The blades convert the kinetic energy of the wind into mechanical energy by rotating a shaft connected to the generator. The shaft may rotate at a variable speed depending upon the wind speed, from zero up to a maximum steady-state speed whereby the turbine is generating a rated power.

[0256] In this embodiment, a sensor assembly is mounted on the hub of the wind turbine in a plane having the rotation axis x of the hub as a normal vector. The hub may comprise an aerodynamically shaped outer surface, i.e., a spinner configured to streamline the flow around the hub.

[0257] The front section of the hub can be shaped spherically. The inlet opening(s) can be disposed such that the component of the fluid velocity is determined above the boundary layer of the hub. Preferably, The measurement system may comprise a measurement head section 203 and a stem section 204. The inlet openings are disposed on the head section. The stem section attaches the head section to the hub.

[0258] The sensors can be mounted such that they are accessible from inside the hub. Preferably, the sensor assembly may be serviceable through the inside of the hub. The sensor assembly, preferably the complete measurement system can be removably attached to the hub, in particular in such a manner that it can be positioned from inside the hub.

[0259] The hub may rotate with the orientation axis x as a rotation axis. A relative rotation angle beta can indicate the rotation period of the hub and thereby of the measurement system. The angle beta can indicate when an inlet opening of the sensor assembly coincides with a previous position of another inlet opening. Due to the mounting the actual position may not coincide. However the angular position can be the same such that the position in the flow can be matched. An orientation difference of the two inlet sections can be taken into account. Such a difference can occur when the sensor assembly is oriented along an axis not parallel to the orientation axis x of the hub.

[0260] Additionally beta can indicate when a full rotation of the hub is completed. The hub may perform an additional movement, e.g., in a pitching plane, which can be described by a variation of the angle gamma. The additional movement can have a periodic component, e.g., excited swaying of the turbine in the flow and / or an aperiodic component, e.g., caused by a wind gust. The hub may also perform an additional periodic or aperiodic movement in the alpha-rotation plane, i.e., the yawing plane. The yaw control of the turbine may rotate the turbine in the yawing plane, in particular to adjust the rotation plane of the turbine to align with the wind vector.

[0261] In addition, the measuring system may include a rotation sensor to provide rotation data, such as rotation angle, angular velocity, or tangential velocity. This data can be used to calculate a pressure gradient. Multiple sensors and pressure buffer tubes can be incorporated into the sensor assembly to enhance measurement capabilities. The rotation sensor may provide data relating to alpha, beta and / or gamma.

[0262] The outputs of the sensor can be recorded at different angular positions. Preferably, at least two angular positions differing by 180° are captured. The angular position of the inlet opening, inlet section and / or sensor can be determined by an angle of rotation sensor. Alternatively, the angular position can be determined based on a previously recorded pressure profile. For example, the control module can determine a periodicity of the pressure data, divide the pressure data in sections according to the periodicity and thereby determine at least a relative angular position. The angle of rotation sensor can continuously determine the angular position of the rotor, i.e., hub. The sensors are fixed to the hub, the angular position of the hub and the sensors, respectively inlet openings and / or inlet sections are fixed relative to each other. The output of the sensors can thus be captured when the angular sensor detects the desired angular position of the rotor. Alternatively, captured pressure data can be matched to angular measurements that correspond in time.

[0263] At a 0° mounting of the sensor assembly, an imperfect rotation of the hub, i.e. a precession or wobble can be used to determine pressure values at offset positions serving as a basis to determine the pressure distribution and hence the wind vector. Herein, a minimal configuration can comprise only a single sensor mapping the pressure over a full rotation to determine the wind direction. Additional sensors can increase the performance of the system, in particular its accuracy in determining a wind vector. Furthermore, additional sensors can make the system independent of a movement of the rotor as pressure data from sensor positioned at a distance to one another can serve as a basis to determine the pressure distribution and thereby the wind vector in a static position, i.e. a non-rotating turbine.

[0264] The hub has an ellipsoidal front surface.

[0265] In the example embodiment as shown in Figure 3 the measurement assembly comprises 5 sensors and correspondingly 5 inlet openings and 5 inlet sections and 5 pressure buffer tubes 104-1 to 104-5. The tubes can be mounted on the ellipsoidal surface of the hub oriented with the axis of rotation of the hub. Four pressure buffer tubes 104-1 to 104-4 can be mounted parallel to the rotation axis but offset from the center of the hub and the fifth pressure buffer tube 104-5 can be mounted with the rotation axis as a symmetry axis. Each of the pressure buffer tubes 104-1 to 104-4 can be disposed at a predetermined distance from the central pressure buffer tube 104-5. Specifically, the corresponding inlet openings can be disposed accordingly. The shape of the inlet openings can correspond to the surface of the hub, i.e., can also be curved whereas the curved surfaces differ between the inlet sections. Alternatively, the inlet sections can be shaped according to a predetermined scheme, e.g. where each of the four offset inlet sections 108-1 to 108-4 is angled with respect to the central inlet opening 108-5 and / or each normal vector of the offset inlet sections can be oriented away from the central inlet opening.

[0266] Preferably, only a corresponding inlet section can protrude from the hub surface and the pressure buffer tubes may continue within the hub to the respective sensor.

[0267] The inlet openings can be oriented arbitrarily, wherein the control module is configured to determine a pressure profile based on the periodicity of the captured pressure data when the hub rotates.

[0268] Figure 4 depicts a schematic representation of an embodiment of the measurement system 100 according to the present invention. The system can comprise a plurality of sensor assemblies 401-1 to 401-5. Each sensor assembly can comprise a stem section and a head section, wherein the respective pressure buffer tube 104-1 to 104-5 is disposed at least partly within the respective head section. The sensor assemblies can comprise a plurality of sensors and corresponding pressure buffer tubes, inlet section and inlet openings. The stem sections can be disposed on the surface of the reference object, in particular a hub 202 of a turbine. The stem section can be angled, in particular angled such that a symmetry axis of the stem section is parallel to a normal vector of the hub 202 at the mounting position of the stem section at the hub. Additionally, at least one inlet section, specifically a normal vector of the inlet opening, of the respective sensor assembly can be oriented parallel to the normal vector of the hub at the mounting position of the stem section.

[0269] Figure 5 schematically depicts an orientation of a wind turbine with a measurement system according to the present invention. The wind turbine, specifically the rotor can have an orientation, i.e., a turbine position, determined by a yaw angle of the rotor. This angle can be determined in reference to true north. The absolute wind direction can also be determined in reference to true north. The control module can determine an angle between an absolute wind direction and the orientation of the turbine, i.e., a relative wind direction. The relative wind direction can indicate an offset between the orientation of the wind turbine and the wind direction. Any offset between wind direction and turbine position may impact the power output of the rotor. The system may determine an optimal yawing angle of the turbine, e.g., in the form of a yaw angle correction. A wind turbine control provided with the yaw angle correction can be configured to yaw the turbine to minimize the angle between relative wind direction and turbine position. The control module may continuously or periodically update the relative wind direction while yawing to minimize the chance of an overshoot or undershoot yaw correction. Preferably the control module can be configured to provide a precision yaw control to reduce a misalignment below 5°, preferably below 2°, more preferably below 1°. The precision can be achieved by the sensor assembly achieving a corresponding accuracy of the relative wind direction.

[0270] Whenever steps were recited in the above or also in the appended claims, it should be noted that the order in which the steps are recited in this text may be accidental. That is, unless otherwise specified or unless clear to the skilled person, the order in which steps are recited may be accidental. That is, when the present document states, e.g., that a method comprises steps (A) and (B), this does not necessarily mean that step (A) precedes step (B), but it is also possible that step (A) is performed (at least partly) simultaneously with step (B) or that step (B) precedes step (A). Furthermore, when a step (X) is said to precede another step (Z), this does not imply that there is no step between steps (X) and (Z). That is, step (X) preceding step (Z) encompasses the situation that step (X) is performed directly before step (Z), but also the situation that (X) is performed before one or more steps (Yl), ..., followed by step (Z). Corresponding considerations apply when terms like "after" or "before" are used.

Claims

Claims1. Measuring system (100) for determining a pressure distribution, comprising a sensor assembly (101) comprising a sensor (102) configured to provide pressure data, and a control module (103) configured to receive position data indicating a spatial characteristic of the sensor assembly (101) and to determine a pressure distribution based on the position data and the pressure data.

2. Measuring system (100) according to claim 1 wherein the sensor assembly (101) comprises a pressure buffer tube (104-1) which comprises a first end (105) and a second end (106) and an inlet section (107), wherein the sensor (102) is disposed at the second end (106), wherein the inlet section (107) is disposed at the first end (105) and wherein the position data indicates the spatial characteristic of the inlet section (107) as the spatial characteristic of the sensor assembly (101).

3. Measuring system (100) according to claim 2 wherein the pressure data comprises at least two pressure measurements, in particular a first pressure measurement captured when the inlet section (107) is at a first position and a second pressure measurement captured when the inlet section (107) is at a second position.

4. Measuring system (100) according to any of the preceding claims wherein the sensor (102) is configured to periodically determine a pressure and to periodically provide corresponding pressure data, and wherein the control module (103) is configured to link the pressure measurements to the position data to create a pressure profile indicating the pressure at specific time instances.

5. Measuring system (100) according to any of the preceding claims wherein the position data comprises one-dimensional rotational data of a physical object, wherein the control module (103) is configured to control capturing pressure measurements or select a set of pressure measurements from a plurality of pressure measurements, to match pressure measurements with corresponding positions of the physical object.

6. Measuring system (100) according to claim 2 wherein the inlet section (107) is aligned with a position axis (x), wherein the trajectory of the position axis (x) comprises an additional movement, and wherein the control module (103) is configured to determine the contribution of the additional movement to the pressure measurement.

7. Measuring system (100) according to claim 2 wherein the control module (103) is configured to determine the pressure distribution based on the additional movement.

8. Measuring system (100) according to claim 4 wherein the control module (103) is configured to compare at least two instances of a pressure profile to determine a drift of the sensor (102), and wherein the control module (103) is configured to adjust a pressure profile based on the drift, in particular to remove a drift-based contribution to the pressure profile.

9. Measuring system (100) according to any of the preceding claims wherein the control module (103) is configured to receive orientation data indicating an orientation of the physical object, wherein the control module (103) is configured to determine a vector component, based on the position data and the pressure data, and wherein the control module (103) is configured to determine a difference between the orientation data and the wind vector based on the pressure distribution.

10. Measuring system (100) according to any of the preceding claims wherein the sensor assembly (101) forms a multi-hole probe.

11. Measuring system (100) according to any of the preceding claims comprising a measurement head section (203) and a stem section (204), wherein the inlet section (107) comprises an inlet opening (108-1) and is configured to fill with a medium through the inlet opening, wherein the inlet opening (108-1) is disposed on the measurement head section (203).

12. Measuring system (100) according to claim 2 comprising an off-phase removal device configured to remove an off-phase medium from the pressure buffer tube (104-1), wherein an off-phase medium is in a state of matter differing from the state matter for the medium inside the pressure buffer tube (104-1).

13. Method for determining a pressure distribution comprising the steps of providing pressure data; receiving position data indicating a spatial characteristic of a sensor assembly (101); and determining a pressure distribution based on the position data and the pressure data.

14. Method according to claim 13 comprising the step of determining the pressure distribution based on the additional movement.

15. Method according to claim 13 or 14 comprising the steps of receiving orientation data indicating an orientation of a reference object, and determining a difference between the orientation data and a wind vector based on the pressure distribution.

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