A method for detecting wind turbine wake

Abstract

This invention provides a method for detecting the wake of a wind turbine, relating to the field of wind power generation technology. It utilizes a lidar lens installed on the wind turbine nacelle to emit a detection beam V towards the area behind the wind turbine. LOS Acquire detection beam V LOS Distance to library B i The corresponding radial velocity library V LOS,i When the detection beam V LOS Within the wake region, wind speed is deficient, and radial velocity is relatively low. When the beam is outside the wake region, wind speed recovers, and radial velocity increases, showing a trend of initially decreasing and then gradually increasing in radial distance. The radial velocity library V is then obtained. LOS,i The corresponding slope library k i Obtain the slope library k i The maximum slope k max This indicates that the radial distance corresponding to this slope is the wake boundary, and the maximum slope k max The corresponding maximum radial distance R max R is the wake boundary. max *sin(α) is the wake radius. This invention uses a lidar mounted on the top of the nacelle to emit a beam towards the rear of the wind turbine for radial velocity measurement. This simple scanning mode of the nacelle-mounted lidar allows for rapid extraction of wake characteristic information.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and more particularly to a method for detecting the wake of a wind turbine. Background Technology

[0002] When a wind turbine extracts energy from the wind, a wake is generated downwind of the turbine. This wake not only causes a loss of power generation from the downwind turbine, affecting its power generation efficiency, but also increases its fatigue load, causing wear on turbine components, reducing the turbine's stability, and shortening its service life.

[0003] To control the wake effect, the spacing between wind turbines in the upwind and downwind directions, as well as the spacing in the crosswind direction, should be as large as possible to avoid efficiency reduction and turbine damage caused by the wake effect. However, this may also result in wasted land area and cabling for the wind farm. Therefore, it is necessary to observe the wake and design the optimal wind turbine layout based on the actual wake size.

[0004] Current methods for observing wake ducts involve installing scanning lidar at a distance from the wind turbine. However, due to the weight of the lidar itself, it is typically mounted on the ground or a fixed platform at a distance of more than 1 km from the wind turbine wake. This allows for multi-layered, high-resolution scanning of the wake area before extracting its characteristics. However, lidar requires a large number of scanning beams and has a long scanning time. Existing technology, by simply observing the wind turbine wake from a distance, merely determines the presence of a wake without performing quantitative analysis of its characteristics.

[0005] For those skilled in the art, how to easily and quickly observe the wake of wind turbines is a technical problem that needs to be solved. Summary of the Invention

[0006] This invention provides a method for detecting wind turbine wake. A lidar is installed on the top of the nacelle, emitting a beam towards the rear of the wind turbine to measure radial velocity. Through this simple scanning mode using a nacelle-mounted lidar, characteristic information of the wake can be quickly extracted. The specific solution is as follows:

[0007] A method for detecting wind turbine wake includes:

[0008] The lidar lens installed on the wind turbine nacelle emits a detection beam V towards the area behind the wind turbine. LOS The detection beam V LOS There is an angle α between it and the centerline of the cabin;

[0009] Obtain the detection beam V LOS Distance to library B i The radial velocity library V corresponding to (i = 1, 2, ..., n) LOS,i (i = 1, 2, ..., n);

[0010] Obtain the radial velocity library V LOS,i The slope library k corresponding to (i = 1, 2, ..., n) i (i = 1, 2, ..., n);

[0011] Obtain the slope library k i The maximum slope k of (i = 1, 2, ..., n) max The maximum slope k max The corresponding maximum radial distance R max R is the wake boundary. max *sin(α) is the wake radius.

[0012] Optionally, the detection beam V LOS Including the first beam V LOS1 Second beam V LOS2 The first beam V LOS1 and the second beam V LOS2 The first and second wake radii are obtained by facing different directions respectively.

[0013] Optionally, the first beam V LOS1 and the second beam V LOS2 Located in the same plane, the sum of the first and second wake radii is the wake diameter.

[0014] Optionally, the first beam V LOS1 and the second beam V LOS2 The angles relative to the centerline of the cabin are ±α.

[0015] Optionally, the first beam V LOS1 The corresponding maximum radial distance R max The first maximum radial distance R 1,max The first beam V LOS1 The corresponding minimum slope k min The first minimum slope k 1,min The second beam V LOS2 The corresponding maximum radial distance R max The second maximum radial distance R 2,max The second beam V LOS2 The corresponding minimum slope k min The second minimum slope k 2,min ;

[0016] The first minimum slope k 1,min The first background wind field radial velocity V, obtained by weighted averaging of the three distances before and after, is... LOS1,0 The second minimum slope k 2,minThe radial velocity V of the second background wind field after weighted averaging of the three distances before and after is corresponding to the following three distances. LOS2,0 The radial velocity of the background wind field is used to calculate the free-flow wind speed V0 and the angle γ between the wind direction and the normal to the wind turbine impeller surface.

[0017]

[0018]

[0019]

[0020]

[0021] Optionally, the free-flow wind speed V0 is substituted into the Jensen wake model to calculate the velocity evolution along the wake centerline:

[0022]

[0023] Where: k w It is the wake spread factor, C T It is the wind turbine thrust coefficient, and D is the wind turbine impeller diameter.

[0024] Optionally, it also includes: calculating the wind speed loss rate.

[0025]

[0026] Optionally, it is determined whether the wind speed loss rate is lower than a threshold δ. th If so, it is assumed that the wake loss has recovered and the wake has completely dissipated; the corresponding axial distance x is the length of the wind turbine wake, and the depth of the wake is calculated by subtracting the minimum velocity from the maximum velocity of the wake cross section at each distance.

[0027] Optionally, the lidar identifies the angle γ between the wind direction and the normal to the wind turbine impeller surface. When the angle γ is greater than a threshold γ, th Then, the servo turntable is controlled to rotate to the wind direction azimuth angle to ensure effective detection of the wake.

[0028] This invention provides a method for detecting the wake of a wind turbine, which utilizes a lidar lens installed on the wind turbine nacelle to emit a detection beam V towards the area behind the wind turbine. LOS Detection beam V LOS An angle α exists between the beam and the centerline of the cabin; the detection beam V is acquired. LOS Distance to library B i The radial velocity library V corresponding to (i = 1, 2, ..., n) LOS,i (i = 1, 2, ..., n); when the detection beam V LOSWithin the wake region, wind speed is deficient, and radial velocity is relatively low. When the beam is outside the wake region, wind speed recovers, and radial velocity increases, showing a trend of initially decreasing and then gradually increasing in radial distance. The radial velocity library V is then obtained. LOS,i The slope library k corresponding to (i = 1, 2, ..., n) i (i = 1, 2, ..., n); Obtain the slope library k i The maximum slope k of (i = 1, 2, ..., n) max This indicates that the radial distance corresponding to this slope is the wake boundary, and the maximum slope k max The corresponding maximum radial distance R max R is the wake boundary. max *sin(α) is the wake radius. This invention uses a lidar mounted on the top of the nacelle to emit a beam towards the rear of the wind turbine for radial velocity measurement. This simple scanning mode of the nacelle-mounted lidar allows for rapid extraction of wake characteristic information. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a top-view diagram of the fan wake.

[0031] Figure 2 This is a side view diagram of the fan wake.

[0032] Figure 3 This is a schematic diagram of the vector decomposition of airflow velocity. Detailed Implementation

[0033] The core of this invention lies in providing a method for detecting wind turbine wakes. A lidar is installed on the top of the nacelle and emits a beam towards the rear of the wind turbine to measure radial velocity. By using this simple scanning mode of nacelle-mounted lidar scanning, the characteristic information of the wake can be quickly extracted.

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the wind turbine wake detection method of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Combination Figure 1 , Figure 2 The diagram illustrates the wake of the airflow after it encounters the fan, where A represents the detection beam V emitted by the lidar lens towards the area behind the fan.LOS B represents the edge of the wake, C represents the centerline of the nacelle top and the radar centerline, D represents the blade, and E represents the nacelle.

[0036] This invention provides a method for detecting the wake of a wind turbine, comprising the following steps:

[0037] S1. The lidar lens installed on the wind turbine nacelle emits a detection beam V towards the area behind the wind turbine. LOS Detection beam V LOS An angle α exists between the nacelle centerline and the nacelle centerline. This invention employs a nacelle-mounted lidar, installed at the top centerline of the wind turbine nacelle, with the lidar lens facing the rear of the wind turbine. Figure 1 Above the middle, Figure 2 (On the right side of the image), the detection beam V is emitted to the rear area via an internal optical switch of the cabin-type lidar. LOS .

[0038] S2, Obtain the detection beam V LOS Distance to library B i The radial velocity library V corresponding to (i = 1, 2, ..., n) LOS,i (i = 1, 2, ..., n). The concept of a distance database is as follows: The lidar emits a laser, and through a data acquisition system, the entire measurement distance is divided into multiple distance regions, called the distance database. Combined with... Figure 1 As shown, the detection beam V LOS In radar echo signal processing, the signal is divided into several small range units along the ray direction. These small range units together constitute a range library, and each small range unit represents a value of i. The detection beam V is then used. LOS It can detect wind speed, identifying the wind speed at each small distance unit. The radial velocity of all beams on a fixed platform within the same distance library (on a plane) can be used to invert the wind speed and direction at that distance. Data from several beams within the same distance library can also be used to invert the wind speed at that distance.

[0039] S3, Obtain the radial velocity library V LOS,i The slope library k corresponding to (i = 1, 2, ..., n) i (i = 1, 2, ..., n). This invention utilizes the following phenomenon: wind speed loss occurs in the wake region, while wind speed recovers outside the wake. When the laser radar beam is in the wake region, the radial velocity is relatively small due to the wind speed loss; when the beam is outside the wake region, the radial velocity increases due to the wind speed recovery, exhibiting a trend line f(V) that is initially small and then gradually increases in radial distance. LOS ,i).

[0040] It should be noted that radial velocity is defined as follows: the velocity component of aerosol particles moving along the radial (line-of-sight) beam of a wind-measuring lidar, i.e., the projection of the wind speed vector onto the radial beam. Radial velocity is also called line-of-sight velocity, which is the velocity of an object or celestial body in the direction of the observer's line of sight; generally, it refers to the velocity component of the object's motion along the observer's line of sight, i.e., the projection of the velocity vector onto the line of sight. Conventionally, a positive line-of-sight velocity indicates that the object is receding, while a negative value indicates that the object is approaching. (Combined with...) Figure 3 As shown, the vector decomposition of airflow velocity is illustrated, where v represents the actual airflow velocity, and v1 represents the radial component of v (along the detection beam V). LOS (the direction of emission), v2 represents the normal component of the airflow v; the radial velocity is also... Figure 3 v1 in the detection beam V LOS It can detect the radial velocity of airflow at small distance units, and the radial velocity is directly proportional to the actual velocity of the airflow.

[0041] S4. Obtain the slope library k i The maximum slope k of (i = 1, 2, ..., n) max The maximum slope k max The corresponding maximum radial distance R max R is the wake boundary. max *sin(α) is the wake radius, such as Figure 1 As shown in Figure y. Due to the difference in radial velocity detected within and outside the wake region, the radial distance exhibits a trend line f(V) that is initially small and then gradually increases. LOS The position corresponding to the maximum slope is the position with the largest change in radial velocity, and this position is considered to be the detection beam V. LOS The intersection point with the edge of the wake. It should be noted that the radial distance is the distance with the radar as the origin; the distance the radar beam travels is generally referred to as the radial distance.

[0042] The above process is performed at a specific angle. If necessary, different angles and orientations can be used to repeat the operation to obtain more data. This invention installs a lidar on the top of the nacelle, emitting a beam towards the rear of the wind turbine for radial velocity measurement. This simple scanning mode using a nacelle-mounted lidar allows for rapid extraction of wake characteristic information. The parameters describing the wake characteristics of a wind turbine mainly include the wake velocity loss rate, wake width, wake length, and wake width. The wake width is the width of the wake velocity loss region perpendicular to the central axis. The wake length is the axial length of the wake velocity loss region. The wake depth is defined as the difference between the highest and lowest velocities in the velocity loss region, given that the wake velocity cross-section is a Gaussian profile.

[0043] Based on the above scheme, combined with Figure 2 The detection beam V of the present invention LOS Including the first beam V LOS1 Second beam V LOS2 First beam V LOS1 Second beam V LOS2 The first and second wake radii are obtained by facing different directions respectively.

[0044] Specifically, the first beam V LOS1 Second beam V LOS2 Located in the same plane, the sum of the first and second wake radii is the wake diameter. For example... Figure 2 As shown, the first beam V LOS1 Second beam V LOS2 Located on the same horizontal plane, viewed from the side, the first beam V LOS1 Second beam V LOS2 Both coincide with the central axis.

[0045] First beam V LOS1 Second beam V LOS2 The angles relative to the centerline of the cabin are ±α, respectively. Preferably, the first beam V... LOS1 Second beam V LOS2 They can be set in the same plane and symmetrically arranged, or they can be set in different planes or at different angles.

[0046] The specific process for transmitting two beams is as follows:

[0047] The nacelle-mounted lidar is installed at the centerline of the top of the wind turbine nacelle, with its lens facing the rear of the turbine. It emits two beams to the rear area via an internal optical switch: the first beam is V... LOS1 Second beam V LOS2 The angles between these angles and the radar's central axis are ±α and ±α, respectively; the range is denoted as B. i The radial distance corresponding to (i = 1, 2, ..., n) is R. i (i = 1, 2, ..., n), the axial distance from the fan is x = R i *cos(α), radial distance is R i The corresponding radial velocities are V LOS1,i and V LOS2,i (i = 1, 2, ..., n), when the beam is in the wake region, the wind speed is deficient and the radial velocity is relatively small; when the beam is outside the wake region, the wind speed recovers and the radial velocity increases, showing a trend line f(V) that is initially small and then gradually increases in radial distance. LOS1 ,i) and f(V LOS2 ,i); calculate f(V LOS1 ,i) and f(VLOS2 The slope k between any two points i) 1,i and k 2,i (i = 1, 2, ..., n-1), find k respectively 1,i and k 2,i Maximum value k1, max and k 2,max The radial distance R corresponding to the maximum value 1,max and R 2,max R is the wake boundary. 1,max *sin(α) and R 2,max The sum of *sin(α) is the wake width, which is also the wake diameter.

[0048] Furthermore, the first beam V of the present invention LOS1 The corresponding maximum radial distance R max The first maximum radial distance R 1,max First beam V LOS1 The corresponding minimum slope k min The first minimum slope k 1,min Second beam V LOS2 The corresponding maximum radial distance R max The second maximum radial distance R 2,max Second beam V LOS2 The corresponding minimum slope k min The second minimum slope k 2,min .

[0049] First minimum slope k 1,min The first background wind field radial velocity V, obtained by weighted averaging of the three distances before and after, is... LOS1,0 The second minimum slope k 2,min The radial velocity V of the second background wind field after weighted averaging of the three distances before and after is corresponding to the following three distances. LOS2,0 The first background wind field radial velocity V LOS1,0 Second background wind field radial velocity V LOS2,0 The radial velocity of the background wind field is used to calculate the free-flow wind speed V0 and the angle γ between the wind direction and the normal to the wind turbine impeller surface:

[0050]

[0051]

[0052]

[0053]

[0054] V0 is the free-flow wind speed, representing the wind speed in the non-wake region, in m / s; γ is the angle between the normal to the impeller surface of the wind turbine, representing the yaw angle, in °.

[0055] Substituting the free-flow wind speed V0 into the Jensen wake model, we can calculate the velocity evolution along the wake centerline:

[0056]

[0057] Where: k w It is the wake spread factor, C T It is the wind turbine thrust coefficient, and D is the wind turbine impeller diameter.

[0058] This also includes calculating the wind speed loss rate. The velocity evolution along the wake centerline is obtained through the model inversion described above, and the wind speed loss rate δ is further calculated.

[0059]

[0060] δ represents the wind speed loss rate, which indicates the proportion of the lost wind speed in the wake region to the total wind speed in the background wind field, expressed as a percentage. The wake wind speed loss rate refers to the wind speed loss caused by the wake at the downwind end of the wind turbine in the wind farm, and can be quantitatively described as the radial wind speed loss rate.

[0061] Determine if the wind speed loss rate is lower than the threshold δ th If so, the wake loss is considered to have recovered, and the wake has completely dissipated; the corresponding axial distance x is the length of the wind turbine wake, and the depth of the wake is calculated by subtracting the minimum velocity from the maximum velocity at each distance. When the wind speed loss rate is below the threshold δ... th It is assumed that the wake loss recovers and the wake completely dissipates, corresponding to the axial distance x (e.g., Figure 1 (As shown) is the length of the wind turbine wake. The depth of the wake is the difference between the maximum and minimum velocity values ​​at each distance. The maximum value is approximately equal to the background wind field value, and the minimum value is approximately equal to the wake center axis velocity.

[0062] Wind turbine yaw correction refers to adjusting the wind turbine so that the turbine impeller is perpendicular to the prevailing wind direction or at a near-perpendicular angle to maximize wind power generation efficiency. In most cases, the turbine impeller is perpendicular to the wind direction. However, if the angle between the turbine impeller normal and the wind direction is too large, the turbine wake will deviate significantly from the nacelle centerline.

[0063] The angle γ between the wind direction and the normal to the wind turbine impeller surface calculated in the above steps is used to correct the yaw angle of the wind turbine. This prevents the wake from deviating beyond the detection range due to the wind turbine not responding to the wind in time, resulting in an excessively large angle between the wind direction and the normal to the wind turbine impeller surface. An azimuth servo turntable is installed below the scanning head of the nacelle-type lidar. The nacelle-type lidar identifies the angle γ between the wind direction and the normal to the wind turbine impeller surface. When the angle γ is greater than a threshold γ... th Then, the servo turntable is controlled to rotate to the wind direction azimuth angle, ensuring that the two beams can effectively detect the wake.

[0064] This invention utilizes a nacelle-mounted lidar mounted on the top of a wind turbine to emit a detection beam towards the rear of the turbine for radial velocity measurement. When the beam is within the wake region, wind speed is reduced, resulting in a lower radial velocity. Conversely, when the beam is outside the wake region, wind speed recovers, and the radial velocity increases, exhibiting a trend of initially decreasing and then gradually increasing radially. The slope of this trend line can be used to determine the wake boundary region and extract wake width information. Furthermore, the radial velocity outside the wake region can be used to invert the background wind field, allowing for the calculation of wind speed loss rate, wake length, and centerline velocity using a model. This simple two-beam scanning mode of the nacelle-mounted lidar enables the rapid extraction of wake characteristics such as wind speed loss rate, width, length, and depth.

[0065] This invention can determine the wake region by the slope change of radial velocity from the wake region to the non-wake region; it can extract characteristic information such as wake wind speed loss rate, width, length and depth of a specific wind turbine with only two beams, which is simple, efficient, fast scanning speed and low cost, and can be deployed on multiple wind turbines.

[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of wind turbine wake detection, characterized in that, Comprising: The laser radar lens installed on the fan cabin emits a detection beam V towards the rear area of the fan LOS , the detection beam V LOS has an angle α with the cabin center line; the cabin laser radar is installed at the center line position on the top of the fan cabin, the lens of the cabin laser radar faces the rear of the fan, and the detection beam V LOS is emitted to the rear area through the internal light switch of the cabin laser radar. Acquire the detection beam V LOS The distance library B i The corresponding radial velocity library V LOS,i , i=1, 2, …n; the laser radar emits laser, through the data acquisition system, the whole measurement distance is divided into multiple distance regions, called distance library, the detection beam V LOS The radar echo signal processing is divided into several small distance units along the ray direction according to distance, and several small distance units jointly constitute a distance library, and each small distance unit respectively represents a value of i; acquiring said radial velocity library V LOS,i corresponding slope library k i , i = 1, 2,... n; obtaining a slope maximum k i of the slope library k max , i = 1, 2,... n, the slope maximum k max corresponding maximum radial distance R max is the wake boundary, R max *sin a is the wake radius; The detection beam V LOS comprises a first beam V LOS1 and a second beam V LOS2 , the first beam V LOS1 and the second beam V LOS2 respectively point to different directions, and respectively acquire a first wake radius and a second wake radius; said first beam V LOS1 and said second beam V LOS2 lie in the same plane, the sum of the first wake radius and the second wake radius is the wake diameter; The first beam V LOS1 And the second beam V LOS2 The included angles with the nacelle centerline are ±α, respectively. said first beam V LOS1 corresponding maximum radial distance R max said first maximum radial distance R 1,max said first beam V LOS1 corresponding minimum slope k min said first minimum slope k 1,min said second beam V LOS2 corresponding maximum radial distance R max said second maximum radial distance R 2,max said second beam V LOS2 corresponding minimum slope k min said second minimum slope k 2,min ; the first minimum slope k 1,min the first background wind field radial velocity V LOS1,0 , the second minimum slope k 2,min the second background wind field radial velocity V LOS2,0 , the free stream wind speed V0 and the angle γ between the wind direction and the normal of the fan impeller face as the background wind field ； determining whether the wind speed loss rate is lower than a threshold value δ th If yes, it is considered that the wake loss is recovered and the wake is completely dissipated. The corresponding axial distance x is the length of the fan wake, and the depth of the wake is calculated by subtracting the minimum velocity from the maximum velocity of the cross-sectional velocity at each distance. The laser radar identifies the angle γ between the wind direction and the normal of the impeller surface of the wind turbine. When the angle γ is greater than a threshold γ th The servo turntable is controlled to rotate to the wind direction azimuth angle, so as to ensure effective detection of the wake.

2. The wind turbine wake detection method of claim 1, wherein, Substituting the free stream wind speed V0 into the Jensen wake model to calculate the velocity evolution of the wake centerline: ； where: k w is the wake expansion coefficient, C T is the fan thrust coefficient, and D is the fan wheel diameter.

3. The wind turbine wake detection method of claim 2, wherein, Further comprising: Calculating the wind speed loss rate δ: 。

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