CN109870693B - Wind turbine clutter detection method - Google Patents
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Abstract
The invention relates to a wind turbine clutter detection method, which is used for detecting meteorological radar wind turbine clutter through the spectrum width difference based on the characteristics of strong power and wide spectrum of the wind turbine clutter, based on the ground clutter, meteorological signals and the wind turbine clutter, and can effectively detect a distance unit where the wind turbine clutter is located.
Description
Technical Field
The invention relates to a wind turbine clutter detection method, and belongs to the technical field of meteorological radar signal detection.
Background
In recent years, with the increasing number and scale of wind farms, noise caused by wind turbine blades in the process of high-speed rotation has become a main factor influencing the detection performance of meteorological radar, and in the case of existing radar systems, when ground noise, meteorological signals and turbine noise exist at the same time, the noise suppression method adopted is mostly to assume that the noise is in a static state or a slow motion state, the blade noise in the fast motion is ignored, and the rotation linear speeds of different parts of the turbine blades in motion are different. Therefore, studying the micro-doppler spectrum of turbine blades is of great significance in reducing false detection and tracking of radar return signals caused by blade clutter.
In order to solve the above problems, Cornwall proposes to select a material having a function of absorbing a beam to manufacture a turbine blade, thereby reducing a Radar Cross Section (RCS) to suppress noise waves of the turbine, but the manufacturing cost of the material is high, so that the popularization is difficult; gallardo B et al propose to estimate the rotational speed of the turbine blade from the radar echo power spectrum, and then judge whether the rotational speed is in the range of the prior rotational speed of the turbine blade, so as to detect the turbine clutter, the method relies too much on the prior number; the simulation method has the advantages that the simulation method provides simulation of the electromagnetic scattering property of the turbine machine based on a mixed model by people who are beautiful and beautiful in China, the influence of factors such as the reflection coefficient of electromagnetic waves on echoes is considered by the model, the modeling time required by FEKO simulation software is long, and the estimation result cannot be obtained quickly.
Disclosure of Invention
The invention aims to provide a wind turbine clutter detection method, which can effectively detect a distance unit where a meteorological radar wind turbine clutter is located by using the characteristics of strong power and wide frequency spectrum of the wind turbine clutter, has small operand, and is suitable for engineering application.
The invention adopts the following technical scheme for solving the technical problems: the invention designs a wind turbine clutter detection method, which is based on wind turbine detection by a meteorological radar and a received echo signal sequence { x (n) }, and realizes detection of wind turbine clutter, wherein n belongs to {1, …, K }, K represents the total number of the echo signals detected by the meteorological radar on the wind turbine and received by the meteorological radar, and x (n) represents the nth echo signal received by the meteorological radar, and the detection method comprises the following steps:
b, carrying out average division on all distance units on the moving path of the echo signal between the meteorological radar and the wind turbine according to the preset number M of the sections to obtain each section of distance unit group and obtain a power threshold value corresponding to each section of distance unit group; then based on each power threshold value, eliminating each distance unit only having ground clutter signals to obtain each remaining distance unit as each distance unit to be processed, and entering the step C;
and C, acquiring spectral width estimated values sigma corresponding to the distance units to be processed respectively based on the echo signal sequence { x (n) }lThen entering step D; wherein, l is belonged to { 1.,. N }, N represents the number of distance units to be processed, and sigma islRepresenting the spectral width estimated value corresponding to the first distance unit to be processed;
d, according to the spectral width estimated value sigma corresponding to each distance unit to be processedlPerforming ascending arrangement on all distance units to be processed, and respectively rejecting preset d distance units to be processed according to the front end and the tail end of the sequence; then obtaining the average value of the spectral width estimated values corresponding to all the remaining distance units to be processed,and combining with a preset spectral width amplification coefficient gamma to obtain a spectral width detection threshold value sigma0And entering step E;
step E, respectively aiming at each distance unit to be processed obtained in the step B, judging the spectral width estimated value sigma corresponding to the distance unit to be processedlWhether or not it is greater than the spectral width detection threshold σ0If so, it is an indication that wind turbine clutter is present in the range unit, otherwise, it is an indication that wind turbine clutter is not present in the range unit.
As a preferred technical scheme of the invention: the detection method also comprises the following steps of A, firstly executing the step A, and then entering the step B;
and A, performing cancellation processing on the echo signal sequence { x (n) } to realize the suppression of the ground clutter signal.
As a preferred technical scheme of the invention: in the step A, a three-pulse canceller formed by cascading two-pulse cancellers is adopted to perform cancellation processing aiming at an echo signal sequence { x (n) }, so that the suppression of ground clutter signals is realized.
As a preferred technical solution of the present invention, in the step a, the following formula result is obtained for each echo signal x (n) in the echo signal sequence { x (n);
x(n)-2x(n+1)+x(n+2)
and updating the corresponding echo signals x (n) according to the result, and respectively finishing the updating of the echo signals x (n), namely performing cancellation processing on the echo signal sequence { x (n) }, so as to realize the suppression of the ground clutter signals.
As a preferred technical solution of the present invention, the step B includes the steps of:
step B-1, aiming at all distance units on the moving path of the echo signal between the meteorological radar and the wind turbine, carrying out average division according to the preset number M of the sections to obtain M sections of distance unit groups, wherein each section of distance unit group respectively comprises Z (L/M) distance units, and then entering the step B-2; wherein L represents the total number of range cells in the path of movement of the echo signal between the weather radar and the wind turbine;
and B-2, aiming at each distance unit group, respectively, according to the following formula:
obtaining power threshold values P corresponding to each distance unit groupdmThen entering step B-3; wherein M is in the range of {1,. eta.,. M }, P ∈dmRepresenting the power threshold value corresponding to the mth distance unit group, G representing a preset amplitude coefficient, and PmiRepresenting the power of an echo signal of an ith range cell in the mth range cell group;
b-3, respectively aiming at each distance unit, judging whether the power of the echo signal of the distance unit is smaller than the power threshold value corresponding to the distance unit group where the distance unit is located, if so, judging that only ground clutter signals exist on the distance unit, and rejecting the distance unit; otherwise, the distance unit is not processed, and after all the distance units finish the judgment operation, the step B-4 is carried out;
and B-4, taking the remaining distance units as the distance units to be processed, and then entering the step C.
As a preferred technical solution of the present invention, the step C includes the steps of:
step C-1, obtaining R corresponding to each distance unit to be processed0lAnd R1lThen entering the step C-2; wherein, l is belonged to { 1.,. N }, N represents the number of distance units to be processed, and R is equal to0lRepresents the zero delay autocorrelation parameter, R, of the echo signal sequence of the ith range unit to be processed1lRepresenting a first-order autocorrelation parameter of an echo signal sequence of the first to-be-processed range unit;
and C-2, aiming at each distance unit to be processed, respectively, according to the following formula:
obtaining the spectral width estimated value sigma corresponding to each distance unit to be processedlThen entering step D; wherein，σlThe spectral width estimated value corresponding to the first distance unit to be processed is shown, lambda represents the wavelength of the meteorological radar, and TrRepresenting the time interval between two adjacent echo signals.
As a preferred technical scheme of the invention, the step C-1 comprises the following steps:
respectively aiming at each distance unit to be processed, according to the following formula:
obtaining a zero delay autocorrelation parameter R of an echo signal sequence of a range unit to be processed0lWherein l is equal to { 1.,. multidata., N }, N represents the number of distance units to be processed, R0lRepresenting a zero delay autocorrelation parameter of an echo signal sequence of the first distance unit to be processed; y isl(n) denotes the nth echo signal of the ith range bin to be processed,
denotes ylConjugation of (n);
meanwhile, according to the following formula:
obtaining a first-order autocorrelation parameter R of an echo signal sequence of the range unit to be processed1lWherein R is1lRepresenting the first-order autocorrelation parameter of the echo signal sequence of the first distance unit to be processed; y isl(b +1) represents the b +1 th echo signal on the l-th range unit to be processed,
denotes yl(b) Conjugation of (a) yl(b) The b-th echo signal of the l-th distance unit to be processed is represented;
further obtain the R corresponding to each distance unit to be processed0lAnd R1lThen enter step C-2。
As a preferred technical scheme of the invention: in the step D, the spectrum width detection threshold σ is obtained by multiplying the average value of the spectrum width estimated values corresponding to all the remaining distance units to be processed by the preset spectrum width amplification factor γ0。
Compared with the prior art, the wind turbine clutter detection method adopting the technical scheme has the following technical effects:
the wind turbine clutter detection method is based on the ground clutter, the meteorological signals and the wind turbine clutter, has large difference in spectrum width, utilizes the characteristics of strong power and wide spectrum of the wind turbine clutter to detect the meteorological radar wind turbine clutter through the difference of the spectrum width, can effectively detect the distance unit where the wind turbine clutter is located, has small calculation amount, and is suitable for engineering application.
Drawings
FIG. 1 is a graph of a wind turbine versus a radar;
FIG. 2 is a signal processing flow diagram according to the present invention;
FIG. 3(a) is a power spectrum of a radar echo signal (ground clutter + meteorological signal) before cancellation by three pulses;
FIG. 3(b) is a power spectrum of a radar echo signal (ground clutter + meteorological signal) after three-pulse cancellation;
FIG. 4(a) is a three-pulse pre-cancellation radar echo signal (ground clutter + WTC) power spectrum;
FIG. 4(b) is a power spectrum of a radar echo signal (ground clutter + WTC) after three-pulse cancellation;
FIG. 5(a) is a power spectrum of a radar echo signal (weather signal + ground clutter + WTC) before cancellation by three pulses;
FIG. 5(b) is a power spectrum of a radar echo signal (weather signal + ground clutter + WTC) after three-pulse cancellation;
FIG. 6 is a meteorological signal spectral width estimate;
FIG. 7 is a meteorological signal + WTC spectral width estimate.
Detailed Description
The following description will explain embodiments of the present invention in further detail with reference to the accompanying drawings.
The invention designs a wind turbine clutter detection method, which is used for realizing detection of wind turbine clutter based on detection of a meteorological radar on a wind turbine and a received echo signal sequence { x (n) }, wherein n belongs to {1, …, K }, K represents the total number of the echo signals detected by the meteorological radar on the wind turbine and received by the meteorological radar, and x (n) represents the nth echo signal received by the meteorological radar.
For each echo signal x (n) in the echo signal sequence { x (n) }, the expression x (n) ═ w (n) + c (n) + s (n) + u (n) or x (n) ═ c (n) + s (n) + u (n), where w (n) denotes a wind turbine clutter signal, c (n) denotes a ground clutter signal, s (n) denotes a meteorological signal, and u (n) denotes noise. In practice, it is shown that for the echo signal x (n), the wind turbine noise signal w (n) may or may not be included.
Ground clutter signal c (n): using a division of the distance units, each distance unit having a width of
fsIs the sampling frequency and c is the speed of light. One distance unit is divided into 180 clutter scattering units, clutter data of each distance unit is superposition of the 180 clutter scattering units, and a ground clutter echo signal of the a-th distance unit is as follows:
in the formula of omegat＝2πfd/frFor time-domain angular frequency, RaIs the distance of the a-th distance unit, F is the antenna gain, FdIs the Doppler frequency, frFor the pulse repetition frequency, n ∈ {1, …, K }, where K represents the total number of echo signals received that were detected by the weather radar on the wind turbine, and L represents the total number of range bins in the path of the echo signals travel between the weather radar and the wind turbine.
Meteorological signal s (n): the meteorological target is a distributed target, and echo signals of the meteorological target can be formed by superposition of echoes of a plurality of scattering units. And performing coherent superposition on the echoes of all the scattering units in the a-th distance unit to obtain meteorological signal echoes. The a-th range unit, the sampling of the meteorological signal at the n-th echo signal, can be represented as:
wherein I is the total number of scattering units in the a-th distance unit, AuThe amplitude of the meteorological target particle u is determined by radar equations. OmegatFor the time domain angular frequency, it can be obtained by the following equation:
Wind turbine signals: the wind turbine consists of blades, a mast and a nacelle, and the wind turbine noise mainly consists of blade and mast noise. The blade is rotating and the mast is stationary, using a scatter point superposition model, the wind turbine is related to radar as shown in figure 1.
Leaf signal: the wind turbine has three blades spaced 120 degrees apart so that there is a 120 degree lag in angle between each blade, first considering one blade and then the other two blades differ by only 120 degrees. Each blade is considered to be composed of a plurality of scattering points, the clutter of one blade is the superposition of the scattering points, and the superposition of the scattering points of three blades is the clutter of the wind turbine blade. Echo signal of one scattering point p of a wind turbine blade:
in the formula, fcIn order to be the frequency of the radar,
for time delay, RpDistance from scattering point p to radar:
Rgdistance of wind turbine to radar, riIs the distance from the scattering point of the blade to the axis of the blade,
is the angle between the reference blade and the radar line of sight:
alpha and beta are azimuth angle and pitch angle respectively, and theta is an included angle between the reference blade and the positive direction of the Y axis.
The carrier is removed, and the baseband signal is obtained as follows:
the total echo signal for all blades is then (the number of wind turbine blades is typically 3):
wherein P is the total number of scattering particles of the blade.
Mast signal: the mast is stationary and the mast clutter is also seen as a superposition of multiple scattering points. The clutter q at the scattering point q of the mast is:
Rqis the distance from the scattering point q to the radar:
hiis the distance from the scattering point q to the blade axisAnd (5) separating.
And (3) removing the carrier wave to obtain a baseband signal:
the echo signal of the whole mast is the superposition of all scattering points:
summarizing, the wind turbine clutter signal:
in practical application, as shown in fig. 2, the method for detecting noise of a wind turbine specifically includes the following steps.
And step A, performing cancellation processing on the echo signal sequence { x (n) } to realize the suppression of the ground clutter signal, and then entering the step B.
In practical application, the step a adopts a three-pulse canceller formed by cascading two-pulse cancellers, and obtains the following formula result for each echo signal x (n) in the echo signal sequence { x (n) };
x(n)-2x(n+1)+x(n+2)
and updating the corresponding echo signals x (n) according to the result, and respectively finishing the updating of the echo signals x (n), namely performing cancellation processing on the echo signal sequence { x (n) }, so as to realize the suppression of the ground clutter signals.
After the distance units only having ground clutter are subjected to triple-pulse cancellation, corresponding power values are suppressed to a large extent, the distance units only having ground clutter are removed according to a power threshold, the distance units possibly having wind turbine clutter and meteorological signals are extracted, and then the range of subsequent data processing is narrowed, namely the following steps are continuously executed.
And B, researching and finding that the distance degrees of the distance radar are different, the power values of radar echo data of different distance units are also different, the farther the distance is, the smaller the power value is, otherwise, the larger the power value is, and providing a segmented average method for improving the calculation accuracy. The method comprises the steps that all distance units on an echo signal moving path between a meteorological radar and a wind turbine are divided averagely according to a preset number M of sections in sequence to obtain distance unit groups of each section, and power threshold values corresponding to the distance unit groups of each section are obtained; and then based on each power threshold value, eliminating each distance unit only having ground clutter signals, obtaining each residual distance unit as each distance unit to be processed, and entering the step C.
In the practical application of the step B, the following steps are specifically executed:
step B-1, aiming at all distance units on the moving path of the echo signal between the meteorological radar and the wind turbine, carrying out average division according to the preset number M of the sections to obtain M sections of distance unit groups, wherein each section of distance unit group respectively comprises Z (L/M) distance units, and then entering the step B-2; where L represents the total number of range cells in the path of movement of the echo signal between the weather radar and the wind turbine.
And B-2, aiming at each distance unit group, respectively, according to the following formula:
obtaining power threshold values P corresponding to each distance unit group respectivelydmThen entering step B-3; wherein M is in the range of {1,. eta.,. M }, P ∈dmThe power threshold corresponding to the mth distance unit group is represented, G represents a preset amplitude coefficient, and in practical application, G is 1.2, and P ismiAnd the power of the echo signal of the ith range cell in the mth range cell group is represented.
B-3, respectively aiming at each distance unit, judging whether the power of the echo signal of the distance unit is smaller than the power threshold value corresponding to the distance unit group where the distance unit is located, if so, judging that only ground clutter signals exist on the distance unit, and rejecting the distance unit; otherwise, the distance unit is not processed, and the step B-4 is carried out after all the distance units finish the judgment operation.
And step B-4, taking each remaining distance unit as each distance unit to be processed, and then entering the step C.
And C, acquiring spectral width estimated values sigma corresponding to the distance units to be processed respectively based on the echo signal sequence { x (n) }lThen entering step D; wherein, l is belonged to { 1.,. N }, N represents the number of distance units to be processed, and sigma islAnd the estimated spectral width value corresponding to the ith distance unit to be processed is shown.
In the practical application of the step C, the following steps are specifically executed:
step C-1, obtaining R corresponding to each distance unit to be processed0lAnd R1lThen entering the step C-2; wherein, l is belonged to { 1.,. N }, N represents the number of distance units to be processed, and R is equal to0lRepresents the zero delay autocorrelation parameter, R, of the echo signal sequence of the ith range unit to be processed1lAnd the first-order autocorrelation parameters of the echo signal sequence of the ith range unit to be processed are shown.
In practical application, each distance unit to be processed corresponds to R0lAnd R1lThe obtaining is specifically performed as follows.
Aiming at each distance unit to be processed, the following formula is adopted:
obtaining a zero delay autocorrelation parameter R of an echo signal sequence of a range unit to be processed0lWherein l is equal to { 1.,. multidata., N }, N represents the number of distance units to be processed, R0lRepresenting a zero delay autocorrelation parameter of an echo signal sequence of the first distance unit to be processed; y isl(n) denotes the nth echo signal of the ith range bin to be processed,
denotes ylConjugation of (n).
Meanwhile, according to the following formula:
obtaining a first-order autocorrelation parameter R of an echo signal sequence of the range unit to be processed1lWherein R is1lRepresenting the first-order autocorrelation parameter of the echo signal sequence of the first distance unit to be processed; y isl(b +1) represents the b +1 th echo signal on the l-th range unit to be processed,
denotes yl(b) Conjugation of (a) yl(b) The b-th echo signal of the l-th distance unit to be processed is represented.
Further obtain the R corresponding to each distance unit to be processed0lAnd R1l。
And C-2, aiming at each distance unit to be processed, respectively, according to the following formula:
obtaining the spectral width estimated value sigma corresponding to each distance unit to be processedlThen entering step D; wherein σlThe spectral width estimated value corresponding to the first distance unit to be processed is shown, lambda represents the wavelength of the meteorological radar, and TrRepresenting the time interval between two adjacent echo signals.
D, according to the spectral width estimated value sigma corresponding to each distance unit to be processedlPerforming ascending arrangement on all distance units to be processed, and respectively rejecting preset d distance units to be processed aiming at the front end and the tail end of the sequence; then obtaining the average value of the spectral width estimated values corresponding to all the remaining distance units to be processed, and obtaining the spectral width detection threshold value sigma through the product of the average value and a preset spectral width amplification coefficient gamma0And proceeds to step E.
Step E, aiming at each distance unit to be processed obtained in the step B,judging the spectral width estimation value sigma corresponding to the distance unit to be processedlWhether or not it is greater than the spectral width detection threshold σ0If so, it indicates that wind turbine noise exists in the distance unit to be processed, otherwise, it indicates that wind turbine noise does not exist in the distance unit to be processed.
The wind turbine clutter detection method provided by the invention is applied to the specific embodiment, the radar system simulation parameters are shown in the following table 1, and the wind turbine system simulation parameters are shown in the following table 2.
| Carrier frequency f0 | 5.5GHz |
| Pulse repetition frequency fr | 1000Hz |
| Number of pulses | 64 |
| Radar height (m) | 1000 |
TABLE 1
| Blade length (m) | 26 |
| Mast height (m) | 70 |
| Distance from axle to radar (km) | 36 |
| Rotating vane speed (r/min) | 15 |
| Included angle of rotation surface | 73.5° |
| Reference blade initial angle | 90° |
TABLE 2
In the simulation experiment, a radar echo signal is subjected to three-pulse cancellation to filter out ground clutter and wind turbine mast clutter. And (4) respectively estimating the spectral width of each distance unit by setting meteorological signals existing in the 1 st to 50 th distance units. Wind turbine clutter is added at the 25 th range cell, and the range cell spectral width is estimated. And comparing the size relationship of the spectral widths of the 25 th distance unit and other distance units, and calculating the spectral width detection threshold value according to the relationship of the 25 th distance unit and other distance units.
In the simulation experiment, the ground clutter is the moving clutter, the Doppler frequency center of the ground clutter is 36Hz, and the spectrum width is 20 Hz. Because the triple-pulse canceller can only effectively suppress clutter near the zero frequency, the frequency spectrum is shifted first before the triple-pulse cancellation is carried out, and the Doppler frequency center of the ground clutter is shifted to the zero frequency. Before the three-pulse cancellation, the power spectrum of the radar echo (ground clutter + meteorological signals) is shown in fig. 3(a), and after the three-pulse cancellation, the power spectrum of the radar echo (ground clutter + meteorological signals) is shown in fig. 3 (b). The graph can show that the ground clutter power is about 38dB before the three-pulse cancellation, and after the three-pulse cancellation, the ground clutter power is reduced to-20 dB and reduced by 58dB, so that the ground clutter is effectively suppressed. Before the three-pulse cancellation, the meteorological signal power is about 48dB, and after the three-pulse cancellation, the meteorological signal power is increased to 55dB, so that the three-pulse canceller has no great influence on the meteorological signal. Before the three-pulse cancellation, the power spectrum of the radar echo (ground clutter + WTC) is shown in fig. 4(a), and after the three-pulse cancellation, the power spectrum of the radar echo (ground clutter + WTC) is shown in fig. 4 (b). As can be seen from the figure, before the three-pulse cancellation, the signal (mast clutter + ground clutter) power at zero frequency is about 49dB, and after the three-pulse cancellation, the signal power is reduced to 0dB and is reduced by 49 dB. And the clutter power in other frequency ranges has little difference before and after the three-pulse cancellation. Fig. 5(a) is a power spectrum of a radar echo (weather signal + ground clutter + WTC) before three-pulse cancellation, and fig. 5(b) is a power spectrum of a radar echo (weather signal + ground clutter + WTC) after three-pulse cancellation.
After passing through the triple-pulse canceller, ground clutter and wind turbine mast clutter are effectively suppressed, leaving meteorological signals and wind turbine blade clutter. Meteorological signals and wind turbine blade clutter vary widely in spectral width. Firstly, assuming that only meteorological signals exist in the 1 st to 50 th distance units, the spectral width estimation is carried out on the meteorological signals, and the obtained result is shown in fig. 6, and the simulation experiment shows that the spectral width sigma of the meteorological signalssAt 0.36-0.54 m/s. Adding WTC to the 25 th range bin, and performing spectral width estimation on the range bin to obtain the spectral width σ of the range bin as shown in FIG. 7d5.0206 m/s. Comparison of sigmadAnd
(
is σsAveraged) and calculating
The bandwidth amplification factor γ can be set to 6, that is, the bandwidth detection threshold σ can be obtained0＝6×σs. As the spectral width σ of the distance unit to be detectedl＞σ0The distance unit is subject to wind turbine noise.
According to the wind turbine clutter detection method designed by the technical scheme, the wind turbine clutter is detected through the spectrum width difference based on the ground clutter, the meteorological signals and the wind turbine clutter with large spectrum width by utilizing the characteristics of strong power and wide spectrum of the wind turbine clutter, the distance unit where the wind turbine clutter is located can be effectively detected, the calculation amount is small, and the wind turbine clutter detection method is suitable for engineering application.
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.
Claims (7)
1. A wind turbine clutter detection method, based on wind turbine detection by weather radar, received echo signal sequence { x (n) }, realizing wind turbine clutter detection, wherein n ∈ {1, …, K }, K represents the total number of echo signals received by wind turbine detection by weather radar, and x (n) represents the nth echo signal received by weather radar, the detection method is characterized by comprising the following steps:
b, carrying out average division on all distance units on the echo signal moving path between the meteorological radar and the wind turbine according to the preset number M of the sections to obtain each section of distance unit group and obtain a power threshold value corresponding to each section of distance unit group; then based on each power threshold value, eliminating each distance unit only having ground clutter signals to obtain each remaining distance unit as each distance unit to be processed, and entering the step C;
in the step B, all distance units on the moving path of the echo signal between the meteorological radar and the wind turbine are evenly divided according to a preset number M of the segments to obtain M segments of distance unit groups, each segment of distance unit group respectively comprises Z ═ L/M distance units, and then the step B-2 is performed; wherein L represents the total number of range cells in the path of movement of the echo signal between the weather radar and the wind turbine;
step C, obtaining each distance unit to be processed based on the echo signal sequence { x (n) }Respectively corresponding spectral width estimation values sigmalThen entering step D; wherein, l is belonged to { 1.,. N }, N represents the number of distance units to be processed, and sigma islRepresenting the spectral width estimated value corresponding to the first distance unit to be processed;
the step C comprises the following steps:
step C-1, obtaining R corresponding to each distance unit to be processed0lAnd R1lThen entering the step C-2; wherein, l is belonged to { 1.,. N }, N represents the number of distance units to be processed, and R is equal to0lRepresents the zero delay autocorrelation parameter, R, of the echo signal sequence of the ith range unit to be processed1lRepresenting a first-order autocorrelation parameter of an echo signal sequence of the first to-be-processed range unit;
and C-2, aiming at each distance unit to be processed, respectively, according to the following formula:
obtaining the spectral width estimated value sigma corresponding to each distance unit to be processedlThen entering step D; wherein σlThe spectral width estimated value corresponding to the first distance unit to be processed is shown, lambda represents the wavelength of the meteorological radar, and TrRepresenting the time interval between two adjacent echo signals;
d, according to the spectral width estimated value sigma corresponding to each distance unit to be processedlPerforming ascending arrangement on all distance units to be processed, and respectively rejecting preset d distance units to be processed according to the front end and the tail end of the sequence; then obtaining the average value of the spectral width estimated values corresponding to all the remaining distance units to be processed, and combining the preset spectral width amplification coefficient gamma to obtain a spectral width detection threshold value sigma0And entering step E;
step E, respectively aiming at each distance unit to be processed obtained in the step B, judging the spectral width estimated value sigma corresponding to the distance unit to be processedlWhether or not it is greater than the spectral width detection threshold σ0If so, it is an indication that wind turbine noise is present in the range unit to be processed, otherwise it is an indication that wind turbine noise is present in the range unit to be processedThe distance unit to be processed is free of wind turbine clutter.
2. The method of wind turbine clutter detection according to claim 1, wherein: the detection method also comprises the following steps of A, firstly executing the step A, and then entering the step B;
and step A, performing cancellation processing on the echo signal sequence { x (n) } to realize the suppression of the ground clutter signal.
3. The method of wind turbine clutter detection according to claim 2, wherein: in the step A, a three-pulse canceller formed by cascading two-pulse cancellers is adopted to perform cancellation processing aiming at an echo signal sequence { x (n) }, so that the suppression of ground clutter signals is realized.
4. A method of wind turbine clutter detection according to claim 2, wherein in step a, for each echo signal x (n) in the sequence of echo signals { x (n) }, the following formula is obtained;
x(n)-2x(n+1)+x(n+2)
and updating the corresponding echo signal x (n) according to the result, and respectively finishing the updating of each echo signal x (n), namely performing cancellation processing on the echo signal sequence { x (n) }, thereby realizing the suppression of the ground clutter signal.
5. A method of wind turbine clutter detection according to claim 1, characterized in that said step B comprises the steps of:
step B-1, aiming at all distance units on the moving path of the echo signal between the meteorological radar and the wind turbine, carrying out average division according to the preset number M of the sections to obtain M sections of distance unit groups, wherein each section of distance unit group respectively comprises Z (L/M) distance units, and then entering the step B-2; wherein L represents the total number of range cells in the path of movement of the echo signal between the weather radar and the wind turbine;
and B-2, aiming at each distance unit group, respectively, according to the following formula:
obtaining power threshold values P corresponding to each distance unit groupdmThen entering step B-3; wherein M is in the range of {1,. eta.,. M }, P ∈dmRepresenting the power threshold value corresponding to the mth distance unit group, G representing a preset amplitude coefficient, and PmiRepresenting the power of an echo signal of an ith range cell in the mth range cell group;
b-3, respectively aiming at each distance unit, judging whether the power of the echo signal of the distance unit is smaller than the power threshold value corresponding to the distance unit group where the distance unit is located, if so, judging that only ground clutter signals exist on the distance unit, and rejecting the distance unit; otherwise, the distance unit is not processed, and after all the distance units finish the judgment operation, the step B-4 is carried out;
and step B-4, taking each remaining distance unit as each distance unit to be processed, and then entering the step C.
6. The method of claim 1, wherein step C-1 comprises the following: respectively aiming at each distance unit to be processed, according to the following formula:
obtaining a zero delay autocorrelation parameter R of an echo signal sequence of a range unit to be processed0lWherein l is equal to { 1.,. multidata., N }, N represents the number of distance units to be processed, R0lRepresenting a zero delay autocorrelation parameter of an echo signal sequence of the first distance unit to be processed; y isl(n) denotes the nth echo signal of the ith range bin to be processed,
denotes yl(n) conjugation;
meanwhile, according to the following formula:
obtaining a first-order autocorrelation parameter R of an echo signal sequence of the range unit to be processed1lWherein R is1lRepresenting the first-order autocorrelation parameter of the echo signal sequence of the first distance unit to be processed; y isl(b +1) represents the b +1 th echo signal on the l-th range unit to be processed,
denotes yl(b) Conjugation of (a) yl(b) The b-th echo signal of the l-th distance unit to be processed is represented;
further obtain the R corresponding to each distance unit to be processed0lAnd R1lThen, the process proceeds to step C-2.
7. A method of wind turbine clutter detection according to claim 1, characterized by: in the step D, the spectrum width detection threshold σ is obtained by multiplying the average value of the spectrum width estimated values corresponding to all the remaining distance units to be processed by the preset spectrum width amplification factor γ0。
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