阅读说明：本技术 一种海上风电场对地波超视距雷达探测效能影响的评估方法 (Method for evaluating influence of offshore wind power plant on ground wave beyond visual range radar detection efficiency ) 是由 吴小川 姚迪 董英凝 索莹 邓维波 于 2020-06-09 设计创作，主要内容包括：本发明公开了一种海上风电场对地波超视距雷达探测效能影响的评估方法。根据地波超视距雷达参数以及风电场的预选区域展开场景分析,筛选出需重点分析的对象；根据提供的风电机组参数建立风机电磁模型,实现单个风机电磁模型的建立；按照预建设风电场风机经纬度坐标与雷达相对位置信息,在FEKO电磁计算软件中建阵列、建场景模型,对遮挡影响进行分析；计算单个风机设备在不同状态下的RCS变化；多普勒频率的影响进行分析；推导多径效应理论公式；场景实测等效,电磁环境噪声数据,评估出风电场影响范围。本发明通过采用电磁仿真计算、理论推导以及实测场景等效等手段,给出定量地评估结果。(The invention discloses an evaluation method for influence of an offshore wind farm on detection efficiency of a ground wave over-the-horizon radar. Performing scene analysis according to the ground wave beyond visual range radar parameters and a preselected region of the wind power plant, and screening out objects needing key analysis; establishing a fan electromagnetic model according to the provided wind turbine generator parameters, and realizing the establishment of a single fan electromagnetic model; according to the longitude and latitude coordinates of a fan of a pre-constructed wind power plant and the relative position information of a radar, an array is built and a scene model is built in FEKO electromagnetic calculation software, and the shielding influence is analyzed; calculating the RCS change of the single fan device in different states; analyzing the influence of Doppler frequency; deducing a multipath effect theoretical formula; and (3) evaluating the influence range of the air outlet electric field according to the actual measurement equivalence of the scene and the noise data of the electromagnetic environment. The method adopts the measures of electromagnetic simulation calculation, theoretical derivation, actual measurement scene equivalence and the like to give quantitative evaluation results.)

1. An evaluation method for influence of an offshore wind farm on detection efficiency of a ground wave over-the-horizon radar is characterized by comprising the following steps:

step 1: according to the basic performance, station arrangement position, beam width and action region parameters of the ground wave over-the-horizon radar and preselected region development scene analysis of the wind power plant, eliminating radars which are not influenced or are influenced very little by the wind power plant at all, and screening out objects needing important analysis;

step 2: establishing a fan electromagnetic model according to the provided wind turbine generator parameters, and realizing the establishment of a single fan electromagnetic model through grid division, grid quantity setting and grid optimization;

and step 3: according to the longitude and latitude coordinates of a fan of a pre-built wind power plant and the relative position information of the radar, a wind turbine generator array is built in FEKO electromagnetic calculation software, a ground wave over-the-horizon radar scene model is built at the same time, the influence of a wind power plant area on the surrounding electric field intensity is simulated, and the shielding influence caused by the wind turbine generator is analyzed;

and 4, step 4: RCS changes of single fan equipment in different states are simulated and calculated;

and 5: analyzing the influence of Doppler frequency generated by the rotation of the fan blade on radar echo;

step 6: deducing a multipath effect theoretical formula and calculating according to the distribution characteristics of the wind turbine generator array;

and 7: and (3) carrying out actual measurement equivalence on the scene, testing electromagnetic environment noise data in a similar environment, carrying out equivalent calculation on the environment of the wind power plant to be built and the power consumption, and evaluating the influence range of the wind power plant.

2. The method for evaluating the influence of the offshore wind farm on the detection efficiency of the ground wave over-the-horizon radar according to claim 1, wherein in the step 2, the wind turbine set consists of a tower, a hub, a nacelle and blades, the blades are made of non-metallic materials, and the energy of reflected signals is small, so that the tower is used as a main modeling calculation object; meanwhile, the lightning protection lead wire is arranged between the blade and the hub, so that the fan model is equivalent; the fan electromagnetic model is based on a curved surface modeling method, and the establishment of a geometric model is realized by utilizing a mode of combining CAD (computer-aided design) and Femap software according to fan parameters.

3. The method according to claim 1, wherein the step 2 of grid division is to adopt grids with different sizes at different structural parts, so that the whole structure shows grid division forms with different densities, and when the target geometric modeling is used for grid division, arch height errors generated by all plane elements on an actual curved surface are smaller than 1/16 of a wavelength.

4. The method for evaluating the influence of the offshore wind farm on the detection efficiency of the ground wave over-the-horizon radar according to claim 1, wherein the optimization of the grids in the step 2 refers to the rationality of the geometric shapes of the grids, the calculation accuracy is influenced by the quality, the calculation is even stopped for grids with poor quality, and each unit of the triangular grids is an equilateral triangle under ideal conditions.

5. The method for evaluating the influence of the offshore wind farm on the detection efficiency of the ground wave beyond visual range radar according to claim 1, wherein the establishing of the ground wave beyond visual range radar scene model in the step 3 is to set a working wave band, a wave beam direction and a polarization mode according to the relative position of the radar and the wind farm, and calculate the change condition of the electric field intensity of a peripheral area of the wind farm, so as to obtain a direct shielding quantitative analysis result.

6. The method according to claim 1, wherein the doppler effect in step 5 is the rotation of a fan blade to make the radar echo have a doppler shift component, the modulation depth is calculated by using an amplitude modulation signal obtained by modulating the radar signal by the rotation frequency of the fan blade, and the doppler effect is determined according to the modulated amplitude ratio.

7. The method as claimed in claim 1, wherein the multipath effect in step 6 is derived and calculated by using a radar equation, the influence of the fan on the radar electromagnetic wave reflection is calculated, the target reflected direct wave and the secondary reflected echo passing through the wind turbine are synthesized at the receiving antenna, if the amplitude of the echo signal reflected by the wind turbine is too large, the radar can be influenced on the target azimuth resolution, a false target can be formed after the radar receiver is processed, a false alarm is caused, and the multipath effect influence range is analyzed according to the distance and angle change among the radar, the target and the wind turbine.

8. The method for evaluating the influence of the offshore wind farm on the detection efficiency of the ground wave over-the-horizon radar according to claim 1, wherein an actual measurement analysis method is adopted in the step 7, and the radiation characteristic of the wind farm to be evaluated can be converted by performing equivalent calculation according to the type, the number, the arrangement position and the regional wind power level factor of the wind farm aiming at the noise comparison of different working states and different frequencies of a fan in a test environment through the actual measurement on similar wind power equipment.

Technical Field

The invention belongs to the field of electromagnetic compatibility of wind power plants and radar systems, and particularly relates to an evaluation method for influence of an offshore wind power plant on ground wave beyond visual range radar detection efficiency.

Background

In recent years, the number and scale of wind power plant construction plans in China are gradually increased, and particularly offshore wind power project construction is vigorously carried out in coastal areas. Offshore wind resources are abundant, and the offshore wind power generation system is an optimal position for building a wind power plant. However, the wind power plant has the advantages of wide occupied area, large fan size and high fan blade rotating speed, and the offshore target environment of the peripheral shore-based radar can be changed. For the sea detection radar, the shielding, diffraction and the like of the object generated by the wind power plant are very adverse factors for the radar. At present, countries and organizations such as the united states and the european union have established an evaluation mechanism related to planning and construction of wind farms, mainly analyze and solve the influence of the wind farms on military facilities, and especially ensure that the early warning detection capability of a radar is not influenced. The technical means mainly adopts an electromagnetic field simulation calculation method, and utilizes electromagnetic calculation to simulate an actual scene to obtain a quantitative result of the influence of the wind power plant on the radar detection efficiency. However, the domestic research on the problems of the wind power plant, such as influence on the electromagnetic environment, radar performance and the like, is late, the technical means is not perfect, and sufficient theoretical and technical support cannot be provided for the planning and construction of the offshore wind power plant.

The ground wave over-the-horizon radar utilizes the diffraction propagation characteristic of high-frequency electromagnetic waves along the earth surface to realize the detection of a remote over-the-horizon target, and due to the diffraction effect of the high-frequency electromagnetic waves along the sea surface, the propagation path is bent along the earth surface instead of being linearly propagated, so that the detection distance can extend to a shielding area of the earth curved surface. In order to reduce the diffraction propagation loss of the high-frequency electromagnetic wave along the sea surface, the radar frequency is usually operated at the low end of the short wave band, and meanwhile, the vertical polarized wave is adopted. An offshore wind farm construction site generally selects an offshore area within 50 kilometers from land, and the wind farm in a detection sector inevitably affects the radar detection performance by considering the characteristics of a specific working frequency band, wide sea area coverage and long coherent accumulation time of a ground wave beyond visual range radar.

Disclosure of Invention

The invention provides an evaluation method for influence of an offshore wind power plant on the detection efficiency of a ground wave beyond visual range radar, which takes a proposed offshore wind power project as an analysis object and gives a quantitative evaluation result by means of electromagnetic simulation calculation, theoretical derivation, actual measurement scene equivalence and the like.

The invention is realized by the following technical scheme:

an evaluation method for influence of an offshore wind farm on detection efficiency of a ground wave over-the-horizon radar comprises the following steps:

step 1: according to the basic performance, station arrangement position, beam width and action region parameters of the ground wave over-the-horizon radar and preselected region development scene analysis of the wind power plant, eliminating radars which are not influenced or are influenced very little by the wind power plant at all, and screening out objects needing important analysis;

step 2: establishing a fan electromagnetic model according to the provided wind turbine generator parameters, and realizing the establishment of a single fan electromagnetic model through grid division, grid quantity setting and grid optimization;

and step 3: according to the longitude and latitude coordinates of a fan of a pre-built wind power plant and the relative position information of the radar, a wind turbine generator array is built in FEKO electromagnetic calculation software, a ground wave over-the-horizon radar scene model is built at the same time, the influence of a wind power plant area on the surrounding electric field intensity is simulated, and the shielding influence caused by the wind turbine generator is analyzed;

and 4, step 4: RCS changes of single fan equipment in different states are simulated and calculated;

and 5: analyzing the influence of Doppler frequency generated by the rotation of the fan blade on radar echo;

step 6: deducing a multipath effect theoretical formula and calculating according to the distribution characteristics of the wind turbine generator array;

and 7: and (3) carrying out actual measurement equivalence on the scene, testing electromagnetic environment noise data in a similar environment, carrying out equivalent calculation on the environment of the wind power plant to be built and the power consumption, and evaluating the influence range of the wind power plant.

Furthermore, the wind turbine generator set in the step 2 is composed of a tower, a hub, an engine room and blades, the blades are made of non-metal materials, and the energy of reflected signals is small, so that the tower is used as a main modeling calculation object; meanwhile, the lightning protection lead wire is arranged between the blade and the hub, so that the fan model is equivalent; the fan electromagnetic model is based on a curved surface modeling method, and the establishment of a geometric model is realized by utilizing a mode of combining CAD (computer-aided design) and Femap software according to fan parameters.

Further, the step 2 of grid division refers to that grids with different sizes are adopted at positions of different structures, the whole structure shows grid division forms with different densities, and when the target geometric modeling divides the grids, it is ensured that arch height errors of all plane elements on the actual curved surface are smaller than 1/16 of the wavelength.

Furthermore, in the step 2, the mesh optimization refers to the rationality of the geometric shape of the mesh, the quality of the mesh affects the calculation accuracy, the poor quality mesh even stops the calculation, and each unit of the triangular mesh in an ideal situation is an equilateral triangle.

Further, the step 3 of establishing the ground wave beyond visual range radar scene model is to set a working wave band, a wave beam direction and a polarization mode according to the relative position of the radar and the wind power plant, and calculate the electric field intensity change condition of the peripheral area of the wind power plant, so as to obtain a direct shielding quantitative analysis result.

Further, the doppler influence in the step 5 is that the rotation of the fan blade causes a radar echo to have a doppler frequency shift component, the modulation depth is calculated by using an amplitude modulation signal of the radar signal after being modulated by the rotation frequency of the fan blade, and the doppler influence is judged according to the amplitude ratio after modulation.

Further, in the step 6, the multipath effect is obtained by deducing and calculating the influence of the fan on the radar electromagnetic wave reflection by using a radar equation, the target reflection direct wave and the secondary reflection echo passing through the wind motor are synthesized at the receiving antenna, if the amplitude of the echo signal reflected by the wind motor is too large, the radar is influenced on the target azimuth resolution, a false target is formed after the radar is processed by a radar receiver, the false alarm influence is caused, and the multipath effect influence range is analyzed according to the distance and angle change among the radar, the target and the wind farm.

Further, an actual measurement analysis method is adopted in the step 7, and the actual measurement is carried out by developing similar established wind power equipment, aiming at the noise comparison of different working states and different frequencies of a fan in a test environment, equivalent calculation is carried out according to the unit type, the number, the arrangement position and the regional wind power level factor of the wind power plant, and then the radiation characteristic of the wind power plant to be evaluated can be converted.

The invention has the beneficial effects that:

1. the invention adopts the MoM electromagnetic calculation method based on the integral equation, so that the calculation result is more accurate; the method is easier to obtain for an actual radar system, can replace an actual radar test or a microwave anechoic chamber scale test, and can save cost.

2. The method analyzes in three aspects of shielding, radiation and scattering, and is more comprehensive and more accurate in evaluation result compared with the conventional analysis method.

3. The method is more specific to actual measurement scene analysis, reasonable equivalent calculation is carried out on parameters, and the method has a reference value for practical engineering application.

Drawings

FIG. 1 is a processing block diagram of an evaluation method for influence of an offshore wind farm on detection efficiency of a ground wave over-the-horizon radar.

FIG. 2 is a schematic diagram of a ground wave over-the-horizon radar and a wind farm location according to the present invention.

FIG. 3 is a diagram of an equivalent electromagnetic simulation model of a wind turbine according to the present invention.

FIG. 4 is a graph of the electric field strength calculation results around the wind farm of the present invention.

FIG. 5 is a graph of electric field intensity at three azimuth angles of a wind farm according to the present invention.

FIG. 6 is a graph of RCS values for three frequencies for a single fan according to the present invention.

Fig. 7 is a schematic diagram of the noise test of the present invention.

Fig. 8 is a comparison graph of radio noise measurement data under different conditions of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, for convenience of explanation, the following scenarios are established:

the wind power plant comprises a square array formed by 25 fans, the distance between the fans is 500m, each fan has the capacity of 6MW, the total installed capacity is 150MW, and the fan parameters are shown in table 1:

TABLE 1 Fan parameters

The relation between the ground wave beyond visual range radar and the position of the wind power plant is shown in figure 2, and three frequency points of 4MHz, 7MHz and 12MHz are selected as the radar working frequency.

Step 1: according to the basic performance, station arrangement position, beam width and action region parameters of the ground wave over-the-horizon radar and preselected region development scene analysis of the wind power plant, eliminating radars which are not influenced or are influenced very little by the wind power plant at all, and screening out objects needing important analysis;

step 2: establishing a fan electromagnetic model according to the provided wind turbine generator parameters, and realizing the establishment of a single fan electromagnetic model through grid division, grid quantity setting and grid optimization;

the wind turbine generator set comprises a tower, a hub, an engine room and blades, wherein the blades are made of non-metal materials, and the energy of reflected signals is small, so that the tower is used as a main modeling calculation object; as shown in fig. 3; meanwhile, the lightning protection lead wire is arranged between the blade and the hub, so that the fan model is equivalent; the fan electromagnetic model is based on a curved surface modeling method, and the establishment of a geometric model is realized by utilizing a mode of combining CAD (computer-aided design) and Femap software according to fan parameters.

The grid division means that grids with different sizes are adopted at parts of different structures, in order to adapt to the distribution characteristics of surface current, in parts with severe surface current changes, in order to better reflect the change rule, relatively dense grids need to be adopted, in parts with small changes, in order to reduce the model scale, relatively sparse grids need to be divided, so that the whole structure presents grid division forms with different densities, although the grid points of the surface of a target body generated by geometric modeling are surface accurate points, because the grid discrete point calculation normal vector is approximately taken as the surface of a small plane bin formed by three grid points, the size of the grid can influence the calculation result of the normal vector, the influence analysis of the radar scattering cross section RCS calculation and the size of the bin is generally called that the height error caused by replacing an original curved surface with a small plane is smaller than 1/16 of the radar wavelength, therefore, when the target geometric modeling is used for meshing, all plane elements are ensured to generate arch height errors on the actual curved surface, which are less than 1/16 of the wavelength.

The grid number directly influences the accuracy of the calculation result and the size of the calculation scale, generally speaking, the grid number is increased, the calculation accuracy is improved, but the calculation scale is also increased, so that two factors are balanced and considered comprehensively when the grid number is determined.

The optimization of the grid refers to the rationality of the geometric shape of the grid, the quality influences the calculation precision, the grid with poor quality even stops the calculation, the triangular grid under the ideal condition is an equilateral triangle, so the minimum internal angle of a triangular unit becomes an important standard for measuring the quality of the grid, the larger the minimum internal angle is (the internal angle of the triangle is fixed by 180 degrees, the larger the minimum internal angle is required to be, the more the triangle is close to the equilateral triangle, when the minimum internal angle of three angles is 60 degrees, the equilateral triangle is, and at the moment, the smaller internal angle cannot be larger), the better the quality of the grid is.

And step 3: according to the longitude and latitude coordinates of a fan of a pre-built wind power plant and the relative position information of the radar, a wind turbine generator array is built in FEKO electromagnetic calculation software, a ground wave over-the-horizon radar scene model is built at the same time, the influence of a wind power plant area on the surrounding electric field intensity is simulated, and the shielding influence caused by the wind turbine generator is analyzed;

the method for establishing the ground wave beyond visual range radar scene model is characterized in that a working wave band, a wave beam direction and a polarization mode are set according to the relative position of a radar and a wind power plant, and the electric field intensity change condition of the peripheral area of the wind power plant is calculated, so that a direct shielding quantitative analysis result is obtained.

And analyzing the electric field intensity of the electromagnetic wave in the peripheral area after passing through the wind power plant, as shown in FIG. 4. The cross sections of three of the orientations are selected, and the calculation result is shown in fig. 5. The fluctuation amplitude of the electric field is within 0.1V/m outside 2.5Km away from the center of the wind power plant, and the shielding signal-to-noise ratio is reduced by 0.83dB at most; and the fluctuation amplitude of the electric field is within 0.05V/m outside 3.5Km away from the center of the wind power plant, and the shielding signal-to-noise ratio is reduced by 0.42dB at most. Besides, the variation range is obviously reduced and is flat beyond 2.5 Km.

And 4, step 4: RCS changes of single fan equipment in different states are simulated and calculated;

the plane wave is vertically polarized, enters in the direction of meeting the fan blades, and is received in the direction of departing from the fan blades, the RCS values of 0-120 degrees of rotation of the fan blades of the fan equivalent model are respectively calculated, and the RCS calculation results are shown in FIG. 6 when the frequencies are 4MHz, 7MHz and 12 MHz. The maximum value of the single fan RCS is reached at the highest frequency of 12MHz and peaks at 45.25dBm²。

And 5: analyzing the influence of Doppler frequency generated by the rotation of the fan blade on radar echo;

the Doppler influence is that the rotation of the fan blade leads the radar echo to have Doppler frequency shift component, the modulation depth is calculated by using the amplitude modulation signal of the radar signal after being modulated by the rotation frequency of the fan blade, and the Doppler influence is judged according to the amplitude ratio after modulation.

According to the maximum 15 rpm of the fan parameter, the maximum rotation frequency of the fan is 0.75Hz, namely 4MHz, 7MHz and 12MHz, the Doppler frequency shift is 0.75Hz, which is equivalent to generating false targets with radial movement speeds of 28.1m/s, 12.5m/s and 7.5m/s on a radar screen; false targets with different radial speeds are still generated when the fan speed is lower than 15 rpm.

Suppose that the radar signal modulated by the rotation of the windmill is

U(t)＝V_c(1+m cosω_ft)cosω_ct (1)

Wherein, ω is_f3 pi/2 is the angular frequency of the modulation signal, V_cIn order to be the amplitude of the carrier signal,is a modulation factor, V_fModulating signal amplitude, omega_cIs the carrier signal angular frequency. The frequency point with the maximum amplitude difference between the two is selected as a reference, namely the frequency point with 4 MHz. The average of the individual fan RCS calculated in FIG. 6 was taken as the carrier amplitude 42.55dBm²Maximum amplitude difference from the mean 41.535dBm²The difference of (d) is taken as the modulation signal amplitude.

The modulation signal is then expressed as:

calculating to obtain U_max＝21750，U_minThe modulation depth was 20.8%, 14250.

Further analysis is made from the spectrum of the signal, the spectrum of the modulated signal being:

thus at a frequency of ω_cHas an amplitude of 18000 pi and a frequency of omega_c±ω_fThe amplitude is 1875 pi and their ratio is-9.8 dB. The rotating frequency of the fan is between 0 Hz and 0.75Hz, and the maximum ratio of the two frequencies is-9.8 dB, so that false targets can be formed in a wind power plant area due to the rotation of the fan, and the detection of the ground wave beyond visual range radar in the area is influenced.

Step 6: deducing a multipath effect theoretical formula and calculating according to the distribution characteristics of the wind turbine generator array;

the multipath effect is obtained by deducing and calculating the influence of a fan on radar electromagnetic wave reflection by using a radar equation, a target reflection direct wave and a secondary reflection echo passing through a wind motor are synthesized at a receiving antenna, if the amplitude of an echo signal reflected by the wind motor is too large, the radar can be influenced on the azimuth resolution of the target, a false target is formed after the radar is processed by a radar receiver, the false alarm influence is caused, and the influence range of the multipath effect is analyzed according to the distance and angle change among the radar, the target and a wind power plant.

Using the maximum RCS value of the individual fan in FIG. 6 as the reference value of 45.25dBm²Let the distance between the target and the radar be r₁Distance between wind power plant and radar is r₂Distance of target from wind farm is r₃. The power of scattering by the target is P_tOne path of the scattering signal directly reaches the receiving antenna, and the power density is as follows:

and the other path of scattered signal reaches the wind power plant, and the power density is as follows:

the signal reaches a receiving antenna through a wind power plant, and the power density expression is as follows:

in the formula (6), N is the number of the wind turbines, and the ratio of the target scattered signal reaching the receiving antenna through the wind farm to the target scattered signal directly reaching the receiving antenna is:

the ratio is the influence caused by the wind turbine generator, and therefore, the influence of the power density when the scattering signal reaches the radar can be calculated by the above formula.

When the target distance is set to be 5Km from the wind power plant, the number of fans is 25 at most in one distinguishing unit of the radar distance and the angle, and the direct wave is calculated according to the formula (7) and is about 25.74dB compared with the direct wave and the target scattered signal which reaches a receiving antenna after passing through the wind power plant. If the radar detection threshold is set to be 20dB, at the moment, the multipath scattering signals cannot form false targets, and the influence on a radar system is small. (mainly, according to the setting of the radar detection threshold at that time, when the ratio of the direct wave to the multipath effect echo is greater than the detection threshold, the target direct wave signal can be detected at that time, but the multipath echo cannot be detected, so that a false target cannot be generated).

And 7: and (3) carrying out actual measurement equivalence on the scene, testing electromagnetic environment noise data in a similar environment, carrying out equivalent calculation on the environment of the wind power plant to be built and the power consumption, and evaluating the influence range of the wind power plant.

Because the internal structure of the wind turbine is complex, the source of the generated electromagnetic radiation is difficult to be determined, so that analysis can not be carried out through theoretical calculation, and only an actual measurement analysis method can be adopted. In addition, because the construction of the wind power plant is not carried out in the evaluation stage, the actual measurement can only be carried out by the built similar wind power equipment. Because the structure, size and the theory of operation of wind-powered electricity generation machine are roughly the same, therefore the actual measurement analysis of radiation influence has the commonality. After actual measurement results of similar scenes are obtained, equivalent calculation is carried out on the type, the number, the arrangement position and the relevant factors of the regional wind power level of the wind power plant, and then the radiation characteristic of the wind power plant to be evaluated can be converted.

The test method comprises the following steps: a broadband active loop antenna is used as a test antenna, a handheld frequency spectrograph is used as a test receiver, and the test principle is shown in fig. 7. The test environment is that a certain built offshore wind power plant is provided with 55 wind power units, wherein the offshore distance of the wind power plant is about 10Km, the direction along the coastline is about 13.4Km, and the total installed capacity of a project is 202 MW. The wind turbine generator is selected to be in a stop state and a rotation working state respectively for noise data measurement, and the test result is shown in fig. 8.

Equivalent calculation: according to an actual measurement result, the noise average elevation value of 13.1dB at 4-5 MHz is used as noise power increased when the wind turbine generator is started and stopped. The actual measured total installed capacity is 202MW, while the planned construction total installed capacity is 150MW, so the power is reduced by 1.29 dB; 55 wind power generators in the experimental data, 25 wind power generators in planned construction, 5.2m/s of wind speed in the working state of the wind power generators during actual measurement, 0.5MW of power and 4MW of rated power of a fan in planned construction, and the maximum power needs to be converted for calculation in consideration of different wind power levels in sea areas, so that 5.61dB of compensation needs to be obtained through calculation; therefore, the working noise of the wind turbine generator is averagely raised by about 17.42dB in a rated power state by being reduced to a wind turbine generator for planned construction. Using free space electromagnetic wave power attenuation formula

Calculating, wherein f is radar working frequency, r is attenuation radius, G_TAmplifying gain for transmitting antenna, G_RFor the amplification gain of the receiving antenna, the attenuation radius is calculated to be about 7.43Km, namely, the electromagnetic noise influence is negligible outside a circular area taking the center of the wind farm as the center and 7.43Km as the radius.