KR102550052B1 - Laser beam steering type lidar for measuring wind speed using 2-axis steering mirror - Google Patents

Abstract

The present invention relates to a lidar for measuring wind speed that measures wind speed data necessary in real time during installation and operation of a wind turbine, and more particularly, to a wind speed measuring period and wind speed data requested by a user using a two-axis steering mirror. It relates to a lidar for measuring wind speed using a laser beam steering method using a two-axis steering mirror that can satisfy reliability.

Description

Laser Beam Steering Type LIDAR FOR MEASURING WIND SPEED USING 2-AXIS STEERING MIRROR}

The present invention relates to a lidar for measuring wind speed that measures wind speed data necessary in real time during installation and operation of a wind turbine, and more particularly, to a wind speed measuring period and wind speed data requested by a user using a two-axis steering mirror. It relates to a lidar for measuring wind speed using a laser beam steering method using a two-axis steering mirror that can satisfy reliability.

Recently, as interest in wind energy (wind energy) as a renewable energy source has increased, the development and installation of wind power generators has been continuously increasing. After a wind farm is completed, output performance evaluation should be performed according to the international standard IEC 61400-12-13) or IEC 61400-12-24) to verify the output performance generally guaranteed by the manufacturer. To this end, a meteorological mast must be installed according to the standards presented by international standards, and wind data must be measured for about six months or more. To measure such wind data, LiDAR (Light Detection And Ranging) is being used.

LIDAR is a remote sensing device (RSD) that can replace traditional weather towers, and is a long-distance sensor based on laser detection that was developed relatively recently for wind condition measurement. Wind direction and speed are measured using the Doppler shift of the laser emission scattered by aerosol particles (dust, water vapor, clouds, fog, pollutants, etc.). In addition, lidar is also used to control the blades of wind turbines according to the wind speed in order to efficiently operate the built wind generators and prevent damage to the wind turbines. .

The Doppler LiDAR used to measure wind conditions is a lidar using the Doppler effect, and measures the wind speed by measuring minute frequency changes of a laser beam by the Doppler effect. In order to measure the three-dimensional wind speed of the sample volume centered on the cross section of a predetermined height vertically from the location where the lidar is installed, the laser beam is sequentially irradiated in four directions as shown in FIG. Wind speed must be measured separately.

2 is a diagram schematically showing a LiDAR of a method of steering a laser beam by rotating a prism having a conventional wedge shape. As shown in FIG. 2, the conventional lidar of the method of steering a laser beam by rotating a wedge-shaped prism uses the principle that the refracted direction by the prism is changed by rotating the prism installed on the upper part of the lens at about one rotation per second.

However, in the lidar of a method of steering a laser beam by rotating a conventional wedge-shaped prism, first, the weight of the prism is considerable, and second, vibration occurs due to rotation of the prism having a non-symmetrical wedge shape, Third, rotation of the prism may cause a problem in that the position of the sample volume is changed. In particular, the problem of changing the position of the sample volume does not have a significant effect when the measurement period is very short, but when the number of aerosol particles in the air is not large, the accuracy of the wind speed calculated based on the data measured while the position of the sample volume is changed is improved. This can lead to significant deterioration problems.

For example, if the number of aerosol particles in the air is not large, the velocity at a specific location should be calculated by averaging about 1,000 cycles. However, since 1,000 cycles corresponds to a period of 0.1 seconds under the condition that the laser driving frequency is 10 kHz, assuming that the prism rotates once per second, the prism rotates 36° during this period, resulting in a situation where the position of the sampling volume changes significantly. can happen In this way, the accuracy of the wind speed calculated based on the measured data in a state where the position of the sample volume is greatly changed is inevitably lowered.

KR 10-1853122 B1, 2018. 04. 23. KR 10-2240887 B1, 2021. 04. 09. KR 10-1383792 B1, 2014. 04. 03. KR 10-2022-0047884 A, 2022. 04. 19.

Therefore, an object of the present invention is a laser beam steering method wind speed measurement lidar using a two-axis steering mirror that can satisfy the wind speed measurement period and reliability of wind speed data required by users even in poor environmental conditions with low aerosol particle concentration. is to provide

In addition, the present invention is not limited to the above-mentioned purpose, and various other objects may be additionally provided through the techniques described through the following embodiments and claims.

The present invention according to an embodiment for achieving the above object is a laser device for transmitting a laser beam in the form of a pulse or continuous wave (CW); It moves sequentially in four directions, and after moving to a position in one direction, it remains stopped for a set time at the position in one direction, and in the stopped state, the laser beam emitted from the laser device is directed in the corresponding direction. A two-axis steering mirror that reflects to the position of; A total of 4 lenses, each installed in 4 directions, for irradiating the laser beam reflected from the 2-axis steering mirror with aerosol particles within a sample volume to be measured; Signal processing for receiving and processing the scattered light signal scattered from the aerosol particles in the sample volume by the laser beam emitted from the laser device and the laser beam irradiated through the transmission/reception lens through the transmission/reception lens and the two-axis steering mirror. Device; and a wind speed data acquisition device for calculating the wind speed within the sample volume based on the output signal of the signal processing device.

In addition, a housing for protecting and fixing the two-axis steering mirror and the transmission/reception lens may be further included.

In addition, the housing includes a body in which the two-axis steering mirror is built-in; and a cover covering an upper portion of the body and having the transmit/receive lenses installed one by one in four directions.

In addition, a steering mirror controller for controlling movement of the two-axis steering mirror may be further included.

In addition, the steering mirror controller sequentially moves the two-axis steering mirror in N (north), W (west), S (south), and E (east) directions according to a preset program, and then moves in any one direction. It is possible to keep the two-axis steering mirror in a stopped state for a predetermined time at the position of .

In addition, the laser device includes a laser beam transmission module for generating and transmitting the laser beam; a reception signal amplification module receiving and amplifying the scattered light signal; and transmitting the laser beam transmitting module to the two-axis steering mirror through an optical fiber, transmitting the scattered light signal received through the optical fiber to the receiving signal amplifying module, and transmitting the scattered light signal amplified by the receiving signal amplifying module to the optical fiber. It may include an optical circulator outputting to a signal processing device.

In addition, the signal processing device includes a 2x2 optical coupler for transmitting the laser beam transmitted from the laser beam transmission module and the amplified scattered light signal output from the optical circulator; and a balanced detector converting a difference between the laser beam output from the 2×2 optical coupler and the amplified scattered light signal into a digital value and outputting the converted digital value to the wind speed data acquisition device.

As described above, according to the lidar for measuring wind speed of the laser beam steering method using the two-axis steering mirror according to the present invention, since the two-axis steering mirror can be stopped for a desired time, as many as 1,000 cycles are averaged. Since measurement is possible under the required conditions, it is possible to meet the wind speed measurement period and reliability of wind speed data required by users even in poor environmental conditions with low aerosol particle concentration.

1 is a conceptual diagram showing a sample volume at a measurement position of a lidar for measuring wind speed.
Figure 2 is a view showing a lidar of a conventional laser beam steering method.
3 is a view showing a lidar for measuring wind speed of a laser beam steering method according to an embodiment of the present invention.
4 is a block diagram of a lidar for measuring wind speed shown in FIG. 3;
5 is a block diagram showing the configuration of the laser beam transmission module shown in FIG. 4 as an example;
6 is a view showing a movement section of the two-axis steering mirror shown in FIG. 4;

Hereinafter, the advantages and features of the present invention, and methods for achieving them will become clear with reference to the embodiments described later in detail in conjunction with the accompanying drawings. Like reference numerals designate like elements throughout this specification. In addition, each component shown in each figure may be excessively illustrated in size and shape, which is for convenience of description and is not intended to be limited.

Hereinafter, technical features of the present invention will be described in detail with reference to the accompanying drawings.

3 is a diagram schematically illustrating a lidar for measuring wind speed using a laser beam steering method according to an embodiment of the present invention, and FIG. 4 is a block diagram of the lidar for measuring wind speed shown in FIG. 3 .

Referring to FIGS. 3 and 4, the laser beam steering method wind speed measurement lidar according to an embodiment of the present invention uses a laser beam steering device including a two-axis steering mirror 12 capable of dual-axis steering at high speed. Thus, even in poor environmental conditions with low aerosol particle concentration, it is possible to satisfy the wind speed measurement period and the reliability of wind speed data required by users.

The laser device 11 includes a laser beam transmission module 111 that generates a laser beam L in the form of a pulse or continuous wave (CW) and transmits the laser beam L to the two-axis steering mirror 12 .

FIG. 5 is a block diagram showing the configuration of the laser beam transmission module shown in FIG. 4 as an example.

As shown in FIG. 5, the laser beam transmission module 111 includes a laser beam generator 111a that generates a laser beam and an erbium doped fiber amplifier (EDFA) that amplifies the laser beam generated by the laser beam generator 111a. 111b, an Acoustic Optic Modulator (AOM) 111c for modulating the amplitude and deflection of the laser beam amplified by the optical fiber amplifier 111b, and the intensity of the laser beam generated by the laser beam generator 111a. It may include a variable optical attenuator (VOA: Variable Optical Attenuato) (111d) for attenuating.

As shown in FIGS. 3 and 4, the laser beam L transmitted from the laser beam transmission module 111 is incident to the 2-axis steering mirror 12 through the optical fiber 2 and reflected by the 2-axis steering mirror 12. Then, through the transmission/reception lens 13, the aerosol particles 1 (hereinafter referred to as 'subject') within the sample volume at a predetermined height to measure wind speed are irradiated. In addition, the laser beam L irradiated to the object 1 is scattered by the object 1, the frequency is changed by the Doppler effect, and the light scattered backward among the scattered light (light) is transmitted and received through the transmitting and receiving lens ( After being incident on the two-axis steering mirror 12 through 13), it is reflected and received by the laser device 11 through the optical fiber 2.

As shown in FIG. 4, the laser device 11 is scattered from the target object 1 and passes through the transmission/reception lens 13 and the two-axis steering mirror 12 in the reverse order to the irradiation direction of the laser beam L to the optical fiber 2. and a reception signal amplifying module 112 that amplifies the scattered light (signal) sL input through the.

The received signal amplification module 112 may include an erbium doped fiber amplifier (EDFA) that receives the scattered light signal input through the optical fiber 2 from the optical circulator 113 and amplifies and outputs the amplified signal. . The optical fiber amplifier of the received signal amplifying module 112 amplifies and outputs the scattered light signal received through the optical circulator 113 . The optical circulator 113 separates the laser beam L transmitted from the laser beam transmitting module 111 to the optical fiber 2 and the scattered light signal received from the optical fiber 2 from each other.

For example, the scattered light signal input from the optical fiber 2 to the 'port 2' of the optical circulator 113 is incident to the optical fiber reflector via the optical fiber amplifier (EDFA) connected to the 'port 1' of the optical circulator 113 and reflected. , The reflected signal may be amplified with a high gain through an optical fiber amplifier (EDFA) and then output to the wind speed data acquisition device 15 through the 'port 3' of the optical circulator 113.

The two-axis steering mirror 12 is a two-axis fast steering mirror, and as shown in FIG. 4, the steering mirror 121 for reflecting the laser beam incident through the optical fiber 2 to the transmission/reception lens , Driving unit 122 that sequentially moves the steering mirror 121 to the N (north), W (west), S (south), and E (east) directions (see FIG. 1), that is, to face each of the four directions, east, west, north, south, and north. ).

The driving unit 122 is controlled through the steering mirror controller 14.

FIG. 6 is a diagram schematically illustrating a movement section of the two-axis steering mirror shown in FIG. 4 .

As shown in FIG. 6, the steering mirror controller 14 controls the driving unit 122 according to a preset program to move the steering mirror 121 in the N (north), W (west), S (south), and E (east) directions. After moving sequentially to , it is maintained in a stopped state for a predetermined time. Laser beam scanning and LIDAR measurement are performed while the steering mirror 121 remains stationary at a position in one direction. That is, the steering mirror controller 14 sequentially moves the steering mirror 121 in the N (north), W (west), S (south), and E (east) directions, and sets the position in each direction. It is maintained in a stationary state for a period of time so that scanning of the laser beam and LIDAR measurement are performed.

As shown in FIG. 3 , a total of four transmit/receive lenses 13 are installed at equal intervals, one for each of the four directions of the four directions of east, west, south, and north, corresponding to the movement positions of the two-axis steering mirror 12 in the four directions.

The laser beam L reflected from the two-axis steering mirror 12 is condensed through the transmission/reception lens 13 and irradiated to the target object 1, and among the light scattered from the object 1, the light scattered backward is transmitted through the transmission/reception lens. After being received by the 2-axis steering mirror 12 through (13), it is input to the laser device 11.

A housing 16 is provided to protect and fix the transmission/reception lens 13 and the two-axis steering mirror 12. As shown in FIG. 3, the housing 16 includes, for example, a body 161 in which a two-axis steering mirror 12 is built-in, and four transmitting and receiving lenses 13 covering the upper portion of the body 161. It may include a cover 162 fixedly installed at regular intervals in the east, west, south, and north directions, respectively.

As shown in FIG. 4 , the laser beam output from the laser beam transmission module 111 and the scattered light signal output through the optical circulator 113 are input to the signal processing device 15 and signal processed.

The signal processing device 15 transmits (or distributes) the laser beam output from the laser beam transmission module 111 and the scattered light signal output through the optical circulator 113, that is, the amplified scattered light signal. 2 optical coupler and a balanced detector (balanced detector).

The output voltage of the signal processing device 15, for example, a digital value, is input to the wind speed data acquiring device 17. The wind speed data acquisition device 17 receives the digital values input from the signal processing device 15 and calculates wind speed data within a sample volume of a predetermined height.

The signal processing device 15 and the wind speed data acquisition device 17 may be provided in the laser device 11 in a module form, respectively. Preferably, as shown in FIG. 4, it may be provided outside independently of the laser device 11. In the latter case, the signal processing device 15 may be connected to the laser device 11 through an optical fiber connector. In addition, the wind speed data acquisition device 17 may be connected to the output terminal of the balanced detector of the signal processing device 15 through a wired connection.

Referring to the operating characteristics of the lidar for wind speed measurement of the laser beam steering method according to the embodiment of the present invention having such a configuration, as shown in FIG. 4, the optical fiber 2 in the laser beam transmission module 111 of the laser device 11 The laser beam (L) transmitted through ) is reflected by the two-axis steering mirror 12 and sequentially moves in 4 directions in N (north), W (west), S (south), and E (east) directions according to the set program. It is irradiated to the center of any one of the two transmit/receive lenses 13.

A laser beam (L) irradiated by any one of the transmission and reception lenses 13 is scattered by aerosol particles moving at the same speed as the air within the sample volume. Among the scattered lights, the light scattered backward is incident to the 2-axis steering mirror 12 through the transmission/reception lens 13 in reverse order, and then reflected and input to the laser device 11 through the optical fiber 2. The scattered light sL input to the laser device 11 is separated from the laser beam L by the optical circulator 113 .

The signal processing device 15 receives the laser beam and the scattered light signal output from the optical circulator 113, converts the difference between them into a digital value, and outputs it to the wind speed data acquisition device 17. The wind speed data acquisition device 17 obtains wind speed data by calculating the wind speed within the corresponding sample volume using the output signal output from the signal processing device 15.

The lidar for wind speed measurement of the laser beam steering method according to an embodiment of the present invention having such a configuration uses a two-axis steering mirror 12 and four transmit/receive lenses 13 in four directions (N→ The laser beam is sequentially generated as W → S → E), but laser beam scanning and LiDAR measurement can be provided in a state where the laser beam is stopped for a desired time.

LIDAR measures the LOS (Line of Sight) wind speed within the sample volume in four directions to measure the three-dimensional wind speed at that altitude, and the required measurement cycle may vary depending on the user's purpose of using LIDAR. In addition, the wind speed measurement accuracy and maximum measurement distance of lidar may vary depending on the concentration of aerosol particles in the air. there is. However, as shown in FIG. 2, since the sample volume rotates like a prism, Lidar applied with a conventional prism rotation method has limitations in application to conditions in which many cycles must be averaged. However, since the lidar for measuring the wind speed of the laser beam steering method according to an embodiment of the present invention can stop the two-axis steering mirror for a desired time, it is possible to measure aerosol particles even under the condition of averaging as many as 1,000 cycles. Even in poor environmental conditions with low concentration, it can satisfy the wind speed measurement cycle and reliability of wind speed data required by users.

As above, although preferred embodiments of the present invention have been described and illustrated using specific terms, such terms are only intended to clarify the present invention. And, it is obvious that various changes and changes can be made to the embodiments of the present invention and the described terms without departing from the technical spirit and scope of the following claims. Such modified embodiments should not be individually understood from the spirit and scope of the present invention, and should be said to fall within the scope of the claims of the present invention.

1: aerosol particle (object) 2: optical fiber
11: laser device 12: 2-axis steering mirror
13: transmitting and receiving lens 14: steering mirror controller
15: signal processing device 16: housing
17: wind speed data acquisition device 111: laser beam transmission module
111a: laser beam generator 111b: optical fiber amplifier
111c: optical modulator 111d: variable optical attenuator
112: reception signal amplification module 113: optical circulator
121: steering mirror 122: driving unit
161: body 162: cover
L : laser beam sL : scattered light (signal)

Claims (7)

A laser device that transmits a laser beam in the form of a pulse or continuous wave (CW);
It moves sequentially in four directions, and after moving to a position in one direction, it remains stopped for a set time at the position in one direction, and in the stopped state, the laser beam emitted from the laser device is directed in the corresponding direction. A two-axis steering mirror that reflects to the position of;
A total of 4 lenses, each installed in 4 directions, for irradiating the laser beam reflected from the 2-axis steering mirror with aerosol particles within a sample volume to be measured;
Signal processing for receiving and processing the scattered light signal scattered from the aerosol particles in the sample volume by the laser beam emitted from the laser device and the laser beam irradiated through the transmission/reception lens through the transmission/reception lens and the two-axis steering mirror. Device; and
a wind speed data obtaining device for calculating a wind speed within the sample volume based on an output signal of the signal processing device;
a housing for protecting and fixing the two-axis steering mirror and the transmission/reception lens;
a steering mirror controller controlling movement of the two-axis steering mirror;
the housing,
A body in which the two-axis steering mirror is built-in; and
a cover covering an upper portion of the body and having one transmit/receive lens installed in each of four directions; including,
The steering mirror controller sequentially moves the two-axis steering mirror in N (north), W (west), S (south), and E (east) directions according to a preset program, and then moves to a position in any one of the moved directions. Controlling to perform laser beam scanning and LiDAR measurement, respectively, while the two-axis steering mirror is maintained in a stopped state for a predetermined time in
A lidar for wind speed measurement using a laser beam steering method for lidar using a two-axis steering mirror.
delete delete delete delete According to claim 1,
The laser device,
a laser beam transmitting module generating and transmitting the laser beam;
a reception signal amplification module receiving and amplifying the scattered light signal; and
The laser beam transmission module transmits the optical fiber to the two-axis steering mirror, transmits the scattered light signal received through the optical fiber to the reception signal amplification module, and transmits the amplified scattered light signal in the reception signal amplification module to the signal an optical circulator that outputs to a processing device;
A lidar for measuring wind speed of a laser beam steering method for lidar using a two-axis steering mirror including a.
According to claim 6,
The signal processing device,
a 2×2 optical coupler for transmitting the laser beam transmitted from the laser beam transmission module and the amplified scattered light signal output from the optical circulator; and
a balanced detector converting a difference between the laser beam output from the 2×2 optical coupler and the amplified scattered light signal into a digital value and outputting the converted digital value to the wind speed data acquisition device;
A lidar for measuring wind speed of a laser beam steering method for lidar using a two-axis steering mirror including a.

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