Method for detecting strain of key part of wind turbine generator by demodulating weak fiber bragg grating array based on temperature compensation OFDR (Optical Frequency Domain Reflectometer)

Abstract

The invention discloses a method for detecting the strain of a key part of a wind turbine generator based on a temperature compensation OFDR demodulation weak fiber bragg grating array, and relates to the technical field of wind turbine generator detection, and the method comprises the steps: installing a weak fiber bragg grating sensor array at the key strain part according to the structural characteristics of the wind turbine generator, a temperature reference grating is arranged in the non-strain area or the constant-temperature area so as to monitor the temperature change in real time; a tunable laser, an optical fiber coupler and a photoelectric detector are utilized to construct an optical frequency domain reflection demodulation system, and system calibration is completed; based on an optical frequency domain reflection demodulation system, reflection spectrum signals are collected, the relation between wind turbine generator strain and temperature change is analyzed through a temperature compensation mechanism, and strain information of key parts of the wind turbine generator is obtained. According to the method, the accuracy and reliability of strain detection are effectively improved, and the problem of measurement errors caused by neglecting the influence of temperature change in a traditional method is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine detection, and in particular to a method for detecting strain at key parts of a wind turbine based on temperature-compensated OFDR demodulation of a weak fiber grating array. Background Art

[0002] As essential equipment for clean energy, wind turbines are subject to deformation in their critical components during long-term operation due to factors such as electromagnetic forces, thermal expansion and contraction, and mechanical stress. This deformation can degrade the turbine's insulation performance, alter electrical parameters, and even cause serious electrical failures, threatening the safe operation of the entire wind power system. Therefore, real-time monitoring of the strain in key wind turbine components is crucial for ensuring safe and efficient operation. Traditional wind turbine deformation detection methods rely on offline techniques, primarily short-circuit impedance testing and frequency response analysis (FRA). These methods require downtime and are unable to meet the continuous operation requirements of wind farms. They also struggle to provide accurate strain distribution information and fail to fully reflect the actual status of the wind turbine.

[0003] With the advancement of sensing technology, weak fiber Bragg grating (WFBG) sensing technology has gained widespread application in strain monitoring of key wind turbine components due to its high sensitivity, resistance to electromagnetic interference, and distributed measurement capabilities. WFBG sensors can simultaneously measure strain and temperature changes at different locations and transmit data via optical signals, effectively avoiding the interference issues associated with traditional electrical signal transmission. Optical frequency domain reflectometry (OFDR), an advanced demodulation method based on weak fiber Bragg gratings, can accurately demodulate the reflection spectrum of fiber Bragg gratings (FBGs), enabling distributed measurement of strain and temperature. OFDR analyzes the spatial distribution of the reflection spectrum to provide high-resolution strain and temperature data, making it particularly suitable for precision monitoring in complex environments such as wind turbines. Furthermore, during wind turbine operation, temperature changes significantly impact strain measurements. To improve measurement accuracy, temperature compensation techniques have been incorporated into WFBG sensing systems. Common temperature compensation methods include differential structures and dual-grating temperature compensation. These ensure accurate strain measurement through real-time calibration and compensation for temperature effects.

[0004] However, existing WFBG-based wind turbine strain detection systems still face several technical challenges. First, wind turbines operate in complex environments with significant temperature fluctuations. Existing temperature compensation methods struggle to completely eliminate temperature interference with strain measurements, resulting in errors in the measurement results. Second, OFDR demodulation technology faces challenges in practical applications, including low signal-to-noise ratios and insufficient demodulation accuracy. Demodulation performance degrades significantly, particularly under weak optical signal conditions. Furthermore, existing systems lack a systematic layout for strain distribution monitoring in key wind turbine locations, making it difficult to comprehensively and accurately reflect the strain status of these critical wind turbine components. These technical challenges severely restrict the application of WFBG technology in wind turbine strain monitoring.

[0005] Currently, no effective solutions have been proposed for the problems in related technologies. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In response to the shortcomings of the existing technology, the present invention provides a method for detecting strain in key parts of wind turbines based on temperature-compensated OFDR demodulation of weak fiber Bragg grating arrays. The method has the advantages of improving the accuracy and reliability of strain detection in key parts of wind turbines, thereby solving the problems of severe temperature interference, insufficient signal demodulation accuracy, and incomplete strain distribution monitoring in the existing technology.

[0008] (2) Technical solution

[0009] In order to achieve the above advantages of improving the accuracy and reliability of strain detection at key parts of wind turbines, the specific technical solutions adopted by the present invention are as follows:

[0010] A method for detecting strains of key parts of a wind turbine generator set based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array, comprising:

[0011] S1. According to the structural characteristics of the wind turbine, a weak fiber Bragg grating sensor array is installed at the key strain position, and a temperature reference grating is arranged in the non-strain area or constant temperature area to monitor the temperature change in real time;

[0012] S2. Use a tunable laser, fiber coupler, and photodetector to construct an optical frequency domain reflectometry demodulation system and complete system calibration.

[0013] S3. Based on the optical frequency domain reflectometry demodulation system, the reflected spectrum signal is collected, and through the temperature compensation mechanism, the relationship between the strain and temperature change of the wind turbine is analyzed to obtain the strain information of the key parts of the wind turbine.

[0014] Furthermore, according to the structural characteristics of the wind turbine, a weak fiber Bragg grating sensor array is installed at the key strain position, and a temperature reference grating is arranged in the non-strain area, including:

[0015] S11. Determine the strain monitoring areas of key parts of the wind turbine according to the stress characteristics of the wind turbine blades, divide them into the root area, middle area and tip area, and perform surface treatment;

[0016] S12. Based on the divided strain monitoring area, weak fiber Bragg gratings with a reflectivity lower than a preset threshold are selected as sensing elements, and are arranged at a preset spacing to form a sensor array;

[0017] S13, using adhesive to fix the weak fiber Bragg grating sensor array to the key position of the wind turbine, and ensure that the sensor is well coupled with the measured surface;

[0018] S14. Arrange temperature reference gratings in the non-strain area or constant temperature area of ​​the wind turbine according to monitoring requirements to form a complete sensing network.

[0019] Furthermore, based on the divided strain monitoring areas, weak fiber Bragg gratings with a reflectivity lower than a preset threshold are selected as sensing elements and arranged at a preset spacing to form a sensor array, including:

[0020] S121, arranging a first preset number of weak fiber Bragg gratings in series at a first preset spacing in the root area to capture stress concentration areas at the bolt connection;

[0021] S122. Arranging a second preset number of weak fiber Bragg gratings in series in the middle region with a second preset spacing to cover the high risk area for fatigue crack growth;

[0022] S123, arranging a third preset number of weak fiber Bragg gratings in series at the tip region with a third preset spacing to monitor strain fluctuations caused by vortex-induced vibration;

[0023] The first preset spacing is smaller than the second preset spacing, and the second preset spacing is smaller than the third preset spacing; the second preset number is larger than the first preset number, and the first preset number is larger than the third preset number.

[0024] Furthermore, an optical frequency domain reflectometry demodulation system is constructed using a tunable laser, a fiber coupler, and a photodetector, and the system calibration is completed, including:

[0025] S21, selecting a tunable laser with a preset wavelength range as a light source, and setting a linear frequency sweep working state;

[0026] S22. Splitting the output light of the tunable laser into reference light and measurement light using a fiber coupler based on a preset light splitting ratio;

[0027] S23, transmitting the light signal reflected by the weak fiber Bragg grating array back to the fiber coupler through the optical fiber, and then transmitting it to the photodetector;

[0028] S24, converting the received optical signal into an electrical signal using a photodetector, and storing and recording the signal through a data acquisition system;

[0029] S25. Calibrate the optical frequency domain reflectometry demodulation system through the main interferometer system and the light source phase monitoring system.

[0030] Furthermore, based on a preset light splitting ratio, using a fiber coupler to split the output light of the tunable laser into reference light and measurement light includes:

[0031] S221. Using a fiber coupler, split the output light of the tunable laser into reference light and measurement light according to a preset light splitting ratio;

[0032] S222, guiding the reference light to the reference optical path for monitoring the wavelength and intensity changes of the light source and serving as a demodulation reference;

[0033] S223. Guide the measurement light to the weak fiber Bragg grating sensor array through a circulator, and collect the reflected light signal.

[0034] Furthermore, based on the optical frequency domain reflectometry demodulation system, collecting the reflection spectrum signal includes:

[0035] S31, based on the optical frequency domain reflectometry demodulation system, linear frequency sweeping is performed through a tunable laser, and a frequency sweep optical signal is output;

[0036] S32, recording the central wavelength of each weak fiber Bragg grating in the initial state as a reference value, and recording the initial temperature;

[0037] S33. During the operation of the wind turbine, the reflection spectrum of each weak fiber Bragg grating is continuously collected, and the wavelength drift is monitored in real time.

[0038] Furthermore, through the temperature compensation mechanism, the relationship between wind turbine strain and temperature change is analyzed, and the strain information of key parts of the wind turbine is obtained, including:

[0039] S34, converting the weak fiber Bragg grating array reflection spectrum signal into an electrical signal through a photodetector, and transmitting the signal to a computer processing unit;

[0040] S35. Based on the temperature reference grating, obtain the reflection spectrum and the corresponding wavelength drift corresponding to the temperature change;

[0041] S36. Determine the wavelength drift caused by strain based on the reflection spectrum of the weak fiber Bragg grating at each key strain location; and determine the wavelength drift caused by temperature based on the reflection spectrum of each temperature reference grating;

[0042] S37. Determine the temperature sensitivity coefficient and strain sensitivity coefficient of the weak fiber Bragg grating, and perform temperature compensation on the wavelength change of the weak fiber Bragg grating at each key strain location to eliminate the influence of temperature on strain measurement.

[0043] Furthermore, temperature compensation is performed on the wavelength change of the weak fiber Bragg grating at each key strain location to eliminate the influence of temperature on strain measurement, including: based on the initial measurement, recording the initial grating reflection wavelength and the initial temperature of the temperature reference grating; according to real-time monitoring, obtaining the reflection wavelength of the weak fiber Bragg grating at each key strain location at the current moment and the reflection wavelength of the temperature reference grating; using wavelength difference calculation to obtain the wavelength drift caused by strain and the wavelength drift caused by temperature, and analyzing the temperature change; using the temperature compensation formula, calculating the strain change after temperature compensation.

[0044] Furthermore, the expression for the strain change after temperature compensation is calculated as:

[0045]

[0046] Where,∈ comp is the strain change value after temperature compensation; Δλ strain is the wavelength drift caused by strain; K T is the temperature sensitivity coefficient of the weak fiber Bragg grating; K ∈ is the strain sensitivity coefficient of the weak fiber Bragg grating; ΔT is the temperature change measured by the temperature reference grating.

[0047] Furthermore, selecting a weak fiber Bragg grating with a reflectivity lower than a preset threshold as a sensing element includes: based on a single-mode optical fiber, removing the optical fiber coating, and inscribing a Bragg grating structure on one end of the outer side of the optical fiber by ultraviolet laser irradiation mask technology to determine the central wavelength of the weak fiber Bragg grating; using an optical fiber coating material to cover the weak fiber Bragg grating, and curing to form a protective layer of a preset thickness; inscribing a weak fiber Bragg grating for temperature compensation on the other end of the outer side of the optical fiber, and encapsulating and protecting it; connecting optical fiber connectors at both ends of the optical fiber, and using standard strain and temperature testing equipment to preliminarily calibrate the sensor to obtain a weak fiber Bragg grating with a reflectivity lower than a preset threshold; and using a weak fiber Bragg grating demodulator and a data acquisition system to monitor the strain and temperature changes of the weak fiber Bragg grating in real time.

[0048] (3) Beneficial effects

[0049] Compared with the existing technology, the present invention provides a method for detecting strain in key parts of wind turbines based on temperature-compensated OFDR demodulation of weak fiber Bragg grating arrays, which has the following beneficial effects:

[0050] (1) The present invention uses a comprehensive temperature compensation algorithm and optical frequency domain reflectometry (OFDR) demodulation technology to achieve accurate strain measurement of key parts of wind turbines. By arranging a temperature reference grating in the non-strain area or constant temperature area to monitor temperature changes in real time, and using a specific temperature compensation formula to eliminate the influence of temperature on strain measurement, the accuracy and reliability of strain detection are effectively improved, and the measurement error problem caused by ignoring the influence of temperature changes in traditional methods is solved.

[0051] (2) The present invention adopts weak fiber Bragg grating array technology. According to the stress characteristics of the wind turbine blades, the strain monitoring area is divided into the root area, the middle area and the tip area, and different numbers of weak fiber Bragg gratings are arranged at different preset intervals. This realizes comprehensive monitoring of the strain of key parts of the wind turbine, can capture the stress concentration area at the bolt connection, cover the high-risk area for fatigue crack propagation, and monitor the strain fluctuation caused by vortex-induced vibration, which greatly improves the comprehensiveness and accuracy of monitoring.

[0052] (3) The present invention establishes a high-precision strain detection platform by constructing an optical frequency domain reflection demodulation system and using devices such as tunable lasers, fiber couplers and photodetectors. It can accurately demodulate the signal of weak fiber Bragg grating sensors, improve the measurement resolution and sensitivity, and realize real-time online monitoring of the strain of key parts of wind turbines compared with traditional offline detection methods such as short-circuit impedance testing and frequency response analysis.

[0053] (4) The temperature compensation mechanism designed in the present invention accurately distinguishes the wavelength drift caused by strain from the wavelength drift caused by temperature by calculating the strain change value after temperature compensation, eliminates the interference of temperature change on strain measurement, greatly improves the accuracy and stability of measurement, and enables the system to provide reliable strain data during the actual operation of the wind turbine.

[0054] (5) The weak fiber Bragg grating preparation process adopted in the present invention uses ultraviolet laser irradiation mask technology to engrave the Bragg grating structure on the optical fiber, and uses optical fiber coating material for coating and protection, thereby ensuring the quality and durability of the sensing element. At the same time, the sensor is preliminarily calibrated by standard strain and temperature testing equipment to ensure the accuracy and reliability of the system, adapting to complex working environments and the requirements of long-term stable operation.

[0055] (6) The present invention simplifies the installation and debugging process of the sensor. By rationally designing the optical path system and the data acquisition system, the operation difficulty is reduced and the experimental efficiency is improved. Compared with traditional methods, the present invention has higher sensitivity, real-time performance and stability. It can timely detect abnormal strain conditions of wind turbines and take corresponding measures, effectively ensuring the safe operation of wind turbines. It provides an innovative solution for the field of wind turbine strain monitoring and has important theoretical value and practical application significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0057] Figure 1 This is a flow chart of a method for detecting strain at key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array according to an embodiment of the present invention;

[0058] Figure 2 1 is a schematic diagram of the basic structure of OFDR in a method for detecting strain at key parts of a wind turbine generator system by demodulating a weak fiber Bragg grating array based on temperature-compensated OFDR according to an embodiment of the present invention;

[0059] Figure 3 The figure is a schematic diagram of the optical path in a method for detecting strain of key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array according to an embodiment of the present invention. DETAILED DESCRIPTION

[0060] To further illustrate each embodiment, the present invention provides drawings, which are part of the disclosure of the present invention. They are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. By referring to these contents, ordinary technicians in this field should be able to understand other possible implementation methods and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0061] According to an embodiment of the present invention, a method for detecting strain at key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array is provided.

[0062] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. Figure 1 As shown, according to an embodiment of the present invention, a method for detecting strain at key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array comprises:

[0063] S1. According to the structural characteristics of the wind turbine, a weak fiber Bragg grating sensor array is installed at the key strain position, and a temperature reference grating is arranged in the non-strain area or constant temperature area to monitor the temperature change in real time;

[0064] S2. Use a tunable laser, fiber coupler, and photodetector to construct an optical frequency domain reflectometry demodulation system and complete system calibration.

[0065] S3. Based on the optical frequency domain reflectometry demodulation system, the reflected spectrum signal is collected, and through the temperature compensation mechanism, the relationship between the strain and temperature change of the wind turbine is analyzed to obtain the strain information of the key parts of the wind turbine.

[0066] It should be noted that the present invention includes a weak fiber Bragg grating (WFBG) sensor and other experimental equipment, such as a tunable laser, a fiber coupler (coupler), a WFBG array, a measurement optical path, a photodetector, a data acquisition system, a temperature compensation system, etc., to ensure the stability of the laboratory environment, especially the temperature and humidity are controlled within a reasonable range to reduce the interference of environmental factors.

[0067] Specifically, if Figure 2 and Figure 3 As shown in the figure, a tunable laser is used to generate laser light, enabling it to operate in a linear frequency sweep state. This swept light passes through a fiber coupler and is split into two optical signals with a ratio of 1:99. One optical signal enters the signal end, and the other enters the reference end. A tunable laser is used. Its output wavelength can be adjusted within a certain range to scan the reflection spectrum of a weak fiber Bragg grating (WFBG) array. The fiber coupler is used to split the single optical signal from the light source into multiple optical signals and also to combine the signals returned by multiple sensing fibers into a single receiving fiber for centralized processing and analysis. The reference light is transmitted to a reference photodetector, which is used to monitor the wavelength and intensity stability of the laser. The measuring light is transmitted to a weak fiber Bragg grating array; a WFBG array is arranged on the surface of key parts of the wind turbine (such as blades, tower bottom, hub, gearbox inside, etc.) with a weak reflection for sensing strain and temperature; a measuring optical path is used to transmit the reflected light signal back to the fiber coupler through the optical fiber and then to the photodetector; a photodetector is installed at the end of the return signal optical path to receive the light signal reflected by the WFBG; a temperature compensation system is arranged in a non-strain area or constant temperature area with a reference WFBG for real-time monitoring of temperature changes; a data processing system collects the converted electrical signal through the photodetector and transmits it to the computer processing unit.

[0068] Specifically, if Figure 2As shown in FIG, a method for detecting strain at key parts of a wind turbine generator set by using a temperature-compensated OFDR demodulation weak fiber Bragg grating array includes a weak fiber Bragg grating (WFBG) sensor and other experimental equipment, such as a tunable laser, a fiber coupler, a WFBG array, a measurement optical path, a photodetector, a data acquisition system, a temperature compensation system, etc. The parameters of the tunable laser are shown in Table 1.

[0069]

[0070]

[0071] Specifically, the present invention provides a method for detecting strain at key parts of a wind turbine generator system based on OFDR demodulation of a weak fiber Bragg grating array, comprising the following steps:

[0072] Step 1: Install weak fiber Bragg grating (WFBG) sensors at key locations on the wind turbine. Ensure the sensors are securely fixed and can accurately sense strain and temperature changes on the wind turbine.

[0073] Step 2: Configure a demodulation system based on optical frequency domain reflectometry (OFDR) technology, including a tunable laser, a fiber coupler, a master interferometer system, and a light source phase monitoring system;

[0074] It should be noted that the main interferometer system is the core module of OFDR technology. Its function is to coherently superimpose the returned measurement light and the reference light by constructing an interference optical path to form an interference signal carrying spatial position information. Specifically, when the tunable laser performs linear frequency sweeping, the optical signal reflected back after the measurement light passes through the WFBG array interferes with the reference light in the interferometer. The frequency of the interference signal is related to the optical path difference. Through Fourier transform or phase demodulation algorithm, the time domain interference signal can be converted into a spectral reflection distribution in the spatial domain, thereby accurately locating the reflection position of each weak fiber Bragg grating and analyzing its wavelength drift. The working principle of the main interferometer system relies on optical path matching and coherence length control to ensure that the signal-to-noise ratio and resolution of the interference signal meet the requirements of high-precision strain detection. The light source phase monitoring system is specifically used to track and compensate for phase nonlinearity problems during the frequency sweeping process of a tunable laser in real time. Since the demodulation accuracy of OFDR is highly dependent on the frequency sweeping linearity of the light source, any slight frequency jitter or phase noise will lead to a decrease in spatial resolution and accumulation of measurement errors. The light source phase monitoring system collects the phase change data of the laser in real time through an independent optical path or electronic feedback mechanism, and dynamically corrects the frequency sweeping nonlinearity in combination with a digital signal processing algorithm to ensure the phase continuity and stability of the optical frequency domain reflection signal. Its working principle is based on high-precision sampling and analysis of the instantaneous frequency and phase of the light wave output by the light source, adjusting the driving parameters of the laser through closed-loop control or eliminating phase noise through post-processing algorithms, thereby ensuring high resolution and high signal-to-noise ratio of the entire demodulation system.

[0075] Step 3: Introduce a temperature compensation mechanism. Using a dual-grating differential structure or other temperature compensation methods, determine the demodulation parameters of temperature and strain through calibration experiments.

[0076] Step 4: Set the experimental parameters, such as temperature range, sampling frequency, and the position of the weak fiber Bragg grating. Ensure the stability of the experimental environment and the normal operation of the data acquisition system;

[0077] Step 5: Start the OFDR demodulation system to collect real-time data. Record the reflection spectrum and strain data of the weak fiber Bragg grating under different temperature conditions.

[0078] Step 6: Perform temperature compensation on the collected data to eliminate the influence of temperature changes on strain measurement. Use algorithms and computer processing units to solve and analyze the data.

[0079] Step 7: Statistically analyze the relationship between wind turbine strain and temperature to evaluate the measurement accuracy and stability of the sensing system. Compare the experimental results with the theoretical model to verify the effectiveness and accuracy of the system.

[0080] In one embodiment, based on the structural characteristics of a wind turbine, a weak fiber Bragg grating sensor array is installed at a key strain location, and a temperature reference grating is arranged in a non-strain area, including:

[0081] S11. Determine the strain monitoring areas of key parts of the wind turbine according to the stress characteristics of the wind turbine blades, divide them into the root area, middle area and tip area, and perform surface treatment;

[0082] S12. Based on the divided strain monitoring area, weak fiber Bragg gratings with a reflectivity lower than a preset threshold are selected as sensing elements, and are arranged at a preset spacing to form a sensor array;

[0083] S13, using adhesive to fix the weak fiber Bragg grating sensor array to the key position of the wind turbine, and ensure that the sensor is well coupled with the measured surface;

[0084] S14. Arrange temperature reference gratings in the non-strain area or constant temperature area of ​​the wind turbine according to monitoring requirements to form a complete sensing network.

[0085] In one embodiment, based on the divided strain monitoring areas, weak fiber Bragg gratings with a reflectivity lower than a preset threshold are selected as sensing elements, and are arranged at a preset spacing to form a sensor array, including:

[0086] S121, arranging a first preset number of weak fiber Bragg gratings in series at a first preset spacing in the root area to capture stress concentration areas at the bolt connection;

[0087] S122. Arranging a second preset number of weak fiber Bragg gratings in series in the middle region with a second preset spacing to cover the high risk area for fatigue crack growth;

[0088] S123, arranging a third preset number of weak fiber Bragg gratings in series at the tip region with a third preset spacing to monitor strain fluctuations caused by vortex-induced vibration;

[0089] The first preset spacing is smaller than the second preset spacing, and the second preset spacing is smaller than the third preset spacing; the second preset number is larger than the first preset number, and the first preset number is larger than the third preset number.

[0090] In one embodiment, an optical frequency domain reflectometry demodulation system is constructed using a tunable laser, a fiber coupler, and a photodetector, and system calibration is performed, including:

[0091] S21, selecting a tunable laser with a preset wavelength range as a light source, and setting a linear frequency sweep working state;

[0092] S22. Splitting the output light of the tunable laser into reference light and measurement light using a fiber coupler based on a preset light splitting ratio;

[0093] S23, transmitting the light signal reflected by the weak fiber Bragg grating array back to the fiber coupler through the optical fiber, and then transmitting it to the photodetector;

[0094] S24, converting the received optical signal into an electrical signal using a photodetector, and storing and recording the signal through a data acquisition system;

[0095] S25. Calibrate the optical frequency domain reflectometry demodulation system through the main interferometer system and the light source phase monitoring system.

[0096] In one embodiment, based on a preset light splitting ratio, using a fiber coupler to split the output light of a tunable laser into reference light and measurement light includes:

[0097] S221. Using a fiber coupler, split the output light of the tunable laser into reference light and measurement light according to a preset light splitting ratio;

[0098] S222, guiding the reference light to the reference optical path for monitoring the wavelength and intensity changes of the light source and serving as a demodulation reference;

[0099] S223. Guide the measurement light to the weak fiber Bragg grating sensor array through a circulator, and collect the reflected light signal.

[0100] Specifically, the optical path working principle of the present invention is as follows:

[0101] Step I: Select a tunable laser that can adjust the output wavelength within a certain range to scan the reflection spectrum of the weak fiber Bragg grating (WFBG) array. Couple the output light of the tunable laser into the optical fiber.

[0102] Step II: Install the fiber coupler: Use a 1:99 fiber coupler to split the laser output into two paths: one for the 1% reference light and the other for the 99% measurement light. The 1% reference light is transmitted to a reference photodetector for monitoring the laser's wavelength and intensity stability, while the 99% measurement light is transmitted to the weak fiber Bragg grating array.

[0103] Step III: Arrange weakly reflective linear arrays of WFBGs on the surfaces of key parts of the wind turbine, such as blades and gearboxes. Multiple WFBGs are connected in series on the same optical fiber and arranged at fixed intervals for strain and temperature sensing. For example, for blades, WFBG linear sensor arrays are arranged along the length of the blade at the root, middle, and tip. By optimizing the sensor density and layout, accurate sensing of the full-scale strain field is achieved. Based on the actual engineering practice of a typical 80-meter-long blade, the monitoring area is divided into the root (0-10 meters), middle (10-60 meters), and tip (60-80 meters). 20, 50, and 10 WFBGs are arranged in series at intervals of 0.5 meters, 1.0 meters, and 2.0 meters, respectively, forming a distributed array with a total of 80 sensing points. The root area bears the greatest dynamic loads, so a high-density arrangement is used to capture stress concentrations at bolted connections. The middle area uses a 1-meter spacing to balance monitoring accuracy and cost, covering areas at high risk of fatigue crack propagation. The tip is sparsely arranged to reduce aerodynamic interference, focusing on monitoring strain fluctuations caused by vortex-induced vibrations. A temperature-compensated WFBG is deployed next to each strain sensor, and the effects of temperature changes are isolated through a coaxial neutral layer installation. A total of 16 temperature monitoring points form a cross-calibration network. The installation process uses UV-curing adhesive to bond the WFBG array to the inner surface of the blade skin. The surface is pre-polished and coated with a 0.2 mm polyurethane protective layer. Silicone clamps are used to secure the optical fiber every 1 meter when wiring along the main beam. A 5-meter redundant optical fiber is reserved at the root for connection to the hub slip ring. The exterior is wrapped with an IP67 protective sleeve, and a streamlined air deflector is added to the tip. Signal demodulation utilizes an optical frequency domain reflectometer (OFDR), equipped with a 10mm spatial resolution and a 100Hz sampling frequency, achieving ±1 microstrain accuracy and ±0.1°C temperature accuracy. Data is connected to the wind turbine SCADA system via the OPC UA protocol to generate real-time strain contours. Static calibration is performed on a static blade test bench, and comparison with resistance strain gauges verifies that the measurement error is less than 3%. Dynamic excitation testing accurately captures the 0.8Hz bending mode and 2.5Hz torsional mode using a 5-50Hz frequency sweep. Sensors are placed circumferentially and radially on the gearbox housing to monitor vibration-induced strain. Temperature sensors are also deployed near each strain sensor, and the WFBG array is connected to the measurement optical path of the fiber coupler to ensure that the optical signal can pass through the WFBG array.

[0104] Step IV: In order to achieve simultaneous measurement of multiple grating sensors (i.e., multi-point sensing), the WFBG array uses wavelength division multiplexing technology. Each fiber grating is designed to reflect different Bragg wavelengths, which are multiplexed and transmitted in the optical fiber. Each WFBG is designed to have a different initial Bragg wavelength during manufacturing. When the optical fiber is subjected to external strain or temperature changes, the Bragg wavelength of each WFBG will drift. By measuring these drifts, the system can distinguish sensors at different positions and calculate the corresponding physical quantities. When the measurement light passes through the WFBG array, the WFBGs at different positions will reflect light of different wavelengths according to the strain and temperature changes. The reflected optical signal is transmitted back to the fiber coupler through the optical fiber and then transmitted to the photodetector.

[0105] Step V: Install a photodetector at the end of the return signal path to receive the optical signal reflected by the WFBG. The photodetector converts the received optical signal into an electrical signal for subsequent data processing and analysis.

[0106] Step VI: Place a reference WFBG in a non-strained or constant-temperature area of ​​the wind turbine (e.g., at the tower base and the flange connecting the tower to the nacelle) to monitor temperature changes in real time. A temperature compensation algorithm is introduced into the data processing unit, using the data from the reference WFBG to compensate the measurement results.

[0107] Step VII: The converted electrical signal is collected by a photodetector and transmitted to a computer processing unit. OFDR technology is used to demodulate the reflection spectrum and analyze the changes in the WFBG reflection wavelength. Based on the demodulated spectral data, a temperature compensation algorithm is applied to eliminate the effects of temperature on strain measurement and calculate the strain in key parts of the wind turbine.

[0108] Specifically, through the above steps, the present invention designed and established an optical system based on temperature-compensated OFDR demodulation of weak fiber Bragg grating arrays (FBGs), enabling accurate strain detection in key wind turbine components. Key components of the optical system include a tunable laser, fiber coupler, WFBG array, and photodetector, supplemented by a temperature compensation algorithm to ensure measurement accuracy and reliability.

[0109] In one embodiment, based on an optical frequency domain reflectometry demodulation system, collecting a reflection spectrum signal includes:

[0110] S31, based on the optical frequency domain reflectometry demodulation system, linear frequency sweeping is performed through a tunable laser, and a frequency sweep optical signal is output;

[0111] S32, recording the central wavelength of each weak fiber Bragg grating in the initial state as a reference value, and recording the initial temperature;

[0112] S33. During the operation of the wind turbine, the reflection spectrum of each weak fiber Bragg grating is continuously collected, and the wavelength drift is monitored in real time.

[0113] In one embodiment, the relationship between the strain and temperature change of the wind turbine is analyzed through a temperature compensation mechanism, and the strain information of key parts of the wind turbine is obtained, including:

[0114] S34, converting the weak fiber Bragg grating array reflection spectrum signal into an electrical signal through a photodetector, and transmitting the signal to a computer processing unit;

[0115] S35. Based on the temperature reference grating, obtain the reflection spectrum and the corresponding wavelength drift corresponding to the temperature change;

[0116] S36. Determine the wavelength drift caused by strain based on the reflection spectrum of the weak fiber Bragg grating at each key strain location; and determine the wavelength drift caused by temperature based on the reflection spectrum of each temperature reference grating;

[0117] S37. Determine the temperature sensitivity coefficient and strain sensitivity coefficient of the weak fiber Bragg grating, and perform temperature compensation on the wavelength change of the weak fiber Bragg grating at each key strain location to eliminate the influence of temperature on strain measurement.

[0118] In one embodiment, temperature compensation is performed on the wavelength change of the weak fiber Bragg grating at each key strain location to eliminate the influence of temperature on strain measurement, including: recording the initial grating reflection wavelength and the initial temperature of the temperature reference grating based on initial measurement; obtaining the reflection wavelength of the weak fiber Bragg grating and the reflection wavelength of the temperature reference grating at each key strain location at the current moment based on real-time monitoring; using wavelength difference calculation to obtain wavelength drift caused by strain and wavelength drift caused by temperature, and analyzing temperature changes; and using a temperature compensation formula to calculate the strain change after temperature compensation.

[0119] In one embodiment, the expression for calculating the strain change after temperature compensation is:

[0120]

[0121] Where,∈ comp is the strain change value after temperature compensation; Δλ strain is the wavelength drift caused by strain; K T is the temperature sensitivity coefficient of the weak fiber Bragg grating; K ∈ is the strain sensitivity coefficient of the weak fiber Bragg grating; ΔT is the temperature change measured by the temperature reference grating.

[0122] Specifically, the present invention calculates the strain of key parts of a wind turbine generator set through an innovative temperature compensation algorithm, and the implementation steps are as follows:

[0123] ① Obtain the reflection spectrum from the weak fiber Bragg grating (WFBG) array, convert the optical signal into an electrical signal through a photodetector, and transmit it to the computer processing unit.

[0124] ② Obtain the reflection spectrum from a reference weak fiber Bragg grating (reference WFBG) and record the wavelength drift corresponding to the temperature change.

[0125] ③Analyze the reflection spectrum of the weak fiber Bragg grating at each key strain location to determine the wavelength drift Δλ caused by strain strain .

[0126] ④Analyze the reflection spectrum of the reference weak fiber Bragg grating to determine the wavelength drift Δλ caused by temperature temp .

[0127] ⑤ The temperature sensitivity coefficient K of the weak fiber Bragg grating was calibrated experimentally T , which is defined as the ratio of the wavelength change caused by the temperature change to the temperature change:

[0128]

[0129] ⑥ The strain sensitivity coefficient K of the weak fiber Bragg grating was calibrated experimentally ∈ , which is defined as the ratio of the wavelength change caused by the strain change to the strain change:

[0130]

[0131] ⑦Use temperature sensitivity coefficient K T and strain sensitivity coefficient K ∈ , temperature compensation is performed on the wavelength change of the strain-weak fiber Bragg grating to eliminate the influence of temperature on strain measurement.

[0132] ⑧Strain changes after temperature compensation where ΔT is the temperature change measured with reference to the weak fiber Bragg grating.

[0133] Specifically, A) recording the initial grating reflection wavelength λ0 and the temperature reference grating initial temperature T0;

[0134] B) Record the reflection wavelength λ of the strain-weak fiber Bragg grating at the current moment strain and the reference weak fiber Bragg grating reflection wavelength λ temp ;

[0135] C) Calculation of wavelength shift Δλ of strain-weak fiber Bragg grating strain =λ strain -λ0;

[0136] D) Calculation of the wavelength drift Δλ of a temperature-weak fiber Bragg grating temp =λ temp -λ0;

[0137] E) Calculate the temperature change by referring to the wavelength drift of the weak fiber Bragg grating

[0138] F) Use the temperature compensation formula to calculate the strain change after temperature compensation

[0139] Specifically, the present invention can effectively eliminate the influence of temperature changes on weak fiber Bragg grating strain measurement through the above-mentioned temperature compensation algorithm, thereby obtaining accurate strain data; at the same time, this algorithm is based on precise spectral analysis and experimentally calibrated sensitivity coefficients to achieve high-precision monitoring of strain in key parts of wind turbines.

[0140] It should be noted that temperature compensation in this invention is intended to address the effects of temperature changes on strain measurement. By installing temperature sensors in key locations within the wind turbine, temperature changes within the wind turbine can be monitored in real time. Based on the impact of temperature changes on the weak fiber Bragg grating sensor, an appropriate algorithm is employed to correct the strain data to eliminate temperature-induced errors. The combined application of OFDR technology and a temperature compensation algorithm enables precise strain measurement of key wind turbine locations, eliminating the effects of temperature changes on measurement results and improving the accuracy and reliability of strain detection.

[0141] In one embodiment, a weak fiber Bragg grating (FBG) with a reflectivity lower than a preset threshold is selected as a sensing element, including: removing a fiber coating based on a single-mode optical fiber, and inscribing a FBG structure on one end of the outer side of the optical fiber using an ultraviolet laser irradiation mask technique to determine the center wavelength of the weak fiber Bragg grating; coating the weak fiber Bragg grating with an optical fiber coating material, and curing it to form a protective layer of a preset thickness; inscribing a weak fiber Bragg grating for temperature compensation on the other end of the outer side of the optical fiber, and encapsulating and protecting it; connecting optical fiber connectors at both ends of the optical fiber, and performing preliminary calibration of the sensor using standard strain and temperature testing equipment to obtain a weak fiber Bragg grating with a reflectivity lower than a preset threshold; and monitoring the strain and temperature changes of the weak fiber Bragg grating in real time using a weak fiber Bragg grating demodulator and a data acquisition system.

[0142] Specifically, the present invention selects a suitable weak fiber Bragg grating (WFBG) sensor according to the experimental requirements to ensure that it has good temperature and strain sensitivity. The detailed steps are as follows:

[0143] Step 1: Clean the surface of key parts of the wind turbine to ensure that there is no oil, dust or other impurities on the surface so that the fiber optic sensor can be firmly attached;

[0144] Step 2: Determine the installation location of the WFBG sensor based on the structure and strain distribution characteristics of the key parts of the wind turbine and install it in the center of the wind turbine;

[0145] Step 3: Apply a thin layer of adhesive (such as epoxy resin or special optical fiber adhesive) to the sensor installation location and gently attach the WFBG sensor.

[0146] Step 4: Temporarily secure the sensor with tape or other fixing devices to ensure that the sensor does not move while the adhesive dries and cures.

[0147] Step 5: Select a WFBG sensor of the same type as the strain grating as the temperature reference grating for temperature compensation;

[0148] Step 6: Install the temperature reference grating near the key parts of the wind turbine but not affected by strain to measure only temperature changes;

[0149] Step 7: Use the same method as the strain gauge grating to fix the temperature reference grating to ensure its stability;

[0150] Step 8: Add protective measures to the installed fiber optic sensor and its connecting parts, such as using a fiber optic protection tube or protective cover to prevent fiber damage caused by external environmental factors;

[0151] Step 9: Connect the optical fiber of the WFBG sensor to the optical fiber coupler, ensuring that the connection is secure and the optical path is clear;

[0152] Step 10: Check all connection points to ensure there is no looseness or broken optical fiber to ensure the stability of signal transmission;

[0153] Step 11: Start the data acquisition system and begin recording real-time sensor data. Monitor the data in real time to ensure the proper functioning of the sensors and system and to promptly troubleshoot any issues that may arise.

[0154] Specifically, the preparation steps of the WFBG sensor in the present invention are as follows:

[0155] Step (a): Select an optical fiber with suitable characteristics, usually a standard single-mode optical fiber. Clean the surface of the optical fiber with anhydrous alcohol and a cleaning paper to ensure there are no contaminants.

[0156] Step (b): Use a fiber stripper to remove the fiber coating to expose the bare fiber. The stripping length depends on the actual needs, usually a few centimeters. Clean the bare fiber again with anhydrous alcohol and wipes to ensure the surface is clean.

[0157] Step (c): Fix the optical fiber on the grating writing stage and adjust the parameters of the ultraviolet laser (wavelength, power, pulse time, etc.) to ensure that the laser is in optimal working condition. Place the phase mask above the optical fiber and illuminate the mask with ultraviolet laser to write the Bragg grating structure on the optical fiber. The period of the phase mask determines the central wavelength of the WFBG. After writing is completed, turn off the laser, remove the optical fiber, and use a microscope to check the quality and integrity of the grating;

[0158] Step (d): Apply a protective coating, typically a UV-curable adhesive or other fiber coating material, to the inscribed WFBG sensor to increase its mechanical strength and environmental tolerance. Use UV light to cure the protective coating on the fiber, ensuring that the fiber Bragg grating is effectively protected.

[0159] Step (e): A WFBG for temperature compensation is inscribed on the same fiber, at a distance from the measurement grating to allow independent temperature measurement. Similar to the measurement grating, the temperature compensation grating is encapsulated and protected to ensure its reliability.

[0160] Step (f): Connect fiber connectors at both ends of the optical fiber to facilitate connection to the weak fiber Bragg grating interrogator. Ensure that the fiber cut is smooth during connection to avoid excessive loss. Secure the packaged WFBG sensor in a bracket or protective cover to prevent mechanical stress from damaging the sensor.

[0161] Step (g): Perform preliminary calibration of the sensor using standard strain and temperature testing equipment, and record the initial reflection wavelength. The sensor is then placed in different environmental conditions to test its stability and response characteristics, verifying its accuracy and reliability.

[0162] Step (h): Connect the fabricated WFBG sensor to a weak fiber Bragg grating (FBG) demodulator to ensure smooth signal transmission. Start the data acquisition system to monitor the strain and temperature changes of the WFBG sensor in real time and record the experimental data.

[0163] Specifically, after the WFBG sensor is manufactured and installed through the above steps, the strain of key parts of the wind turbine can be accurately detected. At the same time, the temperature compensation grating is used to eliminate the temperature influence, ensuring the accuracy and reliability of the measurement results.

[0164] In summary, with the help of the above technical solution of the present invention, the temperature compensation algorithm and optical frequency domain reflectometry (OFDR) demodulation technology are comprehensively used to achieve accurate measurement of the strain of key parts of the wind turbine. By arranging a temperature reference grating in the non-strain zone or constant temperature zone to monitor the temperature change in real time, and using a specific temperature compensation formula to eliminate the influence of temperature on strain measurement, the accuracy and reliability of strain detection are effectively improved, and the measurement error problem caused by ignoring the influence of temperature change in the traditional method is solved. The present invention adopts weak fiber Bragg grating array technology. According to the stress characteristics of the wind turbine blade, the strain monitoring area is divided into the root area, the middle area and the tip area, and different numbers of weak fiber Bragg gratings are arranged at different preset spacings, thereby achieving comprehensive monitoring of the strain of key parts of the wind turbine. It can capture the stress concentration area at the bolt connection, cover the high risk area of ​​fatigue crack propagation, and monitor the strain fluctuation caused by vortex-induced vibration, greatly improving the comprehensiveness and accuracy of monitoring. By constructing an optical frequency-domain reflectometry demodulation system and utilizing a tunable laser, fiber coupler, and photodetector, this invention establishes a high-precision strain detection platform. This platform can accurately demodulate signals from weak fiber Bragg grating (FBG) sensors, improving measurement resolution and sensitivity. Compared to traditional offline detection methods such as short-circuit impedance testing and frequency response analysis, it enables real-time online monitoring of strain in key wind turbine components. The temperature compensation mechanism designed in this invention accurately distinguishes wavelength drift caused by strain from wavelength drift caused by temperature by calculating the temperature-compensated strain change, eliminating the interference of temperature changes on strain measurement. This significantly improves measurement accuracy and stability, enabling the system to provide reliable strain data during actual wind turbine operation. The invention utilizes a weak fiber Bragg grating (FBG) fabrication process, in which the FBG structure is inscribed onto an optical fiber using ultraviolet laser irradiation masking technology and then protected with fiber coating material, ensuring the quality and durability of the sensing element. Furthermore, the sensor is initially calibrated using standard strain and temperature testing equipment, ensuring the system's accuracy and reliability, adapting to complex operating environments and the requirements for long-term stable operation. The present invention simplifies the installation and debugging process of the sensor. By rationally designing the optical path system and data acquisition system, it reduces the operational difficulty and improves the experimental efficiency. Compared with traditional methods, it has higher sensitivity, real-time performance and stability. It can promptly detect abnormal strain conditions of wind turbines and take corresponding measures, effectively ensuring the safe operation of wind turbines. It provides an innovative solution for the field of wind turbine strain monitoring and has important theoretical value and practical application significance.

[0165] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for detecting strain in key parts of wind turbines based on temperature-compensated OFDR demodulation of weak fiber Bragg grating arrays, characterized in that: include: S1. According to the structural characteristics of the wind turbine, a weak fiber Bragg grating sensor array is installed at the key strain position, and a temperature reference grating is arranged in the non-strain area or constant temperature area to monitor the temperature change in real time; S2. Use a tunable laser, fiber coupler, and photodetector to construct an optical frequency domain reflectometry demodulation system and complete system calibration. S3. Based on the optical frequency domain reflectometry demodulation system, the reflected spectrum signal is collected, and through the temperature compensation mechanism, the relationship between the strain and temperature change of the wind turbine is analyzed to obtain the strain information of the key parts of the wind turbine.

2. The method for detecting strain in key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of weak fiber Bragg grating array according to claim 1, characterized in that: The method of installing a weak fiber Bragg grating sensor array at a key strain location according to the structural characteristics of the wind turbine and arranging a temperature reference grating in a non-strain area includes: S11. Determine the strain monitoring areas of key parts of the wind turbine according to the stress characteristics of the wind turbine blades, divide them into the root area, middle area and tip area, and perform surface treatment; S12. Based on the divided strain monitoring area, weak fiber Bragg gratings with a reflectivity lower than a preset threshold are selected as sensing elements, and are arranged at a preset spacing to form a sensor array; S13, using adhesive to fix the weak fiber Bragg grating sensor array to the key position of the wind turbine, and ensure that the sensor is well coupled with the measured surface; S14. Arrange temperature reference gratings in the non-strain area or constant temperature area of ​​the wind turbine according to monitoring requirements to form a complete sensing network.

3. The method for detecting strain in key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array according to claim 2, characterized in that: The method of selecting weak fiber Bragg gratings with a reflectivity lower than a preset threshold as sensing elements based on the divided strain monitoring area and arranging them at a preset spacing to form a sensor array includes: S121, arranging a first preset number of weak fiber Bragg gratings in series at a first preset spacing in the root area to capture stress concentration areas at the bolt connection; S122. Arranging a second preset number of weak fiber Bragg gratings in series in the middle region with a second preset spacing to cover the high risk area for fatigue crack growth; S123, arranging a third preset number of weak fiber Bragg gratings in series at the tip region with a third preset spacing to monitor strain fluctuations caused by vortex-induced vibration; The first preset spacing is smaller than the second preset spacing, and the second preset spacing is smaller than the third preset spacing; the second preset number is larger than the first preset number, and the first preset number is larger than the third preset number.

4. The method for detecting strain in key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array according to claim 1, characterized in that: The method of constructing an optical frequency domain reflectometry demodulation system using a tunable laser, a fiber coupler, and a photodetector and completing system calibration includes: S21, selecting a tunable laser with a preset wavelength range as a light source, and setting a linear frequency sweep working state; S22. Splitting the output light of the tunable laser into reference light and measurement light using a fiber coupler based on a preset light splitting ratio; S23, transmitting the light signal reflected by the weak fiber Bragg grating array back to the fiber coupler through the optical fiber, and then transmitting it to the photodetector; S24, converting the received optical signal into an electrical signal using a photodetector, and storing and recording the signal through a data acquisition system; S25. Calibrate the optical frequency domain reflectometry demodulation system through the main interferometer system and the light source phase monitoring system.

5. The method for detecting strain in key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of weak fiber Bragg grating array according to claim 4, characterized in that: The method of using a fiber coupler to separate the output light of the tunable laser into reference light and measurement light based on a preset light splitting ratio includes: S221. Using a fiber coupler, split the output light of the tunable laser into reference light and measurement light according to a preset light splitting ratio; S222, guiding the reference light to the reference optical path for monitoring the wavelength and intensity changes of the light source and serving as a demodulation reference; S223. Guide the measurement light to the weak fiber Bragg grating sensor array through a circulator, and collect the reflected light signal.

6. The method for detecting strain in key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of weak fiber Bragg grating array according to claim 1, characterized in that: The optical frequency domain reflectometry demodulation system is used to collect the reflected spectrum signal, including: S31, based on the optical frequency domain reflectometry demodulation system, linear frequency sweeping is performed through a tunable laser, and a frequency sweep optical signal is output; S32, recording the central wavelength of each weak fiber Bragg grating in the initial state as a reference value, and recording the initial temperature; S33. During the operation of the wind turbine, the reflection spectrum of each weak fiber Bragg grating is continuously collected, and the wavelength drift is monitored in real time.

7. The method for detecting strain in key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array according to claim 1, characterized in that: The temperature compensation mechanism is used to analyze the relationship between the strain and temperature change of the wind turbine and obtain the strain information of the key parts of the wind turbine, including: S34, converting the weak fiber Bragg grating array reflection spectrum signal into an electrical signal through a photodetector, and transmitting the signal to a computer processing unit; S35. Based on the temperature reference grating, obtain the reflection spectrum and the corresponding wavelength drift corresponding to the temperature change; S36. Determine the wavelength drift caused by strain based on the reflection spectrum of the weak fiber Bragg grating at each key strain location; and determine the wavelength drift caused by temperature based on the reflection spectrum of each temperature reference grating; S37. Determine the temperature sensitivity coefficient and strain sensitivity coefficient of the weak fiber Bragg grating, and perform temperature compensation on the wavelength change of the weak fiber Bragg grating at each key strain location to eliminate the influence of temperature on strain measurement.

8. The method for detecting strain in key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array according to claim 7, characterized in that: The temperature compensation for the wavelength change of the weak fiber Bragg grating at each key strain location to eliminate the influence of temperature on strain measurement includes: Based on the initial measurement, the initial grating reflection wavelength and the initial temperature of the temperature reference grating are recorded; According to real-time monitoring, the reflection wavelength of the weak fiber Bragg grating and the reflection wavelength of the temperature reference grating at each key strain position at the current moment are obtained; Using wavelength difference calculation, we can obtain the wavelength drift caused by strain and the wavelength drift caused by temperature, and analyze the temperature change; The temperature compensation formula is used to calculate the strain change after temperature compensation.

9. The method for detecting strain in key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array according to claim 8, characterized in that: The expression for the strain change after temperature compensation is calculated as follows: Where,∈ comp is the strain change value after temperature compensation; Δλ strain is the wavelength drift caused by strain; K T is the temperature sensitivity coefficient of the weak fiber Bragg grating; K ∈ is the strain sensitivity coefficient of the weak fiber Bragg grating; ΔT is the temperature change measured by the temperature reference grating.

10. The method for detecting strain at key parts of a wind turbine generator system based on temperature-compensated OFDR demodulation of a weak fiber Bragg grating array according to claim 2, characterized in that: The method of selecting a weak fiber Bragg grating with a reflectivity lower than a preset threshold as a sensing element includes: Based on single-mode optical fiber, the optical fiber coating is removed, and a Bragg grating structure is inscribed on the outer end of the optical fiber using ultraviolet laser irradiation mask technology to determine the central wavelength of the weak fiber Bragg grating; The weak fiber Bragg grating is coated with a fiber coating material and solidified to form a protective layer of a preset thickness; A weak fiber Bragg grating for temperature compensation is engraved on the other end of the optical fiber and then packaged for protection; Fiber connectors are connected at both ends of the optical fiber, and the sensor is preliminarily calibrated using standard strain and temperature testing equipment to obtain a weak fiber Bragg grating with a reflectivity lower than a preset threshold. The strain and temperature changes of the weak fiber Bragg grating are monitored in real time through a weak fiber Bragg grating demodulator and a data acquisition system.

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