Method, device and storage medium for monitoring ice coating on fan blades based on natural frequency

Abstract

The present invention discloses a method, device and storage medium for monitoring ice coating on wind turbine blades based on natural frequency. The method comprises: establishing a spring mass damping mechanical model according to a wind turbine blade system; calculating the functional relationship between equivalent mass, equivalent stiffness and natural frequency; performing finite element modeling on the wind turbine blades according to the wind turbine blade system to obtain the deployment position of the fiber grating; determining the wavelength drift data of the windward surface caused purely by strain after the deployment of the fiber grating according to the deployment position of the fiber grating; calculating the natural frequency according to the wavelength drift data of the windward surface caused purely by strain; monitoring the ice coating on the wind turbine blades according to multiple natural frequencies and functional relationships to obtain ice coating monitoring results. The present invention realizes ice coating monitoring on wind turbine blades and improves monitoring accuracy and efficiency. The present invention can be widely used in the technical field of wind turbine monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine monitoring, and in particular to a method, device and storage medium for monitoring ice coating on wind turbine blades based on natural frequency. Background Art

[0002] To vigorously develop the wind power industry and promote the grid connection and consumption of a high proportion of renewable energy, it is necessary to build a new power system that can adapt to the consumption of large-scale wind and solar renewable energy. However, wind turbine blade icing disaster is one of the important factors hindering the development of wind power. At present, the traditional manual observation method has great randomness and time intervals, and cannot detect the occurrence of icing in time; the image recognition method is difficult to identify in low visibility and is greatly disturbed; the method of using the system data of the wind turbine to evaluate the icing condition through energy utilization, but factors such as gearbox failure, pitch abnormality, and anemometer damage may cause the power of the wind turbine to decrease, and then misjudge the icing condition, making the accuracy of the icing monitoring method insufficient and the monitoring accuracy low. At the same time, traditional sensors are easily affected by electromagnetic interference, rain and snow erosion, and have low sensitivity. Point sensing limits the number of sensors in its monitoring area, resulting in low monitoring efficiency.

[0003] In summary, the technical problems existing in the relevant technologies need to be improved. Summary of the invention

[0004] The embodiments of the present invention provide a method, device and storage medium for monitoring ice coating on fan blades based on natural frequency, which effectively improves the monitoring accuracy and monitoring efficiency.

[0005] On the one hand, an embodiment of the present invention provides a method for monitoring ice coating on wind turbine blades based on natural frequency, comprising the following steps:

[0006] According to the fan blade system, a spring mass damping mechanical model is established;

[0007] According to the spring mass damping mechanical model, calculating the functional relationship between equivalent mass, equivalent stiffness and natural frequency;

[0008] According to the fan blade system, finite element modeling is performed on the fan blade to obtain the deployment position of the fiber grating;

[0009] After the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, the wavelength drift data of the windward surface caused purely by the strain is calculated;

[0010] Calculating the natural frequency based on the wavelength drift data of the windward surface caused purely by strain;

[0011] Based on the multiple natural frequencies and the functional relationship, ice coverage monitoring of the wind turbine blades is performed to obtain ice coverage monitoring results.

[0012] In some embodiments, establishing a spring mass damping mechanical model according to the fan blade system includes:

[0013] According to the fan blade system, the blade structure is divided into units to obtain blade units;

[0014] A mass concentration process is performed on the blade unit to obtain a concentrated mass element;

[0015] The total elasticity of the blade unit after the condensation process is used as a massless elastic element;

[0016] The total damping of the blade unit after condensation is used as a massless damping element;

[0017] The elastic element, the damping element and the concentrated mass element are connected to obtain the spring mass damping mechanical model.

[0018] In some embodiments, the calculating the functional relationship between the equivalent mass, the equivalent stiffness and the natural frequency according to the spring mass damping mechanical model includes:

[0019] According to the spring-mass-damping mechanical model, the blade system is equivalently processed to obtain a single-degree-of-freedom system;

[0020] According to the single degree of freedom system, construct a vibration differential equation of the single degree of freedom system;

[0021] Constructing an undamped vibration differential equation according to the damping ratio and the single-degree-of-freedom system vibration differential equation;

[0022] According to the undamped vibration differential equation, construct an undamped characteristic equation;

[0023] Constructing an undamped solution equation according to the undamped characteristic equation and the undamped vibration differential equation;

[0024] According to the undamped solution equation and the system initial conditions, construct the system natural angular frequency equation;

[0025] The functional relationship is constructed according to the system's inherent angular frequency equation.

[0026] In some embodiments, the method of performing finite element modeling on the fan blades according to the fan blade system to obtain the fiber grating deployment position includes:

[0027] According to the fan blade system, construct a three-dimensional model of the fan blade;

[0028] Setting blade material characteristic parameters and blade boundary conditions, wherein the blade material characteristic parameters include elastic modulus, Poisson's ratio or density, and the blade boundary conditions include fixed support, force load or constraint conditions;

[0029] Meshing the three-dimensional model to obtain a plurality of finite element units;

[0030] Calculating strain magnitude distribution according to the blade material characteristic parameters, the blade boundary conditions, the plurality of finite element units and the load conditions;

[0031] Calculating a fiber Bragg grating reference position according to the strain magnitude distribution;

[0032] After the fiber Bragg grating is deployed at the fiber Bragg grating reference position, the load value and the center wavelength drift are calculated;

[0033] Calculating a relationship curve between the load value and the center wavelength drift according to the load value and the center wavelength drift;

[0034] According to the linearity of the relationship curve, a straight line fitting is performed on the relationship curve to obtain sensitivity;

[0035] The fiber grating deployment position is calculated according to the sensitivity.

[0036] In some embodiments, after the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, calculating the wavelength drift data of the windward surface caused purely by strain includes:

[0037] After the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, a first wavelength drift data set is collected through a data acquisition system, wherein the fiber Bragg grating deployment process includes respectively deploying the fiber Bragg grating on the inner side of the windward surface and the inner side of the leeward surface of the wind turbine blade, and the first wavelength drift data set includes two groups of wavelength drift data with opposite strain change trends;

[0038] The two sets of wavelength drift data in the first wavelength drift data set are subtracted by a double grating measurement compensation method to obtain the wavelength drift data of the windward surface purely caused by strain.

[0039] In some embodiments, the calculating of the natural frequency according to the wavelength drift data of the windward surface purely caused by strain comprises:

[0040] According to the center wavelength drift and the effective elastic-optic coefficient, the first stress variation equation is constructed;

[0041] Constructing a second stress variation equation according to the center wavelength drift and strain sensitivity;

[0042] Constructing a first temperature variation equation according to the central wavelength drift, the thermo-optic coefficient and the thermal expansion coefficient;

[0043] Constructing a second temperature variation equation according to the center wavelength drift and temperature sensitivity;

[0044] Constructing a central wavelength drift relationship equation according to the first stress change equation, the second stress change equation, the first temperature change equation, and the second temperature change equation;

[0045] According to the central wavelength drift relationship equation, a central wavelength drift compensation equation is constructed by a double grating measurement compensation method;

[0046] Constructing a target central wavelength drift equation according to the central wavelength drift compensation equation and the temperature coefficient;

[0047] Calculating strain time domain data according to the wavelength drift data of the windward surface purely caused by strain and the target central wavelength drift equation;

[0048] Performing Fourier transform on the strain time domain data to obtain strain frequency domain data;

[0049] The natural frequency is extracted from the strain frequency domain data.

[0050] In some embodiments, the ice coverage monitoring of the wind turbine blades is performed according to the plurality of natural frequencies and the functional relationship to obtain the ice coverage monitoring result, including:

[0051] According to the functional relationship, the natural frequency when there is no ice is taken as the standard value;

[0052] According to multiple natural frequencies of wind turbine blades covered with ice, the mean of the natural frequencies is calculated by using the Gaussian distribution function;

[0053] Subtracting the natural frequency mean from the standard value to obtain a monitoring threshold for ice accumulation;

[0054] Subtracting the real-time monitored natural frequency from the standard value to obtain a real-time monitored difference;

[0055] The ice coverage monitoring result is calculated according to the monitoring threshold and the real-time monitoring difference.

[0056] On the other hand, an embodiment of the present invention provides a wind turbine blade icing monitoring device based on natural frequency, comprising:

[0057] The first module is used to establish a spring mass damping mechanical model based on the fan blade system;

[0058] The second module is used to calculate the functional relationship between the equivalent mass, the equivalent stiffness and the natural frequency according to the spring mass damping mechanical model;

[0059] The third module is used to perform finite element modeling on the fan blades according to the fan blade system to obtain the fiber grating deployment position;

[0060] The fourth module is used to determine the wavelength drift data of the windward surface caused purely by strain after the fiber grating deployment is completed according to the fiber grating deployment position;

[0061] A fifth module is used to calculate the natural frequency according to the wavelength drift data of the windward surface purely caused by strain;

[0062] The sixth module is used to monitor the ice coating on the wind turbine blades according to the plurality of natural frequencies and the functional relationship to obtain the ice coating monitoring result.

[0063] In another aspect, an embodiment of the present invention provides a computer device, comprising:

[0064] at least one processor;

[0065] at least one memory for storing at least one program;

[0066] When the at least one program is executed by the at least one processor, the at least one processor implements the described method.

[0067] On the other hand, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method described above is implemented.

[0068] The beneficial effects of the present invention are as follows:

[0069] The present invention firstly establishes a spring mass damping mechanical model according to a fan blade system, calculates the functional relationship between equivalent mass, equivalent stiffness and natural frequency, then performs finite element modeling on the fan blade according to the fan blade system, obtains the deployment position of the fiber grating, and after the fiber grating is deployed, calculates the wavelength drift data of the windward surface purely caused by strain, and then calculates the natural frequency according to the wavelength drift data of the windward surface purely caused by strain, and finally performs ice coverage monitoring of the fan blade according to multiple natural frequencies and functional relationships to obtain ice coverage monitoring results, thereby realizing ice coverage monitoring of the fan blade and improving monitoring accuracy and monitoring efficiency.

[0070] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0072] Figure 1 This is a flow chart of a method for monitoring icing on wind turbine blades based on natural frequency according to an embodiment of the present invention;

[0073] Figure 2 A schematic diagram of a blade single degree of freedom system according to an embodiment of the present invention;

[0074] Figure 3 A schematic diagram of an xt curve of a blade system according to an embodiment of the present invention;

[0075] Figure 4 A cross-sectional view of the windward surface of a fiber Bragg grating pasting position according to an embodiment of the present invention;

[0076] Figure 5 A side cross-sectional view of a fiber Bragg grating pasting position according to an embodiment of the present invention;

[0077] Figure 6 A schematic diagram of a fiber Bragg grating sensing principle according to an embodiment of the present invention;

[0078] Figure 7 A schematic diagram of a double grating measurement compensation method according to an embodiment of the present invention;

[0079] Figure 8 A schematic diagram of a reference grating measurement compensation method according to an embodiment of the present invention;

[0080] Fig. 9 This is a fiber Bragg grating strain time domain diagram according to an embodiment of the present invention;

[0081] Fig.10 This is a fiber Bragg grating strain spectrum diagram according to an embodiment of the present invention;

[0082] Fig.11 A schematic diagram of a Gaussian distribution function construction process according to an embodiment of the present invention;

[0083] Fig.12 A schematic diagram of a curve fitting Gaussian distribution function according to an embodiment of the present invention. DETAILED DESCRIPTION

[0084] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the embodiments of the present application. They are only examples of devices and methods consistent with some aspects of the embodiments of the present application as detailed in the attached claims.

[0085] It is understood that the terms "first", "second", etc. used in this application can be used to describe various concepts in this article, but unless otherwise specified, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another concept. For example, without departing from the scope of the embodiment of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the words "if" and "if" as used herein can be interpreted as "at the time of" or "when" or "in response to determination".

[0086] The terms "at least one", "multiple", "each", "any", etc. used in this application, at least one includes one, two or more, multiple includes two or more, each refers to each of the corresponding multiple, and any refers to any one of the multiple.

[0087] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0088] Before describing the embodiments of the present application in detail, some nouns and terms involved in the embodiments of the present application are first described. The nouns and terms involved in the embodiments of the present application are subject to the following explanations.

[0089] Natural frequency: Also known as self-vibration frequency, it refers to the inherent vibration frequency of an elastic body or elastic system. It is an inherent property of an elastic body or elastic system, and its value has nothing to do with the initial conditions and the magnitude of the external force. For a multi-particle system, ignoring the influence of damping, the natural frequency is related to its own mass and its distribution (stiffness), boundary support conditions, and vibration form (called "mode").

[0090] In the relevant technologies, the dual-carbon strategic goal proposes the need to build a new power system that can adapt to the large-scale consumption of wind and light renewable energy. Vigorously developing the wind power industry and promoting the grid-connected consumption of a high proportion of renewable energy will become a top priority for my country to build a new power system. However, wind turbine blade icing disasters are one of the important factors hindering the development of wind power. At present, the wind turbine capacity is limited by 42% of the installed capacity due to icing, and some areas are even limited by more than 90%. It can be seen that icing monitoring is an extremely critical safety measure for wind turbines, which is conducive to the construction of a new power system. At present, there are three main methods for wind turbine blade icing monitoring at home and abroad: one is manual observation, which has great randomness and time intervals, and cannot detect icing in time. The second is image recognition, which can be remotely controlled, but icing is often caused in complex meteorological environments. Under these conditions, visibility is low and image recognition will be greatly interfered with. The third method is to use the data from the wind turbine's Supervisory Control And Data Acquisition (SCADA) to evaluate the icing condition through the unit's energy utilization rate. However, in addition to blade icing, gearbox failure, pitch abnormality, anemometer damage and other reasons may cause the wind turbine to reduce power. This method has certain accuracy problems and low monitoring accuracy. In addition, the application of fiber grating sensing technology mostly stays on the realization of blade structure health monitoring or scale monitoring, while ignoring its great potential in the field of icing monitoring technology. Traditional sensors are easily affected by electromagnetic interference and rain and snow erosion. Due to the packaging structure, their sensitivity is not as good as that of bare fiber gratings. Point sensing limits the number of sensors in its monitoring area, resulting in low monitoring efficiency.

[0091] Based on the relationship between the natural frequency and the degree of icing, the present invention applies the fiber grating sensing technology to the data acquisition system, and by determining the optimal deployment mode and position of the grating, the temperature influence is removed, and the strain sensitivity is improved. Then, through the optimized data acquisition system, the monitoring reference value (standard value and monitoring threshold) required for the wind turbine blade icing monitoring is obtained, and based on a large number of sample points, a Gaussian distribution function is constructed, and the icing threshold is set. Combined with the early warning system, the degree of icing on the wind turbine blades is monitored in real time. Subsequently, the deployed deicing scheme can be started according to the diagnosis result, so that it is always in a preset working state where the blade icing degree does not exceed the threshold, the loss caused by the icing disaster is minimized, and the reliability of the wind turbine in extreme weather is ensured. This method is simple to transform, has high accuracy, high sensitivity, timely monitoring, anti-electromagnetic interference, lightning strike and rain and snow erosion, and is suitable for complex meteorological environments. Therefore, the present invention has significant advantages in improving the accuracy and efficiency of wind turbine blade icing monitoring, can effectively improve the performance and reliability of wind turbines, and reduce the losses caused by icing disasters. At the same time, the fiber Bragg grating used can obtain the distribution information of strain and temperature of each sensing segment on the entire optical fiber, which is conducive to the realization of distributed or quasi-distributed monitoring. In the field of ice monitoring, fiber Bragg grating sensing technology has outstanding advantages such as small size, light weight, corrosion resistance, easy deployment, passive sensing, anti-electromagnetic interference, and high sensing accuracy.

[0092] The wind turbine blade icing monitoring method based on natural frequency provided in the embodiment of the present application can be applied to a terminal, can also be applied to a server, and can also be software running in a terminal or a server. In some embodiments, the terminal can be a smart phone, a tablet computer, a laptop computer, a desktop computer, a smart speaker, a smart watch, and a vehicle-mounted terminal, etc., but is not limited thereto; the server side can be configured as an independent physical server, or a server cluster or distributed system composed of multiple physical servers, and can also be configured as a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms. The server can also be a node server in a blockchain network; the software can be an application that implements a wind turbine blade icing monitoring method based on natural frequency, etc., but is not limited to the above forms.

[0093] The present application can be used in many general or special computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc. The present application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present application can also be practiced in distributed computing environments, in which tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0094] The following is a detailed explanation of the embodiments of the present application in conjunction with the accompanying drawings:

[0095] Figure 1 is an optional flow chart of a method for monitoring wind turbine blade icing based on natural frequency provided in an embodiment of the present application. Figure 1 The method may include but is not limited to steps S101 to S106.

[0096] Step S101, establishing a spring mass damping mechanical model according to a fan blade system;

[0097] Step S102, calculating the functional relationship between equivalent mass, equivalent stiffness and natural frequency according to the spring mass damping mechanical model;

[0098] Step S103, performing finite element modeling on the fan blades according to the fan blade system to obtain the fiber Bragg grating deployment position;

[0099] Step S104, after the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, the wavelength drift data of the windward surface caused purely by the strain is calculated;

[0100] Step S105, calculating the natural frequency according to the wavelength drift data of the windward surface purely caused by strain;

[0101] Step S106: monitor the icing of the wind turbine blades according to the multiple natural frequencies and the functional relationship to obtain an icing monitoring result.

[0102] Steps S101 to S106 shown in the embodiment of the present application implement ice coverage monitoring of wind turbine blades, thereby improving monitoring accuracy and efficiency.

[0103] In some embodiments, in step S101, a spring mass damping mechanical model is established according to the wind turbine blade system, which may include but is not limited to the following steps:

[0104] According to the fan blade system, the blade structure is divided into units to obtain blade units;

[0105] The mass of the blade unit is condensed to obtain a concentrated mass element;

[0106] The total elasticity of the blade unit after condensation is taken as a massless elastic element;

[0107] The total damping of the blade unit after condensation is taken as a massless damping element;

[0108] The elastic element, the damping element and the concentrated mass element are connected to obtain a spring-mass-damper mechanical model.

[0109] In some embodiments, a spring-mass-damping mechanical model of the blade system can be established by discretizing the actual fan blade system. When simplifying the actual blade system, the blade structure is first divided into several units according to the fan blade system to obtain blade units, and then the mass of the blade unit is condensed to obtain a concentrated mass element, and then the total elasticity of the blade unit after the condensation process is used as a massless elastic element, and the total damping of the blade unit after the condensation process is used as a massless damping element, and finally the elastic element, the damping element and the concentrated mass element are connected to obtain a spring-mass-damping mechanical model, so that the system with infinite degrees of freedom is simplified to a system with finite degrees of freedom.

[0110] In some embodiments, in step S102, according to the spring mass damping mechanical model, calculating the functional relationship between the equivalent mass, the equivalent stiffness and the natural frequency may include but is not limited to the following steps:

[0111] According to the spring-mass-damper mechanical model, the blade system is treated equivalently to obtain a single-degree-of-freedom system;

[0112] According to the single degree of freedom system, construct the vibration differential equation of the single degree of freedom system;

[0113] According to the damping ratio and the vibration differential equation of the single degree of freedom system, the undamped vibration differential equation is constructed;

[0114] According to the undamped vibration differential equation, the undamped characteristic equation is constructed;

[0115] According to the undamped characteristic equation and the undamped vibration differential equation, the undamped solution equation is constructed;

[0116] According to the undamped solution equation and the system initial conditions, the system's natural angular frequency equation is constructed;

[0117] According to the system's inherent angular frequency equation, a functional relationship is constructed.

[0118] In some embodiments, the functional analytical expression that characterizes the relationship between the natural frequency and the equivalent mass and equivalent stiffness of the blade structure can be analyzed based on the spring mass damping mechanical model. The blade system can be first treated equivalently based on the spring mass damping mechanical model to obtain a single degree of freedom system. Since there are multiple mass elements, multiple elastic elements, and multiple damping elements in the blade system, for the convenience of analysis, the comprehensive effects of these elements can be expressed by equivalent mass, equivalent stiffness, and equivalent damping, and the blade system can be equivalent to a single degree of freedom system. Figure 2 As shown. Then, based on the single degree of freedom system, the single degree of freedom system vibration differential equation is constructed, where the single degree of freedom system vibration differential equation is: In the formula, m is the equivalent mass, c is the equivalent damping, k is the equivalent stiffness, is the vibration acceleration, is the vibration velocity, x is the vibration displacement, and f(t) is the excitation. Then, according to the damping ratio and the single-degree-of-freedom system vibration differential equation, the undamped vibration differential equation is constructed. Among them, the damping ratio ζ of the general fan blade structure system is small. According to the vibration characteristics of the viscous damping system, when the system has weak damping (ζ<1), the system has a damped natural angular frequency w d and the undamped natural angular frequency w n The error is quite small. When discussing the natural frequency of the system in engineering, the damping of the system is often ignored. Therefore, when there is no damping element in the blade single degree of freedom system and the blade is in a free vibration state, the undamped vibration differential equation (a second-order homogeneous constant coefficient linear differential equation) is: Then, according to the undamped vibration differential equation, the undamped characteristic equation is constructed, wherein the solution of the undamped vibration differential equation can be assumed to be: x(t) = Ce λt , where λ is the characteristic value, t is the system response time, x(t) is the solution of the equation, and C is a constant; then substitute the solution of the undamped vibration differential equation into the undamped vibration differential equation, and the undamped characteristic equation is obtained as follows: mλ 2 +k=0. Then, based on the undamped characteristic equation and the undamped vibration differential equation, the undamped solution equation is constructed, where the blade system xt curve is as follows: Figure 3 As shown, the characteristic value can be obtained from the undamped characteristic equation as follows: 1,2 = ±iw n , where i is an imaginary unit, then the solution of the undamped vibration differential equation (i.e., the undamped solution equation) can be written as: In the formula, when the initial condition of the system is x(0) = x0, and When C1=x0,C2=x0 / w n , x0 is the coordinate of the vibration starting point, is the initial velocity. Then solve the equation according to the undamped solution and the system initial conditions (x(0) = x0, and Construct the system's natural angular frequency equation, where the undamped solution equation and The physical meaning of the single-degree-of-freedom system is that the system's natural angular frequency equation for undamped free vibration is: In the formula, w n is the natural angular frequency of the system. Finally, according to the natural angular frequency equation of the system, the functional relationship between equivalent mass, equivalent stiffness and natural frequency is constructed, where w n =2πf n The functional relationship is: In the formula, f n is the system's natural frequency, in Hz, and the system's natural angular frequency w n The unit is rad / s, m ​​is the equivalent mass, and k is the equivalent stiffness. Moreover, from the system's natural angular frequency equation and function relationship, it can be seen that when an undamped single-degree-of-freedom system is in free vibration, the natural frequency is only related to the parameters of the system's own components, that is, the square of the natural frequency is proportional to the system's equivalent stiffness and inversely proportional to the system's equivalent mass.

[0119] In some embodiments, in step S103, according to the fan blade system, finite element modeling is performed on the fan blade to obtain the fiber Bragg grating deployment position, which may include but is not limited to the following steps:

[0120] According to the fan blade system, construct a three-dimensional model of the fan blade;

[0121] Setting blade material characteristic parameters and blade boundary conditions, wherein the blade material characteristic parameters include elastic modulus, Poisson's ratio or density, and the blade boundary conditions include fixed support, force load or constraint conditions;

[0122] Meshing the three-dimensional model to obtain several finite element units;

[0123] Calculate the strain magnitude distribution based on blade material characteristic parameters, blade boundary conditions, several finite element units and load conditions;

[0124] Calculate the reference position of the fiber Bragg grating according to the strain magnitude distribution;

[0125] After deploying the fiber Bragg grating at the fiber Bragg grating reference position, the load value and the center wavelength drift are calculated;

[0126] According to the load value and the center wavelength drift, a relationship curve between the load value and the center wavelength drift is calculated;

[0127] According to the linearity of the relationship curve, a straight line fitting is performed on the relationship curve to obtain the sensitivity;

[0128] According to the sensitivity, the fiber Bragg grating deployment position is calculated.

[0129] In some embodiments, when deploying the fiber Bragg grating, finite element modeling can be performed on the wind turbine blades. The position of the blade with the largest strain after the load is applied can be obtained through numerical simulation methods as the approximate reference position for the deployment of the fiber Bragg grating. The static load experiment finds the specific deployment method and position that makes the fiber Bragg grating sensitivity the highest. The deployment position is optimally selected based on the sensitivity and linearity of the relationship curve between the load size and the center wavelength drift. Generally, the blade axis is selected as the x-axis, and the grating is directly pasted on the inner side of the windward side and the inner side of the leeward side of the blade along the x-axis. The front cross-section of the blade pasted with the grating is as follows: Figure 4 As shown, the side section of the blade with the grating attached is as follows Figure 5As shown in the figure, FBG1 is the first group of fiber Bragg gratings, and FBG2 is the second group of fiber Bragg gratings. In some embodiments, in order to determine the reference position of the fiber Bragg grating deployment, finite element modeling and numerical simulation are performed on the fan blade. It can be that the three-dimensional model of the fan blade is first constructed according to the fan blade system, and the blade material characteristic parameters and blade boundary conditions are set, wherein the blade material characteristic parameters may include elastic modulus, Poisson's ratio or density, etc., and the blade boundary conditions may include fixed support, force load or constraint conditions, etc. Then the three-dimensional model is meshed, divided into small finite element units to obtain a number of finite element units, and the different load conditions to which the blade is subjected in the simulation are defined. Then a numerical simulation is performed, and the strain size distribution of the blade under different loads is calculated according to the blade material characteristic parameters, blade boundary conditions, a number of finite element units and load conditions, and the fiber Bragg grating reference position is calculated according to the strain size distribution. The position with larger strain is the fiber Bragg grating reference position. Deploying the fiber Bragg grating at the reference position can improve the monitoring sensitivity. In order to maximize the sensitivity of the fiber Bragg grating to the blade strain perception, a static load stress experiment can be further performed to calculate the specific deployment position and method. After deploying the FBG at the FBG reference position, fix the blade root, apply a load at one of the fixed positions near the blade tip, and continuously increase the load to calculate the load value and the center wavelength drift. Then, based on the load value and the center wavelength drift, calculate the relationship curve between the load value and the center wavelength drift, and continuously change the deployment method and position to obtain multiple sets of relationship curves. Finally, compare the linearity of the relationship curve. The higher the linearity, the better. Perform a straight line fitting on the relationship curve with higher linearity to obtain the sensitivity, and compare the sensitivity. The larger the slope, the higher the sensitivity. Select the position with high sensitivity to obtain the deployment position of the FBG. Moreover, the results of the static load stress experiment show that the effect of deploying the FBG on the windward or leeward side of the blade along the x-axis with the blade axis as the x-axis is best. At the same time, deployment on the inner side can effectively avoid lightning strikes and rain and snow erosion, thereby extending the service life.

[0130] In some embodiments, in step S104, after the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, the wavelength drift data of the windward surface purely caused by strain is calculated, which may include but is not limited to the following steps:

[0131] After the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, a first wavelength drift data set is collected through a data acquisition system, wherein the fiber Bragg grating deployment process includes respectively deploying the fiber Bragg grating on the inner side of the windward surface and the inner side of the leeward surface of the wind turbine blade, and the first wavelength drift data set includes two groups of wavelength drift data with opposite strain change trends;

[0132] The two sets of wavelength drift data in the first wavelength drift data set are subtracted by a double grating measurement compensation method to obtain the wavelength drift data of the windward surface purely caused by strain.

[0133] In some embodiments, fiber Bragg grating sensing technology is applied to a data acquisition system (which may include fiber Bragg grating, fiber slip ring, fiber Bragg grating demodulator, etc.). Based on the fiber Bragg grating sensing theory, fiber Bragg gratings can be deployed on the inner side of the windward side and the inner side of the leeward side of the fan blade according to the fiber Bragg grating deployment position, so that the positions of the two fiber Bragg gratings are symmetrical about the blade axis, and the first wavelength drift data set is collected through the data acquisition system, wherein the first wavelength drift data set includes two sets of wavelength drift data with opposite strain change trends. These data contain information about the change of the force condition of the blade, but are also affected by temperature. It can be understood that during the data acquisition process, the optical signal enters the sensor grating directly or indirectly through the transmission channel, and the sensor grating modulates the optical signal under the action of the external field (such as strain field, temperature field, etc.), and then the modulated optical signal with external field information is reflected (or transmitted) by the sensor grating, and then received, demodulated and output by the fiber demodulator to obtain the first wavelength drift data set. These data can be further processed later to remove the temperature effect and improve the strain sensitivity. Then, the two fiber gratings led out from the inside of the blade are used to directly transmit the optical signal data through a dual-channel fiber optic rotary connector, which can avoid the fiber entanglement when the blade rotates, while ensuring that the data is maximally undistorted. The two sets of wavelength drift data in the first wavelength drift data set are then subtracted by the dual grating measurement compensation method to obtain the wavelength drift data of the windward surface caused purely by strain, so as to achieve temperature compensation. It can be understood that the first wavelength drift data set contains two components: the wavelength drift component caused by strain and the wavelength drift component caused by temperature. After calculation by the dual grating measurement compensation method, due to the same temperature coefficient, the wavelength drift component caused by temperature is exactly offset, and finally the wavelength drift data of the windward surface caused purely by strain is obtained to remove the influence of temperature.

[0134] In some embodiments, in step S105, calculating the natural frequency based on the wavelength drift data of the windward surface purely caused by strain may include but is not limited to the following steps:

[0135] According to the center wavelength drift and the effective elastic-optic coefficient, the first stress variation equation is constructed;

[0136] According to the center wavelength drift and strain sensitivity, the second stress variation equation is constructed;

[0137] Constructing a first temperature variation equation according to the center wavelength drift, the thermo-optic coefficient and the thermal expansion coefficient;

[0138] Constructing a second temperature variation equation according to the center wavelength drift and temperature sensitivity;

[0139] According to the first stress variation equation, the second stress variation equation, the first temperature variation equation and the second temperature variation equation, a center wavelength drift relationship equation is constructed;

[0140] According to the relationship equation of center wavelength drift, the center wavelength drift compensation equation is constructed by double grating measurement compensation method;

[0141] According to the center wavelength drift compensation equation and the temperature coefficient, a target center wavelength drift equation is constructed;

[0142] Calculate strain time domain data based on the wavelength drift data of the windward surface purely caused by strain and the target center wavelength drift equation;

[0143] Perform Fourier transform on strain time domain data to obtain strain frequency domain data;

[0144] Extract natural frequencies from strain frequency domain data.

[0145] In some embodiments, fiber Bragg gratings (FBG) have temperature and strain sensing principles, such as Figure 6 As shown. Among them, stress (strain) is one of the most direct external factors that cause the drift of the FBG center wavelength, and it is also an important measurement target based on the natural frequency analysis path. When the stress or strain acting on the axial direction of the fiber Bragg grating changes, the elastic-optical effect of the fiber causes the FBG effective refractive index n eff The change of the grating period Λ will also change, making the FBG center wavelength λ B Drift occurs. The first stress variation equation can be constructed based on the center wavelength drift and the effective elastic-optic coefficient, and the second stress variation equation can be constructed based on the center wavelength drift and strain sensitivity, wherein the first stress variation equation is: The second stress variation equation is: Δλ B =K ε Δε, where Δλ B is the center wavelength drift, λ B is the central wavelength, P e is the effective elastic-optical coefficient of the optical fiber, Δε is the strain, K ε is the strain sensitivity of the fiber Bragg grating. When the temperature at the FBG measurement position changes, due to the thermo-optical effect of the fiber itself and its thermal expansion effect, the effective refractive index n eff and the grating period Λ change, the central wavelength λ of the FBG B Drift will also occur. FBG center wavelength drift Δλ BIt changes with the change of the external temperature ΔT. The first temperature change equation can be constructed according to the center wavelength drift, the thermo-optical coefficient and the thermal expansion coefficient, and the second temperature change equation can be constructed according to the center wavelength drift and the temperature sensitivity. The first temperature change equation is: The second temperature change equation is: Δλ B =K T ΔT, where Δλ B is the center wavelength drift, λ B is the central wavelength, α f is the thermo-optical coefficient of the optical fiber, ξ f is the thermal expansion coefficient of the optical fiber, ΔT is the temperature change, K T is the temperature sensitivity of the fiber Bragg grating. It can be seen that strain and temperature are two physical quantities that can be directly measured by the fiber Bragg grating. In practical applications, the fiber Bragg grating is usually affected by strain and temperature. According to the first stress variation equation, the second stress variation equation, the first temperature variation equation and the second temperature variation equation, the central wavelength drift relationship equation is constructed to express the central wavelength drift Δλ B The relationship between the strain Δε and the temperature change ΔT, where the relationship equation of the center wavelength drift is: In the formula, Δλ B =K ε Δε+K T ΔT. Since the ice monitoring project needs to work in an environment with a wide temperature range, this monitoring path needs to eliminate the impact of temperature changes on strain measurement. Low-cost and easy-to-implement temperature compensation methods include: Figure 7 The double grating measurement compensation method shown in the figure comprises a fixed end 701, a movable end 702, an elastic body 703, a first group of fiber gratings FBG1 and a second group of fiber gratings FBG2; and Figure 8 The reference grating temperature compensation method shown includes a fixed end 801, a mobile end 802, a third group of fiber gratings FBG3 and a fourth group of fiber gratings FBG4. This embodiment adopts a dual grating measurement compensation method, and can construct a central wavelength drift compensation equation through the dual grating measurement compensation method according to the central wavelength drift relationship equation, wherein the central wavelength drift compensation equation is: Δλ 12 =K1Δε1-K2Δε2+(B1-B2)ΔT, where, Δλ 12is the center wavelength drift after compensation, K1 is the strain coefficient of the first group of fiber Bragg gratings, K2 is the strain coefficient of the second group of fiber Bragg gratings, Δε1 is the strain of the first group of fiber Bragg gratings, Δε2 is the strain of the second group of fiber Bragg gratings, B1 is the temperature coefficient of the first group of fiber Bragg gratings, B2 is the temperature coefficient of the second group of fiber Bragg gratings, and ΔT is the temperature change. It is easy to know that when the blade vibrates, the strain change trends at the two symmetrical gratings are always opposite, so Δε1=-Δε2. For fiber Bragg gratings using the same material and preparation process, B1=B2 can be set, and then the center wavelength drift compensation equation is simplified according to the center wavelength drift compensation equation and temperature coefficient to construct the target center wavelength drift equation, where the target center wavelength drift equation is: Δλ 12 =(K1+K2)Δε1.

[0146] In some embodiments, it can be seen from the target center wavelength drift equation that the differential processing of the double grating can not only realize the temperature self-compensation of the sensor and eliminate the influence of temperature change on strain measurement, but also theoretically, the measured center wavelength drift Δλ 12 is the wavelength shift Δλ measured by using the first fiber Bragg grating FBG1 alone times, so that the sensing system will be more sensitive to strain, which can effectively improve the measurement accuracy of the sensing system for strain. Therefore, the blade axis can be used as the x-axis, and the grating can be directly pasted symmetrically on the inner side of the windward side and the inner side of the leeward side of the blade along the x-axis to achieve temperature compensation. More, in the field of traditional vibration signal analysis, time domain analysis and frequency domain analysis are common methods for diagnosing ice coverage, which can timely identify and warn the ice coverage of the blade. However, it is not easy to analyze the key signals required for monitoring through time domain signals, and the frequency domain analysis of the collected time domain signal data can analyze the changes in frequency components, phases, amplitudes, etc. Therefore, the analysis in the frequency domain can more easily determine whether the signal is abnormal or not, and at the same time, the occurrence of ice coverage of the fan blade can be judged according to the changes in the spectrum. There are differences in the frequency amplitude and periodicity presented by the ice coverage signal and the normal signal, and their characteristics can be analyzed. Based on this, the ice coverage state of the fan blade can be further judged. In addition, the frequency components of structural vibration are generally obtained by frequency domain analysis of the vibration acceleration signal of the structure. However, in the case of low-frequency vibration, the frequency composition of the structural vibration can also be obtained by Fourier transforming the structural strain signal. The vibration of the wind turbine blade is a low-frequency vibration, so the fiber Bragg grating can be directly used as the sensing system, combined with a rotary connector and a fiber Bragg grating demodulator to build a data acquisition system. The collected strain time domain signal is processed in real time. The strain time domain data can be calculated based on the wavelength drift data caused purely by strain on the windward surface and the target center wavelength drift equation to remove the temperature effect and improve the strain sensitivity. If the original strain time domain data is x(t), the fiber Bragg grating strain time domain diagram is as follows: Fig. 9 As shown in FIG. 1 , the strain time domain data can be Fourier transformed to obtain the strain frequency domain data containing the vibration signal (natural frequency and amplitude), thereby realizing the blade natural frequency monitoring. The calculation formula of the strain frequency domain data is: In the formula, X(f) is the strain frequency domain data, x(t) is the strain time domain data, j is the imaginary unit, f is the frequency, and t is the time. Finally, the natural frequency is extracted from the strain frequency domain data. The fiber Bragg grating strain spectrum data result is as follows: Fig.10 As shown in the figure, by analyzing the strain frequency domain data, the frequency with the largest amplitude can be found, which is the natural frequency of vibration, also known as the characteristic frequency. Moreover, the quantitative characteristics in the time-frequency domain can be further extracted, including the root mean square value (RMS) of the center wavelength drift within a preset period, the average value and standard deviation of the natural frequency, etc., to observe its amplitude characteristics, thereby ensuring the accuracy and reliability of the data and improving the stability and flexibility of the system.

[0147] In some embodiments, in step S106, the ice coverage monitoring of the wind turbine blades is performed according to the multiple natural frequencies and the functional relationship to obtain the ice coverage monitoring result, which may include but is not limited to the following steps:

[0148] According to the functional relationship, the natural frequency when there is no ice is taken as the standard value;

[0149] According to multiple natural frequencies of wind turbine blades covered with ice, the mean of the natural frequencies is calculated by using the Gaussian distribution function;

[0150] Subtract the natural frequency mean from the standard value to obtain the monitoring threshold for ice accumulation.

[0151] Subtract the real-time monitored natural frequency from the standard value to obtain the real-time monitored difference;

[0152] The ice cover monitoring results are calculated based on the monitoring threshold and the real-time monitoring difference.

[0153] In some embodiments, the natural frequency when not covered with ice can be taken as the standard value f0 according to the functional relationship, and the average value can be obtained by multiple measurements to reduce the error. According to the functional relationship, it can be known that the ice covering of the blade will increase the equivalent mass of the blade structure and the equivalent stiffness of the blade structure, that is, the equivalent mass and equivalent stiffness of the fan blade structure are proportional to the degree of ice covering. When the fan blade is covered with ice, the equivalent mass of the blade increases, and the natural frequency of the blade decreases accordingly, while the equivalent stiffness of the blade increases, and the natural frequency of the blade increases accordingly. For the variable cross-section cantilever beam structure of the wind turbine blade, the degree of influence of ice covering on the equivalent mass of the blade structure and the degree of influence of equivalent stiffness are different under different ice covering conditions. In the actual ice covering process, the influence of ice covering on the equivalent mass of the blade is greater than its influence on the equivalent stiffness. Therefore, as the degree of ice covering increases, the natural frequency generally shows a downward trend. According to the relationship between the natural frequency and the degree of ice covering, the occurrence of blade ice covering can be diagnosed by real-time monitoring of the change in the natural frequency of blade vibration. In some embodiments, the real-time change in the natural frequency can be intuitively reflected by the difference K between the real-time monitoring value and the standard value. Keeping the fan speed constant, after measuring the standard value, according to the change of environmental parameters, when obvious ice formation is observed on the blade surface, record the natural frequency f of the fan blade vibration at this time m After recording a sufficient number of sample points, a Gaussian distribution function is constructed, and the mean value μ and standard deviation σ of the natural frequency are calculated by the Gaussian distribution function according to the multiple natural frequencies of the wind turbine blades when ice is applied. Then the natural frequency mean μ is subtracted from the standard value f0 to obtain the monitoring threshold K for ice application. m In actual operation, the natural frequency can be monitored in real time, and the real-time monitoring value (i.e. the natural frequency of real-time monitoring) can be subtracted from the standard value to obtain the real-time monitoring difference. Finally, the ice coverage monitoring result is calculated based on the monitoring threshold and the real-time monitoring difference. If the real-time monitoring difference K is less than the monitoring threshold K m , then the ice coverage monitoring result can be obtained as ice coverage occurs. More, the process of constructing the Gaussian distribution function of the natural frequency is as follows Fig.11 As shown, ice monitoring can be performed according to the change of environmental parameters. If ice occurs, record enough natural frequencies as sample points, and then calculate the natural frequency mean and natural frequency standard deviation to construct a Gaussian distribution function. According to the central limit theorem, no matter what distribution the population is, when the sample size n gradually tends to infinity, the frequency distribution of the mean of the sampled samples tends to normal distribution as the number of samples increases, and their normalized sum increases with the increase of the number of noise sources, such as Fig.12 As shown, it approaches a Gaussian distribution. Based on this, the natural frequency mean μ can be set as the monitoring threshold K based on the occurrence of ice accumulation. m , calculate the natural frequency standard deviation σ of the monitoring value within a certain period, where the calculation formula of the natural frequency standard deviation is: Where σ is the natural frequency, K i is the i-th data point, μ is the mean of the natural frequency, and N is the number of data points. The calculation formula of the Gaussian distribution function is: Where K is the data point.

[0154] The beneficial effects of implementing the embodiments of the present invention include: first, according to the wind turbine blade system, the spring mass damping mechanical model is established to calculate the functional relationship between the equivalent mass, the equivalent stiffness and the natural frequency, then, according to the wind turbine blade system, the wind turbine blade is finite element modeled to obtain the fiber grating deployment position, and after the fiber grating deployment is completed, the wavelength drift data of the windward surface caused purely by strain is calculated, and then the natural frequency is calculated according to the wavelength drift data of the windward surface caused purely by strain, and finally, according to multiple natural frequencies and functional relationships, the wind turbine blade icing monitoring is performed to obtain the icing monitoring result, thereby realizing the wind turbine blade icing monitoring and improving the monitoring accuracy and monitoring efficiency. At the same time, this embodiment has the advantages of small size, simple structure, high accuracy, convenient distributed measurement, anti-electromagnetic interference, lightning protection and rain and snow erosion protection, and has a temperature compensation function, which effectively improves the performance and reliability of the wind turbine generator set, is a cost-effective solution, suitable for wind farm operation under cold wave weather, and has broad application prospects.

[0155] The embodiment of the present invention further provides a wind turbine blade icing monitoring device based on natural frequency, comprising:

[0156] The first module is used to establish a spring mass damping mechanical model based on the fan blade system;

[0157] The second module is used to calculate the functional relationship between equivalent mass, equivalent stiffness and natural frequency according to the spring mass damping mechanical model;

[0158] The third module is used to perform finite element modeling on the fan blades according to the fan blade system to obtain the deployment position of the fiber grating;

[0159] The fourth module is used to determine the wavelength drift data of the windward surface caused purely by strain after the fiber Bragg grating is deployed according to the fiber Bragg grating deployment position;

[0160] The fifth module is used to calculate the natural frequency based on the wavelength drift data of the windward surface caused purely by strain;

[0161] The sixth module is used to monitor the ice coating on the wind turbine blades according to a plurality of natural frequencies and functional relationships, and obtain the ice coating monitoring results.

[0162] The contents of the above method embodiments are all applicable to the present device embodiments. The functions specifically implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0163] An embodiment of the present invention further provides a computer device, comprising:

[0164] at least one processor;

[0165] at least one memory for storing at least one program;

[0166] When at least one program is executed by at least one processor, the at least one processor implements Figure 1 The method shown.

[0167] The contents of the above method embodiments are all applicable to the present device embodiments. The functions specifically implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0168] The embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, Figure 1 The method shown.

[0169] The contents of the above method embodiments are all applicable to the present storage medium embodiments. The functions specifically implemented by the present storage medium embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0170] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the scope of the rights of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the present invention should be within the scope of the rights of the present invention.

Claims

1. A method for monitoring wind turbine blade icing based on natural frequency, characterized in that: The following steps are involved: According to the fan blade system, a spring mass damping mechanical model is established; According to the spring mass damping mechanical model, calculating the functional relationship between equivalent mass, equivalent stiffness and natural frequency; According to the fan blade system, finite element modeling is performed on the fan blade to obtain the deployment position of the fiber grating; After the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, the wavelength drift data of the windward surface caused purely by the strain is calculated; Calculating the natural frequency based on the wavelength drift data of the windward surface caused purely by strain; Based on the multiple natural frequencies and the functional relationship, ice coverage monitoring of the wind turbine blades is performed to obtain ice coverage monitoring results.

2. The method according to claim 1, characterized in that The spring mass damping mechanical model is established according to the fan blade system, including: According to the fan blade system, the blade structure is divided into units to obtain blade units; A mass concentration process is performed on the blade unit to obtain a concentrated mass element; The total elasticity of the blade unit after the condensation process is used as a massless elastic element; The total damping of the blade unit after condensation is used as a massless damping element; The elastic element, the damping element and the concentrated mass element are connected to obtain the spring mass damping mechanical model.

3. The method according to claim 1, characterized in that: The calculation of the functional relationship between the equivalent mass, the equivalent stiffness and the natural frequency according to the spring mass damping mechanical model includes: According to the spring-mass-damping mechanical model, the blade system is equivalently processed to obtain a single-degree-of-freedom system; According to the single degree of freedom system, construct a vibration differential equation of the single degree of freedom system; Constructing an undamped vibration differential equation according to the damping ratio and the single-degree-of-freedom system vibration differential equation; Constructing an undamped characteristic equation according to the undamped vibration differential equation; Constructing an undamped solution equation according to the undamped characteristic equation and the undamped vibration differential equation; According to the undamped solution equation and the system initial conditions, construct the system natural angular frequency equation; The functional relationship is constructed according to the system's inherent angular frequency equation.

4. The method according to claim 1, characterized in that According to the fan blade system, finite element modeling is performed on the fan blade to obtain the fiber grating deployment position, including: According to the fan blade system, construct a three-dimensional model of the fan blade; Setting blade material characteristic parameters and blade boundary conditions, wherein the blade material characteristic parameters include elastic modulus, Poisson's ratio or density, and the blade boundary conditions include fixed support, force load or constraint conditions; Meshing the three-dimensional model to obtain a plurality of finite element units; Calculating strain magnitude distribution according to the blade material characteristic parameters, the blade boundary conditions, the plurality of finite element units and the load conditions; Calculating a fiber Bragg grating reference position according to the strain magnitude distribution; After the fiber Bragg grating is deployed at the fiber Bragg grating reference position, the load value and the center wavelength drift are calculated; Calculating a relationship curve between the load value and the center wavelength drift according to the load value and the center wavelength drift; According to the linearity of the relationship curve, a straight line fitting is performed on the relationship curve to obtain sensitivity; The fiber grating deployment position is calculated according to the sensitivity.

5. The method according to claim 1, characterized in that After the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, the wavelength drift data of the windward surface caused purely by strain is calculated, including: After the fiber Bragg grating deployment is completed according to the fiber Bragg grating deployment position, a first wavelength drift data set is collected through a data acquisition system, wherein the fiber Bragg grating deployment process includes respectively deploying the fiber Bragg grating on the inner side of the windward surface and the inner side of the leeward surface of the wind turbine blade, and the first wavelength drift data set includes two groups of wavelength drift data with opposite strain change trends; The two sets of wavelength drift data in the first wavelength drift data set are subtracted by a double grating measurement compensation method to obtain the wavelength drift data of the windward surface purely caused by strain.

6. The method according to claim 1, characterized in that The calculating of the natural frequency according to the wavelength drift data of the windward surface purely caused by strain comprises: According to the center wavelength drift and the effective elastic-optic coefficient, the first stress variation equation is constructed; Constructing a second stress variation equation according to the center wavelength drift and strain sensitivity; Constructing a first temperature variation equation according to the center wavelength drift, the thermo-optic coefficient and the thermal expansion coefficient; Constructing a second temperature variation equation according to the center wavelength drift and temperature sensitivity; Constructing a central wavelength drift relationship equation according to the first stress change equation, the second stress change equation, the first temperature change equation, and the second temperature change equation; According to the central wavelength drift relationship equation, a central wavelength drift compensation equation is constructed by a double grating measurement compensation method; Constructing a target central wavelength drift equation according to the central wavelength drift compensation equation and the temperature coefficient; Calculating strain time domain data according to the wavelength drift data of the windward surface purely caused by strain and the target central wavelength drift equation; Performing Fourier transform on the strain time domain data to obtain strain frequency domain data; The natural frequency is extracted from the strain frequency domain data.

7. The method according to claim 1, characterized in that The step of monitoring ice coverage of wind turbine blades according to the plurality of natural frequencies and the functional relationship to obtain ice coverage monitoring results includes: According to the functional relationship, the natural frequency when there is no ice is taken as the standard value; According to multiple natural frequencies of wind turbine blades covered with ice, the mean of the natural frequencies is calculated by using the Gaussian distribution function; Subtracting the natural frequency mean from the standard value to obtain a monitoring threshold for ice accumulation; Subtracting the real-time monitored natural frequency from the standard value to obtain a real-time monitored difference; The ice coverage monitoring result is calculated according to the monitoring threshold and the real-time monitoring difference.

8. A wind turbine blade icing monitoring device based on natural frequency, characterized in that: include: The first module is used to establish a spring mass damping mechanical model based on the fan blade system; The second module is used to calculate the functional relationship between equivalent mass, equivalent stiffness and natural frequency according to the spring mass damping mechanical model; The third module is used to perform finite element modeling on the fan blades according to the fan blade system to obtain the deployment position of the fiber grating; The fourth module is used to determine the wavelength drift data of the windward surface caused purely by strain after the fiber grating deployment is completed according to the fiber grating deployment position; A fifth module is used to calculate the natural frequency according to the wavelength drift data of the windward surface purely caused by strain; The sixth module is used to monitor the ice coating on the wind turbine blades according to the plurality of natural frequencies and the functional relationship to obtain the ice coating monitoring result.

9. A computer device, characterized in that: include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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