Blade root load-based blade section load, clearance calculation and blade protection method

Abstract

The invention relates to the technical field of wind turbine generator blade state monitoring, in particular to a blade root load-based blade section load, clearance calculation and blade protection method, which comprises the following steps of: calculating pneumatic thrust of each section of a blade on the basis of pneumatic characteristics and relative wind speed of the blade; the calculated pneumatic thrust of each section of the blade is corrected through monitored blade root load data, the load of each section of the blade is calculated according to the corrected pneumatic thrust of each section of the blade, the load of each section of the blade is inversed through the blade root load, and therefore the load of each section of the blade and the clearance of the blade are calculated. And blade limit protection and blade clearance protection are carried out on the blade according to the load of each section of the blade and the blade clearance, so that the accurate evaluation of the loaded state of the blade is realized, and the safe operation of the wind turbine generator is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine blade status monitoring, and in particular to a method for calculating blade cross-sectional load and clearance based on blade root load, and evaluating blade status based on blade clearance and blade cross-sectional load to achieve blade protection. Background Art

[0002] The blades of wind turbines are key components for converting wind energy into mechanical energy, and their operating status is directly related to the efficiency, stability and service life of the turbine. As wind turbines develop towards larger capacity and longer blades, the design and operational safety of blades face higher requirements. During the operation of wind turbines, the blades are subjected to complex aerodynamic and inertial forces, which will produce dynamic deformation and load distribution changes. This dynamic characteristic not only affects the fatigue life of the blades, but may also lead to insufficient clearance between the blades and the tower, increasing the risk of collision. Therefore, real-time monitoring of the load and clearance status of each section of the blade is of great significance to ensure the safe and efficient operation of wind turbines.

[0003] Currently, the status of blades can be monitored through blade vibration sensors, video clearance monitoring, blade root load sensors, etc. Blade vibration sensors monitor the vibration size of blades to evaluate the vibration status of blades, but cannot infer the status of each section of the blade. Video clearance monitoring can only monitor the clearance, but cannot evaluate the status of blades. Currently, there is no method to evaluate the load and clearance of each section of the blade based on the blade root load sensor. Summary of the invention

[0004] The present invention provides a blade cross-sectional load and clearance calculation and blade protection method based on blade root load. The load of each blade cross section is inverted by the blade root load, so that the load of each blade cross section and the blade clearance are calculated, and blade limit protection and blade clearance protection are performed on the blade according to the load of each blade cross section and the blade clearance, so as to achieve accurate assessment of the load state of the blade and ensure the safe operation of the wind turbine.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] A method for calculating blade cross-sectional load based on blade root load comprises the following steps:

[0007] S1. Install a load sensor at the blade root to monitor the blade root load data in real time;

[0008] S2. Calculate the aerodynamic thrust of each section of the blade based on the aerodynamic characteristics and the relative wind speed of the blade;

[0009] S3, correcting the calculated aerodynamic thrust of each section of the blade by using the monitored blade root load data;

[0010] S4. Calculate the load of each section of the blade based on the corrected aerodynamic thrust of each section of the blade.

[0011] Preferably, the aerodynamic thrust F of each section of the blade in step S2 t (r) is calculated as:

[0012]

[0013] Where r is the blade section length, c(r) is the chord length distribution, ρ is the air density, C t (r,β) is the thrust coefficient of the blade section at different pitch angles, obtained through experiments or simulations; V rel is the relative wind speed, and its calculation formula is:

[0014]

[0015] Where V hab is the incoming wind speed, measured by the unit anemometer; ω is the impeller angular velocity, and R is the total length of the blade.

[0016] Preferably, the correction calculation formula for the aerodynamic thrust of each section of the blade in step S3 is:

[0017]

[0018] where F t (r) corrected is the aerodynamic thrust of each section of the blade after correction, F root,measured The blade root load data obtained by monitoring.

[0019] Preferably, the load calculation formula for each section of the blade in step S4 is:

[0020]

[0021] Wherein Δr is the discrete interval, N is the number of cross-sectional segments of the blade, and N=R / Δr.

[0022] The present invention also provides a blade limit protection method based on blade cross-sectional load, which protects the blade in sections along the span direction, and different limit thresholds γ are determined by blade material properties and structures in different cross-sectional sections. i ; If the blade section load exceeds the limit threshold value γ of the corresponding section segment i , the tower should be shut down for protection in time.

[0023] The present invention also provides a blade clearance calculation method based on blade cross-sectional load, (1) the deformation of the blade is calculated according to the load of each cross section of the blade, and the calculation formula is:

[0024]

[0025] y i =y i-1 -θ i Δr;

[0026] where θ i is the rotation angle of the i-th blade section, θ i-1 is the rotation angle of the i-1th blade section, E is the elastic modulus of the blade, I(r i ) is the section moment of inertia, y i is the deformation of the i-th blade section, y i-1 is the deformation of the i-1th blade section;

[0027] (2) Considering the unit elevation angle and blade cone angle, the blade clearance calculation formula is as follows:

[0028]

[0029] where y N is the deformation of the last section of the blade, that is, the deformation of the blade tip, L y , L z is the horizontal and vertical distance from the blade tip, R tower is the tower radius, θ pitch is the blade pitch angle.

[0030] The present invention also provides a blade clearance protection method based on blade clearance, which calculates the blade clearance in real time and sets a blade clearance safety threshold a;

[0031] If d clearance If it is greater than 1.1a, the unit operates normally without adjustment;

[0032] If d clearance If it is greater than a and less than 1.1a, the crew will issue a warning;

[0033] If d clearance Less than a, greater than 0.1a, the unit adjusts the pitch angle to increase the clearance;

[0034] If d clearance If it is less than 0.1a, the unit will shut down immediately.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention takes into account the influence of the variable pitch angle, combines aerodynamic characteristics and structural mechanics analysis, and inverts the loads of each section of the blade through the blade root load, thereby calculating the loads of each section of the blade and the blade clearance, and performs blade limit protection and blade clearance protection on the blade according to the loads of each section of the blade and the blade clearance, thereby achieving accurate assessment of the load state of the blade and ensuring the safe operation of the wind turbine. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the embodiments.

[0037] The present invention provides a method for calculating blade cross-sectional load based on blade root load, comprising the following steps:

[0038] S1. Install a load sensor at the blade root to monitor the blade root load data in real time;

[0039] S2. Calculate the aerodynamic thrust of each section of the blade based on the aerodynamic characteristics and the relative wind speed of the blade;

[0040] Aerodynamic thrust F of each blade section t (r) is calculated as:

[0041]

[0042] Where r is the blade section length, c(r) is the chord length distribution, ρ is the air density, C t (r,β) is the thrust coefficient of the blade section at different pitch angles, obtained through experiments or simulations; V rel is the relative wind speed, and its calculation formula is:

[0043]

[0044] Where V hab is the incoming wind speed, measured by the unit anemometer; ω is the impeller angular velocity, R is the total length of the blade;

[0045] S3, correcting the calculated aerodynamic thrust of each section of the blade by using the monitored blade root load data. This step compensates for the uncertainty of the aerodynamic model by using the actual load data, thereby improving the accuracy of the load calculation;

[0046] The calculation formula for the correction of aerodynamic thrust of each section of the blade is:

[0047]

[0048] Among them, F t (r) corrected is the aerodynamic thrust of each section of the blade after correction, F root,measured The blade root load data obtained by monitoring.

[0049] S4. Calculate the load of each section of the blade based on the corrected aerodynamic thrust of each section of the blade.

[0050] The load calculation formula for each section of the blade in step S4 is:

[0051]

[0052] In actual use, the formula in discrete form is as follows:

[0053]

[0054] Wherein Δr is the discrete interval, N is the number of cross-sectional segments of the blade, and N=R / Δr.

[0055] Based on the calculated load M(r i ), the present invention also provides a blade limit protection method, which protects the blade in sections along the span direction, and different cross-sectional sections (i = 1, 2, ..., N) determine different limit thresholds γ according to the blade material properties and structure. i ; If the blade calculation load M(r i ) exceeds the limit threshold γ of the corresponding cross-section segment i , the tower should be shut down for protection in time.

[0056] Based on the calculated load M(r i ), the present invention also provides a blade clearance calculation method, which is characterized by: (1) the deformation of the blade is calculated according to the load of each section of the blade, and the calculation formula is:

[0057]

[0058] y i =y i-1 -θ i Δr;

[0059] where θ i is the rotation angle of the i-th blade section, θ i-1 is the rotation angle of the i-1th blade section, E is the elastic modulus of the blade, I(r i ) is the section moment of inertia, y i is the deformation of the i-th blade section, y i-1 is the deformation of the i-1th blade section;

[0060] The tip deformation is the last section y i (i=N) value, taking into account the unit elevation angle and blade cone angle, blade clearance d clearance The calculation formula is as follows:

[0061]

[0062] Where L y , L z is the horizontal and vertical distance from the blade tip, R tower is the tower radius, θ pitch is the blade pitch angle.

[0063] Based on the calculated blade clearance, the present invention also provides a blade clearance protection method, which is characterized by: calculating the blade clearance in real time through the above method, setting the blade clearance safety threshold a;

[0064] If d clearance If it is greater than 1.1a, the unit operates normally without adjustment;

[0065] If d clearance If it is greater than a and less than 1.1a, the crew will issue a warning;

[0066] If d clearance If it is less than a and greater than 0.1a, the unit adjusts the pitch angle to increase the clearance;

[0067] If d clearance If it is less than 0.1a, the unit will shut down immediately.

[0068] The present invention takes the influence of the variable pitch angle into consideration, combines aerodynamic characteristics and structural mechanics analysis, and inverts the loads of each section of the blade through the blade root load, thereby calculating the loads of each section of the blade and the blade clearance. In addition, according to the loads of each section of the blade and the blade clearance, the blade is subjected to blade limit protection and blade clearance protection, thereby achieving an accurate assessment of the blade load state and ensuring the safe operation of the wind turbine.

Claims

1. A method for calculating blade cross-sectional load based on blade root load, characterized in that The following steps are involved: S1. Install a load sensor at the blade root to monitor the blade root load data in real time; S2. Calculate the aerodynamic thrust of each section of the blade based on the aerodynamic characteristics and the relative wind speed of the blade; S3, correcting the calculated aerodynamic thrust of each section of the blade by using the monitored blade root load data; S4. Calculate the load of each section of the blade based on the corrected aerodynamic thrust of each section of the blade.

2. The method for calculating blade cross-sectional load based on blade root load according to claim 1, characterized in that: The aerodynamic thrust F of each blade section in step S2 t (r) is calculated as: Where r is the blade section length, c(r) is the chord length distribution, ρ is the air density, C t (r,β) is the thrust coefficient of the blade section at different pitch angles, obtained through experiments or simulations; V rel is the relative wind speed, and its calculation formula is: Where V hab is the incoming wind speed, measured by the unit anemometer; ω is the impeller angular velocity, and R is the total length of the blade.

3. The method for calculating blade cross-sectional load based on blade root load according to claim 1, characterized in that: The correction calculation formula of the aerodynamic thrust of each section of the blade in step S3 is: where F t (r) corrected is the aerodynamic thrust of each section of the blade after correction, F root,measured The blade root load data obtained by monitoring.

4. The method for calculating blade cross-sectional load based on blade root load according to claim 1, characterized in that: The load calculation formula for each section of the blade in step S4 is: Wherein Δr is the discrete interval, N is the number of cross-sectional segments of the blade, and N=R / Δr.

5. A blade limit protection method based on the blade cross-sectional load according to claim 1, characterized in that: The blade is protected in sections along the span direction, and different limit thresholds γ are determined by the blade material properties and structure in different cross-sections. i ; If the blade section load exceeds the limit threshold value γ of the corresponding section segment i , the tower should be shut down for protection in time.

6. A blade clearance calculation method based on the blade cross-sectional load according to claim 1, characterized in that: (1) The deformation of the blade is calculated based on the load on each section of the blade. The calculation formula is: and i =and i-1 -θ i Δr; where θ i is the rotation angle of the i-th blade section, θ i-1 is the rotation angle of the i-1th blade section, E is the elastic modulus of the blade, I(r i ) is the section moment of inertia, y i is the deformation of the i-th blade section, y i-1 is the deformation of the i-1th blade section; (2) Considering the unit elevation angle and blade cone angle, the blade clearance calculation formula is as follows: where y N is the deformation of the last section of the blade, that is, the deformation of the blade tip, L y , L z is the horizontal and vertical distance from the blade tip, R tower is the tower radius, θ pitch is the blade pitch angle.

7. A blade clearance protection method based on the blade clearance of claim 6, characterized in that: Calculate blade clearance in real time and set blade clearance safety threshold a; If d clearance If it is greater than 1.1a, the unit operates normally without adjustment; If d clearance If it is greater than a and less than 1.1a, the crew will issue a warning; If d clearance Less than a, greater than 0.1a, the unit adjusts the pitch angle to increase the clearance; If d clearance If it is less than 0.1a, the unit will shut down immediately.

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