A fan small-clearance safety control method based on blade root load negative shear characteristics

Abstract

This invention discloses a wind turbine low-headroom safety control method based on blade root load negative shear characteristics. The method includes: real-time acquisition of load data in the blade root flapping direction of three blades using load sensors; acquisition of wind speed, rotational speed, and power data of the wind turbine; acquisition of the impeller azimuth angle; calculation of blade negative shear load and overall impeller negative shear load; three-level risk classification based on the negative shear load of each blade, the overall impeller negative shear load, and their historical load trends; and control of the pitch angle actuator to reduce the negative shear load and avoid tower sweep risk. This invention, by monitoring the blade root flapping direction load of the three blades and dividing the turbine into upper and lower halves by the impeller azimuth angle, can accurately identify the negative shear load state and implement graded control. This method can be adapted to different turbine models and installation scenarios, thereby avoiding tower sweep risk and protecting critical components of the unit.

Description

Technical Field

[0001] This invention relates to the field of wind turbine control technology, and in particular to a wind turbine safety control method based on the negative shear characteristics of blade root load. Background Technology

[0002] Wind turbine generators are susceptible to safety hazards under low headroom conditions (i.e., a small headroom between the rotor and the tower). Among these hazards, negative shear loads caused by negative wind shear are one of the important causes of structural damage to the generator and tower sweeping accidents.

[0003] The core of negative shear load is that when wind speed decreases with increasing height (i.e., negative wind shear, characterized by a negative wind shear index), the wind speed in the lower blade area of ​​the rotor is higher than in the upper area. This causes aerodynamic loads and gravitational loads to superimpose in the transmission chain direction, significantly increasing the mechanical load on key components such as the main shaft, gearbox, and tower. This load condition is the opposite of conventional positive wind shear (where wind speed increases with increasing height). Under positive wind shear, the upper part of the rotor experiences greater forces, and some of the gravitational load is offset by aerodynamic forces. However, under negative wind shear, the lower part of the rotor experiences even stronger forces, causing the blades to be closer to the tower, resulting in a small headroom. In extreme cases, this can lead to blade sweeping the tower, causing blade damage. In more severe cases, it can lead to tower damage or even tower collapse.

[0004] Existing wind turbine clearance control systems mostly rely on solutions such as lidar, millimeter wave, and video algorithms to identify the clearance value of the unit. The calculated clearance value is fed back to the main control PLC, and the pitch is adjusted to avoid the unit sweeping the tower. However, the clearance value calculation is affected by environmental conditions. Extreme weather such as heavy fog and heavy rain can seriously affect the clearance value measurement.

[0005] Currently, some published patents explore how to achieve airspace safety control. For example, CN118669264A proposes a method to predict extreme negative shear loads based on meteorological information and the real-time operating status of the wind turbine. Its main problem is that the turbine's operating parameters are limited to single data such as wind speed and direction, making it impossible to measure the actual wind speed distribution above and below the rotor cross-section, resulting in limited accuracy. CN112610411A attempts to identify negative shear loads using tower overturning moment values ​​to implement an IPC independent pitch strategy to protect the turbine tower's airspace; however, the turbine exhibits yaw. Furthermore, the unit is not an ideal rigid body. The tower overturning moment and the nacelle pitch load (the unit's negative shear load) are somewhat different. The tower overturning moment can reflect the unit's negative shear load in a certain direction, but it cannot reflect the negative shear load acting on the impeller and the overall blade deformation state. This will lead to the inability to identify the negative shear load under certain extreme operating conditions. CN118911917A proposed a method to identify the negative shear load based on the azimuth angle signal of each blade and the blade tip displacement signal in the out-of-plane direction of the impeller. However, the blade tip displacement signal in the out-of-plane direction of the impeller is difficult to obtain and has low reliability.

[0006] Therefore, how to directly use the blade root load to reflect the real aerodynamic load and thus accurately identify the negative shear load is a technical problem that urgently needs to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a wind turbine low headroom safety control method based on the negative shear characteristics of blade root load. By monitoring the blade root flapping direction load of the three blades and dividing the upper and lower halves by the impeller azimuth angle, the negative shear load state can be accurately identified and controlled in stages. This method can be adapted to different turbine models and installation scenarios, thereby avoiding tower sweep risk and protecting key components of the unit.

[0008] This invention provides the following solutions:

[0009] This invention provides a method for safety control of wind turbines with small headroom based on the negative shear characteristics of blade root load, the method comprising:

[0010] S1. Real-time load data of the three blade roots flapping direction is collected using load sensors, and wind speed, rotation speed and power data of the fan are collected to obtain the impeller azimuth angle.

[0011] S2. Calculate the negative shear load on the blades and the overall negative shear load on the impeller using the load data of the blade root flapping direction and the impeller azimuth angle.

[0012] S3. Risk classification is performed based on the negative shear load of each blade, the overall negative shear load of the impeller, and their historical load trends.

[0013] S4. Based on risk rating, control the pitch angle actuator to reduce negative shear load and avoid tower sweep risk.

[0014] Furthermore, step S1 obtains the impeller azimuth angle using one of the following methods:

[0015] Method 1: For units equipped with a complete SCADA system, directly read the hub azimuth data from the SCADA system as the impeller azimuth.

[0016] Method 2: For units equipped with hub azimuth sensors, the data from the hub azimuth sensors is collected by the main control PLC of the wind turbine and used as the impeller azimuth angle.

[0017] Method 3: Collect blade oscillation load data, and use the oscillation load period characteristics to calculate the hub azimuth angle as the impeller azimuth angle.

[0018] Furthermore, the blade negative shear load mentioned in step S2 is calculated through the following process:

[0019] a1. Assuming the impeller azimuth angle is 0° when the first blade is vertically upward, distinguish the blades based on the current impeller azimuth angle, and calculate the negative shear load of each blade using the following formula:

[0020] ,

[0021] ,

[0022] Among them, M flap_top M is the equivalent upper half-plane load on the blade. flap_bottom M is the equivalent lower half-plane load on the blade. flap The load data of the blade root flapping direction collected in step S1 is: when the blade is the first blade, θ is the impeller azimuth angle + 90°; when the blade is the second blade, θ is the impeller azimuth angle + 210°; and when the blade is the third blade, θ is the impeller azimuth angle + 330°.

[0023] a2、M flap_bottom -M flap_top This is the equivalent negative shear load on a single blade. The negative shear loads of the first, second, and third blades are denoted as M, respectively. B1 M B2 and M B3 .

[0024] Furthermore, the impeller negative shear load mentioned in step S2 is calculated through the following process: In each impeller rotation cycle, the total flapping load of all blades in the upper half plane and the total flapping load of all blades in the lower half plane are calculated using the equivalent upper half plane load and the equivalent lower half plane load of each blade. The difference between the two is the impeller negative shear load.

[0025] Furthermore, step S3 includes the following process: The adaptive threshold is corrected based on the real-time wind speed, rotational speed, and power data collected in step S1; the negative shear load is classified into three risk levels:

[0026] Level 1: General risk. If the negative shear load of any blade or impeller as a whole exceeds the corrected adaptive threshold but there is no significant fluctuation and the characteristic value does not show a cumulative increase within 1 to 2 consecutive impeller rotation cycles, it is judged that the negative shear load is large and conventional load control is required.

[0027] Level 2: Dangerous risk. The negative shear load of any blade or impeller as a whole fluctuates rapidly, i.e. the fluctuation frequency exceeds the preset frequency threshold. Regardless of whether it exceeds the adaptive threshold, it is judged as a potential risk of tower sweeping and requires rapid load control.

[0028] Level 3: Emergency Risk. The negative shear load on any blade or impeller as a whole increases cumulatively over three or more consecutive impeller rotation cycles, and the growth rate exceeds the preset rate threshold. This is considered an extremely high risk of tower sweeping and requires strong intervention load control.

[0029] Furthermore, the adaptive threshold is corrected using the following logic: the higher the wind speed, the faster the rotation speed, and the greater the power, the higher the adaptive threshold is.

[0030] Furthermore, in step S4, under each risk level, the pitch angle actuator performs the following actions respectively:

[0031] Level 1: When an IPC system is available, the blades with excessive negative shear loads are individually fine-tuned in pitch angle, with the adjustment range being the preset base range; when an IPC system is not available, the three blades are uniformly fine-tuned in pitch angle to reduce blade aerodynamic loads and avoid load superposition.

[0032] Level 2: When equipped with an IPC system, each blade is individually and rapidly adjusted, with an adjustment range of 1.5 to 2 times the base range, increasing the adjustment rate by 50%; when not equipped with an IPC system, all three blades are adjusted uniformly and rapidly to quickly reduce the overall aerodynamic load on the impeller and suppress load fluctuations.

[0033] Level 3: When an IPC system is available, each blade is individually subjected to strong intervention pitch adjustment, with the adjustment range being 2 to 3 times the base range and the adjustment rate increasing by 100%. When an IPC system is not available, all three blades are subjected to unified strong intervention pitch adjustment. If the load does not decrease after pitch adjustment, the unit can be triggered to operate at reduced power until the negative shear load drops to a safe range, thus completely avoiding tower sweeping accidents.

[0034] The beneficial effects of this invention based on its technical solution are as follows:

[0035] (1) Accurate identification of negative shear load: Based on the waving direction load of the three blade roots, this invention calculates the negative shear load characteristic value of a single blade and the impeller as a whole. Combined with the load difference between the upper and lower halves of the impeller, it accurately captures the true state of negative shear load and overcomes the problem of existing headroom identification technology being affected by extreme environments.

[0036] (2) Intelligent classification judgment logic: This invention establishes a three-level risk judgment system based on adaptive threshold (combined with wind speed, rotational speed and power correction), covering three negative shear load states: "general load exceeding the standard, rapid fluctuation, and continuous cumulative growth", accurately matching different risk levels and avoiding over-control or under-control.

[0037] (3) Diversified azimuth angle acquisition: This invention provides three impeller azimuth angle acquisition methods, which are compatible with units with different hardware configurations (with SCADA, without SCADA, and low-cost retrofit), with strong compatibility and reduced unit retrofit and deployment costs.

[0038] (4) Differentiated control strategy: This invention combines whether the unit has an independent pitch control system (IPC) and adopts a differentiated control method of "individual pitch control / unified pitch control", which takes into account both control accuracy and engineering feasibility. It is also compatible with different aircraft types on land and at sea, and the threshold can be set according to the aircraft type.

[0039] (5) System integration: The present invention can achieve collaborative work through the hardware architecture of the wind turbine itself (main control PLC, blade root sensor, communication module, etc.), and use a common communication protocol to ensure stable data transmission. The control logic runs on the existing wind turbine main control PLC, without the need to add additional core control hardware. The modification is small and the implementation is strong. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the process of the present invention.

[0042] Figure 2 A schematic diagram showing the sensor deployment locations.

[0043] Figure 3 This is a schematic diagram for calculating the negative shear load on a single blade.

[0044] Figure 4 This is a schematic diagram of the flapping load and blade azimuth angle during one rotation cycle of the blade.

[0045] Among them, 1-load sensor. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the protection scope of the embodiments of the present invention.

[0047] This embodiment provides a wind turbine small headroom safety control method based on the negative shear characteristics of blade root load, referring to... Figure 1 The method includes:

[0048] S1. Reference Figure 2 The system uses three load sensors deployed at the blade roots to collect load data in the flapping direction of the three blade roots in real time, and also collects wind speed, rotational speed, and power data of the wind turbine to obtain the impeller azimuth angle. Depending on the hardware environment, the impeller azimuth angle can be obtained through one of the following three methods:

[0049] Method 1: For units equipped with a complete SCADA (Supervisory Control And Data Acquisition) system, directly read the hub azimuth angle data from the SCADA system as the impeller azimuth angle;

[0050] Method 2: For units equipped with hub azimuth sensors, the data from the hub azimuth sensors is collected by the main control PLC of the wind turbine and used as the impeller azimuth angle.

[0051] Method 3: Collect blade oscillation load data, and use the oscillation load period characteristics to calculate the hub azimuth angle as the impeller azimuth angle.

[0052] S2. Calculate the negative shear load on the blades and the overall negative shear load on the impeller using the load data of the blade root flapping direction and the impeller azimuth angle.

[0053] Reference Figure 3 and Figure 4 The negative shear load of a single blade is calculated through the following process:

[0054] a1. Assuming the impeller azimuth angle is 0° when the first blade is vertically upward, distinguish the blades based on the current impeller azimuth angle, and calculate the negative shear load of each blade using the following formula:

[0055] ,

[0056] ,

[0057] Among them, M flap_top M is the equivalent upper half-plane load on the blade. flap_bottom M is the equivalent lower half-plane load on the blade. flap The load data of the blade root flapping direction collected in step S1 is: when the blade is the first blade, θ is the impeller azimuth angle + 90°; when the blade is the second blade, θ is the impeller azimuth angle + 210°; and when the blade is the third blade, θ is the impeller azimuth angle + 330°.

[0058] a2、M flap_bottom -M flap_top This is the equivalent negative shear load on a single blade. The negative shear loads of the first, second, and third blades are denoted as M, respectively. B1 M B2 and M B3 .

[0059] The overall negative shear load of the impeller is calculated through the following process: In each impeller rotation cycle, the total flapping load of all blades in the upper half plane and the total flapping load of all blades in the lower half plane are calculated using the equivalent upper half plane load and the equivalent lower half plane load of each blade. The difference between the two is the negative shear load of the impeller.

[0060] S3. Risk classification is performed based on the negative shear load of each blade, the overall negative shear load of the impeller, and their historical load trends. Specifically, the adaptive threshold is first corrected by combining the real-time wind speed, rotational speed, and power data collected in step S1, using the following logic: the higher the wind speed, the faster the rotational speed, and the greater the power, the higher the adaptive threshold should be appropriately increased. This can be dynamically adjusted using a PID (Proportional Integral Derivative) algorithm.

[0061] Negative shear loads are classified into three risk levels:

[0062] Level 1: General risk. If the negative shear load of any blade or impeller as a whole exceeds the corrected adaptive threshold but there is no significant fluctuation and the characteristic value does not show a cumulative increase within 1 to 2 consecutive impeller rotation cycles, it is judged that the negative shear load is large and conventional load control is required.

[0063] Level 2: Dangerous risk. The negative shear load of any blade or impeller as a whole fluctuates rapidly, i.e. the fluctuation frequency exceeds the preset frequency threshold. Regardless of whether it exceeds the adaptive threshold, it is judged as a potential risk of tower sweeping and requires rapid load control.

[0064] Level 3: Emergency Risk. The negative shear load on any blade or impeller as a whole increases cumulatively over three or more consecutive impeller rotation cycles, and the growth rate exceeds the preset rate threshold. This is considered an extremely high risk of tower sweeping and requires strong intervention load control.

[0065] S4. Utilize the CANopen communication module to achieve communication between the blade root load sensor system and the wind turbine main control PLC (Programmable Logic Controller), and control the blade pitch angle actuator's actions based on risk level assessment:

[0066] Level 1: When equipped with an IPC (Individual Pitch Control) system, the blades with excessive negative shear loads are individually fine-tuned in pitch angle, with the adjustment range being the preset base range; when not equipped with an IPC system, the pitch angles of all three blades are fine-tuned uniformly to reduce blade aerodynamic loads and avoid load superposition.

[0067] Level 2: When equipped with an IPC system, each blade is individually and rapidly adjusted, with an adjustment range of 1.5 to 2 times the base range, increasing the adjustment rate by 50%; when not equipped with an IPC system, all three blades are adjusted uniformly and rapidly to quickly reduce the overall aerodynamic load on the impeller and suppress load fluctuations.

[0068] Level 3: When an IPC system is available, each blade is individually subjected to strong intervention pitch adjustment, with the adjustment range being 2 to 3 times the base range and the adjustment rate increasing by 100%. When an IPC system is not available, all three blades are subjected to unified strong intervention pitch adjustment. If the load does not decrease after pitch adjustment, the unit can be triggered to operate at reduced power until the negative shear load drops to a safe range, thus completely avoiding tower sweeping accidents.

[0069] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0070] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0071] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for safety control of wind turbines with low headroom based on the negative shear characteristics of blade root load, characterized in that, The method includes: S1. Real-time load data of the three blade roots flapping direction is collected using load sensors, and wind speed, rotation speed and power data of the fan are collected to obtain the impeller azimuth angle. S2. Calculate the negative shear load on the blades and the overall negative shear load on the impeller using the load data of the blade root flapping direction and the impeller azimuth angle. S3. Risk classification is performed based on the negative shear load of each blade, the overall negative shear load of the impeller, and their historical load trends. S4. Based on risk rating, control the pitch angle actuator to reduce negative shear load and avoid tower sweep risk.

2. The wind turbine small headroom safety control method based on blade root load negative shear characteristics according to claim 1, characterized in that: Step S1 obtains the impeller azimuth angle using one of the following methods: Method 1: For units equipped with a complete SCADA system, directly read the hub azimuth data from the SCADA system as the impeller azimuth. Method 2: For units equipped with hub azimuth sensors, the data from the hub azimuth sensors is collected by the main control PLC of the wind turbine and used as the impeller azimuth angle. Method 3: Collect blade oscillation load data, and use the oscillation load period characteristics to calculate the hub azimuth angle as the impeller azimuth angle.

3. The wind turbine small headroom safety control method based on blade root load negative shear characteristics according to claim 1, characterized in that: The blade negative shear load mentioned in step S2 is calculated through the following process: a1. Assuming the impeller azimuth angle is 0° when the first blade is vertically upward, distinguish the blades based on the current impeller azimuth angle, and calculate the negative shear load of each blade using the following formula: ， ， Among them, M flap_top M is the equivalent upper half-plane load on the blade. flap_bottom M is the equivalent lower half-plane load on the blade. flap The load data of the blade root flapping direction collected in step S1 is: when the blade is the first blade, θ is the impeller azimuth angle + 90°; when the blade is the second blade, θ is the impeller azimuth angle + 210°; and when the blade is the third blade, θ is the impeller azimuth angle + 330°. a2、M flap_bottom -M flap_top This is the equivalent negative shear load on a single blade. The negative shear loads of the first, second, and third blades are denoted as M, respectively. B1 M B2 and M B3 .

4. The wind turbine small headroom safety control method based on blade root load negative shear characteristics according to claim 3, characterized in that: The impeller negative shear load mentioned in step S2 is calculated through the following process: In each impeller rotation cycle, the total flapping load of all blades in the upper half plane and the total flapping load of all blades in the lower half plane are calculated using the equivalent upper half plane load and the equivalent lower half plane load of each blade. The difference between the two is the impeller negative shear load.

5. The wind turbine small headroom safety control method based on blade root load negative shear characteristics according to claim 1, characterized in that: Step S3 includes the following processes: Based on the real-time wind speed, rotational speed, and power data collected in step S1, the adaptive threshold is corrected, and the negative shear load is classified into three risk levels: Level 1: General risk. If the negative shear load of any blade or impeller as a whole exceeds the corrected adaptive threshold but there is no significant fluctuation and the characteristic value does not show a cumulative increase within 1 to 2 consecutive impeller rotation cycles, it is judged that the negative shear load is large and conventional load control is required. Level 2: Dangerous risk. The negative shear load of any blade or impeller as a whole fluctuates rapidly, i.e. the fluctuation frequency exceeds the preset frequency threshold. Regardless of whether it exceeds the adaptive threshold, it is judged as a potential risk of tower sweeping and requires rapid load control. Level 3: Emergency Risk. The negative shear load on any blade or impeller as a whole increases cumulatively over three or more consecutive impeller rotation cycles, and the growth rate exceeds the preset rate threshold. This is considered an extremely high risk of tower sweeping and requires strong intervention load control.

6. The wind turbine small headroom safety control method based on blade root load negative shear characteristics according to claim 5, characterized in that: The adaptive threshold is corrected using the following logic: the higher the wind speed, the faster the rotation speed, and the greater the power, the higher the adaptive threshold is.

7. The wind turbine small headroom safety control method based on blade root load negative shear characteristics according to claim 5, characterized in that: In step S4, under each risk level, the pitch angle actuator performs the following actions: Level 1: When an IPC system is available, the blades with excessive negative shear loads are individually fine-tuned in pitch angle, with the adjustment range being the preset base range; when an IPC system is not available, the three blades are uniformly fine-tuned in pitch angle to reduce blade aerodynamic loads and avoid load superposition. Level 2: When equipped with an IPC system, each blade is individually and rapidly adjusted, with an adjustment range of 1.5 to 2 times the base range, increasing the adjustment rate by 50%; when not equipped with an IPC system, all three blades are adjusted uniformly and rapidly to quickly reduce the overall aerodynamic load on the impeller and suppress load fluctuations. Level 3: When an IPC system is available, each blade is individually subjected to strong intervention pitch adjustment, with the adjustment range being 2 to 3 times the base range and the adjustment rate increasing by 100%. When an IPC system is not available, all three blades are subjected to unified strong intervention pitch adjustment. If the load does not decrease after pitch adjustment, the unit can be triggered to operate at reduced power until the negative shear load drops to a safe range, thus completely avoiding tower sweeping accidents.

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