A method and system for reducing fatigue loads of an offshore wind turbine by using pneumatic damping

Abstract

The present invention discloses a method and system for reducing the fatigue load of an offshore wind turbine by using pneumatic damping, comprising the following steps: S1: Obtain the information of the wind turbine, and set the thresholds of the absolute value of the acceleration of the wind turbine and the idle speed of the wind turbine rotor; S2: Monitor the maximum value of the acceleration of the wind turbine, the real-time wind speed of the hub and the real-time idle speed of the wind turbine rotor, and calculate the minimum pitch angle of the blade according to the information of the wind turbine, the real-time wind speed of the hub and the threshold of the idle speed of the wind turbine rotor; S3: A judgment module judges whether the wind turbine performs pitch adjustment; S4: If pitch adjustment is performed, adjust the pitch angle according to the real-time idle speed of the wind turbine rotor; S5: The wind turbine obtains out-of-plane pneumatic damping based on the blade pitch angle and the idle speed of the wind turbine rotor, thereby reducing the fatigue load of the tower and the foundation. The beneficial effect of the present invention is that it can reduce the fatigue load of the support structure of the offshore wind turbine and improve the safety of the operation of the wind turbine.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind power, and particularly relates to a method and a system for reducing the fatigue load of an offshore wind turbine by using pneumatic damping. Background Art

[0002] Offshore wind farms have the advantages of high wind speed, low turbulence, being basically unaffected by topography, and not occupying land resources. However, at the same time, in addition to being subjected to the conventional loads similar to those of onshore wind turbines, offshore wind turbines are also additionally subjected to external loads such as wave loads, ocean current loads, ice loads, and ship impacts. Among them, the fatigue load on the support structure of the offshore wind turbine mainly comes from wind loads and wave loads. Fatigue load plays a major role in the design of the support structure tower and foundation of the offshore wind turbine. Excessive fatigue load often results in higher material costs during the design process, and it also poses a safety hazard to the already operating wind turbines. Therefore, how to reduce the fatigue load of the support structure of the offshore wind turbine is particularly important in terms of economy and safety.

[0003] In the prior art, during the operation of the wind turbine, generally, the wind turbine is in a rotating state during normal power generation; while in the non-power generation state, the wind turbine is in a stationary state, and at this time, the wind turbine will be subjected to a large fatigue load. In addition, in order to reduce the fatigue load of the tower of the wind turbine in the non-power generation state, some scholars directly let the wind turbine rotate at a low speed. However, according to the operating characteristics of the wind turbine, when the wind and the wave form a large angle, such as 90 degrees, because the blades are in the feathering state, the lateral damping of the wind turbine is large enough, and the left and right swaying of the tower is small, and the wave will not cause a large fatigue load. However, when the angle between the wind and the wave is small, such as 0 degrees, due to the wave action and the small front and rear pneumatic damping in the feathering state of the blades, the front and rear swaying of the tower is large, and a huge fatigue load will be generated. Blindly pitching and idling cannot reduce the fatigue load at all times, but will introduce excessive pitching actions, resulting in large pitching fatigue, causing the pitching system to be overloaded, and reducing the overall life of the wind turbine.

[0004] For example, a "control method of a wind turbine in low wind" disclosed in a Chinese patent document, with the publication number: CN103883468A and the application date: March 13, 2014. This invention improves the utilization rate of the wind turbine in low wind conditions, avoids the long waiting time when starting the machine again, the repeated start-stop of the wind turbine, and the impact on the power grid caused by the repeated disconnection and connection of the wind turbine to the grid, and avoids the power consumption when the wind turbine operates at negative power. However, it has the problem that it cannot reduce the fatigue load of the support structure of the offshore wind turbine. Summary of the Invention

[0005] In view of the deficiency that the existing technology cannot reduce the fatigue load of the support structure of an offshore wind turbine, the present invention proposes a method and system for reducing the fatigue load of an offshore wind power generation set by using aerodynamic damping, which can reduce the fatigue load of the support structure of the offshore wind turbine and improve the safety of the operation of the wind turbine.

[0006] The following is the technical solution of the present invention. A method for reducing the fatigue load of an offshore wind power generation set by using aerodynamic damping includes the following steps:

[0007] S1: An acquisition module acquires information of the wind power generation set, and a setting module sets a threshold value of the absolute value of the acceleration of the wind power generation set and a threshold value of the idling speed of the wind turbine rotor.

[0008] S2: A monitoring module monitors the maximum value of the acceleration of the wind power generation set, the real-time wind speed of the hub and the real-time idling speed of the wind turbine rotor, and an analysis module calculates the minimum pitch angle of the blade according to the information of the wind power generation set, the real-time wind speed of the hub and the threshold value of the idling speed of the wind turbine rotor.

[0009] S3: A judgment module judges whether the wind power generation set performs pitch adjustment.

[0010] S4: If pitch adjustment is performed, a pitch adjustment module adjusts the pitch angle according to the real-time idling speed of the wind turbine rotor to ensure that the real-time idling speed of the wind turbine rotor is not higher than the threshold value of the idling speed of the wind turbine rotor.

[0011] S5: The wind power generation set obtains out-of-plane aerodynamic damping based on the blade pitch angle and the idling speed of the wind turbine rotor, and reduces the fatigue load of the tower and the foundation based on the out-of-plane aerodynamic damping.

[0012] In this solution, the acquisition module acquires information of the wind power generation set, the setting module sets the threshold value of the absolute value of the acceleration of the wind power generation set and the threshold value of the idling speed of the wind turbine rotor, calculates the minimum pitch angle of the blade according to the information of the wind power generation set, the real-time wind speed of the hub and the threshold value of the idling speed of the wind turbine rotor, ensures the real-time idling speed of the wind turbine rotor according to the minimum pitch angle, and thus obtains out-of-plane aerodynamic damping based on the blade pitch angle and the idling speed of the wind turbine rotor, and reduces the fatigue load of the support structure of the offshore wind turbine.

[0013] Preferably, the information of the wind power generation set includes the model and parameters of the wind power generation set.

[0014] Preferably, the threshold value of the absolute value of the acceleration in the non-power generation state is 0.1 m / s 2 , and the threshold value of the idling speed of the wind turbine rotor is 1.4 rpm.

[0015] Preferably, the condition for the wind power generation set to perform pitch adjustment is that the wind power generation set is in the non-power generation state and the absolute value of the acceleration is greater than the threshold value of the absolute value of the acceleration.

[0016] Preferably, the method for adjusting the pitch angle according to the real-time idling speed of the wind turbine is as follows: the pitch-changing module adjusts the pitch angle of the blade, so that the pitch angle slowly changes from about 90 degrees of the pitch angle to the minimum pitch angle. If the real-time idling speed of the wind turbine is too high, the pitch angle is increased; otherwise, the pitch angle is decreased.

[0017] Preferably, a system for reducing the fatigue load of an offshore wind turbine generator by using aerodynamic damping includes:

[0018] A wind turbine generator for wind power generation;

[0019] An acquisition module for acquiring information of the wind turbine generator and connecting to the wind turbine generator;

[0020] A setting module for setting the threshold value of the absolute acceleration of the wind turbine generator and the threshold value of the idling speed of the wind turbine, and connecting to the wind turbine generator;

[0021] A monitoring module for monitoring the maximum acceleration of the wind turbine generator, the wind speed at the hub and the idling speed of the wind turbine, and connecting to the wind turbine generator;

[0022] An analysis module for calculating the minimum pitch angle of the blade according to the information of the wind turbine generator, the real-time wind speed at the hub and the threshold value of the idling speed of the wind turbine, and connecting to the wind turbine generator, the monitoring module and the setting module;

[0023] A judgment module for judging whether the wind turbine generator performs pitch-changing and connecting to the wind turbine generator;

[0024] A pitch-changing module for adjusting the pitch angle according to the real-time idling speed of the wind turbine to ensure that the real-time idling speed of the wind turbine is not higher than the threshold value of the idling speed of the wind turbine, and connecting to the wind turbine generator.

[0025] Preferably, the monitoring module includes a speed sensor and an acceleration sensor.

[0026] The beneficial effects of the present invention are: it can effectively reduce the fatigue loads of the tower and the foundation of the wind turbine generator in the stationary or idling state, and improve the design cost and service safety of the tower and the foundation. Description of the Drawings

[0027] Figure 1 Schematic diagram of a system for reducing the fatigue load of an offshore wind turbine generator by using aerodynamic damping according to the present invention.

[0028] Figure 2 Flowchart of a method for reducing the fatigue load of an offshore wind turbine generator by using aerodynamic damping according to the present invention.

[0029] Figure 3 Time series diagram of the idling speed corresponding to different pitch angles of a method for reducing the fatigue load of an offshore wind turbine generator by using aerodynamic damping according to the present invention.

[0030] Figure 4 The time series diagram of the tower bottom load corresponding to different pitch angles of a method for reducing the fatigue load of an offshore wind turbine generator by using pneumatic damping according to the present invention.

[0031] Figure 5 The comparison diagram of the fatigue load reduction effect at different pitch angles of a method for reducing the fatigue load of an offshore wind turbine generator by using pneumatic damping according to the present invention.

[0032] In the figure: 1. Wind turbine generator; 2. Acquisition module; 3. Setting module; 4. Monitoring module; 5. Analysis module; 6. Judgment module; 7. Pitch-changing module. Detailed implementation manners

[0033] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the drawings.

[0034] Embodiment: As Figure 1 shown, a system for reducing the fatigue load of an offshore wind turbine generator by using pneumatic damping includes:

[0035] A wind turbine generator 1 for wind power generation;

[0036] An acquisition module 2 for acquiring information of the wind turbine generator 1 and connecting to the wind turbine generator 1;

[0037] A setting module 3 for setting the threshold of the absolute value of the acceleration of the wind turbine generator 1 and the threshold of the idle speed of the wind turbine rotor, and connecting to the wind turbine generator 1;

[0038] A monitoring module 4 for monitoring the maximum acceleration, the real-time wind speed of the hub and the idle speed of the wind turbine rotor of the wind turbine generator 1, and connecting to the wind turbine generator 1;

[0039] An analysis module 5 for calculating the minimum pitch angle of the blade according to the information of the wind turbine generator 1, the real-time wind speed of the hub and the threshold of the idle speed of the wind turbine rotor, and connecting to the wind turbine generator 1, the monitoring module 4 and the setting module 3;

[0040] A judgment module 6 for judging whether the wind turbine generator 1 performs pitch-changing, and connecting to the wind turbine generator 1;

[0041] A pitch-changing module 7 for adjusting the pitch angle according to the real-time idle speed of the wind turbine rotor to ensure that the real-time idle speed of the wind turbine rotor is not higher than the threshold of the idle speed of the wind turbine rotor, and connecting to the wind turbine generator 1.

[0042] The acquisition module 2 acquires the model and its parameters of the offshore wind turbine generator set 1. The setting module 3 sets the thresholds of the absolute value of the nacelle acceleration and the threshold of the idle rotation speed of the wind turbine under the non-generating state. The monitoring module 4 monitors in real time the maximum acceleration in the front and rear directions of the nacelle of the wind turbine generator set 1 within one cycle and the wind speed at the hub. The analysis module 5 calculates the minimum pitch angle that the blade can be set at different wind speeds at the hub according to the attributes of the offshore wind turbine generator set 1 and the set maximum idle rotation speed. The judgment module 6 judges whether the unit is in the generating state or the non-generating state according to the operating state of the unit. If it is in the non-generating state, it judges whether the nacelle acceleration satisfies that the absolute value of the nacelle acceleration is greater than the threshold of the absolute value of the nacelle acceleration. If both are satisfied, a pitch change action is triggered. The pitch change module 7 performs a pitch change action on the unit to adjust the pitch angle of the blade, so that the pitch angle of the target offshore unit slowly changes from the feathering state (pitch angle about 90 degrees) to the minimum pitch angle state. The monitoring module 4 monitors in real time the idle rotation speed of the wind turbine of the offshore wind turbine generator set 1, and the pitch change module 7 timely adjusts the size of the blade pitch angle to ensure that the wind turbine speed does not exceed the set maximum wind turbine idle rotation speed. By setting the blade pitch angle and the wind turbine speed, the offshore wind turbine generator set 1 obtains the corresponding aerodynamic damping in the front and rear directions, that is, out-of-plane, and uses this aerodynamic damping to reduce the fatigue load of the tower and foundation caused by wave loads.

[0043] The monitoring module 4 includes a speed sensor and an acceleration sensor. The speed sensor measures the real-time wind speed at the hub and the idle rotation speed of the wind turbine, and the acceleration sensor measures the maximum acceleration.

[0044] The linear superposition of the fatigue loads caused by wind loads and wave loads respectively is not equal to the fatigue load actually received by the wind turbine, because the wind turbine will generate aerodynamic damping when receiving wind loads, and the aerodynamic damping can reduce the fatigue load generated by the wind turbine under the action of wave loads. Reasonably using the aerodynamic damping in different directions can greatly reduce the fatigue load of the support structure of the unit in the non-generating state. Since the wind turbine is facing the oncoming wind direction, when the angle between the wave and the wind is small, the support structure will generate large oscillations in the front and rear directions. It is possible to judge whether the oscillation of the unit in the front and rear directions is too large according to the acceleration in the front and rear directions of the nacelle. When the acceleration is large, the blades are feathered to make the wind turbine rotate to obtain the aerodynamic damping in the front and rear directions, and suppress the oscillation of the unit in the front and rear directions, thereby reducing the fatigue load of the unit.

[0045] Such as Figure 2 shown, a method for reducing the fatigue load of an offshore wind turbine generator set by using aerodynamic damping includes the following steps:

[0046] Step S1: The acquisition module 2 acquires the information of the wind turbine generator set 1, and the setting module 3 sets the threshold of the absolute value of the acceleration of the wind turbine generator set 1 and the threshold of the idle rotation speed of the wind turbine.

[0047] Specifically, the information of the wind turbine 1 includes the model and parameters of the wind turbine 1. The setting module 3 sets the corresponding threshold value NA of the absolute value of the nacelle acceleration in the non-power generation state according to the model and parameters of the offshore wind turbine 1 min = 0.1 m / s 2 and the threshold value RS of the idle speed of the wind turbine max = 1.4 rpm.

[0048] Step S2: The monitoring module 4 monitors the maximum acceleration a of the wind turbine 1 x , the real-time wind speed v of the hub and the real-time idle speed of the wind turbine. The analysis module 5 calculates the minimum pitch angle PBA of the blade according to the information of the wind turbine 1, the real-time wind speed of the hub and the threshold value of the idle speed of the wind turbine min .

[0049] Specifically, the monitoring module 4 monitors the maximum acceleration a of the nacelle of the wind turbine 1 in one cycle in real time x and the real-time wind speed v of the hub. For the convenience of explanation, assume that the wind speed at the hub of the unit is 10.0 m / s at this time, the wave height is 2 m, the wave period is 6.87 s, and the wind and waves are in the same direction. At this time, the maximum acceleration of the nacelle in one movement cycle is 0.4 m / s.

[0050] According to the information of the offshore wind turbine 1 and the threshold value of the idle speed of the wind turbine, calculate the minimum pitch angle PBA that the blade can set at different wind speeds at the hub min , at this time the wind speed at the hub is 10.0 m / s. After calculation, when the idle speed of the unit is 1.4 rpm, the corresponding pitch angle is 50 deg.

[0051] The allowable idle pitch angle is from about 90 degrees of the pitch angle to the minimum pitch angle. If the real-time idle speed of the wind turbine is too large, increase the pitch angle; otherwise, decrease the pitch angle. When the angle between the wind and the wave is small, such as 0 degrees, due to the wave action and the small aerodynamic damping in the front and back of the blade in the feathering state, the sway of the tower in the front and back directions is large, and huge fatigue loads will be generated. Blindly pitching and idling cannot reduce the fatigue load at all times, but will introduce too many pitching actions, resulting in large pitching fatigue, causing the pitching system to be overloaded and reducing the overall life of the wind turbine.

[0052] Step S3: The judgment module 6 judges whether the wind turbine 1 performs pitching.

[0053] Specifically, the judgment module 6 judges whether the wind turbine 1 performs pitching. Pitching is only performed when the wind turbine 1 is in the non-power generation state and the absolute value of the nacelle acceleration is greater than the threshold value of the absolute value of the nacelle acceleration, that is, |a x | > NA min .

[0054] Step S4: If pitch adjustment is performed, the pitch module 7 adjusts the pitch angle according to the real-time idling speed of the wind turbine to ensure that the real-time idling speed of the wind turbine is not higher than the threshold value RS of the wind turbine idling speed max .

[0055] Specifically, through the pitch module 7 of the wind power generation unit 1, the pitch angle of the blade is slowly adjusted so that the pitch angle of the blade changes from the maximum pitch angle in the feathering state to the minimum pitch angle PBA min Change. By adjusting the pitch angle of the blade through the pitch module 7, the pitch angle of the target offshore unit slowly changes from the feathering state (pitch angle about 90 degrees) to the minimum pitch angle PBA min State. Therefore, the idling speed of this unit should be between 0-1.4 rpm, and the corresponding allowable range of the pitch angle is 89-50 deg. The closer the pitch angle is to 50 deg, the more obvious the load reduction effect is. Here, for the convenience of explanation, the cases where the pitch angles are manually set to 50 deg, 70 deg, and 89 deg are respectively simulated and calculated for 60 s. As Figure 3 shown is the idling speed of this unit at different pitch angles.

[0056] The idling speed of the wind turbine of the wind power generation unit 1 is monitored in real time, and the pitch angle is adjusted to ensure that the wind turbine speed is not higher than the threshold value RS of the wind turbine idling speed max . The idling speed of the wind turbine of this offshore wind power generation unit 1 is monitored in real time, and the size of the blade pitch angle is adjusted in time to ensure that the wind turbine speed is not higher than the set maximum wind turbine idling speed RS max , if the idling speed is too large, the pitch angle is opened wider to make it slowly turn towards the 89 deg direction.

[0057] Step S5: The wind power generation unit 1 obtains the out-of-plane aerodynamic damping based on the blade pitch angle and the wind turbine idling speed, and reduces the fatigue loads of the tower and the foundation based on the out-of-plane aerodynamic damping.

[0058] Specifically, the wind turbine obtains the corresponding out-of-plane aerodynamic damping through the blade pitch angle and the wind turbine idling speed, and uses this aerodynamic damping to reduce the fatigue loads of the tower and the foundation. As Figure 4 shown is the time series diagram of the loads at the bottom of the tower (top of the foundation) of this unit at different pitch angles of 50 deg, 70 deg, and 89 deg. According to the rainflow counting method and the equivalent fatigue load calculation formula:[[]]

[0059]

[0060] In the formula, m is n i In the stress range S i The number of cycles, T is the duration on the original time relationship curve, f is the frequency, and here m takes the value of 4; as Figure 5The figure shows the relationship between the pitch angle and the 10-minute equivalent fatigue load of the unit at a wind speed of 10 m / s at the hub, demonstrating the fatigue load reduction effect of the present invention on the offshore wind turbine 1.

[0061] It can effectively reduce the fatigue loads of the tower and foundation of the wind turbine in the stationary or idling state, and will not introduce excessive pitch fatigue, thereby improving the design cost and service safety of the tower and foundation.

Claims

1. A method for reducing the fatigue load of an offshore wind turbine by using pneumatic damping, characterized in that, It includes the following steps: Step S1: The acquisition module acquires the information of the wind turbine generator set, and the setting module sets the thresholds of the absolute value of the acceleration and the idling speed of the wind turbine rotor of the wind turbine generator set; Step S2: The monitoring module monitors the maximum value of the acceleration of the wind turbine generator set, the real-time wind speed of the hub and the real-time idling speed of the wind turbine rotor. The analysis module calculates the minimum pitch angle of the blade according to the information of the wind turbine generator set, the real-time wind speed of the hub and the threshold of the idling speed of the wind turbine rotor; Step S3: The judgment module judges whether the wind turbine generator set performs pitch adjustment; Step S4: If pitch adjustment is performed, the pitch adjustment module adjusts the pitch angle according to the real-time idling speed of the wind turbine rotor to ensure that the real-time idling speed of the wind turbine rotor is not higher than the threshold of the idling speed of the wind turbine rotor; Step S5: The wind turbine generator set obtains the out-of-plane aerodynamic damping based on the blade pitch angle and the idling speed of the wind turbine rotor, and reduces the fatigue loads of the tower and the foundation based on the out-of-plane aerodynamic damping.

2. A method for reducing the fatigue load of an offshore wind turbine by using pneumatic damping according to claim 1, characterized in that The information of the wind turbine generator set includes the model and parameters of the wind turbine generator set.

3. A method for reducing the fatigue load of an offshore wind turbine by using pneumatic damping according to claim 1, characterized in that, The threshold of the absolute value of acceleration in the non-power generation state is 0.1 m / s 2 , and the threshold of the idle speed of the wind turbine is 1.4 rpm.

4. A method for reducing the fatigue load of an offshore wind turbine using pneumatic damping according to claim 1, characterized in that, The condition for the wind turbine generator set to perform pitch adjustment is that the wind turbine generator set is in a non-generating state and the absolute value of the acceleration is greater than the threshold of the absolute value of the acceleration.

5. A method for reducing the fatigue load of an offshore wind turbine using pneumatic damping according to claim 1, characterized in that The allowable idling pitch angle ranges from about 90 degrees of the pitch angle to the minimum pitch angle. If the real-time idling speed of the wind turbine rotor is too large, the pitch angle is increased; otherwise, the pitch angle is decreased.

6. A system for reducing the fatigue load of an offshore wind turbine by using pneumatic damping, which is applicable to the method for reducing the fatigue load of an offshore wind turbine by using pneumatic damping according to any one of claims 1-5, characterized in that, It includes: A wind turbine generator set for wind power generation; An acquisition module for acquiring the information of the wind turbine generator set and connecting to the wind turbine generator set; A setting module for setting the thresholds of the absolute value of the acceleration and the idling speed of the wind turbine rotor of the wind turbine generator set and connecting to the wind turbine generator set; A monitoring module for monitoring the maximum value of the acceleration of the wind turbine generator set, the wind speed at the hub and the idling speed of the wind turbine rotor and connecting to the wind turbine generator set; An analysis module for calculating the minimum pitch angle of the blade according to the information of the wind turbine generator set, the real-time wind speed of the hub and the threshold of the idling speed of the wind turbine rotor, and connecting to the wind turbine generator set, the monitoring module and the setting module; A judgment module for judging whether the wind turbine generator set performs pitch adjustment and connecting to the wind turbine generator set; A pitch adjustment module for adjusting the pitch angle according to the real-time idling speed of the wind turbine rotor to ensure that the real-time idling speed of the wind turbine rotor is not higher than the threshold of the idling speed of the wind turbine rotor and connecting to the wind turbine generator set.

7. The system for reducing the fatigue load of an offshore wind turbine generator set by using aerodynamic damping according to claim 6, wherein the monitoring module includes a speed sensor and an acceleration sensor.

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