Blade shimmy bending moment limit load reduction method based on impeller azimuth angle

Abstract

The invention discloses a blade shimmy bending moment limit load reduction method based on an impeller azimuth angle, which comprises the following steps: S1.1, acquiring the azimuth angle of a blade on an impeller rotating plane; s1.2, judging whether the fan is in a converter load shedding working condition or not; s1.3, judging whether the azimuth angle of a blade in advance of nine o'clock from the clockwise direction is smaller than a set azimuth angle or not at the load shedding moment, if so, performing synchronous control on the three blades by taking the maximum blade angle as a reference, and if not, entering the next step; s1.4, paddle opening or paddle closing control is conducted on the blades, and paddle opening is stopped after the paddle opening amplitude of the blades reaches a set threshold value; s1.5, after the blades reach nine o'clock, the blades are collected at a third set speed; and S1.6, judging whether the three blades respectively finish one paddle opening action or not, if so, performing synchronous control on the three blades of the fan by taking the maximum paddle angle as a reference, and if not, returning to the step S1.4. On the premise that the operation power of the wind driven generator does not need to be reduced, the shimmy bending moment limit load of each section of the blade can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a method for reducing the ultimate load of blade flapping moment based on the azimuth angle of the impeller. Background Art

[0002] In direct-drive, semi-direct-drive, and doubly-fed wind turbines, when a serious fault occurs in the converter or the alternator, and for doubly-fed wind turbines, when a grid fault occurs, the converter will trigger a load shedding control action in which the electromagnetic torque is directly reduced to zero without delay, which easily leads to the dominant ultimate load of the blade flapping moment at each airfoil section.

[0003] If the converter load shedding action occurs when the wind turbine is operating near the cut-out wind speed, the control can adopt a soft cut-out method of reducing the output power of the wind turbine near the cut-out wind speed and when the operating state of the wind turbine is normal, to reduce the blade flapping moment load at each section under the converter load shedding action. However, when the converter load shedding action occurs in the normal power generation operating range outside the cut-out wind speed, since the wind turbine cannot operate at a reduced power, the maximum value of the blade flapping moment load cannot be reduced. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for reducing the ultimate load of blade flapping moment based on the azimuth angle of the impeller. For the operating range of the wind turbine from the rated speed wind speed to the cut-out wind speed, when a converter load shedding condition occurs, based on the azimuth angle input signal, without reducing the operating power of the wind turbine, the ultimate load of the blade flapping moment at each section can be effectively reduced.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A method for reducing the ultimate load of blade flapping moment based on the azimuth angle of the impeller, which is used to increase the minimum value of the blade flapping moment under the converter load shedding condition, including the steps:

[0007] S1.1. In the grid-connected power generation mode of the wind turbine, the azimuth angle of each blade of the wind turbine in the impeller rotation plane is obtained in real time;

[0008] S1.2. Determine whether the wind turbine is in the converter load shedding condition. If so, proceed to step S1.3; if not, end;

[0009] S1.3. Determine whether there is a blade whose azimuth angle from the clockwise direction before 9 o'clock is less than the set azimuth angle at the moment of load shedding. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle, and after synchronous control, each of the three blades is feathered to the set feathered position. If not, proceed to step S1.4;

[0010] S1.4. When the azimuth angles of the three blades from the clockwise direction ahead of the azimuth at 9 o'clock exceed the set azimuth angle, for the blades rotating between 5 o'clock and 9 o'clock, the blades are pitched at the first set rate, and for the remaining blades, they are feathered at the second set rate. After the pitching amplitude of the blades reaches the set threshold, stop pitching.

[0011] S1.5. After the blades reach 9 o'clock, feather them at the third set rate.

[0012] S1.6. Determine whether each of the three blades has completed a pitching action. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle, and after synchronous control, each of the three blades feathers to the set feathering position. If not, return to step S1.4.

[0013] Furthermore, an absolute encoder installed inside the hub and rotating with the main shaft is used to identify the azimuth angle of each blade in the impeller rotation plane.

[0014] Furthermore, the set azimuth angle is 20deg.

[0015] Furthermore, the three blades are sequentially different in azimuth angle by 120deg in the impeller rotation plane.

[0016] A method for reducing the extreme load of blade flapping moment based on impeller azimuth angle, which is used to reduce the maximum value of blade flapping moment under the condition of converter load shedding, includes the steps

[0017] S2.1. In the grid-connected power generation mode of the wind turbine, the azimuth angle of each blade of the wind turbine in the impeller rotation plane is obtained in real time.

[0018] S2.2. Determine whether the wind turbine is in the converter load shedding condition. If so, enter step S2.3. If not, end.

[0019] S2.3. Determine whether at the moment of load shedding, the azimuth angle of any blade lagging behind 3 o'clock from the clockwise direction is less than the set azimuth angle. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle, and after synchronous control, each of the three blades feathers to the set feathering position. If not, enter step S2.4.

[0020] S2.4. When the azimuth angles of the three blades from the clockwise direction lagging behind 3 o'clock exceed the set azimuth angle, for the blades rotating between 11 o'clock and 3 o'clock, feather them at the fourth set rate, and for the remaining blades, feather them at the fifth set rate. After the feathering amplitude of the blades reaches the set threshold, stop feathering.

[0021] S2.5. After the blades reach 3 o'clock, feather them at the sixth set rate.

[0022] S2.6. Determine whether each of the three blades has completed a pitch - down operation once. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle, and after synchronous control, each of the three blades pitches down to the set feathering position. If not, return to step S2.4.

[0023] Further, an absolute encoder installed inside the hub and rotating with the main shaft is used to identify the azimuth angle of each blade in the plane of the impeller rotation.

[0024] Further, the set azimuth angle is 20deg.

[0025] Further, the three blades are sequentially different in azimuth angle by 120deg in the plane of the impeller rotation.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] The load - reduction method of the present invention is simple to operate and low in cost. For various types of wind turbine generators, in a relatively wide wind speed operating range, without reducing the output power of the wind turbine, it can effectively reduce the ultimate load of the flapping moment of each cross - section of the blade under the condition of the converter shedding load. Description of the Drawings

[0028] Figure 1 It is the control flow chart of the ultimate load - reduction method in Embodiment 1.

[0029] Figure 2 It is the control flow chart of the ultimate load - reduction method in Embodiment 2.

[0030] Figure 3 It is the scatter plot of the root flapping moment VS the impeller azimuth angle at a steady wind speed of 10m / s.

[0031] Figure 4 It is the scatter plot of the root flapping moment VS the impeller azimuth angle at a steady wind speed of 18m / s.

[0032] Figure 5 It is the schematic diagram of increasing the ultimate load - reduction of the algebraic minimum value of the blade flapping moment under the condition of the converter shedding load.

[0033] Figure 6 It is the schematic diagram of reducing the ultimate load - reduction of the maximum value of the blade flapping moment under the condition of the converter shedding load.

[0034] Figure 7 It is the scatter plot of the root flapping moment VS the impeller azimuth angle under the condition of the converter shedding load in the standard scheme.

[0035] Figure 8 It is the operating time sequence of the blade pitch angles of the three blades under the condition of the converter shedding load in the standard scheme.

[0036] Figure 9 The operating time sequence of the blade pitch angles of the three blades under the load reduction scheme of the converter during the load shedding condition of the present invention.

[0037] Figure 10 The operating time sequence of the root flap bending moment of the three blades under the standard scheme of the converter during the load shedding condition.

[0038] Figure 11 The operating time sequence of the root flap bending moment of the three blades under the load reduction scheme of the converter during the load shedding condition of the present invention. Detailed implementation manners

[0039] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] Embodiment 1:

[0041] This embodiment discloses a method for reducing the extreme load of the blade flap bending moment based on the impeller azimuth angle. First, the three blades of the wind turbine are defined as Blade 1, Blade 2, and Blade 3 respectively. The vertical upward direction of Blade 1 is defined as the impeller azimuth angle of 0 deg. When the impeller rotates clockwise, the impeller azimuth angle increases, and the maximum value of the impeller azimuth angle is 360 deg, and then it starts to increase again from 0 deg. In the impeller rotation plane, Blade 1-----Blade 2-----Blade 3 are arranged clockwise.

[0042] When the impeller azimuth angle is 90 deg, Blade 1 rotates to the three o'clock position of the clock. When the impeller azimuth angle is 270 deg, Blade 1 rotates to the nine o'clock position of the clock. When the impeller azimuth angle is 330 deg, Blade 2 rotates to the three o'clock position of the clock. When the impeller azimuth angle is 150 deg, Blade 2 rotates to the nine o'clock position of the clock. When the impeller azimuth angle is 210 deg, Blade 3 rotates to the three o'clock position of the clock. When the impeller azimuth angle is 30 deg, Blade 3 rotates to the nine o'clock position of the clock.

[0043] As Figure 3 、 Figure 4 shown, the scatter diagrams of the root flap bending moment of the three blades and the impeller azimuth angle under the steady winds of 10 m / s and 18 m / s respectively are presented. The maximum value of the flap bending moment appears near the three o'clock position of the clock when each of the three blades rotates to that position. As Figure 6 shown, it is composed of the superposition of the maximum values of the distributed aerodynamic moment and the distributed gravitational moment. The algebraic minimum value of the flap bending moment appears near the nine o'clock position of the clock when each of the three blades rotates to that position. As Figure 5 shown, it is composed of the subtraction of the maximum values of the distributed aerodynamic moment and the distributed gravitational moment. FromFigure 3 , Figure 4 It can be seen from the operation timing of Figure 4 that the maximum value of the flapping moment of the three blades decreases as the wind speed, i.e., the blade angle, increases, while the minimum algebraic value of the flapping moment increases as the wind speed, i.e., the blade angle, decreases.

[0044] As Figure 7 shown, in the converter load rejection condition, the minimum algebraic value of the flapping moment of the three blades still appears near the nine o'clock position of the clock when each blade rotates to it.

[0045] Based on the above analysis, in the grid-connected power generation mode of the wind turbine, the operation timing of the flapping moment of each blade presents a sine wave with a frequency of 1 times the impeller rotation frequency. When the blade rotates to near the three o'clock position of the clock in the impeller rotation plane, the sine wave of the flapping moment timing appears a peak due to the superposition of the maximum distributed gravitational moment and the distributed aerodynamic moment; when rotating to near the nine o'clock position of the clock, the sine wave of the flapping moment timing appears a trough due to the distributed aerodynamic moment minus the maximum distributed gravitational moment; from the rated wind speed to the cut-out wind speed, as the wind speed increases, under the condition that the wind turbine operates without power limitation, the peak of the sine wave of the blade flapping moment gradually decreases, that is, the maximum value of the flapping moment decreases; while the absolute value of the trough of the sine wave of the blade flapping moment gradually increases, that is, the minimum algebraic value of the flapping moment decreases.

[0046] In the converter load rejection condition, when the absolute value of the peak or trough of the sine wave of the blade flapping moment increases, the corresponding higher peak still appears near the three o'clock position of the clock, and the corresponding larger trough also appears near the nine o'clock position of the clock.

[0047] In order to reduce the absolute value of the trough of the sine wave of the blade flapping moment after the converter load rejection, if the azimuth angle difference of the three blades in the clockwise direction is more than 20 deg ahead of the nine o'clock position of the clock in the impeller rotation plane at the load rejection moment, before the blade rotates to near the nine o'clock position of the clock, a certain reduction in the blade pitch angle of the corresponding blade can be completed, and by increasing the angle of attack and lift coefficient of each section of the blade, the aerodynamic moment can be increased while ensuring that no stall occurs at each section. As Figure 5 shown, since the maximum value of the distributed gravitational moment depends on the blade mass and cannot be adjusted after the blade aerodynamics and structure are finalized, the above operation can effectively increase the minimum algebraic value of the blade flapping moment.

[0048] As Figure 1 shown, the specific steps of the load reduction method for increasing the minimum algebraic value of the blade flapping moment in this embodiment are as follows:

[0049] S1.1. In the grid-connected power generation mode of the wind turbine, the azimuth angle of each blade of the wind turbine in the impeller rotation plane is obtained in real time; specifically, the azimuth angle of each blade in the impeller rotation plane can be identified by an absolute encoder installed in the hub and rotating with the main shaft;

[0050] S1.2. Determine whether the fan is in the converter load shedding condition. If so, proceed to step S1.3; if not, end.

[0051] S1.3. Determine whether the azimuth angle of any blade from the clockwise direction ahead of the nine o'clock position is less than the set azimuth angle (set to 20 deg in this embodiment) at the moment of load shedding. If so, synchronously control the three blades of the fan based on the maximum blade angle, and after synchronous control, each of the three blades pitches to the set feathering position. If not, proceed to step S1.4.

[0052] S1.4. When the azimuth angles of all three blades from the clockwise direction ahead of the nine o'clock position exceed the set azimuth angle, for the blade rotating between five o'clock and nine o'clock, pitch it at the first set rate (i.e., set rate 1), and for the remaining blades, feather them at the second set rate (i.e., set rate 2). Stop pitching when the pitching amplitude of the blade reaches the set threshold. The range of the first set rate and the second set rate is 0.5 - 3 deg / s.

[0053] S1.5. After the blade reaches the nine o'clock position, feather it at the third set rate (i.e., set rate 3). The range of the third set rate is 0.5 - 3 deg / s.

[0054] S1.6. In order to reduce the absolute value of the sine wave trough of the blade flapping moment after the converter load shedding, each of the three blades reduces the blade angle by a certain amount before the nine o'clock position at most once. Therefore, determine whether each of the three blades has completed a pitching action. If so, synchronously control the three blades of the fan based on the maximum blade angle, and after synchronous control, each of the three blades pitches to the set feathering position. If not, return to step S1.4.

[0055] Embodiment 2:

[0056] This embodiment discloses a method for reducing the ultimate load of the blade flapping moment based on the impeller azimuth angle. The difference between this embodiment and Embodiment 1 is that the load reduction method in this embodiment is used to reduce the maximum value of the blade flapping moment under the converter load shedding condition.

[0057] In order to reduce the peak amplitude of the sine wave of the blade flapping moment after the converter load shedding, if the azimuth angle difference of the three blades in the clockwise direction behind the three o'clock position in the impeller rotation plane at the moment of load shedding is more than 20 deg, a certain increase in the blade angle of the corresponding blade can be completed before the blade rotates near the three o'clock position, so as to reduce the angle of attack and lift coefficient of each section of the blade, and further reduce the aerodynamic moment of the blade to achieve this. As Figure 6 shown, since the maximum value of the distributed gravity moment depends on the blade mass and cannot be adjusted after the blade aerodynamics and structure are finalized, the maximum value of the blade flapping moment can be effectively reduced through the above operations.

[0058] AsFigure 2 As shown, the specific steps of the load reduction method for reducing the maximum value of the blade flapping moment in this embodiment are as follows:

[0059] S2.1. In the grid-connected power generation mode of the wind turbine, the azimuth angle of each blade of the wind turbine in the impeller rotation plane is obtained in real time; specifically, the azimuth angle of each blade in the impeller rotation plane can be identified by an absolute encoder installed in the hub and rotating with the main shaft.

[0060] S2.2. Determine whether the wind turbine is in the converter load shedding condition. If so, go to step S2.3; if not, end.

[0061] S2.3. Determine whether there is a blade whose azimuth angle lagging from the three o'clock position in the clockwise direction is less than the set azimuth angle at the moment of load shedding. In this embodiment, the set azimuth angle is 20deg. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle. After synchronous control, each of the three blades pitches to the set feathering position. If not, go to step S2.4.

[0062] S2.4. When the azimuth angles of the three blades lagging from the three o'clock position in the clockwise direction all exceed the set azimuth angle, for the blade rotating between eleven o'clock and three o'clock on the clock, pitch at the fourth set rate (i.e., set rate 4), and for the remaining blades, pitch at the fifth set rate (i.e., set rate 5). After the blade pitching amplitude reaches the set threshold, stop pitching. The range of the fourth set rate and the fifth set rate is 0.5 - 3deg / s.

[0063] S2.5. After the blade reaches three o'clock on the clock, pitch at the sixth set rate (i.e., set rate 6). The range of the sixth set rate is 0.5 - 3deg / s.

[0064] S2.6. In order to reduce the peak amplitude of the sine wave of the blade flapping moment after the converter load shedding, each of the three blades increases the blade angle by a certain amplitude at most once before three o'clock on the clock. Therefore, determine whether each of the three blades has completed a pitching action. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle. After synchronous control, each of the three blades pitches to the set feathering position. If not, return to step S2.4.

[0065] As Figure 8 、 Figure 9 shown, they are respectively the standard scheme and the load reduction scheme for enabling the independent pitch control function, and the operating time sequence of the blade angles of the three blades when the converter load shedding condition increases the algebraic minimum value of the blade root flapping moment. The load reduction scheme performs the actions of blade pitching, synchronization, and pitching control for the three blades after the converter load shedding.

[0066] As Figure 10 、 Figure 11As shown, they are respectively the standard solution and the load reduction solution for enabling the independent pitch control function, the operating time sequence of the blade root flapping moment of the three blades when the converter sheds load and the algebraic minimum value of the blade root flapping moment increases, and the algebraic minimum value of the flapping moment of the three blades in the load reduction solution increases by 8%.

[0067] In the present invention, the three blades are sequentially different in azimuth angle by 120deg in the impeller rotation plane. At the moment when the converter sheds load, according to the number of simulated wind seeds, one blade is selected to be 90deg ahead in the clockwise direction or 30deg behind in the clockwise direction of the nine o'clock azimuth angle, and is evenly distributed with a probability within the 120deg azimuth angle, so as to reasonably determine the flapping moment load of each section of the blade under the condition that the converter sheds load.

[0068] The above is only a preferred embodiment of the present invention for patent, but the protection scope of the present invention for patent is not limited thereto. Any person skilled in the art within the scope disclosed by the present invention for patent, according to the technical solution of the present invention for patent and its inventive concept, makes equivalent substitutions or changes, all belong to the protection scope of the present invention for patent.

Claims

1. A method for reducing the ultimate load of blade flapping moment based on the azimuth angle of the impeller, characterized in that This method is used to increase the minimum value of the blade flap moment under the converter load rejection condition, and includes the steps S1.

1. In the grid-connected power generation mode of the wind turbine, the azimuth angle of each blade of the wind turbine in the impeller rotation plane is obtained in real time; S1.

2. Determine whether the wind turbine is in the converter load rejection condition. If so, proceed to step S1.

3. If not, end; S1.

3. Determine whether there is a blade whose azimuth angle ahead of 9 o'clock clockwise at the load rejection moment is less than the set azimuth angle. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle. After synchronous control, each of the three blades pitches to the set feathering position. If not, proceed to step S1.4; S1.

4. When the azimuth angles of the three blades ahead of 9 o'clock clockwise all exceed the set azimuth angle, for the blades rotating between 5 o'clock and 9 o'clock, pitch at the first set rate, and for the remaining blades, pitch at the second set rate. After the blade pitching amplitude reaches the set threshold, stop pitching; S1.

5. After the blade reaches 9 o'clock clock, pitch at the third set rate; S1.

6. Determine whether each of the three blades has completed a pitching action. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle. After synchronous control, each of the three blades pitches to the set feathering position. If not, return to step S1.

4.

2. The method for reducing the ultimate load of the blade flapping moment based on the impeller azimuth angle according to claim 1, wherein The azimuth angle of each blade in the impeller rotation plane is identified by an absolute encoder installed in the hub and rotating with the main shaft.

3. The method for reducing the ultimate load of the blade flapping moment based on the impeller azimuth angle according to claim 1, wherein The set azimuth angle is 20deg.

4. The method for reducing the ultimate load of the blade flapping moment based on the impeller azimuth angle according to claim 1, wherein The three blades are sequentially offset by 120deg azimuth angles in the impeller rotation plane.

5. A method for reducing the ultimate load of blade flapping moment based on the azimuth angle of the impeller, characterized in that, This method is used to reduce the maximum value of the blade flap moment under the converter load rejection condition, and includes the steps S2.

1. In the grid-connected power generation mode of the wind turbine, the azimuth angle of each blade of the wind turbine in the impeller rotation plane is obtained in real time; S2.

2. Determine whether the wind turbine is in the converter load rejection condition. If so, proceed to step S2.

3. If not, end; S2.

3. Determine whether there is a blade whose azimuth angle behind 3 o'clock clockwise at the load rejection moment is less than the set azimuth angle. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle. After synchronous control, each of the three blades pitches to the set feathering position. If not, proceed to step S2.4; S2.

4. When the azimuth angles of the three blades behind 3 o'clock clockwise all exceed the set azimuth angle, for the blades rotating between 11 o'clock and 3 o'clock, pitch at the fourth set rate, and for the remaining blades, pitch at the fifth set rate. After the blade pitching amplitude reaches the set threshold, stop pitching; S2.

5. After the blade reaches 3 o'clock clock, pitch at the sixth set rate; S2.

6. Determine whether each of the three blades has completed a pitching action. If so, synchronously control the three blades of the wind turbine based on the maximum blade angle. After synchronous control, each of the three blades pitches to the set feathering position. If not, return to step S2.

4.

6. The method for reducing the ultimate load of the blade flapping moment based on the impeller azimuth angle according to claim 5, wherein The azimuth angle of each blade in the impeller rotation plane is identified by an absolute encoder installed in the hub and rotating with the main shaft.

7. The method for reducing the ultimate load of the blade flapping moment based on the impeller azimuth angle according to claim 5, characterized in that The set azimuth angle is 20deg.

8. The method for reducing the ultimate load of the blade flapping moment based on the impeller azimuth angle according to claim 5, wherein The three blades are successively offset by an azimuth angle of 120° in the impeller rotation plane.

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