Hydraulic variable-pitch wind generating set, design method and control method

Abstract

The invention discloses a hydraulic variable-pitch wind generating set, a design method and a control method.The hydraulic variable-pitch wind generating set comprises a hub, blades and a variable-pitch bearing, the variable-pitch bearing comprises a fixed ring and a rotating ring which are in running fit, the fixed ring is connected with the hub, the rotating ring is connected with the blades, and the hydraulic variable-pitch wind generating set further comprises a hydraulic oil cylinder; the hydraulic oil cylinder is rotatably installed in the hub, the output end of the hydraulic oil cylinder is connected with the rotating ring, the connecting point of the hydraulic oil cylinder and the rotating ring is a first connecting point, and the connecting point of the hydraulic oil cylinder and the hub is a second connecting point; the connecting line of the rotating center of the variable pitch bearing and the second connecting point is perpendicular to the connecting line of the first connecting point and the second connecting point. The layout and the control strategy of the hydraulic oil cylinder are precisely designed according to time sequence load distribution, it is guaranteed that the output torque of the hydraulic oil cylinder at the maximum load position is maximum, smooth variable pitch of the blade is achieved, and the purposes of reducing cost and increasing efficiency are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and particularly relates to a hydraulic pitch wind turbine generator set, a design method and a control method. Background Art

[0002] Existing hydraulic pitch wind turbine generator sets usually use large-volume power cylinders as power sources to ensure the smooth pitch of the blades through redundant driving force, but this results in high costs of the generator sets and poor market competitiveness; therefore, how to reduce costs and increase efficiency while ensuring the smooth pitch of the blades is still a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0003] The purpose of the present invention is to provide a hydraulic pitch wind turbine generator set, a design method and a control method, which can reduce costs and increase efficiency while ensuring the smooth pitch of the blades.

[0004] To solve the above technical problems, the present invention provides a hydraulic pitch wind turbine generator set, including a hub, blades and a pitch bearing. The pitch bearing includes a fixed ring and a rotating ring that are rotationally matched. The fixed ring is connected to the hub, and the rotating ring is connected to the blades.

[0005] It further includes a hydraulic cylinder rotatably installed inside the hub. The output end of the hydraulic cylinder is connected to the rotating ring. The connection point between the hydraulic cylinder and the rotating ring is the first connection point A1, and the connection point between the hydraulic cylinder and the hub is the second connection point A2. The rotation center of the pitch bearing is O.

[0006] The installation position of the hydraulic cylinder is set as follows: at the preset pitch angle of the blade, the line connecting the rotation center O of the pitch bearing and the second connection point A2 is perpendicular to the line connecting the first connection point A1 and the second connection point A2.

[0007] In order to reduce costs and increase efficiency of the hydraulic pitch wind turbine generator set while ensuring the smooth pitch of the blades, the present invention first obtains a curve graph of the time-sequential load of the blade changing with the pitch angle through simulation. At the preset pitch angle, the blade has the maximum time-sequential load. Therefore, the output torque required by the hydraulic cylinder is also the largest; at the remaining pitch angles, the time-sequential load of the blade is smaller. Therefore, the output torque required by the hydraulic cylinder is also smaller.

[0008] Furthermore, the output torque of the hydraulic cylinder is related to both the driving force and the force arm of the hydraulic cylinder, and the force arm of the hydraulic cylinder is constantly changing. Based on this, the present invention first precisely designs the installation position of the hydraulic cylinder to ensure that at the preset pitch angle, the force arm of the hydraulic cylinder is the largest. Since under the same driving force, the output torque of the hydraulic cylinder is proportional to the force arm, it further enables the hydraulic cylinder to have the largest output torque at the preset pitch angle. And when the line connecting the rotation center O of the pitch bearing and the second connection point A2 is perpendicular to the line connecting the first connection point A1 and the second connection point A2, the hydraulic cylinder has the largest force arm.

[0009] Meanwhile, within the preset pitch angle range where the blade has the maximum time-sequential load, the hydraulic cylinder can also adopt a non-differential control method to further increase the driving force of the hydraulic cylinder by reducing the speed. Under the synergistic effect of these two measures, it is ensured that the hydraulic cylinder has sufficient output torque at the preset pitch angle, thereby ensuring the smooth pitching of the blade.

[0010] It can be seen that the hydraulic pitch wind turbine of the present invention precisely designs the layout and control strategy of the hydraulic cylinder according to the time-sequential load distribution, ensuring that the output torque of the hydraulic cylinder is the largest at the position of the maximum load, and realizing the smooth pitching of the blade. Compared with the prior art solution of obtaining a larger output torque by using a power cylinder with a larger volume, the present invention can reduce the volume of the hydraulic cylinder, effectively reduce the cost of the hydraulic pitch wind turbine, and meet the purpose of cost reduction and efficiency improvement.

[0011] Optionally, the initial position angle β of the hydraulic cylinder = ∠A1OA2, and the value range of β is 35° to 45°.

[0012] Optionally, the hydraulic cylinder includes a cylinder block, and a connecting portion is provided in the middle of the cylinder block, and the connecting portion is rotatably connected to the hub.

[0013] Optionally, it further includes a slewing bearing assembly located inside the hub. The slewing bearing assembly includes a fixed part and a rotating part that are rotationally matched. The fixed part is connected to the hub, and the rotating part is connected to the connecting portion of the cylinder block.

[0014] Optionally, the number of the hydraulic cylinders is one or more, and multiple hydraulic cylinders are rotationally symmetrically arranged about the rotation center of the pitch bearing.

[0015] Optionally, a driving seat is connected to the inner peripheral wall of the rotating ring, and the output end of the hydraulic cylinder is connected to the driving seat.

[0016] Optionally, the number of the hydraulic cylinders is two, the number of the driving seats is two, and it further includes a driving support member that connects the two driving seats.

[0017] Optionally, it further includes a power source component, and the power source component is integrally arranged inside the hub.

[0018] The present invention also provides a design method for a hydraulic variable pitch wind turbine generator set, which is applicable to the aforementioned hydraulic variable pitch wind turbine generator set, and includes the following steps:

[0019] Obtain the time-sequence load diagram of the blade of the hydraulic variable pitch wind turbine generator set changing with the pitch angle through simulation;

[0020] Install the hydraulic cylinder inside the hub so that at a preset pitch angle, the time-sequence load of the blade is the largest and the force arm of the hydraulic cylinder is also the largest.

[0021] The design method of the hydraulic variable pitch wind turbine generator set of the present invention is applicable to the aforementioned hydraulic variable pitch wind turbine generator set, so it has the same technical effects as the aforementioned hydraulic variable pitch wind turbine generator set, which will not be elaborated here.

[0022] The present invention also provides a control method for a hydraulic variable pitch wind turbine generator set, based on the aforementioned hydraulic variable pitch wind turbine generator set, and includes the following steps:

[0023] Within the preset pitch angle range where the blade has the maximum time-sequence load, the hydraulic cylinder adopts non-differential control, and within the remaining pitch angle ranges, the hydraulic cylinder adopts differential control.

[0024] The control method of the hydraulic variable pitch wind turbine generator set of the present invention is based on the aforementioned hydraulic variable pitch wind turbine generator set, so it has the same technical effects as the aforementioned hydraulic variable pitch wind turbine generator set, which will not be elaborated here.

[0025] Meanwhile, within the remaining pitch angle ranges, the hydraulic cylinder adopts differential control, which can improve the pitch speed of the blade, while within the preset pitch angle range where the blade has the maximum time-sequence load, the hydraulic cylinder adopts non-differential control, which can increase the driving force of the hydraulic cylinder by reducing the speed to ensure the smooth pitching of the blade and prevent the problem of insufficient driving force. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram inside the hub of the hydraulic variable pitch wind turbine generator set provided by the present invention;

[0027] Figure 2 is Figure 1 The state diagram of the hydraulic cylinder when the blade of the hydraulic variable pitch wind turbine generator set is in the feathering position;

[0028] Figure 3 is Figure 1 The state diagram of the hydraulic cylinder when the blade of the hydraulic variable pitch wind turbine generator set is in the unfeathering position;

[0029] Figure 4 is Figure 1 a state diagram of a hydraulic cylinder when the blade of a hydraulic pitch wind turbine is in the open pitch position and the feathering position;

[0030] Figure 5 is Figure 1 a curve graph showing the variation of the time-sequential load of the blade in a hydraulic pitch wind turbine with the pitch angle;

[0031] Figure 6 is Figure 1 a schematic structural diagram of another angle inside the hub of a hydraulic pitch wind turbine;

[0032] Among them, Figures 1-6 the descriptions of the reference numerals in the drawings are as follows:

[0033] 1 - hub;

[0034] 2 - pitch bearing; 21 - fixed ring; 22 - rotating ring;

[0035] 3 - hydraulic cylinder; 31 - cylinder block;

[0036] 4 - slewing bearing assembly;

[0037] 5 - drive seat;

[0038] 6 - drive support member;

[0039] 7 - positive pressure oil tank assembly;

[0040] 8 - pitch control cabinet;

[0041] 9 - servo motor pump assembly;

[0042] 10 - accumulator assembly. Specific embodiments

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0044] As used herein, "a plurality of" generally means more than two; and when "a plurality of" is used to represent the quantity of several components, it does not represent the mutual relationship in quantity of these components.

[0045] Please refer to Figures 1-5 , Figure 1 which is a schematic structural diagram of the inside of the hub of the hydraulic pitch wind turbine provided by the present invention; Figure 2 is Figure 1 a state diagram of the hydraulic cylinder when the blade of the hydraulic pitch wind turbine is in the feathering position; Figure 3 is Figure 1State diagram of the hydraulic cylinder when the blade is in the open pitch position in a hydraulic pitch wind turbine generator; Figure 4 is Figure 1 State diagram of the hydraulic cylinder when the blade is in the open pitch position and the feathering position in a hydraulic pitch wind turbine generator; Figure 5 is Figure 1 Variation curve of the time-sequential load of the blade with the pitch angle in a hydraulic pitch wind turbine generator.

[0046] The present invention provides a hydraulic pitch wind turbine generator, including a hub 1, a blade and a pitch bearing 2. The pitch bearing 2 includes a fixed ring 21 and a rotating ring 22 that are rotatably engaged. The fixed ring 21 is connected to the hub 1, and the rotating ring 22 is connected to the blade;

[0047] It further includes a hydraulic cylinder 3. The hydraulic cylinder 3 is rotatably installed inside the hub 1. The output end of the hydraulic cylinder 3 is connected to the rotating ring 22. The connection point between the hydraulic cylinder 3 and the rotating ring 22 is the first connection point A1, and the connection point between the hydraulic cylinder 3 and the hub 1 is the second connection point A2. The rotation center of the pitch bearing 2 is O,

[0048] The installation position of the hydraulic cylinder 3 is set as follows: at the preset pitch angle of the blade, the line connecting the rotation center O of the pitch bearing 2 and the second connection point A2 is perpendicular to the line connecting the first connection point A1 and the second connection point A2.

[0049] When the blade pitches, that is, the blade rotates from the open pitch position to the feathering position. In order to reduce costs and increase efficiency of the hydraulic pitch wind turbine generator while ensuring the smooth pitching of the blade, the present invention first obtains, through simulation, the variation curve of the time-sequential load of the blade with the pitch angle as shown in Figure 5 It can be seen from Figure 5 that at the preset pitch angle of the blade between P1 - P2, the blade has the maximum time-sequential load. Therefore, at the preset pitch angle of the blade, the output torque required by the hydraulic cylinder 3 is also the largest, and the maximum output torque of the hydraulic cylinder 3 needs to reach T2; at the remaining pitch angles, the time-sequential load of the blade is smaller. Therefore, at other pitch angles, the output torque required by the hydraulic cylinder 3 is also smaller.

[0050] Furthermore, the output torque of the hydraulic cylinder 3 is related to both the driving force and the force arm of the hydraulic cylinder 3, and the force arm of the hydraulic cylinder 3 is constantly changing. Based on this, the present invention first precisely designs the installation position of the hydraulic cylinder 3 to ensure that at the preset pitch angle, the force arm of the hydraulic cylinder 3 is the largest. Since, under the same driving force, the output torque of the hydraulic cylinder 3 is proportional to the force arm, it further enables the hydraulic cylinder 3 to have the largest output torque at the preset pitch angle; from Figure 4It can be seen that the lever arm of the blade at the pitch-open position is L1, and the lever arm of the blade at the pitch-feathered position is L2. During the process of the blade rotating from the pitch-open position to the pitch-feathered position, the lever arm of the hydraulic cylinder 3 first increases and then decreases. When the line connecting the rotation center O of the pitch bearing 2 and the second connection point A2 is perpendicular to the line connecting the first connection point A1 and the second connection point A2, the hydraulic cylinder 3 has the maximum lever arm L3, and L3 = OA2. Therefore, the installation of the hydraulic cylinder 3 should ensure that at the preset pitch angle of the blade, OA1⊥A1A2.

[0051] Meanwhile, within the pitch angle range of P1 - P2, the hydraulic cylinder 3 can also adopt a non-differential control method. By reducing the speed and increasing the driving force of the hydraulic cylinder 3, the combined effect of these two measures ensures that the hydraulic cylinder 3 has sufficient output torque within the pitch angle range of P1 - P2, enabling the blade to pitch smoothly. In other pitch angle ranges, the hydraulic cylinder 3 can adopt differential control to increase the pitch speed of the blade.

[0052] It can be seen that the hydraulic pitch wind turbine of the present invention precisely designs the layout and control strategy of the hydraulic cylinder 3 according to the time-sequence load distribution, ensuring that the output torque of the hydraulic cylinder 3 is the largest at the position of the maximum load. In the pitch angle range with a small load position, the output torque of the hydraulic cylinder 3 also decreases, always ensuring that the blade has sufficient driving torque at any pitch angle, realizing smooth pitching of the blade while ensuring the full utilization of the output torque of the hydraulic cylinder 3. Compared with the existing technology that obtains a large output torque by using a large-volume power cylinder, the present invention can reduce the volume of the hydraulic cylinder 3, effectively reduce the cost of the hydraulic pitch wind turbine, and meet the purpose of cost reduction and efficiency improvement.

[0053] Please combine Figure 4 to understand that in the present invention, the output torque T of the hydraulic cylinder 3 is calculated as:

[0054] T = F·L

[0055] In the formula:

[0056] F—the driving force of the hydraulic cylinder 3;

[0057] L—the lever arm of the hydraulic cylinder 3;

[0058] Among them, the lever arm of the hydraulic cylinder 3 is calculated as:

[0059]

[0060] In the formula:

[0061] R—the radius of the pitch bearing 2;

[0062] r—the distance between the second connection point A2 and the rotation center of the pitch bearing 2;

[0063] α—Pitch angle of the blade;

[0064] β—Initial position angle of the hydraulic cylinder 3.

[0065] Wherein, the initial position angle β of the hydraulic cylinder 3 = ∠A1OA2, and the value range of β is 35° to 45°. That is, the initial position angle β is defined as the included angle between the line connecting the first connection point A1 and the rotation center O of the pitch bearing 2 and the line connecting the second connection point A2 and the rotation center O of the pitch bearing 2.

[0066] In the present invention, considering factors such as the internal installation space and load of the hub 1, through multiple iterative calculations, the initial position angle of the hydraulic cylinder 3 is set between 35° and 45°, and the distance between the first connection point A1 and the second connection point A2 at the initial position, and the distance r between the first connection point A1 and the rotation center O of the pitch bearing 2 are adaptively adjusted, which can ensure that during the pitch process of the blade, the force arm of the hydraulic cylinder 3 first increases and then decreases, and the force arm of the hydraulic cylinder 3 is also the largest when the timing load of the blade is the largest, while ensuring the normal operation of the hydraulic cylinder 3 inside the hub 1.

[0067] Please continue to refer to Figure 1 and Figure 4 , in this embodiment, the hydraulic cylinder 3 includes a cylinder block 31, and the middle part of the cylinder block 31 has a connecting part, and the connecting part is rotatably connected to the hub 1.

[0068] Since in the prior art, the oil cylinder usually adopts a two-end trunnion connection scheme, that is, the connecting trunnions are arranged at the tail of the cylinder barrel and the head of the cylinder rod of the oil cylinder, resulting in a limited driving radius of the oil cylinder and unable to meet the pitch requirements of the wind turbine generator set after cost reduction. Based on this, in this embodiment, a connecting part is arranged in the middle of the cylinder block 31 of the hydraulic cylinder 3, shortening the total length of the hydraulic cylinder 3. Under the condition of the same inner diameter of the pitch bearing 2, a larger driving force arm can be achieved, thereby achieving a larger driving torque and further meeting the pitch requirements of the wind turbine generator set after cost reduction.

[0069] As described above, the connecting part is rotatably connected to the hub 1. Specifically, it further includes a slewing bearing assembly 4 located inside the hub 1. The slewing bearing assembly 4 includes a fixed part and a rotating part that are rotationally matched. The fixed part is connected to the hub 1, and the rotating part is connected to the connecting part of the cylinder block 31.

[0070] Among them, the structure of the slewing bearing assembly 4 is not limited. For example, the slewing bearing assembly 4 can adopt the structural form of a thrust bearing. The thrust bearing includes a first thrust washer and a second thrust washer that are rotationally matched. The first thrust washer forms the fixed part for connecting to the hub 1, and the second thrust washer forms the rotating part for connecting to the connecting part of the cylinder block 31.

[0071] ByFigure 1 It can be seen that in this embodiment, the number of hydraulic cylinders 3 is two, and the two hydraulic cylinders 3 are rotationally symmetrically arranged about the rotation center of the pitch bearing 2.

[0072] Of course, the number of hydraulic cylinders 3 is not limited, and the number of hydraulic cylinders 3 can be set by comprehensively considering factors such as the installation space inside the hub and the manufacturing cost. For example, the number of hydraulic cylinders 3 can be at least one.

[0073] As mentioned above, the output end of the hydraulic cylinder 3 is connected to the rotating ring 22. Specifically in this embodiment, a driving seat 5 is connected to the inner peripheral wall of the rotating ring 22. The driving seat 5 is used to provide a connection position for facilitating the connection with the output end of the hydraulic cylinder 3, thereby indirectly realizing the connection between the output end of the hydraulic cylinder 3 and the rotating ring 22.

[0074] Among them, the inner peripheral wall of the rotating ring 22 and the driving seat 5 can be fixed by welding.

[0075] From Figure 1 It can be seen that in this embodiment, the number of hydraulic cylinders 3 is two, the number of driving seats 5 is two, and a driving support member 6 is further included. The driving support member 6 connects the two driving seats 5.

[0076] With the above settings, the two driving seats 5 are connected by the driving support member 6, which can improve the structural stability of the driving seat 5 and ensure the reliable installation position of the hydraulic cylinder 3.

[0077] Please refer to Figure 6 , Figure 6 For Figure 1 a schematic structural diagram of another angle inside the hub of a hydraulic pitch wind turbine generator.

[0078] In this embodiment, the hydraulic pitch wind turbine generator further includes a power source assembly. The power source assembly specifically includes a positive pressure oil tank assembly 7, a pitch control cabinet 8, a servo motor pump assembly 9, an accumulator assembly 10, and a cooling circulation assembly (not shown in the figure). The power source assembly is integrally arranged inside the hub 1.

[0079] In the existing hydraulic pitch scheme, the power source assembly is arranged inside the nacelle. The power source hydraulic oil needs to be transmitted to the rotating hub 1 through a slip ring. This scheme has low efficiency and requires a large pump power to achieve. At the same time, the radiator power needs to be increased, which is not conducive to the miniaturization of the drive scheme and the reduction of the unit cost. Based on this, in this embodiment, the power source assembly is integrally arranged inside the hub 1, reducing the low-efficiency link of the slip ring, improving the efficiency of the hydraulic pitch, making full use of the space inside the hub 1, and being conducive to the integration of the drive scheme and the reduction of the unit cost.

[0080] Among them, the driving pump assembly specifically adopts the form of a servo motor pump assembly 9, which includes a hydraulic pump and a servo motor. The servo motor can reduce the starting impact of the hydraulic pump and improve the reliability of the hydraulic pump; the fuel tank assembly specifically adopts the form of a positive pressure fuel tank assembly 7, and the positive pressure fuel tank assembly 7 can ensure that the oil at the oil suction port of the hydraulic pump in the hub 1 is not affected by the rotation of the impeller.

[0081] The present invention also provides a design method for a hydraulic variable pitch wind turbine generator set, which is applicable to the aforementioned hydraulic variable pitch wind turbine generator set, and includes the following steps:

[0082] Simulate and obtain the time-sequence load diagram of the blade of the hydraulic variable pitch wind turbine generator set changing with the pitch angle.

[0083] Install the hydraulic cylinder 3 inside the hub 1 so that at the preset pitch angle, the time-sequence load of the blade is the largest and the force arm of the hydraulic cylinder 3 is also the largest.

[0084] The design method of the hydraulic variable pitch wind turbine generator set of the present invention is applicable to the aforementioned hydraulic variable pitch wind turbine generator set, so it has the same technical effects as the aforementioned hydraulic variable pitch wind turbine generator set, which will not be elaborated here.

[0085] The present invention also provides a control method for a hydraulic variable pitch wind turbine generator set. Based on the aforementioned hydraulic variable pitch wind turbine generator set, the control method is specifically as follows:

[0086] Within the preset pitch angle range where the blade has the maximum time-sequence load, the hydraulic cylinder 3 adopts non-differential control, and within the remaining pitch angle ranges, the hydraulic cylinder 3 adopts differential control.

[0087] The control method of the hydraulic variable pitch wind turbine generator set of the present invention is based on the aforementioned hydraulic variable pitch wind turbine generator set, so it has the same technical effects as the aforementioned hydraulic variable pitch wind turbine generator set, which will not be elaborated here.

[0088] At the same time, within the remaining pitch angle ranges, the hydraulic cylinder 3 adopts differential control, which can improve the pitch speed of the blade. And within the preset pitch angle range where the blade has the maximum time-sequence load, that is, within the pitch angle range of P1 - P2, the hydraulic cylinder 3 adopts non-differential control, which can increase the driving force of the hydraulic cylinder 3 by reducing the pitch speed to ensure the smooth pitching of the blade.

[0089] Among them, differential control means that when oil is supplied to both the rodless cavity and the rod cavity of the hydraulic cylinder 3 simultaneously (the rodless cavity and the rod cavity are connected), since the effective area of the rodless cavity is large and the effective area of the rod cavity is small, and the hydraulic oil pressure acting on both ends is the same, the force exerted by the hydraulic oil on the rodless cavity end is greater than that on the rod cavity end. The piston will be pushed towards the rod cavity under the action of the resultant force. At this time, the hydraulic oil flowing into the rodless cavity comes not only from the hydraulic pump but also from the rod cavity. Therefore, the extension speed of the piston increases, and the pitch speed of the blade can be increased. However, since the pressure acting on the rodless cavity of the piston needs to offset part of the pressure on the annular area of the rod cavity piston, the driving force of the hydraulic cylinder 3 will decrease;

[0090] Instead of differential control, that is, the hydraulic oil in the rod cavity of the hydraulic cylinder 3 directly returns to the oil tank. At this time, the hydraulic oil flowing into the rodless cavity only comes from the hydraulic pump. When the oil intake is determined, compared with differential control, the amount of hydraulic oil flowing into the rodless cavity decreases. Therefore, the extension speed of the piston decreases, and further the pitch speed of the blade decreases. However, since the pressure in the rod cavity is zero, compared with differential control, the extension force that the piston rod can provide increases, that is, the driving force of the hydraulic cylinder 3 can be increased.

[0091] The above has introduced in detail a hydraulic pitch wind turbine generator set, a design method and a control method provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A hydraulic pitch wind turbine generator, comprising a hub (1), blades and a pitch bearing (2), wherein the pitch bearing (2) comprises a fixed ring (21) and a rotating ring (22) which are rotationally engaged, the fixed ring (21) is connected to the hub (1), and the rotating ring (22) is connected to the blades, and is characterized in that, it further comprises a hydraulic cylinder (3), the hydraulic cylinder (3) is rotatably installed inside the hub (1), the output end of the hydraulic cylinder (3) is connected to the rotating ring (22), the connection point between the hydraulic cylinder (3) and the rotating ring (22) is the first connection point A1, the connection point between the hydraulic cylinder (3) and the hub (1) is the second connection point A2, and the rotation center of the pitch bearing (2) is O. The installation position of the hydraulic cylinder (3) is: at the preset pitch angle of the blade, the line connecting the rotation center O of the pitch bearing (2) and the second connection point A2 is perpendicular to the line connecting the first connection point A1 and the second connection point A2.

2. The hydraulic variable pitch wind turbine according to claim 1, wherein, The initial position angle β of the hydraulic cylinder (3) = ∠A1OA2, and the value range of β is 35° to 45°.

3. The hydraulic variable pitch wind turbine according to claim 1, wherein, The hydraulic cylinder (3) comprises a cylinder block (31), and the middle part of the cylinder block (31) has a connecting part, and the connecting part is rotatably connected to the hub (1).

4. The hydraulic variable pitch wind turbine according to claim 3, characterized in that, It further comprises a slewing bearing assembly (4) located inside the hub (1), the slewing bearing assembly (4) comprises a fixed part and a rotating part which are rotationally engaged, the fixed part is connected to the hub (1), and the rotating part is connected to the connecting part of the cylinder block (31).

5. The hydraulic variable pitch wind turbine according to claim 1, characterized in that, The number of the hydraulic cylinders (3) is one or more, and a plurality of the hydraulic cylinders (3) are arranged rotationally symmetrically about the rotation center of the pitch bearing (2).

6. The hydraulic variable pitch wind turbine according to claim 1, characterized in that, A driving seat (5) is connected to the inner peripheral wall of the rotating ring (22), and the output end of the hydraulic cylinder (3) is connected to the driving seat (5).

7. The hydraulic variable pitch wind turbine according to claim 6, wherein, The number of the hydraulic cylinders (3) is two, the number of the driving seats (5) is two, and it further comprises a driving support member (6), and the driving support member (6) connects the two driving seats (5).

8. The hydraulic variable pitch wind turbine according to claim 1, characterized in that It further comprises a power source assembly, and the power source assembly is integrally arranged inside the hub (1).

9. A design method for a hydraulic pitch wind turbine generator set, applicable to the hydraulic pitch wind turbine generator set according to any one of claims 1-8, characterized in that, It includes the following steps: Simulate to obtain the time-sequence load diagram of the blades of the hydraulic pitch wind turbine generator changing with the pitch angle; Install the hydraulic cylinder (3) inside the hub (1) so that at the preset pitch angle, the time-sequence load of the blade is the largest and the force arm of the hydraulic cylinder (3) is also the largest.

10. A control method for a hydraulic pitch wind turbine generator set, based on the hydraulic pitch wind turbine generator set according to any one of claims 1-8, characterized in that, It includes the following steps: In the preset pitch angle range where the blade has the maximum time-sequence load, the hydraulic cylinder (3) adopts non-differential control, and in the remaining pitch angle ranges, the hydraulic cylinder (3) adopts differential control.

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