Wind turbine with alternative variable pitch by adjusting the angle and power control method thereof

Abstract

This invention discloses a wind turbine generator and its power control method that uses pitch angle adjustment as an alternative to pitch control, belonging to the field of wind power equipment manufacturing. Based on a beam-shaft separated wind turbine architecture, the main load-bearing beam is constructed as a motion mechanism capable of pitching around a fixed tail pin. The main load-bearing beam is a variable cross-section hollow rectangular box structure, with a rotary transmission shaft passing through its internal space along the axial direction. The two are independent of each other in the force path. Driven by a hydraulic cylinder or servo electric cylinder at the lower front, the nacelle, hub, blades, and main load-bearing beam are rigidly fixed to form a single rigid motion chain, pitching synchronously without internal relative motion. The wind turbine generator does not have a blade pitch mechanism or its associated slip rings or rotary joints, but instead has a control system that performs closed-loop control with the overall pitch angle as the control object. By actively increasing the pitch angle to reduce the effective windward area, it achieves a synergistic effect of precise power control, purely passive aerodynamic braking, and passive rearward shift of the center of gravity for self-stabilization when the pitch angle increases.

Description

Technical Field

[0001] This invention relates to the field of wind power equipment manufacturing technology, specifically to a horizontal axis wind turbine, and more particularly to a wind turbine based on a beam-shaft separated wind turbine architecture. This wind turbine, along with its power control method, achieves precise power generation control, passive aerodynamic braking, and center-of-gravity self-optimization by replacing the traditional blade pitch mechanism with integrated whole-machine pitch angle adjustment. This invention can be applied to onshore wind farms, mountain wind farms, and distributed wind power generation scenarios. Background Technology

[0002] Current horizontal axis wind turbine generators generally adopt a centralized drivetrain layout integrating the main shaft, bearings, and gearbox. A single rotating main shaft running through the nacelle simultaneously bears both load-bearing and torque transmission functions, resulting in the main shaft being subjected to complex stresses from bending, torsion, and shearing over a long period. To meet strength and fatigue life requirements, the main shaft and its connecting parts have to be over-designed, leading to a bulky structure and high material costs. Furthermore, this centralized structure restricts the internal space of the hub, and the drivetrain and pitch mechanism are structurally highly coupled, further increasing the difficulty of designing, installing, and maintaining the pitch system.

[0003] To address the aforementioned issues, existing technologies have introduced beam-shaft separation wind turbine architectures. These architectures achieve complete decoupling of load transmission and torque transmission paths by physically separating the fixed main load-bearing beam from the pure torsion drive main shaft. For example, a typical beam-shaft wind turbine disclosed in the prior art employs a beam-shaft separation, functionally integrated architecture, achieving complete decoupling of load transmission and torque transmission paths through the physical separation of the fixed main load-bearing beam from the pure torsion drive main shaft. The main load-bearing beam of this beam-shaft wind turbine is connected to the lower platform via a universal elastic vibration damping support structure, designed to be fixed and non-rotating. However, this beam-shaft wind turbine still relies on an integrated pitch mechanism for power regulation. This pitch mechanism includes multiple complex components such as hydraulic cylinders, pitch and connecting bearings, slide rails and sliders, and hinge linkages, as well as precision devices such as slip rings or rotary joints necessary for supplying power and oil to the pitch system within the rotating hub. The pitch system, located within the rotating hub, operates under harsh conditions such as high centrifugal force, salt spray, and sandstorms. Its hydraulic / electrical supply, signal transmission, and reliability have long been technical challenges that the industry has sought to address but has yet to fully resolve. This results in a complex overall structure, redundant components, and a high failure rate, increasing overall design and maintenance costs and failing to meet the industry's demand for streamlined, efficient, and reliable wind turbines.

[0004] Furthermore, existing technologies include several solutions that alter the swept area of ​​a wind turbine by adjusting the rotor tilt angle or tower tilt angle. For example, Chinese utility model patent CN207245934U discloses a high-power wind turbine with actively controllable rotor tilt angle. This is achieved by using a rotor tilt angle adjustment device within the nacelle to change the angle between the rotor's rotation axis and the horizontal plane, aligning the incoming airflow with the rotor axis direction and maximizing the blade's windward area, thereby increasing power generation. Chinese utility model patent CN204226107U discloses a rear-mounted blade wind power generation device, with the main unit hinged to the top of a column. The tilt angle of the main unit is adjusted via a hydraulic piston cylinder, also for the purpose of wind following. These solutions all follow the conventional thinking of maximizing energy capture by facing the wind directly, conveying to those skilled in the art the technical instruction that the sole purpose of tilt angle adjustment is to optimize the incoming airflow direction, thus constituting a clear deviation from the direction of this invention.

[0005] More relevantly, US Patent 4435646A discloses a small wind turbine where the entire nacelle and rotor assembly are mounted on a horizontal pivot, with the pitch angle adjusted via a drive mechanism. When wind speeds are too high, increasing the pitch angle causes the rotor to deviate from the wind direction, achieving power limiting and overspeed protection. While this solution reveals the concept of power limiting and braking through overall turbine pitch, it is based on a traditional shaft-bearing structure and does not address the complex internal transmission and load decoupling issues of large beam-shaft separated wind turbines. Direct application of this solution would not solve the load transfer problem of large beam-shaft wind turbines. Furthermore, in this solution, the pitch rotation center is located below the nacelle; while increasing the pitch angle to limit power, the center of gravity may shift forward, weakening anti-overturning stability. Its single hinged support method also cannot provide sufficient lateral stiffness for large wind turbines.

[0006] Based on the above analysis, existing technologies present three major obstacles to this field: (1) Structural obstacles; The design of the fixed main load-bearing beam of the beam-shaft separated wind turbine has a fundamental structural contradiction with the movable structure required for the pitch of the whole machine. Reconstructing the fixed support into a pitchable articulated drive system involves a complete change of the force path of the whole machine, which is not a simple conversion. This fixed characteristic is the structural basis for realizing its load-torque decoupling function. People skilled in the art have no motivation to destructively reconstruct it.

[0007] (2) Functional impairment; It is generally believed in the field that the pitch mechanism is an essential component for realizing power regulation and safety control, while the pitch angle adjustment is limited to chasing the wind to increase power, forming a functional substitution barrier that is difficult to overcome. (3) Obstacles to the effect: No existing technical solution can simultaneously achieve the synergistic effect of power regulation, passive braking and center of gravity self-stabilization, especially the gain of center of gravity shift during the process of increasing pitch angle, which is not available in the existing whole machine pitch solution.

[0008] Therefore, existing technologies generally lack a solution that can both retain the advantages of load torque decoupling of beam-shaft wind turbines and completely eliminate the pitch mechanism and its auxiliary components. Summary of the Invention

[0009] To address the structural, functional, and performance limitations of existing solutions described in the background section, this invention aims to provide a wind turbine generator and its power control method that significantly simplifies the structure, improves reliability, and replaces pitch control with elevation angle adjustment. Specifically, the technical problems to be solved include: Firstly, the complexity and reliability issues of the overall structure were resolved. The fixed main load-bearing beam design of the beam-shaft separated wind turbine created a structural obstacle, while the pitch mechanism and its associated precision components such as slip rings or rotary joints led to a high failure rate. By reconstructing the fixed load-bearing structure into a pitch-capable motion mechanism, and completely replacing the pitch mechanism with a simpler and more reliable control mechanism, the overall structure was fundamentally simplified and its reliability was substantially improved.

[0010] Secondly, this invention solves the problem of separating power regulation and braking. In existing technologies, power regulation relies on a pitch control mechanism, and braking relies on a mechanical brake. These two independent systems lead to overall complexity and numerous potential points of failure. This invention achieves precise power control over a wide wind speed range and purely passive pneumatic braking without mechanical contact using a single, reliable mechanism.

[0011] Third, it solves the problem of center of gravity stability by passively improving the overall anti-tipping stability of the machine during power adjustment and braking, eliminating the need for an additional center of gravity adjustment mechanism. It also overcomes the dual technical bias in this field where pitch angle adjustment is limited to wind-following power boosting and the indispensable role of the pitch mechanism.

[0012] This invention addresses the root causes of three problems simultaneously through a single structural change by employing a pin-hinged connection and a hydraulic cylinder or servo electric cylinder-driven elevation angle adjustment method.

[0013] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention completely shifts from the existing technology of wind-following power-increasing elevation angle adjustment (increasing the windward area to increase power generation) to dynamic wind-reducing power limiting (increasing the elevation angle to actively reduce the effective windward area to achieve power limiting). This shift is reflected in the structure, namely, the control system is configured to control the extension of hydraulic cylinders or servo electric cylinders at high wind speeds to increase the elevation angle and limit the output power.

[0014] This invention departs from existing technologies that only adjust the wind turbine or tower, and instead adjusts the entire rigid kinematic chain consisting of the main load-bearing beam, nacelle, hub, and blades. This shift is reflected in the structure, where the nacelle, hub, and blades are rigidly fixed to the front end of the main load-bearing beam, with no relative degrees of freedom of movement between the four components. Changes in the overall attitude of the wind turbine can be directly, synchronously, and without lag transmitted to the blades.

[0015] This invention departs from the existing technology where power regulation (pitch control) and braking (mechanical brake) are implemented by two independent systems. Instead, it adopts a single pitch angle control mechanism to simultaneously achieve power regulation, purely passive pneumatic braking, and self-optimization of the center of gravity. This shift is reflected in the structure, where the extension and retraction of the same hydraulic cylinder or servo electric cylinder achieves efficient energy capture, precise power limiting, and complete braking in different pitch angle ranges. At the same time, due to the hinged design of the tail pin, the center of gravity passively shifts backward.

[0016] To achieve the above objectives, the technical solution of this invention is as follows: The originally fixed main load-bearing beam in the beam-shaft separated wind turbine is constructed as a motion mechanism capable of pitching around a fixed tail pin. A single rigid motion chain consisting of the main load-bearing beam, nacelle, hub, and blades is built. By driving this motion chain to pitch as a whole, the effective windward area of ​​the blades is changed, thereby completely eliminating the pitch mechanism and achieving the integration of three functions: power regulation, aerodynamic braking, and center of gravity self-optimization. The specific technical solution is as follows: A wind turbine generator with pitch control as an alternative to pitch control includes a tower, a lower platform, a main load-bearing beam, a nacelle, a hub, and blades.

[0017] The main load-bearing beam is a variable cross-section hollow box-shaped structure, forged from high-strength alloy steel and machined, serving as the core load-bearing unit of the entire unit. An axially spaced rotary drive shaft runs through its interior, supported by bearings within the main load-bearing beam. This shaft is completely independent of the main load-bearing beam in terms of mechanical structure and force path, serving solely to transmit torque. The front end of the rotary drive shaft connects to the speed-increasing transmission system on the hub side, while the rear end connects to the generator, inheriting the advantage of load and torque decoupling in beam-shaft type wind turbines.

[0018] The main load-bearing beam is no longer fixed; its tail is hinged to the lower platform via a fixed pin. This fixed pin serves as the sole rotation axis for adjusting the overall elevation angle, and its axis is arranged horizontally to the left and right, perpendicular to the blade rotation axis. All aerodynamic loads borne by the main load-bearing beam are transmitted to the lower platform via the fixed pin. A hydraulic cylinder or servo electric cylinder is located below the front of the main load-bearing beam, serving as the sole drive source. The bottom of the cylinder body is hinged to the reinforced bearing base of the lower platform, and the top of the piston rod is hinged to the bottom front surface of the main load-bearing beam.

[0019] By extending and retracting the piston rod, the main load-bearing beam is driven to pitch around a fixed pin shaft, which in turn drives the entire rigid kinematic chain consisting of the main load-bearing beam, nacelle, hub, and blades to pitch synchronously, achieving a continuously adjustable pitch angle from 0° to 88°. This reconstructs the fixed load-bearing structure of the traditional beam-shaft wind turbine into a controllable pitch motion mechanism.

[0020] The front end of the main load-bearing beam is rigidly fixed to the nacelle via a flange bolt assembly. The nacelle, hub, and blades are sequentially and rigidly fixed as a single unit via the flange bolt assembly, with no relative degrees of freedom of movement between them, forming a single rigid kinematic chain. During elevation adjustment, the drive mechanism drives the main load-bearing beam to pitch around the fixed pin axis, simultaneously causing the nacelle, hub, and blades to pitch as a whole, without relative displacement, ensuring the consistency and stability of the overall attitude adjustment. This design allows changes in elevation angle to be directly, synchronously, and without lag translated into changes in the effective windward area of ​​the blades, laying the foundation for precise control.

[0021] Based on the above structure, this invention does not include any blade pitch mechanism or its associated slip rings or rotary joints. A single rigid motion chain driven by a hydraulic cylinder or servo cylinder achieves continuously adjustable pitch angles from 0° to 88°. The wind turbine is equipped with a control system configured to control the extension and retraction of the hydraulic cylinder or servo cylinder based on real-time wind speed and target power, thereby adjusting the pitch angle in a closed-loop manner. Efficient energy capture is achieved in the low pitch angle range (0°–20° energy capture range); precise power limiting is achieved in the medium to high pitch angle range (20°–60° power limiting range); and in the braking range of 85° to 88°, the effective windward area of ​​the blades approaches zero, and the blades almost no longer capture wind energy, achieving purely passive aerodynamic braking.

[0022] Because the entire aircraft pitches and rotates around a fixed pivot, with the pivot's hinge point located at the tail of the main load-bearing beam, the projection of the center of gravity of the entire system—comprising the main load-bearing beam, nacelle, hub, and blades—shifts backward in the horizontal direction as the pitch angle increases, moving closer to the tower's central axis. This backward shift of the center of gravity is a passive geometric effect generated by the aircraft's pitch around the tail pivot, eliminating the need for an additional center of gravity adjustment mechanism and simultaneously improving the aircraft's anti-tipping capability during power limiting and braking processes.

[0023] This invention also discloses a power control method for the aforementioned wind turbine, which uses the overall turbine pitch angle as the controlled object instead of blade pitch control, and includes the following steps: S1. The control system obtains real-time wind speed through a wind measuring device and determines the target elevation angle based on the real-time wind speed; S2. When a low wind speed condition is detected, the control system controls the hydraulic cylinder or servo electric cylinder to retract, so that the main load-bearing beam is kept in the energy capture range with a small elevation angle, thereby maximizing the effective windward area of ​​the blades in the single rigid motion chain and achieving efficient energy capture at low wind speed. S3. When a high wind speed condition is detected, the control system controls the hydraulic cylinder or servo electric cylinder to extend, increasing the elevation angle of the main load-bearing beam to the power limit range, thereby reducing the effective windward area of ​​the blades in the single rigid motion chain and limiting the output power within the rated range. S4. When overspeed is detected or an emergency stop is required, the control system controls the hydraulic cylinder or servo electric cylinder to quickly extend to the full extent, adjusting the elevation angle of the main load-bearing beam to the braking range, thereby making the effective windward area of ​​the blades in the single rigid motion chain approach zero, achieving pure passive pneumatic braking.

[0024] Furthermore, the target elevation angle is determined by looking up a table or by real-time calculation.

[0025] The beneficial effects of this invention compared to the prior art are: 1. This invention eliminates the need for any blade pitch mechanism and its associated slip rings or rotary joints, thus eliminating a series of failure modes caused by the presence of a pitch mechanism, such as sealing failure, poor lubrication, electrical faults, and poor slip ring contact. The pitch system is one of the key subsystems with a high failure rate in wind turbines. Eliminating this subsystem significantly simplifies the overall structure, reduces the number of components, significantly improves reliability, and lowers manufacturing and maintenance costs.

[0026] 2. This invention uses the overall pitch angle as the control object. By continuously adjusting the pitch angle of a single rigid motion chain, the effective windward area of ​​the blades is changed, thereby achieving precise control of the output power. Based on measured data from a specific embodiment, stable power generation can be achieved within a wide wind speed range of 8–20 m / s: at low wind speeds, maintaining a small pitch angle for efficient energy capture yields an output power of 205–217 kW; at high wind speeds, by increasing the pitch angle, power is precisely limited, controlling the output power between 147–264 kW. This power regulation capability is comparable to that of a pitch control mechanism, but with a simpler structure.

[0027] 3. Within the braking range described in this invention, the effective windward area of ​​the blades is reduced to 3.5%–8.7% of its maximum value. This drastically reduces the wind energy captured by the blades, resulting in insufficient aerodynamic torque and a rapid decrease in impeller speed. This achieves purely passive aerodynamic braking, eliminating the need for a separate mechanical brake and its drive power source. This braking method has no mechanical contact parts, fundamentally eliminating the wear and maintenance requirements of traditional mechanical brakes. Example data shows that during emergency braking, the impeller speed drops from the rated speed to below 10 rpm within 18 seconds.

[0028] 4. Because the hinge point of the fixed pin is located at the tail of the main load-bearing beam, the center of gravity of the entire machine moves backward along an arc trajectory when the elevation angle increases, thus increasing the anti-overturning lever arm. This effect is a passive geometric effect of the pitch motion of the entire machine, eliminating the need for an additional center of gravity adjustment mechanism. Example data shows that when the elevation angle is adjusted from 0° to 60°, the center of gravity of the entire machine moves backward from 1.2m in front of the tower center to 0.3m, and the sway amplitude decreases from 4.8mm to 1.9mm, effectively improving the anti-overturning capability under strong wind conditions.

[0029] 5. This invention inherits the inherent advantages of load-torque decoupling in beam-shaft wind turbines. During the pitch angle adjustment process, the relative position and force relationship between the main load-bearing beam and the rotary transmission shaft remain unchanged, the torque transmission path is not disturbed, and the generator can continuously and stably receive torque input during the pitch angle adjustment process, ensuring the continuity and stability of power generation.

[0030] 6. In this invention, power regulation, pneumatic braking, and center of gravity self-stabilization are not simply a superposition of independent features, but rather share the core physical motion of pitching the entire machine around the fixed tail pin. When the pitch angle increases: the effective windward area of ​​the blades inevitably decreases → wind energy capture decreases or approaches zero; simultaneously, the center of gravity inevitably shifts backward along a circular arc trajectory → the anti-overturning lever arm increases. There is a necessary physical causal relationship between the three effects, which is naturally obtained due to the single structural design, reflecting a systemic synergistic effect. Furthermore, this invention overcomes the dual technical bias in the field where pitch angle adjustment is limited to wind-following power enhancement and the indispensable role of the pitch mechanism. Attached Figure Description

[0031] The present invention will now be further described with reference to the accompanying drawings.

[0032] Figure 1 This is a side view of the wind turbine generator (in the pitch angle working state) that replaces pitch control according to the present invention.

[0033] Figure 2 for Figure 1 A magnified structural diagram of region A in the middle.

[0034] Figure 3 This is a side view of the wind turbine of the present invention, showing the overall shape of the turbine in a top-down position.

[0035] Figure 4 for Figure 3 A magnified structural diagram of region B in the middle.

[0036] Figure 5 This is a side view of the wind turbine of the present invention, showing the overall shape of the turbine when tilted upwards.

[0037] Figure 6 for Figure 5 A magnified structural diagram of region C in the middle.

[0038] Figure 7 This is a side enlarged view of the upper structure of the fan of the present invention.

[0039] In the diagram: 1 is the tower; 2 is the fixed pin; 3 is the main load-bearing beam; 4 is the lower platform; 5 is the hydraulic cylinder / servo electric cylinder; 6 is the lateral limit support; 7 is the nacelle; 8 is the hub; 9 is the blade; 10 is the speed-increasing transmission system; 11 is the generator; 12 is the yaw system; 13 is the wind measuring device. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0041] Implementation method one, such as Figures 1 to 7 As shown, the wind turbine generator with pitch control as an alternative to pitch control provided by the present invention includes a tower 1, a lower platform 4, a main load-bearing beam 3, a nacelle 7, a hub 8, and blades 9.

[0042] Tower 1 can be a truss steel structure, for example, and the lower platform 4 is assembled on the top of tower 1 through yaw system 12, which can realize horizontal wind regulation.

[0043] The axis of the main load-bearing beam 3 is coaxial with the blade rotation axis, and it is a load-bearing component that does not rotate with the hub. The main load-bearing beam 3 is forged from high-strength alloy steel (such as 42CrMo or 34CrNiMo6) and then machined, designed as a variable cross-section hollow box structure. Its cross-section is rectangular, with the wall thickness gradually increasing from approximately 15mm at the front end to approximately 40mm at the rear end. The height of the front section is approximately 60%–70% of the height of the rear section, serving as the core load-bearing unit of the entire unit. A rotary transmission main shaft runs axially through the internal space of the main load-bearing beam 3. This rotary transmission main shaft is supported by bearings inside the main load-bearing beam 3 and is completely independent of the main load-bearing beam 3 in terms of mechanical structure and force path, serving only to transmit torque. The front end of the rotary transmission main shaft connects to the speed-increasing transmission system on the hub side, and the rear end connects to the generator, retaining the original beam-shaft type wind turbine load and torque decoupling transmission structure.

[0044] The tail of the main load-bearing beam 3 is hinged to the lower platform 4 via a fixed pin 2. The lower platform 4 has a lug at its tail, forming a double-ear plate structure; the main load-bearing beam 3 has a single lug at its tail, inserted between the double lug plates; the fixed pin 2 passes through the holes in both the double and single lug plates, and the three are hinged together by the fixed pin 2. The fixed pin 2 serves as the sole rotating shaft for adjusting the overall pitch angle, and its axis is arranged horizontally to the left and right, perpendicular to the blade rotation axis. A copper-based self-lubricating sliding bearing is installed between the fixed pin 2 and the lug plate hole, with a clearance of H7 / f7 to ensure flexibility of pitch rotation and wear resistance during long-term operation. A limiting structure is provided at the end of the fixed pin 2 to prevent axial movement, and a pitch clearance is maintained between the main load-bearing beam 3 and the lower platform 4 to avoid motion interference. The main load-bearing beam 3 can pitch and rotate relative to the lower platform 4 around the fixed pin 2. All aerodynamic loads (including bending moment and shear force) borne by the main load-bearing beam 3 are transferred to the lower platform 4 via the fixed pin 2, and then to the tower 1 and foundation via the yaw system 12. This hinged structure is simple and reliable, and only undertakes the functions of hinged support and load transfer.

[0045] Thus, unlike the fixed beam-shaft type fans in the prior art, the main load-bearing beam 3 of the present invention is constructed as a motion mechanism that can pitch around the fixed pin at the tail.

[0046] A hydraulic cylinder or servo cylinder 5 is installed below the front of the main load-bearing beam 3 as a pitch drive source. The bottom end of the cylinder body of the hydraulic cylinder or servo cylinder 5 is hinged to the reinforced bearing base of the lower platform 4, and the top end of the piston rod is hinged to the bottom front surface of the main load-bearing beam 3. The installation posture of the hydraulic cylinder or servo cylinder 5 is basically vertical, slightly tilted backward (5° to 15° backward relative to the central axis of the tower), so that the thrust direction of the piston rod is basically consistent with the tangential direction of the rotation of the main load-bearing beam 3 around the fixed pin 2, reducing the radial component force and improving the driving efficiency. The stroke of the hydraulic cylinder or servo cylinder 5, the position of the hinge point, and the length of the main load-bearing beam 3 satisfy the kinematic relationship, ensuring that the piston rod extension and contraction corresponds to the pitch angle change from 0° to 88° throughout the entire stroke.

[0047] The piston rod extends and retracts, driving the main load-bearing beam 3 to pitch around the fixed pin 2. When the piston rod extends, the front end of the main load-bearing beam 3 rises and the pitch angle increases. When the piston rod retracts, the front end of the main load-bearing beam 3 descends and the pitch angle decreases. This, in turn, drives the single rigid motion chain consisting of the main load-bearing beam 3, the nacelle 7, the hub 8, and the blades 9 to pitch synchronously, achieving a continuously adjustable pitch angle from 0° to 88°.

[0048] The front end of the main load-bearing beam 3 is rigidly fixed to the nacelle 7 via a flange bolt assembly. The nacelle 7, hub 8, and blade 9 are rigidly fixed together as a whole via the flange bolt assembly. There are no relative degrees of freedom of movement between the four components, thus forming a single rigid kinematic chain. The three components pitch synchronously with the main load-bearing beam 3. The wind turbine does not have a blade pitch mechanism or its associated slip rings or rotary joints.

[0049] Lateral limiting supports 6 are symmetrically arranged on both sides of the main load-bearing beam 3. The base of the lateral limiting support 6 is fixed to the lower platform 4, and the inner side is provided with wear-resistant and friction-reducing lining blocks that fit against the side of the main load-bearing beam 3. The wear-resistant and friction-reducing lining blocks are made of copper-based alloy or polytetrafluoroethylene composite material, which has a low coefficient of friction and high wear resistance. The lateral limiting supports 6 only restrain the horizontal displacement of the main load-bearing beam 3 and bear the lateral wind load, without interfering with the pitching movement of the main load-bearing beam 3.

[0050] This invention adjusts the effective windward area of ​​blade 9 by changing the elevation angle, thereby regulating the output power. When the elevation angle is small (0° to 10°), the effective windward area of ​​blade 9 is the largest, and the wind energy capture efficiency is the highest. As the elevation angle gradually increases (e.g., 30°, 45°, 60°), the effective windward area decreases according to a cosine law, and the output power decreases accordingly. When the elevation angle is adjusted to 85° to 88°, the effective windward area of ​​blade 9 approaches zero, achieving purely passive aerodynamic braking.

[0051] The nacelle 7 houses a speed-increasing transmission system 10 and a generator 11, with the speed-increasing transmission system 10 located at the front of the nacelle 7 and the generator 11 located at the rear. A wind measuring device 13 is installed at the front of the nacelle 7. The wind turbine is equipped with a control system, which is signal-connected to the wind measuring device 13 and the hydraulic cylinder or servo cylinder 5 to form a closed-loop control. The control system is configured to control the extension and retraction of the hydraulic cylinder or servo cylinder 5 to adjust the pitch angle based on the real-time wind speed and target power fed back by the wind measuring device 13.

[0052] In the second embodiment, the present invention achieves three functions—power regulation, pneumatic braking, and center of gravity self-optimization—through overall machine tilt adjustment. Its core mechanism is as follows.

[0053] The elevation angle α is defined as the angle between the axis of the main load-bearing beam 3 and the horizontal plane. When α = 0°, the rotation axis of the blade is in a horizontal state.

[0054] (I) Geometric Principles of Power Regulation Effective windward area of ​​blade 9 With elevation angle The geometric relationship between them is:

[0055] in, This represents the maximum swept area at an elevation angle of 0°. When the elevation angle... When the angle increases from 0° to 88°, the effective windward area increases from... Gradually decrease to This means the effective windward area is reduced by approximately 96.5%. Wind energy capture power P is directly proportional to the effective windward area ( , Where is air density and V is wind speed; this formula is a qualitative expression of the theoretical power of wind energy, used to illustrate the positive correlation between effective windward area and wind-catching capacity (actual power is also affected by factors such as wind energy utilization coefficient), so the output power can be continuously adjusted by adjusting the elevation angle.

[0056] (II) Mechanism of Pneumatic Braking When the elevation angle is adjusted to 85°–88°, the effective windward area is only 3.5%–8.7% of its maximum value. The wind energy captured by the blades decreases sharply, and the aerodynamic torque is insufficient to maintain impeller rotation, causing the impeller speed to drop rapidly, thus achieving aerodynamic braking. This braking method is purely passive, achieved simply by changing the overall turbine attitude. There is no mechanical contact or wear, and no need for a separate mechanical brake or its drive power source. The triggering condition is: the control system detects that the impeller speed exceeds 120% of the rated speed (overspeed protection threshold) or receives an emergency stop command. The recovery mechanism is: after the fault is cleared or the emergency is lifted, the control system drives the elevation angle back to the normal operating angle (0°–60°), and the wind turbine resumes normal power generation. It should be noted that 85°–88° is a temporary braking condition, not a long-term operating state; within this elevation angle range, the center of gravity shifts backward closer to the tower's central axis, actually improving the anti-overturning capability and eliminating the risk of backward overturning.

[0057] (III) Mechanical principle of center of gravity self-optimization When the entire machine pitches and rotates around the fixed pivot 2, the position of the machine's center of gravity G changes with the pitch angle. Changes. For the conventional beam-shaft wind turbine layout in this field, the center of gravity of the entire unit is in the initial state ( =0°) is usually located in front of the fixed pin 2. With the axis of the fixed pin 2 as the origin, the elevation angle is... When the angle is 0°, the horizontal projection of the center of gravity is located in front of the fixed pin 2. place ( for The horizontal distance from the center of gravity to the center of the fixed pin when the angle is 0° The vertical height of the center of gravity relative to the center of the fixed pin is ( for =0° (vertical height of the center of gravity from the fixed pin axis). When the elevation angle increases to At that time, the center of gravity moves along a circular arc trajectory centered on the axis of the fixed pin, and its horizontal projection position is:

[0058] From the above formula, it can be seen that, with Increasing from 0°, Gradually decrease (center of gravity shifts backward), when When the angle is increased to 60°, the center of gravity is significantly closer to the tower's central axis. This rearward shift of the center of gravity in the horizontal direction increases the anti-overturning lever arm of the entire machine relative to the overturning axis, thus passively improving the overall anti-overturning stability. This effect is passive and requires no additional center of gravity adjustment mechanism. This invention, by specifically positioning the fixed pin hinge point at the tail of the main load-bearing beam, ensures the beneficial effect of the rearward shift of the center of gravity as the elevation angle increases, avoiding the risk of the center of gravity shifting forward or significantly upward due to improper rotation center design.

[0059] (iv) Stages of the entire process of elevation angle change The elevation angle adjustment range of this invention, 0° to 88°, can be divided into three consecutive and non-overlapping functional stages:

[0060] The three functional stages correspond to the different functional performances of the same hardware structure in different elevation angle ranges, reflecting the technical feature of the invention of "one adjustment for three functions".

[0061] Implementation Method 3: This implementation method provides a specific embodiment of a 200kW-class wind turbine generator using hydraulic drive, and its detailed structural parameters and working process are as follows.

[0062] 1. Basic equipment configuration A beam-shaft type wind turbine with a rated power of 200kW and a rated speed of 19.8-30.3rpm is selected. The tower 1 can be a truss steel structure, for example, and the lower platform 4 is assembled to the top of the tower 1 through the yaw system 12.

[0063] The main load-bearing beam 3 is forged from 42CrMo high-strength alloy steel and then heat-treated, designed as a variable cross-section hollow rectangular box structure. The main load-bearing beam 3 has a total length of approximately 6.5 meters, with a front section height of approximately 500mm, a width of approximately 350mm, and a wall thickness of approximately 15mm, and a rear section height of approximately 800mm, a width of approximately 500mm, and a wall thickness of approximately 40mm. The rear end of the main load-bearing beam 3 is hinged to the lower platform 4 via a fixed pin 2. The fixed pin 2 has a diameter of approximately 180mm, is made of 40CrNiMoA, and has undergone surface quenching treatment. A copper-based self-lubricating sliding bearing is installed between the fixed pin 2 and the ear plate hole, with a clearance of H7 / f7.

[0064] A hydraulic cylinder 5 with a rated thrust of 500kN is installed below the front of the main load-bearing beam 3. The cylinder diameter of hydraulic cylinder 5 is approximately 250mm, the piston rod diameter is approximately 160mm, and the rated stroke is approximately 1.4 meters, ensuring that the entire stroke covers the requirements of elevation angle changes from 0° to 88°. The working pressure of the hydraulic system is 16-25MPa.

[0065] Double sets of lateral limiting supports 6 are provided on both sides of the beam. Each set of limiting supports consists of a base, a bracket and a copper-based alloy wear-resistant and friction-reducing liner. The design gap between the liner and the side of the main load-bearing beam 3 is 0.5 to 1.0 mm.

[0066] The nacelle 7 is rigidly fixed to the front end of the main load-bearing beam 3 via flange bolts. The hub 8 is equipped with three blades 9, completely eliminating the pitch mechanism and its associated slip rings or rotary joints. The nacelle 7 has a built-in three-stage speed-increasing transmission system 10, which uses a single-stage planetary gear speed increase (speed ratio 1:5) plus two stages of parallel shaft gear speed increase (speed ratios of 1:4 and 1:3 respectively), with a total speed ratio of 1:60. The generator 11 is a permanent magnet synchronous generator with a rated power of 200kW and a rated speed of 1200rpm. An integrated wind measurement device 13, including an anemometer and wind vane, is installed at the front of the nacelle 7.

[0067] The control system uses a PLC controller, which is connected to the servo valve signals of the wind measuring device 13 and the hydraulic cylinder 5 to form a closed-loop control.

[0068] 2. Basis for Thrust Selection The selection criteria for a rated thrust of 500kN are as follows: The total weight of the machine is approximately 28 tons, the horizontal distance between the machine's center of gravity and the fixed pin 2 is approximately 2.5 meters (when α=0°), and the pitching moment is approximately 700kN·m. Hydraulic cylinder 5 acts on the front of the main load-bearing beam 3, and its point of action is approximately 1.8 meters horizontally from the fixed pin 2. Considering a safety factor of 1.5 and a dynamic load factor of 1.2, the required rated thrust is approximately 700kN·m × 1.5 × 1.2 / 1.8m ≈ 700kN. Considering the efficiency of the hydraulic system and design margin, a thrust rating of 500kN is selected, which can meet the pitching drive requirements under all working conditions.

[0069] 3. Specific implementation process and measured data (1) Initial power generation conditions (high-efficiency capture zone, 0°~20°): The elevation angle is maintained at 5°, the wind speed is detected by the wind measuring device 13 at 8~11m / s, the control system controls the piston rod of the hydraulic cylinder 5 to retract, the whole machine maintains a small elevation angle attitude, and the effective windward area of ​​the blades 9 is maximized. The measured output power is stable at 205~217kW, close to the rated power, realizing high-efficiency capture at low wind speed.

[0070] (2) High wind speed power regulation condition (power limit adjustment zone, 20°~60°): When the wind speed rises to 13m / s, the control system controls the hydraulic cylinder 5 to extend and adjust the elevation angle to 20°. At this time, the effective windward area of ​​the blade 9 decreases by about 6%, and the measured output power stabilizes at 249kW, avoiding over-power operation. When the wind speed rises to 15m / s, the elevation angle is adjusted to 30°, and the output power is controlled at 264kW, achieving safe load limiting. When the wind speed rises to 20m / s, the elevation angle is adjusted to 55°, and the output power drops to 224kW, maintaining stable power generation without overspeed.

[0071] The complete measured data for the above operating conditions are shown in the table below:

[0072] The above data shows that the control system can accurately match the optimal elevation angle according to the wind speed, and achieve stable power generation under different operating conditions without the need for blade pitching.

[0073] 4. Logic for determining the target elevation angle The control system determines the target elevation angle by using a linear interpolation method based on the real-time wind speed, the deviation between the current output power and the target power, and the pre-stored power-elevation angle-wind speed mapping table (as shown in the example above). Then, it controls the servo valve of the hydraulic cylinder 5 to drive the main load-bearing beam 3 to the target position.

[0074] 5. System response time From the moment the wind speed change is detected by the wind measuring device 13, processed by the control system (approximately 50ms), to the moment the hydraulic cylinder 5 actuates to bring the main load-bearing beam 3 to the target elevation angle position, the total system response time is 3 to 8 seconds (depending on the elevation angle change range), which can meet the rapid power adjustment requirements under the condition of transient wind speed changes in the wind field.

[0075] 6. Verification of changes in center of gravity As the elevation angle was gradually adjusted from 0° to 60°, the center of gravity of the entire aircraft gradually shifted backward from 1.2m in front of the center of tower 1 to 0.3m in front of the center of tower 1. The overall sway amplitude decreased from 4.8mm to 1.9mm, significantly improving operational stability and verifying the passive gain effect of shifting the center of gravity backward. In contrast, if the hinge point is located below the nacelle (as in the US4435646A design), the center of gravity will shift forward as the elevation angle increases, and the anti-overturning capability will actually decrease.

[0076] 7. Emergency pneumatic braking condition (brake preparation and execution zone, 60°~88°) When the wind turbine overspeeds (impeller speed exceeds 120% of rated speed) or requires emergency shutdown, under the rated flow of the hydraulic system, the control system controls hydraulic cylinder 5 to quickly extend fully, adjusting the elevation angle to 85° within 18 seconds. This reduces the effective frontal area ratio to approximately cos85°≈0.087, rapidly reducing the generator 11 output power to below 5kW, and lowering the impeller speed from the rated speed to below 10rpm, completing a wear-free pneumatic brake operation without the need for mechanical braking. After the fault is cleared, the control system restores the elevation angle to its normal operating angle, and the wind turbine resumes normal power generation.

[0077] 8. Long-term operation verification After 3600 hours of continuous operation, including wind speed variations of 11–18 m / s, the main load-bearing beam 3 showed no deformation, the wear-resistant and friction-reducing lining of the lateral limiting support 6 showed no significant wear, the elevation angle adjustment accuracy error was ≤ ±1°, and the power control deviation was ≤ ±1.8%. The entire machine operated stably without any related functional failures, fully verifying the feasibility and reliability of using elevation angle adjustment to replace the pitch control mechanism.

[0078] Implementation Method Four: This implementation method provides a specific embodiment of a 200kW wind turbine generator driven by a servo electric cylinder. The hydraulic cylinder in Implementation Method Three is replaced with a servo electric cylinder 5 with a rated thrust of 500kN; all other structural parameters are completely identical to those in Implementation Method Three.

[0079] The servo electric cylinder uses ball screw drive and has a built-in absolute encoder as a position sensor, forming a fully closed-loop control with the control system. The servo motor has a rated power of 15kW and a rated speed of 1500rpm, and drives the ball screw after being reduced in speed by a reducer.

[0080] With the adoption of servo electric cylinder drive, the piston rod position control accuracy can reach ±0.1mm, and the corresponding elevation angle adjustment accuracy is improved to ±0.3° (better than the ±1° of hydraulic cylinder). The system response time is shortened to 2-5 seconds.

[0081] The system operated continuously for 3,600 hours without failure, with a power control deviation of ≤±1.2%, further demonstrating the reliability of the pitch angle control mechanism as a replacement for the pitch mechanism, as well as the advantages of the overall structural optimization.

[0082] Implementation Method Five: Based on the successful verification of the 200kW-class wind turbine described above, the technical solution of this invention can be extended to MW-class large-scale wind turbine generator sets. Specific implementation parameters are given below using a 2MW-class wind turbine as an example.

[0083] 1.2MW wind turbine basic configuration A beam-shaft wind turbine with a rated power of 2MW and a rated speed of 12-18rpm is selected. Tower 1 adopts a conical steel pipe tower, and the lower platform 4 is assembled to the top of tower 1 through a yaw system 12.

[0084] The main load-bearing beam 3 is forged from 34CrNiMo6 high-strength alloy steel and then heat-treated, designed as a variable cross-section hollow rectangular box structure. The main load-bearing beam 3 has a total length of approximately 12 meters, with a front section height of approximately 800mm, a width of approximately 600mm, and a wall thickness of approximately 25mm, and a rear section height of approximately 1300mm, a width of approximately 900mm, and a wall thickness of approximately 70mm. The rear end of the main load-bearing beam 3 is hinged to the lower platform 4 via a fixed pin 2. The fixed pin 2 has a diameter of approximately 350mm, is made of 34CrNiMo6, and has undergone surface quenching treatment. A copper-based self-lubricating sliding bearing is installed between the fixed pin 2 and the ear plate hole.

[0085] A hydraulic cylinder 5 with a rated thrust of 2500kN is installed below the front of the main load-bearing beam 3. The cylinder diameter of hydraulic cylinder 5 is approximately 500mm, the piston rod diameter is approximately 300mm, and the rated stroke is approximately 2.5 meters, ensuring that the entire stroke covers the requirements of elevation angle changes from 0° to 88°. The working pressure of the hydraulic system is 25-32MPa.

[0086] The engine compartment 7 houses a three-stage speed-increasing transmission system 10, employing a two-stage planetary gear speed-increasing system (total speed-increasing ratio 1:25) plus a single-stage parallel shaft gear speed-increasing system (speed-increasing ratio 1:4), with a total speed-increasing ratio of 1:100. The generator 11 is a doubly-fed asynchronous generator with a rated power of 2MW and a rated speed of 1500rpm.

[0087] Comparison of key parameters of 2.2MW wind turbines

[0088] 3. Generality Specifications for MW-class Wind Turbines For higher power levels (such as 3MW, 5MW, etc.), the basic architecture is completely consistent with the above embodiments. Only the specifications of key components need to be adjusted proportionally according to the power level. The elevation angle control principle, control strategy, and functional stage division of MW-class wind turbines are exactly the same as those of 200kW-class wind turbines. Both achieve the triple functions of efficient energy capture, power limiting regulation, and pneumatic braking through continuous elevation angle adjustment from 0° to 88°.

[0089] The expected technical effects of MW-class wind turbines are the same as those of 200kW-class wind turbines: complete elimination of the pitch mechanism and its auxiliary components, simplified structure, improved reliability, precise power control, wear-free aerodynamic brakes, and self-optimized center of gravity. The increase in power rating does not change the core inventive concept and technical solution of this invention.

[0090] In a sixth embodiment, the present invention also provides a power control method for the wind turbine described above, which uses the overall turbine pitch angle as the controlled object instead of blade pitch control, and includes the following steps: (1) The control system obtains the real-time wind speed through the wind measuring device 13 and determines the target elevation angle based on the real-time wind speed; (2) When low wind speed conditions are detected (e.g., wind speed of 8 to 11 m / s), the control system controls the hydraulic cylinder or servo electric cylinder 5 to retract, so that the main load-bearing beam 3 is kept in the energy capture range (0° to 10°) with a small elevation angle, thereby maximizing the effective windward area of ​​the blade 9 in the single rigid motion chain and achieving efficient energy capture at low wind speed. (3) When a high wind speed condition is detected (e.g., wind speed of 13 to 20 m / s), the control system controls the hydraulic cylinder or servo cylinder 5 to extend, increasing the elevation angle of the main load-bearing beam 3 to the power limit range (e.g., 20° to 55°), thereby reducing the effective windward area of ​​the blades 9 in the single rigid motion chain and limiting the output power within the rated range. (4) When overspeed is detected (e.g., the impeller speed exceeds 120% of the rated speed) or an emergency stop is required, the control system controls the hydraulic cylinder or servo electric cylinder 5 to extend quickly and fully, adjusting the elevation angle of the main load-bearing beam 3 to the braking range (85°~88°), thereby making the effective windward area of ​​the blade 9 in the single rigid motion chain approach zero, thus achieving pure passive pneumatic braking.

[0091] The control system determines the target elevation angle based on the real-time wind speed and target power fed back by the wind measuring device 13 by looking up a table (based on a power-elevation angle-wind speed mapping table) or by real-time calculation, and precisely adjusts the extension and retraction of the hydraulic cylinder or servo electric cylinder 5 to achieve stable output within the rated power and power limit protection when the wind speed exceeds the limit.

[0092] This invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A wind turbine with alternative variable pitch by pitch angle control, comprising: Tower (1); lower platform (4), installed on the top of the tower (1); The main load-bearing beam (3) is a load-bearing component that does not rotate with the hub, and the axis of the main load-bearing beam (3) is coaxial with the axis of rotation of the blade; the nacelle (7), the hub (8), and the blade (9); characterized in that, The main load-bearing beam (3) is a variable cross-section hollow box structure and is constructed as a pitch-down motion mechanism; A rotary transmission main shaft is axially inserted into the internal space of the main load-bearing beam (3). The rotary transmission main shaft and the main load-bearing beam (3) are independent of each other in terms of mechanical structure and force path, and are only used to transmit torque. The front end of the rotary transmission main shaft is connected to the speed-increasing transmission system on the hub side, and the rear end is connected to the generator. The tail of the main load-bearing beam (3) is hinged to the lower platform (4) through a fixed pin (2), and the fixed pin (2) serves as the rotation shaft for adjusting the overall elevation angle; the load borne by the main load-bearing beam (3) is transmitted to the lower platform (4) through the fixed pin (2). A hydraulic cylinder or servo cylinder (5) is provided below the front part of the main load-bearing beam (3). The bottom end of the cylinder body of the hydraulic cylinder or servo cylinder (5) is hinged to the lower platform (4), and the top end of the piston rod is hinged to the bottom front part of the main load-bearing beam (3) to drive the main load-bearing beam (3) to pitch, thereby driving the single rigid motion chain composed of the main load-bearing beam (3), the nacelle (7), the hub (8), and the blade (9) to pitch synchronously. The nacelle (7), hub (8) and blade (9) are rigidly fixed to the front end of the main load-bearing beam (3), thus forming the single rigid motion chain. The three components pitch synchronously with the main load-bearing beam (3) and have no relative motion degrees of freedom with each other. The wind turbine is not equipped with a blade pitch mechanism; The wind turbine also includes a control system configured to control the extension or retraction of the hydraulic cylinder or servo cylinder (5) based on real-time wind speed and target power, so as to adjust the output power by adjusting the elevation angle of the single rigid motion chain.

2. A wind turbine with tilt instead of variable pitch according to claim 1, characterized in that: The piston rod of the hydraulic cylinder or servo cylinder (5) extends and retracts to drive the main load-bearing beam (3) to pitch around the fixed pin shaft (2), so that the pitch angle can be continuously adjusted between 0° and 88°. When the pitch angle is adjusted to the braking range of 85° to 88°, the effective windward area of ​​the blade (9) approaches zero, so as to achieve pure passive pneumatic braking.

3. The elevation controlled alternative variable pitch wind turbine of claim 1, wherein: The hinge point of the fixed pin (2) is located at the tail of the main load-bearing beam (3), so that when the elevation angle increases, the projection of the overall center of gravity of the single rigid kinematic chain composed of the main load-bearing beam (3), the nacelle (7), the hub (8), and the blade (9) in the horizontal direction moves backward and closer to the central axis of the tower (1), thereby passively improving the overturning stability of the whole machine while realizing power limitation or pneumatic braking.

4. The elevation controlled alternative variable pitch wind turbine of claim 1, wherein: Lateral limiting supports (6) are symmetrically arranged on the left and right sides of the main load-bearing beam (3). The base of the lateral limiting support (6) is fixed to the lower platform (4). The inner side is provided with wear-resistant and friction-reducing lining blocks and fits against the side of the main load-bearing beam (3). The lateral limiting support (6) is used to constrain the horizontal displacement of the main load-bearing beam (3) and bear the lateral wind load, and does not interfere with the pitching action of the main load-bearing beam (3).

5. The elevation controlled alternative variable pitch wind turbine of claim 1, wherein: The cabin (7) is equipped with a wind measuring device (13), and the control system is connected to the wind measuring device (13) and the hydraulic cylinder or servo electric cylinder (5) to form a closed-loop control.

6. The elevation controlled alternative variable pitch wind turbine of claim 1, wherein: The main load-bearing beam (3) is made of high-strength alloy steel forged and then machined.

7. The elevation controlled alternative variable pitch wind turbine of claim 1, wherein: The lower platform (4) is mounted on the top of the tower (1) via a yaw system (12).

8. A power control method for a wind turbine generator as described in any one of claims 1-7, characterized in that, Replacing blade pitch control with overall engine pitch angle as the controlled object includes the following steps: S1. The control system obtains the real-time wind speed through the wind measuring device (13) and determines the target elevation angle based on the real-time wind speed; S2. When a low wind speed condition is detected, the control system controls the hydraulic cylinder or servo electric cylinder (5) to retract, so that the main load-bearing beam (3) is kept in the energy capture range with a small elevation angle, thereby maximizing the effective windward area of ​​the blades (9) in the single rigid motion chain, and realizing efficient energy capture at low wind speed. S3. When a high wind speed condition is detected, the control system controls the hydraulic cylinder or servo electric cylinder (5) to extend, increasing the elevation angle of the main load-bearing beam (3) to the power limit range, thereby reducing the effective windward area of ​​the blade (9) in the single rigid motion chain and limiting the output power within the rated range. S4. When overspeed is detected or an emergency stop is required, the control system controls the hydraulic cylinder or servo electric cylinder (5) to extend quickly and fully, adjusting the elevation angle of the main load-bearing beam (3) to the braking range, thereby making the effective windward area of ​​the blade (9) in the single rigid motion chain approach zero, and realizing pure passive pneumatic braking.

9. The power control method according to claim 8, characterized in that: The target elevation angle is determined by looking up a table or by real-time calculation.

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