Small wind driven generator with passive blade pitch angle deflection mechanism

Abstract

The invention discloses a small-sized wind driven generator with a passive blade pitch angle deflection mechanism. The small-sized wind driven generator comprises blades, a hub, a power generator, a torque generator and the pitch angle deflection mechanism, wherein the pitch angle deflection mechanism consists of a driving bevel gear, a passive bevel gear, a tension spring, a limiter, a torque generator rotating shaft and a related bearing; the blades are connected with the hub through bearings, the hub and a power generator rotating shaft fix a driving rotor, and the roots of the blades are connected with a driven bevel gear in the hub and receive torque which is transmitted by a driving bevel gear and generated by a torque generator rotating shaft concentric with the power generator rotating shaft. When the rotating speed of the impeller is lower than the rated rotating speed, the tension spring tensions the driving bevel gear to enable the blades to keep the initial pitch angle, and when the rotating speed of the impeller is higher than the rated rotating speed, the torque of the torque generator begins to overcome the resistance of the tension spring on the driving bevel gear, rotate the blades and increase the pitch angle, and at the moment, the rotating speed is reduced; and the steps are repeated, so that the rotating speed is kept balanced.

Description

Technical Field

[0001] The invention relates to a small permanent magnet synchronous wind generator, in particular to a small wind generator with a passive blade pitch angle deflection mechanism. Background Art

[0002] Wind energy is a renewable, green energy source, and small wind turbines have a wide range of applications. However, due to economic reasons, small wind turbines cannot utilize the complex active control systems of large wind turbines. Currently, simple passive control solutions are primarily used, namely, tail rudder yaw and centrifugal flybars. However, both solutions have drawbacks. The former suffers from high energy loss and low energy conversion efficiency, while the latter suffers from slow wind speed tracking and the tendency for blades to break when stopped against the wind. This proposal utilizes a torque generator and pitch angle deflection mechanism with concentric shafts to provide power for blade deflection. This passive control approach addresses the safety concerns of wind turbines at high wind speeds while also avoiding the drawbacks of the aforementioned two solutions. This proposal addresses four key issues: first, deriving the power source for blade pitch angle deflection; second, how to transmit this power to the blades; third, how to control this power to achieve different effects above and below rated wind speeds; and fourth, how to avoid the need to expose a large area of the blades to the wind when limiting and braking the impeller at high speeds. Summary of the Invention

[0003] The purpose of the present invention is to solve the safety problem of blades under high wind speeds in a passive control manner and to develop a small wind turbine with a passive blade pitch angle deflection mechanism, including blades, a hub, a power generator, a torque generator and a pitch angle deflection mechanism composed of an active bevel gear, a passive bevel gear, a tension spring, a limiter, a torque generator shaft and related bearings; the blades are connected to the hub through bearings, the hub is fixedly connected to the power generator shaft for driving the power generator to generate power with load, the root end face of the blade is connected to the passive bevel gear inside the hub, and receives the torque generated by the torque generator shaft concentric with the power generator shaft transmitted by the active bevel gear, one end of the tension spring 7 is fixed to the active bevel gear 5, and the other end is fixed to the hub 2.

[0004] The operating characteristics of this small wind turbine are that the power generator and the torque generator generate electricity separately under the drive of the rotor's rotational torque. The power generator generates electricity directly for supplying electrical energy to the load, while the torque generator generates electricity for generating torque to provide power for deflecting the blade pitch angle. The torque generator's shaft passes through the inner cavity of the power generator's shaft, forming a concentric structure with a larger outer portion and a smaller inner portion, and supported by different bearing groups. When the wind speed is lower than the rated wind speed, that is, the impeller speed is lower than the rated speed, the torque generated by the torque generator is insufficient to overcome the resistance of the pitch angle deflection mechanism, and the pitch angle remains unchanged at its initial position. When the wind speed exceeds the rated wind speed, that is, the impeller speed exceeds the rated speed, the torque of the torque generator begins to overcome the resistance of the pitch angle deflection mechanism, rotating the blades and increasing their pitch angle. At this time, the windward surface of the blades is reduced, the lift-to-drag ratio decreases, and the speed decreases. If the wind speed increases further and the impeller speed continues to increase, the pitch angle increases again, and the speed decreases. This process repeats. When the wind speed exceeds the rated wind speed, the blade pitch angle is passively adjusted to maintain a balanced speed.

[0005] The pitch angle deflection mechanism is used to passively deflect the pitch angle of the blades when the impeller rotates to the rated speed. The initial tension of the tension spring is designed to be equal to the torsional force generated by the torque of the torque generator transmitted to the active bevel gear and the tension spring fixing point through the torque generator shaft when the impeller is at the rated speed; when the impeller speed is lower than the rated speed, the initial tension of the tension spring is greater than the torsional force of the active bevel gear, and the blades are fastened at the initial pitch angle by the tension of the tension spring, while driving the torque generator shaft to rotate and generate electricity. At this time, the torque generator shaft and the power generator shaft rotate at the same speed and generate electricity respectively; when the impeller speed is greater than the rated speed, the torsional force generated by the pitch angle deflection mechanism is greater than the initial tension of the tension spring 7, the tension spring is stretched, the passive bevel gear starts to rotate, driving the blades to deflect, and the pitch angle increases. At this time, the speed of the torque generator shaft is lower than the speed of the power generator shaft. This is because the torque generator consumes a certain amount of energy to rotate the pitch angle of the blades.

[0006] In the pitch angle deflection mechanism, the torque generated by the torque generator is transmitted to the blades through the torque generator shaft, the active bevel gear, and the passive bevel gear. It is the power that drives the blade deflection. The tension of the tension spring is the resistance that the torque generator needs to overcome. At low wind speeds, the torque is insufficient and cannot overcome the tension, so the pitch angle remains unchanged. At high wind speeds, the torque is sufficient to overcome the tension, and the pitch angle increases. At this time, the leading edge and the upper surface of the blade face the wind, the windward surface is very small, and the wind pressure on the blade is very small. If the lower surface of the blade faces the wind, the windward area of the blade is large and the wind pressure it bears is very large. The limiter is a stop limit position for the deflection angle of the active bevel gear when the blade is deflected to the maximum pitch angle. The pitch angle here is the maximum pitch angle, which is the angle when the blade is deflected to make the lift-to-drag ratio of the blade 0.

[0007] The power generator and the torque generator are both permanent magnet synchronous generators. The output line voltage of the power generator and the torque generator is the same. Their same-phase line voltages are connected in parallel and output to jointly provide electrical energy to the load. The sum of their output power is the output power of the entire wind turbine. The output power of the power generator is much greater than the output power of the torque generator. The rated output power torque of the designed torque generator is equal to the resistance torque of the pitch angle deflection mechanism at the rated wind speed.

[0008] Description of the accompanying drawings.

[0009] Attachment Figure 1 The diagram is a structural diagram of a small wind turbine with a passive blade pitch angle deflection mechanism provided by an embodiment of the present invention.

[0010] Attachment Figure 2 It is a detailed schematic diagram of a pitch angle deflection mechanism of a small wind turbine with a passive blade pitch angle deflection mechanism provided by an embodiment of the present invention.

[0011] Specific application mode.

[0012] The following will refer to the attached Figure 1 , Attachment Figure 2 Exemplary embodiments of the present invention are described. Figure 1 , Attachment Figure 2 While exemplary embodiments of the present invention are shown, it should be understood that the present invention may be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to facilitate a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0013] Refer to the attached Figure 1 , Attachment Figure 2An embodiment of the present invention provides a small wind turbine with a passive blade pitch angle deflection mechanism, including a blade 1, a hub 2, a power generator 3, a torque generator 4 and a pitch angle deflection mechanism consisting of an active bevel gear 5, a passive bevel gear 6, a tension spring 7, a limiter 8, a torque generator shaft 10, and related bearings 11; the blade 1 is connected to the hub 2 through a bearing, and the hub 2 is fixedly connected to the power generator shaft 9 for driving the power generator to generate power with a load. The root of the blade 1 is connected to the passive bevel gear 6 inside the hub 2, and receives the torque generated by the torque generator shaft 10 concentric with the power generator shaft 9 transmitted by the active bevel gear 5. One end of the tension spring 7 is fixed to the active bevel gear 5, and the other end is fixed to the hub 2. The operating characteristics of this small wind turbine are that the power generator 3 and the torque generator 4 generate electricity respectively under the drive of the impeller rotation torque, wherein the power generator 3 generates electricity directly for providing electrical energy to the load, and the torque generator 4 generates electricity for generating torque to provide power for the pitch angle of the deflection blade 1 in addition to providing electrical energy to the load. The torque generator shaft 10 passes through the inner cavity of the power generator shaft 9, and the two form a structure with a larger outer side and a smaller inner side, concentric and different axes, and are supported by different bearing groups respectively; when the wind speed is lower than the rated wind speed, that is, the impeller speed is lower than the rated speed, the torque generator The torque generated by 4 is not enough to overcome the resistance of the pitch angle deflection mechanism, and the pitch angle remains unchanged at the initial position. When the wind speed is greater than the rated wind speed, that is, the impeller speed is higher than the rated speed, the torque of the designed torque generator 4 begins to overcome the resistance of the pitch angle deflection mechanism to rotate the blade 1, increasing its pitch angle. At this time, the windward surface of the blade 1 is reduced, the lift-to-drag ratio decreases, and the speed decreases. If the wind speed increases again and the impeller speed continues to increase, the pitch angle increases again, and the speed decreases. This is repeated. When the wind speed is greater than the rated wind speed, it plays a role in passively adjusting the blade pitch angle and maintaining the speed balance.

[0014] The sum of the output powers of the power generator 3 and the torque generator 4 is the total power output power of the wind turbine. The power distribution between them needs to have a reasonable ratio. The selection of the output power of the torque generator 4 mainly considers whether the output torque of the torque generator 4 can drive the blade deflection under high wind speed. Generally, it can be taken as 10-20% of the total output power. The torque generated at this time can be calculated by the relationship between the power, torque and speed of the generator: power P = torque T * speed n.

[0015] The pitch angle deflection mechanism is used to passively deflect the pitch angle of the blade 1 when the impeller rotates to the rated speed. The initial tension of the tension spring 7 is designed to be equal to the torsional force generated by the torque of the torque generator 4 transmitted to the active bevel gear 5 and the tension spring fixing point through the torque generator shaft 10 when the impeller is at the rated speed; when the impeller speed is lower than the rated speed, the initial tension of the tension spring 7 is greater than the torsional force of the active bevel gear 5, thereby driving the torque generator shaft 10 to rotate and generate electricity. At this time, the initial pitch angle of the blade 1 remains unchanged, and the torque generator shaft 10 rotates at the same speed as the power generator shaft 9; when the impeller speed is greater than the rated speed, the torsional force generated by the pitch angle deflection mechanism is greater than the initial tension of the tension spring 7, the tension spring is stretched, the passive bevel gear starts to rotate, driving the blade 1 to rotate, and the pitch angle increases. At this time, the speed of the torque generator shaft 10 is lower than the speed of the power generator shaft 9. This is because the torque generator consumes a certain amount of energy to rotate the pitch angle of the blade.

[0016] In the pitch angle deflection mechanism, the torque generated by the torque generator 4 is transmitted to the blade 1 as a rotational force through the torque generator shaft 10, the active bevel gear 5, and the passive bevel gear 6. Only when the torque generator 4 overcomes the tension of the tension spring 7 can the blade pitch angle be deflected, otherwise the blade maintains the initial pitch angle unchanged; the function of the limiter 8 is to limit the deflection angle of the active bevel gear 5 when the blade deflects to the maximum pitch angle. The pitch angle here is the maximum pitch angle, which is the angle when the blade deflects to make the lift-to-drag ratio of the blade 0. The limiter 8 consists of a protrusion on the active bevel gear 5 and a protrusion on the front baffle of the hub. The two protrusions collide when the pitch angle deflects to the maximum angle, preventing the pitch angle from increasing further.

[0017] Here it is necessary to calculate the initial tension of the tension spring 7. The calculation basis is that the initial tension of the tension spring 7 is equal to the torsional force generated by the torque of the torque generator 4 transmitted to the driving bevel gear 5 and the tension spring fixing point through the torque generator shaft 10 when the impeller is at rated speed. Therefore, the initial tension of the tension spring 7 can be calculated by the torque of the torque generator 4 and the torsional force transmitted to the connection point between the driving bevel gear 5 and the tension spring 7; in addition, the angular difference from the initial pitch angle of the blade to the maximum pitch angle at high wind speed must also be considered to determine the diameter, length, wire diameter of the tension spring, and the position of the limiter.

[0018] The power generator 3 and the torque generator 4 are both permanent magnet synchronous generators, and the output voltages of the power generator 3 and the torque generator 4 are the same, and their rotation speeds are also the same most of the time. Their same-phase line voltages can be connected in parallel and output to smoothly provide electrical energy to the load; the output power of the power generator 3 is much greater than the output power of the torque generator 4, and the rated output power torque of the torque generator 4 is equal to the resistance torque of the pitch angle deflection mechanism at the rated wind speed.

Claims

1. A small wind turbine with a passive blade pitch angle deflection mechanism, comprising a blade 1, a hub 2, a power generator 3, a torque generator 4, and a pitch angle deflection mechanism consisting of a driving bevel gear 5, a driven bevel gear 6, a tension spring 7, a stopper 8, a torque generator shaft 10, and associated bearings 11. The blade 1 is connected to the hub 2 via a bearing, which is fixedly connected to the power generator shaft 9 for driving the power generator rotor to generate electricity. The root end face of the blade 1 is connected to the driven bevel gear 6 inside the hub 2, which receives torque transmitted from the driving bevel gear 5 by the torque generator shaft 10, which is concentric with the power generator shaft 9. One end of the tension spring 7 is fixed to the driving bevel gear 5, and the other end is fixed to the hub 2. The operating characteristics of this small wind turbine are that the power generator 3 and the torque generator 4 generate electricity respectively under the drive of the impeller rotation torque, wherein the power generator 3 generates electricity directly for providing electrical energy to the load, and the torque generator 4 generates electricity for generating torque to provide power for the pitch angle of the deflection blade 1 in addition to providing electrical energy to the load. The torque generator shaft 10 passes through the inner cavity of the power generator shaft 9, and the two form a structure with a larger outer side and a smaller inner side, concentric and different axes, and are supported by different bearing groups respectively; when the wind speed is lower than the rated wind speed, that is, the impeller speed is lower than the rated speed, the torque generator The torque generated by the motor 4 is not enough to overcome the resistance of the pitch angle deflection mechanism, and the pitch angle remains unchanged at its initial position. When the wind speed is greater than the rated wind speed, that is, the impeller speed is higher than the rated speed, the torque of the designed torque generator 4 begins to overcome the resistance of the pitch angle deflection mechanism to rotate the blade 1, increasing its pitch angle. At this time, the windward surface of the blade 1 is reduced, the lift-to-drag ratio decreases, and the speed decreases. If the wind speed increases again and the impeller speed increases, the pitch angle increases again and the speed decreases. This is repeated. When the wind speed is greater than the rated wind speed, it plays a role in passively adjusting the blade pitch angle and maintaining the speed balance.

2. The pitch angle deflection mechanism is used to passively deflect the pitch angle of the blade 1 when the impeller rotates to the rated speed. The initial tension of the tension spring 7 is designed to be equal to the torsional force generated by the torque of the torque generator 4 transmitted to the active bevel gear 5 and the tension spring fixing point through the torque generator shaft 10 when the impeller is at the rated speed; when the impeller speed is lower than the rated speed, the initial tension of the tension spring 7 is greater than the torsional force of the active bevel gear 5. At this time, the initial pitch angle of the blade 1 remains unchanged, and the torque generator shaft 10 and the power generator shaft 9 rotate at the same speed, generating electricity separately; when the impeller speed is greater than the rated speed, the torque generator 4 outputs a greater torque, causing the torsional force generated by the pitch angle deflection mechanism to be greater than the initial tension of the tension spring 7, the tension spring is stretched, the passive bevel gear 6 starts to rotate, driving the blade 1 to rotate, and the pitch angle increases. At this time, the speed of the torque generator shaft 10 is lower than the speed of the power generator shaft 9.

3. In the pitch angle deflection mechanism, the torque generated by the torque generator 4 is transmitted to the blade 1 via the torque generator shaft 10, the driving bevel gear 5, and the driven bevel gear 6. This is the power that drives the deflection of the blade 1. The tension of the tension spring 7 is the resistance that needs to be overcome by the torque generator 4. The limiter 8 is a stop limit for the deflection angle of the driving bevel gear 5 when the blade is deflected to the maximum pitch angle. Here, the maximum pitch angle is the angle at which the blade is deflected to a point where the lift-to-drag ratio of the blade is 0.

4. The power generator 3 and the torque generator 4 are both permanent magnet synchronous generators. The output line voltages of the power generator 3 and the torque generator 4 are the same. Their in-phase line voltages are connected in parallel and output to provide electrical energy to the load. The output power of the power generator 3 is much greater than the output power of the torque generator 4. The rated output power torque of the torque generator 4 is designed to be equal to the resistance torque of the pitch angle deflection mechanism at the rated wind speed.

5. The bearings 11 are a series of bearings that support the rotation of the blade 1, the power generator shaft 9 and the torque generator shaft 10, wherein the bearings supporting the power generator shaft 9 and the torque generator shaft 10 operate independently.

Images