CN1009020B - wind turbine pitch control hub - Google Patents

Abstract

In pitch wind turbine systems, the pitch angle is determined by a pneumatic-hydraulic actuator connected between cranks on the pitch shaft of the blades. The hydraulic circuit runs concentrically through the rotor drive shaft and, via the rotary union, reaches the gas-filled accumulator on the deflection carrier. The pitch axis is positively connected by a gear train for 1: 1 counter rotation, preferably on one side of the rotor axis, opposite the hydraulic actuator.

Description

The present invention relates generally to control systems for wind turbine rotors, and in particular to automatic The control system, the generator is connected to the power grid. The angle of the blades, that is, the pitch, can be controlled to adjust the output torque and achieve the highest output power within a design range of wind speed. This is an all-mechanical, passive system, which is ideal for reliability because it is relatively immune to environmental factors and failures in the sensing or control systems.

Most existing pitch controllable rotors are of active pitch control. The sensor senses the need, so that the electric system or the hydraulic system will change the pitch. An inherent potential weakness of such systems is the inability to adjust to high pitch angles to slow down or stop the turbine when the sensing system, or the microprocessor system, or the actuation system or mechanism fails.

On the contrary, even if the control system fails, the passive automatic recovery system can still automatically return to the safe pitch, that is, the high angle of attack pitch.

U.S. Patent No. 4,435,646 discloses a wind turbine pitch control system comprising a housing that confines the pitch axes of a pair of spaced parallel blades in a plane between the two pitch axes Intersect the rotor axis near the midpoint, and a mechanical control device actively determines the pitch angle during operation. This arrangement suffers from the deficiencies of most existing wind turbine pitch control systems.

The main purpose of the present invention is to utilize a reliable power mechanical system to control the output torque of the variable-pitch wind turbine, which automatically controls the pitch of the blades as the blade moment changes due to the wind load and centrifugal force.

In the passive pitch control system of a double-blade rotor of the present invention, the two blades are parallel to the pitch adjustment shaft and are directly connected by a gear train. The pitch angle is determined by a gas-hydraulic linear actuator connected between the cranks on the shafts of the two blades. The hydraulic line runs concentrically through the rotor drive shaft and connects to a gas-charged accumulator through a rotary union.

In the ideal structural figure of the upwind stable deflection wind turbine with the deflection hub, the pitching axes of the parallel blades form a rotor plane passing through the rotor transmission axis, and the rotor transmission axis intersects the rotor plane at the midpoint between the two pitching axes. The propeller shafts coaxial with the propeller axis respectively are supported on the hub shell. The shaft ends of the blades overlap each other by a considerable length. In an ideal embodiment, a gear train connects the two shafts on one side of the rotor axis, and on the other side there is a linear actuator connected between the crank on the shaft. The actuator preferably works in parallel with the gear train. A retractable hydraulic linkage and "gas spring" between the blade pitch shafts provides manual manual control and automatic shutdown through blade feathering.

Fig. 1 is a side view of the tower-type double-blade upwind turbine of the present invention, the pitch-controlled rotor hub of which is in working condition.

Fig. 2 is a top view of the wind turbine along the line 2-2 in Fig. 1 .

Fig. 3 is a bottom view of the rotor hub along the line 3-3 in Fig. 1 .

Fig. 4 is a cross-sectional view of the shaft end of the hub in Fig. 1 along line 4-4.

Figure 5 is a schematic diagram of the hydraulic system.

Figure 6 is a graph of predicted power versus wind speed for a wind turbine provided with a pitch control hub of the present invention.

Figure 1 shows an installation diagram of an upwind stable deflection two-blade wind turbine used by a generator synchronously connected to the power grid. A tower 10 supports a horizontal turntable assembly 12 approximately 70 feet above the ground. A carrier 14 is mounted on the turntable assembly 12 for rotation in a yaw direction around the vertical axis of the turntable assembly 12 . A rotating shaft shell 16 is installed on the carrier 14, and the high-torque hollow rotating shaft 17 inside is supported by the shell 16.

The double-blade rotor 18 is connected to the front end of the transmission shaft, and the rear end of the transmission shaft is connected to a pair of induction generators 22 and 24 through the gearbox 20. The generators can operate optimally under high and low wind speed conditions respectively, so that the rotor can According to two corresponding design requirements, rotate at the optimum operating speed. An overrunning clutch (not shown) installed on the output shaft of the gearbox can reduce the number of powertrain control circuits and relay boxes, thereby increasing the overall life of the equipment and reducing maintenance. A one-way overrunning clutch improves alternator/grid connection and disconnection.

The rotor 18 has a generally rectangular hub 28, as shown in Figure 4, which rotates about a drive axis a. Mounted on the hub 28 are two identical wind turbine blades 30 and 32 . In a design rated at 100 kilowatts, the diameter of the rotor blades is approximately 58 feet. The ideal blade has a zero degree taper with a resilient swing hub. The rotor is designed to run in two speeds (48/72 RPM) and should start automatically at about 7 mph. The designed tip speed ratio is 7-9.

Details of the hub 28 are shown in FIGS. 2-4. The hub 28 has a pair of cylindrical bearings 34 and 36, and the blade shafts 38 and 40 are respectively supported inside for rotation. The cylindrical bearings 34 and 36 determine the positions of the blade pitching axes b and c respectively. Circular eccentric mounting flanges 42 and 44 are respectively connected to opposite ends of blade pitching shafts 38 and 40 . Blades 30 and 32 (FIG. 1) have associated flanges 46 and 48 which are bolted to flanges 42 and 44, respectively.

The bearing cylinders 34 and 36 form a solid rigid frame with box-shaped tubular cross braces 50 and 52 welded thereto. The rotor shaft 17 is connected to the hub as shown in FIGS. 3 and 4 . Mounting bracket 54 rigidly connects swing hub assembly 55 , to box tubes 50 and 52 . A gearbox 60 straddles the respective ends of the bearing cylinders 34 and 36 . A group of four spur gears 60 are installed and rotated in the gear box, as shown in FIGS. 1 and 4 . The pitch diameter of the prototype gear is 9 inches. two drives Driven gear 62 and 64 are coaxially installed on pitch adjustment shafts 38 and 40. The eccentric mounting flange 42 is connected to the spur gear 62 . The two shaft gears 62 and 64 are connected for transmission by a pair of transmission gears 66 and 68, which are supported in the gearbox 60 and offset from the plane formed by the axes b and c, as shown in FIG. 4 .

On the other end of the bearing cylinders 34 and 36, the axes are connected by a rotating biasing member, in which a pair of crank throws 70 and 72 placed in the same direction are rigidly connected with the pitching shafts 38 and 40 respectively. The crank throw 72 and the eccentric mounting flange 44 can be integrally cast when needed. The outer ends of the bellcranks 70 and 72 are pivotally connected with the hydraulic linear actuator 74. The actuator 74 has a cylinder body 76, which is pivotally connected with the bellcrank 70. The piston rod 78 slides in the cylinder and is connected with the bellcrank 72. Make a pivot connection. In order to keep the design as compact as possible, the bellcrank preferably extends towards the circular mounting flange in the same direction as the raised center portion of the gearbox 60, as shown in Figure 2. The linear actuator 74 can be provided with a spring bias assist if desired. push pieces.

The hydraulic system is shown in Figure 5. The hydraulic pipeline passes through the rotor drive shaft concentrically towards the gearbox 20 and is connected to the air pressure accumulator through a rotary joint pipe fitting. Other components are installed in the deflection carrier 14, as shown in FIG. 5 . Turning the valve to the closed position frees hydraulic fluid to the sump, allowing centrifugal force to fully feather the blades.

The hydraulic system in Figure 5 is used to control the pitch actuator 74 to adjust the two blades approximately 70° between feathered and operational. In operation, the pitching moment caused by centrifugal force and aerodynamic loading on the blades tends to draw the piston rod out of the reciprocating cylinder. This moment increases with wind speed and is in the same direction as the wind direction. There is a bladder type gas-filled accumulator 80, which absorbs the propeller torque caused by the elongation of the piston rod 78 and squeezes out the liquid of the reciprocating cylinder. The air bladder acts as a spring, absorbing the force of the aerodynamic moment, thereby providing an increased restoring moment to return the blade to the operational position.

Some components of the hydraulic system are placed in a NEMA4 box as shown in Figure 5 (NEMA is the National Electrical Manufacturers Association of the United States)

The system has four programs:

A. Pressurized start procedure;

B. Feather pitch under load;

C. Adjust the pitch to the working state when unloading;

D. Quickly feather (command to stop).

When the power is turned on, the stop valve 82 is closed, and the motor pump 84 is started to increase the system pressure to the operating pressure. The gas spring pressure and liquid inventory in the accumulator 80 are balanced, and the reciprocating cylinder 76 is fully retracted to the starting position (opposite the working position in FIG. 5). When the operating pressure is reached, the pump 84 is stopped by a pressure switch 86 . The pump starts as needed to maintain the system pressure required by the pressure switch range. But when the pump stopped working, the check valve 88 was isolated from the hydraulic system.

In procedure B (pitch turned feathering under load), the centrifugal forces in turbine operation and the aerodynamic increased pitching torque at increased wind speed tend to draw the piston rod 78 out of the reciprocating cylinder 76 . The liquid discharged from the reciprocating cylinder will be sucked into the accumulator 80 through the hydraulic circuit. In the circuit, there is an air release valve 90, a quick breaker 92, a hydraulic circuit passing through the turbine shaft 17 and the rotary joint 94, a quick breaker 96, and a backstop Valve 98, quick disconnect 100 and pressure reducer 102. An increase in liquid inventory will increase the gas spring pressure in accumulator 80 and the system pressure. Accumulators shall be sized to absorb the storage at the highest system pressure. Fluid flowing from the reciprocating cylinder into the accumulator tends to feather the rotor blades.

In sequence C (pitch transition to running with unloading on the blades), hydraulic fluid flows in reverse. When the pitching moment on the blades decreases due to the decrease of wind speed, the gas elastic force in the accumulator 80 provides the control force to return the reciprocating cylinder 74 to the working position. This control force is stored in case B due to spring compression. As the spring returns to equilibrium, fluid is expelled from the accumulator, through valve 104 rather than through check valve 98, through the same hydraulic circuit, and into the actuator.

Procedures B and C often occur when the turbine is running. Due to the loss of stored energy due to flow friction and actuator friction, the pump must be primed to maintain pressure in the system.

Procedure D (quick feathering for shutdown) is obtained by de-energizing solenoid valve 82 and allowing pressure fluid to drain to reservoir 106. Due to centrifugal force or aerodynamic feathering torque, the liquid discharged from the reciprocating cylinder 76 passes through the check valve 98 through the solenoid valve 82 and is discharged into the liquid storage tank. The fluid flow from the accumulator is also directed into the reservoir. After shutdown, the pump 84 must be restarted to restore system pressure.

Increasing wind loads on the blades cause the blade moment to rise, which twists the pitch shaft. This increased torque will encounter increasing resistance from the linear actuator 74 . The greater the wind load, the greater the control torque of the blade, and the more the blade tends to feather.

As shown in the curves for this scenario in Figure 6, the power curves were made to cover the range of wind speeds from 7 to 30 mph. Adding a spring to the linear actuator 74 widens the envelope of the curve of operation. The shape of the curve, the maximum power output straight section curve, and the power curve of the shutdown inclined section, are all determined by the pitch change program with the wind speed. The double descending curve indicates the design criteria for passive control, which can be hydraulic or, in the load control area, increased combination of spring bias. The approximate value of the passively controlled blade pitch angle is represented by a curve.

The blade pitch controller is a passive mechanical device that allows the blade to find its own equilibrium position in the degree of freedom of pitch adjustment when conditions change. The synthesis of several pitching moments determines the pitch balance procedure of the rotor. The blade shape, blade thrust offset and blade centrifugal force offset generate the propeller moment, and its vector sum determines the pitch balance program, which in turn determines the power curve characteristics. The magnitude and change of each moment can be determined by carefully placing the blade center of gravity , the offset of the control axis and the aerodynamic axis, etc. are changed in advance. The Euler angle of the blade axis, that is, the swept cone angle, is equally important in the analysis as the swing dynamic pullback angles △1 and △3.

This passive rotor control system uses wind force, and the inherent inertia of the blades, to automatically change the pitch of the rotor, protecting the turbine in gusts, strong winds and no load. By selecting the appropriate gas spring, the rotor pitch can be adjusted at a given position to obtain the maximum power curve. The level of reliability and safety provided by the automatic rotor hub allows the brakes to be eliminated, making feathering a manual operation.

The 100 kW wind turbine system disclosed in this application is designed to utilize the pitch control hub, and also has the following mechanical technical requirements:

Gearbox 20:

The speed ratio of the two outputs is 25:1 and 37.5:1,

Full load efficiency 95%

low starting torque

1st stage planetary gear

Second stage helical gear with dual output

Output one-way overrunning clutch

Double seal structure

Continuous Oil Lubricated Bearings

dynamo:

Power 100 kW 20 kW

Speed 1800 rpm 1800 rpm

Type Inductive Inductive

480 AC voltage 480 AC voltage

Power factor 0.95 0.85

Efficiency 94% 91%

Base frame 405 turbine transmission 284 turbine transmission

Drip-proof Drip-proof

Structure Class H Class H

yaw drive:

Drive deflection rate 4·/second

Inertial structure with overspeed

Gear ratio 800:1

1/2 hp reversible induction motor

Gears 62 and 64 on the pitch shaft are preferably heat-hardened gears, AGMA (American Gear Manufacturers Association) tolerance class 11. It is better to install these gears on the propeller shaft, and the mounting flange of the rotor blade uses a conical clamp (not shown) to make adjustable installation on the gear and the shaft. The clamp can be adjusted loosely, so that the blade can be very One degree of "timing", then tighten. Idler gears are pushed and pulled and rotated to engage new teeth. Because the idler gear can be replaced, it can be made of softer metal than the end gear to adapt to wear. For the convenience of adjustment, it is better to install the idler gear on the eccentric.

This hub is designed to handle the extreme alternating loads of mid-size range two-blade wind turbines, ranging in size from 50 to 80 feet. Blade weight grows as the third power of radius. The gravitational load on the hub and blades varies with the orientation of the blades as they rotate about the rotor axis. Furthermore, since the center of gravity of the blade is aft of the pitch axis, the gravity term has a secondary angle-dependent alternating effect on the pitch angle. This alternating loading and unloading is accommodated by the rigid frame hub design.

The centrifugal force term, which is proportional to the square of the angular velocity, is more important than the aerodynamic term in the design, so that the rotational speed can be reflected in the blade pitching torque.

If desired, several accumulators of different pressures can be used, and one or more actuators can be used to handle different load ranges. However, a single actuator/single accumulator can represent an elegant all-encompassing pitch control design.

In addition to normal operation as shown in Figure 6, the pitch control hub also compensates for gusts and loss of electrical load. Wind gusts are reflected on the blades as an increase in pitch down moment due to control axis offset. This results in a corresponding immediate change in pitch angle, corrected by the inertia of the blade, relieving the bending moment of the blade. The passive spring arrangement of the pitch control hub does not generate high torque peaks and momentary peak bending moments of the blades, which are reduced by a corresponding passive release of the gust load.

As the load decreases, a corresponding overspeed of the rotor occurs. The passive rotor design also keeps overspeeds from load drops within safe limits. Finally, the use of passive pitch control hubs also eliminates complex electronic control logic loops, cooperating sensors and feedback loops that are difficult to check and complex to operate. A telescopic hydraulic link system is used between the blade pitch load and the air spring to form a direct and effective override capability, further improving the reliability of the system. Automatic and manual shutdown is provided through feathering of the blades, eliminating the need for additional brake or control components.

The embodiments described above are for illustration only and not for limitation system. Many changes, additions and subtractions can be made to the disclosed system without departing from the principles and spirit of the invention. For example, the drive train of the spur gears 62, 64, 66 and 68 can be modified as desired to produce counter-rotation directly connected to the blades. Also, the position of the gear train and the linear actuator along the pitch axes b and c can be changed. If there is enough space, the drive train can also be placed in other locations, such as in the center of the hub, with one (as shown) or more linear actuators and cambers on the shaft ends of the blades protruding from the bearing cylinder. turn connection. Other modifications to the hydraulic system can also be made. For example, a double-acting cylinder can be used to actively push the blades to full feathering when required. In any event the scope of the invention is to be determined by the appended claims.

Claims (19)

1, a kind of wind turbine pitch control wheel hub comprises:

A housing has the parallel blade of spacing to transfer the oar axis to be limited in the plane with a pair of, and near the rotor axis this plane and this two mid point of transferring between the oar axis intersects,

A machine control unit, with the starting pitch angle bias voltage of sharf to a demarcation, bearing the total load of blade, the pitch angle during the decision running initiatively,

It is characterized in that this propeller boss also comprises:

A pair of sharf is bearing on this shell, does part rotation at least around the corresponding oar axis of transferring,

A train of gearings (device) two is transferred between oar axis (in a side of this rotor axis) and is laterally connected at this, this sharf is directly connected do contrary rotation, bearing the stress alternation of blade, and the pitch angle of two blades is interrelated,

Each sharf has the crank of a circumferentially extending,

The device that connects between this crank changes the relative displacement of crank with blade loads, do controllable variation.

This machine control unit that connects between this crank has a linear actuators, and its cylinder body and a crank are done pivotally connected, and a piston rod and another crank are done pivotally connected.

2, hub according to claim 1, it is characterized by this train of gearings has quaternate coplane spur wheel.

3, as the hub as described in the claim 2, it is characterized by four spur wheels has two driving gears, and each transfers coaxial installation on the oar axle corresponding, has at least two driving gears and driving tooth crop rotation to be in transmission connection.

4, hub according to claim 1, it is characterized by this linear actuators is oil hydraulic cylinder.

5, hub according to claim 1, an and hydraulic system is arranged in addition, wherein have pressurization device and with the oil hydraulic circuit of this rotor axis coaxial line, this pressurization device is connected with this oil hydraulic cylinder.

6,, it is characterized by this pressurization device and this rotor axis relative fixed as the hub as described in the claim 5.

7, as the hub as described in the claim 6, it is characterized by this hydraulic system has on-off valve device in circuit apparatus for hydraulic in addition, so that make manual feathering.

8, as the hub as described in the claim 4, it is characterized by this linear actuators has spring-loaded.

9, hub according to claim 1, and a pair of circular blade mounting flange is arranged in addition respectively determines a blade installation Flange Plane, has device that each mounting flange is connected with the respective vanes eccentric shaft, the Flange Plane axis of laterally sizing mixing, and the center-biased of blade flange.

10, as the hub as described in the claim 9, it is characterized by each blade installation flange at same direction upper offset, crank roughly stretches to the axis of respective vanes flange.

11, a kind of wind turbine feather is controlled the wind turbine system, comprising:

A deflection loader,

A rotor wherein has a hub, has the blade of two variablepistons at least, be installed on the hub on the accent oar axle of skew,

Rotating shaft device is done rotatable the connection with this rotor with this loader,

It is characterized in that this system also comprises:

A hydraulic actuator (device) is directly pivotally connected between this two accent oar axle, thereby corresponding blade pitch load directly acts on mutually by this actuator,

Inflation hydraulic accumulator on this loader, the pressure oil pressurization to the inside,

The hydraulic pressure tube connecting device guides this hydraulic fluid, and this actuator devices is connected with this accumulator apparatus.

12,, and there is device will transfer the oar axle to do 1: 1 contrary rotation in addition as the system as described in the claim 11.

13, as the system as described in the claim 11, and control valve unit is arranged in addition, discharge the pressure in this hydraulic pressure tube connecting device according to halt instruction.

14, as the system as described in the claim 13, and the electric-motor pump device is arranged in addition, hydraulic fluid is injected this accumulator apparatus,, be elevated to predetermined working pressure by this hydraulic pressure leverage.

15,, is connected and have pressure switch apparatus and this hydraulic pressure to take in addition, to this energising of electric-motor pump device or outage, maintenance rated working pressure as the system as described in the claim 14.

16, as the system as described in the claim 13, it is characterized by this control valve unit is solenoid valve.

17, as the system as described in the claim 11, it is characterized by this tube connecting device essentially concentric in this driveline and pass.

18, hub according to claim 1 is characterized by this train of gearings and connects this axle in this rotor axis one side, and this linear actuators is connected this rotor axis this between centers of side in addition.

19, hub according to claim 1, it is characterized by has an elastomeric hub that waves in this housing.

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