SYSTEM FOR PROVIDING DYNAMIC PITCH CONTROL IN A WIND TURBINE

• US 20100129215A1
• Filed: 11/20/2009
• Published: 05/27/2010
• Est. Priority Date: 11/21/2008
• Status: Active Grant

• Current Assignee: XZERES Corp.
• Original Assignee: XZERES Corp.
• Inventors: Preus, Robert W.
• Granted Patent: US 8,573,937 B2
• Time in Patent Office: Days
• US Class Current: 416/41
• CPC Class Codes: F03D 7/0224 Adjusting blade pitch
• CPC Class Codes: F03D 7/041 by means of a mechanical governor
• CPC Class Codes: F05B 2260/75 the adjusting mechanism not using auxiliary power sources, e.g. servos
• CPC Class Codes: F05B 2260/77 the adjusting mechanism driven or triggered by centrifugal forces
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction

Abstract

A system for providing dynamic pitch control in a wind turbine. In accordance with an embodiment, the dynamic pitch control uses a starting spring to pitch the blades of the wind turbine into a starting position that is suited for very low wind speeds. The pitch control then automatically pitches the blades into a run position as the rotation speed increases, using a combination of a rotational mass and a restraining spring. This allows the turbine to be started, and to generate power, at a much lower starting wind speed yet still operate at optimal speeds in its typical running range. In accordance with an embodiment, as the wind speed further increases beyond an overspeed limit, the rotational mass overcomes its restraining spring, and automatically pitches the blades back toward and beyond their start position, reducing the likelihood of damage to the turbine caused by high rotation speeds.

Claims

1. A system for providing pitch control in a wind turbine, comprising:

a turbine shaft that is adapted to rotate about its longitudinal axis to generate electrical power;

a plurality of blades coupled to the shaft, and oriented to receive wind power and cause rotation in the turbine shaft, wherein each of the plurality of blades can be pitched about its longitudinal axis to expose more or less of the blade to the wind power; and

a pitch control mechanism including a combination of springs and mass, which pitches the blades at a lower starting wind speed into the wind to start the turbine, and then as the wind speed increases to a running wind speed uses the centripetal force of the mass, counterbalanced by a limit spring, to pitch the blades to the run position and increase the power output of the wind turbine.

2. The system of claim 1, wherein the pitch control mechanism, as the wind speed further increases to an overspeed wind speed, uses the centripetal force to overcome the limit spring, and pitch the blades away from the wind to govern the power output of the wind turbine.

3. The system of claim 1, wherein the pitch control further comprises a beam that is generally linear, and that includes one or more couplings so that the beam has a first portion and a second portion, and so that the beam can be deformed in a direction transverse to its length, and wherein the beam is connected to a spider that in turn can be used to control the pitch of the turbine'"'"'s blades.

4. The system of claim 3, wherein the first portion of the beam is held close to the shaft using a start pitch spring, and a limit pitch spring, and wherein the beam further includes a coupling approximately central to the beam that includes a center mass, and wherein the second portion of the beam is connected to the spider.

5. The system of claim 4, wherein the pitch control further comprises a retaining member together with a stop that ensures that in a first position of the beam, only the start pitch spring has operable tension on the beam, with the stop preventing the retaining member and its limit pitch spring from having any considerable tension on the beam.

6. The system of claim 5, wherein the limit pitch spring is connected to the retaining member using a tension adjustment means, such as a threaded nut or bolt.

7. The system of claim 4, wherein the pitch control operates so that

when the rotational speed of the turbine is zero, or very low, the start pitch spring deforms the beam, pulling it closer to the shaft, which shortens the effective length of the beam and pulls the spider away from the blades,

when the rotational speed of the turbine increases, the center mass exerts a centripetal force on the beam, and the lateral or outward translation of the mass negates the deformation on the beam, which lengthens the effective length of the beam, and causes a corresponding lateral translation of the spider towards the blades, and

when the rotational speed of the turbine increases further to its maximum operating range, the center mass exerts a centripetal force on the beam that exceeds the pre-set tension of the limit pitch spring, which shortens the effective length of the beam and pulls the spider away from the blades.

8. The system of claim 1, wherein the wind turbine generates power in the range of less that 2.5 kilowatts.

9. The system of claim 1, wherein the wind turbine generates power in the range of 2.5 kilowatts to 100 kilowatts.

10. The system of claim 1, wherein the wind turbine generates power in the range of greater than 100 kilowatts.

11. A system for providing pitch control in a wind turbine, comprising:

a turbine shaft that is adapted to rotate about its longitudinal axis to generate electrical power;

a plurality of blades coupled to the shaft at one end, and oriented to receive wind power and cause rotation in the turbine shaft, wherein each of the plurality of blades can be pitched about its longitudinal axis to expose more or less of the blade to the wind power;

a pitch control mechanism including a combination of springs and mass, which pitches the blades at a lower starting wind speed into the wind to start the turbine, and then as the wind speed increases to a running wind speed uses the centripetal force of the mass, counterbalanced by a limit spring, to pitch the blades into the run position and increase the power output of the wind turbine, wherein the pitch control mechanism, as the wind speed further increases to an overspeed wind speed, uses the centripetal force to overcome the limit spring, and pitch the blades into the wind to govern the power output of the wind turbine;

a beam that is generally linear, and that includes one or more couplings so that the beam has a first portion and a second portion, and so that the beam can be deformed in a direction transverse to its length, and wherein the beam is connected to a spider that can be used to control the pitch of the turbine'"'"'s blades, wherein the first portion of the beam is held close to the shaft using a start pitch spring, and a limit pitch spring, and wherein the beam further includes a coupling approximately central to the beam that includes a center mass, and wherein the second portion of the beam is connected to the spider; and

wherein the pitch control operates so that

when the rotational speed of the turbine is zero, or very low, the start pitch spring deforms the beam, pulling it closer to the shaft, which shortens the effective length of the beam and pulls the spider away from the blades,

when the rotational speed of the turbine increases, the center mass exerts a centripetal force on the beam, and the lateral or outward translation of the mass negates the deformation on the beam, which lengthens the effective length of the beam, and causes a corresponding lateral translation of the spider towards the blades.

12. A system for governing power in a motor, comprising:

a motor shaft that is adapted to rotate about its longitudinal axis;

a speed control mechanism including a combination of springs and mass, which uses the centripetal force of the mass, counterbalanced by a limit spring, to govern the power output of the motor;

a beam that is generally linear, but that includes one or more couplings so that the beam has a first portion and a second portion, and so that the beam can be deformed in a direction transverse to its length, and wherein the beam is connected to a spider that in turn can be used to control the rotational speed of the shaft; and

wherein the speed control mechanism, as rotational speed of the shaft increases to a limit, uses the centripetal force to overcome the limit spring, deform the beam, and move the spider to govern the power output of the motor.