U.S. patent application number 12/734539 was filed with the patent office on 2010-09-16 for electro-hydraulic actuator for controlling the pitch of a blade of a wind turbine.
Invention is credited to David Geiger.
Application Number | 20100232964 12/734539 |
Document ID | / |
Family ID | 40419027 |
Filed Date | 2010-09-16 |
United States Patent
Application |
20100232964 |
Kind Code |
A1 |
Geiger; David |
September 16, 2010 |
ELECTRO-HYDRAULIC ACTUATOR FOR CONTROLLING THE PITCH OF A BLADE OF
A WIND TURBINE
Abstract
The present invention provides an improvement for use in a wind
turbine (20) having a plurality of variable-pitch blades (24)
mounted on a hub (23) for rotation relative to a nacelle (22). The
improvement broadly includes: a electro-hydraulic actuator (25) for
controlling the pitch of one of the blades, the actuator including:
a motor (26) adapted to be supplied with a current; a pump (27)
driven by the motor and arranged to provide a hydraulic output as a
function of the current supplied to the motor; and a hydraulic
actuator (28) operatively arranged to selectively vary the pitch of
the associated blade as a function of the hydraulic output of the
pump; and wherein the motor, pump and actuator are physically
arranged within the hub of the wind turbine.
Inventors: |
Geiger; David; (Orchard
Park, NY) |
Correspondence
Address: |
PHILLIPS LYTLE LLP;INTELLECTUAL PROPERTY GROUP
3400 HSBC CENTER
BUFFALO
NY
14203-3509
US
|
Family ID: |
40419027 |
Appl. No.: |
12/734539 |
Filed: |
November 9, 2007 |
PCT Filed: |
November 9, 2007 |
PCT NO: |
PCT/US2007/023681 |
371 Date: |
May 7, 2010 |
Current U.S.
Class: |
416/156 |
Current CPC
Class: |
Y02E 10/72 20130101;
F03D 7/0224 20130101; F05B 2270/604 20130101; F05B 2260/76
20130101; Y02E 10/723 20130101 |
Class at
Publication: |
416/156 |
International
Class: |
F01D 7/00 20060101
F01D007/00 |
Claims
1. In a wind turbine having a plurality of variable-pitch blades
mounted on a hub for rotation relative to a nacelle, the
improvement comprising: a electro-hydraulic actuator for
controlling the pitch of one of said blades, said actuator
including: a motor adapted to be supplied with a current; a pump
driven by said motor and arranged to provide a hydraulic output as
a function of the current supplied to said motor; and a hydraulic
actuator operatively arranged to selectively vary the pitch of the
associated blade as a function of the hydraulic output of said
pump; and wherein said motor, pump and actuator are physically
arranged within the hub of said wind turbine.
2. The improvement as set forth in claim 1 wherein said wind
turbine has three of said variable-pitch blades mounted on said
hub, and wherein one of said electro-hydraulic actuators is
provided for each of said blades.
3. The improvement as set forth in claim 1 wherein said motor is a
d.c. brushless motor.
4. The improvement as set forth in claim 1 wherein said pump is a
fixed displacement pump.
5. The improvement as set forth in claim 1 wherein the polarity of
the hydraulic output from said pump is a function of the polarity
of the current supplied to said motor.
6. The improvement as set forth in claim 1 wherein said actuator
has a piston slidably mounted within a cylinder and sealingly
separating a first chamber on one side of said piston from a second
chamber on the other side of said piston, and wherein a rod is
mounted on said piston and extends through one of said chambers and
penetrates and end wall of said cylinder such that said piston has
unequal-area surfaces facing into said chambers.
7. The improvement as set forth in claim 6 and further comprising a
hydraulic reservoir and an anti-cavitation valve operatively
arranged between said tank and said actuator such that hydraulic
fluid will flow from said reservoir to the chamber facing said
larger-area piston face when such chamber is expanding, and will
flow to said reservoir from the chamber facing said larger-area
piston face when such chamber is contracting.
8. The improvement as set forth in claim 7 wherein said hydraulic
reservoir is pressurized.
9. The improvement as set forth in claim 7 wherein said
anti-cavitation valve operates automatically as a function of the
polarity of the hydraulic output of said pump.
10. The improvement as set forth in claim 1 and further comprising
a pressure relief valve operatively arranged to limit the maximum
pressure of said pump hydraulic output.
11. The improvement as set forth in claim 7 wherein said pump has a
high-pressure side and a low-pressure side, and a case drain.
12. The improvement as set forth in claim 1, and further comprising
a bypass valve positioned selectively operable to communicate said
high- and low-pressure sides.
13. The improvement as set forth in claim 11, wherein said case
drain communicates with said reservoir through a filter.
14. The improvement as set forth in claim 11, and further
comprising a restricted orifice in series with said bypass
valve.
15. The improvement as set forth in claim 1, and further
comprising: a source of pressurized hydraulic fluid communicating
via a conduit with the chamber into which said small-area piston
surface faces, and a normally-open solenoid valve arranged in said
conduit, and wherein said solenoid valve is arranged to be opened
in the event of a power failure to permit hydraulic fluid to flow
from said source through said conduit and into the chamber into
which said small-area piston surface faces to cause such chamber to
expand and to urge said piston to move toward a position relative
to said cylinder at which said blade is feathered.
16. The improvement as set forth in claim 15 and further comprising
blocking valves operatively arranged to selectively isolate said
pump from said small- and large-area actuator chambers.
17. The improvement as set forth in claim 1 wherein power from said
nacelle is provided to said motor through a contactless rotary
transformer.
18. The improvement as set forth in claim 1 and further comprising
a motor controller and a power stage, and wherein said motor
controller and said power stage are also physically arranged within
the hub of said turbine.
19. The improvement as set forth in claim 18 wherein said motor
controller and said power stage are mounted on said
electro-hydraulic actuator.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to the field of wind
turbines, and, more particularly, to an improved wind turbine
having a plurality of electro-hydraulic actuators mounted on the
rotatable hub of the turbine for independently controlling the
pitch of a like plurality of blades.
BACKGROUND ART
[0002] Wind turbines are, of course, known. In recent years, many
of the problems of having a wind turbine supply power synchronously
to an electrical grid have been addressed and overcome.
[0003] Wind turbines today are relatively sophisticated. They are
typically mounted on a tower, and have plurality of blades
(normally three) mounted on a hub for rotation about a horizontal
axis relative to a nacelle. The nacelle may be aimed into the
direction of the oncoming wind. Each of the blades is typically of
variable pitch, and the pitch of each blade may be controlled
independently of the others. These blades are typically arranged at
120.degree. intervals. When one blade is pointing aiming downwardly
toward the 6 o'clock position, the wind proximate the ground is
typically less than the speed of the wind moving over the other two
blades. Hence, the pitch of each blade is controlled independently
of one another with the goal trying to normalize (i.e., keep
reasonably constant) the rotational speed of the hub from ground
effects, gusts, etc.
[0004] Heretofore, wind turbines have been characterized as being
of the electrical-type or of the hydraulic-type. In either case,
the generator is typically mounted in the nacelle. Control signals
and power are supplied up through the tower, and to a
pitch-controlling mechanism. In both cases, this pitch-controlling
mechanism has been heretofore mounted in the nacelle, and this
necessitates a type of slip ring joint between the nacelle and the
rotatable hub. In addition, this arrangement has been accompanied
by the use of a large bull gear, and with various hoses within the
hub. The life expectancy of such an arrangement has been as short
as about four years due to excessive wear on the bull gear caused
principally by variations in the speed of the wind.
[0005] Accordingly, it would be generally desirable to provide an
improved wind turbine in which the pitch-controlling
electro-hydraulic actuator is mounted within the hub, rather then
on the nacelle.
DISCLOSURE OF THE INVENTION
[0006] With parenthetical reference to the corresponding parts,
portions or surfaces of the disclosed embodiment, merely for
purposes of illustration and not by way of limitation, the present
invention provides an improvement for use in a wind turbine (20)
having a plurality of variable-pitch blades (24) mounted on a hub
(23) for rotation relative to a nacelle (22).
[0007] The improvement broadly includes: a electro-hydraulic
actuator (25) for controlling the pitch of one of the blades, the
actuator including: a motor (26) adapted to be supplied with a
current; a pump (27) driven by the motor and arranged to provide a
hydraulic output as a function of the current supplied to the
motor; and a hydraulic actuator (28) operatively arranged to
selectively vary the pitch of the associated blade as a function of
the hydraulic output of the pump; and wherein the motor, pump and
actuator are physically arranged within the hub of the wind
turbine.
[0008] In one form, the wind turbine has three of the
variable-pitch blades (24) mounted on the hub, and wherein one of
the electro-hydraulic actuators (25) is provided for each of the
blades.
[0009] The motor may be a d.c. brushless motor.
[0010] The pump may be a fixed displacement pump.
[0011] In the preferred embodiment, the polarity of the hydraulic
output from the pump is a function of the polarity of the current
supplied to the motor.
[0012] The actuator may have a piston (30) slidably mounted within
a cylinder (31) and sealingly separating a first chamber (35) on
one side of the piston from a second chamber (36) on the other side
of the piston, and wherein a rod (32) is mounted on the piston and
extends through chamber (35) and penetrates and end wall of the
cylinder such that the piston has unequal-area surfaces facing into
the chambers. The improved actuator may further include a hydraulic
reservoir (41) and an anti-cavitation valve (57) operatively
arranged between the tank and the actuator such that hydraulic
fluid will flow from the reservoir to the chamber facing the
larger-area piston face when such chamber is expanding, and will
flow to the reservoir from the chamber facing the larger-area
piston face when such chamber is contracting.
[0013] The hydraulic reservoir may be pressurized.
[0014] The anti-cavitation valve may operate automatically as a
function of the polarity of the hydraulic output of the pump.
[0015] The improvement may further include a pressure relief valve
(48, 52) operatively arranged to limit the maximum pressure of the
pump hydraulic output.
[0016] The pump may have a high-pressure side and a low-pressure
side, and a case drain.
[0017] A bypass valve (54) may be positioned selectively operable
to communicate the high- and low-pressure sides.
[0018] The case drain (40) may communicate with the reservoir
through a filter.
[0019] The improvement may further include a restricted orifice
(56) in series with the bypass valve.
[0020] The improvement may further include: a source (62) of
pressurized hydraulic fluid communicating via a conduit (63) with
the chamber into which the small-area piston surface faces, and a
normally-open solenoid valve (64) arranged in the conduit, and
wherein the solenoid valve is arranged to be opened in the event of
a power failure to permit hydraulic fluid to flow from the source
through the conduit and into the chamber into which the small-area
piston surface faces to cause such chamber to expand and to urge
the piston to move toward a position relative to the cylinder at
which the blade is feathered.
[0021] The improvement may further include blocking valves (59, 60)
operatively arranged to selectively isolate the pump from the
small- and large-area actuator chambers.
[0022] Power and/or control signals to the motor are preferably
supplied form the nacelle to the hub through a contactless rotary
transformer. Examples of these are shown and described in U.S. Pat.
Nos. 5,608,771, 6,813,316 and 5,572,178, the aggregated disclosures
of which are hereby incorporated by reference.
[0023] Accordingly, the general object of the invention is to
provide an improved electro-hydraulic actuator for use in a wind
turbine to control the pitch of one of a plurality of
variable-pitch blades thereon.
[0024] Another object is to provide an improved electro-hydraulic
actuator for use in a wind turbine, wherein the major components of
the actuator are mountable on the rotating hub and not on the
nacelle.
[0025] Another object is to provide an improved actuator for use in
a wind turbine, and wherein the actuator contains a fail-safe
mechanism for urging the associated blade to move toward a
feathered position in the event of a power failure or
interruption.
[0026] These and other objects and advantages will become apparent
from the foregoing and ongoing written specification, the drawings
and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is an isometric view of the upper marginal end
portion of a wind turbine, showing fragmentary portions of the
variable-pitch blades as being mounted on the hub for rotation
about a horizontal axis relative to a nacelle.
[0028] FIG. 2 is a hydraulic schematic of the improved
electro-hydraulic actuator.
[0029] FIG. 3 is a left side elevation of an improved
electro-hydraulic actuator for controlling the pitch of one of the
blades.
[0030] FIG. 4 is a top plan view of the actuator shown in FIG.
3.
[0031] FIG. 5 is a left end elevation of the actuator shown in FIG.
4.
[0032] FIG. 6 is a block diagram of the circuit for independently
controlling the three blades.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] At the outset, it should be clearly understood that like
reference numerals are intended to identify the same structural
elements, portions or surfaces consistently throughout the several
drawing figures, as such elements, portions or surfaces may be
further described or explained by the entire written specification,
of which this detailed description is an integral part. Unless
otherwise indicated, the drawings are intended to be read (e.g.,
cross-hatching, arrangement of parts, proportion, degree, etc.)
together with the specification, and are to be considered a portion
of the entire written description of this invention. As used in the
following description, the terms "horizontal", "vertical", "left",
"right", "up" and "down", as well as adjectival and adverbial
derivatives thereof (e.g., "horizontally", "rightwardly",
"upwardly", etc.), simply refer to the orientation of the
illustrated structure as the particular drawing figure faces the
reader. Similarly, the terms "inwardly" and "outwardly" generally
refer to the orientation of a surface relative to its axis of
elongation, or axis of rotation, as appropriate.
[0034] Referring now to the drawings, and more particularly to FIG.
1 thereof, an improved wind turbine, generally indicated at 20, is
shown as being mounted on the upper marginal end portion of a
tower, a fragmentary portion of which is generally indicated at 21.
A nacelle 22 is rotatably mounted on the upper marginal end portion
of the tower for rotation about a vertical axis y-y. A hub 23 is
mounted on the nacelle for rotation about a horizontal axis x-x. A
plurality of blades, severally indicated at 24, are mounted on the
hub for rotation therewith. The pitch of each blade is
independently controllable by means of the improved
electro-hydraulic actuators disclosed herein. A main shaft (not
shown) transfers rotational movement of the hub into the nacelle,
to drive a generator (not shown) in the usual manner. The nacelle
also includes various usual and typical items such as gear box (not
shown) for increasing the speed of the driven shaft, transformers
(not shown), and the like.
[0035] Heretofore, the mechanism for controlling the pitch of the
blades was mounted on the nacelle, and control was transferred to
the hub by means of a bull gear. In the present invention, however,
the electro-hydraulic actuators are mounted within the hub, and the
bull gear can be eliminated altogether.
[0036] Referring now to FIG. 2, the improved electro-hydraulic
actuator 25 is schematically indicated as including a motor 26, a
pump 27 driven by the motor, and a double-acting hydraulic
actuator, generally indicated at 28.
[0037] In the preferred embodiment, the motor is a brushless D.C.
motor that is supplied with a current from the nacelle via a
contactless rotary transformer (not shown). When the supplied
current is of one polarity, the motor will rotate in one direction.
When the supplied current supplied is of the opposite polarity, the
motor will rotate in the opposite direction.
[0038] Pump 27 is preferably a fixed displacement pump, and is
connected to the motor by means of a shaft 29.
[0039] The actuator 28 is shown as having a piston 30 slidably
mounted within a cylinder 31. A rod 32 as its left end mounted on
the piston, and penetrates the cylinder right end wall. An eye 33
is mounted on the right end of rod 32. Another eye 34 is shown as
being mounted on the cylinder left end wall. The piston is slidably
mounted within the cylinder, and sealingly separates a leftward
chamber 35 from a rightward chamber 36. The entire circular
vertical end surface of piston 30 faces into left chamber 35.
However, an annular vertical surface of the piston faces
rightwardly into right chamber 36. The entire electro-hydraulic
actuator is mounted within the rotatable hub of the wind turbine.
Eye 34 is mounted to the rotatable hub, and eye 33 is mounted to a
lever arm (not shown) connected to control the pitch of the
associated blade.
[0040] One side of pump 27 communicates with actuator left chamber
35 via a conduit 38, and the opposite side of pump 27 communicates
with actuator right chamber 36 via a conduit 39. A drain conduit 40
communicates a portion of the pump flow with a reservoir 41 via a
filter 42 and a check valve 43. More particularly, conduit 40
extends between the case drain and the filter, conduit 44
communicates the filter 42 with check valve 43, and conduit 45
communicates check valve 43 with another conduit 46 communicating
with the reservoir or tank 41. This tank is shown as having a
diaphragm, and is gas pressurized to a pressure of about 90-250
psi.
[0041] Conduit 38 communicates with tank 41 via a conduit 47 which
includes a high-pressure relief valve 48, connected conduits 49, 50
and 46. Conduit 39 communicates with tank 41 via conduit 51 which
contains another high-pressure relief valve 52, and connected
conduits 49, 50 and 46. The function of pressure relief valves 48,
52 is to provide a relief for an over pressure condition depending
on the polarity of the pump operation. Conduit 38 also communicates
with conduit 39 via a conduit 53, a bypass solenoid 54, and a
conduit 55 containing a restricted orifice 56.
[0042] Conduits 38 and 39 also communicate with one another via a
conduit 54, an anti-cavitation valve 55, and a conduit 56.
Solenoid-operated bypass valves 57, 60 are positioned in conduit
38, 39, respectively. The anti-cavitation valve 57 is a type of
inverse shuttle valve that samples the pressure of the fluid in
conduits 38, 39, and moves automatically in response to the
pressure differential therebetween. The function of anti-cavitation
valve 57 is to accommodate the volumetric changes between opposed
actuator chambers 35, 36. In other words, when piston moves
leftwardly within the cylinder, the volume of fluid removed from
collapsing left chamber 35 will be greater than the volume of fluid
supplied to expanding right chamber 36. The anti-cavitation valve
functions to permit the excess or differential fluid to flow
through conduits 46, 49, 50 to the reservoir. Conversely, when the
actuator piston moves rightwardly relative to the cylinder, a
differential amount of fluid may flow from reservoir 41 through
conduit 46 and the anti-cavitation valve into the expanding left
actuator chamber.
[0043] A charge fitting 61 communicates with conduit 39 to allow
fluid to be added to the system. A fail-safe accumulator 62
communicates with conduit 39 via a conduit 63 containing a
normally-opened solenoid valve 64.
[0044] When the wind turbine is first started, bypass valves 59, 60
are closed, and fluid is first pumped into accumulator 62 to charge
and pressurize this accumulator to about 3,000 psi. Thereafter,
valves 59, 60 are opened to permit fluid to flow to the
actuator.
[0045] The function of the fail-safe accumulator 62 is to provide a
source of pressurized hydraulic fluid to the system in the event of
a loss of power to the motor. In the event of a power failure,
fail-safe accumulator 62 will provide a source of pressurized
hydraulic fluid to displace the actuator rod leftwardly toward a
feathered positioned of the blade.
[0046] A commercial form of the apparatus is depicted in FIGS. 3-5,
in which the same number is used to refer to the parts previously
described.
[0047] Referring now to FIG. 6, a larger control system for
independently controlling the pitch of each of three blades is
depicted. A signal from a three phase slip ring 65 is supplied to
each of three motor controllers 66A, 66B, 66C. Each motor
controller supplies a signal to a power stage 67A, 67B, 67C,
respectively, which in turn supplies the current of the appropriate
magnitude and polarity to electro-hydraulic actuators A, B and C,
respectively. The position of each rod 32 is monitored via an LVDT
68A, 68B, 68C, respectively, and the position signals are then fed
back to their associated motor controllers, 66A, 66B, 66C,
respectively. A rotating optical ring for data transmission 69 also
provides an input signal to each motor controller. Thus, in this
manner, the system may control the pitch of each blade
independently. Of course, the arrangement shown in FIG. 6 is
specific to a three-bladed wind turbine. If a greater or lesser
number of blades were to be employed, the number of actuators would
be correspondingly adjusted.
Modifications
[0048] The present invention expressly contemplates that many
changes and modifications may be made. In the improved wind
turbine, an electro-hydraulic actuator is provided for each blade
so that the pitch of the various blades can be controlled
independently of one another. While it is presently preferred to
use a D.C. brushless motor, other types of motors may be used as
well. Similarly, while the fixed-displacement pump is presently
preferred, other types of pumps might possibly be substituted
therefore.
[0049] The actuator might, of course, have a rod penetrating both
cylinder end walls. However, this would like interfere with the
nose of the hub. Nevertheless, if arrangement could be
accommodated, there would be no need for the anti-cavitation valve
since the volume of the expanding chamber would equal the volume of
the collapsing chamber.
[0050] If desired, the motor controller and the power stage can be
incorporated directly into the improved hub-mounted
electro-hydraulic actuator.
[0051] Therefore, while the presently-preferred form of the
improvement has been shown and described, and several modifications
thereof discussed, persons skilled in this art will readily
appreciate that various additional changes and modifications may be
made without departing from the spirit of the invention, as defined
and differentiated by the following claims.
* * * * *