U.S. patent application number 13/193356 was filed with the patent office on 2011-11-17 for long term rotor parking on a wind turbine.
This patent application is currently assigned to Clipper Windpower, Inc.. Invention is credited to Sandeep Gupta, Nathaniel Brook Taylor.
Application Number | 20110280725 13/193356 |
Document ID | / |
Family ID | 42212119 |
Filed Date | 2011-11-17 |
United States Patent
Application |
20110280725 |
Kind Code |
A1 |
Taylor; Nathaniel Brook ; et
al. |
November 17, 2011 |
Long Term Rotor Parking on a Wind Turbine
Abstract
A method for locking a rotor of a wind turbine in a long term
parking state is disclosed. The method may include applying rotor
brakes, enabling a long term parking configuration of the rotor and
providing an emergency feather response for protecting the wind
turbine against faults.
Inventors: |
Taylor; Nathaniel Brook;
(Santa Barbara, CA) ; Gupta; Sandeep; (Ventura,
CA) |
Assignee: |
Clipper Windpower, Inc.
Carpinteria
CA
|
Family ID: |
42212119 |
Appl. No.: |
13/193356 |
Filed: |
July 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/IB2009/006309 |
Jul 22, 2009 |
|
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13193356 |
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Current U.S.
Class: |
416/1 ;
416/169R |
Current CPC
Class: |
F03D 7/043 20130101;
F05B 2270/32 20130101; Y02E 10/72 20130101; F05B 2260/821 20130101;
Y02E 10/723 20130101; F05B 2270/1091 20130101; F03D 7/024 20130101;
F03D 7/0224 20130101 |
Class at
Publication: |
416/1 ;
416/169.R |
International
Class: |
F04D 27/00 20060101
F04D027/00 |
Claims
1. A method for locking a rotor of a wind turbine in a long term
parking state, the method comprising: providing a wind turbine
having a rotor, the rotor having a hub and a plurality of blades
radially extending therefrom; locking the rotor to prevent
rotation; enabling a long term parking configuration of the rotor;
and providing an emergency feather response for protecting the wind
turbine against faults.
2. The method of claim 1, wherein locking the rotor to prevent
rotation comprises inserting a locking pin into a receptacle on the
hub of the wind turbine.
3. The method of claim 1, wherein enabling a long term parking
configuration comprises minimizing rotor torque generated by the
rotor in a locked state.
4. The method of claim 1, wherein enabling a long term parking
configuration comprises adjusting a pitch angle of the plurality of
blades to produce a least amount of torque.
5. The method of claim 4, wherein each of the plurality of blades
are pitched from a standby position near feather towards a power
position near zero degrees.
6. The method of claim 4, wherein a pitching angle of zero degrees
produces the least amount of torque when the rotor is in a locked
state in every wind direction.
7. The method of claim 1, wherein enabling a long term parking
configuration comprises optimizing an azimuthal position of the
plurality of blades.
8. The method of claim 7, wherein an optimal azimuthal position of
the plurality of blades comprises positioning a first blade at a
two o'clock position, a second blade at a six o'clock position and
a third blade at a ten o'clock position.
9. The method of claim 1, wherein enabling a long term parking
configuration comprises adjusting a yaw orientation of the wind
turbine relative to the prevailing wind direction.
10. The method of claim 1, wherein providing an emergency feather
response comprises pitching the plurality of blades to a ninety
degree pitch angle upon the detection of a fault.
11. The method of claim 1, wherein the emergency feather response
is invoked when the rotor begins rotation in the long term parking
configuration.
12. The method of claim 1, wherein the emergency feather condition
is invoked when power to the wind turbine is lost.
13. A method of configuring a rotor of a wind turbine in a long
term parking state, the method comprising: providing a wind turbine
having a rotor, the rotor having a hub and a plurality of blades
radially extending therefrom; locking the rotor against rotation;
and changing a pitch angle of each of the plurality of blades to at
or near zero degrees.
14. The method of claim 13, wherein the pitch angle of each of the
plurality of blades is changed one at a time, a second blade
starting pitching after a first blade has reached zero degree pitch
angle.
15. The method of claim 13, wherein each of the plurality of blades
is pitched simultaneously to zero degrees.
16. The method of claim 13, further comprising: optimizing the yaw
orientation of the wind turbine; and optimizing an azimuthal
position of the plurality of blades.
17. A wind turbine, comprising: a rotor having a hub and a
plurality of blades radially extending from the hub; and a control
system in operable association with the rotor, the control system
configured to put the rotor in a long term parking state.
18. The wind turbine of claim 17, wherein the long term parking
state of the rotor comprises locking the rotor.
19. The wind turbine of claim 17, wherein the long term parking
state of the rotor is characterized by one or more of changing a
pitch angle of the plurality of blades, adjusting an azimuthal
position of the plurality of blades and yawing the wind turbine to
at least substantially face in to the wind.
20. The wind turbine of claim 17, wherein the control system
further controls an emergency feather condition of the long term
parking state of the rotor.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Continuation-In-Part (CIP) Patent
Application claiming priority under 35 U.S.C. .sctn.365(c) to
International Application No. PCT/IB2009/006309 filed on Jul. 22,
2009, and also claims priority to Provisional Patent Application
No. 61/206,207 filed on Jan. 28, 2009.
FIELD OF THE DISCLOSURE
[0002] The present disclosure generally relates to wind turbines
and, more particularly, relates to stopping rotation of rotors of
the wind turbines for extended periods of time.
BACKGROUND OF THE DISCLOSURE
[0003] A utility-scale wind turbine typically includes a set of two
or three large rotor blades mounted to a hub. The rotor blades and
the hub together are referred to as the rotor. The rotor blades
aerodynamically interact with the wind and create lift or drag,
which is then translated into a driving torque by the rotor. The
rotor is attached to and drives a main shaft, which in turn is
operatively connected via a drive train to a generator or a set of
generators that produce electric power. The main shaft, the drive
train and the generator(s) are all situated within a nacelle, which
rests on a yaw system that continuously pivots along a vertical
axis to keep the rotor blades facing in the direction of the
prevailing wind current to generate maximum torque.
[0004] Various situations could necessitate stopping all rotation
of the hub on a wind turbine and placing the rotor in a parked
state for an extended period of time. For example, when performing
maintenance on a wind turbine, for safety and/or practical reasons,
it may be necessary to lock the rotor so that it does not rotate.
Some storm and icing weather situations may also necessitate
locking the rotor. Most wind turbines include a brake and/or a
positive locking pin to stop rotation of the hub (and therefore the
rotor) relative to the nacelle. The rotor can be locked with a
locking pin that can be inserted from the nacelle into a mating
receptacle on the hub. Other mechanisms for locking the rotor into
a stationary position may be employed as well.
[0005] The wind turbine may remain in this rotor locked state for
an extended period of time. Because of the large torques that a hub
can generate during high wind velocities even in the locked state
of the rotor, the brake or locking pin that is holding the hub must
be able to provide a very large counter-rotational torque to
prevent rotation and maintain the rotor in a stationary position.
Specifically, even in the locked state, the wind continues to act
on the rotor blades and produce lift. The continued lift of the
rotor blades creates rotor torque and the brakes or the locking pin
locking the rotor must be able to withstand and counteract this
rotor generated torque.
[0006] Normally, the wind turbine would continue to yaw in the
rotor locked state, to constantly change the orientation of the
turbine into the wind. The loads and torque created by the wind
when the rotor is locked are lowest and most predictable when the
turbine is pointed into the wind. But, some situations and
circumstances may require that the turbine cannot continue to yaw
and adjust its orientation into the wind. In those situations where
the turbine can no longer yaw, the loads and rotor torque may
become a concern and it may be desirable to place the rotor in a
long term parking state to protect the wind turbine from damaging
winds and high loads.
[0007] Accordingly, it would be beneficial if a technique for a
long term rotor parking were developed. It would additionally be
beneficial if such a technique could be employed in addition to any
braking or locking pins used to lock the rotor and to provide an
additional factor of safety during conditions of high loading on
the wind turbine when the rotor is in a locked state.
SUMMARY OF THE DISCLOSURE
[0008] In accordance with one aspect of the present disclosure, a
method for locking a rotor of a wind turbine in a long term parking
state is disclosed. The method may include providing a wind turbine
having a rotor, the rotor having a hub and a plurality of blades
radially extending therefrom. The method may further include
locking the rotor to prevent rotation, enabling a long term parking
configuration of the rotor and providing an emergency feather
response for protecting the wind turbine against faults.
[0009] In accordance with another aspect of the present disclosure,
a method of configuring a rotor of a wind turbine in a long term
parking state is disclosed. The method may include providing a wind
turbine having a rotor, the rotor having a hub and a plurality of
blades radially extending therefrom. The method may further include
locking the rotor against rotation and changing a pitch angle of
each of the plurality of blades to zero degrees.
[0010] In accordance with yet another aspect of the present
disclosure, a wind turbine is disclosed. The wind turbine may
include a rotor having a hub and a plurality of blades radially
extending from the hub and a control system in operable association
with the rotor, the control system configured to put the rotor in a
long term parking state.
[0011] Other advantages and features will be apparent from the
following detailed description when read in conjunction with the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a more complete understanding of the disclosed methods
and apparatuses, reference should be made to the embodiments
illustrated in greater detail on the accompanying drawings,
wherein:
[0013] FIG. 1 is a schematic illustration of a wind turbine, in
accordance with at least some embodiments of the present
disclosure;
[0014] FIG. 2 is an exemplary flowchart outlining steps in parking
a rotor of the wind turbine in a long term parking state;
[0015] FIG. 3 is an exemplary wind rosette showing rotor torque
produced from the wind relative to the wind turbine in every wind
direction for different given blade pitch angles; and
[0016] FIG. 4 is an exemplary illustration of the rotor torque when
blades of the wind turbine are pitched one at a time.
[0017] While the following detailed description has been given and
will be provided with respect to certain specific embodiments, it
is to be understood that the scope of the disclosure should not be
limited to such embodiments, but that the same are provided simply
for enablement and best mode purposes. The breadth and spirit of
the present disclosure is broader than the embodiments specifically
disclosed and encompassed within the claims eventually appended
hereto.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0018] Referring to FIG. 1, an exemplary wind turbine 2 is shown,
in accordance with at least some embodiments of the present
disclosure. While all the components of the wind turbine have not
been shown and/or described, a typical wind turbine may include a
tower section 4 and a rotor 6. The rotor 6 may include a plurality
of blades 8 connected to a hub 10. The blades 8 may rotate with
wind energy and the rotor 6 may transfer that energy to a main
shaft 12 situated within a nacelle 14. The nacelle 14 may
additionally include a drive train 16, which may connect the main
shaft 12 on one end to one or more generators 18 on the other end.
The generators 18 may generate power, which may be transmitted
through the tower section 4 to a power distribution panel (PDP) 20
and a pad mount transformer (PMT) 22 for transmission to a grid
(not shown). The nacelle 14 may be positioned on a yaw system 24,
which may pivot about a vertical axis to orient the wind turbine 2
in the direction of the prevailing wind current or another
preferred wind direction. In addition to the aforementioned
components, the wind turbine 2 may also include a pitch control
system (not visible) situated within the hub 10 for controlling the
pitch (e.g., angle of the blades with respect to the wind
direction) of the blades 8. The pitch control system may include
servo motors, which drives the blades 8 relative to the hub 10 to
change the pitch angle. The pitch control system may further
include a pitch control unit (PCU) for controlling the servo
motors, and a battery back-up system for providing power to the
pitch control unit and the servo motors in the case of an emergency
or in other situations. The wind turbine 2 may also include an
anemometer 26 for measuring the speed and direction of the wind. A
turbine control unit (TCU) 28 and control system 29 may be situated
within the nacelle 14 for controlling the various components of the
wind turbine 2.
[0019] Referring now to FIG. 2, an exemplary flowchart 30 outlining
the procedure for parking the rotor 6 in a long term parking state
are shown, in accordance with at least some embodiments of the
present disclosure. As will be described further below, the long
term parking state may be characterized by, in addition to locking
the rotor, a rotor configuration with the hub 10 and/or blades 8 in
a position which results in the lowest possible loads and/or torque
on the wind turbine 2. Specifically, when the rotor 6 is locked
against rotation, the blades 8 may still interact with the wind to
produce varying amounts of lift. This lift may be translated by the
blades 8 and the hub 10 into torque. The amount of lift and
therefore torque generated from interaction with the wind may
depend upon wind aerodynamics, which may be influenced largely by
the wind direction, the azimuthal location of the rotor blades, and
the pitch angle of the rotor blades. Thus, in order to park the
rotor 6 in a long term parking state, the pitch angle of the blades
8 may be adjusted to be in an optimal state for any wind direction
to minimize loads on the wind turbine 2, such as, by minimizing the
rotor torque, thereby preventing any damage to the wind turbine.
Also, the azimuthal position of the rotor 6 may be adjusted to be
in an optimal state for any wind direction to minimize loads.
Finally, the yaw orientation of the wind turbine 2 may be set to a
particular position to minimize loads. Adjusting the pitch angle
and the azimuthal position of the blades 8 and adjusting the yaw
orientation of the wind turbine 2 are each described in greater
detail below.
[0020] Accordingly, after starting at a step 32, the process may
proceed to a step 34, where it may be determined whether the rotor
6 needs to be parked in a long term parking state. In at least some
embodiments, this determination may be made by a control signal
generated manually (e.g., by maintenance personnel when maintenance
is required) or automatically by the TCU 28 or the control system
29. The determination may be made automatically based upon several
different factors, such as, severe weather conditions, or a damaged
bearing or other component as detected by a condition monitoring
system or the like. If the control signal at the step 34 for
parking the rotor 6 in a long term parking state is, thus, ON, the
process may proceed to a step 36. Otherwise, the process may end at
a step 38.
[0021] At the step 36, it may be determined whether the brakes of
the rotor 6 have already been applied or not, and/or whether the
positive locking pin has engaged the hub 10 to positively lock it
against rotation. If the brakes have not been applied or if the
locking pin has not been engaged, then at a step 40, the brakes of
the rotor and/or the locking pin may be automatically applied. In
other embodiments, other types of braking mechanisms, whether
manual or automatic, may be employed and implemented to lock the
rotor 6.
[0022] On the other hand, if at the step 36, it is determined that
the rotor 6 is already in a locked position, then the process may
proceed directly to a step 42, where the rotor 6 is configured to a
"fetal" or protective state. This protective state may be
characterized by pitching the blades 8 to a specific pitch angle
producing the least amount of torque, as described in FIGS. 3 and 4
below and, also by adjusting the azimuthal position of the blades
to minimize loads on the wind turbine 2, as described further
below.
[0023] Turning now to FIG. 3 in conjunction with FIG. 2, a wind
rosette or graphical representation 44 showing the amount of rotor
torque for several different blade pitch angle position settings
generated from wind in any direction is illustrated, in accordance
with at least some embodiments of the present disclosure. As will
be described further below, it may be seen from the wind rosette 44
that when the blades 8 are pitched towards power (to at or near
zero degrees from the plane of the rotor 6), the least amount of
torque is produced irrespective of the wind direction relative to
the wind turbine 2.
[0024] The wind rosette 44 plots rotor torque relative to the wind
direction at various angles (such as 45.degree., 90.degree.,
135.degree., 180.degree., 225.degree., 270.degree., 315.degree.,
and 360.degree.). The torque generated at a given wind direction is
proportional to the radial distance of the point from the center of
the rosette. It should be noted that the typical convention for
measuring pitch angles is that the pitch angle is the angular
difference between the blade and the rotor plane of rotation, and
that is the convention used herein. By determining the rotor torque
for every wind direction for various pitch angles of the blades 8,
the pitch angle that generates the minimum overall rotor torque may
be observed. As shown, the graph 44 illustrates four different
plots 46, 48, 50 and 52, each representing different pitch angles
of the blades 8 and the corresponding rotor torque for every wind
direction. In particular, the plots 46 and 48 shows the rotor
torque when all of the three blades 8 are pitched at or near zero
degrees)(0.degree.. The plot 50 shows the rotor torque when each of
the three blades 8 of the wind turbine 2 are pitched to different
pitching angles, namely, a first blade may be pitched at ninety
degrees)(90.degree., a second blade may be pitched at (or near)
eighty seven and a half (87.5.degree.) and a third blade may be
pitched at (or near) ninety two and a half degrees (92.5.degree.).
The plot 52 shows the rotor torque when all of the blades 8 are
pitched at or near ninety one degrees)(91.degree.).
[0025] The plots 46, 50 and 52 indicate an instantaneous rotor
torque value when the blades have been pitched to their specific
pitching angles mentioned above. The plot 48 corresponds to the
rotor blades 8 being pitched individually, one at a time, from a
ninety degree)(90.degree. position to a zero degree)(0.degree.)
position, which procedure is illustrated in greater detail in FIG.
4. The plot 48 indicates a maximum torque value that may be
obtained over the entire time period (such as five to ten minutes)
that it takes for all three blades to reach the final zero
degree)(0.degree.) pitch angle. It should be understood that all of
the plots 46-52 may be for a given wind speed, for example, a wind
speed of twenty two meters per second (22 m/sec), and an assumed
rotor azimuth position, wind shear, etc. Similar results in terms
of relative torque were observed at other wind speeds and
conditions.
[0026] Thus, it can be seen that a pitch angle at or near zero
degrees (0.degree.) generates significantly less torque than the
other simulated pitch angles. Therefore, to minimize rotor torque
during long term rotor parking, the blades 8 may be pitched at or
near zero degrees (0.degree.). The zero degree (0.degree.) pitch
position is somewhat counter-intuitive. This position may generate
the most lift and torque (and hence maximum power) during operation
when the rotor 6 is turning at a certain RPM, but when the rotor is
stationary and not turning, the zero degree)(0.degree.) pitch
position may also produce the least amount of torque.
[0027] Notwithstanding the fact that in the present embodiment, a
zero (or near zero) degree pitch position of the blades 8 has been
determined to minimize rotor torque, the pitch angle corresponding
to minimum torque may vary for other wind turbines. Also, it may be
desirable to optimize the rotor position to minimize other loads in
addition to rotor torque. In that case, the pitch position of the
blades 8 may also be different.
[0028] Furthermore, the blades 8 may be pitched all together at the
same time or, alternatively, each blade may be pitched
individually. If all the blades 8 are moved simultaneously from or
near the ninety degree position to the zero degree position, for
example, all three blades may at the same time reach a pitch
position where, despite the lack of rotation of the hub 10, they
may produce a lot of lift and, therefore, torque. In order to avoid
this, the blades 8 may be pitched from or near ninety degrees to at
or near zero degrees one at a time, the next blade not beginning to
pitch until the previous blade has finished pitching to zero
degrees. The rotor torque that may be produced when the blades 8
are pitched one at a time is shown in FIG. 4 below.
[0029] Referring now to FIG. 4 in conjunction with FIGS. 2 and 3,
an exemplary time domain graph 54 showing rotor torque values as
the blades 8 are pitched from or near ninety degrees to near or at
zero degrees is depicted, in accordance with at least some
embodiments of the present disclosure. The time domain graph 54
plots degrees on the left side Y-axis of the table against time in
seconds on the X-axis and the torque on the right side Y-axis. The
time domain graph 54 corresponds to a wind speed of eighteen meters
per second (18 m/sec) and an assumed wind shear value and wind
direction. Similar results are observed at other wind speeds and
conditions. It can be reaches the zero degree pitch angle does a
blade 62 begin pitching. Similarly, blade 64 starts pitching only
after the blade 62 has reached its pitch angle of zero degrees. By
virtue of pitching the blades 8 one by one, it can be seen that the
rotor torque remains relatively stable, and avoids the sharp spike
in torque that may be generated due to pitching all of the blades
simultaneously.
[0030] Thus, in order to park the rotor 6 in a long term parking
state, the pitch angles of each of the blades 8 may be pitched to
at or near zero degrees, and the blades may be moved to that
position either simultaneously or one by one as described above.
The process of moving the blades 8 one by one from their current
blade position to the at or near zero degree position may be
accomplished manually in the step 42, or automatically with
appropriate commands from the control system 29. In a preferred
embodiment, the positioning of the blades 8 may happen
automatically through commands from the control system 29. The
control system 29 could even control the pitch rate of individual
blades 8 to minimize the amount of time the rotor 6 might spend in
a particular position where a large or maximum torque is generated,
in other words, the control system may be programmed to move
through such a large or maximum torque position as quickly as
possible.
[0031] In addition to optimizing the pitch angle position of the
blades 8, in at least some circumstances, the azimuthal position of
the blades 8 may be optimized as well. Specifically, the blades 8
in their stationary position may be placed at an azimuthal position
which may result in a lowest rotor torque, or lowest loads, or some
combination of lowest loads and lowest torque. In at least some
embodiments, an optimal azimuthal position may correspond to a "Y"
position of the blades 8 in which the blades may be positioned at
two o'clock, six o'clock and ten o'clock, respectively. The optimal
azimuthal position may vary in other embodiments. As with pitch
positioning, this azimuthal positioning of the rotor 6 may occur in
the step 42 manually, or automatically with appropriate commands
from the control system 29. The control system 29 may disengage the
brakes and/or the positive locking pin and the hub 10 may be
permitted to rotate a few degrees to obtain the desired azimuthal
position of the blades 8 for long term rotor parking before the
brakes and/or locking pin are re-engaged.
[0032] Furthermore, in addition to adjusting the pitch angle
position of the blades 8 and the azimuthal position thereof, in at
least some embodiments, a particular yaw orientation of the wind
turbine 2 may also be desirable to line up the wind turbine most
favorably with the average or prevailing wind direction at a
particular wind turbine site. Some wind turbines may experience the
lowest rotor torque or other loads when those wind turbines are
facing directly into the wind. For other wind turbines, or for
particular loads that need to be minimized, a yaw angle other than
facing directly into the wind may be the most desirable. For
example, if the wind direction for the strongest or most prevalent
wind patterns for a particular wind turbine site is known, then the
wind turbine may be yawed to face that direction in order to orient
the wind turbine directly into the wind to minimize loads thereon
during a long term rotor parking state or it may be determined that
for a given turbine or a particular load to be minimized the most
optimal yaw position is ninety degrees) (90.degree.) out of the
prevailing wind direction or some other yaw orientation relative to
the wind. Similar to the pitch angle of the blades 8 and the
azimuthal position thereof, the desired yaw orientation for minimal
loads may be achieved manually at the step 42 or automatically
according to appropriate commands from the control system 29.
[0033] Now returning to FIG. 2, thus, at the step 42, the rotor 6
may be adjusted into a "fetal" or protective state to achieve a
long term parking state (in addition to locking the rotor at the
step 40) by (1) changing the pitch angle position of the blades 8
to at or near zero degrees or any other desirable pitching angle,
and/or (2) adjusting the azimuthal position of the blades, and/or
(3) adjusting the yaw orientation to a particular position where it
is expected to generate minimal loads.
[0034] When this long term parking state is enabled, an additional
safety factor to ensure that the rotor 6 safely stays in this
position may be provided. Specifically, extra caution may be
necessary to ensure that in this long term parking position, the
rotor 6 does not begin to turn (or rotate), due to a broken locking
pin or failed brake, for example, which might possibly occur when
power to the wind turbine 2 is lost or when there is some other
type of fault or failure. If the rotor 6 does begin to turn, it may
eventually reach a speed where a lot of torque may be produced,
given especially that the blades 8 have been pitched to the zero
degree position for maximum power, at which point the rotor may
over-speed. So, in this long term parking state, special controls
may be implemented to take action if any rotor rotation begins and
is detected. Accordingly, at a step 66, the rotor 6 may be
monitored (by the control system 29 within the wind turbine 2) for
any faults, such as those described above. If a fault is indeed
detected, then the process may proceed to a step 68, where an
emergency feather response may be taken to prevent damage to the
wind turbine 2. If no faults at the step 66 are detected, then the
control system 29 may continue to monitor the rotor 6 for any
faults and the process may end at the step 38.
[0035] At the step 68, in order to take protective action, if any
rotation of the hub is detected during the long term parking state
of the rotor, or if any other fault is detected such as loss of
power, or if the loss of power is sustained for longer than a set
period of time, the PCU may fault and go into an emergency feather
response. During this emergency feather response, the PCU may
instruct and pitch the blades 8 back to the ninety degrees in a
position of least power generation. The PCU may also be programmed
such that if there is any detection of loss of braking hydraulic
pressure or other brake failure, or if the locking pin is retracted
(e.g., broken off) from the hub 10, the PCU may instruct the blades
8 back to the ninety degrees pitching angle. Furthermore, if power
to the wind turbine 2 is lost, in those situations, the PCU may
employ its battery bank to power the pitch motors to pitch the
blades 8 to the ninety degrees pitching position and prevent any
damage to the wind turbine and enter the emergency feather
condition. In at least some embodiments, the PCU may pitch the
blades 8 to the zero degrees position only when power is supplied
to the wind turbine 2. As soon as the power goes off, the PCU may
command the blades 8 to return to the ninety degree position.
[0036] Notwithstanding the fact that in the present embodiment,
certain types of protective actions have been described, other
types of actions to prevent damage to the wind turbine 2 or any
component thereof may be taken in other embodiments. Subsequent to
activating the emergency feather condition, the process may end at
the step 38.
[0037] In general, the present disclosure sets forth a mechanism
for parking the rotor in a long term parking state. The long term
parking state of the rotor may be characterized by locking the
rotor, changing the pitch angle of the blades to at or near zero
degrees, adjusting the azimuthal position of the blades and
aligning the yaw system to face the direction of wind. An emergency
feather condition to provide any protective measures during
conditions of faults, such as, rotor rotation and power loss, may
be programmed within a control system that controls the long term
parking state of the rotor.
[0038] By virtue of parking the rotor in a long term parking state,
the amount of torque that the rotor produces while it is locked may
be minimized, thereby relieving at least some of the requirement of
the brake or pin to provide a very large counter-rotational force.
The size and structure of the locking pin may also be reduced or
simplified, and implementation of the long term parking state may
provide an extra factor of safety by reducing the torque of the
locked rotor.
[0039] While only certain embodiments have been set forth,
alternatives and modifications will be apparent from the above
description to those skilled in the art. These and other
alternatives are considered equivalents and within the spirit and
scope of this disclosure and the appended claims.
* * * * *