The present disclosure relates in general to wind turbines, and more
particularly to systems and methods for controlling wind turbines in the event of a
blade liberation event.
BACKGROUND
[0002] Wind power is considered one of the cleanest, most environmentally
friendly energy sources presently available, and wind turbines have gained increased
attention in this regard. A modern wind turbine typically includes a tower, a
generator, a gearbox, a nacelle, and one or more rotor blades. The nacelle includes a
rotor assembly coupled to the gearbox and to the generator. The rotor assembly and
the gearbox are mounted on a bedplate support frame located within the nacelle. The
one or more rotor blades capture kinetic energy of wind using known airfoil
principles. The rotor blades transmit the kinetic energy in the form of rotational
energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is
not used, directly to the generator. The generator then converts the mechanical
energy to electrical energy and the electrical energy may be transmitted to a converter
and/or a transformer housed within the tower and subsequently deployed to a utility
grid. Modern wind power generation systems typically take the form of a wind farm
having multiple such wind turbine generators that are operable to supply power to a
transmission system providing power to an electrical grid.
[0003] In certain instances, a portion of a rotor blade (or the rotor blade in its
entirety) may separate from the wind turbine. Such blade liberation events may cause
the rotor to become imbalanced, thereby causing damage or destruction to the wind
turbine.
[0004] The damage resulting from an imbalanced rotor may increase with
continued operation of the wind turbine after the development of the imbalanced
condition. For existing wind turbines, the controller typically decelerates the rotor
using components of the wind turbine operating within nominal design limits.
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However, in certain instances, such a deceleration rate may be inadequate to prevent
or mitigate damage to the wind turbine. Accordingly, it may be desirable in certain
instances to decelerate the rotor in an expedited manner following a blade liberation
event. However, such rapid deceleration of the rotor can be costly. Therefore, it is
important to eliminate the instance of false alarms (i.e. only decelerating the rotor
when the blade liberation event has actually occurred).
[0005] Thus, the art is continuously seeking new and improved systems and
methods that address the aforementioned issues. As such, the present disclosure is
directed to systems and methods for controlling a wind turbine in response to a blade
liberation event.
BRIEF DESCRIPTION
[0006] Aspects and advantages of the invention will be set forth in part in the
following description, or may be obvious from the description, or may be learned
through practice of the invention.
[0007] In one aspect, the present disclosure is directed to a method for controlling
a wind turbine in response to a blade liberation event. The wind turbine may include
a rotor with a rotatable hub and a plurality of rotor blades mounted thereto. The
method may include determining a plurality of estimated response signatures for the
wind turbine corresponding to a plurality of different blade liberation events. The
method may also include collecting sensor data via a plurality of sensors during
operation of the wind turbine. The sensor data may be indicative of a response of at
least one component of the wind turbine to an actual rotor loading. The method may
include identifying at least two actual response signatures within the sensor data.
Additionally, the method may include determining whether the at least two actual
response signatures equal or exceed two or more corresponding estimated response
signatures of the plurality of estimated response signatures so as to determine the
presence of a blade liberation event. In response to detecting the blade liberation
event, the method may include initiating, with a controller, a rapid shutdown control
logic to protect the wind turbine.
[0008] In an embodiment, the plurality of response signatures may include at least
one of a load magnitude, a direction of the load being along a pitch axis, and
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acceleration vector of the at least one component, a first excitation frequency, a sensor
communication loss, an acoustic signature corresponding to a blade liberation, a
vibration signature corresponds to a blade liberation, a bending moment affecting a
rotor shaft or a tower of the wind turbine, and/or a combination thereof.
[0009] In an additional embodiment, the acceleration vector of the at least one
component may include a horizontal and a vertical displacement of the rotor in
response to the load on the rotor.
[0010] In an embodiment, the acceleration vector of the at least one component
may include an acceleration of a nacelle of the wind turbine in response to the wind
loading. The nacelle acceleration may include an oscillation direction, an oscillation
frequency, and an oscillation magnitude of the nacelle.
[0011] In a further embodiment, the acceleration vector of the at least one
component may include a rotor speed response. The rotor speed response may be
indicative of an acceleration or deceleration of the rotor in response to a rotor mass
balance and rotational position.
[0012] In an embodiment, the method may also include determining a type of
blade liberation event based on the at least two actual response signatures. The type
of blade liberation event may include a departure of at least a portion of one of the
plurality of rotor blades.
[0013] In an additional embodiment, the rapid shutdown control logic may
include decelerating the rotor in a shortened time interval relative to a nominal
shutdown control logic.
[0014] In a further embodiment, the rapid shutdown control logic may include
overriding a nominal operational limit of at least one component of the wind turbine.
The rapid shutdown control logic may also include establishing a rapid shutdown
setpoint for the component(s). The rapid shutdown setpoint may have a value greater
than the nominal operational limit such that excessive loading or damage of the
component(s) is permitted.
[0015] In another aspect, the present disclosure is directed to a method for
controlling a wind turbine in response to a blade liberation event. The wind turbine
may have a rotor with a rotatable hub and a plurality of rotor blades mounted thereto.
The method may include receiving, with the controller, data indicative of a blade
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liberation event from a plurality of sensors during operation of the wind turbine. In
response to detecting the blade liberation event, the method may also include
initiating, with the controller, a rapid shutdown control logic protect the wind turbine.
The rapid shutdown control logic may include overriding a nominal operational limit
of at least one component of the wind turbine. The rapid shutdown control logic may
also include establishing a rapid shutdown setpoint for the component(s). The rapid
shutdown setpoint may have a value greater than the nominal operational limit such
that excessive loading or damage of the component(s) is permitted. Additionally, the
rapid shutdown control logic may include establishing a deceleration rate of the rotor
which exceeds a nominal deceleration rate of the rotor.
[0016] In an embodiment, establishing the rapid shutdown setpoint comprises at
least one of generating, with the controller, a pitch setpoint command for the plurality
of rotor blades, wherein the pitch setpoint command directs a pitch control
mechanism to pitch the plurality of rotor blades to feather at a pitch rate exceeding a
nominal pitch rate threshold, and generating, with the controller, a generator setpoint
for a generator of the wind turbine, wherein the generator setpoint directs a converter
controller to develop a generator torque exceeding a nominal generator torque limit.
[0017] In an additional embodiment, the rapid shutdown control logic may also
include triggering, with the controller, a gearbox braking system operably coupled to
a gearbox of the wind turbine.
[0018] In a further embodiment, the wind turbine may also include a high-speed
shaft operably coupling the rotor to the generator via a gearbox. The gearbox may be
operably coupled to the generator via a slip coupling of the high-speed shaft. The
method may also include monitoring a torque level of the slip coupling. The method
may further include reducing the generator setpoint when the torque level of the slip
coupling approaches a release threshold of the slip coupling.
[0019] In an embodiment, the method may also include establishing a one-third
reduction in a rotational speed of the rotor within 720-degrees of rotation of the rotor
following detection of the blade liberation event.
[0020] In yet another aspect, the present disclosure is directed to a wind turbine.
The wind turbine may include a tower, a nacelle mounted atop the tower, and a rotor
mounted to the nacelle. The rotor may include a rotatable hub having a plurality of
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rotor blades secured thereto via a pitch drive mechanism. The wind turbine may also
include a generator disposed within the nacelle and operably coupled to the rotor via a
gearbox and a high-speed shaft. Additionally, the wind turbine may include a
controller communicatively coupled to a plurality of sensors, the generator, and the
pitch drive mechanism. The controller may include at least one processor configured
to perform a plurality of operations. The plurality of operations may include any of
the operations and/or features described herein.
[0021] These and other features, aspects and advantages of the present invention
will become better understood with reference to the following description and
appended claims. The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of the invention and,
together with the description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] A full and enabling disclosure of the present invention, including the best
mode thereof, directed to one of ordinary skill in the art, is set forth in the
specification, which makes reference to the appended figures, in which:
[0023] FIG. 1 illustrates a perspective view of one embodiment of a wind turbine
according to the present disclosure;
[0024] FIG. 2 illustrates a perspective, internal view of one embodiment of a
nacelle of the wind turbine according to the present disclosure;
[0025] FIG. 3 illustrates a schematic diagram of one embodiment of a drivetrain
of the wind turbine according to the present disclosure;
[0026] FIG. 4 illustrates a schematic diagram of one embodiment of a controller
for use with the wind turbine according to the present disclosure;
[0027] FIG. 5 illustrates a schematic diagram of one embodiment of a control
logic of a system for controlling a wind turbine according to the present disclosure;
[0028] FIG. 6 illustrates a schematic diagram of one embodiment of a portion of
the control logic of FIG. 5 according to the present disclosure;
[0029] FIG. 7 illustrates a schematic diagram of one embodiment of a portion of
the control logic of FIG. 5 according to the present disclosure; and
[0030] FIG. 8 illustrates a graphical representation of one embodiment of a
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response of the wind turbine to a blade liberation event according to the present
disclosure.
[0031] Repeat use of reference characters in the present specification and
drawings is intended to represent the same or analogous features or elements of the
present invention.

WHAT IS CLAIMED IS:
1. A method for controlling a wind turbine in response to a blade liberation event,
the wind turbine having a rotor with a rotatable hub and a plurality of rotor blades mounted
thereto, the method comprising:
determining a plurality of estimated response signatures for the wind turbine
corresponding to a plurality of different blade liberation events;
collecting sensor data via a plurality sensors during operation of the wind turbine, the
sensor data being indicative of a response of at least one component of the wind turbine to an
actual rotor loading;
identifying at least two actual response signatures within the sensor data;
determining whether the at least two actual response signatures equal or exceed two or
more corresponding estimated response signatures of the plurality of estimated response
signatures so as to determine the presence of a blade liberation event; and
in response to detecting the blade liberation event, initiating, with a controller, a rapid
shutdown control logic to protect the wind turbine.
2. The method of claim 1, wherein the plurality of response signatures comprise at
least one of a load magnitude, a direction of the load being along a pitch axis, an acceleration
vector of the at least one component, a first excitation frequency, a sensor communication loss,
an acoustic signature corresponding to blade liberation, a vibration signature corresponding to
blade liberation, a bending moment affecting a rotor shaft or a tower of the wind turbine, or a
combination thereof.
3. The method of claim 2, wherein the acceleration vector of the at least one
component comprises:
a horizontal and a vertical displacement of the rotor in response to the load on the rotor.
4. The method of claims 2 or 3, wherein the acceleration vector of the at least one
component comprises:
an acceleration of a nacelle of the wind turbine in response to the wind loading, wherein
the nacelle acceleration comprises an oscillation direction, an oscillation frequency, and an
oscillation magnitude of the nacelle.
5. The method of any of claims 2-4, wherein the acceleration vector of the at least
one component comprises:
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a rotor speed response, wherein the rotor speed response is indicative of an acceleration
or deceleration of the rotor in response to a rotor mass balance and rotational position.
6. The method of any preceding claim, further comprising:
determining a type of blade liberation event based on the at least two actual response
signatures, wherein the type of the blade liberation event comprises a departure of at least a
portion of one of the plurality of rotor blades.
7. The method of any preceding claim, wherein the rapid shutdown control logic
comprises decelerating the rotor in a shortened time interval relative to a nominal shutdown
control logic.
8. The method of any preceding claim, wherein the rapid shutdown control logic
comprises:
overriding a nominal operational limit of at least one component of the wind turbine; and
establishing a rapid shutdown setpoint for the at least one component, wherein the rapid
shutdown setpoint has a value greater than the nominal operational limit such that excessive
loading or damage of the at least one component is permitted.
9. The method of any preceding claim, wherein the rapid shutdown control logic
comprises:
overriding a nominal operational limit of at least one component of the wind turbine;
establishing a rapid shutdown setpoint for the at least one component, wherein the rapid
shutdown setpoint has a value greater than the nominal operational limit such that excessive
loading or damage of the at least one component is permitted; and
establishing a deceleration rate of the rotor which exceeds a nominal deceleration rate of
the rotor.
10. The method of claim 9, wherein establishing the rapid shutdown setpoint
comprises at least one of:
generating, with the controller, a pitch setpoint command for the plurality of rotor blades,
wherein the pitch setpoint command directs a pitch control mechanism to pitch the plurality of
rotor blades to feather at a pitch rate exceeding a nominal pitch rate threshold; and
generating, with the controller, a generator setpoint for a generator of the wind turbine,
wherein the generator setpoint directs a converter controller to develop a generator torque
exceeding a nominal generator torque limit.
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11. The method of claims 9 or 10, wherein the rapid shutdown control logic further
comprises:
triggering, with the controller, a gearbox braking system operably coupled to a gearbox
of the wind turbine.
12. The method of any of claims 9-11, wherein the wind turbine further comprises a
high-speed shaft operably coupling the rotor to the generator via a gearbox, the gearbox being
operably coupled to the generator via a slip coupling of the high-speed shaft, the method further
comprising:
monitoring a torque level of the slip coupling; and
reducing the generator setpoint when the torque level of the slip coupling approaches a
release threshold of the slip coupling.
13. The method of any of claims 9-12, further comprising:
establishing a one-third reduction in a rotational speed of the rotor within 720-degrees of
rotation of the rotor following detection of the blade liberation event.
14. A wind turbine, comprising:
a tower;
a nacelle mounted atop the tower;
a rotor mounted to the nacelle, the rotor comprising a rotatable hub having a plurality
rotor blades secured thereto via a pitch drive mechanism;
a generator disposed within the nacelle and operably coupled to the rotor via a gearbox
and a high-speed shaft; and
a controller communicatively coupled to a plurality of sensors, the generator, and the
pitch drive mechanism, the controller comprising at least one processor configured to perform a
plurality of operations, the plurality of operations comprising:
collecting sensor data via the plurality sensors during operation of the wind
turbine, the sensor data being indicative of a response of a component of the wind turbine
to a rotor loading,
identifying at least two actual response signatures within the sensor data,
determining whether the at least two actual response signatures equal or exceed
two or more corresponding estimated response signatures of a plurality of estimated
response signatures so as to determine the presence of a blade liberation event, wherein
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the plurality of estimated response signatures correspond to a plurality of different blade
liberation events, and
in response to detecting the blade liberation event, initiating, with a controller, a
rapid shutdown control logic to protect the wind turbine.
15. Wind turbine of claim 14, wherein the plurality of response signatures comprise at
least one of a load magnitude, a direction of the load being along a pitch axis, an acceleration
vector of the at least one component, a first excitation frequency, a sensor communication loss,
an acoustic signature corresponding to blade liberation, a vibration signature corresponding to
blade liberation, a bending moment affecting a rotor shaft or a tower of the wind turbine, or a
combination thereof, wherein the plurality of response signatures comprises a plurality of
acceleration vectors, the plurality of acceleration vectors comprising:
an acceleration of the nacelle in response to the wind loading, wherein the nacelle
acceleration comprises an oscillation direction, an oscillation frequency, and oscillation
magnitude of the nacelle,
a horizontal and a vertical displacement of the rotor in response to the load on the
rotor, and
a rotor speed response, wherein the rotor speed response is indicative of an
acceleration or deceleration of the rotor in response to a rotor mass balance and rotational
position.