[0001] The present disclosure relates in general to wind turbines, and more
particularly to systems and methods for controlling wind turbines to increase traction
of the slip coupling in the drivetrain.
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, it may be desirable to apply a braking torque with the
generator to slow the rotor. For example, the wind turbine may experience an
anomalous operational event, such as an overspeed condition, a portion of a rotor
blade (or the rotor blade in its entirety) separating from the wind turbine, and/or other
significant deviation from the normal operating state of the wind turbine. Such events
may cause significant damage to the wind turbine, thereby making it desirable to slow
the rotation of the rotor expeditiously. However, as the rotor is typically rotatably
coupled to the generator via a slip coupling, the generation of torque by the generator
and/or the inertia of the rotor may result in a loss of traction of the slip coupling when it may otherwise be desirable to apply a generator torque to the drivetrain.
Accordingly, it may be desirable to control the generator torque so as to maintain, or
regain, traction of the slip coupling in order to facilitate the application of generator
torque to the drivetrain.
[0004] 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 to maintain or increase
the traction of the slip coupling.
BRIEF DESCRIPTION
[0005] 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.
[0006] In one aspect, the present disclosure is directed to a method for controlling
a wind turbine. The wind turbine may have a drivetrain which includes a rotor
rotatably coupled to a generator via a slip coupling. The method may include
detecting with a controller, which may be a controller of the wind turbine, a loss of
traction of the slip coupling. In response to the detecting the loss of traction, the
method may include overwriting, with the controller, a generator torque setpoint to
alter a rotational speed of the generator. Additionally, the method may include
increasing the traction of the slip coupling in response to the altered rotational speed
of the generator. Thus, increasing the traction of the slip coupling facilitates an
application of generator torque to the drivetrain of the wind turbine.
[0007] In an embodiment, the method may also include receiving, with the
controller, an indication of at least one rotational speed from an encoder operably
coupled to a high-speed shaft of the drivetrain and/or a generator rotor.
[0008] In an additional embodiment, the controller may be a converter controller.
In such embodiments, the converter controller may have a sampling frequency of at
least one sample every 200 microseconds.
[0009] In a further embodiment, the rotational speed(s) may be a rotational speed
of the generator. Additionally, the method may include detecting, with the controller,
the rotational speed at a first sampling interval. The method may also include detecting, with the controller, the rotational speed at a subsequent sampling interval.
Further, the method may include detecting, with the controller, a speed change of the
generator between the sampling intervals. The speed change may indicate a
deceleration.
[0010] In an embodiment, the method may include determining, with the
controller, a rate of deceleration of the generator based on the rotational speeds
detected at the sampling intervals. The rate of deceleration may be greater than a rate
of change threshold for the wind turbine.
[0011] In an additional embodiment, the drivetrain may include a low-speed shaft
coupling the rotor to a gearbox. The gearbox may be coupled to the generator via the
slip coupling. The method may also include detecting, with the controller, a rotational
speed of the low-speed rotor shaft. Also, the method may include detecting, with the
controller, a rotational speed of the generator. Additionally, the method may include
detecting, with the controller, a ratio of the rotational speed of the generator to the
rotational speed of the low-speed rotor shaft which is less than a speed correlation
threshold.
[0012] In a further embodiment, the rotational speed(s) may be a rotational speed
of the generator. The method may include receiving, with the controller, an indication
of at least one operating parameter of the wind turbine. The at least one operating
parameter(s) may include wind speed, wind direction, and/or a collective pitch angle
of the rotor. The method may also include determining, with the controller, a
correlation between the operating parameter(s) and the rotational speed of the
generator which is below a corresponding correlation threshold.
[0013] In an embodiment, the method may include detecting, with the controller,
a decrease in the inertia encountered by the generator. The inertia encountered by the
generator may include at least a rotor inertia.
[0014] In an additional embodiment, the method may include receiving, with the
controller, an indication of the rotational speed of the generator at a first sampling
interval and a subsequent sampling interval. The indications may be indicative of a
change in the rotational speed. The method may also include determining, with the
controller, an air-gap torque of the generator at the sampling intervals. Additionally,
the method may include determining, with the controller, a change in an inertia encountered by the generator based, at least in part, on the change in the rotational
speed and the air-gap torque at the sampling intervals.
[0015] In a further embodiment, the method may include detecting, with the
controller, the operating parameter(s) of the wind turbine. The operating parameter(s)
may include at least one of wind speed, wind direction, or a collective pitch angle of
the rotor. Additionally, the method may include detecting, with the controller, an
output parameter of the wind turbine. The output parameter may include at least one
of voltage, current, or power. Further, the method may include detecting, with the
controller, a correlation between the output parameter and the operating parameter(s)
which is below a correlation threshold.
[0016] In an embodiment, the method may include reducing the torque set point
of the generator so as to facilitate an increase in the rotational speed of the generator.
Increasing the rotational speed of the generator may facilitate increasing the traction
of the slip coupling.
[0017] In an additional embodiment, the method may include increasing the
rotational speed of the generator by motoring the generator.
[0018] In another aspect, the present disclosure is directed to a system for
controlling a wind turbine. The system may include a generator rotatably coupled to a
rotor via a slip coupling and a controller communicatively coupled to the generator.
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.
[0019] 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
[0020] 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: [0021] FIG. 1 illustrates a perspective view of one embodiment of a wind turbine
according to the present disclosure;
[0022] FIG. 2 illustrates a perspective, internal view of one embodiment of a
nacelle of the wind turbine according to the present disclosure;
[0023] FIG. 3 illustrates a schematic diagram of one embodiment of a drivetrain
of the wind turbine according to the present disclosure;
[0024] FIG. 4 illustrates a schematic diagram of one embodiment of an electrical
system for use with the wind turbine according to the present disclosure;
[0025] FIG. 5 illustrates a block diagram of one embodiment of a controller for
use with the wind turbine according to the present disclosure;
[0026] FIG. 6 illustrates a flow diagram of one embodiment of a control logic of a
system for controlling a wind turbine according to the present disclosure;
[0027] FIG. 7 illustrates a flow diagram of one embodiment of a portion of the
control logic of FIG. 6 corresponding to the detection of a loss of traction of the slip
coupling according to the present disclosure;
[0028] FIG. 8 illustrates a flow diagram of one embodiment of a portion of the
control logic of FIG. 6 corresponding to the detection of a loss of traction of the slip
coupling according to the present disclosure;
[0029] FIG. 9 illustrates a flow diagram of one embodiment of a portion of the
control logic of FIG. 6 corresponding to the detection of a loss of traction of the slip
coupling according to the present disclosure; and
[0030] FIG. 10 illustrates a flow diagram of one embodiment of a portion of the
control logic of FIG. 6 corresponding to the detection of a loss of traction of the slip
coupling 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.
DETAILED DESCRIPTION
[0032] Reference now will be made in detail to embodiments of the invention,
one or more examples of which are illustrated in the drawings. Each example is
provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and
variations can be made in the present invention without departing from the scope or
spirit of the invention. For instance, features illustrated or described as part of one
embodiment can be used with another embodiment to yield a still further
embodiment. Thus, it is intended that the present invention covers such modifications
and variations as come within the scope of the appended claims and their equivalents.
[0033] As used herein, the terms “first”, “second”, and “third” may be used
interchangeably to distinguish one component from another and are not intended to
signify location or importance of the individual components.
[0034] The terms “coupled,” “fixed,” “attached to,” and the like refer to both
direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching
through one or more intermediate components or features, unless otherwise specified
herein.
[0035] Approximating language, as used herein throughout the specification and
claims, is applied to modify any quantitative representation that could permissibly
vary without resulting in a change in the basic function to which it is related.
Accordingly, a value modified by a term or terms, such as “about”, “approximately”,
and “substantially”, are not to be limited to the precise value specified. In at least
some instances, the approximating language may correspond to the precision of an
instrument for measuring the value, or the precision of the methods or machines for
constructing or manufacturing the components and/or systems. For example, the
approximating language may refer to being within a 10 percent margin.
[0036] Here and throughout the specification and claims, range limitations are
combined and interchanged, such ranges are identified and include all the sub-ranges
contained therein unless context or language indicates otherwise. For example, all
ranges disclosed herein are inclusive of the endpoints, and the endpoints are
independently combinable with each other.
[0037] Generally, the present disclosure is directed to systems and methods for
controlling a wind turbine so as to facilitate the application of generator torque to the
drivetrain of the wind turbine. In particular, the present disclosure includes systems
and methods which maintain, regain, and/or increase the traction of the slip coupling
between the generator and the rotor of the wind turbine so that generator torque may be applied to the drivetrain. For example, the generator torque may be employed to
slow the rotation of the rotor, such as may be required during an emergency braking
of the wind turbine. Accordingly, the interaction of the generator torque and the
inertia of the rotor may exceed the traction of the slip coupling and the slip coupling
may begin to slip, as it is designed to do. The slipping of the slip coupling may be
detected by, for example, a sudden deceleration of the generator, a rotational speed of
the low-speed shaft which does not correlate to the rotational speed of the generator, a
sudden drop in the inertia seen by the generator, a lack of correlation between the
generator speed and the operating parameters of the wind turbine, and/or a lack of
correlation between the output parameters of the wind turbine and the operating
parameters. These conditions may, for example, indicate that the generator may no
longer be operably coupled to the rotor of the wind turbine and, therefore, any torque
generated by the generator may not affect the rotor. When the slip is detected by a
controller of the wind turbine, the torque set point of the generator may be modified
so that the generator speed may be changed, generally increased, in order to reduce
the torque present in the slip coupling. When the generator reaches the proper
rotational speed, the traction of the slip coupling may be increased so that the slipping
of the slip coupling ceases. Once traction is reestablished, the torque from the
generator may again be transmitted to the drivetrain of the wind turbine.
[0038] Referring now to the drawings, FIG. 1 illustrates a perspective view of one
embodiment of a wind turbine 100 according to the present disclosure. As shown, the
wind turbine 100 generally includes a tower 102 extending from a support surface
104, a nacelle 106, mounted on the tower 102, and a rotor 108 coupled to the nacelle
106. The rotor 108 includes a rotatable hub 110 and at least one rotor blade 112
coupled to and extending outwardly from the hub 110. For example, in the illustrated
embodiment, the rotor 108 includes three rotor blades 112. However, in an alternative
embodiment, the rotor 108 may include more or less than three rotor blades 112.
Each rotor blade 112 may be spaced about the hub 110 to facilitate rotating the rotor
108 to enable kinetic energy to be transferred from the wind into usable mechanical
energy, and subsequently, electrical energy. For instance, the hub 110 may be
rotatably coupled to an electric generator 118 (FIG. 2) of an electrical system 150
(FIG. 2) positioned within the nacelle 106 to permit electrical energy to be produced [0039] The wind turbine 100 may also include a controller 200 centralized within
the nacelle 106. However, in other embodiments, the controller 200 may be located
within any other component of the wind turbine 100 or at a location outside the wind
turbine. Further, the controller 200 may be communicatively coupled to any number
of the components of the wind turbine 100 in order to control the components. As
such, the controller 200 may include a computer or other suitable processing unit.
Thus, in several embodiments, the controller 200 may include suitable computerreadable instructions that, when implemented, configure the controller 200 to perform
various different functions, such as receiving, transmitting and/or executing wind
turbine control signals.
[0040] Referring now to FIGS. 2-4, a simplified, internal view of one embodiment
of the nacelle 106, a schematic diagram of one embodiment of a drivetrain 146, and
an exemplary electrical system 150 of the wind turbine 100 shown in FIG. 1 are
illustrated. As shown, the generator 118 may be coupled to the rotor 108 for
producing electrical power from the rotational energy generated by the rotor 108. For
example, as shown in the illustrated embodiment, the rotor 108 may include a rotor
shaft 122 coupled to the hub 110 for rotation therewith. The rotor shaft 122 may be
rotatably supported by a main bearing 144. The rotor shaft 122 may, in turn, be
rotatably coupled to a high-speed shaft 124 of the generator 118 through an optional
gearbox 126 connected to a bedplate support frame 136 by one or more torque arms
142. As is generally understood, the rotor shaft 122 may provide a low-speed, hightorque input to the gearbox 126 in response to rotation of the rotor blades 112 and the
hub 110. The gearbox 126 may then be configured with a plurality of gears 148 to
convert the low-speed, high-torque input to a high-speed, low-torque output to drive
the high-speed shaft 124 and, thus, the generator 118. In an embodiment, the gearbox
126 may be configured with multiple gear ratios so as to produce varying rotational
speeds of the high-speed shaft for a given low-speed input, or vice versa.
[0041] In an embodiment, the rotor 108 may be slowed via a torque generated by
the generator 118. As the generator 118 may generate a torque counter to the rotation
of the rotor 108, the high-speed shaft 124 may be equipped with a slip coupling 154.
The slip coupling 154 may prevent damage to a component of the drivetrain 146 due
to overloading of the drivetrain 146. As such, the slip coupling 154 may have a release threshold, or traction, above which the slip coupling 154 may permit first and
second portions 162, 164 of the high-speed shaft 124 to have a different rotational
speeds. It should be appreciated that, if the torsional moment at the slip coupling 154
exceeds the release/traction threshold, the generator 118 may be communicatively
decoupled from the rotor 108. In such an event, the torque developed by the
generator 118 may be unavailable to slow the rotor 108 or an increased rotational
speed of the rotor 108 may be unavailable for increased power production.
[0042] Each rotor blade 112 may also include a pitch control mechanism 120
configured to rotate the rotor blade 112 about its pitch axis 116. Each pitch control
mechanism 120 may include a pitch drive motor 128 (e.g., any suitable electric,
hydraulic, or pneumatic motor), a pitch drive gearbox 130, and a pitch drive pinion
132. In such embodiments, the pitch drive motor 128 may be coupled to the pitch
drive gearbox 130 so that the pitch drive motor 128 imparts mechanical force to the
pitch drive gearbox 130. Similarly, the pitch drive gearbox 130 may be coupled to the
pitch drive pinion 132 for rotation therewith. The pitch drive pinion 132 may, in turn,
be in rotational engagement with a pitch bearing 134 coupled between the hub 110
and a corresponding rotor blade 112 such that rotation of the pitch drive pinion 132
causes rotation of the pitch bearing 134. Thus, in such embodiments, rotation of the
pitch drive motor 128 drives the pitch drive gearbox 130 and the pitch drive pinion
132, thereby rotating the pitch bearing 134 and the rotor blade(s) 112 about the pitch
axis 116. Similarly, the wind turbine 100 may include one or more yaw drive
mechanisms 138 communicatively coupled to the controller 200, with each yaw drive
mechanism(s) 138 being configured to change the angle of the nacelle 106 relative to
the wind (e.g., by engaging a yaw bearing 140 of the wind turbine 100).
[0043] Referring particularly to FIG. 2, in an embodiment, the wind turbine 100
may include an environmental sensor 156 configured for gathering data indicative of
one or more environmental conditions. The environmental sensor 156 may be
operably coupled to the controller 200. Thus, in an embodiment, the environmental
sensor(s) 156 may, for example, be a wind vane, an anemometer, a lidar sensor,
thermometer, barometer, or any other suitable sensor. The data gathered by the
environmental sensor(s) 156 may include measures of wind speed, wind direction,
wind shear, wind gust, wind veer, atmospheric pressure, and/or temperature. In at least one embodiment, the environmental sensor(s) 156 may be mounted to the
nacelle 106 at a location downwind of the rotor 108. The environmental sensor(s)
156 may, in alternative embodiments, be coupled to, or integrated with, the rotor 108.
It should be appreciated that the environmental sensor(s) 156 may include a network
of sensors and may be positioned away from the turbine 100.
[0044] In addition, the wind turbine 100 may include a at least one operational
sensor 158. The operational sensor(s) 158 may be configured to detect a performance
of the wind turbine 100, e.g. in response to the environmental condition. For
example, the operational sensor(s) 158 may be a rotational speed sensor operably
coupled to the controller 200. The operational sensor(s) 158 may be directed at the
rotor shaft 122 of the wind turbine 100 and/or the generator 118. The operational
sensor(s) 158 may gather data indicative of the rotational speed and/or rotational
position of the rotor shaft 122, and thus the rotor 108 in the form of a rotor speed
and/or a rotor azimuth. The operational sensor(s) 158 may, in an embodiment, be an
analog tachometer, a D.C. tachometer, an A.C. tachometer, a digital tachometer, a
contact tachometer a non-contact tachometer, or a time and frequency tachometer. In
an embodiment, the operational sensor(s) 158 may, for example, be an encoder, such
as an optical encoder.
[0045] In an embodiment, the operational sensor(s) 158 and/or environmental
sensor(s) 156 may be configured to monitor operating parameters 348 (FIG. 9) of
wind turbine 100. For example, the operational sensor(s) 158 and/or environmental
sensor(s) 156 may monitor at least one of wind speed, wind direction, or a collective
pitch angle of the rotor 108.
[0046] Further, in an embodiment, the wind turbine 100 may include an output
sensor 160 configured to monitor at least one output parameter 360 (FIG. 10) of the
electrical system 150. For example, in monitoring the output parameter(s) 360, the
output sensor 160 may monitor the voltage, current, and/or power generated and/or
consumed by the wind turbine 100. Accordingly, the operational sensor(s) 158 may,
in an embodiment, be an ammeter, a voltmeter, an ohmmeter, and/or any other
suitable sensor for monitoring the operating parameter(s) 360 of the electrical system
150 and thereby the wind turbine 100.
12
[0047] It should also be appreciated that, as used herein, the term “monitor” and
variations thereof indicates that the various sensors of the wind turbine 100 may be
configured to provide a direct measurement of the parameters being monitored or an
indirect measurement of such parameters. Thus, the sensors described herein may, for
example, be used to generate signals relating to the parameter being monitored, which
can then be utilized by the controller 200 to determine a condition or response of the
wind turbine 100.
[0048] Referring particularly to FIG. 4, in an embodiment, the electrical system
150 may include various components for converting the kinetic energy of the rotor
108 into an electrical output in an acceptable form to a connected power grid. For
example, in an embodiment, the generator 118 may be a doubly-fed induction
generator (DFIG) having a stator 117 and a generator rotor 119. The generator 118
may be coupled to a stator bus 166 and a power converter 168 via a rotor bus 170. In
such a configuration, the stator bus 166 may provide an output multiphase power (e.g.
three-phase power) from a stator of the generator 118, and the rotor bus 170 may
provide an output multiphase power (e.g. three-phase power) of the generator rotor
119 of the generator 118. Additionally, the generator 118 may be coupled via the
rotor bus 170 to a rotor side converter 172. The rotor side converter 172 may be
coupled to a line side converter 174 which, in turn, may be coupled to a line side bus
176.
[0049] In an embodiment, the rotor side converter 172 and the line side converter
174 may be configured for normal operating mode in a three-phase, pulse width
modulation (PWM) arrangement using insulated gate bipolar transistors (IGBTs) as
switching devices. Other suitable switching devices may be used, such as insulated
gate commuted thyristors, MOSFETs, bipolar transistors, silicone controlled
rectifier’s, and/or other suitable switching devices. The rotor side converter 172 and
the line side converter 174 may be coupled via a DC link 173 across which may be a
DC link capacitor 175.
[0050] In an embodiment, the power converter 168 may be coupled to the
controller 200 configured as a converter controller 202 to control the operation of the
power converter 168. For example, the converter controller 202 may send control
commands to the rotor side converter 172 and the line side converter 174 to control the modulation of switching elements used in the power converter 168 to establish a
desired generator torque setpoint and/or power output.
[0051] As further depicted in FIG. 4, the electrical system 150 may, in an
embodiment, include a transformer 178 coupling the wind turbine 100 to an electrical
grid 179. The transformer 178 may, in an embodiment, be a 3-winding transformer
which includes a high voltage (e.g. greater than 12 KVAC) primary winding 180.
The high voltage primary winding 180 may be coupled to the electrical grid 179. The
transformer 178 may also include a medium voltage (e.g. 6 KVAC) secondary
winding 182 coupled to the stator bus 166 and a low voltage (e.g. 575 VAC, 690
VAC, etc.) auxiliary winding 184 coupled to the line bus 176. It should be
appreciated that the transformer 178 can be a three-winding transformer as depicted,
or alternatively, may be a two-winding transformer having only a primary winding
180 and a secondary winding 182; may be a four-winding transformer having a
primary winding 180, a secondary winding 182, and auxiliary winding 184, and an
additional auxiliary winding; or may have any other suitable number of windings.
[0052] In an additional embodiment, the electrical system 150 may include an
auxiliary power feed 186 coupled to the output of the power converter 168. The
auxiliary power feed 186 may act as a power source for various components of the
wind turbine system 100. For example, the auxiliary power feed 186 may power fans,
pumps, motors, and other suitable components of the wind turbine system 100.
[0053] In an embodiment, the electrical system 150 may also include various
circuit breakers, fuses, contactors, and other devices to control and/or protect the
various components of the electrical system 150. For example, the electrical system
150 may, in an embodiment, include a grid circuit breaker 188, a stator bus circuit
breaker 190, and/or a line bus circuit breaker 192. The circuit breaker(s) 188, 190,
192 of the electrical system 150 may connect or disconnect corresponding
components of the electrical system 150 when a condition of the electrical system 150
approaches an operational threshold of the electrical system 150.
[0054] Referring now to FIGS. 5-10, multiple embodiments of a system 300 for
controlling the wind turbine 100 according to the present disclosure are presented. As
shown particularly in FIG. 5, a schematic diagram of one embodiment of suitable
components that may be included within the system 300 is illustrated.

WHAT IS CLAIMED IS:
1. A method for controlling a wind turbine, the wind turbine having a
drivetrain comprising a rotor rotatably coupled to a generator via a slip coupling, the
method comprising:
detecting, with a controller, a loss of traction of the slip coupling;
in response to detecting the loss of traction, overriding, with the controller, a
generator torque setpoint to alter a rotational speed of the generator; and
increasing the traction of the slip coupling in response to the altered rotational
speed of the generator, wherein increasing the traction of the slip coupling facilitates
an application of generator torque to the drivetrain of the wind turbine.
2. The method of claim 1, further comprising:
receiving, with the controller, an indication of at least one rotational speed
from an encoder operably coupled to at least one of a high-speed shaft of the
drivetrain or a generator rotor.
3. The method of claim 2, wherein the controller is a converter controller,
and wherein the converter controller has a sampling frequency of at least one sample
every 200 microseconds.
4. The method of claim 2, wherein the at least one rotational speed is a
rotational speed of the generator, and wherein detecting the loss of traction of the slip
coupling further comprises:
detecting, with the controller, the rotational speed at a first sampling interval;
detecting, with the controller, the rotational speed at a subsequent, second
sampling interval; and
detecting, with the controller, a speed change of the generator between the first
and second sampling intervals, wherein the speed change comprises a deceleration.
5. The method of claim 4, wherein detecting the speed change of the
generator further comprises:
determining, with the controller, a rate of deceleration of the generator based
on the rotational speeds detected at the sampling intervals, wherein the rate of
deceleration is greater than a rate of change threshold for the wind turbine. 6. The method of claim 2, wherein the drivetrain further comprises a lowspeed shaft coupling the rotor to a gearbox, the gearbox being coupled to the
generator via the slip coupling, the method further comprising:
detecting, with the controller, a rotational speed of the low-speed rotor shaft;
detecting, with the controller, a rotational speed of the generator;
determining, with the controller, a ratio of the rotational speed of the generator
to the rotational speed of the low-speed rotor shaft which is less than a speed
correlation threshold.
7. The method of claim 2, wherein the at least one rotational speed is a
rotational speed of the generator, the method further comprising:
receiving, with the controller, an indication of at least one operating parameter
of the wind turbine, the at least one operating parameter comprising at least one of
wind speed, wind direction, or a collective pitch angle of the rotor; and
determining, with the controller, a correlation between the at least one
operating parameter and the rotational speed of the generator which is below a
corresponding correlation threshold.
8. The method of claim 1, wherein detecting the loss of traction of the
slip coupling further comprises:
detecting, with the controller, a decrease in an inertia encountered by the
generator, wherein the inertia encountered by the generator includes at least a rotor
inertia.
9. The method of claim 8, wherein detecting the decrease in the inertia
encountered by the generator comprises:
receiving, with the controller, an indication of the rotational speed of the
generator at a first sampling interval and a subsequent, second sampling interval, the
indications being indicative of a change in the rotational speed;
determining, with the controller, an air-gap torque of the generator at the first
and second sampling intervals; and
determining, with the controller, a change in an inertia encountered by the
generator based, at least in part, on the change in the rotational speed and the air-gap
torque at the first and second sampling intervals. 10. The method of claim 1, wherein detecting the loss of traction of the
slip coupling further comprises:
detecting, with the controller, at least one operating parameter of the wind
turbine, the at least one operating parameter comprising at least one of wind speed,
wind direction, or a collective pitch angle of the rotor;
detecting, with the controller, an output parameter of the wind turbine, the
output parameter comprising at least one of voltage, current, or power; and
determining, with the controller, a correlation between the output parameter
and the at least one operating parameter which is below a correlation threshold.
11. The method of claim 1, wherein overriding the generator torque
setpoint to alter the rotational speed of the generator further comprises:
reducing the torque setpoint of the generator so as to facilitate an increase in
the rotational speed of the generator, wherein increasing the rotational speed of the
generator facilitates increasing the traction of the slip coupling.
12. The method of claim 1, wherein increasing the traction of the slip
coupling further comprises:
increasing the rotational speed of the generator by motoring the generator.
13. A system for controlling a wind turbine, the system comprising:
a generator rotatably coupled to a rotor via a slip coupling; and
a controller communicatively coupled to the generator, the controller
comprising at least one processor configured to perform a plurality of operations, the
plurality of operations comprising:
detecting a loss of traction of the slip coupling,
in response to the detecting the loss of traction, overriding a generator
torque setpoint to alter a rotational speed of the generator, and
increasing the traction of the slip coupling in response to the altered
rotational speed of the generator, wherein increasing the traction of the slip
coupling facilitates an application of generator torque to a drivetrain of the
wind turbine.
14. The system of claim 13, wherein the plurality of operations further
comprise: receiving an indication of at least one rotational speed from an encoder
operably coupled to at least one of a high-speed shaft or a generator rotor.
15. The system of claim 14, wherein the controller is a converter
controller, and wherein the converter controller has a sampling frequency of at least
one sample every 200 milliseconds.
16. The system of claim 14, wherein detecting the loss of traction of the
slip coupling further comprises:
detecting the rotational speed at a first sampling interval;
detecting the rotational speed at a subsequent sampling interval; and
detecting a speed change of the generator between the sampling intervals,
wherein the speed change comprises a deceleration.
17. The system of claim 15, wherein detecting the speed change of the
generator further comprises:
determining, with the controller, a rate of deceleration of the generator based
on the rotational speeds detected at the sampling intervals, wherein the rate of
deceleration is greater than a rate of change threshold for the wind turbine.
18. The system of claim 15, wherein detecting the loss of traction of the
slip coupling further comprises:
detecting a decrease in an inertia encountered by the generator, wherein the
inertia encountered the generator includes at least a rotor inertia, wherein detecting
the decrease in the inertia comprises:
receiving an indication of the rotational speed of the generator at a first
sampling interval and a subsequent sampling interval, the indications being
indicative of a change in the rotational speed,
determining an air-gap torque of the generator at the sampling
intervals, and
determining a change in an inertia encountered by the generator based,
at least in part, on the change in the rotational speed and the air-gap torque at
the sampling intervals.
19. The system of claim 13, wherein overriding the generator torque
setpoint altered the rotational speed of the generator further comprises:reducing the torque setpoint of the generator so as to facilitate an increase in
the rotational speed of the generator, wherein increasing the rotational speed of the
generator facilitates increasing the traction of the slip coupling.
20. The system of claim 13, wherein increasing the traction of the slip
coupling further comprises:
increasing the rotational speed of the generator by motoring the generator.