Patent Description:
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 modem 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 the electrical energy may be transmitted to a converter and/or a transformer housed within the tower and subsequently deployed to a utility grid.

During operation, the velocity of the wind which powers the wind turbine may change. The wind turbine may, thus, including a pitch system having a plurality of pitch adjustment mechanisms (i.e. one for each rotor blade) to adjust the pitch of the individual rotor blades about a pitch axis. During normal operations, the pitch adjustment mechanisms receives pitch commands from the turbine controller. For wind speeds below the rated threshold of the wind turbine, the turbine controller may calculate the desired pitch of the individual rotor blades so as to maximize the power produced at the given wind speed. For wind speeds above the rated threshold of the wind turbine, the turbine controller may calculate the desired pitch of the individual rotor blades so as to reduce thrust production below a specified design limit.

If one or more of the pitch adjustment mechanisms experience a fault or software glitch, however, the pitch system may continue pitching the rotor blades in a manner that would overload the wind turbine. Alternatively, faults in other turbine components may lead the controller to send pitch commands towards fine pitch, while the rotor speed is deemed high.

Thus, the art is continuously seeking new and improved systems and methods that address the aforementioned issues. Accordingly, the present disclosure is directed to systems and methods for operating a wind turbine to protect the wind turbine from overloading caused by a fault in a pitch system thereof. In particular, the present disclosure is directed to a system and method for collective pitch rate supervision that allows for flexibility in defining a pitch rate threshold.

<CIT> describes a method for detecting a rotor blade angle adjustment fault of a rotor blade of a wind turbine.

In one aspect, the present disclosure is directed to a method for protecting a wind turbine from overloading during operation caused by a fault. The method includes receiving, via a controller, a plurality of pitch signals from a plurality of pitch control mechanisms of a pitch system of the wind turbine, the pitch system configured to rotate a plurality of rotor blades mounted to a rotatable hub of a rotor of the wind turbine about respective pitch axes. Further, the method includes determining, via the controller, a collective pitch rate of the pitch system as a function of the plurality of pitch signals. The method also includes defining, via the controller, a minimum pitch rate threshold that varies with a speed parameter of the wind turbine. Moreover, the method includes receiving, via the controller, a first speed parameter of the wind turbine. In addition, the method includes comparing, via the controller, the collective pitch rate to the minimum pitch rate threshold for the first speed parameter. Thus, the method includes controlling, via the controller, the wind turbine based on the comparison.

In an embodiment, the method includes measuring the plurality of pitch signals via a plurality of sensors. In one embodiment, the plurality of pitch signals may include plurality of pitch speed signals.

In alternative embodiments, the plurality of pitch signals may include a plurality of pitch position signals. In such embodiments, the method may include determining a derivative of each of the plurality of pitch position signals to obtain a plurality of pitch speed signals. In addition, the method may also include filtering the derivatives of the plurality of pitch positions to reduce noise.

In further embodiments, determining the collective pitch rate as a function of the plurality of pitch signals may include averaging the plurality of pitch signals to obtain the collective pitch rate.

In additional embodiment, the speed parameter of the wind turbine may include rotor speed, generator speed, or derivatives thereof as well as any other suitable speed parameter of the wind turbine.

In certain embodiments, comparing the collective pitch rate to the minimum pitch rate threshold for the first speed parameter may include utilizing a look-up table.

In another embodiment, controlling the wind turbine based on the comparison may include pitching the plurality of pitch control mechanisms at a constrained pitch rate if the speed parameter is below a speed threshold for a certain time period and implementing a control action if the speed parameter is above the speed threshold for a certain time period. In such embodiments, the control action may include shutting down the wind turbine, pitching the plurality of pitch control mechanisms at a maximum pitch rate, derating the wind turbine, or any other suitable corrective actions.

In still another embodiment, the controller may be a turbine controller or a separate controller module communicatively coupled to the turbine controller.

In another aspect, the present disclosure is directed to a pitch system for a wind turbine. The pitch system includes a plurality of pitch control mechanisms for generating a plurality of pitch signals associated with a plurality of rotor blades mounted to a rotatable hub of a rotor of the wind turbine and a controller communicatively coupled to the plurality of pitch control mechanisms. The controller includes at least one processor configured to perform a plurality of operations, including but not limited to determining a collective pitch rate of the pitch system as a function of the plurality of pitch signals, defining a minimum pitch rate threshold that varies with a speed parameter of the wind turbine, receiving a first speed parameter of the wind turbine, comparing the collective pitch rate to the minimum pitch rate threshold for the first speed parameter, and controlling the wind turbine based on the comparison. It should be understood that the pitch system may further include any of the additional steps and/or features described herein.

As used herein, 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.

Generally, the present disclosure is directed to systems and methods for operating a wind turbine to protect the wind turbine from overloading caused by a fault in a pitch system thereof. In particular, the present disclosure may include a system and method that monitors the pitch rate feedback from the pitch system of the wind turbine and converts the individual pitch rates to a collective pitch rate. The collective pitch rate can then be compared to a minimum pitch rate threshold defined as a function of rotor speed. If the collective pitch rate is below the threshold for a defined amount of time, the turbine controller can trigger a turbine shutdown. Further, one aspect of the present disclosure is defining hazardous pitch activity. In particular, the system and method of the present disclosure introduces a concept to define the minimum pitch rate threshold as a function of rotor speed. At low rotor speeds, the wind turbine can continue pitching at its full rate to power. However, at higher rotor speeds, pitching to power at full rate can be hazardous. Therefore, defining the threshold as a function of rotor speed provides the maximum flexibility for this supervision. Accordingly, the present disclosure addresses previous issues associated with defining a constant threshold with a large conservative margin that may delay triggering a shutdown when needed. In addition, the present disclosure also addresses issues associated with defining the constant threshold to minimize the time to trigger a shutdown, which can result in shutting down the wind turbine too quickly, thereby causing nuisance trips or restrictions during service operations. Still further advantages of the present disclosure include protecting the wind turbine against faults/failures that result in pitching in a way to overload the wind turbine.

Referring now to the drawings, <FIG> illustrates a perspective view of one embodiment of a wind turbine <NUM> according to the present disclosure. As shown, the wind turbine <NUM> generally includes a tower <NUM> extending from a support surface <NUM>, a nacelle <NUM>, which includes an outer shell <NUM>, mounted on the tower <NUM>, and a rotor <NUM> coupled to the nacelle <NUM>. The rotor <NUM> includes a rotatable hub <NUM> and at least one rotor blade <NUM> coupled to and extending outwardly from the hub <NUM>. For example, in the illustrated embodiment, the rotor <NUM> includes three rotor blades <NUM>. However, in an alternative embodiment, the rotor <NUM> may include more or less than three rotor blades <NUM>. Each rotor blade <NUM> may be spaced about the hub <NUM> to facilitate rotating the rotor <NUM> to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub <NUM> may be rotatably coupled to an electric generator <NUM> (<FIG>) positioned within the nacelle <NUM> to permit electrical energy to be produced.

The wind turbine <NUM> may also include a controller <NUM> (<FIG>). In an embodiment, the controller <NUM> may be a wind turbine controller <NUM> centralized within the nacelle <NUM>. However, in other embodiments, the controller <NUM> may be located within any other component of the wind turbine <NUM> or at a location outside the wind turbine. Further, the controller <NUM> may be communicatively coupled to any number of the components of the wind turbine <NUM> in order to control the components. As such, the controller <NUM> may include a computer or other suitable processing unit. Thus, in several embodiments, the controller <NUM> may include suitable computer-readable instructions that, when implemented, configure the controller <NUM> to perform various different functions, such as receiving, transmitting and/or executing wind turbine control signals.

Referring now to <FIG>, a simplified, internal view of one embodiment of the nacelle <NUM> of the wind turbine <NUM> shown in <FIG> is illustrated. As shown, the generator <NUM> may be coupled to the rotor <NUM> for producing electrical power from the rotational energy generated by the rotor <NUM>. For example, as shown in the illustrated embodiment, the rotor <NUM> may include a rotor shaft <NUM> coupled to the hub <NUM> for rotation therewith. The rotor shaft <NUM> may be rotatably supported by a main bearing <NUM>. The rotor shaft <NUM> may, in turn, be rotatably coupled to a generator shaft <NUM> of the generator <NUM> through a gearbox <NUM> connected to a bedplate support frame <NUM> by one or more torque arms <NUM>. As is generally understood, the rotor shaft <NUM> may provide a low speed, high torque input to the gearbox <NUM> in response to rotation of the rotor blades <NUM> and the hub <NUM>. The gearbox <NUM> may then be configured to convert the low speed, high torque input to a high speed, low torque output to drive the generator shaft <NUM> and, thus, the generator <NUM>.

The wind turbine <NUM> may also include a pitch system <NUM> for controlling a pitch angle of each of the rotor blades <NUM>. In particular, as shown in <FIG> and <FIG>, the pitch system <NUM> may include a plurality of pitch control mechanisms <NUM>, e.g. one for controlling rotation of each rotor blade <NUM> about its pitch axis <NUM>. The pitch control mechanism(s) <NUM> may include a pitch controller <NUM> configured to receive at least one pitch setpoint command from the controller <NUM>. Further, each pitch control mechanism(s) <NUM> may include a pitch drive motor <NUM> (e.g., any suitable electric, hydraulic, or pneumatic motor), a pitch drive gearbox <NUM>, and a pitch drive pinion <NUM>. In such embodiments, the pitch drive motor <NUM> may be coupled to the pitch drive gearbox <NUM> so that the pitch drive motor <NUM> imparts mechanical force to the pitch drive gearbox <NUM>. Similarly, the pitch drive gearbox <NUM> may be coupled to the pitch drive pinion <NUM> for rotation therewith. The pitch drive pinion <NUM> may, in turn, be in rotational engagement with a pitch bearing <NUM> coupled between the hub <NUM> and a corresponding rotor blade <NUM> such that rotation of the pitch drive pinion <NUM> causes rotation of the pitch bearing <NUM>. Thus, in such embodiments, rotation of the pitch drive motor <NUM> drives the pitch drive gearbox <NUM> and the pitch drive pinion <NUM>, thereby rotating the pitch bearing <NUM> and the rotor blade(s) <NUM> about the pitch axis <NUM>. Similarly, the wind turbine <NUM> may include one or more yaw drive mechanisms <NUM> communicatively coupled to the controller <NUM>, with each yaw drive mechanism(s) <NUM> being configured to change the angle of the nacelle <NUM> relative to the wind (e.g., by engaging a yaw bearing <NUM> of the wind turbine <NUM>).

Rotation of each rotor blade <NUM> about its pitch axis <NUM> by its respective pitch control mechanism <NUM> may establish a pitch angle for each of the rotor blades <NUM>. In an embodiment, the pitch angle may be an angular deviation from a zero-pitch location. The zero-pitch location may, for example, be established during blade installation through reliance on a mechanical reference at the blade root or a protrusion which triggers a limit switch to automate the calibration process. The controller <NUM> may track the pitch angle of the rotor blade(s) <NUM> based on a cumulative deviation from the zero-pitch location. The controller <NUM> may, thus, transmit the pitch setpoint command(s) to the pitch control mechanisms <NUM> directing that the rotor blade(s) <NUM> be rotated through a specified number of degrees, as interpreted by a motor mounted encoder, relative to the perceived pitch angle of the rotor blade(s) <NUM>.

Still referring to <FIG>, one or more sensors <NUM>, <NUM>, <NUM> may be provided on the wind turbine <NUM> to monitor the performance of the wind turbine <NUM> and/or environmental conditions affecting the wind turbine <NUM>. It should also be appreciated that, as used herein, the term "monitor" and variations thereof indicates that the various sensors of the wind turbine <NUM> 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 <NUM> to determine the condition.

Referring now to <FIG>, a schematic diagram of one embodiment of a system <NUM> for controlling a wind turbine <NUM> according to the present disclosure is presented. As shown, suitable components may be included within the controller <NUM> according to the present disclosure. As shown, the controller <NUM> may include one or more processor(s) <NUM> and associated memory device(s) <NUM> configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like and storing relevant data as disclosed herein). Additionally, the controller <NUM> may also include a communications module <NUM> to facilitate communications between the controller <NUM> and the various components of the wind turbine <NUM>. Further, the communications module <NUM> may include a sensor interface <NUM> (e.g., one or more analog-to-digital converters) to permit signals transmitted from one or more sensors <NUM>, <NUM>, <NUM> to be converted into signals that can be understood and processed by the processors <NUM>. It should be appreciated that the sensors <NUM>, <NUM>, <NUM> may be communicatively coupled to the communications module <NUM> using any suitable means. For example, as shown in <FIG>, the sensors <NUM>, <NUM>, <NUM> are coupled to the sensor interface <NUM> via a wired connection. However, in other embodiments, the sensors <NUM>, <NUM>, <NUM> may be coupled to the sensor interface <NUM> via a wireless connection, such as by using any suitable wireless communications protocol known in the art.

As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) <NUM> may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) <NUM> may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) <NUM>, configure the controller <NUM> to perform various functions including, but not limited to, calculating a collective pitch offset and using the collective pitch offset in the control of the turbine <NUM>, as described herein, as well as various other suitable computer-implemented functions.

As shown generally in <FIG>, the system <NUM> may include at least one first sensor <NUM> configured for monitoring a wind condition at the wind turbine or acting on the rotor <NUM>. The first sensor(s) <NUM> may, for example, be a wind vane, an anemometer, a lidar sensor, or other suitable sensor. The wind condition may include and the first sensor(s) <NUM> may be configured to measure wind speed, wind direction, wind shear, wind gust and/or wind veer. In at least one embodiment, the first sensor(s) <NUM> may be mounted to the nacelle <NUM> at a location downwind of the rotor <NUM>. The first sensor(s) <NUM> may, in alternative embodiments, be coupled to or integrated with the rotor <NUM>. It should be appreciated that the first sensor(s) <NUM> may include a network of sensors and may be positioned away from the wind turbine <NUM>. In an embodiment, the system <NUM> may include at least one second sensor <NUM> configured for monitoring a loading condition of the wind turbine <NUM>, such as a loading of one of the rotor blades <NUM>. Moreover, as shown in <FIG> and <FIG>, the system <NUM> may also include at least one third sensor <NUM> configured for monitoring an environmental condition or an operating condition of the wind turbine <NUM>. For example, the third sensor(s) <NUM> may be a power sensor configured to monitor the power output of the generator <NUM>.

In an embodiment, the sensors <NUM>, <NUM>, <NUM> may be any suitable sensor such as a proximity sensor, an inductive sensor, a Miniature Inertial Measurement Unit (MIMU), a pressure sensor, an accelerometer, a SODAR sensor, a LIDAR sensor, an optical sensor, or similar sensor. The sensors <NUM>, <NUM>, <NUM> may, for example, be configured to provide the controller <NUM> with measurements relating to air temperature, component temperature, air pressure, and/or rotational speed of the rotor blade(s) <NUM>. Further, the sensors <NUM>, <NUM>, <NUM> may also include a network of sensors or a single sensor.

In accordance with the present disclosure, the controller <NUM> of the system <NUM>, such as depicted in <FIG>, may include a collective pitch rate module <NUM> for determining the collective pitch rate as described herein. Alternatively, the collective pitch rate module <NUM> may be a component of the wind turbine controller <NUM> or may be a component of a separate controller <NUM>. In such embodiments, the utilization of a separate controller <NUM> may facilitate the determination of the collective pitch rate without requiring access to the software and/or hardware of the wind turbine controller <NUM>.

In addition, in an embodiment, the collective pitch rate module <NUM> may be configured to execute one or more suitable data processing techniques or algorithms. The techniques or algorithms may allow the controller <NUM> or the wind turbine controller <NUM> to accurately and efficiently analyze the sensor data from the sensors <NUM>, <NUM>, <NUM>. Further, the collective pitch rate module <NUM> may apply corrections or adjustments to the received data based on the sensor type, sensor resolution, and/or other parameters associated with the wind conditions or wind turbine <NUM> operations. In one instance, for example, the collective pitch rate module <NUM> may filter the data to remove outliers, by implementing sub-routines or intermediate calculations required to calculate the collective pitch angle, and/or by performing any other desired data processing-related techniques or algorithms.

Referring now to <FIG> and <FIG>, a method <NUM> and system <NUM> for protecting a wind turbine from overloading during operation caused by a fault, e.g. from a pitch system, are illustrated, respectively. In particular, <FIG> illustrates a flow diagram of one embodiment of a method <NUM> for operating a wind turbine to protect the wind turbine from overloading caused by a fault in pitch system thereof is illustrated. The method <NUM> may be implemented using, for instance, the system <NUM> discussed with reference to <FIG>. Further, <FIG> depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that various steps of the method <NUM>, or any of the methods disclosed herein, may be adapted, modified, rearranged, performed simultaneously, or modified in various ways without deviating from the scope of the present disclosure.

As shown at (<NUM>), the method <NUM> receiving, via a controller, a plurality of pitch signals from a plurality of pitch control mechanisms of a pitch system of the wind turbine, the pitch system configured to rotate a plurality of rotor blades mounted to a rotatable hub of a rotor of the wind turbine <NUM> about respective pitch axes. For example, as shown in <FIG>, the system <NUM> may include a controller <NUM> (such as turbine controller <NUM> or a separate controller as described herein) that receives measured pitch signals from each of the pitch controllers <NUM> of each pitch control mechanisms (i.e. one from each rotor blade <NUM>). Thus, in an embodiment, the pitch signals may be measured via a plurality of sensors (such as any of sensors <NUM>, <NUM>, <NUM>). In another embodiment, the plurality of pitch signals may include plurality of pitch speed signals.

Alternatively, in an embodiment, the plurality of pitch signals may include a plurality of pitch position signals. In such embodiments, the method <NUM> may include determining a derivative of each of the pitch position signals (e.g. via numerical derivative modules <NUM>) to obtain a plurality of pitch speed signals. In addition, in such embodiments, where the pitch signals are position signals, the method <NUM> may also include filtering the derivatives of the pitch positions so as to reduce noise in the signals. If, however, the pitch signals correspond to pitch speed signals, such signals can be directly input into the controller <NUM> without first determining the derivatives thereof and/or without filtering.

Referring back to <FIG>, as shown at (<NUM>), the method <NUM> includes determining, via the controller <NUM>, a collective pitch rate of the pitch system <NUM> as a function of the plurality of pitch signals. For example, as shown in <FIG>, the controller <NUM> may include a collective pitch rate module <NUM> for determining the collective pitch rate of the pitch system <NUM>. More particularly, in an embodiment, the collective pitch rate module <NUM> may determine the collective pitch rate by averaging the plurality of pitch signals.

In an embodiment, the controller <NUM> may determine the collective pitch rate continuously, at a predetermined interval, and/or in response to a specified sensor input. In a further embodiment, the controller <NUM> may calculate the collective pitch rate at a predetermined interval (e.g. daily, weekly, monthly, etc.). In yet in an additional embodiment, the receipt of a fault signal from a sensor, such as an indication relating to an unexpected output of the generator, may trigger the controller <NUM> to calculate the collective pitch rate.

Referring back to <FIG>, as shown at (<NUM>), the method <NUM> includes defining, via the controller <NUM>, a minimum pitch rate threshold that varies with a speed parameter of the wind turbine <NUM>. For example, in an embodiment, the speed parameter of the wind turbine <NUM> may include rotor speed, generator speed, or derivatives thereof as well as any other suitable speed parameter of the wind turbine <NUM>. Moreover, in an embodiment, the controller <NUM> may define the minimum pitch rate threshold by generating a plot, table, graph, table, or the like in which pitch rate values correspond with speed parameters.

Further, as shown at (<NUM>), the method <NUM> includes receiving, via the controller <NUM>, a first speed parameter of the wind turbine <NUM>. For example, in an embodiment, as mentioned, the first speed parameter of the wind turbine <NUM> may include rotor speed, generator speed, or any other suitable speed parameter of the wind turbine <NUM>. Thus, such speed parameters may be determined or calculated by the controller <NUM> or may be measured via one of the sensors described herein.

Accordingly, referring still to <FIG>, as shown at (<NUM>), the method <NUM> includes comparing, via the controller <NUM>, the collective pitch rate (e.g. from the collective pitch rate module <NUM>) to the minimum pitch rate threshold for the first speed parameter. In certain embodiments, as shown in <FIG>, the controller <NUM> may include a threshold comparison module <NUM> for comparing the collective pitch rate to the minimum pitch rate threshold for the first speed parameter. More particularly, as shown in the illustrated embodiment, the threshold comparison module <NUM> may receive the collective pitch rate, a look-up table (e.g. the minimum pitch rate table <NUM>) and the rotor speed and may generate an output <NUM>.

Referring back to <FIG>, as shown at (<NUM>), the method <NUM> includes controlling, via the controller <NUM>, the wind turbine <NUM> based on the comparison (e.g. the output <NUM>). For example, in an embodiment, as shown in <FIG>, the controller <NUM> is configured to implement a control action. In particular, in an embodiment, if the speed parameter is below a speed threshold for a certain time period (e.g. as determined via counter <NUM>), the controller <NUM> may pitch the plurality of pitch control mechanisms <NUM> at a constrained pitch rate. Alternatively, if the speed parameter is above the speed threshold for a certain time period, the controller <NUM> may implement a control action to protect the wind turbine <NUM> from overloading. In such embodiments, for example, the control action may include shutting down the wind turbine <NUM>, pitching the plurality of pitch control mechanisms at a maximum pitch rate, derating the wind turbine <NUM>, or any other suitable corrective actions.

According to an advantageous embodiment, the of controlling the wind turbine is based on the comparison comprising pitching the plurality of pitch control mechanisms at a constrained pitch rate if the speed parameter is below a speed threshold for a certain time period and implementing a control action if the speed parameter is above the speed threshold for a certain time period.

According to an advantageous embodiment, the control action comprises at least one of shutting down the wind turbine, pitching the plurality of pitch control mechanisms at a maximum pitch rate, or derating the wind turbine.

According to an advantageous embodiment the controller comprises at least one of a turbine controller or a separate controller module communicatively coupled to the turbine controller.

According to an advantageous embodiment, the wind turbine is controlled based on the comparison comprising pitching the plurality of pitch control mechanisms at a constrained pitch rate if the speed parameter is below a speed threshold for a certain time period and implementing a control action if the speed parameter is above the speed threshold for a certain time period, the control action further comprising at least one of shutting down the wind turbine, pitching the plurality of pitch control mechanisms at a maximum pitch rate, or derating the wind turbine.

Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, as well as other known equivalents for each such methods and feature, can be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

Claim 1:
A method (<NUM>) for protecting a wind turbine (<NUM>) from overloading during operation caused by a fault, the method comprising:
receiving (<NUM>), via a controller (<NUM>), a plurality of pitch signals from a plurality of pitch control mechanisms of a pitch system of the wind turbine (<NUM>), the pitch system configured to rotate a plurality of rotor blades (<NUM>) mounted to a rotatable hub (<NUM>) of a rotor (<NUM>) of the wind turbine (<NUM>) about respective pitch axes;
determining (<NUM>), via the controller (<NUM>), a collective pitch rate of the pitch system as a function of the plurality of pitch signals;
defining (<NUM>), via the controller (<NUM>), a minimum pitch rate threshold that varies with a speed parameter of the wind turbine (<NUM>);
receiving (<NUM>), via the controller (<NUM>), a first speed parameter of the wind turbine (<NUM>);
comparing (<NUM>), via the controller (<NUM>), the collective pitch rate to the minimum pitch rate threshold for the first speed parameter; and,
controlling (<NUM>), via the controller (<NUM>), the wind turbine (<NUM>) based on the comparison.