System and method for reducing loads during an idling or parked state of a wind turbine with a stuck rotor blade

A method for reducing loads of a wind turbine includes determining an angular pitch speed parameter of the rotor blade of the wind turbine. The method also includes determining an operational state of the wind turbine. Further, the method includes comparing the angular pitch speed parameter to a predetermined parameter threshold during turbine shutdown and/or a commanded pitch event. If the operational state corresponds to a predetermined operational state, the method includes yawing a nacelle of the wind turbine away from an incoming wind direction when the angular pitch speed parameter is below the predetermined parameter threshold during the turbine shutdown and/or the commanded pitch event.

FIELD

The present disclosure relates generally to wind turbines, and more particularly to systems and methods for reducing loads during an idling or parked state of a wind turbine with a stuck rotor blade by yawing the wind turbine out of the wind.

BACKGROUND

During operation, the direction of the wind which powers the wind turbine may change. The wind turbine may thus adjust the nacelle through, for example, a yaw adjustment about a longitudinal axis of the tower to maintain alignment with the wind direction. In addition, when the wind turbine is parked or idling, conventional control strategies include actively tracking the wind direction to provide better alignment to the wind direction so as to minimize start-up delays when the wind speed increases or decreases back into the operating range.

However, in a situation where the wind turbine is faulted and one of the rotor blades remains stuck (unlike the normal idling situation), there are limited benefits to tracking the wind as repair is needed before restarting the wind turbine. In addition, in such situations, the wind turbine experiences increased loads due to the stuck rotor blade as well as rotor imbalance.

Accordingly, improved systems and methods for reducing loads during an idling or parked state of a wind turbine would be desired. In particular, the present disclosure is directed to systems and methods which actively yaw the nacelle of the wind turbine out of the wind when the wind turbine is idling or parked and one of the rotor blades is stuck so as to reduce loads during this scenario.

BRIEF DESCRIPTION

In one aspect, the present disclosure is directed to a computer method for reducing loads of a wind turbine. The method includes determining an angular pitch speed parameter of the rotor blade of the wind turbine. The method also includes determining an operational state of the wind turbine. Further, the method includes comparing the angular pitch speed parameter to a predetermined parameter threshold during turbine shutdown and/or a commanded pitch event. If the operational state corresponds to a predetermined operational state, the method includes yawing a nacelle of the wind turbine away from an incoming wind direction when the angular pitch speed parameter is below the predetermined parameter threshold during the turbine shutdown and/or the commanded pitch event.

In one embodiment, the angular pitch speed parameter may be an angular pitch speed or derivatives thereof (such as acceleration). As such, in particular embodiments, the step of determining the angular pitch speed parameter of the rotor blade of the wind turbine may include monitoring sensor signals generated by at least one sensor associated with the rotor blade and determining the angular pitch speed parameter based on the sensor signals. For example, in one embodiment, the sensor may include an encoder, an accelerometer, an inclination sensor, a gyroscopic sensor, a resolver, a tachometer, an optical sensor, a photo sensor, a proximity sensor, a generator, a laser sensor, or any other suitable speed measuring sensor.

In such embodiments, where encoders are used, the step of determining the angular pitch speed parameter of the rotor blade of the wind turbine may include incrementally counting monitored pulses generated by the encoder and determining the angular pitch speed as a function of the counted pulses. In further embodiments, the method can easily include determining a derivative of angular pitch speed, for example, where accelerometers are used. It should be understood that any other angular speed measuring device may also be used to determine the angular pitch speed parameter.

In further embodiments, the step of comparing the angular pitch speed parameter to the predetermined parameter threshold may include comparing the counted pulses to a predetermined pulse threshold. As such, the predetermined pulse threshold represents a minimum amount of counted pulses needed for the rotor blade to be considered rotating.

In several embodiments, the predetermined operational state of the wind turbine comprises at least one of an idling state, a parked state, or a maintenance state.

In additional embodiments, the method may include continuously monitoring the incoming wind direction and yawing the nacelle into the incoming wind direction if the angular pitch speed parameter is above the predetermined parameter threshold.

In particular embodiments, the method may further include monitoring a wind speed at the wind turbine and actively yawing the nacelle of the wind turbine away from the incoming wind direction only if the wind speed exceeds a set wind speed threshold.

In yet another embodiment, the method may include automatically yawing the nacelle of the wind turbine away from the incoming wind direction. In alternative embodiments, the method may include manually yawing the nacelle of the wind turbine away from the incoming wind direction. In such embodiments, when operating in a manual mode, the method may include continuously yawing the nacelle of the wind turbine away from the incoming wind direction.

In another aspect, the present disclosure is directed to a system for reducing loads of a wind turbine. The system includes at least one sensor configured for monitoring a rotor blade of the wind turbine and a controller communicatively coupled to the sensor(s). The controller includes at least one processor configured to perform one or more operations, including but not limited to receiving sensor signals from the sensor(s), determining the angular pitch speed parameter of the rotor blade based on the sensor signals during a turbine shutdown and/or a commanded pitch event, determining an operational state of the wind turbine, comparing the angular pitch speed parameter to a predetermined parameter threshold, and if the operational state corresponds to a predetermined operational state, yawing a nacelle of the wind turbine away from an incoming wind direction for as long as the angular pitch speed parameter is below the predetermined parameter threshold during the turbine shutdown and/or the commanded pitch event. It should also be understood that the system may further include any of the additional features as described herein.

In yet another aspect, the present disclosure is directed to a method for reducing loads of a wind turbine. The method includes monitoring, via an encoder (or any other suitable angular speed sensor), pulse or other speed signals of the rotor blade of the wind turbine. The method also includes determining a pitch angular speed as a function of the pulse signals. Further, the method includes comparing the pitch angular speed to a predetermined speed threshold. If the pitch angular speed is below the predetermined speed threshold, the method includes yawing a nacelle of the wind turbine away from an incoming wind direction. It should also be understood that the method may further include any of the additional features and/or steps as described herein.

DETAILED DESCRIPTION

Referring now toFIG. 2, a simplified, internal view of one embodiment of the nacelle16of the wind turbine10is illustrated. As shown, a generator24may be disposed within the nacelle16. In general, the generator24may be coupled to the rotor18of the wind turbine10for generating electrical power from the rotational energy generated by the rotor18. For example, the rotor18may include a main shaft40coupled to the hub20for rotation therewith. The generator24may then be coupled to the main shaft40such that rotation of the main shaft40drives the generator24. For instance, in the illustrated embodiment, the generator24includes a generator shaft42rotatably coupled to the main shaft40through a gearbox44. However, in other embodiments, it should be appreciated that the generator shaft42may be rotatably coupled directly to the main shaft40. Alternatively, the generator24may be directly rotatably coupled to the main shaft40.

It should be appreciated that the main shaft40may generally be supported within the nacelle16by a support frame or bedplate46positioned atop the wind turbine tower12. For example, the main shaft40may be supported by the bedplate46via a pair of pillow blocks48,50mounted to the bedplate46.

As shown inFIGS. 1 and 2, the wind turbine10may also include a turbine control system or a turbine controller26within the nacelle16. For example, as shown inFIG. 2, the turbine controller26is disposed within a control cabinet52mounted to a portion of the nacelle16. However, it should be appreciated that the turbine controller26may be disposed at any location on or in the wind turbine10, at any location on the support surface14or generally at any other location. The turbine controller26may generally be configured to control the various operating modes (e.g., start-up or shut-down sequences) and/or components of the wind turbine10.

In addition, as shown inFIG. 2, one or more sensors57,58may be provided on the wind turbine10. More specifically, as shown, a blade sensor57may be configured with one or more of the rotor blades22to monitor the rotor blades22. It should also be appreciated that, as used herein, the term “monitor” and variations thereof indicates that the various sensors of the wind turbine10may 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 controller26to determine the condition.

Further, as shown, a wind sensor58may be provided on the wind turbine10. The wind sensor58, which may for example be a wind vane, and anemometer, and LIDAR sensor, or another suitable sensor, may measure wind speed and direction. As such, the sensors57,58may further be in communication with the controller26, and may provide related information to the controller26. For example, yawing of the wind turbine10may occur due to sensing of changes in the wind direction28, in order to maintain alignment of the wind turbine10with the wind direction28. In addition, yawing of the wind turbine10may occur due to sensing a stuck blade, which is described in more detail herein.

Further, the turbine controller26may also be communicatively coupled to various components of the wind turbine10for generally controlling the wind turbine10and/or such components. For example, the turbine controller26may be communicatively coupled to the yaw drive mechanism(s)38of the wind turbine10for controlling and/or altering the yaw direction of the nacelle16relative to the direction28(FIG. 1) of the wind. Further, as the direction28of the wind changes, the turbine controller26may be configured to control a yaw angle of the nacelle16about a yaw axis36to position the rotor blades22with respect to the direction28of the wind, thereby controlling the loads acting on the wind turbine10. For example, the turbine controller26may be configured to transmit control signals/commands to a yaw drive mechanism38(FIG. 2) of the wind turbine10, via a yaw controller or direct transmission, such that the nacelle16may be rotated about the yaw axis36via a yaw bearing56.

Still referring toFIG. 2, each rotor blade22may also include a pitch adjustment mechanism32configured to rotate each rotor blade22about its pitch axis34. Further, each pitch adjustment mechanism32may include a pitch drive motor33(e.g., any suitable electric, hydraulic, or pneumatic motor), a pitch drive gearbox35, and a pitch drive pinion37. In such embodiments, the pitch drive motor33may be coupled to the pitch drive gearbox35so that the pitch drive motor33imparts mechanical force to the pitch drive gearbox35. Similarly, the pitch drive gearbox35may be coupled to the pitch drive pinion37for rotation therewith. The pitch drive pinion37may, in turn, be in rotational engagement with a pitch bearing54coupled between the hub20and a corresponding rotor blade22such that rotation of the pitch drive pinion37causes rotation of the pitch bearing54. Thus, in such embodiments, rotation of the pitch drive motor33drives the pitch drive gearbox35and the pitch drive pinion37, thereby rotating the pitch bearing54and the rotor blade22about the pitch axis34.

As such, the turbine controller26may be communicatively coupled to each pitch adjustment mechanism32of the wind turbine10(one of which is shown) through a pitch controller30for controlling and/or altering the pitch angle of the rotor blades22(i.e., an angle that determines a perspective of the rotor blades22with respect to the direction28of the wind). For instance, the turbine controller26and/or the pitch controller30may be configured to transmit a control signal/command to each pitch adjustment mechanism32such that the pitch adjustment mechanism(s)32adjusts the pitch angle of the rotor blades22as described herein. The turbine controller26may control the pitch angle of the rotor blades22, either individually or simultaneously, by transmitting suitable control signals/commands to a pitch controller of the wind turbine10, which may be configured to control the operation of a plurality of pitch drives or pitch adjustment mechanisms32of the wind turbine, or by directly controlling the operation of the plurality of pitch drives or pitch adjustment mechanisms.

In addition, as shown, the pitch drive mechanism(s)32described herein may also include an encoder59communicatively coupled to the pitch controller30and/or the turbine controller26. In one embodiment, the encoder59may be an incremental encoder that provides encoder signals for input to the controllers26,30via one or more I/O interfaces (not shown). Accordingly, the pitch encoder59may be in communication with the turbine controller26to produce sensor signals representative of the angular pitch speed parameter of the rotor blade22, such as an angular pitch speed. Thus, the turbine controller26may be configured to determine an average encoder speed during certain time intervals.

Referring now toFIG. 3, there is illustrated a block diagram of one embodiment of suitable components that may be included within the controller26according to the present disclosure. As shown, the controller26may include one or more processor(s)60and associated memory device(s)62configured 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 controller26may also include a communications module64to facilitate communications between the controller26and the various components of the wind turbine10. Further, the communications module64may include a sensor interface66(e.g., one or more analog-to-digital converters) to permit signals transmitted from one or more sensors57,58,59to be converted into signals that can be understood and processed by the processors60. It should be appreciated that the sensors57,58,59may be communicatively coupled to the communications module64using any suitable means. For example, as shown inFIG. 3, the sensors57,58,59are coupled to the sensor interface66via a wired connection. However, in other embodiments, the sensors57,58,59may be coupled to the sensor interface66via a wireless connection, such as by using any suitable wireless communications protocol known in the art.

As discussed above, a wind turbine10, such as the nacelle16thereof, may rotate about the yaw axis36as required. In particular, rotation about the yaw axis36may occur due to changes in the wind direction28, such that the rotor18is aligned with the wind direction28. For example, when the wind turbine10is in an idling state, the controller26actively tracks the wind direction to provide better alignment to the wind and minimize start-up delays when the wind speed increases or decreases back into the operating range. However, in a situation where the wind turbine10is in an idling state, a parked state, or a maintenance state and one or more of the rotor blades22is prevented from rotating (i.e. stuck) (unlike the normal idling situation), there are limited benefits to tracking the wind because repair will be required before restarting the wind turbine10. Thus, in such situations, the turbine controller26is configured to implement a control strategy to reduce the drag force on the faulted rotor blade so as to reduce loads thereon and/or to prevent rotor imbalance.

More specifically, as shown inFIG. 4, a flow diagram of one embodiment of a method100for reducing loads of the wind turbine10in situations where the wind turbine10is in an idling state, a parked state, or a maintenance state and one or more of the rotor blades22is prevented from rotating (i.e. stuck). In general, the method100will be described herein with reference to the wind turbine10shown inFIGS. 1 and 2, as well as the various controller components shown inFIG. 3. However, it should be appreciated that the disclosed method100may be implemented with wind turbines having any other suitable configurations and/or within systems having any other suitable system configuration. In addition, althoughFIG. 4depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure.

As shown at102, the method100includes determining an angular pitch speed parameter of the rotor blade22of the wind turbine10. As used herein, the angular pitch speed parameter generally refers to the speed of rotor blade22in a rotating direction or derivatives thereof, such as acceleration. Thus, example angular pitch speed parameters can be measured through movement of the pitch drive motor33, the pitch drive gearbox35, the rotor blade22, the bearing, and/or any blade component that is moving because the rotor blade22is rotating. For example, as shown inFIG. 5, the controller26may be configured to monitor speed signals68generated by a sensor (such as the encoder59). In such embodiments, the controller26may also be configured to incrementally count the monitored pulses68generated by the encoder59and determine the angular pitch speed as a function of the counted pulses. In addition, it should be understood that additional speed signals and components thereof may also be monitored, including but not limited to pulses, sine waves, cosine waves, frequency, amplitude, etc. In further embodiments, the angular pitch speed parameter of the rotor blade22could also be measured using a proximity sensor, an optical sensor, a camera, an accelerometer, an inclination sensor, an gyroscopic sensor, a resolver, a tachometer, an optical sensor, a photo sensor, a proximity sensor, a generator, a laser sensor, or similar. More specifically, in certain embodiments, e.g. where accelerometers are used, the sensors may be used to determine a derivative of the angular pitch speed parameter rather than the speed itself.

Referring back toFIG. 4, as shown at104, the method100includes determining an operational state of the wind turbine10. In such embodiments, the operational state of the wind turbine10may be an idling state, a parked state, and/or a maintenance state or combinations thereof. As used herein, the “idling state” of the wind turbine10generally refers to the operational state where, due to lack of wind or some other operational conditions (e.g. faults), the rotatable hub20of the wind turbine10is allowed to rotate (i.e. idle) at low rotational speeds, e.g. around 0.2 rpm, rather than being stopped completely. In contrast, a “parked state” of the wind turbine10generally refers to the operational state where the rotatable hub20is stopped and prevented from rotating. In addition, a “maintenance state” of the wind turbine10generally refers to operational state where one or more of the rotor blades22is undergoing a maintenance procedure and the wind turbine10is shut down. Therefore, in certain embodiments, the maintenance state and the parked state may be synonymous.

Still referring toFIG. 4, as shown at106, the method100includes comparing the angular pitch speed parameter to a predetermined parameter threshold, such as a predetermined speed threshold, during a shutdown and/or a commanded pitch event. As used herein, a commanded pitch event generally refers to an instance where the rotor blade22is commanded to move. As such, during idling, the rotor blade22is not commanded to move. Therefore, the controller26can detect that the rotor blade22is stuck while the wind turbine10is shutting down (i.e. before idling) or purposely command the rotor blade22to move while in idle to check if the blade is stuck. In further embodiments, the controller26may be configured to compare the counted pulses measured by the encoder59to a predetermined pulse threshold. As such, the predetermined pulse threshold represents a minimum amount of counted pulses needed for the rotor blade22to be considered rotating (i.e. unstuck).

As shown at108, the controller26is configured to determine whether the angular pitch speed parameter (or counted pulses) is below the predetermined parameter threshold (or predetermined pulse threshold). If so, as shown inFIG. 5, the controller26may initiate a counter70for a certain time period, e.g. such as 24 hours. Once the counter70begins, the controller26(or personnel) can implement a pitch test72for the rotor blade22to check whether the blade is still stuck by determining if the angular pitch speed parameter has increased to the predetermined parameter threshold. If the rotor blade22passes the pitch test72, operation of the wind turbine10resumes normal operation as shown at76. If the time period expires and a successful pitch test has not occurred (i.e. the angular pitch speed parameter remains below the predetermined parameter threshold), as shown at110ofFIG. 4, the method100includes yawing the nacelle16of the wind turbine10away from the incoming wind direction28for as long as the angular pitch speed parameter is below the predetermined parameter threshold. More specifically, as shown at78ofFIG. 5, the controller26is configured to yaw the nacelle16. In addition, as shown at80, the controller26may subsequently repair the stuck rotor blade22.

In one embodiment, e.g. during the idling state, the controller26may be configured to automatically yaw the nacelle16away from the incoming wind direction. In alternative embodiments, e.g. during the maintenance state, a user can manually select to yaw the nacelle16away from the incoming wind direction. Accordingly, yawing the nacelle16out of the wind in these situations provides substantial loads reduction. After the stuck rotor blade22has been repaired, the controller26may also be configured to reset the counter and repeat the method100as desired.

In yet another embodiment, the controller26may also be configured to pitch the rotor blades22of the wind turbine10so as to reduce loads. It should be understood that such pitching may be implemented by the controller26in combination with yawing the nacelle16out of the wind or as a separate loads reduction action.

It should also be understood that if the wind turbine10continues to operate normally, the controller26is configured to continuously monitor the incoming wind direction28and yaw the nacelle16into the incoming wind direction28to provide improved alignment to the wind with minimal start-up delays when the wind speed increases or decreases back into the operating range.