Patent Application
20170058871
The present subject matter relates generally to wind turbines and, more particularly, to a system and method for mitigating ice throw from a wind turbine rotor blade.
Generally, a wind turbine includes a tower, a nacelle mounted on the tower, and a rotor coupled to the nacelle. The rotor typically includes a rotatable hub and a plurality of rotor blades coupled to and extending outwardly from the hub. Each rotor blade may be spaced about the hub so as to facilitate rotating the rotor to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy.
Under some atmospheric conditions, ice may be buildup or otherwise accumulate on the rotor blades of a wind turbine. As the ice layer accumulating on a rotor blade becomes increasingly thicker, the aerodynamic surface of the blade is modified, thereby resulting in diminished aerodynamic performance. Moreover, ice accumulation significantly increases the weight of a rotor blade, which can lead to structural damage as an increased amount of bending moments and/or other rotational forces act on the rotor blade. Further, when there is a difference in the amount of ice accumulating on each of the rotor blades, a mass imbalance may occur that can cause significant damage to a wind turbine.
In addition, ice accumulation may be shed or throw from the turbine due to both gravity and/or mechanical forces of the rotating blades. For example, an increase in ambient temperature, wind, and/or solar radiation may cause sheets or fragments of ice to loosen and fall, making the area directly under the rotor subject to the greatest risks. Further, rotating turbine blades may throw or propel ice fragments some distance from the turbine, e.g. up to several hundred meters if conditions are right. Falling ice may cause damage to neighboring structures and/or vehicles, as well as injury to site personnel and/or the general public, unless adequate measures are put in place for protection.
Due to the disadvantages associated with ice accumulation, a wind turbine may be shutdown when it is believed that ice has accumulated on the surface of one or more of the rotor blades. Operation of the wind turbine may then be restarted after it can be verified that ice is no longer present on the rotor blades. Accordingly, upon shutdown of a wind turbine for ice accumulation, each rotor blade is typically inspected to determine whether ice is actually and/or is still present on the blades. Shutting down the wind turbine, however, is not desirable as this impacts power production.
Accordingly, a system and method that mitigates ice throw from the rotor blades of the wind turbine so as to address the aforementioned issues would be welcomed in the technology.
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.
In one aspect, the present disclosure is directed to a method for mitigating ice throw from one or more rotor blades of a wind turbine during operation. The method includes determining one or more ice-related parameters of the wind turbine. Thus, the ice-related parameters are indicative of ice accumulation on one or more of the rotor blades. In response to detecting ice accumulation, the method also includes implementing an ice protection control strategy. More specifically, the ice protection control strategy includes determining a yaw position of the wind turbine and determining at least one of a power set point or a speed set point for the wind turbine based on the yaw position.
In one embodiment, the step of determining at least one of the power set point or the speed set point for the wind turbine based on the yaw position may further include: determining at least one sector for the yaw position, determining if the sector corresponds to one or more predetermined risk sectors, and reducing at least one of the power set point or the speed set point of the wind turbine if the sector corresponds to one of the predetermined risk sectors. In another embodiment, the method may also include maintaining the power set point and the speed set point of the wind turbine, reducing at least one of the power set point or the speed set point of the wind turbine, or increasing the power set point and the speed set point of the wind turbine so as to maximize power production.
In certain embodiments, the step of determining one or more ice-related parameters of the wind turbine may include monitoring one or more ice-related parameters via one or more sensors. More specifically, the one or more sensors may include at least one of accelerometers, internal icing sensors, external icing sensors, vibration sensors, or similar. Alternatively, the step of determining one or more ice-related parameters of the wind turbine may further include calculating one or more ice-related parameters via at least one control algorithm.
In additional embodiments, the ice-related parameters of the wind turbine may include any one of or a combination of ambient conditions, a date, a time, a pitch angle of the one or more rotor blades, a tip-speed-ratio (TSR), a power output, a stall line, torque, thrust, a power coefficient, or similar. For example, in certain embodiments, the ambient conditions near the wind turbine may include one or more of an ambient temperature, a component temperature, pressure, air density, wind speed, humidity, or similar.
In further embodiments, the method may also include starting the ice protection control strategy when the ambient temperature is below a predetermined temperature set point and stopping the ice protection control strategy when the ambient temperature is above the predetermined temperature set point, e.g. for a predetermined time period.
In yet another embodiment, the method may also include initially operating the wind turbine at an initial speed set point that corresponds to an optimal tip-speed-ratio value, an optimal pitch angle curve versus tip-speed-ratio (TSR), and an optimal stall margin. Thus, in response to detecting ice accumulation, the method may include replacing the optimal pitch angle curve versus TSR with an equivalent pitch angle curve representing the iced rotor blade. In addition, the method may also include updating the optimal stall margin based on the equivalent pitch angle curve.
In further embodiments, the method may include initially operating the wind turbine at an initial speed set point with a corresponding minimum pitch setting and, in response to detecting ice accumulation, providing a pitch offset to the minimum pitch setting. In yet another embodiment, the method may include initially operating the wind turbine at a torque-speed curve and, in response to detecting ice accumulation, modifying a torque constant of the torque-speed curve.
In a further embodiment, the method may also include manually implementing the ice protection control strategy via a network. Alternatively, the method may include automatically implementing the ice protection control strategy.
In another aspect, the present disclosure is directed to a method for mitigating ice throw from one or more rotor blades of a wind turbine. The method includes operating the wind turbine at an initial speed set point that corresponds to an optimal tip-speed-ratio value, an optimal pitch angle versus tip-speed-ratio (TSR) curve, and an optimal stall margin. In response to detecting ice accumulation on the rotor blade, the method also includes implementing an ice protection control strategy. More specifically, the ice protection control strategy includes determining a yaw position of a rotor of the wind turbine, determining an updated speed set point for the wind turbine based on the yaw position, replacing the optimal pitch angle versus TSR curve with an equivalent pitch angle curve representing the iced rotor blade, and updating the optimal stall margin based on the equivalent pitch angle curve.
In yet another aspect, the present disclosure is directed to a system for mitigating ice throw from one or more rotor blades of a wind turbine. The system includes one or more sensors configured to monitor one or more ice-related parameters of the wind turbine and a controller communicatively coupled to the one or more sensors. The ice-related parameters are indicative of ice accumulation on one or more rotor blades of the wind turbine. Thus, the controller is configured to perform one or more operations, including but not limited to implementing an ice protection control strategy in response to detecting ice accumulation. More specifically, the ice protection strategy includes determining a yaw position of the wind turbine and determining at least one of a power set point or a speed set point for the wind turbine based on the yaw position. It should be understood that the system may be further configured to include any of the additional features and/or to implement any of the method steps as described herein.
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.
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:
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.
Generally, the present disclosure is directed to a system and method for mitigating ice throw from a rotor blade of a wind turbine during operation. Specifically, the present disclosure provides a controller configured to implement an ice protection control strategy or algorithm that measures ambient conditions and the yaw position of the turbine. The algorithm also creates sectors during which the rotor speed and/or the power output of the turbine can be reduced if, under icing conditions, the rotor speed needs to be reduced (i.e. ice accumulation is present and the yaw position poses a risk or danger to neighboring areas). For example, the sectors may be configured such that a band of impacted operation regions are created. Accordingly, if the yaw position falls within one or more impacted sectors under icing conditions (and/or during specific days and/or hours), the rotor speed and/or power output can be reduced to eliminate the possibility of ice throw in a certain direction.
The present disclosure may be implemented locally on a turbine controller, or, as an alternative, on a remote system, e.g. a farm level controller or a dedicated remote computer. In such an embodiment, the ice protection control strategy may reside remotely and/or sensors may be mounted locally on the wind turbine. Thus, the sensors and/or the remote controller can be connected through a network.
The present disclosure provides many advantages not present in the prior art. For example, the present disclosure addresses safety concerns for neighboring people and/or property of the wind turbine and minimizes turbine output reduction. Thus, the ice protection control strategy of the present disclosure permits extended operation of the turbine thereby avoiding unavailability and lost production under icing conditions.
Referring now to the drawings,
The wind turbine 10 may also include a turbine control system or turbine controller 26 centralized within the nacelle 16. In addition, the turbine controller 26 may be connected to a farm level controller (not shown) via a network. In general, the turbine controller 26 (and/or the farm controller) may include a computer or other suitable processing unit. Thus, in several embodiments, the controller 26 may include suitable computer-readable instructions that, when implemented, configure the controller 26 to perform various different functions, such as receiving, transmitting and/or executing wind turbine control signals. As such, the turbine controller 26 may generally be configured to control the various operating modes (e.g., start-up or shut-down sequences) and/or components of the wind turbine 10. For example, the controller 26 may be configured to adjust the blade pitch or pitch angle of each rotor blade 22 (i.e., an angle that determines a perspective of the blade 22 with respect to the direction of the wind) about its pitch axis 28 in order to control the rotational speed of the rotor blade 22 and/or the power output generated by the wind turbine 10. For instance, the turbine controller 26 may control the pitch angle of the rotor blades 22, either individually or simultaneously, by transmitting suitable control signals to one or more pitch drives or pitch adjustment mechanisms 30 (
Referring now to
Additionally, the turbine controller 26 may also be located within the nacelle 16. As is generally understood, the turbine controller 26 may be communicatively coupled to any number of the components of the wind turbine 10 in order to control operation of such components. For example, as indicated above, the turbine controller 26 may be communicatively coupled to each pitch adjustment mechanism 30 of the wind turbine 10 (one of which is shown) to facilitate rotation of each rotor blade 22 about its pitch axis 28. Similarly, the turbine controller 26 may be communicatively coupled to each yaw drive mechanism 62 of the wind turbine 10 to facilitate rotation of the nacelle 16 about its yaw axis 25 (
In general, each pitch adjustment mechanism 30 may include any suitable components and may have any suitable configuration that allows the pitch adjustment mechanism 30 to function as described herein. For example, in several embodiments, each pitch adjustment mechanism 30 may include a pitch drive motor 38 (e.g., any suitable electric motor), a pitch drive gearbox 40, and a pitch drive pinion 42. In such embodiments, the pitch drive motor 38 may be coupled to the pitch drive gearbox 40 so that the pitch drive motor 38 imparts mechanical force to the pitch drive gearbox 40. Similarly, the pitch drive gearbox 40 may be coupled to the pitch drive pinion 42 for rotation therewith. The pitch drive pinion 42 may, in turn, be in rotational engagement with a pitch bearing 44 coupled between the hub 20 and a corresponding rotor blade 22 such that rotation of the pitch drive pinion 42 causes rotation of the pitch bearing 44. Thus, in such embodiments, rotation of the pitch drive motor 38 drives the pitch drive gearbox 40 and the pitch drive pinion 42, thereby rotating the pitch bearing 44 and the rotor blade 22 about the pitch axis 28.
In alternative embodiments, it should be appreciated that each pitch adjustment mechanism 30 may have any other suitable configuration that facilitates rotation of a rotor blade 22 about its pitch axis 28. For instance, pitch adjustment mechanisms are known that include a hydraulic or pneumatic driven device (e.g., a hydraulic or pneumatic cylinder) configured to transmit rotational energy to the pitch bearing 44, thereby causing the rotor blade 22 to rotate about its pitch axis 28. Thus, in several embodiments, instead of the electric pitch drive motor 38 described above, each pitch adjustment mechanism 30 may include a hydraulic or pneumatic driven device that utilizes fluid pressure to apply torque to the pitch bearing 44.
In additional embodiments, as mentioned, the wind turbine 10 may also include one or more yaw drive mechanisms 62 configured to rotate the nacelle 16 relative to the wind, e.g. about yaw axis 25. For example, the wind turbine 10 may include a yaw bearing 64 configured between the tower 12 and the nacelle 16 that is operatively coupled to one or more yaw drive mechanisms 62. Thus, the yaw drive mechanisms 62 are configured to rotate the yaw bearing 64 so as to rotate the nacelle 16 about the yaw axis 25.
Referring still to
Thus, in several embodiments of the present disclosure, the wind turbine 10 may include one or more sensors 45, 46, 47, 48, 49 configured to monitor one or more ice-related parameters of the wind turbine 10. Specifically, in several embodiments, the wind turbine 10 may include one or more sensors 46 configured to transmit signals to the turbine controller 26 relating directly to the amount of torque generated by each pitch adjustment mechanism 30. For example, the sensor(s) 46 may include one or more torque sensors coupled to a portion of the pitch drive motor 38, the pitch gearbox 40, and/or the pitch drive pinion 42 in order to monitor the torque generated by each pitch adjustment mechanism 30. Alternatively, the sensor(s) 46 may include one or more suitable sensors configured to transmit signals to the turbine controller 26 relating indirectly to the amount of torque generated by each pitch adjustment mechanism 30. For instance, in embodiments in which the pitch drive mechanism 30 is electrically driven, the sensor(s) 46 may include one or more current sensors configured to detect the electrical current supplied to the pitch drive motor 38 of each pitch adjustment mechanism 30. Similarly, in embodiments in which the pitch adjustment mechanism 30 is hydraulically or pneumatically driven, the sensor(s) 46 may include one or more suitable pressure sensors configured to detect the pressure of the fluid within the hydraulically or pneumatically driven device. In such embodiments, the turbine controller 26 may generally include suitable computer-readable instructions (e.g., in the form of suitable equations, transfer functions, models and/or the like) that, when implemented, configure the controller 26 to correlate the current input or the pressure input to the torque generated by each pitch adjustment mechanism 30.
In addition to the sensor(s) 46 described above or as an alternative thereto, the wind turbine 10 may also include one or more sensors 48 configured to monitor the torque required to pitch each rotor blade 22 by monitoring the force(s) present at the pitch bearing 44 (e.g., the force(s) present at the interface between the pitch drive pinion 42 and the pitch bearing 44). For example, the sensor(s) 48 may include one or more pressure sensors and/or any other suitable sensors configured to transmit signals relating to the forces present at the pitch bearing 44. In such an embodiment, similar to that described above, the turbine controller 26 may generally include suitable computer-readable instructions (e.g., in the form of suitable equations, transfer functions, models and the like) that, when implemented, configure the controller 26 to correlate the force(s) present at the pitch bearing 44 to the torque required to pitch each rotor blade 22.
It should be appreciated that the wind turbine 10 may also include various other sensors 45, 47, 49 for monitoring any other suitable parameters and/or conditions of the wind turbine 10. For example, the wind turbine 10 may include sensors for monitoring the pitch angle of each rotor blade 22, bending moments on the rotor blades 22, the speed of the rotor and/or the rotor shaft 32, the speed of the generator 24 and/or the generator shaft 34 (e.g. via sensor 49), the torque on the rotor shaft 32 (e.g. via sensor 47) and/or the generator shaft 34, the wind speed, wind direction or any other ambient conditions (e.g. via sensor 45) and/or any other suitable parameters and/or conditions.
Referring now to
Additionally, the controller 26 may also include a communications module 54 to facilitate communications between the controller 26 and the various components of the wind turbine 10. For instance, the communications module 54 may serve as an interface to permit the controller 26 to transmit control signals to each pitch adjustment mechanism 30 for controlling the pitch angle of the rotor blades 22. Moreover, the communications module 54 may include a sensor interface 56 (e.g., one or more analog-to-digital converters) to permit signals transmitted from the sensors 45, 46, 47, 48, 49 of the wind turbine 10 to be converted into signals that can be understood and processed by the processors 50. In addition, as shown, the controller 26 may be communicatively coupled to a user interface 60 via a network 58 such that a user can implement certain functions to the controller 26, e.g. override one or more functions of the controller 26. For example, in certain embodiments, a user may override operational settings of the wind turbine 10 via the user interface so as to implement the ice protection control strategy as described herein. Alternatively, the controller 26 may be configured to automatically implement the ice protection control strategy as described herein. For example, the turbine controller 26 may be provided with suitable computer-readable instructions that, when implemented, configure the controller 26 to transmit control signals to various components of the wind turbine 10 in order to mitigate ice throw by one or more of the rotor blades 16. In addition, the controller 26 may be connected to the farm controller via the network 58 such that the farm controller can provide commands to the individual wind turbines.
It should be appreciated that the sensors 45, 46, 47, 48, 49 may be communicatively coupled to the communications module 54 using any suitable means. For example, as shown in
Referring now to
In addition, the ice-related parameters of the wind turbine 10 may include any one of or a combination of ambient conditions, a day/time, a pitch angle of the one or more rotor blades, a tip-speed-ratio (TSR), a power output, a stall line, torque, thrust, a power coefficient, or similar, as well as additional parameters and/or conditions as described herein. More specifically, in certain embodiments, the ambient conditions may include one or more of an ambient temperature, a component temperature, pressure, humidity, wind speed, air density, or similar.
In certain embodiments, the ice-related parameter may correspond to the amount of torque required to pitch each rotor blade 22 across the range of pitch angles. Specifically, as indicated above, ice accumulation on a rotor blade 22 may increase the blade weight and may also alter its mass distribution. Thus, the torque required to pitch a rotor blade 22 having no ice accumulation may generally vary from the torque required to pitch the same rotor blade 22 having ice accumulated thereon.
For example, as indicated above, the torque required to pitch each rotor blade 22 may be monitored using one or more suitable sensors 45, 46, 47, 48, 49. For example, the torque generated by each pitch adjustment mechanism 30 may be monitored directly using suitable torque sensors or indirectly using various other suitable sensors (e.g., current sensors and/or pressure sensors configured monitor the current input and/or pressure input to the pitch adjustment mechanism 30). Alternatively, the torque required to pitch each rotor blade may be monitored by monitoring the force present at the pitch bearing 44 of the wind turbine 10.
In other embodiments, the ice-related parameter may correspond to the amount of time required to pitch each rotor blade 22, e.g. across the range of pitch angles. For example, in one embodiment, each pitch adjustment mechanism 30 may be configured to pitch each rotor blade 22 with a constant torque. As such, due to the increase in weight and/or the varied mass distribution caused by ice accumulation, the time required to pitch each rotor blade 22 may vary depending on the presence of ice. In such embodiments, the turbine controller 26 may generally be configured to monitor the time required to pitch each rotor blade 22. For example, the controller 26 may be provided with suitable computer readable instructions and/or suitable digital hardware (e.g., a digital counter) that configures the controller 26 to monitor the amount of time elapsed while each blade 22 is pitched across the range of pitch angles.
In even further embodiments, it should be appreciated that the ice-related parameter(s) may correspond to any other suitable parameter and/or condition of the wind turbine 10 that provides an indication of the presence of ice on a rotor blade 22. For example, the ice-related parameter may correspond to bending moments and/or other stresses acting on the rotor blade 22, as such bending moments and/or other stresses may generally vary due to the increased weight caused by ice accumulations. In such an embodiment, one or more strain gauges and/or other suitable sensors may be installed within the rotor blade 22 to permit such bending moments and/or other stresses to be monitored.
Referring still to
It should be appreciated that the baseline profile for a particular ice-related parameter may generally vary from wind turbine 10 to wind turbine 10 and/or from rotor blade 22 to rotor blade 22. Thus, in several embodiments, individual baseline profiles for the ice-related parameter being monitored may be determined for each rotor blade 22. In general, the baseline profiles for the rotor blades 22 may be determined using any suitable means and/or method known in the art. For instance, in one embodiment, the baseline profile of each rotor blade 22 may be determined experimentally, such as by individually pitching each rotor blade 22 when it is known that no ice is present on the blade 22 and monitoring the ice-related parameter of the blade 22 to establish the baseline profile. In another embodiment, the baseline profile for each rotor blade 22 may be modeled or determined mathematically, such as by calculating the baseline profiles based on, for example, the configuration of each rotor blade 22, the specifications of each pitch adjustment mechanism 30 and/or the anticipated variation in the ice-related parameter due to the presence of ice.
It should also be appreciated that, in several embodiments, the baseline profile established for a particular rotor blade 22 may be continuously updated. Specifically, due to wear and tear on wind turbine components and other factors, the baseline profile for a rotor blade 22 may vary over time. For example, wear and tear on one of the pitch bearings 44 may significantly affect the baseline profile for the corresponding rotor blade 22. Thus, in several embodiments, the turbine controller 26 may be configured to continuously adjust the baseline profile for each rotor blade 22 based on calculated and/or anticipated turbine component wear and/or on any other factors that may cause the baseline profile to vary over time.
Referring still to
Referring now to
During operation, the wind turbine 10 may be initially operated at an initial speed set point that corresponds, e.g. to an optimal tip-speed-ratio value, an optimal pitch angle curve, a minimum pitch setting, a torque-speed curve, and/or an optimal stall margin. When there is ice accumulation, the aerodynamic characteristics of the blade 16 may change. In particular, the stall line (minimum pitch vs. TSR) may change, the optimal pitch (vs. TSR) may change, and the thrust, torque, and power coefficient surfaces, as well as their partial derivative surfaces, may change. Thus, in certain embodiments, in response to detecting ice accumulation, the controller 26 may be configured to reduce the speed set point of the turbine 10, replace the normal pitch angle curve with an equivalent pitch angle curve representing the iced rotor blade 16, and/or update the optimal stall margin based on the equivalent pitch angle curve. In addition, the controller 26 may be configured to provide a pitch offset to the minimum pitch setting. In another embodiment, the controller 26 may also be configured to modify a torque constant of the torque-speed curve.
In additional embodiments, the controller 26 may also be configured to replace the optimal pitch curve by an equivalent curve describing the line corresponding iced blade. In further embodiments, the controller 26 may be configured to apply a worst case stall margin oven the non-iced minimum pitch curve instead of utilizing a completely new curve. In still another embodiment, the controller 26 may be configured to replace the aerodynamic maps affecting the turbine operation, i.e., thrust, torque and partial derivatives as well as the power coefficient map. Thus, the disclosed method 100 provides a simple and accurate method for mitigating ice throw of the wind turbine 10 while also maximizing power production.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
