Patent Publication Number: US-8120194-B2

Title: System, device, and method for wind turbine load reduction in a cold weather environment

Description:
BACKGROUND OF THE INVENTION 
     The subject matter described herein relates generally to operating a wind turbine and, more particularly, to reducing a structural load on a wind turbine in a cold weather environment. 
     A wind turbine site includes one or more wind turbines, which utilize wind energy to generate or produce electrical power. Known wind turbines include a control system for operating a wind turbine in a safe and efficient manner. Control parameters, such as operating threshold values, are used to define the behavior of the wind turbine. For example, a controller of a wind turbine may disable the wind turbine if the current wind speed exceeds a maximum wind speed threshold value. 
     Disabling a wind turbine eliminates all power production from the wind turbine until the wind turbine is reactivated. Efficient operation of a wind farm requires maximizing the amount of time wind turbines operate in safe conditions while avoiding operating wind turbines in potentially damaging conditions such as excessive wind speed, which may induce hazardous structural loads. However, due to variation in factors affecting structural loads (e.g., ambient air density) between warm operating environments and cold operating environments, defining a single operating threshold value that is appropriate for all operating conditions can be difficult. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a system for controlling an operation of a wind turbine is provided. The system includes a meteorological sensor and a wind turbine controller. The meteorological sensor is configured to transmit a meteorological condition signal indicating a meteorological condition. The wind turbine controller is configured to determine a calculated operating threshold value that is based at least in part on a continuous function and the meteorological condition. The wind turbine controller is also configured to control an operation of the wind turbine based at least in part on the calculated operating threshold value. 
     In another aspect, a device is provided for controlling an operation of a wind turbine. The device includes a memory area configured to store at least one meteorological parameter representing a meteorological condition. The device also includes a processor coupled to the memory area and programmed to calculate an operating threshold value at least in part by applying a continuous function to the meteorological parameter. The device further includes a wind turbine control interface configured to control an operation of a wind turbine based at least in part on the calculated operating threshold value. 
     In yet another aspect, a method for controlling a wind turbine is provided. The method includes receiving, from a first sensor, a meteorological condition signal indicating a meteorological condition. An operating threshold value is calculated by a processor, at least in part by applying a continuous function to the meteorological condition. An operating parameter is created based on a wind turbine condition indicated by a wind turbine condition signal received from a second sensor. The wind turbine condition is representative of a structural load on the wind turbine. An operation of the wind turbine is adjusted when the operating parameter exceeds the calculated operating threshold value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary wind turbine. 
         FIG. 2  is a block diagram showing an exemplary wind turbine controller. 
         FIG. 3  is a graph plotting exemplary continuous functions for determining a maximum operating wind speed based on an ambient air temperature. 
         FIG. 4  is a block diagram showing an exemplary system for operating one or more wind turbines, as shown in  FIG. 1 . 
         FIG. 5  is a flowchart of an exemplary method for controlling the wind turbine shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments described herein facilitate operating one or more wind turbines (e.g., in a wind turbine site) using an operating threshold value that varies continuously with a meteorological condition, such as air temperature, air pressure, and/or air density. An operating threshold value may include, without limitation, an operating wind speed threshold value (also known as a maximum operating wind speed). In one embodiment, a maximum operating wind speed is calculated by applying a continuous function to an ambient air temperature and/or an ambient air density. A wind turbine is disabled when a current wind speed exceeds the calculated maximum operating wind speed. Such embodiments facilitate maximizing power production of a wind turbine while avoiding exposing the wind turbine to potentially damaging structural loads. 
     As described herein, a wind turbine may be controlled based on one or more operating parameters. An operating parameter indicates and/or represents a condition of a wind turbine. Wind turbine conditions include, without limitation, operational conditions (e.g., a rotor speed and/or a power output) and meteorological conditions. A meteorological condition may include, for example, an ambient air temperature, an ambient air density, a humidity level, an air pressure, a wind speed, and/or a wind direction. Some wind turbine conditions may indicate and/or represent, directly or indirectly, a structural load on a wind turbine. For example, a structural load may be indirectly represented by a wind speed, a rotor speed, and/or a power output, though the use of any wind turbine condition representing an environmental element and/or a structural load is contemplated. 
     Wind turbine conditions may be encoded in or otherwise conveyed by electronic signals. In some embodiments, a sensor transmits a signal that conveys a wind turbine condition. A device receiving the signal from the sensor may be configured to derive or extract the wind turbine condition from the signal. 
     In some embodiments, a control parameter, such as an operating threshold value, is used to control a wind turbine. An operating threshold value may include, without limitation, a maximum operating wind speed or a maximum rotor speed. For example, if a maximum operating wind speed is defined, the current wind speed may be continuously or periodically monitored. If the current wind speed exceeds the maximum operating wind speed, the wind turbine is disabled to prevent or limit damage to the wind turbine. 
     An exemplary technical effect of the methods, system, and apparatus described herein includes at least one of: (a) receiving, from a first sensor, a meteorological condition signal indicating a meteorological condition; (b) calculating, by a processor, an operating threshold value at least in part by applying a continuous function to the meteorological condition; (c) creating an operating parameter based on a wind turbine condition that is indicated by a wind turbine condition signal received from a second sensor and representative of a structural load on the wind turbine; and, (d) adjusting an operation of the wind turbine when the operating parameter exceeds the calculated operating threshold value. 
       FIG. 1  is a perspective view of an exemplary wind turbine  100 . Wind turbine  100  includes a nacelle  102  that houses a generator (not shown in  FIG. 1 ). Nacelle  102  is mounted on a tower  104  (only a portion of tower  104  is shown in  FIG. 1 ). Tower  104  may have any suitable height that facilitates operation of wind turbine  100  as described herein. In the exemplary embodiment, wind turbine  100  also includes a rotor  106  that includes three rotor blades  108  coupled to a rotating hub  110 . Alternatively, wind turbine  100  may include any number of rotor blades  108  that enables operation of wind turbine  100  as described herein. In the exemplary embodiment, wind turbine  100  includes a gearbox (not shown) that is rotatably coupled to rotor  106  and to the generator. Wind turbine  100  may include one or more control devices  120  and/or sensors  125  (shown in  FIG. 2 ). 
       FIG. 2  is a block diagram showing an exemplary wind turbine controller  205  for controlling operation of wind turbine  100  (shown in  FIG. 1 ). Wind turbine controller  205  is positioned within wind turbine  100 . For example, wind turbine controller  205  may be positioned on or within nacelle  102  or on or within tower  104 . 
     Wind turbine controller  205  includes a memory area  210  configured to store executable instructions and/or one or more meteorological parameters representing and/or indicating a meteorological condition. Meteorological parameters may represent and/or indicate, without limitation, an ambient air temperature, an ambient air density, a humidity level, an air pressure, a wind speed, and/or a wind direction. Memory area  210  may be further configured to store a continuous function defining an operating threshold value based on one or more meteorological conditions, optionally in the form of one or more executable instructions. 
     Wind turbine controller  205  also includes a processor  215  coupled to memory area  210  and programmed to calculate an operating threshold value at least in part by applying a continuous function to the one or more meteorological parameters. For example, processor  215  may be programmed to calculate an operating wind speed threshold value, which may also be referred to as a maximum operating wind speed. In one embodiment, processor  215  is programmed to calculate the operating wind speed threshold value at least in part by applying the continuous function to one or more operating parameters indicating an ambient air temperature and/or an ambient air density. In an alternative embodiment, instead of calculating the operating wind speed threshold value, wind turbine controller  205  is configured to receive the calculated operating wind speed threshold value from a remote device, as described below in reference to  FIG. 4 . 
       FIG. 3  is a graph  300  plotting exemplary continuous functions for determining a maximum operating wind speed v max  based on an ambient air temperature T. Graph  300  includes a first line  305  plotting v max  in relation to T according to Equation 1. Equation 1 is an exemplary continuous function for determining v max  (in meters per second, m/s) based on T (in degrees Celsius, ° C.). 
     
       
         
           
             
               
                 
                   
                     v 
                     max 
                   
                   = 
                   
                     max 
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                       ( 
                       
                         0 
                         , 
                         
                           min 
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                             ( 
                             
                               25 
                               , 
                               
                                 
                                   
                                     1 
                                     3 
                                   
                                   ⁢ 
                                   T 
                                 
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                                 30 
                               
                             
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                   ( 
                   
                     Eq 
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     Equation 1 limits v max  to a minimum of 0 m/s (lower bound) and a maximum of 25 m/s (upper bound). Between the lower and upper bounds, v max  is defined as (⅓)T+30. 
     Graph  300  also includes a second line  310  plotting v max  in relation to T according to Equation 2. Equation 2 is another exemplary continuous function for determining v max  based on T. 
     
       
         
           
             
               
                 
                   
                     v 
                     max 
                   
                   = 
                   
                     max 
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                       ( 
                       
                         0 
                         , 
                         
                           min 
                           ⁡ 
                           
                             ( 
                             
                               26 
                               , 
                               
                                 
                                   
                                     2 
                                     15 
                                   
                                   ⁢ 
                                   T 
                                 
                                 + 
                                 28 
                               
                             
                             ) 
                           
                         
                       
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                   ( 
                   
                     Eq 
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                     2 
                   
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     Between a lower bound of 0 m/s and an upper bound of 26 m/s, Equation 2 defines v max  as ( 2/15)T+28. Although first line  305  and second line  310  depict particular linear continuous functions, any linear or non-linear continuous function suitable for operating wind turbine  100  may be used to calculate an operating threshold value. 
     Referring again to  FIG. 2 , wind turbine controller  205  also includes a wind turbine control interface  220  configured to control an operation of a wind turbine based at least in part on the calculated operating threshold value. In some embodiments, wind turbine control interface  220  is configured to be operatively coupled to one or more wind turbine control devices  120 . Wind turbine control device  120  includes, without limitation, a blade pitch adjustment apparatus and/or a rotor brake. 
     In some embodiments, wind turbine  100  includes one or more sensors  125 . Sensors  125  sense or detect one or more wind turbine conditions. For example, sensor  125  may be an accelerometer, a vibration sensor (e.g., indicating mechanical vibration of one or more components of wind turbine  100 ), a power output sensor, a blade pitch sensor, a rotor speed sensor, a gear ratio sensor, a torque sensor, a turbine temperature sensor, a gearbox temperature sensor, a voltage sensor, a current sensor, and/or a meteorological sensor. Meteorological sensors include, without limitation, an ambient air temperature sensor, a wind speed and/or wind direction sensor (e.g., an anemometer), an ambient air density sensor, an atmospheric pressure sensor, a humidity sensor, and/or any sensor suitable for providing a signal indicating a meteorological condition. 
     Each sensor  125  is located with respect to wind turbine  100  according to its function. For example, an air temperature sensor may be positioned on an outside surface of nacelle  102  or tower  104 , such that the air temperature sensor is exposed to ambient air surrounding wind turbine  100 . Each sensor  125  generates and transmits a signal corresponding to the one or more detected conditions. Moreover, each sensor  125  may transmit a signal continuously, periodically, or only once, for example, though other signal timings are also contemplated. Furthermore, each sensor  125  may transmit a signal either in an analog form or in a digital form. 
     In one embodiment, wind turbine controller  205  receives one or more signals from sensor  125  via a sensor interface  225 , which is configured to be coupled in communication with sensor  125 . Wind turbine controller  205  processes the signal(s) by processor  215  to create one or more operating parameters, including, without limitation, meteorological parameters. In some embodiments, processor  215  is programmed (e.g., with executable instructions in memory area  210 ) to sample a signal produced by sensor  125 . For example, processor  215  may receive a continuous signal from sensor  125  and, in response, produce an operating condition value based on the continuous signal periodically (e.g., once every five seconds). In some embodiments, processor  215  normalizes a signal received from sensor  125 . For example, a temperature sensor may produce an analog signal with a parameter (e.g., voltage) that is directly proportional to a measured temperature. Processor  215  may be programmed to convert the analog signal to a temperature value. 
     In an exemplary embodiment, sensor interface  225  is configured to receive a wind turbine condition signal from sensor  125 . The wind turbine condition signal indicates, directly or indirectly, a structural load on the wind turbine. For example, the wind turbine condition signal may be a wind speed signal that indicates a current wind speed. Wind turbine control interface  220  may be configured to control an operation of wind turbine  100  based on the wind turbine condition signal and the calculated operating threshold value. In one embodiment, wind turbine control interface  220  is configured to disable wind turbine  100  when the current wind speed exceeds an operating wind speed threshold value. For example, wind turbine control interface  220  may disable wind turbine  100  by applying a brake to rotor  106 , by adjusting a pitch angle of rotor blades  108 , and/or by any other means suitable for reducing the structural load applied to wind turbine  100 . 
     Processor  215  may be programmed to create an operating parameter based on signals received from multiple sensors  125 . For example, wind turbine  100  may include multiple air temperature sensors, and processor  215  may calculate an average air temperature based on temperature values from each air temperature sensor. In some embodiments, controller  205  stores one or more signals and/or operating condition values in memory area  210 . 
     In some embodiments, wind turbine controller  205  includes a communication interface  230 . Communication interface  230  is configured to be coupled in communication with one or more remote devices, such as another wind turbine controller  205  and/or a site controller  410  (shown in  FIG. 4 ). Communication interface  230  may be configured to transmit a wind turbine condition, an operating parameter, and/or a control parameter (e.g., a calculated operating threshold value) to a remote device. For example, communication interface  230  may be configured to encode a wind turbine condition, an operating parameter, and/or a control parameter in a signal. In addition, or alternatively, communication interface  230  may be configured to receive an operating parameter (e.g., an ambient air temperature) and/or a control parameter (e.g., a calculated operating threshold value) from a remote device and control an operation of wind turbine  100  based at least in part on the received operating parameter and/or control parameter. 
     Various connections are available between wind turbine control interface  220  and wind turbine control device  120  and between sensor interface  225  and sensor  125 . Such connections may include, without limitation, an electrical conductor, a low-level serial data connection, such as Recommended Standard (RS) 232 or RS-485, a high-level serial data connection, such as Universal Serial Bus (USB) or Institute of Electrical and Electronics Engineers (IEEE) 1394 (a/k/a FIREWIRE), a parallel data connection, such as IEEE 1284 or IEEE 488, a short-range wireless communication channel such as BLUETOOTH, and/or a private (e.g., inaccessible outside wind turbine  100 ) network connection, whether wired or wireless. 
       FIG. 4  is a block diagram showing an exemplary system  400  for controlling an operation of one or more wind turbines  100  in a wind turbine site  405 . System  400  includes a site controller  410  that is coupled in communication with one or more wind turbine controllers  205  via a communication interface  415 . For example, communication interface  415  may be configured to transmit and/or receive a signal in which a wind turbine condition, an operating parameter, and/or a control parameter is encoded. 
     As shown in  FIG. 4 , site controller  410  is located within wind turbine site  405 . However, site controller  410  may be positioned at a location remote to wind turbine site  405 , such as a centralized monitoring and/or control facility. Furthermore, site controller  410  may be coupled in communication with wind turbine controllers  205  at multiple wind turbine sites  405 . 
     Site controller  410  is coupled in communication with a first wind turbine controller  420  of a first wind turbine  425  and a second wind turbine controller  430  of a second wind turbine  435  by communication interface  415 . First wind turbine controller  420  and second wind turbine controller  430  are instances of wind turbine controller  205 . First wind turbine  425  and second wind turbine  435  are instances of wind turbine  100 . Site controller  410  may be coupled in communication with any number of wind turbine controllers  205 . 
     Site controller  410  includes a memory area  440  configured to store operating data and/or executable instructions for execution by a processor  445 . For example, operating data may include data describing wind turbines  100 , wind turbine controllers  205 , and/or wind turbine conditions (e.g., meteorological conditions). Memory area  440  may be further configured to store a continuous function defining an operating threshold value based on one or more meteorological conditions, optionally in the form of one or more executable instructions. 
     Site controller  410  is configured to receive, via communication interface  415 , a meteorological parameter, such as an ambient air temperature and/or an ambient air density, from first wind turbine controller  420  and/or second wind turbine controller  430 . In addition, or alternatively, site controller  410  may include a sensor interface  450  configured to be coupled in communication with one or more sensors  125 . In such an embodiment, site controller  410  may be configured to receive a meteorological condition signal from sensor  125  and to create a meteorological parameter based on a meteorological condition indicated by the meteorological condition signal. 
     Site controller  410  is also configured to transmit, to first wind turbine controller  420  and/or second wind turbine controller  430 , a meteorological parameter and/or a calculated operating threshold value. In one embodiment, site controller  410  is configured to receive a single meteorological parameter from first wind turbine controller  420  or second wind turbine controller  430 , or to create a single meteorological parameter based on a meteorological condition indicated by a meteorological condition signal from sensor  125 . Site controller  410  is further configured to transmit the single meteorological parameter to first wind turbine controller  420  and/or second wind turbine controller  430 , which are configured to calculate an operating threshold value based on the single meteorological parameter. Such an embodiment facilitates meteorology-based control of wind turbines  100  even when one or more of wind turbines  100  does not include an operable meteorological sensor. Furthermore, such an embodiment facilitates calculating an operating threshold value that is specific to a wind turbine  100 . For example, at a given ambient air temperature and/or a given ambient air density, a different maximum operating wind speed may be appropriate for first wind turbine  425  than is appropriate for second wind turbine  435 . 
     In another embodiment, site controller  410  is configured to receive and/or create a plurality of meteorological parameters from first wind turbine controller  420 , second wind turbine controller  430 , and/or sensor  125 . Site controller  410  is also configured to create a calculated meteorological parameter based on the plurality of meteorological parameters. For example, processor  445  may be programmed to calculate an average (e.g., a mean or a median) meteorological parameter from the plurality of meteorological parameters. Site controller  410  is further configured to transmit the calculated meteorological parameter to first wind turbine controller  420  and/or second wind turbine controller  430 , which are configured to calculate an operating threshold value based on the calculated meteorological parameter. 
     In yet another embodiment, site controller  410  is configured to receive and/or create one or more meteorological parameters from first wind turbine controller  420 , second wind turbine controller  430 , and/or sensor  125 . Site controller  410  is also configured to calculate an operating threshold value (e.g., a maximum operating wind speed) at least in part by applying a continuous function to the meteorological parameter(s). If multiple meteorological parameters are available, site controller  410  may be configured to calculate an average (e.g., mean or median) meteorological parameter and apply the continuous function to the average meteorological parameter. Alternatively, site controller  410  may be configured to apply the continuous function to each meteorological parameter to create a plurality of operating threshold values and then calculate an average (e.g., mean or median) operating threshold value. Site controller  410  is further configured to transmit the calculated operating threshold value to first wind turbine controller  420  and/or second wind turbine controller  430 . First wind turbine controller  420  and/or second wind turbine controller  430  are configured to control an operation of corresponding wind turbine  100  based at least in part on the calculated operating threshold value. In such an embodiment, communication interface  415  may be considered a wind turbine control interface. 
     Some embodiments facilitate calculating a moving average for an operating parameter. In one embodiment, site controller  410  and/or wind turbine controller  205  is configured to receive and/or create a plurality of operating parameters based on a plurality of wind turbine conditions indicated by recent wind turbine condition signals. For example, the operating parameters may correspond to a quantity of recently produced wind turbine condition signals (e.g., the five most recent wind turbine condition signals) and/or may correspond to wind turbine condition signals received within a recent duration (e.g., wind turbine condition signals received in the previous five minutes). Site controller  410  and/or wind turbine controller  205  is configured to calculate an average (e.g., mean or median) operating parameter based on the plurality of operating parameters. An operating threshold value may be calculated based on the average operating parameter. 
     Communication between devices such as wind turbine controller  205  and site controller  410  may occur in a variety of forms. For example, communication interfaces  230 ,  415  may use a wired network connection (e.g., Ethernet or an optical fiber), a wireless connection such as radio frequency (RF), BLUETOOTH, an IEEE 802.11 standard (e.g., 802.11(g) or 802.11(n)), Worldwide Interoperability for Microwave Access (WIMAX), or a cellular phone technology (e.g., the Global Standard for Mobile communication (GSM)), and/or any other suitable communication means. Wind turbine controller  205  and/or site controller  410  may include multiple communication interfaces to support additional forms of communication, or multiple forms of communication may be supported by a single communication interface. Devices such as wind turbine controller  205  and site controller  410  may be communicatively coupled directly or indirectly. For example, site controller  410  may communicate with wind turbine controller  205  through a network such as a local area network (LAN), a wide area network (WAN), the Internet, or any other network suitable for communicating with wind turbine controller  205 . 
       FIG. 5  is a flowchart of an exemplary method  500  for controlling a wind turbine, such as wind turbine  100 , shown in  FIG. 1 . Method  500  includes receiving  505 , from a first sensor, a first meteorological condition signal indicating a meteorological condition (e.g., an ambient air temperature and/or an ambient air density). A first operating threshold value is calculated  510  by a processor, at least in part by applying a continuous function to the meteorological condition. For example, a continuous function such as Equation 1 or Equation 2 may be applied to the meteorological condition. The operating threshold value may include, without limitation, a maximum operating wind speed, a maximum power output, a maximum torque, and/or a maximum vibration level. 
     The first operating threshold may be calculated  510  by a first processor of a first wind turbine controller. A second operating threshold may be calculated  515  by a second processor of a second wind turbine controller, at least in part by applying a second continuous function to the meteorological condition. 
     An operating parameter is created  520  based on a wind turbine condition indicated by a wind turbine condition signal received from a second sensor. The wind turbine condition is representative, directly or indirectly, of a structural load on the wind turbine. For example, the wind turbine condition signal may indicate a current wind speed, a current power output, a current torque, and/or a current vibration level. The operating parameter may be created  520  using a moving average, as described above. 
     An operation of the wind turbine is adjusted  525  when the operating parameter exceeds the calculated operating threshold value. For example, adjusting  525  an operation of the wind turbine may include disabling the wind turbine, reducing a power output of the wind turbine, applying a brake to a rotor of the wind turbine, and/or adjusting a blade pitch of the wind turbine. As shown in  FIG. 5 , method  500  may be performed repeatedly (e.g., continuously or periodically). 
     In some embodiments, an operation of multiple wind turbines is adjusted  525  based at least in part on the calculated operating threshold value and/or the created operating parameter. For example, the operating parameter may be created  520  based on a wind turbine condition corresponding to a first wind turbine, and an operation of a second wind turbine may be adjusted  525  when the operating parameter exceeds the calculated operating threshold value. Such an embodiment facilitates reducing a structural load on the second wind turbine regardless of whether the second wind turbine includes operable sensors. 
     The methods described herein may be encoded as executable instructions embodied in a computer readable medium, including a memory area of a computing device such as wind turbine controller  205  and/or site controller  410 . Such instructions, when executed by a processor, cause the processor to perform at least a portion of the methods described herein. 
     Exemplary embodiments of a wind turbine control system are described above in detail. The system, wind turbine, and included assemblies are not limited to the specific embodiments described herein, but rather each component may be utilized independently and separately from other components described herein. 
     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 have 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 language of the claims.