System and method for managing output flicker generated by a wind farm

Abstract

The invention relates to a system and method for managing flicker generated by a wind farm. Thus, a farm controller detects at least one parameter of the wind farm indicative of output flicker caused by synchronization of flicker in at least two of a plurality of wind turbines. Upon detecting the parameter, the farm controller generates a command offset for at least one of the at least two wind turbines. An operating parameter of the at least one wind turbine is changed based on the command offset in order to desynchronize the synchronized flicker in the output signals of the at least two wind turbines.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to wind farms, and more particularly to systems and methods for managing output flicker generated by a wind farm having a plurality of wind turbines. BACKGROUND

[0002] Wind power is considered one of the cleanest, most environmentally friendly energy sources currently available, and, in this regard, wind turbines have gained increased attention. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture the wind's kinetic energy using known aerofoil principles. For example, the rotor blades typically have an aerofoil cross-sectional profile so that, during operation, air flows over the blades creating a pressure difference between the sides. As a result, a lift force from the pressure side to the suction side acts on the blades. The lift force generates a torque on a main rotor shaft, which is meshed to a generator in order to create electricity.

[0003] In many wind turbines, the generator is electrically coupled to a bidirectional power converter, which includes a rotor-side converter that is linked to a line-side converter via a regulated DC link. Such a wind turbine power system is generally referred to as a doubly-fed induction generator (DFIG). DFIG operation is typically characterized by a rotor circuit that is supplied with current from a current-regulated power converter. As such, a wind turbine produces a variable mechanical torque due to variable wind speed, and the power converter ensures that this torque is converted into an electrical output at the same frequency of the grid.

[0004] During operation, the wind impacts the rotor blades, and the blades transform the wind energy into a mechanical rotational torque that drives a low-speed shaft. The low-speed shaft is configured to drive a gearbox, which then steps up the low rotational speed of the low-speed shaft to drive a high-speed shaft at an increased rotational speed. The high-speed shaft is generally coupled to a generator to rotatably drive a generator rotor. As such, a rotating magnetic field can be induced by the generator rotor, and a voltage can be induced within a generator stator. The rotational energy is converted into electrical energy through electromagnetic fields that couple the rotor and stator, which is supplied to the power grid via a grid breaker. Thus, a main transformer steps up the voltage amplitude of the electrical power so that the transformed electrical power can be further transmitted to the power grid.

[0005] For some wind turbines, it is desirable to modify the torque command of the power converter during operation of the wind turbine when each rotor blade is aligned with and passes the tower. However, this modification can tend to cause undesirable low frequency voltage variations on the power grid. Such variations are often referred to as flicker. Thus, as used herein, the term "flicker" generally refers to variations in current or voltage on the power grid that can be perceived at certain frequencies (e.g., from about 1 Hertz (Hz) to about 30 Hz). Additionally, when wind turbines are assembled into a wind farm, the flicker of individual wind turbines or portions thereof can inadvertently be synchronized, resulting in output flicker in the output of the wind farm. Typically, if flicker is present in an amount, the grid code prohibits connection to the power grid.

[0006] In view of the foregoing, there is a continuing need for new and improved systems and methods for managing flicker generated by a wind farm. SUMMARY

[0007] Aspects and advantages of the application will be set forth in part in the following description, or can be obvious from the description, or can be learned through practice of the application.

[0008] In one aspect, the present disclosure relates to a method for managing flicker generated by a wind farm connected to a power grid. The wind farm can include a plurality of wind turbines. The method can include detecting, with a farm controller of the wind farm, at least one parameter of the wind farm indicative of output flicker caused by synchronized flicker of at least two wind turbines of the plurality of wind turbines. Upon detecting the parameter(s), the method can include generating a command offset for at least one of the two wind turbines. Additionally, the method can include changing an operating parameter of the wind turbine(s) based on the command offset in order to desynchronize the synchronized flicker in the output signals of the two wind turbines.

[0009] In an embodiment, generating the command offset can include generating a random bias value.

[0010] In an additional embodiment, changing the operating parameter of the wind turbine(s) can include introducing the random bias value into a speed feedback loop of a turbine controller to produce a variable rotor speed for the wind turbine(s).

[0011] In further embodiments, the wind farm can also include at least one output sensor operably coupled to the farm controller at a point of interconnection (POI) with the power grid. Additionally, detecting the parameter(s) indicative of output flicker can also include monitoring, via the output sensor(s), a frequency and amplitude of a change in current or voltage at the output of the wind farm at the point of interconnection with the power grid. The frequency and amplitude of the change can be indicative of output flicker in the output of the wind turbine(s). The method can also include detecting, with the farm controller, an approach of the output of the output sensor(s) to a flicker threshold for the wind farm.

[0012] In yet further embodiments, the wind farm can include at least one environmental sensor operably coupled to the farm controller. Additionally, detecting the parameter(s) indicative of output flicker can include monitoring, via the environmental sensor(s), at least one environmental parameter indicative of environmental conditions acting on the wind farm. The method can also include correlating, with the farm controller, the environmental parameter(s) with an indication of a level of output flicker detected by the output sensor(s) as in the monitored environmental conditions.

[0013] In embodiments, the method can include determining, with the farm controller, an output flicker likelihood for the wind farm based at least in part on the correlation and the forecasted environmental conditions.

[0014] In additional embodiments, generating the command offset can include generating the command offset when at least one of the output flicker likelihood or the output of the output sensor(s) approaches or exceeds a flicker threshold for the wind farm.

[0015] In further embodiments, the method can include determining an impact on the level of output flicker resulting from changing the operating parameter of the wind turbine(s) based on the command offset. The method can also include correlating, with the farm controller, the impact with the environmental conditions acting on the wind farm. Moreover, the method can include assigning a synchronicity-impact score to the wind turbine(s) based on the calculated correlation for the detected environmental conditions. Additionally, the method can include selecting the wind turbine(s) to receive the command offset from the plurality of wind turbines based at least in part on the synchronicity-impact score.

[0016] In yet further embodiments, detecting the parameter(s) indicative of output flicker can include receiving, with the farm controller, timing signals from two of the wind turbines. The timing signals can be indicative of a rotor position for each of the wind turbines. The method can include determining, with the farm controller, a degree of synchronicity between the two of the plurality of wind turbines based on the respective timing signals. Additionally, the method can include determining, with the farm controller, a difference between the degree of synchronicity and a synchronicity threshold corresponding to the output flicker threshold.

[0017] In embodiments, determining a degree of synchronicity between the plurality of wind turbines can include utilizing the farm controller to establish a plurality of time slices. The method can also include utilizing the farm controller to determine a standard deviation for the timing signal across the time slices. The standard deviation for the timing signal can be indicative of the degree of synchronicity between the plurality of wind turbines.

[0018] In additional embodiments, the two wind turbines of the plurality of wind turbines can include at least a first group of wind turbines and a second group of wind turbines. The timing signal can be indicative of a timing of a combination of the first and second groups of wind turbines, respectively.

[0019] In further embodiments, changing an operating parameter of the wind turbine(s) based on the command offset can include changing an operating parameter corresponding to at least one of a generator torque, a power output, a rotor speed, or a mechanical load of the wind turbine(s).

[0020] In another aspect, the disclosure relates to a system for managing flicker generated by a wind farm. The system can include a plurality of wind turbines coupled to an electrical grid. The system can also include a farm controller communicatively coupled to the plurality of wind turbines and communicatively coupled to the electrical grid. The farm controller can include at least one processor configured to perform a plurality of operations. The plurality of operations can include detecting a parameter(s) of the wind farm indicative of output flicker caused by a synchronization of flicker by two wind turbines of the plurality of wind turbines. Upon detecting the parameter(s), the plurality of operations can include generating a command offset for at least one of the two wind turbines. Additionally, the plurality of operations can include changing an operating parameter of the wind turbine(s) based on the command offset in order to desynchronize the synchronization of flicker in the output signals of the two wind turbines. It should be appreciated that the system can further include any of the additional steps and / or features described herein.

[0021] These and other features, aspects, and advantages of the present application 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 application and serve to explain the principles of the application. BRIEF DESCRIPTION OF DRAWINGS

[0022] A complete and enabling disclosure of the application, including its best mode, directed to one of ordinary skill in the art, is set forth in the specification which follows, and is illustrated in the accompanying drawings which are incorporated herein by reference. The

[0023] Figure 1 FIG. 1 illustrates a perspective view of one embodiment of a wind turbine in accordance with the present disclosure;

[0024] Figure 2 FIG. 1 illustrates a perspective view of one embodiment of a wind turbine in accordance with the present disclosure;

[0025] Figure 3 a schematic diagram of one embodiment of a controller for use with a wind farm as Figure 2 illustrated in FIG. 1 1 ;

[0026] Figure 4 a flowchart illustrating one embodiment of control logic of a system for operating a wind farm according to the present disclosure;

[0027] Figure 5 a portion of the control logic of FIG. 1 1 ; Figure 4

[0028] Figure 6 a graphical representation of output of a wind farm, particularly illustrating synchronized flicker according to the present disclosure; and

[0029] Figure 7 a graphical representation of output of a wind farm, particularly illustrating desynchronized flicker according to the present disclosure.

[0030] The repeated use of reference characters in the specification and drawings is intended to indicate the same or similar elements or features. DETAILED DESCRIPTION

[0031] Reference will now be made in detail to embodiments of the application, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the application and is not meant as a limitation of the application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the scope or spirit of the application. 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 application encompass such modifications and variations as come within the scope of the appended claims and their equivalents.

[0032] As used herein, the terms "first", "second", and "third" can be used interchangeably to distinguish one element from another and are not intended to signify location or importance of the individual elements.

[0033] Unless otherwise defined herein, the terms "coupled", "fixed", "attached" and the like mean both directly coupled, fixed, or attached and indirectly coupled, fixed, or attached through one or more intermediate elements or features unless otherwise specified herein.

[0034] ​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 directed. Accordingly, a value modified by a term or terms, such as "about", "approximately", and "substantially", will not be limited to the precise value specified. In at least some instances, the approximating language can correspond to the precision of an instrument for measuring the value or the precision of the methods or machines for constructing or manufacturing the components and / or systems. For example, the approximating language can refer to being within 10% of the stated value.

[0035] Herein and throughout the specification and claims, range limitations, which are not expressly recited, are to be construed as being included in the specification and claims. For example, a range of "between a and b" is to be construed as including the values of "a" and "b" unless the context or language clearly indicates otherwise. It is intended, for example, that the description of a range also include the description of all sub-ranges of that range. For example, a range of "1 to 10" is intended to include the description of all sub-ranges between and including the minimum value of 1 and the maximum value of 10.

[0036] Generally, the present disclosure relates to systems and methods for controlling a wind farm connected to a power grid. In particular, the present disclosure can include systems and methods that can facilitate managing flicker occurring in the power grid generated by a wind farm. The flicker can be output flicker caused in the output of the wind farm, which is caused by an unintentional alignment / synchronization of flicker that can be present in the output of individual wind turbines of the wind farm. Thus, a farm controller can detect a parameter of the wind farm that can be indicative of the synchronization of two or more wind turbines of the wind farm. In various embodiments, the parameter can include, for example, a measure of flicker, weather conditions, rotor position timing signals, learned wind turbine behavior, and / or wind turbine operating states.

[0037] The farm controller can generate a command offset for at least one of the wind turbines in response to detecting the parameter. The command offset can temporarily alter an operating state or parameter of the wind turbine. For example, when the rotors of two wind turbines pass the six o'clock position at the same time, any flicker in the output of the wind turbines can be synchronized. Upon detecting such a state, the farm controller can instruct one of the wind turbines to immediately change its rotational speed so that the rotors of the two wind turbines pass the six o'clock position at different times. In other words, in accordance with the present disclosure, one of the wind turbines can essentially "miss a beat" so that the rotor position or other aspect of the turbine is desynchronized. Even though the individual wind turbines can produce output with flicker, by desynchronizing the flicker, the combined output of the wind farm delivered to the power grid can be flicker free.

[0038] Reference will now be made to the drawings, in which Figure 1A perspective view of one embodiment of a wind turbine 100 according to the present disclosure is illustrated. The wind turbine 100 generally includes a tower 102 extending from a support surface 104, a nacelle 106 mounted to the tower 102, and a rotor 108 coupled to the nacelle 106. The rotor 108 includes a rotatable hub 110 and at least one rotor blade 112 coupled to and extending outward from the hub 110. For example, in the illustrated embodiment, the rotor 108 includes three rotor blades 112. However, in alternative embodiments, the rotor 108 can include more or less than three rotor blades 112. Each rotor blade 112 can be spaced about the hub 110 to facilitate rotating the rotor 108 to enable kinetic energy to be converted from the wind into usable mechanical energy and subsequently into electrical energy. For example, the hub 110 can be rotatably coupled to an electrical generator (not shown) positioned within the nacelle 106 to allow electrical energy to be generated.

[0039] The wind turbine 100 can also include a controller 200 configured as a turbine controller 204. The controller 200 can be centralized within the nacelle 106. However, in other embodiments, the controller 200 can be located within any other component of the wind turbine 100 or at a location external to the wind turbine 100. Also, the controller 200 can be communicatively coupled to any number of components of the wind turbine 100 in order to control the components. As such, the controller 200 can include a computer or other suitable processing unit. Thus, in several embodiments, the turbine controller 204 can include suitable computer-readable instructions that, when implemented, cause the controller 200 to be configured to perform various different functions, such as receiving, transmitting, and / or executing wind turbine control signals.

[0040] Still referring to Figure 1One or more sensors 156, 158 can be provided on the wind turbines 100 to monitor the performance of the wind turbines 100 and / or environmental conditions acting on the wind turbines 100. It should also be appreciated that, as used herein, the term "monitor" and variations thereof indicate that the various sensors of the wind turbines 100 can be configured to provide a direct measurement of the parameter being monitored or an indirect measurement of such parameter. Thus, the sensors described herein can be used, for example, to generate a signal related to the parameter being monitored which can then be utilized by the controller 200 to determine the condition of the wind turbine 100. For example, as shown, each of the wind turbines 100 can include an environmental sensor 158 configured to gather data indicative of at least one environmental condition. The environmental sensor 158 can be operably coupled to the controller 200. Thus, in embodiments, the environmental sensor(s) 158 can be, for example, a wind vane, an anemometer, a lidar sensor, a thermometer, a barometer, or other suitable sensor. The data gathered by the environmental sensor(s) 158 can include measurements of wind speed, wind direction, wind shear, gusts, wind direction changes, atmospheric pressure, and / or temperature. In at least one embodiment, the environmental sensor(s) 158 can be mounted to the nacelle 106 at a downwind location of the rotor 108. In alternative embodiments, the environmental sensor(s) 158 can be coupled to or integrated with the rotor 108. It should be appreciated that the environmental sensor(s) 158 can include a network of sensors and can be located remotely from the wind turbine 100.

[0041] In addition to the environmental sensor(s) 158, the wind turbines 100 can also include one or more asset condition sensors 156. The asset condition sensor(s) 156 can be configured to monitor, for example, the electrical properties of the output of the generator of each of the wind turbines 100, such as a current sensor, a voltage sensor, a temperature sensor, or a power sensor that directly monitors the power output based on current and voltage measurements. In at least one embodiment, the asset condition sensor(s) 156 can include any other sensors that can be utilized to monitor the operational state of the wind turbines 100, such as rotor position and / or rotor timing.

[0042] Reference is now made to Figure 2FIG. 1 illustrates a schematic diagram of a wind farm 152 controlled in accordance with the systems and methods of the present disclosure. As shown, in an embodiment, the wind farm 152 can include a controller 200 and a plurality of wind turbines 100 as described herein. The controller 200 can be configured as a farm controller 202. For example, as shown in the illustrated embodiment, the wind farm 152 can include twelve wind turbines 100. However, in other embodiments, the wind farm 152 can include any other number of wind turbines 100, such as fewer than twelve wind turbines 100 or more than twelve wind turbines 100. In one embodiment, the turbine controller(s) 204 of the wind turbine(s) 100 can be communicatively coupled to the farm controller 202 by a wired connection, such as by connecting the controller(s) 200 via a suitable communication link 154 (e.g., a suitable cable). Alternatively, the controller(s) 200 can be communicatively coupled to the farm controller 202 by a wireless connection, such as by using any suitable wireless communication protocol known in the art. Additionally, the farm controller 202 can be generally configured similar to the controller 200 for each of the individual wind turbines 100 within the wind farm 152.

[0043] In an embodiment, the farm controller 202 can also be operatively coupled to at least one output sensor 162 at a point of interconnection with the power grid. The output sensor(s) 162 can be configured to monitor the output of the wind farm 152 in order to detect an indication of output flicker in the output.

[0044] Reference is now made to Figures 3-5 presented are schematic diagrams of a number of embodiments of a system 300 for managing flicker generated by a wind farm 152 in accordance with the present disclosure. As particularly shown in Figure 3 illustrated is a schematic diagram of one embodiment of suitable components that can be included within the controller 200. For example, as shown, the controller 200 can include one or more processors 206 and associated memory device(s) 208 configured to carry out a variety of computer-implemented functions (e.g., implementing methods, steps, calculations, etc., and storing related data as disclosed herein). Additionally, the controller 200 can also include a communication module 210 to facilitate communication between the controller 200 and various components of the wind turbine 100. Moreover, the communication module 210 can include a sensor interface 212 (e.g., one or more analog-to-digital converters) to allow signals transmitted from one or more sensors 156, 158, 162 to be converted into signals that can be understood and processed by the processor 206. It should be appreciated that the sensors 156, 158, 162 can be communicatively coupled to the communication module 210 using any suitable means. For example, as shown, the sensors 156, 158, 162 can be communicatively coupled to the communication module 210 by a wired connection, such as by connecting the sensors 156, 158, 162 via a suitable communication link 154 (e.g., a suitable cable). Alternatively, the sensors 156, 158, 162 can be communicatively coupled to the communication module 210 by a wireless connection, such as by using any suitable wireless communication protocol known in the art. Figure 3As shown in the middle, the sensors 156, 158, 162 are coupled to the sensor interface 212 via a wired connection. However, in other embodiments, the sensors 156, 158, 162 can be coupled to the sensor interface 212 via a wireless connection, such as by using any suitable wireless communication protocol known in the art. Additionally, the communication module 210 can also be operably coupled to an operating state control module 214, which is configured to change at least one wind turbine operating state / operating parameter.

[0045] 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) 208 can generally include memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable nonvolatile memory (e.g., 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 appropriate memory elements. Such memory element(s) 208 can generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) 206, cause the controller 200 to be configured to perform various functions including, but not limited to: detecting at least one parameter indicative of output flicker; generating a command offset for a wind turbine; and changing an operating parameter of the wind turbine based on the command offset in order to desynchronize synchronous flicker in an output signal of the wind turbine as described herein, as well as various other suitable computer-implemented functions.

[0046] With particular reference to Figure 4In embodiments, the field controller 202 of the system 300 can be configured to detect at least one parameter 302 of the wind farm 152 indicative of an output flicker occurring in the power grid and generated by at least two of the wind turbines 100. In embodiments, the parameter(s) 302 can be indicated by output sensor data 304, environmental sensor data 306, and / or timing signals 308. In embodiments, the parameter(s) 302 can include a measurement of flicker in the output of the wind farm 152 as indicated by changes in current and / or voltage that can be indicative of synchronized flicker. In additional embodiments, the parameter(s) 302 can include data indicative of environmental conditions acting on the wind turbines 100. In further embodiments, the parameter(s) 302 can include a rotor position of the rotor 108 of the wind turbine 100 as indicated by the timing signals 308. Additionally, in embodiments, the parameter(s) 302 can be learned wind turbine behavior, where historical environmental conditions that resulted in flicker can be relevant to determine an output flicker likelihood corresponding to a weather forecast. In yet further embodiments, the parameter(s) 302 can correspond to an operational state of the wind farm. For example, in embodiments, whenever the wind farm 152 is in operation, it can be assumed that there is synchronized flicker present, and, thus, the control logic of the system 300 can be utilized to desynchronize the output of each wind turbine 100 of the wind farm 152.

[0047] It should be appreciated that the flicker generated by the wind farm 152 can be a result of synchronized flicker present in the output of at least a portion of the plurality of wind turbines 100 of the wind farm 152. For example, Figure 6 Embodiments are depicted in which the output signals of the first wind turbine 164, the second wind turbine 166, and the third wind turbine 168 can be characterized by frequency changes and amplitude changes in current / voltage that can be synchronized. In such embodiments, when the outputs of the three wind turbines 100 are combined at the POI, the resulting output of the wind farm 152 can reflect a combined, synchronized flicker of the wind turbines 100 as indicated by the plot 170. In embodiments, the plot 170 can reflect the flicker in the output of the wind farm 152 as observed by the power grid, and this flicker can be delivered to the power grid consumer. However, as depicted by the plot 172, in embodiments, the system 300 can be employed to change an operational parameter of at least one of the wind turbines 100 in order to desynchronize the synchronized flicker in the output signals. For example, as a result of the operational parameter change, the output signals of the first wind turbine 164, the second wind turbine 166, and the third wind turbine 168 can be characterized by frequency changes and amplitude changes in current / voltage that are desynchronized relative to one another, as indicated by the plot 172. In embodiments, the plot 172 can reflect the flicker in the output of the wind farm 152 as observed by the power grid, and this flicker can be delivered to the power grid consumer. Figure 7 Figure 7 ​As depicted. The combination of the desynchronized output signals can result in an output signal of the wind farm 152 that does not exhibit flicker, as depicted by plot 172.

[0048] It should further be appreciated that, in being desynchronized, the frequency variations and amplitude variations (e.g., flicker) in the output signals of the wind turbines 100 can be substantially masked by the frequency variations and amplitude variations in the output signals of another wind turbine 100 of the wind farm 152. Thus, while in embodiments, flicker can be detectable in the output of an individual wind turbine 100, the combination of the desynchronized outputs, as reflected by the output of the wind farm 152, can be a stable / constant output as perceived by the power grid consumer.

[0049] Referring again to Figure 4 In embodiments, the farm controller 202 of the system 300 can be configured to generate a command offset 310 for at least one wind turbine 100 upon detecting the parameter(s) 302 indicative of synchronized flicker of the outputs of the at least two wind turbines 100. The command offset 310 can facilitate desynchronization of the synchronized flicker in order to produce a wind farm 152 output that does not exhibit the characteristics of flicker.

[0050] In embodiments, the command offset can be employed by the system 300 at 312 to change the operating parameters of the wind turbine(s) 100 in order to desynchronize the synchronized flicker in the output signals of the at least two wind turbines at 314. In embodiments, changing the operating parameters of the wind turbine(s) 100 based on the command offset 310 can include changing operating parameters corresponding to the generator torque, power output, rotor speed, and / or mechanical load of the wind turbine(s) 100. For example, in embodiments, the command offset can be fused with a setpoint command for the wind turbine(s) 100 to generate a modified setpoint command. In embodiments, the modified setpoint command can be communicated to the wind turbine(s) 100 in order to adjust the operating state of the wind turbine(s) 100. In embodiments, the system 300 can follow the transmission of the modified setpoint command with the transmission of the unmodified setpoint command, thereby returning the wind turbine(s) 100 to the original operating state, but without the previously detected synchronized flicker. For example, in embodiments, the torque setpoint of the generator can be temporarily increased before returning to the previously established optimal torque setpoint for a given operating state of the wind turbine(s) 100, resulting in a change in the frequency and / or amplitude of the variations in the output current / voltage of the wind turbine(s) 100.

[0051] In one embodiment, generating command offset 310 may include generating a random bias value 316 by field controller 202. In such an embodiment, the random bias value 316 may be a random value introduced into the control logic of the wind turbine(s)100 to temporarily bias the setpoint of the wind turbine(s)100. For example, as shown at 318, in one embodiment, field controller 202 may be configured to introduce the bias value 316 into the speed feedback loop of the turbine(s)4 of the wind turbine(s)100 to generate a variable rotor speed 320 for the wind turbine(s)100. In one embodiment, the random bias value 316 may include different variables introduced into the different wind turbines 100 of the wind field 152. In an additional embodiment, the random bias value 316 may be a single randomly selected value introduced into the wind turbines 100 of the wind field 152 at a first moment and a single, differently randomly selected value introduced into the wind turbines 100 at a second moment.

[0052] In an embodiment, such as Figure 5 As depicted, the field controller 202 of system 300 can be configured to receive output sensor data 304 from output sensors(s)162. Thus, at 322, the output sensors(s)162 can be used to monitor the frequency and amplitude of changes in current and / or voltage in the output of wind field 152 at POI. In an embodiment, the frequency and / or amplitude of changes in the output of wind field 152 can indicate synchronization of flicker present in the outputs of the various wind turbines 100 of wind field 152. As depicted at 324, in an embodiment, the field controller 202 can compare the monitored changes in current and / or voltage with a flicker threshold 326. Thus, the field controller 202 can detect at 328 the proximity of the outputs of the output sensors(s)162 to the flicker threshold 326 for wind field 152. In an embodiment where the field controller 202 determines at 330 that a flicker level is approaching or exceeding the flicker threshold 326, the field controller 202 can generate a command offset 310.

[0053] In an embodiment, the detection of parameters 302 indicating output flicker may include monitoring environmental sensor data 306. The environmental sensor data 306 may be at least one environmental parameter 332 indicating environmental conditions affecting the wind field 152. In an embodiment, the field controller 202 may correlate the environmental parameter(s) 332 with an indication of the output flicker level at 334. For example, in an embodiment, the field controller 202 may correlate the environmental parameter(s) 332 with the output flicker level detected by the output sensor(s) 162 under the monitored environmental conditions.

[0054] In embodiments, the correlation of environmental conditions to output flicker levels can be done over a specified period of time to establish a historical dataset of correlations based on observed relationships between environmental conditions and resulting output flicker levels. Thus, in embodiments, the farm controller 202 of the system 300 can be configured to receive an environmental condition forecast 336. Based at least in part on the environmental condition forecast 336 and the correlation between the environmental parameter(s) 332 / output flicker levels, the farm controller 202 can determine an output flicker likelihood 338. It should be appreciated that the output flicker likelihood 338 can represent a degree of synchronous flicker that can be expected if the wind farm is subjected to the forecasted environmental conditions.

[0055] As depicted at 340, in embodiments, the farm controller 202 can be configured to compare the output flicker likelihood 338 to the flicker threshold 326 to detect, at 328, the proximity of the flicker likelihood 338 to the flicker threshold 326. In embodiments where the output flicker likelihood 338 approaches or exceeds the flicker threshold 326 for the wind farm 152, the farm controller 202 can generate a command offset 310. For example, the farm controller 202 can receive a weather forecast and can determine an expected output flicker level under the forecasted conditions. In embodiments, this expected level can be compared to the flicker threshold 326. When the expected output flicker level meets or exceeds the flicker threshold 326, the farm controller 202 can predictably generate a command offset 310 to preclude an unacceptable level of output flicker in the output of the wind farm 152. Thus, it should be appreciated that, in embodiments, the farm controller 202 can generate a command offset 310 when the output flicker likelihood 338 of the output sensor(s) 162 and / or the output approaches or exceeds the flicker threshold 326 for the wind farm 152.

[0056] In embodiments, the farm controller 202 of the system 300 can be configured to perform a feedback loop in which the desynchronization efficacy of various wind turbines 100 of the wind farm 152 can be determined for various environmental conditions. Accordingly, the farm controller 202 can determine an impact 342 on the output flicker level caused by changing the operating parameter(s) 310 of the wind turbine(s) 100 at 312 based on the command offset 310. As depicted at 344, the farm controller 202 can correlate the impact 342 with the environmental conditions acting on the wind turbines 152 as indicated by the environmental parameter(s) 332. In embodiments, the farm controller 202 can assign a synchronization-impact score 346 to the wind turbine(s) 100 based on the calculated correlation for the detected environmental conditions. The farm controller 202 can select the wind turbine(s) 100 to receive the command offset 310 from the plurality of wind turbines 100 based at least in part on the synchronization-impact score 346 at 348. In embodiments, the feedback loop can be performed whenever a command offset 310 is generated in response to a detection of the parameter(s) 302 indicative of output flicker for a specified number of command cycles and / or for a specified period of time. Accordingly, a historical data set of the correlation between the desynchronization efficacy of the wind turbine(s) 100 and the environmental parameter(s) 332 (e.g., weather conditions). It should be appreciated that the farm controller 202 can utilize the historical data set at least in part to select the wind turbine(s) 100 from the plurality of wind turbines 100 that can be most effective in desynchronizing flickering output either prospectively or reactively.

[0057] In embodiments, the detection of the parameter(s) 302 indicative of output flicker can be based at least in part on the rotor position of at least two wind turbines 100. As such, in embodiments, the farm controller 202 of the system 300 can be configured to receive timing signals 308 from at least two wind turbines 100 of the wind farm 152. The timing signals 308 can be indicative of the rotor position for the rotor 108 of each of the wind turbines 100. For example, the rotor position can indicate that the rotor blades 112 of each respective rotor 108 can be passing the tower 102 at the same instant in time, thereby indicating that the rotation of the respective rotors 108 can be synchronized. In embodiments, the farm controller 202 can determine a degree of synchronization 350 between the wind turbines 100 based on the respective timing signals 108.

[0058] It should be appreciated that in embodiments, the at least two wind turbines 100 can be at least a first grouping 360 of wind turbines 100 and a second grouping 362 of wind turbines 100. In such embodiments, the timing signals 308 of the individual wind turbines 100 of the respective groupings 360, 362 can be combined into a single timing signal 308 for each of the groupings 360, 362. Thus, in embodiments, the timing signal 308 received by the farm controller 202 can correspond to a combined timing signal for the first grouping 360 and a combined timing signal for the second grouping 362.

[0059] In embodiments, determining the degree of synchronization 350 can include utilizing the farm controller 202 to establish a plurality of time slices 352. The farm controller 202 can then determine a standard deviation 354 for the timing signals 308 across the time slices. The standard deviation 354 can be indicative of the degree of synchronization 350 between the wind turbines 100. It should be appreciated that the lower the standard deviation 354, the greater the degree of synchronization 350 between the wind turbines 100, wherein the converse is also true.

[0060] In embodiments, the farm controller 202 can determine a difference between the degree of synchronization 350 and a synchronization threshold 358 at 356. The synchronization threshold 358 can correspond to the flicker threshold 326, such that an approach to the synchronization threshold 358 can be indicative of an approach to the flicker threshold 326 of the output flicker in the output of the wind farm 152. It should be appreciated that utilizing the degree of synchronization 350 to detect an approach to the flicker threshold 326 of the flicker level can obviate the requirement for monitoring the environmental parameter(s) 332 and / or the output of the wind farm 152 or can be employed in conjunction with the monitoring of the output and / or the environmental parameter(s) 332.

[0061] It should be appreciated that the various embodiments disclosed herein relating to the detection of the parameter(s) 302 indicative of output flicker, the generation of the command offset 310, and the changing of the operating parameter can be combined in various combinations and / or employed individually to facilitate the management of flicker in the output of the wind farm 152 by the system 300.

[0062] Moreover, those skilled in the art will appreciate the interchangeability of various features from different embodiments. Similarly, the various methods described herein can be mixed and matched by one of ordinary skill in the art to construct additional systems and techniques in accordance with the principles of the present disclosure. Of course, it is to be understood that not necessarily all objects or advantages described can be achieved in accordance with any particular embodiment described herein. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein can 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 can be taught or suggested herein.

[0063] This written description uses examples to disclose the application, including the best mode, and also to enable any person skilled in the art to practice the application, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the application is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to fall 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

[0064] Further aspects of the application are provided by the subject matter of the following clauses:

[0065] Clause 1. A method for managing output flicker of a wind farm connected to a power grid, the wind farm comprising a plurality of wind turbines, the method comprising: detecting, with a farm controller of the wind farm, at least one parameter of the wind farm indicative of output flicker caused by a synchronization of flicker from at least two wind turbines of the plurality of wind turbines, the output flicker occurring in the power grid; generating a command offset for at least one wind turbine of the at least two wind turbines upon detecting the at least one parameter; and changing an operating parameter of the at least one wind turbine based on the command offset so as to desynchronize the synchronization of flicker in output signals of the at least two wind turbines.

[0066] Clause 2. The method of claim 1, wherein generating the command offset comprises: generating a random bias value; and introducing the random bias value into a control loop of the at least one wind turbine.

[0067] Clause 3. The method of any preceding clause, wherein changing the operating parameter of the at least one wind turbine comprises: introducing the random bias value into a speed feedback loop of a turbine controller to produce a variable rotor speed for the at least one wind turbine.

[0068] Clause 4. The method of any preceding clause, wherein the wind farm further comprises at least one output sensor operably coupled to the farm controller at a point of interconnection with the power grid, and wherein detecting the at least one parameter indicative of output flicker further comprises: monitoring, via the at least one output sensor, a frequency and amplitude of variations in current or voltage at the output of the wind farm at the point of interconnection with the power grid, wherein the frequency and amplitude of variations are indicative of synchronous flicker; and detecting, with the farm controller, an approach of the output to a flicker threshold for the wind farm.

[0069] Clause 5. The method of any preceding clause, wherein the wind farm further comprises at least one environmental sensor operably coupled to the farm controller, and wherein detecting the at least one parameter indicative of output flicker further comprises: monitoring, via the at least one environmental sensor, at least one environmental parameter indicative of environmental conditions acting on the wind farm; and correlating, with the farm controller, the at least one environmental parameter to a level of output flicker as detected by the at least one output sensor under the monitored environmental conditions.

[0070] Clause 6. The method of any preceding clause, further comprising: determining, with the farm controller, an output flicker likelihood for the wind farm based at least in part on the correlation and the forecasted environmental conditions.

[0071] Clause 7. The method of any preceding clause, wherein generating the command offset further comprises generating the command offset when at least one of the output flicker likelihood or the output of the wind farm approaches or exceeds a flicker threshold for the wind farm.

[0072] Clause 8. The method of any preceding clause, further comprising: determining an impact on a level of output flicker resulting from changing the operating parameter of the at least one wind turbine based on the command offset; correlating, with the farm controller, the impact to environmental conditions acting on the wind farm; assigning a synchronicity-impact score to the at least one wind turbine based on the calculated correlation for the detected environmental conditions; and selecting the at least one wind turbine from the plurality of wind turbines to receive the command offset based at least in part on the synchronicity-impact score.

[0073] Clause 9. The method of any preceding clause, wherein detecting the at least one parameter indicative of output flicker further comprises:

[0074] receiving, with the farm controller, timing signals from the at least two wind turbines, the timing signals being indicative of rotor positions for each of the wind turbines; determining, with the farm controller, a degree of synchronicity between the at least two wind turbines of the plurality of wind turbines based on the respective timing signals; and determining, with the farm controller, a difference between the degree of synchronicity and a synchronicity threshold corresponding to a threshold for synchronous flicker.

[0075] Clause 10. The method of any preceding clause, wherein determining a degree of synchronicity between the at least two of the plurality of wind turbines further comprises: establishing a plurality of time slices with the farm controller; and determining a standard deviation for the timing signal across the time slices with the farm controller, wherein the standard deviation for the timing signal is indicative of the degree of synchronicity between the plurality of wind turbines.

[0076] Clause 11. The method of any preceding clause, wherein the at least two of the plurality of wind turbines comprise at least a first group of wind turbines and a second group of wind turbines, and wherein the respective timing signals are indicative of a timing of a combination of wind turbines comprising the first group and a timing of a combination of wind turbines comprising the second group of wind turbines.

[0077] Clause 12. The method of any preceding clause, wherein changing the operating parameter of the at least one wind turbine based on the command offset further comprises changing an operating parameter corresponding to at least one of a generator torque, a power output, a rotor speed, or a mechanical load of the wind turbine.

[0078] Clause 13. A system for managing output flicker generated by a wind farm, the system comprising: a plurality of wind turbines coupled to an electrical grid; and a farm controller communicatively coupled to the plurality of wind turbines and communicatively coupled to the electrical grid, the farm controller comprising at least one processor configured to perform a plurality of operations, the plurality of operations comprising: detecting at least one parameter of the wind farm indicative of synchronized flicker from at least two of the plurality of wind turbines, the synchronized flicker occurring in the electrical grid, generating a command offset for at least one of the at least two of the plurality of wind turbines upon detecting the at least one parameter, and changing an operating parameter of the at least one wind turbine based on the command offset so as to desynchronize the synchronized flicker in output signals of the at least two of the plurality of wind turbines.

[0079] Clause 14. The system of any preceding clause, wherein changing the operating parameter of the at least one wind turbine comprises: introducing a random bias value into a speed feedback loop of a turbine controller to produce a variable rotor speed for the at least one wind turbine.

[0080] Clause 15. The system of any preceding clause, wherein the wind farm further comprises at least one output sensor operably coupled to the farm controller at a point of interconnection with the power grid, and wherein detecting the at least one parameter indicative of output flicker further comprises: monitoring, via the at least one output sensor, a frequency and amplitude of a variation in current or voltage at the output of the wind farm at the point of interconnection with the power grid, wherein the frequency and amplitude of the variation is indicative of synchronous flicker; and detecting, with the farm controller, an approach of the output to a flicker threshold for the wind farm.

[0081] Clause 16. The system of any preceding clause, wherein the wind farm further comprises at least one environmental sensor operably coupled to the farm controller, and wherein detecting the at least one parameter indicative of output flicker further comprises: monitoring, via the at least one environmental sensor, at least one environmental parameter indicative of environmental conditions acting on the wind farm; and correlating, with the farm controller, the at least one environmental parameter to a level of output flicker as detected by the at least one output sensor under the monitored environmental conditions.

[0082] Clause 17. The system of any preceding clause, further comprising: determining an output flicker likelihood for the wind farm based at least in part on the correlation and the forecasted environmental conditions.

[0083] Clause 18. The system of any preceding clause, wherein generating the command offset further comprises generating the command offset when at least one of the output flicker likelihood for the wind farm or the output approaches or exceeds a flicker threshold for the wind farm.

[0084] Clause 19. The system of any preceding clause, further comprising: determining an impact on the level of output flicker resulting from changing the operating parameter of the at least one wind turbine based on the command offset; correlating the impact to environmental conditions acting on the wind farm; assigning a synchronicity-impact score to the at least one wind turbine based on the calculated correlation for the detected environmental conditions; and selecting the at least one wind turbine from the plurality of wind turbines to receive the command offset based at least in part on the synchronicity-impact score.

[0085] Clause 20. The system of any preceding clause, wherein detecting the at least one parameter indicative of output flicker further comprises: receiving timing signals from the at least two wind turbines, the timing signals being indicative of a rotor position for each of the wind turbines;

[0086] establishing a plurality of time slices; determining a standard deviation for the timing signals across the time slices, wherein the standard deviation for the timing signals is indicative of a degree of synchronicity between the at least two wind turbines; and determining a difference between the degree of synchronicity and a synchronicity threshold corresponding to the output flicker threshold.

Claims

1. A method for managing output flicker of a wind farm connected to a power grid, the wind farm comprising a plurality of wind turbines, the method comprising: detecting, with a farm controller of the wind farm, at least one parameter of the wind farm indicative of output flicker caused by a synchronization of flicker from at least two wind turbines of the plurality of wind turbines, the output flicker occurring in the power grid; upon detecting the at least one parameter, generating a command offset for at least one wind turbine of the at least two wind turbines; and changing an operating parameter of the at least one wind turbine based on the command offset so as to desynchronize the synchronization of flicker in output signals of the at least two wind turbines; wherein detecting the at least one parameter indicative of the output flicker further comprises: receiving, with the farm controller, timing signals from the at least two wind turbines, the timing signals indicative of a rotor position for each of the wind turbines; determining, with the farm controller, a degree of synchronization between the at least two wind turbines of the plurality of wind turbines based on the respective timing signals; and determining, with the farm controller, a difference between the degree of synchronization and a synchronization threshold corresponding to a threshold of synchronized flicker.

2. The method of claim 1, wherein, generating the command offset comprises: generating a random bias value; and introducing the random bias value into a control loop of at least one wind turbine.

3. The method of claim 2, wherein, changing the operating parameter of the at least one wind turbine comprises: introducing the random bias value into a speed feedback loop of a turbine controller to produce a variable rotor speed for the at least one wind turbine.

4. The method of claim 1, wherein, the wind farm further comprises at least one output sensor operably coupled to the farm controller at a point of interconnection with the power grid, and wherein detecting the at least one parameter indicative of output flicker further comprises: monitoring, via the at least one output sensor, a frequency and amplitude of a change in a current or voltage of an output of the wind farm at the point of interconnection with the power grid, wherein the frequency and amplitude of the change is indicative of the synchronization of flicker; and detecting, with the farm controller, an approach of the output to a flicker threshold for the wind farm.

5. The method of claim 4, wherein, the wind farm further comprises at least one environmental sensor operably coupled to the farm controller, and wherein detecting the at least one parameter indicative of the output flicker further comprises: monitoring, via the at least one environmental sensor, at least one environmental parameter indicative of environmental conditions acting on the wind farm; and correlating, with the farm controller, the at least one environmental parameter to an output flicker level detected by the at least one output sensor under the monitored environmental conditions.

6. The method of claim 5, wherein, the method further comprises: determining, with the farm controller, an output flicker likelihood for the wind farm based at least in part on the correlation and a forecasted environmental condition.

7. The method of claim 6, wherein, Generating the command offset further includes generating the command offset when at least one of the output flicker potential or the output of the wind farm approaches or exceeds the flicker threshold for the wind farm.

8. The method of claim 5, wherein, The method further includes: determining an effect on a level of the output flicker resulting from changing the operating parameter of the at least one wind turbine based on the command offset; correlating, with the field controller, the effect with the environmental conditions acting on the wind farm; assigning a synchronicity-effect score to the at least one wind turbine based on the established correlation for the detected environmental conditions; and selecting the at least one wind turbine from the plurality of wind turbines to receive the command offset based at least in part on the synchronicity-effect score.

9. The method of claim 1, wherein, Determining the degree of synchronicity between the at least two of the plurality of wind turbines further includes: establishing, with the field controller, a plurality of time slices; and determining, with the field controller, a standard deviation for the timing signals across the time slices, wherein the standard deviation for the timing signals is indicative of the degree of synchronicity between the plurality of wind turbines.

10. The method of claim 1, wherein, The at least two of the plurality of wind turbines include at least a first grouping of wind turbines and a second grouping of wind turbines, and wherein the respective timing signals are indicative of a combined timing of the wind turbines of the first grouping and a combined timing of the wind turbines of the second grouping.

11. The method of claim 1, wherein, Changing the operating parameter of the at least one wind turbine based on the command offset further includes changing the operating parameter corresponding to at least one of a generator torque, a power output, a rotor speed, or a mechanical load of the wind turbine.

12. A system for managing output flicker generated by a wind farm, the system comprising: a plurality of wind turbines coupled to an electrical grid; and a field controller communicatively coupled to the plurality of wind turbines and communicatively coupled to the electrical grid, the field controller including at least one processor configured to perform a plurality of operations, the plurality of operations including: detecting at least one parameter of the wind farm indicative of synchronous flicker from at least two of the plurality of wind turbines, the synchronous flicker occurring in the electrical grid, upon detecting the at least one parameter, generating a command offset for at least one of the at least two wind turbines, and changing an operating parameter of the at least one wind turbine based on the command offset in order to desynchronize the synchronous flicker in output signals of the at least two wind turbines; wherein detecting the at least one parameter indicative of the output flicker further includes: receiving, with the field controller, timing signals from the at least two wind turbines, the timing signals being indicative of a rotor position for each of the wind turbines; determining, with the field controller, a degree of synchronicity between the at least two of the plurality of wind turbines based on the respective timing signals; and determining, with the farm controller, a difference between the degree of synchronization and a threshold of synchronization corresponding to a flicker threshold.

13. The system of claim 12, wherein, varying the operating parameter of the at least one wind turbine includes: introducing a random bias value into a speed feedback loop of a turbine controller to produce a variable rotor speed for the at least one wind turbine.

14. The system of claim 12, wherein, the wind farm further includes at least one output sensor operably coupled to the farm controller at a point of interconnection with the power grid, and wherein detecting the at least one parameter indicative of the output flicker further includes: monitoring, via the at least one output sensor, a frequency and amplitude of a change in current or voltage at the output of the wind farm at the point of interconnection with the power grid, wherein the frequency and amplitude of the change is indicative of the synchronized flicker; and detecting, with the farm controller, an approach of the output to a flicker threshold for the wind farm.

15. The system of claim 14, wherein, the wind farm further includes at least one environmental sensor operably coupled to the farm controller, and wherein detecting the at least one parameter indicative of the output flicker further includes: monitoring, via the at least one environmental sensor, at least one environmental parameter indicative of environmental conditions acting on the wind farm; and correlating, with the farm controller, the at least one environmental parameter to an output flicker level detected by the at least one output sensor under the monitored environmental conditions.

16. The system of claim 15, wherein, the system further includes: determining an output flicker likelihood for the wind farm based at least in part on the correlation and the forecasted environmental conditions.

17. The system of claim 16, wherein, generating the command offset further includes generating the command offset when at least one of the output flicker likelihood or the output of the wind farm approaches or exceeds the flicker threshold for the wind farm.

18. The system of claim 15, wherein, the system further includes: determining an effect on the output flicker level resulting from varying the operating parameter of the at least one wind turbine based on the command offset; correlating the effect to the environmental conditions acting on the wind farm; assigning a synchronization-impact score to the at least one wind turbine based on the established correlation for the detected environmental conditions; and selecting the at least one wind turbine from the plurality of wind turbines to receive the command offset based at least in part on the synchronization-impact score.

19. The system of claim 12, wherein, determining the degree of synchronization between the at least two wind turbines of the plurality of wind turbines further includes: establishing, with the farm controller, a plurality of time slices; and determining, with the farm controller, a standard deviation for the timing signal across the time slices, wherein the standard deviation for the timing signal is indicative of the degree of synchronization between the plurality of wind turbines. determining the degree of synchronization between the at least two wind turbines of the plurality of wind turbines further includes: establishing, with the farm controller, a plurality of time slices; and determining, with the farm controller, a standard deviation for the timing signal across the time slices, wherein the standard deviation for the timing signal is indicative of the degree of synchronization between the plurality of wind turbines.

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