Patent Description:
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades are the primary elements for converting wind energy into electrical energy. The blades typically have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between its sides. Consequently, a lift force, which is directed from the pressure side towards the suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is connected to a generator for producing electricity.

Typically, wind turbines are designed to operate at a fixed nominal power output over a predetermined or anticipated operating life. For instance, a typical wind turbine is designed for a <NUM>-year life. However, in many instances, this anticipated overall operating life is limited or based on the anticipated fatigue life of one or more of the wind turbine components. The life consumption or operational usage of the wind turbine (which can include fatigue or extreme loads, wear, and/or other life parameters) as used herein generally refers to the life of the wind turbine or its components that has been consumed or exhausted by previous operation. Thus, for conventional wind turbines, various preventative maintenance actions are generally scheduled at predetermined time intervals over the life of the wind turbine to prevent accelerated life consumption that may occur if such maintenance actions were not performed.

However, the cost and associated downtime of such maintenance actions are significant drivers for the overall lifecycle cost of the wind turbine and should therefore be optimized. In addition, wind turbines with higher operational usage may be under-maintained and more at risk for unplanned poor-quality events. Similarly, wind turbines with lower operational usage may over-maintained.

As an example, wind turbine components (such as the rotor blades, tower, pitch bearings, gearbox, etc.) have physics-based life models that are used during design and siting phases to ensure that the component(s) can survive the anticipated lifetime operation. Such a model uses input parameters specific to the component and specific lifetime load histograms determined through simulation of a lifetime of operation. As such, the model is designed to capture the complex and non-linear mechanism by which these loads act upon and damage the physical materials of the component. The model can then output a measure of damage or reliability (failure probability) predicted over the turbine lifetime.

The model output can then be compared to a threshold to determine whether the damage output is acceptable to operate the wind turbine as planned. Generally, the threshold accounts for material strength, acceptable risk, and possible reduction factors to account for uncertainty in aspects of simulation and modeling. If the model output is less than the threshold, turbine operation is deemed safe and acceptable. With such models, the threshold for acceptable operation on the model output can be converted to a damage threshold on damage, which the model also produces.

Moreover, wind turbines are simulated to determine suitability for a specific application. The complex simulation covers aero-elastic mechanical behavior of the entire wind turbine, under control, and in wind conditions anticipated for the turbine design lifetime. These simulations directly produce the loads data needed to create the loads histograms used by the component life models.

Thus, an improved system and method for operating wind turbines, e.g., actual operational data, would be welcomed in the art. Accordingly, the present disclosure is directed to systems and methods for operating a wind turbine using cumulative load histograms based on actual operation thereof rather than simulated data. <CIT> describes a method of operating a wind turbine. The wind turbine is operated over an operating period in accordance with a control strategy. A sensor signal is received over the operating period from a sensor measuring an operational parameter of the turbine. A model is used to obtain a modelled fatigue value based on the sensor signal. The modelled fatigue value provides an estimate of fatigue loading applied to a component of the turbine over the operating period. The control strategy is modified based on the modelled fatigue value. <CIT> describes a method of operating at least one wind turbine is described, including: determining a plurality of stress events of at least one component of the at least one wind turbine; determining at least one accumulated stress from at least two of the plurality of stress events; determining at least one residual lifetime based at least partially on the at least one accumulated stress. <CIT> describes using a tower damping system to reduce oscillations in a wind turbine. To do so, the dampening system may use a metric that is decoupled from the activation strategy in order to control the blade pitch and avoid or mitigate feedback loops. In one embodiment, the dampening system measures a force on the turbine that is correlated to a fatigue loading on the tower. Furthermore, the turbine may perform a calculation to decouple the force from the activation strategy. That is, the turbine determines the value of the force as if the damping system was not activated or present. In addition, the dampening system uses the current wind speed and a wind distribution to generate a pitch reference value. The dampening system may use both the pitch reference value and the fatigue loading on the tower to reduce the tower oscillations. <CIT> describes a wind turbine power plant including a plurality of wind turbines, each having a rated output and under the control of a power plant controller. The power plant also has a rated output which may be over-rated in response to one or more electricity pricing data, power plant age and operator demand. This may comprise a schedule of output set point changes which effect seasonal or intraday changes in electricity prices or which reflect aging of the power plant. It may also reflect the price of electricity on spot or futures markets. Once the over-rating of the power plant has been set, the output may be increased by over-rating individual turbines or operating turbines at rated power if the sum of the rated outputs of the turbines exceeds or is equal to the new power plant output set point. <CIT> describes a method of generating a control schedule for a wind turbine is provided, the control schedule indicating how the turbine maximum power level varies over time, the method comprising: determining a value indicative of the current remaining fatigue lifetime of the turbine, or one or more turbine components, based on measured wind turbine site and/or operating data; applying an optimisation function that varies an initial control schedule to determine an optimised control schedule by varying the trade off between energy capture and fatigue life consumed by the turbine or the one or more turbine components until an optimised control schedule is determined, the optimisation including: estimating future fatigue lifetime consumed by the turbine or turbine component over the duration of the varied control schedule based on the current remaining fatigue lifetime and the varied control schedule; and constraining the optimisation of the control schedule according to one or more input constraints; wherein the input constraints include a target minimum wind turbine lifetime and the optimisation further includes varying an initial value for the number of component replacements, for one or more components, to be performed over the course of the schedule to determine a maximum number of component replacements.

In one aspect, the present disclosure is directed to a method for operating a wind turbine. The method includes determining one or more loading and travel metrics or functions thereof for one or more components of the wind turbine during operation of the wind turbine. The method also includes generating, at least in part, at least one distribution of cumulative loading data for the one or more components using the one or more loading and travel metrics during operation of the wind turbine. Further, the method includes applying a life model, such as a physics-based model, a statistics model, or combinations thereof, of the one or more components to the at least one distribution of cumulative loading data to determine an actual damage accumulation for the one or more components of the wind turbine to date. Moreover, the method includes implementing a corrective action for the wind turbine based on the damage accumulation.

In an embodiment, the loading metrics for one or more components of the wind turbine may include, for example, a bearing load, a tower load, a rotor blade load, a drivetrain load, a shaft load, a thermal load. In another embodiment, the travel metrics may include, for example, time, angular travel, a number of times a component starts up and shuts down, a number of times a component travels a certain angular distance between directional reversals, or a number of times the one or more components go through a stress cycle at a particular load.

In further embodiments, the component(s) may include, for example, a pitch bearing, a yaw bearing, a tower, a gearbox, a generator, a rotor blade, a rotor, a hub, a shaft, a converter, a fan, or a nacelle, or any sub-component of these major components.

In additional embodiments, the functions of the one or more loading and travel metrics may include a mean, a minimum, a maximum, a standard deviation, a median, a quantile, or similar.

In several embodiments, determining the one or more loading and travel metrics for one or more components of the wind turbine during operation of the wind turbine may include measuring the one or more loading and travel metrics for one or more components of the wind turbine via one or more sensors or processors or estimating the one or more loading and travel metrics for one or more components of the wind turbine via the one or more processors.

In another embodiment, the method may include estimating the one or more loading and travel metrics for one or more components of the wind turbine in real-time. In particular embodiments, the method may further include estimating the one or more loading and travel metrics for one or more components of the wind turbine using machine learning.

In an embodiment, the processor may include a physics-based system model for estimating the one or more loading and travel metrics for one or more components of the wind turbine.

In certain embodiments, the method may include determining a plurality of loading and travel metrics for one or more components of the wind turbine during operation of the wind turbine.

According to the invention, generating, at least in part, at least one distribution of cumulative loading data for the one or more components using the one or more loading and travel metrics during operation of the wind turbine may include generating, at least in part, at least one cumulative load histogram for the one or more components using the one or more loading and travel metrics. As opposed to storing time-series data, for example, the use of histograms is beneficial because the storage requirements do not significantly increase with time. As used herein, a distribution generally refers to any data structure, such as a histogram, data binning, or hashing, that can accumulate and represent the frequency and/or counts of numerical data.

Furthermore, generating the at least one cumulative load histogram for the one or more components using the one or more loading and travel metrics may include defining a range and bin regions of the at least one cumulative load histogram, defining a first loading metric of the plurality of loading metrics and a first travel metric of the plurality of travel metrics for the at least one cumulative load histogram, and during operation of the wind turbine, populating the at least one cumulative load histogram using the first loading and travel metrics by adding the first loading and travel metrics to the bin regions of the cumulative load histogram(s).

According to the invention, the method also includes adaptively changing at least one of the range or the bin regions based on on-going operational data of the wind turbine.

In additional embodiments, the method may include applying a life or damage model of the component(s) to a plurality of cumulative load histograms collected over distinct time segments.

In still further embodiments, the method may include processing the cumulative load histogram(s) before applying the life or damage model of the component(s).

In several embodiments, processing the cumulative load histogram(s) before applying the life model of the component(s) may include at least one of re-defining the range or bin regions of the cumulative load histogram(s), smoothing or recalibrating the cumulative load histogram(s) to yield a more accurate estimate of historical loading estimates, or scaling the cumulative load histogram(s) to a desired time duration expected by the life model.

In particular embodiments, implementing the corrective action for the wind turbine based on the damage accumulation may include shutting down the wind turbine, idling the wind turbine, changing a power output, torque, speed, or other control parameter of the wind turbine, and/or scheduling one or more preventative maintenance actions.

In another aspect, the present disclosure is directed to a system for operating a wind turbine. The system includes a controller configured to implement a plurality of operations, including but not limited to determining one or more loading and travel metrics or functions thereof for one or more components of the wind turbine during operation of the wind turbine, generating, at least in part, at least one cumulative load histogram for the one or more components using the one or more loading and travel metrics, applying a life or damage model of the one or more components to the at least one distribution of cumulative loading data to determine an actual damage accumulation for the one or more components of the wind turbine to date, and implementing a corrective action for the wind turbine based on the damage accumulation.

It should be understood that the system may further be configured to with any of the features described herein.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, explain the principles of the invention.

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which refers to the appended figures, in which:.

In general, the present disclosure is directed odometer-based supervisory control of a wind turbine. For example, in an embodiment, as the wind turbine operates, cumulative damage done to turbine components with respect to their failure modes can be estimated and tracked, e.g., using fatigue/damage odometers. Supervisory control adjusts the operation of the wind turbine to achieve a long-term operational goal. The operational goal may be to maximize energy or revenue production while keeping extreme loads and cumulative damage metrics within limits. Alternatively, the operational goal may be to minimize one or more cumulative damage metrics while keeping extreme loads and other cumulative damage metrics within limits. Such fatigue/damage odometers may be developed, for example, using histograms that are populated with actual operational data of the wind turbine.

The present disclosure provides many advantages not present in the prior art. For example, the use of histograms is beneficial because the storage requirements do not significantly increase with time. Moreover, the present disclosure may be implemented within the turbine controller hardware, on a different computer within or at the wind turbine site, or on a network-connected computer elsewhere at the wind farm or other nearby or remote location. Furthermore, the present disclosure can utilize readily-available/already-existing operational data and is not necessarily required to collect new or additional data (although new or additional sensors may be utilized if desired). Further, the present disclosure can be applied to any wind turbine, regardless of model, design, size, or manufacturer. Furthermore, the system and method of the present disclosure enables mechanical design and load margins to be fully utilized for each wind turbine, based upon how each turbine is actually operated and the conditions a particular turbine actually experiences.

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

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

Accordingly, the controller <NUM> may generally be configured to control the various operating modes of the wind turbine <NUM> (e.g., start-up or shut-down sequences), adjust control parameters of the wind turbine <NUM> to alter power production, and/or control various components of the wind turbine <NUM>. For example, the controller <NUM> may be configured to control the blade pitch or pitch angle of each of the rotor blades <NUM> (i.e., an angle that determines a perspective of the rotor blades <NUM> with respect to the direction of the wind) to control the power output generated by the wind turbine <NUM> by adjusting an angular position of at least one rotor blade <NUM> relative to the wind. For instance, the controller <NUM> may control the pitch angle of the rotor blades <NUM> by rotating the rotor blades <NUM> about a pitch axis <NUM>, either individually or simultaneously, by transmitting suitable control signals to a pitch drive or pitch adjustment mechanism (not shown) of the wind turbine <NUM>.

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

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

Referring now to <FIG>, a block diagram of one embodiment of suitable components that may be included within a controller in accordance with aspects of the present disclosure is illustrated. It should be understood that the various components of the controller of <FIG> may be applicable to any suitable controller, including for example, the turbine controller <NUM>, the farm-level controller <NUM>, and/or the supervisory controller <NUM> described herein.

As shown, the controller may include one or more processor(s) <NUM> and associated memory device(s) <NUM> configured to perform a variety of computerimplemented functions (e.g., performing the methods, steps, calculations and the like disclosed herein). As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) <NUM> may generally comprise memory element(s) including, but are not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements.

Additionally, the controller may also include a communications module <NUM> to facilitate communications between the controller and the various components of the wind turbine <NUM>. For instance, the communications module <NUM> may include a sensor interface <NUM> (e.g., one or more analog-to-digital converters) to permit the signals transmitted by one or more sensors <NUM>, <NUM>, <NUM> to be converted into signals that can be understood and processed by the controller. It should be appreciated that the sensors <NUM>, <NUM>, <NUM> may be communicatively coupled to the communications module <NUM> using any suitable means. For example, as shown in <FIG>, the sensors <NUM>, <NUM>, <NUM> are coupled to the sensor interface <NUM> via a wired connection. However, in other embodiments, the sensors <NUM>, <NUM>, <NUM> may be coupled to the sensor interface <NUM> via a wireless connection, such as by using any suitable wireless communications protocol known in the art. As such, the processor <NUM> may be configured to receive one or more signals from the sensors <NUM>, <NUM>, <NUM>.

The sensors <NUM>, <NUM>, <NUM> of the wind turbine <NUM> may be any suitable sensors configured to measure any operational condition and/or wind parameter at or near the wind turbine. For example, the sensors <NUM>, <NUM>, <NUM> may include blade sensors for measuring a pitch angle of one of the rotor blades <NUM> or for measuring a loading acting on one of the rotor blades <NUM>; generator sensors for monitoring the generator (e.g., torque, rotational speed, acceleration and/or the power output); and/or various wind sensors for measuring various wind parameters. In addition, the sensors <NUM>, <NUM>, <NUM> may be located near the ground of the wind turbine, on the nacelle, or on a meteorological mast near the wind turbine.

It should also be understood that any other number or type of sensors may be employed and at any location. For example, the sensors may be analog sensors, digital sensors, optical/visual sensors, accelerometers, pressure sensors, angle of attack sensors, vibration sensors, MIMU sensors, fiber optic systems, temperature sensors, wind sensors, Sonic Detection and Ranging (SODAR) sensors, infra lasers, Light Detecting and Ranging (LIDAR) sensors, radiometers, pitot tubes, rawinsondes, and/or any other suitable sensors. It should be appreciated that, as used herein, the term "monitor" and variations thereof indicate that the various sensors of the wind turbine may be configured to provide a direct measurement of the parameters being monitored or an indirect measurement of such parameters. Thus, the sensors <NUM>, <NUM>, <NUM> may, for example, be used to generate signals relating to the parameter being monitored, which can then be utilized by the controller to determine the actual condition.

As mentioned, the processor(s) <NUM> is configured to perform any of the steps of the methods according to the present disclosure. For example, the processor <NUM> may be configured to determine the operational usage for the wind turbine <NUM>. As used herein, "operational usage" generally refers to the number of operating seconds, minutes, hours, or similar that the wind turbine <NUM> and or its various components has operated at various operational parameters and/or under certain conditions. Such operational parameters that may be considered or tracked may include, for example, one or more of the following: power output, torque, pitch angle, a loading condition, generator speed, rotor speed, wind direction, air density, turbulence intensity, wind gusts, wind shear, wind speed, wind upflow, an amount of yawing, an amount of pitching, or temperature. Moreover, the operational data may include sensor data, historical wind turbine operational data, historical wind farm operational data, historical maintenance data, historical quality issues, or combinations thereof. Thus, the processor <NUM> may also be configured to record and store the operational usage in the memory store <NUM> for later use. For example, the processor <NUM> may store the operational usage in one or more look-up tables (LUTs). Moreover, the operational usage may be stored in the cloud.

Referring now to <FIG>, the system and method as described herein may also be combined with a wind farm controller <NUM> of a wind farm <NUM>. As shown, the wind farm <NUM> may include a plurality of wind turbines <NUM>, including the wind turbine <NUM> described above. For example, as shown in the illustrated embodiment, the wind farm <NUM> includes twelve wind turbines, including wind turbine <NUM>. However, in other embodiments, the wind farm <NUM> may include any other number of wind turbines, such as less than twelve wind turbines or greater than twelve wind turbines. In one embodiment, the controller <NUM> of wind turbine <NUM> may be communicatively coupled to the farm controller <NUM> through a wired connection, such as by connecting the controller <NUM> through suitable communicative links <NUM> (e.g., a suitable cable). Alternatively, the controller <NUM> may be communicatively coupled to the farm controller <NUM> through a wireless connection, such as by using any suitable wireless communications protocol known in the art.

In several embodiments, one or more of the wind turbines <NUM> in the wind farm <NUM> may include a plurality of sensors for monitoring various operating parameters/conditions of the wind turbines <NUM>. For example, as shown, one of the wind turbines <NUM> includes a wind sensor <NUM>, such as an anemometer or any other suitable device, configured for measuring wind speeds. As is generally understood, wind speeds may vary significantly across a wind farm <NUM>. Thus, the wind sensor(s) <NUM> may allow for the local wind speed at each wind turbine <NUM> to be monitored. In addition, the wind turbine <NUM> may also include an additional sensor <NUM>. For instance, the sensors <NUM> may be configured to monitor electrical properties of the output of the generator of each wind turbine <NUM>, such as current sensors, voltage sensors, temperature sensors, or power monitors that monitor power output directly based on current and voltage measurements. Alternatively, the sensors <NUM> may comprise any other sensors that may be utilized to monitor the power output of a wind turbine <NUM>. It should also be understood that the wind turbines <NUM> in the wind farm <NUM> may include any other suitable sensor known in the art for measuring and/or monitoring wind conditions and/or wind turbine conditions.

Referring now to <FIG>, various features of multiple embodiments of an odometer-based control (OBC) system <NUM> and method <NUM> for operating a wind turbine, such as wind turbine <NUM>, are presented in accordance with aspects of the present disclosure. More specifically, <FIG> illustrates a block diagram of one embodiment of system <NUM> for controlling the wind turbine <NUM> according to the present disclosure. For example, as shown, the OBC system <NUM> includes the turbine controller <NUM> and a supervisory controller <NUM> communicatively coupled to the turbine controller <NUM>. In particular, as shown, the turbine controller <NUM> may be part of an inner control loop <NUM> that includes the wind turbine control system. In such embodiments, the wind turbine <NUM> may include one or more sensors read by the turbine controller <NUM>, such as electrical components and accelerometers. Thus, the turbine controller <NUM> is configured to send control signals to actuators, such as blade pitch and nacelle yaw motors. The actuators affect turbine dynamic behavior. Therefore, the turbine controller <NUM> is configured to operate the wind turbine <NUM> to generate power while preventing undesired or damaging behavior. Moreover, the turbine controller <NUM> can have many operational parameters that may be set to alter or tune the turbine performance. The operational parameters are usually unchanged or changed in an ad hoc fashion during turbine operation, however, as will be described herein, the OBC system <NUM> can modify some of these parameters using an optimized policy or control function <NUM>, as described herein below. Such operational parameters may include, for example, torque setpoint, speed setpoint, thrust limit, and/or parameters controlling when active pitching for rotor imbalance control is enabled. Moreover, the turbine controller <NUM> is configured to determine a state estimate <NUM> of the wind turbine <NUM>, which is explained in more detail herein below.

Still referring to <FIG>, the supervisory controller <NUM> may include a middle control loop <NUM> and an outer control loop <NUM>. The middle control loop <NUM>, or supervisory parameter control loop, is configured to improve turbine control and performance by changing turbine controller operational parameters based on estimates of the conditions, such as the wind or grid conditions. In particular, as shown, the middle control loop <NUM> may include a condition estimator module <NUM>, a dynamic function module <NUM>, one or more damage odometers <NUM>, and a power estimator module <NUM>.

Thus, in certain embodiments, the condition estimator module <NUM> is configured to estimate or predict the values of the condition parameters described herein based upon the state estimate <NUM>, and possibly also external measurements. These condition parameters are generally referred to collectively herein as a current condition <NUM>. In other words, the current condition <NUM> generally refers to the current estimate or prediction of the condition parameters in the condition parameter set, which are described herein in more detail below.

In addition, as shown, the damage odometer(s) <NUM> are configured to estimate damage levels of the various wind turbine components as a function of the state estimate <NUM> of the wind turbine <NUM>. In general, each of the damage levels corresponds to a specific component and specific failure mode for that component. As such, the value of the damage level represents cumulative damage. Examples include blade root fatigue, tower base fatigue, and pitch bearing fatigue, though any number of damage levels may be generated and considered. In wind turbine design and siting, damage (generally fatigue) limits are often established to ensure safe and reliable operation. Thus, these limits can be based on damage models for the specific construction materials, manufacturing quality, and stress cycle counting and Goodman or similar damage curves.

Furthermore, the damage odometer(s) described herein may utilize the history of the state estimates from the turbine controller <NUM>, and models of the wind turbine <NUM> and its components to determine damage done to the turbine based on its actual operation over its elapsed lifetime. Accordingly, the damage level for each component in the damage level set can be determined. In certain embodiments, there may be different damage odometers for different parts of the wind turbine <NUM>, and there can be multiple damage odometers for a single part or component of the wind turbine <NUM>, each associated with a different failure mode or wear mechanism. For example, many damage odometers are associated with crack propagation and fatigue failure modes of structural materials. In certain embodiments, damage odometers may be implemented based on the state estimate <NUM> from the turbine controller <NUM>, where the state estimate includes instantaneous loads and forces on the wind turbine <NUM>. In alternative embodiments, the damage odometers may also be based upon special sensors such as strain gauges (not shown). Moreover, in addition to damage levels, the damage odometers may produce an uncertainty level for each damage parameter that can be used by the function design module <NUM>.

In further embodiments, damage assessment may utilize a fusion of damage odometers with a validated diagnostic algorithm, based on real-time operating signals or condition monitoring system. For example, if the pitch motor internal signals or generator acceleration signals suggest an abnormal operation, damage assessment would be high even if odometer reads low. Thus, the OBC system <NUM> may use both to assess real-time damage when addressing same failure mode.

In addition, in an embodiment, the power estimator module <NUM> is configured to computer statistics of the power production of the wind turbine <NUM>. In certain embodiments, this computation will simply be the cumulative energy produced but may also include other cumulative statistics or statistics computed for each dynamic control interval. Accordingly, the power statistics <NUM> may be used to externally evaluate turbine performance, or to learn the power production performance of the wind turbine <NUM>.

Still referring to <FIG>, the current condition <NUM> from the condition estimator module <NUM> can then be used by the dynamic function module <NUM> to set operational parameters for the next time dynamic control interval. The condition estimator module <NUM> may also simply produce an estimate of the current condition parameters (not a prediction). If the dynamic control interval is relatively short, such as <NUM> seconds or one minute, this can be adequate. The condition estimator module <NUM> may also produce a prediction of condition parameters for the next time dynamic control interval. Predicting the future values of the condition parameters becomes more desirable when the dynamic control interval is longer.

Accordingly, the dynamic function module <NUM> is configured to change the operational parameters for the turbine controller <NUM>, depending on the current condition <NUM>. In certain embodiments, the dynamic function module <NUM> may include a lookup operation where the current condition is received and used to determine the operational parameters from the policy table. Thus, in certain embodiments, the dynamic function module <NUM> changes the operational parameters each dynamic control interval. As used herein, the dynamic control interval generally refers to the time duration for which the dynamic function module <NUM> sets the operational parameters.

Moreover, in particular embodiments, the outer control loop <NUM>, or odometer-based control loop, further includes a function design module <NUM> for generating a policy or control function <NUM>. Further, the function design module <NUM> is also configured to update the control function <NUM>, based on the current fatigue damage state, expected future conditions, a system model of the turbine, planned operation horizon, and possibly expected future value of produced electricity.

In an embodiment, for example, the control function <NUM> defines a relationship of the set of condition parameters with a plurality of operational parameters of the wind turbine <NUM>. More particularly, the control function <NUM> may be a mapping from condition parameters in the condition parameter set to operational parameters in the operational parameter set that is essentially executed by the dynamic function module <NUM>. Thus, in an embodiment, the control function <NUM> may be a look up table, an interpolated function, or have any other functional form. In one embodiment, the control function <NUM> may be a constant policy, whereby the operational parameters are the same for any values of the condition parameters. This is equivalent to not having a middle loop. Another simple example of the control function <NUM> is one that stipulates a higher rated torque (for more power) when air density is below a threshold and wind speed is less than <NUM>/s. But in general, the control function <NUM> is an arbitrary function of the current condition <NUM>, may be complex. Thus, in many embodiments, the control function <NUM> may be determined by an optimization process in the function design module <NUM> block.

Furthermore, in certain embodiments, the control function <NUM> may be defined for discrete values of the condition parameters, and the current condition <NUM> may be continuous. In this case, the dynamic function module <NUM> may select the closest entry in the control function <NUM> from the current condition <NUM> to determine the operational parameters, or the dynamic function module <NUM> may interpolate the operational parameters. As such, the dynamic function module <NUM> receives the control function <NUM> from the function design module <NUM>. Moreover, the dynamic function module <NUM> determines and sends operational parameters to the turbine controller <NUM> to dynamically control the wind turbine <NUM> based on the current condition <NUM> and the control function <NUM> for multiple dynamic control intervals.

Still referring to <FIG>, the function design module <NUM> is configured to determine the control function <NUM> through an optimization process, for example, using a condition distribution <NUM>, a model <NUM> of operational behavior of the wind turbine <NUM>, a design lifetime <NUM> of the wind turbine <NUM> (e.g., the total time over which the wind turbine <NUM> is planned to operate), an elapsed lifetime <NUM> of the wind turbine <NUM> (e.g., the amount of time during the design lifetime for which the wind turbine <NUM> has operated thus far), one or more damage limits <NUM>, the one or more damage levels <NUM> (e.g. from the damage odometers), or a future value discount <NUM> (e.g. the value of money in the future for value optimization). Such information represents the current state of the wind turbine <NUM> and the expected future conditions the wind turbine <NUM> will experience and a model of its operational behavior. Given these inputs there are a variety of optimization methods that may be used to produce the control function <NUM>.

As used herein, the condition distribution generally refers to the expected future distribution of condition parameters in the condition parameter set. In one embodiment, for example, the condition distribution is a joint probabilistic distribution of the condition parameters. Thus, in an embodiment, if the condition parameter set consists of wind speed and turbulence intensity, the condition distribution may be a joint distribution of these two values. For practical reasons, the condition distribution may be instead independent distributions of each condition parameter, or some condition parameters may be assumed constant.

In certain embodiments, the condition distribution may be established for a wind turbine and wind farm before commission using, for example, met mast data. Furthermore, the condition distribution may be fixed and unchanging, or it may be adaptively learned and updated over time, as the wind turbine <NUM> operates.

In another embodiment, the model <NUM> of operational behavior of the wind turbine <NUM> may include a table of Condition parameters, Operational parameters, Power, and/or Damage (referred to herein as a COPD table <NUM>), i.e., a model of power produced, and damage done to the wind turbine <NUM>, depending on condition parameters and/or operational parameters. Therefore, in such embodiments, the model <NUM> may be a representation of the turbine operational behavior that models aspects of the turbine system response needed by the OBC system <NUM>. In one embodiment, for example, the model may be a mapping from the condition parameters and the operational parameters to the expected power statistics <NUM> the wind turbine <NUM> will produce, and the expected increment to the damage values done to turbine components in a dynamic control interval. In other words, if wind and grid conditions are known and the operational parameters to be selected are known, then the model/table provides how much power the wind turbine <NUM> will produce and how much damage the wind turbine <NUM> will accumulate during one dynamic control interval. In such embodiments, the expected power statistics <NUM> of the wind turbine <NUM> may include power production, power factor, power stability of the wind turbine <NUM>, or similar.

There are several ways in which the model of operational behavior of the wind turbine <NUM> may be determined. For example, in one embodiment, the model of operational behavior of the wind turbine <NUM> can be determined using a simulation of the wind turbine <NUM>, a design of experiments (DOE) process carried out by the wind turbine <NUM>, adaptive learning as the wind turbine <NUM> operates, and/or combinations thereof.

Furthermore, in an embodiment, the function design module <NUM> is configured to use the design lifetime duration when designing the control function <NUM> to ensure that the expected damage done in the design lifetime is within the damage limits. It should be understood that the OBC system <NUM> can be used with newly installed wind turbines as well as an upgrade to existing wind turbines. Therefore, the design lifetime and the damage limits may be scaled appropriately.

In additional embodiments, the future value discount generally refers to the discount applied to revenue and optionally to the negative value of expense at times in the future. This may be represented simply as a discount rate. The future value discount may also more generally be represented as a specific discount for revenue and expense at future points in time. The future value discount may optionally be used by the function design module <NUM> to optimize value, especially in terms of net present value.

Referring now to <FIG>, a flow diagram of one embodiment of the method <NUM> for operating a wind turbine is illustrated in accordance with aspects of the present disclosure. In particular embodiments, for example, the method <NUM> can be used to generate one or more of the damage odometers <NUM> described herein. The method <NUM> is described herein as implemented using, for example, at least one of the wind turbines <NUM> of the wind farm <NUM> described above, such as wind turbine <NUM>. However, it should be appreciated that the disclosed method <NUM> may be implemented using any other suitable wind turbine now known or later developed in the art. In addition, although <FIG> depicts steps performed in a particular order for purposes of illustration and discussion, the methods described herein are not limited to any order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods can be omitted, rearranged, combined and/or adapted in various ways.

As shown at (<NUM>), the method <NUM> includes determining and travel metrics or functions thereof for one or more components of the wind turbine <NUM> during operation of the wind turbine <NUM>. For example, in one embodiment, the method <NUM> may include collecting loading and travel metrics measurements from one or more sensors, such as a strain gauge or similar sensor. In alternative embodiments, the method <NUM> may include estimating the loading and travel metrics, e.g., via a processor. In particular embodiments, the processor may include a physics-based loads estimators as part of the control system. Such estimators are configured to produce real-time estimates of the loading and travel metrics that are required by component life models. In further embodiments, the loads may also be estimated by a heuristic or machine learning trained function. Thus, the measured or estimated loading and travel metrics reflect the actual operation of the wind turbine <NUM> rather than the pre-commission assumed operation. Accordingly, the present disclosure can eliminate or significantly reduce the modeling error in the simulation.

If the loading metric(s) are obtained from a control-oriented estimator, a smoothing step can be performed to refine the loading metric(s). In such embodiments, a smoother retrospectively improves estimator performance using later observations. An example of smoother is Kalman smoothing, which is the backward version of Kalman filtering. Smoothing can be particularly helpful in the case of missing data or estimator reset.

Further, in such embodiments, to implement the smoother, the online fatigue odometers <NUM> described herein can store measurement data from the current time to the past over a specified time window. The time window, typically a few seconds, can be chosen to cover the transient dynamics of the wind turbine <NUM>. As such, smoothing can be performed with the measurement data within the time window in a moving horizon fashion. The stored data may then be discarded after smoothing if desired. In the case of missing data or estimator reset, the time window can also be reset.

As shown at (<NUM>), the method <NUM> includes generating, at least in part, at least one distribution of cumulative loading data for the one or more components using the loading and travel metrics during operation of the wind turbine <NUM>. For example, in one embodiment, the distribution of cumulative loading data for the component(s) may be at least one cumulative load histogram for the component(s). In further embodiments, the distribution of cumulative loading data may be any sort of data binning or distribution mechanism, bucketizing mechanism or hashing data structure method. Accordingly, in such embodiments, the cumulative load histograms are based upon actual operation of the wind turbine <NUM> and the aforementioned measured/estimated loading and travel metrics are used instead of predicted loads from simulations. In particular embodiments, the specific set of histograms required and used may depend on the component and component life model.

Furthermore, in certain embodiments, each histogram may have a travel metric and a loading metric. In such embodiments, the loading metric(s) may include, for example, a bearing load, a tower load, a rotor blade load, a drivetrain load, a shaft load, a thermal load, or similar (such as an estimated bending moment or torque of part of the turbine, such as the main shaft, blade root, or tower base). In another embodiment, the travel metric(s) may include, for example, time, angular travel, a number of times a component travels a certain angular distance between directional reversals, or a number of times the one or more components go through a stress cycle at a particular load.

In such embodiments, the bending torque may be in a single direction or may be a resultant torque for multiple directions. In further embodiments, statistics of the load time series, such as the standard deviation, mean, median, minimum, maximum, quantiles, the difference between minimum and maximum loading metric(s) during a stress cycle or certain interval, may also be used as the loading metric(s) to form the histogram. In an example, when the loading metric(s) is the difference between minimum and maximum bending moment during a stress cycle, the travel metric(s) may be the count of the number of occurrences of this magnitude of change. In yet another embodiment, the load metric(s) may be a scalar or a vector. For example, in an embodiment, the bending moment in two orthogonal directions may be used together as the loading metric(s). In this case, the histogram may be a two-dimensional histogram.

In one embodiment, for example, original one-second load measurements that exhibit variations of a load over time may no longer be available. In such embodiments, a distribution of the load measurements may be estimated from the statistics to recapture that variation. For example, a truncated Gaussian distribution that has the same mean, standard deviation, minimum and maximum of the measurement statistics may be used. Such an estimated distribution may be used to fill in the histogram, e.g., for a <NUM>-minute time period, capturing the variation of the load measurements. Based on actual load distribution data, other types of distribution models may also be used to better capture empirical data distributions.

In another embodiment, the loading and travel metrics may be received and used to cumulatively populate the histogram. The histogram may be defined in advance with a range and bin regions for the loading metric(s). In such embodiments, as each measurement is received, the travel metric(s) is added to the appropriate bin. In another embodiment, the histogram may also be more sophisticated and may be adaptively changed in real-time, such that its range or bin regions are modified based on data accumulated to date or other requirements. In particular embodiments, the bin regions may have non-uniform bin size, for example, higher resolution where the component life model is more sensitive to variation in load. In another embodiment, the bin regions may be uniform in size. In certain embodiments, the bin width and range may be set to match the expected or required input of an established damage calculation process.

In yet another embodiment, the bin regions may have variable width and may be adapted over time to match the loading metrics data. Moreover, the cumulative load histogram may be an ordinary density-type (or frequency-type or cumulative-type) histogram, or a cumulative probability mass function over discrete values. In addition, accumulation of data into the cumulative load histogram may be done deterministically or stochastically, with some probability of accumulations being made into alternate bin regions.

In further embodiments, for each required histogram, a single histogram may be accumulated. In alternative embodiments, multiple histograms may be accumulated, with each histogram for a different external condition. For example, there may be one histogram for below-rated operation and one for above-rated operation. This may be necessary if the fatigue life model is different under different external conditions. This may also be necessary of the component life model has different accuracy under different operating conditions. This may be necessary if components or software are changed.

In additional embodiments, a preprocess step to determine whether or not histogram data should be included or excluded can be based on a variety of sources that could include, for example, status-based categorical data characterizing the operating state or status of the wind turbine <NUM> and other wind turbines. For example, in some cases, where it is known that the estimator has little predictive power or characterized by excessive scatter, filtering these states may become desirable. Moreover, in the case of unavailable data or when data is corrupted, signals from other wind turbines on the wind farm may be used as a proxy for that wind turbine <NUM>. A crowd-based or collective average or known weighted function based on farm layout and waking conditions may also be used to correct the average proxy replacement signal.

Referring still to <FIG>, as shown at (<NUM>), the method <NUM> includes applying a life model of the component(s) (also referred to herein as the component life model) to the distribution of cumulative loading data to determine an actual damage accumulation for the component(s) of the wind turbine <NUM> to date. For example, in one embodiment, the component life model may be applied to a set of histograms using the actual partial accumulated histograms instead of predicted full-life histograms. Moreover, as an example, the life model may be a physics-based model, a statistics model, or combinations thereof. This resulting damage output represents the damage that the turbine component has accumulated to date, based upon its actual operation. This damage may be used directly as part of a turbine control mechanism or to guide condition-based maintenance of the wind turbine <NUM>. In further embodiments, the component damage model may be applied to histograms collected over distinct time segments. In this mode, a histogram is accumulated for a period of time, the component damage model is applied to the histogram and the output fatigue damage for the time period is recorded. This process can then be repeated. The damage recorded for each period of time can be added up to determine the total damage.

Corrections to the damage accumulation/output determined by the component life model may also be applied to its output. In such embodiments, these corrections may improve the damage estimate and may correct a bias. The corrections may be based on physical understanding, based on observed behavior, engineering safety factors, and/or other any suitable parameter.

Moreover, in an embodiment, the cumulative loads histogram may also be post-processed before application of the component life model. In such embodiments, processing the cumulative load histogram(s) before applying the model of the component(s) may include at least one of re-defining the range or bin regions of the cumulative load histogram(s), smoothing or recalibrating the cumulative load histogram(s) to yield a more accurate estimate of historical loading estimates, or scaling the cumulative load histogram(s) to a desired time duration expected by the life model.

As shown at (<NUM>), the method <NUM> includes evaluating the actual damage accumulation, e.g., to determine if the wind turbine <NUM> has exceeded its design life. In such embodiments, the damage accumulation or output can be divided by a damage threshold to yield a percentage of the design life utilized. Thus, in such embodiments, the damage or rate of damage accumulation may be compared between wind turbines to prioritize inspections or investigations into unusual behavior.

Referring still to <FIG>, as shown at (<NUM>), the method <NUM> includes implementing a corrective action for the wind turbine <NUM> based on the damage accumulation. For example, in particular embodiments, the corrective action may include shutting down the wind turbine <NUM>, idling the wind turbine <NUM>, changing a control parameter of the wind turbine <NUM> (such as power output, speed, torque, etc.), scheduling one or more preventative maintenance actions, and/or any other suitable action.

In certain embodiments, the corrective action may be determined by comparing the actual damage accumulation to one or multiple damage thresholds. In another embodiment, the corrective action may be determined by mapping the actual damage accumulation into at least one of a probability of failure/survival, an economic cost, a simulation of future turbine operations, etc. In still another embodiment, the corrective action may be determined by a machine learning model that receives the actual damage accumulation as an input.

In particular, the damage or fatigue odometers described herein may be used for operation optimization of the wind turbine <NUM> through supervisory control. Through many control system parameters and options, the wind turbine <NUM> can generate more energy with more accumulated damage or less energy with less accumulated damage. In one embodiment, for example, it may be desirable to maximize energy production while accounting for damage accumulated and considering damage limits and risk created by additional damage. In such embodiments, a supervisory control system can make this trade-off and control the wind turbine <NUM> based in part on input from the fatigue/damage odometers <NUM>. This control action can be further completed in conjunction with many other constraints on turbine operation, such as extreme load and electrical system limits.

In additional embodiments, the fatigue/damage odometers <NUM> may also be used to schedule maintenance and inspections of wind turbine components. In addition, the fatigue/damage odometers <NUM> may be used to determine whether the wind turbine <NUM> may continue to safely operate beyond its design life, or what mitigations are required to do so.

In still further embodiments, many histogram-based fatigue odometers <NUM> can be used on the wind turbine <NUM>. In such embodiments, each odometer can be specific to a component and failure mode for which a life model exists. For turbine control and condition-based maintenance, separate odometers for each component may be used. Separate odometers may also be combined into a single metric covering all failure modes of a component or all components of a turbine for other purposes.

In an embodiment, the cumulative loads histogram(s) described herein may be one-dimensional, though it should be understood that the cumulative loads histogram may be two-dimensional or multi-dimensional where the component life model requires an input that is a joint distribution of multiple aspects of one or more loading metric(s). For example, a component life model for part of the structure of the wind turbine <NUM> may require a two-dimensional joint distribution of the load cycle magnitude and load cycle mean, with load cycles determined from a load cycle algorithm, such as rainflow counting. In this case, a two-dimensional histogram of load cycle magnitude and load cycle mean may be used.

Referring now to <FIG>, a block diagram of one embodiment of a design-time damage odometer <NUM> according to conventional construction compared with an online fatigue odometer <NUM> according to the present disclosure are provided. As shown and previously discussed, the design-time damage odometer <NUM> uses simulations <NUM>, whereas the online fatigue odometer <NUM> uses data <NUM> collected during operation of the wind turbine <NUM>. Thus, as shown at <NUM> and <NUM>, respectively, the design-time damage odometer <NUM> also uses a full-life histogram (e.g., assuming a <NUM>-year life), whereas online fatigue odometer <NUM> uses a cumulative load histogram populated to date. Accordingly, the design-time damage odometer <NUM> and the fatigue odometer use their respective, but different histograms <NUM>, <NUM> to determine damage <NUM> or design life utilized (DLU) to date <NUM>. As shown at <NUM> and <NUM>, the design-time damage odometer <NUM> can then compare the damage level <NUM> to a threshold and determines whether the damage level <NUM> is acceptable. In contrast, the online fatigue odometer <NUM> uses the DLU <NUM> to develop a chart <NUM> that can be used to evaluate whether the wind turbine <NUM> damage aligns with predicted levels, or whether the damage or higher or lower than such values.

Referring now to <FIG>, a schematic diagram of one embodiment of an example system <NUM> for generating a pitch bearing (PB) online life odometer according to the present disclosure is illustrated. More particularly, as shown, the system <NUM> includes two options for determining pitch bearing damage. First, as shown, the cumulative load histograms can be transmitted from the controller <NUM> to the cloud <NUM> where the pitch bearing damage model <NUM> can be applied. Second, as shown, the pitch bearing model <NUM> can be applied at the controller <NUM> and the damage level can be transmitted to the cloud <NUM>. In alternative embodiments, the pitch bearing model <NUM> can also be applied at the controller <NUM> and used at the controller <NUM> (not shown).

Referring now to <FIG>, various graphs of embodiments of fatigue accumulation over time are illustrated. In particular, <FIG> illustrates a graph <NUM> of fatigue accumulation over time with <NUM> and without <NUM> odometer-based control (OBC) activated according to the present disclosure. <FIG> illustrates a graph <NUM> of one embodiment of fatigue accumulation over time with <NUM> and without <NUM> odometer-based control activated according to the present disclosure, particularly illustrating the life extension <NUM> provided by the odometer-based control.

Claim 1:
A method for operating a wind turbine, the method comprising:
determining one or more loading and travel metrics or functions thereof for one or more components of the wind turbine during operation of the wind turbine (<NUM>);
generating, at least in part, at least one distribution of cumulative loading data for the one or more components using the one or more loading and travel metrics during operation of the wind turbine (<NUM>);
applying a life model of the one or more components to the at least one distribution of cumulative loading data to determine an actual damage accumulation for the one or more components of the wind turbine to date (<NUM>); and
implementing a corrective action for the wind turbine based on the damage accumulation (<NUM>),
characterized in that the generating comprises:
defining a range and bin regions of at least one cumulative load histogram;
defining a first loading metric of the plurality of loading metrics and a first travel metric of the plurality of travel metrics for the at least one cumulative load histogram;
during operation of the wind turbine, populating the at least one cumulative load histogram using the first loading and travel metrics by adding the first loading and travel metrics to the bin regions of the at least one cumulative load histogram; and
adaptively changing at least one of the range or the bin regions based on on-going operational data of the wind turbine.