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, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid. Such configurations may also include power converters that are used to convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency.

In modern wind turbines, various sensor systems are employed to monitor various conditions of the rotor blades. For example, such conditions may include loading and/or pitch alignment, which can have a negative impact on the annual energy production (AEP) of the wind turbine. In general, for onshore wind turbines, a plurality of proximity sensors are installed on the main shaft to measure various moments of the rotor blades. For offshore wind turbines, a plurality of strain sensors are installed on the rotor blades to measure individual blade root bending moments. More particularly, the strain signals from the strain sensors are converted into bending moments. Such sensors, however, tend to experience performance degradation and drift over time and require continued calibration.

<CIT> relates to a wind turbine with a sensor that measures the out-of-plane deflection of the blades and a controller that uses the signal from the sensor to determine the risk of a tower strike. XP033125250 relates to an inverse kinematic control of an industrial robot used in vessel-to-vessel motion compensation. <CIT> relates to a system for monitoring deflection of turbine blades of a wind turbine comprising a tower. <CIT> relates to a wind-turbine tower to blade-tip measuring system. <CIT> relates to a sensor system that monitors deflection of turbine blades of a wind turbine. <CIT> relates to systems for alleviating loads in off-shore wind turbines. A control system is connected to a load measuring system and to measuring devices of, at least, wind speed, wind direction, pitch angle of each blade, azimuth position of each blade. The control system is arranged for performing a regulation of the wind turbine according to a predetermined power curve for wind speeds below the cut-out wind speed including an individual pitch regulation of each blade based on said load measuring system. <CIT> relates to a method for automatically inspecting an object. <CIT> relates to a method for determining an azimuth angle of a wind turbine. <CIT> relates to wind flow estimation and tracking using tower dynamics.

As to conventional methods for determining pitch alignment, there are several available methods and/or tools for onshore wind turbines. For example, certain wind turbines use image processing technologies combined with the airfoil template of the rotor blades and/or lasers to correct the pitch misalignment. However, these tools/methods cannot be used in offshore wind turbines due to physical constraints (e.g. offshore wind turbines are installed on the sea with no surrounding mounting locations).

In view of the foregoing, the art is continuously seeking new and improved systems and methods for controlling pitch and/or pitch misalignment of a wind turbine. Accordingly, the present disclosure is directed to systems and methods for controlling pitch of a wind turbine using position data from position localization sensors, the position localization sensors including real-time kinematic (RTK) sensors.

In one aspect, the present disclosure is directed to a method for controlling pitching of at least one rotor blade of a wind turbine according to independent claim <NUM>. The method includes receiving, via one or more position localization sensors, position data relating to the at least one rotor blade of the wind turbine. Further, the method includes determining, via a controller, a blade deflection signal of the at least one rotor blade based on the position data. Moreover, the method includes determining, via a computer-implemented model stored in the controller, a pitch command for the at least one rotor blade as a function of the blade deflection signal and an azimuth angle of the at least one rotor blade.

The position localization sensor(s) include one or more real-time kinematic (RTK) sensors. The RTK sensor(s) include a base station and a plurality of mobile stations communicatively coupled to the base station, with the plurality of mobile stations being installed on the at least one rotor blade.

In an embodiment, the position localization sensor(s) may further include one or more of the following: one or more inertial navigation system (INS) sensors, one or more global positioning system (GPS) sensors, or combinations thereof.

In another embodiment, receiving the position data relating to the at least one rotor blade of the wind turbine may include receiving, via the controller, three-dimensional or two-dimensional position data relating to a position of the base station and receiving, via the controller, three-dimensional or two-dimensional position data relating to a position of each of the plurality of mobile stations.

In further embodiments, determining, via the computer-implemented model stored in the controller, the pitch command for the at least one rotor blade as a function of the blade deflection signal and the azimuth angle may include applying, via the controller, direct-quadrature (d-q) transformation to the blade deflection signal to transform the blade deflection signal into d-q coordinates, filtering the d-q coordinates, and inversing the d-q transformation to transform the d-q coordinates into the pitch command for the at least one rotor blade.

In such embodiments, applying the d-q transformation to the blade deflection signal to transform the blade deflection signal into d-q coordinates may include determining a blade bending moment of the at least one rotor blade using the blade deflection and calculating the d-q coordinates as a function of the blade bending moment and the azimuth angle.

In additional embodiments, the method may include adding a collective pitch angle demand to the pitch command for the rotor blade(s).

In another embodiment, the wind turbine may be part of a wind farm having a plurality of wind turbines and a farm-level controller. In such embodiments, the position localization sensor(s) may communicate with the farm-level controller directly using an existing network of the wind farm or a wireless communication system.

In still further embodiments, the method may include adjusting the pitch command of the rotor blade(s) by a pitch angle offset so as to correct for pitch misalignment of the at least one rotor blade.

In an example not covered by the claims, a method for correcting pitch misalignment of at least one rotor blade of a wind turbine, such as an off-shore wind turbine, is described. The method includes receiving, via a controller, a reference pitch angle of the at least one rotor blade. Further, the method includes rotating the rotor blade(s) to a first pitch angle. Moreover, the method includes receiving, via one or more position localization sensors, position data relating to the rotor blade(s) of the wind turbine in the first pitch angle. In addition, the method includes determining, via the controller, a pitch angle offset of the rotor blade(s) based on a difference between the reference pitch angle and the first pitch angle. Thus, the method includes adjusting the first pitch angle of the rotor blade(s) by the pitch angle offset so as to correct the pitch misalignment.

The reference pitch angle and the first pitch angle may be a reference pitch zero position and a first pitch zero position, respectively. Thus, in another example, the position data may include a zero-twist angle of the rotor blade(s). It should be understood that the method may further include any of the additional features and/steps as described herein.

In another aspect, the present disclosure is directed to a system for controlling pitching of at least one rotor blade of a wind turbine according to the independent system claim. The system includes one or more position localization sensors for generating position data relating to the rotor blade(s) of the wind turbine. The one or more position localization sensors include one or more real-time kinematic (RTK) sensors, the one or more RTK sensors including a base station and a plurality of mobile stations communicatively coupled to the base station, the plurality of mobile stations being installed on the at least one rotor blade. The system further includes a controller communicatively coupled to the position localization sensor(s). The controller is configured to perform a plurality of operations, including but not limited to receiving the position data relating to the rotor blade(s) of the wind turbine, determining a blade deflection signal of the rotor blade(s) based on the position data, and determining a pitch command for the rotor blade(s) as a function of the blade deflection signal and an azimuth angle of the rotor blade(s). It should be understood that the wind farm may further include any of the additional features as described herein.

The figures are not necessarily drawn to scale and elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. The figures are only intended to facilitate the description of the various embodiments described herein. The figures do not describe every aspect of the teachings disclosed herein and do not limit the scope of the claims.

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 (not shown) positioned within the nacelle <NUM> to permit electrical energy to be produced. The generators are sometimes, but not always, rotationally coupled to the rotor <NUM> through a gearbox. Thus, the gearbox is configured to step up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electric energy. Gearless direct drive wind turbines also exist. The generated electric power is transmitted to an electric grid via at least one electrical connection. Such known wind may be coupled to the electric grid via a known full power conversion assembly. More specifically, full power conversion assemblies may include a rectifier portion that converts alternating current (AC) generated by the generator to direct current (DC) and an inverter that converts the DC to AC of a predetermined frequency and voltage amplitude.

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 control 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 different 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), de-rate or up-rate the wind turbine <NUM>, control various components of the wind turbine <NUM>, and/or implement the various method steps as described herein.

For example, in certain embodiments, the methods described herein may be at least partially processor-implemented. The one or more processors may also operate to support performance of the relevant operations in a "cloud computer" environment or as a "software service" (SaaS). For example, at least some of the operations may be performed by a group of computers (as examples of machines including processors), these operations being accessible via a network (e.g., the Internet) and via one or more appropriate interfaces (e.g., Application Program Interfaces (APIs).

In additional embodiments, 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>. 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 block diagram of one embodiment of suitable components that may be included within the controller <NUM> (or farm controller <NUM>) is illustrated in accordance with aspects of the present disclosure. The controller(s) <NUM>, <NUM> may operate as a standalone device or may be coupled (e.g., networked) to other machines. In a networked deployment, the controller <NUM> may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. By way of non-limiting example, the controller <NUM> may include or correspond to a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a mobile device, or any machine capable of executing instructions, sequentially or otherwise, that specify actions to be taken by the controller <NUM>.

As shown, the controller <NUM> may include one or more processor(s) <NUM> and associated memory device(s) <NUM> (and/or input/output (I/O) components, not shown) configured to perform a variety of computer-implemented 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, application-specific processors, digital signal processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or any other programmable circuits. Further, the memory device(s) <NUM> may generally include memory element(s) including, but are not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable nonvolatile medium (e.g., a flash memory), one or more hard disk drives, a floppy disk, a compact disc-read only memory (CD-ROM), compact disk-read/write (CD-R/W) drives, a magneto-optical disk (MOD), a digital versatile disc (DVD), flash drives, optical drives, solid-state storage devices, and/or other suitable memory elements.

Additionally, the controller <NUM> may also include a communications module <NUM> to facilitate communications between the controller <NUM> 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>, <NUM>, <NUM> to be converted into signals that can be understood and processed by the controller <NUM>. Furthermore, it should be appreciated that the sensors <NUM>, <NUM>, <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>, <NUM>, <NUM> are coupled to the sensor interface <NUM> via a wired connection. However, in alternative embodiments, the sensors <NUM>, <NUM>, <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. For example, the communications module <NUM> may include the Internet, a local area network (LAN), wireless local area networks (WLAN), wide area networks (WAN) such as Worldwide Interoperability for Microwave Access (WiMax) networks, satellite networks, cellular networks, sensor networks, ad hoc networks, and/or short-range networks. As such, the processor <NUM> may be configured to receive one or more signals from the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

The various components of the controller <NUM>, e.g. I/O components, may include a wide variety of components to receive input, provide output, produce output, transmit information, exchange information, capture measurements, and so on. The specific I/O components that are included in a particular machine will depend on the type of machine. For example, portable machines such as mobile phones will likely include a touch input device or other such input mechanisms, while a headless server machine will likely not include such a touch input device. Further, the I/O components may be grouped according to functionality merely for simplifying the following discussion and the grouping is in no way limiting. In further embodiments, the I/O components may include visual components (e.g., a display such as a plasma display panel (PDP), a light emitting diode (LED) display, a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)), acoustic components (e.g., speakers), haptic components (e.g., a vibratory motor, resistance mechanisms), other signal generators, and so forth. In additional embodiments, the I/O components may include alphanumeric input components (e.g., a keyboard, a touch screen configured to receive alphanumeric input, a photooptical keyboard, or other alphanumeric input components), point based input components (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, or other pointing instrument), tactile input components (e.g., a physical button, a touch screen that provides location and/or force of touches or touch gestures, or other tactile input components), audio input components (e.g., a microphone), and the like.

Referring now to <FIG>, at least some wind turbines are physically positioned in a remote geographical region or in an area where physical access is difficult, such as, off-shore installations. These wind turbines may be physically nested together in a common geographical region to form a wind farm and may be electrically coupled to a common AC collector system. For example, as shown in <FIG>, one embodiment of a wind farm <NUM> that may be controlled according to the present disclosure is illustrated. More specifically, as shown, the wind farm <NUM> may include a plurality of wind turbines <NUM>, including the wind turbine <NUM> described above, communicatively coupled to a farm controller <NUM> via a network <NUM>. 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 the 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 (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 addition, the farm controller <NUM> may be generally configured similar to the controllers <NUM> for each of the individual wind turbines <NUM> within the wind farm <NUM>.

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 data points or control settings of the individual wind turbines <NUM> and/or one or more wind parameters of the wind farm <NUM>. For example, as shown, each of the wind turbines <NUM> includes a wind sensor <NUM>, such as an anemometer or any other suitable device, configured for measuring wind speeds or any other wind parameter.

Accordingly, it should be understood that the various sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> described herein may be any suitable sensors configured to measure any operating data points of the wind turbine <NUM> and/or wind parameters of the wind farm <NUM> (<FIG>). For example, in an embodiment, one or more of the sensors may be a position localization sensor, such as a real-time kinematic sensor or sensor system <NUM>, at least partially locally installed onto one or more of the wind turbines <NUM> and/or integrated with the wind farm controller <NUM>, one or more global positioning system (GPS) sensors, or combinations thereof.

As used herein, position localization sensors, and more particularly real-time kinematic (RTK) sensors, generally refer to sensors that use RTK positioning, which is a satellite navigation technique used to enhance the precision of position data derived from satellite-based positioning systems (global navigation satellite systems, GNSS). Thus, RTK position systems enable a refinement in satellite positioning which is categorized in the frequency range of about <NUM>,<NUM>-<NUM>,<NUM>, which is a different frequency ranges from other RF-based devices (such as cellular <NUM>, Bluetooth, UWB, etc.) that operate at higher frequencies.

Thus, the sensor system <NUM> of the present disclosure is configured to use measurements of the phase of the signal's carrier wave in addition to the information content of the signal and relies on a single reference station or interpolated virtual station to provide real-time corrections, providing up to centimeter-level accuracy. More specifically, in certain embodiments, as shown in <FIG> and <FIG>, the sensor system <NUM> may use a single base-station receiver <NUM> and a plurality of mobile units <NUM> (e.g. rover station(s)). For example, as shown particularly in <FIG>, one or more of the mobile units <NUM> may be locally installed onto each of the rotor blades <NUM> of the wind turbine <NUM>. As such, the base station <NUM> re-broadcasts the phase of the carrier that it observes, and the mobile units <NUM> compare their own phase measurements with the one received from the base station <NUM>. The most popular way to transmit a correction signal from the base station <NUM> to one or more of the mobile stations <NUM> to achieve real-time, low-cost signal transmission is to use a radio modem (not shown). However, in certain embodiments, as shown in <FIG>, rather than using the wireless RF modem, the present disclosure may also implement the communication between the base station <NUM> and the rover station(s) <NUM> using the existing network <NUM> of the wind farm <NUM>. It should also be understood that the position localization sensor(s) may also include inertial navigation system (INS) sensors, global positioning system (GPS) sensors, or combinations of any sensor described herein.

In the present disclosure, for wind turbines, the measurement of positions are used as inputs to incorporate into a wind turbine model and/or algorithm to derive turbine-relevant parameters/variables (such as, model-based estimation) as described herein. Accordingly, the present disclosure encompasses a new system structure that eliminates the radio modems and additional processors of the RTK system, while also providing a more reliable and cost-effective solution. More specifically, in an embodiment, the system of the present disclosure may only need the GPS modules, with the position calculations and the subsequent estimations and controls being implemented in the existing wind turbine controllers.

The sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> described herein may also 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 (e.g. wind speed, wind direction, etc.). Further, the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be located near the ground of the wind turbine <NUM>, on the nacelle <NUM>, on a meteorological mast of the wind turbine <NUM>, or any other location in the wind farm <NUM>.

Accordingly, 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 accelerometers, pressure sensors, strain gauges, angle of attack sensors, vibration sensors, MIMU sensors, camera systems, fiber optic systems, anemometers, wind vanes, Sonic Detection and Ranging (SODAR) sensors, infra lasers, Light Detecting and Ranging (LIDAR) sensors, radiometers, pitot tubes, rawinsondes, other optical sensors, and/or any other suitable sensors. It should be appreciated that, as used herein, the term "monitor" and variations thereof indicates that the various sensors of the wind turbine <NUM> 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>, <NUM>, <NUM> may, for example, be used to generate signals relating to the parameter being monitored, which can then be utilized by the controller <NUM> to determine the actual condition.

Certain embodiments are described herein as including logic or a number of components, modules, or mechanisms. Modules may constitute either software modules (e.g., code embodied on a machine-readable medium or in a transmission signal) or hardware modules. A hardware module is tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. In example embodiments, one or more computer systems (e.g., a standalone, client or server computer system) or one or more hardware modules of a computer system (e.g., a processor or a group of processors) may be configured by software (e.g., an application or application portion) as a hardware module that operates to perform certain operations as described herein.

For example, a hardware module may include dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC)) to perform certain operations. A hardware module may also include programmable logic or circuitry (e.g., as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations.

Referring now to <FIG>, a flow diagram of one embodiment of a method <NUM> for controlling pitching of one or more rotor blades, such as the rotor blade(s) <NUM> of the wind turbine <NUM>, is illustrated. In general, the method <NUM> is described herein with reference to the wind turbine(s) <NUM>, <NUM>, and the controllers <NUM>, <NUM> of <FIG>. However, it should be appreciated that the disclosed method <NUM> may be implemented with wind turbines having any other suitable configurations. In addition, although <FIG> depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure.

As shown at (<NUM>), the method <NUM> includes receiving, via one or more position localization sensors (such as any of sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), position data relating to the rotor blade(s) of the wind turbine <NUM>. More specifically, in an embodiment, the position data may be three-dimensional or two-dimensional position data relating to a position of the base station <NUM> and/or three-dimensional or two-dimensional position data relating to a position of each of the plurality of mobile stations <NUM>.

Referring still to <FIG>, as shown at (<NUM>), the method <NUM> includes determining, via a controller, a blade deflection signal of the rotor blade(s) <NUM> based on the position data. As shown at (<NUM>), the method <NUM> includes determining, via a computer-implemented model stored in the controller, a pitch command for the rotor blade(s) <NUM> as a function of the blade deflection signal and an azimuth angle of the rotor blade(s) <NUM>.

The method <NUM> of <FIG> can be better understood with reference to <FIG>. For example, <FIG> illustrates a block diagram of one embodiment of a system <NUM> for controlling pitching of the rotor blade(s) <NUM> according to the present disclosure. Thus, as shown, the system <NUM> includes the controller <NUM>, such as controller <NUM>, and a computer-implemented model <NUM> stored therein. Accordingly, as shown, position data <NUM> from the position localization sensors can be used by the computer-implemented model <NUM> to determine the pitch command(s) <NUM> for the rotor blade(s) <NUM> as a function of the blade deflection signal <NUM> and the azimuth angle. More specifically, as shown, the controller <NUM> can derive the blade deflection <NUM> of each of the rotor blades <NUM> of the wind turbine <NUM>.

Moreover, the controller <NUM> can then apply direct-quadrature (d-q) transformation <NUM> to the blade deflection signals <NUM> to transform the blade deflection signals <NUM> into d-q coordinates <NUM>. In such embodiments, for example, the controller <NUM> may determine or derive a blade bending moment of the rotor blades <NUM> (e.g. Moutplane1, Moutplane2, Moutplane3) using the respective blade deflection signals <NUM> and calculate the d-q coordinates <NUM> as a function of the blade bending moment and the azimuth angle <NUM>. Generally, a linear relationship exists between the blade bending moment and the blade deflection, therefore, the blade bending moment can be derived from the blade deflection. Accordingly, in one embodiment, the d-q coordinates <NUM> may be derived from Equations (<NUM>) and (<NUM>) below: <MAT> <MAT>.

Still referring to <FIG>, as shown, the controller <NUM> may also filter the d-q coordinates <NUM> using one or more filters <NUM>. As shown at <NUM>, the controller <NUM> can then inverse the d-q transformation to transform the d-q coordinates <NUM> into the pitch commands <NUM> for the rotor blade(s) <NUM>. In additional embodiments, as shown at <NUM>, the controller <NUM> may also be configured to add a collective pitch angle demand <NUM> to the pitch commands <NUM> for the rotor blade(s) <NUM>. Moreover, in an embodiment, the controller <NUM> may be configured to adjust the pitch commands <NUM> of the rotor blade(s) <NUM> by a pitch angle offset <NUM> so as to correct for pitch misalignment of the rotor blade(s) <NUM>, as shown at <NUM>.

Referring now to <FIG>, a flow diagram of a method <NUM> for correcting pitch misalignment of at least one rotor blade, such as the rotor blades <NUM> of the wind turbine <NUM>, is illustrated, wherein the method is not covered by the claims. In general, the method <NUM> is described herein with reference to the wind turbine(s) <NUM>, <NUM>, and the controllers <NUM>, <NUM> of <FIG>. However, it should be appreciated that the disclosed method <NUM> may be implemented with wind turbines having any other suitable configurations. In addition, although <FIG> depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adapted in various ways.

As shown at (<NUM>), the method <NUM> includes receiving, via a controller, a reference pitch angle of the rotor blade(s) <NUM>. As shown at (<NUM>), the method <NUM> includes rotating the rotor blade(s) <NUM> to a first pitch angle. For example, the reference pitch angle and the first pitch angle may be a reference pitch zero position and a first pitch zero position, respectively. In another example, the position data may include a zero-twist angle of the rotor blade(s) <NUM>. As shown at (<NUM>), the method <NUM> includes receiving and storing/recording, via one or more position localization sensors, position data relating to the rotor blade(s) <NUM> in the first pitch angle. As shown at (<NUM>) through (<NUM>), the method <NUM> includes determining, via the controller, a pitch angle offset of the rotor blade(s) <NUM> based on a difference between the reference pitch angle and the first pitch angle. For example, as shown at (<NUM>), the method <NUM> includes determining a desired pitch position based on design models. As shown at (<NUM>), the method <NUM> includes comparing the desired pitch position from the design model with the actual pitch position from the sensors. Thus, as shown at (<NUM>), the blade pitch misalignment value can be determined by the controller. As shown at (<NUM>), the method <NUM> includes sending the pitch angle offset to the controller and adjusting the first pitch angle of the rotor blade(s) <NUM> by the pitch angle offset so as to correct the pitch misalignment.

Claim 1:
A method (<NUM>) for controlling pitching of at least one rotor blade (<NUM>) of a wind turbine (<NUM>), the method comprising:
receiving, via one or more position localization sensors, position data (<NUM>) relating to the at least one rotor blade of the wind turbine;
determining, via a controller (<NUM>,<NUM>), a blade deflection signal (<NUM>) of the at least one rotor blade based on the position data; and,
determining, via a computer-implemented model (<NUM>) stored in the controller, a pitch command (<NUM>) for the at least one rotor blade as a function of the blade deflection signal and an azimuth angle (<NUM>) of the at least one rotor blade;
wherein the one or more position localization sensors comprise one or more real-time kinematic (RTK) sensors, and wherein the one or more RTK sensors comprise a base station (<NUM>) and a plurality of mobile stations (<NUM>) communicatively coupled to the base station, the plurality of mobile stations being installed on the at least one rotor blade.