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 nacelle mounted on the tower, a generator positioned in the nacelle, and a rotor having one or more rotor blades. The one or more rotor blades convert kinetic energy of wind into mechanical energy using known airfoil principles. A drivetrain transmits the mechanical energy from the rotor blades to the generator. The generator then converts the mechanical energy to electrical energy that may be supplied to a utility grid.

In general, when a large mass imbalance is present in the rotor, the wind turbine may experience accelerated wear. For example, large mass imbalances may result in high fatigue loads and increased side-to-side bending moments within the tower as well as large torque cycling within the drivetrain. As such, large mass imbalances may reduce the life of the various components of the wind turbine, such as the tower and/or the drivetrain. Furthermore, the mass imbalances may be amplified as the height of the tower increases and/or the stiffness of the tower decreases. <CIT> and <CIT> provide examples of prior art.

Accordingly, an improved method and system for detecting a mass imbalance in a rotor of a wind turbine would be welcomed in the art.

Various aspects and advantages of the technology will be set forth in part in the following description, or may be clear from the description, or may be learned through practice of the technology.

In one aspect, the present disclosure is directed to a method for detecting a mass imbalance in a rotor of a wind turbine according to claim <NUM>. In another aspect, the present disclosure is directed to a system for detecting a mass imbalance in a rotor of a wind turbine according to claim <NUM>.

Various features, aspects and advantages of the present technology will become better understood with reference to the following description and appended claims.

Reference will now be made in detail to present embodiments of the technology, one or more examples of which are illustrated in the accompanying drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the technology.

Each example is provided by way of explanation of the technology, not limitation of the technology. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present technology without departing from the scope thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present technology covers such modifications and variations as come within the scope of the appended claims.

Referring now to the drawings, <FIG> illustrates a perspective view of one embodiment of an exemplary wind turbine <NUM> in accordance with 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 hub <NUM> and at least one rotor blade <NUM> coupled to and extending outwardly from the hub <NUM>. For example, in the embodiment shown in <FIG>, the rotor <NUM> includes three rotor blades <NUM>. In alternative embodiments, however, 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 rotation of the rotor <NUM> to convert kinetic energy from the wind into usable rotational, mechanical energy. An electric generator <NUM> positioned in the nacelle <NUM> may generate electrical power from the rotational energy of the rotor <NUM>.

Referring now to <FIG>, a drivetrain <NUM> couples the rotor <NUM> to the generator <NUM>. As shown, the drivetrain <NUM> may include a rotor shaft <NUM>, which couples the rotor hub <NUM> to a gearbox <NUM>. The gearbox <NUM> may be supported by and coupled to a bedplate <NUM> within the nacelle <NUM>. The drivetrain <NUM> also includes a generator shaft <NUM>, which couples the gearbox <NUM> to the generator <NUM>. In this respect, rotation of the rotor <NUM> drives the generator <NUM>. More specifically, 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 convert the low speed, high torque input into a high speed, low torque output to drive the generator shaft <NUM> and, thus, the generator <NUM>.

The wind turbine <NUM> may also include one or more pitch adjustment mechanisms <NUM>. Although <FIG> only illustrates one pitch adjustment mechanism <NUM>, the wind turbine <NUM> may include three pitch adjustment mechanisms <NUM>. In this respect, the wind turbine <NUM> may include one pitch adjustment mechanism <NUM> corresponding to each rotor blade <NUM>. In alternate embodiments, however, the wind turbine <NUM> may include more or fewer pitch adjustment mechanisms <NUM>.

Each pitch adjustment mechanism <NUM> may adjust a pitch angle of the corresponding rotor blade <NUM> (i.e., the angular orientation of the rotor blade <NUM> with respect to a direction <NUM> (<FIG>) of the wind). In particular, each rotor blade <NUM> may be rotatably coupled to the hub <NUM> by a pitch bearing (not shown). As such, each pitch adjustment mechanism <NUM> may rotate the corresponding rotor blade <NUM> about a corresponding pitch axis <NUM> relative to the hub <NUM>, thereby adjusting the pitch angle of the rotor blade <NUM>.

<FIG> illustrates an exemplary embodiment of one of the pitch adjustment mechanisms <NUM>. More specifically, the pitch adjustment mechanism <NUM> may include an electric motor <NUM> having a pinion gear <NUM> coupled thereto. The pinion gear <NUM> may engage a ring gear <NUM> formed on or coupled to an inner surface of the rotor blade <NUM>. During operation of the pitch adjustment mechanism <NUM>, the electric motor <NUM> rotates the pinion gear <NUM>. The pinion gear <NUM>, in turn, rotates the ring gear <NUM>, thereby rotating the rotor blade <NUM> about the corresponding pitch axis <NUM>. In alternate embodiments, the pitch adjustment mechanism <NUM> may include any suitable type of actuator and/or any suitable structure or mechanism for transmitting the movement of the actuator to the corresponding rotor blade <NUM>.

As shown in <FIG> and <FIG>, the wind turbine <NUM> may include various sensors. For example, the wind turbine <NUM> may include a rotor shaft position sensor <NUM>, a generator position sensor <NUM>, a pitch angle sensor <NUM>, a wind velocity sensor <NUM>, electric power sensor <NUM>, and an acceleration sensor <NUM>. In alternate embodiments, however, the wind turbine <NUM> may include only some of the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or none of the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. Furthermore, the wind turbine <NUM> may include other sensors (e.g., vibration sensors, force sensors, load sensors, etc.) in addition to or in lieu of the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

The rotor shaft position sensor <NUM> may detect a rotational or azimuthal position of the rotor shaft <NUM>. The rotational position of the rotor shaft <NUM> may, in turn, be used to determine the rotational position and/or the rotational velocity of the rotor <NUM>. As shown in <FIG>, the rotor shaft position sensor <NUM> is operatively associated with the rotor shaft <NUM>. As such, the rotor shaft position sensor <NUM> may be a Hall Effect sensor or any other suitable type of sensor for detecting absolute or incremental rotational position and/or rotational speed.

The generator position sensor <NUM> may detect a rotational or azimuthal position of a component of the generator <NUM>, such as a rotor (not shown) of the generator <NUM>, and/or a component coupled to the generator <NUM>, such as the generator shaft <NUM>. The rotational position of the generator component or the component coupled to the generator <NUM> may, in turn, be used to determine the rotational velocity of that component. As shown in <FIG>, the generator position sensor <NUM> is operatively associated with the generator <NUM>. Although, in alternative embodiments, the generator position sensor <NUM> may be operatively associated with the generator shaft <NUM>. As such, the generator position sensor <NUM> may be a Hall Effect sensor or any other suitable type of sensor for detecting absolute or incremental rotational position and/or rotational speed.

The pitch angle sensor <NUM> detects the pitch angle of the corresponding rotor blade <NUM>. In this respect, the pitch angle sensor <NUM> is operatively coupled to the one of the rotor blades <NUM> as shown in <FIG>. Although only one pitch angle sensor <NUM> is shown in <FIG>, the wind turbine <NUM> may include one pitch angle sensor <NUM> operatively associated with each rotor blade <NUM>. The pitch angle sensor <NUM> may be a Hall Effect sensor or any other suitable type of sensor for detecting absolute or incremental rotational position.

The wind speed sensor <NUM> detects a speed of the wind experienced by the wind turbine <NUM>. In the embodiment in <FIG>, the wind speed sensor <NUM> is mounted or otherwise coupled to the exterior of the nacelle <NUM>. As such, the wind speed sensor <NUM> may be a suitable anemometer or a wind vane. In alternate embodiments, however, the wind speed sensor <NUM> may be a light detection and ranging (LIDAR) sensor or any other suitable type of sensor for detecting wind speed.

The electric power sensor <NUM> detects an electric power output of the generator <NUM>. As shown in <FIG>, the electric power sensor <NUM> is operatively associated with generator <NUM>. As such, the electric power sensor <NUM> may be a suitable power encoder. In alternate embodiments, however, the electric power sensor <NUM> may be a suitable electric meter or any other suitable type of sensor for detecting electric power output.

The acceleration sensor <NUM> detects an acceleration of the tower <NUM> relative to the support surface <NUM>. For example, in one embodiment, the acceleration sensor <NUM> may detect a side-to-side or lateral acceleration (i.e., the acceleration in a direction perpendicular to a longitudinal axis of the rotor shaft <NUM> and parallel to the support surface <NUM>). Although, in other embodiments, the acceleration sensor <NUM> may detect acceleration in another direction. In the embodiment shown in <FIG>, the acceleration sensor <NUM> is operatively associated with the tower <NUM>. As such, the acceleration sensor <NUM> may be a mechanical accelerometer, a capacitive accelerometer, a piezoelectric accelerometer, or any other suitable type of acceleration sensor.

<FIG> illustrate various embodiments of a system <NUM> for detecting a mass imbalance in a rotor of a wind turbine. In general, the system <NUM> will be described herein with reference to the wind turbine <NUM> described above and shown in <FIG> and <FIG>. Nevertheless, the disclosed system <NUM> may generally be used with wind turbines having any other suitable configuration.

As shown in <FIG>, the system <NUM> may include various components of the wind turbine <NUM>. Specifically, the system <NUM> may include one or more sensors for detecting associated parameter(s) indicative of operating characteristic(s) of the wind turbine <NUM>. For example, as shown, the system <NUM> may include various combinations of the rotor shaft position sensor <NUM>, generator positions sensor <NUM>, the pitch angle sensor <NUM>, the wind speed sensor <NUM>, the electric power sensor <NUM>, and/or the acceleration sensor <NUM>. Additionally, the system <NUM> may also include the pitch adjustment mechanisms <NUM>. Nevertheless, the system <NUM> may include other components of the wind turbine <NUM> in addition to or in lieu of one or more the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

The system <NUM> also includes a controller <NUM> communicatively coupled to one or more components of the system <NUM> and/or the wind turbine <NUM>, such as one or more of the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and the pitch adjustment mechanisms <NUM>. In the embodiment shown in <FIG>, for example, the controller <NUM> is disposed within a control cabinet <NUM> mounted within the nacelle <NUM>. In alternate embodiments, however, the controller <NUM> may be disposed at any location on or in the wind turbine <NUM>, at any location on the support surface <NUM> (<FIG>), or any other suitable location.

In general, the controller <NUM> may correspond to any suitable processor-based device, including one or more computing devices. As shown in <FIG>, for example, the controller <NUM> may include one or more processors <NUM> and one or more associated memory devices <NUM> 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, microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit (ASIC), a Field Programmable Gate Array (FPGA), and other programmable circuits. Additionally, the memory device(s) <NUM> may generally include memory element(s) including, but not limited to, a computer readable medium (e.g., random access memory (RAM)), a computer readable nonvolatile medium (e.g., flash memory), a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD), and/or other suitable memory elements or combinations thereof. The memory device(s) <NUM> may store instructions that, when executed by the processor <NUM>, cause the processor <NUM> to perform functions (e.g., method <NUM> described below).

The controller <NUM> may also include a communications module <NUM> to facilitate communications between the controller <NUM> and the various components of the system <NUM> and/or the wind turbine <NUM>. For example, the communications module <NUM> may permit the controller <NUM> to receive data from the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. As such, the communications module <NUM> may include a sensor interface <NUM> (e.g., one or more analog-to-digital converters) that converts measurement signals <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> respectively received from the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> into signals that can be understood and processed by the processor(s) <NUM>. Furthermore, the communications module <NUM> may permit the controller <NUM> to transmit control signals <NUM> to each pitch adjustment mechanism <NUM> for controlling the pitch angle of the rotor blades <NUM>. In this respect, the communications module <NUM> may be any combination of suitable wired and/or wireless communication interfaces that communicatively couple the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and the pitch adjustment mechanisms <NUM> to the controller <NUM>.

Referring again to <FIG>, in some embodiments, the system <NUM> may include a user interface <NUM> configured to allow interaction between a user and the controller <NUM>. More specifically, the user interface <NUM> may be communicatively coupled to the controller <NUM> to permit feedback signals (e.g., as indicated by arrows <NUM> in <FIG>) to be transmitted from the controller <NUM> to the user interface <NUM>. In this respect, the user interface <NUM> may include one or more feedback devices (not shown), such as display screens, speakers, warning lights, etc., which communicate the feedback from the controller <NUM> to the user. In one embodiment, the user interface <NUM> may be located at a remote location (e.g., a control center for a wind farm) from the wind turbine <NUM>. In such embodiment, the controller <NUM> and the user interface <NUM> may be communicatively coupled via the Internet or another suitable network. In alternate embodiments, however, the system <NUM> may not include the user interface <NUM>.

As will be described in greater detail below, the controller <NUM> may be configured to detect a mass imbalance in the rotor <NUM> by executing various logic stored on the memory device(s) <NUM>. In particular, the controller <NUM> (e.g., via the processor(s) <NUM>) executes the logic to determine a mean amplitude of a designated frequency component of an operating characteristic of the wind turbine <NUM> based on the data received from one or more the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and/or data stored in the memory device(s) <NUM>. The designated frequency component comprises a 1P frequency of an operating characteristic. In general, the mean amplitude of the 1P frequency component of an operating characteristic is indicative of a mass imbalance. That is, the mass imbalance increases proportionally with the mean amplitude of a 1P frequency component. The controller <NUM> (e.g., via the processor(s) <NUM>) then executes the logic to determine when a mass imbalance is present in the rotor <NUM> based on the mean amplitude of the 1P frequency component. In alternative embodiments, the designated frequency component may comprise any other suitable frequency component. Furthermore, when the mass imbalance is present, the controller <NUM> may initiate various control actions associated with reducing the effect of the mass imbalance on the wind turbine <NUM>.

<FIG> illustrates one embodiment of the system <NUM> for detecting a mass imbalance in the rotor <NUM> of the wind turbine <NUM>. In the embodiment illustrated in <FIG>, the system <NUM> includes the rotor shaft position sensor <NUM> and the electric power sensor <NUM>. As such, the controller <NUM> may be configured to detect a mass imbalance in the rotor <NUM> based the rotational position of the rotor shaft <NUM> and the electric power output of the generator <NUM>.

In such embodiment, the controller <NUM> may be configured to determine a mean amplitude of the 1P frequency component of the electric power output by the generator <NUM> based on the electric power measurement signals <NUM> and the rotor shaft position measurement signals <NUM>. More specifically, as mentioned above, the controller <NUM> is communicatively coupled to the rotor shaft position sensor <NUM> and the electric power sensor <NUM>. In this respect, the controller <NUM> receives rotor shaft position measurement signals (e.g., as indicated by arrows <NUM> in <FIG>) from the rotor shaft position sensor <NUM> and the electric power measurement signals (e.g., as indicated by arrows <NUM> in <FIG>) from the electric power sensor <NUM>. Furthermore, the controller <NUM> may include 1P frequency component logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the 1P frequency component logic <NUM>, the controller <NUM> may determine a mean amplitude of the 1P frequency component (e.g., as indicated by arrow <NUM> in <FIG>) of the electric power output of the generator <NUM> based on the electric power measurement signals <NUM> and rotor shaft position measurement signals <NUM>.

In certain embodiments, for example, the controller <NUM> may be configured to determine the mean amplitude of the 1P frequency component of the electric power output using sine and cosine modulation. More specifically, the controller <NUM> may be configured to modulate the electric power measurement signals <NUM> based on the sine and cosine of the rotor shaft position measurement signals <NUM>. This modulation shifts the amplitude of the 1P frequency component of the electric power measurement signals <NUM> from a time-dependent portion of the signals <NUM> to a non-time dependent portion of the signals <NUM>. After sine and cosine modulation, the controller <NUM> may be configured to pass the electric power measurement signals <NUM> through one or more low pass filters, such as one or more first-order filters, to remove the time-dependent portions of the signals <NUM>. After filtering, the controller <NUM> may be configured to extract the mean amplitude of the 1P frequency component of the electric power measurement signals <NUM> via a suitable mathematical function. Nevertheless, in alternative embodiments, the controller <NUM> may be configured to determine the mean amplitude of the 1P frequency component of the electric power output in any other suitable manner.

The controller <NUM> may also be configured to determine when a mass imbalance is present in the rotor <NUM> of the wind turbine <NUM> based on the 1P frequency component <NUM> of the electric power output of the generator <NUM>. In general, a mass imbalance in the rotor <NUM> causes oscillations in the electric power measurement signals <NUM>, which are reflected in the 1P frequency component <NUM>. As such, the controller <NUM> may include mass imbalance logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the mass imbalance logic <NUM>, the controller <NUM> may determine when a mass imbalance (e.g., as indicated by arrow <NUM> in <FIG>) is present in the rotor <NUM> based on the 1P frequency component <NUM> of the electric power output of the generator <NUM>. In alternative embodiments,.

Additionally, when the mass imbalance <NUM> is present in the rotor <NUM>, the controller <NUM> may be configured to initiate various control actions to minimize the effect thereof on the wind turbine <NUM>. As such, the controller <NUM> may include control action logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the control action logic <NUM>, the controller <NUM> initiates a control action associated with reducing an effect of the mass imbalance <NUM> on the wind turbine <NUM>. As will be described below, the controller <NUM> may be configured to initiate control actions by at least one of transmitting the feedback signals <NUM> to the user interface <NUM> or transmitting the control signals <NUM> to the pitch adjustment mechanisms <NUM>. In further embodiments, however, the controller <NUM> may be configured to initiate control actions by transmitting control signals to any other suitable component of the wind turbine <NUM> and/or the system <NUM> (e.g., a yaw drive, braking system, etc.).

Furthermore, the controller <NUM> may be configured to initiate a control action associated with notifying an operator of the wind turbine <NUM> that the mass imbalance <NUM> is present within the rotor <NUM>. For example, when the mass imbalance <NUM> is present, the controller <NUM> may be configured to transmit the feedback signals <NUM> to the user interface <NUM>. The feedback signals <NUM> instruct the user interface <NUM> to present a visual or audible notification or indicator to the operator of the wind turbine <NUM> indicating that the mass imbalance <NUM> is present within the rotor <NUM>.

Furthermore, the controller <NUM> may be configured to initiate a control action associated with derating the generator <NUM> (<FIG> and <FIG>). For example, when the mass imbalance <NUM> is present within the rotor <NUM>, the controller <NUM> may be configured to transmit the control signals <NUM> to the pitch adjustment mechanisms <NUM>. The control signals <NUM> instruct each pitch adjustment mechanism <NUM> to adjust the current pitch angle of the corresponding rotor blade <NUM> (<FIG>) to a new pitch angle such that the generator <NUM> produces less power (i.e., is derated). Nevertheless, in alternative embodiments, the controller <NUM> may be configured to initiate any suitable control action associated with derating the generator <NUM>.

Moreover, in several embodiments, the controller <NUM> may be configured to initiate a control action associated with terminating power generation of the generator <NUM> (<FIG> and <FIG>). For example, when the mass imbalance <NUM> is present within the rotor <NUM>, the controller <NUM> may be configured to transmit the control signals <NUM> to the pitch adjustment mechanisms <NUM>. The control signals <NUM> instruct each pitch adjustment mechanism <NUM> to adjust the current pitch angle of the corresponding rotor blade <NUM> (<FIG>) to a feathered position such that the generator <NUM> ceases to produce power. Nevertheless, in such embodiments, the controller <NUM> may be configured to initiate any suitable control action associated with terminating power generation of the generator <NUM>.

<FIG> illustrates another embodiment of the system <NUM> for detecting a mass imbalance in the rotor <NUM> of the wind turbine <NUM>. In the embodiment illustrated in <FIG>, the system <NUM> includes the rotor shaft position sensor <NUM> and the acceleration sensor <NUM>. As such, the controller <NUM> may be configured to detect a mass imbalance in the rotor <NUM> based the rotational position of the rotor shaft <NUM> and the acceleration of the tower <NUM> of the wind turbine <NUM>.

In such embodiment, the controller <NUM> may be configured to determine a mean amplitude of the 1P frequency component of the acceleration of the tower <NUM> based on the acceleration measurement signals <NUM> and the rotor shaft position measurement signals <NUM>. More specifically, as mentioned above, the controller <NUM> is communicatively coupled to the rotor shaft position sensor <NUM> and the acceleration sensor <NUM>. In this respect, the controller <NUM> receives the rotor shaft position measurement signals <NUM> from the rotor shaft position sensor <NUM> and the acceleration measurement signals (e.g., as indicated by arrow <NUM> in <FIG>) from the acceleration sensor <NUM>. Furthermore, the controller <NUM> may include 1P frequency component logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the 1P frequency component logic <NUM>, the controller <NUM> may determine a mean amplitude of a 1P frequency component (e.g., as indicated by arrow <NUM> in <FIG>) of the acceleration of the tower <NUM> based on the acceleration measurement signals <NUM> and the rotor shaft position measurement signals <NUM>.

In certain embodiments, for example, the controller <NUM> may be configured to determine the mean amplitude of the 1P frequency component of the acceleration of the tower <NUM> using sine and cosine modulation. More specifically, the controller <NUM> may be configured to modulate the acceleration measurement signals <NUM> based on the sine and cosine of the rotor shaft position measurement signals <NUM>. This modulation shifts the amplitude of the 1P frequency component of the acceleration measurement signals <NUM> from a time-dependent portion of the signals <NUM> to a non-time dependent portion of the signals <NUM>. After sine and cosine modulation, the controller <NUM> may be configured to pass the acceleration measurement signals <NUM> through one or more low pass filters, such as one or more first-order filters, to remove the time-dependent portions of the signals <NUM>. After filtering, the controller <NUM> may be configured to extract the mean amplitude of the 1P frequency component of the acceleration measurement signals <NUM> via a suitable mathematical function. Nevertheless, in alternative embodiments, the controller <NUM> may be configured to determine the mean amplitude of the 1P frequency component of acceleration of the tower <NUM> in any other suitable manner.

The controller <NUM> may also be configured to determine when a mass imbalance is present in the rotor <NUM> of the wind turbine <NUM> based on the 1P frequency component <NUM> of the acceleration of the tower <NUM>. In general, a mass imbalance in the rotor <NUM> causes oscillations in the acceleration measurement signals <NUM>, which are reflected in the 1P frequency component <NUM>. As such, the controller <NUM> may include mass imbalance logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the mass imbalance logic <NUM>, the controller <NUM> may determine when a mass imbalance (e.g., as indicated by arrow <NUM> in <FIG>) is present in the rotor <NUM> based on the mean amplitude of the 1P frequency component <NUM> of the acceleration of the tower <NUM>.

Additionally, when the mass imbalance <NUM> is present in the rotor <NUM>, the controller <NUM> may be configured to initiate various control actions to minimize the effect thereof on the wind turbine <NUM>. As such, the controller <NUM> may include control action logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the control action logic <NUM>, the controller <NUM> initiates a control action associated with reducing an effect of the mass imbalance <NUM> on the wind turbine <NUM>. For example, such control actions may be the same as the control actions initiated by executing the control action logic <NUM> described above in the context of <FIG>. Nevertheless, in alternative embodiments, the control actions initiated by executed the control logic <NUM> may be different than the control actions initiated by executing the control action logic <NUM>.

<FIG> illustrates a further embodiment of the system <NUM> for detecting a mass imbalance in the rotor <NUM> of the wind turbine <NUM>. In the embodiment illustrated in <FIG>, the system <NUM> includes the generator position sensor <NUM>, the pitch angle sensor <NUM>, and the wind speed sensor <NUM>. As such, the controller <NUM> may be configured to detect a mass imbalance in the rotor <NUM> based the rotational position of a component of the generator <NUM> or the generator shaft <NUM>, the pitch angle of the rotor blades <NUM>, and the wind speed of wind experienced by the wind turbine <NUM>.

In such embodiment, the controller <NUM> may be configured to determine an aerodynamic torque exerted on the rotor <NUM> based on the pitch angle measurement signals <NUM>, the wind speed measurement signals <NUM>, and aerodynamic characteristics <NUM> of the rotor <NUM>. In one embodiment, the aerodynamic characteristic <NUM> may be stored in the memory device(s) <NUM> of the controller <NUM>. As mentioned above, the controller <NUM> is communicatively coupled to the pitch angle sensor <NUM> and the wind speed sensor <NUM>. In this respect, the controller <NUM> receives the pitch angle measurement signals (e.g., as indicated by arrow <NUM> in <FIG>) from the pitch angle sensor <NUM> and the wind speed measurement signals (e.g., as indicated by arrow <NUM> in <FIG>) from the wind speed sensor <NUM>. Furthermore, the controller <NUM> may include aerodynamic torque logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the aerodynamic torque logic <NUM>, the controller <NUM> may determine the aerodynamic torque (e.g., as indicated by arrow <NUM> in <FIG>) exerted on the rotor <NUM> based on the pitch angle measurement signals <NUM>, the wind speed measurement signals <NUM>, and the aerodynamic characteristics <NUM>.

The controller <NUM> may also be configured to determine an inertial torque exerted on the rotor <NUM> based on the generator position measurement signals <NUM>. As mentioned above, the controller <NUM> is communicatively coupled to the generator position sensor <NUM>. In this respect, the controller <NUM> receives the generator position measurement signals (e.g., as indicated by arrow <NUM> in <FIG>) from the generator position sensor <NUM>. Furthermore, the controller <NUM> may include inertial torque logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the inertial torque logic <NUM>, the controller <NUM> may determine the inertial torque (e.g., as indicated by arrow <NUM> in <FIG>) exerted on the rotor <NUM> based on the generator position measurement signals <NUM>. In embodiments of the system <NUM> that do not include the generator position sensor <NUM>, the controller <NUM> may be configured to determine the inertial torque <NUM> based on the rotor shaft position measurement signals <NUM> and a gear ratio of the gearbox <NUM> (<FIG>).

Furthermore, the controller <NUM> may be configured to determine a mass imbalance torque exerted on the rotor <NUM> based on aerodynamic torque <NUM> and the inertial torque <NUM>. As such, the controller <NUM> may include mass imbalance torque logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the imbalance torque logic <NUM>, the controller <NUM> may determine the mass imbalance torque (e.g., as indicated by arrow <NUM> in <FIG>) exerted on the rotor <NUM> based on the aerodynamic torque <NUM> and the inertial torque <NUM>. For example, in one embodiment, the mass imbalance torque <NUM> may be determined by subtracting the inertial torque <NUM> from the aerodynamic torque <NUM>.

Moreover, the controller <NUM> may be configured to determine a mean amplitude of the 1P frequency component of the mass imbalance torque <NUM>. As such, the controller <NUM> may include 1P frequency component logic <NUM> having one or more mathematical functions and/or one or more look-up tables. For example, in one embodiment, the 1P frequency component logic <NUM> may include a 1P filter. By executing the 1P frequency component logic <NUM>, the controller <NUM> may determine a mean amplitude of the 1P frequency component (e.g., as indicated by arrow <NUM> in <FIG>) of the mass imbalance torque <NUM>.

Additionally, the controller <NUM> may also be configured to determine when a mass imbalance is present in the rotor <NUM> of the wind turbine <NUM> based on the mean amplitude of the 1P frequency component <NUM> of the mass imbalance torque <NUM>. In general, a mass imbalance in the rotor <NUM> causes oscillations in the mass imbalance torque <NUM>, which are reflected in the 1P frequency component <NUM>. As such, the controller <NUM> may include mass imbalance logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the mass imbalance logic <NUM>, the controller <NUM> may determine when a mass imbalance (e.g., as indicated by arrow <NUM> in <FIG>) is present in the rotor <NUM> based on the mean amplitude of the 1P frequency component <NUM> of the mass imbalance torque <NUM>. Furthermore, in some embodiments, by executing the mass imbalance logic <NUM>, the controller <NUM> may also determine a magnitude and/or location of the mass imbalance <NUM> based on the mean amplitude of the 1P frequency component <NUM> of the mass imbalance torque <NUM>.

When the mass imbalance <NUM> is present in the rotor <NUM>, the controller <NUM> may be configured to initiate various control actions to minimize the effect thereof on the wind turbine <NUM>. As such, the controller <NUM> may include control action logic <NUM> having one or more mathematical functions and/or one or more look-up tables. By executing the control action logic <NUM>, the controller <NUM> initiates a control action associated with reducing an effect of the mass imbalance <NUM> on the wind turbine <NUM>. For example, such control actions may be the same as the control actions initiated by executing the control action logic <NUM>, <NUM> described above in the context of <FIG> and <FIG>. Nevertheless, in alternative embodiments, the control actions initiated by executed the control logic <NUM> may be different than the control actions initiated by executing the control action logic <NUM>, <NUM>.

As mentioned above, in certain embodiments, the controller <NUM> may be configured to determine the magnitude and/or location of the mass imbalance <NUM>. In such embodiments, the controller <NUM> may be configured to initiate particular control actions based on the determined magnitude and/or location of the mass imbalance <NUM>. As such, in one embodiment, the controller <NUM> may be configured to compare the magnitude of the mass imbalance <NUM> to a plurality of mass imbalance thresholds and initiate specific control actions based on the particular mass imbalance threshold that the magnitude of the mass imbalance <NUM> exceeds. For example, the controller <NUM> may be configured to compare the magnitude of the mass imbalance <NUM> to a first mass imbalance threshold, a second mass imbalance threshold, and a third mass imbalance threshold. In general, the second mass imbalance threshold may be higher than the first mass imbalance threshold, and the third mass imbalance threshold may be higher than the second mass imbalance threshold. As such, the controller <NUM> may be configured to initiate a control action associated with notifying an operator of the wind turbine <NUM> when the magnitude of the mass imbalance <NUM> exceeds the first mass imbalance threshold. When the magnitude of the mass imbalance <NUM> exceeds the second mass imbalance threshold, the controller <NUM> may be configured to initiate a control action associated with derating the generator <NUM>. Furthermore, the controller <NUM> may be configured to initiate a control action initiate a control action associated with terminating power generation of the generator <NUM> when the magnitude of the mass imbalance <NUM> exceeds the third mass imbalance threshold. Nevertheless, the controller <NUM> may be configured to initiate any suitable control action when the magnitude of the mass imbalance <NUM> exceeds any mass imbalance threshold.

The system <NUM> may be configured to detect mass imbalances when the wind turbine <NUM> is operating in a normal, power-generating mode and in a special, non-power-generating mode. For example, the embodiments of the system <NUM> that determine the presence of a mass imbalance <NUM>, <NUM> based on the electric power output of the generator <NUM> (i.e., the embodiment shown in <FIG>) and acceleration of the tower <NUM> (i.e., the embodiment shown in <FIG>) may be used in the normal, power-generating mode. Conversely, the embodiment of the system <NUM> that determine the presence of a mass imbalance <NUM> based on the mass imbalance torque <NUM> may be used during special, non-power-generating mode, such as during commissioning of the wind turbine <NUM>.

<FIG> illustrates one embodiment of a method <NUM> for monitoring wear on a gearbox of a wind turbine in accordance with aspects of the present subject matter. 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. As such, the 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 in <FIG>, at (<NUM>), the method <NUM> may include receiving, with a computing device, sensor data indicative of an operating characteristic of the wind turbine. For example, as described above, the controller <NUM> may be communicatively coupled to various combinations of the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. As such, the controller <NUM> may be configured to receive measurement signals <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> indicative of various operating characteristics of the wind turbine <NUM> from the associated sensors the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

At (<NUM>), the method <NUM> may include determining, with the computing device, a mean amplitude of a 1P frequency component of the operating characteristic. For example, as described above, the controller <NUM> may be configured to execute various logic <NUM>, <NUM>, <NUM> to determine the mean amplitude of the 1P frequency component <NUM>, <NUM>, <NUM> of the operating characteristic.

Furthermore, at (<NUM>), the method <NUM> may include determining, with the computing device, when a mass imbalance is present within the rotor based on the mean amplitude of the 1P frequency component. For example, as described above, the controller <NUM> may be configured to execute various logic <NUM>, <NUM>, <NUM> to determine when the mass imbalance <NUM>, <NUM>, <NUM> is present in the rotor <NUM> based on the associated the mean amplitude of the 1P frequency component <NUM>, <NUM>, <NUM>.

Moreover, at (<NUM>), the method <NUM> may include, when the mass imbalance is present within the rotor, initiating, with the computing device, a control action associated with reducing an effect of the mass imbalance on the wind turbine. For example, as described above, the controller <NUM> may be configured to initiate (e.g., by executing the control action logic <NUM>, <NUM>, <NUM>) a control action associated with reducing the effect of the mass imbalance <NUM>, <NUM>, <NUM> on the wind turbine <NUM>. Such control actions may include notifying an operator of the wind turbine <NUM>, derating the generator <NUM> of the wind turbine <NUM>, and/or terminating power generation of the wind turbine <NUM>.

The disclosed system <NUM> and method <NUM> for detecting a mass imbalance within a rotor of a wind turbine provide various technical advantages. For example, the system <NUM> and the method <NUM> require only sensors that are generally already present on the wind turbine <NUM>. Furthermore, the system <NUM> and the method <NUM> may be used when the wind turbine <NUM> is in a power-generating mode or a non-power-generating mode. Additionally, the system <NUM> and the method <NUM> facilitate increased tower height and/or decreased tower stiffness.

Claim 1:
A method (<NUM>) for detecting a mass imbalance (<NUM>, <NUM>, <NUM>) in a rotor (<NUM>) of a wind turbine (<NUM>), the method (<NUM>) comprising:
receiving (<NUM>), with a computing device, sensor data indicative of an operating characteristic of the wind turbine (<NUM>), wherein the operating characteristic comprises an electric power output of a generator of the wind turbine (<NUM>), an acceleration of a tower (<NUM>) of the wind turbine (<NUM>) or a mass imbalance torque (<NUM>) of a tower (<NUM>) of the wind turbine (<NUM>);
determining (<NUM>), with the computing device, a mean amplitude of a designated frequency component (<NUM>, <NUM>, <NUM>) of the operating characteristic, wherein the designated frequency component (<NUM>, <NUM>, <NUM>) comprises a 1P frequency component (<NUM>, <NUM>, <NUM>) of the operating characteristic;
determining (<NUM>), with the computing device, when a mass imbalance (<NUM>, <NUM>, <NUM>) is present within the rotor (<NUM>) based on the mean amplitude of the designated frequency component (<NUM>, <NUM>, <NUM>); and
when the mass imbalance (<NUM>, <NUM>, <NUM>) is present within the rotor (<NUM>), initiating (<NUM>), with the computing device, a control action associated with reducing an effect of the mass imbalance (<NUM>, <NUM>, <NUM>) on the wind turbine (<NUM>);
characterized in that
when the wind turbine is operating in a power-generating mode, the operating characteristic comprises the electric power output of the generator of the wind turbine (<NUM>) or the acceleration of the tower (<NUM>) of the wind turbine (<NUM>) and when the wind turbine is operating in a non-power-generating mode, the operating characteristic comprises the mass imbalance torque (<NUM>) of the tower (<NUM>) of the wind turbine (<NUM>).