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 modem wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor including 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.

During operation, the direction of the wind which powers the wind turbine may change. The wind turbine may thus adjust the nacelle through, for example, a yaw adjustment about a longitudinal axis of the tower to maintain alignment with the wind direction. In addition, the wind turbine may adjust a pitch angle of one or more of the rotor blades via a pitch drive mechanism configured with a pitch bearing to change the angle of the blades with respect to the wind.

Typical pitch drive mechanisms include pitch drive motor, a pitch drive gearbox, and a pitch drive pinion. In such configurations, the pitch drive motor is coupled to the pitch drive gearbox so that the pitch drive motor imparts mechanical force to the pitch drive gearbox. Similarly, the pitch drive gearbox may be coupled to the pitch drive pinion for rotation therewith. The pitch drive pinion may, in turn, be in rotational engagement with the pitch bearing coupled between the hub and a corresponding rotor blade such that rotation of the pitch drive pinion causes rotation of the pitch bearing. Thus, in such embodiments, rotation of the pitch drive motor drives the pitch drive gearbox and the pitch drive pinion, thereby rotating the pitch bearing and the rotor blade about the pitch axis.

During normal operation, the pitch drive motors are driven by the power grid. However, in some instances, such as during an adverse grid event, the pitch drive motors may be driven by one or more backup batteries. If pitching of the blades relies on such batteries (i.e. due to a grid loss), it is important to ensure that the batteries are capable of operating when needed. Overtime, however, the motor batteries of the pitch drive mechanisms lose their charge and eventually die. Thus, if such batteries die without notice, the rotor blade associated with the dead batteries may become stuck since there is no power available to pitch the blade. In such instances, loads may increase on the stuck rotor blade, thereby causing damage thereto.

As such, a predictive maintenance system and method that addresses the aforementioned issues would be desired. Accordingly, the present disclosure is directed to systems and methods for estimating the consumed battery life of the pitch system of the wind turbine based on temperature.

Documents cited during the patent prosecution are i. : <CIT> and <CIT>.

In one aspect, the present disclosure is directed to a method for estimating consumed battery life of at least one battery of a pitch drive mechanism of a rotor blade of a wind turbine. The method includes monitoring, via at least one sensor, an actual temperature of the battery over a predetermined time period. The method also includes storing, via a turbine controller, the monitored actual temperatures of the battery during the predetermined time period. Further, the method includes determining, via the turbine controller, the consumed battery life as a function of the monitored actual temperatures.

According to the invention the battery is stored in a thermally-isolated battery cabinet. In such embodiments, the temperature of the battery may correspond to a cabinet temperature of the battery cabinet. Since the battery has a thermal time constant, the internal battery temperature will lag the measured temperature in the battery cabinet. Thus, the method may also include calibrating the monitored actual temperatures using a thermal model of the battery cabinet and the battery to improve accuracy. In such embodiments, the calibration can be made either in real time or performed later prior to calculating the consumed life of the battery.

In another embodiment, the step of determining the consumed battery life as a function of the monitored temperature may include determining the consumed battery life using an Arrhenius equation.

In further embodiments, the method may include averaging a subset of the monitored actual temperatures for predetermined time intervals to obtain an average temperature and determining the consumed battery life as a function of the average temperature. More specifically, in certain embodiments, the predetermined time intervals may range from about five (<NUM>) minutes to about twenty (<NUM>) minutes, e.g. such as about ten (<NUM>) minutes.

In several embodiments, the method may further include generating, via the turbine controller, an alarm signal if the consumed battery life exceeds a predetermined threshold. For example, in one embodiment, the predetermined threshold may correspond to <NUM>% or greater of a total battery life of the battery. As such, the method may further include replacing the battery if the consumed battery life exceeds the predetermined threshold.

In yet another embodiment, the battery cabinet may contain a plurality of batteries stored therein. In such embodiments, the method may further include replacing all of the plurality of batteries in the battery cabinet if the consumed battery life exceeds the predetermined threshold.

In still further embodiments, the method may also include replacing additional batteries of pitch drive mechanisms of adjacent rotor blades if the consumed battery life exceeds the predetermined threshold.

In another aspect, the present disclosure is directed to a system for estimating consumed battery life of at least one battery of a pitch drive mechanism of a rotor blade of a wind turbine. The system includes at least one sensor configured for monitoring an actual temperature of the battery over a predetermined time period and a controller communicatively coupled to the at least one sensor. The controller includes at least one processor configured to perform one or more operations, including but not limited to storing the monitored actual temperatures of the battery during the predetermined time period and determining the consumed battery life as a function of the monitored actual temperatures.

According to the invention, the battery (or batteries) is (are) stored in a thermally-isolated battery cabinet. In such embodiments, the monitored temperature of the battery may correspond to a cabinet temperature of the battery cabinet. It should also be understood that the system may further include any of the additional features and/or steps as described herein.

In yet another aspect, the present disclosure is directed to a method for preventing damaging loads from occurring during an adverse grid event of a wind turbine. The method includes monitoring, via at least one sensor, an actual temperature of at least one battery of a pitch drive mechanism of a rotor blade of the wind turbine over a predetermined time period. Another step includes storing, via a turbine controller, the monitored actual temperatures of the battery during the predetermined time period. The method also includes determining, via the turbine controller, the consumed battery life as a function of the monitored actual temperatures. Further, the method includes replacing the battery if the consumed battery life exceeds a predetermined threshold. It should also be understood that the method may further include any of the additional features and/or steps as described herein.

Referring now to the drawings, <FIG> illustrates perspective view of one embodiment of a wind turbine <NUM> according to the present disclosure. As shown, the wind turbine <NUM> 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 <NUM> (<FIG>) positioned within the nacelle <NUM> to permit electrical energy to be produced.

Referring now to <FIG>, a simplified, internal view of one embodiment of the nacelle <NUM> of the wind turbine <NUM> is illustrated. As shown, a generator <NUM> may be disposed within the nacelle <NUM>. In general, the generator <NUM> may be coupled to the rotor <NUM> of the wind turbine <NUM> for generating electrical power from the rotational energy generated by the rotor <NUM>. For example, the rotor <NUM> may include a main shaft <NUM> coupled to the hub <NUM> for rotation therewith. The generator <NUM> may then be coupled to the main shaft <NUM> such that rotation of the main shaft <NUM> drives the generator <NUM>. For instance, in the illustrated embodiment, the generator <NUM> includes a generator shaft <NUM> rotatably coupled to the main shaft <NUM> through a gearbox <NUM>. However, in other embodiments, it should be appreciated that the generator shaft <NUM> may be rotatably coupled directly to the main shaft <NUM>. Alternatively, the generator <NUM> may be directly rotatably coupled to the main shaft <NUM>.

It should be appreciated that the main shaft <NUM> may generally be supported within the nacelle <NUM> by a support frame or bedplate <NUM> positioned atop the wind turbine tower <NUM>. For example, the main shaft <NUM> may be supported by the bedplate <NUM> via a pair of pillow blocks <NUM>, <NUM> mounted to the bedplate <NUM>.

As shown in <FIG> and <FIG>, the wind turbine <NUM> may also include a turbine control system or a turbine controller <NUM> within the nacelle <NUM>. For example, as shown in <FIG>, the turbine controller <NUM> is disposed within a control cabinet <NUM> mounted to a portion of the nacelle <NUM>. However, it should be appreciated that the turbine controller <NUM> may be disposed at any location on or in the wind turbine <NUM>, at any location on the support surface <NUM> or generally at any other location. The turbine controller <NUM> may generally be configured to control the various operating modes (e.g., start-up or shutdown sequences) and/or components of the wind turbine <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>).

Further, the turbine controller <NUM> may also be communicatively coupled to each pitch adjustment mechanism <NUM> of the wind turbine <NUM> (one of which is shown) through a separate or integral pitch controller <NUM> (<FIG>) for controlling and/or altering the pitch angle of the rotor blades <NUM> (i.e., an angle that determines a perspective of the rotor blades <NUM> with respect to the direction <NUM> of the wind).

In addition, as shown in <FIG>, one or more sensors <NUM>, <NUM>, <NUM> may be provided on the wind turbine <NUM>. More specifically, as shown, a blade sensor <NUM> may be configured with one or more of the rotor blades <NUM> to monitor the rotor blades <NUM>. Further, as shown, a wind sensor <NUM> may be provided on the wind turbine <NUM>. For example, the wind sensor <NUM> may a wind vane, and anemometer, a LIDAR sensor, or another suitable sensor that measures wind speed and/or direction. In addition, a pitch sensor <NUM> may be configured with each of the pitch drive mechanism <NUM>, e.g. with one or more batteries of the pitch drive motors <NUM> thereof, which will be discussed in more detail below. As such, the sensors <NUM>, <NUM>, <NUM> may further be in communication with the controller <NUM>, and may provide related information to the controller <NUM>. For example, the pitch sensor(s) <NUM> may correspond to temperature sensors that send temperature signals to the controllers <NUM>, <NUM> to indicate an actual temperature of the pitch batteries, which is described in more detail herein.

It should also 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 and/or an indirect measurement of such parameters. Thus, the sensors described herein 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 condition.

Referring now to <FIG>, there is illustrated a block diagram of one embodiment of suitable components that may be included within the controller <NUM> according to the present disclosure. As shown, the controller <NUM> may include one or more processor(s) <NUM> and associated memory device(s) <NUM> configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like and storing relevant data as disclosed herein). 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>. Further, the communications module <NUM> may include a sensor interface <NUM> (e.g., one or more analog-to-digital converters) to permit signals transmitted from one or more sensors <NUM>, <NUM>, <NUM> to be converted into signals that can be understood and processed by the processors <NUM>. 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 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 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. Such memory device(s) <NUM> may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) <NUM>, configure the controller <NUM> to perform various functions including, but not limited to, transmitting suitable control signals to implement corrective action(s) in response to a distance signal exceeding a predetermined threshold as described herein, as well as various other suitable computer-implemented functions.

Referring now to <FIG>, a schematic diagram of one embodiment an overall pitch system <NUM> for the wind turbine <NUM> is illustrated. More specifically, as shown, the pitch system <NUM> may include a plurality of pitch drive mechanisms <NUM>, i.e. one for each pitch axis <NUM>. Further, as shown, each of the pitch drive mechanisms may be communicatively coupled to the power grid <NUM> as well as one or more backup batteries <NUM>. More specifically, as shown, each pitch drive mechanism <NUM> may be associated with a plurality of backup batteries <NUM> that are stored in a battery cabinet <NUM>. Thus, in certain embodiments, the battery cabinets <NUM> may be thermally isolated containers.

During normal operation of the wind turbine <NUM>, the pitch drive motors <NUM> are driven by the power grid <NUM>. However, in some instances, such as during an adverse grid event or grid loss, the pitch drive motors <NUM> may be driven by one or more backup batteries <NUM>. If pitching of the rotor blades <NUM> relies on such batteries <NUM> (i.e. due to a grid loss), it is important to ensure that the batteries <NUM> are capable of operating when needed. Thus, the turbine controller <NUM> (or pitch controller <NUM>) is configured to implement a control strategy to estimate the consumed battery life of one or more of the batteries <NUM> of the pitch drive mechanisms <NUM> so as to reduce damaging loads from occurring during an adverse grid event of a wind turbine <NUM> or any other scenarios where battery power is used to pitch the rotor blades <NUM>.

More specifically, as shown in <FIG>, a flow diagram of one embodiment of a method <NUM> for estimating consumed battery life of at least one battery <NUM> of the pitch drive mechanism <NUM> is illustrated. As shown at <NUM>, the method <NUM> includes monitoring, via at least one sensor (e.g. one of the pitch sensors <NUM>), an actual temperature of the battery <NUM> over a predetermined time period. More specifically, in one embodiment, the monitored temperature of the battery(ies) <NUM> may correspond to a cabinet temperature of the associated battery cabinet <NUM>. As shown at <NUM>, the method <NUM> also includes storing the monitored actual temperatures of the battery <NUM> during the predetermined time period, e.g. in the memory devices <NUM> of the turbine controller <NUM>.

Since the battery <NUM> has a thermal time constant, the internal battery temperature will lag the measured temperature in the battery cabinet <NUM>. To improve accuracy, the stored temperatures may be calibrated using a thermal model of the battery cabinet <NUM> and associated battery <NUM>. This calibration can be made either in real time (before <NUM>) or performed later prior to calculating the consumed life of the battery (i.e. after <NUM> but before <NUM>).

As shown at <NUM>, the method <NUM> includes determining the consumed battery life as a function of the monitored actual temperatures via the turbine controller <NUM>. For example, in one embodiment, the controller <NUM> may be configured to determine the consumed battery life using an Arrhenius equation. As used herein, an Arrhenius equation generally refers to a formula for the temperature dependence of reaction rates. For example, in one embodiment, the Arrhenius equation may be represented by Equation (<NUM>) below: <MAT> Where.

Thus, the Arrhenius equation provides the dependence of the rate constant of a chemical reaction on the absolute temperature, a pre-exponential factor and other constants of the reaction. Additionally, an acceleration factor (AF) can be derived from the Arrhenius equation in order to obtain the variation of the consumed battery life for any battery temperature with respect to a reference temperature.

In further embodiments, the method <NUM> may include averaging a subset of the monitored actual temperatures for predetermined time intervals to obtain an average temperature. In such embodiments, the controller <NUM> can then determine the consumed battery life as a function of the average temperature. It should be understood that the predetermined time intervals may include any suitable time period, for example, ranging from about five (<NUM>) minutes to about twenty (<NUM>) minutes, e.g. such as about ten (<NUM>) minutes. In additional embodiments, the predetermined time intervals may be less than <NUM> minutes or greater than <NUM> minutes.

If the consumed battery life exceeds a predetermined threshold, the controller <NUM> may be configured to generate an alarm signal, such as a software alarm in the SCADA system. In this way, maintenance manuals for the batteries <NUM> may be modified such that battery replacement in all and/or a single axis could be completed when the alarm signal is generated. As such, the issue of the battery life being dependent on site temperature is effectively eliminated.

In one embodiment, the predetermined threshold as described herein may correspond to <NUM>% or greater of a total battery life of the batteries <NUM>. It should be understood, however, the predetermined threshold may also be set to be less than <NUM>% of the total battery life of the battery <NUM>. Accordingly, setting a minimum threshold for battery life can be useful in order to set a minimum pitch rate in case of grid loss. In other words, the present disclosure ensures all batteries <NUM> have more than the predetermined threshold of life left (e.g. more than <NUM>%); therefore, the probability of having a pitch rate below a certain minimum rate (e.g. <NUM>°/s) is also low, thereby reducing the loads for this scenario. As such, the present disclosure prevents the rotor blades <NUM> from becoming stuck in the instance of a grid loss.

Accordingly, the method <NUM> may also include replacing the battery <NUM> if the consumed battery life exceeds the predetermined threshold. In such embodiments, the method <NUM> may also include replacing all of the batteries <NUM> in the battery cabinet <NUM> if the consumed battery life of one of the batteries <NUM> therein exceeds the predetermined threshold. In addition, the method <NUM> may include replacing additional batteries <NUM> of pitch drive mechanisms <NUM> of adjacent rotor blades <NUM> if the consumed battery life of one of the batteries <NUM> in one of the battery cabinets <NUM> exceeds the predetermined threshold. In other words, for certain embodiments, all of the batteries <NUM> in an axis could be replaced at the same time to save time and costs associated with maintenance of such batteries <NUM>. Alternatively, if all of batteries <NUM> for the axes were not replaced, the controller <NUM> may be configured to calculate the battery life left per axis using, e.g. three separate equations. Such an embodiment may be beneficial in cases where batteries <NUM> were replaced due to other failure modes other than wear out.

Referring now to <FIG>, a flow diagram of one embodiment of a method <NUM> for preventing damaging loads from occurring during an adverse grid event of a wind turbine <NUM> is illustrated. As shown at <NUM>, the method <NUM> includes monitoring an actual temperature of at least one battery <NUM> of a pitch drive mechanism <NUM> of a rotor blade <NUM> of the wind turbine <NUM> over a predetermined time period, e.g. via at least one sensor <NUM>. As shown at <NUM>, the method <NUM> includes storing the monitored actual temperatures of the battery <NUM> during the predetermined time period via the turbine controller <NUM>, e.g. in the memory device(s) <NUM>. As shown at <NUM>, the controller <NUM> then determines the consumed battery life as a function of the monitored actual temperatures. Thus, as shown at <NUM>, the method <NUM> includes replacing the battery <NUM> if the consumed battery life exceeds a predetermined threshold.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art.

Claim 1:
A method for estimating consumed battery life of at least one battery of a pitch drive mechanism of a rotor blade of a wind turbine, the at least one battery being stored in a thermally-isolated battery cabinet, the method comprising:
monitoring, via at least one sensor, an actual temperature of the battery over a predetermined time period;
storing, via a turbine controller, the monitored actual temperatures of the battery during the predetermined time period; and,
determining, via the turbine controller, the consumed battery life as a function of the monitored actual temperatures.