Patent Description:
Batteries can be used to provide power in a variety of different applications. A battery can lose the ability to provide sufficient voltage to power a load as the battery ages. For instance, as a battery approaches end of life, an output voltage provided to a load can drop quickly. The inability of the battery to provide a required output voltage to power a load in certain condition can pose many challenges. For instance, the inability of a battery to power a load in a pitch drive system of a wind turbine system can result in an inability to pitch a wind turbine blade on a wind turbine, potentially leading to damage to the wind turbine. <CIT> relates to wind turbine backup power supply monitoring involving calculating a characteristic of the backup power supply based on monitored voltage and current values.

Various aspects and advantages of the invention 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 invention.

An aspect of the present disclosure is directed to a method for determining the remaining lifetime of a battery used to power a pitch system of a wind turbine. The method includes conducting test operations of the battery, wherein each test operation includes controlling, by one or more control devices, a discharge of the battery through a load. Each test operation includes obtaining, by the one or more control devices, data indicative of a discharge voltage and a discharge current of the battery during discharge through the load. Each test operation includes obtaining, by the one or more control devices, data indicative of a temperature associated with the battery during discharge through the load. Each test operation includes determining, by the one or more control devices, data indicative of remaining lifetime of the battery as a function of the discharge voltage, the discharge current, and the temperature. Each test operation includes performing, by the one or more control devices, at least one control action based at least in part on the data indicative of the remaining lifetime of the battery. The test operations are conducted more frequently as the battery approaches an end of life of the battery.

Another aspect of the present disclosure is directed to a test system configured for testing remaining lifetime of a battery used to power a pitch system in a wind turbine. The test system includes a resistive load. The test system includes a voltage sensor configured to measure a discharge voltage of the battery. The test system includes a current sensor configured to measure a discharge current of the battery. The test system includes a temperature sensor configured to measure a temperature associated with the battery. The test system includes a switching device configured to couple the resistive load to the battery. The test system includes a control device having one or more processors configured to execute computer-readable instructions stored in one or more memory devices to perform test operations of the battery. Each test operation includes controlling the switching device to couple the resistive load to the battery and discharge the battery through the resistive load. Each test operation includes obtaining data indicative of a discharge voltage of the battery during discharge through the resistive load from the voltage sensor. Each test operation includes obtaining data indicative of a discharge current of the battery during discharge through the resistive load from the current sensor. Each test operation includes obtaining data indicative of the temperature associated with the battery during discharge through the resistive load. Each test operation includes determining data indicative of remaining lifetime of the battery as a function of the discharge voltage, discharge current, and the temperature. Each test operation includes performing at least one control action, particularly providing a notification of a fault condition, based at least in part on the data indicative of remaining lifetime of the battery. The control device is configured to conduct the test operations more frequently as the battery approaches an end of life of the battery.

An example aspect of 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 conducting a test operation of at least one battery used to power a pitch drive mechanism of a rotor blade of the wind turbine. The method includes determining data indicative of remaining lifetime of the battery as a result of the one or more test operations as a function of a discharge current and a discharge voltage of the battery during the test operation. The method includes determining a fault condition based at least in part on data indicative of remaining lifetime of the battery. The method includes taking a preventive action based at least in part on the fault condition.

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

Example aspects of the present disclosure are directed to systems and methods for determining a remaining lifetime of a battery. A remaining lifetime of a battery refers to the time remaining before the battery can no longer provide an output voltage above a threshold under load after being fully charged. The remaining lifetime of the battery typically decreases after multiple charging and discharging cycles.

According to particular embodiments of the present disclosure, the remaining lifetime of a battery can be determined by subjecting the battery to a test operation. The test operation can include coupling the battery to a resistive load (e.g., a large resistor) and monitoring a discharge current and a discharge voltage of the battery. For instance, the test operation can close a switching element (e.g., a relay) to couple a battery to a resistive load for a time interval, such as a <NUM> second time interval, <NUM> second time interval, <NUM> second time interval, or other suitable time interval.

At the end of the time interval, a control device associated with the battery can obtain data indicative of a discharge current and a discharge voltage of the battery from suitable voltage and current sensors. Data indicative of a temperature associated with the battery (e.g., a temperature of the battery enclosure or cabinet) can also be obtained at the end of the time interval.

An internal resistance of the battery can be determined based on the discharge voltage and the discharge resistance. For instance, in some embodiments, data indicative of a constant no load voltage for the battery can be obtained (e.g., from data specified by the battery manufacturer or from battery testing). A difference between the no load voltage for the battery and the discharge voltage can be determined. The difference can be divided by the discharge current to determine an internal resistance for the battery.

Using the temperature measurement, the internal resistances for a brand new battery (e.g., beginning of life resistance) and worn out battery (e.g., end of life resistance) can be obtained. For instance, in some embodiments, the beginning of life and end of life resistances can be derived experimentally or from data from the battery manufacturer and correlated as a function of battery temperature. Using the measured battery temperature, data indicative of a beginning of life resistance and an end of life resistance can be obtained.

In some embodiments, data indicative of a remaining lifetime of a battery can be determined based on the determined internal resistance and the beginning of life resistance and end of life resistance. For instance, in some embodiments, the data indicative of a remaining lifetime of a battery can be expressed as a percentage of the difference between beginning of life resistance and the end of life resistance relative to a difference between the internal resistance and the end of life resistance.

A controller associated with the battery can be configured to take a control action based on the determined remaining lifetime of the battery. For instance, in some embodiments, a notification of a fault condition can be provided when a remaining lifetime of the battery falls below a threshold. In some embodiments, the notification for the fault condition can be provided when an average remaining lifetime over several operating tests of the battery falls below the threshold.

The notification can be associated with replacing the battery. For instance, in response to the notification, a technician or other user can replace the battery with a fresh battery or battery with sufficient lifetime remaining. In this way, negative events associated with powering systems with worn out batteries can be reduced.

For example, 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 wind turbine can include 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.

A pitch drive mechanism can include pitch drive motor, a pitch drive gearbox, and a pitch drive pinion. In such configurations, the pitch drive motor can be 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 can be driven by electrical power from 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. Over time, however, the motor batteries of the pitch drive mechanisms lose their capacity to store energy 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.

Determining control actions based on determined remaining lifetime of a battery according to example embodiments of the present disclosure can reduce the likelihood of such damage to a wind turbine. For example, a battery used to drive a pitch drive mechanism for a wind turbine can be periodically subjected to a test operation according to example embodiments of the present disclosure. Data indicative of remaining lifetime of the battery can be determined during the test operation. A fault condition can be determined based at least in part on data indicative of the remaining lifetime of the battery. The battery can be replaced, for instance, in response to the fault condition.

As used herein the use of the term "about" in conjunction with a numerical value is intended to refer to within <NUM>% of the stated amount. The use of the term "obtaining" or "obtain" can include receiving, determining, calculating, accessing, reading or otherwise obtaining data.

Aspects of the present disclosure are discussed with reference to a battery used to power a pitch system in a wind turbine. Those of ordinary skill in the art, using the disclosures provided herein, will understand that aspects of the present embodiments can be used with other applications without deviating from the scope of the present disclosure.

Referring now to the drawings, <FIG> illustrates a perspective view of one embodiment of a wind turbine <NUM> according to example aspects of 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> 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 shut-down 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 be a wind vane, an 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(s) <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. Additional sensors (not illustrated) can include voltage and current sensors used as part of a test system for conducting test operations of a battery to determine remaining lifetime of the battery according to example embodiments of the present disclosure.

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 used herein, a controller is one example of a control device. Other control devices can include microcontrollers, microprocessors, processing devices, application specific integrated circuits, or other devices configured to provide any of the control functionality and/or one or more of the operations of any of the methods disclosed herein.

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>. For instance, the controller <NUM> can send control signals (e.g., via communications module <NUM>) to switching elements (e.g., relays couple batteries to resistive load).

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.

Other sensors can be in communication with the controller <NUM>. For instance, a voltage sensor <NUM> can be in communication with the controller <NUM>. The voltage sensor <NUM> can be part of a test system for a battery for powering a pitch adjustment mechanism. The voltage sensor <NUM> can be configured to measure an output voltage (e.g., discharge voltage) of the battery when the battery is coupled to a test resistive load.

A current sensor <NUM> can be in communication with the controller <NUM>. The current sensor <NUM> can be part of a test system for a battery for powering a pitch adjustment mechanism. The current sensor <NUM> can be configured to measure an output current (e.g., discharge current) of the battery when the battery is coupled to a test resistive load.

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 of 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>.

<FIG> depicts an example test system <NUM> for conducting a test operation of a battery to determine remaining lifetime of a battery (e.g., batteries <NUM>) according to example embodiments of the present disclosure. The test system <NUM> includes a switching element <NUM>, such as one or more relays, transistors, or other switching elements that can be controlled to be in a conducting state or non-conducting state. The test system <NUM> includes a resistive load <NUM> (e.g., a test resistive load). A control device (e.g., controller <NUM>) can control switching element <NUM> to couple the battery <NUM> to the resistive load <NUM> to conduct a test operation for a time interval. The length of the time interval can be, for instance, about <NUM> seconds, about <NUM> seconds, about <NUM> seconds, about <NUM> second, or any other suitable time interval. During the test operation, the battery <NUM> discharges through the resistive load <NUM>.

The test system <NUM> can include a voltage sensor <NUM> and a current sensor <NUM>. The voltage sensor <NUM> can monitor an output voltage/discharge voltage (VL) for the battery <NUM> during discharge of the battery <NUM> through the load <NUM>. The current sensor <NUM> can monitor an output current/discharge current (IL) of the battery <NUM> through the load <NUM>. The test system can also include a sensor <NUM> (<FIG>) that measures a temperature associated with the battery <NUM>. For instance, the sensor <NUM> can measure a temperature of a battery cabinet <NUM> enclosing the battery <NUM>. In some embodiments, because the temperature of the battery can lag the measured temperature in the cabinet, a model can be used to estimate the internal temperature of the battery based on the measured cabinet temperature. The model can correlate internal temperature relative to measured cabinet temperature over time. As another example, the sensor <NUM> can measure a temperature associated with one or more battery chargers used to charge the battery.

The control device (e.g., controller <NUM>) can be configured to determine a remaining lifetime for the battery <NUM> based on data indicative of the temperature associated with the battery, the discharge voltage VL and the discharge current IL. For instance, the controller <NUM> can execute computer-readable instructions stored in a memory to perform operations to determine a remaining lifetime for the battery <NUM>.

For instance, <FIG> depicts a flow diagram of an example method (<NUM>) (e.g., operations) for determining a lifetime remaining of a battery according to example embodiments of the present disclosure. The method (<NUM>) can be implemented, for instance, by controller <NUM> or other control device(s). <FIG> depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that various steps of any of the methods disclosed herein can be adapted, expanded, rearranged, performed simultaneously, and/or rearranged in various ways without deviating from the scope of the present disclosure.

At (<NUM>), the method can include controlling a discharge of the battery through a load. For instance, the controller <NUM> can send a control signal to switching element <NUM> to couple the battery <NUM> to the resistive load <NUM>.

At (<NUM>), the method can include obtaining data indicative of a discharge voltage of the battery during discharge through the load. For instance, the controller <NUM> can obtain data from voltage sensor <NUM> indicative of discharge voltage VL.

At (<NUM>), the method can include obtaining data indicative of a discharge current of the battery during discharge through the load. For instance, the controller <NUM> can obtain data from current sensor <NUM> indicative of discharge current IL.

At (<NUM>), the method can include obtaining data indicative of a temperature associated with the battery, such as a temperature of the cabinet housing the battery and/or a temperature of one or more battery chargers used to charge the battery. For instance, the controller <NUM> can obtain data from temperature sensor <NUM> indicative of a temperature of battery cabinet <NUM> of the battery <NUM>.

At (<NUM>), the method can include determining data indicative of remaining lifetime of the battery. For instance, the controller <NUM> can execute logic (e.g., computer-readable instructions) to perform operations to determine remaining lifetime of the battery based at least in part on the data indicative of the discharge voltage VL, the data indicative of the discharge current IL, and the temperature associated with the battery <NUM>.

In example embodiments, the data indicative of remaining lifetime can be associated with internal resistance of the battery. The internal resistance can be determined as function of at least the discharge voltage and the discharge current as discussed with reference to <FIG> below.

In some embodiments, the data indicative of estimated lifetime of the battery can include a ratio of a difference between the internal resistance and an end of life resistance associated with the battery to a difference between a beginning of life resistance and an end of life resistance associated with the battery.

As used herein, an end of life resistance of a battery refers to a resistance value at or near internal resistance of a battery at end of life (e.g., within <NUM>% of the internal resistance of the battery at end of life). The end of life resistance can vary as a function of temperature associated with the battery. The end of life resistance can be determined from specification from the battery manufacturer or from test data from testing batteries of similar construction.

As used herein, a beginning of life resistance of a battery refers to a resistance value at or near internal resistance of a battery at beginning of life. (e.g., within <NUM>% of the internal resistance of the battery at beginning of life). The beginning of life resistance can vary as a function of temperature associated with the battery. The beginning of life resistance can be determined from specification from the battery manufacturer or from test data from testing batteries of similar construction.

<FIG> depicts a flow diagram of one example method (<NUM>) of performing operations to determine data indicative of remaining lifetime of the battery according to example embodiments of the present disclosure. The method (<NUM>) can be implemented, for instance, by controller <NUM> or other control device(s). <FIG> depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that various steps of any of the methods disclosed herein can be adapted, expanded, rearranged, performed simultaneously, and/or rearranged in various ways without deviating from the scope of the present disclosure.

At (<NUM>), the method includes determining an internal resistance of the battery as a function of at least the discharge voltage and the discharge current. For instance, in one implementation, the internal resistance can be determined by determining a difference between a no load voltage of the battery and the discharge voltage of the battery. The difference can be divided by the discharge current. As an example, the internal resistance of the battery can be determined based at least in part on the following: <MAT> where RInternal is the internal resistance, VNoLoad is a no load voltage associated with the battery, VL is the discharge voltage and IL is the discharge current. In some embodiments, VNoLoad can be a constant that is obtained from manufacturer specifications or testing of batteries of similar construction.

At (<NUM>), the method can include obtaining data indicative of beginning of life resistance and end of life resistance of the battery. As these values can be dependent on temperature, the beginning of life resistance and end of life resistance for the battery can be determined based at least in part on the data indicative of the temperature associated with the battery.

At (<NUM>), the method can include determining a first difference between the internal resistance and the end of life resistance. For instance, the internal resistance can be subtracted from the end of life resistance (or vice versa) to determine the first difference.

At (<NUM>), the method can include determining a second difference between the beginning of life resistance and the end of life resistance. For instance, the beginning of life resistance can be subtracted from the end of life resistance (or vice versa) to determine the second difference.

At (<NUM>), the method can include determining a ratio of the first difference and the second difference. For instance, the first difference can be divided by the second difference.

At (<NUM>), the ratio can be expressed as a percentage of lifetime remaining. For example, if the ratio is determined to be <NUM>, the percentage of lifetime remaining can be <NUM>%. As another example, if the ratio is determined to be <NUM>, the percentage of lifetime remaining can be <NUM>%.

<FIG> depicts a graphical representation of determining a remaining lifetime of a battery according to example embodiments of the present disclosure. <FIG> plots measured temperature along the horizontal axis and internal resistance of the battery along the vertical axis. Curve <NUM> represents the beginning of life resistance as a function of temperature. Curve <NUM> represents the end of life resistance as a function of temperature. Curve <NUM> represents a threshold resistance as a function of temperature. Curve <NUM> can be used to determine when to take a control action based on the internal resistance. As shown in <FIG>, the calculated resistance can be used to determine a percent lifetime remaining. Area <NUM> represents the percent lifetime remaining of the battery. In some embodiments, the threshold curve <NUM> can be compensated based on the charge of the battery, especially in cases where the batteries are not fully charged.

Referring back to <FIG> at (<NUM>), the method can include performing at least one control action based at least in part on the data indicative of remaining lifetime of the battery. For instance, the controller <NUM> can implement at least one control action based at least in part on the data indicative of remaining lifetime of the battery.

In some embodiments, if the data indicative of remaining lifetime of the battery falls below a threshold, the method can include performing the control action. In some embodiments, the test operation can be performed multiple times at regular or irregular time intervals to determine a plurality of estimates of remaining lifetime for the battery (e.g., a plurality of internal resistances for the battery). An average remaining lifetime for the battery can be determined. A control action can be performed when the average remaining lifetime falls below a threshold.

The control action can include providing a notification of a fault condition associated with the battery. For instance, the controller <NUM> can send a notification using any suitable output device (e.g., display screen, visual indicator, audio speaker, or other suitable output device) indicative of a fault condition of the battery. The fault condition can be indicative of the battery nearing end of life. The notification can be associated with replacing the battery. For instance, in response to the notification, the battery can be replaced with a new battery or battery with more remaining lifetime.

Additionally and/or alternatively, the control action can include shutting down the wind turbine until the battery is replaced. For instance, the turbine can be shut down when the remaining lifetime of the battery is below a certain threshold. This threshold can be far enough away from the end of life threshold to avoid battery failure before the next retest.

In some embodiments, the method can be performed and/or modified based on data from multiple batteries. For instance, the data from a battery can be compared to data from a set of batteries, such as a set of batteries within the same axis, turbine, or age group. If, for example, several or all batteries in the set exhibit the same characteristic, such as being at a similar voltage below the end of life threshold, it can be determined that a condition such as temperature is causing the characteristic. In response to this, the method can be modified. For instance, the voltage threshold can be adjusted or trained at varying temperatures to reflect deviation learned from field experience to better reflect the actual end of life threshold at each temperature.

In embodiments, the frequency of the tests is determined based on data from the battery. The frequency of the tests is based upon the remaining lifetime of the battery. The frequency of the tests is increased as the battery approaches end of life. For example, the controller <NUM> can be configured to test the battery infrequently near beginning of life and gradually more frequently as it approaches end of life. This can reduce unnecessary cycling of the batteries caused by testing while ensuring a battery does not reach end of life and fail between tests.

In some embodiments, past patterns of misses, such as if the method was not effective in detecting a failing battery prior to failure, can be identified. These past patterns of misses can be used to modify the method. For instance, the past patterns of misses can be used to detect that the algorithm generally was not efficient at detecting failing batteries under a certain pattern of turbine or environmental conditions. The algorithm can then be adjusted or modified based on the past pattern of misses.

In some embodiments, an additional check can be used to help determine false positives. For instance, the battery can be flagged for recheck based on a recheck algorithm to avoid an early replacement based on a false positive. Additionally and/or alternatively, the battery data can be considered, such as by a human, and determined to be in a false positive condition, in which case steps such as a retest and/or ignoring the false positive can be taken.

<FIG> depicts a flow diagram of an example method (<NUM>) for preventing damage to a wind turbine according to example embodiments of the present disclosure. The method (<NUM>) can be at least partially implemented, for instance, by controller <NUM> or other control device(s). The method (<NUM>) is used to ensure that a battery used to power a pitch system of a wind turbine does not fail during operation. <FIG> depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that various steps of any of the methods disclosed herein can be adapted, expanded, rearranged, performed simultaneously, and/or rearranged in various ways without deviating from the scope of the present disclosure.

At (<NUM>), the method includes conducting a test operation of the battery, such as any of the test operations of the battery disclosed herein. At (<NUM>), the method includes determining data indicative of remaining lifetime of a battery according to any of the methods or operations for determining remaining lifetime disclosed herein. At (<NUM>), a fault condition can be determined based on the remaining lifetime of the battery. For instance, a fault condition can be determined when the remaining lifetime of the battery is below a threshold. At (<NUM>), the method can include replacing the battery in response to the fault condition. In this way, the method can increase the likelihood that a fresh battery will be available to power a pitch system of a wind turbine.

Claim 1:
A method (<NUM>) for determining the remaining lifetime of a battery (<NUM>) used to power a pitch system of a wind turbine, the method (<NUM>) comprising conducting test operations of the battery, wherein each test operation comprises:
controlling (<NUM>), by one or more control devices (<NUM>), a discharge of the battery (<NUM>) through a load (<NUM>);
obtaining (<NUM>), by the one or more control devices (<NUM>), data indicative of a discharge voltage and (<NUM>) a discharge current of the battery (<NUM>) during discharge through the load (<NUM>);
obtaining (<NUM>), by the one or more control devices (<NUM>), data indicative of a temperature associated with the battery (<NUM>) during discharge through the load (<NUM>);
determining (<NUM>), by the one or more control devices (<NUM>), data indicative of remaining lifetime of the battery (<NUM>) as a function of the discharge voltage, the discharge current, and the temperature; and
performing (<NUM>), by the one or more control devices (<NUM>), at least one control action based at least in part on the data indicative of the remaining lifetime of the battery (<NUM>);
wherein the test operations are conducted more frequently as the battery approaches an end of life of the battery.