Patent Description:
Power generating assets may take a variety of forms, including but not limited to assets which rely on renewable and/or nonrenewable sources of energy. Such power generating assets may generally be considered one of the cleanest, most environmentally friendly energy sources presently available. For example, wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The nacelle includes a rotor assembly coupled to the gearbox and to the generator. The rotor assembly and the gearbox are mounted on a bedplate support frame located within the nacelle. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as 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 and the electrical energy may be transmitted to a converter and/or a transformer housed within the tower and subsequently deployed to a utility grid. Modern wind power generation systems typically take the form of a wind farm having multiple wind turbine generators that are operable to supply power to a transmission system providing power to a power grid. <CIT> describes a soh/soc detecting device for power storage element, and power storage element managing unit; <NPL>; <CIT> describes battery management device, battery management method, and electric power storage system.

Certain power generating assets may also include at least one energy storage device, such as a battery or capacitor, which may serve as a backup power supply to a component of the power generating asset. During normal operation, components of the wind turbine, such as pitch drive motors, may be driven by power supplied by the power grid. However, in some instances, such as during a transient grid event, these components may be driven by the energy storage devices. Thus, the utilization of an energy storage device may ensure that the power generating asset may be controlled even in the absence of grid power. For example, the utilization of an energy storage device coupled to the pitch drive system of the wind turbine may permit the pitching of the rotor blades toward feather in the event grid power is lost. This, in turn, may prevent an overspeed event from negatively impacting the wind turbine.

Accordingly, it may be desirable to ensure that the energy storage is capable of operating when needed. As such, it may be desirable to determine a state of health of the energy storage device on a regular basis.

Thus, the art is continuously seeking new and improved systems and methods that address the aforementioned issues. As such, the present disclosure is directed to systems and methods for determining a state-of-health rating for an energy storage device of a power generating asset so as to ensure the energy storage device remains operable.

The invention is defined by a method for operating a power generating asset with the steps of independent method claim <NUM>.

In an additional embodiment, the method may include defining, via the controller, a plurality of temperature intervals across a nominal operating range of temperatures for the energy storage device. A temperature interval of the plurality of temperature intervals may correspond to the ambient temperature. The method may also include determining, via the controller, the nominal ESR function and the potential ESR function(s) at each temperature interval of the plurality of temperature intervals. Additionally, the method may include establishing a correlation between the actual ESR function and the state-of-health rating for the energy storage device at each temperature interval as a function of the second electrical condition of the energy storage device.

In a further embodiment, determining the state-of-health rating for the energy storage device may also include determining the state-of-health rating corresponding to the determined actual ESR function at the ambient temperature of the energy storage device based on the correlation between the actual ESR function and the state-of-health rating.

In yet a further embodiment, the first electrical condition may be a voltage. Determining a change in the first electrical condition of the energy storage device may also include determining a difference between an open-circuit voltage of the energy storage device and an instantaneous voltage of the energy storage device at each of the sampling intervals of the state-change event.

In an embodiment, implementing the control action may include detecting an approach of the state-of-health rating to a state-of-health threshold and generating an alert to facilitate scheduling of a maintenance event.

In an additional embodiment, the state-change event may include a scheduled test event and/or a manipulation of the energy storage device during operation of the power generating asset.

In a further embodiment, the scheduled test event may be accomplished in conjunction with at least one additional component test of the power generating asset and results in an updating of the state-of-health rating.

In yet a further embodiment, the state-change event may include a discharging event of the energy storage device or a charging event of the energy storage device.

In an embodiment, determining the actual ESR function may include determining the actual ESR function as a function of the second electrical condition and independent of a first electrical condition discharge profile and a second electrical condition discharge profile.

In an additional embodiment, the method may include receiving, via the controller, a cycle count and/or a time count elapsed from an installation date. The method may also include determining, via the controller, a correlation between the state-of-health rating and the received cycle count and/or time count. The correlation may be indicative of a rate of degradation of the energy storage device per cycle count and/or, time count. Additionally, the method may include determining a state-of-health threshold for the energy storage device. Based on the correlation of the state-of-health threshold, the method may also include determining, via the controller, a number of cycles and/or time until the state-of-health threshold is reached. The present invention is further directed to a system for operating a power generating asset according to claim <NUM>. Alternative embodiments of this system are described in the dependent system claims.

In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention if they do not depart from the scope spiritof the invention as defined by the appended claims.

As used herein, the terms "first" or "second" may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.

The term "coupled" and the like refers to both direct coupling, as well as indirect coupling, unless otherwise specified herein.

Generally, the present invention is directed to systems and methods for operating a power generating asset. The power generating asset, such as a wind turbine, has an energy storage device operably coupled to at least one component. The energy storage device may, for example, be a battery, a capacitor, or other suitable energy storage device which permits the continued, or emergency, operation of the component should grid power be disrupted. By way of illustration, when configured as a wind turbine, the pitch system of the wind turbine may be equipped with an energy storage device in order to ensure that the pitch system remains operable in the event of a power failure. This, in turn, may permit the pitching of the rotor blades to feather in order to slow the wind turbine as necessary even if the power from the power grid is interrupted. It should be appreciated that the ability to control a component of the power generating asset regardless of whether grid power is being received may facilitate the transition of the power generating asset to a safe operating mode and, thereby serve to prevent/mitigate potential damage to the power generating asset. Therefore, it may be desirable to determine a state of health of the energy storage device in order to ensure the energy storage device may be fully operational when called upon.

In order to determine the state of health of the energy storage device, the present disclosure requires the initiation of a state-change event, such as a charge or a discharge event, for the energy storage device. During the state-change event, the change in a first electrical condition and a second electrical condition of the energy storage device, such as a change in voltage and/or current, is determined. From the change in conditions, an actual equivalent series resistance (ESR) function for the energy storage device is determined. The ESR represents the internal resistance of the energy storage device as seen during a charging or discharging event. The magnitude of ESR may vary depending on the particular characteristics (e.g. materials used, construction quality, degree of degradation, cell chemistry, ambient temperature) of the energy storage device. Accordingly, the ESR may be compared to a nominal ESR and/or projected ESR. This comparison may, for example, include plotting the actual ESR function and the nominal ESR function relative to the second electrical condition (e.g. current). A comparison of the ESR values at a specified value of the second electrical condition may indicate a decline in the state of health of the power generating asset.

For example, at a specific current level, the nominal ESR function may indicate a first ESR value, while at the same current level, the actual ESR function may indicate a second ESR value. A second ESR value which is greater than the first ESR value may be indicative of a decline in the state of health of the energy storage device. In other words, for a given current and temperature, the ESR of the energy storage device may increase as the remaining lifespan of the energy storage device decreases. It should be appreciated that detecting this degradation in the energy storage device may facilitate the generation of an alarm and/or a maintenance schedule.

Referring now to the drawings, <FIG> illustrates a perspective view of one embodiment of a power generating asset <NUM> according to the present disclosure. As shown, the power generating asset <NUM> may be configured as a wind turbine <NUM>. In an additional embodiment, the power generating asset <NUM> may, for example, be configured as a solar power generating asset, a hydroelectric plant, a fossil fuel generator, and/or a hybrid power generating asset. As shown, the wind turbine <NUM> may generally include 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> may include 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 additional 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.

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

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

Each rotor blade <NUM> may also include a pitch control mechanism <NUM> configured to rotate each rotor blade <NUM> about its pitch axis <NUM>. Each pitch control mechanism <NUM> may include a pitch drive motor <NUM>, 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(s) <NUM> about the pitch axis <NUM>.

It should be appreciated that pitching the rotor blade(s) <NUM> about the pitch axis <NUM> may alter an angle of attack between the rotor blade(s) <NUM> and an apparent wind. Accordingly, the rotor blade(s)<NUM> may pitch to feather when the rotor blade(s) <NUM> rotates about the pitch axis <NUM> towards alignment with the apparent wind and to power when the rotor blade(s) rotates towards an orientation generally perpendicular to the apparent wind. It should be further appreciated that pitching to feather generally depowers the rotor blade(s) <NUM> as a result of a reduction in the resultant lift.

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>). It should be appreciated that the controller <NUM> may direct the yawing of the nacelle <NUM> and/or the pitching of the rotor blades <NUM> so as to aerodynamically orient the wind turbine <NUM> relative to a wind acting on the wind turbine <NUM>, thereby facilitating power production.

In an embodiment, the power generating asset <NUM> may also include an environmental sensor <NUM> configured for gathering data indicative of one or more environmental conditions. The environmental sensor <NUM> may be operably coupled to the controller <NUM>. Thus, in an embodiment, the environmental sensor(s) <NUM> may, for example, be a wind vane, an anemometer, a lidar sensor, thermometer, barometer, or any other suitable sensor. The data gathered by the environmental sensor(s) <NUM> may include measures of wind speed, wind direction, wind shear, wind gust, wind veer, atmospheric pressure, and/or ambient temperature. In at least one embodiment, the environmental sensor(s) <NUM> may be mounted to the power generating asset <NUM> (e.g., to the nacelle <NUM> at a location downwind of the rotor <NUM>). For example, the environmental sensor(s) <NUM> may, in alternative embodiments, be coupled to, or integrated with, the rotor <NUM> and/or positioned within the nacelle <NUM>. It should be appreciated that the environmental sensor(s) <NUM> may include a network of sensors and may be positioned away from the power generating asset <NUM>.

It should also be appreciated that, as used herein, the term "monitor" and variations thereof indicates that the various sensors of the power generating asset <NUM> may be configured to provide a direct measurement of the parameters being monitored 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 a condition or response of the power generating asset <NUM> and/or a component thereof.

Referring now to <FIG>, a schematic diagram of one embodiment of an energy storage device <NUM> operably coupled to a component <NUM> of the power generating asset <NUM> is illustrated. In an embodiment such as depicted in <FIG>, the component <NUM> may be configured as the pitch control mechanism <NUM> of the wind turbine <NUM>. In an embodiment, the component <NUM> may be communicatively coupled to the power grid <NUM>. Additionally, the component <NUM> may be communicatively coupled to at least one energy storage device <NUM>. In various embodiments, the energy storage device(s) <NUM> may be a single battery, capacitor, and/or other suitable energy storage device or pluralities thereof.

In an embodiment, at least one condition sensor <NUM> may be communicatively coupled to the energy storage device(s) <NUM>. The condition sensor(s) <NUM> may be configured to monitor at least a first electrical condition and a second electrical condition <NUM>, <NUM> (<FIG>) of the energy storage device(s) <NUM>. For example, in monitoring the electrical conditions <NUM>, <NUM>, the condition sensor(s) <NUM> may monitor an open-circuit voltage, an instantaneous voltage, and/or a current of the energy storage device(s) <NUM>. Accordingly, the condition sensor(s) <NUM> may, in an embodiment, be an ammeter, a voltmeter, an ohmmeter, and/or any other suitable sensor for monitoring the electrical conditions <NUM>, <NUM> of the energy storage device(s) <NUM>.

During normal operation of the power generating asset <NUM>, the component <NUM> may be driven by the power grid <NUM>. However, in some instances, such as during an adverse grid event or grid loss, the component <NUM> may be powered by the energy storage device(s) <NUM>. Therefore, in an embodiment, the energy storage device(s) <NUM> may be configured as an uninterrupted power supply. Accordingly, the energy storage device(s) <NUM> may, in an embodiment, be utilized in a top-of-charge application. For example, when configured as pitch control mechanism <NUM>, the pitch drive motor <NUM> may utilize power from the energy storage device(s) <NUM> in order to pitch the rotor blade(s) <NUM> toward feather in response to an adverse grid event. In an additional example, the component <NUM> may be the controller <NUM> and the energy storage device(s) <NUM> may provide an uninterrupted power source to the controller <NUM> in response to a loss of grid power. In yet a further example, the energy storage device(s) <NUM> may be operably coupled to the generator <NUM> and configured to receive at least a portion of the power output of the generator <NUM> and, in certain instances, deliver the received portion of the power to the power grid <NUM>. It should be appreciated that if control of the component <NUM> relies on the energy storage device(s) <NUM> (i.e., due to a loss of grid power), it may be desirable to ensure that the energy storage device(s) <NUM> are capable of operating when called upon. Thus, the controller <NUM> may, in an embodiment, be configured to determine the state of health of the energy storage device(s) <NUM> on a regular basis.

Referring now to <FIG>, multiple embodiments of a system <NUM> for operating the power generating asset <NUM>, e.g. the wind turbine <NUM>, according to the present disclosure are presented. As shown particularly in <FIG>, a schematic diagram of one embodiment of suitable components that may be included within the system <NUM> is illustrated. For example, as shown, the system <NUM> may include the controller <NUM> communicatively coupled to the environmental sensor(s) <NUM> and/or the condition sensor(s) <NUM>. Further, as shown, the controller <NUM> includes 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 power generating asset <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 the sensor(s) <NUM>, <NUM> to be converted into signals that can be understood and processed by the processors <NUM>. It should be appreciated that the sensor(s) <NUM>, <NUM> may be communicatively coupled to the communications module <NUM> using any suitable means. For example, the sensor(s) <NUM>, <NUM> may be coupled to the sensor interface <NUM> via a wired connection. However, in other embodiments, the sensor(s) <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. Additionally, the communications module <NUM> may also be operably coupled to an operating state control module <NUM> configured to implement a control action based on a determination of the state of health of the energy storage device(s) <NUM>.

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, operating a power generating asset <NUM> as described herein, as well as various other suitable computer-implemented functions.

Referring particularly to <FIG>, the controller <NUM> of the system <NUM> is configured to initiate a state-change event <NUM> for the energy storage device(s) <NUM>. The state-change event <NUM> defines a plurality of sampling intervals. In an embodiment, the plurality of sampling intervals may be time intervals, the sum of which may correspond to a duration of the state-change event <NUM>. As depicted at <NUM>, the controller <NUM> determines a change in the first and second electrical conditions <NUM>, <NUM> at each of the plurality of sampling intervals of the state-change event <NUM>. From the change in the first and second electrical conditions <NUM>, <NUM>, the controller <NUM> determines an actual equivalent series resistance (ESR) value (ESRt) at each of the plurality of sampling intervals of the state-change event <NUM>. The controller utilizes the ESR value (ESRt) to determine an actual ESR function <NUM> for the energy storage device(s) <NUM>. In an embodiment, the controller <NUM> may determine a state-of-health rating <NUM> for the energy storage device(s) <NUM> based on the actual ESR function <NUM> of the energy storage device(s) <NUM>. Based on the state-of-health rating <NUM>, a control action <NUM> is implemented.

In an embodiment, the state-change event <NUM> may be a discharge event. In an additional embodiment, the state-change event <NUM> may be a charging event. Accordingly, the state-change event <NUM> may, for example, be associated with a scheduled test event of the energy storage device(s) <NUM> and/or the component <NUM>. Additionally, the state-change event <NUM> may, in an embodiment, be associated with a manipulation (e.g. usage) of the energy storage device(s) during an operation of the power generating asset <NUM>. In other words, in an embodiment, the scheduled test event may be accomplished in conjunction with at least one additional component test of the power generating asset <NUM> and may result in an updating of the state-of-health rating <NUM>.

In order to determine the state-of-health rating <NUM> for the energy storage device(s) <NUM>, the controller <NUM>, as depicted at <NUM>, determines the change in the first and second electrical conditions <NUM>, <NUM> which may occur during the state-change event <NUM>. In an embodiment, the change is detected, received, and/or computed at each of the sampling intervals defined by the state-change event <NUM>. Accordingly, the change in the first and second electrical conditions <NUM>, <NUM> may reflect a difference between an initial state of the first and second electrical conditions <NUM>, <NUM> and a state of the electrical conditions at each of the sampling intervals.

As depicted in <FIG>, in an embodiment, the first electrical condition <NUM> may, for example, be a voltage (V). In such an embodiment, determining a change in the first electrical condition <NUM> of the energy storage device(s) <NUM> may include determining a difference between an open-circuit voltage (VOC) of the energy storage device(s) <NUM> and an instantaneous voltage (Vt) of the energy storage device(s) <NUM> at each of the plurality of sampling intervals of the state-change event <NUM>. The open-circuit voltage (VOC) may represent a no-load voltage, or a rest potential, of the energy storage device(s) <NUM>. The open circuit voltage (VOC) may depend on a state of charge of the energy storage device(s) <NUM>. In an embodiment wherein the energy storage device(s) <NUM> is configured as a backup energy source, such as an uninterrupted power supply, the open-circuit voltage (VOC) may be considered to be a top-of-charge voltage. As such, the open-circuit voltage (VOC) may be a known/nominal value. In an additional embodiment, the open-circuit voltage (VOC) may be measured prior to the initiation of the state-change event <NUM>.

In an additional embodiment, the second electrical condition <NUM> may, for example, be a current (I). Accordingly, determining a change in the second electrical condition <NUM> of the energy storage device(s) <NUM> may include determining a difference between the initial current (Ii) of the energy storage device(s) <NUM> immediately preceding the state-change event <NUM> and the instantaneous current (It) of the energy storage device(s) <NUM> at each of the plurality of sampling intervals of the state-change event <NUM>. In an embodiment wherein the energy storage device(s) <NUM> is neither charging nor discharging prior to the initiation of the state-change event <NUM>, the initial current (Ii) of the energy storage device(s) <NUM> preceding the state-change event <NUM> may be zero. As such, the change in the current (I) may equal the instantaneous current (It) measured by the condition sensor(s) <NUM> at each of the plurality of sampling intervals during the state-change event <NUM>. In an additional embodiment, wherein the energy storage device(s) <NUM> is in a charging or discharging state immediately prior to the state-change event <NUM>, the initial current (Ii) may be measured by the condition sensor(s) <NUM> at the instant of initiation of the state-change event <NUM>.

It should be appreciated that, in an embodiment, it may be desirable to prefilter the first and second electrical conditions <NUM>, <NUM> in order to ensure the fidelity of the resultant state-of-health rating <NUM> for the energy storage device(s) <NUM>. For example, in an embodiment, the controller <NUM> may be configured to monitor the current (I) prior to the initiation of the state-change event <NUM>. The current (I) may, in an embodiment, indicate a recharging operation for the energy storage device(s) <NUM>. As such, a current (I) above a specified threshold may indicate a degree of charging that may yield uncertainty regarding the open-circuit voltage (VOC). In such an embodiment, the controller <NUM> may be configured to refrain from determining the state-of-health rating <NUM> for the state-change event <NUM> because uncertainty regarding the open-circuit voltage (VOC) exists. Similarly, in an alternative embodiment, a current (I) below the specified threshold may indicate that the recharging operation is complete and that the open-circuit voltage (VOC) may be considered to be a top-of-charge voltage.

As particularly depicted in <FIG> and <FIG>, in an embodiment, the controller <NUM> may utilize the changes in the first and second electrical conditions <NUM>, <NUM> to determine the corresponding ESR value (ESRt) at each of the plurality of sampling intervals of the state-change event <NUM>. The controller <NUM> may then utilize the ESR values (ESRt) to determine an actual ESR function <NUM>. Accordingly, such an embodiment may normalize the actual ESR function <NUM> so that the actual ESR function <NUM> is invariant to a discharge history and discharge profiles, thereby establishing a tractable metric. For example, in an embodiment, the actual ESR function <NUM> may be a function of the second electrical condition <NUM> (e.g., current). Further, in an embodiment, the actual ESR function <NUM> may be independent of a first electrical condition <NUM> discharge profile and a second electrical condition <NUM> discharge profile.

In an embodiment wherein the first electrical condition <NUM> is the voltage (V) and the second electrical condition <NUM> is the current (I), the ESR of the energy storage device(s) <NUM> may be a function of the instantaneous current (It). As such, the ESR values (ESRt) may be determined using the following equation: <MAT>.

In an embodiment, a degradation of the energy storage device(s) <NUM> may be manifest in an increasing ESR for a given second electrical condition (e.g. current). According to the invention, the controller <NUM> may determine a state-of-health rating <NUM> based on the actual ESR function <NUM>. In order to facilitate the determination of the state-of-health rating <NUM>, the controller <NUM> models a nominal ESR function <NUM> at an ambient temperature <NUM>. The nominal ESR function <NUM> may represent the degree of internal resistance for a non-degraded energy storage device(s) <NUM>. Therefore, the nominal ESR function <NUM> may correlate to a state-of-health rating <NUM> of a maximal value (e.g., <NUM>, <NUM>%, etc.) which may decrease with the degradation of the energy storage device(s) <NUM>. It should, however, be appreciated that in an additional embodiment, the state-of-health rating <NUM> may be indicative of a degree of degradation and may therefore be a minimal value (e.g., <NUM>, <NUM>%, etc.) which may increase in proportion to an increasing degradation of the energy storage device(s) <NUM>. It should be appreciated that when the actual ESR function <NUM> corresponds to the nominal ESR function <NUM>, the state-of-health rating <NUM> may be considered to be a non-degraded state-of-health rating.

In addition to modeling the nominal ESR function <NUM>, the controller <NUM> also models at least one potential ESR function <NUM> at the ambient temperature <NUM>. The potential ESR function(s) <NUM> may, as depicted in <FIG>, indicate an increased ESR value <NUM> relative to a nominal ESR value <NUM> as a function of the second electrical condition <NUM>. For example, the potential ESR function(s) <NUM> may indicate that for a given current <NUM>, the energy storage device(s) <NUM> may present a greater degree of resistance (e.g., points <NUM>) than at the nominal ESR value <NUM>. This increase in the ESR value <NUM> may be indicative of a degradation of the energy storage device(s) <NUM>. Therefore, the potential ESR function(s) <NUM> may correspond to a degraded/reduced state-of-health rating <NUM> at the same ambient temperature <NUM>. In an embodiment wherein the non-degraded state-of-health rating <NUM> represents a maximal value, the degraded state-of-health rating <NUM> may represent a percentage of the maximum value (e.g., <NUM>, <NUM>, <NUM>, etc.). Similarly, in an embodiment wherein the non-degraded state-of-health rating <NUM> represents a minimal value, the degraded state-of-health rating <NUM> may represent a degree of degradation (e.g., <NUM>, <NUM>, <NUM>, etc.).

As depicted at <NUM> of <FIG>, the controller <NUM> consolidates the nominal ESR function <NUM> and the potential ESR function(s) <NUM> into a look-up table, a graphical representation, and/or an algorithm. This consolidation may establish a correlation <NUM> between the actual ESR function <NUM> and the state-of-health rating <NUM> for the energy storage device(s) <NUM> at the ambient temperature <NUM> as a function of the second electrical condition <NUM> of the energy storage device(s) <NUM>. Accordingly, determining the state-of-health rating <NUM> for the energy storage device(s) <NUM> may include the utilization of the look-up table, graphic orientation, and/or algorithm to determine the state-of-health rating <NUM> corresponding to the actual ESR function <NUM>, which may be based off of the changes in the electrical conditions during the state-change event <NUM>.

It should be appreciated that the level of internal resistance of the energy storage device(s) <NUM> may, for example, vary with the ambient temperature <NUM> regardless of any degradation of the energy storage device(s) <NUM>. As such, in an embodiment, the controller <NUM> may define a plurality of temperature intervals <NUM> across a nominal operating range of temperatures for the energy storage device(s) <NUM>. In an embodiment, at least one of the plurality of temperature intervals <NUM> may correspond to or overlap the ambient temperature <NUM> at the initiation of the state-change event <NUM>. The plurality of temperature intervals <NUM> may, in an embodiment, correspond to a plurality of less than or equal to ten-degree temperature intervals <NUM>.

Insofar as the nominal ESR function <NUM> and potential ESR function(s) <NUM> may vary at different ambient temperatures at which the energy storage device(s) <NUM> may operate, in an embodiment, the controller <NUM> may determine the nominal ESR function <NUM> and the potential ESR function(s) <NUM> at each of the plurality of temperature intervals <NUM>. In an embodiment, the nominal ESR functions <NUM> and the potential ESR function(s)s <NUM> at each of the plurality of temperature intervals <NUM> may be assembled into a multi-dimensional, look-up table, a multi-dimensional graphical representation, and/or an algorithm. Such an assemblage may facilitate the establishment of a correlation between the actual ESR function <NUM> and the state-of-health rating <NUM> as a function of the second electrical condition <NUM> of the energy storage device(s) <NUM> at each temperature interval of the plurality of temperature intervals <NUM>. In other words, given an ambient temperature <NUM> within the nominal operating range of temperatures for the energy storage device(s) <NUM> and an actual ESR function <NUM> based on the determined electrical condition change for the state-change event <NUM>, the correlations (such as those assembled into the multi-dimensional, look-up table, a multi-dimensional graphical representation, and/or an algorithm) may be utilized to determine the state-of-health rating <NUM> for the energy storage device(s) <NUM>.

Additionally, in an embodiment, the controller <NUM> may correlate the state-of-health rating <NUM> determined for the ambient temperature to a state-of-health rating <NUM> at a second temperature via a correlation function. For example, in an embodiment wherein the second temperature is lower than the ambient temperature, the state-of-health rating <NUM> at the second temperature may indicate a decreased capability of the energy storage device(s) <NUM> than is indicated for the energy storage device(s) <NUM> operating at the ambient temperature. It should be appreciated that the relationship between the state of health rating and the ambient/forecasted temperatures may be employed to predict the ability of the energy storage device(s) <NUM> to provide the necessary power when required during a forecasted period (e.g. winter or summer).

The system <NUM> implements the control action <NUM> based on the state-of-health rating <NUM>. For example, in an embodiment, the control action <NUM> may include generating an alert <NUM>. The generation of the alert <NUM> may facilitate the scheduling of a maintenance event. Accordingly, the alert <NUM> may include an auditory signal, a visual signal, a notification, a system input, and/or any other system which may identify the state-of-health rating <NUM> to an operator. It should be appreciated that the control action <NUM>, as described herein, may further include any suitable command or constraint by the controller <NUM>. For example, in an embodiment, the control action <NUM> may include temporarily de-rating the power generating asset <NUM>. Additionally, in an embodiment, the control action <NUM> may include limiting an operation of at least one component of the power generating asset. For example, the control action <NUM> may limit a pitching of a rotor blade <NUM> and/or a yawing of the nacelle <NUM> of the wind turbine <NUM> when the state-of-health rating <NUM> indicates that the energy storage device(s) <NUM> may not have sufficient health to respond in the expected manner when called upon.

As depicted in <FIG>, in implementing the control action <NUM>, the controller <NUM> may, in an embodiment, receive a state-of-health threshold <NUM>. The state-of-health threshold <NUM> may be indicative of a degree of degradation of the component <NUM> at which a control action may be desirable. In such an embodiment, the controller <NUM> may, at <NUM>, detect an approach of the state-of-health rating <NUM> to the state-of-health threshold <NUM>. In response to detecting the approach of the state-of-health rating <NUM> to the state-of-health threshold <NUM>, the controller <NUM> may implement the control action <NUM> by generating the alert <NUM> to facilitate scheduling of the maintenance event.

Referring still to <FIG>, in an embodiment, the controller <NUM> of the system <NUM> may receive a cycle count <NUM> and/or a time count <NUM> elapsed from an installation date of the energy storage device(s) <NUM>. The controller <NUM> may then determine a correlation <NUM> between the state-of-health rating <NUM> and the cycle count <NUM> and/or time count <NUM>. The correlation <NUM> may be indicative of a rate of degradation of the energy storage device(s) <NUM> per the cycle count <NUM> and/or the time count <NUM>. Based on the correlation <NUM> and the state-of-health threshold <NUM>, the controller <NUM> may, as depicted at <NUM>, in an embodiment, determine a number of cycles and/or time remaining until the state-of-health threshold <NUM> is reached. In other words, in an embodiment, the controller <NUM> may determine a rate of degradation of the energy storage device(s) <NUM> in terms of the cycle/time count <NUM>, <NUM> and utilize the rate of degradation to project a remaining service life until maintenance of the energy storage device(s) <NUM> is required.

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.

In some embodiments, determining state-of-health rating for the energy storage device further comprises: defining, via the controller, a plurality of temperature intervals across a nominal operating range of temperatures for the energy storage device, wherein a temperature interval of the plurality of temperature intervals corresponds to the ambient temperature; modeling, via the controller, a nominal ESR function for the energy storage device at the ambient temperature, wherein the nominal ESR function corresponds to a maximal state-of-health rating at the ambient temperature; modeling, via the controller, at least one potential ESR function for the energy storage device at the ambient temperature, the at least one potential ESR function indicating an increased ESR value relative to a nominal ESR value as a function of current, the at least one potential ESR function corresponding to a reduced state-of-health rating at the ambient temperature; determining, via the controller, the nominal ESR function and the at least one potential ESR function at each temperature interval of the plurality of temperature intervals; establishing a correlation between the nominal ESR function and the at least one potential ESR function at each temperature interval as a function of the current of the energy storage device; and determining the state-of-health rating corresponding to the determined actual ESR function at the ambient temperature of the energy storage device based on the correlation between the actual ESR function and the state-of-health rating.

In some embodiments, determining the actual ESR function further comprises determining the actual ESR function as a function of current and independent of a voltage discharge profile and a current discharge profile.

Claim 1:
A method for operating a power generating asset, the power generating asset having an energy storage device operably coupled to a component of the power generating asset, the method comprising:
Initiating (<NUM>), with a controller, a state-change event for the energy storage device, the state-change event defining a plurality of sampling intervals;
Determining (<NUM>), via the controller, a change in a first electrical condition and a second electrical condition of the energy storage device at each of the plurality of sampling intervals of the state-change event;
Determining (<NUM>), via the controller, an actual equivalent series resistance (ESR) function for the energy storage device based on the change in the first and second electrical conditions at each of the plurality of sampling intervals of the state-change event;
Determining (<NUM>), via the controller, a state-of-health rating for the energy storage device based on the actual ESR function of the energy storage device; and implementing (<NUM>) a control action based on the state-of-health rating; and wherein determining the state-of-health rating for the energy storage device further comprises:
modeling, via the controller, a nominal ESR function for the energy storage device at an ambient temperature, wherein the nominal ESR function corresponds to a maximal state-of-health rating at the ambient temperature;
modeling, via the controller, at least one potential ESR function for the energy storage device at the ambient temperature, the at least one potential ESR function indicating an increased ESR value relative to a nominal ESR value as a function of the second electrical condition, the at least one potential ESR function corresponding to a reduced state-of-health rating at the ambient temperature; and
consolidating, via the controller, the nominal ESR function and the at least one potential ESR function into at least one of a look-up table, a graphical representation, and an algorithm so as to establish a correlation between the actual ESR function and the state-of-health rating for the energy storage device at the ambient temperature as a function of the second electrical condition of the energy storage device.