CHARGE CONTROLLER

A charge controller that responds to extreme transients in current, voltage, and temperature. The charge controller monitors the drift of the battery charging rate versus its request and compensates for wind up that may lead to uncontrolled current into a high-voltage battery. This bi-directional anti-wind up charge controller allows the battery management system to independently adjust the current request to the charger, which is primarily useful during vehicle component failure; charger side faults, over-commend, or uncontrolled current; and allows for safe and continuous charging during unexpected charger events. A dynamic saturation bound allows the charge controller to adjust its requested current and compensate for auxiliary current draws when the charger is capable of providing more current. The charge controller switches between voltage and current control based on the voltage of the battery, adjusting for variability in state-of-health, and temperature of the battery pack.

INTRODUCTION

The present disclosure relates generally to the automotive and battery management fields. More particularly, the present disclosure relates to an anti-wind up charge controller for a battery management system of an electric vehicle (EV), hybrid electric vehicle (HEV), or the like.

While charging an EV, for example, there are a host of variables that can impact the controllability and efficiency of a charge session. Designing for every possible use case using a discrete case-by-case system may result in undesirable “blind spots.” In a worst case scenario, this may lead to battery overcharging and battery life degradation or battery failure. Utilizing a standard control strategy for all batteries and EVs may also result in less-than-optimal battery charging (in terms of energy per minute).

The present introduction is provided as illustrative environmental context only and should not be construed as being limiting in any manner. It will be readily apparent to those of ordinary skill in the art that the concepts and principles of the present disclosure may be applied in other environmental contexts equally and without limitation.

SUMMARY

The present disclosure provides a charge controller that responds to extreme transients in current, voltage, and temperature. The charge controller monitors the drift of the battery charging rate versus its request and compensates for error wind up that may lead to uncontrolled current into a high-voltage battery. This bi-directional anti-wind up charge controller allows the battery management system to independently adjust the current request to the charger, which is primarily useful during vehicle component failure; charger side faults, over-command, or uncontrolled current; and allows for safe and continuous charging during unexpected charger events. A dynamic saturation bound allows the charge controller to adjust its requested current and compensate for auxiliary current draws when the charger is capable of providing more current. This is accomplished while adhering to the charging limit computed by the battery management system. This is primarily useful in high-auxiliary current draw use cases, including cabin heating, ventilation, and air conditioning (HVAC) uses; battery pack thermal management; and other direct current to direct current (DC/DC) conversion load consumption. The charge controller switches between voltage and current control based on the voltage of the battery, adjusting for variability in state-of-health (SOH), and temperature of the battery pack.

In one illustrative embodiment, the present disclosure provides a charge controller. The charge controller includes one or more processors and a memory. The memory stores computer-executable instructions that, when executed, cause the one or more processors to determine a target charging current request for a battery from a charger based on inputs that are current-based and wind-up feedback correction provided by a feedback loop.

In another illustrative embodiment, the present disclosure provides a charge control method. The method includes obtaining inputs that are current-based. The method also includes determining a target charging current request for a battery from a charger based on the inputs that are current-based and wind-up feedback correction provided by a feedback loop.

In a further illustrative embodiment, the present disclosure provides a charge control method. The method includes determining, in response to a voltage of a battery being below a threshold voltage, a target charging current request for a battery from a charger based on inputs that are current-based. The method also includes determining, in response to the voltage of the battery being at or above the threshold voltage, the target charging current request for the battery from the charger based on inputs that are voltage-based.

DETAILED DESCRIPTION

Again, the present disclosure provides a charge controller that responds to extreme transients in current, voltage, and temperature. The charge controller monitors the drift of the battery charging rate versus its request and compensates for error wind up that may lead to uncontrolled current into a high-voltage battery. This bi-directional anti-wind up charge controller allows the battery management system to independently adjust the current request to the charger, which is primarily useful during vehicle component failure; charger side faults, over-commend, or uncontrolled current; and allows for safe and continuous charging during unexpected charger events. A dynamic saturation bound allows the charge controller to adjust its requested current and compensate for auxiliary current draws when the charger is capable of providing more current. This is accomplished while adhering to the charging limit computed by the battery management system. This is primarily useful in high-auxiliary current draw use cases, including cabin heating, ventilation, and air conditioning (HVAC) uses; battery pack thermal management; and direct current-direct current (DCDC) consumption. The charge controller switches between voltage and current control based on the state-of-charge (SOC) window, adjusting for variability in state-of-health (SOH), and temperature of the battery pack. This is unique to each vehicle, and the charge controller is able to control to a precision of about 2 mV.

FIG.1is a schematic diagram of one illustrative embodiment of the anti-wind up charge controller100of the present disclosure, highlighting a current-based implementation. Referring specifically toFIG.1, in one illustrative embodiment of the current-based implementation, the charge controller100of the present disclosure is operable for requesting a charging target current102based on inputs103,104,105that are current-based. In various embodiments, the inputs103,104,105include a charger/Electric Vehicle Supply Equipment (EVSE) current limit103, a battery current limit104, and a measured battery current105. In various embodiments of the current-based implementation, the charger/EVSE current limit103is a set range with a minimum value and a maximum value. In various embodiments, the set range is based on a particular application of the battery, such as based on a size of the vehicle, a desired performance of the vehicle, and the like. For example, the set range can be a predetermined range, such as from 200 Amps to 300 Amps or from 300 Amps to 500 Amps. In some embodiments, the set range can be much higher, such as for large trucking applications. In various embodiments, the set range of the battery current limit104is adjusted based on the battery SOC/voltage, the battery SOH, and the battery temperature. In various embodiments of the current-based implementation, the measured battery current105is based on a current charging state of the battery.

In various embodiments of the current-based implementation, the maximum possible value of the charger/EVSE current limit103acts as a maximum charging current that can possibly be provided during the charging of the battery. Thus, in embodiments, the maximum value for the charger/EVSE current limit103acts as an upper saturation bound106for the request.

In various embodiments of the current-based implementation, a minimum of the charger/EVSE current limit103and the battery current limit104is utilized to determine a limiting charging current108. As such, the minimum of the charger/EVSE current limit103and the battery current limit104may ultimately be safely requested by the charge controller100.

In various embodiments of the current-based implementation, the charge controller100includes a feedback controller111that is fed the limiting charging current108and measured battery current105. In the embodiment illustrated, the feedback controller111includes a proportional-integral (PI) controller that includes a proportional gain path (Kp)110and an integral gain path (Ki)112. In other embodiments, the feedback controller111includes any of the PI controller, a proportional controller, a derivative controller, a proportional-integral-derivative controller, feed-forward controller, and the like. The proportional gain path (Kp)110is configured to add/subtract from a request for error correction. The integral gain path (Ki)112is configured to prevent oscillation by accounting for historical errors. In these embodiments, both the proportional gain path (Kp)110and the integral gain path (Ki)112are saturation bounded114. In some embodiments, the saturation bound is different for each of the proportional gain path (Kp)110and the integral gain path (Ki)112.

In various embodiments of the current-based implementation, the charge controller100includes an anti-wind up error gain/feedback loop116. The anti-wind up error gain/feedback loop116feeds wind-up feedback correction to the feedback controller111, such as to the integral gain path112. The wind-up is the uncontrolled drift of the feedback controller while the battery current limit is beyond the maximum of the charger/EVSE current limit103. The charge controller100is configured to monitor the wind-up downstream of the feedback controller111and provide a wind-up feedback correction to the feedback controller111via the anti-wind up error gain/feedback loop116. In embodiments, the charge controller100determines the wind-up feedback correction by monitoring uncontrolled drift of the feedback controller through a dynamic feedback loop-and-gain on the integral term. With this dynamic closed loop feedback, the charge controller100can account for and minimize any wind-up error to prevent a build-up of such transient errors. Eliminating the uncontrolled drift of the feedback controller with the anti-wind up loop allows the feedback controller to react to changes in the battery current limit while still allowing to compensate for auxiliary High Voltage (HV) loads.

In embodiments, the integral gain path (Ki)112also incorporates an appropriate gain circuit118that is used along with the wind-up feedback correction received from the anti-wind up error gain/feedback loop116, which results in transient errors being accounted for and minimized by the resulting requests.

FIG.2is a schematic diagram of another illustrative embodiment of the anti-wind up charge controller100of the present disclosure, highlighting a current and voltage-based implementation. Referring specifically toFIG.2, in an illustrative embodiment of the current and voltage-based implementation, the charge controller100of the present disclosure is again operable for requesting a charging target current102given multiple inputs103,104,105that are current-based. Similar to the embodiments discussed above with regards to the current-based implementation, in various embodiments of the current and voltage-based implementation, the inputs103,104,105include a charger/Electric Vehicle Supply Equipment (EVSE) current limit103, a battery current limit104, and a measured battery current105. In various embodiments, the charger/EVSE current limit103is a set range with a minimum value and a maximum value. In various embodiments, the set range is based on a particular application of the battery, such as based on a size of the vehicle, a desired performance of the vehicle, and the like. For example, the set range can be a predetermined range, such as from 200 Amps to 300 Amps or from 300 Amps to 500 Amps. In some embodiments, the set range can be much higher, such as for large trucking applications. In various embodiments, the set range of the battery current limit104is adjusted based on the battery SOC/voltage, the battery SOH, and the battery temperature and the battery current limit104includes a minimum value and a maximum value, such as from 200 Amps to 300 Amps. In various embodiments of the current and voltage-based implementation, the measured battery current105is based on a current charging state of the battery.

In various embodiments of the current and voltage-based implementation, the maximum value of the charger/EVSE current limit103acts as a maximum charging current that can possibly be provided during the charging of the battery. Thus, in embodiments, the maximum value for the charger/EVSE current limit103acts as an upper saturation bound106for the request.

In various embodiments of the current and voltage-based implementation, the minimum value of the charger/EVSE current limit103and the minimum value of the battery current limit104may ultimately be safely requested by the charge controller100and are utilized to determine a limiting charging current108.

In various embodiments of the current and voltage-based implementation, the charge controller100includes a feedback controller111that is fed the limiting charging current108and measured battery current105. In some embodiments, the feedback controller111is a PI controller that includes a proportional gain path (Kp)110and an integral gain path (Ki)112. In other embodiments, the feedback controller111includes any of the PI controller, a proportional controller, a derivative controller, a proportional-integral-derivative controller, and the like. The proportional gain path (Kp)110is configured to add/subtract from a request for error correction. The integral gain path (Ki)112is configured to prevent oscillation by accounting for historical errors. In these embodiments, both the proportional gain path (Kp)110and the integral gain path (Ki)112are saturation bounded114. In some embodiments, the saturation bound is different for each of the proportional gain path (Kp)110and the integral gain path (Ki)112.

In various embodiments of the current and voltage-based implementation, the charge controller100includes an anti-wind up error gain/feedback loop116. The anti-wind up error gain/feedback loop116feeds wind-up feedback correction to the feedback controller111, such as to the integral gain path112. The charge controller100is configured to monitor the wind-up downstream of the feedback controller111and provide a wind-up feedback correction to the feedback controller111via the anti-wind up error gain/feedback loop116.

In embodiments, the integral gain path (Ki)112also incorporates an appropriate gain circuit118that is used along with the wind-up feedback correction received from the anti-wind up error gain/feedback loop116, which results in transient errors being accounted for and minimized by the resulting requests.

In various embodiments of the current and voltage-based implementation, the PI controller111also includes a control switch126configured to switch between voltage control and current control.

In various embodiments of the current and voltage-based implementation, the charge controller100is configured to selectively switch to the consideration of voltage, such as via a tracking error switch120. In these embodiments, the PI controller111takes a voltage path122into account, using inputs123,124that are voltage-based. In some of these embodiments, the inputs123,124include a cell voltage target123and a maximum cell voltage124. In this manner, the charge controller100can switch between current based control and voltage based control. In various embodiments, the charge controller100is configured to switch between current based control and voltage based control based on a voltage of the battery/battery cells.

In some embodiments, the charge controller100switches from current based control to voltage based control as a voltage threshold is reached. In some of these embodiments, the voltage threshold is a predetermined voltage that is defined at an amount that is close to the battery being fully charged and is predefined based on where small wind up errors may lead to a relatively large voltage overshoot. In embodiments, the predetermined voltage is a target voltage, such as max battery cell voltage. In other embodiments, the predetermined voltage is a voltage range, such as within a one millivolt (mV) window of max battery cell voltage. In various embodiments, the voltage threshold is adjusted for variability in the SOH of the battery and for a temperature of the battery pack.

In various embodiments, the charge controller100controls the current into a pack and diverts excess current to other systems of the vehicle, such as the thermal management system, for example.

FIG.3is a schematic diagram of the charge controller100ofFIG.2, highlighting an operation case where the charge controller100of the present disclosure switches from current tracking to voltage tracking. Again, in embodiments, in response to the battery reaching the charge threshold, the charge controller100is configured to switch from a current tracking based control to a voltage tracking based control. Referring toFIG.3, in embodiments, the switch from the current tracking based control is performed by switching the inputs from the current based inputs103,104,105to the voltage based inputs123,124, such as the cell voltage target123and the maximum cell voltage124. By so doing, the tracking error becomes a voltage error rather than a current error. In these embodiments, the switch is also performed by switching the controller gains110,112,126from current to voltage.

FIG.4is a schematic diagram illustrating a charge controller operation case in which the charger current limit is higher than the battery current limit and the charger current limit suddenly drops. Referring toFIG.4, pane301illustrates a chart of the current over time of the charger/EVSE current limit and the actual battery current of a system without the charge controller100(such as where a standard controller is configured to compensate for auxiliary loads), while pane302illustrates a chart of the current over time of the charger/EVSE current limit and the actual battery current of a system with an embodiment of the charge controller100.

Referring to pane301, without the charge controller100(but rather with a standard controller configured to compensate for auxiliary loads), the actual battery current320with the higher charger/EVSE current limit310increases steadily and gradually to the value of the higher charger/EVSE current limit310. The actual battery current322, after the saturation bounds where there is a sudden drop311from the higher charger/EVSE current limit to the lower charger/EVSE current limit312, is slow to respond and steadily and gradually decreases to the lower charger/EVSE current limit312. In particular, as can be seen in pane301, the actual battery current322remains at the higher charger/EVSE current limit310beyond the saturation bounds indicating windup past the saturation bounds.

Referring to pane302, with the charge controller100, similar to control without the charge controller100, the actual battery current320with the higher charger/EVSE current limit310increases steadily and gradually to the value of the charger/EVSE current limit310. However, unlike the control without the charge controller100, with the charge controller100, the actual battery current322, after the saturation bounds where there is the sudden drop311from the higher charger/EVSE current limit310to the lower charger/EVSE current limit312, quickly responds and reduces the current to the lower charger/EVSE current limit312. As can be seen in pane302, using the charged controller100, the actual battery charging current closely conforms to the limitation situation experienced by the charger, that results in a quick reduction of the charger/EVSE current limit, without a significant lag/windup.

FIG.5is an illustrative charging profile400achieved using the charge controller of the present disclosure, highlighting the control operation at the charger/EVSE current limit410.FIG.6is an illustrative charging profile402achieved using the charge controller of the present disclosure, highlighting the control operation at the battery current limit440. InFIGS.5and6, the current over time of the charger/EVSE current limit410, the actual battery current420, the actual charger/EVSE current supplied430, and the battery current limit440are plotted over time As can be seen inFIGS.5and6, the actual battery current420tracks and is close to the lower of the charger/EVSE current limit410(FIG.5) and the battery current limit440(FIG.6), while the actual charger/EVSE current supplied430remains slightly above that of the actual battery current420.

FIG.7is a flowchart of an illustrative embodiment of a method700for charge control of the present disclosure. The method700includes obtaining inputs that are current-based at step702. In some embodiments, the inputs that are current-based include a charger current limit, a battery current limit, and a measured battery current.

The method700also includes determining a target charging current request for a battery from a charger based on the inputs that are current-based and wind-up feedback correction provided by a feedback loop at step704. In embodiments, the wind-up feedback correction corrects drift of the feedback controller while the battery current limit is beyond the maximum charger/EVSE current limit. In embodiments, the wind-up feedback correction is determined by monitoring uncontrolled drift of the feedback controller through a dynamic feedback loop-and-gain on the integral term.

In various embodiments, the method700includes determining a limiting charging current that is a minimum of the charger current limit and the battery current limit. In some of these embodiments, the method700includes utilizing a proportional-integral (PI) controller that is fed the limiting charging current and the measured battery current, the PI controller including a proportional gain path that is configured to add or subtract from a request for error correction and an integral gain path that is configured to prevent oscillation by accounting for historical errors. In some of these embodiments, the integral gain path is fed the wind-up feedback correction to account for transient errors.

In various embodiments, the method700includes transitioning, in response to a threshold voltage of the battery being reached, from a current-based implementation to a voltage-based implementation by determining the target charging current request for the battery from the charger based on inputs that are voltage-based. In some of these embodiments, the threshold voltage is a predetermined target voltage, such as max battery cell voltage. In other embodiments, the threshold voltage is a voltage range, such as a range defining voltages within a predetermined amount of a predetermined value In one embodiment, the voltage range includes voltages within a one millivolt (mV) window of max battery cell voltage. In various embodiments, the threshold voltage is adjusted for variability in the SOH of the battery and for a temperature of the battery pack.

In various embodiments, the method700also includes causing current available from the charger, that exceeds the determined current request, to be directed to a thermal management system associated with the battery.

FIG.8is a flowchart of another illustrative embodiment of a method800for charge control of the present disclosure. The method800includes determining, in response to a voltage of a battery being below a threshold voltage, a target charging current request for the battery from a charger based on inputs that are current-based at step802. The method800also includes determining, in response to the voltage of the battery being at or above the threshold voltage, the target charging current request for the battery from the charger based on inputs that are voltage-based at step804. In various embodiments, the inputs that are current-based include a charger current limit, a battery current limit, and a measured battery current and the inputs that are voltage-based include a cell voltage target and a maximum cell voltage.

In various embodiments, the threshold voltage is a predetermined value. In some of these embodiments, the threshold voltage is a predetermined target voltage, such as max battery cell voltage. In other embodiments, the threshold voltage is a voltage range, such as within a one millivolt (mV) window of max battery cell voltage. In various embodiments, the threshold voltage is adjusted for variability in the SOH of the battery and for a temperature of the battery pack.

In some of these embodiments, the threshold voltage is adjusted based on the predetermined value, a State of Health (SOH) of the battery, and a temperature of the battery.

In various embodiments, the target charging current request for the battery from the charger is further determined based on wind-up feedback correction provided by a feedback loop both above and below the threshold voltage. In embodiments, the wind-up feedback correction corrects drift of the actual battery current beyond the maximum charger/EVSE current limit. In embodiments, the wind-up feedback correction is determined by monitoring uncontrolled drift of the actual battery current through a dynamic feedback loop-and-gain on the integral term.

In various embodiments, the target charging current request for the battery from the charger is determined utilizing a proportional-integral controller. The proportional-integral controller includes a proportional gain path that is configured to add or subtract from a request for error correction and an integral gain path that is configured to prevent oscillation by accounting for historical errors. In some of these embodiments, the proportional gain path and the integral gain path are configured as current based gains while operating below the threshold voltage and are configured as voltage based gains while operating above the threshold voltage.

It is to be recognized that, depending on the example, certain acts or events of any of the techniques described herein, such as those inFIGS.7and8, can be performed together, in a different sequence, may be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the techniques). Moreover, in certain examples, acts or events may be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors, rather than sequentially.

FIG.9is a schematic diagram of a charge controller200, which may be used in a charging system, a cloud-based system, in another system, or stand-alone in a charger/EVSE or a vehicle, for example. In various embodiments, the charge controller200is configured to perform any of the methods and processes disclosed herein. In some embodiments, the charge controller200includes a proportional-integral controller. The charge controller200may be a digital computer that, in terms of hardware architecture, generally includes a processor202, input/output (I/O) interfaces204, a network interface206, a data store208, and memory210. It should be appreciated by those of ordinary skill in the art thatFIG.9depicts the charge controller200in an oversimplified manner, and a practical embodiment may include additional components and suitably configured processing logic to support known or conventional operating features that are not described in detail herein. The components (202,204,206,208, and210) are communicatively coupled via a local interface212. The local interface212may be, for example, but is not limited to, one or more buses or other wired or wireless connections, as is known in the art. The local interface212may have additional elements, which are omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers, among many others, to enable communications. Further, the local interface212may include address, control, and/or data connections to enable appropriate communications among the aforementioned components.

The processor202is a hardware device for executing software instructions. The processor202may be any custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors associated with the processing system200, a semiconductor-based microprocessor (in the form of a microchip or chipset), or generally any device for executing software instructions. When the charge controller200is in operation, the processor202is configured to execute software stored within the memory210, to communicate data to and from the memory210, and to generally control operations of the charge controller200pursuant to the software instructions. The I/O interfaces204may be used to receive user input from and/or for providing system output to one or more devices or components.

The network interface206may be used to enable the processing system200to communicate on a network, such as the Internet. The network interface206may include, for example, an Ethernet card or adapter (e.g., 10BaseT, Fast Ethernet, Gigabit Ethernet, or 10 GbE) or a Wireless Local Area Network (WLAN) card or adapter (e.g., 802.11a/b/g/n/ac). The network interface206may include address, control, and/or data connections to enable appropriate communications on the network. A data store208may be used to store data. The data store208may include any of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, and the like)), nonvolatile memory elements (e.g., ROM, hard drive, tape, CDROM, and the like), and combinations thereof. Moreover, the data store208may incorporate electronic, magnetic, optical, and/or other types of storage media. In one example, the data store208may be located internal to the processing system200, such as, for example, an internal hard drive connected to the local interface212in the processing system200. Additionally, in another embodiment, the data store208may be located external to the processing system200such as, for example, an external hard drive connected to the I/O interfaces204(e.g., a SCSI or USB connection). In a further embodiment, the data store208may be connected to the processing system200through a network, such as, for example, a network-attached file server.

Moreover, some embodiments may include a non-transitory computer-readable medium having computer-readable code stored thereon for programming a computer, server, appliance, device, processor, circuit, etc. each of which may include a processor to perform functions as described and claimed herein. Examples of such computer-readable mediums include, but are not limited to, a hard disk, an optical storage device, a magnetic storage device, a Read-Only Memory (ROM), a Programmable Read-Only Memory (PROM), an Erasable Programmable Read-Only Memory (EPROM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), flash memory, and the like. When stored in the non-transitory computer-readable medium, software can include instructions executable by a processor or device (e.g., any type of programmable circuitry or logic) that, in response to such execution, cause a processor or the device to perform a set of operations, steps, methods, processes, algorithms, functions, techniques, etc. as described herein for the various embodiments.