Closed loop battery charging current control

Abstract

A method of charging a vehicle having a battery operable to power an electric traction system includes connecting the battery (20) to a charger (9), wherein the electric vehicle (10) includes a powertrain controller communicatively connected to the battery (20) and the charger (9) when the battery (20) is connected to the charger (9); and by the charge controller: determining a feedforward demand current; receiving a measured battery current indicative of a current received by the battery (20) from the charger (9); determining a current feedback based on an integral of a difference between the measured battery current and the feedforward demand current; and determining a target current based on a sum of the feedforward demand current and the current feedback; and commanding the charger (9) to supply the target current to the electric vehicle (10).

Description

[0001] Cross-references to related applications

[0002] none. Technical Field

[0003] This disclosure relates to apparatus and methods for charging batteries, and methods for controlling power supply equipment for electric vehicles. Background Technology

[0004] The aim is to utilize the charger to quickly charge the battery of an electric vehicle by providing the maximum amount of power that the battery can safely receive. The electric vehicle may include accessories, which may be powered by the battery on the high-voltage bus, or the bus itself, or a battery charger connected to the bus.

[0005] During battery charging, a target current is calculated based on battery power limitations and accessory load requirements. Different high-voltage devices from different manufacturers can be connected to the battery directly or via the bus and draw power during charging. The charger may be unaware of the accessory's power consumption. Furthermore, inaccuracies in current sensing across different components can lead to incorrect target current calculations, potentially resulting in insufficient or excessive current flowing to the battery.

[0006] New control technologies are needed to improve the accuracy of the target current while meeting battery charging power limits. Summary of the Invention

[0007] Among the various aspects of this disclosure, an electric vehicle having a battery and a powertrain controller, a powertrain controller, and a method for charging the battery via the powertrain controller are provided.

[0008] The disclosed implementation ensures that the current required by the battery is delivered to the battery to meet its charging current requirements, regardless of scenarios that would typically impede such delivery.

[0009] In a first aspect, a method for charging a vehicle having a battery operable to power an electric traction system includes: connecting the battery (20) to a charger (9), wherein the electric vehicle (10) includes a powertrain controller, which is communicatively connected to the battery (20) and the charger (9) when the battery (20) is connected to the charger (9); and the charging controller: determining a feedforward demand current; receiving a measured battery current indicating the current received by the battery (20) from the charger (9); determining a current feedback based on an integral of the difference between the measured battery current and the feedforward demand current; determining a target current based on the sum of the feedforward demand current and the current feedback; and commanding the charger (9) to supply the target current to the electric vehicle (10).

[0010] In a second aspect, a powertrain controller controlling charging of an electric vehicle having a battery operable to power an electric traction system includes charging logic operable to determine a feedforward demand current, receive a measured battery current indicative of a current received by the battery (20) from a charger (9), determine a current feedback based on an integral of a difference between the measured battery current and the feedforward demand current, determine a target current based on a sum of the feedforward demand current and the current feedback, and generate a target current command for the charger (9) to supply the target current to the electric vehicle.

[0011] In a third aspect, an electric vehicle includes an electric traction system (12), a battery (20) connected to power the electric traction system (12), and a powertrain controller (40) controlling charging of the battery (20) when the battery (20) is connected to a charger (9), the powertrain controller (40) including charging logic (42) operable to determine a feedforward demand current, receive a measured battery current indicative of a current received by the battery (20) from a charger (9), determine a current feedback based on an integral of a difference between the measured battery current and the feedforward demand current, determine a target current based on a sum of the feedforward demand current and the current feedback, and generate a target current command for the charger (9) to supply the target current to the electric vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0012] The above-mentioned embodiments and additional features and advantages will be further clarified by the following exemplary and non-limiting detailed description of embodiments, disclosed herein with reference to the accompanying drawings, in which:

[0013] Figure 1 is a schematic diagram of a vehicle electrically connected to a charger;

[0014] Figure 2 is a block diagram of an embodiment of battery charging logic; and

[0015] Figure 3 is Figure 3 a schematic diagram of an embodiment of charging logic of

[0016] In the drawings, corresponding reference numerals indicate corresponding parts, functions and features across the several views. The drawings are not necessarily to scale, with some features possibly being exaggerated in order to better illustrate and explain the disclosed embodiments. DETAILED DESCRIPTION

[0017] For the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to embodiments illustrated in the drawings described below. The embodiments disclosed below are not intended to be exhaustive or limit the present disclosure to the precise form disclosed in the following detailed description.

[0018] During charging of a battery of an electric vehicle, there can be different scenarios. As used herein, an electric vehicle includes a vehicle having an electric powertrain. Typically, the electric powertrain includes an electric motor connected directly or indirectly to a traction system. The traction system can include, for example, wheels. For example, the wheels can drive a continuous tread or track. The powertrain can be fully electric, for example, a full electric vehicle, or can include a combustion engine in addition to the electric motor, for example, a hybrid electric vehicle. Thus, as used herein, a hybrid electric vehicle and a full electric vehicle are types of electric vehicles. The charging current can be limited by the electric vehicle supply equipment (EVSE). The EVSE can include a charger, a charger cable, a connector of the charger cable, etc. The charging current can also be limited by the battery. In case of battery limited charging, the charging can be affected during cold pre-heat, start of charge, pack integration, EVSE under / over delivery, and accessory reporting inaccuracies. The logic described below addresses these scenarios.

[0019] Figure 1 is a schematic diagram of a vehicle 10 electrically connected to a charger 8. The electric vehicle 10 includes an electric traction system 12 including a motor-generator 14 and wheels 16 that can be connected to the motor-generator 14 through an axle (not shown) or directly, a battery 20 connected to a busbar 30 to power the electric traction system 12, and a powertrain controller 40 for controlling charging of the battery 20 when the busbar 30 is connected to the charger 8. A charging controller 48 establishes communication between the powertrain controller and the charger as known in the art. The charging controller receives a charge command from the powertrain controller and provides the charge command to the charger. The charging controller can monitor sensor signals and perform safety and performance checks and determine faults based thereon. For example, if charging is started but the physical connection between the charger and the vehicle cannot be detected or is detected to be outside of a safety boundary, the charging controller can determine a fault. Thus, the charging controller acts as a communication interface between the charger and the powertrain controller.

[0020] Reported accessories 50 and non-reported accessories 52 that draw power from the bus 30 are also shown. Communication lines 9, 21, 41, and 51 enable the powertrain controller 40 to communicate with the charger 9, the battery 20, and the reported accessories 50, respectively. Preferably, the communication lines convey digital data between the components. CAN buses can be implemented to provide the communication lines. In a preferred embodiment, a first CAN bus can be implemented to provide the communication lines 21 and 51, and a second CAN bus can be implemented to provide the communication lines 41. Any serial or parallel communication scheme and protocol known in the art can be used to provide the communication lines 9.

[0021] As the name implies, the reported accessories 50 are operable to communicate information to the powertrain controller 40. Such information can include identification, current demand, high or low voltage power draw, and other information. For example, the identification information can convey the maximum current capacity of the accessory. The current demand can be dynamic, such that the current demand of the reported accessory 50 is fluctuating. For example, the reported accessory 50 can be an air conditioning system, and the current demand can vary based on a comparison of the vehicle temperature to a target temperature. By reporting the current demand to the powertrain controller 40, the reported accessory 50 enables the powertrain controller 40 to more accurately determine a target current to generate a charge command to the charger. On the other hand, the load of a non-reported accessory can be dynamic and unknown, resulting in the charger delivering insufficient current to the battery, thus reducing the charge time with the faster charge time resulting from implementing feedback control as discussed herein. The charge command can also take into account the ability of the charger to deliver current. The charge command indicates to the charger what current level to output to the vehicle, which should be sufficient to optimally charge the battery and also power the accessory.

[0022] The battery 20 can include one or more battery packs including a battery management unit (BMU) 22 and battery modules 24. BMUs are generally known. Temperature, voltage, and other sensors can be provided to enable the BMU 22 to manage the charging and discharging of the battery modules 24 without exceeding their limits, to detect and manage faults, and to perform other known functions. The battery 20 has a battery charge power limit that should not be exceeded. The bus voltage can be referred to as the system voltage. Via the communication lines, the BMU 22 can convey information about the battery to the powertrain controller 40, including the battery charge power limit, temperature, faults, etc. The battery 20 can include a current sensor 26 to provide the BMU with a measured current value. The feedback control uses the measured current value to influence the charge command provided to the charger. The current sensor can also be located elsewhere. Multiple current sensors can also be provided, each associated with a battery module of the battery, the sum of the measured currents being the measured battery current.

[0023] The powertrain controller 40 includes charging logic 42 operable to determine a command to cause the charger to supply a target current to the battery, as described below with reference to Figure 2 and Figure 3 The term "logic" as used herein includes software and / or firmware containing processing instructions that are executed on one or more programmable processors, application specific integrated circuits, field programmable gate arrays, digital signal processors, hardwired logic, or combinations thereof, which can be referred to as a "controller." Thus, in accordance with embodiments, various logic can be implemented in any suitable manner and will remain consistent with the embodiments disclosed herein. Additionally, a non-transitory machine-readable medium including logic can be considered to be embodied in any tangible form of computer-readable carrier, such as a solid state memory, containing a suitable set of computer instructions and data structures that would cause a processor to perform the techniques described herein. The non-transitory computer-readable medium or memory can include random access memory (RAM), read only memory (ROM), erasable programmable read only memory (e.g., EPROM, EEPROM, or flash memory), or any other tangible medium that can hold instructions and data used by a processor.

[0024] The powertrain controller 40 can include functionality known in the art of electric vehicles. Such functionality can include logic to control the motor-generator by determining a desired torque and commanding the battery to provide power commensurate with the torque, and can include functionality for range extension, regeneration, torque ratio control when a combustion engine is provided in a hybrid electric vehicle, etc. The powertrain controller 40 can also control all high voltage accessories coupled to the bus. The high voltage bus can have a voltage greater than 500 volts DC, possibly in the range of 550-850 volts DC.

[0025] The powertrain controller 40 can include functionality known in the art of electric vehicles. Such functionality can include logic to control the motor-generator by determining a desired torque and commanding the battery to provide power commensurate with the torque, and can include functionality for range extension, regeneration, torque ratio control when a combustion engine is provided in a hybrid electric vehicle, etc.

[0026] The feedforward current is the power demand divided by the bus voltage. The power demand includes the battery demand plus the demand of the accessories. The battery demand or power limit can be provided by the BMU of the battery. The feedback current control section includes a proportional integral (PI) module that compares the battery demand current to the measured current received by the battery to generate a feedback value. The feedforward current is then adjusted based on the feedback value. If the accessories are non-reporting accessories, the feedback control can increase the target current until the battery demand is met, which requires the target current to be higher than the battery demand current to at least compensate for the unknown demand of the non-reporting accessories. As is known, the BMU can communicate the battery demand based on the state of charge of the battery and other battery characteristics.

[0027] Figure 2 is a block diagram of an embodiment of the battery charging logic 42 that includes feedforward and feedback current control. The minimum of the calibration current limit, the charger current limit, and the feedback compensated feedforward current is the target current 102. The feedforward current 100 is the calculated power demand, such as the accessory power draw plus the battery charging power limit divided by the bus or system voltage. As is known, the battery limit is specified by the BMU, so as the state of charge (SOC) increases, the power required by the battery or the battery limit decreases. The battery limit can also be based on the cell temperature and voltage of the cells in the battery pack. The feedback current control includes a closed loop compensation that compares the battery demand to the measured current provided by the charger to the battery to produce a feedback value and adjusts the feedforward current 100 based on the feedback value to produce a feedback adjusted current value 102 that, if less than the charging hardware limit, becomes the current target, also referred to as the EVSE current target. The calibratable current limit can be a limit that is calibrated to protect non-smart components of the charging system, such as the plug and cable, and the calibration of the calibratable current limit can be part of the vehicle configuration. The calibratable current limit can be provided to the charging logic by the BMU or can exist in the charging logic as, for example, content of a memory unit. The accessory power draw of reporting accessories can be known and used to calculate the calculated power demand, but the accessory power draw of non-reporting accessories is unknown.

[0028] Figure 3 is a block diagram of a variant of the embodiment described with reference to Figure 2 is a block diagram of a variant of the embodiment described with reference to

[0029] The feedforward current control section determines a feedforward current based on the battery charge power limit and the sum of the accessory power draw or demand of accessories electrically connected to the battery divided by the bus voltage. If the charge hardware limit is less than the feedforward current, the integrator of the closed loop current control section is reset, e.g., set to zero, thereby canceling the feedback.

[0030] The closed loop current control section determines a battery current demand and compares it to the measured battery current to determine a difference or error. A PI module, which is well known in the art, includes proportional and integral components that generate a feedback signal or value by integrating the difference after scaling it using a proportional gain. The feedback value is added to the feedforward value to generate a current value, which, if it is less than the charge current limit, becomes the target current. The battery current demand can be determined by dividing the battery charge power limit by the battery voltage. The battery current demand can be provided by the closed loop current control section of the BMU or calculated in any other manner.

[0031] As described with reference to the accompanying drawings, the addition of the feedback loop enhances the performance of the charger to charge the battery of the vehicle and thus increases the charging speed to enable the vehicle to recover operation faster. Furthermore, the improved charging logic increases the predictability of the charging time estimate, which enhances the scheduling and routing planning of electric vehicles, e.g., buses.

[0032] The scope of the application is only limited by the appended claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but

[0033] In the DETAILED DESCRIPTION, references to "one embodiment", "an embodiment”, "example embodiments”, etc., mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

[0034] As used in this document, the terms "includes,” "including,” "has,” "having” or the like are intended to be inclusive of many non-exclusive items, such that a process, method, article, or apparatus that includes items does not, without additional language, remove those items, but permits the inclusion of additional or other items in that process, method, article, or apparatus.

[0035] The above-described embodiments and examples are further modified within the spirit and scope of the disclosure. This application covers any variations, uses, or adaptations of the application claimed by the following claims.

Claims

1. A method for charging an electric vehicle (10) having a battery (20), said battery being operable to supply power to an electric traction system (12), said method comprising: The battery (20) is connected to the charger (9), wherein the electric vehicle (10) includes a powertrain controller and a charging controller, the charging controller serving as a communication interface between the charger (9) and the powertrain controller, and when the battery (20) is connected to the charger (9), the powertrain controller is communicatively connected to the battery (20) and the charger (9); and By the powertrain controller: Determine the feedforward current requirement; Receives a measurement of the battery current indicating the current received by the battery (20) from the charger (9); The current feedback is determined based on the integral of the difference between the measured battery current and the feedforward demand current; and The target current is determined based on the sum of the feedforward demand current and the current feedback; and The charger (9) is instructed to supply the target current to the electric vehicle (10). The feedforward demand current includes the power demand divided by the battery voltage, and the power demand is based on the sum of the battery charging power limit of the battery (20) and the accessory power drawdown of the accessory (50) electrically connected to the high voltage bus of the electric vehicle (10).

2. The method of claim 1, wherein, The target current is the smaller of the sum of the feedforward demand current and the current feedback current, and the charging hardware limitation.

3. The method of claim 1, wherein, Annex (50) is a report attachment.

4. The method according to claim 1, wherein, The powertrain controller (40) includes a proportional-integral module that is operable to determine the current feedback based on the integral of the difference as a function of the proportional value, and to output a current feedback value indicating the current feedback.

5. The method according to claim 4, wherein, The powertrain controller (40) determines the target current based on the sum of the feedforward demand current and the current feedback value.

6. The method according to claim 5, wherein, If the charging hardware limit is less than the sum of the feedforward demand current and the current feedback value, the powertrain controller (40) sets the current feedback to zero.

7. A powertrain controller (40) for controlling the charging of an electric vehicle (10), the electric vehicle having a battery (20) operable to supply power to an electric traction system (12) and a charging controller, the charging controller serving as a communication interface between a charger (9) and the powertrain controller (40), the powertrain controller (40) including charging logic (42) operable to: Determine the feedforward current requirement; Receives a measurement of the battery current indicating the current received by the battery (20) from the charger (9); The current feedback is determined based on the integral of the difference between the measured battery current and the feedforward demand current; The target current is determined based on the sum of the feedforward demand current and the current feedback; and Generate a target current command for the charger (9) to supply the target current to the electric vehicle. The feedforward demand current includes the power demand divided by the battery voltage, and the power demand is based on the sum of the battery charging power limit of the battery (20) and the accessory power drawdown of the accessory (50) electrically connected to the high voltage bus of the electric vehicle (10).

8. The powertrain controller (40) according to claim 7, wherein, The target current is the smaller of the sum of the feedforward demand current and the current feedback current, and the charging hardware limitation.

9. The powertrain controller (40) according to claim 7, wherein, The charging logic (42) includes a proportional-integral module that is operable to determine the current feedback based on the integral of the difference as a function of the proportional value, and to output a current feedback value indicating the current feedback.

10. The powertrain controller (40) according to claim 9, wherein, The charging logic (42) can operate to determine the target current based on the sum of the feedforward demand current and the current feedback value, and / or If the charging hardware limit is less than the sum of the feedforward demand current and the current feedback value, the powertrain controller (40) sets the current feedback to zero.

11. An electric vehicle (10), said electric vehicle comprising: Electric traction system (12); A battery (20) is connected to power the electric traction system (12); as well as The powertrain controller (40) according to any one of claims 7 to 10.

12. The electric vehicle (10) according to claim 11, wherein, The powertrain controller (40) can also be operated to command the charger (9) to supply the target current to the electric vehicle (10).

13. The electric vehicle (10) according to claim 11, the electric vehicle further comprising a reporting attachment communicatively connected to the powertrain controller (40) to provide attachment power draw to the powertrain controller (40).

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