Method and apparatus for controlling electrical power flow in a battery system

Abstract

The present invention relates to a method and apparatus for controlling the flow of electrical power in a battery system. The battery system is electrically connected to a power bus that is arranged to supply electrical power to on-board actuators such as traction motors. Controlling the flow of electrical power in a battery pack includes: determining a state of charge of a plurality of battery packs; identifying one of the battery packs as a weakest battery pack based on the state of charge; and determining an internal circulating current transmitted via a wiring harness associated with the charging of the weakest battery pack. The transmission of electrical power through the wiring harness and the power bus is controlled so that the internal circulating current is less than an internal circulating current limit. In one embodiment, the internal circulating current limit is determined relative to the battery temperature.

Description

Background Art

[0001] Vehicles and other systems employ DC power sources in the form of rechargeable battery packs to supply electrical power for vehicle propulsion and to provide other functions. A battery system may include multiple battery packs arranged in parallel and / or in series.

[0002] There may be an imbalance between the states of charge of battery packs employed in a battery system, wherein one of the battery packs has a higher state of charge than another of the battery packs. Imbalance between the states of charge of battery packs employed in a battery system may be difficult to avoid due to current flow characteristics associated with battery voltage potentials, charging schemes, especially so-called fast charging schemes, differential aging of the battery packs, temperature-induced differences among the battery packs, and errors in estimating the state of charge.

[0003] The difference in state of charge may result in internal circulating currents, in which one battery pack of the battery system with a higher state of charge transfers electrical energy to another battery pack with a lower state of charge. In some cases, including, for example, under very low battery temperature conditions, uncontrolled internal circulating currents occur that charge the weakest battery pack with a lower state of charge, which may result in lithium plating and other effects in the battery. In addition, under cold weather conditions, high discharge loads may drive different amounts of polarization between battery packs in the battery system, which may result in uncontrolled circulating currents once the load is removed, and may result in lithium plating and other effects in the battery. Lithium plating in the battery can act to increase internal battery impedance and reduce the battery charge capacity, thereby affecting the service life of the battery pack.

[0004] As such, there is a need to manage and control internal circulating currents between cells in a battery system employing multiple battery packs, including in a manner that reduces or eliminates the potential for lithium precipitation and other effects to occur. Summary of the invention

[0005] The concepts described herein provide methods and related systems for controlling the flow of electric power in a battery pack, the battery pack including a plurality of electrically connected lithium-ion battery packs, wherein the battery system is electrically connected to a power bus to supply electric power to one or more motors and / or electric actuators. In one embodiment, and as described herein, the battery system is used onboard a vehicle and includes a plurality of lithium-ion battery packs electrically connected via a wiring harness. The battery packs are electrically connected to a power bus, which is arranged to supply electric power to onboard actuators such as traction motors. In general, controlling the flow of electric power in the battery system includes: determining the state of charge of the plurality of battery packs; identifying one of the battery packs as the weakest battery pack based on the state of charge and its impedance; and determining an internal circulating current transmitted via the wiring harness associated with the charging of the weakest battery pack. The transmission of electric power through the wiring harness and the power bus is controlled so that the internal circulating current for charging the weakest battery pack is less than an internal circulating current limit. In one embodiment, the internal circulating current limit is determined relative to the battery temperature.

[0006] One aspect of the present disclosure includes controlling the electric power transfer through the wiring harness and the power bus so that the internal circulating current is less than the internal circulating current limit for the weakest battery pack, including: identifying one of the battery packs as the weakest battery pack based on the charge state and the battery pack impedance; determining the internal circulating current transferred to the weakest battery pack via the wiring harness; and disconnecting the weakest battery pack from the wiring harness when the internal circulating current is greater than the internal circulating current limit.

[0007] Another aspect of the present disclosure includes determining that the vehicle is in a key-off state; and disconnecting the weakest battery pack from the wiring harness when the internal circulating current is greater than the internal circulating current limit and the vehicle is in the key-off state.

[0008] Another aspect of the present disclosure includes controlling the transfer of electric power through the wiring harness and the power bus so that the internal circulation current is less than the internal circulation charging current limit when the vehicle is lightly loaded or the vehicle is stopped, which includes: performing feedforward control based on the battery states of the multiple battery packs to determine a first load current for a given internal circulation current limit; performing feedback control based on the weakest battery pack current measurement result and the corresponding current limit of the internal circulation current to determine a current feedback term; determining a bias load current based on the first load current and the current feedback term; and controlling the operation of the electric accessory device based on the bias load current to control the internal circulation current.

[0009] Another aspect of the present disclosure includes an electric motor electrically connected to a power bus, and further includes: monitoring electric load demand under a high load state of the vehicle; identifying one of the battery packs as the strongest battery pack based on the charge state and the impedance of the battery pack; and reducing the electric load demand delivered to the motor to control the electric power transfer through the wiring harness so that the discharge current of the strongest battery pack is less than a discharge current limit.

[0010] Another aspect of the present disclosure includes introducing the bias load current onto the power bus to control the internal circulating current to be less than an internal circulating current limit.

[0011] Another aspect of the present disclosure includes introducing the bias load current onto the power bus by introducing a resistive load onto the power bus to control the internal circulating current to be less than an internal circulating current limit.

[0012] Another aspect of the present disclosure includes controlling operation of an electric accessory device to control an internal circulating current to be less than an internal circulating current limit.

[0013] Another aspect of the present disclosure includes an electric power system for a vehicle, the electric power system including a battery system, the battery system including a plurality of battery packs, a plurality of sensors arranged to monitor the battery packs, a high voltage DC power bus, a plurality of switches disposed between the plurality of battery packs and the power bus, a motor, and a controller. The battery packs are electrically connected via a wiring harness and are electrically connected to the power bus via a wiring harness. The controller communicates with the plurality of sensors, the plurality of switches, and the motor, and includes an instruction set executable to: monitor parameters associated with the plurality of battery packs via the plurality of sensors; determine a state of charge of the plurality of battery packs; determine an internal circulating current transmitted between the plurality of battery packs via the wiring harness based on the state of charge; and control the transmission of electric power through the wiring harness and the power bus so that the internal circulating current is less than an internal circulating current limit.

[0014] The present invention also includes the following technical solutions.

[0015] Solution 1. A method for controlling electric power flow in a battery system for a vehicle, wherein the battery system includes a plurality of battery packs electrically connected via a wiring harness, and wherein the battery packs are electrically connected to a power bus via the wiring harness, the method comprising:

[0016] determining a state of charge and an impedance of the plurality of battery packs;

[0017] determining an internal circulating current transmitted between the plurality of battery packs via the wiring harness based on the state of charge; and

[0018] Electrical power transfer through the wiring harness is controlled so that the internal circulating current is less than an internal circulating current limit.

[0019] Solution 2. The method according to solution 1, wherein controlling the electric power transfer through the wiring harness so that the internal circulating current is less than the internal circulating current limit comprises:

[0020] identifying one of the battery packs as a weakest battery pack based on the states of charge and the impedances of the battery packs;

[0021] determining the internal circulating current delivered via the wiring harness to the weakest battery pack; and

[0022] When the internal circulation current is greater than the internal circulation current limit, the weakest battery pack is disconnected from the wiring harness.

[0023] Option 3. The method according to Option 2 further includes determining that the vehicle is in a key-off state; and

[0024] When the internal circulating current is greater than the internal circulating current limit and the vehicle is in the key-off state, the weakest battery pack is disconnected from the wiring harness.

[0025] Solution 4. The method according to solution 1, wherein controlling the electric power transfer through the wiring harness so that the internal circulating current is less than the internal circulating current limit comprises:

[0026] performing feed-forward control based on the charge states of the plurality of battery packs and the impedance to determine a first load current;

[0027] performing feedback control based on the internal circulating current and the internal circulating current limit to determine a current feedback term;

[0028] determining a bias load current based on the first load current and the current feedback term; and

[0029] Operation of an electric accessory device is controlled based on the bias load current to control the internal circulating current.

[0030] Option 5. A method according to Option 4, wherein controlling the electric power transfer through the wiring harness so that the internal circulating current is less than the internal circulating current limit includes: introducing the bias load current to the power bus to control the internal circulating current to be less than the internal circulating current limit.

[0031] Embodiment 6. The method according to embodiment 5, wherein introducing a bias load onto the power bus comprises: introducing a resistive load onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

[0032] Solution 7. The method according to Solution 1 further includes a motor, wherein the motor is electrically connected to the power bus; the method further includes:

[0033] monitoring an electrical load demand delivered to the motor;

[0034] identifying one of the battery packs as the strongest battery pack based on the state of charge and the impedance of the battery packs; and

[0035] The electrical load demand delivered to the electric machine is reduced to control the electrical power transfer through the wiring harness such that a discharge current of the strongest battery pack is less than a discharge current limit.

[0036] Solution 8. A method for controlling electric power flow in a battery system for a vehicle, wherein the battery system includes a plurality of lithium-ion battery packs electrically connected via a wiring harness, and wherein the battery system is electrically connected to a power bus via the wiring harness, the method comprising:

[0037] determining a state of charge and an impedance of the plurality of lithium-ion battery packs;

[0038] determining an internal circulating current transmitted through the wiring harness; and

[0039] Electrical power transfer through the wiring harness and the power bus is controlled so that the internal circulating current is less than an internal circulating current limit.

[0040] Solution 9. The method according to Solution 8, wherein controlling the electric power transfer through the wiring harness and the power bus so that the internal circulating current is less than an internal circulating current limit comprises:

[0041] identifying one of the battery packs as a weakest battery pack based on the state of charge;

[0042] determining the internal circulating current delivered via the wiring harness to the weakest battery pack; and

[0043] When the internal circulation current is greater than the internal circulation current limit, the weakest battery pack is disconnected from the wiring harness.

[0044] Option 10. The method according to Option 9 further includes: disconnecting the weakest battery pack from the wiring harness when the internal circulating current is greater than the internal circulating current limit and when the vehicle is in a key-off state.

[0045] Embodiment 11. The method according to embodiment 8, wherein controlling the electric power transfer through the wiring harness and the power bus so that the internal circulating current is less than the internal circulating current limit comprises:

[0046] performing feed-forward control based on the state of charge of the lithium-ion battery pack and the impedance to determine a first load current;

[0047] performing feedback control based on the internal circulating current and the internal circulating current limit to determine a current feedback term;

[0048] determining a bias load current based on the first load current and the current feedback term; and

[0049] Operation of an electric accessory device is controlled based on the bias load current to control the internal circulating current.

[0050] Option 12. A method according to Option 11, wherein controlling the electric power transfer through the wiring harness so that the internal circulating current is less than the internal circulating current limit includes: introducing the bias load current to the power bus to control the internal circulating current to be less than the internal circulating current limit.

[0051] Embodiment 13. The method according to embodiment 12, wherein introducing a bias load onto the power bus comprises: introducing a resistive load onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

[0052] Solution 14. An electric power system for a vehicle, comprising:

[0053] A battery system comprising a plurality of battery packs, a plurality of sensors arranged to monitor the battery packs, a high voltage DC power bus, a plurality of switches disposed between the plurality of battery packs and the power bus, a motor, a wiring harness, and a controller;

[0054] wherein the plurality of battery packs are electrically connected via the wiring harness;

[0055] wherein the plurality of battery packs are electrically connected to the power bus via the wiring harness;

[0056] wherein the controller communicates with the plurality of sensors, the plurality of switches and the motor;

[0057] Wherein, the controller includes an instruction set, wherein the instruction set is executable to:

[0058] monitoring parameters associated with the plurality of battery packs via the plurality of sensors,

[0059] determining a state of charge and an impedance of the plurality of battery packs;

[0060] determining an internal circulating current transmitted between the plurality of battery packs via the wiring harness based on the state of charge and the impedance of the battery pack, and

[0061] Electrical power transfer through the wiring harness and the power bus is controlled so that the internal circulating current is less than an internal circulating current limit.

[0062] Solution 15. The electric power system according to Solution 14, wherein the instruction set executable to control the electric power transfer through the wiring harness and the power bus so that the internal circulating current is less than the internal circulating current limit includes the following instruction set, that is, the instruction set executable to:

[0063] identifying one of the battery packs as the weakest battery pack based on the state of charge,

[0064] determining the internal circulating current delivered via the wiring harness to the weakest battery pack, and

[0065] When the internal circulation current is greater than the internal circulation current limit, the weakest battery pack is disconnected from the wiring harness.

[0066] Solution 16. The electric power system according to Solution 15 further includes the following instruction set, namely: the instruction set is executable to determine that the vehicle is in a key-off state; and

[0067] When the internal circulating current is greater than the internal circulating current limit and the vehicle is in the key-off state, the weakest battery pack is disconnected from the wiring harness.

[0068] Option 17. An electric power system according to Option 14, wherein the instruction set capable of being executed to control the electric power transfer through the wiring harness and the power bus so that the internal circulating current is less than the internal circulating current limit includes the following instruction set, namely: the instruction set is capable of being executed to control the operation of the electric accessory device so as to control the internal circulating current to be less than the internal circulating current limit.

[0069] Option 18. An electric power system according to Option 14, wherein the instruction set capable of being executed to control the transfer of electric power through the wiring harness and the power bus so that the internal circulating current is less than the internal circulating current limit includes the following instruction set, namely: the instruction set is capable of being executed to introduce a bias load onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

[0070] Option 19. An electric power system according to Option 18, wherein the instruction set capable of being executed to introduce the bias load onto the power bus includes the following instruction set, namely: the instruction set is capable of being executed to introduce a resistive load onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

[0071] Solution 20. The electric power system of Solution 14, wherein the instruction set executable to control the electric power transfer through the wiring harness so that the internal circulating current is less than the internal circulating current limit comprises the following instruction set, that is, the instruction set executable to:

[0072] executing a feed-forward control routine based on the state of charge of the plurality of battery packs and the impedance to determine a first load current;

[0073] executing a feedback control routine based on the internal circulating current and the internal circulating current limit to determine a current feedback term;

[0074] determining a bias load current based on the first load current and the current feedback term; and

[0075] Operation of an electric accessory device is controlled based on the bias load current to control the internal circulating current.

[0076] The above summary is not intended to represent every possible embodiment or every aspect of the present disclosure. On the contrary, the above summary is intended to illustrate some of the novel aspects and features disclosed herein. The above features and advantages and other features and advantages of the present disclosure will be apparent from the following detailed description of representative embodiments and modes for implementing the present disclosure when combined with the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] One or more embodiments will now be described by way of example with reference to the accompanying drawings, in which:

[0078] Figure 1 An electric power system according to the present disclosure is schematically illustrated, arranged to supply electric power for operating an electric machine of a vehicle.

[0079] Figure 2 A control routine associated with operations to prevent lithium deposition and plating onto battery electrodes of first and second battery packs in accordance with the present disclosure is schematically illustrated.

[0080] Figure 3 Another control routine associated with operations to prevent lithium deposition and plating onto battery electrodes of first and second battery packs according to the present disclosure is schematically illustrated.

[0081] Figure 4Another control routine associated with operations to prevent lithium deposition and plating onto battery electrodes of first and second battery packs according to the present disclosure is schematically illustrated.

[0082] Figure 5 Another control routine associated with operations to prevent lithium deposition and plating onto battery electrodes of a plurality of battery packs in accordance with the present disclosure is schematically illustrated.

[0083] The drawings are not necessarily drawn to scale and may present somewhat simplified representations of various preferred features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes. The details associated with such features will be determined in part by the specific intended application and use environment. DETAILED DESCRIPTION

[0084] As described and illustrated herein, the components of the disclosed embodiments can be arranged and designed according to a variety of different configurations. Therefore, the following detailed description is not intended to limit the scope of the present disclosure as claimed, but only represents its possible embodiments. In addition, although many specific details are set forth in the following description in order to provide a thorough understanding of the embodiments disclosed herein, some embodiments can be practiced without some of these details. In addition, for the sake of clarity, some technical materials understood in the relevant technical field are not described in detail to avoid unnecessarily blurring the present disclosure. In addition, the accompanying drawings are in simplified form and are not accurate proportions. Only for the purpose of convenience and clarity, directional terms such as top, bottom, left, right, top, above, above, below, below, back and front can be used relative to the accompanying drawings. These and similar directional terms should not be interpreted as limiting the scope of the present disclosure. In addition, as illustrated and described herein, the present disclosure can be practiced without the presence of elements not specifically disclosed herein.

[0085] As used herein, the term "system" may refer to one or a combination of mechanical and electrical hardware, sensors, controllers, application specific integrated circuits (ASICs), combinatorial logic circuits, software, firmware, and / or other components arranged to provide the described functionality.

[0086] Referring to the drawings, wherein the same reference numerals correspond to the same or similar components throughout the several figures, the embodiments disclosed herein are consistent with the present invention. Figure 1An electric power system 10 is illustrated that is arranged to supply electric power for operating an electric machine 12 of a vehicle 100. In one embodiment, the electric machine 12 is a multi-phase traction motor that generates traction torque in response to an operator torque request and transmits it to a vehicle driveline. The vehicle 100 may include, but is not limited to, a mobile platform in the form of a commercial vehicle, an industrial vehicle, an agricultural vehicle, a passenger car, an aircraft, a watercraft, a train, an all-terrain vehicle, a personal mobility device, a robot, etc. for achieving the purposes of the present disclosure. Alternatively, the electric power system 10 may be arranged to supply electric power for operating an electric machine of a stationary system.

[0087] The electric power system 10 includes a battery system 20, which is electrically connected to the motor 12 via a high voltage (HV) DC power bus 15 and a power inverter 14. The battery system 20 is also electrically connected to a controllable electric load 50 via the HV DC power bus 15. The controller 36 monitors and / or controls the operation of the various elements of the electric power system 10. The charger 40 is electrically connected to the battery system 20 via the HV DC power bus 15, which includes a positive HV bus 16 and a negative HV bus 18. The battery system 20 includes a plurality of lithium-ion battery packs, which include first and second battery packs 22, 24, respectively, as shown. As used herein, the battery system 20 is a single device including a plurality of battery packs and is configured to deliver a desired voltage, current and / or power density to the electric power system 10. As used herein, the term "battery pack" describes a subset of a battery system and includes a plurality of identical battery cells arranged in series, parallel, or another combination to deliver a desired voltage, current, and / or power density to a battery system 20. As shown, the first and second battery packs 22, 24 are electrically connected via a wiring harness 26, respectively, which is electrically connected to the positive HV bus 16. The internal circulating current 25 is defined as the magnitude of the current flowing between the first and second battery packs 22, 24 via the wiring harness 26. The wiring harness 26 includes first and second switches 28, 30, respectively, which can be controlled by a controller 36. The first switch 28 is arranged to electrically connect the first battery pack 22 to the positive HV bus 16 or to electrically disconnect it, and the second switch 30 is arranged to electrically connect the second battery pack 24 to the positive HV bus 16 or to electrically disconnect it. The first battery pack 22 is electrically connected to the negative HV bus 18 via a first sensor package 32, and the second battery pack 24 is electrically connected to the negative HV bus 18 via a second sensor package 34. The first and second sensor packages 32, 34 include sensing elements that monitor first and second voltage, current, and temperature (VIT) parameters 33, 35 of the first and second battery packs 22, 24, respectively. The first and second sensor packages 32, 34 transmit the first and second VIT parameters 33, 35 to the controller 36. As non-limiting examples, the controllable electric loads 50 may include electric onboard actuators such as a battery heater, an HVAC compressor, a cabin heater, a cabin fan, a coolant pump, an electric seat heater, a DC-DC charger, etc.

[0088] As reference Figure 2As described below, the controller 36 monitors and / or controls the operation of various elements of the electric power system 10, including monitoring inputs from the first and second sensor packages 32, 34, controlling activation of the first and second switches 28, 30, controlling operation of the controllable electric load 50, and controlling operation of the power inverter 14 to control the motor 12. In general, monitoring and controlling the operation of various elements of the electric power system 10 includes: determining the state of charge and associated temperature of the plurality of battery packs, such as the first and second battery packs 22, 24, respectively; identifying one of the battery packs as the weakest battery based on the state of charge and impedance; and determining the internal circulating current 25, which occurs in the wiring harness 26 and is associated with the weakest battery when the vehicle is lightly loaded or unloaded. The controller 36 controls the transfer of electric power between the first and second battery packs 22, 24, and controls the transfer of electric power between the battery system 20 and the HV DC power bus 15, so that the internal circulating current 25 is less than the internal circulating current limit to prevent lithium deposition and plating on the battery electrodes of the battery packs.

[0089] Figure 2 The following schematically illustrates a control routine associated with a method for controlling the operation of the electric power system 10 and the vehicle 100 to prevent lithium deposition and plating on the battery electrodes of the battery pack that may be caused by internal circulating currents when the vehicle is under load or when the vehicle is not loaded. The method is illustrated as a collection of boxes in a logical flow chart, which represents a series of operations that can be implemented in hardware, software, or a combination thereof. In the context of software, these boxes represent computer instructions that, when executed by one or more processors, perform the operations described.

[0090] Reference now Figure 2 , continue to refer to Figure 1 Elements of an electric power system 10 for a vehicle 100 are described, a first control routine 200 is described, and the first control routine 200 is associated with the operation of preventing lithium deposition and plating onto battery electrodes of first and second battery packs 22, 24, respectively, by controlling an internal circulating current 25, including controlling the internal circulating current 25 under conditions including a key-on / key-off state of the vehicle. Execution of the first control routine 200 includes: determining and evaluating the internal circulating current 25 under vehicle operating conditions including the vehicle 100 being in a key-off state. This includes determining various vehicle parameters by direct monitoring, modeling, simulation, or another method. The vehicle parameters include: vehicle speed (201); state of charge of the first and second battery packs 22, 24 (202); battery temperatures T1 and T2 of the respective first and second battery packs 22, 24 (203); key-off state (204); internal circulating (charging) current limit I of the respective first and second battery packs 22, 24L1 ,I L2 (205); and battery status (206). The internal circulation current limit I of the corresponding first and second battery packs 22, 24 L1 ,I L2 The internal circulating current 25 may be determined correspondingly with respect to the battery temperatures T1 and T2 of the first and second battery packs 22 and 24 and represents the maximum allowable charging current level to prevent lithium precipitation at the corresponding temperature. When the vehicle 100 is in a parked state, the aforementioned vehicle parameters are input to the routine 210 to estimate, measure or otherwise determine the internal circulating current 25. The routine 210 determines the internal circulating current 25 according to the following relationship:

[0091] [1]

[0092] in:

[0093] i 1 represents the internal circulating current 25 and is associated with the weakest of the first and second battery groups 22, 24;

[0094] V T1 represents the terminal voltage measured at the first battery pack 22;

[0095] V T2 represents the terminal voltage measured at the second battery pack 24;

[0096] L represents the inductance in the wiring harness 26; and

[0097] R s2 represents the resistance in the wiring harness 26 .

[0098] Alternatively, the internal circulating current 25 may be directly measured by the first and second sensor packages 32, 34. The internal circulating current 25 is compared to the internal circulating current limit I of the first and second battery packs 22, 24, respectively. L1 ,I L2 Compared with temperature, the internal circulating current limit I L1 ,I L2 The maximum current level (215) was determined to prevent lithium precipitation.

[0099] When the internal circulation current 25 is less than the internal circulation current limit I of the first and second battery groups 22 and 24, respectively L1 ,I L2 When (215)(0), no action is required (216) and the iteration ends.

[0100] When the internal circulation current 25 is greater than the internal circulation current limit I of the first and second battery groups 22 and 24, respectively L1 ,I L2 At (215)(1), the charge states of the first and second battery groups 22, 24 are respectively evaluated to correspondingly identify one of the first and second battery groups 22, 24 as the weakest battery group, wherein the weakest battery group is correspondingly the one of the first and second battery groups 22, 24 having a lower charge state.

[0101] One of the first and second switches 28 , 30 associated with the identified weakest battery pack is opened to electrically disconnect the weakest battery pack from the other battery pack and, thus, interrupt the internal circulating current 25 ( 220 ).

[0102] The vehicle's key-on / key-off state is continuously monitored (222). When the key-on / key-off state indicates that the vehicle 100 is in the key-on state (222)(1), an expected discharge load power for preventing lithium precipitation is estimated (224), and when the actual discharge load power is substantially greater than the expected discharge load power (226), the open switch of the first and second switches 28, 30 associated with the identified weakest battery pack is closed to re-electrically connect the weakest battery pack to another battery pack and the HV DC power bus 15 (226).

[0103] When the key-on / key-off state indicates that the vehicle 100 remains in the key-off state (222)(0), an internal circulating current associated with an elevated battery temperature is estimated (230), and the estimated internal circulating current is calculated by comparing the internal circulating current limit I of the first and second battery packs 22, 24, respectively. L1 ,I L2 When the estimated internal circulating current is greater than the internal circulating current limit I of the first and second battery packs 22 and 24, respectively, L1 ,I L2 When (232)(0), the key start / key off state of the vehicle is monitored again (222). However, when the estimated internal circulating current is less than the internal circulating current limit I of the first and second battery packs 22, 24, respectively L1 ,I L2 At (232)(1), the open switch of the first and second switches 28, 30 associated with the identified weakest battery pack is closed to reconnect the weakest battery pack to the other battery pack and the HV DC power bus 15 (234). In this manner, the first control routine 200 provides operations including the key-off state of the vehicle, including evaluation operations regarding battery temperature.

[0104] Reference now Figure 3 , continue to refer to Figure 1 Elements of the electric power system 10 for the vehicle 100 are described, and a second control routine 300 is described and associated with operations to prevent lithium deposition and plating onto the battery electrodes of the first and second battery packs 22, 24, respectively, by controlling the internal circulating current 25 below the charging current limit when the vehicle is lightly loaded or unloaded, including increasing the power bus load by turning on additional accessory loads such as an electrical system heater, raising the cabin temperature or heating the seats. On the other hand, when the vehicle 100 is operating in a fully loaded discharge state, the discharge current from the strongest of the battery packs 22 or 24 will be controlled to operate below its discharge current limit by operating the motor 12 to produce less traction power. The second control routine 300 may be in the form of an executable instruction set implemented in the controller 36.

[0105] Execution of the second control routine 300 includes determining and evaluating the internal circulating current 25 under vehicle operating conditions including the vehicle 100 being in a key-on or key-off state by determining various vehicle parameters by direct monitoring, modeling, simulation or another method. The vehicle parameters include: the charge state of the respective first and second battery packs 22, 24 (302); the battery temperatures T1 and T2 of the respective first and second battery packs 22, 24 (303); the internal circulating current limit I of the respective first and second battery packs 22, 24 L1 ,I L2 (305); and other battery conditions (306), such as the polarization voltage of the first and second battery packs 22, 24. The polarization voltage is the internal voltage drop of the battery in addition to its open circuit voltage. The aforementioned vehicle parameters are input to the routine 310 to determine a first feed-forward load current 315 for operating the vehicle 100.

[0106] The feed-forward load current 315 may be determined by using a physics-based feed-forward estimator as shown in Equation 2:

[0107] [2]

[0108] in,

[0109] i represents the total current load applied to the battery system 20;

[0110] L represents the inductance in the wiring harness 26;

[0111] R m1 represents the internal resistance of the first battery pack 22;

[0112] R m2represents the internal resistance of the second battery pack 24;

[0113] I L1 represents the internal circulating current limit of the first battery group 22 which is assumed to be the weakest battery;

[0114] IR_Free_V 1 represents the voltage of the first battery pack 22 minus the voltage drop R m1 i 1 ;

[0115] IR_Free_V 2 represents the voltage of the second battery pack 24 minus the voltage drop R m2 i 2 ;as well as

[0116] R s2 represents the resistance in the wiring harness 26 .

[0117] Equation 2 can be simplified as follows:

[0118] [3]

[0119] in:

[0120] i represents the total current load applied to the battery system 20;

[0121] L represents the inductance in the wiring harness 26;

[0122] R m1 represents the internal resistance of the first battery pack 22;

[0123] R m2 represents the internal resistance of the second battery pack 24;

[0124] OCV1 represents the open circuit voltage at the first battery group 22;

[0125] OCV2 represents the open circuit voltage at the second battery pack 24; and

[0126] I L1 Represents the internal circulating current limit of the weakest battery, such as the first battery pack 22 in one embodiment.

[0127] Coincidentally, the respective first and second voltage, current and temperature (VIT) parameters 33, 35 from the first and second battery packs 22, 24 are evaluated in a feedback loop to select the current 29 (332) from the weakest battery pack or from the strongest battery pack based on the control requirements, for example, when controlling the internal circulating current under the charging current limit under the vehicle light load or no load condition, the current of the weakest battery pack under charging is selected; similarly, in the case of a vehicle full load request or discharge state, the discharge current of the strongest battery pack is selected, which is provided as feedback to the adder function 318 and is respectively selected from the corresponding charging current limit I of the first and second battery packs 22, 24. L1 ,I L2 315 to determine a current difference 319, which is provided as an input to a proportional integral (PI) controller 320. The PI controller 320 generates a current feedback term 325 based on the current difference 319. The current feedback term 325 is combined with the feedforward load current 315 by an adder 327 to determine a bias load current 335, which is subjected to the anti-windup and saturation control term 330 depicted graphically.

[0128] The bias load current 335 is provided as feedback to an integrator anti-windup function 336 , which generates an anti-windup term 338 , which is provided to the PI controller 320 to generate the current feedback term 325 .

[0129] In order to control the internal circulating current below the charging current limit when the vehicle is lightly loaded or unloaded, the bias load current 335 is added to the current operating load current 340 to determine the final load current 350. The controller 36 uses the final load current 350 to control the operation of one or more vehicle accessory loads to ensure that the internal circulating current 25 is less than the internal circulating current limit I of the first and second battery packs 22, 24, respectively. L1 ,I L2 , thereby preventing lithium deposition and plating onto the battery electrodes of the first and second battery packs 22, 24, respectively. Similarly, in the case of a full vehicle load demand, the determined final load current 350 from the feedforward and feedback control will be achieved by reducing the motor torque or motor current delivered to the motor 12.

[0130] Reference now Figure 4, which describes another control routine 400 and is associated with the operation of preventing lithium deposition and plating on battery electrodes of first and second battery groups 422, 424 of an electric power system 410 by controlling an internal circulating current 425, respectively. The control routine 400 is associated with and used to control the electric power system 410, which includes a controllable resistive load 450 arranged on a HV DC power bus 415. This includes controlling the controllable resistive load to introduce a bias load on the HV DC power bus 415 to control the internal circulating current 425 to be less than an internal circulating current limit.

[0131] The electric power system 410 includes a battery pack 420, which is electrically connected to a vehicle load 412 via a HV DC power bus 415, which may include a power inverter and a motor. The battery pack 420 is also electrically connected to a controllable resistive load 450 via the HV DC power bus 415. The controller 436 monitors and / or controls the operation of the various elements of the electric power system 410. The HV DC power bus 415 includes a positive HV bus 416 and a negative HV bus 418. The battery pack 420 includes a plurality of lithium-ion battery packs, including first and second battery packs 422, 424, respectively, as shown. As shown, the first and second battery packs 422, 424 are electrically connected via a wiring harness 426, respectively, which is electrically connected to the positive HV bus 416. The internal circulating current 425 is defined as the magnitude of the current flowing between the first and second battery packs 422, 424 via the wiring harness 426. The wiring harness 426 includes first and second switches 428, 430, respectively, which can be controlled by a controller 436. The first switch 428 is arranged to electrically connect the first battery pack 422 to the positive HV bus 416 or to electrically disconnect it, and the second switch 430 is arranged to electrically connect the second battery pack 424 to the positive HV bus 416 or to electrically disconnect it. The first battery pack 422 is electrically connected to the negative HV bus 418 via the first sensor package 432, and the second battery pack 424 is electrically connected to the negative HV bus 418 via the second sensor package 434. The first and second sensor packages 432, 434 include sensing elements that monitor first and second voltage, current and temperature (VIT) parameters of the first and second battery packs 22, 24. The first and second sensor packages 432, 434 transmit the first and second VIT parameters to the controller 436. Controllable resistive load 450 is a variable resistive device that is disposed between positive HV bus 416 and negative HV bus 418 and connected to positive HV bus 416 and negative HV bus 418 through switch 405 controlled by controller 436 .

[0132] The control routine 400 may be implemented in the form of an executable instruction set implemented in the controller 436, including operating the motor 12 to generate traction power under low load or no load conditions. The control routine 400 includes evaluating first and second voltage, current, and temperature (VIT) parameters from the first and second battery packs 422, 424, respectively, to determine a minimum current 429. The minimum current 429 of the first and second battery packs 422, 424 and the internal circulation current limit I L1 ,I L2 (465) is input to the PI feedback controller 480, which generates a resistance correction term 485 based on the current difference between them. The internal circulation current limit I of the first and second battery packs 422, 424 is determined accordingly with respect to the corresponding battery temperatures T1 and T2. L1 ,I L2 . Internal circulating current limit I L1 ,I L2 is also provided to the feed forward routine 470 to determine the feed forward inner loop resistance 475. The feed forward inner loop resistance 475 and the resistance correction term 485 are combined to determine the bias load resistance 495 which is provided as an input to control the controllable resistive load 450.

[0133] The feed forward routine 470 determines the feed forward inner loop resistance 475 according to the following relationship:

[0134] [4]

[0135] in:

[0136] R represents the feedforward internal loop resistance 475;

[0137] V Indicates the battery system terminal voltage;

[0138] i represents the expected load current determined based on Equation 2 and Equation 3; and

[0139] PcqI Indicates the vehicle load power.

[0140] When the expected discharge power V*i Vehicle load power PcqI When the difference between 400 and 410 is greater than zero, controller 436 controls switch 405 to activate controllable resistive load 450 (490) between positive HV bus 416 and negative HV bus 418. The magnitude of bias load resistance 495 caused by controllable resistive load 450 is determined based on the combination of feedforward internal loop resistance 475 and resistance correction term 485.

[0141] Figure 5 An electrical power system 510 is schematically shown, which includes a battery system 520, which is electrically connected to a vehicle load 512, which may include a power inverter and an electric machine, via a HVDC power bus 515, and is electrically connected to other vehicle accessory loads represented by reference numeral 550. The HV DC power bus 515 includes a positive HV bus 516 and a negative HV bus 518. The battery system 520 includes a plurality of lithium-ion battery packs, in one embodiment and as shown, including first, second, third and fourth battery packs 521, 522, 523 and 524, respectively. The first, second, third and fourth battery packs 521, 522, 523 and 524 are electrically connected between the positive HV bus 516 and the negative HV bus 518 via switches 531, 532, 533 and 534, respectively. Currents i1 , i2 , i3 , and i4 from the respective first, second, third, and fourth battery packs 521 , 522 , 523 , and 524 are monitored by VIT sensors 541 , 542 , 543 , and 544 , respectively.

[0142] In operation, the controller 536 monitors information from the VIT sensors 541, 542, 543, and 544 to determine parameters for the corresponding first, second, third, and fourth battery packs 521, 522, 523, and 524, including, for example, current, cell voltage, and battery pack temperature. The parameters for the corresponding first, second, third, and fourth battery packs 521, 522, 523, and 524 are used to determine the corresponding charge and discharge current limits I L1 ,I L2 ,I L3 ,I L4 When the magnitude of one or more of the currents i1, i2, i3 and i4 from the corresponding first, second, third and fourth battery packs 521, 522, 523 and 524 is greater than the corresponding current limit I L1 ,I L2 ,I L3 ,I L4 When a load is applied, action is taken to control the corresponding circulating charging current by deactivating a corresponding one of switches 531, 532, 533 and 534 when there is no load or when the load is light, or by inducing a bias load on one of the vehicle accessories 550 to reduce the corresponding charging current.

[0143] When in full-load driving demand, take action to control the corresponding discharge current from the strongest battery pack within the discharge current limit, which is by reducing the motor torque or current or other electric power consumption in the vehicle. This includes: monitoring the electrical load demand delivered to the motor; identifying one of the battery packs as the strongest battery pack based on the state of charge and the impedance of the battery pack; and reducing the electrical load demand delivered to the motor to control the electric power delivery through the wiring harness so that the discharge current of the strongest battery pack is less than the discharge current limit. This helps to control the electric power delivery through the wiring harness and the power bus so that when the driver requires full power in cold weather, the discharge current of the strongest battery pack in the battery system is less than the battery discharge current limit. This includes: performing feedforward control based on the battery state of the multiple battery packs to determine the first load current for a given discharge current limit; performing feedback control based on the actual strongest battery pack current measurement and the discharge current limit to determine the current feedback term; determining the bias load current based on the first load current and the current feedback term; and controlling the operation of one or more motors or actuators by deducting the bias load current from the motor so that the current of the strongest battery pack will not exceed the discharge current limit.

[0144] The term "controller" and related terms such as microcontroller, control module, module, control, control unit, processor and similar terms refer to one or more combinations of the following: application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), electronic circuits, central processing units, such as microprocessors, and related non-transitory memory components in the form of memory and storage devices (read-only, programmable read-only, random access, hard drives, etc.). The non-transitory memory components can store machine-readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuits, input / output circuits and devices, signal conditioning, buffer circuits, and other components that can be accessed and executed by one or more processors to provide the functions described. The input / output circuits and devices include analog / digital converters and related devices that monitor inputs from sensors, where such inputs are monitored at a preset sampling frequency or in response to a triggering event. Software, firmware, programs, instructions, control routines, codes, algorithms and similar terms mean controller executable instruction sets including calibration and lookup tables. Each controller executes a control routine to provide the desired function. The routine can be executed at regular intervals, such as every 100 microseconds during ongoing operation. Alternatively, the routine may be executed in response to the occurrence of a triggering event. Communication between the controller, actuator and / or sensor may be achieved using a direct wired point-to-point link, a networked communication bus link, a wireless link, or another suitable communication link. Communication includes exchanging data signals in a suitable form, such as electrical signals via a conductive medium, electromagnetic signals via air, optical signals via optical waveguides, etc. The data signal may include discrete, analog, or digitized analog signals representing inputs from sensors, actuator commands, and communication between controllers.

[0145] The term “signal” refers to a physically discernible indication that conveys information, and may be a suitable waveform (e.g., electrical, optical, magnetic, mechanical, or electromagnetic) capable of propagating through a medium, such as DC, AC, sine wave, triangle wave, square wave, vibration, etc.

[0146] The term "model" refers to a processor-based or processor-executable code and associated calibration that simulates the physical existence of a device or physical process. As used herein, the terms "dynamic" and "dynamically" describe a step or process that is performed in real time and is characterized by monitoring or otherwise determining the state of a parameter and updating the state of the parameter regularly or periodically during the execution of a routine or between execution iterations of the routine.

[0147] The terms "calibration," "calibrated," and related terms refer to the result or process of correlating desired parameters to one or more sensed or observed parameters for a device or system. Calibration as described herein may be summarized as a storable parameter table, a plurality of executable equations, or another suitable form that may be used as part of a measurement or control routine.

[0148] A parameter is defined as a measurable quantity representing a physical characteristic of a device or other element that can be discerned using one or more sensors and / or physical models. A parameter may have discrete values, such as "1" or "0", or may vary infinitely in value.

[0149] The flowcharts and block diagrams in the flowchart diagrams illustrate the architecture, functions and operations of possible implementations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram may represent a module, segment or portion of a code, which includes one or more executable instructions for implementing a specified logical function. It will also be noted that each box in the block diagram and / or flowchart illustration and the combination of boxes in the block diagram and / or flowchart illustration can be implemented by a hardware-based system or a combination of hardware and computer instructions for a dedicated function that performs a specified function or action. These computer program instructions may also be stored in a computer-readable medium, which may guide a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable medium produce an article including an instruction set, which implements the function / action specified in one or more boxes of the flowchart and / or block diagram.

[0150] The detailed description and drawings or figures are support and description of the present teaching, but the scope of the present teaching is limited only by the claims. Although some best modes and other embodiments for carrying out the present teaching have been described in detail, there are various alternative designs and embodiments for practicing the present teaching defined in the claims.

Claims

1. A method for controlling the flow of electrical power in a battery system for a vehicle, wherein: The battery system comprises a plurality of battery packs electrically connected via a wiring harness, and wherein the battery packs are electrically connected to a power bus via the wiring harness, the method comprising: determining a state of charge and an impedance of the plurality of battery packs; determining an internal circulating current transmitted between the plurality of battery packs via the wiring harness based on the state of charge; and controlling the transfer of electrical power through the wiring harness so that the internal circulating current is less than an internal circulating current limit, Controlling the transfer of electrical power through the wiring harness includes: performing feed-forward control based on the charge states of the plurality of battery packs and the impedance to determine a first load current; performing feedback control based on the internal circulating current and the internal circulating current limit to determine a current feedback term; determining a bias load current based on the first load current and the current feedback term; and Operation of an electric accessory device is controlled based on the bias load current to control the internal circulating current.

2. The method according to claim 1, wherein: Controlling the electrical power transfer through the wiring harness comprises: identifying one of the battery packs as a weakest battery pack based on the states of charge and the impedances of the battery packs; determining the internal circulating current delivered via the wiring harness to the weakest battery pack; and When the internal circulation current is greater than the internal circulation current limit, the weakest battery pack is disconnected from the wiring harness.

3. The method of claim 2, further comprising determining that the vehicle is in a key-off state; and When the internal circulating current is greater than the internal circulating current limit and the vehicle is in the key-off state, the weakest battery pack is disconnected from the wiring harness.

4. The method according to claim 1, wherein: Controlling electrical power transfer through the wiring harness includes introducing the bias load current onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

5. The method according to claim 4, wherein: Introducing a bias load onto the power bus includes introducing a resistive load onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

6. The method according to claim 1, further comprising a motor, the motor being electrically connected to the power bus; the method further comprising: monitoring an electrical load demand delivered to the motor; identifying one of the battery packs as the strongest battery pack based on the state of charge and the impedance of the battery packs; as well as The electrical load demand delivered to the electric machine is reduced to control the electrical power transfer through the wiring harness such that a discharge current of the strongest battery pack is less than a discharge current limit.

7. A method for controlling the flow of electrical power in a battery system for a vehicle, wherein: The battery system comprises a plurality of lithium-ion battery packs electrically connected via a wiring harness, and wherein the battery system is electrically connected to a power bus via the wiring harness, the method comprising: determining a state of charge and an impedance of the plurality of lithium-ion battery packs; determining an internal circulating current transmitted through the wiring harness; and controlling the transfer of electrical power through the wiring harness and the power bus so that the internal circulating current is less than an internal circulating current limit, Controlling the transfer of electrical power through the wiring harness and the power bus includes: performing feed-forward control based on the state of charge of the lithium-ion battery pack and the impedance to determine a first load current; performing feedback control based on the internal circulating current and the internal circulating current limit to determine a current feedback term; determining a bias load current based on the first load current and the current feedback term; and Operation of an electric accessory device is controlled based on the bias load current to control the internal circulating current.

8. The method according to claim 7, wherein: Controlling electrical power through the wiring harness and the power bus includes: identifying one of the battery packs as a weakest battery pack based on the state of charge; determining the internal circulating current delivered via the wiring harness to the weakest battery pack; and When the internal circulation current is greater than the internal circulation current limit, the weakest battery pack is disconnected from the wiring harness.

9. The method according to claim 8, further comprising: The weakest battery pack is disconnected from the wiring harness when the internal circulating current is greater than the internal circulating current limit and when the vehicle is in a key-off state.

10. The method according to claim 7, wherein: Controlling the transfer of electrical power through the wiring harness and the power bus includes introducing the bias load current onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

11. The method according to claim 10, wherein: Introducing a bias load onto the power bus includes introducing a resistive load onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

12. An electric power system for a vehicle, comprising: A battery system comprising a plurality of battery packs, a plurality of sensors arranged to monitor the battery packs, a high voltage DC power bus, a plurality of switches disposed between the plurality of battery packs and the power bus, a motor, a wiring harness, and a controller; wherein the plurality of battery packs are electrically connected via the wiring harness; wherein the plurality of battery packs are electrically connected to the power bus via the wiring harness; wherein the controller communicates with the plurality of sensors, the plurality of switches and the motor; Wherein, the controller is configured as: monitoring parameters associated with the plurality of battery packs via the plurality of sensors, determining a state of charge and an impedance of the plurality of battery packs; determining an internal circulating current transmitted between the plurality of battery packs via the wiring harness based on the state of charge and the impedance of the battery pack, and controlling the transfer of electrical power through the wiring harness and the power bus so that the internal circulating current is less than an internal circulating current limit, The controller is configured to: executing a feed-forward control routine based on the state of charge of the plurality of battery packs and the impedance to determine a first load current; executing a feedback control routine based on the internal circulating current and the internal circulating current limit to determine a current feedback term; determining a bias load current based on the first load current and the current feedback term; and Operation of an electric accessory device is controlled based on the bias load current to control the internal circulating current.

13. The electric power system according to claim 12, wherein: The controller is configured to: identifying one of the battery packs as the weakest battery pack based on the state of charge, determining the internal circulating current delivered via the wiring harness to the weakest battery pack, and When the internal circulation current is greater than the internal circulation current limit, the weakest battery pack is disconnected from the wiring harness.

14. The electric power system of claim 13, wherein the controller is configured to: determining that the vehicle is in a key-off state; and When the internal circulating current is greater than the internal circulating current limit and the vehicle is in the key-off state, the weakest battery pack is disconnected from the wiring harness.

15. The electric power system according to claim 12, wherein: The controller is configured to introduce a bias load current onto the power bus to control the internal circulating current to be less than the internal circulating current limit.

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