VEHICLE SYSTEM

Abstract

Vehicle system (10) comprising; a first battery pack (102) connected to a second battery pack (104) via a flying capacitor multilevel converter (110) having a plurality of converter strings (330, 340, 350, 530, 540, 550), each converter string (330, 340, 350, 530, 540, 550) arranged in a flying capacitor topology; a motor (20, 21) connected to the flying capacitor multilevel converter (110), the motor (20, 21) having three phases; and a controller (150) connected to the motor (20, 21) and the flying capacitor multilevel converter (110), the controller (150) comprising a memory that stores instructions configured to cause the controller (150) to control the flying capacitor multilevel converter (110) as a direct current (DC)-DC converter such that a circulating current is passed through the motor (20, 21), the first battery pack (102), and the second battery pack (104).

Description

INTRODUCTION

[0001] The subject matter of the disclosure relates to balancing and transferring power between mixed chemistry battery packs using a multilevel converter operating as a direct current (DC) to DC converter.

[0002] Vehicles, including electric and hybrid electric vehicles, are equipped with a battery storage system for purposes such as powering electric motors, electronics, and other vehicle subsystems. The batteries for the battery storage system typically comprise several separate power cells, each of which stores power for later distribution. The power cells are electrically connected to provide an output current to a power distribution bus when needed. During or shortly after charging the battery storage system, care should be taken to ensure that power is properly distributed between the battery packs for optimal operation. Existing systems use identical cell types (called chemistries) within the battery pack. Identical cells can be balanced using passive current balancing techniques.

[0003] Different types of batteries have different characteristics, such as charging speed and power density. In some designs, it may be advantageous to use different types of battery packs in a single battery system, allowing different vehicle operating modes to take advantage of the different battery properties. However, using different battery types in a single battery pack complicates power transfer and balancing between batteries, and existing passive balancing systems are unable to effectively transfer power between batteries of different chemistries.

[0004] WO 2022 / 120436 A1 describes a controller in which a converter for an inductive load connected to a plurality of phases is operated by means of a switching method with at least two parallel driver circuits, each of which is connected to one or more phases of the inductive load connected to the plurality of phases.

[0005] The subsequently published DE 10 2022 002 606 A1 describes a vehicle system in which a drive system has a three-phase machine and an inverter which is electrically coupled to it and is designed as a flying capacitor inverter.

[0006] WO 2022 / 156 171 A1 describes a voltage conversion device for an electric vehicle.

[0007] JP 2021 - 27 698 A describes a system in which two flying capacitor circuits are coupled in series with each other and in parallel with a high-voltage device.

[0008] Accordingly, it is desirable to provide an active power balancing system for a vehicle battery system comprising battery packs of several different types. SUMMARY

[0009] In an exemplary embodiment, a vehicle system includes a first battery pack connected to a second battery pack via a flying capacitor multilevel converter having a plurality of converter strings, each converter string arranged in a flying capacitor topology. A motor is connected to the flying capacitor multilevel converter. A controller is connected to the motor and the flying capacitor multilevel converter, the controller including a memory storing instructions configured to cause the controller to control the flying capacitor multilevel converter as a direct current (DC)-to-DC converter such that a recirculating current is passed through the motor, the first battery pack, and the second battery pack.

[0010] In addition to one or more of the features described herein, each inverter string of the flying capacitor multilevel inverter includes a first transistor connecting a positive bus to a high node, a second transistor connecting the high node to an alternating current (AC) output node, a third transistor connecting the AC output node to a low node, and a fourth transistor connecting the low node to a negative bus, and wherein each phase of the motor is connected to an AC output node of the corresponding inverter string of the flying capacitor multilevel inverter.

[0011] In addition to one or more of the features described herein, the motor is a four-pole motor. Controlling the flying capacitor multilevel inverter as a DC-DC converter comprises, for each inverter string: providing a first control signal to the first transistor and the fourth transistor of each inverter string, wherein the first control signal is inverted for the fourth transistor. Providing a second control signal to the second transistor and the third transistor of each inverter string, wherein the second control signal is inverted for the third transistor. The first control signals and the second control signals control an open / closed state of the first, second, third, and fourth transistors of the corresponding inverter string via pulse width modulation. The first control signal and the second control signal are 120 degrees out of phase with each other first control signal and second control signal.

[0012] In addition to one or more of the features described herein, the motor is a three-pole motor. Controlling the flying capacitor multilevel inverter as a DC-DC converter comprises, for each of a first inverter string and a second inverter string: providing a first control signal to the first and fourth transistors of the corresponding inverter string, wherein the first control signal is inverted for the fourth transistor. Providing a second control signal to the second and third transistors of the corresponding inverter string, wherein the second control signal is inverted for the third transistor. The first control signals and the second control signals control an open / closed state of the first, second, third, and fourth transistors of the corresponding inverter string via pulse width modulation.Each of the first control signal and the second control signal is 180 degrees out of phase with the first control signal and the second control signal, respectively. Providing a third control signal for the first, second, third, and fourth transistors of the third converter string, wherein the third control signal sets the first, second, third, and fourth transistors of the third converter string to off for the duration of controlling the multilevel converter as a DC-DC converter.

[0013] In addition to one or more of the features described herein, the first battery pack and the second battery pack are connected in parallel at one or both of a negative battery terminal and a positive battery terminal.

[0014] In addition to one or more of the features described herein, the first battery pack and the second battery pack are connected in series via a common node, forming a series-connected battery pack.

[0015] In addition to one or more of the features described herein, a neutral node connects each phase of the motor to the common node.

[0016] In addition to one or more of the features described herein, a first-phase pole of the motor is connected to the common node of the series-connected battery pack.

[0017] In addition to one or more of the features described herein, a first inverter string is physically located closer to the first battery pack and closer to the second battery pack than each of the second inverter string and the third inverter string.

[0018] In addition to one or more of the features described herein, the first battery pack includes at least a first set of power cells and a second set of power cells connected to the first set of power cells at the lower node.

[0019] In another exemplary embodiment, a method for transferring power between a first battery pack and a second battery pack of a vehicle system includes causing a controller to control a flying capacitor multilevel inverter as a direct current (DC)-to-DC converter such that a circulating current is passed through the flying capacitor multilevel inverter, a motor, a first battery pack, and a second battery pack. The vehicle system includes the first battery pack connected to the second battery pack via the flying capacitor multilevel inverter, the motor connected to the flying capacitor multilevel inverter, and a motor controller connected to the motor and the flying capacitor multilevel inverter. The motor controller includes a memory that stores instructions configured to cause the vehicle system to implement the method.

[0020] In addition to one or more of the features described herein, the multilevel converter includes three converter strings. Each converter string of the flying capacitor multilevel converter includes a first transistor connecting a positive bus to a high node, a second transistor connecting the high node to an alternating current (AC) output node, a third transistor connecting the AC output node to a low node, and a fourth transistor connecting the low node to a negative bus. Each phase of the motor is connected to the AC output node of a corresponding converter string.

[0021] In addition to one or more of the features described herein, the motor is a four-pole motor. Controlling the flying capacitor multilevel inverter as a DC-DC converter comprises, for each inverter string: providing a first control signal to the first transistor and the fourth transistor of each inverter string, wherein the first control signal is inverted for the fourth transistor. Providing a second control signal to the second transistor and the third transistor of each inverter string, wherein the second control signal is inverted for the third transistor. The first control signals and the second control signals control an open / closed state of the first, second, third, and fourth transistors of the corresponding inverter string via pulse width modulation. The first control signal and the second control signal are 120 degrees out of phase with each other first control signal and second control signal.

[0022] In addition to one or more of the features described herein, the motor is a three-pole motor. Controlling the multilevel inverter as a DC-DC converter comprises, for each of a first inverter string and a second inverter string: providing a first control signal to the first and fourth transistors of the corresponding inverter string, wherein the first control signal is inverted for the fourth transistor. Providing a second control signal to the second and third transistors of the corresponding inverter string, wherein the second control signal is inverted for the third transistor. The first control signals and the second control signals control an open / closed state of the first, second, third, and fourth transistors of the corresponding inverter string via pulse width modulation. The first control signal and the second control signal are 180 degrees out of phase with the other of the first control signal and the second control signal.Providing a third control signal for the first, second, third and fourth transistors of the third converter string, wherein the third control signal sets the first, second, third and fourth transistors of the third converter string to off for the duration of controlling the multilevel converter as a DC-DC converter.

[0023] In addition to one or more of the features described herein, the first battery pack and the second battery pack are connected in parallel at at least one of a negative battery terminal and a positive battery terminal.

[0024] In addition to one or more of the features described herein, the first battery pack and the second battery pack are connected in series via a common node, forming a series-connected battery pack.

[0025] In addition to one or more of the features described herein, the first battery pack is a first chemistry and the second battery pack is a second chemistry that is different from the first chemistry.

[0026] In another exemplary embodiment, a vehicle comprises an electric propulsion system including at least one electric motor, a power distribution system including at least a first battery pack and a second battery pack, the power distribution system being connected to the electric propulsion system via a flying capacitor multilevel converter, and a controller connected to the motor and the flying capacitor multilevel converter, the controller including a memory storing instructions configured to cause the controller to control the flying capacitor multilevel converter as a direct current (DC)-to-DC converter such that a recirculating current is passed through the motor, the first battery pack, and the second battery pack.

[0027] In addition to one or more of the features described herein, wherein the flying capacitor multilevel converter comprises three converter strings, each converter string of the flying capacitor multilevel converter comprises a first transistor connecting a positive bus to a high node, a second transistor connecting the high node to an alternating current (AC) output node, a third transistor connecting the AC output node to a low node, and a fourth transistor connecting the low node to a negative bus, and wherein each phase of the motor is connected to a corresponding converter string of the flying capacitor multilevel converter.

[0028] The above features and advantages, as well as other features and advantages of the disclosure, will be readily apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further features, advantages and details are listed only as examples in the following detailed description, which refers to the drawings, where: Fig. Figure 1 is a schematic diagram of a vehicle incorporating a power distribution system; Fig. 2 is a block diagram of a battery system according to an exemplary embodiment; Fig. 3 is a circuit diagram representation of the power transfer method applied to parallel-arranged battery packs according to a first example; Fig. 4 is a circuit diagram representation of the power transfer method applied to parallel-arranged battery packs according to a second example; Fig. 5 is a circuit diagram of the power transmission method applied to serially arranged battery packs according to a first example; Fig. 6 is a circuit diagram of the power transmission method applied to serially arranged battery packs according to a second example; and Fig. Figure 7 illustrates an optional switch configuration for improving direct current (DC-DC) converter operation in a three-pole machine. DETAILED DESCRIPTION

[0030] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or uses.

[0031] It should be understood that throughout the drawings, corresponding reference numerals designate like or corresponding parts and features. As used herein, the term module refers to a processing circuit, which may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (common, dedicated, or group), and memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.

[0032] According to an exemplary embodiment, a vehicle system for a battery includes multiple battery packs having different battery pack chemistries. A multilevel inverter converts direct current (DC) from the battery into alternating current (AC), which is provided to a motor and drives the motor to rotate. The motor rotation characteristics are controlled by the characteristics of the AC power signal. A motor controller actively controls switching within the multilevel inverter to control the characteristics of the AC power signal.

[0033] A memory is configured to cause the motor controller to perform current balancing or transfer between the different battery packs by operating the multilevel inverter as a DC-DC converter, utilizing the internal inductance of the motor strings without rotating the motor for the DC-DC converter inductors. The internal inductance of the motor strings can be utilized without causing rotation by controlling the phase shift in the inverter's modulation while operating as a DC-DC converter, so that the rotating forces generated by the current flowing through one string are directly counteracted by the rotating forces generated by the current flowing through the other strings of the motor. The DC-DC converter is then capable of transferring power between the battery packs according to known power transfer methods.In some examples, the integrated circuitry to facilitate operation in DC-DC converter mode may be further utilized to provide fault protection and / or isolation of one or more strings during a fault condition by disconnecting the string experiencing the fault condition from the corresponding power buses.

[0034] The systems of Fig. 2-7 illustrate an apparatus and method for providing bidirectional power transfer between mixed-chemistry battery packs 102, 104 (e.g., a mixture of energy and power packs / modules, fuel cell, and Li-ion packs) using a multilevel flying capacitor inverter drive system as a DC-DC converter (using a non-rotating motor and a multilevel inverter during continuous operation or a non-rotating motor and a multilevel inverter during steady-state operation). When operating as a DC-DC converter, the machine winding inductances of each strand of the non-rotating motor, along with the respective phase, act as a synchronized or interleaved two-phase or three-phase multilevel boost converter (DC-DC converter), with the winding inductance of the third motor strand providing additional amplification and filtering.

[0035] A new control scheme is integrated into the motor controller for operation of the multilevel inverter in DC-DC mode. The control system controls an ON / OFF state to control the flow of current in both directions through the non-rotating motor and the multilevel inverter. A charging port can be used to continuously charge one of the two battery packs, and the DC-DC converter mode can be used to simultaneously charge the first battery pack through a charging port and the second battery pack through the first battery pack using the DC-DC mode of the multilevel inverter motor system. In some examples, the switches in the multilevel inverter are insulated-gate bipolar transistors (IGBTs) with antiparallel diodes or Si / SiC / GaN field-effect transistors (FETs).In some examples, the new control system is entirely software-based and can be retrofitted to existing controls without requiring replacement or reconfiguration of parts.

[0036] The charge balancing or power transfer configuration can be used for single port or multi-port charging.

[0037] All phases (in the case of a four-pole motor) or selected phases (in the case of a three-pole motor) are modulated with a logical phase shift (e.g., 180 degrees for a four-pole motor or 120 degrees for a three-pole motor) from every other phase in use. The phase shift is achieved using pulse-width modulation (PWM) control of the internal switches.

[0038] The duty cycle and phase relationship between the internal switches (the transistors that make up the individual phase strings of the converter) are selected to achieve the boost or buck function of the DC-DC converter with current flow in the desired direction (e.g., from the first battery pack to the second battery pack) while avoiding a short circuit of the main bus. The PWM frequency, duty cycle, and phase shift between the switching converter strings are functions of the charging power and current ripple to be achieved during the charging process and can be determined by a specialist.

[0039] In an example with serially arranged battery packs, a multilevel flying capacitor inverter and the corresponding motor windings of the non-rotating motor are used to actively equalize the state of charge of two battery packs during or after serial charging.

[0040] The second battery pack is continuously charged until the difference between the charge levels of the two battery packs is less than a predefined threshold.

[0041] In an example of a four-pole machine, a switch is used to connect the center point of the battery and the star point of the four-pole winding machine. An example of a three-pole machine uses a switch to connect the center point of the battery packs and one phase pole of a three-pole machine.

[0042] In some examples, multiple multilevel converters can be used to share the power being transferred to another pack. Additionally, an N-level converter can be used to further reduce voltage and thermal stresses during DC-DC operation. The control scheme for this function includes continuous monitoring of the battery SOC and energy to control the charging current and command the deactivation of the contactors / breakers.

[0043] The high-voltage lines may include additional voltage and / or current sensors / pyro-fuses for diagnostics and safety of that high-voltage line. The main contactors assigned to each pack may also include a pre-charging device connected in parallel with a main contactor.

[0044] With further reference to the general system described above, Fig. 1 illustrates an embodiment of a motor vehicle 10. The vehicle 10 includes a vehicle body 12 that at least partially defines a passenger compartment 14. The vehicle body 12 also supports various subsystems of the vehicle, including a propulsion system 16, a battery system 22, and other subsystems for supporting functions of the propulsion system 16 and other vehicle components, such as a braking subsystem, a suspension system, a steering subsystem, a fuel injection subsystem, an exhaust subsystem, etc.

[0045] The vehicle 10 may be an internal combustion engine vehicle, an electric vehicle (EV), or a hybrid vehicle. In one embodiment, the vehicle 10 is a hybrid vehicle that includes an internal combustion engine system 18 and at least one electric motor assembly. The drive system 16 includes, for example, a first electric motor 20 and a second electric motor 21. The motors 20 and 21 may be configured to drive wheels (not shown) on opposite sides of the vehicle 10. Any number of motors positioned at various additional locations of the vehicle 10 may be used to provide power to the corresponding systems and subsystems.

[0046] The battery system 22 may be electrically connected to the motors 20 and 21 and / or other components, such as vehicle electronics. The battery system 22 may be configured as a rechargeable energy storage system (RESS) and includes multiple power cells divided into sections. A battery system controller 24 is included within the battery system 22 and controls the charging and discharging functions of the batteries within the battery system 22. In alternative configurations, the battery system controller 24 may be a general vehicle controller remote from the battery system 22 and configured to control multiple systems and / or subsystems. The general vehicle controller may be positioned anywhere within the vehicle 10.In further alternatives, the battery system controller 24 may be a distributed control system that includes multiple coordinating controllers throughout the vehicle 10, including controllers within the battery system 22 and controllers external to the battery system 22.

[0047] In one embodiment, the battery system 22 includes a plurality of battery packs 28. The battery packs 28 include a plurality of different battery cells arranged in parallel and connected to a power distribution bus 29 to provide power to one or more systems. In the exemplary system of Fig. 1, the power distribution bus 29 is illustrated in simplified form as a single line and provides power to the drive systems 16 via an inverter 32.

[0048] With further reference to Fig. 1 illustrates Fig. 2 is a general block diagram of the battery system 22, which includes a first battery pack 102 and a second battery pack 104. Fig. 3 and Fig. 4 illustrate specific examples of the general block diagram of Fig. 2. The first and second battery packs 102, 104 are connected in parallel and via a multilevel converter 110. In the Fig. In the examples illustrated in Figures 3-6, the flying capacitor multilevel converter 110 uses a flying capacitor multilevel converter topology and is referred to as a flying capacitor multilevel converter. The multilevel converter 110 is connected to each phase of a motor 20, 21 and provides AC power to the motor 20, 21 from a positive bus 130 during standard operation. In addition to the converter 110, a load 120 may be connected via a positive bus 130 and a neutral bus 132 and may receive power from the battery packs 102, 104. In some examples, such as the example in Fig. 2 and the specific example of Fig. 3, the motor 20, 21 has a star-phase configuration (alternatively referred to as a four-pole motor) with a reference node 103 connected to the positive bus 130 via a connection 134.

[0049] In other examples, such as the specific example of Fig. 4, the motor 20, 21 has a delta-string configuration (also referred to as a three-pole motor) with a floating star point (i.e., there is no internal connection of the motor string to a star point or reference voltage). The battery system 22 can be connected to a charger 140, such as a wall charger, and the charger 140 allows power to be provided to the battery system 22 to charge the battery packs 102, 104.

[0050] The battery system 22 includes mixed-chemistry battery packs 102, 104, which may include a mixture of fuel cells and lithium (Li)-ion packs. Each battery pack 102, 104 comprises a single chemical composition, and the chemical composition of each battery pack 102, 104 differs from the chemical composition of the other battery pack 102, 104. The mixed chemistries provide different power characteristics for battery packs 102, 104, with some battery packs 102, 104 having a faster charging rate and lower power density, and other battery packs 102, 104 having a slower charging rate and higher power density.Due to the different charging speeds and power densities, passive balancing by placing the batteries in parallel with a filter choke, as is common in standard battery systems, cannot properly redistribute the current from one battery pack to the other.

[0051] To properly balance the battery packs 102, 104 during the charging process and / or immediately after the charging process is completed, the battery system 22 includes a battery system controller 150. In some examples, the battery system controller 24 may be Fig. 1 may assume the functions of the battery system controller 150; in other embodiments, the functions are performed by a dedicated controller 150 distributed across multiple vehicle controllers, or by a similar control scheme. It should be understood that reference herein to the controller 150 encompasses a variety of controller types and configurations and is not limited to the specific battery system controller 150 illustrated.

[0052] During or immediately after charging, the battery packs 102, 104 may be unbalanced, or one battery pack may charge faster than the other. In this case, it is desirable to transfer power from one battery pack 102, 104 to the other battery pack 102, 104. Because the method described herein uses the motor 20, 21 in a non-rotating function, it may not be suitable for use during vehicle operation, depending on the function of the motor. Because the battery packs 102, 104 are different chemistries with different power densities and charging characteristics, a DC-DC converter is required to transfer power from one battery pack 102, 104 to the other battery pack 102, 104.The controller 150 is configured to use switches that connect the charger 140 to the battery packs 102, 104 and operate the inverter 110 in a DC-DC converter mode that utilizes the self-inductance of the motor strands in the motor 132 to transfer power from one battery pack 102, 104 to the other battery pack 102, 104 without generating rotational motion within the motor.

[0053] By modulating the switching action of each phase of the multilevel inverter used for DC-DC conversion so that the switching action in the phase is offset by 180 degrees from the other two phases in a three-pole motor, or offset by 120 degrees from any other phase used as a DC-DC converter in a three-pole motor, current is passed through each motor phase used for DC-DC conversion. This allows the inductance of each motor phase to act as a DC-DC converter inductance for the corresponding converter phase of inverter 110. The modulation of the switches in each converter phase of inverter 110 to achieve DC-DC converter operation is performed according to known techniques.

[0054] With further reference to Fig. 2 illustrates Fig. 3 a more detailed exemplary implementation of the power system of Fig. 2, wherein the motor 20, 21 is arranged in an X-circuit configuration. Each strand of the motor 20, 21 is illustrated as an inductor representing the internal inductance of the respective motor strand 302, 304, 306 of the motor 20, 21. The charger 140 is connected to the first battery pack 102 via a first pair of switches 310, 312 and to the second battery pack 104 via a second pair of switches 314, 316. One switch 310, 314 in each switch pair connects the positive terminal of the charger 140 to the corresponding battery pack 102, 104, and a second switch 312, 316 connects the negative terminal of the charger 140 to the corresponding battery pack 102, 104.

[0055] Additionally, the first battery pack 102 is connected to the positive bus 130 via a switch 320 and to the negative bus 132 via a switch 322. The second battery pack 104 is connected to the positive bus 130 via switches 314 and 310, and a switch 326 connects the positive side of the second battery pack 104 to a motor star point 133 via connection 103. The negative side of the second battery pack 104 is connected to the negative bus 132 via a switch 324.

[0056] The converter 110 is arranged in a multilevel flying capacitor converter topology comprising three converter strings 330, 340, 350. Each converter string 330, 340, 350 has a first transistor X1, X5, X9 connecting the positive bus 130 to a high node HB1, HB3, HB5, a second transistor X2, X6, X10 connecting the high node HB1, HB3, HB5 to an AC output node 332, 342, 352, a third transistor X3, X7, X11 connecting the AC output node 332, 342, 352 to a low node HB2, HB4, HB6, and a fourth transistor X4, X8, X12 connecting the low node HB2, HB4, HB6 to the negative bus 132. A capacitor 301, 303, 305 connects the high node HB1, HB3, HB5 with the low node HB2, HB4, HB6 in each motor phase 302, 304, 306.

[0057] The AC output node 332, 342, 352 of each string 330, 340, 350 is connected to a corresponding motor string 302, 304, 306 of the motor 20, 21. In standard operation, the controller 150 modulates the transistors X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12 in each inverter string 330, 340, 350 of the inverter 110 to drive the motor 20, 21 using the battery pack 102, 104 connected to the positive bus 130 and the negative bus 132.

[0058] During or shortly thereafter during the charging process, it is desirable to equalize the current between battery packs 102 and 104 or to transfer current from one of the battery packs 102 to the other battery pack 104. For example, if a first battery pack has a low power density but a high charging rate, it may be advantageous to transfer the accumulated current from the faster-charging battery pack 102 to the slower-charging battery pack 104 to speed up the overall charging process.

[0059] Balancing and current transfer are achieved by modulating transistors X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12 in inverter 110, so that inverter 110 operates as a DC-DC converter, using the internal inductors of motor train 302, 304, 306 as corresponding DC-DC converter inductors. In this mode, each of the switches 310, 312, 314, 316 connecting battery packs 102, 104 to charger 140 is open, and the switches 320, 322, 324, 326 connecting both battery packs to positive bus 130 and negative bus 132 are closed. Each inverter string 330, 340, 350 is modulated with a phase shift of 120 degrees from every other inverter string 330, 340, 350 so that the current flows through the motor 20, 21 with a net torque generation of zero and the inductances of the motor strings can be utilized.In this configuration, energy circulates through the motor trains 302, 304, 306 and the corresponding inverter trains 330, 340, 350, which convert the direct current into a voltage and current that can be accepted by the receiving battery pack 102, 104. The current with the new characteristics is provided to the power bus 130, 132, allowing power to be transferred from one battery pack 102, 104 to the other battery pack 102, 104.

[0060] Additionally, since each battery pack 102, 104 is connected via switches to both power buses 130, 132 and charger 140, controller 150 can isolate or remove an individual battery pack 102, 104 while one of the battery packs 102, 104 is in a fault condition. To isolate the faulty battery pack 102, 104, the corresponding switches 320, 322, 326, 328 connecting that battery pack 102, 104 to buses 130, 132 are held open, thereby electrically isolating the battery pack 102, 104.

[0061] In some examples, additional switches can be integrated into the system of Fig. 3 so that one or more of the inverter's phase-phase capacitors can be used as a DC-DC input.

[0062] Fig. Figure 7 illustrates such an example with closed switches 310, 314, 320 and closed switches 312, 316, 322. Since the switches 310, 312, 314, 316, 320, 322 are closed and the current flows unhindered, they are omitted from the illustration for reasons of clarity. In the example of Fig. 7, a switch 301 is added that connects the node HB1 connecting the first transistor X1 and the second transistor X2 of the first inverter string 330 to a positive pole 303 of the first battery pack 102, the second battery pack 104 and the charger 140.

[0063] In addition, a second switch 305 is added, which connects the node HB3 of the second inverter string 340 to the positive pole 303 of the first battery pack 102, the second battery pack 104 and the charger 140.

[0064] The addition of switches 301, 305 enables the use of the converter string capacitors 311, 313 as input DC capacitors for the DC-DC converter operation of the converter 110. When a single switch 301, 305 is closed, the corresponding capacitor 311, 313 operates as the input DC capacitor. When both switches 301, 305 are closed, the combined capacitance of 311 and 313 is used as the input DC capacitor. In systems that use only one capacitor 311, 313, one of the switches 301, 305 can be omitted entirely, reducing circuit cost and complexity. The converter string capacitor 315 of the third converter string 350 is bypassed and does not affect the circuit.

[0065] With reference to Fig. 4, when the motor 20, 21 is configured in a delta circuit configuration, there is no star point within the motor 20, 21 to which the switch 326 can be connected. This configuration is in Fig. 4, wherein like reference numerals with Fig. 2 and Fig. 3 identical elements and configurations. Structurally, the example differs from Fig. 4 of the Fig. 3, except that switch 326 connects to AC output node 352 of string 350 of converter 110. Furthermore, for the sake of clarity, certain reference numerals of Fig. 4-7 are omitted. The absence of reference numerals does not indicate any structural difference between the embodiments of the converter strings 302, 304, 306, 530, 540, 550. During operation in DC-DC converter mode, the current is passed through the motor string 306 corresponding to the off-state AC converter string 350, resulting in the current being passed through the motor string 306 and each other string 330, 340 while they are modulated to produce DC current with the corresponding current characteristic. In this mode, the current from the second battery pack 104 is passed through the switch 326 and flows through the third inductor 306 strand of the motor 20, 21 into each of the other inductor 302, 304 strands 302, 304 of the motor 20, 21. The energy is passed through the strands 330, 340 and provided to the first battery pack 102.

[0066] In the example of the Delta engines ( Fig. 4 and Fig. 6) It may be advantageous to ensure that the converter string that is not operated during DC-DC converter operation is the converter string 330, 340, 350, 530, 540, 550 that is physically closest to the serially arranged battery packs 102, 104. In some configurations, this converter string 330, 340, 350, 530, 540, 550 is located between the serially arranged battery packs 102, 104 and the other converter strings 330, 340, 350, 530, 540, 550. Utilizing the converter string 330, 340, 350, 530, 540, 550 that is physically closest to the battery packs 102, 104 provides thermal isolation between the battery packs 102, 104 and the operating converter strings 330, 340, 350, 530, 540, 550, thus minimizing the risk of excessive heating.

[0067] With reference now to Fig. 5 and Fig. 6, in some cases, the battery packs 102, 104 with different chemistry may be arranged in series between a positive bus 130 and a negative bus 132. Such examples are shown in Fig. 5 and Fig. 6, where Fig. 5 represents a connected Y-motor 20, 21, and Fig. 6 shows a connected delta motor 20, 21. The Fig. 5 and Fig. The converter lines 530, 540, 550 illustrated in Figure 6 are arranged identically to those shown in Fig. 3 and Fig. 4 illustrated.

[0068] With reference to Fig. 5, the two sets of battery packs 102, 104 are specifically connected in series via a positive bus 130 and a negative bus 132, with a positive terminal of the second battery pack 104 connected to a negative terminal of the first battery pack 102 at a battery pack node 592. Node 592 of the battery pack is connected to a star node 133 of the motor 20, 21 via a switch 594. While the inverter strings 530, 540, 550 are operating in DC-DC converter mode, the switch 594 is closed, creating a current circulation path between the battery packs 102, 104, with each motor string 502, 504, 506 providing the internal motor string inductance and the switches of the corresponding inverter string 530, 540, 550 being modulated 120 degrees apart from each other inverter string 530, 540, 550.The current circulation between the battery packs 102, 104 in this mode equalizes the charge in each battery pack 102, 104, and the mode can be used during or after serial charging of the battery packs 102, 104.

[0069] With further reference to Fig. 1-5 illustrates Fig. 6 schematically illustrates the series-connected battery packs 102, 104 with a motor 20, 21 having a delta circuit configuration instead of the Y-circuit configuration illustrated in FIG. 5. In the delta circuit configuration, the battery pack node 592 is connected to the motor string 502 when the switch 594 is closed. While the switches in each inverter string 530, 540, 550 operate as a DC-DC converter, the switch 594 creates a current circulation path from the second battery 104 through the first motor string 502 and into each of the second and third motor strings 504, 506, then back into the first battery pack 102. Each of the second and third motor strings 504, 506 is modulated with a phase shift that is 180 degrees offset from the other string 504, 506 to ensure that the motor 20, 21 does not rotate.While the switch 594 is closed (permits current), the charge level between the two battery packs 102, 104 equalizes.

[0070] In each of the above examples, which are in Fig. 3-6, batteries 102, 104 having different chemistries are illustrated as individual batteries. It should be understood that each individual battery pack 102, 104 may be replaced with a set of serially arranged sub-battery packs, provided each serially arranged sub-battery pack comprises an identical chemistry to every other serially arranged sub-battery pack in the battery pack 102, 104. In some cases, the sub-batteries may each have an identical storage capacity. In other examples, the sub-battery packs may have different storage capacities. In any configuration, the total capacity of the battery pack 102, 104 is the sum of the capacities of each sub-battery pack of the battery pack.

[0071] In each of the examples of Fig. 2-6, the operation of the inverter 110 as a DC-DC converter is described in general. It is understood that practical operation will vary slightly depending on whether the motor 20, 21 is operated in a delta ( Fig. 3 and Fig. 5) or a Y configuration ( Fig. 4 and Fig. 6) is switched on.

[0072] With reference to the examples in Fig. 3 and Fig. 5 (Y-motors 20, 21, also referred to as four-pole motors 20, 21), controlling the multilevel converter 110 as a DC-DC converter for each converter string 330, 530, 340, 540, 350, 550 comprises: providing a first control signal for the first transistor X1, X5, X9 and the fourth transistor X4, X8, X12 of each converter string 330, 530, 340, 540, 350, 550, wherein the first control signal is converted for the fourth transistor X4, X8, X12. Providing a second control signal for the second transistor X2, X6, X10 and the third transistor X3, X7, X11 of each converter string 330, 530, 340, 540, 350, 550, wherein the second control signal is converted for the third transistor X3, X7, X11. The first control signals and the second control signals control an open / closed state of the first, second, third, and fourth transistors X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12 of the corresponding converter string 330, 530, 340, 540, 350, 550 via pulse width modulation.The first control signal and the second control signal are 120 degrees out of phase with each other first control signal and second control signal.

[0073] Referring to the examples of Fig. 4 and Fig.6 (delta motors 20, 21, alternatively referred to as three-pole motors 20, 21), which control the multilevel converter 110 as a DC-DC converter for each of a first converter string 330, 530 and a second converter string 340, 540 and provide a first control signal for the first and fourth transistors X1, X4, X5, X8 of the corresponding converter string 330, 340, 530, 540. The first control signal is converted for the fourth transistor X4, X8. Provide a second control signal for the second and third transistors X2, X3, X6, X7 of the corresponding converter string 330, 340, 530, 540. The second control signal is converted for the third transistor X3, X7. The first control signals and the second control signals control an open / closed state of the first, second, third and fourth transistors X1, X2, X3, X4, X5, X6, X7, X8 of the corresponding converter strings 330, 340, 530, 540 via pulse width modulation.The first control signal and the second control signal are 180 degrees out of phase with the other of the first control signal and the second control signal. Providing a third control signal for the first, second, third, and fourth transistors X9, X10, X11, X12 of the third converter string 350, 550, wherein the third control signal sets the first, second, third, and fourth transistors X9, X10, X11, X12 of the third converter string 350, 550 to off for the duration of controlling the multilevel converter 110 as a DC-DC converter.

[0074] The terms "a / an / an" do not imply a quantity limitation, but denote the presence of at least one of the mentioned items. The term "or" means "and / or" unless the context clearly indicates otherwise. References to "an aspect" throughout this specification mean that a particular element (e.g., a feature, structure, step, or property) described in connection with the aspect is included in at least one of the aspects described herein and may or may not be present in other aspects. In addition, it is understood that the described elements in the various aspects may be combined in any suitable manner.

[0075] When an element such as a layer, film, region, or substrate is described as lying "on" another element, it may lie directly on top of the other element, or there may be intervening elements. In contrast, when an element is described as lying "directly on" another element, there are no intervening elements.

[0076] Unless otherwise stated herein, all examination standards are the most recent standard in effect on the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0077] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0078] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalent elements may be substituted without departing from the scope thereof. Furthermore, many changes may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, the present disclosure is not intended to be limited to the particular embodiments disclosed, but is intended to include all embodiments falling within its scope.

Claims

[1] Vehicle system (10) comprising; a first battery pack (102) connected to a second battery pack (104) via a flying capacitor multilevel converter (110) having a plurality of converter strings (330, 340, 350, 530, 540, 550), each converter string (330, 340, 350, 530, 540, 550) arranged in a flying capacitor topology; a motor (20, 21) connected to the flying capacitor multilevel converter (110), the motor (20, 21) having three phases; and a controller (150) connected to the motor (20, 21) and the flying capacitor multilevel converter (110), the controller (150) comprising a memory that stores instructions configured to cause the controller (150) to control the flying capacitor multilevel converter (110) as a direct current (DC)-DC converter such that a circulating current is passed through the motor (20, 21), the first battery pack (102), and the second battery pack (104). [2] The vehicle system (10) of claim 1, wherein each inverter string (330, 340, 350, 530, 540, 550) of the flying capacitor multilevel inverter (110) comprises a first transistor (X1, X5, X9) connecting a positive bus (130) to a high node (HB1, HB3, HB5), a second transistor (X2, X6, X10) connecting the high node (HB1, HB3, HB5) to an alternating current (AC) output node (332, 342, 352), a third transistor (X3, X7, X11) connecting the AC output node (332, 342, 352) to a low node (HB2, HB4, HB6), and a fourth transistor (X4, X8, X12) connecting the low node (HB2, HB4, HB6) to a negative bus (132); and wherein each phase of the motor (20, 21) is connected to an AC output node (332, 342, 352) of a corresponding converter train (330, 340, 350, 530, 540, 550) of the flying capacitor multilevel converter (110). [3] Vehicle system (10) according to claim 2, wherein the motor is a four-pole motor, and wherein the controller (150) of the flying capacitor multilevel converter (110) as a DC-DC converter comprises: for each converter string (330, 340, 350, 530, 540, 550) providing a first control signal for the first transistor (X1, X5, X9) and the fourth transistor (X4, X8, X12), wherein the first control signal is converted for the fourth transistor (X4, X8, X12); Providing a second control signal for the second transistor (X2, X6, X10) and the third transistor (X3, X7, X11) of each converter string (330, 340, 350, 530, 540, 550), wherein the second control signal is converted for the third transistor (X3, X7, X11), wherein the first control signals and the second control signals control an open / closed state of the first, second, third and fourth transistors (X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12) of the corresponding converter string (330, 340, 350, 530, 540, 550) via pulse width modulation (PWM); and wherein each first control signal is 120 degrees out of phase with each other first control signal, and each second control signal is 120 degrees out of phase with each other second control signal and second control signal. [4] Vehicle system (10) according to claim 2, wherein the motor (20, 21) is a three-pole motor, and wherein the control of the flying capacitor multilevel converter (110) as a DC-DC converter comprises: for each of a first converter string (330, 530) and a second converter string (340, 540), providing a first control signal for the first and fourth transistors (X1, X4, X5, X9) of the corresponding converter string (330, 530, 340, 540), the first control signal being inverted for the fourth transistor; Providing a second control signal for the second and third transistors (X2, X3, X6, X7) of the corresponding converter string (330, 530, 340, 540), wherein the second control signal is converted for the third transistor (X3, X7); wherein the first control signals and the second control signals control an open / closed state of the first, second, third and fourth transistors (X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12) of the corresponding converter string (330, 530, 340, 540) via pulse width modulation; wherein each first control signal is 180 degrees out of phase with the other first control signal, and each second control signal is 180 degrees out of phase with the other second control signal; and Providing a third control signal for the first, second, third and fourth transistors (X9, X10, X11, X12) of the third converter string (350, 550), wherein the third control signal sets the first, second, third and fourth transistors (X9, X10, X11, X12) of the third converter string (350, 550) to off for the duration of the control of the multilevel converter as a DC-DC converter. [5] The vehicle system (10) of claim 1, wherein the first battery pack (102) and the second battery pack (104) are connected in parallel at one or both of a negative battery terminal and a positive battery terminal. [6] The vehicle system (10) of claim 1, wherein the first battery pack (102) and the second battery pack (104) are connected in series via a common node (592), forming a series-connected battery pack (102, 104). [7] The vehicle system (10) of claim 6, wherein a neutral node connects each phase of the motor (20, 21) to the common node (592). [8] The vehicle system (10) of claim 6, wherein a first phase terminal of the motor (20, 21) is connected to the common node (592) of the series-connected battery pack (102, 104). [9] The vehicle system (10) of claim 8, wherein a first inverter string (330, 530) is physically located closer to the first battery pack (102) and closer to the second battery pack (104) than each of a second inverter string (340, 540) and a third inverter string (350, 550). [10] The vehicle system (10) of claim 1, wherein the first battery pack (102) comprises at least a first set of power cells and a second set of power cells connected to the first set of power cells at the low node (HB2, HB4, HB6).

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