Hybrid chemical battery power transfer using multi-stage fast capacitor inverter

Abstract

A vehicle system includes a first battery pack connected to a second battery pack through a fast capacitor multi-stage inverter. The fast capacitor inverter has a plurality of inverter branches, each of which is arranged in a fast capacitor topology. The three-phase motor is connected to the inverter. A controller is connected to the motor and the inverter. The controller includes a memory storing instructions configured to cause the controller to control the inverter as a direct current (DC)-DC converter such that current flows through the motor, the first battery pack, and the second battery pack.

Description

Technical Field

[0001] The subject disclosure relates to balancing and transferring power between mixed chemistry battery packs using a multi-level inverter operating as a direct current (DC)-DC converter. Background Art

[0002] Vehicles, including electric and hybrid electric vehicles, feature battery storage systems for purposes such as powering electric motors, electronic devices, and other vehicle subsystems. Batteries used in battery storage systems typically include multiple different power cells, each of which stores power for later distribution. The power cells are electrically connected to provide output power to a distribution bus as needed. During or shortly after charging of a battery storage system, it is desirable to ensure that power is properly distributed among the battery packs to ensure its optimal operation. Existing systems use the same battery cell type (called a battery chemistry) within a battery pack. Passive power balancing techniques can be used to balance identical battery cells.

[0003] Different types of battery packs have different properties, such as charging rate and power density. In some configurations, it is advantageous to use different types of battery packs within a single battery system, allowing different vehicle operating modes to take advantage of different battery characteristics. However, using different battery pack types within a single battery makes power transfer and power balancing between battery packs difficult, and existing passive balancing systems cannot effectively transfer power between battery packs of different chemistries.

[0004] Therefore, it is desirable to provide an active power balancing system for a vehicle battery system that includes multiple different types of battery packs. Summary of the invention

[0005] In an exemplary embodiment, a vehicle system includes a first battery pack connected to a second battery pack via a flying capacitor multi-level inverter having a plurality of inverter branches, each inverter branch arranged in a flying capacitor topology. A motor is connected to the flying capacitor multi-level inverter. A controller is connected to the motor and the flying capacitor multi-level inverter, the controller including a memory storing instructions configured to cause the controller to control the flying capacitor multi-level inverter as a direct current (DC)-DC converter so that a current flows through the motor, the first battery pack, and the second battery pack.

[0006] In addition to one or more features described herein, each inverter branch of the flying capacitor multilevel inverter includes a first transistor connecting the 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 the negative bus, and wherein each phase of the motor is connected to the AC output node of a corresponding branch of the flying capacitor multilevel inverter.

[0007] In addition to one or more features described herein, the motor is a four-terminal motor. Controlling the fast capacitor multi-level inverter as a DC-DC converter includes, for each inverter branch: providing a first control signal to a first transistor and a fourth transistor of each inverter branch, wherein the first control signal is inverted for the fourth transistor. Providing a second control signal to a second transistor and a third transistor of each inverter branch, wherein the second control signal is inverted for the third transistor. The first control signal and the second control signal control the on / off state of the first, second, third and fourth transistors of the corresponding inverter branch by pulse width modulation. Each first control signal and the second control signal are phase-shifted by 120 degrees relative to each other first control signal and the second control signal.

[0008] In addition to one or more features described herein, the motor is a three-terminal motor. For each of the first inverter branch and the second inverter branch, controlling the fast capacitor multi-level inverter as a DC-DC converter includes: providing a first control signal to the first and fourth transistors of the corresponding inverter branch, 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 branch, wherein the second control signal is inverted for the third transistor. The first control signal and the second control signal control the on / off state of the first, second, third and fourth transistors of the corresponding inverter branch by pulse width modulation. Each of the first control signal and the second control signal is phase-shifted 180 degrees from the other of the first control signal and the second control signal. Providing a third control signal to the first, second, third and fourth transistors of the third inverter branch, the third control signal sets the first, second, third and fourth transistors of the third inverter branch to be cut off for a duration of controlling the multi-level inverter as a DC-DC converter.

[0009] In addition to one or more features described herein, the first battery pack and the second battery pack are connected in parallel at one or both of the negative battery terminal and the positive battery terminal.

[0010] In addition to one or more features described herein, the first battery pack and the second battery pack are connected in series through a common node to form a series battery pack.

[0011] In addition to one or more features described herein, a neutral node connects each phase of the motor to a common node.

[0012] In addition to one or more features described herein, a first phase terminal of the motor is connected to a common node of the series connected battery pack.

[0013] In addition to one or more features described herein, the first inverter leg is physically disposed closer to the first battery group and the second battery group than each of the second inverter leg and the third inverter leg.

[0014] In addition to one or more features described herein, the first battery pack includes at least a first group of power cells and a second group of power cells connected to the first group of power cells at a return node.

[0015] 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 fast capacitor multilevel inverter as a direct current (DC)-DC converter so that a current flows through the fast capacitor multilevel inverter, an electric motor, a first battery pack, and a second battery pack. The vehicle system includes a first battery pack connected to the second battery pack via the fast capacitor multilevel inverter, a motor connected to the fast capacitor multilevel inverter, and a motor controller connected to the motor and the fast capacitor multilevel inverter. The motor controller includes a memory storing instructions configured to cause the vehicle system to implement the method.

[0016] In addition to one or more features described herein, the multi-level inverter includes three inverter branches. Each inverter branch of the multi-level inverter includes a first transistor connecting the 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 the negative bus, and each phase of the motor is connected to the AC output node of the corresponding inverter branch.

[0017] In addition to one or more features described herein, the motor is a four-terminal motor. Controlling the fast capacitor multi-level inverter as a DC-DC converter includes, for each inverter branch: providing a first control signal to a first transistor and a fourth transistor of each inverter branch, the first control signal being inverted for the fourth transistor. Providing a second control signal to a second transistor and a third transistor of each inverter branch, the second control signal being inverted for the third transistor. The first control signal and the second control signal control the on / off state of the first, second, third and fourth transistors of the corresponding inverter branch by pulse width modulation. The first control signal and the second control signal are phase-shifted by 120 degrees relative to each other first control signal and second control signal.

[0018] In addition to one or more features described herein, the motor is a three-terminal motor. For each of the first inverter branch and the second inverter branch, controlling the multi-level inverter as a DC-DC converter includes: providing a first control signal to the first and fourth transistors of the corresponding inverter branch, wherein the first control signal is inverted for the fourth transistor. A second control signal is provided to the second and third transistors of the corresponding inverter branch, wherein the second control signal is inverted for the third transistor. The first control signal and the second control signal control the on / off state of the first, second, third and fourth transistors of the corresponding inverter branch by pulse width modulation. The first control signal and the second control signal are phase-shifted 180 degrees relative to the other of the first control signal and the second control signal. A third control signal is provided to the first, second, third and fourth transistors of the third inverter branch, and the third control signal sets the first, second, third and fourth transistors of the third inverter branch to be cut off for a duration of controlling the multi-level inverter as a DC-DC converter.

[0019] In addition to one or more features described herein, the first battery pack and the second battery pack are connected in parallel at at least one of the negative battery terminal and the positive battery terminal.

[0020] In addition to one or more features described herein, the first battery pack and the second battery pack are connected in series via a common node to form a series battery pack.

[0021] In addition to one or more features described herein, the first battery is of a first chemistry and the second battery is of a second chemistry different from the first chemistry.

[0022] In yet another exemplary embodiment, a vehicle includes: an electric drive 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 drive system via a fast capacitor multi-level inverter; and a controller connected to the motor and the fast capacitor multi-level inverter, the controller including a memory storing instructions, the instructions being configured to cause the controller to control the fast capacitor multi-level inverter as a direct current (DC)-DC converter so that current flows through the motor, the first battery pack, and the second battery pack.

[0023] In addition to one or more features described herein, a flying capacitor multilevel inverter includes three inverter branches, each inverter branch of the flying capacitor multilevel inverter including a first transistor connecting the 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 the negative bus, wherein each phase of the motor is connected to a corresponding inverter branch of the flying capacitor multilevel inverter.

[0024] The above features and advantages and other features and advantages of the present disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, advantages and details appear, by way of example only, in the following detailed description, which refers to the accompanying drawings, in which:

[0026] Figure 1 is a schematic diagram of a vehicle including a power distribution system;

[0027] Figure 2 is a block diagram of a battery system according to an embodiment;

[0028] Figure 3 is a circuit diagram representation of a power transmission method applied to parallel arranged battery packs according to a first example;

[0029] Figure 4 is a circuit diagram representation of a power transmission method applied to parallel arranged battery packs according to a second example;

[0030] Figure 5 is a circuit diagram of a power transmission method applied to a battery pack arranged in series according to a first example;

[0031] Figure 6 is a circuit diagram of a power transmission method applied to a battery pack arranged in series according to a second example; and

[0032] Figure 7 An alternative switching configuration for enhancing the operation of a direct current (DC-DC) converter in a three-terminal electric machine is shown. DETAILED DESCRIPTION

[0033] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses.

[0034] It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding components 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 (shared, dedicated or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the functionality described.

[0035] According to an exemplary embodiment, a vehicle system for a battery includes a plurality of battery packs having different battery pack chemistries. A multi-level inverter converts direct current (DC) power from the battery pack into an alternating current (AC) power form, which is provided to a motor and drives the motor to rotate. The characteristics of the motor rotation are controlled by the characteristics of the AC power signal. A motor controller actively controls switches within the multi-level inverter to control the characteristics of the AC power signal.

[0036] The memory is configured to enable the motor controller to achieve power balancing or power transfer operation between different battery packs by operating the multi-level inverter as a DC-DC converter and utilizing the internal inductance of the motor branch without rotating the motor for the DC-DC converter inductance. When the AC inverter is operated as a DC-DC converter, by controlling the phase shift in the AC inverter modulation, the internal inductance of the motor branch can be utilized without causing rotation, so that the rotational force generated by the current through the branch is directly offset by the rotational force generated by the current through other branches of the motor. The DC-DC converter is then able to transfer power between the battery packs according to a known power transfer procedure. In some examples, by disconnecting the branch experiencing a fault condition from the corresponding power bus, the switch incorporated to facilitate operation in the DC-DC converter mode can be further used to provide fault protection and / or isolation of one or more branches during a fault condition.

[0037] Figure 2-7 The system shows an apparatus and method for providing bidirectional power transfer between hybrid chemical battery packs 102, 104 (e.g., a mix of energy and power packs / modules, fuel cells, and Li-ion packs) using a multi-level flying capacitor inverter drive system as a DC-DC converter (using a non-rotating motor and a multi-level inverter during steady drive, or using any non-rotating motor and a multi-level inverter during stationary conditions). When operating as a DC-DC converter, the motor winding inductance of each branch of the non-rotating motor together with the corresponding phase acts as a synchronous or interleaved two-phase or three-phase multi-level boost converter (DC-DC converter), and the winding inductance of the third motor branch provides additional boost and filtering.

[0038] A new control scheme is incorporated into a motor controller for operating a multi-level inverter in DC-DC mode. The control scheme controls on / off conditions to control power flow in either direction through a non-rotating motor and a multi-level inverter. A charging port can be used to continuously charge either battery pack, and a DC-DC converter mode can be used to simultaneously charge a first battery pack from a charging port and a second battery pack from the first battery pack using a DC-DC mode of a multi-level inverter motor system. In some examples, the switches in the multi-level inverter are insulated gate bipolar transistors (IGBTs) or Si / SiC / GaN field effect transistors (FETs) with anti-parallel diodes. In some examples, the new control scheme is entirely software-based and can be retroactively added to existing controllers and applied to existing motor vehicles without the need to replace or reconfigure components.

[0039] Charge balancing or power delivery configurations are available for single-port or multi-port charging events.

[0040] All phases (in the case of a four-terminal motor) or selected phases (in the case of a three-terminal motor) are modulated using logic with a predetermined phase shift (e.g. 180 degrees for a four-terminal motor, or 120 degrees for a three-terminal motor) from every other used phase. The phase shift is achieved by pulse width modulation (PWM) control of the internal switches.

[0041] The duty cycle and phase relationship between the internal switches (the transistors that make up each phase leg of the inverter) are selected to achieve the step-up or step-down function of the DC-DC converter, with power flowing in the desired direction (e.g., from the first battery pack to the second battery pack) while avoiding a main bus short. The PWM frequency, duty cycle, and phase shift between the switching inverter legs are a function of the charging power and current ripple to be achieved during the charging operation, and can be determined by one skilled in the art.

[0042] In the example of battery packs arranged in series, a multi-level flying capacitor inverter and corresponding motor windings of a non-rotating motor are used to actively balance the state of charge of the two battery packs during or after series charging.

[0043] The second battery pack is continuously charged until the difference in the state of charge of the two battery packs is less than a predetermined threshold.

[0044] The four-terminal motor example uses a switch to connect the midpoint of the battery pack to the neutral point of the four-terminal winding motor. The three-terminal motor example uses a switch to connect the midpoint of the battery pack to one of the branch terminals of the three-terminal motor.

[0045] In some examples, multiple multi-level inverter units can be used to share the power delivered to another battery pack. In addition, N-level inverters can be used to further reduce voltage and thermal stress in DC-DC operation. The control scheme for this function includes continuous battery SOC and energy monitoring for shutting off charging current and commanding contactor / switch closure.

[0046] The high voltage line may have additional voltage and / or current sensors / pyro fuses for diagnostics and safety of the high voltage line. The main contactor associated with each battery pack may also include a pre-charge device in parallel with one main contactor.

[0047] Continuing with the general system referenced above, Figure 1 An embodiment of a motor vehicle 10 is shown. The vehicle 10 includes a body 12 that at least partially defines an occupant compartment 14. The body 12 also supports various vehicle subsystems, including a propulsion system 16, a battery system 22, and other subsystems to support the 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.

[0048] 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. For example, the propulsion system 16 includes 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 located in various additional locations around the vehicle 10 may be used to provide power to the respective systems and subsystems.

[0049] The battery system 22 can be electrically connected to the motors 20 and 21 and / or other components, such as vehicle electronics. The battery system 22 can be configured as a rechargeable energy storage system (RESS) and include a plurality of power cells divided into a plurality of sections. The battery system controller 24 is included in the battery system 22 and controls the charging and discharging functions of the batteries in the battery system 22. In an alternative configuration, the battery system controller 24 can be a universal vehicle controller away from the battery system 22 and configured to control a plurality of systems and / or subsystems. The universal vehicle controller can be located anywhere within the vehicle 10. In yet another alternative, the battery system controller 24 can be a distributed control system including a plurality of coordinated controllers throughout the vehicle 10, including a controller within the battery system 22 and a controller away from the battery system 22.

[0050] In one embodiment, the battery system 22 includes a plurality of battery packs 28. The battery packs 28 include a plurality of different battery power units arranged in parallel and connected to a power distribution bus 29 for providing power to one or more systems. Figure 1 In the exemplary system of FIG. 8 , power distribution bus 29 is shown in simplified form as a single line and provides power to propulsion system 16 through inverter 32 .

[0051] Continue to refer Figure 1 , Figure 2 A general block diagram of the battery system 22 including a first battery pack 102 and a second battery pack 104 is shown. Figure 3 and Figure 4 Shows Figure 2 The first and second battery packs 102 and 104 are connected in parallel and connected through a multi-level inverter 110. Figure 3-6 In the example shown, the multilevel inverter 110 uses a flying capacitor multilevel inverter topology and is referred to as a flying capacitor multilevel inverter. The multilevel inverter 110 is connected to each branch of the motors 20, 21 and provides operating AC power to the motors 20, 21 from the positive bus 130 during standard operation. In addition to the inverter 110, a load 120 can be connected across the positive bus 130 and the neutral bus 132 and receive power from the battery packs 102, 104. In some examples, for example Figure 2The examples shown and Figure 3 In the specific example, the motors 20, 21 have a star branch configuration (or a four-terminal motor), and the reference node 103 is connected to the positive bus 130 via the connection 134. In other examples, for example Figure 4 In a specific example, the motors 20, 21 have a delta-branch configuration (or three-terminal motors) with a floating neutral point (i.e., the motor branches have no internal connection to a neutral 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 for charging the battery packs 102, 104.

[0052] The battery system 22 includes mixed chemistry battery packs 102, 104, which may include a mix of fuel cells and lithium (Li) ion packs. Each battery pack 102, 104 includes a single chemistry, and the chemistry of each battery pack 102, 104 is different from the chemistry within the other battery pack 102, 104. The mixed chemistry provides different power characteristics for the battery packs 102, 104, some battery packs 102, 104 have faster charging rates and lower power density, while other battery packs 102, 104 have slower charging rates and higher power density. Due to the varying charging rates and power densities, passive balancing by connecting the battery packs in parallel with filtering inductors (as done in standard battery systems) cannot properly redistribute power from one battery pack to another.

[0053] In order to properly balance the battery packs 102, 104 during charging and / or immediately after charging is completed, the battery system 22 includes a battery system controller 150. In some examples, Figure 1 The battery system controller 24 may provide the functionality of the battery system controller 150, and in other embodiments, these functions are provided by a dedicated controller 150, distributed across multiple vehicle controllers, or any similar control scheme. It should be understood that the controller 150 referred to herein includes a variety of controller types and configurations and is not limited to the dedicated battery system controller 150 shown.

[0054] During charging, or after charging, the battery packs 102, 104 may be unbalanced, or one battery pack may charge faster than the other. When this occurs, it is desirable to transfer power from one battery pack 102, 104 to the other battery pack 102, 104. Since the process described herein utilizes a non-rotational capable motor 20, 21, 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 utilize a switch that connects the charger 140 to the battery packs 102, 104, operate the inverter 110 in a DC-DC converter mode, and utilize the inherent inductance of the motor branch 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.

[0055] Power is passed through each motor branch for DC-DC conversion by modulating the switches of each branch of the multi-level inverter for DC-DC conversion so that the switches in that branch are offset 180 degrees from the other two branches in a three-terminal motor, or 120 degrees from each other branch used as a DC-DC converter in a three-terminal motor. This allows the inductance of each motor branch to serve as the DC-DC converter inductor of the corresponding inverter branch of the inverter 110. The switches in each inverter branch of the inverter 110 are modulated to achieve DC-DC converter operation according to known techniques.

[0056] Continue to refer Figure 2 , Figure 3 Shows Figure 2 A more detailed example embodiment of a power system of FIG. 1 is shown in which the motors 20, 21 are arranged in a star configuration. Each branch of the motors 20, 21 is shown as an inductor representing the internal inductance of that motor branch 302, 304, 306 of the motors 20, 21. The charger 140 is connected to the first battery pack 102 through a first pair of switches 310, 312 and to the second battery pack 104 through a second pair of switches 314, 316. One switch 310, 314 in each pair of switches connects the positive terminal of the charger 140 to the corresponding battery pack 102, 104, and the second switch 312, 316 connects the negative terminal of the charger 140 to the corresponding battery pack 102, 104.

[0057] In addition, the first battery pack 102 is connected to the positive bus 130 through switch 320 and to the negative bus 132 through switch 322. The second battery pack 104 includes a connection to the positive bus 130 through switches 314 and 310, and switch 326 connects the positive side of the second battery pack 104 to the motor neutral point 133 through connection 103. The negative side of the second battery pack 104 is connected to the negative bus 132 through switch 324.

[0058] The inverter 110 is arranged in a multi-stage flying capacitor inverter topology including three inverter branches 330, 340, 350. Each inverter branch 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. Capacitors 301, 303, 305 connect the high node HB1, HB3, HB5 within each inverter branch 302, 304, 306 to a low node HB2, HB4, HB6.

[0059] The AC output node 332, 342, 352 of each branch 330, 340, 350 is connected to the corresponding motor branch 302, 304, 306 of the motor 20, 21. During standard operation, the controller 150 modulates the transistors X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12 within each inverter branch 330, 340, 350 of the inverter 110 to drive the motor 20, 21 using any one of the battery packs 102, 104 connected to the positive bus 130 and the negative bus 132.

[0060] During or shortly after charging, it may be desirable to balance power between the battery packs 102, 104 or to transfer power from one of the battery packs 102 to the other battery pack 104. For example, when the first battery pack has a low power density but a high charge rate, it may be beneficial to transfer the accumulated power from the faster charging battery pack 102 to the slower charging battery pack 104 to speed up the overall charging process.

[0061] Balancing and power transfer are achieved by modulating the transistors X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12 in the inverter 110, so that the inverter 110 operates as a DC-DC converter, using the internal inductance of the motor branches 302, 304, 306 as the corresponding DC-DC converter inductor. In this mode, each of the switches 310, 312, 314, 316 connecting the battery packs 102, 104 to the charger 140 is open, and the switches 320, 322, 324, 326 connecting the two battery packs to the positive bus 130 and the negative bus 132 are closed. Each inverter branch 330, 340, 350 is modulated to be 120 degrees phase-shifted relative to each other inverter branch 330, 340, 350, thereby allowing power to pass through the motor 20, 21, producing a net zero rotational force, and enabling the motor branch inductance to be utilized. When in this configuration, energy flows through the motor branch 302, 304, 306 and the corresponding inverter branch 330, 340, 350, which converts the DC power to a voltage and current level that can be accepted by the receiving battery pack 102, 104. The power with the new characteristics is provided to the power bus 130, 132, allowing power to be transferred from one battery pack 102, 104 to another battery pack 102, 104.

[0062] In addition, since each battery pack 102, 104 is connected to the power bus 130, 132 and the charger 140 through a switch, when one of the battery packs 102, 104 is in a fault condition, the controller 150 can isolate or remove a single battery pack 102, 104. In order to isolate the faulty battery pack 102, 104, the corresponding switch 320, 322, 326, 328 connecting the battery pack 102, 104 to the bus 130, 132 remains open, resulting in the battery packs 102, 104 being electrically isolated.

[0063] In some examples, additional switches may be incorporated Figure 3 in the system in order to allow one or more inverter phase leg capacitors to be used as the DC-DC input.

[0064] Figure 7 One such example is shown where switches 310, 314, 320 are closed and switches 312, 316, 322 are closed. Since switches 310, 312, 314, 316, 320, 322 are closed and current flow is not impeded, they are omitted from the illustration for clarity. Figure 7 In the example of FIG. 3 , a switch 301 is added to connect the node HB1 connecting the first transistor X1 and the second transistor X2 of the first inverter branch 330 to the positive terminal 303 of the first battery pack 102 , the second battery pack 104 and the charger 140 .

[0065] Furthermore, a second switch 305 is added to connect the node HB3 of the second inverter branch 340 to the first battery pack 102 , the second battery pack 104 and the positive terminal 303 of the charger 140 .

[0066] The addition of switches 301, 305 allows the inverter branch capacitors 311, 313 to be used as input DC capacitors for the DC-DC converter operation of the inverter 110. When a single switch 301, 305 is closed, the corresponding capacitor 311, 313 operates as an input DC capacitor. Closing both switches 301, 305 utilizes the combined capacitance of 311 and 313 as an input DC capacitor. In a system designed to utilize only one capacitor 311, 313, one of the switches 301, 305 can be completely omitted, thereby reducing the cost and complexity of the circuit. The inverter branch capacitor 315 of the third inverter branch 350 is bypassed and does not affect the circuit.

[0067] refer to Figure 4 When the motors 20, 21 are arranged in a delta configuration, there is no neutral point in the motors 20, 21 to which the switch 326 can be connected. Figure 4 As shown in Figure 2 and Figure 3 The same numbers represent the same components and configurations. Figure 4 The example is different from Figure 3 , only the switch 326 connects the AC output node 352 of the branch 350 of the inverter 110. In addition, for the sake of clarity, Figure 4-7 Certain numbers are omitted. The absence of reference numerals does not represent structural differences between the embodiments of the inverter branches 302, 304, 306, 530, 540, 550. When operating in the DC-DC converter mode, power passes through the motor branch 306 corresponding to the AC inverter branch 350 that is turned off, resulting in power passing through the motor branch 306 and each other branch 330, 340 as they are modulated to produce DC power with appropriate power characteristics. In this mode, power from the second battery pack 104 passes through the switch 326 and flows into each other inductor branch 302, 304 of the motor 20, 21 through the third inductor 306 branch of the motor 20, 21. Energy passes through the branches 330, 340 and is provided to the first battery pack 102.

[0068] In the delta motor example ( Figure 4 and 6), it may be beneficial to ensure that the inverter branch that is not in operation during DC-DC converter operation is the inverter branch 330, 340, 350, 530, 540, 550 that is physically closest to the battery packs 102, 104 arranged in series. In some configurations, the inverter branch 330, 340, 350, 530, 540, 550 is located between the battery packs 102, 104 arranged in series and the other inverter branches 330, 340, 350, 530, 540, 550. Utilizing the inverter branch 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 inverter branch 330, 340, 350, 530, 540, 550 in operation, thereby minimizing the possibility of overheating.

[0069] Reference now Figure 5 and 6 In some cases, different chemical battery packs 102, 104 may be arranged in series between a positive bus 130 and a negative bus 132. Such an example is Figure 5 and 6 It is shown in Figure 5 The connected star motors 20, 21 are shown, Figure 6 The connected triangular motors 20, 21 are shown. Figure 5 and Figure 6 The arrangement of the inverter branches 530, 540, 550 shown in FIG. Figure 3 and Figure 4 Same as shown in .

[0070] Specific reference Figure 5 , the two battery packs 102, 104 are connected in series on the positive bus 130 and the negative bus 132, and the positive terminal of the second battery pack 104 is connected to the negative terminal of the first battery pack 102 at the battery pack node 592. The battery pack node 592 is connected to the neutral node 133 of the motors 20, 21 through the switch 594. When the inverter 110 branches 530, 540, 550 are driven in the DC-DC converter mode, the switch 594 is closed, which creates a current flow path between the battery packs 102, 104, wherein each motor branch 502, 504, 506 provides an internal motor branch inductance, and the switches of the corresponding inverter branches 530, 540, 550 are modulated to be 120 degrees offset from each other inverter branch 530, 540, 550. In this mode, current flow between the battery packs 102 , 104 equalizes the charge in each battery pack 102 , 104 , and this mode may be used during or after series charging of the battery packs 102 , 104 .

[0071] Continue to refer Figure 1-5 , Figure 6The schematic diagram shows battery packs 102, 104 connected in series, wherein the motors 20, 21 have a triangle configuration instead of Figure 5 The star configuration shown. In the delta configuration, when the switch 594 is closed, the battery pack node 592 is connected to the motor branch 502. When the switch in each inverter branch 530, 540, 550 operates as a DC-DC converter, the switch 594 creates a current flow path from the second battery pack 104 through the first motor branch 502 and into each of the second and third motor branches 504, 506, and then back to the first battery pack 102. Each of the second and third motor branches 504, 506 is modulated with a phase shift of 180 degrees relative to the other branch 504, 506 to ensure that the motors 20, 21 do not rotate. When the switch 594 is closed (allowing current to pass), the charge level between the two battery packs 102, 104 is equalized.

[0072] exist Figure 3-6 In each of the above examples shown, different chemical battery packs 102, 104 are shown as a single battery pack. It should be understood that each single battery pack 102, 104 can be replaced with a group of sub-batteries arranged in series, as long as each sub-battery arranged in series includes the same chemistry as each other sub-battery arranged in series in the battery pack 102, 104. In some cases, each sub-battery can have the same storage capacity. In other examples, the sub-batteries can 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 in the battery pack.

[0073] exist Figure 2-6 In each example, the operation of the AC inverter 110 as a DC-DC converter is generally described. It should be understood that the actual operation will depend on whether the motors 20, 21 are in a triangle ( Figure 3 and 5 ) or star( Figure 4 and 6 ) configuration connections are slightly different.

[0074] refer to Figure 3 and Figure 5In an example of a star motor 20, 21, also referred to as a four-terminal motor 20, 21, controlling the multilevel inverter 110 as a DC-DC converter includes, for each inverter branch 330, 530, 340, 540, 350, 550: providing a first control signal to a first transistor X1, X5, X9 and a fourth transistor X4, X8, X12 of each inverter branch 330, 530, 340, 540, 350, 550, the first control signal being inverted for the fourth transistor X4, X8, X12. providing a second control signal to a second transistor X2, X6, X10 and a third transistor X3, X7, X11 of each inverter branch 330, 530, 340, 540, 350, 550, the second control signal being inverted for the third transistor X3, X7, X11. The first control signal and the second control signal control the on / off states of the first, second, third and fourth transistors X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12 of the corresponding inverter branches 330, 530, 340, 540, 350, 550 by pulse width modulation. The first control signal and the second control signal are phase-shifted by 120 degrees relative to each other first control signal and the second control signal.

[0075] refer to Figure 4 and Figure 6 In the example of the invention, (the triangular motor 20, 21, alternatively referred to as the three-terminal motor 20, 21), for each of the first inverter branch 330, 530 and the second inverter branch 340, 540, the multi-level inverter 110 is controlled as a DC-DC converter, and a first control signal is provided to the first and fourth transistors X1, X4, X5, X8 of the corresponding inverter branch 330, 340, 530, 540. The first control signal is inverted for the fourth transistor X4, X8. A second control signal is provided to the second and third transistors X2, X3, X6, X7 of the corresponding inverter branch 330, 340, 530, 540. The second control signal is inverted for the third transistor X3, X7. The first control signal and the second control signal control the on / off state of the first, second, third and fourth transistors X1, X2, X3, X4, X5, X6, X7, X8 of the corresponding inverter branch 330, 340, 530, 540 by pulse width modulation. The first control signal and the second control signal are phase-shifted by 180 degrees relative to the other of the first control signal and the second control signal. The third control signal is provided to the first, second, third and fourth transistors X9, X10, X11, X12 of the third inverter branch 350, 550, and the third control signal sets the first, second, third and fourth transistors X9, X10, X11, X12 of the third inverter branch 350, 550 to be cut off for a duration of controlling the multi-level inverter 110 as a DC-DC converter.

[0076] The terms "one" and "an" do not indicate a limitation of quantity, but rather indicate the presence of at least one of the referenced items. The term "or" means "and / or", unless the context clearly indicates otherwise. References to "an aspect" throughout the specification mean that a particular element (e.g., feature, structure, step, or characteristic) described in conjunction with that aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it should be understood that the described elements may be combined in any suitable manner in various aspects.

[0077] When an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

[0078] Unless otherwise indicated herein, all test standards are the most recent standards in effect as of the filing date of the present application or, if priority is claimed, the filing date of the earliest priority application in which the test standards appear.

[0079] Unless defined otherwise, 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.

[0080] 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 equivalents may be substituted for its elements without departing from the scope thereof. In addition, many modifications may be made to adapt specific situations or materials to the teachings of the disclosure without departing from the essential scope of the disclosure. Therefore, it is intended that the disclosure is not limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A vehicle system, comprising: a first battery pack connected to a second battery pack via a flying capacitor multi-level inverter having a plurality of inverter legs, each inverter leg being arranged in a flying capacitor topology; a motor connected to a flying capacitor multi-level inverter, the motor having three phases; as well as A controller is connected to the motor and the flying capacitor multi-level inverter, the controller including a memory storing instructions configured to cause the controller to control the flying capacitor multi-level inverter as a direct current (DC)-DC converter so as to flow current through the motor, the first battery pack and the second battery pack.

2. The vehicle system according to claim 1, wherein: Each inverter branch of the flying capacitor multi-level inverter includes a first transistor connecting the 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 the negative bus; and Wherein, each phase of the motor is connected to an AC output node of a corresponding inverter branch of a flying capacitor multi-level inverter.

3. The vehicle system according to claim 2, wherein: The motor is a four terminal motor, and wherein controlling the flying capacitor multi-level inverter as a DC-DC converter comprises: For each inverter branch, providing a first control signal to the first transistor and a fourth transistor, 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 branch, wherein the second control signal is inverted for the third transistor, wherein the first control signal and the second control signal control the on / off states of the first, second, third and fourth transistors of the corresponding inverter branches via pulse width modulation (PWM); and Each first control signal is phase-shifted by 120 degrees relative to each other first control signal, and each second control signal is phase-shifted by 120 degrees relative to each other second control signal.

4. The vehicle system according to claim 2, wherein: The motor is a three terminal motor, and wherein controlling the flying capacitor multi-level inverter as a DC-DC converter comprises: For each of the first inverter branch and the second inverter branch, providing a first control signal to a first and a fourth transistor of the corresponding inverter branch, wherein the first control signal is inverted for the fourth transistor; providing a second control signal to second and third transistors of corresponding inverter branches, wherein the second control signal is inverted for the third transistor; Wherein, the first control signal and the second control signal control the on / off state of the first, second, third and fourth transistors of the corresponding inverter branch via pulse width modulation; wherein each first control signal is phase-shifted by 180 degrees relative to another first control signal, and each second control signal is phase-shifted by 180 degrees relative to another second control signal; and A third control signal is provided to the first, second, third and fourth transistors of the third inverter branch, the third control signal setting the first, second, third and fourth transistors of the third inverter branch off for a duration for controlling the multilevel inverter as a DC-DC converter.

5. The vehicle system according to claim 1, wherein: The first battery pack and the second battery pack are connected in parallel at one or both of the negative battery terminal and the positive battery terminal.

6. The vehicle system according to claim 1, wherein: The first battery group and the second battery group are connected in series through a common node to form a series battery group.

7. The vehicle system according to claim 6, wherein: A neutral node connects each phase of the motor to the common node.

8. The vehicle system according to claim 6, wherein: A first phase terminal of the motor is connected to a common node of the series-connected battery pack.

9. The vehicle system according to claim 8, wherein: The first inverter branch is physically disposed closer to the first battery group and the second battery group than each of the second inverter branch and the third inverter branch.

10. The vehicle system according to claim 1, wherein: The first battery group includes at least a first group of power cells and a second group of power cells connected to the first group of power cells at the low node.

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