Hybrid chemical battery power transfer with multi-level neutral point clamped inverter

Abstract

A vehicle system includes a first battery pack connected to a second battery pack via a multi-level inverter. The motor is connected to the multi-level inverter. A controller is connected to the motor and the multi-level inverter. The multi-level inverter is a neutral point clamped inverter. The controller includes a memory storing instructions configured to cause the controller to control the multilevel inverter as a direct current (DC)-DC converter such that circulating current passes 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 multi-level inverters operating as direct current (DC)-DC converters. Background Art

[0002] Vehicles, including electric vehicles and hybrid electric vehicles, have battery storage devices for purposes such as powering electric motors, electronic devices, and other vehicle subsystems. Batteries for battery storage systems typically include a plurality of different power cells, each of which stores power for later distribution, and the power cells are electrically connected to provide output power to a distribution bus as needed. During or shortly after charging the battery storage system, it is desirable to ensure that power is properly distributed among the battery packs in order to ensure optimal operation of the batteries. Existing systems utilize the same battery cell type (called chemistry) within the battery pack. Identical battery cells can be balanced using passive power balancing techniques known in the art.

[0003] Different types of battery packs have different characteristics, such as charging rate and power density. In some configurations, it may be advantageous to utilize different types of battery packs within a single battery system, thereby allowing different vehicle operating modes to utilize different battery characteristics. However, utilizing 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 including 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 multilevel inverter, a motor connected to the multilevel inverter, and a controller connected to the motor and the multilevel inverter, wherein the multilevel inverter is a neutral point clamped inverter, and the controller includes a memory storing instructions configured to cause the controller to control the multilevel inverter as a direct current (DC)-DC converter so that a circulating current passes through the motor, the first battery pack, and the second battery pack.

[0006] In addition to one or more features described herein, the multilevel inverter includes three inverter legs, each inverter leg having a first transistor connecting a positive node to a high middle node, a second transistor connecting the high middle node to an AC output node of the inverter leg, a third transistor connecting the AC output node of the inverter leg to a low middle node, a fourth transistor connecting the low middle node to a negative node, a first diode connecting the high middle node to a neutral node, and a second diode connecting the low middle node to a neutral node, and wherein each phase of the motor is connected to the AC output node of a corresponding inverter leg of a neutral point clamped inverter.

[0007] In addition to one or more features described herein, the motor is a four-terminal motor, and wherein controlling the multilevel inverter as a DC-DC converter includes: for each inverter branch, providing a first control signal to a first transistor and a third transistor, wherein the first control signal is inverted for the first transistor, providing a second control signal to a second and a fourth transistor, wherein the second control signal is inverted for the second transistor, the first control signal and the second control signal control the open / closed state of the first, second, third and fourth transistors of the corresponding phases through pulse width modulation, and wherein the first control signal and the second control signal in each branch are phase-shifted by 120 degrees from the first control signal and the second control signal of the other branches.

[0008] In addition to one or more features described herein, the motor is a three-terminal motor, and wherein controlling the multilevel inverter as a DC-DC converter includes: for each of a first phase inverter branch and a second phase branch, providing a first control signal to a first transistor and a third transistor of the first inverter branch of the corresponding phase, wherein the first control signal is inverted for the first transistor, providing a second control signal to a second transistor and a fourth transistor of the corresponding first phase branch, wherein the second control signal is inverted for the second transistor, the first control signal and the second control signal control the open / closed state of the first transistor, the second transistor, the third transistor and the fourth transistor of the corresponding first phase inverter branch via pulse width modulation, and for the second inverter branch, providing a third control signal to the first transistor and the third transistor of the second inverter branch, wherein the third control signal is inverted for the first transistor, providing a second control signal to the second transistor and the fourth transistor of the second phase branch a fourth control signal, wherein the fourth control signal is inverted for the second transistor, the third control signal and the fourth control signal control the open / closed state of the first transistor, the second transistor, the third transistor and the fourth transistor of the second inverter branch via pulse width modulation, and wherein the modulated first control signal and the third control signal are phase-shifted by 180 degrees, and the second control signal and the fourth control signal are phase-shifted by 180 degrees, and the second control signal in each branch is phase-shifted by 180 degrees with the first control signal and the second control signal of the other branches, and third and fifth control signals are provided to the first transistor, the second transistor, the third transistor and the fourth transistor of the third phase inverter branch, and the third and fifth control signals set the first transistor, the second transistor, the third transistor and the fourth transistor of the third inverter branch to be turned off during the duration of controlling the multilevel inverter as the DC-DC converter, wherein the third phase inverter branch is connected to the positive terminal of the battery pack.

[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 via a common node.

[0011] In addition to one or more features described herein, a neutral node connecting each phase of the motor is connected to a common node of the series connected battery pack.

[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 of the features described herein, the motor is a three-terminal motor, the first phase leg is physically disposed closer to the first battery pack and closer to the second battery pack than each of the second leg and the third leg, and wherein the first phase leg is connected to the positive terminal of the battery pack during operation of the DC-DC converter.

[0014] In addition to one or more features described herein, the motor is a three-terminal motor and wherein the first inverter branch is connected to the positive DC bus via a first switch, the neutral return node of the first inverter branch is connected to neutral via a second switch, and is connected to the positive terminal of the first battery pack via a third switch.

[0015] In addition to one or more of the features described herein, the first battery pack includes a plurality of modules.

[0016] 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 multilevel inverter as a direct current (DC)-DC converter so that a circulating current passes through the multilevel inverter, a motor, a first battery pack, and a second battery pack, wherein the vehicle system includes a first battery pack connected to the second battery pack via the multilevel inverter, the motor is connected to the multilevel inverter, and a motor controller connected to the motor and the multilevel inverter, the controller including a memory storing instructions configured to cause the vehicle system to implement the method.

[0017] In addition to one or more features described herein, the multilevel inverter is a neutral point clamped inverter, which includes three branches, each branch having a first transistor connecting a positive node to a high intermediate node, a second transistor connecting the high intermediate node to an AC output point of the inverter phase branch, a third transistor connecting the AC output point of the inverter phase branch to a low intermediate node, a fourth transistor connecting the low intermediate node to a negative node, a first diode connecting the high intermediate node to a neutral node of the DC bus, and a second diode connecting the low intermediate node to the neutral node of the DC bus, and wherein each phase of the motor is connected to the neutral point of a corresponding branch of the neutral point clamped inverter.

[0018] In addition to one or more features described herein, the motor is a four-terminal motor, and wherein controlling the multilevel inverter as a DC-DC converter includes: for each phase branch, providing a first control signal to a first transistor and a third transistor, wherein the first control signal is inverted for the first transistor, and providing a second control signal to a second transistor and a fourth transistor, wherein the second control signal is inverted for the second transistor, the first control signal and the second control signal control the open / closed state of the first transistor, the second transistor, the third transistor and the fourth transistor via pulse width modulation, and wherein the first control signal and the second control signal in each branch are phase-shifted by 120 degrees from the first control signal and the second control signal of each other branch.

[0019] In addition to one or more features described herein, the motor is a three-terminal motor, and wherein controlling the multilevel inverter as a DC-DC converter includes: for each of a first phase inverter branch and a second phase branch, providing a first control signal to a first transistor and a third transistor of the corresponding first phase inverter branch, wherein the first control signal is inverted for the first transistor, providing a second control signal to a second transistor and a fourth transistor of the corresponding first phase branch, wherein the second control signal is inverted for the second transistor, the first control signal and the second control signal controlling the open / closed state of the first transistor, the second transistor, the third transistor and the fourth transistor of the corresponding first phase inverter branch via pulse width modulation, and for the second inverter branch, providing a third control signal to the first transistor and the third transistor of the second inverter branch, wherein the third control signal is inverted for the first transistor, providing a second control signal to the second transistor and the fourth transistor of the second phase branch, wherein the third control signal is inverted for the first transistor, providing a third control signal to the second transistor and the fourth transistor of the second phase branch, wherein the third control signal is inverted for the first transistor, providing a third control signal to the first transistor and the third transistor of the second phase branch, wherein the third control signal is inverted for the first transistor, providing a third control signal to the second transistor and the fourth ... second transistor, providing a third control signal to the A fourth control signal is provided, wherein the fourth control signal is inverted for the second transistor, the third control signal and the fourth control signal control the open / closed state of the first transistor, the second transistor, the third transistor and the fourth transistor of the second inverter branch via pulse width modulation, and wherein the modulated first control signal and the third control signal are phase-shifted by 180 degrees, and the second control signal and the fourth control signal are phase-shifted by 180 degrees, and the second control signal in each branch is phase-shifted by 180 degrees with the first control signal and the second control signal of other branches, and third and fifth control signals are provided to the first transistor, the second transistor, the third transistor and the fourth transistor of the third inverter branch, and the third and fifth control signals set the first transistor, the second transistor, the third transistor and the fourth transistor of the third inverter branch to be turned off during the duration of controlling the multilevel inverter as the DC-DC converter, wherein the third inverter branch is connected to the positive terminal of the battery pack.

[0020] 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.

[0021] 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.

[0022] 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 than the first chemistry.

[0023] In yet another exemplary embodiment, a vehicle includes an electric drive system, a power distribution system, and a controller, the electric drive system including at least one electric motor, the 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 multilevel inverter, wherein the multilevel inverter is a neutral point clamped inverter, the controller being connected to the motor and the multilevel inverter, the controller including a memory storing instructions, the instructions being configured to cause the controller to control the multilevel inverter as a direct current (DC)-DC converter so that a circulating current passes through the motor, the first battery pack, and the second battery pack.

[0024] In addition to one or more features described herein, a multilevel inverter includes three branches, each branch having a first transistor connecting a positive node to a high middle node, a second transistor connecting the high middle node to a neutral point, a third transistor connecting the neutral point to a low middle node, a fourth transistor connecting the low middle node to a negative node, a first diode connecting the high middle node to a return node, and a second diode connecting the low middle node to the return node, and wherein each phase of the motor is connected to the neutral point of a corresponding branch of the neutral point clamped inverter.

[0025] The above features and advantages and other features and advantages of the present disclosure are apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, advantages and details appear, by way of example only, in the following detailed description, which refers to the accompanying drawings, in which:

[0027] Figure 1 is a schematic diagram of a vehicle including a power distribution system;

[0028] Figure 2 is a block diagram of a battery system according to one embodiment;

[0029] Figure 3 is a circuit diagram representation of a power transmission method applied to parallel arranged battery packs according to a first example;

[0030] Figure 4 is a circuit diagram representation of a power transmission method applied to parallel arranged battery packs according to a second example;

[0031] Figure 5 is a circuit diagram of a power transmission method applied to a battery pack arranged in series according to a first example;

[0032] Figure 6 is a circuit diagram of a power transmission method applied to a battery pack arranged in series according to a second example;

[0033] Figure 7 is an exemplary physical capacitor mounting configuration according to one example; and

[0034] Figure 8 is used Figure 7 An exemplary circuit diagram of a power transmission method applied to a three-terminal motor and capacitor mounting configuration. DETAILED DESCRIPTION

[0035] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or use. It should be understood that throughout the drawings, corresponding reference numerals represent identical 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 described functionality.

[0036] According to an exemplary embodiment, a vehicle system for a battery includes a plurality of battery packs having different battery pack chemistries. A multilevel 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 switching within the multilevel inverter to control the characteristics of the AC power signal.

[0037] The memory is configured to enable the motor controller to achieve power balancing or power transfer between different battery packs by operating the multilevel inverter as a DC-DC converter and utilizing the internal inductance of the motor branch without rotating the motor for the DC-DC inverter inductor. By controlling the phase shift in the modulation of the AC inverter when the AC inverter operates as a DC-DC converter, 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 internal inductance of the motor branch can be utilized without causing rotation. The DC-DC converter is then able to transfer power between the battery packs according to a known power transfer process. In some examples, switches 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 by disconnecting the branch experiencing the fault condition from the corresponding power bus.

[0038] Continuing with the general system referenced above, Figure 1 An embodiment of a motor vehicle 10 is shown that includes a battery system controller 28 configured to control a battery system. The vehicle 10 includes a vehicle body 12 that at least partially defines an occupant compartment 14. The vehicle body 12 also supports various vehicle subsystems, including a propulsion system 16, a battery system 22, other subsystems for supporting 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.

[0039] The vehicle 10 may be an internal combustion 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 on opposite sides of the vehicle 10. Any number of motors positioned at various additional locations around the vehicle 10 may be used to provide power to corresponding systems and subsystems.

[0040] 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 battery cells divided into a plurality of sections. The battery system controller 28 is included in the battery system 22 and controls the charging and discharging functions of the batteries within the battery system 22. In an alternative configuration, the battery system controller 28 can be a universal vehicle controller that is remote 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 another alternative, the battery system controller 28 can be a distributed control system that includes a plurality of coordinated controllers throughout the vehicle 10, including controllers within the battery system 22 and controllers remote from the battery system 22.

[0041] In one embodiment, the battery system 22 includes one or more battery packs 26. The battery pack 26 includes 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 , the power distribution bus 29 is shown in simplified form as a single line and provides power to the propulsion system 16 through the inverter 32 .

[0042] 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 1. A first battery pack 102 and a second battery pack 104 are connected in parallel and via a multilevel inverter 110. 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 through the connection 134 during normal operation. In addition to the multilevel inverter 110 operating as a DC-DC converter, 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, such as Figure 2 The examples shown and Figure 3 In a specific example, the motors 20, 21 have a Y-branch configuration (alternatively referred to as a four-terminal motor) in which the reference node 103 is connected to the positive bus 130 via a connection. In other examples, for example Figure 4In a specific example of the motors 20, 21 having a delta branch configuration (alternatively referred to as a three-terminal electric motor) with a floating neutral point (i.e., there is no internal connection of the motor branches 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 to charge the battery packs 102, 104.

[0043] The battery system 22 includes mixed chemistry battery packs 102, 104, which may include different lithium-ion-based battery chemistries, such as LFP (lithium iron phosphate), lithium nickel manganese cobalt (NMC), or non-lithium-ion-based battery packs, such as fuel cell cells, lead-acid batteries, solid-state batteries, supercapacitors, ultracapacitors, or electrolytic double-layer capacitors. Each battery pack 102, 104 includes a single chemistry, and the chemistry of each battery pack 102, 104 is different from the chemistry within another battery pack 102, 104. The mixed chemistry provides different power characteristics for the battery packs 102, 104, with some battery packs 102, 104 having 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 placing the battery packs in parallel with filter inductors, as done in conventional battery systems 22, cannot properly redistribute power from one battery pack 102, 104 to another battery pack 104.

[0044] 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 28 may provide the functionality of the battery system controller 150, and in other embodiments, the functionality is provided by a dedicated controller 150 distributed across multiple vehicle controllers or any similar control scheme. It should be understood that references to the controller 150 herein encompass a variety of controller types and configurations and are not limited to the dedicated battery system controller 150 shown.

[0045] During charging, or immediately 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 the motors 20, 21 in a non-rotational capacity, it may not be suitable for use during vehicle operation. Since 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 branches in the motors 20, 21 to transfer power from one battery pack 102, 104 to the other battery pack 102, 104 without generating rotational motion within the motors 20, 21.

[0046] By adjusting the switching of each branch so that the switching in the branch is offset 180 degrees from the other two branches, power passes through each motor branch, and the rotational force generated in each branch is offset by the rotational force generated in each other branch. This allows power to pass through the motors 20, 21 without causing rotation, and allows the inductance of each motor branch to operate as a DC-DC converter inductor for the corresponding branch of the multilevel inverter 110. Modulation of the switches in each branch of the multilevel inverter 110 to achieve DC-DC converter operation occurs according to known techniques.

[0047] Continue to refer Figure 2 , Figure 3 Shows Figure 2 1 , wherein the motors 20, 21 are arranged in a Y-shaped configuration. Each phase leg 302, 304, 306 of the motors 20, 21 is shown as an inductor representing the internal inductance of that leg of the motors 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 pair of switches connects the positive terminal of the charger 140 to the corresponding battery pack 102, 104, and the other switch 312, 316 connects the negative terminal of the charger 140 to the corresponding battery pack 102, 104.

[0048] Additionally, the first battery pack 102 is connected to the positive bus 130 via switch 320 and to the neutral bus 132 via switch 322. The second battery pack 104 includes a direct connection to the positive bus 130, and switch 324 connects the positive side of the second battery pack 104 to the motor neutral point 103. The negative side of the second battery pack 104 is connected to the neutral bus 132 via switch 326.

[0049] The multilevel inverter 110 is arranged in a multilevel neutral point connection topology including three inverter branches 330, 340, 350. Each inverter branch 330, 340, 350 has a first transistor X1, X5, X9 connecting the corresponding positive node 331, 341, 351 to the corresponding high intermediate node 333, 343, 353; a second transistor X2, X6, X10 connecting the corresponding high intermediate node 333, 343, 353 to the AC output node 332, 342, 352; and a first transistor X2, X6, X10 connecting the AC output node 332, 342, 352 to the corresponding low intermediate node 335, 345, 355. Three transistors X3, X7, X11; a fourth transistor X4, X8, X12 connecting the corresponding low intermediate node 335, 345, 355 to the corresponding negative node; a first diode 372, 374, 376 connecting the corresponding high intermediate node 333, 343, 353 to the return node 339, 349, 359; and a second diode 382, ​​384, 386 connecting the corresponding low intermediate node 335, 345, 355 to the return node 339, 349, 359. Figure 5 and Figure 6 The inverter branches 530, 540, 550 shown in FIG. 1 are arranged identically. Figure 5 and Figure 6 The diagram omits Figure 3 and Figure 4 Certain reference numerals are included in the Figure 5 and Figure 6 The omission of explicit numerical designations does not imply that Figure 5 and Figure 6 No such element exists in .

[0050] The AC output node 332, 342, 352 of each inverter branch 330, 340, 350 is connected to the corresponding inductor phase branch (motor branch 302, 304, 306) of the motor 20, 21. During normal operation, the controller 150 modulates the transistors within each inverter branch 330, 340, 350 of the multilevel inverter 110 to drive the motor 20, 21 using any battery pack 102, 104 connected to the positive bus 130 and the neutral bus 132. In addition, a pair of capacitors 390 is connected in parallel to each inverter branch 330, 340, 350. The illustrated pair of capacitors 390 may alternatively be three pairs, with one pair connected in parallel with each inverter branch 330, 340, 350, resulting in a total of 6 capacitors. In order to minimize the loop inductance during the DC-DC power transmission operation, the capacitors 390 are physically arranged in parallel with each other on the capacitor mounting, while forming a series circuit.

[0051] 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. As an 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 in order to speed up the overall charging process.

[0052] Balancing and power transfer are achieved by modulating the transistors in the AC inverter 110 so that the AC inverter operates as a DC-DC inverter using the internal inductance of the motor branches 302, 304, 306 as the corresponding DC-DC converter inductors. 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 neutral bus 132 are closed. Each inverter branch 330, 340, 350 is modulated at a phase offset of 120 degrees from each other inverter branch 330, 340, 350, thereby allowing power to be generated through the motors 20, 21 with a net zero rotational force and enabling the motor branch inductance to be utilized. When in this configuration, energy circulates through the motor branches 302, 304, 306 and the corresponding inverter branches 330, 340, 350, which convert the DC power to voltage and current levels that can be accepted by the receiving battery pack 102, 104. The power with the new characteristics is provided to the power buses (positive bus 130 and neutral bus 132), allowing power to be transferred from one battery pack 102, 104 to another battery pack 102, 104.

[0053] In addition, each battery pack 102, 104 is connected to two power buses and a charger 140 via a switch. When one of the battery packs 102, 104 is in a faulty state, the controller 150 can isolate or remove the individual battery packs 102, 104. In order to isolate the faulty battery packs 102, 104, the corresponding switches 320, 322, 324, 326 connecting the battery packs 102, 104 to the buses 130, 132 remain open, resulting in the battery packs 102, 104 being electrically isolated.

[0054] When the motors 20, 21 are configured in a delta configuration, there is no neutral point within the motors 20, 21 to which the switch 326 can be connected. Figure 4 As shown in Figure 2 and Figure 3 The same reference numerals denote the same elements and configurations. Figure 4 Examples with Figure 3 The example of is different only in that the switch 326 is connected to the AC input node 352 of one of the branch inverters 350 of the multilevel inverter 110. When operating in the DC-DC converter mode, the transistors within the inverter branch 350 remain disconnected, and the inverter 110 operates as a two-phase DC-DC converter, wherein the other two inverter branches 330, 340 are modulated to be 180 degrees apart. When in this mode, power passes through the motor branch 306 corresponding to the inverter branch 350 that is turned off, resulting in power passing through the motor branch 306 and each of the other inverter branches 330, 340 because they are modulated to produce DC power with appropriate power characteristics. In this mode, power from the second battery pack (load 120) passes through the switch 326 and flows through the third motor branch 306 into each of the other motor branches 302, 304 of the motor 20, 21. The energy passes through the inverter branches 330 , 340 and is provided to the first battery group 102 .

[0055] In the example of the delta motor, in some examples, it is beneficial to ensure that the branch of the motor that is not operated during the DC-DC converter mode is the branch that is physically closest to the series arranged battery packs 402, 404. In some configurations, this branch is located between the series arranged battery packs 402, 404 and other branches. Utilizing the branch that is physically closest to the battery packs 402, 404 provides thermal separation between the battery packs 402, 404 and the operating branches, thereby minimizing the chance of excessive heating.

[0056] In some cases, different chemical battery packs can be arranged in series between the positive bus and the negative bus. Such an example is Figure 5 and Figure 6 It is shown in Figure 5 The Y-shaped motors 20, 21 are shown connected, and Figure 6 The connected triangular motors 20, 21 are shown.

[0057] Specific reference Figure 5 , the two battery packs 102, 104 are connected in series across the positive bus 130 and the neutral bus 132, wherein 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 connection node 592. The battery pack node 592 is connected to the neutral node 103 of the motor 20, 21 via a switch 594. When the inverter 110 branch is driven in the DC-DC converter mode, the switch 594 is closed, which creates a current circulation path between the battery packs 102, 104, wherein each motor branch 502, 504, 506 provides an internal 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 circulation 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 .

[0058] Continue to refer Figure 1-5 , Figure 6 The battery packs 102, 104 connected in series are schematically shown, with the motors 20, 21 having a delta configuration rather than a wye configuration. In the wye configuration, the battery pack node 592 is connected to one of the motor branches 506. When the switch in each of the other inverter branches 530, 540, 550 is closed when operating as a DC-DC converter, the switch 594 creates a current circulation path from the second battery pack 104 through the first motor branch 502 and into each of the second motor branch 504 and the third motor branch 506, and then returns to the first battery pack 102. Each of the second and third motor branches 504, 506 is modulated with a phase shift that is 180 degrees offset from 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.

[0059] In each of the above examples, 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 chemical composition as each other sub-battery arranged in series in the battery pack 102, 104. In some cases, the sub-batteries 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 sub-battery capacities.

[0060] Continue to refer to Figure 3 and Figure 5 , controlling the multilevel inverter 110 as a DC-DC converter includes: providing a first control signal to the third transistor X3, X7, X11 and the first transistor X1, X5, X9, wherein the first control signal is inverted for the first transistor X1, X5, X9. In addition, a second control signal is provided to the fourth transistor X4, X8, X12 and the second transistor X2, X6, X10, wherein the second control signal is inverted for the second transistor X2, X6, X10. The first control signal and the second control signal control the open / closed state of the first, second, third and fourth transistors X1-12 of the corresponding phase via pulse width modulation (PWM) control. The modulated first control signal and the second control signal in each branch are phase-shifted by 120 degrees from the first control signal and the second control signal of the other branch.

[0061] Continue to refer to Figure 4 and Figure 6 , (three-terminal motor 20, 21) control of the multilevel inverter 110 as a DC-DC converter includes: for each of the first phase branch 302, 502 and the second phase branch 304, 504, providing a first control signal to the first transistor X1, X5 and the third transistor X3, X7 of the corresponding phase branch 302, 502, wherein the first control signal is inverted for the third transistor X3, X7. The second control signal is provided to the second transistor X2, X6 and the fourth transistor X4, X8 of the corresponding phase branch 302, 502, wherein the second control signal is inverted for the fourth transistor X4, X8. The first control signal and the second control signal control the open / closed state of the first, second, third and fourth transistors X1, X2,, X3, X4, X5, X6, X7, X8 of the corresponding phase branch 304, 504 via pulse width modulation (PWM). The first control signal and the second control signal are phase-shifted 180 degrees from the first control signal and the second control signal of the other phase branch 304, 504. In addition, in the three-terminal example, the third control signal is provided to the first, second, third and fourth transistors X9-12 of the third phase leg 306, 506. During the duration of controlling the multilevel inverter as a DC-DC converter, the third control signal sets the first, second, third and fourth transistors X9-12 to be turned off. As used herein, "first", "second", "third" phase legs are arbitrary indicators for distinguishing the operation of the phase legs, and do not imply any unstated position or operating parameters.

[0062] In a variation of the three-terminal motor, a dedicated switch may be used to switch the inactive branch of the DC-DC converter out of the circuit, rather than controlling the transistors in the inactive branch to remain off. Figure 8An example of this is shown, and Figure 7 It shows that it can be Figure 8 An example capacitor mounting configuration is shown for use in one embodiment of the variation. Structurally, Figure 8 Examples with Figure 4 The example of is different in that the positive bus 130 and the neutral bus 132 include a switch connection 670 (shown via sub-diagram 680), which is configured to disconnect one of the branches 630, 640, 650 (630 in the illustrated configuration) from the positive bus 130 using a first switch 672 for the duration of operation as a DC-DC converter. The second switch 674 disconnects the return node 660 of the branch 620 from the return node 660 of each of the other branches 640, 650 for the duration of operation as a DC-DC converter. The first switch 672 and the second switch 674 can receive the same control signal and will always be in the same state. In addition, the third switch 676 connects the return node 660 of the phase branch 630 to the positive terminal of the battery pack 102 for the duration of operation as a DC-DC converter. This switch arrangement allows power to flow from the battery pack 102 through the first branch 630 to the motor inductor 602 corresponding to the first branch 630 and then through the motor to the other two branches 640 , 650 operating as DC-DC converters.

[0063] and Figure 4 and Figure 6 As in the example of , the inverter 110 operates as a two-phase DC-DC converter, where the other two branches 640, 650 are modulated to be 180 degrees apart. In this mode, the second and third branches 640, 650 are modulated to generate DC power with appropriate power characteristics. Figure 7 A capacitor mounting 700 is shown in FIG. 7 , where six capacitors 702 are mounted to three parallel busbars 704 , 706 , 708 . Figure 7 The capacitor mounting configuration minimizes loop inductance and improves performance when operating in DC-DC converter mode.

[0064] The terms "a" and "an" do not indicate a limitation of quantity, but rather indicate the presence of at least one of the referenced item. Unless the context clearly indicates otherwise, the term "or" means "and / or". References to "aspects" throughout the specification mean that a particular element (e.g., a 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 the various aspects.

[0065] 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.

[0066] Unless stated to the contrary herein, all test standards are the most current standards in effect as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the test standards appear.

[0067] 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.

[0068] 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 its scope. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the disclosure without departing from the basic 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 group connected to a second battery group via a multi-level inverter; a motor connected to the multilevel inverter; as well as A controller is connected to the motor and the multilevel inverter, the multilevel inverter being a neutral point clamped inverter, the controller including a memory storing instructions, the instructions being configured to cause the controller to control the multilevel inverter as a direct current (DC)-DC converter so that a circulating current passes through the motor, the first battery pack and the second battery pack.

2. The vehicle system of claim 1 , wherein the multilevel inverter comprises three inverter legs, each inverter leg having a first transistor connecting a positive node to a high middle node, a second transistor connecting the high middle node to an AC output node of the inverter leg, a third transistor connecting the AC output node of the inverter leg to a low middle node, a fourth transistor connecting the low middle node to a negative node, a first diode connecting the high middle node to a neutral node, and a second diode connecting the low middle node to the neutral node; and Each phase of the motor is connected to an AC output node of a corresponding inverter branch of the neutral point clamped inverter.

3. The vehicle system of claim 2, wherein the motor is a four-terminal motor, and wherein controlling the multilevel inverter as a DC-DC converter comprises: For each inverter branch, a first control signal is provided to the first transistor and the third transistor, wherein the first control signal is inverted for the first transistor, and a second control signal is provided to the second transistor and the fourth transistor, wherein the second control signal is inverted for the second transistor, the first control signal and the second control signal control the open / closed state of the first, second, third and fourth transistors of the corresponding phases via pulse width modulation, and wherein the first control signal and the second control signal in each branch are phase-shifted by 120 degrees from the first control signal and the second control signal of the other branch.

4. The vehicle system of claim 2, wherein the motor is a three-terminal motor, and wherein controlling the multilevel inverter as a DC-DC converter comprises: For the first inverter branch, providing a first control signal to a first transistor and a third transistor of the first inverter branch, wherein the first control signal is inverted for the first transistor, providing a second control signal to a second transistor and a fourth transistor of the first phase branch, wherein the second control signal is inverted for the second transistor, and the first control signal and the second control signal control the open / closed state of the first transistor, the second transistor, the third transistor and the fourth transistor of the first inverter branch via pulse width modulation; For the second inverter branch, a third control signal is provided to the first transistor and the third transistor of the second inverter branch, wherein the third control signal is inverted for the first transistor, a fourth control signal is provided to the second transistor and the fourth transistor of the second phase branch, wherein the fourth control signal is inverted for the second transistor, and the third control signal and the fourth control signal control the open / closed state of the first transistor, the second transistor, the third transistor and the fourth transistor of the second inverter branch via pulse width modulation; wherein the first control signal and the third control signal are phase-shifted by 180 degrees, and the second control signal and the fourth control signal are phase-shifted by 180 degrees; as well as A fifth control signal is provided to the first transistor, the second transistor, the third transistor and the fourth transistor of the third inverter branch, the fifth control signal setting the first transistor, the second transistor, the third transistor and the fourth transistor of the third inverter branch to be turned off for a duration of controlling the multilevel inverter as the DC-DC converter, wherein the third inverter branch is connected to the positive terminal of the battery pack. 5 . The vehicle system of 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 of claim 2 , wherein the first battery pack and the second battery pack are connected in series via a common node. 7 . The vehicle system of claim 6 , wherein a neutral node connecting each phase of the motor is connected to a common node of the series-connected battery packs.

8. A 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 packs, and wherein the motor is a three-terminal motor, the first inverter branch is physically arranged to be closer to the first battery pack and closer to the second battery pack than each of the second inverter branch and the third inverter branch, and wherein during operation of the DC-DC converter, the first inverter branch is connected to the positive terminal of the battery pack.

9. The vehicle system of claim 2, wherein the motor is a three-terminal motor, and wherein a first inverter branch of three inverter branches of a multilevel inverter is connected to a positive DC bus via a first switch, a neutral return node of the first branch is connected to neutral via a second switch, and is connected to a positive terminal of a first battery pack via a third switch.

10. The vehicle system of claim 2, wherein the first battery pack includes a plurality of modules.

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