Vehicle-to-vehicle charging to reduce loss using voltage converter system with bypass switch

Abstract

Vehicle-to-vehicle charging using a voltage converter system with a bypass switch to reduce loss is provided. A direct current to direct current (DC-DC) converter system for charging between donor and acceptor systems for respective charge provision and reception includes input and output filter capacitors of a rechargeable energy storage system (RESS) connected to the donor and acceptor, and link capacitors in parallel with input and output stages of the system. The boost stage has a first switching control circuit including a first plurality of switches. The buck stage has a second control circuit including a second plurality of switches. The first and second plurality of switches have respective bypass switches. The controller identifies respective voltage ranges of the donor and the acceptor. In response to the voltage range, the controller selectively bypasses a charging path in the step-up or step-down stage during charging by closing the first or second bypass switch. This action minimizes losses in the converter system.

Description

TECHNICAL FIELD

[0001] Battery electric vehicles, plug-in hybrid electric vehicles, range-extended electric vehicles, and other electrified mobility systems (collectively referred to herein as electric vehicles (EVs)) are equipped with electrified powertrains. The electrified powertrain of a motor vehicle, for example, includes one or more electric traction motors connected to a set of vehicle wheels. The battery management system of an EV controls discharge of a high-voltage traction battery pack during a propulsion mode to energize the electric traction motor(s) and produce an output torque. As a result, the EV propels along a roadway via electrically driven rotation of the vehicle wheels, with engine-driven rotation also possible in the aforementioned hybrid electric and range-extended electric vehicle configurations. BACKGROUND

[0002] Electrochemical battery cells of a depleted traction battery pack can be selectively recharged using an off-board plug-in charging process. As understood in the art, off-board charging of a battery electric system requires the battery pack to be electrically connected to an electric vehicle supply equipment (EVSE), i.e., an off-board charging station, via a suitably configured charging cable. The charging station and the EV’s communication and control circuitry and corresponding controller establish bidirectional communication in accordance with a suitable charging protocol. Thereafter, the charging station off-loads a charging current to the depleted battery pack to charge the individual battery cells. SUMMARY

[0003] Disclosed herein is a direct current-direct current (DC-DC) converter architecture for use in a representative portable charging unit, as well as a method of performing a charging operation between a charge-providing electrical system (“donor”) and a charge-receiving electrical system (“recipient”) using the portable charging unit and a resident DC-DC converter system. While the example donor and recipient are configured as representative battery electric systems, the present teachings can encompass various other rechargeable energy storage systems (RESSes), including but not limited to on-board fuel cell units, supercapacitors, or hybrid alternative electrical storage devices. Thus, the battery electric systems described herein are merely representative of, and not limiting to, the present teachings.

[0004] The disclosed portable charging architecture and associated charging strategy enables high-voltage power to be transferred from a donor RESS to a recipient RESS with reduced switching and conduction losses typically associated with employing multiple power conversion stages in a charging path. These benefits are provided using selective control of first and second bypass switches as described herein.

[0005] In representative / non-limiting configurations, the donor and recipient are configured as battery electric systems in the form of electric vehicles (EVs), such as all-battery electric, plug-in hybrid, extended-range electric, or other electrified mobile systems having high-voltage direct current (DC) traction battery packs. However, within the scope of the present disclosure, the present teachings can also extend to charging events performed using stationary or non-vehicle donors / recipient, with the described vehicle-to-vehicle (V2V) charging operations using donor and recipient EVs being merely one possible DC-DC charging application.

[0006] In particular embodiments, a DC-DC converter system for use in a charging session performed between a charge-providing electrical system ("donor") and a charge-receiving electrical system ("recipient") includes an input filter capacitor connected to an input stage of the DC-DC converter system, an output filter capacitor connected to an output stage of the DC-DC converter system, and a link capacitor in parallel with and between the input stage and the output stage. A boost converter circuit stage ("boost stage") has a first switching control circuit. A buck converter circuit stage ("buck stage") of the DC-DC converter system includes a second switching control circuit including a second plurality of switches. Each of the first and second pluralities of switches includes a bypass switch, namely a first bypass switch and a second bypass switch, respectively.

[0007] As part of this representative configuration, an electronic control system ("system controller") is in communication with the first and second pluralities of switches. The system controller is configured to identify respective voltage ranges of a donor-side rechargeable energy storage system (RESS) and a recipient-side RESS. In response to the respective voltage ranges, the controller selectively bypasses a charging path in the circuit of the boost or buck converter stage by closing one of the first or second bypass switches. This switching control action minimizes losses in the DC-DC converter system.

[0008] In some implementations, the boost stage is connected to an input side of the system / donor-side RESS. The buck stage in such embodiments is connected to an output side / recipient-side RESS, such that the DC-DC converter system is configured as a boost-buck converter having respective voltage increases and voltage decreases in the boost and buck stages in a charging path extending from the donor to the recipient. The system controller is configured to selectively bypass the buck stage or the boost stage by opening or closing the first or second bypass switches, respectively. The controller is optionally programmed to close the first bypass switch and open the second bypass switch when an input voltage of the boost-buck converter exceeds an output voltage by more than a predetermined fraction, such as about 10%.

[0009] In one or more embodiments, the circuit of the boost stage is connected to the recipient side ESS and the circuit of the buck stage is connected to the donor side RESS, such that the DC-DC converter system is configured as a buck-boost converter. In this embodiment, the system controller is configured to selectively bypass the upper or lower switches of the buck-boost converter through operation of the first or second bypass switches, respectively. The controller is programmed to close the second bypass switch and open the first bypass switch when the input voltage exceeds the output voltage by more than the predetermined fraction described above.

[0010] In one or more implementations, the system controller maintains the first and second bypass switches in an open state when the voltage level of the donor side RESS overlaps or resides within a predetermined range of the voltage level of the recipient side RESS during a charging process. In some implementations, the system controller is configured to pre-charge the input filter capacitor, the output filter capacitor, and the link capacitor prior to closing the first or second bypass switches in order to minimize inrush current.

[0011] In one or more implementations, the DC-DC converter system can be bidirectional.

[0012] In one or more configurations, the first and second bypass switches are embodied as solid state switches having a turn-on state voltage that is less than a predetermined fraction or percentage of the turn-on state voltage of the remaining switches of the first and second switching circuits, particularly at rated current levels of the buck and boost stages. In non-limiting implementations, approximately 10-20% can be used as a possible percentage.

[0013] The first and second bypass switches can optionally comprise an electromechanical relay or contactor. The DC-DC converter system can be used as part of a vehicle-to-vehicle (V2V) charging unit, in which case the system controller is an integral part of the V2V charging unit. As described above, the donor and recipient can be embodied as electric vehicles (EVs).

[0014] Also disclosed herein is a vehicle system having a charge-providing donor EV, a charge-receiving recipient EV, and a V2V charging unit having a system controller and a DC-DC converter system operable to perform a V2V charging session between the donor and recipient EVs. The DC-DC converter can include an input filter capacitor connected to an input stage of the system, an output filter capacitor connected to an output stage of the system, and a link capacitor in parallel with and between the input and output stages. As described herein, the identity of the stages as either a boost stage or a buck stage varies with application.

[0015] A boost stage according to representative embodiments has a first switching control circuit including a first plurality of switches, a constituent switch of the first plurality of switches including a first bypass switch. A buck stage includes a second switching control circuit having a second plurality of switches. The second plurality of switches includes a second bypass switch. A system controller is configured to identify respective voltage ranges of a donor side RESS (input voltage) and a recipient side RESS (output voltage). In response to the respective voltage ranges, the system controller selectively bypasses a charging path in the boost or buck stage, as needed, by closing the first or second bypass switch, thereby minimizing switching and conduction losses in the DC-DC converter system.

[0016] One aspect of the present disclosure relates to a V2V charging method, embodiments of which include identifying, by a system controller, respective voltage ranges of a donor side RESS and a recipient side RESS of respective donor and recipient EVs. In response to the respective voltage ranges, the method includes selectively bypassing a charging path in a boost or buck stage of a DC-DC converter system of a portable V2V charging unit connected between the donor and recipient EVs. This is done by closing a first bypass switch in the boost stage or a second bypass switch in the buck stage to minimize the aforementioned losses in the DC-DC converter system.

[0017] The following solutions are provided:

[0018] 1. A direct current to direct current (DC-DC) converter system for use in a charging session performed between a charge-providing electrical system (“donor”) and a charge-receiving electrical system (“recipient”), the DC-DC converter system comprising:

[0019] an input filter capacitor connecting an input stage of the DC-DC converter system to a rechargeable energy storage system (“donor side RESS”) of the donor;

[0020] an output filter capacitor connecting an output side of the DC-DC converter system to a rechargeable energy storage system (“recipient side RESS”) of the recipient;

[0021] a link capacitor disposed in parallel with and between the input stage and the output stage;

[0022] a boost converter circuit stage (“boost stage”) having a first switching control circuit, wherein the first switching control circuit includes a first plurality of switches having a first bypass switch;

[0023] a buck converter circuit stage (“buck stage”) having a second control circuit, wherein the second switching control circuit includes a second plurality of switches having a second bypass switch; and

[0024] a system controller in communication with the first plurality of switches and the second plurality of switches, wherein the system controller is configured to:

[0025] identify respective voltage ranges for the donor-side RESS and the recipient-side RESS; and

[0026] in response to the respective voltage ranges, selectively bypass the charging path in the boost stage or the buck stage by closing the first bypass switch or the second bypass switch, thereby minimizing losses in the DC-DC converter system.

[0027] 2. The DC-DC converter system of Scheme 1, wherein the boost stage is connected to the donor-side RESS and the buck stage is connected to the recipient-side RESS, such that the DC-DC converter system is configured as a boost-buck converter.

[0028] 3. The DC-DC converter system of Scheme 2, wherein the system controller is configured to selectively bypass the boost stage or the buck stage by opening or closing the first bypass switch or the second bypass switch, respectively.

[0029] 4. The DC-DC converter system of Scheme 2, wherein the system controller is programmed to:

[0030] close the first bypass switch and open the second bypass switch when the input voltage exceeds the output voltage by more than a predetermined fraction; and

[0031] close the second bypass switch and open the first bypass switch when the output voltage exceeds the input voltage by more than a predetermined fraction.

[0032] 5. The DC-DC converter system of Scheme 1, wherein the boost stage is connected to the recipient-side RESS and the buck stage is connected to the donor-side RESS, such that the DC-DC converter system is configured as a buck-boost converter.

[0033] 6. The DC-DC converter system of Scheme 5, wherein the system controller is configured to selectively bypass upper switches of the buck-boost converter via the first bypass switch or the second bypass switch.

[0034] 7. The DC-DC converter system of Scheme 5, wherein the system controller is programmed to:

[0035] close the first bypass switch and open the second bypass switch when the input voltage exceeds the output voltage by more than a predetermined fraction; and

[0036] close the second switch and open the first bypass switch when the output voltage exceeds the input voltage by more than a predetermined fraction.

[0037] 8. The DC-DC converter system of Scheme 1, wherein the system controller is configured to maintain the first bypass switch and the second bypass switch in an open state during the charging process when the voltage level of the donor side RESS overlaps or resides within a predetermined range of the voltage level of the recipient side RESS.

[0038] 9. The DC-DC converter system of Scheme 1, wherein the system controller is configured to pre-charge the input filter capacitor, the output filter capacitor, and the link capacitor prior to closing the first bypass switch or the second bypass switch to minimize inrush current.

[0039] 10. The DC-DC converter system of Scheme 1, wherein the DC-DC converter system is bidirectional.

[0040] 11. The DC-DC converter system of Scheme 1, wherein the first bypass switch is connected between the input node of the boost stage and the switching node, and the second bypass switch is connected between the switching node of the buck stage and the output node.

[0041] 12. The DC-DC converter system of Scheme 1, wherein the first bypass switch and the second bypass switch are solid state switches having a turn-on state voltage that is less than a predetermined fraction of the turn-on state voltage of the remaining switches in the first switching circuit and the second switching circuit at a rated current level of the buck stage and the boost stage.

[0042] 13. The DC-DC converter system of Scheme 1, wherein the first bypass switch and the second bypass switch comprise an electromechanical relay or contactor.

[0043] 14. The DC-DC converter system of Scheme 1, wherein the DC-DC converter system is part of a vehicle-to-vehicle (V2V) charging unit, the system controller is part of the V2V charging unit, the donor and the recipient are electric vehicles, and the donor side RESS and the recipient side RESS are traction battery packs.

[0044] 15. A vehicle system comprising:

[0045] a charge-providing donor electric vehicle (EV) having a donor side rechargeable energy storage system (RESS);

[0046] a charge-receiving recipient EV having a recipient side RESS; and

[0047] a vehicle-to-vehicle (V2V) charging unit having a system controller and a DC-DC converter system for use in performing a V2V charging process between the donor EV and the recipient EV, the DC-DC converter comprising:

[0048] an input filter capacitor connected to the donor side RESS at an input stage of the DC-DC converter;

[0049] an output filter capacitor connected to the recipient side RESS at an output stage of the DC-DC converter;

[0050] a link capacitor disposed in parallel with and between the input stage and the output stage;

[0051] a boost converter circuit stage ("boost stage") having a first switching control circuit including a first plurality of switches having a first bypass switch;

[0052] a buck converter circuit stage ("buck stage") having a second control circuit including a second plurality of switches having a second bypass switch, wherein the system controller is configured to:

[0053] identify respective voltage ranges of the donor side RESS and the recipient side RESS; and in response to the respective voltage ranges, selectively bypass the charging path in the boost stage or the buck stage by closing the first bypass switch or the second bypass switch, thereby minimizing losses in the DC-DC converter system.

[0054] 16. The vehicle system of Scheme 15, wherein the boost stage is connected to the donor side RESS and the buck stage is connected to the recipient side RESS, such that the DC-DC converter system is configured as a boost-buck converter.

[0055] 17. The vehicle system of Scheme 15, wherein the boost stage is connected to the recipient side RESS and the buck stage is connected to the donor side RESS, such that the DC-DC converter system is configured as a buck-boost converter.

[0056] 18. The vehicle system of Scheme 15, wherein the system controller is configured to maintain the first bypass switch and the second bypass switch in an open state during the V2V charging process when the voltage level of the donor side RESS overlaps or resides within a predetermined range of the voltage level of the recipient side RESS.

[0057] 19. A vehicle-to-vehicle (V2V) charging method, comprising:

[0058] identifying, via a system controller, respective voltage ranges of a donor side rechargeable energy storage system (RESS) and a recipient side RESS of a donor electric vehicle (EV) and a recipient EV, respectively; and

[0059] When charging the recipient RSS via the donor-side RSS, in response to the corresponding voltage range, the charging path in the boost converter circuit stage (“boost stage”) or buck converter circuit stage (“buck stage”) of the DC-DC converter system connected to the V2V charging unit between the donor EV and the recipient EV is selectively bypassed, including closing a first bypass switch in the boost stage or a second bypass switch in the buck stage, to minimize losses in the DC-DC converter system.

[0060] 20. The V2V charging method according to Scheme 19, wherein the first bypass switch and the second bypass switch are solid-state switches having an on-state voltage that is less than a predetermined fraction of the on-state voltage of the remaining switches in the buck stage and the boost stage.

[0061] The foregoing features and advantages of this disclosure, as well as other features and accompanying advantages, will become apparent from the following detailed description of illustrative examples and models for carrying out this disclosure, when taken in conjunction with the accompanying drawings and appended claims. Furthermore, this disclosure expressly includes combinations and sub-combinations of the elements and features presented above and below. Attached Figure Description

[0062] Figure 1 This is an illustration of a representative direct charging session performed between a charge-providing electrical system of an electric vehicle in a non-limiting form (“donor EV”) and a charge-receiving electrical system of an electric vehicle in a non-limiting form (“recipient EV”), which is performed using a portable vehicle-to-vehicle (V2V) charging unit having a resident low-loss DC-DC converter system disclosed herein.

[0063] Figure 2 It shows Figure 1 A representative embodiment of a portable V2V charging unit.

[0064] Figure 3A and 3B It shows Figure 1 A representative embodiment of a DC-DC converter system is illustrated schematically.

[0065] Figure 4 It is a description Figure 3A A table showing the possible voltage levels and switching states of a representative DC-DC converter system.

[0066] This disclosure may be modified or embodied in alternative forms, and representative embodiments are shown in the accompanying drawings and described in detail below. The inventive step of this disclosure is not limited to the disclosed embodiments. Rather, this disclosure is intended to cover alternatives that fall within the scope of the disclosure defined by the appended claims. Detailed Implementation

[0067] Referring to the drawings, wherein like reference numbers refer to like features throughout the several views, Figure 1 A representative vehicle-to-vehicle (V2V) charging process 10 is depicted involving a vehicle system 11 having a charge-providing electrical system 12D and a charge-receiving electrical system 12R. During the illustrated V2V charging process 10, the charge-providing battery electric system 12D (hereinafter referred to for clarity as the donor electric vehicle (EV) 12D, which is also labeled EV1 in Figure 1 , discharges a high-voltage direct current (DC) charging current (DC-1) to a portable V2V charging unit 14, a representative embodiment of which is shown in Figure 2 . As contemplated herein, the V2V charging unit 14 includes a direct current to direct current (DC-DC) converter system 30, a representative embodiment of which is shown in Figure 3A and 3B . A resident system controller 40 of the V2V charging unit 14 is programmed and operable to control the DC-DC converter system 30 during operation of the V2V charging unit 14, as described below with reference to Figure 4 .

[0068] The V2V charging unit 14, which is shown schematically in Figure 1 , outputs a DC charging current (DC-2) to the charge-receiving electrical system 12R, hereinafter referred to as the recipient EV 12R (EV2) consistent with the exemplary V2V embodiment. From the perspective of the recipient EV 12R, the donor EV 12D and the V2V charging unit 14 together appear as an electric vehicle supply equipment (EVSE) node, i.e., an off-board charging station. However, in contrast to a fixed off-board charging station capable of providing DC charging functionality, the portability and configuration functionality of the V2V charging unit 14 using the DC-DC converter system 15 of the present disclosure provides enhanced charging mobility, reduced range anxiety, and reduced switching and conduction losses to the owner / operator of the electrified system, among other collateral benefits.

[0069] As used herein, the term “electric vehicle” can encompass a broad range of mobile electrified systems. Although a motor vehicle is shown in Figure 1 to illustrate possible implementations of the V2V charging unit 14, those skilled in the art will appreciate that the present teachings can be extended to many electrified systems having on-board rechargeable energy storage systems (RESS), including but not necessarily limited to rail vehicles, aircraft, watercraft, agricultural vehicles, delivery, service / roadside service or transport vehicles, etc. Thus, Figure 1 the scenarios described are illustrative of only one possible approach.

[0070] In Figure 1In a representative configuration, the donor EV 12D and the recipient EV 12R can include a vehicle body 13D and 13R, respectively, and corresponding electric drive systems 50D and 50R. In a typical configuration, the donor EV 12D includes a charging port 16 connected to a high-voltage (HV) electrochemical traction battery pack (B HV ) referred to herein as a donor-side RESS 18. That is, although lithium-ion or other high-energy batteries are described herein as non-limiting battery electric embodiments, the donor-side RESS 18 (as well as the recipient-side RESS 118 as described herein) can include, for example, fuel cell units, supercapacitors, or hybrid alternative electrical storage devices. A set of HV electrical contactors 20 or another suitable high-voltage switching device can be used to connect / disconnect the donor-side RESS 18. In one or more embodiments, the donor-side RESS 18 is connected to a power inverter module (PIM) 22, i.e., an inverter circuit. During discharge mode, the donor-side RESS 18 delivers a DC voltage (VDC) to the DC side of the PIM 22. The PIM 22, which uses on / off conduction state control of a plurality of solid-state semiconductor switches (not shown) such as insulated-gate bipolar transistors (IGBTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), thyristors, etc., is driven by pulse-width modulation or another suitable switching control technique to convert the DC voltage waveform into an alternating current (AC) voltage waveform, and vice versa, as understood in the art. That is, switching control of the PIM 22 ultimately converts the DC input voltage from the donor-side RESS 18 into an AC voltage (VAC) suitable for exciting the phase windings of an electric traction motor (M E ) 24, resulting in machine rotation. When the charging process shown is not being performed, output torque (arrow T O ) from the electric traction motor 24 can be delivered to one or more wheels 26 of the donor EV 12D or another load.

[0071] Figure 1 The recipient EV 12R shown in FIG. 1 can be similarly or identically configured to include a corresponding charging port 116, a recipient-side RESS 118, contactors 120, a PIM 122, and an electric traction motor 124. Thus, in addition to being equipped to perform the V2V charging process 10 shown in FIG. 1, the respective electric drive systems 50D and 50R are also configured to electrically propel the corresponding donor EV 12D and recipient EV 12R during separate discharge modes of the donor-side RESS 18 and the recipient-side RESS 18. In other words, Figure 1 both the donor EV 12D and the recipient EV 12R in the embodiment shown in FIG. 1 are mobile systems capable of performing propulsion functions in addition to the V2V charging process 10 described herein. Figure 1 both the donor EV 12D and the recipient EV 12R in the embodiment shown in FIG. 1 are mobile systems capable of performing propulsion functions in addition to the V2V charging process 10 described herein.

[0072] V2V charging unit (14): Reference Figure 2 During the operation of the receiver EV 12R, a situation may arise where its RESS118 becomes depleted to the point that the receiver-side RESS118 requires charging. When this occurs, the receiver EV 12R may not be near an available EVSE charging station or a home or office charging station. In this case, the owner / operator can request recharge. Figure 1 The V2V charging process 10 is conducted as a mobile charging session, for example, via a software application (“app”). During this event, the portable V2V charging unit 14 may be transported, for example, to the recipient EV 12R via the donor EV 12D or another vehicle / third-party provider or roadside assistance vehicle, and subsequently connected to the donor EV 12D and recipient EV 12R via charging cable 31 and attached connector 31C and charging ports 16, 116. Depending on the embodiment, charging ports 16 and 116 may be configured differently to accept SAE J1772, National Charging Standard (NACS), Combined Charging System (CCS), CHAdeMO, or other suitable charging connectors.

[0073] The donor EV 12D includes an onboard EV controller (C D )32, which has one or more processors (P)36 and non-transitory computer-readable storage medium / memory (M)38. The host EV 12R is similarly equipped with a vehicle controller 132 (C) R The donor EV 12D and the recipient EV 12R are thus equipped to communicate via data exchange during the V2V charging process 10, manage and coordinate power flow, monitor the correct connection and other condition / error states of the charging cable 30, regulate the temperature of the V2V charging unit 14, and perform other related functions during the V2V charging process 10.

[0074] To perform the V2V charging process 10 using the DC-DC converter system 30 described herein, vehicle controllers 32 and 132 cooperate with the V2V charging unit 14 to perform process steps between the input and output stages of the DC-DC converter system 30, as described below. These functions are embodied in computer-readable instructions and executed from memories 38 and 138, which are, for example, magnetic or optical media, CD-ROMs, and / or solid-state / semiconductor memories (e.g., various types of RAM or ROM). The term "vehicle controller" and related terms (e.g., control module, control unit, processor, and similar terms) may refer to one or various combinations of associated non-transitory memory components in the form of application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), electronic circuits, central processing units (e.g., microprocessors), and memories and storage devices (read-only, programmable read-only, random access, hard disk drives, etc.). The non-transitory components of the memories 38 and 138 used herein are capable of storing one or more machine-readable instructions in the form of software or firmware programs or routines, combinational logic circuits, input / output circuits and devices, signal conditioning and buffering circuits, and other components that can be accessed by one or more processors 36 and 136 to provide the aforementioned functions.

[0075] exist Figure 2 In a representative and therefore non-limiting configuration, the V2V charging unit 14 is configured to output a continuous power of at least about 50-100 kilowatts (kW) of rated charging power and a continuous output current of about 150-300 amperes (A). In possible configurations, the V2V charging unit 14 may receive a voltage of about 350-1000V or higher from the donor EV 12D and, in response, may output a voltage of about 150-1000V or higher to the receiver EV 12R; other voltage ranges are possible depending on the embodiment. The V2V charging unit 14 is also configured with buck / boost capabilities to enable the V2V charging unit 14 to reduce (buck) or increase (boost) the DC voltage supplied from the donor EV 12D. Figure 1 The V2V charging unit 14 does so based on the state of charge (SOC) or voltage capability of the recipient side RESS 118 of the recipient EV 12R, the requested power amount, the power capability / SOC / voltage capability of the donor EV 12D, and other factors.

[0076] The mobile plug-in functionality contemplated herein involves coordinated bi-directional data communication between the donor EV 12D and the recipient EV 12R. Data exchange takes the form of low voltage control pilot or communication (Comms) signals, typically in the range of 0-12V, and a 0-5V proximity voltage signal. Electrical ground (GND) is also provided. For example, an established J1772 connection allows the respective processors of the donor EV 12D and the recipient EV 12R to communicate mutual communication signals using power line communication (PLC), which in turn occurs via coordinated exchange of data messages according to an established communication protocol. The communication signals are typically used to verify the connection between the off-board EVSE charging station and the charging EV to communicate a charging status, the respective locations of the off-board EVSE charging station and the charging EV being occupied here by the donor EV 12D and the V2V charging unit 14 (together acting as such EVSE charging station) and the recipient EV 12R. This can be done, for example, using a fixed PWM duty cycle during the contemplated DC charging. The same signals can be used to adjust the charging rate as needed. Other standards, such as the aforementioned NACS, CCS, CHAdeMO, etc., can be used in a similar manner, and thus the particular charging standard can vary with the desired end use.

[0077] The multi-pin charging connectors 31C provided on each charging cable 31 are connected to a corresponding one of the charging ports 16, 116 located on the donor EV 12D and the recipient EV 12R, respectively. DC charging power is fed through the conductive pins of the charging port 16 of the donor EV 12D, through the V2V charging unit 14, and into the RESS 118 of the recipient EV 12R, in accordance with the relevant charging protocol. When the RESS 18 and / or 118 is embodied as a lithium-ion battery pack or another high-energy DC battery, the charging process is coordinated by data / message exchange between the processor 36 of the donor EV 12D, the processor or system controller 40 of the V2V charging unit 14, and the corresponding processor 136 (e.g., a battery management system or another battery controller) of the recipient EV 12R. Figure 2 The communication and proximity signals described above are exchanged between the processors 36 and 136 and the system controller 40, in accordance with the general process of DC charging according to DIN 70121 or other relevant protocols well understood in the art. As also understood in the art, these protocols proceed according to a defined multi-step electronic "handshake" process before allowing energy transfer.

[0078] Figure 2The V2V charging unit 14 shown in FIG. 1, which is specifically configured to function as a mobile charging accessory that performs V2V charging events / sessions, can include a portable housing 41, e.g., a weatherproof, rugged, and sufficiently lightweight enclosure constructed of molded plastic, aluminum, steel, etc. Portability of the housing 41 can be facilitated by coupling or affixing wheels and / or handles (not shown) to the housing 41. The housing 41 is also coupled to respective inlet and outlet charging ports 42 and 142 of the V2V charging unit 14, which are in turn connectable to the donor EV 12D and the recipient EV 12R, respectively, during the V2V charging process 10. Figure 1

[0079] The DC-DC converter system 30 described above with reference to the remaining figures is disposed within the housing 41, i.e., within a volume or space defined therein, and is coupled to the housing 41 for safe transport and operation. In the embodiment shown, the DC-DC converter system 30 can be configured as a Figure 2 Figure 3A Figure 3B boost-buck converter or a buck-boost converter in different representative embodiments of the DC-DC converter system 30. A high-to-low voltage (HV-LV) converter 43 can also be included in the circuitry of the V2V charging unit 14. An optional LV energy storage device 45, e.g., an electrochemical battery pack, a supercapacitor or ultracapacitor in different implementations, can be coupled to the low voltage side of the HV-LV converter 43, as shown, or LV power can be provided separately, e.g., through a plug-in connection to the on-board / vehicle 12-15 V power.

[0080] The optional LV energy storage device 45, when in use, is also electrically coupled to the DC-DC converter system 30 to provide low voltage (e.g., nominal 12-15 V) power suitable for opening / closing the HV disconnect devices 47 and 147, and to power voltage or current sensors and associated circuitry and diagnostic components. The coupling of the LV energy storage device 45 and the HV-LV converter 43 also enables the HV-LV converter 43 to selectively charge the LV energy storage device 45 during the V2V charging process 10. In some configurations, the optional LV energy storage device 45 can also be recharged via AC grid power, e.g., by plugging the housing 41 into an available wall outlet via a corresponding charging outlet (not shown) disposed thereon.

[0081] Figure 2 The V2V charging unit 14 shown in FIG. 1 also includes a communication processing unit 49 operable to communicate with the donor EV 12D and the recipient EV 12R, e.g., via the respective communication interfaces 48 and 148 of the V2V charging unit 14 and the donor EV 12D and the recipient EV 12R, respectively, during the V2V charging process 10. Figure 1 ​​​establish and maintain bi-directional communication between the donor EV 12D and the recipient EV 12R during the V2V charging process 10. Separate communication circuits / stacks or "communication stacks" 149 and 249 (Comm S) can be included in the communication processing unit 49, between which the application layer 51 is arranged to coordinate the wired / wireless data exchange. Figure 2 The communication stacks 149 and 249 in the non-limiting embodiments can include different connections and components, such as a ground (GND) connection 52A, a SAE J1772 PWM block 52B, and a PLC processor 52C for the communication stack 149, or equivalent structures in other embodiments, and corresponding ground connection 152A, PWM block 152B, and processing device 152C for the communication stack 249.

[0082] To this end, the CPU 49 can be equipped to coordinate with the above-mentioned processors 36 and 136 of the respective donor EV 12D and recipient EV 12R during the V2V charging process 10. The communication is facilitated via one or more communication modules connected to / usable with the application layer 51, such as the BLE / WiFi / LTE software module 53, ISO-20 communication software module 54, DIN communication software module 55, and ISO-3 communication software module 56 shown in the non-limiting example configuration. Such software is generally used during EV charging to facilitate the wireless exchange of data, and is therefore well understood in the art Figure 2

[0083] Still referring to Figure 2 By using the communication stacks 149 and 249, the application layer 51, and the associated software modules 53, 54, and 55, the CPU 49 is able to command the HV-LV converter 43 to pre-charge the HV bus 60 of the V2V charging unit 14 to a level equal to that of the HV bus located on the donor EV 12D, and selectively recharge the LV energy storage device 45 via the HV-LV converter 43 as needed. Furthermore, the CPU 49 (in close coordination with the processors 36 and 136 of the Figure 2 selectively command the transfer of DC charge from the donor side RESS 18 of the donor EV 12D to the recipient side RESS 118 of the recipient EV 12R through the operation of the DC-DC converter system 30. Figure 1 and Figure 2 the donor side RESS 18 of the donor EV 12D to the recipient side RESS 118 of the recipient EV 12R.

[0084] ​The DC-DC converter system 30 described below can be connected to the positive and negative HV rails (+, -) between the inlet charging port 42 and the outlet charging port 142 via first and second sets of HV disconnect devices 47 and 147, respectively. Fault isolation devices (F), such as fuses, pyrotechnic switches, or electronic fuses, can be arranged as shown to provide additional high-voltage protection.

[0085] Figure 2 Other components of the V2V charging unit 14 may include a human-machine interface (HMI) 62, which is connected to the housing 41 and configured to facilitate human-machine interaction during the V2V charging process 10 described herein. The HMI 62 may receive user input to the system controller 40 during the V2V charging process 10 and may also display information about the V2V charging process 10 for the user of the V2V charging unit 14 to view. For example, the HMI 62 may include one or more displays, an alphanumeric touchscreen, a keypad, and / or other peripherals that present prompts and sequential instructions for the owner / operator to follow. The HMI 62 may also present information to the user, such as the current communication and charging offload status of the V2V charging process 10, SOC, voltage, or other status of the batteries 18 and 118 of the corresponding donor EV 12D and recipient EV 12R, charging time, total offload power, etc. A controller area network (CAN) bus may be included in the architecture of the V2V charging unit 14 to communicate between various modules or devices using low-voltage differential signaling.

[0086] Furthermore, the thermal management system (TMS) 25 may be incorporated into or connected to the V2V charging unit 14 to regulate the temperature of the high voltage and other components contained therein, particularly the DC-DC converter system 30 and the optional HV-LV converter 43. By way of example and not limitation, the thermal management system 25 may include radiators (e.g., cooling plates, fans, etc.) with conductive and / or forced convection devices, fluid devices (e.g., coolant loops / pumps), cooling blankets, etc. In some implementations, the thermal management system 25 may include optional phase change materials to optimize mass, instantaneous heat dissipation capacity, etc.

[0087] Boost-buck options: Now for reference Figure 3A The above Figure 1 and Figure 2 The DC-DC converter system 30 can be optionally configured as a boost-buck converter system 30A. As understood in the art, this configuration can be used to reduce (“buck”) or increase (“boost”) the input voltage (Vi), in which case the input voltage comes from... Figure 1 and Figure 2of donor EV 12D. As configured, the boost-buck converter system 30A includes a boost converter circuit stage ("boost stage") 150 and a buck converter circuit stage ("buck stage") 250, as well as selectively actuatable first and second bypass switches SI and S2, such as electromechanical relays or contactors. The boost stage 150 is connected to the donor side battery, and the buck stage 250 is connected to the recipient side battery. As noted above, the use of Figure 3A Embodiments of the present application can be used to eliminate switching and conduction losses of part or all of one stage of the power conversion process. In particular, Figure 3A Embodiments of the present application can be implemented to minimize ripple current between the donor EV 12D and the recipient EV 12R, which is due in part to the inclusion of respective first and second inductors 34 and 134.

[0088] For example, in a representative scenario where the input voltage (Vi) from the donor EV 12D is approximately 400V and the output voltage (Vo) to the recipient EV 12R is approximately 800V, only the boost stage 150 is used. In other words, the buck stage 250 downstream of the boost stage 150 is not needed. This allows the system controller 40 Figure 2 to selectively bypass the buck stage 250 through operation of the second bypass switch S2. A similar approach can be used to bypass the boost stage 150 through control of the first bypass switch SI in Figure 3A the present application when the input voltage (Vi) from the donor EV 12D is approximately 800V and the output voltage (Vo) to the recipient EV 12R is approximately 400V. In this exemplary case, only the buck stage 250 is used. The boost stage 150 upstream of the buck stage 250 is not needed. Thus, the aforementioned losses are reduced by not having to use both stages of the DC-DC converter system 30A.

[0089] In the topology shown in Figure 3A , as shown, the input voltage (Vi) is applied to the input stage of the DC-DC converter system 30A. In this embodiment, the input filter capacitor 37 is charged to the level of the input voltage (Vi) provided at the input stage. The inductor 34 is connected between the input node Nl of the boost stage 150 and the switching node N2. In this particular configuration, the lower switch SB connects the switching node N2 to the negative voltage rail 60 - . The upper switch SA, which can alternatively be embodied as a simple freewheeling diode for simplicity, similarly connects the switching node N2 to the positive voltage rail 60 + at a point labeled V+. Thus, "upper switch" refers here to the connection to the positive voltage rail 60 + , and "lower switch" refers to the connection to the negative voltage rail 60 - .

[0090] The respective lower and upper switches SB and SA are controlled in the usual course of controlling the boost stage 150 using complementary pulse width modulated (PWM) control signals (PWM2 and \PWM2) from the controller 40. As is understood in the art, the duty cycle of such complementary PWM control signals is used to control the charging current, charging voltage, or charging power of the host EV 12R. In this particular embodiment, the first bypass switch SI can be controlled to selectively bypass the first stage of power conversion, i.e., the boost stage 150. When the boost stage 150 is selectively bypassed by closing the first bypass switch SI, the switches SA and SB are disabled or held in an off state (open or non-conductive) by the system controller 40, described below with reference to Table 33 of Figure 4 Table 33 describes exemplary switching logic.

[0091] In the representative configuration of Figure 3A , a DC link capacitor (C L ) 35 is also disposed between the circuits of the boost and buck stages 150 and 250. Similar to the boost stage 150, the buck stage 250 includes respective upper and lower switches SC and SD. The output inductor 134 is connected between the respective switching and output nodes N3 and N4 of the buck stage 250, and the output filter capacitor 137 is connected to the negative voltage rail 60 Figure 3A and Figure 3B . - In this configuration, the upper switch SC (i.e., connected to the positive voltage rail V + ) switches the node N3 to the positive voltage rail V + . The lower switch SD, optionally embodied as a simple freewheeling diode, similarly switches the node N3 to the negative voltage rail 60 - .

[0092] In this implementation, the respective upper and lower switches SC and SD are controlled in the usual course of controlling the circuit of the buck stage 250 using complementary PWM control signals (PWM1 and \PWM1) from the system controller 40. As described above, in this case the commanded duty cycle of the complementary PWM control signals controls the charging current, charging voltage, or charging power of the host EV 12R. Similar to the first bypass switch SI, the second bypass switch S2 is controlled to selectively bypass the buck stage 250. When the buck stage 250 is selectively bypassed, the switches SC and SD are disabled or held in an off state by the controller. Table 33 of Figure 4 describes the control of the first and second bypass switches SI and S2, and the switches SA, SB, SC, and SD.

[0093] Buck-boost option: With reference to Figure 3B , the above Figure 1 and Figure 2The DC-DC converter system 30 can alternatively be configured as a buck-boost converter 30B, wherein a first inductor 34 is shared between the boost stage 150 and the buck stage 250. In this configuration, the boost stage 150 is connected to the recipient-side battery, and the buck stage 250 is connected to the donor-side battery. As exemplarily Figure 3A With that configuration, Figure 3B In the alternative topology, various switches or power conversion stages can be selectively bypassed, wherein the corresponding first and second bypass switches S1 and S2 are located relative to... Figure 3A Different locations, but for the same purpose: the first bypass switch S1 is used to bypass the boost stage 150, and the second bypass switch S2 is used to bypass the buck stage 250.

[0094] Brief Reference Figure 4 Table 33, Figure 3A The control of the 30A boost-buck converter can be achieved by Figure 2 The system controller 40 or another suitable processing node performs operations based on the input and output voltages Vi and Vo. The system controller 40 also uses a calibrable / predetermined threshold differential voltage (Vth) to determine the corresponding on / off states of the respective first and second bypass switches S1 and S2; for example, the threshold differential voltage (Vth) is approximately 50V in a typical application, or... Figure 1 The nominal voltage range used during the V2V charging process 10 is approximately 1 / 10 or 10 percent (10%) of the range, or another predetermined fraction or percentage. In one or more embodiments, the first bypass switch S1 and the second bypass switch S2 may optionally be configured as solid-state switches, such as solid-state relays, whose on-state voltage is less than approximately 10 percent (10%) to 20% of the on-state voltages of the remaining switches SA, SB, SC, and SD in the buck stage 250 and the boost stage 150. Table 33 may be programmed into a memory accessible by the system controller 40, enabling rapid selection and real-time implementation of the on / off states based on the current values ​​of Vi and Vo of the respective input and output stages of the power conversion.

[0095] Using Table 33, when the input voltage (Vi) exceeds the sum of the desired output voltage (Vo) and the threshold differential voltage (Vth), i.e., Vi > Vo + Vth, the system controller 40 can command the first bypass switch S1 to close (X) and the second bypass switch S2 to open (O). This action establishes the "buck-only mode" operating mode. In this case, switches SA and SB are turned off (i.e., open), and switches SC and SD are controlled via complementary PWM signals PWM1 and \PWM1, i.e., PWM signals PWM1 and \PWM1 are 180° out of phase with each other.

[0096] When the sum of the input voltage (Vi) and the threshold differential voltage (Vth) is less than the required output voltage (Vo), i.e., Vi + Vth < Vo, the system controller 40 commands the opposite control action. Then, for the "only boost mode" operation mode, the system controller 40 disconnects the first bypass switch S1 and closes the second bypass switch S2. During this mode, switches SA and SB are controlled by complementary PWM signals PWM2 and \PWM2. Switches SC and SD are turned off, i.e., commanded to be open (O).

[0097] As a third "buck-boost" control option, when the absolute value of the difference between the input and output voltages is less than or equal to the threshold differential voltage (Vth), i.e., |V i -V o | ≤ V th , the system controller can disconnect both the first and second bypass switches S1 and S2. Thereafter, when during the charging process, the voltage level of the donor-side battery overlaps or stays within a predetermined range with the voltage level of the acceptor-side battery, the system controller 40 can maintain the first and second bypass switches S2 in the open state (i.e., turned off). This action allows buck-boost (or boost-buck) operation as needed to control the charging current, charging voltage, or charging power of the acceptor EV 12R. In this case, complementary PWM signals (PWM1, \PMW1) and (PWM2, \PWM2) are applied to switches SC, SD for the buck stage and switches SB and SA for the boost stage with appropriate duty cycles. This control scheme also applies to Figure 3B the topology of.

[0098] Table 33 helps to perform the switching control method during the V2V charging process 10 using the DC-DC converter system 30. To implement this method, computer-readable instructions can be executed by Figure 1 the system controller 40 of or another processing node in response to the voltage comparison result. Referring to the representative Table 33 of Figure 2 , for example, this method may include respectively identifying the corresponding voltage ranges of the donor-side ESS18 of the donor EV 12D and the acceptor-side ESS118 of the acceptor EV 12R by the system controller 40. The system controller 40 then compares the corresponding input and output voltages Vi and Vo to determine the appropriate states of the first and second bypass switches S1 and S2. The comparison may require accessing a pre-populated look-up table, such as Figure 4 Table 33 of, and selecting the corresponding state according to Table 33. As described above, Table 33 corresponds to Figure 4 the topology of Figure 3A and Figure 3B the topology of.

[0099] Such a method thus continues with the following actions by the system controller 40 or other dedicated processing node: selectively bypassing the charging path in the boost stage 150 or the buck stage 250 of the DC-DC converter system 30 of the V2V charging unit 14, e.g. when connected between the donor EV 12D and the recipient EV 12R Figure 1 This action can occur by closing the first bypass switch SI in the boost stage 150 or the second bypass switch S2 in the buck stage 250 to minimize switching and conduction losses in the DC-DC converter system 30 as described above. The methods disclosed herein can be embodied as software stored on a tangible non-transitory medium, such as a flash memory, a solid state drive (SSD) memory, a hard disk drive (HDD) memory, a CD-ROM, a digital versatile disc (DVD), or other suitable computer readable storage device. Moreover, although specific algorithms can be described herein with reference to flow charts and / or work flow diagrams, alternative methods for implementing the example machine readable instructions can be used.

[0100] Thus, due to the multi-stage power conversion in the energy flow path between the donor EV 12D and the recipient EV 12R, the solution presented herein helps to improve the efficiency during the V2V charging process 10. Figure 1 The first and second bypass switches SI and S2 are configured as low conduction loss switches (e.g. electromechanical contactors or relays, or possibly SSRs) can be implemented in bidirectional or unidirectional boost-buck or buck-boost converter topologies to bypass the appropriate stage or switch SA, SB, SC or SD, thereby minimizing losses in the DC-DC converter system 30. These and other attendant benefits will be readily appreciated by those of ordinary skill in the art having the benefit of the foregoing disclosure.

[0101] The present disclosure allows for many different forms of embodiments. Representative examples of the present disclosure are shown in the drawings and described in detail herein as non-limiting examples of the disclosed principles. To this end, elements described in the Abstract, Introduction, Summary, and Detailed Description sections, but not expressly set forth in the claims, should not be incorporated by implication or otherwise into the claims.

[0102] For the purposes of this description, unless otherwise indicated, the use of the word "a" includes plural references and vice versa, the term "and" and "or" shall be both conjunctive and disjunctive, the terms "any" and "all" shall mean "any and all", and the words "including," "containing," "comprising," "having," and the like shall mean "including, but not limited to." Furthermore, the words "about," "nearly," "substantially," "generally," "approximately," and the like, can be used herein in the sense of "at, near, or close to" or "within 0-5% of" or "within acceptable manufacturing tolerances" or logical combinations thereof.

[0103] The detailed description and accompanying drawings or diagrams are supportive and descriptive of the present teachings, but the scope of the present teachings is defined solely by the claims. While there have been described herein the principles of the present teachings and the best mode contemplated by the inventors, various modifications and changes in the implementations and applications of these principles can be made by those skilled in the art without departing from the spirit and scope of the teachings defined by the following claims. It is expressly intended that all combinations of those elements that are presented by the foregoing disclosure and the following claims be expressly incorporated herein by reference and be deemed to be described by the disclosure and the claims.

Claims

1. A direct current to direct current (DC-DC) converter system for use in a charging session performed between a charge-providing electrical system ("donor") and a charge-receiving electrical system ("recipient"), the DC-DC converter system comprising: an input filter capacitor connecting an input stage of the DC-DC converter system to a rechargeable energy storage system ("donor-side RESS") of the donor; an output filter capacitor connecting an output stage of the DC-DC converter system to a rechargeable energy storage system ("recipient-side RESS") of the recipient; a link capacitor disposed in parallel with and between the input stage and the output stage; a boost converter circuit stage ("boost stage") having a first switching control circuit, wherein the first switching control circuit includes a first plurality of switches having a first bypass switch; a buck converter circuit stage ("buck stage") having a second control circuit, wherein the second switching control circuit includes a second plurality of switches having a second bypass switch; and a system controller in communication with the first plurality of switches and the second plurality of switches, wherein the system controller is configured to: identify respective voltage ranges of the donor-side RESS and the recipient-side RESS; and in response to the respective voltage ranges, selectively bypass a charging path in the boost stage or the buck stage by closing the first bypass switch or the second bypass switch, thereby minimizing losses in the DC-DC converter system.

2. The DC-DC converter system of claim 1, wherein the boost stage is connected to the donor-side RESS and the buck stage is connected to the recipient-side RESS, such that the DC-DC converter system is configured as a boost-buck converter.

3. The DC-DC converter system of claim 2, wherein the system controller is configured to selectively bypass the boost stage or the buck stage by opening or closing the first bypass switch or the second bypass switch, respectively.

4. The DC-DC converter system of claim 2, wherein the system controller is programmed to: close the first bypass switch and open the second bypass switch when the input voltage exceeds the output voltage by more than a predetermined fraction; and close the second bypass switch and open the first bypass switch when the output voltage exceeds the input voltage by more than the predetermined fraction.

5. The DC-DC converter system of claim 1, wherein the boost stage is connected to the recipient-side RESS and the buck stage is connected to the donor-side RESS, such that the DC-DC converter system is configured as a buck-boost converter.

6. The DC-DC converter system of claim 5, wherein the system controller is configured to selectively bypass upper switches of the buck-boost converter via the first bypass switch or the second bypass switch.

7. The DC-DC converter system of claim 5, wherein the system controller is programmed to: close the first bypass switch and open the second bypass switch when the input voltage exceeds the output voltage by more than a predetermined fraction; and close the second switch and open the first bypass switch when the output voltage exceeds the input voltage by more than the predetermined fraction. ​ 8. The DC-DC converter system of claim 1, wherein the system controller is configured to maintain the first bypass switch and the second bypass switch in an open state during the charging process when the voltage level of the donor side RESS overlaps or resides within a predetermined range of the voltage level of the recipient side RESS.

9. The DC-DC converter system of claim 1, wherein the first bypass switch and the second bypass switch are solid state switches having a turn-on state voltage that is less than a predetermined fraction of a turn-on state voltage of the remaining switches in the first switching circuit and the second switching circuit at a rated current level of the buck stage and the boost stage.

10. The DC-DC converter system of claim 1, wherein the DC-DC converter system is part of a vehicle-to-vehicle (V2V) charging unit, the system controller is part of the V2V charging unit, the donor and the recipient are electric vehicles, and the donor side RESS and the recipient side RESS are traction battery packs.

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