Patent Description:
In the prior art, electric vehicles are well known comprising an electric train used to drive the electric vehicle. This electric drive train is supplied with energy by an electric energy storage system. From time to time, this energy storage system must be charged with electrical energy, which can be done, e.g., at home or a charging station where the electric vehicle can be connected to an electrical grid via a charging cable for AC charging, e.g., a Type <NUM>/Type <NUM> charging cable. For this purpose, an electric vehicle usually comprises an AC-DC on-board charger to allow charging of the energy storage system, e.g. Lithium-Ion batteries. To do this, the AC power is supplied to the on-board charger from the power grid and the on-board charger converts the AC power into a DC power that can be used to charge the energy storage system of the electric vehicle.

However, one of the main issues of this technology is still the limited range of electric vehicles, wherein a particular issue is considered to be the risk that the electric vehicle could run out of electric charge in a remote location where there is no access to a charging station. A possible solution to reduce this issue is to provide a vehicle-to-vehicle charging. Such a possibility allows an electric vehicle to charge another vehicle, typically via its on-board chargers. For this purpose, a possible source vehicle, the electric vehicle acting as an energy source, must comprise a bi-directional on-board charger that allows current to flow both into and out of the electric vehicle. Examples of on-board chargers are disclosed in the prior art documents <CIT>, <CIT>, <CIT> and a publication titled "Vehicle electrification: Technologies, Challenges, and a Global Perspective for Smart Grids | IntechOpen" of <NUM> November <NUM>. Such an electric vehicle comprising a bi-directional on-board charger is able to supply AC power to the input/interface of the electric vehicle and, via a charging cable, may supply the load electric vehicle, the elective vehicle with an empty battery, with electricity. The on-board charger of the load electric vehicle can be either also a bi-directional or a unidirectional on-board charger.

In view of this, it is found that a further need exists to improve a vehicle-to-vehicle charging. In particular there is a further need to increase the charging efficiency when charging from vehicle-to-vehicle.

In the view of the above, it is an object of the present invention to provide a method as set out in the appended claim <NUM>, a computer program as set out in claim <NUM>, a vehicle as set out in the appended independent claim <NUM> and a system as set out in the appended independent claim <NUM> allowing an improved vehicle-to-vehicle charging. It is in particular an object of the present invention to provide an increased charging efficiency when charging from vehicle-to-vehicle.

These and other obj ects, which become apparent upon reading the following description, are solved by the subject matter of the independent claims. The dependent claims refer to preferred embodiments of the invention.

According to a first aspect, a method for vehicle-to-vehicle charging of electric vehicles is provided. The method comprises the following steps: providing a three phase bi-directional on-board charger of a first electric vehicle comprising at least one power factor correction unit and at least one isolated DC-DC converter, wherein the power factor correction unit comprises switches; providing a multi-port unit; switching the switches of the power factor correction unit of the bi-directional on-board charger of the first electric vehicle such that a DC power is provided at a first terminal L1 and a second terminal L2 of the three phase bi-directional on board-charger of the first electric vehicle ; and transferring the DC power from the first terminal of the first electric vehicle to an energy storage system of a second electric vehicle and from the second terminal L2 of the first electric vehicle to an energy storage system of a third electric vehicle;. The first electric vehicle is connected to the second electric vehicle and to the third electric vehicle by means of the multi-port unit. The multi-port unit is configured to provide a communication between the first electrical vehicle and the second electrical vehicle and the third electrical vehicle and comprises a common neutral conductor.

The present disclosure is based on the finding that in a known vehicle-to-vehicle charging situation, the efficiency of such a charging is comparable low due to the losses when directing the charge through the on-board chargers of both electric vehicles in the intended way, i.e. converting the DC power of the energy storage system of the source electric vehicle into an AC power providing it to the AC inlet of the source electric inlet and converting the transmitted AC power in the load electric vehicle into a DC power for charging the energy storage system of the load electric vehicle. In <FIG>, a schematic illustration of such a known vehicle-to-vehicle charging situation is shown. For example, in case a source electric vehicle <NUM> comprises an <NUM> kW bi-directional on-board charger <NUM> connected to an energy storage system <NUM>, e.g. a high voltage battery <NUM>, and a load electric vehicle <NUM> comprises an <NUM> kW uni-directional on-board charger <NUM> connected to an energy storage system <NUM>, e.g. a high voltage battery <NUM>. The source electric vehicle <NUM> provides AC power at its AC inlet <NUM>, which is transmitted to the AC inlet <NUM> of the load electric vehicle <NUM> via a charging cable <NUM>. Thereby, the load electric vehicle <NUM> may charge its energy storage system <NUM>, similar to when the load electric vehicle <NUM> would be connected to a power grid via a charging station. In praxis, the typical efficiency for known uni-directional on-board chargers and known bi-directional on-board chargers are around <NUM>%. Thus, in such an example, the overall efficiency during this charging will be <NUM> x <NUM> = <NUM>, i.e. <NUM>%, wherein cable losses are negligible relative to the losses in the on-board chargers. As a result, in such a system about <NUM>% losses may occur, i.e. <NUM>% from each on-board charger.

In contrast to this known vehicle-to-vehicle charging, the present disclosure proposes to provide a DC power to the AC inlet of the first electric vehicle and to bypass the on-board charger of the second electric vehicle such that the DC power of an insulated DC-DC converter of the first on-board charger may be directly provided to the energy storage system of the second electric vehicle. According to the invention, a DC power may be provided to the AC inlet of the first electric vehicle by controlling the bi-directional on-board charger of the first electric vehicle to provide DC power from the energy storage system of the first electric vehicle by switching the switches of a power factor correction unit of the bi-directional on-board charger of the first electric vehicle such that that at least a DC+ and a DC- line being provided at AC inlet of the first electric vehicle. Thereby, it is possible that the provide DC power bypasses the on-board charger of the second electric vehicle and the DC power provided by the first/source electric vehicle may charge a high voltage battery of the second electric vehicle. Thereby a higher overall charging system efficiency may be provided. For example, in the above mentioned example, the efficiency may remain at <NUM>%, i.e. <NUM>% higher than the efficiency in the conventional charging method.

In an implementation, the step of controlling the bi-directional on-board charger of a first electric vehicle to provide a DC power from the energy storage system of the first electric vehicle at an electric vehicle inlet may comprise: controlling a charging current by the bi-directional on-board charger of the first electric vehicle. In an example, a data/control communication may be provided by means of a Powerline Communication (PLC) or CAN communication. The on-board charger of the first vehicle may control the charging current to the second/load electric vehicle by regulating the primary side of its isolated DC-DC converter, wherein the Powerline Communication protocol can be used to facilitate the charging between the electric vehicles.

In an implementation, the charging current may be controlled by controlling an isolated DC-DC converter of the bi-directional on-board charger of a first electric vehicle. In the known vehicle-to-vehicle charging, the on-board charger of the source electric vehicle may generate AC power which is fed to the load electric vehicle. However, in this implementation the source vehicle may generate DC power using the same topology. The generated DC power may then fed to the load electric vehicle's high voltage battery directly, rather than having to pass through its on-board charger. The on-board charger of the source electric vehicle may control the charging current to the first electric vehicle by regulating the primary side its isolated DC-DC converter.

In an implementation, the second electric vehicle may comprise a DC inlet, preferably being selected from: a CCS interface, a CHAdeMO interface and/or a GB/T interface. These interfaces comprise a DC inlet allowing to bypass the on-board charger of the second electric vehicle and directly provide the DC power to the energy storage system of the second electric vehicle.

According to the invention, the bi-directional on-board charger comprises at least one power factor correction unit and at least one isolated DC-DC converter.

According to a second aspect, an electric vehicle is provided which is configured to carry out a method described above, comprising: a multi-port unit and at least one three phase bi-directional on-board charger comprising at least one power factor correction unit and at least one isolated DC-DC converter; the power factor correction unit comprising switches. configured to be switched such that from the isolated DC-DC converter to the electric vehicle inlet at least a DC+ and a DC- line being provided. The on-board charger is configured to provide a DC power from an energy storage system of the electric vehicle at a first terminal L1 and a second terminal L2 of the three phase bi-directional on board-charger of electric vehicle by switching the switches of the power factor correction unit. The electric vehicle is connectable to a second electric vehicle and to a third electric vehicle by means of the multi-port unit. The multi-port unit comprises a common neutral conductor. The multi-port unit is configured to provide a communication between the electrical vehicle and the second electrical vehicle and the third electrical vehicle.

According to a third aspect, which is not a part of the present invention, a use of an on-board charger is proposed comprising at least one power factor correction unit and at least one isolated DC-DC converter in an electric vehicle described above. A further aspect, which is also not a part of the present invention, relates to a use of a charging cable for connecting two electric vehicles in a method described above.

A further aspect relates to a control unit for controlling a bi-directional on-board charger of an electric vehicle to provide DC power from the energy storage system of the electric vehicle at an electric vehicle inlet configured to switch the switches of a power factor correction unit of the bi-directional on-board charger to provide at least a DC+ and a DC- line at the electric vehicle inlet of the electric vehicle. A further aspect relates to a computer program element which when executed by a processor is configured to carry out steps: causing switching of switches of a power factor correction unit of a bidirectional on-board charger of a first electric vehicle such that a DC power is provided at a first terminal L1 and a second terminal L2 of a three phase bi-directional on board-charger of the first electric vehicle; and causing a transfer of the DC power from the first terminal L1 of the first electric vehicle to an energy storage system of a second electric vehicle, and from the second terminal L2 of the first electric vehicle to an energy storage system of a third electric vehicle, of a method described above.

Moreover, a further aspect relates to a system for a vehicle-to-vehicle charging configured to carry out the method for charging vehicle-to-vehicle described above, comprising: a bi-directional on-board charger of a first electric vehicle; an energy storage system of the first electric vehicle; an energy storage system of the first electric vehicle; an energy storage system of a second electric vehicle; a control unit configured to control the bi-directional on-board charger of the first electric vehicle to provide a DC power from the energy storage system of the first electric vehicle at an electric vehicle inlet of the first electric vehicle; a charging cable configured to transfer the DC power to an electric vehicle inlet of a second electric vehicle; an on-board charger of the second electric vehicle configured to transfer the DC power from the electric vehicle inlet of the second electric vehicle directly to an energy storage system of the second electric vehicle. In an implementation of the system, the control unit may be configured to control the charging of the energy storage system of the second electric vehicle.

A further aspect relates to a method for vehicle-to-vehicle charging for electric vehicles, controlling a three phase bi-directional on-board charger of a first electric vehicle to provide a DC power from an energy storage system of the first electric vehicle at a first terminal L1 and a second terminal L2 of the three phase bi-directional on board-charger of the first electric vehicle; transferring the DC power from the first terminal L <NUM> of the first electric vehicle to an energy storage system of the second electric vehicle, and from the second terminal L2 of the first electric vehicle to an energy storage system of the third electric vehicle. This may be advantageous as two electric vehicles (i.e. the second and the third electric vehicle) may be charged in parallel by one electric vehicle, i.e. the first vehicle. In this aspect, all above explained explanations with respect to the electric vehicles, the specifics of the bi-directions on board charger of the first electric vehicle also apply here. In the following, only the specifics with respect to this aspect, i.e. a method for charging more than one vehicle by means of the first vehicle, are explained in more detail.

In an implementation, the second electric vehicle and the third electric vehicle are charged simultaneously.

In an implementation, a voltage range of the energy storage system of the second electric vehicle and of the third electric vehicle is smaller than a voltage range of the energy system of the first electric vehicle.

In an implementation, the voltage range of the energy storage system of the second electric vehicle and the voltage range of the energy storage system of the third electric vehicle are different.

According to the invention, the first electric vehicle is connectable to the second electric vehicle and to the third electric vehicle by means of the multi-port unit, wherein the multi-port unit comprises a common neutral conductor and wherein the multi-port unit is configured to provide a communication between the first electrical vehicle and the second electrical vehicle and the third electrical vehicle. The term communication means, as used herein, the exchange of data (e.g. control signal) and electric energy.

In an implementation, the energy storage system of a fourth electrical vehicle is charged by the first electrical vehicle simultaneously to the second electrical vehicle and third electrical vehicle.

A further aspect relates to a system for a vehicle-to-vehicle charging configured to carry out the method for charging vehicle-to-vehicle as described above, comprising: a three phase bi-directional on-board charger of a first electric vehicle; an energy storage system of the first electric vehicle; an energy storage system of a second electric vehicle; an energy storage system of a third electric vehicle; a multi-port unit configured to connect the three phase bi-directional on-board charger of the first electric vehicle and the energy storage system of the second electric vehicle and the energy storage system of a third electric vehicle; a control unit configured to control the three phase bi-directional on-board charger of the first electric vehicle to provide a DC power from the energy storage system of the first electric vehicle at a first terminal L <NUM> and a second terminal L2 of the three phase bi-directional on board-charger of the first electric vehicle.

A further aspect relates to a use of a multi-port unit in a method as described above or in a system as described above. being selected from: a CCS interface, a CHAdeMO interface and/or a GB/T interface. These interfaces comprise a DC inlet allowing to also bypass the on-board charger of the second electric vehicle and directly provide the DC power to the energy storage system of the second electric vehicle. In this respect, it is preferred that the connector between the two electric vehicles comprises a Type <NUM>/Type <NUM> interface to the source electric vehicle and a CCS DC/ CHAdeMO/ GBT DC interface to the load electric vehicle.

In another implementation, a method for vehicle-to-vehicle charging for electric vehicles is provided, comprising: controlling a three phase bi-directional on-board charger of a first electric vehicle to provide a DC power from an energy storage system of the first electric vehicle at a first terminal L1 (<NUM>) of the three phase bi-directional on board-charger, transferring the DC power from the first terminal L1 (<NUM>) of the first electric vehicle to an energy storage system (<NUM>) of the second electric vehicle. the first electric vehicle has a 800V energy storage system and the second electric vehicle has a 400V energy storage system. The switches of the three phase bi-directional on board charger are switched such that the L2 and L3 phases are connected to L1. A DC-DC converter of the three phase bi-directional on-board charger may operate as a regulated 800V-400V DC-DC converter and may charge the energy storage system of the second vehicle. A L1 phase terminal and a neutral terminal may be connected to the DC+ and DC- terminal of the energy storage system of the second vehicle in order to charge the <NUM> Volt energy storage system. In other words, the three phase bi-directional on board charger is used as step-down converter here.

In the following, the disclosure is described exemplarily with reference to the enclosed figure, in which.

Notably, the figures are merely schematic representations and serve only to illustrate an embodiment of the present disclosure.

<FIG> is a schematic view of a known bi-directional on-board charger <NUM> comprising a power factor correction (PFC) <NUM> and an isolated DC-DC converter <NUM> which can be used in both the first/source electric vehicle and the second/load electric vehicle. A known on-board charger has two stage power conversion. The first stage may be connected to AC power grid and is responsible for keeping the power factor close to unity while charging, also known as power factor correction (PFC) <NUM>. The second stage is an isolated DC-DC converter <NUM>, which may regulate the current and voltage in order to charge an energy storage system <NUM>, e.g. a high-voltage (HV) battery <NUM>, as shown in <FIG>. Apart from controlling the charging operation, the second stage also provides isolation from the AC input, and is typically implemented as a full bridge LLC resonator or phase shifted full bridge circuit.

<FIG> is a schematic topology of the single-phase bi-directional on-board charger <NUM>. The power stages for both uni-directional and bi-directional are principally the same, but in bi-directional operation a power factor correction <NUM> may generate either three phase or single phase AC voltages. To achieve bi-directionality from the same power stages, the bi-directional on-board charger <NUM> may be equipped with active switches S1-S4 instead of diodes usually used in uni-directional on-board chargers.

In known vehicle-to-vehicle charging, the on-board charger <NUM> inside the first/source electric vehicle generates AC power, which is fed to the second/load electric vehicle. However, in the shown embodiment, it is proposed that the source vehicle generates DC power using the same topology by permanently closing the power factor correction <NUM> MOSFETs S1 and S4, or S2 and S3. Thereby, the power factor correction <NUM> MOSFETs may be used as two wires to connect to the isolated DC-DC converter <NUM> primary side. The equivalent circuit after closing the MOSFETs S1 and S4 is shown in <FIG>. Now the switches S1 and S4 switch lines may act as DC+ and DC-, respectively. Similarly by closing the MOSFETs S2 and S3 and opening S1 and S4, the on-board charger <NUM> may generate DC power but in the opposite polarity. Either of these combinations can be used.

The generated DC power may then be fed to the second electric vehicle's HV battery directly, rather than having to pass through its on-board charger. The on-boards charger of the first vehicle may control the charging current to the first electric vehicle by regulating the primary side of its isolated DC-DC converter shown in <FIG>. In this respect, a Powerline Communication or CAN communication may be used DC charging, and can be used to facilitate the charging between the electric vehicles. In this way, the electric power from the first vehicle will only pass through one on-board charger and thereby the power losses can be reduced to half. Such an implementation is compatible with both single and three phase configurations. If there are three phases, the AC side of the on-board charger may be reconfigured to single phase through the use of AC relays in order to transfer full power. There are no additional components or modules required in the shown implementation.

In an implementation, the second electric vehicle may comprise a DC inlet, preferably being selected from: a CCS interface, a CHAdeMO interface and/or a GB/T interface. These interfaces comprise a DC inlet allowing to also bypass the on-board charger of the second electric vehicle and directly provide the DC power to the energy storage system of the second electric vehicle. In this respect, it is preferred that the connector between the two electric vehicles comprises a Type <NUM>/Type <NUM> interface to the source electric vehicle and a CCS DC/ CHAdeMO/ GBT DC interface to the load electric vehicle.

However, it is also possible that the parties use a conventional Type <NUM>/Type <NUM> charging cable, which usually comes standard with most electric vehicles. In such a situation, the DC power from source electric vehicle may transfer electric power through an on-board charger <NUM> of a load electric vehicle as shown in <FIG>. The load electric vehicle may still have either a uni-directional or a bi-directional on-board charger. If the load electric vehicle is using a known uni-directional diode rectifier <NUM>, once the DC power is applied, the diodes D1 and D4 or D2 and D3 will conduct depends on the polarity of voltage. The power factor correct <NUM> MOSFETs may be turned off as the voltage on the load electric vehicle's input is already high enough to charge the energy storage system, e.g. the high voltage battery <NUM> and it can be fully regulated by the source electric vehicle's on-board charger, when used as shown in <FIG>. After the power factor corrector <NUM> capacitor, the power may flow through the isolated DC-DC converter <NUM> of the load electric vehicle to charge the high voltage battery <NUM> of the load electric vehicle. In such a way, the load electric vehicle on-board charger <NUM> may be also used as DC-DC converter <NUM> but the overall charging efficiency is in practice just under <NUM>%.

<FIG> is a schematic view of a system <NUM> used in an embodiment of the present disclosure. The system is used for a vehicle-to-vehicle charging configured to carry out a method as described above. The system <NUM> comprises a three phase bi-directional on-board charger (<NUM>) of a first electric vehicle, an energy storage system (<NUM>) of the first electric vehicle, an energy storage system (<NUM>) of a second electric vehicle, an energy storage system (<NUM>) of a third electric vehicle, a multi-port unit (<NUM>) configured to connect the three phase bi-directional on-board charger (<NUM>) of the first electric vehicle and the energy storage system (<NUM>) of the second electric vehicle and the energy storage system (<NUM>) of a third electric vehicle, a control communication between the first vehicle to other vehicles may also be taken care by multi-port unit (<NUM>).

<FIG> is a schematic view of a three phase on board charger (<NUM>) of a first electric vehicle used to charge an energy storage system (<NUM>) of a second electric vehicle. The energy storage system (<NUM>) of the first electric vehicle has 800V. The energy storage system (<NUM>) of the second electric vehicle has 400V. The three-phase full bridge semiconductor switches S1, S2 & S3 are turned-ON and the relays R1 & R2 are switched such that L2 & L3 phases are connected to L1. The relay R3 is connected to mid-point of two capacitors. Each capacitor is rated for at least 500V. In this case, the DC-DC converter of three phase on-board charger inside first electric vehicle operates as a regulated 800V-400V DC-DC converter and charges the second electric vehicle, which is having 400V battery. The first vehicle L1 & Neutral terminals are connected to DC+ & DC- (<NUM>, <NUM>) of the second electric vehicle in order to charge the 400V energy storage system (<NUM>). The main contactors <NUM> & <NUM>, DC charging contactors <NUM> & <NUM> inside the second vehicle are turned ON to charge the 400V energy storage system (<NUM>).

<FIG> is another schematic view of a three phase on-board charger (<NUM>) of first vehicle used to charge a second electric vehicle. In comparison to the description presented in <FIG>, the three phase on-board charger does not support the full voltage range of the energy storage system of the second electric vehicle. For this operation, the relays R1 & R2 are switched to connect to L1, relay R3 is switched to connect to the common source point of S4, S5 & S6. The switches S1, S4 & inductor LA together operated as a first step-down DC-DC converter. The switches S2, S5 & inductor LB together operated as a second step-down DC-DC converter and S3, S6 & inductor LC operated as a third step-down DC-DC converter. These three step-down converters are connected to L1, and there will be a <NUM> deg. phase shift angle between them to reduce the inductor current ripple. The three phase on-board charger of the first electric vehicle operates as a two stage DC-DC converter to charge the energy storage system (<NUM>) of the second electric vehicle with any voltage range window either it can be a 400V energy voltage system or a 800V energy storage voltage system as long as the actual energy storage system voltage of the second electric vehicle is always lower than actual energy storage system voltage of the first electric vehicle. The first electric vehicle L1 & Neutral terminals are connected to DC+ & DC-(<NUM>, <NUM>) of the second electric vehicle in order to charge the 400V energy storage system (<NUM>). The first electric vehicle can also charge from a second electric vehicle. In this case, the switches S <NUM>, S4 & inductor LA operates as a first step-up DC-DC converter. The switches S2, S5 & inductor LB operates as a second step-up DC-DC converter and similarly the switches S3, S6 & inductor LC operates as a third step-up DC-DC converter. These three step-up DC-DC converters are having a <NUM> deg. phase shift to reduce the total current ripple.

As a result, the present disclosure provides vehicle-to-vehicle charging with reduced losses resulting in a greater efficiency and lower charging times without the need of providing additional component. This is because, it is possible, e.g. by means of switching/controlling the switches of the power factor correction of the on-board charger of the first/source electric vehicle, that the DC power of the isolated DC-DC converter can be provided to the AC inlet of the first electric vehicle and then transmitted to the AC inlet of the second/load electric vehicle from which it can be directly provided to the energy storage system of the second electric vehicle.

Claim 1:
A method for vehicle-to-vehicle charging for electric vehicles, comprising the steps:
providing a three phase bi-directional on-board charger (<NUM>) of a first electric vehicle (<NUM>) comprising at least one power factor correction unit (<NUM>) and at least one isolated DC-DC converter, wherein the power factor correction unit (<NUM>) comprises switches (S1-S4),
providing a multi-port unit (<NUM>),
switching the switches (S1-S4) of the power factor correction unit (<NUM>) of the bi-directional on-board charger (<NUM>) of the first electric vehicle (<NUM>) such that a DC power is provided at a first terminal L1 (<NUM>) and a second terminal L2 (<NUM>) of the three phase bi-directional on board-charger (<NUM>) of the first electric vehicle; and
transferring the DC power from the first terminal L1 (<NUM>) of the first electric vehicle to an energy storage system (<NUM>) of a second electric vehicle, and from the second terminal L2 (<NUM>) of the first electric vehicle to an energy storage system (<NUM>) of a third electric vehicle,
wherein the first electric vehicle (<NUM>) is connectable to the second electric vehicle (<NUM>) and to the third electric vehicle by means of the multi-port unit (<NUM>), wherein the multi-port unit (<NUM>) comprises a common neutral conductor (<NUM>) and wherein the multi-port unit (<NUM>) is configured to provide a communication between the first electrical vehicle (<NUM>) and the second electrical vehicle (<NUM>) and the third electrical vehicle.