Vehicle having power circuit arrangement and two electric drive units, and method for operating same

Abstract

The invention relates to a vehicle (1) having a power circuit arrangement (2), the power circuit arrangement (2) having a traction battery (4), an electrical terminal (5) for electrical connection to an external power unit (3), a first high-voltage potential (P1) and a second high-voltage potential (P2), the first high-voltage potential (P1) being a positive high-voltage potential and the second high-voltage potential (P2) being a negative high-voltage potential, or vice versa. In this case, the circuit arrangement (2) has two electric drive units (A1, A2), each having an inverter (I1, I2) and a three-phase electric motor (M1, M2) electrically connected thereto, for driving the vehicle (1), and the circuit arrangement is designed such that the two electric drive units (A1, A2) are electrically connected to the inverter (I1, I2). The electrical drive unit (A1, A2) can be electrically connected in series between the electrical connection (5) and the traction battery (4) in such a way that, from the electrical connection (5) towards the traction battery (4), the first electrical drive unit (A1) increases a first high-voltage potential (P1) and the second electrical drive unit (A2) increases a second high-voltage potential (P2). According to the invention, the inverters (I1, I2) each have a respective capacitor (C1, C2) between the potential line (PL1) of the first high-voltage potential (P1) and the potential line (PL2) of the second high-voltage potential (P2), the circuit arrangement (2) being designed such that the second electric drive unit (A2) can be electrically connected in series to the capacitor terminals of the first electric drive unit (A1).

Description

Technical Field

[0001] The invention relates to a vehicle and a method for operating the vehicle according to the preamble of claim 1. Background Art

[0002] As a document that embodies the essence of the technology type, DE 10 2018 000 465 A1 describes an electric drive system for a vehicle, which includes a battery and two inverters, wherein the battery has two different electrochemical local areas, and each inverter can be electrically connected or electrically connected to a corresponding local area of ​​the battery. To this end, the electric drive system includes two three-phase AC motors, which can be electrically connected or electrically connected to the corresponding inverters, wherein the star points of the three-phase AC motors can be electrically connected or electrically connected to the charging contacts of the DC charging terminals of the electric drive system.

[0003] DE 10 2019 209 786 A1 discloses a system for charging an electric storage device via an electric drive system. In order to electrically isolate the voltage source from the electric storage device to be charged, an inductive coupling between the phase windings or phase lines of the electric machine is provided. For this purpose, the phase windings of the electric machine can be divided into two groups, each of which has a separate star point. Each star point is provided with an independent bridge circuit consisting of a capacitor, a diode or a semiconductor switch.

[0004] Document DE 10 2021 003 851 A1 also relates to an electric drive system for a vehicle, which has a three-phase AC motor, a battery, an inverter of the three-phase AC motor, and a charging terminal for connecting the battery to a charging unit. The switching device has a first switching state, in which the charging terminal is electrically connected to the battery, and the inverter is electrically isolated from the charging terminal and the battery. In the second switching state of the switching device, the charging terminal is electrically connected to the inverter and the battery, and in the third switching state in the switching device, the inverter is electrically connected to the battery, and the charging terminal is electrically isolated from the battery and the inverter.

[0005] In addition, in the prior art, for example, DE 10 2017 009 352 A1 discloses an energy coupler for electrically coupling a vehicle power supply and a vehicle power supply electrically coupling method. The energy coupler is used to electrically couple a first vehicle power supply loaded with a first DC voltage to a second vehicle power supply loaded with a second DC voltage, and has a first and a second periodic energy converter, which respectively have a vehicle power supply terminal and an intermediate circuit terminal. The vehicle power supply terminal of the first periodic energy converter is connected to the first vehicle power supply, and the vehicle power supply terminal of the second periodic energy converter is connected to the second vehicle power supply. The intermediate circuit terminals of the first and second periodic energy converters are connected to a common DC voltage intermediate circuit. The first potential of the DC voltage intermediate circuit is electrically connected to one of the potentials of the first vehicle power supply by means of the first periodic energy converter. The second potential of the DC voltage intermediate circuit is electrically connected to one of the potentials of the second vehicle power supply by means of the second periodic energy converter.

[0006] DE 10 2018 009 840 A1 describes a circuit arrangement for a hybrid vehicle or an electric vehicle. The circuit arrangement comprises a high-voltage battery for storing electrical energy, at least one electric motor for driving the hybrid vehicle or the electric vehicle, a converter capable of converting a high-voltage direct voltage that can be provided by the high-voltage battery into a high-voltage alternating voltage for operating the electric motor, and a charging terminal for providing electrical energy to charge the high-voltage battery. The converter is designed as a three-level converter.

[0007] DE 10 2018 009 848 A1 discloses a circuit device for a hybrid vehicle or an electric vehicle. The circuit device includes a high-voltage battery for storing electrical energy, at least one motor for driving the hybrid vehicle or the electric vehicle, a converter capable of converting a high-voltage DC voltage provided by the high-voltage battery into a high-voltage AC voltage for operating the motor, and a charging terminal for providing electrical energy to charge the high-voltage battery. The converter is designed as a three-level converter and has at least one switching unit assigned to a motor phase, the switching unit including two switch groups connected in series, each switch group having two IGBTs connected in series, wherein a terminal directly electrically connected to a charging terminal wire is provided between the IGBTs of one of the switch groups.

[0008] DE 10 2019 005 621 A1 describes an on-board power supply for an electric vehicle. The on-board power supply comprises a vehicle battery, a multiphase motor and an inverter electrically connected to the vehicle battery, the inverter comprising a series circuit corresponding to each of the motors, each series circuit consisting of respective switching units connected in series. The switching units of each series circuit provide respective central terminals, to which respective phase windings of the motor are connected. The inverter is designed as a three-level inverter, wherein each of the switching units has a series circuit consisting of two switching elements connected at a connection point. In the case of two switching units of at least one of the series circuits, an inductor is connected at each connection point, the inductor having a respective first terminal. The respective second terminals of the inductors can be electrically coupled to the DC voltage charging terminals of the motor vehicle.

[0009] DE 10 2018 000 488 A1 describes a vehicle electric drive system and an operating method thereof. The electric drive system comprises at least one three-phase AC motor and a battery for supplying power to the three-phase AC motor. The three-phase AC motor can be electrically connected or is electrically connected to the battery via an inverter. A star point of the three-phase AC motor can be electrically connected or is electrically connected to a positive terminal of a DC charging terminal of the electric drive system, and a negative terminal of the battery can be electrically connected or is electrically connected to a negative terminal of a DC charging terminal of the electric drive system.

[0010] DE 10 2009 052 680 A1 describes a charging device for charging a motor vehicle battery using a step-down chopper. The charging device comprises an electric motor for driving the motor vehicle and a drive converter for converting the DC voltage of the battery to the electric motor during the driving operation of the motor vehicle. The electric motor and the drive converter are used together as a step-up chopper required for the battery charging operation. A step-down chopper is provided before the step-up chopper for reducing the input DC voltage to a sufficient degree so that it becomes a charging voltage suitable for the battery after being stepped up by the step-up chopper.

[0011] DE 10 2018 000 580 A1 discloses an onboard power supply with an inverter and a DC voltage transformer, which has an energy storage element in the negative path. The onboard power supply of a motor vehicle that can be operated partially or completely electrically comprises an electric power inverter, by means of which an AC voltage can be generated from a DC voltage for a first operating state of the motor vehicle and a DC voltage can be generated from the AC voltage for a second operating state of the motor vehicle, and the onboard power supply also comprises at least one electrically coupled DC voltage transformer connected to the power inverter on the DC voltage side of the power inverter. The at least one DC voltage transformer has a cycleable energy storage element, which is connected in the negative path of the at least one DC voltage transformer. Summary of the invention

[0012] The object of the present invention is to specify a vehicle which is improved compared to the prior art and a method for operating a vehicle which is improved compared to the prior art.

[0013] This object is achieved according to the invention by a vehicle having the features of claim 1 and a method for operating a vehicle having the features of claim 6 .

[0014] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0015] A vehicle has an electric circuit arrangement. The circuit arrangement comprises a traction battery, an electrical connection terminal for electrical connection to an off-board power unit, a first high voltage potential and a second high voltage potential, wherein the first high voltage potential is a positive high voltage potential and the second high voltage potential is a negative high voltage potential, or vice versa. The term "high voltage" (abbreviated HV) refers in particular to a DC voltage, in particular greater than approximately 60 volts. The term "high voltage" is to be interpreted in particular in accordance with the ECE R 100 standard.

[0016] According to the invention, the circuit arrangement comprises two electric drive units, each of which has an inverter and a three-phase AC motor electrically connected thereto for driving the vehicle. The traction battery is provided in particular for supplying the drive units with electrical energy for driving the vehicle.

[0017] According to the invention, the power circuit arrangement is designed in such a way that the two electric drive units can be electrically connected in series between the electrical connection and the traction battery, so that from the electrical connection toward the traction battery, the first electric drive unit increases the first high voltage potential and the second electric drive unit increases the second high voltage potential. In the opposite direction, i.e. from the traction battery toward the electrical connection, the first electric drive unit correspondingly reduces the first high voltage potential and the second electric drive unit reduces the second high voltage potential. The solution according to the invention therefore provides a DC voltage transformer between the electrical connection and the traction battery, which is formed by the two electric drive units (i.e. the circuit described therein) and operates in the described manner. The terms "increase" and "reduce" here each relate to the absolute value of the respective potential voltage relative to a reference potential (in particular ground potential), i.e. regardless of the sign.

[0018] The solution according to the invention thus allows the use of an electric drive unit already present in the vehicle as a DC voltage transformer and thus for additional application purposes. This makes it possible, in particular, to charge the traction battery via an off-board power unit which is electrically connected to the electrical connection and is designed as a DC charging station and whose charging voltage is lower than the nominal voltage of the traction battery. In addition, reverse supply, also known as buck mode, is also possible. In this case, electrical energy is supplied from the traction battery to the off-board power unit which is electrically connected to the electrical connection, for example, in order to feed the traction battery electrical energy into a public power supply network or a building power supply network, in particular via a DC charging station which is electrically connected to the electrical connection. This bidirectional supply is also referred to as bidirectional charging. By means of the solution according to the invention, it is not necessary to provide an additional DC voltage transformer in the vehicle for this purpose, thereby achieving corresponding savings in construction space, weight and costs. With the solution according to the invention, other solutions are no longer necessary to achieve charging of the traction battery at a lower charging voltage, for example, to design the traction battery as a reversible battery and to achieve charging by changing the circuit of the battery modules of the traction battery.

[0019] In the vehicle operating method according to the invention, provision is accordingly made that in order to charge the traction battery via an off-board power unit electrically connected to the electrical terminals, designed as a DC charging station and having a charging voltage lower than the nominal voltage of the traction battery, and / or in order to supply electrical energy to the off-board power unit electrically connected to the electrical terminals via the traction battery, the two electric drive units are electrically connected in series between the electrical terminals and the traction battery.

[0020] The solution according to the invention makes it possible, for example, to charge an 800 V traction battery at a DC charging station with a charging voltage of, for example, 400 V or 500 V.

[0021] The solution according to the invention can also meet the safety requirements related to insulation overload in DC charging stations, realize an unrestricted insulation monitor function, and cut off the traction battery short circuit caused by insulation defects in the vehicle.

[0022] According to the invention, each inverter has a corresponding capacitor between the potential line of the first high voltage potential and the potential line of the second high voltage potential. The circuit arrangement is designed in this case so that the second electric drive unit can be electrically connected in series with the capacitor connection of the first electric drive unit.

[0023] In one possible embodiment, it is provided that the potential line of the inverter of the second electric drive unit is electrically connected to the capacitor terminal contact of the capacitor terminal of the inverter of the first electric drive unit with the same high voltage potential. In order to realize the above-mentioned electrical series connection of the two drive units, it is provided, for example, that the circuit device is designed in such a way that the star point of the three-phase AC motor of the second electric drive unit can be electrically connected to another capacitor terminal contact of the capacitor terminal of the inverter of the first electric drive unit, the potential line of the inverter electrically connected to this capacitor terminal contact can be electrically connected to the terminal contact of the electrical terminal with the same high voltage potential, and a star point of the three-phase AC motor of the first electric drive unit can be electrically connected to another terminal contact of the electrical terminal. Alternatively, in order to realize the above-mentioned electrical series connection of the two drive units, it is provided, for example, that the circuit device is designed in such a way that the winding terminal of the three-phase AC motor of the second electric drive unit can be electrically connected to another capacitor terminal contact of the capacitor terminal of the inverter of the first electric drive unit, the potential line of the inverter electrically connected to this capacitor terminal contact can be electrically connected to a terminal contact of the electrical terminal having the same high voltage potential, and one winding terminal of the three-phase AC motor of the first electric drive unit can be electrically connected to the other terminal contact of the electrical terminal.

[0024] In particular, it is provided that the traction battery is electrically connected to the capacitor terminals of the second electric drive unit. Furthermore, in particular for realizing the basic function of the electric drive unit, namely driving the vehicle, it is advantageously provided that the circuit arrangement is designed in such a way that the traction battery can be electrically connected to the capacitor terminals of the first electric drive unit. As a result, the two electric drive units can be supplied with electrical energy via the traction battery. In the vehicle operating method, it is provided that for driving the vehicle, the two inverters are each directly connected to the traction battery.

[0025] In one possible embodiment of the vehicle, it is provided that the circuit arrangement is designed in such a way that the electrical connection terminal can be electrically connected directly to the traction battery. This also allows the traction battery to be charged by an off-board power unit which is electrically connected to the electrical connection terminal and is designed as a DC charging station and whose charging voltage is at least equal to the nominal voltage of the traction battery. In the vehicle operating method, it is correspondingly provided that the electrical connection terminal is electrically connected directly to the traction battery in order to charge the traction battery by an off-board power unit which is electrically connected to the electrical connection terminal and is designed as a DC charging station and whose charging voltage is at least equal to the nominal voltage of the traction battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The embodiments of the present invention will be explained in detail below with reference to the drawings, wherein:

[0027] Figure 1 An embodiment of a vehicle having a switching device is schematically shown.

[0028] Figure 2Schematically shows the charging operation through Figure 1 The current generated by the switching device,

[0029] Figure 3 Schematically shows the charging operation through Figure 1 The current of the switching device is no-load,

[0030] Figure 4 Schematic diagram showing the voltage drop during step-down operation. Figure 1 The current generated by the switching device,

[0031] Figure 5 Schematic diagram showing the voltage drop during step-down operation. Figure 1 The current of the switching device is no-load,

[0032] Figure 6 A further embodiment of a vehicle having a switching device is schematically shown.

[0033] Figure 7 Schematically shows the charging operation through Figure 6 The current generated by the switching device,

[0034] Figure 8 Schematically shows the charging operation through Figure 6 The current of the switching device is no-load,

[0035] Fig. 9 Schematic diagram showing the voltage drop during step-down operation. Figure 6 The current generated by the switching device,

[0036] Fig.10 Schematic diagram showing the voltage drop during step-down operation. Figure 6 The current of the switching device is no-load,

[0037] Fig.11 An example of a DC voltage transformation by means of a switching device is schematically shown,

[0038] Fig.12 A further example of a DC voltage transformation by means of a switching device is schematically shown,

[0039] Fig.13 A further example of a DC voltage transformation by means of a switching device is schematically shown,

[0040] Fig.14 Schematic diagram showing the short circuit in the vehicle Figure 1 implementation method,

[0041] Fig.15 Schematic diagram showing the short circuit in the vehicle Figure 6 implementation method.

[0042] Parts that correspond to one another are provided with the same reference symbols in all the figures. DETAILED DESCRIPTION

[0043] Figure 1 and Figure 6 Two embodiments of a vehicle 1 with a power circuit arrangement 2 are shown by way of example. In the two embodiments shown, the vehicle 1 is electrically connected to an off-board power unit 3 designed as a DC charging station. The internal resistance Rg of the DC charging station is also shown in each case.

[0044] The circuit arrangement 2 comprises a traction battery 4, wherein the internal resistance Rb of the traction battery 4 is also shown here, an electrical connection terminal 5 for electrical connection to an off-board power unit 3, a first high-voltage potential P1 and a second high-voltage potential P2. In the embodiment shown, the first high-voltage potential P1 is a positive high-voltage potential and the second high-voltage potential P2 is a negative high-voltage potential. In other embodiments, this can also be reversed.

[0045] Furthermore, the circuit arrangement 2 comprises two electric drive units A1 , A2 , each of which has an inverter I1 , I2 and a three-phase AC motor M1 , M2 electrically connected thereto for driving the vehicle 1 .

[0046] In both embodiments, the circuit arrangement 2 is designed such that the two electric drive units A1, A2 can be electrically connected in series between the electrical connection 5 and the traction battery 4 such that, from the electrical connection 5 toward the traction battery 4, the first electric drive unit A1 increases the first high voltage potential P1 and the second electric drive unit A2 increases the second high voltage potential P2, or decreases accordingly in the opposite direction. By means of this solution, the drive units A1, A2 connected in this way form a DC voltage transformer, which allows so-called bidirectional charging, i.e., in one direction, the traction battery 4 is charged by the off-board power unit 3 electrically connected to the electrical connection 5, designed as a DC charging station and having a charging voltage lower than the nominal voltage of the traction battery 4, and in the other direction, the off-board power unit 3 electrically connected to the electrical connection 5 is supplied with electrical energy by the traction battery 4.

[0047] The inverters I1, I2 each have an inverter circuit IS1, IS2, which in particular includes a plurality of inverter switching units IE1 to IE12, in particular semiconductor switching units and in particular transistors, in particular bipolar transistors with isolated gates, in particular each in combination with a diode in particular designed as an empty carrier diode, as shown here. The inverter circuits IS1, IS2 are in particular arranged between a potential line PL1 of a first high voltage potential P1 and a potential line PL2 of a second high voltage potential P2 of the respective inverters I1, I2. The three-phase AC motors M1, M2 of the respective drive units A1, A2 here have three motor windings U1, V1, W1, U2, V2, W2 in a star circuit, which are connected to the inverters I1, I2 of the drive units A1, A2 in the manner shown.

[0048] In addition, the inverters I1 and I2 have a capacitor C1 and C2 between their two potential lines PL1 and PL2, respectively. For the above-mentioned electrical series connection of the two drive units A1 and A2, the circuit device 2 is designed so that the second electric drive unit A2 can be electrically connected in series with the capacitor terminal of the first electric drive unit A1. For this purpose, one of the potential lines (here the first potential line PL1) of the inverter I2 of the second electric drive unit A2 is electrically connected to the capacitor terminal contact having the same high voltage potential (here the first high voltage potential P1) of the capacitor terminal of the inverter I1 of the first electric drive unit A1.

[0049] In addition, Figure 1 The first embodiment shown designs the circuit device 2 in such a way that the star point SP2 of the three-phase AC motor M2 of the second electric drive unit A2 can be electrically connected to another capacitor terminal contact of the capacitor terminal of the inverter I1 of the first electric drive unit A1, and the first switch S1 is closed for this purpose; the potential line PL2 of the inverter I1 electrically connected to this capacitor terminal contact can be electrically connected to a terminal contact of the electrical terminal 5 having the same high-voltage potential P2, and the second switch S2 is closed for this purpose; and the star point SP1 of the three-phase AC motor M1 of the first electric drive unit A1 can be electrically connected to another terminal contact of the electrical terminal 5, and the third switch S3 is closed for this purpose.

[0050] Or, in Figure 6In other embodiments shown, it is provided that one winding terminal of the three-phase AC motor M2 of the second electric drive unit A2 can be electrically connected to another capacitor terminal contact of the capacitor terminal of the inverter I1 of the first electric drive unit A1, and the first switch S1 is closed for this purpose; the potential line PL2 of the inverter I1 electrically connected to this capacitor terminal contact can be electrically connected to a terminal contact of the electrical terminal 5 having the same high voltage potential P2, and the second switch S2 is closed for this purpose; and one winding terminal of the three-phase AC motor M1 of the first electric drive unit A1 can be electrically connected to the other terminal contact of the electrical terminal 5, and the third switch S3 is closed for this purpose.

[0051] Furthermore, in both embodiments, it is provided that the traction battery 4 is electrically connected to the capacitor terminals of the second electric drive unit A2. This allows, on the one hand, the above-mentioned charging of the traction battery 4 and, on the other hand, driving of the vehicle 1. For driving, it is also provided that the circuit arrangement 2 is designed in such a way that the traction battery 4 can be electrically connected to the capacitor terminals of the first electric drive unit A1, for which purpose the fourth switch S4 is closed, and in the example shown, the second potential line PL2 of the inverter I1 of the first electric drive unit A1 is connected to the second high voltage potential P2 of the traction battery 4 via the fourth switch.

[0052] The circuit arrangement 2 also allows the traction battery 4 to be charged via an off-board power unit 3 which is electrically connected to the electrical terminal 5 and is designed as a DC charging station and whose charging voltage is at least equal to the nominal voltage of the traction battery 4. For this purpose, it is provided that the circuit arrangement 2 is designed such that the electrical terminal 5 can be directly electrically connected to the traction battery 4, in the two embodiments, by closing the fifth and sixth switches S5, S6, so that the high voltage potentials P1, P2 of the traction battery 4 and the off-board power unit 3 are directly connected via corresponding through-going potential lines PL1, PL2.

[0053] The switches S1 to S6 are each designed as a contactor, for example.

[0054] In accordance with Figure 1 and Figure 6 In both embodiments, an EMC output filter (EMC=electromagnetic compatibility) (not shown here) from vehicle 1 to the DC charging station can also be provided.

[0055] In order to charge the traction battery 4 via the off-board power unit 3 electrically connected to the electrical terminal 5 and designed as a DC charging station and having a charging voltage lower than the nominal voltage of the traction battery 4, and / or in order to supply electrical energy to the off-board power unit 3 electrically connected to the electrical terminal 5 via the traction battery 4, the two electric drive units A1 and A2 are electrically connected in series between the electrical terminal 5 and the traction battery 4. For this purpose, according to Figure 1 and Figure 6In the illustrated embodiment, the switches S1, S2 and S3 are closed, and the switches S4, S5 and S6 are opened.

[0056] In order to charge the traction battery 4 via the off-board power unit 3 which is electrically connected to the electrical terminal 5 and is designed as a DC charging station and whose charging voltage is at least equal to the nominal voltage of the traction battery 4, the electrical terminal 5 is directly electrically connected to the traction battery 4. Figure 1 and Figure 6 In the embodiment shown in , switches S5, S6 are closed. The switch positions of the other switches S1 to S4 are not important in this case, ie, they can each be open or closed.

[0057] For driving the vehicle 1, the two inverters I1, I2 are directly connected to the traction battery 4. Figure 1 and Figure 6 In the illustrated embodiment, the switch S4 is closed, and the other switches S1, S2, S3, S5, and S6 are open.

[0058] for Figure 1 or Figure 6 The respective embodiments are directed to the case where the traction battery 4 is charged by an off-board power unit 3 which is electrically connected to the electrical terminals 5 and is designed as a DC charging station and whose charging voltage is lower than the nominal voltage of the traction battery 4. Figure 2 and Figure 7 A current generation AB1 in the motor windings U1 , V1 , W1 of the first electric drive unit A1 is shown with solid arrows, and a current generation AB2 in the motor windings U2 , V2 , W2 of the second electric drive unit A2 is shown with dashed arrows.

[0059] For according to Figure 1 or Figure 6 The respective embodiments are directed to the case where the traction battery 4 is charged by an off-board power unit 3 which is electrically connected to the electrical terminals 5 and is designed as a DC charging station and whose charging voltage is lower than the nominal voltage of the traction battery 4. Figure 3 and Figure 8 In FIG. 1 , a current no-load FL1 in the motor windings U1 , V1 , W1 of the first electric drive unit A1 is indicated by a solid arrow, and a current no-load FL2 in the motor windings U2 , V2 , W2 of the second electric drive unit A2 is indicated by a dashed arrow.

[0060] For according to Figure 1 or Figure 6 In the respective embodiments, for the case where the traction battery 4 provides electric energy to the off-board power unit 3 electrically connected to the electrical terminal 5, Figure 4 and Fig. 9A current generation AB1 in the motor windings U1 , V1 , W1 of the first electric drive unit A1 is shown with solid arrows, and a current generation AB2 in the motor windings U2 , V2 , W2 of the second electric drive unit A2 is shown with dashed arrows.

[0061] For according to Figure 1 or Figure 6 In the respective embodiments, for the case where the traction battery 4 provides electric energy to the off-board power unit 3 electrically connected to the electrical terminal 5, Figure 5 and Fig.10 In FIG. 1 , a current no-load FL1 in the motor windings U1 , V1 , W1 of the first electric drive unit A1 is indicated by a solid arrow, and a current no-load FL2 in the motor windings U2 , V2 , W2 of the second electric drive unit A2 is indicated by a dashed arrow.

[0062] Furthermore, the solution described avoids the disadvantages of electrically coupled DC voltage transformers, since this results in a potential change in only one high-voltage potential P1, P2, while the other high-voltage potential P2, P1 is connected from the DC charging station to the vehicle 1. This can lead to insulation overloads during the charging process. A triggering condition can be an asymmetrical insulation resistance distribution in the DC charging station and / or in the vehicle 1. In addition, the insulation monitor also leads to a potential change, which can lead to insulation overloads in the DC charging station.

[0063] In contrast, in the solution described here, the potential change of the two potentials P1, P2 can be controlled, such as Figures 11 to 13 As an example, the charging of a traction battery 4 with a nominal voltage of 800 V at a DC charging station with a charging voltage of 400 V is shown. From the left DC charging station toward the right traction battery 4, the two potentials P1, P2 and a reference potential M of 0 V, in particular a ground potential, are shown.

[0064] In accordance with Fig.11 In the example of , the potential distribution in the vehicle 1 does not lead to insulation overload at the poorly insulated DC charging station. The drive units A1, A2 can therefore select any transmission ratio.

[0065] In accordance with Fig.12 In the example of , the potential distribution in the vehicle 1 will cause insulation overload of the first high voltage potential P1 at the DC charging station with weaker insulation. Therefore, the second drive unit A2 increases the second high voltage potential P2 by a smaller transmission ratio, or is passively switched on, as shown here. The first drive unit A1 increases the first high voltage potential P1 by a larger transmission ratio.

[0066] In accordance with Fig.13In the example of , the potential distribution in the vehicle 1 will cause insulation overload of the second high voltage potential P2 at the DC charging station with weaker insulation. Therefore, the first drive unit A1 increases the first high voltage potential P1 through a smaller transmission ratio, or is passively switched on, as shown here. The second drive unit A2 increases the second high voltage potential P2 with a larger transmission ratio.

[0067] The reaction of the circuit arrangement 2 (in particular the two drive units A1 , A2 electrically connected in series in the above-described manner) to the asymmetrical potential distribution can be carried out, for example, as described in DE 10 2017 009 352 A1, in particular by controlling and / or regulating the inverters I1 , I2 , in particular their inverter circuits IS1 , IS2 .

[0068] During the above-mentioned charging operation, the insulation strength in the charging pile is maintained, in particular in the case of potential changes caused by insulation monitoring, asymmetrical insulation resistance and / or slowly occurring insulation defects.

[0069] Compatibility with insulation monitors is ensured, for example, according to the method described in the following publication: PCIM2021, Quasi-insulated HV / HV-DC / DC transformer for electric vehicles with multiple high-voltage stages (André Haspel, Urs Mercedes-Benz AG, Germany).

[0070] Another disadvantage of the electrically coupled DC voltage transformer, which is avoided by the solution described, is that in the electrically coupled DC voltage transformer, if an insulation defect occurs in the vehicle 1, this can directly lead to another insulation defect in the opposite high voltage potential P2, P1 on the DC charging station side. This causes a short circuit in the traction battery 4, which in turn, according to the so-called CHAdeMO charging standard, would lead to damage to the ground potential line ML in the charging cable 6 which electrically connects the electrical terminal 5 of the vehicle 1 to the DC charging station, because the ground potential line ML in the charging cable 6 is designed to be very thin.

[0071] Fig.14 Shows the use of Figure 1 The implementation method to deal with this problem is to Fig.15 It shows that the adoption of Figure 6 A vehicle 1, in particular a chassis 7 of the vehicle 1, including a circuit arrangement 2, and an off-board unit 3 designed as a DC charging station, in particular a metal housing 8, are shown. The DC charging station has, for example, a design voltage and / or charging voltage of 500 V. The traction battery 4 has, for example, a nominal voltage of 800 V.

[0072] An insulation defect F1 occurs in the vehicle 1. As a direct consequence, the 800 V voltage applied by the traction battery 4 leads to an insulation overload in the DC charging station, so that an insulation defect F2 also occurs here. The resulting battery short-circuit current KS is indicated by an arrow.

[0073] Here, the critical operating states during the step-down operation, i.e. during the feeding of electrical energy from the traction battery 4 into the off-board power unit 3 designed as a DC charging station, for example, to the public power supply network, are shown. In the vehicle 1, the first high-voltage potential P1 has an insulation defect F1 relative to the reference potential M (in particular the ground potential), i.e. in particular relative to the chassis 7 of the vehicle 1. The increase in the short-circuit current is then slowed down through the motor windings U2, V2 and W2 of the second drive unit A2, so that the monitoring system has sufficient time to detect the fault, for example by means of current measurement and / or voltage measurement, in order to avoid overloading / damage to the ground potential line ML in the charging cable 6 of the DC charging station or to parts of the vehicle 1. The step-down operation can be stopped by opening the inverter switching units IE8, IE10, IE12, which are in particular designed as semiconductor switching units. The current inherent in the motor windings U2, V2 and W2 is further conveyed via the free-carrier diodes of the inverter switching units IE7, IE9, IE11, and the inductive energy (including the supply line inductance) is transferred to the capacitor C1. Then, the short-circuit current drops completely to 0A.

[0074] In the vehicle 1, an insulation defect of the second high-voltage potential P2 HV- relative to the reference potential M (especially the ground potential) will correspondingly lead to an overload of the first high-voltage potential P1 in the DC charging station relative to the reference potential M (especially the ground potential). This current can also be interrupted according to the same principle, wherein the corresponding components of the first drive unit A1 are then involved.

[0075] The possibility of reacting to a corresponding short circuit caused by an insulation defect F1 in the vehicle 1 is thus achieved by slowing down the current increase by means of the motor inductance. This provides sufficient time to clearly detect the fault and interrupt the current flow. The current inherent in the motor inductance can be transferred to the capacitor via the freewheeling / body diode.

[0076] Reference numerals list

[0077] 1 Vehicle

[0078] 2 Circuit Devices

[0079] 3 Off-board power unit

[0080] 4 Traction battery

[0081] 5 Terminals

[0082] 6 Charging cable

[0083] 7 Chassis

[0084] 8 Metal housing

[0085] A1, A2 drive unit

[0086] AB1,AB2 current generation

[0087] C1, C2 capacitors

[0088] F1, F2 Insulation defect

[0089] FL1, FL2 current no-load

[0090] I1, I2 inverter

[0091] IE1 to IE12 inverter switching units

[0092] IS1, IS2 inverter circuit

[0093] KS Battery short circuit current

[0094] M Reference potential

[0095] M1,M2 three-phase AC motor

[0096] ML Ground potential line

[0097] P1, P2 High voltage potential

[0098] PL1, PL2 potential line

[0099] Rb Internal resistance of the traction battery

[0100] Rg Internal resistance of the DC charging station

[0101] S1 to S6 switches

[0102] SP1, SP2 star point

[0103] U1, V1, W1 motor windings

[0104] U2, V2, W2 motor windings

Claims

1. A vehicle (1) having a power circuit device (2), wherein: The power circuit device (2) comprises: - traction battery (4), - an electrical terminal (5) for electrical connection to an off-board power unit (3), - a first high voltage potential (P1), and - a second high voltage potential (P2), wherein the first high voltage potential (P1) is a positive high voltage potential, and the second high voltage potential (P2) is a negative high voltage potential, or vice versa, and Wherein, the circuit device (2) - having two electric drive units (A1, A2), each of which has an inverter (I1, I2) and a three-phase AC motor (M1, M2) electrically connected thereto, for driving the vehicle (1), and - designed so that the two electric drive units (A1, A2) can be electrically connected in series between the electric terminal (5) and the traction battery (4) in the following manner: from the electric terminal (5) toward the traction battery (4), the first electric drive unit (A1) increases the first high-voltage potential (P1) and the second electric drive unit (A2) increases the second high-voltage potential (P2), It is characterized in that The inverters (I1, I2) respectively have respective capacitors (C1, C2) between a potential line (PL1) of the first high voltage potential (P1) and a potential line (PL2) of the second high voltage potential (P2), The circuit device (2) is designed so that the second electric drive unit (A2) can be electrically connected in series with the capacitor terminal of the first electric drive unit (A1).

2. The vehicle (1) according to claim 1, characterized in that One of the potential lines (PL1, PL2) of the inverter (I2) of the second electric drive unit (A2) is electrically connected to capacitor terminal contacts of the capacitor terminal of the inverter (I1) of the first electric drive unit (A1) having the same high voltage potential (P1, P2), and the circuit arrangement (2) is designed such that: - the star point (SP2) of the three-phase AC motor (M2) of the second electric drive unit (A2) can be electrically connected to another capacitor terminal contact of the capacitor terminal of the inverter (I1) of the first electric drive unit (A1), the potential line (PL1, PL2) of the inverter (I1) electrically connected to the other capacitor terminal contact can be electrically connected to the terminal contact of the electrical terminal (5) having the same high voltage potential (P1, P2), and the star point (SP1) of the three-phase AC motor (M1) of the first electric drive unit (A1) can be electrically connected to another terminal contact of the electrical terminal (5), or - One winding terminal of the three-phase AC motor (M2) of the second electric drive unit (A2) can be electrically connected to another capacitor terminal line contact of the capacitor terminal of the inverter (I1) of the first electric drive unit (A1), the potential line (PL1, PL2) of the inverter (I1) electrically connected to the other capacitor terminal contact can be electrically connected to the terminal contact of the electrical terminal (5) having the same high voltage potential (P1, P2), and one winding terminal of the three-phase AC motor (M1) of the first electric drive unit (A1) can be electrically connected to another terminal contact of the electrical terminal (5).

3. The vehicle (1) according to claim 1 or 2, characterized in that The traction battery (4) is electrically connected to the capacitor terminals of the second electric drive unit (A2).

4. The vehicle (1) according to one of the preceding claims, characterized in that The circuit arrangement (2) is designed to enable the traction battery (4) to be electrically connected to the capacitor terminals of the first electric drive unit (A1).

5. The vehicle (1) according to one of the preceding claims, characterized in that The circuit arrangement (2) is designed such that the electrical connection terminal (5) can be directly electrically connected to the traction battery (4).

6. A method for operating a vehicle (1) according to one of the preceding claims, wherein: - in order to charge the traction battery (4) via an off-board power unit (3) electrically connected to the electrical terminal (5), designed as a DC charging station and having a charging voltage lower than the nominal voltage of the traction battery (4), and / or in order to supply electrical energy from the traction battery (4) to the off-board power unit (3) electrically connected to the electrical terminal (5), the two electric drive units (A1, A2) are electrically connected in series between the electrical terminal (5) and the traction battery (4), and / or - the electrical terminal (5) is directly electrically connected to the traction battery (4) in order to charge the traction battery (4) via an off-board power unit (3) which is electrically connected to the electrical terminal (5), is designed as a DC charging station and has a charging voltage which is at least equal to the nominal voltage of the traction battery (4), and / or - for driving operation of the vehicle (1), two inverters (I1, I2) are respectively directly connected to the traction battery (4), It is characterized in that To this end, the inverters (I1, I2) of the drive units (A1, A2) each have a corresponding capacitor (C1, C2) between a potential line (PL1) of the first high voltage potential (P1) and a potential line (PL2) of the second high voltage potential (P2), The circuit device (2) can be connected so that the second electric drive unit (A2) is electrically connected in series to the capacitor terminal of the first electric drive unit (A1).

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