Vehicle and method for operating the same

Abstract

The invention relates to a vehicle (1) comprising a traction battery (2), a drive unit (4) which is equipped with a three-phase AC motor (5) and an inverter (6) which is electrically connected to the three-phase AC motor (5), and a charging connection (7) for electrical connection to a DC charging station (3) outside the vehicle, the inverter (6) being electrically connected to the traction battery (2). According to the invention, the inverter (6) is designed as a floating capacitance inverter. The invention further relates to a method for operating a vehicle (1).

Description

Technical Field

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

[0002] In the prior art, for example, DE 10 2019 217 666 A1 and US 2020 / 0361323 A1 disclose a charging system with multiple inputs and a method using a motor drive system, respectively. A multi-input charging system using a motor drive system includes an inverter connected to a rechargeable battery. The inverter includes multiple switching elements. In addition, the multi-input charging system includes: a motor, which is connected to the inverter and is configured to supply the inverter with current provided at the neutral point of the motor; a first relay, one end of which is connected to the battery and the opposite end of which is connected to the charging power input connector (DC charging power is applied to it from the outside); a second relay, one end of which is connected to the neutral point and the opposite end of which is connected to the charging power input connector; a neutral point capacitor, which is connected to the opposite end of the first relay and the opposite end of the second relay and is configured to form an input charging voltage; a third relay, one end of which is connected to the neutral point capacitor and the opposite end of which is connected to the charging power input connector; and a control device, which is configured to turn on the third relay in the charging mode to charge the battery, selectively turn on the first relay and the second relay according to the size of the DC charging voltage so as to supply DC charging power to the battery, and control the multiple switching elements of the inverter to force the neutral point capacitor to discharge when the battery charging is completed.

[0003] DE 10 2019 116 769 A1 describes a bridge circuit and a charge pump. The bridge circuit comprises a first capacitor, a second capacitor, a first switch, a second switch, a first diode and a second diode. The first capacitor and the second capacitor are connected in series and form a power supply circuit. A first half-bridge circuit is connected in parallel with the power supply circuit, and the first half-bridge circuit has a first switch, a second switch, a first diode, a second diode and a first resonant main circuit. The first switch and the second switch are arranged in series at a first bridge point and in parallel with the first capacitor. The first diode and the second diode are arranged in series at a second bridge point and in parallel with the second capacitor. The first resonant main circuit is connected to the first bridge point and the second bridge point. The discharge circuit is connected to the first resonant main circuit and is located at the second bridge point. The discharge circuit is constructed as a second half-bridge circuit and is set up to maintain the current flow in the bridge point during the switching of the first and / or second switches when there is substantially no current flowing in the first resonant main circuit.

[0004] DE 10 2021 003 852 A1 discloses an electric drive system for a vehicle and a method for operating a corresponding electric drive system. The electric drive system comprises a three-phase AC motor for driving the vehicle, a battery for supplying power to the three-phase AC motor during vehicle driving operation, an inverter for the three-phase AC motor electrically connected to the battery, and a vehicle-side charging connector for electrically connecting the battery to a charging unit external to the vehicle. With the inverter, the charging voltage of the vehicle-side charging connector can be converted into a supply voltage for charging the battery.

[0005] DE 10 2021 003 883 describes an electric drive system for a vehicle, a vehicle equipped with a corresponding electric drive system, and a method for operating a corresponding electric drive system. The electric drive system has a switching device. The switching device includes a first switching state, in which the charging connector is directly connected to the battery of the vehicle, so that the battery can be charged by the input voltage applied to the charging connector, and the switching device also includes a second and a third switching state, in which the charging connector is connected to the battery via an inverter, so that the battery can be charged by means of the inverter. Summary of the invention

[0006] The object of the present invention is to provide a vehicle which is improved compared to the prior art and a method for operating the vehicle which is improved compared to the prior art.

[0007] This object is achieved according to the invention by a vehicle having the features of claim 1 and a method for operating the vehicle having the features of claim 8 .

[0008] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0009] A vehicle comprises a traction battery, a drive unit and a charging connector for electrically connecting to a DC charging station outside the vehicle, wherein the drive unit is equipped with a three-phase AC motor and an inverter electrically connected to the three-phase AC motor, wherein the inverter is electrically connected to the traction battery.

[0010] A traction battery is a high-voltage battery. The term "high voltage" (also abbreviated to HV) refers in particular to a DC voltage, in particular above approximately 60 V. In particular, the term "high voltage" is to be interpreted in accordance with the ECE R 100 standard. A traction battery is used in particular to supply power to a drive unit for driving the vehicle.

[0011] According to the present invention, the inverter is designed as a floating capacitor inverter, in particular, a three-phase three-level inverter with floating capacitors.

[0012] In a vehicle operating method according to the present invention, in order to charge the traction battery via a DC charging station electrically connected to the charging terminal and having a charging voltage less than the rated voltage of the traction battery, the charging voltage is converted by means of an inverter into a voltage having a voltage value at least equal to the rated voltage of the traction battery.

[0013] In particular, it is provided that during driving operation of the vehicle, a DC voltage provided by the traction battery is converted into an AC voltage by means of an inverter to supply power to the three-phase AC motor.

[0014] In the solution according to the invention, therefore, advantageously already existing components in the vehicle, in particular the inverter, which is already provided for converting the DC voltage of the traction battery into an AC voltage for the vehicle's three-phase AC motor, are also used for charging the traction battery with a DC voltage provided by the DC charging station which is lower than the rated voltage of the traction battery. For example, only filters and contactors are required as additional components.

[0015] In order to achieve this, it is particularly provided that the inverter has three parallel lines between the positive potential line and the negative potential line, each of which is also referred to as a "phase", and each of which has four semiconductor switching units electrically connected in series, wherein an inverter capacitor is respectively arranged between the "tap between the first semiconductor switching unit and the second semiconductor switching unit" and the "tap between the third semiconductor switching unit and the fourth semiconductor switching unit" of each line. These semiconductor switching units particularly each have a semiconductor switch and a diode. The semiconductor switches are particularly each designed as a bipolar transistor with an insulated gate.

[0016] In particular, it is provided that the center taps of these lines are respectively electrically connected to the motor windings of the three-phase AC motor.

[0017] In particular, it is provided that one potential terminal of the charging connector is electrically connected to the star point of the three-phase AC motor, and the other potential terminal of the charging connector is electrically connected to the same potential of the traction battery via a potential conductor of the inverter having the same potential. The term "same potential" refers in particular to the same potential sign, i.e. the same potential is either a positive potential or a negative potential.

[0018] In one possible embodiment, it is provided that on the traction battery side of the inverter, a series circuit consisting of two output capacitors is arranged between two potential conductors, wherein the potential connection terminal of the charging connection electrically connected to the neutral point of the three-phase AC motor is also electrically connected to a center tap between the two output capacitors. Alternatively, it is provided, for example, that only one output capacitor is arranged between two potential conductors on the traction battery side of the inverter.

[0019] In particular, provision is made for the charging terminal to be electrically connected to the input capacitor.

[0020] In particular, the vehicle operating method provides that, in order to charge the traction battery via a DC charging station electrically connected to the charging terminal and having a charging voltage lower than the rated voltage of the traction battery, in one of the lines of the inverter, in a first step, a semiconductor switch closest to a potential conductor of the inverter electrically connected to the charging terminal is closed, while a subsequent semiconductor switch remains open, and in a second step, a semiconductor switch closest to a potential conductor of the inverter electrically connected to the charging terminal is opened, and then the subsequent semiconductor switch is closed.

[0021] In this solution, the motor inductance of the three-phase AC motor forms a resonant circuit together with the inverter capacitors of the floating capacitance bridge of the inverter. This allows the losses in the semiconductors to be minimized or more cost-effective semiconductors to be used. In addition, the EMC filters (EMC = electromagnetic compatibility) can be kept cost-effective due to the extremely low harmonic content of the interference.

[0022] Thus, with the solution according to the invention, it is also possible to charge the traction battery with no or only little additional expenditure via a DC charging station with a charging voltage lower than the rated voltage of the traction battery. For example, the rated voltage of the traction battery is 800 V and the charging voltage is 400 V. As described above, a floating capacitor inverter is used as the inverter topology for this purpose, wherein, in order to be able to charge the traction battery in this way, i.e., in order to raise the low charging voltage to the level of the rated voltage of the traction battery, one potential terminal of the charging connection (and therefore also one pole of the DC charging station electrically connected to the charging connection) is connected to the star point of the three-phase machine, and the other potential terminal of the charging connection (and therefore also the other pole of the DC charging station electrically connected to the charging connection) is connected to the pole of the traction battery with the same potential. The connection thus produced enables operation as a resonant charge pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, wherein:

[0024] Figure 1 Schematically shows an embodiment of a vehicle connected to a DC charging station,

[0025] Figure 2 Schematically showing the Figure 1 The first step of the working method of the implementation method is,

[0026] Figure 3 Schematically showing the Figure 1 The second step of the working method of the implementation method is,

[0027] Figure 4 Schematically showing the Figure 1 The detailed working method of the implementation method,

[0028] Figure 5 Schematically showing the Figure 1 A variation of the embodiment of

[0029] Figure 6 A first step of a method of operation of another specific embodiment of a vehicle connected to a DC charging station is schematically shown.

[0030] Figure 7 The second step of the working method of another embodiment is schematically shown.

[0031] Figure 8 Schematically illustrates the detailed working mode of another embodiment, and

[0032] Fig. 9 Another embodiment variant is schematically shown.

[0033] Parts that correspond to one another are provided with the same reference symbols in all the figures. DETAILED DESCRIPTION

[0034] Figures 1 to 9 The vehicle 1 and its mode of operation are shown, at which time the traction battery 2 of the vehicle 1 is being charged at a vehicle-external DC charging station 3 at a charging voltage lower than the rated voltage of the traction battery 2 . Figures 1 to 9 The vehicles 1 in FIG. 1 are all electrically connected to the DC charging station 3 . Figures 1 to 9 Also shown are the internal resistance Ril of the DC charging station 3 and the internal resistance Rib of the traction battery 2 .

[0035] The vehicle 1 comprises a traction battery 2 , a drive unit 4 , and a charging connector 7 for electrical connection to an external DC charging station 3 . The drive unit is equipped with a three-phase AC motor 5 and an inverter 6 electrically connected to the three-phase AC motor 5 . The inverter 6 is electrically connected to the traction battery 2 .

[0036] The inverter 6 is designed as a floating capacitor inverter, in particular, a three-phase three-level inverter with floating capacitors.

[0037] The inverter 6 has three parallel lines S1, S2, S3 between the positive potential line and the negative potential line, each of which has four semiconductor switching units S11 to S34 electrically connected in series, wherein inverter capacitors C1, C2, C3 are arranged between the taps between the first semiconductor switching unit S11, S21, S31 and the second semiconductor switching unit S12, S22, S32 of each line S1, S2, S3 and the taps between the third semiconductor switching unit S13, S23, S33 and the fourth semiconductor switching unit S14, S24, S34. The semiconductor switching units S11 to S34 have in particular semiconductor switches and diodes, in particular body diodes.

[0038] The center taps of the lines S1 , S2 , S3 are respectively electrically connected to the corresponding motor windings L1 , L2 , L3 of the three-phase AC motor 5 .

[0039] One potential terminal of the charging connector 7 (and therefore also the pole of the DC charging station 3 connected to this potential terminal) is electrically connected to the star point SP of the three-phase AC motor 5. The other potential terminal of the charging connector 7 (and therefore also the other pole of the DC charging station 3 connected to this potential terminal) is electrically connected to the same potential HV+, HV- of the traction battery 2 through potential wires with the same potential HV+, HV- of the inverter 6.

[0040] like Figures 1 to 4 and Figures 6 to 8 As shown, it can also be provided that a series circuit consisting of two output capacitors Ca1 and Ca2 is arranged between the two potential conductors on the traction battery side of the inverter 6, wherein the potential connection terminal of the charging terminal 7 electrically connected to the star point SP of the three-phase AC motor 5 is also electrically connected to the center tap between the two output capacitors Ca1 and Ca2. Figure 5 and Fig. 9 As shown, provision can be made for only one output capacitor Ca to be arranged between two potential conductors on the traction battery side of the inverter 6 .

[0041] Furthermore, it is provided that the charging terminal 7 is electrically connected to the input capacitor Ce, ie, the potential terminals of the charging terminal 7 are respectively electrically connected to the corresponding terminals of the input capacitor Ce.

[0042] The above connection method (such as Figures 1 to 9 As shown in FIG. 1 , the DC charging station 3 can be operated as a resonant charge pump, thereby increasing the charging voltage of the DC charging station 3 to the rated voltage level of the traction battery 2. Here, a resonant circuit is formed by the motor inductance (i.e., the motor winding L1, L2 or L3) and the inverter capacitor C1, C2 or C3 of the floating capacitance bridge.

[0043] Figures 1 to 4 and Figures 6 to 8 The illustrated embodiment also allows the advantages of power transmission and EMC to be utilized, in which a series circuit consisting of two output capacitors Ca1, Ca2 is arranged between two potential conductors on the traction battery side of the inverter 6, wherein the potential terminal of the charging terminal 7 electrically connected to the star point SP of the three-phase AC motor 5 is also electrically connected to the center tap between the two output capacitors Ca1, Ca2.

[0044] In a method for operating a vehicle 1, it is particularly provided that, in order to charge the traction battery 2 via a DC charging station 3 electrically connected to the charging terminal 7 and having a charging voltage lower than the rated voltage of the traction battery 2, in one of the lines S1, S2, S3 of the inverter 6, in a first step, the semiconductor switch S11, S21, S31, S14, S24, S34 closest to the potential line of the inverter 6 electrically connected to the charging terminal 7 is closed, and the subsequent semiconductor switch S12, S22, S32, S13, S23, S33 is kept open, and in a second step, the semiconductor switch S11, S21, S31, S14, S24, S34 closest to the potential line of the inverter 6 electrically connected to the charging terminal 7 is opened, and then the subsequent semiconductor switch S12, S22, S32, S13, S23, S33 is closed.

[0045] The following, combined Figures 1 to 9 Let me elaborate on the solution again.

[0046] In accordance with Figures 1 to 5 In the embodiment of the present invention, the negative potential terminal of the charging connector 7 (and therefore also the negative pole of the DC charging station 3 connected to the negative potential terminal) is electrically connected to the star point SP of the three-phase AC motor 5. The positive potential terminal of the charging connector 7 (and therefore also the positive pole of the DC charging station 3 connected to the positive potential terminal) is electrically connected to the positive potential HV+ of the traction battery 2 via a potential conductor having a positive potential HV+ of the inverter 6. Therefore, in this embodiment, the negative potential HV- of the DC charging station 3 is further reduced, while the positive potential HV+ between the DC charging station 3 and the traction battery 2 is maintained at a constant level.

[0047] In accordance with Figures 1 to 4 In the embodiment, the negative potential terminal of the charging connector 7 which is electrically connected to the star point SP of the three-phase AC motor 5 is also electrically connected to the center tap between the two output capacitors Ca1 and Ca2.

[0048] Figure 2 and Figure 3 The working mode of the embodiment is shown.

[0049] exist Figure 2 In the first step shown, the first semiconductor switch unit S11 of the first line S1 is closed and the second semiconductor switch unit S12 of the first line S1 is kept open. The charging voltage of the DC charging station 3 is applied to the series circuit formed by the first inverter capacitor C1 and the first motor winding L1. In this case, the first motor winding L1 and the first inverter capacitor C1 form a resonant circuit. The current builds up in the form of a sinusoidal half-wave and decays again. During this time, the first inverter capacitor C1 is charged.

[0050] exist Figure 3In the second step shown, the first semiconductor switch unit S11 of the first line S1 is opened and the second semiconductor switch unit S12 of the first line S1 is subsequently closed. The voltage of the first inverter capacitor C1 is now connected in series with the charging voltage of the DC charging station 3 and added. The current builds up in the form of a sinusoidal half-wave and decays again. During this time, the first inverter capacitor C1 is discharged. Here, the direction of the current in the first motor winding L1 is the same as in the first step. The path of the circuit is now: from the DC charging station 3 through the traction battery 2, the fourth semiconductor switch unit S14 of the first line S1 (in particular its body diode), the first inverter capacitor C1, the second semiconductor switch unit S12 of the first line S1 and the first motor winding L1. As a result, the traction battery 2 is charged.

[0051] The third and fourth semiconductor switching units S13 , S14 of the first line S1 act only as diodes, in particular body diodes, in the entire process.

[0052] Figure 4 Show according to Figures 1 to 3 In the working mode of the embodiment of the present invention, the negative potential terminal of the charging connector 7 electrically connected to the star point SP of the three-phase AC motor 5 is also electrically connected to the center tap between the two output capacitors Ca1 and Ca2. As a result, the first output capacitor Ca1 is always connected in parallel with the DC charging station 3 and the input capacitor Ce. The charge pump increases the voltage thereof so that a voltage boost occurs on the series circuit formed by the two output capacitors Ca1 and Ca2, that is, since the first output capacitor Ca1 is constantly maintained at the charging voltage level of the DC charging station 3, only the second output capacitor Ca2 is charged.

[0053] Figure 5 Show according to Figures 1 to 3 However, only one output capacitor Ca is used, so the negative potential terminal of the charging terminal 7 electrically connected to the star point SP of the three-phase AC motor 5 is not electrically connected to the center tap between the two output capacitors Ca1 and Ca2. Nevertheless, the circuit still has the basic function and can charge the traction battery 2 at the DC charging station 3 where the charging voltage is lower than the rated voltage of the traction battery 2.

[0054] In accordance with Figures 6 to 9In the embodiment of the present invention, the positive potential terminal of the charging connector 7 (and therefore the positive pole of the DC charging station 3 connected to this positive potential terminal) is electrically connected to the star point SP of the three-phase AC motor 5. The negative potential terminal of the charging connector 7 (and therefore the negative pole of the DC charging station 3 connected to this negative potential terminal) is electrically connected to the negative potential HV- of the traction battery 2 via a potential conductor having a negative potential HV- of the inverter 6. Therefore, in this embodiment, the positive potential HV+ of the DC charging station 3 is further reduced, while the negative potential HV- between the DC charging station 3 and the traction battery 2 is maintained at a constant level.

[0055] In accordance with Figures 6 to 8 In the embodiment, the positive potential terminal of the charging connector 7 which is electrically connected to the star point SP of the three-phase AC motor 5 is also electrically connected to the center tap between the two output capacitors Ca1 and Ca2.

[0056] Figure 6 and Figure 7 The working mode of this embodiment is shown.

[0057] exist Figure 6 In the first step shown, the fourth semiconductor switch unit S14 of the first line S1 is closed and the third semiconductor switch unit S13 of the first line S1 is kept open. The charging voltage of the DC charging station 3 is applied to the series circuit consisting of the first inverter capacitor C1 and the first motor winding L1. In this case, the first motor winding L1 and the first inverter capacitor C1 form a resonant circuit. The current builds up in the form of a sinusoidal half-wave and decays again. During this time, the first inverter capacitor C1 is charged.

[0058] exist Figure 7 In the second step shown, the fourth semiconductor switch unit S14 of the first line S1 is opened and the third semiconductor switch unit S13 of the first line S1 is subsequently closed. The voltage of the first inverter capacitor C1 is now connected in series with the charging voltage of the DC charging station 3 and added. The current builds up in the form of a sinusoidal half-wave and decays again. In this process, the first inverter capacitor C1 is discharged. In this case, the direction of the current in the first motor winding L1 remains the same as in the first step. The path of the circuit is now: from the DC charging station 3, through the first motor winding L1, the third semiconductor switch unit S13 of the first line S1, the first inverter capacitor C1, the second semiconductor switch unit S12 of the first line S1 (in particular, its body diode) and the traction battery 2, and finally back. As a result, the traction battery 2 is charged.

[0059] The first and second semiconductor switching units S11 , S12 of the first line S1 merely act as diodes, in particular body diodes, in the entire process.

[0060] Figure 8 Show according to Figure 6 and Figure 7 In the working mode of the embodiment of the present invention, the positive potential terminal of the charging connector 7 electrically connected to the star point SP of the three-phase AC motor 5 is also electrically connected to the center tap between the two output capacitors Ca1 and Ca2. As a result, the second output capacitor Ca2 is always connected in parallel with the DC charging station 3 and the input capacitor Ce. The charge pump generates a boost voltage on the series circuit composed of the two output capacitors Ca1 and Ca2 through its voltage increase, that is, since the second output capacitor Ca2 is constantly maintained at the charging voltage level of the DC charging station 3, only the first output capacitor Ca1 is charged.

[0061] Fig. 9 Show according to Figure 6 and Figure 7 However, only one output capacitor Ca is used, so the positive potential terminal of the charging terminal 7 electrically connected to the star point SP of the three-phase AC motor 5 is not electrically connected to the center tap between the two output capacitors Ca1 and Ca2. Nevertheless, the circuit still has basic functions and can charge the traction battery 2 at the DC charging station 3 where the charging voltage is lower than the rated voltage of the traction battery 2.

[0062] Reference numerals list

[0063] 1 Vehicle

[0064] 2 Traction batteries

[0065] 3 DC Charging Stations

[0066] 4 Drivers

[0067] 5 Three-phase AC motor

[0068] 6 Inverter

[0069] 7 Charging connector

[0070] C1, C2, C3 Inverter capacitors

[0071] Ca, Ca1, Ca2 Output capacitor

[0072] Ce Input capacitor

[0073] HV+, HV- potential

[0074] L1, L2, L3 Motor windings

[0075] Rib Traction battery internal resistance

[0076] Ril DC charging station internal resistance

[0077] S1, S2, S3 lines

[0078] S11 to S34 semiconductor switch units

[0079] SP Star Point

Claims

1. A vehicle (1), comprising: - Traction battery (2), - a drive unit (4), the drive unit being equipped with a three-phase AC motor (5) and an inverter (6) electrically connected to the three-phase AC motor (5), wherein: The inverter (6) is electrically connected to the traction battery (2), and - a charging connector (7) for electrical connection to a DC charging station (3) external to the vehicle, The inverter (6) is designed as a floating capacitor inverter. It is characterized in that One potential terminal of the charging connector (7) is electrically connected to the star point (SP) of the three-phase AC motor (5), and the other potential terminal of the charging connector (7) is electrically connected to the same potential (HV+, HV-) of the traction battery (2) through potential wires of the inverter (6) having the same potential (HV+, HV-), and The charging connector (7) is electrically connected to the input capacitor (Ce).

2. The vehicle (1) according to claim 1, characterized in that On the traction battery side of the inverter (6), a series circuit consisting of two output capacitors (Ca1, Ca2) is arranged between the two potential conductors, wherein the potential terminal of the charging connector (7) electrically connected to the star point (SP) of the three-phase AC motor (5) is also electrically connected to a center tap between the two output capacitors (Ca1, Ca2).

3. A method for operating a vehicle (1) according to one of the preceding claims, characterized in that In order to charge the traction battery (2) via a DC charging station (3) electrically connected to a charging terminal (7) and having a charging voltage lower than the rated voltage of the traction battery (2), an inverter (6) is used to convert the charging voltage into a voltage having a voltage value at least equal to the rated voltage of the traction battery (2).

4. The method according to claim 3, characterized in that In one of the circuits (S1, S2, S3) of the inverter (6), - in a first step, the semiconductor switch (S11, S21, S31, S14, S24, S34) closest to the potential conductor of the inverter (6) electrically connected to the charging terminal (7) is closed, and the subsequent semiconductor switch (S12, S22, S32, S13, S23, S33) is kept open, and In a second step, the semiconductor switch (S11, S21, S31, S14, S24, S34) closest to the potential conductor of the inverter (6) electrically connected to the charging terminal (7) is opened, and the subsequent semiconductor switch (S12, S22, S32, S13, S23, S33) is then closed.

5. The method according to claim 3 or 4, characterized in that During driving operation of the vehicle (1), the inverter (6) converts the DC voltage provided by the traction battery (2) into an AC voltage to power the three-phase AC motor (5).

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