Vehicle and method for operating a vehicle

Abstract

The present invention relates to a vehicle (1), the vehicle (1) comprising: a traction battery (2), a drive unit (4) having a three-phase alternator (5) and an inverter (6) electrically connected to the three-phase alternator (5), the inverter (6) being electrically connected to the traction battery (2), and a charging connection (7) for electrically connecting to a DC charging station (3) outside the vehicle. According to the invention, the inverter (6) is formed as a flying capacitor inverter. Furthermore, the present invention also relates to a method for operating the vehicle (1).

Description

[Technical Field]

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

[0002] A charging system and method with multiple inputs using a motor drive system is known from the prior art, such as Patent Documents 1 and 2. The charging system with multiple inputs using a motor drive system includes an inverter connected to a rechargeable battery. The inverter includes a number of switching elements. The multiple-input charging system further includes a motor connected to the inverter and configured to supply electricity provided to a neutral point of the motor to the inverter; a first relay having one end connected to the battery and an opposite end connected to a charging power input connection to which DC charging power is applied from an external source; a second relay having one end connected to the neutral point and an opposite end connected to the charging power input connection; a neutral capacitor connected to the opposite end of the first relay and the opposite end of the second relay and configured to form an input charging voltage; a third relay having one end connected to the neutral capacitor and an opposite end connected to the charging power input connection; and a control device configured to control multiple switching elements of the inverter to turn on the third relay in a charging mode to charge the battery, selectively turn on the first relay and the second relay based on the value of the DC charging voltage to supply DC charging power to the battery, and to forcibly discharge the neutral capacitor when charging of the battery is completed.

[0003] Patent Document 3 describes a bridge circuit and a charge pump. The bridge circuit includes 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 to form a supply circuit. A first half-bridge circuit is connected in parallel with the supply circuit, and the half-bridge circuit includes 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 connected in series at a first bridge point and are arranged in parallel with the first capacitor. The first diode and the second diode are connected in series at a second bridge point and are arranged in parallel with the second capacitor. The first resonant main circuit is connected between the first bridge point and a second bridge point. A load release circuit is connected to the first resonant main circuit at the second bridge point. The load release circuit is configured as a second half-bridge circuit and is arranged to maintain a flow of electricity at the bridge point when switching the first and / or second switches when substantially no electricity is flowing through the first resonant main circuit.

[0004] From Patent Document 4, an electric drive system for a vehicle and a corresponding method for operating the electric drive system are known, which includes an electric three-phase AC machine for driving the vehicle, an electric energy storage device for supplying electricity to the electric three-phase AC machine while the vehicle is running, an inverter for the electric three-phase AC machine electrically connected to the electric energy storage device, and a vehicle-side charging connection for electrically connecting the electric energy storage device to a charging unit external to the vehicle. With the aid of an inverter, the charging voltage of the vehicle-side charging connection can be converted into a supply voltage for charging the electrical energy storage device.

[0005] Patent Document 5 describes an electric drive system for a vehicle, a vehicle with a corresponding electric drive system, and a method for operating the corresponding electric drive system. The electric drive system includes a switching device with a first switching state in which a charging connection is directly connected to an electric energy storage device of the vehicle, thereby enabling charging of the electric energy storage device with an input voltage present on the charging connection, and second and third switching states in which the charging connection is connected to the electric energy storage device via an inverter, thereby enabling charging of the electric energy storage device depending on the inverter. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] DE102019217666A1 [Patent Document 2] US2020 / 0361323A1 [Patent Document 3] DE102019116769A1 [Patent Document 4] DE102021003852A1 [Patent Document 5] DE102021003883 Summary of the Invention [Problem to be solved by the invention]

[0007] The invention is based on the problem of providing an improved vehicle compared to the prior art and an improved method for operating a vehicle compared to the prior art. [Means for solving the problem]

[0008] According to the invention, this problem is solved by a vehicle having the features of claim 1 and a method for operating a vehicle having the features of claim 8.

[0009] Advantageous embodiments of the invention are the subject of the dependent claims.

[0010] The vehicle includes a traction battery, a drive unit having a three-phase AC machine and an inverter electrically connected to the three-phase AC machine, the inverter being electrically connected to the traction battery, and a charging connection for electrically connecting the drive unit to a DC charging station external to the vehicle.

[0011] A traction battery is in particular a high-voltage battery. The term "high voltage" (abbreviated HV) in particular means an electrical direct current voltage greater than approximately 60 V. In particular, the term "high voltage" must be interpreted in accordance with the standard ECE R 100. A traction battery is in particular used to supply electrical energy to a drive unit for propelling a vehicle.

[0012] According to the invention, the inverter is configured as a flying capacitor inverter, in particular as a three-phase three-level inverter with flying capacitors.

[0013] The method according to the invention for operating a vehicle comprises charging the traction battery using a DC charging station electrically connected to a charging connection, the charging voltage of which is lower than the rated voltage of the traction battery, and converting the charging voltage by means of an inverter into a voltage having a value which corresponds at least to the rated voltage of the traction battery.

[0014] Additionally, particularly during vehicle running operation, the DC voltage provided by the traction battery is converted by means of an inverter into an AC voltage for supplying electrical energy to a three-phase AC machine.

[0015] Therefore, in the solution according to the invention, advantageously, components already present in the vehicle, in particular the inverter already provided in the vehicle for converting the DC voltage of the traction battery into the AC voltage of the three-phase AC machine, are additionally used to charge the traction battery with a DC voltage provided by a DC charging station that is lower than the rated voltage. Only additional components, for example, a filter and a contactor, are required.

[0016] To achieve this, the inverter has three strands, each called a phase, between a positive potential line and a negative potential line, with four semiconductor switching units electrically connected in series on each strand, and an inverter capacitor arranged between the tap between the first and second semiconductor switching units of each strand and the tap between the third and fourth semiconductor switching units. Each semiconductor switching unit has, in particular, a semiconductor switch and a diode. In particular, the semiconductor switches are formed as bipolar transistors with insulated gate electrodes.

[0017] In particular, the center taps of the strands are adapted to be electrically coupled to respective ones of the motor windings of a three-phase AC machine.

[0018] In particular, one potential connection of the charging connection is electrically connected to the neutral point of the three-phase alternator, and the other potential connection of the charging connection is electrically connected to the same potential of the traction battery via a potential line of the inverter having the same potential. The term "same potential" particularly means that the signs of the potentials are the same, i.e., the same potential can be either a positive potential or a negative potential.

[0019] In a possible embodiment, an electrical series connection of two output capacitors is arranged on the traction battery side of the inverter between the two potential lines, and the potential connection of the charging connection electrically connected to the neutral point of the three-phase alternator is also electrically connected to the center tap between the two output capacitors. Alternatively, for example, only one output capacitor is arranged on the traction battery side of the inverter between the two potential lines.

[0020] In particular, the charging connection is adapted to be electrically connected to the input capacitor.

[0021] In a method for operating a vehicle, in particular for charging a traction battery using a DC charging station electrically connected to a charging connection, the charging voltage of which is lower than the rated voltage of the traction battery, in any one of the inverter strands, in a first step, the semiconductor switch closest to the potential line of the inverter electrically connected to the charging connection is closed and the next semiconductor switch is left open, and in a second step, the semiconductor switch closest to the potential line of the inverter electrically connected to the charging connection is opened, followed by closing the next semiconductor switch.

[0022] In this solution, a resonant circuit is formed by the interaction of the motor inductance of the three-phase AC machine with the inverter capacitors of the inverter's flying capacitor bridge. This allows the losses in the semiconductors to be minimized or advantageously used. Furthermore, the harmonic content of the interference is very low, which makes it possible to maintain an advantageous EMC filter (EMC = electromagnetic compatibility).

[0023] The solution according to the present invention therefore makes it possible, without or with only minor additional costs, to charge the traction battery at a DC charging station whose charging voltage is 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 explained above, a flying capacitor inverter is used for this purpose. To enable this charging of the traction battery, i.e., to increase the low charging voltage to the rated voltage level of the traction battery, one potential connection of the charging connection, and therefore one pole of the DC charging station electrically connected to the charging connection, is connected to the neutral point of the three-phase AC machine, and the other potential connection of the charging connection, and therefore the other pole of the DC charging station electrically connected to the charging connection, is connected to a pole of the traction battery having the same potential. The resulting circuit offers the possibility of functioning as a resonant charge pump.

[0024] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of an embodiment of a vehicle coupled to a DC charging station. [Figure 2] 2 is a schematic diagram showing a first step of the mode of operation of the embodiment according to FIG. 1; FIG. [Figure 3] 2 is a schematic diagram showing a second step of the operating mode of the embodiment according to FIG. 1; [Figure 4] 2 is a schematic diagram showing the mode of operation of a detail of the embodiment according to FIG. 1; [Figure 5] FIG. 2 is a schematic diagram showing a modification of the embodiment shown in FIG. [Figure 6] FIG. 10 is a schematic diagram illustrating a first step of an operation mode of a further embodiment of a vehicle coupled to a DC charging station. [Figure 7] FIG. 10 is a schematic diagram illustrating a second step of an operation mode of a further embodiment. [Figure 8] 5A-5C are schematic diagrams showing the mode of operation of further details of the embodiment; [Figure 9] FIG. 10 is a schematic diagram showing a modification of a further embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] In all the drawings, the same reference numerals are used to designate corresponding parts.

[0027] 1 to 9 show a vehicle 1 and its operating mode while the traction battery 2 of the vehicle 1 is being charged at a DC charging station 3 external to the vehicle, the charging voltage of the DC charging station 3 being lower than the rated voltage of the traction battery 2. In this case, the vehicle 1 of each of FIGS. 1 to 9 is already electrically connected to the DC charging station 3. The internal resistance Ril of the charging station 3 and the internal resistance Rib of the traction battery 2 are also shown in each of FIGS.

[0028] The vehicle 1 comprises a traction battery 2, a drive unit 4 having a three-phase AC machine 5 and an inverter 6 electrically connected to the three-phase AC machine 5, wherein the inverter 6 is electrically connected to the traction battery 2 and a charging connection 7 for electrically connecting to a DC charging station 3 external to the vehicle.

[0029] The inverter 6 is configured as a flying capacitor inverter, in particular as a three-phase three-level inverter with flying capacitors.

[0030] The inverter 6 has three strands S1, S2, and S3 between a positive potential line and a negative potential line, and four semiconductor switching units S11 to S34 are electrically connected in series on each strand, and one inverter capacitor C1, C2, and C3 is respectively arranged between a tap between the first semiconductor switching unit S11, S21, and S31 and the second semiconductor switching unit S12, S22, and S32 of each strand S1, S2, and S3, and a tap between the third semiconductor switching unit S13, S23, and S33 and the fourth semiconductor switching unit S14, S24, and S34. Each of the semiconductor switching units S11 to S34 particularly has one semiconductor switch and a diode, particularly a body diode.

[0031] The center taps of the strands S1, S2, and S3 are connected to the motor windings L1, L2, and L3 of the three-phase AC machine 5, respectively.

[0032] One potential connection of the charging connection 7, and therefore the pole of the DC charging station 3 connected to this potential connection, is connected to the neutral point SP of the three-phase AC machine 5. The other potential connection of the charging connection 7, and therefore the other pole of the DC charging station 3 connected to this potential connection, is electrically connected to the same potentials HV+, HV- of the traction battery 2 via potential lines of the inverter 6 which have the same potentials HV+, HV-.

[0033] As shown in Figures 1 to 4 and 6 to 8, an electrical series connection of two output capacitors Ca1, Ca2 is additionally arranged on the traction battery side of the inverter 6 between the two potential lines, and the potential connection of the charging connection 7, which is electrically connected to the neutral point SP of the three-phase AC machine 5, is also electrically connected to the center tap between these two output capacitors Ca1, Ca2. Alternatively, as shown in Figures 5 and 9, only one output capacitor Ca is arranged on the traction battery side of the inverter 6 between the two potential lines.

[0034] Furthermore, the charging connection 7 is electrically coupled to the input capacitor Ce, i.e. a potential connection of the charging connection 7 is electrically coupled to a respective connection of the input capacitor Ce.

[0035] The circuits shown in the described figures 1 to 9 can function as a resonant charge pump, thereby offering the possibility to increase the charging voltage of the DC charging station 3 up to the rated voltage level of the traction battery 2. In this case, the 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 flying capacitor bridge.

[0036] In the embodiment shown in Figures 1 to 4 and 6 to 8, an electrical series connection of two output capacitors Ca1, Ca2 is arranged on the traction battery side of the inverter 6 between the two potential lines, and furthermore the potential connection of the charging connection 7, which is electrically connected to the neutral point SP of the three-phase alternator 5, is also electrically connected to the center tap between these two output capacitors Ca1, Ca2, which also provides the possibility to utilize advantages in power transmission and EMC.

[0037] In a method for operating a vehicle 1, in particular for charging the traction battery 2 using a DC charging station 3 electrically connected to a charging connection 7, the charging voltage of which is lower than the rated voltage of the traction battery 2, in one of the strands S1, S2, S3 of the inverter 6, in a first step, the semiconductor switches S11, S21, S31, S14, S24, S34 closest to the potential line of the inverter 6 electrically connected to the charging connection 7 are closed, and the following semiconductor switches S12, S22, S32, S13, S23, S33 are left open, and in a second step, the semiconductor switches S11, S21, S31, S14, S24, S34 closest to the potential line of the inverter 6 electrically connected to the charging connection 7 are opened, and subsequently the following semiconductor switches S12, S22, S32, S13, S23, S33 are closed.

[0038] The solution will be explained in detail again below using Figures 1 to 9.

[0039] 1 to 5, the negative potential connection of the charging connection 7, and thus the negative pole of the DC charging station 3 connected to this negative potential connection, is electrically connected to the neutral point SP of the three-phase AC machine 5. The positive potential connection of the charging connection 7, and thus the positive pole of the DC charging station 3 connected to this positive potential connection, is electrically connected to the positive potential HV+ of the traction battery 2 via a potential line of the inverter 6 which has a positive potential HV+. Thus, in this embodiment, the negative potential HV− of the DC charging station 3 drops further, while the positive potential HV+ between the DC charging station 3 and the traction battery 2 remains at the same level.

[0040] In the embodiment according to Figures 1 to 4, the negative potential connection of the charging connection 7, which is electrically connected to the neutral point SP of the three-phase AC machine 5, is additionally also electrically connected to the center tap between the two output capacitors Ca1, Ca2.

[0041] 2 and 3 show the mode of operation of this embodiment.

[0042] In the first step shown in Figure 2, the first semiconductor switching unit S11 of the first strand S1 is closed, and the second semiconductor switching unit S12 of the first strand S1 remains open. The charging voltage of the DC charging station 3 is applied to the series connection of the first inverter capacitor C1 and the first motor winding L1. At this time, the first motor winding L1 and the first inverter capacitor C1 form a resonant circuit. The current increases and then decreases again in a half-sine oscillation. At this time, the first inverter capacitor C1 is charged.

[0043] In the second step shown in Figure 3, the first semiconductor switching unit S11 of the first strand S1 is opened, and the second semiconductor switching unit S12 of the first strand S1 is closed. The voltage of the first inverter capacitor C1 is connected in series with the charging voltage of the DC charging station 3 and integrated. The current increases in a half-sinusoidal pattern and then decreases again. This discharges the first inverter capacitor C1. The current direction in the first motor winding L1 remains the same as in the first step. The current flows from the DC charging station 3 to the traction battery 2, through the fourth semiconductor switching unit S14 of the first strand S1 (particularly its body diode), the first inverter capacitor C1, the second semiconductor switching unit S12 of the first strand S1, and the first motor winding L1. This charges the traction battery 2.

[0044] The third and fourth semiconductor switching units S13, S14 of the first strand S1 act only as diodes, in particular as body diodes, throughout the entire current.

[0045] 4 shows the operating mode of the embodiment according to FIGS. 1 to 3, in which the negative potential connection of the charging connection 7, which is electrically connected to the neutral point SP of the three-phase AC machine 5, is additionally electrically connected to the center tap between the two output capacitors Ca1 and Ca2. As a result, the first output capacitor Ca1 is always in parallel with the DC charging station 3 and the input capacitor Ce. The charge pump generates a voltage increase in the series connection of the two output capacitors Ca1 and Ca2. This means that the first output capacitor Ca1 is always at the charging voltage level of the DC charging station 3, so only the second output capacitor Ca2 is charged.

[0046] 5 shows an embodiment according to FIGS. 1 to 3, but in this case there is only one output capacitor Ca, and therefore the negative potential connection of the charging connection 7, which is electrically connected to the neutral point SP of the three-phase alternator 5, is not additionally electrically connected to the center tap between the two output capacitors Ca1, Ca2. Nevertheless, this circuit can still basically continue to function, thereby allowing charging of the traction battery 2 at a DC charging station 3 whose charging voltage is lower than the rated voltage of the traction battery 2.

[0047] 6 to 9, the positive potential connection of the charging connection 7, and thus the positive pole of the DC charging station 3 connected to this positive potential connection, is electrically connected to the neutral point SP of the three-phase AC machine 5. The negative potential connection of the charging connection 7, and thus the negative pole of the DC charging station 3 connected to this negative potential connection, is electrically connected to the negative potential HV− of the traction battery 2 via a potential line of the inverter 6 which has a negative potential HV−. Thus, in this embodiment, the positive potential HV+ of the DC charging station 3 drops further, while the negative potential HV− between the DC charging station 3 and the traction battery 2 remains at the same level.

[0048] In the embodiment according to Figures 6 to 8, the positive potential connection of the charging connection 7, which is electrically connected to the neutral point SP of the three-phase AC machine 5, is additionally also electrically connected to the center tap between the two output capacitors Ca1, Ca2.

[0049] Figures 6 and 7 show the mode of operation of this embodiment.

[0050] In the first step shown in Figure 6, the fourth semiconductor switching unit S14 of the first strand S1 is closed, while the third semiconductor switching unit S13 of the first strand S1 remains open. The charging voltage of the DC charging station 3 is applied to the series connection of the first inverter capacitor C1 and the first motor winding L1. At this time, the first motor winding L1 and the first inverter capacitor C1 form a resonant circuit. The current increases and then decreases again in a half-sine oscillation. At this time, the first inverter capacitor C1 is charged.

[0051] In the second step shown in Figure 7, the fourth semiconductor switching unit S14 of the first strand S1 is opened, and the third semiconductor switching unit S13 of the first strand S1 is closed. The voltage across the first inverter capacitor C1 is connected in series with the charging voltage of the DC charging station 3 and integrated. The current increases in a half-sinusoidal pattern and then decreases again. This discharges the first inverter capacitor C1. The current direction in the first motor winding L1 remains the same as in the first step. The current flows from the DC charging station 3 to the first motor winding L1, through the third semiconductor switching unit S13 of the first strand S1, the first inverter capacitor C1, the second semiconductor switching unit S12 of the first strand S1, and in particular its body diode, and then back through the traction battery. This charges the traction battery 2.

[0052] The first and second semiconductor switching units S11, S12 of the first strand S1 act only as diodes, in particular as body diodes, throughout the entire current.

[0053] Figure 8 shows the operating mode of the embodiment according to Figures 6-7, in which the positive potential connection of the charging connection 7, which is electrically connected to the neutral point SP of the three-phase AC machine 5, is additionally electrically connected to the center tap between the two output capacitors Ca1, Ca2. As a result, the second output capacitor Ca2 is always in parallel with the DC charging station 3 and the input capacitor Ce. The charge pump generates a voltage increase in the series connection of the two output capacitors Ca1, Ca2, i.e., the second output capacitor Ca2 is always at the charging voltage level of the DC charging station 3, so only the first output capacitor Ca1 is charged.

[0054] 6 and 7, but in this case there is only one output capacitor Ca, and therefore the positive potential connection of the charging connection 7, which is electrically connected to the neutral point SP of the three-phase alternator 5, is not additionally electrically connected to the center tap between the two output capacitors Ca1, Ca2. Nevertheless, this circuit can basically still continue to function, thereby allowing charging of the traction battery 2 at a DC charging station 3 whose charging voltage is lower than the rated voltage of the traction battery 2. [Explanation of symbols]

[0055] 1 vehicle 2 Traction Battery 3 DC charging stations 4 Drive Unit 5 Three-phase alternator 6 inverters 7 Charging connector C1, C2, C3 inverter capacitors Ca, Ca1, Ca2 output capacitors Ce input capacitor HV+, HV- potential L1, L2, L3 motor windings Rib Traction battery internal resistance Ril DC charging station internal resistance S1, S2, S3 strands S11~S34 Semiconductor switching units SP neutral point

Claims

1. A vehicle (1), a traction battery (2); a drive unit (4) having a three-phase AC machine (5) and an inverter (6) electrically connected to the three-phase AC machine (5), the inverter (6) being electrically connected to the traction battery (2); a charging connection (7) for electrically connecting to a DC charging station (3) external to the vehicle; In the vehicle (1), the inverter (6) is formed as a flying capacitor inverter, one potential connection part of the charging connection part (7) is electrically connected to a neutral point (SP) of the three-phase AC machine (5), and the other potential connection part of the charging connection part (7) is electrically connected to the same potentials (HV+, HV-) of the traction battery (2) via potential lines of the inverter (6) having the same potentials (HV+, HV-); the charging connection (7) is electrically connected to an input capacitor (Ce); and The vehicle (1) is characterized in that an electrical series connection consisting of two output capacitors (Ca1, Ca2) is arranged on the traction battery side of the inverter (6) between the two potential lines, and further, the potential connection part of the charging connection part (7) electrically connected to the neutral point (SP) of the three-phase AC machine (5) is also electrically connected to a center tap between these two output capacitors (Ca1, Ca2).

2. 2. A method for operating a vehicle (1) according to claim 1, comprising:

1. The method for charging the traction battery (2) using a DC charging station (3) electrically connected to the charging connection (7), the charging voltage of which is lower than the rated voltage of the traction battery (2), characterized in that the charging voltage is converted by the inverter (6) into a voltage having a voltage value which corresponds at least to the rated voltage of the traction battery (2).

3. In any one of the strands (S1, S2, S3) of the inverter (6), In a first step, the semiconductor switches (S11, S21, S31, S14, S24, S34) of the inverter (6) that are electrically connected to the charging connection (7) and that are closest to the potential line are closed, while the following semiconductor switches (S12, S22, S32, S13, S23, S33) are left open; 3. The method according to claim 2, characterized in that in a second step the semiconductor switches (S11, S21, S31, S14, S24, S34) closest to the potential line of the inverter (6) electrically connected to the charging connection (7) are opened, followed by closing the next semiconductor switches (S12, S22, S32, S13, S23, S33).

4. 4. The method according to claim 2 or 3, characterized in that during the driving operation of the vehicle (1), a DC voltage provided by the traction battery (2) is converted by means of the inverter (6) into an AC voltage for supplying electrical energy to the three-phase AC machine (5).

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