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 described in the characterizing portion of the preamble of claim 1 and a method for operating the vehicle.

[0002] From prior arts such as Patent Document 1 and Patent Document 2, a charging system and method with multiple inputs using a motor drive system are well-known. The multiple-input charging system using a motor drive system includes an inverter connected to a rechargeable battery. This inverter includes a number of switching elements. Further, the multiple-input charging system includes a motor connected to the inverter and provided to supply electricity provided at the neutral point of the motor to the inverter, a first relay having one end connected to the battery and the other end connected to a charging power input connection portion to which DC charging power is applied from the outside, a second relay having one end connected to the neutral point and the other end connected to the charging power input connection portion, a neutral point capacitor connected to the other ends of the first relay and the second relay and provided to form an input charging voltage, a third relay having one end connected to the neutral point capacitor and the other end connected to the charging power input connection portion, a control device provided to control a number of switching elements of the inverter so as to turn on the third relay in a charging mode for charging the battery, selectively turn on the first relay and the second relay based on the value of the DC charging voltage to supply the DC charging power to the battery, and forcibly discharge the neutral point capacitor when the charging of the battery is completed.

[0003] In Patent Document 3, a bridge circuit and a charge pump are described. 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. In parallel with the supply circuit, a first half-bridge circuit is connected, and this 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 connected in series at a first bridge point and arranged in parallel with the first capacitor. The first diode and the second diode are connected in series at a second bridge point and arranged in parallel with the second capacitor. The first resonant main circuit is connected to the first bridge point and the second bridge point. A load discharge circuit is connected to the first resonant main circuit at the second bridge point. The load discharge circuit is configured as a second half-bridge circuit and is provided to maintain the 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, a vehicle electric drive system and a method for operating a corresponding electric drive system are well-known. This electric drive system includes an electric three-phase alternator for driving a vehicle, an electrical energy storage device for supplying electricity to the electric three-phase alternator during vehicle travel, an inverter of the electric three-phase alternator electrically connected to this electrical energy storage device, and a vehicle-side charging connection for electrically connecting the electrical energy storage device to a charging unit outside the vehicle. Depending on the 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 having the corresponding electric drive system, and a method for operating the corresponding electric drive system. This electric drive system has a switching device. This switching device has a first switching state in which a charging connection is directly connected to the electrical energy storage device of the vehicle, whereby charging of the electrical energy storage device is possible by an input voltage at the charging connection, and a second and a third switching state in which the charging connection is connected to the electrical energy storage device via an inverter, whereby charging of the electrical energy storage device is possible depending on the inverter.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0008] According to the present 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 present invention are the subject of the dependent claims.

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

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

[0012] According to the present invention, the inverter is formed as a flying capacitor inverter, in particular as a three-phase three-level inverter having a flying capacitor.

[0013] A method according to the present invention for operating a vehicle uses a DC charging station electrically connected to a charging connection, wherein the charging voltage is lower than the rated voltage of the traction battery, to charge the traction battery, and the charging voltage is converted by the inverter to a voltage having a voltage value corresponding to at least the rated voltage of the traction battery.

[0014] In addition, in particular during the running operation of the vehicle, the DC voltage provided by the traction battery is converted into an AC voltage by using the inverter to supply electrical energy to the three-phase alternator.

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

[0016] To enable this, in particular, the inverter has three strands, each called a phase, between the positive potential line and the negative potential line, and four semiconductor switching units are electrically connected in series to each strand. An inverter capacitor is arranged between the tap between the first and the second semiconductor switching units of each strand and the tap between the third and the fourth semiconductor switching units of each strand. The semiconductor switching unit particularly has one semiconductor switch and one diode each. In particular, the semiconductor switch is formed as a bipolar transistor each having an insulated gate electrode.

[0017] In particular, the center tap of the strand is electrically connected to one motor winding of the three-phase AC machine each.

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

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

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

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

[0022] In this solution, due to the interaction between the motor inductance of the three-phase alternator and the inverter capacitor of the flying capacitor bridge of the inverter, a resonant circuit is formed. Thereby, losses in the semiconductor can be minimized, or advantageous semiconductors can be used. Further, since the harmonic components of interference are very small, the EMC filter (EMC = electromagnetic compatibility) can be advantageously maintained.

[0023] Therefore, with the solution according to the invention, it is possible to charge the traction battery at a DC charging station where the charging voltage is lower than the rated voltage of the traction battery, without incurring additional costs or with only minimal additional costs. For example, the rated voltage of the traction battery is 800 V and the charging voltage is 400 V. As explained, for this purpose, a flying capacitor inverter is used as the inverter topology, and in order to enable this charging of the traction battery, i.e., to raise the low charging voltage to the rated voltage level of the traction battery, one potential connection of the charging connection, and thus 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 thus the other pole of the DC charging station electrically connected to the charging connection, is connected to the pole of the traction battery having the same potential. The circuit thus formed offers the possibility of functioning as a resonant charging pump.

[0024] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0026] In any of the figures, the parts corresponding to each other are denoted by the same reference numerals.

[0027] Figures 1 to 9 show the vehicle 1 and the operation mode of the vehicle 1 while the traction battery 2 of the vehicle 1 is being charged at the DC charging station 3 outside the vehicle, and the charging voltage of the DC charging station 3 is lower than the rated voltage of the traction battery 2. In this case, the vehicles 1 in Figures 1 to 9 are already electrically connected to the DC charging station 3 respectively. Figures 1 to 9 also show the internal resistance Ril of the charging station 3 and the internal resistance Rib of the traction battery 2 respectively.

[0028] The vehicle 1 includes 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, and at this time the inverter 6 is electrically connected to the traction battery 2, and also a charging connection part 7 for electrically connecting to the DC charging station 3 outside the vehicle.

[0029] The inverter 6 is formed as a flying capacitor inverter, particularly as a three-phase 3-level inverter having a flying capacitor.

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

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

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

[0033] As shown in FIGS. 1 to 4 and 6 to 8, additionally, an electrical series connection consisting of two output capacitors Ca1 and Ca2 is arranged on the traction battery side of the inverter 6 between the two potential lines. 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 the center tap between these two output capacitors Ca1 and Ca2. Alternatively, as shown in FIGS. 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 portion 7 is electrically connected to the input capacitor Ce. That is, the potential connection portion of the charging connection 7 is electrically connected to each one connection portion of the input capacitor Ce.

[0035] The circuits shown in FIGS. 1 to 9 described can function as a resonant charging pump, thereby providing the possibility of raising the charging voltage of the DC charging station 3 to the rated voltage level of the traction battery 2. At this time, the resonant circuit is formed by the motor inductance, that is, by the motor windings L1, L2 or L3 and the inverter capacitors C1, C2 or C3 of the flying capacitor bridge.

[0036] In the embodiments shown in FIGS. 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 two potential lines, and further, the potential connection portion of the charging connection portion 7 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. In addition, the possibility of utilizing the advantages in power transmission and EMC is also provided.

[0037] In the method for operating the vehicle 1, in particular, in order to charge the traction battery 2 using the DC charging station 3 electrically connected to the charging connection portion 7 where the charging voltage is lower than the rated voltage of the traction battery 2, in any one of the strands S1, S2, S3 of the inverter 6, in the 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 portion 7 are closed, and the next semiconductor switches S12, S22, S32, S13, S23, S33 are left open. In the 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 portion 7 are opened, and subsequently, the next semiconductor switches S12, S22, S32, S13, S23, S33 are closed.

[0038] Hereinafter, with reference to FIGS. 1 to 9, the solution will be described in detail again.

[0039] In the embodiment according to FIGS. 1 to 5, the negative potential connection part of the charging connection part 7, and thus the negative electrode of the DC charging station 3 connected to this negative potential connection part, is electrically connected to the neutral point SP of the three-phase AC machine 5. The positive potential connection part of the charging connection part 7, and thus the positive electrode of the DC charging station 3 connected to this positive potential connection part, is electrically connected to the positive potential HV+ of the traction battery 2 via the potential line of the inverter 6 having the positive potential HV+. 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 remains at the same level.

[0040] In the embodiment according to FIGS. 1 to 4, the negative potential connection part of the charging connection part 7 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.

[0041] FIGS. 2 and 3 show the operating modes of this embodiment.

[0042] In the first step shown in FIG. 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 in a sine half-wave oscillation and then decreases again. At this time, the first inverter capacitor C1 is charged.

[0043] In the second step shown in FIG. 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 sinusoidal half-wave oscillation and then decreases again. At this time, the first inverter capacitor C1 is discharged. The current direction in the first motor winding L1 here remains the same as in the first step. The current circuit is from the DC charging station 3 through the traction battery 2, the fourth semiconductor switching unit S14 of the first strand S1, especially 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. Thereby, the traction battery 2 is charged.

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

[0045] FIG. 4 shows the operating mode of the embodiment according to FIGS. 1 to 3 when the negative potential connection part of the charging connection part 7 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. Thereby, the first output capacitor Ca1 is always in parallel with the DC charging station 3 and the input capacitor Ce. The charge pump causes an increase in the series connection of the two output capacitors Ca1, Ca2 due to its voltage increase. That is, since the first output capacitor Ca1 is always at the charging voltage level of the DC charging station 3, only the second output capacitor Ca2 is charged.

[0046] Figure 5 shows the embodiment according to FIGS. 1 to 3. In this case, there is only one output capacitor Ca. Therefore, the negative potential connection part of the charging connection part 7 that 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 and Ca2. Nevertheless, this circuit can basically continue to function, thereby enabling the charging of 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.

[0047] In the embodiments according to FIGS. 6 to 9, the positive potential connection part of the charging connection 7, and thus the positive electrode of the DC charging station 3 connected to this positive potential connection part, is electrically connected to the neutral point SP of the three-phase alternator 5. The negative potential connection part of the charging connection part 7, and thus the negative electrode of the DC charging station 3 connected to this negative potential connection part, is electrically connected to the negative potential HV- of the traction battery 2 via the potential line of the inverter 6 having the negative potential HV-. 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 remains at the same level.

[0048] In the embodiments according to FIGS. 6 to 8, the positive potential connection part of the charging connection part 7 that is electrically connected to the neutral point SP of the three-phase alternator 5 is additionally electrically connected to the center tap between the two output capacitors Ca1 and Ca2.

[0049] FIGS. 6 and 7 show the operating modes of this embodiment.

[0050] In the first step shown in FIG. 6, the fourth semiconductor switching unit S14 of the first strand S1 is closed, and 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 in a sine half-wave oscillation. At this time, the first inverter capacitor C1 is charged.

[0051] In the second step shown in FIG. 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 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 and then decreases in a sine half-wave oscillation. At this time, the first inverter capacitor C1 is discharged. The current direction in the first motor winding L1 here remains the same as that in the first step. The current circuit returns from the DC charging station 3 through the first motor winding L1, 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, especially its body diode, and the traction battery. Thereby, the traction battery 2 is charged.

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

[0053] FIG. 8 shows the operating mode of the embodiment according to FIGS. 6 to 7 when the positive potential connection part of the charging connection part 7 electrically connected to the neutral point SP of the three-phase alternator 5 is additionally electrically connected to the center tap between the two output capacitors Ca1 and Ca2. Thereby, the second output capacitor Ca2 is always in parallel with the DC charging station 3 and the input capacitor Ce. The charging pump causes an increase in the series connection of the two output capacitors Ca1 and Ca2 by its voltage increase. That is, since the second output capacitor Ca2 is always at the charging voltage level of the DC charging station 3, only the first output capacitor Ca1 is charged.

[0054] FIG. 9 shows the embodiment according to FIGS. 6 and 7, but in this case, there is only one output capacitor Ca, and therefore, the positive potential connection part of the charging connection part 7 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 and Ca2. Nevertheless, this circuit can basically continue to function, thereby enabling the charging of 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.

Description of reference numerals

[0055] 1 Vehicle 2 Traction battery 3 DC charging station 4 Drive unit 5 Three-phase alternator 6 Inverter 7 Charging connection part C1, C2, C3 Inverter capacitors Ca, Ca1, Ca2 Output capacitors Ce Input capacitor HV+, HV- Potentials L1, L2, L3 Motor windings Rib Internal resistance of the traction battery Ril Internal resistance of the DC charging station S1, S2, S3 Strands S11 to S34 semiconductor switching units SP neutral point

Claims

1. A vehicle (1), 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), wherein the inverter (6) is electrically connected to the traction battery (2), a charging connection part (7) for electrically connecting to a DC charging station (3) outside the vehicle, and 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 the neutral point (SP) of the three-phase alternator (5), and the other potential connection part of the charging connection part (7) is electrically connected to the same potential (HV+, HV−) of the traction battery (2) via the potential line of the inverter (6) having the same potential, the vehicle (1), characterized in that the charging connection part (7) is electrically connected to an input capacitor (Ce).

2. On the traction battery side of the inverter (6) between the two potential lines, an electrical series connection composed of two output capacitors (Ca1, Ca2) is arranged, and further, the potential connection part of the charging connection part (7) 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). The vehicle (1) according to Claim 1, characterized by this.

3. In a method for operating the vehicle (1) according to Claim 1 or 2, using a DC charging station (3) electrically connected to the charging connection part (7) where the charging voltage is lower than the rated voltage of the traction battery (2) to charge the traction battery (2), the method is characterized in that the charging voltage is converted to a voltage having a voltage value corresponding to at least the rated voltage of the traction battery (2) using the inverter (6).

4. In any one of the strands (S1, S2, S3) of the inverter (6), In the 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 part (7) are closed, and the next semiconductor switches (S12, S22, S32, S13, S23, S33) are left open. The method according to claim 3, characterized in that, in the 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 part (7) are opened, and subsequently, the next semiconductor switches (S12, S22, S32, S13, S23, S33) are closed.

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

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