Traction network for a motor vehicle

Abstract

The invention relates to a traction network (1) for a motor vehicle, the traction network (1) having at least one high-voltage battery (2), an inverter (6), an electric machine (7), at least one intermediate circuit capacitor (C), a DC voltage charging interface (11) and an AC voltage charging interface, a rectifier (8) and a DC / DC converter (12) being arranged between the AC voltage charging interface and the high-voltage battery (2), the DC / DC converter (12) is also arranged between the high-voltage battery (2) and the inverter (6), the DC / DC converter (12) is designed as a bidirectional DC / DC converter (12), a cooling plate (20) is provided, and the cooling plate (20) is arranged between the high-voltage battery (2) and the inverter (6). At least the inverter (6), the DC / DC converter (12), the at least one intermediate circuit capacitor (C) and the rectifier (8) are arranged on a cooling plate (20) together with an inductance (L) associated with the rectifier.

Description

Technical Field

[0001] The invention relates to a traction network for a motor vehicle. Background Art

[0002] The typical structure of a traction network consists of a traction battery, an inverter and an electric motor. There are many different topologies known for how the individual components of such a traction network are constructed. In order to reduce the current, attempts are made to operate at the highest possible voltage on the vehicle side. For example, the following traction network is known, in which the rated voltage of the traction battery is 800V. This leads to problems with the voltage resistance of the semiconductor switches, so a 3-level inverter as described in patent document DE10 2016206 945A1 is recommended for such a traction network. Another problem is that the charging infrastructure is not unified, with both 400V DC charging stations and 800V DC charging stations. Depending on the topology used, the maximum charging power cannot be fully utilized here, or the complexity of the circuit is very high.

[0003] Furthermore, it is usually desirable to also be able to use AC voltage for charging. In this case, a rectifier is arranged between the AC voltage charging interface and the high-voltage battery, which converts the AC voltage into a DC voltage. A DC / DC converter (DC / DC-Wandler) can be additionally provided here, which adapts the rectified voltage to the voltage level of the high-voltage battery.

[0004] Patent document DE 10 2019 106 485 A1 discloses a Weissach rectifier arrangement which can be adapted to different configurations of the AC voltage charging side.

[0005] A traction network of the type described in the present invention is known from patent document DE 10 2019 209 654 A1. Similar traction networks are known from patent documents DE 10 2015 219 863 A1 and DE 10 2015 207 413 A1.

[0006] Patent document DE 10 2019 117 345 A1 discloses a high-voltage battery having two battery cells, wherein the two battery cells can be connected in parallel or in series via a switching unit. Summary of the invention

[0007] The object of the present invention is to design a traction network of the type described in the invention in a compact manner.

[0008] The solution to the technical problem is provided by a traction network. Other advantageous embodiments of the invention are provided by the description.

[0009] The traction network for a motor vehicle has at least one high-voltage battery, an inverter, an electric machine, at least one intermediate circuit capacitor, a DC voltage charging interface and an AC voltage charging interface. Here, a rectifier and a DC / DC converter are arranged between the AC voltage charging interface and the high-voltage battery, wherein the DC / DC converter is also arranged between the high-voltage battery and the inverter, wherein the DC / DC converter is designed as a bidirectional DC / DC converter. A cooling plate is provided here, wherein at least the inverter, the DC / DC converter, at least one intermediate circuit capacitor and the rectifier are arranged on the cooling plate together with the inductance assigned to the rectifier. A very compact design is thus achieved because only one central cooling system is required. Preferably, these components are arranged both on the upper side of the cooling plate and on the lower side of the cooling plate. This can be achieved because the DC / DC converter has a dual function, thereby saving a separate DC / DC converter. In addition, the intermediate circuit capacitor can also be designed with smaller dimensions through the DC / DC converter. The DC / DC converter is preferably designed as a bidirectional step-up / step-down regulator (or chopper).

[0010] In one embodiment, the cooling plate is designed as a cooling plate through which a liquid flows, wherein the liquid is preferably water. The cooling plate is preferably formed from an aluminum die casting.

[0011] In a further embodiment, the rectifier, the inverter and the DC / DC converter have a common central controller, which further saves components and facilitates integration on a common cooling plate.

[0012] In a further embodiment, the DC / DC converter is designed as a three-phase interleaved DC / DC converter, which is preferably designed asymmetrically, i.e. one of the phases is dimensioned for a lower power. This allows the losses to be reduced when the power demand is low, since only the weaker phase with less losses is used when the power demand is low. This also requires less cooling power.

[0013] In other embodiments, the rectifier is designed as a unidirectional Vienna rectifier or a bidirectional neutral point clamped rectifier or Weissach rectifier. The advantage of a unidirectional Vienna rectifier is that it is very robust and requires fewer components and is easy to scale. This simplifies integration on the one cooling plate. On the other hand, a bidirectional rectifier allows feedback to an external network, while a Weissach rectifier allows simple adaptation to different external AC voltage charging structures.

[0014] In another embodiment, the DC / DC converter has a switching module, which is designed so that in a first switch position, the DC / DC converter is connected to the input interface of the inverter, and in a second switch position, the DC / DC converter is connected to the output interface of the rectifier. This also ensures that when the high-voltage battery is charged, the electric machine is not energized and therefore no undesired drive torque is generated.

[0015] In another embodiment, the high-voltage battery has two battery cells with the same rated voltage and a switch module, wherein the switch module is designed so that the two battery cells can be selectively connected in parallel or in series. For example, the rated voltage is 400V, so a high-voltage battery with 400V or 800V can be used for the drive device, thereby reducing the required current. Here, the two battery cells can be equalized in voltage technology before being connected in parallel through corresponding circuit connections to reduce the compensation current.

[0016] In a further embodiment, the DC / DC converter and the inverter are assigned a common interference suppression filter, which further saves components.

[0017] In other embodiments, the switching elements of the switching module of the DC / DC converter are designed as relays and / or the switching elements of the switching module of the high-voltage battery are designed as relays in order to respectively enable electrical isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention is described in more detail below based on preferred embodiments. In the accompanying drawings:

[0019] Figure 1 A schematic diagram of a traction network is shown;

[0020] Figure 2 shows a schematic diagram of a traction network with a three-phase interleaved DC / DC converter in a first embodiment;

[0021] Figure 3 shows a schematic diagram of a traction network with a three-phase interleaved DC / DC converter in a second embodiment;

[0022] Figure 4 shows a perspective view of a cooling plate; and

[0023] Figure 5 A perspective view of a cooling plate with a further printed circuit board is shown. DETAILED DESCRIPTION

[0024] exist Figure 1The basic structure of the traction network 1 is schematically shown in FIG. The traction network 1 has a high-voltage battery 2, which has two battery cells 3 and a switching module 4. The traction network also has a DC / DC converter 12, an inverter 6, an electric machine 7 and a rectifier 8. The rectifier 8 has three input terminals L1-L3, at which inductors L are arranged respectively, and the other end of the inductor forms an AC voltage interface for an external AC voltage source 10, wherein the neutral conductor zero line of the AC voltage source 10 is led to the connection between the rectifier 8 and the neutral point of the DC / DC converter 12. The DC / DC converter 12 is preferably a bidirectional step-up / step-down regulator, which steps up the rectified voltage at the output of the rectifier 8 to the voltage of the high-voltage battery 2. In addition, the traction network 1 has a DC voltage interface 11, which is connected to the switching module 4 of the high-voltage battery 2. With the help of the switching module 4, two battery cells 3 can be selectively connected in parallel or in series. In addition, the switching module 4 can have a device for compensating the voltage difference between the battery cells 3. If the battery cell 3 has a rated voltage of 400 V, for example, it can be charged selectively at 400 V or 800 V at the DC voltage charging interface 11. The compensation current in the parallel connection is reduced by means of a device for compensating the voltage difference. This voltage compensation can be realized in different ways, for example by cell balancing. Independent of the voltage of the high-voltage battery 2, the required operating point on the electric machine 7 can be adjusted by the DC / DC converter 12 via the inverter 6, wherein the recuperation energy can be fed back into the high-voltage battery 2 by means of a bidirectional design.

[0025] exist Figure 2 According to Figure 1A traction network 1 is shown, in which an AC voltage filter 13 and a DC voltage filter 14 are additionally shown. In addition, a possible circuit connection of a DC / DC converter 12 is shown, by which the DC / DC converter 12 can be operated both as a step-up regulator and as a step-down regulator. It is also shown here that the circuit connection shown has a total of three parallel connections in order to distribute the power. Here, the three phases can be controlled in a time-shifted manner. This represents a three-phase interleaved DC / DC converter 12, wherein the three-phase interleaved DC / DC converter 12 is preferably asymmetrical, that is, one of the phases is designed for lower current or power. It is also shown that the neutral point of the high-voltage battery 2 is connected to the neutral point of the DC / DC converter 12. A switching module 15 in the DC / DC converter 12 is also shown. Switching elements are arranged in the switching module 15, and these switching elements are preferably designed as relays. When charging with an AC voltage, the inverter 6 can be disconnected from the DC / DC converter 12 by means of a switching element so that the output terminals DC+, N and DC- of the rectifier 8 are connected to the points P1-P3 of the DC / DC converter 12. The intermediate circuit capacitor C is formed here by two capacitors C1 and C2, which are shown here as components of the DC / DC converter 12. The half bridges of the DC / DC converter 12 are stacked here so that the transistors do not have to be designed for such a high cut-off voltage. However, four transistors and two inductors are required for each half bridge. This increases the difficulty of integration on the cooling plate.

[0026] exist Figure 3 An alternative embodiment of a DC / DC converter 12 is shown in FIG. 1 , in which each half-bridge has only two transistors, wherein the two half-bridges are each connected at their center taps via an inductor L DC / DC Here, for example, the upper phase is dimensioned for low power, in which case the upper phase is only used for the low power range of the motor 7. Accordingly, the transistors of the two half-bridges of this phase and the inductance L of this phase DC / DC This also allows for a smaller design. This again represents an asymmetrical three-phase interleaved DC / DC converter 12. It should be noted here that instead of separate capacitors (eg C1, C2), a single capacitor can also be used in each case.

[0027] exist Figure 4 1 shows a perspective view of how all components that significantly generate heat loss are arranged on a common cooling plate 20. A control board 23 for the rectifier 8 and the DC / DC converter 12 is arranged on the underside 21 of the cooling plate 20. In addition, the inductors L of the rectifier 8 are arranged, wherein every two inductors are connected in series, so that six inductors L are shown here (instead of 1 as in FIG. 1 ). Figure 3 In addition, the inductance L of the DC / DC converter 12 DC / DCThe three half bridges HB are arranged on the bottom side 21 of the cooling plate 20, wherein the other three half bridges are arranged on the top side 22 of the cooling plate 20, wherein the inductance L DC / DC The electrical connection between the three half bridges on the upper side 22 is realized by busbars 24. Here, the uppermost busbar 24 can also be designed to be narrower than the other two busbars 24, because the uppermost busbar is assigned to the phase for the lower power. The intermediate circuit capacitor C and the control board 25 with the gate driver for the inverter 6 and the power module 26 for the inverter 6 are also arranged on the upper side 22 of the cooling plate 20. Therefore, preferably a single cooling plate 20 through which the liquid flows is sufficient to cool all components that generate significant heat loss, so that a very compact structure is achieved.

[0028] exist Figure 5 , a perspective view is shown of how cooling plate 20 or components arranged thereon are connected to a further printed circuit board 27 , on which AC voltage filter 13 of rectifier 8 and a common interference suppression filter 28 for DC / DC converter 12 and inverter 6 are arranged.

[0029] Reference numerals list

[0030] 1 Traction network

[0031] 2 High voltage battery

[0032] 3 Battery Cells

[0033] 4 Switch module

[0034] 6 Inverter

[0035] 7 Motor

[0036] 8 Rectifier

[0037] 10 AC voltage source

[0038] 11 DC voltage charging interface

[0039] 12 DC / DC Converter

[0040] 13 AC voltage filter

[0041] 20 Cooling Plate

[0042] 21 Lower side

[0043] 22 upper side

[0044] 23 Control Panel

[0045] 24 Bus

[0046] 25 Control Panel

[0047] 26 Power Module

[0048] 27 Printed Circuit Board

[0049] 28 Interference removal filter

[0050] L DC / DC Inductor for DC / DC Converters

[0051] L is the inductance of the rectifier

[0052] C Intermediate circuit capacitor

[0053] N Neutral point

Claims

1. A traction network (1) for a motor vehicle, wherein: The traction network (1) comprises at least one high-voltage battery (2), an inverter (6), an electric machine (7), at least one intermediate circuit capacitor (C), a DC voltage charging interface (11) and an AC voltage charging interface, wherein a rectifier (8) and a DC / DC converter (12) are arranged between the AC voltage charging interface and the high-voltage battery (2), wherein the DC / DC converter (12) is also arranged between the high-voltage battery (2) and the inverter (6), wherein the DC / DC converter (12) is designed as a bidirectional DC / DC converter (12), It is characterized in that A cooling plate (20) is provided, wherein at least the inverter (6), the DC / DC converter (12), at least one intermediate circuit capacitor (C) and the rectifier (8) together with an inductor (L) associated with the rectifier are arranged on the cooling plate (20).

2. The traction network according to claim 1, characterized in that: The cooling plate (20) is designed as a cooling plate (20) through which a liquid flows.

3. The traction network according to claim 1 or 2, characterized in that: The rectifier (8), the inverter (6) and the DC / DC converter (12) have a common central controller.

4. Traction network according to any of the preceding claims, characterized in that The DC / DC converter (12) is designed as a three-phase interleaved DC / DC converter (12).

5. The traction network according to claim 4, characterized in that: The DC / DC converter (12) is designed as an asymmetric three-phase interleaved DC / DC converter (12).

6. Traction network according to any of the preceding claims, characterized in that The rectifier (8) is designed as a unidirectional Vienna rectifier or a bidirectional neutral point clamped rectifier or a Weissach rectifier.

7. Traction network according to any of the preceding claims, characterized in that The DC / DC converter (12) has a switching module (15) which is designed such that in a first switching position the DC / DC converter (12) is connected to an input interface of an inverter (6), and in another switching position the DC / DC converter is connected to an output interface of a rectifier (8).

8. Traction network according to any one of the preceding claims, characterized in that The high-voltage battery (2) has two battery cells (3) with the same rated voltage and a switching module (4), wherein the switching module (4) is designed to selectively connect the two battery cells (3) in parallel or in series.

9. Traction network according to any one of the preceding claims, characterized in that The DC / DC converter (12) and the inverter (6) are equipped with a common interference removal filter (28).

10. The traction network according to claim 7 or 8, characterized in that: The switching element of the switching module (15) of the DC / DC converter (12) is designed as a relay, and / or the switching element of the switching module (4) of the high-voltage battery (2) is designed as a relay.

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