Traction network for a motor vehicle

Abstract

The invention relates to a traction network (1) for a motor vehicle, wherein the traction network (1) has at least one high-voltage battery (2), an inverter (6), an electric machine (7), a DC voltage charging connection (11) and an AC voltage charging connection, wherein a rectifier (8) and a DC / DC converter (9) are arranged between the AC voltage charging connection and the high-voltage battery (2), wherein a DC / DC converter (5) is arranged between the high-voltage battery (2) and the inverter (6).

Description

Technical Field

[0001] This invention relates to a traction network for motor vehicles. Background Technology

[0002] A typical traction network consists of a traction battery, an inverter, and a motor. Many different topologies are known regarding the construction of these components. To reduce current, attempts are made to operate at the highest possible voltage on the vehicle side. For example, traction networks with a traction battery rated at 800V are known. This leads to problems with the withstand voltage of the semiconductor switches, therefore, three-level inverters have been proposed for such traction networks, as described in DE 10 2016206 945A1. Another problem is the lack of a unified charging infrastructure, with both 400V and 800V DC charging stations existing. Depending on the topology used, the maximum charging power cannot be fully utilized, or the circuit overhead is very high.

[0003] Furthermore, it is often desirable to be able to charge using AC voltage as well. In this case, a rectifier is placed between the AC voltage charging terminal and the high-voltage battery, which converts the AC voltage to DC voltage. A DC / DC converter can also be additionally provided here, which adjusts the rectified voltage to the voltage level of the high-voltage battery.

[0004] A Weissach rectifier device is known from DE 10 2019 106 485 A1, which can be adapted to different configurations on the AC voltage charging side. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to establish a traction network in which the operating point setting of the power grid is improved.

[0006] The solution to the aforementioned technical problem is provided by a traction network having the features of the present invention. The present invention also provides other advantageous design solutions.

[0007] Therefore, the traction network for a motor vehicle includes at least one high-voltage battery, an inverter, a motor, a DC voltage charging connector, and an AC voltage charging connector. A rectifier and a DC / DC converter are arranged between the AC voltage charging connector and the high-voltage battery, and the DC / DC converter is arranged between the high-voltage battery and the inverter. This DC / DC converter allows the motor to operate at an optimized operating point, independent of the current voltage level of the high-voltage battery. Optimization can be achieved, for example, in terms of efficiency or drive power.

[0008] In one implementation, the DC / DC converter between the AC voltage connector and the high-voltage battery, and the DC / DC converter between the high-voltage battery and the inverter, are designed as a common DC / DC converter. This saves components, which in turn saves cost and installation space. Another advantage is that this common DC / DC converter can be compactly arranged on a circuit board with corresponding cooling components. Since the DC / DC converter is designed for the inverter in terms of power, the inverter setup is always sufficient for AC voltage charging. If the rectifier is accordingly constructed to be scalable, so that it can, for example, handle charging power of 11, 22, or 43 kW, no further adjustment to the DC / DC converter is required, as it is typically designed for higher power inverters. Therefore, when scaling AC voltage charging power, the changing requirements are reduced to rectifier adjustments.

[0009] In another embodiment, the high-voltage battery has two battery cells with the same rated voltage, and a switching module designed so that the two battery cells can be optionally connected in parallel or in series. For example, with a rated voltage of 400V, the high-voltage battery can be charged with a DC voltage of 400V or 800V, which can be used for driving in an 800V traction network, thereby reducing the required current. Here, appropriate circuit connections ensure that the two battery cells are voltage-balanced before being connected in parallel to reduce compensation current.

[0010] In another implementation, the DC / DC converter is designed as a bidirectional boost-buck chopper, which allows for maximum freedom in setting the motor's operating point. However, this increases circuit overhead.

[0011] Therefore, in an alternative implementation, the DC / DC converter is designed as a bidirectional boost chopper so that the voltage of the high-voltage battery is always boosted.

[0012] Alternatively, the DC / DC converter is designed as a bidirectional buck chopper.

[0013] In another implementation, the rectifier is designed as a unidirectional Vienna rectifier, which is highly robust, requires few components, and is easily scalable. Alternatively, the rectifier is designed as a bidirectional neutral-point-clamped Gleichrichter, whereby power can also be fed back to the external grid. Alternatively, the rectifier is designed as a Weissach rectifier, as described in DE 10 2019 106 485A1. This allows for easy adaptation to different external AC voltage charging configurations.

[0014] In another embodiment, the DC / DC converter has a switching module designed to connect to the inverter's input terminal in a first switching position and to the rectifier's output terminal in a second switching position. This also ensures that the motor is not energized while the high-voltage battery is charging, and therefore no undesirable driving torque is generated.

[0015] In another embodiment, the switching module of the high-voltage battery has a neutral point, wherein the neutral point is connected to the neutral point of the DC / DC converter, wherein the inverter is designed as a 3L inverter, and the neutral point of the DC / DC converter is connected to the neutral point of the inverter.

[0016] In another embodiment, the switching elements of the high-voltage battery switching module are designed as relays and / or the switching elements of the DC / DC converter switching module are designed as relays, thereby enabling current isolation respectively. Attached Figure Description

[0017] The present invention will now be described in more detail with reference to preferred embodiments. (See the accompanying drawings.)

[0018] Figure 1 A schematic circuit arrangement of the traction network in the first embodiment is shown.

[0019] Figure 2 A schematic circuit arrangement of the traction network in the second embodiment is shown.

[0020] Figure 3 A schematic circuit layout of the Vienna rectifier is shown.

[0021] Figure 4 A schematic circuit layout for a bidirectional NPC rectifier is shown.

[0022] Figure 5 A schematic circuit layout of a traction network with a boost chopper is shown.

[0023] Figure 6 A schematic circuit layout of a traction network with a 3L inverter is shown.

[0024] Figure 7 A schematic circuit arrangement of the traction network with a boost chopper in the first embodiment is shown.

[0025] Figure 8 A schematic circuit arrangement of the traction network with a boost chopper in the second embodiment is shown.

[0026] Figure 9 A schematic circuit arrangement of the traction network with a boost chopper in the third embodiment is shown; and

[0027] Figure 10 A schematic circuit arrangement of the traction network with a boost chopper in the fourth embodiment is shown. Detailed Implementation

[0028] exist Figure 1 The diagram schematically illustrates a traction network 1 in the first embodiment. The traction network 1 has a high-voltage battery 2 with two battery cells 3 and a switching module 4. Furthermore, the traction network 1 includes a DC / DC converter 5, an inverter 6, a motor 7, a rectifier 8, and another DC / DC converter 9. The rectifier 8 has three input terminals L1-L3, each with an inductor L. The other end of each inductor L forms an AC voltage connector for an external AC voltage source 10, wherein the neutral line of the AC voltage source 10 is guided to a connection line between the neutral point of the rectifier 8 and the DC / DC converter 9. The DC / DC converter 9 is preferably a boost chopper, which boosts the rectified voltage at the output of the rectifier to the voltage of the high-voltage battery 2. Additionally, the traction network 1 has a DC voltage charging connector 11 connected to the switching module 4 of the high-voltage battery 2. The two battery cells 3 can optionally be connected in parallel or in series using the switching module 4. Furthermore, the switching module 4 may have a device for compensating for voltage differences between the battery cells 3. For example, if battery cell 3 has a rated voltage of 400V, it can be charged at either 400V or 800V at DC voltage charging connector 11. The compensation current is reduced in parallel connections by means of a device for compensating for voltage differences. This voltage compensation can be achieved in different ways, such as by cell balancing. The desired operating point on motor 7 can be set using inverter 6 via DC / DC converter 5, regardless of the voltage of high-voltage battery 2. Here, DC / DC converter 5 is designed to be bidirectional to feed recovered energy back to high-voltage battery 2. Furthermore, preferably, DC / DC converter 5 is designed as a boost-buck chopper, so that the high-voltage battery voltage can be boosted or bucked according to the operating point voltage set on motor 7. Therefore, the traction network 1 shown is very flexible in terms of external charging voltage and in terms of setting the operating point on motor 7. However, the circuit overhead is also considerable.

[0029] Figure 2The diagram now shows a traction network 1, in which a DC / DC converter 9 is integrated into a DC / DC converter 5 as a common DC / DC converter 12. This has several advantages. On one hand, it saves on components, cost, and installation space. Another advantage is that when adjusting the charging power of the AC voltage source 10, only the rectifier 8 needs to be adjusted in terms of power technology, and the DC / DC converter 12 is designed to be sufficient for all common power levels up to 43kW. Another advantage is cooling. The power losses in the rectifier 8 are typically very low, making simple air cooling sufficient, while the DC / DC converter 12 and possibly the inverter 6 have liquid cooling, but this liquid cooling can be designed to be very compact in terms of space.

[0030] In its simplest case, rectifier 8 can be designed as a unidirectional Vienna rectifier, such as... Figure 3 As shown. Here, power factor correction (PFC) can be integrated into rectifier 8. Alternatively, rectifier 8 can also be designed as a bidirectional NPC rectifier, allowing the traction network to also feed power to the AC voltage network. This type of NPC rectifier... Figure 4 As shown, an AC voltage filter 13 may be additionally present at the input.

[0031] exist Figure 5 In the middle, it is now shown that according to Figure 2 The traction network 1 is shown, with additional AC voltage filter 13 and DC voltage filter 14. A possible circuit for the DC / DC converter 12 is also shown, allowing it to operate as both a boost chopper and a buck chopper. Further illustrated, the circuit connections shown are in parallel a total of three times to distribute power. However, this is not mandatory, and more or fewer circuit connections may be provided. The neutral point of the high-voltage battery 2 is further illustrated connected to the neutral point of the DC / DC converter. A switching module 15 is also shown in the DC / DC converter 12. Switching elements, preferably designed as relays, are arranged in the switching module 15. With the aid of these switching elements, the inverter 6 can be disconnected from the DC / DC converter 12 when charging with AC voltage, such that the outputs DC+, N, and DC- of the rectifier 8 are connected to points P1-P3 of the DC / DC converter 12.

[0032] Figure 6 The diagram illustrates an alternative implementation of traction network 1, wherein, with Figure 5 The essential difference is that inverter 6 is designed as a three-level inverter or a 3L inverter, in which the neutral point N of high-voltage battery 2 forms a loop through DC / DC converter 12 to inverter 6.

[0033] Figure 7The diagram illustrates an alternative implementation of the traction network 1, in which the DC / DC converter 12 is designed as a boost chopper, ensuring that the battery voltage of the high-voltage battery 2 is always boosted. This somewhat reduces the possible settings for the operating point of the motor 7, but is sufficient for most applications.

[0034] Figure 8 The diagram illustrates an alternative implementation of a boost chopper that can be easily scaled to distribute power. Furthermore, the number of components is on average slightly less than that according to... Figure 7 This is one possible implementation, but the transistor must have higher voltage withstand capability.

[0035] Figure 9 and Figure 10 Other alternative configurations of the boost chopper are shown in the figure.

[0036] List of reference numerals

[0037] 1 Traction Network

[0038] 2 high-voltage batteries

[0039] 3 battery cells

[0040] 4 switch modules

[0041] 5DC / DC converter

[0042] 6 inverters

[0043] 7 motors

[0044] 8 rectifiers

[0045] 9DC / DC converter

[0046] 10 AC voltage source

[0047] 11 DC voltage charging connector

[0048] 12DC / DC converter

[0049] 13 AC voltage filter

[0050] 14 DC Voltage Filter

[0051] 15 Switching Modules

Claims

1. A traction network (1) for a motor vehicle, wherein The traction network (1) has at least one high-voltage battery (2), an inverter (6), a motor (7), a common DC / DC converter (12), a DC voltage charging connector (11) and an AC voltage charging connector, wherein a rectifier (8) is arranged between the AC voltage charging connector and the high-voltage battery (2). Its features are, The common DC / DC converter (12) has a switching module (15) that is designed such that the common DC / DC converter (12) is connected to the input terminal of the inverter (6) and disconnected from the output terminal of the rectifier (8) in a first switching position for driving, and connected to the output terminal of the rectifier (8) and disconnected from the input terminal of the inverter (6) in a second switching position for charging.

2. The traction network according to claim 1, characterized in that, The high-voltage battery (2) has two battery cells (3) and a switch module (4), the two battery cells having the same rated voltage, wherein the switch module (4) is designed such that the two battery cells (3) can optionally be connected in parallel or in series.

3. The traction network according to claim 1 or 2, characterized in that, The DC / DC converters (5, 12) are designed as bidirectional boost-buck choppers.

4. The traction network according to claim 1 or 2, characterized in that, The DC / DC converters (5, 12) are designed as bidirectional boost choppers.

5. The traction network according to claim 1 or 2, characterized in that, The DC / DC converters (5, 12) are designed as bidirectional buck choppers.

6. The traction network according to claim 1 or 2, characterized in that, The rectifier (8) is designed as a unidirectional Vienna rectifier, a bidirectional neutral point clamp rectifier, or a Weissach rectifier.

7. The traction network according to claim 2, characterized in that, The switching module (4) of the high-voltage battery (2) has a neutral point (N), wherein the neutral point (N) is connected to the neutral point (N) of the DC / DC converter (12), wherein the inverter (6) is designed as a 3L inverter, wherein the neutral point (N) of the DC / DC converter (12) is connected to the neutral point (N) of the inverter (6).

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

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