Circuit arrangement for a motor vehicle and method for adjusting the voltage of a high-voltage DC intermediate circuit in a motor vehicle

Abstract

Circuit arrangement (1) for a motor vehicle, wherein the motor vehicle can be supplied with direct current at least temporarily via an overhead line (20), comprising: a high-voltage battery (4) for providing electrical energy, a high-voltage DC intermediate circuit (5), a coupling device (6) for controllable coupling of the high-voltage DC intermediate circuit (5) with the overhead line (20), and a DC-DC converter (7) between the high-voltage DC link (5) and the high-voltage battery (4), wherein the DC-DC converter (7) is designed to adapt a voltage (UE) of the high-voltage DC link (5) to a voltage (UF) of the overhead line (20) before coupling with the overhead line (20) via the coupling device (6) by means of energy transfer from the high-voltage battery (4), characterized by at least one further coupling device (12), wherein the at least one further coupling device (12) is designed to disconnect at least one high-voltage electrical consumer from the high-voltage battery (4) before adaptation and to connect it to the high-voltage DC intermediate circuit (5).

Description

[0001] The invention relates to a circuit arrangement for a motor vehicle and a method for adjusting a voltage of a high-voltage DC link in a motor vehicle.

[0002] In the field of electromobility, concepts for electrifying the drivetrain of commercial vehicles are increasingly being developed. However, the low energy density of the energy storage systems used is a problem. One solution to this problem is the provision of electrical energy from an external source via an overhead line. The commercial vehicle can then be operated via the overhead line and / or the energy storage system can be charged during a journey. Since overhead lines are generally not available everywhere, establishing an electrical connection to the overhead line is often necessary. However, in most cases, the overhead line has a different voltage than the high-voltage network in the commercial vehicle.

[0003] It is known to equalize DC voltages between an overhead line and an intermediate circuit using a pre-charging resistor. Before establishing a low-impedance electrical connection between the overhead line and the intermediate circuit, an electrical connection is established via the pre-charging resistor. This leads to current limitation and continuous voltage equalization between the overhead line and the intermediate circuit. Once the voltages are equalized, the low-impedance electrical connection is established.

[0004] DE 10 2014 011 795 A1 discloses a circuit arrangement for a motor vehicle, comprising a high-voltage battery for providing energy, which comprises a battery stack and a coupling device, as well as a high-voltage DC intermediate circuit that can be coupled to the battery stack via the coupling device. Before the high-voltage battery is coupled to the high-voltage DC intermediate circuit, the high-voltage DC intermediate circuit is precharged by transferring energy from an on-board battery to the high-voltage DC intermediate circuit with the aid of a DC / DC converter.

[0005] A circuit arrangement is known from DE 20 2014 002 840 U1. To prevent a capacitor in an intermediate circuit and a high-voltage battery from being affected by an inrush current occurring on a supplying power line during the transition from a disconnected state to a contact state, a first converter is controlled to limit a potential difference between a line voltage and a power line supply voltage to a predetermined potential difference. This means that the first converter is controlled to step up the line voltage to a voltage corresponding to the power line supply voltage, with the purpose of limiting the inrush current.

[0006] US 2009 / 0 322 148 A1 discloses a power converter comprising an inverter in which capacitors are connected in parallel on a DC side, and a power supply circuit configured to supply the inverter with DC power from a power supply and an energy storage element. A controller using such a power converter is also provided for electric vehicles. The power supply circuit is provided with a power supply switch arranged between the power supply and the inverter, a DC / DC converter arranged between the power storage element and the inverter, and a bypass switch arranged between the energy storage element and the inverter.

[0007] From DE 10 2018 002 726 A1 a method for charging an energy storage device of a motor vehicle is known, in which the energy storage device is charged with electrical energy by the energy storage device receiving the electrical energy provided by an overhead line of a power grid provided for supplying rail-bound vehicles with electrical energy, wherein data characterising the charging are transmitted to an operator of the power grid via the overhead line by means of the motor vehicle and / or are received by the operator.

[0008] A vehicle control device is known from DE 11 2017 007 607 T5. This device comprises a power converter that converts supplied DC power and supplies the converted DC power to a load device. A first voltage detector detects a first voltage, which represents a voltage of the power supply line. A second voltage detector detects a second voltage, which represents a voltage of the power converter on a side where a power supply source is provided.When a first contactor is closed and placed in a state that allows current to flow through the first contactor, if a decreasing magnitude of the first voltage from a first past time to a current time is greater than or equal to a first threshold and a decreasing magnitude of the second voltage from a second past time to a current time is greater than or equal to a second threshold, a contactor controller opens the first contactor.

[0009] The invention is based on the object of creating a circuit arrangement for a motor vehicle and a method for adjusting a voltage of a high-voltage DC intermediate circuit in a motor vehicle, with which an electrical power loss can be reduced when forming an electrical connection between an overhead line and a high-voltage DC intermediate circuit.

[0010] The object is achieved according to the invention by a circuit arrangement having the features of patent claim 1 and a method having the features of patent claim 8. Advantageous embodiments of the invention emerge from the subclaims.

[0011] In particular, a circuit arrangement for a motor vehicle is created, wherein the motor vehicle can be supplied with a direct current at least temporarily via an overhead line, comprising a high-voltage battery for providing electrical energy, a high-voltage direct current intermediate circuit, a coupling device for controllably coupling the high-voltage direct current intermediate circuit to the overhead line, and a DC-DC converter (also referred to as a DC / DC converter) between the high-voltage direct current intermediate circuit and the high-voltage battery, wherein the DC-DC converter is designed to adapt a voltage of the high-voltage direct current intermediate circuit to a voltage of the overhead line before coupling to the overhead line via the coupling device by means of energy transfer from the high-voltage battery.

[0012] Furthermore, a method for adjusting a voltage of a high-voltage direct current intermediate circuit in a motor vehicle is provided, comprising the steps of: providing electrical energy by means of a high-voltage battery, providing a high-voltage direct current intermediate circuit which can be coupled to a direct current-carrying overhead line via a coupling device, and adjusting a voltage of the high-voltage direct current intermediate circuit before coupling to the overhead line via the coupling device by means of energy transfer from the high-voltage battery to a voltage of the overhead line, wherein the adjustment is carried out by means of a DC-DC converter.

[0013] The circuit arrangement and the method make it possible to reduce electrical power loss when forming an electrical connection between an overhead line and a high-voltage DC intermediate circuit, since the voltage in the high-voltage DC intermediate circuit is no longer passively adjusted via a pre-charging resistor, but actively adjusted using a DC-DC converter. For this purpose, the DC-DC converter provides a current on the high-voltage DC intermediate circuit side, thereby adjusting the voltage of the high-voltage DC intermediate circuit, since the voltage in the high-voltage DC intermediate circuit can be brought to the voltage of the overhead line by the provided current. Once the voltages are adjusted, the coupling device is controlled such that an electrical connection is formed between the overhead line and the high-voltage DC intermediate circuit.

[0014] In addition to lower power loss, another advantage of the circuit arrangement and method is that adaptation can be achieved significantly faster than when using a pre-charging resistor. After mechanically connecting a pantograph to an overhead line, an electrical connection between the overhead line and the high-voltage DC link can be established more quickly, so that power supply via the overhead line is available at an earlier point in time.

[0015] It is provided that the circuit arrangement comprises at least one further coupling device, wherein the at least one further coupling device is designed to disconnect at least one high-voltage electrical load from the high-voltage battery before the adjustment and to connect it to the high-voltage DC link. High-voltage loads are, in particular, an electrical machine and a drive converter that converts a DC voltage into an AC voltage, in particular a three-phase voltage, and thereby drives the electrical machine.

[0016] The circuit arrangement, in particular the DC-DC converter, is controlled or regulated by a control device. The control device can be implemented as a combination of hardware and software, for example, as program code executed on a microcontroller or microprocessor.

[0017] In particular, the DC-DC converter can operate both as a buck converter or step-down converter and as a boost converter or step-up converter. Therefore, the voltage in the high-voltage DC link can be adjusted to both a higher and a lower voltage provided by the overhead line.

[0018] It can be provided that an electrical power transmitted via the DC-DC converter is selected during the adaptation depending on a capacitance and / or other electrical parameters of the high-voltage DC link.

[0019] In one embodiment, the DC-DC converter is designed as a bidirectional DC-DC converter, wherein the DC-DC converter is further designed to convert a DC voltage provided by the overhead line to a charging voltage of the high-voltage battery when required. In a first operating state, the DC-DC converter can adapt a voltage in the high-voltage DC intermediate circuit; in a second operating state, when the overhead line is already connected to the high-voltage DC intermediate circuit, the DC-DC converter can convert a voltage of the overhead line to a charging voltage of the high-voltage battery, so that the high-voltage battery can be charged via the overhead line. This allows for overall component savings because the DC-DC converter can operate in both directions.

[0020] In one embodiment, the DC-DC converter is configured to perform the adjustment based on voltage regulation, wherein a current is regulated to zero upon reaching a target voltage. The regulated voltage is, in particular, the voltage provided by the DC-DC converter on the high-voltage DC link side. The current is, in particular, a current flowing on the high-voltage DC link side toward the DC-DC converter or away from it.

[0021] In one embodiment, the DC-DC converter is configured to perform the adjustment based on current regulation, wherein a current is regulated to zero upon reaching a target voltage. The regulated current is, in particular, a current flowing on the high-voltage DC link side toward the DC-DC converter or away from it. The voltage is, in particular, the voltage provided by the DC-DC converter on the high-voltage DC link side.

[0022] In one embodiment, it is provided that the DC-DC converter is further designed to control the adaptation based on a voltage value of an overhead line voltage that is detected, received and / or retrieved from a memory, wherein the circuit arrangement for this purpose comprises a voltage sensor, a communication device and / or a memory. The adaptation is then controlled such that the voltage value is reached in the high-voltage DC intermediate circuit. In this case, the voltage value can be detected and provided, for example, at a current collector already connected to the overhead line using the voltage sensor. Alternatively or additionally, the voltage value can be provided, for example, by an operator of the overhead line, for example via a communication connection formed by the communication device. Alternatively or additionally, the voltage value can also be stored in the memory.The voltage value is then retrieved from the memory. For example, a map can be provided that is stored in the memory and contains overhead lines with the corresponding voltage values ​​for various roads or road sections. Depending on the position of the vehicle, the voltage value corresponding to the overhead line is then retrieved from the map or memory and made available to a control device of the circuit arrangement.

[0023] It can be provided that the voltage in the high-voltage DC link is adjusted before a mechanical connection between a pantograph and an overhead line is established. This can be done in particular if the overhead line voltage does not need to be detected by a voltage sensor, but can be determined in another way, for example, transmitted by an overhead line operator as described above or retrieved from a memory. This can further accelerate the formation of an electrical connection to the overhead line.

[0024] Features for the design of the method are evident from the description of the circuit configurations. The advantages of the method are the same as those of the circuit configurations.

[0025] The invention will be explained in more detail below using preferred embodiments with reference to the figures. Fig. 1 a schematic representation of an embodiment of the circuit arrangement for a motor vehicle; Fig. 2 a schematic representation of a time course of voltages, currents and switching states in the circuit arrangement during adaptation.

[0026] In Fig. Figure 1 shows a schematic representation of an embodiment of the circuit arrangement 1 for a motor vehicle. The motor vehicle can be supplied with electrical energy via an overhead line 20. For this purpose, an electrical connection must be established between the overhead line 20 and a high-voltage network 3 of the motor vehicle. In the embodiment shown, the circuit arrangement 1 is partially formed in a current collector 2 of the motor vehicle.

[0027] The circuit arrangement 1 comprises a high-voltage battery 4 for providing electrical energy, a high-voltage DC intermediate circuit 5, a coupling device 6 for controllably coupling the high-voltage DC intermediate circuit 5 to the overhead line 20 and a DC-DC converter 7 between the high-voltage DC intermediate circuit 5 and the high-voltage battery 4. The circuit arrangement 1 is controlled or regulated by means of a control device (not shown).

[0028] The motor vehicle comprises an electric machine 10, which can be connected to both the high-voltage battery 4 and the high-voltage DC link 5 via a drive converter 11 and a further coupling device 12. For this purpose, the further coupling device 12 comprises, for example, switching devices 13, 14, with which the electric machine 10 can be connected to the high-voltage battery 4 or to the high-voltage DC link 5 via the drive converter 11. Furthermore, further high-voltage electrical loads 15 can be connected to the high-voltage battery 4.

[0029] The circuit arrangement 1 comprises further electrical components, such as a choke inductance 18 and an electrical fuse 19. The high-voltage battery 4 comprises an electrical fuse 41 and an internal switching device 42 for disconnecting an electrical connection to the high-voltage network 3 in the event of an overload.

[0030] If the high-voltage network 3 is to be connected to the overhead line 20 via the high-voltage DC intermediate circuit 5, a voltage UE of the high-voltage DC intermediate circuit 5 must be adapted to a voltage UF of the overhead line 20. This occurs after the pantograph 2 has been connected to the overhead line 20, but before coupling, i.e. before the coupling device 6 establishes an electrical connection between the overhead line 20 and the high-voltage DC intermediate circuit 5. To adapt the voltage UE, the DC-DC converter 7 on the high-voltage DC intermediate circuit 5 side provides a current ID, which produces a voltage UD in the high-voltage DC intermediate circuit 5. To provide the voltage UD, a battery voltage UB provided by the high-voltage battery 4 is converted accordingly by the DC-DC converter 7. The current ID changes the voltage UE in the high-voltage DC link 5.The voltage UD is changed (increased or decreased) by the DC-DC converter 7 until the voltages UE and UF are adjusted to each other. The coupling device 6 is then controlled such that an electrical connection is established between the high-voltage DC link 5 and the overhead line 20. The voltage UD is then no longer provided by the DC-DC converter 7, but corresponds to the voltage UF of the overhead line.

[0031] During the adjustment of the voltage UE, the electric machine 10 is not actively operated, but runs passively.

[0032] It can be provided that the DC-DC converter 7 is designed as a bidirectional DC-DC converter 17. The DC-DC converter 7 can then convert a DC voltage provided by the overhead line 20 to a charging voltage of the high-voltage battery 4, if necessary.

[0033] It can further be provided that the DC-DC converter 7 is designed to carry out the adaptation on the basis of a voltage regulation, wherein the current ID is set to zero when the voltage UD reaches a target voltage (ie in the present case the voltage UF).

[0034] Alternatively, it can be provided that the DC-DC converter 7 is designed to perform the adaptation on the basis of a current control, wherein the current ID is controlled to zero when the voltage UD reaches a target voltage.

[0035] It can further be provided that the DC-DC converter 7 is designed to control the adjustment based on a detected, received, and / or retrieved voltage value of a voltage UF of the overhead line 20. For this purpose, the control device comprises, for example, a communication interface and / or a memory.

[0036] In Fig. Figure 2 is a schematic representation of a curve of voltages 30 and currents 31 as well as switching states 32 over time 33 to illustrate an embodiment of the method with reference to the Fig. 1 shown embodiment of the circuit arrangement 1. The individual voltages 30 and currents 31 are each connected to the Fig. 1. For clarity, the course of the switching states 32 is designated by the reference numerals of the coupling device 6 and the switching devices 13, 14, respectively.

[0037] The initial situation at time t0 is that the motor vehicle is powered by the high-voltage battery 4. However, a connection has already been established between the pantograph 2 and the overhead line 20, so that the system should switch to an electrical power supply via the overhead line 20. To do this, the voltage UE must be brought from a voltage UB of the high-voltage battery 4 to the voltage UF of the overhead line 20. The coupling device 6 is open, so that there is no electrical connection between the overhead line 20 and the high-voltage DC link 5.

[0038] At a time t1, the electric machine 10 ( Fig. 1) is de-loaded. As a result, the current IE drops to zero. At the same time, the DC-DC converter 7 provides a current ID on the high-voltage DC link 5 side, which generates a voltage UD, with the aim of equalizing the value of the voltage UD to the value of the voltage UE.

[0039] After the electrical machine 10 has been made load-free, the switching device 13 is opened at a time t2, thereby breaking an electrical connection between the electrical machine 10 or the drive inverter 11 and the high-voltage battery 4, which leads to the voltage UE dropping slightly, since the intermediate circuit capacitance CE of the electrical machine is passively discharged via parasitic resistances.

[0040] When the value of voltage UD corresponds to the value of voltage UE, an electrical connection is established between the electric machine 10 or the drive inverter 11 and the high-voltage DC link 5 at a time t3 by means of the switching device 14. The DC-DC converter continues to provide a current ID, which further increases the voltage UE.

[0041] At a time t4, the voltage UE in the high-voltage DC intermediate circuit 5 reaches the value of the voltage UF of the overhead line 20, i.e., the voltages UE and UF are equalized, and an electrical connection between the overhead line 20 and the high-voltage DC intermediate circuit 5 can be established. The DC-DC converter 7 therefore regulates the current ID to zero. At the same time, the coupling device 6 is controlled such that an electrical connection is established between the high-voltage DC intermediate circuit 5 and the overhead line 20. A current IP flowing through the overhead line 20 then corresponds to the current IE.

[0042] In Fig. Figure 3 shows a schematic representation of another embodiment of the circuit arrangement 1 for a motor vehicle. The circuit arrangement 1 is largely similar to that shown in Fig. 1. The same reference numerals denote the same features and terms.

[0043] In contrast to the Fig. However, unlike the embodiment shown in Figure 1, this embodiment has no further coupling device or switching devices. The electric machine 10 and the drive inverter 11 are connected to the high-voltage battery 4 and the DC-DC converter 7 at all times.

[0044] In Fig. 4 is a schematic representation of a curve of voltages 30 and currents 31 as well as a switching state 32 of the coupling device 6 over time 33 to illustrate an embodiment of the method with reference to the Fig. 3 shown embodiment of the circuit arrangement 1. The individual voltages 30 and currents 31 are each connected to the Fig. 3. The course of the switching state 32 of the coupling device 6 is marked with the reference numerals of the coupling device 6 for clarity.

[0045] The initial situation at time t0 is that the motor vehicle is powered by the high-voltage battery 4. However, a connection between the pantograph 2 and the overhead line 20 has already been established, so that the system should switch to an electrical power supply via the overhead line 20. The coupling device 6 is open, so that there is no electrical connection between the overhead line 20 and the high-voltage DC link 5.

[0046] A voltage in the high-voltage DC link 5 must be brought to the voltage UF of the overhead line 20 before the electrical connection to the overhead line is established.

[0047] For this purpose, starting at a time t1, the DC-DC converter 7 provides a current ID on the side of the high-voltage DC link 5, which generates a voltage UD. At a time t2, the voltage UD reaches the voltage UF of the overhead line. At this time t2, an electrical connection is established by means of the coupling device 6. The current ID is simultaneously reduced to zero. The voltage UD is then no longer provided by the DC-DC converter 7, but corresponds to the voltage UF of the overhead line.

[0048] During the adjustment of the voltage UD, the electric machine 10 can be actively operated using electrical energy from the high-voltage battery 4.

[0049] One advantage of the circuit arrangement and method is that electrical power loss can be reduced compared to matching using a passive pre-charging resistor. In addition to lower power loss, another advantage of the circuit arrangement and method is that matching can be performed significantly faster than when using the pre-charging resistor. List of reference symbols 1 Circuit arrangement 2 pantographs 3 High-voltage network 4 high-voltage battery 5 High-voltage DC link 6 Coupling device 7 DC-DC converters 10 electric machine 11 drive inverters 12 additional coupling devices 13 Switching device 14 Switching device 15 additional high-voltage electrical consumers 17 bidirectional DC-DC converter 18 Choke inductance 19 electrical fuse 20 overhead line 30 voltage 31 Electricity 32 Switching state 33 Time 41 electrical fuse 42 Switching device t0-t4 time points UD voltage (DC converter) UF voltage (overhead line) UE voltage (high-voltage DC link) ID current (DC-DC converter) IP power (overhead line) IE current (high-voltage DC link) CE DC link capacity CD converter capacity

Claims

[1] Circuit arrangement (1) for a motor vehicle, wherein the motor vehicle can be supplied at least temporarily with a direct current via an overhead line (20), comprising: a high-voltage battery (4) for providing electrical energy, a high-voltage DC link (5), a coupling device (6) for controllably coupling the high-voltage DC link (5) to the overhead line (20), and a DC-DC converter (7) between the high-voltage DC intermediate circuit (5) and the high-voltage battery (4), wherein the DC-DC converter (7) is designed to adapt a voltage (UE) of the high-voltage DC intermediate circuit (5) to a voltage (UF) of the overhead line (20) by means of energy transfer from the high-voltage battery (4) via the coupling device (6) before coupling to the overhead line (20), characterized byat least one further coupling device (12), wherein the at least one further coupling device (12) is designed to disconnect at least one high-voltage electrical consumer from the high-voltage battery (4) before the adaptation and to connect it to the high-voltage DC voltage intermediate circuit (5). [2] Circuit arrangement (1) according to claim 1, characterized by that the DC-DC converter (7) is designed as a bidirectional DC-DC converter (17), wherein the DC-DC converter (7) is further designed to convert a DC voltage (UF) provided by the overhead line (20) to a charging voltage of the high-voltage battery (4) when required. [3] Circuit arrangement (1) according to claim 1 or 2, characterized by that the DC-DC converter (7) is designed to carry out the adaptation on the basis of voltage regulation, wherein a current (ID) is regulated to zero when a target voltage is reached. [4] Circuit arrangement (1) according to claim 1 or 2, characterized by that the DC-DC converter (7) is designed to carry out the adaptation on the basis of a current control, wherein a current (ID) is regulated to zero when a target voltage is reached. [5] Circuit arrangement (1) according to one of the preceding claims, characterized by that the DC-DC converter (7) is further designed to control the adaptation on the basis of a detected, received and / or retrieved voltage value of a voltage (UF) of the overhead line (20), wherein the circuit arrangement for this purpose comprises a voltage sensor, a communication device and / or a memory. [6] Motor vehicle, comprising at least one circuit arrangement (1) according to one of claims 1 to 5. [7] Motor vehicle according to claim 6, characterized by that the motor vehicle is a commercial vehicle. [8] Method for adjusting a voltage of a high-voltage DC link (5) in a motor vehicle, comprising the steps: Providing electrical energy by means of a high-voltage battery (4), Providing a high-voltage DC intermediate circuit (5) which can be coupled to a DC-carrying overhead line (20) via a coupling device (6), and Adjusting a voltage (UE) of the high-voltage DC intermediate circuit (5) before coupling to the overhead line (20) via the coupling device (6) by means of energy transfer from the high-voltage battery (4) to a voltage (UF) of the overhead line, wherein the adjustment is carried out by means of a DC-DC converter (7), characterized bythat by means of a further coupling device (12) at least one high-voltage electrical consumer is separated from the high-voltage battery (4) before the adaptation and is connected to the high-voltage DC voltage intermediate circuit (5). [9] Method according to claim 8, characterized by that a voltage value of a voltage (UF) of the overhead line (20) is detected, received and / or retrieved from a memory, wherein the adaptation is carried out on the basis of the detected, received and / or retrieved voltage value.

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