Electrical power network in a motor vehicle, motor vehicle, and method for operating an electrical power network

Abstract

The invention relates to an electrical power network (1) in a motor vehicle, the electrical power network (1) having a first voltage level and at least a second voltage level, wherein: the first voltage level contains at least one first energy store (2) which is connected to the second voltage level by means of a DC-to-DC converter (3); the voltage (U1) of the first voltage level is greater than the voltage (U2) of the second voltage level; the second voltage level contains safety-relevant loads (11), non-safety-relevant loads (12) and at least one second energy store (13, 14); the non-safety-relevant loads (12) are assigned at least one switching element (15) by means of which the non-safety-relevant loads (12) can be disconnected from the second voltage level; the DC-to-DC converter (3) and / or the at least one second energy store (13, 14) has a control unit (17) which is designed to determine a degree of loading for the power supply in the second voltage level; the control unit (17) is also designed to disconnect the non-safety-relevant loads (12) from the second voltage level by direct actuation of the at least one switching element (15) in the event of a predefined degree of loading. The invention also relates to a motor vehicle and to a method for operating an electrical power network (1).

Description

[0001] Description

[0002] Electrical energy network in a motor vehicle, motor vehicle and method for operating an electrical energy network

[0003] The invention relates to an electrical energy network in a motor vehicle, a motor vehicle and a method for operating an electrical energy network.

[0004] DE 102021 208 051 A1 discloses an electrical energy network in a motor vehicle, wherein the electrical energy network has a first voltage level and at least one second voltage level, wherein at least one first energy storage device is arranged in the first voltage level and is connected to the second voltage level via a DC / DC converter, wherein the voltage of the first voltage level is greater than the voltage of the second voltage level. The first energy storage device is, for example, a high-voltage battery and has a nominal voltage of 400 V. A second energy storage device is arranged in the second voltage level, which has, for example, a nominal voltage of 12 V. On-board network consumers are arranged in the second voltage level.The energy network comprises a device for controlling energy consumption, comprising a control device configured to determine a state of charge of a traction battery of the vehicle, calculate an energy requirement for reaching a predetermined charging station, and set a maximum quiescent current in the electrical energy network using the determined state of charge and the calculated energy requirement for reaching the predetermined charging station. For this purpose, the control device is configured to completely deactivate one or more electrical consumers of the vehicle and / or to deactivate functions of one or more electrical consumers of the vehicle.

[0005] It is also known that electrical consumers in an on-board electrical system can be divided into safety-relevant and non-safety-relevant consumers, whereby the safety-relevant consumers can also be graded according to their relevance (ASIL AD). Non-safety-relevant consumers are also referred to as convenience consumers, which are not required for vehicle operation. It is also known that in the event of a critical on-board electrical system condition, the non-safety-relevant consumers are switched off or their power consumption is initially reduced. The control commands required for this are generated by a higher-level control unit, which then transmits the control commands to the consumers via a bus system.

[0006] DE 102019 109 722 A1 discloses an electrical power network in a motor vehicle, wherein the electrical power network has a first voltage level and at least one second voltage level. At least one first energy storage device is arranged in the first voltage level and is connected to the second voltage level via a DC / DC converter. The voltage of the first voltage level is greater than the voltage in the second voltage level. Safety-relevant loads, non-safety-relevant loads, and at least one second energy storage device are arranged in the second voltage level. A switching element is assigned to the non-safety-relevant loads, and in the event of a fault in a part containing the non-safety-relevant loads, these are switched off to prevent repercussions on the safety-relevant loads.

[0007] EP 3 146 605 B1 discloses a method for operating an on-board electrical system of a motor vehicle, wherein the on-board electrical system has at least one electrical energy source and consumers, wherein some of the consumers belong to a safety group of safety-relevant consumers whose operation is to be ensured even under heavy loads on the on-board electrical system, wherein at least one voltage threshold is specified for at least some of the consumers. Each consumer monitors whether the on-board electrical system voltage falls below the voltage threshold. If the on-board electrical system voltage falls below the voltage threshold, the power consumption of the respective consumer is reduced by the consumer itself. The time-varying voltage thresholds are selected by a central control unit depending on the operating state of the motor vehicle and specified to the consumers.

[0008] Another method for operating an on-board electrical system is known from DE 102021 206 358 A1.

[0009] The invention is based on the technical problem of further improving the operational reliability of an electrical power grid in a motor vehicle, creating such a motor vehicle, and providing a corresponding method for operating an electrical power grid. The solution to this technical problem is provided by an electrical power grid having the features of claim 1, a motor vehicle having the features of claim 6, and a method having the features of claim 7. Further advantageous embodiments of the invention are set out in the subclaims.

[0010] The electrical power grid in a motor vehicle has a first voltage level and at least one second voltage level, wherein at least one first energy storage device is arranged in the first voltage level and is connected to the second voltage level via a DC / DC converter, wherein the voltage of the first voltage level is greater than the voltage in the second voltage level. Safety-relevant loads, non-safety-relevant loads, and at least one second energy storage device are arranged in the second voltage level, wherein the non-safety-relevant loads are assigned a switching element by means of which the non-safety-relevant loads can be disconnected from the second voltage level.The DC / DC converter and / or the at least one second energy storage device have a control unit designed to determine a load level for the energy supply at the second voltage level, wherein the control unit is further designed to disconnect the non-safety-relevant consumers from the second voltage level at a predetermined load level by directly controlling the switching element. As a result, the electrical power grid reacts somewhat more quickly to a potentially critical on-board network condition, so that voltage dips can be better avoided. Preferably, the first energy storage device is a high-voltage battery, which has, for example, a nominal voltage of 380 V to 800 V. The second energy storage device is, for example, a 12 V battery or a capacitor.

[0011] Furthermore, the control unit is connected directly to the switching element via a control line. Alternatively, the control unit is connected to the switching element via an air interface. The air interface can be, for example, a radio interface or an optical air interface.

[0012] In a further embodiment, the control unit is designed to reconnect the switched off non-safety-relevant consumers when a further predetermined load level is reached. This load level is lower than the load level when switched off. In a further embodiment, the switching element is designed as a relay or as a semiconductor switch. The switching element can also be designed as a pyro-fuse, in which case the separation is irreversible, so that reconnection is not possible. The semiconductor switch can also be designed as an electrical fuse, i.e. the semiconductor switch monitors the current flowing through it and blocks if a predetermined limit is exceeded. This allows two functionalities to be implemented in the semiconductor switch. Such semiconductor switches are also referred to as eFuse.

[0013] In a further embodiment, the control unit is connected to a higher-level control unit via data communication, wherein the higher-level control unit is configured to estimate a future energy requirement and transmit it to the control unit, wherein the control unit is configured to actuate the switching element and / or change control parameters depending on the message received from the higher-level control unit. For example, the higher-level control unit can estimate an impending crash or an energy-intensive driving maneuver, so that the non-safety-relevant consumers are deactivated in advance. This can be used particularly in fully automated vehicles.

[0014] In a further embodiment, the DC / DC converter is bidirectional, so that the DC / DC converter can also be used to precharge an intermediate circuit capacitor in the first voltage level.

[0015] The motor vehicle has at least one electrical energy network as described above.

[0016] Furthermore, a method for operating an electrical energy network in a motor vehicle is proposed, wherein the electrical energy network has a first voltage level and at least one second voltage level. At least one first energy storage device is arranged in the first voltage level and is connected to the second voltage level via a DC / DC converter. The voltage of the first voltage level is greater than the voltage in the second voltage level, wherein safety-relevant consumers, non-safety-relevant consumers and at least one second energy storage device are arranged in the second voltage level. A switching element is assigned to the non-safety-relevant consumers, by means of which switching element the non-safety-relevant consumers can be disconnected from the second voltage level.

[0017] The DC / DC converter and / or the at least one second energy storage device have a control unit that determines a load level for the power supply at the second voltage level and, at a predetermined load level, disconnects the non-safety-relevant loads from the second voltage level by directly controlling the switching element. For further embodiments, reference is made in full to the explanations regarding the electrical power grid.

[0018] The invention is explained in more detail below using a preferred embodiment. The sole figure shows a schematic block diagram of an electrical power grid.

[0019] Fig. 1 shows a schematic block diagram of an electrical power network 1 in a motor vehicle. The electrical power network 1 has a first voltage level and at least one second voltage level, wherein at least one first energy storage device 2 is arranged in the first voltage level and is connected to the second voltage level via a DC / DC converter 3. The voltage U1 of the first voltage level is greater than the voltage U2 of the second voltage level. The first energy storage device 2 is designed, for example, as a high-voltage or traction battery and is connected via switching elements 4 to an intermediate circuit capacitor 5 and an inverter 6. The inverter 6 is connected to an electric machine 7. Further high-voltage consumers can also be connected in the first voltage level. A pre-charging circuit can also be connected in parallel to a switching element 4.Furthermore, the first energy storage device 2 is assigned a battery management control unit 8, which, for example, records and evaluates voltage, current and temperature values ​​of battery cells of the first energy storage device 2. Furthermore, the battery management control unit 8 controls the switching elements 4. The battery management control unit 8 is connected to a higher-level control unit 10 via a bus system 9 (e.g. CAN bus). Arranged in the second voltage level are safety-relevant consumers 11, non-safety-relevant consumers 12, a second energy storage device 13 in the form of an on-board network battery and a further second energy storage device 14 in the form of a capacitor. For reasons of clarity, only one consumer 11, 12 is shown in each case. The non-safety-relevant consumers 12 can be separated from the second voltage level via a switching element 15.The second energy storage device 13 is also assigned a battery management control unit 16, which is also connected to the bus system 9. The DC / DC converter 3 has a control unit 17. The control unit 17 is connected on the one hand to the bus system 9 and on the other hand directly to the switching element 15 via a control line 18. The DC / DC converter 3 is designed as a bidirectional DC / DC converter 3. The DC / DC converter 3 is operated as a boost converter in order to pre-charge the intermediate circuit capacitor 5 before the switching elements 4 are closed, so that a pre-charging circuit in parallel with the switching elements 4 can be dispensed with. If such a pre-charging circuit is present, however, the DC / DC converter 3 can also be designed as a unidirectional buck converter.During normal operation (switching element 4 closed), the DC / DC converter 3 operates as a step-down converter, via which the second energy storage devices 13, 14 are charged and the second voltage level is supported. The DC / DC converter 3 is a galvanically isolated DC / DC converter in order to prevent overvoltages on the second voltage level. The DC / DC converter 3 is designed to keep the set output voltage at the second voltage level constant; for this purpose, it changes a PWM signal, for example, using the control unit 17. The pulse-on to pulse-off ratio indicates a load level for the energy supply of the second voltage level. If the control unit 17 detects a load level greater than a predetermined threshold value (e.g., a ratio of 9 to 1), the switching element 15 is controlled directly.By disconnecting the non-safety-relevant loads 12, the power requirement is reduced accordingly, thus increasing the energy reserve provided by the DC / DC converter 3. If the energy requirement of the second voltage level then decreases, or the load level falls below a further threshold (e.g., a ratio of 6 to 4), the non-safety-relevant loads 12 can be reconnected by closing the switching element 15.

[0020] Alternatively or additionally, the battery management control unit 16 can also be used as a local control unit for the switching element 15. A control unit can also be assigned to the capacitor as a further, second energy storage device 14, which evaluates the voltage at the capacitor and directly controls the switching element 15. The advantage of the local, direct shutdown by the control unit 17 is that the shutdown of the non-safety-relevant loads 12 occurs more quickly than via the higher-level control unit 10.

[0021] In addition, the higher-level control unit 10 can transmit a shutdown command or an expected energy requirement to the control unit 17 if a greater energy requirement is expected in the second voltage level (for example, due to an energy-intensive driving maneuver), which can be used in particular in fully automated motor vehicles. The control unit 17 can then either control the switching element 15 directly or adjust control parameters (e.g., increase the output voltage). For redundancy reasons, it can also be provided that a second DC / DC converter 3 is connected to a further second voltage level. In this case, the safety-relevant loads 11 and the non-safety-relevant loads 12 can be divided between two second voltage levels, which further increases reliability.

[0022] List of reference symbols electrical energy network first energy storage

[0023] DC / DC converter

[0024] switching element

[0025] DC link capacitor

[0026] Inverter

[0027] electric machine

[0028] Battery management control unit

[0029] bus system

[0030] Control unit safety-relevant consumer non-safety-relevant consumer second energy storage device second energy storage device

[0031] switching element

[0032] Battery management control unit

[0033] Control unit

[0034] control line

Claims

Patent claims 1. An electrical energy network (1) in a motor vehicle, wherein the electrical energy network (1) has a first voltage level and at least one second voltage level, wherein at least one first energy storage device (2) is arranged in the first voltage level and is connected to the second voltage level via a DC / DC converter (3), wherein the voltage (U1) of the first voltage level is greater than the voltage (U2) of the second voltage level, wherein safety-relevant consumers (11), non-safety-relevant consumers (12), and at least one second energy storage device (13, 14) are arranged in the second voltage level, wherein a common switching element (15) is assigned to the non-safety-relevant consumers (12), by means of which the non-safety-relevant consumers (12) can be disconnected from the second voltage level, wherein the DC / DC converter (3) and / or the at least one second energy storage device (13, 14) have a control unit (17),which is designed to determine a load level for the energy supply in the second voltage level, wherein the control unit (17) is further designed to disconnect the non-safety-relevant consumers (12) from the second voltage level at a predetermined load level by directly controlling the switching element (15), wherein the control unit (17) is connected directly to the switching element (15) via a control line (18) or the control unit (17) is connected to the switching element (15) via an air interface.

2. Electrical energy network according to claim 1, characterized in that the control unit (17) is designed to reconnect the switched-off non-safety-relevant consumers (12) at a further predetermined load level.

3. Electrical power network according to one of the preceding claims, characterized in that the at least one switching element (15) is designed as a relay or semiconductor switch.

4. Electrical energy network according to one of the preceding claims, characterized in that the control unit (17) is connected to a higher-level control device (10) in terms of data technology, wherein the higher-level control device (10) is configured in such a way is designed to estimate a future energy requirement and to transmit it to the control unit (17), wherein the control unit (17) is further designed to control the switching element (15) and / or to change control parameters depending on the received message from the higher-level control unit (10).

5. Electrical power network according to one of the preceding claims, characterized in that the DC / DC converter (3) is designed as a bidirectional DC / DC converter (3).

6. Motor vehicle, characterized in that the motor vehicle has an electrical energy network (1) according to one of claims 1 to 5.

7. A method for operating an electrical energy network (1) in a motor vehicle, wherein the electrical energy network (1) has a first voltage level and at least one second voltage level, wherein at least one first energy storage device (2) is arranged in the first voltage level and is connected to the second voltage level via a DC / DC converter (3), wherein the voltage (U1) of the first voltage level is greater than the voltage (U2) of the second voltage level, wherein safety-relevant consumers (11), non-safety-relevant consumers (12) and at least one second energy storage device (13, 14) are arranged in the second voltage level, wherein the non-safety-relevant consumers (12) are assigned a common switching element (15), by means of which the non-safety-relevant consumers (12) can be separated from the second voltage level, wherein the DC / DC converter (3) and / or the at least one second energy storage device (13,14) a control unit (17) which determines a load level for the energy supply in the second voltage level and, at a predetermined load level, disconnects the non-safety-relevant consumers (12) from the second voltage level by directly controlling the at least one switching element (15), wherein the control unit (17) is connected directly to the switching element (15) via a control line (18) or is connected to the switching element (15) via an air interface.

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