Vehicle electrical system and method for operating a vehicle electrical system

Abstract

The invention relates to a vehicle electrical system (1) having at least one basic vehicle electrical system (2) with a first voltage source (7), the vehicle electrical system (1) having at least two decoupled vehicle electrical system branches (3, 4), each vehicle electrical system branch being connected to the basic vehicle electrical system (2) by means of a DC / DC converter (5, 6), each DC / DC converter (5, 6) having at least one control unit (10, 11) which is designed to generate a target output voltage or a target output current of the vehicle electrical system branch (3, 4), wherein at least one control unit (10, 11) of a vehicle electrical system branch (3, 4) is designed to superimpose an alternating voltage signal having a predetermined frequency on the target output voltage or the target output current in a test period, the other vehicle electrical system branch (4, 3) being designed to detect a voltage and / or a current in the other vehicle electrical system branch (4, 3), the at least one control unit (10, 11) being designed to carry out a frequency analysis of the voltage signal and / or the current signal in the other vehicle electrical system branch (4, 3), the at least one control unit (10, 11) being designed to generate a fault signal when it is determined that a frequency component in the voltage signal and / or the current signal is greater than a threshold value of the predetermined frequency. The invention relates to an associated method.

Description

[0001] This invention relates to an on-board electrical network and a method for operating an on-board electrical network, particularly for a motor vehicle.

[0002] A general-purpose vehicle electrical network is known from DE 10 201 5 200 121 A1. It provides at least one component that is distributed among multiple vehicle electrical network branches and is designed to perform diagnostics on these branches. It is further proposed that the diagnostics be performed using a DC / DC converter, and particularly based on the output voltage of the DC / DC converter, which is the input voltage of the vehicle electrical network branch. Depending on the design of the vehicle electrical network branch, and particularly which components are arranged within it, such diagnostics are often not easy and may lead to erroneous diagnoses.

[0003] Therefore, the technical problem to be solved by the present invention is to improve such vehicle-mounted electrical networks, especially to improve the diagnosis of current faults, and to provide a corresponding method.

[0004] The solution to this technical problem stems from an onboard electrical system having the features of claim 1 and a method having the features of claim 9. Further advantageous embodiments of the invention arise from the dependent claims.

[0005] The vehicle-mounted electrical network has at least one base vehicle-mounted electrical network with a first power supply. Furthermore, the base vehicle-mounted electrical network has at least two decoupled vehicle-mounted electrical network branches, each connected to the base vehicle-mounted electrical network via a DC / DC converter. Each DC / DC converter has at least one control unit designed to generate a target output voltage or target output current for the vehicle-mounted electrical network branch. At least one control unit of the DC / DC converter of the vehicle-mounted electrical network branch is designed to superimpose an AC voltage signal of a predetermined frequency onto the target output voltage or target output current during a test cycle, while the other vehicle-mounted electrical network branch is designed to measure the voltage and / or current (i.e., its own voltage and / or its own current) in the other vehicle-mounted electrical network branch. Furthermore, at least one control unit is designed to perform frequency analysis on the voltage and / or current signals in the other vehicle-mounted electrical network branch. Additionally, at least one control unit is designed to generate a fault signal when a frequency component greater than a predetermined frequency threshold is identified in the voltage and / or current signals. This allows for highly reliable detection of unwanted current coupling or connections between vehicle-mounted electrical network branches, preventing them from becoming unresponsive. All control units of all DC / DC converters are preferably designed to perform test cycles, especially since they are no longer connected to the hardware. However, it is also possible to specify that only a single control unit can perform a test cycle. More preferably, the AC voltage signal is a voltage signal superimposed on the target output voltage, wherein current is detected in another on-board electrical grid branch. The frequency analysis can be performed by the control unit of the DC / DC converter in the on-board electrical grid branch, wherein current (and / or voltage) is measured, and the results are then transmitted to the control unit to perform a test cycle using the AC voltage signal. Alternatively, the control unit also performs frequency analysis on the measurements from other on-board electrical grid branches. It should be noted that this is very robust for detecting faults in decoupling, superior to simply monitoring voltage or current, especially when highly dynamic electrical loads are arranged in the on-board electrical grid branch.

[0006] In principle, bandpass filters can also be used for frequency analysis. However, the preferred method for frequency analysis is the Fast Fourier Transform.

[0007] In another embodiment, the first voltage source is a high-voltage battery and the DC / DC converter is designed to be an electrically isolated DC / DC converter. The on-board electrical grid branch is preferably a low-voltage on-board electrical grid.

[0008] In another embodiment, at least one DC / DC converter is designed as a bidirectional DC / DC converter, such that, for example, intermediate loop capacitors within the underlying onboard electrical network are pre-charged from an onboard electrical network branch.

[0009] In another embodiment, the amplitude of the AC voltage signal is between 1% and 10% of the target output signal, more preferably between 2% and 5%. This avoids affecting loads in the vehicle's electrical grid branch that are sensitive to voltage fluctuations.

[0010] The specified frequency is preferably between 1 and 100 Hz. In another embodiment, the predetermined frequency is selected based on the switching frequency (DC / DC converter or power-consuming device) used. Specifically, the specified frequency is selected such that it is not a multiple of the switching frequency. Alternatively, the specified frequency is a prime number, such as 19 Hz.

[0011] In another embodiment, the voltage source is arranged in the vehicle electrical grid branch, and the voltage source is preferably designed as a battery.

[0012] Regarding the technical solutions in terms of methodology, please refer to the preceding statements. Attached Figure Description

[0013] The invention will now be explained in more detail using preferred exemplary embodiments.

[0014] Figure 1 A schematic block diagram of the basic vehicle-mounted electrical grid is shown. Detailed Implementation

[0015] Detailed Implementation Figure 1 A schematic block diagram of an on-board electrical network 1 is shown, comprising a basic on-board electrical network 2 and at least two on-board electrical network branches 3 and 4. On-board electrical network branches 3 and 4 are both connected to the basic on-board electrical network 2 via DC / DC converters 5 and 6. The basic on-board electrical network 2 has a first voltage source 7, which is designed, for example, as a high-voltage battery and has a voltage greater than 60V. For example, the voltage is between 380-800V. A load 8 and an intermediate circuit capacitor 9 are also schematically arranged. The DC / DC converters 5 and 6 each have control units 10 and 11, which are interconnected in terms of data technology via a bus system 12 or a direct data line. On-board electrical network branches 3 and 4 are preferably low-voltage on-board electrical networks and have a nominal voltage of 12V. Furthermore, on-board electrical network branches 3 and 4 have at least one electrical load 13 and 14, preferably related to safety. Additionally, on-board electrical network branches 3 and 4 each have their own voltage source 15 and 16, as well as voltage measuring devices 17 and 18 and current measuring devices 19 and 20. The two on-board electrical grid branches 3 and 4 are decoupled from each other through DC / DC converters 5 and 6 without any impact; that is, voltage fluctuations in one on-board electrical grid branch have no effect on the other. However, when faulty conductive coupling occurs in the two on-board electrical grid branches 3 and 4, the above decoupling effect cannot be guaranteed. In order to detect such current coupling and take countermeasures at an early stage if necessary, control unit 10 and / or control unit 11 can superimpose an AC voltage signal onto the output signal during the test cycle.

[0016] The test method is explained below, assuming that control unit 10 generates an AC voltage signal and superimposes it on its target output voltage. The AC voltage signal has a predetermined frequency f and is, for example, a sinusoidal signal. As a result, an AC component with frequency f also appears in the current of vehicle electrical network branch 3. However, if vehicle electrical network branches 3 and 4 are completely decoupled, the AC voltage signal in vehicle electrical network branch 3 has no effect on vehicle electrical network branch 4. Therefore, during the test cycle, the current in vehicle electrical network branch 4 is measured and frequency analysis is performed, specifically a fast Fourier transform is executed. If a frequency component with the specified frequency f is present in the current in vehicle electrical network branch 4, this indicates a fault in the current connection. The frequency analysis can be performed, for example, in control unit 11, and the results can be transmitted to control unit 10 via bus system 12. The predetermined frequency f of control unit 11 can be known in advance. Alternatively, control unit 11 or another unit transmits the measured value of the current in vehicle electrical network branch 4 to control unit 10, and then control unit 10 performs frequency analysis.

[0017] List of reference numerals

[0018] 1. Vehicle-mounted power grid

[0019] 2 Basic vehicle-mounted power grid

[0020] 3, 4 Vehicle-mounted electrical grid branches

[0021] 5, 6 DC / DC converters

[0022] 7 voltage sources

[0023] 8 load

[0024] 9. Intermediate Circuit Capacitor

[0025] 10, 11 Control Units

[0026] 12-bus system

[0027] 13, 14 load

[0028] 15, 16 voltage sources

[0029] 17, 18 Voltage measuring devices

[0030] 19, 20 Current measuring device

Claims

1. An on-board electrical network (1), the on-board electrical network (1) having at least one basic on-board electrical network (2), the basic on-board electrical network having a first voltage source (7), the on-board electrical network (1) having at least two decoupled on-board electrical network branches (3, 4), each on-board electrical network branch being connected to the basic on-board electrical network (2) via a DC / DC converter (5, 6), each DC / DC converter (5, 6) having at least one control unit (10, 11) designed to generate a target output voltage or a target output current of the on-board electrical network branch (3, 4), Its features are, At least one control unit (10, 11) of the vehicle-mounted electrical grid branch (3, 4) is designed to superimpose an AC voltage signal with a predetermined frequency onto a target output voltage or target output current during a test cycle. Another vehicle-mounted electrical grid branch (4, 3) is designed to detect the voltage and / or current in the other vehicle-mounted electrical grid branch (4, 3). At least one control unit (10, 11) is designed to perform frequency analysis on the voltage signal and / or current signal in the other vehicle-mounted electrical grid branch (4, 3). At least one control unit (10, 11) is designed to generate a fault signal when it is determined that the frequency component in the voltage signal and / or current signal is greater than a predetermined frequency threshold.

2. The vehicle-mounted electrical grid according to claim 1, characterized in that, Frequency analysis is based on the Fast Fourier Transform.

3. The vehicle-mounted electrical grid according to claim 1 or 2, characterized in that, The first voltage source (7) is a high-voltage battery, and the DC / DC converters (5, 6) are designed as electrically isolated DC / DC converters.

4. The vehicle-mounted electrical grid according to any one of the preceding claims, characterized in that, At least one DC / DC converter (5, 6) is designed to be a bidirectional DC / DC converter.

5. The vehicle-mounted electrical grid according to any one of the preceding claims, characterized in that... The amplitude of the AC voltage signal is between 1% and 10% of the nominal output signal.

6. The vehicle-mounted electrical grid according to any one of the preceding claims, characterized in that... The predetermined frequency is between 1-100Hz.

7. The vehicle-mounted electrical grid according to claim 6, characterized in that, The predetermined frequency is selected based on the switching frequency used in the vehicle-mounted power grid branch (3, 4), or it has a prime value.

8. The vehicle-mounted electrical grid according to any one of the preceding claims, characterized in that, In each case, the voltage source (1, 5, 16) is arranged in the vehicle electrical grid branch (3, 4).

9. A method for operating an on-board electrical network, wherein the on-board electrical network (1) has at least one base on-board electrical network (2) having a first voltage source (7) and at least two decoupled on-board electrical network branches (3, 4), each on-board electrical network branch being connected to the base on-board electrical network (2) via a DC / DC converter (5, 6), each DC / DC converter (5, 6) having at least one control unit (10, 11) that generates a target output voltage or a target output current for the on-board electrical network branch (3, 4). Its features are, At least one control unit (10, 11) of the DC / DC converter (5, 6) of the vehicle-mounted electrical grid branch (3, 4) superimposes an AC voltage signal with a predetermined frequency onto the target output voltage or target output current during the test cycle, detects the voltage and / or current in another vehicle-mounted electrical grid branch (4, 3), and at least one control unit (10, 11) performs frequency analysis on the voltage signal and / or current signal in the other vehicle-mounted electrical grid branch (4, 3). When it is determined that the frequency component in the voltage signal and / or current signal is greater than a predetermined frequency threshold, a fault signal is generated.

10. The method according to claim 9, characterized in that, The frequency analysis is a Fast Fourier Transform.

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