Method for detecting an insulation fault in an electrical system

Abstract

The system comprises a battery (HV-BATT), a load connection, a first high-voltage supply path (HV+) with a switchable first disconnect device (SW1), a second high-voltage supply path (HV-) with a second switchable second disconnect device (SW2), positive battery-side insulation, negative battery-side insulation, positive load-side insulation, negative load-side insulation, and an insulation monitor (20). Depending on the voltage values ​​provided by the insulation monitor (20), it is detected whether a positive or negative insulation fault is present.If a positive insulation fault is detected, a verification circuit phase is set such that the first disconnecting device (SW1) and the second disconnecting device (SW2) are in an open state and the pre-charge disconnecting device (SW_PRE) is in a closed state; if a negative insulation fault is detected, the verification circuit phase is set such that the first disconnecting device (SW1) is in a closed state and the second disconnecting device (SW2) and the pre-charge disconnecting device (SW_PRE) are in an open state.

Description

[0001] The disclosure relates to a method for detecting an insulation fault in the insulation of an electrical system by means of an insulation monitor. Furthermore, the disclosure relates to a control device for detecting an insulation fault in the insulation of an electrical system. The disclosure also relates to a high-voltage system, a computer program, and a computer-readable medium.

[0002] Diagnostic methods for insulation resistance in isolated voltage distribution networks (IT networks) have been known for a long time. An insulation monitoring device (IMD) is used in particular to monitor the high-voltage system of an electric vehicle. The IMD continuously measures resistance values ​​between individual potentials. If a measured value indicates an excessively low insulation resistance, thus posing a risk of leakage current to ground, an action is taken, such as a hazard warning or a shutdown of the high-voltage system.

[0003] Especially in the event of a repair, reliable detection of an insulation fault is very important.

[0004] From DE 10 2018 217 116 B3, a high-voltage system is known that comprises a high-voltage battery and a DC / DC converter. When the converter is activated, the system has two galvanically connected voltage levels. A first measuring device detects the battery voltage. A second measuring device detects the voltage at the converter output. An insulation resistance measuring device performs measurements only when the converter is deactivated. A third measuring device detects the voltage between a positive high-voltage line and ground. A fourth measuring device detects the voltage between a negative high-voltage line and ground. An insulation monitoring device uses the measured data to monitor the insulation resistances, at least when the converter is activated.

[0005] From US Patent 2020 / 0072896A1, a method for insulation detection is known that comprises several steps. First, a first and a second equivalent resistance are calculated. The smaller of the two equivalent resistances is adopted as the first insulation resistance. This first insulation resistance refers to the high-voltage circuit on the battery side relative to a reference potential. If the first insulation resistance is normal, a switching unit is closed. Then, a second insulation resistance is calculated using the two equivalent resistances and the voltages at two sampling points when the switching unit is closed. The second insulation resistance refers to the high-voltage circuit on the load side relative to the reference potential. The insulation condition of the high-voltage circuit on the load side is determined based on the second insulation resistance.

[0006] The object underlying the invention is therefore to provide a method for detecting an insulation fault in an electrical system that enables reliable detection of an insulation fault.

[0007] The problem is solved by the features of the independent patent claims. Advantageous embodiments are characterized in the dependent claims.

[0008] According to a first aspect and a second aspect, the above-mentioned task is solved by a method and a corresponding control device for detecting an insulation fault in an electrical system by means of an insulation monitor.

[0009] The system is, for example, a high-voltage system of an electric vehicle. The system comprises a battery, in particular a high-voltage battery, with a first battery terminal for providing a first high-voltage supply potential and a second battery terminal for providing a second high-voltage supply potential. The battery is, for example, the vehicle's traction battery.

[0010] Furthermore, the system includes a consumer connection with a first consumer connection point and a second consumer connection point. One or more consumers can be connected to the consumer connection.

[0011] The system further comprises a first high-voltage supply path (HV supply path) between the first battery connection point and the first consumer connection point, wherein the first HV supply path is configured to carry the first high-voltage supply potential. The system further comprises a switchable first disconnecting device, arranged in the first high-voltage supply path and configured to interrupt and establish an electrically conductive connection of the first high-voltage supply path. With the aid of the first disconnecting device, the first high-voltage supply path can be separated into a battery-side first high-voltage supply path and a consumer-side first HV supply path. The system comprises a second HV supply path between the second battery connection point and the second consumer connection point, wherein the second HV supply path is configured to carry the second high-voltage supply potential.The system includes a switchable second disconnect device, arranged and configured within the second high-voltage (HV) supply path, to interrupt and establish an electrically conductive connection of the second HV supply path. With the aid of this second disconnect device, the second HV supply path can be separated into a battery-side second HV supply path and a second consumer-side HV supply path.

[0012] The system features a pre-charging circuit. The pre-charging circuit is arranged in parallel to the second disconnecting device. The pre-charging circuit includes a pre-charging disconnecting device. Preferably, the pre-charging circuit includes a pre-charging resistor, which is connected in series with the pre-charging disconnecting device.

[0013] The system further includes insulation. This insulation comprises positive battery-side insulation between the first high-voltage (HV) supply path on the battery side and a reference potential; negative battery-side insulation between the second battery-side HV supply path and the reference potential; positive load-side insulation between the first load-side HV supply path and the reference potential; and negative load-side insulation between the second load-side HV supply path and the reference potential. The reference potential can be, in particular, a vehicle ground or chassis potential, or terminal 31.

[0014] The system includes an insulation monitor. The insulation monitor has a voltage measurement arrangement and a test circuit and is configured to provide voltage values ​​that are detected during operation of the test circuit and represent at least one of the following voltages: a first voltage between the reference potential and the second HV supply path, a second voltage between the first HV supply path and the second HV supply path, and a third voltage between the first HV supply path and the reference potential.

[0015] The insulation monitor is used to execute the procedure.First, depending on the voltage values ​​provided, which are detected and / or determined by the insulation monitor during operation of the system in which the first disconnecting device and the second disconnecting device are in a closed state and the pre-charge disconnecting device is in an open state, it is detected whether a positive insulation fault or a negative insulation fault is present, whereby the positive insulation fault can be caused by faulty positive battery-side insulation, faulty positive load-side insulation, or faulty positive battery-side and load-side insulation respectively, and the negative insulation fault can be caused by faulty negative battery-side insulation, faulty negative load-side insulation, or faulty negative battery-side and load-side insulation respectively.

[0016] This means that in an operating state of the system where the first disconnect device and the second disconnect device are closed (pre-charge disconnect device open), the system behavior is changed by means of the test circuit and corresponding voltages are recorded and / or determined.

[0017] If a positive insulation fault is detected, a verification circuit phase is then set such that the first and second disconnect devices are in an open state and the pre-charge disconnect device is in a closed state. Furthermore, additional voltage measurements, representative of another voltage between the reference potential and the second load-side HV supply path, are read in. A positive insulation fault on the battery side is detected if the additional voltage values ​​exceed or are equal to a predefined first threshold, and a positive insulation fault on the load side is detected if the additional voltage values ​​fall below a second threshold that is equal to or less than the first threshold.

[0018] The other voltage measurements are preferably provided by the insulation monitor, but can also be provided by another voltage measurement arrangement.

[0019] If a negative insulation fault is detected, the verification circuit phase is set such that the positive disconnect device is in a closed state and the negative disconnect device and the pre-charge disconnect device are in an open state. Furthermore, the additional voltage values ​​detected and / or determined during the verification circuit phase, which represent a further voltage between the reference potential and the consumer-side second HV supply path, are read in.A negative insulation fault on the battery side is detected if the subsequent voltage values ​​fall below or are equal to a predetermined third threshold, and a negative insulation fault on the consumer side is detected if the subsequent voltage values ​​exceed a fourth threshold that is greater than or equal to the third threshold and less than or equal to the second threshold.

[0020] The test circuit is preferably not operated during the verification phase.

[0021] Preferably, when an insulation fault is detected, the vehicle will signal a fault and / or initiate a fault response.

[0022] This method advantageously allows for the very precise localization of an insulation fault within the system, particularly in a vehicle's high-voltage system. The two sides are separated by so-called main contactors, which, when closed, allow current flow from the battery to the drive system. Precise localization of the insulation fault is highly beneficial for vehicle repair or maintenance, as an insulation fault can lead to very high leakage currents, which are life-threatening.

[0023] In at least one advantageous embodiment according to the first and second aspects, the insulation monitor comprises a first series circuit with a first test resistor and a first switch, which is arranged between the first HV supply path, in particular between the consumer-side first HV supply path, and the reference potential, and a second series circuit with a second test resistor and a second switch, which is arranged between the second HV supply path, in particular between the consumer-side second HV supply path, and the reference potential.Detecting whether a positive or negative insulation fault is present includes setting a first circuit phase such that the second switch is in a closed state and the first switch is in an open state, and reading the voltage values ​​that are detected and / or determined by the voltage measurement arrangement during the first circuit phase, as well as setting a second circuit phase such that the first switch is in a closed state and the second switch is in an open state, and reading the voltage values ​​that are detected and / or determined by the voltage measurement arrangement during the second circuit phase.

[0024] Preferably, the first and second circuit phases each last for a predetermined time period. The time period for the first and second circuit phases can be different or the same. In particular, the first and second circuit phases are executed alternately over a predetermined period.

[0025] The first switching phase and the second switching phase are each executed during the operation of the system when the first disconnecting device and the second disconnecting device are in a closed state, while the verification phases are executed in a different system operation.

[0026] In at least one advantageous embodiment according to the first and second aspects, the step of detecting whether a positive or negative insulation fault is present additionally includes comparing the read voltage values ​​with a predetermined upper threshold and a predetermined lower threshold, wherein a positive insulation fault is present if the voltage values ​​do not fall below the predetermined lower threshold, and a negative insulation fault is present if the voltage values ​​do not exceed the predetermined upper threshold. This method enables simple localization of the insulation fault.

[0027] In at least one advantageous embodiment according to the first and second aspects, the positive battery-side insulation is represented by a first battery-side insulation resistor arranged between the first battery connection point / the first battery-side HV supply path and the reference potential. The negative battery-side insulation is represented by a second battery-side insulation resistor arranged between the second battery connection point / the second battery-side HV supply path and the reference potential. The positive load-side insulation is represented by a first load-side insulation resistor arranged between the first load connection point / the first load-side HV supply path and the reference potential.The negative consumer-side insulation is represented by a second consumer-side insulation resistance located between the second consumer connection point / the consumer-side second HV supply path and the reference potential, and the step of detecting whether a positive or negative insulation fault is present further includes detecting / determining a change in a positive insulation resistance and / or a change in a negative insulation resistance.

[0028] The first and second switching phases are each executed during system operation when the first and second disconnect devices are in a closed state. The positive insulation resistance thus represents a parallel connection of the positive battery-side insulation resistance and the positive load-side insulation resistance. The negative insulation resistance represents a parallel connection of the negative battery-side insulation resistance and the negative load-side insulation resistance.

[0029] According to a third aspect, the above-mentioned task is solved by a high-voltage system for a vehicle, the high-voltage system comprising: - a battery connection comprising a first battery connection point to provide a first high-voltage supply potential and a second battery connection point to provide a second high-voltage supply potential, - a consumer connection with a first consumer connection point and a second consumer connection point, - a first high-voltage (HV) supply path between the first battery connection point and the first consumer connection point, which is designed to carry the first high-voltage supply potential, - a switchable first disconnecting device designed to interrupt and establish an electrically conductive connection of the first HV supply path, - a second high-voltage (HV) supply path between the second battery connection point and the second consumer connection point, which is designed to carry the second high-voltage supply potential, - a switchable second disconnecting device designed to interrupt and establish an electrically conductive connection of the second HV supply path, - a pre-charging circuit with a switchable pre-charging disconnect device, wherein the pre-charging circuit is arranged in parallel to the second disconnect device, - an insulation, whereby the insulation - a positive battery-side isolation that acts between the battery-side first HV supply path and a reference potential, - a negative battery-side isolation that acts between the battery-side second HV supply path and the reference potential, - a negative consumer-side isolation that acts between the consumer-side first HV supply path and the reference potential, - includes a negative consumer-side isolation that acts between the consumer-side second HV supply path and the reference potential and - an insulation monitor comprising a voltage measurement arrangement and a test circuit, and configured to provide voltage readings acquired during operation of the test circuit, representing at least one of the following voltages: a first voltage between the reference potential and the second HV supply path, a second voltage between the first HV supply path and the second HV supply path, and a third voltage between the first HV supply path and the reference potential, and - a control device according to the second aspect.

[0030] Advantageous features of the first and second aspects also apply to the third aspect.

[0031] According to a fourth aspect, the aforementioned task is solved by a computer program comprising instructions which, when the program is executed by a control computer, cause it to execute the procedure according to the first aspect or an optional embodiment of the procedure according to the first aspect.

[0032] For the purposes of this document, the term "computer program" is synonymous with "program element and / or software module" containing instructions for controlling the control computer in order to appropriately coordinate the operation of the system or method to achieve the effects associated with the method according to the invention. The computer program can be implemented as computer-readable instruction code in any suitable programming language, such as Java, C++, etc.

[0033] The control computer has a processor and program memory. Alternatively, the program memory can be assigned to the control computer. The processor can be a central processing unit (CPU). The processor can be a general-purpose processor, a microprocessor, a microcontroller, or a digital signal processor (DSP).

[0034] According to a fifth aspect, the above-mentioned task is solved by a computer-readable medium containing instructions which, when executed by a control computer, cause it to execute the procedure according to the first aspect or an optional embodiment of the procedure according to the first aspect.

[0035] The computer program can be stored on a computer-readable storage medium (CD-ROM, DVD, Blu-ray Disc, removable drive, volatile or non-volatile memory, in particular random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), and / or flash memory). The storage medium can be memory integrated into the processor, memory located outside the processor on a circuit board, or portable storage. The memory is configured to store associated program instructions and related data.

[0036] Further advantageous embodiments are disclosed in the appended claims and in the following description of exemplary embodiments with reference to the appended figures. The description of the items specified herein is not limited to the individual specific embodiments. Features of different exemplary embodiments can be combined with one another—where technically feasible—to form further exemplary embodiments. For example, variations or modifications described with regard to one of the exemplary embodiments may also be applicable to other exemplary embodiments, unless otherwise stated.

[0037] They show: Fig. 1 an exemplary equivalent circuit diagram of an electrical system with an embodiment of a high-voltage system according to the invention for a vehicle, Fig. 2. An exemplary flowchart for a program for detecting an insulation fault in the electrical system and Fig. 3 Voltage waveforms in the system during several switching phases of an insulation monitor.

[0038] In the figures, the same reference symbols are used for elements with essentially the same function; however, these elements do not have to be identical in every detail.

[0039] Fig. Figure 1 shows an exemplary equivalent circuit diagram of an electrical system 1 with an embodiment of a high-voltage system 10 according to the invention for a vehicle. In the equivalent circuit diagram shown, specific or general values, rating data, additions, as well as the inclusion or exclusion of components are not intended to affect the scope of protection of the invention.

[0040] Electrical system 1 comprises a high-voltage system for a vehicle and a battery (HV-Bat), in particular a high-voltage battery. The battery (HV-Bat) can comprise one or more battery stacks or cells. The battery (HV-Bat) can be, for example, a lithium-ion battery or a fuel cell. The battery assembly is, for example, isolated from a reference potential (GND), in particular from a chassis potential or the vehicle's ground potential. The vehicle is, for example, a purely electric vehicle.

[0041] The high-voltage system 10 has a battery connection comprising a first battery connection point B1+ to provide a first high-voltage supply potential and a second battery connection point B1- to provide a second high-voltage supply potential.

[0042] The high-voltage system 10 has a consumer side with a first consumer connection point A1+ and a second consumer connection point A1-. The consumer connection is disconnectably connected to the battery connection.

[0043] For this purpose, a first high-voltage supply path HV+ is arranged between the first battery connection point B1+ and the first consumer connection point A1+, which is configured to conduct the first high-voltage supply potential. Furthermore, a second high-voltage supply path HV-, which is configured to conduct the second high-voltage supply potential, is arranged between the second battery connection point B1- and the second consumer connection point A1-.

[0044] In the first high-voltage (HV) supply path HV+, a switchable first disconnecting device SW1 is arranged, configured to interrupt and establish an electrically conductive connection of the first HV supply path HV+. In the second HV supply path HV-, a switchable second disconnecting device SW2 is arranged, configured to interrupt and establish an electrically conductive connection of the second HV supply path HV-. The first disconnecting device SW1 and the second disconnecting device SW2 are preferably designed as contactors.

[0045] One or more devices can be connected to the consumer connection. One of these devices is, for example, an electric motor, particularly one that is at least partially designed to power the vehicle. Other devices can include a lighting system, one or more heat sources, a control unit, an infotainment system, and / or other auxiliary equipment. The consumer side can also be referred to as the link side.

[0046] The first consumer connection point A1+ and the second consumer connection point A1- are each coupled or connected to a reference potential GND of the vehicle, in particular to a vehicle chassis potential, via a capacitor Cy1 and Cy2, respectively. The capacitors Cy1 and Cy2 are configured either as parasitic elements or as dedicated components, such as Y-capacitors.

[0047] Furthermore, the high-voltage system 10 comprises a pre-charging circuit with a pre-charging isolating device SW_PRE and preferably a pre-charging resistor RPRE, which is arranged in parallel to the second isolating device SW2.

[0048] The high-voltage system 10 includes insulation or galvanic isolation. The battery side can be separated from the load side by the first and second isolation devices SW1 and SW2, and the insulation can therefore be divided into battery-side isolation and load-side isolation.

[0049] The isolation of the high-voltage system 10 thus comprises a positive battery-side isolation, a negative battery-side isolation, a positive consumer-side isolation and a negative consumer-side isolation.

[0050] In Fig. A first battery-side resistance RisoBP is arranged between the first battery terminal B1+ and the reference potential GND. This resistance represents the positive battery-side insulation to be monitored and is therefore not physically present as a component. A second battery-side insulation resistance RisoBN is arranged between the second battery terminal B1- and the reference potential GND. This resistance represents the negative battery-side insulation. A first load-side insulation resistance RisoLP is arranged between the first load terminal A1+ and the reference potential GND. This resistance represents the positive load-side insulation. The negative load-side insulation is represented by a second load-side insulation resistance RisoLN, which is arranged between the second load terminal A1- and the reference potential GND.

[0051] The respective insulation resistances RisoBP, RisoBN, RisoLP, RisoLN represent the respective insulations and are therefore not physically present as a component.

[0052] Furthermore, the HV system 10 includes an insulation monitor 20 and a control device (not shown in Fig. 1).

[0053] The insulation monitor 20 has a voltage measurement arrangement and a test circuit and is configured to provide voltage values ​​that are detected during operation of the test circuit and represent at least one of the following voltages: a first voltage between the reference potential GND and the second HV supply path HV-, a second voltage between the first HV supply path HV- and the second HV supply path HV+, and a third voltage between the first HV supply path HV+ and the reference potential GND.

[0054] The insulation monitor 20 comprises in particular a first series circuit with a first test resistor RT1 and a first switch T1, which is arranged between the first HV supply path HV+ and the reference potential GND, and a second series circuit with a second test resistor RT2 and a second switch T2, which is arranged between the second HV supply path HV- and the reference potential GND.

[0055] The control device is designed to detect an insulation fault in the insulation of the electrical high-voltage system 10 by means of the insulation monitor 20.

[0056] The voltage measurement arrangement of the insulation monitor 20 includes, for example, a first measurement circuit which has a first voltage divider which is arranged between the reference potential GND and the second consumer-side HV supply path HVL.

[0057] The voltage measurement arrangement of the insulation monitor 20 can include a second measurement circuit which includes a second voltage divider arranged between the consumer-side first HV supply path HVL+ and the second consumer-side HV supply path HVL-.

[0058] The control device, for example, has a computing unit and is designed to execute a program for detecting an insulation fault using the computing unit.

[0059] Fig. Figure 2 shows an exemplary flowchart for an implementation of the program for detecting an insulation fault.

[0060] The program is started, for example, in step S01. In step S01, program variables are initialized. The program is preferably started when the vehicle is started.

[0061] In step S03, depending on voltage values ​​provided or read by the insulation monitor 20, it is detected whether a positive or negative insulation fault is present, whereby the positive insulation fault can be caused by faulty positive battery-side insulation, faulty positive consumer-side insulation, or faulty positive battery-side and consumer-side insulation respectively, and the negative insulation fault can be caused by faulty negative battery-side insulation, faulty negative consumer-side insulation, or faulty negative battery-side and consumer-side insulation respectively.

[0062] The voltage values ​​provided or read in are recorded and / or determined during operation of system 1, in which the first disconnect device SW1 and the second disconnect device SW2 are in a closed state and the pre-charge disconnect device SW_PRE is in an open state. The HV system 10 is therefore in an active operating state.

[0063] Step S03 can comprise several sub-steps. For example, in step S03a, during operation where the first disconnecting device SW1 and the second disconnecting device SW2 are in a closed state and the pre-charge disconnecting device WW_PRE is in an open state, a first circuit phase is set such that the second switch T2 is in a closed state and the first switch T1 is in an open state. Setting the first circuit phase includes, for example, outputting control signals for the first switch T1 and the second switch T2; in particular, respective driver circuits for the first switch T1 and the second switch T2 can be controlled by means of the control signal. In step S03b, the voltage measurements (first voltage values) acquired by the voltage measurement arrangement of the insulation monitor 20 during the first circuit phase are read in.In step S03c, during operation in which the first disconnecting device SW1 and the second disconnecting device SW2 are in a closed state and the pre-charge disconnecting device SW_PRE is in an open state, a second switching phase is initiated, such that the first switch T1 is in a closed state and the second switch T2 is in an open state. In step S03d, the voltage measurements (second voltage values) acquired by the voltage measuring arrangement of the insulation monitor 20 during the second switching phase are read in.

[0064] The first and second circuit phases are preferably executed alternately. Alternatively, a third circuit phase can be executed between the first and second circuit phases, in which the first switch T1 and the second switch T2 are in a closed state.

[0065] In step S03e, the recorded voltage values ​​are evaluated.

[0066] The voltage values ​​recorded by the voltage measurement arrangement of the insulation monitor 20 represent a charging curve. Depending on the charging curve, it is determined, for example, whether a positive or a negative insulation fault is present.

[0067] Fig. Figure 3 shows several voltage curves, each representing such a charging curve. A deviation of the respective charging curve from the normal case indicates an insulation fault. Reference numeral 41 denotes the voltage curve under normal conditions. Reference numeral 42 denotes the voltage curve when a positive insulation fault is present, and reference numeral 43 denotes the voltage curve when a negative insulation fault is present.

[0068] An insulation fault on the positive side, in particular a positive battery-side insulation fault and / or a positive load-side insulation fault, leads to a shift in the mean value towards higher voltages and simultaneously to a smaller amplitude. An insulation fault on the negative side, in particular a negative battery-side insulation fault and / or a negative load-side insulation fault, leads to a shift in the mean value towards lower voltages and simultaneously to a smaller amplitude.

[0069] The program recognizes that the insulation is fault-free if the voltage values ​​temporarily exceed both a predetermined upper threshold Uth_h and fall below a predetermined lower threshold Uth_l. The program recognizes that the insulation has a fault on the positive side, i.e., a fault in the positive battery-side insulation and / or in the positive load-side insulation, if the predetermined lower threshold Uth_l is not exceeded. The program recognizes that the insulation has a fault on the negative side, i.e., a fault in the negative battery-side insulation and / or in the negative load-side insulation, if the predetermined upper threshold Uth_h is not exceeded.

[0070] Alternatively or additionally, in step S03, instead of evaluating the charging curve, a positive and negative insulation resistance can be determined to detect whether a positive or negative insulation fault is present. Switching the first test resistor RT1 and the second test resistor RT2 on or off results in a new circuit with new network equations. Since there are two unknown variables in the system—the positive insulation resistance (positive battery-side and load-side insulation resistance in parallel) and the negative insulation resistance (negative battery-side and load-side insulation resistance in parallel)—two modifications of the network equations are required (Gaussian elimination algorithm).A positive insulation fault or a negative insulation fault can be detected by comparing the positive insulation resistance with a positive target insulation resistance and by comparing the negative insulation resistance with a negative target insulation resistance.

[0071] If a positive insulation fault Iso_F+ is detected in step S03, a verification circuit phase is set in step S05 such that the first disconnecting device SW1 and the second disconnecting device SW2 are in an open state and the pre-charge disconnecting device SW_PRE is in a closed state.

[0072] Preferably, electrical system 1 is first deactivated, i.e., the first disconnect device SW1, the second disconnect device SW2, and the pre-charge disconnect device SW_PRE are opened. Then, the pre-charge disconnect device SW_PRE is closed.

[0073] During the verification circuit phase, the test circuit is preferably not operated, i.e., the first and second switches T1 and T2 each remain open.

[0074] Setting the verification circuit phase includes, for example, the output of control signals for the first disconnect device SW1 and the second disconnect device SW2 as well as the pre-charge disconnect device SW_PRE; in particular, a respective driver circuit of the first disconnect device SW1, second disconnect device SW2 and the pre-charge disconnect device SW_PRE can be controlled directly or indirectly by means of the control signal.

[0075] Furthermore, in step S05, the additional voltage values ​​recorded and / or determined during the verification circuit phase, representing a further voltage between the reference potential GND and the consumer-side second HV supply path HV-, are read in. In step S05, these additional voltage values ​​are also evaluated. In particular, the program detects a positive insulation fault on the battery side if the additional voltage values ​​exceed a predefined first threshold (e.g., Uth1 = Ubat / 4) or are equal to this first threshold, and detects a positive insulation fault on the consumer side if the additional voltage values ​​fall below a second threshold (e.g., Ubat / 8) that is equal to or less than the first threshold.

[0076] Closing the pre-charge disconnect device SW_PRE via a low positive insulation resistance on the battery side closes a circuit. Depending on the magnitude of the insulation resistance, a positive voltage between one-quarter of the battery voltage (Ubat / 4) and the total battery voltage (Ubat) can be measured at the measuring point. This detects an insulation fault on the positive potential on the battery side (positive battery-side insulation fault). However, if the low positive insulation resistance is applied on the load side, the circuit is prevented from closing. Only a very small voltage in the range of 0V to one-eighth of the battery voltage (Ubat / 8) is measured at the measuring point. This detects an insulation fault on the positive potential on the load side (positive load-side insulation fault).

[0077] If a negative insulation fault Iso_F- is detected in step S03, the verification circuit phase is set in step S06 such that the first disconnecting device SW1 is in a closed state and the second disconnecting device SW2 and the pre-charge disconnecting device SW_PRE are in an open state. Preferably, electrical system 1 is first deactivated, i.e., the first disconnecting device SW1, the second disconnecting device SW2, and the pre-charge disconnecting device SW_PRE are opened. Then, the first disconnecting device SW1 is closed.

[0078] Furthermore, in step S06, the additional voltage values ​​recorded and / or determined during the verification circuit phase, representing the additional voltage between the reference potential GND and the consumer-side second HV supply path HVL-, are read in. In step S06, these additional voltage values ​​are evaluated. In particular, the program detects a negative insulation fault on the battery side if the additional voltage values ​​fall below or are equal to a predefined third threshold (e.g., -Ubat / 4), and detects a negative insulation fault on the consumer side if the additional voltage values ​​exceed a fourth threshold (e.g., Ubat / 8) that is greater than or equal to the third threshold (-Ubat / 4) and less than or equal to the second threshold (e.g., Ubat / 8).

[0079] By closing the first disconnecting device SW1, a circuit can be closed via a low negative insulation resistance on the battery side. Depending on the magnitude of the insulation resistance, a negative voltage between one-quarter of the negative battery voltage (-Ubat / 4) and the total negative battery voltage (-Ubat) can be measured at the measuring point. This detects an insulation fault at the negative potential on the battery side (negative battery-side insulation fault). However, if the low negative insulation resistance is present on the load side, the circuit is prevented from closing. Only a very small voltage, ranging from one-eighth of the battery voltage (Ubat / 8) to one-eighth of the negative battery voltage (-Ubat / 8), is measured at the measuring point. This detects an insulation fault at the negative potential on the load side (negative load-side insulation fault).

[0080] Step S05 and step S06 preferably each include fault signaling and / or initiating a fault response by the vehicle.

[0081] If no isolation fault Iso_F0 is detected in step S03, the program returns to the beginning of step S03.

[0082] If an error is detected, the program terminates, for example, at step S07. Alternatively, the program can terminate in response to a suitable control signal from the vehicle. Reference sign 1 electrical system 10 High-voltage system 20 insulation monitors A1 second consumer connection point A1+ first consumer connection point B1 second battery connection point B1+ first battery connection point Cy1, Cy2 capacity GND reference potential of the vehicle HV second high-voltage supply path HV+ first high-voltage supply path HVB battery-side second high-voltage supply path HVB+ battery-side first high-voltage supply path HVL consumer-side second high-voltage supply path HVL+ consumer-side first high-voltage supply path HV-BAT battery RisoLN negative consumer-side insulation resistance RisoLP positive consumer-side insulation resistance RisoPN negative battery-side insulation resistance RisoPP positive battery-side insulation resistance RPRE pre-charge resistor RT1 first test resistor RT2 second test resistor SW1 first disconnect device SW2 second disconnect device SW_PRE pre-charging separation device T1 first switch T2 second switch Uth_h upper threshold Uth_l lower threshold U_Kl31 is a further voltage between the reference potential and the consumer-side, second high-voltage supply path.

Claims

[1] Method for detecting an insulation fault in an electrical system (1), wherein the electrical system (1) comprises: - a battery (HV-BATT) and a battery connection comprising a first battery connection point (B1+) to provide a first high-voltage supply potential and a second battery connection point (B1-) to provide a second high-voltage supply potential, - a consumer connection with a first consumer connection point (A1+) and a second consumer connection point (A1-), - a first high-voltage supply path (HV+) between the first battery connection point (B1+) and the first consumer connection point (A1+), which is designed to carry the first high-voltage supply potential, - a switchable first disconnecting device (SW1) designed to interrupt and establish an electrically conductive connection of the first supply path (HV+), - a second high-voltage supply path (HV-) between the second battery connection point (B1-) and the second consumer connection point (A1-), which is designed to carry the second high-voltage supply potential, - a switchable second disconnecting device (SW2) designed to interrupt and establish an electrically conductive connection of the second supply path (HV-), - a pre-charging circuit with a switchable pre-charging disconnect device (SW_PRE), wherein the pre-charging circuit is arranged in parallel to the second disconnect device (SW2), - an insulation, whereby the insulation - a positive battery-side isolation that acts between the battery-side first HV supply path (HVB+) and a reference potential (GND), - a negative battery-side isolation that acts between the battery-side second HV supply path (HVB-) and the reference potential (GND), - a positive consumer-side isolation that acts between the consumer-side first HV supply path (HVL+) and the reference potential (GND), - includes a negative consumer-side isolation that acts between the consumer-side second HV supply path (HVL-) and the reference potential (GND) and - an insulation monitor (20) comprising a voltage measurement arrangement and a test circuit and configured to provide voltage values ​​that are detected during operation of the test circuit and represent at least one of the following voltages: a first voltage between the reference potential (GND) and the second HV supply path (HV-), a second voltage between the first HV supply path (HV+) and the second HV supply path (HV-), and a third voltage between the first HV supply path (HV+) and the reference potential (GND), and the method comprising the following steps, - Detect and / or determine, depending on voltage values ​​provided by the insulation monitor (20), which are detected by the insulation monitor (20) during operation of the electrical system (1) in which the first disconnecting device (SW1) and the second disconnecting device (SW2) are in a closed state and the pre-charge disconnecting device (SW_PRE) is in an open state, whether a positive insulation fault or a negative insulation fault is present, - if a positive insulation fault is detected, - -- Setting a verification circuit phase such that the first disconnect device (SW1) and the second disconnect device (SW2) are in an open state and the pre-charge disconnect device (SW_PRE) is in a closed state, and reading in further voltage values ​​recorded and / or determined during the verification circuit phase, which represent a further voltage (U_Kl31) between the reference potential (GND) and the consumer-side second HV supply path (HVL-), - -- Detect a positive insulation fault on the battery side when the subsequent voltage values ​​exceed or are equal to a predetermined first threshold, and detect a positive insulation fault on the consumer side when the subsequent voltage values ​​fall below a second threshold that is equal to or less than the first threshold, and when a negative insulation fault is detected, - - Setting the verification circuit phase such that the first disconnect device (SW1) is in a closed state and the second disconnect device (SW2) and the pre-charge disconnect device (SW_PRE) are in an open state, and reading in the further voltage values ​​recorded and / or determined during the verification circuit phase, which represent a further voltage (U_Kl31) between the reference potential (GND) and the consumer-side second HV supply path (HVL-), -- Detecting a battery-side negative insulation fault when subsequent voltage values ​​fall below or are equal to a predetermined third threshold, and detecting a consumer-side negative insulation fault when subsequent voltage values ​​exceed a fourth threshold that is greater than or equal to the third threshold and less than or equal to the second threshold. [2] Method according to claim 1, wherein the insulation monitor (20) comprises a first series circuit with a first test resistor (RT1) and a first switch (T1) arranged between the first HV supply path (HV+) and the reference potential (GND), and a second series circuit with a second test resistor (RT2) and a second switch (T2) arranged between the second HV supply path (HV-) and the reference potential (GND), and the step of detecting whether a positive or negative insulation fault is present comprises: - Setting a first circuit phase such that the second switch (T2) is in a closed state and the first switch (T1) is in an open state, and reading the voltage values ​​that are recorded and / or determined by the voltage measurement arrangement during the first circuit phase, - Setting a second circuit phase so that the first switch (T1) is in a closed state and the second switch (T2) is in an open state, and reading the voltage values ​​that are recorded and / or determined by the voltage measurement arrangement during the second circuit phase. [3] Method according to claim 2, wherein the step of detecting whether a positive or negative insulation fault is present additionally comprises comparing the read voltage values ​​with a predetermined upper threshold (Uth_h) and a predetermined lower threshold (Uth_I), wherein if the voltage values ​​do not fall below the predetermined lower threshold (Uth_I), a positive insulation fault is present and if the voltage values ​​do not exceed the predetermined upper threshold (Uth_h), a negative insulation fault is present. [4] Method according to claim 2, wherein - the positive battery-side isolation is represented by a first battery-side isolation resistance (RisoBP) located between the first battery-side HV supply path (HVB+) and the reference potential (GND), - the negative battery-side isolation is represented by a second battery-side isolation resistance (RisoBN) located between the second battery-side HV supply path (HVB-) and the reference potential (GND), - the positive consumer-side isolation is represented by a first consumer-side isolation resistance (RisoLP) which is arranged between the first consumer-side HV supply path (HVL-) and the reference potential (GND), - the negative consumer-side insulation is represented by a second consumer-side insulation resistance (RisoLN) located between the second consumer-side HV supply path (HVL-) and the reference potential (GND), and the step of detecting whether a positive or negative insulation fault is present further includes detecting / determining a change in a positive insulation resistance and / or a change in a negative insulation resistance. [5] Control device configured to perform the method according to any one of claims 1 to 4. [6] comprising a high-voltage system (10) for a vehicle: - a battery connection comprising a first battery connection point (B1+) to provide a first high-voltage supply potential and a second battery connection point (B1-) to provide a second high-voltage supply potential, - a consumer connection with a first consumer connection point (A1+) and a second consumer connection point (A1-), - a first high-voltage supply path (HV+) between the first battery connection point (B1+) and the first consumer connection point (A1+), which is designed to carry the first high-voltage supply potential, - a switchable first disconnecting device (SW1) designed to interrupt and establish an electrically conductive connection of the first HV supply path (HV+), - a second high-voltage supply path (HV-) between the second battery connection point (B1-) and the second consumer connection point (A1-), which is designed to carry the second high-voltage supply potential, - a switchable second disconnecting device (SW2) designed to interrupt and establish an electrically conductive connection of the second HV supply path (HV-), - a pre-charging circuit with a switchable pre-charging disconnect device (SW_PRE), wherein the pre-charging circuit is arranged in parallel to the second disconnect device (SW2), - an insulation, whereby the insulation - a positive battery-side isolation that acts between the battery-side first HV supply path (HVB+) and a reference potential (GND), - a negative battery-side isolation that acts between the battery-side second HV supply path (HVB-) and the reference potential (GND), - a positive consumer-side isolation that acts between the consumer-side first HV supply path (HVL+) and the reference potential (GND). - includes a negative consumer-side isolation that acts between the consumer-side second HV supply path (HVL-) and the reference potential (GND) and - an insulation monitor (20) comprising a voltage measurement arrangement and a test circuit and configured to provide voltage values ​​that are detected during operation of the test circuit and represent at least one of the following voltages: a first voltage between the reference potential (GND) and the consumer-side second HV supply path (HVL-), a second voltage between the consumer-side first HV supply path (HVL+) and the consumer-side second HV supply path (HVL-), and a third voltage between the consumer-side first HV supply path (HVL+) and the reference potential (GND), and - a control device according to claim 5. [7] Computer program comprising instructions which, when the program is executed by a control computer, cause the control computer to execute the method according to any one of claims 1 to 4. [8] Computer-readable medium comprising instructions which, when executed by a control computer, cause the control computer to execute the method according to any one of claims 1 to 4.

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