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WO-2026092803-A1 - METHOD FOR MONITORING INSULATION RESISTANCES, AND CORRESPONDING CONTROL DEVICE

WO2026092803A1WO 2026092803 A1WO2026092803 A1WO 2026092803A1WO-2026092803-A1

Abstract

The invention relates to a method for monitoring the insulation between two electrical lines (102, 103), in particular high-voltage electrical lines, and ground (104) by means of an insulation monitoring circuit, wherein the insulation monitoring circuit has two switches (SWTestP, SWTestM). The method has the following steps: (a) changing the switched state (115, 116) of the two switches (SWTestP, SWTestM) at a first point in time (t1); (b) changing the switched state (115, 116) of the two switches (SWTestP, SWTestM) again at a second point in time (t2) which lies a specified time interval (114) after the first point in time (t1); (c) receiving a measured value (Pha2, Pha3) which is representative of a voltage (UChsGnd) between a first electrical line (103) of the two electrical lines (102, 103) and ground (104) at a third point in time (t3) during the specified time interval (114); (d) receiving a change value (ΔUBat) which is representative of a change in the voltage (UBat) between the two electrical lines (102, ̳103) before the third point in time (t3); (e) correcting the measured value (Pha2, Pha3) on the basis of the change value (ΔUBat); and (d) determining an insulation resistance (RisoPP, RisoPM, RisoLP, RisoLM) on the basis of the corrected measured value (Pha2, Pha3). The invention also relates to a corresponding control device and to a computer program.

Inventors

  • ASCHER, STEFAN
  • ERNST, SEBASTIAN

Assignees

  • Schaeffler Technologies AG & Co. KG

Dates

Publication Date
20260507
Application Date
20251021
Priority Date
20241030

Claims (15)

  1. 1. Method for monitoring insulation between two electrical conductors (102, 103), in particular high-voltage electrical conductors, and ground (104) by means of an insulation monitoring circuit, wherein the insulation monitoring circuit has two switches (SWTestP, SWTestM), the method comprising the following steps: Changing the switching state (115, 116) of the two switches (SWTestP, SWTestM) at a first time (t1); changing the switching state (115, 116) of the two switches (SWTestP, SWTestM) again at a second time (t2), which is a predetermined time interval (114) after the first time (t1); Receiving a measured value (Pha2, Pha3) that is representative of a voltage (UChsGnd) between a first electrical line (103) of the two electrical lines (102, 103) and ground (104) at a third time (t3) during the specified time interval (114); Receiving a change value (AUBat) that is representative of a change in voltage (UBat) between the two electrical lines (102, 103) before the third time (t3); Correcting the measured value (Pha2, Pha3) based on the change value (AUBat); and Determining an insulation resistance (RisoPP, RisoPM, RisoLP, RisoLM) based on the corrected measured value (Pha2, Pha3).
  2. 2. Method according to the preceding claim, wherein the method further comprises: determining a time interval (At) between a time point (t4) of the voltage change, in particular a start of the voltage change, and the third time point (t3), wherein the correction of the measured value (Pha2, Pha3) is based on the time interval (At).
  3. 3. Method according to the preceding claim, wherein the voltage change takes place over a period of time and the measured value (Pha2, Pha3) is corrected based on the period of time and/or a trend of the voltage change. 202400931 23
  4. 4. Method according to claim 2 or 3, wherein the measured value (Pha2, Pha3) is only corrected if the change value (AUBat) exceeds a predetermined voltage threshold and/or the time interval (At) exceeds a predetermined time threshold.
  5. 5. Method according to one of the preceding claims, wherein the measured value (Pha2, Pha3) is only corrected if the time interval (At) falls below a predetermined further time threshold.
  6. 6. Method according to any one of claims 2 to 5, wherein the correction of the measured value (Pha2, Pha3) takes into account a calibratable characteristic map (125).
  7. 7. Method according to the preceding claim, wherein the characteristic map (125) has as input parameters at least one of the following parameters: the change value (AUBat); the time interval (At).
  8. 8. Method according to claim 6 or 7, wherein the characteristic map (125) has a correction offset (121) and/or a correction factor (122) as an output parameter and the correction of the measured value (Pha2, Pha3) takes into account the correction offset (121) and/or the correction factor (122).
  9. 9. Method according to one of claims 2 to 6, wherein for correcting the measured value (Pha2, Pha3) a voltage profile of the voltage (UChsGnd) between the first electrical line (103) and ground (104) during the time interval (At) is extrapolated.
  10. 10. Method according to one of the preceding claims, further comprising: determining a time offset between the change in voltage (UBat) between the two electrical conductors (102, 103), in particular the beginning of the voltage change, and a corresponding change in voltage (UChsGnd) between the first electrical conductor (103) and ground (104), wherein the time offset is taken into account when correcting the measured value (Pha2, Pha3). 202400931 24
  11. 11. Method according to one of the preceding claims, wherein the third time point (t3) is in the last quarter of the specified time interval (114), in particular in the last fifth.
  12. 12. Method according to one of the preceding claims, wherein the third time (t3) is selected such that the voltage (UChsGnd) between the first electrical line (103) and ground (104) approximately stabilizes up to the third time (t3), in particular if no change in the voltage (UBat) between the two electrical lines (102, 103) is detected or the detected change in voltage is below a predetermined change threshold.
  13. 13. Method according to the preceding claim, wherein the voltage (UChsGnd) between the first electrical conductor (103) and ground (104) approximately stabilizes up to the third time (t3) if at least one of the following conditions is met: a slope of the voltage profile before or at the third time (t3) is less than a predetermined slope threshold; a voltage change of the voltage (UChsGnd) between the first electrical conductor (103) and ground (104) in an end section of the predetermined time interval (114) is less than five percent of a voltage change during the entire predetermined time interval (114), wherein the third time (t3) lies in the end section.
  14. 14. Computer program comprising instructions which, when executed by a computer, cause the computer to perform a method according to any one of claims 1 to 13.
  15. 15. Control unit, in particular battery management system, configured to perform a method according to any one of claims 1 to 13. Control unit, in particular battery management system, configured to perform a method according to any one of claims 1 to 13.

Description

202400931 1 DESCRIPTION Method for monitoring insulation resistances and corresponding control unit TECHNICAL AREA The present disclosure relates to methods and control devices for monitoring insulation resistances, in particular for a high-voltage system of a motor vehicle. BACKGROUND OF THE INVENTION In high-voltage (HV) battery and drive systems for motor vehicles, insulation resistances between electrical conductors and ground must be determined to ensure safe and reliable operation. It must be ensured that these insulation resistance values do not fall below the threshold values specified by the vehicle manufacturers. Insulation monitoring methods, such as those described in DE 102021 203 919 A1 or DE 10 2018222 123 B4, can be used for this purpose. However, it has been shown that such methods can produce erroneous insulation resistance values under certain conditions. In such cases, safe operation of the battery and drive systems can no longer be guaranteed. Undetected insulation faults can lead to uncontrolled fault currents, which may endanger human lives, cause fires, or result in other property damage. SUMMARY AND FORMS OF EXECUTION Therefore, one objective of the present disclosure is to provide a method and corresponding control device for insulation monitoring, wherein in 202400931 2 Situations in which conventional methods deliver inaccurate or erroneous results, the insulation resistance(s) are corrected accordingly. This task is accomplished by a method for insulation monitoring, a computer program, and a control unit according to the independent patent claims. Advantageous embodiments and further developments are described in the respective dependent claims, the following description, and the drawings. According to a first aspect, a method is provided for monitoring the insulation between two electrical conductors, in particular high-voltage electrical conductors, and ground by means of an insulation monitoring circuit, wherein the insulation monitoring circuit comprises two switches. The method comprises the following steps: (a) changing the switching state of the two switches at a first time point; (b) again changing the switching state of the two switches at a second time point, which is a predetermined time interval after the first time point; (c) receiving a measured value that is representative of and/or corresponds to a voltage between a first electrical conductor of the two electrical conductors and ground at a third time point during the predetermined time interval; (d) receiving a change value that is representative of and/or corresponds to a change in a voltage between the two electrical conductors before the third time point; (e) correcting the measured value based on the change value; and (e) determining, in particular calculating, an insulation resistance based on the corrected measured value. According to another aspect, a control unit, in particular a battery management system, is provided which is configured to carry out the previously described procedure. According to one embodiment, the control unit includes the insulation monitoring circuit. Alternatively, the insulation monitoring circuit can also be arranged in a battery, in particular in or on a battery housing. 202400931 3 According to another aspect, a battery system is provided which includes the previously described control unit including insulation monitoring circuitry and a battery, in particular a vehicle battery and/or a high-voltage battery. According to another aspect, a computer program is provided that includes instructions which, when executed by a computer, cause it to perform the procedure described above. In the context of this disclosure, a computer is defined, for example, as a device that processes data using programmable computational instructions. Computers can be embedded in everyday devices, such as the control units of motor vehicles. According to another aspect, a storage medium is provided with a computer program, wherein the computer program includes instructions which, when the computer program is executed by a computer, cause it to carry out the procedure described above. In the context of this disclosure, an electrical conductor is defined, for example, as a means for transmitting electrical energy and/or electrical signals. The electrical conductor may be a high-voltage conductor. The electrical conductor may connect a terminal of a battery, in particular a positive terminal or a negative terminal of the battery, to a terminal to which one or more loads may be connected. The terminal may be a link terminal. The two electrical conductors may connect a positive terminal of the battery to a positive terminal and a negative terminal of the battery to a negative terminal. In the context of this disclosure, high voltage is defined, for example, as an alternating voltage greater than 30 V, in particular less than 1 kV, and/or a direct voltage greater than 60 V, in particular less than 1.5 kV.