Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
  • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
  • G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass

Definitions

• the invention relates to a method for measuring the insulation of a battery-powered HV system, e.g. a HV drive system, as used in electric vehicles.
• a battery-powered HV system e.g. a HV drive system
• Such systems have operating voltages UB of several hundred volts. They can even be up to 1000 V and more.
• a low-impedance connection between the HV system and ground e.g. a housing or vehicle chassis, must be identified in good time so that safety measures can be taken, e.g. disconnecting the battery from the drive system.
• ECE R100 insulation measurements are prescribed for such systems in order to record the insulation resistance of the system, which must comply with certain limits.
• ECE R100 The basic circuit diagram of such a measurement according to ECE R100 can be found in FIGS. 1 to 3 taken from Appendix 4 of ECE R100.
• the voltages between the positive busbar and ground and between the negative busbar and ground are recorded.
• Measurements of this type are carried out again when a known reference resistance is connected between the corresponding busbar and ground, which reference resistance preferably corresponds to the prescribed minimum value of the insulation resistance multiplied by the operating voltage of the system.
• EP 1 857 825 B1 describes a method for carrying out the insulation measurement in accordance with ECE R100 in an automated manner.
• Mechanical switches or semiconductor switches are provided for this purpose, which automatically switch on the comparison resistor alternately between the positive and negative busbars.
• a disadvantage of this method is that two switches are now involved in the measurement, and that instead of one comparison resistor, which is switched on alternately between the positive or negative rail and ground, two identical comparison resistors must be provided, which are connected to ground by the switches . Both the switches and the provision of two identical ones Resistance can affect the measurement result, which in turn affects the reliability of such an automatic measurement.
• the object of the present invention is to provide a method which increases the reliability of an automated measurement of the insulation resistance. According to the invention, this object is achieved by a method according to claim 1 . Further advantageous aspects, details and configurations of the invention result from the dependent claims, the description and the drawings.
• the method according to the invention is used for self-diagnosis of the circuit for measuring insulation resistance, in particular for checking and thus ensuring the functionality of the switches installed in this circuit and also of the comparison resistors.
• the circuit for measuring the insulation resistance itself contains the following components: a first switch, which connects the positive pole of the battery system to ground via a first comparison resistor connected in series, and a second switch, which connects the negative pole of the battery system to ground via a second comparison resistor connected in series, where the resistance value of the two comparison resistors is identical and, in particular, corresponds to the prescribed minimum value of the insulation resistance multiplied by the operating voltage of the system.
• the theoretical current flow across the switches is calculated based on the operating voltage of the system and the size of the corresponding Comparative resistance calculated.
• the measured current flow is compared with the associated theoretical current flow, and an error signal is output and/or an error action is carried out if the result of the comparison exceeds or falls below a predetermined reference value range.
• Insulation resistance measurement can be completely checked for the functionality of its components, which improves the reliability of the measurement results of the insulation resistance measurement.
• a defect in the switch could be, for example:
• Switch does not switch on -> switch is non-conductive Too high a leakage current flows through the switch (predominantly with semiconductor switches)
• a defect in the comparison resistor Rs could be:
• the result of the insulation measurement can be checked for plausibility, which in turn improves the reliability of the insulation measurement itself.
• a no-load current measurement is carried out in which both switches are open. An error signal is then issued and/or an error action is carried out if the no-load current exceeds a predetermined reference value.
• the reference value range is preferably selected in such a way that temperature-related fluctuations in the measurement results or measurement value tolerances are taken into account in order to generate an error action or an error signal only if an error-related deviation of the determined values occurs.
• the following errors are assumed if the measured current flow falls below the predetermined reference value range:
• R s The resistance of R s is high (break). Appropriate measures to rectify the error can then be initiated immediately, eg replacement of the defective components.
• the following errors are assumed if the measured current flow exceeds the predetermined reference value range:
• the resistor Rs has a low resistance (short circuit).
• the voltage difference between the positive pole of the battery system and ground and the voltage difference between the negative pole of the battery system and ground are preferably measured and the current flow is calculated as follows:
• FIG. 4 shows the equivalent circuit diagram of an HV (high-voltage) drive system 10 with an HV battery 12, in particular based on Li with an output voltage in the range from 60 to 1500 V, and a drive 14 fed by the HV battery 12 becomes.
• Battery 12 and drive 14 are connected via a positive bus bar 16 and a negative bus bar 18 .
• the fault resistance RFP between ground 20 and positive busbar 16 as well as the fault resistance RFM between ground 20 and negative busbar 18 must therefore have an extremely high resistance, since a low-resistance connection of the system 10 to ground 20, e.g. the chassis of a motor vehicle, is life-threatening given the system voltages present can be.
• a low-impedance connection e.g. ⁇ 100 Ohm/V
• a measuring circuit 22 which consists of two identical comparison resistors R Si , Rs2, which are connected in series with an associated switch Si, S 2 to ground 20 in a voltage divider circuit are.
• the switches Si, S 2 are preferably formed by semiconductor switches.
• the two measuring resistors Rsi, Rs2 are only referred to as Rs below.
• the battery voltage UB can be calculated by taking the difference between the two voltages UP and UM.
• the two voltage measurements UP and UM are carried out digitally in practice, i.e. in a known manner using an AD converter and a microcontroller.
• the insulation resistance can be calculated using the formulas from ECE R100, whereby the internal resistance of the voltmeter must be taken into account in the calculation.
• the measuring circuit 22 exactly maps the measuring processes that are required according to ECE R 100 according to FIGS. 1 to 3 for detecting the insulation resistance.
• the insulation resistance is calculated using the mathematical formulas specified in ECE R 100.
• the aim of the invention is to further develop the circuit in such a way that any errors that could flow in through these additional components can be recognized in good time and, if necessary, react to them.
• the current flows are calculated theoretically in connection with the voltage measurement mentioned above and are also recorded in practice using a current measuring device 24 .
• the current I Gi , I G 2 actually flowing is determined using the ammeter 24 .
• the measured current I Gi When Si is closed, the measured current I Gi must match Itl. The same applies to S 2 , I G2 and It2. If the measured current I Gi , I G2 deviates too much from the desired value It1, It2, it can be assumed that the switches Si, S2 or the measuring resistor Rs are defective.
• a defective switch could be:
• Switch does not switch on -> Switch is non-conductive - Too high a leakage current flows through the switch (predominantly with
• a defect in the resistor could be: - Resistance drift upwards -> greater resistance
• the voltage divider ratio results in a voltage across the side with the activated switch from UP or UM.
• Resistance Rs is low-impedance (short circuit)

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Resistance Or Impedance (AREA)

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• 2021
  • 2021-07-30 DE DE102021119830.5A patent/DE102021119830B3/de active Active
• 2022
  • 2022-07-15 CN CN202280061633.6A patent/CN117940780A/zh active Pending
  • 2022-07-15 WO PCT/EP2022/069833 patent/WO2023006443A1/de active Application Filing
  • 2022-07-15 EP EP22744466.8A patent/EP4377703A1/de active Pending

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