Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
  • G01R31/52—Testing for short-circuits, leakage current or ground faults
• • 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
  • G01R27/16—Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
  • G01R27/18—Measuring resistance to earth, i.e. line to ground
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/005—Testing of electric installations on transport means
  • G01R31/006—Testing of electric installations on transport means on road vehicles, e.g. automobiles or trucks
  • G01R31/007—Testing of electric installations on transport means on road vehicles, e.g. automobiles or trucks using microprocessors or computers

Definitions

• the invention relates to the estimation of the insulation resistance between a point of a high voltage circuit and a ground.
• the invention may relate to the detection of insulation faults between any point of a high-voltage circuit comprising a high-voltage battery of a motor vehicle and the mass of this vehicle.
• the high voltage battery of the motor vehicle can be a vehicle traction battery.
• the vehicle may be an electric or hybrid vehicle.
• JP3783633 discloses a circuit for measuring the relatively simple isolation resistance. It is thus possible to deduce an insulation resistance value from a single measured voltage value, but this estimate is made assuming that a capacitance value between the measuring circuit and the battery is perfectly known. However, the value of this capacity is likely to vary, depending on various parameters such as temperature or aging. Such a method may therefore lack robustness.
• the document FR2987133 describes a more robust method, based on parameter identifications, in which several values of a voltage signal across a measurement circuit are measured, and from which this set of values is deduced at the same time. a capacitance value between the measuring circuit and the battery, and an insulation resistance value. Nevertheless, the calculations made are relatively elaborate and the calculation time can be relatively long because of the number of measured values required.
• This process comprises:
• this capacitance value can have an influence on the variations over time of the measured voltage values.
• the averaged deviation value is thus relatively unaffected by any variations in the capacitance value of the capacitive element.
• a regulator is set up to overcome variations related to inaccuracy as to the capacitance value of the capacitive element.
• the method may further comprise a step of generating an alarm signal, according to the insulation resistance value updated in step (d), to prevent the detection of a lack of insulation.
• the modeling may advantageously also be a function of a previous value of insulation resistance between the high-voltage circuit and the ground.
• steps (a), (b), (c), (d) can be repeated regularly.
• At least one, and preferably each, deviation value can be estimated from a measured voltage value and from a theoretical voltage value corresponding to the same iteration.
• the insulation resistance value updated during a current iteration can be chosen as the insulation resistance value preceding the next iteration.
• the capacitance value of the capacitive element used to model the measuring circuit can be chosen to be equal to a constant value over several iterations, for example over a predetermined number of iterations or else throughout the execution of the process.
• this capacitance value for example at each iteration or cycle, as a function of the current insulation resistance value and as a function of the measured voltage value at the output of the measurement circuit.
• the current difference value can be calculated by taking the difference between the theoretical value and the measured value, or vice versa.
• the difference is multiplied by + 1 or -1 as a function of the value of an input signal of the circuit of measured.
• this weighting can be 1 when the input signal is high, that is to say for a rising slot, and is worth 1 in the case of a downlink slot, i.e. when the input signal is low.
• the averaged deviation value can be obtained by adding to the current deviation value a previous averaged deviation value.
• This previous averaged deviation value can advantageously be itself a sum, for example a discrete sum or an integral. Thus, rather than keeping in memory all of the previous deviation values, it is sufficient to simply store the previous averaged deviation value.
• the invention is in no way limited to this use of the previous averaged deviation value, nor even to the choice of a sum of deviation values. For example, it would be possible to calculate a linear combination of the previous and current deviation values, or even a geometric mean, a median, a root mean square, or other.
• the step (e) of estimating the updated insulation resistance value may be a function of a linear combination of the current difference value and the current averaged deviation value.
• the updated insulation resistance value can thus be estimated according to the formula:
• n is the current iteration, (n-1) corresponding to the immediately preceding iteration,
• Risoi (n) represents the updated insulation resistance value for this iteration
• Risoi (n-1) is the updated resistance value at the previous iteration
• ⁇ is a difference value between theoretical and measured voltage values, this difference value being obtained by weighting by + 1 or -1, as a function of the signal at the input of the measuring circuit, a difference value between the theoretical and measured values,
• K i and K p are predetermined constants
• Kvariabie is a dimensionless parameter value.
• the formula used to estimate the current value of the insulation resistance may be a function of the previous insulation resistance value.
• this parameter K is riabie may be itself a function of the value of the previous insulation resistance.
• a pay table can be defined as a function of the insulation resistance value.
• K values will riabie parameter can be defined according to external constraints such as the maximum detection time allowed for calculating and outputting an insulation resistance value. This can make it possible to converge more rapidly towards a relatively stable insulation resistance value.
• the measurement circuit can be modeled, this modeling being used to estimate the theoretical values of the signal from a previous value of the insulation resistance and from known values of the various components. of the measuring circuit.
• the difference between the theoretical and measured values can be weighted by a sign which is a function of the value of the signal at the input of the measuring circuit, then a proportional integral regulator can make it possible to estimate a current value. insulation resistance as a function of this difference and an average of the differences obtained over time. Once the insulation resistance thus updated, the digital model of the circuit can be updated in turn.
• This method may further comprise a step of transmitting to a user interface the prepared alarm signal as a function of the value of the updated isolation resistance.
• this method can make it possible to detect the insulation faults faster than described in the document FR2987133, while at the same time avoiding any errors related to the precision as to the value of the capacitive element.
• a computer program product comprising instructions for performing the steps of the method described above when these instructions are executed by a processor.
• This program can for example be stored on a hard drive type memory, downloaded, or other.
• a device for estimating the insulation resistance between a point of a high-voltage circuit comprising a high voltage battery of a motor vehicle and the mass of the vehicle, comprising:
• receiving means for receiving a measured voltage value across a measuring circuit, said measuring circuit comprising a capacitive element connected to the battery,
• a memory for storing a modeling of the measurement circuit, said modeling being a function of a capacitance value of the capacitive element
• processing means arranged to calculate a current deviation value as a function of the measured voltage value and as a function of a theoretical voltage value estimated from the modeling of the measurement circuit, to calculate a deviation value averaged from the current deviation value and a plurality of previous deviation values, and to estimate an updated insulation resistance value based on said averaged deviation value.
• the device for example a processor of the microprocessor, microcontroller or other type, can make it possible to implement the method described above.
• the device may advantageously furthermore comprise transmission means for transmitting an alarm signal developed as a function of the insulation resistance value estimated by the processing means, in order to signal the detection of an insulation fault. applicable.
• the device can then be a device for detecting insulation defects.
• the invention is in no way limited to this application to the detection of insulation defects.
• the receiving means may for example comprise an input pin, an input port or the like.
• the memory can be a random access memory or Random Access Memory (RAM), an EEPROM (Electrically-Erasable Programmable Read-Only Memory), or other.
• RAM Random Access Memory
• EEPROM Electrically-Erasable Programmable Read-Only Memory
• the processing means may for example a processor core or CPU (Central Processing Unit).
• the transmission means may for example comprise an output pin, an output port, or other.
• a system for estimating the insulation resistance between a point of a high-voltage circuit and a ground for example an insulation fault detection system between a point of a high-voltage circuit. voltage and a ground
• this system comprising a measuring circuit connected to the high-voltage circuit, for example to a battery, by a capacitive component, and an estimation device as described above, this estimating device being electrically connected to an input of the measuring circuit, and to a measurement terminal of the measuring circuit for measuring the voltage values.
• the measuring circuit may be of relatively simple design, for example with an input resistor having a terminal electrically connected to the input of the measuring circuit, and a low-pass filtering part comprising a resistive element and a capacitive element. .
• a motor vehicle for example an electric or hybrid vehicle, comprising a battery adapted to roll the front wheels and / or the rear wheels, and a system as described above.
• FIG. 1 shows an example of an insulation resistance estimation system, here an insulation fault detection system, according to an embodiment of the invention.
• FIG. 2 diagrammatically represents an example of a detection device according to one embodiment of the invention.
• FIG. 3A is a graph showing the evolution over time of a theoretical voltage signal and a measured voltage signal, when applying an exemplary method according to one embodiment of the invention .
• Fig. 3B is a graph, corresponding to the graph of Fig. 3A, showing the evolution over time of the estimated insulation resistance value upon application of this method.
• FIG. 1 there is shown an insulation fault detection system 1 between a terminal 21 of a high voltage circuit, here a high voltage battery 2 of a motor vehicle, and the mass M of this motor vehicle .
• This detection system 1 comprises a measuring circuit 3 and a detection device not shown in FIG. 1, for example a processor.
• the battery 2 is used to turn the front wheels and / or the rear wheels of an electric or hybrid vehicle.
• a regenerative braking can be implemented, that is to say that when the driver imposes a braking instruction, energy can be recovered and stored in the battery 2.
• the measuring circuit 3 comprises an input resistor R between an input terminal 30 and a terminal of attachment to the battery 31.
• the measuring circuit 3 furthermore comprises between the connecting terminal
• An input voltage U e is controlled by the processor and a measurement of the output voltage U ' s , or U'smes, is received by this processor.
• the measuring circuit 3 comprises a capacitive element C e between the battery 2 and the rest of the measuring circuit.
• the capacitance Cisol and the resistor Risol represent the equivalent capacitance and the equivalent resistance, respectively, between the terminal 21 of the high voltage battery 2 and the ground.
• the input signal U e applied between the terminal 30 and the ground may be of the square step type with a frequency f e .
• This signal can be generated relatively easily by the processor, for example a microprocessor of a BMS module.
• the values of the low-pass filter elements Rf and Cf are known and relatively variable in time.
• the value of the input resistance R is also known.
• the value of the capacitive element C e is likely to vary, with variations of the order of 30% compared to the initial value, during the lifetime of the vehicle.
• the value of the insulation resistance Risol can vary especially in case of insulation fault. The value of this isolation resistance is thus likely to go from a few MOhms to only a few kOhms.
• the transfer function between the output voltage and the input signal can be written as:
• the value of the isolation resistance is updated after a relatively long time. For example, for a frequency f e of the input signal U e of the order of 2 Hz, the acquisition frequency of the output signal U ' s being of the order of 100 Hz, if the method requires 100 points In order to be able to produce a correct value, it will take two periods, ie one second, to be able to update the value of the insulation resistance.
• the present invention can allow a faster update and in particular to each measurement, that is to say every 10 ms for example, and this, while ensuring a convergence of the estimate regardless of the capacitance C e .
• a discrete model of the measuring circuit is provided.
• FIG. 2 diagrammatically represents an example of an insulation fault detection device 10 between the traction battery referenced 2 in FIG. 1 and the ground.
• This device comprises a module 1 1 for generating an input signal U e .
• This signal is sent to the terminal 30 of the measuring circuit and is also received at the input of a digital modeling module of the measurement circuit 12.
• This module 12 estimates, using the equations above, and in particular the values common parameters ki, k.2, k3, a theoretical value of the output signal U'smod.
• This value U.sub.mod is received by a weighted deviation estimation module 13.
• This module 13 furthermore receives a measured value of output signal Uths, that is to say a voltage value measured at the terminal 32 of the measuring circuit 3 of FIG.
• the module 13 calculates a difference between these two values Uths and U'smod.
• the sign of this difference is a function of the value of the input signal U e .
• the parameters ki, k2, k3 are regularly updated so that the model of the measurement circuit is regularly updated.
• the model used by the module 12 varies according to the value of the estimated insulation resistance.
• This isolation resistance is estimated by looking for the values which tend to minimize the difference ⁇ between the response of the physical circuit U 'mes and the output U' mod of the model simulating the circuit.
• a regulator 14 makes it possible to estimate values of the insulation resistance Risoi updated in order to converge the output of the U'smod model with the U'smes measurement.
• the value of the estimated insulation resistance Ri SO i is updated at each computation step.
• the module 14 tends to increase the value the resistance Ri SO i estimated.
• the module 14 may be a proportional-integral type regulator with a difference ⁇ between the measured value Uths and the theoretical value Usmod weighted by a sign depending on the value of the input signal U e .
• This weighting will be worth + 1 when the input signal is worth 5 volts, that is to say in the case of a rising slot, and will be worth -1 when the input signal is 0 volts, that is to say in the case of a descending niche.
• this module 12 can implement the following formula:
• T e being the period of the input signal U e .
• the integral proportional regulator 14 can be adjusted according to the need and the compromise between speed and precision that one wishes to have on the estimate.
• the range of insulation resistance values can be very wide, from a few Ohms to a few MOhms, it is also possible to provide a variable gain as a function of the estimated insulation resistance value. If this value is relatively high, of the order of several hundred KOhms or MOhms, the need for precision is lower, but we will be interested in a quick solution. On the contrary, for a relatively low insulation resistance value, of the order of ten kOhms or less, it is necessary to have a better accuracy because this value represents a threshold of dangerousness.
• K values will riabie can be defined according to external constraints such as the maximum detection time allowed for calculating and outputting the value of the insulation resistance.
• the module 14 can thus implement the following formula:
• a module 15 makes it possible to update the values of the parameters k 1, k 2, k 3 using the formula above in which the value of the capacitance
• This can be chosen arbitrarily with an accuracy of plus or minus 50% in real terms.
• the initial value of this capacity can be used throughout the process, or at least for a number of cycles.
• a module 16 makes it possible to generate a Saiarm alarm signal from the insulation resistance value derived from the model 14. This module 16 can for example compare the value of the isolation resistance to a threshold and trigger an alarm when the value of the insulation resistance is below this threshold.
• the value of the insulation resistance calculated by integral proportional regulator 14 drops very rapidly and converges towards the real value.
• the invention thus makes it possible to detect insulation faults in a simple and robust manner because of the tolerance to variations in the value of the capacitance C e .

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
• Electric Propulsion And Braking For Vehicles (AREA)
• Measurement Of Resistance Or Impedance (AREA)

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Citations (4)

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• 2013
  • 2013-12-04 FR FR1362092A patent/FR3014206B1/fr not_active Expired - Fee Related
• 2014
  • 2014-12-02 JP JP2016536133A patent/JP2017501396A/ja active Pending
  • 2014-12-02 US US15/101,741 patent/US10605845B2/en active Active
  • 2014-12-02 CN CN201480073856.XA patent/CN106415284B/zh not_active Expired - Fee Related
  • 2014-12-02 EP EP14821774.8A patent/EP3077834B1/fr active Active
  • 2014-12-02 WO PCT/FR2014/053115 patent/WO2015082825A1/fr not_active Ceased

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