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
  • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
  • G01R31/389—Measuring internal impedance, internal conductance or related variables
• • 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
  • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
  • G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables

Definitions

• the present invention generally relates to the control of an electric battery.
• step b) calculating said quantities, including for example the internal resistance of the battery, according to the voltage and current intensity acquired in step a).
• the invention applies particularly advantageously to motor vehicles equipped with an electric motor powered by an electric traction battery.
• the electric power that an electric battery can provide decreases during a discharge cycle.
• a calculated state of the battery is calculated according to the state of the battery measured at the previous time step, and according to the measured intensity
• This estimation method has two main disadvantages. On the one hand, it is an iterative method in which the aforementioned steps are repeatedly repeated several times until the calculated error is small. The convergence of this iterative calculation to a precise result can be long, and is not always assured. On the other hand, it is a so-called discrete time method which requires that the sampling of the measured signals is regular over time. This is not always the case in practice, which may degrade the accuracy of estimation of the physical characteristics characteristic of the battery.
• the present invention proposes a method for estimating physical quantities characteristic of an electric battery, as defined in the introduction, in which the values of said physical quantities are obtained by resolution a system of linear equations modeling the electric behavior of the electric battery:
• This estimation method is non-iterative and thus inherently free of convergence problems.
• the integration calculation does not require that the sampling of the voltage and the intensity be regular in time. This method is therefore usable without loss of precision even when the voltage or the intensity are not sampled regularly over time.
• this step of integrating the measured signals has a low-pass filtering effect, which makes the method robust with regard to the measurement noise, generally located at high frequencies.
• said system of linear equations is obtained by transforming, by Laplace transform calculations, a differential equation which models the electrical behavior of the battery and which relates the voltage, the intensity, and said physical quantities;
• said coefficients are obtained by calculating successive integrals over a given period of time, of voltage functions or of intensity functions;
• said coefficients of said system of linear equations are obtained by calculating inverse Laplace transforms of quantities equal to
• f (s) represents the Laplace transform of the function f (t), where f (t) represents a function of time, equal to the voltage or the intensity, where s represents the Laplace variable, where m represents an integer, and where n represents a real number that is not necessarily integer;
• said inverse Laplace transform calculations are performed by applying a generalized Cauchy formula when the number n is not integer:
• ⁇ ( ⁇ ) is the Gamm 'Euler function defined by:
• FIG. 1 is a schematic view of an electric battery, sensors and a calculation unit adapted to implement a method according to the invention, making it possible to estimate physical quantities of this battery,
• FIG. 2 is an electrical diagram corresponding to an exemplary modeling of the electric battery of FIG. 1.
• FIG. 1 there is shown an electric battery BAT which supplies electric power to an APP electrical appliance.
• the electrical voltage U at the terminals of this electric battery BAT is measured by a voltage sensor V.
• the intensity I of the electric current delivered by the electric battery BAT is measured by a current sensor A.
• Analog-digital converters allow to sample and to digitize the values of this electric voltage U and of this intensity I. The data thus obtained are used by a CPU to estimate, according to the method which is the subject of the present invention, the RES values of characteristic physical quantities.
• the memory module MEM serves in particular to store the information necessary for this calculation.
• FIG. 2 illustrates an electric diagram corresponding to an exemplary modeling of the electric battery of FIG. 1.
• the electric battery BAT is here modeled by an electric circuit comprising, in series, a perfect voltage source Uoc, a resistor Ro, and a pair comprising a resistor Ri and a capacitor Ci connected in parallel with one another. one of the other.
• the voltage source models the open circuit voltage
• the resistance Ro models the internal resistance of the battery
• the resistance torque Ri and capacitor Ci models the internal diffusion phenomena of the battery.
• the physical quantities that we seek to estimate are the internal resistance Ro of the battery and the torque (Ri, Ci).
• the idle voltage Uoc is assumed to be known.
• the differential equation corresponding to this electric circuit 20 is:
• the processor CPU begins by calculating the value of the three parameters b1, b1 and a1 from the recording, over a period T, of the values of the voltage U and of the current I, according to a detailed calculation below.
• the calculation can for example be carried out by the Gauss-Jordan method, or else by using the well-known technique of factoring the matrix M into two triangular matrices, the upper one and the other lower (decomposition called "LU” according to the acronym “Lower-Upper”).
• the computation of the values bo, bi and ai whether realized by numerical resolution of the system F6, or by a direct calculation using its general solution F8, requires the numerical computation of the mn coefficients at 1TI33 and ⁇ , ⁇ 2 , ⁇ 3 .
• the calculation of these coefficients corresponds to an integration calculation, over the duration T, of functions of the voltage U or the current I.
• This integration can for example be performed as a numerical calculation of discrete sums cumulated.
• a numerical evaluation of the quantity / 1 1 can be obtained by calculating the sum:
• T e (j) is the time between samples j and j + 1
• l (j) is the value of intensity corresponding to sample number j
• k + 1 is the total number of samples acquired during the period T.
• equation F1 lends itself to a numerical computation faster than the one on the left, and with a less accumulation of computational errors.
• the calculation of the physical quantities of the battery makes it possible to follow the evolution of the charge and the behavior of the electric battery BAT. These three physical quantities thus make it possible in particular to obtain parameters for monitoring the electric battery BAT, such as the charge level SOC of the battery, and the state of health SOH of the battery.
• this parameter is the total duration of acquisition T.
• This setting is simpler than that of the methods using state observers (for example with Kalman filter) for which it would have been necessary here to adjust the initial values of three parameters (one by magnitude to be estimated) to ensure a good accuracy of the result.
• This method is intrinsically robust to noise measurement, usually located at high frequencies. Indeed, the use of integrals over time (see the formulas F7, or the formula F1) performs a low-pass type filtering on the measured signal U (t) or l (t). Then, it requires only a few calculating means, since to estimate the three unknown quantities, one has to either calculate three simple expressions (see formula F8), or to solve a system of three equations with three unknowns (system F6 ), whose size is therefore reduced to a minimum.
• the formulas used in practice by the processor for estimating the physical quantities of the battery are mainly the formulas F6 and F7.
• the inverse Laplace transform of the F1 1 system is then calculated. Given the expression of the F1 1 system, its inverse Laplace transform includes quantities such that:
• This estimation method is particularly applicable to the case of differential equations ED of non-integer order, as shown in the example described below.
• This differential equation is transformed as before to obtain a system of three linear equations whose unknowns are the physical parameters b, b and ai.
• the inverse Laplace transform of the F16 system is then calculated to finally result in a system of linear equations similar to the F6 system, which is used by the processor to estimate the value of the physical parameters b1, b1 and b1.
• f (t) is equal to the voltage U (t) or the intensity l (t).
• n is a real number that is not necessarily integral (for this exemplary embodiment, it may for example be equal to 2 + a).
• the method described above applies particularly advantageously to the estimation of physical quantities characteristic of an on-board electric battery, for example in a motor vehicle with electric motor, or in a computer powered by such a battery.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Secondary Cells (AREA)
• Tests Of Electric Status Of Batteries (AREA)

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• 2014
  • 2014-12-22 FR FR1463162A patent/FR3030769B1/fr active Active
• 2015
  • 2015-12-16 KR KR1020177020213A patent/KR20170099970A/ko active Search and Examination
  • 2015-12-16 EP EP15821150.8A patent/EP3237919A1/fr not_active Withdrawn
  • 2015-12-16 US US15/538,549 patent/US20170370997A1/en not_active Abandoned
  • 2015-12-16 CN CN201580074089.9A patent/CN107407712A/zh active Pending
  • 2015-12-16 WO PCT/FR2015/053557 patent/WO2016102823A1/fr active Application Filing

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