Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
  • H01M10/4285—Testing apparatus
• • 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
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/007—Regulation of charging or discharging current or voltage
  • H02J7/0071—Regulation of charging or discharging current or voltage with a programmable schedule
• • 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]
  • G01R31/392—Determining battery ageing or deterioration, e.g. state of health
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a method for estimating the characteristics of an electrochemical system, battery type, which are not directly measurable.
• the method makes it possible to manage an electrochemical battery, in particular during its operation in a hybrid or electric vehicle.
• the electrochemical battery is one of the most critical components of a hybrid or electric vehicle.
• the correct operation of the vehicle is based on an intelligent battery management system (BMS) which is responsible for operating the battery to the best compromise between the different levels of dynamic solicitation.
• BMS battery management system
• SoC state of health
• SoH state of health
• T thermal state
• SoC state of charge of a battery
• available capacity expressed as a percentage of its nominal capacity
• Health status which is the available capacity after recharging (expressed in Ah) is therefore a measure of the point that has been reached in the life cycle of the battery.
• the thermal state (T) of a battery conditions its performance because the chemical reactions and transport phenomena involved in the electrochemical systems are thermally activated.
• the initial thermal state is linked to the temperature outside the vehicle that can be operated over a wide temperature range, typically between -40 0 C and + 40 ° C.
• the thermal state in use changes depending on the load load and discharge of the battery, of its design and its environment. The most accurate and reliable estimation of SoC, SoH and thermal state
• T results in several advantages. This estimate makes it possible to prevent the supervisor of the vehicle from behaving in an overly cautious manner in the use of the energy potential of the battery or vice versa. It also makes it possible to avoid oversized safety of the batteries, thus to save weight on board and, consequently, fuel consumed; it also reduces the total cost of the vehicle. A correct estimator is therefore a guarantee for efficient and safe operation of the battery capacity throughout the vehicle's operating range.
• the present invention relates to a method for estimating the internal state of a rechargeable electrochemical system (battery type) which consists in particular in estimating the characteristics of the battery which are not directly measurable (reference model). It will be a question of using measurements easily obtained by conventional means to reconstruct the internal state of the battery by means of a mathematical model of the battery which can advantageously be executed synchronously with the operation of the battery. -Even (real time). In particular the method will make it possible to estimate the state of charge (SoC), the state of health (SoH) and the thermal state (T) of an electrochemical battery, which are the most interesting internal characteristics for applications. concerning hybrid and electric vehicles.
• SoC state of charge
• SoH state of health
• T thermal state
• the method according to the invention may include the derivation of the reference model (reduced model) to allow simplified use, in particular for on-board control and energy management of a hybrid vehicle. Furthermore, the method according to the invention can be used in a battery simulator, for example in the context of a calibration, optimization or validation of management strategies and estimation.
• the method according to the invention may also be used in an impedance spectroscopy simulator or in a simulator of the thermal state of an electrochemical system.
• the measurement of the no-load voltage as a SoC indicator is also known as a method.
• the use of other indicators, for example the estimation of an internal resistance, (patents US 6191590 B1, EP1835297 A1) is a method also known.
• SIE impedance spectroscopy
• EP880710 (Philips), the description of the electrochemical and physical phenomena at the electrodes and in the electrolyte serving as a support for the development of the RC model, the temperature of the battery being simulated by the model, in order to gain precision, compared to a external measurement.
• the invention relates to a method for estimating the internal state of a rechargeable electrochemical system (battery type) in which: at least one input signal of at least one parameter representative of a physical quantity is measured. of the rechargeable electrochemical system, where a reference model of the system comprising at least:
• the potential and / or the state of charge and / or the temperature of the electrochemical system are collected as an output signal.
• the state of health of the electrochemical system is collected as an output signal.
• the invention further relates to a battery simulator comprising: input means for receiving an input value of at least one parameter representative of a physical quantity of a battery; processing means for generating at least one output characteristic calculated by the method according to the invention.
• the invention also relates to an impedance spectroscopy simulator using the method according to the invention.
• the invention also relates to a simulator of the thermal state of a battery using the method according to the invention.
• Figures 1 to 8 illustrate the invention without limitation and relate to a Ni-MH battery, although the model according to the invention can be applied to any electrochemical system.
• FIG. 1 is a diagrammatic representation of a NiMH battery cell, where MH-el designates the porous negative electrode based on a metal hydride, Ni-el the porous positive electrode based on nickel, ReG the reserve compartment of gas, Sep the separator electrically insulating the two electrodes, col the current collectors, and x the prevailing direction.
• the electrodes and the separator are impregnated with a concentrated alkaline solution.
• the gas (oxygen) that can be released during charging of the battery is concentrated in a common space above the cells.
• Figure 2 represents a possible schema of the model that is used in the method, where the acronyms have the following meaning:
• BMa material assessment
• T The current at the terminals of the cell is considered as an input of the model, while the voltage is one of its outputs.
• the input signals, current and temperature, are representative of physical quantities measured on the battery.
• Processing means based on the Butler Volmer equations, the load balance, the material balance and the energy balance calculate the state of the battery on the basis of the input signals and generate output signals derived from the calculation, like potential, state of charge and temperature.
• FIG. 3 represents an example of associated SoC estimation curves obtained by integrating the current (bold dotted line) and using the models according to the invention, the reduced model (fine dashed line) and the reference model (full fat line). ).
• FIG. 4 represents a diagram of the Kalman filter which is applied to an electrochemical cell according to the method of the invention, with X: internal state calculated by the estimator, U: input, Y: output, F: variation of the internal state according to the model.
• FIG. 5 represents an operating diagram of the SoC estimation algorithm, with Sph: physical system, M: model, FNL: nonlinear filter, East: estimator, U: measured inputs, Y: measured outputs, Ye: outputs calculated by the model, Xe: internal state calculated by the estimator, F: variation of the internal state according to the model, L: output gain of the nonlinear filter.
• FIG. 6 is a functional diagram of a hybrid vehicle simulator using the method for estimating the internal characteristics according to the invention.
• FIGS. 7a and 7b show an example of charge / discharge curves at different current regimes and at ambient temperature; a) IC load, IC slot; b) load IC, slot 1OC Dashed line curve: reduced model according to the invention; solid line curve: reference model according to the invention.
• FIG. 8 shows an example of an electrochemical impedance spectroscopy curve simulated from the method according to the invention, representing the imaginary part of the Imag (Z) impedance as a function of the real part of the Real impedance. (Z).
• Electrochemical reactions take place at the interfaces between the electrodes and the electrolyte.
• the positive electrode is the seat of electrochemical reactions of reduction of the oxidizing species, during the discharge, while the negative electrode is the seat of oxidation reactions of the reducing species.
• the kinetics of electrochemical reactions can be described by the Butler-Volmer equations, whose general form for the generic "z" reaction is
• J x Jo 1 ⁇ exp [a a, z K (A ⁇ z - U m, z) ⁇ - exp [ ⁇ a c, z K (A ⁇ z - U eq, z)] ⁇ -
• J z is the charge transfer current density
• J z0 is the exchange current density
• ⁇ Z is the potential difference between the solid phase (electrode) and the electrolyte
• U eq z is the equilibrium potential of the reaction
• ⁇ z is a symmetry factor (different for the positive electrode, index "c”, and the negative electrode, index "a")
• E a , z is the activation energy.
• n c is the concentration of protons in the positive electrode (nickel hydroxide)
• c e is the electrolyte concentration of OH ions ie "
• c 0 is the concentration of oxygen in the negative electrode and the same crossed-out variable is the interfacial concentration of oxygen, in equilibrium with the gaseous phase
• c m is the concentration of hydrogen in the negative electrode (metallic material)
• the indices "ref” and "max” are refer to the reference and maximum values, respectively;
• ⁇ represents the reaction order.
• Ni (t) -e / g'A-VcCt) - p r ⁇ t) (10)
• Equation (11) as ( ⁇ F ' and also considering equation (10), the conservation equation (9) of the species OH " , is written Hk) + -, - __ TP_ -V V i ⁇ ac ( W t) (14)
• the conversion rate is classically evaluated as
• Equations (12) - (14), (16) constitute a system of four equations with four variables c e , C 0 ⁇ e and i e .
• the equations are differential to partial derivatives in the x domain, as shown in Figure 1.
• boundary conditions for the two OH " and oxygen species are determined by the continuity at the interfaces between the electrodes and the separator, as well as by the zero flow condition at the ends of the cell (current collectors). in the liquid phase is also zero because the total current of cell I passes only through the solid phase.
• V is the volume of the liquid phase, where oxygen is generated
• R 0 / e g is for example calculated for each zone "k" by the
• K is an interfacial mass transport coefficient.
• the temperature of the cell can be calculated as the output of the energy balance, from FIG. 2.
• the internal heat flux ⁇ gen generated by the activity of the cell is given by:
• ⁇ tra (t) hA cell (T (t) ⁇ T a ) (20 ⁇ )
• Equation (4) becomes
• equation (6) becomes:
• C ( 3 ) is the double layer capacity of the electrode 3 (for example MH).
• the function g represents the right term of equation (6).
• equation (21) is written ItH Z (3) ⁇ (3) ⁇ (a) ItP ⁇ + 'h) + ⁇ F ⁇ + F (J3 + JA) ⁇ IH ' (24)
• equation (24) is visibly equivalent to: dt (24a) therefore the concentration of the electrolyte, in the so-called zero-dimensional homogeneous approximation (0-d), is a constant.
• the method according to the invention distinguishes mean concentration of the region c (t) and interfacial concentration in the reduced model.
• the interface concentrations ç m and ç n are used instead of the average concentrations in the Butler-Volmer equations (4) and (6).
• the interface concentrations are calculated, as in the reference model, by the following approximation that replaces equation (20):
• the concentration of oxygen in the gas phase is written as follows using equations (19a) - (19c) and assuming that the concentration in the liquid phase is always in quasi-static equilibrium with its d-value. interface: d_ /, _ R s • ⁇ # b (i) * (i) aq) '-M *) + A (3) ⁇ 3) ⁇ (3) J4 (t), _--.
• Equation (28) thus separates into two equations, each valid for one of the electrodes,
• V (t) ⁇ m (i) - ⁇ ne ⁇ (0 + Mira / (*) (30)
• V is the voltage across the cell
• nt is the internal resistance of the cell resulting from the conductivities of the solid and liquid phases.
• the reduced model of the method according to the invention comprises the equations (4) - (8), (25) - (27), (29) - (30), a total of 15 equations, for the 15 variables J 1 , ..., J 4 , ⁇ 1 # ..., ⁇ 4 , c m / C n , p 0 , ⁇ pos , ⁇ neg , V, T.
• q (t) The state of charge of the cell in the method according to the invention, q (t), is given by the concentration of one of the reactive species, in particular by C n in the example of a Ni-type battery.
• MH q (t) - Cn - ma! r Cv , (32)
• the estimate of q is therefore based on the estimate of C n , whereas this variable is not directly measurable from a battery, in particular on board the vehicle.
• the method advantageously uses a recursive filter to estimate the state of the dynamic system from the available measurements, a schema of which is proposed in Figure 4. Notable characteristics of this estimation problem are the fact that the measurements are affected by noise, and the fact that the system modeled according to the method is strongly non-linear.
• a recursive filter preferably used in the method will be the extended Kalman filter known to those skilled in the art.
• the available measurements are the cell terminal voltage and the battery temperature, which represent the y output of the model, and the I current at the terminals which represents the u input of the model.
• the method then provides a step (M in Fig. 5) where the model provides the vector of the variations f (F in Fig. 5) and the calculated output y (Ye in Fig. 5) according to equation (34). Then, these two variables are manipulated by a second step (East in FIG. 5) which reconstructs the state Xe from F, Ye, and the measure Y.
• the estimation algorithm thus uses the output of a third step (FNL in Figure 5) which provides the variable L according to the reconstructed state, the characteristics of the electrochemical system (according to the model of the method) and the characteristics of the noise that affects the measurements.
• the FNL step may be performed with a method known to those skilled in the art, for example the extended Kalman filter.
• the model directly represents the state of charge as a state variable of the model.
• the known methods use so-called “equivalent electric circuit” models, where the state of charge is not a dynamic variable of the model, but an exogenous variable, according to which other dynamic or static variables are set.
• BMS electrochemical battery management system
• the reduced model according to the invention is based on physical parameters of the system, and not already on equivalent global parameters such as RC models known in the prior art. This property makes it easier to estimate the aging and therefore the state of health of the battery.
• the methods used for estimating the state of charge can be extended to understand a slow adaptation of the model parameters.
• This extension is known in the prior art for several different applications.
• the same signals that flow in Figure 4 can also be used for this adaptive extension.
• the estimated variations of the parameters of the reduced model will be used to detect possible macroscopic variations in the behavior of the battery, and thus alterations in its performance, which is commonly understood as "aging".
• the reference model is also useful as an aid for the dimensioning of traction chains for hybrid vehicles.
• An example of a hybrid vehicle simulator incorporating a battery model is given in FIG.
• the reference model (model 1-D) of the method according to the invention can simulate the dynamic behavior of a traction battery more efficiently and faithfully than models of equivalent electric circuit type, and thus it can be used in a simulator of battery.
• the electrochemical reference model can be used to test "offline" the efficiency of the online estimator (which uses the reduced 0-d model according to the invention) and to calibrate the parameters, adapting them to the specific battery under examination.
• the reference model as the reduced model of the method according to the invention can calculate the variations in time of all the internal electrochemical variables of the battery, and in particular of the state of charge.
• the input of the models is the current at the terminals of the battery, the simulated cases depend on the choice of this last variable. For example, a constant current controlled charge or discharge, or 340
• variable current according to a fixed profile, or variable current depending on the voltage. This last case is representative of the conditions of solicitation of the battery in a vehicle, where the current imposed on the battery depends on the voltage, according to the characteristics of the associated electrical components (power electronics, electric motor (s), etc. .). Typical results of the battery simulator using the models according to the invention are presented in FIG. 7.
• Impedance spectroscopy simulator The models of the estimation method according to the invention (reference model and reduced model) also make it possible to reproduce the experimental impedance spectroscopy tests, in order to predict the relations between these measurements and the internal state of charge of the battery. Equation (30) is then modified to take into account the inductive effects due to the connections between the cells and with the terminals.
• the presence of the energy balance in the reduced model and in the reference model of the method according to the invention makes it possible to simulate the thermal evolution of the system. Consequently, the method according to the invention can thus be used for the dimensioning of the battery and the validation of the thermal management systems, which must necessarily equip the battery itself.
• the heat fluxes generated and the temperature of the battery are input variables for these systems, which are intended to adjust these flows and this temperature around the allowable values.
• thermal transients thus makes it possible to synthesize and validate the control and optimization strategies associated with thermal management systems. These strategies can thus benefit from the presence of a small model during their online use, to have estimates of certain variables that are not measurable (temperatures in specific points, heat fluxes, etc.), or that are measurable, but with response times of the associated sensors too slow.

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• 2008
  • 2008-03-28 FR FR0801709A patent/FR2929410B1/fr active Active
• 2009
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