CN112731179B - Method and device for rapidly detecting health state of battery, detector and storage medium - Google Patents
Method and device for rapidly detecting health state of battery, detector and storage medium Download PDFInfo
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Abstract
The invention discloses a method and a device for rapidly detecting the health state of a battery, a detector and a storage medium, wherein the detector comprises a single chip microcomputer, a nonlinear proportional-integral controller, a BUCK circuit, a two-channel digital lock-in amplifier, a measuring device and a computer, the single chip microcomputer, the nonlinear proportional-integral controller, the BUCK circuit, the two-channel digital lock-in amplifier, the measuring device and the computer are sequentially connected, and the BUCK circuit is also connected with the single chip microcomputer. The invention can quickly and accurately measure the health state of the lithium ion power battery in an application field, can effectively solve the problem that an instrument for reliably and quickly detecting the health state of the battery is lacked in the application field, directly detects the health state of the battery by charging the battery with high multiplying power and heavy current, superposing sine wave ripple current with specific frequency on direct current charging pulse and measuring the Warburg impedance of the battery at a plurality of frequency points, greatly improves the detection efficiency of the health state of the battery and provides a fair and uniform scale for the evaluation of the health state of the battery.
Description
Technical Field
The invention relates to a method and a device for rapidly detecting the state of health of a battery, a detector and a storage medium, and belongs to the field of battery state detection instruments.
Background
A large number of power lithium batteries are used for electric automobiles and electric bicycles, and when the health state of the batteries is attenuated to below 70%, the power batteries need to be recovered and are used for other occasions such as energy storage power stations instead. In application fields such as automobile and bicycle repair workshops and battery recycling workshops, how to quickly judge the health state of the battery is the key.
In practical application fields such as automobile 4S shops, power battery energy storage power stations, battery recycling workshops and the like, simple instruments are basically adopted to judge the battery state. Typically, the battery open circuit voltage OCV is measured with a multimeter; measuring the direct current resistance of the battery by using an internal resistance meter; the accuracy of these methods is poor when observing the work-doing ability of the battery in case of short-circuit discharge of the battery.
In electrochemical laboratories, battery form certification laboratories, expensive precision instruments are used to measure batteries. Measuring an electrochemical impedance spectrum of the cell using a frequency response analyzer; and measuring the characteristics of the anode and cathode materials of the battery by using an electrochemical workstation and adopting cyclic voltammetry. These laboratory instruments are expensive, require at least several hours to complete a measurement of a cell, and are not suitable for use in industrial applications on-site.
The battery manufacturer and the battery seller adopt a capacity grading cabinet to slowly charge and discharge the battery to obtain the actual capacity of the battery, and the actual capacity is used as a basis for judging the health state of the battery, so that the battery measurement usually takes several hours.
The attenuation change of the lithium ion diffusion process in the battery is a main factor influencing the health state of the battery, and the impedance of the battery in a low frequency range (0.001 Hz-10 Hz) can represent the battery diffusion process. The lower the excitation current of the cell, the lower the frequency of the impedance to be measured, e.g. an electrochemical impedance spectrometer measures the impedance of the cell at 10mA excitation current, and the impedance as low as 0.005Hz, resulting in a long measurement time. If the battery excitation current is large, for example, the battery is charged with 10A current, the diffusion process in the battery can be effectively excited, and the impedance measured at the moment of 5Hz can well reflect the characteristics of the diffusion process. So that the impedance is measured quickly, a large excitation current is applied to the battery. Impedance is the ratio of alternating current to alternating voltage, and a small amplitude specific frequency alternating current ripple must be superimposed on a large direct current excitation current to achieve this measurement. Unlike a precise electrochemical impedance spectrometer which measures weak alternating voltage and alternating current signals simultaneously, it is expected that current ripple measurement is realized only by a digital signal processor, which involves the problem of weak signal processing.
Disclosure of Invention
In view of the above, the present invention provides a method, an apparatus, a detector and a storage medium for rapidly detecting a state of health of a battery, which can rapidly and accurately measure the state of health of a lithium ion power battery at an application site, and can effectively solve the problem that an instrument for reliably and rapidly detecting the state of health of the battery is absent at the application site.
The invention aims to provide a method for rapidly detecting the state of health of a battery.
The second purpose of the invention is to provide a device for rapidly detecting the state of health of a battery.
The third purpose of the invention is to provide a rapid detector for the state of health of a battery.
It is a fourth object of the present invention to provide a storage medium.
The first purpose of the invention can be achieved by adopting the following technical scheme:
A method for rapid detection of battery state of health, the method comprising:
acquiring the measured battery temperature and the battery charging current, and calculating the Warburg impedance of the battery based on the set battery charging voltage and the measured battery charging current; wherein the battery charging current is a sinusoidal ripple current;
substituting the temperature of the battery, the charging current of the battery and the Warburg impedance of the battery into a battery diffusion process attenuation factor expression, and calculating to obtain a battery diffusion process attenuation factor so as to represent the health state of the battery; wherein the expression of the attenuation factor of the battery diffusion process is derived from the expression of the Warburg impedance of the battery.
Further, the derivation process of the cell diffusion process attenuation factor expression is as follows:
selecting a diffusion process boundary condition suitable for a large-capacity single battery, and providing an expression for calculating the Warburg impedance of the battery as a first expression of the Warburg impedance of the battery;
establishing a second expression of the battery Warburg impedance according to the physical characteristic that the real part and the imaginary part of the battery Warburg impedance are equal;
simplifying constant terms and other known quantities in a second expression of the battery Warburg impedance, and extracting attenuation factors representing the battery diffusion process to obtain a third expression of the battery Warburg impedance;
And deducing an attenuation factor expression of the battery diffusion process on the basis of a third expression of the battery Warburg impedance according to the amplitude characteristic of the battery Warburg impedance.
Further, the first expression of the battery Warburg impedance is as follows:
wherein, AeIs the effective area of the electrode, D is the diffusion coefficient associated with the material, c is the molar concentration of lithium ions, R is the gas constant, T is the absolute temperature, l is the ion diffusion path length within the cell, n is the number of charge carriers, and F is the faraday constant;
a second expression of the Warburg impedance of the battery, as follows:
the method for simplifying the constant term and other known quantities in the second expression of the battery Warburg impedance extracts attenuation factors representing the battery diffusion process to obtain a third expression of the battery Warburg impedance, and specifically comprises the following steps:
using cA in a second expression for the Warburg impedance of a batteryeAs a characteristic cell diffusion process decay factor and define KD 2＝cAeA third expression of the Warburg impedance of the battery is obtained as follows:
wherein, KDIs a cell diffusion process decay factor.
Further, the deriving an expression of the attenuation factor in the battery diffusion process based on a third expression of the Warburg impedance of the battery according to the amplitude characteristic of the Warburg impedance of the battery specifically includes:
The amplitude characteristic of the Warburg impedance of the battery is obtained through the physical characteristic that the real part and the imaginary part of the Warburg impedance of the battery are equal, and the amplitude characteristic is as follows:
will be provided with
Substituting into the third expression of the battery Warburg impedance yields:
definition n ═ kiAnd i, simplifying constant terms to obtain an attenuation factor expression of the cell diffusion process, wherein the attenuation factor expression comprises the following steps:
wherein C is a physical constant, T is an absolute temperature of the battery, and ZwIs the Warburg impedance of the battery and i is the charging current of the battery.
The second purpose of the invention can be achieved by adopting the following technical scheme:
a battery state of health rapid detection apparatus, the apparatus comprising:
an acquisition unit for acquiring the measured battery temperature and battery charging current, and calculating a Warburg impedance of the battery based on the set battery charging voltage and the measured battery charging current; wherein the battery charging current is a sinusoidal ripple current;
the detection unit is used for substituting the temperature of the battery, the charging current of the battery and the Warburg impedance of the battery into a battery diffusion process attenuation factor expression, and calculating to obtain a battery diffusion process attenuation factor so as to represent the health state of the battery; wherein the expression of the attenuation factor of the battery diffusion process is derived from the expression of the Warburg impedance of the battery.
The third purpose of the invention can be achieved by adopting the following technical scheme:
a battery health state rapid detector comprises a single chip microcomputer, a nonlinear proportional-integral controller, a BUCK circuit, a double-channel digital lock-in amplifier, a measuring device and a computer, wherein the single chip microcomputer, the nonlinear proportional-integral controller, the BUCK circuit, the double-channel digital lock-in amplifier, the measuring device and the computer are sequentially connected, and the BUCK circuit is also connected with the single chip microcomputer;
the single chip microcomputer is used for outputting an ePWM signal of a rated carrier frequency and superposing sinusoidal ripple current on the rectangular charging pulse by using the micro-edge positioner;
the nonlinear proportional-integral controller is used for setting an ePWM signal output by the singlechip into a rectangular charging pulse and inputting the rectangular charging pulse into the BUCK circuit;
the double-channel digital lock-in amplifier is used for solving the amplitude of the measured sine ripple current according to the signal to be measured input by the BUCK circuit and outputting the sine ripple current signal through the measuring equipment;
the computer is used for executing the battery health state rapid detection method.
Further, the BUCK circuit includes a MOSFET driving circuit and a battery current detection circuit;
The MOSFET driving circuit comprises a MOSFET tube, the battery current detection circuit comprises a diode, an inductor, a capacitor, a sampling resistor and a voltage amplification circuit, the grid electrode of the MOSFET tube is connected with an ePWM signal output port of the single chip microcomputer, the drain electrode of the MOSFET tube is connected with a power supply, the source electrode of the MOSFET tube is connected with the cathode of the diode and one end of the inductor, the anode of the diode is grounded, the other end of the inductor is connected with one end of the capacitor and the anode of the battery, the other end of the capacitor is grounded, one end of the sampling resistor is connected with the cathode of the battery, the other end of the sampling resistor is grounded, and two ends of the sampling resistor are connected to the voltage amplification circuit;
the voltage amplifying circuit comprises two operational amplifiers and four resistors, wherein the forward input ends of the two operational amplifiers are grounded, one ends of the two resistors are connected with the reverse input ends of the operational amplifiers, one ends of the other two resistors are connected with the reverse input ends of the two operational amplifiers in a one-to-one correspondence manner, and the other ends of the other two resistors are connected with the output ends of the two operational amplifiers in a one-to-one correspondence manner.
Further, the nonlinear proportional-integral controller adopts a battery charging current control algorithm, the battery charging current control algorithm is a nonlinear combination of a proportional element and an integral element, and a time domain function of the nonlinear combination is as follows:
Wherein e (t) is the deviation between the measured current value and the reference value of the singlechip at the moment t, Kp[e(t)]Is a proportion link P, KpThe gain coefficient of the proportional element P;
is an integration link I, KiIs the gain coefficient of the integral element I.
Further, the dual-channel digital lock-in amplifier comprises a multiplier, a Hilbert filter, a low-pass filter, an integrating element, a divider and an adder;
among the binary channels digital lock-in amplifier, according to the signal to be measured of BUCK circuit input, solve measured sinusoidal ripple current amplitude to through measuring equipment output, specifically include:
the signal i' (f) to be measured0) And a reference signal
Input into the same multiplier and integrated to obtain an intermediate value U0The calculation formula is as follows:
where K is the multiplier gain, A2For the purpose of reference signal amplitude values,
is the unknown phase difference between the reference signal and the signal to be measured;
multiplier outputs intermediate signal U0Feeding the low-pass filter to filter out the high-frequency AC component to obtain another intermediate quantity
Reference signal
Input to a Hilbert filter for Hilbert transform, and then output to a signal i' (f) to be measured0) Multiplying and integrating, filtering out high-frequency AC component by low-pass filter to obtain another intermediate quantity
v0Channel sum v00Inputting the channel into a divider to obtain the phase difference between the measurement signal and the reference signal 
Two v0Channel input multiplier, two v00The channel is input into a multiplier, the results of the two multipliers are input into an adder to obtain the required signal
Measuring the magnitude of the signal v (t), and calculating the amplitude A of the measured sinusoidal ripple current1。
The fourth purpose of the invention can be achieved by adopting the following technical scheme:
a storage medium stores a program that, when executed by a processor, implements the above-described method for rapidly detecting a state of health of a battery.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention assumes that the lithium ion diffusion process in the battery is of limited length and the boundary is surrounded by the enclosing wall, thereby deducing the display expression among the Warburg impedance, the lithium ion concentration of the battery, the effective reaction area of the electrode of the battery, the charging current of the battery and the temperature of the battery, obtaining the relational expression between the attenuation factor of the battery diffusion process and the impedance, the current and the temperature of the battery based on the expression, and estimating the health state of the battery based on the measured attenuation factor of the battery diffusion process.
2. The method is based on the electrochemical reaction principle of the lithium ion diffusion process in the lithium battery, the relationship between the health state factor of the battery diffusion process and the battery impedance is extracted, and the battery impedance of a specific frequency point is measured while the battery is charged at a high rate. The battery health state is directly detected through the measured impedance, the influence of battery current and battery temperature on the estimation precision of the battery health state is overcome, a single chip microcomputer with a high-resolution pulse width modulation (HRPWM) module is adopted to simultaneously superpose small-amplitude specific frequency current ripples in the battery charging process, the amplitude and the phase of sine ripple current are detected through a digital lock-in amplifier, the accurate measurement of the battery impedance is realized, the problem that a reliable and rapid battery health state detection instrument is lacked in the application field of a lithium ion power battery can be effectively solved, and the detection efficiency of the battery health state is greatly improved.
3. The invention uses the characteristic that the singlechip has High Resolution Pulse Width Modulation (HRPWM), subdivides the most marginal PWM clock period (16.67 nanoseconds (10-9S)) into 110 small lattices, each small lattice is 150 picoseconds (10-12S), and a micro-edge positioner in the singlechip is adopted to control the PWM pulse edge to sinusoidally change according to specific frequency by taking 150 picoseconds as a unit, so that small-amplitude alternating current ripple current (sine ripple current) is superposed on large direct current charging pulses; the amplitude and phase of the sinusoidal ripple current are measured by a digital lock-in amplifier, and the sinusoidal ripple controlling the micro-edge positioner is taken as an alternating voltage signal applied to the battery, so that the electrochemical impedance of the battery at a specific charging rate current is calculated.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a block diagram of a battery state of health rapid detector according to embodiment 1 of the present invention.
Fig. 2 is a schematic structural diagram of the BUCK circuit according to embodiment 1 of the present invention.
Fig. 3 is a schematic diagram of a rectangular charging pulse superimposed with a sinusoidal ripple current according to embodiment 1 of the present invention.
FIG. 4 is a schematic diagram of the operation of the micro-edge locator of example 1 of the present invention.
FIG. 5 is a schematic diagram of the micro-edge locator of example 1 varying sinusoidally within one system cycle.
Fig. 6 is a block diagram of a nonlinear proportional-integral control of the battery charging current according to embodiment 1 of the present invention.
Fig. 7 is an operational schematic diagram of a dual channel digital lock-in amplifier according to embodiment 1 of the present invention.
Fig. 8 is a flowchart of a method for rapidly detecting a state of health of a battery according to embodiment 1 of the present invention.
Fig. 9 is a flowchart of the cell diffusion process attenuation factor expression derivation process according to embodiment 1 of the present invention.
Fig. 10 is a block diagram of a battery state of health rapid detection apparatus according to embodiment 2 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
as shown in fig. 1, the present embodiment provides a rapid detector for a state of health of a battery, which includes a single chip 101, a non-linear proportional-integral controller 102, a BUCK circuit 103, a dual-channel digital lock-in amplifier 104, a measurement device 105 and a computer 106, wherein the single chip 101, the non-linear proportional-integral controller 102, the BUCK circuit 103, the dual-channel digital lock-in amplifier 104, the measurement device 105 and the computer 106 are sequentially connected, and the BUCK circuit 103 is further connected to the single chip 101.
As shown in fig. 1 and fig. 2, the BUCK circuit 103 is an analog circuit based on the BUCK conversion principle, and includes a MOSFET driving circuit and a battery current detection circuit, and the BUCK circuit 103 is matched with the single chip microcomputer 101, and can adjust the battery charging current and monitor the battery internal current.
Further, the MOSFET driving circuit comprises a MOSFET tube, the battery current detection circuit comprises a diode D, an inductor L, a capacitor C, a sampling resistor R and a voltage amplification circuit, wherein the diode D is a freewheeling diode, the inductor L adopts four inductors connected in parallel, the capacitor C is a filter capacitor, the grid electrode of the MOSFET tube is connected with an ePWM signal output port of the singlechip 101, and the drain electrode of the MOSFET tube is connected with a power supply (12V voltage V) IN) The sampling resistor R is connected with the cathode of the battery GB, the second end of the sampling resistor R is connected with the ground, and the two ends of the sampling resistor R are connected with a voltage amplifying circuit.
Further, the voltage amplifying circuit includes a first operational amplifier U1, a second operational amplifier U2, a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4, forward input terminals (non-inverting input terminals) of the first operational amplifier U1 and the second operational amplifier U2 are grounded, a first terminal of the first resistor R1 is connected to a first terminal of the sampling resistor R, a second terminal of the first resistor R1 is connected to an inverting input terminal (inverting input terminal) of the first operational amplifier U1, a first terminal of the second resistor R2 is connected to an inverting input terminal of the first operational amplifier U1, a second terminal of the second resistor R2 is connected to an output terminal of the first operational amplifier U1, a first terminal of the third resistor R3 is connected to an output terminal of the first operational amplifier U1, a second terminal of the third resistor R3 is connected to an inverting input terminal of the second operational amplifier U2, a first terminal of the fourth resistor R4 is connected to an inverting input terminal of the second operational amplifier U2, the second terminal of the fourth resistor R4 is connected to the output terminal of the second operational amplifier U2.
In this embodiment, the first ends of the inductor L, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are left ends, the second ends of the inductor L, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are right ends, the first ends of the capacitor C and the sampling resistor R are upper ends, and the second ends of the capacitor C and the sampling resistor R are lower ends.
The process of adjusting the charging current of the battery and monitoring the current inside the battery of the embodiment comprises the following steps:
1) the program generates a rated carrier frequency in the single chip microcomputer 101 by setting the working mode of a time-base counter and controlling a time-base period register in an ePWM module, a pulse width modulation signal output by the ePWM module is the superposition of output signals of a PWM (pulse width modulation) channel and an HRPWM (high resolution pulse width modulation) channel in the single chip microcomputer 101, the PWM channel provides a large signal output for generating a rectangular charging pulse, the HRPWM channel provides a finer signal output for superposing a sinusoidal ripple current on the rectangular charging pulse (namely a direct current pulse), a waveform diagram of the output current of the BUCK circuit when the HRPWM channel function is used is shown in figure 3, and as can be seen from the figure, when a MOSFET (metal-oxide-semiconductor field effect transistor) tube is switched on, the current in the circuit is I PWM+IHRPWM(ii) a When the MOSFET is closed, the current in the circuit is 0; thus, IPWMAnd IHRPWMKeeping high consistency, the single chip 101 can output sine ripple signals superposed on the direct current pulses.
In this embodiment, a micro edge locator (MEP), which is a key technology for superimposing a sine ripple current on a dc pulse, is a technology in HRPWM and is a module inside the single chip microcomputer 101; as shown in fig. 4, a general PWM period is an integral multiple of a system clock period of the single chip microcomputer 101, and the MEP technique continues to divide one system clock period into a plurality of smaller duty cycles of the micro-edge locators; the relationship between the periods shown in FIG. 4 can be as followsThe formula is as follows: t isPWM＝mTsysc、Tsysc＝nTMEP. Wherein T isPWMFor PWM duty cycle, TsyscIs the work period, T, of the singlechip 101 systemMEPM and n are positive integers for the micro-edge locator duty cycle. In practical application, the working frequency of the single chip microcomputer 101 can be set according to requirements, and values of m and n are determined.
Further, as shown in fig. 5, the CMPAHR register in the ePWM module controls the frequency and amplitude of the superimposed current, and the design program makes the value output by the CMPAHR register change according to a certain sine rule in a system duty cycle, that is, the sinusoidal ripple current can be superimposed on the dc pulse.
2) An ePWM signal is sent by the single chip microcomputer 101, the ePWM signal is set into a rectangular charging pulse through the nonlinear proportional-integral controller 102, the rectangular charging pulse flows into a grid electrode of the MOSFET through the MOSFET driving circuit, and a signal amplified by the MOSFET flows into the battery current detection circuit.
3) When the ePWM signal is at a high level, the MOSFET is switched on, the anode voltage of the diode D is zero, the cathode voltage is positive, and the diode D is switched off in the reverse direction; the current in the inductor L is gradually increased, self-inductance potentials with positive left end and negative right end are generated at the two ends of the inductor L to prevent the current from continuously rising, and the inductor L converts the electric energy into magnetic energy to be stored; when the ePWM signal is at a low level, the MOSFET is closed, the current in the inductor L does not change suddenly, and the self-inductance potential of the MOSFET hinders the current from decreasing, so that the diode D is forward biased and conducted, the current in the inductor L forms a loop through the diode D, the current value gradually decreases, and the magnetic energy stored in the inductor L is converted into electric energy to be released to the battery; the capacitor C is grounded and the inductor L reduces the output voltage VOUTIs fluctuating.
4) The resistance values of the first resistor R1 and the third resistor R3 are limited, the sizes of the second resistor R2 and the fourth resistor R4 are changed, the amplification times of voltage can be changed, the voltage amplification circuit feeds a battery voltage measurement value back to the single chip microcomputer 101, the single chip microcomputer 101 outputs an ePWM signal with a proper duty ratio after processing a feedback signal, and therefore the input current of the battery is controllable.
The nonlinear proportional-integral controller 102 may set the ePWM signal output by the single chip microcomputer 101 as a rectangular charging pulse, and input the charging pulse to the BUCK circuit 103, and since the battery charging current measurement value does not change linearly, the conventional PID (proportional-integral-derivative) control cannot meet the control requirement of the fast detector for battery health status of the present embodiment, and the present embodiment establishes a mathematical model according to the change rule of the controlled current, and proposes the nonlinear proportional-integral control shown in fig. 6 to rectify the ePWM signal, so as to reduce the adjustment time and reduce the overshoot.
Further, the non-linear proportional-integral controller adopts a battery charging current control algorithm, the battery charging current control algorithm is a non-linear combination of a proportional link and an integral link, and a time domain function of the non-linear proportional-integral controller is as follows:
wherein e (t) is the deviation between the current value measured by the single chip microcomputer and the reference value at the time t, so the control of the embodiment aims to adjust the value of u (t) to make the value of e (t) stabilize to be close to 0.
Kp[e(t)]Is a proportion link P, KpThe gain coefficient of the proportional link P is a function of the relative e (t), the proportional link has the fastest response speed and the most obvious effect, and K is pThe parameter is one of the main reasons for influencing the system response and generating overshoot; when the system deviation is larger, increasing K in real timep(ii) a When the system deviation becomes smaller, K is properly reduced in real timepThe variation formula is as follows: kp＝a1em(t)+b1In terms of the non-linear characteristics of the battery, m may be 2.
In the embodiment, two nonlinear links are introduced, each nonlinear link has two adjustable parameters, and the nonlinear links have a in total1、b1、a2、b2The four parameters are adjusted according to different test data each time, and the four parameters are adjusted again for each debugging.
Referring to the input signal of fig. 3 and the BUCK circuit diagram of fig. 2, the measured current fed back to the single-chip microcomputer 101 in fig. 2 can be expressed as:
wherein, i (f)0) For the signal to be measured, DC tFor slowly varying high-rate DC signals, and
represents a small amplitude ac signal and u (n) is noise.
Filtering slowly changing direct current item DC by using digital trend filtertAnd obtaining an alternating current change term:
the dual-channel digital lock-in amplifier 104 is configured to calculate a measured sinusoidal ripple current amplitude according to a signal to be measured input by the BUCK circuit 103, and output a sinusoidal ripple current signal through a measurement device, where the measurement device 105 may be a device such as an oscilloscope; specifically, the dual channel digital lock-in amplifier 104 includes a multiplier, a hilbert filter, a low pass filter, an integrating element, a divider, and an adder.
As shown in fig. 7, the operation principle of the dual channel digital lock-in amplifier 104 of the present embodiment is as follows:
1) the signal i' (f) to be measured0) And a reference signal
Input into the same multiplier and integrated to obtain an intermediate value U0The calculation formula is as follows:
where K is the multiplier gain, A2For the purpose of reference signal amplitude values,
is the unknown phase difference between the reference signal and the signal to be measured.
2) Multiplier outputs intermediate signal U0Feeding the low-pass filter to filter out the high-frequency AC component to obtain another intermediate quantity
3) Reference signal
Input to a Hilbert filter for Hilbert transform, and then output to a signal i' (f) to be measured 0) Multiplying, integrating, filtering out high-frequency AC component by low-pass filter to obtain another intermediate quantity
4)v0Channel sum v00Inputting the channel into a divider to obtain the phase difference between the measurement signal and the reference signal
5) Two v0Channel input multiplier, two v00Channel input multiplier, two multiplicationsThe result of the adder is input into the adder to obtain the signal
6) Measuring the magnitude of the signal v (t), and calculating the amplitude A of the measured sinusoidal ripple current1。
A computer 106 for acquiring the measured battery temperature and battery charging current, and calculating a Warburg impedance (a watter impedance, i.e., electrochemical impedance) of the battery based on the set battery charging voltage and the measured battery charging current; substituting the temperature of the battery, the charging current of the battery and the Warburg impedance of the battery into a battery diffusion process attenuation factor expression, and calculating to obtain a battery diffusion process attenuation factor so as to represent the health state of the battery; the temperature of the battery can be measured by a thermocouple, the charging current of the battery is sinusoidal ripple current obtained by the output of the measuring device 105, the Warburg impedance of the battery is impedance representing the diffusion process of the battery, and the calculation formula is as follows:
as shown in fig. 8, the embodiment further provides a method for rapidly detecting a state of health of a battery, which is implemented based on the above apparatus for rapidly detecting a state of health of a battery, and includes the following steps:
And S801, outputting an ePWM signal of a rated carrier frequency by the single chip microcomputer.
S802, the nonlinear proportional-integral controller sets an ePWM signal output by the singlechip into a rectangular charging pulse, and inputs the rectangular charging pulse into a BUCK circuit.
S803, a sine ripple current is superimposed on the rectangular charging pulse using a micro-edge locator.
S804, a double-channel digital lock-in amplifier is used for receiving the signal to be measured input by the BUCK circuit, the amplitude of the measured sine ripple current is calculated, and the sine ripple current signal is output to a computer through measuring equipment.
S805, the computer acquires the measured battery temperature and the sine ripple current, and calculates the Warburg impedance of the battery based on the set battery charging voltage and the measured sine ripple current.
And S806, substituting the temperature of the battery, the charging current of the battery and the Warburg impedance of the battery into a battery diffusion process attenuation factor expression, and calculating to obtain a battery diffusion process attenuation factor so as to represent the health state of the battery.
As shown in fig. 9, the derivation process of the cell diffusion process attenuation factor expression of the present embodiment is as follows:
s901, selecting a diffusion process boundary condition suitable for a large-capacity single battery, and providing an expression for calculating the Warburg impedance of the battery as a first expression of the Warburg impedance of the battery.
Specifically, the present embodiment proposes an expression of the Warburg impedance of a battery in order to quantitatively calculate the diffusion boundary of the internal substance in a lithium battery based on the theory of "limited diffusion length and impenetrable barrier":
wherein, AeFor the effective electrode area, D is the diffusion coefficient associated with the material, c is the lithium ion molar concentration, R is the gas constant, T is the absolute temperature, l is the ion diffusion path length within the cell, n is the number of charge carriers, and F is the faraday constant.
S902, establishing a second expression of the battery Warburg impedance according to the physical characteristics that the real part and the imaginary part of the battery Warburg impedance are equal.
Specifically, the expression of the battery Warburg impedance is redefined from the physical property that the real part and the imaginary part of the battery Warburg impedance are equal, as the second expression of the battery Warburg impedance:
s903, simplifying constant terms and other known quantities in the second expression of the battery Warburg impedance, and extracting attenuation factors representing the battery diffusion process to obtain a third expression of the battery Warburg impedance.
Because the impedance measurement of the battery is completed under the same large current excitation, "A" is used2(ω) (1-j) "is related only to the temperature change of the battery.
Using cA in a second expression for the Warburg impedance of a battery eAs a characteristic of cell diffusion process decay factor, and define KD 2＝cAeA third expression of the Warburg impedance of the battery is obtained as follows:
wherein, KDIs a cell diffusion process decay factor.
And S904, deducing an attenuation factor expression in the battery diffusion process on the basis of a third expression of the battery Warburg impedance according to the amplitude characteristic of the battery Warburg impedance.
The step S904 specifically includes:
s9041, obtaining the amplitude characteristic of the battery Warburg impedance through the physical characteristic that the real part and the imaginary part of the battery Warburg impedance are equal, and as follows:
s9042, mixing
Substituting into a third expression of the Warburg impedance of the battery to obtain:
s9043, definition n ═ kiAnd i, simplifying constant terms to obtain an attenuation factor expression of the cell diffusion process, wherein the attenuation factor expression comprises the following steps:
wherein C is a physical constant, T is an absolute temperature of the battery, and ZwIs the Warburg impedance of the battery and i is the charging current of the battery.
Observing the expression of attenuation factor in the diffusion process of the battery, it can be seen that KDIs a physical quantity that is affected only by the Warburg impedance of the battery, the temperature of the battery, and the charging current of the battery.
It should be noted that although the operations of the above-described embodiment methods are depicted in the drawings in a particular order, this does not require or imply that the operations must be performed in this particular order, or that all of the illustrated operations must be performed, to achieve desirable results. Rather, the depicted steps may change the order of execution. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions.
Example 2:
as shown in fig. 10, the present embodiment provides a device for rapidly detecting the state of health of a battery, which includes an acquiring unit 1001 and a detecting unit 1002, and the specific functions of each unit are as follows:
an acquisition unit 1001 for acquiring the measured battery temperature and battery charging current, and calculating the Warburg impedance of the battery based on the set battery charging voltage and the measured battery charging current; wherein the battery charging current is a sinusoidal ripple current.
The detection unit 1002 is configured to substitute the temperature of the battery, the charging current of the battery, and the Warburg impedance of the battery into a battery diffusion process attenuation factor expression, and calculate a battery diffusion process attenuation factor to represent the state of health of the battery; wherein the expression of the attenuation factor of the battery diffusion process is derived from the expression of the Warburg impedance of the battery.
The specific implementation of the above units is referred to the above embodiment 1, and is not described in detail any more; it should be noted that the apparatus provided in the foregoing embodiment is merely illustrated by dividing the functional units, and in practical applications, the above function allocation may be performed by different functional units according to needs, that is, the internal structure is divided into different functional units to perform all or part of the functions described above.
Example 3:
the present embodiment provides a storage medium, which is a computer-readable storage medium, and stores a computer program, and when the computer program is executed by a processor, the method for rapidly detecting the state of health of the battery according to embodiment 1 is implemented as follows:
acquiring the measured battery temperature and the battery charging current, and calculating the Warburg impedance of the battery based on the set battery charging voltage and the measured battery charging current; wherein the battery charging current is a sinusoidal ripple current;
substituting the temperature of the battery, the charging current of the battery and the Warburg impedance of the battery into a battery diffusion process attenuation factor expression, and calculating to obtain a battery diffusion process attenuation factor so as to represent the health state of the battery; wherein the expression of the attenuation factor of the battery diffusion process is derived from the expression of the Warburg impedance of the battery.
It should be noted that the computer readable storage medium of the present embodiment may be a computer readable signal medium or a computer readable storage medium or any combination of the two. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples of the computer readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
In summary, the invention utilizes the BUCK circuit, the nonlinear proportional-integral control technology, the HRPWM technology and the dual-channel digital lock-in amplifier to calculate the internal impedance of the lithium battery under the charging current of the specific frequency, and based on the theory of "limited diffusion length and impenetrable fence", the impedance is calculated to represent the attenuation degree of the ion diffusion process in the battery, thereby defining the health status of the battery to be tested.
The above description is only for the preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the scope of the present invention.
Claims (8)
1. A method for rapidly detecting the state of health of a battery is characterized by comprising the following steps:
acquiring the measured battery temperature and the battery charging current, and calculating the Warburg impedance of the battery based on the set battery charging voltage and the measured battery charging current; wherein the battery charging current is a sinusoidal ripple current;
substituting the temperature of the battery, the charging current of the battery and the Warburg impedance of the battery into a battery diffusion process attenuation factor expression, and calculating to obtain a battery diffusion process attenuation factor so as to represent the health state of the battery; wherein the expression of the attenuation factor of the battery diffusion process is derived from the expression of the Warburg impedance of the battery;
The derivation process of the attenuation factor expression of the battery diffusion process is as follows:
selecting a diffusion process boundary condition suitable for a large-capacity single battery, and providing an expression for calculating the Warburg impedance of the battery as a first expression of the Warburg impedance of the battery;
establishing a second expression of the battery Warburg impedance according to the physical characteristics that the real part and the imaginary part of the battery Warburg impedance are equal;
simplifying constant terms and other known quantities in a second expression of the battery Warburg impedance, and extracting attenuation factors representing the battery diffusion process to obtain a third expression of the battery Warburg impedance;
deducing an attenuation factor expression of the battery diffusion process on the basis of a third expression of the battery Warburg impedance according to the amplitude characteristic of the battery Warburg impedance;
a first expression of the battery Warburg impedance is as follows:
wherein, AeIs the effective area of the electrode, D is the diffusion coefficient associated with the material, c is the molar concentration of lithium ions, R is the gas constant, T is the absolute temperature, l is the ion diffusion path length within the cell, n is the number of charge carriers, and F is the faraday constant;
a second expression of the battery Warburg impedance, as follows:
the method for simplifying the constant term and other known quantities in the second expression of the battery Warburg impedance extracts attenuation factors representing the battery diffusion process to obtain a third expression of the battery Warburg impedance, and specifically comprises the following steps:
Using cA in a second expression for the Warburg impedance of a batteryeAs a characteristic cell diffusion process decay factor and define KD 2＝cAeA third expression of the Warburg impedance of the battery is obtained as follows:
wherein, KDIs a cell diffusion process decay factor.
2. The method for rapidly detecting the state of health of a battery according to claim 1, wherein the deriving an expression of the attenuation factor of the battery diffusion process based on a third expression of the Warburg impedance of the battery according to the amplitude characteristic of the Warburg impedance of the battery specifically comprises:
the amplitude characteristic of the battery Warburg impedance is obtained through the physical characteristic that the real part and the imaginary part of the battery Warburg impedance are equal, and the amplitude characteristic is as follows:
will be provided with
Substituting into a third expression of the Warburg impedance of the battery to obtain:
definition n ═ kiAnd i, simplifying constant terms to obtain an attenuation factor expression of the cell diffusion process, wherein the attenuation factor expression comprises the following steps:
wherein C is a physical constant, T is an absolute temperature of the battery, and ZwIs the Warburg impedance of the battery and i is the charging current of the battery.
3. A device for rapidly detecting the state of health of a battery, the device comprising:
an acquisition unit for acquiring the measured battery temperature and battery charging current, and calculating a Warburg impedance of the battery based on the set battery charging voltage and the measured battery charging current; wherein the battery charging current is a sinusoidal ripple current;
The detection unit is used for substituting the temperature of the battery, the charging current of the battery and the Warburg impedance of the battery into a battery diffusion process attenuation factor expression, and calculating to obtain a battery diffusion process attenuation factor so as to represent the health state of the battery; wherein the expression of the attenuation factor of the battery diffusion process is derived from the expression of the Warburg impedance of the battery;
the derivation process of the cell diffusion process attenuation factor expression is as follows:
selecting a diffusion process boundary condition suitable for a large-capacity single battery, and providing an expression for calculating the Warburg impedance of the battery as a first expression of the Warburg impedance of the battery;
establishing a second expression of the battery Warburg impedance according to the physical characteristic that the real part and the imaginary part of the battery Warburg impedance are equal;
simplifying constant terms and other known quantities in a second expression of the battery Warburg impedance, and extracting attenuation factors representing the battery diffusion process to obtain a third expression of the battery Warburg impedance;
deducing an attenuation factor expression of the battery diffusion process on the basis of a third expression of the battery Warburg impedance according to the amplitude characteristic of the battery Warburg impedance;
a first expression of the battery Warburg impedance is as follows:
Wherein, AeIs the effective area of the electrode, D is the diffusion coefficient associated with the material, c is the molar concentration of lithium ions, R is the gas constant, T is the absolute temperature, l is the ion diffusion path length within the cell, n is the number of charge carriers, and F is the faraday constant;
a second expression of the Warburg impedance of the battery, as follows:
the method for simplifying the constant term and other known quantities in the second expression of the battery Warburg impedance extracts attenuation factors representing the battery diffusion process to obtain a third expression of the battery Warburg impedance, and specifically comprises the following steps:
using cA in a second expression for the Warburg impedance of a batteryeAs a characteristic of cell diffusion process decayFactor and define KD 2＝cAeA third expression of the Warburg impedance of the battery is obtained as follows:
wherein, KDIs a cell diffusion process decay factor.
4. A quick detector for the health state of a battery is characterized by comprising a single chip microcomputer, a nonlinear proportional-integral controller, a BUCK circuit, a double-channel digital lock-in amplifier, a measuring device and a computer, wherein the single chip microcomputer, the nonlinear proportional-integral controller, the BUCK circuit, the double-channel digital lock-in amplifier, the measuring device and the computer are sequentially connected, and the BUCK circuit is also connected with the single chip microcomputer;
The single chip microcomputer is used for outputting an ePWM signal of a rated carrier frequency and superposing sinusoidal ripple current on the rectangular charging pulse by using the micro-edge positioner;
the nonlinear proportional-integral controller is used for setting an ePWM signal output by the singlechip into a rectangular charging pulse and inputting the rectangular charging pulse into the BUCK circuit;
the double-channel digital lock-in amplifier is used for solving the amplitude of the measured sine ripple current according to the signal to be measured input by the BUCK circuit and outputting the sine ripple current signal through the measuring equipment;
the computer is used for executing the battery state of health rapid detection method of any one of claims 1-2.
5. The battery state of health quick detector of claim 4, wherein the BUCK circuit comprises a MOSFET driving circuit and a battery current detection circuit;
the MOSFET driving circuit comprises a MOSFET tube, the battery current detection circuit comprises a diode, an inductor, a capacitor, a sampling resistor and a voltage amplification circuit, the grid electrode of the MOSFET tube is connected with an ePWM signal output port of the single chip microcomputer, the drain electrode of the MOSFET tube is connected with a power supply, the source electrode of the MOSFET tube is connected with the cathode of the diode and one end of the inductor, the anode of the diode is grounded, the other end of the inductor is connected with one end of the capacitor and the anode of the battery, the other end of the capacitor is grounded, one end of the sampling resistor is connected with the cathode of the battery, the other end of the sampling resistor is grounded, and two ends of the sampling resistor are connected with the voltage amplification circuit;
The voltage amplifying circuit comprises two operational amplifiers and four resistors, wherein the forward input ends of the two operational amplifiers are grounded, one ends of the two resistors are connected with the reverse input ends of the operational amplifiers, one ends of the other two resistors are connected with the reverse input ends of the two operational amplifiers in a one-to-one correspondence mode, and the other ends of the other two resistors are connected with the output ends of the two operational amplifiers in a one-to-one correspondence mode.
6. The rapid detector according to claim 4, wherein the non-linear proportional-integral controller employs a battery charging current control algorithm, the battery charging current control algorithm is a non-linear combination of a proportional element and an integral element, and the time domain function is as follows:
wherein e (t) is the deviation between the measured current value and the reference value of the singlechip at the moment t, Kp[e(t)]Is a proportion link P, KpIs the gain coefficient of the proportional link P;
is an integration link I, KiIs the gain coefficient of the integral element I.
7. The rapid battery state of health detector of claim 4, wherein the dual channel digital lock-in amplifier comprises a multiplier, a Hilbert filter, a low pass filter, an integrator element, a divider, and an adder;
Among the binary channels digital lock-in amplifier, according to the signal to be measured of BUCK circuit input, solve measured sinusoidal ripple current amplitude to through measuring equipment output, specifically include:
the signal i' (f) to be measured0) And a reference signal
Input into the same multiplier and integrated to obtain an intermediate value U0The calculation formula is as follows:
where K is the multiplier gain, A2For the purpose of reference signal amplitude values,
is the unknown phase difference between the reference signal and the signal to be measured;
multiplier outputs intermediate signal U0Feeding the low-pass filter to filter out the high-frequency AC component to obtain another intermediate quantity
Reference signal
Input to a Hilbert filter for Hilbert transform, and then output to a signal i' (f) to be measured0) Multiplying and integrating, filtering out high-frequency AC component by low-pass filter to obtain another intermediate quantity
v0Channel sum v00Inputting the channel into a divider to obtain the phase difference between the measurement signal and the reference signal
Two v0Channel input multiplier, two v00The channel is input into a multiplier, the results of the two multipliers are input into an adder to obtain the required signal
Measuring the magnitude of the signal v (t), and calculating the amplitude A of the measured sinusoidal ripple current1。
8. A storage medium storing a program, wherein the program, when executed by a processor, implements the battery state of health rapid detection method according to any one of claims 1-2.
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