CN111308363A - Lithium battery state of charge estimation device and method based on self-adaptive model - Google Patents
Lithium battery state of charge estimation device and method based on self-adaptive model Download PDFInfo
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Abstract
The invention discloses a lithium battery state of charge estimation device and method based on a self-adaptive model, wherein the method comprises the following steps: establishing a lithium battery aging state mapping model; calculating a first function relation among terminal voltage, charge state and aging state of the lithium battery; according to the first functional relation, parameter identification is carried out on the equivalent circuit of the lithium battery, and a second functional relation among the equivalent circuit parameters of the lithium battery, the state of charge and the aging state is calculated in a fitting mode; judging the aging state of the lithium battery to be detected, obtaining the relation between the equivalent circuit parameter and the charge state of the lithium battery to be detected according to the aging state of the lithium battery to be detected by using a second function relation, and finally estimating the charge state of the lithium battery to be detected based on the initial value of the charge state of the lithium battery to be detected and the mapping relation between the equivalent circuit parameter and the charge state. The method can automatically adjust the parameters of the equivalent circuit model of the lithium battery under the aging states of different batteries, and improve the estimation precision of the state of charge of the lithium battery.
Description
Technical Field
The invention belongs to the technical field of lithium battery state estimation, and relates to a lithium battery state of charge estimation device and method based on a self-adaptive model.
Background
Lithium batteries have found widespread use in the industrial, agricultural, transportation, communication and aerospace industries due to their high energy density, high voltage, low self-discharge and long cycle life. The state of charge can represent the residual capacity of the battery, and in systems such as satellites and electric vehicles, the state of charge estimation of a lithium battery is an important part of a battery management system, and the accuracy of the estimation can directly influence the control strategy of the management system, so that the exertion of the battery is influenced. The charging and discharging of the lithium battery is a complex electrochemical process, and it is difficult to directly describe the electrochemical reaction process of the battery by a mathematical model, so that an equivalent circuit model based on the quantitative description of the battery working characteristics is widely applied. However, the conventional battery state of charge estimation method based on the equivalent circuit model fails to consider the influence of the battery aging state, the electrochemical characteristics of the battery have great difference in different aging states, the parameters of the equivalent circuit model are also different, and if the equivalent circuit model with fixed parameters is adopted to estimate the state of charge of the battery working in different aging states, it is difficult to obtain an accurate estimation result.
Disclosure of Invention
The invention aims to provide a lithium battery state of charge estimation device and method based on a self-adaptive model, which can automatically adjust parameters of an equivalent circuit model of a lithium battery under different aging states of the battery, thereby improving the estimation precision of the state of charge of the lithium battery.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a lithium battery state of charge estimation method based on an adaptive circuit model comprises the following steps:
step S1, establishing an aging state estimation model of the lithium battery: carrying out cyclic charge and discharge experiments on the lithium battery, extracting constant-current charging time and constant-voltage charging time from each experiment as the premonitory characteristics of lithium battery aging, and establishing a mapping model of the premonitory characteristics and the lithium battery aging state;
step S2, when the lithium battery is charged and discharged circularly to a preset aging state, the lithium battery is discharged by adopting a standing method, and the terminal voltage of the lithium battery when the discharge is reduced to different charge states is recorded; when each preset aging state is recorded to obtain all corresponding terminal voltages and charge states, fitting and calculating a first function relation among the terminal voltages, the charge states and the aging states of the lithium battery;
step S3, when the lithium battery is charged and discharged circularly to a preset aging state, carrying out HPPC test on the lithium battery, and acquiring terminal voltages of the current aging state and different charge states by using a first function relation so as to carry out parameter identification on the equivalent circuit of the lithium battery; when all the preset aging states are recorded to obtain equivalent circuit parameters corresponding to different charge states, fitting and calculating a second functional relation between the equivalent circuit parameters of the lithium battery and the charge states and the aging states;
step S4, according to the constant current charging time and the constant voltage charging time of the lithium battery to be tested, the aging state of the lithium battery to be tested is judged by using the mapping model established in the step S1; obtaining the mapping relation between the equivalent circuit parameters and the state of charge of the lithium battery to be tested according to the aging state of the lithium battery to be tested by using a second function relation; and estimating the state of charge of the lithium battery to be measured by using an extended Kalman filtering algorithm according to a state space equation of the equivalent circuit and an ampere-hour integration method based on the initial value of the state of charge of the battery and the mapping relation between the parameters of the equivalent circuit and the state of charge to obtain the state of charge SOC and the voltage of an output end of the lithium battery.
In a more preferred technical solution, each charging experiment in step S1 specifically includes: the method comprises the steps of firstly, charging the lithium battery in a constant current mode at a current of 1C, and after the voltage of the lithium battery reaches a rated voltage, charging the lithium battery in a constant voltage mode at the rated voltage until the charging current drops to a lower limit preset value of the charging current, and finishing the charging.
In a more preferable technical scheme, a mapping model of the premonitory characteristics and the aging state of the lithium battery is established by using a support vector machine.
In a more preferred technical solution, the step S2 of discharging by a standing method specifically includes: and (3) taking the lithium battery in the current aging state and full capacity, discharging at the current of 0.3C, standing for 30 minutes when the discharged capacity reaches 10%, recording the terminal voltage at the moment as OCV, and recording the state of charge as SOC, and ending the discharging by the standing method until the capacity reaches a preset range value.
In a more preferred embodiment, the aging state is: and setting the total chargeable and dischargeable times of the lithium battery in the whole process from the beginning to the end of the service life as N, setting the charged and discharged times from the beginning to the current process as l, and taking the ratio of the charged and discharged times l to the total chargeable and dischargeable times N as the quantized value of the aging state.
In a more preferred technical solution, the step S3 of performing HPPC test on the lithium battery to identify parameters of the equivalent circuit of the lithium battery is as follows:
(1) carrying out constant-current constant-voltage charging on the lithium battery until the state of charge (SOC) is 1;
(2) discharging the lithium battery at a current of 0.2C until the SOC is 0.9, and standing for 30 minutes;
(3) loading HPPC (high Performance liquid Crystal) charge-discharge pulses to the lithium battery: discharging the lithium battery at a current of 1C for 10 seconds, standing for 40 seconds, and charging the lithium battery at a current of 0.75C for 10 seconds;
(4) discharging the lithium battery at a current of 0.2C until the SOC is reduced by 0.1, and standing for 30 minutes;
(5) repeating the step (3) and the step (4) 8 times until the state of charge SOC is 0.1;
(6) discharging the lithium battery at the current of 1C until the discharge cut-off voltage of the lithium battery, and standing for 30 minutes;
during parameter identification, the internal resistance R in the equivalent circuit of the lithium battery is measured0The calculation formula of (a) is as follows:
in the formula, V1The terminal voltage V of the lithium battery at the 1 second moment before the HPPC charge-discharge pulse is loaded2The terminal voltage V of the lithium battery at the moment of starting to load HPPC (high power pulse compressor) charge-discharge pulse3The terminal voltage V of the lithium battery at the moment when the HPPC charging and discharging pulse is loaded is finished4The terminal voltage of the HPPC lithium battery at the moment of 1 second after the HPPC charging and discharging pulse is loaded is obtained;
the identification method of the polarization resistance and the polarization capacitance in the lithium battery equivalent circuit comprises the following steps:
a1, representing the terminal voltage of the lithium battery in 40 seconds after the discharge in the HPPC test step (3) is finished as the zero input voltage response of two RC networks, and the terminal voltage is represented as:
in the formula of UL(t) terminal voltage of lithium battery, UocIs the open circuit voltage, U, of a lithium battery1(0) And U2(0) Respectively electrochemical polarization resistance R1Sum concentration polarization resistance R2The terminal voltage of (a);
the lithium battery terminal voltage OCV obtained by discharging in the step S2 by adopting a standing method is the open circuit voltage U of the lithium battery in the current state of chargeOC(ii) a Then combining the measured terminal voltages U of a plurality of sampling points according to the open circuit voltageL(t), fitting the zero input voltage response curves of the two RC networks by adopting a least square method, and obtaining the current zero input voltage response curves of the two RC networksTime constant of state of charge τ1And τ2；
a2, the terminal voltage of the lithium battery in 10 seconds during the discharging process in the HPPC test step (3) is the zero state voltage response of two RC networks, and is represented as:
wherein I is the charging current, URCFor electrochemical polarization of resistance R1Sum concentration polarization resistance R2The sum of the terminal voltages of;
the voltage of the lithium battery is 0 when the lithium battery responds in a zero state, so that URCBy measuring terminal voltage ULObtaining; then according to the time constant tau1And τ2And the measured charging current I and terminal voltage U of multiple sampling pointsLAnd fitting the zero-state voltage response curves of the two RC networks in the current state of charge by adopting a least square method, so that the electrochemical polarization resistance R of the two RC networks in the current state of charge can be obtained by solving1Sum concentration polarization resistance R2；
a3, and the relationship tau between time constant and resistance1＝R1C1、τ2＝R2C2Then the electrochemical polarization capacitance C can be obtained by solving1Sum concentration polarization capacitance C2。
In a more preferred technical scheme, the state space equation of the equivalent circuit and the calculation formula of the ampere-hour integration method are as follows:
in the formula, SOC (t) is an estimated value of the lithium battery to be tested at the current moment t, SOC (0) is an initial state of charge of the lithium battery to be tested, IL(t) is the current of the lithium battery to be tested, U1And U2Respectively the electrochemical polarization resistance R of the lithium battery to be tested1Sum concentration polarization resistance R2Voltage of ULFor the load terminal voltage, Q, of the lithium battery to be testedNIs the rated capacity of the battery;
the state of charge SOC and the output end voltage of the lithium battery obtained by estimating the state of charge of the lithium battery to be measured by using the extended Kalman filtering algorithm are as follows:
UL(k)＝UOC(SOC(k))-U1(k)-U2(k)-R0IL(k-1)+v(k)
wherein T is a sampling period for acquiring the terminal voltage and the current of the lithium battery, omega (k) is the process noise of the super-capacitor energy storage system, v (k) is the measurement noise for acquiring the terminal voltage and the current of the lithium battery, and QNIs the rated capacity of the battery.
The invention also provides a lithium battery state of charge estimation device based on the self-adaptive model, which comprises the following components: the device comprises an analog quantity acquisition module, an AC-DC conversion module, a DC-DC conversion module, a control module, a power supply module and a high-power resistor;
the AC-DC conversion module is used for converting AC220V into DC so as to charge the lithium battery in a constant current-constant voltage mode;
the DC-DC conversion module is used for outputting the electric quantity of the lithium battery to the high-power resistor to realize the discharging operation of the battery;
the control module is used for outputting PWM control signals to the AC-DC conversion module and the DC-DC conversion module so as to control the lithium battery to work according to a preset voltage and current curve; a computing process further adapted to perform the method of any of claims 1-7;
the power supply module is used for converting the voltage of an external input power supply into a working voltage suitable for the normal operation of the analog quantity acquisition module and the control module;
the high-power resistor is used as a load and consumes the electric quantity of the lithium battery in a mode of converting the electric quantity into heat energy.
Advantageous effects
The invention provides a lithium battery state of charge estimation device and method based on a self-adaptive model, which comprises the steps of firstly establishing an estimation model of a battery aging state, and establishing a mapping relation between parameters of an equivalent circuit model of a lithium battery and the state of charge and the battery aging state by carrying out HPPC (high Performance compressed Power control) experiments under different aging states of the battery; for the battery to be measured, firstly, the aging state of the battery is calculated according to the provided battery aging state estimation method, so that the mapping relation between the parameters of the equivalent circuit model of the lithium battery and the state of charge can be determined according to the aging state, the equivalent circuit model can adapt to the batteries in different aging states, the modeling precision of the equivalent circuit model on the battery is improved, and the estimation precision of the state of charge of the lithium battery is further improved. Meanwhile, the method has good real-time performance and can be applied on line, so that the method can be widely applied to on-line high-precision estimation of the charge state of the lithium battery in the using process.
Drawings
FIG. 1 is a block schematic diagram of a state of charge estimation device provided by the present invention;
FIG. 2 is a schematic diagram of a power supply module provided by the present invention;
FIG. 3 is a flow chart of a state of charge estimation method provided by the present invention
FIG. 4 is a diagram of a second order equivalent circuit model according to the present invention;
FIG. 5 is a graph of HPPC experimental current waveforms in accordance with the present invention;
FIG. 6 is a block diagram of an extended Kalman filtering algorithm according to the present invention.
Detailed Description
The following describes embodiments of the present invention in detail, which are developed based on the technical solutions of the present invention, and give detailed implementation manners and specific operation procedures to further explain the technical solutions of the present invention.
Referring to fig. 1, the present invention provides an adaptive model-based lithium battery state of charge estimation apparatus, including: the device comprises an analog quantity acquisition module, an AC-DC conversion module, a DC-DC conversion module, a control module, a power supply module and a high-power resistor.
The AC-DC conversion module and the DC-DC conversion module are both connected with the control module, the AC-DC conversion module is also connected with the lithium battery, and the DC-DC conversion module is also connected with the high-power resistor and the lithium battery; the analog quantity acquisition module is connected with the AC-DC conversion module, the DC-DC conversion module, the lithium battery and the control module;
the AC-DC conversion module is used for converting AC220V into DC so as to charge the lithium battery in a constant current-constant voltage mode;
the DC-DC conversion module is used for outputting the electric quantity of the lithium battery to the high-power resistor to realize the discharging operation of the battery;
the control module is used for outputting PWM control signals to the AC-DC conversion module and the DC-DC conversion module so as to control the lithium battery to work according to a preset voltage and current curve; a calculation process for also performing a state of charge estimation method;
the power supply module is used for converting the voltage of an external input power supply into a working voltage suitable for the normal operation of the analog quantity acquisition module and the control module;
and the high-power resistor is used as a load and consumes the electric quantity of the lithium battery in a mode of converting the electric quantity into heat energy.
As shown in fig. 2, the power supply module includes an EMI sub-module, a DC-DC conversion sub-module, and a protection circuit sub-module; the power supply module reduces the direct-current 24V voltage to be the working voltage for the normal operation of the analog quantity acquisition module and the control module in the charge state estimation device; the direct current 24V power supply firstly filters high-frequency interference signals through the EMI filtering module, then obtains a stable +/-15V power supply through the conversion of 1 DC-DC conversion submodule so as to supply power to the analog quantity acquisition module, obtains a 5V power supply through the conversion of the other 1 DC-DC conversion submodule, and is used by a minimum system in the control module after being processed.
The control module in this example uses an STM32 series F103ZET6 chip as a CPU, with extremely high noise immunity and an extremely large temperature range.
The analog quantity acquisition module in the embodiment integrates a voltage sensor, a current sensor and a temperature sensor, acquires voltage and current signals input into the lithium battery from the AC-DC conversion module, acquires voltage and current signals output by the lithium battery from the DC-DC conversion module, and acquires the ambient temperature of the lithium battery from the surface of the battery; in addition, the analog quantity acquisition module in the embodiment is internally provided with a level conversion submodule and a data communication submodule, wherein the level conversion submodule is used for converting output signals of the voltage sensor, the current sensor and the temperature sensor into a range (0-5V) acceptable for a CPU, and the data communication submodule is used for exchanging data with the control module through SPI communication.
As shown in fig. 3, based on the foregoing apparatus, the method for estimating a state of charge of a lithium battery based on an adaptive model according to the present invention includes the following steps:
step S1, establishing an aging state estimation model of the lithium battery: carrying out cyclic charge and discharge experiments on the lithium battery, extracting constant-current charging time and constant-voltage charging time from each experiment as the premonitory characteristics of lithium battery aging, and establishing a mapping model of the premonitory characteristics and the lithium battery aging state;
the charging process in each charging and discharging experiment is specifically as follows: the method comprises the steps of firstly, charging the lithium battery in a constant current mode at a current of 1C, and after the voltage of the lithium battery reaches a rated voltage, charging the lithium battery in a constant voltage mode at the rated voltage until the charging current drops to a lower limit preset value of the charging current, and finishing the charging.
According to the invention, the constant-current charging time and the constant-voltage charging time, namely the premonitory characteristics of lithium battery aging, obtained in each lithium battery cycle charging process are used as 1 training data. In this embodiment, preferably, 10 lithium batteries are used for performing an experiment, all the obtained training data are used as input, the corresponding aging state is used as output, and a support vector machine is trained, so as to establish a mapping model for obtaining the premonitory characteristics and the aging state of the lithium batteries.
The aging state in this example means: and setting the total chargeable and dischargeable times of the lithium battery in the whole process from the beginning to the end of the service life as N, setting the charged and discharged times from the beginning to the current process as l, and taking the ratio of the charged and discharged times l to the total chargeable and dischargeable times N as the quantized value of the aging state.
Step S2, when the lithium battery is charged and discharged circularly to a preset aging state, the lithium battery is discharged by adopting a standing method, and the terminal voltage of the lithium battery when the discharge is reduced to different charge states is recorded; when each preset aging state is recorded to obtain all corresponding terminal voltages and charge states, fitting and calculating a first function relation among the terminal voltages, the charge states and the aging states of the lithium battery;
the preset aging state in this embodiment includes: all aging states with 5% as the minimum aging state, 5% as the step length and 100% as the maximum aging state; since the number of times the battery can be charged is gradually reduced with time each time the lithium battery is cycled to the preset aging state, the "each time the lithium battery is cycled to the preset aging state" in the step S2 and the following step S3 means: when the lithium battery is charged and discharged in sequence in a circulating mode until the aging states are 5%, 10%, … … and 100%, the following specific steps are executed.
The specific process of discharging by adopting the standing method in the embodiment is as follows: and (3) taking the lithium battery in the current aging state and full capacity, discharging at the current of 0.3C, standing for 30 minutes when the discharged capacity reaches 10%, recording the terminal voltage at the moment as OCV, and recording the state of charge as SOC, and ending the discharging by the standing method until the capacity reaches a preset range value.
Step S3, when the lithium battery is charged and discharged circularly to a preset aging state, carrying out HPPC test on the lithium battery, and acquiring terminal voltages of the current aging state and different charge states by using a first function relation so as to carry out parameter identification on the equivalent circuit of the lithium battery; and when all the preset aging states are recorded to obtain equivalent circuit parameters corresponding to different charge states, fitting and calculating a second functional relation among the equivalent circuit parameters of the lithium battery, the charge states and the aging states.
In this embodiment, the parameter identification is specifically performed on a second-order equivalent circuit model of the lithium battery, where the second-order equivalent circuit model of the lithium battery is shown in fig. 4 and includes a constant voltage source UOCInternal resistance R0Electrochemical polarization resistance R1Concentration polarization resistance R2Electrochemical polarization capacitance C1Sum concentration polarization capacitance C2。
The HPPC test performed on the lithium battery in this embodiment is performed by using the equivalent circuit of the lithium battery to perform parameter identification:
(1) carrying out constant-current constant-voltage charging on the lithium battery until the state of charge (SOC) is 1;
(2) discharging the lithium battery at a current of 0.2C until the SOC is 0.9, and standing for 30 minutes;
(3) as shown in fig. 5, the lithium battery is loaded with HPPC charge and discharge pulses: discharging the lithium battery at a current of 1C for 10 seconds, standing for 40 seconds, and charging the lithium battery at a current of 0.75C for 10 seconds;
(4) discharging the lithium battery at a current of 0.2C until the SOC is reduced by 0.1, and standing for 30 minutes;
(5) repeating the step (3) and the step (4) 8 times until the state of charge SOC is 0.1;
(6) discharging the lithium battery at the current of 1C until the discharge cut-off voltage of the lithium battery, and standing for 30 minutes;
during parameter identification, the internal resistance R in the equivalent circuit of the lithium battery is measured0The calculation formula of (a) is as follows:
in the formula, V1The terminal voltage V of the lithium battery at the 1 second moment before the HPPC charge-discharge pulse is loaded2The terminal voltage V of the lithium battery at the moment of starting to load HPPC (high power pulse compressor) charge-discharge pulse3The terminal voltage V of the lithium battery at the moment when the HPPC charging and discharging pulse is loaded is finished4The terminal voltage of the HPPC lithium battery at the moment of 1 second after the HPPC charging and discharging pulse is loaded is obtained.
The identification method of the polarization resistance and the polarization capacitance in the lithium battery equivalent circuit comprises the following steps:
a1, representing the terminal voltage of the lithium battery in 40 seconds after the discharge in the HPPC test step (3) is finished as the zero input voltage response of two RC networks, and the terminal voltage is represented as:
in the formula of UL(t) terminal voltage of lithium battery, UocIs the open circuit voltage, U, of a lithium battery1(0) And U2(0) Respectively electrochemical polarization resistance R1Sum concentration polarization resistance R2The terminal voltage of (a);
the lithium battery terminal voltage OCV obtained by discharging in the step S2 by adopting a standing method is the open circuit voltage U of the lithium battery in the current state of chargeOC(ii) a Then combining the measured terminal voltages U of a plurality of sampling points according to the open circuit voltageL(t), fitting the zero input voltage response curves of the two RC networks by adopting a least square method, and obtaining the time constant tau of the two RC networks in the current state of charge1And τ2；
a2, the terminal voltage of the lithium battery in 10 seconds during the discharging process in the HPPC test step (3) is the zero state voltage response of two RC networks, and is represented as:
wherein I is the charging current, URCFor electrochemical polarization of resistance R1Sum concentration polarization resistance R2The sum of the terminal voltages of;
the voltage of the lithium battery is 0 when the lithium battery responds in a zero state, so that URCBy measuring terminal voltage ULObtaining; then according to the time constant tau1And τ2And the measured charging current I and terminal voltage U of multiple sampling pointsLFitting the zero-state voltage response curves of the two RC networks by adopting a least square method, and solving to obtain the electrochemical polarization resistance R1Sum concentration polarization resistance R2；
a3, and the relationship tau between time constant and resistance1＝R1C1、τ2＝R2C2Then the electrochemical polarization capacitance C can be obtained by solving1Sum concentration polarization capacitance C2。
Step S4, according to the constant current charging time and the constant voltage charging time of the lithium battery to be tested, the aging state of the lithium battery to be tested is judged by using the mapping model established in the step S1; obtaining the mapping relation between the equivalent circuit parameters and the state of charge of the lithium battery to be tested according to the aging state of the lithium battery to be tested by using a second function relation; and estimating the state of charge of the lithium battery to be measured by using an extended Kalman filtering algorithm according to a state space equation of the equivalent circuit and an ampere-hour integration method based on the initial value of the state of charge of the battery and the mapping relation between the parameters of the equivalent circuit and the state of charge to obtain the state of charge SOC and the voltage of an output end of the lithium battery.
The equivalent circuit state space equation and the ampere-hour integral method have the following calculation formulas:
in the formula, SOC (t) is an estimated value of the lithium battery to be tested at the current moment t, SOC (0) is an initial value of the state of charge of the lithium battery to be tested, IL(t) is the current of the lithium battery to be tested, U1And U2Respectively the electrochemical polarization resistance R of the lithium battery to be tested1Sum concentration polarization resistance R2Voltage of ULFor the load terminal voltage, Q, of the lithium battery to be testedNIs the rated capacity of the battery;
estimating the state of charge of the lithium battery to be measured by using an extended Kalman filtering algorithm, as shown in FIG. 6, obtaining the state of charge SOC and the output end voltage of the lithium battery as follows:
UL(k)＝UOC(SOC(k))-U1(k)-U2(k)-R0IL(k-1)+v(k)
wherein T is a sampling period for acquiring the terminal voltage and the current of the lithium battery, omega (k) is the process noise of the super-capacitor energy storage system, v (k) is the measurement noise for acquiring the terminal voltage and the current of the lithium battery, and QNIs the rated capacity of the battery.
In the invention, the extended Kalman filtering algorithm is adopted and realized by an algorithm module in matlab, and the invention is repeated for the prior art.
The above embodiments are preferred embodiments of the present application, and those skilled in the art can make various changes or modifications without departing from the general concept of the present application, and such changes or modifications should fall within the scope of the claims of the present application.
Claims (8)
1. A lithium battery state of charge estimation method based on an adaptive circuit model is characterized by comprising the following steps:
step S1, establishing an aging state estimation model of the lithium battery: carrying out cyclic charge and discharge experiments on the lithium battery, extracting constant-current charging time and constant-voltage charging time from each experiment as the premonitory characteristics of lithium battery aging, and establishing a mapping model of the premonitory characteristics and the lithium battery aging state;
step S2, when the lithium battery is charged and discharged circularly to a preset aging state, the lithium battery is discharged by adopting a standing method, and the terminal voltage of the lithium battery when the discharge is reduced to different charge states is recorded; when each preset aging state is recorded to obtain all corresponding terminal voltages and charge states, fitting and calculating a first function relation among the terminal voltages, the charge states and the aging states of the lithium battery;
step S3, when the lithium battery is charged and discharged circularly to a preset aging state, carrying out HPPC test on the lithium battery, and acquiring terminal voltages of the current aging state and different charge states by using a first function relation so as to carry out parameter identification on the equivalent circuit of the lithium battery; when all the preset aging states are recorded to obtain equivalent circuit parameters corresponding to different charge states, fitting and calculating a second functional relation between the equivalent circuit parameters of the lithium battery and the charge states and the aging states;
step S4, according to the constant current charging time and the constant voltage charging time of the lithium battery to be tested, the aging state of the lithium battery to be tested is judged by using the mapping model established in the step S1; obtaining the mapping relation between the equivalent circuit parameters and the state of charge of the lithium battery to be tested according to the aging state of the lithium battery to be tested by using a second function relation; and estimating the state of charge of the lithium battery to be measured by using an extended Kalman filtering algorithm according to a state space equation of the equivalent circuit and an ampere-hour integration method based on the initial value of the state of charge of the battery and the mapping relation between the parameters of the equivalent circuit and the state of charge to obtain the state of charge SOC and the voltage of an output end of the lithium battery.
2. The method according to claim 1, wherein each charging experiment of step S1 is specifically: the method comprises the steps of firstly, charging the lithium battery in a constant current mode at a current of 1C, and after the voltage of the lithium battery reaches a rated voltage, charging the lithium battery in a constant voltage mode at the rated voltage until the charging current drops to a lower limit preset value of the charging current, and finishing the charging.
3. The method of claim 1, wherein a model for mapping the pre-cursor features to the aging state of the lithium battery is established using a support vector machine.
4. The method of claim 1, wherein the step S2 of discharging by static method comprises the following steps: and (3) taking the lithium battery in the current aging state and full capacity, discharging at the current of 0.3C, standing for 30 minutes when the discharged capacity reaches 10%, recording the terminal voltage at the moment as OCV, and recording the state of charge as SOC, and ending the discharging by the standing method until the capacity reaches a preset range value.
5. The method of claim 1, wherein the aging state is: and setting the total chargeable and dischargeable times of the lithium battery in the whole process from the beginning to the end of the service life as N, setting the charged and discharged times from the beginning to the current process as l, and taking the ratio of the charged and discharged times l to the total chargeable and dischargeable times N as the quantized value of the aging state.
6. The method according to claim 1, wherein the step S3 of performing HPPC test on the lithium battery to identify parameters of the equivalent circuit of the lithium battery is as follows:
(1) carrying out constant-current constant-voltage charging on the lithium battery until the state of charge (SOC) is 1;
(2) discharging the lithium battery at a current of 0.2C until the SOC is 0.9, and standing for 30 minutes;
(3) loading HPPC (high Performance liquid Crystal) charge-discharge pulses to the lithium battery: discharging the lithium battery at a current of 1C for 10 seconds, standing for 40 seconds, and charging the lithium battery at a current of 0.75C for 10 seconds;
(4) discharging the lithium battery at a current of 0.2C until the SOC is reduced by 0.1, and standing for 30 minutes;
(5) repeating the step (3) and the step (4) 8 times until the state of charge SOC is 0.1;
(6) discharging the lithium battery at the current of 1C until the discharge cut-off voltage of the lithium battery, and standing for 30 minutes;
during parameter identification, the internal resistance R in the equivalent circuit of the lithium battery is measured0The calculation formula of (a) is as follows:
in the formula, V1The terminal voltage V of the lithium battery at the 1 second moment before the HPPC charge-discharge pulse is loaded2The terminal voltage V of the lithium battery at the moment of starting to load HPPC (high power pulse compressor) charge-discharge pulse3The terminal voltage V of the lithium battery at the moment when the HPPC charging and discharging pulse is loaded is finished4The terminal voltage of the HPPC lithium battery at the moment of 1 second after the HPPC charging and discharging pulse is loaded is obtained;
the identification method of the polarization resistance and the polarization capacitance in the lithium battery equivalent circuit comprises the following steps:
a1, representing the terminal voltage of the lithium battery in 40 seconds after the discharge in the HPPC test step (3) is finished as the zero input voltage response of two RC networks, and the terminal voltage is represented as:
in the formula of UL(t) terminal voltage of lithium battery, UocIs lithiumOpen circuit voltage of battery, U1(0) And U2(0) Respectively electrochemical polarization resistance R1Sum concentration polarization resistance R2The terminal voltage of (a);
the lithium battery terminal voltage OCV obtained by discharging in the step S2 by adopting a standing method is the open circuit voltage U of the lithium battery in the current state of chargeOC(ii) a Then combining the measured terminal voltages U of a plurality of sampling points according to the open circuit voltageL(t), fitting the zero input voltage response curves of the two RC networks by adopting a least square method, and obtaining the time constant tau of the two RC networks in the current state of charge1And τ2；
a2, the terminal voltage of the lithium battery in 10 seconds during the discharging process in the HPPC test step (3) is the zero state voltage response of two RC networks, and is represented as:
wherein I is the charging current, URCFor electrochemical polarization of resistance R1Sum concentration polarization resistance R2The sum of the terminal voltages of;
the voltage of the lithium battery is 0 when the lithium battery responds in a zero state, so that URCBy measuring terminal voltage ULObtaining; then according to the time constant tau1And τ2And the measured charging current I and terminal voltage U of multiple sampling pointsLAnd fitting the zero-state voltage response curves of the two RC networks in the current state of charge by adopting a least square method, so that the electrochemical polarization resistance R of the two RC networks in the current state of charge can be obtained by solving1Sum concentration polarization resistance R2；
a3, and the relationship tau between time constant and resistance1＝R1C1、τ2＝R2C2Then the electrochemical polarization capacitance C can be obtained by solving1Sum concentration polarization capacitance C2。
7. The method of claim 1, wherein the equation of state space of the equivalent circuit and the equation of the ampere-hour integral are calculated as:
in the formula, SOC (t) is an estimated value of the lithium battery to be tested at the current moment t, SOC (0) is an initial state of charge of the lithium battery to be tested, IL(t) is the current of the lithium battery to be tested, U1And U2Respectively the electrochemical polarization resistance R of the lithium battery to be tested1Sum concentration polarization resistance R2Voltage of ULFor the load terminal voltage, Q, of the lithium battery to be testedNIs the rated capacity of the battery;
the state of charge SOC and the output end voltage of the lithium battery obtained by estimating the state of charge of the lithium battery to be measured by using the extended Kalman filtering algorithm are as follows:
UL(k)＝UOC(SOC(k))-U1(k)-U2(k)-R0IL(k-1)+v(k)
wherein T is a sampling period for acquiring the terminal voltage and the current of the lithium battery, omega (k) is the process noise of the super-capacitor energy storage system, v (k) is the measurement noise for acquiring the terminal voltage and the current of the lithium battery, and QNIs the rated capacity of the battery.
8. A lithium battery state of charge estimation device based on an adaptive model is characterized by comprising the following components: the device comprises an analog quantity acquisition module, an AC-DC conversion module, a DC-DC conversion module, a control module, a power supply module and a high-power resistor;
the AC-DC conversion module is used for converting AC220V into DC so as to charge the lithium battery in a constant current-constant voltage mode;
the DC-DC conversion module is used for outputting the electric quantity of the lithium battery to the high-power resistor to realize the discharging operation of the battery;
the control module is used for outputting PWM control signals to the AC-DC conversion module and the DC-DC conversion module so as to control the lithium battery to work according to a preset voltage and current curve; a computing process further adapted to perform the method of any of claims 1-7;
the power supply module is used for converting the voltage of an external input power supply into a working voltage suitable for the normal operation of the analog quantity acquisition module and the control module;
the high-power resistor is used as a load and consumes the electric quantity of the lithium battery in a mode of converting the electric quantity into heat energy.
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