CN109342950B - Method, device and equipment for evaluating state of charge of lithium battery - Google Patents
Method, device and equipment for evaluating state of charge of lithium battery Download PDFInfo
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Abstract
The embodiment of the invention provides a method for evaluating the state of charge of a lithium battery, which comprises the following steps: acquiring actual operation state data of the lithium battery; comparing the actual operation state data with the state parameters corresponding to each open-circuit voltage-charge state curve in a pre-established database, and determining the corresponding open-circuit voltage-charge state curve when the operation state data is matched with the state parameters; and determining the charge state of the lithium battery according to the corresponding open-circuit voltage-charge state curve. The embodiment of the invention also provides a device and equipment for evaluating the state of charge of the lithium battery. The curve cluster obtained by the evaluation method can completely cover the running characteristics of the battery under different working conditions, and the lithium battery charge state is corrected by taking the curve cluster as a reference, so that the accuracy of evaluating the lithium battery charge state is improved.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a method, a device and equipment for evaluating the charge state of a lithium battery.
Background
At present, with the increase of electric vehicles and energy storage applications, lithium batteries are widely used. In order to fully exert the functions of the lithium battery and improve the safety of the lithium battery, the lithium battery needs to be effectively managed. The battery management system becomes an important guarantee for the safe and efficient operation of the lithium battery, and the state of charge of the battery is one of the most important functions of the battery management system as an important state quantity of the lithium battery. The state of charge of the battery is an important parameter for describing the residual capacity of the battery, and has great significance for the reliable operation of a battery system. In the electric automobile, the state of charge of the battery is accurately estimated, so that a user can know the current residual capacity of the battery and the time or mileage for continuous operation under the current state. In addition, adjustments are made to the driving route or driving mode. For the energy storage system, the accurate battery charge state is more beneficial to the power dispatching to make accurate calculation, and is beneficial to the stable and economic operation of the power system. Therefore, the working performance of the battery can be exerted to the maximum extent while the normal work of the battery is ensured.
However, applicants have found that the accumulated state of charge error increases with time due to current sampling errors, reducing the accuracy of the battery state of charge estimation. The applicant finds that the battery state of charge calibration by using the open-circuit voltage of the battery is a commonly adopted means, and the open-circuit voltage is mainly determined by the battery state of charge and the battery temperature and is in a one-to-one correspondence relationship in numerical value. The open-circuit voltage represents the stable electromotive force corresponding to the battery in a certain charge state, is a state quantity with strong description capacity on the battery condition, and can improve the estimation precision of the charge state by improving the precision of the open-circuit voltage.
Disclosure of Invention
In view of this, the present invention provides a method, an apparatus and a device for estimating a state of charge of a lithium battery, which can accurately estimate the state of charge of the lithium battery.
In order to solve the above problem, the embodiments of the present invention mainly provide the following technical solutions:
in a first aspect, an embodiment of the present invention discloses a method for estimating a state of charge of a lithium battery, including:
acquiring actual operation state data of the lithium battery;
comparing the actual operation state data with a state parameter corresponding to each open-circuit voltage-charge state curve in a pre-established database, and determining a corresponding open-circuit voltage-charge state curve when the operation state data is matched with the state parameter;
and determining the charge state of the lithium battery according to the corresponding open-circuit voltage-charge state curve.
Optionally, acquiring actual operating state data of the lithium battery includes:
and acquiring at least one parameter of the actual working temperature, the charging and discharging state, the standing time, the open-circuit voltage and the current of the lithium battery.
Optionally, comparing the actual operating state data with a state parameter corresponding to each open-circuit voltage-state of charge curve in a pre-established database, and determining a corresponding open-circuit voltage-state of charge curve when the operating state data matches the state parameter, includes:
and searching in the database according to at least one parameter of the actual working temperature, the charging and discharging state, the standing time, the open-circuit voltage and the current of the lithium battery, determining the open-circuit voltage-charge state curve as a corresponding open-circuit voltage-charge state curve if the state parameter corresponding to the open-circuit voltage-charge state curve is the same as the parameter, and otherwise, determining the open-circuit voltage-charge state curve without matching with the running state data.
Optionally, when it is determined that the operating state data does not have a matching open circuit voltage-state of charge curve, the method includes:
and according to the actual running state data, selecting two open-circuit voltage-state-of-charge curves from the open-circuit voltage-state-of-charge curves in a set mode, and according to the selected open-circuit voltage-state-of-charge curves, determining the open-circuit voltage-state-of-charge curves of the lithium battery under the actual working condition, thereby determining the state of charge of the lithium battery.
Optionally, selecting two open-circuit voltage-state-of-charge curves from the plurality of open-circuit voltage-state-of-charge curves according to the actual operating state data in a set manner, and determining the open-circuit voltage-state-of-charge curve of the lithium battery under the actual operating condition according to the selected open-circuit voltage-state-of-charge curves, thereby determining the state of charge of the lithium battery, including:
determining the working state and the standing time of the lithium battery;
determining two corresponding temperatures and two corresponding currents in the database, which are respectively close to the actual temperature and the actual current, according to the actual temperature and the actual current in the actual operation state data;
and calculating the open-circuit voltage-charge state curve under the actual temperature and the actual current according to the open-circuit voltage-charge state curve of the corresponding temperature and the corresponding current.
Optionally, the open-circuit voltage-state of charge curves of the actual temperature and the actual current are calculated by interpolation.
Optionally, after the calculating the lower open-circuit voltage-state of charge curve of the actual temperature and the actual current according to the open-circuit voltage-state of charge curve of the corresponding temperature and the corresponding current, the method further includes:
and storing the open-circuit voltage-charge state curve under the actual temperature and the actual current into the database.
Optionally, pre-establishing a database containing a plurality of open circuit voltage-state of charge curves comprises:
s1: determining the preset temperature of the lithium battery, and discharging the lithium battery until the preset lower limit value is reached;
s2: charging the lithium battery within a preset time, and determining the current state of charge of the lithium battery;
s3: determining open-circuit voltages of the lithium battery within different preset standing time until the open-circuit voltages tend to be stable, and obtaining a group of open-circuit voltage-charge state charging curve clusters;
s4: repeatedly performing the steps S2 and S3 on the lithium battery to obtain a plurality of groups of charging curve clusters of the open-circuit voltage-charge state until the lithium battery is fully charged;
s5: storing a plurality of groups of the open circuit voltage-state of charge curve clusters in the database; or
S1: determining the preset temperature of the lithium battery, and charging the lithium battery until the preset upper limit value is reached;
s2: discharging the lithium battery within a preset time, and determining the current state of charge of the lithium battery;
s3: determining open-circuit voltages of the lithium batteries within different preset standing time until the open-circuit voltages tend to be stable, and obtaining a group of open-circuit voltage-charge state discharge curve clusters;
s4: repeatedly carrying out the S2 and S3 on the lithium battery to obtain a plurality of groups of discharge curve clusters of the open-circuit voltage-charge state until the electric quantity of the lithium battery is zero;
s5: storing a plurality of sets of the open circuit voltage-state of charge discharge curve clusters in the database.
In a second aspect, the present application provides an apparatus for assessing the state of charge of a lithium battery, comprising.
The state acquisition module is used for acquiring actual operation state data of the lithium battery;
the control module is used for comparing the actual operation state data with a state parameter corresponding to each open-circuit voltage-charge state curve in a pre-established database and determining a corresponding open-circuit voltage-charge state curve when the operation state data is matched with the state parameter; and determining the state of charge of the lithium battery according to the corresponding open circuit voltage-state of charge curve.
In a third aspect, the present application provides an apparatus for assessing the state of charge of a lithium battery, comprising:
a memory and a processor electrically connected;
at least one program stored in the memory for, when executed by the processor, implementing the evaluation method of any of the first aspects.
By the technical scheme, the technical scheme provided by the embodiment of the invention at least has the following advantages:
the evaluation method in the embodiment of the invention can compare the actual running state data with each open-circuit voltage-charge state curve in a database which is pre-established with a plurality of open-circuit voltage-charge state curves, determine whether the running state data is matched with one of the open-circuit voltage-charge state curves, and obtain a series of curve clusters of the open-circuit voltage of the battery, wherein the curve clusters can completely cover the running characteristics of the battery under different working conditions, and the lithium battery charge state obtained by testing the terminal voltage and the integral of the battery under different working conditions is compared with the curve clusters stored in the database, so that the lithium battery charge state is corrected on the basis of the curve clusters, and the accuracy of evaluating the lithium battery charge state is improved.
The foregoing description is only an overview of the technical solutions of the embodiments of the present invention, and the embodiments of the present invention can be implemented according to the content of the description in order to make the technical means of the embodiments of the present invention more clearly understood, and the detailed description of the embodiments of the present invention is provided below in order to make the foregoing and other objects, features, and advantages of the embodiments of the present invention more clearly understandable.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the alternative embodiments. The drawings are only for purposes of illustrating alternative embodiments and are not to be construed as limiting the embodiments of the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a flow chart of an evaluation method according to an embodiment of the present invention;
FIG. 2 is a graph of open circuit voltage versus state of charge for an embodiment of the present invention with actual temperatures between corresponding temperatures;
FIG. 3 is a graph of open circuit voltage versus state of charge for an embodiment of the present invention with actual current between corresponding currents;
fig. 4 is a schematic structural diagram of an apparatus for evaluating a state of charge of a lithium battery according to an embodiment of the present invention.
The reference numerals are introduced as follows:
1-a device for assessing the state of charge of a lithium battery; 2-a state acquisition module; and 3, controlling the module.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The state of charge of the battery described in the embodiment of the invention refers to the ratio of the remaining electric quantity of the battery to the total chargeable and dischargeable capacity of the battery, and can be calculated by the following formula:
wherein SOC is the state of charge of the battery, QremainIs the remaining capacity of the battery, QtotalIs the total capacity of the battery.
The state of charge is generally taken as 0% as a reference point, i.e. QremainZero ampere-hour. And charging the battery to a full charge state, then discharging to cut-off voltage at a constant rate, wherein the electric quantity discharged in the whole process is the total chargeable and dischargeable electric quantity of the battery. The state of charge of the battery is influenced by various factors such as discharge multiplying power, battery capacity, temperature, battery voltage and the like, the accurate online calculation of the state of charge of the battery is difficult to realize, and if the online calculation is not considered fully, the estimated state of charge of the battery may have no reference value or even be completely unavailable.
Currently, the estimation algorithms for the state of charge of the battery are various, and some algorithms are performed under the special charging and discharging conditions of the battery. Such as open circuit voltage method, ampere-hour integration method, artificial neural network and Kalman filtering method. The open circuit voltage method has advantages of simplicity and easy operation, but requires the battery to be stable at rest, for example, for 2 hours or more, so that the open circuit voltage of the battery can be accurately obtained. The ampere-hour integration method is open-loop prediction, can accurately estimate the state of charge in a short time, but has the problems that the initial state of charge cannot be determined and the accumulated error is larger and larger. In practical engineering applications, the ampere-hour integration method is often used in combination with other methods.
The open-circuit voltage provided by the invention is a stable value reached by the voltage after the battery is powered off. For the battery in the charging process, the voltage gradually decreases to a stable value after power failure, and for the battery in the discharging process, the voltage gradually increases to the stable value after power failure, at the moment, the concentration phenomenon in the battery caused by electrochemical reaction is greatly weakened, and the concentrations of reactants and products are relatively uniform. The time required for the voltage to stabilize is related to various factors such as the current before the battery is powered off, the charge state at the power-off moment, the ambient temperature and the like.
Therefore, in order to solve the above problem, in a first aspect, an embodiment of the present invention provides an evaluation method for a state of charge of a lithium battery, as shown in fig. 1, the method including:
s101: and acquiring actual operation state data of the lithium battery.
S102: and comparing the actual operation state data with the state parameters corresponding to each open-circuit voltage-charge state curve in the pre-established database, and determining the corresponding open-circuit voltage-charge state curve when the operation state data is matched with the state parameters.
S103: and determining the charge state of the lithium battery according to the corresponding open-circuit voltage-charge state curve.
The evaluation method in the embodiment of the invention can compare the actual running state data with each open-circuit voltage-charge state curve in a database which is pre-established with a plurality of open-circuit voltage-charge state curves, determine whether the running state data is matched with one of the open-circuit voltage-charge state curves, and obtain a series of curve clusters of the open-circuit voltage of the battery, wherein the curve clusters can completely cover the running characteristics of the battery under different working conditions, and the lithium battery charge state obtained by testing the terminal voltage and the integral of the battery under different working conditions is compared with the curve clusters stored in the database, so that the lithium battery charge state is corrected on the basis of the curve clusters, and the accuracy of evaluating the lithium battery charge state is improved.
Optionally, the acquiring actual operating state data of the lithium battery in S101 includes:
at least one parameter of actual working temperature, charging and discharging state, standing time, open-circuit voltage and current of the lithium battery is obtained.
Optionally, the step of comparing the actual operating state data with the state parameters corresponding to each open circuit voltage-state of charge curve in the pre-established database in S102 to determine the corresponding open circuit voltage-state of charge curve when the operating state data is matched with the state parameters includes:
and searching in a database according to at least one parameter of the actual working temperature, the charging and discharging state, the standing time, the open-circuit voltage and the current of the lithium battery, determining the open-circuit voltage-charge state curve as a matched open-circuit voltage-charge state curve if the state parameter corresponding to the open-circuit voltage-charge state curve is the same as the parameter, and otherwise, determining the open-circuit voltage-charge state curve without matching the running state data.
Optionally, when it is determined in S103 that the operating state data does not have a matching open circuit voltage-state of charge curve, the method includes:
according to actual operation state data, two open-circuit voltage-state-of-charge curves are selected from the open-circuit voltage-state-of-charge curves in a set mode, and according to the selected open-circuit voltage-state-of-charge curves, the open-circuit voltage-state-of-charge curves of the lithium battery under actual working conditions are determined, so that the state of charge of the lithium battery is determined.
Specifically, according to actual operating state data, two open-circuit voltage-state-of-charge curves are selected from a plurality of open-circuit voltage-state-of-charge curves in a set mode, and according to the selected open-circuit voltage-state-of-charge curves, the open-circuit voltage-state-of-charge curves of the lithium battery under actual working conditions are determined, so that the state of charge of the lithium battery is determined, and the method comprises the following steps:
and determining the working state and the standing time of the lithium battery. According to the actual temperature and the actual current in the actual operation state data, two corresponding temperatures and two corresponding currents which are respectively close to the actual temperature and the actual current in the database are determined. And calculating the open-circuit voltage-charge state curve under the actual temperature and the actual current according to the open-circuit voltage-charge state curve of the corresponding temperature and the corresponding current.
Optionally, the open-circuit voltage-state-of-charge curves for the actual temperature and actual current are calculated by interpolation. Due to the adoption of a conventional interpolation method, the calculation amount required in the evaluation process is greatly reduced, and the state of charge of the battery is easy to evaluate quickly.
Optionally, after the step S103 of calculating a lower open-circuit voltage-state of charge curve of the actual temperature and the actual current according to the open-circuit voltage-state of charge curve of the corresponding temperature and the corresponding current, the method further includes:
and storing the open-circuit voltage-charge state curve under the actual temperature and the actual current into a database. Therefore, the method can be continuously updated in actual operation, more open-circuit voltage-state-of-charge curve clusters are accumulated, the accuracy of battery state-of-charge calibration is improved, the operation times are reduced, and the speed of state-of-charge calibration is improved.
It is understood that in order to implement the evaluation method of the present invention, it is necessary to establish a database regarding the open circuit voltage-state of charge curve of the lithium battery during the charging and discharging processes before S101. Therefore, in the present embodiment, when the lithium battery is to be subjected to a discharging process so as to establish a database containing a plurality of open-circuit voltage-state-of-charge curves in advance, the following steps are required:
s1: and determining the preset temperature of the lithium battery, and discharging the lithium battery until the preset lower limit value is reached.
S2: and charging the lithium battery within a preset time, and determining the current charge state of the lithium battery.
S3: and determining the open-circuit voltage of the lithium battery within different preset standing time until the open-circuit voltage tends to be stable, and obtaining a group of open-circuit voltage-charge state charging curve clusters.
S4: and repeatedly carrying out S2 and S3 on the lithium battery to obtain a plurality of groups of charging curve clusters of open-circuit voltage-charge state until the lithium battery is fully charged.
S5: storing the sets of open circuit voltage-state of charge curve clusters in a database.
In addition, similar to the discharging process, in another embodiment, when the lithium battery is to be charged so as to pre-establish a database containing a plurality of open-circuit voltage-state-of-charge curves, the following steps are required:
s1: and determining the preset temperature of the lithium battery, and charging the lithium battery until the preset upper limit value is reached.
S2: and discharging the lithium battery within a preset time to determine the current state of charge of the lithium battery.
S3: determining the open-circuit voltage of the lithium battery within different preset standing time until the open-circuit voltage tends to be stable, and obtaining a group of discharge curve clusters of open-circuit voltage-charge state.
S4: and repeatedly carrying out S2 and S3 on the lithium battery to obtain a plurality of groups of discharge curve clusters of open circuit voltage-charge state until the electric quantity of the lithium battery is zero.
S5: and storing a plurality of groups of discharge curve clusters of the open circuit voltage-charge state in a database.
The evaluation method according to the embodiment of the present invention is described in detail below with reference to fig. 2 and 3.
Firstly, the invention provides a method for calibrating the state of charge of a battery by using a battery open-circuit voltage-state of charge curve cluster, wherein the open-circuit voltage-state of charge curve cluster is obtained by an off-line experiment and is used as an initial standard curve cluster of the battery. The following 2-step experiment was performed:
experiment 1: the battery operates at a fixed ambient temperature t1Next, a charging experiment of the battery was performed at a constant rate:
a) the battery is first discharged until the battery voltage reaches a predetermined lower limit value, at which time the state of charge of the battery is recorded as 0.
b) Charging the battery at a certain rate for a period of time to make the state of charge of the battery be SOCC1Then stopping charging, and after the battery is stood still for not less than 5 min, starting to record terminal voltage of battery, and using it as U of battery in said stateC1,T1. However, to those skilled in the artThe member can select the appropriate adjustment time according to different batteries. Standing for a period of time delta T, and recording the terminal voltage of the battery to be used as U of the battery under the standing timeC1,T2Until the battery reaches full stability at the present state of charge. Recording the terminal voltage and the standing time of the delta T battery at intervals to obtain the current temperature T and the current state of charge SOCC1The next set of open circuit voltage-state of charge curve clusters.
c) Then, according to the step a), continuing to charge the battery for T, so that the state of charge of the battery is SOCC2Stopping charging, starting to record the terminal voltage of the battery after the battery is not less than 5 minutes of standing, and taking the terminal voltage as the U of the battery in the current stateC2,T1. Standing for a period of time delta T, and recording the terminal voltage of the battery to be used as U of the battery under the standing timeC2,T2Until the battery is completely stable under the state of charge, recording the terminal voltage and the standing time of the delta T battery at intervals to obtain the current temperature T and the current state of charge SOCC2A next set of open circuit voltage-state of charge curve clusters;
d) step a) is repeated, the battery is charged continuously until the battery is fully charged (the battery voltage reaches the specified upper limit voltage), and an open circuit voltage-charge state curve cluster of the battery in different charge states is obtained;
thus, a group of open-circuit voltage-state-of-charge charging curve clusters of the battery at a fixed temperature and a fixed charging rate are obtained, so that a database required by the evaluation method in the embodiment of the invention is obtained, and necessary evaluation steps can be carried out on the lithium battery.
In the evaluation method process of the embodiment of the invention, the following two situations can occur, wherein when the actual working condition of the battery has a corresponding curve in the database, the curve can be directly used for calibrating the state of charge of the battery. In another case, when the actual operating condition of the battery has no corresponding curve in the database, a method of performing the state of charge calibration with reference to the existing open circuit voltage-state of charge can be used, which is described below with reference to fig. 2 and 3.
Fig. 2 is a graph of the open circuit voltage of a battery at different temperatures at a constant discharge current. Fig. 3 is an open-circuit voltage curve of the battery at different discharge currents under a constant ambient temperature, wherein the abscissa of fig. 2 and fig. 3 is time, and the state of charge of the battery can be obtained according to the integral of time and current, so that the open-circuit voltage-state of charge curve of the battery can be obtained. The following shows how the steps of cell state of charge calculation are performed in the case where the cell is not in the cluster of curves, both temperature and current, during actual operation:
1) it is determined whether the battery is operating in a charged state or a discharged state.
2) And determining the standing time of the battery, and if the standing time is less than 5 minutes, not carrying out charge state calibration when the battery stands. And if the standing time is more than 5 minutes, finding the corresponding battery standing time T in the data table.
3) Determining the environment temperature t of the battery operation, and finding the adjacent temperature t in the data table1And t2As shown in FIG. 2, t1<t<t2。
4) Determining the charging or discharging current I of the battery operation, finding the adjacent current I in the data table1And I2As shown in FIG. 3, I1<I<I2。
5) According to the open-circuit voltage-charge state curve cluster obtained by the experiment, the temperature is t1When the battery working current is I1And I2The functional relations corresponding to the curves of the battery state of charge and the open-circuit voltage are respectively recorded as:
SOCI1＝f1(OCV,t1,I1) (2)
SOCI2＝f2(OCV,t1,I2) (3)
6) according to the open-circuit voltage-state of charge curve cluster obtained by the experiment, at the temperature of t2, the functional relations corresponding to the curves of the battery state of charge and the open-circuit voltage when the battery working current is I1 and I2 are respectively recorded as:
7) the current I is obtained from the equations (2) and (4) by interpolation1The curve of the battery operating at ambient temperature t:
8) the current I is obtained from the equations (3) and (5) by interpolation2The curve of the battery operating at ambient temperature t:
9) according to the obtained curve expressions (6) and (7), an open-circuit voltage-state of charge curve of the battery at the current I and the temperature t is obtained by an interpolation method:
SOCt＝g(OCV,t,I) (8)
therefore, the battery state of charge of the battery at the temperature t and the current I is obtained according to the corresponding relation between the battery open-circuit voltage and the battery state of charge, and the battery state of charge can be calibrated. And storing the curve into a curve cluster database as a basic database.
The function f is explained below1Is obtained by the method of function f2，g1，g2，
The calculation method is the same.
In step a) of experiment 1, at a temperature t, the discharge state of charge is SOCC1At different rest times, the terminal voltage measurements of the cells corresponded to (T0, U)C1,T0)、(T1，UC1,T1)、(T2，UC1,T2)、(T3，UC1,T3)、(T4，UC1,T4)、(Tn，UC1,Tn) In actual working conditions, the values are known, and the solution time is TkThe battery terminal voltage at time is calculated using an interpolation polynomial (9).
In the formula: f (T)0)＝UC1,T0，f(T1)＝UC1,T1，f(Tn)＝UC1,Tn
When n is equal to 1, the compound is,
when n is equal to 2, the compound has the following structure,
therefore, the function f can be calculated by the steps1The specific numerical value of (1). Likewise, function f2，g1，g2，
And the calculation can be carried out in the same way to obtain corresponding numerical values, so that an accurate evaluation value of the state of charge of the battery is obtained.
In summary, the evaluation method provided by the embodiment of the invention realizes accurate estimation of the state of charge of the battery. The method comprises the steps of firstly testing an open-circuit voltage-charge state curve database of the battery at different temperatures, charge-discharge rates and standing time, and calibrating the charge state according to the comparison of the open-circuit voltage-charge state curve measured on line in the actual running process of the battery and the database. In practical application, an ampere-hour integration method is used as a basic calculation method of the state of charge, and an open-circuit voltage-state of charge curve cluster is used as a reference to calibrate the state of charge, so that the problem of large error of the state of charge caused by open-circuit voltage-state of charge curve correction in a single battery running state is solved, and the evaluation accuracy is improved.
In a second aspect, as shown in fig. 4, the present application provides an apparatus 1 for evaluating a state of charge of a lithium battery, the apparatus 1 comprising:
and the state acquisition module 2 is used for acquiring actual operation state data of the lithium battery.
The control module 3 is used for comparing the actual operation state data with each open-circuit voltage-charge state curve in a database which is pre-established with a plurality of open-circuit voltage-charge state curves to determine whether the operation state data is matched with one of the open-circuit voltage-charge state curves; and determining the state of charge of the lithium battery according to the matching result and the open-circuit voltage-state of charge curve.
Through the description of the evaluation method in the first aspect, the device in the second aspect can synthesize experiments of the battery at different temperatures, different charging and discharging states, different current magnitudes and different standing times, establish an open-circuit voltage-state-of-charge curve cluster of the battery, perform cross validation of the state-of-charge, and prevent the state-of-charge calibration error caused by data acquisition error or calculation error. Meanwhile, when the battery is subjected to the state of charge calibration, a conventional interpolation method is adopted, the calculation amount is small, and the state of charge of the battery is easy to evaluate quickly.
In a third aspect, the present application also provides an apparatus for assessing the state of charge of a lithium battery, comprising:
a memory and a processor electrically connected;
at least one program, stored in the memory, for execution by the processor to implement the evaluation method of the first aspect.
Since the program in the third aspect includes the evaluation method in the first aspect, it has the same advantageous effects as the evaluation method in the first aspect. Therefore, the advantageous effects of the device of the third aspect will not be repeated.
The beneficial effects obtained by applying the embodiment of the invention comprise:
1. the evaluation method in the embodiment of the invention can compare the actual running state data with each open-circuit voltage-charge state curve in a database which is pre-established with a plurality of open-circuit voltage-charge state curves, determine whether the running state data is matched with one of the open-circuit voltage-charge state curves, and obtain a series of curve clusters of the open-circuit voltage of the battery, wherein the curve clusters can completely cover the running characteristics of the battery under different working conditions, and the lithium battery charge state obtained by testing the terminal voltage and the integral of the battery under different working conditions is compared with the curve clusters stored in the database, so that the lithium battery charge state is corrected on the basis of the curve clusters, and the accuracy of evaluating the lithium battery charge state is improved.
2. By integrating the experiments of the battery under different temperatures, different charging and discharging states, different current magnitudes and different standing times, the open-circuit voltage-charge state curve cluster of the battery is established, the cross verification of the charge state can be performed, and the charge state calibration error caused by data acquisition error or calculation error is prevented.
3. When the battery is subjected to the state of charge calibration, a conventional interpolation method is adopted, the calculation amount is small, and the state of charge of the battery is easy to evaluate quickly. In addition, the battery open-circuit voltage-state-of-charge curve can be continuously updated in actual operation, more curve clusters are accumulated, the accuracy of battery state-of-charge calibration is improved, the operation times are reduced, and the speed of state-of-charge calibration is improved.
The foregoing is only a partial embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (6)
1. A method for assessing the state of charge of a lithium battery, comprising:
acquiring the actual operation state data of the lithium battery, wherein the acquiring the actual operation state data of the lithium battery comprises the following steps: acquiring at least one parameter of actual working temperature, charging and discharging states, standing time, open-circuit voltage and actual current of the lithium battery;
searching in a database according to at least one parameter of the actual working temperature, the charging and discharging state, the standing time, the open-circuit voltage and the actual current of the lithium battery, if the state parameter corresponding to the open-circuit voltage-charge state curve is the same as at least one of the actual working temperature, the charging and discharging state, the standing time, the open-circuit voltage and the actual current, determining the open-circuit voltage-charge state curve as a matched open-circuit voltage-charge state curve, and otherwise, determining the open-circuit voltage-charge state curve without matching of the running state data;
determining the state of charge of the lithium battery according to a corresponding open circuit voltage-state of charge curve;
when it is determined that the operating state data does not have a matching open circuit voltage-state of charge curve, comprising:
determining the working state and the standing time of the lithium battery;
determining two corresponding temperatures and two corresponding currents which are respectively adjacent to the actual temperature and the actual current in the database according to the actual temperature and the actual current in the actual operation state data;
and calculating the open-circuit voltage-charge state curve under the actual temperature and the actual current according to the open-circuit voltage-charge state curve of the corresponding temperature and the corresponding current.
2. The evaluation method according to claim 1, wherein the open-circuit voltage-state-of-charge curves of the actual temperature and the actual current are calculated by interpolation.
3. The method of claim 1, wherein after calculating a lower open-circuit voltage-state-of-charge curve for said actual temperature and actual current based on said open-circuit voltage-state-of-charge curves for said corresponding temperature and said corresponding current, further comprising:
and storing the open-circuit voltage-charge state curve under the actual temperature and the actual current into the database.
4. The method of claim 1, wherein pre-building a database containing a plurality of open circuit voltage-state-of-charge curves comprises:
s1: determining the preset temperature of the lithium battery, and discharging the lithium battery until the preset lower limit value is reached;
s2: charging the lithium battery within a preset time, and determining the current state of charge of the lithium battery;
s3: determining open-circuit voltages of the lithium battery within different preset holding time until the open-circuit voltages tend to be stable, and obtaining a group of open-circuit voltage-charge state charging curve clusters;
s4: repeatedly carrying out the steps S2 and S3 on the lithium battery to obtain a plurality of groups of charging curve clusters of the open circuit voltage-charge state until the electric quantity of the lithium battery is full;
s5: storing a plurality of sets of said open circuit voltage-state of charge curve clusters in said database;
or
S1: determining the preset temperature of the lithium battery, and charging the lithium battery until the preset upper limit value is reached;
s2: discharging the lithium battery within a preset time, and determining the current charge state of the lithium battery;
s3: determining open-circuit voltages of the lithium batteries within different preset standing time until the open-circuit voltages tend to be stable, and obtaining a group of open-circuit voltage-charge state discharge curve clusters;
s4: repeatedly carrying out the S2 and S3 on the lithium battery to obtain a plurality of groups of discharge curve clusters of the open circuit voltage-charge state until the electric quantity of the lithium battery is zero;
s5: storing a plurality of sets of the open circuit voltage-state of charge discharge curve clusters in the database.
5. An apparatus for assessing the state of charge of a lithium battery, comprising:
the state acquisition module is used for acquiring the actual operation state data of the lithium battery, and the actual operation state data of the lithium battery comprises the following steps: at least one parameter of an actual operating temperature, a charging and discharging state, a standing time, an open-circuit voltage and an actual current of the lithium battery;
the control module is used for searching in a database according to at least one parameter of the actual working temperature, the charging and discharging state, the standing time, the open-circuit voltage and the actual current of the lithium battery, determining the open-circuit voltage-charge state curve as a matched open-circuit voltage-charge state curve if the state parameter corresponding to the open-circuit voltage-charge state curve is searched to be the same as at least one of the actual working temperature, the charging and discharging state, the standing time, the open-circuit voltage and the actual current, and otherwise, determining the open-circuit voltage-charge state curve without matching the running state data; determining the state of charge of the lithium battery according to the corresponding open circuit voltage-state of charge curve; when it is determined that the operating state data does not have a matching open circuit voltage-state of charge curve, comprising:
determining the working state and the standing time of the lithium battery;
determining two corresponding temperatures and two corresponding currents adjacent to the actual temperature and the actual current respectively in the database according to the actual temperature and the actual current in the actual operation state data;
and calculating the open-circuit voltage-charge state curve under the actual temperature and the actual current according to the open-circuit voltage-charge state curve of the corresponding temperature and the corresponding current.
6. An apparatus for assessing the state of charge of a lithium battery, comprising:
a memory and a processor electrically connected;
at least one program stored in the memory for execution by the processor to implement the assessment method of any one of claims 1-4.
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| CN111679200B (en) * | 2020-06-03 | 2023-02-10 | 广州小鹏汽车科技有限公司 | Battery state of charge calibration method and device and vehicle |
| WO2022047767A1 (en) * | 2020-09-07 | 2022-03-10 | 海能达通信股份有限公司 | Battery power detection method and apparatus, and portable electronic device |
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| CN114264966A (en) * | 2021-12-06 | 2022-04-01 | 阳光储能技术有限公司 | Method and device for evaluating state of charge of battery, terminal device and medium |
| CN114779098B (en) * | 2022-04-14 | 2022-12-23 | 江苏金锋源新能源有限公司 | State evaluation method and system for lithium ion battery |
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