1. The battery health state estimation method for the real new energy automobile is characterized by comprising the following steps of: the method specifically comprises the following steps:

step 1, screening charging segments with constant current, same current and charging time larger than a preset value from new energy automobile real automobile data collected by a vehicle-mounted big data platform, recording charging voltage, charging current, charging time and other data in the segments, and calculating the charging capacity between every two frames of data;

step 2, calculating a capacity increment IC curve and a battery pack curve peak value ICP for each charging segment screened in the step 1_P；

Step 3, establishing an equivalent circuit model for the battery monomers in the vehicle battery pack, and calculating to obtain an equivalent IC curve peak value ICP of the battery pack according to the grouping form of the monomers in the battery pack_C；

Step 4, establishing a model relation between the peak value of the IC curve of the single battery and the SOH of the single battery based on empirical data of the single battery with known materials and/or structures, and fitting model parameters;

step 5, obtaining the equivalent IC curve peak value ICP obtained in the step 3_CAnd (5) substituting the model relation in the step (4) to finally obtain the complete battery pack SOH corresponding to the whole charging segment.

2. The method of claim 1, wherein: the calculation of the charge capacity between every two frames of data in the step 1 is specifically realized based on an ampere-hour integral method:

Q＝I×t

wherein Q is the charging capacity, I is the current, and t is the charging time.

3. The method of claim 1, wherein: the calculated capacity increment IC curve in step 2 is specifically obtained based on the following formula:

IC＝dQ/dU＝(Q_t-Q_t-1)/(U_t-U_t-1)

wherein Q represents a charging capacity, U represents a charging voltage, d is a differential sign, and t is a charging time; and for each selected charging segment, obtaining an IC curve by using the formula, drawing the IC curve by taking the charging voltage as an abscissa and the IC value as an ordinate, and extracting the peak value ICP of the IC curve in the high-voltage interval.

4. The method of claim 1, wherein: specifically, a first-order equivalent circuit model is established for the battery cell in step 3, and the formula is as follows:

U＝E+IR

wherein, U represents the terminal voltage of the single battery, E represents the electromotive force of the single battery, I represents the charging current of the single battery, and R represents the internal resistance of the single battery.

5. The method of claim 1, wherein: equivalent IC curve peak value ICP of battery pack for different grouping forms of monomers in step 3_CRespectively as follows:

1) cell pack consisting of N cells connected in series, the ICP thereof_c＝N×ICP_p；

2) Cell pack consisting of M cells connected in parallel, its ICP_c＝ICP_p/M；

3) A battery pack formed by connecting N monomers into a module in series, then connecting M modules in parallel/connecting M monomers into a module in parallel, and then connecting N modules in series, and ICP thereof_c＝N×ICP_p/M。

6. The method of claim 1, wherein: in step 4, a first-order polynomial model relationship is specifically established between the peak value of the battery cell IC curve and the battery cell SOH:

SOH＝f(ICP_c)＝A×ICP_c+B

wherein A, B are the model parameters to be fitted respectively, and f represents the function.

7. The method of claim 1, wherein: in step 4, a quadratic polynomial model relationship is specifically established between the peak value of the battery cell IC curve and the battery cell SOH:

SOH＝f(ICP_c)＝C×ICP_c ²+D×ICP_c+E

wherein C, D, E are the model parameters to be fitted respectively, and f represents the function.

8. The method of claim 1, wherein: the empirical data in step 4 are supplemented in particular by cyclic ageing tests carried out on cells of the same material and/or structure.

Background

The power battery is used as a core component in a new energy automobile power system, and the health state of the power battery has important influence on the aspects of the running performance, the safety and the like of the vehicle, so that the estimation of the SOH of the power battery is also one of the hot problems in the field of the current new energy automobile. At present, a power battery usually uses a battery pack, due to the limitation of practical conditions, the real SOH of the battery pack in actual operation is difficult to obtain directly through a measurement mode, the daily charging and discharging behaviors cannot meet the requirement of test calibration, and even if the calibration is executed, the problems of huge workload and low efficiency exist. The prior art mainly focuses on performing operations such as cyclic aging on the cells constituting the battery pack in a test environment, for example, estimating the SOH of the battery by using an Incremental Capacity (IC) method, and indirectly reflecting the SOH of the battery pack through a prediction result of the SOH of the cells. However, because the simulation of the test environment on the real working conditions of the vehicle is not perfect, the performance index differences between different materials and structural batteries make the test results unable to refer to each other, and in order to cover various working conditions and expand the data volume as comprehensively as possible, the problems of large workload and low efficiency still cannot be overcome when the IC method and other suitable methods are used.

Disclosure of Invention

Compared with the traditional fuel vehicle, the new energy vehicle has remarkable advantages in the aspects of vehicle-mounted data collection and processing, and the problem of efficiency of the prior art depending on mass data can be effectively solved if the new energy vehicle can be better utilized. In view of this, the invention provides a method for estimating a state of health of a battery of a real new energy vehicle, which specifically includes the following steps:

step 1, screening charging segments with constant current, same current and charging time larger than a preset value from new energy automobile real automobile data collected by a vehicle-mounted big data platform, recording charging voltage, charging current, charging time and other data in the segments, and calculating the charging capacity between every two frames of data;

step 2, calculating a capacity increment IC curve and a curve peak value ICP for each charging segment screened in the step 1_P；

Step 3, establishing an equivalent circuit model for the battery monomers in the vehicle battery pack, and calculating to obtain an equivalent IC curve peak value ICP of the battery pack according to the grouping form of the monomers in the battery pack_C；

Step 4, establishing a model relation between the peak value of the IC curve of the single battery and the SOH of the single battery based on empirical data of the single battery with known materials and/or structures, and fitting model parameters;

step 5, obtaining the equivalent IC curve peak value ICP obtained in the step 3_CAnd (5) substituting the model relation in the step (4) to finally obtain the complete battery pack SOH corresponding to the whole charging segment.

Further, the calculation of the charge capacity between every two frames of data in the step 1 is specifically realized based on an ampere-hour integral method:

Q＝I×t

wherein Q is the charging capacity, I is the current, and t is the charging time.

Further, the calculated capacity increment IC curve in step 2 is specifically obtained based on the following formula:

IC＝dQ/dU＝(Q_t-Q_t-1)/(U_t-U_t-1)

wherein Q represents a charging capacity, U represents a charging voltage, d is a differential sign, and t is a charging time; and for each selected charging segment, obtaining an IC curve by using the formula, drawing the IC curve by taking the charging voltage as an abscissa and the IC value as an ordinate, and extracting the peak value ICP of the IC curve in the high-voltage interval.

Further, a first-order equivalent circuit model is specifically established for the battery cell in step 3, and the formula is as follows:

U＝E+IR

wherein, U represents the terminal voltage of the single battery, E represents the electromotive force of the single battery, I represents the charging current of the single battery, and R represents the internal resistance of the single battery.

Further, the equivalent IC curve peak ICP of the battery pack for different grouping formats of the cells_CRespectively as follows:

1) cell pack consisting of N cells connected in series, the ICP thereof_c＝N×ICP_p；

2) Cell pack consisting of M cells connected in parallel, its ICP_c＝ICP_p/M；

3) A battery pack formed by connecting N monomers into a module in series, then connecting M modules in parallel/connecting M monomers into a module in parallel, and then connecting N modules in series, and ICP thereof_c＝N×ICP_p/M。

Further, in step 4, a first-order polynomial model relationship is specifically established between the peak value of the battery cell IC curve and the SOH of the battery cell:

SOH＝f(ICP_c)＝A×ICP_c+B

wherein A, B are the model parameters to be fitted respectively, and f represents the function.

Further, in step 4, a quadratic polynomial model relationship is specifically established between the peak value of the battery cell IC curve and the SOH of the battery cell:

SOH＝f(ICP_c)＝C×ICP_c ²+D×ICP_c+E

wherein C, D, E are the model parameters to be fitted respectively, and f represents the function.

Further, the empirical data in step 4 are obtained by performing a cycle aging test on the battery cells of the same material and/or structure.

The method provided by the invention organically combines the conventional and easily obtained single body level SOH prediction equation with the packet level capacity increment IC obtained by calculating mass real vehicle big data, effectively solves the technical problems that the battery packet state cannot be measured and the estimation result cannot meet the precision requirement in the conventional power battery SOH estimation, and avoids the consumption of manpower and material resources caused by carrying out a large amount of cyclic aging tests, calibration and data processing on the single body. The present invention has a number of unexpected advantages over the prior art.

Drawings

FIG. 1 is a schematic flow chart of the method of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. 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.

The method for estimating the state of health of the battery of the real new energy automobile, disclosed by the invention, as shown in fig. 1, specifically comprises the following steps:

step 1, screening charging segments with constant current, same current and charging time larger than a preset value from new energy automobile real automobile data collected by a vehicle-mounted big data platform, recording charging voltage, charging current, charging time and other data in the segments, and calculating the charging capacity between every two frames of data;

step 2, calculating a capacity increment IC curve and a curve peak value ICP for each charging segment screened in the step 1_P；

Step 3, establishing an equivalent circuit model for the battery monomers in the vehicle battery pack, and calculating to obtain an equivalent IC curve peak value ICP of the battery pack according to the grouping form of the monomers in the battery pack_C；

Step 4, establishing a model relation between the peak value of the IC curve of the single battery and the SOH of the single battery based on empirical data of the single battery with known materials and/or structures, and fitting model parameters;

step 5, calculating the equivalent IC curve peak value ICP obtained by using real vehicle big data in the step 3_CSubstituting into the model relationship obtained by fitting the empirical data of the monomers of the same type in the step 4,finally, a complete battery pack SOH corresponding to the entire charging segment is obtained.

In a preferred embodiment of the present invention, the calculating of the charge capacity between every two frames of data in step 1 is specifically implemented based on an ampere-hour integration method:

Q＝I×t

wherein Q is the charging capacity, I is the current, and t is the charging time.

In a preferred embodiment of the present invention, the calculated capacity increment IC curve in step 2 is obtained based on the following formula:

IC＝dQ/dU＝(Q_t-Q_t-1)/(U_t-U_t-1)

wherein Q represents a charging capacity, U represents a charging voltage, d is a differential sign, and t is a charging time; and for each selected charging segment, obtaining an IC curve by using the formula, drawing the IC curve by taking the charging voltage as an abscissa and the IC value as an ordinate, and extracting the peak value ICP of the IC curve in the high-voltage interval. Numerous studies have shown that the decrease in ICP in the high voltage region of lithium ion batteries has a close correlation with battery capacity degradation.

Specifically, a first-order equivalent circuit model is established for the battery cell in step 3, and the formula is as follows:

U＝E+IR

wherein, U represents the terminal voltage of the single battery, E represents the electromotive force of the single battery, I represents the charging current of the single battery, and R represents the internal resistance of the single battery.

Equivalent IC curve peak ICP for different grouping forms of cells_CRespectively as follows:

1) for a battery pack formed by connecting N monomers in series, according to kirchhoff's law, the currents I of the series circuits are the same, and the collected terminal voltage data U_TObtaining the equivalent ICP of the battery pack with N strings of single cells as NU_c：ICP_c＝N×ICP_p；

2) Similarly, for a battery pack formed by connecting M monomers in parallel, the voltage U at the end of the parallel circuit is the same according to kirchhoff's law, because the capacity of the battery of the parallel circuit is M times of that of the monomer battery, if the same charging multiplying power is adopted, the battery pack is formed by connecting M monomers in parallelThe current of the battery pack is M times of that of the single battery pack, i.e. I_pEqual to MI, M single parallel battery pack equivalent ICP_c：ICP_c＝ICP_p/M；

3) If the battery pack is of an N-string M-parallel (the monomers are firstly connected in parallel to form the module, and the module is then connected in series to form the pack) or M-parallel N-string (the monomers are firstly connected in series to form the module, and the module is then connected in parallel to form the pack) structure, distributed calculation can be performed, the equivalent ICP after the monomers are grouped is calculated firstly, then the module is regarded as the monomers, and the equivalent ICP after the module is grouped is calculated. The final expressions for the cell pack equivalent ICP are: ICP_c＝N×ICP_p/M。

In a preferred embodiment of the present invention, in step 4, a first-order polynomial model relationship is established between the peak of the cell IC curve and the cell SOH:

SOH＝f(ICP_c)＝A×ICP_c+B

wherein A, B are the model parameters to be fitted respectively, and f represents the function.

In a preferred embodiment of the present invention, in step 4, a quadratic polynomial model relationship is established between the peak of the cell IC curve and the cell SOH:

SOH＝f(ICP_c)＝C×ICP_c ²+D×ICP_c+E

wherein C, D, E are the model parameters to be fitted respectively, and f represents the function.

In a preferred embodiment of the present invention, for the case that the existing empirical data is not perfect and is not sufficient to fit a good model relationship, the data required for the fitting process can be supplemented and perfected by performing a cyclic aging test on the battery cells of the same material and/or structure.

It should be understood that, the sequence numbers of the steps in the embodiments of the present invention do not mean the execution sequence, and the execution sequence of each process should be determined by the function and the inherent logic of the process, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.