Parameter fitting method and device based on RC fitting model of power battery

Abstract

The application discloses a parameter fitting method and device based on an RC fitting model of a power battery, which combines the observed voltage, current and state of charge in the collected discharge duration with a first-order Thevenin equivalent model to analyze and calculate the RC fitting parameters of the power battery cell, so that the calculation speed of the RC fitting parameters of the battery cell is improved, the operation in a single-chip microcomputer is facilitated, and the program running lag phenomenon is reduced; and through multiple calculation iterations, the calculation precision of the RC fitting parameters is greatly improved, and good conditions are provided for the development of a battery management system of a subsequent power battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a parameter fitting method and device based on RC fitting model of power battery. BACKGROUND

[0002] At present, the calculation of the battery management system of the mainstream power battery is mainly carried out by using open circuit voltage method, ampere-hour integral method, Kalman filtering method, neural network method and the like. Among them, the open circuit voltage method only considers the corresponding relationship of the rated working condition under the static state, and the error will become larger and larger with the extension of the running time; the ampere-hour integral method has a very high requirement for the current accuracy, and cannot fully consider the internal resistance, temperature, aging factor and the like, and it is difficult to accurately estimate, in the case of high temperature or severe current fluctuation, the capacity of the battery will change, and it is difficult to obtain accurate results only by using this method; the neural network method needs to be trained with samples, and has a large amount of calculation and high requirement for hardware; in the Kalman filtering method, the most important thing is the accuracy of the battery performance model and the calculation ability of the battery management system. In order to solve the defects of the open circuit voltage method, the ampere-hour integral method, the Kalman filtering method and the neural network method, the parameter fitting of the RC equivalent circuit model emerges as the times require, which can effectively provide reliable RC fitting parameters for the battery management system of the power battery.

[0003] However, it is found in practice that the RC parameter fitting is mainly in the second order and the third order at present, and the larger the order is, the stronger the required calculation ability is. The battery management system mainly relies on single-chip microcomputer for operation, and a large amount of operation may cause that the calculation result cannot be timely reflected, the program running is stalled and the like. Therefore, it is particularly important to propose a technical scheme for improving the calculation speed of the RC fitting parameters of the battery cell. SUMMARY

[0004] The present application provides a parameter fitting method and device based on RC fitting model of power battery, which can improve the calculation speed of the RC fitting parameters of the battery cell.

[0005] In order to solve the above technical problems, the present application discloses a parameter fitting method based on RC fitting model of power battery in the first aspect, which comprises:

[0006] Obtaining the current, the observed voltage and the target state of charge in a certain discharge duration of the power battery cell during the discharge process, and determining the resistance fitting parameters and the capacitance fitting parameters required for the calculation of the power battery cell;

[0007] According to the resistance fitting parameters, the capacitance fitting parameters, the current, the discharge duration, the observed voltage and the target state of charge, an electric parameter analysis function is constructed, and based on the electric parameter analysis function and the first-order Thevenin model determined in advance, the RC fitting model corresponding to the power battery cell is established;

[0008] Based on the established RC fitting model corresponding to the power battery cell, the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge are analyzed to obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell.

[0009] As an optional implementation, in the first aspect of the present application, the method further comprises:

[0010] According to the determined fitting curve of the state of charge-open circuit voltage, the target open circuit voltage of the target state of charge is calculated, and a first voltage difference between the target open circuit voltage and the observed voltage is calculated.

[0011] The resistance fitting parameter and the capacitance fitting parameter are respectively set with corresponding initial estimated values, and the resistance fitting parameter with the initial estimated value, the capacitance fitting parameter with the initial estimated value, the current and the first voltage difference are analyzed based on the established RC fitting model corresponding to the power battery cell to obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell.

[0012] As an optional implementation, in the first aspect of the present application, the method further comprises:

[0013] The plurality of first states of charge of the power battery cell and the open circuit voltage corresponding to each first state of charge are obtained at intervals, and each first state of charge is collected after the power battery cell stops discharging for a preset duration.

[0014] Each first state of charge and the open circuit voltage corresponding to the first state of charge are fitted to obtain the fitting curve of the state of charge-open circuit voltage of the power battery cell.

[0015] As an optional implementation, in the first aspect of the present application, after the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge are analyzed based on the established RC fitting model corresponding to the power battery cell to obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell, the method further comprises:

[0016] The resistance fitting parameter and the capacitance fitting parameter are input into the first-order Thevenin model and the RC fitting model for analysis, and an analysis result output by the first-order Thevenin model and the RC fitting model is obtained as a fitting voltage of the power battery cell, wherein the fitting voltage of the power battery cell is used for evaluating a fitting condition of the fitting curve of the state of charge-open circuit voltage and / or for evaluating a fitting condition of the resistance fitting parameter and the capacitance fitting parameter.

[0017] As an optional implementation, in the first aspect of the present application, the method further comprises:

[0018] A second voltage difference between the fitting voltage and the observed voltage is calculated, and it is determined whether the second voltage difference is less than or equal to a preset voltage difference value;

[0019] When the determination result is yes, the calculated resistance fitting parameter and voltage fitting parameter are updated to be respectively set to corresponding initial estimated values of the resistance fitting parameter and the capacitance fitting parameter, and the operation of performing analysis on the resistance fitting parameter set with the initial estimated value, the capacitance fitting parameter set with the initial estimated value, the current and the first voltage difference based on the established RC fitting model of the power battery cell is re-executed to obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell.

[0020] As an optional implementation, in the first aspect of the present application, the method further comprises:

[0021] It is determined whether a correction operation needs to be performed on the fitting curve of the state of charge-open circuit voltage, when the determination result is yes, a power stable period of the power battery cell is monitored, and a plurality of second states of charge and an open circuit voltage corresponding to each second state of charge in the power stable period are collected;

[0022] Each second state of charge and the open circuit voltage corresponding to the second state of charge are fitted to obtain a fitting curve of the state of charge-open circuit voltage of the power battery cell as the required fitting curve of the state of charge-open circuit voltage.

[0023] As an optional implementation, in the first aspect of the present application, the determination of whether a correction operation needs to be performed on the fitting curve of the state of charge-open circuit voltage comprises:

[0024] A coincidence degree of the fitting curve of the state of charge-open circuit voltage and a preset fitting curve of the state of charge-open circuit voltage of the power battery cell is calculated, and it is determined whether the coincidence degree is less than or equal to a preset coincidence degree threshold value, when the determination result is no, it is determined that the correction operation needs to be performed on the fitting curve of the state of charge-open circuit voltage; or,

[0025] a second voltage difference between the fitting voltage and the observed voltage is calculated, and it is determined whether the second voltage difference is less than or equal to a preset voltage difference value, and when the determination result is no, it is determined that a correction operation needs to be performed on the fitting curve of the state of charge-open circuit voltage.

[0026] The second aspect of the present application discloses a parameter fitting device based on an RC fitting model of a power battery, and the device comprises:

[0027] The acquisition module is configured to acquire a current, an observed voltage and a target state of charge within a certain discharge duration during a discharge process of the power battery cell.

[0028] The determination module is configured to determine resistance fitting parameters and capacitance fitting parameters that need to be calculated for the power battery cell.

[0029] The establishment module is configured to construct an electrical parameter analysis function based on the resistance fitting parameters, the capacitance fitting parameters, the current, the discharge duration, the observed voltage and the target state of charge, and establish an RC fitting model corresponding to the power battery cell based on the electrical parameter analysis function and a first-order Thevenin model determined in advance.

[0030] The analysis module is configured to analyze the resistance fitting parameters, the capacitance fitting parameters, the current, the discharge duration, the observed voltage and the target state of charge based on the established RC fitting model corresponding to the power battery cell, and obtain the resistance fitting parameters and the capacitance fitting parameters of the power battery cell.

[0031] As an optional implementation, in the second aspect of the present application, the specific manner in which the analysis module analyzes the resistance fitting parameters, the capacitance fitting parameters, the current, the discharge duration, the observed voltage and the target state of charge based on the established RC fitting model corresponding to the power battery cell to obtain the resistance fitting parameters and the capacitance fitting parameters of the power battery cell comprises:

[0032] According to the determined fitting curve of the state of charge-open circuit voltage, a target open circuit voltage of the target state of charge is calculated, and a first voltage difference between the target open circuit voltage and the observed voltage is calculated.

[0033] Initial estimated values corresponding to the resistance fitting parameters and the capacitance fitting parameters are set respectively, and the resistance fitting parameters with the set initial estimated values, the capacitance fitting parameters with the set initial estimated values, the current and the first voltage difference are analyzed based on the established RC fitting model corresponding to the power battery cell to obtain the resistance fitting parameters and the capacitance fitting parameters of the power battery cell.

[0034] As an optional implementation, in the second aspect of the present application, the obtaining module is further configured to obtain a plurality of first states of charge of the power battery cell and an open circuit voltage corresponding to each of the first states of charge, each of the first states of charge being collected after the power battery cell stops discharging and then rests for a preset time length.

[0035] The device further comprises:

[0036] The first fitting module is configured to fit each of the first states of charge and the open circuit voltage corresponding to the first state of charge to obtain a fitting curve of the state of charge-open circuit voltage of the power battery cell.

[0037] As an optional implementation, in the second aspect of the present application, the analysis module is further configured to analyze the resistance fitting parameter, the capacitance fitting parameter, the current, the discharging time length, the observed voltage and the target state of charge based on the established RC fitting model corresponding to the power battery cell, and input the resistance fitting parameter and the capacitance fitting parameter into the first-order Thevenin model for analysis.

[0038] The obtaining module is further configured to obtain an analysis result output by the first-order Thevenin model as a fitting voltage of the power battery cell, wherein the fitting voltage of the power battery cell is used to evaluate the fitting of the fitting curve of the state of charge-open circuit voltage and / or is used to evaluate the fitting of the resistance fitting parameter and the capacitance fitting parameter.

[0039] As an optional implementation, in the second aspect of the present application, the device further comprises:

[0040] The calculating module is configured to calculate a second voltage difference between the fitting voltage and the observed voltage.

[0041] The first judging module is configured to judge whether the second voltage difference is less than or equal to a preset voltage difference value.

[0042] The updating module is configured to, when the first judging module judges that the answer is yes, update the calculated resistance fitting parameter and the voltage fitting parameter to be respectively set to initial estimated values of the resistance fitting parameter and the capacitance fitting parameter, and trigger the analysis module to re-execute the operation of analyzing the resistance fitting parameter set with the initial estimated value, the capacitance fitting parameter set with the initial estimated value, the current and the first voltage difference based on the established RC fitting model corresponding to the power battery cell to obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell.

[0043] As an optional implementation, in the second aspect of the present application, the device further comprises:

[0044] a second judging module, configured to judge whether a correction operation needs to be performed on the fitted curve of the state of charge versus open circuit voltage;

[0045] a monitoring module, configured to monitor the power battery cell in a stable period when the result of the judgment is yes;

[0046] the acquisition module is further configured to collect a plurality of second states of charge and an open circuit voltage corresponding to each of the second states of charge in the stable period;

[0047] a second fitting module, further configured to fit each of the second states of charge and the open circuit voltage corresponding to the second state of charge to obtain a fitted curve of the state of charge versus open circuit voltage of the power battery cell as the required fitted curve of the state of charge versus open circuit voltage.

[0048] As an optional implementation, in the second aspect of the present application, the manner in which the second judging module judges whether a correction operation needs to be performed on the fitted curve of the state of charge versus open circuit voltage specifically comprises:

[0049] calculating a coincidence degree of the fitted curve of the state of charge versus open circuit voltage and a preset fitted curve of the state of charge versus open circuit voltage of the power battery cell, and judging whether the coincidence degree is less than or equal to a preset coincidence degree threshold value, when the result of the judgment is no, it is determined that a correction operation needs to be performed on the fitted curve of the state of charge versus open circuit voltage; or,

[0050] calculating a second voltage difference between the fitted voltage and the observed voltage, and judging whether the second voltage difference is less than or equal to a preset voltage difference value, when the result of the judgment is no, it is determined that a correction operation needs to be performed on the fitted curve of the state of charge versus open circuit voltage.

[0051] The third aspect of the present application discloses another parameter fitting device based on an RC fitting model of a power battery, which comprises:

[0052] a memory storing executable program codes;

[0053] a processor coupled with the memory;

[0054] the processor invokes the executable program codes stored in the memory to perform part or all of the steps of any one of the parameter fitting methods based on the RC fitting model of the power battery disclosed in the first aspect of the present application.

[0055] The fourth aspect of the present application discloses a computer storage medium, the computer storage medium stores computer instructions, when the computer instructions are invoked, part or all steps of any one of the parameter fitting methods based on the RC fitting model of the power battery disclosed in the first aspect of the present application are executed.

[0056] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0057] In the embodiments of the present application, the current, the observed voltage and the target state of charge in a certain discharge duration in the discharge process of the power battery cell are acquired, and the resistance fitting parameter and the capacitance fitting parameter that need to be calculated for the power battery cell are determined; the RC fitting model corresponding to the power battery cell is established based on the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge, and the first-order Thevenin model determined in advance; the resistance fitting parameter with the initial estimated value set, the capacitance fitting parameter with the initial estimated value set, the current and the first voltage difference are analyzed based on the established RC fitting model corresponding to the power battery cell, and the resistance fitting parameter and the capacitance fitting parameter of the power battery cell are obtained. It can be seen that, by combining the observed voltage, the current and the state of charge in the discharge duration collected with the first-order Thevenin equivalent model to analyze and calculate the RC fitting parameter of the power battery cell, the calculation speed of the RC fitting parameter of the battery cell can be improved, the operation in the single-chip microcomputer is facilitated, and the program running lag phenomenon is reduced; and after multiple calculation iterations, the calculation accuracy of the RC fitting parameter is greatly improved, which provides good conditions for the subsequent development of the battery management system of the power battery. BRIEF DESCRIPTION OF DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0059] Figure 1 is a flowchart of a parameter fitting method based on an RC fitting model of a power battery disclosed by the embodiments of the present application;

[0060] Figure 2 is a flowchart of another parameter fitting method based on an RC fitting model of a power battery disclosed by the embodiments of the present application;

[0061] Figure 3 is a flowchart of a parameter fitting device based on an RC fitting model of a power battery disclosed by the embodiments of the present application

[0062] Figure 4 is another structure schematic diagram of a parameter fitting device based on a power battery RC fitting model disclosed by the embodiment of the application;

[0063] Figure 5 is another structure schematic diagram of a parameter fitting device based on a power battery RC fitting model disclosed by the embodiment of the application;

[0064] Figure 6 is a structure schematic diagram of a first-order Thevenin model disclosed by the embodiment of the application. DETAILED DESCRIPTION

[0065] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0066] The terms "first", "second", and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish different objects, not to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product or end including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or end.

[0067] In this paper, the term "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it independent or alternative to other embodiments. The skilled person in the art explicitly and implicitly understands that the embodiments described herein can be combined with other embodiments.

[0068] The present application discloses a parameter fitting method and device based on a power battery RC fitting model. By combining the observed voltage, current and state of charge collected within the discharge duration with the first-order Thevenin equivalent model, the RC fitting parameters of the power battery cell are analyzed and calculated, which can improve the calculation speed of the battery cell RC fitting parameters, facilitate transplantation to the single-chip microcomputer for operation, reduce the program running lag phenomenon, and greatly improve the calculation accuracy of the RC fitting parameters through multiple calculation iterations, providing good conditions for subsequent development of the battery management system of the power battery. The following will be described in detail.

[0069] Embodiment one

[0070] Please refer to Figure 1 , Figure 1 is a flowchart of a parameter fitting method based on a power battery RC fitting model according to an embodiment of the present application. Wherein, Figure 1 The method described can be applied to a parameter fitting device based on a power battery RC fitting model, wherein the parameter fitting device includes one or more of a parameter fitting server, a parameter fitting service device, and a parameter fitting service system. As Figure 1 The parameter fitting method based on the power battery RC fitting model can include the following operations:

[0071] 101, obtaining the current, the observed voltage and the target state of charge in a certain discharge duration of the power battery cell during the discharge process.

[0072] In the embodiment of the present application, the power battery is any battery that needs to be fitted with RC parameters.

[0073] 102, determining the resistance fitting parameter and the capacitance fitting parameter that need to be calculated for the power battery cell.

[0074] 103, constructing an electrical parameter analysis function according to the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge.

[0075] In the embodiment of the present application, optionally, the target open circuit voltage of the target state of charge is calculated according to the determined fitting curve of the state of charge-open circuit voltage, and the first voltage difference between the target open circuit voltage and the observed voltage is calculated, and the electrical parameter analysis function is constructed according to the first voltage difference, the discharge duration, the absolute value of the current, the resistance fitting parameter and the capacitance fitting parameter.

[0076] 104, establishing the RC fitting model corresponding to the power battery cell based on the electrical parameter analysis function and the first-order Thevenin model determined in advance.

[0077] In the embodiment of the present application, the electrical parameter analysis function is: V oc = P((R0R p C p ), V oc , i(k)(t(k)-t(k-1) )); and the first-order Thevenin model is as shown in Figure 6 Figure 6 is a structure diagram of a first-order Thevenin model according to an embodiment of the present application, R p is connected in parallel with C p , R p 0 is connected in parallel with R p ​In series; and, optionally, the RC fitting model is composed as follows:

[0078] V= V oc -i(k)R0-V p (k) ;

[0079] V p (k)= V p (k-i)M+(1-M)R p i(k);

[0080] M=e -m(t(k)-t(k-1)) ;

[0081] m=1 / R p C p ;

[0082] Wherein, R0 is the first sub parameter of the resistance fitting parameter of the power battery cell, R p is the second sub parameter of the resistance fitting parameter of the power battery cell, C p is the capacitance fitting parameter of the power battery cell, wherein, R0 is in series with R p and C p in parallel; V is the observed voltage of the power battery cell; V oc is the target open circuit voltage of the power battery cell; i(k) is the current of the power battery cell at discharge time k; V p (k) is the fitting voltage of R p and C p of the power battery cell at discharge time k; V p (k-i) is the fitting voltage of R p and C p of the power battery cell at discharge time k-1; t(k)-t(k-1) is the discharge time length.

[0083] 105、Based on the established RC fitting model corresponding to the power battery cell, the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge time length, the observed voltage and the target state of charge are analyzed to obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell.

[0084] In the embodiment of the application, the parameters in step 105 are analyzed to obtain the resistance fitting parameter and the capacitance fitting parameter, optionally, in combination with the lsqnonlin function.

[0085] It can be seen that the embodiment Figure 1The described parameter fitting method based on the RC fitting model of the power battery can analyze and calculate the RC fitting parameters of the power battery cell by combining the observed voltage, current and state of charge in the discharge duration with the first-order Thevenin equivalent model, which can improve the calculation speed of the RC fitting parameters of the battery cell, facilitate transplantation to the single-chip microcomputer for operation, reduce the program running lag phenomenon, and greatly improve the calculation accuracy of the RC fitting parameters through multiple calculation iterations, thereby providing good conditions for the subsequent development of the battery management system of the power battery.

[0086] In an optional embodiment, the resistance fitting parameter and the capacitance fitting parameter of the power battery cell are obtained by analyzing the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge based on the established RC fitting model corresponding to the power battery cell, including:

[0087] According to the determined fitting curve of the state of charge-open circuit voltage, the target open circuit voltage of the target state of charge is calculated, and the first voltage difference between the target open circuit voltage and the observed voltage is calculated.

[0088] The initial estimated values corresponding to the resistance fitting parameter and the capacitance fitting parameter are set respectively, and the resistance fitting parameter with the set initial estimated value, the capacitance fitting parameter with the set initial estimated value, the current and the first voltage difference are analyzed based on the established RC fitting model corresponding to the power battery cell, to obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell.

[0089] In the embodiment of the application, the resistance fitting parameter and the capacitance fitting parameter (R0, R p and C p ) are optionally set with corresponding upper and lower bounds, such as the lower bound [0, 0, 0] and the upper bound [1, 1, 10000000].

[0090] It can be seen that the optional embodiment can improve the calculation accuracy and efficiency of the open circuit voltage by combining the fitting curve of the state of charge-open circuit voltage, calculating the open circuit voltage of the observed state of charge of the power battery cell, and analyzing the voltage difference between the calculated open circuit voltage and the observed voltage, the initial estimated value of the parameter to be fitted and the observed current using the established RC fitting parameter model, so as to accurately and efficiently analyze the resistance and capacitance fitting parameters of the power battery cell.

[0091] In another optional embodiment, the method can further include the following steps:

[0092] The method can further include the following steps:

[0093] fitting the first state of charge and the open-circuit voltage corresponding to the first state of charge of each power battery cell to obtain a fitting curve of the state of charge-open-circuit voltage of the power battery cell.

[0094] In the optional embodiment, after obtaining the first state of charge and the corresponding open-circuit voltage of the power battery cell each time, the first state of charge and the corresponding open-circuit voltage of the power battery cell at the preset voltage after the power battery cell is discharged to the preset voltage and then is rested for the preset time length are continuously collected. It should be noted that the interval time length for collecting the state of charge each time can be equal or not equal. Further, when the first state of charge of the power battery cell is collected as 0, the collection of the first state of charge of the power battery cell is stopped.

[0095] In the optional embodiment, after obtaining all the first state of charge and the corresponding open-circuit voltage, the first state of charge and the corresponding open-circuit voltage are fitted based on Matlab and a polynomial equation of n order (such as 9 order) to obtain the fitting curve of the state of charge-open-circuit voltage of the power battery cell.

[0096] It can be seen that the fitting of the plurality of states of charge and the corresponding open-circuit voltage of the power battery cell obtained at intervals in the optional embodiment can obtain the accurate fitting curve of the state of charge-open-circuit voltage, which is beneficial to the subsequent efficient and accurate calculation of the open-circuit voltage corresponding to the state of charge.

[0097] In yet another optional embodiment, the method can further include the following steps:

[0098] determining whether a correction operation needs to be performed on the fitting curve of the state of charge-open-circuit voltage, when the determination result is yes, monitoring the power balance period of the power battery cell, and collecting a plurality of second states of charge and the open-circuit voltage corresponding to each second state of charge in the power balance period;

[0099] fitting each second state of charge and the open-circuit voltage corresponding to the second state of charge to obtain the fitting curve of the state of charge-open-circuit voltage of the power battery cell as the required fitting curve of the state of charge-open-circuit voltage.

[0100] In the optional embodiment, when the correction operation does not need to be performed on the fitting curve of the state of charge-open-circuit voltage, the current process is ended.

[0101] It can be seen that in the optional embodiment, when it is determined that the fitting curve of the state of charge-open-circuit voltage needs to be corrected, the state of charge and the corresponding open-circuit voltage of the power battery cell in the power balance period are collected for re-fitting, which is beneficial to obtaining the accurate and reliable fitting curve of the state of charge-open-circuit voltage, thereby being beneficial to the subsequent accurate acquisition of the open-circuit voltage, and further improving the analysis accuracy of the RC fitting parameters.

[0102] In the optional embodiment, optionally, the operation of judging whether the fitting curve of the state of charge-open circuit voltage needs to be corrected comprises:

[0103] calculating the coincidence degree of the fitting curve of the state of charge-open circuit voltage and the preset fitting curve of the state of charge-open circuit voltage of the power battery cell, and judging whether the coincidence degree is less than or equal to a preset coincidence degree threshold value, and when the result of the judgment is no, it is determined that the fitting curve of the state of charge-open circuit voltage needs to be corrected; or,

[0104] calculating a second voltage difference between the fitting voltage and the observed voltage, and judging whether the second voltage difference is less than or equal to a preset voltage difference value, and when the result of the judgment is no, it is determined that the fitting curve of the state of charge-open circuit voltage needs to be corrected.

[0105] It can be seen that the optional embodiment can also determine that the fitting curve of the state of charge-open circuit voltage needs to be corrected when the coincidence degree of the fitting curve of the state of charge-open circuit voltage and the preset fitting curve is small or the fitting voltage error is large, that is, the fitting curve of the state of charge-open circuit voltage needs to be re-fitted, which can improve the determination efficiency of the fitting curve of the state of charge-open circuit voltage.

[0106] Embodiment two

[0107] Please refer to Figure 2 , Figure 2 is another flowchart of the parameter fitting method based on the RC fitting model of the power battery disclosed in the embodiment of the application. Among them, Figure 2 The method described can be applied to a parameter fitting device based on the RC fitting model of the power battery, wherein the parameter fitting device comprises one or more of a parameter fitting server, a parameter fitting service equipment and a parameter fitting service system. As Figure 2 shown, the parameter fitting method based on the RC fitting model of the power battery can comprise the following operations:

[0108] 201, obtaining the current, observed voltage and target state of charge in a certain discharge duration of the power battery cell during discharge.

[0109] 202, determining the resistance fitting parameter and the capacitance fitting parameter that need to be calculated for the power battery cell.

[0110] 203, constructing an electric parameter analysis function according to the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge.

[0111] 204, establishing the RC fitting model corresponding to the power battery cell based on the electric parameter analysis function and the first-order Thevenin model determined in advance.

[0112] 205. Based on the established RC fitting model corresponding to the power battery cell, the resistance fitting parameters, capacitance fitting parameters, current, discharge duration, observed voltage and target state of charge are analyzed to obtain the resistance fitting parameters and capacitance fitting parameters of the power battery cell.

[0113] 206. Input the resistance fitting parameters and capacitance fitting parameters into the first-order Thevenin model and the RC fitting model for analysis, and obtain the analysis results output by the first-order Thevenin model and the RC fitting model as the fitting voltage of the power battery cell.

[0114] In this embodiment of the invention, the fitted voltage of the power battery cell is used to evaluate the fitting of the state-of-charge-open-circuit voltage fitting curve and / or to evaluate the fitting of the resistance fitting parameters and capacitance fitting parameters.

[0115] It should be noted that for other related descriptions of steps 201-205, please refer to the detailed description of steps 101-105 in Embodiment 1. These descriptions will not be repeated in this embodiment of the invention.

[0116] It is evident that implementation Figure 2 The described parameter fitting method based on the RC fitting model of a power battery can analyze and calculate the RC fitting parameters of the power battery cell by combining the observed voltage, current, and state of charge during the collected discharge time with a first-order Thevenin equivalent model. This improves the calculation speed of the battery cell RC fitting parameters, facilitates porting to a microcontroller for computation, and reduces program lag. Furthermore, through multiple calculation iterations, the calculation accuracy of the RC fitting parameters is greatly improved, providing favorable conditions for the subsequent development of the power battery's battery management system. In addition, after obtaining the RC fitting parameters, they are further substituted back into the first-order Thevenin model to obtain the fitting voltage of the power battery cell. This allows for accurate evaluation of the fitting condition of the state of charge-open circuit voltage curve and determination of whether further RC fitting parameters need to be fitted, thus obtaining more accurate fitting parameters.

[0117] In an optional embodiment, the method may further include the following steps:

[0118] Calculate the second voltage difference between the fitted voltage and the observed voltage, and determine whether the second voltage difference is less than or equal to the preset voltage difference value;

[0119] When the judgment result is yes, the calculated resistance fitting parameter and voltage fitting parameter are updated to set corresponding initial estimated values of the resistance fitting parameter and the capacitance fitting parameter, and the operation of analyzing the established RC fitting model of the power battery cell according to the set initial estimated value of the resistance fitting parameter, the set initial estimated value of the capacitance fitting parameter, the current and the first voltage difference is re-executed.

[0120] In the optional embodiment, when the secondary fitting is completed, the capacitance fitting parameter and the resistance fitting parameter of the secondary fitting can be taken as initial estimated values thereof to participate in the next fitting until the fitting times are greater than or equal to the preset fitting times or the fitted fitting parameters tend to be stable. Further, the parameter analysis function is set with a parameter allowed error value and a residual square.

[0121] It can be seen that, in the optional embodiment, after the fitting voltage of the power battery is obtained, the fitting voltage is further compared with the preset voltage difference value, if the fitting voltage is smaller, the RC fitting parameters obtained at this time are taken as initial estimated values thereof to participate in the next fitting, which can further improve the fitting accuracy of the RC fitting parameters of the power battery cell.

[0122] Embodiment three

[0123] Please refer to Figure 3 , Figure 3 is a structure schematic diagram of a parameter fitting device based on a power battery RC fitting model disclosed by the embodiment of the application, wherein the parameter fitting device comprises one or more of a parameter fitting server, a parameter fitting service device and a parameter fitting service system. As shown in Figure 3 , the device comprises:

[0124] The acquisition module 301 is configured to acquire the current, the observed voltage and the target state of charge in a certain discharge duration of the power battery cell in the discharge process.

[0125] The determination module 302 is configured to determine the resistance fitting parameter and the capacitance fitting parameter to be calculated by the power battery cell.

[0126] The establishment module 303 is configured to construct an electric parameter analysis function according to the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge, and establish the RC fitting model corresponding to the power battery cell based on the electric parameter analysis function and the first-order Thevenin model determined in advance.

[0127] The analysis module 304 is configured to analyze the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge based on the established RC fitting model corresponding to the power battery cell, and obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell.

[0128] It can be seen that the implementation Figure 3 The parameter fitting device based on the RC fitting model of the power battery can improve the calculation speed of the RC fitting parameters of the battery cell by analyzing and calculating the RC fitting parameters of the power battery cell based on the observed voltage, current and state of charge collected within the discharge duration and the first-order Thevenin equivalent model, facilitate transplantation into a single-chip microcomputer for operation, reduce program running lag phenomenon; and through multiple calculation iterations, the calculation accuracy of the RC fitting parameters is greatly improved, providing good conditions for subsequent development of the battery management system of the power battery.

[0129] In an optional embodiment, the analysis module 304 analyzes the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge based on the established RC fitting model corresponding to the power battery cell, and obtains the specific manner of the resistance fitting parameter and the capacitance fitting parameter of the power battery cell, which includes:

[0130] According to the determined fitting curve of the state of charge-open circuit voltage, the target open circuit voltage of the target state of charge is calculated, and the first voltage difference between the target open circuit voltage and the observed voltage is calculated;

[0131] The initial estimated value corresponding to the resistance fitting parameter and the capacitance fitting parameter is set respectively, and based on the established RC fitting model corresponding to the power battery cell, the resistance fitting parameter with the set initial estimated value, the capacitance fitting parameter with the set initial estimated value, the current and the first voltage difference are analyzed, and the resistance fitting parameter and the capacitance fitting parameter of the power battery cell are obtained.

[0132] It can be seen that the implementation Figure 3 The parameter fitting device based on the RC fitting model of the power battery can also calculate the open circuit voltage of the observed state of charge of the power battery cell in combination with the fitting curve of the state of charge-open circuit voltage, improve the calculation accuracy and efficiency of the open circuit voltage, and analyze the voltage difference between the calculated open circuit voltage and the observed voltage, the initial estimated value of the parameter to be fitted and the observed current using the established RC fitting parameter model, which can accurately and efficiently analyze the resistance and capacitance fitting parameters of the power battery cell.

[0133] In another optional embodiment, the acquisition module 301 is also used for acquiring a plurality of first states of charge of the power battery cell and the open circuit voltage corresponding to each first state of charge at intervals, each first state of charge being collected after the power battery cell stops discharging for a preset duration;

[0134] and as Figure 4 shown, the device further comprises:

[0135] The first fitting module 305 is configured to fit each first state of charge and the open-circuit voltage corresponding to the first state of charge to obtain a fitting curve of the state of charge-open-circuit voltage of the power battery cell.

[0136] It can be seen that, in the embodiments of the present application, Figure 4 The parameter fitting device based on the RC fitting model of the power battery described in the present application can fit the multiple states of charge and the corresponding open-circuit voltages of the power battery cell obtained at intervals, and can obtain an accurate fitting curve of the state of charge-open-circuit voltage, which is beneficial to subsequent efficient and accurate calculation of the open-circuit voltage corresponding to the state of charge.

[0137] In yet another optional embodiment, as shown in Figure 4 The analysis module 304 is further configured to, after obtaining the resistance fitting parameter and the capacitance fitting parameter of the power battery cell by analyzing the resistance fitting parameter, the capacitance fitting parameter, the current, the discharge duration, the observed voltage and the target state of charge based on the established RC fitting model corresponding to the power battery cell, input the resistance fitting parameter and the capacitance fitting parameter into the first-order Thevenin model and the RC fitting model for analysis.

[0138] The acquisition module 301 is further configured to acquire the analysis result output by the first-order Thevenin model and the RC fitting model as a fitting voltage of the power battery cell, wherein the fitting voltage of the power battery cell is used to evaluate the fitting situation of the fitting curve of the state of charge-open-circuit voltage and / or to evaluate the fitting situation of the resistance fitting parameter and the capacitance fitting parameter.

[0139] It can be seen that, in the embodiments of the present application, Figure 4 The parameter fitting device based on the RC fitting model of the power battery described in the present application can further input the RC fitting parameter back into the first-order Thevenin model after obtaining the RC fitting parameter to obtain the fitting voltage of the power battery cell, so as to accurately evaluate the fitting situation of the fitting curve of the state of charge-open-circuit voltage and determine whether the RC fitting parameter needs to be continuously fitted, thereby obtaining more accurate fitting parameters.

[0140] In yet another optional embodiment, as shown in Figure 4 The device further comprises:

[0141] The calculation module 306 is configured to calculate a second voltage difference between the fitting voltage and the observed voltage.

[0142] The first judgment module 307 is configured to judge whether the second voltage difference is less than or equal to a preset voltage difference value.

[0143] The updating module 308 is configured to, when the first judging module 307 judges that the result is yes, update the calculated resistance fitting parameter and the voltage fitting parameter to the resistance fitting parameter and the capacitance fitting parameter respectively set with corresponding initial estimated values, and trigger the analyzing module 304 to re-perform the operation of analyzing the established RC fitting model of the power battery cell according to the resistance fitting parameter set with the initial estimated value, the capacitance fitting parameter set with the initial estimated value, the current and the first voltage difference, to obtain the resistance fitting parameter and the capacitance fitting parameter of the power battery cell.

[0144] It can be seen that, in the embodiments Figure 4 The described parameter fitting device based on the RC fitting model of the power battery can further compare the fitting voltage of the power battery with a preset voltage difference value after obtaining the fitting voltage of the power battery, and if the fitting voltage is smaller than the preset voltage difference value, the RC fitting parameter obtained at this time is taken as the initial estimated value to participate in the next fitting, so that the fitting accuracy of the RC fitting parameter of the power battery cell can be further improved.

[0145] In yet another optional embodiment, as Figure 4 The device further comprises:

[0146] The second judging module 309 is configured to judge whether it is necessary to perform a correction operation on the fitting curve of the state of charge-open circuit voltage.

[0147] The monitoring module 310 is configured to monitor the power stable period of the power battery cell when the result of the judgment is yes.

[0148] The acquisition module 301 is further configured to acquire a plurality of second states of charge and the open circuit voltage corresponding to each second state of charge in the power stable period.

[0149] The second fitting module 311 is further configured to fit each second state of charge and the open circuit voltage corresponding to the second state of charge to obtain the fitting curve of the state of charge-open circuit voltage of the power battery cell as the required fitting curve of the state of charge-open circuit voltage.

[0150] It can be seen that, in the embodiments Figure 4 The described parameter fitting device based on the RC fitting model of the power battery can further re-fit the state of charge and the corresponding open circuit voltage of the power battery cell in the power stable period when it is judged that it is necessary to correct the fitting curve of the state of charge-open circuit voltage, which is beneficial to obtaining an accurate and reliable fitting curve of the state of charge-open circuit voltage, and thus is beneficial to subsequently obtaining an accurate open circuit voltage, and further improving the analysis accuracy of the RC fitting parameter.

[0151] In the optional embodiment, optionally, the second judging module 309 judges whether it is necessary to perform a correction operation on the fitting curve of the state of charge-open circuit voltage in the following manner:

[0152] calculate the coincidence degree of the fitted curve of the state of charge-open circuit voltage and the preset fitted curve of the state of charge-open circuit voltage of the power battery cell, and determine whether the coincidence degree is less than or equal to a preset coincidence degree threshold value, and when the determination result is no, it is determined that the fitted curve of the state of charge-open circuit voltage needs to be corrected; or

[0153] calculate a second voltage difference between the fitted voltage and the observed voltage, and determine whether the second voltage difference is less than or equal to a preset voltage difference value, and when the determination result is no, it is determined that the fitted curve of the state of charge-open circuit voltage needs to be corrected.

[0154] It can be seen that the implementation Figure 5 The described parameter fitting device based on the RC fitting model of the power battery can also determine that the fitted curve of the state of charge-open circuit voltage needs to be corrected when the coincidence degree of the fitted curve of the state of charge-open circuit voltage and the preset fitted curve is small or the obtained fitted voltage error is large, that is, the fitted curve of the state of charge-open circuit voltage needs to be refitted, which can improve the determination efficiency of the refitting of the fitted curve of the state of charge-open circuit voltage.

[0155] Embodiment four

[0156] Please refer to Figure 5 , Figure 5 is another structure diagram of the parameter fitting device based on the RC fitting model of the power battery disclosed by the embodiment of the application. As ​ shown, the device can include:

[0157] a memory 401 storing executable program codes;

[0158] a processor 402 coupled with the memory 401;

[0159] Further, it can also include an input interface 403 and an output interface 404 coupled with the processor 402;

[0160] The processor 402 calls the executable program codes stored in the memory 401 to execute part or all of the steps of the parameter fitting method based on the RC fitting model of the power battery disclosed by the embodiment one or the embodiment two of the application.

[0161] Embodiment five

[0162] The embodiment of the application discloses a computer storage medium, which stores computer instructions, and when the computer instructions are called, part or all of the steps of the parameter fitting method based on the RC fitting model of the power battery disclosed by the embodiment one or the embodiment two of the application are executed.

[0163] The apparatus embodiments described above are only illustrative, wherein the modules described as separate components can or can not be physically separated, and the components displayed as modules can or can not be physical modules, i.e., can be located in one place or distributed to multiple network modules. Part or all of the modules can be selected to achieve the purposes of the embodiments according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0164] Through the specific description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be realized by means of software and necessary general hardware platform, and of course can also be realized by hardware. Based on such understanding, the above technical solutions can be embodied in the form of a software product, which can be stored in a computer readable storage medium, including a Read-Only Memory (ROM), a Random Access Memory (RAM), a Programmable Read-Only Memory (PROM), an Erasable Programmable Read-Only Memory (EPROM), a One-time Programmable Read-Only Memory (OTPROM), an Electrically-Erasable Programmable Read-Only Memory (EEPROM), a Compact Disc Read-Only Memory (CD-ROM) or other optical disk storage, a magnetic disk storage, a magnetic tape storage, or any other computer readable medium that can be used to carry or store data.

[0165] Finally, it should be noted that: the parameter fitting method and device based on the RC fitting model of the power battery disclosed by the embodiments of the application are only the preferred embodiments of the application, and are used to illustrate the technical solutions of the application, but not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that; the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application.

Claims

1. A parameter fitting method based on a power battery RC fitting model, characterized in that, The method includes: The current, observed voltage, and target state of charge of the power battery cell are obtained within a certain discharge time during the discharge process, and the resistance fitting parameters and capacitance fitting parameters that need to be calculated for the power battery cell are determined. Based on the resistance fitting parameters, the capacitance fitting parameters, the current, the discharge duration, the observed voltage, and the target state of charge, an electrical parameter analysis function is constructed, and based on the electrical parameter analysis function and a pre-determined first-order Thevenin model, an RC fitting model corresponding to the power battery cell is established. Based on the established RC fitting model corresponding to the power battery cell, the resistance fitting parameters, the capacitance fitting parameters, the current, the discharge duration, the observed voltage, and the target state of charge are analyzed to obtain the resistance fitting parameters and the capacitance fitting parameters of the power battery cell. The lsqnonlin function is used to analyze the RC fitting model to obtain the resistance fitting parameters and the capacitance fitting parameters of the power battery cell. The resistance fitting parameters and the capacitance fitting parameters are set with corresponding upper and lower bounds. The electrical parameter analysis function is: V oc = P((R0R p C p ), V oc , i(k),(t(k)-t(k-1) )); The RC fitting model is composed as follows: V= V oc -i(k)R0-V p (k) ; V p (k)= V p (k-i)M+(1-M)R p i(k); M=e -m(t(k)-t(k-1)) ; m=1 / R p C p ; Wherein, R0 is the first sub-parameter of the resistance fitting parameters of the power battery cell, R p C is the second sub-parameter of the resistance fitting parameters of the power battery cell. p Here are the capacitance fitting parameters for the power battery cell, where R0 and the parallel R are... p C p Series connection; V is the observed voltage of the power battery cell; V oc V is the target open-circuit voltage of the power battery cell; i(k) is the current of the power battery cell at discharge time k; p (k) represents the R of the power battery cell at discharge time k. p With C p The fitted voltage; V p (ki) represents the R of the power battery cell at discharge time k-1. p With C p The fitted voltage is composed of t(k)-t(k-1), which is the discharge duration. Specifically, based on the established RC fitting model corresponding to the power battery cell, the resistance fitting parameters, capacitance fitting parameters, current, discharge duration, observed voltage, and target state of charge are analyzed to obtain the resistance fitting parameters and capacitance fitting parameters of the power battery cell, including: Based on the determined state of charge-open circuit voltage fitting curve, calculate the target open circuit voltage of the target state of charge, and calculate the first voltage difference between the target open circuit voltage and the observed voltage; Set corresponding initial estimates for the resistance fitting parameters and capacitance fitting parameters respectively, and analyze the resistance fitting parameters, capacitance fitting parameters, current and first voltage difference with the set initial estimates based on the established RC fitting model corresponding to the power battery cell to obtain the resistance fitting parameters and capacitance fitting parameters of the power battery cell. The method further includes: Determine whether a correction operation needs to be performed on the fitted curve of the state of charge-open circuit voltage. When the result is yes, monitor the power battery cell's charge stability period and collect multiple second states of charge and the open circuit voltage corresponding to each second state of charge during the charge stability period. For each second state of charge and the corresponding open-circuit voltage, a fitting curve of the state of charge-open-circuit voltage of the power battery cell is obtained, which is used as the required fitting curve of the state of charge-open-circuit voltage.

2. The parameter fitting method based on the RC fitting model of a power battery according to claim 1, characterized in that, The method further includes: Multiple first states of charge of the power battery cell and the open-circuit voltage corresponding to each first state of charge are acquired at intervals. Each first state of charge is collected after the power battery cell has been left to stand for a preset time after it stops discharging. By fitting each first state of charge and the corresponding open-circuit voltage, the state of charge-open-circuit voltage fitting curve of the power battery cell is obtained.

3. The parameter fitting method based on the RC fitting model of a power battery according to claim 1, characterized in that, After analyzing the resistance fitting parameters, capacitance fitting parameters, current, discharge duration, observed voltage, and target state of charge based on the established RC fitting model corresponding to the power battery cell to obtain the resistance fitting parameters and capacitance fitting parameters of the power battery cell, the method further includes: The resistance fitting parameters and the capacitance fitting parameters are input into the first-order Thevenin model and the RC fitting model for analysis, and the analysis results output by the first-order Thevenin model and the RC fitting model are obtained as the fitting voltage of the power battery cell. The fitting voltage of the power battery cell is used to evaluate the fitting of the state of charge-open circuit voltage fitting curve and / or to evaluate the fitting of the resistance fitting parameters and the capacitance fitting parameters.

4. The parameter fitting method based on the RC fitting model of a power battery according to claim 3, characterized in that, The method further includes: Calculate the second voltage difference between the fitted voltage and the observed voltage, and determine whether the second voltage difference is less than or equal to a preset voltage difference value; When the judgment result is yes, the calculated resistance fitting parameters and voltage fitting parameters are updated to the corresponding initial estimated values ​​of the resistance fitting parameters and capacitance fitting parameters, and the operation of analyzing the resistance fitting parameters, capacitance fitting parameters, current and the first voltage difference with the initial estimated values ​​based on the established RC fitting model corresponding to the power battery cell is re-executed to obtain the resistance fitting parameters and capacitance fitting parameters of the power battery cell.

5. The parameter fitting method based on the RC fitting model of a power battery according to any one of claims 1-4, characterized in that, The determination of whether to perform a correction operation on the fitted curve of the state of charge-open circuit voltage includes: Calculate the overlap degree between the fitted curve of the state of charge-open circuit voltage and the preset fitted curve of the state of charge-open circuit voltage of the power battery cell, and determine whether the overlap degree is less than or equal to a preset overlap degree threshold. If the determination result is no, it is determined that a correction operation needs to be performed on the fitted curve of the state of charge-open circuit voltage; or, Calculate the second voltage difference between the fitted voltage and the observed voltage, and determine whether the second voltage difference is less than or equal to a preset voltage difference value. If the determination result is no, it is determined that a correction operation needs to be performed on the fitted curve of the state of charge-open circuit voltage.

6. A parameter fitting device based on a power battery RC fitting model, characterized in that, The device is used to implement the parameter fitting method based on the RC fitting model of a power battery as described in any one of claims 1-5, and the device comprises: The acquisition module is used to acquire the current, observed voltage, and target state of charge of the power battery cell during a certain discharge time. The determination module is used to determine the resistance fitting parameters and capacitance fitting parameters that need to be calculated for the power battery cell; A module is established to construct an electrical parameter analysis function based on the resistance fitting parameters, the capacitance fitting parameters, the current, the discharge duration, the observed voltage, and the target state of charge, and to establish an RC fitting model corresponding to the power battery cell based on the electrical parameter analysis function and a pre-determined first-order Thevenin model. The analysis module is used to analyze the resistance fitting parameters, the capacitance fitting parameters, the current, the discharge duration, the observed voltage, and the target state of charge based on the established RC fitting model corresponding to the power battery cell, so as to obtain the resistance fitting parameters and the capacitance fitting parameters of the power battery cell.

7. A parameter fitting device based on a power battery RC fitting model, characterized in that, The device includes: Memory containing executable program code; A processor coupled to the memory; The processor calls the executable program code stored in the memory to execute the parameter fitting method based on the RC fitting model of the power battery as described in any one of claims 1-5.

8. A computer storage medium, characterized in that, The computer storage medium stores computer instructions, which, when invoked, execute the parameter fitting method based on the RC fitting model of the power battery as described in any one of claims 1-5.

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