A battery remaining power calculation model, construction method and system

Abstract

The present invention relates to the technical field of electric vehicles, and to a battery remaining capacity calculation model, comprising the following steps: obtaining the discharge capacity Q of a battery cell at different temperatures T and discharge rates C, and using the least squares method to calculate the function of the battery cell's Q with respect to T, C, and battery life (SOH); converting the discharge curve V-Q of the battery at different T and C obtained through experiments to obtain a V-SOC curve, using the least squares method to convert it into a functional relationship, and using the least squares method to express the parameters in the functional relationship as functions of T and C, ultimately obtaining the functional relationship of the discharge voltage V with respect to T, C, and the current remaining capacity percentage (SOC); based on the current T and C profile distribution, first integrating and calculating the battery remaining capacity at each C at the current T and SOC, and then using the C distribution to calculate the expected remaining capacity. The present invention solves the problem of large deviation in the calculation of the remaining capacity, has a low computational burden, and can be used on an on-board single-chip computer.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and in particular to a battery remaining power calculation model, construction method and system. Background Art

[0002] With the promotion and popularization of new energy vehicles, electric vehicles are gaining increasing attention. Lithium-ion batteries are widely used in electric vehicles due to their high energy density, light weight, and long lifespan. Battery management systems must constantly display and report the accurate remaining charge level so that the vehicle controller can accurately calculate range and control battery energy output.

[0003] Currently, commonly used methods for calculating remaining battery charge are simple and fail to account for driving habits and temperature fluctuations during battery use under varying ambient temperatures, resulting in significant deviations in remaining charge calculations. While some literature domestically and internationally has studied remaining battery charge and proposed several algorithmic models, these algorithms, due to the large memory usage and computational complexity, cannot be implemented on microcontrollers and, therefore, cannot be used in vehicles. Summary of the Invention

[0004] The purpose of the present invention is to provide a battery remaining power calculation model, construction method and system, aiming to solve the problems pointed out in the background technology.

[0005] The embodiment of the present invention is implemented by the following technical solution: A method for constructing a battery remaining power calculation model includes the following steps:

[0006] The relationship between discharge capacity Q and temperature T, discharge rate C, and battery life SOH is established: Based on the Q of the battery cell under T and C obtained from the experiment, the least squares method is used to calculate the function of the battery cell Q with respect to T, C, and SOH;

[0007] Establish the functional relationship between discharge voltage V and T, C, and the current remaining power percentage SOC: Convert the discharge curve VQ of the battery obtained from the experiment at different T and C into a V-SOC curve, use the least squares method to find the functional relationship of each V-SOC curve, and then use multiple least squares methods to express the parameters in the functional relationship as functions of T and C, and finally obtain the functional relationship of V with respect to T, C, and SOC;

[0008] Calculation of C probability distribution: Set up an arithmetic sequence C and a zero sequence of the same dimension as the arithmetic sequence C, called the C distribution sequence. Round the C collected each time during driving to the nearest value in the arithmetic sequence, and add one to the corresponding position in the C distribution sequence to obtain the C distribution sequence.

[0009] At each specific time interval or mileage interval, the C distribution sequence is divided by the sum of all elements in the C distribution sequence to obtain a single C probability distribution sequence. At the same time as obtaining the single C probability distribution sequence, the C probability distribution sequence is calculated using the first-order lag filtering method;

[0010] Remaining capacity calculation: Based on the functional relationship between V and T, C, and SOC, and the functional relationship between Q and T, C, and SOH, the remaining capacity of the battery cell at each C in the arithmetic progression under the current T, C, and SOC is obtained by integration. The point multiplication is then performed by the C probability distribution sequence to obtain the expected remaining capacity of the battery cell.

[0011] Calculation of the remaining power of the power battery pack: Multiply the expected remaining power of the battery cell by the number of battery cells in the power battery pack to obtain the expected remaining power of the power battery pack.

[0012] According to a preferred embodiment, the step of establishing the relationship between Q and T, C, and SOH further includes: continuously correcting the functional relationship during the charging process.

[0013] According to a preferred embodiment, using the least squares method to obtain the functional relationship of each V-SOC curve under specific T and C conditions includes: segmenting the curve according to its shape characteristics, solving the parameters in the functional relationship of each segment and performing curve fitting to obtain the functional relationship under specific T and C conditions.

[0014] According to a preferred embodiment, the step of establishing a functional relationship between the discharge voltage V and T, C, and the current remaining power percentage SOC also includes: by solving the parameters in each segment of the functional relationship and performing curve fitting, the remaining curve is divided and a voltage value is used to replace a segment of the voltage curve, and a block voltage value is calculated within an operating cycle. The remaining curve refers to the portion of the curve where the power has not been fully discharged.

[0015] According to a preferred embodiment, the remaining power calculation step further includes: according to the current battery T, the ambient temperature T out As well as the previous discharge temperature rise of the battery cell, the battery cell T of each SOC segment is preset, and the preset battery cell T is used to calculate the remaining power.

[0016] According to a preferred embodiment, the C probability distribution calculation step also includes: if the energy consumption per kilometer for M consecutive times is lower than the set value, each subsequent single-kilometer C distribution is not included in the C probability distribution series until the energy consumption per kilometer is higher than the set value.

[0017] The present invention also provides a battery remaining power calculation model construction system, comprising:

[0018] Module for establishing the relationship between discharge capacity Q and temperature T, discharge rate C, and battery life SOH: Based on the experimentally obtained Q of battery cells under different T and C conditions, the least squares method is used to calculate the function of the battery cell Q with respect to T, C, and SOH;

[0019] The module for establishing the functional relationship between the discharge voltage V and T, C, and the current remaining power percentage SOC: The discharge curve VQ of the battery obtained from the experiment at different T and C is converted into a V-SOC curve, and the functional relationship of each V-SOC is obtained using the least squares method. Then, the parameters in the functional relationship are expressed as functions of T and C through multiple least squares methods, and finally the functional relationship of V with respect to T, C, and SOC is obtained;

[0020] C probability distribution calculation module: Set C arithmetic sequence and a zero sequence of the same dimension as C arithmetic sequence, called C distribution sequence, round C collected each time during driving to the nearest value in the arithmetic sequence, and add 1 to the corresponding position in the C distribution sequence to obtain the C distribution sequence;

[0021] At each specific time interval or mileage interval, the C distribution sequence is divided by the sum of all elements in the C distribution sequence to obtain a single C probability distribution sequence. At the same time as obtaining the single C probability distribution sequence, the C probability distribution sequence is calculated using the first-order lag filtering method;

[0022] Remaining power calculation module: Based on the functional relationship between V and T, C, and SOC, and the functional relationship between Q and T, C, and SOH, the remaining power of the battery cell at each C in the arithmetic progression under the current T, C, and SOC is obtained by integration. The point multiplication is then performed by the C probability distribution sequence to obtain the expected remaining power of the battery cell.

[0023] Power battery pack remaining capacity calculation module: multiplies the expected remaining capacity of the battery cell by the number of battery cells in the power battery pack to obtain the expected remaining capacity of the power battery pack.

[0024] The present invention also provides a battery remaining power calculation model, which is constructed based on the battery remaining power calculation model construction method as described above.

[0025] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects: the present invention provides a battery remaining capacity calculation model, according to the discharge curve of the battery under various conditions, the discharge curve is expressed as the battery cell temperature T, the ambient temperature T out , discharge rate C probability distribution, battery life SOH, and discharge capacity Q, thereby calculating the expected remaining battery capacity under current conditions, solving the problem of large calculation deviation of the expected remaining capacity, with a small calculation burden, and can be used on the on-board microcontroller. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the flow of the model building method provided in Example 1 of the present invention;

[0027] Figure 2 and Figure 3 This is a diagram illustrating the relationship between voltage and battery capacity at different discharge rates provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0029] Example 1

[0030] The applicant's research has found that currently used methods for calculating remaining battery charge are simplistic and fail to account for driving habits and temperature fluctuations during use under varying ambient temperatures, resulting in significant deviations in remaining charge calculations. While some literature domestically and internationally has examined remaining battery charge and proposed several algorithmic models, these models, due to the excessive memory usage and computational complexity, have become inoperable on microcontrollers and, therefore, cannot be used in vehicles.

[0031] In view of the above shortcomings, the present invention provides a method for constructing a battery remaining power calculation model, which aims to solve the above shortcomings, and has small calculation deviation and light calculation burden, and can be used on vehicles.

[0032] refer to Figure 1 , the present invention adopts the following technical solutions:

[0033] A method for constructing a battery remaining capacity calculation model comprises the following steps:

[0034] The relationship between discharge capacity Q and temperature T, discharge rate C, and battery life SOH is established: Based on the Q of the battery cell under T and C obtained from the experiment, the least squares method is used to calculate the function of the battery cell's Q with respect to T, C, and SOH, and the functional relationship is continuously corrected during the charging process.

[0035] Establish the functional relationship between discharge voltage V and T, C, and the current remaining power percentage SOC: convert the discharge curve VQ of the battery obtained from the experiment at different T and C into a V-SOC curve, use the least squares method to find the functional relationship of each V-SOC curve, and then use multiple least squares methods to express the parameters in the functional relationship as functions of T and C, and finally obtain the functional relationship of V with respect to T, C, and SOC.

[0036] refer to Figure 2 and Figure 3 In this embodiment, a VQ curve under T and C is used as an example to illustrate the above steps. Specifically, based on the discharge curve of a full-life battery cell under specific T and C conditions, the discharge curve VQ is first converted into a V-SOC curve. Then, the least squares method is used to calculate the functional relationship of each V-SOC curve, including: dividing the VQ curve into three segments based on the curve shape: the first segment is a straight line segment from full charge to 52.5% discharge, the second segment is a concave segment from full charge to 20% discharge, and the third segment is a power function curve from 52.5% discharge to the discharge voltage end point of 3.2V.

[0037] In the curve calculation, the remaining curve is divided and a voltage value is used to replace a section of the voltage curve. A block voltage value is calculated within one operating cycle. The remaining curve refers to the curve portion where the power is not fully discharged. The above method can effectively reduce the calculation burden.

[0038] In addition, if the computational complexity of the functional relationship is large, the function is calculated every certain distance or every certain period of time.

[0039] Furthermore, the least squares method is used to calculate the straight line segment Medium parameters 、 , concave section Medium parameters 、 、 , power function curve Medium parameters 、 ,in The discharge end point is 3.2V; through the above method, the parameters are calculated 、 、 、 、 、 、 The values ​​of T and C are obtained at different times, and then the function of each parameter with respect to T and C is obtained by the least square method, for example ; Further, replace f and x in the equation with V and SOC, and integrate the three functions to obtain .

[0040] Furthermore, an arithmetic sequence C and a zero sequence of the same dimension as the arithmetic sequence C are set, which is called a C distribution sequence. The C collected each time during driving is rounded to the nearest value on the arithmetic sequence, and one is added to the corresponding position on the C distribution sequence to obtain a C distribution sequence. Specifically, the method includes: setting an arithmetic sequence N with n+1 elements according to the maximum C allowed for the entire vehicle, rounding the collected C to the nearest value on the arithmetic sequence, and then adding one to the corresponding element of the C distribution sequence; at each specific time interval or mileage interval, dividing the C distribution sequence by the sum of all elements on the C distribution sequence to obtain a single C probability distribution sequence. When the single C probability distribution sequence is obtained, a first-order lag filtering method is used to calculate the C probability distribution sequence.

[0041] In addition, for the case of a long downhill slope, if the energy consumption per kilometer for M consecutive times is lower than the set value, the C probability distribution per kilometer each time thereafter will not be included in the C probability distribution series until the energy consumption per kilometer is higher than the set value. In this embodiment, M is 5.

[0042] Furthermore, the remaining capacity calculation is performed, including: according to the functional relationship between V and T, C, SOC and the functional relationship between Q and T, C, SOH, integrating to obtain the remaining capacity of the battery cell at each C in the arithmetic progression under the current T, C, and SOC, and multiplying by the C probability distribution sequence to obtain the expected remaining capacity of the battery cell. Specifically: under the current T, calculate the discharge curve function corresponding to each element in the above C distribution sequence , and then take the expected value of the voltage according to the probability distribution of C V f = f (SOC), use the same method to calculate the battery discharge capacity Q = q (C). Integrate the discharge curve from the current SOC to 3.2V to obtain the battery cell capacity. Furthermore, multiply the number of battery cells in the power battery pack by the expected remaining capacity of each battery cell to obtain the expected remaining capacity of the power battery pack.

[0043] In addition, if the temperature of the battery cell rises during use, the battery cell temperature is adjusted according to the current battery T and the ambient temperature T. out As well as the previous battery cell discharge temperature rise, preset battery cells T in each SOC segment, and use the preset battery cells T to calculate the remaining power, so as to improve the accuracy of the calculation.

[0044] In summary, the technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects: the present invention provides a battery remaining capacity calculation model, according to the discharge curve of the battery under various conditions, the discharge curve is expressed as the battery cell temperature T, the ambient temperature T out, discharge rate C probability distribution, battery life SOH, and discharge capacity Q, thereby calculating the expected remaining battery capacity under current conditions, solving the problem of large calculation deviation of the expected remaining capacity, with a small calculation burden, and can be used on the on-board microcontroller.

[0045] An embodiment of the present invention further provides a system for constructing a battery remaining power calculation model, comprising:

[0046] Module for establishing the relationship between discharge capacity Q and temperature T, discharge rate C, and battery life SOH: Based on the experimentally obtained Q of battery cells under different T and C conditions, the least squares method is used to calculate the function of the battery cell Q with respect to T, C, and SOH;

[0047] The module for establishing the functional relationship between the discharge voltage V and T, C, and the current remaining power percentage SOC: The discharge curve VQ of the battery obtained from the experiment at different T and C is converted into a V-SOC curve, and the functional relationship of each V-SOC is obtained using the least squares method. Then, the parameters in the functional relationship are expressed as functions of T and C through multiple least squares methods, and finally the functional relationship of V with respect to T, C, and SOC is obtained;

[0048] C probability distribution calculation module: Set C arithmetic sequence and a zero sequence of the same dimension as C arithmetic sequence, called C distribution sequence, round C collected each time during driving to the nearest value in the arithmetic sequence, and add 1 to the corresponding position in the C distribution sequence to obtain the C distribution sequence;

[0049] At each specific time interval or mileage interval, the C distribution sequence is divided by the sum of all elements in the C distribution sequence to obtain a single C probability distribution sequence. At the same time as obtaining the single C probability distribution sequence, the C probability distribution sequence is calculated using the first-order lag filtering method;

[0050] Remaining power calculation module: Based on the functional relationship between V and T, C, and SOC, and the functional relationship between Q and T, C, and SOH, the remaining power of the battery cell at each C in the arithmetic progression under the current T, C, and SOC is obtained by integration. The point multiplication is then performed by the C probability distribution sequence to obtain the expected remaining power of the battery cell.

[0051] Power battery pack remaining capacity calculation module: multiplies the expected remaining capacity of the battery cell by the number of battery cells in the power battery pack to obtain the expected remaining capacity of the power battery pack.

[0052] An embodiment of the present invention further provides a battery remaining power calculation model, which is constructed based on the battery remaining power calculation model construction method as described above.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for constructing a battery remaining capacity calculation model, characterized in that: The steps include: The relationship between discharge capacity Q and temperature T, discharge rate C, and battery life SOH is established: Based on the Q of the battery cell under T and C obtained from the experiment, the least squares method is used to calculate the function of the battery cell Q with respect to T, C, and SOH; Establish the functional relationship between discharge voltage V and T, C, and the current remaining power percentage SOC: Convert the discharge curve VQ of the battery obtained from the experiment at different T and C into a V-SOC curve, use the least squares method to find the functional relationship of each V-SOC curve, and then use multiple least squares methods to express the parameters in the functional relationship as functions of T and C, and finally obtain the functional relationship of V with respect to T, C, and SOC; Calculation of C probability distribution: Set up an arithmetic sequence C and a zero sequence of the same dimension as the arithmetic sequence C, called the C distribution sequence. Round the C collected each time during driving to the nearest value in the arithmetic sequence, and add one to the corresponding position in the C distribution sequence to obtain the C distribution sequence. At each specific time interval or mileage interval, the C distribution sequence is divided by the sum of all elements in the C distribution sequence to obtain a single C probability distribution sequence. At the same time as obtaining the single C probability distribution sequence, the C probability distribution sequence is calculated using the first-order lag filtering method; Remaining capacity calculation: Based on the functional relationship between V and T, C, and SOC, and the functional relationship between Q and T, C, and SOH, the remaining capacity of the battery cell at each C in the arithmetic progression under the current T, C, and SOC is obtained by integration. The point multiplication is then performed by the C probability distribution sequence to obtain the expected remaining capacity of the battery cell. Calculation of the remaining power of the power battery pack: Multiply the expected remaining power of the battery cell by the number of battery cells in the power battery pack to obtain the expected remaining power of the power battery pack.

2. The method for constructing a battery remaining capacity calculation model according to claim 1, wherein: The step of establishing the relationship between Q and T, C, and SOH further includes: continuously correcting the functional relationship during the charging process.

3. The method for constructing a battery remaining capacity calculation model according to claim 2, wherein: The least square method is used to obtain the functional relationship of each V-SOC curve under specific T and C conditions, including: dividing the curve into segments according to its shape characteristics, solving the parameters in the functional relationship of each segment and performing curve fitting to obtain the functional relationship under specific T and C conditions.

4. The method for constructing a battery remaining capacity calculation model according to claim 3, wherein: The step of establishing a functional relationship between the discharge voltage V and T, C, and the current remaining power percentage SOC also includes: by solving the parameters in each segment of the functional relationship and performing curve fitting, dividing the remaining curve and using a voltage value to replace a segment of the voltage curve, and calculating a block voltage value within an operating cycle, the remaining curve refers to the curve portion where the power is not fully discharged.

5. The method for constructing a battery remaining capacity calculation model according to claim 4, wherein: The remaining power calculation step also includes: out As well as the previous discharge temperature rise of the battery cell, the battery cell T of each SOC segment is preset, and the preset battery cell T is used to calculate the remaining power.

6. The method for constructing a battery remaining capacity calculation model according to claim 5, wherein: The C probability distribution calculation step also includes: if the energy consumption per kilometer for M consecutive times is lower than the set value, each subsequent single-kilometer C distribution is not included in the C probability distribution series until the energy consumption per kilometer is higher than the set value.

7. A battery remaining power calculation model construction system, characterized in that: include: Module for establishing the relationship between discharge capacity Q and temperature T, discharge rate C, and battery life SOH: Based on the experimentally obtained Q of battery cells under different T and C conditions, the least squares method is used to calculate the function between T, C, and SOH of the battery cells; The module for establishing the functional relationship between the discharge voltage V and T, C, and the current remaining power percentage SOC: The discharge curve VQ of the battery obtained from the experiment at different T and C is converted into a V-SOC curve, and the functional relationship of each V-SOC is obtained using the least squares method. Then, the parameters in the functional relationship are expressed as functions of T and C through multiple least squares methods, and finally the functional relationship of V with respect to T, C, and SOC is obtained; C probability distribution calculation module: Set C arithmetic sequence and a zero sequence of the same dimension as C arithmetic sequence, called C distribution sequence, round C collected each time during driving to the nearest value in the arithmetic sequence, and add 1 to the corresponding position in the C distribution sequence to obtain the C distribution sequence; At each specific time interval or mileage interval, the C distribution sequence is divided by the sum of all elements in the C distribution sequence to obtain a single C probability distribution sequence. At the same time as obtaining the single C probability distribution sequence, the C probability distribution sequence is calculated using the first-order lag filtering method; Remaining power calculation module: Based on the functional relationship between V and T, C, and SOC, and the functional relationship between Q and T, C, and SOH, the remaining power of the battery cell at each C in the arithmetic progression under the current T, C, and SOC is obtained by integration. The point multiplication is then performed by the C probability distribution sequence to obtain the expected remaining power of the battery cell. Power battery pack remaining capacity calculation module: multiplies the expected remaining capacity of the battery cell by the number of battery cells in the power battery pack to obtain the expected remaining capacity of the power battery pack.

8. A battery remaining capacity calculation model, characterized in that: The method is constructed based on the method for constructing a battery remaining power calculation model according to any one of claims 1 to 6.

Images