Sodium ion battery fast charging control method and system

Abstract

The invention relates to the technical field of sodium ion battery fast charging, in particular to a sodium ion battery fast charging control method and system. The temperature polarization state of the sodium ion energy storage battery is judged by quantitatively analyzing the temperature difference of each point position of the sodium ion energy storage battery, a temperature polarization performance value is obtained accordingly, and the temperature distribution state can be comprehensively reflected; through drawing a voltage curve graph, identifying existing nonlinear characteristics, and carrying out quantitative analysis on the nonlinear characteristics to accurately measure voltage polarization deviation so as to obtain an electric polarization performance value; the voltage polarization state can be comprehensively reflected; comprehensive analysis is carried out through the temperature polarization representation value and the voltage polarization representation value to evaluate the fast charging strategy regulation and control requirement of the sodium ion energy storage battery, a charging current adjustment value is obtained through calculation, the charging current can be adjusted in real time, it is ensured that the fast charging strategy conforms to the current battery state, and after the charging current is adjusted, the fixed duration is maintained; the regulation and control value is evaluated again, and the effectiveness and safety of adjustment are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion battery fast charging, and in particular to a sodium ion battery fast charging control method and system. Background Art

[0002] Sodium-ion battery is a battery technology that uses sodium ions to embed and de-embed between positive and negative electrodes to achieve energy storage and release. Its working principle is similar to that of lithium-ion battery, but due to the abundant and widespread distribution of sodium resources and the low cost of collection; compared with lithium-ion batteries, sodium-ion batteries can meet the demand for fast charging at a lower cost; therefore, sodium-ion batteries have great potential as energy storage and fast charging batteries;

[0003] At present, the use of high-rate charging during the fast charging process of sodium-ion batteries can easily lead to accelerated aging of electrode materials and increased internal resistance, causing the battery to generate more Joule heat during high-rate charging, aggravating the temperature rise inside the battery, increasing the risk of thermal runaway, and causing problems such as reduced battery cycle life. Summary of the invention

[0004] The object of the present invention is to provide a sodium ion battery fast charging control method and system to solve the problems mentioned in the above background technology.

[0005] According to one aspect of the present invention, a sodium ion battery fast charging control method is provided, comprising the following steps:

[0006] S1: Obtain and store battery information by communicating with the sodium-ion battery and the sensor mounted on the sodium-ion energy storage battery; the specific battery information includes the temperature and voltage of different monitoring points of the sodium-ion energy storage battery;

[0007] S2: Based on the temperature of each point of the sodium-ion energy storage battery, a temperature difference quantitative analysis is performed to determine the temperature distribution state of the sodium-ion energy storage battery, and the temperature polarization performance value is obtained accordingly;

[0008] S3: Based on the voltage at each acquisition moment, a voltage change curve is plotted, and the voltage polarization deviation of the sodium ion energy storage battery is analyzed to obtain nonlinear characteristic parameters. The specific nonlinear characteristic parameters include voltage deviation value, curvature and inflection amplitude; the voltage deviation value ΔVj, curvature Kj and inflection amplitude Gb are normalized and their values ​​are taken, and the values ​​are calculated and analyzed by formula to obtain the voltage polarization performance value VG. The specific calculation formula is:

[0009]

[0010] Among them, β1, β2, and β3 are the set weight constants;

[0011] S4: Set each sodium-ion energy storage battery to correspond to a cycle coefficient, and record it as P N , where N∈ is a positive integer, N represents the total number of cycles; for example, P5 represents the cycle coefficient of the sodium ion energy storage battery after 5 cycles; the cycle coefficient P N , the temperature polarization performance value BF and the voltage polarization performance value VG are numerically calculated and analyzed to obtain the control value Y. The specific calculation formula is:

[0012] Y=P N ×(η1×BF+η2×VG)

[0013] Wherein η1 and η2 are respectively set weight constants; when the control value is greater than the maximum value in the set control range, the fast charging of the sodium ion energy storage battery is stopped; when the control value is within the set control range, S5 is executed; when the control value is less than the minimum value in the set control threshold, the current charging current is maintained;

[0014] S5: The current charging current is retrieved and recorded as A, and the current is calculated and analyzed with the control value Y to obtain the charging current adjustment value A'. The specific calculation formula is:

[0015] A'=A×(1-μ×Y)

[0016] Wherein μ is the set current conversion coefficient; it is adjusted according to the charging current adjustment value, maintained for a fixed time after adjustment, and returns to S2 until the updated control value is less than the minimum value in the set control range;

[0017] S6: Repeat S1-S5 until the sodium ion energy storage battery is fully charged;

[0018] S7: Obtain the historical cycle parameters of the sodium-ion energy storage battery, and perform cycle cumulative analysis based on the historical cycle parameters to obtain the cycle coefficient, and update it to S4.

[0019] Preferably, the specific process of cyclic cumulative analysis is:

[0020] 2-1: Obtain the historical cycle parameters of the sodium-ion energy storage battery. The specific historical cycle parameters include the number of cycles, as well as the internal resistance, charging capacitance and discharging capacitance after each cycle, and record them as Rn, and Where n = 1, 2, 3...N, N is a positive integer, N represents the total number of cycles, and n represents any one of the cycles; each sodium ion energy storage battery is set to have an initial capacity and initial internal resistance, and they are respectively recorded as C 0 and R 0；

[0021] 2-2: If the number of cycles N = 0, the cycle coefficient of the sodium ion energy storage battery is assigned to 1; if the number of cycles N≠0, execute 2-3;

[0022] 2-3: The internal resistance R after each cycle n , charging capacitor Discharge capacitor Initial capacitance C 0 and R 0 Perform normalization and take its value, and perform formula calculation and analysis on the value to obtain the battery performance value CR of this cycle n , the specific calculation formula is:

[0023]

[0024] Among them, α1, α2, and α3 are the set weight constants respectively; thus, the battery performance value after each cycle can be obtained;

[0025] 2-4: Construct a two-dimensional rectangular coordinate system with the number of cycles as the horizontal axis and the battery performance value as the vertical axis. Input the battery performance value into the coordinate axis according to its corresponding number of cycles, and record the position of the battery performance value in the coordinate axis as the performance point. Use a smooth curve to connect them in sequence to draw a battery performance value curve graph; analyze the performance changes based on the battery performance value curve graph to obtain the cycle coefficient.

[0026] Preferably, the specific process of analyzing the performance change according to the battery performance value curve is as follows:

[0027] Draw a tangent line at each performance point, use data fitting to calculate the tangent expression, and calculate the derivative of the tangent expression to obtain the performance derivative M. n ; The performance derivatives greater than zero are summed to obtain the performance increase value recorded as Z1, and the performance derivatives less than zero are summed and then the absolute value is taken to obtain the performance reduction degree recorded as Z2;

[0028] The battery performance value CR after each cycle n , performance derivative M n , the performance increase value Z1 and the performance reduction degree Z2 are numerically calculated and analyzed to obtain the cycle coefficient Y; the specific calculation formula is:

[0029]

[0030] Among them, σ1, σ2, σ3, and σ4 are the set weight constants respectively.

[0031] Preferably, the specific process of performing quantitative analysis of temperature differences based on the temperatures at various points of the sodium ion energy storage battery is as follows:

[0032] 4-1: Retrieve the temperature T ij of the sodium ion energy storage battery at each monitoring point, where i=1,2,3...I, I is a positive integer, I represents the total number of monitoring points in the sodium ion battery, and i represents the number of any monitoring point in the sodium ion battery; j=1,2,3...J, J is a positive integer, J represents the total number of acquisition moments, and j represents the number of any acquisition moment; mark the corresponding monitoring points in the two-dimensional image of the sodium ion energy storage battery to obtain a temperature distribution map of the sodium ion energy storage battery;

[0033] 4-2: Take the temperature of any two adjacent monitoring points and calculate the distance between them as H1; calculate the difference between the temperatures of the two adjacent monitoring points to obtain the temperature difference value as H2; normalize the distance H1 and the temperature difference H2 corresponding to the two adjacent monitoring points and take their values, and perform formulaic calculation and analysis on the values ​​to obtain the temperature gradient value Ha of the adjacent monitoring points. The specific calculation formula is:

[0034]

[0035] Where a1 and a2 are the set weight constants respectively; thus, the temperature gradient value between any two adjacent monitoring points in the temperature distribution of the sodium-ion energy storage battery can be obtained;

[0036] 4-3: Comprehensively analyze each temperature gradient value to obtain the temperature distribution value of the temperature distribution diagram, thereby obtaining the temperature distribution value at each acquisition time;

[0037] 4-4: Construct a two-dimensional rectangular coordinate system with time as the horizontal coordinate and temperature distribution value as the vertical coordinate, input the temperature distribution value into the coordinate system according to its corresponding acquisition time, and record the position of the temperature distribution value in the coordinate system as the distribution point, and use a smooth curve to connect each distribution point in sequence to obtain a temperature distribution value change curve graph; perform image analysis based on the temperature distribution value change curve graph to obtain the temperature polarization performance value.

[0038] Preferably, the specific process of comprehensively analyzing each temperature gradient value is as follows:

[0039] Compare and analyze each temperature gradient value with the set gradient interval. When the temperature gradient value is greater than the maximum value in the set gradient interval, a severe temperature polarization is accumulated; when the temperature gradient value is in the set gradient interval, a moderate temperature polarization is accumulated; when the temperature gradient value is less than the minimum value in the set gradient interval, a mild temperature polarization is accumulated; the accumulated numbers of severe temperature polarization, moderate temperature polarization and mild temperature polarization are counted respectively, and recorded as W1, W2, and W3 respectively; the temperature gradient values ​​corresponding to severe temperature polarization, moderate temperature polarization and mild temperature polarization are summed up to obtain severe polarization value, moderate polarization value and mild polarization value, and recorded as W4, W5 and W6 respectively;

[0040] The cumulative number of severe temperature polarization W1, the cumulative number of moderate temperature polarization W2, the cumulative number of mild temperature polarization W3, the severe polarization value W4, the moderate polarization value W5, the mild polarization value W6 and the temperature Tij are normalized and their values ​​are taken, and the values ​​are calculated and analyzed by formula to obtain the temperature distribution value TWj; the specific calculation formula is:

[0041]

[0042] Wherein, a3, a4, and a5 are respectively set weight constants, and a3>a4>a5>1.

[0043] Preferably, the specific process of performing image analysis based on the temperature distribution value change curve diagram is as follows:

[0044] Draw a tangent line of the curve at each distribution point, and calculate the slope of each tangent line as the distribution slope, so that the distribution slope corresponding to each distribution point can be obtained and recorded as Bj; sum up the slopes greater than zero to obtain the distribution increase degree and record it as F1, and sum up the distribution slopes less than zero and take the absolute value to obtain the distribution decrease degree and record it as F2;

[0045] The temperature distribution value TWj, distribution slope Bj, distribution increase degree and distribution decrease degree F2 are normalized and their values ​​are taken, and the values ​​are calculated and analyzed by formula to obtain the temperature polarization performance value BF; the specific calculation formula is:

[0046]

[0047] Among them, λ1, λ2, and λ3 are the set weight constants, is the mean of the distribution slopes of each distribution point.

[0048] Preferably, the specific process of analyzing the voltage polarization deviation of the sodium ion energy storage battery is:

[0049] 7-1: A two-dimensional time coordinate system is constructed with time as the horizontal coordinate and voltage as the vertical coordinate. The voltage is input into the coordinate system according to its corresponding acquisition time to draw a time-voltage curve. The specific function expression is: V(j); Set each charging current to correspond to a standard voltage linear graph, obtain the charging current of the sodium ion energy storage battery, and compare it with all the set currents to match the corresponding standard voltage linear graph. The specific function expression is: V 标准 (j); where j = 1, 2, 3, ... J, J is a positive integer, J represents the total number of acquisition moments, and j represents the number of any acquisition moment;

[0050] 7-2: Calculate the voltage deviation value ΔVj at each time point: ΔVj = V(j) - V 标准 (j);

[0051] 7-3: Calculate the curvature Kj of the curve at each time point: Where V" (j) is the second order derivative of voltage with respect to time, and V' (j) is the first order derivative of voltage with respect to time;

[0052] 7-4: Identify the inflection points in the time-voltage curve diagram, and quantify the inflection amplitude of the inflection points in the time-voltage curve diagram to obtain the inflection amplitude.

[0053] Preferably, the specific process of quantitatively analyzing the inflection amplitude of the inflection point in the time-voltage curve diagram is as follows:

[0054] The voltage corresponding to the time point before the inflection point is calculated by difference with the voltage corresponding to the inflection point to obtain the front inflection value, and the voltage corresponding to the time point after the inflection point is calculated by difference with the voltage corresponding to the inflection point to obtain the back inflection value; the front inflection value and the back inflection value are summed to calculate the amplitude corresponding to the inflection point; thus, the amplitude of each inflection point can be obtained, and compared with the set amplitude range for analysis:

[0055] When the amplitude is greater than the maximum value in the set amplitude range, the inflection point corresponding to the amplitude is recorded as a high inflection point; when the amplitude is within the set amplitude range, the inflection point corresponding to the amplitude is recorded as a moderate inflection point; when the amplitude is less than the minimum value in the set amplitude range, the inflection point corresponding to the amplitude is recorded as a mild inflection point; the number of high inflection points, moderate inflection points and mild inflection points is counted respectively, and they are recorded as G1, G2 and G3 respectively; the amplitudes corresponding to all inflection points are summed up to obtain the total amplitude value recorded as G4;

[0056] The number of high inflection points G1, the number of moderate inflection points G2, the number of mild inflection points G3 and the total amplitude G4 are numerically calculated and analyzed to obtain the inflection amplitude Gb. The specific calculation formula is:

[0057]

[0058] Wherein b1, b2, and b3 are respectively set weight constants, and b1>b2>b3>1.

[0059] Preferably, the nonlinear characteristic parameters include voltage deviation value, curvature and inflection amplitude; the historical cycle parameters include the number of cycles, and the internal resistance, charging capacitance and discharging capacitance after each cycle.

[0060] According to another aspect of the present invention, there is provided a sodium ion battery fast charging control system, the system comprising: a server, a dynamic monitoring module and a fast charging control module;

[0061] The server communicates with the sodium-ion battery and the sensors mounted on the sodium-ion battery to obtain and store battery information; the specific battery information includes the temperature and voltage of different monitoring points of the sodium-ion energy storage battery;

[0062] The dynamic monitoring module quantifies the temperature difference and voltage polarization deviation of the sodium-ion energy storage battery based on the electrical information to obtain the temperature polarization performance value and the voltage polarization performance value, and sends them to the fast charging control module;

[0063] The fast charging control module adjusts the fast charging strategy of the sodium ion energy storage battery based on the received temperature polarization performance value and voltage polarization performance value, specifically:

[0064] Step 1: Set a cycle coefficient for each sodium-ion energy storage battery and record it as P N , where N∈ is a positive integer, N represents the total number of cycles; for example, P5 represents the cycle coefficient of the sodium ion energy storage battery after 5 cycles; the cycle coefficient P N , the temperature polarization performance value BF and the voltage polarization performance value VG are numerically calculated and analyzed to obtain the control value Y. The specific calculation formula is:

[0065] Y=P N ×(η1×BF+η2×VG)

[0066] Wherein η1 and η2 are respectively set weight constants; when the control value is greater than the maximum value in the set control range, the fast charging of the sodium ion energy storage battery is stopped; when the control value is in the set control range, step 2 is executed; when the control value is less than the minimum value in the set control threshold, the current charging current is maintained;

[0067] Step 2: The current charging current is retrieved and recorded as A, and the charging current adjustment value A' is obtained by formulating and analyzing the current and the control value Y. The specific calculation formula is:

[0068] A'=A×(1-μ×Y)

[0069] Wherein μ is the set current conversion coefficient; it is adjusted according to the charging current adjustment value, maintained for a fixed time after adjustment, and returned to the dynamic monitoring module until the updated control value is less than the minimum value in the set control range;

[0070] Step 3: Repeat the dynamic monitoring module and the fast charging control module until the sodium ion energy storage battery is fully charged;

[0071] Step 4: Obtain the historical cycle parameters of the sodium-ion energy storage battery, and perform cumulative cycle analysis based on them to obtain the cycle coefficient, and update it to step 1.

[0072] Beneficial effects of the present invention:

[0073] 1. By quantitatively analyzing the temperature differences at various points of the sodium-ion energy storage battery, the temperature distribution state of the sodium-ion energy storage battery can be accurately determined, a temperature distribution diagram can be generated, and the temperature distribution can be intuitively displayed. The temperature polarization state of the sodium-ion energy storage battery can be determined based on the change trend of the temperature distribution diagram over time, and the temperature polarization performance value can be obtained accordingly, which can fully reflect the temperature distribution state and provide data reference for the dynamic adjustment of the fast charging strategy;

[0074] 2. By drawing a voltage curve, the voltage change of the sodium-ion energy storage battery during the charging process can be intuitively displayed. The nonlinear characteristics existing in the time-voltage curve can be identified and quantitatively analyzed to accurately measure the voltage polarization deviation and obtain the polarization performance value. It can fully reflect the voltage polarization state and provide data reference for the dynamic adjustment of the fast charging strategy;

[0075] 3. Comprehensively analyze the temperature polarization performance value and the voltage polarization performance value to evaluate the fast charging strategy regulation requirements of the sodium-ion energy storage battery, and calculate the charging current adjustment value accordingly, so as to adjust the charging current in real time to ensure that the fast charging strategy is in line with the current battery status and avoid safety problems or reduced charging efficiency caused by excessive or insufficient charging current; after adjusting the charging current, maintain a fixed duration and re-evaluate the regulation value to ensure the effectiveness and safety of the adjustment;

[0076] 4. By obtaining the historical cycle parameters of the sodium-ion energy storage battery, the performance degradation of the battery can be comprehensively evaluated, and the cycle coefficient can be obtained by numerical analysis. The calculated cycle coefficient is updated to step S4 to achieve dynamic evaluation of the battery status and continuous optimization of the fast charging strategy;

[0077] In summary, the present invention dynamically evaluates the status of the sodium-ion energy storage battery in multiple dimensions, and achieves precise adjustment and safe control of the fast charging strategy through data analysis and formula calculation, thereby ultimately improving the safety and efficiency of the fast charging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] The present invention will be further described below in conjunction with the accompanying drawings.

[0079] Figure 1 It is a schematic diagram of the method flow of the present invention

[0080] Figure 2 It is a schematic diagram of system module connection of the present invention. DETAILED DESCRIPTION

[0081] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0082] See also Figure 1 As shown, the present invention is a sodium ion battery fast charging control method, comprising the following steps:

[0083] S1: Communicate with the sodium ion battery and the sensor mounted on the sodium ion energy storage battery to obtain battery information and store it; the specific battery information includes temperature recorded as Tij and voltage Vj; wherein i = 1, 2, 3 ... I, I is a positive integer, I represents the total number of monitoring points in the sodium ion battery, and i represents the number of any monitoring point in the sodium ion battery; j = 1, 2, 3 ... J, J is a positive integer, J represents the total number of acquisition moments, and j represents the number of any acquisition moment; for example, the installation of the temperature sensor and the acquisition of temperature data are specifically manifested as: embedding multiple temperature sensors in the sodium ion battery to monitor the temperature of different points; it should be noted that sodium ion batteries, as energy storage batteries, are usually large in size, and during the fast charging process, it is easy to cause different heat generated at different positions, local temperature accumulation, and uneven temperature distribution; therefore, it is necessary to monitor the temperature of different positions of the sodium ion energy storage battery;

[0084] S2: Quantitative analysis of temperature differences is performed based on the temperatures of various points of the sodium-ion energy storage battery to determine the temperature distribution state of the sodium-ion energy storage battery, and the temperature polarization performance value is obtained accordingly; specifically:

[0085] The temperature Tij of the sodium ion energy storage battery at each monitoring point is retrieved, and the corresponding monitoring point of the two-dimensional image of the sodium ion energy storage battery is marked to obtain a temperature distribution diagram of the sodium ion energy storage battery; the temperature of two adjacent monitoring points is randomly selected, and the interval distance between them is calculated and recorded as H1; the temperature difference value of the two adjacent monitoring points is calculated by difference and recorded as H2; it should be noted that when the interval distance between the two adjacent monitoring points is smaller and the temperature difference value is larger, it means that the temperature polarization between the two adjacent monitoring points is more serious, and the temperature distribution of the sodium ion energy storage battery is more serious; the interval distance H1 and the temperature difference value H2 corresponding to the two adjacent monitoring points are normalized and their values ​​are taken, and the values ​​are calculated and analyzed by formula to obtain the temperature gradient value Ha of the adjacent monitoring points. The specific calculation formula is:

[0086]

[0087] Among them, a1 and a2 are respectively set weight constants, and their specific values ​​are set by the personnel in this field according to actual needs; for example, a1 is 2.117; a2 is 2.384; it can be seen from the formula that when the interval between two adjacent monitoring points is smaller, the temperature difference is larger, which means that the temperature polarization between the two adjacent monitoring points is more serious, and the temperature gradient value is larger; thus, the temperature gradient value between any two adjacent monitoring points in the temperature distribution of the sodium ion energy storage battery can be obtained; each temperature gradient value is compared and analyzed with the set gradient interval. When the temperature gradient value is greater than the maximum value in the set gradient interval, a severe temperature polarization is accumulated; when the temperature gradient value is in the set gradient interval When , a moderate temperature polarization is accumulated; when the temperature gradient value is less than the minimum value in the set gradient interval, a mild temperature polarization is accumulated; the accumulated numbers of severe temperature polarization, moderate temperature polarization and mild temperature polarization are counted respectively, and they are solved as W1, W2 and W3 respectively; the temperature gradient values ​​corresponding to severe temperature polarization, moderate temperature polarization and mild temperature polarization are summed up to obtain severe polarization value, moderate polarization value and mild polarization value, and they are recorded as W4, W5 and W6 respectively; the accumulated number of severe temperature polarization W1, the accumulated number of moderate temperature polarization W2, the accumulated number of mild temperature polarization W3, the severe polarization value W4, the moderate polarization value W5, the mild polarization value W6 and the temperature Tij are normalized and their values ​​are taken, and the values ​​are analyzed by formula calculation to obtain the temperature distribution value TWj; the specific calculation formula is:

[0088]

[0089] Among them, a3, a4, and a5 are respectively set weight constants, and a3>a4>a5>1; it can be seen from the formula that in the temperature distribution diagram of the sodium-ion energy storage battery, when the temperature gradient value is larger, it means that the uneven temperature distribution is more serious, and the temperature distribution value is larger; when the temperature of each monitoring point is larger, it means that more heat is generated during the charging process, and the temperature distribution value is larger;

[0090] A two-dimensional rectangular coordinate system is constructed with time as the horizontal coordinate and temperature distribution value as the vertical coordinate. The temperature distribution value is input into the coordinate system according to its corresponding collection time, and the position of the temperature distribution value in the coordinate system is recorded as the distribution point. A smooth curve is used to connect each distribution point in sequence to obtain a temperature distribution value change curve. A tangent line of the curve is drawn at each distribution point, and the slope of each tangent line is calculated and recorded as the distribution slope. Thus, the distribution slope corresponding to each distribution point is recorded as Bj. It should be noted that when the distribution slope is greater than zero, it means that the temperature distribution value at the distribution point shows an increasing trend. If the distribution slope is greater than zero, it means that the temperature distribution value at the distribution point shows an increasing trend. The larger the distribution slope is, the greater the increase is; when the distribution slope is less than zero, it means that the temperature distribution value at the distribution point shows a decreasing trend. If the distribution slope is smaller at this time, it means that the decreasing trend is greater; the slopes greater than zero are summed up to obtain the distribution increase degree, which is recorded as F1, and the distribution slopes less than zero are summed up and then the absolute value is taken to calculate the distribution reduction degree, which is recorded as F2; ​​the temperature distribution value TWj, the distribution slope Bj, the distribution increase degree and the distribution reduction degree F2 are normalized and their values ​​are taken, and the values ​​are analyzed by formula calculation to obtain the temperature polarization performance value BF; the specific calculation formula is:

[0091]

[0092] Among them, λ1, λ2, and λ3 are the set weight constants, is the mean value of the distribution slope of each distribution point; it can be seen from the formula that when the temperature distribution value is larger, it means that the temperature polarization of the sodium ion battery is more serious, and the temperature polarization performance value is larger; when the increasing trend of the temperature distribution value is larger (the larger F1 is), and the decreasing trend is smaller (the smaller F2 is), the temperature polarization performance value is larger; when the temperature distribution value at each acquisition moment is more unstable (the more the distribution slope Bj fluctuates), the temperature polarization performance value is larger;

[0093] By quantitatively analyzing the temperature differences at various points of the sodium-ion energy storage battery, the temperature distribution state of the sodium-ion energy storage battery can be accurately determined, a temperature distribution map can be generated, and the temperature distribution can be intuitively displayed. The temperature polarization state of the sodium-ion energy storage battery can be determined based on the changing trend of the temperature distribution map over time, and the temperature polarization performance value can be obtained accordingly, which can comprehensively reflect the temperature distribution state and provide data reference for the dynamic adjustment of the fast charging strategy.

[0094] S3: Based on the voltage at each acquisition moment, a voltage change curve is plotted, and the voltage polarization deviation of the sodium ion energy storage battery is analyzed to obtain nonlinear characteristic parameters. The specific nonlinear characteristic parameters include voltage deviation value, curvature and inflection amplitude; specifically:

[0095] A two-dimensional coordinate system is constructed with time as the horizontal axis and voltage as the vertical axis. The voltage is input into the coordinate system according to its corresponding acquisition time to draw a time-voltage curve. The specific function expression is: V(j); each charging current is set to correspond to a standard voltage linear graph, the charging current of the sodium ion energy storage battery is obtained, and it is compared with all the set currents to match the corresponding standard voltage linear graph. The specific function expression is: V 标准 (j) It should be noted that the standard voltage linear graph of sodium-ion energy storage batteries is usually closer to linear or non-polarized characteristics under ideal conditions, and is almost or rarely affected by polarization; under different charging currents, the degree of voltage polarization is different, so the nonlinear characteristics of the time-voltage curve are more obvious, and the specific nonlinear characteristics are increased curvature and the appearance of inflection points;

[0096] Calculate the voltage deviation value ΔVj at each time point: ΔVj = V(j) - V 标准 (j);

[0097] Calculate the curvature Kj of the curve at each time point (curvature describes the degree of bending of the curve at a certain point): Where V”(j) is the second-order derivative of voltage with respect to time, and V'(j) is the first-order derivative of voltage with respect to time. It should be noted that the larger the curvature, the stronger the nonlinear characteristics, that is, the larger the voltage polarization deviation;

[0098] Identify the inflection points in the time-voltage curve. It should be noted that the inflection point is the point where the curvature kj suddenly increases or decreases. The voltage change rate V'(j) can also be regarded as an inflection point when it undergoes a significant mutation. The voltage corresponding to the time point before the inflection point is calculated by difference with the voltage corresponding to the inflection point to obtain the front inflection value, and then the voltage corresponding to the time point after the inflection point is calculated by difference with the voltage corresponding to the inflection point to obtain the back inflection value. The front inflection value and the back inflection value are summed to calculate the amplitude corresponding to the inflection point. In this way, the amplitude of each inflection point can be obtained, and it is compared and analyzed with the set amplitude range. When the amplitude is greater than the maximum value in the set amplitude range, the inflection point is The inflection point corresponding to the amplitude is recorded as a high inflection point; when the amplitude is in the set amplitude range, the inflection point corresponding to the amplitude is recorded as a moderate inflection point; when the amplitude is less than the minimum value in the set amplitude range, the inflection point corresponding to the amplitude is recorded as a mild inflection point; the number of high inflection points, moderate inflection points and mild inflection points is counted respectively, and they are recorded as G1, G2 and G3 respectively; the amplitudes corresponding to all inflection points are summed up to obtain the total amplitude value recorded as G4; the number of high inflection points G1, the number of moderate inflection points G2, the number of mild inflection points G3 and the total amplitude value G4 are numerically calculated and analyzed to obtain the inflection amplitude Gb. The specific calculation formula is:

[0099]

[0100] Among them, b1, b2, and b3 are respectively the set weight constants, and b1>b2>b3>1; it can be seen from the formula that when there are more inflection points in the time-voltage curve image and the amplitude corresponding to the inflection point is larger, it means that the nonlinear characteristics of the curve are more obvious, and the inflection amplitude is larger; this calculation method is more accurate than the measurement method of directly finding the average value, because finding the average value will smooth the data and ignore an abnormally significant inflection point in the curve, but the voltage polarization performance displayed by such an inflection point is often more serious;

[0101] The voltage deviation value ΔVj, curvature Kj and inflection amplitude Gb are normalized and their values ​​are taken. The values ​​are calculated and analyzed by formula to obtain the voltage polarization performance value VG. The specific calculation formula is:

[0102]

[0103] Among them, β1, β2, and β3 are the set weight constants. It can be seen from the formula that when the voltage deviation value is larger, the curvature is larger, the inflection amplitude is larger, and the nonlinear characteristics of the time-voltage curve are more obvious, then the voltage polarization performance value is larger;

[0104] By drawing a voltage curve, the voltage changes of the sodium-ion energy storage battery during the charging process can be intuitively displayed. The existing nonlinear characteristics can be identified based on the time-voltage curve, and they can be quantitatively analyzed to accurately measure the voltage polarization deviation and obtain the electric polarization performance value. It can comprehensively reflect the voltage polarization state and provide data reference for the dynamic adjustment of the fast charging strategy.

[0105] S4: Set each sodium-ion energy storage battery to correspond to a cycle coefficient, and record it as P N , where N∈ is a positive integer, N represents the total number of cycles; for example, P5 represents the cycle coefficient of the sodium ion energy storage battery after 5 cycles; the cycle coefficient P N , the temperature polarization performance value BF and the voltage polarization performance value VG are numerically calculated and analyzed to obtain the control value Y. The specific calculation formula is:

[0106] Y=P N ×(η1×BF+η2×VG)

[0107] Wherein η1 and η2 are respectively set weight constants; when the control value is greater than the maximum value in the set control range, it indicates that the sodium ion energy storage battery has serious safety hazards, and continuing to charge will cause serious safety threats, so the fast charging of the sodium ion energy storage battery is stopped; when the control value is in the set control range, it indicates that the fast charging strategy at this time does not meet the current state of the sodium ion energy storage battery and needs to be adjusted, then S5 is executed;

[0108] When the control value is less than the minimum value of the set control threshold, it means that the fast charging state of the sodium-ion energy storage battery is good and no adjustment is required, and the current charging current can be maintained;

[0109] S5: The current charging current is retrieved and recorded as A, and the current is calculated and analyzed with the control value Y to obtain the charging current adjustment value A'. The specific calculation formula is:

[0110] A'=A×(1-μ×Y)

[0111] Wherein μ is the set current conversion coefficient; it is adjusted according to the charging current adjustment value, maintained for a fixed time after adjustment, and returns to S2 until the updated control value is less than the minimum value in the set control range;

[0112] S6: Repeat S1-S5 until the sodium ion energy storage battery is fully charged;

[0113] A comprehensive analysis is performed through the temperature polarization performance value and the voltage polarization performance value to evaluate the fast charging strategy control requirements of the sodium-ion energy storage battery, and the charging current adjustment value is calculated accordingly. The charging current can be adjusted in real time to ensure that the fast charging strategy is in line with the current battery status and avoid safety problems or reduced charging efficiency caused by excessive or insufficient charging current. After adjusting the charging current, maintain a fixed duration and evaluate the control value again to ensure the effectiveness and safety of the adjustment.

[0114] S7: Obtain the historical cycle parameters of the sodium ion energy storage battery. The specific historical cycle parameters include the number of cycles, as well as the internal resistance, charging capacitance, and discharging capacitance after each cycle, and record them as Rn, and Where n = 1, 2, 3...N, N is a positive integer, N represents the total number of cycles, and n represents any one of the cycles; each sodium ion energy storage battery is set to have an initial capacity and initial internal resistance, and they are respectively recorded as C 0 and R 0 ; It should be noted that a complete charge and discharge process is a cycle. Under normal conditions, the initial capacity of the sodium-ion energy storage battery is the largest and the initial internal resistance is the smallest; this is because the internal chemical reaction of the battery is most efficient at this time and the material is in the best state; as the number of cycles increases, the capacity gradually decays and the internal resistance gradually increases;

[0115] If the number of cycles N = 0, the cycle coefficient of the sodium ion energy storage battery is assigned a value of 1;

[0116] If the number of cycles N≠0, the cycle state of the sodium ion energy storage battery is cumulatively analyzed, specifically:

[0117] The internal resistance R after each cycle n , charging capacitor Discharge capacitor Initial capacitance C 0 and R 0 Perform normalization and take its value, and perform formula calculation and analysis on the value to obtain the battery performance value CR of this cycle n , the specific calculation formula is:

[0118]

[0119] Among them, α1, α2, and α3 are the set weight constants respectively; from the formula, it can be seen that when the internal resistance is larger, it means that the power performance of the battery decreases, and the heat generation is aggravated, then the battery performance value is smaller; when the discharge capacitance is closer to the initial capacitance, it means that its actual available capacity is larger, and the capacity attenuation of the sodium ion energy storage battery is smaller, then the battery performance value is larger; when the ratio of the discharge capacitance to the charging capacitance is larger, it means that the power loss of the sodium ion energy storage battery is smaller, then the battery performance value is larger; thus, the battery performance value CR after each cycle can be obtained n ;

[0120] A two-dimensional rectangular coordinate system is constructed with the number of cycles as the horizontal axis and the battery performance value as the vertical axis. The battery performance value is input into the coordinate axis according to its corresponding number of cycles, and the position of the battery performance value in the coordinate axis is recorded as a performance point. A smooth curve is used to connect and draw a battery performance value curve graph in sequence; a tangent line is drawn at each performance point, and a tangent expression is obtained by data fitting calculation. The tangent expression is derived and calculated to obtain a tangent derivative, which is recorded as a performance derivative M. n ; It should be noted that when the performance derivative is greater than zero, it indicates that the battery performance value has an increasing trend; when the performance derivative is less than zero, it indicates that the battery performance value has a decreasing trend; the performance derivatives greater than zero are summed up to obtain the performance increase value recorded as Z1, and the performance derivatives less than zero are summed up and then the absolute value is taken to calculate the performance reduction degree recorded as Z2;

[0121] The battery performance value CR after each cycle n , performance derivative M n , the performance increase value Z1 and the performance reduction degree Z2 are numerically calculated and analyzed to obtain the cycle coefficient Y; the specific calculation formula is:

[0122]

[0123] Among them, σ1, σ2, σ3, and σ4 are respectively set weight constants; from the formula, it can be seen that when the battery performance value decreases more, the more cycles are performed, and the battery performance value is smaller, it means that the sodium ion energy storage battery is more seriously attenuated, and the cycle coefficient is larger; the cycle coefficient is updated to S4;

[0124] By obtaining the historical cycle parameters of the sodium-ion energy storage battery, we can comprehensively evaluate the performance degradation of the battery, perform numerical analysis to obtain the cycle coefficient, and update the calculated cycle coefficient to the S4 step to achieve dynamic evaluation of the battery status and continuous optimization of the fast charging strategy.

[0125] See also Figure 2 As shown, the present invention is a sodium ion battery fast charging control system, the system includes: a server, a dynamic monitoring module, and a fast charging control module;

[0126] The server communicates with the sodium-ion battery and the sensors mounted on the sodium-ion battery to obtain and store battery information; the specific battery information includes the temperature and voltage of different monitoring points of the sodium-ion energy storage battery;

[0127] The dynamic monitoring module quantifies the temperature difference and voltage polarization deviation of the sodium-ion energy storage battery based on the electrical information to obtain the temperature polarization performance value and the voltage polarization performance value, and sends them to the fast charging control module;

[0128] The fast charging control module adjusts the fast charging strategy of the sodium ion energy storage battery based on the received temperature polarization performance value and voltage polarization performance value, specifically:

[0129] Step 1: Set a cycle coefficient for each sodium-ion energy storage battery and record it as P N , where N∈ is a positive integer, N represents the total number of cycles; for example, P5 represents the cycle coefficient of the sodium ion energy storage battery after 5 cycles; the cycle coefficient P N , the temperature polarization performance value BF and the voltage polarization performance value VG are numerically calculated and analyzed to obtain the control value Y. The specific calculation formula is:

[0130] Y=P N ×(η1×BF+η2×VG)

[0131] Wherein η1 and η2 are respectively set weight constants; when the control value is greater than the maximum value in the set control range, the fast charging of the sodium ion energy storage battery is stopped; when the control value is in the set control range, step 2 is executed; when the control value is less than the minimum value in the set control threshold, the current charging current is maintained;

[0132] Step 2: The current charging current is retrieved and recorded as A, and the charging current adjustment value A' is obtained by formulating and analyzing the current and the control value Y. The specific calculation formula is:

[0133] A'=A×(1-μ×Y)

[0134] Wherein μ is the set current conversion coefficient; it is adjusted according to the charging current adjustment value, maintained for a fixed time after adjustment, and returned to the dynamic monitoring module until the updated control value is less than the minimum value in the set control range;

[0135] Step 3: Repeat the dynamic monitoring module and the fast charging control module until the sodium ion energy storage battery is fully charged;

[0136] Step 4: Obtain the historical cycle parameters of the sodium-ion energy storage battery, and perform cumulative cycle analysis based on them to obtain the cycle coefficient, and update it to step 1.

[0137] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A sodium ion battery fast charging control method, characterized in that: The following steps are involved: S1: Obtain and store battery information by communicating with the sodium-ion battery and the sensor mounted on the sodium-ion energy storage battery; the specific battery information includes the temperature and voltage of different monitoring points of the sodium-ion energy storage battery; S2: Based on the temperature of each point of the sodium-ion energy storage battery, a temperature difference quantitative analysis is performed to determine the temperature distribution state of the sodium-ion energy storage battery, and the temperature polarization performance value is obtained accordingly; S3: Based on the voltage at each acquisition moment, a voltage change curve is plotted, and the voltage polarization deviation of the sodium ion energy storage battery is analyzed to obtain nonlinear characteristic parameters, and the voltage polarization performance value is obtained by comprehensive analysis; S4: Set a cycle coefficient for each sodium-ion energy storage battery, perform numerical calculation and analysis on the cycle coefficient, temperature polarization performance value and voltage polarization performance value to obtain a control value; when the control value is greater than the maximum value in the set control range, stop fast charging of the sodium-ion energy storage battery; when the control value is within the set control range, execute S5; when the control value is less than the minimum value in the set control threshold, maintain the current charging current; S5: Retrieve the current charging current, and perform a formula calculation and analysis on the current and the control value to obtain a charging current adjustment value; Adjust according to the charging current adjustment value, maintain a fixed time after adjustment, and return to S2 until the updated control value is less than the minimum value in the set control range; S6: Repeat S1-S5 until the sodium ion energy storage battery is fully charged; S7: Obtain the historical cycle parameters of the sodium-ion energy storage battery, and perform cycle cumulative analysis based on the historical cycle parameters to obtain the cycle coefficient, and update it to S4.

2. A sodium ion battery fast charging control method according to claim 1, characterized in that: The specific process of cyclic cumulative analysis is as follows: 2-1: Obtain the historical cycle parameters of the sodium-ion energy storage battery. The specific historical cycle parameters include the number of cycles, as well as the internal resistance, charging capacitance and discharging capacitance after each cycle; set an initial capacity and initial internal resistance for each sodium-ion energy storage battery; 2-2: If the number of cycles N = 0, the cycle coefficient of the sodium ion energy storage battery is assigned to 1; if the number of cycles N≠0, execute 2-3; 2-3: Normalize the internal resistance, charging capacitance, discharging capacitance, initial capacitance and after each cycle and take their values, and perform formula calculation and analysis on the values ​​to obtain the battery performance value of this cycle; thus, the battery performance value after each cycle can be obtained; 2-4: Construct a two-dimensional rectangular coordinate system with the number of cycles as the horizontal axis and the battery performance value as the vertical axis. Input the battery performance value into the coordinate axis according to its corresponding number of cycles, and record the position of the battery performance value in the coordinate axis as the performance point. Use a smooth curve to connect them in sequence to draw a battery performance value curve graph; analyze the performance changes based on the battery performance value curve graph to obtain the cycle coefficient.

3. A sodium ion battery fast charging control method according to claim 2, characterized in that: The specific process of analyzing performance changes based on the battery performance value curve is as follows: Draw a tangent line at each performance point, use data fitting to calculate the tangent expression, and take the derivative of the tangent expression to obtain the tangent derivative, which is recorded as the performance derivative; sum the performance derivatives greater than zero to obtain the performance increase, and sum the performance derivatives less than zero and take the absolute value to obtain the performance reduction degree, which is recorded as; The battery performance value, performance derivative, performance increase value and performance reduction degree after each cycle are numerically calculated and analyzed to obtain the cycle coefficient.

4. A sodium ion battery fast charging control method according to claim 1, characterized in that: The specific process of quantitative analysis of temperature differences based on the temperature of each point of the sodium-ion energy storage battery is as follows: 4-1: Retrieving the temperature of the sodium ion energy storage battery at each monitoring point, and marking the corresponding monitoring point on the two-dimensional image of the sodium ion energy storage battery to obtain a temperature distribution map of the sodium ion energy storage battery; 4-2: Take the temperature of any two adjacent monitoring points, calculate the interval distance between them, and calculate the difference between the temperatures of the two adjacent monitoring points to obtain the temperature difference value; normalize the interval distance and temperature difference value corresponding to the two adjacent monitoring points and take their values, and perform formula calculation and analysis on the values ​​to obtain the temperature gradient value of the adjacent monitoring points; thus, the temperature gradient value between any two adjacent monitoring points in the temperature distribution of the sodium-ion energy storage battery can be obtained; 4-3: Comprehensively analyze each temperature gradient value to obtain the temperature distribution value of the temperature distribution diagram, thereby obtaining the temperature distribution value at each acquisition time; 4-4: Construct a two-dimensional rectangular coordinate system with time as the horizontal coordinate and temperature distribution value as the vertical coordinate, input the temperature distribution value into the coordinate system according to its corresponding acquisition time, and record the position of the temperature distribution value in the coordinate system as the distribution point, and use a smooth curve to connect each distribution point in sequence to obtain a temperature distribution value change curve graph; perform image analysis based on the temperature distribution value change curve graph to obtain the temperature polarization performance value.

5. A sodium ion battery fast charging control method according to claim 4, characterized in that: The specific process of comprehensive analysis of each temperature gradient value is as follows: Compare and analyze each temperature gradient value with the set gradient interval. When the temperature gradient value is greater than the maximum value in the set gradient interval, a severe temperature polarization is accumulated; when the temperature gradient value is in the set gradient interval, a moderate temperature polarization is accumulated; when the temperature gradient value is less than the minimum value in the set gradient interval, a mild temperature polarization is accumulated; the accumulated numbers of severe temperature polarization, moderate temperature polarization and mild temperature polarization are counted respectively; the temperature gradient values ​​corresponding to severe temperature polarization, moderate temperature polarization and mild temperature polarization are summed up and calculated to obtain severe polarization value, moderate polarization value and mild polarization value respectively; The cumulative number of severe temperature polarization, the cumulative number of moderate temperature polarization, the cumulative number of mild temperature polarization, the severe polarization value, the moderate polarization value, the mild polarization value and the temperature are normalized and their numerical values ​​are taken, and the temperature distribution value is obtained by formulating and analyzing the numerical values.

6. A sodium ion battery fast charging control method according to claim 5, characterized in that: The specific process of image analysis based on the temperature distribution value change curve is as follows: Draw a tangent line of the curve at each distribution point, and calculate the slope of each tangent line as the distribution slope, thereby obtaining the distribution slope corresponding to each distribution point; sum up the slopes greater than zero to obtain the distribution increase degree, and sum up the distribution slopes less than zero and take the absolute value to calculate the distribution decrease degree; The temperature distribution value, distribution slope, distribution increase degree and distribution decrease degree are normalized and their numerical values ​​are taken, and the numerical values ​​are calculated and analyzed by formulas to obtain the temperature polarization performance value.

7. A sodium ion battery fast charging control method according to claim 1, characterized in that: The specific process of voltage polarization deviation analysis of sodium ion energy storage batteries is as follows: 7-1: A two-dimensional time coordinate system is constructed with time as the horizontal coordinate and voltage as the vertical coordinate. The voltage is input into the coordinate system according to its corresponding acquisition time to draw a time-voltage curve. The specific function expression is: V(j); Set each charging current to correspond to a standard voltage linear graph, obtain the charging current of the sodium ion energy storage battery, and compare it with all the set currents to match the corresponding standard voltage linear graph. The specific function expression is: V 标准 (j); where j = 1, 2, 3, ... J, J is a positive integer, J represents the total number of acquisition moments, and j represents the number of any acquisition moment; 7-2: Calculate the voltage deviation value ΔVj at each time point: ΔVj = V(j) - V 标准 (j); 7-3: Calculate the curvature Kj of the curve at each time point: Where V" (j) is the second order derivative of voltage with respect to time, and V' (j) is the first order derivative of voltage with respect to time; 7-4: Identify the inflection points in the time-voltage curve diagram, and quantify the inflection amplitude of the inflection points in the time-voltage curve diagram to obtain the inflection amplitude.

8. A sodium ion battery fast charging control method according to claim 7, characterized in that: The specific process of quantitatively analyzing the inflection amplitude of the inflection point in the time-voltage curve is as follows: The voltage corresponding to the time point before the inflection point is calculated by difference with the voltage corresponding to the inflection point to obtain the front inflection value, and the voltage corresponding to the time point after the inflection point is calculated by difference with the voltage corresponding to the inflection point to obtain the back inflection value; the front inflection value and the back inflection value are summed to calculate the amplitude corresponding to the inflection point; thus, the amplitude of each inflection point can be obtained, and compared with the set amplitude range for analysis: When the amplitude is greater than the maximum value in the set amplitude range, the inflection point corresponding to the amplitude is recorded as a high inflection point; when the amplitude is within the set amplitude range, the inflection point corresponding to the amplitude is recorded as a moderate inflection point; when the amplitude is less than the minimum value in the set amplitude range, the inflection point corresponding to the amplitude is recorded as a slight inflection point; The number of high inflection points, medium inflection points and slight inflection points is counted respectively, and the amplitudes corresponding to all inflection points are summed up to obtain the total amplitude value; The number of high inflection points, the number of moderate inflection points, the number of mild inflection points and the total amplitude are numerically calculated and analyzed to obtain the inflection amplitude.

9. A sodium ion battery fast charging control method according to claim 1, characterized in that: The nonlinear characteristic parameters include voltage deviation value, curvature and inflection amplitude; the historical cycle parameters include the number of cycles, as well as the internal resistance, charging capacitance and discharging capacitance after each cycle.

10. A sodium ion battery fast charging control system, characterized in that A sodium ion battery fast charging control method as described in any one of claims 1 to 9, the system comprising: a server, a dynamic monitoring module and a fast charging control module; The server communicates with the sodium-ion battery and the sensors mounted on the sodium-ion battery to obtain and store battery information; the specific battery information includes the temperature and voltage of different monitoring points of the sodium-ion energy storage battery; The dynamic monitoring module quantifies the temperature difference and voltage polarization deviation of the sodium-ion energy storage battery based on the electrical information to obtain the temperature polarization performance value and the voltage polarization performance value, and sends them to the fast charging control module; The fast charging control module adjusts the fast charging strategy of the sodium ion energy storage battery based on the received temperature polarization performance value and voltage polarization performance value, specifically: Step 1: Set a cycle coefficient for each sodium-ion energy storage battery, perform numerical calculation and analysis on the cycle coefficient, temperature polarization performance value and voltage polarization performance value to obtain a control value; when the control value is greater than the maximum value in the set control range, stop fast charging of the sodium-ion energy storage battery; when the control value is within the set control range, execute step 2; when the control value is less than the minimum value in the set control threshold, maintain the current charging current; Step 2: retrieve the current charging current, and perform a formula calculation and analysis on it and the control value to obtain a charging current adjustment value; make adjustments based on the charging current adjustment value, maintain a fixed time after adjustment, and return to the dynamic monitoring module until the updated control value is less than the minimum value in the set control range; Step 3: Repeat the dynamic monitoring module and the fast charging control module until the sodium ion energy storage battery is fully charged; Step 4: Obtain the historical cycle parameters of the sodium-ion energy storage battery, and perform cumulative cycle analysis based on them to obtain the cycle coefficient, and update it to step 1.

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