CN111398834A - A real-time estimation system and estimation method for liquid metal battery SoC - Google Patents

Abstract

The invention discloses a real-time estimation system and estimation method for a liquid metal battery SoC. First, the voltage-capacitance characteristic curves of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process are obtained, and the liquid metal battery is obtained by calculation. Then, according to the collected working current value of the liquid metal battery, use the V-SoC curve data of the liquid metal battery to obtain the V-SoC curve corresponding to the working current; finally, use the terminal voltage value of the liquid metal battery , obtain the SoC value of the liquid metal battery; the present invention obtains the V-SoC curves of several liquid metal batteries under different charge and discharge currents, which effectively improves the accuracy of the estimation result and reduces the result error; The current value and terminal voltage value are used to obtain the SoC value of the liquid metal battery. The estimation process is simple, the calculation load is low, the results can be obtained quickly, and it has good real-time performance, which can meet the SoC estimation of liquid metal batteries under different current states.

Description

A real-time estimation system and estimation method for liquid metal battery SoC

technical field

The invention belongs to the technical field of battery management, and in particular relates to a real-time estimation system and estimation method for a liquid metal battery SoC.

Background technique

Liquid metal battery is a new type of chemical battery with application prospects, which uses medium and low temperature molten salt as electrolyte, and uses molten metal as the positive and negative electrode materials of the battery. Liquid metal batteries have many advantages. First, liquid metal batteries have excellent kinetic transmission characteristics, and have high rate and high current charge and discharge capabilities; secondly, liquid metal batteries have super overload capacity, which will not cause harm to the battery beyond the current range. ; The electrode and electrolyte materials of liquid metal batteries are widely sourced and inexpensive, and the cost of the battery is very low, which can meet the low-cost demand of grid energy storage; finally, the electrode material does not have any internal stress change during the charging and discharging process of the liquid metal battery, so the liquid metal The battery has an extremely long theoretical cycle life. All in all, because liquid metal batteries have the advantages of safety and efficiency, high current charging and discharging capability, and long life, they are suitable for application in grid energy storage.

Since the working voltage of the liquid metal battery is low, the discharge voltage during normal operation is below 0.8V, so when the liquid metal battery is applied to the grid energy storage, it needs to be connected in series and parallel to form a battery pack to meet the voltage and capacity requirements. During the actual use of the battery pack, the charging and discharging performance and various parameters of the single battery will be different for various reasons, which will greatly affect the efficiency and safety of the entire system. The difference is getting bigger and bigger, forming a vicious circle. Therefore, it is very necessary to control the energy balance of the battery pack. The battery management system with battery balance technology is used to control the energy balance of the battery pack, thereby improving the service life and charge-discharge performance of the battery pack.

There are various basis for judging the energy balance control of the battery pack. Compared with other battery parameters as the judgment basis, it is more efficient and accurate to use the SoC of the battery as the judgment basis for the balancing result. However, the battery SoC cannot be measured directly, and can only be estimated by parameters such as battery terminal voltage, charge and discharge current, and internal resistance. Therefore, using a good SoC estimation method is an important prerequisite for battery pack balance.

Common battery SoC estimation methods include open-circuit voltage method, ampere-hour integration method, internal resistance method, and Kalman filter. The open circuit voltage method is the simplest and fastest SoC estimation method, but the open circuit voltage method can only measure the open circuit voltage when the battery is in a stable state and the external circuit current is zero, and is not suitable for real-time estimation of liquid metal battery SoCs. The ampere-hour integration method is the most widely used SoC estimation technology in battery management systems, but the accumulated error caused by the current measurement error is difficult to eliminate. The fluctuation of the working current will cause the change of the battery capacity, thus aggravating the estimation error of the liquid metal battery SoC. The internal resistance law uses the relationship between the internal resistance of the battery and the SoC to estimate the battery SoC, but the internal resistance of the liquid metal battery is generally small, basically at the milliohm level. estimate. The Kalman filter algorithm and derivative algorithms can estimate the battery SoC value more accurately, but due to its complex algorithm and unsatisfactory real-time performance, it is not suitable for the real-time estimation of liquid metal battery SoC.

SUMMARY OF THE INVENTION

Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a real-time estimation system and estimation method for liquid metal battery SoC, so as to solve the technical problems that the estimation process of the prior SoC estimation technology is complicated and the result error is large.

For achieving the above object, the technical scheme of the present invention is:

The present invention provides a real-time estimation method for liquid metal battery SoC, which is characterized by comprising the following steps:

Step 1. Obtain the voltage-capacitance characteristic curves of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process, and calculate the V-SoC curve data of the liquid metal battery;

Step 2, sampling the real-time data of the liquid metal battery to obtain the working current value and terminal voltage value of the liquid metal battery;

Step 3. According to the collected working current value of the liquid metal battery, use the V-SoC curve data of the liquid metal battery to obtain the V-SoC curve corresponding to the working current;

Step 4: According to the collected terminal voltage value of the liquid metal battery, in the V-SoC curve corresponding to the operating current obtained in step 3, obtain the SoC value of the liquid metal battery.

Further, in step 1, using the liquid metal battery experimental platform, through multiple sets of constant current charging and discharging experiments under different charge and discharge current values, during the constant current charge and discharge process, the voltage of the liquid metal battery under different charge and discharge currents - Capacitance characteristic curve;

The liquid metal battery experimental platform includes a computer and a battery tester. The computer is used to input the test plan to the battery tester, and the battery tester is used to collect data on the liquid metal battery and store the collected data information on the computer.

Further, in step 1, according to the voltage-capacitance characteristic curve of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process, the V-capacitance of the liquid metal battery is obtained by calculating the ratio with the battery capacity of the liquid metal battery. SoC curve data.

Further, in step 2, the terminal voltage acquisition module and the current acquisition module are connected to the liquid metal battery by a four-terminal method, and the liquid metal battery is used for real-time data sampling.

Further, in step 3, the collected working current of the liquid metal battery and the charging and discharging current selected by the liquid metal battery in the constant current charging and discharging process in step 1 are searched in a table;

If the collected working current of the liquid metal battery is consistent with a certain charge and discharge current selected during the constant current charge and discharge process, the V-SoC curve under the charge and discharge current is selected to obtain the V-SoC curve corresponding to the working current;

If the collected working current of the liquid metal battery is inconsistent with any charge and discharge current selected during the constant current charge and discharge process, select two current values adjacent to the collected working current of the liquid metal battery and the corresponding V- The SoC curve is calculated by interpolation method to obtain the V-SoC curve corresponding to the operating current value.

Further, when using the interpolation method to calculate the V-SoC curve corresponding to the working current value, the calculation formula is as follows:

Among them, V _x is the battery terminal voltage when SoC=x under the working current; I is the currently collected working current value, I ₁ and I ₂ are the current values adjacent to the collected working current of the liquid metal battery; V _x2 and V _x1 are the battery terminal voltages corresponding to the two V-SoC curves when SoC=x at the current value adjacent to the collected working current of the liquid metal battery, respectively.

Further, in step 4, the collected terminal voltage value of the liquid metal battery and the V-SoC curve of the corresponding operating current obtained in step 3 are looked up in a table;

If there is the same voltage value in the V-SoC curve corresponding to the working current, the corresponding SoC value in the curve is directly used as the SoC value of the liquid metal battery; if there is no same voltage value in the V-SoC curve corresponding to the working current , then the cubic spline interpolation method is used to calculate the SoC of the liquid metal battery.

Further, the calculation formula of the cubic spline interpolation method is as follows:

h _i =x _i -x _i-1 (2)

λ _i =1-μ _i (4)

Among them, x _i is the voltage value at the middle terminal of the V-SoC curve, _yi is the SoC value in the V-SoC curve, _{hi is the voltage step size of the adjacent terminal, μ i and λ i are constants} , and S(x) is the value in [ The cubic polynomial on x _i-1 , x _i ], M is the second derivative of S(x), and x is the terminal voltage value to be interpolated;

In formula (2)-formula (5), i=1,2,3,...,n-1;

In formula (6), i=1,2,3,...,n, x _i-1 ≤x≤x _i ;

Simultaneously solve n-1 formulas (5) to obtain the value of _Mi ; substitute the value of _Mi into formula (6) to obtain the cubic spline function S(x); The terminal voltage value is substituted into the cubic spline function to obtain the estimated value of the liquid metal battery SoC.

The present invention also provides a real-time estimation system for liquid metal battery SoC, comprising a characteristic data determination unit, a data acquisition unit and a data estimation unit;

The characteristic data determination unit is used to obtain the voltage-capacitance characteristic curves of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process, and to calculate the V-SoC curve data of the liquid metal battery;

The data acquisition unit is used for real-time data sampling of the liquid metal battery to obtain the working current value and terminal voltage value of the liquid metal battery;

The data estimation part is used for estimating the real-time SoC value of the liquid metal battery according to the collected working current value of the liquid metal battery.

Compared with the prior art, the beneficial effects of the present invention are:

The invention provides a real-time estimation method for liquid metal battery SoC. By conducting a research experiment on the constant current charge and discharge characteristics of the liquid metal battery under different charge and discharge currents, different charging and discharging processes of the liquid metal battery during the constant current charge and discharge process are obtained. The relationship curve between voltage and capacity under the current, and then calculate the V-SoC curve under different charge and discharge currents of several liquid metal batteries, and then obtain the V-SoC curve corresponding to the working current according to the collected working current value, and then according to the collected working current value. terminal voltage value, and finally the SoC value of the liquid metal battery is obtained; in the present invention, the relationship curve between the voltage and the SoC of the liquid metal battery in the charging state is used, which gradually increases with the increase of the charging current, and the relationship curve between the voltage and the SoC in the discharging state is used. As the discharge current increases, it gradually decreases; for the relationship between the voltage and SoC at a certain current, the V-SoC curve corresponding to the corresponding current value can be estimated; the relationship between the liquid metal battery voltage and SoC has a good relationship The one-to-one correspondence of SoC can be obtained, and the corresponding SoC estimation value can be obtained; the estimation process is simple, the calculation load is low, the result can be obtained quickly, and it has good real-time performance, which can satisfy the SoC estimation of liquid metal batteries under different current states.

Further, using a liquid metal battery experimental platform composed of a computer and a battery tester, multiple groups of constant current charging and discharging experiments are performed on the liquid metal battery under different charge and discharge current values. The advantage is that the computer can be used to test the battery tester. Enter the test plan to monitor and control the state of the liquid metal battery at any time; at the same time, the battery tester will collect the experimental process data of the liquid metal battery, and return the collected data information to the computer for further data analysis. The relationship between voltage and capacity under different charge and discharge currents during constant current charge and discharge of liquid metal batteries;

Further, using the relationship curve between the voltage and capacity of the liquid metal battery under different charge and discharge currents in the constant current charge and discharge process and the battery capacity of the liquid metal battery itself to calculate the ratio, the V of the liquid metal battery under different charge and discharge currents is obtained. -SoC curve data, the advantage of which is that the V-SoC curve data can be obtained more conveniently, which lays the foundation for the subsequent real-time estimation of the liquid metal battery SoC.

Further, the four-terminal wiring method is used to connect the voltage acquisition module and the current acquisition module to the liquid metal battery, and the liquid metal battery performs real-time data sampling, which can eliminate the contact resistance and lead resistance during the measurement process. It reduces the measurement error and makes the measurement result more accurate.

Further, when the V-SoC curve data of the liquid metal battery is obtained by real-time calculation using the look-up table query or interpolation method, the method is simple, the calculation load is low, the result can be obtained quickly, and it has good real-time performance; in the actual application process, it is in different conditions. The liquid metal battery in the current state can use the SoC estimation method, which avoids limiting the SoC estimation algorithm to some liquid metal batteries with a fixed working current, and expands the use range of the real-time estimation algorithm to make it universal.

Further, the SoC value of the liquid metal battery is calculated in real time by using the look-up table interpolation or cubic spline interpolation method. The method is simple, the calculation load is low, the result can be obtained quickly, and it has good real-time performance; in the actual application process, it is in different currents. The SoC estimation method can be used for all liquid metal batteries in the state, which avoids limiting the SoC estimation algorithm to some liquid metal batteries with fixed operating currents, and expands the use range of the real-time estimation algorithm to make it universal.

The present invention conducts a research experiment on the constant current charge and discharge characteristics of the liquid metal battery at different rates of charge and discharge, and can obtain multiple V-SoC curve data through data processing. In the actual application process, the liquid metal battery under different current states is The SoC estimation method can be used; at the same time, the accuracy of the SoC estimation method can be improved by acquiring a plurality of V-SoC curve data; the present invention acquires the liquid metal battery by real-time data acquisition of the working liquid metal battery, and uses the table look-up interpolation method to calculate the liquid state in real time. For the V-SoC data of metal batteries, the SoC value of liquid metal batteries is obtained in real time by cubic spline interpolation. The method is simple, the calculation load is low, and it has good real-time performance and high accuracy.

Description of drawings

1 is a schematic flowchart of the real-time estimation method for liquid metal battery SoC according to the present invention;

2 is a schematic structural diagram of an experimental platform for performing constant-current charge-discharge characteristic detection on a metal liquid battery in the present invention;

Fig. 3 is the relation curve of voltage and capacity under different working currents in the constant current charging working condition measured in the present invention;

FIG. 4 is the relationship curve between the voltage and the capacity under different working currents in the constant current discharge condition measured in the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

As shown in FIG. 1, the present invention provides a real-time estimation method for liquid metal battery SoC, which specifically includes the following steps:

Step 1. Using the liquid metal battery experimental platform, through multiple sets of constant current charging and discharging experiments under different charge and discharge current values, the relationship between voltage and capacity under different charge and discharge currents during the constant current charge and discharge process of the liquid metal battery is obtained. ;According to the relationship curve between the voltage and capacity of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process, and through the ratio calculation with the battery capacity of the liquid metal battery itself, the voltage of the liquid metal battery under different charge and discharge currents is obtained. V-SoC curve data; among them, the liquid metal battery experimental platform includes a computer and a battery tester, the computer is used to input the test plan to the battery tester, and the battery tester is used to collect data on the liquid metal battery, and the collected data information stored on the computer.

Step 2: The terminal voltage acquisition module and the current acquisition module are connected to the liquid metal battery by a four-terminal method, and real-time data sampling is performed on the liquid metal battery to obtain the working current value and terminal voltage value of the liquid metal battery.

Step 3. According to the collected working current value of the liquid metal battery, use the V-SoC curve data of the liquid metal battery to obtain the V-SoC curve corresponding to the working current;

The collected working current of the liquid metal battery and the charging and discharging current selected by the liquid metal battery in the constant current charging and discharging process in step 1 are checked in a table;

If the collected working current of the liquid metal battery is consistent with a certain charge and discharge current selected during the constant current charge and discharge process, the V-SoC curve under the charge and discharge current is selected to obtain the V-SoC curve corresponding to the working current;

If the collected working current of the liquid metal battery is inconsistent with any charge and discharge current selected during the constant current charge and discharge process, select two current values adjacent to the collected working current of the liquid metal battery and the corresponding V- The SoC curve is calculated by interpolation method to obtain the V-SoC curve corresponding to the operating current value.

When using the interpolation method to calculate the V-SoC curve corresponding to the operating current value, the calculation formula is as follows:

Among them, V _x is the battery terminal voltage when SoC=x under the working current; I is the currently collected working current value, I ₁ and I ₂ are the current values adjacent to the collected working current of the liquid metal battery; V _x2 and V _x1 are the battery terminal voltages corresponding to the two V-SoC curves when SoC=x at the current value adjacent to the collected working current of the liquid metal battery, respectively.

In step 4, the collected terminal voltage value of the liquid metal battery and the V-SoC curve corresponding to the operating current obtained in step 3 are looked up in a table;

If there is the same voltage value in the V-SoC curve corresponding to the working current, the corresponding SoC value in the curve is directly used as the SoC value of the liquid metal battery; if there is no same voltage value in the V-SoC curve corresponding to the working current , then the cubic spline interpolation method is used to calculate the SoC of the liquid metal battery.

Among them, the calculation formula of the cubic spline interpolation method is as follows:

h _i =x _i -x _i-1 (2)

λ _i =1-μ _i (4)

Among them, x _i is the voltage value at the middle terminal of the V-SoC curve, _yi is the SoC value in the V-SoC curve, _{hi is the voltage step size of the adjacent terminal, μ i and λ i are constants} , and S(x) is the value in [ The cubic polynomial on x _i-1 , x _i ], M is the second derivative of S(x), and x is the terminal voltage value to be interpolated;

In formula (2)-formula (5), i=1,2,3,...,n-1;

In formula (6), i=1,2,3,...,n, x _i-1 ≤x≤x _i ;

Simultaneously solve n-1 formulas (5) to obtain the value of _Mi ; substitute the value of _Mi into formula (6) to obtain the cubic spline function S(x); The terminal voltage value is substituted into the cubic spline function to obtain the estimated value of the liquid metal battery SoC.

The invention also provides a real-time estimation system for liquid metal battery SoC, including a characteristic data determination unit, a data acquisition unit and a data estimation unit; The voltage-capacitance characteristic curve under different charge and discharge currents, and the V-SoC curve data of the liquid metal battery is calculated; the data acquisition unit is used for real-time data sampling of the liquid metal battery, and the working current value and terminal of the liquid metal battery are obtained. The voltage value; the data estimation part is used to estimate the real-time SoC value of the liquid metal battery according to the collected working current value of the liquid metal battery.

In the real-time estimation method for liquid metal battery SoC according to the present invention, firstly, using the liquid metal battery experimental platform, through multiple groups of constant current charging and discharging experiments under different charging and discharging current values, the constant current of the liquid metal battery is obtained. The relationship curve of voltage-capacity under different charge and discharge currents during the charge and discharge process; through data processing, the V-SoC data of the liquid metal battery under different discharge currents are obtained; the four-terminal wiring method is used to connect the voltage and current acquisition circuit to the liquid metal On the battery, real-time data collection is performed on the liquid metal battery in actual work to obtain the terminal voltage and working current of the liquid metal battery; the working current collected in real time is used to check the V-SoC curve data of the liquid metal battery obtained before. Query, if there is no data of the working current, perform interpolation calculation on the curve data of the adjacent current, and obtain the V-SoC curve data of the liquid metal battery under the working current in real time; use the terminal voltage of the liquid metal battery collected in real time to determine the The V-SoC curve data under the working current is checked by table lookup. If there is no data on the terminal voltage, the V-SoC curve data is interpolated to obtain the SoC estimated value of the liquid metal battery in real time.

Example

The embodiment provides a real-time estimation method for liquid metal battery SoC. First, using the liquid metal battery experimental platform, through multiple sets of constant current charging and discharging experiments under different charging and discharging current values, the constant current of the liquid metal battery is obtained. The relationship between voltage and capacity at different charging and discharging currents during the charging and discharging process.

As shown in Figure 2, the liquid metal battery experimental platform includes a computer, a battery tester, a heating and holding furnace and a temperature control system. The computer and the battery tester are bidirectionally connected, and the battery tester is connected to the liquid metal battery. The liquid metal battery to be tested prevents the In the heating and holding furnace, the heating and holding furnace is connected with the temperature control system; the test plan is input to the battery tester through the computer, and the constant current charge-discharge characteristic experiment of the liquid metal battery to be tested is carried out, and the battery tester collects the data of the liquid metal battery. The measurement data is stored on the computer; the heating and holding furnace is used to heat up and heat the liquid metal battery, and the temperature control system is used to control the heating temperature of the heating and holding furnace.

In this embodiment, multiple sets of constant current charging and discharging experiments under different charge and discharge current values are designed, and the relationship between the voltage and capacity of the liquid metal battery under different charge and discharge currents is obtained. In this embodiment, the charge and discharge current is selected as 25A , 50A and 75A voltage-capacity relationship curve, as shown in accompanying drawing 3 and accompanying drawing 4; It can be seen from accompanying drawing 3 and accompanying drawing 4, in the middle period of charging and discharging of liquid metal battery, the voltage of battery The change is relatively slow; at the end of the charging and discharging of the battery, the voltage of the battery changes sharply and rapidly drops to the cut-off voltage, and the proportion of the process in the entire discharge stage is very low; with the increase of the working current, the charge-discharge cut-off voltage is reached. less time, and less capacity to charge or discharge the battery.

Then, according to the relationship between the voltage and capacity of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process, the V-SoC curve data of the liquid metal battery is obtained by calculating the ratio with the battery capacity of the liquid metal battery itself.

Next, the calculated V-SoC curve data of the liquid metal battery under different charge and discharge currents are saved for use in subsequent estimation methods.

Finally, the experimental terminal voltage acquisition module and current acquisition module are connected to the liquid metal battery by the four-terminal method, and the SoC of the liquid metal battery is estimated in real time through the collected terminal voltage and battery operating current of the liquid metal battery.

The specific estimation process is as follows:

According to the collected working current of the liquid metal battery, find the V-SoC curve data corresponding to the current in the existing V-SoC curve data; if there is no data corresponding to the current, find two adjacent V-SoCs close to the working current. -SoC curve, the V-SoC curve data under working current is obtained by interpolation. The calculation formula is as follows,

Among them, V _x is the battery terminal voltage when SoC=x under the working current; I is the currently collected working current value, I ₁ and I ₂ are the current values adjacent to the collected working current, respectively; V _x2 and V _x1 are respectively The current value adjacent to the collected working current corresponds to the battery terminal voltage value of the two V-SoC curves when SoC=x.

Check the table according to the collected terminal voltage value of the liquid metal battery and the V-SoC curve of the battery under the corresponding working current. If there is no corresponding terminal voltage data, the cubic spline interpolation method is used for interpolation calculation to obtain the SoC value. The calculation formula is as follows,

h _i =x _i -x _i-1 (2)

λ _i =1-μ _i (4)

Among them, _xi is the voltage value at the middle terminal of the V-SoC curve, _yi represents the SoC value in the V-SoC curve, _hi represents the voltage step size of the adjacent terminal, μ _i and λ _i represent constants, and S(x) represents the value in [ The cubic polynomial on x _i-1 , x _i ], M represents the second derivative of S(x), and x represents the terminal voltage value to be interpolated.

In formula (2)-formula (5), i=1,2,3,...,n-1,

In formula (6), i=1, 2, 3, ···, n, and x _i-1 ≤x≤x _i . i in formula (6) has the same meaning as i in the aforementioned formula, and only has different value ranges.

Simultaneously solve the _n -1 formulas (5) to obtain the value of _Mi , and substitute the value of Mi into formula (6) to obtain the cubic spline function S(x). The terminal voltage value is substituted into the cubic spline function to obtain the estimated value of the liquid metal battery SoC.

The real-time estimation method for liquid metal battery SoC according to the present invention estimates the SoC of the liquid metal battery in real time during the charging and discharging process, and grasps the real-time state of charge of the liquid metal battery; Conduct constant-current charge-discharge characteristics research experiments with different charge-discharge currents, obtain multiple V-SoC curve data, and improve the accuracy of the SoC estimation method.

The invention adopts the terminal voltage acquisition circuit and the current acquisition circuit to collect the real-time data of the liquid metal battery through the four-terminal connection method, obtains the terminal voltage and working current of the liquid metal battery, and eliminates the interference of the lead resistance and the contact resistance on the data acquisition. Using the working current and terminal voltage to double-interpolate the V-SoC curve, the real-time estimated SoC value of the liquid metal battery is obtained, and the real-time estimation of the liquid metal battery SoC is realized. The SoC real-time estimation method has simple operation steps, convenient calculation, good real-time performance, can be applied to liquid metal batteries at different working currents, improves the efficiency of SoC real-time estimation of liquid metal batteries, and has good application prospects.

In the real-time estimation system and estimation method for liquid metal battery SoC according to the present invention, since the relationship curve between the voltage and SoC of the liquid metal battery in the charging state increases gradually with the increase of the charging current, the voltage and SoC in the discharging state increase gradually. The relationship curve of the SoC gradually decreases with the increase of the discharge current. The relationship between the voltage and the SoC at a certain current can be estimated by interpolating two V-SoC curves corresponding to adjacent current values. Further, the relationship between the liquid metal battery voltage and the SoC has a good one-to-one correspondence, and the corresponding SoC estimated value can be obtained by using the look-up table query and interpolation method, and its accuracy is high. Therefore, the V-SoC curves of a certain number of liquid metal batteries under different charge and discharge currents can be obtained in advance through the constant current charge and discharge characteristics research experiments. V-SoC curves of liquid metal batteries. After the V-SoC curve is obtained, the current SoC value of the liquid metal battery can be estimated by collecting the terminal voltage of the liquid metal battery, and performing table look-up and interpolation calculation on the curve. Obtaining multiple V-SoC curves under different charge and discharge currents can effectively improve the accuracy of the calculation results and reduce the error of the results in the process of interpolation calculation; the table lookup query and interpolation estimation process is simple, the calculation load is low, and can be quickly obtained. As a result, it has good real-time performance, which satisfies the estimation of SoC for liquid metal batteries under different current states.

Although the present invention has been particularly shown and described in connection with preferred embodiments, it will be understood by those skilled in the art that changes in form and detail may be made to the present invention without departing from the spirit and scope of the invention as defined by the appended claims. Various changes are made within the protection scope of the present invention.

Claims (9)

1. a real-time estimation method for liquid metal battery SoC, characterized in that, comprising the following steps: Step 1. Obtain the voltage-capacitance characteristic curves of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process, and calculate the V-SoC curve data of the liquid metal battery; Step 2, sampling the real-time data of the liquid metal battery to obtain the working current value and terminal voltage value of the liquid metal battery; Step 3. According to the collected working current value of the liquid metal battery, use the V-SoC curve data of the liquid metal battery to obtain the V-SoC curve corresponding to the working current; Step 4: According to the collected terminal voltage value of the liquid metal battery, in the V-SoC curve corresponding to the operating current obtained in step 3, obtain the SoC value of the liquid metal battery. 2. a kind of real-time estimation method for liquid metal battery SoC according to claim 1, is characterized in that, in step 1, utilizes liquid metal battery experimental platform, through multiple groups of constant current charging under the situation of different charging and discharging current values and discharge experiments, the voltage-capacitance characteristic curves of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process; The liquid metal battery experimental platform includes a computer and a battery tester. The computer is used to input the test plan to the battery tester, and the battery tester is used to collect data on the liquid metal battery and store the collected data information on the computer. 3. A real-time estimation method for liquid metal battery SoC according to claim 1, characterized in that, in step 1, according to the voltage-capacitance under different charge and discharge currents of the liquid metal battery in the constant current charge and discharge process The characteristic curve is calculated by the ratio of the battery capacity of the liquid metal battery to obtain the V-SoC curve data of the liquid metal battery. 4. A real-time estimation method for liquid metal battery SoC according to claim 1, wherein in step 2, the terminal voltage acquisition module and the current acquisition module are connected to the liquid metal battery by a four-terminal method. , for real-time data sampling from liquid metal batteries. 5. A real-time estimation method for liquid metal battery SoC according to claim 1, wherein in step 3, the collected working current of the liquid metal battery and the liquid metal battery in step 1 are charged at constant current. The charge and discharge current selected in the discharge process is checked by table lookup; If the collected working current of the liquid metal battery is consistent with a certain charge and discharge current selected during the constant current charge and discharge process, the V-SoC curve under the charge and discharge current is selected to obtain the V-SoC curve corresponding to the working current; If the collected working current of the liquid metal battery is inconsistent with any charge and discharge current selected during the constant current charge and discharge process, select two current values adjacent to the collected working current of the liquid metal battery and the corresponding V- The SoC curve is calculated by interpolation method to obtain the V-SoC curve corresponding to the operating current value. 6. a kind of real-time estimation method for liquid metal battery SoC according to claim 5, is characterized in that, when utilizing interpolation method to calculate the V-SoC curve of corresponding working current value, the calculation formula is as follows:

Among them, V _x is the battery terminal voltage when SoC=x under the working current; I is the currently collected working current value, I ₁ and I ₂ are the current values adjacent to the collected working current of the liquid metal battery; V _x2 and V _x1 are the battery terminal voltages corresponding to the two V-SoC curves when SoC=x at the current value adjacent to the collected working current of the liquid metal battery, respectively. 7. A real-time estimation method for liquid metal battery SoC according to claim 1, wherein in step 4, the collected terminal voltage value of the liquid metal battery and the corresponding operating current obtained in step 3 are calculated. V-SoC curve to look up the table; If there is the same voltage value in the V-SoC curve corresponding to the working current, the corresponding SoC value in the curve is directly used as the SoC value of the liquid metal battery; if there is no same voltage value in the V-SoC curve corresponding to the working current , then the cubic spline interpolation method is used to calculate the SoC of the liquid metal battery. 8. a kind of real-time estimation method for liquid metal battery SoC according to claim 7, is characterized in that, the calculation formula of cubic spline interpolation method is as follows: h _i =x _i -x _i-1 (2)

λ _i =1-μ _i (4)

Among them, x _i is the voltage value at the middle terminal of the V-SoC curve, _yi is the SoC value in the V-SoC curve, _{hi is the voltage step size of the adjacent terminal, μ i and λ i are constants} , and S(x) is the value in [ The cubic polynomial on x _i-1 , x _i ], M is the second derivative of S(x), and x is the terminal voltage value to be interpolated; In formula (2)-formula (5), i=1,2,3,...,n-1; In formula (6), i=1,2,3,...,n, x _i-1 ≤x≤x _i ; Simultaneously solve n-1 formulas (5) to obtain the value of _Mi ; substitute the value of _Mi into formula (6) to obtain the cubic spline function S(x); The terminal voltage value is substituted into the cubic spline function to obtain the estimated value of the liquid metal battery SoC. 9. A real-time estimation system for liquid metal battery SoC, characterized in that it comprises a characteristic data determination unit, a data acquisition unit and a data estimation unit; The characteristic data determination unit is used to obtain the voltage-capacitance characteristic curves of the liquid metal battery under different charge and discharge currents during the constant current charge and discharge process, and to calculate the V-SoC curve data of the liquid metal battery; The data acquisition unit is used for real-time data sampling of the liquid metal battery to obtain the working current value and terminal voltage value of the liquid metal battery; The data estimation part is used for estimating the real-time SoC value of the liquid metal battery according to the collected working current value of the liquid metal battery.

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