A method, system, device and storage medium for online estimation of battery internal resistance

Abstract

The present invention relates to an online estimation method, system, device and storage medium for the internal resistance of a battery. The method specifically comprises the following steps: connecting an AC voltage source in series in a battery circuit, wherein the battery circuit comprises a charger and a plurality of batteries connected in series; sampling the current of the battery circuit after the AC voltage source is connected in series and the voltage at both ends of a battery to be measured, and filtering out the DC component to obtain the AC component of the battery circuit current and the AC component of the voltage at both ends of the battery to be measured; obtaining the maximum current value and the minimum current value of the AC component of the battery circuit current within a given sampling time, and obtaining the corresponding moments when the maximum current value and the minimum current value appear, reading two corresponding voltage values ​​at the AC component of the voltage at both ends of the battery to be measured according to the corresponding moments when the maximum current value and the minimum current value appear, and calculating the internal resistance of the battery to be measured according to the two voltage values ​​and the maximum current value and the minimum current value.

Description

Technical Field

[0001] The invention relates to a method, system, equipment and storage medium for online estimation of internal resistance of a battery, and belongs to the technical field of internal resistance estimation of a battery. Background Art

[0002] The stable operation of secondary equipment in substations is an important guarantee for the reliable power supply of high-voltage primary equipment. The power supply of secondary equipment mostly adopts DC, mainly because the power supply continuity of DC system is high. As the most core component of DC system, the battery does not rely on the power supply of other equipment in the station, and directly converts chemical energy into electrical energy. The most direct factor to characterize the health status of the battery is the change of its internal resistance. At present, there are two main methods for measuring the internal resistance of batteries: DC discharge method and AC injection method. The DC discharge method is to connect a load in series with the battery, and measure the voltage change at the time of discharge and when the discharge stops by controlling the on and off of the switch to measure the internal resistance. The main principle of the AC injection method is to inject a fixed frequency excitation current into the battery circuit, and measure the voltage change at both ends of the battery at the same time, so as to measure the internal resistance. The DC discharge method is mostly offline group measurement, which takes a long time and is very inefficient. In addition, in order to ensure the measurement accuracy, the DC discharge method mostly uses large current charging and discharging, and frequent charging and discharging will affect the battery life. The AC injection method is easily interfered by other factors such as charger ripple due to the small injected excitation current. In addition, complex algorithms are often required to extract the battery excitation voltage. Therefore, although this method can achieve online measurement, the measurement accuracy is not high.

[0003] At present, most of the online monitoring devices for batteries in operation do not have the ability to estimate the internal resistance online in real time, resulting in the failure to detect the deterioration of the battery in time. The literature [Lv Yangmeng, Zhu Ziwei, Liu Baoquan. A calculation method for online estimation of battery internal resistance [J]. Energy Storage Science and Technology. 2019, 08(02): 264-268(11): 1599-1601+1639] introduces a method for online estimation of battery internal resistance. This method is simple and practical, and does not require additional equipment. However, the influence of currents such as equalization charge, floating charge, and discharge is not considered during the measurement process, so the accuracy of the results cannot be fully guaranteed. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention proposes a method, system, device and storage medium for online estimation of battery internal resistance, by connecting an AC voltage source in series in the battery circuit, sampling the battery circuit current and the voltage across the single battery to be measured, filtering out the DC components in the two sampled values, and using the principle that the battery voltage is equal at the maximum and minimum moments of the current peak in the battery circuit, these two moments are selected as observation points to extract the battery voltage and current values, and the battery internal resistance is obtained by calculating the ratio after the difference.

[0005] The technical solution of the present invention is as follows:

[0006] In one aspect, the present invention provides a method for online estimating internal resistance of a battery, comprising the following steps:

[0007] An AC voltage source is connected in series in a battery circuit, wherein the battery circuit includes a charger and a plurality of batteries connected in series;

[0008] Sampling the current of the battery circuit connected in series with the AC voltage source and the voltage across the battery to be tested, and filtering out the DC component in the battery circuit current and the voltage across the battery to be tested, to obtain the AC component of the battery circuit current and the AC component of the voltage across the battery to be tested;

[0009] The maximum current value and the minimum current value of the AC component of the battery loop current are obtained within a given sampling time, and the corresponding moments when the maximum current value and the minimum current value appear are obtained. According to the corresponding moments when the maximum current value and the minimum current value appear, two corresponding voltage values ​​are read from the AC component of the voltage across the battery to be tested, and the internal resistance of the battery to be tested is calculated according to the two voltage values ​​and the maximum current value and the minimum current value.

[0010] As a preferred implementation, the steps of sampling the current of the battery circuit after the AC voltage source is connected in series and the voltage across the battery to be tested are specifically as follows:

[0011] The current of the battery circuit and the voltage across the battery to be tested are discretely sampled according to a preset sampling frequency.

[0012] As a preferred implementation, the step of filtering out the DC component in the battery loop current and the voltage across the battery to be tested is specifically as follows:

[0013] Determine the period T of the AC voltage source;

[0014] The sampling value of the battery loop current is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampling data to obtain the AC component of the battery loop current;

[0015] The sampled value of the voltage at both ends of the battery to be tested is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampled data to obtain the AC component of the voltage at both ends of the battery to be tested.

[0016] On the other hand, the present invention also provides a battery internal resistance online estimation system, comprising:

[0017] An AC voltage source, the AC voltage source is connected in series to a battery circuit, the battery circuit includes a charger and a plurality of batteries connected in series;

[0018] A sampling module, used to sample the current of the battery circuit connected in series with the AC voltage source and the voltage at both ends of the battery to be tested;

[0019] A DC component filtering module is used to filter out the DC component in the battery loop current and the voltage across the battery to be tested, and obtain the AC component of the battery loop current and the AC component of the voltage across the battery to be tested;

[0020] The internal resistance estimation module is used to obtain the maximum current value and the minimum current value of the AC component of the battery loop current within a given sampling time, and obtain the corresponding time when the maximum current value and the minimum current value appear, read the corresponding two voltage values ​​of the AC component of the voltage at both ends of the battery to be tested according to the corresponding time when the maximum current value and the minimum current value appear, and calculate the internal resistance of the battery to be tested based on the two voltage values ​​and the maximum current value and the minimum current value.

[0021] As a preferred implementation, the working method of the sampling module is specifically as follows:

[0022] The current of the battery circuit and the voltage across the battery to be tested are discretely sampled according to a preset sampling frequency.

[0023] As a preferred implementation, the working method of the DC component filtering module is specifically as follows:

[0024] Determine the period T of the AC voltage source;

[0025] The sampling value of the battery loop current is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampling data to obtain the AC component of the battery loop current;

[0026] The sampled value of the voltage at both ends of the battery to be tested is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampled data to obtain the AC component of the voltage at both ends of the battery to be tested.

[0027] On the other hand, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for online estimation of the internal resistance of a battery as described in any embodiment of the present invention is implemented.

[0028] In another aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for online estimation of internal resistance of a battery as described in any embodiment of the present invention.

[0029] The present invention has the following beneficial effects:

[0030] The invention discloses an online estimation method for the internal resistance of a battery. The method comprises the following steps: inserting an AC voltage source in series in a battery circuit, sampling the current of the battery circuit and the voltage across two ends of a single battery to be measured, filtering out the DC components in the two sampled values, and utilizing the principle that the battery voltage is equal at the maximum and minimum moments of the current peak flowing through the battery circuit. The two moments are selected as observation points to extract the battery voltage and current values, and the internal resistance of the battery is obtained by calculating the difference ratio. The invention can realize online real-time estimation of the internal resistance of the battery, is less affected by the ripple of the charger, and has high precision. The algorithm for processing the sampled data is simple, and the hardware implementation effect is relatively easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0032] Figure 2 This is an example diagram of a typical DC system of a substation in an embodiment of the present invention;

[0033] Figure 3 is an example diagram of an equivalent model of a battery in an embodiment of the present invention;

[0034] Figure 4 is an equivalent circuit diagram of a battery circuit in an embodiment of the present invention;

[0035] Figure 5 Schematic diagram of current waveform of an AC circuit in an embodiment of the present invention;

[0036] Figure 6 A schematic diagram of a charger output waveform in a simulation experiment according to an embodiment of the present invention;

[0037] Figure 7 A schematic diagram of the battery loop current and single battery voltage waveforms in a simulation experiment of an embodiment of the present invention;

[0038] Figure 8 A schematic diagram of the waveforms of the current and the voltage of a single battery after signal processing in a simulation experiment of an embodiment of the present invention;

[0039] Fig. 9 A schematic diagram of the measurement results of the internal resistance of a battery in a simulation experiment according to an embodiment of the present invention;

[0040] Fig.10 The figure is a schematic diagram of the measurement results of the change of the internal resistance of the battery in the simulation experiment of the embodiment of the present invention. DETAILED DESCRIPTION

[0041] 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.

[0042] It should be understood that the step numbers used in this document are only for convenience of description and are not intended to limit the order in which the steps are executed.

[0043] It should be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0044] The terms “include” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0045] The term "and / or" means and includes any and all possible combinations of one or more of the associated listed items.

[0046] Embodiment 1:

[0047] See also Figure 1 , a method for online estimation of battery internal resistance, comprising the following steps:

[0048] An AC voltage source with a period of T is connected in series in the battery circuit, and the battery circuit includes a charger and a number of batteries connected in series. The typical structure of the DC system of a substation is as follows: Figure 2 As shown, the charging module, the battery, and the DC load are connected to the DC bus together. Under normal circumstances, the battery is in a floating charge state, the DC load is powered by the charging module (charger), and the DC bus voltage is controlled by the charging module. When the charging module cannot supply power, the battery starts to discharge and supply power to the DC load. When the charging module resumes power supply, the battery needs to be charged. If the charging current meets the equalization charge trigger condition, the output voltage of the charging module increases to the equalization charge voltage, and the battery starts to be equalized charged. This embodiment uses an AC voltage source in series with the battery circuit to charge and discharge it, and estimates the internal resistance of the battery by deriving the relationship between the battery voltage and current fluctuations caused by the AC voltage and the internal resistance.

[0049] In order to assist those skilled in the art to understand the solution of this embodiment, this embodiment will establish a corresponding equivalent model for estimating the internal resistance of a battery; the commonly used models of batteries mainly include the Rint model, the PNGV model, and the Thevenin model. The basic structure of the Rint model is a series connection of a voltage source and a resistor (the voltage source and the resistance value change in real time with the different states of the battery). Compared with the other two complex structure models, this model is relatively simple and practical, and is suitable for use in calculations that do not require high internal resistance measurements. Therefore, this article mainly uses this model. In order to more realistically characterize the capacity and charge and discharge state of the battery, this article uses a large capacitor instead of a voltage source, such as Figure 3 According to the above content, the equivalent model for estimating the internal resistance of the battery is established as follows: Figure 4 shown. Figure 4 Middle,U C Indicates the charger output voltage, u ac (t) represents the voltage of the AC voltage source connected in series, u 1z (t)~u nz (t) and R1~R n Respectively represent the voltage and internal resistance of each single battery, i z (t) represents the battery circuit current.

[0050] According to the superposition principle, Figure 4 The equivalent circuit shown is converted into a circuit in which only a DC circuit and an AC circuit exist.

[0051] For DC circuit: use U X , R X and C X Indicates the voltage, total internal resistance and equivalent total capacitance of the battery pack. C with U X When there is a pressure difference, there is a current i in the battery circuit dc (t), can be expressed as:

[0052]

[0053] At this time, the voltage across each single battery is U dc is a constant that does not change with t.

[0054] For AC circuit: When there is only an AC voltage source in the battery circuit, an AC current will be generated in the circuit. The battery is charged and discharged around the zero-crossing point of the AC current. If the frequency of the AC voltage source is f and the period is T, then the current in the circuit must also be an AC current with a frequency of f. Suppose the current i in the circuit is ac (t) can be expressed as:

[0055]

[0056] It is stipulated that when i>0, the battery is charged; when i<0, the battery is discharged to the outside, and the current waveform is as follows Figure 5 shown.

[0057] If the voltage source frequency f is very large, the internal resistance of the battery will basically not change within a period T. Figure 5 As shown, when i>0, a moment t1 is selected, t2 is the moment when the current crosses zero, and during the time period t1 to t2, the charge change ΔQ1 of the capacitor C is:

[0058]

[0059] Similarly, when i<0, select a time t3. During the time period from t2 to t3, the charge change ΔQ2 of the capacitor C is

[0060]

[0061] To ensure that the charge and discharge amount of capacitor C is equal during the time periods t1 to t2 and t2 to t3, that is, ΔQ1 = -ΔQ2, it must be satisfied:

[0062]

[0063] Because I ac (t) has different directions at t1 and t3, so we get:

[0064]

[0065] Assume that at time t1, the charge on capacitor C is Q1 and the voltage across it is U nC (t1); at t3, the charge on capacitor C is Q2, and the voltage across it is U nC (t3), combined with the formula: U = Q / C, we get U nC (t1) = U nC (t3), that is, at t1 and t3, the amount of charge on the capacitor is equal, and the voltage across the two ends is also equal.

[0066] Depend on Figure 4 From the battery model shown in the figure, it can be seen that the voltage u of the nth battery terminal at time t1 is nac (t1) and current i ac The battery terminal voltage u at (t1) and t3 nac (t3) and current i ac (t3) can be expressed as:

[0067]

[0068] From the above formula, the internal resistance of the battery can be expressed as:

[0069]

[0070] When there is only AC component in the circuit, the internal resistance can be obtained according to the above formula.

[0071] According to the superposition principle, the voltage u of the nth battery nz (t) and the current i in the circuit z (t) can be expressed as:

[0072]

[0073] Right now:

[0074]

[0075] In order to obtain the internal resistance of the battery according to formula (8), the DC component in the above formula needs to be "filtered out". The method in this embodiment is specifically as follows:

[0076] Determine the period T of the AC voltage source;

[0077] The sampling value of the battery loop current is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampling data to obtain the AC component of the battery loop current;

[0078] The sampled value of the voltage at both ends of the battery to be tested is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampled data to obtain the AC component of the voltage at both ends of the battery to be tested.

[0079] That is:

[0080]

[0081] After filtering out the DC component, the battery voltage and current values ​​are extracted by selecting these two moments as observation points based on the principle that the battery voltage is equal at the maximum and minimum moments of the current peak in the battery circuit. The internal resistance of the battery is obtained by calculating the ratio after the difference.

[0082] When the frequency of the AC voltage source is large enough, that is, T is small enough, then:

[0083]

[0084] Right now:

[0085]

[0086] According to a certain sampling frequency f c to i zc (t) is discretely sampled, and each f c *T sampling data are divided into an array, and the data in the group are compared. The time when the maximum value appears is recorded as t1, and the sampling value is recorded as izc (t1), according to formula (6), the minimum value sampled within this period must be i zc (t3), the sampling time is t3, so it satisfies:

[0087]

[0088] Substituting formula (14) into formula (11), we get:

[0089]

[0090] The internal resistance R of the battery can be expressed as:

[0091]

[0092] After processing the signal, the estimated internal resistance can be calculated according to formula (16).

[0093] In order to verify the superiority of the battery internal resistance estimation method proposed in the present invention, this embodiment also carried out a simulation experiment;

[0094] The simulation of this example uses PSIM (Power Simulation) and Matlab / Simulink software; the main circuit is simulated using PSIM, and the signal processing calculation model is built in Matlab / Simulink software. For the simulation parameters of the battery pack: 104 batteries are configured. When in a floating charge state, the voltage of each battery is 2.25V, that is, the voltage across the battery pack is 234V. When the battery is in an equalized charge state, the voltage of each battery is 2.32V, that is, the voltage across the battery pack is 242V; according to the short-term load discharge test standard for batteries in substations, the rear end voltage of the battery pack in a floating charge state at a constant current of 10A (DC load current in the station) for 30 minutes should not be less than 210V. According to the battery model designed in this embodiment, the equivalent capacitance of a single battery can be obtained according to the following formula:

[0095]

[0096] Therefore, the equivalent capacitance of the single battery is set to 78000F, and its initial voltage is 2.25 V. According to the average value of the internal resistance test results of the batteries, the internal resistance of the single battery is set to 1000μΩ, so that the internal resistance of the battery pack is about 0.1Ω.

[0097] For the frequency selection of the AC voltage source in series:

[0098] The number of sampling points in each AC cycle can be expressed as follows:

[0099]

[0100] f c represents the sampling frequency, and f represents the frequency of the series-input AC voltage.

[0101] The larger the n, the more sampling points there are in one cycle, that is, the greater the probability of sampling to obtain the most accurate maximum and minimum points, and the more accurate the internal resistance test results. Therefore, when the sampling frequency is low due to equipment reasons, in order to obtain accurate internal resistance test results, the frequency of the series AC voltage should not be too large.

[0102] According to formula (12), when T is large (i.e., f is small), the DC component cannot be ignored. Therefore, the internal resistance test result obtained by formula (16) is no longer accurate. In addition, in order to track the change of internal resistance more real-time, the frequency of the series AC voltage should not be too small.

[0103] When there is only an AC voltage source in the battery circuit, the AC current should not be too large. Here, the AC voltage source is set to 0.1sin(100πt) (i.e., the peak value is 0.1V and the frequency is 50Hz).

[0104] For the simulated sampled signal:

[0105] The simulation time of the simulation model is 0.5s and the sampling frequency is 10kHz. In Matlab / Simulink, the control signal processing algorithm is: the i zc (t),u nzc (t) Every 200 (the number of samples in each AC cycle) are stored in 2 different locations, and i is calculated zc The maximum value i among these 200 values ​​in (t) zc (t1) and the occurrence time t1, the minimum value i zc (t3) and the occurrence time t3. According to t1 and t3, the u which stores 200 values nzc (t) to retrieve u nzc (t1),u nzc (t3). In this way, the internal resistance of the battery can be calculated according to formula (16).

[0106] Conduct simulation experiments:

[0107] The battery generally has two states: floating charge state and equalizing charge state. The floating charge state means that the output voltage of the charger is basically equal to the voltage across the battery pack (234V in this article), the floating charge current is very small (basically 0), and the charger supplies power to the entire station DC load. The equalizing charge state means that the charger voltage rises to 242V, and the charger not only supplies power to the entire station DC load, but also charges the battery with equalized voltage. At this time, the equalizing charge current is often very large. These two states can generally be switched automatically.

[0108] The simulation implementation of battery floating charge / equalizing charge switching is as follows:

[0109] Simulation settings: The total simulation time is 0.5s. From 0 to 0.25s, the battery is in a floating charge state (i.e., the charger output voltage source is 234V). At 0.25s, the charger output voltage rises to 242V, which means that the battery enters an equalized charge state.

[0110] The charger output voltage waveform is as follows: Figure 6 shown.

[0111] Depend on Figure 6 It can be seen that although there are certain ripples, the charger output voltage basically remains at around 234V for 0.25s, and rises to around 242V after 0.25s.

[0112] The current in the battery main circuit and the battery cell voltage waveform are as follows: Figure 7 shown.

[0113] As can be seen from the above figure, the current instantly increases from a minimum value close to 0 to about -80A (charging) at 0.25s; the battery voltage instantly increases from the original 2.25V to about 2.32V at 0.25s. The changes in these two electrical quantities indicate that the battery has entered the equalization charge state from the original floating charge state.

[0114] The waveforms of the current izc and voltage signal unzc after filtering out the "DC" component are as follows Figure 8 shown.

[0115] Depend on Figure 8 It can be seen that the current and voltage waveforms did not fluctuate significantly around 0.25s, indicating that the change in battery status did not have a significant impact on them.

[0116] The battery internal resistance value obtained by signal processing in Matlab / Simulink is as follows Fig. 9 shown.

[0117] Depend on Fig. 9 It can be seen that the calculated result of the battery internal resistance is basically maintained at 1000μΩ, indicating that the conversion of the battery's equalization and floating charge states has no significant impact on the calculated result of the battery internal resistance.

[0118] The simulation test conditions when the internal resistance of the battery changes are as follows:

[0119] When the battery is in floating charge state, the total simulation time is 0.5s. At 0.25s, the internal resistance increases from 500μΩ to 1000μΩ. The estimated result of the battery internal resistance is as follows: Fig.10 shown.

[0120] Depend on Fig.10It can be seen that the change of the battery internal resistance can be quickly tracked after the transition within 0.02s (i.e., 2 AC cycles).

[0121] It can be seen from the above simulation experiments that the battery internal resistance estimation method proposed in the present invention is not affected by the battery state and can track and estimate the battery internal resistance in real time and accurately.

[0122] Embodiment 2:

[0123] This embodiment provides a battery internal resistance online estimation system, including:

[0124] An AC voltage source, the AC voltage source is connected in series to a battery circuit, the battery circuit includes a charger and a plurality of batteries connected in series;

[0125] A sampling module, used to sample the current of the battery circuit connected in series with the AC voltage source and the voltage at both ends of the battery to be tested;

[0126] A DC component filtering module is used to filter out the DC component in the battery loop current and the voltage across the battery to be tested, and obtain the AC component of the battery loop current and the AC component of the voltage across the battery to be tested;

[0127] The internal resistance estimation module is used to obtain the maximum current value and the minimum current value of the AC component of the battery loop current within a given sampling time, and obtain the corresponding time when the maximum current value and the minimum current value appear, read the corresponding two voltage values ​​of the AC component of the voltage at both ends of the battery to be tested according to the corresponding time when the maximum current value and the minimum current value appear, and calculate the internal resistance of the battery to be tested based on the two voltage values ​​and the maximum current value and the minimum current value.

[0128] As a preferred implementation, the working method of the sampling module is specifically as follows:

[0129] The current of the battery circuit and the voltage across the battery to be tested are discretely sampled according to a preset sampling frequency.

[0130] As a preferred implementation, the working method of the DC component filtering module is specifically as follows:

[0131] Determine the period T of the AC voltage source;

[0132] The sampling value of the battery loop current is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampling data to obtain the AC component of the battery loop current;

[0133] The sampled value of the voltage at both ends of the battery to be tested is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampled data to obtain the AC component of the voltage at both ends of the battery to be tested.

[0134] Embodiment three:

[0135] This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the method for online estimating the internal resistance of a battery as described in any embodiment of the present invention is implemented.

[0136] Embodiment 4:

[0137] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the method for online estimation of the internal resistance of a battery as described in any embodiment of the present invention is implemented.

[0138] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for online estimation of battery internal resistance, characterized in that: The following steps are involved: An AC voltage source is connected in series in a battery circuit, wherein the battery circuit includes a charger and a plurality of batteries connected in series; Sampling the current of the battery circuit connected in series with the AC voltage source and the voltage across the battery to be tested, and filtering out the DC component in the battery circuit current and the voltage across the battery to be tested, to obtain the AC component of the battery circuit current and the AC component of the voltage across the battery to be tested; Obtain the maximum current value and the minimum current value of the AC component of the battery loop current within a given sampling time, and obtain the corresponding time when the maximum current value and the minimum current value appear, read the corresponding two voltage values ​​of the AC component of the voltage at both ends of the battery to be tested according to the corresponding time when the maximum current value and the minimum current value appear, and calculate the internal resistance of the battery to be tested according to the two voltage values ​​and the maximum current value and the minimum current value; The steps of filtering out the DC component in the battery loop current and the voltage across the battery to be tested are specifically as follows: Determine the period T of the AC voltage source; The sampling value of the battery loop current is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampling data to obtain the AC component of the battery loop current; The sampled value of the voltage at both ends of the battery to be tested is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampled data to obtain the AC component of the voltage at both ends of the battery to be tested.

2. A method for online estimation of battery internal resistance according to claim 1, characterized in that: The steps of sampling the current of the battery circuit after the AC voltage source is connected in series and the voltage at both ends of the battery to be tested are specifically as follows: The current of the battery circuit and the voltage across the battery to be tested are discretely sampled according to a preset sampling frequency.

3. A battery internal resistance online estimation system, characterized in that: include: An AC voltage source, the AC voltage source is connected in series to a battery circuit, the battery circuit includes a charger and a plurality of batteries connected in series; A sampling module, used to sample the current of the battery circuit connected in series with the AC voltage source and the voltage at both ends of the battery to be tested; A DC component filtering module is used to filter out the DC component in the battery loop current and the voltage across the battery to be tested, and obtain the AC component of the battery loop current and the AC component of the voltage across the battery to be tested; The internal resistance estimation module is used to obtain the maximum current value and the minimum current value of the AC component of the battery loop current within a given sampling time, and obtain the corresponding time when the maximum current value and the minimum current value appear, read the corresponding two voltage values ​​of the AC component of the voltage at both ends of the battery to be tested according to the corresponding time when the maximum current value and the minimum current value appear, and calculate the internal resistance of the battery to be tested according to the two voltage values ​​and the maximum current value and the minimum current value; The working method of the DC component filtering module is specifically as follows: Determine the period T of the AC voltage source; The sampling value of the battery loop current is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampling data to obtain the AC component of the battery loop current; The sampled value of the voltage at both ends of the battery to be tested is delayed by T / 2 to obtain delayed data, and the delayed data is subtracted from the original sampled data to obtain the AC component of the voltage at both ends of the battery to be tested.

4. A battery internal resistance online estimation system according to claim 3, characterized in that: The working method of the sampling module is specifically as follows: The current of the battery circuit and the voltage across the battery to be tested are discretely sampled according to a preset sampling frequency.

5. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method for online estimating the internal resistance of a battery as described in any one of claims 1 to 2 is implemented.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method for online estimating the internal resistance of a battery as claimed in any one of claims 1 to 2 is implemented.

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