Detection circuit, battery cell voltage compensation method and energy storage system

Abstract

The present application discloses a detection circuit, a cell voltage compensation method and an energy storage system. The detection circuit is applied to an energy storage system, and the energy storage system includes at least two cells. The detection circuit includes: an acquisition module, a detection module and a processing module. The acquisition module includes at least a sampling resistor, and the sampling resistor is arranged in the working circuit of the target cell; the detection module connects the target cell and the acquisition module; and the processing module connects the detection module. In the above manner, by detecting the cell's balancing current, balancing voltage and cell sampling line resistance, the cell's active balancing efficiency and circuit safety and stability are improved.

Description

Technical Field

[0001] The present application relates to the field of electronic circuits, and specifically to a detection circuit, a battery cell voltage compensation method and an energy storage system. Background Art

[0002] With the development of battery technology, the application of industrial and commercial energy storage systems based on battery energy storage technology has also increased. In order to increase the energy of the energy storage system, multiple battery packs need to be connected in series. During the long-term use of batteries, due to differences in cell parameters, the voltage of the cell will be inconsistent. When the battery system is charging, if the voltage of a cell is too high, it will trigger a cell overvoltage alarm; when the battery system is discharging, if the voltage of a cell is too low, it will trigger a cell undervoltage alarm. In order to compensate for the differences in the cells, it is necessary to add high-efficiency active balancing to the cells.

[0003] When the battery cells are actively balanced, there is resistance in the sampling line between the battery cells and the BMU (Battery Monitoring Unit). The current passing through the sampling line will cause voltage changes, resulting in the voltage collected by the BMU being inconsistent with the actual voltage of the battery cells. To solve this problem, the usual practice is to turn off the active balancing function when sampling is required, and turn on the balancing function when sampling is not required. However, this method will result in less energy being balanced for the same rated balancing current and the same balancing time, which limits the balancing efficiency. At the same time, when problems such as poor connection of the battery sampling line cause the equivalent resistance of the circuit to increase, the active balancing current will increase the circuit temperature after passing through the sampling line, causing some safety problems such as insulation layer damage and excessive battery temperature. Summary of the invention

[0004] To solve the above problems, the present application provides a detection circuit, a battery cell voltage compensation method and an energy storage system, which can detect the sampling line resistance and improve the active balancing efficiency of the battery cell and the safety and stability of the circuit.

[0005] A technical solution adopted in the present application is: to provide a detection circuit, which is applied to an energy storage system, the energy storage system includes at least two battery cells, and the detection circuit includes: an acquisition module, the acquisition module at least includes a sampling resistor, the sampling resistor is set in the working circuit of the target battery cell, the acquisition module is configured to acquire the voltage across the sampling resistor and output a first voltage signal; a detection module, connected to the target battery cell, the acquisition module and the power supply, the detection module is configured to detect the voltage of the target battery cell when the target battery cell is in a balanced state, and output a second voltage signal, and detect the voltage of the battery cell adjacent to the target battery cell, and output a third voltage signal; a processing module, connected to the detection module, the processing module is configured to determine the balancing current according to the voltage value of the first voltage signal and the sampling resistor, and determine the equivalent resistance in the working circuit of the target battery cell according to the balancing current, the second voltage signal, the third voltage signal, the first initial voltage signal of the target battery cell and the second initial voltage signal of the adjacent battery cell; wherein the first initial voltage signal and the second initial voltage signal are acquired by the detection module before the balancing function is turned on.

[0006] In one embodiment, the acquisition module further includes: a plurality of sampling units connected in sequence, wherein a first input end of a first sampling unit in the plurality of sampling units is connected to a first end of a sampling resistor, and a second input end of the first sampling unit is connected to a second end of the sampling resistor; the plurality of sampling units are configured to perform an amplification operation based on a voltage across the sampling resistor, and a first voltage signal is output by a last sampling unit in the plurality of sampling units.

[0007] In one embodiment, the first-stage sampling unit includes: a first operational amplifier, a non-inverting input terminal of the first operational amplifier is connected to a first end of a sampling resistor through a first resistor, and an inverting input terminal of the first operational amplifier is connected to a second end of the sampling resistor; a second resistor, a first end of the second resistor is coupled to a reference voltage terminal, and a second end of the second resistor is connected to the non-inverting input terminal of the first operational amplifier.

[0008] In one embodiment, the multi-stage sampling unit further includes: a second-stage sampling unit and a third-stage sampling unit, the third-stage sampling unit being the last-stage sampling unit; a first input end of the second-stage sampling unit is connected to an output end of the first-stage sampling unit; a second input end of the second-stage sampling unit is connected to a first reference ground, and the second-stage sampling unit is configured to differentially amplify a voltage signal output by the first-stage sampling unit; a first input end of the third-stage sampling unit is connected to an output end of the second-stage sampling unit; a second input end of the third-stage sampling unit is connected to a second reference ground; and the third-stage sampling unit is configured to perform in-phase amplification on a voltage signal output by the second-stage sampling unit.

[0009] In one embodiment, the second-stage sampling unit includes: a second operational amplifier, a non-inverting input terminal of the second operational amplifier is connected to the output terminal of the first operational amplifier through a third resistor, and an inverting input terminal of the second operational amplifier is connected to a first reference ground; the second operational amplifier is configured to differentially amplify the voltage signal output by the first operational amplifier; and a fourth resistor, a first end of the fourth resistor is connected to the second reference ground, and a second end of the fourth resistor is connected to the first input terminal of the second operational amplifier.

[0010] In one embodiment, the third-stage sampling unit includes: a third operational amplifier, wherein the non-inverting input terminal of the third operational amplifier is connected to the output terminal of the second-stage sampling unit, and the second terminal of the third operational amplifier is connected to the second reference ground; the third operational amplifier is configured to amplify the voltage signal output by the second-stage sampling unit in the same direction; a fifth resistor, wherein the first terminal of the fifth resistor is connected to the inverting input terminal of the third operational amplifier, and the second terminal of the fifth resistor is connected to the second reference ground; and a sixth resistor, wherein the first terminal of the sixth resistor is connected to the inverting input terminal of the third operational amplifier, and the second terminal of the sixth resistor is connected to the output terminal of the third operational amplifier.

[0011] In one embodiment, the detection circuit also includes: a voltage detection module, which is arranged in the working circuit of the target battery cell and connected to the detection module, and the voltage detection module is configured to detect the equilibrium voltage when the target battery cell is in an equilibrium state; wherein the processing module is also configured to determine the actual voltage of the target battery cell and the actual voltage of the adjacent battery cell based on the equilibrium current, the equivalent resistance, the second voltage signal and the third voltage signal.

[0012] In one embodiment, the voltage detection module includes: a fourth operational amplifier, the non-inverting input terminal of the fourth operational amplifier is connected to the first pole of the target battery cell through a seventh resistor, and the inverting input terminal of the fourth operational amplifier is connected to the first reference ground; an eighth resistor, the first end of the eighth resistor is connected to the second reference ground, and the second end of the eighth resistor is connected to the non-inverting input terminal of the fourth operational amplifier; a fifth operational amplifier, the non-inverting input terminal of the fifth operational amplifier is connected to the output terminal of the fourth operational amplifier, and the second end of the fifth operational amplifier is connected to the second reference ground; a ninth resistor, the first end of the ninth resistor is connected to the second input terminal of the fifth operational amplifier, and the second end of the ninth resistor is connected to the second reference ground; a tenth resistor, the first end of the tenth resistor is connected to the second input terminal of the fifth operational amplifier, and the second end of the tenth resistor is connected to the output terminal of the fifth operational amplifier.

[0013] The present application also provides a cell voltage compensation method, which includes: before the balanced state of the target cell is turned on, obtaining a first initial voltage signal of the target cell and a second initial voltage signal of an adjacent cell; the adjacent cell is adjacent to the target cell; after the balanced state of the target cell is turned on, obtaining a first voltage signal, a second voltage signal, a third voltage signal and a balanced voltage of the target cell; wherein the first voltage signal represents the voltage across a sampling resistor connected in a working loop of the target cell, the second voltage signal represents the detection voltage of the target cell, and the third voltage signal represents the detection voltage of an adjacent cell of the target cell; determining a balanced current of the target cell according to the voltage value of the first voltage signal and the sampling resistor, and determining an equivalent resistance in the working loop of the target cell according to the balanced current, the second voltage signal, the third voltage signal, the first initial voltage signal and the second initial voltage signal; determining an actual voltage of the target cell in the balanced state according to the balanced current, the equivalent resistance and the second voltage signal, and performing voltage compensation on the target cell according to the actual voltage.

[0014] The present application also provides an energy storage system, which includes: at least two battery cells; a power module; a selection module connected to the battery cells, the selection module being configured to select a target battery cell from a plurality of battery cells so that a working circuit of the target battery cell is turned on; a conversion module connected to the selection module and the power module, the conversion module being configured to balance the voltage of the target battery cell through the power module when the working circuit of the target battery cell is turned on; a balancing module connected to the battery cells, the selection module and the conversion module; wherein the balancing module includes the detection circuit as described above.

[0015] The present application provides a detection circuit, a cell voltage compensation method and an energy storage system. The detection circuit is applied to an energy storage system. The energy storage system includes at least two cells. The detection circuit includes: an acquisition module, the acquisition module includes at least a sampling resistor, the sampling resistor is arranged in a working circuit of a target cell, the acquisition module is configured to acquire the voltage across the sampling resistor and output a first voltage signal; a detection module, connected to the target cell and the acquisition module, the detection module is configured to detect the voltage of the target cell when the target cell is in a balanced state, and output a second voltage signal, and detect the voltage of a cell adjacent to the target cell, and output a third voltage signal; a processing module, connected to the detection module, the processing module is configured to determine an equalization current according to a voltage value of the first voltage signal and the sampling resistor, and determine an equivalent resistance in the working circuit of the target cell according to the equalization current, the second voltage signal, the third voltage signal, the first initial voltage signal of the target cell and the second initial voltage signal of the adjacent cell; wherein the first initial voltage signal and the second initial voltage signal are acquired by the detection module before the equalization function is turned on. Through the above method, when the battery cell is in a balanced state, the equivalent resistance in the working circuit of the target battery cell can be collected, and the real-time equivalent resistance can be used to complete the voltage compensation of the active balanced battery cell. In this way, when the equivalent resistance of the circuit increases due to problems such as poor connection of the battery sampling line, the active balanced current will increase the circuit temperature after passing through the sampling line, thereby causing some safety problems such as insulation layer damage and excessive battery temperature, thereby improving the circuit safety and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0017] Figure 1 is a structural schematic diagram of a first embodiment of a detection circuit provided by the present application;

[0018] Figure 2 is a structural schematic diagram of a second embodiment of a detection circuit provided by the present application;

[0019] Figure 3 is a structural schematic diagram of a third embodiment of a detection circuit provided by the present application;

[0020] Figure 4 is a structural schematic diagram of a fourth embodiment of a detection circuit provided by the present application;

[0021] Figure 5 It is a schematic diagram of the target battery cell working circuit provided by this application;

[0022] Figure 6 It is a flow chart of an embodiment of a cell voltage compensation method provided by the present application;

[0023] Figure 7 It is a structural schematic diagram of an embodiment of an energy storage system provided in the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It will be appreciated that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only some but not all structures related to the present application are shown in the drawings. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the art without making creative work are within the scope of protection of the present application.

[0025] The terms "first", "second", etc. in this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] See also Figure 1 , Figure 1 It is a structural schematic diagram of the first embodiment of the detection circuit provided in the present application. The detection circuit 100 is applied to an energy storage system. The energy storage system includes at least two battery cells. The detection circuit 100 includes: an acquisition module 10, a detection module 20 and a processing module 30.

[0028] Among them, the acquisition module 10 at least includes a sampling resistor RS, the sampling resistor RS is set in the working circuit of the target battery cell, and the acquisition module 10 is configured to acquire the voltage across the sampling resistor RS and output a first voltage signal; the detection module 20 is connected to the target battery cell, the acquisition module 10 and the power supply, and the detection module 20 is configured to detect the voltage of the target battery cell when the target battery cell is in a balanced state, and output a second voltage signal, and detect the voltage of the battery cell adjacent to the target battery cell, and output a third voltage signal; the processing module 30 is connected to the detection module 20, and the processing module 30 is configured to determine the balancing current I according to the voltage value of the first voltage signal and the sampling resistor RS, and determine the equivalent resistance in the working circuit of the target battery cell according to the balancing current I, the second voltage signal, the third voltage signal, the first initial voltage signal of the target battery cell and the second initial voltage signal of the adjacent battery cell; wherein the first initial voltage signal and the second initial voltage signal are acquired by the detection module 20 before the balancing function is turned on.

[0029] Among them, the battery cell is connected to the power supply through the detection circuit 100 to realize active balancing of the battery cell. The power supply is a source load device, which can be a bidirectional DC power supply. Specifically, when the battery cell is charged and balanced, the power supply provides power to the detection circuit 100, so that the actual voltage of the battery cell is consistent with the balanced voltage when the battery cell is charged and balanced; when the battery cell is discharged and balanced, the power supply consumes the power output by the detection circuit 100, so that the actual voltage of the battery cell is consistent with the balanced voltage when the battery cell is discharged and balanced.

[0030] Exemplarily, when the battery cell is monitored and controlled by the detection circuit 100, there is resistance in the sampling line between the battery cell and the detection circuit 100, which is caused by the resistance characteristics of the wire itself and the contact resistance that may exist at the connection point. In one embodiment, the second voltage signal and the third voltage signal detected by the detection module 20 are the detection voltages of the target battery cell and the battery cell adjacent to the target battery cell. When the active balancing function is not turned on, the detection voltage is the actual voltage of the target battery cell and the adjacent battery cell. When the active balancing function is turned on, the current passing through the sampling line will cause a voltage change, resulting in a deviation between the actual voltage of the target battery cell and the adjacent battery cell and the voltage detected by the detection module 20.

[0031] In one embodiment, the detection module 20 may be an analog front end, and the processing module 30 may be a single-chip microcomputer. The analog front end uses multiple sampling channels to collect analog signals of the voltage, current, temperature and other parameters of the battery cell. These analog signals are processed and converted into digital signals and then transmitted to the single-chip microcomputer through the communication interface. In other embodiments, the detection module 20 and the processing module 30 may also be integrated on the main control module.

[0032] For example, the equivalent resistance in the working loop of the target cell can be determined according to the balancing current I, the second voltage signal, the third voltage signal, the first initial voltage signal of the target cell, and the second initial voltage signal of the adjacent cell. After the equivalent resistance is determined, on the one hand, the detected voltage can be corrected to obtain an accurate actual voltage value of the cell; on the other hand, the change in the resistance of the sampling line may reflect the aging, poor contact or damage of the connection line. By detecting the resistance of the sampling line, these problems can be discovered in time and corresponding measures can be taken to repair or replace them, thereby improving the reliability of the energy storage system.

[0033] In this embodiment, the cell balancing current I, the cell voltage and the equivalent resistance in the cell balancing working loop can be detected by the acquisition module 10, the detection module 20 and the processing module 30. The detection of the balancing current I is conducive to reducing the risk of excessive charging current and discharging current in the circuit; by detecting and compensating for the influence of the sampling line resistance, the battery balancing strategy can be optimized and the cell active balancing efficiency can be improved. At the same time, by setting the resistance threshold and other methods, when the detected equivalent resistance value exceeds the set threshold, the active balancing function can be turned off to improve the safety and stability of the circuit.

[0034] See also Figure 2 , Figure 2 It is a structural schematic diagram of the second embodiment of the detection circuit provided in the present application. The detection circuit 100 is applied to an energy storage system. The energy storage system includes at least two battery cells. The detection circuit 100 includes: an acquisition module 10, a detection module 20 and a processing module 30.

[0035] Among them, the acquisition module 10 at least includes a sampling resistor RS, the sampling resistor RS is set in the working circuit of the target battery cell, and the acquisition module 10 is configured to acquire the voltage across the sampling resistor RS and output a first voltage signal; the detection module 20 is connected to the target battery cell, the acquisition module 10 and the power supply, and the detection module 20 is configured to detect the voltage of the target battery cell when the target battery cell is in a balanced state, and output a second voltage signal, and detect the voltage of the battery cell adjacent to the target battery cell, and output a third voltage signal; the processing module 30 is connected to the detection module 20, and the processing module 30 is configured to determine the balancing current I according to the voltage value of the first voltage signal and the sampling resistor RS, and determine the equivalent resistance in the working circuit of the target battery cell according to the balancing current I, the second voltage signal, the third voltage signal, the first initial voltage signal of the target battery cell and the second initial voltage signal of the adjacent battery cell; wherein the first initial voltage signal and the second initial voltage signal are acquired by the detection module 20 before the balancing function is turned on.

[0036] In some embodiments, the acquisition module 10 further includes: a plurality of sampling units 11 connected in sequence, wherein a first input end of a first sampling unit 111 in the plurality of sampling units 11 is connected to a first end of a sampling resistor RS, and a second input end of the first sampling unit 111 is connected to a second end of the sampling resistor RS; the plurality of sampling units 11 is configured to perform an amplification operation based on a voltage across the sampling resistor RS, and a first voltage signal is output by a last sampling unit in the plurality of sampling units 11.

[0037] In some embodiments, the multi-stage sampling unit 11 further includes: a second-stage sampling unit 112 and a third-stage sampling unit 113, wherein the third-stage sampling unit 113 is the last-stage sampling unit; a first input terminal of the second-stage sampling unit 112 is connected to an output terminal of the first-stage sampling unit 111; a second input terminal of the second-stage sampling unit 112 is connected to a first reference ground AB.GND, and the second-stage sampling unit 112 is configured to differentially amplify a voltage signal output by the first-stage sampling unit 111; a first input terminal of the third-stage sampling unit 113 is connected to an output terminal of the second-stage sampling unit 112; a second input terminal of the third-stage sampling unit 113 is connected to a second reference ground MGND; and the third-stage sampling unit 113 is configured to amplify in the same direction a voltage signal output by the second-stage sampling unit 112.

[0038] Exemplarily, setting up a multi-stage sampling unit 11 can gradually amplify the voltage signal across the sampling resistor RS. Each stage of the sampling unit can be designed as a sampling unit with different amplification factors and filtering characteristics to adapt to the requirements of different battery cell voltage ranges and noise environments. By adjusting the amplification factors and filtering parameters of each stage of the sampling unit, the signal processing performance of the acquisition module 10 can also be optimized to improve the accuracy and reliability of voltage measurement.

[0039] Specifically, when the balancing current I flows through the sampling resistor RS, a weak bipolar voltage signal will be generated on the sampling resistor RS, and the voltage signal needs to be amplified for processing. After the first-stage sampling unit 111 preliminarily amplifies the voltage across the sampling resistor RS, a voltage signal with the negative electrode of the target battery cell as the reference ground is obtained; after further amplification by the second-stage sampling unit 112, the reference ground of the signal is converted to the first reference ground AB.GND, which can be the reference ground of the battery module; finally, after amplification by the third-stage sampling unit 113, the output first voltage signal is made as close as possible to the maximum input voltage of the detection module 20, thereby improving the sampling accuracy.

[0040] In this embodiment, by providing a multi-stage sampling unit 11, the sampling accuracy of the acquisition unit can be improved, the signal processing capability can be enhanced, and the system flexibility can be improved, which is beneficial to improving the accuracy and reliability of detecting the balancing current I.

[0041] See also Figure 3 , Figure 3 It is a structural schematic diagram of the third embodiment of the detection circuit provided in the present application. The detection circuit 100 is applied to an energy storage system. The energy storage system includes at least two battery cells. The detection circuit 100 includes: an acquisition module 10, a detection module 20 and a processing module 30.

[0042] Among them, the acquisition module 10 at least includes a sampling resistor RS, the sampling resistor RS is set in the working circuit of the target battery cell, and the acquisition module 10 is configured to acquire the voltage across the sampling resistor RS and output a first voltage signal; the detection module 20 is connected to the target battery cell, the acquisition module 10 and the power supply, and the detection module 20 is configured to detect the voltage of the target battery cell when the target battery cell is in a balanced state, and output a second voltage signal, and detect the voltage of the battery cell adjacent to the target battery cell, and output a third voltage signal; the processing module 30 is connected to the detection module 20, and the processing module 30 is configured to determine the balancing current I according to the voltage value of the first voltage signal and the sampling resistor RS, and determine the equivalent resistance in the working circuit of the target battery cell according to the balancing current I, the second voltage signal, the third voltage signal, the first initial voltage signal of the target battery cell and the second initial voltage signal of the adjacent battery cell; wherein the first initial voltage signal and the second initial voltage signal are acquired by the detection module 20 before the balancing function is turned on.

[0043] In some embodiments, the first stage sampling unit 111 includes: a first operational amplifier A1, a first resistor R1, and a second resistor R2. The non-inverting input terminal of the first operational amplifier A1 is connected to the first end of the sampling resistor RS through the first resistor R1, and the inverting input terminal of the first operational amplifier A1 is connected to the second end of the sampling resistor RS; the first end of the second resistor R2 is coupled to the reference voltage terminal REF, and the second end of the second resistor R2 is connected to the non-inverting input terminal of the first operational amplifier A1.

[0044] In some embodiments, the first-stage sampling unit 111 further includes: an eleventh resistor R11, a twelfth resistor R12, a first capacitor C1, and a second capacitor C2. The first end of the eleventh resistor R11 is connected to the second end of the sampling resistor RS, and the second end of the eleventh resistor R11 is connected to the inverting input terminal of the first operational amplifier A1; the first end of the twelfth resistor R12 is connected to the inverting input terminal of the first operational amplifier A1, and the second end of the twelfth resistor R12 is connected to the output terminal of the first operational amplifier A1; the first end of the first capacitor C1 is connected to the first end of the second resistor R2, and the second end of the first capacitor C1 is connected to the non-inverting input terminal of the first operational amplifier A1; the first end of the second capacitor C2 is connected to the inverting input terminal of the first operational amplifier A1, and the second end of the second capacitor C2 is connected to the output terminal of the first operational amplifier A1.

[0045] In one embodiment, the resistance value of the first resistor R1 is equal to the resistance value of the eleventh resistor R11, and the resistance value of the second resistor R2 is equal to the resistance value of the twelfth resistor R12. The output voltage of the first operational amplifier A1 can be expressed by Formula 1:

[0046]

[0047] Wherein, V1 represents the output voltage of the first operational amplifier A1, VRS represents the voltage across the sampling resistor RS, and VREF represents the reference voltage output by the reference voltage terminal REF.

[0048] Exemplarily, the amplification gain G1 of the first stage sampling unit 111 is:

[0049]

[0050] In some embodiments, the second-stage sampling unit 112 includes: a second operational amplifier A2, a third resistor R3, and a fourth resistor R4. The in-phase input terminal of the second operational amplifier A2 is connected to the output terminal of the first operational amplifier A1 through the third resistor R3, and the inverting input terminal of the second operational amplifier A2 is connected to the first reference ground AB.GND; the second operational amplifier A2 is configured to differentially amplify the voltage signal output by the first operational amplifier A1; the first end of the fourth resistor R4 is connected to the second reference ground MGND, and the second end of the fourth resistor R4 is connected to the first input terminal of the second operational amplifier A2.

[0051] In some embodiments, the second-stage sampling unit 112 further includes: a thirteenth resistor R13, a fourteenth resistor R14, a third capacitor C3, and a fourth capacitor C4. A first end of the thirteenth resistor R13 is connected to the first reference ground AB.GND, and a second end of the thirteenth resistor R13 is connected to the inverting input terminal of the second operational amplifier A2; a first end of the fourteenth resistor R14 is connected to the second end of the thirteenth resistor R13, and a second end of the fourteenth resistor R14 is connected to the output terminal of the second operational amplifier A2; a first end of the third capacitor C3 is connected to the second end of the thirteenth resistor R13, and a second end of the third capacitor C3 is connected to the output terminal of the second operational amplifier A2; a first end of the fourth capacitor C4 is connected to the second reference ground MGND, and a second end of the fourth capacitor C4 is connected to the non-inverting input terminal of the second operational amplifier A2.

[0052] In one embodiment, the resistance value of the third resistor R3 is equal to the resistance value of the thirteenth resistor R13, and the resistance value of the fourth resistor R4 is equal to the resistance value of the fourteenth resistor R14. Then, the output voltage V2 of the second operational amplifier A2 can be expressed by Formula 2 as follows:

[0053]

[0054] Exemplarily, the amplification gain G2 of the second-stage sampling unit 112 is:

[0055]

[0056] In some embodiments, the third sampling unit 113 includes: a third operational amplifier A3, a fifth resistor R5, and a sixth resistor R6. The non-inverting input terminal of the third operational amplifier A3 is connected to the output terminal of the second sampling unit 112, and the second terminal of the third operational amplifier A3 is connected to the second reference ground MGND; the third operational amplifier A3 is configured to amplify the voltage signal output by the second sampling unit 112 in the same direction; the first terminal of the fifth resistor R5 is connected to the inverting input terminal of the third operational amplifier A3, and the second terminal of the fifth resistor R5 is connected to the second reference ground MGND; the first terminal of the sixth resistor R6 is connected to the inverting input terminal of the third operational amplifier A3, and the second terminal of the sixth resistor R6 is connected to the output terminal of the third operational amplifier A3.

[0057] In some embodiments, the third-stage sampling unit 113 further includes: a fifteenth resistor R15 and a fifth capacitor C5. A first end of the fifteenth resistor R15 is connected to the output end of the second operational amplifier A2, and a second end of the fifteenth resistor R15 is connected to the non-inverting input end of the third operational amplifier A3; a first end of the fifth capacitor C5 is connected to the non-inverting input end of the third operational amplifier A3, and a second end of the fifth capacitor C5 is connected to the second reference ground MGND.

[0058] In one embodiment, the output voltage V3 of the third operational amplifier A3 can be expressed by Formula 3:

[0059]

[0060] Specifically, the amplification gain G3 of the third-stage sampling unit 113 is:

[0061]

[0062] According to Ohm's law, the relationship between the balancing current I flowing through the sampling resistor RS and the voltage VRS across the sampling resistor RS is:

[0063]

[0064] The input voltage of the detection module 20 is the output voltage V3 of the third operational amplifier A3. The detection module 20 converts the analog quantity into a digital signal and transmits it to the processing module 30. The processing module 30 reversely calculates the balancing current I according to the output voltage V3 of the third operational amplifier A3. Combining the expressions of formula 1, formula 2, formula 3, G1, G2 and G3, the conversion relationship between the output voltage V3 of the third operational amplifier A3 and the balancing current I can be obtained, which can be expressed by formula 4 as follows:

[0065]

[0066] According to formula 4, the size and direction of the balancing current I can be calculated. The balancing charging current is positive, and the balancing discharging current is negative.

[0067] In this embodiment, the accuracy of sampling the balancing current I can be improved by the step-by-step amplification of the three-stage sampling unit. When an overcurrent occurs in the circuit, the size of the balancing current I can be adjusted by adjusting different parameters, such as gains G1, G2 and G3, thereby improving the safety of the line.

[0068] See also Figure 4 , Figure 4 It is a structural schematic diagram of the fourth embodiment of the detection circuit provided in the present application. The detection circuit 100 is applied to an energy storage system. The energy storage system includes at least two battery cells. The detection circuit 100 includes: an acquisition module 10, a detection module 20 and a processing module 30.

[0069] Among them, the acquisition module 10 at least includes a sampling resistor RS, the sampling resistor RS is set in the working circuit of the target battery cell, and the acquisition module 10 is configured to acquire the voltage across the sampling resistor RS and output a first voltage signal; the detection module 20 is connected to the target battery cell, the acquisition module 10 and the power supply, and the detection module 20 is configured to detect the voltage of the target battery cell when the target battery cell is in a balanced state, and output a second voltage signal, and detect the voltage of the battery cell adjacent to the target battery cell, and output a third voltage signal; the processing module 30 is connected to the detection module 20, and the processing module 30 is configured to determine the balancing current I according to the voltage value of the first voltage signal and the sampling resistor RS, and determine the equivalent resistance in the working circuit of the target battery cell according to the balancing current I, the second voltage signal, the third voltage signal, the first initial voltage signal of the target battery cell and the second initial voltage signal of the adjacent battery cell; wherein the first initial voltage signal and the second initial voltage signal are acquired by the detection module 20 before the balancing function is turned on.

[0070] In some embodiments, the detection circuit 100 also includes: a voltage detection module 40, which is arranged in the working circuit of the target battery cell and connected to the detection module 20, and the voltage detection module 40 is configured to detect the equilibrium voltage when the target battery cell is in an equilibrium state; wherein the processing module 30 is also configured to determine the actual voltage of the target battery cell and the actual voltage of the adjacent battery cell based on the equilibrium current I, the equivalent resistance, the second voltage signal and the third voltage signal.

[0071] In some embodiments, the voltage detection module 40 includes: a fourth operational amplifier A4, a seventh resistor R7, and an eighth resistor R8. The in-phase input terminal of the fourth operational amplifier A4 is connected to the first pole AB.POS of the target battery cell through the seventh resistor R7, and the inverting input terminal of the fourth operational amplifier A4 is connected to the first reference ground; the first end of the eighth resistor R8 is connected to the second reference ground MGND, and the second end of the eighth resistor R8 is connected to the in-phase input terminal of the fourth operational amplifier A4.

[0072] In some embodiments, the voltage detection module 40 further includes: a sixteenth resistor R16, a seventeenth resistor R17, a sixth capacitor C6 and a seventh capacitor C7. The first end of the sixteenth resistor R16 is connected to the first reference ground AB.GND, and the second end of the sixteenth resistor R16 is connected to the inverting input terminal of the fourth operational amplifier A4; the first end of the seventeenth resistor R17 is connected to the inverting input terminal of the fourth operational amplifier A4, and the second end of the seventeenth resistor R17 is connected to the output terminal of the fourth operational amplifier A4; the first end of the sixth capacitor C6 is connected to the inverting input terminal of the fourth operational amplifier A4, and the second end of the sixth capacitor C6 is connected to the output terminal of the fourth operational amplifier A4; the first end of the seventh capacitor C7 is connected to the second reference ground AB.GND, and the second end of the seventh capacitor C7 is connected to the non-inverting input terminal of the fourth operational amplifier A4.

[0073] In one embodiment, the resistance of the eighth resistor R8 is equal to the resistance of the seventeenth resistor R17, and the resistance of the seventh resistor R7 is equal to the resistance of the sixteenth resistor R16. Then, the output voltage of the fourth operational amplifier A4 can be expressed by Formula 5 as follows:

[0074]

[0075] Wherein, V4 represents the output voltage of the fourth operational amplifier A4, and VDC represents the balanced voltage in the working loop of the target battery cell.

[0076] Specifically, the amplification gain G4 of the fourth operational amplifier A4 is:

[0077]

[0078] In some embodiments, the voltage detection module 40 further includes: a fifth operational amplifier A5, a ninth resistor R9, and a tenth resistor R10. The in-phase input terminal of the fifth operational amplifier A5 is connected to the output terminal of the fourth operational amplifier A4, and the second terminal of the fifth operational amplifier A5 is connected to the second reference ground MGND; the first terminal of the ninth resistor R9 is connected to the second input terminal of the fifth operational amplifier A5, and the second terminal of the ninth resistor R9 is connected to the second reference ground MGND; the first terminal of the tenth resistor R10 is connected to the second input terminal of the fifth operational amplifier A5, and the second terminal of the tenth resistor R10 is connected to the output terminal of the fifth operational amplifier A5.

[0079] In some embodiments, the voltage detection module 40 further includes: an eighteenth resistor R18 and an eighth capacitor C8. A first end of the eighteenth resistor R18 is connected to the output end of the fourth operational amplifier A4, and a second end of the eighteenth resistor R18 is connected to the non-inverting input end of the fifth operational amplifier A5; a first end of the eighth capacitor C8 is connected to the non-inverting input end of the fifth operational amplifier A5, and a second end of the eighth capacitor C8 is connected to the second reference ground MGND.

[0080] In one embodiment, the output voltage V5 of the fifth operational amplifier A5 can be expressed by Formula 6:

[0081]

[0082] Specifically, the amplification gain G5 of the fifth operational amplifier A5 is:

[0083]

[0084] The input voltage of the detection module 20 is the output voltage V5 of the fifth operational amplifier A5. The detection module 20 converts the analog quantity into a digital signal and transmits it to the processing module 30. The processing module 30 reversely calculates the equalization voltage VDC according to the output voltage V5 of the fifth operational amplifier A5. Combining the expressions of Formula 5, Formula 6, G4 and G5, the conversion relationship between the output voltage V5 of the fifth operational amplifier A5 and the equalization voltage VDC can be obtained, which can be expressed by Formula 7 as follows:

[0085]

[0086] In the present embodiment, when the target battery cell is actively balanced, the voltage detection module 40 detects the balanced voltage of the target battery cell during balanced operation, i.e., the input voltage signal of the fourth operational amplifier A4. The voltage signal is a signal with the negative electrode of the target battery cell as the reference ground, and the reference ground of the output voltage signal of the fourth operational amplifier A4 is the first reference ground AB.GND, i.e., the first operational amplifier A1 completes the transfer of the reference ground of the balanced voltage VDC; the fifth operational amplifier A5 amplifies the output signal of the fourth operational amplifier A4, so that the output voltage of the fifth operational amplifier A5 is as close as possible to the maximum input voltage of the detection module 20, so as to improve the accuracy of the balanced voltage sampling.

[0087] See also Figure 5 , Figure 5 It is a schematic diagram of the working circuit of the target battery cell provided in the present application. The target battery cell is connected to the power supply through the detection circuit 100 to achieve active balancing of the target battery cell.

[0088] In the figure, Bn represents the target battery cell, Bn+1 and Bn-1 respectively represent two adjacent battery cells of the target battery cell Bn. In other embodiments, the target battery cell Bn can be the first battery cell, and its adjacent battery cells only include Bn+1; or the target battery cell Bn is the highest battery cell, and its adjacent battery cells only include Bn-1.

[0089] When the target cell Bn is discharged evenly and the equalizing current I flows through the equivalent resistor Rn, a voltage drop is generated, and the voltage is positive on the left and negative on the right. When the equalizing current I passes through Rn-1, a voltage drop is generated, and the voltage is positive on the right and negative on the left. At this time, the detection voltage Vsn of the target cell Bn detected by the detection module 20, the detection voltage Vsn-1 of the adjacent cell Bn-1, and the detection voltage Vsn+1 of the adjacent cell Bn+1 are different from the actual voltage Vbn of the target cell Bn, the actual voltage Vbn-1 of the adjacent cell Bn-1, and the actual voltage Vbn+1 of the adjacent cell Bn+1. Similarly, when the target cell Bn is charged evenly and the equalizing current I passes through Rn, a voltage drop is generated, and the voltage is negative on the left and positive on the right. When the equalizing current I passes through Rn-1, a voltage drop is generated, and the voltage is negative on the right and positive on the left. At this time, the voltage of the target cell Bn and the adjacent cells Bn+1 and Bn-1 of the target cell detected by the detection module 20 are different from the actual voltage.

[0090] Specifically, the detected voltage Vsn and the actual voltage Vbn of the target battery cell Bn can be expressed by Formula 8:

[0091]

[0092] The detected voltage Vsn-1 and the actual voltage Vbn-1 of the adjacent cell Bn-1 of the target cell Bn can be expressed by Formula 9:

[0093]

[0094] The detected voltage Vbn+1 and the actual voltage Vbn+1 of the adjacent cell Bn+1 of the target cell can be expressed by formula 10:

[0095]

[0096] The balancing current I is the balancing current I expressed by Formula 4. The balancing current I during charge balancing is positive, and the balancing current I during discharge balancing is negative.

[0097] According to Formula 4, Formula 8, Formula 9 and Formula 10, the equivalent resistances Rn and Rn-1 in the working loop of the target battery cell Bn and the actual voltages of the target battery cell Bn and the adjacent battery cells Bn+1 and Bn-1 can be obtained.

[0098] Take the target cell Bn as the first cell in the battery module, and its adjacent cells only include Bn+1 as an example. Before the equalization function is turned on, the equalization current I is zero. At this time, the detection voltage of the cell is equal to the actual voltage of the cell, and the detection voltage of the current cell is used as the actual voltage of the cell. Then the actual voltages Vbn and Vbn+1 of the target cell Bn and the adjacent cell Bn+1 are Vsn1 (i.e., the first initial voltage) and Vsn1+1 (i.e., the second initial voltage), respectively, and the processing module 30 records the voltage values; after the equalization function is turned on, the equalization current I can be obtained according to formula 4, and the processing module 30 records the current value; at the same time, the processing module 30 quickly records the detection voltages Vsn and Vsn+1 of the target cell Bn and the adjacent cell Bn+1 detected by the detection module 20, respectively, as Vsn2 (i.e., the second voltage signal) and Vsn2+1 (i.e., the third voltage signal); finally, according to formulas 8 and 10, the specific values ​​of the equivalent resistances Rn and Rn-1 can be obtained.

[0099] For example, the target cell Bn is one of the second to the second highest cells in the battery module, and its adjacent cells include Bn+1 and Bn-1. Similarly, before the balancing function is turned on, the processing module 30 records the voltage value with the detected voltage at this time as the actual voltage; after the balancing function is turned on, the processing module 30 records the balancing current I value and the detected voltage values ​​of the three cells at this time, and obtains the specific values ​​of the equivalent resistances Rn and Rn-1 according to Formula 9 and Formula 10.

[0100] It can be understood that after the balancing function is turned on, the battery cell voltage compensation is real-time online compensation. There is no need to turn off the balancing function during the compensation process. According to the balancing current I and the equivalent resistances Rn and Rn-1 in the working circuit of the target battery cell Bn, the actual voltage of the target battery cell Bn and the adjacent battery cells Bn+1 and Bn-1 can be obtained.

[0101] Taking the target cell as one of the second to the second highest cells in the battery module as an example, after the balancing function is turned on, there is a difference between the detected voltage and the actual voltage of the target cell Bn and the adjacent cells Bn+1 and Bn-1 detected by the detection module 20. After obtaining the balancing current I according to formula 4, the actual voltage Vbn of the target cell Bn is obtained according to formula 8, the actual voltage Vbn-1 of the adjacent cell Bn-1 is obtained according to formula 9, and the actual voltage Vbn+1 of the adjacent cell Bn+1 is obtained according to formula 10. According to the difference between the actual voltage of each cell and the balancing voltage, each cell is compensated to achieve cell voltage balancing.

[0102] See also Figure 6 , is a flow chart of an embodiment of a cell voltage compensation method provided by the present application, the method comprising:

[0103] Step S61: before the balancing state of the target cell is turned on, obtaining a first initial voltage signal of the target cell and a second initial voltage signal of an adjacent cell; the adjacent cell is adjacent to the target cell.

[0104] Step S62: After the balancing state of the target battery cell is turned on, the first voltage signal, the second voltage signal, the third voltage signal and the balancing voltage of the target battery cell are obtained; wherein the first voltage signal represents the voltage across the sampling resistor RS connected in the working circuit of the target battery cell, the second voltage signal represents the detection voltage of the target battery cell, and the third voltage signal represents the detection voltage of the adjacent battery cells of the target battery cell.

[0105] Step S63: determining the balancing current I of the target cell according to the voltage value of the first voltage signal and the sampling resistor RS, and determining the equivalent resistance in the working loop of the target cell according to the balancing current I, the second voltage signal, the third voltage signal, the first initial voltage signal and the second initial voltage signal.

[0106] Step S64: determining the actual voltage of the target battery cell in the balanced state according to the balanced current I, the equivalent resistance and the second voltage signal, and performing voltage compensation on the target battery cell according to the actual voltage.

[0107] See also Figure 7 , Figure 7 It is a structural diagram of an embodiment of an energy storage system provided by the present application. The energy storage system 1000 includes: at least two battery cells, a power module 200, a selection module 300, a conversion module 400 and a balancing module 500; the selection module 300 connects the battery cells, and the selection module 300 is configured to select a target battery cell from a plurality of battery cells so that the working circuit of the target battery cell is turned on; the conversion module 400 connects the selection module 300 and the power module 200, and the conversion module 400 is configured to balance the voltage of the target battery cell through the power module 200 when the working circuit of the target battery cell is turned on; the balancing module 500 connects the battery cells, the selection module 300 and the conversion module 400, and the balancing module 500 includes the detection circuit 100 as described above, which will not be repeated here.

[0108] Among them, the selection module 300 includes a plurality of first selection switches (not shown) respectively connected to the positive and negative poles of the battery cells and a plurality of second selection switches (not shown) with opposite polarities. The selection module 300 is configured to select a target battery cell from a plurality of battery cells in response to the first selection switches respectively connected to the positive and negative poles of the target battery cell being turned on; the selection module 300 is also configured to turn on a working circuit of the target battery cell in response to the turning on of a group of second selection switches with opposite polarities.

[0109] Among them, the conversion module 400 can be a DCDC bidirectional converter. When the target battery cell is charged and balanced, the bidirectional DCDC charging direction works, and the energy of the power module 200 is converted to the target battery cell; when the target battery cell is discharged and balanced, the bidirectional DCDC discharges and converts the energy of the target battery cell to the power module 200, thereby realizing active balancing of the target battery cell.

[0110] In the several embodiments provided in this application, it should be understood that the disclosed methods and devices can be implemented in other ways. For example, the device implementation described above is only illustrative, for example, the division of the modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0111] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0112] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0113] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A detection circuit, characterized in that: The detection circuit is applied to an energy storage system, the energy storage system includes at least two battery cells, and the detection circuit includes: A collection module, the collection module at least includes a sampling resistor, the sampling resistor is arranged in a working circuit of the target battery cell, and the collection module is configured to collect the voltage across the sampling resistor and output a first voltage signal; A detection module connected to the target battery cell, the acquisition module and a power source, wherein the detection module is configured to detect the voltage of the target battery cell and output a second voltage signal when the target battery cell is in a balanced state, and to detect the voltage of a battery cell adjacent to the target battery cell and output a third voltage signal; A processing module is connected to the detection module, and the processing module is configured to determine the balancing current according to the voltage value of the first voltage signal and the sampling resistance, and determine the equivalent resistance in the working circuit of the target battery cell according to the balancing current, the second voltage signal, the third voltage signal, the first initial voltage signal of the target battery cell and the second initial voltage signal of the adjacent battery cell; wherein the first initial voltage signal and the second initial voltage signal are collected by the detection module before the balancing function is turned on, and the first voltage signal, the second voltage signal and the third voltage signal are obtained after the balancing function is turned on.

2. The detection circuit according to claim 1, characterized in that: The acquisition module also includes: a multi-stage sampling unit connected in sequence, A first input end of a first sampling unit in the multi-stage sampling unit is connected to a first end of the sampling resistor, and a second input end of the first sampling unit is connected to a second end of the sampling resistor; The multi-stage sampling unit is configured to perform an amplification operation according to the voltage across the sampling resistor, and the last stage sampling unit in the multi-stage sampling unit outputs the first voltage signal.

3. The detection circuit according to claim 2, characterized in that: The first-stage sampling unit comprises: A first operational amplifier, wherein a non-inverting input terminal of the first operational amplifier is connected to a first end of the sampling resistor via a first resistor, and an inverting input terminal of the first operational amplifier is connected to a second end of the sampling resistor; A second resistor, wherein a first end of the second resistor is coupled to the reference voltage end, and a second end of the second resistor is connected to the non-inverting input end of the first operational amplifier.

4. The detection circuit according to claim 3, characterized in that: The multi-stage sampling unit further comprises: a second-stage sampling unit and a third-stage sampling unit, wherein the third-stage sampling unit is the last-stage sampling unit; The first input end of the second sampling unit is connected to the output end of the first sampling unit; the second input end of the second sampling unit is connected to the first reference ground, and the second sampling unit is configured to differentially amplify the voltage signal output by the first sampling unit; The first input end of the third sampling unit is connected to the output end of the second sampling unit; the second input end of the third sampling unit is connected to the second reference ground; the third sampling unit is configured to amplify the voltage signal output by the second sampling unit in the same direction.

5. The detection circuit according to claim 4, characterized in that: The second-stage sampling unit comprises: a second operational amplifier, wherein a non-inverting input terminal of the second operational amplifier is connected to an output terminal of the first operational amplifier via a third resistor, and an inverting input terminal of the second operational amplifier is connected to the first reference ground; the second operational amplifier is configured to differentially amplify a voltage signal output by the first operational amplifier; A fourth resistor, wherein a first end of the fourth resistor is connected to the second reference ground, and a second end of the fourth resistor is connected to the first input end of the second operational amplifier.

6. The detection circuit according to claim 4, characterized in that: The third-level sampling unit comprises: a third operational amplifier, wherein a non-inverting input terminal of the third operational amplifier is connected to an output terminal of the second-stage sampling unit, and a second terminal of the third operational amplifier is connected to the second reference ground; the third operational amplifier is configured to perform in-phase amplification on a voltage signal output by the second-stage sampling unit; a fifth resistor, wherein a first end of the fifth resistor is connected to the inverting input terminal of the third operational amplifier, and a second end of the fifth resistor is connected to the second reference ground; A sixth resistor, wherein a first end of the sixth resistor is connected to the inverting input end of the third operational amplifier, and a second end of the sixth resistor is connected to the output end of the third operational amplifier.

7. The detection circuit according to claim 1, characterized in that: The detection circuit also includes: A voltage detection module, disposed in the working circuit of the target battery cell and connected to the detection module, wherein the voltage detection module is configured to detect an equilibrium voltage when the target battery cell is in an equilibrium state; The processing module is further configured to determine an actual voltage of the target battery cell and an actual voltage of an adjacent battery cell according to the balancing current, the equivalent resistance, the second voltage signal and the third voltage signal.

8. The detection circuit according to claim 7, characterized in that: The voltage detection module comprises: a fourth operational amplifier, wherein a non-inverting input terminal of the fourth operational amplifier is connected to the first electrode of the target battery cell through a seventh resistor, and an inverting input terminal of the fourth operational amplifier is connected to the first reference ground; an eighth resistor, a first end of the eighth resistor being connected to the second reference ground, and a second end of the eighth resistor being connected to the non-inverting input end of the fourth operational amplifier; a fifth operational amplifier, wherein a non-inverting input terminal of the fifth operational amplifier is connected to an output terminal of the fourth operational amplifier, and a second terminal of the fifth operational amplifier is connected to the second reference ground; a ninth resistor, wherein a first end of the ninth resistor is connected to the second input end of the fifth operational amplifier, and a second end of the ninth resistor is connected to the second reference ground; A tenth resistor, wherein a first end of the tenth resistor is connected to the second input end of the fifth operational amplifier, and a second end of the tenth resistor is connected to the output end of the fifth operational amplifier.

9. A cell voltage compensation method, characterized in that: The method comprises: Before the balanced state of the target battery cell is turned on, obtaining a first initial voltage signal of the target battery cell and a second initial voltage signal of an adjacent battery cell; the adjacent battery cell is adjacent to the target battery cell; After the balancing state of the target battery cell is turned on, a first voltage signal, a second voltage signal, a third voltage signal and a balancing voltage of the target battery cell are obtained; wherein the first voltage signal represents the voltage across the sampling resistor connected in the working circuit of the target battery cell, the second voltage signal represents the detection voltage of the target battery cell, and the third voltage signal represents the detection voltage of the battery cell adjacent to the target battery cell; Determine the balancing current of the target battery cell according to the voltage value of the first voltage signal and the sampling resistor, and determine the equivalent resistance in the working loop of the target battery cell according to the balancing current, the second voltage signal, the third voltage signal, the first initial voltage signal, and the second initial voltage signal; The actual voltage of the target battery cell in the balanced state is determined according to the balanced current, the equivalent resistance and the second voltage signal, and voltage compensation is performed on the target battery cell according to the actual voltage.

10. An energy storage system, characterized in that: The energy storage system comprises: At least two cells; Power module; A selection module connected to the battery cells, wherein the selection module is configured to select a target battery cell from the plurality of battery cells so as to make the working circuit of the target battery cell conductive; a conversion module, connected to the selection module and the power module, wherein the conversion module is configured to balance the voltage of the target battery cell through the power module when the working circuit of the target battery cell is turned on; A balancing module, connecting the battery cell, the selection module and the conversion module; Wherein, the balancing module comprises the detection circuit as described in any one of claims 1-8.

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