Insulation detection method of energy storage system and energy storage system

Abstract

The invention relates to the technical field of energy storage systems, and discloses an insulation detection method of an energy storage system and the energy storage system. According to the application, the total negative external voltage is sampled for multiple times after the insulation detection switch is closed, when the ratio of the multiple times of sampling meets the preset condition, it can be determined that the voltage does not change and the Y capacitor is stable, and at the moment, according to the stable total negative external voltage obtained by sampling, the Y capacitor is stable by sampling the total negative external voltage for multiple times. The change condition of the Y capacitor is speculated according to the stability condition of the total negative external voltage, so that the total positive external voltage when the Y capacitor is stable is calculated according to the total negative external voltage under the condition that the Y capacitor is stable, and the impedance of the negative electrode to the shell and the impedance of the positive electrode to the shell are further calculated, thereby judging whether the energy storage system is insulated or not. The influence of existence and size change of the Y capacitor on the insulation detection precision is eliminated, so that the insulation detection precision of the energy storage system is improved.

Description

Technical Field

[0001] This application relates to the technical field of energy storage systems, and particularly to an insulation detection method for an energy storage system and an energy storage system. Background Art

[0002] The structure of a battery energy storage system (BESS) is to form a battery cluster by connecting a large number of batteries in series and parallel. During the operation of the energy storage system, the generated voltage is at a relatively high level, and the insulation level of the entire system plays a direct decisive role in the reliable operation of the equipment. When affected by environmental factors (such as changes in humidity or temperature), the aging of system equipment over time, the possible damage to the wire harness insulation layer for various reasons; and the wear of the battery insulation layer during long-term use. These factors combined will ultimately lead to a decrease in the insulation level of the energy storage system. In view of the above situation, in order to ensure the reliable operation of the energy storage system and improve its reliability and stability during operation, it is very necessary to equip a corresponding device to perform necessary and continuous monitoring of the insulation level of the energy storage system. Specifically, before and after closing the relay in the high-voltage box of the energy storage system, insulation detection operations must be performed on the entire system. Especially after the relay is closed, the battery energy storage system will charge the X capacitor inside the power conversion system (PCS). Since there are parasitic Y capacitors between the positive electrode and the negative electrode of the energy storage system and the shell ground, when the battery control unit (BCU) calculates the insulation resistance value, it needs to consider the size of the Y capacitor.

[0003] Therefore, in order to ensure the high precision of insulation detection to ensure the safe and stable operation of the energy storage system, it is urgent to explore an effective algorithm and strategy to eliminate the influence of the presence and size change of the Y capacitor on the insulation detection precision. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide an insulation detection method for an energy storage system and an energy storage system, so as to eliminate the influence of the presence and size change of the Y capacitor on the insulation detection precision, thereby ensuring the high precision of insulation detection and ensuring the safe and stable operation of the energy storage system.

[0005] To solve the above technical problems, an embodiment of the present application provides an insulation detection method for an energy storage system, which is applied to the energy storage system. The energy storage system includes a relay, a battery control unit, a battery cluster, and an insulation detection circuit connected to each other. The insulation detection circuit includes: a first detection circuit and a second detection circuit, and the resistors included in the first detection circuit and the second detection circuit are different; the insulation detection method for the energy storage system includes: closing a first switch, where the first switch is the switch of the first detection circuit; sampling the total negative external voltage to obtain a first sampling voltage and a second sampling voltage; determining a first calculated voltage of the total negative external voltage according to the ratio of the first sampling voltage and the second sampling voltage, and calculating a first total positive voltage of the total positive external voltage according to the first calculated voltage and the total voltage of the battery cluster; closing a second switch, where the second switch is the switch of the second detection circuit; sampling the total negative external voltage to obtain a third sampling voltage and a fourth sampling voltage; determining a second calculated voltage of the total negative external voltage according to the ratio of the third sampling voltage and the fourth sampling voltage, and calculating a second total positive voltage of the total positive external voltage according to the second calculated voltage and the total voltage of the battery cluster; calculating the negative terminal-to-case impedance and the positive terminal-to-case impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage; and determining whether the energy storage system is insulated according to the negative terminal-to-case impedance and the positive terminal-to-case impedance.

[0006] An embodiment of the present application also provides an energy storage system, which includes a relay, a battery control unit, a battery cluster, and an insulation detection circuit connected to each other. The insulation detection circuit includes: a battery cluster, a total negative resistor, a total positive resistor, a first switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a second switch, and a sampling module; wherein, the battery cluster, the total negative resistor, and the total positive resistor are connected in sequence to form a first series circuit; the battery cluster, the first resistor, the second resistor, the third resistor, and the fourth resistor are connected in sequence to form a second series circuit; the sampling module is arranged between the third resistor and the fourth resistor; the first series circuit and the second series circuit are connected in parallel; one end of the first switch is connected between the total negative resistor and the total positive resistor, and the other end of the first switch is connected between the second resistor and the third resistor; one end of the second switch is connected between the first resistor and the second resistor, and the other end of the second switch is connected between the fourth resistor and the battery cluster.

[0007] In the embodiment of the present application, during the insulation detection of the energy storage system, two closed circuits with different resistor combinations are formed for detection. After closing the first switch, the total negative external voltage is sampled multiple times. When the ratio of the multiple samplings meets the preset condition, it can be determined that the voltage does not change and the Y capacitor is stable. At this time, according to the stable total negative external voltage obtained by sampling, that is, the first calculated voltage, the first total positive voltage is calculated, which can eliminate the influence of the Y capacitor on the insulation detection accuracy of the energy storage system. Similarly, after closing the second switch, the stable total negative external voltage obtained by sampling the total negative external voltage multiple times, that is, the second calculated voltage, is used to calculate the second total positive voltage under the condition of eliminating the influence of the change of the Y capacitor. Finally, the negative terminal-to-case impedance and the positive terminal-to-case impedance of the energy storage system are calculated based on the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage, so as to determine whether the energy storage system reaches insulation. That is to say, in the present application, by sampling the total negative external voltage multiple times and inferring the change of the Y capacitor based on the stability of the total negative external voltage, when the Y capacitor is stable, the total positive external voltage when the Y capacitor is stable is calculated according to the total negative external voltage, and further the negative terminal-to-case impedance and the positive terminal-to-case impedance are calculated, so as to determine whether the energy storage system is insulated, eliminating the influence of the existence and size change of the Y capacitor on the insulation detection accuracy, thereby improving the insulation detection accuracy of the energy storage system.

[0008] In addition, the sampling of the total negative external voltage to obtain the first sampling voltage and the second sampling voltage includes: after closing the first switch, at an interval of the first preset duration, the total negative external voltage is sampled in the first group, and the sampling result is filtered to obtain the first sampling voltage; after obtaining the first sampling voltage, at an interval of the second preset duration, the total negative external voltage is sampled in the second group, and the sampling result is filtered to obtain the second sampling voltage.

[0009] In addition, the sampling periods of the first group of sampling and the second group of sampling are the same as the second preset duration, and the number of times of the first group of sampling and the second group of sampling is the same.

[0010] In addition, the first preset duration is 10 ms, the first preset duration is equal to the second preset duration, and the number of times of the first group of sampling and the second group of sampling is 5 times each.

[0011] In addition, the sampling of the total negative external voltage to obtain a third sampling voltage and a fourth sampling voltage includes: after closing the second switch, at an interval of a third preset duration, performing a third group of samplings on the total negative external voltage, and filtering the sampling results to obtain the third sampling voltage; after obtaining the third sampling voltage, at an interval of a fourth preset duration, performing a fourth group of samplings on the total negative external voltage, and filtering the sampling results to obtain the fourth sampling voltage.

[0012] In addition, the sampling periods of the third group of samplings and the fourth group of samplings are the same; the sampling period of the third group of samplings is different from the third preset duration, and the number of samplings in the third group of samplings and the fourth group of samplings is the same.

[0013] In addition, the third preset duration is 1000 ms, the fourth preset duration is the same as the sampling periods of the third group of samplings and the fourth group of samplings, and the fourth preset duration is 10 ms; the number of samplings in the third group of samplings and the fourth group of samplings is 5 times each.

[0014] In addition, the insulation detection circuit further includes: a total negative resistance, a total positive resistance, a first resistor, a second resistor, a third resistor, and a fourth resistor; the battery cluster, the total negative resistance, and the total positive resistance are connected in sequence to form a first series circuit; the battery cluster, the first resistor, the second resistor, the third resistor, and the fourth resistor are connected in sequence to form a second series circuit; the first series circuit and the second series circuit are connected in parallel; the calculating of the negative electrode to housing impedance and the positive electrode to housing impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage includes: calculating the negative electrode to housing impedance Rn through the following formula according to the first resistance value R1 of the first resistor, the second resistance value R2 of the second resistor, the third resistance value R3 of the third resistor, the fourth resistance value R4 of the fourth resistor, the first calculated voltage, the second calculated voltage, the first total positive voltage, and the second total positive voltage: ; where, R1 is the first resistance value of the first resistor; R2 is the second resistance value of the second resistor; R3 is the third resistance value of the third resistor; R4 is the fourth resistance value of the fourth resistor; Un1 is the first calculated voltage; Un2 is the second calculated voltage; Up1 is the first total positive voltage; Up2 is the second total positive voltage.

[0015] In addition, the insulation detection circuit further includes: a total negative resistance, a total positive resistance, a first resistor, a second resistor, a third resistor, and a fourth resistor; the battery cluster, the total negative resistance, and the total positive resistance are connected in sequence to form a first series circuit; the battery cluster, the first resistor, the second resistor, the third resistor, and the fourth resistor are connected in sequence to form a second series circuit; the first series circuit and the second series circuit are connected in parallel; calculating the negative electrode-to-housing impedance and the positive electrode-to-housing impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage includes: according to the first resistance value of the first resistor, the second resistance value of the second resistor, the third resistance value of the third resistor, the fourth resistance value of the fourth resistor, the first calculated voltage, the second calculated voltage, the first total positive voltage, and the second total positive voltage, calculating the positive electrode-to-housing impedance Rp through the following calculation formula: ; where, R1 is the first resistance value of the first resistor; R2 is the second resistance value of the second resistor; R3 is the third resistance value of the third resistor; R4 is the fourth resistance value of the fourth resistor; Un1 is the first calculated voltage; Un2 is the second calculated voltage; Up1 is the first total positive voltage; Up2 is the second total positive voltage.

[0016] In addition, determining the first calculated voltage of the total negative external voltage according to the ratio of the first sampling voltage and the second sampling voltage includes: calculating a first ratio of the first sampling voltage and the second sampling voltage; when the first ratio is greater than or equal to a first preset threshold, determining the second sampling voltage as the first calculated voltage; when the first ratio is less than the first preset threshold, resampling the total negative external voltage; updating the first sampling voltage and the second sampling voltage according to the result of the resampling.

[0017] In addition, determining the second calculated voltage of the total negative external voltage according to the ratio of the third sampling voltage and the fourth sampling voltage includes: calculating a second ratio of the third sampling voltage and the fourth sampling voltage; when the second ratio is greater than or equal to a second preset threshold, determining the fourth sampling voltage as the second calculated voltage.

[0018] In addition, the method further includes: when the second ratio is less than the second preset threshold, disconnecting the second switch, performing a fifth set of sampling on the total negative external voltage after an interval of a fifth preset duration, and filtering the sampling result to obtain a fifth sampled voltage; determining the fifth sampled voltage as the first calculated voltage of the total negative external voltage, and calculating the first total positive voltage of the total positive external voltage according to the first calculated voltage and the total voltage of the battery cluster; reclosing the second switch and calculating the second total positive voltage; and calculating the negative pole-to-case impedance and the positive pole-to-case impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage. Description of the Drawings

[0019] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings represent similar elements. Unless otherwise stated, the drawings in the figures do not constitute a scale limitation.

[0020] Figure 1 is the circuit diagram of the insulation detection circuit of the energy storage system provided by an embodiment of the present application; Figure 2 is the flowchart of the insulation detection method of the energy storage system provided by an embodiment of the present application; Figure 3 is the circuit diagram of the insulation detection circuit of the energy storage system provided by another embodiment of the present application; Figure 4 is the circuit diagram of the insulation detection circuit of the energy storage system provided by yet another embodiment of the present application; Figure 5 is the internal structure schematic diagram of the energy storage device provided by an embodiment of the present application. Detailed Embodiments

[0021] Since the value of the Y capacitor is not constant and generally fluctuates in the order of uF, the fluctuation characteristics of the Y capacitor increase the complexity of insulation detection, thus significantly affecting the accuracy and efficiency of insulation detection calculation. Therefore, in order to ensure high-precision insulation detection to ensure the safe and stable operation of the energy storage system, it is urgent to explore an effective algorithm and strategy to eliminate the influence of the existence and size change of the Y capacitor on the insulation detection accuracy.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will elaborate on each embodiment of this application in conjunction with the accompanying drawings. However, those of ordinary skill in the art can understand that in the embodiments of this application, many technical details are provided to help readers better understand this application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in this application can still be implemented. The division of the following embodiments is for convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined and cross-referenced with each other on the premise of not being contradictory.

[0023] An embodiment of the present application relates to an insulation detection method for an energy storage system, which is applied to an energy storage system. The energy storage system includes a relay, a battery control unit, a battery cluster, and an insulation detection circuit that are connected to each other. The insulation detection circuit includes: a first detection circuit and a second detection circuit, and the resistors included in the first detection circuit and the second detection circuit are different; the insulation detection method for the energy storage system includes: closing a first switch, where the first switch is the switch of the first detection circuit; sampling the total negative external voltage to obtain a first sampling voltage and a second sampling voltage; determining a first calculated voltage of the total negative external voltage according to the ratio of the first sampling voltage and the second sampling voltage, and calculating a first total positive voltage of the total positive external voltage according to the first calculated voltage and the total voltage of the battery cluster; closing a second switch, where the second switch is the switch of the second detection circuit; sampling the total negative external voltage to obtain a third sampling voltage and a fourth sampling voltage; determining a second calculated voltage of the total negative external voltage according to the ratio of the third sampling voltage and the fourth sampling voltage, and calculating a second total positive voltage of the total positive external voltage according to the second calculated voltage and the total voltage of the battery cluster; calculating the negative electrode to housing impedance and the positive electrode to housing impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage; and judging whether the energy storage system is insulated according to the negative electrode to housing impedance and the positive electrode to housing impedance. Since during the insulation detection of the energy storage system, two closed circuits with different resistor combinations are formed for detection. After closing the first switch, the total negative external voltage is sampled multiple times. When the ratio of the multiple samplings meets the preset conditions, it can be determined that the voltage does not change and the Y-capacitor is stable. At this time, based on the stable total negative external voltage obtained by sampling, that is, the first calculated voltage, the first total positive voltage is calculated, which can eliminate the influence of the Y-capacitor on the accuracy of the insulation detection of the energy storage system; similarly, after closing the second switch, the stable total negative external voltage obtained by sampling the total negative external voltage multiple times, that is, the second calculated voltage, is used to calculate the second total positive voltage under the condition of eliminating the influence of the change of the Y-capacitor. Finally, the negative electrode to housing impedance and the positive electrode to housing impedance of the energy storage system are calculated according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage, so as to judge whether the energy storage system is insulated. That is, in the present application, by sampling the total negative external voltage multiple times, the change situation of the Y-capacitor is inferred from the stability of the total negative external voltage. Thus, when the Y-capacitor is stable, the total positive external voltage when the Y-capacitor is stable is calculated according to the total negative external voltage, and further the negative electrode to housing impedance and the positive electrode to housing impedance are calculated, so as to judge whether the energy storage system is insulated, eliminating the influence of the existence and size change of the Y-capacitor on the insulation detection accuracy, thereby improving the insulation detection accuracy of the energy storage system.The implementation details of the insulation detection method for the energy storage system of the embodiments of the present application will be specifically described below. The following content is only the implementation details provided for convenient understanding and is not necessary for implementing this solution.

[0024] As Figure 1 shown, the energy storage system includes a relay, a battery control unit, a battery cluster, and an insulation detection circuit connected to each other. The insulation detection circuit includes: a battery cluster BAT, a total negative resistance Rn, a total positive resistance Rp, a first switch Q1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a second switch Q2, and a sampling module AD. Among them, the battery cluster BAT, the total negative resistance Rn, and the total positive resistance Rp are connected in sequence to form a first series circuit; the battery cluster BAT, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are connected in sequence to form a second series circuit; the sampling module AD is arranged between the third resistor R3 and the fourth resistor R4; the first series circuit and the second series circuit are connected in parallel; one end of the first switch Q1 is connected between the total negative resistance Rn and the total positive resistance Rp, and the other end of the first switch Q1 is connected between the second resistor R2 and the third resistor R3; one end of the second switch Q2 is connected between the first resistor R1 and the second resistor R2, and the other end of the second switch is connected between the fourth resistor R4 and the battery cluster. In addition, one end of the first switch Q1 connected between the total negative resistance Rn and the total positive resistance Rp is grounded.

[0025] As Figure 2 shown, in step 201, the first switch Q1 is closed, and the first switch Q1 is the switch of the first detection circuit.

[0026] Specifically, after the first switch Q1 is closed, the insulation detection circuit is as Figure 3 shown (the second switch Q2 is not shown).

[0027] In step 202, the total negative external voltage is sampled to obtain a first sampling voltage and a second sampling voltage.

[0028] In some embodiments, sampling the total negative external voltage to obtain a first sampling voltage and a second sampling voltage includes: after closing the first switch, at an interval of a first preset duration, performing a first set of samplings on the total negative external voltage, and filtering the sampling results to obtain the first sampling voltage; after obtaining the first sampling voltage, at an interval of a second preset duration, performing a second set of samplings on the total negative external voltage, and filtering the sampling results to obtain the second sampling voltage. Specifically, the total negative external voltage, that is, the voltage of the total negative electrode of the battery cluster relative to the housing, refers to the potential difference between the total negative electrode of the battery cluster and the housing of the battery cluster (usually connected to the ground or the system ground); similarly, the total positive external voltage, that is, the voltage of the total positive electrode of the battery cluster relative to the housing, reflects the insulation state between the positive electrode of the battery cluster and the housing. The total negative external voltage and the total positive external voltage reflect the insulation state between the negative electrode of the battery cluster and the housing, and are mainly used to evaluate the insulation performance and grounding safety of the battery cluster.

[0029] In some embodiments, the sampling periods of the first set of sampling and the second set of sampling are the same as the second preset duration, and the number of samplings of the first set of sampling and the second set of sampling is the same. It should be noted that the same sampling period for the first set of sampling and the second set of sampling ensures the same sampling mode for the two sets of samplings, so as to more accurately eliminate the influence caused by the change of the Y capacitor; at the same time, the third preset duration is the same as the sampling periods of the first set of sampling and the second set of sampling to ensure the sampling continuity between the last sampled data in the first set of sampling and the first sampled data in the second set of sampling.

[0030] In some embodiments, the first preset duration is 10 ms, the first preset duration is equal to the second preset duration, and the number of samplings for both the first set of sampling and the second set of sampling is 5 times.

[0031] In a specific embodiment, after closing the first switch Q1 and delaying for 10 ms, the first set of samples is taken for the total negative external voltage. The sampling period of the first set of samples is 10 ms, that is, the time interval between each sampling in the first set of samples is 10 ms, and the voltage data of the first set of samples is obtained by sampling 5 times. After completing the first set of samples, the results obtained from the first set of samples are processed by software filtering to obtain the first sampled voltage Un1(a); and, after completing the first set of samples, after an interval of a second preset duration, that is, 10 ms later, the second set of samples is taken. The second set of samples has the same mode as the first set of samples, that is, the sampling period of the second set of samples is 10 ms, the time interval between each sampling in the second set of samples is 10 ms, and the number of samplings is also 5 times. After completing the second set of samples, the results obtained from the second set of samples are processed by software filtering to obtain the second sampled voltage Un1(b). Specifically, the filtering process includes any one or more filtering methods such as mean filtering, median filtering, weighted average filtering, and single-point value correction. It should be noted that those skilled in the art can select which filtering to perform on the sampled data according to actual operation requirements. At the same time, the time delay after closing the first switch Q1, the sampling period, the number of sampled data in each group, and the number of sampling groups can also be adjusted accordingly. This application does not make any restrictions here.

[0032] In some embodiments, the determining the first calculated voltage Un1 of the total negative external voltage according to the ratio of the first sampled voltage Un1(a) and the second sampled voltage Un1(b) includes: calculating a first ratio of the first sampled voltage Un1(a) and the second sampled voltage Un1(b); in the case where the first ratio is greater than or equal to a first preset threshold, determining the second sampled voltage Un1(b) as the first calculated voltage Un1; in the case where the first ratio is less than the first preset threshold, resampling the total negative external voltage; and updating the first sampled voltage Un1(a) and the second sampled voltage Un1(b) according to the results of the resampling.

[0033] In step 203, the first calculated voltage of the total negative external voltage is determined according to the ratio of the first sampled voltage and the second sampled voltage, and the first total positive voltage of the total positive external voltage is calculated according to the first calculated voltage and the total voltage of the battery cluster.

[0034] Specifically, the first ratio is calculated by |Un1(a) / Un1(b)|. In a specific embodiment, the first preset threshold is 0.95. When |Un1(a) / Un1(b)|≥0.95, that is, the matching degree between the first sampling voltage Un1(a) and the second sampling voltage Un1(b) is above 95%, it is regarded that the total negative external voltage is stable, that is, the Y-capacitor is stable and will not cause a change in the total negative external voltage. At this time, the second sampling voltage is determined as the first calculated voltage. , that is, Un1 = Un1(b). Further, the first total positive voltage Up1 of the total positive external voltage is calculated according to the first calculated voltage Un1 and the total voltage Ubat of the battery cluster BAT, that is, Up1 = Ubat - Un1. It should be noted that the total voltage Ubat of the battery cluster BAT can be obtained through the voltage value when the battery cluster BAT leaves the factory to reduce the consumption of computing resources, or a more accurate voltage value can be obtained through voltage detection. Those skilled in the art can adjust the acquisition method of the total voltage Ubat of the battery cluster BAT according to actual operation requirements, and this application does not make any restrictions here. In this application, since only the total negative external voltage is sampled, the step of sampling the total positive external voltage is reduced. The total positive external voltage can be obtained only through simple calculation. Without consuming extra computing resources, the sampling module required for the total positive external voltage in the insulation detection circuit is saved. Reducing the setting of the sampling module can reduce the impact on the circuit detection accuracy, and at the same time save the use cost of the insulation detection circuit. Since the size of the Y-capacitor in the energy storage system is not constant and generally fluctuates in the order of uF, the fluctuation characteristics of the Y-capacitor increase the complexity of insulation detection, thus significantly affecting the accuracy and efficiency of insulation detection calculation. In this application, only the total negative external voltage needs to be sampled after a certain delay after closing the detection circuit, and the total positive external voltage can be calculated through simple subtraction. This not only ensures avoiding the influence of the Y-capacitor on the calculation accuracy, but also simplifies the complexity of the insulation detection calculation and improves the efficiency of the insulation detection calculation.

[0035] In step 204, the second switch Q2 is closed, and the second switch Q2 is the switch of the second detection circuit.

[0036] Specifically, after closing the second switch, the insulation detection circuit is as Figure 4 shown. It should be noted that during the process of closing the second switch Q2, the first switch Q1 remains unchanged. That is, after closing the second switch Q2, both the first switch Q1 and the second switch Q2 are closed.

[0037] In step 205, the total negative external voltage is sampled to obtain a third sampling voltage and a fourth sampling voltage.

[0038] In some embodiments, sampling the total negative external voltage to obtain a third sampling voltage Un1(c) and a fourth sampling voltage Un1(d) includes: after closing the second switch Q2, at an interval of a third preset duration, performing a third group of samplings on the total negative external voltage, and filtering the sampling results to obtain the third sampling voltage Un1(c); after obtaining the third sampling voltage, at an interval of a fourth preset duration, performing a fourth group of samplings on the total negative external voltage, and filtering the sampling results to obtain the fourth sampling voltage Un1(d).

[0039] In some embodiments, the sampling periods of the third group of samplings and the fourth group of samplings are the same; the sampling period of the third group of samplings is different from the third preset duration, and the number of samplings in the third group of samplings and the fourth group of samplings is the same.

[0040] In some embodiments, the third preset duration is 1000 ms, the fourth preset duration is the same as the sampling periods of the third group of samplings and the fourth group of samplings, and the fourth preset duration is 10 ms; the number of samplings in the third group of samplings and the fourth group of samplings is 5 times each.

[0041] In a specific embodiment, after closing the second switch Q2 and delaying for 1000 ms, a third group of samplings is performed on the total negative external voltage. The sampling period of the third group of samplings is 10 ms, that is, the duration between each sampling in the third group of samplings is 10 ms, and 5 samplings are performed to obtain the voltage data of the third group of samplings. After completing the third group of samplings, the results obtained from the third group of samplings are processed by software filtering to obtain the third sampling voltage Un2(a); and, after completing the third group of samplings, at an interval of a fourth preset duration, that is, 10 ms later, a fourth group of samplings is performed. The fourth group of samplings has the same mode as the third group of samplings, that is, the sampling period of the fourth group of samplings is 10 ms, the duration between each sampling in the fourth group of samplings is 10 ms, and the number of samplings is also 5 times. After completing the fourth group of samplings, the results obtained from the fourth group of samplings are processed by software filtering to obtain the fourth sampling voltage Un2(b). Specifically, the filtering process includes any one or more of mean filtering, median filtering, weighted average filtering, and single-point value correction filtering methods. It should be noted that those skilled in the art can select which filtering to perform on the sampling data according to actual operation requirements. At the same time, the delay time after closing the second switch Q2, the sampling period, the number of sampling data in each group, and the number of sampling groups can also be adjusted accordingly, and the present application does not limit this here.

[0042] In some embodiments, the second calculated voltage Un2 for determining the total negative external voltage according to the ratio of the third sampling voltage Un2(a) and the fourth sampling voltage Un2(b) includes: calculating a second ratio of the third sampling voltage Un2(a) and the fourth sampling voltage Un2(b); and when the second ratio is greater than or equal to a second preset threshold, determining the fourth sampling voltage Un2(b) as the second calculated voltage Un2.

[0043] In step 206, the second calculated voltage is determined according to the ratio of the third sampling voltage and the fourth sampling voltage, and the second total positive voltage is calculated according to the second calculated voltage and the total voltage of the battery cluster.

[0044] Specifically, the second ratio is calculated by |Un2(a) / Un2(b)|. In a specific embodiment, the second preset threshold is 0.995. When |Un1(a) / Un1(b)|≥0.995, that is, the matching degree of the third sampling voltage Un2(a) and the fourth sampling voltage Un2(b) is above 99.5%, it is considered that the total negative external voltage is stable, that is, the Y capacitor is stable and will not cause a change in the total negative external voltage. At this time, the fourth sampling voltage is determined as the second calculated voltage Un2, that is, Un2 = Un2(b). Further, the second total positive voltage Up2 of the total positive external voltage is calculated according to the second calculated voltage Un2 and the total voltage Ubat of the battery cluster BAT, that is, Up2 = Ubat - Un2. It should be noted that the total voltage Ubat of the battery cluster BAT can be obtained through the voltage value of the battery cluster BAT at the time of leaving the factory to reduce the consumption of computing resources, or a more accurate voltage value can be obtained through voltage detection. Those skilled in the art can adjust the acquisition method of the total voltage Ubat of the battery cluster BAT according to actual operation requirements, and this application does not limit it here. In this application, since only the total negative external voltage is sampled, the steps of sampling the total positive external voltage are reduced, and the total positive external voltage can be obtained only through simple calculation. Without consuming extra computing resources, the sampling module required for the total positive external voltage in the insulation detection circuit is saved. Reducing the setting of the sampling module can reduce the influence on the detection accuracy of the circuit, and at the same time save the use cost of the insulation detection circuit.

[0045] In some embodiments, the method further includes: when the second ratio is less than a second preset threshold, disconnecting the second switch Q2, sampling the total negative external voltage for a fifth group after an interval of a fifth preset duration, and performing a filtering process on the sampling result to obtain a fifth sampled voltage; determining the fifth sampled voltage as the first calculated voltage Un1 of the total negative external voltage, and calculating a first total positive voltage Up1 of the total positive external voltage according to the first calculated voltage Un1 and the total voltage Ubat of the battery cluster BAT; reclosing the second switch Q2 and calculating the second total positive voltage Up2; specifically, the second total positive voltage Up2 is calculated in the manner of steps 204 to 206. Calculate the negative terminal-to-case impedance and the positive terminal-to-case impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage. Specifically, the fifth preset duration is 3000 ms, the sampling period of the fifth sampling is 10 ms, and the number of sampling times is 10 times. Specifically, the filtering process includes any one or more of mean filtering, median filtering, weighted average filtering, and single-point value correction. It should be noted that those skilled in the art can select which filtering to perform on the sampling data according to actual operation requirements. At the same time, the delay time after the second switch Q2 is disconnected, the sampling period, the number of each group of sampling data, and the number of sampling groups can also be adjusted accordingly, which is not limited in this application.

[0046] In step 207, calculate the negative terminal-to-case impedance and the positive terminal-to-case impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage.

[0047] Specifically, in some embodiments, the resistance value of the first resistor R1 is 3060 KΩ, the resistance value of the second resistor R2 is 3060 KΩ, the resistance value of the third resistor R3 is 6000 KΩ, and the resistance value of the fourth resistor R4 is 20 KΩ.

[0048] Calculating the negative terminal-to-case impedance and the positive terminal-to-case impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage includes: according to the first resistance value of the first resistor, the second resistance value of the second resistor, the third resistance value of the third resistor, the fourth resistance value of the fourth resistor, the first calculated voltage, the second calculated voltage, the first total positive voltage, and the second total positive voltage, calculating the negative terminal-to-case impedance Rn through the following formula: ; Calculating the positive terminal-to-case impedance Rp through the following calculation formula: ; Wherein, R1 is the first resistance value of the first resistor; R2 is the second resistance value of the second resistor; R3 is the third resistance value of the third resistor; R4 is the fourth resistance value of the fourth resistor; Un1 is the first calculated voltage; Un2 is the second calculated voltage; Up1 is the first total positive voltage; Up2 is the second total positive voltage.

[0049] In the actual calculation process, the complexity of the calculation is simplified by constructing a relational expression. In some embodiments, let: .

[0050] The calculation formula for the impedance Rn of the negative electrode to the outer shell can be simplified to: ; The calculation formula for the impedance Rp of the positive electrode to the outer shell can be simplified to: ; Wherein, R1 is the first resistance value of the first resistor; R2 is the second resistance value of the second resistor; R3 is the third resistance value of the third resistor; R4 is the fourth resistance value of the fourth resistor; Un1 is the first calculated voltage; Un2 is the second calculated voltage; Up1 is the first total positive voltage; Up2 is the second total positive voltage.

[0051] In step 208, it is determined whether the energy storage system is insulated according to the impedance of the negative electrode to the outer shell and the impedance of the positive electrode to the outer shell.

[0052] In some embodiments, the determining whether the energy storage system is insulated according to the impedance of the negative electrode to the outer shell and the impedance of the positive electrode to the outer shell includes: when both the impedance of the negative electrode to the outer shell and the impedance of the positive electrode to the outer shell are greater than a preset impedance value, the energy storage system is insulated; when the impedance of the negative electrode to the outer shell and / or the impedance of the positive electrode to the outer shell is less than the preset impedance value, the energy storage system is not insulated. It should be noted that the essence of insulation is that the impedance is large enough so that the passing current approaches zero.

[0053] In the embodiments of the present application, during the insulation detection of the energy storage system, two closed circuits with different resistor combinations are formed for detection. After closing the first switch, the total negative external voltage is sampled multiple times. When the ratio of the multiple samplings meets the preset conditions, it can be determined that the voltage does not change and the Y-capacitor is stable. At this time, based on the stable total negative external voltage obtained by sampling, that is, the first calculated voltage, the first total positive voltage is calculated, which can eliminate the influence of the Y-capacitor on the accuracy of the insulation detection of the energy storage system. Similarly, after closing the second switch, the stable total negative external voltage obtained by sampling the total negative external voltage multiple times, that is, the second calculated voltage, is used to calculate the second total positive voltage under the condition of eliminating the influence of the change of the Y-capacitor. Finally, based on the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage, the negative terminal to housing impedance and the positive terminal to housing impedance of the energy storage system are calculated, thereby determining whether the energy storage system meets the insulation requirements. That is to say, in the present application, by sampling the total negative external voltage multiple times and inferring the change of the Y-capacitor based on the stability of the total negative external voltage, when the Y-capacitor is stable, the total positive external voltage when the Y-capacitor is stable is calculated based on the total negative external voltage, and further the negative terminal to housing impedance and the positive terminal to housing impedance are calculated, thereby determining whether the energy storage system is insulated, eliminating the influence of the existence and size change of the Y-capacitor on the insulation detection accuracy, and thus improving the insulation detection accuracy of the energy storage system.

[0054] The step division of the above method is only for clear description. In implementation, it can be combined into one step or some steps can be split into multiple steps. As long as the same logical relationship is included, it is within the protection scope of the present application. Adding insignificant modifications to the algorithm or process or introducing insignificant designs, but not changing the core design of its algorithm and process, are within the protection scope of this application.

[0055] In addition, the examples mentioned in the above embodiments can be freely combined, and any combination method can be understood as an embodiment. The "embodiment" or "example" mentioned at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art can understand that the embodiments described herein can be combined with other embodiments.

[0056] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0057] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: the existence of A, the simultaneous existence of A and B, and the existence of B. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0058] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific situations.

[0059] Another embodiment of the present application relates to an energy storage system as Figure 1 shown, including: a relay, a battery control unit, a battery cluster, and an insulation detection circuit connected to each other. The insulation detection circuit includes: a battery cluster BAT, a total negative resistance Rn, a total positive resistance Rp, a first switch Q1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a second switch Q2, and a sampling module AD. Among them, the battery cluster BAT, the total negative resistance Rn, and the total positive resistance Rp are connected in sequence to form a first series circuit; the battery cluster BAT, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are connected in sequence to form a second series circuit; the sampling module AD is arranged between the third resistor R3 and the fourth resistor R4; the first series circuit and the second series circuit are connected in parallel; one end of the first switch Q1 is connected between the total negative resistance Rn and the total positive resistance Rp, and the other end of the first switch Q1 is connected between the second resistor R2 and the third resistor R3; one end of the second switch Q2 is connected between the first resistor R1 and the second resistor R2, and the other end of the second switch is connected between the fourth resistor R4 and the battery cluster. In addition, one end of the first switch Q1 connected between the total negative resistance Rn and the total positive resistance Rp is grounded.

[0060] In the embodiment of the present application, during the insulation detection of the energy storage system, two closed circuits with different resistor combinations are formed for detection. After closing the first switch, the total negative external voltage is sampled multiple times. When the ratio of the multiple samplings meets the preset conditions, it can be determined that the voltage does not change and the Y-capacitor is stable. At this time, based on the stable total negative external voltage obtained by sampling, that is, the first calculated voltage, the first total positive voltage is calculated, which can eliminate the influence of the Y-capacitor on the accuracy of the insulation detection of the energy storage system. Similarly, after closing the second switch, the stable total negative external voltage obtained by sampling the total negative external voltage multiple times, that is, the second calculated voltage, is used to calculate the second total positive voltage under the condition of eliminating the influence of the change of the Y-capacitor. Finally, the negative electrode to housing impedance and the positive electrode to housing impedance of the energy storage system are calculated based on the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage, so as to determine whether the energy storage system reaches insulation. That is, in the present application, by sampling the total negative external voltage multiple times and inferring the change of the Y-capacitor based on the stability of the total negative external voltage, when the Y-capacitor is stable, the total positive external voltage when the Y-capacitor is stable is calculated based on the total negative external voltage, and further the negative electrode to housing impedance and the positive electrode to housing impedance are calculated, so as to determine whether the energy storage system is insulated, eliminating the influence of the presence and size change of the Y-capacitor on the insulation detection accuracy, thereby improving the insulation detection accuracy of the energy storage system.

[0061] It is not difficult to find that this embodiment is a device embodiment corresponding to the above method embodiment, and this embodiment can be implemented in cooperation with the above method embodiment. The relevant technical details mentioned in the above method embodiment are still valid in this embodiment. To avoid repetition, they will not be elaborated here. Correspondingly, the relevant technical details mentioned in this embodiment can also be applied to the above method embodiment.

[0062] It is worth mentioning that each module involved in this embodiment is a logic module. In practical applications, a logic unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. In addition, to highlight the innovative part of the present application, units that are not closely related to solving the technical problems proposed by the present application are not introduced in this embodiment, but this does not mean that there are no other units in this embodiment.

[0063] Another embodiment of the present application relates to an energy storage device, such as Figure 5 shown, including at least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the insulation detection method of the energy storage system as described above.

[0064] Among them, the memory and the processor are connected in a bus manner. The bus may include any number of interconnected buses and bridges, which connect various circuits of one or more processors and the memory together. The bus may also connect various other circuits such as peripheral devices, voltage regulators, and power management circuits, etc. These are well known in the art, so they will not be further described herein. The bus interface provides an interface between the bus and the transceiver. The transceiver may be a single component or multiple components, such as multiple receivers and transmitters, and provides a unit for communicating with various other devices over a transmission medium. The data processed by the processor is transmitted over a wireless medium via an antenna. Further, the antenna also receives data and transmits the data to the processor.

[0065] The processor is responsible for managing the bus and general processing, and may also provide various functions, including timing, peripheral interface, voltage regulation, power management, and other control functions. The memory may be used to store the data used by the processor when performing operations.

[0066] Another embodiment of the present application relates to a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the method embodiments described above are implemented.

[0067] That is, those skilled in the art can understand that all or part of the steps in implementing the methods of the above embodiments can be completed by instructing relevant hardware through a program. This program is stored in a storage medium and includes several instructions to enable a device (which may be a single-chip microcomputer, a chip, etc.) or a processor to execute all or part of the steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs, etc., which can store program codes.

[0068] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present application, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present application.

Claims

1. An insulation detection method for an energy storage system, applied to an energy storage system, wherein the energy storage system comprises a relay, a battery control unit, a battery cluster and an insulation detection circuit connected to each other, characterized in that: The insulation detection circuit comprises: a first detection circuit and a second detection circuit, wherein the first detection circuit and the second detection circuit include different resistors; The insulation detection method of the energy storage system comprises: closing a first switch, the first switch being a switch of the first detection circuit; Sampling the total negative external voltage to obtain a first sampling voltage and a second sampling voltage; determining a first calculated voltage of the total negative external voltage according to a ratio of the first sampled voltage to the second sampled voltage, and calculating a first total positive voltage of the total positive external voltage according to the first calculated voltage and the total voltage of the battery cluster; closing a second switch, where the second switch is a switch of the second detection circuit; Sampling the total negative external voltage to obtain a third sampling voltage and a fourth sampling voltage; determining a second calculated voltage of the total negative external voltage according to a ratio of the third sampled voltage to the fourth sampled voltage, and calculating a second total positive voltage of the total positive external voltage according to the second calculated voltage and the total voltage of the battery cluster; Calculate the negative electrode-to-shell impedance and the positive electrode-to-shell impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage; Whether the energy storage system is insulated is determined according to the impedance of the negative electrode to the casing and the impedance of the positive electrode to the casing.

2. The insulation detection method of the energy storage system according to claim 1, characterized in that: The method of sampling the total negative external voltage to obtain a first sampling voltage and a second sampling voltage includes: After the first switch is closed, a first set of samples is taken on the total negative external voltage at an interval of a first preset time, and the sampling results are filtered to obtain the first sampled voltage; After obtaining the first sampling voltage, a second set of sampling is performed on the total negative external voltage at intervals of a second preset time, and the sampling results are filtered to obtain the second sampling voltage.

3. The insulation detection method of the energy storage system according to claim 2, characterized in that: The sampling periods of the first group of samples and the second group of samples are the same as the second preset duration, and the number of times of the first group of samples and the second group of samples is the same.

4. The insulation detection method of the energy storage system according to claim 3, characterized in that: The first preset time length is 10 ms, the first preset time length is equal to the second preset time length, and the sampling times of the first group of samples and the second group of samples are both 5 times.

5. The insulation detection method of the energy storage system according to claim 1, characterized in that: The sampling of the total negative external voltage to obtain a third sampling voltage and a fourth sampling voltage includes: After closing the second switch, a third set of samples are taken on the total negative external voltage at an interval of a third preset time, and the sampling results are filtered to obtain the third sampled voltage; After obtaining the third sampling voltage, a fourth group of samples are performed on the total negative external voltage at intervals of a fourth preset time, and the sampling results are filtered to obtain the fourth sampling voltage.

6. The insulation detection method of the energy storage system according to claim 5, characterized in that: The sampling period of the third group of samples is the same as that of the fourth group of samples; the sampling period of the third group of samples is different from the third preset duration, and the number of times of the third group of samples and the fourth group of samples is the same.

7. The insulation detection method of the energy storage system according to claim 6, characterized in that: The third preset duration is 1000ms, the fourth preset duration is the same as the sampling period of the third group of samples and the fourth group of samples, and the fourth preset duration is 10ms; the sampling times of the third group of samples and the fourth group of samples are both 5 times.

8. The insulation detection method of the energy storage system according to claim 1, characterized in that: The insulation detection circuit also includes: a total negative resistor, a total positive resistor, a first resistor, a second resistor, a third resistor and a fourth resistor; The battery cluster, the total negative resistor and the total positive resistor are connected in sequence to form a first series circuit; The battery cluster, the first resistor, the second resistor, the third resistor and the fourth resistor are connected in sequence to form a second series circuit; The first series circuit and the second series circuit are connected in parallel; The calculating the negative electrode-to-shell impedance and the positive electrode-to-shell impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage includes: According to the first resistance of the first resistor, the second resistance of the second resistor, the third resistance of the third resistor, the fourth resistance of the fourth resistor, the first calculated voltage, the second calculated voltage, the first total positive voltage and the second total positive voltage, the negative electrode to shell impedance Rn is calculated by the following formula: ； Among them, R1 is the first resistance of the first resistor; R2 is the second resistance of the second resistor; R3 is the third resistance of the third resistor; R4 is the fourth resistance of the fourth resistor; Un1 is the first calculated voltage; Un2 is the second calculated voltage; Up1 is the first total positive voltage; Up2 is the second total positive voltage.

9. The insulation detection method of the energy storage system according to claim 1, characterized in that: The insulation detection circuit also includes: a total negative resistor, a total positive resistor, a first resistor, a second resistor, a third resistor and a fourth resistor; The battery cluster, the total negative resistor and the total positive resistor are connected in sequence to form a first series circuit; The battery cluster, the first resistor, the second resistor, the third resistor and the fourth resistor are connected in sequence to form a second series circuit; The first series circuit and the second series circuit are connected in parallel; The calculating the negative electrode-to-shell impedance and the positive electrode-to-shell impedance of the energy storage system according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage includes: The impedance Rp of the positive electrode to the housing is calculated by the following calculation formula according to the first resistance of the first resistor, the second resistance of the second resistor, the third resistance of the third resistor, the fourth resistance of the fourth resistor, the first calculated voltage, the second calculated voltage, the first total positive voltage and the second total positive voltage: ； Among them, R1 is the first resistance of the first resistor; R2 is the second resistance of the second resistor; R3 is the third resistance of the third resistor; R4 is the fourth resistance of the fourth resistor; Un1 is the first calculated voltage; Un2 is the second calculated voltage; Up1 is the first total positive voltage; Up2 is the second total positive voltage.

10. The insulation detection method of the energy storage system according to claim 1, characterized in that: The method of determining a first calculated voltage of the total negative external voltage according to a ratio of the first sampled voltage to the second sampled voltage comprises: Calculating a first ratio of the first sampling voltage to the second sampling voltage; When the first ratio is greater than or equal to a first preset threshold, determining the second sampled voltage as the first calculated voltage; When the first ratio is less than the first preset threshold, resampling the total negative external voltage; The first sampling voltage and the second sampling voltage are updated according to the resampling result.

11. The insulation detection method of the energy storage system according to claim 1, characterized in that: The method of determining the second calculated voltage of the total negative external voltage according to the ratio of the third sampling voltage to the fourth sampling voltage includes: Calculating a second ratio of the third sampling voltage to the fourth sampling voltage; When the second ratio is greater than or equal to a second preset threshold, the fourth sampling voltage is determined as the second calculation voltage.

12. The insulation detection method of the energy storage system according to claim 11, characterized in that: The method further comprises: When the second ratio is less than the second preset threshold, the second switch is turned off, a fifth group of samples are taken on the total negative external voltage after a fifth preset time interval, and the sampling results are filtered to obtain a fifth sampling voltage; determining the fifth sampled voltage as the first calculated voltage of the total negative external voltage, and calculating the first total positive voltage of the total positive external voltage according to the first calculated voltage and the total voltage of the battery cluster; reclosing the second switch and calculating the second total positive voltage; The negative electrode-to-shell impedance and the positive electrode-to-shell impedance of the energy storage system are calculated according to the first calculated voltage, the first total positive voltage, the second calculated voltage, and the second total positive voltage.

13. An energy storage system, comprising a relay, a battery control unit, a battery cluster and an insulation detection circuit connected to each other, characterized in that: The insulation detection circuit comprises: a total negative resistor, a total positive resistor, a first switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a second switch and a sampling module; wherein the battery cluster, the total negative resistor and the total positive resistor are connected in sequence to form a first series circuit; The battery cluster, the first resistor, the second resistor, the third resistor and the fourth resistor are connected in sequence to form a second series circuit; The sampling module is arranged between the third resistor and the fourth resistor; The first series circuit and the second series circuit are connected in parallel; One end of the first switch is connected between the total negative resistor and the total positive resistor, and the other end of the first switch is connected between the second resistor and the third resistor; One end of the second switch is connected between the first resistor and the second resistor, and the other end of the second switch is connected between the fourth resistor and the battery cluster.

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