Insulation resistance detection circuit and energy storage system

Abstract

The application provides an insulation impedance detection circuit and an energy storage system. The detection circuit is applied to the energy storage system. The energy storage system comprises a plurality of battery units and a power conversion unit. The positive electrode of each battery unit is connected with a positive bus of the power conversion unit through a positive switch. The negative electrode of each battery unit is connected with a negative bus of the power conversion unit through a negative switch. The detection circuit comprises an insulation impedance detection unit and at least one detection switch. The first end of the insulation impedance detection unit is connected with the positive bus. The second end of the insulation impedance detection unit is directly connected with the negative electrode of any battery unit and is connected with the negative electrode of each remaining battery unit through a detection switch. Alternatively, the second end of the insulation impedance detection unit is connected with the negative electrode of each battery unit through a detection switch. The scheme can realize independent detection of the positive electrode-to-ground impedance and the negative electrode-to-ground impedance of each battery unit and improve the comprehensiveness of detection.

Description

Technical Field

[0001] This application relates to the field of impedance detection technology, specifically to an insulation impedance detection circuit and energy storage system. Background Technology

[0002] An energy storage converter can be connected to multiple battery cells to form an energy storage system. In practical applications, the operational safety of the energy storage system is closely related to the insulation state of the battery cells. Effective insulation impedance testing of each battery cell is one of the keys to the safe operation of the energy storage system.

[0003] In related technologies, in order to save hardware costs, multiple energy storage converter branches share the same insulation impedance detection unit. The obtained positive-to-ground impedance or negative-to-ground impedance is the parallel equivalent impedance of each battery cell, which makes it difficult to independently detect the positive-to-ground impedance and negative-to-ground impedance of each battery cell, resulting in incomplete detection data. Summary of the Invention

[0004] This application provides an insulation resistance detection circuit and an energy storage system, which can independently detect the positive electrode impedance to ground and the negative electrode impedance to ground of each battery cell.

[0005] In a first aspect, this application provides an insulation resistance detection circuit for use in an energy storage system. The energy storage system includes multiple battery cells and a power conversion unit. The positive terminal of each battery cell is connected to the positive bus of the power conversion unit via a positive switch, and the negative terminal of each battery cell is connected to the negative bus of the power conversion unit via a negative switch. The detection circuit includes an insulation resistance detection unit and at least one detection switch. The first end of the insulation resistance detection unit is connected to the positive bus. The second end of the insulation resistance detection unit is directly connected to the negative terminal of any one of the battery cells and is connected to the negative terminals of the remaining battery cells via one of the detection switches. Alternatively, the second end of the insulation resistance detection unit is connected to the negative terminal of each battery cell via one of the detection switches.

[0006] Secondly, this application provides an energy storage system including multiple battery cells and a power conversion unit, as well as an insulation resistance detection circuit as described in the first aspect.

[0007] In several embodiments provided in this application, the first end of the insulation impedance detection unit is connected to the positive bus of the power conversion unit; the second end of the insulation impedance detection unit is directly connected to the negative terminal of any one battery cell, and connected to the negative terminals of each of the remaining battery cells through a detection switch; or, the second end of the insulation impedance detection unit is connected to the negative terminal of each battery cell through a detection switch. In this way, independent detection of the positive-to-ground impedance and negative-to-ground impedance of each battery cell can be achieved without increasing the number of insulation impedance detection units, thus improving the comprehensiveness of the detection data. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0009] Figure 1 This is a schematic diagram of an energy storage system in related technologies.

[0010] Figure 2 This is a schematic diagram of an insulation impedance detection circuit provided in one embodiment of this application.

[0011] Figure 3 This is a schematic diagram of an insulation resistance detection circuit provided for another embodiment of this application.

[0012] Figure 4 This is a schematic diagram of an insulation resistance detection circuit provided for another embodiment of this application.

[0013] Figure 5 The circuit diagram of an insulation impedance detection unit provided in one embodiment of this application is shown.

[0014] Figure 6 This is a schematic diagram of an insulation resistance detection circuit provided for another embodiment of this application. Detailed Implementation

[0015] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0016] In the description of the embodiments of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0017] Energy storage converters are widely used in new energy power plants, distributed generation, and microgrids. They are typically connected to multiple battery cells to form an energy storage system for storing and converting electrical energy. In practical applications, the operational safety of the energy storage system is closely related to the insulation state of each battery cell after the battery cells are connected to the converter. If the insulation impedance of any battery cell is too low, it may lead to an increase in the ground leakage current of the corresponding branch of the energy storage converter, potentially causing equipment damage or electric shock. Therefore, effective insulation impedance testing of each battery cell is crucial for ensuring the safe operation of the energy storage system.

[0018] In related technologies, the insulation impedance detection methods for each battery cell mainly include the following two types: One is to configure an independent insulation impedance detection unit for each energy storage converter branch. This method can independently detect the positive-to-ground impedance and negative-to-ground impedance of each battery cell, but because each branch needs a separate insulation impedance detection unit, the hardware cost of the energy storage system is high. The other type is to share the same insulation impedance detection unit among different energy storage converter branches. In this method, the positive terminals of different battery cells are connected to the first end of the insulation impedance detection unit through their respective corresponding switching devices, while the negative terminals are interconnected and connected to the second end of the insulation impedance detection unit through the same switching device. By closing different switching devices, the insulation impedance detection unit can be reused. Figure 1As shown, taking two battery cells in an energy storage system as an example. In this embodiment, closing the switching devices KM1+ and KM- allows for insulation impedance detection of battery cell 1, and closing the switching devices KM2+ and KM- allows for insulation impedance detection of battery cell 2. While this detection method can save hardware costs to some extent, since the negative terminals of battery cells 1 and 2 are interconnected, the negative terminal impedance to ground is equivalent to the parallel impedance of the negative terminals of battery cells 1 and 2. Therefore, this detection method can only independently detect the positive terminal impedance to ground of each battery cell, making it difficult to independently detect the negative terminal impedance to ground of each battery cell, resulting in incomplete detection results. In addition, during the detection process, since the two ends of the bus capacitor C are connected in parallel with the two ends of the battery cell, in order to reduce or avoid the adverse effects of voltage surges before and after the switching devices are closed on the bus capacitor C, it is necessary to pre-charge the bus before detection, making it difficult to perform insulation impedance detection in a timely manner.

[0019] Therefore, how to achieve independent and comprehensive detection of the positive-to-ground impedance and negative-to-ground impedance of each battery cell without adding an insulation impedance detection unit has become an important technical problem that needs to be solved.

[0020] This application provides an insulation resistance detection circuit for use in an energy storage system. The energy storage system includes multiple battery cells and a power conversion unit. The positive terminal of each battery cell is connected to the positive bus of the power conversion unit via a positive switch, and the negative terminal of each battery cell is connected to the negative bus of the power conversion unit via a negative switch. The detection circuit includes an insulation resistance detection unit and at least one detection switch. The first end of the insulation resistance detection unit is connected to the positive bus; the second end of the insulation resistance detection unit is directly connected to the negative terminal of any one battery cell and connected to the negative terminals of the remaining battery cells via detection switches; alternatively, the second end of the insulation resistance detection unit is connected to the negative terminal of each battery cell via a detection switch.

[0021] Please see Figure 2In this embodiment, the energy storage system 100 includes battery cell 1, battery cell 2, and power conversion unit 140. The positive terminal of battery cell 1 is connected to the positive bus BUS+ of power conversion unit 140 via its corresponding positive switch KM1+, and the negative terminal of battery cell 1 is connected to the negative bus BUS- of power conversion unit 140 via its corresponding negative switch KM1-. ​​Similarly, the positive terminal of battery cell 2 is connected to the positive bus BUS+ of power conversion unit 140 via its corresponding positive switch KM2+, and the negative terminal of battery cell 2 is connected to the negative bus BUS- of power conversion unit 140 via its corresponding negative switch KM2-. An insulation resistance detection circuit 110 is applied to the energy storage system 100 and includes a detection switch 120 and an insulation resistance detection unit 130. The first end of the insulation resistance detection unit 130 is connected to the positive bus BUS+, and the second end of the insulation resistance detection unit 130 is connected to the negative terminal of battery unit 1 through detection switch KM4 and to the negative terminal of battery unit 2 through detection switch KM3.

[0022] exist Figure 2 In this embodiment, the branch corresponding to battery unit 1 and the branch corresponding to battery unit 2 share the same insulation resistance detection unit 130. The positive terminals of battery unit 1 and battery unit 2 are connected to the first terminal of the insulation resistance detection unit 130 via their respective positive terminals KM1+ and KM2+, respectively, and the negative terminals of battery unit 1 and battery unit 2 are connected to the second terminal of the insulation resistance detection unit 130 via their respective detection switches KM4 and KM3, respectively. Thus, closing the positive terminal switch KM1+ and the detection switch KM4 allows for the detection of the positive and negative terminal impedances of battery unit 1 to ground; closing the positive terminal switch KM2+ and the detection switch KM3 allows for the detection of the positive and negative terminal impedances of battery unit 2 to ground. Therefore, this embodiment can achieve independent detection of the positive and negative terminal impedances of each battery unit to ground without increasing the number of insulation resistance detection units 130, improving the comprehensiveness and completeness of the detection data.

[0023] To further reduce the hardware cost of the energy storage system 100, in some embodiments, one of the negative terminals of multiple battery cells can be directly connected to the second terminal of the insulation resistance detection unit 130, while the remaining negative terminals are connected to the second terminal of the insulation resistance detection unit 130 through their respective corresponding detection switches. See also... Figure 3 In this embodiment, the first end of the insulation resistance detection unit 130 is connected to the positive bus BUS+, and the second end of the insulation resistance detection unit 130 is directly connected to the negative terminal of the battery unit 1, and connected to the negative terminal of the battery unit 2 through the detection switch KM3.

[0024] exist Figure 3In this embodiment, the branch corresponding to battery unit 1 and the branch corresponding to battery unit 2 share the same insulation resistance detection unit 130. The positive terminals of battery unit 1 and battery unit 2 are connected to the first terminal of the insulation resistance detection unit 130 via their respective positive terminals KM1+ and KM2+, respectively. The negative terminal of battery unit 1 is directly connected to the second terminal of the insulation resistance detection unit 130, and the negative terminal of battery unit 2 is connected to the second terminal of the insulation resistance detection unit 130 via its corresponding detection switch KM3. Thus, when the positive terminal switch KM1+ is closed, since the negative terminal of battery unit 1 is directly connected to the second terminal of the insulation resistance detection unit 130, the positive terminal-to-ground impedance and negative terminal-to-ground impedance of battery unit 1 can be detected. When the positive terminal switch KM2+ and the detection switch KM3 are closed, the second terminal of the insulation resistance detection unit 130 is simultaneously connected to the negative terminals of both battery unit 1 and battery unit 2. At this time, the positive terminal-to-ground impedance of battery unit 2, as well as the equivalent parallel impedance of the negative terminals of battery unit 1 and battery unit 2, can be obtained. Furthermore, based on the negative electrode impedance to ground of battery cell 1 and the parallel equivalent impedance of battery cell 1 and battery cell 2, the negative electrode impedance to ground of battery cell 2 can be obtained. Therefore, this embodiment can achieve independent detection of the positive electrode impedance to ground and the negative electrode impedance to ground of each battery cell, while saving a switching device for one negative electrode branch, thereby reducing the hardware cost of the energy storage system 100.

[0025] In another embodiment, such as Figure 4 As shown, the negative terminal of battery cell 1 can be connected to the second terminal of the insulation resistance detection unit 130 through its corresponding detection switch KM4, while the negative terminal of battery cell 2 is directly connected to the second terminal of the insulation resistance detection unit 130. Thus, when the positive switch KM2+ is closed, since the negative terminal of battery cell 2 is directly connected to the second terminal of the insulation resistance detection unit 130, the positive-to-ground impedance and negative-to-ground impedance of battery cell 2 can be detected. When the positive switch KM1+ and the detection switch KM4 are closed, the second terminal of the insulation resistance detection unit 130 is simultaneously connected to the negative terminals of both battery cell 1 and battery cell 2. At this time, the positive-to-ground impedance of battery cell 1 and the parallel equivalent impedance of the negative terminals of battery cell 1 and battery cell 2 can be obtained. Furthermore, based on the negative-to-ground impedance of battery cell 2 and the parallel equivalent impedance of battery cell 1 and battery cell 2, the negative-to-ground impedance of battery cell 1 can be obtained. Compared to... Figure 3 This embodiment can save the switching devices of the negative branch of battery cell 1. This embodiment can save the switching devices of the negative branch of battery cell 2 while realizing independent detection of the positive-to-ground impedance and negative-to-ground impedance of each battery cell. It can also reduce the hardware cost of energy storage system 100.

[0026] It should be understood that "battery unit 1" and "battery unit 2" in the above embodiments are merely exemplary expressions used for ease of description and should not be construed as a specific limitation on the number of battery units. The above embodiments are also applicable to structures containing two or more battery units, and have versatility and scalability.

[0027] To stabilize the bus voltage, in some embodiments, the energy storage system 100 further includes a voltage regulator unit connected between the positive bus BUS+ and the negative bus BUS- of the power conversion unit 140. This voltage regulator unit enhances the power conversion unit 140's ability to suppress voltage fluctuations during charging and discharging. The voltage regulator unit includes a bus capacitor.

[0028] In related technologies, when branches corresponding to different battery cells share the same insulation resistance detection unit for detection, such as... Figure 1 As shown, during the detection process, the two ends of the bus capacitor C are connected in parallel with the two ends of the battery cell. When the corresponding switching device of the battery cell is closed, it may cause a voltage surge across the bus capacitor C. For example, when switching devices KM1+ and KM- are closed, the two ends of the bus capacitor C are connected in parallel with the two ends of battery cell 1; when switching devices KM2+ and KM- are closed, the two ends of the bus capacitor C are connected in parallel with the two ends of battery cell 2. To reduce or avoid the adverse effects of voltage surges on the bus capacitor C, the relevant detection methods require pre-charging the bus before detection, which makes it difficult to perform insulation resistance detection in a timely manner.

[0029] In the embodiments of this application, the negative terminal of the battery cell is connected to the second terminal of the insulation resistance detection unit 130 via a detection switch. The detection switch is located in the branch between the negative terminal of the battery cell and the negative terminal switch. Thus, during the insulation resistance detection process, disconnecting the corresponding negative terminal switch prevents the two ends of the bus capacitor from being connected in parallel with the two ends of the battery cell, thereby reducing or avoiding the impact of voltage surges on the safety of the bus capacitor. For example... Figure 2As shown, the negative terminal of battery cell 1 is connected to the second terminal of insulation resistance detection unit 130 via detection switch KM4, which is located in the branch between the negative terminal of battery cell 1 and negative switch KM1-. ​​The negative terminal of battery cell 2 is connected to the second terminal of insulation resistance detection unit 130 via detection switch KM3, which is located in the branch between the negative terminal of battery cell 2 and negative switch KM2-. Thus, when testing battery cell 1, disconnecting negative switch KM1- prevents the bus capacitor C from being connected in parallel with the two ends of battery cell 1; similarly, when testing battery cell 2, disconnecting negative switch KM2- prevents the bus capacitor C from being connected in parallel with the two ends of battery cell 2, thereby reducing or avoiding the impact of voltage fluctuations on the safety of bus capacitor C. Therefore, the above embodiment eliminates the need for pre-charging the bus to achieve safe detection of the insulation resistance of each battery cell, improving the timeliness of detection.

[0030] In some embodiments, the positive switch, negative switch, or detection switch includes a contactor or a relay. The positive and negative switches connected to each battery cell are not closed simultaneously.

[0031] In practical applications, the positive switch, negative switch, or detection switch can be a contactor, relay, or other switching device capable of on / off control. During insulation resistance testing, closing the positive switch connects the positive terminal of the battery cell to the first terminal of the insulation resistance testing unit, and closing the detection switch connects the negative terminal of the battery cell to the second terminal of the insulation resistance testing unit. Simultaneously, to prevent the two ends of the bus capacitor from being connected in parallel with the two ends of the battery cell, the positive and negative switches connected to each battery cell are not closed simultaneously. This achieves electrical isolation between the battery cell and the bus capacitor during insulation resistance testing, reduces the impact of voltage surges on the bus capacitor, and improves the safety of the testing process.

[0032] by Figure 2 For example, in this embodiment, the positive switch, negative switch, or detection switch can be a contactor or relay. For instance, positive switches KM1+ and KM2+ can be positive main contactors, used to control the connection between the positive terminal of the battery cell and the first terminal of the insulation resistance detection unit 130; negative switches KM1- and KM2- can be negative main contactors, which can disconnect the connection between the negative terminal of the battery cell and the bus capacitor C when the positive switch is closed; detection switches KM4 and KM3 can be single-switch contactors, used to control the connection between the negative terminal of the battery cell and the second terminal of the insulation resistance detection unit 130. This embodiment, through the coordinated operation of the positive switch, negative switch, and detection switch, can achieve electrical isolation between the battery cell and the bus capacitor C during insulation resistance detection, reducing the impact of voltage surges on the bus capacitor C and improving the safety of the detection process.

[0033] In some embodiments, the insulation resistance detection unit 130 includes a Y-type unbalanced bridge circuit for detecting the positive-to-ground impedance and negative-to-ground impedance of the battery cell.

[0034] by Figure 5 The single-switch Y-type unbalanced bridge circuit shown is an example. This bridge circuit includes a first resistor R1, a second resistor R2, a third resistor R3, and a bridge switch S. The first terminal of the first resistor R1 serves as the first terminal of the insulation impedance detection unit 130. The second terminal of the first resistor R1 is connected to the second terminals of the second resistor R2, the third resistor R3, and the bridge switch S. The first terminal of the second resistor R2 is connected to the first terminal of the bridge switch S and serves as the second terminal of the insulation impedance detection unit 130. The second terminal of the third resistor R3 is connected to the ground wire (Protecting Earthing, PE). Additionally, resistors Rm and Rn represent the equivalent insulation impedance to ground of other circuits in the energy storage system 100. Resistors R+ and R- represent the positive-to-ground impedance and negative-to-ground impedance of the corresponding battery cell. During insulation impedance detection, by controlling the on / off state of the bridge switch S, the voltage value of the corresponding battery cell branch can be obtained, and the positive-to-ground impedance and negative-to-ground impedance can be obtained accordingly, thereby determining whether the insulation impedance requirements are met. The insulation impedance detection unit in this embodiment has a simple circuit structure and a convenient detection process, which can improve the speed and accuracy of detection.

[0035] In some embodiments, at least one of the positive and negative switches connected to each battery cell may be connected in parallel with the precharge unit. The precharge unit may include a precharge switch and a precharge resistor connected in series.

[0036] In this embodiment, to further improve the safety of the insulation impedance detection process, at least one of the positive or negative switches connected to each battery cell is connected in parallel with the pre-charge unit. Under conditions where the bus capacitor has a large capacity or experiences significant transient impacts, the pre-charge unit can perform current-limited charging of the bus capacitor before insulation impedance detection, thereby reducing the impact of surge current on the switching devices and the bus capacitor. Specifically, the pre-charge unit may include a pre-charge switch and a pre-charge resistor connected in series. When pre-charging is required, the pre-charge switch is closed, allowing current to flow smoothly through the pre-charge resistor to charge the bus capacitor. Once the bus voltage is substantially consistent with the battery cell terminal voltage, insulation impedance detection can be performed. This enhances the safety and stability of the detection process under special operating conditions.

[0037] Please see Figure 6In this embodiment, the positive switch KM1+ connected to battery unit 1 is connected in parallel with the pre-charge unit 151, and the positive switch KM2+ connected to battery unit 2 is connected in parallel with the pre-charge unit 152. Specifically, the pre-charge unit 151 includes a pre-charge switch K1+ and a pre-charge resistor R1 connected in series, and the pre-charge unit 152 includes a pre-charge switch K2+ and a pre-charge resistor R2 connected in series. Under conditions where the bus capacitor capacity is large or there is a large transient impact, when battery unit 1 needs to perform insulation impedance testing, the pre-charge switch K1+ can be closed first, allowing the current to smoothly charge the bus capacitor C through the pre-charge resistor R1. After the bus voltage is basically consistent with the terminal voltage of battery unit 1, the positive switch KM1+ can be closed. Similarly, when battery unit 2 needs to perform insulation impedance testing, the pre-charge switch K2+ can be closed first, allowing the current to smoothly charge the bus capacitor C through the pre-charge resistor R2. After the bus voltage is basically consistent with the terminal voltage of battery unit 2, the positive switch KM2+ can be closed. This setting effectively limits surge current under special operating conditions, reduces the impact of voltage surges on bus capacitors and switching devices, and improves the safety and stability of the testing process.

[0038] This application also provides an energy storage system, which includes multiple battery cells and a power conversion unit, as well as the insulation impedance detection circuit in any of the foregoing embodiments.

[0039] The specific functions and effects of each unit in the energy storage system can be explained by referring to the aforementioned embodiments, and will not be repeated here.

[0040] It is understood that the term "connection" in the embodiments of this application can be interpreted as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc. can transmit electrical signals or data to each other.

[0041] It is understood that the specific examples in this document are only intended to help those skilled in the art better understand the embodiments of this application, and are not intended to limit the scope of the invention.

[0042] It is understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0043] It is understood that the various embodiments described in this application can be implemented individually or in combination, and the embodiments of this application are not limited in this respect.

[0044] Unless otherwise stated, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0045] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0046] The above are merely specific embodiments of this application, but the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. An insulation resistance detection circuit, applied to an energy storage system, the energy storage system comprising multiple battery cells and a power conversion unit, wherein the positive terminal of each battery cell is connected to the positive bus of the power conversion unit via a positive switch, and the negative terminal of each battery cell is connected to the negative bus of the power conversion unit via a negative switch; characterized in that, The detection circuit includes an insulation resistance detection unit and at least one detection switch; wherein... The first end of the insulation impedance detection unit is connected to the positive busbar; The second end of the insulation resistance detection unit is directly connected to the negative terminal of any one of the battery cells, and is connected to the negative terminal of each of the remaining battery cells through a detection switch; or, the second end of the insulation resistance detection unit is connected to the negative terminal of each of the battery cells through a detection switch.

2. The detection circuit according to claim 1, characterized in that, The positive switch, the negative switch, or the detection switch includes a contactor or a relay.

3. The detection circuit according to claim 1, characterized in that, The positive and negative switches connected to each of the battery cells do not close simultaneously.

4. The detection circuit according to claim 1, characterized in that, The insulation impedance detection unit includes a Y-type unbalanced bridge circuit.

5. The detection circuit according to claim 4, characterized in that, The Y-type unbalanced bridge circuit includes a first resistor, a second resistor, a third resistor, and a bridge switch; wherein, The first end of the first resistor serves as the first end of the insulation impedance detection unit. The second end of the first resistor is connected to the second end of the second resistor, the second end of the third resistor, and the second end of the bridge switch. The first end of the second resistor is connected to the first end of the bridge switch and serves as the second end of the insulation impedance detection unit. The second end of the third resistor is connected to the ground wire.

6. The detection circuit according to claim 1, characterized in that, At least one of the positive and negative switches connected to each of the battery cells is connected in parallel with the precharge unit.

7. The detection circuit according to claim 6, characterized in that, The precharge unit includes a precharge switch and a precharge resistor connected in series.

8. The detection circuit according to any one of claims 1 to 7, characterized in that, The energy storage system also includes a voltage stabilizing unit, which is connected between the positive bus and the negative bus.

9. The detection circuit according to claim 8, characterized in that, The voltage stabilizing unit includes a bus capacitor.

10. An energy storage system, characterized in that, It includes multiple battery cells and a power conversion unit, as well as an insulation resistance detection circuit as described in any one of claims 1 to 9.

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