Energy storage system

Abstract

According to the energy storage system, a detection circuit can be configured for each battery pack in the system, and the detection circuit is used for detecting the insulation resistance between each battery pack and a protection ground wire PE and can upload the insulation resistance to a control center of the energy storage system. And the control center can be used for detecting and positioning the liquid leakage problem of the battery pack in time when the insulation resistance is increased abnormally.

Description

Technical Field

[0001] This application relates to the field of energy technology, and in particular to an energy storage system. Background Technology

[0002] In electric vehicles or stationary energy storage systems, the battery pack is the core unit for energy storage, management, and safety protection. A battery pack can consist of multiple cells connected in series or parallel, storing energy through these internal cells. With the large-scale application of energy storage systems, it is often necessary to use cells from multiple manufacturers simultaneously. This can lead to inconsistencies in the quality of the cells within the battery pack, potentially resulting in relatively stable battery pack quality initially, followed by cell leakage after a period of operation. Cell leakage can affect the battery's electrical performance and lead to safety issues.

[0003] Therefore, how to detect cell leakage as accurately and promptly as possible is a problem worth considering. Summary of the Invention

[0004] This application provides an energy storage system in which each battery pack can be equipped with a detection circuit for detecting the insulation resistance between each battery pack and the protective ground wire, and transmitting the insulation resistance data to the control center of the energy storage system. The control center can then promptly detect and locate battery pack leakage problems when an abnormal increase in insulation resistance is observed.

[0005] In a first aspect, this application provides a battery pack, which includes a controller and a detection circuit. The detection circuit is connected in series between the positive or negative terminal of the battery pack and the protective ground wire. The detection circuit is used to detect a first insulation resistance between the positive or negative terminal of the battery pack and the protective ground wire. The controller is used to determine that the battery pack has leaked when the increment of the first insulation resistance in a first time period is greater than or equal to a first threshold.

[0006] In this way, the insulation resistance between the battery pack and the protective ground wire can be detected by the detection circuit. By observing the changes in insulation resistance, the leakage of the battery pack can be determined in a timely manner. When the battery pack leaks, ionic conductive paths are formed in the insulating material between the battery pack and the protective ground wire, causing the impedance to initially decrease. Then, due to phenomena such as electrolyte solvent evaporation, capillary migration, and salification crystallization, the insulation resistance will abnormally rise again. By capturing the characteristics of the rising insulation resistance, the leakage of the battery pack can be determined more accurately.

[0007] In conjunction with the first aspect, the difference between the first insulation impedance during the first time period and the first insulation impedance when the battery pack does not experience cell leakage does not exceed the second value.

[0008] Electrolyte leakage can be broadly categorized into initial leakage, severe leakage, and failure. If leakage continues, these three stages occur sequentially. During this process, the overall insulation resistance of the battery pack exhibits a downward trend; for example, the insulation resistance may gradually decrease from the normal 100MΩ to below 5MΩ. However, due to the phenomena described in the first aspect following electrolyte leakage, an abnormal increase in insulation resistance may occur at each stage. Therefore, detecting the increase in insulation resistance during the initial leakage stage allows for early detection of the problem. In the initial stage, the leakage amount is small, and the minimum decrease in insulation resistance has not yet fallen below the safety threshold. Timely maintenance at this stage can restore the battery pack's function and ensure circuit safety. For example, the insulation resistance range during the initial leakage stage can be 50MΩ-100MΩ. Although the insulation resistance may drop to 50MΩ, it is still higher than the safety requirement of 20MΩ (for example only). Detecting an abnormal increase in insulation resistance during this stage allows for timely detection of cell leakage and earlier problem resolution.

[0009] In conjunction with the first aspect, the detection circuit includes: a first switching circuit and multiple resistors connected in series, the first switching circuit being connected in parallel with one of the multiple resistors, the detection circuit also including a first node located between the first resistor and the positive or negative terminal of the battery pack, the first resistor being the resistor among the multiple resistors closest to the positive or negative terminal of the battery pack, the resistance value of each of the multiple resistors being fixed, and the resistance from the first node to the positive or negative terminal of the battery pack being fixed; the controller is used to determine the first insulation impedance based on the voltage of the first node when the first switching circuit is in the on state and the voltage of the first node when the first switching circuit is in the off state.

[0010] In this way, an equivalent measuring resistance in parallel with the insulation impedance can be created through the detection circuit. The resistance value of this equivalent measuring resistance is then changed using the first switching circuit, creating two unbalanced states. The insulation impedance is then calculated using the principle of an unbalanced bridge. This detection method avoids the problem of directly measuring extremely high insulation impedance. It amplifies the influence of the insulation impedance by utilizing the change in series voltage division, and the positive voltage of the battery pack is eliminated during the derivation process through the two unbalanced states, avoiding interference from voltage fluctuations on the detection accuracy.

[0011] In conjunction with the first aspect, the first switching circuit is electrically connected to the controller, which is used to control the on and off states of the first switching circuit.

[0012] In this way, the state of the switching circuit can be controlled by the controller. When detecting insulation impedance, the first switching circuit is turned on and off sequentially, changing the resistance of the detection circuit and creating an unbalanced state. This makes it easier to calculate the insulation impedance using the principle of an unbalanced bridge. Furthermore, by using two unbalanced states, the positive voltage of the battery pack is eliminated during the derivation process, thus avoiding the interference of voltage fluctuations on the detection accuracy.

[0013] In conjunction with the first aspect, the detection circuit also includes a second switching circuit, which is electrically connected to the controller and is connected in series with the plurality of resistors.

[0014] A second switching circuit, connected in series with multiple resistors, can be controlled to close during detection, activating the entire detection circuit for normal operation. When insulation resistance is not being detected, the second switching circuit can be controlled to open, achieving zero power consumption in the detection circuit and reducing standby power consumption of the battery pack.

[0015] In conjunction with the first aspect, the battery pack also includes a grounding protection circuit and a third switching circuit, the third switching circuit being connected in series between the grounding protection circuit and the protective ground wire, the third switching circuit being electrically connected to the controller, the controller being used to control the third switching circuit to disconnect when the first insulation resistance is detected.

[0016] The third switching circuit can isolate other grounding protection circuits. When the third switching circuit is disconnected, the noise current path is physically interrupted, reducing the ground potential difference and improving detection accuracy.

[0017] In conjunction with the first aspect, this first time period is less than or equal to seven days.

[0018] Since the environment in which the battery pack is located may also cause the insulation resistance to rise slowly, but this rising process is relatively long, judging based on the resistance rising to the first threshold within seven days can screen out cases of battery pack leakage and increase detection accuracy.

[0019] Secondly, this application provides an energy storage system comprising: at least one battery cluster, a protective ground wire, a control center, and a detection circuit. The at least one battery cluster includes multiple battery packs. Each battery pack includes a cell and a controller. A first battery pack is included among the multiple battery packs. The first battery pack includes a first controller, which is electrically connected to the control center and also electrically connected to the detection circuit. The detection circuit is connected in series between the positive or negative terminal of the first battery pack and the protective ground wire. The detection circuit is used to detect a first insulation resistance of the first battery pack, which is the impedance between the positive or negative terminal of the first battery pack and the protective ground wire. The control center is used to determine that cell leakage has occurred in the first battery pack if the increment of the detected first insulation resistance within a first time period is greater than a first value.

[0020] In this way, the phenomenon of rising insulation resistance can be detected by the detection circuit, and leakage of battery packs within the cluster can be detected in time, which facilitates earlier maintenance and treatment, and ensures the function and safety of the energy storage system.

[0021] In conjunction with the second aspect, the control center is specifically used to receive the first insulation impedance uploaded by the first controller; after determining that the first battery pack has experienced cell leakage, the control center is used to control the first battery pack to disconnect from the energy storage system and record the information that the first battery pack has experienced leakage.

[0022] The insulation impedance detected in the energy storage system can be uploaded to the control center for unified processing. In this way, after detecting leakage in the first battery pack, the control center can control the first battery pack to disconnect from the energy storage system through protection circuits and other devices, thus protecting the safety of the overall system. The leakage information of the first battery pack can also be recorded, which will facilitate the quick location of the leaking battery pack during subsequent maintenance.

[0023] In conjunction with the second aspect, the energy storage system also includes a cluster-level detection circuit configured for each of the at least one battery cluster. The cluster-level detection circuit of the battery cluster is connected to the total positive or total negative terminal of the battery cluster and the protective ground wire. The cluster-level detection circuit of the battery cluster is used to detect the insulation resistance of the battery cluster.

[0024] In this way, cluster-level testing can be performed in addition to battery pack testing, and the insulation resistance of the battery clusters can be used to determine whether there is leakage in multiple battery packs.

[0025] In conjunction with the second aspect, the control center is used to detect the insulation impedance of each battery pack within a battery cluster when an abnormal insulation impedance of a battery cluster is detected by the cluster-level detection circuit.

[0026] After detecting a problem at the cluster level, the battery pack within that cluster is then inspected. By combining cluster-level inspection with battery pack inspection, inspection efficiency can be improved. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a battery cluster structure provided in an embodiment of this application;

[0028] Figure 2 This is a schematic diagram of a detection architecture provided in an embodiment of this application;

[0029] Figure 3 This is a schematic diagram of a PACK-level detection architecture provided in an embodiment of this application;

[0030] Figure 4 This is a schematic diagram of a PACK-level detection architecture provided in an embodiment of this application;

[0031] Figure 5 This is a detection circuit topology diagram provided in an embodiment of this application;

[0032] Figure 6A This is a diagram of a PACK-level insulation impedance detection architecture provided in an embodiment of this application;

[0033] Figure 6B This is another PACK-level insulation impedance detection architecture diagram provided in the embodiments of this application;

[0034] Figure 7 This is another PACK-level insulation impedance detection architecture diagram provided in the embodiments of this application;

[0035] Figure 8 This is a diagram of an external insulation impedance detection architecture provided in an embodiment of this application;

[0036] Figure 9 This is a diagram of a cluster-level insulation impedance detection architecture provided in an embodiment of this application;

[0037] Figure 10 This is a topology diagram of an anti-interference dynamic isolation circuit provided in an embodiment of this application;

[0038] Figure 11 This is another anti-interference dynamic isolation circuit topology provided in the embodiments of this application. Detailed Implementation

[0039] The technical solutions of 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, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] The terminology used in the following embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification and appended claims of this application, the singular expressions “a,” “an,” “the,” “the,” “the,” and “this” are intended to include the plural expressions as well, unless the context clearly indicates otherwise. The terms “first” and “second” are used for descriptive purposes only and should not be construed as implying relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as “first” or “second” may explicitly or implicitly include one or more of that feature. “First” and “second,” etc., are used to distinguish different objects, not to describe a particular order of objects. For example, a first object and a second object are used to distinguish different objects, not to describe a particular order of objects.

[0041] In the description of the embodiments of this application, unless otherwise stated, "a plurality of" means two or more.

[0042] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or related scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0043] The term "and / or" in this application is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone.

[0044] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0045] As used in the above embodiments, depending on the context, the term "when..." can be interpreted as meaning "if...", "after...", "in response to determining...", or "in response to detecting...". Similarly, depending on the context, the phrase "when determining..." or "if (the stated condition or event) is interpreted as meaning "if determining...", "in response to determining...", "when (the stated condition or event) is detected", or "in response to detecting (the stated condition or event)".

[0046] In one possible implementation, large-scale battery applications such as electric vehicles and stationary energy storage systems employ a standardized hierarchical structure from the system level to the cell level: clusters, battery packs, and cells. This structure can address the compatibility issues between the high-capacity, high-voltage requirements of electric vehicles and other systems and the small-capacity, low-voltage characteristics of battery cells through modular integration, enabling flexible management and fault isolation. For specific structural logic and hierarchical functions, please refer to [reference needed]. Figure 1 ,like Figure 1 As shown, a cluster can consist of multiple battery packs. For example, the number of packs in a cluster can be 3, 4, 5, 8, 16, etc., and is influenced by factors such as the system voltage, capacity requirements, and design scheme of the energy storage system. Each battery pack comprising a cluster can further include multiple battery cells. For example... Figure 1 Pack 1 in the middle can be assembled from multiple battery cells.

[0047] This structure is both adaptable to the small size characteristics of battery cells and allows for flexible adjustments. For example, increasing or decreasing the number of packs can change the voltage / capacity of the cluster. It also facilitates operation and maintenance. For instance, in the event of a fault, a specific pack or cell can be precisely located, making it the mainstream architecture for current energy storage systems.

[0048] However, the large-scale application of energy storage systems inevitably brings new problems. For example, the large number of battery cells inside the packs in an energy storage system cannot be supplied by a single manufacturer and often requires multiple manufacturers to supply them. Furthermore, the quality of battery materials varies among different manufacturers; some packs may have relatively stable battery quality initially, but leakage may occur after a period of operation. Alternatively, poor operating environments or improper operating conditions of the energy storage system may also lead to battery cell leakage.

[0049] First, cell leakage leads to performance degradation, such as a sharp drop in capacity, decreased charge / discharge efficiency, and a breakdown in cell consistency. Second, since the cells are integrated into the pack, leakage can corrode internal metal components, compromising structural integrity and potentially accelerating the aging of pack insulation materials and compromising the pack's sealing performance, leading to insulation short circuits. Third, the leaked electrolyte, acting as a conductive medium, can directly compromise the pack's electrical isolation, causing multiple electrical risks. Cell leakage can also pose further hazards to equipment and personnel.

[0050] In large-scale energy storage systems, with the structure of clusters, packs, and cells, there are numerous packs and cells. How to accurately and quickly locate a pack or cell when cell leakage occurs has become a problem worthy of attention.

[0051] In one possible implementation, the presence of a corresponding gas concentration within the detection device can be used to detect whether there is electrolyte leakage. Since leakage causes the organic solvent in the electrolyte to react with other substances, generating a characteristic gas, and the gas concentration is positively correlated with the degree of leakage, leakage detection can be based on gas concentration.

[0052] In another possible implementation, leakage can be determined by detecting the resistance data inside the pack. Generally, leakage can be determined when the insulation resistance of the pack drops significantly.

[0053] In electric vehicles or stationary energy storage systems, protective earth (PE) typically refers to the metal casing, frame, or chassis of the equipment. It is ultimately connected to the earth via a grounding wire. The purpose of PE is to provide a low-impedance path for fault current to return in the event of an insulation failure, thereby triggering protective devices such as fuses and circuit breakers to cut off power and prevent electric shock.

[0054] Under normal conditions, the battery pack is isolated from the physical earth (PE) via insulating material. Insulation resistance is the resistance between the battery pack's positive or negative terminals and the PE. It measures the electrical isolation between the high-voltage circuitry inside the battery pack and the equipment casing or vehicle ground (PE). This directly relates to the safety of personnel and equipment. A higher resistance value is better, indicating better insulation performance and a lower possibility of high-voltage leakage to the casing or vehicle body. The insulation resistance must meet industry standards of ≥100Ω / V. For example, a 300V pack needs to meet ≥30kΩ. When the battery cells inside the pack leak, the lithium-ion content... + PF6 - The electrolyte containing conductive ions will flow into the insulating material between the PACK and PE, forming an ionic conductive path, which will cause the insulation resistance of the PACK to drop significantly.

[0055] However, both of these methods have shortcomings in terms of accuracy and real-time performance.

[0056] Gas detection methods aim to capture the characteristic gases emitted from leaked liquids, but due to the influence of gas generation efficiency, diffusion rate, and interference signals, it is difficult to achieve high accuracy and real-time response.

[0057] In some cases, during the initial stages of cell leakage, the daily electrolyte leakage is less than 0.01 mL, corresponding to a very small amount of organic solvent evaporation, and the gas concentration within the device is typically <1 ppm. However, the detection limit of existing mainstream gas sensors is generally 1-5 ppm, which cannot capture the gas signal in the early stages of leakage. This results in the gas concentration only rising to a detectable range 1-2 weeks after the leakage occurs, by which time the leakage has progressed to a minor seepage stage. Furthermore, the gas generated by the leakage needs to reach the sensor through molecular diffusion or convective diffusion, a process with inherent delays. Additionally, the presence of various interfering gases inside the energy storage tank or pack can lead to errors in gas detection. If the insulating material used in the pack volatilizes organic gases when heated, or if volatile organic compounds are introduced from the outside air, the sensor may misinterpret these as characteristic gases from the leakage. Alternatively, the gas generated by the leakage may be absorbed by the metal components inside the pack, causing the gas concentration detected by the sensor to be far lower than the actual value. Therefore, the accuracy and real-time performance of gas detection are difficult to guarantee.

[0058] The core of methods for detecting a decrease in insulation resistance is to capture the change in impedance caused by leakage, but this approach also has limitations. In the early stages of leakage, the electrolyte only penetrates locally, having a negligible impact on insulation resistance. Micro-leakage of electrolyte only forms tiny conductive points on the surface of the insulation layer, and the insulation resistance may drop from 100MΩ to 50MΩ, still far above the safety threshold of 30kΩ. Existing IMD (Insulation Discharge Mechanism) devices typically have a detection accuracy of ±5%, failing to identify such non-threshold changes within 50%. Leakage can only be detected when the electrolyte forms a continuous conductive path and the insulation resistance drops sharply to below 1kΩ, at which point the leakage is already quite severe.

[0059] Furthermore, the effect of leakage on resistance is not instantaneous, but rather delayed by physical or chemical reactions. By the time a significant drop in insulation resistance occurs, the leakage is already quite severe, thus this method also has shortcomings in terms of real-time performance.

[0060] In addition, many non-leakage factors inside the PACK can cause changes in resistance, which can be easily confused with leakage. For example, increased ambient humidity can cause the insulation material to absorb moisture, reducing the insulation resistance from 100MΩ to 1MΩ. Dust accumulation inside the PACK can also lead to a decrease in insulation resistance, which is consistent with the trend of slight leakage and can affect the accuracy of detection.

[0061] To enable more timely and accurate detection of cell leakage, this application provides an energy storage system and a corresponding electrolyte leakage detection method. This method proposes to determine the electrolyte leakage of the cell by detecting the insulation impedance of the PACK and the abnormal increase in impedance, thus enabling early detection of leakage of the cells inside the PACK.

[0062] In one possible implementation, embodiments of this application can be applied to the energy storage system of an electric vehicle to detect battery leakage. The systems and components mentioned in the following description are all understood to refer to systems and components within the electric vehicle. The following description of electric vehicles is merely illustrative; embodiments of this application can also be applied to other energy storage systems, and this application does not limit the scope of the application.

[0063] For reference Figure 2 In this embodiment, a parallel detection unit can be used for pack-level detection. Each pack is configured with a detection circuit to detect the insulation impedance of the corresponding pack. Figure 2As shown, a cluster can include n packs, where n is a positive integer. For each of these n packs, a corresponding pack-level detection circuit can be configured. For example, pack1 can be electrically connected to pack-level detection circuit 1. For packn, detection circuit n can be electrically connected. Detection circuit 1 can be used to detect the insulation impedance of pack1, i.e., the impedance from the positive or negative terminal of pack1 to the PE (protective earth). Detection circuit n can be used to detect the insulation impedance of packn. Furthermore, the n detection circuits from pack1 to packn can also be electrically connected to a control center to transmit the detected impedance to the control center. Figure 2 R_PACK1 shown can be regarded as the insulation resistance of PACK1 detected by detection circuit 1, and R_PACKn can be regarded as the insulation resistance of PACKn relative to PE detected by detection circuit n.

[0064] The control center can determine whether there is cell leakage in the PACK based on the insulation impedance information received from each PACK. The judgment principle used in the embodiments of this application will be introduced below.

[0065] Under normal conditions, the positive or negative copper busbar of the PACK is well insulated from the PE, with only air or insulating material present. The insulation resistance is relatively high, generally above X00MΩ under normal conditions. Here, X can be 1-9, and the specific value depends on the energy storage system specifications, insulating materials, etc.

[0066] In the initial leakage stage, when the electrolyte leakage is less than 5%, the electrolyte seeps into the gaps in the insulation material, forming a weak ionic conductive path. For example, an EC / DMC mixed solvent containing LiPF6 seeps out from the cell cracks, forming an ionic conductive path between the positive copper busbar and the PE of the PACK. Exemplarily, the ionic conductivity of the liquid electrolyte is approximately 10 mS / cm, which causes a sharp drop in impedance between the copper busbar and PE. Exemplarily, in one possible implementation, the PACK insulation impedance may be between 50 and 100 MΩ during this stage.

[0067] If the leakage is in a severe leakage stage with a leakage rate between 15% and 30%, the PACK insulation resistance may drop to the range of 20 to 50 MΩ.

[0068] When the electrolyte leakage is greater, the PACK may be in a failed state. At this time, the insulation resistance may be less than 5MΩ, and the leaked electrolyte may cause a physical short circuit.

[0069] After electrolyte leakage, the insulation resistance initially decreases. However, as the leakage continues and the solvent evaporates, an impedance inflection point emerges. For example, the rapid evaporation of low-boiling-point solvents, such as DMC (boiling point 90°C), increases the ion concentration along the insulation path but reduces the effective conductive path, leading to an increase in the resistive component of the insulation resistance. Simultaneously, the electrolyte can penetrate the pores of the insulating material, reducing the conductive cross-sectional area and also increasing the overall impedance. Furthermore, when the electrolyte comes into contact with air, insulating crystals can form. For example, LiF or Li can be formed from the electrolyte. x POF γ The resistivity of crystals is greater than 10. 9 Ω·m, extremely strong insulation. These changes have a weaker effect than the impedance decrease caused by leakage in the early stages of leakage, but as the solvent continues to evaporate and salt crystals increase, these changes will gradually overtake the impedance in the competition and cause the impedance to rise again.

[0070] As the electrolyte continues to evaporate, LiPF6 decomposes to generate large amounts of LiF and Li. x POF γ Highly insulating crystalline substances can fill the existing ion pathways, completely blocking ion migration. The insulation resistance can rapidly rise from the MΩ level to the GΩ level, or even exceed the initial insulation level, but by this time the cell has already completely failed due to leakage.

[0071] Therefore, based on the chain reaction of conduction, volatilization, crystallization, and polarization that occurs after electrolyte leakage, the change in insulation resistance of PACK can be summarized as: first decrease, then increase or fluctuate increase. Whether it increases or fluctuates depends on whether the cell continues to leak electrolyte and the rate of leakage.

[0072] For example, in the initial leakage stage, the PACK insulation resistance can drop to approximately 17 MΩ. After one week of leakage, the PACK insulation resistance can recover to approximately 100 MΩ. Furthermore, although changes in the environment of the energy storage system may also cause an increase in impedance, the impact of the environment on impedance is relatively small, and it is unlikely to cause a change in impedance from 17 MΩ to 100 MΩ in a short period, such as seven days. Based on this, by detecting the insulation resistance of the PACK cells, an abnormal increase in impedance can be observed in the early stages of leakage within the PACK cells to confirm the occurrence of cell leakage.

[0073] Based on this, the embodiments of this application can be implemented as follows: Figure 2 The detection unit shown describes a method for detecting PACK insulation impedance information. It captures information about an abnormal increase in insulation impedance during cell leakage. Based on the abnormal change in impedance increase, it is possible to determine the leakage of electrolyte from the cell inside the PACK in advance.

[0074] For an example of how to perform insulation resistance testing on a PACK, please refer to [reference needed]. Figure 3 , Figure 3 A schematic diagram of a detection architecture is shown.

[0075] like Figure 3 As shown, in some examples, each PACK can be equipped with a corresponding sensing resistor. The sensing resistor is electrically connected between the positive terminal of the PACK and the PE terminal via a relay. This constitutes a detection circuit, and the insulation impedance to be detected can be calculated based on the circuit principle using a sensing resistor with a known resistance value. Specific calculation methods can be found in the description below, and will not be elaborated upon here.

[0076] exist Figure 3 Each PACK shown may also include a microcontroller unit (MCU), such as MCU1 in PACK1 and MCU8 in PACK8. Each MCU can be connected to the control center via a controller area network (CAN) bus. Each MCU can receive commands from the control center via the CAN bus to control the switching of relays in each PACK, thereby enabling insulation resistance detection for each PACK. Each MCU can also transmit the detected insulation resistance to the control center via the CAN bus for the control center to detect whether leakage has occurred. If leakage is detected, the control center can locate the PACK experiencing the leakage by analyzing the source of the insulation resistance data, and control the protection circuit in that PACK to disconnect, thus disconnecting the leaking PACK from the energy storage system and protecting the overall circuit.

[0077] Optionally, the communication method between the MCU and the control center within the PACK can include other methods besides the CAN bus, such as communication via the RS-485 communication protocol. This application embodiment does not limit the specific communication method between the MCU and the control center.

[0078] The following describes a more specific circuit architecture based on the detection architecture provided in the embodiments of this application, which can be referred to... Figure 4 .

[0079] like Figure 4 As shown, the detection unit can be used to detect individual PACKs within a battery cluster. In some examples, a battery cluster may include eight PACKs. Figure 4 The example shows PACK1 and PACK8. These 8 PACKs can be connected in series to form a battery cluster. Each PACK can consist of multiple cells, and the PACK can be equipped with a balancing DC-DC converter to solve the inconsistency of cells within the PACK and ensure the PACK's capacity and lifespan.

[0080] Each battery cell inside the pack, including its positive and negative terminals and the cell's metal casing, is isolated from the protective earth (PE) by insulating material. High-voltage components inside the pack must also be isolated from the PE through insulation. However, the pack's metal casing and internal metal supports, and other non-energized parts, can be connected to the PE. If a high-voltage component inside the pack, such as the positive copper busbar, comes into contact with the metal casing due to insulation damage (e.g., leakage, insulation aging), the casing will become electrified. In this case, the pack's metal casing is electrically connected to the PE, which quickly conducts the leakage current to the ground, bringing the casing potential close to 0V and preventing electric shock when personnel touch the casing.

[0081] And in Figure 4 In the circuit shown, each PACK can integrate a detection circuit. For example, PACK1 can include a PACK-level detection circuit 1, and PACK8 can include a PACK-level detection circuit 8. One end of the detection circuit can be connected to the positive or negative copper busbar of the PACK, and the other end can be connected to PE. It is connected in parallel with the insulation impedance to be measured to form an impedance detection circuit, used to detect the insulation impedance of the PACK to PE.

[0082] The detection architecture may also include a cluster control box, which may contain protection circuits, a coordination mechanism, and cluster-level detection circuits. The protection circuits can detect abnormal states in the cluster-level circuits and prevent fault propagation by actively cutting off high voltage. The coordination mechanism is a mechanical or electrical component that converts electrical signals into physical actions, and it can be used to coordinate with the protection circuit and detection circuit to execute commands. The cluster-level detection circuits can be used to collect global state parameters of the battery clusters.

[0083] In some examples, the detection architecture provided in this application embodiment may also include a power conversion system (PCS), which is an energy conversion device in the energy storage system used to connect battery clusters and loads. Exemplarily, it may internally include a DC-DC converter and a DC-AC converter. The DC / DC converter can be used to realize voltage transformation and stabilization of DC power, protecting the safe operation of the battery clusters. The DC / AC converter can be used to convert DC power to AC power conforming to grid standards during discharge, or to convert AC power to DC power during charging.

[0084] In terms of connectivity, for example, the cluster control box can be connected in series to the total positive output terminal of the battery cluster. The total positive terminal of the series-connected PACK is connected to the input terminal of the protection circuit, and the output terminal of the protection circuit is then connected to the PCS. One end of the mating mechanism can be electrically connected to the protection circuit, and the other end can be connected to PE. The cluster-level detection circuit can be electrically connected to the output terminal of the protection circuit and also electrically connected to PE. In the PCS, the DC / DC and DC / AC terminals can be connected in series, with the DC / DC terminal electrically connected to the cluster control box and the DC / AC terminal connected to the load or the power grid.

[0085] In this way, the detection circuit can be integrated into each PACK to detect the insulation resistance of the PACK and transmit the insulation resistance information of the PACK to the control center. Combined with protection circuits and other devices, it can realize functions such as timely detection, location and protection of leakage.

[0086] The following section provides a detailed introduction to the methods for detecting insulation resistance and the process for transmitting detection information.

[0087] For reference Figure 5 In some examples, the detection resistors in the detection circuit may specifically include three resistors: R1, R2, and R3. Taking the detection of the insulation impedance between the positive terminal of the PACK and the PE as an example, the three resistors R1, R2, and R3 can be connected in series between the positive terminal of the PACK and the PE. A relay K1 can be connected in parallel across R1, and K1 can be controlled to open or close by the MCU in the PACK. In this embodiment, the insulation impedance to be measured can be calculated by switching different equivalent detection resistors Rd and measuring the change in the voltage divider. The detection circuit may also include a detection point, which can be located between the positive terminal of the PACK and R1, where R1 is the resistor closest to the positive terminal in the series path. The impedance between the detection point and the positive terminal can be called the upper arm resistance Ru. Generally, Ru is usually integrated or explicitly set within the detection circuit, and this resistance is known and fixed.

[0088] The following is a brief introduction to an insulation impedance calculation method used in the embodiments of this application, namely the unbalanced bridge method. It should be understood that, in addition to the detection circuit, the positive terminal of the PACK and the PE can also be "connected" through an insulating material. The positive terminal of the PACK, the insulating material, and the PE can be considered as a path, and the impedance of this path is the insulation impedance of the PACK, hereinafter referred to as the insulation impedance to be measured Zx. For the specific path, please refer to... Figure 5As shown by the dashed line. Based on this, the path from the detection point to PE via R1, R2, and R3 can be considered as a parallel path with the insulation impedance Zx to be measured. The total impedance of the detection circuit can be called the equivalent detection resistance Rd, which varies depending on the switching state of K1. Therefore, the total resistance between the detection point and PE can be considered as the parallel resistance of Zx and the equivalent detection resistance. The voltage at the detection point relative to PE is the voltage from the positive terminal of PACK to PE, divided by Ru and this parallel resistance. By changing the state of relay K1, the equivalent detection resistance Rd in the detection circuit can be changed. When the relay is open, R1 is not short-circuited and is connected in series with R2+R3, so Rd = R1 + (R2+R3); when the relay is closed, R1 is short-circuited by the relay, so Rd = R2+R3. The change in Rd changes the parallel resistance between Rd and Zx, causing a change in the ratio between the parallel resistance and Ru, ultimately resulting in different voltage divisions at the detection point. In both states, based on the voltage at the detection point, and combined with the series voltage divider formula and the parallel resistance calculation formula, two formulas related to the PACK positive voltage can be obtained. By combining the two formulas, the PACK positive voltage can be eliminated.

[0089] The specific measurement process is as follows: 1. Disconnect relay K1. At this time, Rd = Rd_open = R1 + R2 + R3.

[0090] 2. Read the voltage V1 of the measurement point relative to PE when K1 is disconnected.

[0091] 3. When relay K1 is closed, Rd = Rd_closed = R2 + R3.

[0092] 4. When K2 is closed, read the voltage V2 of the measurement point relative to PE.

[0093] 5. Substitute the known Ru, Rd_open, Rd_closed and the measured V1, V2 into the formula to calculate K, and then substitute them into the final formula to calculate the insulation impedance Zx to be measured. The formula for calculating Zx can be Zx=[Ru×(Rd_closed-K×Rd_open)] / [K×Ru+K×Rd_open-Ru-Rd_closed].

[0094] Where K = (V1 / V2) × (Rd_closed / Rd_open).

[0095] Finally, relay K1 can be disconnected to restore the detection circuit to its initial high-resistance state, thereby reducing unnecessary power consumption and heat loss.

[0096] The above measurement method is suitable for detecting high-resistance Zx. Since Zx is an insulation impedance, its resistance is extremely high under normal conditions, and remains high even after leakage, making direct measurement difficult. This method creates two unbalanced states by switching the value of Rd, amplifying the effect of Zx by utilizing the difference in voltage division, thus achieving accurate measurement of high resistance. Simultaneously, by calculating the ratio of V1 and V2 under the two states, the positive voltage of the PACK is completely eliminated, avoiding interference from voltage fluctuations on detection accuracy.

[0097] Optionally, Figure 5 The detection resistor shown can also be connected in series between the negative terminal of the PACK and the PE terminal. This application does not limit this.

[0098] After detecting the insulation resistance of the PACK, the MCU in the PACK can, based on, such as Figure 3 The architecture shown transmits the detection results to the control center via a CAN bus. In some examples, the MCU can receive instructions from the control center to perform the detection. The specific process is as follows.

[0099] For example, the control center can broadcast detection commands via the CAN bus. The broadcast of detection commands by the control center can be periodic or subject to manual control. This application embodiment does not limit the specific timing of the detection.

[0100] After the control center broadcasts the detection command, the MCU inside each PACK can receive the detection command via the CAN bus and control the relays to perform the above actions. Figure 5 The described action. The MCU can also control the analog-to-digital converter (ADC) inside the local PACK to read the voltage at the detection point.

[0101] After calculating the insulation impedance using the read voltage, each MCU can upload the impedance value to the control center via the CAN bus. In this embodiment, the insulation impedance detection at the PACK level is not limited to... Figure 3 , Figure 4 The number of PACKs shown.

[0102] Optionally, in addition to PACK-level insulation resistance testing, embodiments of this application may also include cluster-level testing. Refer to the above. Figure 4The cluster-level detection circuit is shown in the diagram. This circuit can be used to detect the insulation resistance information from the positive or negative terminal of a battery cluster to the PE (protective earth). Specific insulation resistance detection and calculation methods can be found in the PACK-level insulation resistance detection documentation, which will not be elaborated here. This detection architecture can utilize the synergistic mechanism of cluster-level and PACK-level detection. For example, cluster-level detection can be prioritized; when an impedance anomaly is detected in a particular cluster, a detailed PACK-level diagnostic is initiated for that cluster to locate the PACK where cell leakage has occurred.

[0103] Optionally, in this embodiment, the detection circuit can also be externally mounted as a separate device or placed in the cluster control box. This embodiment does not limit the location of the detection circuit. Other exemplary detection architectures are described below.

[0104] like Figure 6A As shown, the detection architecture in this application embodiment can be a PACK cascaded architecture. For details on this PACK cascaded architecture, please refer to the above description. Figure 3 , Figure 4 The description states that a battery cluster may include multiple PACKs, such as Figure 6A The diagram shows PACK1 to PACKn, where n is a positive integer. Each PACK may include a cell module and a detection circuit. The detection circuit can be used to detect the insulation resistance of the PACK, i.e., the impedance of the positive or negative terminal of the cell module within the PACK to the PE (protective earth). The architecture may also include a cluster control box. The control circuit can be located within the cluster control box. The cluster control box may also include protection circuitry and a coordination mechanism. The control circuitry can be used to detect cell status, perform energy management, and coordinate the operation of components within the PACK. The MCU mentioned above can be part of the control circuitry, used to receive external commands and control the operating state of the detection circuitry. The functions of the protection circuitry and coordination mechanism are described above and will not be repeated here. In some examples, the protection circuitry, coordination mechanism, and control circuitry can be integrated into the cluster control box.

[0105] Alternatively, in some other examples, the control circuitry and the mating mechanism can be distributed separately. For example... Figure 6B As shown, the control circuits can be distributed in the cluster control box, while the cooperating mechanisms can be distributed in the PCS, with another protection circuit configured in the PCS. This allows for adaptation to different application scenarios, and different distribution methods can be selected based on factors such as response speed, fault isolation, cost and size, and operational complexity.

[0106] While performing series impedance detection within the PACK, a common bus architecture for the PACK can also be used, such as... Figure 7As shown, the detection architecture can use a common bus connected in series outside the PACK. Each PACK can be connected to the common bus through a selector switch, integrating multiple PACKs to form a unified energy output unit, adapting to high-capacity, high-voltage, or high-efficiency transmission requirements. The common bus can serve multiple roles, including energy convergence and transmission, simplified connections, equipment docking, and safety protection, replacing traditional redundant wiring harnesses and improving system integration and reliability.

[0107] In the common bus architecture, each PACK in the cluster is still equipped with its own detection circuit. One end of the detection circuit is connected to the positive or negative terminal of the cell unit, and the other end can be connected to PE.

[0108] Alternatively, in some other examples, the detection circuitry of the PACK can be externalized to the PACK. For example... Figure 8 As shown, the detection circuit can be externally mounted outside the PACK. This improves the portability and flexibility of the detection circuit. Testing can be performed using an external detection circuit via external wiring, making it suitable for scenarios such as periodic inspections. In the testing scenario, one end of the detection circuit can be connected to the positive terminal of any PACK, and the other end can be connected to PE (protective earth) to detect the insulation resistance of a single PACK.

[0109] Alternatively, in other examples, such as Figure 9 As shown, the detection circuit can also be integrated into the cluster control box. One end of the detection circuit can be connected to the total positive terminal of each PACK in the battery cluster, and the other end can be connected to PE, serving as a cluster-level detection circuit to detect the insulation resistance of the battery cluster, which can be used to detect the overall impedance. When the overall impedance of the battery cluster is abnormal, the insulation resistance of each PACK in the cluster can be further detected. The combination of cluster-level detection and pack-level detection enables layered localization, which is beneficial for quickly narrowing down the fault range and improving detection efficiency.

[0110] Optionally, for the above Figures 7-9 The architecture shown allows for separate distribution of the control circuitry and cooperating mechanisms within the cluster control box. For details, please refer to [reference needed]. Figure 6B The description states that the control circuit can be distributed in the cluster control box, while the cooperating mechanism can be distributed in the PCS, and another protection circuit is configured in the PCS.

[0111] Optionally, for electrolyte leakage detection within each PACK of the cluster, considering the quantity and size, the detection resistor needs to adopt a resistor miniaturization scheme, while simultaneously achieving reliable sealing. In some examples, 4-M layer packaging can be used, which offers better soldering yield and layering technology. In other examples, 4-M layer potting can also be used, which offers better long-term reliability and integration. The packaging type can include ball grid array packaging, chip-level packaging, multi-chip module packaging, etc., and the materials may involve ceramics, plastics, etc. The process may include surface mount technology. The potting compound types include epoxy resin potting compound, polyurethane potting compound, silicone potting compound, etc. Performance indicators may involve viscosity, curing time, thermal conductivity, insulation, etc. The potting process includes normal potting, vacuum potting, etc. The embodiments of this application do not limit the specific scheme of resistor miniaturization.

[0112] Optionally, embodiments of this application may also incorporate designs to resist interference from other grounding loops in the detection circuit. See reference... Figure 10 Multipath interference can be eliminated by dynamically disconnecting the grounding protection circuit using a relay. Other grounding protection circuits may include RCD grounding protection circuits, IMD grounding protection circuits, etc.

[0113] like Figure 10 As shown, relays K_iso1, K_iso2…K_isoN can be set in other grounding protection circuits respectively. When these relays are disconnected, the noise current path of other grounding protection loops can be physically interrupted, reducing the ground potential difference of the detection circuit from a typical 10V to less than 1mV. Furthermore, for the PACK grounding wires, a star grounding topology can be adopted, connecting all PACK grounding wires of equal length to the main grounding stake, which can eliminate the ground potential difference between PACKs, making the ground potential difference between PACKs less than 0.1V.

[0114] To address the interference from the main circuit to the internal detection of a single PACK, the following methods can be used: Figure 11 The detection circuit structure shown allows for the connection of a relay K_detect in series. When K_detect is disconnected, the high-voltage current in the main circuit cannot flow into the detection circuit, preventing power overload of the detection resistor R_d and avoiding errors in insulation resistance calculation due to shunt current. Furthermore, after K_detect is disconnected, the power consumption of the detection circuit is zero, reducing standby power consumption of the battery system.

[0115] Figure 10 and Figure 11 All newly added relays can be controlled by their respective MCUs. The specific anti-interference working timing flow is as follows.

[0116] The MCU controls the isolation relay K_isoN to disconnect other protection circuits from ground, reducing interference to the detection. Then, the MCU controls the main circuit isolation relay K_detect to close, initiating impedance detection of a specific PACK. The MCU can control the ADC to read the voltage at the detection point. For detailed measurement procedures, please refer to the above description. Figure 5 The description will not be repeated here.

[0117] After the detection is completed, the MCU can control K_detect to disconnect, isolate the detection circuit, reduce the standby power consumption of the detection circuit, and control K_isoN to close, restoring the grounding protection of other circuits.

[0118] Thus, through the leakage detection circuit design, arrangement, and combination provided in the embodiments of this application, cell leakage can be detected early, and the leaking cell can be accurately located. This design enables leakage protection of the battery's electrolyte, improving the reliability and safety of the energy storage system.

[0119] It should be understood that the accompanying drawings provided in the embodiments of this application are merely examples, all intended to illustrate the connection relationships between the components used in the embodiments of this application. The circuit structure may include more or fewer components with different connection relationships, and the embodiments of this application do not limit this.

Claims

1. A battery pack, characterized in that, The battery pack includes a controller and a detection circuit. The detection circuit is connected in series between the positive or negative terminal of the battery pack and the protective ground wire. The detection circuit is used to detect the first insulation resistance between the positive or negative terminal of the battery pack and the protective ground wire. The controller is configured to determine that the battery pack is leaking when the increment of the first insulation resistance during a first time period is greater than or equal to a first threshold.

2. The battery pack according to claim 1, characterized in that, The difference between the first insulation impedance during the first time period and the first insulation impedance of the battery pack when no cell leakage occurs does not exceed the second value.

3. The battery pack according to claim 1 or 2, characterized in that, The detection circuit includes: a first switching circuit and multiple resistors connected in series, the first switching circuit being connected in parallel with one of the multiple resistors, and the detection circuit further includes a first node located between the first resistor and the positive or negative terminal of the battery pack. The first resistor is the resistor among the multiple resistors that is closest to the positive or negative terminal of the battery pack. The resistance value of each of the multiple resistors is fixed, and the resistance from the first node to the positive or negative terminal of the battery pack is also fixed. The controller is used to determine the first insulation impedance based on the voltage of the first node when the first switching circuit is in the on state and the voltage of the first node when the first switching circuit is in the off state.

4. The battery pack according to claim 3, characterized in that, The first switching circuit is electrically connected to the controller, which is used to control the switching circuit to turn on and off.

5. The battery pack according to claim 3 or 4, characterized in that, The detection circuit further includes a second switching circuit, which is electrically connected to the controller and is connected in series with the plurality of resistors.

6. The battery pack according to claim 5, characterized in that, The battery pack also includes a grounding protection circuit and a third switching circuit. The third switching circuit is connected in series between the grounding protection circuit and the protective ground wire. The third switching circuit is electrically connected to the controller. The controller is used to control the third switching circuit to disconnect when the first insulation resistance is detected.

7. The battery pack according to any one of claims 1-6, characterized in that, The first time period is less than or equal to seven days.

8. An energy storage system, characterized in that, The energy storage system includes: at least one battery cluster, a protective ground wire, a control center, and a detection circuit; the at least one battery cluster includes multiple battery packs; the battery pack includes: battery cells and a controller. The plurality of battery packs includes a first battery pack, the first battery pack includes a first controller, the first controller is electrically connected to the control center, the first controller is also electrically connected to the detection circuit, and the detection circuit is connected in series between the positive or negative terminal of the first battery pack and the protective ground wire; The detection circuit is used to detect the first insulation resistance of the first battery pack, where the first insulation resistance is the impedance between the positive or negative terminal of the first battery pack and the protective ground wire. The control center is used to determine that the first battery pack has experienced cell leakage if the increment of the first insulation impedance during a first time period is greater than a first value.

9. The energy storage system according to claim 8, characterized in that, The control center is specifically used to receive the first insulation impedance uploaded by the first controller; After determining that the first battery pack has experienced cell leakage, the control center controls the first battery pack to disconnect from the energy storage system and records the information that the first battery pack has experienced leakage.

10. The energy storage system according to claim 8 or 9, characterized in that, The energy storage system further includes a cluster-level detection circuit configured for each of the at least one battery cluster. The cluster-level detection circuit of one battery cluster is connected to the total positive or total negative terminal of the battery cluster and the protective ground wire. The cluster-level detection circuit of one battery cluster is used to detect the insulation resistance of the battery cluster.

11. The energy storage system according to claim 10, characterized in that, The control center is used to detect the insulation impedance of each battery pack within a battery cluster when an abnormal insulation impedance of a battery cluster is detected by the cluster-level detection circuit.

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