Insulation fault detection location method and system for a battery system

Abstract

This application proposes a method and system for detecting and locating insulation faults in a battery system, comprising: S1: obtaining the total insulation impedance value; S2: determining whether the total insulation impedance value is less than a preset safety threshold; if so, proceeding to S3; S3: sequentially controlling the first bypass switches to close one by one, obtaining the insulation impedance value after each closure; S4: calculating the difference between the multiple insulation impedance values ​​and the total insulation impedance value to obtain an insulation impedance enhancement gradient value; S5: if any insulation impedance value reaches the preset safety threshold, determining the corresponding bypassed battery pack as a faulty battery pack; if all insulation impedance values ​​are less than the preset safety threshold, proceeding to S6; S6: sorting the multiple insulation impedance enhancement gradient values ​​in descending order, controlling the first bypass switches corresponding to the top m battery packs in the sorting to close, obtaining a combined insulation impedance value; if the combined insulation impedance value reaches the preset safety threshold, determining that all m battery packs are faulty battery packs. This method can accurately locate faulty battery packs.

Description

Technical Field

[0001] This invention relates to the field of insulation testing technology, and in particular to a method and system for detecting and locating insulation faults in a battery system. Background Technology

[0002] With the rapid development of new energy technologies, high-voltage stacked battery systems are widely used in energy storage power stations, electric commercial vehicles, and industrial backup power supplies. These battery systems typically consist of multiple battery packs connected in series, with a total system voltage ranging from hundreds to thousands of volts. To ensure high-voltage electrical safety, existing technologies usually configure insulation resistance monitoring units (IMUs) between the positive and negative DC buses of the battery system. This allows for the detection of the overall insulation performance of the power circuit, but it cannot locate faulty battery packs, resulting in low efficiency in operation, maintenance, and fault repair.

[0003] Existing insulation testing technologies mainly include overall insulation testing schemes and segmented insulation testing schemes. In overall insulation testing schemes, the mainstream methods include the balanced bridge method, signal injection method, and current sensing method, typically involving an IMU (Insulation Unit) connected between the positive and negative DC buses of the battery system. The IMU can only detect the equivalent impedance to ground of the entire power circuit; when an insulation anomaly occurs, it cannot determine which specific battery pack is faulty. Maintenance personnel need to disassemble each battery pack individually for troubleshooting, which is time-consuming, labor-intensive, and carries high-voltage operation risks. When multiple battery packs simultaneously exhibit slight insulation degradation, this overall insulation testing scheme is prone to missed or false diagnoses. In segmented insulation testing schemes, each battery pack is equipped with an independent insulation testing device, resulting in high hardware costs and system complexity. By collecting the voltage of each battery pack and the bus-to-ground voltage, a mathematical model is established to calculate the fault location, relying on complex algorithms, making it susceptible to interference and resulting in unstable location accuracy.

[0004] In summary, in high-voltage stacked battery systems with multiple battery packs connected in series, there is an urgent need for a low-cost, low-complexity method and system for detecting and locating insulation faults in battery packs that can quickly and accurately detect and locate insulation faults. Summary of the Invention

[0005] In response to the issues mentioned above, such as the inability to locate faulty battery packs in the overall insulation detection scheme and the high hardware cost, high system complexity, reliance on complex algorithms, susceptibility to interference, and unstable positioning accuracy in the segmented insulation detection scheme, this paper addresses these problems.

[0006] This application proposes a method for detecting and locating insulation faults in a battery system. The battery system includes multiple battery packs and an insulation impedance detection circuit. The multiple battery packs are connected in series between a positive DC bus and a negative DC bus. Each battery pack includes a battery pack body and a first bypass switch. The positive terminal of the battery pack body and the first terminal of the first bypass switch are both connected to the first terminal of the battery pack, and the negative terminal of the battery pack body and the second terminal of the first bypass switch are both connected to the second terminal of the battery pack. The insulation impedance detection circuit is connected between the positive DC bus and the negative DC bus. The insulation fault detection and location method includes:

[0007] S1: Obtain the total insulation impedance value output by the insulation impedance detection circuit;

[0008] S2: Determine whether the total insulation resistance value is less than the preset safety threshold. If yes, proceed to step S3; otherwise, return to step S1.

[0009] S3: Sequentially control each of the first bypass switches to close one by one, closing only one first bypass switch at a time, and obtain the insulation impedance value output by the insulation impedance detection circuit after each closure;

[0010] S4: Perform a difference calculation between the multiple insulation impedance values ​​and the total insulation impedance value to obtain the insulation impedance enhancement gradient value corresponding to each bypassed battery pack.

[0011] S5: If any of the insulation resistance values ​​reaches the preset safety threshold, the corresponding bypassed battery pack is determined to be a faulty battery pack; if all insulation resistance values ​​are less than the preset safety threshold, proceed to step S6.

[0012] S6: Sort the multiple insulation impedance enhancement gradient values ​​from largest to smallest, select the battery packs corresponding to the top m insulation impedance enhancement gradient values, where m is ≥2; simultaneously control the first bypass switch corresponding to the m battery packs to close, obtain the combined insulation impedance value, and if the combined insulation impedance value reaches the preset safety threshold, then determine that the m battery packs are all faulty battery packs.

[0013] Optionally, step S6 further includes: if the combined insulation impedance value is less than the preset safety threshold, then add one battery pack at a time according to the sorting result, and at the same time control the first bypass switch corresponding to all currently selected battery packs to close, obtain a new combined insulation impedance value, until the new combined insulation impedance value reaches the preset safety threshold, and determine that all currently selected battery packs are faulty battery packs.

[0014] Optionally, after obtaining the insulation impedance value output by the insulation impedance detection circuit after each closure in step S3, the method further includes: opening the currently closed first bypass switch and then closing the next first bypass switch.

[0015] Optionally, before proceeding to step S3, the method further includes: controlling the bus current of the battery system to decrease to below a preset safe current value to achieve zero-current switching.

[0016] Optionally, after determining that the corresponding bypassed battery pack is a faulty battery pack if the insulation resistance value reaches the preset safety threshold in step S5, the method further includes: outputting a diagnostic report.

[0017] After determining that all m battery packs are faulty in step S6, the process further includes: outputting the diagnostic report.

[0018] Optionally, when obtaining the insulation impedance value, the sampling time constant is adjusted according to the number of bypassed battery packs.

[0019] Optionally, each battery pack further includes a plurality of second bypass switches, each second bypass switch being connected between the positive terminal of the corresponding battery pack body and the first terminal of the corresponding first bypass switch or between the negative terminal of the corresponding battery pack body and the second terminal of the corresponding first bypass switch; the second bypass switch is interlocked with the first bypass switch, such that when the first bypass switch is closed, the second bypass switch is open.

[0020] Optionally, both the first bypass switch and the second bypass switch are contacts of a relay or contactor, or switching transistors.

[0021] Optionally, after determining that the corresponding bypassed battery pack is a faulty battery pack if the insulation resistance value reaches the preset safety threshold in step S5, the method further includes: cutting off the high voltage circuit of the battery system, or reducing the maximum output power or maximum input power of the battery system.

[0022] After determining that all m battery packs are faulty in S6, the process further includes: disconnecting the high-voltage circuit of the battery system, or reducing the maximum output power or maximum input power of the battery system.

[0023] This application also proposes an insulation fault detection and location system for a battery system, comprising:

[0024] Multiple battery packs are connected in series between a positive DC bus and a negative DC bus; each battery pack includes a battery pack body and a first bypass switch, the positive terminal of the battery pack body and the first terminal of the first bypass switch are both connected to the first terminal of the battery pack, and the negative terminal of the battery pack body and the second terminal of the first bypass switch are both connected to the second terminal of the battery pack.

[0025] An insulation resistance detection circuit is connected between the positive DC bus and the negative DC bus to detect the battery system's impedance to ground and output the total insulation resistance value.

[0026] The control unit is connected to the insulation impedance detection circuit and the plurality of first bypass switches respectively, and is used to execute the insulation fault detection and location method of the battery system as described in any embodiment of this application.

[0027] Optionally, the control unit includes:

[0028] A battery control unit, connected to the insulation impedance detection circuit, is used to execute the insulation fault detection and location method of the battery system.

[0029] Multiple battery management units are connected to the battery control unit respectively, and are used to drive the corresponding first bypass switch to close and open.

[0030] The beneficial effects of this application include at least the following:

[0031] In this embodiment, the first bypass switches are closed sequentially, one by one at a time. After each closure, the insulation impedance value output by the insulation impedance detection circuit after the bypassed battery pack is obtained. The multiple insulation impedance values ​​are then subtracted from the total insulation impedance value to obtain the insulation impedance enhancement gradient value corresponding to each bypassed battery pack. If any insulation impedance value reaches the preset safety threshold, the corresponding bypassed battery pack is determined to be a faulty battery pack. If all insulation impedance values ​​are less than the preset safety threshold, the multiple insulation impedance enhancement gradient values ​​are sorted from largest to smallest, and the battery packs corresponding to the top m insulation impedance enhancement gradient values ​​are selected, where m is ≥ 2. Simultaneously, the first bypass switches corresponding to the m battery packs are closed to obtain the combined insulation impedance value. If the combined insulation impedance value reaches the preset safety threshold, all m battery packs are determined to be faulty battery packs. This method can automatically locate insulation faults without the need for manual disconnection and inspection of each battery pack, reducing maintenance time by more than 80%. It can replace expensive distributed insulation detection chips by using existing bypass switches or adding low-cost relays. In addition, the bypass switch only affects a single battery pack and does not interfere with other modules of the system, effectively solving the "shielding effect" when multiple battery packs leak current at the same time. Based on bypass detection logic, there is no algorithm calculation error, resulting in high positioning accuracy. Moreover, by monitoring the change trend of the insulation impedance gradient value corresponding to each battery pack after it is bypassed over a long period of time, the insulation aging state of the battery pack can be predicted.

[0032] The features and technical advantages of this application have been broadly outlined above to facilitate a better understanding of the following detailed description. Additional features and advantages of this application, which form the subject matter of the claims, will be described below. Those skilled in the art will understand that the disclosed concepts and specific embodiments can be readily utilized as the basis for modifying or designing other structures or processes to achieve the same purpose as this application. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of this application as set forth in the appended claims. Attached Figure Description

[0033] To gain a more comprehensive understanding of this application and its advantages, the following description is now taken in conjunction with the accompanying drawings, in which:

[0034] Figure 1 A schematic diagram of the structure of an insulation fault detection and location system for a battery system according to an embodiment of this application is shown;

[0035] Figure 2 A schematic diagram of the structure of an insulation fault detection and location system for a battery system according to another embodiment of this application is shown;

[0036] Figure 3A control flowchart of the insulation fault detection and location method for a battery system according to an embodiment of this application is shown;

[0037] Figure 4 An impedance variation characteristic curve of an embodiment of this application is shown.

[0038] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding parts. The accompanying drawings are provided to clearly illustrate relevant aspects of various embodiments and are not necessarily drawn to scale. Detailed Implementation

[0039] Various exemplary embodiments, features, and aspects of the present invention will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0040] The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment illustrated herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments. The terms "first," "second," "third," etc. (if present) in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "coupled," "connected," and "linked" should be interpreted broadly. For example, they can refer to electrical connection or mutual communication; they can be a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Furthermore, to better illustrate the present invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In some instances, methods, means, elements, and circuits well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0043] Existing insulation testing technologies for battery systems typically employ either a comprehensive insulation testing scheme or a segmented insulation testing scheme. In the comprehensive insulation testing scheme, when an insulation anomaly occurs, it's impossible to pinpoint which specific battery pack is faulty. Maintenance personnel must disassemble each battery pack individually for inspection, which is time-consuming, labor-intensive, and carries the risk of high-voltage operation. When multiple battery packs simultaneously exhibit slight insulation degradation, this comprehensive insulation testing scheme is prone to missed or false diagnoses. In the segmented insulation testing scheme, each battery pack is equipped with an independent insulation testing device, resulting in high hardware costs and system complexity. While it relies on complex algorithms to calculate fault location by collecting voltage data from each battery pack and bus-to-ground voltage, it is susceptible to interference and its location accuracy is unstable.

[0044] To address the aforementioned technical problems, this embodiment provides an insulation fault detection and location system for a battery system. Figure 1 A schematic diagram of the structure of an insulation fault detection and location system for a battery system according to an embodiment of this application is shown, as follows: Figure 1 As shown, the insulation fault detection and location system includes multiple battery packs 41, 42, ..., 4N, a distribution box 6, an insulation impedance detection circuit 5, and a control unit 7. The multiple battery packs 41, 42, ..., 4N are connected in series to form a battery pack string. The battery pack string is connected between the positive DC bus and the negative DC bus; that is, the first end of the first battery pack 41 is connected to the positive DC bus, the first end of the second battery pack 42 is connected to the second end of the first battery pack 41, and so on, with the second end of the last battery pack 4N connected to the negative DC bus. Each battery pack includes a battery pack body and a first bypass switch. The positive terminal of the battery pack body and the first terminal of the first bypass switch are both connected to the first end of the battery pack, and the negative terminal of the battery pack body and the second terminal of the first bypass switch are both connected to the second end of the battery pack. Specifically, the first battery pack 41 includes a battery pack body 11 and a first bypass switch 21. The positive terminal of the battery pack body 11 and the first terminal of the first bypass switch 21 are both connected to the first terminal of the first battery pack 41, and the negative terminal of the battery pack body 11 and the second terminal of the first bypass switch 21 are both connected to the second terminal of the first battery pack 41. The second battery pack 42 includes a battery pack body 12 and a first bypass switch 22. The positive terminal of the battery pack body 12 and the first terminal of the first bypass switch 22 are both connected to the second battery pack 42. The first terminal of the battery pack body 12 and the second terminal of the first bypass switch 22 are both connected to the second terminal of the second battery pack 42; and so on, the Nth battery pack 4N includes a battery pack body 1N and a first bypass switch 2N, the positive terminal of the battery pack body 1N and the first terminal of the first bypass switch 2N are both connected to the first terminal of the Nth battery pack 4N, and the negative terminal of the battery pack body 1N and the second terminal of the first bypass switch 2N are both connected to the second terminal of the Nth battery pack 4N, where N is an integer greater than or equal to 2.

[0045] In this embodiment, the first bypass switches 21, 22, ..., 2N are all contacts of relays or contactors, or switching transistors. The first bypass switches 21, 22, ..., 2N are normally in the open state. The first bypass switches 21, 22, ..., 2N can be existing bypass switches in the battery system, or low-cost relays, etc., which can replace expensive distributed insulation detection chips. The operation of the first bypass switches only affects their corresponding battery packs and will not interfere with other modules in the battery system.

[0046] The distribution box 6 is a high-voltage box used for power distribution. Specifically, the distribution box 6 includes a positive DC bus, a negative DC bus, a relay, a fuse, and a high-voltage interface. The positive DC bus connects to one end of the battery pack string, and the negative DC bus connects to the other end of the battery pack string. Protective devices, such as relays and fuses, can be connected between the positive DC bus and the positive terminal of the high-voltage interface, and similarly, between the negative DC bus and the negative terminal of the high-voltage interface. These protective devices are used for overcurrent and short-circuit protection. The positive and negative terminals of the high-voltage interface are connected to external devices, such as inverters and loads.

[0047] The insulation impedance detection circuit 5 is connected between the positive DC bus and the negative DC bus. It can be located inside or outside the distribution box 6. It is used to detect the battery pack series impedance to ground and output the total insulation impedance value Rtotal.

[0048] The control unit 7 is connected to the insulation impedance detection circuit 5 and the plurality of first bypass switches 21, 22, ..., 2N. The control unit 7 is used to execute the insulation fault detection and location method of the battery system described below, and is mainly responsible for coordinating the operation of the first bypass switches, collecting the total insulation impedance value and multiple insulation impedance values, and locating the faulty battery pack through data processing. In this embodiment, the control unit 7 can be a battery management system (BMS) or an energy management system (EMS).

[0049] In this embodiment, each battery pack further includes a plurality of second bypass switches. Each second bypass switch is connected between the positive terminal of the corresponding battery pack body and the first terminal of the corresponding first bypass switch or between the negative terminal of the corresponding battery pack body and the second terminal of the corresponding first bypass switch. Each second bypass switch is connected to the control unit 7. The second bypass switch is interlocked with the first bypass switch, such that when the first bypass switch is closed, the second bypass switch is opened. Specifically, the first battery pack 41 also includes a second bypass switch 31, connected between the positive terminal of the battery pack body 11 and the first terminal of the first bypass switch 21, or between the negative terminal of the battery pack body 11 and the second terminal of the first bypass switch 21. The second bypass switch 31 is connected to the control unit 7 and is interlocked with the first bypass switch 21, such that when the first bypass switch 21 is closed, the second bypass switch 31 is open, and when the second bypass switch 31 is closed, the first bypass switch 21 is open. The second battery pack 42 also includes a second bypass switch 32, connected between the positive terminal of the battery pack body 12 and the first terminal of the first bypass switch 22, or between the negative terminal of the battery pack body 12 and the second terminal of the first bypass switch 22. Switch 32 is connected to control unit 7. The second bypass switch 32 is interlocked with the first bypass switch 22, such that when the first bypass switch 22 is closed, the second bypass switch 32 is open, and vice versa. Similarly, the Nth battery pack 4N also includes a second bypass switch 3N, connected between the positive terminal of the battery pack body 1N and the first terminal of the first bypass switch 2N, or between the negative terminal of the battery pack body 1N and the second terminal of the first bypass switch 2N. The second bypass switch 3N is connected to control unit 7, and is interlocked with the first bypass switch 2N, such that when the first bypass switch 2N is closed, the second bypass switch 3N is open, and vice versa. In this embodiment, the second bypass switches 31, 32, ..., 3N can be contacts of a relay or contactor, or switching transistors. The second bypass switches 31, 32, ..., 3N can be bypass switches already present in the battery system, or low-cost relays, etc. The second bypass switches 31, 32, ..., 3N are normally closed. The control unit 7 is used to control the closing and opening of the second bypass switches 31, 32, ..., 3N.

[0050] Figure 2 A schematic diagram of the structure of an insulation fault detection and location system for a battery system according to another embodiment of this application is shown, as follows: Figure 2 As shown, this insulation fault detection and location system is... Figure 1The difference in the insulation fault detection and location system shown lies in the further description of the control unit 7. The control unit 7 includes a Battery Control Unit (BCU) 70 and multiple Battery Management Units (BMUs) 71, 72, ..., 7N. The Battery Control Unit 70 is connected to the insulation impedance detection circuit and is used to execute the insulation fault detection and location method of the battery system described below. The multiple BMUs 71, 72, ..., 7N are respectively located in corresponding battery packs; for example, BMU 71 is located in the first battery pack 41, BMU 72 is located in the second battery pack 42, ..., and BMU 7N is located in the Nth battery pack 4N.

[0051] Multiple battery management units (BMUs) 71, 72, ..., 7N are connected to the battery control unit 70 and their corresponding first bypass switches, respectively, and are used to drive the corresponding first bypass switches to close and open according to the control signals output by the battery control unit 70. Specifically, the first battery management unit 71 is connected to the battery control unit 70 and the first bypass switch 21, and is used to drive the first bypass switch 21 to close and open according to the first control signal output by the battery control unit 70; the second battery management unit 72 is connected to the battery control unit 70 and the first bypass switch 22, and is used to drive the first bypass switch 22 to close and open according to the second control signal output by the battery control unit 70; and so on, the Nth battery management unit 7N is connected to the battery control unit 70 and the first bypass switch 2N, and is used to drive the first bypass switch 2N to close and open according to the Nth control signal output by the battery control unit 70.

[0052] like Figure 2 As shown, the first battery management unit 71 is connected to the second bypass switch 31 and is used to drive the second bypass switch 31 to close and open; the second battery management unit 72 is connected to the second bypass switch 32 and is used to drive the second bypass switch 32 to close and open; and so on, the Nth battery management unit 7N is connected to the second bypass switch 3N and is used to drive the second bypass switch 3N to close and open.

[0053] This embodiment provides a method for detecting and locating insulation faults in a battery system. Figure 3 This application shows a control flowchart of an insulation fault detection and location method for a battery system according to an embodiment of the present application, as follows: Figure 3 As shown, the insulation fault detection and location method includes:

[0054] S1: Obtain the total insulation impedance value output by the insulation impedance detection circuit.

[0055] Combination Figure 1 and Figure 3Initially, the first bypass switches 21, 22, ..., 2N are all in the open state, and the battery pack bodies 11, 12, ..., 1N remain in a normal series connection. The insulation impedance detection circuit 5 is used to detect the battery system's impedance to ground. It requires signal processing and algorithmic calculation to finally output the total insulation impedance value Rtotal. The control unit 7 obtains the total insulation impedance value Rtotal from the insulation impedance detection circuit 5.

[0056] Furthermore, in the initial state, the first bypass switches 21, 22, ..., 2N are all in the open state, while the second bypass switches 31, 32, ..., 3N are all in the closed state, and the battery pack bodies 11, 12, ..., 1N maintain a normal series connection.

[0057] S2: Determine whether the total insulation resistance value is less than the preset safety threshold. If yes, proceed to step S3; otherwise, return to step S1.

[0058] Combination Figure 1 and Figure 3 The control unit 7 determines whether the total insulation resistance value Rtotal is less than the preset safety threshold Ts. If yes, it proceeds to step S3; otherwise, it returns to step S1 and continues to acquire the total insulation resistance value Rtotal.

[0059] S3: Sequentially control each of the first bypass switches to close one by one, closing only one first bypass switch at a time, and obtain the insulation impedance value output by the insulation impedance detection circuit after each closure.

[0060] Furthermore, after obtaining the insulation impedance value output by the insulation impedance detection circuit after each closure in step S3, the method further includes: opening the currently closed first bypass switch and then closing the next first bypass switch.

[0061] Combination Figure 1 and Figure 3The control unit 7 sequentially controls the first bypass switches 21, 22, ..., 2N to close one by one, closing only one bypass switch at a time. After each bypass switch is closed, the control unit 7 acquires and records the insulation impedance value output by the insulation impedance detection circuit 5 after the bypassed battery pack is closed. The insulation impedance detection circuit 5 detects the impedance to ground of the battery pack string composed of the unbypassed battery packs and outputs the insulation impedance value. Specifically, in the first instance, the control unit 7 controls the first bypass switch 21 to close, while the other first bypass switches remain open. The battery pack body 11 is bypassed by the first bypass switch 21, meaning the battery pack 41 is bypassed and removed from the power circuit. The insulation impedance detection circuit 5 detects the impedance to ground of the battery pack string composed of the unbypassed battery packs and outputs the insulation impedance value R1. The control unit 7 acquires and records the insulation impedance value R1 after the battery pack 41 is bypassed. In the second instance, control unit 7 first controls the first bypass switch 21 to open, and then controls the first bypass switch 22 to close, while the other first bypass switches remain open. The battery pack body 12 is bypassed by the first bypass switch 22, meaning the battery pack 42 is bypassed and removed from the power circuit. The insulation impedance detection circuit 5 detects the impedance to ground of the battery pack series composed of the unbypassed battery packs and outputs the insulation impedance value R2. Control unit 7 acquires and records the insulation impedance value R2 after the battery pack 42 is bypassed. In the i-th instance, control unit 7 first controls the first bypass switch 2(i-1) to open, and then controls the first bypass switch 2i to close, while the other first bypass switches remain open. The battery pack body 1i is bypassed by the first bypass switch 2i, meaning the battery pack 4i is bypassed and removed from the power circuit. The insulation impedance detection circuit 5 detects the impedance to ground of the battery pack series composed of the unbypassed battery packs and outputs the insulation impedance value Ri. Control unit 7 acquires and records the insulation impedance value Ri after the battery pack 4i is bypassed, where 2≤i≤N.

[0062] In the first operation, control unit 7 closes the first bypass switch 21 and opens the second bypass switch 31, while keeping the other first bypass switches open and the other second bypass switches closed. Battery pack body 11 is bypassed by the first bypass switch 21, and battery pack 41 is bypassed and removed from the power circuit. Control unit 7 acquires and records the insulation resistance value R1 after battery pack 41 is bypassed. In the second operation, control unit 7 first opens the first bypass switch 21 and closes the second bypass switch 31, connecting battery pack body 11 to the power circuit. Then, it controls the first bypass switch 22 to close and the second bypass switch 32 to open, bypassing battery pack body 12 by the first bypass switch 22, and battery pack 42 is bypassed and removed from the power circuit. Control unit 7 acquires and records the insulation resistance value R2 after battery pack 42 is bypassed. In the i-th iteration, control unit 7 first controls the first bypass switch 2 (i-1) to open and the second bypass switch 3 (i-1) to close, connecting battery pack body 1 (i-1) to the power circuit. Then, it controls the first bypass switch 2i to close and the second bypass switch 3i to open, bypassing battery pack body 1i and battery pack 4i, thus removing it from the power circuit. After battery pack 4i is bypassed, control unit 7 acquires and records the insulation resistance value Ri, where 2 ≤ i ≤ N.

[0063] S4: Perform a difference calculation between the multiple insulation impedance values ​​and the total insulation impedance value to obtain the insulation impedance enhancement gradient value corresponding to each bypassed battery pack.

[0064] The control unit 7 receives multiple insulation resistance values ​​R1, R2, ..., RN, and performs a difference calculation between each insulation resistance value R1, R2, ..., RN and the total insulation resistance value Rtotal to obtain the insulation resistance enhancement gradient value corresponding to each bypassed battery pack. Specifically, the control unit 7 performs a difference calculation between the insulation resistance value R1 and the total insulation resistance value to obtain the insulation resistance enhancement gradient value ΔR1 corresponding to the bypassed battery pack 41, i.e., ΔR1 = R1 - Rtotal; the control unit 7 performs a difference calculation between the insulation resistance value R2 and the total insulation resistance value to obtain the insulation resistance enhancement gradient value ΔR2 corresponding to the bypassed battery pack 42, i.e., ΔR2 = R2 - Rtotal; ...; the control unit 7 performs a difference calculation between the insulation resistance value RN and the total insulation resistance value to obtain the insulation resistance enhancement gradient value ΔRN corresponding to the bypassed battery pack 4N, i.e., ΔRN = RN - Rtotal.

[0065] S5: If any insulation resistance value reaches the preset safety threshold, the corresponding bypassed battery pack is determined to be a faulty battery pack; if all insulation resistance values ​​are less than the preset safety threshold, proceed to step S6.

[0066] The control unit 7 compares the insulation resistance value R1 with the preset safety threshold Ts. If the insulation resistance value R1 reaches the preset safety threshold Ts (R1≥Ts), the bypassed battery pack 41 is determined to be a faulty battery pack. If the insulation resistance value R1 is less than the preset safety threshold Ts (R1<Ts), the insulation resistance value R2 is compared with the preset safety threshold Ts. If the insulation resistance value R2 reaches the preset safety threshold Ts (R2≥Ts), the bypassed battery pack 42 is determined to be a faulty battery pack. If the insulation resistance value R2 is less than the preset safety threshold Ts (R2<Ts), subsequent insulation resistance values ​​are compared with the preset safety threshold Ts sequentially until the insulation resistance value reaches the preset safety threshold Ts, at which point the bypassed battery pack corresponding to that insulation resistance value is determined to be a faulty battery pack.

[0067] By sequentially closing the first bypass switch one by one and obtaining the corresponding insulation resistance value, and comparing the insulation resistance value with the preset safety threshold, the faulty battery pack can be automatically located. This eliminates the need for manual disconnection and inspection of each battery pack, reducing maintenance time by more than 80%.

[0068] If all insulation resistance values ​​R1, R2, ..., RN are less than the preset safety threshold, i.e., R1 < Ts, R2 < Ts, ..., RN < Ts, it indicates that there is a multi-point parallel fault, and then proceed to step S6.

[0069] S6: Sort the multiple insulation impedance enhancement gradient values ​​from largest to smallest, select the battery packs corresponding to the top m insulation impedance enhancement gradient values, where m≥2; simultaneously control the first bypass switch corresponding to the m battery packs to close, obtain the combined insulation impedance value, and if the combined insulation impedance value reaches the preset safety threshold, then determine that the m battery packs are all faulty battery packs.

[0070] If multiple insulation impedance gradient values ​​are greater than zero, a recursive combined scan is initiated, requiring the simultaneous closure of multiple first bypass switches to determine multi-point parallel faults. The control unit 7 sorts the multiple insulation impedance gradient values ​​ΔR1, ΔR2, ..., ΔRN according to their priority from largest to smallest. It first selects the battery packs corresponding to the two highest-ranked insulation impedance gradient values, such as battery packs 41 and 43. Simultaneously, it controls the closure of the first bypass switch 21 corresponding to battery pack 41 and the first bypass switch 23 corresponding to battery pack 43, bypassing battery packs 41 and 43. After bypassing battery packs 41 and 43, a combined insulation impedance value is obtained. If the combined insulation impedance value reaches the preset safety threshold Ts, battery packs 41 and 43 are determined to be faulty battery packs. The insulation impedance detection circuit 5 detects the battery pack series impedance to ground composed of the unbypassed battery packs and outputs the combined insulation impedance value. If the combined insulation impedance value is less than the preset safety threshold Ts, then the three battery packs with the highest insulation impedance gradient values ​​are selected, such as battery packs 41, 43, and 45. Simultaneously, the first bypass switch 21 corresponding to battery pack 41, the first bypass switch 23 corresponding to battery pack 43, and the first bypass switch 25 corresponding to battery pack 45 are closed, bypassing battery packs 41, 43, and 45. After bypassing battery packs 41, 43, and 45, a new combined insulation impedance value is obtained. If the new combined insulation impedance value reaches the preset safety threshold Ts, then battery packs 41, 43, and 45 are determined to be faulty battery packs. If the new combined insulation impedance value is less than the preset safety threshold Ts, one more battery pack is added sequentially according to the sorting result. Simultaneously, the first bypass switches corresponding to all currently selected battery packs are closed, and a new combined insulation impedance value is obtained after all currently selected battery packs are bypassed, until the new combined insulation impedance value reaches the preset safety threshold, at which point all currently selected battery packs are determined to be faulty battery packs.

[0071] By comparing the increase in insulation impedance under different combinations, all leakage points are locked using parallel resistor cancellation logic. A recursive identification strategy based on the insulation impedance gradient value narrows the search space; only combinations that cause an increase in insulation impedance after bypassing the corresponding battery pack are included in the next round of recursion. This significantly reduces the number of times the first bypass switch operates, extending hardware lifespan.

[0072] This method achieves a leap from the "circuit level" to the "pack level," automatically locating faulty battery packs without the need for manual disconnection and inspection of each pack, reducing maintenance time by over 80%. This method utilizes existing bypass switches (if present in the system) or adds a low-cost relay as the first bypass switch, replacing expensive distributed insulation detection chips and effectively reducing costs. Furthermore, bypass operation only affects a single battery pack, without interfering with other modules in the system, making it suitable for high-voltage stacked systems with 2 to 9 or more series-connected battery packs, exhibiting strong system compatibility. The recursive algorithm solves the "shielding effect" when multiple battery packs leak simultaneously, resulting in more robust diagnostic logic. Based on an "all or nothing" bypass detection logic, there are no algorithmic calculation errors, achieving 100% location accuracy. By long-term monitoring of the insulation impedance gradient value change trend after each battery pack is bypassed, the insulation aging state of the battery pack can be predicted.

[0073] Furthermore, before proceeding to step S3, the method further includes: controlling the bus current of the battery system to decrease to below a preset safe current value in order to achieve zero-current switching.

[0074] Specifically, before controlling the first bypass switch to close, the control unit 7 will issue a command to reduce the bus current of the battery system to below a preset safe current value in order to achieve zero-current switching, thereby eliminating the arc discharge of the first bypass switch during the energized switching process, thus protecting the first bypass switch and eliminating the influence of electromagnetic transients on the insulation sampling reading.

[0075] Furthermore, after determining that the corresponding bypassed battery pack is a faulty battery pack if the insulation resistance value reaches the preset safety threshold in step S5, step S7 is also included: outputting a diagnostic report.

[0076] After determining in step S6 that all m battery packs are faulty, step S7 is further included: outputting the diagnostic report.

[0077] After identifying the faulty battery pack, the control unit 7 outputs a diagnostic report and uploads the specific faulty battery pack number to the host computer.

[0078] Furthermore, in step S5, if the insulation resistance value reaches the preset safety threshold, the corresponding bypassed battery pack is determined to be a faulty battery pack. The steps further include: cutting off the high-voltage circuit of the battery system, or reducing the maximum output power or maximum input power of the battery system.

[0079] After determining that all m battery packs are faulty in S6, the process further includes: disconnecting the high-voltage circuit of the battery system, or reducing the maximum output power or maximum input power of the battery system.

[0080] The control unit, upon identifying a faulty battery pack, cuts off the high-voltage circuit of the battery system or reduces the maximum output power or maximum input power of the battery system.

[0081] Furthermore, after identifying a faulty battery pack, the control unit 7 either waits for a maintenance instruction or bypasses the faulty battery pack and maintains temporary operation.

[0082] Furthermore, when obtaining the insulation impedance value, the sampling time constant is adjusted according to the number of bypassed battery packs.

[0083] Specifically, when the control unit 7 acquires the insulation impedance value, it adjusts the sampling time constant according to the number of bypassed battery packs to offset the reading fluctuations caused by changes in the parasitic capacitance of the battery system to ground.

[0084] like Figure 4 As shown, in the initial state, the total insulation resistance value is below the preset safety threshold Ts. After bypassing battery pack 41, battery pack 41 exits the power circuit, and the curve fluctuates slightly but remains below the preset safety threshold Ts. Then, battery pack 41 is connected to the power circuit, and after bypassing battery pack 42, battery pack 42 exits the power circuit. The insulation resistance value R2 (curve) experiences an instantaneous vertical step (jump), exceeding the preset safety threshold Ts, thus accurately locating battery pack 42 as the faulty battery pack. If multiple faulty battery packs exist, the curve of a single battery pack will only partially rise after being bypassed; only when the combined battery pack is bypassed will it exceed the preset safety threshold Ts.

[0085] Combination Figure 2 and Figure 3The battery control unit 70 obtains the total insulation impedance value Rtotal from the insulation impedance detection circuit 5. The battery control unit 70 determines whether the total insulation impedance value Rtotal is less than the preset safety threshold Ts. If yes, it proceeds to step S3; otherwise, it returns to step S1 and continues to obtain the total insulation impedance value Rtotal. The battery control unit 70 sequentially outputs control signals to the corresponding battery management units. The corresponding battery management units drive the corresponding first bypass switch to close according to the received control signals, closing only one bypass switch at a time. After each bypass switch closure, the battery control unit 70 obtains and records the insulation impedance value output by the insulation impedance detection circuit after the bypassed battery pack. Specifically, in the first instance, the battery control unit 70 outputs a first control signal, and the battery management unit 71 drives the first bypass switch 21 to close according to the first control signal. The other first bypass switches remain open, and the battery pack body 11 is bypassed by the first bypass switch 21, i.e., the battery pack 41 is bypassed and removed from the power circuit. After the battery pack 41 is bypassed, the battery control unit 70 obtains and records the insulation impedance value R1. The second time, the battery control unit 70 outputs the first control signal and the second control signal successively. The battery management unit 71 drives the first bypass switch 21 to open according to the first control signal, and the battery management unit 72 drives the first bypass switch 22 to close according to the second control signal. The other first bypass switches remain open. The battery pack body 12 is bypassed by the first bypass switch 22, that is, the battery pack 42 is bypassed and removed from the power circuit. After the battery pack 42 is bypassed, the battery control unit 70 acquires and records the insulation resistance value R2. The i-th time, the battery control unit 70 outputs the (i-1)-th control signal and the i-th control signal successively. The battery management unit 7(i-1) drives the first bypass switch 2(i-1) to open according to the (i-1)-th control signal, and the battery management unit 7i drives the first bypass switch 2i to close according to the i-th control signal. The other first bypass switches remain open. The battery pack body 1i is bypassed by the first bypass switch 2i, that is, the battery pack 4i is bypassed and removed from the power circuit. After the battery pack 4i is bypassed, the battery control unit 70 acquires and records the insulation resistance value Ri, where 2≤i≤N.

[0086] The battery control unit 70 receives multiple insulation resistance values ​​R1, R2, ..., RN, and performs difference calculations between the multiple insulation resistance values ​​R1, R2, ..., RN and the total insulation resistance value Rtotal to obtain the insulation resistance enhancement gradient value corresponding to each bypassed battery pack.

[0087] If any of the insulation resistance values ​​reaches the preset safety threshold, the battery control unit 70 determines that the corresponding bypassed battery pack is a faulty battery pack; if all insulation resistance values ​​are less than the preset safety threshold, then proceed to step S6.

[0088] The battery control unit 70 sorts the multiple insulation impedance enhancement gradient values ​​from largest to smallest, selects the battery packs corresponding to the top m insulation impedance enhancement gradient values, where m≥2; at the same time, it controls the first bypass switch corresponding to the m battery packs to close, obtains the combined insulation impedance value, and if the combined insulation impedance value reaches the preset safety threshold, it determines that the m battery packs are all faulty battery packs.

[0089] This application's insulation fault detection and location method and system achieve a leap from the "circuit level" to the "pack level," automatically locating faulty battery packs without requiring manual disconnection and inspection of each pack, reducing maintenance time by over 80%. This method utilizes existing bypass switches (if already present in the system) or adds a low-cost relay as the first bypass switch, replacing expensive distributed insulation detection chips and effectively reducing costs. Furthermore, bypass operation only affects a single battery pack, without interfering with other modules in the system, making it suitable for high-voltage stacked systems with 2 to 9 or more series-connected battery packs, exhibiting strong system compatibility. The recursive algorithm solves the "shielding effect" when multiple battery packs leak simultaneously, resulting in more robust diagnostic logic. Based on an "all or nothing" bypass detection logic, there are no algorithmic calculation errors, achieving 100% location accuracy. By long-term monitoring of the insulation impedance gradient value change trend after each battery pack is bypassed, the insulation aging state of the battery pack can be predicted.

[0090] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the present application as defined by the appended claims.

[0091] Furthermore, the scope of this application is not limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, methods, and steps described herein. Those skilled in the art will readily understand from the disclosure of this application that, according to this application, currently existing or to be developed processes, machines, manufactures, compositions of matter, methods, or steps that perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein can be utilized. Therefore, it is intended that the appended claims encompass such processes, machines, manufactures, compositions of matter, methods, or steps within their scope.

Claims

1. A method for detecting and locating insulation faults in a battery system, characterized in that, The battery system includes multiple battery packs and an insulation resistance detection circuit. The multiple battery packs are connected in series between a positive DC bus and a negative DC bus. Each battery pack includes a battery pack body and a first bypass switch. The positive terminal of the battery pack body and the first terminal of the first bypass switch are both connected to the first terminal of the battery pack, and the negative terminal of the battery pack body and the second terminal of the first bypass switch are both connected to the second terminal of the battery pack. The insulation resistance detection circuit is connected between the positive DC bus and the negative DC bus. The insulation fault detection and location method includes: S1: Obtain the total insulation impedance value output by the insulation impedance detection circuit; S2: Determine whether the total insulation resistance value is less than the preset safety threshold. If yes, proceed to step S3; otherwise, return to step S1. S3: Sequentially control each of the first bypass switches to close one by one, closing only one first bypass switch at a time, and obtain the insulation impedance value output by the insulation impedance detection circuit after each closure; S4: Perform a difference calculation between the multiple insulation impedance values ​​and the total insulation impedance value to obtain the insulation impedance enhancement gradient value corresponding to each bypassed battery pack. S5: If any insulation resistance value reaches the preset safety threshold, the corresponding bypassed battery pack is determined to be a faulty battery pack; if all insulation resistance values ​​are less than the preset safety threshold, proceed to step S6. S6: Sort the multiple insulation impedance enhancement gradient values ​​from largest to smallest, select the battery packs corresponding to the top m insulation impedance enhancement gradient values, where m≥2; simultaneously control the first bypass switch corresponding to the m battery packs to close, obtain the combined insulation impedance value, and if the combined insulation impedance value reaches the preset safety threshold, then determine that the m battery packs are all faulty battery packs.

2. The method for detecting and locating insulation faults in a battery system according to claim 1, characterized in that, Step S6 further includes: if the combined insulation impedance value is less than the preset safety threshold, then add one battery pack at a time according to the sorting result, and at the same time control the first bypass switch corresponding to all currently selected battery packs to close, obtain a new combined insulation impedance value, until the new combined insulation impedance value reaches the preset safety threshold, and determine that all currently selected battery packs are faulty battery packs.

3. The method for detecting and locating insulation faults in a battery system according to claim 1, characterized in that, After obtaining the insulation impedance value output by the insulation impedance detection circuit after each closure in step S3, the method further includes: opening the currently closed first bypass switch and then closing the next first bypass switch.

4. The method for detecting and locating insulation faults in a battery system according to claim 1, characterized in that, Before proceeding to step S3, the method further includes: controlling the bus current of the battery system to decrease to below a preset safe current value in order to achieve zero current switching.

5. The method for detecting and locating insulation faults in a battery system according to claim 1, characterized in that, If the insulation resistance value reaches the preset safety threshold in step S5, the corresponding bypassed battery pack is determined to be a faulty battery pack. The process also includes: outputting a diagnostic report. After determining that all m battery packs are faulty in step S6, the process further includes: outputting the diagnostic report.

6. The method for detecting and locating insulation faults in a battery system according to claim 1, characterized in that, When obtaining the insulation impedance value, the sampling time constant is adjusted according to the number of bypassed battery packs.

7. The method for detecting and locating insulation faults in a battery system according to claim 1, characterized in that, Each of the battery packs further includes a plurality of second bypass switches, each second bypass switch being connected between the positive terminal of the corresponding battery pack body and the first terminal of the corresponding first bypass switch or between the negative terminal of the corresponding battery pack body and the second terminal of the corresponding first bypass switch; the second bypass switch is interlocked with the first bypass switch such that when the first bypass switch is closed, the second bypass switch is open.

8. The method for detecting and locating insulation faults in a battery system according to claim 7, characterized in that, Both the first bypass switch and the second bypass switch are contacts of relays or contactors, or switching transistors.

9. The method for detecting and locating insulation faults in a battery system according to claim 1, characterized in that, If the insulation resistance value reaches the preset safety threshold in step S5, then the corresponding bypassed battery pack is determined to be a faulty battery pack. The steps further include: cutting off the high voltage circuit of the battery system, or reducing the maximum output power or maximum input power of the battery system. After determining that all m battery packs are faulty in S6, the process further includes: disconnecting the high-voltage circuit of the battery system, or reducing the maximum output power or maximum input power of the battery system.

10. A battery system insulation fault detection and location system, characterized in that, include: Multiple battery packs are connected in series between a positive DC bus and a negative DC bus; each battery pack includes a battery pack body and a first bypass switch, the positive terminal of the battery pack body and the first terminal of the first bypass switch are both connected to the first terminal of the battery pack, and the negative terminal of the battery pack body and the second terminal of the first bypass switch are both connected to the second terminal of the battery pack. An insulation resistance detection circuit is connected between the positive DC bus and the negative DC bus to detect the battery system's impedance to ground and output the total insulation resistance value. The control unit is connected to the insulation impedance detection circuit and the plurality of the first bypass switches respectively, and is used to perform the insulation fault detection and location method of the battery system as described in any one of claims 1 to 9.

11. The insulation fault detection and location system for a battery system according to claim 10, characterized in that, The control unit includes: A battery control unit, connected to the insulation impedance detection circuit, is used to execute the insulation fault detection and location method of the battery system. Multiple battery management units are connected to the battery control unit respectively, and are used to drive the corresponding first bypass switch to close and open.

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