Active inverter battery insulation monitoring circuit and patrol control method

Abstract

The application provides an active converter battery insulation monitoring circuit, the active converter comprises at least one converter chain; the converter chain comprises at least two sub-modules connected in series; the sub-module comprises a power unit, and the direct current side of the power unit is connected with an energy storage unit through a series contactor; the energy storage unit comprises N battery packs connected in series, N is an integer greater than or equal to 1, and the battery pack comprises an outer shell; the battery pack outer shell and an equipotential connection point are connected through a first resistance connection to form the insulation monitoring circuit. The application realizes the monitoring of the insulation conditions of a plurality of battery packs connected in series by configuring the insulation monitoring circuit, and adapts to the series application of standard battery packs under higher-level modules.

Description

Technical Field

[0001] This application relates to the field of power electronic converter technology, specifically to an active converter battery insulation monitoring circuit and inspection control method. Background Technology

[0002] In the field of high-capacity, high-power power electronic converter technology, multilevel converters utilize modular cascading technology to integrate energy storage units into sub-modules. This offers advantages such as high modularity, good harmonic characteristics, and low equivalent switching frequency, and has become the standard topology in the high-voltage power electronics field. By integrating energy storage units as sub-modules into modular multilevel converters, AC / DC power conversion and energy storage can be achieved simultaneously.

[0003] The resulting active converter is a feasible solution that can effectively meet the access requirements of energy storage systems and mitigate or isolate fault propagation between AC and DC systems. Based on multi-level technology, the active converter uses a module cascade approach to achieve high-voltage output. Compared to low-voltage energy storage converters, it places higher demands on the insulation withstand capability of the batteries. Typically, the DC voltage of the sub-modules is designed to be around 1kV or even higher, requiring multiple battery packs to be connected in series. Once an insulation failure occurs in one battery pack, the fault can easily propagate, threatening system safety. On the one hand, reasonable electrical and structural design is needed to ensure that the battery packs operate under low-potential conditions as much as possible; on the other hand, monitoring the battery insulation is necessary. Due to the large number of battery packs and the complex distribution of battery-containing sub-modules, existing technologies lack effective means to monitor the battery pack insulation. Summary of the Invention

[0004] To address the aforementioned issues, this application provides an active converter battery insulation monitoring circuit to monitor the insulation status of multiple interconnected battery packs.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0006] As a first aspect of this application, an active converter battery insulation monitoring circuit is proposed. The active converter includes at least one converter chain; the converter chain includes at least two sub-modules connected in series; each sub-module includes a power unit, the DC side of which is connected to an energy storage unit via a series contactor; the energy storage unit includes N battery packs connected in series, where N is an integer greater than or equal to 1, and each battery pack includes a casing; the battery pack casing and an equipotential bonding point are connected via a first resistor to form the insulation monitoring circuit, and the equipotential bonding point is selected in three ways:

[0007] Method 1: Select the positive or negative terminal of the battery pack as the equipotential bonding point;

[0008] Method 2: Select the positive or negative terminal on the DC side as the equipotential bonding point;

[0009] Method 3: Connect at least two second resistors connected in series in parallel on the DC side of the power unit, and take the connection point between the second resistors as the equipotential connection point.

[0010] According to some embodiments, the resistance value of the first resistor is 0 to 100 megohms.

[0011] According to some embodiments, the connection method between the battery pack casing and the equipotential bonding point further includes group connection: the battery pack casings are grouped, and the battery pack casings in the same group are first connected to the convergence point through a first resistor, and the convergence point is then directly or through a resistor connected to the equipotential bonding point.

[0012] According to some embodiments, the insulation monitoring circuit is further configured with a current detection unit, which is configured to detect the current flowing through the first resistor at the first resistor or to detect the current flowing through the second resistor at the second resistor.

[0013] According to some embodiments, the potential difference between the battery port and the equipotential bonding point is less than the insulation voltage that the battery pack casing can withstand.

[0014] According to some embodiments, in the group connection method, the first resistance value of different groups decreases in order from the positive terminal to the negative terminal of the power unit.

[0015] In a second aspect, this application proposes a patrol control method based on the insulation monitoring circuit described above, the control method comprising,

[0016] When the current flowing through the first resistor or the second resistor exceeds the current threshold, it is determined that there is an insulation fault in the battery pack.

[0017] Fault location can be determined by the magnitude of the current, or by a combination of the magnitude and direction of the current, thus identifying the battery pack with the insulation fault.

[0018] According to some embodiments, in the control method, the current threshold used to determine the occurrence of an insulation fault is related to the location of the current detection unit.

[0019] According to some embodiments, the system also includes executing fault handling logic, including: determining whether there is a situation where there is a multi-point insulation fault in the same battery pack; if so, disconnecting the contactor of the battery pack, bypassing the power unit, and stopping the machine for inspection; otherwise, disconnecting the contactor of the submodule where the battery pack is located and cutting off the discharge path.

[0020] According to some embodiments, the method for determining whether there is a multi-point insulation fault in the same battery pack is as follows: when the detected current exceeds the current threshold and the voltage of some battery cells drops below the voltage threshold, it is determined that a multi-point insulation fault has occurred in the same battery pack.

[0021] Compared with the prior art, the beneficial effects of this application are as follows: by configuring an insulation monitoring circuit, the insulation status of multiple battery packs connected in series is monitored; by using a reasonable grouping and equipotential connection method, a stable potential is provided to the battery pack during normal operation; and by judging overcurrent, the insulation problem of the battery is detected, which greatly improves the system reliability and adapts to the series application of standard battery packs in higher-level modules. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a structural diagram of an active converter according to an embodiment of this application;

[0024] Figure 2 This is a schematic diagram of an active converter battery insulation monitoring circuit according to an embodiment of this application;

[0025] Figure 3 This is a schematic diagram of a second type of active converter battery insulation monitoring circuit according to an embodiment of this application;

[0026] Figure 4 This is a schematic diagram of a third type of active converter battery insulation monitoring circuit according to an embodiment of this application;

[0027] Figure 5 This is a schematic diagram showing the connection between the battery pack outer casing group and the equipotential bonding point in an embodiment of this application;

[0028] Figure 6 This is a schematic diagram of the current detection unit configured at the first resistor according to an embodiment of this application;

[0029] Figure 7 This is a schematic diagram showing the current detection unit configured at the second resistor in an embodiment of this application.

[0030] Figure 8 This is a flowchart of an inspection control method for an active converter battery insulation monitoring circuit according to an embodiment of this application.

[0031] Figure 9 This is a schematic diagram of a battery insulation fault according to an embodiment of this application;

[0032] Figure 10 This is an equivalent circuit diagram of a battery insulation fault according to an embodiment of this application;

[0033] Figure 11 This is a flowchart of another inspection and control method for an active converter battery insulation monitoring circuit according to an embodiment of this application. Detailed Implementation

[0034] 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, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0035] It should be understood that the terms "first," "second," etc., in the claims, specification, and drawings of this application are used to distinguish different objects, rather than to describe a specific order. The terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0036] like Figure 1 The diagram shown is a structural diagram of an active converter according to an embodiment of this application. The active converter includes at least one converter chain; the converter chain includes at least two sub-modules 1 connected in series; the sub-module includes a power unit 2 and a DC capacitor 3, and the DC side of the power unit 2 is connected to an energy storage unit through a series contactor 4; the energy storage unit includes N battery packs 5 connected in series, where N is an integer greater than or equal to 1, and the battery pack includes a casing 6.

[0037] like Figures 2-4 The diagram shown is a schematic of an active converter battery insulation monitoring circuit provided in an embodiment of this application. The battery pack casing and the equipotential bonding point are connected via a first resistor 7 to form the insulation monitoring circuit. The selection of the equipotential bonding point includes the following three methods:

[0038] Method 1: Select either the positive or negative terminal of the battery pack as the equipotential bonding point 8; for example... Figure 2 The diagram shows a selection of the negative terminal of the battery pack as the equipotential bonding point.

[0039] Method 2: Select either the positive or negative terminal on the DC side as the equipotential bonding point; for example... Figure 3 The diagram shows a selection of the negative terminal on the DC side as the equipotential bonding point.

[0040] Method 3: Connect at least two interconnected second resistors 9 in parallel on the DC side of the power unit, and take the connection point between the second resistors as the equipotential connection point. For example... Figure 4 As shown.

[0041] In some embodiments, the first resistor has a resistance value of 0 to 100 megohms.

[0042] In a preferred embodiment, the connection between the battery pack casing and the equipotential bonding point further includes group connection: the battery pack casings are grouped, and the battery pack casings in the same group are first connected to the convergence point 10 through a first resistor, and the convergence point is then directly or via a resistor connected to the equipotential bonding point. Figure 5 The battery pack casings in the same group are first connected to the junction point 10 via the first resistor, and then the junction point is directly connected to the equipotential bonding point.

[0043] In some embodiments, the insulation monitoring circuit is further configured with a current detection unit 11, the current detection unit being as follows: Figure 6 The configuration shown detects the current flowing through the first resistor at the first resistor, or as... Figure 7 The configuration shown detects the current flowing through the second resistor at the second resistor.

[0044] In some embodiments, the potential difference between the battery port and the equipotential bonding point is less than the insulation withstand voltage of the battery pack casing. The number of battery pack casings is N; the number of second resistors is M; the number of equipotential points is M-1; Ubat is the battery pack voltage; and Ur is the insulation withstand voltage of the battery pack casing.

[0045] Voltage at equipotential point:

[0046] Where i is the equipotential point number, numbered 1, 2, ..., M-1 sequentially from the negative to the positive terminal of the power unit. The voltages at each equipotential point are as follows: NU bat / M、2NU bat / M、3NU bat / M、…、(M-1)NU bat / M.

[0047] Battery port voltage: Positive port: U j+ =(j-1)·U bat Negative port U j- =j·U bat , where j is the battery pack serial number, which is 1, 2, ..., N in sequence from the negative terminal to the positive terminal of the power unit.

[0048] Potential difference between battery port and equipotential bonding point: Positive port U r+ =U j+ -U ci Negative port Ur- =U j- -U ci

[0049] U should be satisfied r+ ≤U r and U r- ≤U r .

[0050] In some embodiments, the first resistance values ​​of different groups under the group connection method are in descending order from the positive to the negative terminal of the power unit.

[0051] like Figure 8 As shown in the embodiments of this application, an inspection control method for the insulation monitoring circuit is also disclosed, including the following steps:

[0052] S100. When the current flowing through the first resistor or the second resistor exceeds the current threshold, it is determined that there is an insulation fault in the battery pack.

[0053] S200. Fault location is determined based on the magnitude of the current, or by combining the magnitude and direction of the current, to identify the battery pack with the insulation fault.

[0054] like Figure 9 As shown, when a battery insulation failure occurs, its equivalent circuit is as follows: Figure 6 As shown. From Figure 10 As can be seen, when an insulation fault occurs in a battery pack, a fault current flow loop is formed. A current detection unit placed at either the first or second resistor can detect the fault current. When the detected current flowing through the first or second resistor exceeds the current threshold, it is determined that an insulation fault has occurred in the battery pack.

[0055] The current flowing through the first resistor is I1-I2. The location of the fault can be determined based on the magnitude of the current flowing through the first resistor.

[0056] The location of the fault can also be determined by the current flowing through the second resistor and its direction. The basic principle is that the current must flow from the power source to the fault point, and the location of the fault can be deduced based on this principle.

[0057] In some embodiments, the current threshold used to determine the occurrence of an insulation fault is related to the location of the current sensing unit. The closer the current sensing unit is to the power source, the higher the current threshold.

[0058] In some embodiments, such as Figure 11As shown, after determining that a battery pack has an insulation fault, the control method further includes step S300: executing fault handling logic. When executing the fault handling logic, it is necessary to determine whether there are multiple insulation faults in the same battery pack. If so, the contactor of the battery pack in question is disconnected, the power unit is bypassed, and the system is stopped for inspection; otherwise, the contactor of the submodule containing the battery pack is disconnected, cutting off the discharge path.

[0059] In some embodiments, the method for determining whether there is a multi-point insulation fault in the same battery pack is: when the detected current exceeds the current threshold and the voltage of some battery cells drops below the voltage threshold, it is determined that a multi-point insulation fault has occurred in the same battery pack.

[0060] This application combines an insulation monitoring circuit with a patrol control method, enabling real-time diagnosis of insulation faults. Once a problem occurs, the faulty module unit is promptly isolated via contactor disconnection and bypass switch bypass, preventing the fault from escalating. The insulation fault location method in this application facilitates rapid fault elimination during system maintenance, improving system availability.

[0061] It should be clearly understood that this application describes how specific examples are formed and used, but this application is not limited to any details of these examples. Rather, based on the teachings of the disclosure of this application, these principles can be applied to many other embodiments.

[0062] Furthermore, it should be noted that the above figures are merely illustrative representations of the processes included in the method according to exemplary embodiments of this application, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0063] Exemplary embodiments of this application have been specifically shown and described above. It should be understood that this application is not limited to the detailed structures, arrangements, or implementation methods described herein; rather, this application is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

[0064] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. Furthermore, any changes or modifications made by those skilled in the art based on the ideas of this application, and on the specific implementation methods and application scope of this application, are all within the scope of protection of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An active converter battery insulation monitoring circuit, wherein the active converter includes at least one converter chain; the converter chain includes at least two sub-modules connected in series; the sub-module includes a power unit, the DC side of which is connected to an energy storage unit via a series contactor; the energy storage unit includes N battery packs connected in series, where N is an integer greater than or equal to 1, and the battery packs include a casing; characterized in that The battery pack casing and the equipotential bonding point are connected by a first resistor to form the insulation monitoring circuit. The selection of the equipotential bonding point includes the following three methods: Method 1: Select the positive or negative terminal of the battery pack as the equipotential bonding point; Method 2: Select the positive or negative terminal on the DC side as the equipotential bonding point; Method 3: Connect at least two second resistors connected in series in parallel on the DC side of the power unit, and take the connection point between the second resistors as the equipotential connection point; The insulation monitoring circuit is also equipped with a current detection unit, which is configured at the first resistor to detect the current flowing through the first resistor or configured at the second resistor to detect the current flowing through the second resistor. When the current flowing through the first resistor or the second resistor exceeds the current threshold, it is determined that there is an insulation fault in the battery pack.

2. The insulation monitoring circuit of claim 1, characterized by The resistance of the first resistor is 0 to 100 megohms.

3. The insulation monitoring circuit of claim 1, characterized by The connection method between the battery pack casing and the equipotential bonding point also includes group connection: the battery pack casings are grouped, and the battery pack casings in the same group are first connected to the convergence point through a first resistor, and the convergence point is then directly or through a resistor connected to the equipotential bonding point.

4. The insulation monitoring circuit of claim 1, characterized by The potential difference between the battery port and the equipotential bonding point is less than the insulation voltage that the battery pack casing can withstand.

5. The insulation monitoring circuit of claim 3, wherein In the group connection method, the first resistance value of different groups decreases in order from the positive terminal to the negative terminal of the power unit.

6. An inspection control method based on the insulation monitoring circuit according to any one of claims 1 to 5, characterized by The control method includes, Fault location can be determined by the magnitude of the current, or by a combination of the magnitude and direction of the current, thus identifying the battery pack with the insulation fault.

7. The method of claim 6, wherein the method further comprises: determining whether the insulation monitoring circuit is in a normal state or an abnormal state; and determining whether the insulation monitoring circuit is in the normal state or the abnormal state based on the comparison result. In the control method described above The current threshold used to determine the occurrence of an insulation fault is related to the location of the current detection unit.

8. The method of claim 6, wherein the monitoring of the insulation is performed by a periodic inspection control method, and the periodic inspection control method is a method of periodically inspecting the insulation by using a predetermined inspection period. It also includes executing fault handling logic, including: determining whether there is a situation of multiple insulation faults in the same battery pack. If so, disconnecting the contactor of the battery pack, bypassing the power unit, and stopping the machine for inspection; otherwise, disconnecting the contactor of the submodule where the battery pack is located and cutting off the discharge path.

9. The method of claim 8, wherein the method further comprises: determining whether the insulation monitoring circuit is in a normal state or an abnormal state; and determining whether the insulation monitoring circuit is in the normal state or the abnormal state based on the comparison result. The method for determining whether there is a multi-point insulation fault in the same battery pack is as follows: when the detected current exceeds the current threshold and the voltage of some battery cells drops below the voltage threshold, it is determined that a multi-point insulation fault has occurred in the same battery pack.

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