Insulation resistance detection circuit and battery

Abstract

The utility model discloses an insulation resistance detection circuit and a battery. The insulation resistance detection circuit comprises a balanced bridge circuit, an adjusting circuit, a sampling resistor and an insulation resistor, and the balanced bridge circuit comprises a plurality of resistors arranged between a positive bus and a negative bus; the adjusting circuit comprises a plurality of resistors and a plurality of switches, is arranged between the positive bus and the negative bus, and is arranged to form an unbalanced bridge circuit with the balanced bridge circuit by controlling the on-off states of the plurality of switches; one end of the sampling resistor is connected with the negative bus, and the other end is connected with the balanced bridge circuit and the adjusting circuit; and the insulation resistor is arranged between the positive and negative buses and the ground. The problems that in the prior art, insulation detection conducted through an alternating current method is not suitable for being applied to the energy storage industry, and insulation detection conducted through a direct current method cannot be accurately measured, and errors are too large are solved.

Description

Technical Field

[0001] The present application relates to the technical field of insulation resistance detection, and more specifically, to an insulation resistance detection circuit and a battery. Background Art

[0002] In an environment where fossil fuels are becoming increasingly scarce, wind power, photovoltaic power, and tidal power generation have advantages that traditional thermal power generation cannot match in terms of optimizing the power grid structure, energy conservation and emission reduction, curbing the greenhouse effect, and ensuring national energy security. Therefore, they have received extensive attention from all aspects. With the increasing development of wind power, photovoltaic power, and tidal power generation, the impact on the power grid during grid connection and the potential hazards brought about by power grid structure adjustment have also become prominent. To solve the defects and expand the advantages, the battery energy storage industry has developed accordingly. Lithium battery energy storage can reduce the impact on the power grid during grid connection and can also cut peaks and fill valleys to optimize the power grid structure. With the huge development of the lithium battery industry, the application of lithium battery energy storage at the grid matching end between wind power, photovoltaic power, tidal power generation, and the traditional power grid is increasing, and the stored energy is also increasing. As the energy stored in the lithium battery pack increases, its voltage level also increases. In this case, if the insulation performance deteriorates, it will cause immeasurable property losses and personal injuries. To avoid such problems, the ground insulation detection of high-voltage energy storage lithium battery packs is of utmost importance and cannot be ignored.

[0003] The existing insulation detection methods are mainly divided into the AC method and the DC method. The AC method is based on the method of injecting an AC signal, while the DC method is based on the principle of the bridge balance method for detection. First, the AC injection method is not suitable for use in the energy storage industry. Injecting an AC signal into the DC bus will have a certain impact on the battery itself. It will be absorbed by the capacitive load in the energy storage system, resulting in a decrease in measurement accuracy, and it will also bring unnecessary ripple interference to the power consumption equipment end. Secondly, the bridge balance method scheme has a simple hierarchical structure. As shown in [Figure], two resistors R1 and R2 with known resistance values are respectively connected in series between the positive-to-ground and negative-to-ground of the DC system bus. The voltage V1 divided at both ends of the resistor R1 is measured. By combining the known bus voltage VDC and the resistance values of the known resistors R1 and R2, it can be calculated, which is convenient for software detection. However, when there is a short circuit to the ground at the same time for both positive and negative, and when the resistances to the ground of the positive and negative decrease equally, the bridge balance method cannot accurately measure, and there will be a risk of excessive error. Figure 1 As shown in [Figure], two resistors R1 and R2 with known resistance values are respectively connected in series between the positive-to-ground and negative-to-ground of the DC system bus. The voltage V1 divided at both ends of the resistor R1 is measured. By combining the known bus voltage VDC and the resistance values of the known resistors R1 and R2, it can be calculated, which is convenient for software detection. However, when there is a short circuit to the ground at the same time for both positive and negative, and when the resistances to the ground of the positive and negative decrease equally, the bridge balance method cannot accurately measure, and there will be a risk of excessive error. Summary of the Utility Model

[0004] The main purpose of the present application is to provide an insulation resistance detection circuit and a battery to solve the problems in the prior art that the AC method for insulation detection is not suitable for application in the energy storage industry, and the DC method for insulation detection cannot accurately measure and there will be excessive errors.

[0005] According to one aspect of the present application, an insulation resistance detection circuit is provided, including: a balanced bridge circuit, an adjustment circuit, a sampling resistor, and an insulation resistance. Among them, the balanced bridge circuit includes multiple resistors, which are arranged between the positive and negative busbars; the adjustment circuit includes multiple resistors and multiple switches, which are arranged between the positive and negative busbars and are configured to form an unbalanced bridge circuit with the balanced bridge circuit by controlling the switch states of the multiple switches; one end of the sampling resistor is connected to the negative busbar, and the other end is connected to the balanced bridge circuit and the adjustment circuit; the insulation resistance is arranged between the positive and negative busbars and the ground.

[0006] Optionally, the adjustment circuit includes: a first resistor, a second resistor, a first switch, and a second switch. Among them, one end of the first resistor is connected to the positive busbar, and the other end is connected to the first switch; the end of the first switch far from the first resistor is connected to the second switch; the end of the second switch far from the first switch is connected to the second resistor; the end of the second resistor far from the second switch is connected to the sampling resistor.

[0007] Optionally, the balanced bridge circuit includes: a third resistor and a fourth resistor. Among them, one end of the third resistor is connected to the positive busbar, and the other end is respectively connected to the first switch, the second switch, and the fourth resistor; the end of the fourth resistor far from the third resistor is respectively connected to the second resistor and the sampling resistor.

[0008] Optionally, the balanced bridge circuit further includes: a third switch. Among them, one end of the third switch is respectively connected to the first switch, the second switch, the third resistor, and the fourth resistor, and the other end is grounded.

[0009] Optionally, the insulation resistance includes: a first insulation resistance and a second insulation resistance. Among them, one end of the first insulation resistance is connected to the positive busbar, and the other end is respectively connected to the third switch and the second insulation resistance, and this end is grounded; the end of the second insulation resistance far from the first insulation resistance is connected to the negative busbar.

[0010] Optionally, the end of the sampling resistor far from the second resistor and the fourth resistor is connected to the negative busbar.

[0011] According to another aspect of the present application, the present application also provides a battery, including the insulation resistance detection circuit in any of the above embodiments.

[0012] In the present application, an insulation detection circuit based on "balanced bridge - unbalanced bridge" is proposed, which has the advantages of a small sampling voltage range and high precision compared with the existing insulation detection circuits; this solution only uses one voltage sampling circuit, avoiding the error between multiple voltage sampling circuits from affecting the calculation accuracy; and the solution can detect the DC bus voltage at the same time, saving the device cost of the dedicated bus voltage detection circuit, and can also be used as a detection means when the insulation detection circuit fails abnormally in complement with other bus voltage detection circuits. Description of the Drawings

[0013] The accompanying drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0014] Figure 1 is the schematic diagram of insulation detection based on the balanced bridge method;

[0015] Figure 2 is the system block diagram of an insulation resistance detection circuit according to an embodiment of the present application;

[0016] Figure 3 is the schematic diagram of an insulation resistance detection circuit according to an embodiment of the present application;

[0017] Figure 4 is for measuring Figure 3 the working schematic diagram of the voltage Vn across the sampling resistor R5 in;

[0018] Figure 5 is for measuring Figure 3 the working schematic diagram of the voltage Vm across the sampling resistor R5 in;

[0019] Figure 6 is for measuring Figure 3 the working schematic diagram of the voltage Vx across the sampling resistor R5 in;

[0020] Figure 7 is for measuring Figure 3 the working schematic diagram of the voltage Vy across the sampling resistor R5 in. Detailed implementation manners

[0021] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0022] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary implementation manners according to the present application. As used herein, unless otherwise clearly specified in the context, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0024] Figure 2 is a system block diagram of an insulation resistance detection circuit according to an embodiment of the present application, as Figure 2 shown, the insulation resistance detection circuit includes: a balanced bridge circuit 20, an adjustment circuit 22, a sampling resistor 24, and an insulation resistor 26, where

[0025] the balanced bridge circuit 20 includes a plurality of resistors disposed between the positive and negative buses;

[0026] the adjustment circuit 22 includes a plurality of resistors and a plurality of switches, disposed between the positive and negative buses, and is configured to form an unbalanced bridge circuit with the balanced bridge circuit 20 by controlling the switch states of the plurality of switches;

[0027] one end of the sampling resistor 24 is connected to the negative bus, and the other end is connected to the balanced bridge circuit 20 and the adjustment circuit 22;

[0028] the insulation resistor 26 is disposed between the positive and negative buses and the ground.

[0029] Figure 3 is a schematic diagram of an insulation resistance detection circuit according to an embodiment of the present application, as Figure 3 shown, a balanced bridge (i.e., the above-mentioned balanced bridge circuit 20) is formed by adding resistors R3 and R4 between the positive and negative buses.

[0030] By respectively controlling the high-voltage switches K1 and K2 to be closed and conducting, and respectively inserting R1 and R2 (i.e., the above-mentioned adjustment circuit 22), an unbalanced bridge is formed to respectively measure the resistance values of the insulation resistors Rx and Ry.

[0031] Figure 3 R5 in [[ ]] is the sampling resistor 24 mentioned above.

[0032] According to an alternative embodiment of the present application, the adjustment circuit 22 includes: a first resistor, a second resistor, a first switch, and a second switch. One end of the first resistor is connected to the positive busbar, and the other end is connected to the first switch. The end of the first switch remote from the first resistor is connected to the second switch. The end of the second switch remote from the first switch is connected to the second resistor. The end of the second resistor remote from the second switch is connected to the sampling resistor.

[0033] As shown in Figure 3 , the first resistor, the second resistor, the first switch, and the second switch included in the adjustment circuit 22 are respectively Figure 3 R1, R2, K1, and K2 in Figure 3 . It can be seen from

[0034] that one end of R1 is connected to the positive busbar, and the other end is connected to K1. The end of K1 remote from R1 is connected to K2, the other end of K2 is connected to R2, and the other end of R2 is connected to the sampling resistor R5. K1 and K2 are used to insert the resistors to break the balanced bridge. According to an alternative embodiment of the present application, the balanced bridge circuit 20 includes: a third resistor and a fourth resistor. One end of the third resistor is connected to the positive busbar, and the other end is respectively connected to the first switch, the second switch, and the fourth resistor. The end of the fourth resistor remote from the third resistor is respectively connected to the second resistor and the sampling resistor.

[0035] As shown in Figure 3 , the third resistor and the fourth resistor included in the balanced bridge circuit 20 are respectively Figure 3 R3 and R4 in Figure 3 . It can be seen from

[0036] that one end of R3 is connected to the positive busbar, and the other end is respectively connected to K1, K2, and R4. The end of R4 remote from R3 is respectively connected to R2 and R5. As an alternative embodiment of the present application, the balanced bridge circuit 20 further includes: a third switch. One end of the third switch is respectively connected to the first switch, the second switch, the third resistor, and the fourth resistor, and the other end is grounded.

[0037] As shown in Figure 3 , the above-mentioned third switch is Figure 3 K3 in . One end of K3 is respectively connected to K1, K2, R3, and R3, and the other end is grounded. K3 is used to introduce the ground to form the balanced bridge.

[0038] In some alternative embodiments of the present application, the insulation resistance 26 includes: a first insulation resistance and a second insulation resistance. One end of the first insulation resistance is connected to the positive busbar, and the other end is respectively connected to the third switch and the second insulation resistance, and this end is grounded. The end of the second insulation resistance remote from the first insulation resistance is connected to the negative busbar.

[0039] As shown Figure 3 in the figure, the first insulation resistance and the second insulation resistance included in the insulation resistance 26 are Rx and Ry in Figure 3 respectively. It can be seen from Figure 3 that one end of Rx is connected to the positive busbar, and the other end is connected to K3, Ry, and PE respectively. One end of Ry far from Rx is connected to the negative busbar.

[0040] In some other alternative embodiments of the present application, one end of the sampling resistance 24 far from the second resistance and the fourth resistance is connected to the negative busbar.

[0041] As mentioned above, one end of the sampling resistance R5 is connected to R2 and R4, and the other end is connected to the negative busbar.

[0042] The above-mentioned insulation resistance detection circuit proposed by the present application can ensure the accuracy of the insulation resistance value measurement between the DC positive and negative busbars and the ground, and at the same time can measure the bus voltage between the DC positive and negative busbars. Thus, under multiple protections, the normal operation of the high-voltage energy storage lithium battery pack is ensured. In particular, it can avoid property losses and personal injuries caused by too low insulation performance of the high-voltage lithium battery pack. Because the detection method has the advantages of a wide detection voltage range and high precision, it can also be applied to DC high-voltage application scenarios such as photovoltaic inverters and new energy vehicles.

[0043] Based on the above insulation resistance detection circuit, the embodiments of the present application also provide an insulation resistance detection method, and the principle logic is as follows:

[0044] 1. System total voltage measurement

[0045] As shown Figure 4 in the figure, when the high-voltage switches K1, K2, and K3 are disconnected, the voltage Vn across the sampling resistance R5 can be measured, and then the system total voltage Vdc can be calculated using Vn. The calculation formula is as follows:

[0046]

[0047] 2. As shown Figure 5 in the figure, when the high-voltage switches K1 and K2 are disconnected and the high-voltage switch K3 is closed, the system sampling voltage Vm is measured.

[0048] 3. As shown Figure 6 in the figure, when the high-voltage switch K2 is disconnected and the high-voltage switches K1 and K3 are closed, the system sampling voltage Vx is measured.

[0049] 4. As shown Figure 7 in the figure, when the high-voltage switch K1 is disconnected and the high-voltage switches K2 and K3 are closed, the system sampling voltage Vy is measured.

[0050] 5. After comparing Vm and Vn, introduce the calculation formula according to the following conditions to calculate the resistance values of Rx and Ry respectively.

[0051] 1) When Vm < Vn, the calculation formulas for the insulation resistances Rx and Ry are as follows:

[0052]

[0053] 2) When Vm > Vn, the calculation formulas for the insulation resistances Rx and Ry are as follows:

[0054]

[0055] In the embodiments of the present application, the resistance values of the resistors R1, R2, R3, R4, and the sampling resistor R5 on the "balanced bridge - unbalanced bridge" can be adjusted according to the sampling range of the sampling circuit. The resistance values of the resistors R1, R2, R3, R4, and R5 can also be adjusted according to the accuracy and range of the sampling circuit and the sampling chip, so as to match the sampling circuit.

[0056] The insulation resistance detection circuit proposed in the present application will be described below with reference to specific embodiments.

[0057] In the battery management system (BMS) of a lithium battery, this insulation detection scheme is adopted, which improves the accuracy and accuracy of the insulation performance detection of the high - voltage lithium battery system, makes a correct judgment on the problem of the decline in insulation detection performance caused by insulation aging, and makes relevant warning and warning treatments, avoiding a series of safety accidents. At the same time, it saves the DC bus voltage sampling circuit on the BMS system, reduces the relevant material costs, and also has the advantages of clearer logic in the software process, facilitating adjustment and modification.

[0058] In an alternative embodiment, Rx = 35000 (KΩ), Ry = 600 (KΩ), which are the insulation resistances artificially introduced for testing, and VDC = 800 (V) is the total voltage of the battery system to be measured.

[0059] Device parameters: R1 = R2 = R3 = R4 = 3000 (KΩ)

[0060] R5 = 10 (KΩ)

[0061] The specific calculation steps are as follows:

[0062] 1. When the high - voltage switches K1, K2, and K3 are disconnected, read the voltage across the sampling resistor R5, denoted as Vn = 1.3311V, and substitute it into the formula to calculate the total system voltage Vdc

[0063] V dc = 601 * Vn = 799.9911 (V)

[0064] Due to sampling precision

[0065] V dc = 799.9911 ≈ V DC = 800 (V)

[0066] The calculated total system pressure is basically consistent with the actual total system pressure, and the error precision < ±0.5% meets the usage requirements.

[0067] 2. Disconnect the high-voltage switches K1 and K2, and when closing the high-voltage switch K3, read the voltage across the sampling resistor R5, denoted as Vm = 0.4074V.

[0068] 3. Judge the magnitudes of Vn and Vm. If Vn > Vm, then proceed to step 4; if Vn < Vm, then proceed to step 5.

[0069] In this embodiment, V n = 1.3311 > V m = 0.4074. Therefore, execute step 4.

[0070] 4. If Vn > Vm, then disconnect the high-voltage switch K2, close the high-voltage switches K1 and K3, read the voltage across the sampling resistor R5, denoted as Vx, and substitute it into the formula to calculate the positive-to-ground insulation resistance Rx and the negative-to-ground insulation resistance Ry:

[0071]

[0072] The solution is: Rx = 35160 (KΩ), Ry = 600.197 (KΩ). Due to sampling precision issues, there is an error between the calculated insulation resistance and the actual insulation resistance. After comparison and verification, it is confirmed that the error precision < ±0.5% meets the usage requirements.

[0073] 5. If Vn < Vm, then disconnect the high-voltage switch K1 and close the high-voltage switches K2 and K3, read the voltage across the sampling resistor R5, denoted as Vy, and substitute it into the formula to calculate the positive-to-ground insulation resistance Rx and the negative-to-ground insulation resistance Ry (this step has been omitted due to the judgment in step 3)

[0074]

[0075] 6. Compare the calculated positive-to-ground insulation resistance Rx and negative-to-ground insulation resistance Ry with the system preset values to judge whether insulation abnormalities occur. If insulation abnormalities occur, take corresponding alarm action measures.

[0076] The embodiment of the present application also provides a battery, which includes the above-mentioned insulation resistance detection circuit. Therefore, this battery has all the technical effects of the above-mentioned insulation resistance detection circuit. Since the technical effects of the insulation resistance detection circuit have been described in detail above, they will not be elaborated here.

[0077] For the sake of convenience in description, spatial relative terms, such as "above", "on top of", "on the upper surface", "upper", etc., can be used here to describe the spatial position relationship of one device or feature shown in the figure with other devices or features. It should be understood that the spatial relative terms are intended to cover different orientations in use or operation in addition to the orientation described in the figure for the device. For example, if the device in the figure is inverted, the device described as "above" or "on top of" other devices or structures will then be positioned "below" or "beneath" other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations should be made for the spatial relative descriptions used here.

[0078] In addition, it should be noted that using words such as "first" and "second" to limit components is only for the convenience of differentiating the corresponding components. Without additional statements, the above words have no special meanings, so they should not be construed as limiting the protection scope of the present application.

[0079] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. An insulation resistance detection circuit, characterized in that: include: Balanced bridge circuit, adjustment circuit, sampling resistor and insulation resistor, among which, The balanced bridge circuit includes a plurality of resistors arranged between the positive and negative bus bars; The adjustment circuit comprises a plurality of resistors and a plurality of switches, which are arranged between the positive and negative bus bars, and are arranged to form an unbalanced bridge circuit with the balanced bridge circuit by controlling the switch states of the plurality of switches; One end of the sampling resistor is connected to the negative bus, and the other end is connected to the balanced bridge circuit and the adjustment circuit; The insulation resistor is arranged between the positive and negative busbars and the ground.

2. The insulation resistance detection circuit according to claim 1, characterized in that: The adjustment circuit includes: a first resistor, a second resistor, a first switch and a second switch, wherein: One end of the first resistor is connected to the positive bus, and the other end is connected to the first switch; One end of the first switch away from the first resistor is connected to the second switch; One end of the second switch away from the first switch is connected to a second resistor; One end of the second resistor away from the second switch is connected to the sampling resistor.

3. The insulation resistance detection circuit according to claim 2, characterized in that: The balanced bridge circuit includes: a third resistor and a fourth resistor, wherein: One end of the third resistor is connected to the positive bus, and the other end is connected to the first switch, the second switch, and the fourth resistor respectively; One end of the fourth resistor away from the third resistor is connected to the second resistor and the sampling resistor respectively.

4. The insulation resistance detection circuit according to claim 3, characterized in that: The balanced bridge circuit further includes: a third switch, wherein: One end of the third switch is respectively connected to the first switch, the second switch, the third resistor and the fourth resistor, and the other end is grounded.

5. The insulation resistance detection circuit according to claim 4, characterized in that: The insulation resistance includes: a first insulation resistance and a second insulation resistance, wherein: One end of the first insulation resistor is connected to the positive bus, and the other end is connected to the third switch and the second insulation resistor respectively, and the end is grounded; One end of the second insulation resistor away from the first insulation resistor is connected to the negative bus.

6. The insulation resistance detection circuit according to claim 3, characterized in that: One end of the sampling resistor away from the second resistor and the fourth resistor is connected to the negative bus.

7. A battery, characterized in that: An insulation resistance detection circuit comprising the insulation resistance detection circuit according to any one of claims 1 to 6.

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