Insulation resistance detection device and method of power battery system and electric vehicle

Abstract

The invention relates to the field of electronic circuits, in particular to an insulation resistance detection device and method for a power battery system and an electric automobile, and the device comprises a first insulation resistance detection circuit which is connected with a first battery pack in parallel and is used for detecting the first insulation resistance of a positive electrode of a second battery pack to a common ground, and a second insulation resistance of the negative electrode of the first battery pack to the common ground; the second insulation resistance detection circuit is connected in parallel with the second battery pack and is used for detecting third insulation resistance of the positive electrode of the second battery pack to the common ground and fourth insulation resistance of the negative electrode of the first battery pack to the common ground; the first insulation impedance detection circuit or the second insulation impedance detection circuit determines whether the detection of the first insulation impedance and the second insulation impedance is accurate based on the comparison of the third insulation impedance and the first insulation impedance and the comparison of the fourth insulation impedance and the second insulation impedance. The accuracy of insulation resistance detection of the power battery system is improved.

Description

Technical Field

[0001] The present application relates to the field of electronic circuits, and in particular to an insulation impedance detection device and method for a power battery system and an electric vehicle. Background Art

[0002] The power battery system is a crucial component of electric vehicles. As electric vehicles increase their range, different power battery systems are being used for the same model. To standardize the battery pack, the power battery system will be equipped with two 400V battery packs connected in series.

[0003] In the prior art, an insulation impedance detection device is generally used to detect the insulation impedance of a power battery system, but it is impossible to determine whether the insulation impedance detection is accurate. Summary of the Invention

[0004] Based on this, it is necessary to provide an insulation impedance detection device and method for a power battery system and an electric vehicle to address the above technical problems.

[0005] In a first aspect, the present invention provides an insulation impedance detection device for a power battery system, the power battery system comprising a first battery pack and a second battery pack connected in series, the device comprising:

[0006] a first insulation impedance detection circuit connected in parallel with the first battery pack, configured to detect a first insulation impedance between the positive electrode of the second battery pack and a common ground, and a second insulation impedance between the negative electrode of the first battery pack and the common ground;

[0007] a second insulation impedance detection circuit connected in parallel with the second battery pack, configured to detect a third insulation impedance between the positive electrode of the second battery pack and a common ground, and a fourth insulation impedance between the negative electrode of the first battery pack and the common ground;

[0008] The first insulation impedance detection circuit or the second insulation impedance detection circuit determines whether the detection of the first insulation impedance and the second insulation impedance is accurate based on a comparison between the third insulation impedance and the first insulation impedance, and a comparison between the fourth insulation impedance and the second insulation impedance.

[0009] In some embodiments, the first insulation impedance detection circuit includes a first main control chip and a first resistor network connected to the first main control chip, and the first resistor network is connected in parallel with the first battery pack;

[0010] The first main control chip controls the first resistance network to form at least two different resistance circuits, and constructs at least two different equations about the first insulation impedance and the second insulation impedance for the at least two different resistance circuits based on the current method, and obtains the first insulation impedance and the second insulation impedance based on solving the at least two equations.

[0011] In some embodiments, the first resistor network includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a switch S1, a switch S2, and a switch S3; the switch S1, the resistor R1, the resistor R2, and the resistor R3 are sequentially connected in series, the switch S3 is connected in series with the resistor R4, and is connected in parallel with the resistor R2 and the resistor R3; one end of the switch S2 is connected to the midpoint of the resistor R1 and the resistor R2, and the other end is connected to a common ground;

[0012] The first main control chip controls the states of the switches S1, S2, and S3 to form two different resistance circuits, and constructs two different equations about the first insulation impedance and the second insulation impedance for the two different resistance circuits based on the current method, and obtains the first insulation impedance and the second insulation impedance based on the solutions of the two equations.

[0013] In some embodiments, the first main control chip controls the switches S2 and S3 to be closed and the switch S1 to be open, collects a first sampled voltage at the positive electrode of the first battery pack, a second sampled voltage at the positive electrode of the second battery pack, and a third sampled voltage at the midpoint of the resistor R2 and the resistor R3, and constructs a first equation based on the first sampled voltage, the second sampled voltage, and the third sampled voltage, in which the current flowing through the first insulation impedance is equal to the sum of the current flowing through the second insulation impedance, the current flowing through the resistors R2 and R3, and the current flowing through the resistor R4;

[0014] The first main control chip controls the switch S1 and the switch S2 to be closed and the switch S3 to be open, collects a first sampled voltage of the positive electrode of the first battery pack, a second sampled voltage of the positive electrode of the second battery pack, and a third sampled voltage at the midpoint of the resistor R2 and the resistor R3, and constructs a second equation based on the first sampled voltage, the second sampled voltage, and the third sampled voltage, in which the sum of the current flowing through the first insulation impedance and the current flowing through the resistor R1 is equal to the sum of the current flowing through the second insulation impedance, the current flowing through the resistors R2 and R3, and the current flowing through the resistor R4;

[0015] Based on the first equation and the second equation, the first insulation resistance and the second insulation resistance are obtained by solving.

[0016] In some embodiments, the second insulation impedance detection circuit includes a second main control chip and a second resistor network connected to the second main control chip, and the second resistor network is connected in parallel with the second battery pack;

[0017] The second main control chip controls the second resistance network to form at least two different resistance circuits, and constructs at least two different equations about the third insulation impedance and the fourth insulation impedance for the at least two different resistance circuits based on the current method, and obtains the third insulation impedance and the fourth insulation impedance based on solving the at least two equations.

[0018] In some embodiments, the second resistor network includes a resistor R11, a resistor R22, a resistor R33, a resistor R44, a switch S11, a switch S22, and a switch S33; the switch S11, the resistor R11, the resistor R22, and the resistor R33 are connected in series in sequence, the switch S33 is connected in series with the resistor R44, and is connected in parallel with the resistor R22 and the resistor R33; one end of the switch S22 is connected to the midpoint of the resistor R11 and the resistor R22, and the other end is connected to a common ground;

[0019] The second main control chip controls the states of the switch S11, the switch S22, and the switch S33 to form two different resistance circuits, and based on the current method, constructs two different equations about the third insulation impedance and the fourth insulation impedance for the two different resistance circuits, and obtains the third insulation impedance and the fourth insulation impedance based on the solution of the two equations.

[0020] In some embodiments, the second main control chip controls the switch S22 and the switch S33 to be closed and the switch S11 to be open, collects a first sampled voltage at the positive electrode of the first battery pack, a second sampled voltage at the positive electrode of the second battery pack, and a fourth sampled voltage at the midpoint of the resistor R22 and the resistor R33, and constructs a third equation based on the first sampled voltage, the second sampled voltage, and the fourth sampled voltage, in which the current flowing through the third insulation impedance is equal to the sum of the current flowing through the fourth insulation impedance, the current flowing through the resistors R2 and R3, and the current flowing through the resistor R44;

[0021] The second main control chip controls the switch S11 and the switch S22 to be closed and the switch S33 to be open, collects a first sampled voltage of the positive electrode of the first battery pack, a second sampled voltage of the positive electrode of the second battery pack, and a fourth sampled voltage at the midpoint of the resistor R22 and the resistor R33, and constructs a fourth equation based on the first sampled voltage, the second sampled voltage, and the fourth sampled voltage, where the sum of the current flowing through the third insulation resistor and the current flowing through the resistor R11 is equal to the sum of the current flowing through the fourth insulation resistor, the current flowing through the resistors R22 and R33, and the current flowing through the resistor R44;

[0022] Based on the third equation and the fourth equation, the third insulation impedance and the fourth insulation impedance are obtained by solving.

[0023] In some embodiments, the first insulation impedance detection circuit or the second insulation impedance detection circuit calculates a first difference between the third insulation impedance and the first insulation impedance, and a second difference between the fourth insulation impedance and the second insulation impedance. If the first difference and the second difference are both less than a preset value, it is determined that the detection of the first insulation impedance and the second insulation impedance is accurate.

[0024] In a second aspect, an embodiment of the present application further provides an insulation impedance detection method for a power battery system, which is used in the insulation impedance detection device according to the first aspect, and the method includes:

[0025] detecting a first insulation impedance between the positive electrode of the second battery pack and the common ground, and a second insulation impedance between the negative electrode of the first battery pack and the common ground;

[0026] detecting a third insulation impedance between the positive electrode of the second battery pack and the common ground and a fourth insulation impedance between the negative electrode of the first battery pack and the common ground;

[0027] Based on the comparison between the third insulation impedance and the first insulation impedance, and the comparison between the fourth insulation impedance and the second insulation impedance, it is determined whether the detection of the first insulation impedance and the second insulation impedance is accurate.

[0028] In a third aspect, an embodiment of the present application further provides an electric vehicle, comprising a power battery system and an insulation impedance detection device as described in the first aspect, connected to the power battery system.

[0029] The present invention provides an insulation impedance detection device and method for a power battery system and an electric vehicle. A first insulation impedance detection circuit detects a first insulation impedance between the positive electrode of the second battery pack and a common ground, and a second insulation impedance between the negative electrode of the first battery pack and a common ground. A second insulation impedance detection circuit detects a third insulation impedance between the positive electrode of the second battery pack and a common ground, and a fourth insulation impedance between the negative electrode of the first battery pack and a common ground. The first insulation impedance detection circuit or the second insulation impedance detection circuit determines whether the detection of the first and second insulation impedances is accurate based on a comparison of the third insulation impedance with the first insulation impedance, and a comparison of the fourth insulation impedance with the second insulation impedance. This application verifies the first and second insulation impedances by detecting the third and fourth insulation impedances, thereby improving the accuracy of insulation impedance detection in the power battery system.

[0030] The details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0032] Figure 1 is a structural block diagram of an insulation impedance detection device for a power battery system in one embodiment;

[0033] Figure 2 is a specific structural block diagram of an insulation impedance detection device for a power battery system in one embodiment;

[0034] Figure 3 is a circuit schematic diagram of an insulation impedance detection device for a power battery system in an exemplary embodiment;

[0035] Figure 4 is a first equivalent circuit diagram of an insulation impedance detection device for a power battery system in an exemplary embodiment;

[0036] Figure 5 is a second equivalent circuit diagram of an insulation impedance detection device for a power battery system in an exemplary embodiment;

[0037] Figure 6 is a third equivalent circuit diagram of an insulation impedance detection device for a power battery system in an exemplary embodiment;

[0038] Figure 7 is a fourth equivalent circuit diagram of an insulation impedance detection device for a power battery system in an exemplary embodiment;

[0039] Figure 8 The figure is a flow chart of a method for detecting insulation impedance of a power battery system in an exemplary embodiment. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the contents disclosed in the present application, some changes such as design, manufacturing or production based on the technical contents disclosed in the present application are only conventional technical means and should not be understood as the contents disclosed in the present application being insufficient.

[0041] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments unless there is a conflict.

[0042] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. In this application, when an element is referred to as "provided on" another element, it can be directly provided on the other element or there can also be a central element. When an element is considered to be "provided on" another element, it can be directly provided on the other element or there can also be a central element. When an element is considered to be "fixed on" another element, it can be directly fixed on the other element or there can also be a central element. The terms "first", "second", "third" and the like involved in this application are merely to distinguish similar objects and do not represent a specific ordering of objects. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0043] See also Figure 1The present invention provides an insulation impedance detection device for a power battery system, the power battery system comprising a first battery pack and a second battery pack connected in series, the device comprising: a first insulation impedance detection circuit connected in parallel with the first battery pack, for detecting a first insulation impedance between a positive electrode of the second battery pack and a common ground, and a second insulation impedance between a negative electrode of the first battery pack and the common ground; a second insulation impedance detection circuit connected in parallel with the second battery pack, for detecting a third insulation impedance between a positive electrode of the second battery pack and the common ground, and a fourth insulation impedance between a negative electrode of the first battery pack and the common ground, the first insulation impedance detection circuit or the second insulation impedance detection circuit determining whether the detection of the first insulation impedance and the second insulation impedance is accurate based on a comparison of the third insulation impedance with the first insulation impedance, and a comparison of the fourth insulation impedance with the second insulation impedance.

[0044] In this embodiment, a first insulation impedance detection circuit detects a first insulation impedance between the positive electrode of the second battery pack and a common ground, and a second insulation impedance between the negative electrode of the first battery pack and a common ground. A second insulation impedance detection circuit detects a third insulation impedance between the positive electrode of the second battery pack and a fourth insulation impedance between the negative electrode of the first battery pack and a common ground. The first insulation impedance detection circuit or the second insulation impedance detection circuit compares the third insulation impedance with the first insulation impedance, and the fourth insulation impedance with the second insulation impedance, to determine whether the detection of the first insulation impedance and the second insulation impedance is accurate. This application verifies the first insulation impedance and the second insulation impedance by detecting the third insulation impedance and the fourth insulation impedance, thereby improving the accuracy of insulation impedance detection in the power battery system.

[0045] In some embodiments, as Figure 2 As shown, the first insulation impedance detection circuit includes a first main control chip and a first resistor network connected to the first main control chip, and the first resistor network is connected in parallel with the first battery pack. The second insulation impedance detection circuit includes a second main control chip and a second resistor network connected to the second main control chip, and the second resistor network is connected in parallel with the second battery pack.

[0046] The first main control chip controls the first resistance network to form at least two different resistance circuits, and constructs at least two different equations about the first insulation impedance and the second insulation impedance for the at least two different resistance circuits based on the current method, and obtains the first insulation impedance and the second insulation impedance based on solving the at least two equations.

[0047] The second main control chip controls the second resistance network to form at least two different resistance circuits, and constructs at least two different equations about the third insulation impedance and the fourth insulation impedance for the at least two different resistance circuits based on the current method, and obtains the third insulation impedance and the fourth insulation impedance based on solving the at least two equations.

[0048] The structures of the first insulation impedance detection circuit and the second insulation impedance detection circuit may be the same.

[0049] Figure 3 This is a circuit diagram of an insulation impedance detection device for a power battery system in an exemplary embodiment of the present application. Figure 3 The various circuits in this application and their working principles are described in detail.

[0050] The first resistor network includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a switch S1, a switch S2, and a switch S3; the switch S1, the resistor R1, the resistor R2, and the resistor R3 are sequentially connected in series, the switch S3 is connected in series with the resistor R4, and is connected in parallel with the resistor R2 and the resistor R3; one end of the switch S2 is connected to the midpoint between the resistor R1 and the resistor R2, and the other end is connected to a common ground. The second resistor network includes a resistor R11, a resistor R22, a resistor R33, a resistor R44, a switch S11, a switch S22, and a switch S33; the switch S11, the resistor R11, the resistor R22, and the resistor R33 are sequentially connected in series, the switch S33 is connected in series with the resistor R44, and is connected in parallel with the resistor R22 and the resistor R33; one end of the switch S22 is connected to the midpoint between the resistor R11 and the resistor R22, and the other end is connected to a common ground.

[0051] Among them, switches S1, S11, S3, and S33 are, for example, optocouplers, switches S2 and S22 are, for example, relays, and resistors R1, R11, R2, R22, R3, R33, R4, and R44 are all resistors of known values.

[0052] The first main control chip controls the states of the switches S1, S2, and S3 to form two different resistance circuits, and constructs two different equations about the first insulation impedance and the second insulation impedance for the two different resistance circuits based on the current method, and obtains the first insulation impedance and the second insulation impedance based on the solutions of the two equations.

[0053] The second main control chip controls the states of the switch S11, the switch S22, and the switch S33 to form two different resistance circuits, and based on the current method, constructs two different equations about the third insulation impedance and the fourth insulation impedance for the two different resistance circuits, and obtains the third insulation impedance and the fourth insulation impedance based on the solution of the two equations.

[0054] The specific solutions for the first insulation impedance and second insulation impedance detection are as follows:

[0055] Step 1: The first main control chip controls the switches S2 and S3 to close and the switch S1 to open. At this time, the switches S11, S22, and S33 are all open, and the following is obtained: Figure 4 The equivalent circuit diagram shown;

[0056] Step 2: Collect the first sampled voltage U1 of the positive electrode of the first battery pack, the second sampled voltage U2 of the positive electrode of the second battery pack, and the third sampled voltage U1 at the midpoint of the resistor R2 and the resistor R3. AD1 ;

[0057] Step 3: Based on the first sampling voltage U1, the second sampling voltage U2, and the third sampling voltage U AD1 , constructing a first equation (1) in which the current flowing through the first insulation impedance is equal to the sum of the current flowing through the second insulation impedance, the current flowing through the resistor R2 and the resistor R3, and the current flowing through the resistor R4:

[0058] (U2-U3)÷R P1 =U3÷R N1 +U3÷(R2+R3)+U3÷R4(1)

[0059] U AD1 ×(R2+R3)÷R3=U3

[0060] Among them, R P1 Indicates the first insulation resistance, R N1 represents the second insulation impedance, U3 represents the voltage on the high side of the second insulation impedance, and R2, R3, and R4 represent the resistance values ​​of resistor R2, resistor R3, and resistor R4, respectively.

[0061] Step 4: The first main control chip controls the switch S1 and the switch S2 to be closed and the switch S3 to be open, and the following is obtained: Figure 5 The equivalent circuit diagram shown;

[0062] Step 5: Collect the first sampled voltage U1 of the positive electrode of the first battery pack, the second sampled voltage U2 of the positive electrode of the second battery pack, and the third sampled voltage U1 at the midpoint of the resistor R2 and the resistor R3.AD1 ;

[0063] Step 6: Based on the first sampling voltage U1, the second sampling voltage U2, and the third sampling voltage U AD1 , constructing a second equation (2) where the sum of the current flowing through the first insulation impedance and the current flowing through the resistor R1 is equal to the sum of the current flowing through the second insulation impedance, the current flowing through the resistors R2 and R3, and the current flowing through the resistor R4:

[0064] (U2-U3)÷R P1 + (U1-U3)÷R1=U3÷R N1 +U3÷(R2+R3)(2)

[0065] U AD1 ×(R2+R3)÷R3=U3

[0066] Wherein, R1 represents the resistance value of the resistor R1.

[0067] Step 7: Solve the first equation (1) and the second equation (2) to obtain the first insulation resistance R P1 And the second insulation resistance R N1 .

[0068] The solutions for the third and fourth insulation impedance tests are basically the same as the above solutions. The specific solutions are as follows:

[0069] The second main control chip controls the switch S22 and the switch S33 to be closed and the switch S11 to be open. At this time, the switch S1, the switch S2, and the switch S3 are all open. Figure 6 As shown, the first sampling voltage U1 of the positive electrode of the first battery pack, the second sampling voltage U2 of the positive electrode of the second battery pack, and the fourth sampling voltage U at the midpoint of the resistor R22 and the resistor R33 are collected. AD2 , and based on the first sampling voltage U1, the second sampling voltage U2, the fourth sampling voltage U AD2 , constructing a third equation (3) in which the current flowing through the third insulation impedance is equal to the sum of the current flowing through the fourth insulation impedance, the current flowing through the resistor R2 and the resistor R3, and the current flowing through the resistor R44:

[0070] (U2-U4)÷R P2 =U4÷R N2 +(U4-U1)÷(R 22 +R 33 )+(U4-U1)÷R 44 (3)

[0071] U1+U AD2×(R 22 +R 33 )÷R 33 =U4

[0072] Among them, R P2 Indicates the third insulation resistance, R N2 Indicates the fourth insulation impedance, U3 indicates the voltage on the low side of the third insulation impedance, R 22 、R 33 、R 44 Respectively represent the resistance values ​​of resistor R22, resistor R33, and resistor R44;

[0073] The second main control chip controls the switch S11 and the switch S22 to be closed and the switch S33 to be open. Figure 7 As shown, the first sampling voltage U1 of the positive electrode of the first battery pack, the second sampling voltage U2 of the positive electrode of the second battery pack, and the fourth sampling voltage U at the midpoint of the resistor R22 and the resistor R33 are collected. AD2 , and based on the first sampling voltage U1, the second sampling voltage U2, the fourth sampling voltage U AD2 , constructing a fourth equation in which the sum of the current flowing through the third insulation impedance and the current flowing through the resistor R11 is equal to the sum of the current flowing through the fourth insulation impedance, the current flowing through the resistor R22 and the resistor R33, and the current flowing through the resistor R44;

[0074] (U2-U4)÷R P2 + (U2-U4) ÷ R 11 =U4÷R N2 +(U4-U1)÷(R 22 +R 33 )(4)

[0075] U1+U AD2 ×(R 22 +R 33 )÷R 33 =U4

[0076] Among them, R 11 Indicates the resistance value of resistor R11.

[0077] Combine the third equation (3) and the fourth equation (4) to obtain the third insulation resistance R P2 and the fourth insulation resistance R N2 .

[0078] After the first insulation impedance, the second insulation impedance, the third insulation impedance, and the fourth insulation impedance are calculated using the above method, the first insulation impedance detection circuit or the second insulation impedance detection circuit is used to calculate a first difference between the third insulation impedance and the first insulation impedance, and a second difference between the fourth insulation impedance and the second insulation impedance. If the first difference and the second difference are both less than a preset value, it is determined that the detection of the first insulation impedance and the second insulation impedance is accurate.

[0079] If at least one of the first difference and the second difference is greater than or equal to a preset value, it is determined that the detection of the first insulation impedance and the second insulation impedance is inaccurate. At this time, it is necessary to recalculate the first insulation impedance, the second insulation impedance, the third insulation impedance, and the fourth insulation impedance using the above method until both the first difference and the second difference are less than the preset value.

[0080] It should be noted that, in some other embodiments, the first difference and the second difference may be converted into percentages or other forms to determine whether the detection of the first insulation impedance and the second insulation impedance is accurate.

[0081] Based on the above hardware embodiment, the embodiment of the present application also provides a method for detecting insulation impedance of a power battery system, such as Figure 8 As shown, the method includes:

[0082] S802, detecting a first insulation impedance between the positive electrode of the second battery pack and the common ground, and a second insulation impedance between the negative electrode of the first battery pack and the common ground;

[0083] S804, detecting a third insulation impedance between the positive electrode of the second battery pack and the common ground and a fourth insulation impedance between the negative electrode of the first battery pack and the common ground;

[0084] S806: Based on a comparison between the third insulation impedance and the first insulation impedance, and a comparison between the fourth insulation impedance and the second insulation impedance, determine whether the detection of the first insulation impedance and the second insulation impedance is accurate.

[0085] Since the specific scheme and principle of the embodiment of the present method have been described in detail in the above hardware embodiment, they will not be repeated here.

[0086] In one embodiment, the present application further provides an electric vehicle, comprising a power battery system and an insulation impedance detection device as described in the above embodiment connected to the power battery system.

[0087] The electric vehicle in this embodiment includes the insulation impedance detection device in the above embodiment, and thus can solve the same technical problem and achieve the same technical effect. The specific technical solution and principle of the electric vehicle will not be described in detail.

[0088] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. An insulation impedance detection device for a power battery system, wherein the power battery system comprises a first battery pack and a second battery pack connected in series, characterized in that: The device comprises: a first insulation impedance detection circuit connected in parallel with the first battery pack, configured to detect a first insulation impedance between the positive electrode of the second battery pack and a common ground, and a second insulation impedance between the negative electrode of the first battery pack and the common ground; a second insulation impedance detection circuit connected in parallel with the second battery pack, configured to detect a third insulation impedance between the positive electrode of the second battery pack and a common ground, and a fourth insulation impedance between the negative electrode of the first battery pack and the common ground; The first insulation impedance detection circuit or the second insulation impedance detection circuit determines whether the detection of the first insulation impedance and the second insulation impedance is accurate based on a comparison between the third insulation impedance and the first insulation impedance, and a comparison between the fourth insulation impedance and the second insulation impedance.

2. The insulation impedance detection device of the power battery system according to claim 1, characterized in that: The first insulation impedance detection circuit includes a first main control chip and a first resistor network connected to the first main control chip, and the first resistor network is connected in parallel with the first battery pack; The first main control chip controls the first resistance network to form at least two different resistance circuits, and constructs at least two different equations about the first insulation impedance and the second insulation impedance for the at least two different resistance circuits based on the current method, and obtains the first insulation impedance and the second insulation impedance based on solving the at least two equations.

3. The insulation impedance detection device of the power battery system according to claim 2, characterized in that: The first resistor network includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a switch S1, a switch S2, and a switch S3; the switch S1, the resistor R1, the resistor R2, and the resistor R3 are connected in series in sequence, the switch S3 is connected in series with the resistor R4, and is connected in parallel with the resistor R2 and the resistor R3; one end of the switch S2 is connected to the midpoint of the resistor R1 and the resistor R2, and the other end is connected to a common ground; The first main control chip controls the states of the switches S1, S2, and S3 to form two different resistance circuits, and constructs two different equations about the first insulation impedance and the second insulation impedance for the two different resistance circuits based on the current method, and obtains the first insulation impedance and the second insulation impedance based on the solutions of the two equations.

4. The insulation impedance detection device of the power battery system according to claim 3, characterized in that: The first main control chip controls the switches S2 and S3 to be closed and the switch S1 to be open, collects a first sampled voltage at the positive electrode of the first battery pack, a second sampled voltage at the positive electrode of the second battery pack, and a third sampled voltage at the midpoint of the resistor R2 and the resistor R3, and constructs a first equation based on the first sampled voltage, the second sampled voltage, and the third sampled voltage, in which the current flowing through the first insulation impedance is equal to the sum of the current flowing through the second insulation impedance, the current flowing through the resistors R2 and R3, and the current flowing through the resistor R4; The first main control chip controls the switch S1 and the switch S2 to be closed and the switch S3 to be open, collects a first sampled voltage of the positive electrode of the first battery pack, a second sampled voltage of the positive electrode of the second battery pack, and a third sampled voltage at the midpoint of the resistor R2 and the resistor R3, and constructs a second equation based on the first sampled voltage, the second sampled voltage, and the third sampled voltage, in which the sum of the current flowing through the first insulation impedance and the current flowing through the resistor R1 is equal to the sum of the current flowing through the second insulation impedance, the current flowing through the resistors R2 and R3, and the current flowing through the resistor R4; Based on the first equation and the second equation, the first insulation resistance and the second insulation resistance are obtained by solving.

5. The insulation impedance detection device of the power battery system according to claim 1, characterized in that: The second insulation impedance detection circuit includes a second main control chip and a second resistor network connected to the second main control chip, and the second resistor network is connected in parallel with the second battery pack; The second main control chip controls the second resistance network to form at least two different resistance circuits, and constructs at least two different equations about the third insulation impedance and the fourth insulation impedance for the at least two different resistance circuits based on the current method, and obtains the third insulation impedance and the fourth insulation impedance based on solving the at least two equations.

6. The insulation impedance detection device of the power battery system according to claim 5, characterized in that: The second resistor network includes a resistor R11, a resistor R22, a resistor R33, a resistor R44, a switch S11, a switch S22, and a switch S33; the switch S11, the resistor R11, the resistor R22, and the resistor R33 are connected in series in sequence, the switch S33 is connected in series with the resistor R44, and is connected in parallel with the resistor R22 and the resistor R33; one end of the switch S22 is connected to the midpoint of the resistor R11 and the resistor R22, and the other end is connected to a common ground; The second main control chip controls the states of the switch S11, the switch S22, and the switch S33 to form two different resistance circuits, and based on the current method, constructs two different equations about the third insulation impedance and the fourth insulation impedance for the two different resistance circuits, and obtains the third insulation impedance and the fourth insulation impedance based on the solution of the two equations.

7. The insulation impedance detection device of the power battery system according to claim 6, characterized in that: The second main control chip controls the switch S22 and the switch S33 to be closed and the switch S11 to be open, collects a first sampled voltage at the positive electrode of the first battery pack, a second sampled voltage at the positive electrode of the second battery pack, and a fourth sampled voltage at the midpoint of the resistor R22 and the resistor R33, and constructs a third equation based on the first sampled voltage, the second sampled voltage, and the fourth sampled voltage, in which the current flowing through the third insulation impedance is equal to the sum of the current flowing through the fourth insulation impedance, the current flowing through the resistors R2 and R3, and the current flowing through the resistor R44; The second main control chip controls the switch S11 and the switch S22 to be closed and the switch S33 to be open, collects a first sampled voltage of the positive electrode of the first battery pack, a second sampled voltage of the positive electrode of the second battery pack, and a fourth sampled voltage at the midpoint of the resistor R22 and the resistor R33, and constructs a fourth equation based on the first sampled voltage, the second sampled voltage, and the fourth sampled voltage, where the sum of the current flowing through the third insulation resistor and the current flowing through the resistor R11 is equal to the sum of the current flowing through the fourth insulation resistor, the current flowing through the resistors R22 and R33, and the current flowing through the resistor R44; Based on the third equation and the fourth equation, the third insulation impedance and the fourth insulation impedance are obtained by solving.

8. The insulation impedance detection device of the power battery system according to claim 1, characterized in that: The first insulation impedance detection circuit or the second insulation impedance detection circuit calculates a first difference between the third insulation impedance and the first insulation impedance, and a second difference between the fourth insulation impedance and the second insulation impedance. If both the first difference and the second difference are less than a preset value, it is determined that the detection of the first insulation impedance and the second insulation impedance is accurate.

9. A method for detecting insulation impedance of a power battery system, used in the insulation impedance detection device according to any one of claims 1 to 8, characterized in that: The method comprises: detecting a first insulation impedance between the positive electrode of the second battery pack and the common ground, and a second insulation impedance between the negative electrode of the first battery pack and the common ground; detecting a third insulation impedance between the positive electrode of the second battery pack and the common ground and a fourth insulation impedance between the negative electrode of the first battery pack and the common ground; Based on the comparison between the third insulation impedance and the first insulation impedance, and the comparison between the fourth insulation impedance and the second insulation impedance, it is determined whether the detection of the first insulation impedance and the second insulation impedance is accurate.

10. An electric vehicle, characterized in that: The invention comprises a power battery system and an insulation impedance detection device according to any one of claims 1 to 8 connected to the power battery system.

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