Direct current insulation impedance detection method

Abstract

The application is suitable for the field of power electronics, and provides a DC insulation impedance detection method, which comprises the following steps: obtaining a first positive DC bus voltage and a first negative DC bus voltage when a midpoint of a first unbalanced bridge is connected to a grounding line and a midpoint of a second unbalanced bridge is suspended; obtaining a second positive DC bus voltage and a second negative DC bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected to the grounding line; and determining an insulation impedance of a positive DC bus and an insulation impedance of a negative DC bus according to the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage and the second negative DC bus voltage. In the application, the balanced bridge and the unbalanced bridge are both connected between the positive bus and the negative bus, and the detection is performed only after the bridge arm midpoint is connected to the grounding line, so that the fluctuation of the DC bus voltage is reduced, and the detection result is more accurate.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and in particular relates to a method for detecting DC insulation impedance. Background Technology

[0002] DC systems are used to provide DC power to loads. To ensure the continuity and reliability of power supply, DC systems are typically ungrounded. However, an abnormal grounding event in a DC system poses a safety hazard. Therefore, it is necessary to test the insulation impedance of the DC system to detect grounding faults promptly.

[0003] In existing technologies, unbalanced and balanced bridges are typically connected to switches to detect insulation impedance. However, the connection of balanced and unbalanced bridges changes the ground state of the DC system, causing fluctuations in the DC bus voltage, which in turn leads to inaccurate detection of insulation impedance. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a DC insulation impedance detection method to solve the problem in the prior art that the connection of a balanced bridge or an unbalanced bridge changes the ground state of the DC system, resulting in inaccurate DC insulation impedance detection results.

[0005] A first aspect of this invention provides a method for detecting DC insulation resistance, applied to a DC insulation resistance detection device; the DC insulation resistance detection device includes: a first unbalanced bridge, a second unbalanced bridge, and a balanced bridge; wherein the first unbalanced bridge, the second unbalanced bridge, and the balanced bridge are all connected between a positive DC bus and a negative DC bus, and the midpoint of the balanced bridge is connected to a ground wire; the method includes:

[0006] Obtain the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is left floating;

[0007] Obtain the second positive DC bus voltage and the second negative DC bus voltage when the midpoint of the first unbalanced bridge is floating and the midpoint of the second unbalanced bridge is connected to the ground wire;

[0008] The insulation impedance of the positive DC bus and the insulation impedance of the negative DC bus are determined based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage.

[0009] This invention provides a method for detecting DC insulation resistance, applied to a DC insulation resistance detection device. The DC insulation resistance detection device includes a first unbalanced bridge, a second unbalanced bridge, and a balanced bridge. The first unbalanced bridge, the second unbalanced bridge, and the balanced bridge are all connected between a positive DC bus and a negative DC bus, and the midpoint of the balanced bridge is connected to a grounding wire. The method includes: acquiring the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is suspended; acquiring the second positive DC bus voltage and the second negative DC bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected to the grounding wire; and determining the insulation resistance of the positive DC bus and the insulation resistance of the negative DC bus based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage. In this embodiment of the invention, the balanced bridge and the unbalanced bridge are always connected between the positive and negative busbars. The midpoint of the unbalanced bridge is connected to the grounding wire only during measurement, which can greatly reduce the fluctuation of DC busbar voltage and thus effectively improve the detection accuracy of insulation impedance. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the circuit structure of a DC insulation resistance detection device provided in an embodiment of the present invention;

[0012] Figure 2 This is a schematic diagram illustrating the implementation process of a DC insulation resistance detection method provided in an embodiment of the present invention;

[0013] Figure 3 This is the equivalent circuit diagram of the first unbalanced bridge connection provided in the embodiment of the present invention;

[0014] Figure 4 This is the equivalent circuit diagram of the second unbalanced bridge connection provided in the embodiment of the present invention;

[0015] Figure 5 This is a schematic diagram of the circuit structure of a differential sampling circuit provided in an embodiment of the present invention;

[0016] Figure 6 This is a schematic diagram of the DC insulation resistance detection system provided in an embodiment of the present invention;

[0017] Figure 7 This is a schematic diagram of the detection terminal provided in an embodiment of the present invention. Detailed Implementation

[0018] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0019] To illustrate the technical solution of the present invention, specific embodiments are described below.

[0020] refer to Figure 1 and Figure 2 This invention provides a method for detecting DC insulation resistance, applied to a DC insulation resistance detection device. The DC insulation resistance detection device includes a first unbalanced bridge, a second unbalanced bridge, and a balanced bridge. The first unbalanced bridge, the second unbalanced bridge, and the balanced bridge are all connected between the positive DC bus BUS+ and the negative DC bus BUS-, and the midpoint of the balanced bridge is connected to a ground wire. The method includes:

[0021] S101: Obtain the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating.

[0022] S102: Obtain the second positive DC bus voltage and the second negative DC bus voltage when the midpoint of the first unbalanced bridge is floating and the midpoint of the second unbalanced bridge is connected to the ground wire;

[0023] S103: Determine the insulation resistance of the positive DC bus BUS+ and the insulation resistance of the negative DC bus BUS- based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage.

[0024] refer to Figure 1 In this embodiment of the invention, the first unbalanced bridge, the second unbalanced bridge, and the balanced bridge are always connected between the positive DC bus BUS+ and the negative DC bus BUS-, and the midpoint of the balanced bridge is connected to the ground wire. During the insulation testing process, the midpoints of the first unbalanced bridge and the second unbalanced bridge are connected to the ground wire respectively. Since both the first and second unbalanced bridges are bridge circuit structures and are originally connected between the positive DC bus BUS+ and the negative DC bus BUS-, the connection to the ground wire has little impact on the DC system and also little impact on the positive and negative bus voltages, resulting in more accurate positive and negative bus voltages and thus more accurate insulation impedance detection.

[0025] In some embodiments, reference is made to Figure 1 The first unbalanced bridge may include: a fifth resistor R5, a sixth resistor R6, and a first optocoupler U1;

[0026] The first and second input terminals of the first optocoupler U1 are used to receive control signals. The first output terminal of the first optocoupler U1 is connected to the ground wire. The second output terminal of the first optocoupler U1 is connected to the first terminal of the fifth resistor R5 and the first terminal of the sixth resistor R6, respectively.

[0027] The second terminal of the fifth resistor R5 is connected to the positive DC bus BUS+;

[0028] The second terminal of the sixth resistor R6 is connected to the negative DC bus BUS-.

[0029] In this embodiment of the invention, when the first optocoupler U1 is turned on, the midpoint of the first unbalanced bridge is connected to the ground wire; conversely, when the first optocoupler U1 is not turned on, the midpoint of the first unbalanced bridge is left floating. The first optocoupler U1 enables both the floating and grounding of the midpoint of the first unbalanced bridge, simplifying control and facilitating implementation.

[0030] Similarly, the second unbalanced bridge may include: the seventh resistor R7, the eighth resistor R8, and the second optocoupler U2. See [link to circuit diagram] for the specific circuit structure. Figure 1 This will not be elaborated upon here.

[0031] Specifically, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 can be a single resistor, or formed by multiple resistors connected in parallel or series, without any restrictions.

[0032] In some embodiments, S103 may include:

[0033] S1031: Obtain the upper arm resistance of the balanced bridge, the upper arm resistance of the first unbalanced bridge, the lower arm resistance of the first unbalanced bridge, the upper arm resistance of the second unbalanced bridge, and the lower arm resistance of the second unbalanced bridge.

[0034] S1032: Determine the insulation impedance of the positive DC bus BUS+ and the insulation impedance of the negative DC bus BUS- based on the upper arm resistance of the balanced bridge, the upper arm resistance of the first unbalanced bridge, the lower arm resistance of the first unbalanced bridge, the upper arm resistance of the second unbalanced bridge, the lower arm resistance of the second unbalanced bridge, the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage.

[0035] In some embodiments, the formulas for calculating the insulation resistance of the positive DC bus BUS+ and the insulation resistance of the negative DC bus BUS- can be:

[0036]

[0037]

[0038] Among them, U 1+ U is the voltage of the first positive DC bus. 1- U is the voltage of the first negative DC bus. 2+ U is the second positive DC bus voltage. 2- R0 is the voltage of the second negative DC bus; R0 is the resistance of the upper arm of the balanced bridge (the sum of the first resistor R1 and the second resistor R2). x1 R is the insulation resistance of the positive DC bus BUS+. x2 R is the insulation resistance of the negative DC bus BUS-. 11 R is the resistance of the upper arm of the first unbalanced bridge (the resistance value of the fifth resistor R5). 12 R is the resistance of the lower arm of the first unbalanced bridge (the resistance value of the sixth resistor R6). 21 R is the resistance of the upper arm of the second unbalanced bridge (the resistance of the seventh resistor R7). 22 This is the resistance of the lower arm of the second unbalanced bridge (the resistance value of the eighth resistor R8).

[0039] In this embodiment of the invention, the impedances of each arm of the balanced bridge, the first unbalanced bridge, and the second unbalanced bridge are known. The insulation impedance R of the positive DC bus BUS+ can be calculated using Ohm's law. x1 Insulation resistance R of negative DC bus BUS- x2 .

[0040] For example, Figure 3 The equivalent circuit diagram is shown when the first unbalanced bridge is connected. The upper arm of the first unbalanced bridge is connected in parallel with the upper arm of the balanced bridge and the insulation resistance of the positive DC bus BUS+; the lower arm of the first unbalanced bridge is connected in parallel with the lower arm of the balanced bridge and the insulation resistance of the negative DC bus BUS-. Therefore,

[0041] Similarly, Figure 4 The equivalent circuit diagram with the second unbalanced bridge connected is shown, from which we can obtain:

[0042]

[0043] Among them, R x1 and R x2 R is the unknown quantity, and the rest are known quantities. Solving the above bivariate equation yields R. x1 and R x2 The solution.

[0044] The impedances of the first unbalanced bridge and the second unbalanced bridge are not the same, which makes the voltages of the first positive DC bus and the second positive DC bus different, and / or the voltages of the first negative DC bus and the second negative DC bus different. Only then can the values ​​of the two insulation impedances be calculated according to the above binary equation.

[0045] In some embodiments, prior to S103, the method may further include:

[0046] S104: Obtain the first positive bus ripple voltage and the first negative bus ripple voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating.

[0047] S105: Obtain the second positive bus ripple voltage and the second negative bus ripple voltage when the midpoint of the first unbalanced bridge is floating and the midpoint of the second unbalanced bridge is connected to the ground wire;

[0048] S106: Correct the first positive DC bus voltage based on the first positive bus ripple voltage to obtain the corrected first positive DC bus voltage; correct the first negative DC bus voltage based on the first negative bus ripple voltage to obtain the corrected first negative DC bus voltage.

[0049] S107: Correct the second positive DC bus voltage based on the second positive bus ripple voltage to obtain the corrected second positive DC bus voltage; correct the second negative DC bus voltage based on the second negative bus ripple voltage to obtain the corrected second negative DC bus voltage.

[0050] S103 may specifically include: determining the insulation resistance of the positive DC bus BUS+ and the insulation resistance of the negative DC bus BUS- based on the corrected first positive DC bus voltage, the corrected first negative DC bus voltage, the corrected second positive DC bus voltage, and the corrected second negative DC bus voltage.

[0051] In this embodiment of the invention, due to the presence of bus ripple voltage, the obtained DC bus voltages (first positive DC bus voltage, second positive DC bus voltage, first negative DC bus voltage, and second negative DC bus voltage) are inaccurate, resulting in deviations and inaccuracies in the insulation impedance calculated using Ohm's law. Therefore, in this embodiment of the invention, the obtained bus ripple voltages (first positive bus ripple voltage, first negative bus ripple voltage, second positive bus ripple voltage, and second negative bus ripple voltage) are used to correct the DC bus voltage, obtaining a more accurate DC bus voltage. The insulation impedance is then calculated based on the corrected DC bus voltage, resulting in a more precise calculation.

[0052] In some embodiments, S106 may include:

[0053] 1. Determine the effective value of the ripple voltage of the first positive busbar;

[0054] 2. Subtract the effective value of the first positive bus ripple voltage from the first positive DC bus voltage to obtain the corrected first positive DC bus voltage;

[0055] 3. Determine the effective value of the ripple voltage of the first negative bus;

[0056] 4. Subtract the effective value of the first negative bus ripple voltage from the first negative DC bus voltage to obtain the corrected first negative DC bus voltage; wherein, the first negative DC bus voltage is a negative value.

[0057] In this embodiment of the invention, the effective value of the bus ripple voltage is subtracted from the DC bus voltage to filter out the influence of the bus ripple voltage, thereby obtaining a more accurate DC bus voltage.

[0058] Furthermore, S107 can be modified using the same method, which will not be elaborated further.

[0059] In some embodiments, reference is made to Figure 1 The balance bridge may include: a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4; the first end of the first resistor R1 is connected to the positive DC bus BUS+, and the second end of the first resistor R1 is connected to the ground wire through the second resistor R2; the first end of the third resistor R3 is connected to the ground wire, and the second end of the third resistor R3 is connected to the negative DC bus BUS- through the fourth resistor R4.

[0060] S101 may include:

[0061] S1011: Obtain the voltage of the third resistor R3 when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is left floating.

[0062] S1012: Determine the first negative DC bus voltage based on the voltage across the third resistor R3;

[0063] S1013: Determine the first positive DC bus voltage based on the first negative DC bus voltage.

[0064] In some embodiments, S1013 may specifically include: obtaining a first voltage difference between the positive DC bus BUS+ and the negative DC bus BUS-, and subtracting the absolute value of the first negative DC bus voltage from the first voltage difference to obtain the first positive DC bus voltage.

[0065] In this embodiment of the invention, if an insulation impedance fault exists in the DC system, the DC bus midpoint will be unbalanced, and a voltage difference will exist between the DC bus midpoint and the grounding wire. This will result in inaccurate positive and negative DC bus voltages obtained directly. In this embodiment, the midpoint of the balanced bridge is connected to the grounding wire, which is an absolute 0 level. This allows for accurate detection of the voltage across a resistor in the balanced bridge (e.g., the third resistor R3), and then the first negative DC bus voltage can be calculated according to Ohm's law.

[0066] The voltage difference between the positive DC bus BUS+ and the negative DC bus BUS- is more accurate because it is not affected by the 0 level or the bus midpoint voltage. Therefore, the first positive DC bus voltage can be obtained by subtracting the absolute value of the first negative DC bus voltage from the first voltage difference. The bus voltage calculated by the above method is not affected by the bus midpoint voltage and is more accurate, thus making the calculated insulation impedance more accurate as well. The positive and negative DC bus voltages can be calculated using the voltage of any resistor in the balance bridge, not just the third resistor R3.

[0067] Furthermore, a differential voltage sampling circuit can be used to obtain the first voltage difference, which is more accurate.

[0068] In some embodiments, S1011 may include: using a differential voltage sampling circuit to obtain the voltage of the third resistor R3 when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating.

[0069] In this embodiment of the invention, a differential voltage sampling circuit can be used to detect the voltage of the third resistor R3, and the detection result is accurate.

[0070] In some embodiments, reference is made to Figure 5 The differential voltage sampling circuit may include: a first amplification module 11, a second amplification module 12, an isolation module 13, a differential amplification module 14, and a main control module 15;

[0071] The input terminal of the first amplification module 11 is connected to the first terminal of the third resistor R3, and the output terminal of the first amplification module 11 is connected to the first input terminal of the isolation module 13.

[0072] The input terminal of the second amplification module 12 is connected to the second terminal of the third resistor R3, and the output terminal of the second amplification module 12 is connected to the second input terminal of the isolation module 13.

[0073] The first output terminal of the isolation module 13 is connected to the first input terminal of the differential amplifier module 14, and the second output terminal of the isolation module 13 is connected to the second input terminal of the differential amplifier module 14.

[0074] The differential amplifier module 14 outputs a sampled signal.

[0075] In some embodiments, prior to S101, the method may further include:

[0076] S108: Obtain the voltage difference between the midpoint of the busbar and the grounding wire;

[0077] S109: If the voltage difference is greater than the preset voltage value, it is determined that there is an insulation resistance fault. Then, the steps of obtaining the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating are executed. Then, the insulation resistance of the positive DC bus BUS+ and the insulation resistance of the negative DC bus BUS- are determined based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage and the second negative DC bus voltage.

[0078] S1010: If the pressure difference is not greater than the preset difference value, then it is determined that there is no insulation resistance fault.

[0079] When there is no grounding fault in the DC system, the voltage difference between the bus midpoint and the grounding wire is very small. When a grounding fault occurs, due to the imbalance between the insulation resistance of the positive DC bus BUS+ and the negative DC bus BUS-, the first manifestation is an imbalance in the positive and negative bus voltages, and the voltage difference between the bus midpoint and the grounding wire increases rapidly. Therefore, insulation impedance faults can be quickly identified by the voltage difference between the bus midpoint and the grounding wire, allowing for timely countermeasures. Furthermore, the insulation impedance is calculated using methods S101 to S103 to accurately identify the location of the insulation fault.

[0080] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0081] Corresponding to the above embodiments, refer to Figure 6 This invention also provides a DC insulation resistance detection system, applied to a DC insulation resistance detection device; the DC insulation resistance detection device includes: a first unbalanced bridge, a second unbalanced bridge, and a balanced bridge; wherein the first unbalanced bridge, the second unbalanced bridge, and the balanced bridge are all connected between the positive DC bus BUS+ and the negative DC bus BUS-, and the midpoint of the balanced bridge is connected to the ground wire; the above system includes:

[0082] The first voltage acquisition unit 21 is used to acquire the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating.

[0083] The second voltage acquisition unit 22 is used to acquire the second positive DC bus voltage and the second negative DC bus voltage when the midpoint of the first unbalanced bridge is floating and the midpoint of the second unbalanced bridge is connected to the ground wire.

[0084] The insulation impedance calculation unit 23 is used to determine the insulation impedance of the positive DC bus BUS+ and the insulation impedance of the negative DC bus BUS- based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage.

[0085] In some embodiments, the insulation resistance calculation unit 23 may include:

[0086] The resistance acquisition subunit 231 is used to acquire the upper arm resistance of the balanced bridge, the upper arm resistance of the first unbalanced bridge, the lower arm resistance of the first unbalanced bridge, the upper arm resistance of the second unbalanced bridge, and the lower arm resistance of the second unbalanced bridge.

[0087] The result output subunit 232 is used to determine the insulation impedance of the positive DC bus BUS+ and the insulation impedance of the negative DC bus BUS- based on the upper arm resistance of the balanced bridge, the upper arm resistance of the first unbalanced bridge, the lower arm resistance of the first unbalanced bridge, the upper arm resistance of the second unbalanced bridge, the lower arm resistance of the second unbalanced bridge, the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage.

[0088] In some embodiments, the formulas for calculating the insulation resistance of the positive DC bus BUS+ and the insulation resistance of the negative DC bus BUS- can be:

[0089]

[0090]

[0091] Among them, U 1+ U is the voltage of the first positive DC bus. 1- U is the voltage of the first negative DC bus. 2+ U is the second positive DC bus voltage. 2- R0 is the voltage of the second negative DC bus; R0 is the resistance of the upper arm of the balanced bridge. x1 R is the insulation resistance of the positive DC bus BUS+. x2 R is the insulation resistance of the negative DC bus BUS-. 11 R is the resistance of the upper arm of the first unbalanced bridge. 12 R is the resistance of the lower arm of the first unbalanced bridge. 21 R is the resistance of the upper arm of the second unbalanced bridge. 22 This is the resistance of the lower arm of the second unbalanced bridge.

[0092] In some embodiments, the system may further include:

[0093] The first ripple acquisition unit 24 is used to acquire the first positive bus ripple voltage and the first negative bus ripple voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating.

[0094] The second ripple acquisition unit 25 is used to acquire the second positive bus ripple voltage and the second negative bus ripple voltage when the midpoint of the first unbalanced bridge is floating and the midpoint of the second unbalanced bridge is connected to the ground wire.

[0095] The first correction unit 26 is used to correct the first positive DC bus voltage according to the first positive bus ripple voltage to obtain the corrected first positive DC bus voltage; and to correct the first negative DC bus voltage according to the first negative bus ripple voltage to obtain the corrected first negative DC bus voltage.

[0096] The second correction unit 27 is used to correct the second positive DC bus voltage according to the second positive bus ripple voltage to obtain the corrected second positive DC bus voltage; and to correct the second negative DC bus voltage according to the second negative bus ripple voltage to obtain the corrected second negative DC bus voltage.

[0097] The insulation impedance calculation unit 23 can be specifically used to: determine the insulation impedance of the positive DC bus BUS+ and the insulation impedance of the negative DC bus BUS- based on the corrected first positive DC bus voltage, the corrected first negative DC bus voltage, the corrected second positive DC bus voltage and the corrected second negative DC bus voltage.

[0098] In some embodiments, the first correction unit 26 may be specifically used for:

[0099] 1. Determine the effective value of the ripple voltage of the first positive busbar;

[0100] 2. Subtract the effective value of the first positive bus ripple voltage from the first positive DC bus voltage to obtain the corrected first positive DC bus voltage;

[0101] 3. Determine the effective value of the ripple voltage of the first negative bus;

[0102] 4. Subtract the effective value of the first negative bus ripple voltage from the first negative DC bus voltage to obtain the corrected first negative DC bus voltage; wherein, the first negative DC bus voltage is a negative value.

[0103] In some embodiments, the balance bridge includes: a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4; the first end of the first resistor R1 is connected to the positive DC bus BUS+, and the second end of the first resistor R1 is connected to the ground wire through the second resistor R2; the first end of the third resistor R3 is connected to the ground wire, and the second end of the third resistor R3 is connected to the negative DC bus BUS- through the fourth resistor R4.

[0104] The first voltage acquisition unit 21 may include:

[0105] The resistor voltage acquisition subunit 211 is used to acquire the voltage of the third resistor R3 when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating.

[0106] The first DC bus voltage determination subunit 212 is used to determine the first negative DC bus voltage based on the voltage of the third resistor R3.

[0107] The second DC bus voltage determination subunit 213 is used to determine the first positive DC bus voltage based on the first negative DC bus voltage.

[0108] In some embodiments, the resistor voltage acquisition subunit 211 may be specifically used to: acquire the voltage of the third resistor R3 when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating, using a differential voltage sampling circuit.

[0109] In some embodiments, the differential voltage sampling circuit may include: a first amplification module 11, a second amplification module 12, an isolation module 13, a differential amplification module 14, and a main control module 15;

[0110] The input terminal of the first amplification module 11 is connected to the first terminal of the third resistor R3, and the output terminal of the first amplification module 11 is connected to the first input terminal of the isolation module 13.

[0111] The input terminal of the second amplification module 12 is connected to the second terminal of the third resistor R3, and the output terminal of the second amplification module 12 is connected to the second input terminal of the isolation module 13.

[0112] The first output terminal of the isolation module 13 is connected to the first input terminal of the differential amplifier module 14, and the second output terminal of the isolation module 13 is connected to the second input terminal of the differential amplifier module 14.

[0113] The differential amplifier module 14 outputs a sampled signal.

[0114] In some embodiments, the first unbalanced bridge may include: a fifth resistor R5, a sixth resistor R6, and a first optocoupler U1;

[0115] The first and second input terminals of the first optocoupler U1 are used to receive control signals. The first output terminal of the first optocoupler U1 is connected to the ground wire. The second output terminal of the first optocoupler U1 is connected to the first terminal of the fifth resistor R5 and the first terminal of the sixth resistor R6, respectively.

[0116] The second terminal of the fifth resistor R5 is connected to the positive DC bus BUS+;

[0117] The second terminal of the sixth resistor R6 is connected to the negative DC bus BUS-.

[0118] In some embodiments, the system may further include:

[0119] The differential pressure acquisition unit 28 is used to acquire the differential pressure between the midpoint of the busbar and the grounding wire.

[0120] The first insulation fault judgment unit 29 is used to determine that there is an insulation impedance fault if the voltage difference is greater than the preset voltage value, and to execute the steps of obtaining the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating, and then determining the insulation impedance of the positive DC bus BUS+ and the insulation impedance of the negative DC bus BUS- based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage and the second negative DC bus voltage;

[0121] The second insulation fault judgment unit 210 is used to determine that there is no insulation impedance fault if the pressure difference is not greater than a preset difference value.

[0122] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the detection terminal can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above device can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0123] Figure 7 This is a schematic block diagram of a detection terminal provided in an embodiment of the present invention. Figure 7 As shown, the detection terminal 4 in this embodiment includes: one or more processors 40, a memory 41, and a computer program 42 stored in the memory 41 and executable on the processor 40. When the processor 40 executes the computer program 42, it implements the steps in the various DC insulation resistance detection method embodiments described above, for example... Figure 2 The steps S101 to S103 are shown. Alternatively, when the processor 40 executes the computer program 42, it implements the functions of each module / unit in the above-described DC insulation resistance detection system embodiment, for example... Figure 6 The functions of units 21 to 23 are shown.

[0124] Exemplarily, the computer program 42 may be divided into one or more units, one or more of which are stored in the memory 41 and executed by the processor 40 to complete this application. The one or more units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 42 in the detection terminal 4. For example, the computer program 42 may be divided into a first voltage acquisition unit 21, a second voltage acquisition unit 22, and an insulation resistance calculation unit 23.

[0125] The first voltage acquisition unit 21 is used to acquire the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating.

[0126] The second voltage acquisition unit 22 is used to acquire the second positive DC bus voltage and the second negative DC bus voltage when the midpoint of the first unbalanced bridge is floating and the midpoint of the second unbalanced bridge is connected to the ground wire.

[0127] The insulation impedance calculation unit 23 is used to determine the insulation impedance of the positive DC bus BUS+ and the insulation impedance of the negative DC bus BUS- based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage.

[0128] Other units will not be discussed further here.

[0129] The detection terminal 4 includes, but is not limited to, a processor 40 and a memory 41. Those skilled in the art will understand that... Figure 7 This is merely an example of a detection terminal and does not constitute a limitation on detection terminal 4. It may include more or fewer components than shown, or combine certain components, or different components. For example, detection terminal 4 may also include input devices, output devices, network access devices, buses, etc.

[0130] The processor 40 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0131] The memory 41 can be an internal storage unit of the detection terminal, such as a hard disk or RAM. The memory 41 can also be an external storage device of the detection terminal, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card. Furthermore, the memory 41 can include both internal and external storage units. The memory 41 is used to store the computer program 42 and other programs and data required by the detection terminal. The memory 41 can also be used to temporarily store data that has been output or will be output.

[0132] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0133] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0134] In the embodiments provided in this application, it should be understood that the disclosed detection terminal and method can be implemented in other ways. For example, the detection terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0135] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0136] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0137] If an integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0138] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for detecting DC insulation resistance, characterized in that, An application is made in a DC insulation resistance testing device; the DC insulation resistance testing device includes: a first unbalanced bridge, a second unbalanced bridge, and a balanced bridge; wherein the first unbalanced bridge, the second unbalanced bridge, and the balanced bridge are all connected between a positive DC bus and a negative DC bus, and the midpoint of the balanced bridge is connected to a ground wire; the method includes: Obtain the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is floating; Obtain the second positive DC bus voltage and the second negative DC bus voltage when the midpoint of the first unbalanced bridge is floating and the midpoint of the second unbalanced bridge is connected to the grounding wire; Based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage, determine the insulation resistance of the positive DC bus and the insulation resistance of the negative DC bus; The step of obtaining the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is floating includes: When the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is floating, the voltage of the target resistor in the balanced bridge is obtained, and the voltage of the half-bridge in which the target resistor is located is determined based on the voltage of the target resistor; wherein, the target resistor is any resistor in the balanced bridge; Based on the voltage of the half-bridge containing the target resistor, determine the voltage of the other half-bridge; use the voltage of the half-bridge containing the target resistor and the voltage of the other half-bridge as the first positive DC bus voltage and the first negative DC bus voltage.

2. The DC insulation resistance detection method as described in claim 1, characterized in that, The step of determining the insulation impedance of the positive DC bus and the insulation impedance of the negative DC bus based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage includes: Obtain the upper arm resistance of the balanced bridge, the upper arm resistance of the first unbalanced bridge, the lower arm resistance of the first unbalanced bridge, the upper arm resistance of the second unbalanced bridge, and the lower arm resistance of the second unbalanced bridge. The insulation impedance of the positive DC bus and the insulation impedance of the negative DC bus are determined based on the upper arm resistance of the balanced bridge, the upper arm resistance of the first unbalanced bridge, the lower arm resistance of the first unbalanced bridge, the upper arm resistance of the second unbalanced bridge, the lower arm resistance of the second unbalanced bridge, the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage.

3. The DC insulation resistance detection method as described in claim 2, characterized in that, The formulas for calculating the insulation resistance of the positive DC bus and the insulation resistance of the negative DC bus are as follows: in, The voltage of the first positive DC bus is... This is the voltage of the first negative DC bus. This is the voltage of the second positive DC bus. This is the voltage of the second negative DC bus; The resistance of the upper arm of the balanced bridge is... The insulation resistance of the positive DC bus is given. The insulation resistance of the negative DC bus is given. The resistance of the upper arm of the first unbalanced bridge is... The lower arm resistance of the first unbalanced bridge is... The resistance of the upper arm of the second unbalanced bridge is... is the resistance of the lower arm of the second unbalanced bridge.

4. The DC insulation resistance detection method according to any one of claims 1 to 3, characterized in that, Before determining the insulation impedance of the positive DC bus and the insulation impedance of the negative DC bus based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage, the method further includes: Obtain the first positive bus ripple voltage and the first negative bus ripple voltage when the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is floating. Obtain the second positive bus ripple voltage and the second negative bus ripple voltage when the midpoint of the first unbalanced bridge is floating and the midpoint of the second unbalanced bridge is connected to the grounding wire; The first positive DC bus voltage is corrected based on the first positive bus ripple voltage to obtain the corrected first positive DC bus voltage; the first negative DC bus voltage is corrected based on the first negative bus ripple voltage to obtain the corrected first negative DC bus voltage. The second positive DC bus voltage is corrected based on the second positive bus ripple voltage to obtain the corrected second positive DC bus voltage; the second negative DC bus voltage is corrected based on the second negative bus ripple voltage to obtain the corrected second negative DC bus voltage. The step of determining the insulation impedance of the positive DC bus and the insulation impedance of the negative DC bus based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage, and the second negative DC bus voltage includes: The insulation impedance of the positive DC bus and the insulation impedance of the negative DC bus are determined based on the corrected first positive DC bus voltage, the corrected first negative DC bus voltage, the corrected second positive DC bus voltage, and the corrected second negative DC bus voltage.

5. The DC insulation resistance detection method as described in claim 4, characterized in that, The first positive DC bus voltage is corrected based on the first positive bus ripple voltage to obtain the corrected first positive DC bus voltage. The first negative DC bus voltage is corrected based on the first negative bus ripple voltage to obtain the corrected first negative DC bus voltage, including: Determine the effective value of the first positive bus ripple voltage; The corrected first positive DC bus voltage is obtained by subtracting the effective value of the first positive bus ripple voltage from the first positive DC bus voltage. Determine the effective value of the ripple voltage of the first negative bus; The corrected first negative DC bus voltage is obtained by subtracting the effective value of the first negative bus ripple voltage from the first negative DC bus voltage; wherein the first negative DC bus voltage is a negative value.

6. The DC insulation resistance detection method according to any one of claims 1 to 3, characterized in that, The balance bridge includes: a first resistor, a second resistor, a third resistor, and a fourth resistor; the first end of the first resistor is connected to the positive DC bus, and the second end of the first resistor is connected to the ground wire through the second resistor; the first end of the third resistor is connected to the ground wire, and the second end of the third resistor is connected to the negative DC bus through the fourth resistor; The step of obtaining the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is floating includes: Obtain the voltage of the third resistor when the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is left floating; The voltage of the first negative DC bus is determined based on the voltage of the third resistor; The first positive DC bus voltage is determined based on the first negative DC bus voltage.

7. The DC insulation resistance detection method as described in claim 6, characterized in that, The voltage across the third resistor when the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is left floating includes: A differential voltage sampling circuit is used to obtain the voltage of the third resistor when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is left floating.

8. The DC insulation resistance detection method as described in claim 7, characterized in that, The differential voltage sampling circuit includes: a first amplification module, a second amplification module, an isolation module, a differential amplification module, and a main control module; The input terminal of the first amplification module is connected to the first terminal of the third resistor, and the output terminal of the first amplification module is connected to the first input terminal of the isolation module. The input terminal of the second amplification module is connected to the second terminal of the third resistor, and the output terminal of the second amplification module is connected to the second input terminal of the isolation module. The first output terminal of the isolation module is connected to the first input terminal of the differential amplifier module, and the second output terminal of the isolation module is connected to the second input terminal of the differential amplifier module. The differential amplifier module outputs a sampling signal.

9. The DC insulation resistance detection method according to any one of claims 1 to 3, characterized in that, The first unbalanced bridge includes: a fifth resistor, a sixth resistor, and a first optocoupler; The first input terminal and the second input terminal of the first optocoupler are used to receive control signals. The first output terminal of the first optocoupler is connected to the ground wire. The second output terminal of the first optocoupler is connected to the first terminal of the fifth resistor and the first terminal of the sixth resistor, respectively. The second end of the fifth resistor is connected to the positive DC bus; The second end of the sixth resistor is connected to the negative DC bus.

10. The DC insulation resistance detection method according to any one of claims 1 to 3, characterized in that, Before obtaining the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the ground wire and the midpoint of the second unbalanced bridge is floating, the method further includes: Obtain the voltage difference between the midpoint of the busbar and the grounding wire; If the voltage difference is greater than the preset voltage value, an insulation impedance fault is determined, and the steps of obtaining the first positive DC bus voltage and the first negative DC bus voltage when the midpoint of the first unbalanced bridge is connected to the grounding wire and the midpoint of the second unbalanced bridge is floating, to determining the insulation impedance of the positive DC bus and the insulation impedance of the negative DC bus based on the first positive DC bus voltage, the first negative DC bus voltage, the second positive DC bus voltage and the second negative DC bus voltage are executed. If the pressure difference is not greater than the preset voltage value, then it is determined that there is no insulation resistance fault.

Images