Insulation impedance detection method for direct current system and direct current system

Abstract

The application provides a kind of insulation impedance detection method of direct current system and direct current system.Direct current system includes multiple output branch buses, positive electrode is connected with positive electrode common point, and negative electrode is connected with negative electrode common point.Direct current system is provided with insulation impedance detection circuit, insulation impedance detection circuit includes balanced bridge-unbalanced bridge detection circuit connected between positive electrode common point and negative electrode common point and leakage current detection circuit for obtaining leakage current value of each output branch bus;The method comprises: by controlling the switching of balanced bridge and / or unbalanced bridge in balanced bridge-unbalanced bridge detection circuit, obtaining the voltage detection result and leakage current detection result corresponding to each output branch bus;According to the voltage detection result and leakage current detection result corresponding to each output branch bus, the insulation impedance of the abnormal electrode of each output branch bus is determined.The application can realize the detection of the insulation impedance of the abnormal electrode of each output branch bus through insulation impedance detection circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of insulation impedance detection, and particularly to an insulation impedance detection method of a direct current system and the direct current system. BACKGROUND

[0002] In the direct current system, the main bus can branch out multiple branch buses. In order to determine the insulation performance of the branch buses, the insulation impedance of each branch bus needs to be detected so as to find the insulation fault of the branch bus in time.

[0003] At present, the insulation impedance detection method or the insulation impedance detection circuit is usually used for detecting the main bus, and cannot realize the detection of the insulation impedance of the branch bus. SUMMARY

[0004] The embodiments of the present application provide an insulation impedance detection method of a direct current system and the direct current system, so as to solve the problem that the existing method cannot realize the detection of the insulation impedance of the branch bus.

[0005] In a first aspect, the embodiments of the present application provide an insulation impedance detection method of a direct current system, the direct current system comprising multiple output branch buses, each of which is connected to a positive common point and a negative common point; the direct current system is provided with an insulation impedance detection circuit, the insulation impedance detection circuit comprising a balanced-unbalanced bridge detection circuit connected between the positive common point and the negative common point and a leakage current detection circuit used for obtaining the leakage current value of each output branch bus; the insulation impedance detection method of the direct current system comprises:

[0006] obtaining the voltage detection result and the leakage current detection result corresponding to each output branch bus by controlling the switching of the balanced bridge and / or the unbalanced bridge in the balanced-unbalanced bridge detection circuit;

[0007] determining the insulation impedance of the abnormal electrode of each output branch bus according to the voltage detection result and the leakage current detection result corresponding to each output branch bus.

[0008] In a possible implementation manner, when the insulation impedance abnormal type is a positive insulation impedance abnormality, the voltage detection result and the leakage current detection result corresponding to each output branch bus comprise the first positive common point-to-ground voltage value and the first leakage current value of each output branch bus when the balanced bridge is switched on and the unbalanced bridge is switched off.

[0009] Correspondingly, the determination of the insulation impedance of the abnormal electrode of each output branch bus according to the voltage detection result and the leakage current detection result corresponding to each output branch bus comprises:

[0010] According to the first positive electrode common point-to-ground voltage value and the first leakage current value of each output branch bus, the first positive electrode-to-ground impedance of each output branch bus is calculated as the insulation impedance of the abnormal electrode of each output branch bus.

[0011] In a possible implementation, when the insulation impedance abnormality type is a negative electrode insulation impedance abnormality, the voltage detection result and the leakage current detection result corresponding to each output branch bus include a first negative electrode common point-to-ground voltage value and a second leakage current value of each output branch bus when the balanced bridge is turned on and the unbalanced bridges are all turned off.

[0012] Correspondingly, determining the insulation impedance of the abnormal electrode of each output branch bus according to the voltage detection result and the leakage current detection result corresponding to each output branch bus includes:

[0013] According to the first negative electrode common point-to-ground voltage value and the second leakage current value of each output branch bus, the first negative electrode-to-ground impedance of each output branch bus is calculated as the insulation impedance of the abnormal electrode of each output branch bus.

[0014] In a possible implementation, when the insulation impedance abnormality type is a two-pole insulation impedance abnormality, the voltage detection result and the leakage current detection result corresponding to each output branch bus include a second positive electrode common point-to-ground voltage value, a second negative electrode common point-to-ground voltage value, and a third leakage current value of each output branch bus when the balanced bridge and one of the unbalanced bridges are turned on, and a third positive electrode common point-to-ground voltage value, a third negative electrode common point-to-ground voltage value, and a fourth leakage current value of each output branch bus when the balanced bridge and the other unbalanced bridge are turned on; the number of unbalanced bridges is at least two, and the unbalanced bridges turned on twice are different unbalanced bridges.

[0015] Correspondingly, determining the insulation impedance of the abnormal electrode of each output branch bus according to the voltage detection result and the leakage current detection result corresponding to each output branch bus includes:

[0016] According to the second positive electrode common point-to-ground voltage value, the second negative electrode common point-to-ground voltage value, the third leakage current value of each output branch bus, the third positive electrode common point-to-ground voltage value, the third negative electrode common point-to-ground voltage value, and the fourth leakage current value of each output branch bus, the second positive electrode-to-ground impedance and the second negative electrode-to-ground impedance of each output branch bus are calculated as the insulation impedance of the abnormal electrode of each output branch bus.

[0017] In a possible implementation, the calculation formula of the second positive electrode-to-ground impedance of each output branch bus is:

[0018]

[0019] The calculation formula of the second negative electrode-to-ground impedance of each output branch bus is:

[0020]

[0021] wherein, R o2i+ is the second positive pole-to-ground impedance of the i-th output branch bus; R o2i- is the second negative pole-to-ground impedance of the i-th output branch bus; V 2+ is the second positive pole common point-to-ground voltage value; V 2- is the second negative pole common point-to-ground voltage value; V 3+ is the third positive pole common point-to-ground voltage value; V 3- is the third negative pole common point-to-ground voltage value; I 3i is the third leakage current value of the i-th output branch bus; I 4i is the fourth leakage current value of the i-th output branch bus; 1≤i≤N, N is the number of output branch buses.

[0022] In a possible implementation, the DC system further includes a main bus with a positive pole connected to a positive pole common point and a negative pole connected to a negative pole common point;

[0023] The insulation impedance detection method of the DC system further includes:

[0024] The multiplexing insulation impedance detection circuit detects the positive pole insulation impedance of the main bus and the negative pole insulation impedance of the main bus.

[0025] In a possible implementation, the insulation impedance detection method of the DC system further includes:

[0026] According to the positive pole insulation impedance of the main bus and the negative pole insulation impedance of the main bus, the insulation impedance abnormal type is determined;

[0027] Correspondingly, by controlling the switching of the balanced bridge and / or the unbalanced bridge in the balanced-unbalanced bridge detection circuit, the voltage detection result and the leakage current detection result corresponding to each output branch bus are obtained, including:

[0028] Based on the insulation impedance abnormal type, the switching of the balanced bridge and / or the unbalanced bridge in the balanced-unbalanced bridge detection circuit is controlled, and the voltage detection result and the leakage current detection result corresponding to each output branch bus are obtained.

[0029] In a possible implementation, the balanced-unbalanced bridge detection circuit includes a balanced bridge, a first unbalanced bridge, and a second unbalanced bridge;

[0030] The balance bridge comprises a first resistor, a second resistor and a first switch; the first resistor is connected between the positive common point and a midpoint of the balance bridge, the second resistor is connected between the midpoint of the balance bridge and the negative common point, and the midpoint of the balance bridge is grounded through the first switch; when the first switch is closed, the balance bridge is put into operation, and when the first switch is opened, the balance bridge is cut out; the first resistor and the second resistor have equal resistance values;

[0031] The first unbalance bridge comprises a third resistor and a second switch; the third resistor is connected between the positive common point and a midpoint of the first unbalance bridge, and the midpoint of the first unbalance bridge is grounded through the second switch; when the second switch is closed, the first unbalance bridge is put into operation, and when the second switch is opened, the first unbalance bridge is cut out;

[0032] The second unbalance bridge comprises a fourth resistor and a third switch; the fourth resistor is connected between a midpoint of the second unbalance bridge and the negative common point, and the midpoint of the second unbalance bridge is grounded through the third switch; when the third switch is closed, the second unbalance bridge is put into operation, and when the third switch is opened, the second unbalance bridge is cut out.

[0033] In a possible implementation, the leakage current detection circuit comprises a first leakage current sampling device corresponding to each output branch bus line; or,

[0034] The leakage current detection circuit comprises a first leakage current sampling device corresponding to any N-1 output branch bus lines and a second leakage current sampling device for collecting the leakage current between the positive common point and the negative common point; N is the number of output branch bus lines.

[0035] In a second aspect, an embodiment of the present application provides a direct current system, comprising a plurality of output branch bus lines each having a positive electrode connected to a positive common point and a negative electrode connected to a negative common point, and a controller;

[0036] The direct current system is provided with an insulation impedance detection circuit, and the insulation impedance detection circuit comprises a balance bridge-unbalance bridge detection circuit connected between the positive common point and the negative common point and a leakage current detection circuit for obtaining leakage current values of the output branch bus lines.

[0037] The insulation impedance detection circuit is controlled by the controller; and the controller is configured to perform the insulation impedance detection method of the direct current system as described in the first aspect or any possible implementation of the first aspect.

[0038] The embodiment of the present application provides a kind of insulation impedance detection method of direct current system and direct current system, direct current system is provided with insulation impedance detection circuit, insulation impedance detection circuit includes the balanced bridge-unbalanced bridge detection circuit connected between positive common point and negative common point and the leakage current detection circuit for obtaining the leakage current value of each output branch bus;The method obtains the voltage detection result and leakage current detection result corresponding to each output branch bus by controlling the switching of balanced bridge and / or unbalanced bridge in balanced bridge-unbalanced bridge detection circuit, and determines the insulation impedance of abnormal electrode of each output branch bus according to the voltage detection result and leakage current detection result corresponding to each output branch bus, so that the insulation impedance of abnormal electrode of each output branch bus can be detected by insulation impedance detection circuit. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0040] Figure 1 It is the structure schematic diagram of direct current system provided by an embodiment of the present application;

[0041] Figure 2 It is the flow schematic diagram of insulation impedance detection method of direct current system provided by an embodiment of the present application;

[0042] Figure 3 It is the structure schematic diagram of direct current system provided by another embodiment of the present application;

[0043] Figure 4 It is the structure schematic diagram of insulation impedance detection device of direct current system provided by an embodiment of the present application;

[0044] Figure 5 It is the schematic diagram of controller provided by an embodiment of the present application. DETAILED DESCRIPTION

[0045] In the following description, specific details are set forth such as particular system configurations, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, it should be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

[0046] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be described by specific embodiments with reference to the drawings.

[0047] Referring to Figure 1 , which shows a structure schematic diagram of a direct current system provided by an embodiment of the present application. The direct current system comprises a plurality of output branch buses 11, each of which is connected with the positive common point D1 and the negative common point D2. The direct current system is provided with an insulation impedance detection circuit, which comprises a balanced-imbalance bridge detection circuit 14 connected between the positive common point and the negative common point and a leakage current detection circuit 13 for obtaining the leakage current value of each output branch bus.

[0048] The balanced-imbalance bridge detection circuit 14 comprises at least one balanced bridge and at least two imbalance bridges.

[0049] The insulation impedance detection circuit can further comprise a voltage detection device for detecting the voltage value of the positive common point to ground and / or the voltage value of the negative common point to ground.

[0050] The data detected by the leakage current detection circuit 13 can be used to determine the leakage current value of each output branch bus.

[0051] Referring to Figure 2 , which shows an implementation flowchart of an insulation impedance detection method of a direct current system provided by an embodiment of the present application. The execution subject of the insulation impedance detection method of the direct current system can be a controller.

[0052] The insulation impedance detection method of the direct current system comprises:

[0053] In S201, the voltage detection result and the leakage current detection result corresponding to each output branch bus are obtained by controlling the switching of the balanced bridge and / or the imbalance bridge in the balanced-imbalance bridge detection circuit.

[0054] The balanced bridge and / or the imbalance bridge in the balanced-imbalance bridge detection circuit can be in different states, and each output branch bus can correspond to different voltage detection results and leakage current detection results. The embodiment obtains the voltage detection result and the leakage current detection result corresponding to each output branch bus by controlling the switching of the balanced bridge and / or the imbalance bridge in the balanced-imbalance bridge detection circuit.

[0055] The state of the balanced bridge and the imbalance bridge comprises a switching-in state or a switching-out state.

[0056] In S202, the insulation impedance of the abnormal electrode of each output branch bus is determined according to the voltage detection result and the leakage current detection result corresponding to each output branch bus.

[0057] The abnormal electrode insulation impedance of each output branch bus can be obtained based on the voltage detection result and the leakage current detection result corresponding to each output branch bus, so as to realize the detection of the insulation impedance of each output branch bus.

[0058] The DC system of the embodiment is provided with an insulation impedance detection circuit, which comprises a balanced-unbalanced bridge detection circuit connected between the positive common point and the negative common point and a leakage current detection circuit for obtaining the leakage current value of each output branch bus; the method obtains the voltage detection result and the leakage current detection result corresponding to each output branch bus by controlling the switching of the balanced bridge and / or the unbalanced bridge in the balanced-unbalanced bridge detection circuit, and determines the insulation impedance of the abnormal electrode of each output branch bus according to the voltage detection result and the leakage current detection result corresponding to each output branch bus, so as to realize the detection of the insulation impedance of the abnormal electrode of each output branch bus through the insulation impedance detection circuit.

[0059] In some embodiments, when the insulation impedance abnormality type is a positive electrode insulation impedance abnormality, the voltage detection result and the leakage current detection result corresponding to each output branch bus include a first positive common point-to-ground voltage value and a first leakage current value of each output branch bus when the balanced bridge is switched on and the unbalanced bridge is switched off.

[0060] Correspondingly, S202 can include:

[0061] According to the first positive common point-to-ground voltage value and the first leakage current value of each output branch bus, the first positive electrode-to-ground impedance of each output branch bus is calculated as the insulation impedance of the abnormal electrode of each output branch bus.

[0062] The insulation impedance abnormality type of the output branch bus can include a single-pole insulation impedance abnormality or a two-pole insulation impedance abnormality. The single-pole insulation impedance abnormality can include a positive electrode insulation impedance abnormality or a negative electrode insulation impedance abnormality. The positive electrode insulation impedance abnormality means that only the positive electrode insulation impedance is abnormal and the negative electrode insulation impedance is normal. The negative electrode insulation impedance abnormality means that only the negative electrode insulation impedance is abnormal and the positive electrode insulation impedance is normal. The two-pole insulation impedance abnormality means that both the positive electrode insulation impedance and the negative electrode insulation impedance are abnormal.

[0063] Since the positive electrode of each output branch bus is connected to the positive common point and the negative electrode is connected to the negative common point, the insulation impedance abnormality type of each output branch bus is the same.

[0064] When the insulation impedance abnormality type is positive insulation impedance abnormality, the balanced bridge of the balanced bridge-unbalanced bridge detection circuit can be controlled to be put into operation, and the unbalanced bridges in the balanced bridge-unbalanced bridge detection circuit can be controlled to be cut out. Through the voltage detection device, the current positive common point to ground voltage value is obtained as the first positive common point to ground voltage value, and through the leakage current detection circuit, the current leakage current value of each output branch bus is obtained as the first leakage current value of each output branch bus.

[0065] The first positive electrode common point-to-ground voltage value is divided by the first leakage current value of the corresponding output branch bus to obtain the first positive electrode-to-ground impedance of the output branch bus, that is, the insulation impedance of the abnormal electrode (positive electrode) of the current output branch bus.

[0066] In some possible implementations, after obtaining the first leakage current value of each output branch bus, the first leakage current value of each output branch bus can be filtered, and the first positive electrode to ground impedance of each output branch bus can be calculated based on the first leakage current value of each output branch bus after filtering, which can improve the accuracy of the results.

[0067] In some embodiments, when the insulation impedance abnormality type is a negative electrode insulation impedance abnormality, the voltage detection results and leakage current detection results corresponding to each output branch bus include a first negative electrode common point-to-ground voltage value and a second leakage current value of each output branch bus when the balanced bridge is switched on and the unbalanced bridges are switched off;

[0068] Accordingly, the above S202 may include:

[0069] According to the first negative electrode common point-to-ground voltage value and the second leakage current value of each output branch bus, the first negative electrode-to-ground impedance of each output branch bus is calculated respectively as the insulation impedance of the abnormal electrode of each output branch bus.

[0070] When the insulation impedance abnormality type is negative pole insulation impedance abnormality, the balanced bridge of the balanced bridge-unbalanced bridge detection circuit can be controlled to be put in, and the unbalanced bridges in the balanced bridge-unbalanced bridge detection circuit can be controlled to be cut out. Through the voltage detection device, the current negative pole common point to ground voltage value is obtained as the first negative pole common point to ground voltage value, and through the leakage current detection circuit, the current leakage current value of each output branch bus is obtained as the second leakage current value of each output branch bus.

[0071] The voltage value of the first negative electrode common point to ground is divided by the second leakage current value of the corresponding output branch bus to obtain the first negative electrode to ground impedance of the output branch bus, that is, the insulation impedance of the abnormal electrode (negative electrode) of the current output branch bus.

[0072] In some possible implementation manners, after the second leakage current values of the output branch buses are acquired, the second leakage current values of the output branch buses can be filtered, and the first negative pole-to-ground impedance of each output branch bus can be calculated based on the filtered second leakage current values of the output branch buses, so that the result accuracy can be improved.

[0073] In the single-stage insulation impedance anomaly, whether it is a positive pole insulation impedance anomaly or a negative pole insulation impedance anomaly, only one round of switching is needed to obtain two variables, one voltage value and one current value. The voltage value is relatively stable, and the current value may fluctuate. After filtering the current value, the current fluctuation is small, and the calculation accuracy is good. Moreover, only one round of switching is needed, the efficiency is high, the values to be measured are less, and the variables in the calculation process are less, so that the insulation impedance result of the abnormal electrode can be quickly and accurately obtained.

[0074] In some embodiments, when the insulation impedance anomaly type is a two-pole insulation impedance anomaly, the voltage detection result and the leakage current detection result corresponding to each output branch bus include a second positive pole common point-to-ground voltage value, a second negative pole common point-to-ground voltage value, and a third leakage current value of each output branch bus when the balance bridge and one of the unbalanced bridges are turned on, and a third positive pole common point-to-ground voltage value, a third negative pole common point-to-ground voltage value, and a fourth leakage current value of each output branch bus when the balance bridge and the other unbalanced bridge are turned on; the number of unbalanced bridges is at least two, and the unbalanced bridges turned on twice are different unbalanced bridges.

[0075] Correspondingly, S202 can include the following steps.

[0076] According to the second positive pole common point-to-ground voltage value, the second negative pole common point-to-ground voltage value, the third leakage current value of each output branch bus, the third positive pole common point-to-ground voltage value, the third negative pole common point-to-ground voltage value, and the fourth leakage current value of each output branch bus, the second positive pole-to-ground impedance and the second negative pole-to-ground impedance of each output branch bus are calculated respectively as the insulation impedance of the abnormal electrode of each output branch bus.

[0077] When the insulation impedance anomaly type is a two-pole insulation impedance anomaly, two rounds of switching are performed to obtain the voltage detection result and the leakage current detection result corresponding to each output branch bus.

[0078] In the first round of switching, the balance bridge and one of the unbalanced bridges of the balance bridge-unbalanced bridge detection circuit are turned on, and the remaining unbalanced bridges are all turned off. The current positive pole common point-to-ground voltage value is acquired as the second positive pole common point-to-ground voltage value by the voltage detection device, and the current negative pole common point-to-ground voltage value is acquired as the second negative pole common point-to-ground voltage value. The current leakage current values of each output branch bus are acquired as the third leakage current values of each output branch bus by the leakage current detection circuit.

[0079] The second round of switching can control the balanced bridge and another unbalanced bridge of the balanced bridge-unbalanced bridge detection circuit to be put in, and control the remaining unbalanced bridge to be cut out. The current positive common point-to-ground voltage value is obtained as the third positive common point-to-ground voltage value through the voltage detection device, and the current negative common point-to-ground voltage value is obtained as the third negative common point-to-ground voltage value. The current leakage current value of each output branch bus is obtained as the fourth leakage current value of each output branch bus through the leakage current detection circuit. The unbalanced bridges put in twice are different unbalanced bridges, and only one unbalanced bridge can be put in each time, or at least two unbalanced bridges can be put in, which can be determined according to actual conditions.

[0080] The voltage value and the current value obtained through the above two rounds of switching can be used to calculate the second positive-to-ground impedance and the second negative-to-ground impedance of each output branch bus as the insulation impedance of the abnormal electrode (positive electrode and negative electrode) of each output branch bus.

[0081] Exemplarily, the balanced bridge-unbalanced bridge detection circuit can include one balanced bridge and two unbalanced bridges, and the two unbalanced bridges are respectively a first unbalanced bridge and a second unbalanced bridge. In the first round of switching, the balanced bridge and the first unbalanced bridge can be controlled to be put in, and the second unbalanced bridge is cut out. In the second round of switching, the balanced bridge and the second unbalanced bridge can be controlled to be put in, and the first unbalanced bridge is cut out. The two rounds of switching can also be interchanged.

[0082] In some possible implementation manners, after obtaining the third leakage current value of each output branch bus, the third leakage current value of each output branch bus can be filtered; after obtaining the fourth leakage current value of each output branch bus, the fourth leakage current value of each output branch bus can be filtered; and the second positive-to-ground impedance and the second negative-to-ground impedance of each output branch bus are calculated by using the filtered third leakage current value of each output branch bus and the filtered fourth leakage current value of each output branch bus, so that the accuracy of the insulation impedance detection result can be improved.

[0083] In some possible implementation manners, the calculated second positive-to-ground impedance and the second negative-to-ground impedance of each output branch bus can be filtered, and the filtered second positive-to-ground impedance and the second negative-to-ground impedance of each output branch bus are taken as the final insulation impedance of the abnormal electrode of each output branch bus, so that the accuracy of the insulation impedance detection result can be further improved.

[0084] In some possible implementation manners, the second positive electrode common point-to-ground voltage value, the second negative electrode common point-to-ground voltage value, the third positive electrode common point-to-ground voltage value and the third negative electrode common point-to-ground voltage value can be respectively subjected to filtering processing, and the second positive electrode common point-to-ground voltage value after filtering processing, the second negative electrode common point-to-ground voltage value after filtering processing, the third positive electrode common point-to-ground voltage value after filtering processing and the third negative electrode common point-to-ground voltage value after filtering processing are used to calculate the second positive electrode-to-ground impedance and the second negative electrode-to-ground impedance of each output branch bus, so that the accuracy of the insulation impedance detection result can be improved.

[0085] In some embodiments, the calculation formula of the second positive electrode-to-ground impedance of each output branch bus is as follows:

[0086]

[0087] The calculation formula of the second negative electrode-to-ground impedance of each output branch bus is as follows:

[0088]

[0089] wherein, R o2i+ is the second positive electrode-to-ground impedance of the i th output branch bus; R o2i- is the second negative electrode-to-ground impedance of the i th output branch bus; V 2+ is the second positive electrode common point-to-ground voltage value; V 2- is the second negative electrode common point-to-ground voltage value; V 3+ is the third positive electrode common point-to-ground voltage value; V 3- is the third negative electrode common point-to-ground voltage value; I 3i is the third leakage current value of the i th output branch bus; I 4i is the fourth leakage current value of the i th output branch bus; 1≤i≤N, and N is the number of output branch buses. i is a positive integer.

[0090] In this embodiment, according to the Kirchhoff's current law, two rounds of switching can obtain two equations, which are respectively and Solving the two equations can obtain R o2i+ and R o2i- .

[0091] In this embodiment, when the two-pole insulation impedance is abnormal, the corresponding parameters detected through two rounds of switching can be used to calculate the two-pole insulation impedance of each output branch bus.

[0092] In some possible implementations, when there is a single-stage insulation impedance abnormality, the insulation impedance of the abnormal electrode of each output branch can also be detected by the detection method for two-stage insulation impedance abnormality, but this method needs two switching, uses more variables, and the calculation process is more complex, and multiple filtering is required to ensure accuracy. Therefore, when there is a single-stage insulation impedance abnormality, the insulation impedance of the abnormal electrode can be detected by the foregoing method of only one round of switching to quickly obtain an accurate detection result.

[0093] In some embodiments, referring to Figure 1 , the DC system further includes a main bus 12 connected to the positive common point D1 and the negative common point D2.

[0094] The insulation impedance detection method of the DC system further includes:

[0095] The multiplexed insulation impedance detection circuit detects the positive electrode insulation impedance of the main bus and the negative electrode insulation impedance of the main bus.

[0096] The embodiment can detect the insulation impedance of the abnormal electrode of each output branch bus by the insulation impedance detection circuit, and can also multiplex the insulation impedance detection circuit to detect the positive electrode insulation impedance of the main bus and the negative electrode insulation impedance of the main bus.

[0097] The multiplexed insulation impedance detection circuit that detects the positive electrode insulation impedance of the main bus and the negative electrode insulation impedance of the main bus can include:

[0098] The balance bridge and one of the unbalanced bridges of the balance bridge-unbalanced bridge detection circuit are controlled to be turned on, and the fourth positive electrode-to-ground voltage V 4+ and the fourth negative electrode-to-ground voltage V 4- of the main bus are obtained.

[0099] The balance bridge and the other unbalanced bridge of the balance bridge-unbalanced bridge detection circuit are controlled to be turned on, and the fifth positive electrode-to-ground voltage V 5+ and the fifth negative electrode-to-ground voltage V 5- of the main bus are obtained. The two turned-on unbalanced bridges are different unbalanced bridges.

[0100] The positive electrode insulation impedance R 4+ of the main bus and the negative electrode insulation impedance R 4- of the main bus are determined according to V 5+ , V 5- , V + , and V - .

[0101] Exemplarily, the balanced bridge-unbalanced bridge detection circuit can include one balanced bridge and two unbalanced bridges, and the two unbalanced bridges are respectively a first unbalanced bridge and a second unbalanced bridge. In the first round of switching, the balanced bridge and the first unbalanced bridge can be controlled to be put into operation, the second unbalanced bridge is cut out, and the fourth positive pole-to-ground voltage V 4+ and the fourth negative pole-to-ground voltage V 4- of the main bus are obtained. In the second round of switching, the balanced bridge and the second balanced bridge can be controlled to be put into operation, the first unbalanced bridge is cut out, and the fifth positive pole-to-ground voltage V 5+ and the fifth negative pole-to-ground voltage V 5- of the main bus are obtained. The two rounds of switching can also be interchanged.

[0102] In some embodiments, the insulation impedance detection method of the direct current system further includes:

[0103] determining an insulation impedance abnormality type according to the positive pole insulation impedance of the main bus and the negative pole insulation impedance of the main bus;

[0104] Correspondingly, by controlling the switching of the balanced bridge and / or the unbalanced bridge in the balanced bridge-unbalanced bridge detection circuit, the voltage detection result and the leakage current detection result corresponding to each output branch bus are obtained, including:

[0105] based on the insulation impedance abnormality type, controlling the switching of the balanced bridge and / or the unbalanced bridge in the balanced bridge-unbalanced bridge detection circuit, and obtaining the voltage detection result and the leakage current detection result corresponding to each output branch bus.

[0106] Exemplarily, if the positive pole insulation impedance of the main bus is less than a first preset insulation impedance, it is determined that the positive pole insulation impedance is abnormal, and if the negative pole insulation impedance of the main bus is less than a second preset insulation impedance, it is determined that the negative pole insulation impedance is abnormal. If both the positive pole insulation impedance and the negative pole insulation impedance are abnormal, it is determined that the insulation impedance abnormality type is a two-pole insulation impedance abnormality; if only the positive pole insulation impedance is abnormal, it is determined that the insulation impedance abnormality type is a positive pole insulation impedance abnormality; and if only the negative pole insulation impedance is abnormal, it is determined that the insulation impedance abnormality type is a negative pole insulation impedance abnormality.

[0107] Based on the insulation impedance abnormality type, the foregoing different methods can be used to control the switching of the balanced bridge and / or the unbalanced bridge in the balanced bridge-unbalanced bridge detection circuit, and the voltage detection result and the leakage current detection result corresponding to each output branch bus are obtained, and then the insulation impedance of the abnormal pole of each output branch bus is calculated.

[0108] Since each output branch bus is connected with the main bus, the insulation impedance abnormality of the branch bus will be fed back to the main bus, thus, the insulation impedance abnormality type of each output branch bus can be determined by detecting the insulation impedance abnormality type of the main bus.

[0109] In some embodiments, referring to Figure 1 , the balanced bridge-unbalanced bridge detection circuit comprises a balanced bridge P, a first unbalanced bridge J1 and a second unbalanced bridge J2; that is, the number of balanced bridges is one; the number of unbalanced bridges is two, which are the first unbalanced bridge J1 and the second unbalanced bridge J2 respectively;

[0110] The balanced bridge P comprises a first resistor R1, a second resistor R2 and a first switch K1; the first resistor R1 is connected between the positive common point D1 and the midpoint of the balanced bridge P, the second resistor R2 is connected between the midpoint of the balanced bridge P and the negative common point D2, and the midpoint of the balanced bridge P is grounded through the first switch K1; when the first switch K1 is closed, the balanced bridge P is put into, and when the first switch K1 is opened, the balanced bridge P is cut out; the resistance values of the first resistor and the second resistor are equal;

[0111] The first unbalanced bridge J1 comprises a third resistor R3 and a second switch K2; the third resistor R3 is connected between the positive common point D1 and the midpoint of the first unbalanced bridge J1, and the midpoint of the first unbalanced bridge J1 is grounded through the second switch K2; when the second switch K2 is closed, the first unbalanced bridge J1 is put into, and when the second switch K2 is opened, the first unbalanced bridge J1 is cut out;

[0112] The second unbalanced bridge J2 comprises a fourth resistor R4 and a third switch K3, the fourth resistor R4 is connected between the midpoint of the second unbalanced bridge J2 and the negative common point D2, and the midpoint of the second unbalanced bridge J2 is grounded through the third switch K3; when the third switch K3 is closed, the second unbalanced bridge J2 is put into, and when the third switch K3 is opened, the second unbalanced bridge J2 is cut out.

[0113] In some possible implementations, the first unbalanced bridge and the second unbalanced bridge can also be represented in other forms.

[0114] Referring to Figure 3 , the first unbalanced bridge J1 can comprise a fifth resistor R5, a sixth resistor R6 and a fourth switch K4; the fifth resistor R5 is connected between the positive common point D1 and the midpoint of the first unbalanced bridge J1, the sixth resistor R6 is connected between the midpoint of the first unbalanced bridge J1 and the negative common point D2, and the midpoint of the first unbalanced bridge J1 is grounded through the fourth switch K4; when the fourth switch K4 is closed, the first unbalanced bridge J1 is put into, and when the fourth switch K4 is opened, the first unbalanced bridge J1 is cut out; the resistance values of the fifth resistor R5 and the sixth resistor R6 are not equal;

[0115] The second unbalanced bridge J2 can include a seventh resistor R7, an eighth resistor R8 and a fifth switch K5; the seventh resistor R7 is connected between the positive common point D1 and the midpoint of the second unbalanced bridge J2, the eighth resistor R8 is connected between the midpoint of the second unbalanced bridge J2 and the negative common point D2, and the midpoint of the second unbalanced bridge J2 is grounded through the fifth switch K5; when the fifth switch K5 is closed, the second unbalanced bridge J2 is put into, and when the fifth switch K5 is opened, the second unbalanced bridge J2 is cut out; the resistance values of the seventh resistor R7 and the eighth resistor R8 are not equal.

[0116] In Figure 3 The positive insulation impedance R + and the negative insulation impedance R - of the main bus can be calculated by the above method under the balanced bridge-unbalanced bridge detection circuit shown in the figure. 4+ Firstly, the balanced bridge and the first unbalanced bridge are put into, the second unbalanced bridge is cut out, the fourth positive-to-ground voltage V 4- and the fourth negative-to-ground voltage V 5+ of the main bus are obtained; then the balanced bridge and the second unbalanced bridge are put into, the first unbalanced bridge is cut out, the fifth positive-to-ground voltage V 5- and the fifth negative-to-ground voltage V 4+ of the main bus are obtained; finally, according to V 4- , V 5+ , V 5- , the positive insulation impedance R + and the negative insulation impedance R - of the main bus are calculated.

[0117]

[0118] Wherein, R1 is the resistance value of the first resistor; R5 is the resistance value of the fifth resistor; R2 is the resistance value of the second resistor; R6 is the resistance value of the sixth resistor; R7 is the resistance value of the seventh resistor; and R8 is the resistance value of the eighth resistor.

[0119] When the switching sequence changes or the balanced bridge-unbalanced bridge detection circuit adopts other forms, the above formula can be modified adaptively, and details are not described herein.

[0120] In some embodiments, the leakage current detection circuit includes a first leakage current sampling device corresponding to each output branch bus; or,

[0121] The leakage current detection circuit comprises a first leakage current sampling device corresponding to any N-1 output branch bus and a second leakage current sampling device for collecting leakage current between the positive common point and the negative common point, wherein N is the number of output branch buses.

[0122] In the embodiment, referring to Figure 3 , each output branch bus can be provided with a first leakage current sampling device for collecting the leakage current value of the output branch bus. Alternatively, referring to Figure 1 , any N-1 output branch buses can be provided with a corresponding first leakage current sampling device for collecting the leakage current value of the corresponding output branch bus, and the positive common point and the negative common point, i.e. the main bus, are provided with a second leakage current sampling device for collecting the leakage current value between the positive common point and the negative common point. The leakage current value between the positive common point and the negative common point minus the leakage current values of the N-1 output branch buses can obtain the leakage current value of the remaining one output branch bus which is not provided with the first leakage current sampling device.

[0123] In the embodiment, the leakage current sampling device installed on the output branch bus is referred to as the first leakage current sampling device, and the leakage current sampling device installed on the main bus is referred to as the second leakage current sampling device. The first leakage current sampling device and the second leakage current sampling device can both be leakage current sampling Hall.

[0124] In some possible implementation manners, each output branch bus can be connected to a direct current load to supply power to the direct current load. The main bus can be connected to a direct current power supply. The direct current power supply can be one sub-power supply or at least two sub-power supplies connected in parallel. Each sub-power supply is connected to the main bus through a corresponding controllable switch. When the controllable switch is closed, the corresponding sub-power supply is connected; when the controllable switch is opened, the corresponding sub-power supply is disconnected. The sub-power supply connected each time can be controlled, and the insulation impedance of the main bus when different sub-power supplies are connected can be calculated by using the foregoing method. When the insulation impedance of the main bus is found to be abnormal, only one sub-power supply can be connected each time to detect the insulation impedance of the corresponding main bus, so that the sub-power supply that fails can be determined.

[0125] It should be understood that the size of the serial number of each step in the above embodiment does not mean the order of execution. The execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0126] The following is a device embodiment of the present application. For details not described in detail, reference can be made to the corresponding method embodiments described above.

[0127] Figure 4A structure schematic diagram of the insulation impedance detection device of the direct current system is shown, only parts related to the embodiments of the present application are shown for the convenience of description, and the details are as follows:

[0128] The direct current system comprises a plurality of output branch buses, each of whose positive poles is connected to the positive common point and each of whose negative poles is connected to the negative common point; the direct current system is provided with an insulation impedance detection circuit, which comprises a balanced-unbalanced bridge detection circuit connected between the positive common point and the negative common point and a leakage current detection circuit for obtaining the leakage current values of the output branch buses; as shown in the figure, the insulation impedance detection device 30 of the direct current system can comprise a control module 31 and a branch impedance determination module 32. Figure 4

[0129] The control module 31 is configured to obtain the voltage detection results and the leakage current detection results corresponding to each output branch bus by controlling the switching of the balanced bridge and / or the unbalanced bridge in the balanced-unbalanced bridge detection circuit;

[0130] The branch impedance determination module 32 is configured to determine the insulation impedance of the abnormal electrode of each output branch bus according to the voltage detection results and the leakage current detection results corresponding to each output branch bus.

[0131] In a possible implementation, when the insulation impedance abnormality type is positive electrode insulation impedance abnormality, the voltage detection results and the leakage current detection results corresponding to each output branch bus comprise the first positive common point-to-ground voltage value and the first leakage current value of each output branch bus when the balanced bridge is switched on and the unbalanced bridge is switched off;

[0132] Correspondingly, the branch impedance determination module 32 is specifically configured to:

[0133] According to the first positive common point-to-ground voltage value and the first leakage current value of each output branch bus, the first positive electrode-to-ground impedance of each output branch bus is calculated as the insulation impedance of the abnormal electrode of each output branch bus.

[0134] In a possible implementation, when the insulation impedance abnormality type is negative electrode insulation impedance abnormality, the voltage detection results and the leakage current detection results corresponding to each output branch bus comprise the first negative common point-to-ground voltage value and the second leakage current value of each output branch bus when the balanced bridge is switched on and the unbalanced bridge is switched off;

[0135] Correspondingly, the branch impedance determination module 32 is specifically configured to:

[0136] According to the first negative common point-to-ground voltage value and the second leakage current value of each output branch bus, the first negative electrode-to-ground impedance of each output branch bus is calculated as the insulation impedance of the abnormal electrode of each output branch bus.

[0137] ​In a possible implementation, when the insulation impedance abnormality type is a two-pole insulation impedance abnormality, the voltage detection result and the leakage current detection result corresponding to each output branch bus include a second positive common point-to-ground voltage value, a second negative common point-to-ground voltage value and a third leakage current value of each output branch bus when the balanced bridge and one of the unbalanced bridges are put into operation, and a third positive common point-to-ground voltage value, a third negative common point-to-ground voltage value and a fourth leakage current value of each output branch bus when the balanced bridge and the other unbalanced bridge are put into operation; the number of unbalanced bridges is at least two, and the unbalanced bridges put into operation twice are different unbalanced bridges;

[0138] Correspondingly, the branch impedance determination module 32 is specifically configured to:

[0139] According to the second positive common point-to-ground voltage value, the second negative common point-to-ground voltage value, the third leakage current value of each output branch bus, the third positive common point-to-ground voltage value, the third negative common point-to-ground voltage value and the fourth leakage current value of each output branch bus, the second positive pole-to-ground impedance and the second negative pole-to-ground impedance of each output branch bus are calculated respectively as the insulation impedance of the abnormal electrode of each output branch bus.

[0140] In a possible implementation, the calculation formula of the second positive pole-to-ground impedance of each output branch bus is:

[0141]

[0142] The calculation formula of the second negative pole-to-ground impedance of each output branch bus is:

[0143]

[0144] wherein, R o2i+ is the second positive pole-to-ground impedance of the i th output branch bus; R o2i- is the second negative pole-to-ground impedance of the i th output branch bus; V 2+ is the second positive common point-to-ground voltage value; V 2- is the second negative common point-to-ground voltage value; V 3+ is the third positive common point-to-ground voltage value; V 3- is the third negative common point-to-ground voltage value; I 3i is the third leakage current value of the i th output branch bus; I 4i is the fourth leakage current value of the i th output branch bus; 1≤i≤N, and N is the number of output branch buses.

[0145] In a possible implementation, the direct current system further includes a main bus with a positive pole connected to a positive common point and a negative pole connected to a negative common point;

[0146] The insulation impedance detection device 30 of the DC system can further include a main path impedance determination module.

[0147] The main path impedance determination module is configured to multiplex the insulation impedance detection circuit to detect the positive insulation impedance of the main path bus and the negative insulation impedance of the main path bus.

[0148] In a possible implementation, the main path impedance determination module is further configured to determine an insulation impedance abnormality type according to the positive insulation impedance of the main path bus and the negative insulation impedance of the main path bus.

[0149] Correspondingly, the control module 31 is specifically configured to:

[0150] Based on the insulation impedance abnormality type, control switching of the balanced bridge and / or the unbalanced bridge in the balanced-unbalanced bridge detection circuit, and obtain voltage detection results and leakage current detection results corresponding to each output branch bus.

[0151] In a possible implementation, the balanced-unbalanced bridge detection circuit includes a balanced bridge, a first unbalanced bridge, and a second unbalanced bridge.

[0152] The balanced bridge includes a first resistor, a second resistor, and a first switch; the first resistor is connected between the positive common point and a midpoint of the balanced bridge, the second resistor is connected between the midpoint of the balanced bridge and the negative common point, and the midpoint of the balanced bridge is grounded through the first switch; when the first switch is closed, the balanced bridge is switched in, and when the first switch is opened, the balanced bridge is switched out; the first resistor and the second resistor have equal resistance values.

[0153] The first unbalanced bridge includes a third resistor and a second switch; the third resistor is connected between the positive common point and a midpoint of the first unbalanced bridge, and the midpoint of the first unbalanced bridge is grounded through the second switch; when the second switch is closed, the first unbalanced bridge is switched in, and when the second switch is opened, the first unbalanced bridge is switched out.

[0154] The second unbalanced bridge includes a fourth resistor and a third switch; the fourth resistor is connected between a midpoint of the second unbalanced bridge and the negative common point, and the midpoint of the second unbalanced bridge is grounded through the third switch; when the third switch is closed, the second unbalanced bridge is switched in, and when the third switch is opened, the second unbalanced bridge is switched out.

[0155] In a possible implementation, the leakage current detection circuit includes a first leakage current sampling device corresponding to each output branch bus; or,

[0156] The leakage current detection circuit includes a first leakage current sampling device corresponding to any N-1 output branch buses and a second leakage current sampling device configured to sample a leakage current between the positive common point and the negative common point; N is the number of output branch buses.

[0157] Figure 5 is a schematic diagram of a controller provided by an embodiment of the present application. As shown in the figure, the controller 4 of this embodiment comprises a processor 40 and a memory 41. Figure 5 The memory 41 is configured to store a computer program 42, and the processor 40 is configured to invoke and run the computer program 42 stored in the memory 41 to perform the steps in the above-described various embodiments of the insulation impedance detection method for a direct current system, such as S201-S202 shown in the figure. Figure 2 Alternatively, the processor 40 is configured to invoke and run the computer program 42 stored in the memory 41 to implement the functions of the modules / units in the above-described various apparatus embodiments, such as the functions of the modules / units 31-32 shown in the figure. Figure 4

[0158] For example, the computer program 42 can be divided into one or more modules / units, which are stored in the memory 41 and executed by the processor 40 to complete the present application. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the computer program 42 in the controller 4. For example, the computer program 42 can be divided into the modules / units 31-32 shown in the figure. Figure 4

[0159] The controller 4 can include, but is not limited to, the processor 40 and the memory 41. Those skilled in the art can understand that Figure 5 The controller 4 is merely an example and does not constitute a limitation on the controller 4, and can include more or fewer components than those shown in the figure, or combine certain components, or different components, for example, the controller can also include an input / output device, a network access device, a bus, etc.

[0160] The processor 40 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0161] ​​The memory 41 can be an internal storage unit of the controller 4, such as a hard disk or a memory of the controller 4. The memory 41 can also be an external storage device of the controller 4, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the controller 4. Further, the memory 41 can also include both the internal storage unit and the external storage device of the controller 4. The memory 41 is used to store the computer program and other programs and data required by the controller. The memory 41 can also be used to temporarily store data that has been output or is to be output.

[0162] Corresponding to the above controller, the embodiment of the application also provides a direct current system, comprising a plurality of output branch buses, each of whose positive poles is connected with a positive common point and each of whose negative poles is connected with a negative common point, and the above controller;

[0163] The direct current system is provided with an insulation impedance detection circuit, which comprises a balanced-imbalance bridge detection circuit connected between the positive common point and the negative common point and a leakage current detection circuit for obtaining the leakage current value of each output branch bus;

[0164] The insulation impedance detection circuit is controlled by the controller; and the controller is used to execute the insulation impedance detection method of any one of the above direct current systems.

[0165] The detailed description of the direct current system can be referred to the related description in the above method, and will not be repeated here.

[0166] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is exemplified, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for easy distinction, and do not limit the protection scope of the application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the above method embodiments, which will not be repeated here.

[0167] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in detail in a certain embodiment can be referred to the related description of other embodiments.

[0168] Those skilled in the art can understand that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0169] In the embodiments provided by the present application, it should be understood that the disclosed apparatus / controller and method can be implemented in other ways. For example, the apparatus / controller embodiments described above are merely schematic. The division of the modules or units is merely a logical function division, and there can be another division in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed coupling or direct coupling or communication connection between each other can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or in other forms.

[0170] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. they can be located in one place, or distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0171] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0172] The integrated module / unit, if realized in the form of a software function unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer-readable storage medium. The computer program can implement the steps of the above-mentioned DC system insulation impedance detection method embodiments when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, an executable file, or some intermediate form, etc. The computer-readable medium can include any entity or device capable of carrying the computer program code, a recording medium, a U disk, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. It should be noted that the contents included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in a 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.

[0173] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method of detecting an insulation impedance of a direct current system, characterized by, The direct current system comprises a plurality of output branch buses, each of whose positive poles is connected to a positive common point and each of whose negative poles is connected to a negative common point; the direct current system is provided with an insulation impedance detection circuit, which comprises a balanced-imbalance bridge detection circuit connected between the positive common point and the negative common point and a leakage current detection circuit for obtaining leakage current values of each output branch bus; and an insulation impedance detection method of the direct current system comprises: By controlling switching of the balanced bridge and / or the imbalance bridge in the balanced-imbalance bridge detection circuit, voltage detection results and leakage current detection results corresponding to each output branch bus are obtained; According to the voltage detection results and the leakage current detection results corresponding to each output branch bus, insulation impedance of abnormal electrodes of each output branch bus is determined.

2. The insulation impedance detection method of a DC system according to claim 1, characterized by, When the insulation impedance abnormality type is positive electrode insulation impedance abnormality, the voltage detection results and the leakage current detection results corresponding to each output branch bus comprise a first positive common point-to-ground voltage value and first leakage current values of each output branch bus when the balanced bridge is switched on and the imbalance bridges are all switched off; Correspondingly, the determination of the insulation impedance of the abnormal electrodes of each output branch bus according to the voltage detection results and the leakage current detection results corresponding to each output branch bus comprises: According to the first positive common point-to-ground voltage value and the first leakage current values of each output branch bus, first positive-to-ground impedances of each output branch bus are respectively calculated as the insulation impedance of the abnormal electrodes of each output branch bus.

3. The insulation impedance detection method of a DC system according to claim 1, characterized by, When the insulation impedance abnormality type is negative electrode insulation impedance abnormality, the voltage detection results and the leakage current detection results corresponding to each output branch bus comprise a first negative common point-to-ground voltage value and second leakage current values of each output branch bus when the balanced bridge is switched on and the imbalance bridges are all switched off; Correspondingly, the determination of the insulation impedance of the abnormal electrodes of each output branch bus according to the voltage detection results and the leakage current detection results corresponding to each output branch bus comprises: According to the first negative common point-to-ground voltage value and the second leakage current values of each output branch bus, first negative-to-ground impedances of each output branch bus are respectively calculated as the insulation impedance of the abnormal electrodes of each output branch bus.

4. The insulation impedance detection method of a DC system according to claim 1, characterized by, When the insulation impedance abnormality type is two-pole insulation impedance abnormality, the voltage detection results and the leakage current detection results corresponding to each output branch bus comprise a second positive common point-to-ground voltage value, a second negative common point-to-ground voltage value and third leakage current values of each output branch bus when the balanced bridge and one of the imbalance bridges are switched on, and a third positive common point-to-ground voltage value, a third negative common point-to-ground voltage value and fourth leakage current values of each output branch bus when the balanced bridge and the other imbalance bridge are switched on; the number of the imbalance bridges is at least two, and the imbalance bridges switched on twice are different imbalance bridges; Correspondingly, the determination of the insulation impedance of the abnormal electrodes of each output branch bus according to the voltage detection results and the leakage current detection results corresponding to each output branch bus comprises: According to the second positive electrode common point-to-ground voltage value, the second negative electrode common point-to-ground voltage value, the third leakage current value of each output branch bus, the third positive electrode common point-to-ground voltage value, the third negative electrode common point-to-ground voltage value, and the fourth leakage current value of each output branch bus, the second positive electrode-to-ground impedance and the second negative electrode-to-ground impedance of each output branch bus are calculated as the insulation impedance of the abnormal electrode of each output branch bus.

5. The insulation impedance detection method of a DC system according to claim 4, characterized by, The calculation formula of the second positive electrode-to-ground impedance of each output branch bus is: The calculation formula of the second negative electrode-to-ground impedance of each output branch bus is: wherein R o2i+ is the second positive pole-to-ground impedance of the i-th output branch bus; R o2i- is the second negative pole-to-ground impedance of the i-th output branch bus; V 2+ is the second positive pole common point-to-ground voltage value; V 2- is the second negative pole common point-to-ground voltage value; V 3+ is the third positive pole common point-to-ground voltage value; V 3- is the third negative pole common point-to-ground voltage value; I 3i is the third leakage current value of the i-th output branch bus; I 4i is the fourth leakage current value of the i-th output branch bus; 1≤i≤N, N is the number of output branch buses.

6. The insulation impedance detection method of a DC system according to claim 1, characterized by, The DC system further comprises a main bus with a positive electrode connected to the positive electrode common point and a negative electrode connected to the negative electrode common point. The insulation impedance detection method of the DC system further comprises: The insulation impedance detection circuit is multiplexed to detect the positive electrode insulation impedance of the main bus and the negative electrode insulation impedance of the main bus.

7. The insulation impedance detection method of a DC system according to claim 6, characterized by, The insulation impedance detection method of the DC system further comprises: According to the positive electrode insulation impedance of the main bus and the negative electrode insulation impedance of the main bus, the insulation impedance abnormal type is determined; Accordingly, the voltage detection result and the leakage current detection result corresponding to each output branch bus are obtained by controlling the switching of the balanced bridge and / or the unbalanced bridge in the balanced-unbalanced bridge detection circuit, comprising: Based on the insulation impedance abnormal type, the switching of the balanced bridge and / or the unbalanced bridge in the balanced-unbalanced bridge detection circuit is controlled, and the voltage detection result and the leakage current detection result corresponding to each output branch bus are obtained.

8. The method of claim 1 to 7, wherein The balanced-unbalanced bridge detection circuit comprises a balanced bridge, a first unbalanced bridge, and a second unbalanced bridge. The balanced bridge comprises a first resistor, a second resistor, and a first switch; the first resistor is connected between the positive electrode common point and the midpoint of the balanced bridge, the second resistor is connected between the midpoint of the balanced bridge and the negative electrode common point, and the midpoint of the balanced bridge is grounded through the first switch; when the first switch is closed, the balanced bridge is put into operation, and when the first switch is opened, the balanced bridge is cut out; the resistance values of the first resistor and the second resistor are equal; The first unbalanced bridge comprises a third resistor and a second switch; the third resistor is connected between the positive electrode common point and the midpoint of the first unbalanced bridge, and the midpoint of the first unbalanced bridge is grounded through the second switch; when the second switch is closed, the first unbalanced bridge is put into operation, and when the second switch is opened, the first unbalanced bridge is cut out; The second unbalanced bridge comprises a fourth resistor and a third switch, and the fourth resistor is connected between the midpoint of the second unbalanced bridge and the negative electrode common point; the midpoint of the second unbalanced bridge is grounded through the third switch; when the third switch is closed, the second unbalanced bridge is put into operation, and when the third switch is opened, the second unbalanced bridge is cut out.

9. The method of claim 1 to 7, wherein, The leakage current detection circuit comprises a first leakage current sampling device corresponding to each output branch bus; or, The leakage current detection circuit comprises a first leakage current sampling device corresponding to any N-1 output branch bus and a second leakage current sampling device for collecting leakage current between the positive common point and the negative common point; N is the number of output branch buses.

10. A direct current system, characterized by The DC system comprises a plurality of output branch buses, each of which has a positive electrode connected to the positive common point and a negative electrode connected to the negative common point, and a controller. The DC system is provided with an insulation impedance detection circuit, which comprises a balanced-imbalance bridge detection circuit connected between the positive common point and the negative common point and a leakage current detection circuit for obtaining the leakage current value of each output branch bus. The insulation impedance detection circuit is controlled by the controller, and the controller is used to perform the insulation impedance detection method of the DC system as claimed in any one of claims 1 to 9.

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