Charging pile insulation detection system based on unbalanced bridge

Abstract

The invention discloses a charging pile insulation detection system based on an unbalanced bridge, and relates to the technical field of charging pile insulation detection, and the system comprises an unbalanced bridge module which is used for generating a voltage difference signal changing along with insulation resistance through bridge arm circuit and switch control, and providing an original electric signal for detection; the voltage conditioning circuit module is used for receiving the original electric signal of the unbalanced bridge module, and outputting a standard signal adaptive to the data processing module through impedance matching, amplification and filtering processing; and the data processing and transmission module is used for acquiring an output signal of the voltage conditioning circuit module, calculating insulation resistance, judging a fault, transmitting a result and feeding back a working mode of the regulation bridge module. According to the invention, accurate measurement of the insulation resistance can be realized, the measurement error is smaller, and the strict requirement of charging pile insulation detection on high precision can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of charging pile insulation detection technology, and in particular to a charging pile insulation detection system based on an unbalanced bridge. Background Art

[0002] With the global advocacy of green travel and the vigorous promotion of new energy vehicles, the number of electric vehicles has exploded. As the "energy refueling stations" for electric vehicles, the importance of charging stations is self-evident. However, as charging stations become more frequently used and their service life increases, various safety hazards are gradually emerging. Cable wear and tear, aging of internal electronic components, coupled with complex and changing environmental factors such as humidity and high temperatures, can significantly compromise the insulation performance of charging station systems.

[0003] DC charging piles, in particular, offer high power and output voltage. Any insulation failure on the DC output side can be like a ticking time bomb. Insulation failures can cause internal short circuits, resulting in damage and high repair costs. In severe cases, they can also cause fires, posing a significant threat to the safety of surrounding personnel and facilities, and even potentially leading to electric shock accidents, with devastating consequences. Therefore, the ability to accurately and real-timely monitor the insulation status of charging piles has become crucial for ensuring a safe charging process.

[0004] Currently, the main technical approaches for charging pile insulation testing include the balanced bridge method and the unbalanced bridge method. While the balanced bridge method can detect insulation conditions to a certain extent, it has exposed many drawbacks in actual application. Its wiring is extremely complex, which not only increases the difficulty of installation and maintenance but also increases costs. Furthermore, this method cannot effectively detect leakage under high voltage conditions, which presents significant limitations when dealing with high-voltage equipment such as DC charging piles. Furthermore, when insulation problems occur simultaneously on both the positive and negative busbars, the balanced bridge method struggles to accurately measure their respective insulation resistances, making it impossible to accurately determine the location and severity of the fault. In contrast, the unbalanced bridge method, with its unique technical advantages, has gradually emerged in this field, attracting the attention of numerous researchers and companies, and becoming a popular area of ​​research and application. Summary of the Invention

[0005] Aiming at the many drawbacks exposed in actual applications of using a balanced bridge method to perform insulation detection on charging piles, the present invention provides a charging pile insulation detection system based on an unbalanced bridge.

[0006] The present invention provides a charging pile insulation detection system based on an unbalanced bridge, which solves the above technical problems by adopting the following technical solutions:

[0007] A charging pile insulation detection system based on an unbalanced bridge, which includes an unbalanced bridge module, a voltage conditioning circuit module, and a data processing and transmission module;

[0008] The unbalanced bridge module is used to generate a voltage difference signal that changes with the insulation resistance through the bridge arm circuit and switch control, providing the original electrical signal for detection;

[0009] The voltage conditioning circuit module is used to receive the original electrical signal from the unbalanced bridge module, and output the standard signal adapted to the data processing module through impedance matching, amplification, and filtering.

[0010] The data processing and transmission module is used to collect the output signal of the voltage conditioning circuit module, calculate the insulation resistance, judge the fault and transmit the result, and also provide feedback to adjust the working mode of the bridge module.

[0011] Optionally, the unbalanced bridge module is used as the signal generating source of the entire system, and its circuit structure includes voltage divider resistors R3 and R6, unbalanced bridge arm resistors R4 and R5, insulation resistors Rp and Rn, and control switches SW1, SW2 and SW3, wherein:

[0012] One end of the voltage divider resistor R3 is connected to the positive electrode DC+ of the DC power supply, and the other end is connected to node A; node A is respectively connected to one end of the unbalanced bridge arm resistor R4 and the static contact 2 of the control switch SW1;

[0013] The other end of the unbalanced bridge arm resistor R4 is connected to node B, which is connected to one end of the unbalanced bridge arm resistor R5. The other end of the unbalanced bridge arm resistor R5 is connected to node C, which is respectively connected to one end of the voltage divider resistor R6 and the static contact 2 of the control switch SW2. The other end of the voltage divider resistor R6 is connected to the negative electrode DC- of the DC power supply.

[0014] The movable contact 1 of the control switch SW1 is connected in parallel with the movable contact 1 of the control switch SW2 and then connected to the static contact 2 of the control switch SW3; the movable contact 1 of the control switch SW3 is connected to the protective ground PE;

[0015] One end of the insulation resistor Rp is connected to the positive pole of the DC power supply DC+, and the other end is connected to the protective ground PE; one end of the insulation resistor Rn is connected to the negative pole of the DC power supply DC-, and the other end is connected to the protective ground PE;

[0016] The data acquisition port of the single chip microcomputer is connected to the node B and the node C through the voltage conditioning circuit module, and is used to collect the voltage difference between the two ends of the unbalanced bridge arm resistor R5.

[0017] Further optionally, according to the detection requirements, by controlling the on-off combination of the control switches SW1, SW2, and SW3 of the unbalanced bridge module, a bridge circuit associated with the insulation resistance Rp or Rn is constructed;

[0018] When the insulation state of the DC side of the charging pile changes, the bridge balance is broken, and a voltage difference that changes with the insulation resistance value is generated across the unbalanced bridge arm resistor R5, forming the original detection electrical signal.

[0019] Further optionally, when the control switches SW1, SW2, and SW3 are all disconnected, the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are in a series relationship, and the total voltage U is the total voltage from the positive electrode DC+ of the DC power supply to the negative electrode DC- of the DC power supply, that is, the total voltage of the series circuit;

[0020] According to the voltage division theorem of series circuit, the voltage U51 across the unbalanced bridge arm resistor R5 is calculated based on the following formula:

[0021]

[0022] Wherein, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and U is obtained by measurement.

[0023] Further optionally, when the control switches SW1 and SW3 are closed and the control switch SW2 is open:

[0024] The voltage divider resistor R3 is connected in parallel with the insulation resistor Rp, and the equivalent resistance is recorded as R3 / / Rp=(R3·Rp) / (R3+Rp);

[0025] The unbalanced bridge arm resistors R4, R5, and R6 are connected in series first, and then in parallel with the insulation resistor Rn. The equivalent resistance is Rn / / (R4+R5+R6)=[(Rn·(R4+R5+R6)] / [(Rn+(R4+R5+R6)]);

[0026] Finally, a voltage divider structure is formed by connecting (R3 / / Rp) and (Rn / / (R4+R5+R6)) in series, where U is the total voltage from the positive DC power supply DC+ to the negative DC power supply DC-.

[0027] Let the voltage across Rn / / (R4+R5+R6) be Uu2, then the voltage across R3 / / Rp is U-Uu2;

[0028] According to the voltage division theorem of series circuit, we can get:

[0029]

[0030] According to the series branch voltage division theorem, the voltage U52 across the unbalanced bridge arm resistor R5 satisfies:

[0031]

[0032] Where, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and the values ​​of U and Uu2 are measured;

[0033] By changing the on-off states of the control switches SW1, SW3, and SW2, different resistor series-parallel voltage-dividing topologies are constructed. New voltage data is measured again to obtain new equations based on the voltage-dividing principle of the new topology. By combining multiple sets of equations and performing mathematical operations, the specific values ​​of the insulation resistances Rp and Rn are finally solved, thus achieving quantitative monitoring of the system insulation status.

[0034] Further optionally, when the control switches SW2 and SW3 are closed and the control switch SW1 is open:

[0035] The voltage divider resistor R3, the unbalanced bridge arm resistor R4, and the unbalanced bridge arm resistor R5 are first connected in series and then in parallel with the insulation resistor Rp. The equivalent resistance is recorded as (R3+R4+R5) / / Rp=[(R3+R4+R5)·Rp] / [(R3+R4+R5)+Rp];

[0036] The voltage divider resistor R6 is connected in parallel with the insulation resistor Rn, and the equivalent resistance is recorded as Rn / / R6=(Rn·R6) / (Rn+R6);

[0037] Finally, a voltage divider structure is formed with (R3+R4+R5) / / Rp and Rn / / R6 in series, where U is the total voltage from the positive DC+ pole of the DC power supply to the negative DC- pole of the DC power supply.

[0038] Let the voltage across Rn / / R6 be Uu3, then the voltage across (R3+R4+R5) / / Rp is U-Uu3;

[0039] According to the voltage division theorem of series circuit, we can get:

[0040]

[0041] According to the series branch voltage division theorem, the voltage U53 across the unbalanced bridge arm resistor R5 satisfies:

[0042]

[0043] Where, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and the values ​​of U and Uu3 are measured;

[0044] By changing the on-off states of the control switches SW1, SW3, and SW2, different resistor series-parallel voltage-dividing topologies are constructed. New voltage data is measured again to obtain new equations based on the voltage-dividing principle of the new topology. By combining multiple sets of equations and performing mathematical operations, the specific values ​​of the insulation resistances Rp and Rn are finally solved, thus achieving quantitative monitoring of the system insulation status.

[0045] Optionally, the voltage conditioning circuit module involved specifically performs the following operations:

[0046] Receive the original detection electrical signal output by the unbalanced bridge module, that is, the voltage difference;

[0047] The original voltage difference signal is processed in sequence through impedance matching, gain adjustment, filtering and level conversion, and finally outputs a standardized digital signal that meets the ADC input requirements of the microcontroller.

[0048] Optionally, the data processing and transmission module may specifically perform the following operations:

[0049] The conditioned digital signal is subjected to noise reduction processing, and a sliding average filtering algorithm is used to eliminate random fluctuations and extract the real and effective signal;

[0050] Based on the preset mathematical model and the current switch combination status, the actual resistance values ​​of the insulation resistance Rp and Rn are inferred through numerical calculation; the calculated results are compared with the multi-level thresholds in real time to determine the insulation status level;

[0051] The encapsulation processing result is a standard data frame, which is transmitted to the charging pile main control system through the industrial bus protocol or Ethernet interface; at the same time, the unbalanced bridge module is adjusted according to the insulation status feedback.

[0052] The present invention provides a charging pile insulation detection system based on an unbalanced bridge, which has the following beneficial effects compared with the prior art:

[0053] 1. The unbalanced bridge of the present invention, through its unique circuit structure, can independently measure the insulation resistance of the positive and negative busbars to ground. When the insulation resistance of the positive or negative busbar changes slightly, the voltage difference generated by the unbalanced bridge will be reflected with high sensitivity. Combined with the voltage conditioning circuit module and the data processing and transmission module, it can achieve accurate measurement of insulation resistance with smaller measurement errors, which can meet the stringent high-precision requirements of charging pile insulation testing.

[0054] 2. The unbalanced bridge circuit structure of the present invention is simple and compact, with strong anti-interference ability, and can operate stably in complex electromagnetic environments. At the same time, it has good adaptability to voltage fluctuations. Whether the charging pile is started, running or stopped, it can accurately detect the insulation resistance without being affected by system voltage changes, thus ensuring the reliability and stability of the test results.

[0055] 3. The unbalanced bridge of the present invention requires relatively few components and has a simple circuit structure, which not only reduces hardware costs but also simplifies installation and maintenance. In practical applications, fewer components means lower failure rates and more convenient troubleshooting. Maintenance personnel can locate and solve problems more quickly, reducing equipment downtime, lowering operation and maintenance costs, and improving the efficiency and economic benefits of charging piles.

[0056] 4. The unbalanced bridge of the present invention can monitor the dynamic changes of the insulation resistance of the charging pile in real time. During the charging process, the system can continuously collect the voltage signal output by the bridge. Once the insulation resistance is abnormal, it can quickly detect the change in voltage difference and issue an early warning. This real-time dynamic monitoring function enables operation and maintenance personnel to take measures in the early stage of insulation faults to avoid the expansion of faults and effectively ensure the safe operation of the charging pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Attachment Figure 1 It is a system architecture diagram of the present invention;

[0058] Attachment Figure 2 Schematic diagram of the specific circuit structure of the unbalanced bridge module in the present invention;

[0059] Attachment Figure 3 yes Figure 2 Schematic diagram of the equivalent circuit structure when the control switches SW1, SW2 and SW3 are all disconnected;

[0060] Attachment Figure 4 yes Figure 2 Schematic diagram of the equivalent circuit structure when the control switches SW1 and SW3 are closed and the control switch SW2 is open;

[0061] Attachment Figure 5 yes Figure 2 Schematic diagram of the equivalent circuit structure in which the control switches SW2 and SW3 are closed and the control switch SW1 is open. DETAILED DESCRIPTION

[0062] In order to make the technical solution, the technical problems solved and the technical effects of the present invention more clear, the technical solution of the present invention is clearly and completely described below in conjunction with specific embodiments.

[0063] The following specific examples illustrate the principles and implementation methods of the present invention in detail. These examples are only intended to help understand the core technical content of the present invention. Based on the specific embodiments of the present invention, any improvements and modifications made by those skilled in the art without departing from the principles of the present invention shall fall within the scope of patent protection of the present invention.

[0064] Example:

[0065] Combined with attachment Figure 1 This embodiment proposes a charging pile insulation detection system based on an unbalanced bridge, which includes an unbalanced bridge module, a voltage conditioning circuit module, and a data processing and transmission module.

[0066] The unbalanced bridge module is used to generate a voltage difference signal that changes with the insulation resistance through the bridge arm circuit and switch control, providing the original electrical signal for detection.

[0067] The voltage conditioning circuit module is used to receive the original electrical signal from the unbalanced bridge module, and output the standard signal adapted to the data processing module through impedance matching, amplification, and filtering.

[0068] The data processing and transmission module is used to collect the output signal of the voltage conditioning circuit module, calculate the insulation resistance, judge the fault and transmit the result, and also provide feedback to adjust the working mode of the bridge module.

[0069] In this embodiment, based on the original electrical signal provided by the unbalanced bridge module, the voltage conditioning circuit module specifically performs the following operations:

[0070] Receive the original detection electrical signal output by the unbalanced bridge module, that is, the voltage difference;

[0071] The original voltage difference signal is processed in sequence through impedance matching, gain adjustment, filtering and level conversion, and finally outputs a standardized digital signal that meets the ADC input requirements of the microcontroller.

[0072] The data processing and transmission modules involved specifically perform the following operations:

[0073] The conditioned digital signal is subjected to noise reduction processing, and a sliding average filtering algorithm is used to eliminate random fluctuations and extract the real and effective signal;

[0074] Based on a preset mathematical model and the current switch combination status, the actual resistance values ​​of the insulation resistance Rp and Rn are inferred through numerical calculation. The calculated results are compared with multi-level thresholds (such as warning thresholds and fault thresholds) in real time to determine the insulation status level.

[0075] The encapsulation processing result is a standard data frame, which is transmitted to the charging pile main control system through the industrial bus protocol (CAN / Modbus) or Ethernet interface; at the same time, the unbalanced bridge module is adjusted according to the insulation status feedback.

[0076] In this embodiment, combined with the Figure 2 The unbalanced bridge module serves as the signal generator for the entire system. Its circuit structure includes voltage divider resistors R3 and R6, unbalanced bridge arm resistors R4 and R5, insulation resistors Rp and Rn, and control switches SW1, SW2, and SW3.

[0077] One end of the voltage divider resistor R3 is connected to the positive electrode DC+ of the DC power supply, and the other end is connected to node A; node A is respectively connected to one end of the unbalanced bridge arm resistor R4 and the static contact 2 of the control switch SW1;

[0078] The other end of the unbalanced bridge arm resistor R4 is connected to node B, which is connected to one end of the unbalanced bridge arm resistor R5. The other end of the unbalanced bridge arm resistor R5 is connected to node C, which is respectively connected to one end of the voltage divider resistor R6 and the static contact 2 of the control switch SW2. The other end of the voltage divider resistor R6 is connected to the negative electrode DC- of the DC power supply.

[0079] The movable contact 1 of the control switch SW1 is connected in parallel with the movable contact 1 of the control switch SW2 and then connected to the static contact 2 of the control switch SW3; the movable contact 1 of the control switch SW3 is connected to the protective ground PE;

[0080] One end of the insulation resistor Rp is connected to the positive pole of the DC power supply DC+, and the other end is connected to the protective ground PE; one end of the insulation resistor Rn is connected to the negative pole of the DC power supply DC-, and the other end is connected to the protective ground PE;

[0081] The data acquisition port of the single chip microcomputer is connected to the node B and the node C through the voltage conditioning circuit module, and is used to collect the voltage difference between the two ends of the unbalanced bridge arm resistor R5.

[0082] Based on the above circuit, according to the detection requirements, by controlling the on-off combination of the control switches SW1, SW2, and SW3 of the unbalanced bridge module, a bridge circuit associated with the insulation resistance Rp or Rn is constructed;

[0083] When the insulation state of the DC side of the charging pile changes, the bridge balance is broken, and a voltage difference that changes with the insulation resistance value is generated across the unbalanced bridge arm resistor R5, forming the original detection electrical signal.

[0084] To change the on / off state of the control switches SW1, SW2, and SW3, perform the following operations:

[0085] 1. Combined with the Figure 3 , control switches SW1, SW2, and SW3 are all disconnected. At this time, the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are in series. The total voltage U is the total voltage from the positive electrode DC+ of the DC power supply to the negative electrode DC- of the DC power supply, that is, the total voltage of the series circuit;

[0086] According to the voltage division theorem of series circuit, the voltage U51 across the unbalanced bridge arm resistor R5 is calculated based on the following formula:

[0087]

[0088] Wherein, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and U is obtained by measurement.

[0089] 2. Combined with the attachment Figure 4 , control switches SW1 and SW3 are closed, and control switch SW2 is open:

[0090] The voltage divider resistor R3 is connected in parallel with the insulation resistor Rp, and the equivalent resistance is recorded as R3 / / Rp=(R3·Rp) / (R3+Rp);

[0091] The unbalanced bridge arm resistors R4, R5, and R6 are connected in series first, and then in parallel with the insulation resistor Rn. The equivalent resistance is Rn / / (R4+R5+R6)=[(Rn·(R4+R5+R6)] / [(Rn+(R4+R5+R6)]);

[0092] Finally, a voltage divider structure is formed by connecting (R3 / / Rp) and (Rn / / (R4+R5+R6)) in series, where U is the total voltage from the positive DC power supply DC+ to the negative DC power supply DC-.

[0093] Let the voltage across Rn / / (R4+R5+R6) be Uu2, then the voltage across R3 / / Rp is U-Uu2;

[0094] According to the voltage division theorem of series circuit, we can get:

[0095]

[0096] According to the series branch voltage division theorem, the voltage U52 across the unbalanced bridge arm resistor R5 satisfies:

[0097]

[0098] Wherein, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and the values ​​of U and Uu2 are obtained by measurement.

[0099] 3. Combined with the attachment Figure 5 , control switches SW2 and SW3 are closed, and control switch SW1 is open:

[0100] The voltage divider resistor R3, the unbalanced bridge arm resistor R4, and the unbalanced bridge arm resistor R5 are first connected in series and then in parallel with the insulation resistor Rp. The equivalent resistance is recorded as (R3+R4+R5) / / Rp=[(R3+R4+R5)·Rp] / [(R3+R4+R5)+Rp];

[0101] The voltage divider resistor R6 is connected in parallel with the insulation resistor Rn, and the equivalent resistance is recorded as Rn / / R6=(Rn·R6) / (Rn+R6);

[0102] Finally, a voltage divider structure is formed with (R3+R4+R5) / / Rp and Rn / / R6 in series, where U is the total voltage from the positive DC+ pole of the DC power supply to the negative DC- pole of the DC power supply.

[0103] Let the voltage across Rn / / R6 be Uu3, then the voltage across (R3+R4+R5) / / Rp is U-Uu3;

[0104] According to the voltage division theorem of series circuit, we can get:

[0105]

[0106] According to the series branch voltage division theorem, the voltage U53 across the unbalanced bridge arm resistor R5 satisfies:

[0107]

[0108] Where, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and the values ​​of U and Uu3 are measured;

[0109] Assumptions Substituting it into Formula 2 and Formula 3, we can obtain Formula 4 and Formula 5:

[0110]

[0111] Combining Formula 4 and Formula 5, we can get Rn:

[0112]

[0113] Substituting Rn into Formula 5 yields Rp:

[0114]

[0115] Perform steps 1, 2, and 3 above. By changing the on / off states of control switches SW1, SW2, and SW3, different resistor series-parallel voltage-divider topologies are constructed. Measure again to obtain new voltage data. Establish new equations based on the voltage-divider principle of the new topology. Combine multiple sets of equations and perform mathematical operations to ultimately calculate the specific values ​​of insulation resistances Rp and Rn, thus enabling quantitative monitoring of the system's insulation status.

[0116] It should be noted that the insulation detection system of this embodiment can monitor the insulation condition of the charging pile in real time and continuously during the entire charging process in a single-pile application scenario, and promptly detect and warn of potential insulation failure hazards. This not only effectively avoids charging interruptions and equipment damage caused by insulation problems, greatly improves user trust and satisfaction with the charging pile, but also extends the service life of the charging pile and reduces operating costs.

[0117] When the insulation detection system of this embodiment is applied to an intelligent group charging system, by real-time monitoring of the insulation status of each charging pile, the insulation detection system can achieve comprehensive and refined safety management of the entire charging network. Once an insulation fault occurs in a charging pile, the insulation detection system can quickly locate the problem pile and take corresponding measures in a timely manner, such as automatically cutting off the power supply to the faulty pile and notifying operation and maintenance personnel to carry out emergency repairs. This intelligent management model can significantly reduce the probability of large-scale system failures caused by insulation faults, improve the overall operational efficiency and reliability of charging facilities, and provide a solid guarantee for the stable operation of large-scale electric vehicle charging networks.

[0118] Of course, the application scope of the insulation detection system of this embodiment is not limited to the field of electric vehicle charging facilities. With its high precision and high reliability in insulation performance detection, it can also shine in many other fields with strict insulation requirements.

[0119] In industrial power systems, the stable operation of various high-voltage equipment is directly related to the continuity and safety of the entire production process. Insulation failures in high-voltage equipment can lead to production line shutdowns, equipment damage, and even serious accidents such as fires and explosions, resulting in significant economic losses. The insulation detection system of this embodiment monitors the insulation condition of high-voltage equipment in real time, identifying potential insulation defects in advance. This provides a powerful basis for preventive maintenance of equipment, effectively preventing production accidents caused by insulation failures and ensuring the safe and efficient operation of industrial production.

[0120] Rail transit power supply systems also have extremely high insulation performance requirements. The insulation condition of power supply lines directly affects the normal operation of trains and the safety of passengers. The insulation detection system of this embodiment can monitor rail transit power supply lines in real time, promptly detecting problems such as insulation aging and damage, ensuring the safe and reliable operation of power supply lines, improving the overall reliability and safety of rail transit systems, and safeguarding the travel of passengers.

[0121] In summary, the present invention's unbalanced bridge-based charging pile insulation detection system successfully overcomes many of the challenges inherent in existing charging pile insulation detection technology, providing a solid and reliable technical guarantee for the safe operation of charging piles. It exhibits broad application prospects in the field of electric vehicle charging facilities and other related fields with stringent insulation performance requirements. It is expected to become a key force in promoting technological advancement and improving safety standards in the industry, playing an irreplaceable and important role in protecting people's lives and property and promoting the healthy and sustainable development of related fields such as the new energy industry.

Claims

1. A charging pile insulation detection system based on an unbalanced bridge, characterized in that: It includes an unbalanced bridge module, a voltage conditioning circuit module, and a data processing and transmission module; The unbalanced bridge module is used to generate a voltage difference signal that changes with the insulation resistance through the bridge arm circuit and switch control, providing the original electrical signal for detection; The voltage conditioning circuit module is used to receive the original electrical signal from the unbalanced bridge module, and output the standard signal adapted to the data processing module through impedance matching, amplification, and filtering. The data processing and transmission module is used to collect the output signal of the voltage conditioning circuit module, calculate the insulation resistance, judge the fault and transmit the result, and also provide feedback to adjust the working mode of the bridge module.

2. The charging pile insulation detection system based on an unbalanced bridge according to claim 1 is characterized in that: The unbalanced bridge module serves as the signal generating source for the entire system. Its circuit structure includes voltage divider resistors R3 and R6, unbalanced bridge arm resistors R4 and R5, insulation resistors Rp and Rn, and control switches SW1, SW2, and SW3. One end of the voltage divider resistor R3 is connected to the positive electrode DC+ of the DC power supply, and the other end is connected to node A; node A is respectively connected to one end of the unbalanced bridge arm resistor R4 and the static contact 2 of the control switch SW1; The other end of the unbalanced bridge arm resistor R4 is connected to node B, which is connected to one end of the unbalanced bridge arm resistor R5. The other end of the unbalanced bridge arm resistor R5 is connected to node C, which is respectively connected to one end of the voltage divider resistor R6 and the static contact 2 of the control switch SW2. The other end of the voltage divider resistor R6 is connected to the negative electrode DC- of the DC power supply. The movable contact 1 of the control switch SW1 is connected in parallel with the movable contact 1 of the control switch SW2 and then connected to the static contact 2 of the control switch SW3; the movable contact 1 of the control switch SW3 is connected to the protective ground PE; One end of the insulation resistor Rp is connected to the positive pole of the DC power supply DC+, and the other end is connected to the protective ground PE; one end of the insulation resistor Rn is connected to the negative pole of the DC power supply DC-, and the other end is connected to the protective ground PE; The data acquisition port of the single chip microcomputer is connected to the node B and the node C through the voltage conditioning circuit module, and is used to collect the voltage difference between the two ends of the unbalanced bridge arm resistor R5.

3. The charging pile insulation detection system based on unbalanced bridge according to claim 2 is characterized in that: According to the detection requirements, by controlling the on-off combination of the control switches SW1, SW2, and SW3 of the unbalanced bridge module, a bridge circuit associated with the insulation resistance Rp or Rn is constructed; When the insulation state of the DC side of the charging pile changes, the balance of the bridge is broken, and a voltage difference that changes with the insulation resistance value is generated across the unbalanced bridge arm resistor R5, forming the original detection electrical signal.

4. The charging pile insulation detection system based on an unbalanced bridge according to claim 3 is characterized in that: When the control switches SW1, SW2, and SW3 are all off, the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are in series. The total voltage U is the total voltage from the positive terminal of the DC power supply DC+ to the negative terminal of the DC power supply DC-, that is, the total voltage of the series circuit. According to the voltage division theorem of series circuit, the voltage U51 across the unbalanced bridge arm resistor R5 is calculated based on the following formula: Wherein, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and U is obtained by measurement.

5. The charging pile insulation detection system based on unbalanced bridge according to claim 3 is characterized in that: When the control switches SW1 and SW3 are closed and the control switch SW2 is open: The voltage divider resistor R3 is connected in parallel with the insulation resistor Rp, and the equivalent resistance is recorded as R3 / / Rp=(R3·Rp) / (R3+Rp); The unbalanced bridge arm resistors R4, R5, and R6 are connected in series first, and then in parallel with the insulation resistor Rn. The equivalent resistance is Rn / / (R4+R5+R6)=[(Rn·(R4+R5+R6)] / [(Rn+(R4+R5+R6)]); Finally, a voltage divider structure is formed by connecting (R3 / / Rp) and (Rn / / (R4+R5+R6)) in series, where U is the total voltage from the positive DC power supply DC+ to the negative DC power supply DC-. Let the voltage across Rn / / (R4+R5+R6) be Uu2, then the voltage across R3 / / Rp is U-Uu2; According to the voltage division theorem of series circuit, we can get: According to the series branch voltage division theorem, the voltage U52 across the unbalanced bridge arm resistor R5 satisfies: Where, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and the values ​​of U and Uu2 are measured; By changing the on-off states of the control switches SW1, SW3, and SW2, different resistor series-parallel voltage-dividing topologies are constructed. New voltage data is measured again to obtain new equations based on the voltage-dividing principle of the new topology. By combining multiple sets of equations and performing mathematical operations, the specific values ​​of the insulation resistances Rp and Rn are finally solved, thus achieving quantitative monitoring of the system insulation status.

6. The charging pile insulation detection system based on unbalanced bridge according to claim 3, characterized in that: When the control switches SW2 and SW3 are closed and the control switch SW1 is open: The voltage divider resistor R3, the unbalanced bridge arm resistor R4, and the unbalanced bridge arm resistor R5 are first connected in series and then in parallel with the insulation resistor Rp. The equivalent resistance is recorded as (R3+R4+R5) / / Rp=[(R3+R4+R5)·Rp] / [(R3+R4+R5)+Rp]; The voltage divider resistor R6 is connected in parallel with the insulation resistor Rn, and the equivalent resistance is recorded as Rn / / R6=(Rn·R6) / (Rn+R6); Finally, a voltage divider structure is formed with (R3+R4+R5) / / Rp and Rn / / R6 in series, where U is the total voltage from the positive DC+ pole of the DC power supply to the negative DC- pole of the DC power supply. Let the voltage across Rn / / R6 be Uu3, then the voltage across (R3+R4+R5) / / Rp is U-Uu3; According to the voltage division theorem of series circuit, we can get: According to the series branch voltage division theorem, the voltage U53 across the unbalanced bridge arm resistor R5 satisfies: Where, the resistance values ​​of the voltage divider resistor R3, the unbalanced bridge arm resistor R4, the unbalanced bridge arm resistor R5, and the voltage divider resistor R6 are known, and the values ​​of U and Uu3 are measured; By changing the on-off states of the control switches SW1, SW3, and SW2, different resistor series-parallel voltage-dividing topologies are constructed. New voltage data is measured again to obtain new equations based on the voltage-dividing principle of the new topology. By combining multiple sets of equations and performing mathematical operations, the specific values ​​of the insulation resistances Rp and Rn are finally solved, thus achieving quantitative monitoring of the system insulation status.

7. The charging pile insulation detection system based on an unbalanced bridge according to claim 1, characterized in that: The voltage conditioning circuit module specifically performs the following operations: Receive the original detection electrical signal output by the unbalanced bridge module, that is, the voltage difference; The original voltage difference signal is processed in sequence through impedance matching, gain adjustment, filtering and level conversion, and finally outputs a standardized digital signal that meets the ADC input requirements of the microcontroller.

8. The charging pile insulation detection system based on unbalanced bridge according to claim 8, characterized in that: The data processing and transmission module specifically performs the following operations: The conditioned digital signal is subjected to noise reduction processing, and a sliding average filtering algorithm is used to eliminate random fluctuations and extract the real and effective signal; Based on the preset mathematical model and the current switch combination status, the actual resistance values ​​of the insulation resistance Rp and Rn are inferred through numerical calculation; the calculated results are compared with the multi-level thresholds in real time to determine the insulation status level; The encapsulation processing result is a standard data frame, which is transmitted to the charging pile main control system through the industrial bus protocol or Ethernet interface; at the same time, the unbalanced bridge module is adjusted according to the insulation status feedback.

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