Diagnosis circuit and diagnosis method for ground fault of insulation equipment

Abstract

The application provides a diagnosis circuit and diagnosis method for ground wire fault of insulation equipment. The diagnosis circuit comprises an insulation detection circuit and an equivalent circuit. The first end and the second end of the insulation monitoring circuit and the first end and the second end of the equivalent circuit are connected to the positive pole and the negative pole of a battery pack respectively. The middle end of the insulation detection circuit and the middle end of the equivalent circuit are connected to the ground. The capacitor voltage in the equivalent circuit is detected by adjusting the switch state in the insulation detection circuit. Whether the ground wire is faulty is judged according to the detected capacitor voltage. The application can simply detect the ground wire fault and ensure safe and reliable operation of the battery system.

Description

Technical Field

[0001] This invention relates to the field of battery charging and discharging, and in particular to a diagnostic circuit and method for grounding wire faults in insulating equipment. Background Technology

[0002] With the development of the new energy industry, battery systems have been widely used in automobiles and energy storage. To prevent electric shock from system voltage, the system typically provides passive insulation protection as well as active real-time insulation resistance monitoring. When insulation ages and fails, the insulation detection function can provide early warning and disconnect the battery's high-voltage circuit.

[0003] Existing insulation testing equipment generally employs the balanced bridge testing method recommended by national standards. This method calculates the equivalent insulation resistance value by measuring the voltage change between the DC bus and chassis ground, which is achieved by altering the resistance between the DC bus and chassis ground. This equipment requires connection to three wire bundles: the positive and negative DC bus, and the chassis ground wire. However, diagnosing faults in the chassis ground wire connection is particularly difficult. When it is disconnected, the insulation resistance value collected by the equipment is infinite, making it difficult to distinguish from a system with good insulation. This situation leads to the failure of the insulation detection function and the inability to issue early warnings. Furthermore, traditional insulation testing equipment primarily considers the accuracy and speed of insulation resistance monitoring, lacking support for diagnosing the inherent functions of the insulation circuit itself, especially ground wire connection faults. Summary of the Invention

[0004] The purpose of this invention is to provide a diagnostic circuit and method that can effectively monitor grounding wire faults in insulated equipment, thereby solving the problem that it is difficult to diagnose connection faults of chassis grounding wires in the prior art.

[0005] To achieve the above objectives, the present invention provides a diagnostic circuit for grounding wire faults in insulating equipment, comprising an insulation detection circuit and an equivalent circuit. The first and second terminals of the insulation detection circuit and the first and second terminals of the equivalent circuit are respectively connected to the positive and negative terminals of a battery pack. The insulation detection circuit and the equivalent circuit are grounded after being connected. The capacitor voltage in the equivalent circuit is detected by adjusting the switch state in the insulation detection circuit, and the grounding wire fault is determined based on the detected capacitor voltage.

[0006] Optionally, the equivalent circuit includes a first capacitor and a second capacitor, with a first terminal of the first capacitor connected to the positive terminal of the battery pack, a second terminal of the first capacitor connected to the first terminal of the second capacitor, and a second terminal of the second capacitor connected to the negative terminal of the battery pack; the connection point between the first capacitor and the second capacitor is the middle of the equivalent circuit.

[0007] Optionally, the insulation detection circuit includes a first series circuit and a second series circuit. The first series circuit includes a first switch and a resistor; the second series circuit includes a second switch and a resistor. The first terminal of the first series circuit is connected to the positive terminal of the battery pack, and the second series circuit is connected to the negative terminal of the battery pack. The first series circuit and the second series circuit are connected, and the connection terminal of the first series circuit and the second series circuit is the middle terminal of the insulation detection circuit.

[0008] Optionally, when the first switch is turned on, the insulation detection circuit detects the voltage on the first capacitor; when the second switch is turned on, the insulation detection circuit detects the voltage on the second capacitor; if both the voltage of the first capacitor and the voltage of the second capacitor are less than a first threshold, it indicates a grounding wire fault.

[0009] This invention also provides a method for diagnosing grounding wire faults in insulating equipment. The first and second terminals of the insulation monitoring circuit and the first and second terminals of the equivalent circuit are respectively connected to the positive and negative terminals of the battery pack. The insulation detection circuit and the equivalent circuit are connected and then grounded. The capacitor voltage in the equivalent circuit is detected by adjusting the switch state in the insulation detection circuit, and the grounding wire fault is determined based on the detected capacitor voltage.

[0010] Compared with the prior art, the present invention has the following advantages: The present invention indirectly diagnoses grounding harness faults by sampling the voltage changes across the first and second capacitors in a short time through switching the first switch and the second switch, thereby determining whether the first and second capacitors are connected to the insulation monitoring circuit, and ensuring the reliable and safe operation of the insulation monitoring equipment. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the diagnostic circuit for grounding wire faults in the insulating equipment of the present invention. Detailed Implementation

[0012] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention.

[0013] To provide the public with a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the invention, but those skilled in the art can fully understand the invention without these details.

[0014] The invention is described in more detail below by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0015] Figure 1This diagram illustrates the diagnostic circuit principle for grounding wire faults in the insulation equipment of the present invention. It includes an insulation detection device and an equivalent circuit. The equivalent circuit includes a first capacitor Y1, a second capacitor Y2, and resistors R01 and R02. The first capacitor Y1 and the second capacitor Y2 are parasitic capacitances of the high-voltage system, and the resistors R01 and R02 are the equivalent resistances of the battery insulation protection. The insulation detection device detects the equivalent resistance of the insulation protection while simultaneously detecting whether the grounding wire of the insulation detection device is faulty. The insulation detection circuit includes a first series circuit, a second series circuit, and a sampling circuit. A first switch S1 and a first resistor R1 are connected in series to form the first series circuit, and a second switch S2 and a second resistor R2 are connected in series to form the second series circuit. The first terminal of the first series circuit is connected to the positive terminal of the battery pack, and its second terminal is connected to the first terminal of the second series circuit. The second terminal of the second series circuit is connected to the negative terminal of the battery pack. Switch S3 in the diagram illustrates connecting the insulation detection circuit to the chassis ground. A closed S3 indicates a reliable connection, while an open S3 indicates a grounding wire harness fault. When the grounding wire harness is faulty, the insulation detection circuit may mistakenly assume that the external insulation impedance is infinite, thus misjudging that the system's insulation protection is in good condition. When switch S3 is open, the parasitic capacitance also cannot be connected to the insulation monitoring circuit. The diagnostic steps for grounding wire faults in insulation equipment are as follows:

[0016] Step 1: Disconnect switches S1 and S2;

[0017] Step 2: Close switch S1. If S3 closes normally, the voltage of the first capacitor Y1 will be collected. Since the voltage across the capacitor cannot change abruptly, the voltage Va collected in a short time will not be less than the first threshold. The first threshold is usually set to 10% of the total voltage.

[0018] Step 3: Open switch S1 and close switch S2. Similarly, the voltage of the second capacitor Y2 is collected. Since the voltage across the capacitor cannot change abruptly, the voltage Va collected in a short time is not less than the first threshold. The first threshold is usually set to 10% of the total voltage.

[0019] If the voltages of the first and second capacitors collected in steps two and three are both less than the first threshold, it indicates that the parasitic capacitor is not connected to the insulation monitoring circuit, and switch S3 fails to close properly, i.e., the grounding harness is faulty.

[0020] Although the embodiments are described and illustrated separately above, some common technologies are involved. Those skilled in the art can replace and integrate them between the embodiments. If there is any content not explicitly described in one embodiment, then another embodiment that is described can be referred to.

[0021] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A diagnostic circuit for grounding wire faults in insulating equipment, characterized in that: It includes an insulation detection circuit and an equivalent circuit. The first and second terminals of the insulation detection circuit and the first and second terminals of the equivalent circuit are respectively connected to the positive and negative terminals of the battery pack. The insulation detection circuit and the equivalent circuit are grounded after being connected. The capacitor voltage in the equivalent circuit is detected by adjusting the switch state in the insulation detection circuit, and the grounding wire is judged as faulty based on the detected capacitor voltage. The equivalent circuit includes a first capacitor and a second capacitor. The first terminal of the first capacitor is connected to the positive terminal of the battery pack, the second terminal of the first capacitor is connected to the first terminal of the second capacitor, and the second terminal of the second capacitor is connected to the negative terminal of the battery pack. The connection point between the first capacitor and the second capacitor is the middle of the equivalent circuit. The insulation detection circuit includes a first series circuit and a second series circuit. The first series circuit includes a first switch and a resistor. The second series circuit includes a second switch and a resistor. The first terminal of the first series circuit is connected to the positive terminal of the battery pack, and the second series circuit is connected to the negative terminal of the battery pack. The first series circuit and the second series circuit are connected, and the connection terminal of the first series circuit and the second series circuit is the middle terminal of the insulation detection circuit. When the first switch is turned on, the insulation detection circuit detects the voltage on the first capacitor; when the second switch is turned on, the insulation detection circuit detects the voltage on the second capacitor; if both the voltage of the first capacitor and the voltage of the second capacitor are less than a first threshold, it indicates a grounding fault; the first threshold is 10% of the total voltage of the battery pack.

2. A method for diagnosing grounding wire faults in insulating equipment, characterized in that: The first and second terminals of the insulation monitoring circuit and the first and second terminals of the equivalent circuit are respectively connected to the positive and negative terminals of the battery pack; the insulation detection circuit and the equivalent circuit are grounded after being connected; the capacitor voltage in the equivalent circuit is detected by adjusting the switch state in the insulation detection circuit, and the grounding wire is judged as faulty based on the detected capacitor voltage; The equivalent circuit includes a first capacitor and a second capacitor. The first terminal of the first capacitor is connected to the positive terminal of the battery pack, the second terminal of the first capacitor is connected to the first terminal of the second capacitor, and the second terminal of the second capacitor is connected to the negative terminal of the battery pack. The connection point between the first capacitor and the second capacitor is the middle of the equivalent circuit. The insulation detection circuit includes a first series circuit and a second series circuit. The first series circuit includes a first switch and a resistor. The second series circuit includes a second switch and a resistor. The first terminal of the first series circuit is connected to the positive terminal of the battery pack, and the second series circuit is connected to the negative terminal of the battery pack. The first series circuit and the second series circuit are connected, and the connection terminal of the first series circuit and the second series circuit is the middle terminal of the insulation detection circuit. When the first switch is turned on, the insulation detection circuit detects the voltage on the first capacitor; when the second switch is turned on, the insulation detection circuit detects the voltage on the second capacitor; if both the voltage of the first capacitor and the voltage of the second capacitor are less than a first threshold, it indicates a grounding fault; the first threshold is 10% of the total voltage of the battery pack.

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