Insulation resistance detection circuit of direct-current power source system and detection method

Abstract

The invention discloses an insulation resistance detection circuit of a direct-current power source system. The insulation resistance detection circuit comprises a first voltage dividing module, a second voltage dividing module, a detection module and a control module; the control module is used for sending different control signals to the first voltage dividing module and the second voltage dividing module, so that the first voltage dividing module and the second voltage dividing module can be in different voltage division states; the detection module is used for detecting and obtaining the voltage to earth of the positive end busbar of the direct-current power source system and the voltage to earth of the negative end busbar of the direct-current power source system when the first voltage dividing module and the second voltage dividing module are in different voltage division states; and the control module is used for obtaining the resistance value of the positive end insulation resistance to earth of the positive end busbar of the direct-current power source system and the resistance value of the negative end insulation resistance to earth of the negative end busbar of the direct-current power source system on the basis of the voltage to earth of the positive end busbar and the voltage to earth of the negative end busbar. The invention also discloses a detection method basedon the insulation resistance detection circuit of the direct-current power source system.

Description

technical field [0001] The invention relates to a direct current power supply system, in particular to an insulation resistance detection circuit and a detection method of the direct current power supply system. Background technique [0002] In recent years, with the rapid development of electric vehicles, high-voltage DC power systems such as charging piles related to electric vehicles have also achieved rapid development. In the charging pile system, the insulation characteristics of the charging pile system are very important. Therefore, accurate testing of the insulation resistance value of the high-voltage DC power supply system is the guarantee for the safety of the charging pile system. If the insulation test is not accurate, there will be great hidden dangers to personal safety. [0003] Existing DC insulation monitoring techniques include balanced bridge method, unbalanced bridge method and level signal injection method. figure 1 It is a schematic diagram of the ...

AI Technical Summary

Problems solved by technology

figure 1 It is a schematic diagram of the composition and structure of the balanced bridge method circuit. This circuit can measure the static DC voltage of the positive and negative busbars to the ground, so the capacitance of the busbar to the ground does not affect the measurement accuracy; at the same time, because it is not affected by the grounding capacitance, the detection speed fast; but when R p =R n When ≠∞, monitoring cannot be performed

figure 2 It is a schematic diagram of the composition and structure of the unbalanced bridge method circuit. This circuit can detect single-ended grounding, double-ended grounding, and balanced grounding. However, the positive and negative busbars need to be connected to the ground with resistances in the measurement, and the voltage of the positive and negative busbars to the ground changes.

Because it is easily affected by the capacitance of the busbar to ground, a certain delay is required each time a new resistor is connected to the circuit where the busbar is located to wait for the voltage of the busbar to ground to stabilize, and the detection speed is slower than that of the balanced bridge method

In addition, the calculation formula of the unbalanced bridge method is a two-dimensional equation, and the calculation results are not accurate

The low-frequency signal injection method can monitor the insulation resistance. Since high-voltage AC signals need to be injected into the high-voltage circuit, the additional AC signals will affect the power supply quality of the high-voltage DC power supply system, and the distributed capacitance of the system will directly affect the measured voltage value, resulting in measurement low precision

Images