A digital implementation-based insulation resistance real-time detection method

Abstract

The present application belongs to the technical field of digital switching power supply, and particularly relates to an insulation resistance real-time detection method based on digital implementation. The method comprises an insulation detection circuit, which comprises resistance strings, a first branch 5V power supply, a switch optocoupler Q1, switch tube strings G1 and G2, and corresponding driving resistors R6 and R7, and further comprises a second branch 48V power supply and VZ elements. The method controls the optocoupler switch through a single-chip microcomputer to obtain a sampling point 1 of the voltage of R5, and sampling points 2 and 3 of input positive P and input negative N, and cooperates with an algorithm to run. The method realizes the detection of insulation resistance by cooperating the low-voltage power supply with the low-voltage period, combining the switch control of the MOS tube by the switch of the optocoupler, and reducing the cost of the insulation resistance detection.

Description

Technical Field

[0001] This invention belongs to the field of digital switching power supply technology, specifically, it relates to a method for real-time detection of insulation resistance based on digital implementation. Background Technology

[0002] Insulation resistance is the most basic insulation indicator for electrical equipment and circuits. In new energy power supplies, insulation testing of fuel cell stacks and batteries is essential for operational safety. Insulation resistance values ​​are generally used to represent the insulation resistance between the positive and negative terminals of the battery and fuel cell stack to ground. Related technologies use insulation circuits or insulation testing instruments to test the insulation resistance of batteries. Insulation circuits, by closing and opening switches, can separately test the insulation resistance between the positive and negative terminals of the battery to ground. Insulation testing of batteries and fuel cell stacks in related technologies typically takes a long time, resulting in a longer battery power supply response time for electrical equipment. Testing instruments can generally only perform tests before equipment operation; real-time testing during equipment operation is not suitable for equipment requiring long-term stable operation, such as solar power conversion power supplies, pre-fuel power supplies, and vehicle power supplies. Summary of the Invention

[0003] In view of the above-mentioned problems in the existing technology, the purpose of this invention is to provide a digitally implemented real-time insulation resistance detection method to meet the insulation resistance detection requirements while reducing the cost of insulation resistance detection.

[0004] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0005] A digitally implemented real-time insulation resistance detection method includes an insulation detection circuit, which includes a first resistor R1 and a second resistor R2 connected in parallel. The other end of the first resistor R1 is connected to a positive input P, ​​and the other end of the second resistor R2 is connected to a negative input N.

[0006] The positive input P is simultaneously connected to Rspm and Rspn in series, and the other end of Rspn is grounded.

[0007] The input negative N is simultaneously connected to Rsnm and Rsnn in series, and the other end of Rsnn is grounded;

[0008] A third resistor R3 is connected to the connection point of the first resistor R1 and the second resistor R2, and the other end of the third resistor R3 is connected to a power supply V1; a fourth resistor R4 is also connected to the connection point of the first resistor R1 and the second resistor R2, and a fifth resistor R5 is connected in series with the fourth resistor R4.

[0009] The connection point between the positive input P and the first resistor R1 and the Rspm is simultaneously connected to a resistor Rp. The connection point between the negative input N and the second resistor R2 and the Rsnm is simultaneously connected to a resistor Rn. Rp and Rn are connected in series to form a PE point. The PE point is simultaneously connected to a first switch G1 and a second switch G2. The first switch G1 and the second switch G2 are complementary in their control. The PE point is also connected to the positive terminal of the power supply V2.

[0010] The first switch G1 and the second switch G2 are driven by optocoupler Q1, one end of which is grounded and the other end is connected to JY_AC;

[0011] When the optocoupler Q1 is turned on, the second switch G2 is turned on, and the PE is grounded;

[0012] When the optocoupler Q1 is disconnected, the first switching transistor G1 is turned on, and the PE is grounded through the power supply V2;

[0013] The method includes the following steps:

[0014] (1) The voltage at the connection point of the first resistor R1 and the second resistor R2, and the voltage of the positive input P and the negative input N relative to ground are obtained by the microcontroller calculation and processing.

[0015] (2) Using the timing control logic flow for insulation monitoring, in the first timing control, the JY_AC outputs a high level and the PE is grounded. At this time, the voltage Vo1 at the connection point of the first resistor R1 and the second resistor R2, the voltage Vp1 of the positive input P, ​​and the voltage Vn1 of the negative input N are stored.

[0016] (3) In the second timing control, the JY_AC output is low level, the PE is connected to the power supply V2, and the voltage Vo2 at the connection point of the first resistor R1 and the second resistor R2, the voltage Vp2 of the positive input P and the voltage Vn2 of the negative input N are stored again.

[0017] (4) Based on the voltage recorded twice, the KCL equations are combined to calculate the positive insulation resistance Rp and the negative insulation resistance Rn.

[0018] Furthermore, when the PE is grounded, the KCL equation for the PE point is:

[0019]

[0020] make

[0021] but

[0022] Furthermore, when the PE is connected to the power supply V2, the KCL equation for the PE point is:

[0023]

[0024]

[0025] make

[0026] but

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This method combines a low-voltage power supply with a low-voltage period, along with an optocoupler to control the switching of a MOSFET, to achieve insulation resistance detection and reduce the cost of insulation resistance detection. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the circuit structure of the insulation detection circuit described in this invention;

[0030] Figure 2 This is a schematic diagram of the equivalent circuit structure of each power supply at sampling point 1 in its voltage division.

[0031] Figure 3 This is a schematic diagram of the equivalent circuit structure when the first switch G1 is closed.

[0032] Figure 4 This is a schematic diagram of the equivalent circuit structure when the second switch G2 is closed.

[0033] Figure 5 This is a flowchart illustrating the steps of this method. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] The real-time insulation resistance detection method based on digital implementation described in this invention first includes a specially designed insulation detection circuit.

[0036] like Figure 1 As shown, the insulation detection circuit includes a first resistor R1 and a second resistor R2 connected in parallel. The other end of the first resistor R1 is connected to the positive input P, ​​and the other end of the second resistor R2 is connected to the negative input N.

[0037] The positive input P is connected to Rspm and Rspn in series, with the other end of Rspn grounded.

[0038] The negative N input is connected to Rsnm and Rsnn in series, with the other end of Rsnn grounded.

[0039] A third resistor R3 is connected to the junction of the first resistor R1 and the second resistor R2. The other end of the third resistor R3 is connected to a power supply V1 (a 5V power supply is used in this embodiment), and the negative terminal of the power supply V1 is grounded. A fourth resistor R4 is also connected to the junction of the first resistor R1 and the second resistor R2. A fifth resistor R5 is connected in series with the fourth resistor R4. The other end of the fifth resistor R5 is grounded.

[0040] The connection point between the positive input P and the first resistors R1 and Rspm is also connected to a resistor Rp. The connection point between the negative input N and the second resistors R2 and Rsnm is also connected to a resistor Rn. Rp and Rn are connected in series to obtain point PE. Point PE is also connected to the first switch G1 and the second switch G2. The first switch G1 and the second switch G2 are complementary in control. Point PE is also connected to the positive terminal of power supply V2 (48V power supply is used in this embodiment). The negative terminal of power supply V2 is grounded.

[0041] The first switch G1 and the second switch G2 are driven by optocoupler Q1, one end of which is grounded and the other end is connected to JY_AC. The circuit structure also includes a drive control circuit VZ, a sixth resistor R6 connected to the first switch G1, a seventh resistor R7 connected to the second switch G2, and an eighth resistor R8 connected to the optocoupler Q1.

[0042] When optocoupler Q1 is turned on, the second switch G2 is also turned on, and PE is grounded. Figure 3 The equivalent circuit structure diagram when the first switch G1 is closed is shown;

[0043] When optocoupler Q1 is disconnected, the first switching transistor G1 is turned on, and PE is grounded through power supply V2. Figure 4 The equivalent circuit structure diagram when the second switch G2 is closed is shown.

[0044] Then testing is performed, such as Figure 5 As shown, this detection method includes the following steps:

[0045] (1) The insulation resistance is calculated by the microcontroller. The microcontroller processing includes: ADC sampling and conversion processing of sampling point 1, sampling point 2 and sampling point 3, logic control process for insulation detection and algorithm processing for insulation calculation. Figure 1 The image shows the locations of three sampling points. Figure 2The diagram shows the equivalent circuit structure of each power supply in its voltage division for sampling point 1. Therefore, the voltage at each sampling point can be collected and converted using a microcontroller through a 20µs interrupt service, and the voltage at the connection point of the first resistor R1 and the second resistor R2, as well as the voltages of the positive input P and the negative input N relative to ground can be obtained.

[0046] (2) The microcontroller controls the logic flow of insulation monitoring with a 10ms timing. In the first 10ms timing, the JY_AC output is high and PE is grounded. At this time, the voltage Vo1 at the connection point of the first resistor R1 and the second resistor R2, the voltage Vp1 of the positive P input, and the voltage Vn1 of the negative N input are stored.

[0047] (3) During the second 10ms timing control, JY_AC outputs a low level, the PE is connected to the power supply V2, and the voltage Vo2 at the connection point of the first resistor R1 and the second resistor R2, the voltage Vp2 of the positive input P and the voltage Vn2 of the negative input N are stored again.

[0048] (4) Based on the voltage recorded twice, the KCL equations are combined to calculate the positive insulation resistance Rp and the negative insulation resistance Rn.

[0049] When the PE is grounded, the KCL equation for the PE point is:

[0050]

[0051] make

[0052] but

[0053] When PE is connected to power supply V2, the KCL equation for point PE is:

[0054]

[0055] make

[0056] but

Claims

1. A method for real-time detection of insulation resistance based on digital implementation, characterized in that, The method includes an insulation detection circuit, which includes a first resistor R1 and a second resistor R2 connected in parallel. The other end of the first resistor R1 is connected to a positive input P, ​​and the other end of the second resistor R2 is connected to a negative input N. The input positive P is simultaneously connected to resistors Rspm and Rspn in series, and the other end of resistor Rspn is grounded. The input negative N is simultaneously connected to resistors Rsnm and Rsnn in series, and the other end of resistor Rsnn is grounded. A third resistor R3 is connected to the connection point of the first resistor R1 and the second resistor R2, and the other end of the third resistor R3 is connected to a power supply V1; a fourth resistor R4 is also connected to the connection point of the first resistor R1 and the second resistor R2, and a fifth resistor R5 is connected in series with the fourth resistor R4. The connection point between the positive input P and the first resistor R1 and the resistor Rspm is simultaneously connected to a resistor Rp. The connection point between the negative input N and the second resistor R2 and the resistor Rsnm is simultaneously connected to a resistor Rn. The resistor Rp and the resistor Rn are connected to the PE point. The PE point is simultaneously connected to the first switch G1 and the second switch G2. The first switch G1 and the second switch G2 are complementary in control. The PE point is connected to the positive terminal of the power supply V2 through the first switch G1. The first switch G1 and the second switch G2 are driven by optocoupler Q1, one end of which is grounded and the other end is connected to JY_AC; When the optocoupler Q1 is turned on, the second switch G2 is turned on, and the PE is grounded; When the optocoupler Q1 is disconnected, the first switching transistor G1 is turned on, and the PE is grounded through the power supply V2; The method includes the following steps: (1) The voltage at the connection point of the first resistor R1 and the second resistor R2, and the voltage of the positive input P and the negative input N to ground are obtained by the microcontroller calculation and processing. (2) Using the timing control logic flow for insulation monitoring, the JY_AC outputs a high level in the first timing control, and the PE is grounded. At this time, the voltage Vo1 at the connection point of the first resistor R1 and the second resistor R2, the voltage Vp1 of the positive input P, ​​and the voltage Vn1 of the negative input N are stored. (3) In the second timing control, the JY_AC output is low level, the PE is connected to the power supply V2, and the voltage Vo2 at the connection point of the first resistor R1 and the second resistor R2, the voltage Vp2 of the positive input P and the voltage Vn2 of the negative input N are stored again. (4) Based on the voltages stored in the two records, the KCL equations are combined to calculate the positive insulation resistance Rp and the negative insulation resistance Rn.

2. The real-time insulation resistance detection method based on digital implementation according to claim 1, characterized in that, When the PE is grounded, the KCL equation for the PE point is: ; ； make ; but .

3. The real-time insulation resistance detection method based on digital implementation according to claim 1, characterized in that, When the PE is connected to the power supply V2, the KCL equation for the PE point is: ； ； make ; but .

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