Insulation detection device and method

Abstract

The present invention relates to an insulation detection device and method. The insulation detection device includes: a detection circuit, a resistor R1 and a resistor R2 are connected in series, one end of the series circuit is connected to the positive pole of the DC bus, and the other end is connected to the negative pole of the DC bus; after the resistor R3 and the switch S1 are connected in series, they are connected in parallel with the resistor R1; and the connection point of the resistor R1 and the resistor R2 is grounded through the switch S2; a positive voltage acquisition circuit, including an operational amplifier A1 and a first filter branch; the input end of the operational amplifier A1 is connected to the positive pole of the DC bus, and the output end is connected to the positive sampling point of the charging main control module through the first filter branch; a negative voltage acquisition circuit, including an operational amplifier A2 and a second filter branch; the input end of the operational amplifier A2 is connected to the negative pole of the DC bus, and the output end is connected to the negative sampling point of the charging main control module through the second filter branch. The present invention can effectively prevent strong electromagnetic interference, improve the accuracy of DC bus voltage acquisition, and thus improve the accuracy of insulation detection.

Description

Technical Field

[0001] The invention relates to an insulation detection device and method, belonging to the technical field of insulation detection. Background Art

[0002] A DC charger is a device designed for charging electric vehicle batteries. It uses a DC charging mode to charge the power battery assembly of an electric vehicle. DC chargers have the advantages of fast charging speed and high reliability, and are gaining more and more attention in the market.

[0003] However, since DC chargers are generally installed outdoors, they are easily impacted, rained, and other factors that may cause cable damage, water ingress or moisture in the equipment, which may reduce the insulation performance of the DC charger. When the DC side insulation is poor, it may cause equipment damage, fire, electric shock, and other adverse faults. Therefore, insulation testing is particularly important.

[0004] Insulation detection is to calculate the insulation resistance of the positive and negative output terminals of the DC side to the ground. According to the relevant provisions of "GB_T 18487.1-2015 Electric Vehicle Charging System Part 1: General Requirements", when the insulation resistance is greater than 500Ω / V, it is considered safe. When it is 100Ω / V<insulation resistance≤500Ω / V, an insulation abnormality alarm should be issued, but charging can still be performed normally. When the insulation resistance is ≤100Ω / V, it is considered an insulation failure and charging should be stopped.

[0005] In the prior art, the insulation detection of DC chargers generally adopts the unbalanced bridge method. However, since the charger is located in a strong electromagnetic interference environment, the circuit using only the unbalanced bridge method is easily affected by electromagnetic interference, resulting in low insulation detection accuracy or even errors. In addition, the implementation process of the charger insulation detection device requires a matching detection method to ensure the accuracy of the insulation detection process. Summary of the invention

[0006] The purpose of the present application is to provide an insulation detection device and method to solve the problem of low accuracy of existing insulation detection.

[0007] To achieve the above objectives, the present application proposes a technical solution for an insulation detection device, comprising:

[0008] The detection circuit includes a resistor R1, a resistor R2, a resistor R3, a switch S1 and a switch S2. The resistor R1 and the resistor R2 are connected in series, one end of the series circuit is connected to the positive electrode of the DC bus, and the other end is connected to the negative electrode of the DC bus; the resistor R3 is connected in series with the switch S1 and then connected in parallel with the resistor R1; and the connection point between the resistor R1 and the resistor R2 is grounded through the switch S2;

[0009] The positive voltage acquisition circuit includes an operational amplifier A1 and a first filter branch; the input end of the operational amplifier A1 is connected to the positive pole of the DC bus, and the output end is connected to the positive sampling point of the charging main control module through the first filter branch;

[0010] The negative electrode voltage acquisition circuit includes an operational amplifier A2 and a second filter branch; the input end of the operational amplifier A2 is connected to the negative electrode of the DC bus, and the output end is connected to the negative electrode sampling point of the charging main control module through the second filter branch.

[0011] The beneficial effect of the technical solution of the insulation detection device of the present invention is that the present invention can effectively prevent strong electromagnetic interference by setting a filter circuit in the voltage acquisition circuit, improve the accuracy of DC bus voltage acquisition, and further improve the accuracy of insulation detection.

[0012] Furthermore, in order to improve the accuracy of collecting the DC bus positive electrode voltage, the positive electrode sampling point is also connected to the first reference voltage via a resistor R9.

[0013] Furthermore, in order to improve the accuracy of collecting the negative pole voltage of the DC bus, the negative pole sampling point is further connected to a second reference voltage via a resistor R15.

[0014] Furthermore, the first filtering branch includes a resistor R8 and a grounding capacitor C1 connected in series.

[0015] Furthermore, the second filtering branch includes a resistor R14 and a grounding capacitor C3 connected in series.

[0016] In addition, the present application proposes a technical solution of an insulation detection method using the above insulation detection device, comprising the following steps:

[0017] 1) Control switch S2 to close and collect the voltage at the positive sampling point And the voltage at the negative sampling point

[0018] 2) Control switch S2 and switch S1 to close and collect the voltage at the positive sampling point And the voltage at the negative sampling point

[0019] 3) According to Calculate the voltage V at the positive pole of the DC bus when switch S2 is closed. +1 ;according to Calculate the voltage V at the negative pole of the DC bus when switch S2 is closed. -1 ;according to Calculate the voltage V at the positive pole of the DC bus when switches S2 and S1 are closed. +2 ;according to Calculate the voltage V at the negative pole of the DC bus when switches S2 and S1 are closed.-2 ;

[0020] 4) According to V +1 、V -1 、V +2 、V -2 The insulation resistance R+ of the DC bus positive pole to ground and the insulation resistance R- of the DC bus negative pole to ground are calculated. The calculation process is as follows:

[0021]

[0022] 5) Determine the size of the insulation resistance R+ and the insulation resistance R- to complete the insulation test.

[0023] The technical solution of the insulation detection method of the present invention has the beneficial effect that: since a filtering circuit is provided in the voltage acquisition circuit of the insulation detection device, after the charging main control module samples the positive sampling point and the negative sampling point, the positive and negative voltages of the DC bus are calculated in combination with the filtering circuit. The calculation result is the result after effectively preventing strong electromagnetic interference, thereby improving the accuracy of DC bus voltage acquisition and further improving the accuracy of insulation detection.

[0024] Furthermore, in order to improve the accuracy of DC bus positive voltage acquisition, the positive sampling point is also connected to the first reference voltage through a resistor R9. +1 and V +2 The resistor R9, the first reference voltage, and the equivalent resistor Rx of the charging main control module collection pin are also combined.

[0025] Furthermore, in order to improve the accuracy of DC bus negative pole voltage acquisition, the negative pole sampling point is also connected to a second reference voltage through a resistor R15. The calculation of V in step 3) is -1 and V -2 The resistor R15, the second reference voltage and the equivalent resistor Rx of the charging main control module collection pin are also combined.

[0026] Furthermore, in order to expand the scope of insulation detection so that the insulation detection can directly and completely reach the vehicle-end battery without leaving any blind spots, before controlling the switch S2 to close, it also includes the step of controlling the positive DC contactor K1 and the negative DC contactor K2 to close.

[0027] Furthermore, in order to avoid the impact on the vehicle battery after closing the positive DC contactor K1 and the negative DC contactor K2, before controlling the closing of the positive DC contactor K1 and the negative DC contactor K2, the step of detecting the internal and external voltages of the positive DC contactor K1 and the negative DC contactor K2 is also included. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1It is a charging circuit schematic diagram of the DC charger of the present invention;

[0029] Figure 2 It is the main circuit diagram of the insulation detection device of the present invention;

[0030] Figure 3 It is a circuit diagram of a positive voltage acquisition circuit of an insulation detection device of the present invention;

[0031] Figure 4 It is a circuit diagram of a negative voltage acquisition circuit of an insulation detection device of the present invention;

[0032] Figure 5 It is a flow chart of the insulation detection method of the present invention. DETAILED DESCRIPTION

[0033] Insulation detection device embodiment:

[0034] The insulation detection device of this embodiment is installed in the DC charger to perform insulation detection on the DC charger. Figure 1 As shown, the DC charger includes a low-voltage DC power supply, a charging main control module, a power control module, a charging module, a billing control unit, and an insulation detection device.

[0035] Among them, the low-voltage DC power supply is a DC12V power supply, which is connected to the charging main control module, the power control module, and the billing control unit for power supply, and is used to provide low-voltage power supply for the charging main control module, the power control module, and the billing control unit.

[0036] The charging main control module is the core component of the DC charger. The charging main control module is communicated with the billing control unit and the power control module. The charging main control module is also communicated with the vehicle controller through the CAN communication line (S+, S-). The control end of the charging main control module is connected to the electronic lock to realize the control of the electronic lock. The power output end of the charging main control module and the power supply line (A+, A-) of the vehicle controller are connected with low-voltage auxiliary power contactors K3 and K4 to realize the low-voltage power supply of the charging main control module to the vehicle controller. The charging main control module is used to control the entire charging process.

[0037] The power control module is in communication connection with the charging module and is used to receive instructions from the charging main control module to control the power output of the charging module.

[0038] The AC side of the charging module is connected to a 380V three-phase AC power supply, and the output end of the DC side of the charging module is connected to the DC bus positive branch DC+ and the DC bus negative branch DC-. The output ends of the DC bus positive branch DC+ and the DC bus negative branch DC- are used to connect the battery pack through the electric vehicle charging circuit contactors K5 and K6 to charge the battery pack (on-board battery); a discharge branch is set between the DC bus positive branch DC+ and the DC bus negative branch DC- to discharge A discharge branch contactor K7 is provided in series on the branch to control the on and off of the discharge branch; the DC bus positive branch DC+ is also provided with a fuse FU, a shunt RSX, and a positive DC contactor K1, and the DC bus negative branch DC- is provided with a shunt RS and a negative DC contactor K2. An insulation detection device is provided between the shunt RSX and the output end of the shunt RS to detect the insulation resistance R+ of the DC bus positive pole to the ground, and the insulation resistance R- of the DC bus negative pole to the ground.

[0039] Insulation testing equipment includes Figure 2 The detection circuit shown in Figure 3 The positive voltage collection circuit shown in FIG. Figure 4 The negative voltage collection circuit shown.

[0040] The detection circuit is an unbalanced bridge circuit, including resistors R1, R2, R3, switches S1 and S2. Resistors R1 and R2 are connected in series, one end V+ of the series circuit is connected to the positive pole of the DC bus, and the other end V- is connected to the negative pole of the DC bus; after resistor R3 and switch S1 are connected in series, they are connected in parallel with resistor R1; and the connection point of resistor R1 and resistor R2 is grounded through switch S2. The resistance values ​​of resistors R1, R2 and R3 are the same, and switches S1 and S2 are both contactors.

[0041] The positive voltage acquisition circuit is used to obtain the voltage of V+, including resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, operational amplifier A1, capacitor C1, and voltage module. The in-phase input terminal of operational amplifier A1 is connected to the positive pole of the DC bus through resistor R5, and the in-phase input terminal is grounded through resistor R7; the inverting input terminal of operational amplifier A1 is grounded through resistor R4; resistor R6 is set between the output terminal and the inverting input terminal of operational amplifier A1; the first filter branch composed of the series resistor R8 and the grounded capacitor C1; the output terminal of operational amplifier A1 is connected to the positive sampling point of the charging main control module through the first filter branch; and the positive sampling point is also connected to the reference voltage Vref (first reference voltage) through resistor R9, and the reference voltage is provided by the voltage module.

[0042] The negative voltage acquisition circuit is used to obtain the voltage of V-, including resistor R10, resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, operational amplifier A2, capacitor C3, and voltage module. The inverting input terminal of operational amplifier A2 is connected to the negative pole of the DC bus through resistor R10; the non-inverting input terminal of operational amplifier A2 is grounded through resistor R11, and resistor R11 is connected in parallel with resistor R13; resistor R12 is set between the output terminal and the inverting input terminal of operational amplifier A2; a second filter branch is formed by a series resistor R14 and a grounded capacitor C3; the output terminal of operational amplifier A2 is connected to the negative sampling point of the charging main control module through the second filter branch; and the negative sampling point is also connected to the reference voltage Vref (second reference voltage) through resistor R15, and the reference voltage is provided by the voltage module, and the first reference voltage and the second reference voltage are the same.

[0043] In the positive voltage acquisition circuit and the negative voltage acquisition circuit, the resistance values ​​of resistors R4, R5, R10 and R11 are the same; the resistance values ​​of resistors R6, R7, R12 and R13 are the same; the resistance values ​​of resistors R8 and R14 are the same; the resistance values ​​of resistors R9 and R15 are the same, and the capacitance values ​​of capacitors C1 and C3 are the same.

[0044] The insulation detection method of the charging main control module is: control the on and off of switch S1 and switch S2, calculate the voltage of V+ and V- through the voltage of the positive sampling point Vx+ and the voltage of the negative sampling point Vx-, and then calculate the insulation resistance R+ and insulation resistance R-.

[0045] According to the detection circuit, when the switch S2 is closed, the following equation is satisfied:

[0046]

[0047] Where: V +1 is the voltage at point V+ when switch S2 is closed; V -1 is the voltage at point V- when switch S2 is closed.

[0048] With switch S1 and switch S2 closed, the following equation is satisfied:

[0049]

[0050] Where: V +2 is the voltage at point V+ when switches S1 and S2 are closed; V -2 is the voltage at point V- when switches S1 and S2 are closed.

[0051] After getting V +1 、V -1 、V+2 、V -2 Then, the insulation resistance R+ and insulation resistance R- can be calculated by combining the above formula, V +1 、V -1 、V +2 、V -2 The calculation formula is as follows:

[0052]

[0053]

[0054]

[0055]

[0056] in, is the voltage at point Vout+ when switch S2 is closed; is the voltage at point Vx+ when switch S2 is closed; R x The equivalent resistance of the charging main control module collection pin; is the voltage at point Vout- when switch S2 is closed; is the voltage at point Vx when switch S2 is closed; is the voltage at the Vout+ point when the switches S1 and S2 are closed; is the voltage at point Vx+ when switches S1 and S2 are closed; is the voltage at point Vout when switches S1 and S2 are closed; is the voltage at point Vx when switches S1 and S2 are closed.

[0057] In the above formula, and When switch S2 is closed, it is collected by the charging main control module; and When switch S1 and switch S2 are closed, the data is collected by the charging main control module; and After the collection is obtained, it can be calculated and Then calculate V +1 and V -1 ; and After the collection is obtained, it can be calculated and Then calculate V +2 and V -2 .

[0058] Specific insulation testing methods such as Figure 5As shown, the following steps are included:

[0059] 1) After the vehicle is physically connected to the DC charger and the charging main control module is connected to the vehicle controller, insulation detection is performed;

[0060] 2) The charging main control module detects the status of the positive DC contactor K1 and the negative DC contactor K2 (the purpose of detecting the status of K1 and K2 is to avoid contactor malfunction, adhesion, etc. that affect the insulation detection result), and detects whether the voltage outside the positive DC contactor K1 and the negative DC contactor K2 is less than 10V (to ensure that the outside voltage is less than 10V, so that after K1 and K2 are closed, the impact on the circuit equipment, especially the battery pack, can be reduced to prevent the circuit from backflow). If the positive DC contactor K1 and the negative DC contactor K2 are disconnected, and the outside voltage is less than 10V, then go to step 3); otherwise, the charging fails and the charging ends;

[0061] 3) Insulation detection voltage = charger rated voltage (this step is to determine the charger voltage parameter when performing insulation detection in the charging main control module. Since the voltage during insulation detection is generally determined by the charger rated voltage, the charger rated voltage is directly set as the insulation detection voltage as the basis for insulation detection. Of course, after the charging main control module communicates with the vehicle controller, the charging controller will also send other parameters such as the maximum allowable charging current of the vehicle to the charging main control module. This belongs to the parameter setting step of the charging main control module);

[0062] 4) The charging main control module sends a power-on command to the power control module, and the power control module controls the charging module to start working. If the charging module works normally, step 5) is executed; if the charging module works abnormally, the charging fails and the charging is terminated;

[0063] 5) The charging main control module detects the inner voltage of the positive DC contactor K1 and the negative DC contactor K2. If the inner measured voltage is between -(1 and 10V), it goes to step 6) (which has the same meaning as detecting the external measured voltage). Otherwise, it is a charging failure and the charging is terminated.

[0064] 6) The charging main control module controls the positive DC contactor K1 and the negative DC contactor K2 to close. If they are closed, the process goes to step 7). If they are not closed, the charging fails and the charging is terminated.

[0065] 7) Detect the status of switch S1 and switch S2. If switch S1 or switch S2 is not disconnected, charging fails and charging is terminated. If switch S1 and switch S2 are both disconnected, switch S2 is closed and the closing delay of switch S2 is controlled for a certain time (the delay time is adjustable and is generally set within the range of 100ms-1s), so that the charging main control module can collect the fully filtered and

[0066] 8) Then the charging main control module controls switch S1 to close (at this time, both switch S1 and switch S2 should be closed), and also controls switch S1 to close for a period of time so that the charging main control module can collect the fully filtered and

[0067] 9) Insulation resistance R+ and insulation resistance R- can be calculated by combining the above formula;

[0068] 10) Determine whether the insulation resistance R+ and the insulation resistance R- meet the requirements. If not, an alarm will be given. If yes, proceed to step 11);

[0069] 11) The charging main control module controls the charging module to the standby state, controls the discharge branch contactor K7 to close, and discharges the voltage between the positive and negative poles of the DC bus to prevent the circuit from retaining high voltage for a long time and causing damage to people and equipment.

[0070] The above completes the insulation test of the charger. After the insulation test is completed, the pre-charging process begins and the battery pack starts to be charged.

[0071] In the above embodiment, in order to simplify the calculation process, the resistance values ​​of the resistors R1, R2 and R3 are the same. As other implementations, the resistance values ​​of the resistors R1, R2 and R3 may also be different, and the present invention does not limit this.

[0072] In the above embodiments, in order to make the circuit analysis design introduction clear and the results obvious, the positive voltage acquisition circuit and the negative voltage acquisition circuit are symmetrically designed, and some resistance values ​​are the same. As other implementation methods, the positive voltage acquisition circuit and the negative voltage acquisition circuit can also be asymmetrically designed, and the resistance value of the resistor can be set as required.

[0073] In the above embodiment, in order to avoid incorrect insulation detection results and improve the accuracy and safety of insulation detection, before closing switch S2, the status of K1 and K2 and the internal and external voltages of K1 and K2 are detected. As another implementation method, switch S2 can be directly closed while ensuring that the accuracy and safety of insulation detection are not affected.

[0074] In the above embodiment, in order to expand the insulation detection range, K1 and K2 are controlled to be closed before closing switch S2. As another implementation, K1 and K2 may not be closed during insulation detection while ensuring that the insulation in other ranges is normal.

[0075] In the above embodiment, in order to improve the accuracy of voltage acquisition and realize voltage compensation, the voltages at the positive sampling point and the negative sampling point are collected. When calculating, the reference voltage Vref and the equivalent resistance Rx of the acquisition pin of the charging main control module are combined. As other implementation methods, Vref and Rx may not be combined, and the calculation may be performed directly through the operational amplifier and the filter branch.

[0076] There are many forms of implementing the filter branch, and the present invention is not limited to the form of a series resistor and a grounding capacitor.

[0077] The present invention prevents strong electromagnetic interference on voltage collection by arranging a filter circuit in the voltage collection circuit, thereby improving the accuracy of DC bus voltage collection, thereby improving the accuracy of insulation detection, reducing the frequency of electric vehicle charging failures, and increasing the safety of the charging process, which is beneficial to the promotion and application of DC chargers in the field of new energy electric vehicles.

Claims

1. An insulation detection device, characterized in that: include: A detection circuit includes a resistor R1, a resistor R2, a resistor R3, a switch S1 and a switch S2, a resistor R1 and a resistor R2 Series, one end of the series circuit is connected to the positive pole of the DC bus, and the other end is connected to the negative pole of the DC bus; after the resistor R3 and the switch S1 are connected in series, they are connected in parallel with the resistor R1; and the connection point between the resistor R1 and the resistor R2 is grounded through the switch S2; The positive voltage acquisition circuit includes an operational amplifier A1 and a first filter branch; the first filter branch includes a resistor R8 and a grounding capacitor C1; the input end of the operational amplifier A1 is connected to the positive pole of the DC bus, and the output end is connected to the positive sampling point of the charging main control module through the resistor R8; one end of the resistor R8 connected to the positive sampling point is also connected to the grounding capacitor C1; the positive sampling point is also connected to the first reference voltage V through the resistor R9 ref1 ; The negative electrode voltage acquisition circuit includes an operational amplifier A2 and a second filter branch; the second filter branch includes a resistor R14 and a grounding capacitor C3. The input end of the operational amplifier A2 is connected to the negative electrode of the DC bus, and the output end is connected to the negative electrode sampling point of the charging main control module through the resistor R14; one end of the resistor R14 connected to the negative electrode sampling point is also connected to the grounding capacitor C3; the negative electrode sampling point is also connected to the second reference voltage V through the resistor R15 ref2 The charging main control module is used to control the on and off of switches S1 and S2 to obtain the voltage V at the positive sampling point. X1 + 、V X2 + , and the voltage V at the negative sampling point X1 - 、V X2 - , and then calculate V +1 、V +2 and V -1 、V -2 , and then calculate the insulation resistance R+ of the DC bus positive pole to ground and the insulation resistance R- of the DC bus negative pole to ground. The calculation process is as follows: Among them, V out1 + 、V out1 - are the voltages at the output terminals of operational amplifiers A1 and A2 when switch S2 is closed; V out2 + 、V out2 - are the voltages at the output of operational amplifiers A1 and A2 when switches S1 and S2 are closed respectively; Rx is the equivalent resistance of the charging master control module’s acquisition pin; V +1 、V -1 are the voltages of the positive and negative poles of the DC bus when switch S2 is closed, V +2 、V -2 They are the voltages at the positive and negative poles of the DC bus when switches S1 and S2 are closed, respectively.

2. An insulation detection method of the insulation detection device according to claim 1, characterized in that: The following steps are involved: 1) Control switch S2 to close and collect the voltage at the positive sampling point And the voltage at the negative sampling point 2) Control switch S2 and switch S1 to close and collect the voltage at the positive sampling point And the voltage at the negative sampling point 3) According to Calculate the voltage V at the positive pole of the DC bus when switch S2 is closed. +1 ;according to Calculate the voltage V at the negative pole of the DC bus when switch S2 is closed. -1 ;according to Calculate the voltage V at the positive pole of the DC bus when switches S2 and S1 are closed. +2 ;according to Calculate the voltage V at the negative pole of the DC bus when switches S2 and S1 are closed. -2 ; 4) According to V +1 、V -1 、V +2 、V -2 The insulation resistance R+ of the DC bus positive pole to ground and the insulation resistance R- of the DC bus negative pole to ground are calculated. The calculation process is as follows: 5) Determine the size of the insulation resistance R+ and the insulation resistance R- to complete the insulation test.

3. The insulation detection method according to claim 2, characterized in that: Before controlling the switch S2 to close, the method further includes controlling the positive DC contactor K1 and the negative DC contactor K2 to close.

4. The insulation detection method according to claim 3, characterized in that: Before controlling the positive DC contactor K1 and the negative DC contactor K2 to close, the method further includes detecting the voltage inside and outside the positive DC contactor K1 and the negative DC contactor K2.

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