Passive insulation detection device and method for new energy mining vehicle power system

Abstract

The invention discloses a passive insulation detection device and method for a new energy mining vehicle power system. The passive insulation detection device comprises an insulation monitoring circuit, a power circuit and a CAN communication circuit. The insulation monitoring circuit comprises a first isolation resistor, a first solid-state relay, a second solid-state relay and a second isolation resistor which are sequentially connected between the positive bus and the negative bus; the power supply circuit adopts flyback power supply isolation output; the CAN communication circuit sends test data to the CAN communication end of the MCU through the automobile signal CAN FD transceiver with the standby function and the digital isolator. According to the invention, insulation detection can be carried out under the conditions that the working voltage range of the bus is 650V-1200V, the minimum measurement resistance is not greater than 20K and other insulation detectors exist, the requirement that the leakage current threshold value is not greater than 10mA is met, and the insulation detection precision is improved.

Description

Technical Field

[0001] The present invention relates to an insulation detection circuit, and particularly to a passive insulation detection device and method for a power system of a new energy mine vehicle. Background Art

[0002] In the power systems of pure electric vehicles or hybrid electric vehicles, all high-voltage (HV) devices are isolated to the protective grounding (PE) terminal through a high-resistance path. For this type of insulation form, an insulation detection device is usually set up to monitor the insulation resistance and initiate shutdown in the case of insufficient insulation resistance to avoid personal injury caused by contact with the system. Existing insulation detection devices for the power systems of electric vehicles or hybrid electric vehicles require a voltage level of 200V - 400V and a leakage current threshold of ≤30mA. However, existing insulation detection devices cannot be applied to the power system of mine vehicles. On the one hand, the power system of mine vehicles uses an electrical system with a higher voltage, and the voltage level reaches 650V - 1200V. Higher voltages require stricter insulation requirements and lower allowable values of leakage current, with a leakage current threshold of ≤10mA. On the other hand, the working environment of mine vehicles is much harsher than that of ordinary vehicles. There may be high humidity, high dust, flammable and explosive gases, etc. in the mine, and these environmental factors require higher insulation detection requirements. Moreover, the minimum measurable insulation resistance of the insulation measurement scheme for ordinary vehicles is relatively large and cannot be applied to harsh application environments such as mine vehicles. The above requirements cannot be achieved by simply replacing modules of existing insulation detection devices. Therefore, there is an urgent need to propose an insulation detection device suitable for the power system of mine vehicles. Summary of the Invention

[0003] Object of the Invention: Aiming at the above problems, the present invention proposes a passive insulation detection device and method for a power system of a new energy mine vehicle, which can perform insulation detection when the bus working voltage range is 650V - 1200V, the minimum measured resistance is not greater than 20K, and there is already another insulation detector, meeting the requirement of a leakage current threshold of ≤10mA and improving the accuracy of insulation detection.

[0004] Technical Solution: The technical solution adopted by the present invention is a passive insulation detection device for a power system of a new energy mine vehicle, including: an insulation monitoring circuit, a power supply circuit, and a CAN communication circuit;

[0005] Insulation monitoring circuit, including a first isolation resistor, a first solid-state relay, a second solid-state relay, and a second isolation resistor connected in sequence between the positive and negative buses; the solid-state relay is controlled by a microcontroller unit (MCU); a first sampling resistor is connected between the two solid-state relays and grounded, the first sampling resistor is connected to an operational amplifier, and the output of the operational amplifier is sent to the SPI communication terminal of the MCU through an analog-to-digital converter (ADC) and an enhanced digital isolator; the connection of the first sampling resistor to the operational amplifier includes: the grounded end of the first sampling resistor is connected to the grounded end of the operational amplifier through a voltage source, the other end of the first sampling resistor is connected to the positive pole of the operational amplifier, and the negative pole of the operational amplifier is connected to the output of the operational amplifier; a third isolation resistor and a second sampling resistor are also connected in series between the positive and negative voltages; the second sampling resistor is connected to the operational amplifier, and the output of the operational amplifier is sent to the SPI communication terminal of the MCU through an ADC and an enhanced digital isolator;

[0006] The power supply circuit uses a flyback power supply for isolated output;

[0007] The CAN communication circuit sends the test data to the CAN communication terminal of the MCU through an automotive signal CAN FD transceiver with a standby function and a digital isolator.

[0008] The turn-off voltage between the secondary switch terminals of the solid-state relay is not less than 1700V; the isolation gate withstand voltage between the control side and the switch side of the solid-state relay is not less than 3750V RMS 。

[0009] The maximum input offset voltage of the operational amplifier is not greater than 8uV, and the input offset current is not greater than 600pA; the maximum measurement error of the ADC is not greater than 45PPM, and the sampling rate is not greater than 10 times per second.

[0010] The isolation resistor R st has a resistance accuracy value not greater than 5% of the ratio of the measured resistor to the isolation resistor value.

[0011] The sampling resistor R inAMC has an accuracy not greater than 0.01%.

[0012] The isolation voltage in the power supply circuit is not less than 3500Vrms / min.

[0013] The voltage accuracy connected to the reference voltage terminal of the operational amplifier is not greater than 0.02%.

[0014] The present invention provides a passive insulation detection method for a new energy mine vehicle power system. Connect the resistor divider to determine the isolation resistor from DC+ or DC– to PE. The isolation resistor calculation formula between the DC line and PE is as follows:

[0015]

[0016] In the formula, R isoP , R isoN respectively represent the insulation resistances of the positive and negative busbars, R inAMC represents the sampling resistance, R st represents the isolation resistance, V DC is the DC bus voltage, V N is the voltage between the negative of the measured bus voltage and the case ground, V P is the voltage between the positive of the measured bus voltage and the case ground;

[0017] Among them V in1 represents the voltage across the first sampling resistance when the negative-side switch is closed, V inP represents the voltage across the first sampling resistance when the positive-side switch is closed.

[0018] Advantageous effects: Compared with the prior art, the present invention has the following advantages: (1) The passive insulation detection device proposed by the present invention designs an insulation monitoring circuit, a power supply circuit and a CAN communication circuit, comprehensively meeting the requirement of leakage current threshold ≤ 10 mA and improving the accuracy of insulation detection. (2) The solid-state relay is combined with the S117S with high withstand voltage to meet the situation where the bus working voltage is 1200 V. The method of using a high-precision general-purpose operational amplifier plus an isolation chip improves the accuracy compared with the conventional measurement method. The power supply part adopts a flyback power supply, which has stronger load-carrying capacity, higher efficiency and is more suitable for high-power output occasions. (3) This solution transfers the acquired analog quantity to the MCU through the ADC via SPI, with internal and external communication functions added, and is more suitable for actual engineering occasions. Brief Description of the Drawings

[0019] Figure 1 is the insulation monitoring circuit of the passive insulation detection device for the power system of a new energy mine vehicle described in the present invention;

[0020] Figure 2 is the power supply circuit of the passive insulation detection device for the power system of a new energy mine vehicle described in the present invention;

[0021] Figure 3 is the CAN communication circuit of the passive insulation detection device for the power system of a new energy mine vehicle described in the present invention. Detailed Embodiment

[0022] The technical solution of the present invention will be further described below in conjunction with the drawings and embodiments.

[0023] The passive insulation detection device for the power system of a new energy mine vehicle described in the present invention includes an insulation monitoring circuit, a power supply circuit and a CAN communication circuit.

[0024] The insulation monitoring circuit is as follows Figure 1 shown, including a first isolation resistor, a first solid-state relay, a second solid-state relay, and a second isolation resistor connected in sequence between the positive and negative busbars. Among them, the isolation resistor R st selects 9 series-connected 80.6K resistors, 1206 package, rated withstand voltage 200V, accuracy 0.05%. The value and accuracy of the measurement resistor are strongly correlated with the minimum value of the measured resistor. The judgment basis is that the resistor accuracy cannot be worse than 5% of the ratio of the measured resistor to the isolation resistor value. The solid-state relay is controlled by a microcontroller unit (MCU). The positive and negative busbar measurement switching switch selects the solid-state relay S117S. There is a 1700V turn-off voltage between the secondary switch terminals of this device. The isolation gate withstand voltage between the control side and the switch side is 3750V RMS . It meets the condition that the bus working voltage is 1200V.

[0025] A first sampling resistor is connected between the two solid-state relays and grounded. The first sampling resistor is connected to an operational amplifier and connected to the MCU through an analog-to-digital converter ADC and an enhanced digital isolator for measuring the voltage value at both ends of the first sampling resistor. The grounded end of the first sampling resistor is connected to the grounded end of the operational amplifier through a 1.25V voltage source. The other end of the first sampling resistor is connected to the positive pole of the operational amplifier, and the negative pole of the operational amplifier is connected to the output of the operational amplifier. The sampling resistor R inAMC selects 750Ω, 0805 package, accuracy 0.01%. The operational amplifier selects TSZ122IYDT, with a maximum input offset voltage of 8uV and an input offset current of 600pA. The ADC chip selects MAX11205AEUB+, with a maximum measurement error of 45PPM and a sampling rate not greater than 10 times per second. This isolator uses a common digital isolator for isolated transmission of communication signals. The key requirement is that its isolated power supply meets the requirements of the isolation voltage for the high and low voltage sides. The test analog quantity is communicated to the SPI through the ADC chip and then enters the MCU. That is, in the overall design, CAN communication is responsible for external communication, and SPI is responsible for internal communication. The method of using a high-precision ordinary operational amplifier plus an isolation chip further improves the test accuracy.

[0026] A third isolation resistor and a second sampling resistor are also connected in series between the positive and negative voltages. The second sampling resistor is connected to an operational amplifier and connected to the MCU through an analog-to-digital converter ADC and an enhanced digital isolator for measuring the voltage of the second sampling resistor.

[0027] The reference voltage of the operational amplifier selects ISL21090BFB825Z-TK, with a rated output voltage of 2.5V. The voltage accuracy is 0.02%.

[0028] This insulation monitoring circuit can coexist with other insulation monitors to achieve separate measurement of the insulation resistances of the positive and negative busbars. Moreover, the circuit structure itself is a passive monitoring method, and measurements can only be made after the busbar voltage is established.

[0029] The power supply circuit is as Figure 2 shown. The auxiliary power supply uses a flyback power supply, with an input of 9 to 36V and three isolated outputs of 5V voltage. The isolation voltage between ISOGNG2 and the primary side and the other two outputs is not less than 3500Vrms for 1 minute. The power supply part in this solution uses a flyback power supply, which has a stronger load-carrying capacity, higher efficiency, and is more suitable for occasions with high-power output.

[0030] The CAN communication circuit is as Figure 3 shown. The test data is sent to the MCU through an automotive signal-improved CAN FD transceiver with a standby function and a digital isolator, and then communicates with other devices outside the board through the MCU. Adding both internal and external communication makes it more suitable for actual engineering occasions.

[0031] The passive insulation detection device of the new energy mine vehicle power system described in the present invention can perform insulation detection when the busbar operating voltage ranges from 650V to 1200V, the minimum measured resistance is not greater than 20K, and there are already other insulation detectors present, meeting the requirement of leakage current threshold ≤ 10mA.

[0032] The detection method of the passive insulation detection device of the new energy mine vehicle power system described in the present invention is as follows: Connect the resistor divider to determine the isolation resistance from the positive DC+ of the busbar voltage or the negative DC– of the busbar voltage to the protective ground PE. It has an enhanced isolated analog front end (AFE) with a flyback power supply on the hot side, suitable for the MCU located on the cold side.

[0033] The calculation formula for the isolation resistance between the DC line and PE is as follows:

[0034]

[0035] In the formula, R isoP , R isoN respectively represent the insulation resistances of the positive and negative busbars, R inAMC represents the sampling resistor, R st represents the isolation resistor, V DC is the DC busbar voltage, V N is the voltage between the negative of the measured busbar voltage and the case ground, V P is the voltage between the positive of the measured busbar voltage and the case ground. Among them V inN represents the AMC input voltage (negative side switch), V inP represents the AMC input voltage (positive side switch), that is, the voltage across the sampling resistor when the positive side switch is closed.

Claims

1. A passive insulation detection device for a power system of a new energy mining vehicle, characterized in that: It includes an insulation monitoring circuit, a power supply circuit and a CAN communication circuit; The insulation monitoring circuit includes a first isolation resistor, a first solid-state relay, a second solid-state relay and a second isolation resistor connected in sequence between the positive and negative busbars; the solid-state relays are controlled by a microcontroller unit (MCU); a first sampling resistor is connected between the two solid-state relays and grounded, the first sampling resistor is connected to an operational amplifier, and the output of the operational amplifier is sent to the SPI communication port of the MCU through an analog-to-digital converter (ADC) and an enhanced digital isolator; the connection of the first sampling resistor to the operational amplifier includes: the grounded end of the first sampling resistor is connected to the grounded end of the operational amplifier through a voltage source, the other end of the first sampling resistor is connected to the positive pole of the operational amplifier, and the negative pole of the operational amplifier is connected to the output of the operational amplifier; a third isolation resistor and a second sampling resistor are also connected in series between the positive and negative voltages; the second sampling resistor is connected to the operational amplifier, and the output of the operational amplifier is sent to the SPI communication port of the MCU through an ADC and an enhanced digital isolator; The power supply circuit uses flyback power supply for isolated output; The CAN communication circuit sends the test data to the CAN communication port of the MCU through an automotive signal CAN FD transceiver with a standby function and a digital isolator.

2. The passive insulation detection device for the power system of a new energy mine vehicle according to claim 1, wherein: The off-state voltage between the secondary switch terminals of the solid-state relay is not less than 1700V; the withstand voltage of the isolation gate between the control side and the switch side of the solid-state relay is not less than 3750V RMS .

3. The passive insulation detection device for the power system of the new energy mine vehicle according to claim 1, characterized in that: The maximum input offset voltage of the operational amplifier is no greater than 8 μV, and the input offset current is no greater than 600 pA; the maximum measurement error of the ADC is no greater than 45 PPM, and the sampling rate is no greater than 10 times per second.

4. The passive insulation detection device for the power system of the new energy mining vehicle according to claim 1, wherein: Isolation resistor R st The resistance accuracy value is not greater than 5% of the ratio of the measured resistor to the isolation resistor value.

5. The passive insulation detection device for the power system of the new energy mine vehicle according to claim 1, wherein: Sampling resistor R inAMC The accuracy is not greater than 0.01%.

6. The passive insulation detection device for the power system of the new energy mining vehicle according to claim 1, wherein: The isolation voltage in the power supply circuit is not less than 3500 Vrms / min.

7. The passive insulation detection device for the power system of a new energy mine vehicle according to claim 1, characterized in that: The voltage accuracy of the voltage connected to the reference voltage terminal of the operational amplifier is no greater than 0.02%.

8. A passive insulation detection method for the power system of a new energy mining vehicle, characterized in that: Connect the resistance divider to determine the isolation resistance from DC+ or DC– to PE. The calculation formula for the isolation resistance between the DC line and PE is as follows: Wherein, R isoP and R isoN respectively represent the insulation resistances of the positive and negative busbars, R inAMC represents the sampling resistance, R st represents the isolation resistance, V DC is the DC bus voltage, V N is the voltage between the negative of the measured bus voltage and the case ground, V P is the voltage between the positive of the measured bus voltage and the case ground; Among them V inN represents the voltage across the first sampling resistor when the negative-side switch is closed, V inP represents the voltage across the first sampling resistor when the positive-side switch is closed.

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