A system and method for detecting ground faults in real time in a charging pile system

Abstract

The application relates to a system for detecting a grounding fault of a charging pile system in real time, comprising a power supply circuit, a signal generation circuit, a sampling control circuit, a signal processing circuit, a superimposed signal acquisition circuit and an insulation sampling resistance calculation module. The sampling control circuit comprises a sampling network, a switching switch and a control unit, and the sampling network comprises first, second and third sampling resistances. The sampling control circuit generates first and second sampling signals based on a PWM signal generated by the signal generation circuit; the signal processing circuit processes the sampling signals to obtain first and second reference signals; the superimposed signal acquisition circuit is used for acquiring first and second superimposed signals. The insulation sampling resistance calculation module is used for calculating the positive and negative electrode insulation impedance of the charging pile system based on the reference signals, the resistance value of the sampling resistance, the direct current output voltage and the superimposed signals; and judging whether the charging pile system has a grounding fault based on the positive and negative electrode insulation impedance.

Description

Technical Field

[0001] This invention relates to the field of energy conservation and environmental protection, particularly to the field of charging piles, and more specifically, to a system and method for real-time detection of grounding faults in charging pile systems. Background Technology

[0002] With the development of charging pile systems, their voltages are becoming increasingly higher, making their grounding safety more crucial. Therefore, the effectiveness of grounding in a charging pile system has become a critical safety indicator. Grounding faults in the charging pile system can be detected by measuring its insulation resistance. However, existing insulation resistance measurement methods typically have significant errors and cannot accurately and quickly measure the insulation resistance of charging pile systems. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a system and method for real-time detection of grounding faults in charging pile systems, which can detect the insulation impedance of the positive and negative poles of the charging pile system to ground with high accuracy and speed in real time, thereby detecting grounding faults in the charging pile system.

[0004] The technical solution adopted by this invention to solve its technical problem is: to construct a system for real-time detection of grounding faults in a charging pile system, comprising:

[0005] A power supply circuit is used to generate a second power supply voltage, a third positive power supply voltage, and a third negative power supply voltage based on a first power supply voltage.

[0006] The signal generation circuit is used to receive the third positive power supply voltage and the third negative power supply voltage and generate a PWM signal for supplying the PE terminal of the charging pile system.

[0007] A sampling control circuit includes a sampling network, a switching switch, and a control unit. The sampling network includes a first sampling resistor, a second sampling resistor, and a third sampling resistor. The control unit controls the state of the switching switch so that the sampling network operates in different states, thereby generating a first sampling signal and a second sampling signal based on the PWM signal in standby mode.

[0008] Signal processing circuitry is used to process the first sampled signal and the second sampled signal to obtain a first reference signal and a second reference signal;

[0009] The superimposed signal acquisition circuit is used to acquire a first superimposed signal when the first reference signal and the DC output voltage of the charging pile system are superimposed on the third sampling resistor, and a second superimposed signal when the second reference signal and the DC output voltage of the charging pile system are superimposed on the third sampling resistor;

[0010] The insulation sampling resistance calculation module is used to calculate the positive and negative pole insulation impedance of the charging pile system to ground based on the first reference signal, the second reference signal, the resistance value of the first sampling resistor, the resistance value of the second sampling resistor, the resistance value of the third sampling resistor, the DC output voltage, the first superimposed signal, and the second superimposed signal; and to determine whether the charging pile system has a grounding fault based on the positive and negative pole insulation impedance to ground.

[0011] In the system for real-time detection of grounding faults in a charging pile system as described in this invention, the resistance value of the first sampling resistor is equal to the resistance value of the second sampling resistor.

[0012] The insulation sampling resistance calculation module is used to calculate the positive-to-ground insulation impedance and the negative-to-ground insulation impedance based on the following formula:

[0013]

[0014] Wherein, R4 represents the positive-to-ground insulation resistance, R5 represents the negative-to-ground insulation resistance, R1 represents the resistance value of the first sampling resistor, R3 represents the resistance value of the third sampling resistor, VDC represents the DC output voltage, Vc1 represents the first superimposed signal, Vc2 represents the second superimposed signal, V+ represents the third positive power supply voltage, and V- represents the third negative power supply voltage.

[0015] In the system for real-time detection of grounding faults in a charging pile system according to the present invention, the switching switch includes a first switching switch, a voltage divider resistor, and a second switching switch.

[0016] The first end of the first sampling resistor is connected to the positive DC output of the charging pile system, and the second end is connected to the first end of the first switching switch. The first end of the second sampling resistor is connected to the negative DC output of the charging pile system, and the second end is also connected to the first end of the first switching switch. The second end of the first switching switch is grounded through the third sampling resistor. The second end of the first switching switch is also connected to the first end of the second switching switch through the voltage divider resistor. The second end of the second switching switch is grounded.

[0017] The control unit is used to control the first switching switch to be closed and the second switching switch to be open, or the first switching switch to be open and the second switching switch to be closed.

[0018] In the system for real-time detection of grounding faults in a charging pile system as described in this invention, the first switching switch and the second switching switch include a relay coil and a relay switch. The first end and the second end of the relay switch are respectively the first end and the second end of the switching switch. The first end of the relay coil is connected to the relay voltage, and the second end receives the control signal sent by the control unit.

[0019] In the system for real-time detection of grounding faults in a charging pile system according to the present invention, the signal processing circuit includes a filtering unit, an isolation amplification unit, a differential amplification unit, a forward bias unit, and an ADC;

[0020] The filtering unit is used to filter the first sampled signal and the second sampled signal; the isolation amplification unit is used to isolate and amplify the first sampled signal and the second sampled signal; the differential amplification unit is used to differentially amplify the first sampled signal and the second sampled signal; the forward bias unit is used to forward bias the first sampled signal and the second sampled signal; the ADC is used to receive and filter the first sampled signal and the second sampled signal to generate the first reference signal and the second reference signal.

[0021] In the real-time detection system for grounding faults in a charging pile system according to the present invention, the filtering unit includes a first operational amplifier, a first filter resistor, a second filter resistor, a first filter capacitor, and a second filter capacitor; the non-inverting input terminal of the first operational amplifier receives the first sampling signal and the second sampling signal sequentially through the second filter resistor and the first filter resistor, and the inverting input terminal is connected to the output terminal; the first filter capacitor is connected between the non-inverting input terminal of the first operational amplifier and ground; the second filter capacitor is connected between the inverting input terminal of the first operational amplifier and the connection point of the first filter resistor and the second filter resistor;

[0022] The input terminal of the isolation amplification unit receives the first sampling signal and the second sampling signal, and the output terminal outputs the isolated and amplified first sampling signal and the second sampling signal.

[0023] The differential amplifier unit includes a first differential resistor, a second differential resistor, a third differential resistor, a fourth differential resistor, and a second operational amplifier; the non-inverting input terminal of the second operational amplifier is connected to the output terminal of the isolation amplifier unit via the first differential resistor, and is grounded via the second differential resistor; the inverting input terminal of the second operational amplifier is connected to the output terminal of the isolation amplifier unit via the third differential resistor to receive the first sampling signal and the second sampling signal, and is connected to the output terminal of the second operational amplifier via the fourth differential resistor;

[0024] The forward bias unit includes a pull-up resistor, a filter inductor, and a third filter capacitor; the first end of the pull-up resistor receives the second power supply voltage, the second end is connected to the first end of the third filter capacitor and the first end of the filter inductor, the second end of the third filter capacitor is grounded, and the second end of the filter inductor receives the first sampling signal and the second sampling signal output from the output terminal of the second operational amplifier.

[0025] In the system for real-time detection of grounding faults in a charging pile system according to the present invention, the signal generation circuit includes a third operational amplifier, an LC filter unit, a first capacitor, a first resistor, a second resistor, and a third resistor;

[0026] The non-inverting input terminal of the third operational amplifier is grounded via the first capacitor and connected to the output terminal of the third operational amplifier via the first resistor; the inverting input terminal of the third operational amplifier is connected to the output terminal of the third operational amplifier via the second resistor and grounded via the third resistor; the positive power supply terminal of the third operational amplifier receives the third positive power supply voltage, and the negative power supply terminal receives the third negative power supply voltage.

[0027] The first end of the LC filter unit is connected to the output end of the third operational amplifier, the second end is grounded, and the third end is connected to the PE end of the charging pile system to output the PWM signal.

[0028] In the system for real-time detection of grounding faults in a charging pile system according to the present invention, the superimposed signal acquisition circuit includes an ADC, which is used to acquire the first superimposed signal and the second superimposed signal;

[0029] The power supply circuit includes:

[0030] DC / DC conversion module, used to convert the first power supply voltage into a high-voltage side DC voltage;

[0031] The BOOST module is used to generate the third positive power supply voltage and the third negative power supply voltage based on the high-voltage side DC voltage;

[0032] A voltage regulator module is used to generate the second power supply voltage based on the first power supply voltage.

[0033] Another technical solution adopted by the present invention to solve its technical problem is to construct a method for real-time detection of grounding faults in a charging pile system, wherein the method is applied to the aforementioned system for real-time detection of grounding faults in a charging pile system; the method includes the following steps:

[0034] S1) Acquire the first reference signal, the second reference signal, the resistance value of the first sampling resistor, the resistance value of the second sampling resistor, the resistance value of the third sampling resistor, the DC output voltage, the first superimposed signal, and the second superimposed signal;

[0035] S2) Calculate the positive and negative pole insulation impedance of the charging pile system to ground based on the first reference signal, the second reference signal, the resistance value of the first sampling resistor, the resistance value of the second sampling resistor, the resistance value of the third sampling resistor, the DC output voltage, the first superimposed signal, and the second superimposed signal;

[0036] S3) Determine whether the charging pile system has a grounding fault based on the insulation impedance of the positive and negative poles to ground.

[0037] In the method for real-time detection of grounding faults in a charging pile system according to the present invention, in step S3, when the positive electrode insulation resistance to ground is higher than a first positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be normal; when the positive electrode insulation resistance to ground is lower than the first positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be abnormal; when the positive electrode insulation resistance to ground is lower than a second positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be faulty.

[0038] When the insulation resistance of the negative electrode to ground is higher than the first negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be normal; when the insulation resistance of the negative electrode to ground is lower than the first negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be abnormal; when the insulation resistance of the negative electrode to ground is lower than the second negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be faulty.

[0039] The system and method for real-time detection of grounding faults in charging pile systems according to the present invention enable real-time detection of the insulation resistance of the positive and negative DC output terminals to ground during the charging process. This allows for high-precision and rapid real-time detection of the insulation resistance of the positive and negative terminals to ground in the charging pile system, thereby detecting grounding faults in the charging pile system. Attached Figure Description

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0041] Figure 1 This is a schematic diagram of the principle of the real-time detection system for grounding faults in a charging pile system according to the present invention.

[0042] Figure 2 This is a circuit diagram of a preferred embodiment of the power supply circuit of the system for real-time detection of grounding faults in a charging pile system according to the present invention.

[0043] Figure 3 This is a circuit diagram of a preferred embodiment of the signal generation circuit for real-time detection of grounding faults in a charging pile system according to the present invention;

[0044] Figure 4 This is a circuit diagram of a preferred embodiment of the sampling control circuit for real-time detection of grounding faults in a charging pile system according to the present invention;

[0045] Figure 5 This is a circuit diagram of a preferred embodiment of the signal processing circuit for real-time detection of grounding faults in a charging pile system according to the present invention;

[0046] Figure 6 This is a schematic diagram of the circuit analysis model of the sampling control circuit of the charging pile system for real-time detection of grounding faults during charging.

[0047] Figure 7 It is the reference voltage applied during charging at the charging station. Figure 6 Equivalent circuit diagram above;

[0048] Figure 8 The DC output voltage of the charging station during charging acts on... Figure 6 The equivalent circuit diagram. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0050] Figure 1 This is a schematic diagram of the system principle for real-time detection of grounding faults in a charging pile system according to the present invention. Figure 1 As shown, the system for real-time detection of grounding faults in charging pile systems according to the present invention includes a power supply circuit 100, a signal generation circuit 200, a sampling control circuit 300, a signal processing circuit 400, a superimposed signal acquisition circuit 500, and an insulation sampling resistance calculation module 600.

[0051] The power supply circuit 100 is used to generate a second power supply voltage, a third positive power supply voltage, and a third negative power supply voltage based on a first power supply voltage. Here, the power supply circuit 100 can employ any suitable circuit module, especially a DC / DC chip structure, to generate the various power supply voltages required by the entire system. For example, the first power supply voltage provided by the low-voltage side DC power supply can be converted by a DC / DC converter chip to generate a high-voltage side DC voltage, and then a third positive power supply voltage and a third negative power supply voltage of opposite polarity can be generated based on the high-voltage side DC voltage. Simultaneously, the first power supply voltage provided by the low-voltage side DC power supply can also be converted by a DC / DC converter chip to form a low-voltage DC second power supply voltage. Of course, the power supply circuit 100 can also include more modules, chips, or devices to meet various voltage value requirements and withstand voltage requirements.

[0052] The signal generation circuit 200 is used to receive the third positive power supply voltage and the third negative power supply voltage and generate a PWM signal to be supplied to the PE terminal of the charging pile system. Here, the signal generation circuit 200 can be any PWM signal generation circuit, such as a self-excited square wave generator, as long as it can generate a suitable PWM signal.

[0053] The sampling control circuit 300 includes a sampling network 310, a switching switch 320, and a control unit 330. The control unit 330 controls the state of the switching switch 320, causing the sampling network 310 to operate in different states. In standby mode, it generates a first sampling signal and a second sampling signal based on the PWM signal. Preferably, the sampling network 310 includes sampling resistors R1, R2, and R3, wherein sampling resistors R1 and R2 are connected to different voltages and then connected in series with sampling resistor R3. This allows it to generate the first and second sampling signals based on different voltages upon receiving the PWM signal.

[0054] The signal processing circuit 400 is used to process the first sampled signal and the second sampled signal to obtain a first reference signal and a second reference signal. Preferably, the signal processing may include hardware filtering, isolation amplification, differential amplification, forward biasing, and / or digital filtering. For example, the signal processing circuit 400 may include a filtering unit, an isolation amplification unit, a differential amplification unit, a forward biasing unit, and an ADC. The filtering unit is used to filter the first sampled signal and the second sampled signal; the isolation amplification unit is used to isolate and amplify the first sampled signal and the second sampled signal; the differential amplification unit is used to differentially amplify the first sampled signal and the second sampled signal; the forward biasing unit is used to forward bias the first sampled signal and the second sampled signal; and the ADC is used to receive and filter the first sampled signal and the second sampled signal to generate the first reference signal and the second reference signal.

[0055] The superimposed signal acquisition circuit 500 is used to acquire a first superimposed signal when the first reference signal and the DC output voltage of the charging pile system are superimposed on the sampling resistor R3, and a second superimposed signal when the second reference signal and the DC output voltage of the charging pile system are superimposed on the sampling resistor R3. For example, the superimposed signal acquisition circuit 500 is an ADC used to acquire the first superimposed signal and the second superimposed signal, and it can also reuse the ADC in the signal processing circuit 400. Of course, the superimposed signal acquisition circuit 500 can also adopt any suitable voltage sampling circuit, chip or module.

[0056] The insulation sampling resistance calculation module 600 is used to calculate the positive and negative pole insulation impedance of the charging pile system to ground based on the first reference signal, the second reference signal, the resistance value of the sampling resistor R1, the resistance value of the sampling resistor R2, the resistance value of the sampling resistor R3, the DC output voltage, the first superimposed signal, and the second superimposed signal; and to determine whether the charging pile system has a grounding fault based on the positive and negative pole insulation impedance to ground.

[0057] In a preferred embodiment of the present invention, for example, it is assumed that the resistance value of the sampling resistor R1 is equal to the resistance value of the sampling resistor R2. The insulation sampling resistance calculation module 600 is used to calculate the positive-to-ground insulation impedance and the negative-to-ground insulation impedance based on the following formula:

[0058]

[0059] Wherein, R4 represents the positive-to-ground insulation resistance, R5 represents the negative-to-ground insulation resistance, R1 represents the resistance value of the sampling resistor R1, R3 represents the resistance value of the sampling resistor R3, VDC represents the DC output voltage, Vc1 represents the first superimposed signal, Vc2 represents the second superimposed signal, V+ represents the third positive power supply voltage, and V- represents the third negative power supply voltage.

[0060] The system for real-time detection of grounding faults in charging pile systems, which implements the present invention, can detect the insulation impedance of the positive and negative poles of the charging pile system to ground with high accuracy and speed in real time, thereby detecting grounding faults in the charging pile system.

[0061] Figure 2 This is a circuit diagram of a preferred embodiment of the power supply circuit of the system for real-time detection of grounding faults in a charging pile system according to the present invention. (See diagram below.) Figure 2 As shown, the power supply circuit 100 includes a DC / DC conversion module 110, a BOOST module 120, and a voltage regulator module 130. The DC / DC conversion module 110 is used to convert the first power supply voltage into a high-voltage side DC voltage; the BOOST module 120 is used to generate the third positive power supply voltage and the third negative power supply voltage based on the high-voltage side DC voltage; and the voltage regulator module 130 is used to generate the second power supply voltage based on the first power supply voltage.

[0062] Specifically, such as Figure 2As shown, the DC / DC conversion module 110 includes a DC / DC conversion chip U5 and an isolation transformer T1. The DC / DC conversion chip U5 is connected to the low-voltage side DC power supply V1 to receive the first power supply voltage V1. The first power supply voltage V1 is converted into a high-frequency signal by the DC / DC conversion chip U5. This high-frequency signal is transmitted to the high-voltage side through the isolation transformer T1, and then rectified by diodes and filtered by capacitors to generate the high-voltage side DC voltage V2+.

[0063] The BOOST module 120 includes a DC / DC converter chip U6 and a BOOST charge pump circuit. The high-voltage side DC voltage V2+ is pumped out by the DC / DC converter chip U6 to produce a negative voltage V2- of the same amplitude; the high-voltage side DC voltage V2+ is output by the BOOST charge pump circuit composed of the DC / DC converter chip U7 to produce two DC power supplies V- and V+ of the same magnitude but opposite polarity, namely the third positive power supply voltage V+ and the third negative power supply voltage V-.

[0064] The voltage regulator module 130 includes a voltage regulator resistor and a voltage regulator diode, which generates the second power supply voltage VREF based on the first power supply voltage V1.

[0065] Here, the various voltages generated by the power module 100—namely, the high-voltage side DC voltage V2+, the high-voltage side DC voltage V2-, the third positive power supply voltage V+, the third negative power supply voltage V-, and the second power supply voltage VREF—as well as the first power supply voltage V1 output by the low-voltage side DC power supply V1, will all be used in subsequent circuits. The power circuit employing the aforementioned specific structure not only provides accurate voltages to subsequent circuits but also improves the overall circuit's withstand voltage rating, thereby enhancing safety.

[0066] Figure 3 This is a circuit diagram of a preferred embodiment of the signal generation circuit for real-time detection of grounding faults in a charging pile system according to the present invention. Figure 3As shown, the signal generation circuit 200 includes an operational amplifier U1, an LC filter unit, a capacitor C15, resistors R17, R18, and R19. The non-inverting input terminal of the operational amplifier U1 is grounded via capacitor C15 and connected to the output terminal of the operational amplifier U1 via resistor R17; the inverting input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U1 via resistor R18 and grounded via resistor R19; the positive power supply terminal of the operational amplifier U1 receives the third positive power supply voltage V+, and the negative power supply terminal receives the third negative power supply voltage V-. The LC filter unit includes a capacitor C14 and an inductor L1 connected in series. The first end of the LC filter unit (the first end of inductor L1) is connected to the output terminal of the operational amplifier U1, the second end (the second end of capacitor C14) is grounded, and the third end (the second end of inductor L1 and the first end of capacitor C14) is connected to the PE terminal of the charging pile system.

[0067] The signal generation circuit 200 uses the third positive power supply voltage V+ and the third negative power supply voltage V- to power the operational amplifier U1, forming a self-excited square wave generator as a signal source to inject a PWM signal into the PE terminal of the charging pile system.

[0068] Figure 4 This is a circuit diagram of a preferred embodiment of the sampling control circuit for real-time detection of grounding faults in a charging pile system according to the present invention. Figure 3 As shown, the sampling control circuit 300 includes a sampling network 310, a switching switch 320, and a control unit 330. The control unit 330 controls the state of the switching switch 320, causing the sampling network 310 to operate in different states, thereby generating a first sampling signal and a second sampling signal based on the PWM signal in standby mode. Here, the sampling network 310 includes sampling resistors R1, R2, and R3. The switching switch 320 includes a first switching switch 320, a voltage divider resistor R7, and a second switching switch 320.

[0069] The first end of the sampling resistor R1 is connected to the positive DC output (DC+) of the charging pile system, and the second end is connected to the first end of the first switching switch 320. The first end of the sampling resistor R2 is connected to the negative DC output (DC-) of the charging pile system, and the second end is also connected to the first end of the first switching switch 320. The second end of the first switching switch 320 is grounded through the sampling resistor R3. The second end of the first switching switch 320 is also connected to the first end of the second switching switch 320 through the voltage divider resistor R7. The second end of the second switching switch 320 is grounded. The control unit 330 is used to control the first switching switch 320 to close and the second switching switch 320 to open, or the first switching switch 320 to open and the second switching switch 320 to close.

[0070] exist Figure 4 In the preferred embodiment shown, the first and second switching switches 320 include relay coils and relay switches K1 and K2. The first and second terminals of relay switches K1 and K2 are respectively the first and second terminals of the switching switch 320. The first terminal of the relay coil is connected to a relay voltage VP, and the second terminal receives a control signal from the control unit 330. Under the control of the control unit 330, the relay coil controls the relay switches K1 and K2 to close, thereby controlling the first switching switch 320 to close and the second switching switch 320 to open, or the first switching switch 320 to open and the second switching switch 320 to close. Of course, in other preferred embodiments of the present invention, other control switches can also be used, as long as they can achieve the function of a controlled switch.

[0071] exist Figure 4 In the preferred embodiment shown, a sampling network 310 and a switching switch 320 are formed by resistors R1, R2, R3, a relay coil, and relay switching switches K1 and K2. The relay coil can be controlled by software, so the control unit 330 can be constructed using a software module to issue control signals to control the relay coil to engage and disengage, thereby controlling the switching of relay switching switches K1 and K2, and thus making the sampling network formed by resistors R1, R2, and R3 work in different states. When relay switch K1 is closed and relay switch K2 is open, it is in normal working state; when relay switch K1 is open and relay switch K2 is closed, it is in standby state. The PWM signal on the PE terminal of the charging pile system is divided by the Y capacitors of the charging pile system's output positive and negative terminals to ground and the sampling network to obtain the first sampling signal VR1 and the second sampling signal VR2. That is, the first sampling signal VR1 is the voltage division signal of the Y capacitors of the charging pile system's output positive terminal to ground and the sampling network; the second sampling signal VR2 is the voltage division signal of the Y capacitors of the charging pile system's output negative terminal to ground and the sampling network.

[0072] In this preferred embodiment, a relay is used to separate the DC output from the PE terminal of the charging pile system, which improves the withstand voltage level of the entire circuit and enhances safety. Furthermore, real-time sampling of the signal source amplitude avoids amplitude descent affecting circuit accuracy. Therefore, the insulation resistance to ground of both positive and negative terminals can be calculated in real time during the charging process.

[0073] Figure 5 This is a circuit diagram of a preferred embodiment of the signal processing circuit for real-time detection of grounding faults in a charging pile system according to the present invention. Figure 5 As shown, the signal processing circuit 400 includes a filtering unit, an isolation amplification unit, a differential amplification unit, a forward biasing unit, and an ADC. The filtering unit filters the first sampled signal and the second sampled signal; the isolation amplification unit isolates and amplifies the first sampled signal and the second sampled signal; the differential amplification unit differentially amplifies the first sampled signal and the second sampled signal; the forward biasing unit forward biases the first sampled signal and the second sampled signal; and the ADC receives and filters the first sampled signal and the second sampled signal to generate the first reference signal and the second reference signal.

[0074] In a preferred embodiment of the present invention, the aforementioned filtering unit, isolation amplification unit, differential amplification unit, forward bias unit, and ADC can be constructed using any known modules, units, or devices in the art. Subsequent embodiments of the present invention illustrate preferred implementations of the aforementioned units.

[0075] like Figure 5 As shown, the filtering unit includes an operational amplifier U2, filter resistors R11 and R12, filter capacitors C11 and C12; the non-inverting input terminal of the operational amplifier U2 receives the first sampling signal VR1 and the second sampling signal VR2 sequentially through the filter resistors R12 and R11, and the inverting input terminal is connected to the output terminal; the filter capacitor C11 is connected between the non-inverting input terminal of the operational amplifier U2 and ground; the filter capacitor C12 is connected between the inverting input terminal of the operational amplifier U2 and the connection point of the filter resistors R11 and R12.

[0076] The isolation amplification unit includes an isolation optocoupler chip U3. The input terminal of the isolation optocoupler chip U3 is connected to the output terminal of the operational amplifier U2 via a resistor R17 to receive the first sampling signal VR1 and the second sampling signal VR2. The output terminal outputs the isolated and amplified first sampling signal VR1 and the second sampling signal VR2. The input terminal of the isolation optocoupler chip U3 is powered by the high-voltage side DC voltage V2+, and the output terminal is powered by the first power supply voltage V1.

[0077] The differential amplifier unit includes differential resistors R13, R14, and R15, a fourth differential resistor, and operational amplifier U4. The non-inverting input of operational amplifier U4 is connected to the output of the isolation amplifier unit via differential resistor R13 and grounded via differential resistor R14. The inverting input of operational amplifier U4 is connected to the output of the isolation amplifier unit via differential resistor R15 to receive the first sampling signal VR1 and the second sampling signal VR2, and is connected to the output of operational amplifier U4 via the fourth differential resistor. The output of operational amplifier U4 outputs the differentially amplified first sampling signal VR1 and second sampling signal VR2.

[0078] The forward bias unit includes a pull-up resistor R6, a filter inductor L2, a third filter capacitor C13, and a protection resistor R8. The first terminal of the pull-up resistor R6 receives the second power supply voltage, and the second terminal is connected to the first terminal of the third filter capacitor C13 and the first terminal of the filter inductor L2. The second terminal of the third filter capacitor C13 is grounded. The second terminal of the filter inductor L2 receives the first sampling signal VR1 and the second sampling signal VR2 output from the output terminal of the second operational amplifier via the protection resistor R8. The first terminals of the third filter capacitor C13 and the first terminal of the filter inductor L2 are the output terminals of the forward bias unit, which output the processed first sampling signal VR1 and the second sampling signal VR2. Here, the first sampling signal VR1 and the second sampling signal VR2 are output to the ADC through a signal pull-up network composed of the second power supply voltage, the equivalent resistance R5, and the pull-up resistor R65. Of course, in a simplified embodiment of the present invention, the protection resistor R8 can be omitted.

[0079] The ADC receives the first sampling signal VR1 and the second sampling signal VR2, and performs filtering processing on them to obtain the first reference signal Vo1 and the second reference signal Vo2.

[0080] In a preferred embodiment of the present invention, the ADC can be multiplexed as a superimposed signal acquisition circuit to acquire the first superimposed signal Vc1 when the first reference signal Vo1 and the DC output voltage VDC of the charging pile system are superimposed on the sampling resistor R3, and the second superimposed signal Vc2 when the second reference signal Vo2 and the DC output voltage VDC of the charging pile system are superimposed on the sampling resistor R3.

[0081] In this preferred embodiment, the signal source amplitude can be sampled in real time, avoiding the impact of amplitude drop on circuit accuracy. Therefore, the insulation impedance of the positive and negative terminals to ground can be calculated in real time during charging. Furthermore, using hardware circuitry allows for faster speeds. Additionally, the entire circuit is isolated from the low-voltage side, and by selecting a combination of a second-order filter circuit and an isolation operational amplifier, adding an appropriate DC bias, and finally sampling by an ADC, greater accuracy is ensured. Using an ADC for sampling allows determining the appropriate sampling period based on the square wave frequency, ensuring the integrity of the sampled square wave. Furthermore, when using ADC sampling, multiple signal points are sampled within the signal period, the difference between each signal point is judged, and outliers are discarded to ensure the true value of the sampled signal. Calculation errors caused by sampling errors can also be filtered out. Therefore, it is possible to detect the insulation impedance of the positive and negative terminals to ground of the charging pile system with high accuracy and speed in real time, thereby detecting grounding faults in the charging pile system.

[0082] Figure 6 This is a schematic diagram of the circuit analysis model of the sampling control circuit of the charging pile system for real-time detection of grounding faults during charging. Figure 7 It is the reference voltage applied during charging at the charging station. Figure 6 The equivalent circuit diagram is shown above. Figure 8 The DC output voltage of the charging station during charging acts on... Figure 6 The equivalent circuit diagram is shown below. The specific calculation process and principle of the insulation impedance to ground for pairs 6-8 will be explained below.

[0083] After the power supply circuit 100 supplies power to the signal generation circuit 200, the sampling control circuit 300, and the signal processing circuit 400, the signal source (square wave generator) composed of the operational amplifier U1 starts to send a PWM signal to the PE terminal of the charging pile system after being filtered by the LC circuit. At this time, the charging pile system has not started to output DC voltage. The control unit controls the relay switching switch K2 to close. The PWM signal passes through the voltage divider resistor R7 and the sampling resistor R3, and generates two signals on the sampling resistor R3, which are denoted as VR1 and VR2, respectively, namely the first sampling signal VR1 and the second sampling signal VR2.

[0084] Both the first sampling signal VR1 and the second sampling signal VR2 pass through a filter circuit composed of operational amplifier U2, are isolated and amplified by operational amplifier U3, and are differentially output to a differential amplifier circuit composed of operational amplifier U4. Finally, the signals are forward biased by a protection resistor R8 and a pull-up resistor R6. The ADC acquires the first sampling signal VR1 and the second sampling signal VR2, and then performs digital filtering. Based on the filtered first sampling signal VR1 and the second sampling signal VR2 (i.e., the first reference signal Vo1 and the second reference signal Vo2), the amplitudes of the power supply V+ and V- of operational amplifier U1 are calculated, which prepares for calculating the charging pile's impedance to ground during the charging process.

[0085] When the charging pile is ready to charge, the control relay switch K2 is opened and the relay switch K1 is closed. At this time, the charging pile system outputs a DC output voltage VDC. The first sampling signal VR1 and the second sampling signal VR2 (i.e., the first reference signal Vo1 and the second reference signal Vo2) during the charging process are analyzed using the superposition theorem.

[0086] See Figure 6 The model shown first uses the superposition theorem, based on the short circuit of the DC output voltage VDC, to analyze the effect of the PWM signal on the sampling resistor R3 separately. The equivalent impedance of capacitor Y1 is denoted as equivalent resistance R4, and the equivalent impedance of capacitor Y2 is denoted as R5, thus obtaining... Figure 7 The equivalent circuit diagram is shown.

[0087] The first reference signal Vo1 and the second reference signal Vo2 obtained using resistor R3 are as follows:

[0088]

[0089] Wherein, R4 represents the positive terminal insulation resistance to ground, R5 represents the negative terminal insulation resistance to ground, R1 represents the resistance value of the sampling resistor R1, R3 represents the resistance value of the sampling resistor R3, V+ represents the third positive terminal power supply voltage V+, and V- represents the third negative terminal power supply voltage V-.

[0090] Next, using the superposition theorem to short-circuit the PWM signal, we analyze the effect of the DC output voltage VDC on the sampling resistor R3 separately, that is, we calculate and obtain the DC output voltage reference signal V. S The value is:

[0091]

[0092] In the circuit, making the resistance values ​​of resistor R1 and resistor R2 equivalent can be simplified to:

[0093]

[0094] Wherein, R4 represents the positive terminal insulation resistance to ground, R5 represents the negative terminal insulation resistance to ground, R1 represents the resistance value of the first sampling resistor, R3 represents the resistance value of the third sampling resistor, and VDC represents the DC output voltage.

[0095] Finally, the signals are superimposed to obtain the superimposed signal generated by the PWM signal and the DC output voltage VDC across the sampling resistor R3, namely the first superimposed signal Vc1 and the second superimposed signal Vc2:

[0096] V c1 =V s +V 01

[0097] V c2 =V s +V O2

[0098] Wherein VDC represents the DC output voltage, Vc1 represents the first superimposed signal, Vc2 represents the second superimposed signal, V+ represents the third positive power supply voltage, and V- represents the third negative power supply voltage. As mentioned above, the first superimposed signal Vc1 and the second superimposed signal Vc2 can be directly acquired by a superimposed signal acquisition circuit (e.g., an ADC).

[0099] Substituting the aforementioned DC output voltage reference signal VS, the first superimposed signal Vc1, and the second superimposed signal Vc2, we can obtain

[0100]

[0101] By solving equations ① and ② simultaneously, the equivalent resistances R4 and R5 with respect to V can be calculated. C1 V C2 The algebraic expression.

[0102]

[0103] Wherein, R4 represents the positive-to-ground insulation resistance, R5 represents the negative-to-ground insulation resistance, R1 represents the resistance value of the first sampling resistor, R3 represents the resistance value of the third sampling resistor, VDC represents the DC output voltage, Vc1 represents the first superimposed signal, Vc2 represents the second superimposed signal, V+ represents the third positive power supply voltage, and V- represents the third negative power supply voltage.

[0104] Since the first superimposed signal Vc1 and the second superimposed signal Vc2 can be directly obtained through the superimposed signal acquisition circuit (e.g., ADC), the DC output voltage VDC can be directly obtained from the charging pile system, and the third positive power supply voltage V+ and the third negative power supply voltage V- can be obtained through the first sampling signal VR1 and the second sampling signal VR2, or through the first reference signal Vo1 and the second reference signal Vo.

[0105] Therefore, in the aforementioned formulas, R1, R3, VDC, Vc1, Vc2, V+, and V- are all known. By simply solving the above two formulas, we can obtain the positive-to-ground insulation resistance R4 and the negative-to-ground insulation resistance R5.

[0106] Therefore, in this invention, a PWM signal source and a sampling resistor can be used to realize the real-time detection of the insulation impedance of the positive and negative DC output terminals to ground during the charging process, and dual filtering by hardware and software can be used to improve the detection accuracy and speed.

[0107] Furthermore, when the positive electrode insulation resistance to ground is higher than the first positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be normal; when the positive electrode insulation resistance to ground is lower than the first positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be abnormal; when the positive electrode insulation resistance to ground is lower than the second positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be faulty.

[0108] Similarly, when the insulation resistance of the negative electrode to ground is higher than the first negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be normal; when the insulation resistance of the negative electrode to ground is lower than the first negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be abnormal; when the insulation resistance of the negative electrode to ground is lower than the second negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be faulty.

[0109] This invention further discloses a method for real-time detection of grounding faults in a charging pile system, applicable to any of the aforementioned systems for real-time detection of grounding faults in a charging pile system; the method includes the following steps:

[0110] S1) Acquire the first reference signal, the second reference signal, the resistance value of the sampling resistor R1, the resistance value of the sampling resistor R2, the resistance value of the sampling resistor R3, the DC output voltage, the first superimposed signal, and the second superimposed signal;

[0111] S2) Calculate the positive and negative pole insulation impedance of the charging pile system to ground based on the first reference signal, the second reference signal, the resistance value of the sampling resistor R1, the resistance value of the sampling resistor R2, the resistance value of the sampling resistor R3, the DC output voltage, the first superimposed signal, and the second superimposed signal;

[0112] S3) Determine whether the charging pile system has a grounding fault based on the insulation impedance of the positive and negative poles to ground.

[0113] In step S3, when the positive electrode insulation resistance to ground is higher than the first positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be normal; when the positive electrode insulation resistance to ground is lower than the first positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be abnormal; when the positive electrode insulation resistance to ground is lower than the second positive electrode threshold, the positive electrode grounding of the charging pile system is determined to be faulty.

[0114] When the insulation resistance of the negative electrode to ground is higher than the first negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be normal; when the insulation resistance of the negative electrode to ground is lower than the first negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be abnormal; when the insulation resistance of the negative electrode to ground is lower than the second negative electrode threshold, the negative electrode grounding of the charging pile system is determined to be faulty.

[0115] The specific implementation of the method for real-time detection of grounding faults in charging pile systems can refer to the aforementioned system implementation for real-time detection of grounding faults in charging pile systems, and will not be repeated here.

[0116] Although the present invention has been described through specific embodiments, those skilled in the art will understand that various modifications and equivalent substitutions can be made to the invention without departing from its scope. Furthermore, various modifications can be made to the invention for specific situations or materials without departing from its scope. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for real-time detection of grounding faults in a charging pile system, characterized in that, include: A power supply circuit is used to generate a second power supply voltage, a third positive power supply voltage, and a third negative power supply voltage based on a first power supply voltage. The signal generation circuit is used to receive the third positive power supply voltage and the third negative power supply voltage and generate a PWM signal for supplying the PE terminal of the charging pile system. A sampling control circuit includes a sampling network, a switching switch, and a control unit. The sampling network includes a first sampling resistor, a second sampling resistor, and a third sampling resistor. The control unit controls the state of the switching switch so that the sampling network operates in different states, thereby generating a first sampling signal and a second sampling signal based on the PWM signal in standby mode. Signal processing circuitry is used to process the first sampled signal and the second sampled signal to obtain a first reference signal and a second reference signal; The superimposed signal acquisition circuit is used to acquire a first superimposed signal when the first reference signal and the DC output voltage of the charging pile system are superimposed on the third sampling resistor, and a second superimposed signal when the second reference signal and the DC output voltage of the charging pile system are superimposed on the third sampling resistor; An insulation sampling resistance calculation module is used to calculate the positive and negative pole insulation impedance to ground of the charging pile system based on the first reference signal, the second reference signal, the resistance value of the first sampling resistor, the resistance value of the second sampling resistor, the resistance value of the third sampling resistor, the DC output voltage, the first superimposed signal, and the second superimposed signal. And based on the insulation resistance of the positive and negative poles to ground, it is determined whether the charging pile system has a grounding fault; The resistance value of the first sampling resistor is equal to the resistance value of the second sampling resistor; The insulation sampling resistance calculation module is used to calculate the positive-to-ground insulation impedance and the negative-to-ground insulation impedance based on the following formula: ； ； Wherein, R4 represents the positive-to-ground insulation resistance, R5 represents the negative-to-ground insulation resistance, R1 represents the resistance value of the first sampling resistor, R3 represents the resistance value of the third sampling resistor, VDC represents the DC output voltage, Vc1 represents the first superimposed signal, Vc2 represents the second superimposed signal, V+ represents the third positive power supply voltage, and V- represents the third negative power supply voltage. The switching device includes a first switching device, a voltage divider resistor, and a second switching device; The first end of the first sampling resistor is connected to the positive DC output of the charging pile system, and the second end is connected to the first end of the first switching switch. The first end of the second sampling resistor is connected to the negative DC output of the charging pile system, and the second end is also connected to the first end of the first switching switch. The second end of the first switching switch is grounded through the third sampling resistor. The second end of the first switching switch is also connected to the first end of the second switching switch through the voltage divider resistor. The second end of the second switching switch is grounded. The control unit is used to control the first switching switch to be closed and the second switching switch to be open, or the first switching switch to be open and the second switching switch to be closed.

2. The system for real-time detection of grounding faults in a charging pile system according to claim 1, characterized in that, The first and second switching switches each include a relay coil and a relay switch. The first and second ends of the relay switch are respectively the first and second ends of the switching switch. The first end of the relay coil is connected to the relay voltage, and the second end receives the control signal sent by the control unit.

3. The system for real-time detection of grounding faults in a charging pile system according to claim 1, characterized in that, The signal processing circuit includes a filtering unit, an isolation amplification unit, a differential amplification unit, a forward bias unit, and an ADC; The filtering unit is used to filter the first sampled signal and the second sampled signal; the isolation amplification unit is used to isolate and amplify the first sampled signal and the second sampled signal; the differential amplification unit is used to differentially amplify the first sampled signal and the second sampled signal; the forward bias unit is used to forward bias the first sampled signal and the second sampled signal; the ADC is used to receive and filter the first sampled signal and the second sampled signal to generate the first reference signal and the second reference signal.

4. The system for real-time detection of grounding faults in a charging pile system according to claim 3, characterized in that, The filtering unit includes a first operational amplifier, a first filter resistor, a second filter resistor, a first filter capacitor, and a second filter capacitor. The non-inverting input terminal of the first operational amplifier receives the first sampled signal and the second sampled signal sequentially through the second filter resistor and the first filter resistor, and the inverting input terminal is connected to the output terminal. The first filter capacitor is connected between the non-inverting input terminal of the first operational amplifier and ground. The second filter capacitor is connected between the inverting input terminal of the first operational amplifier and the connection point of the first filter resistor and the second filter resistor. The input terminal of the isolation amplification unit receives the first sampling signal and the second sampling signal, and the output terminal outputs the isolated and amplified first sampling signal and the second sampling signal. The differential amplifier unit includes a first differential resistor, a second differential resistor, a third differential resistor, a fourth differential resistor, and a second operational amplifier; the non-inverting input terminal of the second operational amplifier is connected to the output terminal of the isolation amplifier unit via the first differential resistor, and is grounded via the second differential resistor; the inverting input terminal of the second operational amplifier is connected to the output terminal of the isolation amplifier unit via the third differential resistor to receive the first sampling signal and the second sampling signal, and is connected to the output terminal of the second operational amplifier via the fourth differential resistor; The forward bias unit includes a pull-up resistor, a filter inductor, and a third filter capacitor; the first end of the pull-up resistor receives the second power supply voltage, the second end is connected to the first end of the third filter capacitor and the first end of the filter inductor, the second end of the third filter capacitor is grounded, and the second end of the filter inductor receives the first sampling signal and the second sampling signal output from the output terminal of the second operational amplifier.

5. The system for real-time detection of grounding faults in a charging pile system according to claim 1, characterized in that, The signal generation circuit includes a third operational amplifier, an LC filter unit, a first capacitor, a first resistor, a second resistor, and a third resistor; The non-inverting input terminal of the third operational amplifier is grounded through a first capacitor and connected to the output terminal of the third operational amplifier through the first resistor; the inverting input terminal of the third operational amplifier is connected to the output terminal of the third operational amplifier through the second resistor and grounded through the third resistor; the positive power supply terminal of the third operational amplifier receives the third positive power supply voltage, and the negative power supply terminal receives the third negative power supply voltage; The first end of the LC filter unit is connected to the output terminal of the third operational amplifier, the second end is grounded, and the third end is connected to the PE end of the charging pile system to output the PWM signal.

6. The system for real-time detection of grounding faults in a charging pile system according to claim 1, characterized in that, The superimposed signal acquisition circuit includes an ADC, and the ADC is used to acquire the first superimposed signal and the second superimposed signal; The power supply circuit includes: A DC / DC conversion module for converting the first power supply voltage into a high-side DC voltage; A BOOST module for generating the third positive power supply voltage and the third negative power supply voltage based on the high-side DC voltage; A voltage regulation module for generating the second power supply voltage based on the first power supply voltage.

7. A method for real-time detection of grounding faults in a charging pile system, characterized in that, The method is applied to a system for real-time detecting the grounding fault of a charging pile system according to any one of claims 1-6; the method includes the following steps: S1) Obtain the first reference signal, the second reference signal, the resistance value of the first sampling resistor, the resistance value of the second sampling resistor, the resistance value of the third sampling resistor, the DC output voltage, the first superimposed signal and the second superimposed signal; S2) Calculate the positive and negative pole-to-ground insulation impedances of the charging pile system based on the first reference signal, the second reference signal, the resistance value of the first sampling resistor, the resistance value of the second sampling resistor, the resistance value of the third sampling resistor, the DC output voltage, the first superimposed signal and the second superimposed signal; S3) Judge whether the charging pile system has a grounding fault based on the positive and negative pole-to-ground insulation impedances.

8. The method for real-time detection of grounding faults in a charging pile system according to claim 7, characterized in that, In step S3, when the positive pole-to-ground insulation impedance is higher than the first positive threshold, it is determined that the positive pole of the charging pile system is grounded normally; when the positive pole-to-ground insulation impedance is lower than the first positive threshold, it is determined that the positive pole of the charging pile system is abnormally grounded; when the positive pole-to-ground insulation impedance is lower than the second positive threshold, it is determined that the positive pole of the charging pile system has a grounding fault; When the negative pole-to-ground insulation impedance is higher than the first negative threshold, it is determined that the negative pole of the charging pile system is grounded normally; when the negative pole-to-ground insulation impedance is lower than the first negative threshold, it is determined that the negative pole of the charging pile system is abnormally grounded; when the negative pole-to-ground insulation impedance is lower than the second negative threshold, it is determined that the negative pole of the charging pile system has a grounding fault.

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