A metrological calibration device for new energy vehicle charging safety inspection equipment and a control method thereof

Abstract

A new energy vehicle charging safety inspection and calibration device and its control method include a DC charging measurement and calibration module, an insulation resistance calibration module, and a potential equalization calibration module; the DC charging measurement and calibration module includes a DC charging gun holder, a BMS simulator, a high-precision ammeter, and a high-precision voltmeter; the insulation resistance calibration module includes a main control unit, a high-precision resistor, a high-voltage switching unit, and an AC charging gun holder; the potential equalization calibration module includes a high-precision ammeter, a high-precision voltage source, and a low-voltage switching unit; the low-voltage switching unit includes a low-voltage relay group, a first banana head interface, and a second banana head interface; the AC charging gun holder is connected to the calibration circuit via a low-voltage relay group. By integrating a high-precision measurement module, a resistance switching unit, and a BMS simulator, the present invention achieves one-click calibration of DC charging, insulation resistance, and potential equalization, solving the problems of contact resistance interference and multi-instrument collaboration.

Description

Technical Field

[0001] The present invention relates to the technical field of charging piles, and in particular to a metrological calibration device for new energy vehicle charging safety inspection equipment and a control method thereof. Background Art

[0002] With the development of the new energy vehicle annual inspection market, the measurement and calibration of new energy vehicle charging safety inspection equipment has become one of the important links in the development of the industry. Since the intelligent new energy vehicle charging safety inspection equipment is connected to the vehicle through the national standard DC charging gun, national standard AC charging gun, and resistance test clamp, the traditional calibration method of charging piles, high resistance meters, and low resistance meters usually has the following defects:

[0003] 1. Unstable contact resistance: When the resistance test clip is connected to the device, the contact resistance fluctuates greatly, resulting in calibration errors;

[0004] 2. Inefficient equipment dispersion: Multiple independent instruments (such as high resistance meters and low resistance meters) are required, which makes operation complicated and time-consuming;

[0005] 3. Lack of intelligence: Unable to automatically switch calibration modes, relying on manual intervention, which is inefficient.

[0006] As a result, the existing traditional calibration methods of charging piles, high resistance meters, and low resistance meters are difficult to meet the requirements for efficient and convenient testing of charging safety inspection equipment. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention provides a metrology and calibration device for new energy vehicle charging safety inspection equipment and a control method thereof, which overcomes the shortcomings of the existing technology. By integrating a high-precision measurement module, a resistance switching unit and a BMS simulator, one-click calibration of DC charging, insulation resistance and potential equalization is achieved, solving the problems of contact resistance interference and multi-instrument collaboration.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0009] A metrology and calibration device for new energy vehicle charging safety inspection equipment, comprising a DC charging metrology and calibration module, an insulation resistance calibration module, and a potential equalization calibration module;

[0010] The DC charging measurement and calibration module includes a DC charging gun holder, a BMS simulator, a high-precision ammeter, and a high-precision voltmeter. The first port of the DC charging gun holder is connected to the DC charging gun of the device under test, and the second port of the DC charging gun holder is connected to the external load box through a load interface. The high-precision ammeter is connected in series in the DC+ path of the DC charging gun holder, and the high-precision voltmeter is connected in parallel between the DC+ and DC- paths of the DC charging gun holder. The BMS simulator communicates with the device under test via the CAN bus.

[0011] The insulation resistance calibration module includes a main control unit, a high-precision resistor, a high-voltage switching unit and an AC charging gun holder. The main control unit controls the BMS simulator, the high-precision resistor and the high-voltage switching unit through the CAN bus. The high-voltage switching unit is used to control the high-precision resistor to switch to the DC± terminal and PE terminal of the DC charging gun holder or the L / N terminal and PE terminal of the AC charging gun holder;

[0012] The potential equalization calibration module includes a high-precision ammeter, a high-precision voltage source and a low-voltage switching unit. The high-precision ammeter is used to measure the calibration loop current, and the high-precision voltage source is used to measure the standard excitation voltage. The low-voltage switching unit includes a low-voltage relay group, a first banana head interface and a second banana head interface. The first banana head interface and the second banana head interface are respectively connected to the positive and negative poles of the resistance test clip of the device under test. The low-voltage relay group is used to connect the resistance test clip of the device under test to the high-precision ammeter and the high-precision voltage source to form independent current loops and voltage measurement loops, and the PE end of the AC charging gun socket is connected to the calibration circuit through the low-voltage relay group.

[0013] Preferably, the high-voltage switching unit includes a relay K5, a relay K10, a relay K11, a relay K12, a relay K13, a relay K14 and a relay K15, wherein the two ends of the relay K5 are respectively connected to the PE end of the DC charging gun holder and the high-precision resistor, the two ends of the relay K10 are respectively connected to the PE end of the AC charging gun holder and the high-precision resistor, the two ends of the relay K11 are respectively connected to the L / N end of the AC charging gun holder and the high-precision resistor, and the relays K12, K13, K14 and K15 respectively control the high-precision resistor to be connected to the DC± ends of the DC charging gun holder;

[0014] When relay K5, relay K12, relay K13, relay K14 and relay K15 are energized, the high-precision resistor is connected to the DC± terminal and PE terminal of the DC charging gun holder;

[0015] When relay K10 and relay K11 are attracted, the high-precision resistor is connected to the L / N terminal and the PE terminal of the AC charging gun socket.

[0016] Preferably, the DC+ end of the DC charging gun holder is connected to the DC+ end of the external load box through relay K12 and relay K16 in sequence, and the DC- end of the DC charging gun holder is connected to the DC- end of the external load box through relay K13 and relay K17 in sequence.

[0017] Preferably, the low-voltage relay group includes relay K1, relay K2, relay K3, relay K4 and relay K6, relay K7, relay K8, relay K9;

[0018] When relay K1 and relay K3 are closed, the positive electrode of the high-precision voltage source is connected to the positive electrode of the resistance test clip through the first banana plug interface, forming a positive calibration loop at the PE end of the DC charging gun socket;

[0019] When reverse current is detected, relays K2 and K4 are energized to switch the circuit polarity.

[0020] The relays K6, K7, K8 and K9 are used to adapt to the L / N polarity switching of the AC charging gun holder;

[0021] When relay K6 and relay K8 are energized, the L and PE terminals of the AC charging gun socket are connected to the calibration circuit;

[0022] When relay K7 and relay K9 are energized, the N terminal and the PE terminal of the AC charging gun socket are connected to the calibration circuit.

[0023] Preferably, the high-precision resistor is a multi-level standard resistor configured according to the 1-2-2-5 principle, and each level of resistance is switched by an independent relay.

[0024] The present invention also discloses a control method for a measurement and calibration device of a new energy vehicle charging safety inspection device, which comprises the following steps:

[0025] Step S1: Connect the DC charging gun and AC charging gun of the device under inspection to the DC charging gun socket and the AC charging gun socket respectively;

[0026] Step S2: Connect the positive electrode and the negative electrode of the resistance test clip of the device under test to the first banana plug interface and the second banana plug interface respectively;

[0027] Step S3: DC charging current calibration: Relays K12 and K13 are energized to establish a CAN communication link between the BMS simulator and the device under test, transmitting battery parameters. After entering the charging phase, relays K16 and K17 are energized to load a standard current or voltage to the device under test. A high-precision ammeter and high-precision voltmeter measure the charging current and voltage, respectively, and compare them with the values displayed by the device under test.

[0028] Step S4: Current and voltage error calculation:

[0029] Absolute error: , ;

[0030] Relative error: ; ;

[0031] in, is the absolute error of current, is the absolute voltage error; is the current relative error, is the relative voltage error of the device under test; is the current value displayed by the device under test, The current value displayed by the high-precision ammeter; is the voltage value displayed by the device under test, It is the voltage value displayed by the high-precision voltmeter;

[0032] Step S5: Insulation resistance calibration: select DC calibration mode or AC calibration mode;

[0033] When the DC calibration mode is selected, relay K5 and relays K12, K13, K14, and K15 are energized, and the high-precision resistor is controlled via the CAN bus to cut in resistance according to the test requirements. The device under test is then started and the insulation resistance value of the device under test is obtained.

[0034] When in AC calibration mode, relay K11 and relay K10 are energized, and the high-precision resistor is controlled via the CAN bus to change the resistance value according to the test requirements. The device under test is then started and the insulation resistance value of the device under test is obtained.

[0035] Step S6: Calculation of resistance value error:

[0036] Compare the measurement results with the insulation resistance value of the device under test and calculate the error of the device under test:

[0037] ;

[0038] ;

[0039] in, is the absolute error of the resistor, is the relative error of resistance, The insulation resistance value displayed by the device under test, Insulation resistance value displayed for high-precision resistors.

[0040] Step S7: In the potential equalization calibration mode, the relays K1-K4 or K6-K9 are energized, the loop current and voltage are output through a high-precision voltage source and a high-precision ammeter, the on-resistance is measured in combination with the four-wire loop, and the direction error is eliminated by switching the polarity.

[0041] Preferably, it also includes:

[0042] Step S8: Calibrate the on-resistance between the PE terminal of the DC charging gun socket and the resistance test clip;

[0043] Connect the DC charging cable to the DC charging cable holder and remove the two connecting wires from the resistance test clip. Connect the two ends of the resistance test clip to a high-precision ammeter and a high-precision voltage source through the first and second banana plugs, respectively, to form a four-wire calibration loop. Based on the measurement data from the high-precision ammeter and high-precision voltage source, calculate the on-resistance between the PE terminal of the DC charging cable holder and the resistance test clip.

[0044] Step S9: Calibrate the on-resistance between the PE terminal of the AC charging gun socket and the resistance test clip;

[0045] Connect the AC charging gun to the AC charging gun socket and remove the two connecting wires of the resistance test clip. Connect the two ends of the resistance test clip to a high-precision ammeter and a high-precision voltage source through the first and second banana plug interfaces, respectively, to form a four-wire calibration loop. Switch the calibration loop to the PE terminal of the national standard AC charging gun socket and the resistance test clip through the low-voltage switching unit. Perform a four-wire calibration and calculate the on-resistance value between the PE terminal of the AC charging gun socket and the resistance test clip based on the measurement data from the high-precision ammeter and high-precision voltage source.

[0046] The present invention provides a metrology and calibration device for new energy vehicle charging safety inspection equipment and a control method thereof, which has the following beneficial effects: a DC charging metrology and calibration module is formed by a DC charging gun holder, a BMS simulator, a high-precision ammeter, and a high-precision voltmeter. When the DC charging meter of the new energy vehicle charging equipment needs to be calibrated, the DC charging metrology and calibration module simulates a real charging scenario and compares it with high-precision measurements to verify the measurement accuracy of parameters such as voltage and current of the inspected device. An insulation resistance calibration module is formed by a high-precision resistor, a high-voltage switching unit, and an AC charging gun holder. When insulation resistance calibration is required, the insulation resistance calibration module simulates different insulation resistance values to verify the accuracy of insulation resistance measurement of the inspected device in a high-voltage DC / AC environment. A high-precision ammeter, a high-precision voltage source, and a low-voltage switching unit are formed by a potential equalization calibration module to verify whether the on-resistance between the PE terminal of the charging gun holder and other conductive components meets safety standards. By integrating the DC charging metrology and calibration module, the insulation resistance calibration module, and the potential equalization calibration module with the BMS simulator and intelligent resistor switching technology, one-click high-precision calibration is achieved. The use of four-wire measurement and polarity adaptive circuitry solves issues with contact resistance and directional errors, significantly improving calibration efficiency and accuracy. This makes it suitable for the metrological certification of new energy vehicle charging equipment. This addresses the pain points of traditional calibration methods, such as low efficiency, poor accuracy, and dispersed equipment, achieving efficient, high-precision, and intelligent calibration of new energy vehicle charging equipment. It provides reliable technical support for annual inspections of charging piles, on-board equipment testing, and industry standard certification, with significant economic benefits and social value. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the prior art.

[0048] Figure 1 Schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention.

[0050] Example 1, as Figure 1 As shown, a metrology and calibration device for new energy vehicle charging safety inspection equipment includes a DC charging metrology and calibration module, an insulation resistance calibration module, and a potential equalization calibration module;

[0051] The DC charging measurement and calibration module includes a DC charging gun socket 1, a BMS simulator 2, a high-precision ammeter 3, and a high-precision voltmeter 4. The first port of the DC charging gun socket 1 is connected to the DC charging gun of the device under test, and the second port of the DC charging gun socket 1 is connected to the load interface 5. The load interface 5 is connected to the external load box through a relay. The high-precision ammeter 3 is connected in series in the DC+ path of the DC charging gun socket 1, and the high-precision voltmeter 4 is connected in parallel between the DC+ and DC- terminals of the DC charging gun socket 1. The BMS simulator 2 communicates with the device under test via the CAN bus.

[0052] The insulation resistance calibration module includes a main control unit, a high-precision resistor 6, a high-voltage switching unit, and an AC charging gun socket 7. The main control unit controls the BMS simulator 2, the high-precision resistor 6, and the high-voltage switching unit through the CAN bus. The high-voltage switching unit is used to control the high-precision resistor 6 to switch to the DC± terminal and PE terminal of the DC charging gun socket 1 or the L / N terminal and PE terminal of the AC charging gun socket 7.

[0053] The potential equalization calibration module includes a high-precision ammeter 8, a high-precision voltage source 9 and a low-voltage switching unit. The high-precision ammeter 8 is used to measure the calibration loop current, the high-precision voltage source 9 is used to measure the standard excitation voltage, and the low-voltage switching unit includes a low-voltage relay group, a first banana head interface 10 and a second banana head interface 11. The first banana head interface 10 and the second banana head interface 11 are respectively connected to the positive and negative poles of the resistance test clip of the device under test. The low-voltage relay group is used to connect the resistance test clip of the device under test to the high-precision ammeter 8 and the high-precision voltage source 9, and the PE end of the AC charging gun socket 7 is connected to the calibration circuit through the low-voltage relay group.

[0054] Among them, the high-voltage switching unit includes relay K5, relay K10, relay K11, relay K12, relay K13, relay K14 and relay K15. The two ends of relay K5 are respectively connected to the PE end of the DC charging gun holder 1 and the high-precision resistor 6. The two ends of relay K10 are respectively connected to the PE end of the AC charging gun holder 7 and the high-precision resistor 6. The two ends of relay K11 are respectively connected to the L / N ends of the AC charging gun holder 7 and the high-precision resistor 6. Relays K12, relay K13, relay K14 and relay K15 respectively control the high-precision resistor 6 to be connected to the DC± ends of the DC charging gun holder 1;

[0055] When relay K5, relay K12, relay K13, relay K14 and relay K15 are energized, the high-precision resistor 6 is connected to the DC± terminal and the PE terminal of the DC charging gun holder 1;

[0056] When relay K10 and relay K11 are attracted, the high-precision resistor 6 is connected to the L / N terminal and the PE terminal of the AC charging gun socket 7.

[0057] Among them, the DC+ end of the DC charging gun socket 1 is connected to the DC+ end of the external load box through relay K12 and relay K16 in sequence, and the DC- end of the DC charging gun socket 1 is connected to the DC- end of the external load box through relay K13 and relay K17 in sequence.

[0058] Among them, the low-voltage relay group includes relay K1, relay K2, relay K3, relay K4 and relay K6, relay K7, relay K8, relay K9;

[0059] When relay K1 and relay K3 are energized, the positive electrode of the high-precision voltage source 9 is connected to the positive electrode of the resistance test clip through the first banana plug interface 10, forming a positive calibration loop at the PE end of the DC charging gun socket 1;

[0060] When reverse current is detected, relays K2 and K4 are energized to switch the circuit polarity.

[0061] Relay K6, relay K7, relay K8 and relay K9 are used to adapt to the L / N polarity switching of the AC charging gun socket 7;

[0062] When relay K6 and relay K8 are energized, the L and PE terminals of the AC charging gun socket 7 are connected to the calibration circuit;

[0063] When relay K7 and relay K9 are energized, the N terminal and PE terminal of the AC charging gun socket 7 are connected to the calibration circuit.

[0064] Working principle:

[0065] The DC charging calibration module is composed of a DC charging gun holder 1, a BMS simulator 2, a high-precision ammeter 3, and a high-precision voltmeter 4. When the DC charging metering of new energy vehicle charging equipment needs to be calibrated, the DC charging calibration module simulates the actual charging scenario and compares it with the high-precision measurement to verify the measurement accuracy of the voltage, current and other parameters of the device under test. The specific principles are as follows:

[0066] First, BMS Simulator 2 establishes communication with the device under test, simulating a vehicle's battery management system (BMS). Battery parameters and status feedback are sent to the device under test via the CAN bus. High-precision ammeter 3, high-precision voltmeter 4, and an external load box are then used to apply standard current (0-300A) and voltage (0-1500V) to the device under test, serving as a calibration reference. By comparing the displayed value of the device under test with the measured value of the standard source, the absolute and relative errors are calculated, effectively determining whether the device complies with the measurement standard.

[0067] To verify the device's dynamic response, the DC charging cable of the device under test (DUT) is first inserted into the connector of DC charging cable holder 1. After ensuring proper contact, the calibration procedure is initiated. The main control unit (MCU) controls relays K12 and K13 to activate CAN bus communication on the BMS simulator 2, sending virtual battery parameters to the DUT. The DUT interprets the CAN message and enters a charging ready state. Relays K16 and K17 are then controlled to apply a standard current (e.g., 200A) and voltage (e.g., 800V) to the DUT. A 60kW external load box is then connected to simulate high-power charging conditions and verify the device's dynamic response. A high-precision ammeter 3 monitors the DC+ circuit current of DC charging cable holder 1 in real time, while a high-precision voltmeter 4 simultaneously measures the DC+ and DC- voltages of DC charging cable holder 1. The DUT's displayed value is then compared with the standard measured values of the high-precision ammeter 3 and high-precision voltmeter 4 to calculate accurate error data. If the error exceeds a threshold (e.g., a relative error > 1%), a calibration failure report is generated, prompting adjustments to the DUT. Afterward, disconnect all relays to complete the calibration process. Save the calibration data and eject the charging cable from the device under test. Through this process, the DC charging calibration module enables efficient and accurate one-stop metrology certification.

[0068] The insulation resistance calibration module is composed of a high-precision resistor 6, a high-voltage switching unit, and an AC charging gun holder 7. When insulation resistance calibration is required, the insulation resistance calibration module simulates different insulation resistance values to verify the accuracy of the insulation resistance measurement of the device under test in a high-voltage DC / AC environment. The module first uses the high-precision resistor 6 to provide switchable standard resistance values. In this embodiment, the high-precision resistor 6 includes standard resistance values of 50kΩ, 100kΩ, 200kΩ, 200kΩ, 500kΩ, 1MΩ, 2MΩ, 2MΩ, 5MΩ, 10MΩ, 20MΩ, 20MΩ, 50MΩ, 100MΩ, 200MΩ, 200MΩ, 500MΩ, 1GΩ, 2GΩ, 2GΩ, and 5GΩ, according to the 1-2-2-5 principle.

[0069] The "1-2-2-5 principle" is a standardized method for configuring resistor values in bins (this is existing technology). It is used to ensure that the proportional relationship and logarithmic distribution between the various resistor values in a resistor network covering a wide range of resistance values are reasonable. Its core is to generate a series of resistance values by combining four basic coefficients: 1, 2, 2, and 5. The step ratio between adjacent bins is consistent, thereby optimizing measurement accuracy and calibration efficiency.

[0070] The specific logic of the 1-2-2-5 binning is: first use 1, 2, 2, and 5 as basic coefficients and expand them in decimal to form the following typical bins (unit: Ω):

[0071] First cycle: 1, 2, 2, 5;

[0072] Second cycle: 10, 20, 20, 50;

[0073] Third cycle: 100, 200, 200, 500;

[0074] Fourth cycle: 1k, 2k, 2k, 5k;

[0075] ...(and so on, until the target maximum resistance value).

[0076] The present invention configures the above-mentioned standard resistance values through the 1-2-2-5 principle, and each standard resistance value corresponds to an independent relay. By controlling the attraction of each relay, the high-precision resistor 6 is quickly switched to the target resistance value.

[0077] The resistance simulation range reaches 50kΩ-10GΩ, in 10kΩ steps, with an accuracy of 0.1%. Relays within the high-precision resistor 6 are used to switch between different resistance levels, simulating actual insulation fault scenarios. A high-voltage switching unit then selects between DC and AC high-voltage paths. Independent current excitation and voltage detection circuits eliminate contact resistance and lead errors.

[0078] When calibrating insulation resistance, first connect the DC charging gun and AC charging gun of the device under test to the corresponding gun sockets, and initialize the high-voltage switching unit and high-precision resistor 6.

[0079] Then select the corresponding calibration mode: in DC mode, energize relays K5, K12, K13, K14, and K15 to connect the high-precision resistor 6 to the DC± and PE terminals of the DC charging gun socket 1; and in AC mode, energize relays K10 and K11 to connect the high-precision resistor 6 to the L and PE terminals of the AC charging gun socket 7.

[0080] The main control unit then controls the opening and closing of the internal relay of the high-precision resistor 6 via the CAN bus, thereby controlling the high-precision resistor 6 to select the appropriate resistance level based on the test requirements. The device under test is then controlled to start insulation resistance measurement and obtain its insulation resistance value. The actual measured value is then compared with the standard resistance value provided by the high-precision resistor 6 to determine the insulation resistance measurement error of the device under test. If the error is within an acceptable range (e.g., a relative error of less than 5%), the main control unit outputs a calibration success report. If the error exceeds the standard, a calibration failure report is generated and the user is prompted to adjust or repair the device. The high-precision resistor 6 is then controlled to switch to the next resistance level and the above steps are repeated, thus achieving a multi-level cyclic testing effect. When the calibration is complete, the relay is disconnected, restoring the device to standby mode, completing the entire insulation resistance calibration process. Through this process, the insulation resistance calibration module can systematically address the problems of large contact errors, limited range, and low safety in traditional calibration, providing technical support for the safety and compliance of new energy vehicle charging equipment.

[0081] The potential equalization calibration module, comprised of a high-precision ammeter 8, a high-precision voltage source 9, and a low-voltage switching unit, verifies that the on-resistance between the protective earth (PE) terminal of the charging connector and other conductive components (such as the charging connector housing and metal components) meets safety standards. It employs a four-wire measurement method with independent current excitation and voltage detection circuits to eliminate the effects of contact and lead resistance on the measurement results. A high-precision voltage source 9 (10mV-10V, 0.1% accuracy) provides a standard excitation voltage, while a high-precision ammeter 8 (0-10A, 0.2% accuracy) measures the circuit current to calculate the on-resistance. The low-voltage switching unit uses a low-voltage relay group to switch the polarity of the four-wire circuit to accommodate both DC and AC charging connectors 1 and 7. The first and second banana connectors 10 and 11 are directly connected to the resistance test clip of the device under test, forming a four-wire calibration path.

[0082] When the potential equalization calibration module is working, first, the resistance test clamp of the device under test is connected to the calibration device of the present invention through the first banana plug interface 10 and the second banana plug interface 11.

[0083] The main control unit initializes the high-precision voltage source 9 and high-precision ammeter 8. Then, the calibration mode (DC or AC) is selected. In DC mode, relays K1 and K3 (or K2 and K4) are energized, forming a current path: PE terminal of the DC charging connector 1 → relay K1 → first banana connector 10 → resistance test clip of the device under test → second banana connector 11 → relay K3 → high-precision ammeter 8; this forms a four-wire calibration loop. The output of the high-precision voltage source 9 is directly connected to the first and second banana connectors 10, 11, providing a standard excitation voltage (10mV-10V). In AC mode, relays K7 and K9 are energized to connect the PE terminal of the AC charging connector 7 to the positive path of the circuit (compatible with the positive terminals of L1 / L2 / L3), or relays K6 and K8 are energized to connect the PE terminal of the AC charging connector 7 to the positive path of the circuit (compatible with the negative terminal). A high-precision voltage source 9 then outputs a standard voltage (e.g., 1V), which is used in conjunction with a high-precision ammeter 8 to measure the current (e.g., 1A) to simulate a target resistance value (e.g., 1Ω). If the high-precision ammeter 8 detects a reverse current direction (e.g., -1A), the central control unit controls the low-voltage switching unit to automatically switch relay combinations. For example, in DC mode, relays K1 and K3 are disconnected, and relays K2 and K4 are engaged. In AC mode, relays K7 and K9 are disconnected, and relays K6 and K8 are engaged. This prevents the voltage source direction from affecting the resistance measurement of the device under test, effectively ensuring that test accuracy is unaffected by changes in current polarity. The error is then calculated by comparing the displayed value of the device under test with the measured on-resistance value, thereby evaluating the accuracy and safety of the protective grounding terminal of the charging gun socket. If the error exceeds the threshold (such as a relative error > 5%), a calibration failure report is generated and a prompt is given to adjust the device under test. If the error is within an acceptable range, the calibration is successful and the final calibration result is output. Through the above process, the potential equalization calibration module achieves precise calibration of the resistance of DC charging gun socket 1 and AC charging gun socket 7 through four-wire high-precision measurement and polarity adaptive control. Ensure the safety and reliability of the grounding system of DC charging gun socket 1 and AC charging gun socket 7, and provide core protection for the charging safety of new energy vehicles.

[0084] In addition, the calibration device of the present invention can also calibrate the on-resistance between the PE end of the DC charging gun holder 1 and the resistance test clip; connect the DC charging gun to the DC charging gun holder 1, remove the two connecting wires of the resistance test clip, and connect the two ends of the resistance test clip to the high-precision ammeter 8 and the high-precision voltage source 9 through the first banana head interface 10 and the second banana head interface 11 to simulate the four-wire calibration method. The contact resistance between the DC charging gun and the DC charging gun holder 1 is small and negligible, which fundamentally solves the problem of large contact resistance of the resistance test clip during calibration, and also solves the problem of internal resistance change when switching between different standard resistors. When calibrating the on-resistance between the PE end of the AC charging gun holder 7 and the resistance test clip, the circuit will be switched to the AC charging gun holder 7 through the low-voltage switching unit.

[0085] The present invention realizes one-touch high-precision calibration by integrating a DC charging measurement and calibration module, an insulation resistance calibration module, and a potential equalization calibration module in combination with a BMS simulator 2 and intelligent resistance switching technology. The four-wire measurement and polarity adaptive circuit are used to solve the problems of contact resistance and direction error, significantly improve the calibration efficiency and accuracy, and are suitable for the metrology certification of new energy vehicle charging equipment. It solves the pain points of low efficiency, poor accuracy, and equipment dispersion in traditional calibration methods, and realizes the high efficiency, high precision, and intelligent calibration of new energy vehicle charging equipment. It provides reliable technical support for annual inspections of charging piles, vehicle-mounted equipment testing, and industry standard certification, and has significant economic benefits and social value.

[0086] In a second embodiment, the present invention further discloses a control method for a measurement and calibration device of a new energy vehicle charging safety inspection device, which comprises the following steps:

[0087] Step S1: Connect the DC charging gun and AC charging gun of the device under inspection to the DC charging gun socket 1 and the AC charging gun socket 7 respectively;

[0088] Step S2: Connect the positive electrode and the negative electrode of the resistance test clip of the device under test to the first banana plug interface 10 and the second banana plug interface 11 respectively;

[0089] Step S3: DC charging current calibration: Relays K12 and K13 are energized to establish a CAN communication link between the BMS simulator 2 and the device under test, transmitting battery parameters. After entering the charging phase, relays K16 and K17 are energized to load a standard current or voltage to the device under test. High-precision ammeter 3 and high-precision voltmeter 4 measure the charging current and voltage, respectively, and compare them with the values displayed by the device under test.

[0090] Step S4: Current and voltage error calculation:

[0091] Absolute error: , ;

[0092] Relative error: ; ;

[0093] in, is the absolute error of current, is the absolute voltage error; is the current relative error, is the relative voltage error of the device under test; is the current value displayed by the device under test, It is the current value displayed by the high-precision ammeter 3; is the voltage value displayed by the device under test, It is the voltage value displayed by the high-precision voltmeter 4;

[0094] Step S5: Insulation resistance calibration: select DC calibration mode or AC calibration mode;

[0095] When the DC calibration mode is selected, the relay K5 and relays K12, K13, K14 and K15 are energized, and the high-precision resistor 6 is controlled via the CAN bus to cut in the resistance value according to the test requirements, and then the device under test is started and the insulation resistance value of the device under test is obtained;

[0096] When performing AC calibration mode, the relay K11 and relay K10 are energized, and the high-precision resistor 6 is controlled via the CAN bus to cut in the resistance value according to the test requirements, and then the device under test is started and the insulation resistance value of the device under test is obtained;

[0097] Step S6: Calculation of resistance value error:

[0098] Compare the measurement results with the insulation resistance value of the device under test and calculate the error of the device under test:

[0099] ;

[0100] ;

[0101] in, is the absolute error of the resistor, is the relative error of resistance, The insulation resistance value displayed by the device under test, The insulation resistance value shown for high-precision resistor 6.

[0102] Step S7: In potential equalization calibration mode, remove the two wires from the resistance test clip of the device under test and connect the resistance test clip of the device under test to the calibration device via the first banana plug interface 10 and the second banana plug interface 11. Inside the calibration device, the banana plug interfaces are connected to a high-precision ammeter 8 and a high-precision voltage source 9, forming independent current excitation and voltage measurement circuits.

[0103] During potential equalization calibration between the PE terminal of the DC charging connector 1 and the resistance test clamp, relays K1 and K3 are energized, forming a current path: PE terminal of the DC charging connector 1 → relay K1 → first banana connector 10 → resistance test clamp of the device under test → second banana connector 11 → relay K3 → high-precision ammeter 8; this forms a four-wire calibration loop. For example, when simulating a 1Ω standard resistor and the current reading of high-precision ammeter 8 is 1A, high-precision voltage source 9 outputs a 1V voltage. If the current measured by high-precision ammeter 8 is negative, the central control unit controls relays K1 and K3 to disconnect and engage relays K2 and K4.

[0104] When calibrating the potential equalization between the PE terminal of the AC charging connector 7 and the resistance test clamp, relays K7 and K9 are energized to connect the PE terminal of the AC charging connector 7 to the positive path of the circuit (compatible with the positive poles of L1 / L2 / L3), or relays K6 and K8 are energized to connect the PE terminal of the AC charging connector 7 to the negative path of the circuit (compatible with the negative pole). A high-precision voltage source 9 outputs a standard voltage (e.g., 1V) and uses the ammeter to measure the current (e.g., 1A) to simulate the target resistance value (e.g., 1Ω). If the current measured by the high-precision ammeter 8 is negative (e.g., the polarity of the device under test is reversed), the central control unit controls the low-voltage switching unit to automatically energize the reverse relay combination (e.g., relays K6 and K8) to switch the circuit polarity and ensure measurement accuracy.

[0105] Additionally, it includes:

[0106] Step S8: Calibrate the on-resistance between the PE terminal of the DC charging gun socket 1 and the resistance test clip;

[0107] Connect the DC charging gun to the DC charging gun socket 1 and remove the two connecting wires from the resistance test clip. Connect the two ends of the resistance test clip to the high-precision ammeter 8 and the high-precision voltage source 9 through the first banana plug interface 10 and the second banana plug interface 11, respectively, to form a four-wire calibration loop. Based on the measurement data from the high-precision ammeter 8 and the high-precision voltage source 9, calculate the on-resistance value between the PE terminal of the DC charging gun socket 1 and the resistance test clip.

[0108] Step S9: Calibrate the on-resistance between the AC charging gun socket 7PE terminal and the resistance test clip;

[0109] Connect the AC charging gun to the AC charging gun socket 7, and remove the two connecting wires of the resistance test clip; connect the two ends of the resistance test clip to the high-precision ammeter 8 and the high-precision voltage source 9 through the first banana head interface 10 and the second banana head interface 11 respectively to form a four-wire calibration loop; switch the calibration loop to the PE end of the national standard AC charging gun socket 7 and the resistance test clip through the low-voltage switching unit; perform four-wire calibration, and calculate the on-resistance value between the PE end of the AC charging gun socket 7 and the resistance test clip based on the measurement data of the high-precision ammeter 8 and the high-precision voltage source 9.

[0110] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A metrological calibration device for new energy vehicle charging safety inspection equipment, characterized by: Including DC charging measurement calibration module, insulation resistance calibration module and potential equalization calibration module; The DC charging measurement and calibration module comprises a DC charging gun holder (1), a BMS simulator (2), a high-precision ammeter (3) and a high-precision voltmeter (4); the first port of the DC charging gun holder (1) is connected to the DC charging gun of the device under test, and the second port of the DC charging gun holder (1) is connected to the external load box via a load interface (5); the high-precision ammeter (3) is connected in series in the DC+ path of the DC charging gun holder (1), and the high-precision voltmeter (4) is connected in parallel between the DC+ and DC- paths of the DC charging gun holder (1); the BMS simulator (2) communicates with the device under test via a CAN bus; The insulation resistance calibration module includes a main control unit, a high-precision resistor (6), a high-voltage switching unit and an AC charging gun holder (7), wherein the main control unit controls the BMS simulator (2), the high-precision resistor (6) and the high-voltage switching unit via a CAN bus, and the high-voltage switching unit is used to control the high-precision resistor (6) to switch to the DC± terminal and the PE terminal of the DC charging gun holder (1) or the L / N terminal and the PE terminal of the AC charging gun holder (7); The potential equalization calibration module includes a high-precision ammeter (8), a high-precision voltage source (9) and a low-voltage switching unit, wherein the high-precision ammeter (8) is used to measure the calibration loop current, the high-precision voltage source (9) is used to measure the standard excitation voltage, and the low-voltage switching unit includes a low-voltage relay group, a first banana head interface (10) and a second banana head interface (11), wherein the first banana head interface (10) and the second banana head interface (11) are respectively connected to the positive pole and the negative pole of the resistance test clamp of the device under test, and the low-voltage relay group is used to connect the resistance test clamp of the device under test to the high-precision ammeter (8) and the high-precision voltage source (9), and the PE end of the AC charging gun holder (7) is connected to the calibration circuit through the low-voltage relay group; The high-voltage switching unit includes a relay K5, a relay K10, a relay K11, a relay K12, a relay K13, a relay K14, and a relay K15. The two ends of the relay K5 are respectively connected to the PE end of the DC charging gun seat (1) and the high-precision resistor (6). The two ends of the relay K10 are respectively connected to the PE end of the AC charging gun seat (7) and the high-precision resistor (6). The two ends of the relay K11 are respectively connected to the L / N end of the AC charging gun seat (7) and the high-precision resistor (6). The relays K12, K13, K14, and K15 respectively control the high-precision resistor (6) to be connected to the DC± ends of the DC charging gun seat (1). When relay K5, relay K12, relay K13, relay K14 and relay K15 are attracted, the high-precision resistor (6) is connected to the DC± terminal and the PE terminal of the DC charging gun holder (1); When the relay K10 and the relay K11 are attracted, the high-precision resistor (6) is connected to the L / N terminal and the PE terminal of the AC charging gun holder (7); The low-voltage relay group includes relay K1, relay K2, relay K3, relay K4 and relay K6, relay K7, relay K8, and relay K9; When relay K1 and relay K3 are energized, the positive electrode of the high-precision voltage source (9) is connected to the positive electrode of the resistance test clip via the first banana plug interface (10), forming a positive calibration loop at the PE end of the DC charging gun holder (1); When reverse current is detected, relays K2 and K4 are energized to switch the circuit polarity. The relay K6, relay K7, relay K8 and relay K9 are used to adapt to the L / N polarity switching of the AC charging gun holder (7); When relay K6 and relay K8 are energized, the L terminal and the PE terminal of the AC charging gun holder (7) are connected to the calibration circuit; When relay K7 and relay K9 are energized, the N terminal and the PE terminal of the AC charging gun holder (7) are connected to the calibration circuit.

2. The metrology and calibration equipment for new energy vehicle charging safety inspection equipment according to claim 1, characterized in that: The DC+ end of the DC charging gun holder (1) is connected to the DC+ end of the load interface (5) through relays K12 and K16 in sequence, and the DC- end of the DC charging gun holder (1) is connected to the DC- end of the load interface (5) through relays K13 and K17 in sequence.

3. The metrology and calibration equipment for new energy vehicle charging safety inspection equipment according to claim 1, characterized in that: The high-precision resistor (6) is a multi-level standard resistor configured according to the 1-2-2-5 principle, and each level of resistance is switched by an independent relay.

4. The control method of the measurement and calibration equipment of the new energy vehicle charging safety inspection equipment according to claim 2 is characterized in that: The following steps are involved: Step S1: Connect the DC charging gun and AC charging gun of the device under inspection to the DC charging gun base (1) and the AC charging gun base (7) respectively; Step S2: connecting the positive electrode and the negative electrode of the resistance test clip of the device to be tested to the first banana plug interface (10) and the second banana plug interface (11) respectively; Step S3: DC charging current calibration: energize relays K12 and K13 to establish a CAN communication link between the BMS simulator (2) and the device under test, and transmit battery parameters; after entering the charging phase, energize relays K16 and K17 to load a standard current or voltage to the device under test, and use a high-precision ammeter (3) and a high-precision voltmeter (4) to measure the charging current and voltage, respectively, and compare them with the values displayed by the device under test; Step S4: Current and voltage error calculation: Absolute error: , ; Relative error: ; ; in, is the absolute error of current, is the absolute voltage error; is the current relative error, is the relative voltage error of the device under test; is the current value displayed by the device under test, is the current value displayed by the high-precision ammeter (3); is the voltage value displayed by the device under test, is the voltage value displayed by the high-precision voltmeter (4); Step S5: Insulation resistance calibration: select DC calibration mode or AC calibration mode; When the DC calibration mode is selected, the relay K5 and relays K12, K13, K14, and K15 are energized, and the high-precision resistor (6) is controlled via the CAN bus to cut in the resistance value according to the test requirements, and then the device under test is started and the insulation resistance value of the device under test is obtained; When performing the AC calibration mode, the relay K11 and the relay K10 are energized, and the high-precision resistor (6) is controlled via the CAN bus to cut in the resistance value according to the test requirements, and then the device under test is started and the insulation resistance value of the device under test is obtained; Step S6: Calculation of resistance value error: Compare the measurement results with the insulation resistance value of the device under test and calculate the error of the device under test: ； ； in, is the absolute error of the resistor, is the relative error of resistance, The insulation resistance value displayed by the device under test, The insulation resistance value displayed for the high-precision resistor (6); Step S7: In the potential equalization calibration mode, the relays K1-K4 or K6-K9 are energized, the loop current and voltage are outputted through the high-precision voltage source (9) and the high-precision ammeter (8), the on-resistance is measured in combination with the four-wire loop, and the direction error is eliminated by switching the polarity.

5. The control method of the measurement and calibration equipment of the new energy vehicle charging safety inspection equipment according to claim 4 is characterized in that: Also includes: Step S8: calibrate the on-resistance between the PE terminal of the DC charging gun holder (1) and the resistance test clip; Connect the DC charging gun to the DC charging gun holder (1), and remove the two connecting wires of the resistance test clip; connect the two ends of the resistance test clip to the high-precision ammeter (8) and the high-precision voltage source (9) through the first banana head interface (10) and the second banana head interface (11), respectively, to form a four-wire calibration loop; calculate the on-resistance value between the PE terminal of the DC charging gun holder (1) and the resistance test clip based on the measurement data of the high-precision ammeter (8) and the high-precision voltage source (9); Step S9: calibrate the on-resistance between the PE terminal of the AC charging gun holder (7) and the resistance test clamp; Connect the AC charging gun to the AC charging gun holder (7), and remove the two connecting wires of the resistance test clip; connect the two ends of the resistance test clip to the high-precision ammeter (8) and the high-precision voltage source (9) through the first banana head interface (10) and the second banana head interface (11), respectively, to form a four-wire calibration loop; switch the calibration loop to the PE end of the AC charging gun holder (7) and the resistance test clip through the low-voltage switching unit; Perform four-wire calibration and calculate the on-resistance value between the PE terminal of the AC charging gun socket (7) and the resistance test clamp based on the measurement data of the high-precision ammeter (8) and the high-precision voltage source (9).

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