Device for protecting ground wire of three-phase vehicle-mounted charger from being misconnected with power supply live wire

Abstract

The embodiment of the invention provides a protection device for misconnection of a protection ground wire of a three-phase vehicle-mounted charger with a power supply live wire, and belongs to the technical field of charging safety. The invention discloses a protection device for misconnection of a protection ground wire of a three-phase vehicle-mounted charger with a power supply live wire. The protection device comprises an input protection ground wire, a casing protection ground, a three-phase live wire input, a normally open relay and a relay control circuit, and the relay control circuit is used for detecting a three-phase input voltage signal, automatically judging the connection state of an input protection ground wire and a power supply live wire, controlling the closing or opening of a relay based on a judgment result, and ensuring the safe isolation of a casing protection ground and the power supply live wire. According to the scheme, protection when the input protection ground wire of the vehicle-mounted charger is misconnected with the power supply live wire is achieved, isolation and safety of a metal shell of the vehicle-mounted charger and the power supply live wire are guaranteed, and safety of other low-voltage power supply control equipment on a vehicle is also guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of charging safety, and in particular to a protection device for preventing a protective ground wire of a three-phase on-board charger from being mistakenly connected to a live power wire. Background Art

[0002] At present, for the on-board chargers with three-phase AC input, when the charger housing is a metal housing, the gold-plastic housing is usually directly connected to the input protection ground. For example, the on-board chargers of various engineering vehicles are more common, and the charger housing is fixed to the metal frame of the engineering vehicle by screws. However, due to improper wiring or improper operation at the construction site, when the input protection ground wire of the on-board charger is mistakenly connected to the power supply live wire, the charger housing will be directly connected to the live wire and carry high voltage electricity. This situation is because the metal frame of the engineering vehicle is directly connected to the live wire, which poses a hidden danger to personal safety. Secondly, the connection of the gold-plastic frame to the live wire may cause damage or damage to other low-voltage power supply control equipment on the vehicle. What occasionally happens at the construction site is that the on-board power supply protection ground wire is mistakenly connected to the power supply live wire, causing damage to other low-voltage power supply control equipment on the vehicle. Summary of the invention

[0003] In view of the above problems, an embodiment of the present invention aims to provide a protection device for preventing a three-phase vehicle charger from misconnecting a protective ground wire to a live power wire.

[0004] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a protection device for a three-phase on-board charger protective ground wire mistakenly connected to a power supply live wire, the protection device comprising: an input protective ground wire, a casing protective ground, a three-phase live wire input, a normally open relay and a relay control circuit; the relay control circuit is used to detect a three-phase input voltage signal, automatically determine the connection status of the input protective ground wire and the power supply live wire, and control the relay to be closed or disconnected based on the determination result, thereby ensuring the safe isolation of the casing protective ground and the power supply live wire.

[0005] Optionally, the protection device also includes a main control unit circuit; the main control unit circuit is used to receive and calculate the effective value of the voltage detection signal between the three-phase live wire inputs, and judge whether the three-phase input voltage is normal by comparing the difference in the effective values ​​of each phase. If the effective values ​​are not equal, the relay is controlled to be disconnected to achieve safe isolation of the input protection ground wire and the charger casing.

[0006] Optionally, the main control unit circuit is configured with a dynamic adaptive algorithm for real-time calibration and adjustment of the detection accuracy of the three-phase input voltage; based on the dynamic adaptive algorithm, the main control unit circuit determines the connection status of the corresponding input protection ground under different input voltage fluctuations.

[0007] Optionally, the relay control circuit adopts a hybrid control method of analog and digital, and controls the closing or opening of the normally open relay through the control signal output by the main control unit circuit; wherein the control circuit includes a delay circuit composed of an NPN transistor, a resistor and a capacitor, so as to enable the relay to be opened or closed after the fault detection is confirmed.

[0008] Optionally, the main control unit circuit is also configured with a rule-based decision algorithm; the rule-based decision algorithm is used to determine whether the connection status of the input protective ground wire complies with preset rules; when an input protective ground wire connection error is detected, the output instruction controls the relay to disconnect and triggers the alarm module to output an alarm message.

[0009] Optionally, a total equivalent safety Y capacitor is provided between the casing protection ground and each phase input of the three-phase live wire to meet the safety leakage current requirements; wherein the capacitance value of the safety Y capacitor of each phase is equal to ensure the stability of the potential of the casing protection ground.

[0010] Optionally, the main control unit circuit includes an analog-to-digital conversion module and a data processing module; the analog-to-digital conversion module is used to sample the three-phase input voltage signal, and perform a signal denoising operation based on a filtering algorithm through the data processing module.

[0011] Optionally, the main control unit circuit includes an automatic learning module for analyzing voltage fluctuation characteristics under different working conditions and optimizing parameter settings of the control algorithm within a preset range to improve the adaptability of the system.

[0012] Optionally, the protection device also includes at least one set of safety redundant protection mechanism; when the input protection ground is incorrectly connected to the live wire, causing the input voltage detection signal to be abnormal, the backup logic judgment program is automatically triggered to ensure that the relay remains in the disconnected state through multiple judgments.

[0013] Optionally, the protection device further comprises at least one intelligent diagnosis module, which is used to record the number and time of occurrence of abnormal input protection earth connection and generate a diagnosis report after each fault.

[0014] Through the above technical solution, by connecting a normally open relay in series to the internal protective ground wire of the charger and effectively controlling the relay, protection is achieved when the input protective ground wire of the vehicle charger is mistakenly connected to the power supply live wire, ensuring the isolation and safety of the metal casing of the vehicle charger and the power supply live wire, and also ensuring the safety of other low-voltage power supply control devices on the vehicle; fewer components are added, the control is simple, and the additional cost is very small.

[0015] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0017] Figure 1 It is a schematic diagram of the principle of a protection device for a three-phase on-board charger that protects the ground wire from being mistakenly connected to the live wire of the power supply, provided in one embodiment of the present invention;

[0018] Figure 2 A corresponding embodiment of the present invention provides Figure 1 Circuit diagram of a protection device for a three-phase AC input vehicle charger that protects the ground wire from being mistakenly connected to the live wire of the power supply

[0019] Figure 3 It is a principle block diagram of another protection device for preventing the ground wire of a three-phase AC input vehicle charger from being mistakenly connected to the live wire of the power supply, provided by one embodiment of the present invention;

[0020] Figure 4 This embodiment corresponds to the embodiment provided by one embodiment of the present invention. Figure 3 A circuit diagram of another protection device for a three-phase AC input vehicle charger when the protective ground wire is mistakenly connected to the live power wire;

[0021] Figure 5 It is a circuit schematic diagram of an input voltage detection circuit 1, an input voltage detection circuit 2 and an input voltage detection circuit 3 provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0022] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0023] Figure 1 This is a schematic diagram of the principle of a protection device for preventing the ground wire of a three-phase vehicle charger from being mistakenly connected to the live wire of the power supply provided by an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a protection device for a three-phase on-board charger protective ground wire mistakenly connected to a power supply live wire, the protection device comprising: an input protective ground wire, a casing protective ground, a three-phase live wire input, a normally open relay and a relay control circuit; the relay control circuit is used to detect a three-phase input voltage signal, automatically determine the connection status of the input protective ground wire and the power supply live wire, and control the relay to be closed or disconnected based on the determination result, so as to ensure the safe isolation of the casing protective ground and the power supply live wire.

[0024] In a possible implementation, a protection device for a three-phase on-board charger that misconnects the protective ground wire to the live wire includes a relay, a relay control circuit, an auxiliary power supply output power supply, a main control unit circuit, a safety Y capacitor between the input three live wires and the protective ground, a charger metal casing, and other filtering, rectification, PFC, DCDC power conversion, auxiliary power supply, and detection control processing circuits;

[0025] Vin_U signal, Vin_V signal and Vin_W signal are all live wire input, Vin_PE signal is input protection ground, CASE_PE signal is charger metal shell ground, and the protection ground CASE_PE signal is connected to the charger shell;

[0026] Furthermore, the relay is connected in series between the input protection ground Vin_PE of the vehicle power supply and the chassis ground CASE_PE to realize the connection and disconnection of the input protection ground line;

[0027] Furthermore, a total equivalent safety Y capacitor C1 is connected between the charger housing ground CASE_PE and the live wire input Vin_U, a total equivalent safety Y capacitor C2 is connected between the housing ground CASE_PE and the live wire input Vin_V, and a total equivalent safety Y capacitor C3 is connected between the housing ground CASE_PE and the live wire input Vin_W;

[0028] Furthermore, the three live wires of the three-phase input Vin_U, Vin_V and Vin_W are processed by other filtering, rectification, PFC, DCDC power conversion, auxiliary power supply and detection control processing circuits to realize the relevant functions of the charger;

[0029] Further, the line voltage between the live input Vin_U and Vin_V generates a sampling signal Use_UV through the input voltage detection circuit 1, and the Use_UV signal is sent to the main control unit circuit for calculation and processing; the line voltage between the live input Vin_U and Vin_W generates a sampling signal Use_UW through the input voltage detection circuit 1, and the Use_UW signal is sent to the main control unit circuit for calculation and processing; the line voltage between the live input Vin_V and Vin_W generates a sampling signal Use_VW through the input voltage detection circuit 1, and the Use_VW signal is sent to the main control unit circuit for calculation and processing;

[0030] Furthermore, the main control unit circuit calculates and compares the effective values ​​of the three-phase line input voltage detection signals Use_UV, Use_UW and Use_VW. When it is determined that the three-phase input voltage is normal, it gives a command to close the relay to the relay control circuit, and the casing protection ground CASE_PE is connected to the input protection ground Vin_PE; when it is determined that the casing protection ground is connected to a certain input live wire, it continues to give a disconnect relay command to the relay control circuit to maintain the relay disconnected state, effectively preventing the charger casing from being connected to the high voltage of the input live wire;

[0031] Furthermore, the relay control circuit realizes the control of the closing or opening of the relay connected in series to the input protection ground line of the vehicle power supply. The control of the relay can be analog control or digital control, and the relay is controlled according to the specific closing or opening instructions given by the main control unit circuit.

[0032] Furthermore, the protection ground wire is not a fixed connection method. In order to better achieve fault isolation and improve safety performance, it is necessary to ensure that the safety capacitor of the protection ground wire of the AC input part ( Figure 2 The safety Y capacitors C1, C2 and C3 shown in the figure, C1, C2 and C3 are the total equivalent capacitance of the charger input Vin_U, Vin_V and Vin_W lines to CASE_PE respectively) The total capacity cannot be too large to meet the charger leakage current requirements. The key is to require the capacitance values ​​of the safety Y capacitors C1, C2 and C3 to be as equal as possible to ensure the safety of leakage current to people.

[0033] Further, the control and protection principle of the present invention is described as follows:

[0034] When the input protection ground connection of the on-board charger is correctly connected and the AC input voltage is normal, the main control unit circuit calculates the effective value of the three-line input voltage detection signals Use_UV, Use_UW and Use_VW. The effective values ​​of these three sampling signals should be basically equal. The main control unit circuit sends a relay pull-in instruction to the relay control circuit, and the relay control circuit pulls the relay in, thereby connecting the protection ground CASE_PE of the on-board charger with the protection ground Vin_PE of the power supply normally, and entering the normal working mode. After that, the relay will no longer be actively disconnected when the charger has other faults or alarms.

[0035] When the input protection ground connection of the on-board charger is connected to a power supply live wire, there must be a certain input live wire connected to the power supply protection ground at the same time. In this case, the effective values ​​of the input voltage detection signals Use_UV, Use_UW and Use_VW between the three lines will no longer be basically equal, and the effective value voltage of one of them is about 1.73 times the effective value voltage of the remaining two lines. The main control unit circuit determines that the input wiring is incorrect and that a certain input protection ground is mistakenly connected to a power supply live wire. The main control unit circuit continues to give the disconnect relay instruction to the relay control circuit to maintain the relay disconnected state. The protection ground CASE_PE inside the charger, that is, the casing, remains disconnected from the power supply live wire. In this case, it is ensured that the on-board charger casing is not charged and will not cause abnormal damage to the internal circuit of the charger; after the on-board power input line is correctly reconnected, the charger can work normally.

[0036] Furthermore, since the protective ground wire is not a fixed connection method, in order to better achieve fault isolation and improve safety performance, it is necessary to ensure that the safety capacitor capacity of the AC input part to the protective ground wire is not too large to meet the leakage current requirements of the charger. The key is to require the capacitance values ​​of the safety Y capacitors C1, C2 and C3 to be as equal as possible, and the equivalent safety Y capacitors C1, C2 and C3 are star-connected inside the charger. When the capacitance values ​​of C1, C2 and C3 are equal, the casing protection ground CASE_PE is equal to the power supply protection ground when it is not connected to the power supply protection ground, and the potential of the casing protection ground CASE_PE is zero potential, which can ensure the safety of the charging casing.

[0037] Furthermore, the three live wires of the three-phase input Vin_U, Vin_V and Vin_W are processed by other filtering, rectification, PFC, DCDC power conversion, auxiliary power supply and detection control processing circuits to realize the relevant functions of the charger.

[0038] In view of the above problems, the present invention also proposes another optimization solution such as Figure 3 As shown: a normally open relay is connected in series to the input protection ground wire of the vehicle power supply. This relay is used to disconnect or connect the charger housing with the input protection ground Vin_PE. When the protection ground wire is mistakenly connected to the power supply live wire, this relay remains normally open. It is confirmed that the normally open relay is energized when the protection ground wire is connected correctly.

[0039] Embodiment 1:

[0040] refer to Figure 2 , as a specific implementation method, is suitable for normal three-phase 380VAC / 50HZ AC input.

[0041] The whole circuit includes relays, relay control circuits, auxiliary power supply output, main control unit circuit, safety Y capacitors between the three live input wires and the protective ground, metal casing of the charger, and other filtering, rectification, PFC, DCDC power conversion, auxiliary power supply and detection control processing circuits.

[0042] Specifically, Vin_U signal, Vin_V signal and Vin_W signal are all live wire inputs, Vin_PE signal is input protection grounding, CASE_PE signal is charger metal shell grounding, and the protection grounding CASE_PE signal is connected to the charger shell;

[0043] Specifically, a total equivalent safety Y capacitor C1 is connected between the charger shell ground CASE_PE and the live wire input Vin_U, a total equivalent safety Y capacitor C2 is connected between the shell ground CASE_PE and the live wire input Vin_V, and a total equivalent safety Y capacitor C3 is connected between the shell ground CASE_PE and the live wire input Vin_W;

[0044] Furthermore, the three live wires of the three-phase input Vin_U, Vin_V and Vin_W are processed by other filtering, rectification, PFC, DCDC power conversion, auxiliary power supply and detection control processing circuits to realize the relevant functions of the charger;

[0045] Specifically, one end of the normally open relay K1 is connected to the input protection ground Vin_PE, and the other end of the normally open relay K1 is connected to the input charger casing protection ground CASE_PE;

[0046] Specifically, one end of the normally open relay K1 control line package is connected to the anode of the diode VD1 and the collector of the NPN transistor VT1, the other end of the normally open relay K1 control line package is connected to the cathode of the diode VD1 and the positive end VCC of the power supply, the base of the NPN transistor VT1 is connected to one end of the resistor R1, one end of the resistor R2 and one end of the capacitor C4, the other end of the resistor R2, the other end of the capacitor C4 and the emitter of the NPN transistor VT1 are connected to the working digital ground GND_D, and the other end of the resistor R1 is connected to the relay control signal K1_CTL;

[0047] Specifically, the live wire input Vin_U signal is connected to one end of resistor R6, the other end of resistor R6 is connected to one end of resistor R7, the other end of resistor R7 is connected to one end of resistor R8, the other end of resistor R8 is connected to one end of resistor R9, the other end of resistor R9 is connected to one end of resistor R5, one end of capacitor C8, one end of resistor R15, the third pin of diode VD3 and the third pin of the same-direction input terminal of op amp D1A, the other end of resistor R5 is connected to power supply VCC+3.3VA_PFC, the other end of resistor R15, the other end of capacitor C8, the first pin of diode VD3, the fourth pin of op amp D1A and one end of capacitor C5 are connected to the working analog ground GND_A, the second pin of diode VD3 and the other end of capacitor C5 are connected to the power supply VCC+5VA_PFC, the live wire input Vin_V signal is connected to one end of resistor R10, the other end of resistor R10 is connected to one end of resistor R11, and resistor R The other end of 11 is connected to one end of resistor R12, the other end of resistor R12 is connected to one end of resistor R13, the other end of resistor R13 is connected to one end of resistor R14, one end of capacitor C6, one end of resistor R4, the third pin of diode VD4 and the second pin of the reverse input terminal of operational amplifier D1A, the other end of resistor R14 and the first pin of diode VD4 are connected to the working analog ground GND_A, the second pin of diode VD4 is connected to the power supply VCC+5VA_PFC, the other end of capacitor C6, the other end of resistor R4, one end of resistor R3 and the first pin of output of operational amplifier D1A are connected, the other end of resistor R3, one end of capacitor C7 and the third pin of diode VD2 are connected to generate input voltage sampling signal Use_UV, the other end of capacitor C7 and the first pin of diode VD2 are connected to the working analog ground GND_A, and the second pin of diode VD2 is connected to the power supply VCC+3.3VA_PFC;

[0048] Specifically, the live wire input Vin_U signal is connected to one end of resistor R19, the other end of resistor R19 is connected to one end of resistor R20, the other end of resistor R20 is connected to one end of resistor R21, the other end of resistor R21 is connected to one end of resistor R22, the other end of resistor R22 is connected to one end of resistor R18, one end of capacitor C12, one end of resistor R28, the third pin of diode VD6 and the third pin of the same-direction input terminal of op amp D2A, the other end of resistor R18 is connected to the power supply VCC+3.3VA_PFC, the other end of resistor R28, the other end of capacitor C12, the first pin of diode VD6, the fourth pin of op amp D2A and one end of capacitor C9 are connected to the working analog ground GND_A, the second pin of diode VD6 and the other end of capacitor C9 are connected to the power supply VCC+5VA_PFC, the live wire input Vin_W signal is connected to one end of resistor R23, the other end of resistor R23 is connected to one end of resistor R24, and the The other end of resistor R24 ​​is connected to one end of resistor R25, the other end of resistor R25 is connected to one end of resistor R26, the other end of resistor R26 is connected to one end of resistor R27, one end of capacitor C10, one end of resistor R17, the third pin of diode VD7 and the second pin of the reverse input terminal of operational amplifier D2A, the other end of resistor R27 and the first pin of diode VD7 are connected to the working analog ground GND_A, the second pin of diode VD7 is connected to the power supply VCC+5VA_PFC, the other end of capacitor C10, the other end of resistor R17, one end of resistor R16 and the first pin of output of operational amplifier D2A are connected, the other end of resistor R16, one end of capacitor C11 and the third pin of diode VD5 are connected to generate input voltage sampling signal Use_UW, the other end of capacitor C11 and the first pin of diode VD5 are connected to the working analog ground GND_A, and the second pin of diode VD5 is connected to the power supply VCC+3.3VA_PFC;

[0049] Specifically, the live wire input Vin_V signal is connected to one end of resistor R32, the other end of resistor R32 is connected to one end of resistor R33, the other end of resistor R33 is connected to one end of resistor R34, the other end of resistor R34 is connected to one end of resistor R35, the other end of resistor R35 is connected to one end of resistor R31, one end of capacitor C16, one end of resistor R41, the third pin of diode VD9 and the third pin of the same-direction input terminal of op amp D3A, the other end of resistor R31 is connected to the power supply VCC+3.3VA_PFC, the other end of resistor R41, the other end of capacitor C16, the first pin of diode VD9, the fourth pin of op amp D3A and one end of capacitor C13 are connected to the working analog ground GND_A, the second pin of diode VD9 and the other end of capacitor C13 are connected to the power supply VCC+5VA_PFC, the live wire input Vin_W signal is connected to one end of resistor R36, the other end of resistor R36 is connected to one end of resistor R37, and resistor The other end of R37 is connected to one end of resistor R38, the other end of resistor R38 is connected to one end of resistor R39, the other end of resistor R39 is connected to one end of resistor R40, one end of capacitor C14, one end of resistor R30, the third pin of diode VD10 and the second pin of the reverse input terminal of operational amplifier D3A, the other end of resistor R40 and the first pin of diode VD10 are connected to the working analog ground GND_A, the second pin of diode VD10 is connected to the power supply VCC+5VA_PFC, the other end of capacitor C14, the other end of resistor R30, one end of resistor R29 and the first pin of output of operational amplifier D3A are connected, the other end of resistor R29, one end of capacitor C15 and the third pin of diode VD8 are connected to generate input voltage sampling signal Use_VW, the other end of capacitor C15 and the first pin of diode VD8 are connected to the working analog ground GND_A, and the second pin of diode VD8 is connected to the power supply VCC+3.3VA_PFC;

[0050] Specifically, the input voltage sampling signal UsevUV, the input voltage sampling signal Use_UW, the input voltage sampling signal Use_VW and the working analog ground are sent to the main control unit circuit. After the main control unit circuit calculates and processes these three input voltage signals, the relay control signal K1_CTL and the working digital ground GND_D are output.

[0051] The principle of this embodiment is specifically described as follows:

[0052] When the input protection ground connection of the on-board charger is correctly connected and the AC input voltage is normal, the main control unit circuit calculates the effective value of the input voltage detection signals Use_UV, Use_UW and Use_VW between the three lines. The effective values ​​of these three sampling signals should be basically equal. The main control unit circuit sends a high-level relay control signal K1_CTL to the relay control circuit. This high-level signal K1_CTL drives the transistor VT1 to turn on after delaying through resistors R1, R2 and capacitor C4, thereby attracting relay K1, connecting the protection ground CASE_PE of the on-board charger with the protection ground Vin_PE of the power supply normally, and entering the normal working mode. After that, the relay will no longer be actively disconnected when there are other faults or alarms in the charger.

[0053] When the input protection ground connection of the on-board charger is connected to a power supply live wire, there must be a certain input live wire connected to the power supply protection ground at the same time. In this case, the effective values ​​of the input voltage detection signals Use_UV, Use_UW and Use_VW between the three lines will no longer be basically equal, and the effective value voltage of one of them is about 1.73 times the effective value voltage of the other two lines. The main control unit circuit determines that the input wiring is incorrect and judges that a certain input protection ground is mistakenly connected to a power supply live wire. The main control unit circuit continues to give a low-level relay instruction K1_CTL to the relay control circuit, and the transistor VT1 remains cut off, the relay K1 remains disconnected, and the protection ground CASE_PE inside the charger, that is, the casing, remains disconnected from the power supply live wire. In this case, it is ensured that the on-board charger casing is not charged, and it will not cause abnormal damage to the internal circuit of the charger; after the on-board power input line is correctly reconnected, the charger can work normally.

[0054] Embodiment 2:

[0055] like Figure 3 , the technical solution of this embodiment is different from the technical solution Figure 1 The control circuit and principle are basically the same, and the specific scheme will not be repeated. The only difference is the scheme Figure 1 The relay is only used to control the connection or disconnection between the casing and the input protection ground. Since the casing itself is not directly connected to the safety equivalent total capacitors C1, C2 and C3 of the input part, there are no other special requirements for the safety Y capacitor at the input end of the on-board charger. Of course, it is necessary to meet the requirements of the on-board power input safety capacitor for ground leakage current or the specific customer requirements for this indicator.

[0056] Specifically, Figure 4This embodiment is suitable for three-phase 380VAC / 50HZ normal AC input. The circuit as a whole includes a normally open relay, a relay control circuit, an auxiliary power supply, a main control unit circuit, a safety Y capacitor between the three-phase live wire input Vin_U, Vin_V and Vin_W and the protective ground wire, and a charger metal casing. The remaining circuits also include filtering, rectification, PFC (power factor correction), DCDC power conversion, auxiliary power supply and detection control processing circuits.

[0057] 1) Signal connection Vin_U, Vin_V and Vin_W signals are three-phase live wire input, Vin_PE is input protection grounding, CASE_PE is charger metal shell grounding. The protection grounding CASE_PE is connected to the charger shell through a relay.

[0058] 2) Safety Y capacitors: Safety Y capacitors C1, C2 and C3 are connected between the charger casing protection ground CASE_PE and the live wire input Vin_U, Vin_V and Vin_W respectively to ensure that the leakage current meets safety standards.

[0059] 3) Power supply circuit and conversion: The three-phase live wires Vin_U, Vin_V and Vin_W are filtered, rectified, PFC, DCDC power conversion and other circuits to achieve normal operation of the charger.

[0060] 4) Relay control: Normally open relay K1 is used to connect and disconnect the protection ground. One side of the control end of relay K1 is connected to the anode of diode VD1 and the collector of NPN transistor VT1, and the other side is connected to the cathode of diode VD1 and the positive end VCC of the power supply. The base of NPN transistor VT1 is connected to the relay control signal K1_CTL through resistor R1, resistor R2 and capacitor C4. The emitter of VT1 is connected to the working digital ground GND_D.

[0061] 5) Voltage sampling and main control: The line voltage between each live wire is sampled by the detection circuit, and the signals Use_UV, Use_UW and Use_VW are generated and transmitted to the main control unit for effective value calculation. If the calculation result shows that the voltage is abnormal, the main control unit issues a relay disconnection command to ensure that the protective ground CASE_PE is disconnected from the input live wire.

[0062] 6) Control protection logic: When the input protection ground is connected to a live wire and a live wire is connected to the power supply protection ground, the effective value of the detection signal will be different, and the effective value of the voltage of one line is 1.73 times that of the other two lines. At this time, the main control unit issues a disconnect relay command to keep CASE_PE isolated from the live wire.

[0063] 7) Recovery and normal working mode: After detecting that the three-phase input voltage is normal and the input protection ground is correctly connected, the main control unit circuit sends a relay closure command, the relay closure, CASE_PE and Vin_PE are connected, and the charger enters the normal working mode.

[0064] like Figure 5 , corresponding to Figure 2 , Figure 3 The circuit schematic diagram of the input voltage detection circuit 1, the input voltage detection circuit 2 and the input voltage detection circuit 3 is shown in FIG. The specific description is as follows:

[0065] 1) Hot wire input and sampling resistor: The hot wire input Vin_U, Vin_V, and Vin_W are connected through a series of resistors (such as R6 to R9, R10 to R14, etc.) to form a voltage divider network, thereby reducing the voltage and providing a corresponding sampling signal.

[0066] 2) Filtering and rectification: Filter capacitors (such as C5, C6, etc.) and rectifier diodes (such as VD2, VD3, etc.) are set on each sampling line to ensure the stability of the sampling signal and avoid voltage fluctuations affecting the sampling accuracy.

[0067] 3) Operational amplifier configuration: The sampling signal is processed by an operational amplifier (such as D1A, D2A, D3A), and the amplified and filtered signals are used to generate input voltage detection signals Use_UV, Use_UW and Use_VW, which correspond to the voltages between the live wires Vin_U and Vin_V, Vin_U and Vin_W, and Vin_V and Vin_W, respectively.

[0068] 4) Output connected to the main control unit: The generated signals Use_UV, Use_UW, and Use_VW are transmitted to the main control unit circuit. The main control unit calculates the effective values ​​of these signals to determine whether the three-phase input voltage is normal, so as to decide whether to attract or disconnect the relay to realize the protection function.

[0069] Those skilled in the art will understand that all or part of the steps in the method for implementing the above-mentioned embodiments can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions for making a single-chip microcomputer, a chip or a processor (processor) perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0070] The optional embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the technical concept of the embodiments of the present invention, the technical scheme of the embodiments of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0071] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed in the embodiments of the present invention.

Claims

1. A protection device for a three-phase on-board charger that protects the ground wire from being mistakenly connected to the live wire of the power supply, characterized in that: The protection device comprises: Input protection ground wire, housing protection ground, three-phase live wire input, normally open relay and relay control circuit; The relay control circuit is used to detect the three-phase input voltage signal, automatically determine the connection status of the input protection ground wire and the power supply live wire, and control the relay to be closed or disconnected based on the judgment result to ensure the safe isolation of the casing protection ground and the power supply live wire.

2. The protection device according to claim 1, characterized in that: The protection device also includes a main control unit circuit; The main control unit circuit is used to receive and calculate the effective value of the voltage detection signal between the three-phase live wire inputs, and judge whether the three-phase input voltage is normal by comparing the difference in the effective values ​​of each phase. If the effective values ​​are not equal, the relay is controlled to be disconnected to achieve safe isolation of the input protection ground wire and the charger casing.

3. The protection device according to claim 2, characterized in that: The main control unit circuit is configured with a dynamic adaptive algorithm for real-time calibration and adjustment of the detection accuracy of the three-phase input voltage; Based on the dynamic adaptive algorithm, the main control unit circuit determines the connection state of the corresponding input protection ground under different input voltage fluctuation conditions.

4. The protection device according to claim 3, characterized in that: The relay control circuit adopts a mixed analog and digital control method, and controls the normally open relay to be closed or disconnected through the control signal output by the main control unit circuit; wherein, The control circuit includes a delay circuit composed of an NPN transistor, a resistor and a capacitor to enable the relay to be disconnected or closed after the fault detection is confirmed.

5. The protection device according to claim 4, characterized in that: The main control unit circuit is also configured with a rule-based decision algorithm; The rule-based decision algorithm is used to determine whether the connection status of the input protection ground line meets the preset rules; When an input protection ground wire connection error is detected, the output command controls the relay to disconnect and triggers the alarm module to output an alarm message.

6. The protection device according to claim 5, characterized in that: A total equivalent safety Y capacitor is provided between the housing protection ground and each phase input of the three-phase live wire to meet the safety leakage current requirements; wherein, The capacitance value of the safety Y capacitor of each phase is equal to ensure the stability of the potential of the casing protection ground.

7. The protection device according to any one of claim 6, characterized in that: The main control unit circuit includes an analog-to-digital conversion module and a data processing module; The analog-to-digital conversion module is used to sample the three-phase input voltage signal, and perform a signal denoising operation based on a filtering algorithm through the data processing module.

8. The protection device according to claim 7, characterized in that: The main control unit circuit includes an automatic learning module for analyzing voltage fluctuation characteristics under different working conditions and optimizing the parameter setting of the control algorithm within a preset range to improve the adaptability of the system.

9. The protection device according to claim 8, characterized in that: The protection device also includes at least one set of safety redundant protection mechanism; When the input protection ground is connected to the live wire incorrectly, causing the input voltage detection signal to be abnormal, the backup logic judgment program is automatically triggered to ensure that the relay remains in the disconnected state through multiple judgments.

10. The protection device according to claim 9, characterized in that: The protection device also includes at least one intelligent diagnosis module, which is used to record the number and time of occurrence of abnormal input protection ground connection and generate a diagnosis report after each fault.

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