Charging circuit adhesion tripping detection method

Abstract

The invention relates to a charging circuit adhesion tripping detection method. The method comprises the following steps: S1, acquiring load side voltages V1 and V2 of a relay; s2, the control state of the relay is determined, if the control state of the relay is open, the step S3 is executed, and if the control state of the relay is closed, the step S4 is executed; s3, calculating the voltage difference between the V1 and the V2, if the absolute value of the voltage difference is greater than the first set voltage and the V1 or the V2 is greater than the second set voltage, executing the step S5, otherwise, executing the step S1; s4, calculating the voltage difference between the V1 and the V2, if the absolute value of the voltage difference is smaller than the first set voltage and the V1 and the V2 are smaller than the third set voltage, executing the step S6, otherwise, executing the step S1; s5, outputting a relay adhesion alarm, and executing the step S1; and S6, outputting a relay tripping alarm, and executing the step S1. According to the invention, whether the relay is adhered or tripped can be reliably detected.

Description

Technical Field

[0001] This invention relates to the field of charging gun technology, and in particular to a method for detecting sticking and tripping of charging circuits. Background Technology

[0002] In AC charging systems, charging guns typically contain a relay. This relay physically disconnects the high-voltage circuit between the power grid and the vehicle when not charging, ensuring user safety. Because relays can stick or trip, charging guns usually have corresponding detection circuits to monitor for this issue and ensure safe operation.

[0003] However, in practical applications, especially when the charging gun is connected to unreliably grounded aging test load boxes, leakage current testers, and other instruments, a special interference phenomenon often occurs: even if the relay is completely disconnected and charging is not started, tens or even hundreds of volts of induced voltage (commonly known as "phantom voltage") can still be detected at the output of the charging gun. This phantom voltage mainly originates from the parasitic capacitive coupling between the high-voltage cable on the power grid side and the floating metal structure, and manifests as a 50Hz power frequency AC signal. Although it has no actual driving capability, it is enough to be mistakenly identified as "loop continuity" by the voltage sampling circuit in the charging gun control system.

[0004] Although some solutions attempt to suppress interference by adding filtering circuits or increasing the voltage threshold, such methods are difficult to balance sensitivity and immunity. For example, using optocouplers is costly, and if the virtual power can provide enough current to light up the LED, the optocoupler will conduct and misjudge it as sticking.

[0005] Therefore, there is an urgent need for a more reliable adhesion detection method that can accurately distinguish whether a relay is truly conducting or induced with a false current. This method can effectively avoid misjudgments caused by false current while ensuring safety, thereby improving system robustness and user experience. Summary of the Invention

[0006] The purpose of this invention is to provide a method for detecting sticking and tripping in a charging circuit, which can reliably detect the sticking and tripping status of an AC charging circuit and avoid misjudgment caused by false electricity.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for detecting sticking and tripping in a charging circuit includes the following steps: S1. Collect the relay load side voltages V1 and V2: For a single-phase power supply charging circuit, the voltages of the live wire and the neutral wire on the relay load side are V1 and V2, respectively; for a two-phase power supply charging circuit, the voltages of the two live wires on the relay load side are V1 and V2, respectively; for a three-phase power supply charging circuit, the voltages of the neutral wire and any live wire on the relay load side are V1 and V2, respectively. S2. Determine the control state of the relay. If the control state of the relay is open, proceed to step S3. If the control state of the relay is closed, proceed to step S4. S3. Take V1 and V2 collected at the same time, or take V1 collected at any time and V2 collected in the adjacent collection period, and then calculate the voltage difference between V1 and V2. If the absolute value of the voltage difference is greater than the first set voltage, and V1 or V2 is greater than the second set voltage, then execute step S5; otherwise, execute step S1. S4. Take V1 and V2 collected at the same time, or take V1 collected at any time and V2 collected in the adjacent collection period, and then calculate the voltage difference between V1 and V2. If the absolute value of the voltage difference is less than the first set voltage, and V1 and V2 are less than the third set voltage, then execute step S6; otherwise, execute step S1. S5. Output relay sticking alarm, then execute step S1; S6. Output relay trip alarm, then execute step S1; Wherein, the first set voltage is the product of the maximum virtual voltage on the relay load side and the coefficient value when the relay is disconnected, plus the error value, wherein the coefficient value is 1 minus the sine value of the product of the voltage acquisition period and the power supply frequency.

[0008] Preferably, in step S3, when comparing the second set voltage with V1 or V2, the values ​​of V1 and V2 are the maximum values ​​of V1 and V2 within the set period, respectively; in step S4, when comparing the third set voltage with V1 or V2, the values ​​of V1 and V2 are the maximum values ​​of V1 and V2 within the set period, respectively; the set period is not less than the voltage period of the power supply.

[0009] Preferably, the set period is at least 1.5 times the voltage period of the power supply.

[0010] Preferably, in step S5, a fault count is performed first. If the fault count exceeds a first set number, a relay sticking alarm is output, and then step S1 is executed; otherwise, step S1 is executed directly. In step S6, a fault count is performed first. If the fault count exceeds a second set number, a relay tripping alarm is output, and then step S1 is executed; otherwise, step S1 is executed directly.

[0011] Preferably, in step S3, if it is determined that the execution should jump to step S1, before executing step S1, it is first determined whether the fault count has exceeded a first preset number. If so, the fault count in step S5 is reset to zero, and then step S1 is executed; otherwise, step S1 is executed directly. In step S4, if it is determined that the execution should jump to step S1, before executing step S1, it is first determined whether the fault count has exceeded a second preset number. If so, the fault count in step S5 is reset to zero, and then step S1 is executed; otherwise, step S1 is executed directly. This setting can prevent interference from causing the fault count to be reset to zero, thus improving reliability.

[0012] Preferably, the method further includes step SA, which is executed after step S1 and before step S2. This step is to determine whether the control state of the relay has changed. If the control state of the relay has changed, the fault count in steps S5 and S6 is cleared and then step S2 is executed. Otherwise, step S2 is executed directly.

[0013] Preferably, the second set voltage is equal to the third set voltage, and the second set voltage is not lower than the first set voltage.

[0014] Preferably, the voltage acquisition period is no more than 200 microseconds.

[0015] Preferably, the power source is AC mains power.

[0016] Preferably, the relay load-side voltages V1 and V2 are acquired through the following acquisition circuit, which includes a controller, a V1 acquisition circuit, and a V2 acquisition circuit. Both the V1 and V2 acquisition circuits include a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a filter capacitor, and a bidirectional Zener diode. One end of the first resistor is connected to the power supply line corresponding to the relay load side. The other end of the second resistor is connected to one end of the fourth resistor via the second and third resistors. The other end of the fourth resistor is connected to one end of the filter capacitor, the corresponding acquisition pin on the controller, one end of the fifth resistor, and pin 3 of the bidirectional Zener diode. The other end of the filter capacitor, the other end of the fifth resistor, and pin 1 of the bidirectional Zener diode are grounded. Pin 2 of the bidirectional Zener diode is connected to the power input terminal of the controller.

[0017] The present invention has the following beneficial effects: This invention collects the voltages of the two power lines on the load side of the relay separately, and compares the difference between the two voltages collected at the same time or the difference between the two voltages in adjacent collection cycles with a set voltage (first set voltage or second set voltage). In conjunction with the current control state of the relay, it can reliably detect whether the relay is stuck or tripped, thus eliminating judgment errors caused by false voltage. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the principle of the present invention.

[0019] Figure 2 This is a schematic diagram of the data acquisition circuit of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0021] See Figure 1 This invention discloses a method for detecting sticking and tripping in a charging circuit, which includes the following steps: S1. Collect the relay load side voltages V1 and V2: For a single-phase charging circuit, the voltage of the live wire L on the relay load side is V1, and the voltage of the neutral wire N on the relay load side is V1 and V2, respectively. For a two-phase charging circuit, the voltages of the two live wires on the relay load side are V1 and V2, such as the voltage of L1 on the relay load side being V1 and the voltage of L2 on the relay load side being V3. For a three-phase charging circuit, the voltage of the neutral wire and the voltage of any live wire on the relay load side are V1 and V2, respectively, for example, the voltage of L1 on the relay load side being V1 and the voltage of the neutral wire N on the relay load side being V2. This case uses a single-phase power supply as an example, and the power source is AC mains (230V).

[0022] In this case, the acquisition of V1 and V2 is achieved through an acquisition circuit. Specifically, the acquisition circuit includes a controller, an V1 acquisition circuit, and a V2 acquisition circuit, with the controller being a microcontroller. Both the V1 and V2 acquisition circuits include a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a filter capacitor, and a bidirectional Zener diode. One end of the first resistor is connected to the power line corresponding to the relay load side. The other end of the second resistor is connected to one end of the fourth resistor via the second and third resistors. The other end of the fourth resistor is connected to one end of the filter capacitor, the corresponding acquisition pin on the controller, one end of the fifth resistor, and pin 3 of the bidirectional Zener diode. The other ends of the filter capacitor, the other end of the fifth resistor, and pin 1 of the bidirectional Zener diode are grounded. Pin 2 of the bidirectional Zener diode is connected to the power input terminal of the controller. In the circuit, the second, third, fourth, and fifth resistors divide the mains or virtual voltage into a smaller voltage (less than the maximum voltage that the microcontroller's acquisition pin (ADC port) can withstand, typically 3.3V) for acquisition by the microcontroller's ADC port. The filter capacitor is used to filter out high-frequency noise. The bidirectional Zener diode is used to clamp the voltage. That is, if the voltage after the mains voltage or virtual voltage is divided is higher than 3.3V, it will be clamped by the bidirectional Zener diode, thereby protecting the microcontroller's ADC acquisition port.

[0023] For specific circuit details, see [link / reference]. Figure 2The V1 acquisition circuit includes resistors RP11, RP12, RP13, RP14, RP15, capacitor CP6, and Zener diode DP3. Resistor RP11 is connected to the live wire L-out of the relay load, and pin 3 of Zener diode DP3 is connected to the microcontroller's acquisition pin Lout_ADC. The V2 acquisition circuit includes resistors RP16, RP17, RP18, RP19, RP20, capacitor CP8, and Zener diode DP4. Resistor RP16 is connected to the live wire N-out of the relay load, and pin 3 of Zener diode DP4 is connected to the microcontroller's acquisition pin Nout_ADC.

[0024] The microcontroller records the maximum values ​​of V1 (V1_MAX) and V2_MAX within a set period. This set period should be no less than the mains power cycle (20ms), and preferably at least 1.5 times the mains power cycle. In this case, a set period of 30ms is preferred. The set period can be adjusted according to actual conditions. Alternatively, recording V1_MAX and V2_MAX can be performed in step S3, or after steps SA or S2.

[0025] SA: Determine whether the control state of the relay has changed, i.e., whether the relay control state has changed from closed to open or from open to closed. If the control state of the relay has changed, then clear the fault count in subsequent steps S5 and S6, and then execute step S2; otherwise, execute step S2 directly.

[0026] S2. Determine the control state of the relay. If the relay is in an open state, proceed to step S3; if the relay is in a closed state, proceed to step S4. When the relay is closed, there may be sticking, and when the relay is open, there may be tripping.

[0027] S3. Take V1 and V2 acquired at the same time (corresponding to the case where the microcontroller has two ADCs, that is, the two ADCs respectively acquire the Nout_ADC and Nout_ADC ports, thus achieving the acquisition of V1 and V2 at the same time), or take V1 acquired at any time and V2 acquired in the adjacent acquisition cycle (corresponding to the case where the microcontroller has only one ADC, which acquires Nout_ADC and Nout_ADC in a round-robin manner), and then calculate the voltage difference between V1 and V2. If the absolute value of the voltage difference is greater than the first set voltage, and V1_MAX or V2_MAX is greater than the second set voltage, then execute step S5; otherwise, first determine whether the fault count in step S5 exceeds the first set number of times. If yes, clear the fault count and then execute step S1; otherwise, directly execute step S1.

[0028] S4. Take V1 and V2 collected at the same time, or take V1 collected at any time and V2 collected in the adjacent collection period, and then calculate the voltage difference between V1 and V2. If the absolute value of the voltage difference is less than the first set voltage, and V1_MAX and V2_MAX are less than the third set voltage, then execute step S6; otherwise, first determine whether the fault count in step S6 exceeds the second set number. If yes, clear the fault count and then execute step S1; otherwise, directly execute step S1.

[0029] S5. First, perform a fault count. If the fault count exceeds the first preset number, output a relay sticking alarm, and then execute step S1; otherwise, directly execute step S1. Fault counting is used to avoid false alarms. The first preset number can be customized by the user.

[0030] S6. First, perform a fault count. If the fault count exceeds the second preset number, output a relay trip alarm and then execute step S1. Otherwise, directly execute step S1. The second preset number can be customized by the user.

[0031] The first set voltage is the product of the maximum virtual voltage on the relay load side and the coefficient value when the relay is disconnected, plus the error value. The coefficient value is 1 minus the sine value of the product of the voltage acquisition period and the power supply frequency. It is best if the voltage acquisition period ΔT is not greater than 200 microseconds. Of course, it can also be adjusted according to the actual situation.

[0032] When the relay is actually disconnected, if there is a phantom voltage, the phantom voltage measured on the neutral wire N-out and the live wire L-out by the relay load should be in a state of the same frequency and voltage (sine wave). Theoretically, the maximum value of the phantom voltage Vx is the mains voltage, i.e., 230V, but in reality, the phantom voltage usually does not reach 230V. If there is no phantom voltage, the voltages measured on the neutral wire N-out and the live wire L-out by the relay load should theoretically be two parallel straight lines. Therefore, when the relay is actually disconnected, if V1 and V2 are sampled simultaneously, regardless of whether there is a phantom voltage, the voltage difference between the two will be a constant value that is almost zero. If V1 and V2 are sampled alternately (e.g., the microcontroller samples V1 in the current sampling cycle and V2 in the next sampling cycle), then the maximum difference between V1 and V2, Vdiff1, and the maximum digital difference, Dmax1, are calculated using the following formulas: =2.875V(Formula 1) =0.366V (Formula 2) =452 (Formula 3) In Formula 1, RP15 = 5kΩ, RP11 = RP12 = RP13 = RP14 = 2MΩ; in Formula 2, f is the mains frequency (50Hz), and the voltage acquisition period ΔT = 100 microseconds; in Formula 3, “3.3” represents the maximum voltage (operating voltage) of the microcontroller acquisition port.

[0033] Therefore, when the relay control state is closed, if a tripping fault occurs, the relay is actually still in the open state. At this time, the voltage difference between V1 and V2 is less than Dmax1 + Derr, where Derr is an error value set according to the actual situation, and Dmax1 + Derr is the first set voltage VA. In this case, V1_MAX and V2_MAX will also be less than the third set voltage VB. The third set voltage VB is defined by the user and can be a relatively large value, such as 3568 (2.875 * 4096 ÷ 3.3, corresponding to a voltage of 230V before acquisition and a voltage of 2.875V acquired by the microcontroller).

[0034] When the relay is actually closed, the relay load outputs 230V AC mains power. At this time, when the acquisition circuit collects the voltage, after voltage division by resistors, V1 = 2.875V, while V2 is almost 0V. The maximum difference between V1 and V2, Vdiff2 = V1 = 2.875V, and the maximum digital difference, Dmax2 = 3568 (calculation formula reference 3). When the relay control state is open, if a sticking fault occurs, the relay is actually still closed. In this case, within a set period (30ms), if the voltage difference between V1 and V2 is greater than the first set voltage VA, it will inevitably be triggered. Additionally, in this situation, V1_MAX or V2_MAX equals 230V, which will be greater than the second set voltage VC. The second set voltage VC is defined by the user and can be a small value, such as 465 (corresponding to a voltage of 30V before acquisition and 0.375V acquired by the microcontroller). Of course, the second and third set voltages can also be equal, for example, both being 465.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting sticking and tripping in a charging circuit, characterized in that, Includes the following steps: S1. Collect the relay load side voltages V1 and V2: For a single-phase power supply charging circuit, the voltages of the live wire and the neutral wire on the relay load side are V1 and V2, respectively; for a two-phase power supply charging circuit, the voltages of the two live wires on the relay load side are V1 and V2, respectively; for a three-phase power supply charging circuit, the voltages of the neutral wire and any live wire on the relay load side are V1 and V2, respectively. S2. Determine the control state of the relay. If the control state of the relay is open, proceed to step S3. If the control state of the relay is closed, proceed to step S4. S3. Take V1 and V2 collected at the same time, or take V1 collected at any time and V2 collected in the adjacent collection period, and then calculate the voltage difference between V1 and V2. If the absolute value of the voltage difference is greater than the first set voltage, and V1 or V2 is greater than the second set voltage, then execute step S5; otherwise, execute step S1. S4. Take V1 and V2 collected at the same time, or take V1 collected at any time and V2 collected in the adjacent collection period, and then calculate the voltage difference between V1 and V2. If the absolute value of the voltage difference is less than the first set voltage, and V1 and V2 are less than the third set voltage, then execute step S6; otherwise, execute step S1. S5. Output relay sticking alarm, then execute step S1; S6. Output relay trip alarm, then execute step S1; Wherein, the first set voltage is the product of the maximum virtual voltage on the relay load side and the coefficient value when the relay is disconnected, plus the error value, wherein the coefficient value is 1 minus the sine value of the product of the voltage acquisition period and the power supply frequency.

2. The method for detecting sticking and tripping of the charging circuit according to claim 1, characterized in that: In step S3, when comparing the second set voltage with V1 or V2, the values ​​of V1 and V2 are the maximum values ​​of V1 and V2 within the set period, respectively; in step S4, when comparing the third set voltage with V1 or V2, the values ​​of V1 and V2 are the maximum values ​​of V1 and V2 within the set period, respectively; the set period is not less than the voltage period of the power supply.

3. The method for detecting sticking and tripping of the charging circuit according to claim 2, characterized in that: The set period is at least 1.5 times the voltage period of the power supply.

4. The method for detecting sticking and tripping of the charging circuit according to claim 1, characterized in that: In step S5, a fault count is performed first. If the fault count exceeds the first set number, a relay sticking alarm is output, and then step S1 is executed. Otherwise, step S1 is executed directly. In step S6, a fault count is performed first. If the fault count exceeds the second set number, a relay tripping alarm is output, and then step S1 is executed. Otherwise, step S1 is executed directly.

5. The method for detecting sticking and tripping of the charging circuit according to claim 4, characterized in that: In step S3, if it is determined that the execution should jump to step S1, before executing step S1, it is first determined whether the fault count exceeds the first set number. If yes, the fault count in step S5 is cleared to zero, and then step S1 is executed. Otherwise, step S1 is executed directly. In step S4, if it is determined that the execution should jump to step S1, before executing step S1, it is first determined whether the fault count exceeds the second set number. If yes, the fault count in step S5 is cleared to zero, and then step S1 is executed. Otherwise, step S1 is executed directly.

6. The method for detecting sticking and tripping of the charging circuit according to claim 4, characterized in that: It also includes step SA, which is executed after step S1 and before step S2. This step is to determine whether the control state of the relay has changed. If the control state of the relay has changed, the fault count in steps S5 and S6 is cleared and then step S2 is executed. Otherwise, step S2 is executed directly.

7. The method for detecting sticking and tripping of the charging circuit according to claim 1, characterized in that: The second set voltage is equal to the third set voltage, and the second set voltage is not lower than the first set voltage.

8. The method for detecting sticking and tripping of the charging circuit according to claim 1, characterized in that: The voltage acquisition period is no more than 200 microseconds.

9. The method for detecting sticking and tripping of the charging circuit according to claim 1, characterized in that: The power source is AC mains power.

10. The method for detecting sticking and tripping of the charging circuit according to claim 1, characterized in that: The relay load-side voltages V1 and V2 are acquired using the following acquisition circuit, which includes a controller, a V1 acquisition circuit, and a V2 acquisition circuit. Both the V1 and V2 acquisition circuits include a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a filter capacitor, and a bidirectional Zener diode. One end of the first resistor is connected to the power supply line corresponding to the relay load side. The other end of the second resistor is connected to one end of the fourth resistor via the second and third resistors. The other end of the fourth resistor is connected to one end of the filter capacitor, the corresponding acquisition pin on the controller, one end of the fifth resistor, and pin 3 of the bidirectional Zener diode. The other ends of the filter capacitor, the other end of the fifth resistor, and pin 1 of the bidirectional Zener diode are grounded. Pin 2 of the bidirectional Zener diode is connected to the power input terminal of the controller.

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