A control method of a national standard alternating current charging

Abstract

The application discloses a control method for national standard alternating current charging, and relates to the technical field of alternating current charging, and aims to solve the technical problem that when the existing national standard alternating current charging gun is used for a long time, terminal wear or oxidation causes the contact resistance to become large, the temperature of the gun head is too high, the traditional charging scheme only relies on over-temperature power-off, the charging experience is affected, and the charging pile control ability is not fully utilized. The temperature detection unit collects the temperature of the core part of the charging gun head in real time, the MCU control unit dynamically adjusts the output duty cycle of the PWM generation unit according to the comparison result of the real-time temperature and the preset temperature threshold, and then adjusts the charging current, so that the precise control of the temperature rise of the charging gun is realized; meanwhile, the over-temperature protection mechanism and the temperature back-fall recovery mechanism are arranged, and the charging safety and continuity are considered. The application can control precisely, effectively reduce the charging safety hidden danger, improve the charging experience, and is suitable for various national standard alternating current charging piles.

Description

Technical Field

[0001] This invention relates to the field of AC charging technology, specifically to a control method for national standard AC charging. Background Technology

[0002] With the increasing popularity of new energy vehicles, the safety and stability of the national standard AC charging gun, as a core component for charging these vehicles, are of paramount importance. Existing national standard AC charging guns are prone to wear and tear during prolonged use due to frequent plugging and unplugging of the terminals. Environmental factors can also cause terminal oxidation, leading to increased contact resistance. Increased contact resistance generates significant heat during charging, causing excessive temperature rise at the charging head (terminals), posing safety hazards such as fire and short circuits.

[0003] Traditional charging control schemes rely solely on over-temperature power-off mechanisms, which directly cut off the charging circuit and stop charging when the gun head temperature reaches a set over-temperature threshold. While this method can prevent safety accidents to some extent, it severely impacts the user's charging experience, especially in long-term charging scenarios where frequent power outages lead to low charging efficiency. Furthermore, traditional solutions do not fully utilize the charging station's control capabilities, failing to actively adjust charging parameters to control gun head temperature rise, making it difficult to balance charging safety and user experience. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned technical problems by providing a control method for standard AC charging.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A control method for AC charging according to national standards, applied to a charging pile including an MCU, a PWM generator unit, a temperature detection unit, an AC contactor, and a charging gun head, includes the following steps:

[0007] (1) Three temperature thresholds are preset, namely the first temperature threshold T1, the second temperature threshold T2, and the third temperature threshold T3. The initial duty cycle D0 and the minimum duty cycle D of the PWM are preset. min ;

[0008] (2) After the vehicle plugs in the charging gun and starts charging, the temperature detection unit collects the temperature data of the charging gun head in real time with a cycle of 1 second and transmits it to the MCU.

[0009] (3) The MCU processes the collected temperature data and takes the higher of the two temperature values ​​collected by the temperature detection unit as the real-time temperature T;

[0010] (4) The MCU compares the real-time temperature T with three preset temperature thresholds, and dynamically adjusts the PWM duty cycle based on the comparison results, thereby controlling the AC contactor to regulate the charging current.

[0011] (5) When the real-time temperature T drops, the MCU starts the duty cycle recovery process to gradually restore the PWM duty cycle. During the recovery process, the temperature is monitored in real time to ensure that the charging is not interrupted and to avoid the temperature from rising abnormally again.

[0012] The specific control logic for adjusting the charging current in step 3 is as follows:

[0013] ① When T≤T1, the charging pile maintains the initial PWM duty cycle D0 and maintains the maximum charging current;

[0014] ② When T1<T≤T2, the system enters dynamic adjustment mode. The MCU dynamically calculates the target PWM duty cycle D according to the real-time temperature T using a linear formula. D is negatively correlated with T.

[0015] ③ When T2 < T < T3, lock the PWM duty cycle to D. min ;

[0016] ④ When T≥T3, the MCU controls the PWM generator unit to output 0% duty cycle, disconnect the AC contactor, stop charging, and report an over-temperature fault alarm;

[0017] ⑤ When the real-time temperature T drops and remains stable below T1 for 3 consecutive seconds, the recovery process is initiated.

[0018] The temperature detection unit employs two NTC thermistors, embedded within the L-phase and N-phase terminals of the charging gun head, respectively, to collect temperature rise data of the core area of ​​the charging gun head. The sampled values ​​from the two thermistors are input to the MCU after analog-to-digital conversion. NTC thermistors are characterized by high sensitivity and fast response, enabling accurate temperature rise data collection of the core area of ​​the charging gun head, providing a reliable basis for the MCU's control decisions.

[0019] The relationship between D and T is negative; that is, the higher the temperature, the lower the output duty cycle and the corresponding decrease in charging current. The calculation formula is as follows: D = D0 - (D0 - D min )*(T−T1)∕(T2−T1).

[0020] The method for gradually restoring the PWM duty cycle in step 5 is as follows: the duty cycle can be linearly increased at a rate of 5% per minute until the real-time temperature T and the corresponding value of the PWM output reach an equilibrium point.

[0021] The startup and recovery process is as follows:

[0022] 1) Increment the PWM duty cycle linearly by 5% per minute;

[0023] 2) Monitor the temperature in real time during the recovery process. If T rises again, pause the increase and maintain the current duty cycle.

[0024] 3) When the duty cycle recovers to D0 or the temperature reaches a new equilibrium, the recovery stops and steady-state control begins;

[0025] 4) Restore uninterrupted charging throughout the entire process without triggering repeated relay actions.

[0026] The PWM generator unit receives the duty cycle control signal output by the MCU and generates a PWM waveform to control the AC contactor and guiding circuit, thereby adjusting the output current during charging in real time. This ensures that the charging process complies with the national standard GB / T18487.1, improving charging compatibility and safety.

[0027] By employing the above method, the present invention has the following advantages:

[0028] 1. This invention uses two NTC thermistors to collect the temperature of the core part of the gun head in real time. The NTC is embedded in the two core current-carrying terminals L and N respectively, and the maximum value is taken as the judgment basis. It directly targets the source of heat generation of the terminal contact resistance, and at the same time realizes dual-circuit redundancy to prevent failure.

[0029] 2. Three temperature thresholds are set to achieve gradient control from dynamic current adjustment to over-temperature power-off, which can effectively control the temperature rise of the nozzle and avoid safety hazards caused by terminal wear and oxidation.

[0030] 2. This invention abandons the traditional single over-temperature power-off mechanism. The linear adjustment logic of this invention achieves precise matching between temperature and current, avoiding the charging interruption caused by large current jumps and repeated temperature fluctuations. By dynamically adjusting the charging current, frequent power outages are avoided while ensuring safety. At the same time, charging is smoothly resumed when the temperature drops, ensuring the continuity and efficiency of charging.

[0031] 3. The parameters of this invention can be adjusted according to actual scenarios to adapt to various national standard AC charging piles; the control logic is simple, the hardware structure is mature, and it is easy to implement and promote, making full use of the charging pile's control capabilities and improving the charging pile's performance. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the full text.

[0034] Combined with appendix Figure 1This invention provides a control method for standard AC charging. By monitoring the charging gun temperature in real time and dynamically adjusting the charging current, the temperature rise of the charging gun is controlled, achieving a safe and efficient charging mechanism. The charging station mainly includes: an MCU, a PWM generator, a temperature detection unit, an AC contactor, and a charging gun. The method includes the following steps:

[0035] Three temperature thresholds are preset: the first temperature threshold T1, the second temperature threshold T2, and the third temperature threshold T3. The initial duty cycle D0 and the minimum duty cycle Dmin of the PWM are also preset.

[0036] After the vehicle is plugged in and started charging, the temperature detection unit collects the temperature data of the charging gun head in real time at a 1-second cycle and transmits it to the MCU.

[0037] The MCU processes the collected temperature data and takes the higher of the two temperature values ​​collected by the temperature detection unit as the real-time temperature T.

[0038] The MCU compares the real-time temperature T with three preset temperature thresholds, dynamically adjusts the PWM duty cycle based on the comparison results, and then controls the AC contactor to regulate the charging current.

[0039] When the real-time temperature T drops, the MCU starts the duty cycle recovery process to gradually restore the PWM duty cycle. During the recovery process, the temperature is monitored in real time to ensure that charging is not interrupted and to prevent the temperature from rising abnormally again.

[0040] The specific control logic for adjusting the charging current in step 3 is as follows:

[0041] ① When T≤T1, the charging pile maintains the initial PWM duty cycle D0 and maintains the maximum charging current;

[0042] ② When T1<T≤T2, the system enters dynamic adjustment mode. The MCU dynamically calculates the target PWM duty cycle D according to the real-time temperature T using a linear formula. D is negatively correlated with T.

[0043] ③ When T2 < T < T3, lock the PWM duty cycle to Dmin;

[0044] ④ When T≥T3, the MCU controls the PWM generator unit to output 0% duty cycle, disconnect the AC contactor, stop charging, and report an over-temperature fault alarm;

[0045] ⑤ When the real-time temperature T drops and remains stable below T1 for 3 consecutive seconds, the recovery process is initiated.

[0046] The temperature detection unit uses two NTC thermistors, which are embedded in the L-phase terminal and N-phase terminal of the charging gun head, respectively, to collect the temperature rise of the core part of the gun head. The sampled values ​​of the two thermistors are input to the MCU after analog-to-digital conversion.

[0047] The relationship between D and T is negative. That is, the higher the temperature, the lower the output duty cycle and the corresponding decrease in charging current. The calculation formula is as follows: D=D0-(D0-Dmin)∗(T−T1) / (T2−T1).

[0048] The method for gradually restoring the PWM duty cycle in step 5 is as follows: the duty cycle can be linearly increased at a rate of 5% per minute until the real-time temperature T and the corresponding value of the PWM output reach an equilibrium point.

[0049] The startup and recovery process is as follows:

[0050] 1) Increment the PWM duty cycle linearly by 5% per minute;

[0051] 2) Monitor the temperature in real time during the recovery process. If T rises again, pause the increase and maintain the current duty cycle.

[0052] 3) When the duty cycle recovers to D0 or the temperature reaches a new equilibrium, the recovery stops and steady-state control begins;

[0053] 4) Restore uninterrupted charging throughout the entire process without triggering repeated relay actions.

[0054] MCU control unit: Compares two temperature values ​​of the nozzle in real time, compares them with a set threshold, adjusts the PWM duty cycle in real time, and controls the on / off state of the AC contactor.

[0055] Temperature detection unit: Two NTC thermistors are embedded inside the L-phase and N-phase terminals of the charging gun head, respectively, to collect real-time temperature rise data of the core area of ​​the charging gun head. The sampled values ​​from the two thermistors are converted from analog to digital and then input to the MCU. The MCU takes the higher of the two values ​​as the real-time temperature T.

[0056] PWM Generator Unit: Receives the duty cycle control signal output by the MCU and generates a PWM waveform that conforms to the national standard GB / T 18487.1. This waveform is used to control the AC contactor and the guiding circuit, thereby adjusting the output current during charging in real time.

[0057] In a preferred embodiment of the present invention, the first temperature threshold T1 = 55°C, the second temperature threshold T2 = 80°C, the third temperature threshold T3 = 85°C, the initial duty cycle D0 = 25%, and the minimum duty cycle D min=10%, this parameter setting can adapt to the usage scenarios of most national standard AC charging piles. The parameter setting can be finely adjusted up or down by 5-10, or the parameter can be set according to the actual situation, taking into account both safety and charging efficiency.

[0058] Example 1:

[0059] A control method for standard AC charging is applied to charging piles that include an MCU, a PWM generator, a temperature detection unit, an AC contactor, and a charging gun. The specific implementation steps are as follows:

[0060] a) Parameter configuration: Preset first temperature threshold T1=55℃, second temperature threshold T2=80℃, third temperature threshold T3=85℃; configure the initial duty cycle D0=25% and the minimum duty cycle D0=25% for the PWM. min =10%; Among them, the temperature detection unit uses two NTC thermistors, which are embedded in the L-phase terminal and N-phase terminal of the charging gun head respectively, and the PWM waveform generated by the PWM generation unit meets the requirements of national standard GB / T 18487.1.

[0061] b) Charging Start-up: After the vehicle is plugged in, the charging process is started. The temperature detection unit collects the sampling values ​​of two NTC thermistors in real time with a cycle of 1 second. After analog-to-digital conversion, the values ​​are input to the MCU. The MCU takes the higher of the two sampling values ​​as the real-time temperature T.

[0062] c) Steady-state charging: When the real-time temperature T ≤ 55℃, the MCU controls the PWM generator unit to output the initial duty cycle D0=25%, the AC contactor is in the conducting state, the charging pile maintains the maximum charging current of 16.0A, and enters the full power charging state. At this time, the gun head temperature is stable and no adjustment is required.

[0063] d) Dynamic Current Reduction: When 55℃ < T ≤ 80℃, the system enters dynamic adjustment mode. The MCU calculates the target PWM duty cycle in real time using the linear formula D = 25% − 0.6∗(T − 55), updating the PWM duty cycle once per second to smoothly reduce the charging current and achieve precise control of the charging head temperature rise. For example, when T = 62℃, D = 20%, corresponding to an output current of 12.8A; when T = 70℃, D = 15.4%, corresponding to an output current of 9.9A; and when T = 75℃, D = 12%, corresponding to an output current of 7.7A.

[0064] e) Minimum power maintenance: When 80℃ < T < 85℃, the MCU controls the PWM duty cycle to lock at D. min =10%, corresponding to an output current of 6.4A, maintaining minimum power charging to prevent further temperature rise. For example, when T=83℃, maintaining a duty cycle of 10% corresponds to an output current of 6.4A.

[0065] f) Over-temperature protection: When T ≥ 85℃, the MCU immediately controls the PWM generator to output 0% duty cycle, disconnects the AC relay, stops charging output, reports an over-temperature fault, and triggers an alarm to prevent safety accidents. For example, when T = 85℃ and 86℃, charging stops and the output current is 0.0A.

[0066] g) Temperature Drop Recovery: When the real-time temperature T drops and remains stable below 55℃ for 3 consecutive seconds, the recovery process is initiated: the PWM duty cycle is linearly increased at a rate of 5% per minute; the temperature is monitored in real time during the recovery process, and if T rises again, the increase is paused, maintaining the current duty cycle; when the duty cycle recovers to 25% or the temperature reaches a new equilibrium, the recovery stops, and steady-state control is entered. The entire recovery process does not interrupt charging and does not trigger repeated relay actions. Specific recovery process data is shown in Table 1.

[0067] Table 1

[0068]

[0069] In this embodiment, the specific data of the charging control process are shown in Table 2 below, which clearly shows the PWM duty cycle, output current and control status at different temperatures:

[0070] Table 2

[0071]

[0072] This specific embodiment, through dual NTC real-time temperature measurement, three-level temperature threshold gradient control, linear dynamic current adjustment, and smooth temperature fallback recovery, has the following significant advantages compared to traditional over-temperature power-off solutions:

[0073] This invention features precise and reliable temperature control. It employs dual NTC thermistors embedded within the L-phase and N-phase terminals of the charging gun head, respectively, using the higher temperature as the real-time temperature for comprehensive monitoring. Three threshold levels (55℃, 80℃, and 85℃) are set to achieve gradient protection including dynamic current reduction, minimum power maintenance, and over-temperature power-off. This effectively suppresses temperature rise in the charging gun head and prevents safety hazards such as overheating and short circuits caused by terminal wear and oxidation.

[0074] This invention provides continuous charging and a better user experience. It abandons the traditional single over-temperature power-off protection, smoothly reduces current and does not interrupt charging when the temperature rises, and linearly restores power at a fixed rate when the temperature drops. It does not trigger repeated operation of the AC contactor throughout the process, making the charging process smooth and stable and greatly improving the user charging experience.

[0075] This invention offers rapid response and smooth control. It acquires temperature data in 1-second cycles and updates the PWM duty cycle in real time, resulting in fast control response, smooth current regulation, and no shocks or fluctuations. The target duty cycle is calculated using a linear formula, which simplifies the logic, reduces the computational load on the MCU, and is easy to implement in hardware.

[0076] It balances efficiency and safety by charging at full power in low-temperature conditions to ensure charging efficiency, reducing power as needed in high-temperature conditions to control temperature rise, and maximizing charging speed while ensuring safety, thus achieving a balance between safety and efficiency.

[0077] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown throughout are only one of the embodiments of the present invention. The actual structure is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A control method for standard AC charging, applied to a charging pile including an MCU, a PWM generator unit, a temperature detection unit, an AC contactor, and a charging gun head, characterized in that, Includes the following steps: (1) Three temperature thresholds are preset, namely the first temperature threshold T1, the second temperature threshold T2, and the third temperature threshold T3. The initial duty cycle D0 and the minimum duty cycle D of the PWM are preset. min ; (2) After the vehicle plugs in the charging gun and starts charging, the temperature detection unit collects the temperature data of the charging gun head in real time with a cycle of 1 second and transmits it to the MCU. (3) The MCU processes the collected temperature data and takes the higher of the two temperature values ​​collected by the temperature detection unit as the real-time temperature T; (4) The MCU compares the real-time temperature T with three preset temperature thresholds, and dynamically adjusts the PWM duty cycle based on the comparison results, thereby controlling the AC contactor to regulate the charging current. (5) When the real-time temperature T drops, the MCU starts the duty cycle recovery process to gradually restore the PWM duty cycle. During the recovery process, the temperature is monitored in real time to ensure that the charging is not interrupted and to avoid the temperature from rising abnormally again.

2. The control method for a national standard AC charging according to claim 1, characterized in that: The specific control logic for adjusting the charging current in step 3 is as follows: ① When T≤T1, the charging pile maintains the initial PWM duty cycle D0 and maintains the maximum charging current; ② When T1<T≤T2, the system enters dynamic adjustment mode. The MCU dynamically calculates the target PWM duty cycle D according to the real-time temperature T using a linear formula. D is negatively correlated with T. ③ When T2 < T < T3, lock the PWM duty cycle to D. min ; ④ When T≥T3, the MCU controls the PWM generator unit to output 0% duty cycle, disconnect the AC contactor, stop charging, and report an over-temperature fault alarm; ⑤ When the real-time temperature T drops and remains stable below T1 for 3 consecutive seconds, the recovery process is initiated.

3. The control method for national standard AC charging according to claim 2, characterized in that: The temperature detection unit uses two NTC thermistors, which are embedded in the L-phase terminal and N-phase terminal of the charging gun head, respectively, to collect the temperature rise of the core part of the gun head. The sampled values ​​of the two thermistors are input to the MCU after analog-to-digital conversion.

4. The control method for national standard AC charging according to claim 2, characterized in that: The relationship between D and T is negative; that is, the higher the temperature, the lower the output duty cycle and the corresponding decrease in charging current. The calculation formula is as follows: D = D0 - (D0 - D min )*(T−T1)∕(T2−T1).

5. The control method for national standard AC charging according to claim 1, characterized in that: The method for gradually restoring the PWM duty cycle in step 5 is as follows: the duty cycle can be linearly increased at a rate of 5% per minute until the real-time temperature T and the corresponding value of the PWM output reach an equilibrium point.

6. The control method for a national standard AC charging according to claim 1, characterized in that: The startup and recovery process is as follows: 1) Increment the PWM duty cycle linearly by 5% per minute; 2) Monitor the temperature in real time during the recovery process. If T rises again, pause the increase and maintain the current duty cycle. 3) When the duty cycle recovers to D0 or the temperature reaches a new equilibrium, the recovery stops and steady-state control begins; 4) Restore uninterrupted charging throughout the entire process without triggering repeated relay actions.

7. The control method for national standard AC charging according to claim 1, characterized in that: The PWM generation unit is used to receive the duty cycle control signal output by the MCU, generate a PWM waveform, and control the AC contactor and the guiding circuit to adjust the output current during charging in real time.

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