LNG (Liquefied Natural Gas) filling station one-key pump unloading control system and method

Abstract

The invention relates to a one-key pump unloading control system for an LNG filling station. The one-key pump unloading control system comprises a pressurizing liquid phase pipeline, a gas phase pipeline, an unloading liquid phase pipeline, a filling pipeline, a pump unloading pipeline, a storage tank gas phase pipeline, a pump pool, an immersed pump, a storage tank liquid phase pipeline, a tank car liquid phase pipeline and a control unit. And the control system adopts a fuzzy self-adaptive PID control algorithm to adjust the rotating speed of the immersed pump in real time. A sensor is arranged to collect system numerical values in real time, the rotating speed of the immersed pump is controlled through an algorithm, efficient operation of the pump is guaranteed, cavitation is prevented, and therefore automatic one-key pump unloading is achieved. The invention further relates to a method using the one-key pump unloading control system of the LNG filling station. Automatic one-key pump unloading is achieved, the problem that manual judgment and operation are needed in the unloading process is solved, and the operation efficiency of the whole LNG station is improved.

Description

Technical Field

[0001] This invention relates to the field of LNG refueling station tanker unloading technology, specifically to a one-button pump unloading control system and method for LNG refueling stations. Background Technology

[0002] With the advancement of the new national energy strategy, the importance of natural gas in China's energy structure has been clarified, and the construction of LNG-related infrastructure has been accelerated. At present, the automation level of unloading tank trucks at domestic LNG refueling stations is low, and the unloading process still requires manual judgment and operation based on experience. At the same time, LNG is a cryogenic liquid, and there are operational risks for on-site personnel. Common unloading modes at LNG refueling stations include: (1) pressurized unloading, which uses the pressure difference between the storage tank and the tank compartment for unloading; (2) pump unloading, which uses the power of a submersible pump for unloading; and (3) combined unloading, which uses both pressurized unloading and pump unloading.

[0003] The shortcomings of existing technology are: The unloading time of the pressurized unloading mode is long; the traditional pump unloading uses simple PID control. The physical properties of LNG change significantly with temperature and pressure. Cavitation is easily caused at low temperatures, resulting in low pump utilization. Conventional PID control cannot guarantee steady-state performance under nonlinear conditions. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a one-click pump unloading control system and method for LNG refueling stations. The purpose is to achieve automated one-click pump unloading, solve the problem of manual judgment and operation during the unloading process, and improve the overall operating efficiency of LNG refueling stations.

[0005] To solve the above problems, the technical solution provided by the present invention is as follows: An LNG refueling station one-button pump unloading control system includes a pressurized liquid phase pipeline, a gas phase pipeline, an unloading liquid phase pipeline, a refueling pipeline, a pump unloading pipeline, a storage tank gas phase pipeline, a pump pool, a submersible pump, a storage tank liquid phase pipeline, a tank truck liquid phase pipeline, and a control unit, wherein: The pressurized liquid phase pipeline is connected to the pressurized liquid phase port of the tank truck via a metal hose and is used to pressurize the tank truck; the pressurized liquid phase pipeline is equipped with a pressurization control valve and a vaporizer; the gas phase pipeline is connected to the gas connection of the tank truck via a metal hose and is used to balance the pressure between the tank truck and the storage tank; the gas phase pipeline is equipped with a tank truck pressure sensor and a gas phase control valve; a control valve is installed between the gas phase pipeline and the unloading liquid phase pipeline; an unloading control valve is installed on the unloading liquid phase pipeline; the outlet pipeline of the unloading liquid phase pipeline is connected to the storage tank and the pump pool respectively; the inlet of the pump pool... The system is connected to the gas phase pipeline of the storage tank, the liquid phase pipeline of the storage tank, and the liquid phase pipeline of the tank truck, respectively; the outlet of the pump pool is connected to the filling pipeline and the pump unloading pipeline, respectively; the submersible pump, the pump pool temperature sensor, and the pump pool level sensor are installed in the pump pool; a post-pump pressure sensor is installed at the outlet of the pump pool; a filling control valve is installed on the filling pipeline; a pump unloading control valve is installed on the pump unloading pipeline; a pre-pump pressure sensor and a pump return gas control valve are installed on the gas phase pipeline of the storage tank; a first pump inlet control valve is installed on the liquid phase pipeline of the storage tank. A second pump inlet control valve is installed on the liquid phase pipeline of the tank truck; the control unit is electrically coupled to the booster control valve, the gas phase control valve, the tank truck pressure sensor, the control valve, the unloading control valve, the pump pool temperature sensor, the filling control valve, the pump pool level sensor, the pump post-pressure sensor, the pump pre-pressure sensor, the pump unloading control valve, the submersible pump, the second pump inlet control valve, the first pump inlet control valve, and the pump return gas control valve.

[0006] Preferably, the control system employs a fuzzy adaptive PID control algorithm to adjust the rotational speed of the submersible pump in real time; the fuzzy adaptive PID control algorithm specifically includes the following steps: S100. Collect the pump pool liquid level, pump pool temperature, and pump pool inlet pressure, and then calculate the cavitation safety index; the cavitation safety index is expressed by the following formula: in: , and Used to characterize the weighting system, the initial value is set to 1.0 and fine-tuned according to the on-site working conditions; L min Used to characterize the minimum liquid level allowed to prevent cavitation; P min Used to characterize the inlet pressure threshold allowed to prevent cavitation; T max Used to characterize the absolute value threshold of the highest temperature allowed to prevent cavitation; S200. Determine whether the cavitation safety index is greater than or equal to a manually preset safety threshold value, and perform the following operations based on the determination result: If the cavitation safety index is less than the safety value threshold, then the value of the PID proportional parameter increment is set to -100% and the pump speed is reduced. If the cavitation safety index is greater than or equal to the safety value threshold, then the increment of the PID proportional parameter, the increment of the PID integral parameter, and the increment of the PID derivative parameter are output through a fuzzy algorithm. S300. Construct a fuzzy rule base, using the error between the pump outlet pressure and the pressure setpoint, the error change rate, and the cavitation safety index as input variables, perform fuzzification processing, and execute fuzzy inference operations; S400. The increment of the actual PID parameters is obtained through defuzzification calculation; S500. The increments of the actual PID parameters are superimposed to obtain the current PID controller parameter values, expressed by the following formula: Where: K p0 Used to characterize the tuned basic PID proportional parameter; K i0 Used to characterize the tuned basic PID integral parameters; K d0 Used to characterize the tuned basic PID differential parameters; S600. Input the parameters calculated in step S500 into the PID controller. After processing by the PID controller, send the output command to the frequency converter to adjust the speed of the submersible pump.

[0007] Preferably, the safety threshold value is 3.

[0008] A method utilizing the aforementioned one-button pump unloading control system for LNG refueling stations includes the following steps: Sa100. Connect the tank truck to the pressurized liquid phase pipeline, the gas phase pipeline, and the unloading liquid phase pipeline of the gas station; open the corresponding valves on the tank truck, and the operator clicks the one-button pump unloading button on the touch screen to start the system and enter the automatic unloading control process; Sa200. Control the tank pressure sensor to monitor the tank pressure in real time; when the tank pressure is greater than the manually preset pressure stabilization start threshold, the system automatically performs pressure stabilization; control the opening of the gas phase control valve and the control valve until the pressure difference between the tank truck and the tank is less than the manually preset pressure stabilization completion threshold to complete the pressure stabilization. After Sa300 pressure equalization is completed, the control system opens the unloading control valve and the second pump inlet control valve; controls LNG to flow into the pump pool through the unloading liquid phase pipeline and the tank truck liquid phase pipeline using the pressure difference; controls the pump pool temperature sensor and the pump pool level sensor to monitor the LNG level and pump pool temperature in the pump pool in real time until the monitored values ​​meet the manually preset pump precooling completion judgment conditions. After the Sa400 pump precooling is completed, the control system enters the pump unloading process; the pump unloading control valve is opened, the submersible pump is started and unloading is performed; during the unloading process, the pump pool level sensor is controlled to monitor the LNG level in real time. When the LNG level is lower than the manually preset minimum level, the system automatically shuts down the submersible pump. The operator confirms that the tank truck level is zero, and the unloading is completed.

[0009] Preferably, the pressure stabilization start threshold in step Sa200 is 0.4 MPa; the pressure stabilization completion threshold is 0.1 MPa.

[0010] Preferably, the pump precooling completion determination condition in step Sa300 is: the LNG liquid level is higher than 586mm, the temperature in the pump pool is lower than -110℃, and is maintained for not less than 1 minute.

[0011] Preferably, the minimum liquid level in step Sa400 is 586 mm.

[0012] Preferably, in the pump unloading process of step Sa400, the fuzzy adaptive PID control algorithm is used to adjust the rotational speed of the submersible pump.

[0013] Preferably, the pressure setpoint satisfies the current pump inlet pressure plus the pipeline pressure difference that needs to be overcome to achieve efficient pump operation, subject to the specific process design.

[0014] Compared with the prior art, the present invention has the following advantages: 1. This invention achieves automated one-click pump unloading by setting up sensors to collect system values ​​in real time and automatically controlling the opening and closing of valves based on changes in process parameter values, thus solving the problem of manual judgment and operation required during the unloading process.

[0015] 2. This invention achieves automated one-click unloading by setting up sensors to collect system values ​​in real time and adjusting the submersible pump speed based on a fuzzy adaptive PID control algorithm. This solves the problem of low unloading efficiency and improves the overall operating efficiency of the LNG refueling station. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the connection structure between the tanker truck and the LNG refueling station according to a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the pump pool connection structure according to a specific embodiment of the present invention.

[0017] The components are as follows: 1. Pressure boosting control valve, 2. Pressure boosting liquid phase pipeline, 3. Gas phase control valve, 5. Vaporizer, 6. Tank truck pressure sensor, 7. Control valve, 8. Gas phase pipeline, 9. Unloading control valve, 10. Unloading liquid phase pipeline, 100. Filling pipeline, 101. Pump pool temperature sensor, 102. Filling control valve, 103. Pump pool level sensor, 104. Post-pump pressure sensor, 105. Pre-pump pressure sensor, 106. Pump unloading control valve, 107. Pump unloading pipeline, 108. Storage tank gas phase pipeline, 109. Pump pool, 110. Submersible pump, 111. Second pump inlet control valve, 112. First pump inlet control valve, 113. Pump return gas control valve, 114. Tank truck liquid phase pipeline, 115. Storage tank liquid phase pipeline. Detailed Implementation

[0018] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0019] This invention application claims protection for a one-button pump unloading control system for LNG refueling stations, such as... Figure 1 , 2 As shown, it includes a pressurized liquid phase pipeline 2, a gas phase pipeline 8, an unloading liquid phase pipeline 10, a filling pipeline 100, a pump unloading pipeline 107, a storage tank gas phase pipeline 108, a pump pool 109, a submersible pump 110, a storage tank liquid phase pipeline 115, a tank truck liquid phase pipeline 114, and a control unit, wherein: The pressurized liquid phase pipeline 2 is connected to the pressurized liquid phase port of the tank truck via a metal hose and is used to pressurize the tank truck. The pressurized liquid phase pipeline 2 is equipped with a pressurization control valve 1 and a vaporizer 5. During unloading, the program automatically controls the valve opening of the pressurization control valve 1 to adjust the tank truck pressure. The vapor phase pipeline 8 is connected to the gas connection of the tank truck via a metal hose and is used to balance the pressure between the tank truck and the storage tank. The vapor phase pipeline 8 is equipped with a tank truck pressure sensor 6 and a vapor phase control valve 3. The tank truck pressure sensor 6 monitors the tank truck pressure, and the vapor phase control valve 3 controls the pressure balance between the tank truck and the storage tank. A control valve 7 is installed between the unloading liquid phase pipeline 8 and the unloading liquid phase pipeline 10 to ensure the liquid phase pressure equalization of the tank truck. An unloading control valve 9 is installed on the unloading liquid phase pipeline 10. The outlet pipeline of the unloading liquid phase pipeline 10 is connected to the storage tank and the pump pool 109 respectively for unloading liquid from the tank truck. The inlet of the pump pool 109 is connected to the storage tank gas phase pipeline 108, the storage tank liquid phase pipeline 115, and the tank truck liquid phase pipeline 114 respectively. The outlet of the pump pool 109 is connected to the filling pipeline 100 and the pump unloading pipeline 107 respectively. A submersible pump 110 and a pump pool temperature sensor are installed in the pump pool 109. 101 and pump pool level sensor 103 are used to monitor the temperature and level parameters in the pump pool in real time; a pump post-pressure sensor 104 is installed at the outlet of pump pool 109; a filling control valve 102 is installed on the filling pipeline 100; a pump unloading control valve 106 is installed on the pump unloading pipeline 107; a pump pre-pressure sensor 105 and a pump return gas control valve 113 are installed on the gas phase pipeline 108 of the storage tank. The pump pre-pressure sensor 105 is used to monitor the pressure in pump pool 109, and the pump return gas control valve 113 is used to control the gas discharge in the pump pool; a first... A first pump inlet control valve 112 is provided; a second pump inlet control valve 111 is provided on the tank truck liquid phase pipeline 114; the control unit is electrically coupled to the booster control valve 1, the gas phase control valve 3, the tank truck pressure sensor 6, the control valve 7, the unloading control valve 9, the pump pool temperature sensor 101, the filling control valve 102, the pump pool liquid level sensor 103, the pump post-pressure sensor 104, the pump pre-pressure sensor 105, the pump unloading control valve 106, the submersible pump 110, the second pump inlet control valve 111, the first pump inlet control valve 112, and the pump return gas control valve 113.

[0020] It should be noted that this control system monitors the gas phase pressure of the tank truck in real time by configuring the tank truck pressure sensor 6, and automatically executes the pressure equalization process of the control system and the pre-cooling process of the submersible pump.

[0021] It should be noted that if the pressure difference between the tank truck and the storage tank is less than 0.2 MPa after the pressure equalization process, the pressurization control valve 1 and the gas phase control valve 3 are opened to carry out the tank truck self-pressurization process.

[0022] It should be noted that the pump pool temperature sensor 101 and the pump pool level sensor 103 are used for pre-cooling and operation logic judgment of the submersible pump 110. By monitoring the temperature and level parameters in the pump pool 109, the submersible pump 110 is ensured to be fully pre-cooled and operate normally.

[0023] It should be noted that by configuring the pre-pump pressure sensor 105 and the post-pump pressure sensor 104, the differential pressure protection of the pump is set to prevent cavitation in the submersible pump 110 and ensure the normal operation of the submersible pump 110.

[0024] It should be noted that, considering that conventional PID control cannot achieve stable and efficient pump operation during unloading, and that when the pressure at the submersible pump inlet drops below the saturated vapor pressure of LNG during operation, it will cause violent vaporization of LNG, generating bubbles and posing a risk of cavitation, the control system of this invention adopts a fuzzy adaptive PID control algorithm to adjust the speed of the submersible pump 110 in real time; the fuzzy adaptive PID control algorithm specifically includes the following steps: S100. Collect the pump pool liquid level, pump pool temperature, and pump pool inlet pressure, and then calculate the cavitation safety index; the cavitation safety index is expressed by the following formula: in: , and Used to characterize the weighting system, the initial value is set to 1.0 and fine-tuned according to the on-site working conditions; L min Used to characterize the minimum liquid level allowed to prevent cavitation; P min Used to characterize the inlet pressure threshold allowed to prevent cavitation; T max Used to characterize the absolute value threshold of the highest temperature allowed to prevent cavitation; S200. Determine whether the cavitation safety index is greater than or equal to the manually preset safety threshold, and perform the following operations based on the determination result: If the cavitation safety index is less than the safety threshold, then set the PID proportional parameter increment to -100% and reduce the pump speed. If the cavitation safety index is greater than or equal to the safety threshold, then the increment of the PID proportional parameter is output using a fuzzy algorithm. PID integral parameter increment, PID derivative parameter increment; S300. Construct a fuzzy rule base, using the error between the pump outlet pressure and the pressure setpoint, the error change rate, and the cavitation safety index as input variables, perform fuzzification processing, and execute fuzzy inference operations; S400. The increment of the actual PID parameters is obtained through defuzzification calculation; S500. The increments of the actual PID parameters are superimposed to obtain the current PID controller parameter values, expressed by the following formula: Where: K p0 Used to characterize the tuned basic PID proportional parameter; K i0 Used to characterize the tuned basic PID integral parameters; K d0 Used to characterize the tuned basic PID differential parameters; S600. Input the parameters calculated in step S500 into the PID controller. After processing by the PID controller, send the output command to the frequency converter to adjust the speed of the submersible pump 110.

[0025] It should be further explained that the control algorithm takes the error between the pump outlet pressure and the set value, the rate of change of the error, the pump pool level, the pump pool temperature, and the pump pool pressure as inputs, and adjusts the PID parameters in real time according to the preset fuzzy control strategy to achieve adaptive control of the submersible pump.

[0026] In this specific embodiment, the safety threshold value is 3.

[0027] A method utilizing a one-button pump unloading control system for LNG refueling stations includes the following steps: Sa100. Connect the tank truck to the pressurized liquid phase pipeline 2, gas phase pipeline 8 and unloading liquid phase pipeline 10 of the gas station; open the corresponding valves on the tank truck, and the operator clicks the one-button pump unloading button on the touch screen to start the system and enter the automatic unloading control process. Sa200. Control tank pressure sensor to monitor tank pressure in real time; when tank pressure is greater than the manually preset pressure stabilization start threshold, the system automatically performs pressure stabilization; control the opening of gas phase control valve 3 and control valve 7 until the pressure difference between tank truck and tank is less than the manually preset pressure stabilization completion threshold to complete pressure stabilization; Sa300. After the pressure is balanced, the control system opens the unloading control valve 9 and the second pump inlet control valve 111; controls the LNG to flow into the pump pool 109 through the unloading liquid phase pipeline 10 and the tank truck liquid phase pipeline 114 using the pressure difference; controls the pump pool temperature sensor 101 and the pump pool liquid level sensor 103 to monitor the LNG liquid level and pump pool temperature in the pump pool 109 in real time until the monitored values ​​meet the manually preset pump pre-cooling completion judgment conditions. After the Sa400 pump precooling is completed, the control system enters the pump unloading process; the pump unloading control valve 106 is opened, the submersible pump 110 is started and unloading is performed; during the unloading process, the control pump pool level sensor 103 monitors the LNG level in real time. When the LNG level is lower than the manually preset minimum level, the system automatically shuts down the submersible pump 110. The operator confirms that the tanker level is zero and the unloading is completed.

[0028] In this specific embodiment, the pressure stabilization start threshold in step Sa200 is 0.4 MPa; the pressure stabilization completion threshold is 0.1 MPa.

[0029] In this specific embodiment, the conditions for determining the completion of pump precooling in step Sa300 are: the LNG level is higher than 586mm (confirmed according to actual engineering conditions), the temperature inside the pump pool is lower than -110℃, and it is maintained for no less than 1 minute.

[0030] In this specific embodiment, the minimum liquid level in step Sa400 is 586 mm.

[0031] It should be noted that in the pump unloading process of step Sa400, the speed of the submersible pump 110 is adjusted by a fuzzy adaptive PID control algorithm.

[0032] In this specific embodiment, the pressure setpoint satisfies the current pump inlet pressure plus the pipeline pressure difference that needs to be overcome to achieve efficient pump operation, subject to the specific process design.

[0033] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0034] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0035] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

[0036] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A one-button pump unloading control system for LNG refueling stations, characterized in that: Includes a pressurized liquid phase pipeline (2), a gas phase pipeline (8), an unloading liquid phase pipeline (10), a filling pipeline (100), a pump unloading pipeline (107), a storage tank gas phase pipeline (108), a pump pool (109), a submersible pump (110), a storage tank liquid phase pipeline (115), a tank truck liquid phase pipeline (114), and a control unit, wherein: The pressurized liquid phase pipeline (2) is connected to the pressurized liquid phase port of the tank truck via a metal hose and is used to pressurize the tank truck; the pressurized liquid phase pipeline (2) is equipped with a pressurization control valve (1) and a vaporizer (5); the gas phase pipeline (8) is connected to the gas connection of the tank truck via a metal hose and is used to balance the pressure between the tank truck and the storage tank; the gas phase pipeline (8) is equipped with a tank truck pressure sensor (6) and a gas phase control valve (3); a control valve (7) is installed between the gas phase pipeline (8) and the unloading liquid phase pipeline (10); the unloading liquid phase pipeline (10) is equipped with an unloading control valve (9). The outlet of the unloading liquid phase pipeline (10) is connected to the storage tank and the pump pool (109) respectively; the inlet of the pump pool (109) is connected to the storage tank gas phase pipeline (108), the storage tank liquid phase pipeline (115), and the tank truck liquid phase pipeline (114) respectively; the outlet of the pump pool (109) is connected to the filling pipeline (100) and the pump unloading pipeline (107) respectively; the submersible pump (110), the pump pool temperature sensor (101), and the pump pool level sensor (103) are installed in the pump pool (109); the pump pool (109) A post-pump pressure sensor (104) is installed at the outlet of the pump; a filling control valve (102) is installed on the filling pipeline (100); a pump unloading control valve (106) is installed on the pump unloading pipeline (107); a pre-pump pressure sensor (105) and a pump return gas control valve (113) are installed on the gas phase pipeline (108) of the storage tank; a first pump inlet control valve (112) is installed on the liquid phase pipeline (115) of the storage tank; a second pump inlet control valve (111) is installed on the liquid phase pipeline (114) of the tank truck; the control unit is connected to the booster control valve ( 1) The gas phase control valve (3), the tank truck pressure sensor (6), the control valve (7), the unloading control valve (9), the pump pool temperature sensor (101), the filling control valve (102), the pump pool liquid level sensor (103), the pump post-pressure sensor (104), the pump pre-pressure sensor (105), the pump unloading control valve (106), the submersible pump (110), the second pump inlet control valve (111), the first pump inlet control valve (112), and the pump return gas control valve (113) are electrically coupled.

2. The one-button pump unloading control system for LNG refueling stations according to claim 1, characterized in that: The control system employs a fuzzy adaptive PID control algorithm to adjust the rotational speed of the submersible pump (110) in real time; the fuzzy adaptive PID control algorithm specifically includes the following steps: S100. Collect the pump pool liquid level, pump pool temperature, and pump pool inlet pressure, and then calculate the cavitation safety index; the cavitation safety index is expressed by the following formula: in: , and Used to characterize the weighting system, the initial value is set to 1.0 and fine-tuned according to the on-site working conditions; L min Used to characterize the minimum liquid level allowed to prevent cavitation; P min Used to characterize the inlet pressure threshold allowed to prevent cavitation; T max Used to characterize the absolute value threshold of the highest temperature allowed to prevent cavitation; S200. Determine whether the cavitation safety index is greater than or equal to a manually preset safety threshold value, and perform the following operations based on the determination result: If the cavitation safety index is less than the safety value threshold, then the value of the PID proportional parameter increment is set to -100% and the pump speed is reduced. If the cavitation safety index is greater than or equal to the safety value threshold, then the increment of the PID proportional parameter, the increment of the PID integral parameter, and the increment of the PID derivative parameter are output through a fuzzy algorithm. S300. Construct a fuzzy rule base, using the error between the pump outlet pressure and the pressure setpoint, the error change rate, and the cavitation safety index as input variables, perform fuzzification processing, and execute fuzzy inference operations; S400. The increment of the actual PID parameters is obtained through defuzzification calculation; S500. The increments of the actual PID parameters are superimposed to obtain the current PID controller parameter values, expressed by the following formula: Where: K p0 Used to characterize the tuned basic PID proportional parameter; K i0 Used to characterize the tuned basic PID integral parameters; K d0 Used to characterize the tuned basic PID differential parameters; S600. Input the parameters calculated in step S500 into the PID controller. After processing by the PID controller, send the output command to the frequency converter to adjust the speed of the submersible pump (110).

3. The one-button pump unloading control system for LNG refueling stations according to claim 2, characterized in that: The safety threshold value is 3.

4. A method utilizing the one-button pump unloading control system for LNG refueling stations as described in any one of claims 1 to 3, characterized in that: Includes the following steps: Sa100. Connect the tanker to the pressurized liquid phase pipeline (2), the gas phase pipeline (8) and the unloading liquid phase pipeline (10) of the gas station; Open the corresponding valves on the tanker truck, and the operator clicks the one-click pump unloading button on the touch screen to start the system and enter the automatic unloading control process. Sa200. Control the tank pressure sensor to monitor the tank pressure in real time; when the tank pressure is greater than the manually preset pressure stabilization start threshold, the system automatically performs pressure stabilization; control the opening of the gas phase control valve (3) and the control valve (7) until the pressure difference between the tank truck and the tank is less than the manually preset pressure stabilization completion threshold to complete the pressure stabilization. After Sa300 pressure equalization is completed, the control system opens the unloading control valve (9) and the second pump inlet control valve (111); controls LNG to flow into the pump pool (109) through the unloading liquid phase pipeline (10) and the tank truck liquid phase pipeline (114) using the pressure difference; controls the pump pool temperature sensor (101) and the pump pool level sensor (103) to monitor the LNG level and pump pool temperature in the pump pool (109) in real time until the monitored values ​​meet the manually preset pump precooling completion judgment conditions; After the Sa400 pump is pre-cooled, the control system enters the pump unloading process; the pump unloading control valve (106) is opened, the submersible pump (110) is started and unloading is performed; during the unloading process, the pump pool level sensor (103) is controlled to monitor the LNG level in real time. When the LNG level is lower than the manually preset minimum level, the system automatically shuts down the submersible pump (110), and the operator confirms that the tanker level is zero, and the unloading is completed.

5. The method according to claim 4, characterized in that: The pressure stabilization start threshold in step Sa200 is 0.4 MPa; the pressure stabilization completion threshold is 0.1 MPa.

6. The method according to claim 5, characterized in that: The conditions for determining the completion of pump precooling in step Sa300 are: the LNG level is higher than 586 mm, the temperature inside the pump pool is lower than -110°C, and the temperature is maintained for at least 1 minute.

7. The method according to claim 6, characterized in that: The minimum liquid level in step Sa400 is 586 mm.

8. The method according to claim 7, characterized in that: In the pump unloading process of step Sa400, the fuzzy adaptive PID control algorithm is used to adjust the rotational speed of the submersible pump (110).

9. The method according to claim 8, characterized in that: The pressure setpoint satisfies the current pump inlet pressure plus the pipeline pressure difference that needs to be overcome to achieve efficient pump operation.

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