阅读说明：本技术 一种采用单潜液泵输配四台lng单枪加气机控制方法 (Control method for four LNG single-gun gas filling machines for transportation and distribution by adopting single immersed pump ) 是由 白利强 潘自登 于 2019-03-20 设计创作，主要内容包括：本发明公开一种采用单潜液泵输配四台LNG单枪加气机控制方法,可编程控制器分别与变频器、燃气控制器、电磁阀、仪表、急停按钮连接；可编程控制器通过通信控制器与加气机连接；变频器与潜液泵连接；在加气模式中,控制系统根据加气机操作状态,通过互锁及解除互锁,完成加气；在调压模式中,根据储罐压力状况,调整储罐阀门；在自增压卸车模式中,根据储罐压力及储罐调压限定值与储罐保压回差设定值的差的大小；在泵卸车模式中,根据卸车频率进行泵卸车。本发明采用预降压调整的方式来解决管道超压的问题,通过改变加气机的互锁方式实现了部分流量的卸载,通过泄压功能实现超压保护,有效保障单LNG潜液泵输配四台LNG单枪加气机安全。(The invention discloses a control method for four LNG single-gun gas filling machines by adopting single immersed pump transmission and distribution.A programmable controller is respectively connected with a frequency converter, a gas controller, an electromagnetic valve, an instrument and an emergency stop button; the programmable controller is connected with the gas dispenser through the communication controller; the frequency converter is connected with the immersed pump; in the gas filling mode, the control system completes gas filling through interlocking and unlocking according to the operation state of the gas filling machine; in the pressure regulating mode, a storage tank valve is regulated according to the pressure condition of the storage tank; in the self-pressurization unloading mode, according to the pressure of the storage tank and the difference between the pressure regulating limit value of the storage tank and the pressure maintaining return difference set value of the storage tank; in the pump unloading mode, pump unloading is performed according to the unloading frequency. The invention adopts a pre-decompression adjustment mode to solve the problem of overpressure of the pipeline, realizes the unloading of partial flow by changing the interlocking mode of the gas filling machine, realizes overpressure protection by a pressure relief function, and effectively ensures the safety of four LNG single-gun gas filling machines for single LNG immersed pump transportation and distribution.)

1. A control method for four LNG single-gun gas filling machines which are transported and distributed by adopting single immersed pumps is characterized by comprising a control system; the control system comprises a control cabinet and four LNG single-gun gas filling machines;

the control cabinet comprises a programmable controller and a frequency converter; the programmable controller is respectively connected with the frequency converter, the gas controller, the electromagnetic valve, the instrument and the emergency stop button and is connected with the human-computer interface through the Ethernet; the programmable controller is connected with the gas dispenser through the communication controller; the frequency converter is connected with the immersed pump;

the control method comprises a gas filling mode, a pressure regulating mode, a self-pressurization unloading mode and a pump unloading mode;

in the gas filling mode, the control system judges the operation state of the gas filling machine and completes gas filling through interlocking and unlocking;

in the pressure regulating mode, a storage tank valve is regulated according to the pressure condition of the storage tank;

in the self-pressurization unloading mode, a storage tank valve is adjusted according to the pressure of the storage tank and the difference between a storage tank pressure regulation limit value and a storage tank pressure maintaining return difference set value;

in the pump unloading mode, pump unloading is performed according to the unloading frequency.

2. The control method of the four LNG single-gun gas dispenser adopting the single immersed pump for transporting and dispensing according to claim 1, wherein the programmable controller is respectively connected with the frequency converter, the communication controller and the gas controller through RS485 buses; the communication controller is connected with the gas dispenser through a CAN bus.

3. The control method of the four LNG single-gun gas filling machines which are transported and distributed by the single immersed pump according to claim 1, wherein the gas filling mode comprises the following steps:

(1) if the pressure of the storage tank is less than the set storage tank pressure regulation limit value, carrying out gas filling and pressure regulation;

(2) if a certain LNG single-gun gas dispenser has gas filling operation, a liquid outlet valve of the storage tank is opened, the LNG single-gun gas dispenser is put into operation in the forward direction, and whether the gas dispenser which is filling gas exists is judged;

(3) if yes, directly entering a voltage-stabilizing speed-regulating process; if not, starting the pump, and then entering a pressure-stabilizing speed-regulating flow;

(4) when the gas filling of a certain LNG single-gun gas filling machine is finished, judging whether the LNG single-gun gas filling machine is in reverse operation or not;

(5) if the gas filling machine is in reverse operation, entering a frequency conversion speed reduction process, reducing the corresponding frequency according to the number of the currently operated gas filling machines, then sending an interlocking signal to the gas filling machine after gas filling is finished, and enabling the gas filling machine to enter a dormant state and enter a pressure stabilizing and speed regulating process;

(6) judging whether an overpressure phenomenon exists or not, and if so, performing overpressure relief;

(7) if the gas filling machine is not in reverse operation, the gas filling of all the gas filling machines is finished, the control system sends an interlocking releasing command to the gas filling machines, the gas filling machines all enter a standby state, the immersed pump stops working, the control system returns to the standby mode in a delayed mode, and the whole gas filling mode is finished.

4. The method for controlling the four LNG single-gun gas dispenser for transportation and distribution by using the single immersed pump as claimed in claim 1, wherein the pressure regulating mode comprises the following steps:

(1) judging whether the pressure of the storage tank is smaller than a set storage tank pressure regulating limit value or not;

(2) if the pressure is smaller than the preset pressure, the related valve is opened to regulate the pressure;

(3) if not less than or when stopping manually, closing the relevant valve; and returning to the standby mode.

5. The control method of the four LNG single-gun dispenser for transportation and distribution by using the single immersed pump as claimed in claim 1, wherein the self-pressurization unloading mode comprises the following steps:

(1) when the pressure of the storage tank is smaller than the difference between the pressure regulating limit value of the storage tank and the pressure maintaining return difference set value of the storage tank, opening a lower liquid inlet valve of the storage tank in a delayed mode, closing an upper liquid inlet valve of the storage tank, and entering a pressure maintaining state;

(2) when the pressure of the storage tank is greater than the difference between the pressure regulating limit value of the storage tank and the pressure maintaining return difference set value of the storage tank, the original states of the lower liquid inlet valve and the upper liquid inlet valve are restored in a delayed mode.

6. The method for controlling the four LNG single-gun refueling machine for transportation and distribution by using the single immersed pump as claimed in claim 1, wherein the pump unloading mode comprises the following steps:

(1) carrying out pump unloading operation according to the unloading frequency;

(2) judging whether gas filling operation exists or not;

(3) if the gas filling operation exists, closing the unloading valve and opening the gas filling valve to perform the gas filling operation; and automatically returning to the unloading mode after the air charging is finished.

Technical Field

The invention belongs to the technical field of natural gas filling, and particularly relates to a control method of four LNG single-gun gas filling machines which are transported and distributed by adopting single immersed pumps.

Background

At present, an automatic control system (hereinafter referred to as a control system) of an LNG filling station on the market is generally used in cooperation with a single LNG immersed pump for transporting and distributing 2 LNG single-gun gas filling machines (single gun) (hereinafter referred to as a one-pump two-machine). The power of the LNG immersed pump is usually 11 or 15KW, and the outlet flow is 320L/min. One pump is suitable for 2 single guns of supporting LNG and adds mechanism of qi.

When the control system is in actual operation, 2 LNG single-gun gas filling machines can be combined randomly to be put into or quit operation, and the control system can automatically carry out frequency conversion speed regulation on the immersed pump according to the outlet pressure of the immersed pump, so that constant-pressure gas filling is realized.

The situation of mutual interlocking exists in the actual operation of the dispenser, the interlocking is usually realized by directly communicating the two LNG single-gun dispensers or directly connecting the two LNG single-gun dispensers with hard contacts, when one LNG single-gun dispenser operates and the other LNG single-gun dispenser does not operate, all pneumatic valves of the machine can be closed by the inoperative dispenser, and the dispenser which normally works under the influence of liquid bias flow is prevented. The interlocking is essentially a call-only, so the speed is relatively fast.

Just because it has the function of interlocking to add the mechanism of qi, especially when 2 single guns of LNG add the mechanism of qi simultaneous working, one of them end get into the interlocking state at once after the air entrainment, originally supply that 2 single guns of LNG add the flow of mechanism of qi all concentrate on this single gun of LNG of operation adds the mechanism of qi on, the pressure of this pipeline will increase in the twinkling of an eye like this. At this time, the control system detects that the outlet pressure of the pump exceeds the actual set value, and controls the variable frequency speed regulation to reduce the pressure. Thereby guaranteeing the stable work of the gas dispenser.

For the small-flow one-pump two-machine equipment, the control system can achieve the control purpose.

With the development of the industry, the equipment with one pump and two pumps can not meet the requirement of gas filling amount of users. If the gas adding amount needs to be increased in a traditional mode, a set of equipment needs to be added, so that not only is the cost increased, but also the site of a user needs to be re-planned, and various problems are also caused, and the investment cost is far more than the cost of the equipment. In the case of the situation, equipment for 'single LNG immersed pump transporting and distributing four LNG single-gun gas filling machines (single gun)' (hereinafter, referred to as one pump and four machines) appears, and the problems are well solved.

However, for a one-pump-four-machine device, the above control system cannot meet the requirements. In order to meet the flow of the four LNG single-gun gas filling machines, the power of an immersed pump of the system needs to be increased, generally more than 25KW, and the flow is 660L/min. Because the increase of the export flow of pump, add the mechanism of qi and become four, if add the mechanism of qi still like the direct interlocking of traditional interlocking mode, add the mechanism of qi and move simultaneously when four LNG list guns, have 3 gas fillings to finish to get into the interlocking back suddenly, on this moment all flows are concentrated a LNG list gun of operation adds the mechanism of qi. The pipeline is seriously superpressurized, and the gas dispenser directly jumps the gun, and the safety valve of the pipeline can be started and jumped, so that the condition is dangerous, and even has potential safety hazards. In view of the above analysis of the one-pump two-machine control system, it can be seen that the adjustment of the one-pump two-machine control system requires a process of first raising the pressure and then lowering the pressure with variable frequency, and the time duration of the process is influenced by many factors, such as: the response speed of the pressure transmitter, the length of a pipeline, the time of variable frequency speed regulation and the like. If the system is used for controlling the equipment with one pump and four machines, the response speed is insufficient, the safety valve can work before the system speed regulation is finished, and the gas filling machine stops working due to overpressure.

Disclosure of Invention

The invention provides a control method for four LNG single-gun gas filling machines by adopting single immersed pumps for transportation and distribution, which aims to solve the problem of pipeline overpressure by adopting a pre-decompression adjustment mode, realizes partial flow unloading by changing an interlocking mode of the gas filling machines, realizes overpressure protection by a pressure relief function and can effectively ensure the safety of the four LNG single-gun gas filling machines by adopting single LNG immersed pumps for transportation and distribution.

In order to solve the technical problems, the invention adopts the technical scheme that: a control method for four LNG single-gun gas dispensers by adopting single immersed pumps for transportation and distribution comprises a control system; the control system comprises a control cabinet and four LNG single-gun gas filling machines;

the control cabinet comprises a programmable controller and a frequency converter; the programmable controller is respectively connected with the frequency converter, the gas controller, the electromagnetic valve, the instrument and the emergency stop button and is connected with the human-computer interface through the Ethernet; the programmable controller is connected with the gas dispenser through the communication controller; the frequency converter is connected with the immersed pump;

the control method comprises a gas filling mode, a pressure regulating mode, a self-pressurization unloading mode and a pump unloading mode;

in the gas filling mode, the control system judges the operation state of the gas filling machine and completes gas filling through interlocking and unlocking;

in the pressure regulating mode, a storage tank valve is regulated according to the pressure condition of the storage tank;

in the self-pressurization unloading mode, a storage tank valve is adjusted according to the pressure of the storage tank and the difference between a storage tank pressure regulation limit value and a storage tank pressure maintaining return difference set value;

in the pump unloading mode, pump unloading is performed according to the unloading frequency.

Preferably, the programmable controller is respectively connected with the frequency converter, the communication controller and the gas controller through RS485 buses; the communication controller is connected with the gas dispenser through a CAN bus.

Preferably, the gas filling mode comprises the following steps:

(1) if the pressure of the storage tank is less than the set storage tank pressure regulation limit value, carrying out gas filling and pressure regulation;

(2) if a certain LNG single-gun gas dispenser has gas filling operation, a liquid outlet valve of the storage tank is opened, the LNG single-gun gas dispenser is put into operation in the forward direction, and whether the gas dispenser which is filling gas exists is judged;

(3) if yes, directly entering a voltage-stabilizing speed-regulating process; if not, starting the pump, and then entering a pressure-stabilizing speed-regulating flow;

(4) when the gas filling of a certain LNG single-gun gas filling machine is finished, judging whether the LNG single-gun gas filling machine is in reverse operation or not;

(5) if the gas filling machine is in reverse operation, entering a frequency conversion speed reduction process, reducing the corresponding frequency according to the number of the currently operated gas filling machines, then sending an interlocking signal to the gas filling machine after gas filling is finished, and enabling the gas filling machine to enter a dormant state and enter a pressure stabilizing and speed regulating process;

(6) judging whether an overpressure phenomenon exists or not, and if so, performing overpressure relief;

(7) if the gas filling machine is not in reverse operation, the gas filling of all the gas filling machines is finished, the control system sends an interlocking releasing command to the gas filling machines, the gas filling machines all enter a standby state, the immersed pump stops working, the control system returns to the standby mode in a delayed mode, and the whole gas filling mode is finished.

Preferably, the voltage regulation mode includes the following steps:

(1) judging whether the pressure of the storage tank is smaller than a set storage tank pressure regulating limit value or not;

(2) if the pressure is smaller than the preset pressure, the related valve is opened to regulate the pressure;

(3) if not less than or when stopping manually, closing the relevant valve; and returning to the standby mode.

Preferably, the self-pressurization unloading mode comprises the following steps:

(1) when the pressure of the storage tank is smaller than the difference between the pressure regulating limit value of the storage tank and the pressure maintaining return difference set value of the storage tank, opening a lower liquid inlet valve of the storage tank in a delayed mode, closing an upper liquid inlet valve of the storage tank, and entering a pressure maintaining state;

(2) when the pressure of the storage tank is greater than the difference between the pressure regulating limit value of the storage tank and the pressure maintaining return difference set value of the storage tank, the original states of the lower liquid inlet valve and the upper liquid inlet valve are restored in a delayed mode.

Preferably, the pump unloading mode comprises the steps of:

(1) carrying out pump unloading operation according to the unloading frequency;

(2) judging whether gas filling operation exists or not;

(3) if the gas filling operation exists, closing the unloading valve and opening the gas filling valve to perform the gas filling operation; and automatically returning to the unloading mode after the air charging is finished.

Compared with the prior art, the invention has the beneficial effects that: the problem of overpressure of the pipeline is solved by adopting a pre-depressurization adjustment mode, partial flow unloading is realized by changing an interlocking mode of the gas filling machine, overpressure protection is realized by a pressure relief function, and the safety of four LNG single-gun gas filling machines for single LNG immersed pump transportation and distribution can be effectively guaranteed.

Drawings

FIG. 1 is a schematic diagram of a control system of the present invention;

FIG. 2 is a schematic diagram of a control method according to the present invention;

FIG. 3 is a schematic view of the aeration mode of the present invention;

FIG. 4 is a schematic diagram of frequency conversion and speed reduction according to the present invention;

FIG. 5 is a schematic diagram of voltage stabilization and speed regulation according to the present invention;

FIG. 6 is a schematic diagram of the voltage regulation mode of the present invention;

fig. 7 is a schematic view of the unloading mode of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The embodiment of the invention discloses a control method for four LNG single-gun gas filling machines by adopting single immersed pumps for transportation and distribution, which comprises a control system as shown in the figure; the control system comprises a control cabinet and four LNG single-gun gas filling machines;

the control cabinet comprises a programmable controller and a frequency converter; the programmable controller is respectively connected with the frequency converter, the gas controller, the electromagnetic valve, the instrument and the emergency stop button and is connected with the human-computer interface through the Ethernet; the programmable controller is connected with the gas dispenser through the communication controller; the frequency converter is connected with the immersed pump;

the programmable controller is respectively connected with the frequency converter, the communication controller and the gas controller through RS485 buses; the communication controller is connected with the gas dispenser through a CAN bus.

Add mechanism of qi and current truth table contrast as follows in this application:

the control method comprises a gas filling mode, a pressure regulating mode, a self-pressurization unloading mode and a pump unloading mode.

The standby mode is an initial preparation state of the control system and is ready for other modes; in the mode, the gas dispenser is in a standby mode, and an upper liquid inlet valve, a pump gas return valve, a liquid outlet valve 1 and a liquid outlet valve 2 are opened by default; the immersed pump is in a stopped state.

The gas filling mode comprises the following steps:

(1) if the pressure of the storage tank is less than the set storage tank pressure regulation limit value, carrying out gas filling and pressure regulation;

(2) if a certain LNG single-gun gas dispenser has gas filling operation, a liquid outlet valve of the storage tank is opened, the LNG single-gun gas dispenser is put into operation in the forward direction, and whether the gas dispenser which is filling gas exists is judged;

(3) if yes, directly entering a voltage-stabilizing speed-regulating process; if not, starting the pump, and then entering a pressure-stabilizing speed-regulating flow;

(4) when the gas filling of a certain LNG single-gun gas filling machine is finished, judging whether the LNG single-gun gas filling machine is in reverse operation or not;

(5) if the gas filling machine is in reverse operation, entering a frequency conversion speed reduction process, reducing corresponding frequency according to the number of the currently operated gas filling machines, then sending an interlocking signal to the gas filling machine after gas filling is finished, enabling the gas filling machine to enter a dormant state, and entering a pressure stabilizing speed regulating process;

(6) judging whether an overpressure phenomenon exists or not, and if so, performing overpressure relief;

(7) if the gas filling machine is not in reverse operation, the gas filling of all the gas filling machines is finished, the control system sends an interlocking releasing command to the gas filling machines, the gas filling machines all enter a standby state, the immersed pump stops working, the control system returns to the standby mode after 5 minutes of delay, and the whole gas filling mode is finished.

The problem of overpressure of the pipeline is solved by adopting a pre-decompression adjustment mode;

the switching sequence of the gas dispenser is divided into 2 types: forward commissioning and reverse commissioning;

and (3) forward commissioning: all gas dispensers are continuously put into operation, and no LNG single-gun gas dispenser finishes gas filling in the process; if the system is put into operation in the forward direction, the system directly enters a pressure-stabilizing speed-regulating process, and the rotating speed of the immersed pump is automatically regulated according to a preset variable-frequency constant-pressure value; the specific adjusting process is as follows: when the outlet pressure of the submersible pump is smaller than the difference between the variable-frequency constant-pressure value and the variable-frequency dead zone value, the frequency converter operates in an accelerated manner; when the outlet pressure of the pump is greater than the sum of the variable-frequency constant-voltage value and the variable-frequency dead zone value, the frequency converter performs deceleration operation; when the outlet pressure of the submersible pump is in the interval of the frequency conversion constant pressure value plus or minus the frequency conversion dead zone value, the frequency converter operates at the current rotating speed; the following parameters are also relevant for the speed regulation: the upper limit frequency and the lower limit frequency of the variable frequency are the upper limit and the lower limit of the variable frequency speed regulation, the set value of the upper limit frequency is not more than the rated frequency of the immersed pump, and the lower limit is generally set to be 0; the frequency conversion pulse value and the frequency conversion step value can adjust the speed of frequency conversion adjustment, the frequency adjustment speed is faster when the step length is larger, but the speed is fast and the stability is poor, and the speed is generally set to be 5; the pulse value is typically set to 1, with the larger the pulse the slower the speed of adjustment.

And (3) reverse delivery: the running gas dispenser continuously finishes gas dispensing, and no gas dispenser to be started is available in the process (for example, four LNG single-gun gas dispensers stop suddenly for 1, 2 or 3, 3 LNG single-gun gas dispensers stop suddenly for 1 or 2, and 2 LNG single-gun gas dispensers stop suddenly for 1);

the pre-depressurization adjustment scheme mainly aims at the operation mode of 'reverse operation of a gas dispenser', because the 'forward operation of the gas dispenser' has no overpressure problem; the following is the basic principle of implementation of the pre-buck regulation scheme:

firstly, reading the running state of the gas dispenser; when the state of the gas dispenser is changed from gas filling to standby and at least one other gas dispenser is in an operating state, the gas dispenser is considered to be 'reversely put into operation'; if the system is confirmed to be 'reverse operation', the control system firstly reduces the outlet pressure by reducing the operating frequency of the immersed pump, and if 3 units are in operation, the system reduces the frequency by 5 HZ; if 2 stations are in operation, the frequency of the system is reduced by 10 HZ; if 1 station is in operation, the frequency of the system is reduced by 15 HZ; when the frequency is reduced to a preset value (which can be set by an upper computer system), an interlocking command is sent to the gas dispenser which is just stopped, and the gas dispenser which finishes gas dispensing enters a dormant state after receiving the interlocking signal.

After receiving the interlocking command, the gas dispenser closes all pneumatic valves of the machine and then returns to the dormant state; after detecting the dormant state, the control system proves that the interlocking is finished; then the control system automatically adjusts the pressure to a preset pressure according to the outlet pressure of the submerged pump to carry out gas filling; and when the state of the gas dispenser is in a standby state, the control system stops the operation of the immersed pump and then returns to the standby mode according to the return standby time set by the upper computer.

The unloading of partial flow is realized by changing the interlocking mode of the gas dispenser;

2 pneumatic valve shut-off valves are arranged in the gas dispenser, one is a gas filling valve (F1), and the other is a gas return valve (F2), when the gas dispenser is in a gas filling state, F1 is opened, and F2 is closed, so that LNG can only be filled to the outside and cannot return to the storage tank; when the dispenser is in a standby state, F1 is closed, and F2 is opened, so that LNG can return to the storage tank through the return air flow of the dispenser; when the dispenser is in a dormant state, F1 is closed, F2 is closed, and no flow of LNG can remain in the pipeline.

In order to avoid the high pressure problem, the control system needs to be interlocked with the association realized by the gas dispenser, and the specific realization method is that when the gas dispenser finishes gas filling, the control system does not immediately enter a dormant state, but waits for an interlocking command of the control system; the dispenser is kept in a standby state before the interlocking command of the control system comes, so that the LNG can return to the storage tank through the air return valve of the dispenser, partial flow unloading is realized, and the rapid rise of pressure is avoided; meanwhile, the control system performs pressure reduction pretreatment on the immersed pump, and informs the gas dispenser to interlock after the control system finishes pressure reduction, and then the gas dispenser enters a dormant state; four LNG single-gun gas filling machines in the system are mutually interlocked, namely, if only one gas filling machine is used, the other three gas filling machines enter a dormant state to be interlocked if the other three gas filling machines are not in a gas filling state.

Then the system enters a voltage-stabilizing speed-regulating process; when all the gas filling machines fill gas, the system sends a command of releasing the interlocking to the gas filling machines, the gas filling machines all enter a standby state, the immersed pump stops working, the system returns to the standby mode after delaying for 5 minutes, and the whole gas filling mode is finished.

Overpressure protection is realized through a pressure relief function;

the function is mainly to prevent the occurrence of accidents, so the function can not work under the condition that the pressure pre-adjusting function works normally;

the working principle of the pressure relief function is as follows: the control system judges whether the pressure at the outlet of the immersed pump is greater than a preset overpressure relief value in real time, and if so, an overpressure relief valve is opened; after the overpressure relief valve is opened, delaying, and closing the overpressure relief valve after the delay time is reached; in the whole bleeding process, if the pressure at the outlet of the immersed pump is smaller than the preset value of overpressure bleeding, the overpressure bleeding valve is also closed; therefore, the closing of the overpressure relief valve has 2 conditions, one is that the relief time is reached and one is that the pressure is less than the set value, and the two conditions can close the valve as long as one meets the condition, and the series operation mode is adopted.

The control system is specially provided with a frequency mode selection function for adapting to each working condition; because the pressure fluctuation of the outlet of the submersible pump is large under some working conditions, the variable-frequency speed regulation is not suitable, and a fixed-frequency mode is set; the gas filling frequency in the fixed frequency mode can be determined by the gas filling frequency of a pump in the parameters, and the precooling frequency can be determined by the precooling frequency of the pump in the parameters; the specific mode selection may be set in a parameter setting.

The voltage regulation mode comprises the following steps:

(1) judging whether the pressure of the storage tank is smaller than a set storage tank pressure regulating limit value or not;

(2) if the pressure is smaller than the preset pressure, the related valve is opened to regulate the pressure;

(3) if not less than or when stopping manually, closing the relevant valve; and returning to the standby mode.

The voltage regulation mode includes 3 cases: pressure regulating in a pressure regulating mode, air charging pressure regulating and self-pressurization unloading pressure regulating;

when a storage tank pressurization button is clicked, the system automatically opens the lower liquid inlet valve and the pressure regulating valve to enter a pressurization mode, and when the pressure of the storage tank is greater than the pressure regulating limit value of the storage tank, the system automatically restores the states of the upper liquid inlet valve and the lower liquid inlet valve and closes the pressure regulating valve so as to finish pressure regulation in the pressure regulating mode, or manually clicks a pressurization stopping button to finish pressure regulation at any time;

the air-entrapping pressure regulation is that the system automatically opens a lower liquid inlet valve and a pressure regulating valve and closes an upper liquid inlet valve to regulate pressure after the pressure of the storage tank is less than the pressure regulating limit value of the storage tank in an air-entrapping mode; when the pressure of the storage tank is greater than the pressure regulation limit value of the storage tank, the system automatically restores the states of the upper liquid inlet valve and the lower liquid inlet valve, and then the pressure regulating valve is closed after 20 seconds of delay, so that the gas filling pressure regulation mode is finished; the pressure regulation is to maintain the pressure of the storage tank under the condition of large gas filling amount;

the self-pressurization unloading pressure regulation is used when the pressure of a storage tank is difficult to maintain normal gas filling under the self-pressurization unloading condition; because the lower the storage tank pressure is, the better the storage tank pressure is, and the storage tank pressure can be continuously reduced in the unloading process, the outlet pressure of the submerged pump can hardly reach the required value if gas is added again, and pressure regulation is needed; but the normal unloading can be influenced by the constant pressure regulation, and the flow is specially added in order to not influence the unloading but also meet the requirement of gas filling; under the condition of self-pressurization unloading, if the pressure of the storage tank is smaller than the difference between the pressure regulation limit value setting of the storage tank and the pressure maintaining return difference setting value of the storage tank, delaying for 10 seconds, opening a lower liquid inlet valve, closing an upper liquid inlet valve, and entering a pressure maintaining state; if the pressure of the storage tank is greater than the sum of the pressure regulation limit value of the storage tank and the pressure maintaining return difference set value of the storage tank, delaying for 10 seconds, recovering the original states of the lower liquid inlet valve and the upper liquid inlet valve, and finishing pressure maintaining.

The self-pressurization unloading mode comprises the following steps:

(1) when the pressure of the storage tank is smaller than the difference between the pressure regulating limit value of the storage tank and the pressure maintaining return difference set value of the storage tank, opening a lower liquid inlet valve of the storage tank in a delayed mode, closing an upper liquid inlet valve of the storage tank, and entering a pressure maintaining state;

(2) when the pressure of the storage tank is greater than the difference between the pressure regulating limit value of the storage tank and the pressure maintaining return difference set value of the storage tank, the original states of the lower liquid inlet valve and the upper liquid inlet valve are restored in a delayed mode.

The pump unloading mode comprises the following steps:

(1) carrying out pump unloading operation according to the unloading frequency;

(2) judging whether gas filling operation exists or not;

(3) if the gas filling operation exists, closing the unloading valve and opening the gas filling valve to perform the gas filling operation; and automatically returning to the unloading mode after the air charging is finished.

The unloading comprises 2 conditions of pump unloading and self-pressurization unloading;

the pump unloading is carried out by an immersed pump

If the upper liquid inlet valve or the lower liquid inlet valve is closed in the unloading process of the pump, the pump automatically stops running; under the pump unloading mode, if the gas filling operation is carried out, the gas filling flow is immediately started, the gas filling flow automatically returns to the unloading flow after the gas filling is finished, and the liquid outlet 1 and the liquid outlet 2 of the storage tank are not opened in the process, so that the LNG in the tank wagon is directly filled instead of the LNG in the used storage tank; when the unloading mode is exited, firstly clicking a pump stopping button and then clicking an exiting button;

if the air charging amount is extremely large or in order to prolong the service life of the immersed pump, the vehicle can be unloaded by adopting a self-pressurization unloading mode; the self-pressurization unloading is that LNG in a tank car is injected into a storage tank through pressure after the tank car is pressurized to be higher than the pressure of the storage tank; the self-pressurization unloading can be realized only by selecting the self-pressurization unloading at an allowable position, then opening any one of the upper and lower liquid inlet valves of the storage tank and opening the related manual valve;

the upper and lower liquid inlet valves of the storage tank can be automatically switched according to the liquid level of the storage tank whether the pump is used for unloading or the self-pressurization unloading; if the volume of the storage tank is smaller than the set value of the switching volume of the upper and lower liquid inlet valves, opening the upper inlet valve and closing the lower inlet valve; if the volume of the storage tank is larger than the set value of the switching volume of the upper and lower liquid inlet valves, opening the lower liquid inlet valve and closing the upper liquid inlet valve; when the switching of the upper liquid inlet and the lower liquid inlet is enabled, the upper liquid inlet and the lower liquid inlet are not automatically switched after the prohibition is selected.

The alarm plays roles of danger warning and system cut-off in the whole system;

when the emergency stop button of the field equipment, the emergency stop button on the control cabinet and the combustible gas alarm have high-limit alarm, the system enters an emergency cut-off state, and the audible and visual alarm gives an alarm; in the emergency cut-off state, all equipment valves are closed, and the pump stops running;

the alarm of the pressure and the liquid level of the storage tank is respectively provided with 4 levels of alarm, namely high-high limit alarm, low-low limit alarm and low-low limit alarm; the system defaults that the pressure of the storage tank is higher than 1MPa and lower than 1.2MPa, and the pressure is high and alarms when the pressure is higher than 1.2 MPa; when the pressure of the storage tank is lower than 0.3MPa and higher than 0.1MPa, the alarm is sent to the low pressure alarm, and when the pressure of the storage tank is lower than 0.1MPa, the alarm is sent to the low pressure alarm; when the liquid level of the storage tank is higher than 52M3 and lower than 54M3, entering a liquid level high alarm, and when the liquid level of the storage tank is higher than 54M3, entering a liquid level high alarm; when the liquid level of the storage tank is lower than 3M3 and higher than 1.5M3, entering a liquid level low alarm, and when the liquid level is lower than 1.5M3, entering a liquid level low alarm; when the liquid level of the storage tank is low, the system automatically closes the liquid outlet 1, the liquid outlet 2 valve and the immersed pump of the storage tank; when the liquid level of the storage tank is high, the system automatically closes the upper and lower liquid inlet valves of the storage tank; when the pressure of the storage tank is high, the alarm will be given out if a storage tank bleeding valve is arranged;

in order to protect the immersed pump, the system is provided with a pressure difference low alarm and related cut-off operation of the immersed pump; after the immersed pump enters into operation, delaying for 30 seconds, firstly judging whether the actual current of the immersed pump is smaller than the idling current of the pump, and if so, directly stopping the operation of the immersed pump; then judging whether the difference between the outlet pressure and the inlet pressure of the pump pool (hereinafter referred to as pump pool pressure difference) is smaller than a pump pressure difference low alarm set value or not, if so, entering pressure difference low alarm, delaying for 30 seconds after the pressure difference low alarm (the time is determined by pump pressure difference low delay pump stop parameters), continuously judging whether the pump pool pressure difference is smaller than the pump pressure difference low alarm set value or not, and if so, stopping the operation of the pump; in addition, when the pump outlet pressure is higher than the pump outlet pressure and the shutdown parameter set value, the pump also enters a stopped state; all of the above limits can be set in the LNG parameter interface;

the alarm inquiry interface in the system can check related alarm information, and the related alarm information is displayed when an alarm exists and is not displayed when no alarm exists; the specifically displayed alarm information includes: scram of an immersed pump, scram of unloading, scram of a control cabinet, low and low liquid level alarm of a storage tank, low and high liquid level alarm of the storage tank, high pressure alarm of the storage tank, scram of a touch screen, idle pump stop alarm of a pump, low pump pressure difference, high pump outlet pressure, linkage alarm of gas leakage and scram of the pump (the scram signal is triggered by a pump scram button in an upper computer interface); when the pump emergency stop button is pressed, the pump cannot be started, and the emergency stop state of the pump in the system state is changed into green display.

Add the communication controller module between mechanism of qi and the switch board, this module is the bridge module between switch board and the mechanism of qi that adds, not only has the data acquisition function, and data processing calculates in addition to and receive the signal of switch board, control and add functions such as mechanism of qi. The communication management module is added, so that unified scheduling management of the gas dispenser is realized, and convenience is brought to the expansion function of the system in the future. Add between the mechanism of qi and add the communication connection of mechanism of qi and communication controller, adopted CAN bus communication, not only increased the stability of communication, also practiced thrift and added between the mechanism of qi, add the communication cable between mechanism of qi and the switch board. RS485 communication is adopted for communication between the PLC and the communication controller, so that standard interfaces of most PLCs are met, and convenient connection of communication is realized. Just because realized the switch board and added the two-way communication between the mechanism of qi, just can realize that four LNG list guns add the complicated interlocking function of mechanism of qi in the four quick-witted systems of a pump.

The RS485 communication mode is adopted for communication between the control system and the gas dispenser; therefore, the control system can not only read various states of the gas dispenser and the real-time flow and pressure of the gas dispenser, but also send a control command to the gas dispenser to control the gas dispenser; the control of the gas dispenser is particularly important, and the control system realizes the interlocking by sending a valve closing command to the gas dispenser and is a basic premise for realizing the interlocking.

The air charging mode and the pump unloading mode cannot run simultaneously, the air charging mode is preferred, the control system can automatically switch, but the pressure regulating mode and the self-pressurization unloading mode can run simultaneously and do not have the sequence. The pump unloading mode, the self-pressurization unloading mode and the pressure regulating mode can not be operated simultaneously, and only one of the processes can be operated simultaneously, the unloading is preferential, but the pressure maintaining process can be entered during the unloading.

In the standby mode, the user can enter the following steps by clicking the related button: the system comprises a gas filling mode, a pressure regulating mode, a pump unloading mode and a self-pressurization unloading mode. But the gas filling mode is more special and can be automatically entered through an operation button of a gas filling machine panel. And under the gas filling mode, if the pressure of the storage tank is low, the gas filling pressure regulating mode is automatically started, and the gas filling pressure regulating mode is automatically ended when the pressure of the storage tank reaches a preset value.

And when the gas filling is finished, the gas filling mode is automatically returned to the pump unloading mode. In this mode, the voltage regulation mode is automatically closed, and the voltage cannot be regulated.

The self-pressurization unloading mode can automatically close the pressure regulating mode, and cannot regulate pressure, but if the pressure of the storage tank is low, the relevant valves of the storage tank can be opened to enter a pressure maintaining process.

The present invention has been described in detail with reference to the embodiments, but the description is only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The scope of the invention is defined by the claims. The technical solutions of the present invention or those skilled in the art, based on the teaching of the technical solutions of the present invention, should be considered to be within the scope of the present invention, and all equivalent changes and modifications made within the scope of the present invention or equivalent technical solutions designed to achieve the above technical effects are also within the scope of the present invention. It should be noted that for the sake of clarity, parts of the description of the invention have been omitted where there is no direct explicit connection with the scope of protection of the invention, but where components and processes are known to those skilled in the art.