CN114321719A - Automatic distribution and transmission method and automatic distribution and transmission system for natural gas pipeline - Google Patents
Automatic distribution and transmission method and automatic distribution and transmission system for natural gas pipeline Download PDFInfo
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Abstract
The invention provides an automatic distribution and transmission method and an automatic distribution and transmission system for a natural gas pipeline. The method comprises the following steps: dividing gas transmission into N adjusting stages, and arranging N adjusting valves; when the station sub-transmission is started, each adjusting stage is sequentially adjusted by using a mathematical model, so that each adjusting stage sequentially reaches the set sub-transmission pressure and the steady-state error is within 1%, and then the next adjusting stage is switched in until the Nth adjusting stage is started. The system uses the method and comprises at least two Ethernet switches, at least one engineer workstation, at least one operator workstation, a programmable logic controller, N regulating valves, N sets of process pipelines matched with the regulating valves and N pressure transmitters matched with the regulating valves. The beneficial effects of the invention can include: the control system crosstalk caused by fluctuating flow can be avoided when the multi-branch regulating valve is simultaneously regulated on line.
Description
Technical Field
The invention relates to the field of natural gas distribution and transmission, in particular to an automatic distribution and transmission system and method for a natural gas pipeline.
Background
The medium petroleum gas transmission pipeline has the mileage of 8 kilometers, four gas transmission channels at the northeast, the northwest, the southwest and the sea are strategically arranged, the gas transmission supply guarantee capacity is obviously improved, and a nationwide gas transmission pipe network with diversified resources, flexible dispatching and high-efficiency operation is preliminarily formed. This puts higher demands on the automation control level of the gas pipeline and the safety and reliability of the pipeline operation.
At present, companies in the area to which each large energy channel belongs are in enterprise scope, and are greatly popularized and implemented with regional management modes; the dispatching and monitoring modes of the governed primary air-conditioning pipeline adopt three-level regulation and control modes of a center, a station and a site; the automatic control level is used for landing according to the remote control, unmanned operation and manned level.
The change of management modes enables production operation management to depend on the SCADA system more and more, control of station yards and valve chamber equipment is performed more and more automatically by means of logic, and human intervention is less and less.
In the process of regulating and controlling the long-distance natural gas pipeline, the sub-delivery pressure and flow control of a control system are important links in the automatic control process of a station yard. After receiving the daily specified quantity set value of the regulation center, the station control system issues a station basic process control system for realizing automatic distribution control of downstream users.
In order to meet the functional requirements, the station control system needs to have the characteristics of automatic start/stop/switch of split transmission, small control model robustness and output overshoot and the like.
At present, the automatic natural gas pipeline distribution system has the following main problems:
firstly, when a plurality of branches participate in adjustment together, the opening of the adjusting valve is in a small opening for a long time, so that the control model has poor robustness and large output overshoot;
secondly, the multi-branch regulating valve is simultaneously regulated on line, the fluctuating flow can cause crosstalk of a control system, the control variable is not converged, and the regulating valve fluctuates continuously in a small amplitude.
In the automatic distribution and transmission process of a natural gas station, the regulating valve is subjected to floating regulation for a long time at a small flow rate, so that the failure probability of equipment is increased, the reliability of the equipment is reduced, and the risk of fire explosion caused by potential medium leakage and ignition source is reduced.
Chinese patent application publication No. CN109869634A describes an automatic natural gas pipeline distribution implementation system, which includes: at least two industrial Ethernet switches; at least one engineer workstation, which is provided with a first network card and a second network card for accessing two industrial Ethernet switches; at least one operator workstation, which is provided with a third network card and a fourth network card for accessing the two industrial Ethernet switches; the system comprises at least one set of industrial control programmable logic controller, at least one set of industrial control programmable logic controller and at least one set of industrial control programmable logic controller, wherein the at least one set of industrial control programmable logic controller is provided with a first communication card and a second communication card which are accessed into two industrial Ethernet switches; at least one set of regulating valves which are accessed to an industrial control programmable logic controller; the regulating valve is matched with a process pipeline which is matched with the regulating valve; and the at least one pressure transmitter is connected to the industrial control programmable logic controller. The invention discloses a method for realizing automatic distribution and transmission of a natural gas pipeline. The automatic gas pipeline branch transmission control system can realize the automatic stable operation of the natural gas pipeline branch transmission, reduces misoperation caused by manual intervention, but cannot solve the problems that when a plurality of branches participate in adjustment together, the opening of the adjusting valve is in a small opening for a long time, the robustness of the control model is poor, the output overshoot is large, the fluctuating flow can cause control system crosstalk, the control variable is not converged, the adjusting valve is in small-amplitude continuous fluctuation and the like.
Disclosure of Invention
The present invention aims to address at least one of the above-mentioned deficiencies of the prior art. For example, the flow rate that fluctuates when the multi-branch regulating valve simultaneously regulates on-line causes a problem of crosstalk of the control system. For another example, if the regulating valve is subjected to float regulation at a small flow rate for a long time, the probability of equipment failure is increased, and the reliability of the equipment is reduced.
Prior application, prior application CN201910081278.9 of the present inventor discloses an automatic distribution implementation system for natural gas pipelines, comprising: at least two industrial Ethernet switches; at least one engineer workstation, which is provided with a first network card and a second network card for accessing two industrial Ethernet switches; at least one operator workstation, which is provided with a third network card and a fourth network card for accessing the two industrial Ethernet switches; the system comprises at least one set of industrial control programmable logic controller, at least one set of industrial control programmable logic controller and at least one set of industrial control programmable logic controller, wherein the at least one set of industrial control programmable logic controller is provided with a first communication card and a second communication card which are accessed into two industrial Ethernet switches; at least one set of regulating valves which are accessed to an industrial control programmable logic controller; the regulating valve is matched with a process pipeline which is matched with the regulating valve; and the at least one pressure transmitter is connected to the industrial control programmable logic controller. The invention discloses a method for realizing automatic distribution and transmission of a natural gas pipeline. The invention has the beneficial effects that: the automatic stable operation of the natural gas pipeline can be realized, and the misoperation caused by manual intervention is reduced.
In order to achieve the above object, an aspect of the present invention provides an automatic distribution method for a natural gas pipeline. The method comprises the following steps: dividing gas transmission into N adjusting stages according to the designed output, wherein N is a natural number and is more than or equal to 2, the sub-transmission pressure of each adjusting stage is P1, … … and PN which are sequentially increased, and meanwhile, setting N paths of adjusting valves and matched process pipelines thereof according to the number of the adjusting stages and the sub-transmission pressure of each adjusting stage, and establishing a mathematical model; training the mathematical model to obtain a control variable which can enable the steady-state error of the controlled variable to be less than or equal to 1%, wherein the controlled variable is the pressure in the regulating valve and a matched process pipeline thereof, and the control variable comprises a proportional parameter, an integral parameter and a differential parameter of a PID control algorithm; when the substation field split transmission is started, the mathematical model is used for adjusting according to the adjusting stage and the split transmission pressure thereof, so that the steady-state error of the controlled variable in the adjusting stage is smaller than or equal to 1%, then the next adjusting stage is switched in until the Nth adjusting stage is switched in, and the mathematical model is used for adjusting so that the steady-state error of the controlled variable in the Nth adjusting stage is maintained to be smaller than or equal to 1% until the automatic split transmission is quitted.
In an exemplary embodiment of the invention, the mathematical model includes a total output model established from the design output, the N-way regulating valve and the N-way regulating valve matched process pipeline, and N sub-models established with the output pressure of each regulating stage and the N-way regulating valve matched process pipeline.
In an exemplary embodiment of the invention, the N-way regulating valves are connected with and controlled by the programmable logic controller. The engineer workstation assigns the control variable to a PID control algorithm module of the operator workstation, wherein the PID control algorithm module is preset in the operator workstation; an operator workstation sends the control variable to the programmable logic controller for controlling the regulator valve.
In an exemplary embodiment of the invention, the caliber of the regulating valve in the previous regulating stage is greater than or equal to the caliber of the regulating valve in the next regulating stage, and the caliber of the process pipeline matched with the regulating valve in the previous regulating stage is greater than or equal to the caliber of the process pipeline matched with the regulating valve in the next regulating stage.
In an exemplary embodiment of the invention, when the regulation phases are divided into three, the delivery pressure P1 of the first regulation phase is 40-85% of the design delivery, the delivery pressure P2 of the second regulation phase is 75-90% of the design delivery, and the delivery pressure P3 of the third regulation phase is equal to the design delivery.
In an exemplary embodiment of the invention, the aperture of the regulating valve of the first regulating stage is 25 inches, the pressure Class is Class600, and the pressure Class of the pressure transmitter of the first regulating stage is Class 600; the caliber of the regulating valve in the second regulating stage is 25 inches, the pressure grade is Class600, the caliber of the process pipeline matched with the regulating valve in the second regulating stage is 25 inches, the pressure grade is Class600, and the pressure grade of the pressure transmitter in the second regulating stage is Class 600; the aperture of the regulating valve in the third regulating stage is 25 inches, the pressure grade is Class600, the aperture of the process pipeline matched with the regulating valve in the third regulating stage is 3 inches, the pressure grade is Class600, and the pressure grade of the pressure transmitter in the third regulating stage is Class 600.
Another aspect of the invention provides an automatic distribution system for a natural gas pipeline. The system uses the automatic distribution and transmission method of the natural gas pipeline, and comprises the following steps: the system comprises a first Ethernet switch, a second Ethernet switch, at least two Ethernet switches, at least one engineer workstation, at least one operator workstation, a programmable logic controller, N regulating valves, N sets of process pipelines matched with the regulating valves and N pressure transmitters matched with the regulating valves. The engineer workstation comprises a first network card and a second network card, and is accessed into the first Ethernet switch through the first network card and is accessed into the second Ethernet switch through the second network card. The operator workstation comprises a third network card and a fourth network card, and is accessed into the first Ethernet switch through the third network card and is accessed into the second Ethernet switch through the fourth network card. The operator workstation has the preset PID control algorithm module, which can send the control variables to the programmable logic controller. The engineer workstation has the preset PID control algorithm and can assign the control variables to the PID control algorithm module. The programmable logic controller is connected with the N regulating valves and can control the N regulating valves according to the control variable. The N regulating valves can all feed back pressure, flow, temperature and valve position signals to the operator workstation through the programmable logic controller. The pressure transmitters are connected with the regulating valves matched with the pressure transmitters, the N pressure transmitters are connected with the programmable logic controller, pressure signals in the regulating valves matched with the pressure transmitters and the process pipelines matched with the regulating valves can be obtained, and the pressure signals are fed back to the operator workstation through the programmable logic controller.
In an exemplary embodiment of the invention, the engineer workstation accesses the first ethernet switch and the second ethernet switch through five types of twisted pairs, the operator workstation accesses the first ethernet switch and the second ethernet switch through five types of twisted pairs, the N regulator valves are all connected to the programmable logic controller through cables, and the N pressure transmitters are all connected to the programmable logic controller through cables.
In an exemplary embodiment of the present invention, the first ethernet switch has a three-layer routing forwarding function and supports any one or more of standard protocols 802.1d, 802.1p/q, 802.1s, 802.1w, 802.1 x, 802.3ad, and 802.3u, and the first communication card supports the standard protocol supported by the first ethernet switch; the second ethernet switch has a three-layer routing forwarding function and supports any one or more of standard protocols 802.1d, 802.1p/q, 802.1s, 802.1w, 802.1 x, 802.3ad and 802.3u, and the second communication card supports the standard protocol supported by the second ethernet switch.
In an exemplary embodiment of the invention, the processor of the industrial control programmable logic controller is a 32-bit CPU, and the memory of the processor is not less than 8M; the actuating mechanism of the regulating valve receives an analog control signal from the industrial control Programmable Logic Controller (PLC) 4-20 mADC and outputs a valve opening feedback signal of 4-20 mADC, and the pressure transmitter supports a Hart protocol and can output a feedback signal of 4-20 mA.
Compared with the prior art, the beneficial effects of the invention can include:
(1) the floating adjustment of the adjusting valve under a small flow for a long time can be avoided when a plurality of branches participate in adjustment together, so that the failure probability of equipment is reduced, and the reliability of the equipment is improved;
(2) the crosstalk of a control system during multi-branch regulation can be avoided;
(3) the problems of the automatic natural gas pipeline distribution and transmission system in the operation process can be timely solved; the system and the method effectively put an end to potential safety hazards in the operation of the gas pipeline and improve the safety and reliability of the operation of the natural gas pipeline station.
Drawings
Fig. 1 shows a schematic structural diagram of the automatic gas pipeline distribution system in an exemplary embodiment of the present invention;
FIG. 2 illustrates a flow chart of the automatic gas pipeline split delivery method in an exemplary embodiment of the invention;
fig. 3 shows a flow chart of the automatic distribution method of the natural gas pipeline in an exemplary embodiment of the invention.
The labels in the figure are:
1-engineer workstation, 1.1-engineer workstation first network card, 1.2-engineer workstation second network card, 2-operator workstation, 2.1-operator workstation first network card, 2.2-operator workstation second network card, 3-first industrial ethernet switch, 4-second industrial ethernet switch, 5-industrial control programmable logic controller, 5.1-industrial control programmable logic controller first communication card, 5.2-industrial control programmable logic controller second communication card, 6-first regulating valve, 7-first five type twisted pair, 8-second five type twisted pair, 9-third five type twisted pair, 10-fourth fifth type twisted pair, 11-fifth type twisted pair, 12-sixth fifth type twisted pair, 13-a first common cable, 14-a first regulating valve matched process pipeline, 15-a first pressure transmitter, 16-a second common cable, 17-a third common cable, 18-a fourth common cable, 19-a second regulating valve, 20-a second pressure transmitter, 21-a second regulating valve matched process pipeline, 22-a fifth common cable, 23-a sixth common cable, 24-a third regulating valve, 25-a third pressure transmitter and 26-a third regulating valve matched process pipeline.
Detailed Description
Hereinafter, the automatic distribution method and the automatic distribution system of a natural gas pipeline of the present invention will be described in detail with reference to exemplary embodiments. Herein, the terms "first," "second," "third," and the like are used for convenience of description and for convenience of distinction, and are not to be construed as indicating or implying relative importance or order of parts.
The method of adjusting a controlled variable at a certain adjustment stage to a steady state error of less than or equal to 1% in the present application can be implemented by the patent application with application number CN201910081278.9, which is incorporated herein by reference in its entirety.
In a first exemplary embodiment of the present invention, the automatic distribution method of a natural gas pipeline includes the steps of:
the method comprises the following steps: according to the design output, the gas transmission pressure regulation is divided into a first regulation stage, … … and an Nth regulation stage in sequence, N is a natural number and is more than or equal to 2, and the regulation targets of the gas transmission pressure in the first regulation stage to the Nth regulation stage are set as P1, … … and PN which are increased in sequence; configuring a regulating valve and a matched process pipeline for each regulating stage, wherein the regulating valve can regulate the sub-delivery pressure of the corresponding stage;
the partial output pressure PN is equal to the designed output, and the problems that when the output can be simultaneously and jointly regulated by a plurality of branch regulating valves, the control system crosstalk can be caused by the fluctuating flow, the control variable is not converged, and the regulating valve continuously fluctuates in a small amplitude are solved by a sectional regulation mode. The design throughput may also be referred to as a split delivery protocol pressure.
In an exemplary embodiment of the invention, a mathematical model may also be established based on both the number of conditioning stages and the delivery pressure of each conditioning stage. The mathematical model can comprise a total output model and N submodels, wherein the total output model is established according to the design output, the N-path regulating valves and the process pipelines matched with the N-path regulating valves. And the N sub-models are established according to the sub-delivery pressure of each adjusting stage and the N-way adjusting valve matched process pipeline.
Further, the delivery pressures of the N adjustment stages can cover a long-term large flow and a small initial flow to increase the robustness of the mathematical model and reduce overshoot and reference trajectory response time when performing automatic delivery to different downstream users, where the reference trajectory response time refers to the time required to eliminate the overshoot (i.e., to reach a predetermined steady-state error).
In an exemplary embodiment of the invention, when the regulation phases are divided into three, the delivery pressure P1 of the first regulation phase is 40-85% of the design delivery, the delivery pressure P2 of the second regulation phase is 75-90% of the design delivery, and the delivery pressure P3 of the third regulation phase is equal to the design delivery. For example, the delivery pressure P1 in the first regulation phase is 70% of the design delivery, the delivery pressure P2 in the second regulation phase is 87.5% of the design delivery, and the delivery pressure P3 in the third regulation phase is equal to the design delivery.
In an exemplary embodiment of the invention, the design throughput is 4.0MPa, and the gas delivery is divided into three conditioning stages according to the design throughput. The delivery pressure of the first conditioning stage may be 2.5 to 3.0MPa, for example 3.0 MPa. The delivery pressure of the second conditioning stage may be 3.0 to 3.6MPa, for example 3.5MPa, and the delivery pressure of the third conditioning stage may be 4.0 MPa.
In an exemplary embodiment of the present invention, the mathematical model may also be trained to obtain a control variable that can make the steady state error of the controlled variable (i.e., the split pressure P of a certain regulation stage, P-1, … …, PN) less than or equal to 1%, the controlled variable being the pressure within the regulating valve and its associated process line, the control variable including the proportional, integral and derivative parameters of a PID control algorithm.
For example, the mathematical model is trained in an engineer workstation in an off-line manner to obtain proportional, integral and differential parameters of a PID control algorithm, so that the steady-state error of the controlled variable is not more than 1%; assigning proportional, integral and differential parameters of a PID control algorithm trained in an engineer workstation to a PID control algorithm module of the operator workstation, wherein the PID control algorithm module is preset in the operator workstation; and after assignment is completed, sending proportional, integral and differential parameters of the PID control algorithm in the operator workstation to a programmable logic controller for controlling the regulating valve. The programmable logic controller is connected with the N-path regulating valve and can control the regulating valve according to proportional, integral and differential parameters of the PID control algorithm.
Furthermore, the programmable logic controller can also take the pressure, flow, temperature and valve position signals fed back by the regulating valve as input feedback of the PID control algorithm module to realize closed-loop control. Here, the programmable logic controller may be an industrial control programmable logic controller.
Step two: when the substation field is started, according to the adjusting stage and the sub-transmission pressure thereof, the mathematical model (which can be a pre-trained mathematical model) is used for adjusting, so that the sub-transmission pressure in the adjusting stage reaches a set value and the steady-state error is less than or equal to 1%, and then the next adjusting stage is switched in. Namely, when the station field transmission is started, the adjustment is started from the first adjustment stage, so that the next adjustment stage is switched in after the steady-state error of the controlled variable in the first adjustment stage is less than or equal to 1% until the Nth adjustment stage is switched in.
For example, 3 adjustment stages are provided, and the delivery pressure P2 of the second adjustment stage is 3.5MPa, after the second adjustment stage is entered, the mathematical model is needed to perform adjustment, so that the error between the measured pressure in the adjustment valve of the branch corresponding to the second adjustment stage and the matched process pipeline and the delivery pressure P2 is less than or equal to 1%, that is, the measured pressure is 3.45-3.55 MPa, and then the third adjustment stage can be entered.
And after entering the Nth adjusting stage, adjusting by using the mathematical model to ensure that the steady-state error of the controlled variable in the Nth adjusting stage is maintained to be less than or equal to 1% until the automatic sub-transmission is exited.
The mode of carrying out large-flow regulation, medium-flow regulation and small-flow regulation at last is adopted by stage regulation, so that the workload of central manual regulation after regionalization and intellectualization is reduced, the investment of labor cost is reduced, the problem of crosstalk of parallel regulating valves is reduced, and the safety and the reliability of operation are improved.
In an exemplary embodiment of the present invention, for example, as shown in fig. 2, the automatic distribution method of a natural gas pipeline may include the steps of:
classification is made according to gas transmission conditions, and here, reference may be made to the classification of conditions in CN 109869634A;
establishing a mathematical model;
integrating the control algorithm and downloading the algorithm into an operator workstation, for example, presetting a PID control algorithm module in the operator workstation and presetting a predictive control algorithm module in the operator workstation;
training the mathematical model to obtain proportional, integral and differential parameters and the like of a PID control algorithm, so that the control precision reaches 1%;
determining a design output according to the gas transmission working condition;
according to the design output, the gas transmission pressure regulation is divided into a first regulation stage, … … and an Nth regulation stage in sequence, each regulation stage is regulated in sequence, each regulation stage reaches the set output pressure in sequence, the steady state error is within 1%, then the next regulation stage is switched in, and the output pressure of the designed output is kept after the output pressure of the Nth regulation stage is started until the automatic output is stopped.
In the second exemplary embodiment of the present invention, the automatic natural gas pipeline distribution system may use the automatic natural gas pipeline distribution method in exemplary embodiment 1. The system comprises: at least two ethernet switches: the system comprises a first Ethernet switch, a second Ethernet switch, at least one engineer workstation, at least one operator workstation, a programmable logic controller, N regulating valves, N sets of process pipelines matched with the regulating valves and N pressure transmitters matched with the regulating valves.
The engineer workstation comprises a first network card and a second network card, and is accessed into the first Ethernet switch through the first network card and is accessed into the second Ethernet switch through the second network card.
The operator workstation comprises a third network card and a fourth network card, and is accessed into the first Ethernet switch through the third network card and is accessed into the second Ethernet switch through the fourth network card.
The operator workstation has the preset PID control algorithm module, which can send the control variables to the programmable logic controller.
The engineer workstation has the preset PID control algorithm and can assign the control variables to the PID control algorithm module.
The programmable logic controller is connected with the N regulating valves and can control the N regulating valves according to the control variable.
The N regulating valves can all feed back pressure, flow, temperature and valve position signals to the operator workstation through the programmable logic controller.
The pressure transmitters are connected with the regulating valves matched with the pressure transmitters, the N pressure transmitters are connected with the programmable logic controller, pressure signals in the regulating valves matched with the pressure transmitters and the process pipelines matched with the regulating valves can be obtained, and the pressure signals are fed back to the operator workstation through the programmable logic controller.
In an exemplary embodiment of the invention, the engineer workstation accesses the first ethernet switch and the second ethernet switch through five types of twisted pairs, the operator workstation accesses the first ethernet switch and the second ethernet switch through five types of twisted pairs, the N regulator valves are all connected to the programmable logic controller through cables, and the N pressure transmitters are all connected to the programmable logic controller through cables.
In an exemplary embodiment of the present invention, the first ethernet switch has a three-layer routing forwarding function and supports any one or more of standard protocols 802.1d, 802.1p/q, 802.1s, 802.1w, 802.1 x, 802.3ad, and 802.3u, and the first communication card supports the standard protocol supported by the first ethernet switch; the second ethernet switch has a three-layer routing forwarding function and supports any one or more of standard protocols 802.1d, 802.1p/q, 802.1s, 802.1w, 802.1 x, 802.3ad and 802.3u, and the second communication card supports the standard protocol supported by the second ethernet switch.
In an exemplary embodiment of the invention, the processor of the industrial control programmable logic controller is a 32-bit CPU, and the memory of the processor is not less than 8M; the actuating mechanism of the regulating valve receives an analog control signal from the industrial control Programmable Logic Controller (PLC) 4-20 mADC and outputs a valve opening feedback signal of 4-20 mADC, and the pressure transmitter supports a Hart protocol and can output a feedback signal of 4-20 mA.
In a third exemplary embodiment of the present invention, as shown in fig. 1, the automatic natural gas pipeline distribution system includes an engineer workstation 1, an operator workstation 2, a first industrial ethernet switch 3, a second industrial ethernet switch 4, a set of industrial control programmable logic controllers 5, a first regulating valve 6, a first category five twisted pair 7, a second category five twisted pair 8, a third category five twisted pair 9, a fourth category five twisted pair 10, a fifth category five twisted pair 11, a sixth category five twisted pair 12, a first common cable 13, a first regulating valve mating process pipeline 14, a first pressure transmitter 15, a second common cable 16, a third common cable 17, a fourth common cable 18, a second regulating valve 19, a second pressure transmitter 20, a second regulating valve mating process pipeline 21, a fifth common cable 22, a sixth common cable 23, a third regulating valve 24, a fifth common cable 18, a third common cable 23, a third regulating valve 24, a third regulating valve, A third pressure transmitter 25 and a third regulator valve associated process line 26.
Wherein, the aperture of the first regulating valve 6 is 25 inches, and the pressure grade is Class 600; the caliber of a process pipeline matched with the first regulating valve is 25 inches, and the pressure grade is Class 600; the first pressure transmitter 15 has a pressure rating of Class 600; the aperture of the second regulating valve 19 is 25 inches, and the pressure grade is Class 600; the aperture of a process pipeline 21 matched with the second regulating valve is 25 inches, and the pressure grade is Class 600; the second pressure transmitter 20 has a pressure rating of Class 600; the aperture of the third regulating valve 24 is 25 inches, and the pressure grade is Class 600; the aperture of a process pipeline matched with the third regulating valve is 3 inches, and the pressure grade is Class 600; the third pressure transmitter 25 is Class 600.
A first network card 1.1 in an engineer workstation 1 is connected into a first industrial Ethernet switch 3 through a first five-type twisted pair 7, a second network card 1.2 in the engineer workstation 1 is connected into a second industrial Ethernet switch 4 through a second five-type twisted pair 8, a first network card 2.1 in an operator workstation 2 is connected into the first industrial Ethernet switch 3 through a third five-type twisted pair 9, a second network card 2.2 in the operator workstation 2 is connected into the second industrial Ethernet switch 4 through a fourth fifth type twisted pair 10, a first communication card 5.1 of an industrial control programmable logic controller 5 is connected into the first industrial Ethernet switch 3 through a fifth five-type twisted pair 11, a second communication card 5.2 of the industrial control programmable logic controller 5 is connected into the second industrial Ethernet switch 4 through a sixth fifth type twisted pair 12, a first regulating valve 6 is connected into the industrial control programmable logic controller 5 through a first common cable 13, the second regulating valve 19 is connected to the industrial control programmable logic controller 5 through a third common cable 17, and the third regulating valve 24 is connected to the industrial control programmable logic controller 5 through a fifth common cable 22.
In order to implement the automatic distribution function of the gas station, the operator station 2 needs to monitor the valve position of the first control valve 6, the pressure of the medium in the first control valve associated process line 14, the valve position of the second control valve 19, the pressure of the medium in the second control valve associated process line 21, the valve position of the third control valve 24 and the pressure of the medium in the third control valve associated process line 26. The first common cable 13 should carry the valve position status signal of the first regulating valve 6, the second common cable 16 should carry the feedback medium pressure signal of the first pressure transmitter 15, the third common cable 17 should carry the valve position status signal of the second regulating valve 19, the fourth common cable 18 should carry the feedback medium pressure signal of the second pressure transmitter 20, the fifth common cable 22 should carry the valve position status signal of the third regulating valve 24, and the sixth common cable 23 should carry the feedback medium pressure signal of the third pressure transmitter 25.
The industrial control programmable logic controller 5 is characterized in that the first communication card 5.1 and the second communication card 5.2 feed valve position signals back to the operator workstation 2 through the first industrial Ethernet switch 3, the second industrial Ethernet switch 4, the third fifth twisted pair 9, the fourth fifth twisted pair 10, the fifth twisted pair 11 and the sixth fifth twisted pair 12 to form closed-loop control.
The automatic distribution and transmission method of the natural gas pipeline comprises the following steps:
the method comprises the following steps: according to the distribution protocol pressure (3.95MPa), the pressure regulation is divided into 3 regulation stages, the distribution pressure P1 of the first regulation stage is 3.0MPa, the distribution pressure P2 of the second regulation stage is 3.5MPa, and the distribution pressure P3 of the third regulation stage is 3.95MPa, and a mathematical model is established according to the first regulation valve 6, the second regulation valve 19, the third regulation valve 24, the first regulation valve matched process pipeline 14, the second regulation valve matched process pipeline 21 and the third regulation valve matched process pipeline 26.
Step two: taking the adjusting stage, the distribution pressure and the design temperature as model input conditions, taking mathematical models established by a first adjusting valve 6, a first adjusting valve matched process pipeline 14, a second adjusting valve 19, a second adjusting valve matched process pipeline 21, a third adjusting valve 24 and a third adjusting valve matched process pipeline 26 as controlled objects, training proportional, integral and differential parameters of a PID control algorithm in the engineer workstation 1 in an off-line manner to enable a steady-state error to be not more than 1%, and assigning the trained proportional, integral and differential parameters of the PID control algorithm in the engineer workstation 1 to a PID control algorithm module of the operator workstation 2; the adjusted sampling time and the trained reference trajectory response time within the engineer workstation 1 are assigned to the predictive control algorithm module of the operator workstation 2. The predictive control algorithm module may be pre-loaded into the operator workstation 2. For example, the reference trajectory response time may be obtained in the engineer workstation 1 by a method of simulating and optimizing a constraint function, and the response time at this time is assigned to the predictive control algorithm module of the operator workstation as the minimum value of the reference trajectory response time.
Step three: when the substation field split transmission is started, according to the split transmission pressure P1 of the first adjusting stage being 3.0MPa, the operator workstation 2 adjusts the controlled variable (the real-time pressure in the process pipeline 14 matched with the first adjusting valve 6 and the first adjusting valve) of the first adjusting stage by using a mathematical model, so that the steady-state error of the controlled variable of the first adjusting stage is less than or equal to 1%, and then the operator workstation switches into the second adjusting stage to perform split transmission pressure control; the operator workstation 2 adjusts the controlled variable (the real-time pressure in the process pipeline 21 matched with the second adjusting valve 19 and the second adjusting valve) in the second adjusting stage by using a mathematical model, and switches into a third adjusting stage to perform sub-transmission pressure control after the steady-state error of the controlled variable in the second adjusting stage is less than or equal to 1%; the operator workstation 2 uses the mathematical model to adjust the controlled variable (the real-time pressure in the third regulating valve 24 and the third regulating valve associated process line 26) of the third regulating stage so that the steady state error of the controlled variable of the third regulating stage is always less than or equal to 1% until the automatic distribution program is exited.
In an exemplary embodiment of the present invention, for example, as shown in fig. 3, the automatic distribution method for a natural gas pipeline may include the following steps:
starting to transport;
dividing the pressure regulation into 3 regulation stages of P1, P2 and P3 according to the delivery protocol pressure (3.95MPa), and enabling the delivery pressure P1 of the first regulation stage to be P3-1MPa or 3.95MPa-1MPa or 2.95 MPa;
controlling the error between the actual pressure of the first adjusting stage and P1 to be 2.95MPa to be 1 percent;
entering the next adjusting stage;
the delivery pressure P2-P3-0.5 MPa-3.95-0.5 MPa-3.45 MPa in the second adjusting stage;
controlling the error between the actual pressure of the second adjusting stage and P2 to be 2.95MPa to be 1 percent;
entering the next adjusting stage;
and controlling the error between the actual pressure of the third adjusting stage and the protocol pressure P3 to be 1% of 3.95MPa and keeping the error until the automatic delivery is exited.
In summary, the beneficial effects of the invention can include:
(1) the problems that when a plurality of branches participate in adjustment together, the opening of the adjusting valve is in a small opening for a long time, the robustness of a control model is poor, and the output overshoot is large can be solved;
(2) the problems that control variables are not converged and the regulating valve continuously fluctuates in a small amplitude due to control system crosstalk caused by fluctuating flow when a plurality of branch regulating valves are simultaneously regulated on line can be avoided;
(3) the operation of the automatic natural gas pipeline distribution and transmission system tends to be standardized and modularized, the safety, reliability and stability of the system are improved, and the system is convenient to dispatch, operate, manage and maintain;
(4) the realizability is high, hardware equipment of a station site and a regulation and control center SCADA system does not need to be added, and only a corresponding control module needs to be added in an upper computer of a control system;
(5) the problem of the automatic gas pipeline distribution and transmission system in the operation process can be treated as early as possible, potential safety hazards in the operation of the gas pipeline are effectively eliminated, and the safety and reliability of the operation of a natural gas pipeline station are improved.
Although the present invention has been described above in connection with the exemplary embodiments and the accompanying drawings, it will be apparent to those of ordinary skill in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.
Claims (10)
1. An automatic distribution and transmission method for a natural gas pipeline is characterized by comprising the following steps:
according to the design output, the gas transmission pressure regulation is divided into a first regulation stage, … … and an Nth regulation stage in sequence, N is a natural number and is more than or equal to 2, and the regulation targets of the gas transmission pressure in the first regulation stage to the Nth regulation stage are set as P1, … … and PN which are increased in sequence; configuring a regulating valve and a matched process pipeline for each regulating stage, wherein the regulating valve can regulate the sub-delivery pressure of the corresponding stage;
when the station field is started for the split transmission, the mathematical models are used for adjusting the first to Nth adjusting stages in sequence according to the adjusting stages and the split transmission pressure thereof; in the regulation of the non-Nth regulation stage, the sub-output pressure of each regulation stage needs to reach a set value, and the next regulation stage is switched into after the steady-state error of the pressure is less than or equal to 1%; in the regulation of the Nth regulation stage, the sub-delivery pressure in the regulation stage needs to reach a set value, the steady-state error of the pressure is maintained to be less than or equal to 1%, and the automatic sub-delivery is quitted.
2. The automatic gas pipeline splitting method of claim 1, wherein the mathematical model comprises:
a total output model established according to the design output, the N-way regulating valve and the process pipeline matched with the N-way regulating valve,
n submodels are established by the sub-delivery pressure of each adjusting stage and the N-way adjusting valve matched process pipelines.
3. The automatic natural gas pipeline distribution method according to claim 1,
the N paths of regulating valves are connected with and controlled by the programmable logic controller;
training the mathematical model in an engineer workstation to obtain a control variable which enables the steady-state error of the pressure to be less than or equal to 1% in each adjusting stage;
the engineer workstation assigns the control variable to a PID control algorithm module of the operator workstation, wherein the PID control algorithm module is preset in the operator workstation;
an operator workstation sends the control variable to the programmable logic controller for controlling the regulator valve.
4. The automatic natural gas pipeline separation and transportation method according to claim 1, wherein the caliber of the regulating valve in the previous regulating stage is greater than or equal to the caliber of the regulating valve in the next regulating stage, and the caliber of the process pipeline matched with the regulating valve in the previous regulating stage is greater than or equal to the caliber of the process pipeline matched with the regulating valve in the next regulating stage.
5. The automatic natural gas pipeline separation and transportation method according to claim 1, wherein when the number of the adjustment stages is 3, the separation and transportation pressure P1 in the first adjustment stage is 40-85% of the design transportation amount, the separation and transportation pressure P2 in the second adjustment stage is 75-90% of the design transportation amount, and the separation and transportation pressure P3 in the third adjustment stage is equal to the design transportation amount.
6. The automatic natural gas pipeline separation and transportation method according to claim 5, wherein the aperture of the regulating valve in the first regulating stage is 25 inches, the pressure grade is Class600, and the pressure grade of the pressure transmitter in the first regulating stage is Class 600; the caliber of the regulating valve in the second regulating stage is 25 inches, the pressure grade is Class600, the caliber of the process pipeline matched with the regulating valve in the second regulating stage is 25 inches, the pressure grade is Class600, and the pressure grade of the pressure transmitter in the second regulating stage is Class 600; the aperture of the regulating valve in the third regulating stage is 25 inches, the pressure grade is Class600, the aperture of the process pipeline matched with the regulating valve in the third regulating stage is 3 inches, the pressure grade is Class600, and the pressure grade of the pressure transmitter in the third regulating stage is Class 600.
7. An automatic natural gas pipeline distribution and transportation system, which is characterized in that the system uses the automatic natural gas pipeline distribution and transportation method of any one of claims 1-5, and the system comprises:
at least two ethernet switches: a first ethernet switch and a second ethernet switch,
at least one engineer workstation, at least one operator workstation, a programmable logic controller, N regulating valves, N sets of process pipelines matched with the regulating valves and N pressure transmitters matched with the regulating valves,
the engineer workstation comprises a first network card and a second network card, and is accessed into the first Ethernet switch through the first network card and is accessed into the second Ethernet switch through the second network card;
the operator workstation comprises a third network card and a fourth network card, and is accessed into the first Ethernet switch through the third network card and is accessed into the second Ethernet switch through the fourth network card;
the operator workstation is provided with a preset PID control algorithm module, and the PID control algorithm module can send the control variable to the programmable logic controller;
the engineer workstation is provided with the preset PID control algorithm and can assign the control variable to the PID control algorithm module;
the programmable logic controller is connected with the N regulating valves and can control the N regulating valves according to the control variable;
the N regulating valves can feed back pressure, flow, temperature and valve position signals to the operator workstation through the programmable logic controller;
the pressure transmitters are connected with the regulating valves matched with the pressure transmitters, the N pressure transmitters are connected with the programmable logic controller, pressure signals in the regulating valves matched with the pressure transmitters and the process pipelines matched with the regulating valves can be obtained, and the pressure signals are fed back to the operator workstation through the programmable logic controller.
8. The automatic gas pipeline distribution system of claim 7, wherein the engineer workstation accesses the first and second Ethernet switches via five twisted pairs, the operator workstation accesses the first and second Ethernet switches via five twisted pairs, the N regulator valves are each connected to the programmable logic controller via a cable, and the N pressure transmitters are each connected to the programmable logic controller via a cable.
9. The automatic gas pipeline distribution system according to claim 7, wherein the first ethernet switch has a three-layer routing and forwarding function and supports any one or more of standard protocols 802.1d, 802.1p/q, 802.1s, 802.1w, 802.1 x, 802.3ad and 802.3u, and the first communication card supports the standard protocol supported by the first ethernet switch; the second ethernet switch has a three-layer routing forwarding function and supports any one or more of standard protocols 802.1d, 802.1p/q, 802.1s, 802.1w, 802.1 x, 802.3ad and 802.3u, and the second communication card supports the standard protocol supported by the second ethernet switch.
10. The automatic natural gas pipeline distribution system of claim 7, wherein the processor of the industrial control programmable logic controller is a 32-bit CPU, and the memory of the processor is not less than 8M; the actuating mechanism of the regulating valve receives an analog control signal from the industrial control Programmable Logic Controller (PLC) 4-20 mADC and outputs a valve opening feedback signal of 4-20 mADC, and the pressure transmitter supports a Hart protocol and can output a feedback signal of 4-20 mA.
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Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2587070A1 (en) * | 2006-05-05 | 2007-11-05 | Gaz De France | Automatic optimization process for a natural gas transportation network |
| CN201050685Y (en) * | 2007-05-17 | 2008-04-23 | 汉纬尔机械(上海)有限公司 | Sequential filling system |
| CN103822086A (en) * | 2013-12-02 | 2014-05-28 | 宁波力品格工业机械有限公司 | Full-automatic inflating machine |
| CN104006298A (en) * | 2014-06-09 | 2014-08-27 | 广西玉柴机器股份有限公司 | Multifunctional natural gas pressure adjusting cabinet |
| CN205748898U (en) * | 2016-06-20 | 2016-11-30 | 辽宁科技大学 | A kind of flow characteristics of regulating valve closed loop test system |
| CN107228279A (en) * | 2017-07-31 | 2017-10-03 | 特瑞斯能源装备股份有限公司 | A kind of integrated natural gas line pressure testing feeder and its control method |
| CN107584097A (en) * | 2017-08-31 | 2018-01-16 | 江苏天宏机械工业有限公司 | A kind of air injection machine liquid level suspension control method |
| CN109433750A (en) * | 2018-12-25 | 2019-03-08 | 重庆龙煜精密铜管有限公司 | A kind of online purge system of ladder pressurization for copper pipe production |
| CN109491416A (en) * | 2018-10-16 | 2019-03-19 | 中国三峡建设管理有限公司 | A kind of filling stage boost control method |
| CN109827073A (en) * | 2019-01-28 | 2019-05-31 | 中国石油天然气集团公司 | A kind of natural gas line divides defeated implementation method automatically |
| CN109869634A (en) * | 2019-01-28 | 2019-06-11 | 中国石油天然气集团公司 | A kind of natural gas line divides defeated realization system automatically and divides defeated implementation method automatically |
| CN211371929U (en) * | 2019-12-02 | 2020-08-28 | 石家庄钢铁有限责任公司 | Input steam pressure adjusting device of steam vacuum pump |
| CN113397478A (en) * | 2020-11-09 | 2021-09-17 | 华东理工大学 | Automatic pressurization control method for pulse diagnosis device |
-
2022
- 2022-01-04 CN CN202210004224.4A patent/CN114321719A/en active Pending
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2587070A1 (en) * | 2006-05-05 | 2007-11-05 | Gaz De France | Automatic optimization process for a natural gas transportation network |
| CN201050685Y (en) * | 2007-05-17 | 2008-04-23 | 汉纬尔机械(上海)有限公司 | Sequential filling system |
| CN103822086A (en) * | 2013-12-02 | 2014-05-28 | 宁波力品格工业机械有限公司 | Full-automatic inflating machine |
| CN104006298A (en) * | 2014-06-09 | 2014-08-27 | 广西玉柴机器股份有限公司 | Multifunctional natural gas pressure adjusting cabinet |
| CN205748898U (en) * | 2016-06-20 | 2016-11-30 | 辽宁科技大学 | A kind of flow characteristics of regulating valve closed loop test system |
| CN107228279A (en) * | 2017-07-31 | 2017-10-03 | 特瑞斯能源装备股份有限公司 | A kind of integrated natural gas line pressure testing feeder and its control method |
| CN107584097A (en) * | 2017-08-31 | 2018-01-16 | 江苏天宏机械工业有限公司 | A kind of air injection machine liquid level suspension control method |
| CN109491416A (en) * | 2018-10-16 | 2019-03-19 | 中国三峡建设管理有限公司 | A kind of filling stage boost control method |
| CN109433750A (en) * | 2018-12-25 | 2019-03-08 | 重庆龙煜精密铜管有限公司 | A kind of online purge system of ladder pressurization for copper pipe production |
| CN109827073A (en) * | 2019-01-28 | 2019-05-31 | 中国石油天然气集团公司 | A kind of natural gas line divides defeated implementation method automatically |
| CN109869634A (en) * | 2019-01-28 | 2019-06-11 | 中国石油天然气集团公司 | A kind of natural gas line divides defeated realization system automatically and divides defeated implementation method automatically |
| CN211371929U (en) * | 2019-12-02 | 2020-08-28 | 石家庄钢铁有限责任公司 | Input steam pressure adjusting device of steam vacuum pump |
| CN113397478A (en) * | 2020-11-09 | 2021-09-17 | 华东理工大学 | Automatic pressurization control method for pulse diagnosis device |
Non-Patent Citations (1)
| Title |
|---|
| 吴旭光等: "《计算机仿真技术》", 31 December 2015, 西北工业大学出版社, pages: 191 - 193 * |
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