Background
The compressor unit is an important pressure system in the process industry, and the gas circuit system is a core component part of the compressor unit. In the actual production process, the compressor unit is often complicated in operation, and radiation noise generated by unit work is huge in damage to the body of a field operator. The compressor control system CCS (Compressor Control System) is an energy-saving automatic control system facing the compressor unit to work, and based on the control characteristics of the compressor unit, the integrated and automatic control of the compressor unit is realized through a series of control programs, and an operator can remotely control the compressor unit through the compressor control system CCS, so that the energy-saving automatic control system is a great improvement of the control technology of the large-sized compressor unit. The CCS system of the compressor control system mainly comprises load regulation, surge control, turbine rotation speed control, internal unit equipment control, unit safety interlocking, other auxiliary programs, instrument monitoring at various units on the shaft side and the like of the compressor unit, and the like, so that the stable control of the whole flow of the compressor unit is realized.
The process flow and control logic of the learning gas circuit system are the preconditions familiar with compressor unit operation. OTS (Operator TRAINING SYSTEM ) is a software model which combines computer simulation software to simulate the real production process and is mainly used for Operator training and learning, and the field of the OTS comprises various flow industries such as chemical industry, petrochemical industry, oil refining industry and the like. OTS utilizes computer emulation simulation technique and configuration tool such as distributed control system DCS (Distributed Control System) simulation system, can carry out the modeling to compressor unit gas circuit system and restore, gives the operator safer, more effective training platform and opportunity. The simulation reduction degree of the compressor unit gas circuit system directly influences the training effect of operators, thereby relating to the safe and efficient production of the process industry. Therefore, it is important to simulate the compressor train gas circuit system with high reduction degree and the convection Cheng Gongye of the compressor control system CCS control system.
At present, the simulation modeling strategies of the compressor unit mainly comprise the following three types.
1) And (5) simulating a simple mathematical model.
The simple mathematical model simulation generally only establishes partial mathematical model, lacks man-machine interaction, lacks the connection of actual process flow, and has low reduction degree.
For example, by combining the characteristics of the ground source heat pump air conditioner compressor, the self-adaptive fuzzy algorithm and the PID algorithm are used for optimizing the simulation model of the compressor, so that the control effect and efficiency of the simulation compressor are improved. But the relation between the simulation mathematical model and the process flow is not strong, and the reduction degree is not high enough. (Dan Jianhua, yang Jie, simulation of adaptive fuzzy PID control in ground source heat pump air conditioner compressor System [ J ], university of Wuhan occupational technology academy of sciences 2016,15 (3): 4.DOI: CNKI: SUN: WHZB.0.2016-03-017)
For another example, a mathematical model was built using a Modelica language and Dymola compiler in combination with the compressor performance equation, and simulation verification of the compressed fluid was performed. However, the mathematical model is not only lack of a visual man-machine interaction interface, which is unfavorable for training and learning of operators, but also the simulation equation is only remained on the mathematical fitting level and is not combined with the actual process, and the model is only aimed at the compression process of the compressor gas circuit. (Wang Tingxing, li Fangzhan, meng Guang et al, modeling and simulation methods for Modelica and Dymola based compressor systems [ J ], gas turbine experiments and research, 2004,17 (3): 6.DOI:10.3969/J. Issn. 1672-2620.2004.03.009.)
2) And simulating the working process of the compressor unit by using configuration model software.
The simulation modeling can not completely simulate the actual work of the compressor unit only by combining a certain technological process, and also has the problem of low reduction degree.
For example, a compressor is built by means of the HYSYS dynamic module and the driving process is studied, or the stopping process is studied by means of the HYSYS dynamic module. However, all the models only relate to a single working condition, and the dynamic model has a large limitation.
For another example, the actual working state of the compressor unit is simulated by using iFIX 4.0 configuration software (Wang Li, cai Wenxuan, implementation of a reciprocating compressor unit teaching simulation system [ J ], coal technology, 2011,30 (4): 3.DOI: CNKI: SUN: MTJS.0.2011-04-100.), teaching simulation of a compressor unit gas circuit system is realized, and the training difficulty of using and maintaining a compressor unit operator is solved to a great extent. However, the bottom layer mechanism database is imperfect, and only a mathematical model is used for fitting, so that the simulation degree is reduced to a certain extent.
Researchers also build a two-stage compression dynamic model through HYSYS software, and study the running condition of the unit under various working conditions, and the simulation model has more completeness and great progress (Wang Li, cai Wenxuan, realization of a reciprocating compressor unit teaching simulation system [ J ], coal technology, 2011,30 (4): 3.DOI: CNKI: SUN: MTJS.0.2011-04-100). Or a simulation teaching system of the compressor unit is developed on the basis of a combined model as in the patent with the publication number of CN 115206152A. However, in general, this kind of simulation strategy still lacks program control modules of a real production environment, such as an interlock program, a start-stop logic program, etc., and the simulation reduction degree is not high enough.
3) Simulation of the compressor package program.
Such simulation, such as the patent with publication number CN208270980U, simulates a turbo compressor set in combination with the compressor control system CCS and the simulation controller, but lacks a complete process, which is not conducive to the knowledge of the system flow by the operator.
In a word, the compressor unit gas circuit simulation strategy has a larger lifting space in the reduction degree of models or programs and the like. The improvement of the strategy is beneficial to further improving the knowledge of people on the operation regulations of the compressor unit gas circuit system, and is convenient for improving the professional ability of operators more efficiently.
Detailed Description
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention, and are not limiting of the claims of the invention.
Term interpretation:
OTS, an Operator training system (Operator TRAINING SYSTEM), i.e. a software model which combines computer simulation software to simulate the real production process and is mainly used for Operator training and learning, and the field of the OTS comprises various flow industries such as chemical industry, petrochemical industry, oil refining and the like.
The compressor control system CCS is a compressor control system (Compressor Control System), namely, the integrated and automatic control of the compressor unit is realized through a series of control programs based on the control characteristics of the compressor unit.
The distributed control system DCS is a distributed control system (Distributed Control System), is combined with a network communication technology, a computer technology and the like, collects data of all parts of a factory, transmits the data to the central control system through a communication bus, and gives real-time feedback according to the situation. It is an important tool for the flow industrial monitoring, operation and management.
Valve Cv value-valve flow coefficient, typically, the Cv of the on-off valve is constant, and the Cv of the regulating valve can be generally calculated according to the formulaTo simply estimate, where F is flow, OP is valve opening, and Δp is the pressure drop across the valve at the specified opening.
Example 1:
Referring to fig. 1, the embodiment provides a method for modeling a dynamic mechanism of a gas circuit system of a compressor unit, and a specific implementation mode of gas circuit simulation of the compressor unit mainly comprises two major parts, namely building a turbine compressor process model and controlling logic configuration of a compressor. And data transmission is carried out between the compressor process model data and the compressor control logic configuration, so that the dynamic mechanism modeling of the compressor unit gas circuit system is realized. The details of the two embodiments are described in detail below.
S1, building a process simulation model of a compressor is conducted according to a process flow chart of a compressor gas circuit. The specific process is that,
S101, establishing a compressor gas circuit system model according to the process flow.
The gas circuit system is a main process flow of the compression part. The steam turbine mainly provides a power source for the compressor, the medium-pressure steam impacts the turbine to generate power to drive the compressor to rotate, and the medium-pressure steam is changed into turbine condensate to be discharged after energy conversion. The gas circuit system process model comprises a turbine compressor model, a heat exchanger, an intersegmental condensate tank, an anti-surge valve, an expander, a condensate tank, a vacuum pump and other main equipment. By integrating the equipment models and carrying out dynamic simulation analysis, the performance of the system under different working conditions is simulated, and a complete turbine compressor gas circuit system model can be established for analyzing and optimizing the performance of the compressor.
The gas circuit system model can help understand and predict the behavior of the compressor under different working conditions, and theoretical support is provided for actual engineering design and operation. In the embodiment, the gas circuit system model is that raw oil gas with the pressure of 0.2MPa (G) enters a section of compressor to 0.6MPa (G) through an inlet regulating valve, is cooled to 40 ℃ through a cooler, then enters a condensate tank between sections of the compressor for separation, and is mixed with the raw oil gas before returning to the section of compressor by a section of anti-surge valve FZT 31202. The rich gas enters a second section of the compressor from the top of the condensate tank to be further compressed to 1.4MPa (G), and finally is sent to a subsequent process flow through an outlet regulating valve, and the second section is provided with an anti-surge valve FZT31202 and returns to the outlet of the first section of the compressor. And establishing a compressor gas circuit system model according to the process flow.
S102, setting the parameters of the compressor according to the design data of the compressor.
In this embodiment, the maximum rotation speed of the compressor is 9500rpm, and the characteristic curves and the efficiency curves are shown in fig. 2 and 3, respectively. Wherein, FIG. 2 shows a characteristic curve of a section of the compressor at the rotation speeds of 5919, 6248, 6577 and 6906rpm in sequence from the curves 1 to 4, and FIG. 3 shows a section of the efficiency curve of the compressor at the rotation speeds of 5919, 6248, 6577 and 6906rpm in sequence from the curves 1 to 4;
parameters of the two-stage compressor are set according to design data of the compressor, in this embodiment, the maximum rotation speed of the two-stage compressor is set to 9500rpm, and the characteristic curves and the efficiency curves are shown in fig. 4 and 5, respectively. Wherein, FIG. 4 shows the characteristic curves of the two-stage compressor at the rotation speeds of 5919, 6248, 6577 and 6906rpm in sequence from the curves 1 to 4, and FIG. 5 shows the efficiency curves of the two-stage compressor at the rotation speeds of 5919, 6248, 6577 and 6906rpm in sequence from the curves 1 to 4.
S103, setting the attribute of the steam according to the design condition of the steam turbine.
The steam properties are set according to the design conditions of the steam turbine, the power provided by different steam grades is different, and the steam properties comprise pressure, humidity, temperature, specific volume and the like. In the model, the boundary steam pressure of the turbine side is 2MPa (G), and the turbine side mainly drives the turbine shaft to rotate through the medium pressure steam of 2MPa and drives the compressor rotor to rotate at a high speed to generate centrifugal force, so that the rich gas pressure is improved. The rotation speed of the compressor is controlled by a steam speed regulating valve (SIC 1742), and only energy is transferred between the steam turbine and the compressor, so that the speed regulating valve is the driving end of the first-stage compressor and the second-stage compressor. After being cooled, the exhaust gas from the steam turbine becomes hydraulic liquid, and enters a condensate tank, and meanwhile, non-condensable gas is discharged out of the tank through a vacuum system.
And S2, the compressor control logic configuration is a control logic module of a distributed control system DCS translation compressor control system CCS, and the gas circuit logic of the compressor unit is restored, so that the control of starting, stopping and anti-surge of the compressor can be realized, and the safe and efficient operation of the compressor is ensured.
The CCS control logic of the compressor control system mainly comprises turbine rotation speed control, anti-surge control, internal unit equipment control, unit safety interlocking, other auxiliary programs, instrument monitoring at various units on the shaft side and the like of the compressor unit, and the like, so that the stable control of the whole flow of the compressor unit is realized.
The control logic construction scheme of the simulation compressor unit gas circuit system by combining CCS control logic of the on-site compressor control system and utilizing DCS configuration software of the distributed control system and assisting with a self-defined program built in an OTS (on-site training system) of an operator is as follows:
S201, a turbine rotating speed logic module is built, and turbine rotating speed control is performed.
And adopting a general PID algorithm, taking the measured value as the rotating speed N of the steam turbine, comparing the rotating speed N with a speed control set point SV, and calculating the deviation e. In each execution period, according to the deviation e, the speed control PID calculates a speed control response value CRN, and the speed control response value CRN is then sent to an output response selection module to be selected with other control outputs, and finally acts on a speed regulating valve to regulate the rotating speed of the steam turbine.
Wherein a speed control set point (SV) is selected based on the configuration and the current operating mode. When in the auto-start or park sequence control process, the auto-sequence control logic will automatically generate a local set point. The local or remote set point is selected by the operator while in normal operation.
The local setpoint mode includes a RUN state and a non-RUN state. The RUN state operator selects the local setpoint mode by pressing the local button. The controller automatically selects the local setpoint mode in the non-RUN state. In the local mode, the range of local settings depends on the state in which the speed controller is located. Wherein, during the automatic sequence control process (start or stop), the local set value is automatically generated by the sequence control logic. For example, in the up-speed and standby state, the variable range of the local set point is between the minimum control speed and the minimum governor control speed. In the stop state, the variable range of the local set value is between the minimum control rotation speed and the maximum speed regulator control rotation. In the running state, the variable range of the local set value is between the minimum speed control rotation speed and the maximum speed control rotation speed. The local set point can be adjusted by pressing up and down buttons to increase or decrease the rotational speed set point, or by setting a target value command (SV). When the up or down button is pressed, the setpoint will be moved up or down at a configured rate.
In this embodiment, a cascade PID control system is established to control the rotational speed of the steam turbine, including establishing a section of inlet pressure control PID and speed PID to perform cascade control, and the output of the speed PID is used as the input of a main MANUAL valve operator (MANUAL) to realize MANUAL automatic mode control of the rotational speed.
The output of the manual operator is connected with the rotation speed adjustment 048_SIC_31602 of the compressor. The PIC31202 is a pressure regulating controller of a section of inlet of the compressor, speedPID is a distributed control system DCS speed regulation control module of the steam turbine, 049ZQM is an opening control module of the air speed valve, and a logic program diagram of the distributed control system DCS is shown in fig. 6, and connection and logic relation among the modules are shown.
S202, building a turbine power correlation module to correlate the rotating speed of a turbine with the output power of the turbine;
There is a close relationship between the rotational speed and power of the turbine. At a certain load, the rotational speed of the turbine is relatively stable. When the load increases, the power output of the turbine increases correspondingly, but the rotational speed decreases slightly.
In this embodiment, the steam turbine adopts the expander, and the Cv value and the expansion coefficient are set according to the turbine design data table and the logistics balance data, the medium entropy efficiency in the expander model is set to be 1, and the Cv value is set to be 100, so that the input of steam can be adjusted according to the real-time rotation speed and the power requirement, and the stable operation of the steam turbine can be maintained.
S203, building an output power module of the compressor, correlating the output power of the two sections of compressors with corresponding rotating speeds by multiplying the output power of the turbine by a proportional coefficient, and establishing a dynamic balance relation between the work of the high-pressure steam on the turbine and the mechanical energy of the compressor so as to ensure conservation of energy of the system;
The output power ratio coefficients of the steam turbine and the two sections of compressors can be subjected to self-defining correction according to actual conditions, the ratio coefficients comprise but are not limited to constants, and can also be functional curves and characteristic curves, and the specific program is shown in figure 7. Wherein R1 refers to the output power of a first section of the compressor, R2 refers to the output power of a second section of the compressor, P refers to the output power of a steam turbine, PC refers to the state of a jigger motor, OP refers to the opening degree of a gas speed valve of the steam turbine, st1, st2 and st3 are respectively VI31401, VI31402 and VI31403, st1 refers to the on-off state of a medium-pressure steam inlet stop valve, and st2 and st3 refer to the quick-opening valve of the inlet of the steam turbine.
S204, a start-stop program module of the compressor is built, a speed regulation mode program is built according to a speed-up curve of the compressor, corresponding start-stop stages are automatically identified according to the rotating speed and state conditions of the steam turbine, and automatic or manual start-up is performed according to the sequence of reaching the start-up conditions, the first-stage warm-up, the second-stage warm-up, critical acceleration, normal acceleration and normal operation. In addition, the speed regulation mode program is additionally provided with an overspeed mode and a shutdown mode. Wherein, the status condition of self-identification includes, but is not limited to, a start-up condition, an interlock condition.
Specifically, in the critical acceleration stage, the acceleration rate is higher than that of other links; different starting modes can be selected, the automatic starting is performed automatically according to a preset program in an automatic mode to reach the minimum rotating speed value of the compressor, judgment and prompt are carried out after the preset program conditions of each step are met in a manual mode, namely whether the next step is carried out or not, the permission of a user speed regulation input box is opened after the normal running state of the compressor is reached, and the input value can only be between the minimum rotating speed of the compressor and the electronic tripping speed.
In overspeed mode, the actual speed of the compressor must not exceed the electronic trip speed of the compressor, otherwise an electronic trip interlock is triggered.
And S205, constructing a first-section surge valve program module and a second-section surge valve program module of the compressor to perform anti-surge control, wherein the anti-surge control comprises surge line drawing, surge detection, surge circling point and surge PID control. Wherein,
(1) Surge line mapping the X, Y axis coordinates of the surge line are determined from the compressor design data, the X axis being the ratio of the compressor inlet flow to the inlet flow multiplied by 100, the Y axis being the compression ratio, i.e., the compressor outlet pressure to the inlet pressure. The surge point coordinates at 5919, 6248, 6577, 6906rpm are taken on the performance curves and converted to the required surge line. The surge line is generally provided with a certain safety margin (7-10%), called surge line. For example, by setting a safety margin of 10%, the surge line, also called surge control line, is obtained by shifting the surge line 10 units to the right.
(2) Surge detection after the surge line is plotted, the actual operating point, i.e., the determined inlet or outlet flow and compression ratio of the compressor at the current rotational speed, is determined. When the operating point is calculated, it is displayed in the surge line coordinate system. The actual margin is the abscissa of the operating point minus the abscissa of the surge point at the current rotational speed. When the actual margin is less than the safety margin, the anti-surge valve opens quickly, otherwise closes slowly. When the operating point crosses the surge line, the system determines that a surge is triggered, counts, and the surge line moves down by 2 (2%) fine-tuning per surge, with a maximum fine-tuning number of 10.
(3) Surge HOVER point-the HOVER point is defined as the safety margin minus the surge HOVER margin (surge HOVER margin k1HOVER is typically set to 5) and the surge HOVER slope klHOVER is set to 3 (%/secs). When the current operating point approaches the surge line, the hover control point setting is selected low from the surge control line as a new operating point set point, i.e., the hover point minimum will not be below the control line.
(4) Surge PID control is controlled by calculating the deviation of the hover point from the operating point. The PID control parameters act in a reactive manner. The controller slow off function is set. The slow off slope is set to 2 (%/sec). The amplification and integration times are self-adjusting using a self-tuning function. If the actual margin exceeds the control line operation margin, the proportional function doubles and the 1/4 integration time is set.
Specifically, in this embodiment, the opening degree of the anti-surge valve is controlled by calculating the model operating point through the first and second inlet flow rates, comparing the surge curves of the compressors, and giving a safety margin.
The surge curve is obtained according to the designed standard molar flow and the fitted curve of the pressure ratio of the first inlet and the second inlet of the compressor, and the general processing method is that a plurality of points on the performance curve are obtained through image point-taking software (such as Engauge Digitizer software), more than 10 points are recommended to be taken, and the fidelity of curve fitting is ensured.
The safety margin value can be automatically corrected according to the actual surge times, and in the default, the safety margin value is automatically increased by 2 for 5 times at most, namely the margin is automatically increased by 10 at most. The safety margin may be returned to the original safety margin by a reset button.
S206, building an interlocking program and other auxiliary modules;
the interlocking program is built according to actual interlocking requirements, including but not limited to startup condition interlocking, shutdown interlocking and public interlocking programs, and other auxiliary modules are built according to actual process requirements, including but not limited to a hydrocarbon pump self-startup program, a warming timing program and an intersegmental separation tank liquid level split-control program.
S207, restoring the simulation interactive picture by taking the picture configuration of the real distributed control system DCS and the compressor control system CCS as templates.
The dynamic mechanism modeling method of the compressor unit gas circuit system based on the virtual simulation technology is more in line with the actual production working condition through mechanism and dynamic modeling, in addition, the simulation strategy is completely matched with the DCS configuration of the distributed control system, the original DCS configuration of the distributed control system is directly adopted, the actual configuration control system is not influenced, safety is guaranteed, the actual production environment is restored to a high degree, for a third party configuration software such as a compressor control system CCS, the simulation strategy restores the internal program of the third party configuration software by means of one-to-one translation of the DCS configuration of the distributed control system, the actual logic is completely restored, the simulation adopts the compressor control system CCS and the DCS picture of the distributed control system which are actually produced, the human-computer interaction interface is completely restored, the highest operation rate of the simulation modeling can reach 50 times of speed, and the training and learning efficiency of operators is improved. In a word, the simulation strategy has the advantages of higher simulation reduction degree, high transportation processing speed and stronger interactivity, and is beneficial to the improvement of the professional capability of process operators.
Example 2:
Referring to fig. 8, the present embodiment provides a compressor unit gas circuit system dynamic mechanism modeling system for implementing the compressor unit gas circuit system dynamic mechanism modeling method in embodiment 1, where the system architecture includes a compressor process simulation model, a virtual controller, a distributed control system DCS monitoring and a compressor control system CCS monitoring. In particular to the preparation method of the composite material,
The compressor process simulation model is used for building a compressor process model in the simulation modeling platform according to the design data;
the data communication module is used for establishing communication between the distributed control system DCS and the CCS configuration bit number of the compressor control system and the compressor process simulation model data so as to realize data bidirectional transmission;
and the virtual controller is used for simulating the operation of the simulation controller, realizing the control logic operation of the compressor and finally feeding data back to the distributed control system DCS and the CCS monitoring picture of the compressor control system.
The above description of the embodiments is only for aiding in the understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the principles of the invention, which are also intended to fall within the scope of the appended claims.