RU2454569C1 - Control method of hydraulic conditions of compressor shop with optimum load distribution between gas compressor units - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention refers to control of gas compressor units during gas transportation. Specified rotor speed values of injectors are determined as per ratio in the range of allowable values of load change of each gas compressor unit considering the limitation of maximum allowable load difference between neighbouring gas compressor units. Arbitrary load ratio specified by the operator is included in calculation, or load ratio corresponding to minimum fuel gas consumption is calculated as per optimisation method. Optimisation method of multidimensional models is applied at limitations for calculation of optimum load ratio. Search of optimum load ratio of injectors is performed within the whole range of allowable frequency values of injectors by considering limitations of maximum possible difference between loads of injectors. In the calculation the change in fuel gas consumed with the unit relates to change of energies of thermal interaction, mechanical interaction and gas dynamic interaction of working media in turbine according to energy saving principle. Change in the above four types of energy by means of mathematical models is expressed through the change in parameters measured in automatic control system of gas compressor units. As per the measured data and model relations there built are the main models of energy interaction in gas compressor units in current modes and a number of possible modes of various rotation frequencies of gas compressor units. As per model of energy interaction there calculated are values of volume and commercial efficiency of gas compressor unit, which correspond to those modes, as well as fuel gas consumption. Obtained sets of values are included in static relations. The latter and limitations are processed by applying optimisation calculation method, at operation of which there calculated are assignments of rotation frequencies of injectors by means of non-linear programming method, assignments of frequencies are supplied to control system of gas compressor unit as control action. Maximum allowable working limits of each individual gas compressor unit are calculated continuously as per functional relations, and creation of model relations of energy balance for optimisation calculation is performed momentarily for optimisation calculation.

EFFECT: enlarging the possibility of load distribution at a shop, and application of optimisation method in the whole operating range of gas compressor unit.

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Description

Technical field

The invention as a whole relates to the field of controlling the operation of gas pumping units (GPU) of the compressor workshop (CC) while ensuring gas transportation. More specifically, the invention relates to a method for controlling the hydraulic mode of the compressor shop of gas pumping units. The method provides control according to the selected parameter of the workshop mode — volumetric productivity of the workshop, or commercial productivity of the workshop, or gas pressure at the outlet of the workshop, or the degree of gas compression in the compressor workshop, at which the value of the parameter is compared with the set value, and the control action of the workshop control system is formed. This impact of the workshop control system is distributed to the automatic control systems (ACS) of the gas compressor unit, which are part of the compressor shop in the form of compressor speed settings. Each GPA self-propelled guns fulfills a preset value of the supercharger rotation speed through a change in the position of the control valve (PK) supplying fuel gas to the turbine combustion chamber; a change in the fuel gas supply leads to a change in the energy of the gas-air mixture rotating the low-pressure turbine shaft that is common with the supercharger. The gas pumped by each GPU supercharger is collected in a common shop manifold and forms measured or calculated mode parameters - gas pressure at the outlet of the workshop, volumetric capacity of the workshop, commercial productivity of the workshop. Thus, the required value of the adjustable operating parameter of the workshop is ensured by the operation of the control and task allocation method implemented in the form of a control program in the control system of the compressor workshop.

State of the art

The compressor shop of gas pumping units is a combination of equipment and equipment control systems that ensure the transport of natural gas by adding additional compression energy to the gas stream.

The compressor shop consists of a group of gas pumping units, a pipe-and-piping arrangement along with equipment for cleaning and cooling the pumped gas, a control system for the compressor shop combining a set of control systems for gas pumping units, and a number of subsystems not considered in this description that ensure the operation of the listed main components of the compressor shop .

Figure 1 shows the main elements of the overall control system of the compressor shop, interacting with each other in the process control mode,

where MG is the main gas pipeline (connecting compressor shops located between the gas from the gas field to the consumer);

H - supercharger gas pumping unit;

T _in - gas temperature, P _in - gas pressure, Q _in - the volume of gas supplied to the input of the unit per unit time;

T _out - gas temperature, P _out - gas pressure, Q _out - gas volume entering the main gas pipeline from the workshop per unit time;

GPA - gas pumping unit;

in - inlet of the compressor workshop together with a pipe-crane harness; dust collectors, measuring equipment, etc. gas preparation elements;

out - the output of the compressor shop together with a pipe-crane harness, air-cooling units and measuring equipment;

A - operator of the compressor shop;

B - compressor shop control system with built-in mathematical and software for the workshop mode controller;

C - automatic control systems for gas pumping units;

D - gas pumping units of the compressor shop, which include power turbines that provide rotation of the supercharger, fuel and measuring equipment.

Gas from the main gas pipeline enters the inlet of the workshop through a crane harness and enters the superchargers of the gas pumping units D.

In superchargers, gas is simultaneously compressed and pumped, i.e. it is compressed when it enters the waste collector, after which it enters the outlet from the workshop, where it is cooled, and where the gas parameters are measured - gas pressure, gas temperature, the amount of gas passing through the workshop per unit time is calculated, this amount is expressed in volumetric or commercial capacity workshop (current volumetric productivity reduced to normal conditions).

The operation of the gas pumping unit is controlled by the automatic control system C of the gas compressor unit. Under the control of the automatic control system of the gas compressor unit, there are many mechanisms and subsystems of the gas compressor unit, the integrated control of which serves the main task - maintaining (stabilizing) the given speed of the supercharger pumping the gas, figure 2.

Considering the work of the gas compressor unit in the scope of management tasks, we denote the main elements presented in figure 2,

where OK - axial compressor;

KS - combustion chamber;

TVD - high pressure turbine;

ТНД - low pressure turbine;

RK - control valve;

1 - tap No. 1 (compressed gas inlet);

2 - valve No. 2 (compressed gas outlet);

T _i is the temperature of the gas (gas-air mixture) of the i-th measuring point;

P _i is the pressure of the gas (gas-air mixture) of the i-th measuring point;

G _i - gas flow rate (gas-air mixture) of the i-th measuring point;

ω is the shaft speed.

In a gas turbine, fuel gas energy is used to rotate the shaft of an axial compressor (OK) and a high pressure turbine (HPT), compress, heat and move atmospheric air, heat the air in the regenerator and combustion chamber; the enthalpy of a heated mixture of combustion products with excess air is transformed due to adiabatic expansion into the kinetic energy of gases, which in turn is converted through the rotation of the turbine blades of the high-pressure turbine and the supercharger into gas compression work.

In each automatic control system ACS, the operator manually changes the tasks according to the frequency of rotation of the supercharger in such a way as to obtain the required values of the gas pressure (P _out ) or volumetric gas output (Q _out ) parameters at the compressor outlet.

From the joint work of all the gas compressor units of the compressor shop, a hydraulic mode is formed - the value of the total pumped gas through the shop with the required parameters P _out , Q _out . The mode actually represents a gas flow with certain values of the listed parameters. The operator, when setting the rotational speeds of the superchargers, takes into account the boundaries of the GPU and CC equipment. There are dozens of parameters in each gas compressor unit, exceeding the values of which leads to technologically unsafe operating modes of the gas compressor unit. Predicting and preventing such regimes is a laborious task that requires concentration of a person’s attention, especially in situations where a quick, rapid change in frequency tasks is required. To improve the safety and quality of control of the compressor shop equipment, the proposed method solves the problem of organizing automatic control of the compressor shop mode by controlling the frequency assignments of GPU superchargers.

From the patent RU 2181854, a method for controlling the operation of a complex of assemblies of the compressor shop is known, which measures the pressure of the transported gas at the inlet and outlet of the superchargers, the temperature of the transported gas at the inlet and outlet of the superchargers, the rotor speed of the superchargers, the value of the main gas parameter of the compressor shop (pressure or flow rate), which is compared with a given value of the main parameter, and control actions are formed on the fuel supply systems of the drives of gas-pumping units gates (GPA), which are part of the compressor shop, characterized in that the specified values of the rotational speeds of the rotors of the superchargers are determined using static functions, while the pressure of the process gas at the inlet and outlet of the parallel superchargers, the temperature at the inlets and outlets of the superchargers, and the rotational speeds blower rotors determine volumetric productivity, polytropic efficiency and required to provide a given output pressure polytropic compressive power Each compressor, summing up which obtain the required polytropic compression power of the compressor shop, from the polytropic compression power and polytropic efficiency for each unit, determine the mechanical power on the compressor drive shaft, from which the fuel gas flow rate of the gas turbine drive of each unit and the total fuel gas consumption of the compressor are calculated shop, then by repeatedly repeating these actions with enumerating the values of the rotational speeds of the rotors of the superchargers provided that the polytropic compression power of the compressor shop is kept constant and equal to the required polytropic power of the compressor shop, a series of values of the rotor speeds of the blowers are obtained, of which, at a minimum of the total fuel gas consumption of the compressor shop and taking into account the restrictions, choose the one that is considered the optimal frequency reference rotation of the rotors of the superchargers at this step and served in the ACS GPA as a control action, while the functional dependencies for each supercharger continuously parametrically adjusted using the values of the pressure of the transported gas at the inlet and outlet of the supercharger, the temperatures of the transported gas at the inlet and outlet of the supercharger and the fuel gas flow obtained by direct or indirect measurements during operation of the unit.

Unfortunately, this method has the following disadvantages.

The patent states that the work of the considered optimization calculation sometimes leads to the “loss” of technologically acceptable solutions, which requires the termination of the optimization mode and the transition to the load distribution according to the criterion of surge reserves. This disadvantage arises due to the fact that for the optimization calculation it is necessary to take into account the mutual influence of the units, expressing this effect in the form of values of an adjustable parameter and forming additional boundaries of the GPU operation according to the values of all key parameters technologically dependent on changes in the speed of the supercharger.

In the mode control method, the optimization method is applied, which is based on the dependences of the consumed fuel gas and the polytropic power of the gas compressor units. At the same time, the polytropic power characterizes only the useful work of the gas compressor unit (constituting less than 40% of energy costs). Processing incomplete information of the control object reduces the possibility of obtaining the required accurate calculation result.

From patent RU 2219375 a method for controlling the operation of a complex of gas turbine compressor units is known, which consists in measuring the gas pressure at the inlet and outlet of the compressors, the rotor speed of the blowers, the value of the controlled parameter of the gas of the complex of units (pressure, compression ratio or flow rate), which is compared with a predetermined value of an adjustable parameter, and control actions are formed on the fuel supply systems of the drive engines of the compressor units included in the complex of units, characterized in that, based on the difference measured directly or indirectly, the values of the controlled variable (pressure at the output of the compressor unit complex, the compression ratio of the compressor unit complex or the flow rate of the transported gas through the compressor unit complex) with a given value of this value, determine the value by assigning it to the number of employees on the compressor load, the average value of the required rotor speed of the compressor rotor of each compressor unit is obtained, after four o for each compressor unit, according to the measured rotation frequencies of the gas generator shaft of the gas turbine drive, the compressor shaft, the temperature of the combustion products in front of the gas generator turbine and / or the power turbine of the gas turbine drive of the compressor, the pressure behind the compressor of the gas turbine drive, the gas pressure at the compressor inlet and the pressure drop across the compressor confuser stock values up to restrictions on shaft rotation frequencies, temperature of combustion products, pressure in the combustion chamber, pressure at the inlet com the spring and the distance to the compressor surge border, the obtained values lead to the same range of values using normalizing factors, from the normalized values they obtain generalized stock values up to the upper and lower limits for each compressor unit and from the generalized stock values and the average required value of the compressor rotor speed are determined the required value of the rotor speed for each compressor, which is fed to the local ACS of the compressor units as a control its job (action).

Unfortunately, this method has the following disadvantages.

The method does not take into account the maximum allowable load difference between the gas compressor units, expressed in the values of the control parameter, and the link used in the method to the average values of the gas compressor speed in the control zone while simultaneously operating significantly different in technical condition or power of the gas compressor unit, will cause an unaccounted critical load difference between GPA, resulting in loss of stable operation of the GPA. Thus, the method in calculating the regulation boundaries by each gas compressor unit operates with incomplete information, which limits the possible load distribution in the compressor shop and does not allow the optimization method to be applied in the entire allowable range of operation of the units.

Thus, the objective of this invention is to solve the problems inherent in the prior art.

SUMMARY OF THE INVENTION

In the framework of the present invention, the problem is solved by developing a method of load distribution when controlling the hydraulic mode of the compressor shop of gas pumping units, which consists in the fact that in each gas compressor unit the pressure of the transported gas at the inlet and outlet of the superchargers is measured, the temperature of the transported gas at the inlet and outlet of the superchargers, blower rotors, gas pressure differences in blowers, air pressure at the inlet and outlet of axial compressors, air inlet temperature and the output of axial compressors, as well as air temperature behind the recuperators, compressor rotor speeds, turbine fuel gas flow rates, air-gas mixture temperatures in turbine ducts, combustion chambers and recuperators, air-gas mixture pressure in turbine ducts, combustion chambers and recuperators, the values of the main gas parameters of the compressor shop - gas pressure at the outlet of the shop, volumetric capacity of the compressor shop, the degree of gas compression in the compressor shop, commercial productivity s compressor shop, which are compared with desired values of basic parameters, and control actions are generated in an automatic control system for gas pumping units (GPU), a part of the compressor plant. The method is characterized in that the set values of the rotor rotor rotational frequencies are determined by the ratio in the range of permissible load changes of each gas compressor unit taking into account the limitation of the maximum allowable load difference between adjacent gas compressor units, and the arbitrary load ratio specified by the operator is selected and entered into the calculation, or by the included method optimizations calculate the load ratio corresponding to the minimum consumption of fuel gas, to calculate the optimal load ratio apply This is a method of optimizing multidimensional models under constraints, searching for the optimal ratio of supercharger loads over the entire range of permissible frequencies of the superchargers, while taking into account the limitations of the maximum possible difference between the supercharger loads, in calculating the change in the consumption of fuel gas (chemical energy) by the unit is associated with a change in the thermal interaction energies in the turbine , mechanical interaction and gas-dynamic interaction of working media (air flow, fuel flow o and the gas being pumped, the gas-air mixture flow) according to the principle of energy conservation, and the change in these four types of energy using mathematical models is expressed through the change in the parameters characterizing them measured in the ACS of the GPA - working fluid temperatures, working fluid pressures, working fluid pressure drops and rotational speeds turbine shafts, thus, according to the measured data and model dependencies form the main models of energy interaction in the gas turbine engine at the current and a number of possible modes of different frequencies GPA rotations, according to the model of energy interaction, the GPA volumetric and commercial productivity values corresponding to these modes are calculated, as well as fuel gas consumption, the obtained sets of volumetric and commercial productivity values, fuel gas consumption and rotation frequencies are formed into static dependencies, the formed functional static dependencies and constraints are processed by the method of optimization calculation, during the operation of which the frequency of rotation of the supercharger is calculated by nonlinear programming reference frequency fed to the compressor unit control system as a manipulated variable, wherein the maximum permissible operating limits for each HPA is calculated according to the functional dependencies continuously, and formation of the model dependency of the energy balance for the optimization calculation is performed once for the optimization calculation.

The proposed method is devoid of the disadvantages inherent in the solutions of the prior art, due to the following features.

Arbitrary load distribution between the gas compressor units, satisfying technologically possible ratios, allowing expanding the possible load distribution strategies, is ensured by:

a) control of all technological limitations of the operation of each individual gas compressor unit by forming the maximum and minimum permissible values of the rotation frequency of the gas compressor units, using an algorithm for monitoring the allowable load difference between the gas unit, which corrects the maximum and minimum permissible values of the rotation frequency of the gas compressor units;

b) an algorithm for storing and further maintaining a given load ratio;

Explanation

The task of regulating the regime of the compressor shop is inextricably linked with the task of load distribution between the gas compressor units, since the automatic control system self-propelled guns are the executive mechanisms of the mode controller. The load in this case is the rotational speed of the supercharger or its productivity (commercial productivity), which characterizes the useful work of the gas compressor. The complexity of solving the load distribution problem is simultaneously associated with the requirement:

- taking into account the mutual influence of working gas compressor units;

- taking into account the technological features of equipment management that have developed in this compressor shop related to its technical condition, information available on the relationship of the changing parameters of each individual gas compressor unit, information on possible conditions for the parameters to switch to technological, warning and even emergency values, etc. .

The listed features characterize additional computational and algorithmic tasks that require solutions for the full integration of the automatic control system of automatic control units into the automatic control system of the CC level, without which automatic control is possible only in limited cases of coincidence of favorable (for a set of unworked technical solutions) conditions. The regimen-technological tasks of gas transport are inherently multi-criteria. Information on the most effective control criteria in these operating conditions of the workshop and each unit is known to the operator. Therefore, a method has been developed for regulating the basic gas parameters of the compressor shop, which implements a multivariate choice of the ratio of the distribution of loads between units, which is set by the operator or optimization calculation.

II. Improving the accuracy of the optimization calculation is achieved by:

a) the use of functional design dependencies that describe the main types of energy interaction in GPA;

b) the application of the method of nonlinear optimization programming that processes the model of energy interaction in GPA.

Explanation

Optimization of the load distribution between the gas compressor units within the compressor shop in order to reduce the total fuel costs is a well-founded task, which, however, has not been previously solved by widely known optimization methods allocated to the nonlinear programming class.

In general terms, in order to successfully solve the optimization problem, it is necessary to solve two problems:

- describe the behavior of the system in technically possible modes by the model as adequate as possible to the behavior of the optimization object;

- apply an optimization method that allows you to find the most acceptable solution (global minimum).

The first task is solved the more successfully, the more accurately the relationship between the optimized parameter and the array of control actions is taken into account in the model. When optimizing the total fuel gas, which represents the sum of the consumed fuel gas consumption by each gas compressor unit, it is required to determine for each gas compressor unit the relationship between the useful and spent energy under the current operating conditions of the gas compressor unit. The indicated dependencies are formed as a result of an active experiment - according to the set of measured parameters of the object at various fixed speeds of the gas compressor unit and the corresponding fuel gas consumption, in the dependencies there is the possibility of using power as a reference control parameter. The problem is that the obtained functional dependences correspond to the behavior of the object only in the current conditions with constant values of the outdoor temperature, chemical composition of the gas, the density of the pumped gas, and a number of other variable parameters that affect the expended and useful work. Due to the large set of varying parameters and the non-linear effect of these parameters on each other, it is possible to adjust the obtained functional dependence to the changed conditions of the gas compressor unit without performing another active experiment using reliable functional dependencies that take into account the physics of changes in the measured parameters.

The models closest to the behavior of the object are obtained by using the fundamental law of energy conservation. To calculate the energy balance, there are the necessary measuring instruments that transmit data to the automatic control system of the gas compressor and the control center of the control center, therefore it is enough to build calculations of various types of energy in conjunction with the calculation of fuel gas.

To model subsequent changes in energies, it is advisable to rely on the relationship of relative changes (Δ) of parameters relative to the current state, and not to operate with absolute values of energies. This transition also allows you to "bind" the calculation to the current state of the system without any additional computational procedures. As a result, to simulate the behavior of the system, it is required to construct functional dependences between Δω _H and Δ parameters included in the calculation of energies that change with a change in the frequency of rotation ω _H. Functional dependencies make it possible to calculate the energy for all changes of ω _H and as a result to obtain fuel gas consumption by the gas pumping unit at the corresponding speeds of the supercharger in the current conditions of the gas compressor.

The sets of ω _H and G values of _{fuel gas} obtained in this way under the current conditions of the gas compressor _unit are included in the optimization calculation.

The solution of the optimization problem of a multidimensional (in accordance with the number of GPU) model with restrictions by the method of enumerating values is even a difficult task for modern technology, requiring significant technical and time resources.

To solve the optimization problem, in this paper we use any of the nonlinear programming methods, for example, the gradient descent method.

Brief Description of the Drawings

Below the invention is described in more detail by the example of a preferred embodiment disclosed with reference to the attached drawings, in which:

Figure 1 depicts a simplified diagram of a compressor workshop.

Figure 2 depicts a simplified process flow diagram of the GPU.

Figure 3. depicts a block diagram of the operation of the mode controller with the function of optimizing fuel costs.

Figure 4 depicts the formation of the acceptable boundaries of the GPU, KC for four full-pressure GPU.

Figure 5 depicts the operation of the method of calculating permissible frequencies (MPDF).

6 depicts the formation of permissible boundaries for four full-pressure gas compressor units taking into account the maximum load difference.

Fig.7 depicts a field of valid modes, the search for a global minimum.

Fig. 8 depicts a surface of volumetric performance values of the compressor department of two gas compressor units.

Fig.9 depicts the search for the optimal load ratio for two gas compressor units.

Detailed Description of a Preferred Embodiment

The operation of the compressor shop of gas-pumping units is, in accordance with Fig. 1, an organized pumping of natural gas from the inlet to the CC to the out of the CC using a group of gas-pumping units and control systems of the automatic control system of the gas compressor unit, informationally interacting with the automatic control system of the control center. The task for the CC operation, or the task according to the mode, is the requirement to maintain at the output out of the workshop a certain required value P _out or Q _out . In the existing compressor workshops, the value of the mode setting is maintained by a person, the operator, who enters the compressor speed setting into each automatic control unit of the gas compressor unit and controls the reaction at the output of the compressor department, P _out , or Q _out . At the same time, the input of the task according to the rotation frequency is preceded by the analysis by the operator of a number of important technological parameters measured and calculated by each automatic control system of the gas compressor unit, critical changes of which lead to emergency situations. To prevent such changes, the operator relies on previous experience, including knowledge of the real technical condition of each gas compressor unit and its individual components, an approximate knowledge of the relationships between the change in the speed of the supercharger and the change in important technological parameters. In addition to the data listed, the choice of task values is influenced by information received from operators of neighboring compressor shops about a possible upcoming change in the hydraulic mode P _in or О _in , as well as knowledge about the errors and the degree of reliability of the measured and calculated information in the automatic control system of the gas compressor unit and the control system of the control center.

The speed reference value entered in the automatic control system self-propelled guns enters the microprocessor module, which compares it with the current measured frequency value and forms the control action on the fuel gas supply control valve according to the PI control law by the difference between the indicated values.

Fuel gas, burning in the combustion chamber, is mixed with air coming from the regenerator, the resulting gas-air mixture is fed to the blades of a high pressure turbine. Part of the energy of the gas-air mixture is taken away by a high-pressure turbine, the rest is supplied to the blades of the next low-pressure turbine. Energy extraction by a turbine is accompanied by a drop in temperature and pressure of the gas-air mixture. The high pressure turbine and axial compressor have a single shaft. Thus, the part of the energy of the gas-air mixture selected by the HPT is spent on the absorption of atmospheric air by the axial compressor and the movement of this air through the regenerator.

The high pressure pump is connected by a shaft with a supercharger, so the gas-air mixture fed to the high pressure pump blades rotates the supercharger at the same time. At the outlet of the low pressure pump, the gas-air mixture retains a still high value of thermal energy, which is transferred to the injected atmospheric air in the regenerator.

The rotation of the GPU centrifugal supercharger leads to gas suction from the loop of crane No. 1, giving the gas a speed equal to the supercharger rotation speed, and subsequent gas compression in the supercharger diffuser. Compressed gas flows through valve No. 2 to the outlet of the compressor department out.

The information on the measured values of temperatures, pressures, rotational speeds, flow rates, vibration values and axial shift is received in the microprocessor module of the automatic control system of the gas compressor unit, part of the listed measurement parameters is shown in figure 2. The collected information is automatically processed and participates in the algorithms of the automatic control system of automatic control systems, according to it, in the case of approaching some of the technologically important parameters to the warning values, limiting regulators are activated that can block the operator’s task and change the supercharger speed arbitrarily according to limiting control algorithms that prevent an emergency . At the same time, the mode of the compressor shop, respectively, has the ability to change uncontrollably until the ACS of the GPU reaches a safe mode remote from the restriction. Not all technologically important parameters that depend on changes in rotational speeds participate in the warning algorithms of the automatic control system of automatic control units, but most of them, during a critical change, can cause an emergency stop. Therefore, the analysis of the values of the important technological parameters of each gas compressor unit is a mandatory cyclic procedure of the human operator.

Human processing of the entire list of important technological information is impossible in situations requiring urgent action and long-term attention switching. Therefore, a person does not have the ability to control the CC mode with the necessary accuracy and speed. A person, without the availability of appropriate hardware and software, is not able to determine the optimal load ratio between the GPU CC and thereby reduce the consumption of fuel gas by the workshop. In modern conditions, the complication of the gas transmission network, in which the operation of the compressor shops is combined into one main gas pipeline, requires the combination of the compressor shops into a single inter-workshop control system of the compressor station (KS).

Based on a number of the listed reasons at the compressor shop level, the implementation of automatic mode control and load balancing between gas compressor units is relevant.

Description of the operation of the method of controlling the hydraulic mode of the compressor shop with optimal load distribution between gas pumping units

Figure 3 shows the operation of the method of automatic control of the compressor shop. The figure highlights the main components of the compressor shop control that distinguish it from the manual control mode by the CC operator. The value of the task for the mode is selected and entered into the control system ACS either by the operator of the compressor workshop, or by a higher-level control system of the compressor station via information communication channels. The obtained reference value for the control parameter of the compressor workshop enters the control unit, which forms the reference control parameter of the workshop. The selected control reference parameter is one of ΣQ _{workshop productivity} , ΣQ _{commercial. the productivity of the workshop} or Σω _H is supplied to the optimization calculation unit or, if the load distribution optimization is not turned on, the parameter value goes directly to the load distribution unit, in which the load ratios stored at the time the automatic control was switched on by the compressor workshop are saved. The change in the ratio of distributed loads is adjusted in four cases:

- by the operator by turning off the automatic control mode, subsequently setting the rotational speeds of the superchargers to each automatic control system automatic control unit and manually turning on the mode controller;

- a unit for the formation of acceptable limits for the operation of the gas compressor unit and the compressor center if, as a result of the task completion, the gas compressor unit approaches the maximum or minimum possible regulation value;

- introduced a new value of the reference parameter of regulation, in the case when maintaining the current ratio takes the GPA beyond the maximum or minimum possible values of the regulation of sleep;

- a unit for optimizing the load distribution between the gas compressor units.

The boundary formation unit also transmits initial information about a possible change in ω _H relative to the current value to the maximum and minimum boundaries, i.e. two ranges of values are formed from - Δω _{H_i} to + Δω _{H_i} . Further, for each value of this region, with a step of 1 rpm, the change in kinetic, thermal, gas-dynamic energy and loss energy is calculated. The obtained energies of each step are summed and expressed relative to the current value in the change in fuel gas consumption + ΔG _{fuel_i} and _{-ΔG fuel_i} , where i is one of the points in the array of values corresponding to the frequency array in the region (-Δω _{H_i} ; + Δω _{H_i} ). According to the functional dependences for each i-th step, the change ± ΔQ is calculated for the _{capacity of the GPA_i supercharger} and ± Δρ is _{the gas density at the inlet H_i} . The resulting sets of relative values form arrays (± ΔG _{fuel_i} ; ± Δω _{H_i} , ± ΔQ _{GPA_i supercharger productivity} , ± ΔQ _{commercial GPA_i supercharger performance} ). Depending on the selected one of the three reference control parameters, the transition from relative values to absolute values in sets of the array of values (G _{fuel_i} , ω _{H_i} ) or (G _{fuel_i} , Q _{volumetric capacity of the GPA_i supercharger} ), or (G _{fuel_i} , Q _{commercial productivity of the supercharger GPA_i} ). The selected set of arrays of values is approximated.

The procedure is performed for each GPU. Thus, nonlinear model dependencies of the regulation parameter and fuel gas consumption for each gas compressor unit are formed. The obtained functional dependencies go to the optimization calculation block, where, when searching for solutions, the maximum load difference between the units is additionally taken into account. The obtained calculated task values fall into the load distribution unit. Due to the fact that the optimization module calculates tasks in the field of permissible values, the load distribution unit does not perform additional adjustments to the calculated optimal task values.

The load distribution unit additionally verifies that the conditions for the assignment of the loads to their permissible control limits are met. In the event that there is going beyond the regulation border, the task for the gas compressor unit is adjusted at the maximum or minimum possible value. In this case, the difference between the required task of the gas compressor unit and its maximum possible value is distributed between the tasks of neighboring gas compressor units according to the principle of maintaining the load ratio. In the event that several gas treatment units go beyond the control border, their load is accordingly distributed to the remaining gas-compressor units. When all the gas control units have exhausted the regulatory reserves, the maximum possible task values for each gas compressor unit are established, the value of the reference regulation parameter is adjusted in accordance with its maximum permissible value, and the corresponding alarm is given - “CC reached the limit”.

Generated tasks of GPU loads under control by QA _of GPA _productivity or Q _commercial GPA _performance is transferred to the PI controller, which maintains the selected GPA control parameter equal to the specified value through the issuance of control values of ω _N.

Thus, in the automatic control system of the gas compressor unit, the values for setting the frequency of rotation of the supercharger ω _N in the automatic control mode by the compressor workshop are received.

In more detail, the operation of the individual parts of the control method is illustrated by the following figures.

The formation of the acceptable boundaries of the GPU, CC is illustrated by the example in figure 4. The total load, expressed in rotational speeds of the blowers of the four units (Fig. 4), is divided into the field of feasible solutions according to the ratio according to the position of points A1, A2, A3, A4. In figure 4, the position of the point corresponds to the value of the rotational speed of the supercharger between 3600-5100 rpm.

The range of permissible operating modes of each unit is determined by the maximum permissible rotation frequency ω _Hmax and the minimum permissible frequency ω _{Hmin of the} supercharger, obtained by calculating the permissible frequencies (Fig. 5) taking into account additional control parameters.

The method of calculating permissible frequencies (MPDF) establishes the functional relationships between important technological parameters and ω _H. This functional dependence is F (Δx) = Δω _H , where Δx is the change in the value of the process parameter from the current value to its warning value corresponding to the pre-emergency situation.

The obtained values of Δω _{H are} added to the current value of ω _H for calculating the upper permissible control _margin ω _{H_UP_CL} and are subtracted to calculate the lower permissible control _margin ω _{H_LO_CL} . After calculating a number of boundary values, a comparison procedure is performed for both types of boundaries and the smallest value is selected from the set of values of the maximum allowable boundaries and the largest value from the set of values of the minimum allowable boundaries.

The obtained boundaries are formed by calculating the functional dependencies of the main technological parameters of the unit, which determine the individual boundaries of its operation. In the example (figure 4), the upper frequency limits are formed by the parameter Tmax - "temperature behind the low-pressure turbine low pressure turbine", and the lower boundaries are formed by the value of the minimum allowable blower performance. Under other operating conditions, the limiting parameters may be any other GPA that are involved in the calculation of the permissible limits of regulation. If the gas compressor unit has important technological parameters that are not listed in the standard list, such a parameter is added and participates in the calculation of the regulation boundaries of the gas compressor unit. If the gas compressor unit has important technological parameters that are not listed in the standard list, such a parameter is added and participates in the calculation of the regulation boundaries of the gas compressor unit.

In addition to the listed restrictions, which determine the boundaries of each unit according to the MPDC, boundaries are formed taking into account restrictions on the maximum allowable load difference between the superchargers of the workshop Δω _max , for a parallel circuit are shown in the drawings by lines x 1 and x 2.

These lines are constructed for the minimum MIN ω _H (point A1) and maximum MAX ω _H (point A3) from the current speeds of the superchargers. If the condition is met for all GPUs:

MIN ω _H + Δω _max <ω _{H_UP_CL} , then ω _{H_UP_CL} = MIN ω _H + Δω _max .

If the condition is met for all GPUs:

MAX ω _H -Δω _max <ω _{H_UP_CL} , then ω _{H_UP_CL} = MAX ω _H -Δω _max .

If the conditions are not satisfied for the GPA, then the boundaries of this GPU ω _{H_UP_CL} or ω _{H_LO_CL are} not adjusted.

That is, taking into account the maximum permissible load difference between the gas _{compressor units} is an additional restriction for the values of ω _{Н_UP_CL} and ω _{H_LO_CL of the} individual boundaries of the gas _{compressor unit} .

The x 2 line is located above the GPA1-4 temperature limits, so the units will not reach the x 2 limit for the maximum allowable load difference at the upper boundaries. Line x 1 is above the restrictions on the minimum permissible capacity of GPA1-4, therefore, the units are not unloaded to the speed of line x 1, because they will go beyond the limits of the permissible difference in loads. Based on the described, the technological boundaries of collaboration calculated by the MDRC will create a field of acceptable GPA modes, which corresponds to Fig.6.

In the indicated area, it is possible to set a new mode, for example, B1, B2, B3, B4, by the human operator of the control center or by an automatic load balancing algorithm that uses the method of optimizing fuel costs. If the operator introduces a new task, he will thereby establish the load ratio, which the system remembers and maintains over time. In the event that the automatic control system ACS reaches the operation limiter, the support of the adjustable main parameter of the workshop is supported by the unit (s), which has a larger margin for regulation.

In figure 4, the position of points C1, C2, C3, C4 corresponds to the new GPU operation mode, in which point C3 goes beyond the boundaries of the zone of permissible robots of the current mode A1, A2, A3, A4. For the optimization method to work, it is important to evaluate all possible load ratios in order to find the global minimum fuel cost. Therefore, the operation of the MPDF in the mode of optimizing fuel costs is divided into the search for the optimal load ratio in the entire area of permissible GPA modes and the subsequent assessment of the resulting load ratio taking into account the allowable load difference, Fig.7.

An explanation of the principle of finding the optimal load ratio is considered on the example of Fig.8 and Fig.9. In accordance with the figures, the mode of the compressor shop is set by two gas pumping units. The frequencies of rotation of gas pumping units can vary in the range: for gas compressor unit No. 1 from ω _{Н1 min} to ω _{Н2 max} and for gas compressor unit No. 2 from ω _{Н2 min} to ω _{H2 max} . The field of possible tasks of rotation frequencies is limited by the figure ABCDEF on the plane of coordinates of rotation frequencies (ωH1, ω _H2 ). In accordance with the figure of ABCDEF, there is a surface of values of the total productivity of both gas compressor units, equal to Q the _{productivity of the workshop} , limited by points ABCDEF. This surface covers all possible modes of operation of each gas compressor unit, taking into account the allowable difference in loads between the units. The permissible load difference of the figure is limited by the sections of the curves AB and ED. When controlling the mode, it is required to maintain a constant value of Q _{workshop productivity} , i.e. so that the performance is equal to a constant. Thus, on the surface of possible values of the workshop productivity, a segment of the curve of the line L is highlighted, the points of which correspond to the condition Q _{workshop productivity} = const, and this segment corresponds to various combinations of rotation frequencies ω _Н1 and ω _Н2 .

Considering the operation of the units in the coordinates (ω _Н1 , ω _Н2 , ΣG of _{fuel gas} ), (Fig. 9), the curve (Q _{workshop productivity} = const corresponds to the curve ΣG of _{fuel gas} with different values depending on the characteristics of each individual unit at certain rotation speeds Of all the values of this segment ΣG of _{fuel gas,} there is a value at which ΣQ of _{fuel gas} has a minimum combination and the optimal values of ω _H1 and ω _H2 corresponding to this value are in Fig. 9, this point corresponds to the point G _min .

The work of the optimization method is the sequential construction of multidimensional surfaces in the coordinates (ω _Н1 , ω _Н2 , ... ω _HN , Q _{productivity of the workshop} ) and (ω _Н1 , ω _Н2 , ... ω _HN , ΣG _{fuel gas} ), the formation of restrictions in the form of observing the reference parameter constant regulation and restrictions on frequency changes within the ranges of permissible operation of each gas compressor unit, where N is the number of units operating in the CC. The surface of values thus obtained is processed by the nonlinear programming method (the simplest of which is the gradient descent method). The search for the optimization method ends with a set of frequency reference values (ω _H1 , ω _H2 , ... ω _HN ) that enter the load distribution unit of the compressor shop mode controller.

Claims (1)

The method of load distribution when controlling the hydraulic mode of the compressor shop of gas pumping units (GPU), which consists in the fact that in each GPU measure the pressure of the transported gas at the inlet and outlet of the superchargers, the temperature of the transported gas at the inlet and outlet of the superchargers, the pressure drop in the superchargers, the rotor speed blowers, air pressure at the inlet and outlet of axial compressors, air temperature at the inlet and outlet of axial compressors, as well as air temperature behind the recuperators, cha rotational speeds of compressor rotors, gas flow rates of turbines, air-gas mixture temperatures in turbine ducts, combustion chambers and recuperators, gas-air mixture pressure in turbine ducts, combustion chambers and recuperators, also measure the main gas parameters of the compressor shop - gas pressure at the outlet of the shop, volumetric the productivity of the compressor shop, the degree of gas compression in the compressor shop, the commercial productivity of the compressor shop, which is compared with the specified values of the main parameters ditch, and form the control actions in the automatic control systems of the gas compressor units included in the compressor shop, characterized in that the set values of the rotor speeds of the rotors of the superchargers are determined by the ratio in the range of permissible load changes of each gas compressor unit, taking into account the limitation of the maximum permissible load difference between neighboring gas compressor units, at the same time, the arbitrary load ratio specified by the operator is selected and entered into the calculation, or the load ratio is calculated using the included optimization method, respectively There is a minimum consumption of fuel gas, to calculate the optimal load ratio, the method of optimizing multidimensional models with restrictions is used, the search for the optimal load ratio of the blowers is carried out over the entire range of permissible frequencies of the blowers, while taking into account the limitations of the maximum possible difference between the loads of the blowers, in the calculation of the change in the consumption of fuel gas by the unit (chemical energy) is associated with a change in the turbine thermal interaction energies , mechanical interaction and gas-dynamic interaction of working media (air flow, fuel and pumped gas flow, air-gas mixture flow) according to the principle of energy conservation, and the change in these four types of energy using mathematical models is expressed through a change in the parameters measured in the automatic control systems of GPA - operating temperatures environments, working medium pressures, differential pressures of working environments and rotational speeds of turbine shafts, thus, according to measured data and model curves the main models of energy interaction in the gas compressor unit are formed at the current and a number of possible modes of various gas turbine engine rotation speeds, the model of energy interaction is used to calculate the volume and commercial gas generator capacity values corresponding to these modes, as well as the fuel gas consumption, the obtained sets of volume and commercial gas productivity, fuel consumption gas and rotational speeds form in static dependencies, the formed functional static dependencies and The values are processed by the method of optimization calculation, during which the task of the rotational speeds of the superchargers is calculated by non-linear programming, the frequency set is fed to the GPU control system as a control action, while the maximum allowable limits of the operation of each individual GPU are calculated continuously based on the functional dependencies, and the formation of model dependencies of the energy balance sheet for the optimization calculation is performed once for the optimization calculation.

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