Compression system optimization method and a compression system using such a method

Abstract

A method for controlling a compression system is disclosed, specifically designed for a compression train. The compression train includes a variable speed driver unit for mechanical drive applications, a variable speed compressor with an impeller for gas compression, and an inlet guide vanes unit with an actuator. The method involves determining the initial operating state of the compressor based on operating variables, such as rotating speed, positioning angle of the inlet guide vanes, and process mass gas flow rate. The method allows minimizing an operating function of the compression train, based on constraints, to adjust the speed of the driver unit and the position of the inlet guide vanes to achieve an optimized operating state.

Description

Compression System Optimization Method and a Compression System Using such a Method TECHNICAL FIELD

[0001] The present disclosure concerns a compression system optimization method, acompression system that employs this method to enhance the overall efficiency and performance of compression systems. BACKGROUND ART

[0002] In the field of compressor control technology, it is known the use of Compres-sor Inlet Guide Vane (CC IGV) adjustment and variable speed mechanisms to achieve turndown optimization. The adjustment of such variables ensures that a plant operates efficiently across various loads. However, these methods present several technical problems.

[0003] In general, compression trains or compression strings comprise a driver unit,such as a gas turbine\electric motors\other, and a compressor. A first significant tech- nical problem with the compression train controlling methods according to the prior art is that they tend to focus on the optimization of individual components rather than considering the system as a whole. This approach, while it may improve the operation of a single element, such as the compressor, does not necessarily lead to the optimal performance of the entire compression system. The ASV (Anti-Surge Valve) opening avoidance strategy, where the control system adjusts the inlet guide vanes angle (indi- cated by ^^^) or the speed (indicated by ^) to keep the ASV closed as much as pos- sible, exemplifies this issue. It aims to prevent the compressor from operating in surge conditions but does not ensure the compression system is operating at peak efficiency.

[0004] Another issue with prior art is the reliance on a single manipulated variable -either speed ^, or the inlet guide vanes angle ^^^ position, or throttling - to control the compressor throughput. While this might suffice to meet the main plant require- ment, such as maintaining a certain output pressure or a flow rate, it significantly limits the ability to optimize the compression system’s efficiency. The compressor's opera- tion can be sub-optimal if the only consideration is avoiding surge or meeting thethroughput requirement, without taking into account the energy efficiency of the sys- tem.

[0005] A technical problem is then the inability of traditional compressor controlmethods to facilitate compression system optimization in terms of efficiency. Where previous systems have focused on avoiding ASV opening or maintaining basic opera- tional requirements through the manipulation of a single variable, a more comprehen- sive approach would be welcomed in the technology. SUMMARY

[0006] In one aspect, the subject matter disclosed herein concerns a method of con-trolling a compression system, featuring a compression train with a variable speed driver unit for generating power, variable speed compressors with statoric and rotoric assemblies for gas compression, and an inlet guide vanes unit with adjustable vanes and an actuator. This method comprises the steps of determining the initial operating state of the compression train based on operating variables, providing an operating factor to optimize, calculating variations of adjustable operating variables, computing the operating factor based on these variations to satisfy process requirements and min- imize the operating factor, and controlling the operation of the compression train by adjusting the speed of the driver unit and positioning of the inlet guide vanes.

[0007] A further aspect of the present disclosure is drawn to the fact that the operatingfactor comprises one or more weighted operating variables of the compression system. The operating factor is a multivariable factor, calculated using a specific equation in- volving factors like power consumption, pollutant emission, and life consumption of the compression train, each weighted accordingly.

[0008] In another aspect, disclosed herein is a method that includes a step for calcu-lating the variation of the operating factor as a function of varied operating variables, and evaluating if the varied operating factor is optimized based on construction con- straints of the compression train, to determine a new operating state. It is also provided a working curve of the operating factor as a function of the adjustable operating vari- ables, to determine a point on this curve that minimizes the operating factor.

[0009] In another aspect, the subject matter disclosed herein involves calculating var-iations in the speed and positioning angle of the inlet guide vanes and using these cal- culations to maintain a constant compression ratio. Also, the optimized set of operating variables is carried out by finding a point on the working curve that satisfies process requirements and minimizes the operating factor.

[0010] A further aspect of the method disclosed herein is a step of calculating the totalpower consumption of the driver unit, as sum of compression power and power losses.

[0011] In another aspect, the subject matter disclosed herein involves a step for calcu-lating the power consumption in a varied operating state and evaluating the variation in power consumption to determine whether the operating state is optimized. Also, the variation of operating variables and the calculation of the operating factor with at least one constraint is also carried out. This aspect includes steps of checking if the driver unit is steady and repeating the determining step if a steady state is not detected, or proceeding if it is. The method also includes a step of checking if the operating state is near the surge line and proceeding accordingly based on the detection.

[0012] Disclosed herein is also a method wherein the variable speed driver unit is agas turbine.

[0013] A further aspect of the present disclosure is drawn to a compression systemcomprising a compression train with a variable speed driver unit, a variable speed compressor with a statoric and rotoric assembly, an inlet guide vanes unit, a coupling shaft, and an optimization unit with a control logic unit equipped with a software pro- gram for controlling the compression system.

[0014] In another aspect, the compression system includes a gas turbine; the gas tur-bine may be either single or multi shafts and the control unit that controls the GT op- eration us-es the GT control parameters to meet the load flange speed required by the control unit 3. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] A more complete appreciation of the disclosed embodiments of the inventionand many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein: Fig. 1 illustrates a schematic of a compression system according to a first em- bodiment; Fig.2 illustrates a flowchart of the method of controlling the compression sys- tem, according to a first embodiment; Fig.3 illustrates a Cartesian plane having at the abscissa the gas mass flow rate and on the ordinate the compression ratio showing the operating point of the initial operating state of a gas turbine; Fig.4 illustrates a heat ratio map; Fig.5 illustrates a curve of the fuel consumed by a compression train with respect to the N-IGV plane; Fig.6 illustrates the calculated varied operating state; and Fig. 7 illustrates an N / IGV adjustment for optimization to minimize event of process control reaction. DETAILED DESCRIPTION OF EMBODIMENTS

[0016] According to one aspect, the present subject matter is directed to a control sys-tem designed for applications typical of the Oil and Gas industry, which controls both the speed of a drive unit, such as engines including turbines or electric motor, and the positioning of Inlet Guide Vanes (PC_IGV). This dual-modulation control allows for meeting the core operational process requirements and eventually the optimal equip- ment’s requirements when needed.

[0017] The present subject matter features the integration of an optimization algorithmthat dynamically selects the most efficient combination of speed and IGV settings for a set of operational constraints, such as lower energy consumption and / or lower pol- lution. The algorithm analyzes potential speed and IGV configurations and identifies the pair that e.g. minimizes the energy consumption without compromising the opera- tion of the plant.

[0018] Referring now to the drawings, Fig.1 shows a scheme of a compression systemD designed for efficient and optimized control of gas compression processes. The com- pression system D comprises a compression train 1 (or compression string), which is an assembly of components working to compress the gas.

[0019] The compression train 1 comprises a variable speed drive unit 2, engineered togenerate power. This unit can be a gas turbine 2. The gas turbine 2, still referring to Fig. 1, comprises a low pressure power turbine 213 and a gas turbine generator 21, which in its turn comprises a gas-turbine compressor 211, a high-pressure turbine 212, a combustor 22.

[0020] The gas turbine 2, as a driver, converts fuel energy into mechanical energy, andit is used to energize the power turbine low pressure power turbine 213. The operation of a gas turbine 2 is a continuous process. specifically, the gas-turbine compressor 211, which draws in ambient air and compresses it to high pressures. The compressed air, now at high pressure and temperature, is then directed into the combustor 22. In the combustor 22 the high-pressure and high-temperature air mixes and oxidizes the fuel and the combustion products are injected into the high pressure turbine 212 first and then into the low pressure turbine 213 to produce mechanical power to drive the GT air compressor 211 and the low pressure turbine 213.

[0021] The low-pressure turbine 213 is where the kinetic energy of the hot gases isconverted into mechanical energy to rotate, at variable speed, the driven equipment by means of the coupling shaft 6 or load coupling in general. After passing through the turbine 213, the exhaust gases are expelled from the system, often used for additional energy recovery processes, such as in combined cycle power plants or for heating pur- poses.

[0022] The compression train 1 also comprises a variable speed process compressor4, equipped with a process statoric and rotoric assembly 41. The process statoric and rotoric assembly 41 is responsible for compressing the process gas by reducing its volume, thereby serving as the primary component in the gas compression process.

[0023] The process statoric and rotoric assembly 41 may comprise a plurality of im-pellers or diffusers, and the like.

[0024] Specifically, the operation of the variable speed process compressor 4 involvesseveral components in addition to the process statoric and rotoric assembly 41, such as a plant suction equipment 42, and plant discharge equipment 43.

[0025] The variable speed process compressor 4 operating process starts with the suc-tion equipment 42, which comprises isolation valves and gas scrubber and other pro- cess equipment. (not shown in the figure). The suction equipment 42 is responsible for isolating, pressurizing, and cleaning processed gas.

[0026] The process statoric and rotoric assembly 41 is designed to impart kinetic en-ergy to the gas. It is driven by the variable speed driver unit 2, through the coupling shaft 6.

[0027] After passing through the process statoric and rotoric assembly 41, the high-pressure process gas reaches the discharge equipment 43, which typically comprises gas coolers, isolation valves and check valves (not shown in the figure). Gas coolers are used to remove heat generated during compression, thereby reducing the tempera- ture of the compressed gas.

[0028] The compression train 1 comprises also an inlet guide vanes unit 5. The inletguide vanes unit 5 comprises variable inlet guide vanes 51, positioned at the entrance of the variable speed process compressor 4. The inlet guide vanes 51 direct the com- pressed gas flow into the process statoric and rotoric assembly 41 of the variable pro- cess compressor 4. An actuator 52, connected to the inlet guide vanes 51, allows for adjustment of the gas flow direction.

[0029] The coupling shaft 6, as said, mechanically connects the variable speed driverunit 2 and the variable speed process compressor 4, transmitting the generated torque from the driver unit 2 to the variable speed process compressor 4. This ensures a seam- less transfer of energy, facilitating the continuous operation of the variable speed pro- cess compressor 4.

[0030] The compression system D comprises also the optimization unit 3, which isoperatively connected to the actuator 52. The optimization unit 3 is capable of adjust- ing the speed setpoint of the gas turbine 2 by a control logic unit 31 equipped with a software program that embodies the steps of the method of controlling the compression system D, as better specified below.

[0031] The control logic unit 31 can be implemented in several ways.

[0032] In one embodiment, the control logic unit 31 can be implemented as a program-mable microprocessor, which is a compact and highly efficient option. Microproces- sors offer high processing speeds and can be customized for specific control tasks.

[0033] In another embodiment, the control logic unit 31 can be a PLC (ProgrammableLogic Controller). On the other hand, the PLC is specifically designed for industrial control applications, making it a robust and reliable choice. PLCs are known for their durability and resistance to harsh industrial environments, including vibrations, tem- perature variations, and electrical noise.

[0034] In some other embodiments, the control logic unit 31 can be integrated in acomputer, thus offering the most flexibility and computational power among the alter- natives.

[0035] The optimization unit 3 also comprises an inlet guide vanes position control32, which is an actuator 32 and a speed actuator 33. The guide vanes position control 32, operatively connected to the control logic unit 31, controls the actuator 52 to adjust the position of the inlet guide vanes 51.

[0036] The speed actuator 33, also connected to the control logic unit 31, operates thegas control valve 34 to control the fuel injected by the fuel nozzles 22 to adjust the speed of the gas turbine 2. Specifically, the output of the speed actuator 33 will deter- mine the speed setpoint of the gas turbine generator 21. Thus, the output of the speed actuator 33 will enter the gas turbine controller, which will determine the control val- ues so that the gas turbine generator 21 can operate according to its operating mode.

[0037] The compression train 1 operates as follows.

[0038] Referring now to Fig. 2, a flow chart of the method 100 of controlling a com-pression system D according to the optimization algorithm mentioned above is shown. The controlling method 100 comprises several steps and it is run by the control logic unit 31, to control the actuator 52 of the inlet guide vanes 51 and the fuel injected by the fuel nozzles 22 into the gas turbine 2 (or the variable speed driver unit 2 in general).

[0039] Initially, the controlling method comprises the first step of determining 110 theinitial operating state ^^^of the compression train 1.

[0040] The general operating state ^^ of the compression train 1 is determined byoperating variables, which, in the present embodiment of the method 100, comprise the rotating speed ^ of the coupling shaft 6, the positioning angle ^^^ of the inlet guide vanes 51, and the process gas mass flow ^. These operating data can be retrieved through various sensor technologies that measure these variables in real-time. As men- tioned above, the inlet guide vanes position control 32 provide the set point of the system compression system D.

[0041] For instance, several types of sensors are commonly used to detect the rota-tional speed of the coupling shaft 6 of the gas turbine 2, such as: -flow element for flow measurement, for example one of those described by theIEC 5167 standard, such as a Venturi or orifice; -magnetic pick-up sensors, capable of detecting the speed of a shaft by sensingthe passage of gear teeth or metal targets using a magnetic field; -optical sensors, which use a light source and a photodetector to sense the pass-ing of a marked disc attached to the shaft; -Hall effect sensors, which detect the presence of a magnetic field generated bya magnet attached to the shaft; or -piezoelectric sensors, which can be used to detect the vibrational frequenciesof a shaft, which can be correlated with rotational speed.

[0042] Fig. 3 shows the operating point of the initial operating state ^^^ plotted on aCartesian plane having at the abscissa the gas flow rate ^ and on the ordinate the com- pression ratio ^^of the gas turbine 2. Given the curve of the positioning angle ^^^^of the inlet guide vanes 51, the operating point of the initial operating state ^^^is deter- mined by fixing the speed of the gas turbine ^^. The typical measures of such operating variables are: N0 [rpm]; IGV0 [deg A]; and G0 [kg / s].

[0043] The controlling method 100 also comprises the step of providing or calculating130 an operating factor to be optimized. In one embodiment, the operating factor to be optimized is a multifunctional operating factor or ^^^. In this case, the controlling method 100, as mentioned, coordinates the adjustment of the rotating speed ^ of thecoupling shaft 6 and the positioning angle ^^^ of the inlet guide vanes 51 to optimize a multifunctional objective ^^^ weighted principally on following multiple operating factors:^^^ = ^^^^ + ^^^^^^^^ + ^^^^^^^^ + ^^^^^^^^^^where: -^^ is the compression train or string power consumption;- ^^^^ is NOx produced and emitted;- ^^^^ is the pollutant emission; and- ^^^^^ is the life consumption of the compression train 1.

[0044] In general, the weights ^^ are different from zero. In some embodiment at leastone of the weights ^^may be equal to zero. In some other embodiment, two of the weights ^^may be equal to zero.

[0045] Specifically, the two degrees of freedom of the variable speed, and variableIGV are used to satisfy process requirements and to maximize the above multifunc- tional objective. The weights ^ are evaluated against specific requirements, which can be set by the operator depending on the needs.

[0046] The gas turbine 2 illustrated in Fig. 1 is used as an example, also for the opti-mization procedure described below. But the same optimization algorithm can be used with any kind of variable speed driver unit, including, for instance, steam turbine, VSD, a fixed speed motor with a variable ratio gearbox, , hydraulic torque converters, or any variable speed drivers.

[0047] In another embodiment, such as the one disclosed in the following, the operat-ing factor to be minimized is the total power consumption ^^^^^(which corresponds to the factor ^^of the multifunctional objective ^^^ expression). In other words, in the embodiment at issue, the method 100 of controlling a compression system D ad- dresses the calculation of power consumption ^^^^^^of the driver unit 2 as a parameter to be optimized, as discussed in the following.

[0048] The power consumption ^^^^^^is determined by the sum of two components: the compression power ^^^^and the power losses ^^^^^^^^of the speed variable speed process compressor 4, namely

[0049] The compression power ^^^^refers to the amount of power used by the variable speed process compressor 4 specifically for the process of compressing the gas. On the other hand, the power losses ^^^^^^^^account for the energy that is used in the com- pression system D but does not contribute directly to the compression of the gas. These losses can occur due to a variety of factors, such as friction, heat dissipation, and inef- ficiencies in the mechanical and electrical components of the compression system D.

[0050] As mentioned, the sum of these two components,gives a comprehensive picture of the power consumption ^^^^^^of the speed variable speed process compressor 4.

[0051] The check of the driver unit 2 is carried out in step 120 of the Fig. 2.

[0052] In the variation calculation step 140 the variation of operating variables ^, ^^^with at least a constraint, which in the case at issue is the process gas mass flow rate ^. In fact, modifying ^^would mean modifying the general process regulation. The method 100 involves adjusting these variables to optimize the compression train’s op- eration minimizing, in the present embodiment, the total power consumption ^^^^^^, keeping ^^, namely in the present embodiment, the process mass flow rate, is constant. In other embodiment, the target variable to be minimized can be a weighted linear combination of a plurality of variables, above indicated with ^^^.

[0053] As an example, in the case of PGT25 gas turbine 2, the calculation of the ex-pected heat ratio (^^) is carried out through the ^^ map illustrated in Fig.4, as fol- lows: ^^^^^^ [^^] = ^^^ [^^] + ^^^^^^^ [^^]^^^ = ^(^^^^^,^,^^^^)^^^^^ = ^ ^^^^^ × ^^^where ^^^^is the ambient temperature. By determining the ^^ coefficient the total consumed power ^^^^^can be determined. The abscissa of Fig. 4 is the output shaft speed (as a percentage of a reference), while the ordinate is the output shaft power (asa percentage of a reference), at the ambient temperature of 40°C. The heat rate ^^ point on the graph is not yet close to the Max Power curve.

[0054] Coming back to Fig. 2, the variation calculating 140 step involves a series ofequations and adjustments, beginning with the modification of the adjustable operating (which are a subset of the operating variables ^, ^^^, and ^) speed ^ of the variable speed process compressor 4. In this process, the initial speed ^^is varied by a change ^^ to arrive at a varied speed ^^. Similarly, the angular position of the inlet guide vanes ^^^, initially at ^^^^, is adjusted by an amount ^^^^ to achieve a varied posi- tion ^^^^. These adjustments allow for achieving the desired operational characteris- tics of the compressor. Normally, e.g. by non-dimensional analysis or equivalent com- pressor model, the decrement of inlet guide vanes angle ^^^ that cancels an increment of speed ^ in terms of pressure ratio once mass flow ^ is kept constant is determined. The set of equations carried out by the control logic unit 31 are the following in the embodiment disclosed^^ = ^^ + Δ^^^^^ = ^^^^ − Δ^^^^^(^^, ^^^^,^^) = ^^(^^, ^^^^,^^)where ^^(^, ^^^,^) is the compression ratio. It is noted that in the calculation of thevariation, the algorithm keep ^^constant. The calculation determines the variation of the speed ^ and the positioning angle ^^^, without varying the compression ratio ^^.

[0055] Calculated variation ∆^ and ∆^^^ defined above, which at this stage are onlycalculated and do not imply any physical actuation, allow to identify an additionalpoint trajectory ^ in ^ − ^^^ plane, as shown in Fig. 5, where the third (vertical) axisreports the fuel consumed by the compression train 1 ^^^^. Each point of trajectoryshown in Fig. 5 satisfies the process requirement. The optimization procedure is de- fined to find the point of ^ that minimizes total power requirements as mentioned above.

[0056] In general, each point of the trajectory of the working curve T shown in Fig. 5satisfies a process requirement. The optimization procedure is defined to find the point of the curve T that minimizes total power requirements.

[0057] After the variation calculation step 140, the controlling method 100 comprisesa checking step 150 to determine the proximity of the operating state ^^ of the variable speed process compressor 4 to the surge line.

[0058] The surge line is a predefined threshold in the operating parameters of the var-iable speed process compressor 4, beyond which the variable speed process compres- sor 4 may be unstable, leading to potential damage or failure.

[0059] If, during the checking step 150, it is determined that the operating state ^^ isin a steady state and the variable speed process compressor 4 is operating at a safe distance from the anti-surge control line, the process proceeds to the next step of de-termining the optimized set of operating variables 160 ^, ^^^, better explained below.On the other hand, if the checking step 150 reveals that the operating state ^^ is close to or approaching the surge control line, which is the line where the anti-surge valve (ASV) opens with negative effects on the efficiency, crossing a presettable threshold, the controlling method 100 shifts to the output controlling step 170 (see below). The determining step 160 comprises specific sub-steps focused on optimizing the operation of the variable speed process compressor 4, determining if the operating factor is max- imum or not. Thus, the steps carried out are a calculating 161 the operating factor in the state corresponding to the varied operating state ^^^, and then calculating 162 the operating factor is carried out, to check if it is at a minimum or not (optimal consump- tion for the embodiment at issue). In other words, the operating factor ^^^ or ^^^^calculating step 160 is carried out with at least a constraint.In the embodiment dis- closed, the first sub-step of the determining step 160 comprises the step of power con- sumption calculation 161, where the power consumption ^^^^^of the variable speed process compressor 4 in a varied operating state ^^^is calculated, where the varied operating state ^^^is shown in Fig.6. As it can be seen, the varied operating state ^^^is very close to the initial operating state ^^^, also, the initial curve of the positioning angle ^^^^is now shifted in the curve of the varied angle ^^^^. This calculation is achieved through the equation^^^^^ = ^^^^^− ^^^^ ^where ^^^^^is the power loss in the current varied operating state ^^^, and ^^^^^is the power loss in the initial operating state. The calculation ofi.e., the change in power loss, allows determining the variation in operating parameters affects the sys- tem’s efficiency.

[0060] The determining step 160 comprises also the step of power consumption cal-culation 162, where the variation of power consumption ^^^^^is calculated, so that if ^^^^^is greater than zero, then the current changes have led to an increase in power consumption. In response, the speed ^ is reduced, and the positioning angle ^^^ of the inlet guide vanes 51 is increased. This adjustment aims at reducing the total power consumption, thus continuing the optimization process.

[0061] Conversely, if ^^^^^ is less than zero, it implies that the recent simulated ad-justments would successfully decrease power consumption. In this case, the speed ^ would be increased, and the positioning angle ^^^ would be decreased, still according to the simulations. The continuous monitoring and adjustment of these parameters al- lows for achieving the optimized performance.

[0062] In case of ^^^^^ is approximately zero, then the operating state ^^^ (namely^^^in the case at issue) of the variable speed process compressor 4 is already opti- mized with respect to power consumption. Therefore, no further variations or incre- ments in the operating variables are required. This state represents an ideal balance, where the variable speed process compressor 4 operates at optimized efficiency.

[0063] Finally, the controlling step 170 for controlling the operation of the compres-sion train 1 involves adjusting the speed ^ of the variable speed driver unit 2 and positioning the actuator 52 to adjust the position of the inlet guide vanes 51 if the variation of the operating factor (the ^^^^^) is different from zero. This step might employ real-time control systems that can rapidly respond to changes in operating con- ditions and maintain optimal performance.

[0064] In the embodiment disclosed, this procedure step (step (170) outputs the posi-tion command to both speed ^ and ^^^ for the current scan, as follows. The speed regulator setpoint is set to^^^^ = ^^ − ∆^ × ^^^^^ × ∆^^^^and IGV positioner is set to^^^^^^ = ^^^^ + ∆^^^ × ^^^^^ × ∆^^^^

[0065] In case ∆^^^^ = 0, ^^^ and ^ are not moved by optimization strategy. Insteadwith ∆^^^^ ≠ 0, optimization will move ^^^ and speed ^, with a rate also defined by^^^^^parameter.

[0066] The procedure is executed in a time interval Δ^ of a few milliseconds, such as40 milliseconds.

[0067] Referring back to the checking step 150, if the current operating state ^^ of thevariable speed process compressor 4 is close to the surge line step, the controlling method 100 comprises finally the step of keeping a minimum distance to the surge control line (SCL) closing the inlet guide vanes 51, by appropriately setting the ^^^ and canceling the reaction through increasing speed ^ as follows, setting the speed regulator, and the ^^^ positioner, as follows^^^^ = ^^ + ∆^ × ^^^^

[0068] After the output controlling step 170, the procedure restart from the first stepof determining 110 the current state of the compression train 1, which becomes the initial operating state ^^^of the optimization procedure.

[0069] Finally, Fig. 7 shows ^ / ^^^ adjustments for optimization minimize event ofprocess control reaction, due to the positioning angle ^^^ adjustment is calculated to cancel the speed ^ adjustment. Instead, in case process control reacts requiring ^ / ^^^ manipulation, process control output is balanced between the speed ^ and the posi-tioning angle IGV introducing a gain on the positioning angle ^^^ branch to equalizethe speed ^ and the positioning angle ^^^ reaction as in the scheme of Fig. 7. For process control, an incremental PID is used which requires an integrator (1 / s) in the output.ADVANTAGES

[0070] An advantage of the preset disclosure is that it considers multiple variables andtheir impact on the entire compressor string, allowing for a more nuanced control that can optimize the system’s efficiency. This comprehensive control strategy not only prevents the compressor from operating in undesirable conditions but also ensures that the entire string of equipment works together in the most energy-efficient manner pos- sible.

[0071] Another advantage of the present disclosure is the capability of simultaneouslymanage multiple aspects of the compressor string’s operation, which represents a sig- nificant step forward from the prior art, addressing the critical need for energy-efficient and optimized compressor control in industrial settings.

[0072] While aspects of the invention have been described in terms of various specificembodiments, it will be apparent to those of ordinary skill in the art that many modi- fications, changes, and omissions are possible without departing form the spirit and scope of the claims. In addition, unless specified otherwise herein, the order or se- quence of any process or method steps may be varied or re-sequenced according to alternative embodiments.

[0073] Reference has been made in detail to embodiments of the disclosure, one ormore examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclo- sure. Reference throughout the specification to “one embodiment” or “an embodi- ment” or “some embodiments” means that the particular feature, structure or charac- teristic described in connection with an embodiment is included in at least one embod- iment of the subject matter disclosed. Thus, the appearance of the phrase “in one em- bodiment” or “in an embodiment” or “in some embodiments” in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0074] When elements of various embodiments are introduced, the articles “a”, “an”,“the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0075] The subject matter described herein can be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including the structural means disclosed in this specification and structural equivalents thereof, or in combi- nations of them. The subject matter described herein can be implemented as one or more computer program products, such as one or more computer programs tangibly embodied in an information carrier (e.g., in a machine-readable storage device), or embodied in a propagated signal, for execution by, or to control the operation of, data processing apparatus (e.g., a programmable processor, a computer, or multiple com- puters). A computer program (also known as a program, software, software applica- tion, or code) can be written in any form of programming language, including com- piled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily corre- spond to a file. A program can be stored in a portion of a file that holds other programs or data, in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub-programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a com- munication network.

[0076] The processes and logic flows described in this specification, including themethod steps of the subject matter described herein, can be performed by one or more programmable processors executing one or more computer programs to perform func- tions of the subject matter described herein by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus of the subject matter described herein can be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific inte- grated circuit).

[0077] Processors suitable for the execution of a computer program include, by wayof example, both general and special purpose microprocessors, and any one or moreprocessors of any kind of digital computer. Generally, a processor will receive in- structions and data from a read-only memory, or a random access memory, or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-opti- cal disks, or optical disks. Information carriers suitable for embodying computer pro- gram instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, (e.g., EPROM, EEPROM, and flash memory devices); magnetic disks, (e.g., internal hard disks or removable disks); mag- neto-optical disks; and optical disks (e.g., CD and DVD disks). The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0078] To provide for interaction with a user, the subject matter described herein canbe implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, (e.g., a mouse or a trackball), by which the user can provide input to the computer. Other kinds of devices can be used to provide interac- tion with a user as well. For example, feedback provided to the user can be any form of sensory feedback, (e.g., visual feedback, auditory feedback, or tactile feedback), and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0079] The techniques described herein can be implemented using one or more mod-ules. As used herein, the term “module” refers to computing software, firmware, hard- ware, and / or various combinations thereof. At a minimum, however, modules are not to be interpreted as software that is not implemented on hardware, firmware, or rec- orded on a non-transitory processor readable recordable storage medium (i.e., modules are not software per se). Indeed “module” is to be interpreted to always include at least some physical, non-transitory hardware such as a part of a processor or computer. Two different modules can share the same physical hardware (e.g., two different mod- ules can use the same processor and network interface). The modules described herein can be combined, integrated, separated, and / or duplicated to support various applica- tions. Also, a function described herein as being performed at a particular module can be performed at one or more other modules and / or by one or more other devices insteadof or in addition to the function performed at the particular module. Further, the mod- ules can be implemented across multiple devices and / or other components local or remote to one another. Additionally, the modules can be moved from one device and added to another device, and / or can be included in both devices.

[0080] The subject matter described herein can be implemented in a computing systemthat includes a back-end component (e.g., a data server), a middleware component (e.g., an application server), or a front-end component (e.g., a client computer having a graphical user interface or a web browser through which a user can interact with an implementation of the subject matter described herein), or any combination of such back-end, middleware, and front-end components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a com- munication network. Examples of communication networks include a local area net- work (“LAN”) and a wide area network (“WAN”), e.g., the Internet.

Claims

Compression System Optimization Method and a Compression System Using such a Method CLAIMS 1. A method (100) of controlling a compression system (D), wherein the compression system (D) comprises a compression train (1), in its turn comprising: a variable speed driver unit (2), configured to generate power; one or more variable speed process compressor (4), each one having at least a process statoric and rotoric assembly (41) to compress a gas by reducing its volume; and an inlet guide vanes unit (5) per variable speed process compressor (4), com- prising variable inlet guide vanes (51), arranged at the entrance of the rele- vant variable speed process compressors (4), and an actuator (52), connected to the inlet guide vanes (51), for adjust- ing the direction of the compressed gas flow into the process statoric and ro- toric assembly (41) of the variable speed process compressor (4); wherein the controlling method (100) comprises the steps of: determining (110) an initial operating state (^^^) of the compression train (1),defined by one or more operating variables (^^, ^^^^,^^);providing (130) an operating factor (^^^,^^^^) to be optimized; calculating (140) a variation of one or more adjustable operating variables(^, ^^^);calculating (160) the operating factor (^^^,^^^^) based on the varied oneor more operating variables (^, ^^^) to satisfy process requirements and minimize theoperating factor (^^^,^^^^) and determining a possible new operating state (^^^,^^^^^); and controlling (170) the operation of the compression train (1) by adjusting the speed of the variable speed driver unit (2) in accordance with the rotating speed (^^,^^^^) of the new operating state (^^^,^^^^^), and by positioning the actuator (52) to adjust the position of the inlet guide vanes (51) in accordance with the newpositioning angle (^^^^, ^^^^^^) of the new optimized operating state (^^^,^^^^^);wherein the operating variables (^, ^^^,^) comprise, the rotating speed (^)of the variable speed process compressor (4), the positioning angle (^^^) of the inlet guide vanes (51), and the gas flow rate (^), and wherein the adjustable operating variables (^, ^^^) are a subset of the oper-ating variables (^, ^^^,^).

2. The method (1) according to the preceding claim, wherein the oper- ating factor (^^^) is comprised of one or more weighted operating variables of the compression train (1).

3. The method (100) according to the preceding claim, wherein the op- erating factor (^^^) is a multivariable factor, calculated according to the following equation: ^^^ = ^^^^ + ^^^^^^^^ + ^^^^^^^^ + ^^^^^^^^^^where: - ^^is the compression string power consumption; - ^^^^is the emission of NOx; - ^^^^is a pollutant emission; - ^^^^^is a life consumption of the compression train (1); and - ^ are weights.

4. The method (100) according to any one of the preceding claims, wherein the determining (160) step, comprises the following sub-steps: calculating (161) the variation of the operating factor (^^^,^^^^) to be op-timized as a function of the varied one or more adjustable operating variables (^, ^^^),and valuating (162) if the varied operating factor (^^^,^^^^) is optimized based on a set of construction constraints of the compression train (1), such as power, vol- umes, pressures and the like, to determine the new operating state (^^^^^) if the op- erating factor (^^^,^^^^) is optimized.

5. The method (100) according to the preceding claim, wherein the val- uating step (162) comprises the sub-steps of:providing a working curve (T) of the operating factor (^^^,^^^^) as a func-tion of the adjustable operating variables (^, ^^^); anddetermining a point of the working curve (T) that minimizes the operating factor (^^^,^^^^).

6. The method (100) according to any one of the preceding claims, wherein the variation of the speed (^) and the variation of the positioning angle (^^^) of the inlet guide vanes (51) calculated in the variation calculating (140) step com- prises the following steps: ^^ = ^^ + Δ^^^^^ = ^^^^ − Δ^^^^^(^^, ^^^^,^^) = ^^(^^, ^^^^,^^)wherein: ^ is the speed of the variable speed process compressor (4); ^^^ is the angular position of the inlet guide vanes (51); and^^(^, ^^^,^) is a compression ratio.

7. The method (100) according to claim 5, wherein the optimized setof operating variables (^, ^^^) determination step (160) is carried out by determininga point of the working curve (^) that satisfies process requirement, wherein the opti- mization procedure is defined to find the point that minimize the operating factor (^^^,^^^^).

8. The method (100) according to any one of the preceding claims, wherein in the providing step (130) the power consumption (^^^^^) of the driver unit (2) is calculated.

9. The method (1) according to the preceding claim, wherein the power consumption (^^^^^^) of the driver unit (2) in an operating state (^^^) is calculated as:wherein: ^ is an index of the state;^^^^^^is the power consumption of the variable speed process compressor (4); ^^^^is the compression power of the variable speed process compressor (4); and ^^^^^^^^is the power loss of the variable speed process compressor (4).

10. The method (100) according to any one of the preceding claims, wherein the determining (160) step, comprises the following sub-steps: calculating (161) the power consumption (^^^^^^) of the speed variable speed process compressor (4) in the varied operating state (^^^), in accordance with the fol- lowing equation: Δ^^^^ = ^ ^^^ − ^^^^ ^^calculating (162) the variation of the power consumption (Δ^^^^), so that: if Δ^^^^ > 0, then a decrement of speed (^) and increment of the positioningangle (^^^) decreases total power, such that optimization is continued; if Δ^^^^ < 0, then an increment of speed (^) and decrement of the position-ing angle (^^^) decreases total power, such that optimization is continued; and if Δ^^^^ ≈ 0, then the operating state (^^^) is already optimized, such thatno additional variations / increments are required.

11. The method (100) according to any one of the preceding claims, wherein the variation of one or more operating variables (^, ^^^) in the cal-culating (140) is carried out with at least a constraint (^^); and wherein the operating factor (^^^,^^^^) calculating step (160) is carried out with at least a constraint (^^).

12. The method (100) according to any one of the preceding claims, wherein between the determining step (110) and the providing step (130), the follow- ing steps are executed: checking (120) that the driver unit (2) is steady by reading the initial operating state (^^^);if a steady state is not detected (120), then the determining step (110) is re- peated, else, if the steady state is detected (120), the calculating step is carried out.

13. The method (100) according to any one of the preceding claims, wherein after the variation calculation (140) step, the step of checking (150) if the operating state (^^) is near the surge line, such that, if a steady state is detected, with the variable speed process compressor (4) operating state (^^) far from anti-surge con- trol line of a presettable threshold, then the optimized set of operating variables (^, ^^^) determination (160)step is carried out and the controlling (170) step is carried out; else the calculation (180) of the outputs when near the surge line is carried out.

14. The method (100) according to any one of the preceding claims, wherein the variable speed driver unit is a gas turbine (2).

15. The method (1) according to the preceding claim, when depending on claim 11, wherein a constraint is the gas flow rate (^) of the gas turbine (2).

16. A compression system (D) comprising a compression train (1) in its turn comprising: a variable speed driver unit (2), configured to generate a power; a variable speed process compressor (4) having a process statoric and rotoric assembly (41) to compress a gas by reducing its volume, and an inlet guide vanes unit (5), comprising inlet guide vanes (51), arranged at the entrance of the variable speed process compressor (4), and an actuator (52), connected to the inlet guide vanes (51), for adjust- ing the direction of a compressed gas flow into the process statoric and rotoric assembly (41) of the variable speed process compressor (4); a coupling shaft (6), mechanically connecting the variable speed driver unit (2) and the variable speed process compressor (4), for transmitting the torque gener- ated by the variable speed driver unit (2) to the variable speed process compressor (4); andan optimization unit (3), operatively connected to the actuator (52) and capa- ble of adjusting the speed of the variable speed driver unit (2) and comprising a control logic unit (31) equipped with a software program comprising the steps of the method of controlling the compression system (D) according to any one of claims 1-15.

17. The compression system (D) according to the preceding claim, wherein the variable speed driver unit (2) is a gas turbine.

18. The compression system (D) according to the preceding claim, wherein gas turbine (2) comprises a gas turbine generator (21), comprising a gas-generator compressor (211), a high-pressure turbine (212), and a combustor (213).

19. The compression system (D) according to any one of claims 17 or 18, wherein the gas turbine comprises fuel nozzles (22), to inject fuel into the combustor (213), and wherein the optimization unit (3) comprises: a guide vanes position control (32) operatively connected to the con- trol logic unit (31), configured to control the actuator (52), to adjust the posi- tion of the inlet guide vanes (51); and a speed actuator (33) operatively connected to the control logic unit (31), configured to control the fuel injected by the fuel nozzles (22) to adjust the speed of the gas turbine (2).

20. The compression system (D) according to any one of claims 16-19, wherein the variable speed process compressor (4) comprises: plant suction equipment (42), such as filters and / or air intakes, for sucking a suitable mix of air; and plant discharge equipment (43), comprising heat exchangers, aftercoolers, moisture separators, and / or discharge valves.

21. Computer program comprising instructions that, when the programis executed by the control logic unit (2) of the compression system of any one of the claims 16-20, cause it to execute the steps of the method according to any one of the claims 1-15. 22 Computer-readable storage medium comprising instructions which, when executed by the control logic unit (2) of the compression system of any one of the claims 16-20, cause the execution of the method steps by it according to any one of the claims 1-15.

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