EP2598754A1

EP2598754A1 - Method for controlling a compressor

Info

Publication number: EP2598754A1
Application number: EP11757265.1A
Authority: EP
Inventors: Georg Winkes
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2010-09-09
Filing date: 2011-09-09
Publication date: 2013-06-05
Also published as: US20130173063A1; CN103097737A; RU2013115761A; DE102010040503A1; WO2012032164A1; RU2570301C2; CN103097737B; DE102010040503B4

Abstract

The invention relates to a method for controlling a compressor (10). In order to achieve high efficiency, it is proposed that the method have the following steps: a transmission of at least one nominal value (12) of a parameter (14) of the compressor (10), b determination of at least two actuation values (16, 18, 20, 90) of at least two actuating elements (22, 24, 26, 94) of the compressor (10) on the basis of the nominal value (12), c determination of a model-based theoretical state of the compressor (10) on the basis of the actuation values (16, 18, 20, 90), d iterative correction of at least one of the actuation values (16, 18, 20, 90) depending on the theoretical state, e control of at least one of the actuation elements (22, 24, 26, 94) on the basis of an actuation value (16, 18, 20, 90).

Description

description

Method for controlling a compressor

The invention relates to a method for controlling a compressor.

Compressors for providing compressed gas for industrial purposes are usually controlled by means of one or more maps. From DE 195 06 790 A such a method for controlling a compressor is known, in which by means of sensors of the compressor actual values of the

Compressor are measured and from these measurements and a default value for the throughput, the isentropic

Compressor work and the inlet flow rate is determined. Using a map stored in a computer efficiency-optimized control values for the angular positions of the nozzles during operation of the compressor are gradually adjusted.

From EP 1 069 314 AI a compressor control known. EP 1 069 314 A1 proposes for this purpose a setpoint value,

for example for a mass flow of the compressor,

provide. Based on two maps of the compressor, two control values are determined from this, for example a lead-in row angle and a set value for a valve lift. By means of these two manipulated variables as setpoint values of two regulators, the (on) control of the compressor or the adjustment of the pilot row and the valve of the compressor then takes place.

US 2009/0274565 A1 discloses a method for controlling a compressor, in which current measured values for three parameters of the compressor are determined. Based on three characteristics of the compressor - each map describes the relationship between two of these parameters - working points of the compressor are determined for the current measured values. It is an object of the present invention to provide a

To provide control of a compressor with which a good efficiency is achieved.

The object is achieved by the features of claim 1. Cheap designs and

Advantages of the invention will become apparent from the others

Claims, the drawing and the description.

The invention is based on a method for controlling a compressor. According to the invention, the method comprises the following steps:

a providing at least one setpoint of a parameter of the compressor,

b determination of at least two control values at least

two actuating elements of the compressor based on the

Setpoint,

c determination of a model-based theoretical state of the compressor based on the control values,

d iterative correction of at least one of the control values in

Dependence on the theoretical state,

e control at least one of the actuating elements based on a

Control value.

The inventive design, a good efficiency and a large driving range of the compressor can be advantageously achieved. Furthermore, energy consumption can be kept cost-saving low.

In this context, under a "compressor" each of the expert appears reasonable sense compressor, such as a motor-driven, in particular

Multi-stage compressor with intermediate cooling and constant speed and / or a turbine-driven gear compressor or single-shaft compressor can be understood.

A "setpoint" is here in particular a

Required power to the compressor, which in the Determination of the control values should be considered and, in particular, sought. It is also possible that the setpoint contains another or different request, such as

For example, a distance to a surge line, a

Minimum load of individual transmission components such as.

Pinion shafts of the compressor, a compliance with the intake limits of individual stages of the compressor, holding a

Total capacity of the compressor below one

Maximum power of the compressor and / or another, to those skilled in the seeming appropriate requirement. These requirements can be firmly stored in the control of the compressor and / or supplied from outside. The setpoint can be specified by a control means or an operator and thus provided, wherein the

Control means a part of the compressor or an external one

Can be means.

Under a "parameter" is here in particular a

Final temperature, a final pressure, an efficiency, a

Energy consumption, a flow rate, a mass flow and in particular an effective mass flow are understood and / or another, the expert appears reasonable parameter and / or a quotient of an absolute value of a parameter and a limit of that parameter, the "limit" a maximum or minimum value at which the compressor is still reliably operable.

The control values of the control elements are expediently taken from a data memory, e.g. from a map, or calculated. You can each have a state of

Indicate actuator, e.g. a position of a valve or the like, the state usually not the

is the current state of the relevant control element, but a desired state, which may result from the predetermined setpoint.

The determination of the control values on the basis of the desired value is preferably carried out by means of a control unit, which for this purpose each, the Professional for judiciously considered investigation or

Calculation method and / or optimization algorithm

apply, such as the downhill simplex method, the gradient method, the quasi-Newton method and / or, more preferably, the numerical

Method of sequential quadratic programming. In this case, the setpoint value to be maintained is passed to the method as a secondary condition. The determined control values are transmitted by the control unit to a model unit.

In general, a determination of more than two control values of more than two control elements would also be conceivable here. The control values and the control elements can have different or the same parameters or different or the same

be executed components. For the sake of simplicity, only the control values and the control elements will be discussed below. A "model-based theoretical state" here represents in particular a state that is based on a

Computational model of the model unit and in particular based on a thermodynamic model is determined.

Advantageously, a behavior of the compressor is simulated to determine the theoretical state. In this case, the model unit calculates with the transmitted control values on the basis of the thermodynamic model expediently what a state of the compressor would be if these control values were set on the control elements and the compressor would be operated with these parameters. This can be independent of direct changes to the compressor

gentle on equipment and process-reliable behavior of the

Compressor can be determined. In addition, fluctuations in a flow rate during operation can be advantageously prevented.

Furthermore, in the determination of the theoretical state, the behavior of the compressor in a control loop is gradually adjusted to the setpoint. In this context, under a "control loop" next to a strictly targeted

Determining the state can also be understood as a determination that is undirected and / or diffuse and / or also "false "and / or in particular according to a numerical method of sequential quadratic programming." The control loop is preferably located between the control unit and the model unit

Model unit the information of the determined theoretical state or an associated parameter to the

Control unit, determines this from, at a

predetermined deviation of the parameter from the setpoint, again set values. These are returned to the model unit for recalculation of the theoretical state

Behavior of the compressor under the new conditions

given. In a determination and modification of the manipulated variables using a numerical method of sequential

quadratic programming, this is done in a manner known to those skilled in the art. Through the realization of the control loop can be a fine-tuning of the control values

especially effective and easy.

Preferably, at least one of the actuating elements is only actuated with a control value when a parameter of the theoretical state corresponding to the desired value reaches a predetermined proximity to the desired value. In this case, the phrase "a predetermined proximity to the desired value" should be understood to mean, in particular, that a value is present in the control unit

is stored and / or determinable by the latter, which defines a permissible degree of deviation of the parameter from the desired value and / or represents an abort condition which relates to a speed of a reduction of a

Optimization function of the method relates. The expert selects the value of the given proximity adapted to the

Process and / or the parameters of the compressor used expedient. As a result, an unfavorable or even damaging operation of the compressor resources can be gently prevented.

In a further embodiment of the invention

provided that in the determination of the model-based

at least one actual value of the state of the theoretical state Compressor arrives. In this context, an "actual value of the state of the compressor" should in particular be a measured and / or momentary or current state value of the compressor, such as a pressure

Volume flow, a temperature and / or another, the

Expert for pertinent state value understood that is located in a time window of less than 60 seconds, preferably less than 30 seconds, and more preferably less than 10 seconds from the time of determination removed. Preferably, one and more preferably at least two temperatures go into the calculation or into the thermodynamic model and in particular an inlet temperature or a measured suction temperature of the compressor or a first stage of the compressor and a measured recooling temperature of the compressor or the first stage, which corresponds to a suction temperature of at least a second stage of the compressor. By determining the state by means of an actual value and in particular by means of a

Temperature, the state can be determined particularly simple and inexpensive.

It is also proposed that the determined model-based theoretical state be corrected on the basis of at least one further actual value of the state of the compressor. This further actual value preferably represents at least one pressure and / or one volume flow and in particular a measured suction pressure of the first stage and / or the second stage and / or a measured intermediate pressure and / or a measured one

Volume flow. In general, however, any other actual value that appears to be suitable for a person skilled in the art would also be conceivable.

The thermodynamic model preferably compensates the determination of the theoretical state permanently by these further measured actual values, as a result of which the actual actual state of the compressor is as up-to-date and precise as possible in the actual state

State prediction is included. This allows a particularly accurate to the actual state of the compressor

coordinated control of the compressor can be achieved. Furthermore, it may be advantageous if, when at least one predetermined state of at least one of the adjusting elements is bypassed, the model-based correction is controlled directly by means of at least one uncorrected control value. In this context, under a "predetermined state", in particular, a state of

Compressor be understood in which a determination of the theoretical state by means of the model unit or the thermodynamic model would take too long, such as

For example, a dynamic change of a final pressure of the compressor and / or a rapid increase of the setpoint. An "uncorrected manipulated variable" should be understood here to mean, in particular, a manipulated variable which was determined independently of the thermodynamic model The uncorrected manipulated variable can be independent of the desired value

reliable and safe control of the compressor

to be provided.

In addition, it is proposed that the predetermined state is a critical state of the compressor, which is converted by the direct control of at least one of the control elements in a non-critical state. In this context, under a "critical state" in particular a

Be understood state in which the compressor is operated above a predetermined load limit and / or in the operation of a risk of damage to the

Compressor and / or individual stages of the compressor

consists. Thus, a "non-critical state" is a state where the compressor is below the load limit

is working. In particular, in the critical state, the control values determined from the desired value or the determined control value for the actual state of the compressor are unadapted or no longer satisfy the actual state. Under one

"Direct control" is here in particular a

immediate control without intervening determination of the theoretical state are understood. The direct control enables process-reliable control realized and thus a reliable compressor control are designed advantageous.

A preferred development consists in that at least one control value which is corrected as a function of the theoretical state and at least one uncorrected manipulated variable are interconnected via at least one comparator. The comparator receives the at least one corrected manipulated variable from the control unit and the at least one uncorrected manipulated variable from a safety device, such as

for example, a surge limit regulator. By means of the

Comparator can make a decision on the direct

Actuation of an applied actuating element can be realized structurally simple.

It is also proposed that at least one of the uncorrected manipulated values actuate at least one valve. The valve is preferably a continuous valve and particularly preferably a control valve. Through the valve can a

Transfer from the critical state into the uncritical one

Condition quickly and structurally simple.

Furthermore, it is proposed that the predetermined

State a change in the setpoint above one

includes setpoint gradient. This is under the phrase "change the setpoint above a

setpoint gradient "understood in particular that the change in time of the setpoint and / or the actual value takes place so fast that the

Determining the control values based on the target value by means of the optimization algorithm is incapable or unable to react quickly enough to this change. This value depends on a processing speed of the

Control unit and is for example 0.5% / s.

This can ensure that only at

serious setpoint changes bypassing the

model-based correction is triggered. Furthermore, it is advantageous if the direct control of at least one of the adjusting elements causes a faster adaptation of an actual value of the compressor to the desired value than by means of the model-based correction. The actual value is

Preferably, a final pressure of the compressor, but in principle may be any other, the skilled worker considered useful actual value. This direct control is done by means of

Control unit and based on at least one determined there uncorrected control value. This can be a mode of

Be provided independently of the controller

Model calculation works and looking ahead one

provisionally still uncorrected control value passes quickly to adjust a state of the compressor to a new set point and thus to improve a workload of the compressor.

Conveniently, the compressor is controlled and the

Setpoint used as controlled variable. Here, the

Control preferably by means of a process controller, such as

for example, a final pressure regulator and / or any other, those skilled in the appear appropriate regulator. The inventive design, the control of the compressor can be done very easily. Furthermore, it is proposed that a control value at least one angle of attack of at least one guide device of

Compressor and / or a position of a valve. In this case, preferably more than one or more guide devices with a control value or with multiple control values

applied, wherein each guide device can be controlled with the same or with different control values.

In general, it is also possible for a group of guide devices to be subjected to the same control value and a second one to be used

Group with another control value. Particularly advantageous in a compressor with more than two stages each

Guide device of each stage with a control value

applied, which differs from another control value of another guide. This is preferred a number of guide devices less than or equal to the number of stages of the compressor. By means of the adjustment of the guide devices, a free cross-section of the compressor can be structurally simply changed and / or a flow of a fluid of the compressor can be missed, whereby a conveyed fluid quantity of the compressor can be advantageously modulated. Furthermore, a pressure and / or a fluid amount in the compressor can be easily changed by the valve quickly and structurally.

Basically, it would also be conceivable, the speed of the

To vary compressor. For this must be adapted

Value tables of maps are stored in the model unit. This could, for example, at a

two-stage compressor three degrees of freedom can be achieved, which advantageously increases the possibilities of variation.

Thus, it is advantageous if a control value is a position of a valve and / or a rotational speed of the compressor. Consequently, it may further be advantageous if a

Stellwert at least one angle of at least one

Guide device of the compressor and / or a speed of the compressor and / or a position of a valve. Is now a variety of guiding devices, preferably in

according to the number of stages of the compressor,

provided, it may also be advantageous if the

Stellwerte a variety of angles of attack ( _s ) one

Variety of guide devices of the compressor and / or a speed of the compressor and / or a position of a valve.

A further embodiment of the invention provides that a gas composition is measured and taken into account in the determination of the model-based theoretical state, whereby the determination or the thermodynamic model by, for example, inclusion of a real gas equation for operation with a non-ideal gas or on a

used gas can be adjusted. Basically However, also an input of the gas composition based on numerical values in the control unit possible, by the

Model unit should be included in the determination and / or in the presence of at least one constant compressor field would be a determination of the gas composition based on at least one actual value or on the basis of measured quantities and the

Pressure ratios that create the stages, conceivable.

The invention is further based on a compressor with a control unit and a model unit.

It is proposed that the control unit be provided to determine at least two control values of at least two control elements of the compressor on the basis of a transmitted nominal value of a parameter of the compressor and that the

Model unit is provided to determine a model-based theoretical state of the compressor based on the control values and that the control unit is provided to at least one of the control values as a function of

correct theoretical state and at least one of the control elements based on a control value to control. By this configuration, an optimal efficiency of the compressor synonymous with a minimum energy consumption

will be realized.

In addition, it would be possible to determine the model-based theoretical state or the thermodynamic model to a polytrope flow work and / or a polytropic efficiency in a manner known in the art

adapt.

The invention will be explained in more detail with reference to an embodiment which is shown in the drawing.

The sole figure of the drawing shows a schematic

Representation of a compressor 10 in the form of a

two-stage motor-driven transmission compressor with a controller according to the invention. The compressor 10 has a Variety Z or a first stage 64 and a second stage 66, which in each case a heat exchanger 68 for example to

Intermediate cooling is connected downstream. Further, at each stage 64, 66 is an actuator 22, 24 in the form of a

Guide device 56, 58 arranged by means of which a

Anstellwinkel ι, a.2 of blades of the guide devices 56, 58 can be changed or adjusted. Thus, the plurality Z of stages corresponds to a plurality Z of

Leitvorrichtungen 56, 58. The heat exchanger 68 of the second stage 66 downstream in the process in the flow direction 70 of a working fluid, not shown here, such as a gas, is a valve 52 in the form of a

Regulating valve 72 arranged on the position ß a

Draining the fluid can be adjusted.

In addition, at the end of the compressor chain 74 a

Non-return valve 76 is arranged, which separates the compressor 10 from another system not shown here. Before and during start-up of the compressor 10, the valve 52 is open and the fluid can escape, whereby in the compressor 10, a low pressure prevails. If a pressure above the pressure of the compressor 10 now prevails in the further system, the non-return valve 76 is kept closed. Now increases the pressure in the compressor 10 by a start-up of the compressor 10 and the closing of the valve 52 and the pressure exceeds a characteristic of the check valve 76, it is opened and the fluid can escape.

Furthermore, a plurality of measuring elements 78, for example in the form of temperature sensors, pressure transmitters and

Flow transmitters, for measuring actual values 32, 34, 36, 38, 40, 42, 54 arranged on the compressor chain 74. In this case, in the flow direction 70 before the first stage 64 a

Actual value 32 of a suction temperature Ti, an actual value 36 of a suction pressure pi and an actual value 38 of a suction side

Volume flow V determined. Before the second stage 66, an actual value 34 of the suction temperature T ₂ and an actual value 40 of a suction pressure P _{2 are} measured. Further, after the second stage 66 and in front of the check valve 76 is an actual value 42 one

Zwischendrucks p _zw and after the check valve 76 a

Actual value 54 of a final pressure p _E n _d determined. In addition, the compressor 10 has a control unit 60 and a model unit 62, which operate a method for controlling the compressor 10. In this case, a desired value 12 of a parameter 14 of the compressor 10, such as a

Mass flow m, and thus m _so ii transmitted to the control unit 60. This is done by a process controller 80 in the form of a final pressure regulator, which has calculated the desired value 12 from the actual value 54 of the final pressure P _E n _d fed to it, whereby the compressor 10 is regulated and the desired value 12 is used as the controlled variable. In addition, the process controller 80 receives a maximum value 82 of the control unit 60

Parameters 14, here m _max . If the setpoint 12 is above the

Maximum value 82 is this as setpoint 12 to the

Control unit 60 given. The control unit 60 now determines three control values 16, 18, 20 of the adjusting elements 22, 24, 26 or the guide devices 56, 58 and the valve 52 of the compressor 10 based on the desired value 12. This determination is carried out in a manner known to those skilled in the art by means of a The control unit 60 stored numerical algorithm in the form of a sequential quadratic programming. These three determined

Control values 16, 18, 20 are now transmitted to the model unit 62, which determines a model-based theoretical state of the compressor 10 based on the control values 16, 18, 20, wherein a behavior of the compressor 10 is simulated to determine the theoretical state

(See below for the calculation model).

This model-based theoretical state or this

associated predicted parameters 30, for example an efficiency η, an energy consumption P, a distance from a surge limit S _PG or a mass flow m, becomes the control unit 60 given. In this case, only one parameter 30 or preferably several different parameters 30 can be given to the control unit 60, for the sake of simplicity, only one parameter 30 is treated here. The control unit 60 compares the parameter 30 or the determined mass flow m with the desired value 12 and, in the case of a deviation of the values from one another, uses the numerical method to correct the value

Control values 16, 18, 20 depending on the theoretical

Status. Further, it compares the parameter 30 with other requirements, such as a distance to the surge limit SPG, a minimum load on individual pinion shafts of the compressor 10, a compliance with the absorption limit of the stages 64, 66, a

Maintaining a total power of the compressor 10 below a maximum power of the compressor 10 and fits

if necessary, the control values 16, 18, 20 on it. These

Requirements may be stored in the control unit 60 and / or supplied from the outside. The corrected

Control values 16, 18, 20 are given again to the model unit 62 for determining the model-based theoretical state. Thus, the behavior of the compressor 10 is gradually adjusted to the desired value 12, as in a control loop 28 between the control unit 60 and the model unit 62.

A control of the adjusting elements 22, 24, 26 based on the corrected in dependence on the theoretical state

Control values 16, 18, 20 takes place only when the

Setpoint 12 corresponding parameter 30 of the theoretical state has reached a predetermined proximity to the setpoint 12. Here are the control values 16, 18 Anstellwinkel ι, a. _{2 of} the guide devices 56, 58 of the compressor 10 and the control value 20, the position ß of the valve 52nd

They thus control over an interaction of the thermodynamic model and the numerical algorithm. It is thus during operation of the compressor 10 constantly by variations of the three control values 16, 18, 20 and ι, a. ₂ and ß by the control unit 60 scenarios the

thermodynamic model or the model unit 62 sent. The thermodynamic model then determines and returns which theoretical state, for example based on the mass flow m, the efficiency η or the

Energy consumption P, then using this

Setting values 16, 18, 20 would set. Thus, it can be determined how, while maintaining a total delivery quantity, these three control values 16, 18, 20 have to be changed so that, for example, B. the power consumption P is as small as possible. The thermodynamic model determines the effective

delivered mass flow m _eff . For this are the following

Previews necessary:

A molecular weight of the pumped fluid and a speed of the compressor 10 are assumed to be constant. An overall pressure increase rges of the compressor 10 is composed of the pressure ratios ττ ₁ , π _{2 of} the individual stages 64, 66 and is in accordance with

n, ^{= 1}

to determine. Here, the distribution to the individual stages 64, 66 is to be determined so that a drive line assumes a minimum. Total energy consumption P of the

Compressor 10 is determined by:

p = - ^ - _m

¹ k, step '"-> where e _{s is} the specific isentropic flow work

Efficiency k _fs are both losses of isentropic

Change of state, further flow losses and mechanical losses, for example. Include a transmission. The specific isentropic flow work can be described as e _sj = f {a _i ^ _i ) and the

Efficiency as V _{s ki} = be described. The

Flow index φ is proportional to the suction-side volume flow V at constant speed, which results in e _sl = f ( ₁ , Vi) and r] _{s ki} = f ( _l , Vi). These functional relationships of the individual stages 64, 66 are as predicted and trial-corrected values in 2-dimensional Stored value tables. In principle, these tables could also be changed or improved in the process.

To determine the energy consumption P, the effective mass flow m _eff must now be calculated. This is determined by ^m eff - f {Pi, T _l , T ₂ , a _l , a ₂ , p _zw , ß). This can be derived as follows:

A suction pressure P2 of the second stage 66 is dependent on the suction pressure pi and the pressure ratio π _{1 of} the first stage 64: ρ ₂ = ρ _ι π _ι , where π _ι 1 + - and e _sl = / ( _ι , φ _ι ).

K

RT,

Analogously, it results for the intermediate pressure p _zw that this is dependent on the suction pressure p ₂ and the pressure ratio π _{2 of} the second stage 66:

^■ 2 where π _Ί 1 + - "i2 and e _s2 = f ( ₂ , p ₂ ) = f (a ₂ , V ₂ ), V ₂ " Vi Pl ^T 2

IC

^■ RT,

κ- \

From this it can be generalized that

= f (P _ii , T ₂ , _I , a ₂ , V ₁ ).

If the compressor 10 now conveys a pressure-side volume, the pressure in this volume changes if a balance of an added and / or discharged quantity remains unbalanced. The intermediate pressure p _{zw of} the compressor 10 is through

Integration of the mass flow balance, whereby m = f (Pi, i, ₂ > ^a i> ^a 2> Pzw)

results. Consider now a mass flow m after the

Non-return valve 76 can be the position ß and thus the um- and / or blown off amount of fluid are taken into account and it follows:

The control values 1 6, 1 8, 2 0, the angle of attack oii and c < ₂ and the position ß are of the control elements 22, 24, 2 6th

influenced. ΤΊ, T ₂ , pi and p _zw represent disturbance variables that depend on external boundary conditions. The suction pressure pi can be assumed to be constant as a rule. Of the

Intermediate pressure p _zw can by the above-described

calculable dependence on the other values. Thus, in the determination of the model-based theoretical state by means of the thermodynamic model, two actual values 32, 34 of the state of the compressor 1 0 and the measured intake temperatures ΊΊ and T _{2 of} the two stages 64,

66. With the sole knowledge of these two actual values 32, 34, the model can determine the model-based theoretical state. Furthermore, however, the determined model-based theoretical state is corrected on the basis of further actual values 3 6, 38, 40, 42, the state of the compressor 10 or on the basis of the measured suction pressures pi, P ₂ , the measured intermediate pressure p _zw , and the measured volumetric flow V. ,

Furthermore, the compressor 10 has a safety device 84 in the form of a surge limit controller 8 6. Of the

Pump limit controller 8 6 constantly determines whether a distance to the pumping limit S _{PG is} maintained. For this he receives from the model unit 60 there theoretically determined parameter 30 of the distance of the pumping limit S _PG and compares this with a stored in the surge limit 8 8 8 8 setpoint. If the parameter 30 approaches a range with, for example, 7%,

1 0% deviation from the setpoint 8 8 or falls below this, both for example in a dynamic

Change in the pressure in the compressor 1 0 may occur, the surge regulator 8 6 is activated. It now determines based on a PI algorithm an uncorrected control value 4 8 or a position ß of the valve 52 in which or in which the distance to the pumping limit S _{PG is} maintained. This uncorrected Control value 48 is sent to a comparator 50, which also depends on the theoretical state

corrected control value 20 receives from the control unit 60. The comparator 50 now determines by comparing the

Control values 20, 48 which control value conveys a greater open position of the valve 52 and forwards this determined control value 20, 48 to the valve 52 for its control. Upon intervention of the surge limit regulator 86, this is

for example, the uncorrected manipulated value 48.

Thus, in the presence of a predetermined condition, such as a critical condition of rapid pressure change in the compressor 10, the actuator 26 or valve 52 is bypassed, bypassing the model-based correction directly by means of the uncorrected control value 48, whereby the

Compressor 10 is converted into a non-critical state and it is not operated at its load limit. The surge limit regulator 86 is disengaged once the thermodynamic model has responded to the pressure change by adjusting its predictions.

During operation of the compressor 10 on the basis of

theoretical determination of the control values 16, 18, 20 is given by the comparator 50 of the control value 20 to the valve 52. In this case, a resulting actuation value βi _St for the position β of the valve 52 to the surge limit controller 86th

so that this is in accordance with that actual

Control value ßi _St can be tracked. The thermodynamic model thus has two functions; on the one hand the theoretical prediction of the state on the basis of the calculation with assumed control values 16, 18, 20 and on the other hand that of a control of the compressor 10 via the

Surge limit controller 86.

Likewise, upon occurrence of a predetermined condition in the form of a change in set point 12 above a predetermined setpoint gradient, the actuators 22, 24, 26, bypassing the model-based correction directly by means of uncorrected control values 44, 46, 48 driven. In this case, this direct control of the adjusting elements 22, 24, 26 effects a faster adaptation of the actual values 34, 40, 42, 54 of the compressor 10 to the desired value 12 than by means of the model-based correction. The control unit 60 thus determines during a large jump of the setpoint 12 during the

Model calculation of the model unit 62 using a

Linearization as the adjusting elements 22, 24, 26 would have to be changed in order to meet the changed setpoint 12.

A display of relevant control values, actual values, setpoints, information on differences between these values and values that would have been achieved without the model-based correction, and / or a summation, for example. B. the energy savings can be via a display unit, not shown here for a

Operating personnel indirectly via the compressor control

be provided, which benefits the system

can be seen beneficial.

In addition, in addition to the control values 16, 18, 20, a control value 90 in the form of a rotational speed n of an actuating element 94, indicated only by dashed lines, in the form of a motor 96 can be determined, corrected and adjusted. Also, in the presence of a predetermined state, the actuator 94 can be controlled directly by means of an uncorrected manipulated variable 92, bypassing the model-based correction. Alternatively and / or additionally, a

Speed of a turbine can be adjusted.

Furthermore, in the case of a work of the compressor 10 with a variable gas composition G, this can be measured with a measuring element 78 shown only dashed in the figure and taken into account in the determination of the model-based theoretical state. Alternatively, it is possible to dispense with the process controller 80, in which case the desired value 12 is otherwise supplied externally to the system. Further, in an alternative embodiment, the surge limit regulator 86 and the comparator 50 are also

dispensable if the calculation of the optimized control values 16, 18, 20 is fast enough to react adequately even in the event of sudden process changes.

The exemplary embodiment describes the method by way of example for a two-stage compressor with a

Internal pressure state change. In principle, the model is applicable to any multi-stage compressor. By doing

thermodynamic model can be used instead of isentropic

Flow work or efficiencies can also be calculated with polytropic quantities. Furthermore, other representations of the compressor map can be used, which allows a calculation of power and delivery quantity based on the given input variables.

Claims

claims

A method of controlling a compressor (10) comprising the steps of: a providing at least one set point (12) of a

Parameters (14) of the compressor (10),

b Determination of at least two control values (16, 18, 20, 90) of at least two control elements (22, 24, 26, 94) of the compressor (10) on the basis of

provided setpoint (12) from a map of the compressor (10),

c Determination of a model-based, theoretical

State of the compressor (10) based on the control values (16, 18, 20, 90) using a

State model of the compressor (10), wherein the model-based, theoretical state of the compressor (10) at least one

model-based, theoretical set point of the parameter (14) of the compressor (10) is described,

d Determination of at least two corrected

Control values (16, 18, 20, 90) of the at least two control elements (22, 24, 26, 94) on the basis of the model-based, theoretical setpoint from the

Characteristic map of the compressor (10),

e iterative correction by iterative repetition of steps c and d until the model-based theoretical setpoint determined in the respective iteration has a specific proximity to the provided desired value (12), control of at least one of the control elements (22, 24, 26, 94 ) as a function of the control value (16, 18, 20, 90) of this control element (22, 24, 26, 94) corrected in the last iteration.

2. The method according to claim 1,

characterized in that for the determination of the theoretical state, a behavior of the compressor (10) is simulated, wherein the behavior in a control loop (28) is gradually adjusted to the provided set value (12).

3. The method according to claim 1 or 2,

characterized in that at least one of

Adjusting elements (22, 24, 26, 94) only then with a

Control values ": (16, 18, 20, 90) is controlled if the model-based, determined in the respective iteration,

theoretical setpoint a certain proximity to the

reached setpoint (12) reached.

4. The method according to any one of the preceding claims, characterized in that in the determination of the

model-based, theoretical state at least one actual value (32, 34) of the state of the compressor (10) is received.

5. The method according to claim 4,

characterized in that the determined model-based, theoretical state is corrected on the basis of at least one further actual value (36, 38, 40, 42) of the state of the compressor (10).

6. The method according to any one of the preceding claims, characterized in that in the presence of at least one predetermined state of at least one of the adjusting elements (22, 24, 26, 94), bypassing the model-based correction directly by means of at least one uncorrected manipulated variable (44, 46, 48, 92) is controlled.

7. The method according to claim 6,

characterized in that the predetermined state is a critical state of the compressor (10), which is converted by the direct control of at least one of the adjusting elements (26) in a non-critical state.

8. The method according to claim 6 or 7,

characterized in that at least one control value (20) corrected in dependence on the theoretical state and at least one uncorrected manipulated variable (48) are interconnected via at least one comparator (50).

9. The method according to any one of claims 6 to 8,

characterized in that at least one of

uncorrected control values (48) at least one valve (52) is driven.

10. The method according to any one of claims 6 to 9,

characterized in that the predetermined state comprises a change of the provided setpoint (12) above a predetermined setpoint gradient and the direct

Actuation of at least one of the adjusting elements (22, 24, 26, 94) effects a faster adaptation of an actual value (34, 40, 54) of the compressor (10) to the provided desired value (12) than by means of the model-based correction.

11. The method according to any one of the preceding claims, characterized in that the compressor (10) is controlled and the provided setpoint value (12) is used as a controlled variable.

12. The method according to any one of the preceding claims, characterized in that a control value (16, 18, 20) at least one angle of attack (ι, 0: ₂ ) at least one

Guide device (56, 58) of the compressor (10) and / or a position (ß) of a valve (52).

13. The method according to any one of the preceding claims, characterized in that the control values (16, 18, 20, 90) a plurality (Z) of angles of attack (ι, 0.2) a plurality (Z) of guide devices (56, 58) of the compressor (10) and / or a speed (n) of the compressor (10) and / or a position (ß) of a valve (52).

14. The method according to any one of the preceding claims, characterized in that a gas composition (G) is measured and taken into account in the determination of the model-based, theoretical state.

15. Compressor with a control unit (60) and a

Model unit (62),

characterized in that

- The control unit (60) is provided to at least two control values (16, 18, 20, 90) of at least two

Control elements (22, 24, 26, 94) of the compressor (10) based on a transmitted setpoint (12) of a

Parameters (14) of the compressor (10) from a map of the compressor (10) or at least two corrected control values (16, 18, 20, 90) of the at least two

Control elements (22, 24, 26, 94) based on a

model based, theoretical setpoint from the

Map of the compressor (10) to determine

- The model unit (62) is provided to a

model-based, theoretical state of the compressor (10) based on the control values (16, 18, 20, 90) or the corrected control values (16, 18, 20, 90) below

Using a state model of the compressor (10) to determine, the model-based, theoretical

Condition of the compressor (10) at least with the

model-based, theoretical setpoint of the parameter (14) of the compressor (10) is described, and

- The control unit (60) is provided to at least one of the adjusting elements (22, 24, 26, 94) in response to the corrected control value (16, 18, 20, 90) of this control element (22, 24, 26, 94) to control ,