EP2376783B2 - Simulation-supported method for controlling and regulating compressed air stations - Google Patents

Description

The invention relates to a method for controlling or regulating a compressed air station, which comprises at least a plurality of interconnected compressors, in particular different technical specifications, and optionally further devices of compressed air technology, which in particular in control cycles both switching strategies via an electronic system control to influence a quantity of a can cause pressure fluid available for one or more users of the compressed air station in the compressed air station, as well as being able to adapt the amount of pressure fluid available for one or more users of the compressed air station to future operating conditions of the compressed air station to the withdrawal amount of pressure fluid from the compressed air station.

Furthermore, the present invention relates to a method for controlling or regulating a compressed air station which comprises at least a plurality of compressors networked with one another, in particular different technical specifications, and optionally further devices of compressed air technology, the method which is implemented in an electronic control of a compressed air station , Processes information about essential state variables of the compressed air station as input information, and outputs control commands for controlling at least some compressors and optionally further components of the compressed air station, according to the preamble of claim 34.

The present invention also relates to a system control for a compressed air station.

The use of compressed air stations has established itself in many industrial as well as private environments. The provision of larger amounts of pressurized fluid are, for example, indispensable in industrial production plants not only for the operation of hydraulic devices, but also, for example, for the provision of pressurized fluid to chemical reaction areas as well as physical production environments for using the same. Compressed air stations, which typically include at least a plurality of compressors, pressurized fluid containers and the corresponding adjusting means and actuators, often require a well thought-out and usually complex control system that is capable of serving a possibly larger number of users at different consumer stations of the compressed air station at all desired times To provide pressure fluid available. By performing different switching operations, for example, valves are switched on or off, whereby the enrichment or depletion of pressure fluid takes place in predetermined areas of the compressed air station, and the supply of the user with sufficient pressure fluid can be guaranteed. Further possible switching operations also relate, for example, to switching individual compressors or groups of compressors on or off, or, in contrast to discrete switching on or off, continuous regulation of individual actuators or actuators.

In order to be able to carry out an advantageous control of the compressed air station, the system control of the compressed air station needs information about the state of the compressed air station. Such information can be fixed system parameters predetermined by the compressed air station, or also measurable state variables, such as the pressure, or discrete or information technology state variables, such as the operating state of a compressor (standstill, idling, load running), which draws conclusions about the state of the compressed air station allow at a certain time. Furthermore, boundary conditions must be observed for controlling the compressed air station, compliance with which is desirable or sometimes essential for the operation of the compressed air station. These include, for example, specifications on compliance with maximum permissible maximum pressures in the pressurized line and pressure vessel network of the compressed air station, as well as specifications on a minimum pressure to be observed at the connection stations for users.

A number of control or regulation methods which are used for compressed air station control are already known from the prior art. A relatively simple control method uses a cascade circuit which assigns a predetermined pressure range to each compressor. If the pressure falls below the lower limit of the pressure range, a compressor is switched on. If the upper pressure band limit is exceeded, a compressor is switched off accordingly. By overlapping different pressure bands of the individual compressors comprised by the compressed air station, a minimum pressure can be regulated which enables the users of the compressed air station to withdraw a desired amount of pressure fluid from the system.

The DE 198 26 169 A1 describes an electronic control for aggregates of compressed air or vacuum generation with programmable electronic circuits for the control, regulation and monitoring of the technical function of such aggregates. The electronic control is designed as a standardized control for use in a large number of different units for compressed air and / or vacuum generation and has an industrial PC or industrial microcomputer with one or more microprocessors and one that is monitored and controlled by an operating system central data storage which contains at least control and regulation software and a large number of unit-specific data profiles, which are each provided for a certain unit type and can be called up separately.

Other control methods make use of a sequence control which requires a common predetermined print band. When leaving the printing band, a previously defined Sequence a compressor either switched on or off. With each switching process, a timer is started which measures a predetermined period of time. If the pressure prevailing in the compressed air station has not reached the pressure regime predetermined by the pressure band before this time has elapsed, another compressor is switched on or off in a previously defined sequence.

A further development of the sequence control is justified by the printing belt control. Instead of the relatively inflexible switching on and off of individual compressors, compressors are switched on and off in previously predetermined group sequences. The selection of the switching compressor within a group is made on the basis of heuristic rules, which have proven suitable over time to minimize the operating costs of a compressed air station.

All of these methods of controlling compressed air stations are purely process-driven. Accordingly, switching operations on the actuators included in the compressed air station, as well as compressors, are only carried out in response to previously defined compressed air events in the compressed air station. Here, every action of the control of the compressed air station is merely a reaction to an event that is taking place or has taken place in the present or in the past. Only after suitable observation of this event can the pressure fluid conditions in the compressed air station be regulated again. The controller therefore only ever reacts to an event which should have been averted if the compressed air station had been optimally controlled.

In order to be able to trigger a sufficiently early implementation of switching actions which are intended to counteract the impending event, the trend of which is already emerging, some control methods known from the prior art use a larger number of nested print tapes. The different pressure ranges defined by the individual pressure bands allow early definition of changes in the pressure conditions that may only be recognizable in the beginning and counteract any exceeding or falling below a maximum or minimum pressure in the compressed air station in good time with suitable control actions. However, such methods can only be viewed as purely reactive control methods, since a corresponding control action is only carried out when predetermined pressure conditions are present in the compressed air station.

The control actions carried out in the control method shown also have to take into account dead times of all control elements in order to prevent an overreaction to a corresponding control action in the compressed air station. Accordingly, the calculation of new control actions only takes place after a typical delay time caused by the dead times of the control elements. In this way, however, it cannot be avoided that the effect of an actuating action carried out can only be observed if the state in the compressed air station is re-evaluated and a new reaction is calculated through further actuating actions. As a result, there is an artificial reduction in the response speed of the control, which has a negative effect on the control quality of the compressed air station.

The control methods known from the prior art also only allow boundary conditions to be taken into account insofar as these can be explicitly inspected when parameterizing the control calculations. The relationships between many physical variables of the compressed air stations can only be parameterized by specifying empirical rules, which merely represent purely heuristic relationships in possibly extremely limited pressure regimes. It is known, for example, that in many cases (not in all) energy savings can be achieved by lowering the maximum permissible pressure of the compressed air station. In addition, it has also proven advantageous to reduce energy costs to switch small compressors or groups of compressors on or off before large ones. The implementation of such knowledge in a control method for compressed air stations turns out to be very difficult and in many cases impossible, since the superimposition of different parameter settings can result in opposing effects on a boundary condition to be influenced, whereby the heuristic parameterization represents a complication that is undesirable for the system operator .

The present invention is based on the task of proposing a control method for compressed air stations which avoids the disadvantages of the approaches known from the prior art. In particular, the control method according to the invention should make it possible to anticipate changes in the pressure in the compressed air station as early as possible in order to initiate suitable switching operations.

This object is achieved by a method for controlling a compressed air station according to claims 1 and 35 or by a system control of a compressed air station according to claim 37.

In particular, the object is achieved by a method for controlling a compressed air station, which comprises at least a plurality of interconnected compressors, in particular different technical specifications, and optionally further devices of compressed air technology, which in particular in control cycles both switching strategies via an electronic system control to influence a quantity of a can cause pressure fluid available at any time in the compressed air station for one or more users of the compressed air station, as well as adaptively adjust the amount of pressure fluid available at any time for one or more users of the compressed air station to future operating conditions of the compressed air station to the amount of pressure fluid withdrawn from the compressed air station capable, whereby a switching strategy is to be understood as a sequence of switching operations, ie a discrete or continuous change of manipulated variables, which is a change cause the operation of one or more components of the compressed air station, with various switching strategies being checked in a pre-simulation process on the basis of a model of the compressed air station before a switching strategy is initiated and the most advantageous switching strategy is selected from the checked switching strategies based on at least one specified quality criterion and the selected switching strategy to the System control is forwarded to the initiation in the compressed air station.

It should be pointed out here that the compressors and the other compressed air technology devices optionally included in the compressed air station are not exclusively controlled or regulated by the system control, but also in certain aspects (e.g. safety shutdowns, implementation of simple switching sequences after changing external manipulated variables) by internal control or regulation devices. can be regulated.

Furthermore, the object is provided by a method for controlling or regulating a compressed air station, which comprises at least a plurality of compressors networked with one another, in particular different technical specifications, and optionally other compressed air technology devices, the method which is implemented in an electronic control of a compressed air station , Processes information about essential state variables of the compressed air station as input information, and outputs control commands to control at least some compressors and optionally other components of the compressed air station, the method having the following functional structures: a simulation core in which to describe the behavior of at least some components of the compressed air station dynamic and preferably non-linear models of these components are included, the simulation kernel being configured in such a way that it shows the time course of all in the M as the simulation result odell contained state variables of the components of the compressed air station calculated in advance on the basis of assumed alternative switching strategies, the models of the simulation core taking into account the essential non-linearities and / or discontinuities and / or dead times in the behavior of the components, in particular the compressors; an algorithm core that contains parameters for characterizing the components of the compressed air station, information about the interconnection of the individual components, heuristics for the formation of alternative switching strategies and evaluation criteria for the time courses of the state variables of the components of the compressed air station for the alternative switching strategies determined by the simulation kernel, and which is based on this selects the relatively most advantageous switching strategy and holds or transfers corresponding control commands to at least some compressors; and an information base which, in addition to a process image formed from sensor values and possibly actuator values provided by the algorithm kernel, also contains the simulation results for alternative switching strategies, the information base representing at least part of the common database of algorithms and simulation kernels and used for data exchange between the algorithm and simulation kernels .

According to the embodiment, the information base can contain a process image of the compressed air station, that is to say essentially the measured values of state variables and the current manipulated variables, supplemented by the pre-simulation results of the time courses of the state variables for different scenarios. The algorithm core can also contain the information about the configuration of the compressed air station and the types of components contained therein and their parameters. In addition, it can have heuristics for the formation of different scenarios to be examined. The algorithm core then typically transfers this information to the simulation core. Furthermore, the algorithm core typically transfers to the simulation core the status information of the compressed air station that originates from the information base and is relevant for the pre-simulation. The simulation core can have models for the usual components of a compressed air station. He is also able to create a model of the compressed air station from these models using the information received from the algorithm core about the structure of the compressed air station and the types of components and their parameters contained therein, which he completes with further information about the current state of the compressed air station from the information base. On this basis, the simulation kernel can typically simulate the temporal progression of all state variables of the model of the compressed air station over the pre-simulation period and stores them in the information base. In addition, the simulation core can supply the algorithm core with status messages in connection with the implementation of the advance simulations.

On the basis of the alternative time courses of all state variables of the model of the compressed air station stored by the simulation core in the information base, the algorithm core can also evaluate these for the examined scenarios and select the relatively most advantageous scenario according to the quality criterion and transmit the associated switching strategies to the components of the compressed air station or has this switching strategy ready for retrieval. As a result, the simulation core, as a relatively extensive and complex part of the implementation, is independent of the specific compressed air station, i.e. universally applicable. The modeling and description can also be done with object-oriented software methods.

Furthermore, the object is achieved by a system control of a compressed air station which has a plurality of compressors networked with one another, in particular different technical specifications, and optionally further devices of compressed air technology, which can initiate switching strategies of actuating elements of the compressed air station and / or different compressors to influence the amount of pressure fluid in the compressed air station that is available at any time for one or more users of the compressed air station, in particular in control cycles, as well as the amount of pressure fluid available at any time for one or more users of the compressed air station to future operating conditions adaptively to the amount of pressure fluid withdrawn from the compressed air station, with different switching strategies in a real-time pre-simulation process based on a model of the Compressed air station are checked and selected from the switching strategies based on at least one specified quality criterion, a relatively advantageous switching strategy and the system control generates a switching command based on the selected switching strategy.

A main idea on which the invention is based is to calculate different switching strategies, for example comparably different scenarios of switching operations, with the aid of a pre-simulation method, which allows the behavior of the entire compressed air station, or individual subcomponents thereof, to be simulated accordingly. Accordingly, no optimization calculation is carried out which, for example, would optimize the value of a functional describing the compressed air station in the mathematical sense, but only a number of scenarios of the compressed air station are determined for different conditions.

A scenario is to be understood here as an assumed or predicted course of disturbance variables, in particular the compressed air consumption, in connection with a switching strategy to be examined. A switching strategy should continue to be a sequence of switching operations, i.e. a discrete or continuous change of manipulated variables can be understood, which cause a change in the operation of one or more components of the compressed air station. This includes, for example, switching between a load run and an idle run or a standstill as well as stepped or continuous changes in the speed or the throttle or blow-off state of compressors, and also includes changes to parameter settings on compressors or other optional components of the compressed air station.

In the following, switching operations should not only be understood as individual discrete switching actions, but also as a time-staggered sequence of switching actions in the sense of a switching strategy. In addition, the term switching action includes not only discrete changes in the operating status of components (for example switching between standstill, idling and load operation), but also continuous changes, for example the second change in the speed of a variable-speed compressor or the continuous closing or opening of valves.

A clear advantage of the method according to the invention in contrast to methods which are based on the optimization of a functional describing a compressed air station in order to achieve optimal control of the compressed air station over a predetermined time range, is that the implementation of complex, non-linear, time-dependent and possibly . discontinuous models is relatively easy because the implemented models do not have to be brought to an analytical form using mathematical methods in which they can be made accessible to an optimization calculation to determine optimal manipulated variables. Restrictions associated with optimization calculations, such as constant disturbance and manipulated variables in a time step, do not represent any restrictions for the method according to the invention.

The advance simulation method according to the invention is carried out on the basis of a model of the compressed air station, which can be parameterized and described according to the number and type of components implemented in the model of the compressed air station. Parameters are typically to be understood as parameters that are structurally determined properties (in this case the number of pressure vessels, actuators, or compressors, electrical properties of the drive motors, volumes of lines and pressure vessels, the nature of the pressure lines included in the compressed air station, etc.) or specified Describe settings (programmed switching delays, etc.) and are integrated into the modeling. Parameters typically show no change over time, but can, under certain circumstances, be tracked and / or adapted adaptively in order to take into account wear and tear of individual components.

In addition to parameters that describe devices in a structural or functional way, models also require state variables for description, which are the current values of individual components or the physical processes describing the compressed air station. This includes electrical power consumption, the pressure volume flow produced, internal pressures, speeds of drive motors, compressor elements or fan motors, positions of actuators and the like. It should be emphasized here, however, that compressors, for example, have relevant state variables, the values of which do not result from the current values of disturbance or manipulated variables, but from the past time course, which is why suitable models must also take past events into account. Consequently, a dynamic approach with "memory" is advantageous for creating a model of the compressed air station or individual components, which is achieved by the method according to the invention is particularly easy to implement.

The construction of models to describe the compressed air station or individual components of it is particularly advantageous in the case of an object-oriented implementation. The pre-simulation process applied to these models can also be carried out largely independently of the structure of the specific compressed air station or the models created for it.

The results in the pre-simulation method are typically calculated as the time courses of the, preferably all, state variables of compressors or other compressed air technology devices optionally included in a model. For this purpose, time courses of the state variables describing the compressed air station in the selected model, for example pressure curves, electrical power consumption, compressed air volume flows, speeds of drive motors, compressor elements or fan motors or positions of internal actuators, are to be recorded. These results are then evaluated for each alternative switching strategy using a quality criterion, whereby a preference order can be created. The shift strategy, which finally comes first in the order of preference out of a series of examined shift strategies, is selected as the relatively most advantageous shift strategy and kept ready or initiated accordingly. In this case, a selected, relatively most advantageous switching strategy does not have to be retained until the end of the pre-simulation period, but can already be replaced in the next control cycle by possibly determined more favorable switching strategies. The length of the pre-simulation period taken into account in the evaluation of the quality criterion can also be variable and, if necessary, be adapted adaptively by the control method to courses of disturbance variables, manipulated variables and / or state variables.

An essential point of the invention is also that the control or regulation method can appropriately take into account time delays (dead times) or abruptly changing state variables (discontinuities) in the pre-simulation, such as a sudden release of compressed air from a compressor after the Switching from standstill or idling to load operation. Due to the occurring dead times and discontinuities, the time delay of which can be greater than the duration of the control cycles, it is not only necessary to consider the effects of switching operations at the beginning of the current control cycle on the progression of the state variables in a current control cycle, but also to consider the effects of Switching operations within control cycles, in previous control cycles and the effects of switching operations on future control cycles. Such a holistic approach in terms of time is particularly easy to implement with the present method. Only through such an approach does a realistic, i.e. In particular, modeling of compressed air stations that reproduces the pressure curve and energy consumption with high accuracy is possible.

In contrast to known open-loop and closed-loop control methods, the present open-loop and closed-loop control method can also be used to examine switching strategies whose switching operations take place within the pre-simulation period. This also makes it possible to determine at which relatively most favorable point in time certain switching operations should be carried out. In addition, the method according to the invention also has the great advantage of being able to take into account variable temporal progressions of disturbance variables within the pre-simulation period. When using suitable prognoses for the disturbance variables, for example the temporal course of the compressed air extraction from the compressed air station, a pre-simulation with improved accuracy over longer periods of time is possible and thus also a better evaluation of the effects of switching operations.

Another idea of the invention consists in an expansion of the information base due to the implementation of the advance simulation method. The knowledge gained through the pre-simulation (simulation results) represent a set of information that relate to future changes in the state of the compressed air station, whereby further boundary conditions can also be taken into account. The system control of the compressed air station can consequently not only fall back on currently known process values, but rather also has knowledge about future effects and states of control or switching actions that have already been carried out in the past or in the present. At the same time, the pre-simulation also allows information values to be generated that only relate to future switching strategies. The present control method as an "acting" control method thus differs from the "reactive" control method known from the prior art. Only the implementation of the advance simulation also allows virtual pressure events to be defined, which relate to events that occur in the advance simulation, but are not motivated by current measured values of the real compressed air station. Avoiding undesirable events in the compressed air station that will only occur in the future thus allows the real pressure conditions in the compressed air station to be controlled early, but not prematurely.

In connection with at least one defined quality criterion, the pre-simulation method allows the evaluation of various alternative switching strategies for controlling the compressed air station. Several (in principle any number) variants of switching strategies can be calculated in the advance simulation in order to determine the reaction of the compressed air station to the to be able to determine and evaluate initiated switching strategies. According to the definition of the quality criterion, from a set of alternative switching strategies that one can be selected which delivers the relatively most advantageous result under predetermined boundary conditions. Here it is not only possible to simulate the switching strategies for a predetermined next switch-off time, but the switching strategies can extend practically as far into the simulated future. In addition, sequences of switching strategies can also be processed in the simulation, which enables the evaluation of switching strategies that build on one another. In addition to testing various switching strategies, various boundary conditions can also be simulated in advance. By varying the boundary conditions, it is possible, for example, to determine switching strategies for the actuators which meet the conditions most advantageously (or at least satisfactorily) in as many scenarios to be expected as possible.

In an advantageous embodiment of the method according to the invention, the advance simulation method for checking a switching strategy is carried out faster than it corresponds to the simulated time span, and preferably in a shorter time than the duration of a control cycle. Such a calculation speed allows a number of switching strategies to be simulated in advance, from which a relatively most advantageous one can then be selected by means of a quality criterion.

In a further advantageous embodiment of the method according to the invention, the pre-simulation method for checking a switching strategy in each case comprises, in particular, the time profile of state variables contained in the model of the compressed air station for the period of the pre-simulation. The future course of the state variables allows the information base to be enlarged, on the basis of which more precise and improved control or regulation is made possible.

In a further preferred embodiment of the method according to the invention, the model of the compressed air station is based on a set of time-dependent and / or non-linear as well as for the simulation of discontinuities and / or dead times in the behavior of the compressors and / or optional further devices of the compressed air technology, preferably structure-variant differential equations, which in this respect preferably also allow the recording of the impact of past events on the current state variables of the compressed air station. Structural variance should be understood to mean that only a changing subset of the set of differential equations is taken into account on a case-by-case basis. This plays a role in particular for the simulation of discontinuities and / or dead times in the behavior of the compressors and / or optional devices of compressed air technology, because their behavior in different operating states or when transitioning between different operating states can usually be described or respectively by different or changing differential equations . got to. The selection of the differential equations to be taken into account can be made by the differential equation itself or by external specification. Although the differential equations in a particularly preferred embodiment are time-dependent, non-linear and structurally variant, these properties do not necessarily have to be satisfied all together or not simultaneously for all differential equations. For example, instead of non-linear differential equations, a plurality of piece-wise or time-segment-wise linear differential equations can be used as an approximation, some differential equations can be time-dependent while the others are not time-dependent, some differential equations can be linear while the others are non-linear, and / or some differential equations can always be considered, others only on a case-by-case basis.

In an advantageous embodiment of the method according to the invention, it can be provided that a development of the various switching strategies is calculated over a predetermined period of time in discrete or continuous steps within the advance simulation method. The length of the time span can be specified externally by an operator of the compressed air station, for example, or it can also be permanently parameterized. The length of the time span can also be adapted adaptively to the events in the compressed air station. In this way, the system control can be set to the period durations of specific fluctuations in the pressure conditions that typically occur in a compressed air station.

In a continuation of the control method, it can be provided that the advance simulation is carried out over a predetermined period of time from 1 second to 1000 seconds, preferably from 10 seconds to 300 seconds. A time span of this length typically allows the changes and fluctuations in the pressure conditions caused by the initiation of switching strategies in the compressed air station to be recorded reliably, as well as ensuring a sufficient advance simulation span for most applications.

In a preferred embodiment of the method according to the invention, it is provided that the time span of the pre-simulation is adaptively adapted by a termination criterion on the basis of parameters and / or state variables of the model of the compressed air station, in particular of pressure events, and / or of recordings or forecasts of the pressure consumption. In this way, the duration of the pre-simulation can be advantageously adapted to the course of the compressed air consumption and consequently allows a faster or more extensive pre-simulation.

In a further embodiment of the method according to the invention it is provided that the checked with the advance simulation method Switching strategies include discrete or continuous changes in the operating state of compressors and optionally of further devices of the compressed air station at the beginning, at the end and / or at any time within the time span of the pre-simulation. The method according to the embodiment thus allows the changes in manipulated variables or disturbance variables to be taken into account within a simulated period of time and consequently enables the time course of these variables to be taken into account more realistically.

Furthermore, it can be provided that the length of the simulated time period of the pre-simulation method is determined as a function of the technical performance data of the compressors of the compressor system and / or as a function of the current load of individual compressors and / or past load fluctuations. Depending on the configuration of the compressed air station, the length of the pre-simulation can thus be restricted in such a way that the computing resources required to calculate the results of the pre-simulation are used as advantageously as possible. The length of the simulated time span is preferably dimensioned in such a way that it is longer than the shortest typically occurring load fluctuations of the compressed air station.

According to the embodiment, provision can also be made for the advance simulation to be carried out in discrete steps of 0.1 seconds to 60 seconds, preferably 1 second. According to this step size, immediate changes in the pressure conditions in the compressed air station, for example after a switching operation has been carried out, can be reliably recorded in the pre-simulation while the computing resources used by the system control are used economically.

In a further embodiment, the method for controlling a compressed air station can also be characterized in that, within the pre-simulation, at least some of the discontinuities and / or dead times in the behavior of the compressors and / or optional other compressed air technology devices, in particular the delayed compressed air delivery and the additional energy consumption of the compressors in connection with changes in their operating state, are taken into account in such a way that separate consideration outside of the advance simulation in the system control is no longer absolutely necessary. The actuators present in a compressed air station have typical dead times, which are in the range between 1 second and several tens of seconds. In contrast to the control methods known from the prior art, it is possible in the present case to calculate the effective dead times and other discontinuities in the preliminary simulation and thus to take these variables into account when calculating the switching operations. However, the prerequisite for taking the dead times into account is that the model of the compressed air station used contains the dead time behavior in parameterized form. Consequently, it is no longer necessary to take into account the dead times of the actuators in the system control itself. Overcoming the dead times is automatically present in the results of the advance simulation. On the one hand, this makes it possible to find out whether the control actions carried out in the past were sufficient to avert undesired pressure curves; on the other hand, it can be checked whether the control actions initiated in the present can have a positive effect on the time behavior of the pressure conditions in the compressed air station.

In a further embodiment of the present control method it can be provided that, as a group of alternative switching strategies, different upper pressure values or lower pressure values are considered as a criterion for initiating a previously defined switching strategy within the framework of the pre-simulation method. In contrast to the conventional pressure band control known from the prior art, the pressure values are not fixed in the present case, but can be adapted to the conditions in the compressed air station. The pressure values can also be determined using the advance simulation method. The definition of suitable upper and lower pressure values can be determined from multiple repeated previous simulations with pressure values that differ from one another. If such pressure values are first determined in advance, they can represent the basis for the calculation of different simulations in a fixed manner, in which the pressure values themselves remain unchanged, but variables such as manipulated variables characterized by switching operations are modified. In response to a change in state in the compressed air station that does not require a new definition of the upper pressure values, a switching strategy that is as advantageous as possible can be determined in that only a predetermined number of manipulated variables characterizing the actuating actions are determined in the advance simulation method.

In a further development, it can also be provided that different upper pressure values and / or lower pressure values for at least one previously specified switch-off strategy or at least one previously specified switch-on strategy are considered as a group of alternative switching strategies as part of the pre-simulation method. As a result, a series of switch-off strategies or switch-on strategies of the compressors included in the compressed air station can take place, for example in a simplified advance simulation with unchangeable pressure values or at least one unchangeable pressure value, by means of which a preferably averting of a future pressure event in the compressed air station can be determined.

In addition, in a further embodiment it can be provided that the at least one previously defined shutdown strategy or the at least a previously determined connection strategy results from a disconnection or connection sequence that is fixed in the form of a list. The respective sequences for switching off or switching on, for example, individual compressors or compressor groups can also be based on heuristic findings or on results from numerical calculations. By restricting the variable space restricted by the definition of the specified switch-off or switch-on sequences, the computing time for calculating individual alternative switching strategies can be shortened to a technically advantageous level.

Furthermore, in a further embodiment it can be provided that, as a group of alternative switching strategies, the connection or disconnection of different compressor groups in the case of fixed upper pressure values or lower pressure values that are still to be assessed in advance simulation methods are considered. The switching on or off of different compressor groups can again be based on heuristic knowledge or else on predetermined sequences which have been created by means of numerical calculations. By switching entire compressor groups on or off, it is possible to influence changes in pressure conditions in the compressed air station in a more targeted and sometimes longer-term manner.

In another embodiment of the method for controlling a compressed air station, it can be provided that the advance simulation method is carried out based on the theory for hybrid machines. This means that the implementation of the pre-simulation method has a broad basis for calculation, which can be carried out with high efficiency. The execution of the pre-simulation method based on hybrid automats, in contrast to the conventional calculation based exclusively on digital values, also enables the recording of analog values such as e.g. B. that of real-time metrics. The continuous measured variables do not take one value from a series of possible values, but can be changed continuously and therefore require special treatment. Hybrid automata represent an extension of the concept of finite automata with which practically any discrete system can be modeled.

Although hybrid machines do not necessarily have to be used to carry out the method according to the invention, according to the embodiment they are nevertheless a prerequisite for setting up the simulation model considered advantageous here.

In a continuation of the control method for controlling a compressed air station, provision can also be made for the advance simulation method to be carried out on the basis of a computer-implementable and preferably deterministic model. This allows previously known computer-implemented algorithms and mathematical methods to be used as they are widely available in numerical mathematics.

Furthermore, the method for controlling a compressed air station can also be distinguished by the fact that the quality criterion is defined or at least significantly co-determined by the lowest possible energy consumption. The energy consumption, which is sometimes the largest cost factor when operating a compressed air station, can consequently be determined in advance before specific changes in the pressure conditions in the compressed air station occur and can be suitably influenced by a selection criterion, for example to reduce or reduce energy consumption. A significant increase in profitability in the operation of the compressed air station can thus be the result.

In a further embodiment of the method for controlling a compressed air station, provision can also be made for the advance simulation method to include at least one data set with predicted future time courses of the state variables of the model of the compressed air station in different switching strategies at different, not necessarily equidistant points in time and / or with key figures derived therefrom, preferably for the entire control cycle. Due to the creation of such at least one data record, it is possible for the system control of the compressed air station, for example, to initiate corresponding switching strategies without the system control itself having to use the advance simulation method as an immediate control algorithm or part of an immediate control algorithm. Rather, the advance simulation method can be implemented as an independent numerical module, which is initialized and executed by the system control as required.

In another embodiment, the method for controlling a compressed air station can also include an optionally automatic adaptation of the model of the compressed air station to updated and / or initially only approximately known and / or not precisely set system parameters. This update ensures that at every point in time at which the pre-simulation method is carried out, suitable system parameters are available for the entire duration of the operation of the compressed air station. An automatic adaptation of the model of the compressed air station with regard to updated system parameters can, in addition to guaranteeing a more precise prediction, sometimes also result in an increased speed for executing the advance simulation method.

Furthermore, in one embodiment, the method according to the invention can also be characterized in that the model of the compressed air station is adapted to updated system parameters by selecting the one with which the subsequent simulation of the operation of the compressed air station is selected from several alternative sets of system parameters for a past time interval best matches the actually observed course of the operation of the compressed air station. This selection strategy can also be supported in that sequential, targeted changes to the operating status of individual compressors and / or devices of the compressed air station are carried out, and that only alternative parameters of the respective compressor and / or device are examined and selected in the context of the subsequent simulation.

According to the embodiment, it can also be provided that current variable system state variables of the compressed air station are taken into account in the advance simulation method, in particular information about the operating state of at least one pressure fluid tank, for example its pressure and / or its temperature and / or information about the operating states of individual compressors, for example their current control states and / or or current functional states and / or also information relating to the change in the amount of pressure fluid in the compressed air station, for example the decrease in the amount of pressure fluid per unit of time. By taking current, variable system state variables of the compressed air station into account, a more complete and more precise calculation can be carried out, which results in a higher control quality.

The method for controlling a compressed air station can also be characterized in that, in the pre-simulation method, information about the delivery volume of pressure fluid of individual compressors and / or about the power consumption of individual compressors in different load states and / or information about the dead times of the compressors and / or or minimum pressure or maximum pressure limits characteristic of the compressor system are taken into account. Taking into account the fixed system parameters of the compressed air station also allows a more detailed description of the compressed air station itself as well as boundary conditions important for the execution of the pre-simulation method, and consequently results in an improved prediction of the pressure conditions in the compressed air station by means of the pre-simulation.

The method for controlling the compressed air station can also provide that in the pre-simulation over the simulated period of time there is no change in the configuration of the compressors that are in load in the pre-simulation and the compressors of the compressed air station that are not in load in the pre-simulation. By reducing the possible variable space in this way, the advance simulation can be carried out more quickly and consequently increases the prediction speed. A distinction must be made here between the fact that the configuration of the compressors of the compressed air station that are in load or not in load in the pre-simulation does not have to match the currently prevailing configuration of load or non-load compressors of the compressor systems at the time the pre-simulation is carried out. Rather, it can be decisive to assume in a preliminary simulation a configuration of compressors that are under load or compressors that are not under load, which does not correspond to the real, current situation in order to consequently determine the switching strategy that is relatively most favorable for the control of the compressed air stations .

The method for controlling a compressed air station can also provide that a pressure compensation compressor is selected from the number of compressors that are in load in the pre-simulation, the smallest compressor in relation to the compressor output, which, according to the pre-simulation, has the longest remaining running time in an idle state if this compressor were to be transferred in a compressor that is in load in the pre-simulation to a compressor not in load in the pre-simulation. The division of the compressors into compressors that are in load in the pre-simulation or compressors that are not in load is done on the basis of process information and the parameterization stored in the controller. To bring about a future pressure equalization in the compressed air station, a compressor can be designated as a pressure equalization compressor, which in the future has to ensure a corresponding real pressure equalization. Typically, this pressure compensation compressor is selected from the set of compressors that are in load in the pre-simulation. Both preset parameters and process information (state variable) of the compressed air station can be used to select the pressure compensation compressor. By selecting the smallest compressor in terms of compressor power as a pressure compensation compressor from the number of compressors in load in the pre-simulation, the power consumption of the compressed air station can also be reduced and the costs for the operation of the compressed air station lowered.

Furthermore, the method for controlling a compressed air station can provide that for the determination of the lower pressure value at least two preliminary simulations with the same parameterization but differently selected numerical values are carried out for the lower pressure value and determine the simulated times when the lower pressure value is not reached. Here, the lower pressure value is typically only determined when the pressure compensation compressor is currently not under load. The control of the pressure compensation compressor can be taken over by an algorithm which works with the pressure values (lower pressure value and upper pressure value), which can always be adapted to the changing conditions in the compressed air station. Different pressure values can be specified in a stochastic process and by means of the pre-simulation process can be tried out. The lower pressure value is typically only determined when the pressure compensation compressor is currently not under load. Using the pre-simulation method, it is thus possible to determine the probable point in time at which the pressure below a previously parameterized minimum pressure of the compressed air station occurs. Using heuristic rules, it can also be determined when the pressure compensation compressor is treated as a load compressor in the advance simulation method. For example, if the compressor is in an idle state 5 seconds before the pressure falls below the minimum, the lower pressure value is the pressure 5 seconds before the pressure falls below the minimum. If, on the other hand, the pressure compensation compressor is switched off 5 seconds before the pressure falls below the minimum pressure, the lower pressure value is the pressure at the time 15 seconds before the pressure falls below the minimum. The time span of 5 seconds can correspond to the approximate dead time of a compressor for the state change from an idle state to a load state. The time span of 15 seconds, on the other hand, can correspond to the approximate dead time of a compressor for the state change from a switched-off state to a load state.

The method for controlling a compressed air station can also be characterized in that at least two preliminary simulations with the same parameterization but differently selected numerical values are carried out for the upper pressure value for the determination of the upper pressure value and then transfer the pressure compensation compressor to a compressor that is under load in the preliminary simulation , when the pressure of the pressure fluid in the compressed air station falls below the lower pressure value, and then transferred to a compressor that is not under load when the pressure of the pressure fluid in the compressed air station exceeds the upper pressure value. The upper pressure value is typically redefined before each preliminary simulation. A minimum and a maximum value can be specified for the upper pressure value. The minimum value typically corresponds to the lower pressure value. The maximum value of the upper pressure value can also result from the maximum pressure permissible for the operation of the compressed air station. If the pressure in the compressed air station exceeds, for example, the maximum pressure, the pressure compensation compressor must be switched off automatically. All values between the minimum and the maximum value for the upper pressure value are permissible pressure values in the pre-simulation. By dividing this pressure regime into, for example, equally spaced pressure limits, a predetermined number of upper pressure values can be examined for their properties suitable for controlling the compressed air station by means of the pre-simulation. Provision can be made for that pressure value to be determined as the upper pressure value which, over the simulated temporal course of the pressure conditions in the compressed air station, allows the most stable course of the pressure to be expected. In a continuation of the method for controlling a compressed air station, it can be provided that the upper pressure value determined to be relatively advantageous in the preliminary simulation comes from the entirety of all upper pressure values set in the preliminary simulations, and is relatively advantageous in terms of energy consumption in terms of the simulated energy consumption of all Compressors has been selected. Accordingly, a suitable choice of an upper pressure value can already make a considerable contribution to reducing the operating costs of the compressed air station.

It should be noted at this point that the upper and lower pressure values are not to be understood as the limits of a real or even fixed pressure range, but rather as alternative upper or lower pressure values that trigger switching operations in relation to compressors to different and alternative switching times can be "tried out".

It can also be provided that the upper pressure values set in the previous simulations are set in increments of 0.5 bar, especially in increments of 0.1 bar, in order to determine an advantageous upper pressure value, the increments of the subsequently set or examined upper pressure values do not have to be equidistantly spaced, or the step size between the examined upper pressure values does not have to be constant. These step sizes allow a reliable determination of that upper pressure value which is to be classified as relatively most advantageous. The step sizes relate to operating pressures or fluctuations in operating pressures in compressor systems such as those used in an industrial environment.

In a continuation of the control method for controlling a compressed air station, it can be provided that the advance simulation uses stochastic models of the development of consumer behavior over time with regard to the extraction of pressure fluid from the compressed air station. Accordingly, the withdrawal of pressurized fluid can also be taken into account in the preliminary simulation, as it occurs approximately in the regular operation of the compressed air station.

In an alternative embodiment, it can also be provided that the advance simulation uses artificially intelligent and / or adaptive numerical routines with regard to the development of consumer behavior over time with regard to the removal of pressure fluid from the compressed air station. As a result, a relatively precise recording of consumer behavior is guaranteed after a long period of use of the compressed air station. A consideration of consumer behavior with regard to the development over time can be thus take place in a particularly favorable manner.

In a further embodiment of the method according to the invention, it can be provided that the technical implementation of the method is defined using object-oriented programming methods, with at least the compressors being viewed as objects. Accordingly, the development and implementation of the model of the compressed air station is particularly simple.

In a preferred embodiment of the system control of a compressed air station, separate hardware is used to carry out the pre-simulation, which communicates via a bus system with the system control, which in turn is in communication with the compressors and optionally with other compressed air technology devices.

In a further preferred embodiment of the method according to the invention, the heuristics for the formation of alternative switching strategies are implemented by a model of a system control of a compressed air station contained in the simulation model, the system control model taking over the control and regulation of the simulated compressed air station in the simulation and alternative switching strategies by specifying alternative ones Control and regulating parameters are formed for the model of the system control, from which the relatively most advantageous switching strategy is selected to initiate in the real compressed air station.

Further embodiments of the invention emerge from the subclaims.

Fig. 1

eine schematische Darstellung einer Druckluftstation mit einer Anlagensteuerung, gemäß einer ersten Ausführungsform der vorliegenden Erfindung,

Fig. 2

eine schematische Darstellung einer Druckluftstation mit einer Anlagensteuerung, gemäß einer weiteren Ausführungsform der vorliegenden Erfindung,

Fig. 3

ein Modell der Druckluftstation gemäß der Ausführungsform der realen Druckluftstation in Fig. 2,

Fig. 4

eine Darstellung des zeitlichen Verlaufes des Drucks in einer Druckluftstation in Abhängigkeit der Änderung einer Stellgröße durch eine Stellhandlung,

Fig. 5

ein Flussdiagramm zur Verdeutlichung des Verfahrens unter Verwendung einer Voraussimulation zur Steuerung einer Druckluftstation gemäß einer Ausführungsform des erfindungsgemäßen Verfahrens,

Fig. 6

ein Flussdiagramm zur Darstellung der Verwendung einer Voraussimulation in einer Ausführungsform des erfindungsgemäßen Steuerungs- bzw. Regelungsverfahrens,

Fig. 7

eine Darstellung des zeitlichen Druckverlaufs einer Druckluftstation unter Verwendung von Druckbandgrenzen,

Fig. 8

eine Darstellung des Druckverlaufs in einer Druckluftstation, welche ein Drucksteuerungsverfahren unter Verwendung dreier ineinander geschachtelter Druckbänder einsetzt,

Fig. 9

zeitlicher Verlauf des Drucks in einer Druckluftstation gemäß einer Ausführungsform der Erfindung über eine zukünftige simulierte Zeitspanne bei virtuellen Stellgrößenänderungen,

Fig. 10

einen Druckverlauf in einer Druckluftstation gemäß einer Ausführungsform der Erfindung über eine simulierte zukünftige Zeitspanne bei virtuellen Stellgrößenänderungen zur Ermittlung einer bevorzugten Schaltstrategie, und

Fig. 11

eine zeitliche Druckänderung in einer Druckluftstation mittels eines Steuerverfahrens unter Berücksichtigung der Totzeit zweier Steuerungselemente.

The invention is described below on the basis of exemplary embodiments, which are explained in more detail using the illustration. Here show:

Fig. 1

a schematic representation of a compressed air station with a system control, according to a first embodiment of the present invention,

Fig. 2

a schematic representation of a compressed air station with a system control, according to a further embodiment of the present invention,

Fig. 3

a model of the compressed air station according to the embodiment of the real compressed air station in Fig. 2 ,

Fig. 4

a representation of the time profile of the pressure in a compressed air station as a function of the change in a manipulated variable caused by an actuation,

Fig. 5

a flowchart to illustrate the method using a pre-simulation for controlling a compressed air station according to an embodiment of the method according to the invention,

Fig. 6

a flowchart to illustrate the use of a pre-simulation in an embodiment of the control or regulation method according to the invention,

Fig. 7

a representation of the pressure curve of a compressed air station over time using pressure band limits,

Fig. 8

a representation of the pressure curve in a compressed air station, which uses a pressure control method using three nested pressure bands,

Fig. 9

Temporal progression of the pressure in a compressed air station according to an embodiment of the invention over a future simulated time span in the case of virtual manipulated variable changes,

Fig. 10

a pressure curve in a compressed air station according to an embodiment of the invention over a simulated future time span with virtual manipulated variable changes to determine a preferred switching strategy, and

Fig. 11

a change in pressure over time in a compressed air station by means of a control method taking into account the dead time of two control elements.

In the following description, the same reference symbols are used for parts that are the same or have the same effect.

Fig. 1 shows a schematic representation of a first embodiment of a compressed air station 1, which interacts with an embodiment of a system control 3 according to the invention and is also controlled or regulated by this. The compressed air station 1 further comprises three compressors 2, which are connected to two compressed air dryers 14 via pressure lines 9 and actuators 5 designed as valves. The pressure fluid 4 (not shown here) provided for one or more users is stored in the pressure fluid tank 8. In order to be able to make the necessary manipulated variable changes by the system control 3, each actuator 5 can be addressed to the system control 3 via a connection not further designated here. The functional principle of the system control 3 corresponds in principle to that of the further, somewhat more complex embodiment according to Fig. 2 .

Fig. 2 shows a schematic representation of a in comparison to the embodiment according to Fig. 1 somewhat more complex compressed air station 1, which interacts with a system control 3 and is controlled by this or is regulated. The compressed air station 1 comprises three compressors 2 in the system control 3, which, with appropriate control or regulation, are provided to provide pressurized fluid 4 (not shown here) at three pressurized fluid tanks 8. The pressure fluid 4 is distributed from each compressor 2 via a pressure line 9 to three actuators 5, which are designed as valves 5 in the present case, which are in fluid connection with the three pressure fluid tanks 8 and can supply each pressure fluid tank 8 with pressure fluid if required. The pressure fluid 4 can be taken from the compressed air station 1 by a user or several users if necessary. In this case, the withdrawal takes place at a consumer station (consumer point), which is not further designated here, in such a way that pressure fluid 4 can be withdrawn from all pressure fluid tanks 8. According to the switching operations performed on the actuators 5 by the system control 3, on the one hand, pressure fluid 4 can be directed from the pressure fluid tanks 8 to the user station to the user, on the other hand pressure equalization of the individual pressure fluid tanks 8 with one another is also possible. In order to be able to carry out the necessary manipulated variable changes or switching strategies by the system control 3, each actuator 5 can be addressed to the system control 3 via a connection not further designated here. For reasons of clarity, not every actuator 5 has been expressly provided with a connection to the system control. However, it should be apparent to those skilled in the art that such a connection can be implemented. The control signals for switching operations transmitted by the system control 3 to the actuators 5 can be of the most varied of types and, moreover, can be both discrete and continuous in nature. Typically customary control signals of the actuators 5, in particular at valves, can include switching on, switching on or even only gradual switching on or on. Connections between the receiving station of individual fluid tanks 8 can thus be established via controllable actuators 5. Furthermore, possible initial actuators (for example pressure reducing valves) can be installed between the pressure fluid tanks 8 and the consumer station. The connection of several consumer stations to a compressed air station 1 is also conceivable. Furthermore, the compressed air station 1 can include sensors that detect system state variables 56 (not shown here) that change over time and make them available to the system controller 3 for controlling or regulating the compressed air station 1. For example, the pressurized fluid tanks 8 can be provided with sensors, which are not further designated in the present case, which enable the pressures in the individual pressurized fluid tanks 8 to be measured. Furthermore, the compressed air station 1 can also be provided with further sensors, not shown here, which allow the detection of fluid-technical variables for characterizing the compressed air station 1.

Fig. 3 represents a model of the compressed air station as in Fig. 2 shown, which is used, for example, in a system control 3 for controlling the real compressed air station. Here, the system control 3 can use a pre-simulation method 20 (not designated in the present case) in accordance with an embodiment of the present invention or can also embody only a symbolic representation for the parameterization of a compressed air station 1. If the model of the compressed air station 21 is used in a control or regulation method according to an embodiment of the invention, then each component essential for the operation of the compressed air station is characterized by a numerical parameterization (parameterization). The format of this parameterization must be suitable in order to be used in a suitable manner by the system control 3 or a pre-simulation method 20 (not shown here). The parameterization can take place here not only through numerical, but also through symbolic values, for example through the specification and selection of functional principles, designs, series or type designations of compressors.

Fig. 4 represents the time course of the pressure in the compressed air station 1, or a pressure fluid tank 8, not further designated here, under the influence of a switching strategy 10 (switching operation, manipulated variable change). The switching operation occurs at the present time. The switching strategy 10 is carried out, for example, in order to compensate accordingly for the pressure of the compressed air station 1 that has fallen in the past. It is clearly visible here that with a corresponding switching action in the present, for example switching on a pressure valve, an increase in the pressure in the compressed air station 1 occurs over time in the future. Depending on the size of the manipulated variable change, there will be a lesser or greater pressure increase in the future. In the case of a small manipulated variable change S _{3 in} terms of size, a future pressure curve occurs, which is designated by T ₃ . Corresponding to the change in the manipulated variable S ₂ , there is a future pressure profile T _2, and if the manipulated variable S _{1 changes} , a pressure profile according to curve T ₁ occurs. All three manipulated variable changes S ₁ , S ₂ and S ₃ are suitable for preventing a pressure drop below a predetermined minimum pressure P _min . According to a decision criterion, it is now the task of the system control 1 to decide which manipulated variable change is suitable in order to bring about a future desired pressure profile. In the present case, such a decision criterion could, for example, be responsible for the fact that the course of the continuously lined manipulated variable change S _{3 is} viewed by the system control 1 as the preferred switching strategy 10.

A preferred switching strategy 10 is selected according to the present inventive method for controlling a compressed air station also by means of a pre-simulation.

Fig. 5 shows a flowchart of such a selection process using advance simulation. Here, a advance simulation procedure (advance simulation) is initialized at time t = 0 s (present) with the state variables which reflect the current state of the compressed air station 1. The pre-simulation process is started immediately after the initialization t≈0 s, i.e. a point in time that can still be referred to as the present within the scope of the simulation time spans) and delivers three in the present case after the process has run or after the pre-simulation process 20 has run several times with changed output parameters alternative switching strategies 11 (Alt.1, Alt.2 and Alt.3) from which the suitable alternative switching strategy 11 is selected by means of a quality criterion 22 in order to induce the system control to generate a switching command 30 for generating a switching strategy 10. According to the embodiment, the alternative switching strategies 11 can result in future and predicted pressure profiles in the compressed air station 1, such as in the pressure profiles T ₁ , T ₂ and T _{3 of} the pressure profile in FIG Fig. 4 .

Fig. 6 FIG. 11 shows a further flow diagram for the representation of a data record 6 which contains simulation results of the advance simulation 20. How to Fig. 5 already explained, in one embodiment of the control method according to the invention, a preferred switching strategy 10 can be determined from the data record 6 by means of a quality criterion 22. To initialize a pre-simulation or a sequence of pre-simulations, you need to enter system-relevant variables. System-relevant variables can be fixed system parameters 55, which contain, for example, information about the delivery amount of pressure fluid of individual compressors, or about the power consumption of individual compressors in different load states, information about the dead times of the compressors or actuators, as well as minimum pressure and pressure values characteristic of the compressed air station Maximum pressure limits. Furthermore, system-relevant parameters can also consist of system state variables 56 which represent variables that change over time. Such system state variables 56 of the compressed air station 1 can contain the information about the operating state of at least one pressure fluid tank 8 or its pressure, its temperature; they can include information about the operating states of individual compressors 2, as well as their current control states or functional states, as well as information relating to the Change in the amount of pressure fluid 4 in the compressed air station 1, such as the change in pressure fluid per unit of time, its flow or its other physical parameters. The quality of the advance simulation 20 is based on the quality or number of fixed system parameters 55 and system state variables 56 on which the advance simulation 20 is based.

Fig. 7 shows the representation of a pressure curve of a compressed air station in relation to a pressure band, which defines a pressure band lower limit 42 with a minimum pressure P _min and an upper pressure band limit 41 with a maximum pressure P _max . When using a single fixed, predetermined pressure band to control a compressed air station 1, as is the case with a sequence control known from the prior art, the pressure curve causes a corresponding switching action when the pressure band leaves the pressure band. For example, when leaving the pressure curve downward beyond the lower pressure band limit 42, a connection action can be initiated which provides an additional compressor for the delivery of pressure fluid. Such a switching action is initiated at the point in time at which the pressure profile leaves the pressure band lower limit 42, whereby the delivery of additional pressure fluid takes place in such a way that after a short period of time the pressure profile is again within the limits of the fixed predetermined pressure band. If, on the other hand, the pressure profile leaves the upper pressure band limit 41 upwards, the pressure profile can be corrected, for example, by a shutdown action at the time of leaving the upper pressure band limit 41, so that after a short period of time it is exceeded again within the pressure band limits.

In order to be able to influence the pressure curve in the compressed air station 1 in terms of control technology before the minimum pressure P _{min is} undershot or the maximum pressure P _{max is} exceeded, further nested pressure bands can also be defined in the calculations to initiate the switching operations. So shows Fig. 8 for example the pressure curve of a compressed air station 1 relative to three nested pressure bands. The smallest pressure band with the lower pressure limit 42 of P _U1 and the upper pressure limit 41 with the pressure P _O1 lies within the next larger pressure band with the lower pressure limit 42 of P _U2 and the upper pressure band 41 with the pressure P _O2 . Both previously described pressure bands are again within the largest pressure band, which has a lower pressure limit 42 of P _min and a maximum pressure of the upper pressure band limit 41 of P _max . In order to prevent the pressure curve from being exited beyond the pressure band limits of the largest pressure band, the system control 3 (not listed here) can initiate switching operations at the times at which the pressure profile exceeds the pressure band limits of the smallest or next larger pressure band. Due to the delay times inherent in the compressed air station after a switching action has been carried out, the pressure curve is corrected after correspondingly short periods of time.

The ones in the Figures 7 and 8 The pressure curves shown result from switching operations that have been initiated by purely reactive control processes. Only if a predetermined one at a time If a pressure event has occurred (e.g. leaving the pressure band limits), a corresponding switching action is initiated. In contrast to this, according to the present invention, switching strategies are simulated in the future in order to set a desired pressure profile.

Fig. 9 shows such a simulation over a future simulated time span 23. Here, at a point in time in the present, a switching strategy 10 is carried out which reduces the manipulated variable from a value a) to a smaller value b). The expected future course of the pressure in the compressed air station follows a drop that is slightly delayed. In order to avoid a pressure drop below a predetermined value or to set a stable pressure curve, a virtual change in the manipulated variable from value b) to the higher value c) is carried out in the advance simulation at a future point in time. This virtual change in the manipulated variable results in a virtual increase in the pressure in the compressed air station 1. Here, for example, the virtual change in the manipulated variable can lie in a connection strategy 13 of a compressor. However, in order to avoid an excessively large virtual pressure increase, another manipulated variable change from value c) to value d) is carried out at a later simulated point in time. This second virtual manipulated variable change to value d) can lie in a shutdown strategy 12, for example. Due to the combination of both virtual manipulated variable changes, it is possible to set a stable virtual pressure curve towards the end of the simulated time span 23. If, for example, the two virtual manipulated variable changes are now made at the corresponding points in time in the real future as an actual switching strategy 10, a stable pressure curve can be expected to be set. By executing the advance simulation, the future behavior of the compressed air station can thus be predicted, and the information base on the state of the compressed air station can be expanded to include future points in time.

Fig. 10 represents in comparison to the pressure curve, which in Fig. 9 is shown, represents three possible virtual pressure curves as they would result as a result of different manipulated variable changes according to the advance simulation 20 over the simulated time span 23. Depending on the virtual switch-on strategies 13 or switch-off strategies 12, a stable or rising or falling pressure curve results at the end of the simulated time span 23. It should also be noted here that the virtual switching strategies 10 carried out in the different simulations can also take place at different times. Furthermore, the different changes in the manipulated variable can also be influenced by the behavior of one or more users taking pressure fluid from the compressed air station 1. Correspondingly, the sequence of switching operations, which is denoted by S ₁ , results in a pressure profile T ₁ increasing towards the end of the simulated time span 23. The sequence of switching operations, which is denoted by S ₂ , results in a largely stable course of the pressure in the compressed air station 1 towards the end of the simulated time period 23. The sequence of switching operations, which is denoted by S ₃ , results at the end of the simulated time period 23 in a falling pressure curve T ₃ . If that pressure curve were selected from the three possible, simulated pressure curves by means of a quality criterion 22 (not listed here), which shows the relatively smallest fluctuations at the end of the simulated time span 23, then the pre-simulation 20 carried out suggests switching operations 10 in accordance with the S ₂ to execute the specified sequence of switching operations at the corresponding future times. As will be understood by a person skilled in the art, numerous possible virtual pressure curves can also be generated by varying numerous other parameters in the preliminary simulation, from which the best can then be selected according to a quality criterion 22.

By introducing a pre-simulation method 20, it is possible to calculate the effective dead times of the elements used in the compressed air station 1 in the simulation and thus implicitly include them in the calculation of the times at which switching strategies 10 are carried out. A prerequisite for this, however, is that the models of the compressed air station 21 used contain the dead time behavior. Consequently, it is no longer necessary to explicitly take into account the dead times of individual actuators 5 in the system control 3. Actuators 5 can here also be comprised of compressors 2 and other optional devices of the compressed air station, which can be controlled for example by suitable control signals for the purpose of changing the control variable. Actuators 5 are consequently not only on external valves 5, as in FIG Fig. 2 shown, limited. The dead times are overcome automatically with the help of the generated pre-simulation. On the one hand, this makes it possible to find out whether the manipulated variable changes made in the past were sufficient to avert undesirable events, and on the other hand, it can be checked whether the manipulated variable changes introduced in the present can have an additional positive influence on the behavior of the pressure curve over time.

In Fig. 11 the pressure curve of a compressed air station 1 is shown over time. In the past, a switching action was carried out on the first actuator at time T1. Due to the dead time of the first actuator 5, the effect of this switching action in the pressure curve cannot yet be seen in the present. In the present, there is consequently the possibility of performing a further switching operation on a second actuator. However, only when the future pressure curve can be simulated can a decision be made as to whether the switching action should be taken the degree of fulfillment of a boundary condition (for example avoidance of falling below the minimum pressure P _min ) can be improved on the second actuator, or was necessary at all. If the pre-simulation for both possible switching strategies is carried out over the simulated time span 23, it becomes apparent that the switching action on the second actuator 5 is not necessary in order to ensure compliance with the boundary conditions. In addition, it can be seen that the dead time of the second actuator 5 is only overcome after the pressure in the compressed air station 1 is already well above the minimum pressure P _min . As a result, it could be decided on the basis of the pre-simulation method 20 carried out that the switching action on the second actuator to improve the pressure profile in the compressed air station 1 should not be performed.

At this point it should be pointed out that all of the parts described above, seen on their own and in any combination, in particular the details shown in the drawings, are claimed to be essential to the invention. Changes to this are familiar to the person skilled in the art.

Reference number:

1

Compressed air station

2

compressor

3

Plant control

4th

Pressure fluid

5

Actuator

6th

record

8th

Pressurized fluid tank

9

Pressure line

10

Shift strategy

11

alternative shift strategy

12

Shutdown strategy

13

Connection strategy

14th

Compressed air dryer

20th

Advance simulation process

21st

Model of the compressor system

22nd

Quality criterion

23

Period of time

30th

Switching command

41

Upper limit of pressure range

42

Pressure range lower limit

54

Pressure equalization compressor

55

System parameters

56

System state quantity

60

hardware

61

Bus system

70

Simulation core

71

Algorithm core

72

Information base

Claims (15)

1. Method for controlling and regulating a compressed air station (1) comprising at least a plurality of interlinked compressors (2), which method is capable of initiating both switching strategies (10) via an electronic plant control (3) for influencing an amount of a compressed fluid (4) that is available at any time in the compressed air station (1) to one or more users of the compressed air station (1) and is able to adjust the amount of compressed fluid (4) that is available at any time to one or more users of the compressed air station (1) to future operating conditions of the compressed air station (1) in an adaptive manner to the withdrawal quantity of compressed fluid (4) from the compressed air station,
   wherein a switching strategy is a sequence of switching actions, i.e. a discrete or continuous change of manipulated variables, which cause a change in the operation of one or more components of the compressed air station,
   wherein, prior to initiating a switching strategy (10), different switching strategies (10) are checked in a preliminary simulation method (20) on the basis of a model (21) of the compressed air station (1), and the relatively most beneficial switching strategy (10) is selected from the checked switching strategies (10) using at least one fixed quality criterion (22), and the selected switching strategy (10) is forwarded to the plant control (3) for being initiated in the compressed air station (1).
2. Method according to claim 1, characterized in that predetermined upper pressure limits and/or lower pressure limits are taken into account as boundary conditions to be met in the method (20).
3. Method according to any one of the preceding claims, characterized in that the model (21) of the compressed air station (1) is based on a set of differential equations that are time-dependent and/or non-linear as well as from case to case for modelling discontinuities and/or dead times in the compressors' behavior and/or structurally variable, which equations also allow the effect of past events on the current state variables of the compressed air station (1) to be taken into account.
4. Method according to any one of the preceding claims, characterized in that, within the preliminary simulation method (20), a development of the different switching strategies (10) over a predetermined period of time (23) in discrete or continuous steps is predicted or calculated.
5. Method according to any one of the preceding claims, characterized in that the period of time of the preliminary simulation (20) is adjusted in an adaptive manner by an abort criterion on the basis of parameters and/or state variables of the model of the compressed air station (1) and/or records or predictions of the compressed air consumption.
6. Method according to any one of the preceding claims, characterized in that, as a group of alternative switching strategies (10), differing upper pressure values (41) or lower pressure values (42) are considered within the framework of the preliminary simulation method (20) as a criterion for initiating a previously specified switching strategy (10).
7. Method according to any one of the preceding claims, characterized in that, as a group of alternative switching strategies (10) for at least one of the interlinked compressors, differing upper pressure values (41) or lower pressure values (42) are considered within the framework of the preliminary simulation method (20) for at least one previously specified switch-off strategy (12) and at least one previously specified switch-on strategy (13), respectively.
8. Method according to any one of the preceding claims, characterized in that, as a group of alternative switching strategies (10), even the switching-on or switchingoff of various compressor groups (5a, 5b) is considered at upper pressure values (41) or lower pressure values (42) that are fixed or still to be evaluated in the preliminary simulation method (20).
9. Method according to any one of the preceding claims, characterized in that the quality criterion (22) is defined or at least co-determined in a decisive manner by a lowest possible energy consumption.
10. Method according to any one of the preceding claims, characterized in that the preliminary simulation method (20) renders at least one data set (6) including predicted future temporal progresses of the state variables of the compressed air station (1) model under various switching strategies (10) at different, not necessarily equidistant points of time and/or including characteristic numbers derived therefrom, preferably for the entire control cycle.
11. Method according to any one of the preceding claims, characterized in that the method comprises an optionally automated adaption of the compressed air station (1) model to plant parameters that are upgraded and/or initially only approximately known and/or not precisely set.
12. Method according to any one of the preceding claims, characterized in that in the preliminary simulation method (20), current variable system state variables (56) of the compressed air station (1) are taken into account, and/or information on the operating states of individual compressor (2) and/or else information referring to the change in the amount of compressed fluid (4) in the compressed air station (1), for example the decrease of the compressed fluid amount per time unit and/or that in the preliminary simulation method (20), as fixed system parameters (55) of the compressed air station (1), information on the delivery quantity of compressed fluid (4) of individual compressors (2) and/or on the energy input of individual compressors (2) under differing load conditions and/or information on dead times of the compressors (2) and/or minimum pressure and maximum pressure limits that are characteristic for the compressed air station (1) are taken into account.
13. Method according to any one of claims 1 to 12, characterized in that the preliminary simulation (20) uses artificially intelligent and/or adaptive numerical routines referring to the temporal development of consumer behavior with respect to the withdrawal of compressed fluid (4) from the compressed air station (1).
14. Method according to any one of the preceding claims, wherein the method which is implemented in an electronic control of a compressed air station (1) processes information on essential state variables of the compressed air station (1) as input information and outputs control instructions for controlling at least some compressors (2) as an output, characterized in that the method exhibits the following function structures:

    - a simulation core (70) in which, for describing the behavior of at least some components of the compressed air station (1), dynamic models of these components are included, wherein the simulation core (70) is configured to calculate in advance as a simulation result the temporal progress of all of the model-related state variables of the components of the compressed air station (1) on the basis of assumed alternative switching strategies (10), the model of the simulation core (70) taking into account the essential non-linearities and/or discontinuities and/or dead times in the behavior of the components;

    - an algorithm core (71) which contains parameters for characterizing the components of the compressed air station (1), topology information on the interconnection of individual components, heuristics for creating alternative switching strategies (10) and evaluation criteria for the temporal evolutions of the state variables of the compressed air station's (1) components for the alternative switching strategies (10) obtained by the simulation core (70), and selects, on this basis, the relatively most beneficial switching strategy and keeps and hands over corresponding control commands to at least some compressors (2);

    - an information base (72) which includes, in addition to a process map formed from sensor values and actuator values optionally provided by the algorithm core (71), also the simulation results for alternative switching strategies (10), wherein the information base (72) represents at least part of a common data base of the algorithm core (71) and simulation core (70) and serves to exchange data between the algorithm core (71) and simulation core (70).
15. Plant control (3) of a compressed air station (1) comprising a plurality of interlinked compressors (2), which plant control is capable of initiating both switching strategies (10) of actuators (7) of the compressed air station (1) and/or of various compressors (2) for influencing the amount of the compressed fluid (4) that is available at any time in the compressed air station (1) to one or more users of the compressed air station (1) and is able to adjust the amount of compressed fluid (4) that is available at any time to one or more users of the compressed air station (1) to future operating conditions in an adaptive manner to the withdrawal quantity of compressed fluid (4) from the compressed air station,
    wherein a switching strategy is a sequence of switching actions, i.e. a discrete or continuous change of manipulated variables, which cause a change in the operation of one or more components of the compressed air station,
    wherein, prior to performing a switching strategy (10), different switching strategies (10) are checked in a preliminary simulation method (20) on the basis of a model (21) of the compressed air station (1), and the relatively most beneficial switching strategy (10) is selected from the switching strategies (10) using at least one fixed quality criterion (22), and the plant control (3) generates a switching command (30) based on the selected switching strategy (10).

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