Method for controlling a compressor system having multiple compressors

Abstract

The present invention relates to a method for controlling a compressor system (100) comprising a number of compressors (C1, C2, ...) for producing compressed gas, in particular compressed air, for at least one consumer (200), as well as a corresponding control unit (300) and compressor system (100). The method comprises the steps of: simulating a number of future system states (S) of the compressor system (100); tn,m ) and a step of determining a future time point (t n ) for the future system state (S tn ) from the set of similar system states (S tn,sim ) and determining the determined similar system state (S tn,sim ) by discarding at least one system state from the set at a future time (t n ) is determined for the system state (S tn ) and determining an optimal compressor operating state combination sequence (CSseq) with respect to a quality criterion, which is preferably an energy efficiency criterion. opt ) suitable for controlling the operation of a plurality of compressors (C1, C2, ...) of the compressor system, and determining an optimal compressor operating state combination sequence (CSseq opt and issuing at least one control command (LC1, LC2, LC1 / LC2) corresponding to at least a portion of the control command (LC1, LC2, LC1 / LC2).

Description

[Technical Field]

[0001] The present invention relates to a method for controlling a compressor system including a plurality of compressors for generating compressed gas, in particular compressed air, for at least one consumer, as well as a control unit for the compressor system and the compressor system. [Background technology]

[0002] Industrial compressor systems for compressed air generation (compressed air systems) are operated to supply compressed air for process or machine operation. A compressed air system typically includes one or more compressors as compressed air generators. One or more compressed air consumers are connected to the compressed air system via a compressed air network and supplied with compressed air as needed.

[0003] The compressed air demand of a compressed air consumer is generally expressed as a consumption volume flow rate, but it is not constant over time. The total demand of all compressed air consumers is the sum of their individual demands, resulting in the instantaneous consumption volume flow rate CVF(t). The operation of the connected consumers is usually not synchronized in time, so the compressed air demand fluctuates.

[0004] Compressed air systems typically also include compressed air treatment components (such as filters, condensate separators, oil separators, and dryers), compressed air storage tanks, and other components such as piping and valves. Oil-injected compressors include an oil circuit and use oil injected into the compression chambers for cooling and lubrication.

[0005] For decades, the use of pressure-switched cascade circuits has been common in the field of compressed air generation, where multiple compressors are switched on or off in a defined sequence by the pressure switches. A specified pressure band is limited by a minimum and maximum pressure. When the pressure falls below the specified minimum pressure, the compressor is switched to a loaded state (compressed air is supplied); when the pressure rises above the specified maximum pressure, the compressor is switched to an unloaded state (no compressed air is supplied). The upper and lower pressure limits of the individual compressors are usually shifted relative to each other so that the pressure switches switch the compressors on or off in sequence. The specific operating state of a particular compressor (e.g., stopped, idling, loaded) is only indirectly affected by the pressure switch.

[0006] Known cascade circuits with pressure switches do not adapt to changes and fluctuations in compressed air consumption. The pressure switch setting is always the same for the different operating phases of compressed air consumption, and the selected setting must cover all phases of compressed air consumption. In this respect, a properly set pressure switch is a compromise that does not guarantee optimal control. Finding the right pressure switch setting requires a lot of system- and consumer-specific knowledge and experience. Furthermore, pressure switches do not take into account the fact that when a load command is issued to the compressor (a command to switch the compressor to the loaded state), the motor may first need to start. Therefore, the minimum pressure must be set significantly higher than the pressure that the compressed air reservoir should not actually fall below in order to cover the desired compressed air consumption. This leads to an increase in the average system pressure, which has a negative impact on energy efficiency.

[0007] WO 2010 / 072803 A1 describes a simulation-based method for controlling or regulating a compressed air station. Pressure changes in the compressed air station must be predicted as early as possible to initiate appropriate switching actions. Before a switching strategy is initiated, various switching strategies are tested in a preliminary simulation procedure based on a model of the compressed air station. A switching strategy is understood to be a sequence of switching actions, i.e., discrete or continuous changes in a control variable, that result in a change in the operation of one or more components of the compressed air station. The most advantageous switching strategy is selected based on quality criteria and implemented in the compressed air station. While the optimization problem is not solved, only a limited number of switching strategies are selected for investigation, which are then investigated in more detail in a preliminary simulation to determine the best solution from this limited selection of switching strategies. It is highly likely that an optimal switching strategy will not be found.

[0008] EP3974918A1 describes a computer-implemented control method for a compressed air system with one or more compressors. The future course of a process variable is sampled at a sampling rate based on the volume of the compressed air system. Using an MPC method (Model Predictive Control, MPC), the future course of the sampled process variable is converted into an operational course over a predetermined first time horizon and into a state course over a predetermined second time horizon of equal or greater size. Here, the operational course includes the switching of a particular compressor. The time resolution can be adaptively changed by using different sampling rates. Especially for dynamic processes, the increased sampling rate (higher time resolution) and the time horizon that can be predicted with sufficient accuracy are limited by the available computing power. Summary of the Invention

[0009] The object of the present invention is to overcome the drawbacks of the prior art. In particular, the present invention aims to provide a control method for a compressor system having multiple compressors for generating compressed gas (compressed air) for at least one consumer, which control method ensures the best possible, and in particular the most efficient, operation of the compressor system to supply the demand for compressed gas (compressed air). In particular, the control method should be able to react as early as possible to future consumption of compressed gas (compressed air) and, in particular, to take into account dynamic influencing variables and / or processes in the compressor system as accurately as possible. Preferably, the control method should be real-time.

[0010] This object is solved by a method according to claim 1, a control unit according to claim 19, a compressor system according to claim 20, a computer program according to claim 21, and a computer-readable storage medium.

[0011] Said object is solved in particular by a method for controlling a compressor system comprising a plurality of compressors for generating compressed gas, in particular compressed air, for at least one consumer device, said method comprising: determining a plurality of future system states of the compressor system for at least one future time point, the future system state being defined by at least a state parameter and a compressor operating state combination, the state parameter preferably indicating a system pressure of the compressor system, and values ​​of the state parameter for the at least one future time point being calculated by simulation based on an initial system state of the compressor system, a future consumption curve of compressed gas, in particular compressed air, and possible compressor operating state combination sequences, the compressor operating state combinations in particular indicating combinations of defined possible operating states of the plurality of compressors of the compressor system for the future time point, and the compressor operating state combination sequence in particular indicating a time sequence of the compressor operating state combinations; determining similar system states from the set of future system states determined for future time points, each similar system state being defined by similar values ​​of the state parameter and at least partially matching compressor operating condition combinations, each similar value of the state parameter being in the same defined value range of the state parameter, preferably the same defined pressure value range; - reducing the set of determined system states for a future time point by discarding at least one system state from the set of determined similar system states based in particular on an evaluation of the compressor operating state combination sequences corresponding to each similar system state with respect to a first quality criterion, preferably an energy efficiency criterion; determining an optimal compressor operating state combination sequence from the reduced set of system states with respect to a second quality criterion, preferably an energy efficiency criterion, based on an evaluation of the compressor operating state combination sequences corresponding to the system states; Issuing at least one control command suitable for executing an operation of a plurality of compressors of the compressor system corresponding to at least a portion of the optimal compressor operating state combination sequence.

[0012] One idea of ​​the present invention is that reducing the number of system states to be considered by grouping similar system states together reduces the computational power required to predict future system behavior of the compressor system. Discarding at least one system state from the determined set of similar system states corresponds to grouping similar system states in that only the similar system states that were not discarded are further considered for predicting future system behavior.

[0013] In particular, the method is computer-implemented, and the method steps are preferably computer-based, in particular executed by a computer unit (processor). The determining method step is in particular based on arithmetic and / or comparison operations and can in this respect be called a calculating step. The future point in time in particular refers to a time discretization of a predetermined simulation period. The method for controlling a compressor system (control method) can be part of a regulating method for the compressor system, in particular part of a regulating algorithm for regulating at least one system state of the compressor system.

[0014] The simulation is in particular based on a (mathematical) model of the compressor system, which model describes the dynamic (time-dependent) behavior of the compressor and preferably other components of the compressor system (e.g. compressed air reservoir, pipelines, valves, oil separator, oil circuit, heat exchangers, etc.). The model can be based on structural modeling of the compressor system, in particular the compressor, on modeling of transitions between operating states of the compressor and optionally other components, and / or on modeling of the progression of state parameters over time. The model is preferably based on a (hybrid) system of (time-dependent) equations, in particular nonlinear differential equations. In particular, the control method is a model predictive control method (MPC).

[0015] In particular, the future system state is in each case defined at least by calculated values ​​of state parameters for the respective future time points, the calculated values ​​of the state parameters indicating a calculated future course of the state parameters, preferably indicating a future course of the system pressure. The future system state is in particular (additionally) defined in each case by a compressor operating state combination for the respective future time points, which indicates the (mechanical) operating state of the plurality of compressors. The future system state may (additionally) be defined by further state parameters. Preferably, the future system state is defined by values ​​of the state parameters, the (mechanical) operating states of the compressors, and / or the (software-related) state of the control algorithm of the compressor system.

[0016] The initial system state is defined, inter alia, by initial values ​​of state parameters, preferably indicative of system pressure (e.g., initial system pressure or initial stored gas or air volume), and in particular by an initial compressor operating state combination. Preferably, the values ​​of the state parameters are calculated by simulation starting from the initial time point for each future time point up to the end of a specified simulation period.

[0017] The future consumption curve of a compressed gas, in particular compressed air, shows the future time curve of the consumed volumetric flow rate (CVFR(t)) of the compressed gas (compressed air), in particular the consumed volumetric flow rate of the compressed gas (compressed air), preferably the consumed volumetric flow rate of the compressed air. The consumed volumetric flow rate usually refers to the (atmospheric) ambient pressure. The future consumption is specified by one or more users of the compressor system (which varies over time) or is determined by estimation or calculation. Preferably, the future consumption is specified as a (time-dependent) consumed volumetric flow rate.

[0018] The state parameter indicative of the system pressure of the compressor system may be the system pressure, in particular in the form of a pressure variable (e.g., in units of bar or Pa), or a state parameter from which the system pressure can be derived, preferably by calculation, optionally taking into account other parameters. For example, the system pressure may be derived from the gas volume (air volume) stored in the compressor system (e.g., in units of m^3 or kg). In particular, a predetermined pressure range between a predetermined lower limit pressure and a predetermined upper limit pressure of the pressure supplied by the compressor system has several defined pressure value ranges. The defined pressure value ranges in particular refer to a discretization of the system pressure (pressure discretization), preferably dividing the (total) pressure range into, in particular, discontinuous pressure subranges. However, overlapping pressure value ranges may also be defined. The lower and / or upper pressure limits may be variably specified over time, in particular by a user or operator via software or by (automatic) calculation based on other parameters.

[0019] In particular, the defined possible operating states of the compressor at least indicate whether the compressor is operating under load ("load") or not ("no load"). Preferably, the defined possible operating states of the compressor at least indicate whether the compressor is in "stand by," "idle," or "load" mode. In the case of a variable speed compressor, the defined possible operating states of the compressor preferably also specify a possible speed or a possible speed range.

[0020] In particular, a compressor operating state combination specifies a combination of defined possible (discrete) operating states of multiple compressors in a compressor system at a future time. An exemplary compressor operating state combination is when a first compressor is operating under load and a second compressor is not operating under load, which may be expressed as “load / no load” (“L / nL”). Another exemplary compressor operating state combination is when a first compressor is in a stopped state and a second compressor is in an idling state, which may be referred to as “stopped / idle.” In particular, a compressor operating state combination sequence indicates a time sequence of compressor operating state combinations. In particular, a compressor operating state combination sequence specifies a time sequence of defined possible operating state combinations of compressors in a compressor system. In particular, a compressor operating state combination sequence includes a time sequence of multiple compressor operating state combinations. In this regard, a compressor operating state combination sequence also specifies (temporal) transitions between the operating states of each compressor. A compressor operating state combination sequence can be understood as a history of compressor operating states underlying the system state. In particular, each compressor operating state combination sequence corresponds to a system state, i.e., is assigned to a system state, for example, in a data structure, and vice versa.

[0021] The first quality criterion and / or the second quality criterion are preferably energy efficiency criteria, in particular minimum energy consumption (energy efficiency), preferably minimum total energy consumption (total energy efficiency). The energy efficiency criterion (total energy efficiency criterion) preferably relates to the amount of electrical energy, thermal energy and / or fuel, and preferably can take into account possible heat recovery. The first quality criterion and the second quality criterion are preferably identical. The quality criterion can (additionally) relate to minimizing compressor wear, in particular with regard to the properties of the machinery or oil used for cooling and / or lubrication.

[0022] The evaluation of the compressor operating state combination sequences with respect to the first and / or second quality criterion is based in particular on a comparison of the energy consumptions calculated based on each compressor operating state combination sequence (and other parameters) with each other, with the lowest energy consumption preferably best satisfying the quality criterion. An optimal compressor operating state combination sequence can be understood in particular in the sense of a solution found to an optimization problem as the best possible compressor operating state combination sequence.

[0023] In particular, from a set of system states determined for future time points, similar system states are determined as similar system states, where similarity is determined, in particular, based on similar values ​​of state parameters. The step of determining similar system states from a set of system states determined for future time points is preferably based on a mutual comparison of the system states determined for future time points with respect to values ​​of the state parameter (system pressure) and / or a mutual comparison with respect to combinations of compressor operating conditions. Similar values ​​of the state parameter include the same (identical) values ​​of the state parameter. A similar system state can be defined by a (perfectly) matching combination of compressor operating conditions, and a deviation with respect to a certain defined possible operating state of the compressor is sufficient for similarity, in particular a deviation with respect to speed. A plurality of similar system states can be understood as a group of similar system states, each group being defined by similar (or identical) values ​​of a state variable (of system pressure), in particular values ​​of the state variable (of system pressure) in the same defined value range (pressure value range). Several groups of similar system states can be determined for a future time point, each group defined by values ​​of the state variable (of the system pressure) in the same value range (pressure value range), the value ranges (pressure value ranges) of each group being different from each other. The set of system states determined for a future time point does not (anymore) need to include all system states that (theoretically) could be determined for this time point, but may have been previously reduced, in particular by discarding system states whose values ​​of the state parameter (system pressure) lie outside the pressure range.

[0024] The step of reducing the set of system states determined for a future time point can be understood as a step of reducing the number of system states to be considered in further steps of the method, in particular as a step of summarizing similar system states. Preferably, all system states are discarded from the set of similar system states determined except for the system state that best satisfies the (first) quality criterion. The discarding of the system states is particularly implemented as deleting (or overwriting) variables or data structures representing the system states in the computer memory.

[0025] In particular, all compressor operating state combination sequences corresponding to one of the system states from the reduced set of system states are evaluated with respect to a (second) quality criterion, and preferably, the compressor operating state combination sequence that best satisfies the (second) quality criterion is determined as the optimal compressor operating state combination sequence.

[0026] Preferably, at least one control command combination is issued, which includes one control command for each of several (all) compressors of the compressor system. In particular, the control command combination includes one control command for each compressor of the compressor system. The issued at least one control command may include a sequence of control commands for the same compressor and / or may be part of a control command combination. The control command may represent a change in the operating state of the compressor, in particular a switch process (transition) to another operating state, or the compressor remaining in its current operating state. The control command (control command combination) can be understood as a load command (load command combination) for the compressor (or several compressors). In particular, at least one control command is issued that is suitable for effective operation of the compressors of the compressor system corresponding to the first (in time) part of the optimal compressor operating state combination sequence. Preferably, the at least one control command (combination of control commands) issued is suitable for causing operation of a compressor of the compressor system corresponding (only) to the first (in time) compressor operating state combination included in the optimal compressor operating state combination sequence, in particular corresponding to the (first) future time point following the initial time point.

[0027] The method is preferably performed by a higher-level control unit of the compressor system, which in particular controls a number of (all) compressors of the compressor system. The compressor system in particular interacts with a higher-level control system (system control), which is provided directly on the compressor system (compressed air system) or is specifically assigned to the compressor system. However, the higher-level control system can also control other technical systems and components in addition to the compressor system.

[0028] However, the method steps can also be distributed among several control and / or computing units: in particular, the method steps up to the output of the control commands can be executed by at least one (external) computing unit, in particular by at least one processor of an (external) server, e.g. an operator or manufacturer of the compressor system, and only the output of the control commands can be executed by a (superior) control unit of the compressor system.

[0029] The present invention is based on the recognition that, when calculating dynamically changing state parameters in the future, the higher the time resolution, the more accurate the prediction of the state parameter's evolution. It has also been recognized that extending the prediction period (simulation period) of the state parameters as long as possible enables the earliest possible reaction to the future evolution of the state parameters. However, a high time resolution and a long prediction period simultaneously increase the required computational power. Furthermore, it has been recognized that, in a sufficiently long simulation period with sufficient time resolution for the control of a compressed air system having one or more compressors, the available computational power is insufficient to consider all possible sequences of control commands (e.g., load commands: "load" or "unload") for each compressor and / or control commands for other components of the compressed air system. This is because the number of control commands (load commands) to be considered for several compressors and their combinations of possible sequences grows exponentially with the number of time steps. For example, a simulation period of 600 seconds (10 minutes) with a 1-second time resolution results in 4^600 = 1.72 * 10^361 different possible sequences of control commands for a combination of two fixed-speed compressors. Due to the size of the solution space, it is impossible to determine the optimal sequence of control commands in real time. Lowering the time resolution is insufficient for mapping the (highly) dynamic processes that may be required. The simulation period cannot be arbitrarily shortened if future events are to be considered as early as possible in the control of a compressed air system. Reducing the time resolution to 60 seconds (1 minute) in the previous example reduces the number of control command sequences to 4^10 = 1,048,576 for a 10-minute simulation period. However, because the relevant dynamic processes in compressed air systems typically have time constants on the order of seconds, such a reduction in time resolution is not practical for the control of a compressor in a compressed air system. Reliable prediction of state variables requires a high time resolution and a sufficient simulation period.

[0030] The method according to the present invention ensures the best possible operation of the compressor system, especially with regard to quality criteria. Compared to the prior art, a longer prediction period (simulation period) of the system state can be achieved, which makes it possible to output optimal control commands under given boundary conditions at an earlier stage. At the same time, the high time resolution allows dynamic influences and / or processes in the compressor system to be taken into account more accurately.

[0031] In one embodiment of the method, the state parameter identifies the system gas volume, particularly the system air volume, stored in the compressor system. In particular, the system pressure can be derived from the system gas volume, particularly based on the buffer volume of the compressor system. The (effective) buffer volume of the compressor system is determined, in particular, by the (total) gas storage (air storage) volume of the compressor system, particularly the volume from the inlet (air inlet) to the consumer (compressed air consumer), including, in particular, the volume of the compressed air tank, compressed air lines, and other types of compressed air storage components (such as oil separators). The stored system gas volume (system air volume) as a state parameter allows for simple calculation of the state parameter, particularly based on the initial stored system gas volume, in particular by calculating the difference between the discharge volumetric flow rate supplied by the compressor and the consumed volumetric flow rate drawn by the consumer. The buffer volume determines the extent to which the difference between the compressor's supply volumetric flow rate and the consumed volumetric flow rate results in a change in system pressure. The larger the buffer volume, the smaller the pressure change (all other things being equal).

[0032] One embodiment comprises a method step of discarding system states determined for a future time point that are outside a predetermined pressure range for the pressure delivered by the compressor system, in particular that indicate a system pressure above a predetermined upper pressure limit or below a predetermined lower pressure limit. This method step can be implemented, in particular, as an additional process step before the method step of determining a similar system state. The step of discarding the system state is implemented, in particular, as a deletion (or overwriting) of variables or data structures representing the system state in a computer memory. In this way, system states that do not satisfy boundary conditions for the system pressure and the corresponding compressor operating state combination sequence can be eliminated as early as possible in the method to avoid wasting computing power.

[0033] One embodiment includes a method step of determining a further future system state of the compressor system by calculating, by simulation, at least one state parameter for a further future time point in each case based on an initial system state of the compressor system and further possible compressor operating state combination sequences, wherein a compressor operating state combination sequence corresponding to a system state from a limited set of system states for a preceding future time point is part of the further possible compressor operating state combination sequence. This method step is preferably performed after the set of system states determined for the future time point has been reduced. This ensures that the further future system state is determined only based on the future system state prior to the compressor operating state combination sequence that can be considered to be selected as the optimal compressor operating state combination sequence. In this way, computational power can be saved.

[0034] In one embodiment, future system states of the compressor system are determined for future times included in a predetermined simulation period, which is divided into equally spaced time steps. The time step is preferably between 0.1 and 10 seconds. The simulation period is, in particular, 1 minute or more, preferably between 1 and 60 minutes. The time step is, in particular, the interval between two consecutive times. Reducing the number of system states calculated by the simulation allows for savings in computational power. As a result, smaller time steps can be selected compared to prior art. In particular, (relatively small) time steps can be selected to be constant (equidistant) over the simulation period. This ensures high time resolution throughout the simulation period. The simulation period can also be calculated based on, in particular, the (estimated) remaining time available until the next time step. The remaining time may depend on the computation speed of the computer on which the simulation is performed. This procedure is called adaptive simulation period determination. In this way, the real-time capability of the control method is guaranteed.

[0035] In one embodiment, a method step involves periodically rejecting system states determined for future time points based on the first and / or second quality criterion after a particularly defined number of time steps (periods). In particular, a time step specifies the interval between two consecutive time points. This method step is preferably performed incrementally, i.e., after reducing the set of system states determined for future time points by discarding at least one system state from the set of similar system states determined, preferably several times during a specified simulation period, for example, every 5 to 25 time steps. Preferably, system states determined for future time points that do not satisfy the first and / or second quality criterion better than other system states determined for this time point are discarded. For example, only the best 10 to 50% of system states determined for future time points in terms of the quality criterion are further considered, while the remaining system states are discarded. By periodically reducing the system states, the number of system states to be considered can be reduced, saving computational power.

[0036] In one embodiment, future system states, preferably through repeated execution of process steps, are mapped in computer memory by a branching data structure, where future system states correspond to nodes of the branching data structure, and the branching data structure includes multiple node levels, with each future system state determined for one future time point being assigned to the same node level. The nodes can be mapped as data structures (data objects, e.g., classes) in computer memory and can therefore be referred to as node data structures. The step of discarding a system state can be understood as deleting a node corresponding to the system state (node ​​data structure). Preferably, further nodes (node ​​data structures) are generated (recursively) by determining further future system states of the compressor system by calculating state parameters for at least one further future time point through simulation. It is not necessary to generate a new node (node ​​data structure) at the next node level for each node at the next time step. For example, a certain compressor operating state combination may be maintained for several time steps, especially when the compressor is in a stopped state. In particular, the branching data structure is generated by an algorithm using the so-called "branch-and-bound method." Branching data structures can be understood as the implementation of a tree that maps hierarchical structures, especially those generated by recursive loops.

[0037] In one embodiment, at least one control command is issued when a future system state of the compressor system is determined for a future time point included in a predetermined simulation period and an optimal compressor operating state combination sequence is determined. The issued at least one control command is, in particular, a control command combination for some (all) compressors of the compressor system, preferably including a control command for each compressor of the compressor system. This determines an optimal compressor operating state combination sequence taking into account the entire specified simulation period. Depending on the length of the specified simulation period, the issued control command reacts as early as possible to the calculated future course of the state parameter. The control command issued at the current real time causes the best (currently) operation of the compressor system for the entire specified future-related simulation period.

[0038] In one embodiment, at least one issued control command, preferably at least one issued control command combination, corresponds to a transition from a compressor operating state combination corresponding to an initial system state to a compressor operating state combination corresponding to a subsequent future system state that is part of the optimal compressor operating state combination sequence. In particular, the issued control command combination causes the compressor system to implement (only) the first compressor operating state combination (in time) of the optimal compressor operating state combination sequence, i.e., to implement the corresponding operation of the compressor. At the end of the process execution, in particular after determining the future system state for the entire simulation period (i.e., from the initial time point to the final time point) and determining the optimal compressor operating state combination sequence, preferably, only the first compressor operating state combination of the entire optimal compressor operating state combination sequence is executed by the (single) control command combination. Then, to output the next control command combination, a further process execution can be started with the next future time point as the initial time point and by appropriately shifting the simulation period back (by one time step).

[0039] In one embodiment, the evaluation of the first quality criterion and / or the second quality criterion is based on the calculated energy consumption of the compressor when passing through the compressor operating state combination sequence from the initial time point to each time point, and the optimal compressor operating state combination sequence is in particular the compressor operating state combination sequence that results in the lowest calculated energy consumption of the compressor.

[0040] In one embodiment, at least one of the following parameters is included in the calculation of energy expenditure: Switch energy for starting the compressor; Switch energy for compressor pressure rise; Switch energy for compressor pressure drop; · Compressor idle power; · Compressor load capacity, especially pressure dependent load capacity.

[0041] In particular, the parameters include stored specification data for each compressor. The calculation of energy consumption can include further parameters, particularly taking into account the energy consumption of other components of the compressor system. In particular, the energy consumption indicates the consumption of electrical energy and / or fuel. At the end of a specified simulation period, the optimal compressor operating state combination sequence determined for a future time point is, in particular, the optimal compressor operating state combination sequence in terms of energy consumption over the entire simulation period. Thus, the compressor system can be operated with the highest possible energy efficiency.

[0042] In one embodiment, the evaluation of the first and / or second quality criteria takes into account possible heat recovery, particularly for heat transfer to a (preferably external) heat consumer. In particular, possible heat recovery is determined by calculating the amount of heat recoverable (heat output) from the oil circuit (100) of the compressor system and / or by calculating the amount of heat recoverable from the compressed gas stream, preferably the compressed air stream. In the latter case, the amount of heat can be recovered from the compressed air stream, preferably by intercooling and / or aftercooling. The recoverable heat can be stored in the oil of the oil circuit or in the compressed gas stream (compressed air stream), particularly as heat of compression. In principle, other forms of recoverable compressor waste heat can also be taken into account. The recoverable heat output can be modeled using analytical equations or implemented using metamodel-based optimization. An external heat consumer can be understood as a heat consumer that is not part of the compressor system, such as a heated room or an (industrial) process based on heat supply.

[0043] In one embodiment, the calculation of the amount of heat that can be recovered (heat output) is based on at least one of the following parameters: · The temperature of the oil in the oil circuit of the compressor system; Ambient temperature of the compressor system; · The oil flow rate in the oil circuit of the compressor system; · Final compression temperature of compressed gases, especially compressed air; · specified or calculated heating energy of the compressor; · Compressor cooling energy.

[0044] The parameters may include measured variables, calculated values, or stored specification data of the compressor and / or compressor system.

[0045] The calculation of the recoverable heat amount (heat output) may include calculating the amount of heat that can be transferred (directly or indirectly) from the oil circuit of the compressor system to a heat utilization circuit (heating circuit) having a heat carrier (air or water) in an oil / air heat exchanger (in) and / or in an oil / water heat exchanger (at) of the compressor system. Preferably, the calculation is based on the temperature of the oil in the oil circuit of the compressor system, the ambient temperature of the compressor system, and / or the flow rate of the oil in the oil circuit of the compressor system.

[0046] Alternatively or additionally, the calculation of the recoverable heat amount (heat output) may include the calculation of the heat amount that can be transferred from the compressed gas flow (compressed air flow) in the compressor system to a heat utilization circuit (heating circuit) having a heat carrier (air) in a gas-to-air (air-to-air) heat exchanger of the compressor system. In particular, but not exclusively, in the case of an oil-free compressor (dry-running compressor), the heat of compression stored in the compressed air can be transferred to the heat transfer air flow for heat utilization by intercooling in an air-to-air heat exchanger after the first compression stage and / or by postcooling in an air-to-air heat exchanger after the second compression stage. Preferably, the calculation is based on the ambient temperature of the compressor system and / or the final compression temperature of the compressed gas, in particular the compressed air.

[0047] In particular, the heat stored in the oil circuit and / or compressed gas flow (compressed air flow) of the compressor system is determined based on the compressor operating state combination sequence. Continuous (long-term) operation of the compressor, preferably over several time steps, in a heat-generating operating state, in particular idling or loaded operation, can be advantageous in terms of energy efficiency criteria, taking into account possible heat recovery. In particular, a compressor operating state combination sequence corresponding to the continued energy-consuming operation of the compressor at idling (or loaded operation) may be more advantageous overall in terms of energy in terms of possible heat recovery of the heat stored in the oil circuit and / or compressed gas flow (compressed air flow) than a compressor operating state combination sequence corresponding to a change in the compressor operating state due to a transition from idling to off (or from loaded operation to idling). Taking into account possible heat recovery allows the selection of an optimal compressor operating state combination sequence in terms of overall energy efficiency and the issuance of a corresponding combination of control commands, resulting in the most energy-efficient operation of the compressor system as a whole.

[0048] In one embodiment, the defined possible operating states of the compressor preferably additionally indicate at least one rotational speed of the compressor, preferably with each different rotational speed or rotational speed range corresponding to the defined possible operating state. The defined possible operating states of the compressor preferably specify the rotational speed as a (percentage) share of the compressor's maximum rotational speed. Different possible operating states can be defined for different compressors, preferably for each compressor type. The compressor system can include fixed-speed and variable-speed compressors. By (additionally) considering different operating states of variable-speed compressors as the defined possible operating states, an optimal combination sequence of compressor operating states can be determined, taking into account the technical capabilities of variable-speed compressors in modern compressor systems. The output of control commands corresponding to the variable-speed compressors utilizes the functional ranges of these compressors for the best possible operation of the compressor system.

[0049] In one embodiment, the future system state is further defined by one (particularly software-related) control state parameter, which in particular indicates the state of a control algorithm of the compressor system. Preferably, the control state parameter indicates the previous operating time of the compressor in the same defined possible operating state. In particular, two system states of the compressor are similar with respect to the (software-related) control state parameter if the time since the compressor has been in an idle state is similar (or the same). Similar system states are preferably defined by similar values ​​of the state parameter, by matching compressor operating state combinations, and by at least one matching control state parameter, respectively. This ensures that only similar system states are discarded that are sufficiently similar in terms of the technical state description that is relevant to the technically practically possible transitions from one future time point to the next.

[0050] In one embodiment, permissible transitions between successive defined possible operating states of the compressor are defined, and preferably additionally, transition conditions are defined for at least one specific transition of the compressor between two defined possible operating states, in particular for a transition of the compressor from idle to stopped and / or from idle to loaded operation. Preferably, the compressor must be operated in idle mode for a predetermined first minimum operating time before transitioning from idle mode to stopped mode, and / or preferably, the compressor must be operated in idle mode for a predetermined second minimum operating time before transitioning from idle mode to loaded mode. In particular, the first minimum idling time prevents oil foaming when the compressor is switched to stopped. In particular, the second minimum operating time ensures sufficient time for the pressure to build up. Preferably, a (direct) transition from loaded operation to stopped is not possible. In particular, the compressor must first be switched from loaded operation to idle operation (preferably for the specified first minimum operating time). Preferably, only defined transitions between certain speeds or speed ranges are possible.

[0051] In one embodiment, a compressor transition condition from loaded to stopped can be provided, especially for compressors that cannot operate in idle mode. The compressor can have only two defined possible operating states (stopped and loaded). The transition condition is that a minimum load time must not be exceeded before the compressor is switched off. This ensures that the compressor motor winding temperature does not exceed a temperature limit. In particular, when starting from a stopped state, high motor currents occur, which increase the motor winding temperature. Before switching (re)switched to stopped, a minimum load time can be provided as a transition condition to allow the motor windings to cool before switching off. This ensures that the compressor or its cooled motor can be restarted at any time without overheating the motor windings. This ensures that the compressor can be switched to all defined possible operating states without damaging the compressor.

[0052] By defining permissible transitions between defined possible operating states, the method takes into account the actual technical behavior of the compressor system and can also guarantee safe operation under all circumstances.

[0053] In one embodiment, at least one of the following parameters is included in determining the future system state: Buffer volume of the compressor system. The buffer volume indicates in particular the volume of the compressor system in which compressed gas, in particular compressed air, is stored during operation; The compressor's volumetric discharge flow rate (which is especially pressure-dependent); the (especially time-dependent) volumetric consumption flow rate of at least one consumer; Ambient pressure.

[0054] The parameters may include measured variables, calculated values, or stored specification data of the compressor and / or compressor system, as well as parameters specified by the user, preferably via software.

[0055] In particular, the consumed volumetric flow rate indicates the (time-dependent) course of the (future) consumption (compressed air consumption) of compressed gas, in particular compressed air. The consumed volumetric flow rate can be specified (time-variable) or estimated or determined by calculation. The ambient pressure is in particular the ambient pressure of the compressor system.

[0056] In one embodiment, all steps of the method are repeatedly executed in succession, starting from different initial times, in several method runs. In particular, the compressor operating state combination of the optimal compressor operating state combination sequence of a previous method run corresponding to a first future time point is used as the compressor operating state combination of a subsequent method run corresponding to an initial time point. In particular, each successive execution of the method is executed with the current real time as the initial time. Alternatively, further executions of the method can use the current actual (e.g., measured) system state of the compressor system as the initial system state for the next simulation. Preferably, when the method is repeatedly executed, the end of the (fixed) predetermined simulation period is continuously shifted into the future. The duration of the simulation period can be specified to vary. In particular, the method allows for the output of control commands (combinations of control commands) in real time.

[0057] The object is also solved by a control unit for a compressor system, in particular comprising a plurality of compressors for generating compressed gas, in particular compressed air, for at least one consumer, which control unit is designed to perform at least one step, preferably all steps, of the method according to the invention. The control unit is in particular a superordinate control unit of the compressor system, and in particular controls some (all) of the compressors and preferably other components of the compressor system. The control unit is (only) capable of issuing at least one control command, the other method steps being performed on a server (e.g. of the operator or manufacturer of the compressor system) communicatively connected to the control unit.

[0058] The object is also solved by a compressor system comprising a plurality of compressors for generating compressed gas, in particular compressed air, for at least one consumer device, and a control unit according to the invention.

[0059] The object is in particular also solved by a computer program comprising instructions which, when executed on at least one processor, cause the processor to carry out all the steps of the method according to the invention, in particular the instructions cause a control unit according to the invention to carry out at least one step, preferably all the steps, of the method according to the invention.

[0060] Said object is in particular also solved by a computer-readable storage medium on which a computer program according to the invention is stored, which may comprise a plurality of storage media, which may be distributed among different computing units, in particular those of a control unit and those of a server.

[0061] The control unit, the compressor system, the computer program and the computer readable storage medium have the same advantages as those already explained in connection with the method according to the invention. [Brief explanation of the drawings]

[0062] The invention will now be explained in more detail with reference to the drawings, in which: [Figure 1] 1 shows a schematic diagram of one embodiment of a compressor system having multiple compressors and a control unit designed to implement the method; [Figure 2] An exemplary time sequence of a state parameter indicating system pressure is shown; [Figure 3] illustrating future system state diagrams for multiple compressors of a compressor system in a time sequence of one embodiment of the method; [Figure 4] showing a diagram of a future system state of a compressor system having multiple compressors in a time sequence of the method; [Figure 5] 1 shows a diagram of a future system state of a compressor system having multiple variable speed compressors in a time sequence of a further embodiment of the method; [Figure 6A] A comparison of two embodiments of the method (Fig. 6B and Fig. 6C) with the prior art brute force method (Fig. 6A) is shown; [Figure 6B] A comparison of two embodiments of the method (Fig. 6B and Fig. 6C) with the prior art brute force method (Fig. 6A) is shown; [Figure 6C] A comparison of two embodiments of the method (Fig. 6B and Fig. 6C) with the prior art brute force method (Fig. 6A) is shown; [Figure 7] An illustration of the determination of future system states according to one embodiment of the method is shown as a hybrid automaton; [Figure 8] A diagram of the determination of future system states according to one embodiment of the method is shown as a Petri net; [Figure 9] A diagram of the determination of future system states according to one embodiment of the present method with heat recovery is shown as a hybrid automaton. DETAILED DESCRIPTION OF THE INVENTION

[0063] In the following description of the invention, the same reference numerals are used for the same elements and elements that operate in the same manner.

[0064] FIG. 1 shows an example of a compressor system 100 according to the present invention, which includes multiple compressors for generating compressed air for a consumer 200. In this embodiment, there are two compressors C1 and C2 (a two-compressor compressed air station), which are connected via a pipeline to a compressed air reservoir R1 and further to a consumer 200, allowing for the connection of multiple consumers. The compressor system 100 may include additional compressors and additional compressed air system components, such as filters, dryers, and valves. Compressor systems with oil-lubricated compressors typically include an oil circuit for cooling and / or lubricating the compressor and an oil separator. There may also be at least one heat exchanger for recovering heat from the oil circuit. At least one heat exchanger for recovering heat from the compressed air stream may also be provided.

[0065] A control algorithm is executed in the control unit 300 according to the present invention, which outputs respective control commands (load commands) LC1, LC2 to the compressors C1, C2. The combination of both control commands LC1, LC2 represents a control command combination LC1 / LC2, also called a load command combination. The control algorithm uses the control commands LC1, LC2 to specify when the compressor C1 or C2 should deliver compressed air (control command: "load") or not (control command: "no load"), taking into account the system pressure p in the compressed air reservoir R1. The operating state of the compressor indicates whether it is operating under load ("load") or not ("no load"), i.e., whether it is stopped or idle. Knowing the operating state and technical characteristics of the compressors C1, C2, the control algorithm can determine the delivery volume flow rate (DVFR). The DVFR is typically pressure-dependent (DVFR(p)). The consumer volume flow rate (CVFR) required by the consumer 200 is typically time-dependent (CVFR(t)) and is drawn from the compressed air reservoir R1. The difference between DVFR and CVFR determines how the amount of system air NV stored in the buffer volume V of the compressor system 100 changes. The buffer volume V includes the total air storage volume of the compressor system 100 and is represented here primarily by the volume of the compressed air reservoir R1. The system pressure p is derived from the stored system air volume NV and the buffer volume V. In this regard, the stored system air volume NV, specifically the amount of air stored in the compressed air reservoir R1, indicates the system pressure.

[0066] 2 shows an exemplary curve of the system pressure p as a state parameter of the system state of the compressor system versus time t. The pressure delivered by the compressor system 100 to the consumer 200 is limited to a lower limit pressure p min and upper pressure p max The pressure should always be within a specified pressure range Δp between

[0067] In the method according to the invention, the future course of a state parameter indicative of the system pressure p is calculated by simulation. For this purpose, the time t is taken as a predetermined simulation period t sim Over time t n , t n+1 The time step Δt between two successive future time points (Δt=t n+1 -t n ) (time discretization), and the time steps Δt are preferably equally spaced. sim corresponds to the predicted period of the state parameter. The value of the state parameter is calculated based on the initial system state S at the initial time t based on a mathematical model that maps the dynamic behavior of the compressor system 100. t0 The time step Δt is preferably between 0.1 and 10 seconds, and the simulation period t sim is in particular 1 minute or more, preferably between 1 and 60 minutes.

[0068] In this method, the pressure range Δp is determined by dividing the pressure range Δp by some defined pressure value range Δp i (Pressure discretization) Pressure value range Δp i preferably extends over a value range between 0.005 bar and 0.1 bar, for example 0.02 bar. i is the similar system state S tn,sim is used to determine the similar system state S tn,sim is the defined pressure range Δp where the system pressure p has the same value. i is defined by a similar value of the system pressure p as long as

[0069] The control task of the method, executed by the control unit 300, is to control the compressors C1, C2 by means of appropriate control commands LC1, LC2 in such a way that the consumption of compressed air required by the consumers is met, so that the system pressure is maintained, in particular within a pressure range Δp, and the compressor system 100 is operated as efficiently, in particular energy-efficiently, as possible, i.e. the energy consumption E is minimized. The determination of the energy consumption E depends on the power consumed by at least the compressors C1, C2, in particular the idle power P idle and pressure-dependent load power P load (p) is considered and explained below.

[0070] In the periodic execution of the method, preferably at each time step Δt, an optimal sequence of operating states of the plurality of compressors C1, C2 (optimal compressor operating state combination sequence CSseq opt , ) for the simulation period t sim The future course of the state parameters indicative of the system pressure p, preferably the stored system gas volume NV, and in particular the system gas volume, is determined over a future time step t n The compressor operating state combination sequence CSseq is determined by the simulation and is not possible. tn,m is excluded from the outset. The future consumption of compressed air is estimated and specified as the future consumption volume flow CVFR(t). In particular, the calculated system pressure p is limited to the lower pressure limit p min and upper pressure p max The optimum compressor operating state combination sequence CSseq satisfies the specified pressure range Δp between opt At least a first part of is performed by issuing at least one control command LC1, LC2 to control the actual compressor system 100. In this way, the method finds an optimal solution for controlling the compressor system.

[0071] In a preferred embodiment of the method, the tree structure of nodes and node connections is constructed to represent all (theoretically) possible compressor operating state combination sequences CSseq tn,m , or corresponding control command sequences (load command sequences), which is necessary as part of the optimization. Such a tree structure, or more precisely a portion of it, is shown in Figures 3 to 5. The nodes represent the system states S of the compressor system 100. tn,m and the node connections correspond to the system state S tn,m The control commands LC1, LC2, or the control command combination LC1 / LC2 for the transition between them correspond to the control commands LC1, LC2, or the control command combination LC1 / LC2. In order to reduce the number of nodes, i.e., system states, to be considered when building the tree structure and to save computational power, similar invalid system states S tn,m can be discarded early ("tree pruning").

[0072] System State S tn,m By discarding, preferably as early as possible, the number of computationally intensive simulations that would be performed to calculate the future course of the state parameters can be reduced to the extent that the stated optimization problem can be solved with currently available computational power, even for a sufficiently long prediction horizon and a sufficiently precise time discretization. In particular, this allows the real-time capable method to be realized.

[0073] The tree structure is reduced to the extent that it is possible to explore the tree structure in real time and find the optimal path (corresponding to the optimal load command sequence) over the forecast horizon.

[0074] In the described embodiment, the method according to the present invention comprises the following steps: In a first step, a number of future system states S of the compressor system 100 are identified. tn,m (Hereafter, we often refer to this as "System State S tn,m ") at least one future time point t nThe future system state S tn,m is at least the combination of state parameters and compressor operating state CS tn where the state parameter indicates the system pressure p of the compressor system 100. The value of the state parameter is determined by the initial system state S of the compressor system 100. t0 , future consumption of compressed air, and possible compressor operating state combination sequence CSseq tn,m At least one future time t n is calculated.

[0075] In the second step, the similar system state S tn,sim But at a future time t n The future system state S determined for tn The set of similar system states S tn,sim are compressor operating state combinations CS that at least partially match with similar values ​​of the state parameters, respectively. tn Similar values ​​of the state parameter are each within the same defined value range, i.e., the same defined pressure value range Δp i is located.

[0076] In the third step, at a future time t n The system state S determined for tn The set of similar system states S tn,sim This reduces the set of similar system states S by discarding at least one system state from the set S. tn,sim Compressor operating state combination sequence CSseq corresponding to tn,m The first quality standard is the energy efficiency standard.

[0077] In the fourth step, the system state S is determined with respect to the second quality criterion. tn The sequence of compressor operating states CSseq corresponding to the system states from the reduced set tn,mBased on the evaluation of opt The second quality standard is the same energy efficiency standard.

[0078] In the fifth step, the optimal compressor operating state combination sequence CSseq opt At least one control command LC1, LC2 or control command combination LC1 / LC2 is issued suitable for causing operation of the compressors C1, C2 of the compressor system 100 corresponding to at least a portion of the above.

[0079] Compressor operating state combination CS tn is the time in the future t n 1 shows the defined possible combinations of operating states of the compressors C1 and C2 of the compressor system 100 for the compressor operating state combination sequence CSseq. tn,m is the compressor operation state combination CS tn Specifies the time sequence of

[0080] Figures 3 to 5 show the future system state S tn,m It shows a collection of, and is shown in a tree structure.

[0081] The tree structure is preferably implemented as a branching data structure and is generated by an algorithm using the so-called "branch-and-bound method". The tree structure represents a hierarchical structure, in particular generated by a recursive loop. The future system state S tn,m is mapped in computer memory by a branching data structure and represents a future system state S tn,m corresponds to a node, and the branching data structure contains multiple node levels. The nodes are stored as a data structure (node ​​data structure). Each node level is a time-discretized data structure representing a future time point t n corresponds to a future time (t n ) is determined for the future system state (S tn ) are assigned to the same node level. t0), a tree structure ("branch") is constructed with interconnected nodes (future system states S tn,m ) and branch out over several levels (node ​​levels) to reach the final node. The final node is defined here as the node that is the node within the specified simulation period t sim is the node level corresponding to the end point of

[0082] The tree structure can be used to map a finite number of combinatorial possibilities (combinations). The nodes of the tree structure (future system states S tn,m ) spans the solution space in which an (optimal) solution can be found. By checking appropriate bounds, suboptimal combinations can be filtered out early. In this way, the size of the tree structure (number of nodes) and therefore the combinations that will be performed are effectively limited.

[0083] In the method according to the present invention, a time in the future t n The node-level system state S determined for tn Among them, the similar system state S tn,sim is determined, and only the system state that best satisfies the quality criteria is pursued further. Other similar system states are discarded. tn,m Destroying a node corresponds to deleting the corresponding node from the tree structure or merging the corresponding nodes into one node.

[0084] Figures 3 to 5 show how: The tree structure is constructed step by step (from left to right). This tree structure is generated in a computer, preferably as a branching data structure. In the first time step, starting from an initial time t0, an initial system state S t0 and initial compressor operating state combination CS t0 An initial node is created corresponding to the time t n First, let us consider all possible compressor operating state combinations CS tn A node is generated for each compressor operation state combination CS tnis the compressor operating state combination CS tn corresponds to the relevant load command combination (control command combination) that can cause the initial node to move along the node connection at time t n The entire path to each node at the node level is the possible compressor operating state combination sequence CSseq tn,m Corresponds to.

[0085] Figure 3 shows the generation of a tree structure for two compressors C1 and C2 using three consecutive points in time t0, t1, and t2. n In Figure 4, compressor 1 is switched to a loaded state (L1) or unloaded state (nL1), and compressor 2 is switched to a loaded state (L2) or unloaded state (nL2). This results in a load command combination corresponding to each node. A possible load command combination consists of load commands (L1 and L2) or unload commands (nL1 and nL2) for the two compressors. For example, the load command combination "L1 / nL2" is a combination in which the first compressor C1 is loaded and the second compressor C2 is unloaded (i.e., stopped or idle). Figure 4 shows a tree structure corresponding to four consecutive time points t0, t1, t2, and t3.

[0086] Each node represents the future system state S of the compressor system. tn,m Each system state S tn,m is the corresponding compressor operating state combination sequence CSseq tn,m The future system state S at time t2 is determined for each node based on t2,1 ~S t2,16 For example, the operating state combination sequence CSseq t2,1 ~CSseq t2,16 (see Figure 3). The stored system air volume NV is calculated as a state parameter and indicates the system pressure p derived therefrom. In each case, an additional time step t n+1 After the tree structure is extended by the nodes of tn+1,m is determined, and for this purpose, the compressor operating state combination sequence CSseqtn+1,m A simulation is performed to calculate the state parameters based on

[0087] Using the simulation model, the system state S tn,m is determined, which is shown in simplified form in Figure 7 and in another form in Figure 8, both for one compressor. An extended simulation model that takes into account the possibility of heat recovery is shown in Figure 9. By using a mathematical model that maps the dynamic behavior of the compressor system to calculate its future behavior, the method can be described as a model predictive control (MPC) method.

[0088] When generating the tree structure, we identify future system states S that cannot be part of the optimal solution and are therefore "invalid." tn,m or the corresponding compressor operating state combination sequence CSseq tn,m are preferably discarded as soon as possible. In other words, the tree structure is "pruned" at the corresponding nodes. In particular, system states S where the value of the state parameter is outside the specified pressure range Δp of the pressure delivered by the compressor system 100 are discarded. tn,m Specifically, the specified upper limit pressure p max Upper or lower limit pressure p min System state S under tn,m As a result, the corresponding node is discarded as soon as possible. tn,m The next time point t n+1 This means that the discarded system state S tn,m potential future system states S that could result from tn+1,m This significantly reduces the number of possible solutions in the solution space, since it is not necessary to run simulations for

[0089] To further counteract the fundamental problem of exponential growth of the solution space (see Figure 6A), the similar system state Stn,sim are determined and specifically classified as similar system states by comparing them with each other. tn,sim The nodes representing the similar system state S are combined into one node. tn,sim One of the system states S tn This means that only the values ​​in the future t are kept and the others are discarded. n A set of system states S determined for tn,m Let S be the determined similar system state S tn,sim This procedure of reducing by discarding system states from the set is illustrated in Figure 4 using the example of two nodes at time t2, and in particular the system state S t2,7 and S t2,11 is shown in terms of two system states S t2,7 and S t2,11 are similar because the state parameters have similar values ​​and the compressor operating state combination ("nL1 / L2") is the same. These two nodes are combined into one node. System state S t2,11 The node in is energetically favorable and is preserved. t2,7 is discarded. This reduces the number of nodes at time t3 from 64 to only 60. t2,11 Only the remaining nodes corresponding to the next time point t n+1 In addition, the possible compressor operating state combination sequence CSseq tn+1,m (Here, CSseq at time t3 t3,m , m=37,…,40, i.e., CSseq t3,37 ,CSseq t3,38 ,CSseq t3,39 ,CSseq t3,40 ) is pursued. This reduction in the number of nodes is achieved by dividing the state variables into discrete value ranges, e.g., pressure value range Δp i The beneficial effect of this procedure in accordance with the method of the present invention on limiting the solution space is illustrated in FIG.

[0090] Similar system state S tn,simTo determine the system pressure p, the system pressure p is preferably divided into a predetermined number of discrete pressure value ranges Δp i (e.g., multiple value ranges of 0.02 bar each). i The value of the state parameter indicating the value of the system pressure p at time t n All system states S tn are similar in terms of state parameters. Furthermore, similar system states S tn are considered to be similar with respect to the states of the compressors C1 and C2, so that the compressor operating state combinations CS tn must have.

[0091] future time t n The system state S determined for tn,m is determined for the same time period, in particular with respect to the state parameters that indicate the system pressure p. tn,m and both system states S tn,m But at each time t n Compressor operating state combination CS corresponding to tn In particular, two system states S tn,m One of them is an optimal compressor operating state combination sequence CSseq based on an evaluation of the (first) quality criterion. opt It is guaranteed that the future system state S can be discarded without losing the option to determine tn,m is preferably at least one software-related control state parameter t state The software-related control state parameter t state indicates the state of the control algorithm of the compressor system 100. The control state parameter t state denotes the aforementioned operating time of the compressors C1, C2 in the same defined possible operating state, i.e., the residence time in the current operating state, in particular in idle mode. tn,sim Preferably, the operating state combinations CS of the compressors that match each other by similar values ​​of the state parameters aretn Furthermore, the control state parameter t state is defined by the matching values ​​of

[0092] Similar system state S tn,sim From the set of compressor operating state combination sequences CSseq tn In this embodiment, the similar system state S tn,sim Only the most energetically favorable of the states S are pursued further. tn,sim The evaluation of energy efficiency using the first quality criterion is performed by determining whether the compressors C1 and C2 are in a state where the compressors ... n All similar system states S that result in the least energy consumption of the compressor system 100 when operated through the entire compressor operating state combination sequence up to tn,sim Operation state combination sequence CSseq tn,m Specifically, the energy consumption E is determined based on the initial system state S t0 (root node) to the similar system state S tn,sim A particular system state S corresponds to (tn,m) (Time t n The energy consumption E of each node is calculated. The calculation of the energy consumption E can include at least one of the following parameters (see Figures 7, 8, and 9): Switch energy E for starting compressors C1 and C2 Start ; Switch energy E for pressure rise of compressors C1 and C2 loading ; Switch energy E for pressure drop of compressors C1 and C2 unloading ; Idle power P of compressors C1 and C2 idle ; Load capacity P, which depends on the pressure of compressors C1 and C2 load(p).

[0093] Time t n future system state S tn Based on the reduced set of tn+1 can be determined for at least one future time point t n+1 The state parameters of the compressor system 100 are calculated in each case from the initial system state S t0 and further possible compressor operating state combination sequence CSseq tn+1,m The compressor operating state combination sequence CSseq is calculated by simulation based on the tn,m is the future time t n System State S tn corresponding to the system states from a limited set of , and further possible compressor operating state combination sequences CSseq tn+1,m forms the first part of

[0094] The last node level of the tree, i.e., the simulation period t sim When the end of S is reached, the node and the corresponding system state S tn , and the compressor operating state combination sequence CSseq tn,m is known, and the optimal solution to the given optimization problem can be derived. opt is the quality of the last time point t based on the (second) quality criterion. n Compressor operating state combination sequence CSseq tn,m Each compressor operating state combination sequence CSseq tn,m Since a sequence of control command combinations or a let command combination (a path along node connections) is assigned to , the optimal compressor operating state combination sequence CSseq optPreferably, only the first combination of control commands in time is output to the compressors C1 and C2. The control command combination LC1 / LC2 thus issued is the first combination of control commands in time to be output to the compressors C1 and C2 in the initial system state S. t0 Compressor operating state combination CS corresponding to t0 From the following future system state S t1 Compressor operating state combination CS corresponding to t1 Both of these correspond to the optimal compressor operating state combination sequence CSseq opt is part of the simulation period t sim Overall, the control commands issued result in optimal operation of the compressor system in terms of energy efficiency from a current point of view.

[0095] The method steps are then executed again, preferably starting from the current time point corresponding to real time, in order to search again for a current optimal solution and control the compressor system 100 accordingly. This procedure makes sense because compressed air consumption can change over short periods of time, especially within one time step. This results in different compressed air consumption over the forecast period, during which boundary conditions of the optimization problem can change radically. Due to the reduced demands on computing power, the method can be executed repeatedly at short intervals, especially in real time, thus also taking into account dynamic changes and fluctuations in compressed air consumption predicted for the future.

[0096] For the control of a compressor system for compressed air production, the prediction horizon is preferably at least 10 minutes and the time resolution is preferably a time step of 1 second or less. In a practical application of the method, the tree structure shown in Figures 3 to 5 is therefore n and system state S tn,m For example, if the simulation time is 10 minutes and the time step is 1 second, the system state S tn,m is 600 future time points t1-t 600must be considered. Furthermore, compressor systems may contain more than two compressors, greatly increasing the number of possible combinations. The advantages of this method become more apparent as more time points and compressors are considered.

[0097] FIG. 5 shows a portion of a tree structure of an embodiment of the present method for controlling a compressor system having multiple variable speed compressors C1, C2. In addition to the previously described defined possible operating states os of compressors "Standby," "Idle," or "Load," additional defined possible operating states in this embodiment indicate different speeds for the compressors C1, C2. The possible operating states of the compressors specify speeds as discrete speed steps in the form of percentages of the compressor's maximum speed. For example, speeds are defined as load commands of 0%, 25%, 50%, 75%, or 100% of maximum speed. In this possible example, two possible operating states or load commands (nL or L, see FIGS. 3 and 4) for the fixed speed compressors are used to provide six possible load commands (nL, L) for the variable speed compressors. 0% , L 25% , L 50% , L 75% , L 100% ) In the tree structure of two variable speed compressors, n Starting from node t, at the next time step t n+1 In this case, 31 different load command combinations are possible (see Figure 5). Each of the two compressors C1 and C2 can be switched to "no load" (nL1 or nL2) or switched to "load" at a specific speed. For example, the load command combination nL1 / L 25%,2 means that compressor C1 is switched to "no load" and compressor C2 is switched to load at 25% speed. At the next time point, all the above load command combinations must be considered again. In this way, the time from t0 to t1 to t2 and finally to t3 is calculated as described above in connection with Figures 3 and 4. n By taking the variable speed compressor into consideration, a tree structure is constructed that leads to the possible compressor operating state combinations CS tn, the future system state S tn,m , and the resulting compressor command state combination sequence CSseq tn,m The advantages of the method according to the invention now become even more apparent.

[0098] 6 shows the advantages of the method according to the invention (FIGS. 6B and 6C) compared to the brute force method from the prior art (FIG. 6A). In each case, the possible compressor operating state combination sequences CSseq tn,m The progression over time of the number of system states S to be considered is shown. tn,m Or it corresponds to the number of nodes in the correspondingly constructed tree structure.

[0099] While the brute force method maps all possible combinations, causing the number of nodes to grow exponentially over time (see Figure 6A), our method has the effect of limiting the number of nodes that can be controlled. It can be seen that the number of nodes remains limited after an initial increase from a certain point (see Figures 6B and 6C).

[0100] Figure 6B shows the lower limit pressure p min and upper pressure p max Based on the consideration of the system state S tn,m and the pressure value range Δp of the system pressure p i Based on the discretization into the analogous system state S tn,sim 1 shows a method according to the present invention for discarding

[0101] Figure 6C shows the system state S tn,m This shows the effect of adding an optional process step of cyclic shrinking at a future time t n The system state S determined for tn is discarded based on quality criteria after a defined number of time steps Δt, for example at periodic intervals of 20 seconds. tn,sim or the system state S based on observed limits on the state parameters. tn,mIn addition to the method steps described for reducing σ (see FIG. 6B), the system state S σ that meets the quality criteria, preferably the energy efficiency criteria, worse than the others is also considered. tn,m Each compressor operating state combination sequence CSseq can be periodically discarded. tn,m The energy consumption E of the system is preferably calculated as described above, and the evaluation of the quality criteria is based on this energy consumption E. For example, the most energy-efficient system state S of 10 to 50%, preferably 20%, tn,m Only this can be pursued further.

[0102] 6 shows that the method according to the invention reduces the computational complexity so that the exponential dependence of the number of nodes on the length of the forecast period is restricted to a linear dependence, always linear in the case of FIG. 6B. This creates the prerequisites for using the method to control a real compressor system 100.

[0103] Figure 7 shows the future system state S using the simulation model as a hybrid automaton. tn,m The hybrid automaton models discrete operating states, in this case the defined possible operating states of the compressor ("os" in Figure 7), as automaton states connected to each other via so-called directed edges. Directed edges are used to define which state transitions are possible in the system and under what conditions the transitions occur (transition conditions). In the automaton states, differential equations describe the system's behavior. When a state transition occurs, the state variables can be reinitialized. For illustrative purposes, the hybrid automaton shown here represents the structure of a simplified mathematical model for mapping the dynamic behavior of a compressor system with one compressor. Hybrid automata for compressor systems with two or more compressors need to be extended accordingly.

[0104] The hybrid automaton distinguishes between three discrete states: "Standby" (stand still), "Idle" (idle), and "Load" (load operation). If the automaton is in the discrete "Standby" state and a load command is present (LC equals "true"), a transition to the discrete "Idle" state is made. During the transition from the discrete "Standby" state to the discrete "Idle" state, the control state parameter t state is initialized to the value 0, and the energy consumption E is the value E+E start It is reinitialized with E+E start is the value E of energy consumption E start While the "Idle" state is assumed, the energy consumption E increases by the value P idle *Increase by 1 s. Here, the assumption is made that the time step Δt covers a time span of 1 s.

[0105] In this simple model, the three states of compressor C1 or C2 (standby, idle, load) are linked by specific switch conditions, which allow a transition from one operating state to another, if the switch conditions are met.

[0106] Since no energy is required in the "Standby" state, the new energy value E + is the previous energy value E - Since the compressor does not produce compressed air, DVFR = 0 (Delivery Volume Flow Rate). The system pressure p is equal to the ambient pressure p amb The Consumer Volume Flow Rate (CVFR(t)) is calculated by subtracting the amount of compressed air contained in the buffer volume V as a function of t. When the load changes from "Standby" to "Idle", State is set to 0 and the energy E Start is required to get started.

[0107] In the "Idle" state, the compressor operates at idle power P idle Since the intake valve of compressor C1 or C2 is closed and cannot supply compressed air to the connected compressed air network, the minimum pressure check valve (not shown in Figure 1) is closed, so the volume of compressed air produced DVFR is still 0 m 3 / s. The minimum pressure check valve releases compressed air to the connected compressed air reservoir R1 or to the consumer 200 connected via the compressed air network only when the internal pressure of the oil separator tank of the compressors C1, C2 is higher than the system pressure p. Furthermore, the minimum pressure check valve only opens when the internal pressure of the oil separator tank is higher than the set minimum pressure, for example, 4 bar. The system pressure p and the system air volume (compressed air volume) NV stored in the buffer volume V are calculated in the same way as in the "Standby" state.

[0108] In this simple model, the compressor pressure rise occurs over a minimum operating time t loading This is achieved through a time counter: t>t loading As soon as this happens, the compressor can be switched to the "Load" operating state, where t is the elapsed time from the start of the calculation. It is also possible to switch to the "Standby" state in the same way, but with a minimum idle time t coasting must be met. This is a simple implementation of the idle time required before the compressor is switched to standby, i.e. switched off.

[0109] In the "Load" state, the variable E + , DVFR, p and NV + is calculated in the same way as the formula in Figure 7. Starting from the "Load" state, the model can be returned to the "Idle" state if there is a corresponding load command LC = false. The switch energy for pressure reduction is calculated by the parameter E unloading is considered by

[0110] In particular, to extend this simplified model for a one-compressor system to a two-compressor system with two compressors C1, C2, significantly more discrete operating states must be considered. Instead of the three possible, i.e., discrete, operating states defined (standby, idle, load), the model for a two-compressor system has nine compressor operating state combinations: Compressor 1 standby / Compressor 2 standby Compressor 1 idle / Compressor 2 standby Compressor 1 standby / Compressor 2 idle Compressor 1 idle / Compressor 2 idle Compressor 1 on load / Compressor 2 on standby Compressor 1 load / Compressor 2 idle Compressor 1 standby / Compressor 2 load Compressor 1 idle / Compressor 2 load Compressor 1 load / Compressor 2 load Individual discrete compressor operating state combination CS tn and the discrete compressor operating state combination CS at the next time step tn+1 The possible transitions for each state are listed in the table below: [Table 1-1] [Table 1-2]

[0111] The extended hybrid automaton for mapping the dynamic behavior of the two-compressor system according to these possible combinations of operating states of compressors C1 (compressor 1) and C2 (compressor 2) and the transitions between the operating state combinations is represented similarly to Figure 7. Among the nine compressor operating state combinations corresponding to the states of the automaton, the behavior of the system is again described by differential equations that correspond approximately to Figure 7.

[0112] Using a simulation model, the future system state S of the two compressor systems tn,mAn alternative representation of the determination is shown in Figure 8 in the form of a Petri net. This form of representation includes the possible transition conditions between various compressor operating state combinations. Additionally, the boundary conditions for transitions from one operating state combination to another are integrated into the specified transition conditions.

[0113] The Petri net models the discrete operating states of two compressors in a two-compressor compressed air station. The left side of the Petri net describes the three operating states of the first compressor C1. The right side of the Petri net describes the three operating states of the second compressor C2. The three operating states are standby (stopped), idling, and loaded. The calculation of the system pressure p is described in the middle part of the Petri net. The system pressure p is calculated by dividing the ambient pressure p by the amb The system air volume (compressed air volume) NV stored in the buffer volume V as a function of . The calculation of the stored system air volume NV is determined at each time step after the discharge air volumes DVFR1 and DVFR2 of the respective compressors C1 and C2 are calculated. The stored system air is calculated by dividing NV by the volume of the buffer volume V as a function of . The stored system air volume NV is calculated at each time step after the discharge air volumes DVFR1 and DVFR2 of the respective compressors C1 and C2 are calculated. + and the storage system air volume at the previous time step, NV - , can be calculated from the two delivery flow rates DVFR1, DVFR2 and the consumed volumetric flow rate CVFR(t).

[0114] The left and right parts of the Petri net describe the operating states of the two compressors C1 and C2, respectively. The following description will refer only to the left part and the operating states of the first compressor C1. The description applies equally to the right part for the second compressor C2. The Petri net in FIG. 8 is designed so that the two compressors C1 and C2 operate independently of each other and there is no dependency between their operating states.

[0115] The left side of the Petri net distinguishes three discrete nodes. The term "node" in this context should not be confused with the nodes of the branching tree structure described earlier (see Figures 3-5): "Standby" (stop, standstill), top node, "Idle" (Idle), intermediate node, "Load" (load operation) lowest node.

[0116] In the discrete "Standby" state, the current time t1 + is the time t1 of the previous step - The residence time in the "Standby" state is determined by t1. state remains unchanged at 0 seconds, regardless of the calculation in the simplified model. In the "Standby" state, no electrical energy E is required, and the total energy E1 + is the total energy E1 of the previous time step - Since no compressed air is generated, the amount of compressed air generated DVFR1 is 0 m 3 Equals / s.

[0117] If a load command is present (LC1 is "true"), a transition to the discrete "Idle" state is made. During the transition from the discrete "Standby" state to the discrete "Idle" state, the control state parameter tstate1 + is initialized with a value of 0, and the energy consumption E1 + is the value E1 - +E1 start It is reinitialized with E1. - +E1 start is the value E at energy consumption E1 start This corresponds to an increase of only

[0118] While the “Idle” state is assumed, the energy consumption E is constant for each execution of the hybrid automaton, with a value P idle *1 s. Here, the assumption is made that the time step Δt covers a time span of 1 s. The suction valve of compressor C1 is closed and it is not possible to supply compressed air to the connected compressed air network, so the generated compressed air DVFR1 is 0 m 3 / s. In this simple model, the pressure rise of compressor C1 is proportional to the time counter t1 state This is achieved through t1 state>t1 loading As soon as t1 is reached, the compressor can switch to the "Load" operating state. state is the time spent in the current operating state. It is possible to switch to the "Standby" state, but there is a minimum idle time t coasting must satisfy the time counter condition. This is a simple implementation of the idle time required before the compressor is switched to standby, i.e. switched off.

[0119] In the "Load" state, variable E1 + ,DVFR1 is calculated in the same way as the formula in Figure 7. Starting from the "Load" state, the model can be returned to the "Idle" state if there is a corresponding load command LC = false. The switch energy for pressure reduction is calculated by the parameter E1 unloading is considered by

[0120] 9 shows an embodiment of the method according to the invention with heat recovery as a hybrid automaton. In this embodiment of the method, the compressor operating state combination sequence CSseq with respect to the quality criterion is tn,m The evaluation of ( ) is based not only on the (preferably electrical) energy consumption of the compressors C1 and C2, but also on the recoverable heat amount ("WRG" in FIG. 9). The recoverable heat amount is determined, in particular, by the heat amount recoverable from the oil circuit (not shown in FIG. 1) of the compressor system 100, which depends on the heat output of the compressors C1 and C2. By compressing air in the compressors C1 and C2, heat is transferred to the oil circuit for cooling the compressors C1 and C2, which are designed as oil-lubricated compressors, preferably oil-lubricated screw compressors. Via a heat exchanger (not shown in FIG. 1) of the compressor system 100, at least a portion of the heat output generated by the compressors C1 and C2 can be recovered and preferably used for external heat consumption devices, for example, for heating a room external to the compressor system 100. Instead of or in addition to heat recovery from the oil circuit, the heat amount recoverable from the compressed air flow (preferably at the outlet of the compressors C1 and C2) can be determined.

[0121] Although considering energy consumption alone they should actually be switched off, possible heat recovery has an overall positive impact on the energy balance, so considering overall energy efficiency as a quality criterion it may be energetically advantageous to continue operating compressors C1, C2 in idle mode.Since the energy consumption of compressors C1, C2 in idle mode is relatively low, the residual heat stored in the oil circuit can be used for heat recovery during continued operation in idle mode, increasing overall energy efficiency.

[0122] Modeling using analytical equations can be used to take into account possible heat recovery. If this significantly increases the computational effort, meta-model-based optimization can be used. Here, correlations between variables are learned using a suitable meta-model before the actual optimization. Such meta-models can be, for example:

[0123] · Response surfaces with linear, quadratic and cubic approximation functions; Artificial Neural Networks · Support Vector Regression; Gaussian process.

[0124] The hybrid automaton shown in Figure 9 is expanded compared to the diagram in Figure 7 and has similar functionality. This automaton shows the structure of a simplified mathematical model for simulating the dynamic behavior of a single compressor station, taking into account a heat recovery circuit for utilizing the heat contained in the oil generated during the compression of air in the compressor block of compressor C1 or C2. The model in Figure 7 calculates the oil temperature T oil , ambient temperature T amb , the heat quantity W of the compressor, the heat recovery variable WRG, the heat quantity Heat recovered by the heat recovery circuit, and other related parameters, as well as the cooling behavior W of the compressor C1 or C2. Abkuehl (t state ,T amb ,T oil - ) (metamodel) and heating behavior W aufheiz( tstate ,T amb ,T oil - ) (metamodel). In addition, the parameter deltaToilAbkuehl(t state ,T amb ,T oil - ) is determined for the cooling behavior of the oil temperature, and the parameter deltaToilIdle(t state ,T amb ,T oil - ) is determined for the oil temperature heating behavior during idle operation, and the parameter deltaToilLoad(t state ,T amb ,T oil - ) is determined for the oil temperature heating behavior under load operation conditions. Energy consumption E represents the electrical energy consumed since the start of the calculation. The amount of recoverable heat can be calculated according to the formula shown in Figure 9. For a two-compressor station, the hybrid automaton can be extended to include the discrete compressor operation state combinations in Table 1.

[0125] WRG represents the ability to use heat recovery and assumes a value of true or false. When compressors C1 or C2 are in standby (stopped) state, heat recovery does not take place. This is because in standby mode the oil circuit is no longer active and therefore oil is not pumped through the heat exchangers of the heat recovery system. As a result, the amount of available heat that can be dissipated through the heat recovery system WRG is HEAT + also becomes zero.

[0126] In the standby state, no air is compressed and no heat is transferred to the oil during compression. As a result, the oil temperature T oil This cooling occurs relatively slowly, with a waiting residence time t state , ambient temperature T amb , the oil temperature at the previous time step T oil -Therefore, the amount of heat stored in the compressor, W, can be expressed as a function of the cooling function (W Abkuehl ) by the parameter t state , T amb , T oil - It can also be written as a function of the waiting time t state is modeled similarly to two states: idle and loaded, and is initialized to 0s every time it changes to the standby state.

[0127] At idle, the oil temperature T oil The increase in the heat storage amount W is expressed by a function (deltaToilIdle,W) that models the increase in idling. aufheiz,Idle ) can be mapped. Heat recovery is possible at a certain threshold W threshold It can be used at idle only if the system has an inherent thermal budget greater than T oil + An alternative modelling can be done using a predefined threshold for . If the threshold is exceeded, heat can be recovered (WRG:=true) and the amount of heat that can be dissipated Heat + is the oil temperature T oil and the heat energy at the current time step W + A further function HEAT can be used to determine the heat transfer rate as a function of . If the temperature is below a threshold, heat recovery is not available (WRG:=false) and the amount of heat transferable Heat + becomes zero.

[0128] In the load state (Load), the variable Toil + ,W + ,WRG,Heat + can be determined in the same way as in the idle operating condition, except for a different heating function (deltaToilLoad) and the amount of heat W + (W aufheiz,Load ) are used.

[0129] The method according to the invention and the control unit 300 according to the invention described in relation to the compressor system 100 ensure optimal control of the compressor system 100 from an energy-efficient perspective in order to provide the required consumption of compressed gas (compressed air). The control method can take into account long prediction horizons with fine time discretization, particularly in real time, due to reduced demands on computing power. Dynamic fluctuations and changes in compressed air consumption and dynamic processes within the compressor system can be taken into account early on by the control system. The method (implicitly) considers all possible combinations of control commands for the compressors C1 and C2. The quality of the solution found by the control method for the issued control command combinations, from an optimality perspective, depends only on the quality of the prediction of future compressed air consumption.

[0130] At this point, it should be noted that all the features of the invention described above, both individually and in any combination that makes technical sense, and in particular the details shown in the drawings, form part of the invention. [Explanation of symbols]

[0131] 100 Compressor System 200 Consumers 300 Control Unit C1, C2 compressors R1 Compressed Air Reservoir LC, LC1, LC2 control command (load command) LC1 / LC2 control command combination (load command combination) S tn,m Future System State S tn future time t n Future system state in S tn+1 future time t n+1 Future system state in S t0 Initial System State S tn,sim Similar System Conditions t0 initial point t1: The first time point in the future t n ,t n+1 future point in time Δt time step t is the time from the start of the calculation t sim Simulation Period CS t0 Compressor operating state combination at time t0 CS t1 Compressor operating state combination at time t1 CS tn Time t n Compressor operating state combination CSseq tn,m Compressor operating state combination sequence CSseq tn+1,m Possible compressor operating state combination sequences CSseq opt Optimal compressor operating state combination sequence p System pressure Δp pressure range p min Lower Pressure Limit p max Upper limit pressure Δp i Pressure Value Range NV system gas volume (system gas volume) V Buffer volume of the compressor system p amb Ambient pressure T amb Ambient temperature T oil Oil circuit oil temperature t state Control State Parameters os Compressor operating status (standby / idle / load) E. Energy consumption E start Switch energy for compressor start E loading Switch energy for compressor pressure rise E unloading Switch energy for decompressing the compressor P アイドル Compressor idle power Pload (p) Compressor load operating power, pressure dependency t coasting Minimum idling time before switching the compressor off t loading Minimum idle time for pressure build-up before switching the compressor to load mode W Heat storage capacity of compressor W threshold Compressor heat storage threshold WRG Heat Recovery Variables Heat The amount of heat that can be recovered through the heat recovery cycle W Abkuehl Compressor cooling behavior (metamodel) W aufheiz Compressor heating behavior (metamodel) deltaToilAbkuehl Oil temperature cooling behavior deltaToilIdle Oil temperature heating behavior during idle operation deltaToilLoad Oil temperature heating behavior under load operation DVFR(p) Discharge volume flow rate, pressure dependent CVFR(t) Consumption volumetric flow rate, time dependence

Claims

1. A method for controlling a compressor system (100) comprising a plurality of compressors (C1, C2, ...) for generating compressed gas, in particular compressed air, for at least one consumer (200), comprising: At least one future time point (t ｎ ) of the compressor system (100) with respect to a plurality of future system states (S ｔｎ，ｍ ) determining The future system state (S ｔｎ，ｍ ) is a combination of at least one state parameter and one compressor operating state (CS ｔｎ ) wherein said state parameter preferably indicates the system pressure (p) of said compressor system (100); The at least one future time point (t ｎ ) is the initial system state (S ｔ０ ), the future consumption curve of the compressed gas, in particular the compressed air, and the possible compressor operating state combination sequences (CSseq ｔｎ，ｍ ) was calculated by simulation based on Compressor operating state combination (CS ｔｎ ) is, in particular, a time in the future (t ｎ ) of the compressor system (100) for a combination of defined possible operating states of the compressors (C1, C2, . . . ), Compressor operating state combination sequence (CSseq ｔｎ，ｍ ) is particularly a compressor operating state combination (CS ｔｎ ) a time sequence of steps; ・Future time (t ｎ ) is a set of future system states (S ｔｎ ) to the similar system state (S ｔｎ，ｓｉｍ ) determining The similar system state (S ｔｎ，ｓｉｍ ) each represent a compressor operating state combination (CS) that at least partially coincides with a similar value of the state parameter. ｔｎ ) and is defined by Each similar value of the state parameter falls within the same defined value range of the state parameter, preferably within the same defined pressure value range (Δp ｉ ) and With respect to the first quality criterion, which is preferably an energy efficiency criterion, in particular the similar system state (S ｔｎ，ｓｉｍ ) the compressor operating state combination sequence (CSseq ｔｎ，ｍ ) based on the evaluation of the determined similar system state (S ｔｎ，ｓｉｍ ) by discarding at least one system state from the set of ｎ ) the set of system states (S ｔｎ ) and the reduced set of system states (S) with respect to a second quality criterion, which is preferably an energy efficiency criterion ｔｎ ) from the compressor operation state combination sequence (CSseq) corresponding to the system state ｔｎ，ｍ ) based on the evaluation of the optimal compressor operating state combination sequence (CSseq ｏｐｔ ) The optimal compressor operating state combination sequence (CSseq ｏｐｔ and issuing at least one control command (LC1, LC2, LC1 / LC2) suitable for effecting operation of the plurality of compressors (C1, C2, ...) of the compressor system (100), the control command corresponding to at least a portion of the plurality of compressors (C1, C2, ...).

2. 2. The method of claim 1, wherein the state parameter indicates a system gas amount (NV), in particular a system air amount, stored in the compressor system (100), and the system pressure (p) can be derived in particular from the system gas amount (NV), in particular based on a buffer volume (V) of the compressor system (100).

3. At a future time (t ｎ ) determined for the system state (S ｔｎ ), which is outside a predetermined pressure range (Δp) of the pressure supplied by the compressor system (100), in particular a predetermined upper limit pressure (p ｍａｘ ) or exceeds a predetermined lower limit pressure (p ｍｉｎ 3. The method of claim 1, wherein the system pressure (p) is rejected.

4. Further future system states (S ｔｎ＋１ ) to the initial system state (S ｔ０ ) and further possible compressor operating state combination sequences (CSseq ｔｎ＋１ , ｍ ) for each case based on the time t ｎ＋１ ) by calculating the state parameters at a preceding future time point (t ｎ ) system state (S ｔｎ ) the compressor operating state combination sequence (CSseq) corresponding to the system state from the limited set of ｔｎ，ｍ ) is the further possible compressor operating state combination sequence (CSseq ｔｎ＋１，ｍ 4. The method according to claim 1, wherein the method is part of a

5. The future system state (S ｔｎ，ｍ ) is the time period for a given simulation (t ｓｉｍ ) included in the future time point (t ｎ ) and the simulation period (t ｓｉｍ ) is subdivided into equally spaced time steps (Δt), which are preferably between 0.1 and 10 seconds, and the simulation period (t ｓｉｍ 5. The method according to claim 1, wherein the heating time is in particular 1 minute or more, preferably between 1 and 60 minutes.

6. Based on the first quality criterion and / or the second quality criterion, a future time (t ｎ ) determined for the system state (S ｔｎ ) are cyclically discarded, in particular after a fixed number of time steps (Δt), in particular between two successive time points (t ｎ , t ｎ＋１ 6. The method according to claim 1, wherein the distance between the first and second electrodes is 1 / 2.

7. The future system state (S ｔｎ，ｍ ) is preferably mapped by a branching data structure in computer memory, by repeated execution of the method steps, to future system states (S ｔｎ，ｍ ) corresponds to a node of the branching data structure, the branching data structure includes multiple node levels, and one future time point (t ｎ ) for some future system state (S ｔｎ 7. The method according to claim 1, wherein each of the nodes is assigned to the same node level.

8. The at least one control command (LC1, LC2, LC1 / LC2) is a control command for determining the future system state (S ｔｎ，ｍ ) for a given simulation period (t ｓｉｍ ) included in the future time point (t ｎ ) and the optimum compressor operating state combination sequence (CSseq ｏｐｔ 8. The method according to claim 1, wherein the at least one control command (LC1, LC2, LC1 / LC2) is issued when a predetermined value of the control command (LC1, LC2, LC1 / LC2) is determined, and wherein the issued at least one control command (LC1, LC2, LC1 / LC2) is a control command combination (LC1 / LC2) for a plurality of compressors (C1, C2, ...) of the compressor, preferably comprising a control command (LC1, LC2) for each compressor (C1, C2, ...) of the compressor system (100).

9. At least one of the issued control commands (LC1, LC2, LC1 / LC2), preferably at least one of the issued control command combinations (LC1 / LC2), is / are used to set the initial system state (S ｔ０ ) the compressor operating state combination (CS ｔ０ ) to obtain the optimal compressor operating state combination sequence (CSseq ｏｐｔ ) that is part of the subsequent future system state (S ｔ１ ) the compressor operating state combination (CS ｔ１ 9. The method according to claim 1, wherein the transition corresponds to a transition from

10. The evaluation of the first quality criterion and / or the second quality criterion is performed at an initial time point (t ０ ) to each time point (t ｎ ) Compressor operating state combination sequence (CSseq ｔｎ，ｍ ) based on the calculated energy consumption (E) of the plurality of compressors (C1, C2, . . . ) when passing through the The optimal compressor operating state combination sequence (CSseq ｏｐｔ ) particularly determines the compressor operating state combination sequence (CSseq) that has the lowest calculated energy consumption of the plurality of compressors (C1, C2, . . . ). ｔｎ，ｍ The method according to any one of claims 1 to 9, wherein

11. 11. The method of claim 10, wherein the calculation of energy expenditure (E) includes at least one of the following parameters: Switch energy (E) for starting the compressors (C1, C2,...) Ｓｔａｒｔ ); Switching energy (E ｌｏａｄｉｎｇ ); Switch energy (E ｕｎｌｏａｄｉｎｇ ); Idle power (P ｉｄｌｅ ); Load capacity (P ｌｏａｄ (p)), especially pressure-dependent load capacity

12. The evaluation of the first quality criterion and / or the second quality criterion takes into account in particular a possible heat recovery for heat transfer to a (preferably external) heat consuming device, the possible heat recovery being in particular by calculating the amount of heat that can be recovered from the oil circuit of said compressor system (100), and / or By calculating the amount of heat that can be recovered from a compressed gas stream, preferably a compressed air stream, The method according to any one of claims 1 to 11, wherein the temperature is determined.

13. 13. The method of claim 12, wherein the calculation of the amount of heat recoverable is based on at least one of the following parameters: the temperature of the oil in the oil circuit of said compressor system (100); the ambient temperature (T ａｍｂ ); - the oil flow rate in the oil circuit of said compressor system (100); the final compression temperature of the compressed gas, in particular the compressed air; - specified or calculated heating energy of the compressors (C1, C2, ...); - specified or calculated cooling energy of the compressors (C1, C2,...)

14. The defined possible operating states of the compressors (C1, C2, ...) preferably additionally indicate at least one rotation speed of the compressors (C1, C2, ...), A method according to any one of the preceding claims, wherein the different rotational speeds or rotational speed ranges each correspond to defined possible operating states.

15. The future system state (S ｔｎ，ｍ ) is a parameter that determines at least one (particularly software-related) control state parameter (t ｓｔａｔｅ ), wherein the control state parameter specifically indicates the state of the control algorithm of the compression system (100), and the control state parameter (t ｓｔａｔｅ ) preferably indicates the previous operating time of the compressors (C1, C2, . . .) in the same defined possible operating state, and ｔｎ，ｓｉｍ ) are preferably determined by similar values ​​of said state parameters, respectively, to correspond to a combination of compressor operating conditions (CS ｔｎ ) and at least one matching control state parameter (t ｓｔａｔｅ 15. The method according to claim 1, wherein the .alpha.-methyl-.beta ...

16. Allowable transitions between successive defined possible operating states of the compressors (C1, C2, . . .) are defined; Preferably, additionally, a transition condition is defined for at least one specific transition of the compressor (C1, C2, ...) between two defined possible operating states, in particular for a transition of the compressor (C1, C2, ...) from an idle state to a stopped state and / or a transition of the compressor (C1, C2, ...) from an idle state to a loaded operation, Preferably, the compressors (C1, C2, . . .) are operated for a predetermined first minimum operating time (t ｃｏａｓｔｉｎｇ ) must be operated in idle mode during Preferably, the compressors (C1, C2, . . .) are operated for a predetermined second minimum operating time (t ｌｏａｄｉｎｇ 16. The method according to claim 1, wherein the engine must be operated in idle mode during the period of time.

17. The future system state (S ｔｎ，ｍ 17. The method according to claim 1, wherein the determination of (a) comprises at least one of the following parameters: a buffer volume (V) of said compressor system (100), said buffer volume (V) indicating in particular the volume of said compressor system (100) in which compressed gas, in particular compressed air, is stored during operation; the (in particular pressure-dependent) discharge volumetric flow rate (DVFR(p)) of the compressors (C1, C2, ...); the (in particular time-dependent) consumption volumetric flow rate (CVFR(t)) of said at least one consumer; Ambient pressure (p ａｍｂ )

18. All steps of the method are performed at different initial times (t ０ ) and are executed repeatedly one after another, In particular, the first future time point (t １ The optimal compressor operating state combination sequence (CSseq) of the previous execution of the method corresponding to ｏｐｔ ) the compressor operating state combination (CS ｔ１ ) is the initial time (t ０ ) the compressor operating state combination (CS ｔ０ 18. The method according to claim 1, wherein the composition is used as a

19. A control unit (300) for a compressor system (100) comprising a plurality of compressors (C1, C2, . . . ) for generating compressed gas, in particular compressed air, for at least one consumer (200), comprising: The control unit (300) is designed to perform at least one step, preferably all steps, of the method according to any one of claims 1 to 18.

20. 20. A compressor system (100) comprising a plurality of compressors (C1, C2, ...) for generating compressed gas, in particular compressed air, for said at least one consumer (200), and a control unit (300) according to claim 19.

21. A computer program comprising instructions which, when executed on at least one processor, cause said processor to perform all the steps of the method according to any one of claims 1 to 18, said instructions in particular causing a control unit (300) according to claim 19 to perform at least one step, preferably all the steps, of the method according to one of claims 1 to 18.

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