EP1340919B1 - Method for controlling a set of turbomachines in series or parallel - Google Patents

Abstract

A preset common process variable is sent directly to machine controllers (28-30). The preset common process variable is controlled based on deviation of preset common process variable and an actual value associated with the variable sensed at the particular machine unit exclusively via the machine controllers associated with the particular machine unit. The machine unit of each turbo engine with a drive machine (4-6), with which a machine controller is associated, is formed after presetting a process variable common to all turbo engines (1-3) of a station. An Independent claim is also included for a control system for turbo engines.

Description

The invention relates to a method for controlling a plurality of turbomachines operating in a station in parallel or in series operation for maintaining at least one process variable predetermined by the station and common to all turbomachines with the features of the preamble of claim 1.

In EP-B-0 132 487 a method for operating a plurality of parallel-connected turbocompressors is described, which are each provided to prevent the pumping with a surge limit control. The turbo compressors are controlled jointly by load distribution regulators and individually by a pressure regulator. The load distribution controllers regulate the adjustment of the compressors with one another such that equal distances of the operating point with respect to the blow-off line are present in all compressors. Only one of the compressors is controlled by its pressure regulator, while the others are tracked via the load distribution control.

From EP-B-0 431 287 a method for optimized operation of multiple compressors in parallel or series operation is known. In this case, the combination of machine parameters is always determined for any operating point using algorithms, in which the total power consumption of all drive machines is minimal. This procedure uses a higher-level master controller.

According to the cited prior art (EP-A-0 576 238, FR-A-2 234 911) is usually in a series or parallel circuit of turbomachines with individual control elements and individual controllers always a higher-level master controller, also called master controller required. The master controller has a higher-level task. It determines the required positioning commands for the individual machine units from the required total capacity (desired pressure or desired flow rate of all compressors). Especially with asymmetrically constructed systems, the master controller calculates different manipulated variables for the individual machine controllers.

In the methods known from EP-A-0 576 238 and FR-A-2 234 911 for controlling a plurality of turbomachines interacting in a station, the process variable setpoint, e.g. As the flow, given for the entire station and the measured in the output line of the station, actual, common to all turbomachine flow transmitted. In the method known from FR-A-2 234 911, a second control loop is added to such a first control loop. In this second control loop, the flow rate of the station is compared with the flow rate of each individual turbomachine and additionally transmitted to the individual regulators of the relevant turbomachine as a disturbance variable

According to the relevant state of the art, it is repeatedly emphasized that there may be only one controller for the load distribution of the load on different compressors, which processes only one nominal value and only one actual value as measured variable, since otherwise conflicts may occur in the downstream machine controllers , Each machine unit requires a unique manipulated variable, which is tuned to the other manipulated variables in such a way that no contradictions can occur. For flow control, flow may only be measured at a single point. With a pressure control, the pressure may also be measured only at a single point. There may also be only one setpoint for the common pressure or flow controller. Compliance with this rule is particularly important when used as a pressure regulator for the final pressure or the suction pressure. If each machine unit were equipped with its own pressure regulator, and pressure setpoint and pressure actual value between the various controllers would differ only slightly, which can be done solely by the analog / digital conversion of the input signals, the controller of the parallel compressors would work against each other so that the one controller the machine shuts down and the other one goes up. The machine controllers with their downstream machines work against each other until one of the two machines has reached the upper or lower power limit. In addition, the master controller is a complex component whose failure leads to a standstill of the entire system.

The invention has for its object to simplify the generic control to increase the availability of the individual controllers and to avoid colliding interactions of the controller to each other.

The object is achieved in a generic method according to the invention by the characterizing features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

In the method according to the invention, a master controller influencing all flow machines for controlling the process variable is dispensed with by dividing the functionality of this process variable controller into the individual machine controllers. The algorithm for the distribution of the load on the individual compressors, which runs according to the known state of the art exclusively in the master controller, is realized according to the invention in each individual machine controller. As a process variable, individually or in combination, the flow rate, the discharge pressure, the suction pressure, the pressure ratio, the temperature, the level in a container, the power of the engine or the load distribution of the compressors can be used. Since storage space and computing power are sufficiently available with modern hardware, there are no restrictions from this side. By eliminating the higher-level master controller, an existing station can easily be extended by further machine units. It is merely to add one machine unit to a machine controller, which contains the same control and regulation as each of the existing machine units. By applying the method according to the invention, there are no investment, operating or maintenance costs for a master controller. Nor can there be malfunctions in the station due to a failure of the master controller. Since there are no higher-level and lower-level controllers, colliding interactions of different controllers are eliminated. The inventive method is applicable to the parallel operation, the series operation and the combined parallel and series operation of the turbomachinery in a station. Further advantages of the invention will be described in connection with the following description of embodiments of the invention and of the prior art shown in the drawing.

Fig. 1

ein Regelsystem für Kompressoren im Parallelbetrieb gemäß dem Stand der Technik,

Fig. 2

ein Regelsystem für Kompressoren im Reihenbetrieb gemäß dem Stand der Technik,

Fig. 3

ein Signalflussdiagramm für das Regelsystem nach Fig. 1 oder 2,

Fig. 4

ein Regelsystem für Kompressoren im Parallelbetrieb gemäß der Erfindung,

Fig. 5

ein Regelsystem für Kompressoren im Reihenbetrieb gemäß der Erfindung,

Fig. 6

ein System zur Pumpgrenzregelung gemäß dem Stand der Technik,

Fig. 7

ein Signalflussdiagramm für das Regelsystem nach Fig. 4 oder 5,

Fig. 8

ein Regelsystem für Kompressoren im Parallelbetrieb gemäß einer anderen Ausführungsform der Erfindung,

Fig. 9

ein Regelsystem für Kompressoren im Parallel- und Reihenbetrieb,

Fig. 10

ein Regelsystem für Kompressoren im Parallel- und Reihenbetrieb, wobei die Regelung eines der Kompressoren aufgeblendet ist und

Fig. 11

ein Regelsystem für Kompressoren im Parallel- und Reihenbetrieb, wobei die Regelung eines der Kompressoren aufgeblendet ist, gemäß einer anderen Ausführungsform der Erfindung.

Several embodiments of the invention are illustrated in the drawing and are explained in more detail below. Show it

Fig. 1

a control system for compressors in parallel operation according to the prior art,

Fig. 2

a control system for compressors in series operation according to the prior art,

Fig. 3

a signal flow diagram for the control system of FIG. 1 or 2,

Fig. 4

a control system for compressors in parallel operation according to the invention,

Fig. 5

a control system for compressors in series operation according to the invention,

Fig. 6

a system for surge limit control according to the prior art,

Fig. 7

a signal flow diagram for the control system of FIG. 4 or 5,

Fig. 8

a control system for compressors in parallel operation according to another embodiment of the invention,

Fig. 9

a control system for compressors in parallel and in-line operation,

Fig. 10

a control system for compressors in parallel and in-line operation, wherein the control of one of the compressors is displayed and

Fig. 11

a control system for compressors in parallel and in-line operation, wherein the control of one of the compressors is displayed, according to another embodiment of the invention.

Fig. 1 shows three compressors 1, 2, 3 in parallel operation, which are each driven by a drive machine serving as a turbine 4, 5, 6. In each case a compressor forms a machine unit with a drive machine. The three machine units are combined into one station, which in turn can be part of a pipeline system or integrated into a process. By varying the turbine speed, the delivery capacity of the compressor 1, 2.3 can be varied. Alternatively, the turbines may also be replaced by fixed speed engines, in which case adjustable vanes are used with the actuators 7, 8, 9 in the compressors 1, 2, 3 or throttles upstream of the compressors (not shown).

The compressors 1, 2, 3 are connected by inlet ducts 10, 11, 12 to a suction-side busbar 13, which in turn has a connection to a suction-side process 14 or to a pipeline or to a gas reservoir. On the pressure side, the compressors 1, 2, 3 via outlet lines 15, 16, 17 with a pressure-side Busbar 18 which in turn has connection to a pressure-side process 19 or to a pipeline or to a gas storage.

Superimposed over the entire station is a station control level, which specifies the setpoint values for the operation of the station as setpoint specification 20. The actual capacity of the machinery, usually the final pressure or the suction pressure of the compressor system or the flow is measured by a sensor 22 and transmitted via a signal line 23 to a master controller 24 as an actual value. The process variable setpoint for the entire station is given by the setpoint input 20 via a signal line 21 to the master controller 24, which calculates the required load of the individual machine units according to a predetermined algorithm and the respective machine controllers 28, 29, 30 via the signal lines 25, 26 and 27 set the desired value for the speed or the position of the guide vanes or the throttle valve. The machine controllers 28, 29, 30 in turn set the speed of the turbines 4, 5, 6 or the position of the throttle valves or suction throttles on this target value.

The master controller 24 has a higher-level task. He determined from the required total capacity (desired pressure or desired flow) of all three compressors 1, 2, 3, the required positioning commands for the individual machine units. Particularly in asymmetrically constructed systems, the master controller 24 calculates different manipulated variables for the individual machine controllers 28, 29, 30.

Fig. 2 shows the application for three compressors 1, 2.3 in series operation. The structure of this station largely corresponds to that of the station shown in Fig. 1 for the parallel operation. The only difference is that the first compressor 1 is connected to the inlet line 11 and via the outlet line 15 to the second compressor 2, and this is connected via the outlet line 16 and the inlet line 12 to the third compressor 3. The suction-side busbar 13 does not exist, the process 14 is directly with the serving as a suction line Inlet line 10 connected. Likewise, the pressure-side busbar is missing, but rather the outlet of the third compressor 3 is connected directly to the process 19 via the outlet line 17.

For the control of compressors in series operation apply exactly the same statements in accordance with the prior art as for the parallel operation. If the compressors 1, 2, 3 are to be driven to constant flow in series operation, the master controller 24 determines which rotational speeds the individual machine units are to be driven so that the desired flow rate is achieved. If the compressors 1, 2, 3 are driven to a constant discharge pressure or to a constant pressure ratio, the master controller 24 determines which pressure ratio each individual compressor 1, 2, 3 has to provide in order to achieve the required total pressure ratio. Also for the series operation applies according to the general state of the art that there may be only one master controller, which receives only one setpoint and one actual value.

FIG. 3 shows a signal flow diagram for a control system for a station with three compressors 1, 2, 3. The station setpoint (flow setpoint or pressure setpoint) is applied via the signal line 21 and a converter 31 to a reference / actual reference junction 32. The actual value (measured flow or pressure) passes via the signal line 23 and a converter 33 to the same reference junction 32. In this reference junction 32, the difference between the nominal value and the actual value is formed and given to a station controller 34. The station controller 34 adjusts its output until the actual value corresponds to the desired value. The output of the station controller 34 is supplied to the signal lines 25, 26, 27 via share plates 35, 36, 37 and transducers 38, 39 and 40. These signal lines 25, 26, 27 connect the station controller 34 to the three unit controllers 41, 42, 43. Each unit controller 41, 42, 43 has an input quantity converter 44, 45 and 46 and another input converter (not shown) for the actual machine value , Typically, the speed of the drive turbine 4, 5. 6 or the position of the inlet guide vanes in vane-controlled compressors. In the comparators 47, 48 and 49, the difference between the actual machine value and the machine setpoint is formed and the respective unit controller 41, 42 and 43 supplied. These now turn on their turn via converter 50 51 52, the speed of the turbine 4, 5, 6 (or the position of the vanes) such that the actual machine value corresponds exactly to the machine setpoint.

In the share controllers 38, 39 and 40, the manipulated variable of the station controller 34 is divided among the individual machine units. The adjustment law can be linear or nonlinear depending on the system requirement. It can be dependent on different parameters if required. It is simplistic to assume a linear adjustment law, according to which the turbines 4 and 6 have to apply 30% of the total power and the turbine 5 40% of the total power. As a result, a factor of 0.3 is set in the dividing units 35 and 37, and a factor of 0.4 is set in the proportioning member 36. Should the station controller 34 now demand 10% more power and therefore its output increase by 10%, the machine setpoint supplied to the turbine 4 via the signal line 25 increases by 3%, the machine setpoint of the turbine 5 by 4% and the machine setpoint of Turbine 6 by 3%.

Referring to Figure 3, elements 31-40 belong to the common master controller 24, components 44, 47, 41 and 50 belong to the machine controller 28 of the turbine 4 with the compressor 1, the components 45 48, 42 and 51 belong to the machine controller 29 of the turbine 5 with the compressor 2 and the components 46, 49, 43 and 52 belong to the engine controller 30 of the turbine 6 with the compressor 3.

In many applications, it is common for the machine controller to contain another control function. So z. B. a pressure control circuit be constructed such that the master pressure regulator flow controller are subordinate, which regulate the respective flow through the individual machines. These flow controllers are again underlain by speed controllers, which then regulate the speed. In these applications, the flow controller associated with the machines is part of the respective unit controller 41, 42 43.

Each turbo compressor requires a surge limit control, which is part of every engine control and whose job it is to protect the compressor from operating in the unstable working environment. Operation in the unstable working area is called compressor pumping. 6 is a block diagram of a typical surge limit control for a variable suction pressure compressor. A compressor 53 is equipped with a suction pipe 54 and a pressure pipe 55. A blow-down valve 56 in a blow-off line 57 may be opened in a controlled manner as needed, thereby increasing the flow through the compressor when the gas decrease through the process is less than the minimum allowable compressor flow. A Umblaseventil 56, also referred to as surge limit control valve, is controlled via a control line 58 from the surge limit regulator 59, the input variables of the measured with the sensor 60 inlet pressure, measured with the sensor 61 inlet flow, measured by the sensor 62 final pressure and measured with the sensor 63 Inlet temperature is. Since the surge limiter 59 is typically implemented within the same controller hardware as the governor (it is an integral part of the governor), signals such as compressor flow and pressure are available within and in front of the compressor within the governor and can thus also be used by the load balancer and capacity controller be used.

4 and 5, the control method according to the invention for three summarized to a station compressors 1, 2, 3 is shown in parallel operation and in series operation. As already described in connection with FIGS. 1 and 2, the compressors 1, 2, 3 are coupled with turbines 4, 5, 6 as drive machines and are driven by them. By varying the turbine speed, the delivery capacity of the compressor 1, 2, 3 can be varied. Alternatively, the power turbines may also be replaced by fixed speed motors, in which case adjustable vanes are used with the actuators 7, 8, 9 in the compressors 1, 2, 3 or throttles upstream of the compressors (not shown).

The compressors 1, 2, 3 shown in Fig. 4 are connected through the inlet ducts 10, 11, 12 to the suction-side bus bar 13, which in turn has connection to the suction-side process 14 or to a pipeline or to a gas storage. On the pressure side, the compressors 1, 2, 3 via the outlet lines 15, 16, 17 connected to the pressure-side busbar 18, which in turn has connection to a pressure-side process 19 or to a pipeline or to a gas storage. According to FIG. 5, the first compressor 1 of the series-connected compressors 1, 2, 3 is connected to the inlet line 11 and via the outlet line 15 to the second compressor 2. This is connected via the outlet line 16 and the inlet line 12 to the third compressor 3. The process 14 is directly connected to the suction line 10 and the outlet of the third compressor 3 is connected via the outlet line 17 directly to the process 19.

In the control method according to the invention eliminates the master controller. Instead, each of the machine controllers 28, 29, 30 receives the total setpoint from the setpoint input 20 of the station directly via the signal line 21. The actual value is also supplied directly to each machine controller 28, 29, 30 via the signal line 23, so that each machine controller 28, 29, 30 can carry out the necessary calculations and adjust the downstream actuators as if a common superimposed master controller were used.

Fig. 7 shows the signal flow diagram for a parallel or series connection of three compressors 1, 2, 3 according to the invention. The station setpoint of the setpoint input 20 is split, connected in parallel to three converters 64, 65, 66 and forwarded to the comparators 70, 71, 72. The actual value from the signal line 23 is connected to three converters 67, 68, 69 and forwarded to the comparators 70, 71, 72. In the share plates 35, 36 and 37, which are arranged between the transducers 64, 65, 66, the target value is divided among the individual machine units, consisting of the compressors 1, 2, 3 and the turbines 4, 5, 6. In the comparators 70, 71, 72, the difference between the setpoint and the actual value is formed and each one Amplifier 73, 74, 75 the unit controllers 76, 77, 78 supplied. The unit regulators 76, 77, 78 in turn adjust via the transducers 79, 80 and 81, the turbine speed or the vanes of the respective compressor 1, 2 or 3. The converter 67, 64, the proportioner 35, the comparator 70, the amplifier 73, the unit controller 76 and the converter 79 are collectively parts of the engine controller 28 associated with the engine unit formed of the turbine 4 and compressor 1. The transducers 68, 65, the proportioner 36, the comparator 71, the amplifier 74, the unit controller 77 and the converter 80 are common parts of the engine controller 29 associated with the engine unit formed by the turbine 5 and compressor 2. The transducers 69, 66, the proportioner 37, the comparator 72, the amplifier 75, the unit controller 78 and the converter 81 are together parts of the machine controller 30 associated with the machine unit formed of the turbine 5 and compressor 3.

Actual value and setpoint of the process variable as the input of the transducers 67 to 66 can be of any desired size. Often it is the flow through the compressors, the pressure in front of or behind the station, but it can also be the load distribution of the compressors in series or parallel operation. Also conceivable is the pressure ratio of the entire station or a temperature or a liquid level in a container.

The essential difference between the state of the art according to FIG. 3 and the invention according to FIG. 7 is that the master controller 24 shown in FIG. 3 is completely omitted with the elements 31 to 40 and its function is applied to the machine controllers 28, which are present anyway. 29, 30 are divided. The elements 31 to 34 are omitted without substitution and by three elements 64, 70 and 76; 65, 71 and 77 and 66, 72 and 78. For this purpose, the transducers 38 to 46 are dispensed with. Much more essential, however, is that the functionalities shown are purely software-implemented additional functions in the respectively already existing machine controllers.

Hereinafter, the advantages of the inventive solution over the prior art will be described by way of example by comparison of the prior art with the invention. Three compressors 1, 2, 3 as shown in FIG. 2 are driven with a control system according to FIG. 3 in series operation (prior art). Each of the compressors 1, 2, 3 drive at the beginning of the control process with a pressure ratio of 3. The controlled variable is the pressure in the pressure-side manifold 19. The setpoint amounts to 99 bar and the actual value is 90 bar. The compressors 1 to 3 should each apply one third of the total pressure ratio. The comparator 32 detects a deviation of 9 bar and transmits it to the station controller 34. This station controller 34 increases its output by a proportion that corresponds to an increase in the pressure ratio of 10% from 90 bar to 99 bar, it should be an example here an increase of the output signal from 45 to 50%. Each of the three machine units increases its power to the same extent until the measured actual value corresponds to the setpoint.

In a system according to the invention according to FIG. 7, the following functional sequence results. The actual value on the signal line 23 is 90 bar and the desired value on the signal line 21 is 99 bar. Via the transducers 67 to 69, all three unit controllers (capacity controllers) 76, 77 and 78 receive the same control difference of 9 bar. Each of the three unit controllers 76, 77 and 78 responds in exactly the same way as the master controller 24 in FIG. 3. Each of the three machine units increases its power to the same extent until the measured actual value corresponds to the desired value.

In compressors in series operation with variable suction pressure regulation of the discharge pressure is always such that the control variable is the pressure ratio over the entire station, that is, the series connection of all compressors. Even with compressors in series operation, which are driven to constant flow, the ratio of the pressure ratios of the individual compressors is the variable to be controlled for the unit controller.

According to the state of the art, it must be assumed that problems can arise if the input transducers for the nominal value and the actual value of the individual unit controllers have a different drift or if the incremental analog / digital conversion determines different numerical values for the nominal value or actual value of the individual machine controllers. In this case, there will be a deviation of the total capacity of all compressors from the required performance. According to the prior art, this disadvantage is considered to be the reason that an overlaid master controller is absolutely necessary. At the beginning, this drawback has already been pointed out when using three individual pressure regulators.

According to the invention, this problem is solved by the use of a load distribution controller. This load distribution controller acts in addition to the unit controller 76 to 78 (capacity controller) and uses the same machine controller 28, 29, 30. Hereinafter, only the function of the load distribution controller using the known function groups will be described. Subsequently, the combination of capacity controller and load distribution controller will be described. This load distribution controller is constructed exactly like the unit controller 76 to 78 (capacity controller) as shown in FIG. 7. However, the target value of a load distribution control, the target load proportion of the compressor and the actual value is the current load. It is common for compressors in parallel operation, the distance of the operating point from the stability limit is the control variable and for compressors in series operation, the pressure ratio. 7, the actual value for each machine unit is the respective pressure ratio of the respective compressor, and the desired value is the desired proportion of the respective compressor in the total pressure ratio. The actual value of the pressure ratio can be determined by dividing the end pressure measured for the surge limit control by the suction pressure measured for the surge limit control. The total pressure ratio is calculated by dividing the station outlet pressure by the station inlet pressure. It is usual that all compressors are operated in serial operation with the same pressure ratio, so that the setpoint for each individual load distribution controller is one third of the total station pressure ratio. If the ratio is different for individual machines, a scaling factor can be taken into account within the setpoint formation. If the load proportion of the individual machine units depends on further process variables, variable scaling factors can be introduced.

The load distribution algorithm calculates a partial load for each of the compressors, for compressors in parallel operation z. B. a pre-existing proportion of the total flow. In series operation, the algorithm gives e.g. a fixed predetermined proportion of the total required pressure ratio before. The unit controller of each compressor now adjusts the individual machine unit to this value.

If, due to a measurement error or a converter error, the actual value processed in the controller deviates from the actual value actually traveled in the compressor, all load distribution controllers detect this supposed deviation from the target load distribution and regulate this by adjusting all three compressors such that the load distribution controllers see a uniform load distribution. If the actual value converter of the unit 1 supplies the converter 67, e.g. 10% too high a value, each of the unit controller associated with each compressor (load distribution controller) notices this deviation and moves its downstream actuator by the predetermined ratio. In the balanced state, the machine unit 1 drives stably with a low load of 6.66% and the machine units 2 and 3 stably each with a 3.33% excess load. The result is an imbalance of all three compressors. However, this is less than the single error of the affected machine unit.

The system even works robustly if the setpoint and the actual value are determined separately for each machine unit, resulting in larger deviations between the setpoints and actual values of the individual controllers. This provides a further advantage of the method A fault in a common actual value measurement affects the operation of all machine units in the station. The same applies to a fault of the setpoint adjuster. According to this method, the actual value measurement can be assigned to each individual machine unit. Fig. 8 shows z. B. an arrangement with individual actual value measurement. Instead of a common actual value measurement in the pressure-side busbar 18, the actual value (final pressure behind the compressors, upstream of the compressors or through the compressors) in the respective outlet lines 15, 16 and 17 can be measured with sensors connected to transducers 90, 91 and 92 are. The individual actual values are then applied via the transducers 69, 64 and 65 to the comparators 70, 71 and 72 according to FIG. 7 and fed to the machine controllers 28, 29, 30. It is also possible to specify the setpoint individually. This means that all necessary functionalities are assigned individually to each machine unit. Conversion errors of setpoint and actual value detection when using the control method according to the invention as a capacity controller (flow controller, pressure regulator) are compensated in the same way.

The advantage of such an arrangement is, on the one hand, that each of the actual value measurements can be assigned to a machine unit and that the supply of the converters with auxiliary energy can take place from the control cabinets of the respectively assigned machine unit. Furthermore, even with a total failure of setpoint or actual value converters of a machine unit, the corresponding units of the other machine units are active and thereby reduce the negative effects of this failure. It is also possible to set the setpoint and the actual value separately for each machine unit. The advantage is that there are no more common components and only identical machine systems are used without superimposed system components.

As an example, the case described above when using the unit controller is named as a pressure regulator. The desired final pressure is 99 bar. Compressors 1 to 3 are each intended to provide one third of the total power currently required. For this purpose, each turbine 4 to 6 each yield 20% of the total available power. Now drop the actual value measurement in the pressure line 17 of the compressor 3 and output an actual value of 0 bar. The turbine 6 moves because of the lack of actual value to its maximum power and thereby provides 33% of the total power .. This increases the pressure in the pressure-side manifold 18 and thus the final pressure of all compressors 1, 2, 3. The two intact measuring devices in the compressor discharge lines 15th and 16 of the compressors 1 and 2 note this increase and drive the compressors 1 and 2 in the power down so far that the final pressure of all three compressors 1, 2, 3 again corresponds to the setpoint 99 bar. A state-of-the-art station controlled by the master controller will drive all compressors to 100% power in this operation. The same happens if a setpoint fails. A master controller shuts down all machines to zero and the entire station stops delivering power. In a control method according to the invention, the compressor, whose setpoint falls to zero, runs in its power to zero, the other two compressor controls note this deviation and regulate them by increasing their own power, so that the operation of the station as a whole not being affected.

The advantage of the solution according to the invention is obvious, it can be dispensed with the master controller, thereby costs are saved and increased availability. In addition, this method has the advantage of dispensing with a common actual value measurement and a common setpoint generation and assigning both actual value measurement and setpoint adjustment of each compressor unit. It is also essential that the availability is increased and the overall system less susceptible to interference

Below are some variants and designs for the distribution of the load on the individual compressors will be described.

In many applications it is necessary to be able to influence the proportion of the individual machine units in the total load. In some cases, for. B. the staff who dictates the driving style of the station, want to influence the proportion of load on individual machine units. Should z. B. a machine unit out of service it makes sense to reduce the unit's share of the total load. This can be done by adding a fixed value to the summing point 70, 71 or 72 to balance the equilibrium. As a result, the load distribution controller no longer loads all machine units equally, but varies. Example: Without this trimming, each of three compressors runs in series operation with one third of the total pressure ratio. If the totalizer 71 (for the middle compressor) adds a minus 20% duty factor, the three machine regulators regulate until the pressure ratio of the middle compressor is exactly 20% smaller than that of the other two.

Another possibility is to specify the setpoint for the load distribution for each of the compressors individually and differently. This can be z. B. may be required if there is an imbalance in the machine units. It can z. B. drive machine units of different sizes together in a station. In this case, the factor must be adapted to the size of the machine units.

Another possibility is that an optimization algorithm determines an optimum combination of the machine load of the individual machine units for the respective operating point. Such optimization algorithms are described, for example, in the aforementioned EP-B-0 431 287. When applying the invention to this known method can be dispensed with in the known method to a higher-level computer and master controller when the algorithm is programmed into each machine controller.

Another need for intervention in the choice of load distribution on the individual machine units can, for. B. also be reaching a limit of the permissible operating range on one of the components. Are z. B. gas turbines of different types used as prime movers for compressors, one of the gas turbines z. B. have reached the maximum exhaust gas temperature, while the other gas turbines still have control reserves. The Invention offers two approaches to this problem. One approach is to vary the load sharing factor among the non-bordered machine units so as to increase the factors in proportion to the unavailable machine units. The factor for the machine in the limit mode is set to zero as long as the machine is operating in the limit. However, the method according to the invention compensates for this process even without this intervention. Since the unit operated at the limit no longer delivers any additional power, the capacity controller determines a deviation from the setpoint and increases the power of the other unit so that the process variable to be controlled corresponds exactly to the setpoint. Actuator or intervention point for all of these factors to the trims are the proportioners 35 to 37 or the addition of a fixed value to the totalizer 70 to 72.

In Figs. 9 to 11 are three parallel-connected compressors of the low-pressure stage (ND-A, ND-B, ND-C) with three parallel-connected compressors of medium-pressure stages (MD-A, MD-B, MD-C) and three in parallel switched high-pressure stage compressors (HD-A, HD-B, HD-C) connected in series. In Figs. 10 and 11, the control system for the compressor MD-B is shown enlarged. The remaining compressors are equipped with an identical control system. Each compressor is provided with a surge limit control, which has already been described in connection with FIG. Furthermore, each machine unit consisting of compressor and turbine is assigned a machine controller 85.

In the pressure-side busbar 18, a sensor for determining the actual value of the final pressure of the station is arranged. The measured value is fed to a converter 86, which is connected to a comparator 88 via a signal line 87. This comparator 88 is also supplied by the setpoint specification of the setpoint of the final pressure.

In the pressure-side busbar 18, a sensor for determining the actual value of the flow of the station is also arranged. The measured value is fed to a converter 89 which is connected via a signal line 90 is connected to a comparator 91. This comparator 91 is also supplied from the setpoint specification of the setpoint of the flow.

In the suction-side busbar 13, a sensor for determining the actual value of the suction pressure of the station is arranged. The measured value is fed to a converter 92, which is connected via a signal line 93 to a comparator 94. This comparator 94 is also supplied from the setpoint specification of the setpoint of the suction pressure.

The signal line 93 of the suction pressure and the signal line 87 of the final pressure are led to a computer 95, in which the total pressure ratio is calculated. The pressure ratio can additionally be evaluated with a fixed or a variable factor dependent on other variables. In the first approach, the factor is 1/3, which means that all three compressors are loaded equally. Behind the transducer 62 for the final pressure of the compressor MD-B, a signal line 96 is branched, which is guided to a computing unit 97. Behind the converter 61 for the suction pressure of the compressor MD-B, a signal line 98 is branched off, which is also guided to a computer 97. In the computing unit 97, the pressure ratio of a single compressor is determined. The arithmetic units 95 and 97 are connected to a comparator 99 in which the single pressure ratio of this compressor MD-B is compared with its desired proportion (of the factor-weighted) total pressure ratio.

From the surge limit regulator 59, a signal line 100 is led to a computing location 101. The signal line 100 carries a signal including the distance of the operating point of a single compressor. The computing unit 101 are also supplied with the corresponding signals of the other parallel-connected compressors. In the computing unit 101, the mean value of the distances of the operating points is determined. In a comparator 102, the mean value of the distances is compared with the individual value of a compressor. The comparators 88, 91, 94 are connected to a summer 104 via signal lines, in each of which a changeover switch 103 is arranged. The comparators 99, 102 are via signal lines, in each of which a switch 105 is connected to a summer 106. The summer 104 is also connected to the summer 106

The summers 104, 106 are connected via a signal line 107, in which a hand engagement 108 is arranged, to the machine controller 85 associated with a machine unit which performs the functions of capacity, discharge pressure, suction pressure, flow and load distribution control exercises.

The control system illustrated in FIG. 11 additionally contains a maximum selection 109 and a minimum selection 110 in order to limit the speed and load of the drive machine or other variables.

In the closed-loop and parallel-mode control system shown, capacity control and load-sharing control of the station is performed by a single machine controller associated with each machine unit. Control differences for the capacity control, the load distribution control in parallel operation and the load distribution control in series operation are formed in front of the machine controller. In this control system, three different capacity control algorithms can be selected (flow control, final pressure control behind the high pressure compressor and suction pressure control upstream of the low pressure compressor). Since the capacity controller can regulate only one size, the two other control differences of the capacity control via the switches 103 are switched to zero. Here a mutual locking makes sense. Should z. B. the flow control be active, the control difference for the suction pressure and the final pressure control is switched to zero. Alternatively, the setpoint for the non-active controller can also be switched to the actual value. This also makes the control difference to zero.

If one of the load distribution controllers is to be deactivated, the same happens. The associated control difference is simply switched to zero. This can be done in an elegant way by setting the optimization variable (actual value of the load distribution) to the setpoint is switched. The same happens when a compressor is out of service. The load balancers of the other compressors simply assume that the out-of-service compressors are optimized and thus have no effect on the load distribution on the other compressors.

It is also possible to operate the machines exclusively in manual mode. For this purpose, all control differences are switched to zero, d. H. all controllers are switched off. The hand engagement shown in Figs. 10 and 11 can be used to impart manually controlled artificial control difference as a control variable. The respective machine controller follows this difference as long as the size is present. Since the controller usually also has integral behavior (PI or PID controller), the integral part of the controller reacts to this fixed control difference in the input by continuously adjusting the output. In a particular embodiment, this manual adjustment can only act on the integral part of the controller, so that the Proprotional (P) and the differential component (D) do not respond to this manual intervention. Alternatively, the manual adjustment can also take place in that the controller 85 is switched to "hand".

For clarity, an example will be described below. The compressors in series are called low pressure (ND), medium pressure (MD) and high pressure (HD) compressors. The parallel compressors are called A, B, C. It is assumed that the system is in flow control mode and all compressors are in operation.

In parallel operation, the flow set point is 2% greater than the actual value, compressor ND-A delivers exactly 1/3 of the total mass flow, compressor ND-B 5% too little and compressor ND-C 5% too much. Compressor MD-A and MD-B convey 30% of the mass flow and compressor MD-C 40%. Each of the HD compressors promotes the same mass flow.

In series operation, compressor ND-A is loaded 2% too low, compressor MD-A is loaded correctly and compressor HD-A 2% is loaded too high. Compressor ND-B is loaded correctly, compressor MD-B 3% too high and compressor HD-B 3% too low. Compressor ND-C is charged with 29%, MD-C with 36% and HD-C with 35%.

The following control differences occur at the summers: Totalizer of the MD-B compressor HD-A HD-B HD-C capacity +2 +2 +2 Parallel +2 0 -2 series -2 +3 -1.7 MD-A MD-B MD-C capacity (104) +2 +2 +2 Parallel (102) +3.3 +3.3 -6.6 series (99) 0 -3 -3.3 ND-A ND-B ND-C capacity +2 +2 +2 Parallel 0 0 0 series +2 0 +5.1

The rule algorithm now forms the resulting control difference before the controllers. This results in A HD HD-B HD-C capacity +2 +2 +2 Parallel +2 0 -2 series -2 +3 -1.7 total +2 +5 -1.7 HD-A HD-B HD-C capacity +2 +2 +2 Parallel +3.3 +3.3 -6.6 series 0 -3 -3.3 total +5.3 +2.3 -7.9 HD-A HD-B HD-C capacity +2 +2 +2 Parallel 0 0 0 series +2 0 +5.1 total +4 +2 +7.1

Despite the z. T. contradictory requirements of the individual control tasks (capacity controller requires an increase in performance, the load distribution controller a reduction) receives each machine controller a clear control command in the required direction to directly achieve the optimum. An interaction between the different requirements is excluded by design.

In a further embodiment, further algorithms can be added. The prime movers of one or more compressors can z. B. achieve a performance limit. This may additionally be processed in the algorithm such that the control difference of the machine controllers of the prime movers operating at the limit are made zero (as in manual mode). These drive machines then no longer participate in a further increase in performance. To compensate for this influence, the difference between the optimum adjustment difference according to the above table and the actually effective difference can be added to the control difference of the other parallel and series compressors. This also optimally compensates for this procedure. Of course, the method also works for several limiters per machine unit.

In a further embodiment, the limiting regulators can be connected via an extreme value selection (maximum selection or minimum selection), as shown in FIG. 11. In addition to the control differences described above, control differences for the distances of the operating point are formed by the boundaries, so in Fig. 11 z. B. from the maximum speed and the minimum speed. In addition, the formation of each further control difference for a maximum and minimum limit are shown. The control differences for limits to maximum values are switched to a minimum selection, the control differences for a minimum limit act on a maximum selection. The effective control difference for the machine controller is thus either the control difference according to the above algorithm or the distance of the operating point from the limit, if this distance is less. If a limit is exceeded, the output of the max / min selector 109/110 always controls the machine unit, even in the case of a contradictory request from the capacity or load distribution controller, always in such a way that the limit is not exceeded in steady-state operation.

In the above example, the compressor ND-C is to be increased with a control difference of 6.3% in its performance. However, the drive turbine is 3% below the maximum operating speed. The effective regulatory difference is therefore limited to 3%. As soon as the turbine has reached the maximum operating speed, the control difference of the speed limitation control becomes zero and prevents any positive control difference to the machine controller via the minimum selection. Only negative control differences in the direction of speed reduction can happen. When the maximum speed is exceeded, the unit controller shuts down the speed.

Occasionally, it may be necessary to set the individual control loops (pressure regulator, flow controller, load distribution controller in series, load distribution in parallel) to different controller parameters, as the time response of the controlled system differs for the individual controlled variables. This can be done in a simple manner by subjecting the respective control differences to different amplification factors. If z. As the control difference of the pressure regulator multiplied by a factor of 1, the control difference of the flow controller with a factor of 2 and the load distribution controller with a factor of 3, this leads to the fact that the loop gain of the Lastvereilungsreglers is three times that of the pressure regulator.

If the controller Nachstellzeit be customized, this can be done by a simple way. From a comparison of the individual inputs of the maximum and minimum selection with the output, it can be determined which size is the leading one. From a position of the switch for the control differences of the capacity controller and the Load distribution controller can be determined which of these controller is in operation. A selection matrix can now determine at which controller combination which controller reset time should be effective. The controller time constant that is effective in the machine controller can now be adaptively adjusted as tightly as the selection matrix requires.

Figure 11 shows an application with a total of nine control loops. If such a system according to the prior art of nine individual controllers are built, extensive tracking and mutual interlocks would be required to prevent that some non-active controller run into saturation. Furthermore, there is a great risk that the nine controllers influence each other dynamically. All these disadvantages are avoided according to the invention. There is only one machine controller per machine unit. Any tracking can be omitted and there can be no interaction between controllers. The machine controllers of the other compressors can not influence each other, since all machine controllers are set to the same parameters for the same control variables. Since all load distribution controllers are optimized with the same parameters, they have the same time behavior. Consequently, it can not happen that individual machines in different directions and thus diverge.

Claims (31)

1. Method of regulating several fluid-flow machines (1, 2, 3), which co-operate in a station, in parallel or serial operation for maintenance of at least one process magnitude predetermined by the station and common to all flow machines, wherein each flow machine forms together with the driving drive engines (4, 5, 6) a machine unit with which a machine regulator (28, 29, 30) is associated, characterised in that the predetermined, common process magnitude is delivered only directly to each of the machine regulators (28, 29, 30) and that this predetermined, common process magnitude is regulated out exclusively by way of the machine regulators (28, 29, 30) associated with the respective machine unit.
2. Method according to claim 1, characterised in that the end pressure of the compressors is used as process magnitude.
3. Method according to claim 1, characterised in that the throughflow through the compressors is used as process magnitude.
4. Method according to claim 1, characterised in that the induction pressure of the compressors is used as process magnitude.
5. Method according to claim 1, characterised in that the pressure ratio of the compressors is used as process magnitude.
6. Method according to claim 1, characterised in that the load distribution in parallel operation is used as process magnitude.
7. Method according to claim 1, characterised in that the load distribution in serial operation is used as process magnitude.
8. Method according to claim 1, characterised in that the power of the turbines serving as drive engines is used as process magnitude.
9. Method according to claim 1, characterised in that the inlet pressure of the turbines serving as drive engines is used as process magnitude.
10. Method according to claim 1, characterised in that the outlet pressure of the turbines serving as drive engines is used as process magnitude.
11. Method according to claim 1, characterised in that the extraction pressure of the turbines serving as drive engines is used as process magnitude.
12. Method according to claim 1, characterised in that the throughflow through a turbine serving as drive engine is used as process magnitude.
13. Method according to claim 1, characterised in that the current of an electrical drive engine is used as process magnitude.
14. Method according to one of claims 1 to 13, characterised in that several process magnitudes are combined within one station.
15. Method according to claim 1, characterised in that the output magnitudes of the capacity regulators are disposed in the same ratio to one another in order to achieve uniform loading of all machines.
16. Method according to claim 1, characterised in that the target values for the load distribution regulators are disposed in fixed ratio, but not in the same ratio, to one another in order to achieve a predetermined non-uniform loading of all machines.
17. Method according to claim 1, characterised in that the factor by which the target values of the load distribution regulators deviate from one another is a function of a process magnitude in order to achieve a desired loading of all machines.
18. Method according to claim 17, characterised in that the power of the turbine serving as drive engine is used as influencing process magnitude.
19. Method according to claim 17, characterised in that the spacing of a process magnitude from a limit or a desired other optimisation algorithm is determined.
20. Method according to claim 1, characterised in that the factor by which the target values of the load distribution regulators deviate from one another can be intentionally influenced in order to achieve a desired loading of all machines.
21. Method according to claim 1, characterised in that target values and actual values are predetermined and measured in common for all machine units.
22. Method according to claim 1, characterised in that target values and actual values are predetermined and measured individually for each machine unit.
23. Method according to one of claims 1 to 14, characterised in that between the regulating differences of several process magnitudes one is selected and the remaining regulating differences, which are not needed, are switched to zero.
24. Method according to one of claims 1 to 14, characterised in that between the regulating differences of several process magnitudes one is selected and the target value of one of the process magnitudes which is not selected is switched to the actual value.
25. Method according to one of claims 1 to 14, characterised in that the regulating differences of all process magnitudes are switched to zero and the regulation is undertaken manually.
26. Method according to claim 23, characterised in that in the case of use of a machine regulator with a proportional component and an integral component the regulation is undertaken manually in such a manner that the manual intervention acts only on the integral component.
27. Method according to one of claims 1 to 14, characterised in that the regulating difference of the machine regulators of the machine units, which are operated at the upper power limit, is made zero and that the actually effective regulating difference is added to the regulating difference of the other machine units.
28. Method according to one of claims 1 to 25, characterised in that the regulating difference is switched by way of an extreme selection.
29. Method according to one of claims 1 to 26, characterised in that the regulating differences are, for limitations, switched from maximum values to the minimum selection and that the regulating differences for a minimum limit act on a maximum selection.
30. Method according to one of claims 1 to 26, characterised in that the regulating differences for different process magnitudes are multiplied by different amplification factors.
31. Method according to one of claims 1 to 28, characterised in that the reset time of the regulators is individually adapted in the manner that it is ascertained from a comparison of the individual inputs of the maximum and minimum selection with the output which process magnitude is the leading one, that from the setting of the changeover switches of the regulators for the process magnitudes it is ascertained which regulator is in operation and that by way of a selection matrix it is determined in which regulator combination which reset time shall be effective.

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