EP3334934B1

EP3334934B1 - System for the control of a compression system

Info

Publication number: EP3334934B1
Application number: EP16836699.5A
Authority: EP
Inventors: Sami Nyman; Simo HEIMONEN; Heikki Laurila
Original assignee: Sarlin Oy AB
Current assignee: Sarlin Oy AB
Priority date: 2015-08-14
Filing date: 2016-06-30
Publication date: 2021-08-04
Anticipated expiration: 2036-06-30
Also published as: EP3334934A1; EP3334934A4; CN108138760B; CN108138760A; WO2017029427A1; PL3334934T3; ES2900024T3

Description

Field of the invention

The object of the present invention is a compression system of a fluid medium and a method for controlling the compression system.

Background of the invention

In industrialized countries, about 10% of the electrical energy consumed by industry is spent on the production of compressed air. In addition, compressed air is a critical production factor, and consequently quality problems appearing in compressed air are in many cases economically significant. Ineffective use of compressed air has been found to be a significant problem in many countries.
In the compression systems of compressed air networks, compressors are used to produce compressed air, which is conducted via a cooler and a pressure tank into a secondary treatment unit, which is provided with filters and driers, and into a second pressure tank, from where the compressed air is supplied to the place of consumption. The compressors are controlled by means of controllers connected via a data communication bus to a control computer controlling the system. Connected to the control computer are additionally e.g. pressure sensors, and the data obtained from these is used in the control of the system.
WO specification 91/06762 discloses a compressor control apparatus of this type, which can be connected to a computer. Via a data communication bus, several compressors can be connected to the computer. An individual controller can control the mode of operation of an individual compressor, said modes being on/off-line, modulating operation and deloaded operation. In WO specification 91/06762 , each controller of a compressor can be controlled individually by means of a signal obtained from a computer. In addition, the apparatus comprises a graphic display, such as a LED display, on which it is possible to present e.g. controller parameters, and the operator of the apparatus can operate the apparatus via a user interface by pressing different switches.
To save energy in the production of compressed air, various methods have been developed. Among the most typical solutions are standard controllers provided by compressor manufacturers and having their own control programs, which can not be customized to suit other manufacturers' compressors and which comprise no verification of the efficiency of control. In addition, partly modular methods have been developed that are customizable for several compressor types and permit the connection of several pressure sensors.
There are also measuring methods that can be used to ascertain the benefit regarding energy economy achieved by the control. However, these measuring methods are of a single-operation nature, and they have to be repeated at regular intervals if the aim is to ensure a continuous high quality of performance. The prices of customizable solutions are high due to, among other things, the large amount of programming work needed. Under these circumstances, the apparatuses have to be built in small production series, and consequently they are expensive.
A large proportion, up to 80%, of maintenance visits associated with control systems is attributable to failure caused by misuse. This is because current control systems are separate systems that are not maintained after their introduction, except sporadically. When users are replaced the training they have once received is no longer useful. The actual compressed air system to be controlled is developed over many years, and the control systems do not necessarily suit the changed situation. This leads to a situation where, over the course of time, even a well performing control system does not necessarily meet its purpose.
US patent specification 4502842 discloses a system composed of a plurality of compressors, which system can be preset to function in different situations e.g. in such a way that only some of the compressors work or work at reduced power. US patent specification 4526513 presents another system for the control of a compressor system.
Current systems known in the art do not enable the best possible energy efficiency, but instead the compressors in them are often driven in a range at which the efficiency ratio of the compressors and/or of the entire system is not good.
Publication WO 96/16271 A1 discloses a method and a control system for controlling a fluid compression system. Using such methods and control systems, savings in excess of 30 % over conventional techniques may be achieved in the energy consumption of compressed-air production.
Publication US 2004/151593 A1 relates to a modular system for controlling a compression system for the compression a fluid medium. Due to its architecture, the system can be constructed from standard components produced by automation manufacturers.

Summary of the invention

The object of the present invention is to achieve a new type of control system and a new type of control method in order to enable the operation of pneumatic systems and equivalent to be rendered more effective on a large scale at a reasonable cost and with limited personnel resources. The details of the features characteristic of the system of the invention are presented in the claims below.
In the system according to the invention one or more compressors and the associated secondary treatment devices, connected to one or more compressed air networks or equivalent, are controlled and monitored. The system of the invention is a compression system of a fluid medium. The compression system comprises compressors, and their associated controllers, for compressing the fluid medium, secondary treatment devices for the treatment of the medium delivered from the compressors, piping systems for conducting the fluid medium to a place of consumption, and a control system. The control system comprises a control unit containing a data processing system for controlling the compression system, a user interface including a display associated with it, and transmission means for the transmission of control data between the control unit, the controllers and the pressure sensors. A control mode specific to the compressor type can be selected in the compression system, the control mode determining the adjustment value to be used. The adjustment value determines the requirement for fluid medium, the change in direction of it and the rate of change. Parameters given from the user interface can act on the adjustment value. The control system is adapted to convert an adjustment value into delivery requests and control requests for the compressors that are based on the regulating mode selected for a compressor. Selection of the control and regulating modes for the compressors is made from the user interface of the control system.
The system according to the invention is specified in more detail in the characterization part of claim 1.
By means of the system according to the invention variable delivery compressors can be run in a good compressor-specific efficiency range, thereby attaining the best possible energy efficiency. By means of the system according to the invention the range in which compressors are run can be demarcated to the specific compressor. In addition to this, measuring data can be utilized in controlling the delivery rates of the compressors.

Brief description of the figures

In the following, the invention will be described in more detail by the aid of some embodiments with reference to the attached drawings, wherein

Fig. 1 presents a compression system according to an embodiment of the invention,
Fig. 2 presents the operation of a system according to an embodiment of the invention,
Figs. 3A - 3D present as flow charts the operation of the control modes and regulating modes of compressors according to some embodiments of the invention,
Figs. 4A - C present the defining of a network delivery request according to an embodiment of the invention,
Fig. 5 presents the defining of a compressor delivery request according to an embodiment of the invention,
Fig. 6 presents an example of the operation of the control mode and regulating mode of a compressor according to an embodiment of the invention.

Detailed description of the invention

In the following, the invention will be described in more detail by means of an example of its embodiment with reference to the attached drawing 1, which presents a block diagram of a pneumatic system comprising a control unit 3 according to the invention.
The pneumatic system, according to an embodiment of the invention, that is presented in Fig. 1 comprises two compressed air networks 1, 2, which are connected to a control system that controls them. The first network 1 comprises six compressors C1-C6 with their controllers A1-A6, a pressure tank 11 connected to three compressors C2-C4, four secondary treatment units 12-15, a place of consumption 16 and piping systems 17-19 for their interconnection. The second network 2 correspondingly comprises one compressor C7 with its controller A7, a secondary treatment unit 21, a place of consumption 22 and a piping system 23 for their interconnection.
In addition, both networks are provided with pressure sensors PI1-PI5, of which PI1 is connected to the piping 17 between compressor C1 and secondary treatment unit 12, PI2 to the pressure tank, 11, PI3 to the piping 19 between compressors C5, C6 and secondary treatment unit 14, 15, PI3 and PI4 to the place of consumption 16 and PI5 to the piping 23 between compressor C7 and secondary treatment unit 21 as well as to the place of consumption 22, and of pneumatic station controllers AS1-AS3, of which AS1 is connected to sensors PI2, PI4, PI1 and to secondary treatment unit 13, AS2 is connected to controllers A5, A6 and sensor PI3, while AS3 is connected to sensors PI5.
The above-described controllers and sensors can be connected e.g. via three serial communication buses 30-32 common to both devices to a serial port 33 of the control unit 3 and further to the control computer 34, which comprises a display and a user interface 35. The controllers, sensors and other components of the system can also be connected with some other wireless or wireline data communication bus or data communication method. The user interface is provided with a user interface program, and the control computer is provided with a group control program and a controller unit.
Via the user interface 35, the user can observe the operation of the pneumatic system, configure the control and monitoring system and output reports concerning the functioning of the system. The control program regulates and controls the pneumatic system via the pneumatic station controllers and compressor controllers, based on the information obtained by means of the data communication devices and programs and on the instructions given by the user.
The pneumatic station controller AS1-AS3 reads the data, such as pressures and alarm data, that are specific to a pneumatic station from the pneumatic system. The compressor controller A1-A7 reads data regarding the compressor and the control commands sent by the control program via the data communication bus 30-32, and executes the commands, such as start, stop and load.
The number of compressors can be given as parameters to the group control program. The control program need not be altered in any way when compressors are added or removed. This is because, as far as the compressors are concerned, the program has been constructed according to a modular design in such a way that each compressor C1-C7 is an embodiment of its category that, depending on the parameter given, is either commissioned or decommissioned.
Each compressor C1-C7 can be configured via the user interface 35 as any compressor type by means of parameters. Therefore, when the control system is being configured for the first time or when an individual compressor type is later changed, the control system need not be tailored at all. This is due to the fact that, by means of parameters, the above-described embodiments of compressor category can be configured as any basic compressor type. These are e.g. constant speed control, frequency converter drive control or turbocompressor control.
It is possible to connect to the control system a required number of pressure sensors PI1-PI5 to read the delivery pressure of each compressor and the desired network pressures. This makes it easier to control the compressors and gives a general view of the state of the pneumatic network. Any one of the pressure sensors can be configured to indicate the delivery pressure of any one of the compressors, and any of the pressure sensors can be configured to function as the control pressure of the entire system. The addition or removal of pressure sensors does not involve any changes in the control program.
Each pressure data item can also contain information as to how large a volume it pertains to and what is the rate of change of the pressure. Based on these data, it is possible to calculate the exact change in the amount of compressed air for the volume in question. By computing the change in the amount of air for each volume and combining this information with the data regarding the state of all the compressors, real-time actual consumption of compressed air is obtained. This method considerably improves the accuracy and reacting capability of the control.
Also other measurements or controllable devices can be connected to the control system. These can be e.g. measurement of dew point, heat or flow rate, control of a valve, dryer, fan, ventilation damper or pump. The properties of additional measurements and additional devices are defined with parameters. Adding or removing additional measurements and additional devices does not involve any changes in the application software.
The control system can control and monitor a number of separate pneumatic systems 1, 2. This makes it possible to select any one of the pressure sensors PI1-PI5 connected to the system as a control pressure sensor for each compressor C1-C7, and in addition any one of the compressors can be set via the user interface to be controlled according to a pressure sensor value selected in accordance with separate pressure settings.
The operation of the compressors can thus be controlled with the system according to the invention for controlling a compression system. In the compression system according to the invention, the mode of controlling and regulating the compressor-specific delivery can be selected from the user interface. Based on the selection made from the user interface, control of the delivery of a compressor can be based either on a delivery reference value that is calculated from a network delivery request, or based directly on a network pressure setting or on a compressor-specific pressure setting as is presented in Fig. 3A.
The mode for regulating the compressor is selected for the specific compressor from the user interface. How regulation of a compressor operates depends on which control mode is selected for the compressor. Regulation of the compressors is effected either with a direct adjustment, e.g. by changing a rotation speed, or by changing a pressure setting or by changing the delivery pressure reading of a compressor
If a delivery request is selected as the control mode of a compressor, as in the diagram of Fig. 3B, the network delivery request is an adjustment value, which determines the air requirement, or more generally the requirement for fluid medium, the change in direction of it and the rate of change. The determination of a network delivery request (0-100%) according to one embodiment of the invention is described in Figs. 4A - C. As presented in Fig. 3B, a regulating mode for a compressor is selected from the user interface. If a direct reference (e.g. speed) is selected as the method of regulating the compressor, the delivery request of the compressor is scaled to the format required by the compressor. If a pressure setting is selected as the regulating mode, the network delivery request is converted into a compressor delivery request and further into a pressure setting that takes into account the limits given from the user interface. In such a case, at first the rate of adjustment can be checked, a new pressure setting can be calculated from the magnitude of the compressor delivery request, from the derivative of it, and from the value and derivative of the delivery pressure sensor of the compressor. In addition, the pressure difference over the secondary treatment unit can be taken into account if the compressor's own pressure sensor is not on the network side. If a pressure data item is selected as the regulating mode, a rate check can at first be performed and the same value can be supplied to the compressor for a pressure transmitter signal as the pressure setting of the compressor. A value larger than the aforementioned value can be set as the value if a smaller delivery is required, and a smaller value if a larger delivery is required, according to the delivery request. The determination of a delivery request of a compressor according to one embodiment is presented in more detail in Figs. 5 and 6.
If the compressor control mode is a network pressure setting, as in the diagram of Fig. 3C, the network pressure setting is an adjustment value, with the requirement for fluid medium, the change in direction of it and the rate of change being determined by comparing said adjustment value to the reading of the controlling pressure sensor. The compressor regulating mode is selected from the user interface, which regulating mode can, in the case in question, be a direct reference, a pressure setting or a pressure data item. The network pressure setting can be converted e.g. into a compressor pressure setting value taking into account the pressure loss caused by secondary treatment of the compressed air. If a direct reference is used as the compressor regulating mode in the case of a network pressure setting, a check of the adjustment rate can be performed, how much the network pressure data item differs from the network pressure setting can be calculated and the direct reference can be changed on the basis of this information. With a slow adjustment rate the change is distributed to the desired time period and the direct reference is also updated between checks of the adjustment. If a pressure setting is used as the mode of regulating the compressor, a check of the adjustment rate can be performed and the network pressure setting can be supplied to the compressor. The setting can be corrected by the pressure difference over the secondary treatment unit if the compressor's own sensor is not on the network side. If a pressure data item is used as the mode of regulating the compressor, a check of the adjustment rate can be performed and how much the network pressure data item differs from the network pressure setting can be calculated. The pressure data item to be supplied as a pressure transmitter signal to the compressor can be corrected as necessary.
If the compressor control mode is a compressor-specific pressure setting, as in the diagram of Fig. 3D, the compressor-specific pressure setting is an adjustment value, with the fluid medium requirement, change in direction of it and the rate of change being determined by comparing said adjustment value to the reading of the controlling pressure sensor. The compressor regulating mode is selected from the user interface, which regulating mode can, in the case in question, be a direct reference, a pressure setting or a pressure data item. If in the case of a compressor-specific pressure setting a direct reference is used as a regulating mode, a check of the adjustment rate can be performed, how much the compressor pressure data item differs from the compressor-specific pressure setting can be calculated and the direct reference can be changed on the basis of this information. With a slow adjustment rate the change is distributed to the desired time period and the direct reference is also updated between checks of the adjustment. If a pressure setting is used as a mode of regulating the compressor, a compressor-specific pressure setting is supplied to the compressor. If a pressure data item is used as a mode of regulating the compressor, a check of the adjustment rate can be performed and how much the compressor pressure data item differs from the compressor-specific pressure setting can be calculated. The pressure data item to be supplied as a pressure transmitter signal to the compressor can be corrected as necessary.
Fig. 4B describes how determination of a network delivery request progresses. If the network pressure is near the setting (i.e. inside the limit values nearer the setting), the rate of change in the network pressure is checked. If the rate of change is great, the change is slowed down by changing the network delivery request rapidly, and if the rate of change is small, the network delivery request is changed slowly. An averaged change in network pressure can be utilized in evaluating the rate of change in network pressure, and the setting for the rate of change can be used as a parameter in checking the rate of change, said setting being intended for a situation in which the network pressure is near the setting (i.e. inside the limit values nearer the setting). If the network pressure is farther from the setting (i.e. outside the limit values nearer the setting but inside the limit values farther from the setting), the rate of change of the network pressure is checked. If the rate of change is great, the change is slowed down by changing the network delivery request rapidly, and if the rate of change is small, the network delivery request is changed slowly. An averaged change in network pressure can be utilized in evaluating the rate of change in network pressure and the setting for the rate of change can be used as a parameter in checking the rate of change, said setting being intended for a situation in which the network pressure is farther from the setting (i.e. outside the limit values nearer the setting but inside the limit values farther from the setting). If the network pressure is far from the setting (i.e. outside the limits farther from the setting), the network delivery request is changed quickly. The rate of change setting can be used as a parameter in checking the rate of change, said setting being intended for a situation in which the network pressure is far from the setting (i.e. outside the limits farther from the setting).
Fig. 4C describes how determination of a network delivery request can further progress. After the above-mentioned procedures are performed, it can be checked whether there is a change in the number of compressors needed to deliver air. If the number of compressors needed changes, the increasing/decreasing compressor capacity can be compensated by changing the network delivery request. If the number does not change, no other steps are needed. The number of compressors delivering air and their delivery, said number and said delivery being known by the system, can be utilized in evaluating the number of compressors needed.
The diagram of Fig. 5 presents the determination of a compressor delivery request in the case of one embodiment of the invention. At first the delivery requests of compressors are determined from the network delivery request. The limits of a compressor regulating range, for example, can influence this determination. After this the efficiency ratios of the compressors are checked and the delivery requests of the compressors are changed so as to be as effective as possible from the viewpoint of the efficiency ratio of the compressors. When evaluating a compressor efficiency ratio, the efficiency ratio of the compressor in question can be utilized and e.g. the efficiency curve of said compressor.
Fig. 6 presents an example according to an embodiment of the invention wherein the compressor control mode is a delivery request and the compressor regulating mode is a pressure setting. Set points can be selected via the user interface of the control system and it is possible to select a delivery request, a network pressure setting or a compressor-specific pressure setting as a control mode for the compressor. Of these, a delivery request has been selected for this example. A direct delivery reference, a pressure setting or a delivery pressure reading can be selected as the regulating mode for a compressor. In this example a pressure setting has been selected as the mode for regulating the compressor.
In the embodiment of Fig. 6, initially the network delivery request (0 - 100%) is determined. The change of direction and rate of change of the network pressure, the difference to the set pressure and the rate of change selected from the user interface affect this calculation. After this, the delivery request (0 - 100%) for the compressor is determined. The range of regulation that is adjusted via the user interface and is available for the compressor is taken into account in determining the compressor delivery request. Finally the pressure setting for the compressor is determined, and here e.g. the efficiency curve of the compressor can be taken into account in such a way that the compressor is always used with the best possible efficiency ratio. In determining the pressure setting of a compressor, the regulating range of the compressor, the delivery request value and magnitude of change in said value, and the value of the delivery pressure sensor of the compressor are taken into account, and additionally the pressure difference over the secondary treatment unit is taken into account if the compressor's own delivery pressure sensor is not on the network side.
A user can optimize the operation of the entire pneumatic system by selecting the control mode and regulating mode of the compressors as well as with the parameters of the selected adjustment value. The control system is adapted for the control and delivery regulation of all known compressor types. In the system according to the invention there is no limit to how many variable delivery compressors can be controlled and regulated together. This enables accomplishment of the best possible energy economy.
In controllers known in the art, the regulating range of the compressors is kept fixed. In practice, however, regulating ranges of compressors are of differing magnitudes, and consequently the entire regulating range of compressors in solutions known in the art is not utilized, or it is not possible to select the desired machine to run always at the best efficiency ratio. This results in unnecessary consumption of energy.
In the solution of the invention, when converting a network adjustment value into delivery requests for variable delivery compressors, the direction of the network air requirement and the amount of change in it can be calculated. This change is distributed to each variable delivery compressor. After this a check is made as to whether the requirement can be corrected in a more energy efficient direction, e.g. by means of the efficiency curves of the compressors.
The effect of an efficiency curve can be taken into account if one or more of the compressors have a better efficiency ratio with a larger delivery and some of the compressors with a smaller delivery. The effect of an efficiency curve can also be taken into account if some compressor has a better efficiency ratio with a smaller delivery and its capacity is significantly greater than the other compressors even though the efficiency ratio of all the machines would be better with a smaller delivery. The effect of an efficiency curve can also be taken into account if one some compressor has a better efficiency ratio with a larger delivery and its capacity is significantly greater than the other compressors even though the efficiency ratio of all the machines would be better with a larger delivery.
In the solution according to the invention the compressors can also be deloaded and stopped. In this case the wasted capacity of the variable delivery compressors is calculated and, if necessary, the small compressors are shut down so that the variable delivery compressors run with a larger delivery.
Controllers that are known in the art can have a deloading limit and loading limit for the compressors. In a normal situation in solutions known in the art a number of variable delivery compressors run at minimum delivery and in this case the pressure rises very slowly or does not rise at all. The next compressor is deloaded only when the deloading limit is reached. In such prior art solutions variable delivery compressors are driven for long periods of time at poor efficiency ratios.
In the solution according to one embodiment of the invention, the compressor next in turn to be deloaded is identified. In addition to this, the wasted capacity of variable delivery compressors is calculated. The capacity of the compressor in line for deloading is not included in this calculation. A safety factor, which is given from a user interface or calculated automatically, is deducted from the wasted capacity and a computed wasted capacity is thus obtained. The delivery of a compressor in line for deloading at the moment in question is deducted from the computed wasted capacity. If the calculated result is positive, the compressor is deloaded.
The advantage of this solution is that deloading of the next compressor is performed significantly earlier and the driving of variable delivery compressors in an ineffective efficiency range is reduced compared to solutions known in the art. Using a safety margin can avoid continuous loading and deloading of a machine. If consumption fluctuates, hysteresis can be used, which reduces "unnecessary" on/off switchings.
Fig. 2 presents an example of a compressor deloading situation of the operation of a system according to an embodiment of the invention.
The areas marked in Fig. 2 are defined as follows:

1 = compressors that are running
2 = compressor that has stopped
3 = compressor to be deloaded next
4 = variable delivery compressors that are running

In the embodiment presented in Fig. 2 the compressor next in turn to be deloaded is identified, i.e. in this case compressor 2 because it has the lowest priority (=4). The delivery of the compressor to be deloaded next is at this moment 50% * 80 m3/min = 40 m3/min.
After this the wasted capacity of the variable delivery compressors that are running (area 4) is calculated: (100%-75%) * 100 m3/min + (100%-75%) * 80 m3/min = 45 m3/min.
A safety factor is deducted from the wasted capacity, thus obtaining a computed wasted capacity. For example, if the safety factor is 4m3/min, the computed wasted capacity is 45m3/min - 4 m3/min = 41 m3/min. The delivery of the compressor to be deloaded is deducted from the computed wasted capacity and if the end result is positive, the compressor is deloaded. Thus, for example, if the safety factor is 4 m3/min, the final result achieved is: 45 m3/min - 4m3/min - 40m3/min = 1 m3/min. In other words, with the safety factor in question the compressor is deloaded. Thus, for example, if the safety factor is 6 m3/min, the final result achieved is: 45 m3/min - 6m3/min - 40m3/min = -1 m3/min. With this safety factor the compressor is not deloaded.
The compressor to be deloaded can also be a fixed-delivery or some other type of compressor. All compressors that are able to run with a partial load (e.g. frequency-converter driven or turbocompressor, multistroke piston compressor, et cetera) are deemed to be a variable delivery compressor.
In the solution according to the invention the regulating range of a variable delivery compressor can be set from the user interface. In this way the compressor can be run with the best efficiency ratio and turbocompressor discharging can be avoided.
Deloading and a loading limit for pressure are set in some central controllers known in the art. It is also possible that a central controller has a pressure setting and a loading limit or a setting and a deloading limit. If a controller is also able to drive variable delivery compressors, the system also often has a pressure setting for a compressor. In combinations that are known in the art it is not, however, taken into account how variable delivery compressors and deloading-loading compressors are set to run together. A problem occurs especially in situations in which a base load is run with a variable delivery compressor and there are times when, if its capacity comes to an end midstream, a deloading-loading compressor is taken into use to support the pressure delivery. In this case what generally happens is that the variable delivery compressor is run at a high or medium-to-high pressure level when there is sufficient capacity. When the capacity comes to an end, the pressure is allowed to drop and when the pressure has dropped sufficiently a supporting compressor is started up.
In the solution of the present invention a deloading setting limit and loading setting limit can be set for the central controller in such a way that the setting limit of the loading machine is very close to the loading limit. The range between the deloading setting and loading setting limits can also be calculated automatically by studying the pressure and fluctuation range driven by a single variable delivery compressor. One advantage of this solution is that when a variable delivery compressor runs alone, the pressure level is lower and energy can be saved.
In solutions known in the art compressors usually have three settings in a central controller: a deloading pressure, a loading pressure and a set pressure. In some compressors, when they are driven at the smallest possible delivery, surplus air starts to be dumped. Dumping excess air wastes significantly more power than if running was at minimum delivery and no outlet valve were opened. In some compressed air networks, in which consumption fluctuates significantly, there are very many situations in which running is on the limit of minimum delivery.
In the solution according to the invention, exceeding the normal pressure setting can be allowed e.g. in these types of situations. In such a case, for example, a turbocompressor is allowed to run at a higher pressure than that specified by the pressure settings. In such a case the turbo does not dump, but instead the discharge valve is kept closed. This achieves better energy efficiency.
In the solution according to the invention a different deloading limit can be added for deloading-loading compressors and for variable delivery compressors. The limit of variable delivery compressors can be set to be higher than the limit of deloading-loading compressors. In this case, therefore, the pressure is allowed to rise slightly in the network before the compressors are allowed to dump. The limit can be set e.g. via a user interface. By using the solution described above, compressor dumping is reduced at minimum delivery and thereby the need for power loss is reduced.
Further conversion of delivery requests into control requests for compressors, i.e. adjustment of the delivery of a variable delivery compressor, is possible in the solution of the invention in a number of ways, e.g. with a direct reference derived from revolutions per minute, from a delivery percentage, or from the attitude of suction blades. Adjustment of the delivery of a variable delivery compressor is also possible with a change in the pressure setting, automatically or by simulation of a network pressure data item together with the pressure setting. These methods are applicable in all compressor types, regardless of model and make.
In the system of the invention an adjustment value can be calculated for a compressor, the value specifying the desired delivery of the compressor, or a pressure level and the sensor that it is desired the compressor drives can be given to the compressor. By means of this, either rotation speed or IVG position, a pressure setting or a simulated network pressure data item is calculated as a value to be supplied to the compressor. After this, compressor power or sensor pressure is measured. Based on the measuring data, the value to be supplied to the compressor is corrected in such a way that the set point is reached. In this way, compressors being controlled with a different control mode can be controlled together in a uniform manner. Also the compressors can be parameterized easily from a user interface.
By means of the system of the invention, a number of different factories having a number of different compressed air networks or air networks can be controlled with the same controller. In this case the controller of the system of the invention can have set points, a user interface and control logic for very many points. A computer able to process data sufficiently rapidly, and to form controls from said data, can be reserved for the center. The system can also be configured in such a way that outages in the computer network do not prevent the production of compressed air. In this way, a platform for the servers of a corporate group can be connected to the control and does not require separate systems. This produces savings in costs and the management of groupwide updates is easy. Also a factory-specific or pneumatic-network-specific comparison is then possible.
In one embodiment of the system of the invention, one compressed air network can be controlled in a number of sections. In this case one compressed air network is divided, in terms of its control, into a number of "virtual networks". These sections of the compressed air network are controlled as separate entities. In this case the pressure reduction of a faster section of the network can be taken into account and can be reacted to in the best possible manner.
The system of the invention can have a contingency sequence if any of the selected compressors is inoperable. In such a case the larger compressors running as a base load are placed in a list that produces the selection of a contingency sequence when a compressor for some unforeseen reason stops or does not deliver air. The larger replacement compressors are arranged in the contingency sequence such that they are taken into use earlier. The use of a contingency sequence can be interrupted automatically when it is detected that the system has returned to normal status. The operator can start and interrupt use of the contingency sequence from a user interface, or the starting can be automatic.
By means of the contingency sequence according to the system of the invention, compressors not normally run as a base load can, in a situation where a compressor fails, also be used as a compressor running as a base load to replace a failed or stalled compressor normally run as a base load. In this case a more even pressure is attained both when a large compressor fails and in operation after the failure. In this case the lowest operating pressure can also be calculated and energy is saved continuously during normal operation.
In one embodiment of the invention a compressor can run to become hotter in a timed manner according to a setting given in the user interface or by direct selection from the user interface. After this the compressor returns to normal automatic drive. A dedicated run state can be constructed in the central controller for the purpose of hotter operation (local, automat, manual, in addition to normal states). Each compressor can be switched separately to the state in question, e.g. either in a timed manner or via a user interface. A compressor is moved in front of the other compressors in terms of priority and becomes a compressor that is very easily driven. The compressor can be returned from the state in question back to automated or to some other previous state either according to the compressor oil temperature (or other measurement), running it through all the phases/states, or in a timed manner. Finally the compressor stops and shuts down when it is no longer at the top of the priority list.
With the solution described above, manual work is reduced when standby compressors can be run hotter in a controlled manner automatically and it can be ensured that the compressor definitely runs hotter and all the phases/states needed for proper implementation can be implemented. A standby compressor is not, however, used for unnecessarily long periods.
In one embodiment of the invention there can be a special point in the network and the system can take the special point into account. Thus, if there is some important point in the network, the pressure of this place can be monitored and the place can be set as a special point in the system. If the pressure drops, the setting for the delivery end can be increased. Consequently, for a large part of the time the pressure of the delivery end can be lower, and when higher delivery end pressure is needed it can be raised to the desired level. In this way unnecessarily high pressure is not produced with the compressors. Also the effect of spikes in consumption on the pressure level of special points can be detected more quickly and the network pressure can be kept lower when consumption spikes do not occur in the network.
In this embodiment an extra sensor or sensors can be added to the place of consumption and/or measurements that are available in the network can be utilized. There can also be a setting for the desired minimum pressure of a special point or of special points. Additionally, there can also be a setting for how much the network pressure can fall or rise according to the special point, as well as parameters for the controller. The settings can be selected by the operator. Compressors can be controlled and the level of the network pressure raised in accordance with the given settings.
In one embodiment of the invention a higher-pressure network can be supported by a lower-pressure network in desired situations. In this embodiment the system can identify a pressure drop in the higher pressure network. Support of a second network can also be started for another reason. In the solution of this embodiment a second sequence is selected in the lower-pressure network, in which sequence the pressure level of the lower-pressure network is higher. After this, it is verified that the pressure has risen in the lower-pressure network to become higher than the pressure of the higher-pressure network. After this, a valve is opened to support the higher-pressure network. The normal sequences can be returned to when it is verified based on measurements that this can be performed. The return can also be effected from a user interface.
In the system according to the invention maximum and minimum pressure limits can be set for each compressor and for the pneumatic system. When these values are exceeded, control of the compressors is handed over to their own control system. The order in which the compressors are started and loaded is determined by an operating sequence table.
The compressors can be set to work in accordance with as many operating sequence tables as desired. This is possible because each individual operating sequence is an embodiment of its category that can be commissioned or decommissioned by changing a program parameter determining the number of embodiments. Therefore, the program need not be altered at all when operating sequences are added or removed.
The manner of changing the operating sequence is selected by changing one control parameter. The operating sequence can be changed e.g. on the basis of a weekly calendar, a stoppage of compressors or an automatic arrangement. Automatic alternation is based on continuous computation of the required idling power for all compressor combinations possible, which, combined with the observation of the required compressors to be kept active and free selection of the observation interval, results in automatic selection of the most effective operating sequence possible.
In one embodiment of the invention the compressors can be rotated by restricting their starts, if there are sufficient compressors. For example, when a large motor is involved, starts can be limited to e.g. 2 per hour. If the requirement is three 10-minute cycles per hour, the first 2 cycles are run by one compressor and the last cycle by another compressor. This can reduce excessive idling. The rules can be compressor-specific and they can be set e.g. with a central controller.
The method of starting and stopping a compressor can be selected via the user interface. These are starting and stopping with a continuous signal or with a pulse, run-on stopping or stopping based on allowed numbers of starts.
The starting, loading and deloading delays for each compressor can be adjusted separately. This allows correct operation of the method in every situation regardless of the pneumatic system's own dynamics.
The compressor controller reads information from the compressor and transmits the information to the control program, reads the control commands from the group control program and executes them in accordance with its own control program while also monitoring the validity of the commands and the condition of the data communication bus and the programs. In current solutions, even a single non-standard compressor model to be incorporated under the control system requires relatively extensive tailoring of the control programs. This problem is now limited to the tailoring of a simple compressor controller program. Even this tailoring work will be reduced when this solution gains ground, because it will be easy to form a library of compressor controller programs.
The control program can calculate the total output and power input of the pneumatic system on a continuous basis. These data can be stored on a mass storage medium. In the user interface, these data can be presented in the same diagram so that they can be viewed in a graphic form from instant to instant. In addition, the user interface calculates the average consumption and power over a selected period of time. Moreover, the points of the diagram can be printed to a file with a desired time interval. The report thus produced allows verification of the actual benefit yielded by the control system and continuous measurement of performance even over a long period.
The information regarding compressor states and pressure values received by the control program via the data communication means is continuously stored on a mass storage medium, which can be in the control computer. The state of operation and pressure level of the compressors can be presented in the same diagram so that they can be viewed in a graphic form from instant to instant. This enables the operation of the pneumatic system to analyzed in real-time or afterwards.
The basic architecture of the method allows the use of a device of any manufacturer in the compressor controller. This makes it possible to utilize the invention in many cases in which it has not been possible before.
When a disturbance, e.g. a connection fault, occurs in any part of the system, the compressor controller hands over the control to the compressor's own control system. This guarantees disturbance-free production of compressed air in almost all situations.
The operation of the compressor controller can be tested either by means of a group controller or any device that is capable of writing the run and load commands to the controller. This is made possible by the structure of the controller program, in which the outward interface can be kept as simple and standard as possible regardless of compressor type and model. Only the run/stop commands and the desired load factor are written via the interface.
It is obvious to the person skilled in the art that the different embodiments of the invention are not limited solely to the example described above, but that they may be varied within the scope of the claims presented below.

Claims

A compression system comprising compressors (C1-C7) and their controllers (A1-A7) for the compression of fluid medium, secondary treatment devices for the treatment of the fluid medium delivered from the compressors, piping systems (17-19, 23) for conducting the fluid medium to a place of consumption (16, 22), and a control system comprising a control unit (3) containing a data processing system (34) for controlling the compression system, a user interface (35) including a display associated with it and transmission means for the transmission of control data between the control unit, the controllers and pressure sensors,
characterized in that
the compression system has at least one compressor-specific adjustment value, which determines the requirement for fluid medium, the change in direction of it and the rate of change, wherein a control mode is selectable for a compressor from the user interface (35), the control mode determining the adjustment value to be used,
wherein control of the delivery of the compressor is based either on a delivery reference value that is calculated from a network delivery request, or based directly on a network pressure setting or on a compressor-specific pressure setting,
wherein the control system is adapted to convert the network delivery request or the network pressure setting or the compressor-specific pressure setting into compressor-specific control requests via direct control data, a pressure setting or a pressure data item of the compressor.
Compression system as defined in claim 1, characterized in that the compressor has regulating range limits, said limits being adapted to be determined from the user interface.
Compression system as defined in claim 1 or 2, characterized in that the control system is adapted to convert a delivery request or pressure setting of the network into delivery requests for variable delivery compressors based on the permitted regulating range of a compressor and/or based on the efficiency curve of a compressor.
Compression system as defined in claim 3, characterized in that the control system is adapted to take into account the effect of the efficiency curve if one or more of the compressors has a better efficiency ratio with an essentially large delivery and some of the compressors with an essentially small delivery.
Compression system as defined in any of the preceding claims, characterized in that the deloading limit of variable delivery compressors is adapted to be higher than the deloading limit of deloading-loading compressors.
Compression system as defined in any of the preceding claims, characterized in that the control system is adapted:
to calculate the unused capacity of variable delivery compressors,

to further calculate the delivery at the moment in question of the next compressor to be deloaded according to the sequence,

to deduct from the unused capacity the delivery of the next compressor to be deloaded,

to deduct from the unused capacity the safety margin given from a user interface or automatically calculated,

and to deload the compressor if the calculated result is positive.
Compression system as defined in any of the preceding claims, characterized in that the compression system comprises a sensor/sensors in the place of consumption or it is adapted to utilize measurements already available in the network,
the system further comprises a setting for the desired minimum pressure for a special point as well as a setting for how much the network pressure can fall or rise according to the special point,
wherein the system is adapted to control the compressors and to regulate the level of the network pressure according to the given settings.
Method for the control of a compression system, said compression system comprising compressors (C1-C7) and their controllers (A1-A7) for the compression of fluid medium, secondary treatment devices for the treatment of the fluid medium delivered from the compressors, piping systems (17-19, 23) for conducting the fluid medium to a place of consumption (16, 22), and a control system comprising a control unit (3) containing a data processing system (34) for controlling the compression system, a user interface (35) including a display associated with it and transmission means for the transmission of control data between the control unit, the controllers and pressure sensors,
characterized in that
the compression system has at least one compressor-specific adjustment value, which determines the requirement for fluid medium, change in direction of it and the rate of change, wherein a control mode is selectable for a compressor from the user interface (35), the control mode determining the compressor-specific adjustment value to be used,
wherein control of the delivery of the compressor is based either on a delivery reference value that is calculated from a network delivery request, or based directly on a network pressure setting or on a compressor-specific pressure setting,
wherein the network delivery request or the network pressure setting or the compressor-specific pressure setting is converted into compressor-specific control requests via direct control data, a pressure setting or a pressure data item of the compressor.
Method as defined in claim 8, characterized in that the compressor has regulating range limits, said limits being determined from the user interface.
Method as defined in claim 8 or 9, characterized in that a delivery request or pressure setting of the network is converted into delivery requests for variable delivery compressors based on the permitted regulating range of a compressor and/or based on the efficiency curve of a compressor.
Method as defined in claim 10, characterized in that the effect of the efficiency curve is taken into account if one or more of the compressors have a better efficiency ratio with an essentially large delivery and some of the compressors with an essentially small delivery.
Method as defined in any of claims 8 - 11, characterized in that the deloading limit of variable delivery compressors is higher than the deloading limit of deloading-loading compressors.
Method as defined in any of claims 8 - 12, characterized in that in the method:
the unused capacity of variable delivery compressors is calculated,

the delivery at the moment in question of the next compressor to be deloaded according to the sequence is further calculated,

the delivery of the next compressor to be deloaded is deducted from the unused capacity,

the safety margin given from a user interface or automatically calculated is deducted from the unused capacity,

and the compressor is deloaded if the calculated result is positive.
Method as defined in any of claims 8 - 13, characterized in that the compression system comprises a sensor/sensors in the place of consumption or utilizes measurements already available in the network,
the system further comprises a setting for the desired minimum pressure for a special point as well as a setting for how much the network pressure can fall or rise according to the special point,
wherein the system controls the compressors and regulates the level of the network pressure according to the given settings.