JPS63295884A - Method of controlling number of compressors - Google Patents

Abstract

PURPOSE:To cope with changes in loads by checking the presence of a reservation for an air consumption amount after a specified time and, in the case the reservation is present, selecting the number of compressors enough to meet the reserved air consumption amount. CONSTITUTION:Registering a reservation list of air consumption amount displayed on a display 1 to a data base 50, a reserved air amount monitoring section 4 monitors a reservation pattern stored in a reservation list memory section 50A. Checking the presence of a reservation after a specified time, a unit number control section 40 selects the number of compressors enough to meet the reserved air consumption amount. As a result, even in the case of a large load, the load can be coped with an automatic operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for controlling the number of compressors in which a plurality of compressors are selected and operated in accordance with changes in load.

[Conventional technology]

FIG. 8 shows a system for collecting compressed air discharged by a plurality of compressors and then supplying it to a load, for example, in Japanese Patent Laid-Open No.
This is an example of a system such as that described in Publication No. 60084. In the same figure, 11.12.
13,...IN is a compressor, 21.22.23,...
2N is the drive motor that drives the compressor, 31.32.33
, . . 3N is an individual control device (start/stop device), and each compressor 11.1 sent from the number control device 40
2. Start/stop command S for IN.

, S2, ... In response to SIN, each drive motor 2
1. Performs start/stop control of 22, . . . 2N. Each pressure 1
? The compressed air discharged by fall, 12, . . . . A pressure detector 10 detects the pressure (discharge pressure) Po in the receiver tank 7 and sends an analog pressure signal to the number control device 40. In addition, 101.102.103, . . . ION are suction pressure detectors, and compressors 11.12.13,
...IN suction pressure P, Ps□1, ...p
sn is detected and sent to the number control device 40.

This unit number control device 40 classifies and ranks the supplyable air volume in stages, stores in its memory a rank table that defines the number or combination of compressors to be operated for each rank, and stores in its memory a rank table that defines the number or combination of compressors to be operated for each rank. When the discharge pressure PO rises to the upper limit set pressure PM as shown in Fig. 9 ta) due to a sudden decrease in the air consumption (air consumption), the current rank in terms of the total discharge air volume is Select a lower subordinate rank, issue a rank down command, and stop the operation of compressors that do not belong to a lower rank among the operating compressors belonging to the current rank, or The operation of all the compressors in the current compressor is stopped and another compressor is started, and conversely, due to the increase in the load usage, the discharge pressure decreases to the lower limit set pressure PL as shown in Figure 9 (bl). If so, select a higher rank than the current rank in terms of total discharge air volume,
Number control that generates a rank-up command to start a compressor that belongs to a higher rank but is not currently in operation, or stops all compressors that are currently in operation and starts another compressor. I do.

[Problem that the invention seeks to solve]

In this way, the conventional number control system monitors the discharge pressure PO, detects in real time that the discharge pressure PO is out of the pressure control range PH to PL, and adjusts the discharge pressure PO to the pressure control range PH"P. The purpose is to change the number or combination of compressors in order to bring the level within L. However, as is well known, compressors take time to start and stop, so even if the rank down command or rank up command is given, , the discharge pressure Po continues to increase or decrease for a while after these commands.

For this reason, the above method of controlling the number of units is effective when the load fluctuations are small, but when the load changes significantly,
For example, there was a problem in that it could not be applied in cases where large loads were coming in.

This invention was made to solve the above problem.
To provide a method for controlling the number of compressors that can automatically cope with a large load even when the load comes in.

[Means for solving problems]

In order to achieve the above object, this invention creates a reservation table specifying the required air consumption volume at one or more future times on a display, registers it in a database, monitors the registered reservation table, and monitors the reservation table after the set time. If the reserved air volume for consumption is insufficient compared to the air volume that can currently be supplied, the number or combination of compressors that satisfies the insufficient air volume is selected by starting or adjusting the capacity, and the selected compressor is The configuration is such that the startup or capacity adjustment of the compressor is completed according to a schedule.

[Effect]

In this invention, the presence or absence of a reservation is monitored, and if there is a reservation, compressors whose supplyable air volume is sufficient to satisfy the reservation consumption air volume are selected a set time before the reservation time, and these compressors are selected as described above. Scheduled operation is performed so that startup or capacity adjustment is completed before the set time elapses, so even if there is a large load demand, it can be handled automatically.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a display device (CRT), 2
3 is a keyboard, 3 is a consumption air volume calculation unit of the system control device, 4 is a reservation air volume monitoring unit, 40 is a number control unit, 50 is a database, and 50A is a reservation table memory unit.

The operation of this embodiment will be explained below with reference to the flow shown in FIG.

The operator selects display 1 through keyboard 2.
For example, a consumption air volume reservation table as shown in FIG. 3 is created on the screen, and the created air consumption volume reservation table is registered in the reservation table memory 50A of the database 50. This reservation table is
The contents include the reservation time, the reservation time, and the air consumption amount during the reservation time. Incidentally, FIG. 4 shows a part of the reservation table in the form of a pattern diagram.

The air consumption calculation unit 3 samples and takes in the discharge pressure Po sent out by the pressure detector 10 at a predetermined time interval t3, and also inputs the discharge pressure Po sent out by the pressure detector 10 at a predetermined time interval t3.
...Suction pressure P3 sent out by ION. ,P,3,
... P and fi are sampled and taken in, and the consumption wind 'I Q o + is calculated according to the following formula.

1゜ΣQ in・M7: Total supplyable air volume Q at current rank N, H qin: Rated air volume of the compressor specified by current rank N M7: Operation rate ■: Capacity P of receiver tank 7,: Current sampling discharge pressure Pi -1: The previous sampling discharge pressure reservation air volume monitoring unit 4 monitors the reservation pattern stored in the reservation table memory unit 50A, and the set time T.

Check if there are any later reservations, and if there are reservations,
Execute the calculation of the following formula.

Reservation air volume Q7. 〉Currently available air volume Q i i...
(2) Insufficient air volume ΔQ=QTi-Qii>K...
- (3) If the insufficient air volume ΔQ<K, the number control unit 40 is in a state where it can be operated among the N compressors defined by the current rank (assuming that the number of operating units is i). Among the compressors (stopped machines, scheduled to stop), the number of compressors that satisfy the following formula (4) starting from the compressor with the largest rated capacity, that is, the total supplyable air volume with the currently operating machine supplyable air volume Q i i is reserved. The number of compressors (for example, N-l-3) that satisfies the consumption wind IQa8 is selected.

QTikuΣQ i i+ΣQ5. 4-1.・・・・・・
・(4) ΣQ i i+ΣQ= +N-=-s,? T
Supplyable air volume Q after 0 minutes.

Once this compressor selection is completed, start the compressors in sequence and calculate the time it takes to complete the start. For example, if you start one compressor at a time and the time it takes to complete the start is t1 minutes for each, then the total (N-1-3) Instruct the operation schedule to start starting xt minutes before.

Therefore, if the air consumption pattern from now until after the set time To is a pattern that rapidly increases after the set time To, as shown in FIG.
I3) After xi,), the compressor that is first in the startup order among the compressors selected above is started, and as time passes, the supplyable air volume increases step by step as shown by the dotted line in the figure. After (N-1-3)Xtm, the above equation (3) is satisfied.

The total rated capacity of the compressors in the current rank is insufficient,
If the condition (3) 2 above is not satisfied, the air consumption calculation unit 3 registers the reserved air volume QT as the target air volume Q r A in the memory unit (not shown) of the database 50, and the reserved air volume monitoring unit 4 Request a rank upgrade to a rank that satisfies the condition of equation (3). When there is a request to increase the rank, the number control unit 40 selects a rank corresponding to the updated target air volume Q, A, and completes startup of the compressors belonging to the rank before the predetermined time To elapses. to start in order.

In this way, in this embodiment, when there is a reservation after the set time To, the air consumption volume is predicted, compressors whose supplyable air volume is sufficient to satisfy the reservation consumption air volume are selected, and these compressors are Since all of the startups are completed when the set time TO has elapsed, even if a large load comes in, this can be fully handled by automatic operation.

The number-of-units control unit 4 further includes an air volume surplus determination logic shown in FIG. 5 and an air volume deficiency determination logic shown in FIG. 6. This logic will be explained below.

(t) When QiN>QOi, the above-mentioned air volume surplus determination logic is activated. In this logic, in order to prevent rank down at low pressure, it is checked whether the discharge pressure PO is 25% or more of the pressure control range Pl+""'PL, and if it is 25% or more, the next step is performed. Proceed to the total supplyable air volume Q of the compressor specified by the lower rank (N-1). −I, is calculated. However, in this calculation, if the minimum capacity machine in operation is set as the unloading machine, the minimum capacity machine is excluded. Total supplyable air volume Q,,N-
When the calculation of , , is completed, Q, H and Qi, , -, , are compared, and the difference is more than a predetermined value (if the minimum capacity machine is used as the unloading machine, the capacity of the minimum capacity machine is more than the capacity) If,
Request a rank down. As a result, the supply air volume is switched to a lower rank that matches the consumption air volume, and the supply air volume decreases, so that an excessive rise in the discharge pressure PO is suppressed, as shown in Figure 6 (a). become.

(Tl) When QIll<QOi, the insufficient air volume determination logic is activated. In this logic, when it is determined that the air volume is insufficient, the presence or absence of an unloading machine is checked, and if there is no unloading machine, the expected pressure drop time tL until the discharge pressure Po reaches the lower limit set pressure PL is calculated. Then, the expected pressure drop time tL is compared with the waiting time t for the start of pumping of the next (second-starting compressor) belonging to the higher rank N+1, and if 1L<t, a rank up is immediately requested. As a result, the supplyable air volume is switched to a higher rank that matches the consumed air volume, and the supplied air volume increases, thereby suppressing an excessive drop in the discharge pressure PO as shown by the chain line in Fig. 6 ('b). In this example, if 1L>1., there is time, so
This will require the compressor to be ready for operation. If there is an unloading machine, calculate the air volume that can be supplied including the unloading machine, cancel the unloading of the unloading machine, and then check again to see if there is an insufficient air volume. If the air volume is insufficient, In the same way as when there is no unloading machine, a request is made to upgrade the rank or to prepare the compressor to be started next.

In this way, when the consumed air volume suddenly decreases and exceeds the air volume that can be supplied for the current rank, a rank down command is issued, so at the time of this rank down command, the discharge pressure Po is in a state where it has begun to show an upward trend. The discharge pressure Po continues to rise until the compressor defined by the current rank is completely switched to the compressor defined by the lower rank, but the rank switching can be completed before reaching the upper limit setting pressure P. Similarly, even when the air consumption increases rapidly, the rank switching from the compressor specified by the current rank to the compressor specified by the higher rank is completed before the discharge pressure Po decreases to the lower limit setting pressure P. be able to.

Therefore, by having the above logic, even if there is a sudden load change that may cause the pressure to deviate from the pressure control range in a certain rank, it is possible to suppress an excessive rise or fall in the discharge pressure, compared to the conventional method. , the operating efficiency of the compressor group can be increased.

〔Effect of the invention〕

As explained above, this invention, when there is a large load, reserves the air consumption for that volume, checks whether there is a reservation after the set time, and if there is a reservation, the book is used to fill the reserved air volume. By selecting enough compressors and operating the compressors on a schedule so that the startup or capacity adjustment is completed before the predetermined time elapses, even if there is a large load, it can be handled by automatic operation. Can be done.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an operation flow diagram of the above embodiment, Fig. 3 is a diagram showing an example of a reservation table, and Fig. 4 is an example of a reservation pattern diagram. Figures 5 and 6 are examples of the surplus air volume determination logic and insufficient air volume determination logic used in the above embodiment, respectively, and Figures 7 (a) and (bl) illustrate the effects of the above embodiment. A consumption air volume-supplied air volume relation diagram for explanation, Fig. 8 shows a conventional pressurized air supply system and its control, and Fig. 9
and (bl is a discharge pressure car setting pressure relationship diagram for explaining the problems of the conventional number-of-units control method. 3-consumption air volume calculation unit, 4...reservation air volume monitoring unit, 40-number of units control unit, 50--database, 50A--reservation table memory section

Claims (1)

[Claims] (1) Classify and rank the air volume that can be supplied by multiple compressors in stages, specify the number or combination of compressors to be operated for each rank, and specify the above ranks in response to load fluctuations. In order to control the number of compressors to operate the number of compressors without excess or deficiency, a reservation table specifying the required air consumption at one or more future times is created on the display and registered in the database, and the registered reservation table is If the reserved air volume after the set time from the current time is insufficient compared to the currently available air volume, select the number or combination of compressors that satisfies the insufficient air volume, and A method for controlling the number of compressors, characterized in that starting or adjusting the capacity of the selected compressor is completed according to a schedule.