JPH02203983A - Device for controlling number of operating pumps - Google Patents

Abstract

PURPOSE:To prevent frequency start/stop of a pump by providing a number of operating pumps controlling section, a pump speed control section and a pump well target water level determining section. CONSTITUTION:Based on the pump well water level WL from a water level detector 12 of a pump well 4, the number of operating pumps M corresponding to the pump water level WL are determined by a number of operating pumps determining section 8, and the number of operating units M are given to a number of operating pumps controlling section 9. An instruction for further starting one more pump 5 or stopping one more pump 5 based on the priority in the relationship of the pump numbers in operation at the moment is given to the pumps 5, 5... by the number of operating pumps controlling section 9. PID control for speed control of the pump 5 to correspond to the pump well water level WL to the target water level Lrm in compliance with the number of operating pumps instruction M issued from a pump well target water level determining section 13 is carried out by a pump speed control section 10.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Field of Industrial Application) This invention controls the increase or decrease of the number of pumps in operation according to the water level of the pump well, and also maintains the pump well at a predetermined water level. This invention relates to a device for controlling the number of pumps in operation that also controls pump speed.

(Conventional technology) In the past, sewage was temporarily stored in a pump well, and multiple pumps were pumped out to the sewage treatment facility while increasing or decreasing the number of pumps in operation depending on the rise and fall of the water level. As a device for controlling the number of pumps in operation for controlling the water level to a target level, one having a configuration as shown in FIG. 3 is known.

In the conventional pump operation number control device shown in Fig. 3,
Sewage from a pipe 1 is led to a pump well 4 through a settling basin 2 and a screen 3, and the sewage temporarily stored in the pump well 4 is pumped up to a sewage treatment facility 6 by a pump 5. An operating number control device 7 is provided for controlling the number of operating pumps 5 in accordance with the rise and fall of the water level in the pump well 4.

This pump operation number control device 7 includes a pump operation number determination section 8, a pump number control section 9, and a pump speed control section 10.
It is composed of.

The pump operation number determining unit 8 determines the number M of pumps in operation corresponding to the water level WL detected by the water level detector 12 of the pump well 4 based on the number determination table 11 shown in FIG.

Then, the pump number control section 9 compares the current number of pumps in operation with the required number M of pumps determined by the pump operation number determination section 8, and starts the pumps 5 in priority order so that the required number M is reached. Alternatively, a command to stop is output to each pump 5, and the number of pumps 5 corresponding to the water level of the pump well 4 is operated.

Furthermore, the pump speed control unit 10 performs PI control on the operating speed of each pump 5 so that the pump well water level WL detected by the water level detector 12 of the pump well 4 matches a preset pump well target water level Lr. Alternatively, it is controlled by PID control.

(Problem to be Solved by the Invention) However, in such a conventional pump operation number control device, the pump well target water level Lr of the pump speed control section is fixed at a fixed value set in advance by the operator. 2 if the capacity is small and the water level controllable range is small.
There was a problem in which the pumps after the first pump started/stopped frequently.

In other words, since the pump well target water level Lr, which is a fixed value, is lower than the first pump operating water level L1, when one pump is in operation and the pump well water level reaches the second pump operating water level L2, the operating pump is is at maximum speed,
When the second pump is started at the operating water level L2, both pumps are operated near the maximum speed.

When the second pump starts operating, the inflow flow rate to pump well 4 is higher than the discharge flow rate for one pump, but smaller than the discharge flow rate for two pumps. , the pump well water level WL will fall, but since the target water level Lr for speed control is at a low position, the speed will not fall immediately, and therefore the water level will fall faster.

Here, if the pump well capacity is large compared to the response of the speed control device, the water level will be stabilized near the target water level by speed control without overshooting, but speed control using a liquid resistor, etc. The control response is slow (compared to this, when the pump well capacity is small, the water level falls rapidly, resulting in overshooting the target standard Lr).

The overshooting water level is the second pump stop water level,
If the value drops below the value transiently, the second gold pump will stop at this point. And when the second gold pump stops,
Originally, the inflow flow into the pump well 4 is an amount that cannot be covered by one pump, so when the water level WL rises again and exceeds the second pump operating water level L2, the second pump is started again. Become.

In this way, the second gold pump starts and stops frequently,
It will be done. This phenomenon is more likely to occur as the control response of the speed control device is slower, the pump well capacity is smaller, and the water level controllable range is narrower, and the more likely it is that the third or subsequent pumps will start up.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a pump operation number control device that does not cause frequent starting/stopping of each pump even when a plurality of pumps are operated simultaneously. With the goal.

[Structure of the Invention] (Means for Solving the Problems) A device for controlling the number of pumps in operation of the present invention includes a pump well water level detection means and a pump well water level detected from the water level detection means to determine the number of pumps in operation. , a pump operation number control unit that controls the operation and stop of the required number of pumps, and a pump speed control unit that controls the operating speed of the pumps in operation in order to maintain the pump well water level by the water level detection means at a predetermined target value. and a pump well target water level determination unit that changes the pump well water level target value to a different value depending on the number of operating pumps.

(Function) In the pump operation number control device of the present invention, the pump operation number control section determines the number of pumps to be operated according to the rise and fall of the pump well water level, and simultaneously operates the required number of pumps to pump out sewage from the pump well. Let's do it. Further, the pump operating speed is controlled by the pump speed control section so that the pump well water level reaches a predetermined target value.

Furthermore, the target water level of the pump well set by this pump speed control unit is an intermediate water level between the starting water level and the stopping water level of each pump in order to prevent frequent starting/stopping of each pump depending on the number of operating pumps. The target water level of the pump well is determined by the pump well target water level determination unit.

In this way, the number of pumps in operation can be increased or decreased depending on the pump well water level, the operating speed of each pump can be controlled to match the target water level, and the target water level can be made variable according to the number of pumps in operation. The number of pumps in operation is controlled so that stoppages do not occur frequently.

(Example) Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

FIG. 1 shows the circuit configuration of an embodiment of the present invention.
The same elements as those of the conventional system for controlling the number of pumps in operation shown in FIG. 3 are denoted by the same reference numerals. Therefore, sewage flowing from pipe 1 to settling basin 2 passes through screen 3 and is introduced into pump well 4, from which pumps 5, 5
．． The pumps 5, 5. The number of pumps in operation and the speed of pumps in operation are controlled by a device 7 for controlling the number of pumps in operation.

The device 7 for controlling the number of pumps in operation according to this embodiment includes a pump operation number determination unit 8, a pump number control unit, and a pump speed control unit 1-O similar to the conventional example, and further features features of the embodiment of the present invention. The target water level command Lr is provided to the pump speed control unit 10. (m=1.2°3).

Regarding the operation of the pump operation number control device with the above configuration,
This will be explained next.

Based on the pump well water level WL from the water level tester 12 of the pump well 4, the pump operation number determination unit 8 determines the current pump well water level WL from the water level vs. pump operation number comparison table shown in FIG. The corresponding number M of pumps in operation is determined, and this number M of pumps in operation is given to the pump number control section 9.

In response to the operating number command M from the pump operating number determining unit 8, the pump number control unit 9 starts one more pump 5 in the order of priority seats in relation to the number of pumps currently in operation, or starts one more pump 5. A command to stop pump 5 is sent to pumps 5 and 5.
．． give to...

In addition, the pump speed control unit 10 controls the pumps in operation so that the pump well water level WL matches the target water level Lr□, which changes according to a pump operation number command M from the pump well target water level determination unit]-3, which will be described later. 5 speed control is PI control or P
This is done by ID control.

The pump well target water level determination unit 13 receives the pump operation number command M from the pump operation number determination unit 8 and calculates the target water level Lr□ corresponding to the operation number M, and calculates the target water level Lr□ based on the following formula. The water level Lr□ is determined and given to the pump speed control section 10.

Lr--α (M,, Mott) +Mo
rtwhere, M: Number of pumps in operation m・1, 2. or 3 (corresponding to the number of pumps in operation M) M. ,: Mott pump operating water level (=L 1. L 2.+ or L3) Mott:
M metal pump stop water level ('-L4.L5. or L6) α: Constant (0,0 × α<1.0).

In other words, in this pump well l] water level determination unit] 3, in response to the pump operation number command M from the pump operation number determination unit 8, the M water level obtained from the water level-operation number comparison table 11 in FIG. Water level: Stop water level L1, L, L2: L
5. Alternatively, the intermediate water level between L3 and L6 is determined as the target water level Lr, and this target water level Lr. is given to the pump speed control section 10.

Therefore, the pump speed control unit 10 is given a pump well target water level Lr□ that changes depending on the number of pumps in operation, and as the number M of operating pumps increases, the target water level Lr□ will be at a higher position than before. As a result, when the pump well water level exceeds the M gold starting water level and the Mth pump is started, all M pumps start operating at maximum speed, but as a result, the target water level Lr is reached. This means that the operating speed of each pump will be lowered earlier, and the speed at which the water level will fall will be suppressed.
This means that the overshoot phenomenon near the target water level can be reduced.

Furthermore, even if overshoot may occur, the water level of the M-Kaneme pump well M0. .

Since the interval between the target water level Lr and the target water level Lr is maintained, the water level reaches the stop water level M 6 (M) due to overshoot.

('=L4.L, or L6) is less likely to fall below this, which also makes it possible to reduce the frequency of starting/stopping the pump.

In addition, in the above embodiment, the pump operation number control device for a pump well equipped with three pumps was shown, but the number of pumps may be larger depending on the capacity of the pump well.

[Effects of the Invention] As described above, according to the present invention, the number of operating pumps is controlled according to the water level of the pump well, and the speed of the operating pumps is controlled in order to maintain the water level of the pump well at the target water level. In this case, the target water level is set at a position midway between the start water level and the stop water level of that number of pumps depending on the number of pumps in operation, so the target water level can be reached relatively quickly. Pumps are not operated at maximum speed for long periods of time, and even in small-capacity pump wells, it is possible to avoid overshoot from quickly reaching the stop level of the most recently started pump. It can be made less likely to occur.

In addition, since there is always a relatively large gap between the stop water level of the most recently started pump and the target water level, even if the pump well capacity is small and the water level rises quickly, the pump will be started most recently. A restart command is rarely issued immediately after the pump is stopped, and the frequency of starting/stopping can be kept low.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram of an embodiment of this invention, Fig. 2 is a water level vs. number of operating units comparison table used in the above embodiment, and Fig. 3
The figure is a circuit block diagram of the conventional example, and FIG. 4 is a water level vs. number of operating units comparison table used in the conventional example. 4...Pump well 5...Pump 7...Pump operation number control device 8...Pump operation number determination section 9...Pump number control section 1'0...Pump speed control section 11...・Water level - number of operating units comparison table 12...Water level detector 13...Pump well target water level determination unit

Claims (1)

[Scope of Claims] Pump well water level detection means; A pump operation number control unit that determines the number of pumps to be operated according to the pump well water level from the water level detection means and controls the operation and stop of the required number of pumps. , a pump speed control unit that controls the operating speed of the pump during operation in order to maintain the pump well water level by the water level detection means at a predetermined target value; and a pump speed control unit that controls the pump well water level target value to a different value depending on the number of pumps in operation. A device for controlling the number of pumps in operation, comprising a pump well target water level determination unit that changes the pump well water level.