JPH03182696A - Number of pumps control device for variable speed pump - Google Patents

Abstract

PURPOSE:To suppress the frequency of the start and stop of a pump to a necessary minimum limit and to rapidly respond to a fluctuation in a demand amount by determining an average flow rate, a maximum flow rate, and a minimum flow rate in a given time, and increasing or decreasing the number of pumps by one pump according to the increase or the decrease of the average flow rate. CONSTITUTION:A present average flow rate Q and an average flow rate Q0 at (t) minutes before are calculated by a computing part 12 from a flow rate (q) inputted into a sequence controller 1. A maximum flow rate Qmax and a minimum flow rate Qmin till (t) minutes before are fetched from memory data during 0-(t) minutes before of a shift register part 11 and stored in memory parts 14 and 15. Flow rate set values ak and bk and flow rate set values bk-1 and ak+1 in relation to the initial number K of pumps are compared with Qmax and Qmin from the memory parts 14 and 15 by comparing parts 16-19, and an increased and decreased value Q-Q0 is calculated by a computing part 13. In the case of Q-Q0<=0 and Qmax<bk-1 in the case of ak<=Q<bk-1, a deciding part 20 varies the number K of pumps to the number K-1 of pumps, and in the case of Q-Q0>=C and Qmin>ak+1, it varies the number K of pumps to the number K+1 pumps.

Description

[Detailed description of the invention] A. Industrial application field The present invention relates to a device for controlling the number of variable speed pumps.

B1 Summary of the Invention The present invention provides a flow rate range in which the flow rate overlaps between the number of pumps in operation and the number of pumps in operation (K11).
When the flow rate is in the desired flow range, select one more pump when the flow rate is increasing, and select one fewer pump when the flow rate is decreasing. In addition, the number of operating units within the lapped flow rate range can be kept to the necessary minimum.

C Conventional technology When using variable speed pumps of the same capacity, each pump's 100
The number of pumps to be operated is shown in FIG. 7 based on the pump characteristics at % speed and n% speed.

Conventionally, in a sewerage plant, a device for controlling the number of variable speed pumps has been used to control the minimum value of the flow rate f in the number of valleys so that the wrap range α of the number of pumps when switching the number of pumps is constant, as shown in Fig. 8. A1 to a4 and maximum values bl to b4 are fixedly set by an alarm setting device.

Note that it is possible to externally set which pumps to start and stop.

■) 8 Problems to be Solved by the Invention However, with conventional devices that fix the flow level and set the number of pumps in operation, ■If the wrap range α of the number of pumps is made small, the frequency of starting and stopping increases, and the pump motor has a lifespan. It affects me.

Also, if the lap range α is set too large, the discharge flow rate will be sufficient if n units are operated at high speed, but at low speed (n+1)
In many cases, the vehicle is operated by a stand-alone vehicle, and even if variable speed control is performed, power cannot be saved.

■If the discharge flow rate increases rapidly, the response will be delayed, and the number of pumps will not be able to keep up with the sudden change in demand.

There are drawbacks such as.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to minimize the frequency of starting and stopping the pump, and also to reduce the frequency of starting and stopping the pump to the necessary minimum. It is an object of the present invention to provide a device for controlling the number of variable speed pumps that can quickly respond to such problems.

Means for Solving Problem E3 In order to achieve the goal, the device for controlling the number of variable speed pumps in the present invention sets the minimum and maximum values of the flow level for the number of pumps, and adjusts the flow level according to the flow 111. 4- A processing unit that calculates the average flow rate, maximum flow rate, and minimum flow rate within a predetermined time period and the average flow rate within the previous predetermined time period from the flow rate, and the maximum flow rate and the minimum flow rate. is within the flow rate range in which the number of pumps overlaps, the number of pumps in the flow rate range in which the number of pumps in the flow rate control range of the number of pumps at that time overlaps is determined by the above-mentioned ・[
The system is equipped with a determining unit that increases or decreases the flow rate by one unit depending on the increase or decrease in the average flow rate.

F Effect minutes (set arbitrarily) Average flow rate from previous to present Find Q.

The average flow rate Qo from the time t minutes ago to t minutes ago is determined.

[ ■ In Figure 5, when the pump is in operation and the flow rate range is within the lap range of −1 to the number of pumps in operation, Q −Q a
≦O and the maximum flow rate Q□8 up to t minutes before now is 1 in b
If the relationship is smaller than Q , -< b *-+, then
The number of pumps in operation is reduced by one from 2 to (K-1).

■ When the flow rate range is within the range of -1 during operation of 11 units, Q-Qo>C (C is set arbitrarily) and the minimum flow rate up to t minutes before the current time Q wa l n>ax If the relationship is satisfied, the number of pumps in operation is increased by one to (n-1) - n units.

Q, Qo, Q−x, Q−+ are constant periods (lO
The calculation is updated in about 60 seconds).

In this way, the optimum number of pumps to be operated can be determined based on the fixed set value and by adding the flow rate fluctuation tendency. It can be wide as shown in the figure. In addition, conventionally, when the flow rate increases and enters the α region, the number of pumps in operation is fixed at 100, and when the flow rate decreases and enters the α region, it is fixed at (K+1), but the number of pumps in operation in the α region is changed depending on the flow rate fluctuation. You can choose the most suitable one.

G. Example Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a device for controlling the number of variable speed pumps.

This number control device is composed of a sequence controller 1 consisting of a CPU, memory, Ilo, and a program loader. The sequence controller l has the same minimum flow rate setting value a I + a t for the number of pumps as before.
'...an and maximum setting value,,b.

....bn, the survey q measured by the flowmeter, the time in minutes for finding the average value, and Δt are input.

FIG. 2 shows the flow for determining the number of sequence controllers 1, and FIG. 3 shows the functions of the CPU in blocks.

The current average flow rate Q is the average flow rate Q minutes ago. As shown in FIG.
Q l + Q t... Qn is stored for 2 minutes and Δ is refreshed every minute in the shift register section I
The 0 to L minutes of I and t to 2 are calculated by the calculation unit +2 using the stored data for the minutes.

Also, the maximum flow rate Q1°8. and the minimum flow En Q wa i n is 0 of the shift register section 11.
~ L minutes of stored data are extracted and stored in the memory section 1415.
to be memorized.

The initial number of pumps K (FIG. 5) is determined by selecting the flow set value aK≦Q<aK*1 corresponding to the current average flow rate Q in step 22 of FIG.

Therefore, the flow rate setting value al for the initial number K.

bK and the flow rate set value between b x-+, a *
** Comparison of Figure 3 + I < 16 to 19 and memory 14.
15, and the calculation unit 13 calculates the increase and decrease value Q- of the average flow rate.
Qo is calculated and these results are input to the judgment section 20.

Based on the flow shown in FIG. 2, the determining unit 20 determines that a8≦Q<
When bK-+, Q-Q, ≦0 and Q, , <b K-
If it is 1, change the pump to (K-1) and Q-Qo.
If ≧C and Q mtn> a x, pump (Kl)
Outputs the operation command to change the machine to the machine, and also outputs aK□≦
When Q < b K, Q-Qo≦0 and Q-i < b
If it is K, change the (K+1) unit to the unit, Q-Q,
If ≧C and Q anIn> a K*1, set the stand (
It is designed to output an operation command to change to K+1).

Figure 6 shows an example of the relationship between the flow rate q and the number of pumps in operation.
This allows for more energy-saving operation compared to conventional stand-alone operation. In addition, in the part (■), the increase in the average flow '+t results in a standstill operation, and the operation can respond to changes in the flow j11 more quickly than the conventional 11-interval operation.

In this example, the flow rate q is manually inputted to the controller, but instead of the flow rate ri1q, water from the distribution reservoir (1'
It is also possible to use the system by manually detecting /h and calculating the change in water level Δ using the CPU.

11 Effects of the Invention Since the present invention is structured as described in L, it produces the effects described below.

0) The minimum set value of flow rate (al,...an) for setting the optimal number of operating pumps of multiple pumps is the maximum set value of flow rate (bl,...b,) Since the flow rate can be determined by adding the flow rate fluctuation tendency based on the flow rate, the flow rate region α in which the number of pumps in operation overlaps can be widened as shown in FIG. 4(a), commensurate with the pump characteristics. Therefore, the frequency of starting and stopping can be minimized.

(2) The optimal number of operating units (N1) and N units or N units and (N+1) units to be lapped in the flow rate region α can be selected depending on the fluctuation of the average flow rate. Therefore, the flow rate area α
The number of pumps in operation can be kept to the minimum necessary, and power can be saved. Further, when the flow rate tends to increase, the number of pumps in operation can be increased by one in advance, so that it is possible to quickly respond to the increase in the flow rate.

[Brief explanation of drawings]

Figure 1 (Yonken controller person, output explanation,
Figure 2 is a pump life determination flowchart, Figure 3 is CI
' tJ functional block diagram, Figure 4 is a flow rate setting explanatory diagram,
Fig. 5 is an explanatory diagram of the number of operating pumps, Fig. 6 is an explanatory diagram of the relationship between flow: [1 change and the number of pumps in operation, Fig. 7 is an explanatory diagram of the relationship between the operating characteristics of the number of stage pumps and the pump flow rate control range, and Fig. 8 is an explanatory diagram of conventional tn setting. l - Nokenos Controller. Figure 1 Figure 4 Figure 5 Figure 6 Figure 8

Claims (1)

[Claims] (1) In systems where the minimum and maximum flow levels are set for the number of pumps and the number of pumps in operation is controlled according to the flow rate, the average flow rate, maximum flow rate, minimum flow rate, and the previous flow rate within a predetermined time from the flow rate are a processing unit that calculates an average flow rate within a predetermined time; and a processing unit that calculates an average flow rate within a flow rate range that the number of pumps in the flow rate control range of the number of pumps at that time overlaps, on the condition that the maximum flow rate and the minimum flow rate are within the flow rate range that the number of pumps overlaps. A device for controlling the number of variable speed pumps, comprising: a determining unit that increases or decreases the number of pumps by one according to an increase or decrease in the average flow rate from the average flow rate.