JP2734698B2 - Variable speed pump unit control device - Google Patents

Description

The present invention relates to a variable speed pump number control device.

B. Summary of the Invention The present invention relates to a method in which the flow rate is equal to K pump operation units and (K-1)
When the number of pumps operating is within the flow rate range where the number of laps overlaps and the flow rate range where the number K and the number of laps (K + 1) overlaps, the flow rate is increasing. In some cases, the smaller one is selected so that the increase in the flow rate can be promptly dealt with and the number of operating units in the flow range where the number of laps overlaps can be minimized.

C. Conventional technology 100% of each pump when the same speed variable speed pump is used
The number of pumps operated based on the pump characteristics at the time of% speed and at the time of n% speed is as shown in FIG.

Conventionally, in a water supply and sewage plant, as shown in FIG. 8, the number control device of variable speed pumps has a minimum flow rate level a ₁ to the a ₄ and a maximum value b ₁ ~b ₄ are fixedly set in the alarm setting device. Note that which pump to start and stop can be set externally.

D. Problems to be Solved by the Invention However, in the conventional device for setting the number of pumps to be operated while fixing the flow rate level, when the lap range α of the number of units is reduced, the frequency of starting and stopping becomes severe, which affects the life of the pump motor. Effect. Also, if the lap range α is too large, the discharge flow rate will be sufficient if n units are operated at high speed, but (n + 1) units will be operated at low speed in many cases. Will not be.

The response to a rapid increase in the discharge flow rate is delayed, and the number of pumps cannot keep up with a sudden change in demand.

There are drawbacks such as.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and an object of the present invention is to minimize the frequency of starting and stopping pumps and to reduce the demand fluctuation. It is an object of the present invention to provide a variable speed pump number control device capable of responding quickly.

E. Means for Solving the Problems In order to achieve the above object, the present invention provides a method for controlling the flow rate for each operating number of pumps so as to partially overlap each controllable flow rate control range for each operating number of pumps. In a variable speed pump unit control device in which a minimum value and a maximum value of a level are set and the number of pumps operated according to the flow rate, a current average flow rate, a minimum flow rate, and a maximum flow rate within a predetermined time from a measured flow rate to the present time. Means for determining the flow rate and the previous average flow rate within a predetermined time period before, and comparing the previous average flow rate with the current average flow rate on condition that the flow rate falls within the wrapping range of the flow rate control range. Comparing the minimum flow rate with the flow rate minimum value of the flow control range with the larger number of pumps operating or the maximum flow rate with the maximum flow level of the flow control range with the smaller number of pumps operated If the current average flow rate is larger than the previous average flow rate and the minimum flow rate is larger than the minimum flow level in the flow control range of the larger number of pump operation units, a command to increase the number of pump operation units is output and the previous average Means for outputting a command to decrease the number of pumps operated when the current average flow rate is smaller than the flow rate and the maximum flow rate is smaller than the maximum flow level of the flow control range of the smaller number of pumps operated. is there.

F. Action The average flow rate Q from t minutes (arbitrarily set) to the present is calculated.

The average flow rate Q ₀ from the time point t minutes before to the time point t is obtained.

In FIG. 5, when the flow rate range is in the lap range of the number of operating units K and K-1 during the operation of the K pump units, the maximum flow rate _Qmax from the present time to Q-Q ₀ ≦ 0 and t minutes before the present is equal to the operating number K− If there is a relationship of Q _max <b _K−1 smaller than the maximum flow level b _{K−1 of one} , the number of pumps operated is reduced by one from K to (K−1).

When the flow rate range to K-1 units during operation is K, the lap range of _{K-1, Q-Q 0} > C minimum flow up to (C is arbitrarily set) and t minutes prior to the current Q _min> number of operating K Minimum level of a _K
In this case, the number of operating pumps is increased by one from (n-1) to n.

Q, Q ₀ , Q _max , and Q _min are updated at regular intervals (about 10 to 60 seconds).

By doing so, the setting of the optimal number of operating pumps
Since it can be determined by adding the flow rate fluctuation tendency based on the fixed set value, the number lap range α can be widened as shown in FIG. Conventionally, when the flow rate increases and enters the α region, K units are used,
When the flow rate decreases and enters the area α, the number of pumps that has been fixed at (K + 1) is fixed, but the optimum number of pumps operated in the area α can be selected according to the flow rate fluctuation.

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

FIG. 1 shows a variable-speed pump number control device. This number control device includes a sequence controller 1 including a CPU, a memory, an I / O, and a program loader. The sequence controller 1 has the same flow rate minimum setting values a ₁ , a _2, ..., _Ann and maximum setting values b ₁ , b ₂ ,.
.., _Bn , the flow rate q measured by the flow meter, the time t for obtaining the average value, and Δt are input. FIG. 2 shows a flow of determining the number of units in the sequence controller 1, and FIG. 3 shows the functions of the CPU in blocks.

Currently the average flow rate Q, the average of t minutes before flow Q _0, as shown in FIG. 3, the flow rate q ₁ for each Δt flow q inputted, q ₂ ...... q _n
Is stored in the shift register unit 11 for 2t minutes and refreshed every Δt minutes, and is calculated by the arithmetic unit 12 using the stored data for 0 to t minutes and t−2t minutes.

In addition, the maximum flow rate Q _max and the minimum flow rate Q until t minutes ago
_{The min} is extracted from the data stored in the shift register unit 11 for 0 to t minutes and stored in the memory units 14 and 15.

Pump Initial number K decision (Figure 5) is the flow rate set value a _K ≦ commensurate with the current average flow rate Q in step 22 of FIG. 2
Perform by selecting Q <a _{K + 1} .

Then, the flow rate set values a _K , b _k and the flow rate set values b _K−1 , a _{K + 1} between them for the initial number K are compared with the comparison unit 16 in FIG.
Q _max of from the memory 14 and 15 to 19, compared to Q _min, also increase in the average flow rate computation unit 13, the reduction value Q-Q ₀ is calculated and put the results in determination section 20.

The determination unit 20 determines that a _K ≦ Q <b based on the flow of FIG.
_{When K−1} , if Q−Q ₀ ≦ 0 and Q _max <b _K−1 , the _K pumps are changed to (K−1) pumps, and Q−Q ₀ ≧ C and Q _min > a _K
The pump (K-1) stage outputs the operation command to change the K heights if, also, when _{a K + 1 ≦ Q <b} K, Q-Q 0 ≦ 0 and
If Q _max <b _k , the (K + 1) units are changed to K units, and Q−Q ₀
If ≧ C and Q _min > a _{K + 1} , an operation command to change K units to (K + 1) units is output.

FIG. 6 shows an example of the relationship between the flow rate q and the number of pumps operated.
One unit is operated, and energy saving operation can be performed as compared with the conventional K-unit operation. In addition, the portion becomes K-unit operation due to an increase in the average flow rate, and can operate more quickly in response to a flow rate change than the conventional K-1 unit operation.

In this embodiment, the flow rate q is input to the sequence controller, but instead of the flow rate q, the water level h of the reservoir is detected and input, and the CPU changes the water level Δh and the bottom area S of the reservoir.
From Can also be used.

H. Effects of the Invention Since the present invention is configured as described above, the following effects can be obtained.

The minimum flow setting (a ₁ ,..., A _n ) for setting the optimum number of pumps to be operated is the maximum flow setting (b
₁ ,..., B _n ), the flow rate fluctuation tendency can be determined as a base. Therefore, the flow area α in which the number of operating pumps overlaps can be widened as shown in FIG. it can. Therefore, the frequency of starting and stopping can be minimized.

In the flow rate area α, the most suitable one can be selected from (N-1) and N or N and (N + 1) units to be wrapped according to the fluctuation of the average flow rate. Therefore, the number of operating pumps can be minimized in the flow rate region α, and power can be saved. In addition, when the flow rate is increasing, the pump can be operated by increasing the number of pumps by one in advance, so that it is possible to quickly respond to the increase in the flow rate.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of input and output of the sequence controller, FIG. 2 is a flowchart for determining the number of pumps, FIG. 3 is a functional block diagram of the CPU, FIG. 4 is an explanatory diagram of flow rate setting, FIG. FIG. 6 is an explanatory diagram of a relationship between a change in flow rate and the number of pumps operated, FIG. 7 is an explanatory diagram of a relationship between operating characteristics of a plurality of pumps and a pump flow control range, and FIG. 1. Sequence controller.

Claims (1)

(57) [Claims] A minimum value and a maximum value of a flow level for each operating number of pumps are set so as to partially overlap each controllable flow rate control range for each operating number of pumps. In the variable speed pump number control device that controls the number of operating pumps, the average flow rate from the measured flow rate to the current
Means for calculating a minimum flow rate, a maximum flow rate, and a previous average flow rate within a predetermined time before the flow rate; and a condition that the flow rate is within a range where the flow rate control range overlaps with the previous average flow rate and the current average flow rate. And comparing the minimum flow rate with the flow rate minimum value of the flow rate control range of the larger number of pumps operated or the maximum flow rate and the flow rate maximum value of the flow rate control range of the smaller number of pumps operated. If the current average flow rate is larger than the average flow rate and the minimum flow rate is larger than the flow rate minimum value of the flow control range of the larger number of pump operation units, a command to increase the number of pump operation units is output, and the If the current average flow rate is small and the maximum flow rate is smaller than the maximum flow level in the flow control range with the smaller number of pumps operating, a command to reduce the number of pumps operating is issued. Output means; and a variable speed pump number control device.