JP4270620B2 - Control method for parallel operation start and release of water supply equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention comprises a plurality of pumps as a water supply facility for supplying clean water to buildings having a large number of demand terminals such as apartment houses, office buildings, factories, etc., and the number of operating pumps according to increase or decrease in demand, The present invention relates to control at the start and release of parallel operation of a water supply device that controls the number of revolutions of each pump and performs constant discharge pressure control or constant estimated terminal pressure control.
[0002]
[Prior art]
Conventionally, when a plurality of pumps are operated in parallel, a confirmation time of several seconds has been provided in order to prevent chattering at the start of parallel operation of the pumps and when canceling the parallel operation. That is, as shown in FIG. 6, when this is explained by a graph showing the discharge amount and discharge pressure of a water supply device in which up to three pumps are operated in parallel, the curve a shows the maximum actual head of the customer, Curves showing the relationship between the water supply pressure required for the water supply equipment used at the highest point, the pressure plus the pipe resistance, and the amount of water. B _max, c _max , d _max were operated by one, two and three pumps, respectively. It is a curve which shows the relationship between discharge pressure and the amount of discharged water when the pump of the water supply unit at the time is operated at the maximum rotation speed. For the start and release of the parallel operation of the pumps, the start pressure p _ON2 slightly lower than the pressure at the intersection of b _max and a and the stop pressure p _OF2 slightly higher than the pressure at the intersection of b _max and a are started third. Similarly, the starting pressure p _ON3 and the stop pressure p _OF3 are respectively determined for the pump to be _operated .
[0003]
A control method when the usage amount of the water supply device set in this way changes from Q ₀ to Q ₁ will be described. At the water quantity Q ₀ , the pump that was started first is operating at the highest frequency, and the pump that was started second is operating at a frequency below the maximum rotational speed of this pump. When operating the faucet so as to increase the amount of water to Q _1, to the amount of water F point corresponding to increase the rotational speed of the pump was started in the second. After reaching point F, the piping route can feed water Q ₁ by operating the faucet, but only the amount of water at the maximum number of revolutions of the two pumps can flow, so the operating point is on the curve c _max Is moved in the direction of point G. Check that the pressure at point G is the starting pressure p _ON3 of the pump that starts third, and that the discharge pressure of the water supply device has kept below this pressure for 1-2 seconds. Start at the minimum rotation speed d _min . Thereafter, the number of revolutions of the pump is controlled so that the discharge pressure matches the pressure at the point H, and the process until the amount of water Q ₁ is supplied is terminated.
[0004]
Conversely, the control method when the amount of water used changes from Q ₁ to Q ₀ is as follows. In the first the water Q _1, pump the highest frequency to start the second, pump started third are operated at a frequency below the maximum rotational speed of the pump. If the faucet is operated so as to reduce the amount of water to Q _{0, the} number of rotations of the pump started third is reduced to the amount of water at point F. After reaching point F, the pipe resistance is larger than the assumed pipe resistance in the discharge water amount for the two pumps, so the operating point of the water supply apparatus moves on the curve c _{max in} the direction of point J. Check that the pressure at point J is the stop pressure p _ON3 of the pump that was started third, and that the discharge pressure of the water supply device has maintained this pressure or more for 1 to 2 seconds, and stop the pump that started third. . The confirmation time at the G point and the J point is a measure for preventing chattering at the start and stop of the pump whose pressure starts third.
[0005]
[Problems to be solved by the invention]
As described above, in the conventional water supply apparatus that operates a plurality of pumps in parallel, the confirmation time is provided at the point G when the amount of water increases, and at the point J when the amount of water decreases. When the amount of water used increases, the water supply pressure continues to decrease, and when the amount of water used decreases, the water supply pressure continues to increase, so the water supply pressure at the customer's site fluctuates greatly and the water supply amount does not respond correctly to opening and closing of faucets etc. was there. An object of the present invention is to reduce pressure fluctuation generated at a demand destination at the time of starting parallel operation of pumps and at the time of releasing parallel operation, and to shorten the time required for shifting.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention controls the pump start pressure and the stop pressure for the second and subsequent pumps in a water supply apparatus including a plurality of pumps that control the rotation speed of the pump and perform constant discharge pressure control. In addition, for the number of pumps operating simultaneously, except for the pump that starts last, except for the first rotation speed less than the maximum rotation speed and the pump that starts first and last, corresponding to the pump start sequence The second rotation speed is set between the minimum rotation speed and the first rotation speed, and the second rotation speed is set between the minimum rotation speed and the maximum rotation speed in the pump that starts last, and is equal to or less than the first rotation speed. If the pump that was operating at the maximum speed of the pump reaches its maximum speed without decelerating on the way, the pump in the next start sequence is immediately set to the minimum speed that is set in advance corresponding to the start sequence. Start and over 2nd speed When the pump that was being operated reached the minimum number of rotations without any increase in speed, the pump was immediately stopped. Later, when a pump reaches the maximum rotation speed of the pump and the discharge pressure becomes lower than the starting pressure of the next pump, the discharge pressure is maintained at a value lower than the starting pressure for a predetermined time. After confirming, start the pump of the next starting sequence, and after passing through other than the above, regardless of the number of rotations initially operated, a certain pump reaches the minimum number of rotations of the pump, and the discharge pressure stops the pump When the pressure becomes higher than the pressure, the pump is stopped after confirming that the pressure is maintained at a value equal to or higher than the discharge pressure for a predetermined time .
[0008]
Furthermore, the present invention is characterized in that a method similar to the control method of the preceding paragraph is used even in a water supply apparatus including a plurality of pumps that perform constant control of estimated terminal pressure.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a graph showing the relationship between the discharge amount and discharge pressure of a water supply device in which three pumps are operated in parallel. The horizontal axis shows the discharge amount of the water supply device, and the vertical axis shows the discharge pressure. The reference numerals in the figure are the same as those in FIG. FIG. 2 schematically shows the configuration of a water supply apparatus that implements the control method of the present invention.
[0010]
The arithmetic unit of the control unit 12, as a number to be used to control the initiation and release of parallel operation of the pump, two sets of start-up of the same P _ON2 and P _OF2, P _ON3 and P _OF3 the conventional method, the stopping pressure In addition, an arbitrary rotation speed b _{1 that} is less than the maximum rotation speed b _max of the pump that starts first and exceeds the minimum rotation speed b _min , and a minimum rotation speed c _min that is less than the maximum rotation speed c _max of the second start pump , Any rotational speed c ₁ (first rotational speed) exceeding, and any rotational speed c ₂ (second rotational speed) that exceeds the minimum rotational speed c _min of the second starting pump and is less than c ₁ And an arbitrary rotational speed d ₂ (second rotational speed) that exceeds the minimum rotational speed d _min of the pump to be started third and is less than the maximum rotational speed d _max is stored. Similarly, in the case of a water supply system equipped with four or more pumps, the range that is less than the maximum number of revolutions of each pump and exceeds the minimum number of revolutions, except for the pump that starts last, with the pressure to start and release the parallel operation. The first starting speed is between the minimum speed of each pump and the first speed except for the pump that starts last, except for the pump that starts first. A second rotational speed is set and stored between the rotational speed and the maximum rotational speed.
[0011]
A control method of the pump using the pressure for starting and canceling the paralleling as described above, and the first rotation speed and the second rotation speed will be described. After the pump to be started first or after the pump to be started last, the pump that was operating stably at the rotation speed lower than the first rotation speed is increased due to the increase in the amount of water used. When the pump speed increases monotonously to the maximum rotation speed of the pump, the pumps in the next starting sequence are started immediately even if the detected pressure of the pressure detector 9 does not decrease to the starting pressure of the pump to be started next. In addition, when the pump that has been operating stably at the second rotation speed or higher, except for the pump that starts first, the pump rotation speed decreases monotonously to the minimum rotation speed of this pump due to a decrease in the amount of water used. Even if the detected pressure of the pressure detector 9 does not increase to the stop pressure of the pump, the pump is immediately stopped. Thus, when starting and stopping, no confirmation time is provided by a timer.
[0012]
Even if the operating point of the pump before the amount of water used is within the range shown above, if the progress up to the maximum or minimum rotational speed is not monotonically increasing or decreasing, and the first operating point is the first rotation In the case of exceeding the maximum number and below the maximum number of rotations and below the second number of rotations and exceeding the minimum number of rotations, the detection pressure of the pressure detector is changed to the start pressure of the next pump by the conventional parallel operation start and release method. Then, the pump is started or the pump in operation is stopped after a confirmation time by a timer.
[0013]
The control mechanism of the water supply apparatus controlled by the above method will be described with reference to FIGS.
FIGS. 3 to 5 are simplified flowcharts of the control program stored in the calculation unit of the water supply device, and the flow related to the control of the rotational speed and the parallel start and release control. It is.
[0014]
FIG. 3 is a flowchart when the rotational speed of the pump does not change and when the rotational speed of the pump started last is changed to correspond to the amount of water used. The control flow for starting the parallel operation of the pump is as shown in FIG. 4. In step 201 of FIG. 3, the pump is operating at the maximum rotation speed (N _max ), and the pressure detector from the target pressure (SV). When the detected pressure (PV) is low, the process proceeds to step 211 in FIG.
[0015]
On the other hand, the control flow for canceling the parallel operation is as shown in FIG. 5. In step 301 of FIG. 3, when the pump is operating at the minimum rotation speed (N _min ) and PV is higher than SV, FIG. Go to step 311. When SV and PV are equal, the discharge amount of the pump is balanced with the amount of water used by the customer. Therefore, based on the rotation speed (N ₀ ) at this time, in order to determine the control method when the subsequent change in the rotation speed reaches N _max and N _min , the flag value used is initially set in 103 steps. Set to value. In the example shown in FIG. 3, when the rotation speed when SV and PV are equal is equal to or greater than N _{min and} equal to or less than the first rotation speed (N ₁ ), the variable FLG1 is set to 1, FLG2 is set to 0, When the rotation speed is greater than or equal to the second rotation speed (N ₂ ) and less than or equal to N _max , the variable FLG1 is set to 0 and FLG2 is set to 1.
[0016]
A control flow for starting parallel operation will be described with reference to FIG. It is determined whether or not the pump last started in step 211 has monotonically increased from the number of revolutions between N _min and N ₁ and has reached N _{max of the} pump. The determination is made with the value of FLG1 set when the number of revolutions (N _o ) is a balance between the discharge amount and the amount of water used. As shown by step 305 in FIG. 3, the value of FLG1 is set to 0 when pump deceleration processing is performed. Therefore, when the value of FLG1 is 1, it can be determined that the value monotonically increases from N ₀ to N _max . When the pump operating between N _max and N ₁ reaches N _max, or when the pump operating at the rotational speed between N _min and N ₁ reaches N _max while repeatedly increasing and decreasing, 212. Proceed to step and compare the starting pressure (P _ON ) of the pump to be started next with PV. When PV> P _ON , it is determined that the pressure is not set to start parallel operation, and the process returns to step 101 in FIG. 3 to read PV.
[0017]
In order to prevent chattering at the start of the pump to be started next when PV ≦ P _ON , it is confirmed that the pressure of P _ON or less continues for a certain time, in this embodiment, for 2 seconds, and then the pump of the next starting sequence Start. The control flow from step 212 to step 216 is the same as that of the conventional water supply device of the estimated terminal pressure constant control and the discharge pressure constant control method. On the other hand, when it is confirmed that the value monotonously increases to N _{max in} step 211, the control flow is configured to proceed to step 216.
[0018]
Next, the control flow of parallel operation cancellation will be described with reference to FIG. In step 311, it is determined whether the pump has monotonously decreased from the rotational speed between N ₂ and N _max to reach the pump's N _min . The determination is made based on the value of FLG2 set in step 103 based on the value of N ₀ . The value of FLG2 is set to 0 when the pump is accelerated as shown at step 205 in FIG. Therefore, when the value of FLG2 is 1, it can be determined that the value has decreased monotonically from N ₀ to N _min . And when the pump was driving between N _min and N ₂ are led to N _min, also be operated with N ₂ or more, when reached N _min while repeating increase and decrease, the process proceeds to 312 steps, and PV The pump stop pressure (P _OF ) is compared. When PV <P _OF , it is determined that the pressure is not sufficient to cancel the parallel operation, and the process returns to step 101 in FIG. 3 to read PV. When PV ≧ P _OF , in order to prevent pump chattering, the pump is stopped after confirming that the pressure of P _OF or more continues for a certain time, in this embodiment, for 2 seconds. The control flow from step 312 to step 316 is the same as that of a conventional water supply device of the estimated terminal pressure and discharge pressure constant control method. On the other hand, if it is confirmed in step 311 that the monotonic decrease has reached N _min , the control flow is configured to proceed to step 316.
[0019]
【The invention's effect】
According to the control of the water supply device according to the present invention at the start and release of parallel operation, when the amount of water used changes simply from a certain amount or simply decreases, and the number of pumps operated changes to correspond to the amount of water Provides a water supply device that changes the number of operating pumps without taking time at the time of parallel operation start and release, so that there is little pressure fluctuation at the place where water is used and water supply with good responsiveness to increase or decrease in usage I can do it.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between a discharge amount and a discharge pressure of a water supply unit performing parallel operation according to the present invention, a curve using the number of pumps operated and pump rotation speed as parameters, and a resistance curve of a water supply piping system. .
FIG. 2 is a diagram schematically showing a device configuration of a water supply apparatus according to the present invention.
FIG. 3 is a diagram showing a control flowchart according to the present invention.
FIG. 4 is a diagram showing a control flowchart according to the present invention.
FIG. 5 is a diagram showing a control flowchart according to the present invention.
FIG. 6 is a graph showing the relationship between the discharge amount and the discharge pressure of a conventional water supply unit performing parallel operation, a curve using the number of pumps operated and the number of pump rotations as parameters, and a resistance curve of the water supply piping system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Water receiving tank 4 Pump 5 Discharge piping 6 Discharge side gate valve 7 Check valve 8 Water supply pipe 9 Pressure detector 10 Pressure tank 11 Customer 12 Controller 13 Power supply

Claims (2)

  In the water supply system with multiple pumps that control the pump rotation speed and perform constant discharge pressure control, the pump start pressure and the stop pressure that start the second and subsequent pumps together with the number of pumps operating simultaneously Except for the pump that starts, the first rotation speed that is less than the maximum rotation speed and the minimum rotation speed and the first rotation speed except for the pump that starts first and last, according to the pump start sequence In addition, in the pump to be started last, the second rotation speed is set between the minimum rotation speed and the maximum rotation speed, and the pump operating at the first rotation speed or less decelerates halfway. If the maximum number of revolutions of the pump is reached, the pumps in the next starting sequence are immediately started at the predetermined minimum number of revolutions corresponding to the starting sequence, and the pumps are operated at the second or higher number of revolutions. The pump that had been If the minimum speed of the pump is reached, the pump is immediately stopped, and a pump reaches the maximum speed of the pump after the passage of other than the above, regardless of the initial rotational speed. If the discharge pressure falls below the starting pressure of the next pump, the pump of the next starting sequence is started after confirming that the discharging pressure is maintained at a value below the starting pressure for a predetermined time. Regardless of the rotational speed at which the pump was initially operated, if a pump reaches the minimum rotational speed of the pump after the passage of other than the above, and the discharge pressure becomes equal to or higher than the stop pressure of the pump, it is determined in advance. A control method at the time of starting and releasing the parallel operation of the water supply device, wherein the pump is stopped after confirming that the discharge pressure is maintained at a value equal to or higher than the discharge pressure for a predetermined time.   In the water supply system with multiple pumps that control the number of rotations of the pump and perform constant control of the estimated end pressure, together with the starting pressure and stopping pressure of the pump that starts the second and later, Corresponding to the starting sequence of the pumps, except for the first starting number of rotations less than the maximum number of rotations and the minimum number of rotations and the first number of rotations except for the first and last starting pumps. In the meantime, in the last pump to be started, the second rotation speed is set between the minimum rotation speed and the maximum rotation speed, and the pump operating at or below the first rotation speed is decelerated halfway. If the maximum rotation speed of the pump is reached without starting, the pump in the next starting sequence is immediately started at the predetermined minimum rotation speed corresponding to the starting sequence, and the pump is operated at the second rotation speed or higher. The pump I was using increased speed If the minimum speed of the pump is reached without stopping, the pump is immediately stopped. Regardless of the speed at which the pump was originally operated, after the passage of other than the above, a pump reaches the maximum speed of the pump. When the discharge pressure falls below the starting pressure of the next pump, the pump in the next starting sequence is started after confirming that the discharging pressure is maintained at a value below the starting pressure for a predetermined time. Regardless of the rotational speed at which the pump was originally operated, if a pump reaches the minimum rotational speed of the pump and the discharge pressure becomes equal to or higher than the stop pressure of the pump after a passage other than the above, it is determined in advance. A control method at the time of starting and canceling parallel operation of the water supply device, wherein the pump is stopped after confirming that the pump pressure is maintained at a value equal to or higher than the discharge pressure for a given time.

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