Pump system and control method of pump system

Abstract

To suppress an operation / stop frequency of a pump device to enable a unit number control with an excellent energy efficiency and to suppress a pressure insufficiency on a demand side.SOLUTION: A pump system includes: a plurality of pump devices for sucking water from an intake water tank and sends out the water to a discharge water tank; a discharge water tank water level gauge for measuring a water level of the discharge water tank; and a control device for controlling the drive of the pump device. The control device includes: a demanded water flow rate calculation part for calculating a demanded water flow rate required on a downstream side of the discharge water tank every predetermined time; and a drive control part for controlling the number of pump devices driven based on the demanded water flow rate and a discharge water tank level. Further, the pump system includes a discharge valve provided between the pump device and the discharge water tank, and capable of increasing and decreasing a water amount sent to the discharge water tank depending on an opening degree. The control device includes a discharge valve opening degree control part for controlling the opening degree of the discharge valve depending on the demanded water flow rate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pump system for pumping irrigation water or drinking water to a discharge tank for distribution by gravity, and a method for controlling such a pump system. [Background technology]

[0002] In a semi-closed pipeline pumping system using multiple fixed-speed pumps to pump irrigation water or drinking water to a discharge tank for distribution by gravity, the number of pumps in operation is increased or decreased depending on the fluctuations in the water level in the tank on the discharge side of the pump (discharge tank). That is, when the water level in the discharge tank drops and reaches the lower limit, the number of pumps in operation is increased in sequence, thereby increasing the amount of water pumped to the discharge tank. On the other hand, when the water level in the discharge tank rises and reaches the upper limit, the number of pumps in operation is decreased in sequence, thereby decreasing the amount of water pumped to the discharge tank. In this way, the amount of water pumped to the discharge tank is adjusted by controlling the number of pumps in operation depending on the water level in the discharge tank. Summary of the Invention [Problem to be solved by the invention]

[0003] Here, the outflow rate from the discharge tank fluctuates continuously depending on the usage status of downstream consumers, and the pumping rate from multiple fixed-speed pumps changes in stages, so the water level in the discharge tank does not remain constant.Since the pumping rate to the discharge tank is accompanied by a sudden flow rate fluctuation equivalent to that of one pump when the number of pumps in operation increases or decreases, if it is not balanced with the outflow rate from the discharge tank, the water level in the discharge tank will deviate from the range of increase or decrease in the number of pumps, and the number of pumps in operation will have to be repeatedly increased or decreased, resulting in poor energy efficiency.

[0004] In addition, because the pump starts with the discharge valve fully closed, harmful cavitation occurs when the discharge valve is slightly or slightly opened immediately after the pump starts. If the pump is repeatedly started and stopped, the frequency of cavitation increases, which also affects the pump's lifespan.

[0005] Here, operating the pump with the water level in the discharge tank low reduces the actual pump head and reduces operating power, which is desirable from an energy-saving perspective, but the water level setting in the discharge tank is predetermined due to the control of the number of pumps. Also, when the water demand increases, the water level in the discharge tank becomes relatively low, but in that case, the water level falls below the level that can maintain the pressure required by the consumer, causing problems such as a partial pressure shortage on the demand side.

[0006] The present invention has been made in consideration of the above, and its object is to provide a pump system and a control method for such a pump system that uses multiple fixed-speed pumps, and that can perform energy-efficient pump number control by reducing the frequency of pump operation / stop, and can also prevent pressure shortages on the demand side. [Means for solving the problem]

[0007] In view of the above, one aspect of the present invention is a pump system comprising a plurality of pump units that suck water from a suction tank and deliver it to a discharge tank, a discharge tank water level meter that measures the water level in the discharge tank, and a control device that controls the operation of the pump units. The control device is configured to include a water demand flow rate calculation unit that calculates the water demand flow rate required downstream of the discharge tank at predetermined intervals, and a drive control unit that controls the number of pump units to be operated based on the water demand flow rate and the discharge tank water level.

[0008] The control device in the above pump system may be configured to increase the number of pump devices to be driven when the demand water flow rate reaches a first set value, and to decrease the number of pump devices to be driven when the measured water level in the discharge tank reaches a second set value.

[0009] The pump system may further include a discharge valve disposed between the pump device and the discharge tank, and capable of increasing or decreasing the amount of water delivered to the discharge tank depending on the valve opening, and the control device may further include a discharge valve opening control unit that controls the valve opening depending on the amount of water demand. In this case, the control device may control the number of pump devices to be driven to increase after the discharge valve is fully opened.

[0010] Another aspect of the present invention is a control method for a pump system having multiple pump devices that suck water from an suction tank and deliver it to a discharge tank, and a discharge tank water level meter that measures the water level in the discharge tank, and includes a demand water flow rate calculation step that calculates the demand water flow rate required downstream of the discharge tank at predetermined time intervals, and a drive control step that controls the number of pump devices to be driven based on the demand water flow rate and the discharge tank water level. [Effects of the Invention]

[0011] According to the present invention, by reducing the frequency of pump operation / stop, it is possible to perform energy-efficient pump number control and also to prevent pressure shortages on the demand side. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a pump system according to a first embodiment. [Figure 2] 10 is a flowchart showing an example of a demand water flow rate calculation. [Figure 3] 10 is a flowchart illustrating an example of control of the number of pumps. [Figure 4] 4 is a graph showing an example of drive characteristics of a pump system. [Figure 5] 10 is a graph showing the simulation results of the pump discharge water level, discharge flow rate, shaft power, and number of starts in the switching control between the first and second pumps. [Figure 6] 10 is a graph showing the simulation results of the pump discharge water level, discharge flow rate, shaft power, and number of starts in the switching control between the second and third pumps. [Figure 7]FIG. 10 is a schematic configuration diagram of a pump system according to a second embodiment. [Figure 8] 10 is a flowchart showing an example of a demand water flow rate calculation and a discharge valve control opening target value calculation. [Figure 9] 4 is a graph showing an example of opening characteristics of a discharge valve. [Figure 10] 10 is a flowchart illustrating an example of control of the number of pumps. [Figure 11] 10 is a flowchart illustrating an example of control of the number of pumps. [Figure 12] 4 is a graph showing an example of drive characteristics of a pump system. [Figure 13] 10 is a graph showing the simulation results of the pump discharge water level, discharge flow rate, shaft power, and number of starts in the switching control between the first and second pumps. [Figure 14] 10 is a graph showing the simulation results of the pump discharge water level, discharge flow rate, shaft power, and number of starts in the switching control between the second and third pumps. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram of a pump system according to a first embodiment. Pump system 10 includes a suction tank 11, pump units 20-1, 20-2, and 20-3, a discharge tank 30, and a control device 40. Pump system 10 in this embodiment constitutes a system that pumps water, for example, irrigation water or clean water, to a discharge tank for distribution by gravity.

[0014] Pump units 20-1, 20-2, and 20-3 are fixed-speed pumps, and their suction pipe 24 side is connected to suction tank 11 via stop valve 12, and they are driven by motors 21-1, 21-2, and 21-3, respectively. When pump units 20-1, 20-2, and 20-3 are driven, impellers (not shown) installed inside rotate at a predetermined speed, pumping up liquid (e.g., irrigation water or drinking water) stored in suction tank 11 and sending it to discharge tank 30 via discharge pipe 25.

[0015] Pump devices 20-1, 20-2, 20-3 are each provided with pump discharge valves 22-1, 22-2, 22-3 on the discharge pipe side, allowing adjustment of the flow rate of water discharged from pump devices 20-1, 20-2, 20-3. Discharge pipe 25 is provided with a water flow meter 26 that measures the water flow rate, which is the flow rate of water delivered to discharge water tank 30, and a pressure gauge 27 that measures the water pressure, which is the pressure of water delivered to discharge water tank 30.

[0016] A suction tank water level gauge 13 that measures the water level is attached to the suction tank 11. In addition, on the upstream side (suction side) of the suction tank 11, a water intake flow meter 14 that measures the amount of water flowing into the suction tank 11 and a water intake valve 15 installed at the suction port of the suction tank 11 are provided.

[0017] A discharge tank water level gauge 31 is attached to the discharge tank 30 to measure its water level (discharge tank water level). A demand water outflow valve 33 is provided downstream (on the discharge side) of the discharge tank 30 to adjust the flow rate of demand water discharged from the discharge tank 30. As will be described later, the demand water flow rate is calculated by the control device 40, but a demand water flow meter may be provided to measure the gravity outflow rate (demand water volume) from the discharge tank 30 as a backup in case the calculated demand water flow rate is abnormal.

[0018] With conventional pump operation number control, a new pump is started when the discharge tank water level reaches a predetermined lower limit and the currently operating pump is stopped when it reaches an upper limit. However, if the discharge tank water level is maintained within a certain range based on the amount of water supplied by the currently operating pumps, the pump water volume and water demand will be balanced, and pump operation will be stable. However, with conventional pump operation number control, an additional pump will be started if the discharge tank water level reaches a predetermined lower limit, even if the water demand is not that high. On the other hand, a pump will be stopped if the discharge tank water level reaches a predetermined upper limit, even if the water demand is high. As a result, even when there is relatively little need to start and stop a pump, there is the problem of one pump repeatedly starting and stopping, wasting power.

[0019] Therefore, in the pump system 10 according to this embodiment, the drive and stop of the pump are controlled based not only on the discharge tank water level but also on the calculated water demand. The control device 40 according to this embodiment is, for example, a general-purpose computer, and operates as a control unit including a water demand flow rate calculation unit 41 and a motor drive control unit 42 by starting a control program stored in a storage unit 43. The control program may be installed in the computer constituting the control device 40, or may be stored in a storage medium such as a DVD, BD, or SSD, or may be installed in the control device 40 via the Internet.

[0020] The demand water flow rate calculation unit 41 calculates the demand water flow rate QD at regular intervals (Δtd) according to a flowchart (see FIG. 2) described later. The motor drive control unit 42 is connected to the motor devices 20-1, 20-2, and 20-3, and controls the number of motor devices to be driven according to a flowchart (see FIG. 3) described later. In addition to the control program described above, the memory unit 43 stores set values ​​for the demand water flow rate and discharge tank water level that serve as the basis for starting and stopping the pump devices, and data on the actual head curve (the curve relating flow rate to discharge pressure) for each pump device that is determined in advance through testing.

[0021] 2 is a flowchart showing an example of the calculation process of the demand water flow rate in the demand water flow rate calculation unit 41. The calculation of the demand water flow rate QD is performed based on the calculated value of the discharge flow rate Qp calculated for each set period (Δtp) pre-recorded in the storage unit 43.

[0022] In step S10, the actual head H0 (=Ld-Ls) is calculated from the discharge tank water level Ld measured by the discharge tank water level gauge 31 and the suction tank water level Ls measured by the suction tank water level gauge 13. Next, in step S11, the discharge flow rate Qp corresponding to the calculated actual head H0 is calculated based on the actual head curve data (corresponding to the pump device currently being driven) previously recorded in the memory unit 43. i (where i is the number of the pump device currently being driven). In step S12, the discharge flow rate Qp corresponding to the pump device currently being driven is calculated. i The total value (discharge flow rate) Qp (=ΣQp i ) is calculated.

[0023] In step S13, the calculated discharge flow rate Qp and the piping loss coefficient α stored in the storage unit 43 are used to calculate the piping loss Hf (=α×Qp 2 Next, in step S14, the sum of the piping loss Hf and the actual head H0 is calculated as the total head Hp.

[0024] The demand water flow rate QD can be calculated at each cycle (Δtd) preset in the memory unit 43 as follows. In step S20, the discharge tank water level difference ΔLd (= Ld - Ld [-Δtd]) is calculated from the value of the discharge tank water level Ld measured by the discharge tank water level gauge 31 and the value of the discharge tank water level Ld [-Δtd] measured the previous cycle (one cycle before). Then, in step S21, the discharge tank storage change amount ΔVd (= Ad × ΔLd) is calculated based on the discharge tank bottom area Ad pre-stored in the memory unit 43. Next, in step S22, the demand water flow rate QD (= Qp - ΔVd / Δtd) is calculated from the total discharge flow rate Qp calculated in step S12 and the value of the discharge tank storage change amount ΔVd calculated in step S21. In step S23, the conversion value QD of the demand water flow rate per pump device according to the number i of pump devices currently being driven is calculated. i Calculate (=QD / i).

[0025] FIG. 3 is a flowchart showing an example of motor device drive / stop control by the motor drive control unit 42. In step S30, the motor drive control unit 42 acquires the demand water flow rate QD calculated as described above and the discharge tank water level Ld measured by the discharge tank water level gauge 31. Next, in step S31, it is determined whether the demand water flow rate QD is equal to or greater than the set value Qp1s and whether the discharge tank water level Ld is equal to or less than the set value Ld1s. If the demand water flow rate QD is equal to or greater than the set value Qp1s or if the discharge tank water level Ld is equal to or less than the set value Ld1s ("Y" in step S31), it is determined that the demand water flow rate is high or the discharge tank water level is low, and the first pump device 20-1 is started. Note that in this embodiment, the pump device to be driven or stopped among the three pump devices 20-1 to 20-3 can be determined as appropriate.

[0026] When the first pump unit 20-1 is driven, water is pumped from the suction tank 11 to the discharge tank 30, and the water level in the discharge tank 30 fluctuates depending on the amount of water sent out from the discharge tank 30 (demanded water flow rate) and the amount of water pumped by the pump unit 20-1. In step S33, the motor drive control unit 42 acquires the demanded water flow rate QD calculated as described above and the discharge tank water level Ld measured by the discharge tank water level gauge 31. Next, in step S34, it is determined whether the discharge tank water level Ld exceeds a set value Ld1e. If it does ("Y" in step S34), it is determined that the amount of water supplied by the pump unit 20-1 is too high, and the pump unit 20-1 is stopped (step S35). Thereafter, the process returns to step S30, where it is determined whether to drive the first pump unit 20-1.

[0027] On the other hand, if the discharge tank water level Ld does not exceed the set value Ld1e ("N" in step S34), the process proceeds to step S36, where it is determined whether the calculated water demand flow rate QD is equal to or greater than the set value Qp1max. If the water demand flow rate QD is equal to or greater than the set value Qp1max ("Y" in step S34), it is determined that one pump device alone cannot meet the water demand flow rate, and the second pump device 20-2 is started (step S37). On the other hand, if the water demand flow rate QD has not reached the set value Qp1max ("N" in step S34), the process returns to step S33, and the same determination process is performed again.

[0028] As the second pump unit 20-2 is driven, the amount of water pumped from the suction tank 11 to the discharge tank 30 increases, and the water level in the discharge tank 30 fluctuates depending on the amount of water sent out from the discharge tank 30 (demanded water flow rate) and the amount of water pumped by the pump units 20-1 and 20-2. In step S38, the motor drive control unit 42 acquires the demanded water flow rate QD calculated as described above and the value of the discharge tank water level Ld measured by the discharge tank water level gauge 31. Next, in step S39, it is determined whether the discharge tank water level Ld exceeds the set value Ld2e. If it does ("Y" in step S39), it is determined that the amount of water supplied by the two pump units 20-1 and 20-2 is too high, and the second pump unit 20-2 is stopped (step S40), and the process proceeds to step S33.

[0029] On the other hand, if the discharge tank water level Ld does not exceed the set value Ld2e ("N" in step S39), the process proceeds to step S41, where it is determined whether the calculated water demand flow rate QD is equal to or greater than the set value Qp2max. If the water demand flow rate QD is equal to or greater than the set value Qp2max ("Y" in step S41), it is determined that the water demand flow rate cannot be met with just two pump devices, and the third pump device 20-3 is started (step S42). On the other hand, if the water demand flow rate QD has not reached the set value Qp2max ("N" in step S41), the process returns to step S38, and the same determination process is performed again.

[0030] By driving the third pump unit 20-3, the amount of water pumped from the suction tank 11 to the discharge tank 30 further increases, and the water level in the discharge tank 30 fluctuates depending on the amount of water sent out from the discharge tank 30 (demanded water flow rate) and the amount of water pumped by the pump units 20-1 to 20-3. In step S43, the motor drive control unit 42 acquires the demanded water flow rate QD calculated as described above and the value of the discharge tank water level Ld measured by the discharge tank water level gauge 31. Next, in step S44, it is determined whether the discharge tank water level Ld exceeds a set value Ld3e. If it does ("Y" in step S44), it is determined that the amount of water supplied by the three pump units 20-1 to 20-3 is too high, and the third pump unit 20-3 is stopped (step S45), and the process proceeds to step S38.

[0031] On the other hand, if the discharge tank water level Ld does not exceed the set value Ld3e ("N" in step S44), the process proceeds to step S46, where it is determined whether the calculated water demand flow rate QD is equal to or greater than the set value Qp3max. If the water demand flow rate QD is equal to or greater than the set value Qp3max ("Y" in step S46), it is determined that the three pump devices are not sufficient to handle the water demand flow rate, and a warning message is displayed (step S47). On the other hand, if the water demand flow rate QD has not reached the set value Qp3max ("N" in step S46), the process returns to step S43, and the same determination process is performed again.

[0032] FIG. 4 shows an example of a characteristic curve for a pump system according to this embodiment. In FIG. 4, the horizontal axis represents flow rate, and the vertical axis represents discharge pressure. "HQ1" represents the characteristic curve for a single pump unit, "HQ2" represents the characteristic curve for two pump units, and "HQ3" represents the characteristic curve for three pump units. Also, in FIG. 4, "h1" represents the discharge pressure (water level equivalent to the first pump unit start-up flow rate) corresponding to the demand water flow rate (calculated based on the flowchart in FIG. 2) required to start the first pump unit, "h2" represents the discharge pressure (water level equivalent to the second pump unit start-up flow rate) corresponding to the demand water flow rate required to start the second pump unit, and "h3" represents the discharge pressure (water level equivalent to the third pump unit start-up flow rate) corresponding to the demand water flow rate required to start the third pump unit. The graph at the bottom of FIG. 4 shows the relationship between flow rate and driving force, and "P1," "P2," and "P3" represent graphs for a single, two, and three pump units, respectively.

[0033] In Figure 4, when all three pump units are stopped, the discharge tank water level drops due to the supply of demand water, and when the discharge tank water level Ld reaches the first unit start-up water level or the demand water flow rate QD reaches the first unit start-up flow rate (discharge pressure: h1), the first pump unit 20-1 starts operating, and its operating point reaches the intersection of curves HQ1 and h1 (flow rate q2). Note that when operating the first pump unit, in order to prevent an abnormal drop in the discharge tank water level, the decision is made not only based on the demand water flow rate QD but also on the discharge tank water level Ld.

[0034] Thereafter, if the water demand is small, the water level in the discharge tank increases, the operating point moves toward the upper left on curve HQ1, and when the water level in the discharge tank 30 reaches the stop water level Ld1e (flow rate q1), the first pump device 20-1 stops.

[0035] On the other hand, if the water demand is large, the water level in the discharge tank drops further, the operating point moves downward and to the right on curve HQ2, and when the water demand flow rate QD reaches the second pump unit starting flow rate (discharge pressure: h2), the second pump unit 20-2 starts operating, and its operating point reaches the intersection of curves HQ2 and h2 (flow rate q5). After that, if the water demand is small, the water level in the discharge tank increases, the operating point moves upward and to the left on curve HQ2, and when the water level in the discharge tank 30 reaches the stop water level Ld2e (flow rate q4), the second pump unit 20-2 stops.

[0036] On the other hand, if the water demand is large, the water level in the discharge tank drops further, the operating point moves downward and to the right on curve HQ2, and when the water demand flow rate QD reaches the third pump unit starting flow rate (discharge pressure: h3), the third pump unit 20-3 starts operating, and its operating point reaches the intersection of curves HQ3 and h3 (flow rate q8). After that, if the water demand is small, the water level in the discharge tank increases, the operating point moves upward and to the left on curve HQ3, and when the water level in the discharge tank 30 reaches the stop water level Ld3e (flow rate q7), the third pump unit 20-3 stops.

[0037] In the example of Figure 4, each pump device 20-1 to 20-3 is stopped with the water level in the discharge tank kept high, which allows for more time (stop time) until the water level in the discharge tank drops and the pump device is started again, thereby reducing the frequency of operation / stop of the pump device.

[0038] Figures 5 and 6 are graphs showing an example of the time-dependent changes in the water level, flow rate, shaft power of the pump units, and start count of the discharge tank 30. Figure 5 shows the operation and stop of the second pump unit while the first pump unit is operating, and Figure 6 shows the operation and stop of the third pump unit while the first and second pump units are operating. Figures 5 and 6 also show a conventional example (dotted line) in which the operation and stop of the pump units is switched based only on the discharge tank water level, and an example of the first embodiment (solid line) in which the operation and stop of the pump units is switched based on the demand water flow rate and the discharge tank water level.

[0039] Compared to the conventional example, the pump system according to the embodiment shows that the time interval for switching on / off the pump device is longer and the number of times the pump is started is reduced. Therefore, the pump system according to this embodiment makes it possible to control the number of pumps in an energy-efficient manner by reducing the frequency of pump operation / stop, and also to prevent pressure shortages on the demand side.

[0040] (Second embodiment) Figure 7 is a schematic diagram of a pump system 50 according to a second embodiment. In this second embodiment, the drive and stop control of pump devices is performed based on the demand water flow rate and the discharge tank water level, and the discharge tank water level is controlled by adjusting the opening of the discharge valve connected to each pump device. Note that components that are the same as those according to the first embodiment (see Figure 1) above are given the same reference numerals and detailed description will be omitted.

[0041] 7, pump system 50 includes suction tank 11, pump units 20-1, 20-2, and 20-3, discharge tank 30, and control device 60. Control device 60 is, for example, a general-purpose computer, and operates as a control unit including a demand water flow rate calculation unit 61, a motor drive control unit 62, a discharge valve opening target value calculation unit 63, and a discharge valve opening control unit 64 by starting a control program stored in memory unit 65.

[0042] Similar to the first embodiment, the demand water flow rate calculation unit 61 calculates the demand water flow rate QD for each fixed period (Δtd) (see the flowchart in FIG. 2). The motor drive control unit 42 is connected to the motor devices 20-1, 20-2, and 20-3, and controls the number of motor devices to be driven according to the flowcharts (see FIGS. 9 and 10) described later. The discharge valve opening target value calculation unit 63 calculates the openings of the discharge valves 22-1, 22-2, and 22-3 connected to the motor devices being driven according to the flowchart (see FIG. 8) described later. The discharge valve opening control unit 64 is connected to the discharge valves 22-1, 22-2, and 22-3, and controls the openings of the corresponding discharge valves based on the calculation results by the discharge valve opening target value calculation unit 63.

[0043] In addition to the control program mentioned above, the memory unit 63 stores various information such as the set values ​​of the demand water flow rate and discharge tank water level that serve as the basis for starting and stopping the pump device, data on the actual head curve (the curve relating flow rate to discharge pressure) for each pump device that is determined in advance through testing, and the opening characteristic value of the discharge valve.

[0044] 8 is a flowchart showing an example of a process for calculating the target value of the discharge valve opening in the discharge valve opening target value calculation unit 63. iSV The calculation is performed for each set period (Δtv) recorded in advance in the storage unit 63.

[0045] In step S100, the discharge water tank water level Ld measured by the discharge water tank water level gauge 31 and the suction water tank water level Ls measured by the suction water tank water level gauge 13 are used to calculate the discharge flow rate Qp corresponding to the actual head H0 calculated based on the data of the actual head curve. i (where i is the number of the pump device currently in operation), the total discharge flow rate Qp (=ΣQp i In step S102, the demand water flow rate QD is calculated in the same manner as in the first embodiment. The above processing can be performed in the demand water flow rate calculation unit 61.

[0046] In step S103, the discharge valve opening target value calculation unit 63 calculates the total discharge flow rate target value Qp based on the demand water flow rate QD calculated in step S101. SV Next, in step S105, the target discharge flow rate per unit Qp iSV (=Qp SV In step S106, the piping loss coefficient α recorded in the storage unit 43 is used to calculate the piping loss (target value) Hf SV (=α×(Qp SV ) 2 ) is calculated.

[0047] In step S107, the discharge valve differential pressure (target value) Hfv is calculated based on the actual head H0 and the total head Hp calculated in the same manner as described in the first embodiment. SV (=Hp-H0-Hf SV ) is calculated. Then, in step S108, the discharge valve opening Zv is calculated based on the opening characteristic. iSV Calculate the following.

[0048] Discharge valve opening Zv based on opening characteristics iSV The calculation of the discharge valve loss coefficient ζ and the discharge valve opening Zv iSV 1 is a graph showing an example of the relationship between the discharge valve loss coefficient ζ and the pressure loss coefficient ζ. ζ=2×g×Av 2 ×Hfv SV / Qp iSV Here, g represents the gravitational acceleration, and Av represents the cross-sectional area of ​​the discharge valve flow path. iSV and the discharge valve differential pressure (target value) Hfv calculated in step S107. SV Then, based on the data of the opening characteristic shown in Figure 9, the discharge valve opening Zv corresponding to the loss coefficient ζ can be calculated. iSV The value of can be obtained.

[0049] FIG. 10 is a flowchart showing an example of motor drive / stop control by the motor drive control unit 62. In step S110, the motor drive control unit 62 acquires the demand water flow rate QD calculated as described above and the discharge tank water level Ld measured by the discharge tank water level gauge 31. Next, in step S111, it is determined whether the demand water flow rate QD is equal to or greater than the set value Qp1s and whether the discharge tank water level Ld is equal to or less than the set value Ld1s. If the demand water flow rate QD is equal to or greater than the set value Qp1s or if the discharge tank water level Ld is equal to or less than the set value Ld1s ("Y" in step S111), it is determined that the demand water flow rate is high or the discharge tank water level is low, and the first pump unit 20-1 is started (step S112). When the first pump unit 20-1 is driven, water is pumped from the suction tank 11 to the discharge tank 30. The water level in the discharge tank 30 fluctuates depending on the amount of water sent out from the discharge tank 30 (demanded water flow rate) and the amount of water pumped up by the pump device 20-1.

[0050] After the first pump device 20-1 is driven, discharge valve opening control is performed on the first pump device 20-1 (step S113). For example, based on the demand water flow rate and the discharge flow rate, the discharge valve opening can be gradually increased if the demand water flow rate is large, and conversely, gradually decreased if the discharge flow rate is large. In step S114, the motor drive control unit 62 acquires the demand water flow rate QD calculated as described above and the discharge water tank water level Ld measured by the discharge water tank water level gauge 31. Next, in step S115, it is determined whether the demand water flow rate QD has reached the set value Qp1. If it has not reached the set value Qp1 ("N" in step S115), the process proceeds to step S116, where it is determined whether the demand water flow rate QD has reached the set value Qp1min. If it has not reached the set value Qp1min ("N" in step S116), the process proceeds to step S113, and the discharge valve opening control is repeated.

[0051] On the other hand, if the demand water flow rate QD reaches the set value Qp1min, the flow rate target value is set to Qp1min (step S117), and a determination is made in step S118 as to whether the discharge tank water level Ld has exceeded the set value Ld1e. If it has not reached the set value Ld1e ("N" in step S118), the process proceeds to step S113, and discharge valve opening control is repeated. On the other hand, if it has reached the set value Ld1e ("Y" in step S118), the process determines that the amount of water supply by pump unit 20-1 is too high, and pump unit 20-1 is stopped (step S119). Thereafter, the process returns to step S110, and a determination is made as to whether to drive the first pump unit 20-1.

[0052] In step S115, if the demand water flow rate QD reaches the set value Qp1 ("Y" in step S115), the discharge valve 22-1 is fully opened (step S120). Then, in step S121, it is determined whether the calculated demand water flow rate QD is equal to or greater than the set value Qp1max. If the demand water flow rate QD is equal to or greater than the set value Qp1max ("Y" in step S121), it is determined that one pump device alone cannot meet the demand water flow rate, and the second pump device 20-2 is started (step S122). On the other hand, if the demand water flow rate QD has not reached the set value Qp1max ("N" in step S121), the process returns to step S113 and the discharge valve opening control is repeated.

[0053] After the second pump unit 20-2 is driven, discharge valve opening control is performed on the two pump units 20-1 and 20-2 (step S123). For example, based on the demand water flow rate and the discharge flow rate, the discharge valve opening can be gradually increased if the demand water flow rate is large, and conversely, gradually decreased if the discharge flow rate is large. In step S124, the motor drive control unit 62 acquires the demand water flow rate QD calculated as described above and the discharge water tank water level Ld measured by the discharge water tank water level gauge 31. Next, in step S125, it is determined whether the demand water flow rate QD has reached the set value Qp2. If it has not reached the set value Qp2 ("N" in step S125), the process proceeds to step S126, where it is determined whether the demand water flow rate QD has reached the set value Qp2min. If it has not reached the set value Qp2min ("N" in step S126), the process proceeds to step S123, and the discharge valve opening control is repeated.

[0054] On the other hand, if the demand water flow rate QD reaches the set value Qp2min, the flow rate target value is set to Qp2min (step S127), and a determination is made in step S128 as to whether the discharge tank water level Ld has exceeded the set value Ld2e. If it has not reached the set value ("N" in step S128), the process proceeds to step S123, and discharge valve opening control is repeated. On the other hand, if it has reached the set value ("Y" in step S128), it is determined that the water supply amount from the two pump devices 20-1 and 20-2 is too large, and pump device 20-2 is stopped (step S129). Thereafter, the process returns to step S113, and processing for controlling the discharge valve opening of the first pump device 20-1 is performed.

[0055] In step S125, if the demand water flow rate QD reaches the set value Qp2 ("Y" in step S125), the discharge valve 22-2 is fully opened (step S130). Then, in step S131, it is determined whether the calculated demand water flow rate QD is equal to or greater than the set value Qp2max. If the demand water flow rate QD is equal to or greater than the set value Qp2max ("Y" in step S131), it is determined that two pump devices alone cannot meet the demand water flow rate, and the third pump device 20-3 is started (step S132). On the other hand, if the demand water flow rate QD has not reached the set value Qp3max ("N" in step S131), the process returns to step S123 and the discharge valve opening control is repeated.

[0056] After the third pump unit 20-3 is driven, discharge valve opening control is performed on the three pump units 20-1, 20-2, and 20-3 (step S133). For example, based on the demand water flow rate and the discharge flow rate, the discharge valve opening can be gradually increased if the demand water flow rate is large, and conversely, gradually decreased if the discharge flow rate is large. In step S134, the motor drive control unit 62 acquires the demand water flow rate QD calculated as described above and the discharge water tank water level Ld measured by the discharge water tank water level gauge 31. Next, in step S135, it is determined whether the demand water flow rate QD has reached the set value Qp3. If it has not reached the set value Qp3 ("N" in step S135), the process proceeds to step S136, where it is determined whether the demand water flow rate QD has reached the set value Qp3min. If it has not reached the target value ("N" in step S136), the process proceeds to step S133, and the discharge valve opening control is repeated.

[0057] On the other hand, if the demand water flow rate QD reaches the set value Qp3min, the flow rate target value is set to Qp3min (step S137), and a determination is made in step S138 as to whether the discharge tank water level Ld has exceeded the set value Ld3e. If it has not reached the set value ("N" in step S138), the process proceeds to step S133, and discharge valve opening control is repeated. On the other hand, if it has reached the set value ("Y" in step S138), it is determined that the water supply amount from the three pump devices 20-1 to 20-3 is too high, and pump device 20-3 is stopped (step S139). Thereafter, the process returns to step S123, and processing for controlling the discharge valve opening of the two pump devices 20-1 and 20-2 is performed.

[0058] In step S135, if the demand water flow rate QD reaches the set value Qp3 ("Y" in step S135), the discharge valve 22-3 is fully opened (step S140). Then, in step S141, it is determined whether the calculated demand water flow rate QD is equal to or greater than the set value Qp3max. If the demand water flow rate QD is equal to or greater than the set value Qp3max ("Y" in step S141), it is determined that the three pump devices cannot handle the demand water flow rate, and excessive flow rate processing is performed (step S142). On the other hand, if the demand water flow rate QD has not reached the set value Qp3max ("N" in step S141), the process returns to step S133 and the discharge valve opening control is repeated.

[0059] Fig. 11 shows an example of a characteristic curve of a pump system according to the second embodiment. In Fig. 11, the horizontal axis represents flow rate and the vertical axis represents discharge pressure. "HQ1" is the characteristic curve when one pump unit is operating, "HQ2" is the characteristic curve when two pump units are operating, and "HQ3" is the characteristic curve when three pump units are operating. Furthermore, "HQ1'", "HQ2'", and "HQ3'" are the characteristic curves when one, two, and three pump units are operating at the minimum operable flow rate (minimum discharge opening), respectively.

[0060] In Figure 11, "h1", "h2", and "h3" respectively represent the discharge pressures (water levels equivalent to starting flow rates) corresponding to the demand water flow rates that start the first, second, and third pump devices, as in the flowchart of Figure 4.

[0061] In Figure 11, when all three pump devices are stopped, the discharge tank water level drops due to the supply of demand water, and when the discharge tank water level Ld reaches the first unit start-up water level or the demand water flow rate QD reaches the first unit start-up flow rate (discharge pressure: h1), the first pump device 20-1 starts up, and its operating point reaches the intersection (flow rate q1) of curves HQ1' and h1. Note that when driving the first pump device, in order to prevent an abnormal drop in the discharge tank water level, judgment is made not only based on the demand water flow rate QD but also on the discharge tank water level Ld.

[0062] Thereafter, the opening degree of the discharge valve 22-1 corresponding to the pump device 20-1 is controlled according to the magnitude of the water demand and discharge water volume. Here, when the water demand is large, the discharge valve 22-1 gradually opens, and when the flow rate reaches q2, the discharge valve 22-1 is fully opened, and the pump device 20-1 is operated according to the characteristic curve HQ1.

[0063] On the other hand, when the water demand is small, the discharge valve 22-1 is controlled to have a smaller opening, but when the water level in the discharge tank increases and reaches Ld1e, the first pump device 20-1 stops.

[0064] When discharge valve 22-1 is fully open, if the water demand is high, the discharge tank water level will further drop, and the operating point will move downward and to the right along curve HQ1. When the water demand flow rate QD reaches the second-unit starting flow rate (discharge pressure: h2), the second pump unit 20-2 will be activated, and its operating point will reach the intersection of curves HQ2' and h2 (flow rate q4). Thereafter, the opening degrees of discharge valves 22-1 and 22-2 corresponding to pump units 20-1 and 20-2 are controlled according to the magnitude of the water demand and discharge rate. Here, if the water demand is high, discharge valves 22-1 and 22-2 will gradually open, and when the flow rate reaches q6, discharge valves 22-1 and 22-2 will be fully open, and pump units 20-1 and 20-2 will operate according to characteristic curve HQ2.

[0065] On the other hand, when the water demand is small, the discharge valves 22-1 and 22-2 are controlled to have a smaller opening, but when the discharge tank water level increases and reaches the stop water level Ld2e, the second pump device 20-2 is stopped.

[0066] When discharge valves 22-1 and 22-2 are fully open, if the water demand is large, the discharge tank water level will further drop, the operating point will move downward and to the right on curve HQ2, and when the water demand flow rate QD reaches the third-unit starting flow rate (discharge pressure: h3), the third pump unit 20-3 will be activated. Thereafter, the apertures of discharge valves 22-1 to 22-3 corresponding to pump units 20-1 to 20-3 are controlled according to the water demand and discharge rate. Here, if the water demand is large, discharge valves 22-1 to 22-3 will gradually open, and when the flow rate reaches q8, discharge valves 22-1 to 22-3 will be fully opened, and pump units 20-1 to 20-3 will operate according to characteristic curve HQ3.

[0067] On the other hand, when the water demand is small, the discharge valves 22-1 to 22-3 are controlled to have a smaller opening, but when the discharge tank water level increases and reaches the stop water level Ld3e, the third pump device 20-3 is stopped.

[0068] In the example of Figure 11, each pump device 20-1 to 20-3 is stopped with the discharge tank water level kept high, so that the time (stop time) until the discharge tank water level drops and the pump device is started can be gained, thereby reducing the frequency of operation / stop of the pump device.

[0069] Figures 12 and 13 are graphs showing an example of time-dependent changes in the water level, flow rate, shaft power, and start count of the pump units in the discharge tank 30 in the second embodiment. Figure 12 shows the operation and stop of the second pump unit while the first pump unit is operating, and Figure 13 shows the operation and stop of the third pump unit while the first and second pump units are operating. Figures 12 and 13 also show a conventional example (dotted line) in which the operation and stop of the pump units is switched based only on the discharge tank water level, and an example (solid line) in which the operation and stop of the pump units is switched based on the demand water flow rate and the discharge tank water level, and discharge valve openness control is also performed.

[0070] Compared to conventional examples, the pump system according to the embodiment can maintain a constant water level and flow rate in the discharge tank without switching the pump device on and off. Therefore, the pump system according to this embodiment can reduce the frequency of pump operation / stop, thereby enabling energy-efficient unit number control and further suppressing pressure shortages on the demand side.

[0071] The pump system 1 according to the above embodiment is configured to include three pump devices 20-1, 20-2, and 20-3, but the number is not limited to three as long as there is a plurality of pump devices, and may be two or four or more. Also, while the pump devices are described as being driven by motors, they are not necessarily limited to being motor-driven and may be driven by other drive mechanisms such as prime movers.

[0072] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would naturally be possible for a person skilled in the art, and the technical concept of the present invention may also be applied to other embodiments. The present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0073] 10,50 Pump System 11 Suction tank 20-1, 20-2, 20-3 Pump equipment 21-1, 21-2, 21-3 Motors 22-1, 22-2, 22-3 Discharge valve 30 Discharge water tank 31 Discharge tank water level gauge 40,60 Control device 41, 61 Demand water flow rate calculation section 42, 62 Motor drive control unit 43, 65 Storage section 63 Discharge valve opening target value calculation unit 64 Discharge valve opening control section

Claims

1. A plurality of pump devices that suck water from a suction tank and send it to a discharge tank; a discharge water tank water level meter that measures the water level of the discharge water tank; a control device for controlling the operation of the pump device; The control device is a pump system characterized by having a demand water flow rate calculation unit that calculates the demand water flow rate required downstream of the discharge water tank at predetermined intervals, and a drive control unit that controls the number of pump devices to be driven based on the demand water flow rate and the discharge water tank water level.

2. The pump system of claim 1, characterized in that the control device increases the number of pump devices to be driven when the demand water flow rate reaches a first set value, and decreases the number of pump devices to be driven when the measured water level in the discharge tank reaches a second set value.

3. a discharge valve provided between the pump device and the discharge water tank, the discharge valve being capable of increasing or decreasing the amount of water sent to the discharge water tank depending on the opening degree; 2. The pump system according to claim 1, wherein the control device further comprises a discharge valve opening control unit that controls an opening of the discharge valve in accordance with the demanded water amount.

4. The pump system according to claim 3 , wherein the control device controls the number of pump devices to be driven to increase after the discharge valve is fully opened.

5. A control method for a pump system including a plurality of pump devices that suck water from a suction tank and send it to a discharge tank, and a discharge tank water level meter that measures the water level of the discharge tank, comprising: a demand water flow rate calculation step for calculating a demand water flow rate required downstream of the discharge water tank at predetermined time intervals; A pump system control method comprising a drive control step of controlling the number of pump devices to be driven based on the demand water flow rate and the discharge water tank water level.

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