JP7769601B2 - Pump control method and pump control device - Google Patents

Description

The present invention relates to a pump control method and pump control device for a manhole pump device that starts a pump device when the water level in a water tank detected by a water level sensor reaches a start-up water level, and then stops the pump device when the water level reaches a stop-up water level.

The drainage pump device installed in the manhole pump device's water tank is selected to meet the preset total head H0 and discharge volume Q0. The total head H0 is the actual head h plus losses such as pipeline resistance, while the discharge volume Q0 is determined by the volume of the water tank and the maximum amount of inflow sewage. The discharge pipe connected to the pump device has a predetermined diameter and flow velocity within the pipe to prevent foreign matter from becoming trapped or clogging, and the discharge volume Q0, which is the specified flow rate, is set based on this.

A pump device selected based on these conditions will exceed the required performance, and when operated at the rated rotational speed, the flow rate will be ΔQ greater than the specified discharge rate Q0.

As a result, the time required to drain the water from the starting water level to the stopping water level is shortened, but the frictional resistance in the pipeline increases in proportion to the flow rate ΔQ, and the total head H1 becomes higher by ΔH than the specified total head H0, resulting in energy loss.

Patent Document 1 proposes a control device for controlling the rotation speed of a manhole pump device, with the aim of providing a control device for the pump device that prevents foreign matter from becoming entangled in the impeller or becoming lodged inside the pump casing and causing blockages, without increasing the startup frequency.

The control device is equipped with a control unit that starts the submersible pump when the water level measured by the water level sensor reaches a predetermined pump start level and stops the submersible pump when it reaches the pump stop level.The control unit is configured to control the submersible pump by combining a first rotation control that drives the submersible pump at a predetermined steady rotation speed and a second rotation control that includes control to drive the submersible pump at a rotation speed different from the steady rotation speed, from when the submersible pump is started until the water level reaches the pump stop level.

This control device controls the submersible pump by freely combining a first rotation control that drives the submersible pump at a predetermined steady rotation speed and a second rotation control that drives the submersible pump at a rotation speed different from the steady rotation speed. This changes the flow speed around the impeller and within the pump casing, and by changing the flow conditions, it is possible to avoid foreign matter becoming entangled around the impeller or clogging due to foreign matter remaining inside the pump casing, thereby enabling the sewage to be pumped efficiently.

JP 2010-236498 A

The conventional pump control devices described above use technology that switches the rotation speed to prevent foreign matter from becoming entangled in the impeller or clogging due to foreign matter remaining inside the pump casing, but there is still room for improvement in terms of improving the operating efficiency of the pump.

In order to improve the operating efficiency of the pump unit, it is possible to operate it at a speed lower than the rated speed. However, this can lead to problems such as longer operating times for the pump unit if the amount of wastewater inflow increases, resulting in energy losses, the risk of the reservoir water level rising above the start-up water level and causing overflow, and the risk of the pump unit overheating because it takes a long time to reach the stop water level even after the water level in the reservoir drops below the pump unit's minimum submersion water level.

In view of the above-mentioned problems, the object of the present invention is to provide a pump control method and pump control device that can effectively utilize the capacity of pump equipment and operate the pump device in an energy-efficient manner.

In order to achieve the above-mentioned object, a first characteristic configuration of the pump control method of the present invention is a pump control method for a manhole pump device that starts the pump device when the water level in a water tank detected by a water level sensor rises to a startup water level, and then stops the pump device when it falls to a shutdown water level, and performs operation mode switching control to switch between a rated operation mode in which the pump device is operated at a rated rotational speed and an energy-saving operation mode in which the pump device is operated at a rotational speed that consumes less power than the rated rotational speed, depending on the water level in the water tank , and when the pump efficiency η1 and head H1 in the rated operation mode and the pump efficiency η2 and head H2 in the energy-saving operation mode are taken as pump efficiency η2, the rotational speed of the pump device is set so that the pump efficiency η2 in the energy-saving operation mode satisfies η2 > η1 · (H2/H1) .

By switching between rated operation mode and energy-saving operation mode depending on the water level in the water tank, which changes between starting and stopping the pump device, the pump device can be operated in an energy-efficient manner.

In the energy-saving operation mode, it is preferable to set the rotation speed so that the pump efficiency η2 satisfies η2>η1·(H2/H1).
As shown in FIG. 6, the discharge volume V1 in the rated operation mode is expressed by the following equation, where Q1 is the flow rate and T1 is the operation time.
V = Q1 x T1
The output P1 of the pump device at this time is expressed by the following equation, where H1 is the head and η1 is the pump efficiency.
P1=(0.163×Q1×H1)/η1
The amount of power Wh is expressed by the following formula.
Wh=P1×T1=(0.163×Q1×H1)/η1×V1/Q1
When the power and time in the energy-saving operation mode are P2 and T2, and the following formula is satisfied, the power consumption is lower than in the rated operation mode.
P1×T1>P2×T2, V1=V2
That is, when the pump is operated at a pump efficiency η2 that satisfies the following condition, power consumption is reduced.
(0.163×Q1×H1)/η1×V1/Q1>(0.163×Q2×H2)/η2×V2/Q2
η2>η1・(H2/H1)

The second characteristic configuration is that, in addition to the first characteristic configuration described above, the energy-saving operation modes include a first energy-saving operation mode in which the rotational speed of the pump device is set so that the pump efficiency η2 in the energy-saving operation mode becomes the maximum value that satisfies η2 > η1 · (H2/H1), and a second energy-saving operation mode in which the rotational speed is set in a rotational speed range faster than that in the first energy-saving operation mode so as to avoid an increase in the water level in the water tank.

In the first energy-saving operation mode, emphasis is placed on the energy-saving effect, and in the second energy-saving operation mode, emphasis is placed on the energy-saving effect as well as on avoiding overflow due to a rise in the water level in the water tank.
The maximum power saving effect is achieved when the rotation speed of the pump device is set so that the pump efficiency η2 in the energy saving operation mode is the maximum value that satisfies η2 > η1 · (H2/H1). Note that when the pump rotation speed is reduced from the rated rotation speed N0 to N1, the discharge volume Q2, total head H2, and efficiency η2 become as follows:
Q2=(N1/N0)×Q1
H2=(N1/N0) ² ×H1
η2=1-(1-η1)/(N2/N1) ^1/5

If the pump's rotation speed is reduced when the water level in the water tank is close to the startup water level, the water level in the tank will rise if the amount of sewage flowing into the tank is greater than the amount of water discharged by the pump. If the water level reaches an abnormally high level that could cause sewage to overflow from the tank, the alarm will be activated, requiring the manhole pump's manager to respond to what would otherwise be an unnecessary alarm. Even in such cases, by operating the pump in the second energy-saving operation mode, the pump's rotation speed is set so that the water level in the water tank does not rise above the startup water level, allowing operation in the energy-saving operation mode while avoiding false alarms.

The third characteristic configuration is, in addition to the second characteristic configuration described above, that the water tank operates in the second energy-saving operation mode when the water level in the water tank is between the startup water level and an energy-saving operation mode switching water level set below the startup water level, and operates in the first energy-saving operation mode when the water level in the water tank is between the energy-saving operation mode switching water level and a rated operation mode switching water level set below the energy-saving operation mode switching water level.

Between the start-up water level and the energy-saving operation mode switch level, which is set below the start-up water level, there is a risk that the water level in the water tank will rise above the start-up water level. By operating the pump device in the second energy-saving operation mode, this avoids the water level from rising due to the inflow of sewage, and by operating in the first energy-saving operation mode, which has a high energy-saving effect, between the energy-saving operation mode switch level and the rated operation mode switch level, which is set below the energy-saving operation mode switch level, safe energy-saving operation is possible.

The fourth characteristic configuration is that, in addition to the third characteristic configuration described above, the pump device is operated in the rated operation mode when the water level in the water tank is between a high water level higher than the start-up water level and the start-up water level, or between the rated operation mode switching water level and the stop water level.

The specified flow rate, discharge rate Q0, is a value set as the discharge rate that can be discharged without overflowing from the water tank, even when the maximum anticipated inflow of wastewater flows into the water tank. The discharge flow rate Q1 from a pump device operating at the rated rotation speed will be at least equal to or greater than the specified flow rate, discharge rate Q0. Therefore, if the pump is operated in rated operation mode between a high water level higher than the start-up water level and the start-up water level, the stored water level will reliably drop.

In addition, between the low water level, which is lower than the water level at which the pump device switches to rated operation mode, and the stop water level, the cooling effect on the pump device's motor decreases. If the pump device were to operate in energy-saving operation mode during this period, the operation time would be longer and there is a risk of the motor overheating abnormally. In such cases, if the pump device is operated in rated operation mode, the water level will drop to the stop water level in a shorter time than in energy-saving operation mode, allowing the pump device to be stopped in a normal state.

The fifth characteristic configuration is that, in addition to the first characteristic configuration described above, when operating in the energy-saving operation mode, if the blockage status of the pump device or the discharge pipe connected to the pump device is evaluated and it is determined that there is a risk of blockage, the operation mode is switched from the energy-saving operation mode to a blockage removal operation mode in which the rotational speed of the pump device is increased.

Even if operation in the energy-saving operation mode causes foreign matter to accumulate in the discharge pipe, potentially leading to blockage, the inclusion of a blockage assessment unit makes it possible to assess the blockage status of the discharge pipe. If the blockage assessment unit assesses that there is a risk of blockage in the discharge pipe, the system can switch from the energy-saving operation mode to the blockage elimination operation mode, thereby preventing abnormalities such as blockage of the discharge pipe. The rotational speed of the pump device in the blockage elimination operation mode can be any value that ensures that the flow velocity in the discharge pipe is equal to or greater than a predetermined flow velocity that allows foreign matter to be expelled, and the rotational speed in the rated operation mode can be suitably used.

The sixth characteristic configuration is that, in addition to the first characteristic configuration described above, even if the water level in the water tank is at a level corresponding to operation in the energy-saving operation mode, the system operates in the rated operation mode during times when electricity rates correspond to late-night rates.

Commercial electricity rates are set lower during the night when demand is low than during the day. Therefore, even if the water level in the water tank is at a level that would allow operation in energy-saving mode, by operating in rated operation mode during the night-time rate period, it is possible to safely drain water while reducing power consumption.

In order to achieve the above-mentioned object, the characteristic configuration of the pump control device according to the present invention is a pump control device for a manhole pump device that starts the pump device when the water level in a water tank detected by a water level sensor rises to a startup water level and then stops the pump device when it drops to a shutdown water level, and performs operation mode switching control to switch between a rated operation mode in which the pump device is operated at a rated rotational speed and an energy-saving operation mode in which the pump device is operated at a rotational speed that consumes less power than the rated rotational speed , depending on the water level in the water tank, and when the pump efficiency η1 and head H1 in the rated operation mode and the pump efficiency η2 and head H2 in the energy-saving operation mode are taken as the pump efficiency η2 in the energy-saving operation mode, the rotational speed of the pump device is set so that η2 > η1 · (H2/H1) .

As described above, the present invention provides a pump control method and pump control device that can effectively utilize the capacity of the pump equipment and operate the pump device in an energy-efficient manner.

An explanatory diagram of a manhole pump device used in the present invention. 1 is a flowchart showing a method for controlling a pump device. 1A is an explanatory diagram of a rated operation mode using a performance curve of a pump device, and FIG. 1B is an explanatory diagram of an energy-saving operation mode using a performance curve of a pump device. Illustrative diagram of dynamic energy-saving operation modes using pump unit performance curves Graph showing rotation speed and pump efficiency in energy-saving operation mode An explanatory diagram of the rotation speed setting algorithm in the energy-saving operation mode 1 is a flowchart showing a method for controlling a pump device based on fluctuations in water level.

A pump control method and a pump control device according to the present invention will be described below.
[Configuration of manhole pump device]
As shown in Figure 1, the manhole pump device 10 includes a manhole 11 that stores wastewater flowing in from an inlet pipe 12, two submersible pumps P that pump the wastewater stored in the manhole 11 through a discharge pipe 13a and a riser pipe 13 to an outlet pipe 14, and a water level sensor 15 that measures the water level of the wastewater stored in the manhole 11. The submersible pumps P serve as the pump device P of the present invention, and the manhole 11 serves as the water tank 11.

A plunge pressure or air bubble type water level sensor is used as the water level sensor 15, which is installed at the bottom of the manhole 11 and is configured to continuously detect the water level of the wastewater stored in the manhole 11. Furthermore, in case of a malfunction of the water level sensor 15, a backup float type water level sensor 16 is installed at a height where the water level becomes abnormally high, and the water level sensors 15 and 16 are configured to detect abnormally high water levels.

A control panel 20 equipped with a pump control device 21 that controls the start and stop of the submersible pump P is installed near the ground level of the manhole pump device 10. A power supply line 27 for supplying power to the electric motor M incorporated in the submersible pump P is wired between the pump control device 21 and the submersible pump P, and a water level detection signal line 28 is wired between the pump control device 21 and the water level sensor 15.

[Configuration of pump control device]
The pump control device 21 includes a microcomputer, a memory for storing a control program executed by the microcomputer, and an input/output circuit for outputting a power supply control signal to the electric motor M and inputting a signal from the water level sensor 15. The control program is executed by the microcomputer, thereby realizing the pump control device of the present invention, and the pump control method of the present invention is executed by the pump control device.

The pump control device 21 also includes a communication circuit that transmits a status signal indicating the operating status of the manhole pump device 10 to the remote monitoring device. For example, information such as the water level detected by the water level sensor 15, the start time and number of times the submersible pump P is started per day as determined by the pump control device 21, whether or not an abnormally high water level has occurred, and information regarding abnormal conditions such as abnormal overheating detected by a temperature sensor provided in the submersible pump P, is transmitted to the remote monitoring device via the communication circuit. The manager of the manhole pump device 10 can monitor the system by accessing the remote monitoring device via the Internet, and if an abnormality occurs, the remote monitoring device will send an emergency alert to the manager of the manhole pump device 10.

The pump control device 21 controls the electric motor M incorporated in the submersible pump P based on the water level measured by the water level sensor 15. The water levels recognized by the pump control device 21 via the water level sensor 15 include the abnormally high water level HHWL, the starting water level HWL, the energy-saving operation mode switching water level PWL, the rated operation mode switching water level MWL, and the stop water level LWL.

The abnormally high water level HHWL indicates the water level at which sewage may overflow from the manhole 11. The start-up water level HWL indicates the water level at which the submersible pump P is started to drain the sewage stored in the manhole 11. The energy-saving operation mode switching water level PWL is a water level a predetermined level lower than the start-up water level HWL and indicates the water level at which the system switches from the second energy-saving operation mode (described below) to the first energy-saving operation mode. The rated operation mode switching water level MWL is the water level at which the system switches from the energy-saving operation mode to the rated operation mode, and preferably indicates the water level just before the submersible pump P changes from a submerged state to the water surface. The stop water level LWL indicates the water level at which the submersible pump P is stopped. The first energy-saving operation mode switching water level PWL and the rated operation mode switching water level MWL may be set appropriately depending on the actual volume of the manhole 11 and the model of the submersible pump P, or may be set arbitrarily by the administrator.

When the water level in the manhole 11 detected by the water level sensor 15 reaches the starting water level HWL, the pump control device 21 starts one of the submersible pumps P to begin draining the water, and stops that submersible pump P when it reaches the stopping water level LWL. Then, when the water level in the manhole 11 reaches the starting water level HWL again, the pump control device 21 starts the other submersible pump P, and then stops that submersible pump P when it reaches the stopping water level LWL. In other words, the two submersible pumps P are operated alternately. Furthermore, when the abnormally high water level HHWL is reached, the pump control device 21 operates the two submersible pumps P simultaneously.

As shown in Figure 2, the pump control device 21 is configured to input the water level in the manhole 11 measured by the water level sensor 15 (SA1) and execute predetermined control of the submersible pump P depending on the water level.

If the water level in the manhole 11 is at the rated operating level (SA2), the submersible pump P is controlled in the rated operating mode (SA7); if it is at the second energy-saving operating level (SA3), the submersible pump P is controlled in the second energy-saving operating mode (SA8); if it is at the first energy-saving operating level (SA4), the submersible pump P is controlled in the first energy-saving operating mode (SA9); if it is at the stop water level LWL (SA5), the submersible pump P is stopped (SA10); and if it is at the abnormally high water level HHWL (SA6), the two submersible pumps P are driven simultaneously (SA11).

The rated operating water level refers to a water level below the abnormally high water level HHWL but above the start-up water level HWL, and a water level below the rated operation mode switching water level MWL but above the shutdown water level LWL. When the water level in the manhole 11 is at the rated operating water level, the pump control device 21 places more importance on the time required for drainage than on pump efficiency, and operates the submersible pump P in rated operating mode. The rated operating mode can also be called drainage priority mode.

When the water level is below the abnormally high water level HHWL but above the start-up water level HWL, the pump operates in rated operation mode so that the water level does not exceed the abnormally high water level HHWL even if a large amount of sewage flows into the manhole 11. Furthermore, when the water level is below the rated operation mode switching level MWL but above the stop water level LWL, the cooling effect of the sewage on the motor M is reduced, and the pump control device 21 operates the submersible pump P in rated operation mode and quickly stops it to prevent it from reaching an abnormally overheated state.

The submersible pump P may be stopped immediately when the stop water level LWL is detected, or may be stopped after a predetermined time has passed since the stop water level LWL was detected, specifically after the time required to pump a volume of water equivalent to the water level from the stop water level LWL to the vicinity of the suction port SP of the submersible pump P has passed.

The second energy-saving operation water level refers to the water level between the starting water level HWL and the energy-saving operation mode switching water level PWL. If the submersible pump P is operated in the first energy-saving operation mode during this period, there is a risk that the starting water level HWL will be exceeded and the abnormally high water level HHWL will be reached if the amount of sewage flowing in from the inlet pipe 12 is greater than the amount of sewage pumped out from the outlet pipe 14. Therefore, the pump control device 21 operates the submersible pump P with higher pump efficiency than in the rated operation mode, but within a range that does not cause the water level to rise. This operation mode, which prioritizes water level management, is called the second energy-saving operation mode.

The energy-saving operation mode switching water level PWL is a water level that is a predetermined level lower than the start-up water level HWL. The maximum depth of the manhole 11 is often set to approximately 1500 to 2000 mm, and in this embodiment, the predetermined water level is set to several hundred mm (approximately 200 to 300 mm). The predetermined water level is set appropriately based on the maximum depth of the manhole, the amount of wastewater flowing in, etc.

The first energy-saving operation water level is the level between the energy-saving operation mode switching water level PWL and the rated operation mode switching water level MWL. At the first energy-saving operation water level, the pump control device 21 operates the submersible pump P in the first energy-saving operation mode. In other words, the energy-saving operation modes include the first energy-saving operation mode and the second energy-saving operation mode.

[Explanation of rated operation mode]
Figure 3(a) shows the performance curve for the rated operation mode. h is the actual head from the starting water level HWL to the discharge well. The submersible pump P is selected to satisfy the preset total head H0 and discharge rate Q0. The total head H0 is shown by a system curve obtained by adding losses such as pipeline resistance to the actual head h, and varies depending on the flow rate Q. The discharge rate Q0 is determined by the volume of the manhole 11 and the maximum amount of inflow sewage.

In other words, the discharge rate Q0 is set to a flow rate that allows sewage to be drained without overflow even when the maximum amount of sewage flows into the manhole 11, and is set to a flow rate that allows sewage to be drained from the starting water level HWL to the stopping water level LWL within a specified time. Furthermore, the diameter and flow rate within the discharge pipe 13a connected to the submersible pump P are predetermined to prevent foreign matter from accumulating or clogging, and the discharge rate Q0, which is the specified flow rate, is set based on this.

Submersible pump P selected based on these conditions will ultimately exceed the required performance, and when operated at the rated rotational speed (rated operation), the intersection HQ1 of the total head curve and the system curve will be the operating point. As a result, it will operate at a flow rate Q1 that is ΔQ higher than the specified discharge rate Q0.

In this case, the time required to drain the water from the starting water level to the stopping water level will be shorter, but the frictional resistance in the pipes will increase in response to the flow rate ΔQ, and the total head H1 will be higher by ΔH than the specified total head H0, resulting in energy loss and increased power consumption.

[Explanation of energy-saving operation mode]
In the energy-saving operation mode, the rotation speed is set so that the pump efficiency η2 satisfies η2>η1·(H2/H1).
As shown in FIG. 6, the discharge volume V1 in the rated operation mode is expressed by the following equation, where Q1 is the flow rate and T1 is the operation time.
V = Q1 x T1
The output P1 of the submersible pump P at this time is expressed by the following equation, where H1 is the head and η1 is the pump efficiency.
P1=(0.163×Q1×H1)/η1
The amount of power Wh is expressed by the following formula.
Wh=P1×T1=(0.163×Q1×H1)/η1×V1/Q1
When the power and time in the energy-saving operation mode are P2 and T2, and the following formula is satisfied, the power consumption is lower than in the rated operation mode.
P1×T1>P2×T2, V1=V2
That is, when the pump is operated at a pump efficiency η2 that satisfies the following condition, power consumption is reduced.
(0.163×Q1×H1)/η1×V1/Q1>(0.163×Q2×H2)/η2×V2/Q2
η2>η1・(H2/H1)

In the first energy-saving operating mode, it is preferable to set the rotational speed of the submersible pump P so that the pump efficiency η2 is the maximum value that satisfies η2 > η1 · (H2/H1), thereby achieving the maximum power saving effect and enabling the pump device to be operated in an energy-efficient state.
Furthermore, when the rotational speed of the submersible pump P is reduced from the rated rotational speed N0 to N1, the discharge volume Q2, total head H2, and pump efficiency η2 become as follows.
Q2=(N1/N0)×Q1
H2=(N1/N0) ² ×H1
η2=1-(1-η1)/(N2/N1) ^1/5

Figure 3(b) shows the performance curve of the first energy-saving operating mode when the rotational speed of the submersible pump P is set so that the pump efficiency η2 is the maximum value that satisfies η2 > η1 · (H2/H1) with a dotted line.
In the first energy-saving operation mode, the flow rate is reduced to Q2 by shifting the operating point from HQ1 in the rated operation mode to HQ2, but the pipeline loss is also reduced. Note that the efficiency may be the overall efficiency that takes into account the efficiency of the electric motor M in addition to the pump efficiency.

As the submersible pump P operates, the actual head increases as the water level in the manhole 11 drops. The pump control device 21 follows the system curve, which fluctuates with the actual head, and controls the rotational speed of the submersible pump P so that the operating point of the first energy-saving operating mode, i.e., the pump efficiency η2, reaches the maximum value that satisfies η2 > η1 · (H2/H1).

In Figure 4, the performance curve of the first energy-saving operation mode when the actual head increases from h1 to h2 is shown by a dashed line. The pump control device 21 performs feedback control so that the operating point in the first energy-saving operation mode transitions from HQ2h1, the operating point when the actual head is h1, to HQ2h2 as the actual head increases to h2. The rotational speed of the submersible pump P at this time is the same as that calculated above.

The rotation speed may be adjusted continuously or in stages in response to the fluctuation Δh in the actual head. The initially set rotation speed may be maintained regardless of the fluctuation Δh in the actual head.

[Explanation of the second energy-saving operation mode]
In the second energy-saving operation mode described above, the pump control device 21 monitors the water level detected by the water level sensor 15, and when the water level rises, it performs feedback control to increase the rotation speed within a range that satisfies η2 > η1 · (H2/H1), thereby controlling the submersible pump P at a rotation speed that consumes less power than in the rated operation mode and that does not cause the water level to rise. When the water level changes from rising to falling, it performs feedback control to decrease the rotation speed within a range that satisfies η2 > η1 · (H2/H1). In this case, too, the adjustment of the rotation speed in response to the fluctuation Δh in the actual head may be continuous or stepwise.

In other words, the rotation speed of the submersible pump P in the second energy saving operation mode is controlled between the upper limit rotation speed of the rated operation mode and the lower limit rotation speed of the first energy saving mode.
Furthermore, when transitioning between the rated operation mode, the second energy-saving operation mode, and the first energy-saving operation mode, or when switching the rotation speed of the underwater pump P in each operation mode, it is preferable to control the rotation speed so that it switches in steps, preferably continuously, rather than switching suddenly.

Figure 5 shows the relationship between rotational speed, output, and pump efficiency in the first energy-saving operating mode. Pump efficiency η is maximum at the rated rotational speed and decreases as the rotational speed decreases. However, output per discharge volume does not monotonically decrease as the rotational speed decreases, but rather reaches a minimum value at a certain point. In the above formula, the minimum value is reached at the rotational speed corresponding to the maximum rotational speed of the submersible pump P that satisfies η2 > η1 · (H2/H1). Note that in Figure 5, the rated rotational speed is represented as 100% and the rotational speed (%) is displayed, but this is not substantially different.

[System curve explanation]
In the completion inspection carried out when the submersible pump P is installed in the manhole 11, after storing wastewater up to a predetermined water level, the submersible pump P is operated at at least three rotation speed patterns, for example, 100% rotation speed (rated rotation speed), 90% rotation speed, and 80% rotation speed, with no new wastewater flowing in.
The system curve is obtained by determining the respective discharge rates from the amount of change in water level at this time and calculating the pipeline resistance curve from the total head determined from the total head curve of the submersible pump P. The obtained system curve is stored in a memory provided in the pump control device 21, and the rotation speed in the power saving operation mode is calculated based on the system curve and the water level detected by the water level sensor 15, etc.

[Explanation of pump control method]
As shown in Figure 7, sewage flows into the manhole 11 at irregular intervals. When the water level measured by the water level sensor 15 is input to the pump control device 21 at a predetermined cycle (SB0, SB1), the pump control device 21 controls the operation of the two submersible pumps P so that they are driven alternately according to the measured water level WL. In this embodiment, the predetermined cycle is set to one second, and the following processes are repeated at one-second intervals. The predetermined cycle is not limited to one second and can be set as appropriate.

If the water level WL exceeds the abnormally high water level HHWL (SB2, Y), an alarm is output to the remote monitoring device or the manager's mobile terminal, and the two submersible pumps P are operated simultaneously (SB3). Furthermore, if the water level WL falls below the abnormally high water level HHWL, the alarm output is stopped.

If the water level WL is lower than the abnormally high water level HHWL (SB4, N) but higher than the start-up water level HWL (SB4, Y), one of the submersible pumps P is operated in rated operation mode, thereby prioritizing drainage over power consumption (SB5). By continuing to drain in this state, the water level WL will decrease without rising even if sewage flows in.

If the water level WL is below the start-up water level HWL (SB4, N) but higher than the energy-saving operation mode switching water level PWL (SB6, Y), the submersible pump P is operated in the second energy-saving operation mode, thereby controlling the pump to prioritize avoiding a rise in the water level due to the inflow of sewage, even in the power-saving operation mode (SB7). If the amount of inflow of sewage increases in this state and the water level WL rises above the start-up water level HWL, the rated operation mode of step SB5 will be executed in the next loop.

If the water level WL is below the energy-saving operation mode switching level PWL (SB6, N) but higher than the rated operation mode switching level MWL (SB8, Y), the submersible pump P is operated in the first energy-saving operation mode, controlling the submersible pump P at the rotation speed that maximizes the power saving effect (SB9). Furthermore, if the amount of wastewater inflow increases in this state and the water level WL rises above the energy-saving operation mode switching level PWL, the second energy-saving operation mode will be executed in step S7 in the next loop.

If the water level WL is below the rated operation mode switching water level MWL (SB8, N) but higher than the stop water level LWL (SB10, Y), one of the submersible pumps P will be operated in rated operation mode (SB11) to prevent foreign matter from accumulating in the discharge pipe, etc., and to prevent the electric motor driving the submersible pump P from abnormally overheating.

When the water level WL falls below the stop water level LWL (SB10, N), the submersible pump P is stopped after a predetermined time has elapsed (SB12). As mentioned above, the predetermined time refers to the time required to pump a volume of water equivalent to the water level from the stop water level LWL to the vicinity of the suction port SP of the submersible pump P. Note that the pump may be stopped immediately without waiting for the predetermined time to elapse.

[Description of Alternative Embodiment 1]
Commercial electricity rates are set lower during late-night hours (11:00 PM to 7:00 AM) when demand is low than during daytime hours. Therefore, even if the water level in the manhole 11 is at a level that corresponds to operation in the energy-saving operation mode, it is possible to control the system to operate in the rated operation mode during hours when the electricity rate corresponds to the late-night rate. As a result, it is possible to reduce electricity costs while safely and quickly draining water.

For example, even if the water level in the manhole 11 is at a level corresponding to the second energy-saving operation or the first energy-saving operation, the submersible pump P can be operated uniformly in the rated operation mode during the late night hours.

For example, if a predetermined amount of wastewater is predicted to inflow, the submersible pump P may be operated in rated operation mode even if the water level in the manhole 11 is below the start-up water level HWL and the pump P is stopped before the end of the midnight rate period (7:00 a.m. the following morning).

By draining the wastewater from manhole 11 down to the stop water level LWL before the end of the late-night rate period (7:00 a.m. the following morning), electricity costs can be reduced compared to draining the same amount of wastewater during the subsequent daytime hours. This is particularly effective when the electricity cost in rated operation mode during late-night hours is cheaper than the electricity cost in energy-saving operation mode during the daytime hours.

Specifically, for example, if the pump control device 21 calculates the predicted storage amount, taking into account a predetermined predicted inflow of sewage, that is, the amount at which the water level in the manhole 11 will reach the allowable storage level that is lower than the abnormally high water level HHWL but higher than the start-up water level HWL, i.e., the amount that does not reach the abnormally high water level HHWL but exceeds the start-up water level HWL, the operating time required to drain the predicted storage amount of sewage down to the stop-up water level LWL by operating the submersible pump P in rated operating mode can be calculated as the predicted operating time, and this can be achieved by operating the submersible pump P at a time that is the predicted operating time prior to the end of the late-night rate (7:00 a.m. the following day).

The pump control device 21 of each manhole pump device 10 sends a status signal indicating the operating status to the remote monitoring device. Such status signals include the start and stop times of the submersible pump P for the day. Based on the start and stop times, the remote monitoring device performs statistical analysis or executes learning using a machine learning device installed in the remote monitoring device, thereby determining the daily trend, weekly trend, and even the predicted amount of sewage inflow at any given time for the amount of sewage flowing into the manhole 11. The pump control device 21 obtains the results from the remote monitoring device, allowing it to calculate the predicted amount of sewage inflow.

The remote monitoring device may be configured to calculate the predicted water storage volume and predicted operating time described above, and instruct the pump control device 21 to operate the submersible pump P at a time that is the predicted operating time before the end of the late-night rate (7:00 a.m. the following morning). In this case, the pump control method of the present invention is executed by each pump control device 21 and the remote monitoring device.

[Description of Alternative Embodiment 2]
If it is determined that the allowable storage water level will not be exceeded before the midnight rate start time (11:00 PM) by taking into account the predicted wastewater inflow volume described above, the submersible pump P can be operated in the second energy-saving operation mode or the first energy-saving operation mode even if the water level would normally require operation in the rated operation mode. Also, the submersible pump P can be operated in the first energy-saving operation mode even if the water level would normally require operation in the second energy-saving operation mode.

Specifically, when the pump control device 21 calculates the predicted storage volume, taking into account a predetermined predicted inflow of sewage, so that the water level in the manhole 11 reaches the allowable storage volume that is lower than the abnormally high water level HHWL and higher than the start-up water level HWL (i.e., the volume that will not reach the abnormally high water level HHWL), it can calculate the predicted operating time as the operating time during which the predicted storage volume of sewage can be drained to the stop level LWL, or at least to the start-up water level HWL, by operating the submersible pump P in the first or second energy-saving operating mode. This can be achieved by operating the submersible pump P in the energy-saving operating mode at a time that is the predicted operating time prior to the midnight rate discontinuation time (11:00 PM). Note that even if it is not possible to drain the sewage down to the stop level LWL, the submersible pump P can simply be operated in the rated operating mode after the midnight rate discontinuation time is reached.

As described above, the remote monitoring device may be configured to calculate the predicted water storage volume and predicted operating time described above, and instruct the pump control device 21 to operate the submersible pump P at a time that is the predicted operating time before the late-night rate start time (11:00 p.m.). In this case, the pump control method of the present invention is executed by each pump control device 21 and the remote monitoring device.

[Description of Alternative Embodiment 3]
The pump control device 21 may be configured to include a blockage evaluation unit that evaluates the blockage status of the pump device P or the discharge pipe 13a connected to the pump device P, and if the blockage evaluation unit evaluates that there is a risk of blockage, the pump control device 21 may be configured to transition from an energy-saving operation mode to a blockage avoidance operation mode in which the rotational speed of the underwater pump P is switched so that the flow velocity inside the discharge pipe 13a is equal to or greater than a predetermined flow velocity.

Even if operation in energy-saving mode causes foreign matter to accumulate in the discharge pipe 13a, potentially leading to blockage, the blockage assessment unit makes it possible to assess the blockage status of the discharge pipe 13a.

If the blockage assessment unit assesses that there is a risk of blockage in the discharge pipe 13a, the pump control device 21 switches from energy-saving operation mode to blockage avoidance operation mode and switches the rotation speed of the pump device so that the flow velocity within the discharge pipe 13a is equal to or greater than a predetermined flow velocity at which foreign matter can be discharged, thereby preventing abnormalities such as blockage of the discharge pipe 13a.

The blockage assessment method executed by the blockage assessment unit is not particularly limited, and any known method can be applied. For example, if the time it takes for the water level in the manhole to reach the rated operation mode switching water level MWL and switch to the rated operation mode, and then reach the stop water level LWL, is longer than a preset reference time, it can be assessed that there is a risk of blockage.

The remote monitoring device uses past operating information for each manhole pumping device 10 to determine the duration of rated operation mode and the relationship between the time and amount of wastewater flowing into the manhole 11. Therefore, the average duration of rated operation mode is determined for each time period of the day. If rated operation mode continues for a threshold time (reference time) or longer that is longer than the average duration of rated operation mode for each time period, it can be assessed as a risk of blockage. As the cumulative operating time in energy-saving operation mode, which tends to reduce the conveying power for foreign matter mixed in with wastewater, increases, foreign matter will adhere to and accumulate on the discharge pipe 13a and other areas, and the extent of this is assessed from the duration of operation in rated operation mode.

The rated operation mode can be used as the clogging avoidance operation mode. If the risk of clogging does not improve in the rated operation mode, the reverse rotation mode can be used. By gradually reducing the rotation speed from the rated operation mode and stopping it, and then rotating the motor M in reverse, it is possible to shake off any foreign matter clinging to the impeller. The condition can then be improved by switching back to the rated operation mode and pumping the foreign matter out together with the wastewater. The motor M may be rotated forward and reverse multiple times.

[Description of Alternative Embodiment 4]
As another aspect of configuring the blockage evaluation unit, an AI diagnostic processing technique such as that disclosed in Japanese Patent Application Laid-Open No. 2022-075128 can be adopted.
The AI diagnostic process involves a sampling step in which measurement data indicating the characteristics of the submersible pump are sampled in a time series to obtain diagnostic characteristic data, a normalization step in which the characteristic data obtained in the sampling step is normalized based on predetermined statistical data, and a diagnosis step in which the normalization process is performed based on the characteristic data normalized in the normalization step and a preset boundary threshold value to diagnose whether the manhole pump is normal or abnormal. For example, the operating time and number of times the submersible pump is operated can be selected as the measurement data.

The system also includes a statistical data update step that, when a predetermined update condition is met, updates predetermined statistical data based on characteristic data before normalization that was diagnosed as normal in the diagnosis step during the immediately preceding predetermined period.

By normalizing the diagnostic characteristic data obtained from the measurement data sampled in a time series manner in the sampling step in the normalization step, it is possible to extract characteristic data as features that eliminate the effects of inherent mechanical differences in the submersible pump and the effects of the installation environment, and the diagnostic step appropriately diagnoses whether the manhole pump is normal or abnormal based on the characteristic data and a preset boundary threshold.

When a specified update condition is met, the specified statistical data used for normalization is updated based on the characteristic data before normalization that was sampled during the immediately preceding specified period and diagnosed as normal in the diagnostic step, thereby appropriately eliminating the effects of the passage of time.

The boundary threshold referenced in the diagnosis step is automatically generated by inputting past characteristic data as learning data into a machine learning device, and determining whether something is normal or abnormal. The abnormality and its cause are diagnosed based on the location and magnitude of the deviation from the boundary threshold. The machine learning device can be implemented, for example, as a computer that executes a one-class support vector machine algorithm.

The machine learning device may be installed in the remote monitoring device, and the results of the diagnosis made by the remote monitoring device may be transmitted to the pump control device 21, or the machine learning device may be incorporated into the pump control device 21.

As described above, the pump control method of the present invention is characterized by performing operation mode switching control that switches the pump device between a rated operation mode, in which the pump device operates at a rated rotational speed, and an energy-saving operation mode, in which the pump device operates at a rotational speed that consumes less power than the rated rotational speed, depending on the water level in the water tank between the start-up water level and the stop water level.

When the pump efficiency in rated operation mode is η1 and the head is H1, and the pump efficiency in energy-saving operation mode is η2 and the head is H2, it is preferable to set the rotational speed of the pump device so that the pump efficiency η2 in energy-saving operation mode satisfies η2 > η1 · (H2/H1).

It is even more preferable that the rotational speed of the pump device be set so that the pump efficiency η2 in the energy-saving operation mode is the maximum value that satisfies η2 > η1 · (H2/H1).

When the water level in the water tank is between the startup water level and the energy-saving operation mode switching water level, which is a specified level lower than the startup water level, the pump efficiency η2 in the energy-saving operation mode satisfies η2 > η1 · (H2/H1), and the rotational speed of the pump device is set so that the water level in the water tank does not rise above the startup water level.

When the water level in the water tank is between a high water level higher than the start-up water level and the start-up water level, or between a low water level lower than the pump device's lower submergence water level and the stop-up water level, the pump device will operate in rated operation mode.

If the system evaluates the blockage status of the pump device or the discharge pipe connected to the pump device and determines that there is a risk of blockage, it will switch from energy-saving operation mode to blockage avoidance operation mode, which changes the rotational speed of the pump device so that the flow velocity in the discharge pipe is equal to or greater than a predetermined flow velocity.

Taking into account a predetermined predicted inflow of wastewater, the pump device operates in energy-saving operation mode at the time, prior to the late-night rate start time, when the water level in the water tank is predicted to reach an allowable storage water level higher than the startup water level, by the predicted operating time. Even if the water level in the water tank is below the startup water level, the pump device operates in energy-saving operation mode.

Taking into account the inflow of a specified predicted amount of sewage, the pump device will operate in rated operation mode at the time, prior to the end of the late-night rate period, when the water level in the water tank is predicted to reach the stop level, even if the water level in the water tank is below the start-up level.

The above explanation has been given of an example in which sewage flows into the manhole 11, but this is not limited to sewage and can also be applied to liquids other than sewage.

The embodiment described above is merely one example of the present invention, and is not intended to limit the technical scope of the present invention. It goes without saying that the specific configurations of the manhole pump device and control device can be modified and designed as appropriate within the scope of the effects of the present invention.

10: Manhole pump device 12: Inlet pipe 11: Water tank (manhole)
13: Rising pipe 13a: Discharge pipe 14: Outlet pipes 15, 16: Water level sensor M: Electric motor P: Pump device (submersible pump)
20: Control panel 21: Pump control device HHWL: Abnormally high water level HWL: Start-up water level LWL: Stop water level MWL: Rated operation mode switching water level PWL: Energy-saving operation mode switching water level

Claims (7)

A pump control method for a manhole pump device, which starts a pump device when the water level of a water tank detected by a water level sensor rises to a start water level, and stops the pump device when the water level thereafter falls to a stop water level,
executing an operation mode switching control to switch the pump device between a rated operation mode in which the pump device is operated at a rated rotation speed and an energy-saving operation mode in which the pump device is operated at a rotation speed that consumes less power than the rated rotation speed, according to the water level of the water tank ;
A pump control method in which the rotational speed of the pump device is set so that the pump efficiency η2 in the energy-saving operation mode satisfies η2 > η1 · (H2/H1), where η1 is the pump efficiency and H1 is the head in the rated operation mode, and η2 is the pump efficiency and H2 in the energy-saving operation mode. 2. The pump control method according to claim 1, wherein the energy-saving operation modes include a first energy-saving operation mode in which the rotational speed of the pump device is set so that the pump efficiency η2 in the energy-saving operation mode becomes a maximum value that satisfies η2 > η1 · (H2/H1), and a second energy-saving operation mode in which the rotational speed is set in a rotational speed range faster than that in the first energy-saving operation mode so as to avoid an increase in the water level in the water tank. The water supply system operates in the second energy-saving operation mode while the water level in the water tank is between the startup water level and an energy-saving operation mode switching water level set below the startup water level,
A pump control method as described in claim 2 , wherein the pump is operated in the first energy-saving operation mode while the water level in the water tank is between the energy-saving operation mode switching water level and a rated operation mode switching water level set below the energy-saving operation mode switching water level. A pump control method as described in claim 3, wherein the pump device is operated in the rated operation mode when the water level in the water tank is between a high water level higher than the start- up water level and the start-up water level, or between the rated operation mode switching water level and the stop water level. A pump control method as described in claim 1, wherein, if a blockage condition of the pump device or a discharge pipe connected to the pump device is evaluated during operation in the energy-saving operation mode and it is determined that there is a risk of blockage, the operation mode is switched from the energy-saving operation mode to a blockage removal operation mode in which the rotational speed of the pump device is increased. A pump control method as described in claim 1, wherein even if the water level in the water tank is at a level corresponding to operation in the energy-saving operation mode, operation is performed in the rated operation mode during times when electricity rates correspond to late-night rates. A pump control device for a manhole pump device that starts a pump device when the water level in a water tank detected by a water level sensor rises to a start water level, and then stops the pump device when the water level falls to a stop water level,
executing an operation mode switching control to switch the pump device between a rated operation mode in which the pump device is operated at a rated rotation speed and an energy-saving operation mode in which the pump device is operated at a rotation speed that consumes less power than the rated rotation speed, according to the water level of the water tank ;
A pump control device in which the rotational speed of the pump device is set so that the pump efficiency η2 in the energy-saving operation mode satisfies η2 > η1 · (H2/H1), where η1 is the pump efficiency and H1 is the head in the rated operation mode, and η2 is the pump efficiency and H2 in the energy-saving operation mode.