JPH09217684A - Variable speed water feed equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress delivery pressure by a simple control from transitionally fluctuating when a pump is additionally charged, and when parallel-off is suspended by letting the number of revolution of the additional pump be so designed as to allow PI control to be started at a specified number of revolution at the time of pump operations when the pump out of operation is additionally charged thereto. SOLUTION: The equipment is provided with a plurality of pumps 13a and 13b, variable speed means 19a and 19b which perform variable speed drive respectively, and with a control means 17 executing variable speed control under PI control, and also performing additional parallel-off. The control means 17 in particular, when the pump 13b out of operation is additionally charged thereto at the time of operating at least, the pump 13a, the number of revolution of the additional pump 13b is so designed as to allow PI control to be started at a specified number of revolution. By this constitution, delivery pressure can be prevented under simple control from transitionally fluctuated when the pump is additionally charged, and when parallel-off is suspended without executing complex and difficult control such as forcing control. Therefore, water can thereby be stably fed without fluctuating in pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable-speed water supply device capable of operating two or more pumps in parallel, and in particular, it is possible to reduce fluctuations in discharge pressure when adding and disconnecting pumps that are operated in parallel. Regarding the configuration of the control system.

[0002]

2. Description of the Related Art FIG. 1 shows a system outline of a variable speed water supply system provided with two pumps. For example, an inflow pipe 12 is connected to a water distribution pipe 11 which is a main pipe of water supply, and two pumps 13a and 13b are connected to the inflow pipe 12. A water meter (not shown) is connected to the inflow pipe 12 to measure the amount of water used. A discharge pipe 15 connected to the terminal water supply device 14 is connected to the discharge side of each pump 13a, 13b.

A pressure tank 16 is connected to the discharge pipe 15. A discharge pressure detector 18 for detecting the discharge pressure of the pump in the discharge pipe 15 and sending this pressure signal to the control means 17 is provided on the discharge side of the pumps 13a and 13b. The pumps 13a and 13b are each connected to a commercial power source of, for example, three-phase 200V.
It is equipped with variable speed means 19a, 19b consisting of an electric motor equipped with a voltage converter (inverter), and is driven at a variable speed.

The control means 17 includes a discharge pressure detector 18
A signal is sent to each of the variable speed means 19a and 19b based on the above signal, and the rotation speed of each pump 13a and 13b is feedback-controlled so as to reach a predetermined control target pressure. As the speed control, PI (proportional integration) control is used because of the stability of normal control.

Further, each pump 13 is attached to the discharge pipe 15.
Located on the discharge side of a, 13b, small water amount detecting means 20a, 20b, which are, for example, flow switches, and check valves 21a, 21b for backflow prevention are respectively interposed, and the small water amount detecting means 20a, The signal from 20b is sent to the control means 17. When the small amount of water detection means detects that the customer side 14 has almost no water consumption, the control means 17 controls the pump to be stopped in order to prevent the pump from shutting off and save energy. Be done.

By the way, the two pumps 13a and 13b are
The rotation speed is controlled so that one unit or two units maintain the control target pressure in accordance with the amount of water to be sent. When the amount of water used is small, only one unit is operated, the amount of water used increases, and when the operation of one pump is insufficient to maintain the control target pressure, that is, the rotation speed of one pump 13a during operation is When the maximum rotation speed is reached, the operation of the second pump 13b is started (additional input). Then, after that, when the amount of water used on the consumer side decreases, the rotation speed of the pump 13b decreases, and the control target pressure can be maintained by one pump, one of the two pumps can be maintained. Pump 13a or 13
It is designed to stop the parallel disconnection of b.

[0007]

FIG. 7 shows a control flow when the pump is additionally charged. First pump 13 in operation
When it is decided to add the second pump 13b to a, the deviation (EN) between the target pressure value (SV) and the actual pressure value (PV) is calculated, and the PI calculation is performed based on this deviation. After this, the calculation result (DMV) is added to the previous rotation speed command (MV) and a new rotation speed command MV is output. As for the previous rotation speed command (MV) at this time, since the pump in operation is operating at the maximum rotation speed, the maximum rotation speed is also output as the speed command for the pump to be additionally supplied.

FIG. 8 shows how the pump discharge pressure fluctuates during additional charging. As shown in the figure, a high rotation speed is output at the time of additional charging, and the discharge pressure rises momentarily and then drops.

In this case, during parallel operation, one pump is operated at a constant speed near the maximum rotation speed, the other pump is operated at a variable speed according to the amount of water to be fed, and two pumps are operated. It is considered that variable speed operation is performed at a uniform speed. After that, when the amount of water used decreases, one of the two pumps is disconnected. The condition of the disconnection operation is that the amount of water used decreases and the rotation speed of the variable speed pump decreases, and when one reaches a predetermined rotation speed, one pump stops disconnecting.

FIG. 9 shows a control flow when the pump is disconnected. For the two pumps 13a and 13b in operation,
When the disconnection of one pump 13b is determined, the deviation (EN) between the target pressure value (SV) and the actual pressure value (PV) is calculated, and PI calculation is performed based on this deviation, and then this calculation is performed. The result (DMV) is added to the previous rotation speed command (MV) and a new rotation speed command MV is output. Regarding the previous rotation speed command (MV) at this time, since the pump that is operating is operating at the minimum rotation speed, the minimum rotation speed is also output to the speed command for the pump 13a that continues to operate.

FIG. 10 shows how the pump discharge pressure fluctuates when the parallel disconnection is stopped. Since the minimum rotation speed is output at the time of disconnection and then rises, a phenomenon occurs in which the discharge pressure falls for a moment and then rises as shown in the figure.

In the past, forcing control was used to avoid the occurrence of pressure fluctuations when adding or disconnecting a pump. This forcing control lowers the rotation speed of the pump that continues to operate during additional operation of the pump and adds another pump to the rotation speed of the pump. The pump is stopped while the pump is raised.

The suppression of the pressure fluctuation by the forcing control depends on the timing and the load condition, and it is very difficult to adjust the setting. In other words, the forcing operation is started first, but if it is too early, there is a problem that the pressure fluctuation width such that the pressure drops and then rises, or rises and then falls, conversely.

The present invention has been made in view of the above-mentioned circumstances, and it is a complicated and difficult control such as forcing control that the discharge pressure fluctuates transiently when a pump is additionally turned on or when the parallel disconnection is stopped. It is an object of the present invention to provide a variable speed water supply device that can be suppressed by simple control without performing the above.

[0015]

A variable speed water supply system of the present invention comprises a plurality of pumps which are rotationally driven by an electric motor, a check valve provided on the discharge side of the pumps, and a check valve provided downstream of the check valves. A pressure detector and a pressure tank provided, a small water amount detecting means for the pump, a variable speed means for driving the pump at a variable speed, and a control means for controlling the operation of the pump at a variable speed and additionally disconnecting the pump. In the variable speed water supply device, the control means starts the PI control of the operating speed of the other additional pump from a predetermined rotation speed when the other stopped pump is additionally supplied during operation of at least one pump. It is characterized by having means. Further, the rotation speed output at the time of additional addition of the other pump is set to a rotation speed corresponding to the control target pressure at the time of shutoff, from the relationship between the pressure at the time of pump shutoff and the rotation speed.

According to the present invention having such a configuration, the PI control is started for the additionally pumped pump from a predetermined low rotational speed output which does not affect the fluctuation of the discharge pressure at the time of the pumping. As a result, the deviation of the rotational speed output at the time of additional charging becomes small, and it is possible to prevent the discharge pressure from rising momentarily.

Another variable speed water supply device of the present invention is a plurality of pumps that are driven to rotate by an electric motor, a check valve provided on the discharge side of the pumps, and a pressure detection device provided on the downstream side of the check valves. And a pressure tank, and a small water amount detecting means of the pump,
In a variable speed water supply device comprising a variable speed means for driving the pump at a variable speed, and a control means for controlling the operation of the pump at a variable speed and additionally disconnecting the pump, the control means includes a plurality of pumps in operation. When one of the pumps is stopped in parallel, a means is provided for starting the PI control from the rotation speed of the other pump that continues to operate from a rotation speed near the maximum rotation speed of the pump.

According to the present invention thus constructed, the PI control is started from the rotational speed output near the maximum rotational speed at the time of the parallel disconnection of the pump which continues operation after the parallel disconnection of one pump. As a result, it is possible to prevent the discharge pressure from temporarily lowering due to the response delay in the PI control of the pump that continues to operate.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. In addition, the outline of the system which is the premise of the pump operation control in each of the following embodiments is as shown in FIG. Inflow pipe 12 connected to water distribution pipe 11, and a plurality of pumps 13a, 13b connected to this inflow pipe 12
And a discharge pipe 15 connected to the discharge side of each of the pumps 13a and 13b and connected to the terminal water supply device 14, and a discharge pressure detector provided on the discharge pipe 15 for detecting the discharge pressure of the pumps 13a and 13b. 18 and each of the pumps 13
Variable speed means 19 for respectively driving a and 13b at variable speeds
a, 19b and the control means 1 for controlling the operation of the pumps 13a, 13b at a variable speed by PI control and additionally disconnecting
7 and are provided.

Further, each pump 13 is attached to the discharge pipe 15.
Located on the discharge side of a, 13b, the small water amount detecting means 20a,
20b and check valves 21a, 21b are interposed, and signals from the small water amount detecting means 20a, 20b are sent to the control means 17.

2 to 4 show a first embodiment of the present invention, FIG. 2 is a control flow chart, FIG. 3 is a diagram showing a relationship between pump shutoff pressure and rotational speed, FIG. [Fig. 4] is a graph showing pressure fluctuation measurement results.

This embodiment is based on the control means 1 shown in FIG.
7. When the other pump 13b that is stopped is additionally operated when one pump 13a is operating, the rotation speed of one pump 13a is fixed and PI control of the other pump 13b is changed from a predetermined rotation speed output. It is equipped with a means to start.
In this embodiment, the predetermined rotational speed output of the pump 13b to be additionally operated is set to the rotational speed corresponding to the control target pressure at the deadline, based on the relationship between the pressure at the pump deadline and the rotational speed.

That is, when the amount of water used increases while one pump 13a is operating at a variable speed, and this rotational speed reaches the maximum rotational speed and a predetermined time elapses, the amount of water to be supplied is supplemented, so as shown in FIG. Then, the additional start of the other pump 13b is determined, and the rotation speed of the first pump 13a is fixed.

Then, the pump 13b to be additionally operated is PI-controlled at a variable speed. At this time, as shown in FIG. 2, at the time of the first calculation after the addition, a predetermined rotation speed HzB is added to the rotation speed command MV. Substituting and outputting this rotation speed, PI control of the additional pump 13b is performed. Then, after the second addition, the deviation (EN) between the target value (SV) and the actual value (PV) is calculated in the same manner as in the conventional example, and PI calculation is performed based on this deviation, and then this calculation result ( DMV) is added to the previous rotation speed command (MV) and a new rotation speed command M is added.
Output V.

Here, the predetermined rotation speed HzV which is the first output of the pump 13b is determined so as not to affect the pressure increase immediately after the pump is started. As shown in FIG. 3, when the pump is shut off ( The minimum rotation speed (NB) that generates the target pressure (PB) on the control target curve for the flow rate 0) is used.

With this configuration, the PI control of the pump 13b to be added has a low rotational speed that does not affect the discharge pressure such that the pump is operated with the dead (the flow switch is closed), for example. Starting from the output, it is possible to suppress a transient increase in the discharge pressure.

The pressure fluctuation measurement results of this embodiment are shown in FIG. As is clear from the measurement results, according to the present embodiment, it is possible to prevent the discharge pressure from increasing during additional operation of the pump and prevent the occurrence of a response delay, and always maintain a stable discharge pressure. You can

The relationship between the discharge pressure and the rotational speed when the pump is shut off may be stored in advance as a data table, or may be automatically measured and stored at the time of test operation of the pump. As the pressure control method, either the discharge pressure constant control or the estimated end pressure constant control for keeping the pressure at the demand destination constant may be adopted.

FIG. 5 and FIG. 6 show the case of the off-line of the pump of the second embodiment, FIG. 5 is a control flow chart, and FIG. 6 is a graph showing the measurement result of the pressure fluctuation. . In this embodiment, the control means 17 shown in FIG. 1 controls the PI control of the other pumps in operation when the one of the plurality of pumps in operation is stopped by parallel disconnection. It is provided with a means for starting from the rotation speed output.

That is, when the two pumps 13a and 13b are operated in parallel, the first pump 13a is operated at a fixed rotation speed and the second pump 13b is operated at a variable speed. Then, when the amount of water used decreases from this state and the rotation speed of the second pump 13b decreases and reaches a predetermined rotation speed, as shown in FIG. 5, it is determined to stop the parallel disconnection of the pump 13a. . At this time, 1 just before the disconnection to continue the operation
The third pump 13a operates while being fixed at the maximum rotation speed or a speed close thereto.

Then, the pump 13b is stopped in parallel, and the operation of the pump 13a is continued while PI control of the pump 13a is performed at a variable speed. At this time, as shown in FIG. 5, in the first calculation after disconnection, the maximum rotation speed is substituted into the rotation speed command MV, and this rotation speed is output to perform PI control of the pump 13a. Then, after the second disconnection, the deviation (EN) between the target value (SV) and the actual value (PV) is the same as in the conventional example.
After performing the PI calculation based on this deviation, the calculation result (DMV) is added to the previous rotation speed command (MV) to output a new rotation speed command MV, and the rotation speed control is performed. ing.

With this configuration, the rotational speed of the pump 13a that continues to operate is set to an output close to the actually required rotational speed, so that the PI control quickly follows up to the required rotational speed, and the response is obtained. It is possible to prevent a temporary drop in pressure due to delay. The pressure fluctuation measurement result of this example is shown in FIG. As is clear from this measurement result, according to the present embodiment, the discharge pressure is prevented from temporarily lowering when one pump is stopped during parallel operation, and the discharge is always stable. Can hold pressure.

In this embodiment, the maximum rotation speed is substituted into the rotation speed command MV at the time of the first calculation after the parallel disconnection, but a value close to this maximum rotation speed may be substituted. It can be decided as appropriate according to the individual circumstances of the system.

In the above embodiment, the pump that continues to be operated was operated near the maximum rotation speed before the stop of the disconnection of one pump, but it may be operated at a uniform speed. In this case, since the rotation speed of the pump that continues to operate immediately before the parallel disconnection is reduced, it is possible to more effectively suppress the variation in the discharge pressure.

Further, in each of the above-mentioned embodiments, an example in which the present invention is applied to a variable speed water supply device provided with two pumps is shown, but the same applies to a variable speed water supply device provided with three or more pumps. Of course you can. Further, although each of the above embodiments has been described with respect to the example of the variable speed water supply device directly connected to the mains of the water supply, the same applies to the variable speed water supply device that temporarily stores water in the water tank or the like and supplies it to the demand destination. You can also
Of course.

[0036]

As described above, according to the present invention, the discharge pressure transiently fluctuates during the additional pump operation or the disconnection stop without performing complicated and difficult control such as forcing control. It can be suppressed by simple control. Therefore, according to the variable speed water supply apparatus of the present invention, it is possible to stably supply water without pressure fluctuation.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a system configuration of a variable speed water supply device.

FIG. 2 is a control flow chart of the first embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a pump shutoff pressure and a rotation speed.

FIG. 4 is a graph showing measurement results of pressure fluctuations in the first embodiment.

FIG. 5 is a control flow chart of the second embodiment of the present invention.

FIG. 6 is a graph showing the measurement result of pressure fluctuations.

FIG. 7 is a control flow chart at the time of additional pump operation in the conventional example.

8 is a graph showing the measurement results of pressure fluctuations in FIG.

FIG. 9 is a control flow diagram when the pump is stopped in the conventional example.

10 is a graph showing the measurement results of pressure fluctuations in FIG.

[Explanation of symbols]

 12 inflow pipe 13a, 13b pump 15 discharge pipe 16 pressure tank 17 control means 18 discharge pressure detector 19a, 19b variable speed means 20a, 20b small water amount detection means (flow switch)

Front Page Continuation (72) Inventor Tomoharu Teshima 4-1-1 Motofujisawa, Fujisawa City, Kanagawa Prefecture Ebara Densan Co., Ltd.

Claims (3)

[Claims] 1. A plurality of pumps rotationally driven by an electric motor, a check valve provided on the discharge side of the pumps, a pressure detector and a pressure tank provided on the downstream side of the check valve, and a pump of the pump. In a variable speed water supply device comprising a small amount of water detection means, a variable speed means for driving the pump at a variable speed, and a control means for controlling the operation of the pump at a variable speed and additionally disconnecting the pump, the control means is at least A variable speed water supply device comprising means for starting the PI control from a predetermined rotation speed of the operating speed of the other additional pump when the other pump that is stopped is additionally supplied when one pump is operating. . 2. The rotation speed output when the other pump is additionally charged is set to a rotation speed corresponding to a control target pressure at the time of shutoff, from the relationship between the pressure at the time of pump shutoff and the rotation speed. The variable speed water supply device according to claim 1. 3. A plurality of pumps rotationally driven by an electric motor, a check valve provided on the discharge side of the pumps, a pressure detector and a pressure tank provided on the downstream side of the check valve, and a pump of the pump. In a variable speed water supply apparatus comprising a small amount of water detection means, a variable speed means for driving the pump at a variable speed, and a control means for controlling the operation of the pump at a variable speed and additionally disconnecting the pump, the control means comprises a plurality of When one of the operating pumps is stopped by parallel disconnection, the means for starting the PI control of the rotational speeds of the other pumps that continue the operation from the rotational speed near the maximum rotational speed of the pump is provided. Characteristic variable speed water supply device.