JP3938369B2 - Variable speed water supply system - Google Patents

Description

  The present invention relates to a variable speed water supply apparatus capable of operating two or more pumps in parallel, and more particularly to a control system configuration capable of reducing fluctuations in discharge pressure when adding / disconnecting pumps operating in parallel.

  FIG. 1 shows a system outline of a variable speed water supply apparatus having two pumps. For example, an inflow pipe 12 is connected to a water distribution pipe 11 that is a main pipe of water supply, and two pumps 13 a and 13 b 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. Further, on the discharge side of the pumps 13a and 13b, 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.
Each of the pumps 13a and 13b includes variable speed means 19a and 19b made of an electric motor including a frequency / voltage converter (inverter) connected to, for example, a three-phase 200V commercial power supply, and is driven at a variable speed.

  Based on the signal from the discharge pressure detector 18, the control means 17 sends a signal to each variable speed means 19a, 19b, and performs feedback control so that the rotational speed of each pump 13a, 13b becomes a predetermined control target pressure. For this speed control, PI (proportional integral) control is used in view of stability of normal control.

  Further, the discharge pipe 15 is provided with small water amount detection means 20a, 20b made of, for example, a flow switch and check valves 21a, 21b for preventing backflow, which are located on the discharge side of the pumps 13a, 13b. The signals from the small water quantity detection means 20a and 20b are sent to the control means 17. When the consumer 14 detects that there is almost no water usage on the customer side 14, the control means 17 performs control such as stopping the pump in order to prevent pump shut-off and save energy. It is.

  By the way, the two pumps 13a and 13b are operated with the rotation speed controlled so that the control target pressure is maintained by one or two pumps according to the amount of water to be fed. When the amount of water used is small, only one unit is operated, the amount of water used increases, and when the control target pressure cannot be maintained by the operation of one pump, that is, the rotational speed of one pump 13a during operation is When the maximum rotational speed is reached, the operation of the second pump 13b is started (added). After that, when the amount of water used on the consumer side decreases, the rotational speed of the pump 13b decreases, and the control target pressure can be maintained with one pump, one of the two The pump 13a or 13b is stopped from being disconnected.

  FIG. 7 shows a control flow when the pump is additionally turned on. When it is determined that the second pump 13b is additionally charged with respect to the first pump 13a in operation, the deviation (EN) between the target pressure value (SV) and the actual pressure value (PV) is calculated. After the PI calculation is performed based on this deviation, 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 rotational speed command (MV) at this time, since the pump being operated is operating at the maximum rotational speed, the maximum rotational speed is also output as the speed command for the pump that is additionally supplied.

  FIG. 8 shows the state of fluctuations in the pump discharge pressure at the time of additional charging. As shown in the figure, a high rotational speed is output at the time of additional charging, and a phenomenon occurs that the discharge pressure rises for a moment and then falls.

  In this case, during parallel operation, one pump is operated at a constant speed near the maximum rotation speed, and the other pump is operated at a variable speed according to the amount of water supplied, and the two pumps are operated at a uniform speed. The case of variable speed operation is considered. Thereafter, 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 is reduced, the rotational speed of the variable speed pump is reduced, and one pump is stopped when the predetermined rotational speed is reached.

  FIG. 9 shows a control flow when the pump is stopped. When the disconnection of one pump 13b is determined for the two pumps 13a and 13b in operation, a deviation (EN) between the target pressure value (SV) and the actual pressure value (PV) is calculated. After the PI calculation is performed based on this deviation, 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 rotational speed command (MV) at this time, since the pump being operated is operating at the minimum rotational speed, the minimum rotational speed is also output as the speed command for the pump 13a to be continuously operated.

  FIG. 10 shows the state of fluctuations in the pump discharge pressure when the disconnection is stopped. Since the minimum rotation speed is output at the time of disconnection and then increases, a phenomenon occurs in which the discharge pressure increases after a momentary decrease as shown in the figure.

  Conventionally, forcing control avoids the occurrence of pressure fluctuations when a pump is added or disconnected. In this forcing control, during the additional operation of the pump, other pumps are added while lowering the rotational speed of the pump that continues operation, and during the parallel operation of the pump, the rotational speed of the pump that continues operation The pump to be stopped is disengaged while raising the pressure.

  Suppression of pressure fluctuation by forcing control depends on the timing and load status, and setting adjustment is very difficult. In other words, the forcing operation is started first, but if it is too early, there is a problem that the pressure fluctuation range increases such that the pressure decreases after rising or decreases after rising.

  The present invention has been made in view of the above-described circumstances, and performs complicated and difficult control such as forcing control that the discharge pressure fluctuates transiently when the pump is additionally turned on or stopped. An object of the present invention is to provide a variable speed water supply apparatus that can be suppressed by simple control.

  The variable speed water supply apparatus of the present invention includes a plurality of pumps that are rotationally driven by an electric motor, a check valve provided on the discharge side of the pump, a pressure detector provided on the downstream side of the check valve, and the pump In a variable speed water supply apparatus comprising: variable speed means for driving the engine at a variable speed; and control means for controlling the operation of the pump to a variable speed and additionally disconnecting the pump, the control means is stopped when at least one pump is operated. When an additional pump is added, a rotation speed corresponding to the control target pressure at the time of pump closing is output as the rotation speed of the added pump.

  Another variable speed water supply apparatus of the present invention includes a plurality of pumps that are rotationally driven by an electric motor, a check valve provided on the discharge side of the pump, a pressure detector provided on the downstream side of the check valve, In a variable speed water supply apparatus comprising: variable speed means for driving the pump at a variable speed; and control means for controlling the operation of the pump at a variable speed and additionally disconnecting the pump. When an additional pump is stopped, the rotation speed of the added pump is output as a low rotation speed at which the pump operates in a deadline.

According to the present invention configured as above, PI control is started from a predetermined low rotational speed output that does not affect the fluctuation of the discharge pressure when the pump is additionally charged. Thereby, 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 for a moment.
Further, according to the present invention, a PI pump that continues operation after disconnecting one pump starts PI control from a rotational speed output near the maximum rotational speed when the pump is disconnected. As a result, it is possible to prevent the discharge pressure from temporarily decreasing due to a response delay in the PI control of the pump that continues to operate.

The plurality of pumps may be connected to an inflow pipe connected to a water pipe.
In addition, the estimated terminal pressure is controlled constant.
The variable speed means drives each of the plurality of pumps at a variable speed.
Further, there are three or more pumps.

  According to the present invention, without performing complicated and difficult control such as forcing control, it is possible to suppress, with simple control, that the discharge pressure fluctuates transiently at the time of additional pump operation or when the disconnection is stopped. . Therefore, according to the variable speed water supply apparatus of the present invention, it is possible to stably supply water having no pressure fluctuation.

Embodiments of the present invention will be described below with reference to the drawings.
In addition, the outline | summary of the system used as the premise of the pump operation control in each following Example is as showing in FIG. An inflow pipe 12 connected to the water distribution pipe 11, a plurality of pumps 13a, 13b connected to the inflow pipe 12, and a discharge connected to the end water supply device 14 connected to the discharge side of each of the pumps 13a, 13b A pipe 15; a discharge pressure detector 18 for detecting the discharge pressure of the pumps 13a and 13b provided in the discharge pipe 15; variable speed means 19a and 19b for driving the pumps 13a and 13b at variable speeds; Control means 17 is provided for controlling the operation of each pump 13a, 13b at a variable speed by PI control and additionally disconnecting.

  Further, the discharge pipe 15 is provided with small water amount detection means 20a, 20b and check valves 21a, 21b located on the discharge side of the respective pumps 13a, 13b, and the small water amount detection means 20a, 20b. Is sent to the control means 17.

  2 to 4 show a first embodiment of the present invention. FIG. 2 is a control flow diagram, FIG. 3 is a diagram showing a relationship between a pump shut-off pressure and a rotational speed, and FIG. It is a graph which shows a fluctuation | variation measurement result.

In this embodiment, the control means 17 shown in FIG. 1 fixes the rotational speed of one pump 13a when the other pump 13b is additionally operated when one pump 13a is operated. A means for starting PI control of the pump 13b from a predetermined rotational speed output is provided.
In this embodiment, the predetermined rotational speed output of the pump 13b to be additionally operated is set to a rotational speed corresponding to the control target pressure at the shut-off time from the relationship between the pressure and the rotational speed at the pump shut-off time.

  That is, when one pump 13a is operating at a variable speed, the amount of water used increases, and when this rotational speed reaches the maximum rotational speed and a predetermined time elapses, another amount of water is supplied as shown in FIG. The additional start of the pump 13b is determined, and the rotational speed of the first pump 13a is fixed.

  Then, the additional operation pump 13b 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 rotational speed HzB is substituted into the rotational speed command MV, This rotational speed is output and PI control of the additional pump 13b is performed. Thereafter, 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 the PI calculation is performed based on this deviation. DMV) is added to the previous rotational speed command (MV), and a new rotational speed command MV is output.

  Here, the predetermined rotational 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, and as shown in FIG. 3, when the pump is closed (flow rate 0). The minimum rotational speed (NB) that generates the target pressure (PB) on the control target curve is set.

  By configuring in this way, the PI control of the pump 13b to be added is started, for example, from an output with a low rotational speed that does not affect the discharge pressure so that the pump is operated in a deadline (the flow switch is closed). Thus, a transient increase in the discharge pressure can be suppressed.

The pressure fluctuation measurement result of this example is shown in FIG.
As is apparent from this measurement result, according to the present embodiment, it is possible to prevent the discharge pressure from increasing during the additional operation of the pump or to delay the response, and to maintain a stable discharge pressure at all times. Can do.

The relationship between the discharge pressure and the rotation speed when the pump is shut off may be stored in advance as a data table, or may be automatically measured and stored during a pump trial operation or the like.
Further, as the pressure control method, either the discharge pressure constant control or the estimated terminal pressure constant control in which the demand destination pressure is constant may be adopted.

5 and 6 show the case of disengagement of the pump according to the second embodiment, FIG. 5 is a control flow diagram, and FIG. 6 is a graph showing the measurement result of the pressure fluctuation.
In this embodiment, when one of a plurality of operating pumps is disconnected from the control means 17 shown in FIG. 1, PI control of other operating pumps is performed near the maximum rotational speed of the pumps. Means for starting from the output of the rotational speed.

  That is, when the two pumps 13a and 13b are operated in parallel, the first pump 13a is operated at a fixed rotational 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 rotational speed of the second pump 13b decreases and reaches a predetermined rotational speed, as shown in FIG. 5, it is decided to stop the disconnection of the pump 13a. . At this time, the first pump 13a immediately before the disconnection to continue the operation is operated at a maximum rotational speed or a speed close thereto.

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

By configuring in this way, the rotational speed of the pump 13a that continues to operate is set to an output that is close to the actually required rotational speed. Can be prevented temporarily.
FIG. 6 shows the pressure fluctuation measurement result of this example. As is apparent from this measurement result, according to the present embodiment, when one of the pumps in parallel operation is stopped from being disconnected, the discharge pressure is prevented from temporarily decreasing, and the discharge is always stable. The pressure can be kept.

  In this embodiment, the maximum rotation speed is substituted for the rotation speed command MV at the first calculation after the separation, but a value close to this maximum rotation speed may be substituted. The decision should be made according to the situation.

  In the above-described embodiment, the pump to be operated is operated near the maximum rotation speed before the disconnection of one pump is stopped, but it may be operated at a uniform speed. In this case, since the rotational speed of the pump that continues to operate immediately before the disconnection is reduced, the fluctuation of the discharge pressure can be more effectively suppressed.

  Moreover, in each said Example, although the example applied to the variable speed water supply apparatus provided with two pumps is shown, of course, it can apply similarly to the variable speed water supply apparatus provided with three or more pumps. It is. Moreover, although each said Example demonstrated the example of the variable speed water supply apparatus directly connected to the mains etc. of water supply, it applies similarly to the variable speed water supply apparatus which stores water once in a water tank etc. and supplies it to a demand destination. Of course, it can be done.

The schematic diagram of the system configuration | structure of a variable speed water supply apparatus. The control flow figure of the 1st example of the present invention. The figure which shows the relationship between the pressure at the time of a pump cutoff, and rotational speed. The graph which shows the measurement result of the pressure fluctuation of 1st Example. The control flowchart of 2nd Example of this invention. Similarly, the graph which shows the measurement result of pressure fluctuation. The control flow figure at the time of the pump additional operation of a prior art example. The graph which shows the measurement result of the pressure fluctuation | variation in FIG. The control flow figure at the time of the pump disconnection stop of a prior art example. The graph which shows the measurement result of the pressure fluctuation | variation in FIG.

Explanation of symbols

12 Inflow pipes 13a and 13b Pump 14 Terminal water supply equipment 15 Discharge pipe 16 Pressure tank 17 Control means 18 Discharge pressure detectors 19a and 19b Variable speed means 20a and 20b Low water quantity detection means (flow switch)
21a, 21b Check valve

Claims (6)

A plurality of pumps driven to rotate by an electric motor; a check valve provided on the discharge side of the pump; a pressure detector provided on the downstream side of the check valve; and variable speed means for driving the pump at a variable speed. In the variable speed water supply apparatus comprising a control means for controlling the operation of the pump at a variable speed and additionally disconnecting the pump,
The control means outputs a rotational speed corresponding to a control target pressure at the time of shutting off the pump as the rotational speed of the added pump when the other stopped pump is additionally turned on during operation of at least one pump. Variable speed water supply device. A plurality of pumps driven to rotate by an electric motor; a check valve provided on the discharge side of the pump; a pressure detector provided on the downstream side of the check valve; and variable speed means for driving the pump at a variable speed. In the variable speed water supply apparatus comprising a control means for controlling the operation of the pump at a variable speed and additionally disconnecting the pump,
The control means outputs a low rotational speed at which the pump operates at the deadline as the rotational speed of the added pump when the other stopped pump is additionally turned on during the operation of at least one pump. A variable speed water supply device characterized by The variable speed water supply apparatus according to claim 1 or 2 , wherein the plurality of pumps are connected to an inflow pipe connected to a water distribution pipe. The variable speed water supply apparatus according to any one of claims 1 to 3 , wherein the estimated terminal pressure constant control is performed. The variable speed water supply apparatus according to any one of claims 1 to 4 , wherein the variable speed means drives each of the plurality of pumps at a variable speed. The variable speed water supply apparatus according to any one of claims 1 to 5 , wherein there are three or more pumps.

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