Water pump operation method, water pump control device, air compression system

Abstract

This invention provides a method for operating a water pump, a control device for a water pump, and an air compression system that enable highly efficient operation of water pumps used in applications where pressure is constantly changing. [Solution] A method for operating a water pump 16 that supplies water into a compression tank 12 in order to compress the air in the compression tank 12, wherein the rotational speed of the water pump 16 is controlled so that the flow rate of the water does not change regardless of the increase in the air pressure, thereby increasing the air pressure to a target value.

Description

Technical Field

[0001] The present invention relates to an operation method of a water pump suitable for supplying water to a region with a large pressure change such as a compressed air tank, a control device for the water pump, and a pneumatic compression system provided with the same.

Background Art

[0002] Conventionally, water pumps used for pumping water and the like are known. A common method for boosting pressure by a water pump is to operate at a constant pressure not exceeding the pump rated pressure and supply a constant flow rate.

[0003] On the other hand, an air compression device for compressing air (for example, see Patent Document 1), and CAES (Compressed Air Energy Storage) technology for storing electrical energy as compressed air are known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Regarding the CAES technology described above, the patent applicant has developed an isothermal air compression system that compresses air isothermally. This system comprises a compression tank capable of storing a mixture of water and air, a water tank for storing water, and a water pump for supplying water from the water tank to the compression tank. The system isothermally compresses the air in the compression tank by raising the water level in the compression tank with the water supplied by the water pump (water piston). Thus, this system uses a water pump in the water-assisted air pressurization process. In normal processes, including water pumping, water pumps are rarely used with variable pressure except during transient states such as startup and shutdown, but in this system, the water pump's pressure changes are constant. If the rotational speed (rotational speed) of this water pump is fixed, the following problems (1) and (2) arise.

[0006] (1) If the rotation speed is reduced, the water flow rate will be insufficient when the air pressure is high, and the required pressure will not be reached. (2) To avoid the above (1), the rotation speed can be increased, but if the air pressure is low, the water flow rate will be excessive, so the water flow rate must be restricted by a throttle valve or other means (or restricted by the piping) to prevent the water pump from being overloaded, which will result in significant losses.

[0007] The present invention has been made in view of the above, and aims to provide a method for operating a water pump, a control device for a water pump, and an air compression system that can operate a water pump used in applications where the pressure is constantly changing with high efficiency. [Means for solving the problem]

[0008] To solve the above-mentioned problems and achieve the objective, the water pump operation method according to the present invention is a method for operating a water pump that supplies water into a compression tank in order to compress the air in the compression tank, characterized in that the rotational speed of the water pump is controlled so that the flow rate of the water does not change regardless of the increase in the air pressure, thereby increasing the air pressure to a target value.

[0009] Furthermore, another operating method according to the present invention is characterized in that, in the invention described above, the rotational speed of the water pump is set based on the detected value of the water pump pressure or the detected value of the air pressure, and the water pump is controlled based on this rotational speed.

[0010] Furthermore, another operating method according to the present invention is characterized in that, in the invention described above, the rotational speed of the water pump is set based on the difference between the detected value and the set value of the water flow rate.

[0011] Furthermore, the water pump control device according to the present invention is a water pump control device that supplies water into a compression tank in order to compress the air in the compression tank, and is characterized in that it controls the rotational speed of the water pump so that the flow rate of water does not change regardless of the increase in the air pressure, thereby increasing the air pressure to a target value.

[0012] Furthermore, another control device according to the present invention is characterized in that, in the above-described invention, the rotational speed of the water pump is set based on the detected value of the water pump pressure or the detected value of the air pressure, and the water pump is controlled based on this rotational speed.

[0013] Furthermore, another control device according to the present invention is characterized in that, in the above-described invention, the rotation speed of the water pump is set based on the difference between the detected value and the set value of the water flow rate.

[0014] Furthermore, the air compression system according to the present invention is characterized by comprising a compression tank, a water pump that supplies water into the compression tank to compress the air in the compression tank, and a control device for the water pump described above. [Effects of the Invention]

[0015] According to the water pump operation method of the present invention, a water pump is operated by supplying water into a compression tank to compress air in the compression tank, and the rotation speed of the water pump is controlled so that the flow rate of water does not change regardless of the increase in the air pressure, thereby raising the air pressure to a target value. This method has the effect of enabling highly efficient operation of a water pump used in applications where the pressure is constantly changing.

[0016] Furthermore, according to another operating method of the present invention, the rotational speed of the water pump is set based on the detected pressure value of the water pump or the detected air pressure value, and the water pump is controlled based on this rotational speed. By controlling the rotational speed according to the pressure, it becomes possible to avoid a sudden decrease in flow rate when the pressure rises, and the effect of being able to continue supplying water at a predetermined flow rate is achieved.

[0017] Furthermore, according to another operating method of the present invention, the rotation speed of the water pump is set based on the difference between the detected value and the set value of the water flow rate. By controlling the rotation speed according to the pressure and flow rate, it becomes possible to avoid a sudden decrease in flow rate when the pressure rises, and it is possible to continue supplying water at a predetermined flow rate without large fluctuations in flow rate.

[0018] Furthermore, the water pump control device according to the present invention is a control device for a water pump that supplies water into a compression tank to compress the air in the compression tank, and controls the rotational speed of the water pump so that the flow rate of the water does not change regardless of the increase in the air pressure, thereby raising the air pressure to a target value. This has the effect of enabling highly efficient operation of a water pump used in applications where the pressure is constantly changing.

[0019] Also, according to another control device according to the present invention, based on the detected value of the pressure of the water pump or the detected value of the pressure of the air, the rotational speed of the water pump is set, and based on this rotational speed, the water pump is controlled. Therefore, by controlling the rotational speed according to the pressure, it becomes possible to avoid a rapid decrease in the flow rate when the pressure increases, and there is an effect that water supply at a predetermined flow rate can be continued.

[0020] Also, according to another control device according to the present invention, based on the difference between the detected value and the set value of the flow rate of the water, the rotational speed of the water pump is set. Therefore, by controlling the rotational speed according to the pressure and the flow rate, it becomes possible to avoid a rapid decrease in the flow rate when the pressure increases, and there is an effect that water supply at a predetermined flow rate can be continued without significant fluctuation in the flow rate.

[0021] Also, according to the air compression system according to the present invention, since it includes a compression tank, a water pump for supplying water into the compression tank to compress the air in the compression tank, and a control device for the water pump described above, there is an effect that the water pump used in the air compression system can be operated with high efficiency.

Brief Description of Drawings

[0022] [Figure 1] FIG. 1 is a schematic configuration diagram showing an embodiment of an operation method of a water pump, a control device of the water pump, and an air compression system according to the present invention. [Figure 2] FIG. 2(1) is a diagram showing an example of a characteristic curve of a water pump, and FIG. 2(2) is a diagram showing an example of the relationship between rotational speed, flow rate, and pressure. [Figure 3] FIG. 3 is a diagram showing an example of the relationship between pressure and rotational speed. [Figure 4] FIG. 4(1) is a diagram corresponding to a comparative example, and FIG. 4(2) is a diagram corresponding to Example 1. [Figure 5] FIG. 5 is a diagram corresponding to Example 2.

Modes for Carrying Out the Invention

[0023] The following describes in detail, with reference to the drawings, embodiments of the water pump operation method, water pump control device, and air compression system according to the present invention. However, the present invention is not limited to these embodiments.

[0024] As shown in Figure 1, the air compression system 10 according to an embodiment of the present invention comprises a compression tank 12 capable of storing a mixture of water and air, a water tank 14 for storing water, a water pump 16, and a control device 18. The system is used to isothermally compress the air in the compression tank 12 by raising the water level in the compression tank 12 with water supplied from the water pump 16 (water piston).

[0025] The water pump 16 supplies water from the water tank 14 to the compression tank 12 and is installed in the piping 20 connecting the compression tank 12 and the water tank 14. The water pump 16 is driven by a motor 22. When the motor 22 drives the water pump 16, it can pump water from the water tank 14 and send it to the compression tank 12 via the piping 20. The water pump 16 does not pump water against the head, but rather pumps water to compress the air inside the compression tank 12. Therefore, the pressure inside the compression tank 12 increases with the water being pumped, depending on the volume inside the tank. When the water pump is used to pump water to the upper reservoir in pumped-storage hydroelectric power generation, the volume of water in the upper reservoir is usually large, and the water level fluctuation is small relative to the total head, so the pressure fluctuation is small.

[0026] A butterfly-type valve 24 is provided in the piping 20 on the outlet side of the water pump 16. The valve 24 is provided to limit the amount of water supplied by the water pump 16 and to avoid overload operation.

[0027] This air compression system 10 further includes a pressure sensor 26 for detecting the pressure inside the compression tank 12, a pressure sensor 28 for detecting the pressure of the water pump 16, a flow sensor 30 for detecting the flow rate of the water pump 16, and a rotational speed sensor 32 for detecting the rotational speed of the water pump 16. The pressure detection values ​​detected by the pressure sensors 26 and 28, the flow detection values ​​detected by the flow sensor 30, and the rotational speed detection values ​​detected by the rotational speed sensor 32 are transmitted to the control device 18.

[0028] The control device 18 controls the water pump 16 by controlling the rotational speed (rotational rate) of the motor 22 via an inverter. The only parameter that can be directly changed when supplying water with the water pump 16 is the rotational speed of the water pump 16. By changing and controlling the rotational speed of the water pump 16, the flow rate of the water pump 16 and the pressure in the compression tank 12 are indirectly controlled. Specifically, the control device 18 sets the rotational speed of the water pump 16 using pressure as a parameter and controls the water pump 16 to operate at the set rotational speed. Furthermore, to improve responsiveness, the control device 18 may perform flow rate feedback control. These control methods will be described later.

[0029] This air compression system 10 includes a hydroelectric power generation device 34 that generates hydroelectric power using water pressurized with compressed air. The hydroelectric power generation device 34 has a branch pipe 36 that branches off from piping 20 near the compression tank 12 and connects to a water tank 14, a water turbine 38 installed in the middle of the branch pipe 36, a generator 40 that generates electricity by the rotation of the water turbine 38, and a butterfly-type valve 42 installed in the branch pipe 36, and generates hydroelectric power using water supplied from the compression tank 12 to the water turbine 38 via piping 20 and branch pipe 36. Note that the hydroelectric power generation device 34 is not essential to the present invention and can be omitted.

[0030] (Embodiment 1) Next, Embodiment 1 using the control device 18 will be described. This Embodiment 1 controls the rotational speed of the water pump 16 using pressure as a parameter.

[0031] Figure 2(1) shows an example of a characteristic curve for a water pump. Note that the numerical values ​​for each data point in the figure are examples only and do not restrict the actual numerical range. The horizontal axis represents the flow rate of the water pump, and the vertical axis represents the pressure head. The curve shows the relationship between flow rate and pressure when the rotational speed of the water pump is changed from 25% to 100%. As shown in this figure, when the pressure is increased while keeping the rotational speed of the water pump constant, the flow rate decreases sharply as the pressure rises. To avoid this, it is necessary to control the rotational speed according to the pressure.

[0032] Figure 2(2) shows an example of operating the water pump 16 while sequentially changing its rotational speed (rotational speed), and plotting the flow rate and pressure. Note that the numerical values ​​of each data point in the figure are examples only and do not restrict the actual numerical range. The horizontal axis represents the flow rate of the water pump 16, and the vertical axis represents the air pressure in the compression tank 12. To control the rotational speed so that the flow rate remains constant regardless of pressure increase, for example, the flow rate is set to 0.6 m³. 3 When the flow rate is 600 l / min and the pressure is 0.7 MPaG or less, the operation is controlled along the circle marks within the dashed ellipse shown in Figure 2(2).

[0033] Figure 3 shows an example plotting the relationship between pressure (marked with a circle in Figure 2(2)) and rotational speed. From the regression line or other approximation lines obtained from this plot, the value of rotational speed (rotational speed) in relation to pressure can be approximately determined. The pressure is determined by the operation of the air compression system 10. The rotational speed is set according to the pressure value so that the flow rate does not fluctuate regardless of the pressure increase. The pressure value can be either the pressure detected by the water pump 16 or the pressure detected inside the compression tank 12.

[0034] An example of an approximate formula for roughly calculating the rotational speed set value in relation to pressure is shown in equation (1) below. C1 and C2 are constants. The rotational speed set value WP.REV.SET of the water pump 16 can be approximately calculated from the pressure detection value WP.PM.PRE. The control device 18 controls the water pump 16 based on the calculated rotational speed set value. When using equation (1), when the pressure rises, control is performed to increase the rotational speed. The approximate formula is not limited to a simple linear equation like equation (1), and other approximate formulas may also be used.

[0035]

number

[0036] In this way, by controlling the rotational speed according to the pressure, it is possible to avoid a sudden decrease in flow rate when the pressure rises, and to continue supplying water at a predetermined flow rate. This allows the air pressure to be raised to the target value. Furthermore, the water pump 16, which is used in applications where the pressure is constantly changing, can be operated with high efficiency.

[0037] (Embodiment 2) Next, the control of Embodiment 2 by the control device 18 will be described. In Embodiment 2, in addition to pressure, the flow rate is used as a parameter to control the rotational speed of the water pump 16, as in Embodiment 1 described above.

[0038] In Embodiment 1 described above, by parameterizing the pressure, the rotational speed can be increased as the pressure rises, allowing water supply to continue. However, since Embodiment 1 is an open-loop control, it is difficult to suppress flow rate fluctuations. If the flow rate fluctuates at the stage where qualitative pressurization operation becomes possible, the pressurization time may vary depending on the conditions, which may not meet the requirements of actual operation, such as wanting to increase the pressure in a constant time. To solve this problem, the flow rate is actively controlled by flow rate feedback control, which incorporates the flow rate detection value as a parameter.

[0039] For flow rate control, the difference ΔF between the detected flow rate and the set flow rate of the water pump 16 is used. If the detected flow rate is WP.FM.PRE and the set flow rate is WP.FM.SET, then ΔF = WP.FM.PRE - WP.FM.SET. For example, when PI control is added to equation (1) above, the rotational speed set value WP.REV.SET is described by the following equation (2) using the difference ΔF and the detected pressure value WP.PM.PRE of the water pump 16. The two terms on the right side of the right-hand side of equation (2) represent the flow rate control elements. p , C i θ is a constant, and t is time. Note that flow rate control is not limited to linear control such as PI control; other control methods may also be used.

[0040]

number

[0041] In this way, by controlling the rotational speed according to the pressure and flow rate, it is possible to avoid a sudden decrease in flow rate when the pressure rises, and to continue supplying water at a predetermined flow rate without large fluctuations in flow rate. This allows the air pressure to be raised to the target value. Furthermore, the water pump 16, which is used in applications where the pressure is constantly changing, can be operated with high efficiency.

[0042] (Verification of the effects of the present invention) To verify the effects of the present invention, the time changes in pressure and flow rate were compared under three conditions: no control, open control where the rotation speed is set from the pressure, and with the addition of flow rate feedback control. The case without control corresponds to the comparative example, while the open control case where the rotation speed is set from the pressure and the case with the addition of flow rate feedback control correspond to the examples.

[0043] <Comparative Example> The comparative example is the case without control, that is, when the water pump 16 is operated without changing the rotational speed. Figure 4(1) shows the time changes of various data (water level in the compression tank, compression tank pressure, water pump flow rate, water pump rotational speed, water pump power, water pump pressure) in this case. The water pump rotational speed (rotational speed) is the value on the right vertical axis multiplied by 5. As shown in this figure, it can be seen that as the pressure increases, the flow rate decreases and only rises to about 0.4 MPaG.

[0044] <Example 1> Example 1 is an embodiment of the above-described Embodiment 1, and is an open control case where the rotation speed is set from the pressure. Figure 4(2) shows the time changes of various data (water level in the compression tank, compression tank pressure, water pump flow rate, water pump rotation speed, water pump power, water pump pressure) in this case. As shown in this figure, it can be seen that the decrease in flow rate is suppressed and the pressure reaches 0.7 MPaG. However, as the pressure increases, the flow rate decreases.

[0045] <Example 2> Example 2 is an embodiment of the above-described embodiment 2, in which flow rate feedback control is added to open control, which sets the rotation speed from the pressure. Figure 5 shows the time changes of various data (water level in the compression tank, compression tank pressure, water pump flow rate, water pump rotation speed, water pump power, water pump pressure) in this case. As shown in this figure, it can be seen that the decrease in flow rate is suppressed.

[0046] Note that the numerical values ​​of each data point shown in Figures 4 and 5 are scalable and do not restrict the actual numerical range.

[0047] As described above, the water pump operation method according to the present invention is a method for operating a water pump that supplies water into a compression tank to compress the air in the compression tank, and controls the rotation speed of the water pump so that the flow rate of water does not change regardless of the increase in the air pressure, thereby raising the air pressure to a target value. This makes it possible to operate a water pump used in applications where the pressure is constantly changing with high efficiency.

[0048] Furthermore, according to another operating method of the present invention, the rotational speed of the water pump is set based on the detected pressure value of the water pump or the detected air pressure value, and the water pump is controlled based on this rotational speed. By controlling the rotational speed according to the pressure, it is possible to avoid a sudden decrease in flow rate when the pressure rises, and to continue supplying water at a predetermined flow rate.

[0049] Furthermore, according to another operating method of the present invention, the rotation speed of the water pump is set based on the difference between the detected value and the set value of the water flow rate. By controlling the rotation speed according to the pressure and flow rate, it is possible to avoid a sudden decrease in flow rate when the pressure rises, and to continue supplying water at a predetermined flow rate without large fluctuations in flow rate.

[0050] Furthermore, according to the water pump control device of the present invention, a water pump control device that supplies water into a compression tank to compress air in the compression tank controls the rotational speed of the water pump so that the flow rate of water does not change regardless of the increase in the air pressure, thereby raising the air pressure to a target value, and thus enabling highly efficient operation of a water pump used in applications where the pressure is constantly changing.

[0051] Furthermore, according to another control device of the present invention, the rotation speed of the water pump is set based on the detected pressure value of the water pump or the detected air pressure value, and the water pump is controlled based on this rotation speed. By controlling the rotation speed according to the pressure, it is possible to avoid a sudden decrease in flow rate when the pressure rises, and to continue supplying water at a predetermined flow rate.

[0052] Furthermore, according to another control device of the present invention, the rotation speed of the water pump is set based on the difference between the detected value and the set value of the water flow rate. By controlling the rotation speed according to the pressure and flow rate, it is possible to avoid a sudden decrease in flow rate when the pressure rises, and to continue supplying water at a predetermined flow rate without large fluctuations in flow rate.

[0053] Furthermore, the air compression system according to the present invention includes a compression tank, a water pump that supplies water into the compression tank to compress the air in the compression tank, and a control device for the water pump described above, so that the water pump used in the air compression system can be operated with high efficiency. [Industrial applicability]

[0054] As described above, the water pump operating method, water pump control device, and air compression system according to the present invention are useful for water pumps used in applications where the pressure is constantly changing, and are particularly suitable for operating water pumps with high efficiency. [Explanation of Symbols]

[0055] 10 Air Compression System 12 Compression Tank 14 Water Tanks 16 Water pump 18 Control device 20 Piping 22 motors 24,42 valves 26,28 Pressure Sensor 30 Flow Sensor 32 Rotation speed sensor 34 Hydroelectric power generation equipment 36 Branch pipes 38 Waterwheels 40 Generators

Claims

1. A method for operating a water pump that supplies water into a compression tank in order to compress the air inside the compression tank, A method for operating a water pump, characterized by controlling the rotational speed of the water pump so that the water flow rate does not change regardless of the increase in air pressure, thereby increasing the air pressure to a target value.

2. The method for operating a water pump according to claim 1, characterized in that the rotation speed of the water pump is set based on a detected value of the pressure of the water pump or a detected value of the air pressure, and the water pump is controlled based on this rotation speed.

3. The water pump operation method according to claim 2, characterized in that the rotation speed of the water pump is set based on the difference between the detected value and the set value of the water flow rate.

4. A control device for a water pump that supplies water into a compression tank in order to compress the air inside the compression tank, A water pump control device characterized by controlling the rotational speed of the water pump so that the water flow rate does not change regardless of the increase in air pressure, thereby increasing the air pressure to a target value.

5. The water pump control device according to claim 4, characterized in that the rotation speed of the water pump is set based on the detected pressure of the water pump or the detected air pressure, and the water pump is controlled based on this rotation speed.

6. The water pump control device according to claim 5, characterized in that it sets the rotation speed of the water pump based on the difference between the detected value and the set value of the water flow rate.

7. An air compression system comprising a compression tank, a water pump that supplies water into the compression tank to compress the air in the compression tank, and a control device for the water pump according to any one of claims 4 to 6.

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