Water level control device for head tank of hydroelectric power plant

Abstract

To provide a water level control device capable of keeping a water level in a head tank in a full water state without using a water level sensor (detector).SOLUTION: In a hydroelectric power plant comprising a head tank which reserves water flowing in from a river etc., a hydraulic turbine which rotates with water flowing in from the head tank through a water conduit pipe, inflow amount adjusting means which adjusts an inflow amount of water to the hydraulic turbine, and a power generator which is coupled to the hydraulic turbine and generates electricity through the rotation of the hydraulic turbine, a water level control device for the head tank comprises a controller which adjusts an opening of the inflow amount adjusting means, a measuring instrument which measures an electric signal obtained from the power generator, and an arithmetic unit which outputs an opening / closing control signal to the controller so that the inflow amount adjusting means attains to an optimum opening corresponding to a measured value obtained by the measuring instrument.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a water level control device for a head tank installed in a hydroelectric power plant, particularly a small-scale hydroelectric power plant without a dam (hereinafter referred to as a small hydropower plant).

Background Art

[0002] In recent years, due to limited suitable sites for newly constructing large dams and concerns about environmental damage, the number of small hydropower plants without dams is increasing. In a small hydropower plant, a weir is provided on a nearby small river to take water into a water tank called a head tank, store it temporarily, and then generate electricity. The output P in hydropower generation is expressed as P = 9.8 × Q × H × η. Here, Q is the flow rate flowing into the water turbine, H is the effective head, and η is the efficiency of the water turbine and generator. In order to perform hydropower generation efficiently, when the flow rate Q is kept constant, it is desirable to make the effective head H as high as possible. In the above-mentioned small hydropower plant, it is desirable to control the water level of the head tank and maintain it in a full water state.

[0003] As technologies related to water level control in a hydroelectric power plant, for example, Patent Documents 1 and 2 are disclosed. That is, Patent Document 1 calculates the deviation between the measured value of the water level sensor provided in the head tank and the reference water level set value by PID control in a programmable controller, outputs the opening set value of the guide vane as the operation output, and calculates the deviation between the measured value of the opening sensor provided in the guide vane and the opening set value by PI control in a pulse width output controller, and outputs the operation output given by the pulse width signal to the guide vane operation mechanism to operate the opening of the guide vane, thereby maintaining the head tank at the reference water level. In addition, Patent Document 2 discloses a technique in which the water level of a regulating pond is measured by a water level detector, the opening degree of a guide vane is measured by an opening degree detector, and the generator voltage or generator current of a generator is measured by a converter. Based on these measurement results, the opening degree of the guide vane is adjusted by a water level regulator to prevent the generator from overcurrent, while making the inflow of water into the regulating pond equal to the water turbine flow rate to keep the water level of the regulating pond constant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technologies described in Patent Documents 1 and 2, in both cases, the water level of the head tank (regulating pond) measured by a water level sensor (detector) is used to control the water level. That is, since it is necessary to install a water level sensor (detector) in the head tank (regulating pond), there is a problem that the installation cost of the water level sensor (detector) is high, and since the head tank is located at a relatively distant place from the power plant building, there is also a cost for laying the cable of the water level sensor (detector) to the power plant building. In addition, when the cable length of the water level sensor (detector) becomes long, it is likely to be affected by induced lightning due to lightning strikes, so the frequency of failures increases and the repair cost also increases. Moreover, due to a failure of the water level sensor (detector), water level control may not be possible, leading to a situation where power generation stops.

[0006] In view of the above problems, an object of the present invention is to provide a water level control device that can maintain the water level of a head tank in a full water state without using a water level sensor (detector).

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention provides a water level control device for a head tank, comprising: a head tank for storing water flowing in from a river or the like; a waterwheel rotated by water flowing in from the head tank through a water conduit; an inflow rate adjusting means for adjusting the inflow rate of water to the waterwheel; a generator connected to the waterwheel for generating electricity by the rotation of the waterwheel; a controller for adjusting the opening degree of the inflow rate adjusting means; a measuring device for measuring an electrical signal obtained from the generator; and an arithmetic device for outputting an opening / closing control signal to the controller so that the inflow rate adjusting means has an optimal opening degree corresponding to the measured value by the measuring device.

[0008] Further, the arithmetic device gradually changes the opening degree of the inflow rate adjusting means from a fully closed state to a fully open state, records in advance the measured value of the electrical signal that becomes the maximum value obtained from the generator when the water level of the head tank is in a full water state at each opening degree, compares the measured value of the electrical signal obtained from the generator at the current opening degree of the inflow rate adjusting means with the measured value of the electrical signal corresponding to the current opening degree recorded in advance, and when the current measured value of the electrical signal is smaller than the measured value of the electrical signal recorded in advance, controls to close the inflow rate adjusting means by one step after a certain period of time, and when the current measured value of the electrical signal is the same as or larger than the measured value of the electrical signal recorded in advance, controls to open the inflow rate adjusting means by one step after a certain period of time.

Effects of the Invention

[0009] In the present invention, since the opening degree of the inflow rate adjusting means is controlled using the measured value of the electrical signal obtained from the generator, the water level in the head tank can be maintained at a full water state without using a water level sensor (detector). As a result, it is not necessary to install a water level sensor (detector) in the head tank or lay a cable of the water level sensor (detector) from the head tank to the power plant building, so that the cost can be reduced. Also, since there is no need to lay a cable over a long distance, it is not affected by induced lightning due to lightning strikes. Furthermore, power generation will not stop due to a failure of the water level sensor (detector).

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Best Mode for Carrying Out the Invention

[0011] Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS. 1 to 3. The feature of the present invention is that by controlling the opening degree of the inflow rate adjusting means using the electrical signal obtained from the generator, the water level in the head tank is maintained at a full water state without using a water level sensor (detector). Here, the electrical signal obtained from the generator is any one of voltage, current, and power.

[0012] FIG. 1 is a configuration diagram schematically showing a small hydropower plant and a water level control device according to the present invention. As shown in FIG. 1, the small hydropower plant A includes a head tank 1 for storing water flowing in from a river or the like, a water turbine (for example, a reaction turbine such as a Francis turbine) 3 rotated by the water flowing in from the head tank 1 through a water conduit 2, a guide vane 4 as an inflow rate adjusting means for adjusting the inflow rate of water to the water turbine 3, and a generator 5 connected to the water turbine 3 for generating electricity by the rotation of the water turbine 3. Further, the water level control device B includes a voltage measuring device 6 for measuring the voltage obtained from the generator 5, a power measuring device 7 for measuring the power obtained from the generator 5, a controller 8 for adjusting the opening degree of the guide vane 4, and an arithmetic unit 9 for outputting an opening / closing control signal to the controller 8 so that the guide vane 4 has an optimal opening degree corresponding to the measured value by the voltage measuring device 6 or the power measuring device 7. Note that a program for executing the flowcharts shown in FIGS. 2 and 3 is incorporated in the arithmetic unit 9. Further, a current measuring device for measuring the current obtained from the generator 5 may be provided in the water level control device B.

[0013] Next, the case where the water level of the head tank 1 is maintained in a full water state by the water level control device B configured as described above will be described with reference to FIGS. 2 and 3. FIG. 2 is a flowchart showing an operation of measuring an electrical signal (voltage or power) that becomes the maximum value obtained from the generator 5 when the water level of the head tank 1 is in a full water state at each opening degree while gradually changing the opening degree of the guide vane 4 from a fully closed state to a fully open state. FIG. 3 is a flowchart showing an operation of controlling the opening and closing of the guide vane 4 to maintain the water level of the head tank 1 in a full water state.

[0014] First, according to the flowchart shown in FIG. 2, the opening degree of the guide vane 4 is gradually changed from the fully closed state to the fully open state, and at each opening degree, when the head tank 1 is full, the electrical signal that reaches the maximum value obtained from the generator 5 is measured and recorded. Note that this routine is executed when the water level of the head tank 1 is maintained at the full level even when the guide vane 4 is fully open. Also, the measurement of the electrical signal obtained from the generator 5 is performed by the voltage measuring device 6 and the power measuring device 7 in FIG. 1, and the opening and closing of the guide vane 4 is performed by the controller 8 in FIG. 1, but the description thereof is omitted in the following text.

[0015] In step S11 of FIG. 2, when the guide vane 4 is in the fully closed state, the variable designating counter n is changed to 0 in step S12. On the other hand, when the guide vane 4 is not in the fully closed state in step S11, after setting the guide vane 4 to the fully closed state in step S13, the variable designating counter n is changed to 0 in step S12. Subsequently, after waiting for t1 seconds in step S14 to stabilize the water level of the head tank 1, the electrical signal that reaches the maximum value obtained from the generator 5 at present (with the guide vane 4 in the fully closed state) is measured in step S15 and stored (recorded) in the generator electrical signal storage variable GS(n). Next, when the variable designating counter n is not max in step S16, after adding 1 to the variable designating counter n in step S17, the opening degree of the guide vane 4 is opened by one step in step S18, and the process returns to step S14. After that, after waiting for t1 seconds again in step S14 to stabilize the water level of the head tank 1, the electrical signal that reaches the maximum value obtained from the generator 5 at present (with the opening degree of the guide vane 4 opened by one step) is measured in step S15 and stored (recorded) in the generator electrical signal storage variable GS(n). In this way, by repeatedly executing steps S14 to S18, while opening the opening degree of the guide vane 4 step by step, the electrical signal that reaches the maximum value obtained from the generator 5 at each opening degree is measured. When the variable designating counter n reaches max in step S16 (i.e., when the guide vane 4 is fully open), in step S19, the guide vane 4 is returned to the fully closed state and the routine ends.

[0016] Next, according to the flowchart of FIG. 3, the opening and closing control of the guide vane 4 is performed so that the water level of the head tank 1 is maintained in the full water state. The measurement of the electrical signal obtained from the generator 5 is performed by the voltage measuring device 6 and the power measuring device 7 in FIG. 1, and the opening and closing of the guide vane 4 is performed by the controller 8 in FIG. 1, but the description thereof is omitted in the following text.

[0017] First, after waiting for t2 seconds to stabilize the water level of the head tank 1 in step S21 of FIG. 3, in step S22, the current opening degree of the guide vane 4 is stored (recorded) in the guide vane opening degree storage variable GVnow, and in step S23, the current electrical signal obtained from the generator 5 is measured and stored (recorded) in the generator electrical signal storage variable GSnow. Subsequently, when the measured value of the current generator electrical signal stored in the generator electrical signal storage variable GSnow is smaller than the measured value of the generator electrical signal corresponding to the current opening degree of the guide vane 4 measured and recorded in advance according to the flowchart shown in FIG. 2, when tclose seconds have elapsed while maintaining the above state in step S26, in step S28, the opening degree of the guide vane 4 is closed by one step and the process returns to step S21. Otherwise (when there is a change in the state), the process returns to step S24. Here, if the measured value of the current generator electrical signal stored in the generator electrical signal storage variable GSnow is smaller than the measured value of the generator electrical signal corresponding to the current opening degree of the guide vane 4 measured and recorded in advance according to the flowchart shown in FIG. 2, it indicates that the water level in the head tank 1 has dropped below the full water level. Therefore, if this state continues for a certain period of time (tclose seconds), control is performed to return the water level in the head tank 1 to the full water level by closing the opening degree of the guide vane 4 by one step. And until the water level in the head tank 1 returns to the full water level, the loop of step S21→S22→S23→S24→S26→S28→S21 is repeatedly executed.

[0018] On the other hand, in step S24, if the measured value of the current generator electrical signal stored in the generator electrical signal storage variable GSnow is the same as or greater than the measured value of the generator electrical signal corresponding to the current opening degree of the guide vane measured and recorded in advance according to the flowchart shown in FIG. 2, when topen seconds have elapsed while maintaining the above state in step S25, in step S27, the opening degree of the guide vane 4 is opened by one step and returns to step S21. Otherwise (if there is a change in the state), it returns to step S24. Here, if the measured value of the current generator electrical signal stored in the generator electrical signal storage variable GSnow is the same as or greater than the measured value of the generator electrical signal corresponding to the current opening degree of the guide vane 4 measured and recorded in advance according to the flowchart shown in FIG. 2, it means that even if there is no change in the water level in the head tank 1 or the inflow water volume into the head tank 1 increases, the water overflows from the head tank 1 and the change in the water level cannot be detected. Therefore, if this state continues for a certain period of time (topen seconds), control is performed to lower the water level in the head tank 1 at once by opening the opening degree of the guide vane by one step. And until the water level in the head tank 1 drops below the full water level, the loop of step S21→S22→S23→S24→S25→S27→S21 is repeatedly executed. Also, the opening degree of the guide vane 4 is gradually increased step by step. When the measured value of the current generator electrical signal stored in the generator electrical signal storage variable GSnow in step S24 becomes smaller than the measured value of the generator electrical signal corresponding to the current opening degree of the guide vane 4 measured and recorded in advance according to the flowchart shown in FIG. 2, since the water level of the head tank 1 has dropped below the full water level, in step S28, the opening degree of the guide vane 4 is closed by one step and the process returns to step S21. Then, until the water level of the head tank 1 returns to the full water level, the loop of step S21→S22→S23→S24→S26→S28→S21 is repeatedly executed. When the fluctuation of the water volume flowing into the head tank 1 is large, topen and tclose may be adjusted as appropriate.

[0019] In this way, when it is determined that the water level of the head tank 1 has dropped below the full water level, by gradually closing the opening degree of the guide vane 4, the water level of the head tank 1 is controlled to return to the full water level. Also, when there is no change in the water level of the head tank 1 or the change in the water level cannot be detected due to an increase in the inflow water volume causing overflow from the head tank 1, by gradually opening the opening degree of the guide vane 4, the water level of the head tank 1 is once controlled to drop below the full water level. And if it is determined that the water level of the head tank 1 has dropped below the full water level, by gradually closing the opening degree of the guide vane 4, the water level of the head tank 1 is controlled to return to the full water level again, so that the water level of the head tank 1 can be maintained at the full water level.

[0020] Since the present invention is configured as described above, it is possible to control the water level of the head tank 1 without using a water level sensor (detector). Therefore, it is possible to effectively suppress the increase in cost due to installing a water level sensor (detector) and laying cables from the head tank 1 to the power plant building. Also, since there is no need to lay cables over a long distance, there is no influence of induced lightning caused by lightning strikes. Furthermore, there is no situation where power generation stops due to a failure of the water level sensor (detector).

[0021] In the embodiment of the present invention, the case where the guide vane 4 is used as the inflow rate adjusting means has been described as an example, but the present invention is not limited thereto, and various modifications are possible. For example, when an impulse turbine such as a Pelton turbine or a Turgo impulse turbine is used as the turbine 3, the present invention can be applied even if a needle valve is used as the inflow rate adjusting means. Further, when a cross-flow turbine is used as the turbine 3, the present invention can be applied even if a guide vane divided into two sheets (equivalent to 1 / 3 and 2 / 3 of the inflow rate) at a ratio of, for example, 1:2 in the width direction is used. Furthermore, the present invention can be applied even if a gate valve or a butterfly valve is used instead of the guide vane or the needle valve.

Explanation of Reference Numerals

[0022] 1 Head tank 2 Turbine 3 Draft tube 4 Guide vane 5 Generator 6 Voltage measuring device 7 Power measuring device 8 Controller 9 Arithmetic unit A Small hydropower plant B Water level control device

Claims

1. A head tank for storing water flowing in from a river or the like, a waterwheel rotated by the water flowing in from the head tank through a water conduit, an inflow rate adjusting means for adjusting the inflow rate of water to the waterwheel, and a generator connected to the waterwheel and generating electricity by the rotation of the waterwheel. In a hydroelectric power plant, A controller for adjusting the opening degree of the inflow rate adjusting means, a measuring instrument for measuring an electrical signal obtained from the generator, and an arithmetic unit for outputting an opening / closing control signal to the controller so that the inflow rate adjusting means has an optimal opening degree corresponding to the measured value by the measuring instrument. A water level control device for a head tank in a hydroelectric power plant, characterized in that it is configured to include these components.

2. The arithmetic unit gradually changes the opening degree of the inflow rate adjusting means from a fully closed state to a fully open state, and records in advance the measured value of the electrical signal that becomes the maximum value obtained from the generator when the water level of the head tank is in a full water state at each opening degree. At the same time, Compare the measured value of the electrical signal obtained from the generator at the current opening degree of the inflow rate adjusting means with the measured value of the electrical signal corresponding to the recorded opening degree. When the currently measured value of the electrical signal is smaller than the previously recorded measured value of the electrical signal, control is performed to close the inflow rate adjusting means by one step after a certain period of time. At the same time, When the currently measured value of the electrical signal is the same as or larger than the previously recorded measured value of the electrical signal, control is performed to open the inflow rate adjusting means by one step after a certain period of time. The water level control device for a head tank in a hydroelectric power plant according to Claim 1, characterized by the above.

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