Pumped storage system based on library-in-library adjustment and working method thereof

Abstract

The invention provides a pumped storage system based on reservoir-in-reservoir regulation and a working method thereof, a lower reservoir is internally provided with an inter-reservoir isolation structure, the lower reservoir is divided into a first lower reservoir and a second lower reservoir by the inter-reservoir isolation structure, and the first lower reservoir and the second lower reservoir are internally provided with water level monitoring and control systems respectively; a lifting pump station controlled by a water level monitoring and control system is arranged on the inter-reservoir isolation structure, a pump set water inlet of the lifting pump station is located in the second lower reservoir, a pump set water outlet of the lifting pump station is located in the first lower reservoir, the tail water flow channel is communicated with the first lower reservoir, and the water level in the first lower reservoir is always higher than that in the tail water flow channel. A communicating pipe or a lifting pump station is used for actively maintaining the first lower reservoir water level to be above the minimum operation water level under the working condition of a water pump all the time, the site selection of the pumped storage power station is not limited by the natural water level of the lower reservoir any more, the tail water level can be kept stable, the water pump is in a reasonable water suction pressure range all the time, and the cavitation phenomenon is basically avoided. And unit operation safety is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower technology, and in particular to a pumped storage system based on reservoir-within-a-reservoir regulation and its operating method. Background Technology

[0002] Pumped storage technology is an energy storage technology for power systems. It utilizes electricity generated during off-peak hours to pump water to an upper reservoir, and then releases the water to a lower reservoir to generate electricity during peak hours, thus achieving efficient storage and release of electrical energy. During the initial site selection and design of pumped storage power stations, it is usually necessary to reasonably control the water level fluctuation ratio, i.e., the ratio of the highest head to the lowest head. Excessive water level fluctuations cannot meet the operational needs of the units. In conventional pumped storage power stations, the operation of the pump-turbine unit is significantly affected by changes in the water levels of the upper and lower reservoirs, especially when the unit is operating under pump conditions. When the lower reservoir water level is low, the subsequent drop in tailwater level causes a decrease in the pressure at the pump suction end, deteriorating pump conditions and leading to cavitation, which affects the safe and stable operation of the unit. Traditional cavitation optimization measures for pumped storage units, such as adjusting pump operation strategies or implementing cavitation protection measures, are usually unable to dynamically adapt to changes in the lower reservoir water level and may incur additional maintenance costs. The results are often less than ideal; high water levels result in high suction pressure, reducing efficiency and impacting economic benefits.

[0003] The head variation of the pump-turbine unit is typically positively correlated with the water level variation of the upstream and downstream reservoirs, which in turn are influenced by local topography. While theoretically feasible, artificially expanding the reservoir area through excavation to reduce water level fluctuations often leads to significantly increased costs and reduced economic benefits. Given this performance characteristic of pump-turbine units, this requirement may result in the abandonment of some sites with large water level variations but good performance in other aspects (such as geographical location, environmental impact, and economics), thus posing a significant obstacle to the development of the pumped storage industry. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pumped storage system based on reservoir-within-reservoir regulation, which can solve the site selection limitations and unit operation safety problems caused by the large fluctuations in the natural water levels of the upper and lower reservoirs of pumped storage power stations.

[0005] Therefore, the present invention adopts the following technical solution: A pumped storage system based on reservoir-within-reservoir regulation includes an upper reservoir, an underground powerhouse equipped with pump-turbine units, and a lower reservoir. The upper reservoir and the underground powerhouse are connected via a water diversion channel, and the underground powerhouse and the lower reservoir are connected via a tailrace channel. The lower reservoir is equipped with an inter-reservoir isolation structure, which divides the lower reservoir into a first lower reservoir and a second lower reservoir. The first lower reservoir and the second lower reservoir are respectively equipped with water level monitoring and control systems. A booster pump station controlled by the water level monitoring and control system is installed on the inter-reservoir isolation structure. The pump inlet of the booster pump station is located in the second lower reservoir, and the pump outlet of the booster pump station is located in the first lower reservoir. The tailrace channel is connected to the first lower reservoir, and the water level in the first lower reservoir is always higher than that in the tailrace channel.

[0006] Based on the above technical solutions, the present invention may also employ the following further technical solutions, or combine these further technical solutions: The inter-reservoir isolation structure is provided with several connecting structures, and the two end openings of the connecting structures connect the first lower reservoir and the second lower reservoir. The connecting structures are provided with an opening and closing system.

[0007] The opening and closing system includes a working valve controlled by the water level monitoring and control system.

[0008] The opening and closing system also includes a manual maintenance valve, which is located after the working valve.

[0009] The opening and closing system also includes a flow monitoring device.

[0010] The pump inlet of the booster pump station is located below the minimum operating water level of the pump turbine unit, and a filter screen is installed at the pump inlet of the booster pump station.

[0011] The purpose of this invention is also to overcome the shortcomings of the prior art and provide a working method for a pumped storage system based on reservoir-within-reservoir regulation, which can solve the site selection limitations and unit operation safety problems caused by the large fluctuations in the natural water levels of the upper and lower reservoirs of pumped storage power stations.

[0012] Therefore, the present invention adopts the following technical solution: A method for operating a pumped storage system based on reservoir-within-reservoir regulation includes the following steps: S1. During periods of low power load, the pump turbine unit operates in pump mode, and the water level monitoring and control system monitors the water levels of the first and second lower reservoirs in real time. S2. When the water level of the second reservoir is higher than the minimum operating water level under the pump condition, the water level monitoring and control system controls the opening of the working valve in the connecting structure so that the water level of the first reservoir is consistent with the water level of the second reservoir. S3. When the water level of the second lower reservoir drops to the minimum operating water level under pump conditions, the water level monitoring and control system closes the working valve in the connecting structure and starts the booster pump station. The number of pump sets in the booster pump station is adjusted in real time according to the water level of the second lower reservoir to maintain the water level of the first lower reservoir at no lower than the minimum operating water level under pump conditions. S4. When the water level of the second reservoir drops to the dead water level and the water level of the first reservoir drops to the minimum operating water level under pump operation, the pump operation is stopped. During peak power load, the operation is switched to turbine operation as needed. At this time, the water level monitoring and control system controls the opening of the working valve in the connecting structure until the turbine operation ends.

[0013] Compared with the prior art, the present invention has the following advantages and beneficial effects: by constructing the lower reservoir into a separate first lower reservoir and a second lower reservoir, and using a connecting pipe or a booster pump station to actively maintain the water level of the first lower reservoir so that it is always above the minimum operating water level under pump conditions, the head (lift) variation of the unit is controlled within a reasonable range, solving the problem that traditional pumped storage units cannot develop sites with large water level fluctuations. The site selection of pumped storage power stations is no longer limited by the natural water level of the lower reservoir. Even when the water levels of the upper and lower reservoirs change significantly, the tailrace water level can be kept stable, and the pump is always within a reasonable suction pressure range, which basically avoids the occurrence of cavitation and ensures the safe operation of the unit. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0015] Figure 2 This is a detailed diagram of the interconnection structure of the present invention. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote elements with the same or similar functions throughout. However, it should be understood that the drawings are for illustrative purposes only and should not be construed as limiting the present invention. To better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size. It is understandable for those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present invention.

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0018] This invention provides a pumped storage system based on reservoir-within-reservoir regulation, comprising an upper reservoir 1, an underground powerhouse 3 equipped with pump-turbine units, and a lower reservoir 6. The upper reservoir 1 and the underground powerhouse 3 are connected by a water diversion channel 2, and the underground powerhouse 3 and the lower reservoir 6 are connected by a tailrace channel 4. The lower reservoir 6 is equipped with an inter-reservoir isolation structure 7, which divides the lower reservoir 6 into a first lower reservoir 61 and a second lower reservoir 62. The first lower reservoir 61 and the second lower reservoir 62 are respectively equipped with a water level monitoring and control system 8. The inter-reservoir isolation structure 7 is equipped with a booster pump station 13 controlled by the water level monitoring and control system 8. The pump inlet of the booster pump station 13 is located in the second lower reservoir 62, and the pump outlet of the booster pump station 13 is located in the first lower reservoir 61. The tailrace channel 4 is connected to the first lower reservoir 61, and the water level in the first lower reservoir 61 is always higher than that in the tailrace channel 4.

[0019] In this embodiment, the inter-reservoir isolation structure 7 can be a reservoir partition wall or a dam, which can divide the lower reservoir 6 into a first lower reservoir 61 and a second lower reservoir 62. The booster pump station 13 can be set on the reservoir partition wall or inside the dam, etc., according to the actual project.

[0020] The inter-reservoir isolation structure 7 is equipped with several connecting structures 9. The two ends of the connecting structure 9 are connected to the first lower reservoir 61 and the second lower reservoir 62. The connecting structure 9 is equipped with an opening and closing system.

[0021] In this embodiment, the openings of the channels at both ends of the connecting structure 9 are lower than the dead water level of the second lower reservoir 62. Two connecting structures 9 are provided on the inter-reservoir isolation structure 7, and the two connecting structures 9 serve as backups for each other.

[0022] The opening and closing system includes a working valve 10 controlled by a water level monitoring and control system 8.

[0023] In this embodiment, the working valve 10 is preferably a pneumatic working valve, but other pressure valves, submersible solenoid valves, or electric valves can also be used instead, but it is necessary to ensure that the valve control is flexible and reliable, and easy to inspect and maintain.

[0024] The opening and closing system also includes a manual maintenance valve 11, which is located upstream of the working valve 10 and is used to maintain the working valve 10. The manual maintenance valve 11 is normally open.

[0025] The opening and closing system also includes a flow monitoring device 12, which is used to monitor the working status of the connecting structure 9 in real time and determine the fault type of the connecting structure 9, so as to avoid operational accidents caused by blockage of the connecting structure 9 channel or by abnormality of the working valve 10.

[0026] In this embodiment, the flow monitoring device 12 can be selected from electromagnetic flow meters, ultrasonic flow meters, turbine flow meters, etc., according to the actual working conditions.

[0027] The pump inlet of the booster pump station 13 is located below the minimum operating water level of the pump turbine unit. A filter screen is installed at the pump inlet of the booster pump station 13, and a filter screen can also be installed at the outlet of the booster pump station 13.

[0028] The forebay at the outlet of the pump set in pump station 13 can be appropriately expanded downwards to increase the water intake depth of the pump set outlet. The forebay can also be used as a sedimentation tank to prevent silt from entering the connecting structure 9.

[0029] The present invention provides a method for operating a pumped storage system based on reservoir-in-reservoir regulation, comprising the following steps: S1. When the power load is low, the pump turbine unit is in pump operation mode, and the water level monitoring and control system 8 monitors the water level of the first lower reservoir 61 and the second lower reservoir 62 in real time. S2. When the water level of the second lower reservoir 62 is higher than the minimum operating water level under the pump condition, the water level monitoring and control system 8 controls the opening of the working valve 10 in the connecting structure 9 so that the water level of the first lower reservoir 61 is consistent with the water level of the second lower reservoir 62. S3. When the water level of the second lower reservoir 62 drops to the minimum operating water level under the pump condition, the water level monitoring and control system 8 controls the closure of the working valve 10 in the connecting structure 9 and starts the lift pump station 13. The number of pump sets in the lift pump station 13 is adjusted in real time according to the water level of the second lower reservoir 62 to maintain the water level of the first lower reservoir 61 not lower than the minimum operating water level under the pump condition. S4. When the water level of the second lower reservoir 62 drops to the dead water level and the water level of the first lower reservoir 61 drops to the minimum operating water level under the pump condition, the pump condition operation is stopped. During peak power load, the operation is switched to turbine condition as needed. At this time, the water level monitoring and control system 8 controls the opening of the working valve 10 in the connecting structure 9 until the turbine condition operation ends.

[0030] This embodiment controls the head (lift) variation of the unit within a reasonable range. Even when there are large changes in the water levels of the upper and lower reservoirs, it can ensure that the pump turbine operates stably and efficiently at this site.

[0031] When the pumped storage system based on the first lower reservoir 61 of this invention is used during off-peak hours, the unit operates in pump mode and consumes excess electrical energy. That is, water from the second lower reservoir 62 enters the first lower reservoir 61 through the connecting structure 9, then flows through the tailrace channel 4 into the pump turbine unit of the underground powerhouse 3, and is transported to the upper reservoir 1 by the water diversion channel 2.

[0032] When the pumped storage system based on the first lower reservoir 61 of this invention is used during peak electricity demand, the unit operates in turbine mode to generate electricity to supply power to the system. That is, water in the upper reservoir 1 enters the pump turbine unit in the underground powerhouse 3 through the water diversion channel 2, then flows through the tailrace channel 4 into the first lower reservoir 61, and finally enters the second lower reservoir 62 through the connecting structure 9.

[0033] In the design and manufacture of pump-turbine systems, the most important head (lift) parameter is the pump-to-flow ratio. The pump-to-flow ratio is the ratio of the maximum head under pump operating conditions to the minimum head under turbine operating conditions. This invention does not change the minimum head under turbine operating conditions; instead, it reduces the power station's pump-to-flow ratio by lowering the maximum head under pump operating conditions. The maximum head under pump operating conditions equals the highest water level in the upper reservoir minus the lowest water level in the lower reservoir, plus the hydraulic losses in the water conveyance channel. The highest water level in the upper reservoir and the hydraulic losses in the water conveyance channel can be considered constant. Therefore, the key function of this invention is to increase the minimum operating water level in the lower reservoir's inner reservoir during power station pump operation, thus solving the safety and stability issues during unit operation.

[0034] Furthermore, by using a reservoir-within-a-reservoir water level control system, which involves setting up booster pump stations on (or inside) the reservoir-within-a-reservoir and the reservoir partition wall (or dam), the water level in the reservoir-within-a-reservoir can be maintained at an appropriate height even when the water level in the lower reservoir is too low. This fundamentally avoids cavitation operation of the unit when the water level in the lower reservoir is low. It also helps to avoid efficiency reduction caused by deviating from the operating point when the water level is high, thereby eliminating the limitation of the lower reservoir water level on the unit's operation and expanding the operating range of the unit's pumps.

[0035] Based on the description and accompanying drawings of this invention, those skilled in the art can readily manufacture or use the pumped storage system and its operating method based on reservoir-in-reservoir regulation of this invention, and can achieve the positive effects described in this invention.

[0036] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. The terms "installed," "set," "equipped with," "connected," "linked," and "sleeve" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral construction; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two mechanisms, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0037] In the description of this invention, it should be understood that the terms "one end," "the other end," "outer side," "inner side," "horizontal," "end," "length," "outer end," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the mechanism or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. The terms "first" and "second" are also used only for the sake of brevity in description and do not indicate or imply relative importance.

[0038] Furthermore, in practicing the claims of this invention, those skilled in the art can understand and influence variations to the disclosed embodiments through a study of the drawings, the disclosure, and the appended claims. Additionally, in the claims and description, words such as "comprising" and "containing" do not exclude other elements or steps, and non-plural nouns do not exclude their plural forms.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes and modifications made in accordance with the present invention are covered by the scope of the claims of the present invention, and will not be listed here.

Claims

1. A pumped storage system based on reservoir-within-reservoir regulation, comprising an upper reservoir (1), an underground powerhouse (3) equipped with pump-turbine units, and a lower reservoir (6), wherein the upper reservoir (1) and the underground powerhouse (3) are connected by a water diversion channel (2), and the underground powerhouse (3) and the lower reservoir (6) are connected by a tailrace channel (4), characterized in that, The lower reservoir (6) is provided with an inter-reservoir isolation structure (7). The lower reservoir (6) is divided into a first lower reservoir (61) and a second lower reservoir (62) by the inter-reservoir isolation structure (7). The first lower reservoir (61) and the second lower reservoir (62) are respectively provided with a water level monitoring and control system (8). The inter-reservoir isolation structure (7) is provided with a booster pump station (13) controlled by the water level monitoring and control system (8). The pump inlet of the booster pump station (13) is located in the second lower reservoir (62), and the pump outlet of the booster pump station (13) is located in the first lower reservoir (61). The tailwater channel (4) is connected to the first lower reservoir (61), and the water level in the first lower reservoir (61) is always higher than that in the tailwater channel (4).

2. The pumped storage system based on reservoir-in-reservoir regulation as described in claim 1, characterized in that, The inter-reservoir isolation structure (7) is provided with several connecting structures (9), the two ends of the connecting structure (9) are connected to the first lower reservoir (61) and the second lower reservoir (62), and the connecting structure (9) is provided with an opening and closing system.

3. A pumped storage system based on reservoir-in-reservoir regulation as described in claim 2, characterized in that, The opening and closing system includes a working valve (10) controlled by the water level monitoring and control system (8).

4. A pumped storage system based on reservoir-within-a-reservoir regulation as described in claim 3, characterized in that, The opening and closing system also includes a manual maintenance valve (11) and the manual maintenance valve (11) is located after the working valve (10).

5. A pumped storage system based on reservoir-in-reservoir regulation as described in claim 2, characterized in that, The opening and closing system also includes a flow monitoring device (12).

6. A pumped storage system based on reservoir-in-reservoir regulation as described in claim 1, characterized in that, The pump inlet of the booster pump station (13) is located below the minimum operating water level of the pump turbine unit, and a filter screen is installed at the pump inlet of the booster pump station (13).

7. A method for operating a pumped storage system based on reservoir-within-a-reservoir regulation, characterized in that, Includes the following steps: S1. When the power load is low, the pump turbine unit is in pump operation mode, and the water level monitoring and control system (8) monitors the water level of the first lower reservoir (61) and the second lower reservoir (62) in real time. S2. When the water level of the second lower reservoir (62) is higher than the minimum operating water level under the pump condition, the water level monitoring and control system (8) controls the opening of the working valve (10) in the connecting structure (9) so that the water level of the first lower reservoir (61) is consistent with the water level of the second lower reservoir (62). S3. When the water level of the second lower reservoir (62) drops to the minimum operating water level under the pump condition, the water level monitoring and control system (8) controls the closure of the working valve (10) in the connecting structure (9) and starts the booster pump station (13). The number of pump sets in the booster pump station (13) is adjusted in real time according to the water level of the second lower reservoir (62) to maintain the water level of the first lower reservoir (61) not lower than the minimum operating water level under the pump condition. S4. When the water level of the second lower reservoir (62) drops to the dead water level and the water level of the first lower reservoir (61) drops to the minimum operating water level under the pump condition, the pump condition is stopped. During peak power load, the operation is switched to turbine condition as needed. At this time, the water level monitoring and control system (8) controls the opening of the working valve (10) in the connecting structure (9) until the turbine condition operation ends.

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