A method for idling operation of a pumped storage power station

Abstract

The application discloses a kind of emptying operation methods of pumped storage power station, belong to the technical field of water conservancy and hydropower engineering, can solve the problem that existing pumped storage power station upper and lower reservoir emptying is not synchronized, corresponding emergency and maintenance condition is difficult to realize fine management.The method comprises the following steps: S1, the minimum emptying flow of upper reservoir is determined according to the emptying requirement time of upper reservoir;S2, the emptying operation flow of upper reservoir is determined according to the minimum emptying flow of upper reservoir;S3, the design size of lower reservoir emptying structure and its minimum emptying operation flow are determined according to the emptying operation flow of upper reservoir, and the design size of lower reservoir emptying structure is adjusted according to the minimum emptying operation flow and the emptying operation flow of upper reservoir, to obtain the final size of lower reservoir emptying structure;S4, emergency emptying of upper reservoir is carried out by using unit, and emergency emptying of lower reservoir is carried out synchronously by using the final size of lower reservoir emptying structure.The application is used for the emptying design and operation of pumped storage power station.

Description

Technical Field

[0001] This invention relates to a method for venting operation of a pumped storage power station, belonging to the field of water conservancy and hydropower engineering technology. Background Technology

[0002] Currently, the construction of pumped storage power stations in my country has entered a stage of large-scale development. These power stations possess key functions in power system peak shaving, frequency regulation, and energy storage, and are of great value in ensuring the stable operation of the power system.

[0003] Pumped storage power stations are equipped with upper and lower reservoirs. Under normal circumstances, the flood control requirements can be met by reserving the superelevation of the dam crest. The lower reservoir venting facility is mainly to ensure the safety of the project during operation under emergency conditions and to meet the requirements of emergency venting and maintenance venting. However, the upper and lower reservoirs of pumped storage power stations need to be vented in a coordinated manner, and the venting flow rate is difficult to regulate. The existing venting methods of pumped storage power stations have two major defects: (1) The existing schemes are all designed based on a single reservoir and do not consider the coordinated venting of the upper and lower reservoirs. This can easily lead to a mismatch between the venting rate of the upper reservoir and the venting rate of the lower reservoir, resulting in problems such as high water level in the lower reservoir. (2) In the western region, the lower reservoir of power stations is mostly formed by dredging and filling the riverbank beach or gully. The downstream river channel has a small flood peak flow once every 20 years. The existing venting structure is constrained by the conditions of mechanized construction. The diameter of the flood discharge venting tunnel of pumped storage power station is large. The maximum discharge capacity does not match the downstream flood control capacity. Open discharge operation is prone to causing man-made floods and causing downstream overflow risk. It is necessary to control the discharge capacity by controlling the gate opening. The gate is operated at a small opening for a long time, which is prone to vibration, cavitation and other problems.

[0004] In summary, the lack of coordination or improper control in the venting process of existing pumped storage power stations can easily lead to sudden changes in reservoir water levels, posing a serious threat to the safe operation of the power station under extreme conditions. Summary of the Invention

[0005] This invention provides a method for the venting operation of a pumped storage power station, which can solve the problems of asynchronous venting of the upper and lower reservoirs, mismatch between the discharge volume and the downstream flood control capacity, and the inability to distinguish between emergency and maintenance conditions for precise control in existing pumped storage power stations.

[0006] This invention provides a method for venting operation of a pumped storage power station, the method comprising:

[0007] S1. Determine the venting type of the pumped storage power station. When the venting type is emergency venting, determine the minimum venting flow rate of the upper reservoir based on the venting time requirement of the upper reservoir in the pumped storage power station.

[0008] S2. Determine the operating flow rate of the upper reservoir based on the minimum discharge flow rate of the upper reservoir and the no-load flow rate of the units in the water conveyance and power generation system of the pumped storage power station.

[0009] S3. Based on the discharge flow rate of the upper reservoir and the required discharge time of the lower reservoir in the pumped storage power station, determine the design dimensions of the lower reservoir discharge structure and its minimum discharge flow rate, and adjust the design dimensions of the lower reservoir discharge structure according to the minimum discharge flow rate and the discharge flow rate of the upper reservoir to obtain the final dimensions of the lower reservoir discharge structure.

[0010] S4. The upper reservoir is emptied in an emergency using the generator units of the water conveyance and power generation system, and the lower reservoir is simultaneously emptied in an emergency using the final-sized lower reservoir emptying structure.

[0011] Optionally, in step S3, the design dimensions of the lower reservoir venting structure and its minimum venting flow rate are determined based on the upper reservoir venting operation flow rate and the required venting time of the lower reservoir in the pumped storage power station. Specifically, this includes:

[0012] S31. Based on the discharge flow rate of the upper reservoir, the dimensions of the discharge structure of the lower reservoir in the pumped storage power station are initially estimated.

[0013] S32. Determine the relationship curve between the reservoir water level and the reservoir discharge flow rate during the operation of the reservoir discharge structure, and determine the reservoir discharge time based on the relationship curve;

[0014] S33. Adjust the size of the lower reservoir emptying structure according to the lower reservoir emptying time and the lower reservoir emptying requirement time in the pumped storage power station;

[0015] S34. Repeat steps S32 and S33 until the lower reservoir emptying time is less than or equal to the lower reservoir emptying requirement time, and obtain the design dimensions of the lower reservoir emptying structure and its minimum emptying operation flow rate.

[0016] Optionally, S33 specifically includes:

[0017] When the lower reservoir emptying time exceeds the required lower reservoir emptying time in the pumped storage power station, the size of the lower reservoir emptying structure is updated by increasing the discharge size of the lower reservoir emptying structure.

[0018] Optionally, in step S3, the design dimensions of the lower reservoir venting structure are adjusted based on the minimum venting operation flow rate and the upper reservoir venting operation flow rate to obtain the final dimensions of the lower reservoir venting structure. Specifically, this includes:

[0019] S35. Determine whether the minimum venting operation flow rate is greater than or equal to the upper reservoir venting operation flow rate. If yes, proceed to S36; otherwise, proceed to S37.

[0020] S36. The design dimensions of the reservoir discharge structure shall be used as the final dimensions of the reservoir discharge structure;

[0021] S37. The design dimensions of the lower reservoir venting structure are updated by increasing the discharge size of the lower reservoir venting structure, and the minimum venting operation flow of the updated lower reservoir venting structure is determined.

[0022] S38. Repeat S35 to S37.

[0023] Optionally, the discharge size of the lower reservoir venting structure increases by 100mm to 300mm each time.

[0024] Optionally, S2 specifically includes:

[0025] When the total no-load flow of N units in the pumped storage power station's water conveyance and power generation system is less than the minimum discharge flow of the upper reservoir, and the total no-load flow of N+1 units is greater than or equal to the minimum discharge flow of the upper reservoir, the N+1 units are used as the upper reservoir discharge operation equipment, and the total no-load flow of the N+1 units is used as the upper reservoir discharge operation flow; wherein, N is an integer greater than or equal to 1.

[0026] Optionally, the method further includes:

[0027] When the venting type is maintenance venting, the reservoir that needs to be vented is determined;

[0028] When the reservoir that needs to be emptied is the upper reservoir, the upper reservoir is emptied for maintenance using the water conveyance and power generation system and the lower reservoir.

[0029] When the reservoir that needs to be emptied is the lower reservoir, the water conveyance and power generation system and the upper reservoir are used to carry out maintenance and emptying of the lower reservoir.

[0030] Optionally, the upper reservoir can be emptied for maintenance using the aforementioned water conveyance and power generation system and the lower reservoir, specifically as follows:

[0031] The water volume below the normal water level of the upper reservoir is released into the lower reservoir using the turbine operating condition or no-load operation condition of the water conveyance and power generation system, and the capacity difference between the upper and lower reservoirs is emptied using the lower reservoir's venting structure.

[0032] Optionally, the lower reservoir can be emptied for maintenance using the aforementioned water conveyance and power generation system and the upper reservoir, specifically as follows:

[0033] The water volume above the dead water level in the lower reservoir is pumped into the upper reservoir using the pumps of the water conveyance and power generation system, and the water volume below the dead water level in the lower reservoir is emptied using the lower reservoir emptying structure or pumping equipment.

[0034] Optionally, the downstream of the reservoir venting structure is provided with multiple downstream spillway structures; before step S4, the method further includes:

[0035] The maximum operating flow of the lower reservoir discharge structure is compared sequentially with the peak flow of each downstream spillway structure in a year (T). The downstream spillway structure corresponding to the peak flow of the year (T) that is greater than the maximum operating flow is connected to the outlet of the lower reservoir discharge structure; wherein, T is a positive integer.

[0036] The beneficial effects that this invention can produce include:

[0037] The present invention provides a method for the emptying operation of a pumped storage power station. This method involves emptying the upper reservoir to the lower reservoir using the generator units of a water conveyance and power generation system. The size of the lower reservoir's emptying structure is determined by the emptying flow rate of the upper reservoir, and the lower reservoir's emptying structure is used to achieve synchronous emptying of the lower reservoir, thus realizing coordinated control of the upper and lower reservoirs. This invention improves the safety management, operation and maintenance, and emergency response capabilities of pumped storage power station dams. Simultaneously, by coordinating the operation of the upper and lower reservoirs, this invention reduces the amount of water released during emergency air defense and maintenance emptying, improving the economic efficiency of the pumped storage power station. This invention is particularly applicable to two types of pumped storage power stations: first, pumped storage power stations with large-scale flood discharge structures that require long-term low-flow operation; and second, power stations that require the construction of a dedicated lower reservoir in a river channel or on the riverbank, specifically including the construction of a sand-blocking dam and flood discharge tunnel in the river channel, or the excavation and filling of riverbank beaches and gullies to form a reservoir. Attached Figure Description

[0038] Figure 1 A flowchart of the venting operation method of a pumped storage power station provided in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of a pumped storage power station provided in an embodiment of the present invention.

[0040] Figure label:

[0041] 11. Upper reservoir; 12. Water conveyance and power generation system; 13. Lower reservoir; 14. Lower reservoir venting structure. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0043] This invention provides a method for venting operation of a pumped storage power station, such as... Figure 1 As shown, the method includes:

[0044] S1. Determine the venting type of the pumped storage power station. When the venting type is emergency venting, determine the minimum venting flow rate of the upper reservoir based on the venting time requirement of the upper reservoir in the pumped storage power station.

[0045] refer to Figure 2 As shown, the pumped storage power station consists of an upper reservoir 11, a water conveyance and power generation system 12, a lower reservoir 13, and a lower reservoir discharge structure 14. Working valves and valve opening control devices are installed at any position on the lower reservoir discharge structure 14. An inlet is installed at the inlet of the lower reservoir discharge structure 14, and an energy dissipation structure is installed at the outlet of the lower reservoir discharge structure 14.

[0046] Pumped storage power stations typically venting types include emergency venting and maintenance venting.

[0047] Emergency venting refers to the situation where, in extreme circumstances, both the upper reservoir 11 and the lower reservoir 13 need to be vented simultaneously.

[0048] Emergency venting indicators are generally determined based on a combination of factors, including dam type, reservoir venting rate, head reduction, and head reduction rate. Typically, depending on the dam type, one or more control indicators are required to exceed a certain critical value within a fixed time period.

[0049] For example, if both the upper and lower reservoirs of a pumped storage power station are earth-rock dams, then the venting capacity within 7 days must meet the following requirements:

[0050] 1) The head reduction rate should not be less than 15%;

[0051] 2) The reservoir emptying rate should not be less than 40% or the emptying head reduction should not be less than 20m.

[0052] The aforementioned required emptying time for the upper reservoir refers to the time within which the upper reservoir 11 of the pumped storage power station meets the emergency emptying requirements. In practical applications, the minimum emptying flow rate of the upper reservoir 11 can be calculated based on its capacity and the required emptying time.

[0053] S2. Determine the operating flow rate of the upper reservoir based on the minimum discharge flow rate of the upper reservoir and the no-load flow rate of the units in the water conveyance and power generation system 12 of the pumped storage power station.

[0054] Specifically, when the total no-load flow of N units in the pumped storage power station's water conveyance and power generation system 12 is less than the minimum discharge flow of the upper reservoir, and the total no-load flow of N+1 units is greater than or equal to the minimum discharge flow of the upper reservoir, N+1 units will be used as the upper reservoir discharge operation equipment, and the total no-load flow of N+1 units will be used as the upper reservoir discharge operation flow; where N is an integer greater than or equal to 1.

[0055] The no-load flow rate is the minimum flow rate required to maintain stable operation of the pumped storage unit when it is not under load (output power is 0), which is usually 5% to 20% of the rated flow rate of the unit.

[0056] The upper reservoir 11 is generally emptied using the no-load flow of the water conveyance and power generation system 12. When the water conveyance and power generation system 12 has unfavorable factors such as fracture zones and cannot be emptied, an upper reservoir emptying structure needs to be built separately on the upper reservoir 11 to meet the requirement that the emergency emptying time minus the technical guidelines is less than 0.

[0057] The upper reservoir 11 is vented using the no-load flow of the water conveyance and power generation system 12. In practical applications, a cyclical calculation method can also be used to determine the number of generating units required for venting. Specifically, the emergency venting time is first checked using the venting flow of a single generating unit under no-load operation. When the emergency venting time of the upper reservoir minus the time required by the technical guidelines is less than or equal to 0, the venting design of the upper reservoir 11 is completed. When the emergency venting time of the upper reservoir minus the time required by the technical guidelines is greater than 0, the no-load flow of one more generating unit is added for design. This process is repeated until the emergency venting time of the upper reservoir minus the time required by the technical guidelines is less than or equal to 0, at which point the venting design of the upper reservoir 11 is completed.

[0058] It should be noted that if increasing the number of generating units to M (where M is the total number of generating units) still cannot meet the technical guidelines requirements, the upper reservoir 11 needs to be constructed separately at a suitable location. The upper reservoir venting structure should be connected to the water conveyance and power generation system 12 for venting, so as to ensure that the emergency venting time minus the time required by the technical guidelines is less than or equal to 0.

[0059] S3. Based on the discharge flow rate of the upper reservoir and the discharge time requirement of the lower reservoir in the pumped storage power station, determine the design dimensions of the lower reservoir discharge structure 14 and its minimum discharge flow rate. Adjust the design dimensions of the lower reservoir discharge structure 14 according to the minimum discharge flow rate and the discharge flow rate of the upper reservoir to obtain the final dimensions of the lower reservoir discharge structure 14.

[0060] Based on the upper reservoir's emptying operation flow rate and the required emptying time of the lower reservoir in the pumped storage power station, the design dimensions of the lower reservoir's emptying structure 14 and its minimum emptying operation flow rate are determined, specifically including:

[0061] S31. Based on the discharge flow rate of the upper reservoir, the dimensions of the discharge structure 14 of the lower reservoir of the pumped storage power station are initially determined.

[0062] S32. Determine the relationship curve between the reservoir water level and the reservoir discharge flow rate when the reservoir discharge structure 14 is in operation, and determine the reservoir discharge time based on the relationship curve.

[0063] S33. Adjust the dimensions of the lower reservoir emptying structure 14 according to the lower reservoir emptying time and the lower reservoir emptying requirement time in the pumped storage power station.

[0064] Specifically, when the emptying time of the lower reservoir exceeds the emptying time required for the middle and lower reservoirs of the pumped storage power station, the size of the lower reservoir emptying structure 14 is updated by increasing the discharge size of the lower reservoir emptying structure 14.

[0065] In this embodiment of the invention, the discharge size of the lower reservoir venting structure 14 increases by 100mm to 300mm each time. In practice, the discharge size can be any value during the design process; choosing an integer is for standardization and to facilitate the procurement of prefabricated pipes during construction. For example, in practical applications, the discharge size of the lower reservoir venting structure 14 is typically chosen to be 200mm each time.

[0066] S34. Repeat steps S32 and S33 until the reservoir emptying time is less than or equal to the required reservoir emptying time, and obtain the design dimensions of the reservoir emptying structure 14 and its minimum emptying operation flow rate.

[0067] The above-mentioned lower reservoir emptying requirement refers to the time required for the pumped storage power station's lower reservoir 13 to meet the emergency emptying index requirements.

[0068] The lower reservoir 13 is emptied using a separate lower reservoir emptying structure 14, first based on the lower reservoir emptying flow rate. > Upper Reservoir Emptying Operation Flow The initial dimensions of the lower reservoir venting structure 14 are determined. Then, the minimum venting flow rate of the lower reservoir venting structure 14 during operation is determined, as well as the relationship curve between the lower reservoir water level and the lower reservoir venting flow rate. Based on this relationship curve, the lower reservoir venting time is calculated. When the lower reservoir venting time minus the time required by the technical guidelines is less than or equal to 0, the design dimensions of the lower reservoir venting structure 14 and its minimum venting flow rate are obtained, and the next design step is performed. When the lower reservoir venting time minus the time required by the technical guidelines is greater than 0, the discharge size of the lower reservoir venting structure 14 is increased (by 200mm each time). This process is repeated until the lower reservoir venting time minus the time required by the technical guidelines is less than or equal to 0.

[0069] The design dimensions of the lower reservoir venting structure 14 are adjusted based on the minimum venting flow rate and the upper reservoir venting flow rate to obtain the final dimensions of the lower reservoir venting structure 14, specifically including:

[0070] S35. Determine whether the minimum venting operation flow rate is greater than or equal to the upper reservoir venting operation flow rate. If yes, proceed to S36; otherwise, proceed to S37.

[0071] S36. The design dimensions of the reservoir discharge structure 14 shall be taken as the final dimensions of the reservoir discharge structure 14.

[0072] S37. The design dimensions of the lower reservoir venting structure 14 are updated by increasing the discharge size of the lower reservoir venting structure 14, and the minimum venting operation flow of the updated lower reservoir venting structure 14 is determined.

[0073] S38. Repeat S35 to S37.

[0074] When a pumped-storage power station performs emergency venting, it is necessary to ensure that the water levels of the upper reservoir 11 and the lower reservoir 13 decrease synchronously during venting. Therefore, it is necessary to calculate the minimum venting flow rate for the lower reservoir venting structure 14 during operation. The minimum discharge flow rate is determined by whether it is greater than or equal to the upper reservoir's discharge flow rate. When the difference between the minimum discharge flow rate and the upper reservoir's discharge flow rate is less than 0, the discharge size of the lower reservoir's discharge structure 14 is increased (by 200mm each time). This process is repeated until the difference between the minimum discharge flow rate and the upper reservoir's discharge flow rate is greater than or equal to 0. The current design size of the lower reservoir's discharge structure 14 is then taken as its final size. This yields the final size of the lower reservoir's discharge structure 14 that meets both the lower reservoir's discharge time requirements and the upper reservoir's discharge flow rate.

[0075] Furthermore, multiple downstream spillway structures are provided downstream of the reservoir venting structure 14; prior to S4, the method further includes:

[0076] The maximum operating flow of the lower reservoir discharge structure 14 is compared with the annual flood peak flow of each downstream spillway structure. The downstream spillway structure corresponding to the annual flood peak flow of T years that is greater than the maximum operating flow is connected to the outlet of the lower reservoir discharge structure 14; where T is a positive integer.

[0077] Among them, the T-year return period peak flow is the maximum peak flow with a return period of T years, calculated using frequency analysis based on downstream river hydrological data. It is a key indicator for determining whether the discharge capacity is safe. In practical applications, T years can be 5 years, 10 years, 15 years, 20 years, or other custom-defined years.

[0078] The maximum operating flow rate when the lower reservoir 13 is emptied is compared with the peak flow rate of the downstream spillway structure (such as the downstream river / ditch) during the T-year flood event. When the maximum operating flow rate minus the peak flow rate of the T-year flood event is less than 0, the downstream spillway structure is connected to the outlet of the lower reservoir emptying structure 14, and the emergency emptying design is completed. When the maximum operating flow rate minus the peak flow rate of the T-year flood event is greater than or equal to 0, the outlet position of the lower reservoir emptying structure 14 is reselected, and the above process is repeated.

[0079] S4. The upper reservoir 11 is emptied in an emergency using the generator unit of the water conveyance power generation system 12, and the lower reservoir 13 is emptied in an emergency using the lower reservoir emptying structure 14 of the final size.

[0080] In this invention, the method further includes:

[0081] When the venting type is maintenance venting, the reservoir that needs to be vented is determined.

[0082] When the upper reservoir 11 needs to be emptied, the upper reservoir 11 is emptied for maintenance using the water conveyance and power generation system 12 and the lower reservoir 13.

[0083] Specifically: the water capacity below the normal water level of the upper reservoir 11 is released into the lower reservoir 13 using the turbine operating condition or no-load operation condition of the water conveyance and power generation system 12, and the capacity difference between the upper reservoir 11 and the lower reservoir 13 is released using the lower reservoir emptying structure 14.

[0084] Maintenance venting refers to the separate venting of the upper reservoir 11 and the lower reservoir 13 during maintenance; that is, only one needs to be vented. When a reservoir needs maintenance venting, the total discharge volume must be controlled to reduce the water loss rate and avoid water waste that could affect power generation efficiency. The water loss rate is the proportion of vented water that is not recovered and reused during maintenance venting out of the total vented water volume.

[0085] When the upper reservoir 11 is under maintenance and emptied, the water can be completely discharged to the lower reservoir 13 using the turbine operating condition or no-load operation condition of the water conveyance and power generation system 12. The difference in reservoir capacity between the upper reservoir 11 and the lower reservoir 13 needs to be emptied through the lower reservoir emptying structure 14.

[0086] When the reservoir that needs to be emptied is the lower reservoir 13, the maintenance and emptying of the lower reservoir 13 is carried out using the water conveyance and power generation system 12 and the upper reservoir 11.

[0087] Specifically: the water volume above the dead water level in the lower reservoir 13 is pumped to the upper reservoir 11 using the water pumping operation of the water conveyance and power generation system 12, and the water volume below the dead water level in the lower reservoir 13 is emptied using the lower reservoir emptying structure 14 or pumping equipment.

[0088] Among them, the dead water level refers to the lowest water level allowed in a reservoir during normal operation to ensure that air does not enter the unit's water intake and that the venting structure does not become clogged. The reservoir capacity below the dead water level is called dead reservoir capacity and is usually not involved in normal regulation.

[0089] When the lower reservoir 13 is under maintenance and emptied, the water pumps of the water conveyance and power generation system 12 can be used to pump the water above the dead water level to the upper reservoir 11. The reservoir capacity below the dead water level is emptied through the lower reservoir emptying structure 14 (such as an emptying pipe) or through pumping equipment (such as a water pump).

[0090] This invention provides a specific embodiment to describe in detail the venting operation of a pumped storage power station.

[0091] A certain pumped storage power station's upper reservoir has a storage capacity of 7.43 million cubic meters below the normal water level. 3 The reservoir capacity emptying rate was verified, and it was found to be 40%, with a single unit's no-load flow rate of 10.89 m³ / h. 3 / s, the emergency venting time is 3.25 days, at which point the head reduction rate is 33%. The emergency venting time is less than 7 days, meeting the emergency venting requirements. The venting design for Upper Reservoir 11 is complete.

[0092] The reservoir's capacity below the normal water level is 6.92 million cubic meters. 3 Emergency venting is controlled at 40% of the reservoir's capacity. The venting pipe is integrated with the outflow drainage corridor, located below the corridor, and is a pressure steel pipe. A maintenance valve is installed at the head, and a working valve is located in the outlet valve chamber. The venting pipe operates under pressure, lowering the water level from the normal storage level. Release to any water level Time required The following formula is used for calculation.

[0093] ;

[0094] Lower Reservoir Water Level With the discharge flow of the lower reservoir The expression corresponding to the relationship curve is shown below:

[0095] ;

[0096] In the formula, The flow coefficient of the vent pipe; This refers to the cross-sectional area of ​​the pipe. The elevation difference between the bottom of the reservoir 13 and the outlet of the vent pipe; It is the acceleration due to gravity; The water level of the lower reservoir is The corresponding storage capacity at that time; Water level The volume reduction per unit height decrease can be accounted for by water levels. With storage capacity The storage capacity curve between the two is calculated, which is a conventional technical method and will not be elaborated here.

[0097] The initial plan is to use a venting pipe diameter of 1000mm. After calculation, the reservoir venting time is 3.32 days, at which time the water head reduction rate is 34%. The venting time is less than 7 days, which meets the requirements of the "Technical Guidelines for Reservoir Venting".

[0098] When the reservoir water level drops to the bottom elevation, the minimum venting flow rate of the venting pipe is 8.07 m³. 3 The flow rate is less than the no-load operating flow rate of a single unit in the upper reservoir (11). Therefore, the diameter of the vent pipe is adjusted to 1200mm. At this time, the minimum venting flow rate of the vent pipe is 12.71m³ / s. 3 / s, which is greater than the no-load operating flow of a single unit in the upper reservoir.

[0099] The maximum operating flow rate of the vent pipe is 15.62 m³ / h. 3 If the flow rate is less than the 20-year flood peak flow rate of the downstream river channel, then the emergency venting design of the lower reservoir 13 is completed.

[0100] When the Upper Reservoir 11 was emptied for maintenance, its storage capacity below the normal water level was 7.43 million cubic meters. 3 The reservoir's capacity below the normal water level is 6.92 million cubic meters. 3 The water turbines of the water conveyance and power generation system 12 can be fully discharged into the lower reservoir 13 under either operating or no-load conditions. The difference in reservoir capacity between the upper and lower reservoirs is 743-692=510,000 m³. 3 Then it is necessary to empty the reservoir through the lower reservoir emptying structure 14.

[0101] When the lower reservoir 13 is being emptied for maintenance, the pumps of the water conveyance and power generation system 12 can be used to pump water from the dead water level of 692-13=6790,000 m³. 3 Water was pumped to the upper reservoir 11, with a storage capacity of 130,000 m³ below the dead water level. 3 The air will still be vented through the vent pipe.

[0102] Within the existing technological framework, research and engineering practice on reservoir venting design primarily focus on single reservoirs, with operational analyses centered around these individual reservoirs. However, pumped-storage power stations have upper and lower reservoirs, and their water conveyance and power generation system 12 can maintain no-load operation within a 5%–20% load range, and can also operate at full load during maintenance venting. Existing reservoir venting technologies and design methods cannot fully meet the hydraulic characteristics of pumped-storage power stations.

[0103] The present invention provides a method for the emptying operation of a pumped storage power station. The method involves emptying the upper reservoir 11 to the lower reservoir 13 via the generating units of the water conveyance and power generation system 12. The size of the lower reservoir emptying structure 14 is determined by the emptying flow rate of the upper reservoir, and the lower reservoir 13 is simultaneously emptied using the lower reservoir emptying structure 14, thereby achieving coordinated control of the upper and lower reservoirs. This invention improves the safety management, operation and maintenance, and emergency response capabilities of pumped storage power station dams. Furthermore, by coordinating the operation of the upper and lower reservoirs, this invention reduces the amount of water released during emergency air defense and maintenance emptying, thus improving the economic efficiency of the pumped storage power station. This invention is particularly applicable to pumped storage power stations in western regions where high river sediment content affects unit operation or where the flood discharge structures are large, and where the lower reservoir 13 is formed by excavating and filling riverbank beaches or gullies.

[0104] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for venting operation of a pumped storage power station, characterized in that, The method includes: S1. Determine the venting type of the pumped storage power station. When the venting type is emergency venting, determine the minimum venting flow rate of the upper reservoir based on the venting time requirement of the upper reservoir in the pumped storage power station. S2. Determine the operating flow rate of the upper reservoir based on the minimum discharge flow rate of the upper reservoir and the no-load flow rate of the units in the water conveyance and power generation system of the pumped storage power station. S3. Based on the discharge flow rate of the upper reservoir and the required discharge time of the lower reservoir in the pumped storage power station, determine the design dimensions of the lower reservoir discharge structure and its minimum discharge flow rate, and adjust the design dimensions of the lower reservoir discharge structure according to the minimum discharge flow rate and the discharge flow rate of the upper reservoir to obtain the final dimensions of the lower reservoir discharge structure. S4. The upper reservoir is emptied in an emergency using the generator units of the water conveyance and power generation system, and the lower reservoir is simultaneously emptied in an emergency using the final-sized lower reservoir emptying structure. In step S3, the design dimensions of the lower reservoir venting structure and its minimum venting flow rate are determined based on the upper reservoir venting operation flow rate and the required venting time of the lower reservoir in the pumped storage power station. Specifically, this includes: S31. Based on the discharge flow rate of the upper reservoir, the dimensions of the discharge structure of the lower reservoir in the pumped storage power station are initially estimated. S32. Determine the relationship curve between the reservoir water level and the reservoir discharge flow rate during the operation of the reservoir discharge structure, and determine the reservoir discharge time based on the relationship curve; S33. Adjust the size of the lower reservoir emptying structure according to the lower reservoir emptying time and the lower reservoir emptying requirement time in the pumped storage power station; S34. Repeat steps S32 and S33 until the lower reservoir emptying time is less than or equal to the lower reservoir emptying requirement time, and obtain the design dimensions of the lower reservoir emptying structure and its minimum emptying operation flow rate; In step S3, the design dimensions of the lower reservoir venting structure are adjusted based on the minimum venting operation flow rate and the upper reservoir venting operation flow rate to obtain the final dimensions of the lower reservoir venting structure. Specifically, this includes: S35. Determine whether the minimum venting operation flow rate is greater than or equal to the upper reservoir venting operation flow rate. If yes, proceed to S36; otherwise, proceed to S37. S36. The design dimensions of the reservoir discharge structure shall be used as the final dimensions of the reservoir discharge structure; S37. The design dimensions of the lower reservoir venting structure are updated by increasing the discharge size of the lower reservoir venting structure, and the minimum venting operation flow of the updated lower reservoir venting structure is determined. S38. Repeat S35 to S37.

2. The method according to claim 1, characterized in that, Specifically, S33 is: When the lower reservoir emptying time exceeds the required lower reservoir emptying time in the pumped storage power station, the size of the lower reservoir emptying structure is updated by increasing the discharge size of the lower reservoir emptying structure.

3. The method according to claim 1, characterized in that, The discharge size of the lower reservoir's venting structure increases by 100mm to 300mm each time.

4. The method according to claim 1, characterized in that, S2 specifically includes: When the total no-load flow of N units in the pumped storage power station's water conveyance and power generation system is less than the minimum discharge flow of the upper reservoir, and the total no-load flow of N+1 units is greater than or equal to the minimum discharge flow of the upper reservoir, the N+1 units are used as the upper reservoir discharge operation equipment, and the total no-load flow of the N+1 units is used as the upper reservoir discharge operation flow; wherein, N is an integer greater than or equal to 1.

5. The method according to claim 1, characterized in that, The method further includes: When the venting type is maintenance venting, the reservoir that needs to be vented is determined; When the reservoir that needs to be emptied is the upper reservoir, the upper reservoir is emptied for maintenance using the water conveyance and power generation system and the lower reservoir. When the reservoir that needs to be emptied is the lower reservoir, the water conveyance and power generation system and the upper reservoir are used to carry out maintenance and emptying of the lower reservoir.

6. The method according to claim 5, characterized in that, The maintenance and venting of the upper reservoir is carried out using the aforementioned water conveyance and power generation system and the lower reservoir, specifically as follows: The water volume below the normal water level of the upper reservoir is released into the lower reservoir using the turbine operating condition or no-load operation condition of the water conveyance and power generation system, and the capacity difference between the upper and lower reservoirs is emptied using the lower reservoir's venting structure.

7. The method according to claim 5, characterized in that, The maintenance and venting of the lower reservoir is carried out using the aforementioned water conveyance and power generation system and the upper reservoir, specifically as follows: The water volume above the dead water level in the lower reservoir is pumped into the upper reservoir using the pumps of the water conveyance and power generation system, and the water volume below the dead water level in the lower reservoir is emptied using the lower reservoir emptying structure or pumping equipment.

8. The method according to claim 1, characterized in that, The downstream of the reservoir's venting structure is equipped with multiple downstream spillway structures; Prior to S4, the method further includes: The maximum operating flow of the lower reservoir discharge structure is compared sequentially with the peak flow of each downstream spillway structure in a year (T). The downstream spillway structure corresponding to the peak flow of the year (T) that is greater than the maximum operating flow is connected to the outlet of the lower reservoir discharge structure; wherein, T is a positive integer.

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