A method for determining the volume of a multi-stage, hydraulically coupled, series-connected regulating tank.

Abstract

This invention relates to water conservancy and hydropower engineering technology, and discloses a method for determining the volume of regulating reservoirs in multi-stage series hydropower stations with small tributary flow capacity and high requirements for coordinated operation of water volume between cascades. This method ensures the safety requirements of coordinated operation of the cascade power stations while also considering the economic efficiency of the project. The method for determining the volume of regulating reservoirs between strong hydraulic coupling multi-stage series hydropower stations provided by this invention includes: firstly, decomposing the total volume into normal operating regulating volume, emergency standby volume, and dead storage volume. The former is calculated based on the objective water volume deviation during power generation of the upstream and downstream power stations connected to the regulating reservoir, as well as the water volume deviation caused by unit output adjustments. The latter is determined based on the extreme accident condition of all power stations connected to the regulating reservoir being shut down in an emergency, combined with the emergency response time. Then, multiple total volume schemes under different emergency response times are proposed, and a reasonable regulating reservoir volume is recommended through comprehensive comparison from multiple dimensions, including safety, emergency response flexibility, and economy.

Description

Technical Field

[0001] This invention relates to water conservancy and hydropower engineering technology, specifically to a method for determining the volume of a multi-stage, hydraulically coupled regulating reservoir between series stages. Background Technology

[0002] In the development of river hydropower resources, for rivers or river sections with large drops and steep gradients, diversion-type or mixed-flow development methods are usually adopted to improve the economic efficiency of development. When the usable drop of a river or river section exceeds 1000m, considering the existing level of unit equipment manufacturing and engineering construction, it is necessary to reduce the power generation head of each station through staged or segmented development, requiring the construction of multiple power plants. At this time, the upper-level power plant and the water intake of the lower-level power plant are hydraulically connected through regulating reservoirs or forebays, thus forming a series of multiple diversion-connected hydropower stations. The Jinping I and Jinping II "two-stage" cascade power stations, the Tianwan River "one reservoir, three stages" cascade power station, and the Nanya River "one reservoir, six stages" cascade power station in Sichuan are typical examples. Compared with conventional cascade power stations developed step by step, this type of multi-stage water diversion cascade power station has the characteristic of "connecting the beginning and the end". The hydraulic connection between the stages is extremely close. Its power generation is mainly controlled by the power generation flow of the first-stage reservoir power station. Under normal circumstances, the upper and lower stage power stations will operate in coordination according to the power generation flow.

[0003] The regulating reservoir plays a crucial role as a key structure for achieving hydraulic connection between cascade power stations. The tailwater from the upstream power station enters the regulating reservoir, where it is then used by the downstream power station to draw water for power generation. The regulating reservoir not only ensures coordinated operation of the multi-stage cascade power stations under various normal operating conditions, but also mitigates risks such as excessive overflow of excess water due to asynchronous water flow between the cascade power stations or hydraulic runoff due to water shortages in emergency situations. This ensures the safe, stable, and coordinated operation of the multi-stage cascade power stations.

[0004] The determination of the regulating pool volume primarily considers the needs of both normal power plant operation regulation and emergency backup regulation. From a safety-oriented perspective, a larger regulating pool volume allows for greater adaptability to various operating conditions, thereby increasing the flexibility and safety of power plant operation and dispatch. However, in reality, the layout of the regulating pool is also limited by regional topography and geological conditions. Furthermore, the structural safety and construction difficulty of underground excavation for the regulating pool must be considered. Therefore, a reasonable regulating pool volume must be determined while maintaining a certain level of economic efficiency.

[0005] It is worth noting that existing similar water diversion series cascade projects, due to their small scale and relatively small imbalance in water volume between cascades, can generally be discharged through river channels, and their regulating reservoirs are designed according to conventional operating methods. However, for projects with limited tributary flow capacity and high requirements for water volume matching and coordinated operation between cascades, the existing regulating reservoir volume design has significant limitations: on the one hand, the regulating reservoir size designed according to conventional operating methods is difficult to adapt to the complex water volume changes and strict coordinated operation requirements in such projects, and cannot effectively cope with the risks of excess water overflow or hydraulic depletion of the channel caused by asynchronous water flow; on the other hand, how to accurately determine the reasonable volume of the regulating reservoir to simultaneously meet the dual needs of normal power station operation regulation and emergency backup has not yet been scientifically and comprehensively resolved, while taking into account topographical and geological conditions, structural safety, construction difficulty, and economy. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for determining the volume of regulating pools in multi-stage series hydropower stations with small tributary flow capacity and high requirements for water volume matching and coordinated operation between cascades, so as to ensure the safety requirements of coordinated operation of cascade power stations, while taking into account the economic efficiency of the project.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0008] A method for determining the volume of the regulating reservoir between multiple cascade hydropower stations with strong hydraulic coupling is applicable to cascade hydropower stations where the flow capacity of the tributaries does not meet the requirements for unbalanced water discharge between the cascades, and where the volume design of the regulating reservoir is necessary to ensure water flow matching and coordinated operation between the cascades. The method includes:

[0009] For the regulating reservoir to be designed in a multi-stage cascade hydropower station group, the volume of the regulating reservoir is determined as follows:

[0010] S1. Calculate the total volume of the equalization tank. :

[0011] ;

[0012] in, The regulating volume for normal operation is determined based on the power generation flow deviation and allowable duration of the power plant connected to the regulating pool during the power generation process;

[0013] The emergency reserve capacity is determined based on the maximum power generation flow rate and emergency response time under the emergency conditions of all power plants connected to the regulating reservoir being shut down in an emergency.

[0014] S2. Based on the calculation of emergency reserve volume Different emergency response times are used to calculate different emergency backup volumes. Each is related to the normal operating regulating volume. Add them together to obtain the total volume of the corresponding regulating tanks. Alternative volumetric design options;

[0015] S3. Taking into account the operational safety, emergency response flexibility, and economy of the upstream and downstream power stations corresponding to the regulating pool, the optimal total volume of the regulating pool is recommended from multiple alternative volume design schemes.

[0016] Furthermore, in step S1, the normal operation regulating volume consists of the volume required to regulate two types of water volume deviations, wherein the first type of water volume deviation is an objectively existing water volume deviation, including the actual power generation flow deviation caused by the efficiency deviation of the hydropower unit of the power station connected to the regulating pool, the actual power generation flow deviation caused by the water loss deviation of the water diversion tunnel, and the water level hydraulic fluctuation of the regulating pool.

[0017] The second type of water volume deviation is the water volume deviation caused by the adjustment and change of the unit output, including the water flow lag time between the power stations connected to the regulating pool, and the average flow deviation of the hydropower units of the two power stations during the ramp-up process.

[0018] Furthermore, the normal operation adjustment volume The calculation is as follows:

[0019] ;

[0020] ;

[0021] ;

[0022] in, The volume required to adjust for objectively existing water volume deviations; The volume required to adjust the water volume deviation caused by changes in the unit's output; The deviation in actual power generation flow rate caused by the inconsistency between the unit's design efficiency and its actual efficiency is expressed in units of... ; The deviation in actual power generation flow rate caused by the inconsistency between the designed head loss and the actual head loss of the water diversion tunnel connecting the regulating reservoir and the power station is expressed in units of... t represents the allowable deviation duration in seconds; W represents the hydraulic fluctuation range of the water level in the regulating tank in meters; and S represents the bottom area of ​​the regulating tank in square meters. 2 ; The maximum power generation flow rate of the hydropower station, in units ; The time, in seconds, for the tailrace of the upstream power station to reach the regulating reservoir of the downstream power station at the maximum power generation flow rate. The average flow deviation between upstream and downstream power plants as they simultaneously ramp up from minimum load or no-load operation to rated output during stable operation is expressed in units of... ; The time taken to climb the hill is measured in seconds (s).

[0023] Furthermore, in step S1, the emergency backup volume The calculation is as follows:

[0024] ;

[0025] in, The maximum power generation flow rate of the hydropower station, in units ; Emergency response time to ensure power plant safety in the event of an accident, measured in seconds (s).

[0026] Furthermore, the emergency response time includes equipment shutdown time, manual response time, and the time required for the power system emergency dispatch to activate backup power or corresponding power rationing measures.

[0027] Furthermore, in step S3, the comprehensive consideration of the operational safety, emergency response flexibility, and economy of the upstream and downstream power plants corresponding to the regulating pool includes:

[0028] Safety: Compare the safety margins of the regulating tank volume for each scheme under the conditions of normal shutdown and water flow cutoff time of power plant equipment, manual emergency response time, and emergency dispatch time of power system;

[0029] Emergency response flexibility: Compare the time margins of each option for emergency response operations in the event of an accident at the power plant;

[0030] Economic efficiency: Calculate the unit volume investment of each scheme and the supplementary unit volume investment between schemes, and compare the investment rationality.

[0031] Furthermore, the calculation method for the unit volume investment is as follows:

[0032] ;

[0033] in: Let be the unit volume investment for the i-th regulating tank volume scheme, expressed in yuan / m³. Let be the total static investment in the i-th regulating pool scheme, expressed in yuan.

[0034] Furthermore, the calculation method for the supplementary unit volumetric investment is as follows:

[0035] ;

[0036] in, The unit volume investment for supplementing the volume of the regulating tank is RMB / m3; The static total investment for the (i+1)th regulating pool scheme is expressed in yuan.

[0037] Furthermore, in step S3, the method of recommending a superior total volume of the regulating tank from multiple alternative volume design schemes includes:

[0038] Among the various volume design options, the option with better safety and emergency response flexibility should be given priority, that is, the option with a larger equalization tank volume, higher safety margin and more time margin for emergency operation.

[0039] Provided that safety and emergency response flexibility requirements are met, the more economical option is selected. That is, when the supplementary unit volume investment between the (i+1)th option and the ith option is greater than the unit volume investment of the ith option, the ith option is the more economical option.

[0040] Furthermore, step S3 also includes: after recommending a better total volume of the equalization tank, the final equalization tank volume is based on the better total volume of the equalization tank, plus the dead storage capacity. The dead storage capacity The system is set up according to the inflow and sediment conditions of the river where the regulating reservoir is located.

[0041] The beneficial effects of this invention are:

[0042] (1) The present invention clarifies the composition and determination method of the total volume of the regulating pool. By decomposing the total volume into the normal operation regulating volume and the emergency standby volume, and performing precise calculations for normal operation and emergency conditions respectively, it provides a clear and systematic method for determining the volume of the regulating pool, ensuring that the volume scale can be adapted to the actual operation needs of the cascade power station.

[0043] (2) The present invention comprehensively considers the objectively existing water volume deviation (such as unit efficiency deviation, tunnel water loss deviation, water level fluctuation) and the water volume deviation caused by unit output adjustment (such as water flow lag time, slope rate) in the calculation of the normal operation regulation volume, and determines the volume through quantitative formula, which can effectively balance the water volume matching between the upper and lower level power stations during normal operation, and ensure the stability and flexibility of the coordinated operation of the cascade power stations.

[0044] (3) The present invention provides a backup capacity for accidents based on the extreme unfavorable condition of all power plants being shut down in an emergency. It is calculated in combination with the maximum power generation flow rate and emergency response time. Furthermore, by formulating multiple plans and considering time factors such as equipment shutdown, manual response, and power system dispatch, it can fully address the risk of water imbalance in the event of an accident, avoid the engineering safety problems caused by excess water overflow or water shortage, and improve the safety margin of cascade power plants.

[0045] (4) The present invention introduces a multi-scheme comparison mechanism, which comprehensively evaluates the safety (safety margin under equipment shutdown, emergency response, etc.), emergency response flexibility (operation time margin) and economy (unit volume investment, supplementary unit volume investment) from three dimensions, and finally recommends a reasonable volume scheme, which takes into account the engineering economy while ensuring safety, and achieves a balance between safety and economy.

[0046] (5) The present invention is applicable to multi-stage water diversion series cascade power stations where the tributary flow capacity does not meet the unbalanced water volume between the cascades and the water volume matching and coordination requirements are high. It fills the technical gap in determining the volume of the regulating pool in such scenarios, provides reliable technical support for the hydraulic connection design of such cascade power stations, and ensures the safe and efficient operation of cascade power station groups under complex hydraulic connections. Attached Figure Description

[0047] Figure 1 This is an exemplary schematic diagram of the hydropower development layout of a multi-stage cascade hydropower station group.

[0048] Figure 2 This is a schematic diagram of the volume composition of the regulating tank in this invention.

[0049] Figure 3 This is a simplified longitudinal layout diagram of a cascade power station in an embodiment of the present invention. Detailed Implementation

[0050] This invention aims to provide a method for determining the volume of regulating reservoirs in multi-stage cascade hydropower stations with limited tributary flow capacity and high requirements for coordinated operation and water volume matching between cascades. This method ensures the safety of coordinated operation of the cascade power stations while also considering engineering economics. The core idea is as follows: For multi-stage cascade hydropower stations with insufficient tributary flow capacity to discharge unbalanced water volumes between cascades, and where regulating reservoir volume design is necessary to ensure coordinated operation and water volume matching between cascades, the total volume of the regulating reservoir is determined by decomposing it into a normal operation regulating volume and an emergency standby volume. The former is calculated based on objective water volume deviations during power generation by the power stations connected to the regulating reservoir and water volume deviations caused by unit output adjustments. The latter is determined based on extreme accident conditions where all power stations connected to the regulating reservoir are shut down, combined with the maximum power generation flow rate and emergency response time. Furthermore, by proposing multiple total volume schemes under different emergency response times, and comprehensively comparing and selecting from multiple dimensions such as safety, emergency response flexibility, and economy, a reasonable regulating reservoir volume is recommended to ensure the safe, stable, and coordinated operation of the cascade power stations.

[0051] This invention is applicable to multi-stage cascade hydropower station groups where the flow capacity of tributaries is insufficient to meet the unbalanced water volume between discharge cascades, and where the design of regulating reservoir volume is necessary to ensure water volume matching and coordinated operation between cascades. For ease of understanding, Figure 1A typical layout structure of a multi-stage water diversion series cascade hydropower station group is shown. In this exemplary layout structure, since the available head exceeds 1,000 meters, in order to achieve centralized and efficient utilization of water resources, a three-stage development is adopted, with three power plants and two connecting regulating pools arranged to form a three-stage water diversion series cascade.

[0052] Figure 1 The key hydraulic structures and elements corresponding to each designation are as follows:

[0053] (1) The upstream river / reservoir serves as the starting point for the water source of the cascade power station.

[0054] (2) It is a dam used to control the water level and volume of the upstream river / reservoir.

[0055] (3) is a water intake point, used to draw water from the upstream river / reservoir into the water diversion system.

[0056] (4) is a water intake tunnel, which is a key water conveyance channel connecting the water intake with the downstream power plant and regulating pool, and transports the upstream water to power stations at all levels.

[0057] (5) is power plant A, which is the first power plant in the cascade and generates electricity using water transported by the water diversion tunnel.

[0058] (6) It serves as regulating reservoir A, receiving tailwater from power plant A, and providing water intake for the next-level power station, thus achieving hydraulic connection with the next-level power station.

[0059] (7) is power plant B, i.e., the second-level power plant.

[0060] (8) It is the regulating pool B, which receives the tailwater of the power plant B and connects to the next level power station.

[0061] (9) is power plant C, i.e., the third-level power plant.

[0062] (10) is a natural river channel and serves as the tailwater discharge channel for the cascade hydropower station group.

[0063] (11) To utilize the drop, which refers to the drop between the normal water level of the upstream reservoir and the power plant, is the core energy source for realizing hydropower generation.

[0064] from Figure 1As shown in the diagram, the overall layout visually presents the characteristics of a multi-stage, cascaded water diversion system: water from the upstream river / reservoir enters the water diversion tunnel through the intake, flowing sequentially through Power Plant A, Regulating Reservoir A, Power Plant B, Regulating Reservoir B, and Power Plant C, finally discharging the tailwater into a natural river channel. Each power station is hydraulically connected through the regulating reservoirs, forming a tight series connection. In this layout, the regulating reservoir plays a crucial role, its volume needing to match the flow changes of the upstream and downstream power stations: during normal operation, regulating reservoirs A and B balance the water volume deviations between Power Plant A and Power Plant B, and between Power Plant B and Power Plant C, respectively; in case of an accident, it can store surplus water or replenish water shortages, preventing water imbalances that could lead to safety risks.

[0065] Figure 2 This demonstrates the volumetric composition of the equalization tank and the logic of its volume utilization under different operating conditions. Figure 2 It can be known that the total volume of the equalization tank is... Adjustable volume during normal operation Emergency reserve capacity and dead storage capacity Composition, and each volume corresponds to different water level ranges in the regulating tank: Normal operating regulating volume Located between the high and low water levels during normal operation, it is used to balance the water volume deviation between upstream and downstream power stations during normal operation; emergency reserve volume. It is divided into two parts. One part is located between the high water level during normal operation and the highest operating water level, used to store surplus water for power generation by the upper-level power station in case of an accident at this / lower-level power station. The other part is located between the low water level during normal operation and the lowest operating water level, used to supply the water demand for power generation by the lower-level power station in case of an accident at this / higher-level power station; dead storage capacity. It is located below the minimum operating water level to address long-term operational issues such as siltation.

[0066] During normal unit operation, the water level in the regulating tank is maintained near the normal operating level. When there is an objective deviation in water volume or a deviation in unit output adjustment, it is addressed through... To achieve water volume regulation; in the event of an accident at this / lower-level power station, the tailrace regulating reservoir of the upper-level power station utilizes the water level between the normal operating high water level and the highest operating water level. The regulating reservoir stores water to prevent excess water from overflowing; in the event of a failure at this or a higher-level power station, it supplies water to the lower-level power station, utilizing the water level between the normal operating low level and the minimum operating level. Release water volume to prevent hydraulic depletion of the flow channel.

[0067] Based on the above, the method for determining the volume of a multi-stage, hydraulically coupled, series-connected regulating tank for water diversion provided by the present invention includes the following implementation process:

[0068] S1. Calculate the total volume of the equalization tank. :

[0069] ;

[0070] in, The regulating volume for normal operation is determined based on the power generation flow deviation and allowable duration of the power plant connected to the regulating pool during the power generation process; The emergency reserve capacity is determined based on the maximum power generation flow rate and emergency response time under the emergency conditions of all power plants connected to the regulating reservoir being shut down in an emergency.

[0071] More specifically, the regulating volume of the regulating tank during normal operation The volume required to adjust the objectively existing water volume deviation The volume required to regulate water volume deviations caused by changes in the output of cascade hydropower stations. The composition, and its calculation formula are as follows:

[0072] ;

[0073] ;

[0074] ;

[0075] in, This deviation in actual power generation flow is due to manufacturing and control errors, resulting in a discrepancy between the designed and actual unit efficiencies. ; Due to construction deviations and calculation errors in tunnels, the designed head loss of the water diversion tunnel differs from the actual head loss, resulting in a deviation in the power generation head and consequently, a deviation in the actual power generation flow rate. t represents the allowable deviation duration (s); W represents the hydraulic fluctuation range of the water level in the regulating tank (m); S represents the bottom area of ​​the regulating tank (m²). 2 ; This is the maximum power generation flow rate of the hydropower station. ; The time, in seconds, for the tailrace of the upstream power station to reach the regulating reservoir of the downstream power station at the maximum power generation flow rate. The average flow deviation between upstream and downstream power plants as they simultaneously ramp up from minimum load or no-load operation to rated output during stable operation. ; Let be the ramp-up time, in seconds. Since the deviation in water volume requires adjustment above or below the normal operating water level, the volume required is twice the volume caused by each factor's deviation. Therefore, a multiplication by 2 will appear on the right side of the equation above. Emergency reserve volume of the regulating reservoir. The calculation formula is as follows:

[0076] ;

[0077] in, This is the maximum power generation flow rate of the hydropower station. ; The emergency response time to ensure the safety of the power plant in the event of an accident mainly considers the time required for equipment shutdown, manual response, and the power system emergency dispatch to activate the backup power supply or corresponding power rationing measures.

[0078] S2. Based on the calculation of emergency reserve volume Different emergency response times are used to calculate different emergency backup volumes. Each is related to the normal operating regulating volume. Add them together to obtain the total volume of the corresponding regulating tanks. Alternative volumetric design options;

[0079] In this step, due to the emergency backup volume of the equalization tank... In the calculation, emergency response time The value of is determined by comprehensively considering the time required for equipment shutdown, manual response time, and the time needed for the power system's emergency dispatch to activate backup power or corresponding power rationing measures. Under different values, the calculated emergency reserve volume of the regulating pool is... They are also different, depending on the volume of the regulating tank required for normal operation. The total volume calculated later is also different. Therefore, multiple alternative schemes for the volume of the regulating pool can be formed, and a comprehensive comparison can be carried out on this basis.

[0080] S3. Taking into account the operational safety, emergency response flexibility, and economy of the upstream and downstream power plants corresponding to the regulating reservoir, recommend the optimal total volume of the regulating reservoir from multiple alternative volume design schemes. The factors considered in this step are as follows:

[0081] ① Operational security:

[0082] Increasing the regulating reservoir volume allows for a longer emergency response time and higher operational safety. Based on the unit's emergency shutdown water flow operation procedure, the time required to normally shut down the equipment and cut off the water flow is analyzed. Based on engineering surveys, the manual emergency response time is analyzed. Based on the "Standard for Configuration of Power System Emergency Reserve Capacity" (DL / T 2238-2021) and surveys, the power system emergency dispatch time is analyzed. The differences among various schemes in terms of normal shutdown water flow time, manual emergency response time, and power system emergency dispatch time are compared.

[0083] ② Flexibility in emergency response:

[0084] Increasing the volume of the regulating reservoir allows for more operational time to be reserved for emergency dispatching of power plants and the power grid; it also provides more time for emergency response in the event of a partial unit failure at the power plant. This study compares the impact of different regulating reservoir options on emergency response and the flexibility of emergency dispatching operations within the system.

[0085] ③ Economic efficiency:

[0086] Economic efficiency is compared from two dimensions: investment per unit volume and investment in supplementary unit volume. Investment per unit volume reflects the total static investment of the project per unit volume under a specific regulating pool volume scheme, reflecting the cost efficiency of the scheme itself per unit volume. Investment in supplementary unit volume reflects the additional cost required for each additional unit volume, used to measure the incremental investment efficiency caused by volume changes between volume schemes, and is a key indicator for comparing the economic differences between adjacent schemes.

[0087] 1) Investment per unit floor area:

[0088] Based on the equalization tank volume plan and investment estimate, the unit volume investment for multiple equalization tank volume plans is calculated using the following formula:

[0089] ;

[0090] in, Let be the unit volume investment for the i-th regulating tank volume scheme, expressed in yuan / m³. The static total investment for the i-th regulating pool scheme is expressed in yuan.

[0091] 2) Supplementary unit floor area ratio investment:

[0092] The supplementary unit volume investment among multiple equalization tank volume schemes is calculated using the following formula:

[0093] ;

[0094] in, The supplementary unit volume investment between the (i+1)th regulating tank volume scheme and the ith scheme is in yuan / m3. The static total investment for the (i+1)th regulating pool scheme is expressed in yuan.

[0095] The comprehensive selection strategy includes:

[0096] Among the various volume design options, the option with better safety and emergency response flexibility should be given priority, that is, the option with a larger equalization tank volume, higher safety margin and more time margin for emergency operation.

[0097] Under the premise of meeting the requirements of safety and emergency response flexibility, the more economical option is selected. That is, when the supplementary unit volume investment between the (i+1)th option and the i-th option is greater than the unit volume investment of the i-th option, it means that if the volume scheme of the regulating pool is switched from the i-th option to the (i+1)th option, the additional investment cost required for each additional unit volume will be higher than the unit volume investment of the i-th option, and the investment efficiency will be reduced. Therefore, the i-th option is the more economical option.

[0098] Example

[0099] This embodiment uses a cascade hydropower station in the Dadu River basin of Sichuan Province as an example to verify the effectiveness of the invention. The planned development scheme for this area is "one reservoir, three cascades," see [link to relevant documentation]. Figure 3 From top to bottom, the cascade power stations are reservoir power station A (240MW), hydropower station B (280MW), and hydropower station C (240MW), with a total installed capacity of 760MW. All three cascade power stations are high-head diversion-type power stations, and hydraulic connections between them are achieved through regulating reservoirs. The kinetic energy indicators and main parameters of each station are shown in Table 1. The diversion tunnels for hydropower stations A, B, and C are approximately 7.5km, 7.6km, and 9.4km long, respectively.

[0100] Table 1. Main kinetic energy parameters of a cascade hydropower station

[0101]

[0102] (1) Normal operating regulating volume of the regulating tank:

[0103] For regulating reservoir A: During normal operation of the cascade power station, the deviations in actual power generation flow caused by the planned unit efficiency versus the actual unit efficiency and the planned head loss in the water diversion tunnel versus the actual head loss shall not exceed 0.5% (0.27m) of the maximum power generation flow, respectively. 3 / s), to avoid frequent scheduling adjustments during actual operation, the deviation lasts for 1 hour; the hydraulic fluctuation range of the regulating pool water level is ±0.5m, and the bottom area of ​​the regulating pool is 12500m². 2 The required volume due to objectively existing water volume deviations. 16,390 m 3 The maximum power generation flow rate of hydropower station A is 54 m³ / h. 3 / s, at the maximum power generation flow rate, the time for the tailrace of the upstream power station A to reach the regulating reservoir A is approximately 70s; both upstream and downstream power stations use bucket turbines with the same grade gradient, and the average flow deviation to the rated output is 0, with a grade gradient time of 5 minutes. The volume required to cause the water flow deviation due to changes in power station output is... It is 0.756 million m 3 The normal operating regulating volume of regulating tank A is 23,950 m³. 3 .

[0104] For regulating reservoir B: the deviations in actual power generation flow caused by the planned unit efficiency versus the actual unit efficiency, and the planned head loss in the water diversion tunnel versus the actual head loss, shall not exceed 0.5% (0.27m) of the maximum power generation flow, respectively. 3 / s), to avoid frequent scheduling adjustments during actual operation, the deviation lasts for 1 hour; the hydraulic fluctuation range of the regulating pool water level is ±0.5m, and the bottom area of ​​the regulating pool is 10800m². 2 The required volume due to objectively existing water volume deviations. 14,690 m 3 The maximum power generation flow rate of hydropower station B is 54 m³ / h. 3 / s, at the maximum power generation reference flow, the time for the tailwater of the upstream power station B to reach the regulating reservoir B is approximately 70s; the average flow deviation between the upstream and downstream power stations simultaneously ramping up from 50% load rate to rated output is 27m³ / s. 3 / s, climbing time 5min; volume required to cause water volume deviation due to power station output change. 23,760 m 3 The calculated normal operating regulating volume is 38,450 m³. 3 .

[0105] The calculation parameters for the regulating volume of the equalization tank during normal operation are shown in Table 2.

[0106] Table 2 Calculation Parameters for Normal Operation of the Equalization Tank

[0107]

[0108] (2) Emergency reserve capacity of the equalization tank:

[0109] Under normal circumstances, the emergency shutdown procedure for the generating unit is as follows: The water flow is cut off by closing the nozzle (1-1.5 min) or guide vane (0.5 m). If the nozzle or guide vane cannot cut off the water flow, the ball valve is closed (2.5 min) to cut off the water flow. If the ball valve still cannot cut off the water flow, the emergency gate valve (gate valve / butterfly valve) is closed (3-5 min) to cut off the water flow. Considering the severity and hazards of an extremely adverse accident that could cause the entire generating unit of a power station to shut down, to ensure project safety, in the event of an extremely adverse accident, multiple processes of various equipment are activated simultaneously for emergency water shut-off, with an emergency shutdown time of approximately 5 minutes.

[0110] Further considering the actual dispatching operation process, the shutdown operation requires a certain amount of manual response time. The emergency shutdown time of the normally operating power plant unit is calculated as 10 minutes, based on the 5 minutes required for equipment shutdown plus an additional 5 minutes for manual response time.

[0111] In addition to the equipment shutdown and manual response time, the time required for the power system emergency dispatch to start the backup power supply or corresponding power rationing measures should be appropriately increased. The emergency shutdown of normally operating power plant units should be considered as 15 minutes.

[0112] Taking a slightly unfavorable approach, the power generation flow rate before the water flow is cut off is always considered based on the maximum power generation reference flow rate. The emergency shutdown time is calculated as 5 minutes, 10 minutes, and 15 minutes. The emergency standby volumes of regulating tank A and regulating tank B are 32,400 m³. 3 64,800 m 3 97,200 m 3 .

[0113] The required equalization tank volume for normal operation is superimposed to form multiple alternative equalization tank volume schemes, as shown in Table 3.

[0114] Table 3 Alternative Schemes for Equalization Tank Volume

[0115]

[0116] (3) Comparison of equalization tank volume schemes:

[0117] Comparison of operational safety: Option 1's emergency backup capacity only meets the normal water flow cutoff of the equipment. The upstream and downstream power station units must strictly follow the preset plan for automatic execution, with no time reserved for manual emergency response. Its safety margin, fault tolerance rate, and reliability are relatively low. Option 2 provides a certain amount of manual response time compared to Option 1, which can meet the needs of manual response and cope with unforeseen failures such as self-shutdown, further ensuring the safety of the power station. Option 3, based on Option 2, provides sufficient emergency response time margin, which can better cope with unforeseen accident conditions and the possible superposition of failures during the accident response process. Its safety and reliability are relatively the highest.

[0118] Comparison of emergency response flexibility: One unit of a certain power station will be shut down due to an accident, and the flow mismatch between the cascades is 27m³. 3 / s, Scheme 1, Scheme 2 and Scheme 3 can provide 10min, 20min and 30min respectively for normal operation of the unit. Each scheme has sufficient emergency response time, and Scheme 3 has the best emergency response flexibility.

[0119] Economic comparison: Based on the static total investment calculation of the equalization tank volume scheme, < , > That is, the additional unit volume investment from Scheme 1 to Scheme 2 is less than that of Scheme 1, and the additional unit volume investment from Scheme 2 to Scheme 3 is greater than that of Scheme 2. Therefore, Scheme 2 of the regulating pool is more economical.

[0120] Based on the above, Option 2 is recommended as the design scheme for the volume of the equalization tank.

[0121] Although embodiments of the present invention have been described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, and all such changes and alterations shall not depart from the protection scope of the present invention.

Claims

1. A method for determining the volume of a regulating reservoir between multiple cascade hydropower stations with strong hydraulic coupling, applicable to cascade hydropower stations where the flow capacity of tributaries does not meet the requirements for unbalanced water volume discharge between cascades, and where regulating reservoir volume design is needed to ensure water volume matching and coordinated operation between cascades, characterized in that... The method includes: For the regulating reservoir to be designed in a multi-stage cascade hydropower station group, the volume of the regulating reservoir is determined as follows: S1. Calculate the total volume of the equalization tank. : ； in, The regulating volume for normal operation is determined based on the deviation of power generation flow and the allowable duration of deviation between the upstream and downstream power stations connected to the regulating pool during the power generation process. The regulating pool consists of the volume required to regulate two types of water volume deviations: the first type of water volume deviation is an objectively existing water volume deviation, including the actual power generation flow deviation caused by the efficiency deviation of the hydropower units of the upstream and downstream power stations connected to the regulating pool, the actual power generation flow deviation caused by the water loss deviation of the water diversion tunnel, and the hydraulic fluctuation of the water level in the regulating pool; the second type of water volume deviation is the water volume deviation caused by the adjustment and change of the unit output, including the water flow lag time between the power stations connected to the regulating pool, and the average flow deviation during the ramp-up process of the hydropower units of the two power stations. The emergency reserve capacity is determined based on the maximum power generation flow rate and emergency response time under the emergency conditions of all power plants connected to the regulating reservoir being shut down in an emergency. ; in, The maximum power generation flow rate of the hydropower station, in units ; Emergency response time to ensure power plant safety in the event of an accident, measured in seconds (s). S2. Based on the calculation of emergency reserve volume Different emergency response times are used to calculate different emergency backup volumes. Each is related to the normal operating regulating volume. Add them together to obtain the total volume of the corresponding regulating tanks. Alternative volumetric design options; S3. Taking into account the operational safety, emergency response flexibility, and economy of the upstream and downstream power plants corresponding to this regulating reservoir, the optimal total volume of the regulating reservoir is recommended from multiple alternative volume design schemes: The aforementioned safety refers to the safety margin of the corresponding regulating pool volume of each scheme under the conditions of normal shutdown and water flow cutoff time of power plant equipment, manual emergency response time, and emergency dispatch time of power system; The emergency response flexibility refers to the time margin for emergency response operations when each scheme is compared in the event of an accident at the power plant. The economic efficiency is calculated by taking into account the unit volume investment of each scheme and the supplementary unit volume investment between schemes, and comparing the rationality of the investment. Among the various volume design options, the option with better safety and emergency response flexibility should be given priority, that is, the option with a larger equalization tank volume, higher safety margin and more time margin for emergency operation. Under the premise of meeting the requirements of safety and emergency response flexibility, the more economical option is selected. That is, when the supplementary unit volume investment between the (i+1)th option and the ith option is greater than the unit volume investment of the ith option, the ith option is the more economical option. After recommending the optimal total volume of the equalization tank, the final equalization tank volume is calculated by adding the dead storage capacity to the optimal total volume. The dead storage capacity The system is set up according to the inflow and sediment conditions of the river where the regulating reservoir is located.

2. The method for determining the volume of a multi-stage, hydraulically coupled, series-connected regulating tank as described in claim 1, characterized in that, The normal operating adjustment volume The calculation is as follows: ； ； ； in, The volume required to adjust for objectively existing water volume deviations; The volume required to adjust the water volume deviation caused by changes in the unit's output; The deviation in actual power generation flow rate caused by the inconsistency between the unit's design efficiency and its actual efficiency is expressed in units of... ; The deviation in actual power generation flow rate caused by the inconsistency between the designed head loss and the actual head loss of the water diversion tunnel between the upstream and downstream power stations connected to the regulating reservoir is expressed in units of [missing information]. t represents the allowable deviation duration in seconds; W represents the hydraulic fluctuation range of the water level in the regulating tank in meters; and S represents the bottom area of ​​the regulating tank in square meters. 2 ; The maximum power generation flow rate of the hydropower station, in units ; The time, in seconds, for the tailrace of the upstream power station to reach the regulating reservoir of the downstream power station at the maximum power generation flow rate. The average flow deviation between upstream and downstream power plants as they simultaneously ramp up from minimum load or no-load operation to rated output during stable operation is expressed in units of... ; The time taken to climb the hill is measured in seconds (s).

3. The method for determining the volume of a multi-stage, hydraulically coupled, series-connected regulating tank as described in claim 1, characterized in that... The emergency response time includes equipment shutdown time, manual response time, and the time required for the power system's emergency dispatch to activate backup power supplies or corresponding power rationing measures.

4. The method for determining the volume of a multi-stage, hydraulically coupled, series-connected regulating tank as described in claim 1, characterized in that... The calculation method for the unit volume investment is as follows: ； in: Let be the unit volume investment for the i-th regulating tank volume scheme, expressed in yuan / m³. Let be the total static investment in the i-th regulating pool scheme, expressed in yuan.

5. The method for determining the volume of a multi-stage, hydraulically coupled, series-connected regulating tank as described in claim 4, characterized in that... The calculation method for the supplementary unit volume investment is as follows: ； in, To supplement the unit volume investment between the equalization tank volume schemes, yuan / m 3 ; The static total investment for the (i+1)th regulating pool scheme is expressed in yuan.

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