A method and system for optimizing the orientation angle of the intake and outlet of the lower reservoir of a pumped storage power station

Abstract

The application discloses a kind of water intake and outlet orientation angle optimization method and system of pumped storage power station lower reservoir, comprising: first, carry out water intake upstream and downstream aquatic ecological survey, clear upstream key ecological parameters of spawning drift egg fish;Second, construct three-dimensional hydrodynamic model, simulate the flow field characteristics under original design scheme, quantify the baseline value of fish egg entrainment influence;Then design multiple groups of water intake and outlet deflection downstream of comparison scheme, simulate and quantify the ecological protection benefits of each scheme;Again, carry out multi-dimensional quantitative analysis of each scheme engineering safety, cost, power generation benefit;Finally, build engineering-ecological double-benefit comprehensive evaluation system, determine the optimal orientation scheme combined with pareto optimal analysis.The application realizes the quantification, systematization optimization of water intake and outlet orientation, while ensuring engineering safety and economic benefit, effectively reducing the entrainment influence of pumped working condition on early resources of spawning drift egg fish, and can be widely applied to pumped storage power station engineering design relying on built reservoir.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, specifically to a method and system for optimizing the orientation angle of the inlet and outlet of the lower reservoir of a pumped storage power station. Background Technology

[0002] Pumped storage, as a technologically mature and economically efficient large-scale energy storage method, is a core supporting facility for ensuring the safe and stable operation of the power system and promoting the consumption of new energy sources. Among its applications, the development model that uses existing reservoirs as downstream reservoirs and constructs only upstream reservoirs can significantly reduce engineering construction costs, minimize land acquisition and ecological disturbance, and fully leverage the comprehensive utilization benefits of existing reservoirs. This model has become an important development approach for pumped storage power stations in China.

[0003] However, under this development model, the tail sections of most existing reservoirs contain river sections with well-preserved natural river morphology, which are often key spawning grounds for drifting fish. The fertilized eggs of these drifting fish are non-adhesive and require continuous drifting in the river current for a certain period, meeting specific flow velocity and water temperature conditions, to hatch. The eggs and newly hatched larvae are in a passive drifting state, lacking active avoidance capabilities. During pumping operation, the inlet and outlet of the lower reservoir of a pumped-storage power station generate a strong suction effect, easily drawing fish eggs and larvae drifting downstream from the upstream spawning grounds into the power station's water conveyance system. This results in significant early-stage fish resource loss, seriously impacting the protection of fish resources and the ecological balance of the watershed. This has become a core issue that must be addressed in the environmental impact assessment and engineering design phases of such pumped-storage power stations.

[0004] Currently, the industry commonly uses fish barriers as a mitigation measure to address the impact of power plant water intake on fish resources, with electric fish barriers being the most widely used. However, electric fish barriers can only effectively intercept adult fish and large-sized fry that have the ability to actively swim. They cannot effectively intercept fish eggs and newly hatched fry that lack the ability to actively avoid harm and are passively drifting with the water flow, thus failing to solve the core problem of fish egg entanglement under pumping conditions.

[0005] From an engineering design and operation control perspective, theoretically, the impact of pumping on fish egg entrapment can be mitigated in three ways: first, by optimizing the intake layout, such as moving the intake downwards or adjusting its horizontal position; second, by optimizing the power station's scheduling and operation, such as stopping pumping during the fish spawning and breeding season; and third, by optimizing the intake orientation, adjusting the direction of the inlet and outlet to catch the flow. However, in actual engineering, the overall layout of the upper and lower reservoirs and the water conveyance and power generation system of a pumped storage power station is strictly limited by factors such as topography, geology, overall project layout, and investment scale, making it difficult to significantly adjust the horizontal position and elevation of the intake. Furthermore, after the power station is put into operation, its scheduling and operation must comply with the unified scheduling of the power grid company, undertaking core tasks such as peak shaving, valley filling, and frequency regulation. Completely stopping pumping during the fish spawning season is not feasible. Therefore, adaptively adjusting the orientation of the lower reservoir's inlet and outlet is the core optimization path that balances engineering feasibility and ecological protection needs.

[0006] Currently, the design of inlet and outlet angles for pumped-storage power stations primarily focuses on engineering safety, hydraulic characteristics, and cost-effectiveness as core control factors, rarely considering the impact of pumping operation on the early-stage resources of drifting-egg-laying fish. While a few projects have considered this ecological impact during the design phase, they have only conducted qualitative analyses and lack quantitative and systematic optimization methods. This makes it impossible to accurately balance the economic benefits of the project with the ecological protection benefits, and thus difficult to guide actual project design. Therefore, developing a quantitatively implementable method for optimizing the orientation angles of the lower reservoir inlet and outlet of pumped-storage power stations that balances engineering benefits and ecological protection is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0007] In order to overcome the above-mentioned defects of the prior art, the purpose of this invention is to provide a method for optimizing the orientation angle of the inlet and outlet of the lower reservoir of a pumped storage power station. This method solves the problems in the prior art where the design of the inlet and outlet of pumped storage power stations cannot take into account both engineering benefits and the protection of drifting egg-laying fish, and lacks a quantitative system optimization method. This method achieves scientific optimization of the orientation of the inlet and outlet, and effectively reduces the entrapment effect of pumping conditions on fish eggs and larvae while ensuring engineering safety and economic benefits.

[0008] To address the aforementioned technical problems, the present invention adopts the following technical solution: A method for optimizing the orientation angle of the inlet and outlet of the lower reservoir of a pumped storage power station includes the following steps: Conduct a water ecological survey of the upstream and downstream waters of the lower reservoir of the target pumped storage power station to determine the species composition, resource quantity, spawning and breeding period, spatial location of spawning grounds and their relative position to the inlet and outlet, as well as the key ecological parameters required for fish egg hatching. Numerical simulation was used to determine the flow field characteristics near the inlet and outlet of the original design scheme under the most unfavorable hydrological combination of pumping conditions, and to quantify the ecological impact benchmark value of fish egg entrainment. Based on the orientation of the original design scheme, multiple alternative schemes with the inlet and outlet orientations deflected downstream were designed. The flow field distribution of each alternative scheme was simulated, and the ecological protection benefit indicators of each alternative scheme were quantified. A quantitative analysis was conducted on each alternative scheme from three dimensions: engineering safety impact, engineering cost, and power generation benefit, to determine the quantitative indicators of engineering benefits for each alternative scheme. A comprehensive evaluation index system for both engineering and ecological benefits was constructed. Based on the ecological protection benefit index and engineering benefit quantitative index of each comparative scheme, the optimal deflection angle scheme for the inlet and outlet orientation was determined through Pareto optimality analysis and multi-objective decision-making.

[0009] Furthermore, the numerical simulation adopts a three-dimensional hydrodynamic mathematical model, with the calculation range extending upstream to 1 km above the inlet and outlet and downstream to more than 0.5 km downstream of the inlet and outlet. A structured grid is used, and the grid is densified in the water area near the inlet and outlet.

[0010] Furthermore, the most unfavorable hydrological combination for pumping operation is the combination of minimum upstream inflow, minimum downstream reservoir operating water level, and full-load pumping operation of the power station; where minimum upstream inflow is the sum of the minimum downstream discharge flows of the upstream cascade hydropower stations during the spawning period of drifting fish, and minimum downstream reservoir operating water level is the dead water level of the reservoir or the flood season restriction water level.

[0011] Furthermore, the ecological impact benchmark value for quantifying the fish egg entrainment effect is determined based on the flow velocity index of a characteristic area near the inlet and outlet; the characteristic area is the water area with significant entrainment impact at a distance from the inlet and outlet embankment; the flow velocity index includes at least one of the following: cross-sectional average flow velocity, the proportion of water area with flow velocity greater than the critical flow velocity for fish egg drift, and the fish egg entrainment risk rate.

[0012] Furthermore, the selection scheme for the multiple sets of inlet and outlet deflecting downstream is as follows: the deflection angle gradient is 5°, including at least three schemes with downstream deflections of 5°, 10°, and 15°; the ecological protection benefit indicators include at least one of the following: characteristic area flow velocity reduction rate, fish egg suction risk reduction rate, and suction impact range reduction rate; wherein the formula for calculating the fish egg suction risk reduction rate is: η i =(P0-Pi) / P0×100% In the formula η i Let P0 be the fish egg aspiration risk reduction rate of the i-th deflection scheme, P0 be the fish egg aspiration risk rate of the original design scheme, and Pi be the fish egg aspiration risk rate of the i-th deflection scheme.

[0013] Furthermore, the quantitative indicators of engineering benefits include quantitative indicators of engineering safety impact, quantitative indicators of engineering cost, and quantitative indicators of power generation benefits. The quantitative indicators of engineering safety impact include the maximum height of the inlet and outlet slopes and the slope stability safety factor. The quantitative indicators of engineering cost include the increment of total engineering cost and the increment of civil engineering cost. The quantitative indicators of power generation benefits include the increment of water head loss in the water conveyance system and the annual power generation loss rate.

[0014] Furthermore, the comprehensive evaluation index system for engineering-ecological dual benefits is divided into a target layer, a criterion layer, and an indicator layer. The target layer is the comprehensive superiority of the inlet and outlet orientation schemes. The criterion layer includes engineering benefit criteria and ecological benefit criteria. The indicator layer includes ecological protection benefit indicators and engineering benefit quantitative indicators. The weights of each indicator are determined by entropy weight-analytic hierarchy process, and the comprehensive superiority value of each scheme is calculated by weighted summation.

[0015] Furthermore, the construction of the comprehensive evaluation index system for engineering-ecological dual benefits includes drawing a two-dimensional scatter plot of dual benefits with engineering benefit quantitative indicators as the horizontal axis and ecological protection benefit indicators as the vertical axis, and combining Pareto optimality analysis to screen the schemes located at the Pareto front, with the scheme having the highest comprehensive goodness value as the optimal scheme.

[0016] Furthermore, the target pumped storage power station is a pumped storage power station that uses an existing reservoir as its lower reservoir, and has a spawning ground for drifting fish distributed at the tail of the lower reservoir.

[0017] On the other hand, the present invention provides a system for optimizing the orientation angle of the inlet and outlet of a pumped storage power station reservoir, comprising: The ecological parameter acquisition module is used to conduct aquatic ecological surveys of the upstream and downstream waters of the lower reservoir of the target pumped storage power station, determine the species composition, resource quantity, spawning and reproduction period, spatial location of spawning grounds and their relative position to the inlet and outlet, as well as the key ecological parameters required for fish egg hatching. The original scheme simulation module is used to determine the flow field characteristics near the inlet and outlet of the original design scheme under the most unfavorable hydrological combination of pumping conditions through numerical simulation, and to quantify the ecological impact benchmark value of fish egg entrainment. The comparative scheme design module is used to design multiple comparative schemes with the inlet and outlet orientations deflected downstream, based on the orientation of the original design scheme, to simulate the flow field distribution of each comparative scheme, and to quantify the ecological protection benefit indicators of each comparative scheme. The engineering benefit analysis module is used to conduct quantitative analysis of each alternative scheme in three dimensions: engineering safety impact, engineering cost, and power generation benefit, and to determine the quantitative indicators of engineering benefits for each alternative scheme. The comprehensive evaluation module is used to construct a comprehensive evaluation index system for both engineering and ecological benefits. Based on the ecological protection benefit index and engineering benefit quantitative index of each comparative scheme, the optimal deflection angle scheme of the inlet and outlet orientation is determined through Pareto optimality analysis and multi-objective decision-making.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention forms a quantitative and systematic method for optimizing the orientation of the inlet and outlet of the lower reservoir of a pumped storage power station, filling the gap in the industry for inlet and outlet design methods that take into account both engineering benefits and the protection of drifting-egg fish, and solving the problem that existing technologies only perform qualitative analysis and cannot accurately balance the dual benefits.

[0019] 2. This invention uses the most unfavorable working conditions as the basis for simulation, ensuring that the optimized scheme can still play an effective protective role in the scenario with the highest risk of fish egg entrainment, thus guaranteeing the reliability of the ecological protection effect; through three-dimensional hydrodynamic numerical simulation, the control effect of different deflection angles on the flow field is accurately quantified, realizing a quantitative assessment of the ecological protection benefits.

[0020] 3. This invention simultaneously conducts multi-dimensional quantitative analysis of engineering safety, cost, and power generation benefits, and constructs a comprehensive evaluation system for engineering-ecological dual benefits. Through the coupled weighting method and Pareto optimality analysis, it achieves a scientific balance between the two core objectives. The selected optimal solution combines ecological effectiveness and engineering feasibility, avoiding significant losses in engineering cost and power generation benefits due to excessive pursuit of ecological benefits.

[0021] 4. The method of the present invention has a clear operation process and is highly reproducible. Those skilled in the art can use this method to complete the optimization design of the inlet and outlet orientation of different projects. It can be widely applied to pumped storage power station projects with existing reservoirs as the lower reservoirs. It is especially suitable for engineering scenarios where there are spawning grounds for drifting fish at the tail of the reservoir. It has high engineering application value and ecological protection significance. Attached Figure Description

[0022] Figure 1 This is an overall flowchart of the optimization method in Embodiment 1 of the present invention; Figure 2 The diagram shows the flow field velocity distribution at different elevations under the most unfavorable working conditions in the embodiments of the present invention, wherein (a) is a flow field velocity distribution diagram at an elevation of 935m, (b) is a flow field velocity distribution diagram at an elevation of 940m, and (c) is a flow field velocity distribution diagram at an elevation of 945m. Figure 3 This is a schematic diagram of the system for optimizing the orientation angle of the inlet and outlet of the pumped storage power station reservoir in Embodiment 2 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Example 1 like Figure 1 As shown, this specific implementation method takes the Renhe pumped storage power station in the Jinsha River basin as the implementation object. The power station uses the existing Wudongde hydropower station reservoir as its lower reservoir. Key spawning grounds for drifting fish are distributed upstream of the lower reservoir's tail. The power station's pumping operation can easily cause a suction effect on the drifting fish eggs and larvae. The schematic diagram of the inlet and outlet structure of the lower reservoir of this pumped storage power station is shown in this embodiment. To mitigate this ecological impact, the orientation angle of the lower reservoir's inlet and outlet is optimized using the method of this invention. The specific implementation steps are as follows: Step 1: Conduct an aquatic ecological survey of the upstream and downstream waters of the lower reservoir of the target pumped storage power station to determine the species composition, resource quantity, spawning and breeding period, spatial location of spawning grounds and their relative position to the inlet and outlet, as well as the key ecological parameters required for fish egg hatching. Step 2: Determine the flow field characteristics near the inlet and outlet of the original design scheme under the most unfavorable hydrological combination of pumping conditions through numerical simulation, and quantify the ecological impact benchmark value of fish egg entrainment. Step 3: Based on the orientation of the original design scheme, design multiple sets of comparative schemes with the inlet and outlet orientations deflected downstream, simulate the flow field distribution of each comparative scheme, and quantify the ecological protection benefit indicators of each comparative scheme. Step 4: Conduct quantitative analysis of each alternative scheme from three dimensions: engineering safety impact, engineering cost, and power generation benefits, and determine the quantitative indicators of engineering benefits for each alternative scheme; Step 5: Construct a comprehensive evaluation index system for both engineering and ecological benefits. Based on the ecological protection benefit index and engineering benefit quantitative index of each alternative scheme, determine the optimal deflection angle scheme for the inlet and outlet orientation through Pareto optimality analysis and multi-objective decision-making.

[0025] In step 1 of this embodiment, the core survey content includes: ① the species composition, resource quantity, and protection level of drifting-egg-laying fish in the survey waters; ② the spatial location and distribution range of spawning grounds, and the relative position of spawning grounds to the inlet and outlet; ③ the spawning and reproduction period of fish, and the hydrological rhythm during the spawning period; ④ key ecological parameters such as the critical flow velocity, drifting duration, and water temperature threshold required for fish egg drifting and hatching. A two-year aquatic ecological survey was conducted on the upstream and downstream waters of the lower reservoir of the Renhe pumped storage power station, covering the entire spawning and reproduction period of fish. The survey results clearly state: ① Six species of drifting fish are distributed in the surveyed waters, namely, *Siniperca chuatsi*, *Siniperca chinensis*, *Gnaphalium affine*, *Siniperca chinensis*, *Siniperca chuatsi*, and *Siniperca chuatsi*. The spawning grounds are located approximately 60 km upstream of the inlet and outlet. ② The core spawning and breeding period for these fish is from May to July each year. During the spawning period, the critical flow velocity for drifting and hatching of the fish eggs is 0.2 m / s, and the accumulated temperature range required for drifting and hatching is 660–1300 °C·h. ③ The spawning grounds and the inlet and outlet are located in a straight river channel. The main current flows along the left side of the river channel, while the inlet and outlet are located on the right bank of the river channel, and there is a direct hydraulic connection between them and the spawning grounds.

[0026] Step 2 of this embodiment includes the following sub-steps: S2.1 Constructing a 3D hydrodynamic mathematical model: 3D hydrodynamic models such as Flow-3D, MIKE 3D, or EFDC can be used. In this embodiment, the Flow-3D 3D hydrodynamic model is used to construct the calculation model of the target water area. The calculation range of the model extends upstream to 0.6km and downstream to 0.4km downstream of the inlet and outlet, with a total calculation length of 1km. The model adopts structured mesh generation, and the core area within 1km of the inlet and outlet is meshed with a density of 2m×2m. The mesh size of the density area is 5m×5m, and the mesh size of the remaining areas is 2m×2m, to ensure the simulation accuracy.

[0027] S2.2 Determining the Most Unfavorable Operating Condition: The most unfavorable hydrological combination for pumping operations during the fish spawning period is selected, namely, the combination of minimum upstream inflow, lowest downstream reservoir operating water level, and full-load pumping operation of the power station. The minimum upstream inflow is the sum of the minimum downstream ecological flows of the upstream cascade hydropower stations during the spawning period, and the lowest downstream reservoir operating water level is the dead water level of the reservoir. Under this condition, the river baseflow is minimum, the impact of inlet and outlet pumping on the flow field is greatest, and the risk of fish egg entrainment is highest. In this embodiment, combining engineering hydrological data and fish spawning period characteristics, the most unfavorable hydrological combination is determined as follows: upstream inflow of 902 m³ / s (the sum of the minimum downstream ecological flows of the upstream Jinsha Hydropower Station and the tributary Yalongjiang Tongzilin Hydropower Station during the spawning period), Wudongde Reservoir at a dead water level of 945 m, and the power station operating at full load (pumping flow rate of 190.62 m³ / s).

[0028] S2.3 Flow Field Simulation and Benchmark Evaluation of the Original Scheme: Taking the original design scheme as Scheme 1, the constructed model is used to simulate the flow field distribution under the most unfavorable operating conditions, such as... Figure 2 As shown, the results indicate that the main current of the river is located near the left side of the river channel. The main current velocity at elevations of 935m, 940m, and 945m is 0.18-0.38m / s, while the velocity near the inlet and outlet on the right side of the river channel is 0.08-0.26m / s. Due to the pumping effect of the power station, the velocity in the characteristic area 10-50m away from the inlet and outlet is 0.27-0.36m / s, with an average cross-sectional velocity of 0.315m / s, exceeding the critical velocity for fish egg drift. The risk of fish egg entrapment is 68.2%, which is used as the baseline value for ecological impact.

[0029] The formula for calculating the risk rate of fish egg aspiration is as follows: P = A risk / A total ×100% In the formula: P is the risk rate of fish egg aspiration, in %; A risk The area of ​​water at risk of fish egg entrapment, expressed in m², refers to the water area within the target river section that simultaneously meets the following two conditions: ① Water flow velocity ≥ critical velocity for fish egg drift; ② Angle between the water flow direction and the water intake direction at the inlet / outlet ≤ 90°; A total The effective drift area of ​​fish eggs is expressed in m², which refers to the total area of ​​water within the target river section where the current velocity is greater than or equal to the critical velocity for fish egg drift.

[0030] Statistical analysis of the total effective drift area A of fish eggs total Based on the model simulation results, the total number of grid cells with a flow velocity ≥ 0.2 m / s in the target river section is 42,500. Therefore, the total effective drift area of ​​the fish eggs is: A total =42500×4m 2 =170000m 2 Statistics on the area of ​​water at risk of fish egg suction A risk Of the 42,500 valid grids mentioned above, grid cells with an angle ≤90° between the water flow direction and the water intake direction at the inlet / outlet were further screened. The total number of grids meeting this condition was 28,970. Therefore, the area of ​​water at risk of fish egg entrapment is: A risk =28970×4m 2 =115880m 2 The risk rate of fish egg aspiration under the original design scheme is calculated as: P = 115880 / 170000 × 100% = 68.2% Step 3 includes the following sub-steps: S3.1 Multiple Scheme Design: Based on the original design scheme (Scheme 1), three sets of downstream deflection schemes are designed for comparison. Scheme 2 deflects the inlet and outlet orientation by 5° downstream, Scheme 3 deflects the inlet and outlet orientation by 10° downstream, and Scheme 4 deflects the inlet and outlet orientation by 15° downstream, covering the deflection range that the project can implement.

[0031] S3.2 Multi-scheme flow field simulation: Using the same model, boundary conditions and most unfavorable working conditions as in step 2, numerical simulations were performed on schemes 2, 3 and 4 respectively to obtain the flow field distribution characteristics of each scheme. The simulation results of flow velocity at different elevations are detailed in Table 1.

[0032] Table 1 Comparison of Flow Velocity and Flow Field Simulation Results for Four Schemes

[0033] S3.3 Quantitative Comparison of Ecological Benefits: Calculate the quantitative indicators of ecological benefits for each scheme, including the rate of reduction in flow velocity in the characteristic area, the rate of reduction in the risk of fish egg entrainment, and the rate of reduction in the area affected by entrainment; compare and analyze the mitigation effect of different deflection angles on the impact of fish egg entrainment, and clarify the response relationship between deflection angle and ecological protection benefits.

[0034] The formula for calculating the reduction rate of fish egg aspiration risk is as follows: η=(P0-Pi) / P0×100% In the formula, η is the reduction rate of fish egg aspiration risk of the i-th deflection scheme, P0 is the fish egg aspiration risk rate of the original design scheme, and Pi is the fish egg aspiration risk rate of the i-th deflection scheme. The formula for calculating the velocity reduction rate in the characteristic region is: vδ=(v0-vi) / v0×100% In the formula, vδ is the velocity reduction rate of the characteristic region of the i-th deflection scheme, v0 is the cross-sectional average velocity of the characteristic region of the original design scheme, and vi is the cross-sectional average velocity of the characteristic region of the i-th deflection scheme. The formula for calculating the reduction rate of the area affected by the entrainment effect is: Rδ=(R0-Ri) / R0×100% In the formula, Rδ is the reduction rate of the entrainment influence range of the i-th deflection scheme, R0 is the fish egg entrainment influence range of the original design scheme, and Ri is the fish egg entrainment influence range of the i-th deflection scheme (the entrainment influence range is defined as the total area of ​​water near the inlet and outlet where the flow velocity is greater than the critical flow velocity of fish egg drift).

[0035] The results of this embodiment show that: Scheme 2 reduced the flow velocity in the characteristic region by 11.1%, reduced the risk of fish egg entrapment by 18.5%, and reduced the entrapment impact area by 9.1%; Scheme 3 reduced the flow velocity in the characteristic region by 14.3%, reduced the risk of fish egg entrapment by 21.0%, and reduced the entrapment impact area by 13.6%; Scheme 4 reduced the flow velocity in the characteristic region by 15.9%, reduced the risk of fish egg entrapment by 22.8%, and reduced the entrapment impact area by 15.5%. Compared with Scheme 2, the improvement in ecological protection benefits in Scheme 3 has narrowed significantly; compared with Scheme 3, the improvement in ecological protection benefits in Scheme 4 has further decreased, with only a 1.8 percentage point increase in the reduction rate of fish egg entrapment risk and a 1.6 percentage point increase in the reduction rate of flow velocity in the characteristic region, without significant ecological protection gains. The deflection angle and ecological benefits show a significant nonlinear response relationship.

[0036] In step 4 of this embodiment, quantitative analysis is conducted on the original design scheme and each deflection comparison scheme from three core dimensions: engineering safety, engineering cost, and power generation efficiency, to determine the quantitative indicators of engineering benefits for each scheme: S4.1 Engineering Safety Impact Analysis: Calculate the maximum height of the inlet and outlet slopes, the slope stability safety factor, and the hydraulic smoothness of the water conveyance system for each scheme, and quantitatively evaluate the impact of different deflection schemes on the structural safety and operational safety of the project. S4.2 Engineering Cost Analysis: Calculate the increase in civil engineering excavation and support work, building cost, and supporting facility cost of each scheme relative to the original design scheme, and obtain the total engineering cost increase of each scheme; S4.3 Power generation benefit analysis: Calculate the increase in head loss and annual power generation loss rate of the water conveyance system for each scheme, and quantitatively evaluate the impact of different deflection schemes on the power generation benefit of the power station.

[0037] This embodiment conducts a quantitative analysis of engineering safety, engineering cost, and power generation benefits. The results are detailed in Table 2.

[0038] Table 2. Quantitative Analysis Results of the Engineering Benefits of the Four Schemes

[0039] Step 5 of this embodiment includes the following sub-steps: S5.1 Construct a comprehensive evaluation index system: Establish a three-level comprehensive evaluation index system of "target layer - criterion layer - index layer"; among which, the target layer is the comprehensive excellence of the inlet and outlet orientation scheme; the criterion layer includes engineering benefit criteria and ecological benefit criteria; the index layer consists of various quantitative indicators determined in steps 3 and 4, including ecological benefit indicators such as the reduction rate of fish egg entrainment risk and the reduction rate of flow velocity in characteristic areas, as well as engineering benefit indicators such as the slope stability safety factor, the increase in total engineering cost, and the annual power generation loss rate.

[0040] S5.2 Determination of Indicator Weights: The weights of each evaluation indicator are determined by a coupling method of entropy weight and analytic hierarchy process (AHP). The AHP determines the subjective weights of the indicators, while the entropy weight method determines the objective weights. The combined weights of the indicators are obtained through coupling calculations, eliminating the bias of the single weight method.

[0041] The specific calculation process is as follows: (1) Analytic Hierarchy Process (AHP) for calculating subjective weights The Analytic Hierarchy Process (AHP) constructs a judgment matrix based on the experience of industry experts, quantifies the relative importance of each indicator, and calculates the subjective weights. The steps are as follows: Constructing a judgment matrix: Five experts with associate senior or higher professional titles in the fields of engineering design, water environment, and water ecology were invited to conduct pairwise comparisons and scores on the relative importance of the criterion layer and the indicator layer using the 1-9 scale method, thus constructing a judgment matrix: Criterion-level judgment matrix (engineering benefits B1, ecological benefits B2):

[0042] The indicator-level judgment matrix under the engineering benefit criterion (slope stability safety factor C1, engineering cost increment C2, annual power generation loss rate C3):

[0043] The indicator-level judgment matrix under the ecological benefit criterion (reduction rate of fish egg entrainment risk C4, reduction rate of flow velocity in characteristic areas C5, reduction rate of entrainment influence range C6):

[0044] Consistency test: The consistency test of the above judgment matrix is ​​performed. The calculated consistency ratios are CR=0.000<0.1 for the criterion layer judgment matrix, CR=0.009<0.1 for the engineering benefit quantitative index layer, and CR=0.007<0.1 for the ecological benefit index layer. All of these meet the consistency test requirements of the analytic hierarchy process, and the judgment matrix is ​​valid.

[0045] Calculation of subjective weights: The subjective weights of the criteria layer and the indicator layer are calculated by the square root method, where the subjective weight of the engineering benefit criterion is 0.55 and the subjective weight of the ecological benefit criterion is 0.45.

[0046] (2) Calculation of objective weights using the entropy weight method (EWM) The entropy weight method calculates objective weights based on the dispersion of indicator data for each scheme. The greater the dispersion of the indicator data, the higher the distinguishing power for the comprehensive evaluation of the schemes, and the greater the corresponding weight. The steps are as follows: Constructing the initial decision matrix: Based on the measured data of 6 indicators for the 4 schemes in this embodiment, an initial decision matrix is ​​constructed. ,in For the first The first scheme The original measured values ​​of the indicators; Indicator standardization: The initial decision matrix is ​​standardized using the extreme value method (same as the dimensionless processing method in S5.3) to eliminate differences in the dimensions and orders of magnitude of the indicators, thus obtaining the standardized matrix. ; Calculate the entropy value of the index: the first Entropy value of the item index The calculation formula is:

[0047] In the formula: This embodiment represents the total number of possible solutions. ; ,like Then define To avoid meaningless calculations; Calculate objective weights: Objective weight of each indicator The calculation formula is:

[0048] In the formula: This embodiment represents the total number of indicators. The calculated objective weights of each indicator are shown in Table 3.

[0049] (3) Coupled calculation of comprehensive weight By employing a multiplicative synthesis normalization method, subjective weights and objective weights are coupled to obtain the comprehensive weights of each indicator. The calculation formula is:

[0050] In the formula: For the first Subjective weighting of each indicator For the first The objective weight of each indicator.

[0051] The calculation results of the subjective weight, objective weight, and comprehensive weight of each indicator in this embodiment are shown in Table 3.

[0052] Table 3. Calculation Results of Weights for Each Evaluation Indicator

[0053] S5.3 Comprehensive Superiority Calculation and Scheme Selection: After dimensionless processing of each indicator, the comprehensive superiority value of each scheme is calculated by weighted summation. Simultaneously, a two-dimensional scatter plot of the dual benefits of each scheme is plotted with the engineering benefit quantification index as the horizontal axis and the ecological benefit quantification index as the vertical axis. Combined with Pareto optimality analysis, the scheme with the highest comprehensive superiority value, which balances engineering feasibility and ecological protection benefits, is selected as the optimal deflection angle scheme for the inlet and outlet orientation. Specifically, this includes: (1) Method for dimensionless processing of indicators To eliminate the impact of differences in dimensions and orders of magnitude of different indicators on the comprehensive evaluation results, the extreme value method (Min-Max standardization) is used to perform dimensionless processing on each indicator, and corresponding standardization formulas are used for positive and negative indicators respectively: Standardized formula for positive indicators (the larger the indicator value, the better the performance of the solution):

[0054] Standardized formula for negative indicators (the smaller the indicator value, the better the performance of the solution):

[0055] In the formula: For the first The first scheme The standardized value of the item (the numerical range after dimensionless conversion is...) ); For the first The first scheme The original measured values ​​of the indicators; For the first The maximum value among all possible options for this indicator; For the first The minimum value among all possible options for this indicator.

[0056] Based on the original measured data of the six indicators of the four schemes in this embodiment, the above formula was used to perform dimensionless processing to obtain the standardized values ​​of each indicator. The results are shown in Table 4.

[0057] Table 4. Original values ​​and dimensionless standardized values ​​of indicators for each scheme

[0058] (2) Calculation of overall excellence value The overall goodness value of each scheme is calculated using the linear weighted summation method. The calculation formula is as follows:

[0059] In the formula: For the first The overall goodness value of each scheme, with a numerical range of [value missing]. A higher value indicates a better overall performance of the solution; For the first The first scheme The standardized value of the indicator; For the first The overall weight of each indicator.

[0060] Substituting the comprehensive weights from Table 3 and the standardized values ​​from Table 4 into the formula, the comprehensive goodness values ​​of each scheme are calculated: Overall superiority score of Option 1 (Original Option):

[0061] Option 2 (deflected downstream by 5°) Overall superiority value:

[0062] Option 3 (deflected downstream by 10°) Overall superiority value:

[0063] Option 4 (deflected downstream by 15°) Overall goodness value:

[0064] Meanwhile, with the incremental engineering cost as the horizontal axis and the reduction rate of fish egg entrapment risk as the vertical axis, a two-dimensional scatter plot of engineering-ecological dual benefits for each scheme was drawn. Combined with Pareto optimality analysis, Scheme 1 and Scheme 2 are located at the Pareto front, while Scheme 3 and Scheme 4 are Pareto inferior solutions (Scheme 3 has a significant increase in cost, but the increase in ecological benefits is very small; Scheme 4 suffers serious losses in cost and power generation benefits, and has no engineering feasibility).

[0065] Based on the comprehensive goodness-of-excellence calculation results and Pareto optimality analysis, Scheme 2, with a comprehensive goodness-of-excellence of 0.89, is the highest and also the Pareto optimal solution. Considering engineering safety, environmental impact, cost, and power generation benefits, Scheme 2 (with the inlet and outlet facing downstream at a 5° angle) is ultimately recommended as the optimal solution. This scheme effectively mitigates the entrapment effect of pumping operations on the early-stage resources of drifting-egg-laying fish, achieving an optimal balance between engineering benefits and ecological protection benefits, while ensuring controllable engineering safety and minimal loss of cost and power generation benefits.

[0066] This embodiment verifies the feasibility and effectiveness of the method of the present invention. Through quantitative simulation analysis and comprehensive evaluation, the scientific optimization of the orientation angle of the inlet and outlet has been achieved, which can provide a reference for similar pumped storage power station projects.

[0067] Example 2 like Figure 3 As shown, this embodiment provides a system for optimizing the orientation angle of the inlet and outlet of a pumped storage power station reservoir, including: The ecological parameter acquisition module is used to conduct aquatic ecological surveys of the upstream and downstream waters of the lower reservoir of the target pumped storage power station, determine the species composition, resource quantity, spawning and reproduction period, spatial location of spawning grounds and their relative position to the inlet and outlet, as well as the key ecological parameters required for fish egg hatching. The original scheme simulation module is used to determine the flow field characteristics near the inlet and outlet of the original design scheme under the most unfavorable hydrological combination of pumping conditions through numerical simulation, and to quantify the ecological impact benchmark value of fish egg entrainment. The comparative scheme design module is used to design multiple comparative schemes with the inlet and outlet orientations deflected downstream, based on the orientation of the original design scheme, to simulate the flow field distribution of each comparative scheme, and to quantify the ecological protection benefit indicators of each comparative scheme. The engineering benefit analysis module is used to conduct quantitative analysis of each alternative scheme in three dimensions: engineering safety impact, engineering cost, and power generation benefit, and to determine the quantitative indicators of engineering benefits for each alternative scheme. The comprehensive evaluation module is used to construct a comprehensive evaluation index system for both engineering and ecological benefits. Based on the ecological protection benefit index and engineering benefit quantitative index of each comparative scheme, the optimal deflection angle scheme of the inlet and outlet orientation is determined through Pareto optimality analysis and multi-objective decision-making.

[0068] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0069] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Therefore, if these modifications and variations to the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

[0070] All other parts not described in detail are existing technologies.

Claims

1. A method for optimizing the orientation angle of the inlet and outlet of the lower reservoir of a pumped storage power station, characterized in that, Includes the following steps: Conduct a water ecological survey of the upstream and downstream waters of the lower reservoir of the target pumped storage power station to determine the species composition, resource quantity, spawning and breeding period, spatial location of spawning grounds and their relative position to the inlet and outlet, as well as the key ecological parameters required for fish egg hatching. Numerical simulations were used to determine the flow field characteristics near the inlet and outlet of the original design scheme under the most unfavorable hydrological combination of pumping conditions, and to quantify the ecological impact benchmark value of fish egg entrainment. The ecological impact benchmark value of fish egg entrainment was determined based on the flow velocity index of a characteristic area near the inlet and outlet. The characteristic area is the water area with significant entrainment impact at a distance from the inlet and outlet sill. The flow velocity index includes at least one of the following: cross-sectional average flow velocity, the proportion of water area with flow velocity greater than the critical flow velocity for fish egg drift, and the fish egg entrainment risk rate. Based on the orientation of the original design scheme, multiple alternative schemes with the inlet and outlet orientations deflected downstream were designed. The flow field distribution of each alternative scheme was simulated, and the ecological protection benefit indicators of each alternative scheme were quantified. The ecological protection benefit indicators include at least one of the following: the rate of reduction in flow velocity in the characteristic area, the rate of reduction in the risk of fish egg entrainment, and the rate of reduction in the area affected by entrainment; wherein the formula for calculating the rate of reduction in the risk of fish egg entrainment is: η i =(P0−P) / P0×100% In the formula η i Let P0 be the fish egg aspiration risk reduction rate of the i-th deflection scheme, P0 be the fish egg aspiration risk rate of the original design scheme, and Pi be the fish egg aspiration risk rate of the i-th deflection scheme. A quantitative analysis was conducted on each alternative scheme from three dimensions: engineering safety impact, engineering cost, and power generation benefit, to determine the quantitative indicators of engineering benefits for each alternative scheme. A comprehensive evaluation index system for both engineering and ecological benefits was constructed. Based on the ecological protection benefit index and engineering benefit quantitative index of each comparative scheme, the optimal deflection angle scheme for the inlet and outlet orientation was determined through Pareto optimality analysis and multi-objective decision-making.

2. The method for optimizing the orientation angle of the inlet and outlet of a pumped storage power station reservoir according to claim 1, characterized in that, The numerical simulation adopts a three-dimensional hydrodynamic mathematical model, with the calculation range extending upstream to 1 km above the inlet and outlet and downstream to more than 0.5 km downstream of the inlet and outlet. The three-dimensional hydrodynamic mathematical model adopts structured grid division and the grid is densified in the water area near the inlet and outlet.

3. The method for optimizing the orientation angle of the inlet and outlet of the lower reservoir of a pumped storage power station according to claim 1, characterized in that, The most unfavorable hydrological combination for pumping operations is the combination of minimum upstream inflow, minimum operating water level in the downstream reservoir, and full-load pumping operation of the power station. The minimum upstream inflow is the sum of the minimum downstream discharges of the upstream cascade hydropower stations during the spawning period of drifting fish, and the minimum operating water level in the downstream reservoir is the dead water level or the flood season restriction level.

4. The method for optimizing the orientation angle of the inlet and outlet of the lower reservoir of a pumped storage power station according to claim 3, characterized in that, The selection scheme for the multiple sets of inlet and outlet deflecting downstream is as follows: the deflection angle gradient is 5°, and it includes at least three schemes with downstream deflection of 5°, 10° and 15°.

5. The method for optimizing the orientation angle of the inlet and outlet of the lower reservoir of a pumped storage power station according to claim 1, characterized in that, The quantitative indicators of project benefits include quantitative indicators of project safety impact, quantitative indicators of project cost, and quantitative indicators of power generation benefit. The quantitative indicators of project safety impact include the maximum height of the inlet and outlet slopes and the slope stability safety factor. The quantitative indicators of project cost include the increment of total project cost and the increment of civil engineering cost. The quantitative indicators of power generation benefit include the increment of water head loss in the water conveyance system and the annual power generation loss rate.

6. The method for optimizing the orientation angle of the inlet and outlet of a pumped storage power station reservoir according to claim 1, characterized in that, The comprehensive evaluation index system for engineering and ecological dual benefits is divided into three layers: target layer, criterion layer, and index layer. The target layer is the comprehensive superiority of the inlet and outlet orientation scheme. The criterion layer includes engineering benefit criteria and ecological benefit criteria. The indicator layer includes ecological protection benefit indicators and engineering benefit quantitative indicators; the weight of each indicator is determined by entropy weight-analytic hierarchy process, and the comprehensive goodness value of each scheme is calculated by weighted summation.

7. The method for optimizing the orientation angle of the inlet and outlet of a pumped storage power station reservoir according to claim 6, characterized in that, The proposed comprehensive evaluation index system for engineering and ecological dual benefits includes drawing a two-dimensional scatter plot with engineering benefit quantitative indicators as the horizontal axis and ecological protection benefit indicators as the vertical axis, and combining Pareto optimality analysis to screen the schemes located at the Pareto front, with the scheme having the highest comprehensive goodness value as the optimal scheme.

8. The method for optimizing the orientation angle of the inlet and outlet of the lower reservoir of a pumped storage power station according to claim 1, characterized in that, The target pumped storage power station is a pumped storage power station that uses an existing reservoir as its lower reservoir, and has a spawning ground for drifting fish distributed at the tail of the lower reservoir.

9. A system for optimizing the orientation angle of the inlet and outlet of a pumped-storage power station's lower reservoir, characterized in that, include: The ecological parameter acquisition module is used to conduct aquatic ecological surveys of the upstream and downstream waters of the lower reservoir of the target pumped storage power station, determine the species composition, resource quantity, spawning and reproduction period, spatial location of spawning grounds and their relative position to the inlet and outlet, as well as the key ecological parameters required for fish egg hatching. The original scheme simulation module is used to determine the flow field characteristics near the inlet and outlet of the original design scheme under the most unfavorable hydrological combination of pumping conditions through numerical simulation, and to quantify the ecological impact benchmark value of fish egg entrainment. The comparative scheme design module is used to design multiple comparative schemes with the inlet and outlet orientations deflected downstream, based on the orientation of the original design scheme, to simulate the flow field distribution of each comparative scheme, and to quantify the ecological protection benefit indicators of each comparative scheme. The engineering benefit analysis module is used to conduct quantitative analysis of each alternative scheme in three dimensions: engineering safety impact, engineering cost, and power generation benefit, and to determine the quantitative indicators of engineering benefits for each alternative scheme. The comprehensive evaluation module is used to construct a comprehensive evaluation index system for both engineering and ecological benefits. Based on the ecological protection benefit index and engineering benefit quantitative index of each comparative scheme, the optimal deflection angle scheme for the inlet and outlet orientation is determined through Pareto optimality analysis and multi-objective decision-making. The system for optimizing the orientation angle of the inlet and outlet of the pumped storage power station reservoir is used to perform the steps in the method for optimizing the orientation angle of the inlet and outlet of the pumped storage power station reservoir according to any one of claims 1-8.

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