A method for quickly identifying downstream navigable risk areas of large cascade hydropower stations in peak shaving period

Abstract

The application provides a large-scale cascade hydropower station peak-shaving period downstream navigable risk area rapid identification method, including collecting research area hydrology, terrain and other measured basic data; constructing a hydropower station downstream water level amplitude risk analysis model; constructing a hydropower station downstream water flow flow pattern risk analysis model; drawing a hydropower station downstream navigable risk area map, and rapidly identifying the navigable risk. The application can provide an effective means for rapid identification and evaluation of the hydropower station downstream navigable risk area, and also can provide technical support for hydropower station downstream navigable safety guarantee.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to a method for rapid identification of downstream navigation risk zones during peak-shaving periods of large-scale cascade hydropower stations. Background Technology

[0002] When large-scale cascade hydropower stations participate in grid peak shaving, their output often needs to be adjusted significantly and frequently in a short period of time according to load demand, resulting in drastic fluctuations in downstream flow and forming a complex unsteady flow process in the downstream river channel.

[0003] This unsteady current propagation can cause rapid rises and falls in water levels and rapid changes in current velocity in downstream waterways, threatening navigation safety. The main risks include: 1) Sudden rises and falls in water levels, making mooring difficult and increasing the risk of drifting, grounding, or collisions; 2) Sudden increases in current velocity can lead to difficulties in ship maneuvering and loss of course control, with a particularly significant impact on heavily loaded vessels traveling upstream; 3) Dramatic changes in current conditions can generate unfavorable eddies and crossflows, affecting navigation stability. Therefore, quickly and accurately identifying navigation risk areas in downstream waterways during peak-shaving operations is crucial for implementing scientific shipping scheduling and issuing navigation warnings.

[0004] Currently, most risk assessment methods focus on the independent analysis of single risk factors (such as minimum navigable water level or maximum surface velocity), lacking rapid identification and visualization of the spatiotemporal distribution characteristics of risks under the coupled effects of multiple factors such as water level fluctuations and flow regime changes. Although existing numerical simulation methods have high accuracy, they are complex to model and computationally time-consuming, making it difficult to meet the real-time requirements for rapid risk assessment during peak periods.

[0005] Therefore, this application provides a method for quickly and intuitively identifying downstream navigation risk areas during the peak-shaving period of large-scale cascade hydropower stations, in order to make up for the deficiencies of existing technologies and provide technical support for the coordinated management of power station peak-shaving and navigation safety. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the prior art by providing a rapid identification method for downstream navigation risk zones during peak-shaving periods of large-scale cascade hydropower stations. By coupling two key risk factors—water level fluctuation and water flow pattern—and based on probability statistics and mathematical models, the method achieves risk zone classification, rapid identification, and visualization, providing a direct basis for navigation safety management.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for rapid identification of downstream navigation risk zones during peak-shaving periods of large-scale cascade hydropower stations. S1. Collect basic measured data on hydrology and topography of the study area; S2. Construct a risk analysis of downstream water level fluctuations at the power station; S3. Conduct a risk analysis of the downstream water flow pattern of the power station; S4. Draw a navigation risk zone map downstream of the power station to quickly identify navigation risks.

[0008] Furthermore, S1 specifically includes: historical discharge flow processes of the power station, measured water levels at the downstream control station of the power station, measured water levels at various cross-sections downstream of the dam, water level processes in the downstream reservoir, and basic data on cross-sections downstream of the dam.

[0009] Furthermore, S2 specifically refers to: S201. Based on preliminary analysis, the water level fluctuation limit value was determined. ; S202. Establish the relationship between the downstream control station and the time-varying amplitude of water level at each cross-section: Based on the aforementioned measured data, define the time-varying amplitude of water level at the downstream control station as... Downstream The hourly water level variation at each cross-section is ( By fitting measured data, the mapping relationship is established as follows: (1); in, The formula for linear regression is: In the formula, , The coefficients are obtained using the least squares method; S203. Determine the reference value for water level time-varying amplitude under a given probability: Collect historical measured water level data from downstream control stations and calculate the water level time-varying amplitude. Given a sample sequence and a fitted probability distribution, let the cumulative distribution function be... For a given probability The corresponding water level time variation reference value Defined by quantiles: (2); in, It is the inverse cumulative distribution function; S204. Determine the range of influence of the reference value, and use the water level time-varying amplitude reference value obtained in S203. Substituting into formula (1), calculate the frequency-level time variation amplitude corresponding to each cross section. The set of affected sections is defined as follows: (3); Let the first The distance from each cross-section to the dam site is The length of the affected area The furthest distance in the affected cross section: ; S205. Determine the critical section corresponding to the limit amplitude: Take the amplitude when the historical maximum water level of the downstream control station is reached. Find the condition that satisfies ΔZ i,max= ΔZ 限 Critical section, let it be numbered as The corresponding distance is The distance from the critical position to the dam site is ; If there are no precisely equal critical sections, then they are obtained by interpolation; S206. Delineate water level fluctuation risk zones: based on the length of the affected area. and the distance from the critical location to the dam site The downstream river section is divided into two risk levels: the first-level risk zone is the length from the dam site to the affected area. The section of the river, namely Level 2 risk zone is defined by the length of the affected area. Distance from the critical position to the dam site The section of the river, namely .

[0010] Furthermore, S3 specifically refers to: S301. Establish a two-dimensional mathematical model of water flow based on topographic and roughness data; ;

[0011] in: For water depth; , The vertical average velocity component; This refers to the elevation of the riverbed. , For the shear stress of the subbed; It is the acceleration due to gravity; Given the density of water, an arbitrary flow rate can be obtained through numerical solution. and downstream boundary water level Combined velocity field ,mold ; S302, Calculate the spatial distribution of flow velocity exceeding limits: [This refers to the flow rate...] and water level Discrete is a typical operating condition: , For each set of working conditions ,in, For the flow rate corresponding to the operating condition, The water level corresponds to the operating condition; the positional velocity of the entire river section is calculated using a mathematical model. Define the flow rate safety threshold Then the first The area where the flow velocity exceeds the limit under this operating condition is: ; S303. Based on historical data of actual power station discharge and downstream reservoir water level, statistical analysis was conducted on various operating condition combinations. probability of occurrence For any point in the downstream river channel The process exceeds the flow rate safety threshold. The probability is: ; S304. Divide the flow velocity risk ranges with different probabilities: Define the distance along the downstream main channel line. Extract the probability corresponding to each point Set two probability thresholds. and ,but: Flow rate exceeds flow rate safety threshold The probability is close to the range of river sections where it is certain to occur: ; Identify the river segment with a moderate probability of occurrence: ; Identify the river segment range with a low probability of occurrence: ; S305. Draw a navigation risk zone map downstream of the power station to quickly identify navigation risks.

[0012] Furthermore, S4 specifically includes: S401. Based on the combination of the water level fluctuation risk zone in S2 and the hydrodynamic risk zone in S3, draw a navigation risk zone map downstream of the power station. S402. By using the location coordinates, query the navigation risk zone map downstream of the power station to quickly identify the risk at that location.

[0013] The beneficial effects of this invention are as follows: This method comprehensively considers two core navigation risk factors: drastic water level fluctuations and excessive flow velocity, overcoming the limitations of single-indicator assessment and making risk identification more scientific and comprehensive. By employing probabilistic statistical methods to analyze the probability of risk indicators occurring, the spatial range of different risk levels is clarified, enhancing the representativeness and reliability of the assessment results. Through pre-modeling and calculation, a comprehensive risk zone map is drawn. In actual peak-shaving operations, without the need for complex real-time simulations, the risk level at any location in the waterway can be quickly determined by querying the chart, greatly improving response speed and practicality. The final result is presented in the form of a risk zone map, clearly showing the spatial distribution of different risk levels, facilitating intuitive understanding and application by shipping management, dispatching departments, and navigating vessels. Attached Figure Description

[0014] Figure 1A flowchart of a method for rapid identification of downstream navigation risk zones during peak-shaving periods of large-scale cascade hydropower stations; Figure 2 This is a diagram showing the layout of the observation section downstream of power station A. Figure 3 The relationship between the time-varying water level at the downstream control station A of a certain power station and the time-varying water level at various downstream observation sections; Figure 4 This is a navigation risk zone map downstream of a certain power station A. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] A rapid identification method for downstream navigation risk zones during peak-shaving periods of large-scale cascade hydropower stations. S1. Collect basic measured data on hydrology and topography of the study area; S2. Construct a risk analysis of downstream water level fluctuations at the power station; S3. Conduct a risk analysis of the downstream water flow pattern of the power station; S4. Draw a navigation risk zone map downstream of the power station to quickly identify navigation risks.

[0017] The S1 specifically includes: historical discharge flow of the power station, measured water level at the downstream control station of the power station, measured water level at each section downstream of the dam, water level process of the reservoir downstream of the dam, and basic data of the downstream section of the dam.

[0018] Specifically, S2 is: S201. Based on preliminary analysis, the water level fluctuation limit value was determined. ; S202. Establish the relationship between the downstream control station and the time-varying amplitude of water level at each cross-section: Based on the aforementioned measured data, define the time-varying amplitude of water level at the downstream control station as... Downstream The hourly water level variation at each cross-section is ( By fitting measured data, the mapping relationship is established as follows: (1); in, The formula for linear regression is: In the formula, , The coefficients are obtained using the least squares method; S203. Determine the reference value for water level time-varying amplitude under a given probability: Collect historical measured water level data from downstream control stations and calculate the water level time-varying amplitude. Given a sample sequence and a fitted probability distribution, let the cumulative distribution function be... For a given probability The corresponding water level time variation reference value Defined by quantiles: (2); in, It is the inverse cumulative distribution function; S204. Determine the range of influence of the reference value, and use the water level time-varying amplitude reference value obtained in S203. Substituting into formula (1), calculate the frequency-level time variation amplitude corresponding to each cross section. The set of affected sections is defined as follows: (3); Let the first The distance from each cross-section to the dam site is The length of the affected area The furthest distance in the affected cross section: ; S205. Determine the critical section corresponding to the limit amplitude: Take the amplitude when the historical maximum water level of the downstream control station is reached. Find satisfaction The critical section, let be numbered as The corresponding distance is The distance from the critical position to the dam site is ; In this example, the maximum hourly water level fluctuation at the downstream control station is 4.5 m / h, according to the relationship... ,like Figure 3 As shown, the critical section for downstream flow exceeding 1 m / h is determined. The location is 29.5km downstream of the dam.

[0019] If there are no precisely equal critical sections, then they are obtained by interpolation; S206. Delineate water level fluctuation risk zones: based on the length of the affected area. and the distance from the critical location to the dam site The downstream river section is divided into two risk levels: the first-level risk zone is the length from the dam site to the affected area. The section of the river, namely Level 2 risk zone is defined by the length of the affected area. Distance from the critical position to the dam site The section of the river, namely .

[0020] In the example, the water level fluctuation risk zone is 0-4.3km downstream of the dam in the first-level zone and 4.3km-29.5km downstream of the dam in the second-level risk zone.

[0021] Specifically, S3 is: S301. Establish a two-dimensional mathematical model of water flow based on topographic and roughness data; ;

[0022] in: For water depth; , The vertical average velocity component; This refers to the elevation of the riverbed. , For the shear stress of the subbed; It is the acceleration due to gravity; Let the density of water be denoted; then, through numerical solutions, the flow rate can be obtained. and downstream boundary water level Combined velocity field ,mold ; S302, Calculate the spatial distribution of flow velocity exceeding limits: [This refers to the flow rate...] and water level Discrete is a typical operating condition: , For each set of working conditions ,in, For the flow rate corresponding to the operating condition, The water level corresponds to the operating condition; the positional velocity of the entire river section is calculated using a mathematical model. Define the flow rate safety threshold Then the first The area where the flow velocity exceeds the limit under this operating condition is: ; S303. Based on historical data of actual power station discharge and downstream reservoir water level, statistical analysis was conducted on various operating condition combinations. probability of occurrence For any point in the downstream river channel The process exceeds the flow rate safety threshold. The probability is: ; S304. Divide the flow velocity risk ranges with different probabilities: Define the distance along the downstream main channel line. Extract the probability corresponding to each point Set two probability thresholds. and ,but: Flow rate exceeds flow rate safety threshold The probability is close to the range of river sections where it is certain to occur: ; Identify the river segment with a moderate probability of occurrence: ; Identify the river segment range with a low probability of occurrence: ; S305. Draw a navigation risk zone map downstream of the power station to quickly identify navigation risks.

[0023] Specifically, S4 is: S401. Based on the combination of the water level fluctuation risk zone in S2 and the hydrodynamic risk zone in S3, draw a navigation risk zone map downstream of the power station. S402. By using the location coordinates, query the navigation risk zone map downstream of the power station to quickly identify the risk at that location.

[0024] Example 1: Taking a hydropower station in the upper reaches of the Yangtze River as an example, this study conducts rapid identification of navigation risk areas downstream during peak-shaving periods to verify the feasibility and effectiveness of the method of this invention.

[0025] Figure 2 A study area map of a power station in the upper reaches of the Yangtze River was drawn. Approximately 12 cross-sections were arranged downstream of power station A to collect the continuous water level changes at these cross-sections, the discharge flow process of power station A, the water level in front of the dam of downstream power station B, and the water level at the control station downstream of power station A.

[0026] Based on the research on power station A and the characteristics of the river channel, the time-varying limit value of water level was determined. It is 1 m / h.

[0027] Water level fluctuation at downstream control station of power plant A The time variation of water levels at various downstream sections Relationships such as Figure 3 As shown.

[0028] ; ;

[0029] The probability of water level fluctuation at the downstream control station of power station A is 20%. It is 1 m / h.

[0030] Response time-varying amplitude The downstream control station section is 1 m / h. It is 4.3 km downstream of the dam.

[0031] The example calculates a flow rate of 1000m³. 3 / s、2000m 3 / s, 3000m 3 / s, 4000m 3 / s, 5000m 3 / s, 6000m 3 / s、7000m 3 / s, 8000m3 / s、9000m 3 / s, 10000m 3 The combined working conditions of flow velocity exceeding 3 m / s and water levels of 770 m, 775 m, 780 m, 785 m, 790 m, 795 m, 800 m, 805 m, 810 m, 815 m, 820 m, and 825 m were analyzed.

[0032] In this example, based on the actual discharge flow of the power station and the water level of the downstream reservoir over the years, the probability of occurrence of each combination of operating conditions is calculated, and then the probability of the flow velocity exceeding 3m / s in each section of the river in the region is analyzed and evaluated, as shown in Table 1.

[0033] Table 1. Probability of river velocity exceeding 3 m / s downstream of Dam A of the power station

[0034] The downstream river section of Power Station A is determined as follows: the range with a 100% probability of a flow velocity exceeding 3 m / s is 0-0.5 km downstream of the dam; the range with a probability greater than 20% but less than 100% of a flow velocity exceeding 3 m / s is 8.0-8.4 km, 11.6-12.0 km, 15.5 km, 17.2-18.0 km, 18.6-23 km, and 30-34.3 km downstream of the dam; and the range with a probability greater than 0% but less than 20% of a flow velocity exceeding 3 m / s is within 30 km downstream of the dam (excluding the ranges of 8.0-8.4 km, 11.6-12.0 km, 15.5 km, 17.2-18.0 km, and 18.6-23 km).

[0035] Based on the above flow velocity data, the primary risk zone for the water flow pattern is defined as 0-0.5 km downstream of the dam; the secondary risk zones are defined as 8.0-8.4 km, 11.6-12.0 km, 15.5 km, 17.2-18.0 km, 18.6-23 km, and 30-34.3 km downstream of the dam; and the tertiary risk zone is defined as the area within 34.3 km downstream of the dam (excluding the areas of 8.0-8.4 km, 11.6-12.0 km, 15.5 km, 17.2-18.0 km, and 18.6-23 km). Figure 4 As shown.

[0036] This invention, based on a series of measured data and considering various factors such as water level fluctuations and flow velocity changes, employs fitting formulas and probabilistic analysis to quickly identify navigation risk zones downstream of power stations. Examples demonstrate the feasibility and effectiveness of this method. Therefore, this method exhibits superior application results in identifying downstream navigation risk zones.

[0037] The method of this invention is highly practical and can effectively solve the problem of the inability to quickly identify navigation risk areas.

[0038] In summary, this invention has advantages such as practicality and strong operability, and can quickly identify downstream navigation risk areas during the peak-shaving period of large-scale cascade hydropower stations, obtain results of important risk areas, and provide more scientific and efficient technical support for reservoir scheduling and navigation management.

[0039] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be defined by the appended claims.

Claims

1. A method for rapid identification of downstream navigation risk zones during peak-shaving periods of large-scale cascade hydropower stations, characterized in that: S1. Collect basic measured data on hydrology and topography of the study area; S2. Construct a risk analysis of downstream water level fluctuations at the power station; S3. Conduct a risk analysis of the downstream water flow pattern of the power station; S4. Draw a navigation risk zone map downstream of the power station to quickly identify navigation risks; S1 specifically includes: historical discharge flow of the power station, measured water level at the downstream control station of the power station, measured water level at each section downstream of the dam, water level process of the reservoir downstream of the dam, and basic data of the downstream section of the dam. Specifically, S2 is: S201. Based on preliminary analysis, the water level fluctuation limit value was determined. ; S202. Establish the relationship between the downstream control station and the time-varying amplitude of water level at each cross-section: Based on the aforementioned measured data, define the time-varying amplitude of water level at the downstream control station as... Downstream The hourly water level variation at each cross-section is ( By fitting measured data, the mapping relationship is established as follows: （1）； in, The formula for linear regression is: In the formula, , The coefficients are obtained using the least squares method; S203. Determine the reference value for water level time-varying amplitude under a given probability: Collect historical measured water level data from downstream control stations and calculate the water level time-varying amplitude. Given a sample sequence and a fitted probability distribution, let the cumulative distribution function be... For a given probability The corresponding water level time variation reference value Defined by quantiles: （2）； in, It is the inverse cumulative distribution function; S204. Determine the range of influence of the reference value, and use the water level time-varying amplitude reference value obtained in S203. Substituting into formula (1), calculate the frequency-level time variation amplitude corresponding to each cross section. The set of affected sections is defined as follows: （3）； Let the first The distance from each cross-section to the dam site is The length of the affected area The furthest distance in the affected cross section: ; S205. Determine the critical section corresponding to the limit amplitude: Take the amplitude when the historical maximum water level of the downstream control station is reached. Find satisfaction The critical section, let be numbered as The corresponding distance is The distance from the critical position to the dam site is ; If there are no precisely equal critical sections, then they are obtained by interpolation; S206. Delineate water level fluctuation risk zones: based on the length of the affected area. and the distance from the critical location to the dam site The downstream river section is divided into two risk levels: the first-level risk zone is the length from the dam site to the affected area. The section of the river, namely Level 2 risk zone is defined by the length of the affected area. Distance from the critical position to the dam site The section of the river, namely .

2. The method for rapid identification of downstream navigation risk areas during peak-shaving periods of large-scale cascade hydropower stations according to claim 1, characterized in that, Specifically, S3 is: S301. Establish a two-dimensional mathematical model of water flow based on topographic and roughness data; in: For water depth; , The vertical average velocity component; This refers to the elevation of the riverbed. , For the shear stress of the subbed; It is the acceleration due to gravity; Given the density of water, an arbitrary flow rate can be obtained through numerical solution. and downstream boundary water level Combined velocity field ;mold ; S302. Calculate the spatial distribution of flow velocity exceeding limits: Consider any flow rate... and downstream boundary water level Discrete is a typical operating condition: , For each set of working conditions ,in, For the flow rate corresponding to the operating condition, The water level corresponds to the operating condition; the positional velocity of the entire river section is calculated using a mathematical model. Define the flow rate safety threshold Then the first The area where the flow velocity exceeds the limit under this operating condition is: ; S303. Based on historical data of actual power station discharge and downstream reservoir water level, statistical analysis was conducted on various operating condition combinations. probability of occurrence ; S304. Divide the flow velocity risk ranges with different probabilities: Define the distance along the downstream main channel line. Extract the probability of each point Set two probability thresholds. and ,but: Flow rate exceeds flow rate safety threshold The probability is close to the range of river sections where it is certain to occur: ; Identify the river segment with a moderate probability of occurrence: ; Identify the river segment range with a low probability of occurrence: ; S305. Draw a navigation risk zone map downstream of the power station to quickly identify navigation risks.

3. The method for rapid identification of downstream navigation risk areas during peak-shaving periods of large-scale cascade hydropower stations according to claim 2, characterized in that, Specifically, S4 is: S401. Based on the combination of the water level fluctuation risk zone in S2 and the hydrodynamic risk zone in S3, draw a navigation risk zone map downstream of the power station. S402. By using the location coordinates, query the navigation risk zone map downstream of the power station to quickly identify the risk at that location.

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