Reservoir staged and graded drought limit water level determination method and system based on hedera helix algorithm

Abstract

The invention provides a reservoir staged and graded drought limit water level determination method and system based on a hedera helix algorithm. The method comprises the steps that 1, reservoir incoming water data, water demand data and reservoir dispatching regulations are collected and sorted; 2, performing preliminary staging on a reservoir scheduling period based on the reservoir scheduling procedure, and adding staging nodes based on the incoming water data and the water demand data of the reservoir; further grading based on the water demand data to obtain a plurality of staged and graded drought limit water levels; 3, the multiple stages and stages of drought limit water levels serve as parameters, and a drought limit water level multi-target optimization model is constructed; and 4, solving the drought limit water level multi-objective optimization model to obtain non-inferior solution sets obtained through optimization, sorting the non-inferior solution sets obtained through optimization, and determining final staged and graded drought limit water levels. The method has the characteristics of high convergence speed and few algorithm parameters; and a parameter simulation optimization method is adopted, so that the obtained explicit scheduling rule better meets the actual requirement, and the drought-resistant water replenishing scheduling can be better guided.

Description

Technical Field

[0001] The present invention belongs to the technical field of reservoir operation, and particularly relates to a method and system for determining the stage-based and level-based drought limit water levels of a reservoir based on the ivy algorithm. Background Art

[0002] Affected by extreme climate, severe droughts are often accompanied by low river water levels, making it difficult for drought-stricken areas to receive effective water resource replenishment and greatly affecting water supply security. By using reservoirs to supply water for drought resistance in drought-stricken areas, a series of water resource, water environment, and water ecological problems caused by drought and water shortage can be alleviated to a certain extent. As the water level for initiating drought resistance measures, the drought limit water level is of great significance for guiding the optimal allocation of water resources by reservoirs during droughts.

[0003] Existing methods for determining the drought limit water level include the monthly sliding method and the long series optimization method. Calculating the drought limit water level based on the sliding of typical years is simple and easy to implement, but the representativeness of typical years is insufficient and there is a certain degree of subjectivity in the later correction; calculating based on long series optimization can fully exploit the storage capacity of the reservoir, but the extraction of rules is greatly affected by the selection of later data mining methods. The parameter simulation and optimization method, as a method of presetting a reservoir operation rule with parameters and continuously improving the rule through an optimization algorithm, can make full use of long series data, and the explicit operation rule obtained by optimization is also more in line with the actual operation needs. The present invention proposes a method and system for determining the stage-based and level-based drought limit water levels of a reservoir based on the ivy algorithm. The application of this method and system provides important technical support for the decision-making of reservoir drought resistance water supply operation, makes full use of water resources, and improves the comprehensive utilization efficiency of reservoirs. Summary of the Invention

[0004] In view of the above actual needs, the present invention provides a method and system for determining the stage-based and level-based drought limit water levels of a reservoir based on the ivy algorithm, which can provide a new method for determining the stage-based and level-based drought limit water levels of a reservoir, aiming to provide a reference for reservoir drought resistance water supply operation decision-making under similar operation scenarios.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for determining the stage-based drought limit water level of a reservoir by parameter simulation and optimization based on the ivy algorithm, the method comprising the following steps:

[0007] Step 1: Collect and organize the reservoir inflow data, water demand data, and reservoir operation regulations;

[0008] Step 2: Based on the reservoir operation regulations, conduct a preliminary staging of the reservoir operation period, and based on the reservoir inflow data and water demand data, add staging nodes to obtain the stage-based drought limit water levels of the reservoir; further conduct grading based on the water demand data to obtain multiple stage-based and level-based drought limit water levels;

[0009] Step 3: Taking multiple phased and graded drought limit water levels as parameters, comprehensively considering water use demands and reservoir operation objectives, construct a multi-objective optimization model for drought limit water levels;

[0010] Step 4: Solve the multi-objective optimization model for drought limit water levels to obtain the optimized non-dominated solution set, sort the optimized non-dominated solution set, and determine the final phased and graded drought limit water levels.

[0011] Furthermore, in Step 1, the incoming water data is the reservoir inflow data; the water demand data is the water use demands of downstream water replenishment objects and their requirements for the minimum discharge flow of the reservoir. The water use demands of downstream water replenishment objects include domestic water demand targets, production water demand targets, and ecological water demand targets.

[0012] Furthermore, the reservoir inflow data is the restored flow or the current restored flow.

[0013] Furthermore, Step 2 for obtaining the phased drought limit water levels of the reservoir includes:

[0014] Based on the reservoir operation regulations, conduct a preliminary phasing of the reservoir operation period. Use the mean change point phasing method to add phasing nodes based on the reservoir incoming water data, and add phasing nodes based on the core water use periods of the water demand data. Add phasing nodes on the basis of the preliminary phasing to obtain the phased drought limit water levels of the reservoir.

[0015] Furthermore, Step 2 for obtaining multiple phased and graded drought limit water levels includes:

[0016] On the basis of the phased drought limit water levels of the reservoir, further conduct grading according to the water use demands of different levels in different periods.

[0017] Furthermore, in Step 3, use the parameter simulation optimization method to construct a multi-objective optimization model for drought limit water levels.

[0018] Furthermore, the multi-objective optimization model for drought limit water levels includes an objective function and constraint conditions. The objective function includes but is not limited to the total water demand guarantee rate and the reservoir fullness rate. The constraint conditions include different water demand guarantee rate constraints, water balance constraints, reservoir water level constraints, water level amplitude constraints, and discharge flow constraints.

[0019] Furthermore, the total water demand guarantee rate P in Step 3 is:

[0020]

[0021] The reservoir fullness rate V f is:

[0022]

[0023] The different water demand guarantee rate constraints are: Pj ≥P j,d ;

[0024] The water balance constraint is: V i,t+1 =V i,t +(I i,t -Q i,t )×Δt

[0025] The reservoir water level constraint is:

[0026] The water level fluctuation constraint is: Z i,t -Z i,t-1 ≤ΔZ xs,t , Z i,t-1 -Z i,t ≤ΔZ xl,t

[0027] The outflow discharge constraint is:

[0028] Among them, M is the number of different water demand categories, w j is the weight of water demand j, P j is the guarantee rate of water demand j;

[0029]

[0030] N is the number of years, T j is the total number of time periods that water demand j needs to meet, R j,i,t represents the satisfaction situation of water demand j in the t-th time period of the i-th year. If the water use demand is met, then R j,i,t =1; otherwise R j,i,t =0;

[0031] V (i,high) represents the reservoir capacity corresponding to the highest water level during the end-of-year storage period of the i-th year; V max , V min represent the reservoir capacities corresponding to the normal storage water level and the dead water level respectively;

[0032] P j,d represents the design guarantee rate of water demand j, V i,t+1 , V i,t are the reservoir storage volumes at the (t + 1)-th and t-th moments of the i-th year respectively; I i,t and Q i,t are the inflow discharge and outflow discharge of the reservoir in the t-th time period of the i-th year; Δt represents the calculation time step; Z t , are the lower and upper limits of the reservoir water level at the t-th moment respectively; Z i,t is the water level of the reservoir at the t-th moment of the i-th year; Z i,t-1 is the water level of the reservoir at the (t - 1)-th moment of the i-th year; ΔZ xs,t , ΔZxl,t They are the requirements for the daily amplitude of the reservoir water level during the impoundment and drawdown periods of the reservoir respectively; Q t and They are the lower and upper limits of the reservoir discharge during the t period respectively.

[0033] Furthermore, the process of determining the phased drought-limited water level of the reservoir in step 4 is as follows:

[0034] Step 4.1 Initialize the population by setting the population size Npop and the number of decision variables D, and describe the coordinated and orderly growth process of the population, describe how members select neighbors, describe how the population obtains sunlight for growth, describe the spread and evolution of the population, and solve the multi-objective optimization model of the drought-limited water level based on the ivy algorithm to obtain the optimized non-dominated solution set;

[0035] Step 4.2 Sort the optimized non-dominated solution set according to the double-base point method to determine the satisfactory phased and graded drought-limited water levels.

[0036] On the other hand, the present invention provides a system for determining the phased drought-limited water level of a reservoir based on the ivy algorithm, including:

[0037] Data collection module: It is used to collect and collate the reservoir inflow data, water demand data, and reservoir operation rules;

[0038] Drought-limited water level phasing and grading module: It is used to preliminarily phase the reservoir operation period based on the reservoir operation rules, and add phasing nodes based on the reservoir inflow data and water demand data to obtain the phased drought-limited water level of the reservoir; further classify based on the water demand data to obtain multiple phased and graded drought-limited water levels;

[0039] Optimization model construction module: It is used to take multiple phased and graded drought-limited water levels as parameters, and comprehensively consider the water use demand and the reservoir operation target to construct a multi-objective optimization model of the drought-limited water level;

[0040] Solution module: It is used to solve the multi-objective optimization model of the drought-limited water level to obtain the optimized non-dominated solution set, sort the optimized non-dominated solution set, and determine the final phased and graded drought-limited water levels;

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The method and system for determining the phased drought-limited water level of a reservoir based on the ivy algorithm provided by the present invention use the ivy algorithm with fast optimization speed and few algorithm parameters, showing stronger optimization ability in engineering optimization problems; aiming at the deficiencies of the existing methods for determining the phased drought-limited water level of a reservoir, the parametric simulation optimization method is proposed, and the explicit operation rules obtained by optimization are more in line with the actual needs and can better guide the drought relief and water supply operation. Description of the Drawings

[0043] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the attached drawings required for the description of the embodiments or the prior art. Obviously, the attached drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other attached drawings can also be obtained based on these drawings.

[0044] Figure 1 It is a schematic flow chart of the method for determining the phased drought limit water level of the reservoir in the present invention;

[0045] Figure 2 It is a schematic flow chart of the ivy algorithm in the present invention;

[0046] Figure 3 It is a schematic diagram of the phased results of the mean change point in the present invention;

[0047] Figure 4 It is a schematic diagram of the operation chart of the Three Gorges Reservoir in the present invention;

[0048] Figure 5 It is a box plot of the phased and graded drought limit water levels of the Three Gorges Reservoir in the present invention. Specific Embodiments

[0049] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will make a detailed description of the specific embodiments of the present application in conjunction with the attached drawings. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0050] As Figure 1 shown, the present invention includes the following processes:

[0051] Step 1: Collect and organize the reservoir inflow data, water demand data, and reservoir operation regulations;

[0052] In Step 1, collect the original data such as the reservoir inflow, water demand requirements of the water supply objects, and reservoir operation regulations. It should be noted that for the selection of the reservoir inflow data, that is, the inflow data, it usually includes natural flow (restored flow) and the current flow. If the upstream reservoir group of the reservoir has a significant impact on its inflow regulation, it is more appropriate to select the current flow data of the reservoir under the current situation. The water demand data refers to the water use demand of the downstream water supply objects and their requirements for the minimum discharge flow of the reservoir. The water use demand includes the water demand targets in the aspects of life, production, and ecology, which are mainly determined according to the water level or flow requirements of the corresponding control sections. The reservoir operation regulation data refers to the operation mode based on which the comprehensive benefits are fully exerted while ensuring the safety of the hub project during the normal operation period of the reservoir.

[0053] Step 2: Based on the reservoir operation rules, conduct a preliminary staging of the reservoir operation period, and based on the reservoir inflow data and water demand data, add staging nodes to obtain the staged drought-limiting water levels of the reservoir; further classify based on the water demand data to obtain multiple staged and classified drought-limiting water levels.

[0054] Step 2 for obtaining the staged drought-limiting water levels of the reservoir includes:

[0055] Adopt the mean change point staging method to add staging nodes based on the reservoir inflow data, and add staging nodes for staging based on the core water use periods of the water demand data. Add staging nodes on the basis of the preliminary staging to obtain the staged drought-limiting water levels of the reservoir. On the basis of the staged drought-limiting water levels of the reservoir, further classify according to the water use requirements of different levels in different periods.

[0056] The mean change point is some points that divide the time series so that the mean values of the series before and after the division change significantly. Its model description is that for a time series x that follows a normal distribution i :

[0057] x i = u i + e i (1)

[0058] In the formula, u i is the mean; the variance of the random error term e i is 0 and the expected value is 0.

[0059] If there exists

[0060]

[0061] In the formula, 1 < m 1 < m 2 <…< m q ≤ n; if b j ≠ b j+1 , then m j is a change point.

[0062] Let m 0 = 1, m q+1 = n + 1, the change point m j can be estimated by the least squares method, that is, minimize:

[0063]

[0064] In the formula, q is the number of change points, b j is the data x i (i = m j-1 , m j-1 + 1,…, m jMean estimation of (-1).

[0065] The water demand data is staged according to the core water use periods of the demands in three aspects: living, ecological, and production. Generally speaking, the water demands for living and ecological purposes are required throughout the year, while the agricultural water demand in production water demand is mainly concentrated in a certain period. If the water demand data and the incoming water data are long series data of the same type, the mean change point analysis method can also be used for staging.

[0066] Based on the staging results of the incoming water and water demand, add staging nodes on the basis of the existing reservoir operation rules staging to obtain the staging of the reservoir's drought limit water level. After the staging of the drought limit water level, it can be further classified according to the water use demands of different levels in different periods. Generally speaking, the larger the reservoir storage volume, the stronger the water supply guarantee ability. That is, when the reservoir water level is high, the storage volume is large, and when supplying water, it can meet higher water use demands, such as production water demand; when the reservoir water level is low, the storage volume is small, and it gives priority to meeting the core water use demands, such as living and ecological water demands. By classifying the reservoir's drought limit water level, the reservoir can supply water according to the water level classification limit to meet the water use demands of different levels. When the water level is higher than the drought limit water level, it is scheduled according to the existing rules. If the downstream discharge is insufficient, make up water to the corresponding water demand; when the water level is lower than the drought limit water level, schedule according to the classification limit supply rules formulated for the water demand.

[0067] Step 3: Take multiple staged and classified drought limit water levels as parameters, and comprehensively consider the water use demand and the reservoir operation goal to construct a multi-objective optimization model for the drought limit water level;

[0068] In Step 3, use the parameter simulation optimization method, regard the staged and classified drought limit water levels as parameters, and comprehensively consider the water use demand and the reservoir operation goal to construct a multi-objective optimization model for the drought limit water level. The optimization model consists of an objective function and constraint conditions. Among them, the objective function usually includes different water demand guarantee rates, reservoir full storage rates, shipping guarantee rates, etc., and the constraint conditions usually include different water demand guarantee rate constraints, water volume balance constraints, reservoir water level constraints, water level fluctuation constraints, downstream discharge constraints, etc. The specific steps are as follows:

[0069] Objective function:

[0070] ① The maximum multi-year average water demand guarantee rate. The water demand guarantee rate represents the probability that the reservoir meets different water demand requirements, and the larger the better. The multi-year average guarantee rate P of water demand j j The calculation formula is:

[0071]

[0072] In the formula, N is the number of years, T j is the total number of periods that water demand j needs to meet, and R j,i,t represents the satisfaction situation of water demand j in the t period of the i-th year. If the water use demand is met, then R j,i,t = 1; otherwise Rj,i,t = 0。

[0073] The differences in the guarantee priorities of different water demands are reflected through weight settings. The calculation formula for the multi-year average water demand guarantee rate P is:

[0074]

[0075] In the formula, M is the number of different water demand categories, and w j is the weight of water demand j. The greater the weight, the higher the guarantee priority.

[0076] ② The multi-year average reservoir fullness rate is maximized. The reservoir fullness rate represents the fullness of the reservoir at the end of the annual water storage period, and the larger the better. The calculation formula is:

[0077]

[0078] In the formula, V (i,high) represents the reservoir capacity corresponding to the highest water level during the water storage period at the end of the i-th year, and V max , V min represent the reservoir capacities corresponding to the normal water storage level and the dead water level of the reservoir.

[0079] ③ The multi-year average shipping guarantee rate is maximized. The shipping guarantee rate represents the probability that the reservoir area meets the shipping requirements, and the larger the better. The calculation formula is:

[0080]

[0081] In the formula, T hy is the total number of days in the shipping statistical period, and H i,t represents the satisfaction situation of shipping in the t-th period of the i-th year. If the shipping demand is met, then H i,t = 1; otherwise H i,t = 0.

[0082] ④ The multi-year average power generation is maximized. The calculation formula is:

[0083]

[0084] In the formula, P i,t represents the average output of the reservoir in the t-th period of the i-th year, and Δt is the time step.

[0085] Constraint conditions:

[0086] ① Different water demand guarantee rate constraints.

[0087] P j ≥ P j,d (10)

[0088] In the formula, P j,d represents the design guarantee rate of water demand j.

[0089] ② Water balance constraint.

[0090] V i,t+1 = V i,t + (I i,t - Q i,t ) × Δt (11)

[0091] Where, V i,t+1 , V i,t are the reservoir storage volumes at the (t + 1)-th moment and the t-th moment in the i-th year, I i,t and Q i,t are the inflow and outflow discharges of the reservoir in the t-th period of the i-th year.

[0092] ③ Water level constraint.

[0093]

[0094] Where, Z t , are the lower and upper limits of the water level of the reservoir at the t-th moment, and Z i,t is the water level of the reservoir at the t-th moment in the i-th year.

[0095] ④ Water level fluctuation constraint.

[0096] Z i,t - Z i,t-1 ≤ ΔZ xs,t (13)

[0097] Z i,t-1 - Z i,t ≤ ΔZ xl,t (14)

[0098] Where: ΔZ xs,t , ΔZ xl,t are the requirements for the daily water level fluctuation of the reservoir during water storage and drawdown in the t-th period respectively.

[0099] ⑤ Outflow discharge constraint.

[0100]

[0101] Where: Q t , are the lower and upper limits of the outflow discharge of the reservoir in the t-th period respectively.

[0102] Step 4: Solve the multi-objective optimization model of the drought limit water level to obtain the optimized non-dominated solution set, sort the optimized non-dominated solution set, and determine the final phased and graded drought limit water levels.

[0103] In Step 4, the ivy algorithm is used for optimization and solution, as Figure 2As shown, the non - dominated solution set obtained by optimization is sorted according to the double - base point method to screen the satisfactory dry - season limited water level scheme. Among them, the Ivy Algorithm, as a new type of meta - heuristic algorithm (intelligent optimization algorithm), is inspired by the growth pattern of ivy plants. It searches for the optimal solution by simulating the coordinated and orderly population growth and expansion evolution of this plant, and has excellent performance in parameter optimization. The algorithm initialization requires setting the population size Npop and the number of decision variables D. The calculation formula for population initialization is shown in (15), the calculation formulas describing the coordinated and orderly growth process of the population are shown in (16) and (17), the calculation formula describing the member's selection of neighbors is shown in (18), the calculation formulas describing the population's acquisition of sunlight for growth are shown in (19) and (20), and the calculation formulas describing the population's propagation and evolution are shown in (21) and (22).

[0104] I i =I min +rand(1,D)⊙(I max -I min ),i = 1,…,Npop (16)

[0105] In the formula, rand(1,D) represents a vector of dimension D of uniformly distributed random numbers in the interval [0,1]. I max and I min are the upper and lower bounds of the search space respectively, and the Hadamard product of the two vectors is represented by ⊙.

[0106]

[0107] In the formula, Gv is the growth rate, Ψ is the growth speed, is the correction coefficient for deviation from growth.

[0108]

[0109] In the formula, ΔGv i (t) and ΔGv i (t + 1) represent the growth rates of the discrete - time system (at time t and time t + 1), rand is a random real number in the interval [0,1]; N(1,D) represents a random vector of dimension D, which is a random number in the standard Gaussian normal distribution.

[0110]

[0111] In the formula, the population is sorted according to the fitness from good to bad There is I ii is the member I i selects its nearest and most important (according to the value of the fitness function) neighbor in the search space as a means of self - improvement.

[0112]

[0113]

[0114] In the formula, the components of |N(1, D)| are the absolute values of the components of N(1, D); the element-by-element division of two vectors is represented by ; Iter represents the number of iterations; is the new value of the growth rate of the current member .

[0115] Furthermore, according to the double-base point method (TOPSIS method), the non-inferior solution set obtained by optimization is sorted to determine a satisfactory dry-limit water level scheme. This method calculates the positive and negative ideal solutions and sorts each scheme according to its proximity to the most ideal target. The calculation formula for establishing the weighted matrix is shown in (23), the calculation formula for describing the ideal solution of each index is shown in (24), the calculation formula for describing the distance from the ideal solution is shown in (25), and the calculation formula for quantifying the degree of approximation to the ideal solution is shown in (26).

[0116] R = (r ij ) m×n , r ij = w j × C ij (i = 1, 2,..., n; j = 1, 2,..., m) (24)

[0117] In the formula, R is the weighted matrix, w j is the comprehensive weight of the j-th index, and C ij is the value after the index is positive-ized and normalized.

[0118]

[0119] In the formula, and are the optimal ideal solution and the worst ideal solution of the j-th index, respectively.

[0120]

[0121] In the formula, and are the distances between the i-th solution and the positive and negative ideal solutions, respectively.

[0122]

[0123] In the formula, C i represents the relative proximity of the i-th solution to the positive ideal solution, and the larger the value of C i , the higher the ranking of the scheme.

[0124] Example 1

[0125] Taking the Three Gorges Reservoir as an example, the Three Gorges Reservoir undertakes comprehensive utilization tasks such as flood control, power generation, shipping, and water resource utilization. Since its completion, it has played a key backbone role in the Yangtze River flood control system. In recent years, extreme events of rapid alternation between floods and droughts have occurred frequently in the Yangtze River Basin. The Three Gorges Project is located at the junction of the upper and middle reaches of the Yangtze River. To meet the requirements of joint flood and drought prevention and control, its role in the drought resistance system needs to be further improved. As an important basis for the reservoir to initiate the drought resistance emergency response, the application of the drought limit water level is of great significance for enhancing the drought resistance and disaster reduction level of the Yangtze River Basin. Based on the above background, through a method for determining the staged drought limit water level of a reservoir based on parameter simulation and optimization using the ivy algorithm provided by the present invention, the staged drought limit water level of the Three Gorges Reservoir is studied.

[0126] In step 1, according to the research needs, incoming water data, water demand data, and reservoir operation regulations are collected and sorted. Affected by the regulation of the upstream reservoir group, taking 2022 as the reference year, the daily natural flow of the Three Gorges Reservoir from 1970 to 2010 is back-calculated according to the current operation mode of the upstream reservoir group to obtain the inflow; the difficulties in ensuring the water use safety along the middle and lower reaches of the Yangtze River are in the Jingjiang River section and the Wuhan River section. The "three livelihoods" water demand data of the section from Yichang to Hankou and the minimum discharge of the Three Gorges Reservoir are used as the water demand requirements, as shown in Table 1; the reservoir operation regulations are mainly based on the "Three Gorges (Normal Operation Period) - Gezhouba Water Control Project Cascade Operation Regulations (Revised Edition in 2019)".

[0127] In step 2, the staging of the drought limit water level of the Three Gorges Reservoir should be further refined based on the reservoir operation staging according to the incoming water of the Three Gorges Reservoir and the water demand in the middle and lower reaches of the Yangtze River. According to the "Three Gorges (Normal Operation Period) - Gezhouba Water Control Project Cascade Operation Regulations (Revised Edition in 2019)", considering that some of the upstream cascade reservoirs in the Yangtze River enter the impoundment operation on August 1, the operation period of the Three Gorges Reservoir can be divided into five periods: from June 10 to July 31, from August 1 to September 9, from September 10 to October 31, from November 1 to December 31, and from January 1 to June 9. The mean change point analysis method is used to stage the incoming water of the Three Gorges Reservoir, and the staging results are as Figure 3 shown. Two staging nodes, December 1 and April 30, are added on the basis of the operation regulations. According to the "three livelihoods" water demand data in the middle and lower reaches of the Yangtze River, the water demand for living and ecological needs should be guaranteed throughout the year, while the water demand for agriculture mainly needs to be considered from April to September. Two staging nodes, April 1 and October 1, are added on the basis of the operation regulations.

[0128] Table 1 "Three Livelihoods" Water Demand of the Section from Yichang to Hankou and the Minimum Discharge of the Three Gorges Reservoir

[0129]

[0130] The phased drought-limited water levels of the Three Gorges Reservoir can be further classified according to the water use requirements of different levels in different periods. The larger the water storage capacity of the reservoir, the stronger the water supply guarantee ability. According to the Yangtze River Protection Law, the discharge of the Three Gorges Reservoir should give priority to meeting the domestic water use of urban and rural residents, ensuring basic ecological water use, and coordinating the needs of agricultural, industrial water use and shipping, etc. Therefore, the drought-limited water levels from April to September are divided into 3 levels, corresponding to ensuring the water demand of old irrigation areas, new irrigation areas, urban and ecological water demand respectively; the drought-limited water levels in the remaining periods are divided into 1 level, corresponding to ensuring urban and ecological water demand. To sum up, the phased classification of the drought-limited water levels of the Three Gorges Reservoir is shown in Table 2, and the classified water supply restriction rules of the Three Gorges Reservoir are shown in Table 3.

[0131] Table 2 Phased Classification of Drought-Limited Water Levels of the Three Gorges Reservoir

[0132]

[0133] Table 3 Classified Water Supply Restriction Rules of the Three Gorges Reservoir

[0134]

[0135]

[0136] In Step 3, the parameter simulation optimization method is adopted. Regarding the phased classified drought-limited water levels as parameters, considering the water use requirements and the reservoir operation objectives comprehensively, a multi-objective optimization model for the drought-limited water levels is constructed.

[0137] In Step 4, the ivy algorithm is used for optimization and solution. According to the double base point method, the non-dominated solution set obtained by optimization is sorted, and a satisfactory drought-limited water level scheme is selected. To compare the changes of multi-objectives after adding the drought-limited water level, the following operation schemes are set:

[0138] Scheme A: Conventional operation scheme

[0139] The operation of the Three Gorges Reservoir is mainly guided by the "Regulations on the Cascade Operation of the Three Gorges (Normal Operation Period) - Gezhouba Water Control Project (Revised Edition in 2019)" and the conventional operation chart of the Three Gorges Reservoir, where the conventional operation chart is as Figure 4 shown. From June 10th to September 9th, flood control operation is carried out according to the classified operation rules, and in the remaining periods, water is determined according to electricity based on the conventional operation chart, and the discharge of the Three Gorges Reservoir obtained is corrected according to the operation regulations.

[0140] Scheme B: Conventional operation + drought-limited water level scheme

[0141] On the basis of the conventional operation scheme, the drought-limited water level is added. When the reservoir water level is higher than the drought-limited water level, the reservoir operates according to the existing operation regulations and the minimum discharge requirements; when the reservoir water level is lower than the drought-limited water level, the reservoir supplies water according to the water level classification and gradually restricts water supply.

[0142] The non - inferior solution set is obtained through optimization. The box - type diagram of the stage - by - stage and level - by - level drought - limit water levels of the Three Gorges Reservoir is as Figure 4 shown. The best optimization scheme is selected through the TOPSIS method, and the indexes under different dispatching operation schemes are counted, as shown in Table 4. It can be seen that after the drought - limit water level is added, the Three Gorges Reservoir has been improved to varying degrees in terms of water storage, power generation, water supply, and shipping benefits.

[0143] Table 4 Index statistics of the Three Gorges Reservoir under different dispatching operation schemes

[0144]

[0145] As Figure 5 shown is the box - type diagram of the stage - by - stage and level - by - level drought - limit water levels of the Three Gorges Reservoir of the present invention. Based on the above conclusions, a method for determining the stage - by - stage drought - limit water level of a reservoir by parameter simulation optimization based on the ivy algorithm provided by the present invention. The ivy algorithm adopted has excellent performance, with the characteristics of fast convergence speed and few algorithm parameters. Aiming at the deficiencies of the existing calculation methods for the stage - by - stage drought - limit water level of reservoirs, a parameter simulation optimization method is proposed. The explicit dispatching rules obtained are more in line with actual needs and can better guide the drought - resistance water - supply dispatching.

[0146] Embodiment 2

[0147] This embodiment provides a system for determining the stage - by - stage and level - by - level drought - limit water levels of a reservoir based on the ivy algorithm, including:

[0148] A data collection module: It is used to collect and collate the reservoir inflow data, water demand data, and reservoir dispatching regulations;

[0149] A drought - limit water level stage - by - stage and level - by - level module: It is used to preliminarily stage the reservoir dispatching period based on the reservoir dispatching regulations, and add staging nodes based on the reservoir inflow data and water demand data to obtain the stage - by - stage drought - limit water levels of the reservoir; further classify based on the water demand data to obtain multiple stage - by - stage and level - by - level drought - limit water levels;

[0150] An optimization model construction module: It is used to take multiple stage - by - stage and level - by - level drought - limit water levels as parameters, and comprehensively consider the water use demand and the reservoir dispatching objectives to construct a multi - objective optimization model for the drought - limit water level;

[0151] A solution module: It is used to solve the multi - objective optimization model of the drought - limit water level to obtain the non - inferior solution set obtained through optimization, sort the non - inferior solution set obtained through optimization, and determine the final stage - by - stage and level - by - level drought - limit water levels;

[0152] As mentioned above, the above is only the preferred specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered within the protection scope of the present application.

[0153] It should be understood that the parts not elaborated in detail in this specification all belong to the prior art.

[0154] It should be understood that the above description of the preferred embodiments is relatively detailed, and it should not be considered as a limitation to the protection scope of the invention patent. Under the inspiration of the present invention, those of ordinary skill in the art can also make substitutions or deformations without departing from the protection scope defined by the claims of the present invention, and all fall within the protection scope of the present invention. The scope of protection claimed by the present invention shall be subject to the appended claims.

Claims

1. A method for determining the drought limit water level of a reservoir in stages and grades based on the Ivy algorithm, characterized in that: The method comprises the following steps: Step 1: Collect and organize reservoir water inflow data, water demand data and reservoir operation procedures; Step 2: Preliminarily divide the reservoir operation period into stages based on the reservoir operation regulations, and add stage nodes based on the reservoir water inflow data and water demand data to obtain the reservoir drought limit water level stages; further perform grading based on the water demand data to obtain multiple staged and graded drought limit water levels; Step 3: Taking multiple staged and graded drought limit water levels as parameters, comprehensively considering water demand and reservoir scheduling objectives, a multi-objective optimization model for drought limit water levels is constructed; Step 4: Solve the multi-objective optimization model of drought-limited water level to obtain the optimized non-inferior solution set, sort the optimized non-inferior solution set, and determine the final staged and graded drought-limited water level.

2. The method for determining the drought limit water level of a reservoir in stages and grades based on the Ivy algorithm according to claim 1 is characterized by: The water inflow data in step 1 is the reservoir inflow data; the water demand data is the water demand of the downstream water replenishment object and its requirement for the minimum downstream discharge flow of the reservoir. The water demand of the downstream water replenishment object includes living water demand targets, production water demand targets, and ecological water demand targets.

3. The method for determining the drought limit water level of a reservoir in stages and grades based on the Ivy algorithm according to claim 2 is characterized by: The inflow data of the reservoir is the restored flow or the current flow.

4. According to claim 1, a method for determining drought limit water level of reservoirs in stages and grades based on the Ivy algorithm is characterized by: The step 2 of obtaining the reservoir drought limit water level in stages includes: The reservoir scheduling period is preliminarily divided into stages based on the reservoir scheduling regulations, and the mean change point stage method is used to increase the stage nodes based on the reservoir water inflow data, and the stage nodes are increased based on the core water use period of the water demand data. The stage nodes are increased on the basis of the preliminary stage division to obtain the reservoir drought limit water level stage.

5. According to claim 4, a method for determining drought-limited water levels of reservoirs in stages and grades based on the Ivy algorithm is characterized in that: In step 2, obtaining multiple drought limit water levels in stages and grades includes: Based on the classification of reservoir drought limit water levels, further classification is carried out according to different levels of water demand in different periods.

6. The method for determining the drought limit water level of a reservoir in stages and grades based on the Ivy algorithm according to claim 1 is characterized by: In step 3, the parameter simulation optimization method is used to construct a multi-objective optimization model of drought-limited water level.

7. The method for determining the drought limit water level of a reservoir in stages and grades based on the Ivy Algorithm according to claim 6 is characterized by: The drought-limited water level multi-objective optimization model includes an objective function and constraints, wherein the objective function includes but is not limited to the total water demand guarantee rate and the reservoir fullness rate, and the constraints include different water demand guarantee rate constraints, water balance constraints, reservoir water level constraints, water level variation constraints, and outflow flow constraints.

8. The method for determining the drought limit water level of a reservoir in stages and grades based on the Ivy Algorithm according to claim 7 is characterized by: The total water demand guarantee rate P in step 3 is: Reservoir filling rate V f for: Different water demand guarantee rate constraints are: P j ≥P j,d ; The water balance constraint is: V i,t+1 =V i,t +(I i,t -Q i,t )×Δt The reservoir water level constraint is: The water level fluctuation constraint is: Z i,t -Z i,t-1 ≤ΔZ xs,t , Z i,t-1 -Z i,t ≤ΔZ xl,t The outbound flow constraints are: Where M is the number of different water demand categories, w j is the weight of water demand j, P j is the guaranteed rate of water demand j; N is the number of years, T j is the total number of time periods that water demand j needs to meet, R j,i,t Indicates the satisfaction of water demand j in period t of year i. If the water demand is met, then R j,i,t =1; otherwise R j,i,t =0; V (i,high) V represents the storage capacity corresponding to the highest water level of the reservoir at the end of the i-th year; max 、V min Indicates the storage capacity corresponding to the normal water level and dead water level of the reservoir; P j,d represents the design guarantee rate of water demand j, V i,t+1 、V i,t are the reservoir water storage at time t+1 and time t in year i; I i,t and Q i,t is the inflow and outflow of the reservoir in the t period of the i-th year; Δt represents the step length of the calculation period; Z t , are the lower and upper limits of the reservoir water level at time t; Z i,t is the water level of the reservoir at time t in year i; Z i,t-1 is the water level of the reservoir at time t-1 in year i; ΔZ xs,t , ΔZ xl,t They are the requirements of the reservoir for water storage in period t and the daily fluctuation of the reservoir water level due to water drawdown; Q t , are the lower and upper limits of the outflow of the reservoir in period t respectively.

9. The method for determining the drought limit water level of a reservoir in stages and grades based on the Ivy Algorithm according to claim 1 is characterized by: The process of determining the reservoir's drought limit water level in stages in step 4 is as follows: Step 4.1 Set the population size Npop and the number of decision variables D to initialize the population, and describe the coordinated and orderly growth process of the population, describe the members' selection of neighbors, describe the population's growth by obtaining sunlight sources, describe the population's propagation and evolution, solve the drought-limited water level multi-objective optimization model based on the Ivy algorithm, and obtain the optimized non-inferior solution set; Step 4.2 sorts the non-inferior solution set obtained by optimization according to the double base point method, and determines a satisfactory drought limit water level in stages and grades.

10. A reservoir drought limit water level determination system based on the Ivy algorithm, characterized in that: include: Data collection module: It is used to collect and organize reservoir water inflow data, water demand data and reservoir scheduling procedures; Drought limit water level stage classification module: it is used to preliminarily stage the reservoir scheduling period based on the reservoir scheduling regulations, and add stage nodes based on the reservoir water inflow data and water demand data to obtain the reservoir drought limit water level stage; further perform classification based on the water demand data to obtain multiple stage-classified drought limit water levels; Optimization model building module: It is used to take multiple staged and graded drought limit water levels as parameters, comprehensively consider water demand and reservoir scheduling objectives, and build a multi-objective optimization model for drought limit water levels; Solution module: It is used to solve the multi-objective optimization model of drought limit water level to obtain the optimized non-inferior solution set, sort the optimized non-inferior solution set, and determine the final staged and graded drought limit water level; The system for determining drought-limited water levels of reservoirs in stages and grades based on the Ivy algorithm is used to execute the steps in the method for determining drought-limited water levels of reservoirs in stages and grades based on the Ivy algorithm described in any one of claims 1-9.

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