CN113590676B - Drainage basin flood control scheduling method and system based on step joint equivalent flood control storage capacity - Google Patents

Abstract

The invention belongs to the technical field of flood control scheduling of a cascade reservoir in a drainage basin, and discloses a method and a system for flood control scheduling of the drainage basin based on cascade joint equivalent flood control reservoir capacity, which are used for identifying a flood control target and a main control factor of the cascade reservoir; flood encounters of different main streams are extracted; establishing a step reservoir combined flood control scheduling scheme set; constructing a step reservoir combined flood control dispatching fitness function CF (); initializing a step reservoir combined flood control initial process; calculating a combined operation state set of the cascade reservoirs; and extracting a step combined equivalent flood control storage capacity scheme set. The step combined equivalent flood control storage capacity scheme set by the invention can meet basic scheduling operation modes and constraint limits of reservoir flood control, water storage, power generation and the like, provides theory and data support for setting a reasonable operation mode of a drainage basin flood control system, has engineering practicability, can meet the drainage basin flood control requirement and the step hydroenergy power generation benefit, and provides a new idea for the optimized operation of the drainage basin flood control system.

Description

Basin flood control dispatching method and system based on cascade joint equivalent flood control storage capacity

Technical Field

The present invention belongs to the technical field of flood control dispatching of cascade reservoirs in a river basin, and in particular relates to a method and system for flood control dispatching of a river basin based on cascade joint equivalent flood control storage capacity.

Background Art

In 2020, in the joint dispatch of water projects in the Yangtze River Basin, there are 22 control reservoirs above the Three Gorges of the Yangtze River, with a flood control storage capacity of 35.2 billion ^m3 (excluding Wudongde 2.44 billion ^m3 ), of which the Three Gorges Reservoir has a flood control storage capacity of 22.15 billion ^m3 , accounting for 63% of the flood control storage capacity of the reservoir group. The four control reservoirs above the Three Gorges that are about to be completed and put into operation are Lianghekou, Shuangjiangkou, Wudongde, and Baihetan. The flood control storage capacity of the four cascade reservoirs of Lianghekou, Shuangjiangkou, Wudongde, and Baihetan is 12.4 billion ^m3 in total, and the flood control storage capacity of the control reservoirs above the Three Gorges has increased by 35% to 47.6 billion ^m3 . With the development and construction of water conservancy hub projects in the basin, the basin's flood control capacity, flood control objects, flood control tasks and regulation methods have all undergone major changes.

At present, the flood control storage capacity of water conservancy hubs is set for the flood control safety of dams or downstream protection objects, mainly through the independent operation of water conservancy hubs to defend against standard floods and ensure the flood control safety of specific protection objects. Domestic and foreign research also focuses on analyzing the operation mode of single or cascade reservoirs for specific flood control tasks, and there is less quantitative research on the role of flood control scheduling of sub-district cascade reservoirs in flood defense in the whole basin.

At the same time, although the existing technology is trying to form an overall defense plan when defending against basin-wide floods, the joint operation mode of the water conservancy hub group still needs to be improved, and it is difficult to give full play to the regulation and storage role of the zoned controlled reservoirs; when solving basin flood control problems, the existing technology still adopts the method of lowering the operating water level of the reservoir to the flood limit water level and reserving planned flood control storage capacity. It cannot take into account the comprehensive benefits of cascade reservoirs and cannot achieve efficient use of basin water resources.

Through the above analysis, the problems and defects of the prior art are as follows:

(1) Existing technologies still require each water conservancy hub to reach a pre-set flood control limit water level to prevent floods. When preventing different types of basin-wide floods, it is difficult to give full play to the regulation and storage function of the zoned control reservoirs.

(2) When solving the problem of flood control in river basins, existing technologies still adopt the method of lowering the operating water level of the reservoir to the flood limit water level and reserving planned flood control storage capacity. This method fails to take into account the comprehensive benefits of cascade reservoirs and cannot achieve efficient utilization of water resources in the river basin.

(3) Domestic and foreign research has mostly focused on analyzing the operation modes of single or cascade reservoirs for specific flood control tasks, and less on quantitative research on the role of sub-regional cascade reservoir flood control scheduling in basin-wide flood defense.

The difficulty of solving the above problems and defects is:

In response to the problem of basin-wide floods, research on the joint dispatching of cascade reservoirs is being carried out at home and abroad, aiming to give full play to the flood control role of cascade reservoirs in the basin as a whole. However, the current research work is still in the initial practice stage, and the control indicators such as the single reservoir flood control limit water level and reserved flood control storage capacity defined in the reservoir design stage or dispatching regulations are maintained. A basin-wide joint reserved flood control storage capacity strategy has not yet been formed for the entire basin, making it difficult to give full play to the regulation and storage role of the zoned control reservoirs.

The significance of solving the above problems and defects is:

In view of the problem of joint flood control scheduling of cascade reservoirs under the new situation of river basin flood control, further research is conducted on the joint flood control scheduling mode of cascade reservoirs in each sub-district, and the strategy of cascade joint equivalent flood control storage capacity for river basin flood control safety and comprehensive benefits is sought. The method of reserving flood control storage capacity of sub-district cascade reservoirs in flood season is optimized. Starting from the unified flood control scheduling of river basin reservoir groups, a set of cascade joint equivalent flood control storage capacity plans is formulated, which can give full play to the joint interception and storage role of cascade reservoirs, not only ensure the flood control safety of the river basin, but also take into account the comprehensive utilization benefits of water resources in the river basin, and provide technical support for the efficient development and utilization of water resources in the river basin and the improvement of the comprehensive utilization benefits of water resources.

Summary of the invention

In view of the problems existing in the prior art, the present invention provides a basin flood control scheduling method based on cascade joint equivalent flood control storage capacity, and more particularly relates to a cascade joint equivalent flood control storage capacity strategy for basin flood control safety and comprehensive benefits.

The present invention is implemented as follows: a basin flood control dispatching method based on cascade joint equivalent flood control storage capacity, the basin flood control dispatching method based on cascade joint equivalent flood control storage capacity comprises the following steps:

Step 1: Identify the flood control objectives and main control factors of cascade reservoirs;

Step 2: Extract typical flood occurrences of different main and tributary rivers;

Step 3: Establish a set of joint flood control scheduling plans for cascade reservoirs;

Step 4: construct the fitness function CF() of the joint flood control dispatching of cascade reservoirs;

Step 5, initializing the initial process of joint flood control of cascade reservoirs;

Step six, deriving the joint operation state set of cascade reservoirs;

Step seven: extract the set of cascade joint equivalent flood control storage capacity solutions.

Further, in step 1, the identification of flood control targets and main control factors of cascade reservoirs includes:

The flood control tasks of the cascade reservoirs in the basin include three levels: first, ensuring the flood control safety of the cascade reservoirs themselves; second, ensuring the flood control safety of the downstream protection objects; and third, cooperating with the basin control reservoir group to undertake the downstream basin flood control tasks. In view of the different flood control goals and tasks of the cascade reservoirs, starting from the unified flood control dispatch of the basin reservoir group, the flood control goals and main control conditions of the cascade reservoir flood control dispatch operation are analyzed in detail, and the flood control goals and main control factors of the cascade reservoirs are identified.

The first level is flood control safety, which is reflected in the fact that the water level in front of the cascade reservoir dam must be lower than the flood control high water level FHL, and the discharge flow must obey the maximum flood discharge capacity MFC; the second level is flood control safety of downstream flood control objects, which is reflected in the fact that the discharge flow of the cascade reservoir must be less than the river flood discharge capacity RFC within the flood defense standard of the downstream protection object; the third level is to cooperate in the downstream basin flood control task, which is reflected in the fact that the joint flood storage volume CFS of the cascade reservoirs during the scheduling period must meet the basin flood control requirements. Therefore, according to the characteristics of the three levels of flood control tasks of the cascade reservoirs, the first and second levels can be used as hard constraints in the joint scheduling model of the cascade reservoirs, and the third level can be used as the target fitness function.

Among them, _F1 is the first-level flood control task, _F2 is the second-level flood control task, and _F3 is the third-level flood control task.

Furthermore, in step 1, the identification of flood control targets and main control factors of cascade reservoirs also includes:

(1) If the flood control task of the cascade reservoirs in this sub-district includes the above three levels, the cascade reservoir operation model can transform the first and second level flood control targets into water level and flow constraints, taking the maximum combined flood storage volume as the main objective function and the maximum comprehensive utilization benefit of water resources as the secondary objective function. After the combined flood storage volume of the cascade reservoirs meets the requirements of the flood control task of the basin, the comprehensive utilization benefit of water resources in the basin is optimized;

(2) If there is no second-level flood control task in the flood control task of the cascade reservoirs in this sub-district, the flood control target set of the cascade reservoirs can be simplified to _F1 and _F3 ; the cascade reservoir operation model can transform the first-level flood control target into water level and flow constraints, and take the maximum joint flood storage volume as the main objective function and the maximum comprehensive utilization benefit of water resources as the secondary objective function. After the joint flood storage volume of the cascade reservoirs meets the requirements of the flood control task of the basin, the comprehensive utilization benefit of water resources in the basin is optimized;

(3) If there is no third-level flood control task in the flood control task of the cascade reservoirs in this zone, the flood control target set of the cascade reservoirs can be simplified to _F1 and _F2 ; therefore, the cascade reservoir operation model can transform the flood control target into water level and flow constraints, and then maximize the comprehensive utilization benefit of water resources as the objective function.

Further, in step 2, extracting typical flood encounters of different main and tributary rivers includes:

(1) Analyze and determine the characteristics and regional composition of river basin floods: Collect historical flood data and long-series measured flood data of different sub-areas of the main control sections of the river basin, analyze the number of floods in different sub-areas by statistically analyzing the regularity of flood occurrence time and frequency, and form a typical flood set Flood Set (FS = {FS ₁ , FS ₂ , ..., FS _n , ..., FS _N }). On this basis, consider the flood propagation time, and statistically calculate the flood volume of each control section with different durations, and obtain ^the regional composition of river basin floods in different years W _tTotal :

W _t ^total ={W _t ¹ , W _t ² ,..., W _t ^a ,..., W _t ^A }

t∈{1d, 3d, 5d, 7d, 15d, 30d, 60d};

Where _Wt ^a is the flood volume of the ath sub-area in period t, and A is the number of sub-areas. In particular, t can be selected according to the characteristics of regional floods. For the Yangtze River Basin, a flood process can last up to 60 days, while for general small and medium-sized basins, 7 days, 15 days or shorter durations can be selected as the flood volume calculation period.

(2) According to the flood control tasks and targets of cascade reservoirs, combined with the flood season dispatching mode of each reservoir, under the same frequency flood conditions of the downstream control section, the flood control role of the upstream cascade reservoir group is analyzed for the flood processes in different typical years in the typical flood set FS, and the most unfavorable typical flood composition for each flood control target is clarified.

i∈{1, 2, ..., D};

Among them, CFS _i is the total flood storage capacity of the i-th target, Q _t,s represents the water storage flow of the reservoir in period t, and D is the number of flood control targets.

Furthermore, in step 3, the establishment of a set of joint flood control scheduling schemes for cascade reservoirs includes:

On the basis of identifying the flood control objectives and main controlling factors of cascade reservoirs, an initial scheme OS ₀ for the flood season water level control process line is set according to the flood season dispatching mode of each reservoir. Combined with the results of the flood area composition of the main and tributary rivers, the total flood control storage capacity V _{Total of} the cascade reservoirs is kept unchanged, and the reserved flood control storage capacity of the cascade reservoirs in the main flood season is adjusted with a fixed step length ΔV, and a derived scheme set OS = {OS ₁ , OS ₂ ,…, OS _m ,…, OS _M } for the joint flood control dispatching of M cascade reservoirs is derived.

Further, in step 4, the construction of the cascade reservoir joint flood control dispatch fitness function CF() includes:

Starting from the unified flood control dispatch of the basin reservoir group and giving full play to the joint interception and storage function of the cascade reservoirs, the maximum joint interception and storage volume of the cascade reservoirs is taken as the main optimization target CF ₁ , and the maximum total cascade power generation TP is taken as the secondary objective function CF ₂ , which is expressed as follows:

Among them, CFS _n ^m is the total flood storage capacity of the nth typical flood and the mth joint flood control scheduling scheme.

Among them, TP _n ^m is the total cascade power generation of the nth typical flood and the mth joint flood control scheduling scheme, and P _t represents the power generation of the reservoir in period t.

Further, in step 5, the initialization process of the cascade reservoir joint flood control includes:

According to the initial scheme OS ₀ of the flood season water level control process line, the typical flood set FS is used as the model water condition in turn, and the flood control dispatching procedures f() of each reservoir in the flood season are used to obtain the joint flood storage volume and flood control dispatching process of the cascade reservoirs under different typical flood conditions of the initial scheme OS ₀ , forming the initial set of joint flood storage volume INIV = {INIV ₁ , INIV ₂ , …, INIV _n , …, INIV _N } and the initial set of reservoir flood control dispatching process INIP = {INIP ₁ , INIP ₂ , …, INIP _n , …, INIP _N }:

INI _n (INIV _n , INIP _n ) = f (FS _n , OS ₀ , CF (F ₂ , F ₃ )).

Among them, _F1 is the first-level flood control task, _F2 is the second-level flood control task, and _F3 is the third-level flood control task.

Further, in step 6, the derivation of the joint operation state set of cascade reservoirs includes:

When the combined flood storage and flood control process INI _n (INIV _n , INIP _n ) of the cascade reservoirs is determined, the initial flood control process of the cascade reservoirs may not meet the derived scheme OS _m based on the joint flood control operation derivative scheme of M cascade reservoirs, considering the requirements of the flood control operation regulations of reservoirs during the flood season. The water level and flow constraints of the cascade reservoirs at different times during the flood season are adjusted according to the water balance calculation to obtain the nth typical flood and the mth joint flood control operation result RES _n,m , including the combined flood storage and flood volume of the cascade reservoirs, the flood peak and flood volume of the river where the downstream protection object is located, and form the combined flood control operation result set RES (N×M) of the cascade reservoirs. The model constraints are:

① Reservoir water balance constraints:

V _t =V _t-1 +(I _t -Q _t -S _t )Δt

t＝2,3,...,T;

② Upper and lower limits of reservoir capacity (water level):

③ Upper and lower limits of outbound traffic:

④ Time period water level/flow fluctuation constraints:

⑤Water level constraints at the end of the dispatch period:

Z _c =Z _g ;

分别为水库t时段水位上下限；

分别为水库t时段下泄流量上下限；ΔZ、ΔQ分别为水库时段允许最大水位变幅和流量变幅；Z_c与Z_g分别为水库计算末水位及调度期末水位控制值。Among them, V _t , I _t , Q _t are the reservoir capacity, inflow and outflow of the reservoir in the scheduling period t period respectively; S _t is the water supply flow;

are the upper and lower limits of the reservoir water level in period t respectively;

are the upper and lower limits of the discharge flow of the reservoir in period t, respectively; ΔZ and ΔQ are the maximum allowable water level fluctuation and flow fluctuation of the reservoir in period, respectively; Z _c and Z _g are the calculated final water level of the reservoir and the control value of the water level at the end of the dispatching period, respectively.

Further, in step seven, the step of extracting a set of cascade joint equivalent flood control storage capacity schemes includes:

Through the fitness function CF(), the joint flood storage capacity CFS and the total cascade power generation TP of the cascade reservoir joint flood control scheduling results set RES(N×M) are statistically analyzed to determine the joint equivalent flood control storage capacity strategy existing in the results set.

(1) If CFS _n ^m > INIV _n , RES _n,m is the joint equivalent flood control storage capacity scheme JFC _n,j ;

(2) If CFS _n ^m <INIV _n , RES _n,m is the non-joint equivalent flood control capacity scheme NJFC _n,k .

The equivalent flood control storage capacity schemes in RES (N×M) are integrated, and the joint equivalent flood control storage capacity strategy set _JFCn of a typical flood _FSn is integrated. By comparing the change relationship between CFS and TP of different schemes in the strategy set, ^{the joint equivalent flood control storage capacity scheme with CFSnm} _{＝ INIVn} is selected as the optimal joint equivalent flood control storage capacity strategy for _FSn .

The present invention provides a basin flood control dispatching method based on the cascade joint equivalent flood control storage capacity, which is applied to a basin flood control dispatching system, comprising:

Target and main controlling factor identification module, used to identify flood control targets and main controlling factors of cascade reservoirs;

Flood typical extraction module, used to extract flood typicalities of different main and tributary rivers;

A flood control scheduling scheme set establishment module is used to establish a set of joint flood control scheduling schemes for cascade reservoirs;

Fitness function construction module, used to construct the fitness function CF() of cascade reservoir joint flood control dispatch;

Process initialization module, used to initialize the initial process of joint flood control of cascade reservoirs;

An operation status set derivation module is used to derive a joint operation status set of cascade reservoirs;

The flood control storage capacity scheme set extraction module is used to extract the cascade joint equivalent flood control storage capacity scheme set.

Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, enables the processor to execute the basin flood control scheduling method based on the cascade joint equivalent flood control storage capacity.

Another object of the present invention is to provide an information data processing terminal, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the basin flood control scheduling method based on the cascade joint equivalent flood control reservoir capacity.

Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: the provided basin flood control dispatching method based on cascade joint equivalent flood control storage capacity aims at the joint flood control dispatching problem of cascade reservoirs under the new situation of basin flood control, seeks a cascade joint equivalent flood control storage capacity strategy for basin flood control safety and comprehensive benefits, optimizes the flood season flood control storage capacity reservation method of sub-district cascade reservoirs, and improves the comprehensive utilization efficiency of basin water resources. The present invention also provides a cascade joint equivalent flood control storage capacity strategy for basin flood control safety and comprehensive benefits, and formulates a flood control dispatching plan that can not only ensure basin flood control safety, but also take into account the comprehensive utilization efficiency of basin water resources.

While meeting the requirements of flood control in the river basin, the present invention can take into account the benefits of cascade hydropower generation and give full play to the regulation and storage function of the zoned controlled reservoir. The flood dispatching scheme formulated by the present invention can meet the basic dispatching operation modes and constraints of reservoir flood control, water storage and power generation, and can provide theoretical and data support for the formulation of a reasonable operation mode of the river basin flood control system, and has certain practical application value. At the same time, the present invention innovatively proposes the concept of a zoned joint equivalent flood control storage capacity strategy, which provides a new idea for the optimized operation of the river basin flood control system.

The results after the implementation of the technical solution show that the optimal joint equivalent flood control strategy fully utilizes the joint regulation and storage capacity of Lianghekou, Jinping I and Ertan reservoirs. On the basis of meeting the flood control needs of the basin, it can take into account the benefits of cascade hydropower generation and improve the comprehensive utilization benefits of water resources in the basin. Figures 2 and 3 show the flow process and water level process of the Yalong River outlet and downstream flood control section of the optimal joint equivalent flood control storage capacity strategy for typical floods in 1998, both of which meet the flood control requirements of the basin. Therefore, the cascade reservoir joint equivalent flood control storage capacity strategy obtained by the present invention can meet the actual operation and management requirements of the basin flood control system and has certain engineering practicality.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution of the embodiment of the present invention, the following is a brief introduction to the drawings required for use in the embodiment of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, they can also obtain the corresponding cascade joint equivalent flood control storage capacity solution set for other research objects based on these drawings without paying any creative work.

FIG1 is a flow chart of a method for flood control scheduling in a river basin based on cascade joint equivalent flood control storage capacity provided in an embodiment of the present invention.

2 is a structural block diagram of a basin flood control dispatching system based on cascade joint equivalent flood control storage capacity provided by an embodiment of the present invention;

In the figure: 1. Target and main control factor identification module; 2. Flood encounter typical extraction module; 3. Flood control scheduling plan set establishment module; 4. Fitness function construction module; 5. Process initialization module; 6. Operation status set deduction module; 7. Flood control storage capacity plan set extraction module.

3 is a diagram showing the relationship between the flood control storage capacity reserved for the cascade reservoirs and the cascade joint flood storage volume provided by an embodiment of the present invention.

FIG. 4 is a diagram of the Xiaodeshi flood process after the Yalong River cascade impoundment in Solution 3 provided in an embodiment of the present invention.

FIG. 5 is a diagram of the flood process in Chenglingji after the Yalong River cascade impoundment in Solution 3 provided in an embodiment of the present invention.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

In view of the problems existing in the prior art, the present invention provides a basin flood control scheduling method based on cascade joint equivalent flood control storage capacity. The present invention is described in detail below with reference to the accompanying drawings.

As shown in FIG1 , the basin flood control dispatching method based on cascade joint equivalent flood control storage capacity provided by an embodiment of the present invention includes the following steps:

S101, identify flood control objectives and main controlling factors of cascade reservoirs;

S102, extract flood occurrence characteristics of different main and tributary rivers;

S103, establish a set of joint flood control scheduling schemes for cascade reservoirs;

S104, constructing a fitness function CF() for joint flood control operation of cascade reservoirs;

S105, initializing the initial process of joint flood control of cascade reservoirs;

S106, deriving a joint operation state set of cascade reservoirs;

S107, extracting a set of cascade joint equivalent flood control storage capacity schemes.

As shown in FIG2 , the basin flood control dispatching system based on cascade joint equivalent flood control storage capacity provided by the embodiment of the present invention includes:

Target and main control factor identification module 1, used to identify the flood control targets and main control factors of cascade reservoirs;

Flood typical extraction module 2 is used to extract flood typicalities of different main and tributary rivers;

A flood control scheduling scheme set establishment module 3 is used to establish a cascade reservoir joint flood control scheduling scheme set;

Fitness function construction module 4, used to construct the fitness function CF() of cascade reservoir joint flood control dispatching;

Process initialization module 5, used to initialize the initial process of joint flood control of cascade reservoirs;

An operation state set derivation module 6 is used to derive a joint operation state set of cascade reservoirs;

The flood control storage capacity scheme set extraction module 7 is used to extract the cascade joint equivalent flood control storage capacity scheme set.

The technical solution of the present invention is further described below in conjunction with embodiments.

The basin flood control dispatching method based on cascade joint equivalent flood control storage capacity provided by the embodiment of the present invention includes:

(1) Selection of control reservoirs and dispatching scale

The present invention takes the Lianghekou, Jinping I and Ertan reservoirs, the controlling reservoirs in the middle and lower reaches of the Yalong River basin, as embodiments, and takes the day as the scheduling period. According to the joint equivalent flood control storage capacity strategy method flow of cascade reservoirs oriented to basin flood control safety and comprehensive benefits, the joint flood control scheduling of the Lianghekou, Jinping I and Ertan reservoirs is simulated to obtain a typical set of joint equivalent flood control storage capacity strategies for different main and tributary floods, and typical schemes are selected for comparative analysis to demonstrate the effect achieved by the present invention.

(2) Steps for solving the joint equivalent flood control storage capacity

Step 1: Identify the flood control objectives and main controlling factors of cascade reservoirs.

The Lianghekou, Jinping I and Ertan reservoirs on the Yalong River are important components of the Yangtze River Basin flood control system. According to the Yangtze River Basin Comprehensive Plan (2012-2030), the Yalong River Basin Comprehensive Plan and the 2020 Yangtze River Basin Water Project Joint Dispatch and Utilization Plan, the flood control objectives of the Lianghekou, Jinping I and Ertan cascade reservoirs are: to cooperate with the Three Gorges Reservoir to undertake the flood control tasks in the middle and lower reaches of the Yangtze River, and to reduce the flood control pressure in the lower reaches of the Yalong River, the lower reaches of the Jinsha River and the Sichuan and Chongqing river sections when necessary. The main controlling factor is the flood control task in the middle and lower reaches of the Yangtze River: to achieve the overall defense of the 1954 flood, reduce the diversion volume and the probability of using flood storage areas. When floods occur in the Jingjiang River and Chenglingji area, make full use of the river discharge, river and lake discharge and storage floods, and use the reservoirs above the Three Gorges to jointly intercept and store floods. Lianghekou, Jinping I and Ertan implement a dispatching method of synchronous flood interception and storage with the Three Gorges Reservoir, and appropriately control the discharge of reservoirs.

Step 2: Extract typical flood occurrences of different main and tributary rivers;

According to the flood control tasks of the Yalong River cascade reservoirs, this time we selected seven stations as analysis objects, including Xiaodeshi Hydrological Station, the base station of Yalong River Lianghekou, Jinping I and Ertan Reservoirs, Panzhihua Station and Pingshan Station of Jinsha River control stations, Lizhuang Station, Cuntan Station, Yichang Station and Luoshan Station on the main stream of the Yangtze River, to analyze the flood encounter patterns in the lower reaches of the Yalong River and Jinsha River, the Sichuan River and the middle and lower reaches of the Yangtze River.

1) Flood frequency

The time of the annual maximum floods from 1959 to 2018 at the seven control stations and the number of times the annual maximum flood occurred at the corresponding Xiaodeshi station when the annual maximum flood occurred were counted respectively. The flood encounter results of Xiaodeshi station and Panzhihua, Pingshan, Lizhuang, Cuntan, Yichang, Luoshan and other hydrological stations were obtained, see Table 1.

Table 1 Statistics of floods in the Yalong River and the Yangtze River mainstream

After analyzing the flood encounters of Xiaodeshi Station on the Yalong River and Panzhihua Station, Pingshan Station, Lizhuang Station and Cuntan Station on the Jinsha River, it can be seen that the frequency of flood encounters of Yalong River and Jinsha River is relatively high, and the frequency of occurrence of Xiaodeshi Station is relatively low when the annual maximum flood of less than 7 days occurs at Yichang Station and Luoshan Station.

2) Flood composition

Based on the annual maximum flood time of Yichang and Luoshan stations from 1965 to 2018 and considering the flood propagation time, the flood volumes at Panzhihua, Xiaodeshi, Pingshan, Lizhuang and Cuntan stations were counted respectively, and the composition of the multi-year average annual maximum flood at the seven control stations was obtained (see Table 2).

Table 2 Statistics of the components of the average annual maximum flood at the seven control stations over the years

It can be seen that the Yalong River flood is one of the main sources of floods in the lower reaches of the Jinsha River and the Sichuan River, but it accounts for a very small proportion of floods in the middle and lower reaches of the Yangtze River, and the proportion of floods is similar to the proportion of area. For the protection objects below Cuntan, the proportion of Yalong River floods is relatively small.

According to the analysis of measured hydrological data from 1965 to 2018, the Yangtze River Basin experienced a basin-wide flood in 1998, which was the second largest basin-wide flood in the 20th century, second only to 1954. Although the flood magnitude was smaller than that in 1954, the water level in the middle and lower reaches was generally higher than that in 1954, and the highest flood level in a 360-kilometer river section exceeded the highest record in history. Combined with the Yalong River cascade cooperating with the Three Gorges Reservoir to undertake the flood control task in the middle and lower reaches of the Yangtze River, the 1998 flood was selected as the most unfavorable typical flood in the Yalong River and the Yangtze River mainstream, so the 1998 typical flood was selected as the model input.

Step 3: Establish a set of joint flood control scheduling plans for cascade reservoirs.

The typical flood in 1998 was selected, and the dynamic control index of the operating water level of the cascade reservoirs in the lower reaches of the Yalong River during the flood season was considered. By simulating multiple dispatching schemes for typical floods, the impact of the cascade reservoirs in the lower reaches of the Yalong River on the flood volume of the middle and lower reaches of the Yangtze River was quantitatively analyzed. The setting of the joint reserve scheme for flood control storage capacity is shown in Table 3. The four dispatching schemes are:

① Adopt the joint reservation plan 1 for flood control storage capacity, maintain the flood limit water level, and the reservoir does not play a flood control role;

② Adopt the joint reservation plan 2 for flood control storage capacity, maintain the flood limit water level in the early stage, and store flood water simultaneously when it is necessary to cooperate with the Three Gorges Dam to start flood control in the middle and lower reaches;

③ Adopt the joint reservation plan 3 for flood control storage capacity, maintain the flood limit water level in the early stage, and store flood water simultaneously when it is necessary to cooperate with the Three Gorges Dam to start flood control in the middle and lower reaches;

④ Adopt the joint reservation plan 4 for flood control reservoir capacity, maintain the flood limit water level in the early stage, and simultaneously intercept and store flood water when it is necessary to cooperate with the Three Gorges Dam to start flood control in the middle and lower reaches.

Table 3 Joint reserve plan for flood control storage capacity of Lianghekou, Jinping I and Ertan cascade control reservoirs

Solution No. Lianghekou Jinping Level 1 Ertan Solution 1 0 0 0 Solution 2 20 16 9 Solution 3 30 6 9 Solution 4 35 3 7

Step 4: Construct the fitness function CF() of the joint flood control operation of cascade reservoirs.

Starting from the unified flood control dispatch of the basin reservoir group and giving full play to the joint interception and storage function of the cascade reservoirs, the maximum joint interception and storage volume of the cascade reservoirs is taken as the main optimization target CF ₁ , and the maximum total cascade power generation TP is taken as the secondary objective function CF ₂ , which is specifically expressed as follows:

In this example, only the typical flood in 1998 is selected, n=1, and there are four schemes with m=4.

Step 5: Initialize the initial process of joint flood control of cascade reservoirs.

According to the initial scheme OS ₀ of the flood season water level control process line, that is, the second scheme of the joint flood control dispatching of cascade reservoirs, the typical flood in 1998 was used as the model water condition. Through the flood control dispatching regulations of each reservoir during the flood season, the joint flood storage capacity and flood control dispatching process of the cascade reservoirs of the initial scheme OS ₀ under typical flood conditions were obtained. The flood storage capacity is shown in Table 4.

Step 6: Derivation of the joint operation state set of cascade reservoirs.

According to the derived plan of joint flood control dispatching of four cascade reservoirs, considering meeting the requirements of flood control dispatching regulations of reservoirs during flood season, adjustments are made according to water balance calculations to obtain four joint flood control dispatching results that meet the water level and flow constraints at different times of the flood season, as shown in Table 4.

Table 4 Comparative analysis of multiple dispatching schemes in 1998

Step 7: Extract the set of cascade joint equivalent flood control storage capacity solutions.

In 1998, the water level at Shashi Station exceeded the warning level on July 2 and dropped below the warning level on September 4. Considering that the Three Gorges Reservoir began to intercept and store flood water on July 2, the Yalong River began to intercept and store flood water simultaneously. The regulation and storage process is shown in Figure 3.

Option 1: The cascades in the lower reaches of the Yalong River do not play any role in flood control.

Scheme 2 to Scheme 4: Considering that the water level in Shashi will exceed the warning level by 43m on July 2, flood storage will begin. From July 2 to September 3, the basin outlet will be controlled at ^6000m3 /s, and the total flood storage capacity will be about 4.4 ^billionm3 .

As can be seen from Table 4, compared with Scheme 1, Schemes 2 to 4 have obvious reservoir storage effects, with a flood storage volume of about 3.84 to 4.36 billion m3 ^. Although Schemes 2 and 3 have different dispatching methods, their impact on the Three Gorges Reservoir is basically the same, while Scheme 4 has the least obvious impact on the flood control effect, increasing the Three Gorges Reservoir flood volume by 530 million ^m3 compared with Schemes 2 and 3. On the other hand, Scheme 3 has increased the total cascade power generation by 797 million kWh compared with Scheme 2 without reducing the total flood storage volume of the cascade. As can be seen from Figure 3, when the reserved flood control storage capacity of Lianghekou increases from 2 billion ^m3 to 3 billion ^m3 , the total flood storage volume of the cascade remains unchanged; when the reserved flood control storage capacity of Lianghekou continues to increase from 3 billion ^m3 , the total flood storage volume of the cascade shows a decreasing trend. Therefore, Scheme 3 is the "inflection point" where the total flood storage volume of the cascade changes with the reserved flood control storage capacity of the cascade reservoirs.

In summary, it can be concluded that scheduling plan three is the optimal joint equivalent flood control storage capacity strategy for the typical flood in 1998. The use of this flood control plan can effectively prevent the adverse situations encountered by floods in the Yalong River and the main stream of the Yangtze River.

(3) The results after the implementation of the technical solution show that the optimal joint equivalent flood control strategy fully utilizes the joint regulation and storage capacity of Lianghekou, Jinping I and Ertan reservoirs. On the basis of meeting the flood control needs of the basin, it can take into account the benefits of cascade hydropower generation and improve the comprehensive utilization benefits of water resources in the basin. Figures 4 and 5 show the flow process and water level process of the Yalong River outlet and downstream flood control section of the optimal joint equivalent flood control storage capacity strategy for typical floods in 1998, both of which meet the flood control requirements of the basin. Therefore, the cascade reservoir joint equivalent flood control storage capacity strategy obtained by the present invention can meet the actual operation and management requirements of the basin flood control system and has certain engineering practicality.

The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims (4)

1. A basin flood control dispatching method based on cascade joint equivalent flood control storage capacity, comprising: identifying the flood control objectives and main control factors of cascade reservoirs, extracting typical flood encounters of different main and tributary rivers, characterized in that the basin flood control dispatching method based on cascade joint equivalent flood control storage capacity further comprises: Establish a set of joint flood control and dispatching schemes for cascade reservoirs; Construct the fitness function CF() of the joint flood control operation of cascade reservoirs; Initialize the initial process of joint flood control of cascade reservoirs; Derivation of the joint operation state set of cascade reservoirs; Extract the set of cascade joint equivalent flood control storage capacity schemes; The establishment of a set of joint flood control and dispatching schemes for cascade reservoirs includes: On the basis of identifying the flood control objectives and main control factors of cascade reservoirs, according to the flood season dispatching mode of each reservoir, the initial scheme of flood season water level control process line OS ₀ is set; combined with the results of the flood area composition of the main and tributary rivers, based on the principle of keeping the total flood control storage capacity V _{Total of} the cascade reservoirs unchanged, the reserved flood control storage capacity of the cascade reservoirs in the main flood season is adjusted with a fixed step length ΔV, and the derived scheme set OS = {OS ₁ , OS ₂ ,…, OS _m ,…, OS _M } of the joint flood control dispatching of M cascade reservoirs is derived; The initialization process of the cascade reservoir joint flood control includes: According to the initial scheme OS ₀ of the flood season water level control process line, the typical flood set FS is used as the model water condition in turn, and the flood control dispatching procedures f() of each reservoir in the flood season are used to obtain the joint flood storage volume and flood control dispatching process of the cascade reservoirs under different typical flood conditions of the initial scheme OS ₀ , forming the initial set of joint flood storage volume INIV = {INIV ₁ , INIV ₂ , …, INIV _n , …, INIV _N } and the initial set of reservoir flood control dispatching process INIP = {INIP ₁ , INIP ₂ , …, INIP _n , …, INIP _N }: INI _n (INIV _n , INIP _n ) = f (FS _n , OS ₀ , CF (F ₂ , F ₃ )); Among them, FS _n is the nth typical flood, F ₁ is the first-level flood control task, F ₂ is the second-level flood control task, and F ₃ is the third-level flood control task; The construction of the cascade reservoir joint flood control dispatch fitness function CF() includes: Starting from the unified flood control dispatch of the basin reservoir group and giving full play to the joint interception and storage function of the cascade reservoirs, the maximum joint interception and storage volume of the cascade reservoirs is taken as the main optimization target CF ₁ , and the maximum total cascade power generation TP is taken as the secondary objective function CF ₂ , which is expressed as follows:

Where, CFS _n ^m is the total flood storage capacity of the nth typical flood and the mth joint flood control scheduling scheme, Q _t,s represents the water storage flow of the reservoir in period t,

Among them, TP _n ^m is the total cascade power generation of the nth typical flood and the mth joint flood control scheduling scheme, and P _t represents the power generation of the reservoir in period t; The method of deducing the joint operation state set of cascade reservoirs includes: When the combined flood storage and flood control process INI _n (INIV _n , INIP _n ) of the cascade reservoirs is determined, according to the derived scheme of the combined flood control operation of M cascade reservoirs, the requirements of the flood control operation regulations of the reservoirs during the flood season are considered. During the initial flood control process of the cascade reservoirs, the constraints of the derived scheme OS _m on the water level and flow of the cascade reservoirs at different times during the flood season may not be met. It is necessary to make adjustments based on the water balance calculation to obtain the nth typical flood and the mth combined flood control operation result RES _n,m , including the combined flood storage and flood volume of the cascade reservoirs, the flood peak and flood volume of the river where the downstream protection object is located, and form the combined flood control operation result set RES (N×M) of the cascade reservoirs. The model constraints are as follows: ① Reservoir water balance constraints: V _t =V _t-1 +(I _t -Q _t -S _t )Δt t＝2,3,...,T; ② Upper and lower limits of storage capacity:

③ Upper and lower limits of outbound traffic:

④ Time period water level/flow fluctuation constraints:

⑤Water level constraints at the end of the dispatch period: Z _c =Z _g ; Among them, V _t , I _t , Q _t are the reservoir capacity, inflow and outflow of the reservoir in the scheduling period t period respectively; S _t is the water supply flow;

are the upper and lower limits of the reservoir water level in period t respectively;

are the upper and lower limits of the discharge flow of the reservoir in period t, respectively; ΔZ and ΔQ are the maximum allowable water level fluctuation and flow fluctuation of the reservoir in the period, respectively; Z _c and Z _g are the calculated final water level of the reservoir and the control value of the water level at the end of the dispatching period, respectively; The extraction of the cascade joint equivalent flood control storage capacity scheme set includes: Through the fitness function CF(), the joint flood storage capacity CFS and the total cascade power generation TP of the cascade reservoir joint flood control dispatch results set RES (N×M) are statistically analyzed to determine the joint equivalent flood control storage capacity strategy in the results set; (1) If CFS _n ^m > INIV _n , RES _n,m is the joint equivalent flood control storage capacity scheme JFC _n,j ; (2) If CFS _n ^m <INIV _n , RES _n,m is the non-joint equivalent flood control storage capacity scheme NJFC _n,k ; The equivalent flood control storage capacity schemes in RES (N×M) are integrated, and the joint equivalent flood control storage capacity strategy set _JFCn of a typical flood _FSn is integrated. By comparing the change relationship between CFS and TP of different schemes in the strategy set, ^{the joint equivalent flood control storage capacity scheme with CFSnm} _{＝ INIVn} is selected as the optimal joint equivalent flood control storage capacity strategy for _FSn . 2. A basin flood control dispatching system based on cascade joint equivalent flood control storage capacity, which uses the basin flood control dispatching method based on cascade joint equivalent flood control storage capacity as claimed in claim 1, characterized in that the basin flood control dispatching system based on cascade joint equivalent flood control storage capacity comprises: Target and main controlling factor identification module, used to identify flood control targets and main controlling factors of cascade reservoirs; Flood typical extraction module, used to extract flood typicalities of different main and tributary rivers; A flood control scheduling scheme set establishment module is used to establish a set of joint flood control scheduling schemes for cascade reservoirs; Fitness function construction module, used to construct the fitness function CF() of cascade reservoir joint flood control dispatch; Process initialization module, used to initialize the initial process of joint flood control of cascade reservoirs; An operation status set derivation module is used to derive a joint operation status set of cascade reservoirs; The flood control storage capacity scheme set extraction module is used to extract the cascade joint equivalent flood control storage capacity scheme set. 3. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the basin flood control scheduling method based on cascade joint equivalent flood control storage capacity as described in claim 1. 4. An information data processing terminal, characterized in that the information data processing terminal includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the basin flood control scheduling method based on cascade joint equivalent flood control storage capacity as described in claim 1.

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