A forward-reverse sequence combined water quantity scheduling algorithm

Abstract

The application discloses a positive and negative sequence combined water quantity scheduling calculation method, comprising the following steps: building a river basin water quantity allocation calculation framework based on a positive algorithm; building a water quantity allocation calculation general module based on a reverse algorithm, and processing water quantity allocation operation between upstream and downstream calculation units; embedding and adding the upstream and downstream unit reverse algorithm in the positive algorithm from upstream to downstream circulation structure; during operation, the reverse algorithm is preferentially adopted to search for a scheduling scheme of the current calculation step; when the solution obtained by the reverse algorithm is feasible, the positive algorithm adopts the solution and enters the next calculation step; if a feasible solution cannot be obtained after 19 times of repetition, the reverse algorithm is exited, and the positive algorithm is used for solution, and thus the calculation is performed from top to bottom by time period until the whole river basin water resource scheduling operation is completed. The application builds an overall calculation framework by using the positive algorithm, improves the local calculation efficiency by using the reverse algorithm, and improves the searching speed and reliability of the water quantity scheduling scheme.

Description

Technical Field

[0001] This invention relates to the field of hydrology and water resources technology, and in particular to a water allocation calculation method that combines forward calculation from upstream to downstream with backward calculation from downstream to upstream. Background Technology

[0002] Current water resource scheduling calculations often rely primarily on forward calculations. Using pre-defined parameters, these calculations proceed from upstream to downstream, following the flow direction from tributaries to the main stream, to progressively calculate the allocated water volume and determine the scheduling method for the downstream and main stream. For example, the water resource management software MIKEBASIN developed by the Danish Hydraulic Institute (DHI) and the water resource allocation software GWAS (General Water Allocation and Simulation System) developed by the China Institute of Water Resources and Hydropower Research both employ forward calculations as the sole solution for scheduling calculations. Besides forward calculations, there are also related studies on reverse calculations for water volume scheduling both domestically and internationally. The logic of these calculations involves first assuming the downstream water intake, and then progressively backtracking to deduce the upstream discharge volume, scheduling method, and evaluation of the rationality of the scheme. Such research is relatively limited, with common applications including back-calculating reservoir inflows. For instance, Li Yugang (2019) et al. back-calculated reservoir inflows and then deduced the reservoir scheduling operation method. Overall, the depth of research and the breadth of application of reverse calculation methods are relatively insufficient.

[0003] In practical applications, both forward and inverse calculation methods for water resource scheduling have their own advantages and disadvantages. Forward calculation methods have simple operational logic, clear physical meanings of parameters, and are easy to program; however, the number of parameters is directly proportional to the complexity of the watershed, resulting in extremely large trial-and-error scales for optimization calculations, and even making it difficult to obtain reasonable results. Inverse calculation methods can quickly search for a set of feasible local parameter schemes between control nodes and a few upstream nodes; however, when simulating upstream, there is a high probability that the downstream demand of upstream units will exceed the water supply capacity, leading to divergence in the simulation. Furthermore, because the objective function of the inverse algorithm has many maxima points caused by computational failures, it is difficult to couple with existing multi-objective optimization algorithms. Further, for forward algorithms, the large parameter scale and low parameter quality of the generated scheduling schemes limit the algorithm's practical performance; while inverse algorithms are more efficient when handling smaller-scale nodes, they are not suitable for parameter searching between larger-scale nodes. The reliability of both forward and inverse calculation schemes is insufficient, and the computational requirements are extremely large, which is one of the bottleneck problems limiting the performance improvement of mathematical models for water resource scheduling.

[0004] Based on research on relevant technologies and advancements at home and abroad, this invention starts from the water cycle process in the watershed water resources system, fully considers the relative advantages and disadvantages of traditional "forward calculation" and "inverse calculation" methods, and proposes a water quantity scheduling calculation method with a clear physical basis and complementary advantages of forward and inverse calculation methods. This method aims to improve the shortcomings of the current mainstream forward algorithm, such as its excessively large trial calculation scale and the tendency of the inverse algorithm to diverge, thereby improving the calculation efficiency of the water resources scheduling mathematical model. Summary of the Invention

[0005] This invention addresses the problems of large-scale calculations and low efficiency in traditional forward and inverse water allocation methods. It proposes a watershed water allocation calculation method that combines forward calculation from upstream to downstream with backward calculation from downstream to upstream. The purpose of this invention is to fully utilize the advantages of forward algorithms (facilitating modeling and simple logic) and inverse algorithms (facilitating the search for scheduling parameters near nodes). By using forward algorithms to build the overall calculation framework and inverse algorithms to improve local calculation efficiency, the search speed and reliability of water allocation schemes are enhanced.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A combined forward and reverse order water allocation calculation method includes the following steps:

[0008] 1) Enter the downstream unit L water balance adjustment, obtain the water production, initial water storage, water supply of unit L at time t, and the discharge value of upstream unit K.

[0009] 2) Obtain the discharge amount of unit L at time t-1;

[0010] 3) Set the initial value of the discharge volume of unit L at time t (by default, the discharge volume of unit L at time t-1 is used as the initial value), calculate the water storage volume of unit L at the end of the time period using the inverse algorithm, and verify whether the water volume is balanced;

[0011] 4) If balanced, the L unit is finished and proceeds to the next unit;

[0012] If there is no balance, new alternative values ​​are selected for the discharge volume of unit L in turn, and the water balance is recalculated and verified. If there is a balance, the adjustment of unit L is completed and the next unit is started. If there is no balance, the forward algorithm is used to calculate the discharge volume of unit L and the water storage at the end of the time period, and the calculation is performed from top to bottom for each time period until the water resources scheduling of the entire basin is completed.

[0013] Further technology of the present invention:

[0014] Preferably, the specific steps of the inverse algorithm are as follows:

[0015] ① Enter the water balance adjustment in unit L;

[0016] ② Obtain the water production, initial storage, water supply, and discharge of unit L at time t, as well as the initial storage of unit K;

[0017] ③ Randomly generate the water distribution ratio of unit K at time t, and calculate the discharge volume of unit L using formulas (1)-(3);

[0018] Max{S L,t}=Q K,t +W L,t +S L,t-1 -U L,t (1)

[0019] Q K,t =Max{S K,t}*r K,t (2)

[0020] Q L,t =Max{S L,t}*r L,t (3)

[0021] In the formula: t is the time stamp, t-1 is the time before t, Q is the discharge volume of the calculation unit, W is the production volume of the calculation unit, S is the storage volume of the calculation unit, and U is the supply volume of the calculation unit; Max{S L,t}、Max{S L,t} refers to the maximum water supply capacity of units K and L after considering the impact of water supply; r is the water distribution ratio;

[0022] ④ Calculate the water storage S of unit L at the end of the time period according to the water balance equation (4). L,t ;

[0023] S L,t =Q K,t +W L,t +S L,t-1 -U L,t -Q' L,t (4)

[0024] In the formula: Q' is a candidate value for the discharge volume of the calculation unit, such as S L,t If the value is greater than or equal to zero, it is considered that the water balance equation is satisfied and the set discharge volume of unit L is feasible.

[0025] ⑤ The calculation of unit L is complete, proceed to the next unit.

[0026] Preferably, the specific steps of the forward algorithm are as follows:

[0027] ① Enter the water balance adjustment in unit L;

[0028] ② Obtain the water production, initial storage, water supply, and discharge of unit L at time t, as well as the initial storage of unit K;

[0029] ③ Randomly generate the water distribution ratio of unit K at time t, and calculate the discharge volume of unit L using formulas (1)-(3);

[0030] ④ Calculate the water storage S of unit L at the end of the time period according to the water balance equation (5). L,t ;

[0031] S L,t =Q K,t +W L,t +S L,t-1 -U L,t -Q L,t (5)

[0032] Verify S L,t If the value is greater than or equal to zero, then the water balance equation is considered to be satisfied and the set discharge volume of unit L is feasible.

[0033] ⑤ The calculation of unit L is complete, proceed to the next unit.

[0034] Preferably, step 4) specifically comprises:

[0035] Handle the following three scenarios in sequence: a), b), and c).

[0036] a) If the water storage volume of unit L at time t is not less than zero as calculated in step 3), then the water balance equation (4) is considered to be valid. The water storage volume and discharge volume of unit L at time t are based on the results of equation (4). Then, skip the positive algorithm operation module below, do not try to calculate parameters such as water distribution ratio, and proceed to the next calculation step.

[0037] b) When the water balance equation (4) for unit L does not hold at time t, let Q L,t Take Q values ​​of 0.1 to 0.9, 2 to 10 times respectively. L,t-1 Value, such as Q L,t If the new value makes the water balance equation true, then adopt the current value and proceed to the processing method in a); otherwise proceed to c).

[0038] c) If conditions a) and b) are not met, then the current inverse algorithm is considered unable to obtain a feasible solution, and the forward algorithm is entered.

[0039] The beneficial effects of this invention are:

[0040] This invention is based on extensive practical experience in watershed water resource allocation and scheduling. It fully considers the performance requirements of water conservancy industries for water resource scheduling mathematical models, integrates the current state of development of water resource scheduling calculation methods both domestically and internationally, and combines and modifies forward and inverse algorithms to achieve new technological methods. This invention possesses a sound physical foundation, reliable methods, high computational efficiency, and relatively optimal scheduling parameters. This invention can be widely applied to watershed water resource allocation and scheduling calculations, improving the computational performance of water resource scheduling mathematical models and providing technical support for cross-basin and regional water resource scheduling or water project scheduling simulation. Attached Figure Description

[0041] Figure 1 Technical flowchart of the present invention;

[0042] Figure 2 A schematic diagram of the water balance principle of the calculation unit (let the unit number be L). Detailed Implementation

[0043] This invention addresses the problems of large-scale and low-efficiency existing water allocation forward and reverse calculation methods by proposing a watershed water allocation calculation method that combines forward calculation from upstream to downstream with backward calculation from downstream to upstream.

[0044] See attached document Figure 1 The specific implementation steps of this method are as follows:

[0045] A combined forward and reverse order water allocation calculation method includes the following steps:

[0046] 1) Enter the downstream unit L water balance adjustment, obtain the water production, initial water storage, water supply of unit L at time t, and the discharge value of upstream unit K.

[0047] 2) Obtain the discharge amount of unit L at time t-1;

[0048] 3) Set the initial value of the discharge volume of unit L at time t (by default, the discharge volume of unit L at time t-1 is used as the initial value), calculate the water storage volume of unit L at the end of the time period using the inverse algorithm, and verify whether the water volume is balanced;

[0049] 4) If balanced, the L unit is finished and proceeds to the next unit;

[0050] If there is no balance, new alternative values ​​are selected for the discharge volume of unit L in turn, and the water balance is recalculated and verified. If there is a balance, the adjustment of unit L is completed and the next unit is started. If there is no balance, the forward algorithm is used to calculate the discharge volume of unit L and the water storage at the end of the time period, and the calculation is performed from top to bottom for each time period until the water resources scheduling of the entire basin is completed.

[0051] Further technology of the present invention:

[0052] Preferably, the specific steps of the inverse algorithm are as follows:

[0053] ① Enter the water balance adjustment in unit L;

[0054] ② Obtain the water production, initial storage, water supply, and discharge of unit L at time t, as well as the initial storage of unit K;

[0055] ③ Randomly generate the water distribution ratio of unit K at time t, and calculate the discharge volume of unit L using formulas (1)-(3);

[0056] Max{S L,t}=Q K,t +W L,t +S L,t-1 -U L,t (1)

[0057] Q K,t =Max{S K,t}*r K,t (2)

[0058] Q L,t =Max{S L,t}*r L,t (3)

[0059] In the formula: t is the time stamp, Q is the discharge volume of the calculation unit, W is the production volume of the calculation unit, S is the storage volume of the calculation unit, and U is the supply volume of the calculation unit; Max{S L,t}、Max{S L,t} refers to the maximum water supply capacity of units K and L after considering the impact of water supply; the forward algorithm uses Max{S} L,t Its split ratio at time t, r L,t The result of the multiplication is used as the discharge volume of unit L at time t. The diversion ratio parameter values ​​of each unit at each time step are generated by random generation or optimization algorithm recommendation.

[0060] ④ Calculate the water storage S of unit L at the end of the time period according to the water balance equation (4). L,t ;

[0061] S L,t =Q K,t +W L,t +S L,t-1 -U L,t -Q' L,t (4)

[0062] In the formula: Q' is a candidate value for the discharge volume of the calculation unit, such as S L,t If the value is greater than or equal to zero, it is considered that the water balance equation is satisfied and the set discharge volume of unit L is feasible.

[0063] ⑤ The calculation of unit L is complete, proceed to the next unit.

[0064] The constructed inverse algorithm is independent of the forward algorithm. The discharge volume of upstream unit K at time t is known. Its construction process first assumes an initial value for the discharge volume of unit L at time t, preferentially using the discharge volume Q' of unit L from the previous time step. L,t-1 As the discharge amount at time t of unit L (i.e., Q') L,t =Q' L,t-1 At this point, the water balance of unit L can be written in the form of the aforementioned equation (3). As calculated by equation (3), the water storage S of unit L at time t is... L,t If the value is not less than zero, then equation (3) is considered to be valid and the discharge amount of the set L unit at time t is acceptable.

[0065] Preferably, the specific steps of the forward algorithm are as follows:

[0066] ① Enter the water balance adjustment in unit L;

[0067] ② Obtain the water production, initial storage, water supply, and discharge of unit L at time t, as well as the initial storage of unit K;

[0068] ③ Randomly generate the water distribution ratio of unit K at time t, and calculate the discharge volume of unit L using formulas (1)-(3);

[0069] ④ Calculate the water storage S of unit L at the end of the time period according to the water balance equation (5). L,t ;

[0070] S L,t =Q K,t +W L,t +S L,t-1 -U L,t -Q L,t (5)

[0071] Verify S L,t If the value is greater than or equal to zero, then the water balance equation is considered to be satisfied and the set discharge volume of unit L is feasible.

[0072] ⑤ The calculation of unit L is complete, proceed to the next unit.

[0073] The forward calculation loop executes in a top-down, time-by-time, unit-by-unit order. Its loop structure includes an outer time loop and inner calculation processes between upstream and downstream, tributary-mainstream calculation units. The added inverse calculation module is embedded in the loop between inner units. The inverse algorithm takes precedence over the forward algorithm, and the discharge volume of upstream K unit at time t required by the inverse algorithm is provided by the previous inner loop.

[0074] In the inner loop of each time step of the forward algorithm, cases a), b), and c) are processed sequentially until the water allocation calculation for the entire time period is completed. The water release and storage volumes generated for each unit at each time period serve as the key parameters of the watershed water allocation scheme.

[0075] a) If the water balance equation (4) of unit L at time t holds, the water storage capacity of unit L at time t is the result of equation (1). Then, without trying to calculate parameters such as the water distribution ratio, skip the positive algorithm operation module below and proceed to the next calculation step.

[0076] b) If the water balance equation (4) for unit L does not hold at time t, then try to let Q L,t Take Q values ​​successively from 0.1 to 0.9 (with a step size of 0.1) and from 2 to 10 (with a step size of 1). L,t-1 Value, such as Q L,t If the new value makes the water balance equation true, then adopt the current value and proceed to the processing method in a); otherwise proceed to c).

[0077] c) If conditions a) and b) are not met, then the current inverse algorithm is considered unable to obtain a feasible solution, and the forward algorithm is entered.

[0078] In step 4) above, within the inner loop of each time step of the forward algorithm, the three scenarios a), b), and c) are processed sequentially until the water allocation calculation for the entire time period is completed. The water release volume and water storage volume generated for each unit at each time period serve as the key parameters of the watershed water allocation scheme.

[0079] The above description is merely a preferred embodiment of the present invention. Any person skilled in the art can modify the present invention or modify it into an equivalent technical solution using the technical solutions described above. Therefore, any simple modifications or equivalent substitutions made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A combined forward and reverse order water allocation calculation method, characterized in that, The steps include the following: 1) Enter the downstream unit L water balance adjustment, obtain the water production, initial water storage, water supply of unit L at time t, and the discharge value of upstream unit K. 2) Obtain the discharge amount of unit L at time t-1; 3) Set the initial value of the discharge volume of unit L at time t, calculate the water storage volume of unit L at the end of the time period using the inverse algorithm, and verify whether the water volume is balanced; 4) If balanced, the L unit is finished and proceeds to the next unit; If there is no balance, new alternative values ​​are selected for the discharge volume of unit L in turn, and the water balance is recalculated and verified. If there is a balance, the adjustment of unit L is completed and the next unit is entered. If there is no balance, the forward algorithm is used to calculate the discharge volume of unit L and the water storage at the end of the time period, and the calculation is performed from top to bottom time period by time until the water resource scheduling of the entire basin is completed. The specific steps of the inverse algorithm are as follows: ① Enter the water balance adjustment in unit L; ② Obtain the water production, initial storage, water supply, and discharge of unit L at time t, as well as the initial storage of unit K; ③ Randomly generate the water distribution ratio of unit K at time t, and calculate the discharge volume of unit L using formulas (1)-(3); Max{S L,t }=Q K,t +W L,t +S L,t-1 -U L,t (1); Q K,t = Max{S K,t }*r K,t (2); Q L,t = Max{S L,t }*r L,t (3); In the formula: t is the time stamp, t-1 is the time before t, Q is the discharge volume of the calculation unit, W is the production volume of the calculation unit, S is the storage volume of the calculation unit, and U is the supply volume of the calculation unit; Max{S L,t }、Max{S L,t } refers to the maximum water supply capacity of units K and L after considering the impact of water supply; r is the water distribution ratio; ④ Calculate the water storage S of unit L at the end of the time period according to the water balance equation (4). L,t ; S L,t =Q K,t +W L,t +S L,t-1 -U L,t -Q’ L,t (4); In the formula: Q' is a candidate value for the discharge volume of the calculation unit, such as S L,t If the value is greater than or equal to zero, it is considered that the water balance equation is satisfied and the set discharge volume of unit L is feasible. ⑤ Unit L calculation complete, proceed to the next unit; The specific steps of the forward algorithm are as follows: ① Enter the water balance adjustment in unit L; ② Obtain the water production, initial storage, water supply, and discharge of unit L at time t, as well as the initial storage of unit K; ③ Randomly generate the water distribution ratio of unit K at time t, and calculate the discharge volume of unit L using formulas (1)-(3); ④ Calculate the water storage S of unit L at the end of the time period according to the water balance equation (5). L,t ; S L,t =Q K,t +W L,t +S L,t-1 -U L,t -Q L,t (5); Verify S L,t If the value is greater than or equal to zero, then the water balance equation is considered satisfied and the set discharge volume of unit L is feasible. ⑤ Unit L calculation complete, proceed to the next unit; Step 4) specifically refers to: Handle the following three scenarios in sequence: a), b), and c). a) If the water storage volume of unit L at time t is not less than zero as calculated in step 3), then the water balance equation (4) is considered to be valid. The water storage volume and discharge volume of unit L at time t are based on the results of equation (4). Then, skip the positive algorithm operation module below, do not try to calculate parameters such as water distribution ratio, and proceed to the next calculation step. b) When the water balance equation (4) of unit L does not hold at time t, let Q L,t Take Q values ​​of 0.1 to 0.9, and 2 to 10 times respectively. L,t-1 Value, such as Q L,t If the new value makes the water balance equation true, then adopt the current value and proceed to step a); otherwise, proceed to step c). c) If conditions a) and b) are not met, then the current inverse algorithm is considered unable to obtain a feasible solution, and the forward algorithm is entered.

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