Cascade reservoir dispatching method based on dynamic programming joint step-by-step optimization algorithm

Abstract

The invention relates to a cascade reservoir dispatching method based on a dynamic planning joint gradual optimization algorithm, which fully considers the characteristics of close cascade hydraulic connection and complex relation in the dispatching process of a cascade power station, and is used for dispatching the cascade reservoir on the basis of different dispatching scenes such as a water dispatching process and a total water dispatching amount. The method comprises the following steps: establishing an objective function by considering the requirements of watershed water consumption, cross-watershed water transfer, power station benefit-making application and the like, determining constraint conditions by considering water supply and power generation joint optimization scheduling limitation of a cascade hydropower station group, and then solving by adopting a dynamic planning joint gradual optimization algorithm to select an optimal scheduling scheme. The method can more scientifically, accurately and efficiently dispatch the cascade hydropower stations in the drainage basin, provides more high-quality and stable power supply for a power grid, improves the power generation income of a hydropower development company, and supports the actual production and operation of the cascade hydropower stations.

Description

Technical Field

[0001] The present invention relates to the technical field of water resource dispatching and management, and in particular to a cascade reservoir dispatching method based on a dynamic programming combined step-by-step optimization algorithm. Background Art

[0002] In order to solve the problem of water shortage caused by the uneven spatial distribution of water resources, water diversion projects are usually used to connect reservoirs in the water source area and the water receiving area, giving full play to the hydrological and storage capacity compensation functions of the reservoir group, and realizing the optimal allocation and efficient utilization of system water resources. However, in the multi-reservoir scheduling, especially the joint water supply scheduling of large-scale complex reservoir groups, how to efficiently and accurately solve the scheduling model is an urgent problem to be solved. Although there are attempts in the prior art, such as scheduling diagram models and multi-objective optimization scheduling models for reservoir groups, the application of this solution method is not ideal due to the problem of dimensionality curse. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a cascade reservoir scheduling method based on a dynamic programming combined stepwise optimization algorithm which can improve scheduling efficiency and accuracy.

[0004] The technical solution adopted by the present invention to solve the above technical problems is: a cascade reservoir scheduling method based on dynamic programming combined with step-by-step optimization algorithm, comprising:

[0005] S1, comprehensively considers the water use of the basin itself, inter-basin water transfer and power generation demand of cascade power stations, and constructs the objective function of the scheduling model;

[0006] S2, comprehensively consider the constraints of the joint optimization scheduling of cascade reservoir water supply and power generation, and determine the constraints of the scheduling model;

[0007] S3, the dispatching model is solved by combining the dynamic programming algorithm and the stepwise optimization algorithm to obtain the optimal time series of the water storage capacity of the cascade reservoirs, and then the dispatching plan of the cascade reservoirs is formulated.

[0008] Furthermore, the objective function described in step S1 is as follows:

[0009]

[0010] In the formula, F 1 is the water use target of the basin itself, that is, the total water shortage of all sub-regions, S ij is the water shortage for production and living water in the jth period of the sub-region where the i-th hydropower station is located, b ij and x ijThey represent the water demand and water supply for production and domestic water in the jth period of the sub-region where the i-th hydropower station is located, M is the number of hydropower stations in the basin, i.e., the number of sub-regions, T is the total number of time periods in the scheduling period, and Δt is the time interval of the scheduling period; F 2 is the inter-basin water transfer target, i.e. the total water shortage of all water transfer projects, R ij is the water shortage of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located, K i Indicates whether there is an inter-basin water diversion project in the sub-region where the i-th hydropower station is located. If yes, K i =1, otherwise K i =0,d ij and ij They represent the water demand and water supply of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; F 3 is the cascade power generation dispatch target, that is, the total power generation of all hydropower stations during the entire dispatch period, A i is the output coefficient of the i-th hydropower station, N ij and H ij Represent the output and net generating head of the i-th hydropower station in the j-th period, q ij Represents the power generation flow of the i-th hydropower station in the j-th period.

[0011] Furthermore, the constraints described in step S1 include:

[0012] 0≤x ij ≤ b ij

[0013] 0≤y ij ≤d ij

[0014] d ij,min ≤d ij ≤d ij,max ,

[0015] Q ij,min ≤Q ij ≤Q ij,max

[0016] I ij =Q (i-1)j +B ij +C ij

[0017] V i(j+1) =V ij +[I ij -x ij -K i y ij -Q ij ]Δt

[0018] Z ij,min ≤Z ij ≤Z ij,max

[0019] N ij,min ≤N ij ≤N ij,max

[0020] H ij =(Z ij +Z i(j+1) ) / 2-f i,zd (Q ij )

[0021] q ij =min{Q ij ,q i,max} ,p ij =max{Q ij -q i,max，0}

[0022] Z i0 =Z i begin , Z iT =Z i end

[0023] Where b ij and x ij They represent the water demand and water supply for production and domestic water in the jth period of the sub-region where the i-th hydropower station is located; d ij and ij They represent the water demand and water supply of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; d ij,min and d ij,max They represent the minimum and maximum water flow required for inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; Di represents the total water flow for inter-basin water transfer in the sub-region where the i-th hydropower station is located; Q ij represents the discharge flow of the i-th hydropower station in the j-th period, Q ij,min and Q ij,max They represent the minimum and maximum discharge flow of the i-th hydropower station in the j-th period respectively; I ij and B ij They represent the total inflow and interval runoff in the jth period of the sub-region where the i-th hydropower station is located, and C ij represents the inflow of the inter-basin water diversion project in the jth period of the sub-region where the i-th hydropower station is located, Q (i-1)j represents the discharge flow of the i-1th hydropower station in the jth period; V ij represents the water storage capacity of the i-th hydropower station in the j-th period; Z ij represents the operating water level of the i-th hydropower station in the j-th period, Z ij,minand Z ij,max Respectively represent the minimum and maximum operating water level boundaries of the i-th hydropower station in the j-th period; N ij represents the output of the i-th hydropower station in the j-th period; N ij,min and N ij,max They represent the minimum and maximum output of the i-th hydropower station in the j-th period respectively; f i,zd represents the relationship function between the discharge flow of the i-th hydropower station and the downstream water level; p ij and q ij They represent the abandoned water flow and the generated water flow of the i-th hydropower station in the j-th period, respectively, and q i,max represents the maximum power generation flow of the i-th hydropower station; Z i begin and Z i end Represent the initial water level and final water level of the i-th hydropower station respectively.

[0024] Furthermore, solving the scheduling model in step S3 specifically includes:

[0025] S31, divide the scheduling period into T time periods at fixed intervals, with t representing the stage variable, then t = l, 2, ..., T, the corresponding time t ~ t + 1 is the facing time period, and the time t + 1 ~ T is the remaining time period;

[0026] S32, take the reservoir water storage V in each period as the state variable, and record V(t) and V(t+1) as the water storage at the beginning and end of the period respectively, and take the working flow Q(t) in each period as the decision variable;

[0027] S33, the water balance equation in reservoir operation is listed as the state transfer equation:

[0028] V(t+1)=V(t)+(I(t)-Q(t))△t

[0029] Where I(t) is the inflow flow during a period, and △t is the length of the period.

[0030] S34, assuming that the initial decision sequence is {V t0}, where t0 = 1, 2, ..., n;

[0031] S35, fix the two values ​​of V(t-1) and V(t+1), adjust V(t), use the one-dimensional search method to solve and obtain V'(t), set V(t) = V'(t), where the initial value of t is 2;

[0032] S36, determine whether t is equal to n, if not, execute t=t+1, and return to execute S35, if yes, output the first decision sequence {V'(t)};

[0033] S37, taking the first decision sequence {V'(t)} as the initial trajectory, returns to execute S34 to obtain the second decision sequence {V"(t)}, compares the absolute errors between the first decision sequence and the second decision sequence, if the absolute error is less than or equal to the set value, outputs the second decision sequence, and compiles a scheduling plan accordingly, if the absolute error is greater than the set value, sets {V'(t)}={V"(t)}, and returns to execute S34.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] The method of the present invention takes into account the characteristics of close and complex cascade hydraulic connections during the scheduling process of cascade power stations, and based on different scheduling scenarios such as the water diversion process and the total amount of water diversion, takes into account the needs of the basin's own water use, inter-basin water diversion and the beneficial use of power stations, establishes an objective function, and considers the constraints of the joint optimization scheduling of water supply and power generation of the cascade hydropower station group to determine the constraints, and then uses the dynamic programming combined with the step-by-step optimization algorithm to solve and select the optimal scheduling plan, so as to accurately and efficiently schedule the reservoirs of the cascade power stations, thereby providing the power grid with better quality and more stable power supply, improving the power generation income of the hydropower development company, and supporting the actual production and operation of the cascade hydropower stations. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with specific embodiments, and the same or similar reference numerals throughout the examples of the embodiments represent the same or similar elements or elements with the same or similar functions. The embodiments described below are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0037] In the description of the present application, it should be noted that the directional words, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like, which indicate the directional and positional relationship, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific protection scope of the present application. The terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0038] The present invention relates to a cascade reservoir dispatching method based on dynamic programming combined with step-by-step optimization algorithm, comprising:

[0039] S1, comprehensively considers the water use of the basin itself, inter-basin water transfer and power generation demand of cascade power stations, and constructs the objective function of the scheduling model;

[0040] S2, comprehensively consider the constraints of the joint optimization scheduling of cascade reservoir water supply and power generation, and determine the constraints of the scheduling model;

[0041] S3, the dispatching model is solved by combining the dynamic programming algorithm and the stepwise optimization algorithm to obtain the optimal time series of the water storage capacity of the cascade reservoirs, and then the dispatching plan of the cascade reservoirs is formulated.

[0042] In this embodiment, the objective function described in the above step S1 is as follows:

[0043]

[0044] In the formula, F 1 is the water use target of the basin itself, that is, the total water shortage of all sub-regions, S ij is the water shortage for production and living water in the jth period of the sub-region where the i-th hydropower station is located, b ij and x ij They represent the water demand and water supply for production and domestic water in the jth period of the sub-region where the i-th hydropower station is located, M is the number of hydropower stations in the basin, i.e., the number of sub-regions, T is the total number of time periods in the scheduling period, and Δt is the time interval of the scheduling period; F 2 is the inter-basin water transfer target, i.e. the total water shortage of all water transfer projects, R ij is the water shortage of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located, K i Indicates whether there is an inter-basin water diversion project in the sub-region where the i-th hydropower station is located. If yes, K i =1, otherwise K i =0,d ij and ij They represent the water demand and water supply of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; F 3 is the cascade power generation dispatch target, that is, the total power generation of all hydropower stations during the entire dispatch period, A i is the output coefficient of the i-th hydropower station, N ij and H ij Represent the output and net generating head of the i-th hydropower station in the j-th period, q ij Represents the power generation flow of the i-th hydropower station in the j-th period.

[0045] In this embodiment, the constraints described in the above step S1 include that the water supply and power generation joint optimization scheduling of the cascade hydropower station group has many equality and non-equality constraints such as water flow, water transfer flow, operating water level, time output, water balance, hydraulic connection, etc. These constraints will greatly increase the complexity of the optimization solution, but can effectively ensure the effectiveness of the optimization results. The corresponding constraints are as follows:

[0046] 0≤x ij ≤ b ij

[0047] 0≤y ij ≤d ij

[0048] d ij,min ≤d ij ≤d ij,max ,

[0049] Q ij,min ≤Q ij ≤Q ij,max

[0050] I ij =Q (i-1)j +B ij +C ij

[0051] V i(j+1) =V ij +[I ij -x ij -K i y ij -Q ij ]Δt

[0052] Z ij,min ≤Z ij ≤Z ij,max

[0053] N ij,min ≤N ij ≤N ij,max

[0054] H ij =(Z ij +Z i(j+1) ) / 2-f i,zd (Q ij )

[0055] q ij =min{Q ij ,q i,max},p ij =max{Q ij -q i,max ,0}

[0056] Z i0 =Z i begin , Z iT =Z i end

[0057] Where b ij and x ij They represent the water demand and water supply for production and domestic water in the jth period of the sub-region where the i-th hydropower station is located; d ij and ij They represent the water demand and water supply of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; d ij,min and d ij,max They represent the minimum and maximum water flow required for inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; Di represents the total water flow for inter-basin water transfer in the sub-region where the i-th hydropower station is located; Q ij represents the discharge flow of the i-th hydropower station in the j-th period, Q ij,min and Q ij,max They represent the minimum and maximum discharge flow of the i-th hydropower station in the j-th period respectively; I ij and B ij They represent the total inflow and interval runoff in the jth period of the sub-region where the i-th hydropower station is located, and C ij represents the inflow of the inter-basin water diversion project in the jth period of the sub-region where the i-th hydropower station is located, Q (i-1)j represents the discharge flow of the i-1th hydropower station in the jth period; V ij represents the water storage capacity of the i-th hydropower station in the j-th period; Z ij represents the operating water level of the i-th hydropower station in the j-th period, Z ij,min and Z ij,max Respectively represent the minimum and maximum operating water level boundaries of the i-th hydropower station in the j-th period; N ij represents the output of the i-th hydropower station in the j-th period; N ij,min and N ij,max They represent the minimum and maximum output of the i-th hydropower station in the j-th period respectively; f i,zd represents the relationship function between the discharge flow of the i-th hydropower station and the downstream water level; p ij and q ij They represent the abandoned water flow and the generated water flow of the i-th hydropower station in the j-th period, respectively, and q i,max represents the maximum power generation flow of the i-th hydropower station; Z i begin and Z i end Represent the initial water level and final water level of the i-th hydropower station respectively.

[0058] In addition to considering the forecast of incoming water, the hydraulic connection between cascade hydropower stations, the requirements for comprehensive utilization of reservoirs and operational boundary constraints, and the time lag of water flow propagation, the power generation dispatching of reservoirs must also consider the long-term, medium-term, and real-time connection of power reservoirs to fully tap the head benefit, water volume benefit, and compensation benefit between reservoirs. In addition, the dispatching plan must also consider the characteristics of the power station. These characteristics directly affect the modeling and solution methods of reservoir operation dispatching. The established model must consider the operation constraints of each power station, the mutual influence between the operation of each power station, the planning and coordination of conventional power stations and pumped storage power stations, the hydraulic connection between each other, and the operation mode of the upper and lower reservoirs of the pumped storage power station. The cascade hydraulic connection is close and the relationship is complex, so it is required to establish a network topology diagram that can adapt to this relationship, and the human-computer interface and model can distinguish. The complexity of the model also determines the complexity of the solution method, and the problem of multiple dimensions of the solution space, numerous design data objects, and the inability to guarantee the solution speed all have an impact on the results of power generation dispatching.

[0059] In view of this, under the condition of introducing multiple scheduling models, the constraints added to each model are fully considered to form a technical roadmap for the overall cascade reservoir power generation scheduling.

[0060] In the formulation of medium- and short-term power generation plans for cascade power stations, namely weekly and daily plans, the optimization model mainly optimizes the reservoir scheduling process. This study uses a dynamic programming step-by-step optimization algorithm to solve the multi-objective and dimensionality disaster problems faced in cascade optimization.

[0061] Specifically, the steps of solving the scheduling model using dynamic programming combined with stepwise optimization algorithm include:

[0062] S31, divide the scheduling period into T time periods at fixed intervals, with t representing the stage variable, then t = l, 2, ..., T, the corresponding time t ~ t + 1 is the facing time period, and the time t + 1 ~ T is the remaining time period;

[0063] S32, take the reservoir water storage V in each period as the state variable, and record V(t) and V(t+1) as the water storage at the beginning and end of the period respectively, and take the working flow Q(t) in each period as the decision variable;

[0064] S33, the water balance equation in reservoir operation is listed as the state transfer equation:

[0065] V(t+1)=V(t)+(I(t)-Q(t))△t

[0066] Where I(t) is the inflow flow during a period, and △t is the length of the period.

[0067] S34, assuming that the initial decision sequence is {V t0}, where t0 = 1, 2, ..., n;

[0068] S35, fix the two values ​​of V(t-1) and V(t+1), adjust V(t), use the one-dimensional search method to solve and obtain V'(t), set V(t) = V'(t), where the initial value of t is 2;

[0069] S36, determine whether t is equal to n, if not, execute t=t+1, and return to execute S35, if yes, output the first decision sequence {V'(t)};

[0070] S37, taking the first decision sequence {V'(t)} as the initial trajectory, returns to execute S34 to obtain the second decision sequence {V"(t)}, compares the absolute errors between the first decision sequence and the second decision sequence, if the absolute error is less than or equal to the set value, outputs the second decision sequence, and compiles a scheduling plan accordingly, if the absolute error is greater than the set value, sets {V'(t)}={V"(t)}, and returns to execute S34.

[0071] Although embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A cascade reservoir dispatching method based on dynamic programming combined with stepwise optimization algorithm, characterized by: include, S1, comprehensively considers the water use of the basin itself, inter-basin water transfer and power generation demand of cascade power stations, and constructs the objective function of the scheduling model; S2, comprehensively consider the constraints of the joint optimization scheduling of cascade reservoir water supply and power generation, and determine the constraints of the scheduling model; S3, the dispatching model is solved by combining the dynamic programming algorithm and the stepwise optimization algorithm to obtain the optimal time series of the water storage capacity of the cascade reservoirs, and then the dispatching plan of the cascade reservoirs is formulated.

2. The cascade reservoir scheduling method based on dynamic programming combined with stepwise optimization algorithm according to claim 1 is characterized in that: The objective function described in step S1 is as follows, In the formula, F 1 is the water use target of the basin itself, that is, the total water shortage of all sub-regions, S ij is the water shortage for production and living water in the jth period of the sub-region where the i-th hydropower station is located, b ij and x ij They represent the water demand and water supply for production and domestic water in the jth period of the sub-region where the i-th hydropower station is located, M is the number of hydropower stations in the basin, i.e., the number of sub-regions, T is the total number of time periods in the scheduling period, and Δt is the time interval of the scheduling period; F 2 is the inter-basin water transfer target, i.e. the total water shortage of all water transfer projects, R ij is the water shortage of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located, K i Indicates whether there is an inter-basin water diversion project in the sub-region where the i-th hydropower station is located. If yes, K i =1, otherwise K i =0,d ij and ij They represent the water demand and water supply of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; F 3 is the cascade power generation dispatch target, that is, the total power generation of all hydropower stations during the entire dispatch period, A i is the output coefficient of the i-th hydropower station, N ij and H ij Represent the output and net generating head of the i-th hydropower station in the j-th period, q ij Represents the power generation flow of the i-th hydropower station in the j-th period.

3. The cascade reservoir scheduling method based on dynamic programming combined with stepwise optimization algorithm according to claim 2 is characterized in that: The constraints described in step S1 include: 0≤x ij ≤b ij 0≤y ij ≤d ij Q ij,min ≤Q ij ≤Q ij,max I ij =Q (i-1)j +B ij +C ij V i(j+1) =V ij +[I ij -x ij -K i y ij -Q ij ]Δt WITH ij,min ≤Z ij ≤Z ij,max N ij,min ≤N ij ≤N ij,max H ij =(Z ij +Z i(j+1) ) / 2-f i，zd (Q ij ) q ij =min{Q ij ,q i,max },p ij =max{Q ij -q i,max ,0} WITH i0 =Z ibegin ,WITH iT =Z iend Where b ij and x ij They represent the water demand and water supply for production and domestic water in the jth period of the sub-region where the i-th hydropower station is located; d ij and ij They represent the water demand flow and water supply flow of inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; d ij,min and d ij,max They represent the minimum and maximum water flow required for inter-basin water transfer in the jth period of the sub-region where the i-th hydropower station is located; Di represents the total water flow for inter-basin water transfer in the sub-region where the i-th hydropower station is located; Q ij represents the discharge flow of the i-th hydropower station in the j-th period, Q ij,min and Q ij，max They represent the minimum and maximum values ​​of the discharge flow of the i-th hydropower station in the j-th period respectively; I ij and B ij They represent the total inflow and interval runoff in the jth period of the sub-region where the i-th hydropower station is located, and C ij represents the inflow of the inter-basin water diversion project in the jth period of the sub-region where the i-th hydropower station is located, Q (i-1)j represents the discharge flow of the i-1th hydropower station in the jth period; V ij represents the water storage capacity of the i-th hydropower station in the j-th period; Z ij represents the operating water level of the i-th hydropower station in the j-th period, Z ij,min and Z ij,max Respectively represent the minimum and maximum operating water level boundaries of the i-th hydropower station in the j-th period; N ij represents the output of the i-th hydropower station in the j-th period; N ij,min and N ij，max They represent the minimum and maximum output of the i-th hydropower station in the j-th period respectively; f i,zd represents the relationship function between the discharge flow of the i-th hydropower station and the downstream water level; p ij and q ij They represent the abandoned water flow and the generated water flow of the i-th hydropower station in the j-th period, respectively, and q i,max represents the maximum power generation flow of the i-th hydropower station; Z ibegin and Z iend Represent the initial water level and final water level of the i-th hydropower station respectively.

4. The method for cascade reservoir operation based on dynamic programming combined with stepwise optimization algorithm according to claim 3 is characterized in that: The step S3 of solving the scheduling model specifically includes: S31, divide the scheduling period into T time periods at fixed intervals, with t representing the stage variable, then t = l, 2, ..., T, the corresponding time t ~ t + 1 is the facing time period, and the time t + 1 ~ T is the remaining time period; S32, take the reservoir water storage V in each period as the state variable, and record V(t) and V(t+1) as the water storage at the beginning and end of the period respectively, and take the working flow Q(t) in each period as the decision variable; S33, the water balance equation in reservoir operation is listed as the state transfer equation: V(t+1)=V(t)+(I(t)-Q(t))△t Where I(t) is the inflow flow during a period, and △t is the length of the period. S34, assuming that the initial decision sequence is {V t0}, where t0 = 1, 2, ..., n; S35, fix the two values ​​of V(t-1) and V(t+1), adjust V(t), use the one-dimensional search method to solve and obtain V'(t), set V(t) = V'(t), where the initial value of t is 2; S36, determine whether t is equal to n, if not, execute t=t+1, and return to execute S35, if yes, output the first decision sequence {V'(t)}; S37, taking the first decision sequence {V'(t)} as the initial trajectory, returns to execute S34 to obtain the second decision sequence {V"(t)}, compares the absolute errors between the first decision sequence and the second decision sequence, if the absolute error is less than or equal to the set value, outputs the second decision sequence, and compiles a scheduling plan accordingly, if the absolute error is greater than the set value, sets {V'(t)}={V"(t)}, and returns to execute S34.

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