Cascade hydropower and photovoltaic short-term complementary scheduling method and system using units as scheduling units

Abstract

The embodiments of the present invention provide a method and system for short-term complementary scheduling of cascade hydropower and photovoltaic power with units as scheduling units, and relate to the field of clean energy technology. The method comprises: based on the predicted output data of photovoltaic power stations, taking one day as the scheduling cycle, constructing a model for short-term optimal scheduling of the maximum amount of electricity that can be absorbed by the cascade hydro-photovoltaic complementary system; and performing the model conversion and solution. In this way, taking the unit as the smallest scheduling unit, the power station constraints, unit constraints and power grid constraints faced by the complementary system are carefully considered, and a short-term optimal scheduling model for the maximum amount of electricity that can be absorbed by the cascade hydro-photovoltaic complementary system is constructed. Through the hydraulic and electric power redistribution of cascade hydropower, the overall electricity absorption level of the complementary system and the executability of the scheduling plan are improved.

Description

Technical Field

[0001] The present invention relates to the field of clean energy technology, and in particular to a method and system for short-term complementary scheduling of cascade hydropower and photovoltaic power generation using units as scheduling units. Background Art

[0002] Building a multi-energy complementary system including wind power and photovoltaic power is an important way to solve the flexibility of new energy grid connection. The research results on the optimization operation of complementary systems at home and abroad are mainly concentrated on the output fluctuation, system peak regulation, and complementary characteristics analysis of complementary systems. Most of these models take the power station as the minimum dispatching unit, without finely considering the complex operation constraints of the units and the power grid, which makes the power stations have deviations when executing the plan, or even difficult to execute. For example, the same power station may contain multiple units of different types. Different types of units have different climbing capabilities, vibration zones, start-stop times and other constraints, which cannot be generalized; different units of the same power station and different power stations between upstream and downstream of the cascade may be connected to the grid step by step through different partition sections, subject to the transmission capacity constraints of multi-level partition sections.

[0003] In addition, in order to achieve complementarity with fluctuating power sources such as photovoltaic and wind power, hydropower output may fluctuate frequently, causing losses in hydropower units. How to fully consider the operating constraints of hydropower units, upstream and downstream hydraulic connections of cascades, and grid constraints in short-term multi-energy complementary scheduling, and improve the power generation level of the complementary system and the executability of the scheduling plan are practical technical issues that need to be considered and solved in the scheduling and operation of the water-wind-solar complementary system. Summary of the invention

[0004] The purpose of the present invention includes providing a cascade hydropower and photovoltaic short-term complementary scheduling method and system with units as scheduling units, which can avoid unit vibration, grid constraint failure, etc. caused by using power stations as the minimum scheduling units, and improve the overall power consumption level of the complementary system and the executability of the scheduling plan.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a method for short-term complementary scheduling of cascade hydropower and photovoltaic power generation using a unit as a scheduling unit, the method comprising:

[0007] Based on the predicted output data of photovoltaic power stations, a model for short-term optimal scheduling of the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system is constructed with one day as the scheduling cycle;

[0008] The model conversion and solution are performed.

[0009] In an optional implementation, the model takes the predicted output data of the photovoltaic power station as the determined value, takes the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system as the optimization target, and takes into account the constraints of cascade hydropower stations, units and power grids, including water balance, final water level control, inflow and outflow, water level-reservoir capacity, tail water level-discharge flow, unit vibration zone, unit climbing, unit output fluctuation, unit start-up and shutdown duration, cascade power station power generation plan, and transmission section constraints.

[0010] In an optional implementation, the expression for maximizing the amount of electricity that can be absorbed by the cascaded water-photovoltaic complementary system as the optimization target is as follows:

[0011]

[0012] Where PH i,t PV j,t are the outputs of hydropower station i and photovoltaic power station j in period t respectively; It represents the amount of power abandoned at the g-th constraint section in time period t.

[0013] In an optional implementation, the performing of the model conversion and solution includes:

[0014] Converting nonlinear constraints in the model into linear constraints;

[0015] The constraint relaxation method is used to convert the linear equality constraints in the model into linear inequality constraints;

[0016] The model of short-term optimal scheduling of the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system is converted into a standard mixed integer linear programming model, and the model solution, model data input and result analysis are realized by calling CPLEX optimization software in JAVA.

[0017] In an optional implementation, the performing of the model conversion and solution includes:

[0018] The relationship between water level-reservoir capacity and tailwater level-discharge flow is linearized and processed by water level discretization and piecewise linear interpolation. Linear functions are used to represent the relationship between water level and reservoir capacity and the relationship between tailwater level and discharge flow at the initial pre-dam water level and initial tailwater level.

[0019] In an optional implementation, the performing of the model conversion and solution includes:

[0020] Linear processing of unit vibration zone constraints. Based on the K vibration zones of the unit, K+1 non-continuous safe operation zones of the unit can be divided within the maximum and minimum output range. Introducing 0-1 variable Vib i,n,t,k Indicates the safe range of the unit output, and transforms the unit vibration zone constraint into K+1 linear constraints and 1 integer variable equality constraint:

[0021]

[0022]

[0023]

[0024] In the formula, They represent the upper and lower limits of the safe operating range output corresponding to the kth vibration zone; u i,n,t Turn on the shutdown state variable for the motor group.

[0025] In an optional implementation, the performing of the model conversion and solution includes:

[0026] Linearize the dynamic characteristics of the unit. The dynamic characteristics of the unit are the two-dimensional nonlinear relationship between the unit output and the generating head and the generating flow. The triangle weight technology is used for linearization. The initial head corresponding curve and its two adjacent head lines are used as boundaries to divide 9 triangular areas. The nonlinear relationship is converted into the following substitution:

[0027] Z i，n，t，l ∈{0,1},l=1,2,3,…,9

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] Where: l is the number of the divided triangle, l = 1, 2, 3, ..., 9; ind is the number of the triangle vertex, ind = 1, 2, 3; z i，n，t，l is the indicator variable, z i，n，t，l =1 means that the power characteristic relationship of the nth unit of power station i in time period t is within the lth triangle; Represents the weight of the ind-th vertex of the l-th triangle; They respectively represent the power generation head, power generation flow and power generation output corresponding to the ind-th vertex of the l-th triangle.

[0035] In an optional implementation, the performing of the model conversion and solution includes:

[0036] The output fluctuation limit constraints of hydropower units are processed linearly, and the adjustment index variables are introduced to process the output fluctuation limit constraints of the units:

[0037] (P i，n，t -P i，n，t-σ-1 )(P i，n，t -P i，n，t-1 )≥0,σ=1,2,…,t e -1

[0038] -α i，n，t ·≤P i，n，t+1 -P i，n，t ≤β i，n，t ΔP i，n

[0039]

[0040] Where: t e is the minimum number of time periods that the unit needs to maintain during a round of output increase or decrease, t e >1;α i，n，t ∈{0,1},β i，n，t ∈{0,1} is the indicator variable for upward and downward adjustment of unit power, α i，n，t =1 means the power is adjusted downward in time period t+1; β i,n,t =1 means the power in period t+1 is adjusted upward; when the power does not change, α i,n,t =0 or β i,n,t =0;MAX αβ Indicates the upper limit of the power adjustment period.

[0041] In an optional implementation, the performing of the model conversion and solution includes:

[0042] The hydropower unit output duration constraint is used to ensure that the hydropower unit maintains the output period t after each output adjustment. e :

[0043]

[0044] In a second aspect, the present invention provides a cascade hydropower and photovoltaic short-term complementary scheduling system with a unit as a scheduling unit, the system is used to implement the method described in the above embodiment, and the system includes:

[0045] Data input module, used to realize automatic reading and modification of cascade hydropower, photovoltaic and power grid related data;

[0046] Model building module, used to construct the maximum objective function of the power consumption that can be absorbed by the short-term complementary system, and set the constraints related to the power station, unit and power grid;

[0047] Model linearization conversion module, used to convert the constructed nonlinear model into a standard MILP model, using different linearization processing methods according to different constraint types;

[0048] The model solving module solves the model by calling CPLEX optimization software in the JVAV environment to obtain the optimization scheduling results;

[0049] The result output and analysis module is used to generate graphic reports related to the output process of cascade hydropower, unit output process, and section transmission process, compare the scheduling results of different models, and analyze the rationality of the scheduling results and the effect of model implementation.

[0050] The beneficial effects of the cascade hydropower and photovoltaic short-term complementary scheduling method and system with units as scheduling units provided by the embodiments of the present invention include:

[0051] Taking the unit as the smallest dispatching unit, the power station constraints, unit constraints and grid constraints faced by the complementary system are carefully considered, and a short-term optimal dispatching model with the maximum amount of electricity that can be absorbed by the cascaded hydropower and photovoltaic complementary system is constructed. Through the hydraulic and electric power redistribution of cascade hydropower, the overall electricity absorption level of the complementary system and the feasibility of the dispatching plan are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0053] Figure 1 A schematic flow chart of a method for short-term complementary scheduling of cascade hydropower and photovoltaic power with units as scheduling units provided in this embodiment;

[0054] Figure 2 This is a schematic diagram of the triangle weight linearization processing method;

[0055] Figure 3 This is a schematic diagram of the change in the state of increasing and decreasing the output of the hydropower unit;

[0056] Figure 4 It is a schematic diagram of hydraulic relationship and grid topology of cascade power stations;

[0057] Figure 5 This is a schematic diagram of the power output process of cascade hydropower stations;

[0058] Figure 6 This is a schematic diagram of the power output process of some hydropower units;

[0059] Figure 7This is a schematic diagram of the power transmission process in a partitioned section. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0061] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0063] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0064] Please refer to Figure 1 This embodiment provides a method for short-term complementary scheduling of cascade hydropower and photovoltaic power generation with a unit as a scheduling unit, comprising the following steps:

[0065] S1: Based on the predicted output data of photovoltaic power stations and with one day as the scheduling cycle, a model for short-term optimal scheduling of the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system is constructed.

[0066] The model of short-term optimal dispatching of the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system takes the predicted output data of the photovoltaic power station as the determined value and takes the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system as the optimization goal:

[0067]

[0068] Where PH i,t PV j,t are the outputs of hydropower station i and photovoltaic power station j in period t respectively; It represents the amount of power abandoned at the g-th constraint section in time period t.

[0069] The refinement considers the constraints of cascade hydropower stations, units and power grids, including water balance, final water level control, inflow and outflow, water level-storage capacity, tailwater level-discharge flow, unit vibration zone, unit climbing, unit output fluctuation, unit start-up and shutdown duration, cascade power station generation plan, transmission section constraints, etc. The expressions of various constraints are as follows.

[0070] (1) Power station related constraints

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] Formulas (19)-(25) are respectively the water balance constraint, reservoir water level constraint, initial and final water level control constraint, outflow constraint, power station output constraint, water level-reservoir capacity relationship, and tailwater level-discharge flow relationship constraint.

[0079] Where V i,t is the storage capacity of power station i at the end of time period t; I i,t The inflow of power station i in time period t; τ is the water lag time between power station i and its upstream power station i-1; Q i-1,t-τ is the flow rate of power station i-1 in the period t-τ after considering the water flow lag; R i,t is the interval flow between power station i-1 and power station i; are the power generation flow and abandoned water flow of power station i in time period t respectively; The water level in front of the dam and its upper and lower limits of the reservoir where power station i is located in time period t; are the target control water levels at the beginning and end of the dispatch period of the reservoir where power station i is located; ΔZ is the allowable water level deviation at the end of the dispatch period; Q i,t , Q i,t The outflow rate and its upper and lower limits of power station i in time period t respectively.

[0080] (2) Unit-related constraints

[0081]

[0082]

[0083]

[0084]

[0085] -ΔP i，n ≤P i，n，t+1 -P i，n，t ≤ΔP i，n (30)

[0086] P i，n，t -P i，n，t-σ-1 )(P i，n，t -P i，n，t-1 ≥0,σ=1,2,…,t e -1 (31)

[0087]

[0088]

[0089] Formulas (26)-(33) are the unit output constraint, unit power generation flow constraint, unit vibration zone constraint, unit start-up and shutdown duration constraint, unit climbing constraint, hydropower unit output fluctuation limit constraint, unit power generation head constraint, and unit dynamic characteristic relationship constraint, respectively.

[0090] Where P i，n，t , P i，n are the output of the nth unit of power station i and its upper and lower limits respectively; It is divided into the power generation flow of the nth unit of power station i and its upper and lower limits; and are the upper and lower limits of the output of the kth vibration zone of the nth unit in power station i; u i，n，t is the start and stop state variable of the nth unit of power station i in time period t, 1 represents the start state, and 0 represents the stop state; is the startup operation variable of the nth unit in power station i in time period t, 1 indicates startup operation; is the shutdown operation variable of the nth unit of power station i in time period t, 1 indicates shutdown operation; are the minimum startup and shutdown durations of the nth unit in power station i, respectively; Represents the maximum number of startup times during the scheduling period; ΔP i,n is the climbing capacity of the nth unit in power station i; t e H is the minimum number of time periods that the unit needs to maintain during a round of output increase or decrease; i,n,t , are the generating head and head loss of the nth unit in power station i in time period t respectively.

[0091] (3) Grid-related constraints

[0092]

[0093]

[0094] Equations (34) and (35) represent the constraints on cascade hydropower generation and transmission section, respectively.

[0095] Where P t plan The cascade hydropower generation plan issued by the power grid is jointly coordinated and compiled by the power grid and the cascade control center of the river basin; CO g,t They represent the power abandonment and transmission capacity upper limit of the g-th constraint section in time period t respectively; P g,t , L g,t They respectively represent the output and load of all units under the g-th constraint section. The load of each node can be obtained through the bus load prediction system.

[0096] S2: Perform model conversion and solution.

[0097] Model transformation mainly refers to the transformation of nonlinear constraints and equality constraints involved in the model.

[0098] The method of model conversion and solution is to first convert the nonlinear constraints in the model into linear constraints, and then use the constraint relaxation method to convert the linear equality constraints in the model into linear inequality constraints, and convert the model of the maximum short-term optimal scheduling of the cascaded hydro-photovoltaic complementary system that can absorb the maximum amount of electricity into a standard mixed integer linear programming (MILP) model, and then call CPLEX optimization software in JAVA to realize model solution and model data input and result analysis. The model conversion and solution specifically include the following steps:

[0099] S2.1: Linearization of the relationship between water level-reservoir capacity and tailwater level-discharge rate.

[0100]

[0101]

[0102] In the formula, V i,t , Q i,t They represent the water level before the reservoir dam, tailwater level, reservoir capacity and outflow flow respectively; f i zv (·),f i zq(·) respectively represent the nonlinear relationship curve function between water level and reservoir capacity and the nonlinear relationship curve function between tailwater level and discharge. The water level discretization and piecewise linear interpolation method are used for processing. Considering that the water level variation of the reservoir is small within a day, linear functions are used to approximate the water level-reservoir capacity relationship and the tailwater level-discharge relationship near the initial dam front water level and the initial tailwater level, which can not only meet the accuracy requirements, but also reduce the number of decision variables and improve the solution efficiency.

[0103] S2.2: Linearization of unit vibration zone constraints.

[0104] For safety reasons, the unit should avoid operating in the vibration zone or frequently crossing the vibration zone. Based on the K vibration zones of the unit, the unit can be divided into K+1 non-continuous safe operating intervals within the maximum and minimum output range. Introducing 0-1 variable Vib i,n,t,k Indicates the safe range of the unit output, and transforms the unit vibration zone constraint into K+1 linear constraints such as equation (4) and integer variable equality constraints such as equation (5):

[0105]

[0106]

[0107]

[0108] In the formula, They represent the upper and lower limits of the safe operating range output corresponding to the kth vibration zone; u i,n,t Turn on the shutdown state variable for the motor group.

[0109] S2.3: Linearization of unit dynamic characteristics.

[0110] The dynamic characteristics of the unit are the two-dimensional nonlinear relationship between the unit output and the generating head and generating flow:

[0111]

[0112] Where P i,n,t , H i,n,t They represent the unit output, unit power flow and unit power head respectively; The nonlinear relationship function representing the output-head-flow of the unit is expressed as a cluster of two-dimensional curves with the power flow as the horizontal coordinate and the output as the vertical coordinate. Multiple curves are directly processed by piecewise linearization, which requires the introduction of a large number of integer variables and reduces the efficiency of the solution. The triangle weight technology is used for linearization to reduce the scale of integer variables. The initial head corresponding curve and its two adjacent head lines are used as boundaries to divide 9 triangular areas, as shown in the attached figure. Figure 2As shown, the nonlinear relationship of formula (6) is converted into formulas (7)-(13) instead:

[0113] z i，n，t，l ∈{0,1},l=1,2,3,…,9 (7)

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120] Where: l is the number of the divided triangle, l = 1, 2, 3, ..., 9; ind is the number of the triangle vertex, ind = 1, 2, 3; z i，n，t，l is the indicator variable, z i，n，t，l =1 means that the power characteristic relationship of the nth unit of power station i in time period t is within the lth triangle; Represents the weight of the ind-th vertex of the l-th triangle; They respectively represent the power generation head, power generation flow and power generation output corresponding to the ind-th vertex of the l-th triangle.

[0121] S2.4: Linearization of the output fluctuation limit constraints of hydropower units.

[0122] As shown in equations (15) and (16), the introduction of adjustment index variables to deal with the unit output fluctuation constraint can avoid frequent changes in the adjustment direction of the unit in adjacent time periods:

[0123] (P i，n，t -P i，n，t-σ-1 )(P i，n，t -P i，n，t-1 )≥0,σ=1,2,…,t e -1 (14)

[0124] -α i，n，t ΔP i，n ≤P i，n，t+1 -P i，n，t ≤β i，n，t ΔP i，n (15)

[0125]

[0126] Where: te is the minimum number of time periods that the unit needs to maintain during a round of output increase or decrease, t e >1;α i，n，t ∈{0,1},β i，n，t ∈{0,1} is the indicator variable for upward and downward adjustment of unit power, α i，n，t =1 means the power is adjusted downward in time period t+1; β i，n，t =1 means the power in period t+1 is adjusted upward; when the power does not change, α i，n，t =0 or β i，n，t =0;MAX αβ Indicates the upper limit of the power adjustment (upward and downward) time periods.

[0127] In addition, in order to ensure that the hydropower unit can maintain stable output for a certain period of time after each output adjustment, e The introduction of the duration constraint of formula (17) can reduce the loss caused by frequent adjustments of the units. More importantly, it can reduce the frequent fluctuations of the downstream flow, which is conducive to ensuring the stability of the ecological flow.

[0128] The schematic diagram of the change of the output of the hydropower unit is shown in the attached figure. Figure 3 shown.

[0129]

[0130] S2.5: Use relaxation method to convert linear equality constraints in the model into linear inequality constraints. The details are as follows:

[0131]

[0132] Where: ε is the allowable deviation of the cascade power generation plan, and the above formula replaces the equality constraint of formula (34) in the model.

[0133] S2.6: Based on the processing methods of S2.1-S2.5, a standardized MILP model is obtained, the model input data is sorted, and the model solution and result analysis are realized by calling CPLEX optimization software in JAVA.

[0134] The method provided in this embodiment is tested with a complementary system consisting of 15 units of 4 hydropower stations and 2 photovoltaic groups in a cascade of a river basin in the southwest region as the actual engineering background. The simplified cascade hydraulic relationship and grid topology are shown in the attached figure. Figure 4As shown. After the cascade hydropower and photovoltaic groups are connected to the grid, they are sent out by step-by-step voltage boosting, facing section constraints of different voltage levels. There are different sending sections for different units of the same power station, and there are also situations where units of different power stations send out at the same section. A typical day scene in the dry season is selected, with 1d as the scheduling cycle and 15min as the scheduling period. The interval flow, cascade hydropower station load, photovoltaic predicted output, and grid parameters are all set with reference to the actual situation of the grid, and the uncertainty of photovoltaic prediction is not considered for the time being. JAVA1.7 coding is used, and the computing environment is a Dell workstation with 4 cores, 8 threads, 8.0G memory, and a main frequency of 3.6GHz. The calculation parameters of the MILP model include 9680 variables (including the introduced auxiliary variables), 11410 constraints, the convergence accuracy is set to the default 1.0e-4, the calculation time is 27.28s, and the optimal solution is obtained by convergence, which can fully meet the short-term optimization scheduling timeliness of the complementary system. Appendix Figure 5-7 The cascade hydropower output process, the output process of some hydropower units and the power transmission process of each section are given respectively. It can be seen intuitively that the output of each power station obtained by the method provided in this embodiment meets the requirements of the cascade power generation plan very well, and the average deviation between the actual output process and the power generation plan is 0.84%, which meets the actual operation requirements; the output of each unit effectively avoids the vibration area, meets the unit climbing capacity constraint requirements, ensures the safe operation of the unit, and meets the unit's stable output duration (1h) and minimum start-up and shutdown duration (2h) requirements, ensuring the stability of the unit output; fully utilize the cascade hydropower regulation capacity and section transmission capacity to achieve the spatiotemporal redistribution of electric power, reduce the output of hydropower units during peak hours, promote the level of photovoltaic consumption, reduce the amount of abandoned electricity and improve the executability of the scheduling results.

[0135] Compared with the previous single-stage hydropower and photovoltaic system independent operation mode, the independent operation mode aims to minimize water consumption under a given stage load. By comparison, it is found that the method provided in this embodiment has improved both in terms of increasing the overall power consumption and reducing the abandoned water power, and better promoted the consumption of photovoltaic power. The comparison results are shown in Table 1.

[0136] Table 1 Comparison between the method provided in this embodiment and the water-light independent operation mode

[0137]

[0138] In order to realize the above-mentioned cascade hydropower and photovoltaic short-term complementary scheduling method with the unit as the scheduling unit, this embodiment also provides a cascade hydropower and photovoltaic short-term complementary scheduling system with the unit as the scheduling unit, and the system includes:

[0139] The data input module is used to automatically read and modify data related to cascade hydropower, photovoltaics and power grid.

[0140] The model building module is used to construct the maximum objective function of the short-term complementary system that can absorb the maximum amount of electricity, and set the constraints related to the power station, unit and power grid. The model here is the model of the short-term optimal dispatch of the maximum amount of electricity that can be absorbed by the cascade hydro-photovoltaic complementary system mentioned above.

[0141] The model linearization conversion module is used to convert the constructed nonlinear model into a standard MILP model. Different linearization processing methods are used according to different constraint types. For the specific conversion process, please refer to S2.

[0142] The model solving module solves the model by coding and calling CPLEX optimization software in the JVAV environment to obtain the optimization scheduling results. For the specific solution process, please refer to S2.

[0143] The result output and analysis module is used to generate relevant graphic reports such as the output process of cascade hydropower, the output process of units, and the cross-section transmission process, compare the scheduling results of different models, and analyze the rationality of the scheduling results and the effect of model implementation.

[0144] Compared with the prior art, the method and system for short-term complementary scheduling of cascade hydropower and photovoltaic power with units as scheduling units provided in this embodiment have the following beneficial effects:

[0145] (1) Taking the unit as the smallest dispatching unit, the refined modeling of each unit is realized. The results show that the operation of the unit can not only meet various constraints such as the duration of start-up and shutdown, climbing ability, and non-continuous vibration zone, but also avoid frequent output fluctuations, improve the executability of the complementary system power generation plan, and better meet the actual dispatching needs.

[0146] (2) By adopting linearization methods and modeling techniques such as piecewise linear approximation, introduction of 0-1 integer variables, power head discretization, triangle weight technology, and constraint relaxation, the original MINLP model is transformed into a standard MILP model, which is suitable for mature commercial solution tools, greatly improves the solution efficiency, and meets the requirements of short-term optimization scheduling;

[0147] (3) It can give full play to the regulatory capacity of cascade hydropower in the river basin, effectively increase the overall amount of electricity that can be absorbed by the hydro-solar complementary system, and provide a reference for the complementary scheduling and operation of new energy such as wind and solar power and hydropower under the "dual carbon" goal.

[0148] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A short-term complementary scheduling method for cascade hydropower and photovoltaic power generation with units as scheduling units, characterized in that: The method comprises: Based on the predicted output data of photovoltaic power stations, a model for short-term optimal scheduling of the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system is constructed with one day as the scheduling cycle; The model conversion and solution are performed, including: Linearization processing unit vibration zone constraints, based on the unit's existing K Vibration zones can be divided into units within the maximum and minimum output range K+1 Non-continuous safe operating range Introducing 0-1 variable Vib i,n,t,k Indicates the safe range of the unit output, transforming the unit vibration zone constraint into K+1 Linearization constraints and 1 integer variable equality constraint: Where P i,n,t is the output of the nth unit in power station i; They represent the upper and lower limits of the safe operating range output corresponding to the kth vibration zone; u i,n,t Open and close state variables for the motor group; The output fluctuation limit constraints of hydropower units are processed linearly, and the adjustment index variables are introduced to process the output fluctuation limit constraints of the units: Where: t e is the minimum number of time periods that the unit needs to maintain during a round of output increase or decrease, t e >1;α i,n,t ∈{0,1},β i,n,t ∈{0,1} is the indicator variable for upward and downward adjustment of unit power, α i,n,t =1 means the power is adjusted downward in period t+1; β i,n,t =1 means the power in period t+1 is adjusted upward; when the power does not change, α i,n,t =0 or β i,n,t =0;MAX αβ Indicates the upper limit of the power adjustment period; ΔP i,n is the first n The climbing ability of the unit.

2. The method for short-term complementary scheduling of cascade hydropower and photovoltaic power generation with the unit as the scheduling unit according to claim 1 is characterized in that: The model takes the predicted output data of the photovoltaic power station as the determined value, takes the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system as the optimization goal, and takes into account the constraints of cascade hydropower stations, units and power grids, including water balance, final water level control, inflow and outflow, water level-reservoir capacity, tail water level-discharge flow, unit vibration zone, unit climbing, unit output fluctuation, unit start-up and shutdown duration, cascade power station power generation plan, and transmission section constraints.

3. The method for short-term complementary scheduling of cascade hydropower and photovoltaic power with units as scheduling units according to claim 2 is characterized in that: The expression for maximizing the amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system as the optimization target is as follows: Where PH i,t PV j,t Hydropower Station i and the output of PV plant j in period t; It represents the amount of power abandonment of the g-th constraint section in time period t.

4. The method for short-term complementary scheduling of cascade hydropower and photovoltaic power with units as scheduling units according to claim 1 is characterized in that: The steps of converting and solving the model include: Converting nonlinear constraints in the model into linear constraints; The constraint relaxation method is used to convert the linear equality constraints in the model into linear inequality constraints; The model of short-term optimal scheduling of the maximum amount of electricity that can be absorbed by the cascaded hydro-photovoltaic complementary system is converted into a standard mixed integer linear programming model, and the model solution, model data input and result analysis are realized by calling CPLEX optimization software in JAVA.

5. The method for short-term complementary scheduling of cascade hydropower and photovoltaic power with units as scheduling units according to claim 1 is characterized in that: The steps of converting and solving the model include: The relationship between water level-reservoir capacity and tailwater level-discharge flow is linearized and processed by water level discretization and piecewise linear interpolation. Linear functions are used to represent the relationship between water level and reservoir capacity and the relationship between tailwater level and discharge flow at the initial pre-dam water level and initial tailwater level.

6. The method for short-term complementary scheduling of cascade hydropower and photovoltaic power with units as scheduling units according to claim 1 is characterized in that: The steps of converting and solving the model include: Linearize the dynamic characteristics of the unit. The dynamic characteristics of the unit are the two-dimensional nonlinear relationship between the unit output and the generating head and the generating flow. The triangle weight technology is used for linearization. The initial head corresponding curve and its two adjacent head lines are used as boundaries to divide 9 triangular areas. The nonlinear relationship is converted into the following substitution: z i，n，t，l ∈{0,1},l＝1,2,3,…,9 Where: H i,n,t They represent the generating flow rate and generating head of the unit respectively; represents the nonlinear relationship function of the unit's output-head-flow; l is the number of the divided triangle, l = 1, 2, 3, ..., 9; ind is the number of the triangle vertex, ind = 1, 2, 3; z i,n,t,l is the indicator variable, z i,n,t,l =1 means that the power characteristic relationship of the nth unit of power station i in time period t is within the lth triangle; Represents the weight of the ind-th vertex of the l-th triangle; They respectively represent the power generation head, power generation flow and power generation output corresponding to the ind-th vertex of the l-th triangle.

7. The method for short-term complementary scheduling of cascade hydropower and photovoltaic power with units as scheduling units according to claim 1 is characterized in that: The steps of converting and solving the model include: The hydropower unit output duration constraint is used to ensure that the hydropower unit maintains the output period t after each output adjustment. e :

8. A cascade hydropower and photovoltaic short-term complementary dispatching system with units as dispatching units, characterized in that: The system is used to implement the method described in any one of claims 1 to 7, and the system includes: Data input module, used to realize automatic reading and modification of cascade hydropower, photovoltaic and power grid related data; Model building module, used to construct the maximum objective function of the power consumption that can be absorbed by the short-term complementary system, and set the constraints related to the power station, unit and power grid; Model linearization conversion module, used to convert the constructed nonlinear model into a standard MILP model, using different linearization processing methods according to different constraint types; The model solving module solves the model by calling CPLEX optimization software in the JVAV environment to obtain the optimization scheduling results; The result output and analysis module is used to generate graphic reports related to the output process of cascade hydropower, unit output process, and section transmission process, compare the scheduling results of different models, and analyze the rationality of the scheduling results and the effect of model implementation.

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