A cascade hydropower station reservoir operation method based on the sorting of the incremental power generation benefit rate

Abstract

The present invention belongs to the technical field related to reservoir scheduling and discloses a method for scheduling cascade hydropower stations based on ranking by power generation benefit increment rate. The method includes the following steps: S1 constructs the constraint conditions and long-term optimization scheduling maximum power generation model for the cascade hydropower station to be processed; S2 calculates the total power generation benefit increment rate and total decision space between the hydropower stations in each time period; S3 sorts the total power generation benefit increment rate corresponding to each time period in descending order, determines whether the total decision space corresponding to each time period is zero, and terminates when the total decision space corresponding to each time period is zero; otherwise, selects the time period corresponding to the maximum total power generation benefit from all time periods for which the water consumption of the time period has not been solved, solves the water consumption corresponding to the time period, and returns to step S2 until the total decision space corresponding to all time periods is zero. The present invention avoids the curse of dimensionality problem that exists in complex reservoir group scheduling problems.

Description

Technical Field

[0001] The present invention belongs to the technical field related to reservoir scheduling, and more specifically, relates to a reservoir scheduling method for cascade hydropower stations based on ranking by slight increase rate of power generation benefits. Background Art

[0002] Over the years, numerous scholars at home and abroad have conducted extensive research on the theories and methods of reservoir optimization and operation, proposing methods such as linear programming, nonlinear programming, dynamic programming, and intelligent computing. These methods have yielded a wealth of results, with dynamic programming currently being the most mature and effective solution. However, dynamic programming is essentially an enumeration method. As the number of states increases, the computational complexity increases exponentially, resulting in the "curse of dimensionality" problem, which significantly increases computational time and can even render the solution impossible. Therefore, it is of great significance to find a new method for cascade reservoir operation that avoids the curse of dimensionality and allows for rapid computational solutions. Summary of the Invention

[0003] In response to the above defects or improvement needs of the existing technology, the present invention provides a cascade reservoir scheduling method for hydropower stations based on the slight increase rate of power generation benefits, which solves the dimensionality curse problem existing in the dynamic programming of reservoir scheduling methods when calculating complex reservoir group scheduling problems.

[0004] To achieve the above object, according to the present invention, a method for dispatching reservoirs of cascade hydropower stations based on the ranking of power generation benefit micro-increase rate is provided, the method comprising the following steps:

[0005] S1 divides the dispatch period of each hydropower station in the cascade hydropower station to be processed into multiple time periods, and constructs the constraint conditions and long-term optimal dispatching power generation maximum model of the cascade hydropower station to be processed;

[0006] S2 uses the maximum power generation model to calculate the power generation benefit increment rate and decision space of each hydropower station in each time period, and uses this to calculate the total power generation benefit increment rate and total decision space formed by the mutual association between the hydropower stations in each time period;

[0007] S3 sorts the slight increase rates of the total power generation benefits corresponding to each time period in descending order, and determines whether the total decision space corresponding to each time period is zero. When the total decision space corresponding to each time period is zero, the process ends; otherwise, the process selects the time period corresponding to the maximum total power generation benefit from all time periods whose water consumption has not been solved, solves the water consumption corresponding to the time period, and returns to step S2 until the total decision space corresponding to all time periods is zero.

[0008] Further preferably, in step S1, the constraint conditions include:

[0009] (1) Water balance constraints

[0010] V t (t)=V0(t)+(I(t)-Q fd (t)-Q qs (t))×Δt

[0011] Where V t is the water storage at the end of the period, V0 is the water storage at the beginning of the period, I t Q is the water supply during the time period. fd is the power generation flow, Q qs is the abandoned water flow, Δt is the time interval;

[0012] (2) Reservoir water level constraints

[0013] V min ≤V t (t)≤V max

[0014] V min is the reservoir capacity corresponding to the minimum water level, V max is the reservoir capacity corresponding to the maximum water level;

[0015] (3) Water level and storage capacity curve constraints

[0016] Z sy (t) = f ZV [V(t)]

[0017] Z sy (t) is the upstream water level during period t, f ZV Represents the water level and storage capacity relationship curve;

[0018] (4) Tailwater level discharge curve constraint

[0019] Z xy (t) = f ZQ [Q fd (t)]

[0020] Z xy is the downstream water level, f ZQ Represents the relationship curve between tailwater level and power generation flow;

[0021] (5) Power generation flow constraints

[0022] Q fd ≤Q max

[0023] Maximum power generation flow Q max It should be related to the gate discharge capacity and output limit.

[0024] Further preferably, in step S1, the long-term optimal scheduling maximum power generation model is performed as follows:

[0025]

[0026] N t =KQ t H t

[0027] Among them, E represents the total power generation, N t Indicates the power generation during the period, K indicates the output coefficient of the hydropower station, Q t represents the power generation flow during period t, H t Indicates the generating head.

[0028] Further preferably, in step S2, the power generation benefit increase rate of each hydropower station is calculated according to the following formula:

[0029]

[0030] Among them, E is the total power generation benefit of each hydropower station, Q t is the water consumption of the hydropower station in period t, b t is the slight increase rate of power generation efficiency of the hydropower station in period t, which represents the efficiency brought by the unit water volume used for power generation in this period.

[0031] Further preferably, in step S2, the decision space corresponding to each time period of each hydropower station is calculated according to the following formula:

[0032]

[0033] in, is the decision space of the i-th reservoir in period t, is the minimum discharge of the i-th reservoir in period t, is the maximum discharge of the i-th reservoir in period t, is the available water volume of the i-th reservoir in period t, is the maximum water storage capacity allowed for the i-th reservoir, It represents the maximum value of the reserved water volume of the i-th reservoir in all periods after period t.

[0034] Further preferably, the decision space corresponding to each time period of each hydropower station is calculated according to the following steps:

[0035] S21 calculates the water storage capacity V of the i-th reservoir at the end of period t t i (t) (t=1,2,...,T; i=1,2,...,n).

[0036]

[0037] in, is the initial water storage capacity of the i-th reservoir in period t, I i (t) is the water inflow of the i-th reservoir in period t, Q i (t) is the water consumption of the i-th reservoir in time period t, i is the reservoir number, n is the total number of reservoirs, t is the time period, and T is the total number of water in the time period;

[0038] S22 reverse calculation to obtain the reserved water volume for each period

[0039]

[0040] in, is the reserved water volume of reservoir i in the period before period t, is the reserved water volume of reservoir i in period t, I i (t) is the water inflow of reservoir i in period t;

[0041] S23 calculates the available water volume of each reservoir at each time period

[0042]

[0043] in, represents the available water volume of reservoir i in period t, V t i (t) water storage capacity of reservoir i at the end of period t, represents the reserved water volume of reservoir i in period t.

[0044] S24 calculates the decision space of each reservoir at each time period

[0045] Further preferably, in step S2, the total power generation benefit increase rate is calculated according to the following relationship:

[0046] b s =b0+b i

[0047] Among them, b s is the slight increase rate of total power generation benefit, b0 is the slight increase rate of power generation benefit of the upstream reservoir during the calculation period, b i is the slight increase rate of power generation benefit of the downstream reservoir in period i.

[0048] Further preferably, the total decision space is calculated according to the following formula:

[0049] If t0=t i , the total decision space is: Q js =min{Q j (t0),Q j (t i =t0)};

[0050] If t0<t i , the total decision space is:

[0051] Q js =min{Q j (t0),Q j (t i =t0),V max -max{V t (t i )}};

[0052] If t0>t i , the total decision space is: Q js =min{Q j (t0),Q j (t i =t0),min{V0(t i )}};

[0053] Among them, t0 is the calculation period of the upstream reservoir, t i The calculation period for the downstream reservoir, Q js is the total decision space, Q j (t0) is the decision space of the upstream reservoir at time t0, Q j (t i =t0) is the decision space of the downstream reservoir at time t0, V max is the maximum water storage capacity downstream, max{V t (t i )} is the downstream reservoir t0 period and t i The maximum water storage capacity at the end of each period, min{V0(t i )} is the downstream reservoir t i The minimum initial water storage between the period and the t0 period.

[0054] Further preferably, in step S3, the water consumption is the maximum value of the total decision space.

[0055] Further preferably, in step S3, it is necessary to pre-process the reservoirs whose initial water level during the scheduling period is inconsistent with the required water level at the end of the scheduling period. The specific steps are as follows:

[0056] If the final water level of a reservoir is lower than the water level constraint at the end of the period, water will be released during the period with the maximum upstream power generation benefit increment rate, and the amount of water released will just be enough to raise the water level of the reservoir at the end of the period to the constraint position;

[0057] If the final water level of a reservoir is higher than the water level constraint at the end of the period, water will be released during the period with the maximum slight increase in power generation benefit. The amount of water released can just reduce the water level of the reservoir at the end of the period to the constraint position.

[0058] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0059] 1. This invention introduces the concept of marginal benefit from economics, assuming that the same amount of water generates different benefits when generating electricity at different times. Therefore, prioritizing the use of water for power generation during periods with high power generation benefits within the permitted constraints can bring greater power generation benefits to the hydropower station. This method greatly reduces the computational complexity of cascade reservoir scheduling problems, can quickly calculate results, and provides technical support for reservoir scheduling.

[0060] 2. The present invention achieves greater benefits for the reservoir by maximizing the marginal benefit of water volume. This approach avoids the curse of dimensionality problem inherent in dynamic programming, resulting in accurate and rapid calculations and higher efficiency. The physical meaning of the calculation process is clear, facilitating analysis and discussion of the calculation process, and contributing to a deeper understanding of the essence of the reservoir operation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a flow chart of a reservoir scheduling method based on the ranking of power generation benefit micro-increase rate constructed according to the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0062] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0063] like Figure 1 As shown, the present invention provides a method for dispatching cascade reservoirs of hydropower stations based on the sorting of power generation benefit micro-increase rate, comprising the following steps:

[0064] Step 1: Determine and divide the scheduling period and establish constraints based on the actual operation of the hydropower station.

[0065] The scheduling period is divided into T time periods with equal intervals, where T is a positive integer. The constraints that the hydropower station should consider include the following:

[0066] 1. Water balance constraints

[0067] V t (t)=V0(t)+(I(t)-Q fd (t)-Q qs (t))×Δt

[0068] Where V tis the water storage at the end of the period, V0 is the water storage at the beginning of the period, I t Q is the water supply during the time period. fd is the power generation flow, Q qs is the abandoned water flow, Δt is the time interval;

[0069] 2. Reservoir water level constraints

[0070] V min ≤V t (t)≤V max

[0071] V min is the reservoir capacity corresponding to the minimum water level, V max is the reservoir capacity corresponding to the maximum water level;

[0072] 3. Water level and storage capacity curve constraints

[0073] Z sy (t) = f ZV [V(t)]

[0074] Z sy (t) is the upstream water level during period t, f ZV Represents the water level and storage capacity relationship curve;

[0075] 4. Tailwater level discharge curve constraints

[0076] Z xy (t) = f ZQ [Q fd (t)]

[0077] Z xy is the downstream water level, f ZQ Represents the relationship curve between tailwater level and power generation flow;

[0078] 5. Power generation flow constraints

[0079] Q fd ≤Q max

[0080] Maximum power generation flow Q max It should be related to the gate discharge capacity and output limit.

[0081] Step 2: Based on the scheduling periods of the cascade hydropower stations and the above constraints, a model for maximizing the long-term optimal scheduling of cascade hydropower stations is established. This model uses the inflow of each reservoir in each period as the input variable and the power generation flow of each reservoir in each period as the decision variable. The model for maximizing the cascade power generation is established as follows:

[0082]

[0083] N t =KQ tH t

[0084] Among them, E represents the total power generation, N t Indicates the power generation during the period, K indicates the output coefficient of the hydropower station, Q t represents the power generation flow during period t, H t Indicates the generating head.

[0085] Step 3: Determine the incremental rate of power generation benefit of each reservoir in each period. The incremental rate of power generation benefit is the incremental benefit brought by the unit water volume used for power generation in this period, that is, the partial derivative of the power generation benefit of this period with respect to the power generation flow in this period:

[0086]

[0087] When calculating, the power generation flow ΔQ of this period can be taken as a smaller value, and the power generation benefit increment brought by the current power generation flow is calculated as ΔE. When ΔQ approaches 0, the ratio That is the slight increase rate of power generation efficiency.

[0088] Step 4 calculates the decision space for each reservoir in each time period based on the water inflow and constraints in each time period. This includes the following sub-steps:

[0089] (4-1) Calculate the water storage capacity V of each reservoir at the end of each period t i (t) (t=1,2,...,T; i=1,2,...,n).

[0090] The initial water storage capacity of each reservoir at each time period is known Water volume I i (t), water consumption Q i (t), calculate the water storage capacity V at the end of each period according to the following formula t i (t):

[0091]

[0092] Water storage at the end of the previous period V t i and the initial water storage capacity of the next period There is a recursive relationship between:

[0093]

[0094] (4-2) Reverse calculation to obtain the reserved water volume for each period

[0095] Known reservoir reserved water volume for the next period Water volume I i (t), water consumption Qi (t), calculate the reserved water volume for the previous period according to the following formula. Note that the reserved water volume for each period should not be less than 0:

[0096]

[0097] Reserved water volume for Qiemo period Known

[0098] (4-3) Calculate the available water volume of each reservoir at each time period

[0099]

[0100] (4-4) Based on the available water volume in each period, combined with the minimum discharge flow, maximum discharge flow and reservoir water level and other constraints, calculate the decision space of each reservoir in each period

[0101]

[0102] Step 5 calculates the slight increase rate of total power generation benefit of each reservoir in each period and the corresponding total decision space.

[0103] The calculation of a cascade reservoir consisting of two reservoirs is now used to illustrate how to calculate the total power generation benefit incremental rate and its corresponding decision space. Assume that the upstream period is t0, the corresponding power generation benefit incremental rate is b0, and the single reservoir decision space is Q j (t0), the downstream period is t i (t i＝ t 1, t 2,..., t n ), the corresponding downstream power generation benefit slightly increased by b i (b i＝ b 1, b 2,..., b n ), the single database decision space is Q j (t i ), there are three cases:

[0104] If t0=t i , then the total power generation benefit slight increase rate b s =b0+b i , the total decision space is

[0105] Q js =min{Q j (t0),Q j (t i =t0)};

[0106] If t0<t i , b s =b0+bi , the total decision space is

[0107] Q js =min{Q j (t0),Q j (t i =t0),V max -max{V t (t i )}};

[0108] If t0>t i , b s =b0+b i , the total decision space is

[0109] Q js =min{Q j (t0),Q j (t i =t0),min{V0(t i )}};

[0110] The maximum value of the slight increase rate of total power generation benefit corresponding to the period in which the total decision space is not 0 is taken as the slight increase rate of total power generation benefit in this period.

[0111] The calculation order is from downstream to upstream. When calculating one of the reservoirs, all downstream reservoirs can be regarded as a whole, and the total downstream power generation benefit increase rate and total decision space are used to replace the single reservoir power generation benefit increase rate and single reservoir decision space in the calculation.

[0112] Step 6: Based on the order of the total power generation benefit increment rate and the total decision space of each reservoir, decisions are made from upstream to downstream. After each decision, steps 4 to 6 are repeated to update the total power generation benefit increment rate and total decision space of each reservoir in each period until the decision space of all reservoirs is an empty set, and the final calculation result is obtained. It includes the following sub-steps:

[0113] (6-1) Make a preliminary decision. Determine whether the water levels of all reservoirs at the end of the period meet the constraints. If not, make a preliminary decision to ensure that the water levels at the end of the period meet the constraints. Specifically:

[0114] (6-1-1) If the final water level of a reservoir is lower than the water level constraint at the end of the period, water will be released during the period with the maximum micro-increase rate of upstream power generation benefits. The amount of water released will just be enough to raise the water level of the reservoir at the end of the period to the constraint position.

[0115] (6-1-2) If the final water level of a reservoir is higher than the water level constraint at the end of the period, water will be released during the period with the maximum slight increase in power generation benefit of the reservoir. The amount of water released will just reduce the water level of the reservoir at the end of the period to the constraint position.

[0116] (6-2) The total power generation benefit increment rates whose total decision space is not 0 are arranged in order of size, and the line with the largest total power generation benefit increment rate is decided. At this time, all reservoirs generate electricity according to the total decision space in the corresponding period.

[0117] (6-3) Determine whether all reservoirs have no decision space. If so, the optimal solution is obtained. At this time, the decision of each reservoir in each time period is the power generation plan of each reservoir; otherwise, repeat steps 4 to 6 to make the next round of decision-making.

[0118] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for dispatching reservoirs of cascade hydropower stations based on the ranking of power generation benefit increment rate, characterized in that: The method comprises the following steps: S1 divides the dispatch period of each hydropower station in the cascade hydropower station to be processed into multiple time periods, and constructs the constraint conditions and long-term optimal dispatching power generation maximum model of the cascade hydropower station to be processed; S2 uses the maximum power generation model to calculate the power generation benefit increment rate and decision space of each hydropower station in each time period, and uses this to calculate the total power generation benefit increment rate and total decision space formed by the mutual association between the hydropower stations in each time period; S3 sorts the slight increase rates of the total power generation benefits corresponding to each time period in descending order, and determines whether the total decision space corresponding to each time period is zero. If the total decision space corresponding to each time period is zero, the process ends. Otherwise, the time period corresponding to the maximum total power generation benefit is selected from all time periods for which the water consumption of the time period has not been solved, and the water consumption corresponding to the time period is solved. The process returns to step S2 until the total decision space corresponding to all time periods is zero. In step S1, the long-term optimal scheduling model for maximum power generation is performed as follows: N t Result t H t Among them, E represents the total power generation, N t Indicates the power generation during the period, K indicates the output coefficient of the hydropower station, Q t represents the power generation flow during period t, H t Indicates the generating head; In step S2, the power generation benefit increase rate of each hydropower station is calculated according to the following formula: Among them, E is the total power generation benefit of each hydropower station, Q t is the water consumption of the hydropower station in period t, b t is the incremental rate of power generation benefit of the hydropower station in period t, representing the benefit brought by unit water volume used for power generation in this period; In step S2, the decision space corresponding to each time period of each hydropower station is calculated according to the following formula: in, is the decision space of the i-th reservoir in period t, is the minimum discharge of the i-th reservoir in period t, is the maximum discharge of the i-th reservoir in period t, is the available water volume of the i-th reservoir in period t, is the maximum water storage capacity allowed for the i-th reservoir, It represents the maximum value of the reserved water volume of the i-th reservoir in all periods after period t.

2. The method for dispatching reservoirs of cascade hydropower stations based on the order of slight increase in power generation benefits according to claim 1, characterized in that: In step S1, the constraints include: (1) Water balance constraints V t (t)=V0(t)+(I(t)-Q fd (t)-Q qs (t))×Δt Where V t is the water storage at the end of the period, V0 is the water storage at the beginning of the period, I t Q is the water supply during the time period. fd is the power generation flow, Q qs is the abandoned water flow, Δt is the time interval; (2) Reservoir water level constraints V min ≤V t (t)≤V max V min is the reservoir capacity corresponding to the minimum water level, V max is the reservoir capacity corresponding to the maximum water level; (3) Water level and storage capacity curve constraints Z sy (t)=f ZV [V(t)] Z sy (t) is the upstream water level during period t, f ZV Represents the water level and storage capacity relationship curve; (4) Tailwater level discharge curve constraint Z xy (t)=f ZQ [Q fd (t)] Z xy is the downstream water level, f ZQ Represents the relationship curve between tailwater level and power generation flow; (5) Power generation flow constraints Q fd ≤Q max Maximum power generation flow Q max It should be related to the gate discharge capacity and output limit.

3. The method for dispatching reservoirs of cascade hydropower stations based on the order of power generation benefit increment as claimed in claim 1, characterized in that: The decision space corresponding to each time period of each hydropower station is calculated according to the following steps: S21 calculates the water storage capacity V of the i-th reservoir at the end of period t t i (t)(t=1,2,...,T; i=1,2,...,n) in, is the initial water storage capacity of the i-th reservoir in period t, I i (t) is the water inflow of the i-th reservoir in period t, Q i (t) is the water consumption of the i-th reservoir in time period t, i is the reservoir number, n is the total number of reservoirs, t is the time period, and T is the total number of water in the time period; S22 reverse calculation to obtain the reserved water volume for each period in, is the reserved water volume of reservoir i in the period before period t, is the reserved water volume of reservoir i in period t, I i (t) is the water inflow of reservoir i in period t; S23 calculates the available water volume of each reservoir at each time period in, represents the available water volume of reservoir i in period t, V t i (t) water storage capacity of reservoir i at the end of period t, represents the reserved water volume of reservoir i in period t; S24 calculates the decision space of each reservoir at each time period 4. A method for dispatching reservoirs of cascade hydropower stations based on the order of slight increase in power generation benefits according to claim 1 or 2, characterized in that: In step S2, the total power generation benefit increase rate is calculated according to the following relationship: b s =b0+b i Among them, b s is the slight increase rate of total power generation benefit, b0 is the slight increase rate of power generation benefit of the upstream reservoir during the calculation period, b i is the slight increase rate of power generation benefit of the downstream reservoir in period i.

5. The method for dispatching reservoirs of cascade hydropower stations based on the order of power generation benefit increment as claimed in claim 1, characterized in that: The total decision space is calculated according to the following formula: If t0=t i , the total decision space is: Q js =min{Q j (t0),Q j (t i =t0)}; If t0<t i , the total decision space is: Q js =min{Q j (t0),Q j (t i =t0),V max -max{V t (t i )}}; If t0>t i , the total decision space is: Q js =min{Q j (t0),Q j (t i =t0),min{V0(t i )}}; Among them, t0 is the calculation period of the upstream reservoir, t i The calculation period for the downstream reservoir, Q js is the total decision space, Q j (t0) is the decision space of the upstream reservoir at time t0, Q j (t i =t0) is the decision space of the downstream reservoir at time t0, V max is the maximum water storage capacity downstream, max{V t (t i )} is the downstream reservoir t0 period and t i The maximum water storage capacity at the end of each period, min{V0(t i )} is the downstream reservoir t i The minimum initial water storage between the period and the t0 period.

6. A method for dispatching reservoirs of cascade hydropower stations based on the order of slight increase in power generation benefits according to claim 1 or 2, characterized in that: In step S3, the water consumption is the maximum value of the total decision space.

7. A method for dispatching reservoirs of cascade hydropower stations based on the order of slight increase in power generation benefits as claimed in claim 1 or 2, characterized in that: In step S3, it is also necessary to pre-process the reservoirs whose initial water level during the scheduling period is inconsistent with the required water level at the end of the scheduling period. The specific steps are as follows: If the final water level of a reservoir is lower than the water level constraint at the end of the period, water will be released during the period with the maximum upstream power generation benefit increment rate, and the amount of water released will just be enough to raise the water level of the reservoir at the end of the period to the constraint position; If the final water level of a reservoir is higher than the water level constraint at the end of the period, water will be released during the period with the maximum slight increase in power generation benefit. The amount of water released can just reduce the water level of the reservoir at the end of the period to the constraint position.

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