A deterministic optimal scheduling method for hydropower stations based on marginal benefit

Abstract

The present invention belongs to the technical field related to hydropower generation, and discloses a deterministic optimal scheduling method for a hydropower station based on marginal benefit. The method includes: S1 dividing the scheduling period of the hydropower station into multiple time intervals with equal time intervals, setting the initial conditions and constraint conditions within the scheduling period of the hydropower station, and constructing a long-term optimal scheduling power generation maximization model for the hydropower station; S2 constructing a relational expression of the marginal benefit with respect to the power generation maximization model, constructing a calculation method for the remaining benefit, and sequentially calculating the water level remaining benefits of each time interval by using the reverse order recursion method; S3 according to the remaining benefits calculated in step S2, judging the magnitude between the marginal benefit of the current time interval and the remaining benefit of the next time interval, and constructing the relationship between the current water consumption and each reservoir capacity, incoming flow, maximum discharge flow and minimum out-flow according to this, and using this relationship to calculate the water consumption of each time interval to realize the scheduling of the hydropower station. Through the present invention, the problem of optimizing the scheduling of the water consumption of the hydropower station is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to hydropower generation, and more specifically, relates to a deterministic optimal scheduling method for a hydropower station based on marginal benefit. Background Art

[0002] In the long-term scheduling of hydropower stations, a maximum power generation model is usually established, and the dynamic programming method and its improved algorithms are used for solution. The improved algorithms mainly include the progressive optimization method, the dynamic programming successive approximation method, the state-by-state dynamic programming method, and the incremental dynamic programming method, etc. As a mathematical programming method, dynamic programming obtains the optimal solution of the reservoir scheduling problem through an exhaustive method, and what is obtained is the solution of the problem rather than a set of rules, resulting in the poor interpretability of the obtained scheme. It only solves the problem of "how to schedule", but does not answer the question of "why schedule like this". Summary of the Invention

[0003] Aiming at the above defects or improvement requirements of the prior art, the present invention provides a deterministic optimal scheduling method for a hydropower station based on marginal benefit, which solves the optimal scheduling problem of the water consumption of the hydropower station.

[0004] To achieve the above object, according to the present invention, there is provided a deterministic optimal scheduling method for a hydropower station based on marginal benefit, and the method includes the following steps:

[0005] S1 Divide the scheduling period of the hydropower station into multiple time intervals with equal time intervals, set the initial conditions and constraint conditions within the scheduling period of the hydropower station, and construct a maximum power generation model for the long-term optimal scheduling of the hydropower station;

[0006] S2 Construct a relational expression of the marginal benefit with respect to the maximum power generation model, construct a calculation method for the remaining benefit, and calculate the remaining benefit of the water level in each time interval in turn by using the reverse order recurrence method;

[0007] S3 According to the remaining benefit calculated in step S2, judge the magnitude between the marginal benefit of the current time interval and the remaining benefit of the next time interval, and construct the relationship between the current water consumption and each reservoir capacity, incoming flow, maximum discharge flow, and minimum outflow according to this, and use this relationship to calculate the water consumption in each time interval to realize the scheduling of the hydropower station.

[0008] Further preferably, in step S2, the remaining benefit in each time interval is calculated according to the following method:

[0009] S21 Calculate the marginal benefit f(V t ,Q t ) and the remaining benefit F(V t+1 ) corresponding to any time t respectively;

[0010] S22 Judge f(V t ,Qt ) and F(V t+1 ). When F(V t+1 ) ≥ f(V t , Q T ), F(V t ) = F(V t+1 ); otherwise, judge the size of the current water consumption Q t and the maximum discharge :

[0011] When , F(V t ) = f(V t , Q t );

[0012] Otherwise, update the current water consumption Q t and the reservoir capacity V at the end of the period t+1 , and return to step S22;

[0013] S23 t = t - 1 until the remaining benefits of all periods are obtained.

[0014] Further preferably, in step S23, for the last period T, the remaining benefit F(V T+1 ) corresponding to the period T + 1 below the end water level limit is M, and M is an arbitrarily large positive number.

[0015] Further preferably, in step S22, update the current water consumption Q t and the reservoir capacity V at the end of the period t+1 according to the following relationship:

[0016] Q t = Q t + ΔQ;

[0017] V t+1 = V t + (I t - Q t ) × Δt

[0018] where Q t is the water consumption of the hydropower station at time t; ΔQ is the unit water volume; V t+1 is the reservoir capacity at time t + 1; V t is the reservoir capacity at time t; I t is the incoming flow at time t; Δt is the time interval.

[0019] Further preferably, in step S3, the water consumption of each period is calculated according to the following steps:

[0020] S31 Obtain the initial storage state V t and the incoming flow It ;

[0021] S32 Determine the relationship between the marginal benefit f(V t , Q t ) in this time period and the remaining benefit F(V t+1 ) in the next time period. When f(V t , Q t ) ≤ F(V t+1 ), the current water consumption is calculated according to the following relational expression:

[0022] Otherwise, update the current water consumption and the reservoir storage at the end of the time period V t+1 , Q t = Q t + ΔQ, V t+1 = V t + (I t - Q t ) × Δt, update and calculate the marginal benefit f(V t , Q t ) in this time period and the remaining benefit F(V t+1 ) in the next time period until f(V t , Q t ) ≤ F(V t+1 ), and the current water consumption is calculated according to the following relational expression:

[0023] S33 t = t + 1, return to step S31 until the water consumption of each time period is obtained.

[0024] Further preferably, in step S1, the constraint conditions are:

[0025] (1) Water level constraint: Z t and represent the minimum water level and the maximum water level limits in the t (t = 1, 2,..., T) time periods respectively;

[0026] (2) Reservoir storage constraint: V t and represent the minimum reservoir storage and the maximum reservoir storage limits in the t (t = 1, 2,..., T) time periods respectively;

[0027] (3) Output constraint: N t and represent the minimum output and the maximum output limits in the t (t = 1, 2,..., T) time periods respectively;

[0028] (4) Discharge flow constraint: Q t and represent the minimum and maximum out - flow limits during the t - th (t = 1, 2, …, T) period respectively.

[0029] Further preferably, in step S1, the maximum power generation model is carried out according to the following relational formula:

[0030]

[0031] where E is the total power generation benefit during the scheduling period; A is the reservoir output; Q t is the water consumption in the t - th period; H t is the net head of the reservoir in the t - th period.

[0032] Further preferably, the relational formula of the marginal benefit with respect to the maximum power generation model is carried out according to the following relational formula:

[0033]

[0034] where E is the total power generation benefit during the scheduling period; Q t is the water consumption in the t - th period.

[0035] Generally speaking, compared with the prior art, the above - mentioned technical solution conceived by the present invention has the following beneficial effects:

[0036] 1. Incorporate the marginal benefit in economics and the reservoir scheduling rules into the method itself, clarify that when allocating water consumption in multiple periods, with the power generation water volume unchanged, there is a competitive relationship between the current period and future periods for water volume, and ensure that water is used at the time of maximum benefit based on the marginal benefit. The method itself is easy for dispatchers to understand and master, and corresponding decisions can be made at any time according to the current water storage state and incoming water state of the hydropower station, with stronger understandability and guiding significance;

[0037] 2. The present invention combines the marginal benefit theory in economics with the reservoir scheduling theory, uses the marginal benefit as a guide to show that each cubic meter of water has a corresponding benefit, and realizes the maximum power generation benefit; compared with the mathematical programming method, this method intuitively shows the problem of "when to use water" through the marginal benefit and the remaining benefit of the period, with stronger understandability;

[0038] 3. What the present invention obtains is a scheduling rule rather than just a scheduling plan. With the goal of achieving the optimal benefit water level in each period, dispatchers can make optimal decisions at any time according to the current water level and incoming water, without the need to re - seek the power generation plan, with stronger guiding significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1It is a flowchart of the deterministic optimal scheduling method for a hydropower station based on marginal benefit constructed according to the preferred embodiment of the present invention;

[0040] Figure 2 It is a flowchart for solving the water consumption in each period constructed according to the preferred embodiment of the present invention. Detailed implementation manners

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] The essence of the optimal scheduling problem is essentially two problems: "when to use water" and "water use decision". Starting from the essential problems, the economic analysis of the optimal scheduling problem is carried out with the help of the marginal benefit framework, and it is clear that when allocating water in multiple periods, with the power generation water volume unchanged, there is a competitive relationship between the current period and the future period for the same water volume. "When to use water" can be determined by when the water of this side has greater benefits when used in the current period or the future period. The marginal benefit f(V t , Q t ) in each period can be considered as the benefit brought by this unit of water in this period, that is The remaining benefit F(V t ) of the period refers to the benefit brought by this water at this storage level for the subsequent periods.

[0043] If the remaining benefits of the reservoir levels in each period are known and combined with the marginal benefit of the reservoir in this period, it is possible to judge whether to use water and how much water to use to maximize the reservoir benefit by comparing the sizes of the benefits.

[0044] Figure 1 It is a flowchart of the optimal scheduling method for a hydropower station based on marginal benefit, specifically including the following steps:

[0045] Step 1: Set the scheduling period, evenly divide the scheduling period (1 year) into T (T is a positive integer) equal-spacing periods; set the constraint conditions during the scheduling period of the hydropower station, where

[0046] (1) Water level constraint: Z t , respectively represent the minimum water level and the maximum water level limits in the t (t = 1, 2,..., T) period;

[0047] (2) Storage capacity constraint: V t , represent the minimum storage capacity and the maximum storage capacity limits for each time period \(t (t = 1, 2, \ldots, T)\) respectively;

[0048] (3) Output constraint: N t and represent the minimum output and the maximum output limits for each time period \(t (t = 1, 2, \ldots, T)\) respectively;

[0049] (4) Discharge flow constraint: Q t and represent the minimum discharge flow and the maximum discharge flow limits for each time period \(t (t = 1, 2, \ldots, T)\) respectively;

[0050] Water balance equation: \(V\) t+1 = \(V\) t + (\(I\) t - \(Q\) t ) \(\times \Delta t\), where \(I\) t represents the incoming flow in time period \(t\), and \(\Delta t\) represents the time interval of one time period; Set the initial scheduling conditions: The initial water level of the hydropower station at the beginning of the scheduling period is \(Z\) ini , and the final water level at the end of the scheduling period is \(Z\) end .

[0051] Step 2: According to the optimal scheduling objective function of the hydropower station and the above constraints, establish the following maximum long - term optimal scheduling power generation model for the hydropower station:

[0052]

[0053] where \(E\) represents the total power generation during the scheduling period; \(A\) is the reservoir output; \(Q\) t is the discharge in a time period; \(H\) t is the net head of the reservoir in time period \(t\).

[0054] Step 3: Determine the remaining benefits \(F(V\) t ) of each time - period water level by reverse recursive method. Combining the incoming water \(I\) during the scheduling period, the remaining benefits \(F(V\) t+1 ) of the next time period and the marginal benefit \(f(V\) t , \(Q\) t ), determine the remaining benefits of the reservoir water level for each time period, which specifically includes the following sub - steps:

[0055] (3 - 1) Clearly define: The marginal benefit \(f(V\) t , \(Q\) t ) in this time period refers to the increment of power generation brought by a unit of water volume when the storage level is at this level, and can be considered as the benefit brought by the local water at this level in this time period. The magnitude of its benefit is affected by the water level and water use in this time period; The remaining benefit \(F(V\) t) It refers to the benefits that can be brought in subsequent time periods if the water storage volume is at this water level, which can be considered as the benefits that the water of this side can obtain if it is reserved until the next stage.

[0056] (3-2) Given the incoming water I in each time period during the scheduling period and the constraints during the scheduling period, determine the remaining benefits F(V) of the water level in each time period t ) It includes the following sub-steps:

[0057] (3-2-1) Constraint handling: Due to the limitation of the final reservoir storage volume V end must be satisfied, and it is considered that the remaining benefits F(V) of this time period t ) = M (M is an arbitrarily large positive number); the minimum discharge flow rate in each time period Q limitation must be satisfied, so it is considered that the marginal benefit f(V t ,Q t ) = M (M is an arbitrarily large positive number); when the water volume exceeds the upper limit of the maximum reservoir storage volume, the water will be discarded, and the discarded water cannot bring benefits to this time period or subsequent time periods, so the marginal benefit f(V t ,Q t ) and the remaining benefits F(V) of this time period t ) are both 0;

[0058] (3-2-2) Calculate the marginal benefit f(V t ,Q t ) of this time period. The benefit that can be brought by using one more unit of water of this side in this time period is considered as the marginal benefit of this side of water, that is

[0059] By comparing the marginal benefit f(V t ,Q t ) of this side of water with the remaining benefits F(V) of the next time period t+1 ), determine the remaining benefits F(V) of this time period by judging when to use the water of this side can bring greater benefits t ).

[0060] For the last moment, the remaining benefits below the water level limit corresponding to the next moment are M, and the marginal benefit is calculated according to the formula;

[0061] If the remaining benefits F(V) of the next time period t+1 ) ≥ the marginal benefit f(V t ,Q t ) of this time period, it means that storing the water of this side can bring greater benefits, and the water of this side is used for storage; if the remaining benefits F(V) of the next time period t+1 ) < the marginal benefit f(V t ,Q t ) of this time period, it means that generating electricity with the water of this side in this time period can bring greater benefits, and the water of this side is used for power generation;

[0062] (3 - 2 - 3) Combine the incoming water I during the time period t , and through the water balance equation

[0063] V t+1 = V t +(I t - Q t )×Δt

[0064] Determine V t and V t+1 during this time period, compare the marginal benefit of each cubic meter of water during this time period with the remaining benefit of the next time period, and determine how to use this cubic meter of water to bring greater benefits. If at the beginning of the time period F(V t+1 )≥f(V t , Q t ), it means that storing water for this cubic meter of water can bring greater benefits. At this time, F(V t ) = F(V t+1 ); if at the beginning of the time period F(V t+1 )<f(V t , Q t ), it means that using this amount of water for power generation during this time period can achieve greater benefits. If the water consumption is less than the maximum downstream discharge Modify Q t = Q t +ΔQ, update V t+1 Judge the relationship between F(V t+1 ) and f(V t , Q t ) again until F(V t+1 )≥f(V t , Q t ), at this time F(V t ) = F(V t+1 ). If At this time, generate electricity according to the maximum downstream discharge during this time period, and at this time F(V t ) = f(V t , Q t ).

[0065] (3 - 2 - 4) Recursively calculate from the end of the scheduling period to the beginning of the scheduling period according to steps (3 - 2 - 1), (3 - 2 - 2), and (3 - 2 - 3) to obtain the remaining benefits F(V t ) of the reservoir water levels for each time period;

[0066] Step 4: According to the marginal benefit f(V t , Q t ) of this time period and the remaining benefit F(V t+1 ) of the next time period, combined with the initial water storage state V t of the hydropower station at the beginning of the time period, the incoming flow I t , and the reservoir constraint conditions, recursively explore the water consumption of the current time period.

[0067] As shown Figure 2 in the figure, assume that the initial Q t in each period is ΔQ, the initial reservoir capacity and the inflow in the period are known, and the end-of-period reservoir capacity is calculated according to the water balance equation. Calculate f(V t , Q t ) based on the initial reservoir capacity of the reservoir, and combine with the end-of-period reservoir capacity V t+1 to obtain F(V t+1 ); if the marginal benefit f(V t , Q t ) in this period ≤ the remaining benefit F(V t+1 ) in the next period, it means that retaining the water to the next period can bring greater benefits. At this time, storing the water can obtain greater benefits. Combine with the minimum discharge Q t , and take Q t = max(0, Q t ); if the marginal benefit f(V t , Q t ) in this period > the remaining benefit F(V t+1 ) in the next period, it means that using the water in this period can bring greater benefits. Let Q t = Q t + ΔQ, update V t+1 , compare the magnitudes of f(V t , Q t ) and F(V t+1 ) until f(V t , Q t ) ≤ F(V t+1 ). At this time combine with the maximum discharge and take

[0068] According to the obtained Q t , calculate the optimal end water level V t+1 of this period as the initial water level of the next period, and recursively deduce in sequence until the end of the scheduling period. The subsequent periods determine the corresponding water consumption and operate according to the above method until the end of the said scheduling period.

[0069] It is easy for those skilled in the art to understand that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A deterministic optimal scheduling method for hydropower stations based on marginal benefit, characterized in that The method includes the following steps: S1 Divide the scheduling period of the hydropower station into multiple time intervals of equal duration, set the initial conditions and constraint conditions within the scheduling period of the hydropower station, and construct a long-term optimal scheduling model for maximizing the power generation of the hydropower station; S2 Construct a relationship between the marginal benefit and the power generation maximization model, construct a calculation method for the remaining benefit, and calculate the remaining benefit of the water level in each time period in turn using the reverse order recurrence method; S3 According to the remaining benefit calculated in step S2, judge the magnitude between the marginal benefit of the current time period and the remaining benefit of the next time period, and construct the relationship between the current water consumption and each storage capacity, incoming flow, maximum downstream discharge flow, and minimum out-of-storage flow based on this. Use this relationship to calculate the water consumption in each time period to achieve the scheduling of the hydropower station. In step S2, the remaining benefit of each time period is calculated in the following manner: S21 calculates the marginal benefit corresponding to any moment t and the remaining benefit in the next period ; S22 Judgment and to determine the magnitude relationship. When , ; otherwise, judge the current water consumption and the maximum discharge : At that time , ; Otherwise, update the current water consumption and the reservoir capacity at the end of the period , and return to step S22; S23 t = t - 1 until the remaining benefits of all time periods are obtained; In step S3, the water consumption of each time period is calculated according to the following steps: S31 Obtain the initial water storage state at the beginning of the time period and the inflow ; S32 Determine the marginal benefit of this period and the remaining benefit of the next period and when the current water consumption is as follows according to the following relationship: ; Otherwise, update the current water consumption and the reservoir storage at the end of the period , , , update and calculate the marginal benefit of this period and the remaining benefit of the next period , until , the current water consumption is as follows: ; S33 t = t + 1, return to step S31 until the water consumption of each time period is obtained.

2. The deterministic optimal scheduling method for a hydropower station based on marginal benefit as described in claim 1, wherein In step S23, for the last period T, the remaining benefit corresponding to the water level limit at the end of the next period T+1 is M, where M is any large positive number.

3. The deterministic optimal scheduling method for a hydropower station based on marginal benefit according to claim 1, wherein In step S22, update the current water consumption and the reservoir capacity at the end of the period The update is performed according to the following relationship: ； Among them, is the water consumption of the hydropower station at a certain moment; is the unit water volume; is the reservoir capacity at time t + 1; is the reservoir capacity at time t; is the incoming flow at time t; is the time interval.

4. A deterministic optimal scheduling method for a hydropower station based on marginal benefit according to claim 1 or 2, characterized in that, In step S1, the constraint conditions are: (1) Water level constraint: , and represent the minimum water level and the maximum water level limits in the t-th (t = 1, 2, …, T) period, respectively; (2) Storage capacity constraint: , and represent the minimum and maximum storage capacity limits for period t (t = 1, 2, …, T), respectively; (3) Output constraint: , and represent the minimum and maximum output limits for the t-th (t = 1, 2, …, T) period, respectively; (4) Outflow constraint: , and represent the minimum and maximum outflow limits during the t-th (t = 1, 2, …, T) period respectively.

5. A deterministic optimal scheduling method for a hydropower station based on marginal benefit according to claim 1 or 2, characterized in that, In step S1, the power generation maximization model is as follows: Among them, E is the total power generation benefit during the scheduling period; A is the reservoir output; is the water consumption in period t; is the net head of the reservoir in period t.

6. A deterministic optimal scheduling method for a hydropower station based on marginal benefit according to claim 1 or 2, characterized in that, The relationship between the marginal benefit and the power generation maximization model is as follows: Among them, E is the total power generation benefit during the scheduling period; is the water consumption at time t.

Images