CN109002936A - Consider the hydropower station Optimization Scheduling of flexibility - Google Patents

Abstract

The present invention provides a kind of hydropower station Optimization Schedulings for considering flexibility, power benefit and flexibility can be taken into account during optimizing scheduling of reservoir, it is characterized in that, the following steps are included: step 1 indicates the uncertainty of two Phase flow using flexibility index, two Phase flow is expressed as a range format；Step 2 establishes the double-goal optimal model for taking into account power benefit and flexibility: power benefit target is that total power generation is maximum under becoming a mandarin most bad situation in schedule periods, and flexibility target is that flexibility index is maximum；Step 3 solve double-goal optimal model, using leash law by flexibility targeted transformation be constraint condition, then solved using dynamic programming method；Or Noninferior Solution Set is sought using Multiobjective Intelligent algorithm.

Description

Optimal scheduling method for reservoir power generation considering flexibility

technical field

The invention belongs to the field of reservoir dispatching, and in particular relates to a method for optimal dispatching of reservoir power generation considering flexibility.

technical background

The development of hydropower is an important measure to alleviate the future energy crisis and improve the energy structure. Reservoir optimal dispatching is based on the regulation and storage capacity of the reservoir, using the optimal dispatching theory to adjust the process of runoff out of the reservoir, so as to maximize the comprehensive benefits of flood control, power generation, irrigation, and shipping. However, the inflow flow used in the actual operation of the reservoir is obtained from the forecast, so the uncertainty of the inflow runoff process should be considered in the optimal operation of the reservoir. The flexibility (flexibility) of reservoir dispatching refers to the adaptability of the reservoir to deal with uncertain factors (inflow runoff uncertainty, etc.). Improving the flexibility of the dispatching process can greatly reduce the impact of uncertain factors on reservoir operation. It is of great practical significance to balance flexibility and power generation efficiency in reservoir optimal dispatching.

The traditional deterministic optimization scheduling model fails to fully consider the uncertainty of inflow runoff, while the stochastic optimization model relies too much on the assumption of the distribution type and distribution function of uncertain factors. However, due to the influence of climate change and human activities, the distribution type and distribution function of inflow runoff will become increasingly difficult to predict. Therefore, how to increase the power generation and flexibility of the reservoir under the condition of uncertain inflow flow is a problem that needs to be solved.

Contents of the invention

The present invention is made to solve the above problems, and the purpose is to provide a flexible reservoir power generation optimization scheduling method, which can take into account both power generation efficiency and flexibility in the reservoir optimal scheduling process.

In order to achieve the above object, the present invention adopts the following scheme:

The present invention provides a method for optimal dispatching of reservoir power generation considering flexibility, which is characterized in that it comprises the following steps:

Step 1. Use the flexibility index to represent the uncertainty of the inflow runoff, and express the inflow runoff as an interval form;

The expression of inflow runoff is:

In the formula: T is the number of reservoir scheduling periods; I _t is the inflow flow in period t; is the predicted value of inbound flow in time period t; and is the maximum offset; μ is the flexibility index;

Step 2. Establish a dual-objective optimization model that takes into account both power generation efficiency and flexibility;

The power generation benefit target is the maximum total power generation under the worst case of inflow during the dispatch period, and the calculation formula is:

The flexibility target is the maximum flexibility index, and the expression is:

max μ

In the formula, N _t is the output of time period t; Δt is the length of time period;

The constraints are:

In the formula, v _t+1 and v _t are the storage capacity at period t+1 and the beginning of period t respectively; q _t is the outbound flow of period t; v _max and v _min are the maximum and minimum storage capacity allowed respectively; q _max and q _min is the allowable maximum and minimum discharge flow; N _max and N _min are the maximum and minimum output;

Step 3. Solve the dual-objective optimization model, use the constraint method to convert the flexibility objective into constraint conditions, and then use the dynamic programming method to solve; or use the multi-objective intelligent algorithm to find the non-inferior solution set.

The flexible reservoir power generation optimization scheduling method provided by the present invention may also have the following characteristics: In step one: first, use a mathematical statistical model or a physical model to predict the future runoff process of entering the reservoir Then, set the maximum offset for inbound traffic and Finally, the inbound flow is expressed in interval form by using the flexibility coefficient μ (0≤μ≤1).

The flexible reservoir power generation optimization scheduling method provided by the present invention may also have the following characteristics: in step 2:

N _t =min(N _c ,N _e )

N _e =f _Nh (h _t )

Z _d (q)=a·q ^b +c

Z _u (v) = f _zv (v)

In the formula: N _c calculates the output of time period t; _Ne is the limited output; h _t is the water head of time period t; Z _u and Z _d are the upstream and downstream water levels of time period t; hl is the head loss of time period t; q _emax is the maximum power generation flow; a, b, c and k are constants.

The method for optimal dispatching of reservoir power generation considering flexibility provided by the present invention may also have the following features: In Step 3: First, convert the multi-objective problem into a single-objective problem, and the specific method is to convert the flexibility index into a constraint: 0≤μ ≤1, the discrete form is: μ＝0,0.1,...,1; then, the objective function of the maximum power generation is simplified, and the specific method is to calculate the derivative of the output with respect to the outflow:

N _e = f _Nh (h _t ) = m·h _t +n=m·(Z _u -Z _d (q)-hl)+n

N′ _e ＝-m·a·b·q ^b-1 <0

When the upstream water level is determined, the time-period output increases first and then decreases with the increase of the outflow, because there is a linear relationship between the outflow and inflow during the time period:

q _t =I _t +(v _t -v _t+1 )/Δt

The time-period output increases first and then decreases with the increase of the inflow. At this time, the objective function can be simplified as:

In the formula: I _m is the boundary of the inflow interval in time period t;

Finally, when dynamic programming is used for optimal scheduling, the two-stage recursive equation is:

F _t (v _t )＝max[f _t (q _t )+F _t+1 (v _t+1 )]

In the formula: f _t () is the utility function of the reservoir in period t, and F _t () is the maximum cumulative utility function from period T to t.

Function and Effect of Invention

The invention fully considers the uncertainty characteristics of the inflow flow, and can still provide a flexible and stable reservoir dispatching process for guiding the power generation and actual operation of the reservoir when the inflow flow prediction is inaccurate.

Description of drawings

Fig. 1 is a flow chart of a method for optimal dispatching of reservoir power generation considering flexibility involved in an embodiment of the present invention.

Detailed ways

The flexible reservoir power generation optimization scheduling method involved in the present invention will be described in detail below in conjunction with the accompanying drawings.

<Example>

As shown in Fig. 1, the method for optimal scheduling of reservoir power generation considering flexibility provided in this embodiment includes the following steps:

Step 1. Use the flexibility coefficient to express the inflow runoff as an interval form:

First, use mathematical statistical models or physical models to predict the future inflow runoff process

Then, set the maximum offset for inbound traffic and

Finally, the uncertainty of the inflow runoff is represented by the flexibility coefficient μ (0≤μ≤1), and the inflow flow is expressed in interval form, the expression is:

In the formula: T is the number of reservoir scheduling periods; I _t is the inflow flow in period t; is the predicted value of inbound flow in time period t; and is the maximum offset; μ is the flexibility index.

Step 2. Establish a dual-objective optimization model that takes into account power generation efficiency and flexibility:

The power generation benefit target is the maximum total power generation under the worst case of inflow during the dispatch period, and the calculation formula is:

The flexibility target is the maximum flexibility index, and the expression is:

max μ

In the formula, N _t is the output of time period t; Δt is the length of time period.

The constraints considered by the established dual-objective optimization model include: water balance constraints, storage capacity constraints, outflow flow constraints, output constraints, maximum power generation flow constraints, etc. The corresponding expressions are as follows:

In the formula, v _t+1 and v _t are the storage capacity at period t+1 and the beginning of period t respectively; q _t is the outbound flow of period t; v _max and v _min are the maximum and minimum storage capacity allowed respectively; q _max and q _min is the allowable maximum and minimum discharge flow; N _max and N _min are the maximum and minimum output respectively.

Among them, the actual output of the hydropower station is calculated as:

N _t =min(N _c ,N _e )

N _e =f _Nh (h _t )

Z _d (q)=a·q ^b +c

Z _u (v) = f _zv (v)

In the formula: N _c calculates the output of time period t; _Ne is the limited output; h _t is the water head of time period t; Z _u and Z _d are the upstream and downstream water levels of time period t; hl is the head loss of time period t; q _emax is the maximum power generation flow; a, b, c and k are constants.

Step 3. Solve the dual-objective optimization model: use the constraint method to convert the flexibility objective into constraint conditions, and then use the dynamic programming method to solve; or use the multi-objective intelligent algorithm to find the non-inferior solution set.

First, convert the multi-objective problem into a single-objective problem by converting the flexibility index into a constraint: 0≤μ≤1, and the discrete form is: μ=0,0.1,...,1;

Then, the objective function of maximum power generation is simplified. The specific method is to verify that when the upstream water level of the reservoir is constant, the power generation increases first and then decreases with the increase of inflow. At this time, the objective function can be simplified as:

In the formula: I _m is the boundary of the inflow interval in time period t;

Finally, dynamic programming is used for optimal scheduling, and the two-stage recursive equation is:

F _t (v _t )＝max[f _t (q _t )+F _t+1 (v _t+1 )]

In the formula: f _t () is the utility function of the reservoir in period t, and F _t () is the maximum cumulative utility function from period T to t.

The above embodiments are merely illustrations for the technical solution of the present invention. The flexible reservoir power generation optimization scheduling method involved in the present invention is not limited to the content described in the above embodiments, but is subject to the scope defined in the claims. Any modifications, supplements or equivalent replacements made by those skilled in the art of the present invention on the basis of the embodiments are within the protection scope of the claims of the present invention.

Claims (4)

1. A method for optimal dispatching of reservoir power generation considering flexibility, is characterized in that, comprising the following steps: Step 1. Use the flexibility index to represent the uncertainty of the inflow runoff, and express the inflow runoff as an interval form; The expression of inflow runoff is: In the formula: T is the number of reservoir scheduling periods; I _t is the inflow flow in period t; is the predicted value of inbound flow in time period t; and is the maximum offset; μ is the flexibility index; Step 2. Establish a dual-objective optimization model that takes into account both power generation efficiency and flexibility; The power generation benefit target is the maximum total power generation under the worst case of inflow during the dispatch period, and the calculation formula is: The flexibility target is the maximum flexibility index, and the expression is: maxμ In the formula, N _t is the output of time period t; Δt is the length of time period; The constraints are: In the formula, v _t+1 and v _t are the storage capacity at period t+1 and the beginning of period t respectively; q _t is the outbound flow of period t; v _max and v _min are the maximum and minimum storage capacity allowed respectively; q _max and q _min is the allowable maximum and minimum discharge flow; N _max and N _min are the maximum and minimum output; Step 3. Solve the dual-objective optimization model, use the constraint method to convert the flexibility objective into constraint conditions, and then use the dynamic programming method to solve; or use the multi-objective intelligent algorithm to find the non-inferior solution set. 2. The reservoir power generation optimization scheduling method considering flexibility according to claim 1, characterized in that: Among them, in step 1: first, use mathematical statistics model or physical model to predict the future inflow runoff process Then, set the maximum offset for inbound traffic and Finally, the inbound flow is expressed in interval form by using the flexibility coefficient μ (0≤μ≤1). 3. The optimal dispatching method for generating electricity in reservoirs considering flexibility according to claim 1, characterized in that: Among them, in step two: N _t =min(N _c ,N _e ) N _e =f _Nh (h _t ) Z _d (q)=a·q ^b +c Z _u (v) = f _zv (v) In the formula: N _c calculates the output of time period t; _Ne is the limited output; h _t is the water head of time period t; Z _u and Z _d are the upstream and downstream water levels of time period t; hl is the head loss of time period t; q _emax is the maximum power generation flow; a, b, c and k are constants. 4. The optimal dispatching method for generating electricity in reservoirs considering flexibility according to claim 1, characterized in that: Among them, in Step 3: First, convert the multi-objective problem into a single-objective problem, the specific method is to convert the flexibility index into a constraint: 0≤μ≤1, and the discrete form is: μ=0,0.1,...,1 ; Then, simplify the objective function of the maximum power generation, the specific method is to calculate the derivative of the output with respect to the outflow: N _e = f _Nh (h _t ) = m·h _t +n=m·(Z _u -Z _d (q)-hl)+n N′ _e ＝-m·a·b·q ^b-1 <0 When the upstream water level is determined, the time-period output increases first and then decreases with the increase of the outflow, because there is a linear relationship between the outflow and inflow during the time period: q _t =I _t +(v _t -v _t+1 )/Δt The time-period output increases first and then decreases with the increase of the inflow. At this time, the objective function can be simplified as: In the formula: I _m is the boundary of the inflow interval in time period t; Finally, when dynamic programming is used for optimal scheduling, the two-stage recursive equation is: F _t (v _t )＝max[f _t (q _t )+F _t+1 (v _t+1 )] In the formula: f _t () is the utility function of the reservoir in period t, and F _t () is the maximum cumulative utility function from period T to t.