Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a power system unit combination method based on opportunity constraint. The invention provides an effective solving method for sequentially determining the output of a traditional generator and the electricity abandonment amount of renewable energy sources so as to reduce the total operation cost to the maximum extent and limit the operation risk, and the method is suitable for being applied to the power system unit combination scene with high renewable energy permeability.
The invention provides an opportunity constraint-based power system unit combination method which is characterized in that the method comprises the steps of firstly establishing an opportunity constraint-based power system unit combination model composed of a target function and constraint conditions, then converting the model, writing opportunity constraints in the model into a quantile form, introducing relaxation variables, establishing a relaxed opportunity constraint-based power system unit combination model, and solving to obtain values of the relaxation variables; and obtaining constraint conditions with feasible solutions of a power system unit combination model based on opportunity constraint by using the values of all relaxation variables, then sequentially establishing a renewable energy power curtailment scheduling model and a generator output optimization model and respectively solving the models to obtain the curtailment power of each renewable energy source at each time interval and the active power and the start-stop state of each generator, thereby obtaining a final unit combination result. The method comprises the following steps:
1) Establishing an opportunity constraint-based power system unit combination model, wherein the model consists of an objective function and constraint conditions; the method comprises the following specific steps:
1-1) determining an objective function of a power system unit combination model, wherein the expression is as follows:
wherein T is the number of time segments of the optimization cycle, N
G In order to access the set of nodes of the generator,
for the active power of the ith generator during time period t,
for the power generation cost of the ith generator in the time period t,
for the startup cost of the ith generator during time period t,
cost of shutdown for ith generator in time period t, N
R In order to access the set of nodes of the renewable energy source,
the active power output upper limit of the jth renewable energy source,
the electricity abandon penalty cost of the ith renewable energy source in the time period t;
wherein the content of the first and second substances,
wherein A is gi ,B gi ,C gi Generating cost coefficients of the ith generator are respectively;
therein su
i For the start-up cost of the ith generator,
the starting and stopping state of the ith generator in a time period t is set;
wherein sd i The shutdown cost of the ith generator;
wherein, K
j Penalty cost coefficient for jth renewable energy source, C
j Is the jth oneThe maximum capacity of the renewable energy source,
a probability density function of available capacity for the jth renewable energy source over time period t;
1-2) determining constraint conditions of a power system unit combination model, comprising the following steps:
1-2-1) generator power constraint:
wherein the content of the first and second substances,
P i upper and lower active power limits, rup, of the ith generator, respectively
i ,Rdown
i The power limit of the ith generator is limited by upward climbing power and downward climbing power;
1-2-2) minimum start-stop time constraint of the generator:
wherein, UT i ,DT i Respectively the minimum startup time and the minimum shutdown time of the ith generator;
1-2-3) renewable energy power constraints:
wherein the content of the first and second substances,
scheduling power for the jth renewable energy source for time period t,
the predicted power for the jth renewable energy source over time period t,
the actual power for the jth renewable energy source during time period t,
available power for the jth renewable energy source for time period t;
1-2-4) power balance constraints:
wherein the content of the first and second substances,
for node k load demand over time period t, N
D A node set for accessing the load;
1-2-5) affine control and backup constraints:
wherein, the first and the second end of the pipe are connected with each other,
actual power, beta, for the ith generator under consideration of affine control
i Affine control factor, α, for the ith generator
UR ,α
DR Respectively the maximum allowable probability of the shortage of the up-regulation equipment and the maximum allowable probability of the shortage of the down-regulation equipment;
1-2-6) line transmission capacity constraints:
wherein, N
W Is a collection of lines, and is,
power transfer factors, P, of the line L with respect to the nodes i, j, k, respectively
L For the maximum transmission capacity of the line L,
respectively the maximum allowable probability of forward out-of-limit and the maximum allowable probability of reverse out-of-limit of the transmission capacity of the line L;
2) Converting the model established in the step 1), establishing a relaxed opportunity constraint-based power system unit combination model and solving the model; the method comprises the following specific steps:
2-1) by substitution in formula (16)
Writing the opportunity constraints (17) - (20) in the model of step 1) into the form of quantiles as follows:
wherein M is a positive number, Q (ξ | p) is the p-quantile of the random variable ξ,
to account for the equivalent power transfer factor of line L with respect to node j under affine control, M
L Correction coefficients for affine control to the branch L power transfer factors;
let the joint distribution of renewable energy power over time period t be as follows:
wherein the content of the first and second substances,
a random variation of the available power composition for each renewable energy source over time t,
random variables composed of power output of each renewable energy source in a time period t;
2-2) use
In alternative quantiles (21) to (24)
And introducing relaxation variables in the lower modulation reserve constraint (16) and the transmission power constraints (17) - (18) to obtain equations (29) - (32):
wherein, drs
t Slack variables in the standby constraints are adjusted for a period of time t,
the relaxation variables in the forward constraint and the reverse constraint of the line transmission capacity in the t period are respectively;
2-3) establishing a relaxed opportunity constraint-based power system unit combination model and solving;
wherein the objective function of the model is formula (33), and the constraints include formulas (6) - (8), (13), (15), (29) - (32) and (34);
s.t. formulae (6) - (8), (13), (15), (, 29) - (32) and (34)
Wherein the content of the first and second substances,
wherein the content of the first and second substances,
respectively adjusting the standby weight coefficient and the section risk weight coefficient in t time;
solving the model to obtain
The optimal solution of (a);
3) Determining the electric quantity discarded by each renewable energy source and the active power of each generator to obtain a unit combination result of the power system; the method comprises the following specific steps:
3-1) utilizing the solving result of the model in the step 2-3) and relaxing the variable
Value of (1) establishing based on the chance constraintThe power system unit combination model has constraint conditions of feasible solution:
if the slack variable drs t After the renewable energy is abandoned, if the model in the step 1) has a feasible solution, the inequality constraint shown in the following formula is satisfied:
if the relaxation variable
If the value is not zero, the quantile in the line transmission capacity constraint equation (23) satisfies the inequality constraint represented by the following equation (36):
if the relaxation variable is changed
If the value is not zero, the quantile in the line transmission capacity constraint equation (24) satisfies an inequality constraint represented by the following equation (37):
the constraints (35) - (37) are written as shown in the following formula:
wherein Ω is a subscript set of renewable energy sources participating in electricity abandonment, c j ,c k Is a constant coefficient;
3-2) establishing a renewable energy power abandoning scheduling model and solving;
the objective function of the renewable energy power curtailment scheduling is shown as the following formula:
the first and second derivatives of equation (39) are as follows:
the curtailment penalty in equation (39) is approximated by a linear inequality shown in equation (42):
obtaining the electricity abandon quantity of each renewable energy source in each time period by solving the formula (42)
Then, based on the probability distribution of available power obtained by probability prediction and quantiles in the electric quantity abandoning calculation expressions (21) to (24) obtained by solving, the constraint expressions (21) to (24) become deterministic linear constraints;
3-3) establishing a generator output optimization model and solving by using the result of the step 3-2) to obtain the starting and stopping state of each generator at each time period
And active power
Thereby obtaining the unit combination optimization result of the generator;
the objective function of the optimization model is equation (43), and the constraint conditions include: formulae (6) to (13), formula (15), formulae (21) to (24), and formula (44), the expressions are as follows:
s.t. formulae (6) - (13), (15), (21) - (24) and (44)
Wherein the content of the first and second substances,
the invention provides an opportunity constraint-based power system unit combination method, which has the advantages that:
(1) The opportunity constraint-based power system unit combination method provided by the invention optimizes the output of the conventional generator and the renewable energy power-abandoning strategy at the same time, so as to reduce the total operation cost to the maximum extent and limit the operation risk.
(2) The invention provides an effective solving method for sequentially determining the output of a traditional generator and the electric quantity of renewable energy, establishes an easily-solved optimization model for each step, and is suitable for being applied to a power system unit combination scene with high renewable energy permeability.
Detailed Description
The invention provides an opportunity constraint-based power system unit combination method, which comprises the steps of firstly establishing an opportunity constraint-based power system unit combination model composed of a target function and constraint conditions, then converting the model, writing opportunity constraints in the model into quantiles and introducing relaxation variables, establishing a relaxed opportunity constraint-based power system unit combination model, and solving to obtain values of the relaxation variables; and obtaining constraint conditions with feasible solutions of the power system unit combination model based on opportunity constraint by using the values of the relaxation variables, then sequentially establishing a renewable energy power curtailment scheduling model and a generator output optimization model and respectively solving the models to obtain the power curtailment of the renewable energy sources in each time period and the active power and the start-stop state of each generator, thereby obtaining a final unit combination result. The method comprises the following steps:
1) Establishing an opportunity constraint-based power system unit combination model, wherein the model consists of an objective function and constraint conditions; the method comprises the following specific steps:
1-1) determining an objective function of a power system unit combination model;
the objective of the power system unit combination is to minimize the total cost, which includes the cost of generating power, the cost of starting and stopping the generator, and the cost of the renewable energy power abandonment penalty, and the objective function is shown as the following formula:
wherein T is the number of time segments of the optimization cycle, N
G In order to access the set of nodes of the generator,
for the active power of the ith generator during time period t,
for the power generation cost of the ith generator in the time period t,
for the startup cost of the ith generator during time period t,
cost of shutdown for ith generator in time period t, N
R In order to access the set of nodes of the renewable energy source,
the active power output upper limit of the jth renewable energy source,
charging penalty cost for the electricity abandon of the ith renewable energy source in the time period t;
wherein the power generation cost can be represented by a quadratic function of the following formula:
wherein A is gi ,B gi ,C gi The coefficients are the power generation cost coefficients of the ith generator.
The starting cost of the generator is shown as follows:
therein, su
i For the start-up cost of the ith generator,
the starting and stopping states of the ith generator in the time period t are shown (the variable is 0-1).
The cost of the generator shutdown is shown as follows:
wherein sd i The shutdown cost of the ith generator.
The penalty charge for electricity abandonment of renewable energy sources is shown as follows:
wherein, K
j Penalty cost coefficient for jth renewable energy source, C
j Is the maximum capacity of the jth renewable energy source,
a probability density function of available capacity for the jth renewable energy source over time period t;
1-2) determining constraint conditions of a power system unit combination model, comprising the following steps:
1-2-1) generator power constraint:
wherein the content of the first and second substances,
P i upper and lower active power limits, rup, of the ith generator, respectively
i ,Rdown
i The power limit of the ith generator is limited by the upward climbing power and the downward climbing power respectively.
1-2-2) minimum start-stop time constraint of the generator:
wherein, UT i ,DT i Respectively the minimum startup time and the minimum shutdown time of the ith generator;
1-2-3) renewable energy power constraints:
wherein, the first and the second end of the pipe are connected with each other,
the power is scheduled for the jth renewable energy source for time period t,
the predicted power for the jth renewable energy source over time period t,
the actual power for the jth renewable energy source during time period t,
available power for the jth renewable energy source during time period t.
1-2-4) power balance constraints:
wherein the content of the first and second substances,
for node k load demand over time period t, N
D Is the set of nodes accessing the load.
1-2-5) affine control and backup constraints:
wherein, the first and the second end of the pipe are connected with each other,
actual power, beta, for the ith generator under consideration of affine control
i Affine control participation factor, alpha, for the i-th generator
UR ,α
DR The maximum allowable probability of under-provisioning and the maximum allowable probability of under-provisioning are respectively up-provisioning and down-provisioning.
1-2-6) line transmission capacity constraints:
wherein N is
W In order to be a set of lines,
the power transfer factors of the line L with respect to the nodes i, j, k,
for the maximum transmission capacity of the line L,
respectively, a maximum allowed probability of the transmission capacity of the line L being out of limit in the forward direction and a maximum allowed probability of the transmission capacity being out of limit in the reverse direction.
2) Detecting infeasible constraints and renewable energy power curtailment, converting the model established in the step 1), establishing a relaxed power system unit combination model based on opportunity constraints, and solving; the method comprises the following specific steps:
2-1) by substitution in formula (16)
Writing the opportunistic constraints (17) - (20) in the model of step 1) into the form of quantiles as follows:
where M is a large positive number, in this example 10, Q (ξ | p) is the p-quantile of the random variable ξ,
to account for the equivalent power transfer factor of line L relative to node j in affine control, M
L And controlling a correction coefficient of the power transfer factor of the branch L for affine control.
Assuming that the joint distribution of renewable energy power over time period t is known, as follows:
wherein the content of the first and second substances,
a random variation of the power available for each renewable energy source over a period of time t,
random variables composed of power output of each renewable energy source in a time period t;
actual renewable energy power in traditional opportunity constrained unit combination without considering renewable energy power abandon
Equal to available renewable energy power
However, the calculation of the quantiles in equations (22) - (24) is based on the assumption that renewable energy sources do not have a power dump, which may result in conventional generator power
There is no feasible solution.
2-2) renewable energy power can be cut down by reducing the quantile on the right of the equations (22) - (24), thereby reducing the risk of down-regulation of backup shortages and transmission blockages. By using
In alternative quantiles (21) to (24)
And introducing relaxation variables in and among the lower modulation use constraint (16) and the transmission power constraints (17) to (18), the following equations (29) to (32) can be obtained:
wherein, drs
t Slack variables in the standby constraints are adjusted for a period of time t,
the relaxation variables in the forward constraint and the reverse constraint of the line transmission capacity in the t period are respectively;
2-3) establishing a relaxed opportunity constraint-based power system unit combination model and solving;
wherein the objective function of the model is equation (33), which is a weighted sum of the minimized relaxation variables to account for generator power
There is no feasible solution case. In the calculation of linear combination
After the quantiles are divided, the following relaxed opportunity constraint-based power system unit combination model can be directly solved by linear programming.
s.t. formulae (6) - (8), (13), (15), (, 29) - (32) and (34)
Wherein the content of the first and second substances,
wherein the content of the first and second substances,
and adjusting the standby weight coefficient and the section risk weight coefficient in the time period t respectively.
Solving the model to obtain
The optimal solution of (2);
3) Determining the electric quantity discarded by each renewable energy source and the active power of each generator to obtain a unit combination result of the power system; the method comprises the following specific steps:
3-1) after solving the electric power system unit combination model based on the opportunity constraint after the relaxation in the step 2-3), the relaxation variables can be passed
Obtaining the constraint condition that the opportunity constraint-based power system unit combination model established in the step 1) has a feasible solution:
if the slack variable drs in the backup constraint is adjusted downward t After the renewable energy is abandoned, in order to make the model of step 1) feasible, the inequality constraint shown in the following formula must be satisfied:
if the relaxation variable is changed
If the value is not zero, the quantile in the line transmission capacity constraint equation (23) satisfies an inequality constraint represented by the following equation (36):
if the relaxation variable
If the number of quantiles is not zero, the quantile in the line transmission capacity constraint equation (24) satisfies an inequality constraint represented by the following equation (37):
the constraints (35) - (37) can be written as shown in the following formula:
wherein Ω is a subscript set of renewable energy sources participating in electricity abandonment, c j ,c k Is a constant coefficient.
3-2) establishing a renewable energy power abandoning scheduling model and solving;
the objective function of renewable energy power curtailment scheduling is to minimize the overall power curtailment penalty cost as shown in the following formula:
the quantile in equation (38) and the objective function in equation (39) are related to the upper limit of renewable energy power
The linear approximation of equations (38) and (39) can be used to obtain a solvable renewable energy curtailment scheduling model whose first and second derivatives of the objective function equation (39) are as follows:
since the second derivative of the objective function (39) is equal to or greater than zero, the power curtailment penalty is related to the upper power limit of the renewable energy source
A convex function of (a). The curtailment penalty in equation (39) is approximated by a linear inequality shown in equation (42) below, according to the nature of the convex function:
by solving the formula (42), the electricity abandon quantity of each renewable energy source in each time period can be obtained
Then, based on the probability distribution of the available power obtained by the probability prediction and the quantiles in the calculation expressions (21) to (24) obtained by solving the expression (42), the constraint expressions (21) to (24) become deterministic linear constraints.
3-3) obtaining the starting and stopping states of each generator in each time period by solving the generator output optimization model shown in the following step 3-2) according to the result of the step 3-2)
And active power
Thereby obtaining the unit combination optimization result of the generator.
The objective function of the optimization model is equation (43), and the constraint equation (44) is used to limit the scheduled output of the renewable energy source to be lower than the upper power limit thereof.
s.t. formulae (6) - (13), (15), (21) - (24) and (44)
Wherein the content of the first and second substances,