CN111711185B - Day safety checking and blocking management method based on linearized alternating current power flow - Google Patents

Abstract

The invention relates to a safety check and blocking management method for an electric power system, which comprises the steps of establishing a linearized alternating current power flow model, establishing and solving a daily safety check model and establishing and solving a daily blocking management model. Firstly, an alternating current power flow model is established according to various operation constraints of a power system, and the alternating current power flow is approximated to a linear power flow model through a series of approximation means such as Taylor expansion. And then, establishing a daily safety check model on the basis of the alternating current power flow by adopting an optimization algorithm based on feasibility detection, checking whether a feasible scheduling solution exists under a bid power plan of a certain unit, and judging the safety and reliability of the system according to the feasible scheduling solution. And finally, establishing a detailed daily congestion management model by taking the minimum adjustment cost as a target and taking the linearized alternating current flow as a constraint, and providing an efficient solving algorithm to convert the problem into a linear programming model, thereby ensuring the rapidity and the high efficiency of congestion adjustment.

Description

Day safety checking and blocking management method based on linearized alternating current power flow

Technical Field

The invention relates to a day safety checking and blocking management method for a power system, in particular to a day safety checking and blocking management method based on linearized alternating current power flow, and belongs to the technical field of energy economy calculation.

Background

With the continuous promotion of the reform of the electric power market, the electric power industry gradually introduces market competition to reduce cost, improve efficiency and promote the long-term stable development of an electric power system. However, the more competitive power market environment also introduces more uncertainty, making the power flow in the grid heavy and the manner of power flow variable, which is a serious challenge to grid safety. Security checking and blocking management techniques are powerful tools to address this challenge. The aim of safety check and block management is to judge whether the safety and reliability of system operation can be ensured under the current power generation plan; if the system cannot be controlled, how to effectively control the generator and the load enables the short-term operation of the system to have certain safety and reliability margins, and meanwhile, effective information is provided for the long-term investment planning of the system. In short term, blocking management needs to make a fair trade-reducing plan and new adjustment criteria, so that optimal safe and economic dispatching of the power system is realized, and safe and reliable operation of the system is guaranteed; in the long term, congestion management should provide incentives for long term health development of the system through price signals.

The direct current power flow analysis in the traditional safety check algorithm cannot consider power loss and voltage change, and the reliability of the check result is difficult to ensure. The load flow calculation analysis aiming at the scheduling plan is relied on, and key information such as reactive power, voltage plan and the like is lacked in the load flow calculation, so that great difficulty is brought to the load flow analysis and subsequent security check. Meanwhile, the traditional blocking management algorithm depends on the nonlinear alternating current optimal power flow problem, the solution is difficult, the convergence is difficult to ensure, the algorithm robustness is poor, and an effective adjustment result is difficult to provide. Aiming at the problem, an optimization algorithm based on feasibility detection is adopted in the invention, and the safety check is modeled into a feasibility detection problem. Specifically, on the basis of the active power of a given generator set, a reactive power plan of the generator set is regarded as an optimization variable, and whether a feasible reactive power generation plan exists under the operation condition is found, so that various safety constraints of the system are met, and the safety check of the system is completed. In addition, the invention provides a linear approximation method of the alternating current power flow, which increases the consideration of power loss and voltage change compared with the traditional direct current power flow, changes the original nonlinear constraint into linear constraint compared with the traditional alternating current power flow, and embeds the linear constraint into the blocking management model, thereby greatly improving the solving efficiency and robustness of the problem and providing an effective and reliable adjustment result.

Disclosure of Invention

The invention aims to provide a method for day safety checking and blocking management of an electric power system, which is provided on the basis of considering linear approximate alternating current power flow and improves the accuracy of results.

The invention provides a day safety checking and blocking management method based on linearized alternating current power flow, which comprises the following steps: (1) establishing a linearized alternating current power flow model

First, a linearized network power flow model is introduced. In the power network, the model for accurately describing the power flow distribution is an alternating current power flow model, wherein the active and reactive power flows on one branch (i, j) are described as follows.

Due to the phase angle difference theta between two nodes_ij1 while the node voltage amplitude v ≈ 1.0p.u., the partial expressions in equations (1) and (2) may be approximated as follows:

substituting equations (3) and (4) into equations (1) and (2) can obtain the following branch power flow equation:

wherein the content of the first and second substances,

and

representing active and reactive power losses on the branch. In equations (5) and (6), the square v of the voltage amplitude is expressed²When considered as one variable, both equations (5) and (6) are linear equations. However, the only non-linear term in the power flow equation exists in the branch loss

And

expressions (7) and (8) of (a), here, a further linearized approximation can be made in the manner of a taylor expansion approximation. By branch active loss

For example, suppose we know the initial power flow state θ of the system_ij,0And v_ij,0Then, then

Middle firstItem(s)

The following expression can be written:

wherein, theta_ij-θ_ij,00 and treat it as a variable to perform Taylor expansion and retain the first order term:

can be seen as being approximated

Is a linear equation.

In the same way, the method for preparing the composite material,

second item of (1)

The approximation can also be made by means of taylor expansion as follows:

to this end, the active loss of the line

Approximated as a linearized expression. Similarly, reactive loss of the line

It can also be approximated as a linear expression as follows.

Defining the square term of the voltage

The complete linearized power flow equation can be written as the following expression:

(2) establishing a day safety check model

On the basis of a refined alternating current power flow model, various constraints which need to be met by a power generation plan in security check are defined.

Node power balance constraint: for a certain node in the power grid, the power injected into the node is equal to the power flowing out of the node. The injected power is equal to the power of the generator connected to the node minus the node load, and the outflow power is equal to the line power connected to the node plus the loss power of the node admittance.

Wherein, P_GkIndicating the winning active power of unit k, Q_GkRepresenting the reactive power of the unit k, G (i) representing the set of generator units connected to node i; p_DqRepresenting the active power of the load Q, Q_DqRepresenting the reactive power of the load q, d (i) representing the set of loads connected to node i; p_ijRepresenting the active power on the line (i, j), Q_ijRepresents the active power on line (i, j), L represents the set of lines connected to node i; v_iRepresents the square of the voltage magnitude of node i; g_ijIs the portion of the susceptance at position (i, j) in the nodal admittance matrix.

Power constraint of the power transmission line: in ac power flow, there are active and reactive losses on the transmission line, so the line power is related to the voltage at two nodes of the line, the phase angle, the line impedance, etc.

Wherein the content of the first and second substances,

representing the active loss of the line (i, j),

representing the reactive loss of the line (i, j); g_ijSusceptance portion, b, representing the admittance of the line (i, j)_ijA reactive part representing the admittance of the line (i, j); theta_ijRepresenting the difference in the phase angle of the voltage, theta, at the nodes at the two ends of the line (i, j)_ij,0Representing an initial value of a voltage phase angle difference value of nodes at two ends of a line (i, j) in hot start calculation; v. of_iRepresenting the magnitude of the voltage, v, at node i_i,0Indicating the initial value of the voltage amplitude at node i in the warm start calculation.

Line and node security constraints: in the operation of an electric power system, active power flow and reactive power flow of a system circuit are not out of limit, and node voltage amplitude and phase angle are not out of limit, so that the safe and reliable operation of the system is ensured.

P_ij,min≤P_ij≤P_ij,max，Q_ij,min≤Q_ij≤Q_ij,max (25)

θ_i,min≤θ_i≤θ_i,max，v_i,min≤v_i≤v_i,max (26)

Wherein, P_ij,max/P_ij,minRepresents the maximum/minimum active power flow limit of the line (i, j); q_ij,max/Q_ij,minRepresents the maximum/minimum reactive power flow limit of the line (i, j); theta_i,max/θ_i,minRepresents the maximum/minimum voltage phase angle limit of node i; v. of_i,max/v_i,minRepresenting the maximum/minimum voltage magnitude limit of node i.

Safety restraint of the unit: in the day safety checking model, the winning active power P of each unit_GkAt a given value, but with reactive power Q_GkIn order to optimize the participation of the variables in the safety check, the corresponding reactive power output limit needs to be met.

Q_Gk,min≤Q_Gk≤Q_Gk,max (27)

Wherein Q is_Gk,max/Q_Gk,minIndicating max/min of unit iAnd (4) limiting reactive power output.

In a day safety checking model of the electric power market, the winning active power P of each unit_GkAnd each node load P of the power grid_DqIs a given value, and the reactive power Q of the unit_GkLine transmission power P_ijAnd Q_ijAmplitude v of node voltage_iAnd phase angle theta_iWaiting for optimization variables, the task of security check is to judge whether the given P is_GkAnd P_DqUnder the condition, whether the state quantities such as system line power, node voltage and the like can meet the safety requirements or not is judged, and the daily safety check model is expressed in the following mathematical expression:

wherein, I₁～I₁₆Is a positive relaxation vector s⁺And s^-Index set of (2). The daily safety check model is used for checking the active power P in the current unit_GkAnd whether the power and the node voltage of each line can meet the safe and stable operation requirement of the power grid or not. Here, a pair of positive relaxation vectors s is introduced for each constraint⁺And s^-Thus ensuring that the entire model must be feasible. If F_RFTIf 0, indicating the winning active power P in the unit_GkThen, the dispatching mechanism can find a reasonable dispatching solution to enable all constraints of the system to be met, so that the winning plan of the unit can be used for final market transaction through safety check; if F_RFT>0 indicates the winning active power P in the unit_GkAnd then, the dispatching mechanism cannot find a reasonable dispatching solution to enable all constraints of the system to be met, so that the unit bid-winning plan does not pass the safety check, and blocking management must be carried out to adjust the unit bid-winning condition until the safety check passes.

Compared with the traditional safety checking of the day degree, the model (28) adopts an optimization method based on feasibility detection, considers the network loss and the voltage change of the system, can efficiently and reliably provide a more precise checking result, and improves the safety and the reliability of a power grid. Meanwhile, the objective function and the constraint in the model (28) are linear functions, the whole problem is still a linear programming problem, and the problem can be efficiently solved by utilizing mature commercial optimization software in the market, so that the application requirement of rapid online security check can be met.

(3) Establishing a daily block management model

When winning active power P in given unit_GkWhen the system cannot pass the safety check, the scheduling mechanism needs to adjust the winning bid amount of each unit to meet the system operation requirement, and the process is called blocking management. In the process of blocking management, the scheduling mechanism adjusts the bid power of the unit according to the principle that the cost of output adjustment of all units is minimum, and a mathematical model of the scheduling mechanism is shown as follows.

P_ij,min≤P_ij≤P_ij,max，Q_ij,min≤Q_ij≤Q_ij,max (47)

θ_i,min≤θ_i≤θ_i,max，v_i,min≤v_i≤v_i,max (48)

P_Gk,min≤P_Gk+ΔP_Gk≤P_Gk,maxQ_Gk,min≤Q_Gk≤Q_Gk,max (49)

Wherein, Δ P_GkIndicating the active power adjustment value, C, of the unit k_GkRepresents the compensation price for the unit k, which can be generally set as the clearing price of the system; p_Gk,max/P_Gk,minRepresenting the maximum/minimum active power limit for the unit k. In the daily congestion management model, an objective function shows that the objective of a scheduling mechanism is to minimize the adjustment cost of each unit, and constraints show that various safety constraints such as system power balance, network power flow distribution constraints, node voltage safety constraints, unit output constraints and the like must be met in the adjustment process.

The optimal adjustment quantity delta P of each unit is obtained by calculation of the daily blockage management model (40)_GkAnd the scheduling mechanism rearranges the bid-winning plans of each unit according to the bid-winning plans, so that the safety and stability of the system are ensured.

In the aspect of solving the strategy, the constraints of the model (40) are all linear constraints, but the objective function is a nonlinear absolute value function, so that certain difficulty is brought to the problem solving. Similarly, by using the mathematical processing means of the monthly block management model, the auxiliary variable sigma is introduced_iThe objective function is converted into a linear form as follows.

s.t. σ_k≥C_GkΔP_Gk,σ_k≥-C_GkΔE_Gk (51)

Substituting the equations (50) - (51) into the daily blockage management model (40) to replace the objective function, converting the daily blockage management model (40) into a linear programming problem with linear objective function and constraint, and efficiently solving by utilizing mature commercial optimization software in the market, so that the application requirement of rapid online blockage management can be met.

The day safety checking and blocking management technology based on the linearized alternating current power flow has the advantages that: the direct current power flow analysis in the traditional safety check algorithm cannot consider power loss and voltage change, and the reliability of the check result is difficult to ensure. The load flow calculation analysis aiming at the scheduling plan is relied on, and key information such as reactive power, voltage plan and the like is lacked in the load flow calculation, so that great difficulty is brought to the load flow analysis and subsequent security check. Meanwhile, the traditional blocking management algorithm depends on the nonlinear alternating current optimal power flow problem, the solution is difficult, the convergence is difficult to ensure, the algorithm robustness is poor, and an effective adjustment result is difficult to provide. Aiming at the problem, an optimization algorithm based on feasibility detection is adopted in the invention, and the safety check is modeled into a feasibility detection problem. Specifically, on the basis of the active power of a given generator set, a reactive power plan of the generator set is regarded as an optimization variable, and whether a feasible reactive power generation plan exists under the operation condition is found, so that various safety constraints of the system are met, and the safety check of the system is completed. In addition, the invention provides a linear approximation method of the alternating current power flow, which increases the consideration of power loss and voltage change compared with the traditional direct current power flow, changes the original nonlinear constraint into linear constraint compared with the traditional alternating current power flow, and embeds the linear constraint into the blocking management model, thereby greatly improving the solving efficiency and robustness of the problem and providing an effective and reliable adjustment result. In addition, the models are all linear programming models, and the method has the advantages of high efficiency and simplicity in calculation, easiness in engineering practice investment and the like.

Drawings

None.

Detailed Description

The invention provides a day safety checking and blocking management method based on linearized alternating current power flow, which comprises the following steps: (1) establishing a linearized alternating current power flow model

First, a linearized network power flow model is introduced. In the power network, the model for accurately describing the power flow distribution is an alternating current power flow model, wherein the active and reactive power flows on one branch (i, j) are described as follows.

Due to the phase angle difference theta between two nodes_ij1 while the node voltage amplitude v ≈ 1.0p.u., the partial expressions in equations (1) and (2) may be approximated as follows:

substituting equations (3) and (4) into equations (1) and (2) can obtain the following branch power flow equation:

wherein the content of the first and second substances,

and

representing active and reactive power losses on the branch. In equations (5) and (6), the square v of the voltage amplitude is expressed²When considered as one variable, both equations (5) and (6) are linear equations. However, the only non-linear term in the power flow equation exists in the branch loss

And

expressions (7) and (8) of (a), here, a further linearized approximation can be made in the manner of a taylor expansion approximation. By branch active loss

For example, suppose we know the initial power flow state θ of the system_ij,0And v_ij,0Then, then

The first item in (1)

The following expression can be written:

wherein, theta_ij-θ_ij,00 and treat it as a variable to perform Taylor expansion and retain the first order term:

can be seen as being approximated

Is a linear equation.

In the same way, the method for preparing the composite material,

second item of (1)

The approximation can also be made by means of taylor expansion as follows:

to this end, the active loss of the line

Approximated as a linearized expression. Similarly, reactive loss of the line

It can also be approximated as a linear expression as follows.

Defining the square term of the voltage

The complete linearized power flow equation can be written as the following expression:

(2) establishing a day safety check model

On the basis of a refined alternating current power flow model, various constraints which need to be met by a power generation plan in security check are defined.

Node power balance constraint: for a certain node in the power grid, the power injected into the node is equal to the power flowing out of the node. The injected power is equal to the power of the generator connected to the node minus the node load, and the outflow power is equal to the line power connected to the node plus the loss power of the node admittance.

Wherein, P_GkIndicating the winning active power of unit k, Q_GkRepresenting the reactive power of the unit k, G (i) representing the set of generator units connected to node i; p_DqRepresenting the active power of the load Q, Q_DqRepresenting the reactive power of the load q, d (i) representing the set of loads connected to node i; p_ijRepresenting the active power on the line (i, j), Q_ijRepresenting the active power on the line (i, j), L representing the set of lines connected to node iCombining; v_iRepresents the square of the voltage magnitude of node i; g_ijIs the portion of the susceptance at position (i, j) in the nodal admittance matrix.

Power constraint of the power transmission line: in ac power flow, there are active and reactive losses on the transmission line, so the line power is related to the voltage at two nodes of the line, the phase angle, the line impedance, etc.

Wherein the content of the first and second substances,

representing the active loss of the line (i, j),

representing the reactive loss of the line (i, j); g_ijSusceptance portion, b, representing the admittance of the line (i, j)_ijA reactive part representing the admittance of the line (i, j); theta_ijRepresenting the difference in the phase angle of the voltage, theta, at the nodes at the two ends of the line (i, j)_ij,0Representing an initial value of a voltage phase angle difference value of nodes at two ends of a line (i, j) in hot start calculation; v. of_iRepresenting the magnitude of the voltage, v, at node i_i,0Indicating the initial value of the voltage amplitude at node i in the warm start calculation.

Line and node security constraints: in the operation of an electric power system, active power flow and reactive power flow of a system circuit are not out of limit, and node voltage amplitude and phase angle are not out of limit, so that the safe and reliable operation of the system is ensured.

P_ij,min≤P_ij≤P_ij,max，Q_ij,min≤Q_ij≤Q_ij,max (25)

θ_i,min≤θ_i≤θ_i,max，v_i,min≤v_i≤v_i,max (26)

Wherein, P_ij,max/P_ij,minRepresents the maximum/minimum active power flow limit of the line (i, j); q_ij,max/Q_ij,minRepresents the maximum/minimum reactive power flow limit of the line (i, j); theta_i,max/θ_i,minRepresents the maximum/minimum voltage phase angle limit of node i; v. of_i,max/v_i,minRepresenting the maximum/minimum voltage magnitude limit of node i.

Safety restraint of the unit: in the day safety checking model, the winning active power P of each unit_GkAt a given value, but with reactive power Q_GkIn order to optimize the participation of the variables in the safety check, the corresponding reactive power output limit needs to be met.

Q_Gk,min≤Q_Gk≤Q_Gk,max (27)

Wherein Q is_Gk,max/Q_Gk,minRepresenting the maximum/minimum reactive power output limit for unit i.

In a day safety checking model of the electric power market, the winning active power P of each unit_GkAnd each node load P of the power grid_DqIs a given value, and the reactive power Q of the unit_GkLine transmission power P_ijAnd Q_ijAmplitude v of node voltage_iAnd phase angle theta_iWaiting for optimization variables, the task of security check is to judge whether the given P is_GkAnd P_DqUnder the condition, whether the state quantities such as system line power, node voltage and the like can meet the safety requirements or not is judged, and the daily safety check model is expressed in the following mathematical expression:

wherein, I₁～I₁₆Is a positive relaxation vector s⁺And s^-Index set of (2). The daily safety check model is used for checking the active power P in the current unit_GkAnd whether the power and the node voltage of each line can meet the safe and stable operation requirement of the power grid or not. Here, a pair of positive relaxation vectors s is introduced for each constraint⁺And s^-Thus ensuring that the entire model must be feasible. If F_RFTIf 0, indicating the winning active power P in the unit_GkThen, the dispatching mechanism can find a reasonable dispatching solution to enable all constraints of the system to be met, so that the winning plan of the unit can be used for final market transaction through safety check; if F_RFT>0 indicates the winning active power P in the unit_GkAnd then, the dispatching mechanism cannot find a reasonable dispatching solution to enable all constraints of the system to be met, so that the unit bid-winning plan does not pass the safety check, and blocking management must be carried out to adjust the unit bid-winning condition until the safety check passes.

Compared with the traditional safety checking of the day degree, the model (28) adopts an optimization method based on feasibility detection, considers the network loss and the voltage change of the system, can efficiently and reliably provide a more precise checking result, and improves the safety and the reliability of a power grid. Meanwhile, the objective function and the constraint in the model (28) are linear functions, the whole problem is still a linear programming problem, and the problem can be efficiently solved by utilizing mature commercial optimization software in the market, so that the application requirement of rapid online security check can be met.

(3) Establishing a daily block management model

When winning active power P in given unit_GkWhen the system cannot pass the safety check, the scheduling mechanism needs to adjust the winning bid amount of each unit to meet the system operation requirement, and the process is called blocking management. In the process of blocking management, the scheduling mechanism adjusts the bid power of the unit according to the principle that the cost of output adjustment of all units is minimum, and a mathematical model of the scheduling mechanism is shown as follows.

P_ij,min≤P_ij≤P_ij,max，Q_ij,min≤Q_ij≤Q_ij,max (47)

θ_i,min≤θ_i≤θ_i,max，v_i,min≤v_i≤v_i,max (48)

P_Gk,min≤P_Gk+ΔP_Gk≤P_Gk,maxQ_Gk,min≤Q_Gk≤Q_Gk,max (49)

Wherein, Δ P_GkIndicating the active power adjustment value, C, of the unit k_GkRepresents the compensation price for the unit k, which can be generally set as the clearing price of the system; p_Gk,max/P_Gk,minRepresenting the maximum/minimum active power limit for the unit k. Day blocking management mouldIn the type, the objective function shows that the objective of the scheduling mechanism is to minimize the adjustment cost of each unit, and the constraint shows that each safety constraint such as system power balance, network power flow distribution constraint, node voltage safety constraint, unit output constraint and the like must be met in the adjustment process.

The optimal adjustment quantity delta P of each unit is obtained by calculation of the daily blockage management model (40)_GkAnd the scheduling mechanism rearranges the bid-winning plans of each unit according to the bid-winning plans, so that the safety and stability of the system are ensured.

In the aspect of solving the strategy, the constraints of the model (40) are all linear constraints, but the objective function is a nonlinear absolute value function, so that certain difficulty is brought to the problem solving. Similarly, by using the mathematical processing means of the monthly block management model, the auxiliary variable sigma is introduced_iThe objective function is converted into a linear form as follows.

s.t.σ_k≥C_GkΔP_Gk,σ_k≥-C_GkΔE_Gk (51)

Substituting the equations (50) - (51) into the daily blockage management model (40) to replace the objective function, converting the daily blockage management model (40) into a linear programming problem with linear objective function and constraint, and efficiently solving by utilizing mature commercial optimization software in the market, so that the application requirement of rapid online blockage management can be met.

Claims (1)

1. A day safety checking and blocking management method based on linearized alternating current power flow is characterized by comprising the following steps:

(1) establishing a linear alternating current power flow model, wherein in the power network, a model for accurately describing power flow distribution is an alternating current power flow model, and active power flow and reactive power flow on one branch (i, j) are described as follows:

wherein, P_ijRepresenting the active power on the line (i, j), Q_ijRepresenting the reactive power on the line (i, j), g_ijSusceptance portion, b, representing the admittance of the line (i, j)_ijRepresenting the reactive part of the admittance of the line (i, j), θ_ijRepresenting the difference, v, of the phase angles of the voltages at the nodes of the two ends of the line (i, j)_iRepresents the voltage amplitude of the node i;

due to the phase angle difference theta between two nodes_ij< 11 while the node voltage amplitude v ≈ 1.0p.u., the partial expressions in equations (1) and (2) can be approximated as follows:

substituting equations (3) and (4) into equations (1) and (2) can obtain the following branch power flow equation:

wherein the content of the first and second substances,

and

representing the active and reactive power losses in the branch, the square v of the voltage amplitude is expressed in equations (5) and (6)²When the variables are regarded as one variable, the equations (5) and (6) are both linear equations; however, the only non-linear term in the power flow equation exists in the branch loss

And

expressions (7) and (8) of (a), where a further linearized approximation can be made in the manner of a taylor expansion approximation; branch active loss

Given the initial power flow state θ of the known system_ij,0And v_ij,0Then, then

The first item in (1)

The following expression can be written:

wherein, theta_ij-θ_ij,00 and treat it as a variable to perform Taylor expansion and retain the first order term:

can be seen as being approximated

Is a linear equation; in the same way, the method for preparing the composite material,

second item of (1)

The approximation can also be made by means of taylor expansion as follows:

to this end, the active loss of the line

An expression approximated as linearized; similarly, reactive loss of the line

It can also be approximated as a linear expression as follows:

defining the square term of the voltage

The complete linearized power flow equation can be written as the following expression:

wherein, P_ijRepresenting the active power on the line (i, j), Q_ijRepresenting the reactive power on the line (i, j), L representing the set of lines connected to node i, V_iRepresenting the square of the voltage magnitude of node i, G_ijFor the portion of the susceptance at position (i, j) in the nodal admittance matrix, θ_ij,0Initial value, v, representing the difference in the phase angle of the voltage at the nodes of the two ends of the line (i, j) during the warm-start calculation_i,0Representing the initial value of the voltage amplitude of the node i in the hot start calculation;

(2) establishing a daily safety check model, and defining various constraints which need to be met by a power generation plan in safety check on the basis of a refined alternating current power flow model;

node power balance constraint: for a certain node in the power grid, the power injected into the node is equal to the power flowing out of the node; the injected power is equal to the power of a generator connected to a node minus the node load, and the outflow power is equal to the line power connected to the node plus the loss power of the node admittance;

wherein, P_GkIndicating the winning active power of unit k, Q_GkRepresenting the reactive power of the unit k, G (i) representing the set of generator units connected to node i; p_DqRepresenting the active power of the load Q, Q_DqRepresenting the reactive power of the load q, d (i) representing the set of loads connected to node i; p_ijRepresenting the active power on the line (i, j), Q_ijRepresenting the reactive power on line (i, j), L representing the set of lines connected to node i; v_iRepresents the square of the voltage magnitude of node i; g_ijIs the portion of the susceptance at position (i, j) in the nodal admittance matrix;

power constraint of the power transmission line: in alternating current power flow, active loss and reactive loss exist on a power transmission line, so that the line power is related to the voltage of two-point nodes of the line, a phase angle and line impedance factors;

wherein the content of the first and second substances,

representing the active loss of the line (i, j),

representing the reactive loss of the line (i, j); g_ijSusceptance portion, b, representing the admittance of the line (i, j)_ijA reactive part representing the admittance of the line (i, j); theta_ijRepresenting the difference in the phase angle of the voltage, theta, at the nodes at the two ends of the line (i, j)_ij,0Representing an initial value of a voltage phase angle difference value of nodes at two ends of a line (i, j) in hot start calculation; v. of_iRepresenting the magnitude of the voltage, v, at node i_i,0Representing the initial value of the voltage amplitude of the node i in the hot start calculation;

line and node security constraints: in the operation of an electric power system, active power flow and reactive power flow of a system circuit are not out of limit, and node voltage amplitude and phase angle are not out of limit, so that the safe and reliable operation of the system is ensured;

P_ij,min≤P_ij≤P_ij,max，Q_ij,min≤Q_ij≤Q_ij,max (25)

θ_i,min≤θ_i≤θ_i,max，v_i,min≤v_i≤v_i,max (26)

wherein, P_ij,max/P_ij,minRepresents the maximum/minimum active power flow limit of the line (i, j); q_ij,max/Q_ij,minRepresents the maximum/minimum reactive power flow limit of the line (i, j); theta_i,max/θ_i,minRepresents the maximum/minimum voltage phase angle limit of node i; v. of_i,max/v_i,minRepresents the maximum/minimum voltage magnitude limit of node i; safety restraint of the unit: in the day safety checking model, the winning active power P of each unit_GkAt a given value, but with reactive power Q_GkThe optimization variables participate in the safety check, so that corresponding reactive power output limit needs to be met;

Q_Gk,min≤Q_Gk≤Q_Gk,max (27)

wherein Q is_Gk,max/Q_Gk,minRepresenting the maximum/minimum reactive power output limit of the unit i; in a day safety checking model of the electric power market, the winning active power P of each unit_GkAnd each node load P of the power grid_Dq

Is a given value, and the reactive power Q of the unit_GkLine transmission power P_ijAnd Q_ijAmplitude v of node voltage_iAnd phase angle theta_iTo optimize the variables, the task of the security check is to determine that at a given P_GkAnd P_DqUnder the condition, whether the system line power and the node voltage state quantity can meet the safety requirement or not is judged, and the daily safety check model is expressed in the following mathematical expression:

wherein, I₁～I₁₆Is a positive relaxation vector s⁺And s^-The index set of the model is used for checking the active power P of the current unit_GkWhether the power and the node voltage of each line can meet the safe and stable operation requirement of the power grid or not; here, a pair of positive relaxation vectors s is introduced for each constraint⁺And s^-Thus ensuring that the whole model is certainly feasible; if F_RFTIf 0, indicating the winning active power P in the unit_GkThen, the dispatching mechanism can find a reasonable dispatching solution to enable all constraints of the system to be met, so that the winning plan of the unit can be used for final market transaction through safety check; if F_RFT>0 indicates the winning active power P in the unit_GkUnder the condition, the dispatching mechanism cannot find a reasonable dispatching solution to enable all constraints of the system to be met, so that the winning plan of the unit does not pass the safety check and must perform blocking managementThe bid winning condition of the unit is adjusted until the safety check is passed;

compared with the traditional safety checking of the day, the model (28) adopts an optimization method based on feasibility detection, considers the network loss and the voltage change of the system, can efficiently and reliably provide a more precise checking result, and improves the safety and the reliability of a power grid; meanwhile, the objective function and the constraint in the model (28) are linear functions, the whole problem is still a linear programming problem, and the problem can be efficiently solved by utilizing mature commercial optimization software in the market, so that the application requirement of rapid online security check can be met;

(3) establishing a daily block management model

When winning active power P in given unit_GkWhen the system cannot pass the safety check, the scheduling mechanism needs to adjust the winning bid amount of each unit to meet the system operation requirement, and the process is called blocking management; in the process of blocking management, the scheduling mechanism adjusts the bid power of the unit according to the principle that the minimum cost of output adjustment of all units is the minimum, and the mathematical model of the scheduling mechanism is as follows:

P_ij,min≤P_ij≤P_ij,max,Q_ij,min≤Q_ij≤Q_ij,max (47)

θ_i,min≤θ_i≤θ_i,max,v_i,min≤v_i≤v_i,max (48)

P_Gk,min≤P_Gk+ΔP_Gk≤P_Gk,max,Q_Gk,min≤Q_Gk≤Q_Gk,max (49)

wherein, Δ P_GkIndicating the active power adjustment value, C, of the unit k_GkRepresents the compensation price for the unit k, which can be generally set as the clearing price of the system; p_Gk,max/P_Gk,minRepresents the maximum/minimum active power limit for unit k; in the daily blocking management model, an objective function shows that the objective of a scheduling mechanism is to minimize the adjustment cost of each unit, and constraints show that various safety constraints such as system power balance, network power flow distribution constraints, node voltage safety constraints, unit output constraints and the like must be met in the adjustment process;

the optimal adjustment quantity delta P of each unit is obtained by calculation of the daily blockage management model (40)_GkThe scheduling mechanism rearranges the bid-winning plans of each unit according to the bid-winning plans, so that the safety and stability of the system are ensured; in the aspect of solving the strategy, the constraints of the model (40) are linear constraints, but the objective function is a nonlinear absolute value function, so that certain difficulty is brought to the problem solving; similarly, by using the mathematical processing means of the monthly block management model, the auxiliary variable sigma is introduced_iThe objective function is converted to a linear form as follows:

s.t.σ_k≥C_GkΔP_Gk,σ_k≥-C_GkΔE_Gk (51)

substituting the equations (50) - (51) into the daily blockage management model (40) to replace the objective function, converting the daily blockage management model (40) into a linear programming problem with linear objective function and constraint, and efficiently solving by utilizing mature commercial optimization software in the market, so that the application requirement of rapid online blockage management can be met.