CN110797863A - Economic dispatching method considering safety constraints of N-1 and N-2 of power grid - Google Patents

Economic dispatching method considering safety constraints of N-1 and N-2 of power grid Download PDF

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CN110797863A
CN110797863A CN201911008395.9A CN201911008395A CN110797863A CN 110797863 A CN110797863 A CN 110797863A CN 201911008395 A CN201911008395 A CN 201911008395A CN 110797863 A CN110797863 A CN 110797863A
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黄丽平
狄方涛
龙洁
王逸飞
郭俊韬
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Abstract

The application discloses an economic dispatching method considering the safety constraints of a power grid N-1 and a power grid N-2, heavy load lines which are easy to have cascading failures are screened out by carrying out power grid N-1 power flow analysis on an economic dispatching model P0 which does not consider the safety constraints, N-2 fault pairs are formed by the heavy load lines and corresponding branches which are analyzed by the N-1 one by one to generate a new N-2 fault set, then power flow verification is carried out on the fault set based on branch breaking distribution factors to obtain harmful fault scenes, the harmful fault scenes are added to P0 to obtain a new economic dispatching model P1, P1 is updated through continuous verification and re-verification steps until the number of the harmful N-1 and N-2 fault scenes is zero to obtain a final dispatching model P2, a dispatching scheme meeting the criteria of the line N-1 and the N-2 is obtained by solving P2, the further propagation and development of the initial fault of the power grid N-1 are effectively avoided, and the problem that the power grid cascading failure power failure is caused by the fact that the secondary fault is easy to occur on a heavy-load line after the N-1 fault is not considered in the existing economic dispatching method considering the safety constraint of the power grid N-1 is solved.

Description

Economic dispatching method considering safety constraints of N-1 and N-2 of power grid
Technical Field
The application relates to the technical field of economic dispatching of power systems, in particular to an economic dispatching method considering safety constraints of power grids N-1 and N-2.
Background
The economic dispatching is one of the most basic and important problems in the operation of the power system, and the main task of the economic dispatching is to make a power generation plan of a whole-grid thermal power generating unit with the lowest power generation cost on the premise of meeting certain power system safe operation constraints and meet the safe and reliable power utilization requirements of users.
In a conventional economic dispatching method aiming at economic optimization, an operation state of a power grid is generally optimized and adjusted under the condition that a structure state of the power grid is assumed to be unchanged. The optimization result obtained by the method usually utilizes the power carrying capacity of certain branches in the power grid to the maximum extent, and is digitally embodied, namely that certain branches of the power grid in the optimization result are usually adjusted to operate near the operation limit of the certain branches. Such optimization results are possible for research analysis, but if used for practical grid operation adjustment guidance, it is economically redundant and not safe enough. With the increasing frequency of serious natural disasters, information network attacks and other problems, the conventional power system economic dispatching method considering the safety constraint of the power grid N-1 is not enough to ensure the safe operation of the power grid to a certain extent, which causes the attention of the power system industry to multiple faults. However, after the N-1 fault is calculated, the redundant lines of the power grid can have heavy load lines which are easy to have cascading faults, and the faults are caused again. Because the power system comprises a large number of power transmission elements, the multiple fault analysis has the difficulty of dimension disaster, and the research of the multiple fault analysis method and the operation mode which are feasible and can effectively improve the operation safety of the power system has important significance for preventing the power grid blackout accident and ensuring the operation reliability of the power grid. The existing economic dispatching method considering the N-1 safety constraint of the power grid is based on Benders decomposition, the N-1 safety check of the power grid is carried out or a line state indicator is introduced, N groups of line N-1 constraints are directly constructed and added into an economic dispatching model, the method enables the number of constraint conditions of the optimized model to be increased greatly, and the solving difficulty and speed of the model are greatly increased.
Disclosure of Invention
The application provides an economic dispatching method considering power grid N-1 and N-2 safety constraints, which is used for solving the technical problems that the existing economic dispatching method considering power grid N-1 safety constraints does not analyze the faults of a heavy load line after not considering N-1 faults, cascading fault power failure is easy to generate, the reliability is low, the number of constraint conditions of economic dispatching models of the existing method is large, and the solving difficulty and the solving speed influence of the economic dispatching models are increased.
In view of this, the present application provides an economic dispatching method considering the safety constraints of the power grids N-1 and N-2, comprising the following steps:
acquiring network parameters of a power grid, solving an established economic dispatching model P0 without considering fault state constraints, and defining branches for N-1 analysis;
carrying out N-1 fault influence analysis on the branches with the N-1 analysis defined one by one, calculating a first load flow of the rest branches without the N-1 analysis defined, and determining the load rate of the rest branches;
when the remaining branches have heavy load lines, combining the heavy load lines in the remaining branches which are not defined with the N-1 analysis with the branches which are defined with the N-1 analysis one by one to form an N-2 fault pair, wherein the heavy load lines are the branches with the load rate exceeding a first threshold value;
calculating a second load flow of the rest branch of the non-N-2 fault pair, and determining the load rate of the rest branch of the non-N-2 fault pair;
when N-1 harmful fault scenes exist, calculating the number of the N-1 harmful fault scenes, wherein the N-1 harmful fault scenes are scenes enabling the load rate of the residual branches which are not defined with the N-1 analysis to exceed a second threshold value, and the second threshold value is larger than the first threshold value;
when N-2 harmful fault scenes exist, calculating the number of the N-2 harmful fault scenes, wherein the N-2 harmful fault scenes are scenes enabling the load rate of the remaining branches of the non-N-2 fault pairs to exceed a third threshold value;
establishing N-1 harmful fault scene constraints of each N-1 harmful fault scene based on the single branch disconnection distribution factor, and establishing N-2 harmful fault scene constraints of each N-2 harmful fault scene based on the double branch disconnection distribution factor;
adding the N-1 harmful fault scene constraint and the N-2 harmful fault scene constraint into the economic dispatching model P0 to obtain a new economic dispatching model P1;
solving the new economic dispatch model P1;
if the sum of the number of the N-2 harmful fault scenes and the number of the N-1 harmful fault scenes is zero, obtaining a power grid safe and economic dispatching scheme according to a solving result of the new economic dispatching model P1, otherwise, returning to the step to carry out N-1 fault influence analysis on the branches with the defined N-1 analysis one by one, calculating a first power flow of the rest branches without the defined N-1 analysis, determining the load rate of the rest branches, and solving the new economic dispatching model P1 until the sum of the number of the N-2 harmful fault scenes and the number of the N-1 harmful fault scenes is zero.
Optionally, the economic dispatch model P0 is:
Figure BDA0002243451510000031
wherein, ai、biAnd ciThe second, first and constant cost coefficients of the generator set i are respectively; PG (Picture experts group)iThe output of the generator set i is obtained;
Figure BDA0002243451510000032
and
Figure BDA0002243451510000033
respectively representing the upper limit and the lower limit of the allowable output of the generator set i; PLjIs the active power flow through line j; SFj,bNode b, line j power flow distribution factor; KGb,iGenerating a generator association matrix KG for the node, wherein the generator association matrix KG comprises the b-th row elements and the i-th column elements; KDb,dThe b-th row and d-th column elements of the node load incidence matrix KD; KLb,jThe node line association matrix KL has the b th row and j th column elements.
Optionally, the N-2 nuisance fault scenario constraints are:
wherein the content of the first and second substances,after a failure of line p, q, the power flow of line j,
Figure BDA0002243451510000036
for the open distribution factor of the p-line,for the breaking distribution factor, PL, of q linespFor active power flow through line p, PLqIs the active power flow through line q.
Optionally, the N-1 nuisance fault scenario constraints are:
Figure BDA0002243451510000038
wherein the content of the first and second substances,
Figure BDA0002243451510000039
after a fault on line l, the power flow on line j,
Figure BDA00022434515100000310
the distribution factor of the disconnection of the line is l.
Optionally, the new economic dispatch model P1 is:
Figure BDA0002243451510000041
wherein, Δ DdA load shedding variable being the load d; cEENSCost system for cutting loadAnd (4) counting.
Optionally, the first threshold is 0.8.
Optionally, the second threshold and the third preset are both 1.
Optionally, the performing N-1 fault impact analysis on the branches with the N-1 analysis defined one by one, calculating a first power flow of the remaining branches without the N-1 analysis defined, and determining a load rate of the remaining branches specifically includes:
and performing N-1 fault influence analysis on the branches with the N-1 analysis defined one by one based on the single-branch cut-off distribution factor, calculating a first load flow of the rest branches without the N-1 analysis defined, and determining the load rate of the rest branches.
Optionally, the calculation formula of the first power flow is as follows:
Figure BDA0002243451510000042
wherein the content of the first and second substances,
Figure BDA0002243451510000043
the power flow of the line j after the line l has a fault; PLjIs the active power flow through line j;
Figure BDA0002243451510000044
is the breaking distribution factor of the l line; PLlIs the active power flow through line i.
Optionally, the calculating a second power flow of the remaining branch of the non-N-2 fault pair and determining a load rate of the remaining branch of the non-N-2 fault pair specifically include:
calculating a second load flow of the remaining branch of the non-N-2 fault pair based on the double-branch cut-off distribution factor, and determining the load rate of the remaining branch of the non-N-2 fault pair;
the calculation formula of the second power flow is as follows:
Figure BDA0002243451510000045
wherein the content of the first and second substances,the power flow of the line j is obtained after the line p and the line q simultaneously have faults;
Figure BDA0002243451510000047
is the break distribution factor of the p line;
Figure BDA0002243451510000051
is the break distribution factor of q lines; PLjIs the active power flow through line j; PLpIs the active power flow through line p; PLqIs the active power flow through line q.
According to the technical scheme, the embodiment of the application has the following advantages:
the economic dispatching method considering the safety constraints of the power grids N-1 and N-2 comprises the steps of firstly carrying out fault verification on the power grid N-1, calculating the power flow of the rest lines, screening out the heavy-load lines which are easy to generate cascading faults, then combining the heavy-load lines and the branches which are defined for N-1 analysis into N-2 fault pairs one by one, combining the N-2 fault pairs which can cause the power flow of the power grid to exceed the limit and the corresponding lines which generate the power flow to exceed the limit to construct N-2 fault safety constraints, adding the N-2 fault safety constraints into an economic dispatching model P0, effectively avoiding further propagation and development of the initial fault of the power grid N-1, obtaining a new economic dispatching model P1, continuously verifying, adding and verifying steps to update P1, and obtaining a final economic dispatching model P2 until the number of harmful fault scenes is zero, the P2 is solved to obtain a power grid safe and economic dispatching scheme meeting the N-1 and N-2 of the line, and the technical problems that the existing economic dispatching method considering the N-1 safety constraint of the power grid is not considered, the fault of the heavy-load line is not analyzed after the fault of the N-1 is not considered, the cascading failure is easy to generate, the reliability is low, the number of constraint conditions of an economic dispatching model of the existing method is large, the solving difficulty of the economic dispatching model is increased, and the solving speed is influenced are solved.
Drawings
FIG. 1 is a schematic flow chart diagram illustrating an embodiment of an economic dispatch method considering grid N-1 and N-2 safety constraints according to the present disclosure;
FIG. 2 is a topological diagram of an IEEE-RTS79 test system according to an application example of the economic dispatching method considering the safety constraints of the power grids N-1 and N-2 provided by the application.
Detailed Description
In order to make the technical solutions of the present application better understood by those skilled in the art, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments that can be derived by a person skilled in the art from the embodiments given in the present application without making any creative effort shall fall within the protection scope of the present application.
For easy understanding, please refer to fig. 1 and fig. 2, an embodiment of an economic dispatching method considering safety constraints of power grids N-1 and N-2 provided by the present application includes:
step 101, obtaining network parameters of a power grid, solving the established economic dispatching model P0 without considering fault state constraints, and defining branches for N-1 analysis.
It should be noted that, first, the network parameters of the power grid need to be acquired, and the network parameters of the power grid may include: node number, branch number, node numbers corresponding to two sides of the branch, electrical parameters and operation limit values of the branch, cost coefficient of power generation, operation parameters, node numbers of the branch, and active requirements of system load. And establishing an economic dispatching model P0 without considering fault state constraints, defining branches needing N-1 analysis in advance, wherein the branches without N-1 analysis defined are residual branches. The N-1 fault in the power grid means that after any one independent element (a generator, a transmission line, a transformer and the like) in N elements of the power system is cut off due to fault, no power failure of a user due to overload tripping of other lines is caused, the stability of the system is not damaged, and accidents such as voltage breakdown and the like do not occur.
And 102, performing N-1 fault influence analysis on the branches with the N-1 analysis defined one by one, calculating a first load flow of the rest branches without the N-1 analysis defined, and determining the load rate of the rest branches.
It should be noted that the first power flow of the remaining branches not defined with N-1 analysis may be calculated based on a single branch open distribution factor (LODF), where a Line Output Distribution Factor (LODF) refers to a proportional relation value between an increase amount of current (current transfer component) on the remaining branches except the open branch and an original power flow of the disconnected branch when the current injected into the network by a node in the network remains unchanged before and after the cut of the faulty branch of the power grid and the current is a linear element in the network. And (4) carrying out N-1 fault influence analysis on the branches with the N-1 analysis defined one by one based on the single-branch break distribution factor, and calculating the first load flow of the rest branches without the N-1 analysis defined. The disconnection distribution factor of single or multiple branches can be obtained by the following formula:
LODFM,O＝PTDFM,O(E-PTDFO,O)；
PTDFM,O＝XM -1ΦTB0 -1Ψ；
PTDFO,O＝XO -1ΨTB0 -1Ψ；
when N-1 fault analysis is carried out on the preselected lines one by one, the distribution factor of the disconnection of a certain line j to a single line l is obtained by using the formulaAt this time, LODFM,OIs a 1 × 1 vector; xMIs a 1 × 1 vector with the element xjThe reactance of branch j; phi is a node-branch correlation NB multiplied by 1 vector of the branch j, the corresponding position of the branch initial node is +1, the corresponding position of the branch final node is-1, and the rest are 0 elements; psi is a node-branch correlation NB x 1 vector of the branch l, and the meaning of the elements is the same as phi; b is0An NB × NB order susceptance matrix is created for the grid with reactances as branch parameters.
Calculating the breaking distribution factor of line j to line l
Figure BDA0002243451510000071
Then, the power flow of the line j after the line l has a fault is obtained according to the following formula
Figure BDA0002243451510000072
And 103, when the remaining branches have the heavy load lines, combining the heavy load lines in the remaining branches which are not defined with the N-1 analysis with the branches which are defined with the N-1 analysis one by one to form an N-2 fault pair, wherein the heavy load lines are the branches of which the load rate exceeds a first threshold value.
The N-2 fault in the power grid means that after any two independent elements (a generator, a transmission line, a transformer and the like) in N elements of the power system are cut off due to a fault, no power failure of a user due to overload tripping of other lines is caused, the stability of the system is not damaged, and accidents such as breakdown and the like do not occur. If for all lines
Figure BDA0002243451510000074
Where 0.8 is the first threshold, the procedure is concluded, demonstrating that the scheduling scheme meets the N-1 requirements and has no potentially harmful N-2 failures. If there is a line
Figure BDA0002243451510000075
Step 104 is executed next.
And 104, calculating a second load flow of the remaining branch circuit of the non-N-2 fault pair, and determining the load rate of the remaining branch circuit of the non-N-2 fault pair.
And 105, when N-1 harmful fault scenes exist, calculating the number of the N-1 harmful fault scenes, wherein the N-1 harmful fault scenes are scenes enabling the load rate of the residual branches which are not defined to be analyzed by the N-1 to exceed a second threshold, and the second threshold is larger than the first threshold.
And 106, when N-2 harmful fault scenes exist, calculating the number of the N-2 harmful fault scenes, wherein the N-2 harmful fault scenes are scenes enabling the load rate of the remaining branches of the non-N-2 fault pairs to exceed a third threshold value.
It should be noted that, whether an N-2 harmful fault scenario exists is determined, that is, after the power grid N-2 fault is determined, whether a line with a load factor greater than 1 exists in the remaining lines of the power grid, where 1 is a third threshold, and if not, the N-2 harmful fault scenario number Cn2 is made to be 0; if yes, enabling Cn2 to be N-2 harmful fault scenes, namely after the power grid N-2 fails, enabling lines with power flows exceeding the limit in the rest lines of the power grid to form harmful fault pairs with the N-2 line groups.
The line load rate in the rest lines of the power grid exceeds 0.8 after the N-1 fault of the power grid
Figure BDA0002243451510000076
In combination with the N-1 lines to form a potential N-2 fault pair. And analyzing the influence of each N-2 fault according to a double-branch disconnection distribution factor (LODF) on each N-2 fault. The dual branch outage profile factor may be determined from the 3 equations provided in step 102, for example, assuming that line p and line q are a certain N-2 fault pair, when line p and line q are simultaneously disconnected, the outage profile factor of line j for line p and line q, respectively, is determined
Figure BDA0002243451510000081
At this point in step 102, the formula, LODFM,OIs a 2 x 1 vector, the first element represents the distribution factor of line j to line p when line p and line q are simultaneously disconnected
Figure BDA0002243451510000082
The second element represents the distribution factor of the line j to the line q when the line p and the line q are simultaneously disconnected
Figure BDA0002243451510000083
XMIs a 1 × 1 vector with the element xjThe reactance of branch j; phi is a node-branch correlation NB multiplied by 1 vector of the branch j, the corresponding position of the branch starting node is +1, the corresponding position of the branch ending node is-1, and the rest are 0 elements; psi is a node-branch correlation NB x 2 vector of the branches p and q, and the meaning of the elements is the same as phi; b is0Built for electric networks with reactance as a branch parameterNB × NB order susceptance matrix.
When the line p and the line q are simultaneously disconnected, the disconnection distribution factor of the line j to the line p and the line q is obtained
Figure BDA0002243451510000084
Then, the power flow of the line j after the line p and the line q simultaneously have faults is obtained according to the following formula
Figure BDA0002243451510000085
It should be noted that, for the power flow calculated in step 102, it is determined whether an N-1 harmful fault scenario exists, that is, after it is determined that the power grid N-1 has a fault, whether a line with a load rate greater than 1, that is, a second threshold exists in the remaining lines of the power grid, and if not, the N-1 harmful fault scenario Cn1 is made equal to 0; if yes, enabling Cn1 to be N-1 harmful fault scenes, namely after the power grid N-1 fails, enabling lines with power flow exceeding the limit in the rest lines of the power grid to form harmful fault pairs with the N-1 lines.
And 107, establishing N-1 harmful fault scene constraints of each N-1 harmful fault scene based on the single branch disconnection distribution factors, and establishing N-2 harmful fault scene constraints of each N-2 harmful fault scene based on the double branch disconnection distribution factors.
It should be noted that, whether the total number of the N-2 and N-1 fault scenes is 0 is judged, that is, whether Cn2+ Cn1 is 0, if yes, the program is ended, it is proved that the economic dispatching scheme has met the requirements of N-1 and N-2, if not, the N-1 harmful fault scene constraint of each N-1 harmful fault scene is established based on the single branch disconnection distribution factor, and the N-2 harmful fault scene constraint of each N-2 harmful fault scene is established based on the double branch disconnection distribution factor. The N-1 harmful fault scene constraint established based on the single branch disconnection distribution factor is as follows:
the N-2 harmful fault scene constraint established based on the double-branch disconnection distribution factor is as follows:
wherein the content of the first and second substances,after a fault on line l, the power flow on line j,
Figure BDA0002243451510000089
the distribution factor of the disconnection of the line is l.
The N-1 harmful fault scene constraint established based on the single branch disconnection distribution factor is as follows:
Figure BDA0002243451510000091
wherein the content of the first and second substances,
Figure BDA0002243451510000092
after a failure of line p, q, the power flow of line j,
Figure BDA0002243451510000093
for the open distribution factor of the p-line,
Figure BDA0002243451510000094
for the breaking distribution factor, PL, of q linespFor active power flow through line p, PLqIs the active power flow through line q.
And 108, adding the N-1 harmful fault scene constraint and the N-2 harmful fault scene constraint into the economic dispatching model P0 to obtain a new economic dispatching model P1.
It should be noted that the economic dispatch model P0 may specifically be:
Figure BDA0002243451510000095
in the formula, ai、biAnd ciThe second, first and constant cost coefficients of the generator set i are respectively; PG (Picture experts group)iFor the output of the generator set i and for economic regulationA control variable in the degree model;
Figure BDA0002243451510000096
andrespectively representing the upper limit and the lower limit of the allowable output of the generator set i; PLjIs the active power flow through line j; SFj,bThe node b and the line j have power flow distribution factors, namely, active components flowing through the line j when the node b injects unit power; KGb,iAssociating the elements of the b-th row and the i-th column of the matrix KG for the node generator; KDb,dThe b-th row and d-th column elements of the node load incidence matrix KD; KLb,j node line association matrix KL the b th row and j th column elements; KG. The specific definitions of KD and KL are as follows: the node generator association matrix KG is a (NG multiplied by NB) matrix, wherein NG is the total number of thermal power generating units of the system, and NB is the number of nodes of the system; the line of KG corresponds to the node, the column corresponds to the generator, any element KG of itjkThe definition is as follows: KG jk1, the node where the generator k is located is j; KGjk0 indicates that generator k is not at node j. The node generator incidence matrix KD is an (ND multiplied by NB) matrix, wherein ND is the system load number; the rows of KD correspond to nodes, the columns correspond to loads, any element of KDjkThe definition is as follows: KD jk1, the node where the load k is located is j; KDjk0 indicates that the load k is not present at the node j. The node generator incidence matrix KL is an (NL multiplied by NB) matrix, wherein NL is the number of system lines; KL has a row corresponding to a node, a column corresponding to a line, and any element KLjkThe definition is as follows: KL jk1, meaning that line k is associated with node j and its direction is away from the node; KLjk-1, meaning that line k is associated with node j and it points to a node; KLjk0 indicates that line k is not associated with node j. PD (photo diode)dIs the active demand of load d.Is the maximum power transfer capacity of line j.
Adding the N-1 harmful fault scene constraint and the N-2 harmful fault scene constraint into the established economic dispatching model P0, wherein the obtained new economic dispatching model P1 specifically comprises the following steps:
Figure BDA0002243451510000102
wherein, Δ DdA load shedding variable being the load d; cEENSThe load shedding cost coefficient is a relatively large constant, so that the load shedding is avoided as much as possible by the optimization result. Introducing variable Δ DdAnd the model can be guaranteed to have solutions under various fault scenes.
And 109, solving a new economic dispatching model P1, when the sum of the number of the N-2 harmful fault scenes and the number of the N-1 harmful fault scenes is zero, taking a dispatching scheme corresponding to the solution of the new economic dispatching model P1 as a target power grid safe economic dispatching scheme, and when the sum of the number of the N-2 harmful fault scenes and the number of the N-1 harmful fault scenes is not zero, returning to the steps 102 to 109 until the sum of the number of the N-2 harmful fault scenes and the number of the N-1 harmful fault scenes is zero.
It should be noted that, the optimization solver solution model P1 may be called, after the model P1 is solved, if the sum of the number of N-2 harmful fault scenes and the number of N-1 harmful fault scenes is zero, a power grid safe and economic dispatching scheme is obtained according to the solution result of the new economic dispatching model P1, otherwise, the steps 102 to 109 are returned until the sum of the number of N-2 harmful fault scenes and the number of N-1 harmful fault scenes is zero, and the dispatching scheme corresponding to the solution result of the new economic dispatching model P1 is used as the power grid safe and economic dispatching scheme when the sum of the number of N-2 harmful fault scenes and the number of N-1 harmful fault scenes is zero.
The economic dispatching method considering the safety constraints of the power grids N-1 and N-2 provided in the embodiment of the application screens out heavy-load lines which are easy to have cascading failures by carrying out power grid N-1 power flow analysis on an economic dispatching model P0 which does not consider the safety constraints, forms N-2 failure pairs with corresponding branches analyzed by the N-1 one by one to generate a new N-2 failure set, carries out power flow verification on the failure set based on branch disconnection distribution factors to obtain harmful failure scenes, adds the harmful failure scenes to P0 to obtain a new economic dispatching model P1, updates P1 by continuous verification and addition re-verification steps until the number of the harmful N-1 and N-2 failure scenes is zero to obtain a final dispatching model P2, solves P2 to obtain a dispatching scheme which can meet the criteria of the line N-1 and the N-2, the further propagation and development of the initial fault of the power grid N-1 are effectively avoided, and the problem that the power grid cascading failure power failure is caused by the fact that the secondary fault is easy to occur on a heavy-load line after the N-1 fault is not considered in the existing economic dispatching method considering the safety constraint of the power grid N-1 is solved.
Referring to fig. 2 and tables 1 to 6, in order to more specifically describe that the economic dispatching method considering the safety constraints of the power grids N-1 and N-2 provided in the embodiment of the present application can effectively improve the safety of power dispatching, taking an improved IEEE-RTS79 test system as an example, the economic dispatching method considering the safety constraints of the power grids N-1 and N-2 provided in the embodiment of the present application is used to optimize power dispatching of the test system. Node test system node 13 is defined as a balanced node. Table 1, table 2, table 3 list the parameters required for step 101 in the previous method example, respectively. Table 4 is a comparison of results of the scheduling schemes obtained by the economic scheduling method considering the security constraints of the power grid N-1 and N-2 and the conventional economic scheduling method provided in the embodiment of the present application.
The IEEE-RTS79 test system in the present example has a total of 38 branches, a split system of branches L11, thus excluding L11 when performing the N-1 test analysis. And for 37 lines, the lines are disconnected one by one, and then the load flow distribution condition of the rest lines of the power grid after each line is disconnected is calculated and analyzed. When the scheduling result obtained by the traditional scheduling method is used for N-1 fault analysis, the line overload is generated for 2 times in total, and the method comprises the following steps: when the line L10 is disconnected, the load factor of the line L5 in the rest lines is 1.55, which greatly exceeds the operation limit of the line; when the line L17 is disconnected, the load factor of the line L3 in the remaining lines is 1.007, which also exceeds the line operation limit. And secondly, 13 heavy-load lines with the load rate exceeding 0.8 in the rest lines of the power grid after each N-1 fault. When the scheduling result obtained by the invention is used for analyzing the N-1 fault, the N-1 fault of each line and no overload generated by the rest lines of the power grid are generated, and the scheduling result meets the requirement of the N-1 standard. Secondly, after each N-1 fault, the load rate of the heavy load lines exceeding 0.8 in the rest lines of the power grid is only 5 times, and compared with the traditional scheduling scheme, the load rate is reduced by half. These two schemes, specifically reloading the line number and its load, are listed in table 5.
The heavy haul line pairs given in Table 5 were each individually subjected to N-2 analysis. Obviously, in the economic dispatching method considering the safety constraints of the power grid N-1 and N-2 in the embodiment of the application, in the 5 pairs of N-2 fault detection given in the table 5, the power flow of the remaining lines of the power grid does not exceed the operation limit. For the conventional economic dispatch scheme, 13 pairs of N-2 fault pair analyses are given for table 5, and a total of 10 line overloads occur, with the results shown in table 6.
According to the analysis, the economic dispatching method considering the safety constraints of the power grid N-1 and N-2 can effectively improve the safety of power dispatching.
TABLE 1
Figure BDA0002243451510000121
Figure BDA0002243451510000131
TABLE 2
Figure BDA0002243451510000132
Figure BDA0002243451510000151
TABLE 3
Figure BDA0002243451510000152
TABLE 4
Figure BDA0002243451510000161
Figure BDA0002243451510000171
TABLE 5
Figure BDA0002243451510000172
TABLE 6
Figure BDA0002243451510000182
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims (10)

1. An economic dispatching method considering safety constraints of N-1 and N-2 of a power grid is characterized by comprising the following steps:
acquiring network parameters of a power grid, solving an established economic dispatching model P0 without considering fault state constraints, and defining branches for N-1 analysis;
carrying out N-1 fault influence analysis on the branches with the N-1 analysis defined one by one, calculating a first load flow of the rest branches without the N-1 analysis defined, and determining the load rate of the rest branches;
when the remaining branches have heavy load lines, combining the heavy load lines in the remaining branches which are not defined with the N-1 analysis with the branches which are defined with the N-1 analysis one by one to form an N-2 fault pair, wherein the heavy load lines are the branches with the load rate exceeding a first threshold value;
calculating a second load flow of the remaining branch of the non-N-2 fault pair, and determining the load rate of the remaining branch of the non-N-2 fault pair;
when N-1 harmful fault scenes exist, calculating the number of the N-1 harmful fault scenes, wherein the N-1 harmful fault scenes are scenes enabling the load rate of the residual branches which are not defined with the N-1 analysis to exceed a second threshold value, and the second threshold value is larger than the first threshold value;
when N-2 harmful fault scenes exist, calculating the number of the N-2 harmful fault scenes, wherein the N-2 harmful fault scenes are scenes enabling the load rate of the remaining branches of the non-N-2 fault pairs to exceed a third threshold value;
establishing N-1 harmful fault scene constraints of each N-1 harmful fault scene based on the single-branch on-off distribution factors, and establishing N-2 harmful fault scene constraints of each N-2 harmful fault scene based on the double-branch on-off distribution factors;
adding the N-1 harmful fault scene constraint and the N-2 harmful fault scene constraint into the economic dispatching model P0 to obtain a new economic dispatching model P1;
solving the new economic dispatch model P1;
if the sum of the number of the N-2 harmful fault scenes and the number of the N-1 harmful fault scenes is zero, obtaining a power grid safe and economic dispatching scheme according to a solving result of the new economic dispatching model P1, otherwise, returning to the step to carry out N-1 fault influence analysis on the branches with the N-1 analysis defined one by one, calculating a first power flow of the rest branches without the N-1 analysis defined, determining the load rate of the rest branches, and solving the new economic dispatching model P1 until the sum of the number of the N-2 harmful fault scenes and the number of the N-1 harmful fault scenes is zero.
2. The branch circuit breaking distribution factor consideration-based power grid safety and economy scheduling method according to claim 1, wherein the economy scheduling model P0 is:
Figure FDA0002243451500000021
wherein, ai、biAnd ciThe second, first and constant cost coefficients of the generator set i are respectively; PG (Picture experts group)iThe output of the generator set i is obtained;and
Figure FDA0002243451500000023
respectively representing the upper limit and the lower limit of the allowable output of the generator set i; PLjIs the active power flow through line j; SFj,bNode b, line j power flow distribution factor; KGb,iAssociating the elements of the b-th row and the i-th column of the matrix KG for the node generator; KDb,dThe b-th row and d-th column elements of the node load incidence matrix KD; KLb,jThe node line association matrix KL has the b th row and j th column elements.
3. The branch circuit breaking distribution factor consideration-based power grid safety and economy scheduling method according to claim 2, wherein the N-2 harmful fault scenario constraints are:
Figure FDA0002243451500000024
wherein the content of the first and second substances,
Figure FDA0002243451500000025
after a failure of line p, q, the power flow of line j,for the open distribution factor of the p-line,
Figure FDA0002243451500000027
for the breaking distribution factor, PL, of q linespFor active power flow through line p, PLqIs the active power flow through line q.
4. The branch circuit breaking distribution factor consideration-based power grid safety and economy scheduling method according to claim 3, wherein the N-1 harmful fault scenario constraints are:
Figure FDA0002243451500000028
wherein the content of the first and second substances,
Figure FDA0002243451500000029
after a fault on line l, the power flow on line j,
Figure FDA00022434515000000210
is the breaking distribution factor of the l lines.
5. The branch circuit breaking distribution factor consideration-based power grid safety and economy scheduling method according to claim 4, wherein the new economy scheduling model P1 is:
Figure FDA0002243451500000031
wherein, Δ DdA load shedding variable being the load d; cEENSIs the load shedding cost factor.
6. The branch cut distribution factor-based grid safety and economy scheduling method according to claim 1, wherein the first threshold is 0.8.
7. The branch circuit breaking distribution factor-based grid safety and economy scheduling method according to claim 6, wherein the second threshold and the third preset are both 1.
8. The grid safety and economic dispatching method based on branch circuit breaking distribution factor consideration as claimed in claim 1, wherein the N-1 fault impact analysis is performed on the branches with N-1 analysis defined one by one, the first load flow of the remaining branches without N-1 analysis defined is calculated, and the load rate of the remaining branches is determined, specifically comprising:
and carrying out N-1 fault influence analysis on the branches with the N-1 analysis defined one by one based on the single-branch cut-off distribution factor, calculating a first load flow of the rest branches without the N-1 analysis defined, and determining the load rate of the rest branches.
9. The branch circuit breaking distribution factor consideration-based power grid safety and economy scheduling method according to claim 1, wherein the calculation formula of the first power flow is as follows:
Figure FDA0002243451500000032
wherein the content of the first and second substances,
Figure FDA0002243451500000033
the power flow of the line j after the line l has a fault; PLjIs the active power flow through line j;
Figure FDA0002243451500000034
is the breaking distribution factor of the l line; PLlIs the active power flow through line i.
10. The grid safety and economic dispatching method based on branch circuit breaking distribution factor consideration as claimed in claim 1, wherein the calculating of the second power flow of the remaining branches of the non-N-2 fault pairs and the determining of the load ratios of the remaining branches of the non-N-2 fault pairs specifically comprises:
calculating a second load flow of the remaining branch of the non-N-2 fault pair based on the double-branch cut-off distribution factor, and determining the load rate of the remaining branch of the non-N-2 fault pair;
the calculation formula of the second power flow is as follows:
Figure FDA0002243451500000041
wherein the content of the first and second substances,
Figure FDA0002243451500000042
the power flow of the line j is obtained after the line p and the line q simultaneously have faults;
Figure FDA0002243451500000043
is the break distribution factor of the p lines;
Figure FDA0002243451500000044
is the break distribution factor of q lines; PLjIs the active power flow through line j; PLpIs the active power flow through line p; PLqIs the active power flow through line q.
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