CN110556824A - Power transmission capacity improving method based on bus splitting - Google Patents
Power transmission capacity improving method based on bus splitting Download PDFInfo
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- CN110556824A CN110556824A CN201910786754.7A CN201910786754A CN110556824A CN 110556824 A CN110556824 A CN 110556824A CN 201910786754 A CN201910786754 A CN 201910786754A CN 110556824 A CN110556824 A CN 110556824A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
Abstract
The embodiment of the invention discloses a transmission capacity improving method based on bus splitting, which is used for determining the most serious fault needing to be brought into a maximum transmission capacity model of a reference mode; solving a maximum power transmission capacity model in a reference mode according to the expected fault section set psi; determining whether the solving result of the maximum power transmission capacity model in the reference mode meets the N-1 safety requirement of the alternating current power flow; judging whether the maximum power transmission capacity model meets the maximum power transmission capacity requirement in a reference mode; disconnecting the corresponding line according to the most serious fault, and solving a maximum power transmission capacity model based on bus splitting operation; and determining whether the bus splitting optimization result meets the N-1 safety requirement of the alternating current power flow, and judging whether the maximum power transmission capacity model based on the bus splitting operation meets the maximum power transmission capacity requirement. According to the embodiment of the invention, the bus splitting is added as a regulation and control means, so that the optimal splitting scheme of the bus is determined, the transmission capacity is improved, and the power supply of a target area is ensured.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to a method for improving power transmission capacity based on bus splitting.
Background
the method has the advantages that the transmission capacity of the power network is improved on the premise of meeting safety constraints, the method is an important way for guaranteeing power supply and clean energy consumption, and an important means for promoting full competition among market main bodies in the power market environment is provided.
the method for calculating the power transmission capacity mainly comprises a distribution factor method, a repeated power flow method, a continuous power flow method and an optimal power flow method. The distribution factor can conveniently reflect the influence of injection power change and line outage on the tidal current of the critical section, has obvious speed advantage when being used for calculating the power transmission capacity, but can change along with the change of operation conditions such as a power grid structure and the like. And (4) gradually increasing the load of the target area by a repeated load flow method, and repeatedly performing complete load flow calculation until the key constraint reaches the boundary. And starting from the reference power flow by the continuous power flow rule, and gradually determining the maximum load increase value of the target area corresponding to the key constraint boundary through estimation-correction calculation. The distributed factor method, the repeated power flow method and the continuous power flow method can only calculate the power transmission capacity result under the determined condition of the power grid, and the space for further improving the power transmission capacity by adopting measures such as optimizing the output of a unit cannot be considered. The optimal power flow rule can fully exploit the effects of various regulation and control means and determine the maximum power transmission capacity of the power grid meeting various safety and stability constraints under different operation conditions.
At present, the electric load of most areas is in a rapid increase stage, and the situation that the planning and construction of a power grid lags behind the load increase exists in local areas. At the moment, the requirement of the transmission capacity of the target area cannot be met by a conventional operation optimization means, and under the condition, the method for improving the transmission capacity by properly arranging the bus splitting operation and changing the connection mode of the power grid is a quick, effective and low-cost method. The bus splitting is widely applied in the fields of electricity purchasing cost optimization, static stability margin improvement, short-circuit current limitation and the like. The method for searching bus splitting through an enumeration method can be used for eliminating line overload, but the enumeration amount of the method is large, and an optimal scheme cannot be found by matching with other adjusting means. The optimization model of the line and bus operation with the aim of lowest average load rate has the following problems: the influence on the transmission capacity in the power grid is only a certain key fault section, the average load rate of a large number of lines is reduced comprehensively, the capacity of reducing the load rate of the key section is weakened, and the N-1 safety of the system is not considered by the model. The way of building the split model for all the buses in the system faces the problem of dimension disaster as the system scale increases.
According to experience, the bus on the two sides of the line forming the key section is split, and the split operation is a direct choice for eliminating section constraint and improving the power transmission capacity. However, it is still a complex optimization problem to be studied how to distribute the elements connected to the buses to maximize the power supply capability of the target area by specifically selecting which bus to split.
disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a transmission capacity improving method based on bus splitting.
In order to solve the above problems, the present invention provides a method for improving power transmission capacity based on bus splitting, which comprises the following steps:
S11, setting an expected fault section set psi as an empty set;
S12, performing N-1 safety scanning by adopting AC power flow, determining the most serious fault needing to be included in the maximum transmission capacity model of the reference mode, and adding the most serious fault section into the set expected fault section set psi;
s13, solving a maximum power transmission capacity model in a reference mode according to the predicted fault section set psi;
S14, performing N-1 safety scanning by adopting AC power flow, determining whether the solving result of the maximum transmission capacity model in the reference mode meets the N-1 safety requirement of the AC power flow, if so, entering S15, otherwise, updating the set psi of the expected fault sections, and continuing to S13;
s15, judging whether the maximum transmission capacity model in the reference mode meets the maximum transmission capacity requirement, if so, ending the process, otherwise, entering S16;
s16, disconnecting the corresponding line according to the most serious fault, and solving a maximum transmission capacity model based on bus splitting operation;
s17, performing N-1 safety scanning by adopting AC power flow, determining whether a bus splitting optimization result meets the N-1 safety requirement of the AC power flow, if so, entering S18, otherwise, updating the set psi of the expected fault section, and continuing to S16;
And S18, judging whether the maximum transmission capacity model based on bus splitting operation meets the maximum transmission capacity requirement, if so, ending the process, otherwise, updating the bus to be split, and continuing S16.
the method for solving the maximum transmission capacity model in the reference mode according to the predicted fault section set psi comprises the following steps:
In the reference mode, the maximum transmission capacity model takes the maximum available load of a target area as a target function:
Wherein phi represents a target area node set, and P Di is the active load of a node i;
a direct current flow equation under a maximum transmission capacity model in a reference mode:
P＝B0θ (2)
b 0 is a network susceptance matrix, P is a node injection active vector, and theta is a node voltage phase angle vector;
The output of the unit needs to be controlled and adjusted within an allowable range, and an adjustment equation is as follows:
PG,min≤PG≤PG,max (3)
wherein P G,min is the lower limit of the output adjustment of the unit, P G,max is the upper limit of the output adjustment of the unit, and P G is the output vector of the unit;
The active power flowing through each operating branch is within the thermal stability limit, which is as follows:
-PL,max≤PL≤PL,max (4)
Wherein P L,max is the branch active power thermal stability limit, and P L is the branch tide vector;
Adding fault section constraints according to safety check scanning results
-Ph,max≤LODFh,kPk+Ph≤Ph,max,(h,k)∈Ψ (5)
Ψ represents the set of critical fault sections and LODF h,k is the line outage transfer factor.
the LODF h,k was calculated as follows:
the power transfer distribution factor PTDF s,r,h which reflects the relation between the power transfer from the node s to the node r and the power change of the branch h is obtained by calculation according to the formula (5),
X is, X ir, X js and X jr are elements in a node reactance matrix X, i is the number of a head end node of the branch h, and j is the number of a tail end node of the branch h;
The line shutdown transfer factor LODF hk is formulated as follows:
Wherein u is the head end node number of the branch k, and v is the tail end node number of the branch k.
The step of disconnecting the corresponding line according to the most serious fault and solving the maximum transmission capacity model based on the bus splitting operation comprises the following steps:
Setting a bus m to be split into a bus m-1 and a bus m-2, representing the condition that a unit i is connected with the bus by eta Gi epsilon {0, 1}, representing the condition that the unit i is connected with the bus m-1 by eta Gi epsilon 0, representing the condition that the unit i is connected with the bus m-2 by eta Gi epsilon 1, representing the condition that a load j is connected with the bus by eta Dj epsilon {0, 1}, representing the condition that the load j is connected with the bus m-1 by eta Dj eta 380, representing the condition that the load j is connected with the bus m-2 by eta Dj eta 1, and corresponding constraint conditions are as follows:
0≤PGi-1≤(1-ηGi)PGmaxi (8)
0≤PGi-2≤ηGiPGmaxi (9)
PGi＝PGi-1+PGi-2 (10)
0≤PDj-1≤(1-ηDj)PDmaxj (11)
0≤PDj-2≤ηDjPDmaxj (12)
PDj＝PDj-1+PDj-2 (13)
The method comprises the following steps that P Gi-1 is the generated power of a unit i injected into a bus m-1, P Gi-2 is the generated power of the unit i injected into a bus m-2, P Gi is the generated power of the unit i, P Gmaxi is the maximum generated power of the unit i, P Dj-1 is the power of a load j connected to the bus m-1, P Dj-2 is the power of the load j connected to the bus m-2, P Dj is the size of the load j, and P Dmaxj is the maximum value of the load j;
The connection situation of the line l connected between the buses m and n is represented by η sl, η sl ═ 0 represents that the head end is connected to the m-1 bus, η sl ═ 1 represents that the head end is connected to the m-2 bus, and the corresponding constraints are:
-(1-ηsl)Pmaxl≤Psl-1≤(1-ηsl)Pmaxl (14)
-ηslPmaxl≤Psl-2≤ηslPmaxl (15)
Psl＝Psl-1+Psl-2 (16)
-ηslM≤δsl-δm1≤ηslM (17)
-(1-ηsl)M≤δsl-δm2≤(1-ηsl)M (18)
Psl＝(δrl-δsl)/xl (19)
Wherein P sl-1 represents the power of the sending end of the branch I connected with the bus M-1, P sl-2 represents the power of the sending end of the branch I connected with the bus M-2, P sl represents the power of the sending end of the branch I, P rl represents the power of the receiving end of the branch I, P maxl represents the maximum transmission power of the branch I, delta m1 represents the phase angle of the split bus M-1, delta m2 represents the phase angle of the split bus M-2, delta sl represents the phase angle of the sending end of the branch I, delta rl represents the phase angle of the receiving end of the branch I, x l represents the reactance value of the branch I, and M represents a larger positive number;
The maximum power transmission capability model based on the split model is formed by the expressions (1), (3), (4) and (5) and the bus split models (8) to (19).
The direct current power flow equation of the formula (2) is replaced by branch power of the formula (19) and node power balance equations (20) - (22) of the original network node and the split node, and the following constraint equations are formed:
the number of the branch power of the split node m-1 is P sk-1, the number of the branch power of the split node m-1 is P rk-1, the number of the branch power of the split node m-1 is P sk-2, the number of the branch power of the split node m-2 is P rk-2, the number of the branch power of the split node m-2 is F m, the number of the branch power of the split node m is T m, the number of the branch power of the split node m is N bus, and the number of the branch power of the split node m is N m.
according to the embodiment of the invention, the most serious fault is determined according to the fault flow scanning, and the most serious fault is considered in a normal mode to carry out the optimal calculation of the maximum transmission capacity. When the transmission capacity cannot meet the load requirement of a target area due to the fact that section safety constraint limits still exist only through optimizing unit output, bus splitting is added to serve as a regulation and control means, first and last nodes of a key section are preferentially selected to serve as alternative splitting nodes, modeling is conducted on a bus splitting mode, a maximum transmission capacity mixed integer linear programming model is constructed on the basis that the number of optimization variables is not increased greatly, and the bus optimal splitting mode and the maximum transmission capacity of the system are determined through model solving.
Compared with the direct current optimal power flow under the normal mode, for each bus to be split, if the number of loads connected with the bus to be split in an original network is n D, the number of sets is n G, the number of branches is n Br, the number of nodes in a target region node set phi is n T, the number of discrete optimization variables added to the model is n D + n G + n Br, the number of continuous optimization variables added is 2+2 (n D + n G + n Br) + n T, the number of the added optimization variables is only related to the number of split nodes, the number of equipment connected with the split nodes and the number of target region nodes, is unrelated to the scale of a power grid, the number of the added optimization variables can be ignored, and the model is a mixed integer linear programming problem.
Drawings
in order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
fig. 1 shows a flow chart of a transmission capacity improving method based on bus splitting in an embodiment of the present invention;
Fig. 2 shows a schematic diagram of a bus bar splitting structure in an embodiment of the present invention.
Detailed Description
the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
According to the bus splitting-based optimal power transmission capacity improving method provided by the embodiment of the invention, when the load requirement of a target area cannot be met due to the fact that the safety constraint of the section still exists only by optimizing the output of the unit, bus splitting is added as a regulation and control means, a bus splitting model is constructed to carry out maximum power transmission capacity optimization calculation, a bus optimal splitting scheme is determined, the power transmission capacity is improved, and the power supply of the target area is ensured.
and determining the most serious fault according to the fault flow scanning, and performing the maximum transmission capacity optimization calculation by considering the most serious fault in a normal mode. When the transmission capacity cannot meet the load requirement of a target area due to the fact that section safety constraint limits still exist only through optimizing unit output, bus splitting is added to serve as a regulation and control means, first and last nodes of a key section are preferentially selected to serve as alternative splitting nodes, modeling is conducted on a bus splitting mode, a maximum transmission capacity mixed integer linear programming model is constructed on the basis that the number of optimization variables is not increased greatly, and the bus optimal splitting mode and the maximum transmission capacity of the system are determined through model solving.
specifically, fig. 1 shows a flow chart of a transmission capacity improving method based on bus splitting in the embodiment of the present invention, which specifically includes the following steps:
s11, setting an expected fault section set psi as an empty set;
S12, performing N-1 safety scanning by adopting AC power flow, determining the most serious fault needing to be included in the maximum transmission capacity model of the reference mode, and adding the most serious fault section into the set expected fault section set psi;
s13, solving a maximum power transmission capacity model in a reference mode according to the predicted fault section set psi;
In the reference mode, the maximum transmission capacity model takes the maximum available load of a target area as a target function:
Wherein phi represents a target area node set, and P Di is the active load of a node i;
A direct current flow equation under a maximum transmission capacity model in a reference mode:
P＝B0θ (2)
b 0 is a network susceptance matrix, P is a node injection active vector, and theta is a node voltage phase angle vector;
the output of the unit needs to be controlled and adjusted within an allowable range, and an adjustment equation is as follows:
PG,min≤PG≤PG,max (3)
wherein P G,min is the lower limit of the output adjustment of the unit, P G,max is the upper limit of the output adjustment of the unit, and P G is the output vector of the unit;
the active power flowing through each operating branch is within the thermal stability limit, which is as follows:
p L,max is more than or equal to P L is more than or equal to P L,max (4), wherein P L,max is a branch active power thermal stability limit value, and P L is a branch current vector;
Adding fault section constraints according to safety check scanning results
-Ph,max≤LODFh,kPk+Ph≤Ph,max,(h,k)∈Ψ (5)
Ψ represents the set of critical fault sections and LODF h,k is the line outage transfer factor.
LODF h,k was calculated as follows:
the power transfer distribution factor PTDF s,r,h which reflects the relation between the power transfer from the node s to the node r and the power change of the branch h is obtained by calculation according to the formula (5),
x is, X ir, X js and X jr are elements in a node reactance matrix X, i is the number of a head end node of the branch h, and j is the number of a tail end node of the branch h;
the line shutdown transfer factor LODF h,k is formulated as follows:
wherein u is the head end node number of the branch k, and v is the tail end node number of the branch k.
s14, performing N-1 safety scanning by adopting AC power flow, determining whether the solving result of the maximum transmission capacity model in the reference mode meets the N-1 safety requirement of the AC power flow, if so, entering S15, and if not, entering S12, updating the set psi of the expected fault sections and continuing to S13;
s15, judging whether the maximum transmission capacity model in the reference mode meets the maximum transmission capacity requirement, if so, ending the process, otherwise, entering S16;
in particular, line splitting is not the preferred strategy for operating mode scheduling. In order to fully utilize the operated equipment in the power grid and ensure the reliability of the operation of the power grid, it is often desirable to be able to keep the full-wiring operation of the power grid. And (4) the maximum transmission capacity model takes the maximum load available in the target area as an objective function when the bus splitting operation is not considered. That is, steps S11 to S15 first realize the solution and determination in the reference method, and when the reference method is not satisfied, the bus split model is constructed.
s16, disconnecting the corresponding line according to the most serious fault, and solving a maximum transmission capacity model based on bus splitting operation;
bus connection modes (double bus connection, single bus section with bypass, 3/2 connection) which are common in the power transmission network can be operated in a split mode, and the bus connection mode is represented as a double bus model shown in fig. 2 in the embodiment of the invention.
setting the bus m to be split into a bus m-1 and a bus m-2, representing the condition that a unit i is connected with the bus by eta Gi epsilon {0, 1}, representing the condition that the unit i is connected with the bus m-1 by eta Gi eta 0, representing the unit i is connected with the bus m-2 by eta Gi eta 1, representing the condition that a load j is connected with the bus by eta Dj epsilon {0, 1}, representing the condition that the load j is connected with the bus m-1 by eta Dj eta 0, representing the condition that the load j is connected with the bus m-2 by eta D j eta 1, and corresponding constraint conditions are as follows:
0≤PGi-1≤(1-ηGi)PGmaxi (8)
0≤PGi-2≤ηGiPGmaxi (9)
PGi＝PGi-1+PGi-2 (10)
0≤PDj-1≤(1-ηDj)PDmaxj (11)
0≤PDj-2≤ηDjPDmaxj (12)
PDj＝PDj-1+PDj-2 (13)
the method comprises the following steps that P Gi-1 is the generated power of a unit i injected into a bus m-1, P Gi-2 is the generated power of the unit i injected into a bus m-2, P Gi is the generated power of the unit i, P Gmaxi is the maximum generated power of the unit i, P Dj-1 is the power of a load j connected to the bus m-1, P Dj-2 is the power of the load j connected to the bus m-2, P Dj is the size of the load j, and P Dmaxj is the maximum value of the load j;
The connection situation of the line l connected between the buses m and n is represented by η sl, η sl ═ 0 represents that the head end is connected to the m-1 bus, η sl ═ 1 represents that the head end is connected to the m-2 bus, and the corresponding constraints are:
-(1-ηsl)Pmaxl≤Psl-1≤(1-ηsl)Pmaxl (14)
-ηslPmaxl≤Psl-2≤ηslPmaxl (15)
Psl＝Psl-1+Psl-2(16)
-ηslM≤δsl-δm1≤ηslM (17)
-(1-ηsl)M≤δsl-δm2≤(1-ηsl)M (18)
Psl＝(δrl-δsl)/xl(19)
wherein P sl-1 represents the power of the sending end of the branch I connected with the bus M-1, P sl-2 represents the power of the sending end of the branch I connected with the bus M-2, P sl represents the power of the sending end of the branch I, P rl represents the power of the receiving end of the branch I, P maxl represents the maximum transmission power of the branch I, delta m1 represents the phase angle of the split bus M-1, delta m2 represents the phase angle of the split bus M-2, delta sl represents the phase angle of the sending end of the branch I, delta rl represents the phase angle of the receiving end of the branch I, x l represents the reactance value of the branch I, and M represents a larger positive number;
the maximum power transmission capability model based on the split model is formed by the expressions (1), (3), (4) and (5) and the bus split models (8) to (19).
the dc power flow equation of equation (2) is replaced by the branch power of equation (19) and the node power balance equations (20) - (22) of the original network node and the split node, forming the following constraint equation:
the number of the branch power of the split node m-1 is P sk-1, the number of the branch power of the split node m-1 is P rk-1, the number of the branch power of the split node m-1 is P sk-2, the number of the branch power of the split node m-2 is P rk-2, the number of the branch power of the split node m-2 is F m, the number of the branch power of the split node m is T m, the number of the branch power of the split node m is N bus, and the number of the branch power of the split node m is N m.
S17, carrying out N-1 safety scanning by adopting AC power flow, determining whether the bus splitting optimization result meets the N-1 safety requirement of the AC power flow, if so, entering S18, and if not, entering S19;
s18, judging whether the maximum transmission capacity model based on bus splitting operation meets the maximum transmission capacity requirement, if so, ending the process, otherwise, entering S20;
s19, updating the set psi of the predicted fault sections, and re-entering S16 to solve;
s20, updating the bus to be split, and re-entering S16 to solve;
and (6) ending.
in summary, the embodiment of the invention determines the most serious fault according to the fault flow scanning, and performs the maximum power transmission capability optimization calculation by considering the most serious fault in the normal mode. When the transmission capacity cannot meet the load requirement of a target area due to the fact that section safety constraint limits still exist only through optimizing unit output, bus splitting is added to serve as a regulation and control means, first and last nodes of a key section are preferentially selected to serve as alternative splitting nodes, modeling is conducted on a bus splitting mode, a maximum transmission capacity mixed integer linear programming model is constructed on the basis that the number of optimization variables is not increased greatly, and the bus optimal splitting mode and the maximum transmission capacity of the system are determined through model solving.
compared with the direct current optimal power flow under the normal mode, for each bus to be split, if the number of loads connected with the bus to be split in the original network is n D, the number of sets is n G, the number of branches is n Br, the number of nodes in a target region node set phi is n T, the number of discrete optimization variables added to the model is n D + n G + n Br, the number of continuous optimization variables added is 2+2 (n D + n G + n Br) + n T, the number of the added optimization variables is only related to the number of split nodes, the number of equipment connected with the split nodes and the number of target region nodes, is unrelated to the power grid scale, the number of the added optimization variables can be ignored, the model is a mixed integer linear problem, and the hidden integer linear method can be used for solving the problem
in addition, the method for improving the transmission capacity based on bus splitting provided by the embodiment of the invention is described in detail, a specific example is applied in the method for explaining the principle and the implementation mode of the invention, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (5)
1. A transmission capacity improving method based on bus splitting is characterized by comprising the following steps:
s11, setting an expected fault section set psi as an empty set;
S12, performing N-1 safety scanning by adopting AC power flow, determining the most serious fault needing to be included in the maximum transmission capacity model of the reference mode, and adding the most serious fault section into the set expected fault section set psi;
s13, solving a maximum power transmission capacity model in a reference mode according to the predicted fault section set psi;
s14, performing N-1 safety scanning by adopting AC power flow, determining whether the solving result of the maximum transmission capacity model in the reference mode meets the N-1 safety requirement of the AC power flow, if so, entering S15, and if not, entering S12, updating the set psi of the expected fault sections and continuing to S13;
S15, judging whether the maximum transmission capacity model in the reference mode meets the maximum transmission capacity requirement, if so, ending the process, otherwise, entering S16;
s16, disconnecting the corresponding line according to the most serious fault, and solving a maximum transmission capacity model based on bus splitting operation;
s17, performing N-1 safety scanning by adopting AC power flow, determining whether a bus splitting optimization result meets the N-1 safety requirement of the AC power flow, if so, entering S18, and if not, updating the set psi of the expected fault section and continuing to S16;
And S18, judging whether the maximum transmission capacity model based on bus splitting operation meets the maximum transmission capacity requirement, if so, ending the process, otherwise, updating the bus to be split and continuing to S16.
2. The bus bar splitting-based transmission capacity improving method according to claim 1, wherein the solving of the maximum transmission capacity model in the reference mode according to the set Ψ of the expected fault sections comprises:
in the reference mode, the maximum transmission capacity model takes the maximum available load of a target area as a target function:
wherein phi represents a target area node set, and P Di is the active load of a node i;
A direct current flow equation under a maximum transmission capacity model in a reference mode:
P＝B0θ (2)
B 0 is a network susceptance matrix, P is a node injection active vector, and theta is a node voltage phase angle vector;
the output of the unit needs to be controlled and adjusted within an allowable range, and an adjustment equation is as follows:
PG,min≤PG≤PG,max (3)
wherein P G,min is the lower limit of the output adjustment of the unit, P G,max is the upper limit of the output adjustment of the unit, and P G is the output vector of the unit;
the active power flowing through each operating branch is within the thermal stability limit, which is as follows:
-PL,max≤PL≤PL,max (4)
Wherein P L,max is the branch active power thermal stability limit, and P L is the branch tide vector;
adding fault section constraints according to safety check scanning results
-Ph,max≤LODFh,kPk+Ph≤Ph,max,(h,k)∈Ψ (5)
Ψ represents the set of critical fault sections and LODF h,k is the line outage transfer factor.
3. the bus bar splitting-based power transmission capacity improving method according to claim 2, wherein the LODF h,k is calculated as follows:
the power transfer distribution factor PTDF s,r,h which reflects the relation between the power transfer from the node s to the node r and the power change of the branch h is obtained by calculation according to the formula (5),
X is, X ir, X js and X jr are elements in a node reactance matrix X, i is the number of a head end node of the branch h, and j is the number of a tail end node of the branch h;
the line shutdown transfer factor LODF h,k is calculated as follows:
wherein u is the head end node number of the branch k, and v is the tail end node number of the branch k.
4. the method according to claim 3, wherein the breaking of the corresponding line according to the most serious fault and the solving of the maximum transmission capacity model based on the bus splitting operation comprise:
setting a bus m to be split into a bus m-1 and a bus m-2, representing the condition that a unit i is connected with the bus by eta Gi epsilon {0, 1}, representing the condition that the unit i is connected with the bus m-1 by eta Gi epsilon 0, representing the condition that the unit i is connected with the bus m-2 by eta Gi epsilon 1, representing the condition that a load j is connected with the bus by eta Dj epsilon {0, 1}, representing the condition that the load j is connected with the bus m-1 by eta Dj eta 380, representing the condition that the load j is connected with the bus m-2 by eta Dj eta 1, and corresponding constraint conditions are as follows:
0≤PGi-1≤(1-ηGi)PGmaxi (8)
0≤PGi-2≤ηGiPGmaxi (9)
PGi＝PGi-1+PGi-2 (10)
0≤PDj-1≤(1-ηDj)PDmaxj (11)
0≤PDj-2≤ηDjPDmaxj (12)
PDj＝PDj-1+PDj-2 (13)
the method comprises the following steps that P Gi-1 is the generated power of a unit i injected into a bus m-1, P Gi-2 is the generated power of the unit i injected into a bus m-2, P Gi is the generated power of the unit i, P Gmaxi is the maximum generated power of the unit i, P Dj-1 is the power of a load j connected to the bus m-1, P Dj-2 is the power of the load j connected to the bus m-2, P Dj is the size of the load j, and P Dmaxj is the maximum value of the load j;
The connection situation of the line l connected between the buses m and n is represented by η sl, η sl ═ 0 represents that the head end is connected to the m-1 bus, η sl ═ 1 represents that the head end is connected to the m-2 bus, and the corresponding constraints are:
-(1-ηsl)Pmaxl≤Psl-1≤(1-ηsl)Pmaxl (14)
-ηslPmaxl≤Psl-2≤ηslPmaxl (15)
Psl＝Psl-1+Psl-2 (16)
-ηslM≤δsl-δm1≤ηslM (17)
-(1-ηsl)M≤δsl-δm2≤(1-ηsl)M (18)
Psl＝(δrl-δsl)/xl (19)
wherein P sl-1 represents the power of the sending end of the branch I connected with the bus M-1, P sl-2 represents the power of the sending end of the branch I connected with the bus M-2, P sl represents the power of the sending end of the branch I, P rl represents the power of the receiving end of the branch I, P maxl represents the maximum transmission power of the branch I, delta m1 represents the phase angle of the split bus M-1, delta m2 represents the phase angle of the split bus M-2, delta sl represents the phase angle of the sending end of the branch I, delta rl represents the phase angle of the receiving end of the branch I, x l represents the reactance value of the branch I, and M represents a larger positive number;
the maximum power transmission capability model based on the split model is formed by the expressions (1), (3), (4) and (5) and the bus split models (8) to (19).
5. The method for improving power transmission capacity based on bus splitting according to claim 4, wherein the DC power flow equation of the formula (2) is replaced by branch power of the formula (19) and node power balance equations (20) - (22) of the original network node and the splitting node, and the following constraint equations are formed:
the number of the branch power of the split node m-1 is P sk-1, the number of the branch power of the split node m-1 is P rk-1, the number of the branch power of the split node m-1 is P sk-2, the number of the branch power of the split node m-2 is P rk-2, the number of the branch power of the split node m-2 is F m, the number of the branch power of the split node m is T m, the number of the branch power of the split node m is N bus, and the number of the branch power of the split node m is N m.
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