CN102163846B - Regional power grid network reconstruction method taking loss reduction and load balancing as targets - Google Patents

Abstract

The invention relates to a regional power grid network reconstruction method taking loss reduction and load balancing as targets and belongs to the field of scheduling operation and control of a power system. The method comprises the following steps of: defining a power grid comprehensive impedance model and a power grid comprehensive index which comprehensively consider the loss reduction and load balancing, and deducing an estimation formula of power grid comprehensive index variation caused by connecting or disconnecting a branch on a loop under the power grid comprehensive impedance model; reconstructing a regional power grid network by a branch exchange method, and estimating the power grid comprehensive index variation caused by disconnecting or connecting the branch by utilizing the power grid comprehensive index variation estimation formula; selecting a branch with maximum absolute value of the power grid comprehensive index variation for connecting, and selecting a branch with minimum power grid comprehensive index variation for disconnecting; and repeatedly executing the operation until the power grid comprehensive index variation is smaller than a fixed threshold value. The method contributes to reducing the loss of a power grid and balancing the transmission power of a transmission line, and better improves the economy and safety of the power grid.

Description

A kind of to fall damage and load balancing as the regional power grid network reconstruction method of target

Technical field

The invention belongs to the dispatching automation of electric power systems technical field, particularly to fall damage and load balancing as the regional power grid network reconstruction field of target.

Background technology

Area power grid has the characteristics of radial open loop operation usually.In order to realize the area power grid economic dispatch, need to be according to the different load level, the interconnection switch in the folding electrical network and block switch to change topological structure of electric, reduce grid loss, eliminate circuit overload, improve the load bus voltage levvl.This process is called network reconfiguration.

Network reconfiguration can be realized with lower cost economy and the fail safe of operation of power networks, is regional power grid scheduling auxiliary decision-making support system important component part.Expanding day along with the electrical network scale, various operational modes are more and more, the optimizing operating mode that tradition relies on artificial experience to carry out can not satisfy the demand of actual electric network, therefore in the urgent need to there being practical algorithm can provide comparatively desirable power system operating mode scheme, with auxiliary electrical network operation managerial decision making.

Network reconfiguration is a mixed integer nonlinear optimization problem in essence, finds the solution comparatively complicated.In order to adapt to on-the-spot actual needs, need research how to search in solution space within acceptable computing time, to approach as far as possible locally optimal solution or even globally optimal solution.The network reconfiguration technology of existing employing traditional mathematics law of planning and intelligent algorithm in various degree have a more problem consuming time.Secondly, network reconfiguration is a multi-objective optimization question, and Optimized model and algorithm all need to consider to fall to damage and load balancing two class targets, and the heuristic search technique in the existing network restructing algorithm can not be considered this two classes optimization aim simultaneously.

Summary of the invention

The objective of the invention is for overcoming the weak point of existing network reconfiguration method, propose a kind of to fall damage and load balancing as the regional power grid network reconstruction method of target.The present invention can consider to fall to damage and load balancing two class targets in optimizing process simultaneously.Provided the electric network synthetic index change amount estimation equation that the electrical network loop cut-offs or the branch road that puts into operation causes, the method can restrain in less iterations, can obtain fast the optimum topological structure of electrical network.

of the present invention to fall damage and load balancing as the regional power grid network reconstruction method of target, it is characterized in that, the method comprises: at first definition considers electric network synthetic impedance model and the electric network synthetic index of falling damage and load balancing, then derive and obtain putting into operation under the electric network synthetic impedance model or cut-off electric network synthetic index change amount estimation equation that branch road causes on loop, on the first two steps bases, adopt the branch exchange method to carry out regional power grid network reconstruction, utilize electric network synthetic index change amount estimation equation to estimate to cut-off or electric network synthetic index change amount that the branch road that puts into operation causes, selection puts into operation the branch road of electric network synthetic index change amount absolute value maximum, and select electric network synthetic index change amount minimum branch breaking, repeatedly carry out aforesaid operations, set of fingers is cut-off in continuous renewal, until electric network synthetic index change amount less than certain threshold value till, namely obtain the optimum topological structure of electrical network.

Said method can comprise the following steps:

1) comprise by the maximum current of grid branch and the impedance structure of grid branch the electric network synthetic impedance model that falls damage and load balancing, and obtain comprising the electric network synthetic index of falling damage and load balancing, damage and load balancing to realize falling of area power grid;

2) based on step 1) electric network synthetic impedance model and electric network synthetic index, comprising of obtaining that the electrical network loop cut-offs that a branch road causes fall by circuit Kirchhoff's current law (KCL) (KCL) and Kirchhoff's second law (KVL) equation inference and damage and the overall target change amount estimation equation of load balancing, and put into operation branch road of electrical network consists of the overall target change amount estimation equation that loop causes, is used for regional power grid network reconstruction;

3) based on step 2) overall target change amount estimation equation, adopt the branch exchange method to carry out regional power grid network reconstruction, obtain the optimum topological structure of area power grid.

Characteristics of the present invention and benefit thereof

The present invention proposes a kind of to fall damage and load balancing as the regional power grid network reconstruction method of target, by electric network synthetic index change amount estimation equation, the electrical network loop is put into operation or cut-offs a branch road and carry out the estimation of electric network synthetic index change amount, guaranteeing that per step puts into operation or cut-offs electric network synthetic index that dataway operation causes descends maximumly, realizes namely that per step operation descends to damage and the comprehensive optimum of load balancing.This heuritic approach can restrain in less iterations, can obtain fast the optimum topological structure of electrical network.

The present invention can consider to fall in restructuring procedure and damages and two targets of load balancing, helps to reduce grid net loss and balanced power line transmission power, better improves electrical network economy and fail safe.

Description of drawings

Fig. 1 is for adopting the electrical network loop schematic diagram of the inventive method;

Fig. 2 is method overall procedure block diagram of the present invention;

Fig. 3 is step 3 of the present invention) the idiographic flow block diagram.

Embodiment

What the present invention proposed damages and load balancing is described in detail as follows as the regional power grid network reconstruction method of target reaches embodiment by reference to the accompanying drawings to fall:

method of the present invention comprises: at first definition considers electric network synthetic impedance model and the electric network synthetic index of falling damage and load balancing, then derive and obtain putting into operation under the electric network synthetic impedance model or cut-off electric network synthetic index change amount estimation equation that branch road causes on loop, on the first two steps bases, adopt the branch exchange method to carry out regional power grid network reconstruction, utilize electric network synthetic index change amount estimation equation to estimate to cut-off or electric network synthetic index change amount that the branch road that puts into operation causes, selection puts into operation the branch road of electric network synthetic index change amount absolute value maximum, and select electric network synthetic index change amount minimum branch breaking, repeatedly carry out aforesaid operations, set of fingers is cut-off in continuous renewal, until electric network synthetic index change amount less than certain threshold value till, namely obtain the optimum topological structure of electrical network.

Electrical network loop in the inventive method as shown in Figure 1, in figure, (a) electrical network is Single-ring network, be that a loop is only arranged in electrical network, the outer radial branch road equivalence of loop is the load of node on loop, establishes except total n node on two end node outer rings, from 1 to n number consecutively, it is 0 and n+1 that loop two end nodes are compiled respectively, and the branch number between every two nodes is taken as the large size in two nodes; (b) voltage difference between electrical network loop two end nodes remains unchanged before and after loop cut-offs branch road; (c) after the electrical network loop cut-off a branch road, each node load electric current remained unchanged.

Overall procedure of the present invention as shown in Figure 2; The method comprises the following steps:

1) comprise by the maximum current of grid branch and the impedance structure of grid branch the electric network synthetic impedance model that falls damage and load balancing, and obtain comprising the electric network synthetic index of falling damage and load balancing; Specifically comprise:

(11) comprise by the maximum current of grid branch and the impedance structure of grid branch the electric network synthetic impedance model that falls damage and load balancing:

$C_i=(w_1{Z}_i+w_2\frac{1}{I_{i\max }^2}),$ i＝1，2，…，n _b (1)

Wherein, positive integer i is branch number in electrical network, n _bBe branch road quantity in electrical network, C _iThe comprehensive impedance of branch road i in the expression electrical network, Z _iAnd I _ImaxThe impedance and the maximum current that represent respectively branch road i in electrical network, w ₁And w ₂Be weight coefficient, satisfy w ₁+ w ₂=1.

(12) according to formula (1), definition electric network synthetic index is the comprehensive impedance of branch road i and the real part of the current squaring product of branch road i, and the electric network synthetic index comprises the index of falling damage and load balancing two aspects:

$P=\underset{i=1}{\overset{n_b}{\mathrm{\&Sigma;}}}\mathrm{Re}\left[C_i{I}_i^2\right]=\underset{i=1}{\overset{n_b}{\mathrm{\&Sigma;}}}\left[{\mathrm{<figure-callout\; id="1"\; label="w"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">w</figure-callout>}}_1\mathrm{Re}\right[Z_i{I}_i^2]+w_2\mathrm{Re}[\frac{I_i^2}{I_{i\max }^2}\left]\right]---\left(2\right)$

Wherein, P is the electric network synthetic index, n _bBe branch road quantity in electrical network, I _iBranch road i electric current in the expression electrical network, C _iBranch road i comprehensive impedance in the expression electrical network, Re represents that plural number gets real part.

2) based on step 1) electric network synthetic impedance model and electric network synthetic index, comprising of obtaining that the electrical network loop cut-offs that a branch road causes fall by circuit Kirchhoff's current law (KCL) (KCL) and Kirchhoff's second law (KVL) equation inference and damage and the overall target change amount estimation equation of load balancing, and put into operation branch road of electrical network consists of the overall target change amount estimation equation that loop causes, is used for regional power grid network reconstruction; Specifically comprise:

(21) electric network synthetic index change amount estimation equation has following hypotheses:

A. electrical network is Single-ring network, be that a loop is only arranged in electrical network, the outer radial branch road equivalence of loop is the load of node on loop, if except total n node on two end node outer rings, from 1 to n number consecutively, it is 0 and n+1 that loop two end nodes are compiled respectively, and the branch number between every two nodes is taken as the large size in two nodes;

B. the voltage difference between electrical network loop two end nodes remains unchanged before and after loop cut-offs branch road;

C. after the electrical network loop cut-off a branch road, each node load electric current remained unchanged;

(22) under above-mentioned hypothesis, based on electric network synthetic impedance model and electric network synthetic index computing formula, obtaining the electrical network loop by circuit KCL and KVL equation inference, to cut-off the electric network synthetic index change amount estimation equation that a branch road causes as follows:

$\mathrm{\&Delta;}{P}_{O,\mathrm{loss}}^k=\mathrm{Re}[\frac{{\mathrm{<figure-callout\; id="11"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{11}\&CenterDot;{\mathrm{<figure-callout\; id="12"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{12}+m_{21}\&CenterDot;{\mathrm{<figure-callout\; id="22"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{22}}{\underset{i=1}{\overset{n+1}{\mathrm{\&Sigma;}}}{C}_i}-\frac{{\mathrm{<figure-callout\; id="11"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{11}\&CenterDot;{\mathrm{<figure-callout\; id="22"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{22}+{\mathrm{<figure-callout\; id="12"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{12}\&CenterDot;m_{21}}{\underset{i=1}{\overset{n+1}{\mathrm{\&Sigma;}}}{C}_i}]---\left(3\right)$

M11, m12, m21, m22 is intermediate variable, expression formula is as follows,

${\mathrm{<figure-callout\; id="11"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{11}=\underset{i=1}{\overset{k-1}{\mathrm{\&Sigma;}}}\left(D_i\underset{j=1}{\overset{i}{\mathrm{\&Sigma;}}}{C}_j\right),$ ${\mathrm{<figure-callout\; id="12"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{12}=\underset{i=1}{\overset{k-1}{\mathrm{\&Sigma;}}}\left(D_i^{*}\underset{j=1}{\overset{i}{\mathrm{\&Sigma;}}}{C}_j\right)$

$m_{21}=\underset{i=k}{\overset{n}{\mathrm{\&Sigma;}}}\left(D_i\underset{j=i+1}{\overset{n+1}{\mathrm{\&Sigma;}}}{C}_j\right),$ ${\mathrm{<figure-callout\; id="22"\; label="m"\; filenames="HDA0000063342440000011.png"\; state="\{\{state\}\}">m</figure-callout>}}_{22}=\underset{i=k}{\overset{n}{\mathrm{\&Sigma;}}}\left(D_i^{*}\underset{j=i+1}{\overset{n+1}{\mathrm{\&Sigma;}}}{C}_j\right)$

Wherein, k represents on loop the branch road that cut-off number,

The expression electrical network cut-offs the electric network synthetic index change amount that on loop, k bar branch road causes, C _iBranch road i comprehensive impedance in the expression electrical network, D _iThe load current of node i on the expression loop,

The load current conjugation of node i on the expression loop, Re represents that plural number gets real part.N represents the number of nodes except two end nodes on loop, and n+1 represents branch road quantity on loop;

(23) under above-mentioned hypothesis, based on electric network synthetic impedance model and electric network synthetic index computing formula, obtain electrical network by circuit KCL and KVL equation inference and put into operation that to consist of the electric network synthetic index change amount estimation equation that Single-ring network causes as follows for branch road:

$\mathrm{\&Delta;}{P}_{C,\mathrm{loss}}^k=-\mathrm{\&Delta;}{P}_{O,\mathrm{loss}}^k---\left(4\right)$

Wherein,

The expression electric network synthetic index change amount that k bar branch road causes on loop that puts into operation,

The expression electrical network cut-offs the electric network synthetic index change amount that on loop, k bar branch road causes.

3) based on step 2) overall target change amount estimation equation, adopt the branch exchange method to carry out regional power grid network reconstruction, obtain the optimum topological structure of area power grid; Its flow process specifically comprises as shown in Figure 3:

(31) set iteration threshold ε, the number between ε general desirable 0～0.001;

(32) build the electric network synthetic impedance model according to formula (1);

(33) electrical network is carried out topological analysis, form the connected graph that is formed by branch road between node and node.

(34) in radial electrical network, the branch road that statistics has been cut-off consists of and moves back fortune set of fingers M; Electric network synthetic index change amount Δ P is set _Totalloss=0;

(35) according to formula (4), calculate the electric network synthetic index change amount that causes after in fortune set of fingers M, each branch road puts into operation of moving back;

In pair set M, branch road i carries out respectively following operation:

(351) branch road i is put into operation, form Single-ring network;

(352) calculate with formula (4) the electric network synthetic index change amount that causes after branch road i puts into operation

(353) branch road i is cut-off, recover radial electrical network;

(36) cause the branch road of electric network synthetic index change amount absolute value maximum after selection puts into operation in the M set, be made as numbering imax; To being numbered the branch road of imax, carry out following operation:

(361) the imax bar branch road that puts into operation consists of loop, and establishing the set of fingers that forms this loop is L;

(362) with the electric network synthetic index change amount that causes after each branch breaking in formula (3) set of computations L, establish and cut-off the electric network synthetic index change amount that branch road j causes and be

(363) make the branch road of electric network synthetic index change amount minimum after selecting to cut-off in set L, be made as numbering jmin; Branch road jmin is cut-off, recover radial electrical network;

(364) distribute with trend in electrical network after the loop trend method calculating topologies change that is applicable to radial electrical network;

(365) branch road imax is deleted from set M;

(366) the branch road imax that puts into operation, and after cut-offfing branch road jmin two steps, operation being finished, electric network synthetic index change amount is

Electric network synthetic index change amount is cumulative:

(37) judgement moves back in fortune set of fingers M whether still have branch road, if turn (35), otherwise turn (38);

(38) moving back in fortune set of fingers M all branch roads always change amount of rear electric network synthetic index that is disposed is Δ P _TotallossIf, | Δ P _Totalloss|≤ε, think that iteration has reached optimum point, turn (39), otherwise, think that the electric network synthetic index still has the possibility of further reduction, turns (34);

(39) after iteration finishes, obtain the optimum topological structure of electrical network after reconstruct.

Claims (5)

1. one kind take fall damage and load balancing as the regional power grid network reconstruction method of target, it is characterized in that, the method comprises: at first definition considers electric network synthetic impedance model and the electric network synthetic index of falling damage and load balancing, then derive and obtain putting into operation under the electric network synthetic impedance model or cut-off electric network synthetic index change amount estimation equation that branch road causes on loop, on the first two steps bases, adopt the branch exchange method to carry out regional power grid network reconstruction, utilize electric network synthetic index change amount estimation equation to estimate to cut-off or electric network synthetic index change amount that the branch road that puts into operation causes, selection puts into operation the branch road of electric network synthetic index change amount absolute value maximum, and select electric network synthetic index change amount minimum branch breaking, repeatedly carry out aforesaid operations, set of fingers is cut-off in continuous renewal, until electric network synthetic index change amount less than certain threshold value till, namely obtain the optimum topological structure of electrical network.
2. 2. the method for claim 1, is characterized in that, the method comprises the following steps:

   1) comprise by the maximum current of grid branch and the impedance structure of grid branch the electric network synthetic impedance model that falls damage and load balancing, and obtain comprising the electric network synthetic index of falling damage and load balancing, damage and load balancing to realize falling of area power grid;

   2) based on step 1) electric network synthetic impedance model and electric network synthetic index, comprising of obtaining that the electrical network loop cut-offs that a branch road causes fall by circuit Kirchhoff's current law (KCL) (KCL) and Kirchhoff's second law (KVL) equation inference and damage and the overall target change amount estimation equation of load balancing, and put into operation branch road of electrical network consists of the overall target change amount estimation equation that loop causes, is used for regional power grid network reconstruction;

   3) based on step 2) overall target change amount estimation equation, adopt the branch exchange method to carry out regional power grid network reconstruction, obtain the optimum topological structure of area power grid.
3. 3. method as claimed in claim 2, is characterized in that, described step 1) specifically comprises following:

   (11) comprise by the maximum current of grid branch and the impedance structure of grid branch the electric network synthetic impedance model that falls damage and load balancing:

   $C_i=\left(w_1{Z}_i{+w}_2\frac{1}{I_{i\max }^2}\right),i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,n_b---\left(1\right)$

   Wherein, positive integer i is branch number in electrical network, n _bBe branch road quantity in electrical network, C _iThe comprehensive impedance of branch road i in the expression electrical network, Z _iAnd I _ImaxThe impedance and the maximum current that represent respectively branch road i in electrical network, w ₁And w ₂Be weight coefficient, satisfy w ₁+ w ₂=1;

   (12) according to formula (1), definition electric network synthetic index is the comprehensive impedance of branch road i and the real part of the current squaring product of branch road i, and the electric network synthetic index comprises the index of falling damage and load balancing two aspects:

   $P=\underset{i=1}{\overset{n_b}{\mathrm{\&Sigma;}}}\mathrm{Re}\left[C_i{I}_i^2\right]=\underset{i=1}{\overset{n_b}{\mathrm{\&Sigma;}}}\left[w_1\mathrm{Re}\right[Z_i{I}_i^2]+w_2\mathrm{Re}[\frac{I_i^2}{I_{i\max }^2}\left]\right]---\left(2\right)$

   Wherein, P is the electric network synthetic index, n _bBe branch road quantity in electrical network, I _iBranch road i electric current in the expression electrical network, C _iBranch road i comprehensive impedance in the expression electrical network, Re represents that plural number gets real part.
4. 4. method as claimed in claim 3, is characterized in that described step 2) specifically comprise following:

   (21) electric network synthetic index change amount estimation equation has following hypotheses:

   A. electrical network is Single-ring network, be that a loop is only arranged in electrical network, the outer radial branch road equivalence of loop is the load of node on loop, if except total n node on two end node outer rings, from 1 to n number consecutively, it is 0 and n+1 that loop two end nodes are compiled respectively, and the branch number between every two nodes is taken as the large size in two nodes;

   B. the voltage difference between electrical network loop two end nodes remains unchanged before and after loop cut-offs branch road;

   C. after the electrical network loop cut-off a branch road, each node load electric current remained unchanged;

   (22) under above-mentioned hypothesis, based on electric network synthetic impedance model and electric network synthetic index computing formula, obtaining the electrical network loop by circuit KCL and KVL equation inference, to cut-off the electric network synthetic index change amount estimation equation that a branch road causes as follows:

   ${\mathrm{\&Delta;P}}_{O,\mathrm{loss}}^k=\mathrm{Re}[\frac{m_{11}\&CenterDot;m_{12}+m_{21}\&CenterDot;m_{22}}{\underset{i=1}{\overset{n+1}{\mathrm{\&Sigma;}}}{C}_i}-\frac{m_{11}\&CenterDot;m_{22}+m_{12}\&CenterDot;m_{21}}{\underset{i=1}{\overset{n+1}{\mathrm{\&Sigma;}}}{C}_i}]---\left(3\right)$

   M11, m12, m21, m22 is intermediate variable, expression formula is as follows,

   $m_{11}=\underset{i=1}{\overset{k-1}{\mathrm{\&Sigma;}}}\left(D_i\underset{j=1}{\overset{i}{\mathrm{\&Sigma;}}}{C}_j\right),$ $m_{12}=\underset{i=1}{\overset{k-1}{\mathrm{\&Sigma;}}}\left(D_i^{*}\underset{j=1}{\overset{i}{\mathrm{\&Sigma;}}}{C}_j\right)$

   $m_{21}=\underset{i=k}{\overset{n}{\mathrm{\&Sigma;}}}\left(D_i\underset{j=i+1}{\overset{n+1}{\mathrm{\&Sigma;}}}{C}_j\right),$ $m_{22}=\underset{i=k}{\overset{n}{\mathrm{\&Sigma;}}}\left(D_i^{*}\underset{j=i+1}{\overset{n+1}{\mathrm{\&Sigma;}}}{C}_j\right)$

   Wherein, k represents on loop the branch road that cut-off number,

   

   The expression electrical network cut-offs the electric network synthetic index change amount that on loop, k bar branch road causes, C _iBranch road i comprehensive impedance in the expression electrical network, D _iThe load current of node i on the expression loop,

   

   The load current conjugation of node i on the expression loop, Re represents that plural number gets real part; N represents the number of nodes except two end nodes on loop, and n+1 represents branch road quantity on loop;

   (23) under above-mentioned hypothesis, based on electric network synthetic impedance model and electric network synthetic index computing formula, obtain electrical network by circuit KCL and KVL equation inference and put into operation that to consist of the electric network synthetic index change amount estimation equation that Single-ring network causes as follows for branch road:

   ${\mathrm{\&Delta;P}}_{C,\mathrm{loss}}^k=-{\mathrm{\&Delta;P}}_{O,\mathrm{loss}}^k---\left(4\right)$

   Wherein,

   

   The expression electric network synthetic index change amount that k bar branch road causes on loop that puts into operation,

   

   The expression electrical network cut-offs the electric network synthetic index change amount that on loop, k bar branch road causes.
5. 5. method as claimed in claim 4, is characterized in that, described step 3) specifically comprises the following steps:

   (31) set iteration threshold ε, ε gets the number between 0～0.001;

   (32) build the electric network synthetic impedance model according to formula (1);

   (33) electrical network is carried out topological analysis, form the connected graph that is formed by branch road between node and node;

   (34) in radial electrical network, the branch road that statistics has been cut-off consists of and moves back fortune set of fingers M; Electric network synthetic index change amount Δ P is set _Totalloss=0;

   (35) according to formula (4), calculate the electric network synthetic index change amount that causes after in fortune set of fingers M, each branch road puts into operation of moving back;

   In pair set M, branch road i carries out respectively following operation:

   (351) branch road i is put into operation, form Single-ring network;

   (352) calculate with formula (4) the electric network synthetic index change amount that causes after branch road i puts into operation

   

   (353) branch road i is cut-off, recover radial electrical network;

   (36) cause the branch road of electric network synthetic index change amount absolute value maximum after selection puts into operation in the M set, be made as numbering imax; To being numbered the branch road of imax, carry out following operation:

   (361) the imax bar branch road that puts into operation consists of loop, and establishing the set of fingers that forms this loop is L;

   (362) with the electric network synthetic index change amount that causes after each branch breaking in formula (3) set of computations L, establish and cut-off the electric network synthetic index change amount that branch road j causes and be

   

   (363) make the branch road of electric network synthetic index change amount minimum after selecting to cut-off in set L, be made as numbering jmin; Branch road jmin is cut-off, recover radial electrical network;

   (364) distribute with trend in electrical network after the loop trend method calculating topologies change that is applicable to radial electrical network;

   (365) branch road imax is deleted from set M;

   (366) the branch road imax that puts into operation, and after cut-offfing branch road jmin two steps, operation being finished, electric network synthetic index change amount is

   

   Electric network synthetic index change amount is cumulative: ${\mathrm{\&Delta;P}}_{\mathrm{totalloss}}={\mathrm{\&Delta;P}}_{\mathrm{totalloss}}+{\mathrm{\&Delta;P}}_{C,\mathrm{loss}}^i+{\mathrm{\&Delta;P}}_{O,\mathrm{loss}}^j;$

   (37) judgement moves back in fortune set of fingers M whether still have branch road, if turn (35), otherwise turn (38);

   (38) moving back in fortune set of fingers M all branch roads always change amount of rear electric network synthetic index that is disposed is Δ P _TotaossIf, | Δ P _Totalloss|≤ε, think that iteration has reached optimum point, turn (39), otherwise, think that the electric network synthetic index still has the possibility of further reduction, turns (34);

   (39) after iteration finishes, obtain the optimum topological structure of electrical network after reconstruct.

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