CN102163846A - 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 is the area power grid network reconfiguration method of target to fall damage and load balancing

Technical field

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

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 be according to the different load level, 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 the economy and the fail safe of operation of power networks with lower cost, is regional power grid scheduling auxiliary decision-making support system important component part.Expansion day by day along with scale of power, 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 pressing for 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 optimal problem in essence, finds the solution comparatively complicated.In order to adapt to on-the-spot actual needs, need research how in acceptable computation time, in solution space, to search for, to approach locally optimal solution or even globally optimal solution as far as possible.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 Optimization Model and algorithm all need to consider to fall to decrease 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, proposing a kind of is the area power grid network reconfiguration method of target to fall damage and load balancing.The present invention can consider to fall to decrease 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, this method can restrain in less iterations, can obtain the optimum topological structure of electrical network fast.

Of the present invention is the area power grid network reconfiguration method of target to fall damage and load balancing, it is characterized in that, this method comprises: at first the electric network synthetic impedance model and the electric network synthetic index of falling damage and load balancing taken all factors into consideration in definition, derivation obtains putting into operation under the electric network synthetic impedance model or cut-offs electric network synthetic index change amount estimation equation that branch road causes on the loop then, on the first two steps basis, adopt the branch road exchange process to carry out the area power grid network reconfiguration, 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, carry out aforesaid operations repeatedly, set of fingers is cut-off in continual renovation, till electric network synthetic index change amount is less than certain threshold value; Promptly obtain the optimum topological structure of electrical network.

Said method can may further comprise the steps:

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

2) based on the electric network synthetic impedance model and the electric network synthetic index of step 1), 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 to decrease and the overall target change amount estimation equation of load balancing, and put into operation branch road of electrical network constitutes the overall target change amount estimation equation that loop causes, is used for the area power grid network reconfiguration;

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

Characteristics of the present invention and benefit thereof

The present invention proposes a kind of is the area power grid network reconfiguration method of target to fall damage and load balancing, 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 electric network synthetic index change amount estimation, guaranteeing that per step puts into operation or cut-offs electric network synthetic index that dataway operation causes descends maximumly, realizes promptly that per step operation descends to decrease and the comprehensive optimum of load balancing.This heuritic approach can restrain in less iterations, can obtain the optimum topological structure of electrical network fast.

The present invention can take all factors into consideration to fall in restructuring procedure and decreases 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 a method overall procedure block diagram of the present invention;

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

Embodiment

What the present invention proposed decreases and load balancing is that the area power grid network reconfiguration method of target reaches embodiment in conjunction with the accompanying drawings and is described in detail as follows to fall:

Method of the present invention comprises: at first the electric network synthetic impedance model and the electric network synthetic index of falling damage and load balancing taken all factors into consideration in definition, derivation obtains putting into operation under the electric network synthetic impedance model or cut-offs electric network synthetic index change amount estimation equation that branch road causes on the loop then, on the first two steps basis, adopt the branch road exchange process to carry out the area power grid network reconfiguration, 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, carry out aforesaid operations repeatedly, set of fingers is cut-off in continual renovation, till electric network synthetic index change amount is less than certain threshold value; Promptly obtain the optimum topological structure of electrical network.

Electrical network loop in the inventive method as shown in Figure 1, among the figure, (a) electrical network is a Single-ring network, be that a loop is only arranged in the electrical network, the outer radial branch road equivalence of loop is the load of node on the loop, establishes and removes total n node on the 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 per 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; This method may further comprise the steps:

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

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

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

Wherein, positive integer i is a branch number in the electrical network, n _bBe branch road quantity in the electrical network, C _iThe comprehensive impedance of branch road i in the expression electrical network, Z _iAnd I _ImaxImpedance and the maximum current of representing branch road i in the electrical network respectively, 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:

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

Wherein, P is the electric network synthetic index, n _bBe branch road quantity in the 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 the electric network synthetic impedance model and the electric network synthetic index of step 1), 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 to decrease and the overall target change amount estimation equation of load balancing, and put into operation branch road of electrical network constitutes the overall target change amount estimation equation that loop causes, is used for the area power grid network reconfiguration; Specifically comprise:

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

A. electrical network is a Single-ring network, be that a loop is only arranged in the electrical network, the outer radial branch road equivalence of loop is the load of node on the loop, if remove total n node on the 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 per 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:

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

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

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

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

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

The expression electrical network cut-offs the electric network synthetic index change amount that k bar branch road causes on the loop, 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 that two end nodes on the loop, and n+1 represents branch road quantity on the loop;

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

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

Wherein,

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

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

3) based on step 2) overall target change amount estimation equation, adopt the branch road exchange process to carry out the area power grid network reconfiguration, 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 the ε general desirable 0～0.001;

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

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

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

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

Branch road i carries out following operation respectively among the pair set M:

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

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

(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 constitutes loop, and establishing the set of fingers of forming this loop is L;

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

(363) make after selecting to cut-off among the set L and the branch road of electric network synthetic index change amount minimum be made as numbering jmin; Jmin cut-offs with branch road, recovers radial electrical network;

(364) distribute with trend in the 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 added up:

(37) judge to move back among the fortune set of fingers M whether still have branch road, if change (35), otherwise change (38);

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

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

Claims (5)

1. one kind is the area power grid network reconfiguration method of target to fall damage and load balancing, it is characterized in that, this method comprises: at first the electric network synthetic impedance model and the electric network synthetic index of falling damage and load balancing taken all factors into consideration in definition, derivation obtains putting into operation under the electric network synthetic impedance model or cut-offs electric network synthetic index change amount estimation equation that branch road causes on the loop then, on the first two steps basis, adopt the branch road exchange process to carry out the area power grid network reconfiguration, 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, carry out aforesaid operations repeatedly, set of fingers is cut-off in continual renovation, till electric network synthetic index change amount is less than certain threshold value; Promptly obtain the optimum topological structure of electrical network.

2. the method for claim 1 is characterized in that, this method may further comprise the steps:

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

2) based on the electric network synthetic impedance model and the electric network synthetic index of step 1), 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 to decrease and the overall target change amount estimation equation of load balancing, and put into operation branch road of electrical network constitutes the overall target change amount estimation equation that loop causes, is used for the area power grid network reconfiguration;

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

3. method according to claim 1 is characterized in that described step 1) specifically comprises following:

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

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

Wherein, positive integer i is a branch number in the electrical network, n _bBe branch road quantity in the electrical network, C _iThe comprehensive impedance of branch road i in the expression electrical network, Z _iAnd I _ImaxImpedance and the maximum current of representing branch road i in the electrical network respectively, 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:

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

Wherein, P is the electric network synthetic index, n _bBe branch road quantity in the 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. method according to claim 1 is characterized in that described step 2) specifically comprise following:

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

A. electrical network is a Single-ring network, be that a loop is only arranged in the electrical network, the outer radial branch road equivalence of loop is the load of node on the loop, if remove total n node on the 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 per 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:

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

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

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

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

Wherein, k represents on the loop branch road that cut-off number, The expression electrical network cut-offs the electric network synthetic index change amount that k bar branch road causes on the loop, 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 that two end nodes on the loop, and n+1 represents branch road quantity on the loop;

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

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

Wherein,

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

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

5. method according to claim 1 is characterized in that described step 3) specifically may further comprise the steps:

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

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

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

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

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

Branch road i carries out following operation respectively among the pair set M:

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

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

(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 constitutes loop, and establishing the set of fingers of forming this loop is L;

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

(363) make after selecting to cut-off among the set L and the branch road of electric network synthetic index change amount minimum be made as numbering jmin; Jmin cut-offs with branch road, recovers radial electrical network;

(364) distribute with trend in the 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 added up:

(37) judge to move back among the fortune set of fingers M whether still have branch road, if change (35), otherwise change (38);

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

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

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