CN103427484A - Centralized control method of regional power grid spare power automatic switching devices - Google Patents

Abstract

A centralized regional power grid backup and automatic switching control method, according to the characteristics of the closed-loop design and open-loop operation of the regional power grid, according to the backup and automatic switching status, switch status, distribution of power points, distribution of branch points and basic topology information of the power grid, using A method of topology identification forms a power flow matrix with the direction of the power flow as the direction. The matrix describes the real-time topology of the network. When a component fails in the expected accident concentration, the matrix is used to search for the standby self-switching set that should act. Auto-injection for centralized control. The invention overcomes the disadvantages that the traditional backup self-switching will cause unnecessary action delay of the next level of backup self-switching and it is difficult to distinguish the subordinate relationship of the backup self-switching.

Description

A Centralized Control Method for Self-commissioning of Regional Power Grid Standby

Patent field

The invention belongs to the technical field of fault recovery of regional power grid and the technical field of electric power system automation, relates to fault recovery of regional power grid, and specifically relates to a centralized control method for self-switching of regional power grid backup.

Background technique

Electricity plays an important role in the national economy and people's lives, and a power outage due to a fault will bring serious damage to social production and people's lives, so it is imminent to improve the reliability of power supply. my country's regional power grids are different from national grids and provincial power grids in that they are designed in a closed loop and operate radially. When an electrical component fails and quits operation, it will cause a power outage in the downstream non-faulty area. In order to improve the reliability of power supply, a large number of backup power automatic switching devices are installed in the power grid, referred to as standby automatic switching. When the power grid fails and the bus fails, a series of switch actions satisfying the working principle of standby automatic switching will make the backup power supply power to the lost bus. Due to the operation characteristics and the complexity of the structure of the regional power grid, after a fault occurs, multiple buses may be blacked out, which may cause multiple backup and automatic switching actions, but not all of these backup and automatic switching actions are necessary. The more backup and auto-inputs of the action, it may cause further failures, so it is very necessary to consider the combination of backup and auto-injections. The traditional standby automatic switching uses the voltage level to set the action time to realize the action combination of the standby automatic switching. Some unnecessary action delays. In addition, the regional power grid contains a large number of T-connection methods, and sometimes it is difficult to distinguish the subordinate relationship of the standby automatic switching system according to the voltage level.

Contents of the invention

In order to overcome the disadvantages of the traditional standby automatic switching which easily causes unnecessary action delay of the next-level standby automatic switching and the difficulty in distinguishing the subordinate relationship of the standby automatic switching, the present invention proposes a centralized regional power grid standby automatic switching control method. This application specifically adopts the following technical solutions:

A centralized regional power grid equipment self-switching control method, characterized in that the method comprises the following steps:

(1) Monitor the electrical information of the regional power grid, treat the busbar and branch points as nodes, and regard the lines, transformers and bus-tie switches as branches, and establish the network base structure matrix D, standby self-injection state matrix B, and switch state matrix K. Expected accident set matrix F, power point distribution matrix M and branch point distribution matrix T;

(2) Generate power flow direction matrix C according to the established network base structure matrix, standby self-switching state matrix, switch state matrix, power point distribution matrix and branch point distribution matrix;

(3) If a component in the predicted accident set fails, modify the corresponding element in the predicted accident set matrix.

(4) Obtain the set of standby automatic switching after a component in the expected accident set fails:

If a component in the expected accident concentration fails, judge the node conditions at both ends of the component through the power flow matrix, the node where the power flow flows out is the first node, and the node where the power flow flows in is the tail node;

The regional power grid operates in a radial manner, and the power flow flows from the power point to the load node. When a component fails and exits operation, the downstream load node of the component loses power. The power flow matrix describes the directional path of the power flow from the power point to the load node. When a component fails and exits operation, the tail node of the component is used as the starting node, and all nodes read in the power flow matrix are power-off area;

If the nodes contained in the power-off area do not contain branch points, search for the backup auto-input in which only one node on both sides appears in the power-off area in the backup auto-input state matrix, and the voltage level of the searched backup auto-input is the highest The backup self-investment is used as a set of backup self-investment;

If the power-off area contains a branch point, the search area is divided into two parts, and the final set of backup and auto-input is the sum of the search results of these two parts of the area. In the first part, the nodes connected to the branch points are used as the starting nodes, and each starting node reads out the respective downstream nodes, that is, the respective power supply areas, and searches each power supply area separately to obtain the respective backup self-input gather. The search method for a certain power supply area is to search for the backup auto-switch in which only one of the nodes on both sides appears in the power supply area in the backup auto-switch state matrix, and use the backup auto-switch with the highest voltage level among the searched backup auto-switches as Prepare self-injection collection. The second part is the power-off area except the area included in the first part. The search method for this part of the area is to search for the standby automatic switching in which only one of the nodes on both sides appears in this area in the standby automatic switching state matrix. Use the standby automatic switch with the highest voltage level among the searched standby automatic switches as the standby automatic switch set;

(5) Perform power flow calculation on the regional power grid obtained in step (4) after the centralized operation of standby and automatic switching, and judge whether there are lines with current and voltage exceeding the limit. If there is no line with current and voltage exceeding the limit, then output the step (4) For the obtained backup self-switching set, if there are lines with current and voltage exceeding the limit, output the backup self-switching set obtained in step (4) and the information of the out-of-limit line.

The beneficial effects of the present invention are:

The invention discloses a centralized control method for self-commissioning of regional power grid backup. Aiming at the characteristics of closed-loop design and open-loop operation of regional power grids, a topology recognition method is used to form a power flow matrix with the power flow as the direction. The matrix describes The real-time topological structure of the network is used to search for the set of backup auto-initialization that should be acted on, and to perform centralized control on the backup auto-initialization. Overcoming the traditional standby automatic switch using the voltage level to set the action time to realize the action combination of the standby automatic switch, which leads to the fixed logic of the traditional standby automatic switch operation, and there is a fixed time coordination between the upper and lower levels, which will cause the next level of standby automatic switch Unnecessary action delay. In addition, there are a large number of T-connection methods in the regional power grid, and it is sometimes difficult to distinguish the superior-subordinate relationship of backup and automatic switching according to the voltage level.

Description of drawings

Fig. 1 is the flow chart of the centralized regional grid equipment self-switching control method of the present invention;

Figure 2 is a wiring diagram of the regional power grid in normal operation.

Detailed ways

The content of the invention will be further described below in conjunction with the accompanying drawings and examples.

Accompanying drawing 1 shows the flow chart of the centralized regional power grid equipment automatic switching control method of the present invention, a kind of centralized regional grid equipment automatic switching control method, it is characterized in that, described method comprises the following steps:

(1) Monitor the electrical information of the regional power grid, treat the busbar and branch points as nodes, and regard the lines, transformers and bus-tie switches as branches, and establish the network base structure matrix D, standby self-injection state matrix B, and switch state matrix K. Expected accident set matrix F, power point distribution matrix M and branch point distribution matrix T;

Treat busbars and branch points as nodes, and treat lines, transformers, and busbar switches as branches. The basic electrical information that needs to be established in the regional power grid is as follows:

(a) The network-based structure matrix D is an N×N matrix, which describes the potential topology of the regional power grid, that is, when generating the network-based structure matrix, even if the branch switch between two nodes is disconnected, the It is still regarded as a branch and reflected in the network structure matrix D. The network-based structure matrix treats each branch of the regional power grid as an undirected edge. If there is a branch between node i and node j of the regional power grid, then d _ij =d _ji =1, and the other elements are 0. Among them, N is the total number of nodes, d _ij is the element in row i and column j in network-based structure matrix D, and _dji is the element in row j and column i in network-based structure matrix D;

(b) The state matrix B of standby automatic switching is a matrix of B×4, which describes the operation status and electrical information of standby automatic switching, and the number of standby automatic switching. The first two columns are the node numbers on both sides of standby automatic switching; The third column is the working state of the standby automatic switch. If the standby automatic switch is in the closed state, the element is 1, otherwise it is 0; the fourth column is the voltage level of the bus where the standby automatic switch is located;

(c) The switch state matrix K is a K×3 matrix, which describes the operating state of the switch and the number of behavior switches. The first two columns are the node numbers on both sides of the switch, and the third column is the switch state. If the switch In the closed state, the element is 1, otherwise it is 0;

(d) The distribution matrix M of power supply points is a matrix of M×1, which describes the distribution of power supply and the number of behavior nodes. The distribution matrix M of power supply points describes the distribution of power supply points of the regional power grid. , then m _p =1, otherwise m _p =0, where m _p is the element of the pth row in the power point distribution matrix; (e) the branch point distribution matrix T is a T×1 matrix, which describes the branch node Distribution, behavior node number, regional power grid contains a large number of T connection methods, and the power flow of each feeder branch converges and diverges at the branch point. The branch point distribution matrix T describes the distribution of regional power grid branch points. If the regional power grid node q is a branch point, then t _q = 1, otherwise t _q = 0, where t _q is the element of the qth row in the branch point distribution matrix; (f) The expected accident set matrix F is a matrix of F×1, which describes Possible faulty components, F is the number of expected accidental components, if component r is faulty, then f _r =1, otherwise f _r =0, where f _r is the element in row r of the expected accident set matrix.

(2) Generate power flow direction matrix C according to the established network base structure matrix, standby self-switching state matrix, switch state matrix, power point distribution matrix and branch point distribution matrix;

In the centralized regional power grid self-commissioning control method, in the step (2), the power flow matrix describes the directed path of the power flow from the power point to the load node, and the power flow matrix C is composed of the network-based matrix Based on D, the branch of the regional power grid is regarded as a directed edge, and the direction of the directed edge is determined by the flow direction of the branch. If there is a branch between nodes i and j, and the flow direction is determined by i point to j, then c _ij =1, c _ji =0.

This application preferably adopts the following steps to obtain the power flow direction matrix C:

(a) From the switch state matrix K and the standby automatic switching state matrix B, find the switch in the off state and the standby automatic switching in the off state, and find the areas on both sides of the switch in the off state and the standby automatic switching in the off state For grid nodes i and j, set the j element of the i-th row and the i element of the j-th row in the network-based structure matrix D to 0;

(b) Correct the distribution matrix of branch points after the operation state of the regional power grid is changed. If a switch is disconnected, causing the corresponding branch point to change to a common node, then set the corresponding element to 0 in the branch point distribution matrix;

(c) Obtain the node number of the power supply from the distribution matrix M of power supply points, start the search with the power supply point as the starting point, find the i-th row where the power supply node i is located in the network-based structure matrix D, and search for the node in the i-th row j, then keep the j element in the i-th row unchanged in the network-based structure matrix D, and set the i-element in the j-th row to 0, and then use the same method to continue the search by the j node until the end node is searched, that is A node whose line is all 0;

(d) If the end condition is satisfied, the search is completed and the result of the power flow direction matrix C is output; otherwise, go to step (c) to continue the search, wherein the end condition is the number of rows in the power flow direction matrix whose elements are all 0 and the actual The number of grid end nodes is the same.

(3) If a component in the predicted accident set fails, modify the corresponding element in the predicted accident set matrix.

(4) Obtain the set of standby automatic switching after a component in the expected accident set fails:

If a component in the expected accident concentration fails, judge the node conditions at both ends of the component through the power flow matrix, the node where the power flow flows out is the first node, and the node where the power flow flows in is the tail node;

The regional power grid operates in a radial manner, and the power flow flows from the power point to the load node. When a component fails and exits operation, the downstream load node of the component loses power. The power flow matrix describes the directional path of the power flow from the power point to the load node. When a component fails and exits operation, the tail node of the component is used as the starting node, and all nodes read in the power flow matrix are power-off area;

If the nodes contained in the power-off area do not contain branch points, search for the backup auto-input in which only one node on both sides appears in the power-off area in the backup auto-input state matrix, and the voltage level of the searched backup auto-input is the highest The backup self-investment is used as a set of backup self-investment;

If the power-off area contains a branch point, the search area is divided into two parts, and the final set of backup and auto-input is the sum of the search results of these two parts of the area. In the first part, the nodes connected to the branch points are used as the starting nodes, and each starting node reads out the respective downstream nodes, that is, the respective power supply areas, and searches each power supply area separately to obtain the respective backup self-input gather. The search method for a certain power supply area is to search for the backup auto-switch in which only one of the nodes on both sides appears in the power supply area in the backup auto-switch state matrix, and use the backup auto-switch with the highest voltage level among the searched backup auto-switches as Prepare self-injection collection. The second part is the power-off area except the area included in the first part. The search method for this part of the area is to search for the standby automatic switching in which only one of the nodes on both sides appears in this area in the standby automatic switching state matrix. Use the standby automatic switch with the highest voltage level among the searched standby automatic switches as the standby automatic switch set;

(5) Perform power flow calculation on the regional power grid obtained in step (4) after the centralized operation of standby and automatic switching, and judge whether there are lines with current and voltage exceeding the limit. If there is no line with current and voltage exceeding the limit, then output the step (4) For the obtained backup self-switching set, if there are lines with current and voltage exceeding the limit, output the backup self-switching set obtained in step (4) and the information of the out-of-limit line.

Taking the regional power grid as shown in Figure 2 as an example below, further introduce the technical solution of the application. The power grid includes one 220kV substation, five 110kV substations, two three-winding transformers, 10 double-winding transformers and 11 lines . A total of 9 places in the system are equipped with standby automatic switching, which are marked in Figure 2;

Although the regional power grid generally contains many nodes, the nodes in the power grid are only connected to a limited number of nodes, so the network base structure matrix D is a sparse matrix. In order to facilitate the description and reduce the amount of input, the network-based structure matrix D is input as an N×d matrix, N is the node number, and d is the maximum value of the node degree in the power distribution network. As shown in Figure 2, the maximum node degree Value is 5, like node 2, 3, etc. The elements in the network-based structure matrix D are the node numbers connected to the row nodes, and those connected nodes with less than the maximum node degree are filled with 0.

The application takes the regional power grid shown in accompanying drawing 2 as an embodiment, and introduces the technical solution of the present invention in detail, and the present invention includes the following steps:

(1) Input the basic electrical information of the regional power grid, and establish the grid structure matrix D=[2 3 11 23;1 4 20 24;1 45 0;2 3 6 0;3 6 0 0;4 5 0 0;8 9 23 0;7 10 24 0;7 10 0 0;8 9 0 0;1 12 13 0;11 1419 0;11 14 0 0;12 13 0 0;16 17 23 0;2 15 18 0;15 18 0 0;16 17 0 0;12 20 21 0;219 22 0;19 22 0 0;20 21 0 0;1 7 15 0;2 8 16 0]; standby self-injection state matrix B=[3 4 0 110; 5 6 010;7 8 0 110;9 10 0 10;13 14 0 10;15 16 0 110;17 18 0 10;12 19 0 110;21 22 0 110]; switch state matrix K=[1 11 1; 1 23 1;1 3 1;2 4 1;2 24 1;2 20 1;24 8 1;2 16 1;7 23 1;2315 1;12 19 1]; the expected accident set matrix F includes the line 1...11 and transformers 12...21, the numbers are shown in Figure 2, and the expected accident set matrix F=[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00] is established in this order; Power point distribution matrix M=[1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] and branch point distribution matrix T=[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1];

(2) Traverse the regional power grid, and generate a power flow matrix C=[0 3 11 23;04 20 24;0 0 5 0;0 0 6 0;0 0 0 0;0 0 0 0 according to the actual power flow direction ;0 9 0 0;0 10 0 0;0 0 0 0;0 0 0 0;0 12 130;0 14 0 0;0 0 0 0;0 0 0 0;0 17 0 0;0 0 18 0; 0 0 0 0;0 0 0 0;0 0 21 0;0 19 22 0;00 0 0;0 0 0 0;0 7 15 0;0 8 16 0];

(3) If a component in the expected accident set fails, the matrix of the expected accident set is modified. If a fault occurs on Line 3 in Example 1, the expected accident set matrix is modified to F=[0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]; the switch between nodes 1 and 3 is opened, and the corresponding The switch state matrix changes to K=[1 11 1;1 23 1;1 3 0;2 4 1;2 241;2 20 1;24 8 1;2 16 1;7 23 1;23 15 1;12 19 1];

Example 2 If line 2 fails, the expected accident set matrix is modified to F=[0 1 0 0 0 0 0 0 0 0 0 0 0 00 0 0 0 0 0]; nodes 1 and 23, 7 and 23, 23 and 15 The switch between is opened, and the corresponding switch state matrix changes as K=[1 11 1;1 23 0;1 3 1;2 4 1;2 24 1;2 20 1;24 8 1;2 16 1;723 0 ;23 15 0;1219 1];

(4) Search to obtain the set of self-investment;

In Example 1, the power flow of the faulty element 3 flows from node 1 to node 3, so node 3 is the tail node, that is, the de-energized area is read from the power flow matrix from node 3 [35]. This area does not contain a branch point. Nodes 3 and 5 correspond to standby automatic switching devices 1 and 2 respectively. Backup automatic switching device 1 has the highest voltage level, and standby automatic switching device 1 is the standby automatic switching device that should act. Get the self-injection set[1]

In Example 2, the power flow of faulty element 2 flows from node 1 to node 23, so node 23 is the tail node, that is, the power-off area is read from the power flow matrix from node 23 [23 7 9 15 17]. This area contains branch points, and the first part searches the power supply areas connected to nodes 7 and 15 connected to the branch points, namely [7 9] and [15 17]. Nodes 7 and 9 correspond to backup auto-switching devices 3 and 4 respectively, and backup auto-switching device 3 has the highest voltage level, and backup auto-switching device 3 is a set of backup auto-switching devices; The voltage level of the automatic switching device 6 is the highest, and the backup automatic switching device 6 is a set of backup automatic switching devices. The second part is [23]. There is no corresponding backup self-injection in this area, so there is no set of backup self-injection. Then add up the results to get the self-injection set [3 6];

(5) In Example 1, the power flow calculation is performed on the regional power grid obtained in step (4) after the set operation of the backup and automatic switching. If there is no current and voltage exceeding the limit of the line in the calculation result, the backup and automatic switching set is output [1].

Example 2 performs power flow calculation on the regional power grid obtained in step (4) after the set operation of standby automatic switching. If there is no current and voltage exceeding the limit of the line in the calculation result, the set of standby automatic switching is output [3 6].

Finally, it should be noted that: the combination of the above embodiments only illustrates the technical solution of the present invention rather than limiting it. Those skilled in the art should understand that: those skilled in the art can modify or equivalently replace the specific embodiments of the present invention, but these modifications or changes are all within the protection scope of the pending claims.

Claims (5)

1. a centralized area power grid prepared auto restart control method, is characterized in that, described method comprises the steps:

(1) electric information of monitoring area power grid, bus and breakout are considered as to node processing, circuit, transformer and bus connection switch are considered as to branch road, set up net based structures matrix D, prepared auto restart state matrix B, on off state matrix K, contingency set matrix F, power supply point distribution matrix M and breakout distribution matrix T;

(2) generate trend according to the net based structures matrix of setting up, prepared auto restart state matrix, on off state matrix, power supply point distribution matrix and breakout distribution matrix and flow to Matrix C;

(3) if certain element that forecast accident is concentrated breaks down, revise the corresponding element in the contingency set matrix;

(4) draw the prepared auto restart set after certain concentrated element of forecast accident breaks down;

(5) area power grid after the resulting prepared auto restart assembling operation of step (4) is carried out to trend calculating, judge whether to exist the circuit of electric current, voltage out-of-limit, if there is no the situation of circuit electric current, voltage out-of-limit, export the resulting prepared auto restart set of step (4), if have circuit to have the situation of electric current, voltage out-of-limit, export the resulting prepared auto restart set of step (4) and out-of-limit line information.

2. centralized area power grid prepared auto restart control method as claimed in claim 1 is characterized in that:

In step (4), if certain element that forecast accident is concentrated breaks down, by trend, flow to the node situation that matrix judges these element two ends, node headed by the node that trend flows out, the node that trend flows into is tail node;

Area power grid moves radially, trend flow to matrix description trend flowed to the directed walk of load bus by power supply point, when certain element breaks down when out of service, to take the tail node of this element be start node, flows in trend all nodes of reading in matrix and be the dead electricity zone;

If the node that this dead electricity zone comprises does not contain breakout, in the prepared auto restart state matrix, search two side gussets the prepared auto restart of only occurs in this dead electricity zone, and the prepared auto restart that in the prepared auto restart that search is obtained, electric pressure is the highest is as the prepared auto restart set;

If breakout is contained in this dead electricity zone, region of search is divided into to two parts, final prepared auto restart set for this two parts zone search for respectively acquired results and, wherein, node that breakout was connected is usingd respectively as start node in first, read respectively downstream node separately by each start node, i.e. power supply area separately, and each power supply area is searched for respectively to the prepared auto restart set drawn separately, in the prepared auto restart state matrix, the prepared auto restart of only appears in search two side gussets in this power supply area, the prepared auto restart that in the prepared auto restart that search is obtained, electric pressure is the highest is as the prepared auto restart set.

Second portion is that the zone outside the contained zone of first is removed in the dead electricity zone, the searching method regional to this part is, in the prepared auto restart state matrix, the prepared auto restart of only appears in search two side gussets in this zone, and the prepared auto restart that in the prepared auto restart that search is obtained, electric pressure is the highest is as the prepared auto restart set.

3. centralized area power grid prepared auto restart control method as claimed in claim 1 or 2 is characterized in that:

(a) described net based structures matrix D is the matrix of N * N, what describe is the potential topological structure of area power grid, when generating net based structures matrix, even the branch switch between two nodes disconnects, also still be considered as existing a branch road and reflected in net based structures matrix D.Net based structures matrix is each branch road of area power grid to be used as to nonoriented edge process, if having branch road, a d between area power grid node i and node j _Ij=d _Ji=1, all the other elements are 0, and wherein, N is the node sum, d _IjFor the element of the capable j row of i in net based structures matrix D, d _JiElement for the capable i row of j in net based structures matrix D;

(b) prepared auto restart state matrix B is the matrix of B * 4, description be running status and the electric information of prepared auto restart, the number of behavior prepared auto restart, the node serial number that first two columns is the prepared auto restart both sides; The 3rd classifies the operating state of prepared auto restart as, if prepared auto restart in closure state, this element is 1, otherwise is 0; The 4th classifies the electric pressure of this prepared auto restart place bus as;

(c) matrix that described on off state matrix K is K * 3, description be the running status of switch, the number of behavior switch, the node serial number that first two columns is these switch both sides, the 3rd classifies on off state as, if switch in closure state, this element is 1, otherwise is 0;

(d) power supply point distribution matrix M is the matrix of M * 1, description be the distribution situation of power supply, the behavior node serial number, what power supply point distribution matrix M described is the distribution situation of area power grid power supply point, if regional node p is power supply point, m _p=1, otherwise m _p=0, m wherein _pFor the capable element of p in the power supply point distribution matrix;

(e) breakout distribution matrix T is the matrix of T * 1, what describe is the distribution situation of branch node, the behavior node serial number, contain a large amount of T modes of connection in area power grid, each feeder line Branch Power Flow converges and shunts at the breakout place, what breakout distribution matrix T described is the distribution situation of area power grid breakout, if area power grid node q is breakout, t _q=1, otherwise t _q=0, t wherein _qFor the capable element of q in the breakout distribution matrix;

(f) the contingency set matrix F is the matrix of F * 1, description be possible fault element, F is the number of forecast accident element, if element r fault, f _r=1, otherwise f _r=0, f wherein _rFor the capable element of r in the contingency set matrix.

4. the described centralized area power grid prepared auto restart control method of claim as arbitrary as claim 1-3, it is characterized in that: in described step (2), trend flow to matrix description trend flowed to the directed walk of load bus by power supply point, it is that basis draws by net basic matrix D that trend flows to Matrix C, be that the branch road of area power grid is used as to directed edge, the direction of directed edge determines by the Branch Power Flow direction, if having a branch road between node i, j, and direction of tide is to point to j, c by i _Ij=1, c _Ji=0.

5. centralized area power grid prepared auto restart control method as claimed in claim 3 is characterized in that:

Preferably adopt following steps to show that trend flows to Matrix C:

(a) from off state matrix K and prepared auto restart state matrix B, find in the switch of off-state and the prepared auto restart of off-state, find area power grid node i, the j of the prepared auto restart both sides of the switch of off-state and off-state, j element and the capable i element of j that the i in net based structures matrix D is capable are set to 0;

(b) revise the breakout distribution matrix after the area power grid running status changes, if a certain switch disconnects, cause corresponding breakout to be changed to ordinary node, in the breakout distribution matrix, corresponding element is set to 0;

(c) obtain the node serial number of power supply from power supply point distribution matrix M, take power supply point as starting point start the search, in net based structures matrix D, find the i at power supply node i place capable, search node j in i is capable, in net based structures matrix D, retain the j element that i is capable constant, by j, capable i element sets to 0 simultaneously, and then continues search by the j node by identical method, until search endpoint node, this row is 0 node entirely;

(d) if meet termination condition, searched for, the output trend flows to the Matrix C result; Continue search otherwise go to step (c), wherein, described termination condition is that trend flows to matrix and occurs that element is that the number of 0 row is identical with actual electric network endpoint node number entirely.

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