CN115603326A - Power distribution network load transfer method and system based on tree topology - Google Patents
Power distribution network load transfer method and system based on tree topology Download PDFInfo
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Abstract
The invention discloses a power distribution network load transfer method based on tree topology, which comprises the following steps: step 1, establishing a load model of a power distribution network; step 2, establishing a layered power supply tree model according to the load model of the power distribution network; step 3, if a power-off line appears, reconstructing a layered power supply tree model corresponding to the power-off line; step 4, acquiring a load transfer scheme through the reconstructed layered power supply tree model; step 5, trying to close a plurality of interconnection switches to transfer the load of the power-off line; step 6, trying to ignore partial loads in the power-losing line and searching a scheme for recovering power supply of other loads in the power-losing line; and 7, transferring the load of the power-off line according to a transfer scheme. The invention makes up the transfer capacity of the distribution network load transfer branch and the subsection transfer layer, so that the transfer handling of the power-loss fault is more precise and refined, the realization process is simple to calculate, and the regulation and control working accuracy and efficiency of the distribution network are effectively improved.
Description
Technical Field
The invention relates to the technical field of load transfer of a power distribution network, in particular to a method and a system for load transfer of the power distribution network based on tree topology.
Background
The existing scheduling load transfer methods can be basically divided into the following categories:
1) Based on a heuristic search algorithm. Searching available interconnection switches according to the power loss area information, and trying to completely recover all power loss loads by using one or more interconnection switches in combination with information such as electrical distance, transfer capacity and the like; if the entire outage region cannot be fully restored, a portion of the relatively unimportant load is cut off to meet safety constraints, taking into account the importance of the load. Considering the influence of load change on load transfer, the load transfer scheme considering recovery time is further provided due to different load values at different times.
2) Based on a stochastic optimization algorithm. In order to have a relatively high calculation speed, the method has the advantages that the control variables only comprise the opening and closing of the circuit, the controllability and the cutting of the load are not taken into consideration, and the obtained scheme is relatively simple. And applying a non-dominated sorting genetic algorithm (NSGA-II) to the multi-objective multi-constraint power recovery of the power distribution network, and obtaining a pareto optimal solution through multiple optimizing sorting. The model is relatively complete, and the obtained scheme has optimality in a certain sense (relative to the calculation time); but have relatively long computation times. The method has the outstanding characteristics that the model is relatively complete, the optimal or suboptimal scheme can be obtained within enough calculation time, and the method has better optimization capability; however, the method has the disadvantages that the calculation time is often long, the calculation speed of online application cannot be achieved, and the method is not suitable for large-scale networks.
3) Expert system method. The expert system can automatically generate a scheme which needs to be operated for recovering the fault, has good real-time performance and wide applicability, and can be applied to solving the scheme when the network is larger. However, the expert system only needs to establish and integrate the library, which is time-consuming and labor-consuming, and in practice, the fault types are various, and all situations cannot be recorded.
The prior art includes:
in the prior art 1, patent application No. 202210801365.9 discloses a distribution network line partial load transfer analysis method and system, firstly, based on a distribution network line single line diagram, a direct transfer line, an indirect transfer line and a corresponding ring network switch of a distribution network line ring network to be analyzed are obtained, and a ring network data record table is generated; then, acquiring an alternative indirect power supply conversion and transfer switch and an alternative indirect power supply conversion and transfer load based on a ring network data record table and in combination with a power supply path of a distribution network line, and analyzing according to data information of the alternative indirect power supply conversion and transfer load to obtain a final alternative indirect power supply conversion scheme; and then, based on a ring network data record table and in combination with a final alternative indirect power transfer scheme, carrying out power transfer load analysis on the distribution network line at the side of the direct power transfer and supply and all the distribution network lines at the opposite side of the ring network to obtain a final direct power transfer scheme and a corresponding indirect power transfer scheme. The traditional manual data statistics and analysis process is replaced, the working efficiency is greatly improved, the rapid load transfer under the emergency condition of the power grid is guaranteed, and the safe and stable operation level of the power grid and the power supply reliability of users are improved. However, the method has the disadvantages of long calculation time, difficult application and low use efficiency for the power transfer scheme.
In the prior art 2, patent application No. 201811574651.6 discloses a regional power grid load transfer method, which includes that 500KV partition division and 220KV partition division are performed on a regional power grid; then searching various load transfer measures respectively aiming at the out-of-limit conditions of the 500KV main transformer and the 220KV main transformer; evaluating the influence degree of various load transfer measures on the power supply reliability, and performing priority classification on the load transfer measures according to the influence degree; and then, preferentially selecting and executing a load transfer measure with a higher priority level aiming at the out-of-limit conditions of the 500KV main transformer and the 220KV main transformer respectively until the corresponding main transformers are not out-of-limit any more. The method can quickly select the load transfer measure, improve the selection efficiency and the load transfer effect, and is favorable for reducing the adverse effect of the load transfer on the operation of the power grid. However, the method of the present invention cannot ensure that all the power-shortage loads are transferred as much as possible, and is limited in use.
Disclosure of Invention
The invention aims to overcome the defects that in the prior art, a load transfer method is single, the use is limited, and the optimum method for transferring the power-shortage load cannot be found quickly, so that the efficiency of the transfer method is low, and provides a power distribution network load transfer method and system based on tree topology.
The purpose of the invention is realized by the following technical scheme:
the method for transferring the load of the power distribution network based on the tree topology comprises the following steps:
step 1, establishing a load model of a power distribution network;
step 2, establishing a layered power supply tree model according to the power distribution network load model, wherein the step of establishing the layered power supply tree model specifically comprises the following steps: taking a power supply end as a root node, taking a feeder line with the longest power supply radius as a trunk, taking the rest feeder lines as branches, taking the branch end points in a disconnected state as interconnection switches, then layering the trunks of the power supply trees, sequencing layer numbers according to the electrical distance between each switch and the node, calculating the load carried by each layer, and regarding the load and the branches of the layer as the same layer;
step 3, if a power-off line appears, reconstructing a layered power supply tree model corresponding to the power-off line;
step 4, acquiring a load transfer scheme through the reconstructed hierarchical power supply tree model: judging whether a contact switch is closed, and whether the load of the power-off line can be completely transferred to the opposite line or not, if so, acquiring a transfer scheme of the power-off line, and otherwise, jumping to the step 5;
step 5, trying to close the plurality of interconnection switches to transfer the load of the power-off line, if the plurality of interconnection switches are closed to recover the load power supply of the power-off line, obtaining a transfer scheme of the power-off line, and if the plurality of interconnection switches are not closed, skipping to the step 6;
step 6, neglecting part of loads in the power-off line, and searching a power supply transfer scheme for restoring power supply of the rest loads in the power-off line;
and 7, transferring the load of the power-off line according to a transfer scheme.
According to the scheme, firstly, a layered power supply tree model is established, power grid equipment is related through topology, the layered power supply tree model is reconstructed in the load transfer analysis process, the topological relation of power loss lines is determined, and the purpose of segmented transfer is achieved through layered quantitative analysis and calculation in the load transfer analysis process. According to the scheme, the situation that important loads or the largest loads can be transferred as far as possible under the condition that a single power-losing line is transferred and supplied by a single opposite-side line and the condition that a plurality of opposite-side lines transfer and supply single power-losing lines and the load of all power-losing lines cannot be transferred and supplied is considered, so that the transfer and supply capacity of distribution network load transfer branch and subsection transfer and supply layers is compensated, the power-losing fault transfer and supply handling is more accurate and detailed, the calculation of the implementation process is simple, and the regulation and control working accuracy and efficiency of the power distribution network are effectively improved.
Preferably, the step 3 specifically comprises: the method comprises the steps that an available interconnection switch communicated with a power-off line is used as a target, one end, which does not belong to the power-off line, of the available interconnection switch is merged, the merged end serves as a virtual power supply point, all branches are closed, and the formed network is a target network; when a plurality of available interconnection switches exist for a certain power loss, a formed target network comprises a plurality of rings, the network is guaranteed to meet topological constraint during coding, the target needs to be optimized, and control variables are the switch and load shedding amount in the network.
If the number of available interconnection switches of one power-loss line is more than one, a ring is generated in a formed target network, if n interconnection switches are provided, n-1 rings are formed in the target network, and a branch is disconnected in each ring to enable the network to keep radial shape;
the method comprises the following steps of reconstructing a layered power supply tree model through the operation of constructing a matrix to realize radial network maintenance, wherein the operation of constructing the matrix specifically comprises the following steps:
establishing a dimension of n (A) L ) Line, n (A) T ) A matrix M of columns, wherein A T and AL The number of branches and the number of branches are respectively, each row represents one branch, each column represents one branch, and the ith row and the jth column m in the matrix L ij The values are as follows:
wherein ,ej Represents the j-th branch of the tree,
reference tree t represented in the supply tree 0 Middle connecting branch l i Each branch corresponds to a basic loop, if a certain branch belongs to the basic loop corresponding to the branch, the numerical value in the column of the position of the branch corresponding to the row is 1, and if the numerical value is 0, the branch is not in the basic loop corresponding to the branch;
from the reference tree t 0 Starting from trees of different structure formed by exchanging branches, known from methods for generating treesThe branches undergoing exchange must satisfy the condition:
wherein ,eik In order to exchange the branches required to be carried out,
in order to carry out the branch connection with the branch exchange,
for branches e in the current spanning tree ik The set of basic cut-sets is,
is in reference tree e ik A set of base cutsets;
according to the spanning tree process, firstly
Selecting a branch to replacee 1 There are two cases:
case 1: selected branch ise 1 By itself, the resulting tree t 1 =t 0 ；
Case 2: the selected branch is t 0 Twig connecting l i Then, it means that i The closing process is carried out in a closed mode,e 1 is broken to obtain a tree t 1 At this time, mark l i Have been used to exchange branches; for all satisfies M 0 [j][i]Exclusive or XOR operation XOR (rowi, rowj, 2) for j rows =1 and j ≠ i;
the exclusive-or operation XOR (rowi, rowj, 2) between two rows is defined as: for s =2 to N-1, new [ m ], [ j ]][s]=m 0 [i][s] xor m 0 [j][s](ii) a Then using new m [ j ]][s]Substitution m 0 [j][s]To update the jth row to obtain a new matrix M 1 For all unlabeled t 0 Twig connecting l i ，m 1 [i][s](s is a branch tree from 2 to N-1) has the following meanings:
；
next, the exchange t is emulated 0 The time matrix operation method sequentially exchanges the rest branches in the branch set, and the rest branches e k The exchange process of (a) is specifically described as follows:
A. if t 0 Twig connecting l i Satisfies the following conditions: l i Unlabeled for exchange, and m 0 [i][k]=m k-1 [i][k]=1 then these l i And e k Is itself composed of
；
B. From
In the branch replacement e k If e is selected k Then the obtained tree t k =t k-1 ，M k =M k-1 (ii) a Otherwise, if select l i Is prepared by i Label switching, for any unlabeled l i If M is present k-1 [j][k]=1, perform XOR (rowi, rowj, k + 1) operation to obtain a new matrix M; and replacing all branches in the reference tree to obtain a new tree, namely obtaining a solution meeting the topological requirement, and completing reconstruction of the layered power supply tree model corresponding to the power loss line.
Preferably, if a plurality of power-losing lines exist, the power-losing lines are sorted from high to low according to the occupation proportion of important loads, each power-losing line is processed according to the sort, each power-losing line executes the steps 3 to 5, the step 4 further comprises the step of calculating the residual capacity of the interconnection switch after the load of the power-losing line can be completely transferred to the opposite line, and the residual capacity can still be transferred to other power-losing lines;
the step 5 specifically comprises the following steps: trying to close a plurality of interconnection switches to supply the load of the power-loss line, if the total load I of the power-loss line lost < sum of interconnection switch capacities ∑ I m，si Obtaining the transfer scheme of the power-off line, if not, skipping to the stepThe sum of the tie switch capacities includes the un-transponded tie switch capacity and the remaining capacity of the transponded tie switch, step 6.
Preferably, the step 5 of switching the power-off line by the plurality of interconnection switches specifically comprises:
(a) And (3) taking a certain interconnection switch i as an initial point to perform recovery search towards the power failure area layer by layer, and assuming that the kth layer is searched, the front switch and the rear switch are respectively S (k-1)-(k) and S(k)-(k+1) Judging the kth layer back switch S (k)-(k+1) Whether it is an openable switch;
(b) If S is (k)-(k+1) To open and close the switch, let the total load of the k-th layer be I lost,k The voltage obtained by load flow calculation is V k With an approximate current of I k =I lost,k /V k Judging whether the current voltage on the power supply path exceeds the limit or not (assuming that the total current of the transferred load is I at the moment load Judgment of I m,si ＞I load+Ik ；|V k Less than or equal to 5 percent under-1 |). If not, continuing to supply power for downward search, otherwise, turning to (c);
if S is (k)-(k+1) In order to keep the switch from being turned off, the loads of the layers after the k layer are accumulated to the k layer, and the total load is
∑(I lost,k ) Judging whether the current and voltage on the power supply path are out of limit, if not, switching the direction for searching, otherwise, turning to (c);
(c) Opening switch S in front of the kth layer (k－1)-(k) And the plurality of interconnection switches transfer the power-off line at this time.
Preferably, if a plurality of power transfer schemes exist for the power loss line, the load shedding amount, the switching action frequency, the line loss after load transfer, the voltage threshold value and the power threshold value of each power transfer scheme are acquired, and then an objective function C is constructed:
wherein ,
in the formula ,
is the sum of the load shedding amounts, d j Is a weighting factor for the jth load, the factor depending on the kind of load,
the total number of the switch actions is the total number of times,
in order to be the value of the line loss,
for the voltage over-limit penalty value,
for power over-limit penalty values, V j Is the voltage amplitude of the j point, V j，max and Vj，min Respectively, the upper and lower limits of j point voltage amplitude, S j Is the current apparent power of the jth line, S j，max At its upper power limit, λ p ，λ n ，λ k ，λ u ，λ s Respectively are the weight coefficients of each item in the objective function;
and taking the transfer scheme of the minimum value of the objective function C in all the transfer schemes as the transfer scheme of the power-losing line.
The design of this scheme has guaranteed that the result of use of switching confession scheme is best, and the holistic safe operation of distribution network has been guaranteed again to the power loss that both reduced.
Preferably, the method for transferring load of the power distribution network based on the tree topology further comprises the step of optimizing the objective function C by adjusting the weight coefficient, so as to obtain an optimal transfer scheme, and specifically comprises the following steps: for the set of the power-off schemes of all the power-off lines, calculating the total power-off success rate or the total power-off load of the power-off loads of all the power-off lines, judging whether the set of the power-off schemes obtained through the minimum value of a target function C is the set of the power-off schemes with the highest power-off success rate or the maximum total power-off load, if so, not adjusting the weight coefficient, wherein the power-off scheme obtained through the minimum value of the target function C is the optimal power-off scheme, otherwise, adjusting the weight coefficients of one or more power-off line target functions C to obtain a new power-off scheme, and until the set of the power-off schemes obtained through the minimum value of the target function C is the set of the power-off schemes with the highest power-off success rate or the maximum total power-off load, wherein the new power-off scheme is the optimal power-off scheme; and for a plurality of power loss events, a plurality of corresponding optimal power transfer schemes exist, each power loss event comprises the sum of a plurality of power loss lines generated in a time period, and if the number of times of the optimal power transfer schemes acquired by the weight coefficient value of a certain objective function C or the weight coefficient interval of the certain objective function C is the largest, the objective function C is optimized and completed. Because the initial weight coefficient is given according to expert experience, the error is larger due to different situations in actual use, and the purpose of the highest success rate of the total transfer or the maximum load of the total transfer can be achieved by optimizing the objective function C, namely optimizing the weight. In addition, for the objective functions C of different power-off lines, the weight coefficient of a single objective function C can be adjusted, and the weight coefficients of a plurality of objective functions C can be adjusted. The design of the scheme further improves the effectiveness of the transfer scheme.
Preferably, in step 4, one interconnection switch is closed, the load of the power-off line can be completely transferred to the opposite line, then transfer supply checking is performed, after the load of the power-off line is assumed to be transferred to the opposite line, the coincidence rate of the opposite line is calculated, if the coincidence rate is smaller than a set threshold value, it is determined that transfer supply checking is unsuccessful, the load of the power-off line cannot be completely transferred to the opposite line, and if the coincidence rate is larger than or equal to the set threshold value, it is determined that checking is successful, and the load of the power-off line can be completely transferred to the opposite line. According to the scheme, the loads of the power-losing line are transferred to be checked, and the loads of the power-losing line can be completely transferred to the opposite line only when the checking is successful; if the checking is unsuccessful, the coincidence rate is judged to be too low, and the situation that overload operation is easily generated when the load of the power-off line is transferred by the opposite line is indicated to cause potential safety hazards.
Preferably, if in step 4, one interconnection switch is closed, and the load of the power-losing line can be completely transferred to the opposite side line, the capacity richness of the opposite side line is considered, and if the ratio of the load of the power-losing line to the capacity richness of the opposite side line is smaller than a set value, the opposite side line is not taken as the load transfer target of the power-losing line, and the next interconnection switch is continuously searched. The scheme is not preferable to match the opposite side line with the capacity margin obviously far greater than the target of the interconnection switch, and the capacity margin of the opposite side line is matched as much as possible with the condition that the capacity margin is slightly greater than the target of the interconnection switch, so that the opposite side line with the large capacity margin can meet the load of other power-off lines with large requirements, and the efficiency of the power transfer scheme is further improved.
The distribution network load transfer system based on the tree topology comprises:
the data acquisition unit is used for acquiring power-off line information, normal line information and interconnection switch information in the distribution network load model;
the data processing unit is used for processing the data of the multiple data acquisition unit and selecting a power supply transfer scheme to transfer the load of the power-loss line;
the power transfer execution unit is used for executing the power transfer scheme to transfer the load of the power-loss line;
the load transfer system of the power distribution network based on the tree topology executes the load transfer method of the power distribution network based on the tree topology when running.
Preferably, the distribution network load transfer system based on the tree topology further includes a verification unit, where the verification unit is configured to verify the transfer scheme, and the distribution network load transfer system based on the tree topology executes the distribution network load transfer method based on the tree topology when operating.
An electronic device comprising a processor and a memory, the memory having stored therein a computer program that is loaded and executed by the processor to implement a method for load shedding for a power distribution network based on a tree topology.
Computer-readable storage medium, on which a computer program is stored which is readable by a computer, the computer program being arranged to execute, when running, a method for load shedding for a power distribution network based on a tree topology.
The invention has the beneficial effects that: according to the scheme, firstly, a layered power supply tree model is established, power grid equipment is related through topology, the layered power supply tree model is reconstructed in the load transfer analysis process, the topological relation of power loss lines is determined, and the purpose of segmented transfer is achieved through layered quantitative analysis and calculation in the load transfer analysis process. The scheme considers the conditions that a single contralateral line transfers and supplies the load of the single power-losing line, a plurality of contralateral lines transfer and supplies the load of the single power-losing line and cannot transfer and supply the load of all the power-losing lines, and the important load or the maximum load can be transferred and supplied as much as possible.
According to the scheme, the loads of the power-losing line are transferred to be checked, and the loads of the power-losing line can be completely transferred to the opposite line only when the checking is successful; if the checking is unsuccessful, the coincidence rate is judged to be too low, and the situation that overload operation is easy to occur when the load of the power-off line is transferred by the opposite line is indicated to cause potential safety hazards.
The scheme does not match the target that the capacity margin of the opposite side line is obviously far larger than that of the interconnection switch, but matches the condition that the capacity margin of the opposite side line is slightly larger than that of the interconnection switch as much as possible, so that the opposite side line with high capacity margin can meet the load of other power-off lines with large requirements, and the efficiency of the power transfer scheme is further improved.
Drawings
FIG. 1 is a schematic of one embodiment of the present invention;
fig. 2 is a schematic block diagram of the system of the present invention.
Wherein: 1. the device comprises a data acquisition unit 2, a data processing unit 3, a transfer execution unit 4 and a verification unit.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
It should be understood that, in various embodiments of the present invention, the sequence numbers of the processes do not mean the execution sequence, and the execution sequence of the processes should be determined by the functions and the internal logic of the processes, and should not constitute any limitation on the implementation process of the embodiments of the present invention.
It should be understood that in the present application, "comprising" and "having" and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is further described below with reference to the figures and examples.
Example 1:
the method for transferring the load of the power distribution network based on the tree topology, as shown in fig. 1, comprises the following steps:
step 1, establishing a load model of a power distribution network;
step 2, establishing a layered power supply tree model according to the power distribution network load model, wherein the step of establishing the layered power supply tree model specifically comprises the following steps: taking a power supply end as a root node, taking a feeder with the longest power supply radius as a trunk when the power supply end operates normally, taking other feeders as branches, taking the branch end points in an off state as interconnection switches, then layering the trunks of the power supply trees, sequencing layer numbers according to the electrical distance between each switch and the node, calculating the load carried by each layer, and taking the load and the connection branches of the layer as the same layer;
step 3, if a power-off line appears, reconstructing a layered power supply tree model corresponding to the power-off line;
step 4, acquiring a load transfer scheme through the reconstructed hierarchical power supply tree model: judging whether a contact switch is closed, and whether the load of the power-off line can be completely transferred to the opposite line or not, if so, acquiring a transfer scheme of the power-off line, and otherwise, jumping to the step 5;
step 5, trying to close the plurality of interconnection switches to transfer the load of the power-off line, if the plurality of interconnection switches are closed to recover the load power supply of the power-off line, obtaining a transfer scheme of the power-off line, and if the plurality of interconnection switches are not closed, skipping to the step 6;
step 6, neglecting part of loads in the power-off line, and searching a power supply transfer scheme for restoring power supply of the rest loads in the power-off line;
and 7, transferring the load of the power-off line according to a transfer scheme.
According to the scheme, firstly, a layered power supply tree model is established, power grid equipment is related through topology, the layered power supply tree model is reconstructed in the load transfer analysis process, the topological relation of power loss lines is determined, and the purpose of segmented transfer is achieved through layered quantitative analysis and calculation in the load transfer analysis process. The scheme considers the conditions that a single contralateral line transfers and supplies the load of the single power-losing line, a plurality of contralateral lines transfer and supplies the load of the single power-losing line and cannot transfer and supply the load of all the power-losing lines, and the important load or the maximum load can be transferred and supplied as much as possible.
The step 3 specifically comprises the following steps: the method comprises the steps that an available interconnection switch communicated with a power-off line is used as a target, one end, which does not belong to the power-off line, of the available interconnection switch is merged, the merged end serves as a virtual power supply point, all branches are closed, and the formed network is a target network; when a plurality of available interconnection switches exist for a certain power loss, a formed target network comprises a plurality of rings, the network is guaranteed to meet topological constraint during coding, the target needs to be optimized, and control variables are the switch and load shedding amount in the network.
If the number of available tie switches of a power-loss line is more than one, a ring is generated in a formed target network, if n tie switches are provided, n-1 rings are formed in the target network, and a branch is disconnected in each ring to enable the network to keep radial shape;
the method comprises the following steps of reconstructing a layered power supply tree model through the operation of constructing a matrix to realize radial network maintenance, wherein the operation of constructing the matrix specifically comprises the following steps:
establishing a dimension of n (A) L ) Line, n (A) T ) A matrix M of columns, wherein A T and AL The number of branches and the number of branches are respectively, each row represents one branch, each column represents one branch, and the ith row and the jth column m in the matrix L ij The values are as follows:
wherein ,ej Represents the j-th branch of the tree,
reference tree t represented in the supply tree 0 Middle connecting branch l i Each branch corresponds to a basic loop, if a certain branch belongs to the basic loop corresponding to the branch, the numerical value in the column of the position of the branch corresponding to the row is 1, and if the numerical value is 0, the branch is not in the basic loop corresponding to the branch;
from the reference tree t 0 Starting with the exchange of branches to form trees of different structure, it is known from the method of generating trees that the branches undergoing exchange must satisfy the condition:
wherein ,e ik in order to exchange the branches required to be carried out,
in order to carry out the branch connection with the branch exchange,
for currently generating branches in treese ik The set of basic cut-sets is,
as in the reference treee ik A set of base cut sets;
according to the spanning tree procedure, firstly
Selecting a branch to replacee 1 There are two cases:
case 1: selected branch ise 1 By itself, the resulting tree t 1 =t 0 ；
Case 2: the selected branch is t 0 Twig connecting l i Then, it means that i Closure, e 1 Is broken to obtain a tree t 1 At this time, mark l i Have been used to exchange branches; for all satisfies M 0 [j][i]Exclusive or XOR operation XOR (rowi, rowj, 2) for j rows =1 and j ≠ i;
the exclusive-or operation XOR (rowi, rowj, 2) between two rows is defined as: pair s =2 to N-1,new [ m ], [ j ]][s]=m 0 [i][s] xor m 0 [j][s](ii) a Then using new m [ j ]][s]Substitution of m 0 [j][s]To update the jth row to obtain a new matrix M 1 For all unlabeled t 0 Twig connecting l i ，m 1 [i][s](s is a branch tree from 2 to N-1) has the following meanings:
；
next, the exchange t is emulated 0 The time matrix operation method sequentially exchanges the rest branches in the branch set, and the rest branches e k The exchange process of (2) is specifically described as follows:
A. if t 0 Twig connecting l i Satisfies the following conditions: l i Unlabeled for exchange, and m 0 [i][k]=m k-1 [i][k]=1 then these l i Ande k is itself formed of
；
B. From
In the branch replacemente k If selected, if soe k Then the resulting tree t k =t k-1 ，M k =M k-1 (ii) a Otherwise, if select l i Is prepared by i Label switching, for any unlabeled l i If M is present k-1 [j][k]=1, perform XOR (rowi, rowj, k + 1) operation to obtain a new matrix M; and after all branches in the reference tree are replaced, obtaining a new tree, namely obtaining a solution meeting the topological requirement, and completing reconstruction of the hierarchical power supply tree model corresponding to the power failure line.
When the load of the power distribution network is transferred, the load can be transferred only by meeting constraint conditions, wherein the constraint conditions comprise:
and (3) network topology constraint: the distribution network must meet radial operating conditions.
And (3) constraint of a power flow equation: the system must satisfy the flow equation constraint after the load is transferred.
in the formula 
Is always node i withA work value;
is the voltage value of the node i;
is the voltage value of the node j;
is the reactive value of the node i;
is the voltage phase angle difference of node i and node j;
node voltage constraint: all node voltages in the network after switching do not exceed the given upper limit and the given lower limit.
, in the formula 
And
respectively, the upper and lower limit values of the node voltage.
And (4) equipment capacity constraint: and equipment elements such as a circuit, a main transformer and the like are prevented from being overloaded after the load is transferred.
Embodiment 2, a method for transferring load of a power distribution network based on a tree topology is different from the embodiment in that, if a plurality of power-losing lines exist, the power-losing lines are sorted from high to low according to the proportion of important loads, each power-losing line is processed according to the sort, each power-losing line executes steps 3 to 5, the step 4 further includes calculating the residual capacity of the interconnection switch after the load of the power-losing line can be completely transferred to the opposite line, and the residual capacity can still be transferred to other power-losing lines;
the step 5 specifically comprises the following steps: trying to close a plurality of interconnection switches to supply the load of the power-loss line, if the total load I of the power-loss line lost < sum of interconnection switch capacities ∑ I m，si If the connection switch capacity sum comprises the connection switch capacity which is not transferred and the residual capacity of the connection switch which is transferred.
In the step 5, the specific steps of transferring the power-off line by the plurality of interconnection switches are as follows:
(a) And (3) taking a certain interconnection switch i as an initial point to perform recovery search towards the power failure area layer by layer, and assuming that the kth layer is searched, the front switch and the rear switch are respectively S (k-1)-(k) and S(k)-(k+1) Judging the kth layer back switch S (k)-(k+1) Whether it is an openable switch;
(b) If S is (k)-(k+1) To open and close the switch, let the total load of the k-th layer be I lost,k And obtaining a voltage V through load flow calculation k With an approximate current of I k =I lost,k /V k Judging whether the current voltage on the power supply path is out of limit or not (assuming that the total current of the transferred load is I at the moment load Judgment of I m,si ＞I load+Ik ；|V k -1| ≦ 5%). If not, continuing to supply power for downward search, otherwise, turning to (c);
if S is (k)-(k+1) In order to keep the switch on and off, the loads of the layers after the k layer are accumulated to the k layer, and the total load is
∑(I lost,k ) Judging whether the current and voltage on the power supply path are out of limit, if not, switching the direction for searching, otherwise, turning to (c);
(c) Opening switch S in front of k-th layer (k－1)-(k) And the plurality of interconnection switches transfer the power-off line at this time.
If a plurality of transfer schemes exist for the power-loss line, acquiring the load shedding amount, the switching action times, the line loss after load transfer, the voltage threshold value and the power threshold value of each transfer scheme, and then constructing an objective function C:
wherein ,
in the formula ,
d is the sum of the load shedding amounts j Is a weighting factor for the jth load, the factor depending on the kind of load,
the total times of the switch actions are the total times,
in order to be the value of the line loss,
for the voltage to be an off-limit penalty value,
for power over-limit penalty values, V j Is the voltage amplitude of the j point, V j，max and
Vj，min Respectively, the upper and lower limits of j point voltage amplitude, S j Is the current apparent power of the jth line, S j，max At its upper power limit, λ p ，λ n ，λ k ，λ u ，λ s Respectively the weight coefficients of each item in the objective function;
and taking the transfer scheme of the minimum value of the objective function C in all the transfer schemes as the transfer scheme of the power-losing line.
The design of this scheme has guaranteed that the result of use of switching confession scheme is best, and the holistic safe operation of distribution network has been guaranteed again to the power loss that both reduced.
The method for transferring the load of the power distribution network based on the tree topology further comprises the step of optimizing the objective function C by adjusting the weight coefficient so as to obtain an optimal transfer scheme, and specifically comprises the following steps: for the set of the power transferring schemes of all the power losing lines, calculating the total power transferring success rate or the total power transferring load quantity of the power losing loads of all the power losing lines, judging whether the set of the power transferring schemes obtained through the minimum value of an objective function C is the set of the power transferring schemes with the highest power transferring success rate or the maximum power transferring load quantity with the highest total power transferring success rate or the maximum total power transferring load quantity, if so, not adjusting the weight coefficient, wherein the power transferring scheme obtained through the minimum value of the objective function C is the optimal power transferring scheme, otherwise, adjusting the weight coefficient of one or more power losing line objective functions C to obtain a new power transferring scheme, and until the set of the power transferring schemes obtained through the minimum value of the objective function C is the set of the power transferring schemes with the highest power transferring success rate or the maximum total power transferring load quantity, and the new power transferring scheme is the optimal power transferring scheme; and for a plurality of power loss events, a plurality of corresponding optimal power transfer schemes exist, each power loss event comprises the sum of a plurality of power loss lines generated in a time period, and if the number of times of the optimal power transfer schemes acquired by the weight coefficient value of a certain objective function C or the weight coefficient interval of the certain objective function C is the largest, the objective function C is optimized and completed. Because the initial weight coefficient is given according to expert experience, the error is larger due to different conditions in actual use, and therefore the purpose of the highest total transfer success rate or the maximum total transfer load can be achieved by optimizing the objective function C, namely optimizing the weight. In addition, for the objective functions C of different power-off lines, the weight coefficient of a single objective function C can be adjusted, and the weight coefficients of a plurality of objective functions C can be adjusted. The design of the scheme further improves the effectiveness of the transfer scheme.
Embodiment 3, a method for transferring load of a power distribution network based on a tree topology, which is different from embodiment 2, in that if one tie switch is closed in step 4, load of a power-off line can be completely transferred to an opposite-side line, transfer and check are performed, after assuming that load of the power-off line is transferred to the opposite-side line, a concurrency rate of the opposite-side line is calculated, if the concurrency rate is less than 80%, it is determined that transfer and check are unsuccessful, load of the power-off line cannot be completely transferred to the opposite-side line, and if the concurrency rate is greater than or equal to a set threshold, it is determined that check is successful, and load of the power-off line can be completely transferred to the opposite-side line. The scheme is used for checking the load of the power-off line, and the load of the power-off line can be completely transferred to the opposite line only when the checking is successful; if the checking is unsuccessful, the coincidence rate is judged to be too low, and the situation that overload operation is easy to occur when the load of the power-off line is transferred by the opposite line is indicated to cause potential safety hazards.
If in step 4, one interconnection switch is closed, the load of the power-off line can be completely transferred to the opposite line, the capacity richness of the opposite line is considered, and if the ratio of the load of the power-off line to the capacity richness of the opposite line is smaller than a set value, the opposite line is not taken as the load transfer target of the power-off line, and the next interconnection switch is continuously searched. The scheme is not preferable to match the opposite side line with the capacity margin obviously far greater than the target of the interconnection switch, and the capacity margin of the opposite side line is matched as much as possible with the condition that the capacity margin is slightly greater than the target of the interconnection switch, so that the opposite side line with the large capacity margin can meet the load of other power-off lines with large requirements, and the efficiency of the power transfer scheme is further improved.
The application also discloses a system for transferring load of a power distribution network based on tree topology, as shown in fig. 2, including:
the data acquisition unit 1 is used for acquiring power-loss line information, normal line information and interconnection switch information in a distribution network load model;
the data processing unit 2 is used for processing the data of the multi-data acquisition unit and selecting a power supply transfer scheme to transfer the load of the power-loss line;
the power transfer execution unit 3 is used for executing the power transfer scheme to transfer the load of the power-off line;
and the checking unit 4 is used for checking the transfer scheme.
The load transfer system of the power distribution network based on the tree topology executes the load transfer method of the power distribution network based on the tree topology when running.
The application also discloses an electronic device, which comprises a processor and a memory, wherein the memory stores a computer program, and the computer program is loaded and executed by the processor to realize the load transfer method of the power distribution network based on the tree topology.
The application also discloses a computer readable storage medium, which stores a computer program readable by a computer, and the computer program is configured to execute a load transfer method of a power distribution network based on tree topology when running.
The processor in the above embodiments may be a central processing unit CPU, a general purpose processor, a digital signal processor DSP, an ASIC, an FPGA or other programmable logic device, a transistor logic device, a hardware component, or any combination thereof. Which may implement or perform the various illustrative logical blocks, modules, and circuits described in connection with the disclosure. Or a combination that performs a computing function, e.g., comprising one or more microprocessors, DSPs, and microprocessors, etc. The memory may include, but is not limited to: u disk, read-only memory, removable hard disk, magnetic or optical disk, etc. various media capable of storing computer programs.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The scheme in the embodiment of the application can be implemented by adopting various computer languages, such as object-oriented programming language Java and transliterated scripting language JavaScript.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
The technical characteristics form the best embodiment of the application, the best embodiment has strong adaptability and best implementation effect, and unnecessary technical characteristics can be increased or decreased according to actual needs to meet the requirements of different situations.
Claims (12)
1. The load transfer method of the power distribution network based on the tree topology is characterized by comprising the following steps of:
step 1, establishing a load model of a power distribution network;
step 2, establishing a layered power supply tree model according to the power distribution network load model, wherein the step of establishing the layered power supply tree model specifically comprises the following steps: taking a power supply end as a root node, taking a feeder line with the longest power supply radius as a trunk, taking the rest feeder lines as branches, taking the branch end points in a disconnected state as interconnection switches, then layering the trunks of the power supply trees, sequencing layer numbers according to the electrical distance between each switch and the node, calculating the load carried by each layer, and regarding the load and the branches of the layer as the same layer;
step 3, if a power-off line appears, reconstructing a layered power supply tree model corresponding to the power-off line;
step 4, acquiring a load transfer scheme through the reconstructed hierarchical power supply tree model: judging whether a contact switch is closed, and whether the load of the power-off line can be completely transferred to the opposite line or not, if so, acquiring a transfer scheme of the power-off line, and otherwise, jumping to the step 5;
step 5, trying to close the plurality of interconnection switches to transfer the load of the power-off line, if the plurality of interconnection switches are closed to recover the load power supply of the power-off line, acquiring a transfer scheme of the power-off line, and if the plurality of interconnection switches are not closed, skipping to the step 6;
step 6, neglecting part of loads in the power-off line, and searching a power supply transfer scheme for restoring power supply of the rest loads in the power-off line;
and 7, transferring the load of the power-off line according to a transfer scheme.
2. The method for transferring the load of the power distribution network based on the tree topology, according to claim 1, wherein the step 3 is specifically: the method comprises the steps that an available interconnection switch communicated with a power-off line is used as a target, one end, which does not belong to the power-off line, of the available interconnection switch is merged, the merged end serves as a virtual power supply point, all branches are closed, and the formed network is a target network;
if the number of available tie switches of a power-loss line is more than one, a ring is generated in a formed target network, if n tie switches are provided, n-1 rings are formed in the target network, and a branch is disconnected in each ring to enable the network to keep radial shape;
the method comprises the following steps of reconstructing a layered power supply tree model through the operation of constructing a matrix to realize radial network maintenance, wherein the operation of constructing the matrix specifically comprises the following steps:
establishing a dimension of n (A) L ) Line, n (A) T ) A matrix M of columns, wherein A T and AL The number of branches and the number of branches are respectively, each row represents one branch, each column represents one branch, and the ith row and the jth column m in the matrix L ij The values are as follows:
wherein ,ej RepresentThe number j of the branches is the same as the number,
reference tree t represented in the supply tree 0 Middle connecting branch l i Each branch corresponds to a basic loop, if a certain branch belongs to the basic loop corresponding to the branch, the numerical value in the column of the position of the branch corresponding to the row is 1, and if the numerical value is 0, the branch is not in the basic loop corresponding to the branch;
from the reference tree t 0 Starting with the exchange of branches to form trees of different structure, it is known from the method of generating trees that the branches undergoing exchange must satisfy the condition:
wherein ,eik In order to exchange the branches required to be carried out,
in order to carry out the branch connection with the branch exchange,
for branches e in the current spanning tree ik The set of basic cut-sets is,
is in reference tree e ik A set of base cutsets;
according to the spanning tree procedure, firstly
Selecting a branch to replace e 1 There are two cases:
case 1: the selected branch is e 1 By itself, the resulting tree t 1 =t 0 ；
Case 2: the selected branch is t 0 Twig connecting l i Then, it means that i Closure, e 1 Is broken to obtain a tree t 1 At this time, mark l i Have been used to exchange branches; for all satisfies M 0 [j][i]Performing exclusive or operation XOR on j rows of =1 and j ≠ i;
the exclusive-or operation XOR between two rows is defined as: for s =2 to N-1, new [ m ], [ j ]][s]=m 0 [i][s] xor m 0 [j][s](ii) a Then using new m [ j ]][s]Substitution m 0 [j][s]To update the jth row to obtain a new matrix M 1 For all unlabeled t 0 Twig connecting l i ，m 1 [i][s]The meaning of (A) is:
；
next, the exchange t is emulated 0 The time matrix operation method sequentially exchanges the rest branches in the branch set, and the rest branches e k The exchange process of (2) is specifically described as follows:
A. if t 0 Twig connecting l i Satisfies the following conditions: l. the i Unlabeled for exchange, and m 0 [i][k]=m k-1 [i][k]=1, then l i And e k Is itself formed of
；
B. From
In the branch selection replacement e k If e is selected k Then the resulting tree t k =t k-1 ，M k =M k-1 (ii) a Otherwise, if select l i Is prepared by i Label switching, for any unlabeled l i If M is present k-1 [j][k]If =1, performing XOR (rowi, rowj, k + 1) operation to obtain a new matrix M; and after all branches in the reference tree are replaced, obtaining a new tree, namely obtaining a solution meeting the topological requirement, and completing reconstruction of the hierarchical power supply tree model corresponding to the power failure line.
3. The method for transferring the load of the power distribution network based on the tree topology as claimed in claim 1 or 2, wherein if a plurality of power-losing lines exist, the power-losing lines are sorted from high to low according to the proportion of important loads, each power-losing line is processed according to the sort, each power-losing line executes the steps 3 to 5, the step 4 further comprises the steps of calculating the residual capacity of the interconnection switch after the load of the power-losing line can be completely transferred to the opposite line, and the residual capacity can still be transferred to the rest power-losing lines;
the step 5 specifically comprises the following steps: trying to close a plurality of interconnection switches to transfer the load of the power-loss line, if the total load I of the power-loss line lost < sum of interconnection switch capacities ∑ I m，si If the connection switch capacity sum comprises the connection switch capacity which is not transferred and the residual capacity of the connection switch which is transferred, the transfer scheme of the power-losing line is obtained, if the connection switch capacity sum does not comprise the transfer scheme, the step 6 is skipped to, and the sum of the connection switch capacity sum comprises the connection switch capacity which is not transferred and the residual capacity of the connection switch which is transferred.
4. The method for transferring the load of the power distribution network based on the tree topology as claimed in claim 3, wherein the transferring of the load of the power loss line by the plurality of interconnection switches in the step 5 is specifically as follows:
(a) And (3) taking a certain interconnection switch i as an initial point to perform recovery search towards the power failure area layer by layer, and assuming that the kth layer is searched, the front switch and the rear switch are respectively S (k-1)-(k) and S(k)-(k+1) Judging the kth layer back switch S (k)-(k+1) Whether it is an openable switch;
(b) If S is (k)-(k+1) Setting the total load of the k-th layer as I for opening and closing the switch lost,k The voltage obtained by load flow calculation is V k With an approximate current of I k =I lost,k /V k Judging whether the current and voltage on the power supply path are out of limit, if not, continuing to supply power for downward search, otherwise, turning to (c);
if S is (k)-(k+1) In order to keep the switch on and off, the loads of the layers after the k layer are accumulated to the k layer, and the total load is
∑(I lost,k ) Determining the current on the power supply pathIf the pressure is out of limit, if not, the direction is changed for searching, otherwise, the step (c) is carried out;
(c) Opening switch S in front of k-th layer (k－1)-(k) And the plurality of interconnection switches transfer the power-losing circuit at this time.
5. The method for load transfer of the power distribution network based on the tree topology as claimed in claim 4, wherein if a plurality of transfer schemes exist for a power-loss line, the load shedding amount, the switching action times, the line loss after load transfer, the voltage threshold value and the power threshold value of each transfer scheme are obtained, and then an objective function C is constructed:
wherein ,
in the formula ,
d is the sum of the load shedding amounts j Is a weighting factor for the jth load, the factor depending on the kind of load,
the total number of the switch actions is the total number of times,
in order to be the value of the line loss,
for the voltage to be an off-limit penalty value,
for power over-limit penalty values, V j Is the voltage amplitude of the j point, V j，max and Vj，min Respectively, the upper and lower limits of j point voltage amplitude, S j Is the current apparent power of the jth line, S j，max At its upper power limit, λ p ，λ n ，λ k ，λ u ，λ s Respectively are the weight coefficients of each item in the objective function;
and taking the transfer scheme of the minimum value of the objective function C in all the transfer schemes as the transfer scheme of the power-losing line.
6. The method for load transfer of the power distribution network based on the tree topology according to claim 5, further comprising the step of optimizing the objective function C by adjusting the weight coefficient to obtain an optimal transfer scheme, specifically: for the set of the power transferring schemes of all the power losing lines, calculating the total power transferring success rate or the total power transferring load quantity of the power losing loads of all the power losing lines, judging whether the set of the power transferring schemes obtained through the minimum value of an objective function C is the set of the power transferring schemes with the highest power transferring success rate or the maximum power transferring load quantity with the highest total power transferring success rate or the maximum total power transferring load quantity, if so, not adjusting the weight coefficient, wherein the power transferring scheme obtained through the minimum value of the objective function C is the optimal power transferring scheme, otherwise, adjusting the weight coefficient of one or more power losing line objective functions C to obtain a new power transferring scheme, and until the set of the power transferring schemes obtained through the minimum value of the objective function C is the set of the power transferring schemes with the highest power transferring success rate or the maximum total power transferring load quantity, and the new power transferring scheme is the optimal power transferring scheme; and for a plurality of power loss events, a plurality of corresponding optimal power transfer schemes exist, each power loss event comprises the sum of a plurality of power loss lines generated in a time period, and if the number of times of the optimal power transfer schemes acquired by the weight coefficient value of a certain objective function C or the weight coefficient interval of the certain objective function C is the largest, the objective function C is optimized and completed.
7. The method for transferring the load of the power distribution network based on the tree topology as claimed in claim 1, wherein if a tie switch is closed in step 4, the load of the power-losing line can be completely transferred to the opposite line, the transfer and check is performed, after the load of the power-losing line is assumed to be completely transferred to the opposite line, the concurrency rate of the opposite line is calculated, if the concurrency rate is less than a set threshold, the transfer and check is determined to be unsuccessful, the load of the power-losing line cannot be completely transferred to the opposite line, and if the concurrency rate is greater than or equal to the set threshold, the check is determined to be successful, and the load of the power-losing line can be completely transferred to the opposite line.
8. The method according to claim 1, wherein if in step 4, one tie switch is closed, and the load of the power-losing line can be completely transferred to the opposite line, the capacity richness of the opposite line is considered, and if the ratio of the load of the power-losing line to the capacity richness of the opposite line is smaller than a set value, the opposite line is not taken as the load transfer target of the power-losing line, and the next tie switch is continuously searched.
9. Distribution network load transfer system based on tree topology, characterized by includes:
the data acquisition unit is used for acquiring power-off line information, normal line information and interconnection switch information in the distribution network load model;
the data processing unit is used for processing the data of the multiple data acquisition units and selecting a power transfer scheme to transfer the loads of the power-off line;
the power transfer execution unit is used for executing the power transfer scheme to transfer the load of the power-off line;
the load transfer system of the power distribution network based on the tree topology executes the load transfer method of the power distribution network based on the tree topology according to any one of claims 1 to 6 when running.
10. The system according to claim 9, further comprising a verification unit, wherein the verification unit is configured to verify the power distribution network load transfer scheme, and specifically includes:
if the interconnection switch is closed in the step 4, the load of the power-off line can be completely transferred to the opposite side line, then transfer supply check is carried out, after the assumption that the load of the power-off line is transferred to the opposite side line, the concurrence rate of the opposite side line is calculated, if the concurrence rate is smaller than a set threshold value, the transfer supply check is judged to be unsuccessful, the load of the power-off line cannot be completely transferred to the opposite side line, if the concurrence rate is larger than or equal to the set threshold value, the check is judged to be successful, and the load of the power-off line can be completely transferred to the opposite side line;
or if in the step 4, closing one interconnection switch, and completely transferring the load of the power-off line to the opposite line, considering the capacity richness of the opposite line, and if the ratio of the load of the power-off line to the capacity richness of the opposite line is smaller than a set value, not taking the opposite line as the load transfer target of the power-off line, and continuously searching the next interconnection switch.
11. Electronic device, characterized in that it comprises a processor and a memory, in which a computer program is stored, which computer program is loaded and executed by the processor to implement the method for load shedding of a power distribution network based on a tree topology according to any of the claims 1 to 8.
12. Computer-readable storage medium, characterized in that a computer program is stored on the storage medium, which computer program can be read by a computer and is configured to execute the method for load transfer of a distribution network based on a tree topology according to any one of claims 1 to 8 when running.
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