CN113315130B - Parallel power distribution network reconstruction method and system - Google Patents
Parallel power distribution network reconstruction method and system Download PDFInfo
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- CN113315130B CN113315130B CN202110516837.1A CN202110516837A CN113315130B CN 113315130 B CN113315130 B CN 113315130B CN 202110516837 A CN202110516837 A CN 202110516837A CN 113315130 B CN113315130 B CN 113315130B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The invention relates to a parallel power distribution network reconstruction method and a parallel power distribution network reconstruction system, which divide the reconstruction problem of a power distribution network into three stages: the method comprises the steps of network decomposition, ring level reconstruction and merging, wherein a parallelization power distribution network reconstruction system is divided into sub-networks with the same number of loops, a ring level reconstruction model of each sub-network is established, a branch exchange method is adopted to calculate the on-off state of a contact switch and the on-off state of a section switch in each sub-network, and the on-off state of the contact switch and the on-off state of the section switch of an uncompressed loop in all the sub-networks are extracted to form a reconstruction result of the parallelization power distribution network, so that parallelization network reconstruction is realized, the calculation time of network reconstruction is effectively reduced, and the network reconstruction efficiency is improved.
Description
Technical Field
The invention relates to the technical field of power distribution network reconstruction, in particular to a method and a system for reconstructing a parallelized power distribution network.
Background
The reconstruction of the power distribution network is based on one or more network operation targets, such as minimum network loss, and on the premise of meeting the requirements of radial operation, voltage and transmission line operation of the power distribution network, the optimal on-off state of a tie switch and a section switch in the power distribution network is searched. The reconstruction problem is influenced by the switch state and the network flow, wherein the switch state is a binary variable, and the network flow is a continuous variable, so that the solution of the reconstruction problem of the power distribution network faces challenges. With the wide access of distributed photovoltaic to a power distribution network and the increasing expansion of the scale of the power distribution network, the traditional heuristic and mathematical solving algorithms need longer calculation time and are difficult to deal with the situation of rapid change of photovoltaic power generation. Moreover, the traditional algorithm mostly takes a centralized algorithm as a main part, and when a large-scale network is faced, excessive computing resources are required to be occupied. However, most of the existing distributed algorithms need time-consuming iterative processes or hierarchical serial execution architectures, and thus the efficiency is low. The traditional parallelization reconstruction method is mainly directed at the heuristic algorithm, each filial generation generated in the heuristic algorithm is divided into different processors for parallel computation, and the computation efficiency is still not high because the heuristic algorithm still needs a serial process, namely the next filial generation in the heuristic algorithm is obtained on the basis of the previous filial generation.
Therefore, a suitable parallel power distribution network reconstruction algorithm needs to be designed according to the characteristics of the power distribution network reconstruction problem and the characteristics of the power distribution network, so that the efficiency of power distribution network reconstruction is improved.
Disclosure of Invention
The invention aims to provide a method and a system for reconstructing a parallel power distribution network, so as to improve the reconstruction efficiency of a power distribution network.
In order to achieve the purpose, the invention provides the following scheme:
a method of parallelizing power distribution network reconstruction, the method comprising:
constructing a parallel power distribution network reconstruction system; the parallel power distribution network reconstruction system comprises a plurality of loops, wherein each loop consists of an interconnection switch and a plurality of section switches;
determining an mth loop in the parallel distribution network reconstruction system as an mth uncompressed loop, and determining each loop except the mth uncompressed loop as a loop to be compressed;
combining a plurality of continuous nodes with the same node degree in each loop to be compressed into a node, wherein corresponding branches and switches are equivalent to a branch and a switch respectively to obtain a plurality of compressed loops;
the mth uncompressed loop and the plurality of compressed loops form an mth sub-network of the parallel distribution network reconstruction system;
establishing a ring level reconstruction model of each sub-network;
calculating the on-off state of a tie switch and the on-off state of a section switch in each sub-network according to the ring level reconstruction model of each sub-network;
and extracting the on-off state of the interconnection switches and the on-off state of the section switches of the uncompressed loops in all the sub-networks to form a reconstruction result of the parallel distribution network.
Further, the step of combining a plurality of continuous nodes with the same degree of nodes in each loop to be compressed into one node, where the corresponding branch and the switch are equivalent to one branch and one switch, respectively, to obtain a plurality of compressed loops, further includes:
respectively determining that a first power loss of a branch where continuous nodes with the same degree of nodes in a loop to be compressed are located and a branch where the continuous nodes with the same degree of nodes in the compressed loop are located are equivalent to a second power loss after one branch;
and obtaining equivalent active power and equivalent reactive power which are combined into a node by the continuous nodes with the same degree of the node based on the principle that the first power loss is equal to the second power loss according to the resistance and the reactance of a branch where the continuous nodes with the same degree of the node in the loop to be compressed are located.
Further, the ring-level reconstruction model is:
wherein f () is a reconstruction objective function; k is a radical of ij For uncompressed loops l m The state of the switch on the middle branch i-j, if the switch is open, k ij 0, otherwise k ij ＝1；k′ ij For compressed loop l -m The state of the switches on the middle branch i-j; k S And K' S Are each k ij And k' ij Vector of (A), R i-j And R' i-j Respectively uncompressed loop l m And a compressed loop l -m Resistance of the middle branch i-j, P j And P' j Respectively uncompressed loop l m And a compressed loop l -m Active power of intermediate node j, Q j And Q' j Respectively uncompressed loop l m And a compressed loop l -m Reactive power of intermediate node j, U j And U' j Node voltages, P, of node j, respectively ij Is the power of branch i-j, P c_min And P c_max Is the upper and lower limits, U, of the power line transmission capacity min 、U max Respectively the lowest and highest node voltages, alpha ij Representing nodesWhether j is the parent of node i, α ji Is whether node i is the parent of node j, N Sub Is a transformer node set, and N is the number of nodes.
Further, the calculating the on-off state of the tie switch and the on-off state of the segment switch in each sub-network according to the ring level reconstruction model of each sub-network further includes:
the on-off states of the section switches of all compressed loops corresponding to each uncompressed loop form a section switch state set;
comparing whether the on-off state of each section switch of each uncompressed loop is contained in the section switch state set or not to obtain a comparison result;
if the comparison result shows that the connection switch is not disconnected or the connection switch of the uncompressed loop is disconnected, respectively obtaining third power loss of the uncompressed loop in the parallel power distribution network reconstruction system when the connection switch is disconnected and all section switches are closed, and sequentially disconnecting the section switches and simultaneously closing the connection switch, and obtaining fourth power loss of the uncompressed loop in the parallel power distribution network reconstruction system;
and obtaining the minimum loss in the third power loss and the fourth power loss, and selecting the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop corresponding to the minimum loss as the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop in the sub-network.
A parallelized power distribution network reconfiguration system, the system comprising:
the parallel power distribution network reconstruction system construction module is used for constructing a parallel power distribution network reconstruction system; the parallel power distribution network reconstruction system comprises a plurality of loops, wherein each loop consists of an interconnection switch and a plurality of section switches;
the uncompressed loop and loop to be compressed determining module is used for determining an mth loop in the parallelization power distribution network reconstruction system as an mth uncompressed loop, and each loop except the mth uncompressed loop is determined as a loop to be compressed;
the compressed loop obtaining module is used for combining a plurality of continuous nodes with the same node degree in each loop to be compressed into a node, and corresponding branches and switches are equivalent to a branch and a switch respectively to obtain a plurality of compressed loops;
a sub-network forming module, configured to form an mth sub-network of the parallel power distribution network reconfiguration system by the mth uncompressed loop and the plurality of compressed loops;
the ring level reconstruction model establishing module is used for establishing a ring level reconstruction model of each sub-network;
the on-off state calculation module is used for calculating the on-off state of the interconnection switch and the on-off state of the section switch in each sub-network according to the ring level reconstruction model of each sub-network;
and the reconstruction result forming module is used for extracting the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop in all the sub-networks to form the reconstruction result of the parallelized power distribution network.
Further, the system further comprises:
the first power loss and second power loss determining module is used for respectively determining that a first power loss of a branch where continuous nodes with the same degree of nodes in a loop to be compressed are located and a branch where continuous nodes with the same degree of nodes in the compressed loop are located are equivalent to a second power loss after one branch;
and the equivalent active power and equivalent reactive power obtaining module is used for obtaining the equivalent active power and the equivalent reactive power which are combined into a node by the continuous nodes with the same node degree based on the principle that the first power loss is equal to the second power loss according to the resistance and the reactance of the branch where the continuous nodes with the same node degree in the loop to be compressed are located.
Further, the ring-level reconstruction model is:
wherein f () is a reconstruction objective functionCounting; k is a radical of ij For uncompressed loops l m The state of the switch on the middle branch i-j, if the switch is open, k ij 0, otherwise k ij ＝1；k′ ij For compressed loop l -m The state of the switches on the middle branch i-j; k S And K' S Are each k ij And k' ij Vector of (A), R i-j And R' i-j Respectively uncompressed loop l m And a compressed loop l -m Resistance of the middle branch i-j, P j And P' j Respectively uncompressed loop l m And a compressed loop l -m Active power of intermediate node j, Q j And Q' j Respectively uncompressed loop l m And a compressed loop l -m Reactive power of intermediate node j, U j And U' j Node voltages, P, of node j, respectively ij Is the power of branch i-j, P c_min And P c_max Is the upper and lower limits, U, of the power line transmission capacity min 、U max Respectively the lowest and highest node voltages, alpha ij Indicates whether node j is the parent node of node i, α ji Is whether node i is the parent of node j, N Sub Is a transformer node set, and N is the number of nodes.
Further, the system further comprises:
the segmented switch state set forming module is used for forming the on-off states of the segmented switches of all compressed loops corresponding to each uncompressed loop into a segmented switch state set;
a comparison result obtaining module, configured to compare whether the on-off state of each section switch of each uncompressed loop is included in the section switch state set, and obtain a comparison result;
a third power loss and fourth power loss obtaining module, configured to obtain, if the comparison result indicates that the connection switch is not disconnected or the disconnection state of the connection switch of the uncompressed loop is disconnected, third power loss of the uncompressed loop in the parallelized power distribution network reconfiguration system when the connection switch is disconnected and all the section switches are closed, and fourth power loss of the uncompressed loop in the parallelized power distribution network reconfiguration system when the section switches are sequentially disconnected and the connection switch is closed;
and the on-off state correction module is used for obtaining the minimum loss in the third power loss and the fourth power loss, and selecting the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop corresponding to the minimum loss as the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop in the sub-network.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a parallel power distribution network reconstruction method, which divides the reconstruction problem of a power distribution network into three stages: the method comprises the steps of network decomposition, ring level reconstruction and combination, wherein a parallelization power distribution network reconstruction system is divided into sub-networks with the same number of loops, a ring level reconstruction model of each sub-network is established, a branch exchange method is adopted to calculate the on-off state of a tie switch and the on-off state of a section switch in each sub-network, and the on-off state of the tie switch and the on-off state of the section switch of an uncompressed loop in all the sub-networks are extracted to form a reconstruction result of the parallelization power distribution network. The invention realizes parallelization network reconstruction, effectively reduces the calculation time of network reconstruction and improves the efficiency of network reconstruction.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive labor.
FIG. 1 is a flow chart of a parallelized power distribution network reconstruction method according to the present invention;
FIG. 2 is a schematic diagram of a parallelized power distribution network reconfiguration method according to the present invention;
fig. 3 is a structural diagram of a power distribution network according to an embodiment of the present invention;
fig. 4 is a process diagram of a parallelized power distribution network reconfiguration system according to an embodiment of the present invention;
FIG. 5 is a diagram of a network compression model according to an embodiment of the present invention; FIG. 5(a) shows an N-node network before compression, and FIG. 5(b) shows a loop l 1 (N-1) node network kept uncompressed, loop l in FIG. 5(c) 2 A 12-node network that remains uncompressed, loop l in FIG. 5(d) 3 A 14-node network that remains uncompressed;
fig. 6 is a diagram of a node network compression process provided in an embodiment of the present invention; fig. 6(a) shows a node network before compression, and fig. 6(b) shows a node network after compression.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a method and a system for reconstructing a parallel power distribution network, so as to improve the reconstruction efficiency of a power distribution network.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The invention provides a parallel power distribution network reconstruction method, as shown in fig. 1, the method comprises the following steps:
s101, constructing a parallel power distribution network reconstruction system; the parallel power distribution network reconstruction system comprises a plurality of loops, wherein each loop consists of an interconnection switch and a plurality of section switches;
s102, determining an mth loop in the parallel power distribution network reconstruction system as an mth uncompressed loop, and determining each loop except the mth uncompressed loop as a loop to be compressed;
s103, combining a plurality of continuous nodes with the same node degree in each loop to be compressed into a node, wherein corresponding branches and switches are equivalent to a branch and a switch respectively, and a plurality of compressed loops are obtained;
s104, the mth uncompressed loop and the plurality of compressed loops form the mth sub-network of the parallel power distribution network reconstruction system;
s105, establishing a ring level reconstruction model of each sub-network;
s106, calculating the on-off state of the interconnection switch and the on-off state of the section switch in each sub-network according to the ring level reconstruction model of each sub-network;
and S107, extracting the on-off states of the interconnection switches and the on-off states of the section switches of the uncompressed loops in all the sub-networks to form a reconstruction result of the parallelized power distribution network.
Step S103, then further comprising:
respectively determining that a first power loss of a branch where continuous nodes with the same degree of nodes in a loop to be compressed are located and a branch where the continuous nodes with the same degree of nodes in the compressed loop are located are equivalent to a second power loss after one branch;
according to the resistance and the reactance of a branch where continuous nodes with the same node degree in a loop to be compressed are located, and on the basis of the principle that the first power loss and the second power loss are equal, the continuous nodes with the same node degree are obtained and combined into equivalent active power and equivalent reactive power at one node.
In step S105, the ring-level reconstruction model is:
wherein f () is a reconstruction objective function; k is a radical of ij For uncompressed loops l m The state of the switch on the middle branch i-j, if the switch is open, k ij 0, otherwise k ij ＝1；k′ ij For compressed loop l -m The state of the switches on the middle branch i-j; k S And K' S Are each k ij And k' ij Vector of (A), R i-j And R' i-j Respectively uncompressed loop l m And a compressed loop l -m Resistance of the middle branch i-j, P j And P' j Respectively uncompressed loop l m And a compressed loop l -m Active power of intermediate node j, Q j And Q' j Respectively uncompressed loop l m And a compressed loop l -m Reactive power of intermediate node j, U j And U' j Node voltages, P, of node j, respectively ij Is the power of branch i-j, P c_min And P c_max Is the upper and lower limits, U, of the power line transmission capacity min 、U max Are the lowest and highest node voltages, alpha, respectively ij Indicating whether node j is the parent node, alpha, of node i ji Is whether node i is the parent of node j, N Sub Is a transformer node set, and N is the number of nodes.
Step S106, then further comprising:
the on-off states of the section switches of all compressed loops corresponding to each uncompressed loop form a section switch state set;
comparing whether the on-off state of each section switch of each uncompressed loop is contained in the section switch state set or not to obtain a comparison result;
if the comparison result shows that the connection switch is not disconnected or the connection switch of the uncompressed loop is disconnected, respectively obtaining third power loss of the uncompressed loop in the parallel distribution network reconstruction system when the connection switch is disconnected and all section switches are closed, and sequentially disconnecting the section switches and simultaneously closing the connection switch, and obtaining fourth power loss of the uncompressed loop in the parallel distribution network reconstruction system;
and obtaining the minimum loss in the third power loss and the fourth power loss, and selecting the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop corresponding to the minimum loss as the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop in the sub-network.
The invention considers the network trend which is complicated after the new energy is distributed and accessed into the power grid, changes the optimal operation structure of the power grid, and divides the network reconstruction problem into three parts of network decomposition, ring level network reconstruction and combination from the characteristics of the reconstruction problem. The method comprises the steps of dividing a network into a plurality of parts according to a ring, forming each independent sub-network by combining a compression model, reducing the solution space of reconstruction problems in each sub-network, proposing a parallel reconstruction method of each sub-network, finally obtaining the optimal reconstruction strategy of the whole network through a merging process, and improving the efficiency of network reconstruction by combining parallel calculation.
The invention also provides an embodiment of a parallelized power distribution network reconstruction method, which is shown in fig. 2.
Step 1: and constructing a parallel power distribution network reconstruction system and providing a distribution network reconstruction task dividing method.
The distribution network is a directed graph G (M, B, A) composed of nodes and branches, wherein M is a set of nodes in the network, B is a set of branches in the network, and A is an adjacency matrix. According to the knowledge of graph theory, the number of branches connected by a node is called the degree D of the node. As shown in fig. 3, each branch corresponds to a section switch or a tie switch for connecting any two nodes, and the network can be divided into a plurality of loops, each loop is composed of a tie switch and a plurality of section switches, such as l in fig. 3 1 ，l 2 ，l 3 As shown. In addition, a switch needs to be opened in the loop to meet the radial operating conditions of the distribution network. When the power distribution network is reconstructed, the state of the switch can be dynamically changed according to the node power, so that the operation of the power distribution network is optimized under the condition that the radial operation condition of the power distribution network is met.
In order to realize the parallel solution of the power distribution network reconstruction problem, the invention provides a parallel power distribution network reconstruction system, as shown in fig. 4, and a power distribution network reconstruction task is divided into three parts, namely network decomposition, ring level network reconstruction and merging.
(1) Network decomposition: the network decomposition divides the network into a plurality of independent sub-networks according to the loop, and each sub-network consists of the loop and other parts of the network. In order to reduce the solution space of the reconstruction problem under the condition of keeping loop information, a network compression model is adopted to compress other parts of the original network, and a simplified network structure is obtained. The sub-networks reduce the number of branches and nodes of the network while maintaining the network structure. Therefore, the reconstruction problem of the original network can be equivalently replaced by the reconstruction problems of a plurality of sub-networks, and the solution of a plurality of reconstruction problems can be executed in parallel.
(2) And (3) ring level reconstruction: the ring level reconstruction refers to the reconstruction calculation of the sub-networks obtained by the network decomposition, wherein each sub-network comprises an uncompressed ring and other compressed parts. Therefore, a ring level network reconstruction model considering both the uncompressed loop and the compressed part is established, and by the model, an accurate solution of the uncompressed loop and a fuzzy solution of the compressed part network can be obtained. Furthermore, each sub-network is independent of the other, and the ring level network reconstruction models for different sub-networks can be executed on different processors.
(3) Merging: and after ring level network reconstruction is executed, combining ring level reconstruction solutions of a plurality of sub-networks to obtain the optimal solution of the whole network. The network decomposition reduces the solution space of the reconstruction problem, however, because of the network compression, a tiny error occurs in the merging process, and in order to avoid the misjudgment of the switch state, a correction method is executed to correct the reconstruction result, so that the optimal solution of the whole network is obtained.
Step 2: based on the distribution network reconstruction task division method in the step 1, a distribution network decomposition mechanism based on a network compression model is provided, the distribution network is divided into a plurality of independent sub-networks according to a ring, and the solution space of the distribution network reconstruction problem is reduced under the condition that the distribution network loss is kept unchanged.
According to different rings in the distribution network, the distribution network can be divided into different parts, namely one ring corresponds to one part. However, the loops are coupled and cannot be optimized independently. Therefore, for a ring, the parts of the original network except the ring are compressed by using a compression model, a sub-network is formed together with the ring, the topological structure of the sub-network is consistent with that of the original network, and the number of branches and nodes is reduced due to network compression, so that the solution space for reconstructing each sub-network is reduced.
1) Network compression model
FIG. 5 is a diagram of a network compression model according to an embodiment of the present invention; FIG. 5(a) shows an N-node network before compression, and FIG. 5(b) shows l 1 (N-1) node network kept uncompressed, l in FIG. 5(c) 2 A 12-node network that remains uncompressed, fig. 5(d) is l 3 A 14-node network that remains uncompressed;
as can be seen from FIG. 5(a), nodes (15,16, …, N-1, N) are all on legs 1-N, and the degrees of the nodes are all 2. The load of a node (15,16, …, N-1, N) may be equivalent to a composite load, and the corresponding node and branch may also be equivalent to a node and a branch, respectively.
Definition 1: in the power distribution network, a plurality of continuous nodes with the degree of 2 are combined into one node, and corresponding branches and switches are respectively equivalent to one branch and one switch.
In the network compression process, in order to ensure the equivalence of the compression process, equivalent processing needs to be performed on the electrical parameters (branch impedance and node power) of the power distribution network, the equivalence of the electrical parameters is described by taking the branches 1-N in the original network shown in fig. 5(a) as an example, and the resistances and impedances of the branches 1-11' in the sub-network shown in fig. 5(c) need to satisfy the following formulas.
R′ 1-11′ ＝R 1-15 +R 15-16 +…+R (N-1)- N (1)
X′ 1-11 ＝X 1-15 +X 15-16 +…+X (N-1)-N (2)
Wherein R' 1-11′ 、X′ 1-11′ Respectively the resistance and reactance, R, of the branches 1-11 (N-1)-N 、X (N-1)-N Respectively the resistance and reactance of the branch (N-1) -N, N being the number of nodes.
The power at node (15,16, …, N-1, N) and node 11 'should be equivalent for node 1, however, the equivalent power at node 11' is not simply the sum of the power at node (15,16, N1, N) because of branch losses due to branch impedances. The goal of the node power equivalence procedure is to achieve the same node power with the same power loss at branches 1-N and equivalent branches 1-11'. The power losses of branches 1-N and 1-11' for a constant node voltage are calculated as follows.
Wherein, P loss Is the power loss of branches 1-N and 1-11', P N 、Q N Respectively active and reactive power, U, of node N N Is the node voltage of node N, P' L11′ Is the equivalent active power of the equivalent node 11'.
The influence of the reactive power of the node and the power loss of the downstream branch is ignored in the calculation process of the power loss because the reactive power of the node and the power loss of the single branch are smaller, and in addition, the P 'is obtained according to the formula (1) and the formula (3-4) in consideration of smaller deviation of the node voltage in normal operation' L11′ The calculation method of (a) is as follows:
the calculation method of the equivalent reactive power of the equivalent node 11' is as follows:
2) network decomposition mechanism
The invention provides a network decomposition mechanism based on a loop structure and a network compression model of a power distribution network, wherein the network decomposition mechanism is a process of decomposing an original network into a plurality of parts according to a loop and forming an independent sub-network by combining a compression model, and the sub-network obtained by decomposition is composed of an uncompressed loop l m And the number of sub-networks is equal to the number of rings in the original networkThe number of ways. Wherein for the simultaneous inclusion in loop l m And other parts of the network l -m Node and branch in loop l m The specific network decomposition process is shown in fig. 5, which is to be handled, i.e. kept uncompressed.
There are three loops in the N-node network shown in fig. 5(a), and thus three sub-networks shown in fig. 5(b), (c) and (d) can be obtained. To maintain loop l 2 Uncompressed example, loop l 2 Node and branch in (1) remain unchanged, while loop l 1 And l 3 The nodes and branches in (1) are compressed. Nodes (6, 7,8,9), (15,16, N-1, N) and (13,14) in fig. 5(a) are compressed to nodes 6', 10' and 11', respectively, in the sub-network shown in fig. 5(c), and branches 5' -6', 9' -10' and 1' -11', respectively, in the sub-network shown in fig. 5(c) are compressed equivalent branches. And, the nodes (3,4,5) are both in loop l 1 Also in loop l 2 In accordance with loop l 2 I.e. remain uncompressed.
And step 3: and (3) establishing a ring level reconstruction model based on the sub-network with the compressed area and the uncompressed area obtained in the step (2), solving the established reconstruction model by adopting a branch exchange method, and executing a ring level reconstruction process in a parallelization mode.
(1) Establishing a ring level reconstruction model
In order to save computation time and computation resources, parallelized ring-level reconstruction is performed based on the information of the plurality of subnetworks obtained in step 2. Ring level reconstruction refers to reconstructing a sub-network that holds one ring uncompressed while the other ring compresses. The reconstruction aims to optimize the operation of the power distribution network, the reconstruction problem comprises various objective functions such as voltage, power loss, control of three-phase balance and the like, and the power loss is used as the reconstruction objective function. For loop l m The ring level reconstruction model is expressed as
s.t.P c_min ≤P ij ≤P c_max (8)
U min ≤U j ≤U max (9)
∑ i,j∈N k ij ＝N-1 (10)
α ij +α ji ＝k ij (11)
In the formula, k ij Is the state of the switch on branch i-j, if the switch is open, k ij 0, otherwise k ij ＝1， K S And K' S Are each k ij And k' ij Vector of (A), P c_min 、P c_max Is the upper and lower limits of the transmission capacity of the power line, U min 、 U max Respectively the lowest and highest node voltages, alpha ij Indicating whether node j is the parent node of node i, is a binary variable, N Sub Is a set of transformer nodes. Equations (8-9) are constraints on transmission line power flow and node voltage, respectively, and equations (10-13) are constraints on radial operation of the distribution network. Wherein, the formula (10) shows that the network topology is a tree structure, namely a radial structure; the expression (11) represents that one of the two nodes is a parent node and one is a child node; equation (12) indicates that each node has only one parent node at most.
By solving the ring level reconstruction model, a loop l can be obtained m And the optimal reconstruction result, i.e. the state combination of the corresponding branch switch at the minimum power loss. However, determining the state of the switches is a discrete problem, and the solution space increases as the number of switches increases, so the ring level reconstruction problem is a nonlinear combinatorial optimization problem, which is difficult to solve by a general mathematical method.
(2) Parallelization solution established model based on branch exchange method
Aiming at the ring level reconstruction problem difficult to solve, a branch exchange method is adopted for solving, and the branch exchange method is used for searching an optimal reconstruction result by continuously exchanging switch states. The solving process of the branch exchange method comprises three steps of selecting an exchange switch, calculating the power loss after the exchange switch and determining the switch state according to the calculated power loss. By selecting the switch, the number of feasible solutions is reduced, and the rapid solution of the ring level reconstruction problem is realized.
The solution process of the branch exchange method is to close a connection switch, select a section switch as an exchange switch in the loop, and traverse all switches in the loop. In selecting a sectionalizer, changing the switch state may reduce power loss when the following two conditions are met.
Condition 1: there is a significant voltage difference across the tie switch.
Condition 2: the selected section switch is located on the low voltage side of the tie switch.
And (3) executing the branch switching method in parallel in different processors according to the plurality of independent sub-networks obtained in the step (2), thereby quickly obtaining the reconstruction result of each sub-network.
And 4, step 4: and (3) executing a merging process based on a reconstruction result obtained by the ring level reconstruction model in the step (3), and providing a correction method to correct the switch state misjudgment possibly occurring in the summarizing process and prove the effectiveness of the correction model.
(1) Merging process
Based on the reconstruction results of the sub-networks obtained in step 3. For loop l m The sub-network is kept uncompressed, and the loop l can be obtained by solving m With other compression loops l -m The fuzzy reconstruction result of (1). And combining the reconstruction results obtained by all the sub-networks to obtain the reconstruction result of the whole power distribution network. Among the plurality of reconstruction results obtained after the merging, there is one accurate reconstruction result and a plurality of fuzzy reconstruction results for the same loop, and the fuzzy reconstruction results obtained from different subnetworks should be the same and the accurate reconstruction result should be included in the fuzzy reconstruction result. Taking the sub-networks shown in FIGS. 5(c) and (d) as an example, if the loop l is in the sub-network shown in FIG. 5(c) 2 The switches that are open are 2'-3', 3'-4' or 4'-5', the subnet shown in FIG. 5(d)The switches that are turned on in the network must be 2'-3', and in addition, the switches 2-3, 3-4 and 4-5 in the original network shown in fig. 5(a) are all included in the switches 2'-3' of the sub-network shown in fig. 5 (d).
(2) Correction method
The reconstruction results from the merging process will have a slight error due to network compression. For a sub-network, the uncompressed loop is referred to as the inner network and the other part as the outer network. According to the definitions 1 and the expressions (1-2) and (5-6), the electrical parameters of the compressed branch are only determined by the impedance and the node power of the corresponding branch, so that the compressed loop is ensured not to be influenced when the external network of the compressed loop is changed, the dynamic network equivalence is avoided, the complexity of the network equivalence is reduced, and the equivalence time is shortened. However, the compression model is completely equivalent to a network with only nodes with the degree D less than or equal to 2, and if the network contains nodes with the degree D greater than 2, the power loss of the power distribution network is influenced by all branch impedances and node powers, so that the compression model generates a little deviation when calculating the power loss. In order to correct the misjudgment of the switch state possibly caused by the error, the invention provides a corresponding correction method.
The correction method comprises the following steps: when the initial solution of the sub-network obtained by the ring level reconstruction is to disconnect the tie switch in the loop, the power losses under the two conditions of disconnecting the tie switch and the section switch in the original network are compared, and the minimum power loss is selected as the optimal reconstruction result, as shown in the following formula.
In the formula (I), the compound is shown in the specification,
and
are respectively a loop l m The set of section switches and tie switches in (1),
is the node voltage of node j.
The effectiveness of the correction model proves that:
to illustrate the effectiveness of the correction method, a mathematical demonstration is made based on fig. 6, assuming a node voltage of 1p.u. and ignoring the effect of other branches on the single branch power loss calculation.
The power distribution network comprises two switches, namely a section switch and an interconnection switch, so that analysis is performed under two scenes of disconnection of the interconnection switch and section opening.
Disconnecting the interconnection switch: it is assumed that the optimal reconfiguration of the 6-node network shown in fig. 6(a) is to open tie switches 3-5, i.e. satisfy the following set of inequalities:
in the formula, P loss_35 ，P loss_45 ，P loss_14 ，P loss_23 And P loss_12 The power losses of the open branches 3-5, 4-5, 1-4, 2-3 and 1-2, respectively.
Based on equation (7) and the assumptions made above regarding the effects of node voltage and power loss, P loss_35 ， P loss_45 And P loss_14 The calculation can be made by the following formula.
P ∑ ＝P 2 +P 3 +P 4 +P 5 (19)
In the formula, P 2 ，P 3 ，P 4 ，P 5 Node powers, R, of nodes 2, 3,4,5, respectively 1-2 ，R 2-3 ， R 1-4 ，R 4-5 Are the branch resistances of branches 1-2, 2-3, 1-4, 4-5, respectively, and P Σ is the sum of the node powers of nodes 2, 3,4, 5.
From the equations (15 to 19), the following inequalities can be obtained.
R 1-4 +R 4-5 -R≤R 1-2 +R 2-3 ≤R 1-4 +R 4-5 +R (20)
Where R is the resistance of branches 3-5.
Based on equations (1) and (5), the branch resistances and node powers of the sub-networks shown in FIG. 6(b) can be expressed as
In the formula (II), R' 1′-2′ ，R′ 2′-3′ Is the equivalent resistance of equivalent branches 1' -2 ' and 3' -4', P ' 2′ ，P′ 3′ Is the equivalent node power for equivalent nodes 2 'and 3'.
In the sub-network shown in fig. 6(b), the difference in the network losses of disconnecting tie switches 2'-3' and section switches 1 '-3' is as follows:
according to formula (20-22), P loss_2′3′ -P loss_1′3′ 0 or less, and likewise, P can be obtained loss_2′3′ -P loss_1′2′ Less than or equal to 0. Thus, when the most reconstructed result of the original network is to open the tie switch, the optimal reconstructed result of the sub-network is also to open the tie switch.
Disconnecting the section switch: suppose that the optimal reconfiguration result for the 6-node network shown in fig. 6(a) is to open the sectionalizers 4-5, i.e., satisfy the following set of inequalities:
from the equations (16-19) and (24), the inequalities shown below are obtained.
R 1-2 +R 2-3 +R≤R 1-4 +R 4-5 (26)
P 2 R 1-2 ≤P 4 R 1-4 (27)
R 1-4 ≤R 1-2 +R 2-3 +R+R 4-5 (28)
In the sub-network shown in fig. 6(b), the difference in network losses for opening the segment switches 1 '-3' and 1 '-2' is as follows:
obtaining P according to formulae (22), (26) and (29-31) loss_1′3′ -P loss_1′2′ Less than or equal to 0. Therefore, when the optimal reconstruction result of the original network is to disconnect the sectional switch, the optimal reconstruction result of the sub-network does not disconnect the sectional switches on other equivalent branches.
The difference in the network losses of the section switches 1 '-3' and the tie switches 2'-3' in the disconnection sub-network is as follows.
From the formulae (21-22), (29) and (31), P cannot be directly judged loss_1′3′ And P loss2′3′ Is connected, it may be misjudged in the sub-network that the tie switch is open.
Through the analysis of the two scenes, the optimal reconstruction result of the corresponding original network can be misjudged only when the optimal reconstruction result of the sub-network is the disconnection of the interconnection switch. Therefore, the power loss of the two scenes of respectively opening the tie switch and the section switch needs to be compared and corrected in the original network.
And 5: and (4) obtaining an optimal target reconstruction scheme of the power distribution network based on the power distribution network reconstruction process in the steps 2, 3 and 4.
And (3) executing the correction method in the step (4) on the reconstruction result of each sub network, finally taking out the reconstruction result of the uncompressed ring from each reconstruction result correspondingly, and combining the reconstruction results to obtain the optimal target reconstruction scheme of the power distribution network, namely the on-off state of the switches in all the power grid branches.
The key points and protection points of the invention are as follows:
(1) according to the invention, by establishing a parallel power distribution network reconstruction system, the power distribution network reconstruction problem is divided into three stages, namely a network decomposition process, a ring level reconstruction process and a merging process, and the connection relation among the three stages is determined, so that the parallel network reconstruction is realized, the calculation time of the network reconstruction is effectively reduced, and the network reconstruction efficiency is improved.
(2) The invention provides a method for parallelization network reconstruction by providing a network decomposition mechanism, and decomposes the network according to the ring of the power distribution network and a network compression model to obtain sub-networks with the same number as the rings. The sub-networks comprise a ring and other areas of the original network, the ring information is reserved, and the other area networks are compressed by using a network compression model so as to reduce the reconstructed solution space of each sub-network.
(3) The invention carries out parallelization network reconstruction by constructing a ring level reconstruction model, each sub-network comprises an uncompressed ring and other compressed parts, and each sub-network is independent. And performing reconstruction on each sub-network through the parallelization of the ring-level reconstruction model to obtain a ring-level reconstruction solution, including an accurate solution of an uncompressed ring and a fuzzy solution of other regional networks.
(4) The invention combines the reconstruction results obtained by each sub-network by proposing a combining process, corrects the misjudgment possibly generated in the combining process by respectively disconnecting the interconnection switch and the section switch obtained by reconstruction, selects the result of the optimal reconstruction target as the final result of reconstruction so as to ensure the optimality of the solution, and proves the effectiveness of the correction model based on mathematical derivation.
By adopting the parallelization network reconstruction method, the method can be applied to the existing power distribution and utilization system, the power distribution network reconstruction process is executed in power distribution network management mechanisms such as power distribution network operators and the like, the power distribution network reconstruction process is divided into three tasks, each sub-network structure of the power distribution network is obtained by combining a network decomposition mechanism and a network compression model, each sub-network is distributed to different processors of computing resources of an execution mechanism, the ring level reconstruction process is executed in a parallelization manner, the merging process is executed finally, the dimensionality of the power distribution network is reduced by utilizing the modes of task division and parallel computing, the computing time of network reconstruction is reduced, and the efficiency of power distribution network reconstruction is improved.
Under the energy background that a large number of distributed photovoltaics are connected into a power distribution network and the technical background that the scale of the power distribution network is gradually enlarged, an efficient solution is provided for power distribution network reconstruction. The proposed power distribution network decomposition mechanism can obtain a plurality of independent sub-networks, and the ring level reconstruction process can be executed in parallel in different processors for each independent sub-network. During actual execution, load and photovoltaic information of each user node in the network and line impedance information of the network are brought in, and the optimal state of all switches in the network can be obtained. The system comprising the decomposition, parallel execution and combination processes can be used in power distribution network reconstruction, and can also be used in various distributed computing scenarios which cannot be completely decoupled, such as optimized scheduling of the internet of vehicles and optimized scheduling of P2P energy, and under the condition of coupling influence, iterative processes are avoided, computing time is reduced, and computing efficiency is improved.
The invention also provides a system for reconstructing the parallelization power distribution network, which comprises the following steps:
the parallel power distribution network reconstruction system construction module is used for constructing a parallel power distribution network reconstruction system; the parallel power distribution network reconstruction system comprises a plurality of loops, wherein each loop consists of a tie switch and a plurality of section switches;
the device comprises an uncompressed loop and loop to be compressed determining module, a compressing module and a compressing module, wherein the uncompressed loop and the loop to be compressed determining module are used for determining the mth loop in the parallelization power distribution network reconstruction system as the mth uncompressed loop, and each loop except the mth uncompressed loop is determined as the loop to be compressed;
the compressed loop obtaining module is used for combining a plurality of continuous nodes with the same node degree in each loop to be compressed into a node, and corresponding branches and switches are equivalent to a branch and a switch respectively to obtain a plurality of compressed loops;
the sub-network forming module is used for forming the mth sub-network of the parallel power distribution network reconstruction system by the mth uncompressed loop and the plurality of compressed loops;
the ring level reconstruction model establishing module is used for establishing a ring level reconstruction model of each sub-network;
the on-off state calculation module is used for calculating the on-off state of the interconnection switch and the on-off state of the section switch in each sub-network according to the ring level reconstruction model of each sub-network;
and the reconstruction result forming module is used for extracting the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop in all the sub-networks to form the reconstruction result of the parallelized power distribution network.
The system further comprises:
the first power loss and second power loss determining module is used for respectively determining that a first power loss of a branch where continuous nodes with the same degree of nodes in a loop to be compressed are located and a branch where continuous nodes with the same degree of nodes in the compressed loop are located are equivalent to a second power loss after one branch;
and the equivalent active power and equivalent reactive power obtaining module is used for obtaining the equivalent active power and the equivalent reactive power which are combined into a node by the continuous nodes with the same degree of the node based on the principle that the first power loss and the second power loss are equal according to the resistance and the reactance of the branch where the continuous nodes with the same degree of the node in the loop to be compressed are located.
The ring level reconstruction model is as follows:
wherein f () is a reconstruction objective function; k is a radical of formula ij For uncompressed loops l m The state of the switch on the middle branch i-j, if the switch is open, k ij 0, otherwise k ij ＝1；k′ ij For compressed loop l -m The state of the switches on the middle branch i-j; k S And K' S Are each k ij And k' ij Vector of (A), R i-j And R' i-j Respectively uncompressed loop l m And a compressed loop l -m Resistance of the middle branch i-j, P j And P' j Respectively uncompressed loop l m And a compressed loop l -m Active power of intermediate node j, Q j And Q' j Respectively uncompressed loop l m And a compressed loop l -m Reactive power of intermediate node j, U j And U' j Node voltages, P, of node j, respectively ij Is the power of branch i-j, P c_min And P c_max Is the upper and lower limits, U, of the power line transmission capacity min 、U max Respectively the lowest and highest node voltages, alpha ij Indicating whether node j is the parent node, alpha, of node i ji Is whether node i is the parent of node j, N Sub Is a transformer node setAnd N is the number of nodes.
The system further comprises:
the segmented switch state set forming module is used for forming the on-off states of the segmented switches of all compressed loops corresponding to each uncompressed loop into a segmented switch state set;
the comparison result obtaining module is used for comparing whether the on-off state of each section switch of each uncompressed loop is contained in the section switch state set or not to obtain a comparison result;
a third power loss and fourth power loss obtaining module, configured to obtain, if the comparison result indicates that the connection switch is not disconnected or the disconnection state of the connection switch of the uncompressed loop is disconnected, third power losses of the uncompressed loop in the parallelized power distribution network reconfiguration system when the connection switch is disconnected and all the section switches are closed, and fourth power losses of the uncompressed loop in the parallelized power distribution network reconfiguration system when the section switches are sequentially disconnected and the connection switch is closed;
and the on-off state correction module is used for obtaining the minimum loss in the third power loss and the fourth power loss, and selecting the on-off state of the interconnection switch of the uncompressed loop and the on-off state of the section switch corresponding to the minimum loss as the on-off state of the interconnection switch of the uncompressed loop and the on-off state of the section switch in the sub network.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (8)
1. A parallelized power distribution network reconstruction method, the method comprising:
constructing a parallel power distribution network reconstruction system; the parallel power distribution network reconstruction system comprises a plurality of loops, wherein each loop consists of an interconnection switch and a plurality of section switches;
determining an mth loop in the parallel distribution network reconstruction system as an mth uncompressed loop, and determining each loop except the mth uncompressed loop as a loop to be compressed;
combining a plurality of continuous nodes with the same node degree in each loop to be compressed into a node, wherein corresponding branches and switches are equivalent to a branch and a switch respectively to obtain a plurality of compressed loops;
the mth uncompressed loop and the plurality of compressed loops form an mth sub-network of the parallel distribution network reconstruction system;
establishing a ring level reconstruction model of each sub-network;
calculating the on-off state of a tie switch and the on-off state of a section switch in each sub-network according to the ring level reconstruction model of each sub-network;
and extracting the on-off states of the interconnection switches and the on-off states of the section switches of the uncompressed loops in all the sub-networks to form a reconstruction result of the parallelized power distribution network.
2. The method according to claim 1, wherein the method for reconstructing the parallelized power distribution network combines a plurality of nodes with the same degree of nodes in each loop to be compressed into one node, and the corresponding branch and switch are equivalent to one branch and one switch, respectively, so as to obtain a plurality of compressed loops, and then further comprises:
respectively determining that a first power loss of a branch where continuous nodes with the same degree of nodes in a loop to be compressed are located and a branch where the continuous nodes with the same degree of nodes in the compressed loop are located are equivalent to a second power loss after one branch;
and according to the resistance and the reactance of a branch where continuous nodes with the same node degree in the loop to be compressed are located, obtaining the equivalent active power and the equivalent reactive power which are obtained by combining the continuous nodes with the same node degree into one node based on the principle that the first power loss and the second power loss are equal.
3. The parallelized power distribution network reconstruction method of claim 1, wherein the ring level reconstruction model is:
wherein f () is a reconstruction objective function; k is a radical of ij For uncompressed loops l m The state of the switch on the middle branch i-j, if the switch is open, k ij 0, otherwise k ij ＝1；k′ ij For compressed loop l -m The state of the switches on the middle branch i-j; k S And K' S Are each k ij And k' ij Vector of (A), R i-j And R' i-j Respectively uncompressed loop l m And a compressed loop l -m Resistance of the middle branch i-j, P j And P' j Respectively uncompressed loop l m And a compressed loop l -m Active power of intermediate node j, Q j And Q' j Respectively uncompressed loop l m And a compressed loop l -m Reactive power of intermediate node j, U j And U' j Node voltages, P, of node j, respectively ij Is the power of branch i-j, P c_min And P c_max Is the upper and lower limits, U, of the power line transmission capacity min 、U max Respectively the lowest and highest node voltages, alpha ij Indicates whether node j is the parent node of node i, α ji Is whether node i is the parent of node j, N Sub Is a transformer node set, and N is the number of nodes.
4. The method for reconstructing the parallelized power distribution network according to claim 1, wherein the calculating the on-off state of the tie switches and the on-off state of the section switches in each sub-network according to the ring level reconstruction model of each sub-network further comprises:
the on-off states of the section switches of all compressed loops corresponding to each uncompressed loop form a section switch state set;
comparing whether the on-off state of each section switch of each uncompressed loop is contained in the section switch state set or not to obtain a comparison result;
if the comparison result shows that the connection switch is not disconnected or the connection switch of the uncompressed loop is disconnected, respectively obtaining a third power loss of the uncompressed loop in the parallel power distribution network reconstruction system when the connection switch is disconnected and all section switches are closed, and sequentially disconnecting the section switches and simultaneously closing the connection switch, and obtaining a fourth power loss of the uncompressed loop in the parallel power distribution network reconstruction system;
and obtaining the minimum loss in the third power loss and the fourth power loss, and selecting the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop corresponding to the minimum loss as the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop in the sub-network.
5. A parallelized power distribution network reconfiguration system, the system comprising:
the parallel power distribution network reconstruction system construction module is used for constructing a parallel power distribution network reconstruction system; the parallel power distribution network reconstruction system comprises a plurality of loops, wherein each loop consists of an interconnection switch and a plurality of section switches;
the uncompressed loop and loop to be compressed determining module is used for determining the mth loop in the parallelization power distribution network reconstruction system as the mth uncompressed loop, and each loop except the mth uncompressed loop is determined as a loop to be compressed;
the compressed loop obtaining module is used for combining a plurality of continuous nodes with the same node degree in each loop to be compressed into a node, and corresponding branches and switches are equivalent to a branch and a switch respectively to obtain a plurality of compressed loops;
a sub-network forming module, configured to form a mth sub-network of the parallelized power distribution network reconfiguration system from the mth uncompressed loop and the plurality of compressed loops;
the ring level reconstruction model establishing module is used for establishing a ring level reconstruction model of each sub-network;
the on-off state calculation module is used for calculating the on-off state of the interconnection switch and the on-off state of the section switch in each sub-network according to the ring level reconstruction model of each sub-network;
and the reconstruction result forming module is used for extracting the on-off state of the interconnection switch and the on-off state of the section switch of the uncompressed loop in all the sub-networks to form the reconstruction result of the parallelized power distribution network.
6. The parallelized power distribution network reconfiguration system according to claim 5, further comprising:
the first power loss and second power loss determining module is used for respectively determining that a first power loss of a branch where continuous nodes with the same degree of nodes in a loop to be compressed are located and a branch where continuous nodes with the same degree of nodes in the compressed loop are located are equivalent to a second power loss after one branch;
and the equivalent active power and equivalent reactive power obtaining module is used for obtaining the equivalent active power and the equivalent reactive power which are combined into a node by the continuous nodes with the same node degree based on the principle that the first power loss is equal to the second power loss according to the resistance and the reactance of the branch where the continuous nodes with the same node degree in the loop to be compressed are located.
7. The parallelized power distribution network reconstruction system of claim 5, wherein the ring level reconstruction model is:
wherein f () is a reconstruction objective function; k is a radical of ij For uncompressed loops l m The state of the switch on the middle branch i-j, if the switch is open, k ij 0, otherwise k ij ＝1；k′ ij For compressed loop l -m The state of the switches on the middle branch i-j; k S And K' S Are each k ij And k' ij Vector of (A), R i-j And R' i-j Respectively uncompressed loop l m And a compressed loop l -m Resistance of the middle branch i-j, P j And P' j Respectively uncompressed loop l m And a compressed loop l -m Active power of intermediate node j, Q j And Q' j Respectively uncompressed loop l m And a compressed loop l -m Reactive power of intermediate node j, U j And U' j Node voltages, P, of node j, respectively ij Is the power of branch i-j, P c_min And P c_max Is the upper and lower limits, U, of the power line transmission capacity min 、U max Respectively the lowest and highest node voltages, alpha ij Indicating whether node j is the parent node, alpha, of node i ji Is whether node i is the parent of node j, N Sub Is a transformer node set, and N is the number of nodes.
8. The parallelized power distribution network reconfiguration system according to claim 5, further comprising:
the segmented switch state set forming module is used for forming the on-off states of the segmented switches of all compressed loops corresponding to each uncompressed loop into a segmented switch state set;
a comparison result obtaining module, configured to compare whether the on-off state of each section switch of each uncompressed loop is included in the section switch state set, and obtain a comparison result;
a third power loss and fourth power loss obtaining module, configured to obtain, if the comparison result indicates that the connection switch is not turned on or the connection switch of the uncompressed loop is turned off, a third power loss of the uncompressed loop in the parallelized power distribution network reconfiguration system when the connection switch is turned off and all the section switches are turned on, and obtain, when the section switches are turned off in sequence and the connection switch is turned on at the same time, a fourth power loss of the uncompressed loop in the parallelized power distribution network reconfiguration system;
and the on-off state correction module is used for obtaining the minimum loss in the third power loss and the fourth power loss, and selecting the on-off state of the interconnection switch of the uncompressed loop and the on-off state of the section switch corresponding to the minimum loss as the on-off state of the interconnection switch of the uncompressed loop and the on-off state of the section switch in the sub-network.
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