CN115986813A - Power distribution network fault recovery method considering island dynamic division - Google Patents
Power distribution network fault recovery method considering island dynamic division Download PDFInfo
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Abstract
The invention discloses a power distribution network fault recovery method considering island dynamic division, which comprises the following steps: based on the balance capability of the distributed photovoltaic power supply relative to the local load, solving the action time setting values of the reclosing devices at different positions by adopting a reclosing coordination method in the distributed power generation distribution network under the weak communication condition; dividing a planned island operation area based on DG and load capacity in a distribution network; taking the load with the maximized recovery load amount and the heavy priority recovery load as an objective function, and constructing a mathematical model of a distributed fault recovery scheme based on the dynamic island; and acquiring power distribution network parameters required by a mathematical model of the distributed fault recovery scheme based on the dynamic island by adopting a multi-agent system reference average consistency algorithm. The method provided by the invention is an active power distribution network self-adaptive robust optimization method considering a large amount of renewable energy sources and can ensure economic, safe and efficient operation of the active power distribution network under an uncertain condition.
Description
Technical Field
The invention relates to the technical field of reclosing and fault recovery strategies of a photovoltaic power distribution network, in particular to a power distribution network fault recovery method considering island dynamic division.
Background
The fault recovery means that after a fault occurs and is isolated, the corresponding interconnection switch and the corresponding line switch are operated to change a network topology structure so as to recover the power supply of the non-fault power-loss load to the maximum extent and reduce the loss caused by power failure after the fault. The fault power supply recovery is one of the most basic and important functions in the current power distribution network automation, and the power supply quality of a power distribution network is directly influenced by the fault recovery capability. The power distribution network is directly oriented to users, and the perfect and quick fault recovery system can effectively reduce the power failure range, shorten the power failure time and improve the intelligent level of fault treatment.
In the early stage of the distributed power supply being connected to the power distribution network, in order to avoid adverse effects of DGs on the traditional protection of the power distribution network, the control device actively quits all DGs from running when the feeder line fails, so that the power distribution network is restored to a passive radial network, and the original protection can normally act. However, with the increase of the permeability of the DG in the power distribution network, the total removal of the DG not only does not play a positive role in supporting the system voltage given by the DG when the DG is connected to the distribution network and but also may further aggravate the power imbalance of the power grid and influence the stable operation of the power grid. In order to maximize the generation capacity of the DG, the ieee e new standard no longer prohibits conscious islanding, but encourages grid operators and users to achieve planned islanding operation of the distributed power source by technical means as much as possible.
Most of the existing fault recovery methods are traditional centralized control, and the traditional fault recovery methods depend on master station control. Therefore, a distribution network distributed control method independent of a main station becomes a hotspot of research 23428in recent years, each intelligent terminal has calculation and control capabilities, and information exchange of the whole network can be completed through mutual communication between the terminals, so that fault recovery of the whole network is realized.
Disclosure of Invention
This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and title of the application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.
The present invention has been made in view of the above-mentioned conventional problems.
Therefore, the invention aims to provide a power distribution network fault recovery method considering islanding dynamic partitioning, which solves the problem that the traditional centralized control is too dependent on master station control.
In order to solve the technical problems, the invention provides the following technical scheme:
in a first aspect, an embodiment of the present invention provides a power distribution network fault recovery method considering islanding dynamic partitioning, including:
based on the balance capability of the distributed photovoltaic power supply relative to the local load, a reclosing coordination method in the distributed power generation distribution network under the weak communication condition is adopted, the action time setting values of reclosing devices at different positions are obtained, and the impact on the distribution network during reclosing is reduced;
dividing a planned island operation area based on DG and load capacity in a distribution network, and avoiding the removal of the DG due to fault coincidence failure in the fault recovery process of the distribution network;
taking the load with the maximized recovery load amount and the high priority recovery load weight as a target function, and constructing a mathematical model of a distributed fault recovery scheme based on a dynamic island;
and acquiring power distribution network parameters required by a mathematical model of the distributed fault recovery scheme based on the dynamic island by adopting a multi-agent system reference average consistency algorithm.
The invention relates to a power distribution network fault recovery method considering island dynamic division, which comprises the following steps: dividing the planned island operation area comprises that,
one or more appropriate planned island operation areas are divided for each DG in advance;
detecting whether a planned island operation area divided by each DG is still complete after fault isolation, and determining to implement different reclosing schemes;
when a fault occurs and is isolated, if a load in a non-fault power loss area is not connected with a main power supply due to the fault, but a path connected with a DG exists between the load and the DG, and the DG in a power distribution network has relatively stable power supply capacity, a power distribution network fault recovery scheme containing the DG is constructed through a planned isolated island of the DG, fault recovery is realized, and power supply reliability of the power distribution network is improved.
The invention relates to a power distribution network fault recovery method considering island dynamic division, which comprises the following steps: the DG-containing power distribution network fault recovery scheme includes,
dividing a planned island region in advance, detecting a fault occurrence region, and judging whether the fault occurs on the downstream side of a DG or an adjacent feeder line;
if not, power supply recovery is carried out according to the traditional reclosing program, and the fault recovery of the power distribution network is completed;
if so, judging whether a complete island region exists or not;
if the complete island region does not exist, power supply recovery is carried out according to the traditional reclosing program, and the fault recovery of the power distribution network is completed;
if the complete island region exists, judging whether the voltage at the PCC drops below 50 percent of rated voltage for the first time;
if the voltage is lower than 50% of the rated voltage, actively disconnecting the corresponding switch to realize planned isolated island operation, closing the interconnection switch, recovering the fault of the feeder line, synchronously connecting DGs (distributed generation) which are planned isolated island operation to the grid, and completing the fault recovery of the power distribution network;
and if the voltage is not lower than 50% of the rated voltage, power supply recovery is carried out according to the traditional reclosing program, and the fault recovery of the power distribution network is completed.
The invention relates to a power distribution network fault recovery method considering island dynamic division, which comprises the following steps: the mathematical model of the dynamic island based distributed fault recovery scheme includes,
according to a radial distribution network consisting of N nodes, a node set is represented as N = {1, Λ N }, distribution network branches are represented as L = { (i-j) }, i belongs to N, j belongs to N, and fault recovery of a complex distribution network containing DG is represented as a mixed integer programming problem, wherein an objective function expression of the problem is as follows:
wherein f is pload Representing the amount of load recovered, w, taking into account the priority of the load i Represents a priority weight associated with the load at node i, and w i Larger value of (a) represents higher priority, N represents a set of nodes, K represents an island formed by DG, K represents a set of all islands, γ represents a set of islands ik Denotes the connection relationship between node i and island k, γ ik =1 indicating that node i can be powered by islanding k, γ ik =0 indicates that node i cannot be powered by islanding k;
the objective function simultaneously meets node concentration constraint, network connectivity constraint, load constraint to be recovered in an island, active power constraint, node voltage constraint and switch constraint.
The invention relates to a power distribution network fault recovery method considering island dynamic division, which comprises the following steps: the node concentration constraint, the network connectivity constraint and the load constraint to be recovered in the island comprise,
the node set constraint is expressed as:
defining a is a epsilon {0,1}, representing whether the node i belongs to the island K, and if the node i belongs to the island K, a ik =1, otherwise a ik ＝0；
When the node i and the DG are connected to the same bus, the node i belongs to an island where the DG is located;
setting a dominating power distribution network as a tree network, each island is a subtree network, and a root node is a node at a DG installation position, wherein the network connectivity constraint is expressed as:
a ik ≤a jk
j represents a father node of a node i in an island k, and only when the father node belongs to the island k, one node belongs to the island k;
the load constraint to be recovered in the island is expressed as:
γ ik ≤a ik
γ ik ≤s i
γ ik ≥a ik +s i -1
wherein, γ ik E {0,1} represents an auxiliary variable to set, and γ ik ＝a ik ·s i ，s i The load switch state represented as node i is closed to 1 and open to 0.
The invention relates to a power distribution network fault recovery method considering island dynamic division, which comprises the following steps: the active power constraints, node voltage constraints and switching constraints include,
according to the fact that the power flowing into the node is equal to the power flowing out of the node, the active power constraint at each node in the island k is represented as:
wherein, P i k Representing the active power flowing into node i in island k,
a set of child nodes representing nodes in island k;
assuming that the voltage at the node where DG is located is the reference value, the node voltage constraint is expressed as:
wherein, the first and the second end of the pipe are connected with each other,
voltage, V, representing islanding k i k Representing the voltage at node i, R i And X i Respectively, represents the resistance and reactance of branch i-j, respectively>
Is a slack variable set so that the equality constraint is still valid when node i does not belong to island k but its parent node j belongs to island k.
The switch constraints include that for line switches on both sides of the fault area, only the trip condition is available during fault recovery, i.e. c ij ＝-1；
When the load must ensure the power supply, the load switch is in the closing state, i.e. s i ＝1。
The invention relates to a power distribution network fault recovery method considering island dynamic division, which comprises the following steps: the average consensus algorithm comprises the following steps,
the information obtaining process of each bus agent i is iterated as follows:
wherein i =1, Λ n, n represents the number of agents in the distribution network,
represents a local initialization status quantity of agent i, based on the status of the agent i>
And &>
Respectively representing state quantity information acquired by the agent i in the k iteration and the k +1 iteration, a ij Represents the step size of information exchange between the neighboring agents i and j, and if the agents i and j are adjacent, 0 < a ij < 1, otherwise a ij ＝0，R i Representing a set of agents immediately adjacent to agent i;
through the iterative calculation formula, each agent finally obtains the active power of all n nodes of the power distribution network and the global information of the states of all line switches and load switches.
In a second aspect, an embodiment of the present invention provides a method for recovering a fault of a power distribution network considering islanding dynamic partitioning, including,
the method construction module is used for solving the action time setting values of the reclosing devices at different positions by adopting a reclosing coordination method in the distributed power generation distribution network under the weak communication condition based on the balance capacity of the distributed photovoltaic power supply relative to the local load, and reducing the impact on the distribution network during the reclosing period;
the dividing module is used for dividing a planned island operation area based on DGs and load capacity in a distribution network, and preventing the DGs from being cut off due to fault coincidence failure in the fault recovery process of the distribution network;
the model building module is used for building a mathematical model of a distributed fault recovery scheme based on a dynamic island by taking the load with the maximized recovery load capacity and the priority recovery load with large weight as an objective function;
and the calculation module is used for acquiring the power distribution network parameters required by the mathematical model of the distributed fault recovery scheme based on the dynamic isolated island by adopting a multi-agent system reference average consistency algorithm.
In a third aspect, an embodiment of the present invention provides a computing device, including:
a memory and a processor;
the memory is configured to store computer-executable instructions, and the processor is configured to execute the computer-executable instructions, when the one or more programs are executed by the one or more processors, to cause the one or more processors to implement a method for fault recovery of a power distribution network considering islanding dynamic partitioning according to any embodiment of the present invention.
In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium storing computer-executable instructions, which when executed by a processor, implement the method for recovering a power distribution network fault considering islanding dynamic partitioning.
The invention has the beneficial effects that: the method provided by the invention is an active power distribution network self-adaptive robust optimization method considering a large amount of renewable energy sources and can ensure economic, safe and efficient operation of the active power distribution network under an uncertain condition.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced 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 to obtain other drawings based on these drawings without inventive exercise. Wherein:
fig. 1 is a schematic diagram of a reclosing of a power distribution network double-side power supply with photovoltaic access in a power distribution network fault recovery method considering island dynamic division.
Fig. 2 is a diagram of a fault recovery scheme of a distribution network including a DG according to a fault recovery method of a distribution network based on island dynamic partitioning.
Fig. 3 is a schematic diagram of information interaction of a multi-agent system of the power distribution network fault recovery method considering island dynamic division.
Fig. 4 is a schematic diagram of information interaction between BAs of the power distribution network fault recovery method considering islanding dynamic division.
Fig. 5 is a schematic diagram of a DG1 partition planned island of the power distribution network fault recovery method considering island dynamic partition of the present invention.
Fig. 6 is a graph of voltage change at the DG1 common coupling point in the whole fault process of the method for recovering a power distribution network fault considering islanding dynamic division of the present invention.
Fig. 7 is a graph of a voltage change at a DG1 common coupling point in the whole fault recovery process of the method for recovering a power distribution network fault considering islanding dynamic division of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.
Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Furthermore, the present invention is described in detail with reference to the drawings, and for convenience of illustration, the cross-sectional views illustrating the device structures are not enlarged partially according to the general scale when describing the embodiments of the present invention, and the drawings are only exemplary, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.
Example 1
Referring to fig. 1 to 4, in an embodiment of the present invention, a method for recovering a power distribution network fault considering islanding dynamic partitioning is provided, including:
s1: based on the balance capability of the distributed photovoltaic power supply relative to the local load, the action time setting values of the reclosing devices at different positions are obtained by adopting a reclosing coordination method in the distributed power generation distribution network under the weak communication condition, and the impact on the distribution network during the reclosing period is reduced. It should be noted that:
as shown in fig. 1, when a grid-connected tie line breaks down, the two sides of the line have no time delay and are quickly disconnected by directional current to protect the circuit breakers B3 and B5 from tripping, the system side protection 3 proposes to adopt a mode of detecting no voltage on the line for reclosing, the photovoltaic side protection 5 proposes to adopt a mode of detecting no voltage on the line for reclosing, the power supply is recovered after the distributed photovoltaic power supply jumps away from the line, and the specific scheme of the reclosing configuration at the system side protection 3 is as follows: detecting line voltage when the reclosing is started, and when the line voltage-free condition is not met, indicating that the distributed photovoltaic power supply is not correctly tripped, shutting off the reclosing to exit; otherwise, when the non-voltage detection condition is met, reclosing is carried out, and if the fault is a transient fault, reclosing is successful. If the fault is a permanent fault, the reclosing is unsuccessful, the protection acts on the tripping again, and the reclosing lock exits; the action time of a reclosing device at the system side protection 3 is set as follows:
t AR3 ＝t protection 5 -t Protection 3 +t u
Wherein, t Protection 3 The sum of the time t of the quick-break protection action of the photovoltaic side direction current and the action of the breaker B5 Protection 5 The sum of the time t of the quick-break protection action of the photovoltaic side direction current and the action of the breaker B5 u The sum of the arc extinguishing time of the fault point, the recovery time of the insulation strength and the margin time.
The reclosing at the system side protection 3 is unsuccessful, and the protection 5 does not perform reclosing action any more; when the protection 3 is successfully reclosed, the specific scheme of reclosing configuration at the protection 5 of the distributed photovoltaic side is as follows: the photovoltaic side detects that a link line has voltage, and the photovoltaic side bus detects that a bus has no voltage; when the pressure condition of the voltage-free line is met, reclosing is carried out, and if the fault is an instantaneous fault, reclosing is successful; if the fault is a permanent fault and the reclosing is unsuccessful, the protection acts on the tripping again, and the reclosing lock exits; when the distributed photovoltaic works in an island with extremely low occurrence probability due to high matching degree with the local load, the reclosing will not act due to the fact that the photovoltaic side detects that the bus has pressure; therefore, the method can effectively avoid the damage of the photovoltaic inverter in the non-synchronous reclosing dynamic process in the reclosing process; the action time of the reclosing device at the photovoltaic side protection 5 is set as follows:
t AR5 ＝max{(t protection 3 -t Protection 5 +t u )，t Island }
Wherein, t Island The sum of the maximum action time for the protection of the melon island.
S2: and dividing a planned island operation area based on the DG and the load capacity in the distribution network, and avoiding the removal of the DG due to fault reclosing failure in the fault recovery process of the distribution network. It should be noted that:
in order to fully play the active role of the DG when the power distribution network fails, the planned isolated island operation of the DG is realized through a technical mode, and the power supply reliability of the power distribution network is improved.
One or more suitable planned islanding operation areas are pre-partitioned for each DG based on the DG and the load capacity in the distribution network.
And detecting whether the planned island operation area divided by each DG is still complete after fault isolation, and determining to implement different reclosing schemes.
When a fault occurs and is isolated, if a load in a non-fault power loss area is not connected with a main power supply due to the fault, but a connection path exists between the load and a DG, and the DG in a power distribution network has relatively stable power supply capacity, the fault recovery is realized by considering a planned isolated island of the DG, and the power supply reliability of the power distribution network is improved. Thus, several suitable planned island areas are divided for each DG; a specific flowchart of a fault recovery scheme for a distribution network including a DG is shown in fig. 2:
dividing a planned island region in advance, detecting a fault occurrence region, and judging whether the fault occurs on the downstream side of a DG or an adjacent feeder line;
if not, power supply recovery is carried out according to the traditional reclosing program, and the fault recovery of the power distribution network is completed;
if yes, judging whether a complete island region exists or not;
if the complete island region does not exist, power supply recovery is carried out according to the traditional reclosing program, and the fault recovery of the power distribution network is completed;
if the complete island region exists, judging whether the voltage at the PCC drops below 50 percent of rated voltage for the first time;
if the rated voltage is lower than 50%, actively disconnecting the corresponding switch to realize planned isolated island operation, closing the interconnection switch, recovering the fault of the feeder line, synchronously connecting DGs (distributed generation) in the planned isolated island operation, and completing the fault recovery of the power distribution network;
and if the voltage is not lower than 50% of the rated voltage, power supply recovery is carried out according to the traditional reclosing program, and the fault recovery of the power distribution network is completed.
S3: and taking the load with the maximized recovery load amount and the heavy priority recovery load as an objective function, and constructing a mathematical model of the distributed fault recovery scheme based on the dynamic island. It should be noted that:
according to a radial distribution network consisting of N nodes, a node set is represented as N = {1, lambda N }, distribution network branches are represented as L = { (i-j) }, i belongs to N, j belongs to N, fault recovery of a complex distribution network containing DG is represented as a mixed integer programming problem, and an objective function expression is as follows:
wherein f is pload Representing the amount of load recovered, w, taking into account the priority of the load i Represents a priority weight associated with the load at node i, and w i Larger value of (a) represents higher priority, N represents a set of nodes, K represents an island formed by DG, K represents a set of all islands, γ represents a set of islands ik Denotes the connection relationship between node i and island k, γ ik =1 indicating that node i can be powered by islanding k, γ ik =0 indicates that node i cannot be powered by islanding k.
The objective function simultaneously satisfies node concentration constraint, network connectivity constraint, load constraint to be recovered in an island, load constraint to be recovered in the island, active power constraint, node voltage constraint and switch constraint.
In the node concentration constraint, if the load at the node i can be restored from the island, the node i can only belong to one of the K islands.
If a permanent fault occurs on a line, some nodes may not be connected to any island and an isolated state exists.
The node set constraint is expressed as:
defining a to be the element {0,1}, representing whether the node i belongs to the island K, and if the node i belongs to the island K, a ik =1, otherwise a ik ＝0。
When the node i and the DG are connected to the same bus, the node i belongs to an island where the DG is located.
In the network connectivity constraint, if a jurisdictional distribution network is regarded as a tree network, each island can be set as a subtree network, a root node is a node at which a DG is installed, and due to the connectivity characteristic of the tree, only when a parent node (for the island) belongs to an island k, one node belongs to the island k, which can be expressed as the following inequality constraint:
the network connectivity constraint is expressed as:
a ik ≤a jk
where j represents the parent of node i in island k.
If the load of node i can be supplied by islanding k, the following two conditions should be satisfied simultaneously:
node i belongs to island k denoted as a ik ＝1。
The switch associated with the load is closed so that the load is connected to node i, denoted s i ＝1。
These two conditions can be unified as: a is ik ·s i =1, this is quadratic constraint, is a non-linear problem, and for easier computation it is linearized, and an auxiliary variable γ is set ik E {0,1} and is defined as gamma ik ＝a ik ·s i The quadratic nonlinear equality constraint can be further converted into the following three linear inequality constraints, and then the load constraint to be recovered in the island is expressed as:
γ ik ≤a ik
γ ik ≤s i
γ ik ≥a ik +s i -1
wherein s is i The load switch state, represented as node i, is 1 closed and 0 open.
The stable operation of each island also needs to meet the operation constraints such as power balance of each node, and because reactive power is generally compensated on site, only the active power balance constraint is considered and analyzed in the process of constructing the island for fault recovery.
Let P i k Representing the active power flowing into node i in island k; since each island is a tree topology of DG at the root node, each node has only one incoming power. According to the fact that the power flowing into the node is equal to the power flowing out of the node, the active power balance, namely the active power constraint, at each node in the island k is represented as follows:
wherein s is i k Representing the child node set of the node in the island k if the node i does not belong to the island k (i.e. a) ik = 0), active power (i.e. P) flowing into island k i k ) Should be zero, if node i determines that power is restored from island a, its incoming active power should be no less than its own load power, which can be represented by the following inequality constraint:
γ ik ·p i ≤P i k ≤a ik ·P i max
wherein, P i max Representing the active capacity of DG in island k.
The voltage at the node where DG is located is taken as a reference value, and the voltage is used for island k
Indicating that the voltage on node i is->
Expressed, the node voltage constraint is expressed as:
wherein R is i 、X i Representing the resistance and reactance of the branches i-j respectively,
representing a slack variable set such that the equality constraint is still valid when node i does not belong to island k but its parent node j belongs to island k, the constraint of the slack variable is expressed as:
if the node i belongs to the island k,
otherwise, V i k =0, this case can be represented by the following inequality constraint:
the switch constraints include that for line switches on both sides of the fault area, only the "tripped" state can be set during the fault recovery process, i.e. c ij = -1; when the load must ensure power supply, the load switch can only be in a 'closing' state, i.e. s i ＝1。
The method comprises the following steps of adopting a multi-agent system reference average consistency algorithm to obtain power distribution network parameters required by a mathematical model of a distributed fault recovery scheme based on a dynamic island as follows:
as shown in fig. 4, in order to obtain the power distribution network parameters necessary for obtaining the mathematical model of the distributed fault recovery scheme based on the dynamic island, a multi-agent system (MAS) is used, that is, each bus of the power distribution network system is assigned with a Bus Agent (BA), and the information obtained by the BA includes the voltage of the connected bus, the related parameters of the power source and load nodes connected with the bus, the state information of the controllable switch connected with the bus, the information of the current flowing through the controllable switch, and the related information of the line connected with the bus. The status of each agent is equal, and each agent has enough data processing capacity and certain autonomy; each agent in the MAS does not have the capability of independently completing a control target, and a single agent cannot make correct switching action if the single agent does not perform information interaction only by depending on the information acquired by the agent; in order to achieve a common goal, the agents need to coordinate with each other and exchange information.
The average consensus algorithm comprises:
the net active power time-varying signals flowing into the nodes and the switching state signals of the lines and the loads in the power distribution network are dynamically tracked, and finally, each agent achieves the consistency and the average of the tracked signals, so that the global information of the states of all the line switches and the load switches is obtained.
As shown in fig. 3, the following iteration is performed through the information obtaining process of each bus agent i:
wherein i =1, Λ n, n represents the number of agents in the distribution network,
represents a local initialization status quantity of agent i, based on the status of the agent i>
Respectively representing state quantity information acquired by the agent i in the k iteration and the k +1 iteration, a ij Representing the step size of the information exchange between the adjacent agents i and j, if the agents i and j are adjacent, 0 < a ij < 1, otherwise a ij ＝0，R i Representing a set of agents immediately adjacent to agent i.
Assuming that N represents a set of agents in the power distribution network, N represents the number of the agents, a line switch set is represented as L, and a load switch set is represented as S, each agent is designed to have three vectors p in order to acquire global information i 、c i And s i Respectively, the net active power (active power available from the power source at this node minus the load power) flowing into node i in the distribution network, BA i The controlled line switch state and the node i load switch state.
Vector p i Of length n, where the mth position corresponds to the mth node in the network, each agent initializes its vector p according to the net active power it represents flowing into the local node i By using
Indicates, and pick>
The mth element of (c) can be expressed as:
at this time, through iterative convergence of the average consistency algorithm, all the agents finally acquire global information of the active power of the n nodes.
Similarly, for line switches, we define a set of { -1,0,1} to represent different switch states, where "1" represents a closed state, with the set L c A total representation; "-1" indicates a disconnected state, with the set L 0 Representing; "0" indicates a normal operation state. The same switch state definition applies equally to the load switches, vector c i The length is 1, and the mth position corresponds to the mth line; similarly, vector s i Length n, mth position corresponds to mth node. Each agent initializes its vector c based on the local switch it represents i And s i Respectively, respectivelyBy using
And &>
Means for>
And &>
The mth element of (c) can be expressed as follows:
at this time, through iterative convergence of the consistency algorithm, finally all agents acquire global information of the states of all line switches and load switches.
This embodiment still provides a distribution network fault recovery system who considers island dynamic partition, includes:
the method building module is used for solving the action time setting values of the reclosing devices at different positions by adopting a reclosing coordination method in the distributed power generation distribution network under the weak communication condition based on the balance capacity of the distributed photovoltaic power supply relative to the local load, and reducing the impact on the distribution network during reclosing.
And the dividing module is used for dividing a planned island operation area based on DG and load capacity in the distribution network, and avoiding the removal of the DG due to fault coincidence failure in the fault recovery process of the distribution network.
And the model building module is used for building a mathematical model of the distributed fault recovery scheme based on the dynamic island by taking the load with the maximized recovery load amount and the heavy priority recovery load as an objective function.
And the calculation module is used for acquiring power distribution network parameters required by a mathematical model of a distributed fault recovery scheme based on a dynamic island by adopting a multi-agent system reference average consistency algorithm.
The embodiment further provides a computing device, which is suitable for a condition of a power distribution network fault recovery method considering islanding dynamic partitioning, and includes:
a memory and a processor; the storage is used for storing computer executable instructions, and the processor is used for executing the computer executable instructions to realize the method for recovering the power distribution network fault considering the island dynamic division, which is provided by the embodiment.
The computer device may be a terminal comprising a processor, a memory, a communication interface, a display screen and an input means connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The communication interface of the computer device is used for carrying out wired or wireless communication with an external terminal, and the wireless communication can be realized through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, a key, a track ball or a touch pad arranged on the shell of the computer equipment, an external keyboard, a touch pad or a mouse and the like.
The present embodiment also provides a storage medium, on which a computer program is stored, and when the program is executed by a processor, the method for recovering a power distribution network fault considering island dynamic partitioning is implemented as proposed in the above embodiments.
The storage medium proposed by the present embodiment belongs to the same inventive concept as the data storage method proposed by the above embodiments, and technical details that are not described in detail in the present embodiment can be referred to the above embodiments, and the present embodiment has the same beneficial effects as the above embodiments.
Example 2
Referring to fig. 5 to 7, a verification test of a power distribution network fault recovery method considering islanding dynamic partitioning is provided for another embodiment of the present invention, and technical effects adopted in the method are verified and explained.
Compared with the traditional power distribution network fault recovery method, the power distribution network fault recovery method considering the dynamic island division of the invention is explained by the following simulation case:
taking fig. 5 as an example, assuming that the load capacities of bus 2 and bus 4, bus 5 are 2mw, and the rated power of dg1 is 2MW, DG1 may be divided into planned island regions as shown in fig. 5 according to the load capacities of DG and connected buses, and the planned island regions are shown by dashed boxes in fig. 5.
Assuming that a permanent fault occurs at the F1 position, enabling the distance between the F1 position and the DG1 downstream to be 100m, selecting a three-phase short-circuit fault as a fault type, and enabling the voltage at the DG1 public coupling position to be always higher than a ride-through condition of grid-connected operation in the fault recovery process; according to the conventional reclosing scheme, a voltage change curve at the common coupling of the DG1 in the whole fault process is shown in FIG. 6.
When a fault occurs at about t =0.3s, the voltage at the common coupling of the DG1 drops to below 50% of the rated voltage of the system for the first time, and when the voltage at the common coupling of the DG1 drops to about t =1.1s, the switch K5 near the power supply side performs fault reclosing operation, but the reclosing operation fails in permanent fault reclosing, and the voltage drops suddenly for the second time, at this time, the voltage at the common coupling of the DG1 does not meet the ride-through condition of grid-connected operation, and then the switch K7 at the common coupling of the DG1 is disconnected, so that the DG1 stops operating.
According to the fault recovery scheme of the power distribution network, when a permanent fault occurs at the F2, the feeder line circuit breakers K5 and K6 are tripped to isolate the fault, the fault position is located at the downstream side of a bus connected with the DG1, the planned island region 1 of the DG1 is kept complete, and the situation that the voltage at the public coupling position of the DG1 is reduced to 50% or below of the rated voltage for the first time is detected, so that the fault condition meets the planned island operation condition of the DG 1. After the fault at the F2 is isolated, the switch K4 should be actively tripped, the DG1 is enabled to plan isolated island operation, and then the DG1 and the power distribution network are synchronously connected in a grid mode; the voltage variation curve at the DG1 common coupling obtained in the whole fault recovery process is shown in FIG. 7.
By comparing fig. 6 and fig. 7, in the method for recovering the fault of the power distribution network considering the dynamic islanding division, the voltage at the public coupling position of the distributed generation DG1 does not drop suddenly for the second time, so that the impact of reclosing failure on the distributed generation and even the whole power distribution network is effectively avoided, and the safe and stable operation of the power distribution network is favorably realized.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (10)
1. A power distribution network fault recovery method considering island dynamic division is characterized by comprising the following steps:
based on the balance capacity of the distributed photovoltaic power supply relative to local loads, a coordinated coordination method of reclosure in the distributed power generation distribution network under a weak communication condition is adopted to obtain setting values of action time of reclosure devices at different positions, and impact on the distribution network during reclosure is reduced;
dividing a planned island operation area based on DGs and load capacity in a distribution network, and avoiding the removal of the DGs due to fault coincidence failure in the fault recovery process of the distribution network;
taking the load with the maximized recovery load amount and the heavy priority recovery load as an objective function, and constructing a mathematical model of a distributed fault recovery scheme based on the dynamic island;
and acquiring power distribution network parameters required by a mathematical model of the distributed fault recovery scheme based on the dynamic island by adopting a multi-agent system reference average consistency algorithm.
2. The method for recovering the fault of the power distribution network considering the dynamic island division according to claim 1, wherein the method comprises the following steps: the division of the planned island operation area comprises,
one or more appropriate planned island operation areas are divided for each DG in advance;
detecting whether a planned island operation area divided by each DG is still complete after fault isolation, and determining to implement different reclosing schemes;
when a fault occurs and is isolated, if a load in a non-fault power loss area is not connected with a main power supply due to the fault, but a path connected with a DG exists between the load and the DG, and the DG in a power distribution network has relatively stable power supply capacity, a power distribution network fault recovery scheme containing the DG is constructed through a planned isolated island of the DG, fault recovery is realized, and power supply reliability of the power distribution network is improved.
3. The method for recovering the fault of the power distribution network considering the dynamic island division according to claim 2, wherein the method comprises the following steps: the fault recovery scheme for a distribution network including a DG includes,
dividing a planned island region in advance, detecting a fault occurrence region, and judging whether the fault occurs on the downstream side of a DG or an adjacent feeder line;
if not, power supply recovery is carried out according to the traditional reclosing program, and fault recovery of the power distribution network is completed;
if so, judging whether a complete island region exists or not;
if the complete island region does not exist, power supply recovery is carried out according to the traditional reclosing program, and the fault recovery of the power distribution network is completed;
if the complete island region exists, judging whether the voltage at the PCC drops below 50 percent of rated voltage for the first time;
if the voltage is lower than 50% of the rated voltage, actively disconnecting the corresponding switch to realize planned isolated island operation, closing the interconnection switch, recovering the fault of the feeder line, synchronously connecting DGs (distributed generation) which are planned isolated island operation to the grid, and completing the fault recovery of the power distribution network;
and if the voltage is not lower than 50% of the rated voltage, power supply recovery is carried out according to the traditional reclosing program, and the fault recovery of the power distribution network is completed.
4. The method for recovering the fault of the power distribution network considering the dynamic island division according to claim 3, wherein the method comprises the following steps: the mathematical model of the dynamic island based distributed fault recovery scheme comprises,
according to a radial distribution network consisting of N nodes, a node set is represented as N = {1, Λ N }, distribution network branches are represented as L = { (i-j) }, i belongs to N, j belongs to N, and fault recovery of a complex distribution network containing DG is represented as a mixed integer programming problem, wherein an objective function expression of the problem is as follows:
wherein, f pload Representing the amount of load recovered, w, taking into account the priority of the load i Represents a priority weight associated with the load at node i, and w i Is higher priority, N denotes a set of nodes, K denotes islands formed by DG, K denotes all islandsSet, γ ik Denotes the connection relationship between node i and island k, γ ik =1 indicating that node i can be powered by islanding k, γ ik =0 indicates that node i cannot be powered by islanding k;
the objective function simultaneously meets node concentration constraint, network connectivity constraint, load constraint to be recovered in an island, active power constraint, node voltage constraint and switch constraint.
5. A method for recovering a power distribution network fault considering island dynamic division according to any one of claim 4, characterized in that: the node concentration constraint, the network connectivity constraint and the load constraint to be recovered in the island comprise,
the node set constraint is expressed as:
defining a to be the element {0,1}, and indicating whether the node i belongs to the island K, if the node i belongs to the island K, a ik =1, otherwise a ik ＝0；
When the node i and the DG are connected to the same bus, the node i belongs to an island where the DG is located;
setting a dominating power distribution network as a tree network, each island is a subtree network, and a root node is a node at a DG installation position, wherein the network connectivity constraint is expressed as:
a ik ≤a jk
j represents a father node of a node i in an island k, and only when the father node belongs to the island k, one node belongs to the island k;
the load constraint to be recovered in the island is expressed as:
γ ik ≤a ik
γ ik ≤s i
γ ik ≥a ik +s i -1
wherein, γ ik E {0,1} represents a secondary variable of the settingAnd γ ik ＝a ik ·s i ，s i The load switch state represented as node i is closed to 1 and open to 0.
6. The method for recovering the fault of the power distribution network considering the dynamic island division according to claim 4, wherein the method comprises the following steps: the active power constraints, node voltage constraints and switching constraints include,
according to the fact that the power flowing into the node is equal to the power flowing out of the node, the active power constraint at each node in the island k is represented as:
wherein, P i k Representing the active power flowing into node i in island k,
a child node set representing nodes in island k;
assuming that the voltage at the node where DG is located is the reference value, the node voltage constraint is expressed as:
wherein, the first and the second end of the pipe are connected with each other,
voltage, V, representing islanding k i k Representing the voltage at node i, R i And X i Respectively represents the resistance and reactance of branch i-j, respectively>
Is a slack variable set so that the equality constraint is still valid when node i does not belong to island k but its parent node j belongs to island k.
The switch constraints includeFor line switches on both sides of the fault area, only the trip state can be reached during fault recovery, i.e. c ij ＝-1；
When the load must ensure the power supply, the load switch is in the closing state, i.e. s i ＝1。
7. The method for recovering the fault of the power distribution network considering the dynamic island division according to claim 1, wherein the method comprises the following steps: the average consensus algorithm comprises the following steps,
the information obtaining process of each bus agent i is iterated as follows:
wherein i =1, Λ n, n represents the number of agents in the distribution network,
represents a local initialization status quantity of agent i, based on the status of the agent i>
And &>
Respectively representing state quantity information acquired by the agent i in the k iteration and the k +1 iteration, a ij Representing the step size of the information exchange between the adjacent agents i and j, if the agents i and j are adjacent, 0 < a ij < 1, otherwise a ij ＝0，R i Representing a set of agents immediately adjacent to agent i;
through the iterative calculation formula, each agent finally obtains the active power of all n nodes of the power distribution network and the global information of the states of all line switches and load switches.
8. A power distribution network fault recovery system considering island dynamic division is characterized by comprising,
the method construction module is used for solving the action time setting values of the reclosing devices at different positions by adopting a reclosing coordination method in the distributed power generation distribution network under the weak communication condition based on the balance capacity of the distributed photovoltaic power supply relative to the local load, and reducing the impact on the distribution network during the reclosing period;
the dividing module is used for dividing a planned island operation area based on DGs and load capacity in a distribution network, and preventing the DGs from being cut off due to fault coincidence failure in the fault recovery process of the distribution network;
the model building module is used for building a mathematical model of a distributed fault recovery scheme based on the dynamic island by taking the load with the maximized recovery load amount and the high priority recovery load weight as an objective function;
and the calculation module is used for acquiring the power distribution network parameters required by the mathematical model of the distributed fault recovery scheme based on the dynamic isolated island by adopting a multi-agent system reference average consistency algorithm.
9. A computing device, comprising:
a memory and a processor;
the memory is used for storing computer executable instructions, and the processor is used for executing the computer executable instructions, and the computer executable instructions when executed by the processor realize the steps of the method for recovering the power distribution network fault considering island dynamic division in any one of claims 1 to 7.
10. A computer-readable storage medium storing computer-executable instructions which, when executed by a processor, implement the steps of a method for fault recovery of a power distribution network in consideration of islanding dynamic partitioning according to any one of claims 1 to 7.
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