CN113193557B

CN113193557B - Determination method and device for switching equipment in microgrid and storage medium

Info

Publication number: CN113193557B
Application number: CN202110518875.0A
Authority: CN
Inventors: 潘凯宁; 刘志勇; 黄慧; 温敏
Original assignee: Guangdong Power Grid Co Ltd; Shaoguan Power Supply Bureau Guangdong Power Grid Co Ltd
Current assignee: Guangdong Power Grid Co Ltd; Shaoguan Power Supply Bureau Guangdong Power Grid Co Ltd
Priority date: 2021-05-12
Filing date: 2021-05-12
Publication date: 2023-02-10
Anticipated expiration: 2041-05-12
Also published as: CN113193557A

Abstract

The application discloses a method, a device and a storage medium for determining switching equipment in a microgrid, and relates to the technical field of power systems. According to the switching equipment determined by the method, the power of the distributed power supply and the power of the load point can be balanced under the condition that a fault line occurs in the power grid. The method comprises the following steps: determining at least one target line according to the power flow data of the downstream line of the fault position; then, dividing a downstream line into at least two isolated islands by taking at least one target line as a splitting point; and then determining equipment to be switched in the island according to the load power of the load points in the at least two islands and the output power of the distributed power supply in the at least two islands. Wherein the downstream line comprises a first load point and a second load point, and the energy flow in the grid before the fault is from the fault location to the second load point via the first load point.

Description

Method and device for determining switching equipment in microgrid and storage medium

Technical Field

The embodiment of the application relates to the technical field of power systems, in particular to a method and a device for determining switching equipment in a microgrid and a storage medium.

Background

With the increasing proportion of distributed power generation, micro-grids have received much attention. The micro-grid is a small power generation system formed by converging a distributed power supply, energy storage equipment, an energy conversion device and related load and monitoring and protecting devices. Distributed power sources such as small hydropower stations and the like have the advantages of short construction period, easy standardization, cleanness and no pollution, so that the distributed power sources are widely applied to regions such as remote villages or mountainous areas with abundant hydraulic resources. Distributed power supplies such as small hydropower stations are generally directly connected to the feeder side of a power distribution network in a T connection mode. Referring to fig. 1, a typical topology containing a small hydropower station microgrid is provided. In mountainous areas and rural areas where small hydropower stations are distributed more, the power consumption load is smaller, and the active power generated by each small hydropower station is far larger than the active power consumed by local loads, so that the small hydropower stations are generally operated in a grid-connected mode with an external large power grid, and extra active power is output to the large power grid through a connecting line.

However, when a certain feeder of a microgrid including a small hydropower station is cut off due to a fault, the small hydropower station and a load point in a downstream line at the fault position form an island, output power and consumption power of the load point of the small hydropower station in the island are unbalanced, voltage and frequency stability in the island are damaged, and electric energy quality is affected. Therefore, it is urgent to provide a method for determining switching devices in a microgrid to solve the problem of power balance inside an "island".

Disclosure of Invention

The application provides a method and a device for determining switching equipment in a microgrid and a storage medium. According to the switching equipment determined by the method, the power of the distributed power supply and the power of the load point can be balanced under the condition that a fault line occurs in the power grid.

In order to achieve the purpose, the technical scheme is as follows:

in a first aspect, the present application provides a method for determining switching devices in a microgrid, including: determining at least one target line according to the power flow data of the downstream line of the fault position; then, dividing a downstream line into at least two isolated islands by taking at least one target line as a splitting point; and then determining equipment to be switched in the island according to the load power of the load points in the at least two islands and the output power of the distributed power supply in the at least two islands. The downstream line comprises a first load point and a second load point, and the energy flow direction in the power grid before the fault is from the fault position to the second load point through the first load point.

Because the tidal current data is generally the difference of power between two load points, the island is divided by taking a downstream line with smaller tidal current data as a splitting point, and the power in the island is more easily balanced. Therefore, according to the method and the device, the target line can be selected from the downstream lines according to the power flow data of the downstream lines at the fault positions, and then the target line is taken as a disconnection point to be subjected to islanding. In addition, in the island, the distributed power supply transmits energy for the load point, so the equipment to be switched can be determined according to the load power of the load point in the island and the output power of the distributed power supply. Therefore, after the device to be switched is determined, the load point or the distributed power supply can be cut off according to the determined device to be switched, and therefore the power of the distributed power supply and the power of the load point can be balanced under the condition that a fault line occurs in a power grid.

Optionally, in a possible design manner, before the "determining at least one target line according to the power flow data of the downstream line of the fault location", the method for determining the switching device in the microgrid according to the embodiment of the present application may include: obtaining the power flow data and the energy flow direction of a line in a power grid before a fault; establishing an edge-weighted tree diagram according to the power flow data and the energy flow direction of the line in the power grid before the fault; and determining a fault position and a downstream line of the fault position in the edge weighted tree diagram according to the fault output information of the fixed-section protection equipment.

The edge weighted tree graph comprises a plurality of load points; the connecting line of every two load points in the plurality of load points corresponds to one line.

Optionally, in another possible design, the "determining at least one target line according to the power flow data of the downstream line of the fault location" may include: obtaining the load flow data of a downstream line of a fault position from the load flow data of the line in the power grid before the fault; determining N lines with the minimum numerical value of the power flow data in the downstream lines as at least one target line; wherein N is a positive integer.

Optionally, in another possible design manner, the determining the device to be switched in the island according to the load power of the load point in the at least two islands and the output power of the distributed power source in the at least two islands may include: determining total load power according to the load power of a load point in a target island, and determining total output power according to the output power of a distributed power supply in the target island; the target island is any one of at least two islands; acquiring a first sequencing result and a second sequencing result; the first sequencing result is the magnitude sequencing of the load power of the load points in the target island, and the second sequencing result is the magnitude sequencing of the output power of the distributed power supply in the target island; and determining the cutting equipment from the load point in the target island or the distributed power supply based on the first sequencing result and the second sequencing result according to the magnitude relation between the total load power and the total output power.

Optionally, in another possible design manner, the total load power includes a total load active power and a total load reactive power, and the total output power includes a total output active power and a total output reactive power; the "determining the total load power according to the load power of the load point in the target island and determining the total output power according to the output power of the distributed generator in the target island" may include:

determining total load active power and total load reactive power according to the load power of a load point in the target island and a first power factor, and determining total output active power and total output reactive power according to the output power of the distributed power supply in the target island and a second power factor; the first power factor is used for representing the ratio relation between the total load active power and the total load reactive power in the total load power; the second power factor is used for representing the ratio relation between the total output active power and the total output reactive power in the total output power.

Optionally, in another possible design manner, the "determining, according to a magnitude relationship between total load power and total output power, an ablation device from a load point in a target island or a distributed power source based on the first sorting result and the second sorting result" may include: determining that the difference value between the total load active power and the total output active power is greater than a first preset value, and/or the difference value between the total load reactive power and the total output reactive power is greater than a second preset value; and determining the equipment to be cut from the load point or the distributed power supply in the target island based on the first sequencing result and the second sequencing result according to the magnitude relation between the total load active power and the total output active power and the magnitude relation between the total load reactive power and the total output reactive power.

Optionally, in another possible design manner, under the condition that the total output active power is less than the total load active power and the total output reactive power is less than the total load reactive power, the method for determining the switching device in the microgrid provided by the application further includes: determining the standby distributed power supply as an input device under the condition that the standby distributed power supply is determined; determining whether the input requirement is met or not according to the output power of the standby distributed power supply; and under the condition that the investment requirement is determined not to be met, determining the cutting equipment from the load points in the target island according to the first sequencing result.

In a second aspect, the application provides a device for determining switching equipment in a microgrid, which comprises a determining module and a dividing module; the determining module is used for determining at least one target line according to the power flow data of the downstream line of the fault position; the downstream line comprises a first load point and a second load point, and the energy flow direction in the power grid before the fault is from the fault position to the second load point through the first load point; the dividing module is used for dividing the downstream line into at least two isolated islands by taking at least one target line determined by the determining module as a splitting point; and the determining module is further used for determining the equipment to be switched in the island according to the load power of the load points in the at least two islands divided by the dividing module and the output power of the distributed power supply in the at least two islands.

Optionally, in a possible design manner, the determining apparatus for a switching device in a power grid provided in an embodiment of the present application further includes: the acquisition module is used for acquiring the tidal current data and the energy flow direction of a line in the power grid before the fault; the establishing module is used for establishing an edge weighting tree diagram according to the flow data and the energy flow direction of the line in the power grid before the fault, which are acquired by the acquiring module; and the determining module is used for determining the fault position and the downstream line of the fault position in the edge weighted tree diagram according to the fault output information of the fixed-section protection equipment. Wherein, the edge weighted tree graph comprises a plurality of load points; the connecting line of every two load points in the plurality of load points corresponds to one line.

Optionally, in another possible design manner, the determining module is specifically configured to: obtaining the load flow data of a downstream line of a fault position from the load flow data of the line in the power grid before the fault; determining N lines with the minimum numerical value of the power flow data in the downstream lines as at least one target line; wherein N is a positive integer.

Optionally, in another possible design manner, the determining module is specifically configured to:

determining total load power according to the load power of a load point in a target island, and determining total output power according to the output power of a distributed power supply in the target island; the target island is any one of at least two islands;

acquiring a first sequencing result and a second sequencing result; the first sequencing result is the magnitude sequencing of the load power of the load points in the target island, and the second sequencing result is the magnitude sequencing of the output power of the distributed power supply in the target island;

and determining the cutting equipment from the load point in the target island or the distributed power supply based on the first sequencing result and the second sequencing result according to the magnitude relation between the total load power and the total output power.

Optionally, in another possible design manner, the total load power includes a total load active power and a total load reactive power, and the total output power includes a total output active power and a total output reactive power; the determining module is specifically configured to:

determining total load active power and total load reactive power according to the load power and a first power factor of a load point in the target island, and determining total output active power and total output reactive power according to the output power and a second power factor of a distributed power supply in the target island; the first power factor is used for representing the ratio relation between the total load active power and the total load reactive power in the total load power; the second power factor is used for representing the ratio relation between the total output active power and the total output reactive power in the total output power.

determining that the difference value between the total load active power and the total output active power is larger than a first preset value, and/or determining that the difference value between the total load reactive power and the total output reactive power is larger than a second preset value; and determining the cutting equipment from the load point in the target island or the distributed power supply based on the first sequencing result and the second sequencing result according to the magnitude relation between the total load active power and the total output active power and the magnitude relation between the total load reactive power and the total output reactive power.

Optionally, in another possible design manner, when the total output active power is smaller than the total load active power, and the total output reactive power is smaller than the total load reactive power, the determining module is further configured to: determining the standby distributed power supply as an input device under the condition that the standby distributed power supply is determined; determining whether the input requirement is met or not according to the output power of the standby distributed power supply; and under the condition that the investment requirement is determined not to be met, determining the cutting equipment from the load points in the target island according to the first sequencing result.

In a third aspect, the present application provides a device for determining switching devices in a microgrid, including a memory, a processor, a bus and a communication interface; the memory is used for storing computer execution instructions, and the processor is connected with the memory through a bus; when the determination device for the switching device in the microgrid is operated, the processor executes the computer execution instructions stored in the memory, so that the determination device for the switching device in the microgrid performs the determination method for the switching device in the microgrid as provided in the first aspect.

Optionally, the determining apparatus for switching devices in the microgrid may further include a transceiver, and the transceiver is configured to execute steps of transceiving data, signaling or information under the control of the processor of the determining apparatus for switching devices in the microgrid, for example, obtaining tidal current data and energy flow direction of lines in the power grid before a fault.

Further optionally, the determining device for the switching device in the microgrid may be a physical machine for determining the switching device in the microgrid, or may be a part of the physical machine, for example, a system on chip in the physical machine. The chip system is used for supporting the determination device for the switching device in the microgrid to realize the functions related to the first aspect, for example, receiving, sending or processing the data and/or information related to the determination method for the switching device in the microgrid. The chip system includes a chip and may also include other discrete devices or circuit structures.

In a fourth aspect, the present application provides a computer-readable storage medium, in which instructions are stored, and when the instructions are executed by a computer, the computer is enabled to execute the determining method for the switching device in the microgrid provided in the first aspect.

In a fifth aspect, the present application provides a computer program product comprising computer instructions which, when run on a computer, cause the computer to perform the method for determining a switching device in a microgrid as provided in the first aspect.

It should be noted that the computer instructions may be stored in whole or in part on a computer-readable storage medium. The computer-readable storage medium may be packaged with a processor of a determination device for switching devices in a microgrid, or may be packaged separately from a processor of a determination device for switching devices in a microgrid, which is not limited in this application.

For the description of the second, third, fourth and fifth aspects in this application, reference may be made to the detailed description of the first aspect; in addition, for the beneficial effects described in the second aspect, the third aspect, the fourth aspect, and the fifth aspect, reference may be made to the beneficial effect analysis of the first aspect, and details are not repeated here.

In the present application, the names of the above-mentioned determining devices for switching devices in a microgrid do not limit the devices or functional modules themselves, which may appear under other names in practical implementations. As long as the functions of the respective devices or functional modules are similar to those of the present application, they fall within the scope of the claims of the present application and their equivalents.

These and other aspects of the present application will be more readily apparent from the following description.

Drawings

Fig. 1 is a schematic topology diagram of a microgrid of a small hydropower station provided in an embodiment of the application;

fig. 2 is a schematic flowchart of a method for determining switching devices in a microgrid according to an embodiment of the present disclosure;

fig. 3 is an edge weighted tree diagram according to an embodiment of the present application;

FIG. 4 is a schematic diagram of a power circle provided in an embodiment of the present application;

fig. 5 is a schematic flowchart of another determination method for switching devices in a microgrid according to an embodiment of the present application;

fig. 6 is a schematic flowchart of another method for determining a switching device in a microgrid according to an embodiment of the present application;

fig. 7 is a schematic node topology diagram according to an embodiment of the present application;

FIG. 8 is a line graph of per unit values of node voltages according to an embodiment of the present disclosure;

fig. 9 is a schematic structural diagram of a device for determining a switching device in a microgrid according to an embodiment of the present application;

fig. 10 is a schematic structural diagram of another device for determining a switching device in a microgrid, according to an embodiment of the present application.

Detailed Description

The following describes in detail a determination method, an apparatus, and a storage medium for a switching device in a microgrid, which are provided in an embodiment of the present application, with reference to the accompanying drawings.

The term "and/or" herein is merely an association relationship describing an associated object, and means that there may be three relationships, for example, a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone.

The terms "first" and "second" and the like in the description and drawings of the present application are used for distinguishing different objects or for distinguishing different processes for the same object, and are not used for describing a specific order of the objects.

Furthermore, the terms "including" and "having," and any variations thereof, as referred to in the description of the present application, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

It should be noted that in the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described herein as "exemplary" or "e.g.," is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present relevant concepts in a concrete fashion.

In the description of the present application, the meaning of "a plurality" means two or more unless otherwise specified.

Distributed power sources such as small hydropower stations and the like have the advantages of short construction period, easy standardization, cleanness and no pollution, so that the distributed power sources are widely applied to regions such as remote villages or mountainous areas with abundant hydraulic resources. Distributed power supplies such as small hydropower stations are generally directly connected to the feeder side of a power distribution network in a T connection mode. Referring to fig. 1, a typical topology is provided that includes a small hydropower station. In mountainous areas and rural areas where small hydropower stations are distributed more, the power consumption load is smaller, and the active power generated by each small hydropower station is far larger than the active power consumed by local loads, so that the small hydropower stations are generally operated in a grid-connected mode with an external large power grid, and extra active power is output to the large power grid through a connecting line. As shown in fig. 1, in the microgrid topology, a small hydropower plant a, a small hydropower plant B, a small hydropower plant C and a small hydropower plant D are connected to a main network line to deliver energy to a load a, a load B and a load C.

However, when a certain feeder of a microgrid including a small hydropower station is cut off due to a fault, the small hydropower station and a load point in a downstream line at the fault position form an island, output power and consumption power of the load point of the small hydropower station in the island are often unbalanced, voltage and frequency stability in the island can be damaged, and electric energy quality is affected. Therefore, a determination method for switching equipment in a microgrid is urgently needed to solve the problem of power balance inside an island.

In order to solve the problems in the prior art, embodiments of the present application provide a method, an apparatus, and a storage medium for determining a switching device in a microgrid, where the method selects a target line from downstream lines according to power flow data of the downstream lines at a fault location, then performs islanding with the target line as a disconnection point, and determines a device to be switched according to load power of a load point in an islanding and output power of a distributed power supply. After the device to be switched is determined, the load point or the distributed power supply can be cut off according to the determined device to be switched, so that the power of the distributed power supply and the power of the load point can be balanced under the condition that a fault line occurs in a power grid.

The method for determining the switching equipment in the microgrid can be suitable for a device for determining the switching equipment in the microgrid.

The determining device for the switching device in the microgrid may be a physical machine (such as a server) or a Virtual Machine (VM) deployed on the physical machine.

The following describes in detail a determination method for switching devices in a microgrid provided by the present application.

Referring to fig. 2, the method for determining switching devices in a microgrid provided in the embodiment of the present application includes steps S201 to S203:

s201, determining at least one target line according to the power flow data of the downstream line of the fault position.

Wherein the power flow data may be a difference in power between two load points in the line.

Optionally, in a possible implementation manner, the determining device for the switching device in the microgrid may determine the at least one target line by establishing an edge-weighted tree diagram. Specifically, the determining device for the switching device in the microgrid can acquire the tidal current data and the energy flow direction of a line in the power grid before a fault; then, establishing an edge weighting tree diagram according to the power flow data and the energy flow direction of the line in the power grid before the fault; and then determining a fault position and a downstream line of the fault position in the edge weighted tree diagram according to the fault output information of the fixed-section protection equipment.

The edge weighted tree graph comprises a plurality of load points, and a connecting line of every two load points in the plurality of load points corresponds to one line.

Illustratively, referring to fig. 3, an embodiment of the present application provides an edge-weighted tree graph. As shown in fig. 3, the edge weighted tree includes 7 load points, load points 1 and 2 constituting a route W12, load points 2 and 3 constituting a route W23, load points 3 and 7 constituting a route W37, load points 3 and 4 constituting a route W34, load points 4 and 5 constituting a route W45, and

load points

5 and 6 constituting a route W56. The direction of the arrow in fig. 3 is the energy flow direction of the line in the grid before the fault, that is, the positive direction of each side of the tree structure in the edge-weighted tree diagram is from the tie node to the end of the feeder line.

It should be noted that, in practical applications, because an island can be formed only when a line connecting bus interior points is disconnected, when the edge-weighted tree graph is established, power branches and load branches of small hydropower stations can be omitted, and only the edges of the bus interior points and the connection interior points in the system are reserved, that is, the edge-weighted tree graph shown in fig. 3 is determined.

When the edge weighting tree diagram shown in fig. 3 is established, each line (i.e., each edge in fig. 3) may be weighted according to the power flow data of the line in the grid before the fault. Illustratively, where W represents the set of busbar nodes, the weight W of the edge connecting points i and j within the busbar _ij Can be expressed by expression (1):

w _ij ＝S _eij (i，j∈W) (1)

wherein S is _eij A value representing the power flow data of the line in the grid before the fault.

In one possible implementation, the recorded power flow data of the lines in the pre-fault power grid may be obtained from a Feeder Terminal Unit (FTU).

After the edge weighted tree graph is established, the fault position can be determined in the edge weighted tree graph according to the fault output information of the fixed-section protection equipment, and the downstream line of the fault position is determined.

Wherein the downstream line comprises a first load point and a second load point, and the energy flow in the grid before the fault is from the fault location to the second load point via the first load point. As shown in fig. 3, if the fault location is between the wires W34, the downstream wires are the wires W45 and W56. In the line 45, the load point 4 is a first load point, the load point 5 is a second load point, and the energy flow is from the load point 3 to the load point 5 through the load point 4. In the line 56, the load point 5 is the first load point, the load point 6 is the second load point, and the energy flow is from the load point 3 to the load point 6 via the load point 5.

Optionally, in a possible implementation manner, the load flow data of the downstream line at the fault position may be obtained from the load flow data of the lines in the grid before the fault, and then the N lines with the minimum value of the load flow data in the downstream line are determined as the at least one target line; n is a positive integer.

S202, dividing the downstream line into at least two isolated islands by taking at least one target line as a splitting point.

Because the stability in the power grid system is difficult to control when the number of the splitting points is too large, one splitting point is generally selected, that is, a target line is determined. For example, the line with the smallest value of the power flow data in the downstream line may be determined as a target line, and then the downstream line is divided into two islands with the target line as a splitting point.

S203, determining equipment to be switched in the island according to the load power of the load points in the at least two islands and the output power of the distributed power supply in the at least two islands.

For example, in the embodiment of the present application, the distributed power source may be a small hydropower station.

Optionally, in a possible implementation manner, the total load power may be determined according to the load powers of all load points in the target island, and the total output power may be determined according to the output powers of all distributed power supplies in the target island; then sorting the load power of all load points in the target island to obtain a first sorting result, and sorting the output power of all distributed power supplies in the target island to obtain a second sorting result; and then determining the cutting equipment from the load point or the distributed power supply in the target island based on the first sequencing result and the second sequencing result according to the magnitude relation between the total load power and the total output power.

Wherein the target island is any one of at least two islands.

The output power of the distributed power supply and the load power of the load point both comprise active power and reactive power, and correspondingly, the total load power comprises total load active power and total load reactive power, and the total output power comprises total output active power and total output reactive power. In addition, the power factor can represent the ratio relation between active power and reactive power in power. Therefore, optionally, in a possible implementation manner, the total load active power and the total load reactive power may be determined according to the load powers of all load points in the target island and the corresponding first power factor of the load power of each load point, and the total output active power and the total output reactive power may be determined according to the output powers of all distributed power supplies in the target island and the corresponding second power factor of each output power.

The first power factor is used for representing the ratio relation between the total load active power and the total load reactive power in the total load power, and the second power factor is used for representing the ratio relation between the total output active power and the total output reactive power in the total output power.

When the difference value between the load power and the output power is not in the regulation and control range of the distributed power supply in the island, the power in the island cannot be balanced, the frequency and the voltage of the island system are unstable, and the power grid system is unstable. All, optionally, in a possible implementation manner, in a case that it is determined that a difference between the total load active power and the total output active power is greater than a first preset value, and/or a difference between the total load reactive power and the total output reactive power is greater than a second preset value, the cut-off device may be determined from the load point in the target island or the distributed power supply based on the first sorting result and the second sorting result according to a magnitude relationship between the total load active power and the total output active power and a magnitude relationship between the total load reactive power and the total output reactive power. And then, the determined cutting equipment is cut off, so that the frequency and the voltage of an island system formed after the fault are stabilized as soon as possible, and the fault power failure range is narrowed.

The first preset value and the second preset value may be power difference values determined manually in advance according to the adjusting capability of the distributed power supply. The first preset value and the second preset value may be equal to or different from each other, which is not limited in the embodiment of the present application.

In practical application, the downstream of the fault position generally has spare distributed power sources which are not put into use, so that the power balance inside the island can be realized not only by means of equipment removal, but also by putting into the spare distributed power sources. Therefore, optionally, in a possible implementation, in the case that it is determined that there is a standby distributed power source, the standby distributed power source may be determined as a commissioning device, and then it is determined whether the commissioning requirement is met according to the output power of the standby distributed power source. If the switching requirement is met, the standby distributed power supplies can be switched in according to the sequence of the output power of the standby distributed power supplies from small to large, and the equipment is not required to be determined to be cut from the load point in the target island. If the switching requirement is not met, determining equipment to be cut off from the load points in the target island according to the first sequencing result after all the standby distributed power supplies are switched on.

Specifically, if it is determined that the total output active power is greater than the total load active power and the total output reactive power is greater than the total load reactive power, the distributed power supplies may be marked as the shedding devices according to the second sorting result and in an order from small to large of the active power of the distributed power supplies until a difference between the total output active power and the total load active power is smaller than a first preset value; if the total output active power is determined to be smaller than the total load active power and the total output reactive power is determined to be larger than the total load reactive power, marking the load points as cut-off equipment according to a first sequencing result and the sequence of the active power of the load points from small to large until the difference value of the total output active power and the total load active power is smaller than a first preset value, and then marking the reactive power sources as cut-off equipment according to a second sequencing result and the sequence of the reactive power sources in the distributed power supply from small to large until the difference value of the total output reactive power and the total load reactive power is smaller than a second preset value; if the total output active power is smaller than the total load active power and the total output reactive power is smaller than the total load reactive power, marking the load points as the cutting equipment according to the first sequencing result and the sequence of the active power of the load points from small to large until the difference value of the total output active power and the total load active power is smaller than a first preset value; if the total output active power is determined to be greater than the total load active power and the total output reactive power is determined to be less than the total load reactive power, the load points can be marked as the cut-off devices according to the first sequencing result and the sequence of the reactive power of the load points from small to large until the difference value between the total output reactive power and the total load reactive power is less than a second preset value, and then the distributed power sources can be marked as the cut-off devices according to the second sequencing result and the sequence of the active power of the distributed power sources from small to large until the difference value between the total output active power and the total load active power is less than a first preset value. After the ablation device is marked, the marked device may be ablated.

In the case that the first preset value and the second preset value are equal, for example, the embodiment of the present application further provides a method for determining an ablation apparatus according to a vector diagram and a power circle. Referring to fig. 4, a schematic diagram of a power circle is provided, wherein the radius of the power circle is a first preset value or a second preset value.

For example, after islanding at the splitting point, the determining device for the switching device in the microgrid can determine all small hydropower stations and load points contained in the target islanding and determine whether a standby small hydropower station exists. The total output power of all small hydropower stations, as well as the total load power of all load points, can then be calculated. The total output power can be S _out∑ The total load power can be represented by S _load∑ Is represented by the formula, wherein S _out∑ And S _load∑ Are complex numbers and comprise real number parts and imaginary number parts, wherein the real number parts represent active power, the imaginary number parts represent reactive power, and S _out∑ Can be calculated according to expression (2), S _load∑ Can be calculated according to expression (3):

wherein m represents the total amount of connected small hydropower stations before the internal fault of the target island, n represents the total amount of connected load points before the internal fault of the target island, and S _outk Representing the output power of the small hydropower station k, S _loadk Representing the load power of load point k, S _loadk May be obtained from historical data.

If S _out∑ And S _load∑ If the relation between the target island and the target island satisfies expression (4), the complex power difference value Δ S inside the target island does not fall within the power circle of fig. 4, and the ablation equipment can be determined according to the quadrant of Δ S falling in fig. 4.

|ΔS|＝|S _out∑ -S _loadk |>ε (4)

Wherein epsilon represents the first preset value or the second preset value.

Specifically, if the real part and the imaginary part of Δ S are both positive numbers, that is, Δ S falls in the area a of the first quadrant in fig. 4, the small hydroelectric generating sets may be sequentially marked as the cutting-off set according to the sequence from small to large of the rated capacity of each small hydroelectric generating set, and Δ S is recalculated after each marking is completed until Δ S falls inside the power circle.

If the real part of Δ S is a negative number and the imaginary part is a positive number, that is, Δ S falls in the area B of the second quadrant in fig. 4, the load points may be marked as removed in sequence according to the sequence of the load active power of each load point in the target island from small to large, and Δ S is recalculated after each marking is completed until the island system active power difference Δ P is smaller than ∈; and then, marking reactive power supplies in the small hydroelectric generating sets as cut-off according to the sequence of the reactive power from small to large, and recalculating the delta S after marking is completed each time until the delta S falls into a power circle.

If the real part and the imaginary part of Δ S are both negative numbers, that is, Δ S falls in the area D of the third quadrant in fig. 4, the load points may be marked as removed in sequence according to the order from small to large of the load capacity of each load point in the target island, and Δ S is recalculated after each marking is completed until Δ S falls in the power circle.

If the real part of the delta S is a positive number and the imaginary part of the delta S is a negative number, namely the delta S falls in a region C of a fourth quadrant in the graph 4, marking the load points as cutting off according to the sequence of the reactive power of each load point in the target island from small to large, and recalculating the delta S after each marking is finished until the reactive power difference value delta Q of the island system is smaller than epsilon; and then, marking the small hydroelectric generating sets as cutting off according to the sequence of the active power from small to large, and recalculating the delta S after each marking is finished until the delta S falls into a power circle.

In summary, in the method for determining switching devices in a microgrid provided in the embodiment of the present application, because the tidal current data is generally the difference of power between two load points, an island is divided by using a downstream line with smaller tidal current data as a splitting point, and power inside the island is more easily balanced. Therefore, the target line can be selected from the downstream lines according to the power flow data of the downstream lines at the fault positions, and then the target line is taken as a splitting point to perform islanding. In addition, in the island, the distributed power supply transmits energy for the load point, so the equipment to be switched can be determined according to the load power of the load point in the island and the output power of the distributed power supply. Therefore, after the device to be switched is determined, the load point or the distributed power supply can be cut off according to the determined device to be switched, and therefore the power of the distributed power supply and the power of the load point can be balanced under the condition that a fault line occurs in the microgrid. Furthermore, the method for determining the switching equipment in the microgrid, provided by the embodiment of the application, can promote the frequency and the voltage of an island system formed after the fault in the microgrid to be stable as soon as possible, so that the fault power failure range is reduced, and the stability of the microgrid system is facilitated.

In summary, as shown in fig. 5, before step S201 in fig. 2, the method for determining a switching device in a microgrid according to the embodiment of the present application may further include S2001-S2003:

s2001, obtaining the power flow data and the energy flow direction of the line in the power grid before the fault.

And S2002, establishing an edge weighted tree diagram according to the power flow data and the energy flow direction of the line in the power grid before the fault.

And S2003, determining a fault position and a downstream line of the fault position in the edge weighted tree diagram according to the fault output information of the fixed-segment protection device.

Alternatively, as shown in fig. 6, step S201 in fig. 2 may be replaced with S2011-S2012:

and S2011, obtaining the power flow data of the downstream line at the fault position from the power flow data of the line in the power grid before the fault.

S2012, determining the N lines with the minimum numerical value of the power flow data in the downstream line as at least one target line.

Alternatively, as shown in fig. 6, step S203 in fig. 2 may be replaced with S2031 to S2033:

s2031, determining total load power according to the load power of the load point in the target island, and determining total output power according to the output power of the distributed power source in the target island.

S2032, a first sorting result and a second sorting result are obtained.

S2033, according to the size relation between the total load power and the total output power, based on the first sequencing result and the second sequencing result, determining the cutting equipment from the load point in the target island or the distributed power supply.

In order to more clearly illustrate the determination method for the switching device in the microgrid provided in the embodiment of the present application, an embodiment will be described in detail below.

Specifically, the energy flow direction of the line in the power grid before the fault may be obtained first, and a node topology diagram as shown in fig. 7 is established. Referring to fig. 7, a node topology diagram using a 33-node model of the IEEE standard is provided. Then, the recorded load flow data of the line in the power grid before the fault can be obtained from the FTU, for example, the load flow data can be a node voltage per unit value, referring to fig. 8, a graph of a node voltage per unit value recorded by the FTU is provided, as shown in fig. 8, an abscissa is a node serial number, an ordinate is a node voltage (unit: p.u), and an edge weighted tree graph can be established by assigning a value to the line formed by every two nodes in fig. 7 according to the node voltage per unit value in fig. 8. And then, determining that the fault position is between the node 9 and the node 10 in the edge weighted tree diagram according to the fault output information of the fixed-segment protection device, wherein the downstream line of the fault position comprises the node 10 to the node 18. According to the per unit value of the node voltage in fig. 8, it can be determined that the numerical value of the power flow between the node 13 and the node 14 is minimum, and then the line between the node 13 and the node 14 can be used as a disconnection point, and the line downstream of the fault point can be divided into two islands. As shown in fig. 7, island 1 is an island including nodes 10 to 13, and island 2 is an island including nodes 14 to 18.

After islanding, the load points in the grid and the operating parameters of the small hydropower stations before the fault can be obtained. Referring to table 1, a list of operating parameters of load points is provided in the embodiment of the present application, where table 1 includes three operating parameters, i.e., a node number, a load capacity, and a power factor. The node serial number is the identifier of the load point, the load capacity is the effective load power value of the corresponding load point, the power factor can be cos alpha value, and alpha is the included angle between the load active power and the load reactive power.

TABLE 1

Referring to table 2, a list of operating parameters of the small hydropower stations provided in the embodiment of the present application is shown, where table 2 includes three operating parameters, i.e., a node number, a generator capacity, and a power factor. The node serial number represents an identification of a load point connected with the small hydropower station, the generator capacity is an effective output power value corresponding to the small hydropower station, the power factor can be a cos beta value, and the beta is an included angle between output active power and output reactive power.

TABLE 2

Then, the parameters in table 2 may be calculated according to expression (2) to determine the total output power, the parameters in table 1 may be calculated according to expression (3) to determine the total load power, and then the complex power difference may be calculated according to the total output power and the total load power, and the calculation result is shown in table (3):

TABLE 3

Setting the first preset value and the second preset value to be both 30, that is, the radius epsilon =30 of the power circle, and obtaining the calculation result according to table 3, the complex power difference vector end points of the island 1 and the island 2 do not fall within the power circle and are both in the area D. And marking the loads as cut-off according to the sequence of the load capacities in the island from small to large. For the island 1, after loads at the node 10 and the node 11 are cut off, the complex power difference value falls into a power circle; for island 2, after the load at nodes 15 and 16 is removed, the complex power difference falls within the power circle.

It can be seen that, in the embodiment of the application, the target line is selected from the downstream lines, the target line is used as the splitting point to perform island division, and the device to be switched is determined according to the load power of the load point in the island and the output power of the distributed power supply. After the device to be switched is determined, the load point or the distributed power supply can be cut off according to the determined device to be switched, so that the power of the distributed power supply and the power of the load point can be balanced under the condition that a fault line occurs in a power grid.

As shown in fig. 9, an embodiment of the present application further provides a device for determining a switching device in a microgrid, where the device includes: a determination module 11 and a division module 12.

The determining module 11 executes S201 and S203 in the above method embodiment, and the dividing module 12 executes S202 in the above method embodiment.

Specifically, the determining module 11 is configured to determine at least one target line according to power flow data of a downstream line of the fault location; the downstream line comprises a first load point and a second load point, and the energy flow direction in the power grid before the fault is from the fault position to the second load point through the first load point;

a dividing module 12, configured to divide the downstream line into at least two islands with at least one target line determined by the determining module 11 as a splitting point;

the determining module 11 is further configured to determine the device to be switched in the island according to the load power of the load point in the at least two islands and the output power of the distributed power source in the at least two islands, which are divided by the dividing module 12.

Optionally, in a possible implementation manner, the apparatus for determining a switching device in a power grid provided in the embodiment of the present application further includes:

the acquisition module is used for acquiring the tidal current data and the energy flow direction of a line in the power grid before the fault;

the establishing module is used for establishing an edge weighting tree diagram according to the flow data and the energy flow direction of the line in the power grid before the fault, which are acquired by the acquiring module;

the determining module 11 is configured to determine a fault location and a downstream line of the fault location in the edge weighted tree diagram according to fault output information of the fixed-segment protection device;

Optionally, in another possible implementation manner, the determining module 11 is specifically configured to:

obtaining the current data of a downstream line of a fault position from the current data of the line in the power grid before the fault;

determining N lines with the minimum numerical value of the power flow data in the downstream lines as at least one target line; wherein N is a positive integer.

Optionally, in another possible implementation manner, the total load power includes a total load active power and a total load reactive power, and the total output power includes a total output active power and a total output reactive power; the determining module 11 is specifically configured to:

determining that the difference value between the total load active power and the total output active power is larger than a first preset value, and/or determining that the difference value between the total load reactive power and the total output reactive power is larger than a second preset value;

and determining the equipment to be cut from the load point or the distributed power supply in the target island based on the first sequencing result and the second sequencing result according to the magnitude relation between the total load active power and the total output active power and the magnitude relation between the total load reactive power and the total output reactive power.

Optionally, in another possible implementation manner, in a case that the total output active power is less than the total load active power, and the total output reactive power is less than the total load reactive power, the determining module 11 is further configured to:

under the condition that the standby distributed power supply is determined, determining the standby distributed power supply as a switching device;

determining whether the input requirement is met or not according to the output power of the standby distributed power supply;

and under the condition that the investment requirement is determined not to be met, determining cutting equipment from the load point in the target island according to the first sequencing result.

Optionally, the determining apparatus for a switching device in a microgrid may further include a storage module, where the storage module is configured to store program codes of the determining apparatus for a switching device in a microgrid, and the like.

As shown in fig. 10, an embodiment of the present application further provides a determining apparatus for a switching device in a microgrid, including a memory 41, a processor 42, a bus 43, and a communication interface 44; the memory 41 is used for storing computer execution instructions, and the processor 42 is connected with the memory 41 through a bus 43; when the determination apparatus for a switching device in a microgrid is operating, the processor 42 executes computer-executable instructions stored in the memory 41 to cause the determination apparatus for a switching device in a microgrid to perform the determination method for a switching device in a microgrid provided in the above-described embodiments.

In particular implementations, processor 42 (42-1 and 42-2) may include one or more Central Processing Units (CPUs), such as CPU0 and CPU1 shown in FIG. 10, as one embodiment. And as an example, the determining means for switching devices in the microgrid may include a plurality of processors 42, such as processor 42-1 and processor 42-2 shown in fig. 10. Each of the processors 42 may be a single-Core Processor (CPU) or a multi-Core Processor (CPU). Processor 42 may refer herein to one or more devices, circuits, and/or processing cores that process data (e.g., computer program instructions).

The memory 41 may be, but is not limited to, a read-only memory 41 (ROM) or other type of static storage device that can store static information and instructions, a Random Access Memory (RAM) or other type of dynamic storage device that can store information and instructions, an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compact disc, laser disc, optical disc, digital versatile disc, blu-ray disc, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. The memory 41 may be self-contained and coupled to the processor 42 via a bus 43. The memory 41 may also be integrated with the processor 42.

In a specific implementation, the memory 41 is used for storing data in the present application and computer-executable instructions corresponding to software programs for executing the present application. The processor 42 may be used for various functions of the determination means of the switching device in the microgrid by running or executing software programs stored in the memory 41 and calling up data stored in the memory 41.

The communication interface 44 is any device, such as a transceiver, for communicating with other devices or communication networks, such as a control system, a Radio Access Network (RAN), a Wireless Local Area Network (WLAN), and the like. The communication interface 44 may include a receiving unit implementing a receiving function and a transmitting unit implementing a transmitting function.

The bus 43 may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an extended ISA (enhanced industry standard architecture) bus, or the like. The bus 43 may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 10, but this is not intended to represent only one bus or type of bus.

As an example, referring to fig. 9, the function implemented by the obtaining module in the device for determining the switching device in the microgrid is the same as the function implemented by the receiving unit in fig. 10, the function implemented by the determining module in the device for determining the switching device in the microgrid is the same as the function implemented by the processor in fig. 10, and the function implemented by the storage module in the device for determining the switching device in the microgrid is the same as the function implemented by the storage in fig. 10.

For the explanation of the related contents in this embodiment, reference may be made to the above method embodiments, which are not described herein again.

Through the above description of the embodiments, it is clear to those skilled in the art that, for convenience and simplicity of description, the foregoing division of the functional modules is merely used as an example, and in practical applications, the above function distribution may be completed by different functional modules according to needs, that is, the internal structure of the device may be divided into different functional modules to complete all or part of the above described functions. For the specific working processes of the system, the apparatus and the unit described above, reference may be made to the corresponding processes in the foregoing method embodiments, and details are not described here again.

The embodiment of the application further provides a computer-readable storage medium, wherein instructions are stored in the computer-readable storage medium, and when the instructions are executed by the computer, the computer is enabled to execute the method for determining the switching device in the microgrid, which is provided by the embodiment.

The computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a RAM, a ROM, an erasable programmable read-only memory (EPROM), a register, a hard disk, an optical fiber, a CD-ROM, an optical storage device, a magnetic storage device, any suitable combination of the foregoing, or any other form of computer readable storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. Of course, the storage medium may also be integral to the processor. The processor and the storage medium may reside in an Application Specific Integrated Circuit (ASIC). In embodiments of the present application, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

The above description is only an embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for determining switching equipment in a microgrid is characterized by comprising the following steps:

obtaining the power flow data and the energy flow direction of a line in a power grid before a fault;

establishing an edge weighting tree diagram according to the power flow data and the energy flow direction of the line in the power grid before the fault; the edge weighted tree graph comprises a plurality of load points; the connecting line of every two load points in the plurality of load points corresponds to one line;

determining the fault position and a downstream line of the fault position in the edge weighted tree diagram according to fault output information of the fixed-segment protection equipment;

determining at least one target line according to the power flow data of the downstream line of the fault position; the downstream line comprises a first load point and a second load point, and the energy flow direction in the power grid before the fault is from the fault position to the second load point through the first load point; wherein the determining at least one target line according to the power flow data of the downstream line of the fault location comprises: obtaining the current data of the downstream line of the fault position from the current data of the line in the power grid before the fault; determining N lines with the minimum numerical value of the power flow data in the downstream line as the at least one target line; n is a positive integer;

dividing the downstream line into at least two isolated islands by taking the at least one target line as a splitting point;

and determining the equipment to be switched in the islands according to the load power of the load points in the at least two islands and the output power of the distributed power sources in the at least two islands.

2. The method according to claim 1, wherein the determining the device to be switched in the island according to the load power of the load points in the at least two islands and the output power of the distributed power source in the at least two islands comprises:

determining total load power according to the load power of a load point in a target island, and determining total output power according to the output power of a distributed power supply in the target island; the target island is any one of the at least two islands;

and determining cutting equipment from a load point in the target island or a distributed power supply based on the first sequencing result and the second sequencing result according to the magnitude relation between the total load power and the total output power.

3. The method of claim 2, wherein the total load power comprises a total load active power and a total load reactive power, and the total output power comprises a total output active power and a total output reactive power;

the determining total load power according to the load power of a load point in a target island and determining total output power according to the output power of a distributed power supply in the target island includes:

determining the total load active power and the total load reactive power according to the load power and a first power factor of a load point in the target island, and determining the total output active power and the total output reactive power according to the output power and a second power factor of a distributed power supply in the target island; the first power factor is used for representing the ratio relation between the total load active power and the total load reactive power in the total load power; the second power factor is used for representing the ratio relation between the total output active power and the total output reactive power in the total output power.

4. The method according to claim 3, wherein the determining, based on the first and second sorting results, a cut-off device from a load point or a distributed power source in the target island according to a magnitude relation between the total load power and the total output power comprises:

determining that the difference value between the total load active power and the total output active power is greater than a first preset value, and/or the difference value between the total load reactive power and the total output reactive power is greater than a second preset value;

and determining cutting equipment from a load point or a distributed power supply in the target island based on the first sequencing result and the second sequencing result according to the magnitude relation between the total load active power and the total output active power and the magnitude relation between the total load reactive power and the total output reactive power.

5. The method of claim 4, wherein in the case that the total output active power is less than the total load active power and the total output reactive power is less than the total load reactive power, the method further comprises:

determining a standby distributed power source as a switching device under the condition that the standby distributed power source is determined;

and under the condition that the investment requirement is determined not to be met, determining the cutting equipment from the load points in the target island according to the first sequencing result.

6. A device for determining switching equipment in a microgrid, comprising:

the acquisition module is used for acquiring the power flow data and the energy flow direction of a line in the power grid before the fault;

the establishing module is used for establishing an edge-weighted tree diagram according to the flow data and the energy flow direction of the line in the power grid before the fault, which are acquired by the acquiring module;

the determining module is used for determining a fault position and a downstream line of the fault position in the edge weighted tree diagram according to the fault output information of the fixed-section protection equipment; the edge weighted tree graph comprises a plurality of load points; the connecting line of every two load points in the plurality of load points corresponds to one line;

the determining module is used for determining at least one target line according to the power flow data of the downstream line of the fault position; the downstream line comprises a first load point and a second load point, and the energy flow direction in the power grid before the fault is from the fault position to the second load point through the first load point; the determining module is specifically configured to: obtaining the current data of a downstream line of a fault position from the current data of the line in the power grid before the fault; determining N lines with the minimum numerical value of the power flow data in the downstream lines as at least one target line; wherein N is a positive integer;

the dividing module is used for dividing the downstream line into at least two isolated islands by taking the at least one target line determined by the determining module as a splitting point;

the determining module is further configured to determine the device to be switched in the island formation according to the load power of the load points in the at least two islands and the output power of the distributed power source in the at least two islands, which are divided by the dividing module.

7. The device for determining the switching equipment in the microgrid is characterized by comprising a memory, a processor, a bus and a communication interface; the memory is used for storing computer execution instructions, and the processor is connected with the memory through the bus;

when the determination device for the switching device in the microgrid is operated, a processor executes the computer-executable instructions stored in the memory to cause the determination device for the switching device in the microgrid to execute the determination method for the switching device in the microgrid according to any one of claims 1 to 5.

8. A computer-readable storage medium, wherein instructions are stored therein, which when executed by a computer, cause the computer to perform the method for determining a switching device in a microgrid according to any one of claims 1 to 5.