CN113659540B

CN113659540B - Power distribution network setting calculation method considering distributed power supply and storage medium

Info

Publication number: CN113659540B
Application number: CN202110700677.6A
Authority: CN
Inventors: 张骏; 邵庆祝; 汪伟; 谢民; 于洋; 俞斌; 叶远波; 程晓平; 赵晓春; 丁津津; 孙辉
Original assignee: Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd; State Grid Anhui Electric Power Co Ltd
Current assignee: Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd; State Grid Anhui Electric Power Co Ltd
Priority date: 2021-06-23
Filing date: 2021-06-23
Publication date: 2023-09-08
Anticipated expiration: 2041-06-23
Also published as: CN113659540A

Abstract

The invention relates to a power distribution network setting calculation method and a storage medium considering a distributed power supply, which are based on a distribution network automation system data model, and comprise the steps of considering the change of a setting calculation model when wind power and photovoltaic are connected into the power distribution network, analyzing the influence on the original protection configuration and setting principle when the wind power and photovoltaic power generation system is connected into the power distribution network by theory, identifying the fault type by utilizing fault current sequence components, finding out the change rule of the equivalent impedance of the system, establishing a distributed power plant station-level equivalent power supply model, and determining the protection setting principle suitable for the connection of the distributed power supply.

Description

Power distribution network setting calculation method considering distributed power supply and storage medium

Technical Field

The invention relates to the technical field of power distribution networks, in particular to a power distribution network setting calculation method considering a distributed power supply and a storage medium.

Background

The power distribution network is used as the last link of a power transmission and distribution system, closely contacts with terminal power utilization users, and the safe and stable operation of the power distribution network is the guarantee of high quality and high reliability of power utilization of the users, so that the relay protection of the power distribution network serving as the first defense line of the safe operation of the power distribution network is particularly important, and the following problems mainly exist in the aspect of the current power distribution network setting calculation:

(1) The power distribution network equipment is huge in volume, complex in wiring mode, more in T wiring paths, large in traditional graphic modeling setting workload and incapable of guaranteeing the accuracy of equipment parameters;

(2) The grid structure of the power distribution network system equipment is complex, the operation mode is frequently changed, the calculation principle of the current distribution network setting calculation is rough, a necessary checking means is lacked, the adaptability to the grid structure change is poor, and the fixed value safety is insufficient;

(3) The existing setting calculation system device is complex in modeling, cannot be well suitable for setting calculation of the distribution network, and causes that the setting calculation of the distribution network is carried out manually, a setting list is modified, the manual intervention is more, the working efficiency is low, and errors are easy to occur;

(4) The distributed power supply is accessed in a large scale, the traditional single-side power supply is converted into double-end power supply or multi-end power supply, so that the setting calculation difficulty of the relay protection setting value is increased, the adaptability of the protection setting value is not strong, and the power supply reliability level is reduced;

(5) The fixed value list is paper archiving, so that the searching is very inconvenient, and the unified management is difficult to realize.

In order to solve the current situation of the current power distribution network setting calculation, the power distribution network setting calculation efficiency is improved, and the relay protection power distribution network setting calculation system is necessary to be researched.

At present, the setting calculation software in the market is developed aiming at the characteristics of a high-voltage power system, but the relay protection setting calculation of a high-voltage power grid and the relay protection setting calculation of a power distribution network are not completely the same, because in the relay protection setting calculation of the power system, the power distribution network has certain difference in terms of parameter composition, network structure, setting mode and the like compared with the high-voltage power network, and the existing relay protection setting software is generally high in price and is difficult for basic-level power enterprises to bear.

Specifically, the DG is added into the power distribution network, so that the complexity of dispatching operation management is increased, firstly, the distributed power supply is concentrated and connected to the transformer substation, the situation of upward power flow transmission possibly occurs, the unstable larger power supply is increased, and the uncertainty of operation of the large power grid is further increased. Secondly, the distributed power supply has the phenomena of poor equipment quality and untimely maintenance, so that frequent off-grid or protection override actions are caused, and a certain threat is formed to the safety of the power grid. Thirdly, except for the influence of weather, the user self-provided distributed power supply can also carry out switching machine sets according to own needs, and under the condition that the main network is abandoned by wind and light, the output of the distributed power supply cannot be restrained, so that peak regulation and voltage regulation are difficult.

When the lines on the transformer station and the grid-connected channel of the distributed power supply are in fault, if the distributed power supply is not timely disconnected from the system after the protection action of the large system side trips, the fault line is prevented from extinguishing arcs for a long time, the transient fault can be developed into a permanent fault, and the damage to equipment is large. If a temporary island is formed, the high-voltage side of the main transformer is possibly caused to perform grounding protection or non-grounding protection, the switch on each side of the jump transformer can also cause the transformer station to lose electricity for a long time even though reclosing or spare power automatic switching action is performed, the power transmission of the circuit is recovered, and meanwhile, the transformer station can also be caused to cause the spare power automatic switching device to be not operated due to the fact that the bus is pressed, the low-frequency low-voltage load-reducing device is caused to perform action, and part of load circuits are cut off. Finally, when the power supply of the transformer substation is quickly restored, the part of load circuit is lost for a long time because the part of load circuit cannot be quickly restored.

Faults at different positions, different access capacities of DGs, access positions and the like have different effects on various protections:

(1) When a fault occurs at the downstream of the DG, the protection sensitivity at the upstream of the DG is reduced, the fault current flowing through the upstream protection is smaller than the current of the actual fault point, the setting value can not be reached, the protection at the upstream of the DG is refused, and the protection range is reduced. The protection range between DG downstream and fault point is enlarged, partial selectivity is lost, and lower fault override trip can be caused.

(2) When a fault occurs upstream of DG, the protection sensitivity upstream of DG is also reduced, and island is easily caused downstream of DG.

(3) When a fault occurs in an adjacent feeder line of the feeder line where the DG is located, short-circuit current flowing to a fault point from the DG also passes through the DG upstream switch, and the current is increased to a certain degree, so that misoperation of the DG upstream switch can be caused. The current flowing through the protection upstream of the adjacent feeder fault increases, which reduces its protection range.

Disclosure of Invention

The power distribution network setting calculation method considering the distributed power supply provided by the invention can solve the technical problems.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

a power distribution network setting calculation method considering distributed power sources comprises the following steps:

the method comprises the steps of considering the change of a setting calculation model when wind power and photovoltaic are connected into a power distribution network, analyzing the influence of the wind power and photovoltaic power generation system on the original protection configuration and setting principle by theory when the wind power and photovoltaic power generation system is connected into the power distribution network, identifying fault types by using fault current sequence components, finding out the change rule of the equivalent impedance of the system, establishing a distributed power plant-level equivalent power model, and determining the protection setting principle suitable for the connection of a distributed power supply.

In another aspect, the invention also discloses a computer readable storage medium storing a computer program, which when executed by a processor causes the processor to perform the steps of the method as described above.

According to the power distribution network setting calculation method considering the distributed power supply, the change of a setting calculation model when wind power and photovoltaic power are connected into the power distribution network is considered, the influence on the original protection configuration and setting principle when the wind power and photovoltaic power generation system is connected into the power distribution network is analyzed through theory, then the fault type is identified by using fault current sequence components, the change rule of the equivalent impedance of the system is found out, a plant-level equivalent power supply model of the distributed power supply is established, and the protection setting principle suitable for the connection of the distributed power supply is researched.

Drawings

FIG. 1 is an overall frame diagram of an intelligent distribution network tuning and management system of the present invention;

FIG. 2 is a deployment architecture diagram of the distribution network tuning computing platform of the present invention;

FIG. 3 is a functional architecture diagram of a distribution network tuning computing platform of the present invention;

FIG. 4 is a schematic diagram of a grid model map file of the distribution automation system of the present invention;

FIG. 5 is a schematic diagram of a data file of an automated grid model for a distribution network according to the present invention;

FIG. 6 is a schematic diagram of a 10kV outlet primary and secondary switch;

FIG. 7 is a graph of proportional differential operating characteristics;

FIG. 8 is a schematic diagram of a ratio differential equation of motion curve;

FIG. 9 is a logic diagram of interval 1, interval 2 overcurrent segment I protection;

FIG. 10 is a logic diagram of the over-current I-segment protection at intervals 3-8;

FIG. 11 is a logic diagram of interval 1, interval 2 zero sequence overcurrent I segment protection;

FIG. 12 is a logic diagram of the zero sequence overcurrent I section protection at intervals 3-8;

FIG. 13 is a flow chart of the adaptive tuning of the present invention;

FIG. 14 is a schematic diagram of an adaptive tuning mode of operation file of the present invention;

fig. 15 is an illustration of an open-close;

FIG. 16 is a schematic diagram of a branch in the outlet unit;

FIG. 17 is a schematic diagram of the protection impact of an embodiment three adjacent line photovoltaic access;

fig. 18 is a schematic view of adjacent line photovoltaic access after embodiment three is simplified;

fig. 19 is a schematic diagram of the effect of the three-line photovoltaic access on protection;

fig. 20 is a simplified photovoltaic access schematic of the present line according to embodiment three;

FIG. 21 is a model icon for a photovoltaic, fan, energy storage device of example three;

FIG. 22 is a parameter interface for the third embodiment.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention.

According to the power distribution network setting calculation method considering the distributed power supply, which is disclosed by the embodiment, the whole frame diagram is shown in fig. 1 based on an intelligent power distribution network setting and management system;

the distribution network model data sources are divided into two stages:

the first stage: a distribution network automation system (or a pattern management system) data model (part) is adopted. The current distribution network automation system (or graph model management system) model is imperfect and cannot meet the working requirement of intelligent distribution network setting, so that in order to simplify the requirement of manual modeling, the distribution network automation system (or graph model management system) power grid data are adopted, and meanwhile, manual intervention (manual correction) is performed to ensure the correctness of the distribution network model data. Firstly, obtaining the equivalent value and the fixed value allowance which are issued to the distribution network by the main network, and then realizing the functions of graphic modeling, setting calculation, fault analysis and the like of a distribution network setting calculation system; and reporting the generated electronic fixed value list and the generated computer book for verification, and finally transmitting the fixed value list to an OMS system for circulation.

And a second stage: the distribution network model of the distribution network automation system (or the pattern management system) is completely adopted. And automatically acquiring a power grid model of the distribution network for analysis, and automatically generating a power grid setting model required by an intelligent distribution network setting system. Thus realizing the self-adaptive setting of the distribution network and the management of related data.

The following is a specific description:

deployment architecture:

the deployment architecture of the distribution network setting computing platform is distributed, and the "distributed" deployment architecture shown in fig. 2 means that each county scale maintains respective basic data on a local scale server, each county scale maintains respective setting computing basic data according to a dispatching jurisdiction, and the county scale can interact with the local scale in a boundary equivalence mode.

Functional architecture:

as shown in fig. 3, the platform function architecture is divided into a data layer, a base layer, an application layer and a user layer, and the functions of the layers are as follows:

data layer: corresponding to the database, is used for storing all data of the platform, including original data, intermediate data, output data and the like.

Base layer: including a base support assembly and a base application assembly. The basic supporting component comprises a power grid model management component, a power grid graph management component, a topology analysis component and the like, and is mainly used for providing management of basic metadata such as models, graphs, topologies and the like; the basic application component comprises a simple fault component, a current maximum component, a branch coefficient component, a principle setting component, a device setting component and the like, encapsulates the platform computing function in a component mode, provides a service interface for an application layer and is a core of the platform.

Application layer: is a specific embodiment of the platform function requirement, comprising: modeling and tuning, data management and system setup, etc.

User layer: the user layer is mainly the interaction of the client with the platform.

Modeling based on a distribution network model system:

and importing a graphic file (SVG format) containing complete connection relation and a model file (XML format) containing equipment parameters and topological connection into a system by a power grid model data interface provided by a power distribution network automation system (or a graphic model management system) to automatically generate a power distribution network graph and a calculation model. The distribution network graph is displayed in a unified SVG format, as shown in the following figure 4, the display effect is consistent with the display of a power grid model in the distribution network automation system, and the distribution network setting calculation personnel are facilitated to be familiar with the power grid structure. By analyzing the power grid model data file (XML format), parameters such as line length, model, transformer model, capacity and the like are obtained as shown in fig. 5, the reference parameters are obtained by automatically matching the model of the equipment according to the parameter reference library of the distribution network equipment, and then the impedance parameters of each equipment are automatically calculated.

Description of data file:

the extension name of the distribution network model data file is xml, and the xml comprises a device name, a topological connection relationship, basic device parameters, a device subordinate relationship and the like.

(1) Primary data type

At least contains the necessary data analyzed by the distribution network setting system shown in the table below.

(2) Data presentation form

The first line of data marks a unique ID, < cim: XXrdf: ID= "XXXXXX" >, with device information in the middle, ending with </cim: XX >.

(3) Basic parameters of the device

V-shaped ac line

V-shaped transformer

Other V-shaped

Graphic file description

The extension name of the distribution network model graphic file is svg, and the data format meets the requirements of the graphic file description specification in the line standard. Including primitives, device angles, sizes, coordinates, etc. And the ID of the device in the graphic svg file should be consistent with that in the data xml file.

Graphic batch modeling technology

The batch modeling technology of the distribution network automatically generates main lines according to the set segmentation number, randomly adds branch lines on the existing lines, adds cable tapping boxes, power distribution cabinets, ring main units and the like in batches, and adds extension branches in the existing power grid model of the distribution network. The equipment connected with each branch in the cable tapping box, the power distribution cabinet and the ring main unit is set at one time to automatically generate a graph. The distribution network tool box contains all devices of the distribution network and supports arbitrary modification of graphics.

Topology generation and graph generation technique

And automatically generating a power distribution network graph in a standard SVG format for display by analyzing data topological connection. The technical problems of complex modeling and large workload of the distribution network are solved. The graphic element objects contained in the distribution network typical model are in one-to-one correspondence with the database records, a record is automatically added into the database while an equipment graphic element (line, transformer and bus) object is defined, and the attribute parameters of the equipment graphic element and the input interface thereof can be modified according to the requirements of users, so that one-to-one correspondence between the graphics and the database is realized, and the compatibility of the system is ensured.

(1) The following basic primitives can be automatically generated: external equivalent system, two-coil transformer, circuit breaker, circuit, busbar.

(2) And supporting graphical display, wherein the graphic elements in the graph correspond to actual equipment in the power grid, analyzing physical topological relation according to the connection relation of parameter input during modeling, and establishing a connection diagram of an outlet unit. The trunk lines set up for modeling are shown in red lines.

(3) During graphic display, the length, the impedance, the sectional line model name, the CT transformation ratio, the protection device model and the protection constant value and time constant value of each section of the phase current can be selectively displayed.

(4) The whole graphic picture can be arbitrarily enlarged, reduced and restored, and the labels in the drawing are synchronously scaled during scaling;

(5) Establishing a distribution network tree resource tree according to the hierarchical structure and the regional structure of the power grid, and realizing the navigation and positioning functions of the resource tree; the platform can automatically position the graph by double-clicking the plant area tree node, and can also position the plant or outgoing line unit tree node during graph switching.

The following describes intelligent setting calculation of the distribution network based on the adaptive setting principle:

firstly, setting principle schemes corresponding to a first-level switch and a second-level switch are established according to different wiring modes (public network wiring, private network wiring, hand-in-hand wiring and the like), the upper and lower level relations of the switches which are configured and protected are automatically analyzed through analyzing received operation mode files (stored locally), the corresponding setting principle schemes are matched, self-adaption of setting principles under different grid structures and operation modes is realized, then fixed value calculation is carried out, and one-key setting of device fixed values is completed.

Setting principle expert base establishment:

principle setting

The development of the expert base of the distribution network setting platform principle is completed according to the distribution network protection operation setting principle of the city company, and the expert base is shown in fig. 6.

The protection operation setting principle is as follows:

(1) First stage, second stage switch protection

The protection of the 10kV line switch outside the transformer substation is reasonably switched according to the configuration principle, and the protection is regularly graded and layered according to the installation position and the upper and lower level relation of the switch, so that the switch is divided into a first-level switch and a second-level switch. The first-stage switch refers to an off-site switch which is in protective fit with the outlet switch of the transformer substation, and the first-stage switch and the second-stage switch comprise the pole-mounted switch and the ring network outlet switch in the ring main unit.

1) First stage switch protection

Overcurrent I-section protection

Principle 1: and setting according to 0.9 times of the constant value of the overcurrent II section of the 10kV outlet switch of the transformer substation.

Principle 2: and setting the constant value of the overcurrent I section of the 10kV outlet switch of the transformer substation by 0.8 times.

Description of principle: the method is generally carried out according to the principle 1. For 10kV lines of a part of 35kV transformer substations, because of larger system equivalent impedance, the overcurrent II section of the outlet switch has smaller fixed value (limited by less than 600A), when the protection of the overcurrent I section of the first-stage switch is set according to the principle 1, the protection of the overcurrent I section of the first-stage switch is smaller, and the protection of the lower-stage switch is not beneficial to the cooperation of protection, and at the moment, the overcurrent I section of the first-stage switch is set according to the principle 2.

Action time: 0.1s; and (3) setting according to the principle 2, and taking 0s.

Overcurrent II section protection

Principle 1: and setting according to the value which is not more than 0.9 times of the constant value of the overcurrent III section of the 10kV outgoing switch of the transformer substation.

Principle 2: the maximum load current of the back-end circuit of the switch is set according to the hiding speed, and is generally 1.3 times of the maximum load current.

Description of principle: and comprehensively considering principle 1 and principle 2 setting.

Action time: 0.4s.

Reclosing valve

And when the reclosing input condition is met, the reclosing time is 2.5s.

2) Second stage switch protection

Overcurrent I-section protection

Principle 1: setting the constant value of the overcurrent I section according to the first-stage switch by 0.8 times.

Action time: 0s.

Overcurrent II section protection

Principle 1: setting according to the value which is not more than 0.8 times of the constant value of the overcurrent II section of the first-stage switch.

Description of principle: and comprehensively considering principle 1 and principle 2 to set and take values.

Action time: 0.2s.

Reclosing valve

And when the reclosing input condition is met, the reclosing time is 2.5s.

(2) Terminal feeder switch protection

The switching station switch, the ring main unit load outlet switch and the user demarcation switch are regarded as terminal feeder switches, the two-stage attribution is not included, and the protection setting principle is as follows.

1) Switch protection for switching station

Overcurrent I-section protection

Principle 1: setting according to 3-6 times of the sum of the rated current of the distribution transformer carried by the outlet switch.

Action time: 0s.

Overcurrent II section protection

Principle 1: setting according to 1.3-1.5 times of the sum of the rated current of the distribution transformer carried by the outlet switch.

Action time: 0.2s.

2) Ring main unit load outgoing line switch protection

The ring main unit load outgoing switch is similar to an switching station outgoing switch, and the protection setting principle is as follows:

overcurrent I-section protection

Principle 1: setting according to 3-6 times of the maximum load current carried by the outlet switch.

Action time: 0s.

Overcurrent II section protection

Principle 1: setting according to 1.3-1.5 times of the maximum load current carried by the outlet switch.

Action time: 0.2s.

(3) User demarcation switch (watchdog) protection

1) Private line user

Overcurrent I-section protection

Principle 1: and setting the overcurrent II section fixed value of the 10kV outgoing switch of the transformer substation by 0.9 times.

Principle 2: setting according to 3-6 times of the sum of rated currents of all the distribution transformers of users.

Principle 3: and setting the constant value of the overcurrent I section of the 10kV outlet switch of the transformer substation by 0.8 times.

Description of principle: setting is generally carried out according to principle 1 and principle 2. For special line users of part 35kV transformer substations, because the value of the overcurrent II section of the outgoing line switch is smaller (limited by less than 600A), when the values according to the principle 1 and the principle 2 contradict, the special line users can be set according to the principle 3.

Action time: 0.1s; when the setting is made according to principle 3, 0s is taken.

Overcurrent II section protection

Principle 1: setting according to 1.1-1.2 times of the sum of rated currents of all the distribution transformers of the users.

Action time: 0.4s.

2) T-connect user

Overcurrent I-section protection

Principle 1: setting according to 3-6 times of the sum of rated currents of all the distribution transformers of users.

Action time: 0s.

Overcurrent II section protection

Action time: 0.2s.

Device setting

The device setting mainly takes PCS-9721S-NB as a main part, and the device is mainly suitable for power distribution automation DTU devices in places such as switching stations, distribution rooms, ring main units and the like, and each terminal is suitable for electric quantity access within 8 intervals. The main functions of the device are shown in Table 4-1

TABLE 4-1PCS-9721S-NB device function Table

The setting principle of the device is as follows:

(1) Differential protection

The action criteria of the ratio differential element are 4-1 and 4-2

The action criteria of the ratio differential elements in the formulas 4-1 and 4-2; the operation characteristic curves are shown in fig. 7.

(2) Differential protection of circuit

The equation of motion of the ratio differential relay is shown in equations 4-3, and the motion characteristic curve is shown in fig. 8.

Equation of action for the 4-3 ratio differential relay;

the motion equation of the zero sequence differential relay is as follows in 4-4:

Equation of motion for 4-4 zero sequence differential relay

(3) Overcurrent protection

The device is provided with two sections of time-limiting overcurrent protection, and each section is provided with an independent current fixed value, an independent time fixed value and a control word. The overcurrent I-section protection logic of interval 1 and interval 2 is different from the logic of intervals 3-8. The overcurrent I sections of the intervals 1 and 2 are in a locking state by default and are opened only when the bus differential protection exits or the network topology protection corresponding to the intervals exits, and the overcurrent I section protection of the intervals 3 to 8 is not limited by the condition.

The judgment logic of the overcurrent protection is as shown in fig. 9 and 10.

(4) Zero sequence overcurrent protection

When the device is used for a small-resistance grounding system, the grounding zero-sequence current is relatively large, and a direct tripping method can be used for isolating faults. Correspondingly, the device provides two sections of zero sequence overcurrent protection, and only alarms and does not exit when the II section control word is 0. The judgment logic is as shown in fig. 11 and 12.

The zero sequence overcurrent II section protection logic is similar to the zero sequence overcurrent I section protection logic, but all the interval zero sequence overcurrent II sections are directly opened. By combining the actual conditions of the project, the zero sequence overcurrent protection only alarms and cannot be output.

Overcurrent/zero sequence acceleration protection

When the line is put into operation or power is restored, there may be a fault on the line. In such cases, it is often desirable for the protection device to be able to cut the fault in as short a time as possible, rather than cut the fault with time-limited over-current protection. This function can be switched on/off as required.

Reclosing valve

And (5) reclosing at line intervals. The closed weight signal is: a bus differential protection action, a failure protection action, a non-voltage tripping action, a remote tripping action, a CT disconnection tripping, a high-current locking tripping, a hand tripping signal and a TWJ abnormal signal. This function can be switched on/off as required.

(6) Failure protection

The failure protection function of each interval is realized: if the protection element (other protection except failure protection, long jump protection and CT broken line tripping) does not receive the switch tripping position after the failure protection is set and delayed, the switch is judged to be refused to jump, other switches on the jump bus are closed again, and the other switches are not judged to flow.

This function can be switched on/off as required.

(7) Non-pressure tripping

The circuit interconnecting switch is in a self-switching charging state, is in a combined state and a pressed state before being put into a switch with a non-voltage tripping function, is converted into a non-current state and a non-voltage state of a bus, and is tripped and closed again after time delay, so that only one action is ensured. The opposite side switch of the transformer substation and the opposite side switch of the interconnecting switching room on the main path can be selectively put into the function. Other switches on the backbone path do not require this function.

(8) High current lockout trip function

When the protection element judges that the transformer substation is to be tripped, if the phase current is larger than a high-current locking tripping fixed value, locking tripping and memorizing are carried out, after the transformer substation side outlet switch is subjected to protection tripping, the transformer substation side outlet switch is detected to be tripped and closed again after no voltage and no current are detected, and meanwhile the transformer substation side outlet switch is far jumped. This function can be switched on/off as required.

Self-adaptive setting technology

And selecting an established setting scheme or a setting scheme corresponding to a wiring mode according to the actual setting condition, realizing the self-adaption of the setting principle under different grid structures and operation modes, and completing the one-key setting of principle-level and device-level setting values. The overall flow of the scheme is shown in fig. 13.

Operation mode file analysis technology

(1) The method comprises the steps of scanning real-time operation mode files at fixed time and obtaining the latest files: the method comprises the steps of locally establishing a folder of a real-time running mode of the power distribution network, defining the name of the folder as RunWayInfo, scanning a running mode file once in five minutes by a program, and automatically acquiring a latest running mode file according to the running mode file name;

(2) The running mode file format is shown in fig. 14;

(3) According to the content of fig. 14, the switch ID in the file is automatically matched with the switch in the interface according to the outgoing line unit ID in the file, so as to obtain the on-off state of the switch.

(4) And comparing the switch state in the operation mode file with the switch state in the current library, if the switch state is changed, correcting the state of the switch in the existing outlet unit according to the real-time operation mode file, starting self-adaptive setting, and performing the next analysis operation of the upper and lower switches.

Upper and lower stage switch analysis technology:

(1) The selection rule of the zero-level, first-level and second-level switches in the wiring form of the switching station is described by taking fig. 15 as an example;

1) The sum of the capacities of the transformers under all the switching stations in the outgoing line unit is calculated, and the calculation formula is as follows:

note that: s is S _ti Represents the rated capacity of the transformer, R _i Representing the transformer operating rate (output), L _i Representing load importance.

2) Trisecting the total capacity;

3) Searching for an opening and closing station under one third and two thirds of capacity, and selecting an opening and closing station which is closer to a power supply if a demarcation point is positioned between the two opening and closing stations;

4) The wire inlet switch of the wire outlet unit is a zeroth-order switch; the first-stage switching station at the first demarcation point and the switch of the ring main unit, which is closed and protected by configuration, are first-stage switches, and the switch connected with the transformer or the line transformer group, which is directly connected with the transformer at the other side of the line, is second-stage switch; the first-stage switching station at the second branch point and the incoming line switch (closed and configured for protection) of the ring main unit are second-stage switches;

5) When a multi-stage switching station and a ring main unit exist at the downstream of a one-stage switching station between the zero-stage switch and the one-stage switch and a ring main unit outlet switch, the multi-stage switching station and the ring main unit can be selected as one-stage matching point switches, and a lower-stage switching station and a wire inlet switch of the ring main unit are selected as two-stage switches; when the multi-stage switching station and the ring main unit exist at the downstream of the primary switching station and the ring main unit outlet switch between the primary switch and the secondary switch, protection can be put into according to a mismatch point setting principle, and the primary switch is selected; the other switches (closed, configuration protected) are second stage switches;

(2) The selection rules of the zero-level, first-level and second-level switches in the form of branch wiring are described by taking fig. 16 as an example;

1) The sum of the capacities of transformers under all branches in the outgoing line unit is calculated, and the calculation formula is as follows:

2) Trisecting the total capacity;

3) The main line switch under the third and the second thirds capacity is searched and used as a first-stage switch and a second-stage switch respectively, and if the third demarcation point is positioned between the two switches, the switch which is closer to the power supply is selected as the first-stage switch and the second-stage switch;

4) The switch at the outlet of the branch line between the zero-level switch and the first-level switch is preferably selected as a first-level switch (such as 2584 column switch in fig. 16), and the sectional switch below the branch, the secondary branch outlet switch and the branch switch directly connected to the main line in a T manner (such as 2585 column switch in fig. 16) are preferably selected as second-level switches;

5) The branch switch between the primary switch and the secondary switch is preferably selected as the secondary junction, as shown by the 2587 column in fig. 4.

(3) The divided zero-level switch, the first-level switch and the second-level switch are filled with red in the figure and flash for visual display of the switches at all levels.

Study on tuning principle matching technique

Matching according to the set tuning principle schemes of the zero-level switch, the first-level switch and the second-level switch, then tuning the fixed value, and displaying the tuned fixed value in the interface;

and finally generating a proposal scheme according to the associated protection device. The proposal comprises displaying a zero-level switch, a first-level switch and a second-level switch, and displaying the fixed value of each switch;

clicking 'downloading', creating a CIME folder locally when the CIME is used for the first time, and then generating a fixed value single file in CIME format in the local CIME folder according to the protection device associated with each switch, wherein the fixed value single file name is as follows: and when the user clicks again, only a fixed value single file is generated, and the folder is not required to be repeatedly built.

In summary, the rapid modeling technology of the distribution network based on the objectification technology, namely the rapid modeling technology of the objectification based on the ring main unit, the switching station and the multistage serial supply model, automatically generates the distribution network data model by only inputting the number of incoming and outgoing lines, the serial supply stage number and the like. And analyzing data topological connection through a depth-first search algorithm, and automatically generating a power distribution network graph in a standard SVG format for display. The technical problems of complex modeling and large workload of the distribution network are solved.

Meanwhile, a distribution network intelligent setting calculation technology based on a self-adaptive setting principle is used for establishing setting principle expert libraries of different wiring types, self-adaptive matching of the setting principles under different network structures is realized through topology analysis, and automatic setting of a setting value is realized on the basis of objective modeling.

Based on the intelligent distribution network setting and management system, the invention also provides a distribution network setting calculation model considering the distributed power supply, which comprises the following specific steps:

the method comprises the steps of considering the change of a setting calculation model when wind power and photovoltaic are connected into a power distribution network, analyzing the influence of the wind power and photovoltaic power generation system on the original protection configuration and setting principle by theory when the wind power and photovoltaic power generation system is connected into the power distribution network, identifying fault types by using fault current sequence components, finding out the change rule of the equivalent impedance of the system, establishing a distributed power plant-level equivalent power model, and researching the protection setting principle suitable for the connection of a distributed power supply.

The following is a specific description:

equivalent model research of distributed power plant station

The capacity of the inverter switching tubes is a major factor limiting the output current of the photovoltaic device. Typically the maximum current output by the inverter does not exceed 1.2 times the rated current. The method comprises the following steps:

this is essentially a limitation on the photovoltaic device output power, as:

In the formula (3), U is grid-connected point voltage, UB is grid-connected point voltage reference value, and S is rated capacity of the photovoltaic equipment.

By combining a low-voltage ride through control strategy of the photovoltaic equipment, performing simulation analysis by using a full-electromagnetic transient model of the photovoltaic equipment in PSCAD, and analyzing the output current condition of the photovoltaic equipment under the fault condition, the photovoltaic equipment can be equivalent to a voltage controlled current source, the output fault current of the photovoltaic equipment changes along with the change of the voltage of a grid-connected point, and the output current of the photovoltaic equipment is 1.2 times of the rated current at the maximum when the power grid fails. When the voltage of the grid-connected point of the photovoltaic equipment is larger than 0.9p.u, the photovoltaic equipment adopts a control mode of normal operation, namely a maximum power tracking mode; when the voltage of the grid connection point of the photovoltaic equipment is lower than 0.9p.u, the photovoltaic equipment enters a low voltage ride through state: when the voltage of the grid-connected point of the photovoltaic equipment is higher than 0.83p.u and lower than 0.9p.u, the photovoltaic adopts a constant power output mode, namely the power is kept unchanged before failure; when the voltage of the grid-connected point of the photovoltaic equipment is lower than 0.83p.u, the photovoltaic equipment outputs the maximum fault current, namely 1.2 times of rated current, and the relation between the fault current output by the photovoltaic equipment and the voltage of the grid-connected point is shown as a formula (4)

The power distribution network comprising the photovoltaic equipment can be simplified by equivalent of the photovoltaic equipment as a voltage controlled current source, and the protection fixed value is automatically set according to the operation conditions and the fault types of the system and the photovoltaic equipment. Conventional adaptive current protection only considers the influence of the system operation mode on the protection fixed value. When the photovoltaic device is connected in, the short-circuit current provided by the photovoltaic device is also considered when automatically setting the protection fixed value.

After the photovoltaic device is connected in, the current flowing through the protection installation part mainly comprises three parts: the short-circuit current provided by the system, the boosting current of the photovoltaic equipment of the adjacent line and the external drain current of the photovoltaic equipment of the line can be overlapped by utilizing the overlapping theorem, and the self-adaptive protection fixed value of the photovoltaic equipment after being connected is calculated by considering the three parts of current.

The system provides for calculation of short circuit current:

the short-circuit current of the system can be determined according to the electromotive force of the back side system, the back side impedance of the system and the impedance of the protected line, and the specific calculation expression is shown as the formula (5)

wherein ,E_s For the equivalent phase potential of the system, 1.05p.u is usually taken; z is Z _s To protect the comprehensive impedance of the power supply side; z is Z _L Is the impedance of the protected line.

Boosting current of adjacent line photovoltaic equipment

The short-circuit current flowing through the protection part of the line can be increased by the photovoltaic equipment connected with other lines, so that the protection sensitivity is improved, and as shown in fig. 17, when the photovoltaic is connected with the No. 5 bus, according to the superposition theorem, the short-circuit current provided by the current removing system of the protection 1 is also partially provided for the photovoltaic.

The system is simplified and calculated by using the superposition theorem, and the boosting current provided by the photovoltaic equipment of the adjacent line can be calculated according to the information such as the short-circuit current, the line parameter and the like provided by the photovoltaic, and the simplified photovoltaic access schematic diagram of the adjacent line is shown in fig. 18.

By equating the photovoltaic device to a controlled current source, the short circuit current of the photovoltaic device at the time of failure can be calculated as I according to formula (1) _PV From FIG. 3, it can be calculated that the component of the photovoltaic device providing the short-circuit flow-through protection installation is shown as formula (6)

wherein ,Z_S Z is the short-circuit impedance at the system side _T Z is the impedance of the transformer _L The impedance of the line from the outlet bus of the transformer substation to the short circuit point.

When a plurality of photovoltaic devices are connected to adjacent lines, because the photovoltaic devices are controlled current sources, the short-circuit current provided by the photovoltaic devices is only related to the voltage drop degree of the grid-connected point, and the short-circuit currents can be linearly overlapped when a plurality of photovoltaic equivalent are carried out, namely I in the formula _PV Short circuit for adjacent line-connected photovoltaic devicesAnd (5) summing the path currents.

External current drawing of the line photovoltaic device

The short-circuit current flowing through the protection installation part of the line can be reduced when the photovoltaic equipment with larger capacity is connected to the line, so that the protection refusal operation is caused when the line end is in fault, as shown in fig. 19, when the photovoltaic equipment is connected to the node 1, the short-circuit current provided by the photovoltaic equipment can lead to the reduction of the short-circuit current measured by the protection 1, and the refusal operation of the protection 1 can be caused when the short-circuit current is serious.

The system is simplified by using the superposition theorem, and a specific schematic diagram is shown in fig. 20, a plurality of photovoltaic devices are connected at different positions of a line, and short-circuit currents provided by the photovoltaic devices all lead to reduction of the short-circuit currents measured at a protection place.

By equating the photovoltaic device to a controlled current source, the short circuit current of the photovoltaic device at the time of failure can be calculated as I according to equation (4) _PV1 and I_PV2 The component of the short-circuit current provided by the photovoltaic equipment at the protection installation position can be calculated by utilizing the superposition theorem as

According to the formula (7), it can be deduced that when the photovoltaic equipment is connected to different positions of the circuit, the photovoltaic equipment simultaneously measures the influence of short-circuit current on the protection place as

wherein ,I_PV Short-circuit current, Z, output for each photovoltaic device _{Downstream of} Z is the line impedance from the photovoltaic device access point to the short circuit point _S Z is the short-circuit impedance at the system side _T Z is the impedance of the transformer _L The impedance of the line from the outlet bus of the transformer substation to the short circuit point.

The relevant model icons provided by the modeling module in the system are shown in fig. 21; wherein the parameter interface is shown in fig. 22.

Protection setting principle suitable for distributed power supply access

With the continuous increase of the scale of the power distribution network and the access of new energy sources such as photovoltaics, the output of the new energy sources randomly fluctuates along with natural conditions, and the operation mode of the system is more changeable, so that the fixed value of the traditional current is difficult to set, and the coordination between protection is also difficult to coordinate. In order to adapt to the randomness of new energy, a protection capable of automatically setting a protection value according to the running mode of the system and the change of fault types needs to be studied.

(1) Setting and checking of constant value of overcurrent I section

When setting the constant value of the overcurrent I section, under the condition that the three-phase metallic short circuit occurs at the tail end of the outgoing line in the maximum operation mode of the system, the maximum short circuit current flowing through the protection installation part is considered, under the condition that the short circuit current is reduced due to the fact that the photovoltaic external current on the circuit is ignored, and after the clustering treatment is carried out on the photovoltaic equipment of other circuits, the setting equation of the constant value of the overcurrent I section can be obtained as follows:

I ^I _set ＝K ^I _rel (I _1.max +I ₂ ) (11)

wherein ,is a reliable coefficient; i _1.max For short-circuit current supplied by the system in maximum operation mode, I ₂ The auxiliary current of other line photovoltaic devices after the clustering treatment is increased.

When the sensitivity verification of the overcurrent section I is carried out, the protection sensitivity during slight faults is required to be considered, calculation is carried out under the condition that the auxiliary current of other line photovoltaics is not considered and the external current of the photovoltaic of the line is considered, and a specific sensitivity calculation formula is shown in a formula (12) when the two-phase metallic short circuit occurs at the tail end of the outgoing line in a minimum operation mode.

wherein ,I_1.min For short-circuit current supplied by the system in minimum operation mode, I ₃ The auxiliary current of the line photovoltaic equipment after the clustering treatment is increased.

(2) Setting and checking of overcurrent III section fixed value

When the overcurrent III section is regulated, the full length of the line is considered to be protected by the overcurrent III section, and the traditional regulation scheme is less influenced by photovoltaic access, so that the overcurrent III section protection is regulated according to the regulation scheme before photovoltaic access, namely, the regulation is carried out according to the maximum load current, and a specific expression is shown as a formula (13).

wherein ,for the reliability coefficient, 1.15-1.25 is generally adopted; k (K) _ss For the self-starting coefficient, the numerical value is larger than 1, and the self-starting coefficient is determined by the specific wiring and load property of the network; k (K) _re The relay return coefficient is generally 0.85-0.95.

When the sensitivity of the overcurrent III section is verified, the verification is carried out under the condition that the two-phase short circuit occurs at the tail end of the circuit in the minimum operation mode, and the external current provided by the photovoltaic equipment of the circuit is considered, and the boosting current provided by the photovoltaic equipment of other circuits is not considered; over-current section III protection is used as the main protection of the circuit, and the sensitivity coefficient K of the over-current section III protection is ensured in consideration of photovoltaic equipment _sen ≥1.3～1.5。

In summary, the embodiment of the invention establishes a setting calculation model when wind power and photovoltaic are connected into the power distribution network, researches the influence on the three-section current protection fixed value when the wind power and photovoltaic power generation system is connected into the power distribution network in a mode of combining theory and simulation, further researches the change rule of equivalent impedance, establishes a distributed power plant-level equivalent power model, and finally obtains a protection setting principle suitable for the connection of a distributed power supply.

In another aspect, an embodiment of the present invention further discloses a computer readable storage medium storing a computer program, where the computer program when executed by a processor causes the processor to perform the steps of the method as described above.

The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power distribution network setting calculation method considering distributed power sources is based on a distribution network automation system data model, and is characterized in that: comprises the steps of,

considering the change of a setting calculation model when wind power and photovoltaic are connected into a power distribution network, analyzing the influence of the wind power and photovoltaic power generation system on the original protection configuration and setting principle by theory, identifying the fault type by using fault current sequence components, finding out the change rule of the equivalent impedance of the system, establishing a distributed power supply plant-level equivalent power supply model, and determining the protection setting principle suitable for the connection of a distributed power supply;

the distributed power plant-level equivalent power model comprises:

Since the maximum current output by the inverter is not more than 1.2 times the rated current

（1）

This is essentially a limitation on the photovoltaic device output power, as:

（2）

（3）

in the formula (3), U is grid-connected point voltage, UB is grid-connected point voltage reference value, and S is rated capacity of photovoltaic equipment;

then combining a low voltage ride through control strategy of the photovoltaic equipment, performing simulation analysis by using a full electromagnetic transient model of the photovoltaic equipment in PSCAD, and equivalently converting the photovoltaic equipment into a voltage controlled current source by analyzing the output current condition of the photovoltaic equipment under the fault condition, wherein the output fault current of the photovoltaic equipment changes along with the change of the voltage of a grid-connected point, and the output current of the photovoltaic equipment is 1.2 times of the rated current at maximum when the power grid fails;

when the voltage of the grid-connected point of the photovoltaic equipment is larger than 0.9p.u, the photovoltaic equipment adopts a control mode of normal operation, namely a maximum power tracking mode; when the voltage of the grid connection point of the photovoltaic equipment is lower than 0.9p.u, the photovoltaic equipment enters a low voltage ride through state: when the voltage of the grid-connected point of the photovoltaic equipment is higher than 0.83p.u and lower than 0.9p.u, the photovoltaic adopts a constant power output mode, namely the power is kept unchanged before failure; when the voltage of the grid-connected point of the photovoltaic equipment is lower than 0.83p.u, the photovoltaic equipment outputs the maximum fault current, namely 1.2 times of rated current, and the relation between the fault current output by the photovoltaic equipment and the voltage of the grid-connected point is shown as a formula (4)

(4)

The power distribution network comprising the photovoltaic equipment is simplified by equivalent of the photovoltaic equipment as a voltage controlled current source, and a protection fixed value is automatically set according to the operation condition and the fault type change of the system and the photovoltaic equipment;

after the photovoltaic device is connected in, the current flowing through the protection installation place comprises three parts: the short-circuit current provided by the system, the boosting current of the photovoltaic equipment of the adjacent line and the external drain current of the photovoltaic equipment of the line are overlapped by utilizing the overlapping theorem, and the self-adaptive protection fixed value of the photovoltaic equipment after being connected is calculated by considering the three parts of current;

the distributed power plant-level equivalent power model also includes calculations that provide short-circuit currents,

that is, the short-circuit current of the system is determined according to the electromotive force of the back side system, the back side impedance of the system and the impedance of the protected line, and the specific calculation expression is shown as the formula (5)

(5)

wherein ,for the equivalent phase potential of the system, 1.05p.u is usually taken; />To protect the comprehensive impedance of the power supply side; />Is the impedance of the protected line;

the distributed power plant station-level equivalent power model further comprises the steps of simplifying the system by utilizing a superposition theorem, and calculating auxiliary current provided by photovoltaic equipment of adjacent lines according to short-circuit current and line parameter information provided by the photovoltaic;

By equating the photovoltaic device to a controlled current source, calculating the short circuit current of the photovoltaic device at the time of failure as according to equation (1)The component of the photovoltaic equipment providing the short-circuit flow through protection installation part is calculated as shown in a formula (6)

（6）

wherein ,is short at the system sidePath impedance, < >>Is the impedance of the transformer, ">The impedance of the line between the outlet bus of the transformer substation and the short circuit point is set;

when a plurality of photovoltaic devices are connected to adjacent lines, because the photovoltaic devices are controlled current sources, the short-circuit current provided by the photovoltaic devices is only related to the voltage drop degree of the grid-connected point, and the short-circuit currents of the photovoltaic devices are linearly overlapped when the photovoltaic devices are in the equivalent of a plurality of photovoltaic devices, namely, the short-circuit currents in the formulaThe sum of short-circuit currents provided for photovoltaic devices connected to adjacent lines;

the distributed power plant station-level equivalent power model also comprises protection refusal when the photovoltaic equipment with larger capacity of the line is connected with the line end fault because the short-circuit current flowing through the line protection installation part is reduced due to the connection of the photovoltaic equipment of the line; the system is simplified and calculated by utilizing the superposition theorem, a plurality of photovoltaic devices are connected at different positions of the circuit, and short-circuit current provided by the photovoltaic devices all leads to reduction of the short-circuit current measured at the protection place;

By equating the photovoltaic device to a controlled current source, calculating the short circuit current of the photovoltaic device at the time of failure as in equation (4) and />The component of the short-circuit current provided by the photovoltaic equipment at the protection installation position can be calculated by utilizing the superposition theorem as

（7）

Deducing according to formula (7) that when the photovoltaic equipment is connected to different positions of the circuit, the photovoltaic equipment simultaneously measures the influence of short-circuit current on the protection place as

（8）

wherein ,short-circuit current output for each photovoltaic device, +.>Line impedance for photovoltaic device access point to short-circuit point, +.>For short-circuit impedance on the system side, +.>Is the impedance of the transformer, ">The impedance of the line between the outlet bus of the transformer substation and the short circuit point is set;

the protection setting principle for determining the adaptation to the distributed power supply access comprises the following steps:

setting and checking of the constant value of the overcurrent section I, namely when the constant value of the overcurrent section I is set, under the condition that three-phase metallic short circuit occurs at the tail end of an outgoing line in the maximum operation mode of the system, the maximum short circuit current flowing through a protection installation part is required to be considered, under the condition that the short circuit current is reduced due to the fact that the photovoltaic external current on the circuit is ignored, and after the clustering treatment is carried out on other circuit photovoltaic devices, the setting equation of the constant value of the overcurrent section I is obtained as follows:

（11）

wherein ,is a reliable coefficient; i _1.max For short-circuit current supplied by the system in maximum operation mode, I ₂ The auxiliary current of other line photovoltaic devices after the clustering treatment is carried out is increased;

when the sensitivity verification of the overcurrent section I is carried out, the protection sensitivity during slight faults is considered, calculation is carried out under the condition that the auxiliary current of other line photovoltaics is not considered and the external current of the photovoltaic of the line is considered, and when the two-phase metallic short circuit of the tail end of the outgoing line occurs in a minimum operation mode, a specific sensitivity calculation formula is shown as a formula (12);

（12）

wherein ,I_1.min For short-circuit current supplied by the system in minimum operation mode, I ₃ The auxiliary current of the line photovoltaic equipment after the clustering treatment is increased;

the protection tuning principle for determining the adaptation to the distributed power access comprises,

setting and checking of the constant value of the overcurrent III section, namely setting the protection of the overcurrent III section according to a setting scheme before photovoltaic access, namely setting according to the maximum load current, wherein a specific expression is shown in a formula (13):

（13）

wherein ,is a reliable coefficient; />The self-starting coefficient is a numerical value greater than 1 and is determined by specific wiring and load properties of the network; />The relay return coefficient;

When the sensitivity of the overcurrent III section is verified, the test is performed under the condition that the tail end of the circuit is in a two-phase short circuit under the minimum operation mode, the external current provided by the photovoltaic equipment of the circuit is considered, and the boosting current provided by the photovoltaic equipment of other circuits is not considered; over-current section III protection is used as main protection of the circuit, and the sensitivity coefficient of the over-current section III protection is ensured in consideration of photovoltaic equipment。

2. A computer readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of the method of claim 1.