CN115441458A

CN115441458A - Active defense method, device and system for cascading failures of power system

Info

Publication number: CN115441458A
Application number: CN202211168342.5A
Authority: CN
Inventors: 戎士洋; 梁纪峰; 李晓军; 于腾凯; 王蕾报; 李安燚; 李铁成
Original assignee: State Grid Corp of China SGCC; Electric Power Research Institute of State Grid Hebei Electric Power Co Ltd; State Grid Hebei Energy Technology Service Co Ltd
Current assignee: State Grid Corp of China SGCC; Electric Power Research Institute of State Grid Hebei Electric Power Co Ltd; State Grid Hebei Energy Technology Service Co Ltd
Priority date: 2022-09-23
Filing date: 2022-09-23
Publication date: 2022-12-06

Abstract

The embodiment of the disclosure provides a method, a system and a device for actively defending cascading failures of a power system, and relates to the field of safe operation of the power system. The method comprises the following steps: respectively calculating the fault rate of each line under the extreme meteorological condition, and generating an initial planned disconnection line set according to the lines with the fault rates higher than a preset threshold value; and carrying out load flow and stability calculation on the initial planned disconnection line set based on a power grid load loss minimum principle, and determining a planned disconnection line set and a disconnection sequence of each line in the planned disconnection line set. In this way, the fault-free disconnection of partial lines can be actively carried out in sequence according to the optimal sequence, a power grid capable of running safely and stably is formed in advance, complex accident chain search and emergency blocking control are not needed, the off-grid probability of the generator, particularly a new energy source, after being impacted by faults is remarkably reduced, and the power load loss and equipment damage are reduced to the maximum extent on the premise of guaranteeing the safe running of a power system.

Description

Active defense method, device and system for cascading failures of power system

Technical Field

The disclosure relates to the field of operation safety of power systems, in particular to the technical field of active defense of cascading failures of power systems.

Background

Extreme meteorology such as typhoon, snow storm, lightning stroke and the like are main reasons causing cascading failures of a power grid, and have a huge damage effect on power grid equipment. Challenges facing these cascading failure blocking approaches include: 1) The initial fault selection has less influence on extreme weather, so that the accident chain identification is inaccurate, and the selection of the breaking point and the selection of the control quantity are wrong; 2) Due to the rapidity and the weak immunity of the dynamic response of the new energy, the accident chain has the characteristics of short evolution time, less related links and high occurrence probability, so that the time for blocking control is greatly shortened, and even the system accidents are diffused in a large range before being implemented. Therefore, a safe and stable active defense method for cascading failure is urgently needed.

Disclosure of Invention

The disclosure provides a method, a device and a system for actively defending cascading failures of a power system.

According to a first aspect of the present disclosure, there is provided a power system cascading failure active defense method, including:

respectively calculating the fault rate of each line under the extreme meteorological condition, and generating an initial plan disconnection line set according to the lines of which the fault rates are higher than a preset threshold value;

and carrying out load flow and stability calculation on the initial planned disconnected line set based on a power grid load loss minimum principle, and determining a planned disconnected line set and a disconnection sequence of each line in the planned disconnected line set.

The above aspect and any possible implementation further provides an implementation, where the separately calculating the failure rate of each line under the extreme meteorological condition includes:

acquiring historical extreme weather grade, duration, line position information and line average fault rate in a specified time period of a target area, and counting to obtain total line fault times and fault times of each line under extreme weather conditions;

multiplying the reciprocal of the product of the total number of the faults of the line and the duration time with the number of the faults of each line, the duration of the specified time period and the average fault rate of the line in sequence to obtain the historical fault rate of each line under different meteorological grades and different duration times;

respectively determining linear coefficients of the historical fault rate and the historical extreme meteorological grade of each line and the historical fault rate and the duration of each line, and determining a quantitative linear relation between the historical fault rate and the historical extreme meteorological grade and the duration of each line according to the linear coefficients;

and acquiring the extreme weather forecast grade and the forecast duration, and calculating the fault rate of each line of the power grid under the conditions of the extreme weather forecast grade and the forecast duration according to the quantitative linear relation.

As to the above-mentioned aspect and any possible implementation manner, there is further provided an implementation manner, in which the method for calculating the preset threshold includes:

acquiring the upper limit of the tolerance capacity of the line equipment under the corresponding extreme meteorological condition, the line load rate and the line fault short-time recovery rate after the equipment is actually configured with the action of a protection control system;

and multiplying the reciprocal of the tolerance upper limit and the line load rate difference by the line fault short-time recovery rate to obtain a preset threshold of the line fault rate.

The foregoing aspect and any possible implementation manner further provide an implementation manner, where the performing load flow and stability calculation on the initial planned broken line set based on the minimum grid load loss principle, and determining a planned broken line set and a broken order of each line in the planned broken line set includes:

acquiring power grid line parameter information;

respectively disconnecting each line in the initial planned disconnection line set in the power grid digital twin model, and respectively performing analog calculation on the power grid load flow after each line is disconnected;

and determining a planned disconnection line set and a disconnection sequence of each line in the planned disconnection line set according to the result of the simulation calculation.

The foregoing aspect and any possible implementation manner further provide an implementation manner, where the determining, according to the result of the simulation calculation, a planned disconnection line set and a disconnection order of each line in the planned disconnection line set includes:

step (1): determining i lines with current not overloaded in the initial planned disconnection line set as a planned disconnection line set according to a result obtained by simulation calculation, wherein i is equal to the number of lines in the planned disconnection line set, and i = i-1;

step (2): respectively acquiring transient voltage and frequency of the i lines which are not overloaded from a normal state to disconnection;

and (3): selecting the line with the minimum transient voltage and frequency change amplitude as an a-th disconnection circuit, and deleting the line from the planned disconnection line set, wherein the initial value of a is 1,a = a +1;

and (4) circularly executing the steps (1) (2) (3) until i =0.

The above-described aspects and any possible implementations further provide an implementation, and the method further includes:

and according to the result of the simulation calculation, if the current of each line in the initial planned disconnection line set is overloaded, adjusting the load and the output of the generator according to the overload degree of the line, and acquiring the adjusted power grid line parameter information again so as to perform the simulation calculation again according to the adjusted power grid line parameter information.

and when extreme weather occurs, sequentially disconnecting all the lines in the planned disconnection line set according to the line disconnection sequence to form a defense power grid line.

performing N-1 load flow calculation and N-2 stability calculation on the defense power grid line;

if the defense power grid line still has line overload and/or loses stability, continuing to adjust and reduce the load;

and if the defense power grid line is not overloaded and keeps stable, taking the defense power grid line as the final power grid form in the extreme weather.

According to a second aspect of the present disclosure, a power system cascading failure active defense device is provided. The device comprises:

the calculation module is used for calculating the fault rate of each line under extreme meteorological conditions respectively and generating a planned disconnection line set according to the line with the fault rate higher than a preset threshold value;

and the determining module is used for determining the disconnection sequence of each line in the planned disconnection line set based on the power grid load loss minimum principle.

According to a third aspect of the present disclosure, there is provided a power system cascading failure active defense system, the system comprising:

a meteorological unit: sending extreme weather forecast information to the user unit, and sending the extreme weather forecast information and historical extreme weather information to the power grid unit;

a power grid unit: the active defense method is used for realizing the active defense method for cascading failures of the power system in the first aspect of the disclosure, and sending power failure information to the user unit;

a subscriber unit: and performing load control and power grid feedback according to the extreme weather forecast information and the power failure information.

It should be understood that the statements herein reciting aspects are not intended to limit the critical or essential features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become apparent from the following description.

Drawings

The above and other features, advantages and aspects of various embodiments of the present disclosure will become more apparent by referring to the following detailed description when taken in conjunction with the accompanying drawings. The accompanying drawings are included to provide a further understanding of the present disclosure, and are not intended to limit the disclosure thereto, and the same or similar reference numerals will be used to indicate the same or similar elements, where:

FIG. 1 is a schematic diagram of the interaction between a meteorological department, a power grid enterprise, and a power consumer provided by an embodiment of the present disclosure;

fig. 2 is a flowchart of an active defense method for cascading failures of a power system according to an embodiment of the present disclosure;

FIG. 3 is a flow chart for calculating the fault rate of each line of the power grid under extreme weather conditions provided by the embodiment of the present disclosure;

FIG. 4 is a flow chart provided by an embodiment of the present disclosure for determining a sequence of disconnections for planned disconnections of lines in a set of lines;

FIG. 5 is a system block diagram of a regional power system provided by an embodiment of the present disclosure;

FIG. 6 is a final grid state diagram formed under extreme weather conditions as provided by embodiments of the present disclosure;

fig. 7 is a block diagram of an active defense apparatus for cascading failures in a power system according to an embodiment of the present disclosure;

fig. 8 is a block diagram of an exemplary electronic device provided by an embodiment of the present disclosure.

Detailed Description

To make the objects, technical solutions and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be described clearly and completely with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are some, but not all embodiments of the present disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

In addition, the term "and/or" herein is only one kind of association relationship describing an associated object, and means that there may be three kinds of relationships, for example, a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

The invention provides an active defense method for cascading failures of a power system, which comprises the following steps: respectively calculating the fault rate of each line under the extreme meteorological condition, and generating an initial plan disconnection line set according to the lines of which the fault rates are higher than a preset threshold value; and carrying out load flow and stability calculation on the initial planned disconnection line set based on a power grid load loss minimum principle, and determining a planned disconnection line set and a disconnection sequence of each line in the planned disconnection line set. In this way, when extreme weather occurs, partial lines can be actively and sequentially disconnected without faults according to the optimal sequence, an N-k power grid capable of safely and stably running is formed in advance (the total equipment number of the power grid is N, and planned disconnection of the lines is k), the time for disconnecting the lines is sufficient, and the problems that an accident chain is not matched with the reality and the time for blocking and controlling in an accident is insufficient are solved.

Fig. 1 shows a schematic diagram of the interaction between a meteorological department, a grid enterprise and a power consumer in which embodiments of the present disclosure can be implemented, as shown in fig. 1,

the meteorological department 102 sends future weather forecast data to the grid enterprise 104 and the power consumers 106, and also sends historical weather data (extreme weather type, weather level, duration) to the grid enterprise 104; the power grid enterprise 104 determines the sequence of the disconnected lines and the load to be controlled by each disconnected line according to the received future weather forecast information and historical weather data, and sends the load to the power consumer 106; the power consumer 106 receives the weather forecast and the power failure information issued by the power grid enterprise, and a power failure plan is made in advance. It should be noted that the interaction between the three is not static, the weather department 102 will update the future weather forecast information in a rolling manner, the power grid enterprise 104 also needs to update the disconnected line and the pre-controlled load in time according to the real-time weather forecast, and the close cooperation of the power consumers 106 is also needed in the disconnection operation process, which is an alternate process of load control-disconnection-load control-disconnection.

Fig. 2 illustrates a flow chart of a power system cascading failure active defense method 200 in which embodiments of the present disclosure can be implemented, as shown in fig. 2,

and S210, respectively calculating the fault rate of each line under the extreme meteorological condition, and generating an initial planned disconnected line set according to the lines of which the fault rates are higher than a preset threshold value.

In some embodiments, extreme weather conditions refer to infrequent weather events over a period of time in a region, such as typhoons, snowstorms, lightning strikes, and the like.

In some embodiments, the method for determining the fault probability of each line of the power grid under the impending extreme meteorological event can determine the fault probability of each line of the power grid under the impending extreme meteorological event through statistical data of extreme meteorological grade, duration, line fault and location information in the ground, as shown in fig. 3, and specifically includes the following steps:

step (1): counting the weather level D of extreme weather events occurring within a period of time T in the research area _k Duration T _k According to the positioning information of the power grid equipment, the average fault rate lambda of the regional line in the time T is counted ₀ The total failure times C isFailure times C of each line under extreme meteorological conditions _k 。

Step (2): according to the data provided in the step 1, calculating the historical fault rate lambda of each line under the conditions of different meteorological grades and different duration _k The derivation is as follows:

therefore, the first and second electrodes are formed on the substrate,

and (3): determining historical fault rate and meteorological grade D of each line _k Duration T _k The expression is as follows:

λ _k ＝αD _k +βT _k (2)

by means of steps (1), (2), statistically derived lambda can be used _k ，D _k ，T _k The result is a back-calculation of the values of the coefficients alpha and beta.

According to the reversely deduced alpha and beta values, the failure rate lambda of each line under the impending extreme weather can be determined _k0 And forecast weather level D _k0 And forecast duration T _k0 Binary function expression in between:

λ _k0 ＝αD _k0 +βT _k0 (3)

and (4): extreme weather forecast grade D updated according to weather department _k0 And forecast duration T _k0 And calculating the fault rate of each line of the power grid under the impending extreme meteorological event by using a formula (3).

In some embodiments, the failure rates of the lines may be ranked from high to low, and the line with the failure rate greater than the preset threshold is taken as the initial planned disconnection line and recorded as the set L.

In some embodiments, the upper limit of the tolerance capability of the line equipment under the extreme meteorological conditions, the line load rate, and the line fault short-time recovery rate after the equipment is actually configured with the protection control system to act may be obtained, and the inverse of the difference between the upper limit of the tolerance capability and the line load rate is multiplied by the line fault short-time recovery rate to be used as the preset threshold of the line fault rate.

And S220, carrying out load flow and stability calculation on the initial planned disconnection line set based on the power grid load loss minimum principle, and determining a planned disconnection line set and a disconnection sequence of each line in the planned disconnection line set.

In some embodiments, the disconnection sequence of each line in the planned disconnection line set is used as an optimal sequence, and when extreme weather occurs, the planned disconnection line set can be actively disconnected without fault in sequence according to the optimal sequence, so that an N-k power grid capable of safe and stable operation is formed in advance (the total equipment number of the power grid is N, and the planned disconnection line is k).

In some embodiments, the determining of the disconnection order of each line in the planned disconnection line set is shown in fig. 4, and specifically includes the following steps:

and (5): the method can obtain the power grid line parameter information from the background of the power dispatching department, and comprises the following steps: reading a grid structure, a predicted load, electric parameter information of a generator, a line and a transformer before a power grid line is disconnected, and the like, and building calculation data;

and (6): respectively disconnecting each line in the initial planned disconnection line set L in the power grid digital twin model, and performing analog power flow calculation by adopting a Newton-Raphson method in combination with the calculation data in the step 5;

and (7): checking the result of the simulation calculation, counting the lines of which the current of the power grid equipment does not exceed the current-carrying limit of the lines after the lines are respectively disconnected, taking the lines without overload as a planned disconnection line set, calculating the transient voltage and frequency changes of the lines in the transition from a normal state to disconnection one by one, selecting the line with the minimum amplitude change as a first disconnection line, marking as a line i, and deleting the line i from the planned disconnection line set; and (4) if the line overload condition occurs after each line in the set L is disconnected, adjusting and reducing the load and the generator according to the line overload degree, reacquiring the parameter information of the power grid line, forming new calculation data, and repeating the step (6).

And (8): and recording the load loss caused by disconnecting the line i, wherein the load loss comprises two parts, namely an isolated node load formed after the line is disconnected, and the load loss caused by the disconnection of the generator in the transition process.

And (9): and adjusting the power grid calculation data after the line i is disconnected according to the load loss and the off-line condition of the generator, repeating the steps 6-8, sequentially obtaining a second disconnected line, a third disconnected line, … and an Nth disconnected line (the number of the lines in the planned disconnected line set), and correspondingly and actively reducing the load.

And (4) taking the first disconnected line, the second disconnected line, the third disconnected line, the … and the Nth disconnected line determined in the steps (6) to (9) as the disconnection sequence of each line in the planned disconnected line set.

In some embodiments, when extreme weather occurs, each line in the planned disconnection line set can be disconnected in sequence according to the line disconnection sequence to form a defensive power grid line.

In some embodiments, N-1 load flow calculation and N-2 stability calculation may be performed on the defense power grid line, where the N-1 load flow calculation means that any element (such as a line, a generator, a transformer, a dc monopole, etc.) in the power system in the normal operation mode is not faulty or disconnected due to a fault, the power system should maintain stable operation and normal power supply, and other elements are not overloaded, and the voltage and the frequency are within an allowable range; the N-2 stable calculation means that after any two independent elements (a generator, a transmission line, a transformer and the like) in N elements of the power system are cut off due to faults, no power failure of a user due to overload tripping of other lines is caused, the stability of the system is not damaged, and accidents such as voltage breakdown and the like do not occur.

In some embodiments, if N-1 has equipment overload or N-2 loses stability under fault, load reduction still needs to be adjusted or a line needs to be actively disconnected, and after no problem exists through power flow stability calculation and verification, the defensive power grid line is used as a final power grid form in extreme weather.

According to the embodiment of the disclosure, the following technical effects are achieved:

(1) The active disconnection before the chain accident happens does not need to carry out complex chain identification and analysis of the chain accident, the disconnection time is sufficient, and the problems that the chain accident is not matched with the actual chain accident and the blocking control time in the accident is not enough do not exist.

(2) The line is slowly disconnected without faults in sequence, so that the adverse effect of protection refusal or misoperation is avoided, voltage and frequency disturbance can be almost ignored relative to the simultaneous disconnection of line faults, the probability of the generator, particularly the new energy source, being disconnected is obviously reduced, compared with the power grid passively formed by short-time large disturbance impact, the load and equipment loss are greatly reduced, and the method has higher engineering application value.

According to a third embodiment of the present disclosure, the present disclosure is further described in detail, specifically, a regional power system is taken as a research object, and the system structure thereof is shown in fig. 5.

As shown in fig. 5, "fire", "wind" and "light" refer to thermal power generation, wind power generation and light power generation, the load in the network is 2000MW, and the storm weather records in the area are large historically.

According to the storm weather grade and duration provided by the weather department, the fault rate of part of lines obtained by the power grid enterprise under the weather condition of one lightning stroke in 7 months is shown in the following table:

the power grid enterprise considers that the cost of 220kV lines is high, the maintenance work amount is large, the time is long, important power users are few, and the personal safety during and after disasters is considered, and the threshold value is set to be 0.45.

The broken line is thus determined to be: 6-22, 15-17 and 11-17.

Determining the sequence after calculating the load flow and the transient stability: 11-17, 15-17 and 6-22, and the matched pre-control loads are respectively as follows: 0MW,140MW.

The failure rate of the lines 11-18 is lower than 0.45, after the lines with high failure rate are disconnected, the lines 11-18 do not meet the N-1 safety requirement, the lines 11-18 are in contact with the power grids in the two regions, if the lines are not disconnected, the reduced load of the sending end is too large, the direct disconnection load loss is small, the operation requirement is met, the two are optimal, the lines 11-18 are actively disconnected, the load is limited by 320WM, and the finally formed power grid structure and state are shown in fig. 6.

(1) The line is actively broken before the chain accident happens, complex chain identification and analysis of the chain are not needed, the time for breaking the line is sufficient, and the problems that the chain is not matched with the reality and the blocking control time in the accident is not enough do not exist.

It is noted that while for simplicity of explanation, the foregoing method embodiments have been described as a series of acts or combination of acts, it will be appreciated by those skilled in the art that the present disclosure is not limited by the order of acts, as some steps may, in accordance with the present disclosure, occur in other orders and concurrently. Further, those skilled in the art should also appreciate that the embodiments described in the specification are exemplary embodiments and that acts and modules referred to are not necessarily required by the disclosure.

The above is a description of embodiments of the method, and the embodiments of the apparatus are further described below.

Fig. 7 illustrates a block diagram of a power system cascading failure active defense apparatus 700, according to an embodiment of the present disclosure. The apparatus 700 comprises:

the calculation module 710 is configured to calculate fault rates of the lines under extreme meteorological conditions, and generate an initial planned disconnection line set according to the line with the fault rate higher than a preset threshold;

and a determining module 720, configured to perform load flow and stability calculation on the initial planned disconnection line set based on a power grid load loss minimum principle, and determine a planned disconnection line set and a disconnection order of each line in the planned disconnection line set.

In some embodiments, the computing unit 710 is specifically configured to: acquiring historical extreme weather grade, duration, line position information and line average fault rate in a specified time period of a target area, and counting to obtain total line fault times and fault times of each line under extreme weather conditions;

and acquiring the extreme weather forecast grade and the forecast duration, and calculating the fault rate of each line of the power grid under the conditions of the extreme weather forecast grade and the forecast duration according to the quantitative linear relation. .

In some embodiments, the determining unit 720 is specifically configured to: acquiring power grid line parameter information; respectively disconnecting each line in the initial planned disconnection line set in the power grid digital twin model, and respectively carrying out analog calculation on the power grid load flow after each line is disconnected; and determining a planned disconnection line set and a disconnection sequence of each line in the planned disconnection line set according to the result of the simulation calculation.

It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process of the described module may refer to the corresponding process in the foregoing method embodiment, and is not described herein again.

In the technical scheme of the disclosure, the acquisition, storage, application and the like of the personal information of the related user all accord with the regulations of related laws and regulations, and do not violate the good customs of the public order.

The present disclosure also provides an electronic device, a readable storage medium, and a computer program product according to embodiments of the present disclosure.

FIG. 8 illustrates a schematic block diagram of an electronic device 800 that may be used to implement embodiments of the present disclosure. Electronic devices are intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions, are meant to be examples only, and are not meant to limit implementations of the disclosure described and/or claimed herein.

The device 800 comprises a computing unit 801 which may perform various suitable actions and processes in accordance with a computer program stored in a Read Only Memory (ROM) 802 or a computer program loaded from a storage unit 808 into a Random Access Memory (RAM) 803. In the RAM 803, various programs and data required for the operation of the device 800 can also be stored. The calculation unit 801, the ROM 802, and the RAM 803 are connected to each other by a bus 804. An input/output (I/O) interface 805 is also connected to bus 804.

A number of components in the device 800 are connected to the I/O interface 805, including: an input unit 806, such as a keyboard, a mouse, or the like; an output unit 807 such as various types of displays, speakers, and the like; a storage unit 808, such as a magnetic disk, optical disk, or the like; and a communication unit 809 such as a network card, modem, wireless communication transceiver, etc. The communication unit 809 allows the device 800 to exchange information/data with other devices via a computer network such as the internet and/or various telecommunication networks.

Computing unit 801 may be a variety of general and/or special purpose processing components with processing and computing capabilities. Some examples of the computing unit 801 include, but are not limited to, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), various dedicated Artificial Intelligence (AI) computing chips, various computing units running machine learning model algorithms, a Digital Signal Processor (DSP), and any suitable processor, controller, microcontroller, and the like. The computing unit 801 performs the various methods and processes described above, such as the method 200. For example, in some embodiments, the method 200 may be implemented as a computer software program tangibly embodied in a machine-readable medium, such as the storage unit 808. In some embodiments, part or all of a computer program may be loaded onto and/or installed onto device 800 via ROM 802 and/or communications unit 809. When loaded into RAM 803 and executed by computing unit 801, may perform one or more of the steps of method 200 described above. Alternatively, in other embodiments, the computing unit 801 may be configured to perform the method 200 in any other suitable manner (e.g., by way of firmware).

Various implementations of the systems and techniques described here above may be implemented in digital electronic circuitry, integrated circuitry, field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), application Specific Standard Products (ASSPs), system on a chip (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include: implemented in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, receiving data and instructions from, and transmitting data and instructions to, a storage system, at least one input device, and at least one output device.

Program code for implementing the methods of the present disclosure may be written in any combination of one or more programming languages. These program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, causes the functions/acts specified in the flowchart and/or block diagram to be performed. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this disclosure, a machine-readable medium may be a tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

To provide for interaction with a user, the systems and techniques described here can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to a user; and a keyboard and a pointing device (e.g., a mouse or a trackball) by which a user may provide input to the computer. Other kinds of devices may also be used to provide for interaction with a user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form, including acoustic, speech, or tactile input.

The systems and techniques described here can be implemented in a computing system that includes a back-end component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front-end component (e.g., a user computer having a graphical user interface or a web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: local Area Networks (LANs), wide Area Networks (WANs), and the Internet.

The computer system may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server may be a cloud server, a server of a distributed system, or a server with a combined blockchain.

It should be understood that various forms of the flows shown above, reordering, adding or deleting steps, may be used. For example, the steps described in the present disclosure may be executed in parallel, sequentially or in different orders, and are not limited herein as long as the desired results of the technical aspects of the present disclosure can be achieved.

The above detailed description should not be construed as limiting the scope of the disclosure. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made in accordance with design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. An active defense method for cascading failures of a power system is characterized by comprising the following steps:

respectively calculating the fault rate of each line under the extreme meteorological condition, and generating an initial planned disconnection line set according to the lines with the fault rates higher than a preset threshold value;

2. The method of claim 1, wherein said separately calculating the fault rate of each line under extreme meteorological conditions comprises:

multiplying the reciprocal of the product of the total number of faults of the line and the duration time with the number of faults of each line, the duration of the specified time period and the average fault rate of the line in sequence to obtain the historical fault rate of each line under different weather levels and different duration times;

3. The method according to claim 1, wherein the method for calculating the preset threshold value comprises:

acquiring the upper limit of the tolerance capacity of the line equipment under the corresponding extreme meteorological condition, the line load rate and the line fault short-time recovery rate after the equipment is actually configured with a protection control system to act;

and multiplying the reciprocal of the difference value between the tolerance upper limit and the line load rate by the short-time recovery rate of the line fault to obtain a preset threshold value of the line fault rate.

4. The method according to claim 1, wherein the performing load flow and stability calculations on the initial planned broken line set based on the minimum grid load loss principle to determine a planned broken line set and a broken sequence of each line in the planned broken line set comprises:

acquiring power grid line parameter information;

respectively disconnecting each line in the initial planned disconnection line set in the power grid digital twin model, and respectively carrying out analog calculation on the power grid load flow after each line is disconnected;

5. The method of claim 4, wherein determining a set of planned disconnection lines and a sequence of disconnections for each line in the set of planned disconnection lines based on the results of the simulation calculations comprises:

step (1): according to the result obtained by the simulation calculation, i lines with current not overloaded in the initial planned disconnection line set are determined as a planned disconnection line set, wherein i is equal to the number of lines in the planned disconnection line set, and i = i-1;

and (3) circularly executing the steps (1) (2) and (3) until i =0.

6. The method of claim 4, further comprising:

and according to the result of the simulation calculation, if the current of each line in the initial planned disconnection line set is overloaded, adjusting the load and the output of the generator according to the overload degree of the line, and acquiring the parameter information of the adjusted power grid line again so as to perform the simulation calculation again according to the parameter information of the adjusted power grid line.

7. The method of claim 4, further comprising:

8. The method of claim 7, further comprising:

9. An active defense device for cascading failures of a power system, comprising:

the calculation module is used for calculating the fault rate of each line under extreme meteorological conditions respectively and generating an initial planned disconnection line set according to the lines with the fault rates higher than a preset threshold value;

and the determining module is used for carrying out load flow and stability calculation on the initial planned disconnection line set based on the power grid load loss minimum principle, and determining the planned disconnection line set and the disconnection sequence of each line in the planned disconnection line set.

10. An active defense system against cascading failures of a power system, comprising:

a meteorological unit: transmitting extreme weather forecast information to a user unit, and transmitting extreme weather forecast information and historical extreme weather information to a power grid unit;

a power grid unit: for implementing the active defense method against cascading failures of a power system according to claims 1-8, and sending a power outage message to a user unit;

the user unit: and carrying out load control and power grid feedback according to the extreme weather forecast information and the power failure information.