CN114460414A - Method for verifying breaking capacity of breaker of power grid bus - Google Patents

Abstract

The invention provides a method for verifying the breaking capacity of a circuit breaker of a power grid bus, comprising the following steps: calculating the basic short-circuit current of a faulty bus of a power grid excluding new energy power stations and flexible DC; calculating the decay time of the DC component of the short-circuit current of the faulty bus and calculate the AC short-circuit breaking capacity of the circuit breaker after considering the DC component according to the decay time constant of the DC component of the short-circuit current of the faulty busbar and the shortest breaking time of the circuit breaker of the faulty busbar; calculate the short-circuit current provided by the new energy power station in the power grid ; Calculate the short-circuit current provided by the flexible DC in the power grid; according to the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, the basic short-circuit current, the short-circuit current provided by the new energy power station in the power grid, and the short-circuit current provided by the flexible DC in the power grid Determine whether the breaking capacity of the circuit breaker meets the requirements. The present invention can more accurately judge whether the breaking capacity of the circuit breaker meets the requirements.

Description

The method of checking the breaking capacity of the circuit breaker of the power grid bus

technical field

The invention relates to the technical field of power grids, in particular to a method for verifying the breaking capacity of a circuit breaker of a power grid bus.

Background technique

my country will transform and upgrade to a new power system with new energy as the main body, and the short-circuit current control of the power grid will face greater challenges. After that, the short-circuit current will be provided to the power grid in the form of a current source; on the other hand, due to the unbalanced development of clean power resources and loads in my country, it is necessary to build a grid with a higher voltage level to meet the needs of inter-regional power exchange. With the continuous improvement of the voltage level, the reactance/resistance ratio of the power grid continues to increase, and the problem of the DC component of the short-circuit current will become increasingly prominent. In response to the above-mentioned new situation, the present invention proposes a method for verifying the breaking capacity of a circuit breaker considering new energy power stations, flexible DC grid connection and short-circuit current DC components.

Defects and deficiencies of the existing technology: At present, various types of wind power, photovoltaics or flexible DC transmission are mostly connected to the grid through full-power converters, and the short-circuit current characteristics provided to the grid are quite different from those of traditional rotary generators. At present, there are existing calculation methods for the short-circuit current provided by the new energy power station or the flexible DC transmission body, which generally requires detailed electromagnetic transient modeling. For the calculation of the DC component, the formula for calculating the aperiodic component Idc of the short-circuit current using the equivalent frequency method is given in "Calculation of Short-Circuit Current of Three-Phase AC System" (GB/T 15544.1-2013).

At present, the calculation methods of short-circuit current provided by new energy power plants or flexible DC transmission generally require detailed electromagnetic transient modeling, and only consider the short-circuit current injected by the body, which cannot be compared with the "Calculation of Short-Circuit Current in Three-phase AC System". 》(GB/T 15544.1-2013), the organic combination of the equivalent voltage source calculation method is not conducive to the rapid judgment of the boosting effect of the substation in the power system, and it is very cumbersome in planning, operation and engineering use. On the other hand, in general power grid planning and operation, only the calculation of the AC component of the short-circuit current is considered, and the national standard only gives the calculation method of the aperiodic component of the short-circuit current, but it also fails to consider the AC or the periodic component as a whole to guide the judgment of the circuit breaker. Whether the comprehensive breaking capacity meets the requirements.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned technical problems, the present invention provides a method for verifying the breaking capacity of a circuit breaker of a power grid bus, which comprehensively considers the influence of various factors on the short-circuit current under the new power system, and compares the short-circuit current provided by the new energy power station and the flexible direct current transmission. The current is superimposed on the AC short-circuit current of the traditional network, so that the obtained short-circuit current is more real and accurate, and the breaking capacity of the circuit breaker is attenuated by the attenuation time constant of the DC component of the short-circuit current of the faulty bus, so that the obtained circuit breaker The breaking capacity of the circuit breaker is more real and accurate, so that it can be more accurately judged whether the breaking capacity of the circuit breaker meets the requirements.

The technical scheme adopted in the present invention is as follows:

A method for verifying the breaking capacity of a circuit breaker of a power grid bus, comprising the steps of: calculating a basic short-circuit current of a faulty bus of a power grid that does not contain a new energy power station or a flexible DC; calculating a decay time constant of a DC component of the short-circuit current of the faulty bus , and calculate the AC short-circuit breaking capacity of the circuit breaker after considering the DC component according to the decay time constant of the short-circuit current DC component of the faulty busbar and the shortest breaking time of the circuit breaker of the faulty busbar; calculate the new energy power station in the power grid Provided short-circuit current; calculate the short-circuit current provided by the flexible DC in the power grid; according to the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, the basic short-circuit current, and the power provided by the new energy power station in the power grid The short-circuit current provided by the flexible DC in the power grid determines whether the breaking capacity of the circuit breaker meets the requirements.

Calculate the AC short-circuit breaking capacity of the circuit breaker after considering the DC component according to the following formula:

Wherein, S _fR is the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, S _fN is the rated breaking capacity of the circuit breaker, t _min is the shortest breaking time of the circuit breaker, T _dcf.R is the decay time constant of the DC component of the short-circuit current of the faulty bus, and T _dcf.N is the decay time constant of the rated DC component of the circuit breaker.

Calculating the short-circuit current provided by the new energy power station in the power grid, specifically includes: judging whether each new energy power station is connected to the main grid through boosting; if a new energy power station is connected to the main grid through boosting, then The preset injection current is used as the short-circuit current provided by the new energy power station; if a new energy power station is not connected to the main grid through boosting, calculate the maximum short-circuit current of the new energy power station at the moment when the circuit breaker operates, And calculate the impedance between the new energy power station and the short-circuit point and the system impedance of the short-circuit point, and according to the maximum short-circuit current of the new energy power station at the time of the circuit breaker action, the impedance and short-circuit between the new energy power station and the short-circuit point The point system impedance calculates the short-circuit current provided by the new energy power station; the short-circuit current provided by all the new energy power stations in the grid is accumulated.

If a new energy power station is connected to the main grid via boost, the short-circuit current provided by the new energy power station is:

Among them, I _REi represents the short-circuit current provided by the ith new energy power station, U _i is the busbar voltage value of the ith new energy power station, and I _Ni is the rated current of the ith new energy power station.

If a new energy power station is not connected to the main grid by boosting, the short-circuit current provided by the new energy power station is:

I _REi =I _REi,max ×X _sysi /(X _sysi +X _fi )

Among them, I _REi,max is the maximum short-circuit current of the i-th new energy power station at the moment when the circuit breaker operates, X _fi is the impedance between the i-th new energy power station and the short-circuit point, and X _sysi is the i-th new energy power station. The system impedance of the short-circuit point corresponding to the power station.

Calculating the short-circuit current provided by the flexible DC in the power grid specifically includes: calculating the maximum short-circuit current of each of the flexible DCs at the moment when the circuit breaker operates; judging whether each of the flexible DCs emits reactive power during a fault; If a certain flexible DC emits reactive power during the fault, the impedance between the flexible DC and the short-circuit point and the system impedance of the short-circuit point are calculated, and according to the maximum short-circuit current of the flexible DC at the moment of operation of the circuit breaker, the flexible DC The short-circuit current provided by the flexible DC is calculated based on the impedance between the short-circuit point and the short-circuit point system impedance; the short-circuit current provided by all the flexible DCs in the power grid is accumulated.

If a flexible DC generates reactive power during the fault, the short-circuit current provided by the flexible DC is:

I _VSCj =I _VSCj,max ×X _sysj /(X _sysj +X _fj )

Among them, I _VSCj represents the short-circuit current provided by the j-th flexible DC, X _fj is the impedance between the j-th flexible DC and the short-circuit point, and X _sysj is the system impedance of the short-circuit point corresponding to the j-th flexible DC.

The circuit breaker is judged according to the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, the basic short-circuit current, the short-circuit current provided by the new energy power station in the power grid, and the short-circuit current provided by the flexible DC in the power grid Whether the breaking capacity of the circuit breaker meets the requirements specifically includes: judging whether there is S _Rf > I _f0 +∑I _REi +∑I _VSCj , where I _f0 is the basic short-circuit current, and ∑I _REi is all the new The accumulated value of the short-circuit current provided by the energy power station, ∑I _VSCj is the accumulated value of the short-circuit current provided by all the flexible DCs in the power grid; if so, the breaking capacity of the circuit breaker meets the requirements, otherwise the circuit breaker The breaking capacity of the device does not meet the requirements.

Beneficial effects of the present invention:

The invention calculates the attenuation time constant of the short-circuit current DC component of the faulty bus, and calculates the AC short-circuit breaking capacity of the circuit breaker after considering the DC component based on this calculation, and calculates the short-circuit current provided by the new energy power station in the power grid and the flexible DC provided by the flexible DC. short-circuit current, and based on this, the basic short-circuit current, and the AC short-circuit breaking capacity of the circuit breaker after considering the DC component to judge whether the breaking capacity of the circuit breaker of the faulty busbar meets the requirements. Therefore, various factors under the new power system are comprehensively considered. Influence on the short-circuit current, the short-circuit current provided by the new energy power station and the flexible DC transmission is superimposed on the AC short-circuit current of the traditional network, so that the obtained short-circuit current is more realistic and accurate, and the DC component of the short-circuit current of the fault bus is used to decay the time constant. To attenuate the breaking capacity of the circuit breaker, so that the obtained breaking capacity of the circuit breaker is more real and accurate, so that it can be more accurately judged whether the breaking capacity of the circuit breaker meets the requirements.

Description of drawings

1 is a flowchart of a method for verifying the breaking capacity of a circuit breaker of a power grid bus according to an embodiment of the present invention;

2 is a flowchart of a method for verifying the breaking capacity of a circuit breaker of a power grid bus according to a specific embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a power grid according to a specific embodiment of the present invention.

Detailed ways

The technical solutions in 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. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in FIG. 1 , the method for verifying the breaking capacity of a circuit breaker of a power grid bus according to an embodiment of the present invention includes the following steps:

S1, calculate the basic short-circuit current of the faulty busbar of the power grid excluding the new energy power station and the flexible DC power grid.

In the embodiment of the present invention, the new energy power station may be a wind power station or a photovoltaic power station or the like. When a certain busbar of the power grid fails, the basic short-circuit current I _f0 of the faulty busbar f can be calculated first, excluding the new energy power station and the flexible DC switching station.

S2: Calculate the attenuation time constant of the DC component of the short-circuit current of the faulty bus, and calculate the AC short-circuit breaking capacity of the circuit breaker after considering the DC component according to the attenuation time constant of the DC component of the short-circuit current of the faulted bus and the shortest breaking time of the circuit breaker of the faulted bus .

In an embodiment of the present invention, the AC short-circuit breaking capacity of the circuit breaker after considering the DC component can be calculated according to the following formula:

Among them, S _fR is the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, S _fN is the rated breaking capacity of the circuit breaker, t _min is the shortest breaking time of the circuit breaker, and T _dcf.R is the short-circuit current of the faulty busbar DC component decay time constant, T _dcf.N is the rated DC component decay time constant of the circuit breaker.

S3, calculate the short-circuit current provided by the new energy power station in the power grid.

Specifically, firstly, it can be determined whether each new energy power station is connected to the main grid by boosting, for example, whether it is connected to the grid through a 220kV (330kV) photovoltaic power collection system boosted to a voltage level of 500kV (750kV).

If a certain new energy power station is connected to the main grid through boosting, the preset injection current is used as the short-circuit current provided by the new energy power station. In an embodiment of the present invention, the preset injection current, that is, the short-circuit current provided by the new energy power station connected to the main grid via boosting is:

Among them, I _REi represents the short-circuit current provided by the ith new energy power station, U _i is the busbar voltage value of the ith new energy power station, and I _Ni is the rated current of the ith new energy power station.

If a new energy power station is not connected to the main grid through boosting, calculate the maximum short-circuit current of the new energy power station at the moment when the circuit breaker operates, and calculate the impedance between the new energy power station and the short-circuit point and the system impedance of the short-circuit point. And calculate the short-circuit current provided by the new-energy power station according to the maximum short-circuit current of the new-energy power station when the circuit breaker operates, the impedance between the new-energy power station and the short-circuit point, and the system impedance at the short-circuit point. In an embodiment of the present invention, the maximum short-circuit current of the new energy power station at the time of the circuit breaker action is generally the maximum working current of the new energy power station in normal operation at rated full power multiplied by an overload factor of 1.1 to 1.2 times. The short-circuit current provided by the new energy power station that is not connected to the main grid by boosting is:

I _REi =I _REi,max ×X _sysi /(X _sysi +X _fi )

Among them, I _REi,max is the maximum short-circuit current of the ith new energy power station at the moment when the circuit breaker operates, X _fi is the impedance between the ith new energy power station and the short-circuit point, and X _sysi is the corresponding value of the ith new energy power station. The short-circuit point system impedance.

Finally, the short-circuit currents provided by all the new energy power stations in the power grid are accumulated to obtain the short-circuit current ∑I _REi provided by the new energy power stations in the power grid.

S4, calculate the short-circuit current provided by the flexible DC in the power grid.

Specifically, the maximum short-circuit current of each flexible DC when the circuit breaker is actuated can be calculated. In an embodiment of the present invention, the maximum short-circuit current of the flexible DC at the moment when the circuit breaker is actuated is generally the maximum rated full power of the flexible DC during normal operation. The working current is multiplied by 1.1 to 1.2 times the overload factor.

Then, it is judged whether each flexible DC emits reactive power during the fault. If a flexible DC does not generate reactive power during the fault, the increase of the flexible DC to the short-circuit current of the system does not need to be considered. If a certain flexible DC emits reactive power during the fault, the impedance between the flexible DC and the short-circuit point and the system impedance of the short-circuit point are calculated, and according to the maximum short-circuit current of the flexible DC at the moment of circuit breaker operation, the flexible DC and the short-circuit The impedance between the points and the system impedance at the short-circuit point calculate the short-circuit current provided by this flexible DC. The short-circuit current provided by the flexible DC emitting reactive power during the fault is:

I _VSCj =I _VSCj,max ×X _sysj /(X _sysj +X _fj )

Among them, I _VSCj represents the short-circuit current provided by the j-th flexible DC, X _fj is the impedance between the j-th flexible DC and the short-circuit point, and X _sysj is the system impedance of the short-circuit point corresponding to the j-th flexible DC.

Finally, the short-circuit currents provided by all the flexible DCs in the power grid are accumulated to obtain the short-circuit current ΣI _VSCj provided by the flexible DCs in the power grid.

S5, according to the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, the basic short-circuit current, the short-circuit current provided by the new energy power station in the power grid, and the short-circuit current provided by the flexible DC in the power grid. Determine whether the breaking capacity of the circuit breaker meets the requirements .

It should be understood that the short-circuit current provided by the new energy power station and the short-circuit current provided by the flexible DC are both superimposed with the basic short-circuit current to constitute the total short-circuit current. Therefore, it can be judged whether the breaking capacity of the circuit breaker meets the requirements by comparing the AC short-circuit breaking capacity of the circuit breaker after considering the DC component with the total short-circuit current.

Specifically, it can be determined whether there is S _Rf >I _f0 +∑I _REi +∑I _VSCj , where I _f0 is the basic short-circuit current, ∑I _REi is the accumulated value of the short-circuit current provided by all new energy power stations in the power grid, ∑ I _VSCj is the cumulative value of the short-circuit current provided by all flexible DCs in the power grid; if it is, the breaking capacity of the circuit breaker meets the requirements, otherwise the breaking capacity of the circuit breaker does not meet the requirements.

In an embodiment of the present invention, a specific flow of a method for verifying the breaking capacity of a circuit breaker of a power grid bus is shown in FIG. 2 .

According to the method for verifying the breaking capacity of the circuit breaker of the grid bus in the embodiment of the present invention, by calculating the attenuation time constant of the DC component of the short-circuit current of the faulty bus, and calculating the AC short-circuit breaking capacity of the circuit breaker after considering the DC component based on this, and calculating The short-circuit current provided by the new energy power station in the power grid and the short-circuit current provided by the flexible DC, and based on this, the basic short-circuit current, and the AC short-circuit breaking capacity of the circuit breaker after considering the DC component to judge the breaking capacity of the circuit breaker of the faulty bus Whether the requirements are met, therefore, the influence of various factors on the short-circuit current under the new power system is comprehensively considered, and the short-circuit current provided by the new energy power station and the flexible DC transmission is superimposed on the AC short-circuit current of the traditional network, so that the obtained short-circuit current The current is more real and accurate, and the breaking capacity of the circuit breaker is attenuated by the decay time constant of the DC component of the short-circuit current of the faulty bus, so that the obtained breaking capacity of the circuit breaker is more real and accurate, so that the circuit breaker can be judged more accurately. Whether the breaking capacity meets the requirements.

In a specific embodiment of the present invention, taking the local power grid (voltage level of 750kV/330kV) in a certain area shown in FIG. 3 as an example, the basic three-phase short-circuit current I _f0 =55.0kA excluding new energy power stations and flexible DC , the fault bus is the 330kV bus of 750kV substation S1. Calculate the decay time constant T _dcf.R =151.7ms of the DC component of the short-circuit current of the faulty bus. The shortest breaking time of the circuit breaker t _min = 40ms, the rated DC component attenuation time constant of the circuit breaker T _dcf.N = 45ms, the rated breaking capacity S _fN of the circuit breaker of the fault bus f is 63kA, and the circuit breaker after considering the DC component is calculated. The AC short-circuit breaking capacity S _fR = 49.4kA.

There is a new energy power station in this area connected to substation S1-5 through a 110kV voltage level, and the short-circuit current provided by the new energy power station is calculated as ∑I _REi =I _REi =0.2kA. There is one flexible DC converter station connected to the 330kV side of substation S1 in this area. Considering the reactive power generated during the fault, the short-circuit current provided by the flexible DC is calculated ∑I _VSCj =I _VSCj =3.2kA. Finally compare S _Rf =49.4kA and I _f0 +∑ I _REi +∑I _VSCj =58.4kA, if the latter is larger, the breaking capacity of the circuit breaker of the fault bus does not meet the requirements.

In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other.

Any description of a process or method in the flowcharts or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing a specified logical function or step of the process , and the scope of the preferred embodiments of the invention includes alternative implementations in which the functions may be performed out of the order shown or discussed, including performing the functions substantially concurrently or in the reverse order depending upon the functions involved, which should It is understood by those skilled in the art to which the embodiments of the present invention belong.

The logic and/or steps represented in flowcharts or otherwise described herein, for example, may be considered an ordered listing of executable instructions for implementing the logical functions, may be embodied in any computer-readable medium, For use with, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other system that can fetch instructions from and execute instructions from an instruction execution system, apparatus, or apparatus) or equipment. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport the program for use by or in connection with an instruction execution system, apparatus, or apparatus. More specific examples (non-exhaustive list) of computer readable media include the following: electrical connections with one or more wiring (electronic devices), portable computer disk cartridges (magnetic devices), random access memory (RAM), Read Only Memory (ROM), Erasable Editable Read Only Memory (EPROM or Flash Memory), Fiber Optic Devices, and Portable Compact Disc Read Only Memory (CDROM). In addition, the computer readable medium may even be paper or other suitable medium on which the program may be printed, as the paper or other medium may be optically scanned, for example, followed by editing, interpretation, or other suitable medium as necessary process to obtain the program electronically and then store it in computer memory.

It should be understood that various parts of the present invention may be implemented in hardware, software, firmware or a combination thereof. In the above-described embodiments, various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or a combination of the following techniques known in the art: Discrete logic circuits, application specific integrated circuits with suitable combinational logic gates, Programmable Gate Arrays (PGA), Field Programmable Gate Arrays (FPGA), etc.

Those skilled in the art can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, and the program can be stored in a computer-readable storage medium. When executed, one or a combination of the steps of the method embodiment is included.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (8)

1. A method for verifying the breaking capacity of a circuit breaker of a power grid bus, comprising the following steps: Calculate the basic short-circuit current of the faulty busbar of the power grid excluding new energy power stations and flexible DC; Calculate the attenuation time constant of the short-circuit current DC component of the faulty bus, and calculate the AC circuit breaker after considering the DC component according to the attenuation time constant of the short-circuit current DC component of the faulty bus and the shortest breaking time of the circuit breaker of the faulty bus Short circuit breaking capacity; calculating the short-circuit current provided by the new energy power station in the power grid; calculating the short-circuit current provided by the flexible DC in the power grid; The circuit breaker is judged according to the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, the basic short-circuit current, the short-circuit current provided by the new energy power station in the power grid, and the short-circuit current provided by the flexible DC in the power grid Whether the breaking capacity of the device meets the requirements. 2. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 1, wherein the AC short-circuit breaking capacity of the circuit breaker after considering the DC component is calculated according to the following formula:

Wherein, S _fR is the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, S _fN is the rated breaking capacity of the circuit breaker, t _min is the shortest breaking time of the circuit breaker, T _dcf.R is the decay time constant of the DC component of the short-circuit current of the faulty bus, and T _dcf.N is the decay time constant of the rated DC component of the circuit breaker. 3. The method for verifying the breaking capacity of a circuit breaker of a power grid busbar according to claim 2, wherein calculating the short-circuit current provided by a new energy power station in the power grid specifically includes: Judging whether each of the new energy power stations is connected to the main grid through boosting; If a new energy power station is connected to the main grid via boosting, the preset injection current is used as the short-circuit current provided by the new energy power station; If a new energy power station is not connected to the main grid through boosting, calculate the maximum short-circuit current of the new energy power station at the moment when the circuit breaker operates, and calculate the impedance between the new energy power station and the short-circuit point and the short-circuit point system impedance, and calculate the short-circuit current provided by the new-energy power station according to the maximum short-circuit current of the new-energy power station at the moment when the circuit breaker operates, the impedance between the new-energy power station and the short-circuit point, and the system impedance at the short-circuit point; Accumulate the short-circuit currents provided by all new energy power stations in the power grid. 4. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 3, wherein if a certain new energy power station is connected to the main power grid via a boost, the short-circuit current provided by the new energy power station for:

Among them, I _REi represents the short-circuit current provided by the ith new energy power station, U _i is the busbar voltage value of the ith new energy power station, and I _Ni is the rated current of the ith new energy power station. 5. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 4, wherein if a certain new energy power station is not connected to the main power grid via a boost, the short-circuit current provided by the new energy power station for: I _REi =I _REi,max ×X _sysi /(X _sysi +X _fi ) Among them, I _REi,max is the maximum short-circuit current of the i-th new energy power station at the moment when the circuit breaker operates, X _fi is the impedance between the i-th new energy power station and the short-circuit point, and X _sysi is the i-th new energy power station. The system impedance of the short-circuit point corresponding to the power station. 6. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 5, wherein calculating the short-circuit current provided by the flexible DC in the power grid specifically includes: calculating the maximum short-circuit current of each flexible DC at the moment when the circuit breaker operates; judging whether each of the flexible DCs emits reactive power during the fault; If a certain flexible DC emits reactive power during the fault, the impedance between the flexible DC and the short-circuit point and the system impedance of the short-circuit point are calculated, and according to the maximum short-circuit current of the flexible DC at the moment of operation of the circuit breaker, the flexible DC Calculate the short-circuit current provided by the flexible DC with the impedance between the short-circuit point and the short-circuit point system impedance; Accumulate the short-circuit currents provided by all flexible DCs in the power grid. 7. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 6, wherein, if a certain flexible DC emits reactive power during a fault, the short-circuit current provided by the flexible DC is: I _VSCj =I _VSCj,max ×X _sysj /(X _sysj +X _fj ) Among them, I _VSCj represents the short-circuit current provided by the j-th flexible DC, X _fj is the impedance between the j-th flexible DC and the short-circuit point, and X _sysj is the system impedance of the short-circuit point corresponding to the j-th flexible DC. 8 . The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 7 , wherein, according to the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, the basic short-circuit current, the power grid The short-circuit current provided by the China New Energy Power Station and the short-circuit current provided by the flexible DC in the power grid determines whether the breaking capacity of the circuit breaker meets the requirements, specifically including: Determine whether there is S _Rf >I _f0 +∑I _REi +∑I _VSCj , where I _f0 is the basic short-circuit current, ∑I _REi is the accumulated value of the short-circuit current provided by all new energy power stations in the power grid, ∑ I _VSCj is the accumulated value of short-circuit currents provided by all flexible DCs in the power grid; If yes, the breaking capacity of the circuit breaker meets the requirements, otherwise the breaking capacity of the circuit breaker does not meet the requirements.

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