Method for verifying the breaking capacity of circuit breaker of power grid busbar

Abstract

The present 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 fault bus of a power grid that does not contain a new energy power station or a flexible direct current (DC); calculating the decay time constant of the DC component of the short-circuit current of the fault bus, and calculating the AC short-circuit breaking capacity of the circuit breaker after considering the DC component based on the decay time constant of the DC component of the short-circuit current of the fault bus and the shortest breaking time of the circuit breaker of the fault bus; 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; and judging whether the breaking capacity of the circuit breaker meets the requirements based on 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. The present invention can more accurately judge whether the breaking capacity of the circuit breaker meets the requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of power grids, and in particular to a method for verifying the breaking capacity of a circuit breaker of a power grid bus. Background Art

[0002] my country will transform and upgrade to a new power system with new energy as the main body. The short-circuit current control of the power grid will face greater challenges. On the one hand, a large number of new power electronic equipment including wind farms, photovoltaic power stations, flexible AC and DC equipment, etc. will provide short-circuit current to the power grid in the form of current source after being connected to the power grid; on the other hand, due to the uneven 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 power exchange between regions. As the voltage level continues to increase, 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 new situation, the present invention proposes a circuit breaker breaking capacity verification method that takes into account new energy power stations, flexible DC grid connection and the DC component of the short-circuit current.

[0003] The shortcomings and deficiencies of existing technologies: Currently, most types of wind power, photovoltaic power, and flexible direct current transmission are connected to the grid through full-power converters. The short-circuit current characteristics they provide to the grid are significantly different from those of traditional rotating generators. There are currently methods for calculating the short-circuit current provided by new energy plants or flexible direct current transmission systems, which generally require detailed electromagnetic transient modeling. For the calculation of the DC component, the "Calculation of Short-Circuit Current in Three-Phase AC Systems" (GB / T 15544.1-2013) provides a formula for calculating the non-periodic component of the short-circuit current, Idc, using the equivalent frequency method.

[0004] Current calculation methods for short-circuit currents provided by renewable energy plants or flexible direct current transmission (HVDC) generally require detailed electromagnetic transient modeling and only consider the short-circuit current injected by the main body. These methods fail to integrate with the equivalent voltage source calculation method recommended in "Calculation of Short-Circuit Current in Three-Phase AC Systems" (GB / T 15544.1-2013). This hinders rapid assessment of the substation's contribution to the power system and is cumbersome during planning, operation, and engineering implementation. Furthermore, typical grid planning and operation only considers the AC component of short-circuit current. The national standard also provides methods for calculating the non-periodic component of short-circuit current, but fails to comprehensively consider the AC, or periodic, component to guide the determination of whether the circuit breaker's overall breaking capacity meets requirements. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for verifying the breaking capacity of a circuit breaker of a power grid busbar. The method comprehensively considers the influence of various factors on the short-circuit current under the new power system, and superimposes the short-circuit current provided by the new energy power station and flexible direct current transmission on the AC short-circuit current of the traditional network, so that the obtained short-circuit current is more real and accurate. 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 busbar, so that the obtained breaking capacity of the circuit breaker is more real and accurate, thereby being able to more accurately judge whether the breaking capacity of the circuit breaker meets the requirements.

[0006] The technical solution adopted in the present invention is as follows:

[0007] A method for verifying the breaking capacity of a circuit breaker of a power grid busbar comprises the following steps: calculating the basic short-circuit current of a fault busbar of a power grid that does not contain a new energy power station or a flexible direct current (DC); calculating the decay time constant of the DC component of the short-circuit current of the fault busbar, and calculating the AC short-circuit breaking capacity of the circuit breaker after considering the DC component based on the decay time constant of the DC component of the short-circuit current of the fault busbar and the shortest breaking time of the circuit breaker of the fault busbar; 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; and judging whether the breaking capacity of the circuit breaker meets the requirements based on 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.

[0008] Calculate the AC short-circuit breaking capacity of the circuit breaker after considering the DC component using the following formula:

[0009]

[0010] 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, T dcf.R is the decay time constant of the DC component of the short-circuit current of the fault bus, T dcf.N is the rated DC component decay time constant of the circuit breaker.

[0011] Calculating the short-circuit current provided by the new energy power stations in the power grid specifically includes: determining whether each of the new energy power stations is connected to the main power grid via boosting; if a new energy power station is connected to the main power grid via boosting, using a preset injection current as the short-circuit current provided by the new energy power station; if a new energy power station is not connected to the main power grid via boosting, calculating the maximum short-circuit current of the new energy power station at the moment of circuit breaker operation, and calculating the impedance between the new energy power station and the short-circuit point and the system impedance of the short-circuit point, and calculating the short-circuit current provided by the new energy power station based on the maximum short-circuit current of the new energy power station at the moment of circuit breaker operation, the impedance between the new energy power station and the short-circuit point, and the system impedance of the short-circuit point; and accumulating the short-circuit currents provided by all the new energy power stations in the power grid.

[0012] If a new energy power station is connected to the main grid via boosting, the short-circuit current provided by the new energy power station is:

[0013]

[0014] Among them, I REi It represents the short-circuit current provided by the i-th renewable energy power station, U i is the bus voltage value of the i-th new energy power station, I Ni is the rated current of the i-th new energy power station.

[0015] If a new energy power station is not connected to the main grid through voltage boosting, the short-circuit current provided by the new energy power station is:

[0016] I REi =I REi,max ×X sysi / (X sysi +X fi )

[0017] Among them, I REi,max is the maximum short-circuit current of the i-th renewable energy power station at the moment of circuit breaker operation, X fi is the impedance between the i-th new energy power station and the short-circuit point, X sysi is the short-circuit point system impedance corresponding to the i-th new energy power station.

[0018] 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 is operated; judging whether each flexible DC generates reactive power during the fault; if a certain flexible DC generates reactive power during the fault, calculating the impedance between the flexible DC and the short-circuit point and the system impedance of the short-circuit point, and calculating the short-circuit current provided by the flexible DC based on the maximum short-circuit current of the flexible DC at the moment when the circuit breaker is operated, the impedance between the flexible DC and the short-circuit point, and the system impedance of the short-circuit point; and accumulating the short-circuit currents provided by all flexible DCs in the power grid.

[0019] If a flexible DC system generates reactive power during a fault, the short-circuit current provided by the flexible DC system is:

[0020] I VSCj =I VSCj,max ×X sysj / (X sysj +X fj )

[0021] Among them, I VSCj represents the short-circuit current provided by the jth flexible DC line, X fj is the impedance between the jth flexible DC line and the short-circuit point, X sysj is the short-circuit point system impedance corresponding to the j-th flexible DC line.

[0022] 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, it is judged whether the breaking capacity of the circuit breaker meets the requirements, specifically including: judging whether there is S Rf >I f0 +∑I REi +∑I VSCj , where I f0 is the basic short-circuit current, ∑I REi is the cumulative value of the short-circuit current provided by all the new energy power stations in the grid, ∑I VSCj is the cumulative value of the short-circuit current provided by all flexible DC systems in the power grid; if yes, the breaking capacity of the circuit breaker meets the requirement; otherwise, the breaking capacity of the circuit breaker does not meet the requirement.

[0023] Beneficial effects of the present invention:

[0024] The present invention calculates the attenuation time constant of the DC component of the short-circuit current of the fault bus, and based on this calculates the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, and calculates the short-circuit current provided by the new energy power station and the short-circuit current provided by the flexible DC in the power grid, and based on this and the basic short-circuit current and the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, judges whether the breaking capacity of the circuit breaker of the fault bus meets the requirements. 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 is more real and accurate. 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 fault bus, so that the obtained breaking capacity of the circuit breaker is more real and accurate, so that it can more accurately judge whether the breaking capacity of the circuit breaker meets the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Flowchart of a method for verifying the breaking capacity of a circuit breaker of a power grid busbar according to an embodiment of the present invention;

[0026] Figure 2 This is a flow chart 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;

[0027] Figure 3 The figure is a schematic diagram of the power grid structure of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, the method for verifying the breaking capacity of a circuit breaker of a power grid busbar according to an embodiment of the present invention includes the following steps:

[0030] S1, calculates the basic short-circuit current of the fault bus of the power grid that does not include new energy power stations or flexible DC.

[0031] In the embodiment of the present invention, the new energy power station can be a wind power station or a photovoltaic power station. When a busbar of the power grid fails, the basic short-circuit current I of the faulty busbar f can be calculated without including the new energy power station and the flexible DC switching station. f0 .

[0032] S2, calculate the decay 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 based on the decay time constant of the DC component of the short-circuit current of the faulty bus and the shortest breaking time of the circuit breaker of the faulty bus.

[0033] In one embodiment of the present invention, the AC short-circuit breaking capacity of the circuit breaker after taking the DC component into account can be calculated according to the following formula:

[0034]

[0035] Among them, S fR S is the AC short-circuit breaking capacity of the circuit breaker after considering the DC component. 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 fault bus, T dcf.N is the rated DC component decay time constant of the circuit breaker.

[0036] S3, calculates the short-circuit current provided by the new energy power station in the power grid.

[0037] Specifically, it is first possible to determine whether each new energy power station is connected to the main grid through voltage boosting, for example, whether it is connected to the grid through a 220kV (330kV) photovoltaic power generation collection system that boosts the voltage to a 500kV (750kV) voltage level.

[0038] 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. In one embodiment of the present invention, the preset injection current, i.e., the short-circuit current provided by the new energy power station connected to the main grid via boosting, is:

[0039]

[0040] Among them, I REi It represents the short-circuit current provided by the i-th renewable energy power station, U i is the bus voltage value of the i-th new energy power station, I Ni is the rated current of the i-th new energy power station.

[0041] If a new energy power station is not connected to the main grid via boosting, the maximum short-circuit current of the new energy power station at the time of circuit breaker operation is calculated, and the impedance between the new energy power station and the short-circuit point and the system impedance of the short-circuit point are calculated, and the short-circuit current provided by the new energy power station is calculated based on the maximum short-circuit current of the new energy power station at the time of circuit breaker operation, the impedance between the new energy power station and the short-circuit point and the system impedance of the short-circuit point. In one embodiment of the present invention, the maximum short-circuit current of the new energy power station at the time of circuit breaker operation is generally the maximum working current of the new energy power station under 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 via boosting is:

[0042] I REi =I REi,max ×X sysi / (X sysi +X fi )

[0043] Among them, I REi,max is the maximum short-circuit current of the i-th renewable energy power station at the moment of circuit breaker operation, X fi is the impedance between the i-th new energy power station and the short-circuit point, X sysi is the short-circuit point system impedance corresponding to the i-th new energy power station.

[0044] Finally, the short-circuit currents provided by all the renewable energy power stations in the grid are accumulated to obtain the short-circuit current ∑I provided by the renewable energy power stations in the grid. REi .

[0045] S4, calculate the short-circuit current provided by the flexible DC in the power grid.

[0046] Specifically, the maximum short-circuit current of each flexible DC at the moment of circuit breaker operation can be calculated. In one embodiment of the present invention, the maximum short-circuit current of the flexible DC at the moment of circuit breaker operation is generally the maximum operating current of the flexible DC under rated full power normal operation multiplied by an overload factor of 1.1 to 1.2 times.

[0047] Then, determine whether each flexible DC line generates reactive power during the fault. If a flexible DC line does not generate reactive power during the fault, there is no need to consider the incremental short-circuit current of the system caused by the flexible DC line. If a flexible DC line generates reactive power during the fault, calculate the impedance between the flexible DC line and the short-circuit point and the system impedance at the short-circuit point. The short-circuit current provided by the flexible DC line is calculated based on the maximum short-circuit current of the flexible DC line at the moment of circuit breaker operation, the impedance between the flexible DC line and the short-circuit point, and the system impedance at the short-circuit point. The short-circuit current provided by the flexible DC line that generates reactive power during the fault is:

[0048] I VSCj =IVSCj,max ×X sysj / (X sysj +X fj )

[0049] Among them, I VSCj represents the short-circuit current provided by the jth flexible DC line, X fj is the impedance between the jth flexible DC line and the short-circuit point, X sysj is the short-circuit point system impedance corresponding to the j-th flexible DC line.

[0050] Finally, the short-circuit currents provided by all flexible DC in the grid are accumulated to obtain the short-circuit current ∑I provided by the flexible DC in the grid. VSCj .

[0051] S5, judging whether the breaking capacity of the circuit breaker meets the requirements based on 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.

[0052] It should be understood that the short-circuit current provided by the renewable energy power station and the short-circuit current provided by the flexible DC system are superimposed on the basic short-circuit current to form the total short-circuit current. Therefore, the AC short-circuit breaking capacity of the circuit breaker, after accounting for the DC component, can be compared with the total short-circuit current to determine whether the circuit breaker's breaking capacity meets the requirements.

[0053] 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 cumulative value of the short-circuit current provided by all renewable energy power stations in the grid, ∑I VSCj It is the cumulative value of the short-circuit current provided by all flexible DC systems 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.

[0054] In one embodiment of the present invention, the specific process of the method for verifying the breaking capacity of the circuit breaker of the power grid bus is as follows: Figure 2 shown.

[0055] According to an embodiment of the present invention, a method for verifying the breaking capacity of a circuit breaker of a power grid bus is provided. The attenuation time constant of the DC component of the short-circuit current of the faulty bus is calculated, and based on this, the AC short-circuit breaking capacity of the circuit breaker after considering the DC component is calculated. The short-circuit current provided by the new energy power station and the short-circuit current provided by the flexible DC in the power grid are calculated. Based on this and the basic short-circuit current and the AC short-circuit breaking capacity of the circuit breaker after considering the DC component, it is judged whether the breaking capacity of the circuit breaker of the faulty bus meets the requirements. Thus, 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 is more real and accurate. 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 breaking capacity of the circuit breaker is more real and accurate, thereby being able to more accurately judge whether the breaking capacity of the circuit breaker meets the requirements.

[0056] In a specific embodiment of the present invention, Figure 3 Taking the local power grid (voltage level is 750kV / 330kV) in a certain area as an example, the basic three-phase short-circuit current I f0 =55.0kA, the fault bus is the 330kV bus of the 750kV substation S1. Calculate the decay time constant T of the DC component of the short-circuit current of the fault bus dcf.R =151.7ms. The shortest breaking time of the circuit breaker is t min =40ms, rated DC component decay time constant of circuit breaker T dcf.N =45ms, the rated breaking capacity S of the circuit breaker of the fault bus f fN The AC short-circuit breaking capacity S of the circuit breaker after considering the DC component is calculated to be 63kA. fR =49.4kA.

[0057] There is a new energy power station in the area that is connected to substation S1-5 via 110kV voltage level. The short-circuit current ∑I REi =I REi =0.2kA. There is a flexible DC converter station in the area connected to the 330kV side of substation S1. Considering the reactive power generated during the fault, the short-circuit current ∑I provided by the flexible DC is calculated. VSCj =I VSCj =3.2kA. Final comparison S Rf =49.4kA and I f0 +∑ I REi +∑I VSCj =58.4kA, the latter is larger, then the breaking capacity of the circuit breaker of the fault bus does not meet the requirements.

[0058] In the description of the present invention, “plurality” means two or more, unless otherwise clearly defined.

[0059] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0060] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

[0061] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection having one or more wires (electronic devices), a portable computer disk cartridge (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disc read-only memory (CDROM). Furthermore, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing it in another suitable manner if necessary, and then storing it in a computer memory.

[0062] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0063] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0064] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for verifying the breaking capacity of a circuit breaker of a power grid bus, characterized in that: The following steps are involved: Calculate the basic short-circuit current of the fault busbar of a power grid that does not include new energy power plants or flexible DC power stations; Calculate the decay time constant of the DC component of the short-circuit current of the faulty busbar, and calculate the AC short-circuit breaking capacity of the circuit breaker after taking the DC component into account 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, T dcf.R is the decay time constant of the DC component of the short-circuit current of the fault bus, T dcf.N is the rated DC component decay time constant of the circuit breaker; 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 direct current in the power grid; Whether the breaking capacity of the circuit breaker meets the requirements is judged based on 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.

2. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 1, characterized in that: Calculating the short-circuit current provided by the new energy power station in the power grid, specifically including: Determining whether each of the new energy power stations is connected to the main power grid after voltage 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 power grid via a booster, the maximum short-circuit current of the new energy power station at the time when the circuit breaker is actuated is calculated, and the impedance between the new energy power station and the short-circuit point and the system impedance of the short-circuit point are calculated. Furthermore, the short-circuit current provided by the new energy power station is calculated based on the maximum short-circuit current of the new energy power station at the time when the circuit breaker is actuated, the impedance between the new energy power station and the short-circuit point, and the system impedance of the short-circuit point; The short-circuit currents provided by all the new energy power stations in the power grid are accumulated.

3. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 2, characterized in that: If a new energy power station is connected to the main grid via boosting, the short-circuit current provided by the new energy power station is: Among them, I REi It represents the short-circuit current provided by the i-th renewable energy power station, U i is the bus voltage value of the i-th new energy power station, I Ni is the rated current of the i-th new energy power station.

4. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 3, characterized in that: If a new energy power station is not connected to the main grid through voltage 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 renewable energy power station at the moment of circuit breaker operation, X fi is the impedance between the i-th new energy power station and the short-circuit point, X sysi is the short-circuit point system impedance corresponding to the i-th 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, characterized in that: Calculating the short-circuit current provided by the flexible direct current in the power grid specifically includes: Calculating the maximum short-circuit current of each flexible DC circuit at the moment when the circuit breaker is actuated; Determining whether each of the flexible DC channels generates reactive power during a fault; If a certain flexible DC system generates reactive power during a fault, the impedance between the flexible DC system and the short-circuit point and the system impedance at the short-circuit point are calculated. The short-circuit current provided by the flexible DC system is calculated based on the maximum short-circuit current of the flexible DC system at the moment the circuit breaker is operated, the impedance between the flexible DC system and the short-circuit point, and the system impedance at the short-circuit point. The short-circuit currents provided by all flexible direct currents in the power grid are accumulated.

6. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 5, characterized in that: If a flexible DC system generates reactive power during a fault, the short-circuit current provided by the flexible DC system is: I VSCj =I VSCj,max ×X sysj / (X sysj +X fj ) Among them, I VSCj represents the short-circuit current provided by the jth flexible DC line, X fj is the impedance between the jth flexible DC line and the short-circuit point, X sysj is the short-circuit point system impedance corresponding to the j-th flexible DC line.

7. The method for verifying the breaking capacity of a circuit breaker of a power grid bus according to claim 6, characterized in that: Judging whether the breaking capacity of the circuit breaker meets the requirements based on 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 specifically includes: 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 cumulative value of the short-circuit current provided by all the new energy power stations in the grid, ∑I VSCj The cumulative value of the short-circuit current provided by all flexible DC systems in the power grid; If yes, the breaking capacity of the circuit breaker meets the requirement; otherwise, the breaking capacity of the circuit breaker does not meet the requirement.

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