CN112487650B - Monopole short-circuit current calculation method and device for flexible direct-current power grid - Google Patents
Monopole short-circuit current calculation method and device for flexible direct-current power grid Download PDFInfo
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Abstract
The application discloses a monopole short-circuit current calculation method and a monopole short-circuit current calculation device for a flexible direct current power grid, which are used for processing an initial arc resistance input constructed simulation model and outputting an initial monopole short-circuit current; calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current, inputting the new arc resistance into a simulation model for processing, and outputting the new unipolar short-circuit current; and judging whether the new unipolar short-circuit current converges or not based on the new arc resistance and the initial arc resistance, if yes, outputting the new unipolar short-circuit current, if not, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and performing iterative calculation until the new unipolar short-circuit current converges, thereby solving the technical problems that modeling parameters and actual operating parameters have larger errors and arc resistance can be generated during actual direct-current side unipolar manual short-circuit fault test because parameters such as grounding resistance, a lightning arrester and the like have larger influence on fault current in the prior art, and the unipolar short-circuit current calculation accuracy is lower.
Description
Technical Field
The application relates to the technical field of power system fault analysis, in particular to a monopole short-circuit current calculation method and device of a flexible direct current power grid.
Background
The converter stations at two ends in the flexible direct current power grid system all utilize flexible direct current transmission and are composed of a converter, converter transformer equipment, converter reactance equipment and the like. Unlike current source converter type high voltage direct current transmission based on phase control commutation technology, the most critical core part is a Voltage Source Converter (VSC) which consists of a converter bridge and a direct current capacitor. The biggest characteristic is that a turn-off device (usually an IGBT) and a high-frequency modulation technology are adopted. By adjusting the amplitude of the converter outlet voltage and the power angle difference with the system voltage, the output active power and reactive power can be independently controlled. Thus, through the control of the two-end converter stations, the mutual transmission of active power between two alternating current networks can be realized, and meanwhile, the two-end converter stations can also independently adjust the reactive power absorbed or emitted by the two-end converter stations, so that reactive support is given to the connected alternating current systems.
The flexible direct current power grid is used for carrying out a direct current pole artificial monopole artificial short circuit test to verify the performance of the flexible direct current power transmission system equipment. The test is generally carried out on a direct current circuit, one of the poles is short-circuited to the ground, and the fault is manufactured artificially. In the test, arc resistance is generated by short circuit faults between a fault pole line and the ground. After the fault occurs, the fault current is increased rapidly, and whether the primary equipment overcurrent capacity of the system and the secondary control protection of the system act correctly or not is tested. With the correct action of the secondary control protection, the fault will be isolated or cut off and the test is completed. The existing modeling simulation technology aiming at the flexible direct current power grid has high calculation accuracy under the steady-state operation working condition, but has lower accuracy of the calculated monopole short-circuit current under the transient working condition of the direct current side monopole artificial short-circuit fault test, mainly because the grounding resistance, the lightning arrester and other parameters have larger influence on the fault current, the modeling parameters have larger error with the actual operation parameters, and the arc resistance can be generated during the actual direct current side monopole artificial short-circuit fault test to influence the calculation result of the monopole short-circuit current.
Disclosure of Invention
The application provides a method and a device for calculating unipolar short-circuit current of a flexible direct-current power grid, which are used for solving the technical problems that in the prior art, because parameters such as a grounding resistor, a lightning arrester and the like have larger influence on fault current, errors between modeling parameters and actual operating parameters are larger, arc resistance is generated during actual direct-current side unipolar artificial short-circuit fault test, and the unipolar short-circuit current calculation accuracy is lower.
In view of the foregoing, a first aspect of the present application provides a method for calculating a unipolar short-circuit current of a flexible dc power grid, including:
s1, checking parameters in a constructed flexible direct-current power transmission model, a grounding network parameter model and an electromagnetic transient model of a lightning arrester to obtain a simulation model;
S2, inputting the initial arc resistance into the simulation model for processing, and outputting initial unipolar short-circuit current;
s3, calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current, inputting the new arc resistance into the simulation model for processing, and outputting a new unipolar short-circuit current;
And S4, judging whether the new unipolar short-circuit current converges or not based on the new arc resistance and the initial arc resistance, outputting the new unipolar short-circuit current if yes, taking the new unipolar short-circuit current as the initial unipolar short-circuit current if no, and returning to the step S3.
Optionally, the calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current includes:
Discretizing the initial unipolar short-circuit current, and calculating a short-circuit current estimated value based on the discretized initial unipolar short-circuit current;
a new arc resistance is calculated based on the arc length and the short circuit current estimate.
Optionally, the calculating a new arc resistance based on the arc length and the short circuit current estimation value includes:
And calculating the product of the arc length and a preset coefficient, and calculating the ratio of the product to the short-circuit current estimated value to obtain a new arc resistance.
Optionally, the determining whether the new unipolar short-circuit current converges based on the new arc resistance and the initial arc resistance includes:
calculating a difference between the new arc resistance and the initial arc resistance;
And judging whether the ratio of the difference value to the initial arc resistance is smaller than or equal to a preset threshold value, if so, judging that the new unipolar short-circuit current converges, and if not, judging that the new unipolar short-circuit current does not converge.
The second aspect of the present application provides a unipolar short-circuit current calculation device for a flexible dc power grid, comprising:
The construction unit is used for checking parameters in the constructed flexible direct-current transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model to obtain a simulation model;
The input unit is used for inputting the initial arc resistance into the simulation model for processing and outputting initial unipolar short-circuit current;
the calculation unit is used for calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current, inputting the new arc resistance into the simulation model for processing, and outputting a new unipolar short-circuit current;
And the judging unit is used for judging whether the new unipolar short-circuit current converges or not based on the new arc resistance and the initial arc resistance, outputting the new unipolar short-circuit current if yes, taking the new unipolar short-circuit current as the initial unipolar short-circuit current if no, and triggering the calculating unit.
Optionally, the computing unit specifically includes:
A processing subunit, configured to perform discretization processing on the initial unipolar short-circuit current, and calculate a short-circuit current estimation value based on the discretized initial unipolar short-circuit current;
A calculation subunit for calculating a new arc resistance based on the arc length and the short-circuit current estimation value;
And the input subunit is used for inputting the new arc resistance into the simulation model for processing and outputting new unipolar short-circuit current.
Optionally, the computing subunit is specifically configured to:
And calculating the product of the arc length and a preset coefficient, and calculating the ratio of the product to the short-circuit current estimated value to obtain a new arc resistance.
Optionally, the judging unit is specifically configured to:
calculating a difference between the new arc resistance and the initial arc resistance;
And judging whether the ratio of the difference value to the initial arc resistance is smaller than or equal to a preset threshold value, if so, judging that the new unipolar short-circuit current converges, outputting the new unipolar short-circuit current, and if not, judging that the new unipolar short-circuit current does not converge, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and triggering the computing unit.
A third aspect of the application provides a unipolar short-circuit current computing device for a flexible direct current grid, the device comprising a processor and a memory;
The memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the unipolar short-circuit current calculation method of the flexible direct current power grid according to any one of the first aspect according to the instructions in the program code.
A fourth aspect of the present application provides a computer readable storage medium for storing program code for performing the unipolar short-circuit current calculation method of the flexible direct current network according to any one of the first aspects.
From the above technical scheme, the application has the following advantages:
The application provides a monopole short-circuit current calculation method of a flexible direct current power grid, which comprises the following steps: s1, checking parameters in a constructed flexible direct-current power transmission model, a grounding network parameter model and an electromagnetic transient model of a lightning arrester to obtain a simulation model; s2, inputting the initial arc resistance into a simulation model for processing, and outputting an initial unipolar short-circuit current; s3, calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current, inputting the new arc resistance into a simulation model for processing, and outputting the new unipolar short-circuit current; and S4, judging whether the new unipolar short-circuit current converges or not based on the new arc resistance and the initial arc resistance, outputting the new unipolar short-circuit current if yes, taking the new unipolar short-circuit current as the initial unipolar short-circuit current if no, and returning to the step S3.
In the application, after a flexible direct-current power transmission model, a grounding network parameter model and an electromagnetic transient model of the lightning arrester are constructed, parameters of the flexible direct-current power transmission model, the grounding network parameter model and the electromagnetic transient model of the lightning arrester are checked, so that errors between model parameters and actual operation parameters are reduced, and the accuracy of an operation result of a simulation model is ensured; considering the influence of the arc resistance on the unipolar short-circuit current, the arc resistance is combined with the simulation model in an iterative manner until the unipolar short-circuit current converges, and the accuracy and the reliability of a calculation result are further ensured, so that the technical problems that in the prior art, the error between a modeling parameter and an actual operation parameter is large because of the large influence of parameters such as a grounding resistor, a lightning arrester and the like on the fault current, the arc resistance is generated during the actual direct-current side unipolar artificial short-circuit fault test, and the calculation accuracy of the unipolar short-circuit current is low are solved.
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In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the application, and that other drawings can be obtained from these drawings without inventive faculty for a person skilled in the art.
Fig. 1 is a schematic flow chart of a method for calculating unipolar short-circuit current of a flexible dc power grid according to an embodiment of the present application;
fig. 2 is a flow chart of a process for calculating unipolar short-circuit current of a flexible dc power grid according to an embodiment of the present application;
fig. 3 is a schematic structural diagram of a monopole short-circuit current calculating device of a flexible dc power grid according to an embodiment of the present application.
Detailed Description
The application provides a method and a device for calculating unipolar short-circuit current of a flexible direct-current power grid, which are used for solving the technical problems that in the prior art, because parameters such as a grounding resistor, a lightning arrester and the like have larger influence on fault current, errors between modeling parameters and actual operating parameters are larger, arc resistance is generated during actual direct-current side unipolar artificial short-circuit fault test, and the unipolar short-circuit current calculation accuracy is lower.
In order to make the present application better understood by those skilled in the art, the following description will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
For easy understanding, referring to fig. 1, an embodiment of a method for calculating a unipolar short-circuit current of a flexible dc power grid according to the present application includes:
And 101, checking parameters in the constructed flexible direct-current transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model to obtain a simulation model.
The soft-direct transmission model is built according to actual soft-direct transmission engineering parameters, and comprises main primary component parts of a soft-direct system and secondary control protection parameters. The primary component parameters include a current limiting resistance value, a primary electrical parameter (electrical parameters such as capacity, voltage level, impedance, iron loss and the like) of a converter transformer, a bridge arm reactance value, a converter valve parameter (parameters such as MMC submodule number, MMC submodule capacitance, on resistance and the like), an alternating current side power grid system parameter (parameters such as system impedance, system frequency, voltage and the like), a direct current side parameter (direct current voltage level), a neutral point mode parameter and a direct current power transmission network line equivalent parameter. The secondary control protection parameters comprise voltage, current signal acquisition points, control modes of a converter station (VdcQ, PQ, island, PV and the like) and control parameters corresponding to the control modes, such as inner loop control parameters and outer loop control parameters, circulation suppression parameters (control parameters of proportion, integration, enabling and the like) and a mode of controlling output to a valve module. And checking the flexible direct current transmission model according to the actual flexible direct current transmission engineering parameters, so that the primary electric parameters and the secondary control protection parameters are consistent with the actual flexible direct current transmission network as much as possible, and are consistent with the control mode of the actual flexible direct current transmission network as much as possible, and the flexible direct current transmission model achieves the effect that the transient error is less than 5% under the definite conditions of steady state, dynamic state and parameters of the actual flexible direct current transmission system.
Because the monopole short-circuit current is related to the actual topographic resistance, the embodiment of the application constructs a grounding network parameter model according to the grounding impedance test data of the actual flexible direct current transmission system, and the grounding network parameter model comprises a test site grounding network topological structure and an overhead ground wire resistance. And then checking parameters in the grounding network parameter model according to the grounding impedance test data of the actual flexible direct current transmission system.
For the flexible direct current power transmission network with the pseudo-bipolar structure, parameters of the lightning arrester need to be checked, when the fault to the ground occurs to one pole of the flexible direct current power transmission network with the pseudo-bipolar structure, the voltage of the other pole of the flexible direct current power transmission network with the pseudo-bipolar structure can be increased, and the lightning arrester acts. Therefore, the flexible direct current transmission network monopole short circuit of the pseudo bipolar structure is related to the lightning arrester, and the parameter of the lightning arrester needs to be checked.
After the result is checked, a simulation model of a single pole to ground artificial short circuit test is built, namely the simulation model is composed of a flexible direct current transmission model built according to actual engineering parameters, a grounding network parameter model built according to grounding impedance test data of a flexible direct current transmission system and an electromagnetic transient model of the lightning arrester built according to lightning arrester parameters, such as a PSCAD model, and the built simulation model can carry out simulation calculation.
And 102, inputting the initial arc resistance into a simulation model for processing, and outputting an initial unipolar short-circuit current.
And 103, calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current, inputting the new arc resistance into a simulation model for processing, and outputting the new unipolar short-circuit current.
The arc length is measured based on in-situ test conditions, such as the distance from the short circuit point on the transmission line to ground in a test plan.
The specific process of calculating the new arc resistance based on the arc length and the initial unipolar short circuit current is: discretizing an initial unipolar short-circuit current I n-1 (n is the iteration number, and n=1 when I n-1 is the initial unipolar short-circuit current), and calculating a short-circuit current estimated value I n-1 based on the discretized initial unipolar short-circuit current I n-1; a new arc resistance R n is calculated based on the arc length l and the short-circuit current estimation value I n-1, and the initial arc resistance R 1 is 0. Specifically, discretizing the initial unipolar short-circuit current I n-1, sorting the discretized initial unipolar short-circuit current in ascending order or descending order, removing a certain number (25%) of larger values, removing a certain number (20%) of smaller values, and averaging the rest initial unipolar short-circuit current to obtain a short-circuit current estimated value I n-1; then, the product of the arc length l and the preset coefficient K is calculated, and the ratio of the product to the short-circuit current estimated value I n-1 is calculated, so as to obtain a new arc resistance R n, namely:
Rn＝K*l/In-1；
wherein the preset coefficient k= 1080.4.
Step 104, judging whether the new unipolar short-circuit current converges or not based on the new arc resistance and the initial arc resistance, if yes, outputting the new unipolar short-circuit current, if not, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and returning to step 103.
Judging whether the new unipolar short-circuit current converges or not based on the new arc resistance and the initial arc resistance, and specifically calculating a difference value between the new arc resistance and the initial arc resistance; and judging whether the ratio of the difference value to the initial arc resistance is smaller than or equal to a preset threshold value, if so, judging that the new unipolar short-circuit current converges, and if not, judging that the new unipolar short-circuit current does not converge. In the embodiment of the application, the preset threshold value is preferably 3%, namely: when R n-Rn-1)/Rn-1 is less than or equal to 3%, the new unipolar short-circuit current is judged to be converged, otherwise, the new unipolar short-circuit current is judged to be not converged.
In one embodiment, 1 is output when it is determined that the new unipolar short-circuit current is converging, and 0 is output when it is determined that the new unipolar short-circuit current is not converging. And when the output is 1, finally outputting a new unipolar short-circuit current to obtain a fault current i, and when the output is 0, taking the new unipolar short-circuit current as an initial unipolar short-circuit current, and returning to step 103 to perform iterative calculation until the new unipolar short-circuit current converges, wherein the specific process can refer to fig. 2.
In the embodiment of the application, after a flexible direct-current power transmission model, a grounding network parameter model and an electromagnetic transient model of the lightning arrester are constructed, parameters of the flexible direct-current power transmission model, the grounding network parameter model and the electromagnetic transient model of the lightning arrester are checked, so that errors between model parameters and actual operation parameters are reduced, and the accuracy of an operation result of a simulation model is ensured; considering the influence of the arc resistance on the unipolar short-circuit current, the arc resistance is combined with the simulation model in an iterative manner until the unipolar short-circuit current converges, and the accuracy and the reliability of a calculation result are further ensured, so that the technical problems that in the prior art, the error between a modeling parameter and an actual operation parameter is large because of the large influence of parameters such as a grounding resistor, a lightning arrester and the like on the fault current, the arc resistance is generated during the actual direct-current side unipolar artificial short-circuit fault test, and the calculation accuracy of the unipolar short-circuit current is low are solved.
The foregoing is an embodiment of a method for calculating a unipolar short-circuit current of a flexible dc power grid provided by the present application, and the following is an embodiment of a device for calculating a unipolar short-circuit current of a flexible dc power grid provided by the present application.
Referring to fig. 3, a monopole short-circuit current calculating device of a flexible dc power grid according to an embodiment of the present application includes:
the construction unit 301 is configured to check parameters in the constructed flexible direct-current transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model to obtain a simulation model;
the input unit 302 is configured to input an initial arc resistance into the simulation model for processing, and output an initial unipolar short-circuit current;
a calculating unit 303, configured to calculate a new arc resistance based on the arc length and the initial unipolar short-circuit current, and input the new arc resistance into the simulation model for processing, and output the new unipolar short-circuit current;
the judging unit 304 is configured to judge whether the new unipolar short-circuit current converges based on the new arc resistance and the initial arc resistance, if yes, output the new unipolar short-circuit current, and if not, take the new unipolar short-circuit current as the initial unipolar short-circuit current, and trigger the calculating unit 303.
As a further improvement, the calculation unit 303 specifically includes:
A processing subunit 3031, configured to perform discretization processing on the initial unipolar short-circuit current, and calculate a short-circuit current estimated value based on the discretized initial unipolar short-circuit current;
a calculation subunit 3032, configured to calculate a new arc resistance based on the arc length and the short-circuit current estimation value;
and the input subunit 3033 is used for inputting the new arc resistance into the simulation model for processing and outputting a new unipolar short-circuit current.
As a further refinement, the computing subunit 3032 is specifically configured to:
And calculating the product of the arc length and a preset coefficient, and calculating the ratio of the product to the short-circuit current estimated value to obtain a new arc resistance.
As a further improvement, the judging unit 304 specifically is configured to:
calculating the difference between the new arc resistance and the initial arc resistance;
And judging whether the ratio of the difference value to the initial arc resistance is smaller than or equal to a preset threshold value, if so, judging that the new unipolar short-circuit current converges, outputting the new unipolar short-circuit current, if not, judging that the new unipolar short-circuit current does not converge, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and triggering the calculation unit.
The embodiment of the application also provides monopole short-circuit current calculation equipment of the flexible direct current power grid, which comprises a processor and a memory;
The memory is used for storing the program codes and transmitting the program codes to the processor;
The processor is configured to execute the method for calculating the unipolar short-circuit current of the flexible direct current power grid in the embodiment of the method for calculating the unipolar short-circuit current of the flexible direct current power grid according to the instruction in the program code.
The embodiment of the application also provides a computer readable storage medium, which is used for storing program codes, wherein the program codes are used for executing the method for calculating the unipolar short-circuit current of the flexible direct current power grid in the embodiment of the method for calculating the unipolar short-circuit current of the flexible direct current power grid.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the apparatus and units described above may refer to corresponding procedures in the foregoing method embodiments, which are not described herein again.
In the several embodiments provided by the present application, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in the embodiments of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.
The integrated units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be embodied in essence or a part contributing to the prior art or all or part of the technical solution in the form of a software product stored in a storage medium, comprising several instructions for executing all or part of the steps of the method according to the embodiments of the present application by means of a computer device (which may be a personal computer, a server, or a network device, etc.). And the aforementioned storage medium includes: u disk, mobile hard disk, read-Only Memory (ROM), random access Memory (Random Access Memory, RAM), magnetic disk or optical disk, etc.
The above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (4)
1. A monopole short-circuit current calculation method of a flexible direct current power grid is characterized by comprising the following steps of:
s1, checking parameters in a constructed flexible direct-current power transmission model, a grounding network parameter model and an electromagnetic transient model of a lightning arrester to obtain a simulation model;
S2, inputting the initial arc resistance into the simulation model for processing, and outputting initial unipolar short-circuit current;
s3, calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current, inputting the new arc resistance into the simulation model for processing, and outputting a new unipolar short-circuit current;
The calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current includes:
Discretizing the initial unipolar short-circuit current, and calculating a short-circuit current estimated value based on the discretized initial unipolar short-circuit current;
calculating the product of the arc length and a preset coefficient, and calculating the ratio of the product to the short-circuit current estimated value to obtain a new arc resistance;
s4, judging whether the new unipolar short-circuit current converges or not based on the new arc resistance and the initial arc resistance, if so, outputting the new unipolar short-circuit current, if not, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and returning to the step S3;
the determining whether the new unipolar short-circuit current converges based on the new arc resistance and the initial arc resistance includes:
calculating a difference between the new arc resistance and the initial arc resistance;
And judging whether the ratio of the difference value to the initial arc resistance is smaller than or equal to a preset threshold value, if so, judging that the new unipolar short-circuit current converges, and if not, judging that the new unipolar short-circuit current does not converge.
2. A unipolar short-circuit current calculation device of a flexible direct current power grid, comprising:
The construction unit is used for checking parameters in the constructed flexible direct-current transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model to obtain a simulation model;
The input unit is used for inputting the initial arc resistance into the simulation model for processing and outputting initial unipolar short-circuit current;
the calculation unit is used for calculating a new arc resistance based on the arc length and the initial unipolar short-circuit current, inputting the new arc resistance into the simulation model for processing, and outputting a new unipolar short-circuit current;
the computing unit specifically comprises:
A processing subunit, configured to perform discretization processing on the initial unipolar short-circuit current, and calculate a short-circuit current estimation value based on the discretized initial unipolar short-circuit current;
A calculating subunit, configured to calculate a product of the arc length and a preset coefficient, and calculate a ratio of the product to the short-circuit current estimated value, to obtain a new arc resistance;
the input subunit is used for inputting the new arc resistance into the simulation model for processing and outputting new unipolar short-circuit current;
the judging unit is used for judging whether the new unipolar short-circuit current converges or not based on the new arc resistance and the initial arc resistance, if so, outputting the new unipolar short-circuit current, and if not, taking the new unipolar short-circuit current as the initial unipolar short-circuit current and triggering the calculating unit;
The judging unit is specifically configured to:
calculating a difference between the new arc resistance and the initial arc resistance;
And judging whether the ratio of the difference value to the initial arc resistance is smaller than or equal to a preset threshold value, if so, judging that the new unipolar short-circuit current converges, outputting the new unipolar short-circuit current, and if not, judging that the new unipolar short-circuit current does not converge, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and triggering the computing unit.
3. A unipolar short-circuit current computing device of a flexible direct current grid, the device comprising a processor and a memory;
The memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the method for calculating the unipolar short-circuit current of the flexible direct current network according to claim 1 according to the instructions in the program code.
4. A computer readable storage medium for storing program code for performing the method of calculating a unipolar short circuit current of a flexible direct current network according to claim 1.
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