CN112487650A - Unipolar short-circuit current calculation method and device of flexible direct-current power grid - Google Patents
Unipolar short-circuit current calculation method and device of flexible direct-current power grid Download PDFInfo
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Abstract
The application discloses a monopole short-circuit current calculation method and a device thereof of a flexible direct-current power grid, wherein an initial arc resistance is input into a constructed simulation model for processing, and an initial monopole short-circuit current is output; 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 a new unipolar short-circuit current; whether the new unipolar short-circuit current is converged is judged based on the new arc resistance and the initial arc resistance, if yes, the new unipolar short-circuit current is output, if not, the new unipolar short-circuit current is used as the initial unipolar short-circuit current to conduct iterative calculation until convergence, and the technical problems that in the prior art, due to the fact that parameters such as ground resistance and a lightning arrester have large influences on fault current, errors of modeling parameters and actual operation parameters are large, arc resistance can be generated during actual direct-current side unipolar manual short-circuit fault testing, and calculation accuracy of the unipolar short-circuit current is low are solved.
Description
Technical Field
The application relates to the technical field of power system fault analysis, in particular to a method and a device for calculating unipolar short-circuit current of a flexible direct-current power grid.
Background
The converter stations at two ends of the flexible direct current grid system 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 Voltage Source Converter (VSC), which is composed of converter bridge and dc capacitor. The biggest characteristic lies in the adoption of a turn-off device (usually an IGBT) and a high-frequency modulation technology. By adjusting the amplitude of the outlet voltage of the converter and the power angle difference between the outlet voltage of the converter and the system voltage, the output active power and reactive power can be independently controlled. Therefore, the mutual transmission of active power between two alternating current networks can be realized by controlling the converter stations at the two ends, and simultaneously, the converter stations at the two ends can independently adjust the reactive power absorbed or emitted by the converter stations respectively, so that the connected alternating current system is supported in a reactive mode.
The flexible direct-current power grid is used for verifying the performance of the flexible direct-current transmission system equipment by carrying out a direct-current pole artificial monopole artificial short circuit test. The test is generally carried out on a direct current line, one of the polar lines is short-circuited with the ground, and a fault is artificially produced. During the test, short circuit fault between the fault pole line and the ground can generate arc resistance. After the fault occurs, the fault current is rapidly increased, and the overcurrent capacity of primary equipment of the system and the correct action of secondary control protection of the system are tested. With the correct action of the secondary control protection, the fault is isolated or cut off, and the test is completed. The existing modeling simulation technology for the flexible direct-current power grid has high calculation accuracy under a steady-state operation condition, but under a transient condition of a direct-current side monopole artificial short-circuit fault test, the accuracy of the computed monopole short-circuit current is low, mainly because parameters such as grounding resistance and a lightning arrester have large influence on the fault current, so that the error between the modeling parameters and actual operation parameters is large, and an 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 monopole short-circuit current calculation method and a device thereof for a flexible direct current power grid, which are used for solving the technical problems that in the prior art, parameters such as grounding resistance and an arrester have large influence on fault current, so that errors of modeling parameters and actual operation parameters are large, and arc resistance is generated during actual direct current side monopole manual short-circuit fault testing, so that the computation accuracy of the monopole short-circuit current is low.
In view of the above, a first aspect of the present application provides a unipolar short-circuit current calculation method for a flexible dc power grid, including:
s1, checking parameters in the constructed flexible direct power transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model to obtain a simulation model;
s2, inputting the initial arc resistance into the 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 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, if so, outputting the new unipolar short-circuit current, otherwise, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, 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;
calculating a new arc resistance 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 estimated short circuit current value includes:
and calculating the product of the arc length and a preset coefficient, and calculating the ratio of the product to the estimated value of the short-circuit current to obtain the 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 is converged, and if not, judging that the new unipolar short-circuit current is not converged.
The present application provides in a second aspect 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 power transmission model, the constructed grounding network parameter model and the constructed 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 the 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 the new unipolar short-circuit current converges or taking the new unipolar short-circuit current as the initial unipolar short-circuit current if the new unipolar short-circuit current does not converge, and triggering the calculating unit.
Optionally, the computing unit specifically includes:
the processing subunit is used for 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 calculating subunit for calculating a new arc resistance based on the arc length and the estimated value of the short circuit current;
and the input subunit is used for inputting the new arc resistance into the simulation model for processing and outputting a 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 estimated value of the short-circuit current to obtain the new arc resistance.
Optionally, the determining 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 is converged, outputting the new unipolar short-circuit current, otherwise, judging that the new unipolar short-circuit current is not converged, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and triggering the calculation unit.
A third aspect of the application provides a unipolar short-circuit current calculation 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 unipolar short-circuit current calculation method of the flexible direct current power grid according to any one of the first aspect according to instructions in the program code.
A fourth aspect of the present application provides a computer-readable storage medium for storing program code for executing the unipolar short-circuit current calculation method of the flexible direct current power grid according to any one of the first aspects.
According to the technical scheme, the method 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 the constructed flexible direct power transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model 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 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, if so, outputting the new unipolar short-circuit current, otherwise, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and returning to the step S3.
In the method, after a flexible direct power transmission model, a grounding network parameter model and a lightning arrester electromagnetic transient model are constructed, parameters of the flexible direct power transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model are checked so as to reduce errors between model parameters and actual operation parameters and ensure the accuracy of a simulation model operation result; the influence of the arc resistance on the unipolar short-circuit current is considered, the arc resistance and the simulation model are combined in an iterative mode until the unipolar short-circuit current converges, and the accuracy and the reliability of the calculation result are further guaranteed, so that the technical problems that in the prior art, due to the fact that parameters such as the ground resistance and the lightning arrester have large influence on the fault current, the error between the modeling parameters and the actual operation parameters is large, and the arc resistance is generated during actual direct-current side unipolar manual short-circuit fault testing, 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 present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic flowchart of a method for calculating a unipolar short-circuit current of a flexible dc power grid according to an embodiment of the present disclosure;
fig. 2 is a block flow diagram of a unipolar short-circuit current calculation process of a flexible dc power grid according to an embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of a unipolar short-circuit current calculation device of a flexible direct current power grid according to an embodiment of the present application.
Detailed Description
The application provides a monopole short-circuit current calculation method and a device thereof for a flexible direct current power grid, which are used for solving the technical problems that in the prior art, parameters such as grounding resistance and an arrester have large influence on fault current, so that errors of modeling parameters and actual operation parameters are large, and arc resistance is generated during actual direct current side monopole manual short-circuit fault testing, so that the computation accuracy of the monopole short-circuit current is low.
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present 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 provided by the present application includes:
and 101, checking parameters in the constructed flexible direct power transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model to obtain a simulation model.
The flexible-direct power transmission model is established according to actual flexible-direct power transmission engineering parameters and comprises main primary component parts and secondary control and protection parameters of a flexible-direct system. The parameters of the primary components comprise current-limiting resistance values, main electrical parameters (such as capacity, voltage level, impedance and iron loss) of the converter transformer, bridge arm reactance values, converter valve parameters (such as the number of MMC sub-modules, capacitance of the MMC sub-modules, and on-resistance), alternating-current side power grid system parameters (such as system impedance, system frequency and voltage), direct-current side parameters (direct-current voltage level), neutral point modes and parameters, and direct-current transmission network line equivalent parameters. The secondary control and protection parameters comprise voltage and current signal acquisition points, control modes (VdcQ, PQ, island, PV and the like) of the converter station, control parameters corresponding to the control modes, such as inner loop control parameters and outer loop control parameters, circulation inhibition parameters (control parameters such as proportion, integral, enabling and the like), and a mode of controlling and outputting to the valve module. And (3) checking the flexible direct-current transmission model according to the actual flexible direct-current transmission engineering parameters, so that the main primary electrical parameters and the secondary control and protection parameters are consistent with the real flexible direct-current transmission network as far as possible and are consistent with the control mode of the real flexible direct-current transmission network as far as possible, and the flexible direct-current transmission model achieves the effect that the transient error is less than 5% under the conditions of steady state, dynamic state and definite parameters of the actual flexible direct-current transmission system.
Because the unipolar short-circuit current is related to the actual terrain resistance, the grounding network parameter model is constructed according to the actual grounding impedance test data of the flexible direct-current transmission system, and comprises a test field 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.
The lightning arrester parameter is needed to be checked for the flexible direct current transmission network with the pseudo-bipolar structure, and when the monopole has a ground fault, the voltage of the other electrode of the flexible direct current transmission network with the pseudo-bipolar structure is increased, so that the lightning arrester acts. Therefore, the flexible dc transmission network unipolar short circuit of the pseudo-bipolar structure is associated with the lightning arrester, and the lightning arrester parameters need to be checked.
And after the result is checked, a simulation model of the monopole ground artificial short circuit test is built, namely the simulation model is composed of a flexible direct current power transmission model built according to actual engineering parameters, a grounding network parameter model built according to grounding impedance test data of the flexible direct current power transmission system and a lightning arrester electromagnetic transient model built according to lightning arrester parameters, and the built simulation model can be subjected to simulation calculation like a PSCAD model.
And 102, inputting the initial arc resistance into a simulation model for processing, and outputting the 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 according to field test conditions, such as the distance from the short circuit point on the transmission line to earth 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 as follows: for initial unipolar short-circuit current in-1(n is the number of iterations, i)n-1When the initial unipolar short-circuit current is obtained, n is 1), discretization is carried out, and the discretization is based on the initial unipolar short-circuit current in-1Calculating short circuit current estimated value In-1(ii) a Based on arc length l and short circuit current estimate In-1Calculating a new arc resistance RnInitial arc resistance R1Is 0. In particular, for the initial unipolar short-circuit current in-1Discretizing, sorting the discretized initial unipolar short-circuit current in ascending or descending order, eliminating the large value of certain amount (25%), eliminating the small value of certain amount (20%), averaging the rest initial unipolar short-circuit current to obtain estimated short-circuit current value In-1(ii) a Then, the product of the arc length l and a preset coefficient K is calculated, and the product is calculatedProduct and short circuit current estimation value In-1To obtain a new arc resistance RnNamely:
Rn＝K*l/In-1；
wherein, the preset coefficient K is 1080.4.
And 104, 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 the new unipolar short-circuit current converges or taking the new unipolar short-circuit current as the initial unipolar short-circuit current if the new unipolar short-circuit current does not converge, and returning to the 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 is converged, and if not, judging that the new unipolar short-circuit current is not converged. In the embodiment of the present application, the preset threshold is preferably 3%, that is: when (R)n-Rn-1)/Rn-1And when the current is less than or equal to 3%, judging that the new unipolar short-circuit current is converged, otherwise, judging that the new unipolar short-circuit current is not converged.
In one embodiment, when the new unipolar short-circuit current is judged to be converged, 1 is output, and when the new unipolar short-circuit current is judged to be not converged, 0 is output. When 1 is output, a new unipolar short-circuit current is finally output to obtain a fault current i, when the output is 0, the new unipolar short-circuit current is used as an initial unipolar short-circuit current, and the step 103 is returned to perform iterative calculation until the new unipolar short-circuit current converges, and the specific process can refer to fig. 2.
In the embodiment of the application, after a flexible direct power transmission model, a grounding network parameter model and a lightning arrester electromagnetic transient model are constructed, parameters of the flexible direct power transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model are checked so as to reduce errors between model parameters and actual operation parameters and ensure the accuracy of a simulation model operation result; the influence of the arc resistance on the unipolar short-circuit current is considered, the arc resistance and the simulation model are combined in an iterative mode until the unipolar short-circuit current converges, and the accuracy and the reliability of the calculation result are further guaranteed, so that the technical problems that in the prior art, due to the fact that parameters such as the ground resistance and the lightning arrester have large influence on the fault current, the error between the modeling parameters and the actual operation parameters is large, and the arc resistance is generated during actual direct-current side unipolar manual short-circuit fault testing, 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, and the following is an embodiment of a device for calculating a unipolar short-circuit current of a flexible dc power grid.
Referring to fig. 3, an apparatus for calculating a unipolar short-circuit current of a flexible dc power grid according to an embodiment of the present application includes:
the building unit 301 is configured to check parameters in the built flexible-direct power transmission model, the built grounding network parameter model and the built lightning arrester electromagnetic transient model to obtain a simulation model;
an input unit 302, configured to input the initial arc resistance into the simulation model for processing, and output an initial unipolar short-circuit current;
the calculation unit 303 is configured to calculate a new arc resistance based on the arc length and the initial unipolar short-circuit current, input the new arc resistance into the simulation model for processing, and output a new unipolar short-circuit current;
the determining unit 304 is configured to determine 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, use the new unipolar short-circuit current as the initial unipolar short-circuit current, and trigger the calculating unit 303.
As a further improvement, the calculating unit 303 specifically includes:
a processing sub-unit 3031, configured to perform discretization 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 for calculating a new arc resistance based on the arc length and the estimated value of the short circuit current;
and the input subunit 3033 is configured to input the new arc resistance into the simulation model for processing, and output a new unipolar short-circuit current.
As a further improvement, the calculating 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 estimated value of the short-circuit current to obtain the new arc resistance.
As a further improvement, the determining unit 304 is specifically configured to:
calculating the 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 is converged, outputting the new unipolar short-circuit current, otherwise, judging that the new unipolar short-circuit current is not converged, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and triggering a calculation unit.
The embodiment of the application also provides unipolar short-circuit current calculation equipment of the flexible direct-current power grid, and the equipment 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 unipolar short-circuit current calculation method of the flexible direct current grid in the aforementioned unipolar short-circuit current calculation method embodiment of the flexible direct current grid according to instructions in the program code.
The present application further provides a computer-readable storage medium, which is configured to store program codes, where the program codes are configured to execute the unipolar short-circuit current calculation method of the flexible direct current power grid in the foregoing unipolar short-circuit current calculation method embodiment of the flexible direct current power grid.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed 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 can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for executing all or part of the steps of the method described in the embodiments of the present application through a computer device (which may be a personal computer, a server, or a network device). And the aforementioned storage medium includes: a U disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (10)
1. A unipolar short-circuit current calculation method of a flexible direct current power grid is characterized by comprising the following steps:
s1, checking parameters in the constructed flexible direct power transmission model, the grounding network parameter model and the lightning arrester electromagnetic transient model to obtain a simulation model;
s2, inputting the initial arc resistance into the 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 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, if so, outputting the new unipolar short-circuit current, otherwise, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and returning to the step S3.
2. The method of calculating a unipolar short-circuit current of a flexible direct current power grid according to claim 1, wherein the calculating a new arc resistance based on an arc length and the initial unipolar short-circuit current comprises:
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 a new arc resistance based on the arc length and the short circuit current estimate.
3. The unipolar short-circuit current calculation method of a flexible direct current power grid according to claim 2, wherein the calculating a new arc resistance based on the arc length and the short-circuit current estimation value comprises:
and calculating the product of the arc length and a preset coefficient, and calculating the ratio of the product to the estimated value of the short-circuit current to obtain the new arc resistance.
4. The method according to claim 1, wherein the determining whether the new unipolar short-circuit current converges based on the new arc resistance and the initial arc resistance comprises:
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 is converged, and if not, judging that the new unipolar short-circuit current is not converged.
5. 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 power transmission model, the constructed grounding network parameter model and the constructed 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 the 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 the new unipolar short-circuit current converges or taking the new unipolar short-circuit current as the initial unipolar short-circuit current if the new unipolar short-circuit current does not converge, and triggering the calculating unit.
6. The unipolar short-circuit current calculation device of a flexible direct current power grid according to claim 5, characterized in that the calculation unit comprises in particular:
the processing subunit is used for 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 calculating subunit for calculating a new arc resistance based on the arc length and the estimated value of the short circuit current;
and the input subunit is used for inputting the new arc resistance into the simulation model for processing and outputting a new unipolar short-circuit current.
7. The single-pole short-circuit current calculation apparatus of a flexible direct current power grid according to claim 6, wherein the calculation 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 estimated value of the short-circuit current to obtain the new arc resistance.
8. The unipolar short-circuit current calculation device of the flexible direct current power grid according to claim 5, wherein the determination 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 is converged, outputting the new unipolar short-circuit current, otherwise, judging that the new unipolar short-circuit current is not converged, taking the new unipolar short-circuit current as the initial unipolar short-circuit current, and triggering the calculation unit.
9. A unipolar short-circuit current calculation device of a flexible direct current grid, characterized in that the device comprises 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 grid according to any one of claims 1-4 according to instructions in the program code.
10. A computer-readable storage medium, characterized in that the computer-readable storage medium is configured to store program code for performing the unipolar short-circuit current calculation method of the flexible direct current power grid of any one of claims 1-4.
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