A method and system for calculating line reactance from compensation voltage

Abstract

The application discloses a method and system for calculating line reactance according to compensation voltage. The method comprises the following steps: collecting three-phase currents and three-phase voltages on both sides of a line, and determining current sampling values and voltage sampling values on both sides of the line; determining voltage phasors and current phasors on both sides of the line according to the current sampling values and the voltage sampling values; determining phase compensation voltages on both sides of the line according to the voltage phasors and the current phasors on both sides of the line; and calculating line reactance according to the phase compensation voltages and the current phasors on both sides of the line. Thus, the protection method for calculating line reactance according to compensation voltage is not affected by the size of short-circuit current, and the sensitivity of protection during line internal fault can be improved.

Description

Technical Field

[0001] This invention relates to the field of [field], and more specifically, to a method and system for calculating line capacitive reactance based on compensation voltage. Background Technology

[0002] With the large-scale development of offshore wind power, using flexible DC systems to transmit offshore wind power and connect it to the onshore AC power grid is a typical scenario for the future transmission of offshore wind power.

[0003] The protection principle of AC submarine cable lines mainly adopts current differential protection. Its basic principle is based on Kirchhoff's current law. When an internal fault occurs in the submarine cable line, the differential current is greater than the braking current, and the line protection acts quickly and isolates the fault. When an external fault occurs in the submarine cable line, the differential current is less than the braking current, and the line protection does not operate.

[0004] Offshore wind power is collected through submarine cables and transmitted to the flexible DC system. When a fault occurs in the AC submarine cable line, the short-circuit current provided by the flexible DC system is relatively small. At the same time, the control strategy of the flexible DC system suppresses the negative sequence current after the fault. The short-circuit current provided by the wind turbine is affected by the control strategy, and the fault characteristics are significantly weakened. This results in a significant reduction in the operating current of the current differential protection of the submarine cable line. When the differential current is less than the braking current, the current differential protection will fail to operate, which seriously affects the fault identification capability of the current differential protection of the AC submarine cable line. Summary of the Invention

[0005] According to the present invention, a protection method and system for calculating line capacitive reactance based on compensation voltage are provided to solve the problem of insufficient ability of differential protection for AC transmission lines of offshore wind power through flexible direct transmission systems to identify internal faults, and to solve the technical problem of insufficient protection sensitivity after offshore wind power collects line faults through AC submarine cables.

[0006] According to a first aspect of the present invention, a method for calculating line capacitive reactance based on compensation voltage is provided, comprising:

[0007] Collect the three-phase current and three-phase voltage on both sides of the line, and determine the current sampling value and voltage sampling value on both sides of the line, wherein the two sides of the line include the m side and the n side;

[0008] Based on the current and voltage sample values, the m-side voltage phasors on both sides of the line are determined by Fourier transform. n-side voltage phasor m-side current phasor and n-side current phasor

[0009] Based on the m-side voltage phasors on both sides of the line n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on both sides of the line. and n-side phase compensation voltage And according to the phase compensation voltage on the m side and n-side phase compensation voltage Determine the phase compensation voltage

[0010] According to the phase compensation voltage m-side current phasor and n-side current phasor Calculate the line capacitive reactance Z c .

[0011] Optionally, based on the m-side voltage phasors on both sides of the line. n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on both sides of the line. and n-side phase compensation voltage include:

[0012] The formula for calculating the compensation voltage on the m-side is as follows:

[0013] The formula for calculating the compensation voltage on the n-side phase is as follows:

[0014] Where k is the zero-order compensation coefficient, Z set This is the set impedance.

[0015] Optionally, based on the phase compensation voltage m-side current phasor and n-side current phasor Calculate the line capacitive reactance Z c ,include:

[0016] Calculate the line capacitive reactance Z using the following formula. c

[0017]

[0018] in For phase compensation voltage;

[0019] If the line capacitance Z c The protection will activate when the capacitance is less than a certain multiple of the total length of the line.

[0020] If the line capacitance Z c When the capacitance is several times greater than the total length of the line, the protection will not operate.

[0021] Optionally, it also includes:

[0022] According to the m-side current phasor and n-side current phasor Determine and current

[0023] If the current The threshold value I of the current is greater than that of the current. set According to the voltage phasor on the m side n-side voltage phasor m-side current phasor and side current phasors m-side phase compensation voltage and n-side phase compensation voltage Selecting the compensation voltage: Comparison and The phase relationship between them, where if and Phase in On the same side, the compensation voltage is like and Phase in On both sides, the compensation voltage is like or Amplitude is 0, select or To compensate for voltage;

[0024] If the current Less than and current threshold value I set According to the voltage phasor on the m side m-side current phasor Select compensation voltage:

[0025] Optionally, based on the m-side current phasor and n-side current phasor Determine and current include:

[0026] According to the m-side current phasor and n-side current phasor The formula for determining the current is as follows:

[0027] According to another aspect of the present invention, a system for calculating line capacitive reactance based on compensation voltage is also provided, comprising:

[0028] The sampling value acquisition module is used to acquire the three-phase current and three-phase voltage on both sides of the line, and determine the current sampling value and voltage sampling value on both sides of the line, wherein the two sides of the line include the m side and the n side;

[0029] The phasor determination module is used to determine the m-side voltage phasors on both sides of the line based on the current and voltage sample values ​​through Fourier transform. n-side voltage phasor m-side current phasor and n-side current phasor

[0030] The phase compensation voltage module is used to determine the phase compensation voltage phasors based on the m-side voltage phasors on both sides of the line. n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on both sides of the line. and n-side phase compensation voltage And according to the phase compensation voltage on the m side and n-side phase compensation voltage Determine the phase compensation voltage

[0031] The line capacitive reactance calculation module is used to calculate the phase compensation voltage. m-side current phasor and n-side current phasor Calculate the line capacitive reactance Z c .

[0032] Optionally, the phase compensation voltage module is determined, including:

[0033] The m-phase compensation voltage submodule is used to determine the calculation formula for the m-phase compensation voltage:

[0034] The n-phase compensation voltage submodule is used to determine the calculation formula for the n-phase compensation voltage:

[0035] Where k is the zero-order compensation coefficient, Z set This is the set impedance.

[0036] Optionally, the line capacitance calculation module includes:

[0037] The line capacitance calculation submodule is used to calculate the line capacitance Z according to the following formula. c

[0038]

[0039] in For phase compensation voltage;

[0040] The protection action submodule is used to address the issue of line capacitance Z. c The protection will activate when the capacitance is less than a certain multiple of the total length of the line.

[0041] The non-operating protection submodule is used to protect against line capacitance Z. c When the capacitance is several times greater than the total length of the line, the protection will not operate.

[0042] Optionally, it also includes:

[0043] Determine and current modules, used to determine based on the m-side current phasors and n-side current phasor Determine and current

[0044] The first selection is a compensation voltage module, used if the sum and current... The threshold value I of the current is greater than that of the current. set According to the voltage phasor on the m side n-side voltage phasor m-side current phasor and side current phasors m-side phase compensation voltage and n-side phase compensation voltage Selecting the compensation voltage: Comparison and The phase relationship between them, where if and Phase in On the same side, the compensation voltage is like and Phase in On both sides, the compensation voltage is like or Amplitude is 0, select or To compensate for voltage;

[0045] The second selection compensation voltage module is used to, if the sum and current... Less than and current threshold value I set According to the voltage phasor on the m side m-side current phasor Select compensation voltage:

[0046] Optionally, the determination and current module includes:

[0047] Determine and current submodules for determining the current based on the m-side current phasor. and n-side current phasor The formula for determining the current is as follows:

[0048] Therefore, the protection method using compensation voltage to calculate line capacitive reactance is unaffected by the magnitude of the short-circuit current, which can improve the sensitivity of protection during internal line faults. Since the capacitive reactance characteristics of cable lines differ significantly before and after a fault, and during internal and external faults, the reliability of protection can also be considered during external faults. The operating performance of this invention patent is explained by comparing it with conventional current differential protection criteria. Attached Figure Description

[0049] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0050] Figure 1 This is a flowchart illustrating a protection method for calculating line capacitive reactance based on compensation voltage according to this embodiment.

[0051] Figure 2 This is a schematic diagram of the AC line protection installation for the offshore wind power transmission system via flexible direct current transmission as described in this embodiment.

[0052] Figure 3 This is a schematic diagram of the protection process for calculating line capacitive reactance using compensation voltage according to this embodiment.

[0053] Figure 4 This is a schematic diagram of a protection system for calculating line capacitive reactance based on compensation voltage according to this embodiment. Detailed Implementation

[0054] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0055] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0056] According to a first aspect of the present invention, a method 100 for calculating line capacitive reactance based on compensation voltage is provided, with reference to... Figure 1 As shown, the method 100 includes:

[0057] S101: Collect the three-phase current and three-phase voltage on both sides of the line, and determine the current sampling value and voltage sampling value on both sides of the line, wherein the two sides of the line include the m side and the n side;

[0058] S102: Based on the current and voltage sample values, determine the m-side voltage phasors on both sides of the line using Fourier transform. n-side voltage phasor m-side current phasor and n-side current phasor

[0059] S103: Based on the m-side voltage phasors on both sides of the line n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on both sides of the line. and n-side phase compensation voltage And according to the phase compensation voltage on the m side and n-side phase compensation voltage Determine the phase compensation voltage

[0060] S104: According to the phase compensation voltage m-side current phasor and n-side current phasor Calculate the line capacitive reactance Z c .

[0061] Specifically, the following examples illustrate this:

[0062] (1)Reference Figure 2 and Figure 3 As shown, the AC submarine cable line protection device is installed on both sides of the submarine cable line. The protection device collects the three-phase current and three-phase voltage on both sides of the submarine cable line through current transformers and voltage transformers, and sends the current and voltage sampling values ​​on this side to the protection device on the opposite side of the line.

[0063] (2) The protection device will collect the current and voltage sample values ​​and calculate the current and voltage phasors through Fourier transform;

[0064] (3) Calculate the sum of the currents using the current phasors on both sides of the line. The formula for calculating the sum of the currents is: In the formula, These are the phasors of the current phases on both sides of the line.

[0065] (4) Calculate the phase compensation voltage using the voltage phasors and current phasors on both sides of the line. The formula for calculating the phase compensation voltage is: In the formula, These are the compensation voltages for each phase on both sides of the line. These are the phase voltages on both sides of the line. These are the zero-sequence currents on both sides of the line, where k is the zero-sequence compensation coefficient, and Z is the zero-sequence current. set This is the set impedance.

[0066] (5) If the current Greater than I set ,Compare and The phase relationship between them, if and Phase in On the same side, the compensation voltage is Calculating line capacitive reactance using compensation voltage and current

[0067] (6) If the current Greater than I set ,Compare and The phase relationship between them, if and Phase in On both sides, the compensation voltage is Calculating line capacitive reactance using compensation voltage and current If the line capacitance Z c The protection trips when the line capacitance is less than 0.9 times the total length of the line; if the line capacitance is less than 0.9 times the total length of the line capacitance, the protection trips. c When the capacitance is greater than 0.9 times the total length of the line, the protection will not operate.

[0068] (7) If the current Greater than I set , Amplitude is 0, select To compensate for the voltage, the line capacitive reactance is calculated using the compensation voltage and current. If the line capacitance Z c The protection trips when the line capacitance is less than 0.9 times the total length of the line; if the line capacitance is less than 0.9 times the total length of the line capacitance, the protection trips. c When the capacitance is greater than 0.9 times the total length of the line, the protection will not operate.

[0069] (8) If the current Greater than I set , Amplitude is 0, select To compensate for the voltage, the line capacitive reactance is calculated using the compensation voltage and current. If the line capacitance Z c The protection trips when the line capacitance is less than 0.9 times the total length of the line; if the line capacitance is less than 0.9 times the total length of the line capacitance, the protection trips. c When the capacitance is greater than 0.9 times the total length of the line, the protection will not operate.

[0070] (9) If the current Less than I set Select To compensate for the voltage, the line capacitive reactance is calculated using the compensation voltage and current. in For phase compensation voltage, if the line capacitive reactance Z c The protection trips when the line capacitance is less than 0.9 times the total length of the line; if the line capacitance is less than 0.9 times the total length of the line capacitance, the protection trips. c When the capacitance is greater than 0.9 times the total length of the line, the protection will not operate.

[0071] Therefore, the protection method using compensation voltage to calculate line capacitive reactance is unaffected by the magnitude of the short-circuit current, which can improve the sensitivity of protection during internal line faults. Since the capacitive reactance characteristics of cable lines differ significantly before and after a fault, and during internal and external faults, the reliability of protection can also be considered during external faults. The operating performance of this invention patent is explained by comparing it with conventional current differential protection criteria.

[0072] Optionally, based on the m-side voltage phasors on both sides of the line. n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on both sides of the line. and n-side phase compensation voltage include:

[0073] The formula for calculating the compensation voltage on the m-side is as follows:

[0074] The formula for calculating the compensation voltage on the n-side phase is as follows:

[0075] Where k is the zero-order compensation coefficient, Z se t is the set impedance.

[0076] Optionally, based on the phase compensation voltage m-side current phasor and n-side current phasor Calculate the line capacitive reactance Z c ,include:

[0077] Calculate the line capacitive reactance Z using the following formula. c

[0078]

[0079] in For phase compensation voltage;

[0080] If the line capacitance Z c The protection will activate when the capacitance is less than a certain multiple of the total length of the line.

[0081] If the line capacitance Z c When the capacitance is several times greater than the total length of the line, the protection will not operate.

[0082] Optionally, it also includes:

[0083] According to the m-side current phasor and n-side current phasor Determine and current

[0084] If the current The threshold value I of the current is greater than that of the current. set According to the voltage phasor on the m side n-side voltage phasor m-side current phasor and side current phasors m-side phase compensation voltage and n-side phase compensation voltage Selecting the compensation voltage: Comparison and The phase relationship between them, where if and Phase in On the same side, the compensation voltage is like and Phase in On both sides, the compensation voltage is like or Amplitude is 0, select or To compensate for voltage;

[0085] If the current Less than and current threshold value I set According to the voltage phasor on the m side m-side current phasor Select compensation voltage:

[0086]

[0087] Optionally, based on the m-side current phasor and n-side current phasor Determine and current include:

[0088] According to the m-side current phasor and n-side current phasor The formula for determining the current is as follows:

[0089] According to another aspect of the invention, reference Figure 4 As shown, a system 400 for calculating line capacitive reactance based on compensation voltage is also provided, comprising:

[0090] The sampling value acquisition module 410 is used to acquire the three-phase current and three-phase voltage on both sides of the line, and determine the current sampling value and voltage sampling value on both sides of the line, wherein the two sides of the line include the m side and the n side;

[0091] The phasor module 420 is used to determine the m-side voltage phasors on both sides of the line by means of Fourier transform based on the current and voltage sample values. n-side voltage phasor m-side current phasor and n-side current phasor

[0092] The phase compensation voltage module 430 is used to determine the phase compensation voltage phasor based on the m-side voltage phasors on both sides of the line. n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on both sides of the line. and n-side phase compensation voltage And according to the phase compensation voltage on the m side and n-side phase compensation voltage Determine the phase compensation voltage

[0093] The line capacitive reactance calculation module 440 is used to calculate the phase compensation voltage based on the phase compensation voltage. m-side current phasor and n-side current phasor Calculate the line capacitive reactance Z c .

[0094] Optionally, the phase compensation voltage module 430 is defined as including:

[0095] The m-phase compensation voltage submodule is used to determine the calculation formula for the m-phase compensation voltage:

[0096] The n-phase compensation voltage submodule is used to determine the calculation formula for the n-phase compensation voltage:

[0097] Where k is the zero-order compensation coefficient, Z set This is the set impedance.

[0098] Optionally, the line capacitance calculation module 440 includes:

[0099] The line capacitance calculation submodule is used to calculate the line capacitance Z according to the following formula. c

[0100]

[0101] in For phase compensation voltage;

[0102] The protection action submodule is used to address the issue of line capacitance Z. c The protection will activate when the capacitance is less than a certain multiple of the total length of the line.

[0103] The non-operating protection submodule is used to protect against line capacitance Z. c When the capacitance is several times greater than the total length of the line, the protection will not operate.

[0104] Optionally, the system 400 also includes:

[0105] Determine and current modules, used to determine based on the m-side current phasors and n-side current phasor Determine and current

[0106] The first selection is a compensation voltage module, used if the sum and current... The threshold value I of the current is greater than that of the current. set According to the voltage phasor on the m side n-side voltage phasor m-side current phasor and side current phasors m-side phase compensation voltage and n-side phase compensation voltage Selecting the compensation voltage: Comparison and The phase relationship between them, where if and Phase in On the same side, the compensation voltage is like and Phase in On both sides, the compensation voltage is like or Amplitude is 0, select or To compensate for voltage;

[0107] The second selection compensation voltage module is used to, if the sum and current... Less than and current threshold value I set According to the voltage phasor on the m side m-side current phasor Select compensation voltage:

[0108]

[0109] Optionally, the determination and current module includes:

[0110] Determine and current submodules for determining the current based on the m-side current phasor. and n-side current phasor The formula for determining the current is as follows:

[0111] The system 400 for calculating line capacitive reactance based on compensation voltage according to an embodiment of the present invention corresponds to the protection method 100 for calculating line capacitive reactance based on compensation voltage according to another embodiment of the present invention, and will not be described again here.

[0112] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0113] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0114] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0115] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0116] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0117] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for calculating line capacitive reactance based on compensation voltage, characterized in that, include: Collect the three-phase current and three-phase voltage on both sides of the line, and determine the current sampling value and voltage sampling value on both sides of the line, wherein the two sides of the line include the m side and the n side; Based on the current and voltage sample values, the m-side voltage phasors on both sides of the line are determined by Fourier transform. n-side voltage phasor m-side current phasor and n-side current phasor ; Based on the m-side voltage phasors on both sides of the line n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on the m side of both sides of the line. and n-side phase compensation voltage And according to the phase compensation voltage on the m side and n-side phase compensation voltage Determine the phase compensation voltage ; According to the phase compensation voltage m-side current phasor and n-side current phasor Calculate the line capacitance ; Also includes: According to the m-side current phasor and n-side current phasor Determine and current ; If the current Greater than the threshold value of current According to the voltage phasor on the m side n-side voltage phasor m-side current phasor and side current phasors m-side phase compensation voltage and n-side phase compensation voltage Selecting the compensation voltage: Comparison and , The phase relationship between them, where if and Phase in On the same side, the compensation voltage is ;like and Phase in On both sides, the compensation voltage is ;like or Amplitude is 0, select or To compensate for voltage; If the current Less than and current threshold value According to the voltage phasor on the m side m-side current phasor Select the compensation voltage: .

2. The method according to claim 1, characterized in that, Based on the m-side voltage phasors on both sides of the line n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on the m side of both sides of the line. and n-side phase compensation voltage ,include: The formula for calculating the compensation voltage on the m-side is as follows: ; The formula for calculating the compensation voltage on the n-side phase is as follows: ; in, The zero-order compensation coefficient is... This is the set impedance.

3. The method according to claim 1, characterized in that, According to the phase compensation voltage m-side current phasor and n-side current phasor Calculate the line capacitance ,include: Calculate the line capacitive reactance using the following formula. in For phase compensation voltage; If the line capacitance The protection will activate when the capacitance is less than a certain multiple of the total length of the line. If the line capacitance When the capacitance is several times greater than the total length of the line, the protection will not operate.

4. The method according to claim 1, characterized in that, According to the m-side current phasor and n-side current phasor Determine and current ,include: According to the m-side current phasor and n-side current phasor The formula for determining the current is as follows: .

5. A system for calculating line capacitive reactance based on compensation voltage, characterized in that, include: The sampling value acquisition module is used to acquire the three-phase current and three-phase voltage on both sides of the line, and determine the current sampling value and voltage sampling value on both sides of the line, wherein the two sides of the line include the m side and the n side; The phasor determination module is used to determine the m-side voltage phasors on both sides of the line based on the current and voltage sample values ​​through Fourier transform. n-side voltage phasor m-side current phasor and n-side current phasor ; The phase compensation voltage module is used to determine the phase compensation voltage phasors based on the m-side voltage phasors on both sides of the line. n-side voltage phasor m-side current phasor and n-side current phasor Determine the phase compensation voltage on the m side of both sides of the line. and n-side phase compensation voltage And according to the phase compensation voltage on the m side and n-side phase compensation voltage Determine the phase compensation voltage ; The line capacitive reactance calculation module is used to calculate the phase compensation voltage. m-side current phasor and n-side current phasor Calculate the line capacitance ; Also includes: Determine and current modules, used to determine based on the m-side current phasors and n-side current phasor Determine and current ; The first selection is a compensation voltage module, used if the sum and current... Greater than the threshold value of current According to the voltage phasor on the m side n-side voltage phasor m-side current phasor and side current phasors m-side phase compensation voltage and n-side phase compensation voltage Selecting the compensation voltage: Comparison and , The phase relationship between them, where if and Phase in On the same side, the compensation voltage is ;like and Phase in On both sides, the compensation voltage is ;like or Amplitude is 0, select or To compensate for voltage; The second selection compensation voltage module is used to, if the sum and current... Less than and current threshold value According to the voltage phasor on the m side m-side current phasor Select the compensation voltage: .

6. The system according to claim 5, comprising a phase compensation voltage determination module, including: The m-phase compensation voltage submodule is used to determine the calculation formula for the m-phase compensation voltage: ; The n-phase compensation voltage submodule is used to determine the calculation formula for the n-phase compensation voltage: ; in, The zero-order compensation coefficient is... This is the set impedance.

7. The system according to claim 5, characterized in that, The module for calculating line capacitive reactance includes: The line capacitance calculation submodule is used to calculate the line capacitance according to the following formula. in For phase compensation voltage; The protection action submodule is used to protect the line capacitance. The protection will activate when the capacitance is less than a certain multiple of the total length of the line. The non-operating protection submodule is used to protect against line capacitance. When the capacitance is several times greater than the total length of the line, the protection will not operate.

8. The system according to claim 5, characterized in that, Determine and current modules, including: Determine and current submodules for determining the current based on the m-side current phasor. and n-side current phasor The formula for determining the current is as follows: .

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