A short-circuit current suppression method and device, a power flow controller and a medium

Abstract

The application discloses a short-circuit current suppression method and device, a power flow controller and a medium, and belongs to the field of power systems and their automation. The method is as follows: when a first power grid line in which a short-circuit fault occurs is detected, electrical signals of each power grid line are collected; according to the electrical signals, a first voltage phase of an equivalent fault power source corresponding to the first power grid line is calculated; according to the first voltage phase, a first series power flow regulation module connected with the first power grid line is controlled to output a first suppression alternating-current voltage to the first power grid line; wherein a second voltage phase of the first suppression alternating-current voltage is opposite to the first voltage phase. Therefore, by implementing the application, the problem of poor short-circuit current suppression effect in the prior art can be solved.

Description

Technical Field

[0001] This application relates to the field of power systems and their automation, and in particular to a short-circuit current suppression method, device, power flow controller and medium. Background Technology

[0002] Power flow controllers, as key power electronic devices for regulating power flow in power lines, have power semiconductor devices that are extremely sensitive to overcurrent. When a short-circuit fault occurs in the power grid, the huge short-circuit current can seriously threaten the safety of the equipment, and may even lead to damage to the entire device and an expansion of the fault area. Therefore, effectively suppressing short-circuit current under short-circuit fault conditions is crucial.

[0003] Existing short-circuit current suppression solutions mainly fall into two categories: adding dedicated current-limiting equipment and bypassing the entire power flow controller. Adding dedicated current-limiting equipment requires additional space, resulting in high investment costs and increased system operating losses. While bypassing protects the equipment itself, it is a passive withdrawal; the power flow controller completely loses its ability to regulate and support the power grid during a fault, unable to actively participate in short-circuit current suppression, and has a long recovery time after the fault is cleared. For the recently proposed delta-type transformerless unified power flow controller, the need for short-circuit current suppression is even more urgent because the natural limiting effect of the short-circuit impedance provided by the traditional transformer on fault current is eliminated. However, none of the above solutions utilize the power flow controller's own voltage output capability to actively suppress short-circuit current, resulting in poor short-circuit current suppression performance. Summary of the Invention

[0004] This application provides a short-circuit current suppression method, device, power flow controller, and medium, which can solve the problem of poor short-circuit current suppression effect in the prior art.

[0005] This application provides a short-circuit current suppression method in some embodiments, applied to a power flow controller. The power flow controller includes: a plurality of series power flow regulation modules, each of which is connected to a power grid line; the short-circuit current suppression method includes: When a short-circuit fault is detected in the first power grid line, electrical signals of each of the power grid lines are collected; Based on each of the electrical signals, calculate the first voltage phase of the equivalent fault power source corresponding to the first power grid line; Based on the first voltage phase, the first series power flow regulation module connected to the first power grid line is controlled to output a first suppressed AC voltage to the first power grid line; wherein, the second voltage phase of the first suppressed AC voltage is opposite to the first voltage phase.

[0006] Compared with existing technologies, the above embodiments have the following advantages: When a short-circuit fault is detected in the first power grid line, the electrical signals of each power grid line are collected, the first voltage phase of the equivalent fault power source corresponding to the first power grid line is calculated, and then the first series power flow regulation module connected to the fault line is controlled to output a first suppression AC voltage opposite to the first voltage phase. By outputting a voltage opposite to the equivalent fault power source, the voltage component driving the short-circuit current is actively canceled, thereby achieving active suppression of the short-circuit current. Compared with the existing technology that adds a dedicated current limiting device or bypasses the entire power flow controller, this application makes full use of the voltage output capability of the power flow controller itself, and can achieve active and effective short-circuit current suppression during a fault without adding additional primary equipment. It has the advantages of low cost, fast response, and good suppression effect.

[0007] Further, the step of calculating the first voltage phase of the equivalent fault power source corresponding to the first power grid line based on each of the electrical signals includes: Identify at least one second power grid line that has not experienced a short-circuit fault from the aforementioned power grid lines; Based on the electrical signal, determine the power supply voltage vector and line impedance of the second power grid line, as well as the first equivalent impedance between the fault point of the first power grid line and the grid connection point of the power flow controller. The first voltage phase of the equivalent fault power source generated by the short-circuit current on the first power line is calculated based on the power supply voltage vector of each of the second power lines, the line impedance of each of the second power lines, and the first equivalent impedance.

[0008] Compared to existing technologies, the above embodiments have the following advantages: By identifying a second, fault-free power grid line from the existing power grid lines, the voltage phase of the equivalent faulty power source is calculated based on its power supply voltage vector, line impedance, and the equivalent impedance of the faulty line. This application transforms the complex multi-port power grid fault analysis problem into an equivalent calculation problem based on circuit parameters. Since the calculation process is based on the actual collected electrical signals of the non-faulty lines and system impedance parameters, it can accurately reflect the current fault state of the power grid, providing a precise phase reference for the subsequent output of the reverse-phase suppression voltage, thus ensuring the accuracy and effectiveness of short-circuit current suppression.

[0009] Further, the step of calculating the first voltage phase of the equivalent fault power source generated by the short-circuit current on the first power grid line based on the power supply voltage vector of each of the second power grid lines, the line impedance of each of the second power grid lines, and the first equivalent impedance includes: Divide the power supply voltage vector of each of the second power grid lines by the corresponding line impedance to obtain the current component of each of the second power grid lines. Summing up all the current components of the second power grid line yields the short-circuit current vector injected into the first power grid line. Calculate the second equivalent impedance of the first power grid line based on the first equivalent impedance and the line impedance of each of the second power grid lines; Multiply the short-circuit current vector by the second equivalent impedance of the first power grid line to obtain the voltage vector of the equivalent fault power source; The phase angle is extracted from the voltage vector of the equivalent fault power source to obtain the first voltage phase.

[0010] Compared with the prior art, the above embodiments have the following advantages: Based on the principle of circuit superposition and Ohm's law, the current component is obtained by dividing the power supply voltage vector of each non-faulty line by the line impedance, the total short-circuit current vector is obtained by summing the components, and then multiplied by the equivalent impedance of the faulty line to obtain the voltage vector of the equivalent faulty power supply. Finally, the phase angle is extracted. This is easy to program and implement in the controller, has high computational efficiency, and can meet the time requirements for rapid response under fault conditions.

[0011] Further, the step of controlling the first series power flow regulation module connected to the first power grid line to output a first suppressed AC voltage to the first power grid line according to the first voltage phase includes: Determine a second voltage phase that is opposite to the first voltage phase, and use the second voltage phase as the output phase of the first suppressed AC voltage; The output amplitude of the first suppressed AC voltage is determined based on the current withstand limit of the power devices in the first series power flow regulation module. The first series power flow regulation module is controlled to output a first suppressed AC voltage having the output phase and the output amplitude.

[0012] Compared with existing technologies, the above embodiments have the following advantages: On the one hand, the output phase of the suppressed AC voltage is determined to be opposite to the phase of the equivalent fault power supply to achieve maximum voltage cancellation effect; on the other hand, the output amplitude of the suppressed AC voltage is determined according to the current withstand limit of the power device, and the output voltage is increased as much as possible while ensuring device safety, thereby maximizing the short-circuit current suppression capability and achieving directional and quantitative suppression of short-circuit current. The output inverse voltage ensures the correctness of the suppression direction, and the maximum output amplitude constrained by the current withstand limit fully taps the voltage output potential of the device itself, achieving the optimal suppression effect without increasing hardware costs.

[0013] Furthermore, the power flow controller further includes: a plurality of power balancing adjustment modules and a delta-connected parallel converter, one end of each power balancing adjustment module being connected to one of the series power flow adjustment modules, and the other end of each power balancing adjustment module being connected to the parallel converter; the step of outputting a first suppressed AC voltage to the first grid line includes: Control the power balance adjustment module corresponding to the first series power flow adjustment module to output a preset first and third harmonic voltage; Based on the first and third harmonic voltages, the parallel converter is controlled to output the second and third harmonic voltages to generate circulating current in the loop formed by the parallel converter and the power balance adjustment module. Through the interaction between the circulating current and the first third harmonic voltage, energy is transferred from the DC bus of the first series power flow regulation module to the parallel converter, so as to maintain the energy balance inside the first series power flow regulation module.

[0014] Compared to existing technologies, the above embodiments have the following advantages: By introducing a power balance regulation module and a delta-connected parallel converter, the power balance regulation module is controlled to output a preset first and third harmonic voltage, and then the parallel converter is controlled to output a second and third harmonic voltage. A circulating current is generated in the loop formed by these two components. The interaction between the circulating current and the first and third harmonic voltages transfers energy from the DC bus to the parallel converter. This solves the problem that energy on the DC bus may continuously accumulate and lead to voltage runaway when the series side outputs suppression voltage under fault conditions. Active energy transfer is achieved through the injection of third harmonic circulating current, maintaining energy balance and stable operation on the series side while avoiding interference from the third harmonic on the fundamental frequency power control. This ensures the safe and stable operation of the device during fault suppression, making the active short-circuit current suppression strategy practical in engineering applications.

[0015] Further, controlling the parallel converter to output a second or third harmonic voltage based on the first third harmonic voltage includes: Obtain the DC bus voltage of the first series power flow regulation module, and calculate the voltage deviation between the DC bus voltage and the preset DC bus voltage reference value; Based on the voltage deviation, determine the target amplitude of the circulating current required; Based on the target amplitude of the circulating current and the first third harmonic voltage, the second third harmonic voltage that the parallel converter needs to output is determined, and the parallel converter is controlled to output the second third harmonic voltage.

[0016] Compared to existing technologies, the above embodiments have the following advantages: By acquiring the DC bus voltage and calculating its deviation from a reference value, the target amplitude of the circulating current is determined based on the deviation, and then the second and third harmonic voltages are determined by combining the amplitude and phase of the first and third harmonic voltages. Using the DC bus voltage deviation as feedback, the circulating current is dynamically adjusted through closed-loop control, achieving precise control of energy balance. When the voltage deviation is large, the circulating current increases to accelerate energy transfer; when the deviation is small, the circulating current decreases to reduce losses. The control strategy has adaptive capabilities, automatically adjusting the energy balance intensity under different fault conditions, balancing control accuracy and system efficiency.

[0017] Furthermore, when a short-circuit fault is detected in the first power grid line, it also includes: Identify the second power grid line that has not experienced a short circuit fault, and obtain the power supply voltage phase of the second power grid line; The second series power flow regulation module connected to the second power grid line outputs a second suppression AC voltage that is out of phase with the power supply voltage of the second power grid line, so as to suppress the short-circuit current flowing from the second power grid line to the first power grid line.

[0018] Compared to existing technologies, the above embodiments have the following beneficial effects: By identifying a second power grid line that has not experienced a fault and obtaining its power supply voltage phase, the second series power flow regulation module connected to this faultless line is controlled to output a second suppression AC voltage that is out of phase with the power supply voltage of the faultless line. This extends short-circuit current suppression from the faulty line side to the faultless line side, suppressing the short-circuit current component flowing from the faultless line to the fault point at its source. Through coordinated control of the faulty line side and the faultless line side, bidirectional suppression of short-circuit current is achieved. On the one hand, the driving voltage of the equivalent fault power source is canceled on the faulty line side; on the other hand, the outflow of short-circuit current is suppressed on the faultless line side. The combination of these two measures maximizes the suppression effect of short-circuit current, further improving the comprehensiveness and effectiveness of fault suppression.

[0019] Another embodiment of this application provides a short-circuit current suppression device applied to a power flow controller. The power flow controller includes: a plurality of series power flow regulation modules, each of which is connected to a power grid line. The short-circuit current suppression device includes: a data acquisition module, a calculation module, and a control module. The acquisition module is used to acquire electrical signals of each of the power grid lines when a short-circuit fault is detected in the first power grid line. The calculation module is used to calculate the first voltage phase of the equivalent fault power supply corresponding to the first power grid line based on each of the electrical signals. The control module is configured to control the first series power flow regulation module connected to the first power grid line to output a first suppressed AC voltage to the first power grid line according to the first voltage phase; wherein, the second voltage phase of the first suppressed AC voltage is opposite to the first voltage phase.

[0020] Another embodiment of this application also provides a power flow controller, which includes: a plurality of series power flow regulation modules, wherein the series power flow regulation modules are controlled by the short-circuit current suppression method of this application.

[0021] Another embodiment of this application also provides a computer-readable storage medium item, including: a stored computer program, which, when the computer program is running, controls the device where the computer-readable storage medium is located to perform steps such as the short-circuit current suppression method of this application. Attached Figure Description

[0022] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating a short-circuit current suppression method provided in some embodiments of this application; Figure 2 This is a schematic diagram of the structure of a power flow controller provided in some embodiments of this application; Figure 3 This is a schematic diagram of the structure of a short-circuit current suppression device provided in some embodiments of this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0030] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0031] Existing short-circuit current suppression solutions mainly fall into two categories: adding dedicated current-limiting equipment and bypassing the entire power flow controller. Adding dedicated current-limiting equipment requires additional space, resulting in high investment costs and increased system operating losses. While bypassing protects the equipment itself, it is a passive withdrawal; the power flow controller completely loses its ability to regulate and support the power grid during a fault, unable to actively participate in short-circuit current suppression, and has a long recovery time after the fault is cleared. For the recently proposed delta-type transformerless unified power flow controller, the need for short-circuit current suppression is even more urgent because the natural limiting effect of the short-circuit impedance provided by the traditional transformer on fault current is eliminated. However, none of the above solutions utilize the power flow controller's own voltage output capability to actively suppress short-circuit current, resulting in poor short-circuit current suppression performance.

[0032] Please refer to Figure 1 To address the problem of poor short-circuit current suppression in existing technologies, this application provides a short-circuit current suppression method applied to a power flow controller. The power flow controller includes several series-connected power flow regulation modules, each of which is connected to a power grid line.

[0033] refer to Figure 2 This is a schematic diagram of a power flow controller provided in some embodiments of this application. The power flow controller includes a series side and a parallel side. The series side includes several series power flow control modules (PFCMs) and several power balance control modules (PBCMs). Each series power flow control module is connected to a corresponding power grid line through an AC port, used to regulate the power flow of the line during normal operation and to suppress AC voltage during faults. Structurally, each series power flow control module and each power balance control module is a single-phase modular multilevel converter bridge arm, consisting of upper and lower bridge arms. Each bridge arm is composed of multiple cascaded half-bridge sub-modules (HBSMs). The parallel side includes a delta-connected parallel converter (CMI) for providing reactive power compensation to the system. Each phase of the parallel converter is composed of multiple cascaded full-bridge sub-modules (FBSMs). Each power balance regulation module is connected at one end to the DC bus of a series power flow regulation module and at the other end to a parallel converter, thereby establishing an energy transmission channel between the series and parallel sides. The parallel converter adopts a delta connection structure, which can provide a closed loop for the injection of third harmonic circulating current, enabling the device to maintain the energy balance inside the series power flow regulation module through circulating current injection in the event of a fault.

[0034] Furthermore, in some embodiments of this application, the short-circuit current suppression method includes the following steps S101 to S103: S101: When a short-circuit fault is detected in the first power grid line, the electrical signals of each of the power grid lines are collected.

[0035] In some embodiments of this application, when a short-circuit fault occurs in the power grid, the voltage and current signals of each power grid line are first acquired in real time through voltage transformers and current transformers installed at each line port. After the fault occurs, the power flow controller determines whether the current amplitude flowing through each series power flow regulating module exceeds a preset short-circuit threshold based on the acquired current signal, thereby identifying the first power grid line where the short-circuit fault occurred. At the same time, the power flow controller also needs to determine whether the short-circuit current amplitude is within the safe tolerance range of the power semiconductor device. If the short-circuit current exceeds the maximum value that the device can withstand, the AC port of the corresponding series power flow regulating module is bypassed through the thyristor bypass switch, allowing the fault current to flow through the bypass switch to protect the power device from damage. If it is determined that the short-circuit current is within the current tolerance range of the device, the bypass protection is not triggered, but the series power flow regulating module continues to be connected to the power grid, and active suppression control is initiated. At this time, in addition to acquiring the current amplitude information of the faulty line itself, the controller also needs to synchronously acquire the voltage and current signals of each non-faulty line, specifically including the instantaneous values ​​of the three-phase voltage and current at the grid connection point of each line. The collected voltage and current signals, after analog-to-digital conversion, are sent to the controller's arithmetic unit for subsequent calculation of the voltage phase of the equivalent fault power source corresponding to the faulty line, and to determine the amplitude and phase of the suppressed AC voltage to be output by the series power flow regulation module. It should be noted that electrical signals from all lines, not just the faulty line, are collected because the short-circuit current of the faulty line is essentially fed in by the non-faulty lines through the electrical connection of the power flow controller. Therefore, it is necessary to obtain the power supply voltage and line impedance information of the non-faulty lines to accurately calculate the phase of the equivalent fault power source driving the short-circuit current, thus providing a correct phase reference for the subsequent output of the anti-phase suppression voltage.

[0036] S102: Calculate the first voltage phase of the equivalent fault power supply corresponding to the first power grid line based on each of the electrical signals.

[0037] Furthermore, in some embodiments of this application, the step of calculating the first voltage phase of the equivalent fault power supply corresponding to the first power grid line based on each of the electrical signals includes: Identify at least one second power grid line that has not experienced a short-circuit fault from the aforementioned power grid lines; Based on the electrical signal, determine the power supply voltage vector and line impedance of the second power grid line, as well as the first equivalent impedance between the fault point of the first power grid line and the grid connection point of the power flow controller. The first voltage phase of the equivalent fault power source generated by the short-circuit current on the first power line is calculated based on the power supply voltage vector of each of the second power lines, the line impedance of each of the second power lines, and the first equivalent impedance.

[0038] In some embodiments of this application, after the electrical signals of each line are collected and it is determined that a short circuit fault has occurred in the first power grid line, the controller needs to further identify the lines that have not experienced a short circuit fault from all the power grid lines and identify them as the second power grid lines.

[0039] Preferably, in some embodiments of this application, the second power grid line is determined as follows: if the current amplitude of a certain line does not exceed a preset short-circuit judgment threshold and its current waveform does not show obvious short-circuit characteristic distortion, then the line is determined to be a non-faulty line.

[0040] In some embodiments of this application, for each second power grid line, the controller extracts the phase angle of the voltage signal through a phase-locked loop based on the instantaneous values ​​of the three-phase voltage and current at the port of the line, and simultaneously calculates the fundamental frequency amplitude of the voltage and current, thereby obtaining the power supply voltage vector of the second power grid line. Regarding line impedance, the line impedance of each second power grid line is a known system parameter, including the inductance and resistance of the line itself, which is pre-stored in the controller and directly retrieved during calculation. For the first power grid line, the equivalent impedance between its fault point and the power flow controller's grid connection point needs to be determined based on the location of the fault and the fault location information reported by the protection device. Specifically, the equivalent impedance includes the impedance of the section of the line from the AC grid connection point of the power flow controller along the faulty line to the short-circuit fault point, and its value is equal to the impedance per unit length of the line multiplied by the fault distance. Once the fault location is determined, the controller retrieves the unit impedance value of that section of the line from the pre-stored line parameter table and calculates the amplitude and phase of the equivalent impedance in conjunction with the fault distance.

[0041] It should be noted that accurately obtaining the aforementioned parameters such as power supply voltage vector, line impedance, and equivalent impedance is fundamental for subsequent calculations of the equivalent fault power supply voltage phase. According to circuit principles, the short-circuit current flowing through the faulty line is essentially formed by the power supplies from each non-faulty line converging at the grid connection point through their respective line impedances, and then flowing through the faulty line to the fault point. Therefore, to calculate the phase of the equivalent fault power supply driving this short-circuit current, it is necessary to first determine the power supply voltage vector and line impedance of each non-faulty line, as well as the equivalent impedance of the faulty line from the grid connection point to the fault point, in order to establish a correct equivalent circuit model for solution.

[0042] This application identifies a second, fault-free power grid line from the main grid and calculates the voltage phase of the equivalent faulty power source based on its power supply voltage vector, line impedance, and the equivalent impedance of the faulty line. This application transforms the complex multi-port power grid fault analysis problem into an equivalent calculation problem based on circuit parameters. Because the calculation process is based on actually collected electrical signals from the non-faulty line and system impedance parameters, it accurately reflects the current fault state of the power grid, providing a precise phase reference for the subsequent output of the reverse-phase suppression voltage, thus ensuring the accuracy and effectiveness of short-circuit current suppression.

[0043] Further, in some embodiments of this application, the step of calculating the first voltage phase of the equivalent fault power source generated by the short-circuit current on the first power grid line based on the power supply voltage vector of each second power grid line, the line impedance of each second power grid line, and the first equivalent impedance includes: Divide the power supply voltage vector of each of the second power grid lines by the corresponding line impedance to obtain the current component of each of the second power grid lines. Summing up all the current components of the second power grid line yields the short-circuit current vector injected into the first power grid line. Calculate the second equivalent impedance of the first power grid line based on the first equivalent impedance and the line impedance of each of the second power grid lines; Multiply the short-circuit current vector by the second equivalent impedance of the first power grid line to obtain the voltage vector of the equivalent fault power source; The phase angle is extracted from the voltage vector of the equivalent fault power source to obtain the first voltage phase.

[0044] In some embodiments of this application, after obtaining the power supply voltage vector and line impedance of each second power grid line and the first equivalent impedance of the first power grid line, the controller begins to calculate the voltage phase of the equivalent fault power source. It should be clarified that the equivalent fault power source described here is not a physical power source actually existing in the power grid, but rather a virtual voltage source abstracted from the electrical characteristics of the faulty line under short-circuit conditions based on circuit principles for analysis and control purposes. Its physical meaning is the equivalent electromotive force driving the short-circuit current from the grid connection point to the fault point.

[0045] Specifically, in some embodiments of this application, the formula for calculating the first voltage phase is: ; in, This refers to the short-circuit current before suppression, i.e., the short-circuit current vector injected into the first power grid line; This represents the total number of the second power grid lines; The power supply voltage vector of the second power grid line; The line impedance of the second power grid line; The second equivalent impedance of the first power grid line; The first equivalent impedance is the distance between the fault point of the first power grid line and the grid connection point of the power flow controller. The voltage vector of the equivalent fault power source; The magnitude of the voltage vector of the equivalent fault power source; This is the first voltage phase.

[0046] Furthermore, the voltage vector of the equivalent fault power source can be physically understood as: when the power sources of the non-faulty lines each form a composite voltage at the grid connection point after passing through the line impedance voltage drop, and then the voltage drop across the faulty line impedance is subtracted, the portion of the equivalent electromotive force ultimately acting on the fault point is the equivalent electromotive force. After completing the voltage vector multiplication operation, the phase angle is directly extracted from the resulting voltage vector. This phase angle is the first voltage phase used to guide subsequent suppression control. The entire calculation process described above is performed in complex form in the controller's arithmetic unit. Using the fundamental frequency phasor data extracted from the acquired signal through Fourier transform, it can be completed within a few power frequency cycles, meeting the requirements for rapid response under fault conditions.

[0047] Based on the principle of circuit superposition and Ohm's law, this application obtains the current component by dividing the power supply voltage vector of each non-faulty line by the line impedance, sums them to obtain the total short-circuit current vector, multiplies it by the equivalent impedance of the faulty line to obtain the voltage vector of the equivalent faulty power supply, and finally extracts the phase angle. It is easy to program and implement in the controller, has high computational efficiency, and can meet the time requirements for rapid response under fault conditions.

[0048] S103: Based on the first voltage phase, control the first series power flow regulation module connected to the first power grid line to output a first suppressed AC voltage to the first power grid line; wherein, the second voltage phase of the first suppressed AC voltage is opposite to the first voltage phase.

[0049] Furthermore, in some embodiments of this application, the step of controlling the first series power flow regulation module connected to the first power grid line to output a first suppressed AC voltage to the first power grid line according to the first voltage phase includes: Determine a second voltage phase that is opposite to the first voltage phase, and use the second voltage phase as the output phase of the first suppressed AC voltage; The output amplitude of the first suppressed AC voltage is determined based on the current withstand limit of the power devices in the first series power flow regulation module. The first series power flow regulation module is controlled to output a first suppressed AC voltage having the output phase and the output amplitude.

[0050] After calculating the first voltage phase, the controller immediately begins generating voltage output commands for the first series power flow regulation module. First, the phase of the output voltage is determined. Since the core idea of ​​this scheme is to use the series power flow regulation module to output a voltage opposite in phase to the fault equivalent power source to counteract the equivalent electromotive force of the driving short-circuit current, the phase of the first suppressed AC voltage should be exactly 180 degrees different from the previously calculated first voltage phase, i.e., in the opposite direction. The controller adds or subtracts π radians to the value of the first voltage phase, and the result is the second voltage phase, which is used as the reference value for the output phase of the first suppressed AC voltage.

[0051] Next, the amplitude of the output voltage is determined. For a series power flow regulation module, each arm consists of multiple cascaded half-bridge sub-modules, each containing a DC capacitor and two power switching devices. The maximum effective value of the fundamental frequency AC voltage that the module can output is determined by multiplying the rated value of the capacitor voltage of a single sub-module by the number of sub-modules in each arm and then dividing by the square root of two. This is the physical upper limit determined by the voltage modulation principle of the half-bridge sub-modules. Under this constraint, in order to achieve the maximum short-circuit current suppression effect, this scheme requires the series power flow regulation module to determine the amplitude of the output voltage according to the maximum current that its power switching devices can withstand. Specifically, while ensuring that the arm current amplitude does not exceed the safe operating range specified in the power device datasheet, the amplitude command of the module's output voltage is set to the aforementioned modulation limit value, that is, to make the DC bus voltage modulation close to its maximum allowable value. In this way, the series power flow regulation module can output the highest possible AC voltage within the safe operating area of ​​the devices, thereby maximizing the ability to suppress short-circuit current.

[0052] Preferably, in some embodiments of this application, the output amplitude of the first suppressed AC voltage is determined by the following formula: ; in, This is the maximum effective value of the fundamental frequency voltage that the series power flow regulation module can output, and also the output amplitude of the first suppressed AC voltage; This refers to the number of submodules in a single bridge arm. This refers to the rated capacitor voltage for a single submodule.

[0053] Finally, the controller synthesizes the aforementioned phase and amplitude commands, and generates trigger pulses for the power switching devices of each submodule using sinusoidal pulse width modulation. This controls the first series power flow regulation module to continuously output a first suppressed AC voltage with the stated output phase and amplitude during a fault, which is then superimposed onto the port of the first power grid line to counteract the driving effect of the equivalent fault power source and compress the amplitude of the short-circuit current. It should be noted that when carrier phase-shifting sinusoidal pulse width modulation is used, the triangular carriers of each submodule are staggered by a fixed angle, ensuring that the fundamental components of the output voltage of each submodule are superimposed in phase and the equivalent switching frequency is multiplied. This guarantees the quality of the output voltage waveform while reducing the requirements for the switching speed of individual devices.

[0054] This application, on the one hand, determines the output phase of the suppressed AC voltage to be opposite to the phase of the equivalent fault power supply to achieve the maximum voltage cancellation effect; on the other hand, it determines the output amplitude of the suppressed AC voltage based on the current withstand limit of the power device, maximizing the output voltage while ensuring device safety, thereby maximizing the short-circuit current suppression capability and achieving directional and quantitative suppression of short-circuit current. The output inverse voltage ensures the correctness of the suppression direction, while the maximum output amplitude constrained by the current withstand limit fully utilizes the device's own voltage output potential, achieving optimal suppression effect without increasing hardware costs.

[0055] Furthermore, in some embodiments of this application, the power flow controller further includes: a plurality of power balance adjustment modules and a parallel converter connected in a delta configuration, one end of each power balance adjustment module being connected to one of the series power flow adjustment modules, and the other end of each power balance adjustment module being connected to the parallel converter; when outputting the first suppressed AC voltage to the first grid line, the following steps S104 to S106 are included: S104: Control the power balance adjustment module corresponding to the first series power flow adjustment module to output a preset first and third harmonic voltage.

[0056] Preferably, in some embodiments of this application, during fault suppression, the controller also needs to control the power balance adjustment module corresponding to the first series power flow adjustment module to output a preset first third harmonic voltage. This power balance adjustment module consists of upper and lower bridge arms, each of which is also composed of multiple cascaded half-bridge sub-modules. Its output voltage contains two components: a DC component to support the DC bus voltage and a third harmonic AC component to generate circulating current. Under fault conditions, in order to fully utilize the voltage modulation capability of the power balance adjustment module, the amplitude of its third harmonic component is preset to half the reference value of the DC bus voltage. This is the maximum third harmonic voltage amplitude that the power balance adjustment module can output without overmodulation. Its phase is preset to maintain a fixed relationship with the phase of the first grid line voltage, specifically, subtracting π / 6 radians from the phase of the first grid line voltage. This preset phase value is not dynamically adjusted with changes in fault conditions, and is therefore called the preset first third harmonic voltage. The controller directly generates modulation commands according to the preset amplitude and phase, and drives the power switching devices of each sub-module of the power balance adjustment module through sinusoidal pulse width modulation, so that they output the preset third harmonic voltage, providing a fixed and determined voltage excitation source for subsequent circulating current injection.

[0057] S105: Based on the first third harmonic voltage, control the parallel converter to output the second third harmonic voltage to generate circulating current in the loop formed by the parallel converter and the power balance adjustment module.

[0058] Furthermore, in some embodiments of this application, controlling the parallel converter to output a second or third harmonic voltage based on the first third harmonic voltage includes: Obtain the DC bus voltage of the first series power flow regulation module, and calculate the voltage deviation between the DC bus voltage and the preset DC bus voltage reference value; Based on the voltage deviation, determine the target amplitude of the circulating current required; Based on the target amplitude of the circulating current and the first third harmonic voltage, the second third harmonic voltage that the parallel converter needs to output is determined, and the parallel converter is controlled to output the second third harmonic voltage.

[0059] During the period when the series power flow regulation module outputs the first suppressed AC voltage, due to the fault current flowing through each sub-module of the module, the DC capacitors of some sub-modules will continuously absorb or release energy, causing the DC bus voltage to deviate from its preset rated reference value. Therefore, the controller needs to implement energy balance control synchronously, transferring the accumulated energy from the DC bus through circulating current injection.

[0060] Specifically, the controller first acquires the DC bus voltage sample value of the first series power flow regulation module in real time through a voltage sensor, compares it with a preset DC bus voltage reference value, and calculates the voltage deviation between the two. The sign and magnitude of this voltage deviation reflect whether the DC bus is currently in a state of excess or insufficient energy, and the degree of imbalance. Subsequently, the controller sends the voltage deviation to a proportional-integral (PI) controller. The output of the PPI controller is the target amplitude of the circulating current to be injected, while the frequency and phase reference of the circulating current are provided by the preset first and third harmonic voltages output by the power balance regulation module.

[0061] After determining the target amplitude of the circulating current, it is necessary to further calculate the second and third harmonic voltages that the parallel converter should output. This calculation is based on Kirchhoff's voltage law relationship of the loop formed between the parallel converter and the power balance regulation module. Specifically, this loop includes the second and third harmonic voltages output by the parallel converter, the first and third harmonic voltages output by the power balance regulation module, and the voltage drops across the loop inductor and parasitic resistance. The inductor voltage drop is proportional to the rate of change of the circulating current, and at the third harmonic frequency, it is expressed as inductive reactance multiplied by the circulating current; the resistor voltage drop is the circulating current multiplied by the equivalent resistance of the loop. By vector combining these voltage components in the complex plane, the second and third harmonic voltages that the parallel converter needs to output can be obtained. The loop voltage relationship can be expressed as follows: the third harmonic voltage of the parallel converter equals the third harmonic voltage of the power balance regulation module plus the sum of the loop inductor voltage drop and resistor voltage drop, specifically: ; in, This refers to the second and third harmonic voltages, i.e., the third harmonic voltage output by the parallel converter; The inductance value of the parallel converter; For the injected circulation; Take the partial derivative with time t for the circulation; The parasitic resistance of the inductor in the parallel converter; This refers to the first and third harmonic voltages.

[0062] Finally, based on the calculated second and third harmonic voltages, the controller generates modulation signals for each submodule of the parallel converter and controls the parallel converter to output this voltage, thereby generating the required circulating current in the loop. When this circulating current flows through the power balance regulation module, it interacts with the first and third harmonic voltages output by the power balance regulation module itself, generating active power exchange. This transfers excess energy accumulated on the DC bus to the parallel converter side through the loop between the power balance regulation module and the parallel converter, where it is redistributed to each phase or fed back to the grid. Ultimately, this restores the DC bus voltage to the reference value, maintains the energy balance within the series power flow regulation module, and ensures the continuous and stable operation of the device during fault suppression.

[0063] This application obtains the DC bus voltage and calculates its deviation from a reference value. Based on the deviation, it determines the target amplitude of the circulating current, and then combines the amplitude and phase of the first and third harmonic voltages to determine the second and third harmonic voltages. Using the DC bus voltage deviation as feedback, the circulating current is dynamically adjusted through closed-loop control, achieving precise control of energy balance. When the voltage deviation is large, the circulating current increases to accelerate energy transfer; when the deviation is small, the circulating current decreases to reduce losses. The control strategy has adaptive capabilities, automatically adjusting the energy balance intensity under different fault conditions, balancing control accuracy and system efficiency.

[0064] S106: Through the interaction between the circulating current and the first third harmonic voltage, energy is transferred from the DC bus of the first series power flow regulation module to the parallel converter to maintain the energy balance inside the first series power flow regulation module.

[0065] This application introduces a power balance regulation module and a delta-connected parallel converter. The power balance regulation module outputs a preset first and third harmonic voltage, while the parallel converter outputs a second and third harmonic voltage. A circulating current is generated in the loop formed by these two modules. The interaction between this circulating current and the first and third harmonic voltages transfers energy from the DC bus to the parallel converter. This solves the problem of potential energy accumulation on the DC bus leading to voltage runaway during fault conditions when the series-side output suppression voltage is applied. Active energy transfer through third harmonic circulating current injection maintains energy balance and stable operation on the series side while avoiding interference from the third harmonic on the fundamental frequency power control. This ensures the safe and stable operation of the device during fault suppression, making the active short-circuit current suppression strategy practical in engineering applications.

[0066] Furthermore, in some embodiments of this application, when a short-circuit fault is detected in the first power grid line, the method further includes: Identify the second power grid line that has not experienced a short circuit fault, and obtain the power supply voltage phase of the second power grid line; The second series power flow regulation module connected to the second power grid line outputs a second suppression AC voltage that is out of phase with the power supply voltage of the second power grid line, so as to suppress the short-circuit current flowing from the second power grid line to the first power grid line.

[0067] Preferably, in some embodiments of this application, while controlling the first series power flow regulation module on the faulty line side to output a first suppression AC voltage, this scheme also simultaneously applies active control to the series power flow regulation module on the non-faulty line side to reduce the inflow of short-circuit current from the source. After determining the first grid line, the controller determines the remaining lines in the grid whose current amplitude does not exceed the short-circuit judgment threshold as the second grid lines. For each second grid line, the controller extracts the fundamental frequency phase of the voltage at the line port in real time through a phase-locked loop to obtain the power supply voltage phase of the second grid line. Since the power supply of the second grid line itself is the source driving the short-circuit current to the fault point, if an AC voltage with an opposite phase to the power supply voltage of the line can be output at the series power flow regulation module of the second grid line, the combined voltage at the line port will be significantly reduced under the combined effect of the power supply voltage of the second grid line itself and the suppression AC voltage, thereby weakening the ability of the non-faulty line to inject short-circuit current into the fault point. Based on this principle, the controller adds or subtracts π radians to the phase of the power supply voltage of the second power grid line to obtain the output phase command of the second suppressed AC voltage. At the same time, it determines the output voltage amplitude according to the safe current withstand range of the power devices in the second series power flow regulation module. After synthesizing the phase and amplitude commands, the controller drives the second series power flow regulation module to output the second suppressed AC voltage through sinusoidal pulse width modulation.

[0068] This application identifies a second, fault-free power grid line and obtains its power supply voltage phase. It then controls a second series power flow regulation module connected to this fault-free line to output a second suppression AC voltage with a phase opposite to the power supply voltage of the fault-free line. This extends short-circuit current suppression from the faulty line side to the fault-free line side, suppressing the short-circuit current component flowing from the fault-free line to the fault point at its source. Through coordinated control of both the faulty and fault-free line sides, bidirectional suppression of short-circuit current is achieved. On the one hand, the driving voltage of the equivalent fault power source is canceled on the faulty line side; on the other hand, the outflow of short-circuit current is suppressed on the fault-free line side. The combination of these two measures maximizes the suppression effect, further improving the comprehensiveness and effectiveness of fault suppression.

[0069] In summary, the short-circuit current suppression method provided in this application has the following advantages compared to the prior art: When a short-circuit fault is detected in the first power grid line, the electrical signals of each power grid line are collected, the first voltage phase of the equivalent fault power source corresponding to the first power grid line is calculated, and then the first series power flow regulation module connected to the fault line is controlled to output a first suppression AC voltage opposite to the first voltage phase. By outputting a voltage opposite to the equivalent fault power source, the voltage component driving the short-circuit current is actively canceled, thereby achieving active suppression of the short-circuit current. Compared to the prior art's solution of adding dedicated current limiting equipment or bypassing the entire power flow controller, this application fully utilizes the voltage output capability of the power flow controller itself, and can achieve active and effective short-circuit current suppression during a fault without adding additional primary equipment. It has the advantages of low cost, fast response, and good suppression effect.

[0070] like Figure 3 As shown, based on the above-described method embodiments, this application provides a short-circuit current suppression device applied to a power flow controller. The power flow controller includes: a plurality of series power flow regulation modules, each of which is connected to a power grid line. The short-circuit current suppression device includes: a data acquisition module 201, a calculation module 202, and a control module 203. The acquisition module 201 is used to acquire electrical signals of each of the power grid lines when a short-circuit fault is detected in the first power grid line. The calculation module 202 is used to calculate the first voltage phase of the equivalent fault power supply corresponding to the first power grid line based on each of the electrical signals. The control module 203 is used to control the first series power flow regulation module connected to the first power grid line to output a first suppressed AC voltage to the first power grid line according to the first voltage phase; wherein, the second voltage phase of the first suppressed AC voltage is opposite to the first voltage phase.

[0071] Further, in some embodiments of this application, the calculation module 202 includes: a first identification unit, a first calculation unit, and a second calculation unit; the calculation module 202 is used to calculate the first voltage phase of the equivalent fault power supply corresponding to the first power grid line based on each of the electrical signals, including: The first identification unit is used to identify at least one second power grid line from the power grid lines that has not experienced a short-circuit fault; The first calculation unit is used to determine the power supply voltage vector and line impedance of the second power grid line, as well as the first equivalent impedance between the fault point of the first power grid line and the grid connection point of the power flow controller, based on the electrical signal. The second calculation unit is used to calculate the first voltage phase of the equivalent fault power source generated by the short-circuit current on the first power line based on the power supply voltage vector of each of the second power lines, the line impedance of each of the second power lines, and the first equivalent impedance.

[0072] Further, in some embodiments of this application, the second calculation unit is configured to calculate the first voltage phase of the equivalent fault power supply generated by the short-circuit current on the first power grid line based on the power supply voltage vector of each second power grid line, the line impedance of each second power grid line, and the first equivalent impedance, including: Divide the power supply voltage vector of each of the second power grid lines by the corresponding line impedance to obtain the current component of each of the second power grid lines. Summing up all the current components of the second power grid line yields the short-circuit current vector injected into the first power grid line. Calculate the second equivalent impedance of the first power grid line based on the first equivalent impedance and the line impedance of each of the second power grid lines; Multiply the short-circuit current vector by the second equivalent impedance of the first power grid line to obtain the voltage vector of the equivalent fault power source; The phase angle is extracted from the voltage vector of the equivalent fault power source to obtain the first voltage phase.

[0073] Further, in some embodiments of this application, the control module 203 includes: a third computing unit, a fourth computing unit, and a first control unit; the control module 203 is used to control the first series power flow regulation module connected to the first power grid line to output a first suppressed AC voltage to the first power grid line according to the first voltage phase, including: The third calculation unit is used to determine the second voltage phase that is opposite to the first voltage phase, and to use the second voltage phase as the output phase of the first suppressed AC voltage. The fourth calculation unit is used to determine the output amplitude of the first suppressed AC voltage based on the current withstand limit of the power devices in the first series power flow regulation module. The first control unit is used to control the first series power flow regulation module to output the first suppressed AC voltage having the output phase and the output amplitude.

[0074] Furthermore, in some embodiments of this application, the power flow controller further includes: a plurality of power balancing adjustment modules and a parallel converter connected in a delta configuration, one end of each power balancing adjustment module being connected to one of the series power flow adjustment modules, and the other end of each power balancing adjustment module being connected to the parallel converter; the control module 203 further includes: a second control unit, a third control unit, and a fourth control unit; the control module 203, when outputting a first suppressed AC voltage to the first power grid line, includes: The second control unit is used to control the power balance adjustment module corresponding to the first series power flow adjustment module to output a preset first third harmonic voltage; The third control unit is used to control the parallel converter to output a second and third harmonic voltage based on the first and third harmonic voltage, so as to generate circulating current in the loop formed by the parallel converter and the power balance adjustment module. The fourth control unit is used to transfer energy from the DC bus of the first series power flow regulation module to the parallel converter through the interaction between the circulating current and the first third harmonic voltage, so as to maintain the energy balance inside the first series power flow regulation module.

[0075] Furthermore, in some embodiments of this application, the third control unit is used to control the parallel converter to output a second or third harmonic voltage based on the first third harmonic voltage, including: Obtain the DC bus voltage of the first series power flow regulation module, and calculate the voltage deviation between the DC bus voltage and the preset DC bus voltage reference value; Based on the voltage deviation, determine the target amplitude of the circulating current required; Based on the target amplitude of the circulating current and the first third harmonic voltage, the second third harmonic voltage that the parallel converter needs to output is determined, and the parallel converter is controlled to output the second third harmonic voltage.

[0076] Furthermore, in some embodiments of this application, the control module 203 further includes: a second identification unit and a fifth control unit; The second identification unit is used to determine the second power grid line that has not experienced a short circuit fault and to obtain the power supply voltage phase of the second power grid line; The fifth control unit is used to control the second series power flow regulation module connected to the second power grid line to output a second suppression AC voltage that is out of phase with the power supply voltage of the second power grid line, so as to suppress the short-circuit current flowing from the second power grid line to the first power grid line.

[0077] In summary, the short-circuit current suppression device provided in this application has the following advantages compared to the prior art: When a short-circuit fault is detected in the first power grid line, the electrical signals of each power grid line are collected, the first voltage phase of the equivalent fault power source corresponding to the first power grid line is calculated, and then the first series power flow regulation module connected to the fault line is controlled to output a first suppression AC voltage opposite to the first voltage phase. By outputting a voltage opposite to the equivalent fault power source, the voltage component driving the short-circuit current is actively canceled, thereby achieving active suppression of the short-circuit current. Compared to the prior art's solution of adding a dedicated current limiting device or bypassing the entire power flow controller, this application makes full use of the voltage output capability of the power flow controller itself, and can achieve active and effective short-circuit current suppression during a fault without adding additional primary equipment, which has the advantages of low cost, fast response, and good suppression effect.

[0078] It is understood that the above-described device embodiments correspond to the method embodiments of this application, and can implement the short-circuit current suppression method provided by any of the above-described method embodiments of this application.

[0079] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided in this application, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0080] Based on the above-described embodiments of the short-circuit current suppression method, another embodiment of this application provides a power flow controller, which includes: a plurality of series power flow regulation modules, wherein the series power flow regulation modules are controlled by the short-circuit current suppression method of any embodiment of this application.

[0081] Based on the above embodiments of the short-circuit current suppression method, another embodiment of this application provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the short-circuit current suppression method of any embodiment of this application.

[0082] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete this application. The one or more module units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0083] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0084] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0085] Based on the above-described method embodiments, another embodiment of this application provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform the short-circuit current suppression method described in any of the above-described method embodiments of this application.

[0086] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

Claims

1. A short-circuit current suppression method, characterized in that, The method is applied to a power flow controller, which includes: a plurality of series-connected power flow regulation modules, each of which is connected to a power grid line; the short-circuit current suppression method includes: When a short-circuit fault is detected in the first power grid line, electrical signals of each of the power grid lines are collected; Based on each of the electrical signals, calculate the first voltage phase of the equivalent fault power source corresponding to the first power grid line; Based on the first voltage phase, the first series power flow regulation module connected to the first power grid line is controlled to output a first suppressed AC voltage to the first power grid line; wherein, the second voltage phase of the first suppressed AC voltage is opposite to the first voltage phase.

2. The short-circuit current suppression method as described in claim 1, characterized in that, The step of calculating the first voltage phase of the equivalent fault power source corresponding to the first power grid line based on each of the electrical signals includes: Identify at least one second power grid line that has not experienced a short-circuit fault from the aforementioned power grid lines; Based on the electrical signal, determine the power supply voltage vector and line impedance of the second power grid line, as well as the first equivalent impedance between the fault point of the first power grid line and the grid connection point of the power flow controller. The first voltage phase of the equivalent fault power source generated by the short-circuit current on the first power line is calculated based on the power supply voltage vector of each of the second power lines, the line impedance of each of the second power lines, and the first equivalent impedance.

3. The short-circuit current suppression method as described in claim 2, characterized in that, The step of calculating the first voltage phase of the equivalent fault power source generated by the short-circuit current on the first power grid line based on the power supply voltage vector of each of the second power grid lines, the line impedance of each of the second power grid lines, and the first equivalent impedance includes: Divide the power supply voltage vector of each of the second power grid lines by the corresponding line impedance to obtain the current component of each of the second power grid lines. Summing up all the current components of the second power grid line yields the short-circuit current vector injected into the first power grid line. Calculate the second equivalent impedance of the first power grid line based on the first equivalent impedance and the line impedance of each of the second power grid lines; Multiply the short-circuit current vector by the second equivalent impedance of the first power grid line to obtain the voltage vector of the equivalent fault power source; The phase angle is extracted from the voltage vector of the equivalent fault power source to obtain the first voltage phase.

4. The short-circuit current suppression method as described in claim 1, characterized in that, The step of controlling the first series power flow regulation module connected to the first power grid line to output a first suppressed AC voltage to the first power grid line according to the first voltage phase includes: Determine a second voltage phase that is opposite to the first voltage phase, and use the second voltage phase as the output phase of the first suppressed AC voltage; The output amplitude of the first suppressed AC voltage is determined based on the current withstand limit of the power devices in the first series power flow regulation module. The first series power flow regulation module is controlled to output a first suppressed AC voltage having the output phase and the output amplitude.

5. A short-circuit current suppression method as described in claim 1, characterized in that, The power flow controller further includes: a plurality of power balancing adjustment modules and a delta-connected parallel converter, one end of each power balancing adjustment module being connected to one of the series power flow adjustment modules, and the other end of each power balancing adjustment module being connected to the parallel converter; when outputting the first suppressed AC voltage to the first power grid line, it includes: Control the power balance adjustment module corresponding to the first series power flow adjustment module to output a preset first and third harmonic voltage; Based on the first and third harmonic voltages, the parallel converter is controlled to output the second and third harmonic voltages to generate circulating current in the loop formed by the parallel converter and the power balance adjustment module. Through the interaction between the circulating current and the first third harmonic voltage, energy is transferred from the DC bus of the first series power flow regulation module to the parallel converter, so as to maintain the energy balance inside the first series power flow regulation module.

6. The short-circuit current suppression method as described in claim 5, characterized in that, The step of controlling the parallel converter to output a second and third harmonic voltage based on the first and third harmonic voltage includes: Obtain the DC bus voltage of the first series power flow regulation module, and calculate the voltage deviation between the DC bus voltage and the preset DC bus voltage reference value; Based on the voltage deviation, determine the target amplitude of the circulating current required; Based on the target amplitude of the circulating current and the first third harmonic voltage, the second third harmonic voltage that the parallel converter needs to output is determined, and the parallel converter is controlled to output the second third harmonic voltage.

7. The short-circuit current suppression method as described in claim 1, characterized in that, When a short-circuit fault is detected in the first power grid line, the following is also included: Identify the second power grid line that has not experienced a short circuit fault, and obtain the power supply voltage phase of the second power grid line; The second series power flow regulation module connected to the second power grid line outputs a second suppression AC voltage that is out of phase with the power supply voltage of the second power grid line, so as to suppress the short-circuit current flowing from the second power grid line to the first power grid line.

8. A short-circuit current suppression device, characterized in that, The device is applied to a power flow controller, which includes: a plurality of series power flow regulation modules, each of which is connected to a power grid line; the short-circuit current suppression device includes: a data acquisition module, a calculation module, and a control module. The acquisition module is used to acquire electrical signals of each of the power grid lines when a short-circuit fault is detected in the first power grid line. The calculation module is used to calculate the first voltage phase of the equivalent fault power supply corresponding to the first power grid line based on each of the electrical signals. The control module is configured to control the first series power flow regulation module connected to the first power grid line to output a first suppressed AC voltage to the first power grid line according to the first voltage phase; wherein, the second voltage phase of the first suppressed AC voltage is opposite to the first voltage phase.

9. A power flow controller, characterized in that, include: A plurality of series power flow regulation modules, wherein the series power flow regulation modules are controlled by a short-circuit current suppression method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed, it controls the device in which the computer-readable storage medium is located to perform a short-circuit current suppression method as described in any one of claims 1 to 7.

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