Direct current system impedance frequency sweeping method, device, equipment and medium

Abstract

The invention discloses a direct current system impedance frequency sweeping method, device and equipment and a medium, and relates to the field of flexible direct current transmission, and the method comprises the steps: applying an alternating current disturbance signal on a modulation coefficient of a modular multilevel converter (MMC) control system; measuring a measurement signal when an alternating current disturbance signal is applied to a direct current system of the flexible direct current converter station, and determining the number of MMC sub-modules input by an upper bridge arm and a lower bridge arm of an MMC in the flexible direct current converter station under the alternating current disturbance signal; the measurement signal comprises a voltage signal and a current signal; analyzing disturbance measurement signals corresponding to the measurement signals under different disturbance frequency points based on fast Fourier transform; the disturbance signal comprises disturbance voltage and disturbance current; on the basis of the number of MMC sub-modules input into the upper and lower bridge arms of the MMC in the flexible direct current converter station, the impedance characteristic of the direct current system of the flexible direct current converter station is determined according to the disturbance signal on the basis of the Ohm law, the disturbance signal can be effectively controlled, and the impedance characteristic can be dynamically updated in real time.

Description

Technical Field

[0001] The present application relates to the field of flexible DC power transmission, and particularly to a DC system impedance sweep method, device, equipment and medium. Background Art

[0002] With the rapid development of high-voltage DC power transmission technology and flexible DC power transmission systems, the application of modular multilevel converters (MMCs) in DC power grids is becoming increasingly widespread. As the core equipment of DC power transmission, the operating state of the MMC directly affects the stability and reliability of the entire DC system.

[0003] In practical applications, in order to ensure stable interaction between the MMC and the external system, it is necessary to accurately measure the impedance characteristics of the external system at the DC port of the MMC. Accurate impedance information can not only help analyze the interaction behavior between the MMC and the external power grid, but also provide necessary data support to enable a rapid response in the event of system disturbances, ensuring the stability and reliability of the system.

[0004] The current measurement techniques for the DC-side impedance of flexible DC converter stations have obvious limitations: (1) Limitations of traditional measurement methods: The DC system is relatively sensitive to external disturbances. The amplitude of traditional disturbance signals is mostly around 5%, which is likely to cause system instability and increase the risk of measurement, especially in large flexible DC power grids, and the existing methods lack effective control and optimization of disturbance signals. (2) Difficulty in dynamically monitoring changes in the external system: As the system load or the external network changes, the impedance of the external system at the DC port also changes accordingly. Traditional measurement methods are difficult to update the impedance characteristics in real time and dynamically, thereby affecting the stability analysis and control strategy optimization of the system. Summary of the Invention

[0005] The purpose of the present application is to provide a DC system impedance sweep method, device, equipment and medium to solve the problems of ineffective control of disturbance signals and difficulty in real-time dynamic updating of impedance characteristics.

[0006] To achieve the above object, the present application provides the following solutions.

[0007] In a first aspect, the present application provides a DC system impedance sweep method, including the following steps.

[0008] Apply an AC disturbance signal to the modulation coefficient of the modular multilevel converter (MMC) control system.

[0009] Measure the measurement signals when an AC disturbance signal is applied to the DC system of a flexible DC converter station, and determine the number of MMC sub-modules put into operation in the upper and lower bridge arms of the MMC in the flexible DC converter station under the AC disturbance signal; the measurement signals include voltage signals and current signals.

[0010] Based on the fast Fourier transform, analyze the disturbance measurement signals corresponding to the measurement signals at different disturbance frequency points; the disturbance measurement signals include disturbance voltage and disturbance current.

[0011] Based on the number of MMC sub-modules put into operation in the upper and lower bridge arms of the MMC in the flexible DC converter station, determine the impedance characteristics of the DC system of the flexible DC converter station according to the disturbance measurement signals; the impedance characteristics include impedance and admittance.

[0012] Optionally, apply an AC disturbance signal to the modulation coefficient of the MMC control system, specifically including: using Determine the AC disturbance signal; where is the AC disturbance signal; K is the disturbance voltage amplitude coefficient; is the DC system voltage of the flexible DC converter station; is the disturbance voltage angular frequency; is the time variable; is the disturbance voltage phase angle.

[0013] Superimpose the AC disturbance signal on the modulation coefficient of the MMC control system.

[0014] Optionally, superimposing the AC disturbance signal on the modulation coefficient of the MMC control system specifically includes: applying the AC disturbance signal to the upper-arm voltage modulation wave and the lower-arm voltage modulation wave of the MMC in the flexible DC converter station, specifically including: using Apply the AC disturbance signal to the upper-arm voltage modulation wave; where is the j phase upper-arm voltage modulation wave; is the upper-arm voltage modulation wave; is the j phase common-mode voltage of the upper and lower arms; is the j phase corresponding modulation wave.

[0015] Using Apply the AC disturbance signal to the lower-arm voltage modulation wave; where is the j phase lower-arm voltage modulation wave; is the lower-arm voltage modulation wave.

[0016] Optionally, determine the number of MMC sub-modules inserted in the upper and lower bridge arms of the MMC in the flexible DC converter station, specifically including: using to determine the number of MMC sub-modules inserted in the upper bridge arm of the MMC in the flexible DC converter station; where is the number of MMC sub-modules inserted in the upper bridge arm of the j -th phase MMC; is the rated capacitor voltage; is the rounding function.

[0017] Using to determine the number of MMC sub-modules inserted in the lower bridge arm of the MMC in the flexible DC converter station; is the number of MMC sub-modules inserted in the lower bridge arm of the j -th phase MMC.

[0018] Optionally, based on the fast Fourier transform, analyze the disturbance measurement signals corresponding to the measurement signals at different disturbance frequency points, specifically including: using the fast Fourier transform to convert the time-domain signals of the measurement signals at different disturbance frequency points into frequency-domain signals.

[0019] Extract the amplitudes and phases of the frequency components of the frequency-domain signals.

[0020] Determine the disturbance measurement signals according to the amplitudes and the phases.

[0021] Optionally, determine the impedance characteristics of the DC system of the flexible DC converter station according to the disturbance measurement signals, specifically including: using to determine the impedance of the DC system of the flexible DC converter station; where is the impedance of the DC system of the flexible DC converter station; is the disturbance voltage; is the disturbance current.

[0022] Using to determine the admittance of the DC system of the flexible DC converter station; is the admittance of the DC system of the flexible DC converter station.

[0023] In a second aspect, the present application provides a DC system impedance sweep device, including the following modules.

[0024] A disturbance input module, configured to apply an AC disturbance signal to the modulation coefficient of the modular multilevel converter (MMC) control system.

[0025] A data acquisition module, configured to measure the measurement signals when an AC disturbance signal is applied to the DC system of the flexible DC converter station, and determine the number of MMC sub-modules inserted in the upper and lower bridge arms of the MMC in the flexible DC converter station; the measurement signals include voltage signals and current signals.

[0026] A signal processing module, configured to analyze a perturbation measurement signal corresponding to a measurement signal at different perturbation frequency points based on a fast Fourier transform; the perturbation measurement signal includes a perturbation voltage and a perturbation current.

[0027] An impedance measurement module, configured to determine an impedance characteristic of a DC system of a flexible DC converter station based on the number of MMC sub-modules put into operation in the upper and lower bridge arms of the MMC in the flexible DC converter station, according to the perturbation measurement signal; the impedance characteristic includes impedance and admittance.

[0028] Optionally, the perturbation input module specifically includes: an AC perturbation signal determination unit, configured to use to determine an AC perturbation signal; where is the AC perturbation signal; K is the perturbation voltage amplitude coefficient; is the voltage of the DC system of the flexible DC converter station; is the angular frequency of the perturbation voltage; is the time variable; is the phase angle of the perturbation voltage.

[0029] A superimposing unit, configured to superimpose the AC perturbation signal on the modulation coefficient of the MMC control system.

[0030] Optionally, the superimposing unit specifically includes: an applying unit, configured to apply an AC perturbation signal to the voltage modulation wave of the upper bridge arm and the voltage modulation wave of the lower bridge arm of the MMC in the flexible DC converter station.

[0031] The applying unit specifically includes: an upper bridge arm voltage modulation wave applying sub-unit, configured to use to apply an AC perturbation signal to the voltage modulation wave of the upper bridge arm; where is the voltage modulation wave of the upper bridge arm of the j th phase; is the voltage modulation wave of the upper bridge arm; is the common-mode voltage of the upper and lower bridge arms of the j th phase; is the corresponding modulation wave of the j th phase.

[0032] A lower bridge arm voltage modulation wave applying sub-unit, configured to use to apply an AC perturbation signal to the voltage modulation wave of the lower bridge arm; where is the voltage modulation wave of the lower bridge arm of the j th phase; is the voltage modulation wave of the lower bridge arm.

[0033] Optionally, the data acquisition module specifically includes: a determining unit for the number of MMC sub-modules put into operation in the upper bridge arm, configured to use Determine the number of MMC sub - modules put into operation in the upper bridge arm of the MMC in the flexible DC converter station; where is the number of MMC sub - modules put into operation in the upper bridge arm of the j -th phase MMC; is the rated capacitor voltage; is the rounding function.

[0034] The determining unit for the number of MMC sub - modules put into operation in the lower bridge arm is used to utilize to determine the number of MMC sub - modules put into operation in the lower bridge arm of the MMC in the flexible DC converter station; is the number of MMC sub - modules put into operation in the lower bridge arm of the j -th phase MMC.

[0035] Optionally, the signal processing module specifically includes: a conversion unit for converting the time - domain signal of the measured signal at different disturbance frequency points into a frequency - domain signal by using the fast Fourier transform.

[0036] An extraction unit for extracting the amplitude and phase of each frequency component of the frequency - domain signal.

[0037] The disturbance measurement signal determining unit is used to determine the disturbance measurement signal according to the amplitude and the phase.

[0038] Optionally, the impedance measurement module specifically includes: an impedance determining unit for using to determine the impedance of the DC system of the flexible DC converter station; where is the impedance of the DC system of the flexible DC converter station; is the disturbance voltage; is the disturbance current.

[0039] A admittance determining unit for using to determine the admittance of the DC system of the flexible DC converter station; is the admittance of the DC system of the flexible DC converter station.

[0040] In a third aspect, the present application provides a computer device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor executes the computer program to implement the DC system impedance sweep method described in any one of the above.

[0041] In a fourth aspect, the present application provides a computer - readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the DC system impedance sweep method described in any one of the above.

[0042] According to the specific embodiments provided in this application, the following technical effects are disclosed in this application: By applying a small AC perturbation signal with a specific frequency to the modulation coefficient of the MMC control system, effective control of the perturbation signal can be achieved. Without significantly affecting the stability of the DC system of the flexible DC converter station (hereinafter referred to as the DC system), the voltage signal and current signal at the port of the DC system can be measured in real time, so as to accurately obtain the impedance characteristics of the DC system of the flexible DC converter station and update the impedance characteristics in real time dynamically. This can not only dynamically reflect the changes in the DC system, but also provide important data support for the stability assessment, control strategy optimization and real-time fault detection of the DC system of the flexible DC converter station. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0044] Figure 1 It is a flowchart of the DC system impedance sweep method provided in this application.

[0045] Figure 2 It is a schematic diagram of the topology of the flexible DC converter station and the DC system impedance sweep device provided in this application.

[0046] Figure 3 It is a schematic diagram of the control loop of the MMC system.

[0047] Figure 4 It is a structural diagram of the DC system impedance sweep device provided in this application.

[0048] Figure 5 It is a comparison diagram of the amplitude between this application and the analytical model.

[0049] Figure 6 It is a comparison diagram of the phase between this application and the analytical model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] The following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, rather than all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0051] To make the above objects, features and advantages of this application more obvious and understandable, the following will further describe this application in detail with reference to the drawings and specific embodiments.

[0052] An embodiment of the present application provides a DC system impedance sweep method, which is executed by a computer device. Specifically, it can be executed independently by a computer device such as a terminal or a server, or jointly executed by a terminal and a server. In the embodiment of the present application, as Figure 1 shown, the method includes the following steps.

[0053] S1: Apply an AC perturbation signal to the modulation coefficient of the modular multilevel converter (MMC) control system.

[0054] S2: Measure the measurement signal when an AC perturbation signal is applied to the DC system of the flexible DC converter station, and determine the number of MMC sub-modules put into operation in the upper and lower bridge arms of the MMC in the flexible DC converter station; the measurement signal includes a voltage signal and a current signal.

[0055] S3: Based on the fast Fourier transform, analyze the perturbation measurement signals corresponding to the measurement signals at different perturbation frequency points; the perturbation measurement signals include perturbation voltage and perturbation current.

[0056] S4: Based on the number of MMC sub-modules put into operation in the upper and lower bridge arms of the MMC in the flexible DC converter station, determine the impedance characteristics of the DC system of the flexible DC converter station according to the perturbation measurement signals; the impedance characteristics include impedance and admittance.

[0057] The present application accurately obtains the impedance characteristics of the DC system by applying an AC perturbation signal to the modulation coefficient of the modular multilevel converter (MMC) control system and measuring the perturbation voltage and perturbation current of the DC system.

[0058] As Figure 2 shown, it includes an MMC, an AC-DC system, and a DC system impedance sweep device. By applying a small-amplitude AC perturbation signal with a specific frequency to the modulation coefficient of the MMC control system and using the DC system impedance sweep device to measure the measurement signal of the DC system, the measurement signal includes a voltage signal and a current signal, and the impedance characteristics of the DC system are calculated.

[0059] Specifically, apply a perturbation to the modulation coefficient of the MMC control system, Figure 2 in which, is the DC side voltage, and this DC side is the DC system, is the DC side current, is the voltage of the upper bridge arm of the j th phase, is the voltage of the lower bridge arm of the j th phase, is the current of the upper bridge arm of the j th phase, is the current of the lower bridge arm of the j th phase, is the arm inductor, is the j phase alternating current, is the j phase alternating voltage, is the equivalent inductor from the AC outlet of the converter to the AC system, SM1 - SM N are the MMC sub - modules.

[0060] Figure 3 is the schematic diagram of the control loop of the MMC system. Among them, is the reference value of the alternating current, is the reference value of the alternating voltage, is the reference value of the common - mode voltage, is the input AC disturbance signal, N is the number of sub - modules put into each arm. In this embodiment, only the nearest level modulation (NML) part needs to be concerned about.

[0061] From Figure 3 it can be seen that under steady state, the number of sub - modules put into the upper and lower arms of the MMC is as follows.

[0062]

[0063] Among them, and are respectively the number of sub - modules put into the upper and lower arms of the j - th phase, is the rated capacitor voltage, is the rounding function.

[0064] Based on this, the voltage modulation waves of the upper and lower arms under steady state are as follows.

[0065]

[0066]

[0067] Among them, and are respectively the voltage modulation waves of the upper and lower arms, is the DC system voltage of the flexible DC converter station, is the j phase common - mode voltage of the upper and lower arms, is the j corresponding modulation wave of the phase.

[0068] In an exemplary embodiment, S1 can be replaced by the following steps.

[0069] S11: Use to determine the AC disturbance signal; among them, is an AC disturbance signal; K is the disturbance voltage amplitude coefficient; is the DC system voltage of the flexible DC converter station; is the disturbance voltage angular frequency; is the time variable; is the disturbance voltage phase angle.

[0070] S12: Superimpose the AC disturbance signal on the modulation coefficient of the MMC control system.

[0071] In an exemplary embodiment, applying a disturbance to the modulation coefficient of the MMC means applying a disturbance to the voltage modulation waves of the upper bridge arm and the lower bridge arm and At this time, the number of sub-modules inserted in the upper and lower bridge arms of the MMC will also be affected by the disturbance.

[0072] S12 can be replaced by the following steps.

[0073] S121: Apply an AC disturbance signal to the voltage modulation waves of the upper bridge arm and the lower bridge arm of the MMC in the flexible DC converter station, which specifically includes the following steps.

[0074] Use to apply an AC disturbance signal to the voltage modulation wave of the upper bridge arm; where is the voltage modulation wave of the upper bridge arm of the j th phase.

[0075] Use to apply an AC disturbance signal to the voltage modulation wave of the lower bridge arm; where is the voltage modulation wave of the lower bridge arm of the j th phase.

[0076] In an exemplary embodiment, S2 can be replaced by the following steps.

[0077] S21: Use to determine the number of MMC sub-modules inserted in the upper bridge arm of the MMC in the flexible DC converter station; where is the number of MMC sub-modules inserted in the upper bridge arm of the MMC of the j th phase; is the rated capacitor voltage; is the rounding function.

[0078] S22: Use to determine the number of MMC sub-modules inserted in the lower bridge arm of the MMC in the flexible DC converter station; is the number of MMC sub-modules inserted in the lower bridge arm of the MMC of the j th phase.

[0079] What is different from the traditional disturbance signal application in this application is that the disturbance voltage amplitude coefficient is about 1% - 2%, which can realize the real-time measurement of the voltage signal and current signal of the DC system without significantly affecting the system stability.

[0080] In an exemplary embodiment, the extraction of the disturbance signal is related to the calculation of the impedance characteristics of the DC system. When a small AC disturbance signal with a specific frequency is applied to the modulation coefficient, after the action of the MMC and the DC system line, the voltage and current in the DC system will also contain disturbance components.

[0081] The signal extraction method adopted in this application is based on Fast Fourier Transform (FFT) analysis. By inputting the DC voltage signal and DC current signal, the parameter information related to the disturbance voltage and disturbance current corresponding to different disturbance frequency points can be obtained through FFT analysis. Then, the extracted disturbance signal is input into the impedance measurement module, and the impedance and admittance of the required DC system can be obtained according to Ohm's law.

[0082] S3 can be replaced by the following steps.

[0083] S31: Use the Fast Fourier Transform to convert the time-domain signal of the measured signal at different disturbance frequency points into a frequency-domain signal.

[0084] S32: Extract the amplitude and phase of each frequency component of the frequency-domain signal.

[0085] S33: Determine the disturbance measurement signal according to the amplitude and the phase.

[0086] In an exemplary embodiment, S4 can be replaced by the following steps.

[0087] S41: Use to determine the impedance of the DC system of the flexible DC converter station; where is the impedance of the DC system of the flexible DC converter station; is the disturbance voltage; is the disturbance current.

[0088] S42: Use to determine the admittance of the DC system of the flexible DC converter station; is the admittance of the DC system of the flexible DC converter station.

[0089] Based on the same inventive concept, an embodiment of the present application also provides a DC system impedance sweep device for implementing the DC system impedance sweep method involved above. The solution provided by this device for solving problems is similar to the solution described in the above method. Therefore, the specific limitations in one or more embodiments of the DC system impedance sweep device provided below can refer to the limitations on the DC system impedance sweep method in the above text, and will not be repeated here.

[0090] The DC system impedance sweep device provided by the present application is as Figure 4 shown, and mainly consists of four parts: a disturbance input module, a data acquisition module, a signal processing module, and an impedance measurement module.

[0091] The disturbance input module is responsible for generating an AC disturbance signal, superimposing it on the modulation coefficient of the MMC control system, and also providing a frequency input excitation for the DC system impedance sweep device. This disturbance input module is directly connected to the MMC control system in the flexible DC converter station.

[0092] The data acquisition module real-time collects the voltage and current signals at the DC port of the MMC and transmits the data to the signal processing module.

[0093] The signal processing module receives the signals from the data acquisition module, and uses FFT to obtain the amplitude and phase information of the voltage and current signals at different frequencies for calculating the impedance characteristics.

[0094] The impedance measurement module uses the processed signals to calculate the impedance characteristics of the MMC DC system. Calculate according to the formula and record the results, and finally draw the impedance characteristic curve.

[0095] In an exemplary embodiment, a DC system impedance sweep device is provided, including: A disturbance input module for applying an AC disturbance signal to the modulation coefficient of the modular multilevel converter (MMC) control system.

[0096] A data acquisition module for measuring the measurement signals when an AC disturbance signal is applied to the DC system of the flexible DC converter station, and determining the number of MMC sub-modules put into operation in the upper and lower bridge arms of the MMC in the flexible DC converter station under the AC disturbance signal; the measurement signals include voltage signals and current signals.

[0097] A signal processing module for analyzing the disturbance measurement signals corresponding to the measurement signals at different disturbance frequency points based on the fast Fourier transform; the disturbance measurement signals include disturbance voltage and disturbance current.

[0098] An impedance measurement module, configured to determine the impedance characteristics of the DC system of the flexible DC converter station based on the number of MMC sub-modules put into the upper and lower arms of the MMC in the flexible DC converter station; the impedance characteristics include impedance and admittance.

[0099] In an exemplary embodiment, the disturbance input module specifically includes: An AC disturbance signal determination unit, configured to use to determine an AC disturbance signal; where is the AC disturbance signal; K is the disturbance voltage amplitude coefficient; is the DC system voltage of the flexible DC converter station; is the disturbance voltage angular frequency; is the time variable; is the disturbance voltage phase angle.

[0100] A superimposing unit, configured to superimpose the AC disturbance signal on the modulation coefficient of the MMC control system.

[0101] In an exemplary embodiment, the superimposing unit specifically includes: An application unit, configured to apply an AC disturbance signal to the upper-arm voltage modulation wave and the lower-arm voltage modulation wave of the MMC in the flexible DC converter station.

[0102] The application unit specifically includes: An upper-arm voltage modulation wave application sub-unit, configured to use to apply an AC disturbance signal to the upper-arm voltage modulation wave; where is the upper-arm voltage modulation wave of the j th phase; is the upper-arm voltage modulation wave; is the common-mode voltage of the upper and lower arms of the j th phase; is the corresponding modulation wave of the j th phase.

[0103] A lower-arm voltage modulation wave application sub-unit, configured to use to apply an AC disturbance signal to the lower-arm voltage modulation wave; where is the lower-arm voltage modulation wave of the j th phase; is the lower-arm voltage modulation wave.

[0104] In an exemplary embodiment, the data acquisition module specifically includes: An MMC sub-module number determination unit for the upper arm, configured to use to determine the number of MMC sub-modules put into the upper arm of the MMC in the flexible DC converter station; where is the number of MMC sub - modules put into the upper arm of the j phase MMC; is the rated capacitor voltage; is the rounding function.

[0105] The determining unit for the number of MMC sub - modules put into the lower arm is used to utilize to determine the number of MMC sub - modules put into the lower arm of the MMC in the flexible DC converter station; is the j number of MMC sub - modules put into the lower arm of the

[0106] In an exemplary embodiment, the signal processing module specifically includes: The conversion unit is used to convert the time - domain signal of the measurement signal at different disturbance frequency points into a frequency - domain signal by using the fast Fourier transform.

[0107] The extraction unit is used to extract the amplitude and phase of each frequency component of the frequency - domain signal.

[0108] The disturbance measurement signal determining unit is used to determine the disturbance measurement signal according to the amplitude and the phase.

[0109] In an exemplary embodiment, the impedance measurement module specifically includes: The impedance determining unit is used to utilize to determine the impedance of the DC system of the flexible DC converter station; where is the impedance of the DC system of the flexible DC converter station; is the disturbance voltage; is the disturbance current.

[0110] The admittance determining unit is used to utilize to determine the admittance of the DC system of the flexible DC converter station; is the admittance of the DC system of the flexible DC converter station.

[0111] In an exemplary embodiment, the disturbance input module is responsible for applying a small - amplitude AC disturbance signal to the DC modulation coefficient of the MMC control system, superimposing it on the DC modulation coefficient to stimulate the dynamic response of the system, and also providing an input excitation for the impedance measurement device. This module allows controlling the frequency and amplitude of the disturbance signal so as to achieve accurate impedance characteristic measurement in different working conditions and frequency ranges.

[0112] The specific way of disturbance injection is as described in the above method, injecting a small - amplitude AC disturbance signal with a specific frequency into the modulation coefficient , and the upper and lower arm voltage modulation waves after adding the disturbance are as and as shown, which further affects the number of sub-modules inserted in the upper and lower arms of the MMC and , and finally outputs voltage signals and current signals with disturbance components.

[0113] In an exemplary embodiment, the data acquisition module real-time acquires the voltage and current signals of the DC system after applying disturbances to capture the dynamic response of the external system. This module ensures high-precision and high-speed signal sampling, providing accurate data for subsequent signal processing. The module contains a data buffer that stores data during the acquisition process to ensure signal continuity and prevent data loss.

[0114] In an exemplary embodiment, the signal processing module processes the voltage and current signals transmitted by the data acquisition module. It mainly converts the time-domain signals into frequency-domain signals through FFT, extracts the amplitude and phase information of each frequency component in the frequency-domain signals, provides basic data for the impedance calculation of the DC system, and transmits the processed frequency-domain data to the impedance measurement module for subsequent calculation and analysis.

[0115] In an exemplary embodiment, the impedance measurement module receives the frequency-domain signals transmitted by the signal processing module. As and shown, it calculates the impedance characteristics of the DC system and displays the results on the interface to provide visual measurement data. The impedance measurement module also has a data storage function, supporting long-term preservation of measurement results for subsequent analysis and query. The above four modules cooperate with each other, forming a complete impedance measurement link from the generation of input signals to data acquisition, signal processing, and impedance calculation. This device not only achieves accurate measurement of the impedance of the DC system but also ensures system stability and security during the measurement process.

[0116] (1) Improve measurement accuracy and response speed: Compared with traditional methods, this application uses the method of applying small-amplitude AC disturbance signals with a modulation coefficient, combined with precise data acquisition and signal processing technologies, which significantly improves the accuracy and response speed of DC system impedance measurement and meets the requirements of high dynamicity.

[0117] (2) Real-time dynamic monitoring ability: This application can monitor the dynamic changes of the external system in real time and update the impedance characteristics in a timely manner. This dynamic monitoring ability provides a reliable data basis for system stability analysis and control strategy optimization, helping the system to respond to changes in load or external network in a timely manner.

[0118] (3) Improve equipment cost - effectiveness and installation convenience: By optimizing the way of applying the perturbation signal, this application can effectively avoid the problems of high cost and inconvenient installation caused by using external impedance measurement equipment. Traditional external impedance measurement equipment not only requires additional investment but also may face many challenges during installation and operation and maintenance, such as space limitations and complex wiring. However, through the built - in signal modulation and processing mechanism of this application, direct monitoring of impedance characteristics is achieved, which not only reduces the overall cost but also greatly simplifies the installation and operation and maintenance processes, improving the overall efficiency and reliability of the system.

[0119] Through the above technical effects, this application overcomes the limitations of the existing technology in the DC system impedance sweep of flexible DC converter stations, provides effective technical support for the stable operation of high - voltage DC transmission and flexible DC power grids, and promotes the further development of related fields.

[0120] According to Figure 2 The corresponding simulation model was built in MATLAB / Simulink according to the shown topological structure to verify the effectiveness and feasibility of the DC system impedance sweep method provided by this application. Among them, the DC system consists of a T - type line composed of inductors and capacitors in series with an ideal DC voltage source. Table 1 is a schematic table of DC system impedance and perturbation parameters, and the DC system parameters are shown in Table 1.

[0121] Table 1

[0122] It can be seen from Figures 5 - 6 that the impedance characteristics calculated by this application are consistent with the theoretical analysis results.

[0123] In an exemplary embodiment, a computer device is provided. The computer device can be a server or a terminal. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O), and a communication interface. Among them, the processor, the memory, and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non - volatile storage medium and an internal memory. The non - volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non - volatile storage medium. The database of the computer device is used to store DC system impedance sweep data. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals through a network connection. When the computer program is executed by the processor, it implements a DC system impedance sweep method.

[0124] In an exemplary embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, the above method is implemented.

[0125] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, the above method is implemented.

[0126] Those of ordinary skill in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0127] In this application, all actions of obtaining signals, information, or data are carried out on the premise of complying with the corresponding data protection regulations and policies of the country where it is located and obtaining authorization from the owner of the corresponding device.

[0128] The databases involved in the embodiments provided in the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., and are not limited thereto. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., and are not limited thereto.

[0129] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0130] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A DC system impedance sweep method, characterized in that, Including: Applying an AC disturbance signal to the modulation coefficient of the Modular Multilevel Converter (MMC) control system; Measuring the measurement signal when an AC disturbance signal is applied to the DC system of the flexible DC converter station, and determining the number of MMC sub-modules incorporated in the upper and lower bridge arms of the MMC in the flexible DC converter station under the AC disturbance signal; Analyzing the disturbance measurement signals corresponding to the measurement signals at different disturbance frequency points based on the Fast Fourier Transform (FFT); the disturbance measurement signals include disturbance voltage and disturbance current; Determining the impedance characteristics of the DC system of the flexible DC converter station based on the number of MMC sub-modules incorporated in the upper and lower bridge arms of the MMC in the flexible DC converter station according to the disturbance measurement signals.

2. The DC system impedance sweep method according to claim 1, characterized in that, Applying an AC disturbance signal to the modulation coefficient of the MMC control system specifically includes: Utilize to determine an AC disturbance signal; wherein is the AC disturbance signal; K is the disturbance voltage amplitude coefficient; is the DC system voltage of the flexible DC converter station; is the disturbance voltage angular frequency; is the time variable; is the disturbance voltage phase angle; Superimposing the AC disturbance signal on the modulation coefficient of the MMC control system.

3. The DC system impedance sweep method according to claim 2, characterized in that, Superimposing the AC disturbance signal on the modulation coefficient of the MMC control system specifically includes: Applying an AC disturbance signal to the upper-bridge-arm voltage modulation wave and the lower-bridge-arm voltage modulation wave of the MMC in the flexible DC converter station, specifically including: Utilize Apply an AC perturbation signal to the upper-bridge-arm voltage modulation wave; wherein, is the upper-bridge-arm voltage modulation wave of the j phase; is the upper-bridge-arm voltage modulation wave; is the j phase common-mode voltage of the upper and lower bridge arms; is the modulation wave corresponding to the j phase; Utilize Apply an AC disturbance signal to the lower-arm voltage modulation wave; wherein, is the j lower-arm voltage modulation wave of the phase; and is the lower-arm voltage modulation wave.

4. The DC system impedance sweep method according to claim 3, characterized in that, Determining the number of MMC sub-modules incorporated in the upper and lower bridge arms of the MMC in the flexible DC converter station under the AC disturbance signal specifically includes: Utilize to determine the number of MMC sub-modules put into operation in the upper arm of the MMC in the flexible DC converter station; where is the number of MMC sub-modules put into operation in the upper arm of the j phase MMC; is the rated capacitor voltage; is the rounding function; Utilize to determine the number of MMC sub-modules put into operation in the MMC lower arm of the flexible HVDC converter station; For the j number of MMC sub-modules put into operation in the MMC lower arm of the [[phase]].

5. The DC system impedance sweep method according to claim 1, characterized in that, Analyzing the disturbance measurement signals corresponding to the measurement signals at different disturbance frequency points based on the Fast Fourier Transform (FFT), specifically including: Using the Fast Fourier Transform to convert the time-domain signals of the measurement signals at different disturbance frequency points into frequency-domain signals; Extracting the amplitudes and phases of the frequency components of the frequency-domain signals; Determining the disturbance measurement signals according to the amplitudes and the phases.

6. The DC system impedance sweep method according to claim 1, characterized in that, Determining the impedance characteristics of the DC system of the flexible DC converter station according to the disturbance measurement signals specifically includes: Utilize to determine the impedance of the DC system of a flexible DC converter station; wherein, is the impedance of the DC system of the flexible DC converter station; is the disturbance voltage; is the disturbance current; Utilize Determine the admittance of the DC system of a flexible DC converter station; The admittance of the DC system of a flexible DC converter station.

7. A DC system impedance sweep device, characterized in that, The DC system impedance sweep device includes: A disturbance input module for applying an AC disturbance signal to the modulation coefficient of the Modular Multilevel Converter (MMC) control system; A data acquisition module for measuring the measurement signal when an AC disturbance signal is applied to the DC system of the flexible DC converter station, and determining the number of MMC sub-modules incorporated in the upper and lower bridge arms of the MMC in the flexible DC converter station under the AC disturbance signal; A signal processing module for analyzing the disturbance measurement signals corresponding to the measurement signals at different disturbance frequency points based on the Fast Fourier Transform (FFT); the disturbance measurement signals include disturbance voltage and disturbance current; An impedance measurement module for determining the impedance characteristics of the DC system of the flexible DC converter station based on the number of MMC sub-modules incorporated in the upper and lower bridge arms of the MMC in the flexible DC converter station according to the disturbance measurement signals.

8. The DC system impedance sweep device according to claim 7, characterized in that, The disturbance input module specifically includes: An alternating current disturbance signal determination unit, which is used to utilize to determine an alternating current disturbance signal; where is the alternating current disturbance signal; K is the disturbance voltage amplitude coefficient; is the DC system voltage of the flexible DC converter station; is the disturbance voltage angular frequency; is the time variable; is the disturbance voltage phase angle; A superimposing unit for superimposing the AC disturbance signal on the modulation coefficient of the MMC control system.

9. The DC system impedance sweep device according to claim 8, characterized in that, The superimposing unit specifically includes: An applying unit for applying an AC disturbance signal to the upper-bridge-arm voltage modulation wave and the lower-bridge-arm voltage modulation wave of the MMC in the flexible DC converter station; The applying unit specifically includes: The upper-bridge-arm voltage modulation wave application subunit is used to apply an AC disturbance signal to the upper-bridge-arm voltage modulation wave; where is the j phase upper-bridge-arm voltage modulation wave; is the upper-bridge-arm voltage modulation wave; is the j phase upper and lower bridge-arm common-mode voltage; is the j corresponding modulation wave of the The lower-bridge-arm voltage modulation wave application subunit is used to apply an AC disturbance signal to the lower-bridge-arm voltage modulation wave; where is the j lower-bridge-arm voltage modulation wave of the phase; is the lower-bridge-arm voltage modulation wave.

10. The DC system impedance sweep device according to claim 9, characterized in that, The data acquisition module specifically includes: The MMC sub-module number determination unit for the upper bridge arm is used to utilize to determine the number of MMC sub-modules in the upper bridge arm of the MMC in the flexible DC converter station; where is the number of MMC sub-modules in the upper bridge arm of the j th phase MMC upper bridge arm; is the rated capacitor voltage; is the rounding function; The MMC sub-module number determination unit for the lower arm input is used to utilize to determine the number of MMC sub-modules input in the MMC lower arm of the flexible DC converter station; is the number of MMC sub-modules input in the j lower arm of the phase MMC.

11. The DC system impedance sweep device according to claim 7, characterized in that, The signal processing module specifically includes: A conversion unit for using the Fast Fourier Transform to convert the time-domain signals of the measurement signals at different disturbance frequency points into frequency-domain signals; An extraction unit for extracting the amplitudes and phases of the frequency components of the frequency-domain signal; A perturbation measurement signal determination unit for determining a perturbation measurement signal based on the amplitude and the phase; 12. The DC system impedance sweep device according to claim 7, characterized in that, An impedance measurement module, specifically including: An impedance determination unit for using to determine the impedance of the DC system of a flexible DC converter station; wherein, is the impedance of the DC system of the flexible DC converter station; is the disturbance voltage; is the disturbance current; An admittance determination unit for using to determine the admittance of the DC system of a flexible DC converter station; is the admittance of the DC system of a flexible DC converter station.

13. A computer device, comprising: A memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that the processor executes the computer program to implement the DC system impedance sweep method according to any one of claims 1-6.

14. A computer-readable storage medium, on which a computer program is stored, characterized in that, When the computer program is executed by the processor, it implements the DC system impedance sweep method according to any one of claims 1-6.

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