A method and system for real-time suppression of DC current harmonics of a converter valve and a storage medium

Abstract

The present application belongs to the technical field of flexible direct current power transmission, and particularly relates to a real-time suppression method and system for DC current harmonics of a converter valve and a storage medium. The real-time spectrum of the DC current of the converter valve is collected; the distribution level of the DC current and the historical harmonic level are determined according to the real-time spectrum of the DC current and the historical harmonic characteristics; the harmonic suppression strategy during the operation of the converter valve is generated according to the distribution level of the DC current and the historical harmonic level; the higher the distribution level of the DC current and the historical harmonic level, the higher the priority of executing the harmonic suppression strategy; the harmonic suppression operation of the converter valve is controlled according to the generated harmonic suppression strategy; and different modulation intensities are adopted for the DC currents with different distribution levels and historical harmonic levels in the harmonic suppression strategy. The present application can formulate differentiated strategies according to the actual complexity and suppression requirements of the harmonics, and improves the real-time performance, accuracy and efficiency of the harmonic suppression of the converter valve.

Description

Technical Field

[0001] This invention belongs to the field of flexible DC transmission technology, specifically relating to a real-time suppression method, system, and storage medium for DC current harmonics in converter valves. Background Technology

[0002] In flexible DC transmission systems, converter valves, as core equipment, generate DC current harmonics during operation, which have always been a key factor affecting system stability and power quality. With the expansion of new energy grid connection and the rapid development of DC transmission technology, higher requirements are placed on the real-time performance, accuracy, and efficiency of converter valve harmonic suppression.

[0003] Traditional harmonic suppression methods are mostly based on a single control strategy with fixed parameters, achieving harmonic suppression through passive filtering schemes or frequency domain analysis methods based on Fourier transform. For example, Chinese utility model patent document CN201994674U discloses a reactive power compensation and harmonic suppression device for a photovoltaic grid-connected system. This device directly collects the current from the harmonic source, uses Fourier transform to decompose the collected current into harmonic current, fundamental current, reactive current, and active current. The harmonic current and reactive current to be compensated are added together to obtain the compensation current. The compensation current is compared with the command current, and based on the comparison result, a PWM tracking control method is used to output a PWM waveform. After being driven, the PWM waveform controls the state of each switch in the inverter unit, thereby controlling the current output by the inverter unit. This causes the current on the load to track the command current in a sawtooth wave shape, thus canceling out the harmonic current and reactive current, achieving the purpose of harmonic suppression and reactive power compensation. Although passive filtering schemes have a simple structure, their filtering effect is greatly affected by power grid parameters and they are prone to resonance problems. On the other hand, frequency domain analysis methods based on Fourier transform have the drawback of insufficient time resolution when processing non-stationary harmonic signals, and cannot track abrupt changes in harmonic components in real time.

[0004] With the increasing complexity of converter valve topologies (such as the widespread application of multilevel converters), the composition of harmonic components in DC current has become more complex, and the impact of harmonics in different frequency bands on the system varies significantly. Traditional single suppression strategies are insufficiently targeted, easily leading to over-suppression or incomplete suppression, which in turn affects the operating efficiency and service life of the converter valve, making it difficult to meet the differentiated suppression requirements of multi-frequency bands and multi-level harmonics. For example, low-frequency harmonics may cause system power oscillations, while high-frequency harmonics may cause electromagnetic compatibility issues, resulting in insufficient targeting of suppression strategies and easily leading to over-suppression or incomplete suppression, thus affecting the operating efficiency and service life of the converter valve.

[0005] Furthermore, existing control systems lack dynamic monitoring and adaptive adjustment mechanisms for real-time operating status during converter valve operation. When grid conditions fluctuate or converter valve connection points switch, the suppression strategy cannot be adjusted promptly based on real-time spectrum data and modulation waveforms, easily leading to lag or deviation in the suppression process, affecting system stability and reliability. For example, when the converter valve switches from one DC current branch to another, if the harmonic characteristics of the new branch cannot be quickly identified and parameters adjusted, new harmonic interference may be introduced or existing harmonic problems may be exacerbated. Summary of the Invention

[0006] The purpose of this invention is to provide a real-time suppression method, system, and storage medium for DC current harmonics in converter valves, in order to solve the problem of inaccurate control caused by the single strategy of existing harmonic suppression methods.

[0007] To address the aforementioned technical problems, the first aspect of this invention provides a real-time suppression method for DC current harmonics in a converter valve, comprising:

[0008] Collect the real-time spectrum of the DC current of the converter valve;

[0009] The distribution level and historical harmonic level of DC current are determined based on the real-time spectrum and historical harmonic characteristics of DC current; the historical harmonic characteristics of DC current include the number of historical amplitude fluctuations of DC current and the adjustment time corresponding to each fluctuation.

[0010] Harmonic suppression strategies for converter valve operation are generated based on the DC current distribution level and historical harmonic levels; the higher the DC current distribution level and historical harmonic levels, the higher the priority of implementing the harmonic suppression strategy.

[0011] The control converter valve performs harmonic suppression operation according to the generated harmonic suppression strategy; in the harmonic suppression strategy, different modulation intensities are used for DC currents with different distribution levels and historical harmonic levels.

[0012] In one possible implementation, the process of determining the historical harmonic level is as follows: calculate the average adjustment time of the DC current based on the historical harmonic characteristics, determine the characteristic coefficient of the DC current based on the number of historical amplitude fluctuations and the average adjustment time, and determine the historical harmonic level based on the determined characteristic coefficient; wherein, the more fluctuations and the longer the average adjustment time, the larger the corresponding characteristic coefficient and the higher the historical harmonic level.

[0013] In one possible implementation, the real-time spectrum includes amplitude deviation and frequency fluctuation; the process for determining the distribution level is as follows: the distribution coefficient of the DC current is calculated based on the amplitude deviation and frequency fluctuation of the real-time DC current spectrum, and the distribution level of the DC current is determined based on the distribution coefficient; the distribution coefficient is used to characterize the comprehensive deviation of the DC current in amplitude and frequency. The greater the amplitude deviation and frequency fluctuation, the greater the corresponding distribution coefficient and the higher the distribution level.

[0014] In one possible implementation, the harmonic suppression strategy is generated as follows: the distribution level of the DC current is used as the first priority factor, and the historical harmonic level of the DC current is used as the second priority factor. The DC current with the highest distribution level is prioritized for harmonic suppression. If there are DC currents with the same distribution level, the DC current with the highest historical harmonic level is preferred for harmonic suppression.

[0015] In one possible implementation, the generation process of the harmonic suppression strategy is as follows:

[0016] The distribution level of DC current is used as the first priority factor, the historical harmonic level of DC current is used as the second priority factor, and the physical distance between the current connection point of the converter valve and the starting point of DC current is used as the third priority factor.

[0017] Taking the current connection point of the converter valve as the reference origin, if there are DC currents with the same distribution level near the starting point of the DC current, the DC current with the highest historical harmonic level is selected for processing first; if the distribution level and historical harmonic level of each DC current are the same, the DC current with the smallest physical distance is selected for processing.

[0018] When the converter valve reaches the switching point, if the switching point is connected to only a single DC current, the converter valve directly performs harmonic suppression on that DC current; if the switching point is connected to at least two DC currents, the DC current with the highest distribution level is prioritized for harmonic suppression; if the DC currents connected to the switching point have the same distribution level, the DC current with the highest historical harmonic level is prioritized for harmonic suppression; if the DC currents connected to the switching point have the same distribution level and historical harmonic level, a DC current is randomly selected for harmonic suppression.

[0019] In one possible implementation, the method further includes:

[0020] During the suppression operation, the real-time modulated waveform of the DC current is also collected simultaneously;

[0021] Whether to enter the adjustment frequency band is determined based on the real-time modulation waveform and frequency band difference characteristics of the DC current; the frequency band difference characteristics include the core frequency point, the reference fluctuation amplitude, and the attenuation change slope;

[0022] If the frequency band is adjusted, the real-time modulation waveform within the frequency band is used to determine whether the converter valve deviates from the reference frequency band during operation. If it deviates, a modulation correction command is sent.

[0023] In one possible implementation, the method further includes: acquiring and analyzing the real-time waveform of the DC current; if the analysis generates a distorted signal or an overshoot signal, then marking the frequency band and displaying the corresponding real-time waveform.

[0024] To address the aforementioned technical problems, a second aspect of the present invention provides a real-time suppression system for DC current harmonics in a converter valve, comprising a processor that executes a computer program to implement the steps of the method described above.

[0025] In one possible implementation, a display module is also included to display the real-time waveform of the DC current when a distortion signal or overshoot signal occurs.

[0026] To address the aforementioned technical problems, a third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0027] The beneficial effects of this invention are as follows: It accurately divides the main harmonic frequency band and the frequency band to be suppressed for DC current. By combining historical harmonic characteristic data (such as historical amplitude fluctuation frequency and adjustment duration) with the collected real-time spectrum data, it classifies the historical harmonic levels and distribution levels of DC current. Within each frequency band, different harmonic suppression is applied to DC currents with different distribution levels and historical harmonic levels. This refined classification mechanism enables the development of differentiated strategies based on the actual complexity of harmonics and suppression requirements, changing the traditional "one-size-fits-all" suppression mode, improving resource utilization efficiency, and enhancing the real-time performance, accuracy, and efficiency of harmonic suppression in converter valves. For example, for the third-order harmonic frequency band, a higher-intensity modulation strategy can be automatically matched, while the first-order harmonic uses a basic suppression mode, reducing energy consumption while ensuring suppression effectiveness.

[0028] A hierarchical suppression logic was constructed, prioritizing distribution level as the first priority, historical harmonic level as the second priority, and the distance between connection points as the third priority. During converter valve operation, currents with high distribution levels and high historical harmonic levels are processed first, and the processing order is dynamically selected at switching points based on the connection situation (e.g., prioritizing currents with high distribution levels, prioritizing currents with high historical harmonic levels when levels are the same, prioritizing currents with closer distances, etc.). This priority strategy ensures that the system can quickly locate critical harmonic issues, reduce ineffective operation time, and improve suppression efficiency. Simultaneously, different modulation intensities are used for frequency bands with different distribution or harmonic levels, achieving "precision targeting" and avoiding potential damage to the system from over-modulation.

[0029] When the converter valve executes the suppression strategy, it not only collects real-time spectrum data but also simultaneously monitors the real-time modulation waveform. By comparing the real-time modulation waveform with stored frequency band difference characteristics (core frequency, reference fluctuation amplitude, attenuation slope, etc.), it accurately determines whether the converter valve has entered the frequency band that needs adjustment. If it needs to enter the adjustment frequency band, it further analyzes whether the real-time modulation waveform deviates from the reference frequency band. If it deviates, it sends a modulation correction command to achieve real-time fine-tuning of the suppression strategy. This closed-loop feedback mechanism enables the system to dynamically adapt to changes in harmonic characteristics, avoiding suppression deviations caused by power grid operating condition fluctuations or parameter drift, and significantly improving the adaptive capability and robustness of harmonic suppression.

[0030] By analyzing the real-time waveform of DC current, distorted or overshoot signals can be accurately identified and their corresponding frequency bands can be marked. The real-time waveform data is visualized, providing maintenance personnel with an intuitive monitoring interface. This facilitates the timely detection of potential harmonic anomalies or equipment failures, enabling preventative maintenance and reducing the risk of system downtime. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the working principle of the real-time suppression system for DC current harmonics of the converter valve of the present invention.

[0032] Figure 2 A flowchart for harmonic monitoring;

[0033] Figure 3 A flowchart for determining historical harmonic levels and distribution levels in the spectrum partitioning module;

[0034] Figure 4 Workflow diagram for the strategy generation module;

[0035] Figure 5 This is a design diagram for the linkage between difference determination and distribution detection. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0037] This invention collects real-time spectrum data, combines historical harmonic characteristics to determine historical harmonic levels and distribution levels, and formulates a graded control harmonic suppression strategy based on historical harmonic levels and distribution levels. This achieves dynamic graded harmonic suppression and adaptive adjustment, thereby improving the stability and power quality of flexible DC transmission systems.

[0038] System Implementation

[0039] This invention discloses a real-time suppression system for DC current harmonics in a converter valve, comprising a processor for executing a computer program to implement a real-time suppression method for DC current harmonics in a converter valve. The method includes:

[0040] The system acquires the real-time spectrum of the DC current in the converter valve; determines the distribution level and historical harmonic level of the DC current based on the real-time spectrum and historical harmonic characteristics; the historical harmonic characteristics of the DC current include the number of historical amplitude fluctuations and the corresponding adjustment time for each fluctuation; generates a harmonic suppression strategy for the converter valve operation based on the distribution level and historical harmonic level of the DC current; the higher the distribution level and historical harmonic level of the DC current, the higher the priority of implementing the harmonic suppression strategy; controls the converter valve to perform harmonic suppression operation according to the generated harmonic suppression strategy; in the harmonic suppression strategy, different modulation intensities are used for DC currents with different distribution levels and historical harmonic levels. The real-time spectrum includes amplitude deviation and frequency fluctuation.

[0041] The process involves calculating the average regulation time of the DC current based on historical harmonic characteristics, determining the characteristic coefficient of the DC current based on the number of historical amplitude fluctuations and the average regulation time, and then determining the historical harmonic level based on the determined characteristic coefficient. The more fluctuations and the longer the average regulation time, the larger the corresponding characteristic coefficient and the higher the historical harmonic level. Higher levels prioritize suppression.

[0042] The process for determining the distribution level is as follows: The distribution coefficient of the DC current is calculated based on the amplitude deviation and frequency fluctuation of the real-time DC current spectrum. The distribution level of the DC current is then determined based on this distribution coefficient. The distribution coefficient characterizes the overall deviation of the DC current in terms of amplitude and frequency. The greater the amplitude deviation and frequency fluctuation, the larger the corresponding distribution coefficient, and the higher the distribution level. Higher levels prioritize suppression.

[0043] In one embodiment, the generation process of the harmonic suppression strategy is as follows: taking the distribution level of DC current as the first priority element and the historical harmonic level of DC current as the second priority element, the DC current with the highest distribution level is given priority for harmonic suppression; if there are DC currents with the same distribution level, the DC current with the highest historical harmonic level is preferred for harmonic suppression.

[0044] In another embodiment, when generating the harmonic suppression strategy, a three-level priority mechanism including physical topology constraints is introduced: the distribution level of DC current is used as the first priority element, the historical harmonic level of DC current is used as the second priority element, and the physical distance between the current connection point of the converter valve and the starting point of DC current is used as the third priority element.

[0045] The starting point of the DC current is the source of harmonics; the current connection point of the converter valve is the actual connection position of the converter valve in the electrical network, which can be changed between different candidate switching points.

[0046] When making harmonic suppression decisions, the current connection point of the converter valve is used as the reference origin: if there are multiple DC currents with the same distribution level near the starting point of the DC current, the one with the highest historical harmonic level is selected for processing first. If the distribution level and historical harmonic level of each DC current are the same, the physical distance between each starting point and the current connection point of the converter valve is measured, and the DC current with the smallest physical distance, i.e., the closest distance, is selected for processing first.

[0047] Before moving, the converter valve scans all candidate switching points. If multiple points have the same current distribution level and historical harmonic level, the closest switching point wins, and the converter valve decides to go there. This section describes the scenario after the converter valve has reached the selected switching point. When the converter valve reaches the switching point, if the switching point is connected to only a single DC current, the converter valve directly performs harmonic suppression on that DC current; if the switching point is connected to at least two DC currents, the DC current with the highest distribution level is prioritized for harmonic suppression; if the DC currents connected to the switching point have the same distribution level, the DC current with the highest historical harmonic level is prioritized for harmonic suppression; if the DC currents connected to the switching point have the same distribution level and historical harmonic level, it means that all electrical characteristics and distance optimization performed at that point cannot be further distinguished, and a DC current is randomly selected for harmonic suppression.

[0048] During suppression operations, the real-time modulation waveform of the DC current is also collected simultaneously. Based on the real-time modulation waveform of the DC current and the frequency band difference characteristics, it is determined whether the adjustment frequency band has been entered. The frequency band difference characteristics include the core frequency point, the reference fluctuation amplitude, and the attenuation change slope. If the adjustment frequency band is entered, it is determined whether the converter valve deviates from the reference frequency band during the adjustment frequency band operation based on the real-time modulation waveform within the adjustment frequency band. If it deviates, a modulation correction command is sent.

[0049] The method also includes: acquiring and analyzing the real-time waveform of the DC current; if the analysis generates a distorted signal or an overshoot signal, the frequency band is marked and the corresponding real-time waveform is displayed.

[0050] The system includes a harmonic detection module, a parameter processing module, a spectrum partitioning module, a storage unit, a strategy generation module, a status monitoring module, a distribution detection module, and a difference determination module.

[0051] The harmonic detection module is used to divide the main harmonic frequency band of DC current into the frequency band to be suppressed, so as to distinguish between the inherent characteristic harmonics and abnormal harmonics of the converter valve, avoid false suppression of the main harmonic frequency band, and provide the frequency band basis for the strategy generation module to determine the target of differentiated modulation.

[0052] The parameter processing module is used to control the converter valve to start harmonic suppression operation after receiving the command; when performing the initial suppression operation, the status monitoring module is used to collect real-time spectrum data of DC current and transmit it to the spectrum division module; the storage unit is used to store historical harmonic characteristic data of DC current and transmit it to the spectrum division module.

[0053] The spectrum partitioning module is used to determine the harmonic level and distribution level of DC current based on historical harmonic characteristic data and real-time spectrum data, generate historical harmonic levels and distribution levels, and transmit them to the strategy generation module. For example, the spectrum partitioning module obtains the historical amplitude fluctuation count of each DC current, then obtains the adjustment duration corresponding to each fluctuation of each DC current, and calculates the average adjustment duration of each DC current by accumulating the adjustment durations corresponding to each fluctuation; it calculates the characteristic coefficient of each DC current based on the historical amplitude fluctuation count and the average adjustment duration; it obtains the historical harmonic level corresponding to the characteristic coefficient, wherein the historical harmonic level includes first-order harmonics, second-order harmonics, and third-order harmonics; it simultaneously obtains the amplitude deviation value and frequency fluctuation value of each DC current, calculates the distribution coefficient of each DC current; and it compares the distribution coefficient with a preset distribution threshold to determine whether the distribution level of the DC current is a first-order distribution, a second-order distribution, or a third-order distribution. The complexity corresponding to the third-order harmonic is higher than that of the second-order harmonic, and the complexity corresponding to the second-order harmonic is higher than that of the first-order harmonic; the suppression requirement corresponding to the third-order distribution is higher than that of the second-order distribution, and the suppression requirement corresponding to the second-order distribution is higher than that of the first-order distribution.

[0054] The strategy generation module generates a dynamic suppression strategy for the converter valve based on the current distribution level and historical harmonic levels, and then transmits this strategy to the parameter processing module. For example, the converter valve prioritizes the current distribution level as the first priority factor, the historical harmonic levels as the second priority factor, and the distance between the current valve's current connection point and the starting point of the current source as the third priority factor. The converter valve starts operation from the current connection point. If multiple currents with the same distribution level exist near the starting point, the current with the highest historical harmonic level is selected for processing. If both the current distribution level and historical harmonic level are the same, the current closest to the connection point is selected for processing. When the converter valve reaches the switching point: if the switching point is connected to only a single DC current, the converter valve directly processes that DC current; if the switching point is connected to two or more DC currents, the DC current with the highest distribution level is processed first; when multiple DC currents connected to the switching point have the same distribution level, the DC current with the highest historical harmonic level is processed first; when the DC currents connected to the switching point have the same distribution level and historical harmonic level, one DC current is randomly selected for processing; if the switching point is not connected to any other DC current and there is an unsuppressed frequency band, the nearest unsuppressed frequency band is processed first; when the converter valve reaches any switching point, if all other frequency bands have been processed, it returns to the initial access point and stops.

[0055] The above rules are used to generate a dynamic suppression strategy for the converter valve during operation. When the converter valve operates according to the dynamic suppression strategy, different modulation intensities are used to perform the operation at different distribution levels or corresponding frequency bands of the third harmonic.

[0056] When the converter valve performs suppression operations according to the dynamic suppression strategy, the status monitoring module is also used to collect the real-time modulation waveform of the converter valve and transmit it to the difference determination module; the storage unit is also used to store the frequency band difference characteristics and corresponding fluctuation parameters in the DC current and transmit them to the difference determination module. The difference determination module is used to determine whether the converter valve has entered the adjustment frequency band. If a frequency band correction signal is generated, the real-time modulation waveform of the converter valve in the adjustment frequency band is transmitted to the distributed detection module; the distributed detection module is used to determine whether the converter valve deviates from the reference frequency band during the adjustment frequency band operation based on the real-time modulation waveform. If it deviates, a modulation correction command is sent to the parameter processing module.

[0057] The difference determination module calculates the frequency band difference between the real-time modulation waveform of the converter valve and the core frequency point of the frequency band difference feature; it obtains the fluctuation parameters corresponding to the frequency band difference feature of the DC current, extracts the core frequency point, the reference fluctuation amplitude, and the attenuation change slope, and obtains the adjustment threshold of the frequency band difference feature by dividing the reference fluctuation amplitude by the attenuation change slope; it constructs the adjustment frequency band of the frequency band difference feature with the core frequency point as the center frequency point and the adjustment threshold as the coverage area; when the frequency band difference is greater than the adjustment threshold, the converter valve performs operations outside the adjustment frequency band and maintains the current operating state; when the frequency band difference is less than or equal to the adjustment threshold, the converter valve enters the adjustment frequency band to perform operations and generates a frequency band correction signal.

[0058] The distributed detection module sets the standard current range and allowable offset threshold for the operation of the converter valve; if the current sensor feedback value is within the allowable offset threshold and the converter valve modulation speed is within the standard current range, the current operating parameters are maintained; if the current sensor feedback value exceeds the allowable offset threshold or the converter valve modulation speed deviates from the standard current range, a modulation correction command is generated.

[0059] The system also includes a waveform analysis module and a monitoring terminal. The status monitoring module is used to collect real-time waveform data of DC current and transmit it to the waveform analysis module. The waveform analysis module is used to analyze the real-time waveform data of DC current in real time. If distortion signals or overshoot signals are generated during analysis, the frequency band markers and corresponding real-time waveform data are transmitted to the monitoring terminal. The monitoring terminal is used for visualization processing of the real-time waveform data of DC current.

[0060] Furthermore, for the detection of anomalies in DC current waveforms, most existing technologies rely solely on single time-domain or frequency-domain analysis, lacking a comprehensive assessment of waveform distortion and overshoot phenomena. This can easily lead to missed or false detections of anomalies. For example, overshoot detection based solely on time-domain waveforms may be affected by noise interference, while relying solely on frequency-domain analysis may fail to capture abnormal changes in transient processes in a timely manner, resulting in the system being unable to provide timely warnings and handle potential faults.

[0061] To address the aforementioned issues, the waveform analysis module of this invention employs the following specific analysis process: It captures the time-domain waveform data of the DC current; converts the time-domain data into a frequency-domain distribution map; uses a moving average filter to eliminate high-frequency noise; sets a filtering threshold based on the amplitude difference between harmonic components and the fundamental frequency; extracts the effective harmonic frequency bands of the DC current; applies wavelet transform to separate low-frequency interference components while preserving complete harmonic spectrum characteristics; identifies the main harmonic components using a peak detection algorithm; matches the frequency-domain structure characteristics of the DC current; and filters out non-harmonic interference components. Simultaneously, it acquires the transient response data of the DC current; sets an amplitude gradient range to identify abnormal overshoot regions; uses dynamic compression technology to enhance the display of transient differences; combines a slope detection algorithm to extract abrupt waveform boundaries; and identifies transient anomalies in the current. If both the frequency-domain distribution map and the transient response data show anomalies, a distortion signal is generated and the corresponding frequency band is marked. If neither set of data shows anomalies, the normal operating procedure is maintained. If either set of data shows anomalies, an overshoot signal is generated and the corresponding frequency band is marked.

[0062] The following is combined Figures 1-5 The system proposed in this invention will be described in detail.

[0063] Harmonic band division and initial suppression: The harmonic detection module first performs frequency band analysis on the DC current, dividing it into the main harmonic frequency band and the frequency band to be suppressed. The parameter processing module controls the converter valve to receive commands and initiate harmonic suppression. During the initial suppression operation, the status monitoring module collects the DC current's spectral data in real time (including amplitude deviation and frequency fluctuation values) and transmits the data to the spectrum division module. Simultaneously, the storage unit retrieves pre-stored historical harmonic characteristic data (historical amplitude fluctuation count and adjustment duration corresponding to each fluctuation) and transmits it to the spectrum division module.

[0064] Harmonic Level and Distribution Level Determination: The spectrum division module determines the harmonic level and distribution level of DC current based on real-time spectrum data and historical harmonic characteristic data. The specific determination process is as follows: First, the average adjustment time of each DC current is calculated (the cumulative average of the adjustment time for each fluctuation). Then, characteristic coefficients are calculated based on the historical amplitude fluctuation count. By comparing these coefficients with preset characteristic thresholds, the harmonic levels are divided into Level 1, Level 2, and Level 3 (complexity increases sequentially). Next, the distribution coefficient is calculated based on the amplitude deviation value and frequency fluctuation value. After comparing this coefficient with a preset distribution threshold, the distribution levels are divided into Level 1, Level 2, and Level 3 (suppression requirements increase sequentially). The generated historical harmonic levels and distribution levels are then transmitted to the strategy generation module.

[0065] Dynamic suppression strategy generation and execution: The strategy generation module generates a dynamic suppression strategy based on the distribution level and historical harmonic levels. The converter valve executes operations with the distribution level as the first priority, the historical harmonic level as the second priority, and the distance between the current connection point and the starting end as the third priority. For example, when there are multiple DC currents with the same distribution level near the starting end, the current with the highest historical harmonic level is processed first; if all levels are the same, the current with the closest distance is selected. During switching point processing, the rule of "distribution level > historical harmonic level > random selection" is followed, and different modulation intensities are used according to different levels or third-order harmonic frequency bands.

[0066] Operation Process Monitoring and Adjustment: When the converter valve performs suppression operations according to the dynamic suppression strategy, the status monitoring module synchronously acquires the real-time modulation waveform and transmits it to the difference determination module. The storage unit calls the pre-stored frequency band difference characteristics (core frequency, reference fluctuation amplitude, attenuation change slope, and other fluctuation parameters) and transmits them to the difference determination module. The difference determination module calculates the frequency band difference between the real-time modulation waveform and the core frequency, and constructs an adjustment frequency band based on the fluctuation parameters: if the difference is greater than the adjustment threshold, the converter valve maintains its current state outside the adjustment frequency band; if the difference is less than or equal to the adjustment threshold, it enters the adjustment frequency band and generates a frequency band correction signal, transmitting the real-time modulation waveform to the distributed detection module. The distributed detection module sets a standard current range and an allowable offset threshold. If the current feedback value or modulation speed exceeds the threshold, it sends a modulation correction command to the parameter processing module to achieve dynamic adjustment of the suppression strategy.

[0067] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0068] Example 1:

[0069] In the real-time suppression and control system for DC current harmonics in flexible DC converter valves, a waveform analysis module and a monitoring terminal are also included to further enhance the monitoring and anomaly identification capabilities of the DC current state. The implementation method including this part is described in detail below.

[0070] During system operation, the status monitoring module, as a key unit for data acquisition, simultaneously acquires real-time waveform data of the DC current while performing real-time spectrum data acquisition tasks. This real-time waveform data encompasses the dynamic changes of the current in both the time and frequency domains, forming the basis for in-depth analysis by the waveform analysis module. The status monitoring module uses high-precision sensors or detection devices to capture the DC current waveform in real time at a set sampling frequency, ensuring that the acquired data accurately reflects the actual operating state of the current. The acquired real-time waveform data is transmitted in a specific format (such as a digital signal sequence) to the waveform analysis module in real time via a data transmission link, providing raw data support for subsequent analytical processing.

[0071] After receiving real-time waveform data, the waveform analysis module captures and preprocesses the time-domain waveform data. The time-domain waveform data visually displays the trend of current change over time, but it may contain various noise and interference components, requiring signal processing techniques for purification and feature extraction. The specific processing flow is as follows: The time-domain data is converted into a frequency domain distribution map using Fourier transform, achieving a conversion from the time domain to the frequency domain for clearer observation of the frequency component distribution of the current. In the frequency domain analysis, a moving average filtering algorithm is used to process the frequency domain spectrum to eliminate the influence of high-frequency noise. Moving average filtering smooths the spectral curve by averaging the amplitudes of several adjacent frequency points, reducing the interference of random noise on the effective signal.

[0072] By setting a filtering threshold based on the amplitude difference between harmonic components and the fundamental frequency, the effective harmonic frequency band of the DC current can be extracted. The fundamental frequency is the basic frequency component of the current, while harmonics are components whose frequencies are integer multiples of the fundamental frequency, and they usually have an adverse effect on the stable operation of the system. By setting a reasonable filtering threshold, non-harmonic components with amplitudes below the threshold (such as measurement noise, environmental interference, etc.) can be filtered out, retaining only the effective harmonic frequency band with higher amplitudes, thereby focusing on the main harmonic components that need to be suppressed.

[0073] In handling low-frequency interference, wavelet transform technology is applied to separate frequency domain data. Wavelet transform features multi-resolution analysis, enabling signal decomposition at different scales, effectively separating low-frequency interference components while preserving complete harmonic spectral characteristics. Through wavelet transform, low-frequency noise and harmonic components in the frequency domain spectrum can be distinguished, avoiding interference from low-frequency interference in harmonic analysis and ensuring the accuracy and reliability of the extracted harmonic features.

[0074] After completing the frequency domain analysis, the waveform analysis module identifies the main harmonic components using a peak detection algorithm. This algorithm scans the frequency domain distribution spectrum to detect frequency points with large amplitudes; these frequency points correspond to the main harmonic components. By matching the frequency domain structure characteristics of the DC current, the authenticity of these harmonic components is further verified, and non-harmonic interference components are filtered out to ensure that the identified harmonic components are real and need to be suppressed.

[0075] In addition to frequency domain analysis, the waveform analysis module also needs to process the transient response data of the DC current. Transient response data reflects the instantaneous changes in current when subjected to disturbances and is a crucial basis for identifying transient anomalies in the current. During transient response data processing, an amplitude gradient range is first set to identify abnormal overshoot regions. This amplitude gradient range is determined based on the system's normal operating parameters and historical data; when the current amplitude changes beyond this range, an abnormal overshoot is identified.

[0076] To more clearly display transient differences, dynamic compression technology is used to process transient response data. Dynamic compression technology amplifies minute transient changes by adjusting the display scale, allowing operators to more intuitively observe abnormal fluctuations in current during transient processes. Simultaneously, a slope detection algorithm is used to extract the boundaries of abrupt waveform changes. This algorithm calculates the slope of the current amplitude change to determine the time and amplitude of the waveform abrupt change, thereby accurately identifying the start and end points of transient current anomalies.

[0077] Based on the comprehensive frequency domain distribution spectrum and transient response data, the waveform analysis module determines abnormal signals. The specific determination logic is as follows: If both the frequency domain distribution spectrum and the transient response data show abnormalities (such as the presence of high-amplitude harmonic components in the frequency domain and obvious overshoot or distortion in the transient response), a distortion signal is generated, and the corresponding frequency band is marked; if only one of the two data sets shows an abnormality (such as a normal frequency domain spectrum but an overshoot in the transient response, or a normal transient response but an abnormal harmonic in the frequency domain spectrum), an overshoot signal is generated, and the corresponding frequency band is marked; if neither data set shows an abnormality, the DC current operation is determined to be normal, and the normal operating procedure is maintained.

[0078] The marked frequency bands and their corresponding real-time waveform data are transmitted to the monitoring terminal. The monitoring terminal, acting as a human-machine interface, is responsible for visualizing this data. Visualization methods include, but are not limited to, waveform display, spectrum plotting, and abnormal frequency band marking. Through this intuitive graphical interface, operators can monitor real-time changes in DC current waveforms, harmonic distribution, and abnormal states, promptly identifying harmonic problems in the system and taking appropriate measures to address them.

[0079] Throughout the process, efficient data transmission and collaborative operation among the modules enable real-time monitoring, analysis, and anomaly identification of DC current harmonics. The waveform analysis module, through comprehensive processing of time and frequency domain data, accurately detects harmonic components and transient anomalies in the current, providing a reliable basis for subsequent harmonic suppression strategy adjustments. The monitoring terminal transforms complex data into intuitive visualizations, improving system operability and human-machine interaction efficiency. This allows operators to more effectively manage and control the operating status of the flexible DC converter valve, ensuring stable and reliable system operation and achieving real-time suppression and optimization of DC current harmonics.

[0080] Example 2:

[0081] In the real-time suppression control system for DC current harmonics in flexible DC converter valves, real-time spectrum data and historical harmonic characteristic data are the key basis for the spectrum division module to determine the harmonic level and distribution level. The implementation method based on these two types of data is described in detail below.

[0082] During system operation, the status monitoring module continuously collects real-time spectrum data of the DC current using built-in high-precision detection elements, explicitly including amplitude deviation and frequency fluctuation values. The amplitude deviation reflects the degree of deviation of the current DC current amplitude from its rated value and can be calculated by the difference between the actual measured value and the rated value. The frequency fluctuation value reflects the dynamic changes in the current frequency during operation, obtained by real-time monitoring of the current cycle and calculating the frequency. This real-time data is transmitted in real-time to the spectrum partitioning module in the form of a data stream, providing immediate information for dynamic analysis.

[0083] The storage unit stores historical harmonic characteristic data, specifically the number of historical amplitude fluctuations in DC current and the corresponding adjustment time for each fluctuation. The number of historical amplitude fluctuations is obtained by statistically analyzing the number of times the current amplitude exceeds the normal fluctuation range during long-term system operation. The adjustment time for each fluctuation records the time spent by the converter valve adjusting for each amplitude fluctuation until stability is restored. This data is recorded and stored in real time during system operation to form a database, which can be accessed at any time according to the needs of the spectrum partitioning module.

[0084] The spectrum division module's determination process is divided into two stages: harmonic level determination and distribution level determination. In the harmonic level determination stage, the historical amplitude fluctuation count of each DC current is first obtained. For example, if the amplitude fluctuation count of a certain DC current within a certain period is N times, then the adjustment duration corresponding to each fluctuation is obtained, such as t1 for the first fluctuation, t2 for the second, and so on, up to tN for the Nth. The adjustment durations corresponding to each fluctuation are accumulated (t1 + t2 + ... + tN), and the average is calculated to obtain the average adjustment duration T of the DC current, i.e., T = (t1 + t2 + ... + tN) / N.

[0085] Based on the historical amplitude fluctuation count and average adjustment time, the spectrum partitioning module calculates the characteristic coefficients of each DC current through a preset logical relationship. The calculation logic of the characteristic coefficients comprehensively considers the fluctuation count and adjustment difficulty; for example, the more fluctuation counts and the longer the average adjustment time, the more complex the harmonic problem, and the larger the characteristic coefficient value. The historical harmonic level of the DC current is determined by comparing the characteristic coefficients with preset characteristic thresholds. These preset characteristic thresholds are pre-set according to system design standards and historical operating data, and are divided into first-order harmonic thresholds, second-order harmonic thresholds, and third-order harmonic thresholds, corresponding to different complexity levels. If the characteristic coefficient is lower than the first-order harmonic threshold, it is determined to be a first-order harmonic, with the lowest complexity; if it is between the first and second-order thresholds, it is a second-order harmonic; if it is higher than the third-order harmonic threshold, it is a third-order harmonic, with the highest complexity, and requires priority processing.

[0086] In the distribution level determination stage, the spectrum division module simultaneously acquires the amplitude deviation and frequency fluctuation values ​​of each DC current. A larger amplitude deviation indicates a greater deviation of the current amplitude from its rated value; a larger frequency fluctuation indicates poorer frequency stability. These two parameters together reflect the degree of anomaly in the DC current's spectral distribution. The spectrum division module, through preset analysis logic, comprehensively processes the amplitude deviation and frequency fluctuation values ​​to calculate the distribution coefficient of each DC current. The calculation logic for the distribution coefficient aims to quantify the combined deviation of the current in amplitude and frequency. For example, a current with a large amplitude deviation and severe frequency fluctuation will also have a large distribution coefficient value.

[0087] The distribution coefficient is compared with a preset distribution threshold to determine the DC current distribution level. The preset distribution threshold is also divided into Level 1, Level 2, and Level 3 distribution thresholds based on system operating requirements, corresponding to different suppression needs. If the distribution coefficient is below the Level 1 threshold, it is classified as Level 1 distribution, with the lowest suppression requirement; if it is between the Level 1 and Level 2 thresholds, it is Level 2 distribution; if it is above the Level 3 threshold, it is Level 3 distribution, with the highest suppression requirement, and targeted suppression strategies should be prioritized.

[0088] The classification rules clearly state that the complexity of third-order harmonics is higher than that of second-order harmonics, and second-order harmonics are more complex than first-order harmonics. This means that third-order harmonics require more complex suppression strategies and longer processing times, while first-order harmonics are relatively simple to handle. Similarly, the suppression requirements for third-order distributions are higher than those for second-order distributions, and for second-order distributions, they are more complex than those for first-order distributions. In other words, the higher the distribution level of a DC current, the wider its harmonic distribution range or the greater its intensity, requiring the converter valve to invest more resources in suppression.

[0089] The spectrum partitioning module, through the aforementioned process, combines real-time acquired data with historically stored data to achieve quantitative analysis and classification of DC current harmonic states. This multi-dimensional data-based judgment method can more comprehensively and accurately reflect the harmonic characteristics of DC current, providing detailed priority criteria for the strategy generation module. For example, for DC currents that simultaneously belong to the third harmonic and the third-level distribution, the strategy generation module will consider them as the highest priority and prioritize the generation of high-intensity suppression strategies; while for currents that are the first harmonic and the first-level distribution, more basic suppression measures can be adopted, thereby achieving reasonable resource allocation and optimization of suppression efficiency.

[0090] Throughout the entire judgment process, data acquisition, storage, and processing follow a strict logical workflow to ensure the scientific validity and reliability of the classification results. Real-time spectrum data guarantees immediate awareness of the current harmonic state, while historical harmonic characteristic data provides long-term statistical patterns. The combination of these two allows the system to dynamically adapt to different harmonic environments, providing precise guidance for the real-time suppression operation of converter valves. Through this hierarchical judgment mechanism, the system can adopt differentiated processing strategies for harmonic problems with different characteristics, improving the overall suppression effect while enhancing the system's flexibility and adaptability.

[0091] Example 3:

[0092] In the real-time suppression control system for DC current harmonics in flexible DC converter valves, the strategy generation module generates dynamic suppression strategies based on preset priority rules to guide the operation of the converter valve. The module's operation uses the distribution level of the DC current, historical harmonic levels, and the distance between the current connection point of the converter valve and the starting point of the DC current as core judgment factors, and dynamically optimizes the suppression strategy through multi-level logic rules. Its implementation method is described in detail below.

[0093] The strategy generation module first establishes the priority order for converter valve operations, specifically: the distribution level of DC current is the first priority factor, the historical harmonic level is the second priority factor, and the distance between the current connection point of the converter valve and the starting point of the DC current is the third priority factor. This priority order is based on the actual needs of harmonic suppression. The distribution level directly reflects the spatial distribution range and intensity of the current harmonics, and currents with higher distribution levels should be processed first; the historical harmonic level reflects the historical complexity of the harmonic problem and can help determine the difficulty of suppression; the distance between connection points affects the efficiency of the operation path, and prioritizing the processing of currents with shorter distances can reduce the movement loss of the converter valve.

[0094] The converter valve operation begins at the current connection point. In the vicinity of the starting point, if multiple DC currents with different distribution levels exist, the converter valve will select the current to be processed sequentially in descending order of distribution level. For example, when currents with tertiary, secondary, and primary distribution levels exist simultaneously, the converter valve will prioritize suppressing the tertiary current. If multiple DC currents with the same distribution level exist near the starting point, the second priority judgment is entered, prioritizing the current with the highest historical harmonic level. For example, if two currents are both secondary distributions, one with a tertiary historical harmonic level and the other with a tertiary historical harmonic level, the converter valve will prioritize processing the tertiary historical harmonic level current. If both the distribution level and historical harmonic level are the same, the third priority judgment is entered, selecting the DC current closest to the connection point for processing to shorten the operation path and improve efficiency.

[0095] When the converter valve completes its current processing task and reaches the switching point, the system enters the switching point processing logic. The switching point is a node in the converter valve's operating path that has multiple current branches, and its processing rules are as follows:

[0096] Single-path scenario: If the switching point is connected to only a single DC current, the converter valve does not need to perform priority judgment and can directly process that DC current. In this scenario, the operating path is clear, and the converter valve can quickly enter the suppression process.

[0097] In multi-path scenarios: If a switching point connects two or more DC currents, the distribution levels of each current are first compared, and the current with the highest distribution level is processed first. For example, when the switching point connects a tertiary and a secondary distribution current, the tertiary current is processed first. If the distribution levels are the same, the historical harmonic levels are compared, and the current with the highest historical harmonic level is processed first. For example, if two currents are both secondary distributions, with tertiary and secondary historical harmonic levels respectively, the current with the tertiary historical harmonic level is processed first. If both the distribution level and the historical harmonic level are the same, a random selection mechanism is used to randomly select one current from multiple currents for processing to avoid processing stagnation caused by identical levels.

[0098] Scenario where no current is connected but an unsuppressed frequency band exists: If the switching point is not connected to any other DC current, but the system detects an unsuppressed frequency band, the converter valve will prioritize processing the unsuppressed frequency band closest to its current location, ensuring that all areas to be suppressed are covered. When the converter valve reaches any switching point, if all frequency bands have been processed, it will execute a return-to-initial-access shutdown operation, ending the current suppression process.

[0099] When generating dynamic suppression strategies, the strategy generation module must comprehensively consider the operating path and processing sequence of the converter valves to ensure the logic and executability of the strategies. For example, in complex multi-branch current networks, converter valves may need to pass through different switching points multiple times, and the processing objects must be re-evaluated according to priority rules each time. To avoid duplicate processing or omissions, the system ensures the rationality of the operating path by recording the status of processed and unprocessed frequency bands in real time.

[0100] Furthermore, when implementing the dynamic suppression strategy, the converter valve employs different modulation intensities for different distribution levels or frequency bands corresponding to third-order harmonics. The modulation intensity setting is directly related to the distribution level, specifically: for frequency bands corresponding to third-order distributions or third-order harmonics, due to high suppression requirements and complexity, high-intensity modulation is used, i.e., increasing the amplitude or frequency of the modulation signal to enhance the suppression effect on harmonics; for frequency bands corresponding to second-order distributions or second-order harmonics, medium-intensity modulation is used; and for frequency bands corresponding to first-order distributions or first-order harmonics, low-intensity modulation is used. This differentiated modulation method can optimize the energy consumption and operating efficiency of the converter valve while ensuring the suppression effect, and avoid over-processing of low-order harmonics.

[0101] During the priority determination process, when quantifying the distance between access points, the Euclidean distance formula is used to calculate the distance between the current position of the converter valve and the starting point of each DC current. The Euclidean distance formula is:

[0102]

[0103] Where D represents the distance between the current connection point of the converter valve and the starting point of the DC current. These are the coordinates of the current connection point of the converter valve. These are the coordinates of the starting point of the DC current. By calculating the distance between each current starting point and the connection point, the distances can be compared intuitively, providing data support for the third priority determination.

[0104] The entire strategy generation process revolves around priority rules, ensuring that the converter valve can efficiently and orderly perform suppression operations in complex harmonic environments through hierarchical judgment and path optimization. From the initial selection at the starting point to the dynamic adjustment of the switching point, each step is based on real-time collected harmonic level data and spatial location information, achieving intelligent generation of suppression strategies. This decision-making mechanism based on multi-dimensional data not only improves the targeting and effectiveness of harmonic suppression but also reduces the energy consumption and mechanical losses of the converter valve by rationally planning the operation path, thus extending the service life of the equipment.

[0105] The strategy generation module, along with other components such as the spectrum allocation module and the status monitoring module, forms a complete closed-loop control system. The hierarchical data provided by the spectrum allocation module lays the foundation for strategy generation, while the real-time operational status data from the status monitoring module provides the basis for strategy adjustments. Through this dynamic interaction, the system can adapt to harmonic variations under different time periods and operating conditions, maintaining optimal suppression effects at all times, ensuring the stable operation of the flexible DC converter valve and continuous optimization of power grid quality.

[0106] Example 4:

[0107] In the real-time suppression control system for DC current harmonics in a flexible DC converter valve, the difference determination module analyzes the real-time modulation waveform of the converter valve based on the fluctuation parameters pre-stored in the storage unit to determine whether it has entered the frequency band that needs adjustment. The specific process and logic of this implementation method are described in detail below.

[0108] The pre-stored fluctuation parameters in the storage unit serve as core data for frequency band difference characteristics, specifically including the core frequency, reference fluctuation amplitude, and attenuation slope. The core frequency refers to the center frequency of the frequency band to be suppressed, reflecting the main frequency location where harmonic energy is concentrated; the reference fluctuation amplitude is the typical amplitude of current fluctuation within that frequency band, reflecting the intensity of the harmonics; and the attenuation slope represents the rate of attenuation of the current amplitude with frequency change within that frequency band, used to describe the distribution pattern of the harmonic spectrum. These three parameters are obtained through statistical analysis of historical harmonic data, stored in the system database, and can be retrieved in real time during the difference determination process.

[0109] The workflow of the difference determination module begins with the analysis of the real-time modulation waveform of the converter valve. While the converter valve is performing suppression operations, the status monitoring module continuously collects the frequency data of its modulation waveform and transmits it to the difference determination module. The difference determination module first calculates the frequency difference between the center frequency of the real-time modulation waveform and the core frequency point of the frequency band difference characteristic. This difference reflects the degree of deviation between the frequency center of the current modulation operation and the center of the target suppression frequency band.

[0110] To determine whether the converter valve needs to adjust its operating frequency band, the difference determination module needs to construct an adjustment frequency band based on fluctuation parameters. The specific steps are as follows: First, retrieve the fluctuation parameters corresponding to the current DC current frequency band being processed from the storage unit, and extract the core frequency point. Benchmark fluctuation amplitude and the slope of decay change Then, the adjustment threshold for the frequency band difference characteristics is obtained by dividing the baseline fluctuation amplitude by the attenuation change slope. ,Right now:

[0111]

[0112] in, This indicates the adjustment threshold, measured in Hertz (Hz), and is used to measure the allowable frequency deviation range. The baseline fluctuation amplitude is expressed in amperes (A) and reflects the energy intensity of harmonics. The slope of the attenuation change, measured in amperes per hertz (A / Hz), describes the rate at which the harmonic amplitude changes with frequency.

[0113] With core frequency Center frequency point, to adjust threshold To determine coverage, an adjustment band is constructed based on frequency band difference characteristics, the range of which is: This adjustment frequency band represents the frequency range that the converter valve needs to be monitored and adjusted. When the center frequency of the real-time modulation waveform falls into this range, it indicates that the converter valve has entered the frequency band that requires fine adjustment.

[0114] After the frequency band difference calculation is completed, the difference determination module performs a logical judgment: if the frequency band difference is greater than the adjustment threshold... This indicates that the center frequency of the real-time modulated waveform is outside the adjustment band. In this case, the converter valve operating in the current frequency band will not significantly affect the target harmonics; therefore, the current operating state should be maintained without adjustment. If the frequency band difference is less than or equal to the adjustment threshold... If the frequency of the real-time modulated waveform has entered the adjustment band, it indicates that the operation of the converter valve may have a direct effect on the target harmonics, but it may also cause the suppression effect to deviate due to frequency offset. Therefore, a frequency band correction signal is generated, and the real-time modulated waveform of the converter valve in the adjustment band is transmitted to the distributed detection module for further analysis and adjustment.

[0115] This determination process achieves accurate identification of the converter valve's operating frequency band by comparing quantified frequency differences with adjustment thresholds. The core frequency point serves as the benchmark for the target suppression frequency band, ensuring the accuracy of the adjustment direction; the adjustment threshold, through dynamic calculation of fluctuation parameters, allows the adjusted frequency band to adapt to the needs of frequency bands with different harmonic characteristics. For example, for frequency bands with large benchmark fluctuation amplitudes and small attenuation slopes, the adjustment threshold... A larger threshold means a wider permissible frequency deviation range, allowing the converter valve to effectively suppress harmonics over a wider frequency range; however, for frequency bands with smaller reference fluctuation amplitudes and steeper attenuation slopes, adjusting the threshold... The smaller frequency requires the operating frequency of the converter valve to be closer to the core frequency to ensure the suppression effect.

[0116] The collaborative operation of the difference determination module, storage unit, and status monitoring module forms a dynamic monitoring mechanism for the operating frequency band of the converter valve. Historical fluctuation parameters provided by the storage unit offer benchmark data for the determination, while real-time data from the status monitoring module ensures the timeliness of the judgment. The logical processing of the difference determination module converts data into control commands. Through this mechanism, the system can promptly trigger adjustment procedures when the converter valve approaches the target suppression frequency band, avoiding decreased suppression efficiency or ineffective operation due to frequency deviation, thereby improving the accuracy and effectiveness of harmonic suppression.

[0117] In practical applications, different DC current frequency bands may have different combinations of fluctuation parameters, and the difference judgment module needs to dynamically adjust the judgment criteria based on the parameters called in real time. For example, for high-frequency harmonic bands, the attenuation change slope is usually larger, the adjustment threshold is relatively smaller, and higher frequency control accuracy of the converter valve is required; while for low-frequency harmonic bands, the attenuation change slope is smaller, the adjustment threshold is relatively larger, and the fault tolerance margin of frequency control is larger. This differentiated judgment method enables the system to adapt to complex and ever-changing harmonic environments, improving the flexibility and adaptability of the overall suppression strategy.

[0118] In summary, the difference determination module achieves intelligent judgment and precise control of the converter valve's operating frequency band through quantitative analysis of real-time modulation waveforms and pre-stored frequency band characteristics. This process does not rely on subjective experience or fixed thresholds, but rather dynamically generates adjustment standards based on actual harmonic characteristics, ensuring the scientific validity and reliability of the judgment results. Through linkage with the subsequent distributed detection module, the system can form a complete closed loop from frequency band identification to strategy adjustment, providing solid technical support for real-time harmonic suppression of flexible DC converter valves.

[0119] Example 5:

[0120] In the real-time suppression and control system for DC current harmonics of flexible DC converter valves, the distributed detection module undertakes the key task of monitoring the current parameters and modulation state during the operation of the converter valve, and dynamically identifies and corrects operational deviations through preset standard ranges and thresholds.

[0121] Method Implementation

[0122] The present invention provides a real-time suppression method for DC current harmonics in a converter valve, comprising:

[0123] The system acquires the real-time spectrum of the DC current of the converter valve; determines the distribution level and historical harmonic level of the DC current based on the real-time spectrum and historical harmonic characteristics; the historical harmonic characteristics of the DC current include the number of historical amplitude fluctuations and the adjustment duration corresponding to each fluctuation; generates a harmonic suppression strategy for the converter valve operation based on the distribution level and historical harmonic level of the DC current; the higher the distribution level and historical harmonic level of the DC current, the higher the priority of executing the harmonic suppression strategy; controls the converter valve to execute harmonic suppression operation according to the generated harmonic suppression strategy; in the harmonic suppression strategy, different modulation intensities are used for DC currents with different distribution levels and historical harmonic levels.

[0124] The process involves calculating the average regulation time of the DC current based on historical harmonic characteristics, determining the characteristic coefficient of the DC current based on the number of historical amplitude fluctuations and the average regulation time, and determining the historical harmonic level based on the determined characteristic coefficient. The more fluctuations and the longer the average regulation time, the larger the corresponding characteristic coefficient and the higher the historical harmonic level.

[0125] The real-time spectrum includes amplitude deviation and frequency fluctuation. The process of determining the distribution level is as follows: the distribution coefficient of the DC current is calculated based on the amplitude deviation and frequency fluctuation of the real-time DC current spectrum, and the distribution level of the DC current is determined based on the distribution coefficient. The distribution coefficient is used to characterize the comprehensive deviation of the DC current in amplitude and frequency. The greater the amplitude deviation and frequency fluctuation, the greater the corresponding distribution coefficient and the higher the distribution level.

[0126] In one embodiment, the generation process of the harmonic suppression strategy is as follows: taking the distribution level of DC current as the first priority element and the historical harmonic level of DC current as the second priority element, the DC current with the highest distribution level is given priority for harmonic suppression; if there are DC currents with the same distribution level, the DC current with the highest historical harmonic level is preferred for harmonic suppression.

[0127] In another embodiment, the generation process of the harmonic suppression strategy is as follows:

[0128] When generating the harmonic suppression strategy, a three-level priority mechanism including physical topology constraints is introduced: the distribution level of DC current is used as the first priority element, the historical harmonic level of DC current is used as the second priority element, and the physical distance between the current connection point of the converter valve and the starting end of DC current is used as the third priority element.

[0129] The starting point of the DC current is the source of harmonics; the current connection point of the converter valve is the actual connection position of the converter valve in the electrical network, which can be changed between different candidate switching points.

[0130] When making harmonic suppression decisions, the current connection point of the converter valve is used as the reference origin: if there are multiple DC currents with the same distribution level near the starting point of the DC current, the one with the highest historical harmonic level is selected for processing first. If the distribution level and historical harmonic level of each DC current are the same, the physical distance between each starting point and the current connection point of the converter valve is measured, and the DC current with the smallest physical distance, i.e., the closest distance, is selected for processing first.

[0131] When the converter valve reaches the switching point, if the switching point is connected to only a single DC current, the converter valve directly performs harmonic suppression on that DC current; if the switching point is connected to at least two DC currents, the DC current with the highest distribution level is prioritized for harmonic suppression; if the DC currents connected to the switching point have the same distribution level, the DC current with the highest historical harmonic level is prioritized for harmonic suppression; if the DC currents connected to the switching point have the same distribution level and historical harmonic level, a DC current is randomly selected for harmonic suppression.

[0132] During suppression operations, the real-time modulation waveform of the DC current is also collected simultaneously. Based on the real-time modulation waveform of the DC current and the frequency band difference characteristics, it is determined whether the adjustment frequency band has been entered. The frequency band difference characteristics include the core frequency point, the reference fluctuation amplitude, and the attenuation change slope. If the adjustment frequency band is entered, it is determined whether the converter valve deviates from the reference frequency band during the adjustment frequency band operation based on the real-time modulation waveform within the adjustment frequency band. If it deviates, a modulation correction command is sent.

[0133] The method also includes: acquiring and analyzing the real-time waveform of the DC current; if the analysis generates a distorted signal or an overshoot signal, the frequency band is marked and the corresponding real-time waveform is displayed.

[0134] The specific implementation process of this method has been described in detail in the system implementation, and will not be repeated here.

[0135] Storage Media Implementation

[0136] The present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of a real-time suppression method for DC current harmonics in a converter valve. The specific implementation process of this method has been described in detail in the system implementation, and will not be repeated here.

[0137] This invention divides the frequency bands into primary harmonics and those to be suppressed, collects real-time spectrum data and modulation waveforms, and determines the harmonic level and distribution level by combining historical harmonic characteristics. A dynamic suppression strategy is generated based on the distribution level, historical harmonic level, and priority of access point spacing, controlling the converter valves to operate according to the strategy. Real-time fine-tuning of the strategy is achieved by calculating frequency band differences and analyzing modulation waveforms. The waveform data is analyzed and visualized on the monitoring terminal. This achieves dynamic hierarchical suppression and adaptive adjustment of harmonics, improving the stability and power quality of flexible DC transmission systems.

[0138] The implementation methods of this invention will be described in detail below with reference to specific application scenarios.

[0139] I. Standard Parameter Setting and Real-time Data Acquisition

[0140] During system initialization, the distributed detection module needs to set the standard current range and allowable offset threshold. The standard current range is determined based on the rated operating parameters of the converter valve and the power grid operation specifications. For example, the standard current range of a converter valve can be set to ±5% of the rated current value (e.g., if the rated current is 1000A, the standard range is 950A-1050A). This range reflects the current fluctuation range during normal system operation. The allowable offset threshold is set based on the equipment's safety margin and harmonic suppression accuracy requirements, and is usually ±2% of the upper or lower limit of the standard current range (e.g., in the above scenario, the allowable offset threshold can be set to ±20A, meaning an alarm is triggered when the actual current exceeds the range of 930A-1070A).

[0141] During the execution of the dynamic suppression strategy by the converter valve, the distributed detection module acquires the current feedback value in real time through the current sensor and simultaneously monitors the modulation speed of the converter valve (i.e., the adjustment range of the modulation parameters per unit time, such as the rate of change of the modulation frequency or the increase or decrease of the modulation amplitude). The current sensor uses a high-precision electromagnetic induction device to continuously collect current data at a millisecond-level sampling frequency to ensure real-time performance; the modulation speed data is obtained by analyzing the command output frequency or parameter change step size of the converter valve's internal control system.

[0142] II. Normal Operation Determination in a Single Scenario

[0143] Taking the suppression operation of a certain DC current frequency band as an example, assume that the converter valve is currently performing medium-intensity modulation on the frequency band of the second-level distribution and the second-level historical harmonic level. If the real-time value fed back by the current sensor is always within the standard current range of 950A~1050A, and the modulation speed is maintained within the preset standard range (such as adjusting the frequency by no more than 5Hz per minute), the distribution detection module determines that the operation is normal, does not trigger any adjustment command, and the converter valve continues to perform the suppression operation according to the current parameters.

[0144] During this process, the distributed detection module continuously monitors the data, performing compliance checks on the current value and modulation speed at regular intervals (e.g., 1 second). If the data meets the standard for multiple consecutive sampling periods, the system confirms the effectiveness of the current suppression strategy and no intervention is required. If the data shows slight fluctuations at a certain moment but does not exceed the allowable offset threshold, the module initiates short-term trend analysis, using a sliding window algorithm to predict the subsequent data trend and avoid erroneous adjustments triggered by accidental interference.

[0145] III. Generation of Correction Instructions in Abnormal Scenarios

[0146] Scenario 1: Current feedback value exceeds the allowable offset threshold

[0147] Suppose that when the converter valve is handling the third-level distributed frequency band, a sudden increase in harmonic intensity causes the current sensor feedback value to jump from 1000A within the standard range to 1100A, exceeding the upper limit of the allowable offset threshold (1070A). Upon detecting this anomaly, the distributed detection module immediately initiates the following process:

[0148] Anomaly localization: By comparing the real-time modulation waveform with the pre-stored frequency band difference characteristics, it is confirmed whether the current anomaly is caused by the converter valve operating within the adjusted frequency band. If the difference determination module has previously generated a frequency band correction signal, it indicates that the converter valve has entered the target frequency band, but the modulation parameters have failed to effectively suppress harmonics, resulting in excessive current.

[0149] Correction instruction generation: Based on the anomaly type (such as amplitude exceeding the limit), the distribution detection module generates targeted modulation correction instructions, such as increasing the modulation intensity (upgrading medium-intensity modulation to high-intensity modulation) or adjusting the modulation frequency (fine-tuning the frequency towards the core frequency point).

[0150] Command transmission: The correction command is transmitted to the parameter processing module via a high-speed communication bus. After parsing the command, the parameter processing module immediately adjusts the modulation parameters of the converter valve, such as increasing the amplitude of the modulation signal by 20% or decreasing the frequency by 3Hz.

[0151] Scenario 2: Modulation speed deviates from the standard current range

[0152] In another operating scenario, when the converter valve performs low-intensity modulation on the primary distributed frequency band, the modulation speed suddenly increases due to control system parameter drift (e.g., the frequency adjustment rate increases from the standard 2Hz to 8Hz per minute), far exceeding the allowable range. After detecting the abnormal modulation speed, the distributed detection module performs the following operations:

[0153] Rate verification: By comparing the real-time modulation rate with the standard modulation rate curve, it is confirmed whether the rate deviation persists (e.g., exceeding the standard for three consecutive sampling periods).

[0154] Risk assessment: Analyze the potential consequences of rapid modulation, such as current overshoot or increased equipment losses. Based on the harmonic levels (first-order distribution) of the current frequency band, the risk level is determined to be low, but timely correction is necessary to avoid a chain reaction.

[0155] Command generation and execution: Generate correction commands to reduce modulation speed, such as limiting the frequency adjustment rate to no more than 3 Hz per minute, and force the converter valve to execute them through the parameter processing module. At the same time, record the abnormal log for subsequent fault analysis.

[0156] Scenario 3: Composite anomaly (current exceeding limits and modulation speed abnormality)

[0157] In complex harmonic environments, situations may arise where the current feedback value exceeds the allowable offset threshold and the modulation speed simultaneously deviates from the standard. For example, when a converter valve handles harmonics in cross-bands, the current value drops to 900A (below the lower limit of the allowable offset threshold of 930A) due to interference from adjacent bands, while the modulation speed fluctuates drastically due to algorithm conflicts (e.g., the frequency adjustment rate changes randomly between 0 and 15 Hz per minute). In this case, the distributed detection module processes the problem according to the following logic:

[0158] Multi-parameter correlation analysis: By aligning current data and modulation speed data with timestamps, it is determined whether there is a causal relationship between the two (such as whether a sudden change in modulation speed leads to an abnormal current).

[0159] Priority processing: First, address the current over-limit problem, which poses a greater threat to system safety, and generate instructions to increase the modulation strength or adjust the frequency to stabilize the current; at the same time, handle the modulation speed anomaly in parallel, triggering the parameter reset or algorithm switch of the internal control system to restore the stability of the modulation speed.

[0160] Dynamic monitoring and feedback: After the correction command is executed, the recovery status of current and modulation speed is continuously monitored. If the current and modulation speed do not return to normal within a preset time (e.g., 5 minutes), a cascading alarm is issued to prompt the operator to intervene.

[0161] IV. Execution and Effect Verification of Correction Instructions

[0162] After the modulation correction command generated by the distributed detection module is transmitted to the actuator of the converter valve through the parameter processing module, the state monitoring module collects the corrected current data and modulation waveform in real time, forming a closed-loop feedback. For example, after high-intensity modulation is performed in scenario 1, if the current value gradually falls back to the standard range in subsequent sampling periods (e.g., from 1100A to 1030A), it indicates that the correction command is effective, and the distributed detection module maintains the currently adjusted parameters; if the current value continues to exceed the limit, a secondary correction process is initiated, such as further adjusting the modulation phase or activating a backup suppression strategy.

[0163] Throughout the process, the distributed detection module does not rely on a preset fixed correction mode, but dynamically generates instructions based on real-time data. For example, the correction direction may differ for current over-limit problems in different frequency bands: in the high-frequency harmonic band, the modulation frequency may be increased to match the harmonic frequency; in the low-frequency band, the modulation amplitude may be increased to enhance the suppression. This adaptive adjustment based on actual operating conditions ensures the pertinence and effectiveness of the correction instructions.

[0164] V. System Collaboration and Data Recording

[0165] The distributed detection module, the difference determination module, and the strategy generation module collaborate through real-time data interaction. For example, when the difference determination module confirms that the converter valve has entered the adjustment frequency band and transmits the real-time modulation waveform, the distributed detection module automatically switches to a refined monitoring mode, reducing the sampling interval and increasing the threshold sensitivity. If the strategy generation module adjusts the modulation intensity due to changes in harmonic levels, the distributed detection module synchronously updates the standard current range and the allowable offset threshold to adapt to the new operating parameters.

[0166] Furthermore, the distributed detection module meticulously records all abnormal events, correction commands, and processing results, forming a historical database. The records include the time of the anomaly, current value, modulation speed, correction command content, and processing time, providing system maintenance personnel with information to analyze harmonic suppression effectiveness, optimize threshold settings, or troubleshoot equipment malfunctions. For example, by statistically analyzing the number of abnormal triggers in a specific frequency band, it can be determined whether the harmonic characteristics of that band need reassessment or whether the hardware configuration of the converter valve needs upgrading.

[0167] In summary, the distributed detection module achieves accurate identification and rapid response to converter valve operational deviations through real-time monitoring, dynamic threshold comparison, and intelligent correction command generation. Its core lies in combining dual monitoring of current parameters and modulation status. Through multi-dimensional data analysis and logical judgment, it ensures that the converter valve always operates within the reference frequency band in complex harmonic environments, thereby guaranteeing the stability of the flexible DC transmission system and the reliability of harmonic suppression. This scenario-based processing logic avoids the limitations of over-reliance on fixed algorithms and enhances the overall robustness of the system through a flexible collaborative mechanism.

[0168] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0169] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for real-time suppression of DC current harmonics in a converter valve, characterized in that, include: Collect the real-time spectrum of the DC current of the converter valve; The distribution level and historical harmonic level of the DC current are determined based on the real-time spectrum and historical harmonic characteristics of the DC current. The historical harmonic characteristics of DC current include the number of historical amplitude fluctuations of DC current and the adjustment time corresponding to each fluctuation. Harmonic suppression strategies for converter valve operation are generated based on the DC current distribution level and historical harmonic levels. The higher the DC current distribution level and historical harmonic level, the higher the priority of implementing harmonic suppression strategies; The control converter valve performs harmonic suppression operation according to the generated harmonic suppression strategy; in the harmonic suppression strategy, different modulation intensities are used for DC currents with different distribution levels and historical harmonic levels.

2. The real-time suppression method for DC current harmonics in a converter valve according to claim 1, characterized in that, The process for determining the historical harmonic level is as follows: calculate the average adjustment time of the DC current based on the historical harmonic characteristics, determine the characteristic coefficient of the DC current based on the number of historical amplitude fluctuations and the average adjustment time, and determine the historical harmonic level based on the determined characteristic coefficient; wherein, the more fluctuations and the longer the average adjustment time, the larger the corresponding characteristic coefficient and the higher the historical harmonic level.

3. The real-time suppression method for DC current harmonics in a converter valve according to claim 1 or 2, characterized in that, The real-time spectrum includes amplitude deviation and frequency fluctuation; the process of determining the distribution level is as follows: the distribution coefficient of the DC current is calculated based on the amplitude deviation and frequency fluctuation of the real-time DC current spectrum, and the distribution level of the DC current is determined based on the distribution coefficient; the distribution coefficient is used to characterize the comprehensive deviation of the DC current in amplitude and frequency. The greater the amplitude deviation and frequency fluctuation, the greater the corresponding distribution coefficient and the higher the distribution level.

4. The real-time suppression method for DC current harmonics in a converter valve according to claim 1, characterized in that, The generation process of the harmonic suppression strategy is as follows: the distribution level of DC current is used as the first priority factor, and the historical harmonic level of DC current is used as the second priority factor. The DC current with the highest distribution level is given priority for harmonic suppression; if there are DC currents with the same distribution level, the DC current with the highest historical harmonic level is preferred for harmonic suppression.

5. The real-time suppression method for DC current harmonics in a converter valve according to claim 1, characterized in that, The generation process of the harmonic suppression strategy is as follows: The distribution level of DC current is used as the first priority factor, the historical harmonic level of DC current is used as the second priority factor, and the physical distance between the current connection point of the converter valve and the starting point of DC current is used as the third priority factor. Taking the current connection point of the converter valve as the reference origin, if there are DC currents with the same distribution level near the starting point of the DC current, the DC current with the highest historical harmonic level is selected for processing first; if the distribution level and historical harmonic level of each DC current are the same, the DC current with the smallest physical distance is selected for processing. When the converter valve reaches the switching point, if the switching point is connected to only a single DC current, the converter valve directly performs harmonic suppression on that DC current; if the switching point is connected to at least two DC currents, the DC current with the highest distribution level is prioritized for harmonic suppression; if the DC currents connected to the switching point have the same distribution level, the DC current with the highest historical harmonic level is prioritized for harmonic suppression; if the DC currents connected to the switching point have the same distribution level and historical harmonic level, a DC current is randomly selected for harmonic suppression.

6. The real-time suppression method for DC current harmonics in a converter valve according to claim 1, characterized in that, The method also includes: During the suppression operation, the real-time modulated waveform of the DC current is also collected simultaneously; Whether to enter the adjustment frequency band is determined based on the real-time modulation waveform and frequency band difference characteristics of the DC current; the frequency band difference characteristics include the core frequency point, the reference fluctuation amplitude, and the attenuation change slope; If the frequency band is adjusted, the real-time modulation waveform within the frequency band is used to determine whether the converter valve deviates from the reference frequency band during operation. If it deviates, a modulation correction command is sent.

7. The real-time suppression method for DC current harmonics in a converter valve according to claim 1, characterized in that, The method also includes: acquiring and analyzing the real-time waveform of the DC current; if the analysis generates a distorted signal or an overshoot signal, the frequency band is marked and the corresponding real-time waveform is displayed.

8. A real-time suppression system for DC current harmonics in a converter valve, comprising a processor, characterized in that, The processor executes a computer program to implement the steps of the method according to any one of claims 1-6.

9. The real-time suppression system for DC current harmonics of the converter valve according to claim 8, characterized in that, It also includes a display module, which is used to display the real-time waveform of the DC current when a distortion signal or overshoot signal occurs in the DC current.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the method according to any one of claims 1-6.

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