Harmonic suppression control method for dual flyback transformer rectifier

Abstract

The present application relates to a kind of double anti-star transformer rectification harmonic suppression control method.By establishing the rectification bridge arm phase characteristic parameter table in control platform, the theoretical conduction phase of bridge arm, winding attribution and waveform synchronization characteristic are recorded;In the operation process of rectification control unit, the output current of transformer and bridge arm conduction state are collected, and rectification operation state data set is generated;The conduction phase offset of bridge arm is calculated, the corresponding harmonic component is analyzed, and the mapping relationship between bridge arm state and harmonic distribution is obtained.According to the mapping result, it is judged whether the current bridge arm configuration meets the phase coverage requirement of target rectification pulse number, if not, select the standby bridge arm group with preset phase difference and generate switching instruction.Rectification control unit responds to instruction to lock current bridge arm conduction path and release target bridge arm group, realize bridge arm resource dynamic reconstruction and rectification performance optimization.The present application can effectively suppress harmonic, improve the topology adaptability and output quality of rectification system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformers, in particular to a double anti-star transformer rectification harmonic suppression control method. BACKGROUND

[0002] With the continuous development of power electronic technology and the increasing demand for high-current low-voltage DC power quality in terminal applications, the double anti-star rectification topology structure is widely used in controllable rectification devices due to its strong current output capability. In existing engineering practice, one or two dry-type current conversion transformers are often used to provide input power for the double anti-star rectification system. The valve side winding of each transformer is split into four windings along the axial direction, and the two anti-star connected windings are used to build the rectification bridge arm to achieve the goal of low-voltage high-current output. In some high-capacity applications, the equivalent twelve-pulse or even twenty-four-pulse rectification can be achieved by connecting two rectification units in parallel, thereby reducing output ripple and improving power supply quality.

[0003] Although the existing rectification structure has high output capability and certain harmonic suppression performance in hardware configuration, the conduction phase of each rectification bridge arm is often affected by factors such as load fluctuation, power grid disturbance, and equipment aging during rectification operation, resulting in deviations between the actual conduction state and the theoretical expectation, and further causing harmonic distribution imbalance and affecting output current quality. In addition, the traditional system usually lacks real-time identification and configuration capability of the rectification bridge arm operating state, and cannot dynamically adjust the bridge arm resources according to the operating parameters, nor can it flexibly configure different phase difference bridge arm combinations in the multi-bridge arm parallel structure to improve the rectification pulse number and waveform quality.

[0004] Therefore, it is necessary to propose a new rectification control method to improve the operating stability and harmonic control capability of the multi-bridge arm parallel rectification structure. SUMMARY

[0005] The present application provides a double anti-star transformer rectification harmonic suppression control method to improve the harmonic control capability.

[0006] The present application provides a double anti-star transformer rectification harmonic suppression control method, comprising:

[0007] Establishing a rectification bridge arm phase characteristic parameter table in the control platform, the rectification bridge arm phase characteristic parameter table is used to record the theoretical conduction phase of each rectification bridge arm corresponding to the rectification control unit connected by the double anti-star transformer, the winding group to which the bridge arm belongs, and the synchronization characteristics with the target rectification waveform;

[0008] During operation of the rectification control unit, output current values of each valve-side winding of the dual flyback star rectifier transformer and conduction states of each rectifier bridge arm in the rectification control unit are collected, the collected data are compared with a phase characteristic parameter table of the rectifier bridge arm, and a rectification operation state data set corresponding to a current rectification state is generated;

[0009] Based on the rectification operation state data set, an offset value between an actual conduction phase of each rectifier bridge arm and a theoretical conduction phase thereof is calculated, a harmonic component amplitude in a rectification output current is analyzed according to the offset value, and a mapping result between a bridge arm conduction state and a harmonic distribution is generated.

[0010] According to the mapping result, whether a bridge arm configuration that has been enabled in the current rectification control unit meets a conduction phase coverage requirement corresponding to a target rectification pulse number is judged; if the judgment result is that the bridge arm configuration does not meet the requirement, a target bridge arm group that has a preset phase displacement difference with a current bridge arm group is selected from a standby bridge arm group, and a bridge arm switching control instruction is generated based on the judgment result;

[0011] The bridge arm switching control instruction is sent to the rectification control unit, and the rectification control unit performs adjustment of a bridge arm conduction state according to the bridge arm switching control instruction, specifically including: synchronously locking part of a conduction path in the current bridge arm group and releasing a conduction path of the selected target bridge arm group, so as to complete dynamic reconstruction of bridge arm resources and improve a rectification pulse number.

[0012] The beneficial effects of the technical solutions provided in the application include:

[0013] (1) By calculating the offset of the rectifier bridge arm conduction phase in real time and analyzing the influence of the offset on the harmonic distribution, the bridge arm configuration can be dynamically adjusted during operation, so that the harmonic amplitude in the rectification output current is significantly suppressed, which helps to improve power quality and reduce interference on the power grid.(2) By establishing a mapping relationship between the bridge arm conduction state and the harmonic characteristic, and automatically switching the bridge arm group with a phase displacement difference according to the operation state, the optimal configuration of the rectification topology structure can be realized without changing the hardware connection mode, so as to improve the pulse number of the rectification system and reduce the output ripple. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a flowchart of a dual flyback star transformer rectification harmonic suppression control method provided by the first embodiment of the application.

[0015] Figure 2 is a same-phase core column four-split low-voltage winding arrangement structure suitable for a dual flyback rectification structure and related to the first embodiment of the application.

[0016] Figure 3 is an assembly structure and lead terminal distribution diagram of a dry-type four-split dual flyback rectifier transformer. Detailed Implementation

[0017] Many specific details are set forth in the following description to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of this application; therefore, this application is not limited to the specific embodiments disclosed below.

[0018] The first embodiment of this application provides a method for suppressing harmonics in a dual-star transformer rectifier. Please refer to... Figure 1 This figure is a schematic diagram of the first embodiment of this application. The following is in conjunction with... Figure 1 The first embodiment of this application provides a detailed description of a method for suppressing harmonics in a dual-reverse-star transformer rectifier.

[0019] Step S101: Establish a rectifier bridge arm phase characteristic parameter table in the control platform. The rectifier bridge arm phase characteristic parameter table is used to record the theoretical conduction phase of each rectifier bridge arm in the rectifier control unit connected to the double-reflector transformer, the winding group to which the bridge arm belongs, and the synchronization characteristics with the target rectified waveform.

[0020] In establishing the rectifier bridge arm phase characteristic parameter table in the control platform, the first step is to identify and classify each rectifier bridge arm based on the physical structure and working topology of the rectifier control unit connected to the double-star transformer. This involves clarifying the arm's number, its associated winding, conduction path, connection relationship with the transformer winding, and the corresponding output phase in the control logic. Electrically, each bridge arm typically corresponds to an independent power switching unit. Its conduction state determines the conduction period and phase during the AC input to DC output conversion process. Therefore, it is essential to first map each bridge arm to its specific winding endpoint according to the transformer winding connection method (e.g., upper A phase, lower A phase, upper B phase, etc.) and label the bridge arm group to which it belongs for subsequent switching control.

[0021] Next, the theoretical conduction phase of each bridge arm needs to be recorded. This refers to the phase angle position at the intersection of the conduction time range of the bridge arm and the voltage zero point during the rectification cycle under standard ideal conditions. This theoretical conduction phase can be obtained through system simulation, transformer phase shift angle calculation, and rectifier pulse number setting. For example, if the goal is to achieve twelve-pulse rectification, the conduction cycle of each phase should be evenly distributed throughout the entire cycle, with a clearly defined starting phase angle and duration angle. In the characteristic parameter table, the theoretical conduction start angle, end angle, and center phase angle of each bridge arm need to be accurately recorded. It is recommended that all angle information be uniformly expressed in electrical angles (e.g., 0°–360°) or as a percentage of the grid cycle, and stored in a table or matrix structure in the control platform's data structure for easy subsequent retrieval.

[0022] In addition, a synchronization characteristic index should be configured for each bridge arm to measure the synchronization characteristic between the bridge arm and the target rectified waveform. This index quantifies the degree of matching between the output current of the bridge arm in the conducting state and the desired target rectified waveform (such as an approximately ideal DC waveform or a specified harmonic component suppression target). Such indices can be represented by parameters such as peak error, RMS deviation, harmonic spectrum deviation, and frequency domain overlap rate. Specific synchronization characteristic parameters should be obtained through offline simulation, experimental data fitting, or typical operating condition modeling, and a corresponding relationship should be established in the parameter table. For example, for a certain bridge arm, if it may significantly amplify the 3rd or 5th harmonics when conducting alone or in combination with a certain combination of conducting states, the synchronization characteristic index of that bridge arm should be marked as "mismatched" or assigned a lower matching weight.

[0023] The rectifier arm phase characteristic parameter table should be stored electronically within the control platform. It is recommended to use a structured storage format such as a two-dimensional hash table or a structure array. Its fields should include at least the arm's unique identifier, its winding group number, the theoretical start and end phases of conduction, the target synchronization weight or error tolerance, and the recommended arm group ID. Furthermore, to enable subsequent comparison and optimized control, the table should also allow dynamic writing of offset records from actual operation, historical evaluation values, and other feedback data fields, thus forming an updatable and adaptive data template.

[0024] The core of this step is to build a comprehensive, callable, and scalable data structure that enables the control platform to compare the current conduction state in actual operation based on the physical connection relationship of the bridge arms, theoretical conduction characteristics, and matching relationship with the target waveform, identify deviation behavior, and support dynamic bridge arm resource scheduling and rectified pulse number increase operations.

[0025] Taking a dry-type double-reverse-star transformer as an example, its valve-side winding is split into four parts along each phase axis, forming two reverse-star structures, with a total of twelve bridge arms participating in rectification. Each group of three bridge arms forms a star structure, corresponding to a typical six-pulse rectifier unit. Theoretically, there is a 30° phase shift between the two groups of bridge arms, thus achieving the twelve-pulse rectification effect. To meet the control requirements of dynamic bridge arm switching and pulse number optimization, the system needs to establish the following rectifier bridge arm phase characteristic parameter table in the control platform.

[0026] The table below is a specific example; in a real system, it can contain more fields and higher precision numerical representations:

[0027]

[0028] In the table above, each bridge arm is identified by a unique bridge arm ID. For example, "A1" indicates the first bridge arm connected to the upper winding of phase A. The winding group field indicates which specific winding segment the bridge arm originates from. The theoretical start and end phases are calculated based on the transformer phase shift angle and rectifier pulse configuration, representing the conduction window range in electrical degrees. The theoretical center phase is the midpoint between the start and end phases, used for quickly assessing whether the bridge arm is synchronized with the system.

[0029] The "Star Group" field identifies the logical grouping relationship of each three-phase bridge arm for subsequent group switching operations. The "Expected Harmonic Characteristics" field uses simulation or empirical data to identify the harmonic frequency bands that the bridge arm primarily affects or suppresses under standard operation. The "Synchronization Weight Value" is represented as a decimal between 0 and 1; the closer to 1, the higher the matching degree between its output current in frequency, amplitude, and the target rectified waveform. The "Recommended" bridge arm group field indicates the optimal combination for bridge arm switching, allowing the control platform to quickly select a backup bridge arm group based on operating conditions.

[0030] In this example, the system can perform difference calculations between the theoretical conduction phase in the table and the actual acquired value to assess the degree of offset. When the center phase drift of the three bridge arms A1, B1, and C1 exceeds ±10° under high temperature or load skew conditions, and the 3rd and 5th harmonics in the harmonic spectrum increase significantly, the system can query the table to identify the corresponding backup bridge arms A2, B2, and C2, and dynamically switch the bridge arm combination based on synchronization weights and harmonic characteristics, thereby improving the rectification effect and reducing harmonic pollution.

[0031] This example demonstrates that the bridge arm parameter table is not only a static data configuration table, but also a core information carrier for the dynamic bridge arm configuration management of the control platform. The correlation between its fields directly determines the operating strategy, adaptive capability, and scheduling accuracy of the rectifier control system. Through the establishment and maintenance of this parameter table, the system can achieve real-time optimization of the bridge arm level reconstruction and rectified waveform quality of the dual-star rectifier topology.

[0032] In the dual-reverse-star transformer rectifier harmonic suppression control method proposed in this invention, the rectifier control unit is the core actuator for key operations such as rectifier bridge arm conduction state management, rectifier process coordination control, and harmonic feedback adjustment.

[0033] The rectifier control unit is typically deployed at the field-side control layer of the rectifier system. It mainly consists of several power switch arms, drive trigger circuits, conduction state sampling modules, arm identification units, communication interface modules, and a local embedded microcontroller. The entire unit is connected to each output port of the double anti-star winding in a distributed manner. Each arm contains multiple controlled semiconductor devices (such as thyristors, IGBTs, or SiC devices), whose conduction and turn-off states are precisely controlled by trigger circuits, and a phase-programmable conduction strategy is implemented under the guidance of control commands.

[0034] The embedded controller within the rectifier control unit performs multiple tasks, including signal reception, status judgment, data buffering, and logic response. This controller maintains a stable data exchange channel with the host control platform via industrial communication protocols (such as CAN, Modbus, EtherCAT, or RS485) to receive bridge arm turn-on commands, parameter setting information, or bridge arm switching control commands from the control platform. Based on the received commands, the controller generates precise PWM or pulse trigger signals, which are then sent to the trigger pin of the target bridge arm through the corresponding drive circuit to control its conduction behavior.

[0035] To ensure real-time observability of the conduction status, the rectifier control unit is equipped with a conduction status sampling module. This module employs a high-speed digital isolation sampling scheme to sample the current flow direction, voltage distribution, and conduction indication signals of semiconductor devices in each bridge arm. Through internal encoding and status logic processing, the data is fed back to the controller as a basis for status confirmation. All conduction status data can be transmitted back to the control platform for subsequent comparison and status evaluation.

[0036] In addition, the rectifier control unit has bridge arm resource identification and group management functions. Each bridge arm is assigned a unique number (e.g., BR01, BR02, etc.) during the initial configuration phase and is grouped according to the anti-star group to which its connected winding belongs (e.g., Group A, Group B). This facilitates the system to quickly locate the target bridge arm group and perform conduction locking and release operations during bridge arm switching. When executing bridge arm switching control commands, the rectifier control unit ensures that the switching sequence of each bridge arm meets the zero-voltage or zero-current condition during conduction path switching according to pre-set synchronization rules, preventing risks such as surges, arcs, and system short circuits.

[0037] In practical applications, the rectifier control unit can be constructed as a centralized architecture, with a central rectifier control cabinet managing the status and operation of all bridge arms; alternatively, a modular structure can be adopted, with each group of three-phase bridge arms independently equipped with a local control unit, all linked together via a bus to achieve greater flexibility and maintainability. The rectifier control unit can also integrate sensor interfaces for temperature, voltage, and current, enabling self-monitoring of the power device's operating status and fault protection functions, further improving the system's reliability and safety.

[0038] Furthermore, the establishment of the rectifier bridge arm phase characteristic parameter table in the control platform includes:

[0039] By loading the topology connection data of the dual-star transformer and the bridge arm distribution configuration of the rectifier control unit, the theoretical conduction timing of each rectifier bridge arm in the standard working cycle is generated in the control platform, and the theoretical conduction phase of each rectifier bridge arm is calculated based on the theoretical conduction timing as the bridge arm conduction baseline information.

[0040] Based on the bridge arm conduction baseline information and the phase connection relationship of the corresponding windings in the double-reflection transformer, the winding group to which each rectifier bridge arm belongs is determined, and the fixed physical connection correspondence between the bridge arm and the winding is marked.

[0041] For all rectifier bridge arms that have been divided into groups, analyze the relative coverage position of their conduction timing within a unit rectification cycle, extract the set of bridge arms that have timing overlap characteristics with the target rectified waveform within the conduction phase range, and record their synchronization characteristics with the target rectified waveform.

[0042] The bridge arm conduction baseline information, the winding group to which the bridge arm belongs, and the synchronization characteristics with the target rectified waveform are uniformly encoded and written into the rectified bridge arm phase characteristic parameter table.

[0043] In implementing the dual-star transformer rectifier harmonic suppression control method described in this invention, the establishment of the rectifier arm phase characteristic parameter table is crucial. This process requires fully considering the transformer topology and the physical configuration of the rectifier control unit's arms in the control platform, and achieving accurate modeling through multi-stage calculations and structural mapping, thereby providing complete data support for subsequent harmonic suppression and arm switching control. Specifically, firstly, the system imports the topology connection data of the dual-star transformer into the control platform. This data includes the physical wiring method, electrical connection direction, and winding arrangement sequence between each phase winding and the rectifier arm. Based on this, combined with the actual arrangement of the arms in the rectifier control unit, the system extrapolates the conduction probability of each arm within a standard rectification cycle, constructing a theoretical conduction timing sequence. This conduction timing sequence does not consider load disturbances and real-time control offsets, and serves as the basis for the arm conduction behavior under stable operating conditions, referred to as the arm conduction baseline information.

[0044] Next, the system takes each bridge arm as a unit and compares its corresponding conduction baseline information with the phase connection relationship in the double-star transformer topology one by one to determine which valve-side winding group the bridge arm belongs to. Based on the physical connection data, it records the static binding relationship between the bridge arm and the specific winding, such as whether the bridge arm is connected to the upper arm of phase A, the lower arm of phase B, or a Y-type star connection node. This grouping operation is of great significance in the control logic, affecting not only the subsequent phase matching accuracy but also determining the replaceability and mutual exclusion of the spare bridge arms.

[0045] Then, the system performs time series analysis on the bridge arm cluster with completed winding groups. Specifically, within a unit rectification cycle (e.g., within 20ms), the theoretical start and end times of each bridge arm are normalized to form a unified time vector. Based on the theoretical conduction interval of the target rectified waveform, the system searches for bridge arms with overlapping time domain characteristics within this vector. The so-called "timing overlap characteristic" refers to the time intersection between the conduction time window of a certain bridge arm and the pulse output requirement of the target waveform within a preset threshold (e.g., ±5 electrical degrees). The set of bridge arms with the above-mentioned timing overlap characteristic is considered to have synchronous rectification capability in the current rectification task. The system will further analyze its key characteristics such as whether its phase coverage is continuous and whether it can achieve a smooth transition of the rectified waveform, and record the analysis results as the synchronization characteristics between the bridge arm and the target rectified waveform.

[0046] Finally, the system uniformly encodes the structural information of the three core dimensions mentioned above—namely, the bridge arm conduction baseline information, the winding group to which the bridge arm belongs, and the synchronization characteristics between the bridge arm and the target rectified waveform. The encoding scheme can adopt a multi-field structure; for example, each bridge arm corresponds to a set of tuple data, including the conduction angle (in degrees or radians), group identifier (such as Group_A, Group_B, etc.), and synchronization flag (such as Sync_Level: High / Medium / Low). Furthermore, to achieve efficient execution of control logic, the encoded fields can support fast indexing and logical operations. After encoding, the system writes all the bridge arm information into the rectified bridge arm phase characteristic parameter table within the control platform. This parameter table not only participates in the initial loading of rectification operation as a static configuration file but also serves as an indispensable data foundation for subsequent steps such as rectification operation status identification, bridge arm offset detection, harmonic distribution mapping, and switching decisions, possessing high accuracy, high stability, and good scalability.

[0047] By establishing this parameter table, the rectifier system gains a structural description of the conduction behavior of the bridge arm, which provides the prerequisite for implementing intelligent judgment and dynamic optimization, and can effectively improve the control accuracy of the rectifier pulse number and the response speed of harmonic suppression.

[0048] Step S102: During the operation of the rectifier control unit, the output current values ​​of each valve-side winding of the dual-star converter transformer and the conduction status of each rectifier bridge arm in the rectifier control unit are collected. The collected data are compared with the rectifier bridge arm phase characteristic parameter table to generate a rectifier operation status dataset corresponding to the current rectification status.

[0049] During the operation of the rectifier control unit, the system needs to acquire the output current data of each valve-side winding in the dual-star converter transformer in real time, and simultaneously acquire the conduction status information of each rectifier bridge arm in the rectifier control unit.

[0050] To collect the output current of each valve-side winding, a high-precision current transformer (CT) or Rogowski coil current sensor can be installed at the output end of each winding of the transformer. These current signals should be processed with anti-interference filtering before being sampled by a high-resolution analog-to-digital converter (ADC). The sampling frequency should typically be no less than 20 times the fundamental frequency of the power grid to ensure that sufficiently fine current change characteristics are captured. Each set of current data must be timestamped and recorded synchronously with the conduction status of the rectifier bridge arm to ensure the timing consistency of subsequent phase analysis results.

[0051] Meanwhile, the rectifier control unit should have the ability to accurately identify the current conduction state of each rectifier bridge arm. Typically, each bridge arm corresponds to a switching device (such as IGBT, GTO, SCR, etc.), and its conduction state can be obtained through control command logs, device drive signal feedback, or gate state monitoring circuits. The conduction state can be encoded as a logic value, for example, "1" represents conduction and "0" represents cutoff. The start time and duration of each conduction must be recorded and aligned with the current sampling data.

[0052] After time-synchronizing the collected current output data with the bridge arm conduction status data, the system organizes them into a structured data record set on the control platform, forming a complete rectification operation status dataset. This dataset not only includes the current waveform and its amplitude variation sequence, but also embeds the corresponding bridge arm conduction sequence, conduction timing label, phase time point, and relative position within the cycle. The rectification operation status dataset can be stored using a time series database or a multi-dimensional structure, enabling a clear mapping and calculation of the relationship between subsequent bridge arm conduction behavior and the output current waveform.

[0053] Furthermore, the data acquisition process must also consider the stability and robustness of the system operation. To prevent misjudgments caused by transient fluctuations or short-term disturbances, the control system can be configured with a data averaging or sliding window evaluation mechanism for multiple consecutive rectification cycles. The system can continuously record multiple bridge arm and current data samples within a certain time window (e.g., 5 rectification cycles) to form a rectification operation status dataset with temporal continuity, providing a sufficient statistical basis for the next stage of phase difference identification and harmonic analysis.

[0054] In summary, the implementation of this step requires not only high-precision and synchronized data acquisition capabilities, but also that the control platform has the ability to integrate, label, and organize time-series data.

[0055] Here is an example. Assume an industrial-grade rectifier uses a double-reverse-star topology. Each phase of its three-phase dry-type transformer is axially split into four windings, forming two star-connected six-pulse rectifier units, thus achieving twelve-pulse rectification. The rectifier control unit contains twelve bridge arms, each connected to an independent silicon controlled rectifier (SCR). During system operation, rectification is performed based on a 50Hz power frequency input voltage.

[0056] After the system stabilizes, the control platform collects the output current of all valve-side windings every millisecond. In this embodiment, the sampling device uses Hall current sensors installed at the output of each phase winding. The output analog signal enters a dedicated data acquisition card (DAQ), is converted by an A / D converter, and then uploaded to the operation monitoring module of the control platform. Simultaneously, the drive controller in the rectifier control unit feeds back the control command status of the twelve bridge arms (i.e., the trigger status of each SCR) to the control platform every 1 millisecond, forming a complete conduction status data stream. To ensure data timing consistency, the system uses a global synchronization clock (such as PTP synchronization or GPS timing) to ensure that the time stamps for current sampling and conduction status recording are perfectly aligned.

[0057] For example, within a certain rectification cycle (20ms is one power grid cycle), the control platform records the following data:

[0058] At 0ms, bridge arm A1 is in the on state, and the output current of valve side A1 winding is 110A;

[0059] At 3ms, bridge arm B1 is turned on, and the output current of B1 winding rises to 108A.

[0060] At 6ms, bridge arm C1 is turned on, and the output current of C1 winding is 109A;

[0061] Around 10ms, A1 turns off and A2 turns on, and the current in the A2 winding rises from 0 to 112A.

[0062] Throughout the entire cycle, the conduction time of each bridge arm is approximately 6.7 ms, corresponding to a 60° electrical angle;

[0063] At the same time, the control platform summarizes and stores the above-mentioned time points, corresponding bridge arm numbers, conduction status ("1" or "0"), current amplitude, duration, and other information into a structured data table, such as:

[0064]

[0065]

[0066] Based on this data, the control platform automatically generates a rectification operation status dataset for each power grid cycle at the end of that cycle, including:

[0067] The actual start and end points of conduction for each bridge arm;

[0068] The offset angle between the conduction duration and the theoretical conduction phase (unit: degrees);

[0069] Corresponding winding current change trajectory;

[0070] Overall conduction sequence and coverage area.

[0071] For example, the theoretical conduction of bridge arm A1 should be from 0° to 60° (i.e., 0ms to 3.33ms), but the actual conduction was from 0ms to 10ms, which is obviously off. The platform recorded it as "conduction ahead of time +0°, delay +133°". Bridge arm A2 was conducted in this cycle. It was originally a spare bridge arm, which indicates that the control system triggered active compensation behavior.

[0072] Ultimately, these datasets, serving as snapshots of the current operating cycle's status, are compared with the rectifier arm phase characteristic parameter table, providing comprehensive data support for subsequent steps such as offset identification, harmonic analysis, and arm switching judgment.

[0073] Step S103: Based on the rectification operation status dataset, calculate the offset value between the actual conduction phase and the theoretical conduction phase of each rectifier bridge arm, and analyze the amplitude of the harmonic components in the rectified output current according to the offset value to generate the mapping result between the bridge arm conduction state and the harmonic distribution.

[0074] After completing the acquisition and structured processing of the rectifier operation status dataset, the system enters the critical stage of accurately calculating the conduction phase offset of the bridge arm and identifying harmonic components.

[0075] For each rectifier arm, the control platform first locates its actual on-start and off times within the current rectification cycle, and calculates its actual on-phase window accordingly. Assuming the target system is a 50Hz three-phase input grid, one rectification cycle is 20ms, corresponding to a 360° electrical angle. If an arm turns on at 3ms and off at 9ms, its actual on-phase angle can be calculated to be between 54° and 162°. The theoretical on-phase of this arm, preset in the rectifier arm phase characteristic parameter table, is between 60° and 180°. Therefore, based on the difference between the start and end points of these two intervals, the system can calculate an offset starting point of -6° and an ending point of -18°, indicating that the arm turns on earlier and its on-phase range is narrowed. Similar calculations are performed synchronously for each arm and each cycle, resulting in a complete set of offsets.

[0076] After calculating the offset values, the system further correlates these bridge arm offset characteristics with the spectral information of the rectified output current. During this process, the control platform calls upon periodically acquired rectified output current waveform data, performs Discrete Fourier Transform (DFT) or Fast Fourier Transform (FFT) processing, and extracts the fundamental component and the amplitude and phase information of specific harmonics (such as the 3rd, 5th, 7th, and 11th harmonics). By comparing the harmonic distribution templates of historical rectified bridge arms in their theoretical conduction state, a mapping model of "bridge arm conduction offset - harmonic amplification response" can be established. For example, if the conduction offset of a certain bridge arm causes a significant increase in the amplitude of the 5th harmonic exceeding 20%, the platform marks this bridge arm as a "harmonic amplification sensitive bridge arm" and records it in the bridge arm evaluation label.

[0077] As data accumulates over multiple cycles, the system continuously superimposes the changing trends of bridge arm conduction behavior and output harmonic components, gradually establishing a stable mapping result set between bridge arm conduction state and harmonic distribution. This result is not merely a static table, but a dynamic evaluation mechanism that evolves over time. The amplification or suppression capability of the conduction behavior of each bridge arm for certain harmonic components is quantitatively evaluated and, along with its corresponding conduction offset, serves as an important input parameter for the next step of bridge arm configuration determination.

[0078] The following example illustrates a rectifier system employing two parallel double-anti-star structures, each containing three rectifier arms, for a total of six arms participating in the rectification cycle. Each group of three arms forms an anti-star structure, theoretically conducting sequentially within electrical angle ranges of 0°–60°, 120°–180°, and 240°–300°, thus constituting a typical six-pulse rectifier combination. The rectifier control platform has established a detailed rectifier arm phase characteristic parameter table in step S101 and obtained complete arm conduction state data and valve-side winding current output values ​​in step S102.

[0079] Within a certain sampling period, the control platform recorded the actual conduction start time of bridge arm A1 as 2.3ms and the termination time as 8.6ms. Based on the 50Hz power frequency conversion, this conduction interval corresponds to an electrical angle of 41.4° to 154.8°. However, in the rectifier bridge arm phase characteristic parameter table, the theoretical conduction start and termination electrical angles of bridge arm A1 are 60° and 180°, respectively. The platform immediately performed offset calculations, obtaining a conduction start offset of -18.6° and a termination offset of -25.2°. The conduction period also decreased from 120° to 113.4°, indicating that the overall conduction behavior was advanced and that there was a conduction compression phenomenon.

[0080] Following this, the platform enters the harmonic identification phase. The system invokes the current monitoring channel on the rectifier output bus to perform Fast Fourier Transform (FFT) processing on the current waveforms continuously sampled within 20ms. Spectrum analysis results show that the fundamental effective value of the rectified output current within this cycle is 190A, the amplitude of the 5th harmonic component is 38A, and the amplitude of the 7th harmonic component is 27A. Compared to the reference template, if bridge arm A1 is in the theoretically conducting state, the system expects the 5th harmonic amplitude to be 22A. Therefore, this offset causes the 5th harmonic to increase by approximately 73%. Based on this, the platform records the gain response label of bridge arm A1 to the 5th harmonic and writes this label, along with the offset data, into the "Bridge Arm Conductivity State – Harmonic Distribution Mapping Result Set".

[0081] Within the same cycle, the platform simultaneously analyzes the remaining bridge arms. The actual conduction of bridge arm B1 is delayed from 120° to 128°, with an amplitude delay of 8°. The corresponding harmonic change is not significant, and it is labeled as "within the offset tolerance range". The conduction offset of bridge arm C1 is delayed, with its starting point changing from the theoretical 240° to 252°. The corresponding 7th harmonic in the FFT result shows a significant increase, so C1 is marked as "7th harmonic enhancement source".

[0082] Ultimately, based on the offset values ​​of multiple bridge arms and their corresponding harmonic responses, the control platform generates the following partial mapping record:

[0083]

[0084] The control platform updates the operational status assessment results accordingly and prepares to support the next step of bridge arm replacement decision-making.

[0085] Furthermore, based on the rectifier operating state dataset, the offset between the actual conduction phase and the theoretical conduction phase of each rectifier bridge arm is calculated, and the harmonic component amplitude in the rectified output current is analyzed based on the offset value to generate a mapping result between the bridge arm conduction state and the harmonic distribution, including:

[0086] Based on the rectification operation status dataset, the conduction timing information of each rectifier bridge arm in the current operation cycle is extracted and compared with the theoretical conduction phase recorded in the rectifier bridge arm phase characteristic parameter table to obtain the offset value dataset between the actual conduction phase and the theoretical conduction phase of each rectifier bridge arm.

[0087] The offset value dataset is synchronously matched with the output current value in the rectifier operation status dataset. The weighted Fourier transform method within the sliding window is used to extract the amplitude of the main harmonic components in the rectifier output current within the corresponding time period, and generate a harmonic component amplitude dataset.

[0088] Using the offset value dataset and the harmonic component amplitude dataset, a correspondence between the conduction phase offset and harmonic influence for each rectifier bridge arm is constructed, forming an intermediate mapping table. The intermediate mapping table reflects the numerical mapping characteristics between the offset degree and the amplitude gain of a specific harmonic.

[0089] Based on the intermediate mapping table and the conduction state of each rectifier bridge arm in the rectifier operation status dataset, a mapping result between the bridge arm conduction state and the harmonic distribution is generated.

[0090] First, within each rectification operation cycle, the system extracts the conduction timing information of each rectifier arm from the rectification operation status dataset, specifically including the arm's conduction start time, end time, and duration within that cycle. Then, the system precisely compares this conduction timing information with the theoretical conduction phase recorded in the rectifier arm phase characteristic parameter table. Through time-point alignment calculations, the difference between the actual conduction phase of each arm within that operation cycle and its preset theoretical conduction phase can be obtained; this difference is the offset value. This offset value can be expressed not only as an absolute angle difference but also as a percentage of the electrical cycle in a normalized manner. The system then compiles all the offset results for all arms in the current cycle into a unified offset value dataset, which serves as the basic data for measuring the degree of conduction timing deviation.

[0091] After obtaining the offset value dataset, the system extracts the output current waveform sequence from the rectification operation status dataset within the same operating cycle and synchronizes the time axis using a sampling frequency consistent with the bridge arm conduction timing. To accurately analyze the impact of the offset on current harmonics, the system uses a weighted Fourier transform within a sliding window to perform spectral decomposition on the output current. The length of the sliding window is typically set according to the rectification pulse period, for example, in the range of 10ms to 20ms, and the weighting factor uses a Gaussian window or a Hamming window to enhance frequency resolution. This transformation process extracts the amplitude of the main harmonic components of the output current within each window and precisely aligns it with the time axis of the offset value according to the start time marker of each window, forming a harmonic component amplitude dataset, which includes the amplitude data of each harmonic (such as the 5th, 7th, 11th, etc.).

[0092] Next, based on the two datasets mentioned above—the offset value dataset and the harmonic component amplitude dataset—the system performs a correlation analysis on each rectifier arm. For each arm, the system establishes a mapping relationship between its conduction phase offset and the amplitude of each harmonic within the arm's main conduction window. This mapping relationship is represented by an intermediate mapping table, which records the numerical relationship between the arm's conduction phase offset and the amplitude gain of a specific harmonic (e.g., the 5th harmonic). This intermediate mapping table can adopt a two-dimensional matrix structure, with each row corresponding to an arm and each column corresponding to a harmonic order. The matrix elements represent the change in harmonic amplitude caused by a unit offset, supporting subsequent interpolation inference and trend analysis.

[0093] Finally, based on the existing intermediate mapping table, the system further generates a mapping result between the arm conduction state and harmonic distribution by combining the conduction state of each rectifier arm in the current rectification operation status dataset. This mapping result can be in the form of a composite table or graph, clearly indicating which arm conduction offsets significantly contribute to specific harmonic components under the current arm configuration, and which arms can achieve optimal harmonic suppression by fine-tuning the conduction timing. This result can not only be used to assess the harmonic risk of the current rectification state, but also to guide the arm configuration adjustment strategy in reverse, realizing dynamic reconfiguration of the rectification system and improvement of power quality.

[0094] Step S104: Based on the mapping result, determine whether the enabled bridge arm configuration in the current rectifier control unit meets the conduction phase coverage requirement corresponding to the target rectifier pulse number; if the determination result is not met, select the target bridge arm group from the spare bridge arm group that has a preset phase shift difference with the current bridge arm group, and generate a bridge arm switching control command based on the determination result.

[0095] After identifying the conduction offset of the bridge arms and analyzing the harmonic components in the rectified output current, the control platform needs to determine whether the currently operating bridge arm combination can achieve the conduction phase coverage required by the target number of rectified pulses. The core basis for this judgment is that the target rectified waveform typically requires precise phase intervals between the conduction phases of multiple bridge arms. For example, in a twelve-pulse rectifier structure, there should be a 30° electrical angle phase shift between the conduction center points of adjacent bridge arms, thus forming a complete and symmetrical conduction coverage. This equidistant distribution has a decisive impact on the waveform continuity and harmonic attenuation of the output current.

[0096] The control platform first extracts the conduction start angle and termination angle of each bridge arm in the currently activated bridge arm group based on the mapping result between the bridge arm conduction state and harmonic distribution. Then, it calculates the conduction center angle of each bridge arm and further obtains the electrical angle difference between any two bridge arm conduction center angles. The system constructs a conduction phase coverage map based on the relative spacing between all conduction center points and compares it with the theoretical phase distribution map required for the target number of rectified pulses. For example, in an ideal twelve-pulse rectification, twelve conduction zones should be uniformly covered within 360°, with a set of bridge arm center angles arranged every 30° electrical angle.

[0097] If the comparison results show that the conduction areas of the current bridge arm group overlap, have excessively wide intervals, or have some conduction areas completely missing, it indicates that the current bridge arm configuration cannot meet the conduction phase coverage requirements for the target pulse number. In this case, the platform further combines the degree of bridge arm conduction offset with the corresponding harmonic amplification response to select a bridge arm combination with phase difference compensation capability from the available backup bridge arm groups. This backup bridge arm group must meet the following conditions: First, the phase shift angle of its corresponding winding should have at least one controllable preset phase difference with the current bridge arm group, such as 30° or 60°; second, its theoretical conduction center point should be located at the gap or imbalance position of the current conduction area; finally, it has not been marked as a "harmonic-sensitive" bridge arm in previous operation, meaning its conduction will not further amplify higher-order harmonic components.

[0098] By comprehensively analyzing the above conditions, the platform prioritizes selecting a target bridge arm group that meets the conduction phase compensation requirements and calculates whether this combination can form a new, complete, and symmetrically phased conduction segment combination after being connected to the system. For example, if the current bridge arm group has conduction coverage of [0°–60°], [120°–180°], and [240°–300°], and the system determines that three conduction edge segments are missing: 30°–60°, 150°–180°, and 270°–300°, the selected backup bridge arm group has a theoretical conduction range of [30°–90°], [150°–210°], and [270°–330°], and the phase misalignment structure can achieve effective compensation.

[0099] Once it is determined that the target bridge arm group can optimize the existing structure in terms of conduction angle and current distribution, the control platform will generate the corresponding bridge arm switching control command. The command will clearly indicate the bridge arm number that needs to be locked, the corresponding target bridge arm number, and the execution conditions for switching (such as the cycle in which it takes effect, the synchronization point of switching, the voltage zero crossing time, etc.) to ensure the continuity of system current, power stability and consistency of control closed loop during the switching process.

[0100] This step, through quantitative calculation and precise comparison, enables the rectifier system to dynamically judge the rationality of the rectifier structure, identify electrical angle coverage defects, and perform real-time optimization based on bridge arm resources. Its core advantage lies in the fact that it can complete topology reconstruction and harmonic optimization through the control layer without changing the primary side wiring of the transformer, ensuring that the system always operates in a high-quality, high-pulse-number rectification state.

[0101] Taking a typical double-star transformer rectifier system as an example, the system is configured as a 12-pulse rectifier structure, consisting of two star windings, A and B. The B winding has a 30° electrical angle phase shift compared to the A winding, to achieve the six pairs of bridge arms required for twelve-pulse rectification, evenly distributed within a 360° cycle. Each bridge arm is numbered B1 to B6 (belonging to A) and B7 to B12 (belonging to B), with the theoretical conduction center angles as follows:

[0102] B1: 0°, B2: 60°, B3: 120°, B4: 180°, B5: 240°, B6: 300°;

[0103] B7: 30°, B8: 90°, B9: 150°, B10: 210°, B11: 270°, B12: 330°.

[0104] Within a given rectification control cycle, assuming the system currently activates bridge arm groups B1, B2, B3, B4, B5, and B6, meaning only bridge arms group A are active, the system determines, based on current sampling values ​​and the bridge arm conduction status, that their actual conduction center angles are approximately still located at 0°, 60°, 120°, 180°, 240°, and 300°. The platform marks these conduction center points on a 360° electrical angle periodicity diagram and constructs a current conduction phase coverage diagram.

[0105] Subsequently, the system compared the current conduction phase diagram with the theoretical 12-pulse conduction requirement. Theoretically, the 12-pulse rectification requires the phase distribution at the center of the bridge arm to be evenly distributed every 30° electrical angle, i.e., [0°, 30°, 60°, ..., 330°]. Through comparison, the platform found that the current phase diagram only covers even-numbered multiples of 30° positions, missing six key conduction points: 30°, 90°, 150°, 210°, 270°, and 330°.

[0106] To verify whether the missing component affects rectification quality, the platform further analyzed the harmonic characteristics in the rectified output current based on the bridge arm conduction and harmonic mapping model, discovering that the amplitudes of the 11th and 13th harmonic components in the current system were abnormally high. This phenomenon verifies that the insufficient conduction symmetry caused by the missing phase-shifting winding bridge arm (i.e., group B) leads to a significant enhancement of higher-order harmonics in the rectified output.

[0107] To optimize this structure, the platform selected a set of bridge arms with the required conduction center angles from the spare bridge arms, namely B7, B8, B9, B10, B11, and B12, with theoretical conduction center angles of 30°, 90°, 150°, 210°, 270°, and 330°, respectively. The system simulation confirmed that if this set of bridge arms replaces the original B set and is added to the rectification system, all conduction center angles can form a complete and symmetrical twelve-part conduction structure within a 360° electrical cycle, meeting the requirements of high-pulse rectification and significantly suppressing odd-order high-order harmonics.

[0108] Therefore, based on the above judgment, the control platform generates a bridge arm switching control command, the content of which includes:

[0109] Target bridge arm numbers: B7 to B12;

[0110] Arm numbers requiring locking: The two weakest arms in the current arm group (e.g., B3, B5);

[0111] Synchronous execution time point: the next voltage zero crossing moment;

[0112] Switching strategy: Soft handover to ensure no conflict between adjacent conductions.

[0113] After the switch is completed, the platform collects the rectified current again and reconstructs the conduction state dataset. It confirms that the conduction center angle has been fully covered by 0°–330°, distributed every 30°. The rectified waveform tends to be smooth, and the corresponding harmonic components decrease by about 40%.

[0114] As can be seen from the above examples, the system can not only identify conduction defects based on the collected data and bridge arm parameter model, but also dynamically compensate for conduction coverage by combining preset strategies, thereby realizing intelligent optimization of the rectifier structure and effective suppression of harmonics.

[0115] Furthermore, based on the mapping result, it is determined whether the configured bridge arm in the current rectifier control unit meets the conduction phase coverage requirement corresponding to the target rectified pulse number; if the determination result is not met, a target bridge arm group with a preset phase shift difference from the current bridge arm group is selected from the backup bridge arm group, and a bridge arm switching control command is generated based on the determination result, including:

[0116] Based on the mapping result between the conduction state of the bridge arm and the harmonic distribution, the set of conduction phases corresponding to the current bridge arm configuration is extracted, and its coverage index is calculated. The coverage index is used to characterize whether the conduction phase distribution can form a complete rectified pulse sequence.

[0117] Based on the coverage index, the current bridge arm configuration is matched and compared with the target rectified pulse number requirement. If there is a coverage discontinuity area or a phase over-density area, it is determined that the current bridge arm configuration does not meet the conduction phase coverage requirement, and a bridge arm replacement requirement set is generated.

[0118] From the spare bridge arm groups maintained by the rectifier control unit, based on the theoretical conduction phase information recorded in the bridge arm phase characteristic parameter table, target bridge arm groups with a preset phase shift difference from the current bridge arm group are screened, and sorted and selected according to the minimum harmonic contribution path priority criterion to form a candidate set of target bridge arm groups.

[0119] Based on the candidate set of target bridge arm groups, and combined with the set of bridge arm replacement requirements, a bridge arm switching control command is generated. The bridge arm switching control command instructs the rectifier control unit to perform a conduction path switching operation that matches the target number of rectified pulses, so as to ensure that the uniform distribution of conduction phase and the optimal target of harmonic suppression are achieved after the bridge arm is dynamically reconfigured.

[0120] First, the system extracts the set of conducting phases for all currently enabled bridge arms based on the conduction status and corresponding phase information recorded in the mapping results. This set constitutes the conduction phase distribution map under the current bridge arm configuration. The system analyzes this phase set and calculates its coverage index within a standard rectification cycle. This index can be defined as a measure of the uniformity of the conducting phases within a unit phase interval within the sampled cycle, specifically including statistics such as the minimum interval between adjacent conducting phases, phase overlap areas, and missing segments. This coverage index is used to objectively evaluate whether the current set of conducting phases has the ability to constitute the target number of rectified pulses, that is, whether it can form equally spaced, conflict-free conducting paths with full phase coverage within the rectification cycle.

[0121] Then, the system matches and compares the coverage index calculated above with the theoretical conduction phase distribution model required for the target rectified pulse number. If a coverage discontinuity zone (i.e., no bridge arm conducts on certain phase segments) or a phase-dense zone (i.e., multiple bridge arms conduct near the same phase, causing waveform distortion) is found, it can be determined that the current bridge arm configuration does not meet the conduction phase coverage requirements. At this time, the system will generate a bridge arm replacement requirement set based on the specific coverage defect analysis results. This set indicates the bridge arm number that needs to be replaced or adjusted, the missing target phase segment, and its corresponding priority compensation strategy.

[0122] After identifying the bridge arm replacement requirements, the system switches to the spare bridge arm resource pool maintained by the rectifier control unit and filters them according to the theoretical conduction phase information of each bridge arm recorded in the rectifier bridge arm phase characteristic parameter table. The system searches for bridge arms among the existing spare bridge arms that have a preset phase shift difference (e.g., 60 degrees, 120 degrees, or equivalent electrical angle difference) with the current bridge arm group. These bridge arms are considered to have the potential to compensate for the current missing phase and constitute the candidate set of the target bridge arm group. To further improve system performance, the system can introduce a minimum harmonic contribution path priority criterion to rank the candidate bridge arm set. This criterion is based on the gain impact of the bridge arms on the harmonic distribution recorded in the mapping results, prioritizing bridge arm groups that can minimize newly introduced harmonic components while providing phase compensation, ensuring that the harmonic suppression target is not compromised.

[0123] Finally, the system combines the candidate set of target bridge arm groups with the set of bridge arm replacement requirements, and generates bridge arm switching control commands by means of rules such as bridge arm matching degree scoring, voltage fluctuation impact assessment, and synchronization timing adjustability analysis.

[0124] First, the system quantifies the matching degree between each candidate bridge arm group in the target bridge arm group candidate set and the current bridge arm group, forming a bridge arm matching degree score. This score is constructed based on two dimensions: on the one hand, it examines the degree to which the candidate bridge arm group covers the missing phase segments marked in the bridge arm replacement requirement set in the conduction phase space; on the other hand, it evaluates the coupling interference degree between the conduction phase of the candidate bridge arm group and the conduction phase of the existing bridge arm, i.e., whether it will introduce additional conduction overlap or phase jump. The higher the matching degree score, the more suitable the bridge arm group is to replace the current configuration to restore the rectified target waveform.

[0125] After obtaining the initial bridge arm matching score, the system further evaluates the impact of each bridge arm switching candidate scheme on the transient fluctuations of the rectifier system voltage output. This evaluation is based on calculations of the actual current carried by each bridge arm, voltage polarity, and conducting load path within the current rectification cycle. It simulates the transition state during the bridge arm blocking and new bridge arm activation process, and then analyzes the potential voltage drops, current jumps, or short-term harmonic increases in the system. For candidate bridge arm groups that may cause voltage fluctuations exceeding the allowable threshold, the system will introduce a penalty weight into the score, thereby reducing their final priority.

[0126] Assuming voltage stability is met, the system also needs to evaluate the timing adjustability of each bridge arm group. This evaluation determines whether the turn-on timing of the candidate bridge arm group can seamlessly connect with the conduction cycle boundary of the currently activated bridge arm in the rectifier control unit, avoiding conduction blind spots or overlapping detuning. Based on the reference time base and phase trigger sequence within the control cycle, the system constructs a synchronization window model, analyzes the timing buffer conditions required for the candidate bridge arm group to enter the conduction state, and assigns higher evaluation scores to bridge arm groups with higher synchronization flexibility.

[0127] After completing the evaluation across the three dimensions above, the system weights and fuses the bridge arm matching score, voltage fluctuation impact assessment result, and synchronization timing adjustability score to generate a comprehensive score for each target bridge arm group candidate scheme. The score fusion weights can be adaptively adjusted based on dynamic parameters such as the system's current operating status, load characteristics, and external power supply network fluctuation levels to optimize the response of the control strategy.

[0128] Based on the comprehensive scoring results, the system selects the target boom group with the highest score and, in conjunction with the boom numbers listed in the boom replacement demand set, constructs a boom switching control command. This command includes:

[0129] Indicates the original bridge arm number that needs to be locked and its expected locking time (usually aligned with the current zero crossing point);

[0130] Indicates the target bridge arm number to be activated and its corresponding conduction phase;

[0131] Synchronous control parameters include voltage polarity confirmation, transition period soft start time window, and crossover overlap time limit;

[0132] The bridge arm interlock flag update parameter in the rectifier control unit is updated to prevent bridge arm mis-triggering or repeated conduction.

[0133] Furthermore, after generating the instruction, the system also writes the predicted impact of the switching scheme (including conduction path diagram updates, current simulation trajectories, and harmonic prediction curves) into the control platform's data buffer for use in the next control cycle's state verification and feedback optimization. In this way, the generation of the bridge arm switching control instruction not only completes the current dynamic reconfiguration task but also lays the data foundation for the stability and continuity of subsequent control.

[0134] In summary, through three closely related sub-processes—arm matching degree scoring, voltage fluctuation impact assessment, and synchronization timing adjustability analysis—the system can achieve a logical closed-loop generation of arm switching control commands.

[0135] This control command is used to guide the rectifier control unit to perform specific bridge arm switching operations. Its content clearly indicates the current bridge arm number that needs to be locked, the target bridge arm number that needs to be activated, the conduction phase range for synchronous release, and related transition control parameters.

[0136] Step S105: Send the bridge arm switching control command to the rectifier control unit. The rectifier control unit performs the adjustment of the bridge arm conduction state according to the bridge arm switching control command. Specifically, this includes: synchronously blocking some conduction paths in the current bridge arm group and releasing the conduction path of the selected target bridge arm group to complete the dynamic reconstruction of bridge arm resources and increase the number of rectified pulses.

[0137] After analyzing the conduction state of the bridge arm and generating the switching command, the rectifier control platform needs to send the bridge arm switching control command to the rectifier control unit to ensure that the system can dynamically adjust the conduction path in a timely manner based on the analysis results. In actual operation, bridge arm switching not only involves opening the backup bridge arm, but also requires precise locking of the conduction path in the current bridge arm to achieve disturbance-free resource reconfiguration. During the specific execution process, the system needs to comprehensively consider multiple factors, including conduction synchronization, winding impedance differences, electrical angle switching window, and power flow distribution stability, to ensure that the conduction state adjustment process is stable and reliable, and to avoid introducing voltage surges or current jumps.

[0138] First, upon receiving the bridge arm switching control command, the rectifier control unit needs to parse the command content, confirm the target bridge arm number to be switched and the existing bridge arm number it should replace, and simultaneously identify the current system's voltage zero-crossing moment or zero-current window. To ensure that the switching process does not interfere with the original rectified waveform, the system typically adopts a synchronous trigger-based switching mechanism. That is, the bridge arm state adjustment process is triggered at the instant the system voltage crosses zero or at the current minimum point, ensuring that the current carried by the bridge arm during the conduction transition is close to zero, thereby minimizing the impact on the system.

[0139] Based on this, the rectifier control unit will first perform a synchronous blocking operation on some of the conducting paths in the current bridge arm group. Synchronous blocking refers to the process where, under conditions of multiple bridge arms conducting simultaneously, the bridge arm being replaced synchronously exits the conducting state and is completely disconnected after a brief short-circuit protection delay. During this process, the system needs to detect and confirm that the blocking process does not cause current interruption or intermittent operation, thereby ensuring the controllability and continuity of the switching process.

[0140] Subsequently, the system releases the conduction path of the target bridge arm group, that is, issues a turn-on command to the power electronic devices (such as thyristors, IGBT modules, etc.) in the bridge arm, and confirms that the target bridge arm has entered the normal conduction state, provided that the gate response and drain voltage drop trend meet expectations. This operation often requires coordination with the PWM control module or DSP of the control platform to achieve precise conduction phase control.

[0141] During the release of the conduction path, to ensure that the bridge arm conduction sequence is consistent with the original rectification rhythm, the system also needs to automatically correct the synchronization characteristics between the new bridge arm and the target rectification waveform according to the rectifier bridge arm phase characteristic parameter table, ensuring that the new bridge arm conduction angle covers the electrical angle range not yet covered within the rectification cycle. For example, in a 12-pulse rectification system, if the target rectification waveform requires a set of bridge arms to be in conduction every 30° electrical angle, then the newly added bridge arm conduction angle must precisely fall on the conduction point missing in the original system.

[0142] Through the execution of the above process, the rectifier control unit completes a dynamic reconfiguration of bridge arm resources. Some bridge arms in the original conduction path that have degraded performance or poor symmetry are replaced, and the introduction of new bridge arm groups improves the conduction coverage of the rectifier structure and optimizes the waveform quality of the rectified output. Especially in complex scenarios facing sudden load changes, power flow reconfiguration, or winding aging, this method can achieve adaptive reconfiguration of rectifier resources without manual intervention. Furthermore, it effectively increases the number of rectified pulses through a real-time switching mechanism, thereby maximizing the suppression of rectified harmonics, improving the input power factor, and enhancing the system's energy utilization efficiency without increasing hardware complexity.

[0143] The entire adjustment process is completed within a few rectification cycles, ensuring sufficient system response speed and switching accuracy. Through the introduction of a dynamic reconfiguration mechanism, the system can continuously monitor the arm status and make optimal configuration decisions during operation, achieving the rectification harmonic suppression control target based on arm configuration optimization, thus providing strong technical support for high-performance industrial rectifier equipment.

[0144] For example, in a 12-pulse dual-reflector rectifier system, the rectifier control unit controls six bridge arms, denoted as A1, B1, C1 (currently active group) and A2, B2, C2 (standby group). Each bridge arm corresponds to a valve-side winding of a dual-reflector transformer with a different phase sequence and has specific conduction phase characteristics. Based on the aforementioned mapping analysis, the control platform determines that the currently operating bridge arm B1 has experienced a phase shift due to excessive temperature rise, resulting in enhanced harmonic distortion in the rectified output current and a decrease in the system's rectification performance.

[0145] Based on this, the control platform generates a bridge arm switching control command, which locks bridge arm B1 and replaces it with bridge arm B2. To ensure that the system continuity is not affected during the switching process, the execution of this command must meet two core operational requirements: synchronous locking and synchronous release.

[0146] In practice, the rectifier control unit first identifies which phase of each electrical cycle the current system is in and calculates the ideal switching window for the next bridge arm conducting phase. For example, if B1 is currently conducting at phase 120°, the ideal switching window is selected within the synchronization range of ±5° before and after the voltage natural zero crossing point to avoid inrush currents caused by voltage and current jumps.

[0147] The control logic first confirms that the current in the B1 bridge arm is about to naturally cross zero through the real-time current detection module. Then, at the beginning of the synchronization window, it sends a gate turn-off signal to "lock B1 bridge arm" and activates the voltage clamping monitoring mechanism to ensure that the power devices (such as IGBTs or SCRs) in the B1 bridge arm are shut down naturally rather than being forcibly shut down.

[0148] After detecting that the B1 bridge arm has successfully turned off, the current has returned to zero, and the voltage rise is normal, the system immediately proceeds to the next step: after a precise delay of 2ms (corresponding to an electrical angle of approximately 12°), a "release bridge arm conduction path" command is sent to the B2 bridge arm, activating its gate drive circuit, while simultaneously monitoring the decreasing conduction voltage and increasing leakage current trends. At this point, the voltage waveform will be smoothly connected by the B2 bridge arm, completing a bumpless transition of the rectification path.

[0149] Throughout the process, the control platform continuously compares the conduction status data of bridge arms B1 and B2, and verifies whether the voltage and current changes are stable through high-speed ADC sampling and software filtering. If no abnormal oscillation or impact is detected within 2ms after the switch, the system automatically records this switch as a "successful event" and updates the corresponding item in the bridge arm operation status table, marking B1 status as "dormant" and B2 status as "active".

[0150] Ultimately, with the addition of the B2 bridge arm, the system conduction phase was reconstructed from the original 0°, 120°, 240° to 0°, 150°, 240°, achieving optimization of the number of rectified pulses (reconstructed from 12 pulses to 18 pulses), making the harmonic energy distribution more uniform, and the output voltage waveform closer to the ideal DC waveform, with both rectification efficiency and power quality significantly improved.

[0151] The entire process is driven in real time by the FPGA+DSP joint control structure in the control platform. The switching operation accuracy can reach the microsecond level, which meets the control requirements of industrial-grade high-performance rectifier systems. Moreover, it does not introduce additional hardware. It can be achieved by simply adding a bridge arm status monitoring and dynamic reconfiguration scheduling module to the existing rectifier control logic.

[0152] Furthermore, the step of sending the bridge arm switching control command to the rectifier control unit, which then adjusts the bridge arm conduction state according to the command, specifically includes: synchronously blocking some conduction paths in the current bridge arm group and releasing the conduction paths of the selected target bridge arm group, thereby completing the dynamic reconfiguration of bridge arm resources and increasing the rectifier pulse count, including:

[0153] Based on the bridge arm switching control command, the set of conduction paths corresponding to the target number of rectified pulses in the current bridge arm group is identified, and real-time current acquisition is performed on the set of conduction paths to obtain the start and end times of the current zero crossover interval of each bridge arm in the set of conduction paths, which are used as the input basis for the synchronous blocking criterion.

[0154] Based on the start and end times of the current zero-crossing interval, a synchronous blocking window is generated, and a voltage polarity confirmation judgment is performed within the synchronous blocking window to identify the conduction path in the current bridge arm group that can be blocked. The judgment result is used as the electrical state protection condition input for the subsequent target bridge arm group release operation.

[0155] Under the premise of meeting the electrical state protection conditions, according to the target bridge arm group specified in the bridge arm switching control command, an interleaved conduction trigger sequence is constructed, and the interleaved conduction trigger sequence is used to control the conduction start time of each conduction path in the target bridge arm group. The conduction start time is used to avoid instantaneous current jumps between adjacent paths to the greatest extent.

[0156] Based on the state of the locked conduction path within the synchronous locking window and the state of the target bridge arm group conduction path formed at the start of conduction, the bridge arm conduction state configuration in the rectifier control unit for controlling the conduction behavior of the next cycle is updated as the result of dynamic reconfiguration of bridge arm resources, and the rectifier control unit is driven to output a control signal sequence that increases the number of rectified pulses.

[0157] In this rectifier harmonic suppression control method, after the system generates the bridge arm switching control command, it needs to send the command to the rectifier control unit, which then performs the adjustment operation of the bridge arm conduction state accordingly. This operation is the core link in realizing dynamic reconfiguration of bridge arm resources and increasing the number of rectifier pulses. It involves the blocking and replacement of conduction paths and the continuous control of rectification behavior, and must ensure the stability and synchronization of all electrical processes.

[0158] Upon receiving the bridge arm switching control command, the system first analyzes the set of conduction paths corresponding to the current bridge arm group according to the target rectified pulse count requirement specified in the command, and then performs real-time current data acquisition on this set. The acquired current signal undergoes high-frequency synchronous sampling to extract the start and end times of the zero-crossing interval of each bridge arm current. These times represent the instants when each bridge arm current transitions from positive to negative or from negative to positive, and are the safest window boundaries for performing conduction blocking operations. Therefore, they can serve as the basis for synchronous blocking criteria input into subsequent judgment processes.

[0159] Based on the extracted current zero-crossing interval information, the system constructs a set of synchronous blocking windows to limit the effective time period of bridge arm blocking operations. Within the synchronous blocking window, the rectifier control unit needs to further confirm the voltage polarity of the target bridge arm path to prevent blind blocking when the voltage direction is positive and the current direction has just crossed zero, which could lead to reverse breakdown or freewheeling failure. Only conducting paths where the current is near zero and the voltage direction meets the blocking conditions will be identified as bridge arm paths where blocking operations can be performed. This judgment result serves as the electrical state protection condition for subsequent conduction operations to prevent short circuits, oscillations, or a surge in transient harmonics caused by premature switching.

[0160] After confirming that the aforementioned electrical protection conditions are correct, the system constructs an interleaved conduction trigger sequence according to the target bridge arm group marked in the bridge arm switching control command. This trigger sequence is constructed based on the theoretical conduction phase in the bridge arm phase characteristic parameter table and the reference time base of the current control cycle. The system sets the conduction trigger time for each target bridge arm by staggering the conduction start times of adjacent conduction paths. This interleaved timing configuration helps to minimize the risk of sudden current changes or harmonic accumulation caused by path concurrency during conduction switching, ensuring a smooth transition of the electromagnetic state of the rectifier system at the moment of switching.

[0161] As the specified current arm conduction paths in the synchronous locking window are locked one by one, and the corresponding conduction paths in the target arm group are released sequentially, the system records the new arm conduction state formed by the above operations as the dynamic reconstruction result. This reconstruction result not only includes the updated information of the current conduction state, but is also used to reconfigure the arm state table in the rectifier control unit for conduction control in the next rectification cycle. Based on this updated result, the control unit will output the conduction control signal sequence for the control logic of the next cycle, thereby achieving the goal of increasing the number of rectified pulses based on the arm resource reconstruction.

[0162] Throughout the entire execution process, the result of any step serves as the input basis for subsequent control operations. For example, the current zero-crossing interval is used to construct a synchronous blocking window, which is used to determine the voltage polarity of the bridge arm and confirm the effectiveness of the blocking. The blocking determination is used to trigger the conduction start of the target bridge arm, and the conduction start process needs to refer to the synchronous window and the staggered timing sequence to construct the rectification control signal in reverse. This interlocking, real-time dynamic adjustment control mechanism ensures the electrical stability of the rectification system, the integrity of the bridge arm reconfiguration, and the effectiveness of the rectification pulse count increase during bridge arm switching.

[0163] In summary, this implementation method fully utilizes real-time current data, voltage polarity judgment, staggered conduction strategy, and bridge arm state update mechanism to achieve closed-loop control of the rectifier bridge arm switching process.

[0164] In the rectifier harmonic suppression control method proposed in this invention, in addition to the core control steps of dynamically adjusting the rectifier bridge arm configuration to increase the number of rectified pulses and reduce harmonic components, a feedback correction mechanism is further introduced to continuously optimize the system's control strategy after completing a bridge arm switching operation. This step is of great significance for maintaining long-term stable operation of the system and improving response accuracy and rectification quality. The specific implementation path is as follows.

[0165] After the rectifier control unit completes the conduction path adjustment according to the bridge arm switching control command, the system does not immediately end the monitoring process. Instead, it continues to collect real-time data on the operating status of the rectifier bridge arms and the output current of each valve-side winding of the transformer. This data collection relies on the high-speed sampling circuit and data processing module configured in the control platform to ensure that continuous current, voltage, and conduction status information can be obtained at a time resolution of milliseconds or even microseconds.

[0166] The collected data is reorganized into a new rectifier operating status dataset. This dataset records not only the specific conduction time, phase position, and duration of each bridge arm after switching, but also the response transition characteristics and stability indicators reflected in the current waveform after switching. Based on this, the system uses an embedded Fast Fourier Transform (FFT) module or an equivalent harmonic analysis algorithm to perform spectral decomposition on the updated current waveform and extract harmonic spectral indicators, mainly including the amplitude, phase, and relative energy proportion of each harmonic.

[0167] These harmonic spectral indices are constructed into multi-dimensional harmonic feature vectors and synchronously uploaded to the bridge arm control optimization module in the control platform. This module compares and analyzes the currently extracted harmonic indices with the expected target values ​​(e.g., the ideal spectral characteristics under a specific number of rectified pulses) to identify whether there are frequency bands that still need optimization or abnormal harmonic peaks. Once it is detected that the harmonic suppression effect after switching is poor or that there is a subharmonic shift, the system will further initiate a correction process.

[0168] During the correction process, the control platform fine-tunes the original rectifier arm phase characteristic parameter table based on the latest feedback on harmonic distribution results. This adjustment is usually reflected in two aspects: first, correcting the theoretical conduction phase value of certain arms to make it closer to the actual performance, so as to avoid similar errors in the next switchover; second, adjusting the priority ordering and phase shift matching rules of the spare arm group to optimize the combination efficiency of conduction resources in subsequent switchover paths.

[0169] The entire correction process is dynamic, closed-loop, and highly adaptive. Each arm switching and its subsequent operating status are recorded and analyzed by the system, thereby continuously improving the predictive accuracy of the arm switching strategy and the effectiveness of rectification performance optimization. In addition, the control platform also trains decision rules or models based on accumulated historical harmonic spectrum data to construct a high-dimensional nonlinear mapping relationship between arm conduction and harmonic distribution, in order to predict possible switching effects in future operations.

[0170] For example, in a certain actual operating condition, when the system initially switches one set of three-phase bridge arms A1, B1, C1 to another set A2, B2, C2, although the rectified current waveform does not show obvious distortion, spectrum analysis reveals that the amplitude of the 11th harmonic is abnormally high, exceeding the system's set allowable range. Based on this feedback, the platform infers that the actual conduction phase of bridge arm B2 is systematically advanced compared to the theoretical value. Accordingly, it fine-tunes the theoretical conduction angle of bridge arm B2 in the characteristic parameter table. Simultaneously, in the next round of bridge arm replacement candidate schemes, it prioritizes bridge arms with complementary phase characteristics to B2, thereby effectively preventing the recurrence of similar problems in subsequent operation.

[0171] Through the above feedback correction and strategy adaptive optimization mechanism, the entire bridge arm configuration optimization process can not only effectively increase the number of rectified pulses and reduce the harmonic content in the initial switching stage, but also continuously evolve itself in long-term operation to ensure that the system always maintains a stable output with high efficiency and low harmonics under varying operating conditions.

[0172] The double-reverse-star transformer rectifier harmonic suppression control method described in this invention is applicable to a type of dry-type double-reverse-star converter transformer system, the transformer structure of which is as follows: Figure 2 and Figure 3As shown, a bridge arm connection infrastructure suitable for low-voltage, high-current rectification applications is provided. Specifically, considering the bridge arm requirements on the transformer input side of a dual-star rectifier circuit, the dry-type transformer used in this embodiment has its valve-side structure optimized to meet the structural support requirements of the rectification control method for bridge arm distribution flexibility, phase consistency, and electrical isolation characteristics.

[0173] In this reference structure, the valve-side winding of a single dry-type transformer is axially divided into four groups: the upper low-voltage 1 and low-voltage 2, and the lower low-voltage 3 and low-voltage 4, forming two symmetrical anti-star connection groups. Each low-voltage winding in the above split structure is equipped with an independent output terminal, allowing the rectifier control unit to perform dynamic reconfiguration based on the physical topology and conduction path of the winding when implementing bridge arm switching control commands. During the structural fabrication process, low-voltage 1 is wound first and its leads are fabricated. Then, low-voltage 2 is wound and solidified sequentially to form the upper bridge arm connection path. Similarly, the lower low-voltage 3 and low-voltage 4 are assembled. The above bridge arm physical structure clarifies the fixed correspondence between each conduction path and the winding, providing a direct basis for the subsequent construction of bridge arm conduction baseline information and serving as the hardware input basis for the rectifier bridge arm phase characteristic parameter table.

[0174] like Figure 3 As shown, to meet the requirement of minimizing electrical disturbances during bridge arm switching in the rectification control method, this reference structure is assembled as a whole by mounting the grid-side winding outside the valve-side winding. The lower valve-side winding, the grid-side winding, and the upper valve-side winding are sequentially mounted on the core column. This results in a smaller stray inductance and current circulation path during bridge arm locking and switching operations, which is beneficial for harmonic suppression and the realization of control behavior within the synchronization window. Furthermore, considering the frequent pulse switching during the dynamic adjustment of the bridge arm conduction state, this structural design fully considers the principle of symmetry in the arrangement of the outgoing terminals, ensuring that adjacent leads and terminals carry currents of equal amplitude but opposite direction, forming an electromagnetic cancellation mechanism between adjacent paths. This reduces voltage surges and rectified inrush currents caused by bridge arm reconfiguration.

[0175] It is worth noting that this transformer structure supports a bridge arm redundancy configuration mechanism. The control platform maintains a set of spare bridge arms and dynamically selects a set of bridge arms with a preset phase shift difference as the target bridge arm group based on a matching strategy between the bridge arm phase characteristic parameter table and the target rectified pulse number. This achieves precise control of conduction path switching and rectification behavior optimization. The bridge arm switching operation uses current zero crossover detection and voltage polarity determination as the basic thresholds. It controls the locking of the old bridge arm through a synchronous blocking window and then releases the target bridge arm with an interleaved conduction sequence. This ensures the continuity of the conduction phase distribution during the switching process, avoids transient harmonic abrupt changes, and completes the update of the control signal sequence for the next cycle in the rectifier control unit.

[0176] Alternatively, as an alternative, this reference structure also supports an assembly method with the transformer winding structure reversed, where the grid-side winding is arranged inside the core column and the valve-side winding is fitted onto its outside. Under this configuration, the bridge arm control strategy and synchronous conduction mechanism described in this invention can still be adapted, but the absorption capacity of the inrush current and the limitation of instantaneous voltage fluctuations during the rectification start-up phase need to be additionally considered. Therefore, this assembly method needs to be adapted and optimized in conjunction with the system electrical parameters in specific applications, and this structure will not be illustrated in this paper.

[0177] In summary, this reference structure provides solid physical support for realizing a rectification harmonic suppression control method based on bridge arm configuration optimization. While meeting the requirements of high-frequency stability of rectified current, controllability of bridge arm conduction path and system harmonic suppression, it also has good manufacturing process feasibility and engineering deployment flexibility, and can effectively adapt to the multi-scenario application needs of this invention in high-performance industrial rectifier equipment.

[0178] A second embodiment of this application provides an electronic device, the electronic device comprising:

[0179] processor;

[0180] The memory is used to store a program, which, when read and executed by the processor, executes a dual-reverse-star transformer rectifier harmonic suppression control method provided in the first embodiment of this application.

[0181] The third embodiment of this application provides a computer-readable storage medium storing a computer program thereon. When the program is executed by a processor, it performs a dual-reverse-star transformer rectifier harmonic suppression control method provided in the first embodiment of this application.

[0182] Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

Claims

1. A method for suppressing and controlling rectified harmonics in a dual-star transformer, characterized in that, include: A rectifier bridge arm phase characteristic parameter table is established in the control platform. The rectifier bridge arm phase characteristic parameter table is used to record the theoretical conduction phase, winding group to which the bridge arm belongs, and synchronization characteristics with the target rectified waveform of each rectifier bridge arm in the rectifier control unit connected to the double anti-star transformer. During the operation of the rectifier control unit, the output current values ​​of each valve-side winding of the dual-star converter transformer and the conduction status of each rectifier bridge arm in the rectifier control unit are collected. The collected data are compared with the rectifier bridge arm phase characteristic parameter table to generate a rectifier operation status dataset corresponding to the current rectification status. Based on the rectifier operation status dataset, the offset between the actual conduction phase and the theoretical conduction phase of each rectifier bridge arm is calculated, and the amplitude of the harmonic components in the rectified output current is analyzed based on the offset value to generate a mapping result between the bridge arm conduction state and the harmonic distribution. Based on the mapping result, it is determined whether the configured bridge arm in the current rectifier control unit meets the conduction phase coverage requirement corresponding to the target number of rectified pulses; if the determination result is not met, a target bridge arm group with a preset phase shift difference from the current bridge arm group is selected from the spare bridge arm group, and a bridge arm switching control command is generated based on the determination result. The bridge arm switching control command is sent to the rectifier control unit, which then adjusts the bridge arm conduction state according to the bridge arm switching control command. Specifically, this includes: synchronously blocking some conduction paths in the current bridge arm group and releasing the conduction path of the selected target bridge arm group, so as to complete the dynamic reconstruction of bridge arm resources and increase the number of rectified pulses.

2. The method for suppressing harmonics in a dual-star transformer rectifier according to claim 1, characterized in that, Also includes: After the bridge arm switching is completed, the updated rectifier bridge arm conduction status and the output current of each valve-side winding of the dual-reverse-star transformer are collected. The rectifier operation status dataset is updated based on the collected operating data, and harmonic spectrum indicators are extracted from it. The harmonic spectrum indicators are fed back to the control platform to correct the rectifier bridge arm phase characteristic parameter table and optimize the subsequent bridge arm switching strategy.

3. The method for suppressing harmonics in a dual-star transformer rectifier according to claim 1, characterized in that, The establishment of the rectifier bridge arm phase characteristic parameter table in the control platform includes: By loading the topology connection data of the dual-star transformer and the bridge arm distribution configuration of the rectifier control unit, the theoretical conduction timing of each rectifier bridge arm in the standard working cycle is generated in the control platform, and the theoretical conduction phase of each rectifier bridge arm is calculated based on the theoretical conduction timing as the bridge arm conduction baseline information. Based on the bridge arm conduction baseline information and the phase connection relationship of the corresponding windings in the double-reflection transformer, the winding group to which each rectifier bridge arm belongs is determined, and the fixed physical connection correspondence between the bridge arm and the winding is marked. For all rectifier bridge arms that have been divided into groups, analyze the relative coverage position of their conduction timing within a unit rectification cycle, extract the set of bridge arms that have timing overlap characteristics with the target rectified waveform within the conduction phase range, and record their synchronization characteristics with the target rectified waveform. The bridge arm conduction baseline information, the winding group to which the bridge arm belongs, and the synchronization characteristics with the target rectified waveform are uniformly encoded and written into the rectified bridge arm phase characteristic parameter table.

4. The method for suppressing and controlling rectified harmonics in a dual-star transformer according to claim 1, characterized in that, Based on the rectifier operating status dataset, the offset between the actual conduction phase and the theoretical conduction phase of each rectifier bridge arm is calculated. The amplitude of harmonic components in the rectified output current is analyzed based on the offset values ​​to generate a mapping result between the bridge arm conduction state and the harmonic distribution, including: Based on the rectification operation status dataset, the conduction timing information of each rectifier bridge arm in the current operation cycle is extracted and compared with the theoretical conduction phase recorded in the rectifier bridge arm phase characteristic parameter table to obtain the offset value dataset between the actual conduction phase and the theoretical conduction phase of each rectifier bridge arm. The offset value dataset is synchronously matched with the output current value in the rectifier operation status dataset. The weighted Fourier transform method within the sliding window is used to extract the amplitude of the main harmonic components in the rectifier output current within the corresponding time period, and generate a harmonic component amplitude dataset. Using the offset value dataset and the harmonic component amplitude dataset, a correspondence between the conduction phase offset and harmonic influence for each rectifier bridge arm is constructed, forming an intermediate mapping table. The intermediate mapping table reflects the numerical mapping characteristics between the offset degree and the amplitude gain of a specific harmonic. Based on the intermediate mapping table and the conduction state of each rectifier bridge arm in the rectifier operation status dataset, a mapping result between the bridge arm conduction state and the harmonic distribution is generated.

5. The method for suppressing harmonics in a dual-star transformer rectifier according to claim 1, characterized in that, Based on the mapping result, it is determined whether the configured bridge arms in the current rectifier control unit meet the conduction phase coverage requirement corresponding to the target number of rectified pulses; if the determination result is not met, a target bridge arm group with a preset phase shift difference from the current bridge arm group is selected from the spare bridge arm group, and a bridge arm switching control command is generated based on the determination result, including: Based on the mapping result between the conduction state of the bridge arm and the harmonic distribution, the set of conduction phases corresponding to the current bridge arm configuration is extracted, and its coverage index is calculated. The coverage index is used to characterize whether the conduction phase distribution can form a complete rectified pulse sequence. Based on the coverage index, the current bridge arm configuration is matched and compared with the target rectified pulse number requirement. If there is a coverage discontinuity area or a phase over-density area, it is determined that the current bridge arm configuration does not meet the conduction phase coverage requirement, and a bridge arm replacement requirement set is generated. From the spare bridge arm groups maintained by the rectifier control unit, based on the theoretical conduction phase information recorded in the bridge arm phase characteristic parameter table, target bridge arm groups with a preset phase shift difference from the current bridge arm group are screened, and sorted and selected according to the minimum harmonic contribution path priority criterion to form a candidate set of target bridge arm groups. Based on the candidate set of target bridge arm groups, and combined with the set of bridge arm replacement requirements, a bridge arm switching control command is generated. The bridge arm switching control command instructs the rectifier control unit to perform a conduction path switching operation that matches the target number of rectified pulses, so as to ensure that the uniform distribution of conduction phase and the optimal target of harmonic suppression are achieved after the bridge arm is dynamically reconfigured.

6. The method for suppressing harmonics in a dual-star transformer rectifier according to claim 1, characterized in that, The step of sending the bridge arm switching control command to the rectifier control unit, which then adjusts the bridge arm conduction state according to the command, specifically includes: synchronously blocking some conduction paths in the current bridge arm group and releasing the conduction paths of the selected target bridge arm group, thereby completing the dynamic reconfiguration of bridge arm resources and increasing the rectifier pulse count. Based on the bridge arm switching control command, the set of conduction paths corresponding to the target number of rectified pulses in the current bridge arm group is identified, and real-time current acquisition is performed on the set of conduction paths to obtain the start and end times of the current zero crossover interval of each bridge arm in the set of conduction paths, which are used as the input basis for the synchronous blocking criterion. Based on the start and end times of the current zero-crossing interval, a synchronous blocking window is generated, and a voltage polarity confirmation judgment is performed within the synchronous blocking window to identify the conduction path in the current bridge arm group that can be blocked. The judgment result is used as the electrical state protection condition input for the subsequent target bridge arm group release operation. Under the premise of meeting the electrical state protection conditions, according to the target bridge arm group specified in the bridge arm switching control command, an interleaved conduction trigger sequence is constructed, and the interleaved conduction trigger sequence is used to control the conduction start time of each conduction path in the target bridge arm group. The conduction start time is used to avoid instantaneous current jumps between adjacent paths to the greatest extent. Based on the state of the locked conduction path within the synchronous locking window and the state of the target bridge arm group conduction path formed at the start of conduction, the bridge arm conduction state configuration in the rectifier control unit for controlling the conduction behavior of the next cycle is updated as the result of dynamic reconfiguration of bridge arm resources, and the rectifier control unit is driven to output a control signal sequence that increases the number of rectified pulses.

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