Bridge arm circulation suppression method and system, electronic equipment and medium

Abstract

The invention relates to the technical field of flexible direct-current power transmission, in particular to a bridge arm circulation suppression method and system, electronic equipment and a medium, and the method comprises the steps: obtaining the capacitor voltage information of each sub-module; according to the obtained capacitor voltage information and the configuration information of the currently put-into-operation sub-module, calculating the actual generated voltage of each bridge arm in the current control period; according to a difference value between each actually generated voltage and a target modulation voltage configured by a corresponding bridge arm, calculating the number of target sub-modules; and executing sub-module switching operation based on the current current direction of each bridge arm and the corresponding target sub-module number, and reducing the difference value between the actual generated voltage of each bridge arm and the corresponding target modulation voltage. In this way, the technical problem that it is difficult to achieve cooperative consideration between the suppression effect and the operation efficiency in an existing MMC bridge arm circulating current suppression technology is solved, and the steady-state performance and the operation reliability of the system are improved.

Description

Technical Field

[0001] This invention relates to the field of flexible DC transmission technology, and in particular to a method, system, electronic device, and medium for suppressing circulating current in a bridge arm. Background Technology

[0002] With the continuous and rapid development of DC transmission technology, the construction scale of UHVDC transmission projects is constantly expanding, and the practical demand for the steady-state operation performance and reliability of Modular Multilevel Converters (MMCs) is becoming increasingly urgent. As the core topology in the field of Flexible DC Transmission (Voltage-Sourced Converter based High Voltage Direct Current, VSC-HVDC), MMCs have become the mainstream technology in current DC transmission systems due to their modular structure, low harmonic distortion, and high efficiency. They have been successfully applied in major projects such as the Wudongde DC project and the Rudong offshore wind power flexible DC transmission project, providing crucial support for large-scale clean energy integration and grid interconnection. In the operation of MMC systems, arm circulating current suppression is a core aspect of ensuring equipment safety and stability. Unsuppressed second-harmonic circulating currents increase the current stress on power devices, leading to increased heating and losses in submodule capacitors, directly affecting system lifespan and reliability, and even causing oscillation problems. Therefore, efficient circulating current suppression technology has become a key task in the optimization of DC transmission systems.

[0003] In the field of bridge arm circulating current suppression, existing technologies have made some progress. Control strategies based on submodule capacitor voltage balancing aim to reduce bridge arm voltage errors and suppress circulating current by adjusting the switching method in real time. Current mainstream circulating current suppression methods mostly rely on feedback control mechanisms, such as detecting circulating current components and injecting compensation voltage to offset imbalance factors. However, the MMC operating environment is highly dynamic and complex. The submodule capacitor voltage fluctuates continuously during charging and discharging, resulting in an inherent error between the actual bridge arm voltage and the target modulation voltage. This error introduces power imbalance, further exacerbating circulating current. Existing technologies still have significant limitations in addressing this problem.

[0004] Prior art document 1 (application publication number CN107196539B) discloses a zero DC voltage fault ride-through control method for MMC under asymmetrical arm parameters. This method achieves voltage equalization during faults through an auxiliary voltage equalization loop and a deviation adjustment mechanism, thereby improving fault ride-through capability. However, this method mainly targets fault scenarios such as DC-side short circuits, and its control logic focuses more on transient voltage balance, failing to fully consider the need for arm circulating current suppression under steady-state operation. Specifically, existing technologies generally suffer from two prominent problems: firstly, they rely on complex coordinate transformations, decoupling links, and PI controllers, resulting in a heavy computational burden, difficult parameter tuning, and difficulty adapting to dynamic system changes; secondly, they lack sufficient handling of native errors caused by submodule voltage fluctuations, leading to a persistent deviation between the actual arm voltage and the target modulation voltage, resulting in limited circulating current suppression effectiveness. These problems combine to make it difficult for existing technologies to balance the accuracy and computational efficiency of circulating current suppression in actual MMC operation, failing to meet the requirements of high-reliability DC transmission systems for fast and stable control. Therefore, existing MMC arm circulating current suppression technologies face the technical challenge of achieving a synergistic balance between suppression effectiveness and operational efficiency. Summary of the Invention

[0005] In view of the above-mentioned shortcomings or disadvantages, the present invention provides a bridge arm circulating current suppression method, system, electronic device and medium, which can solve the technical problem that existing MMC bridge arm circulating current suppression technology is difficult to achieve a synergistic balance between suppression effect and operating efficiency.

[0006] This invention provides a bridge arm circulating current suppression method based on a multilevel converter. The multilevel converter includes multiple bridge arms, and each bridge arm is configured with one or more sub-modules, including: Obtain the capacitor voltage information of each submodule.

[0007] Based on the obtained capacitor voltage information and the configuration information of the currently operating sub-modules, the actual generated voltage of each bridge arm in the current control cycle is calculated.

[0008] The number of target submodules is calculated based on the difference between each actual generated voltage and the target modulation voltage configured in the corresponding bridge arm.

[0009] Based on the current direction of each bridge arm and the corresponding number of target sub-modules, a sub-module switching operation is performed to reduce the difference between the actual generated voltage of each bridge arm and the corresponding target modulation voltage.

[0010] Among them, the input submodule refers to the submodule that is configured to connect the capacitor of the submodule to the main circuit path of the bridge arm to construct the output voltage of the bridge arm.

[0011] According to a second aspect, the present invention provides a bridge arm circulating current suppression system, the system being based on a multilevel converter, the multilevel converter comprising multiple bridge arms, each bridge arm being configured with one or more sub-modules, including: The capacitor voltage information acquisition module is used to acquire the capacitor voltage information of each sub-module.

[0012] The actual generated voltage calculation module is used to calculate the actual generated voltage of each bridge arm in the current control cycle based on the acquired capacitor voltage information and the configuration information of the currently running sub-modules.

[0013] The target submodule quantity calculation module is used to calculate the target submodule quantity based on the difference between each actual generated voltage and the target modulation voltage configured in the corresponding bridge arm.

[0014] The bridge arm circulating current differential voltage suppression module is used to perform sub-module switching operations based on the current current direction of each bridge arm and the corresponding number of target sub-modules, so as to reduce the difference between the actual generated voltage of each bridge arm and the corresponding target modulation voltage.

[0015] Among them, the input submodule refers to the submodule that is configured to connect the capacitor of the submodule to the main circuit path of the bridge arm to construct the output voltage of the bridge arm.

[0016] According to a third aspect, the present invention provides an electronic device comprising: At least one processor; and a memory communicatively connected to the at least one processor; The memory stores instructions that can be executed by the at least one processor, which enables the at least one processor to perform any of the bridge arm circulating current suppression methods in the embodiments of the present invention.

[0017] According to another aspect of the present invention, a non-transitory computer-readable storage medium storing computer instructions is provided, wherein the computer instructions are used to cause a computer to execute any of the bridge arm circulating current suppression methods in the embodiments of the present invention.

[0018] The present invention provides a bridge arm circulating current suppression method based on real-time voltage feedback. This method is achieved through four core steps: capacitor voltage information acquisition, actual generated voltage calculation, target quantity decision-making, and dynamic switching execution. Specifically, the method involves: acquiring capacitor voltage information of each submodule to collect the real-time electrical status of the converter bridge arm; calculating the actual generated voltage of each bridge arm based on the capacitor voltage information and the current submodule configuration information to accurately characterize the actual output capability of the bridge arm within the current control cycle; calculating the target submodule quantity based on the difference between the actual generated voltage and the target modulation voltage to quantify the module adjustment amount required to eliminate voltage errors; and executing submodule switching operations based on the bridge arm current direction and the target quantity to dynamically adjust the bridge arm topology to actively compensate for voltage deviations.

[0019] In this technical solution, the present invention addresses the problem described in the background art where the actual voltage of the bridge arm differs from the target voltage due to neglecting capacitor voltage fluctuations. By acquiring the capacitor voltage information of each submodule in real time, a precise sensing basis for the instantaneous output capability of the bridge arm is established, overcoming the shortcomings of traditional strategies that treat capacitor voltage as a constant value, thus introducing calculation errors. Addressing the fundamental problem of circulating current in the bridge arm caused by voltage errors, the present invention calculates the actual generated voltage and compares it with the target modulation voltage to obtain the difference, achieving direct measurement and location of the circulating current excitation source (i.e., voltage imbalance). To address the issue that injecting a general compensation amount to suppress circulating current may affect the external characteristics of the system or cause computational complexity, the present invention converts the voltage difference into the target number of submodules, constructing a direct and physically meaningful suppression strategy with the number of modules as the control variable. To meet the real-time and accuracy requirements of circulating current suppression, the present invention combines the current direction with the execution of submodule switching operations, achieving dynamic and directional compensation of the voltage difference, reducing errors at their source to suppress circulating current. Therefore, the technical solution of the present invention solves the technical problem that existing MMC arm circulating current suppression technology is difficult to achieve a synergistic balance between suppression effect and operating efficiency. By directly controlling the generated voltage of the arm to approach the target value, the excitation of circulating current is weakened from the source, thereby improving the steady-state performance and operational reliability of the system. Attached Figure Description

[0020] Figure 1 This is a structural diagram of an MMC system adopted in an embodiment of the present invention; Figure 2 This is a flowchart of a bridge arm circulation suppression method according to an embodiment of the present invention; Figure 3 This is a flowchart of a bridge arm circulation suppression strategy based on submodule switching, according to some other embodiments of the present invention. Figure 4 This is a simulation diagram of the bridge arm circulation suppression effect according to an embodiment of the present invention; Figure 5This is a structural block diagram of a bridge arm circulation suppression system according to an embodiment of the present invention; Figure 6 This is a block diagram of an electronic device used to implement embodiments of the present invention. Detailed Implementation

[0021] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These details should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0022] During the development of this invention, the inventors, through extensive experiments and data analysis, revealed the fundamental flaws of traditional circulating current suppression methods: these methods not only ignore the dynamic fluctuation characteristics of submodule capacitor voltages but also cause systematic errors between the actual bridge arm voltage and the target modulation voltage by simply treating the capacitor voltage as a rated value. Based on this discovery, the inventors innovatively proposed this technical solution, which utilizes a real-time capacitor voltage feedback mechanism to accurately calculate the difference between the actual generated voltage and the target modulation voltage. Combined with an intelligent switching strategy based on current direction, this achieves the technical effect of eliminating circulating current excitation at its source, embodying the core concept of "precise voltage tracking and natural circulating current suppression."

[0023] Specifically, through comparative experiments, the invention team discovered a significant technical bottleneck in traditional proportional-integral (PI) control methods: an inherent contradiction exists between their circulating current suppression effect and system operating efficiency. These technical defects necessitate a substantial increase in switching frequency when pursuing better suppression effects, making it impossible to achieve synergistic optimization of high performance and high efficiency. However, the real-time voltage difference compensation method proposed in this invention can reduce the circulating current amplitude by approximately 67% while maintaining a relatively constant switching frequency, achieving a synergistic improvement in both suppression effect and operating efficiency.

[0024] Therefore, this invention provides a bridge arm circulating current suppression method according to the first aspect. This method can be applied to a modular multilevel converter circulating current suppression system (hereinafter referred to as "this system"). This system operates independently or as a core control module integrated into the converter control system in scenarios such as flexible DC transmission projects and new energy power generation grid-connected systems to achieve real-time monitoring and dynamic suppression of bridge arm circulating current. The physical equipment deployed in the system includes, but is not limited to: bridge arm sub-modules with fully controllable devices, bridge arm current sensors, sub-module capacitor voltage monitoring units, real-time calculation controllers, and valve base control devices. These physical devices need to have high-precision data acquisition, millisecond-level real-time calculation, and high-speed communication capabilities to support synchronous monitoring of sub-module capacitor voltage, instantaneous judgment of bridge arm current direction, and rapid trigger signal generation based on preset switching rules, ensuring that the system can achieve rapid dynamic compensation for the deviation between the actual generated voltage and the target modulation voltage of the bridge arm.

[0025] In some embodiments, the bridge arm circulation suppression method of the present invention can be applied to, for example... Figure 1 The diagram illustrates a typical application scenario for a modular multilevel converter (MMC). The system consists of three parts: the AC side, the MMC converter body, and the DC side. The AC side includes a three-phase AC power supply (represented by A, B, and C in the diagram) and its equivalent inductance (…). Its three-phase port voltage is denoted as The system provides AC power or connects to the AC grid; the MMC converter itself is the core of the system, and each phase unit consists of upper and lower bridge arms. Each bridge arm contains several half-bridge sub-modules composed of Insulated Gate Bipolar Transistors (IGBTs) and anti-parallel diodes (represented in the figure by multiple switching device symbols connected in series), and one bridge arm inductor ( ) and sensors for monitoring the electrical status of the bridge arms, with the output voltages of the upper and lower bridge arms denoted as . and (where j represents phases a, b, and c), and the bridge arm currents are denoted as follows: and These voltages and currents are direct physical quantities used to calculate the actual generated voltage, determine the current direction, and perform circulating current suppression; the DC side includes the supporting capacitor and the DC voltage source (or load), whose voltage and current are denoted as follows: and The control method of this invention involves real-time acquisition of the capacitor voltage of each submodule (corresponding to the capacitor C of each half-bridge submodule in the figure) and the bridge arm current (…). ), calculate the actual generated voltage of the bridge arm (and (Related), and compared with the target modulation voltage given by the system-level control to make a decision, ultimately generating switching signals for the switching devices of each submodule in the figure, through dynamic adjustment. and Thus achieving AC side voltage With DC side voltage While achieving efficient power conversion between bridge arms, it effectively suppresses circulating currents caused by voltage imbalance between bridge arms.

[0026] like Figure 2 As shown, the method may include: Step S110: Obtain the capacitor voltage information of each submodule.

[0027] Among them, capacitor voltage information refers to the instantaneous voltage value across the supporting capacitor in each submodule, which is monitored and collected in real time. This information is a key physical quantity characterizing the current energy storage state and output voltage capability of the submodule.

[0028] Specifically, the system can synchronously acquire the analog voltage signals of all submodule capacitors at a fixed control period (e.g., 50 microseconds) by using voltage sensors (such as Hall voltage sensors or differential amplification sampling circuits) deployed across the capacitors of each submodule, and convert them into digital quantities via an analog-to-digital converter.

[0029] For example, in a bridge arm containing 200 sub-modules, the system acquires 200 capacitor voltage values ​​within the same control cycle through 200 independent voltage sampling channels, which are respectively... Fu, Fu, ... Fu.

[0030] Step S120: Based on the obtained capacitor voltage information and the configuration information of the currently running sub-modules, calculate the actual generated voltage of each bridge arm in the current control cycle.

[0031] Among them, the configuration information of the currently operational submodules refers to a binary vector used to identify whether each submodule in the bridge arm is in the "operational" or "disconnected" state during the current control cycle; the actual generated voltage refers to the total voltage that the bridge arm can output instantaneously under the set of currently operational submodules, and its value is the sum of the capacitor voltages of all submodules in the set.

[0032] Specifically, the system can read the configuration information register representing the switching status of the submodule through the logic operation unit of the controller, and based on this status, filter out the capacitor voltage values ​​corresponding to all submodules with the status of "engaged" from all capacitor voltage information obtained in step S110, and sum these voltage values.

[0033] For example, for the aforementioned bridge arm, if the current configuration information indicates that 100 sub-modules are in the operational state, their numbers are as follows: The system then sums the capacitor voltage values ​​corresponding to these 100 sub-modules. Assuming the sum is 300150 volts, this value is the actual generated voltage of that bridge arm in the current control cycle. .

[0034] Step S130: Calculate the number of target submodules based on the difference between each actual generated voltage and the target modulation voltage configured in the corresponding bridge arm.

[0035] The target modulation voltage refers to the ideal voltage reference value that the bridge arm is expected to output, calculated by the upper-level control system (such as the current regulator) according to the system operation requirements; the target sub-module number refers to the total number of sub-modules that need to be put into operation in the current cycle so that the actual generated voltage of the bridge arm is close to the target modulation voltage.

[0036] Specifically, the system can first calculate the actual generated voltage using an arithmetic logic unit. With target modulation voltage The difference Then, this difference Divide by the average value of the capacitor voltages of all sub-modules in the bridge arm. This yields a rough estimate of the change in the number of modules. Finally, this change is rounded (e.g., to the nearest integer) to obtain the final target number of submodules. .

[0037] For example, continuing from the previous example, if the target modulation voltage of this bridge arm If it is 301000 volts, then the voltage difference is... Assume the average voltage of the bridge arm submodule capacitors is... If the voltage is 3000 volts, then the quotient is calculated as follows: The number of target submodules after rounding. One. The calculation here shows that, in order to compensate Theoretically, a voltage deviation of 1 volt would require the reduction of less than one sub-module. After rounding, the decision is to maintain the current number of modules in operation.

[0038] Step S140: Based on the current current direction of each bridge arm and the corresponding number of target sub-modules, perform sub-module switching operation to reduce the difference between the actual generated voltage of each bridge arm and the corresponding target modulation voltage.

[0039] Among them, the current direction of the bridge arm refers to the sign of the instantaneous current flowing through the bridge arm. The positive direction is usually defined as the direction from the midpoint of the bridge arm to the positive terminal of the DC side (or from the negative terminal to the midpoint); the submodule switching operation refers to the action of connecting or disconnecting the submodule capacitor from the main circuit path of the bridge arm by controlling the on and off state of the insulated gate bipolar transistor in the submodule.

[0040] Specifically, the system can compare the number of target sub-modules. Number of sub-modules currently deployed Determine the number of modules that need to be added or removed (i.e., the number of changes). Then, combining the bridge arm current direction obtained from real-time sampling, a preset switching rule is applied. If a submodule needs to be switched on (… Then, based on the current direction, select the capacitor with the most suitable voltage from the submodules currently in the "cut off" state (select the lowest voltage when the current is positive, and the highest voltage when the current is negative). One input; if it is necessary to cut off a submodule ( Then, from the submodules currently in the "activated" state, select the capacitor with the most suitable voltage (the highest voltage when the current is positive, and the lowest voltage when the current is negative). One resection.

[0041] For example, continuing from the previous example, the system compares and concludes (100) and (100) equal, number of changes Therefore, no switching operation will be performed in this cycle, and the submodule configuration will remain unchanged. In another example, if a certain bridge arm... indivual, If the current direction is negative, then The system will select the three sub-modules with the lowest capacitor voltage from the current 105 connected sub-modules according to the rule of "prioritizing the cut-off of the sub-module with the lowest voltage when the current is negative". Then, it will send a pulse signal to turn off the connected switching transistors of the three sub-modules and cut them off from the main path.

[0042] Among them, the input submodule refers to the submodule that is configured to connect the capacitor of the submodule to the main circuit path of the bridge arm to construct the output voltage of the bridge arm.

[0043] Specifically, in a common half-bridge submodule topology, when the insulated gate bipolar transistor (IGBT) of the upper bridge arm is turned on and the IGBT of the lower bridge arm is turned off, the submodule capacitor is connected to the bridge arm current path, and its capacitor voltage contributes to the total bridge arm voltage. At this time, the submodule is in the "on" state.

[0044] For example, for a submodule with a rated capacitor voltage of 3000 volts, when it is in the working state, if the bridge arm current flows into its positive terminal and out of its negative terminal, the current will charge the capacitor, and the capacitor voltage will tend to rise; conversely, if the current direction is opposite, the capacitor will discharge, and the voltage will tend to fall.

[0045] In other embodiments, the bridge arm circulation suppression strategy based on submodule switching is as follows: Figure 3 As shown, in this circulating current suppression strategy, the bridge arm circulating current suppression method can be specifically implemented through a closed-loop control process that includes voltage detection, sorting decision, and dynamic switching feedback. This process begins at the start of the control cycle. First, the controller detects and records the voltage values ​​of all half-bridge submodule capacitors at the current moment to obtain the real-time status of each energy storage unit within the bridge arm. Then, the system sorts all the acquired submodule capacitor voltage values ​​in ascending order, establishing an ordered data foundation for subsequent decisions based on the voltage balancing strategy. After sorting, the process enters the pre-investment decision stage, that is, pre-selecting and investing a certain number (denoted as n) of submodules according to the conventional submodule capacitor voltage balancing strategy. Here, "pre-investment" is a decision state, referring to the set of submodules planned to be put into operation in this cycle, determined by the controller logic before the final trigger signal is issued. Next, the system calculates the voltage that the bridge arm can generate under this configuration based on this pre-invested set of submodules and their corresponding capacitor voltage values. Next, the process enters the core judgment stage: the calculated... With reference voltage given by the upper layer of the system Compare them. If the judgment is... This means that the currently pre-generated bridge arm voltage is higher than the target value, and the process enters the "removal" stage. The path of "one sub-module" reduces the bridge arm voltage by decreasing the number of modules deployed; if determined to be... This means the current voltage is insufficient, and the process enters the "supplement" stage. The "sub-module" path increases the bridge arm voltage by increasing the number of modules deployed. This represents the number of submodules that need to be adjusted, and its value is determined by... The quotient of the average voltage of the submodule capacitors is rounded to determine the value. Finally, after making the decision to add or remove, the controller applies a specific trigger pulse signal to the corresponding submodule power device to execute the actual switching operation, thus completing the adjustment of one control cycle and enabling the system to enter the next cycle. This process clearly demonstrates how the voltage difference is... The sorting and comparison logic is transformed into specific instructions for adjusting the number of sub-modules. or This allows for precise and dynamic tracking of the actual generated voltage of the bridge arm through trigger signal execution.

[0046] Therefore, according to the above implementation, the system can acquire the capacitor voltage information of each submodule to collect the real-time electrical status of the converter arm; calculate the actual generated voltage of each arm based on the capacitor voltage information and the current submodule configuration information to accurately characterize the actual output capability of the arm in the current control cycle; calculate the target submodule number based on the difference between the actual generated voltage and the target modulation voltage to quantify the module adjustment amount required to eliminate voltage error; and perform submodule switching operation based on the arm current direction and the target number to dynamically adjust the topology of the arm to actively compensate for voltage deviation.

[0047] In this technical solution, this embodiment addresses the problem described in the background art where the actual voltage of the bridge arm differs from the target voltage due to neglecting capacitor voltage fluctuations. By acquiring the capacitor voltage information of each submodule in real time, it establishes a precise perception basis for the instantaneous output capability of the bridge arm, overcoming the shortcomings of traditional strategies that treat capacitor voltage as a constant value, thus introducing calculation errors. Addressing the fundamental problem of circulating current in the bridge arm caused by voltage errors, it calculates the actual generated voltage and compares it with the target modulation voltage to obtain the difference, achieving direct measurement and location of the circulating current excitation source (i.e., voltage imbalance). To address the issue that injecting a general compensation amount to suppress circulating current may affect the external characteristics of the system or cause computational complexity, traditional methods convert the voltage difference into the target number of submodules, constructing a direct and physically meaningful suppression strategy with the number of modules as the control variable. To meet the real-time and accuracy requirements of circulating current suppression, it combines the current direction with the execution of submodule switching operations, achieving dynamic and directional compensation of the voltage difference, reducing errors at their source to suppress circulating current. Therefore, the technical solution of this embodiment solves the technical problem that existing MMC arm circulating current suppression technology is difficult to achieve a balance between suppression effect and operating efficiency. By directly controlling the generated voltage of the arm to approach the target value, the excitation of circulating current is weakened from the source, thereby improving the steady-state performance and operational reliability of the system.

[0048] In other embodiments, such as Figure 4 The figure shown is a simulation diagram of the bridge arm circulation suppression effect. This diagram visually illustrates the changes in bridge arm circulation before and after the implementation of the method described in this invention. The horizontal axis represents time (unit: seconds), and the vertical axis represents the bridge arm circulation value (unit: kiloamperes). The diagram contains two clear curves: within a time period of approximately 1.35 seconds to 1.5 seconds, both curves show an amplitude of approximately... The significant periodic fluctuations (in kiloamperes) represent a typical state of the arm circulation under traditional control strategies, indicating that the circulation has not been effectively suppressed. However, after approximately 1.5 seconds (the critical point at which the control strategy proposed in this embodiment takes effect), the amplitude of one of the curves (i.e., the circulation of the controlled target arm) rapidly decays, converging from a state of large fluctuations and stabilizing at near-percentages within a very short time. Near the horizontal line, another curve serving as a reference (or the circulating current of another phase arm) maintains its original fluctuation pattern. This stark contrast directly demonstrates that by applying the method proposed in this invention based on real-time voltage detection and precise submodule switching compensation, the system can quickly and effectively suppress the circulating current in the bridge arm, reducing the circulating current amplitude to an ideal level close to zero, thereby significantly reducing system losses and improving operational stability. These simulation results provide strong experimental data support for the effectiveness and superiority of the technical solution of this invention.

[0049] In some embodiments, the above method further includes: Based on the current direction of each bridge arm, the capacitor voltage information of the corresponding submodule of each bridge arm is sorted.

[0050] Here, sorting refers to rearranging all sub-modules belonging to the same bridge arm in ascending or descending order according to their capacitor voltage values ​​to form an ordered list.

[0051] Specifically, the system can use the controller's sorting algorithm unit (such as quicksort or heapsort) to reorganize the capacitor voltage data of all submodules belonging to a specific bridge arm obtained in step S110 within each control cycle. If ascending order is used, the first element in the list is the submodule with the lowest voltage; if descending order is used, the first element is the submodule with the highest voltage.

[0052] For example, for a certain phase upper arm, which contains 120 sub-modules, the capacitor voltage values ​​obtained by the system are distributed between 2980 volts and 3020 volts. The controller uses an ascending sorting algorithm to arrange these 120 voltage values ​​from smallest to largest, generating an ordered sequence: [2985 volts (corresponding to sub-module number 47), 2987 volts (corresponding to sub-module number 12), ..., 3018 volts (corresponding to sub-module number 89)].

[0053] Based on the sorting results and current direction, the sub-modules to be put into operation are selected according to the preset switching rules, and the sub-module configuration information is generated.

[0054] The submodule configuration information refers to a data table or bitmap that clearly records whether each submodule in the bridge arm should be in an "engaged" or "disabled" state in the current and next control cycles.

[0055] Specifically, the system can use a decision logic unit to combine the sorted ordered list with the real-time sampled and determined bridge arm current direction sign (positive or negative), starting from a specific end (start or end) of the list, to sequentially select a specified number (i.e., the target number of sub-modules calculated by S130). The system selects the sub-modules and marks the selected sub-modules as "input" and the remaining sub-modules as "removed", thereby generating a complete configuration information.

[0056] For example, continuing the previous example, if the current direction of this bridge arm is positive in this control cycle, and the target number of sub-modules is... The number is calculated to be 118. According to the rules, the system will start from the beginning of the above ascending sequence list (i.e., the lowest voltage end), select the first 118 sub-modules in sequence, set the status bit corresponding to their numbers (such as 47, 12, ...) to "1" (representing activation), and set the status bit of the last 2 sub-modules in the list to "0" (representing deactivation), thereby generating the configuration information of this bridge arm for this cycle.

[0057] The preset switching rules are configured as follows: the priority order of capacitor voltage of the sub-modules to be put into operation is determined according to the direction of the bridge arm current; when the direction of the bridge arm current is positive, the sub-modules to be put into operation are selected in order of capacitor voltage value from low to high; when the direction of the bridge arm current is negative, the sub-modules to be put into operation are selected in order of capacitor voltage value from high to low.

[0058] Specifically, the underlying principle of this rule is as follows: When the bridge arm current is in the positive direction, the capacitor of the submodule being connected will be in a charging state, and the voltage will rise. Therefore, prioritizing the connection of the submodule with the lowest current voltage allows for the most efficient use of the charging process to raise its voltage, thereby reducing the difference with the submodules with higher voltage. Conversely, when the current is in the negative direction, the capacitor of the submodule being connected will be in a discharging state, and the voltage will drop. Therefore, prioritizing the connection of the submodule with the highest current voltage allows for the most efficient use of the discharging process to lower its voltage, which also contributes to overall balance.

[0059] For example, in another scenario, if the current direction of a certain bridge arm is detected as negative, the capacitor voltages of all its submodules, sorted in descending order, would be listed as: [3050V (number 5), 3048V (number 21), ..., 2980V (number 100)]. If 110 submodules need to be deployed, the system would start from the beginning of this descending list (i.e., the highest voltage level) and select the first 110 submodules with the highest voltages (e.g., numbers 5, 21, ...) for operation. In this way, these high-voltage capacitors will discharge under negative current, and their voltages will naturally decrease, approaching the average voltage value.

[0060] Therefore, according to the above implementation method, when deciding which specific sub-modules to deploy, the system not only considers the quantity requirements but also combines the direction of the bridge arm current with the capacitor voltage ranking, intelligently selecting those sub-modules that are most conducive to maintaining the capacitor voltage balance of all sub-modules. This proactively creates conditions for natural voltage balance at the operational level and is one of the fundamental measures to suppress circulating currents caused by inconsistent capacitor voltages.

[0061] In some embodiments, based on the acquired capacitor voltage information and the configuration information of the currently operating submodules, the actual generated voltage of each bridge arm in the current control cycle is calculated, including: Based on the submodule configuration information, determine the set of submodules that will be put into operation in the current cycle.

[0062] The submodule set refers to the group of submodules that are actually connected to the main circuit path of the bridge arm and whose capacitor voltages together constitute the output voltage of the bridge arm within a specific control cycle according to the predetermined switching command.

[0063] Specifically, the system can read the configuration bitmap or status register stored in the controller's memory, which represents the "engaged" or "disengaged" status of all submodules within the bridge arm. The controller traverses this configuration information, extracts the unique identifiers (such as numbers or memory addresses) of all submodules with a status bit of "1" (representing "engaged"), and summarizes them into a logical "set".

[0064] For example, for a bridge arm composed of submodules numbered 1 to 200, if the submodule configuration information of the current control cycle indicates that the status of submodules numbered 1, 3, 5, ..., 199 is "in operation", then the set of submodules in operation for this cycle determined by the system is {1, 3, 5, ..., 199}, which contains a total of 100 submodules.

[0065] Obtain the capacitor voltage information of each submodule from the submodule set.

[0066] Here, "acquisition" refers to retrieving and reading the real-time voltage value of the corresponding submodule from the system's cache of capacitor and voltage data for all submodules, based on the determined set of submodules.

[0067] Specifically, the system can access a global capacitor voltage data array through the controller's data addressing unit, using the identifiers in the submodule set as indexes. This array is updated in step S110, and its indices typically correspond to submodule numbers, with each array element representing the capacitor voltage value of that submodule. The controller sequentially reads the data from these addresses to obtain the capacitor voltage of each submodule within the set.

[0068] For example, continuing from the previous example, the system has determined the set of submodules to be {1,3,5,...,199}. The controller then uses submodule number 1 as an index to retrieve data from the global voltage array. Read from The value is assumed to be 3005 volts; then, the value is read using index 3. The voltage is 2992 volts; and so on, until the reading is... The value is obtained to obtain the capacitor voltage information of each of the 100 sub-modules.

[0069] The actual generated voltage of the bridge arm is obtained by summing up the various capacitor voltage values ​​obtained from the capacitor voltage information.

[0070] In this context, cumulative calculation refers to summing a set of values ​​one by one. Specifically, it refers to arithmetically summing the instantaneous capacitor voltage values ​​of all submodules belonging to the same bridge arm and in the current cycle.

[0071] Specifically, the system can perform an accumulation loop operation through the controller's Arithmetic Logic Unit (ALU). An accumulator register is initialized to 0. Then, each capacitor voltage value obtained from the submodule set is iterated over, added to the current value of the accumulator, and the result is stored back in the accumulator. After the iteration is complete, the final value in the accumulator is the sum of the capacitor voltages of all the input submodules, which is the actual generated voltage that the bridge arm can output at the current moment. Its calculation formula can be expressed as: , where i iterates through all submodules that are in the active state.

[0072] For example, continuing with the data from the previous example, the system will obtain 100 capacitor voltage values: Fu, Fu, ..., The 100 numbers are sequentially input into an accumulator for summation. Assuming the sum of these 100 numbers is calculated to be 300150 volts, then the actual generated voltage of this bridge arm in this control cycle is... That is, 300150 volts.

[0073] Therefore, according to the above implementation method, the system can map abstract configuration information to specific physical module groups and accurately retrieve the real-time state parameters (capacitor voltage) of each member in the group. Finally, it synthesizes the bridge arm-level, quantifiable key output variables (actual generated voltage) through determined mathematical operations (accumulation). This provides accurate and reliable input data for subsequent precise control decisions based on voltage differences.

[0074] In some embodiments, the number of target submodules is calculated based on the difference between each actual generated voltage and the target modulation voltage configured in the corresponding bridge arm, including: The difference between each actual generated voltage and the target modulation voltage configured in the corresponding bridge arm is divided by the average value of the submodule capacitor voltage of the corresponding bridge arm to obtain the calculated quotient.

[0075] The calculated quotient is an intermediate variable that physically represents the change (which can be a decimal) in the number of sub-modules theoretically needed to compensate for the deviation between the actual generated voltage and the target modulation voltage. This value intuitively reflects the "equivalent" voltage of how many sub-module capacitors the voltage difference is equivalent to.

[0076] Specifically, the system can perform the following calculations through the division unit of the controller: This operation converts the difference in voltage dimensions into an estimated adjustment amount in terms of the number of sub-modules, thus establishing a bridge between the voltage control target and the switching action decision.

[0077] For example, suppose the actual generated voltage of a certain bridge arm The target modulation voltage is 301500 volts. The voltage difference is calculated to be 302,000 volts. The average capacitor voltage of all submodules (e.g., 200) in this bridge arm. The voltage is 3000 volts. Therefore, the quotient is calculated as follows: This result indicates that the current bridge arm voltage is approximately 0.1667 times lower than the target value, representing the voltage contribution of a submodule.

[0078] The calculated quotient is rounded down to obtain the number of target submodules.

[0079] The rounding operation refers to rounding a quotient with decimals towards the nearest integer to obtain a definite, executable integer number of submodule instructions. Since the number of submodules must be an integer, the theoretically calculated decimal values ​​must be converted to integers.

[0080] Specifically, the system can employ rounding, rounding up, or rounding down rules. In a preferred embodiment, rounding is used to achieve an overall unbiased adjustment. The calculation formula is: ,in This represents the rounding function.

[0081] For example, continuing from the previous example, the current number of sub-modules deployed. For 100, calculate the quotient value. After rounding to the nearest integer, Therefore, the number of target submodules This indicates that the system decision does not change the input quantity in this control cycle. In another example, if the quotient value is 0.6, then , pieces, indicating that it is necessary to increase the input by 1 sub-module.

[0082] Among them, the average value of the sub-module capacitor voltage refers to the arithmetic average of the capacitor voltages of all sub-modules corresponding to the bridge arm.

[0083] Specifically, when calculating this average value, the system needs to sum all the capacitor voltage values of all sub-modules of this bridge arm obtained in step S110, and then divide by the total number of sub-modules of this bridge arm. Its calculation formula is: , where n is the total number of sub-modules of the bridge arm, to are the capacitor voltages of each sub-module.

[0084] For example, for the bridge arm with 200 sub-modules mentioned above, the controller adds up all the 200 capacitor voltage sampling values. Assuming the sum is 600000 volts, then the average value of the sub-module capacitor voltage volts. This average value is used as a scale to measure the typical voltage output ability of a single sub-module, and is used to "normalize" the voltage difference.

[0085] Therefore, according to the above embodiments, the system can convert the abstract voltage tracking error into an intuitive quantity adjustment instruction directly related to the physical execution unit (sub-module) by dividing by the average voltage, which is a localized and adaptive "scale". After rounding operation, this instruction is clarified as a definite executable integer operation quantity, thus providing a clear and quantitative decision basis for the subsequent precise switching operation based on this quantity, effectively avoiding the problems of frequent jitter or fuzzy decision-making that may exist in analog control.

[0086] In some embodiments, the steps of performing the sub-module switching operation based on the current current direction of each bridge arm and the corresponding target number of sub-modules include: Compare and calculate the number of sub-modules currently put into operation of each bridge arm with the target number of sub-modules to obtain a plurality of quantity differences.

[0087] Among them, the quantity difference is an integer, and its value is equal to the target number of sub-modules minus the number of sub-modules currently put into operation. Its sign (positive or negative) indicates whether it is necessary to increase or decrease the number of sub-modules, and its absolute value represents the magnitude of the quantity to be adjusted.

[0088] Specifically, the system can perform the following arithmetic operation through the subtraction operation unit of the controller: . This calculation is performed independently for each bridge arm once in each control cycle.

[0089] For example, for a certain phase upper bridge arm, if the target number of sub-modules is calculated by step S130... The number is 102, while the actual number of sub-modules of this bridge arm that have been put into operation during this period is... If there are 105, then the calculated difference in quantity is... .

[0090] Based on the differences in quantity and the current direction of the corresponding bridge arm, determine the number of input submodule changes for each bridge arm. The number of input submodule changes refers to the number of input submodules that need to be added or removed.

[0091] Determining the number of submodule changes to be implemented refers to clarifying the specific number of submodules that ultimately require either "implementation" or "removal" operations. Its value is equal to the absolute value of the quantity difference, while its "action" attribute (whether it's "implementation" or "removal") is determined by the sign of the quantity difference and the direction of the bridge arm current.

[0092] Specifically, the system first reads the quantity difference. .like If the value is positive, it indicates that an additional submodule needs to be added, and the number of submodule changes is [number missing]. (The "+" sign represents an action to be performed). If A negative number indicates that the number of submodules to be added needs to be reduced, i.e., a cut-off action needs to be performed. The number of submodule changes is... (“ The ">" sign indicates a cut-off action, and the value is an absolute value. The current direction information is used in subsequent steps to select the specific sub-module to be operated on by applying preset switching rules.

[0093] For example, continuing from the previous example, the quantity difference Since the value is negative, it is determined that this bridge arm needs to be cut off in this cycle, and the number of submodule changes is 3 (i.e., 3 submodules need to be cut off). The current direction information (assuming the detection is negative) will be used to guide which 3 submodules to cut off from the currently deployed 105 submodules.

[0094] The submodule switching operation is executed based on the number of changes to each input submodule, the preset switching rules, and the current direction of the corresponding bridge arm, so as to update the submodule configuration of each bridge arm.

[0095] The execution of submodule switching operation refers to the controller generating specific switching transistor trigger pulse signals for a particular submodule based on the determined number of submodule changes (and action types) and preset switching rules. These signals are then applied to the gate of the corresponding insulated gate bipolar transistor through the drive circuit, thereby changing its on / off state and enabling the submodule capacitor to be connected to or disconnected from the main circuit of the bridge arm.

[0096] Specifically, the system invokes preset switching rules based on the sign of the submodule change count and the current direction. If it's an input operation (positive change count), a specified number of submodules are selected from the list of submodules currently in a "disconnected" state, according to the rules (selecting the lowest voltage when current is positive, and the highest voltage when current is negative), and an "input" trigger signal is issued. If it's a disconnect operation (negative change count), a specified number of submodules are selected from the list of submodules currently in a "input" state, according to the rules (selecting the highest voltage when current is positive, and the lowest voltage when current is negative), and a "disconnect" trigger signal is issued. All trigger signals are issued simultaneously or almost simultaneously to update the bridge arm topology.

[0097] For example, continuing the previous example, if three submodules need to be disconnected with negative current, the system calls the preset switching rule: "When a negative current direction is detected in a bridge arm, submodules with the highest to lowest capacitor voltage values ​​are selected for operation first." In this case, for the disconnection operation, this rule is applied in reverse, prioritizing the disconnection of the submodule with the lowest capacitor voltage among the currently operational submodules. Assume that from the list of 105 operational submodules, the three with the lowest voltages are 2990 volts (number 15), 2992 volts (number 88), and 2995 volts (number 42). The system then generates a turn-off pulse (or a turn-on pulse, depending on the specific submodule topology), for the insulated gate bipolar transistor (IGBT) of the lower bridge arm of submodules numbered 15, 88, and 42, thus switching these three submodules from the operational state to the disconnected state.

[0098] Therefore, according to the above implementation method, the system can transform the abstract quantitative adjustment target (target sub-module quantity) obtained from the previous calculation stage into a series of physically implementable, specific switching device control commands through precise comparison, decision-making, and execution logic. This process ensures that the control intention is executed accurately and unambiguously, thereby dynamically adjusting the equivalent output voltage of the bridge arm, and is an indispensable final execution stage in closed-loop control.

[0099] In some embodiments, the number of input submodule changes for each bridge arm is determined based on the quantity differences and the current direction of the corresponding bridge arm, including: Based on the absolute value of each quantity difference, the adjustment value of the number of sub-modules corresponding to each bridge arm is calculated.

[0100] The submodule quantity adjustment value is a non-negative integer, which is equal to the absolute value of the quantity difference. It represents the number of submodules that need to be changed when the direction of action (injection or removal) is not considered.

[0101] Specifically, the system can use the absolute value calculation unit of the controller to calculate the quantity difference obtained in the previous steps. Perform absolute value calculation, that is: ,in The sign for absolute value.

[0102] For example, for a certain bridge arm, if we compare the calculated differences in quantity... for The adjustment value for the number of its submodules is then... If the other arm for Then its adjustment value is .

[0103] The sign of each quantity difference is determined based on the current direction of each bridge arm and the preset sign determination rules.

[0104] In this context, determining the numerical sign refers to the sign used for the calculated quantity difference. A new symbol representing the direction of the final operation instruction is assigned ("+" indicates an input operation, "-" indicates a cut-off operation). This final symbol is derived from the original... The sign is determined by the direction of the bridge arm current detected in real time.

[0105] Specifically, the system reads The system retrieves the original sign (positive or negative) and the direction (positive or negative) of the bridge arm current, queries a preset sign determination rule mapping table, and outputs a final sign. This process can be implemented using logical conditional statements (if-else).

[0106] For example, suppose a bridge arm was originally for (Indicating the target number is greater than the current number), the bridge arm current direction is detected to be positive. According to the rule "when the bridge arm current direction is positive, the difference in quantity is positive and therefore assigned a positive sign", it is determined that... The numerical symbol is " This means that, despite a larger target number, it is still classified as an "input" operation under positive current.

[0107] By combining the submodule quantity adjustment value with the corresponding numerical symbol, the number of submodule changes to be implemented in each bridge arm is determined.

[0108] Here, "combination" refers to combining the adjustment value representing the quantity of operations with the final numerical symbol representing the direction of operations into a complete, signed integer instruction, i.e., the number of submodule changes to be implemented. Its numerical part equals the adjustment value, and its sign part is the final determined numerical symbol.

[0109] Specifically, the system will adjust the calculated number of submodules (positive integer) with the determined numerical sign ("..."). "or" Combine them using ) . If the symbol is " If the symbol is "", then the number of changes to the submodule is + adjustment value; if the symbol is " If the value is "", then the number of changes to the submodule is -adjustment value.

[0110] For example, continuing from the previous two examples, regarding for For bridge arms with negative current direction, the adjustment value is 3. According to the rule "when the bridge arm current direction is negative, a negative difference in quantity is assigned a positive sign," the following is determined: The numerical symbol is " After combining these parameters, the number of changes to the input submodule of this bridge arm was determined to be: .for for For the bridge arm with positive current direction, the adjustment value is 2, and the numerical sign is "+". Therefore, the number of submodule changes is [number missing]. .

[0111] The sign determination rule is configured as follows: when the direction of the bridge arm current is positive, a positive sign is assigned if the difference in quantity is positive, and a negative sign is assigned if the difference in quantity is negative; when the direction of the bridge arm current is negative, a negative sign is assigned if the difference in quantity is positive, and a positive sign is assigned if the difference in quantity is negative.

[0112] Specifically, this rule is designed based on the dynamic optimization objective of maintaining capacitor voltage balance. Its core lies in ensuring that the sign of the final number of changes to the submodule indicates the " "Actions can produce effects that promote capacitor voltage convergence. For example, when the current is positive (charging), if a module needs to be added (the change number is positive), adding a low-voltage module will help its voltage rise; if a module needs to be removed (the change number is negative), removing a high-voltage module will slow its voltage rise, both of which promote equilibrium. The rules ensure this through the mapping of symbols."

[0113] For example, consider a scenario where the bridge arm current is in the negative direction (discharge), and the original... +1 (one more target). If simply pressed... The symbol performs a connection operation; connecting any module under negative current will cause its voltage to drop. However, according to this rule, A negative sign is assigned when the current is negative, meaning the final instruction is "disconnect one module". At this time, the system will prioritize disconnecting a lower voltage module from the already connected modules (according to the switching rules). The disconnected module stops discharging, and its voltage is retained (relatively high), while the higher voltage modules that are not being operated continue to discharge, thereby promoting overall voltage balance.

[0114] Therefore, according to the above implementation method, the system is able to process simple quantity comparison results ( By introducing the key operating status information of the bridge arm current direction and applying a carefully designed set of symbol determination rules, this is transformed into an intelligent control command (input submodule change number) that not only meets the quantity adjustment requirements but also implies voltage balance optimization. This reflects the optimization layer above the control precision of the present invention and is one of the key mechanisms for achieving synergistic optimization of suppressing circulating current and maintaining the healthy state of capacitor voltage.

[0115] In some embodiments, the submodule switching operation includes: If the sign of the number of submodules to be added is positive, the number of submodules to be added for that bridge arm is determined from the currently non-operational submodules according to the current current direction of the corresponding bridge arm and the preset switching rules; or, if the sign of the number of submodules to be added is negative, the number of submodules to be cut off for that bridge arm is determined from the currently operational submodules according to the current current direction of the corresponding bridge arm and the preset switching rules.

[0116] "Response" refers to the control logic automatically executing the corresponding branch process based on the input judgment conditions (here, the positive or negative sign of the number of changes to the input submodule). "Determination" refers to clarifying, through calculation and logical selection, the specific submodules or groups that need to be operated on (input or removed).

[0117] Specifically, the system executes this step through a conditional logic unit. This unit reads the sign of the number of submodule changes to be added. If the sign is positive, the "Add" branch is triggered. The system selects a specified number (equal to the number of submodules to be added) from the list of submodules that are still in the "Not Added" state after the "Pre-Add" operation in the current cycle, according to preset switching rules (e.g., selecting the lowest voltage when the current is positive, and selecting the highest voltage when the current is negative), and marks them as objects to be added. If the sign is negative, the "Remove" branch is triggered. The system also selects a specified number (equal to the number of submodules to be removed) from the list of submodules in the current "Added" state, according to preset switching rules (in this case, selecting the highest voltage when the current is positive, and selecting the lowest voltage when the current is negative), and marks them as objects to be removed.

[0118] For example, referring to the process shown in the attached diagram, after completing "pre-deploying according to the conventional submodule capacitor voltage balancing strategy, assuming the number of deployed submodules is n" and calculating the bridge arm voltage... Then, if the comparison and judgment result is This means that "resection" needs to be performed. The path to "each submodule". At this point, the number of submodule changes invested is... (Negative number). The system enters the "cut-off" branch. Based on the current direction of the bridge arm current (e.g., positive direction), and following the rule of "prioritizing the cut-off of the submodule with the highest capacitor voltage when the current is positive," it determines from the n pre-installed submodules... There are 10 submodules to be removed (i.e., the number of submodules to be removed is 100). Conversely, if Then proceed to "Supplement" The path to the submodule has been changed. (Positive number) The system enters the "Activation" branch, and determines the module to be activated from the unactivated submodules based on the current direction. Sub-modules.

[0119] Based on the number of sub-modules to be added or the number of sub-modules to be removed, perform the corresponding sub-module addition or removal operation on the current sub-module configuration of each bridge arm.

[0120] Among them, performing the corresponding submodule input or output operation means that the controller sends a precise trigger pulse signal to the gate drive circuit of the power semiconductor device (such as an insulated gate bipolar transistor) of the determined submodule to be operated, thereby changing its on or off state, and finally realizing the physical action of the submodule capacitor being connected to or disconnected from the bridge arm main circuit path.

[0121] Specifically, for the "engage" operation, the system generates and sends a set of "engage" trigger pulses to the gates of the upper arm insulated-gate bipolar transistors (IGBTs) of all submodules to be engaged (for half-bridge submodule topologies), while ensuring that the lower arm IGBTs are turned off. For the "disengage" operation, a "disengage" trigger pulse (a combination of pulses indicating lower arm conduction and upper arm deactivation) is generated and sent. These pulse signals are synchronously applied to the corresponding submodules via isolated drive circuits such as optical fibers, updating the submodule configuration state of all bridge arms in a near-simultaneous manner, thereby changing the total output voltage of the bridge arms.

[0122] For example, continuing from the previous example, in "resection" In the "submodule" path, the system has determined the number of submodules to be removed to be [number]. (Assuming there are 2), and specifically determine the submodule numbers to be removed (e.g., submodules numbered 47 and 89). The system then generates a "removal" trigger pulse sequence for submodules numbered 47 and 89 and issues it through the valve base control device. Within the same control cycle, upon receiving the pulses, these two submodules perform the operation of turning off the input switch and turning on the bypass switch (or similar actions), thereby switching from the input state to the removed state. Accordingly, the actual number of submodules engaged in the bridge arm increases from... Become Bridge arm voltage Consequently, it decreases, towards Approaching.

[0123] The number of sub-modules to be deployed refers to the number of sub-modules that need to be deployed, while the number of sub-modules to be removed refers to the number of sub-modules that need to be removed.

[0124] Specifically, these two values ​​are the quantifications of the number of submodules requiring physical switching actions, obtained after the sign-based branching of the number of submodule changes to be added. The number of submodules to be added is equal to the absolute value of the positive number of submodule changes to be added, and the number of submodules to be cut is equal to the absolute value of the negative number of submodule changes to be added.

[0125] For example, if the calculated number of submodule changes to be added is +3, then the number of submodules to be added is 3, and the number of submodules to be removed is 0. The system will perform the operation of adding 3 submodules, but will not perform any removal operations. If the number of changes is... If the number of submodules to be added is 0, the number of submodules to be removed is 2. The system will then perform the operation of removing 2 submodules.

[0126] Therefore, according to the above implementation method, the system is able to process the abstract change command (based on voltage comparison and current direction decision) or This process transforms control decisions into precise operational commands targeting specific, identifiable sub-modules. Through the closely linked steps of "identifying the object to be operated on" and "executing the physical operation," the control decisions are accurately and reliably translated into the actual actions of the power electronic switching devices, thereby achieving real-time, closed-loop control of the bridge arm output voltage. This is the ultimate execution guarantee for achieving the goal of suppressing bridge arm circulating current control.

[0127] In other embodiments, the system can calculate the measured voltage value of the bridge arm using the following formula (a): ;(a) in, This represents the measured voltage of the bridge arm, which is the sum of the capacitor voltages of all the submodules that are in operation at the current moment. This represents the capacitor voltage value of the i-th submodule, and N is the total number of submodules contained in a single bridge arm. This formula achieves rapid and accurate detection of the generated voltage of the bridge arm by real-time acquisition and accumulation of the capacitor voltages of each submodule.

[0128] Next, in this embodiment, the system can also calculate the number of sub-modules that need to be added and switched using formula (b). : (b) in, This represents the target modulation voltage, which is the ideal voltage value expected to be output by the bridge arm in the current cycle; This represents the average capacitor voltage of all submodules in this bridge arm; function This is a rounding function used to round non-integer values ​​obtained from calculations to the nearest integer to determine the number of operable submodules. The numerator of formula (b) This reflects the deviation between the current measured voltage of the bridge arm and the target voltage, divided by the average voltage of the submodule. Then, the theoretical number of sub-modules that need to be increased or decreased to eliminate this deviation is obtained. After rounding and taking the absolute value, the final number that needs to be actually deployed is obtained. .

[0129] Therefore, by combining the above formulas (a) to (b), the system can detect the actual voltage of the bridge arm in real time and accurately calculate the number of sub-modules required to be switched to approximate the target modulation voltage. By controlling the corresponding number of sub-modules to be added or removed, the output voltage of the bridge arm can be dynamically adjusted, thereby effectively reducing the inherent error of the bridge arm voltage caused by the traditional balancing strategy, improving the voltage balance between bridge arms, suppressing the circulating current in the bridge arms, and ultimately achieving the goal of improving system operating efficiency and reducing losses.

[0130] Figure 5 This is a structural block diagram of a bridge arm circulation suppression system according to an embodiment of the present invention.

[0131] like Figure 5 As shown, this bridge arm circulating current suppression system is based on a multilevel converter, which includes multiple bridge arms, each configured with one or more sub-modules, including: The capacitor voltage information acquisition module 210 is used to acquire the capacitor voltage information of each sub-module.

[0132] The actual generated voltage calculation module 220 is used to calculate the actual generated voltage of each bridge arm in the current control cycle based on the acquired capacitor voltage information and the configuration information of the currently running sub-modules.

[0133] The target submodule quantity calculation module 230 is used to calculate the target submodule quantity based on the difference between each actual generated voltage and the target modulation voltage configured in the corresponding bridge arm.

[0134] The bridge arm circulating current differential voltage suppression module 240 is used to perform sub-module switching operations based on the current current direction of each bridge arm and the corresponding number of target sub-modules, so as to reduce the difference between the actual generated voltage of each bridge arm and the corresponding target modulation voltage.

[0135] Among them, the input submodule refers to the submodule that is configured to connect the capacitor of the submodule to the main circuit path of the bridge arm to construct the output voltage of the bridge arm.

[0136] The specific functions and examples of each module and submodule of the device in this embodiment of the invention can be found in the relevant descriptions of the corresponding steps in the above method embodiments, and will not be repeated here.

[0137] According to embodiments of the present invention, the above-described method of the present invention can be applied to an electronic device and a readable storage medium.

[0138] Figure 6 A schematic block diagram of an example electronic device 600 that can be used to implement embodiments of the present invention is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital assistants, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the invention described and / or claimed herein.

[0139] like Figure 6 As shown, the electronic device 600 includes a computing unit 601, which can perform various appropriate actions and processes based on a computer program stored in a read-only memory (ROM) 602 or a computer program loaded from a storage unit 608 into a random access memory (RAM) 603. The RAM 603 may also store various programs and data required for the operation of the electronic device 600. The computing unit 601, ROM 602, and RAM 603 are interconnected via a bus 604. An input / output (I / O) interface 605 is also connected to the bus 604.

[0140] Multiple components in electronic device 600 are connected to I / O interface 605, including: input unit 606, such as keyboard, mouse, etc.; output unit 607, such as various types of displays, speakers, etc.; storage unit 608, such as disk, optical disk, etc.; and communication unit 609, such as network card, modem, wireless transceiver, etc. Communication unit 609 allows electronic device 600 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0141] The computing unit 601 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 601 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. The computing unit 601 performs the various methods and processes described above, such as a bridge arm circulating current suppression method. For example, in some embodiments, a bridge arm circulating current suppression method may be implemented as a computer software program tangibly contained in a machine-readable medium, such as storage unit 608. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 600 via ROM 602 and / or communication unit 609. When the computer program is loaded into RAM 603 and executed by the computing unit 601, one or more steps of a bridge arm circulating current suppression method described above may be performed. Alternatively, in other embodiments, the computing unit 601 may be configured to perform a bridge arm circulation suppression method by any other suitable means (e.g., by means of firmware).

[0142] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), payload-programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0143] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0144] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0145] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device for displaying information to the user (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor); and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0146] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as a data server), or computing systems that include middleware components (e.g., an application server), or computing systems that include frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), and the Internet.

[0147] Computer systems can include clients and servers. Clients and servers are generally located far apart and typically interact via communication networks. Client-server relationships are created by computer programs running on the respective computers and having a client-server relationship with each other. Servers can be cloud servers, servers in distributed systems, or servers incorporating blockchain technology.

[0148] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0149] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for suppressing bridge arm circulation, characterized in that, The method is based on a multilevel converter, which includes multiple bridge arms, each bridge arm being configured with one or more sub-modules, including: Obtain the capacitor voltage information of each of the sub-modules; Based on the acquired capacitor voltage information and the configuration information of the currently operating sub-modules, calculate the actual generated voltage of each bridge arm in the current control cycle; The number of target sub-modules is calculated based on the difference between the actual generated voltage and the target modulation voltage configured in the corresponding bridge arm. Based on the current current direction of each bridge arm and the corresponding number of target sub-modules, a sub-module switching operation is performed to reduce the difference between the actual generated voltage of each bridge arm and the corresponding target modulation voltage. The input submodule refers to the submodule configured to connect the capacitor of the submodule to the main circuit path of the bridge arm to construct the bridge arm output voltage.

2. The method according to claim 1, characterized in that, The method further includes: Based on the current direction of each bridge arm, sort the capacitor voltage information of the corresponding sub-module of each bridge arm; Based on the sorting results and the current direction, the sub-modules to be put into operation are selected according to the preset switching rules, and the configuration information of the sub-modules is generated. The preset switching rules are configured as follows: the priority order of capacitor voltage of the sub-modules to be put into operation is determined according to the direction of the bridge arm current; when the direction of the bridge arm current is detected to be positive, the sub-modules to be put into operation are selected in order of capacitor voltage value from low to high; when the direction of the bridge arm current is detected to be negative, the sub-modules to be put into operation are selected in order of capacitor voltage value from high to low.

3. The method according to claim 2, characterized in that, The step of calculating the actual generated voltage of each bridge arm in the current control cycle based on the acquired capacitor voltage information and the configuration information of the currently operating sub-modules includes: Based on the submodule configuration information, determine the set of submodules to be put into operation in the current cycle; Obtain the capacitor voltage information of each submodule from the set of submodules; The actual generated voltage of the bridge arm is obtained by summing up the capacitor voltage values ​​from the acquired capacitor voltage information.

4. The method according to claim 1, characterized in that, The calculation of the target sub-module number based on the difference between the actual generated voltage and the target modulation voltage configured in the corresponding bridge arm includes: The difference between each actual generated voltage and the target modulation voltage configured in the corresponding bridge arm is divided by the average value of the submodule capacitor voltage of the corresponding bridge arm to obtain the calculated quotient. The calculated quotient is rounded down to obtain the number of target sub-modules; The average value of the submodule capacitor voltage refers to the arithmetic mean of the capacitor voltages of all submodules in the corresponding bridge arm.

5. The method according to claim 1, characterized in that, The step of performing submodule switching operations based on the current current direction of each of the bridge arms and the corresponding number of target submodules includes: The number of sub-modules currently in operation in each of the bridge arms is compared with the target number of sub-modules to obtain multiple quantity differences; Based on the difference in quantity and the current direction of the corresponding bridge arm, determine the number of input submodule changes for each bridge arm. The number of input submodule changes refers to the number of input submodules that need to be added or removed. The submodule switching operation is performed according to the number of changes to each input submodule, the preset switching rules, and the current direction of the corresponding bridge arm, so as to update the submodule configuration of each bridge arm.

6. The method according to claim 5, characterized in that, The step of determining the number of input submodule changes for each bridge arm based on the quantity difference and the current direction of the corresponding bridge arm includes: Based on the absolute value of each of the quantity differences, the adjustment value of the number of sub-modules corresponding to each of the bridge arms is calculated; The sign of each quantity difference is determined according to the current direction of each bridge arm and the preset sign determination rule; The number of sub-module quantity adjustment values ​​is combined with the corresponding numerical symbols to determine the number of sub-module changes for each bridge arm; The sign determination rule is configured as follows: when the direction of the bridge arm current is positive, the quantity difference is assigned a positive sign if it is positive and a negative sign if it is negative; when the direction of the bridge arm current is negative, the quantity difference is assigned a negative sign if it is positive and a positive sign if it is negative.

7. The method according to claim 6, characterized in that, The submodule switching operation includes: In response to a positive sign for the number of submodule changes, the number of submodules to be added for the corresponding bridge arm is determined from the currently non-operational submodules according to the preset switching rules, based on the current current direction of the corresponding bridge arm; or, in response to a negative sign for the number of submodule changes, the number of submodules to be removed for the corresponding bridge arm is determined from the currently operational submodules according to the preset switching rules, based on the current current direction of the corresponding bridge arm. Based on the number of sub-modules to be added or the number of sub-modules to be removed, perform corresponding sub-module addition or removal operations on the current sub-module configuration of each bridge arm. The number of sub-modules to be deployed refers to the number of sub-modules that need to be deployed, and the number of sub-modules to be removed refers to the number of sub-modules that need to be removed.

8. A bridge arm circulation suppression system, characterized in that, This system is based on a multilevel converter, which includes multiple bridge arms, each bridge arm being configured with one or more sub-modules, including: A capacitor voltage information acquisition module is used to acquire the capacitor voltage information of each of the sub-modules; The actual generated voltage calculation module is used to calculate the actual generated voltage of each bridge arm in the current control cycle based on the acquired capacitor voltage information and the configuration information of the currently running sub-modules. The target submodule quantity calculation module is used to calculate the target submodule quantity based on the difference between the actual generated voltage and the target modulation voltage configured in the corresponding bridge arm. The bridge arm circulating current voltage difference suppression module is used to perform sub-module switching operation based on the current current direction of each bridge arm and the corresponding number of target sub-modules, so as to reduce the difference between the actual generated voltage of each bridge arm and the corresponding target modulation voltage. The input submodule refers to the submodule configured to connect the capacitor of the submodule to the main circuit path of the bridge arm to construct the bridge arm output voltage.

9. An electronic device, characterized in that, include: At least one processor; and a memory that is communicatively connected to the at least one processor; The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method of any one of claims 1-7.

10. A non-transitory computer-readable storage medium storing computer instructions, characterized in that, Computer instructions are used to cause a computer to perform the method according to any one of claims 1-7.

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