A sub-module capacitor voltage balance control method and device

Abstract

The application provides a kind of sub-module capacitor voltage balance control method and device.The first sub-module set and the second sub-module set are selected according to the actual voltage of multiple sub-module capacitors.The sub-modules in the first sub-module set and the second sub-module set are controlled according to the bridge arm current.The application realizes the directional discharge of the sub-module with high actual voltage and the directional charging of the sub-module with low actual voltage by accurately pairing the actual voltage of the sub-module capacitor according to high and low, and using the switching logic coordinated with the bridge arm current, so that the balance control logic is smoother, the voltage convergence process is accelerated, and the efficiency of voltage balance control is improved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a method and apparatus for controlling the voltage balance of a submodule capacitor. Background Technology

[0002] Modular multilevel converters achieve high-voltage, high-capacity power conversion through cascading sub-modules and modular topology. They offer advantages such as high power quality, excellent harmonic performance, flexible expansion, and high fault tolerance, and are widely used in fields such as flexible DC transmission and new energy grid connection.

[0003] Submodules are typically H-bridge topologies and can be either half-bridge or full-bridge submodules. Full-bridge submodules support switching between positive, negative, and off states, and have bidirectional charge / discharge control capabilities, making them suitable for DC fault ride-through and high-reliability power supply scenarios. Half-bridge submodules, characterized by their simple topology and controllable cost, dominate economical engineering applications.

[0004] While full-bridge submodules offer high state redundancy, existing algorithms often rely on bypass state regulation, failing to fully exploit the precise synergy between high / low voltage module pairing and current-state coupling logic, thus limiting regulation efficiency. Half-bridge submodules only support on / off states, with capacitor charging and discharging strictly constrained by the unidirectional coupling of current direction and switching state, resulting in significantly lower regulation freedom compared to full-bridge submodules. To achieve balanced control of submodule capacitor voltages, related technologies simply screen high / low voltage submodules without meticulously deriving how paired submodules can achieve high discharge and low charge through state switching. Many pairs are skipped due to exacerbated imbalance after switching, leading to low balance control efficiency. Summary of the Invention

[0005] To address the problem of low efficiency in existing balance control technologies, this application provides a method and apparatus for controlling the voltage balance of a submodule capacitor.

[0006] In a first aspect, this application provides a submodule capacitor voltage balance control method, which may include: Obtain the actual voltage of capacitors in multiple submodules.

[0007] The first and second submodule sets are selected based on the actual voltage of the capacitors in the multiple submodules.

[0008] The submodules in the first and second submodule sets are controlled based on the bridge arm current.

[0009] In some possible implementations, the first submodule set and the second submodule set are selected based on the actual voltage of the capacitors in the multiple submodules, including: Sort the actual voltages of the capacitors in the multiple submodules in ascending order.

[0010] Select the first M sub-modules to form the first sub-module set, and select the last M sub-modules to form the second sub-module set.

[0011] In other possible implementations, submodules in the first and second submodule sets are controlled based on the bridge arm current, including: If a submodule in the second submodule set is in a positive input state, and a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, then the submodules in the second submodule set that are in a positive input state and the submodules in the first submodule set that are in a negative input state are switched off.

[0012] If a submodule in the second submodule set is in the active state and a submodule in the first submodule set is in the cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in the active state to cut out, and control the submodule in the first submodule set that is in the cut-out state to be active.

[0013] In some other possible implementations, the submodules in the first and second submodule sets are controlled based on the bridge arm current, including: If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively input, and control the submodule in the first submodule set that is in a negative input state to be cut out.

[0014] If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively connected, and control the submodule in the first submodule set that is in a cut-out state to be positively connected.

[0015] If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a cut-out state to be positively connected, and control the submodule in the first submodule set that is in a cut-out state to be negatively connected.

[0016] If a submodule in the second submodule set is in the cut-out state, a submodule in the first submodule set is in the positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in the cut-out state to be positive input, and control the submodule in the first submodule set that is in the positive input state to be cut out.

[0017] In another possible implementation, the submodules in the first and second submodule sets are controlled based on the bridge arm current, including: If a submodule in the second submodule set is in a negative input state, and a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to cut out, and control the submodule in the first submodule set that is in a cut-out state to be negative input.

[0018] If a submodule in the second submodule set is in a negative input state, and a submodule in the first submodule set is in a positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to disconnect, and control the submodule in the first submodule set that is in a positive input state to disconnect.

[0019] Secondly, this application provides a submodule capacitor voltage balancing control device, which may include: The acquisition module is used to acquire the actual voltage of capacitors in multiple sub-modules.

[0020] The selection module is used to select the first submodule set and the second submodule set based on the actual voltage of the capacitors in multiple submodules.

[0021] The control module is used to control the submodules in the first and second submodule sets based on the bridge arm current.

[0022] In some possible implementations, the selected module is specifically used for: Sort the actual voltages of the capacitors in the multiple submodules in ascending order.

[0023] Select the first M sub-modules to form the first sub-module set, and select the last M sub-modules to form the second sub-module set.

[0024] In some other possible implementations, the control module is specifically used for: If a submodule in the second submodule set is in a positive input state, and a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, then the submodules in the second submodule set that are in a positive input state and the submodules in the first submodule set that are in a negative input state are switched off.

[0025] If a submodule in the second submodule set is in the active state and a submodule in the first submodule set is in the cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in the active state to cut out, and control the submodule in the first submodule set that is in the cut-out state to be active.

[0026] In some other possible implementations, the control module is specifically used for: If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively input, and control the submodule in the first submodule set that is in a negative input state to be cut out.

[0027] If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively connected, and control the submodule in the first submodule set that is in a cut-out state to be positively connected.

[0028] If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a cut-out state to be positively connected, and control the submodule in the first submodule set that is in a cut-out state to be negatively connected.

[0029] If a submodule in the second submodule set is in the cut-out state, a submodule in the first submodule set is in the positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in the cut-out state to be positive input, and control the submodule in the first submodule set that is in the positive input state to be cut out.

[0030] In another possible implementation, the control module is specifically used for: If a submodule in the second submodule set is in a negative input state, and a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to cut out, and control the submodule in the first submodule set that is in a cut-out state to be negative input.

[0031] If a submodule in the second submodule set is in a negative input state, and a submodule in the first submodule set is in a positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to disconnect, and control the submodule in the first submodule set that is in a positive input state to disconnect.

[0032] In another aspect, this application also provides a computer device, including: one or more processors.

[0033] A processor is used to execute one or more programs.

[0034] When one or more programs are executed by one or more processors, the balance control method described above is implemented.

[0035] Furthermore, this application also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, it implements the balance control method described above.

[0036] Compared with the prior art, the beneficial effects of this application are as follows: In the submodule capacitor voltage balance control method provided in this application, a first submodule set and a second submodule set are selected based on the actual voltages of multiple submodule capacitors. The submodules in the first and second submodule sets are controlled based on the bridge arm current. It can be seen that this application improves the efficiency of balance control by combining the actual voltages of the submodule capacitors with the bridge arm current to achieve coordinated switching logic.

[0037] This application achieves directional discharge of submodules with high actual voltages and directional charging of submodules with low actual voltages by precisely pairing the actual voltages of the capacitors according to their voltage levels and by using a switching logic coordinated with the bridge arm current. This makes the balance control logic smoother, accelerates the voltage convergence process, and improves the response efficiency of voltage balance control.

[0038] This application adapts to the simplified adjustment requirements of half-bridge unidirectional charge and discharge constraints, while leveraging the operational condition adaptability advantages of H-bridge cut-out state redundancy, supporting complex engineering topologies with mixed connection of half-bridge and H-bridge sub-modules, and enhancing topology adaptability.

[0039] This application tracks the direction of the bridge arm current in real time, dynamically matches the additional switching logic based on the positive / negative of the bridge current, and adjusts the submodule state switching strategy in a timely manner for transient conditions such as current surges, suppresses submodule voltage fluctuations, ensures the operational stability of the modular multilevel converter under dynamic conditions, and improves the response resilience to complex power grid conditions.

[0040] This application avoids the direct switching state from a pair of positive and negative input submodules without passing through zero, thus avoiding excessive switching frequency and reducing submodule power consumption.

[0041] This invention supports flexible configuration of parameters such as the number of extreme modules, adapts to modular multilevel converters with different power levels and different numbers of sub-modules, meets diverse topology and scale requirements in engineering scenarios, and improves the universality and customization adaptability of the method.

[0042] Based on the principle of free and flexible adjustment, this application allows the output submodule state switching commands to be directly connected to the valve-level physical controller, constructing a closed-loop test link of voltage screening-regulation-feedback. This provides a realistic voltage balance simulation environment for the engineering commissioning and controller prototype verification of modular multilevel converters, shortening the technology iteration cycle. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic structural diagram of a cascaded submodule in an embodiment of this application; Figure 2 This is a schematic structural diagram of a half-bridge submodule in an embodiment of this application; Figure 3 This is a schematic structural diagram of a full-bridge submodule in an embodiment of this application; Figure 4 This is a schematic flowchart of a submodule capacitor voltage balance control method in an embodiment of this application; Figure 5 This is a schematic structural diagram of a submodule capacitor voltage balance control device in an embodiment of this application. Detailed Implementation

[0045] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0046] The terms "first," "second," etc., used in the specification, embodiments, claims, and drawings of this application are for distinguishing purposes only and should not be construed as indicating or implying relative importance or order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as including a series of steps or units. A method, system, product, or apparatus is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0047] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0048] Example 1: This application provides a submodule capacitor voltage balance control method. For example... Figure 1 As shown, submodules can be cascaded to form bridge arms. Multiple bridge arms can form modular multilevel converters, etc.

[0049] Furthermore, submodules can be such as Figure 2 The half-bridge submodule shown can also be used for, for example Figure 3 The full-bridge submodule shown.

[0050] like Figure 4 As shown, the balance control method 100 includes the following steps: Step S1: Obtain the actual voltage of the capacitors in multiple sub-modules.

[0051] Step S2: Select the first submodule set and the second submodule set based on the actual voltage of the capacitors in the multiple submodules.

[0052] Step S3: Control the submodules in the first and second submodule sets according to the bridge arm current.

[0053] In some possible implementations, the selection of the first submodule set and the second submodule set in S2 above based on the actual voltage of the multiple submodule capacitors includes: Sort the actual voltages of the capacitors in the multiple submodules in ascending order.

[0054] Select the first M sub-modules to form the first sub-module set, and select the last M sub-modules to form the second sub-module set.

[0055] In other words, the first submodule set can include the first M submodules with relatively low actual capacitor voltages. The second submodule set can include the last M submodules with relatively high actual capacitor voltages. For example, if there are 100 submodules in total, ordered from low to high actual voltage, submodules 1-20 can be selected to form the first submodule, and submodules 81-100 can be selected to form the second submodule.

[0056] In some other possible implementations, step S3 above can specifically be implemented by controlling the sub-modules according to the sign of the bridge arm current and the state of the sub-modules of the first and second sub-module sets, thereby achieving sub-module capacitor voltage balance control.

[0057] Optionally, the state of a submodule can include a positive input state, a negative input state, and a cut-out state.

[0058] The "positive engagement" state refers to the submodule being fully connected, receiving input, performing calculations / processing normally according to the preset logic, and outputting valid results. This is the normal working state of the submodule.

[0059] Negative input state refers to a state where the submodule is connected but is in a loaded or reverse / limited state, does not perform the full core functions, and only maintains basic operation or handles abnormal input. It is a transitional state between positive input and cut-out.

[0060] The "cut-out" state refers to the state where the submodule is completely physically or logically isolated from the system, does not receive any input, does not perform any processing, and does not output any signals; it is the offline state of the submodule.

[0061] Furthermore, step S3 above may specifically include: (1) If the submodules in the second submodule set are in a positive input state, the submodules in the first submodule set are in a negative input state, and the bridge arm current is positive, control the submodules in the second submodule set that are in a positive input state and the submodules in the first submodule set that are in a negative input state to be cut off.

[0062] (2) If the submodules in the second submodule set are in the positive input state, the submodules in the first submodule set are in the cut-out state, and the bridge arm current is positive, control the submodules in the second submodule set that are in the positive input state to cut out, and control the submodules in the first submodule set that are in the cut-out state to be in the positive input state.

[0063] (3) If the submodules in the second submodule set are in the cut-out state, the submodules in the first submodule set are in the negative input state, and the bridge arm current is positive, control the submodules in the second submodule set that are in the cut-out state to be negatively input, and control the submodules in the first submodule set that are in the negative input state to be cut out.

[0064] (4) If the submodules in the second submodule set are in the cut-out state, the submodules in the first submodule set are in the cut-out state, and the bridge arm current is positive, control the submodules in the second submodule set that are in the cut-out state to be negatively connected, and control the submodules in the first submodule set that are in the cut-out state to be positively connected.

[0065] (5) If the submodules in the second submodule set are in the cut-out state, the submodules in the first submodule set are in the cut-out state, and the bridge arm current is negative, control the submodules in the second submodule set that are in the cut-out state to be positively connected, and control the submodules in the first submodule set that are in the cut-out state to be negatively connected.

[0066] (6) If the submodules in the second submodule set are in the cut-out state, the submodules in the first submodule set are in the positive input state, and the bridge arm current is negative, control the submodules in the second submodule set that are in the cut-out state to be positive input, and control the submodules in the first submodule set that are in the positive input state to be cut out.

[0067] (7) If the submodules in the second submodule set are in a negative input state, the submodules in the first submodule set are in a cut-out state, and the bridge arm current is negative, control the submodules in the second submodule set that are in a negative input state to cut out, and control the submodules in the first submodule set that are in a cut-out state to be negative input.

[0068] (8) If the submodule in the second submodule set is in a negative input state, the submodule in the first submodule set is in a positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to cut off, and control the submodule in the first submodule set that is in a positive input state to cut off.

[0069] The above controls can also be referenced in Table 1: Table 1

[0070] Optionally, in the first and second submodule sets, each pair of submodules with the highest actual voltage (of the submodule capacitor) and the submodule with the lowest actual voltage (of the submodule capacitor) are controlled as above in sequence until all comparisons and controls are completed.

[0071] Understandably, taking 100 sub-modules as an example again, if the first sub-module does not require control, then the 100th and second sub-modules can be controlled as described above. Alternatively, if the 100th sub-module does not require control, then the 99th and first sub-modules can be controlled as described above, and so on. This application will not provide a more detailed description.

[0072] The technical solution provided in this application is based on the precise adaptation capability of module voltage extreme value pairing and bridge arm current coordinated adjustment logic to multi-state redundancy characteristics and unidirectional charging and discharging constraints, which improves the fineness of voltage balance. By selectively adjusting sub-modules, it reduces invalid switching operations and optimizes the balance speed and adjustment stability. It achieves efficient coordination between directional discharge of high-voltage sub-modules and directional charging of low-voltage sub-modules, providing technical support for cross-topology engineering joint debugging of modular multilevel converters, multi-scenario verification of controllers, and in-depth analysis of system dynamic balance characteristics.

[0073] Example 2: Based on the same inventive concept, this application also provides a submodule capacitor voltage balancing control device. For details regarding the submodule, please refer to the above text and related drawings; further elaboration will not be repeated here.

[0074] like Figure 5 As shown, the balance control device 200 may include: The acquisition module 201 is used to acquire the actual voltage of the capacitors in multiple sub-modules.

[0075] Module 202 is used to select the first submodule set and the second submodule set based on the actual voltage of the capacitors in the multiple submodules.

[0076] The control module 203 is used to control the submodules in the first submodule set and the second submodule set according to the bridge arm current.

[0077] In some possible implementations, module 202 is specifically used for: Sort the actual voltages of the capacitors in the multiple submodules in ascending order.

[0078] Select the first M sub-modules to form the first sub-module set, and select the last M sub-modules to form the second sub-module set.

[0079] In some other possible implementations, the control module 203 is specifically used for: If a submodule in the second submodule set is in a positive input state, and a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, then the submodules in the second submodule set that are in a positive input state and the submodules in the first submodule set that are in a negative input state are switched off.

[0080] If a submodule in the second submodule set is in the active state and a submodule in the first submodule set is in the cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in the active state to cut out, and control the submodule in the first submodule set that is in the cut-out state to be active.

[0081] In some other possible implementations, the control module 203 is specifically used for: If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively input, and control the submodule in the first submodule set that is in a negative input state to be cut out.

[0082] If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively connected, and control the submodule in the first submodule set that is in a cut-out state to be positively connected.

[0083] If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a cut-out state to be positively connected, and control the submodule in the first submodule set that is in a cut-out state to be negatively connected.

[0084] If a submodule in the second submodule set is in the cut-out state, a submodule in the first submodule set is in the positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in the cut-out state to be positive input, and control the submodule in the first submodule set that is in the positive input state to be cut out.

[0085] In another possible implementation, the control module 203 is specifically used for: If a submodule in the second submodule set is in a negative input state, and a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to cut out, and control the submodule in the first submodule set that is in a cut-out state to be negative input.

[0086] If a submodule in the second submodule set is in a negative input state, and a submodule in the first submodule set is in a positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to disconnect, and control the submodule in the first submodule set that is in a positive input state to disconnect.

[0087] Example 3: Based on the same inventive concept, this application also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the balance control method provided in the above embodiments.

[0088] Example 4: Based on the same inventive concept, this application also provides a computer-readable storage medium, specifically a computer-readable storage medium (Memory). A computer-readable storage medium is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the balance control method provided in the above embodiments.

[0089] Those skilled in the art will understand that the embodiments of the application can be provided as a method, system, or computer program product. Therefore, the application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0090] The application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0091] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0092] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0093] The above are merely examples of the application and are not intended to limit the application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the application shall be included within the scope of the claims of the pending application.

Claims

1. A method for controlling the voltage balance of a submodule capacitor, characterized in that, include: Obtain the actual voltage of capacitors in multiple submodules; The first submodule set and the second submodule set are selected based on the actual voltage of the capacitors in the multiple submodules. The submodules in the first submodule set and the second submodule set are controlled based on the bridge arm current.

2. The balance control method according to claim 1, characterized in that, The step of selecting the first submodule set and the second submodule set based on the actual voltage of the multiple submodule capacitors includes: Sort the actual voltages of the capacitors in multiple submodules in ascending order; The first M sub-modules are selected to form the first sub-module set, and the last M sub-modules are selected to form the second sub-module set.

3. The balance control method according to claim 2, characterized in that, The control of submodules in the first submodule set and the second submodule set based on the bridge arm current includes: If a submodule in the second submodule set is in a positive input state, a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, then control the submodule in the second submodule set that is in a positive input state and the submodule in the first submodule set that is in a negative input state to be switched off. If a submodule in the second submodule set is in the active state, a submodule in the first submodule set is in the cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in the active state to cut out, and control the submodule in the first submodule set that is in the cut-out state to be active.

4. The balance control method according to claim 2, characterized in that, The control of submodules in the first submodule set and the second submodule set based on the bridge arm current includes: If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively input, and control the submodule in the first submodule set that is in a negative input state to be cut out. If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively connected, and control the submodule in the first submodule set that is in a cut-out state to be positively connected. If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a cut-out state to be positively connected, and control the submodule in the first submodule set that is in a cut-out state to be negatively connected. If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a cut-out state to be positively input, and control the submodule in the first submodule set that is in a positive input state to be cut out.

5. The balance control method according to claim 2, characterized in that, The control of submodules in the first submodule set and the second submodule set based on the bridge arm current includes: If a submodule in the second submodule set is in a negative input state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to cut out, and control the submodule in the first submodule set that is in a cut-out state to be negative input. If a submodule in the second submodule set is in a negative input state, a submodule in the first submodule set is in a positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to switch off, and control the submodule in the first submodule set that is in a positive input state to switch off.

6. A submodule capacitor voltage balancing control device, characterized in that, include: The acquisition module is used to acquire the actual voltage of capacitors in multiple sub-modules. A selection module is used to select a first submodule set and a second submodule set based on the actual voltage of the capacitors of the plurality of submodules. The control module is used to control the submodules in the first submodule set and the second submodule set according to the bridge arm current.

7. The balance control device according to claim 6, characterized in that, The selection module is specifically used for: Sort the actual voltages of the capacitors in multiple submodules in ascending order; The first M sub-modules are selected to form the first sub-module set, and the last M sub-modules are selected to form the second sub-module set.

8. The balance control device according to claim 7, characterized in that, The control module is specifically used for: If a submodule in the second submodule set is in a positive input state, a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, then control the submodule in the second submodule set that is in a positive input state and the submodule in the first submodule set that is in a negative input state to be switched off. If a submodule in the second submodule set is in the active state, a submodule in the first submodule set is in the cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in the active state to cut out, and control the submodule in the first submodule set that is in the cut-out state to be active.

9. The balance control device according to claim 7, characterized in that, The control module is specifically used for: If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a negative input state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively input, and control the submodule in the first submodule set that is in a negative input state to be cut out. If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is positive, control the submodule in the second submodule set that is in a cut-out state to be negatively connected, and control the submodule in the first submodule set that is in a cut-out state to be positively connected. If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a cut-out state to be positively connected, and control the submodule in the first submodule set that is in a cut-out state to be negatively connected. If a submodule in the second submodule set is in a cut-out state, a submodule in the first submodule set is in a positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a cut-out state to be positively input, and control the submodule in the first submodule set that is in a positive input state to be cut out.

10. The balance control device according to claim 7, characterized in that, The control module is specifically used for: If a submodule in the second submodule set is in a negative input state, a submodule in the first submodule set is in a cut-out state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to cut out, and control the submodule in the first submodule set that is in a cut-out state to be negative input. If a submodule in the second submodule set is in a negative input state, a submodule in the first submodule set is in a positive input state, and the bridge arm current is negative, control the submodule in the second submodule set that is in a negative input state to switch off, and control the submodule in the first submodule set that is in a positive input state to switch off.

11. A computer device, characterized in that, include: One or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the balance control method as described in any one of claims 1 to 5 is implemented.

12. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the balance control method as described in any one of claims 1 to 5.

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