A method and apparatus for balancing phase-to-phase voltage of a converter, a converter and a medium

Abstract

This application discloses a method, apparatus, converter, and medium for phase-to-phase voltage equalization in a converter, belonging to the field of power grid equipment control. The method involves: connecting a corresponding isolated energy conversion unit to each submodule, and connecting each isolated energy conversion unit to a switch matrix; connecting the switch matrix to a dual active bridge, with the other end of the dual active bridge connected to a buffer bus; when the voltage deviation between two submodules meets a preset condition, selecting the two target submodules with the largest voltage deviation; controlling the switch matrix to open, connecting the isolated energy conversion units of each target submodule to the dual active bridge; adjusting the phase shift angle of the dual active bridge based on the absolute value of the deviation between the voltage amplitude of each target submodule and a preset rated value, to perform bidirectional energy transfer between each target submodule and the buffer bus until the voltage between the submodules returns to the preset equalization range. This application can improve the voltage equalization performance of the converter.

Description

Technical Field

[0001] This application relates to the field of power grid equipment control, and in particular to a method, apparatus, converter, and medium for phase-to-phase voltage equalization of a converter. Background Technology

[0002] With the development of power electronics technology, a new AC / DC (Alternating Current to Direct Current Converter) topology has been proposed to replace traditional modular multilevel converters, aiming to achieve goals such as reduced device size, improved efficiency, and lower costs. This new type of converter uses a three-phase switched capacitor module chain directly connected in series to form the DC output port. Each phase module is structurally independent and lacks a direct energy exchange channel. During operation, due to factors such as three-phase load imbalance, control errors, and differences in device parameters, the capacitor voltages of each phase module are prone to deviation and gradual divergence. Uneven phase-to-phase voltage not only leads to output voltage distortion and increased harmonics but may also cause overvoltage in individual modules, thus affecting the safety and stability of the converter. Therefore, for this new AC / DC converter, achieving phase-to-phase voltage balance during operation is a key control issue to ensure its reliable operation.

[0003] Existing phase-to-phase voltage equalization methods for converters mostly achieve this by adjusting the DC-side output voltage of each phase or redistributing the three-phase power, which essentially relies on the energy flow path in the main power loop. In traditional topologies, this type of method can achieve phase-to-phase energy redistribution to a certain extent. However, in the aforementioned novel AC / DC converter structure, since the three-phase modules are connected in series on the DC side and there are no inherent energy paths between phases, relying solely on power regulation results in poor phase-to-phase voltage equalization capability. Therefore, improving the phase-to-phase voltage equalization performance of the aforementioned novel AC / DC converter is a technical problem that needs to be solved. Summary of the Invention

[0004] This application provides a method, apparatus, converter, and medium for phase-to-phase voltage equalization of a converter, which can solve the problem of low phase-to-phase voltage equalization performance in existing novel AC / DC converters.

[0005] This application provides a phase-to-phase voltage equalization method for a converter in some embodiments. The converter includes: multiple phase sub-modules, each sub-module being connected in series on the DC side, each sub-module being connected to an isolated energy conversion unit, each isolated energy conversion unit being connected to a switching matrix, the switching matrix being connected to one end of a dual active bridge, and the other end of the dual active bridge being connected to a buffer bus; the phase-to-phase voltage equalization method includes: The voltage amplitude of each sub-module is collected in real time. The voltage deviation between any two sub-modules is calculated based on the voltage amplitude. When the voltage deviation meets a preset condition, the two target sub-modules with the largest voltage deviation are selected. The switch matrix is ​​turned on to enable the isolated energy conversion unit corresponding to each target submodule to conduct with the dual active bridge. With the isolated energy conversion unit and the dual active bridge in operation, the absolute value of the deviation between the voltage amplitude of each target submodule and the preset rated value is calculated, and the phase shift angle of the dual active bridge is adjusted according to the absolute value of the deviation to perform bidirectional energy transfer between each target submodule and the buffer bus, so that the voltage between the target submodules is restored to the preset equalization range.

[0006] Compared to existing technologies, the above embodiments have the following advantages: The converter phase-to-phase voltage equalization method provided in this application connects an isolated energy conversion unit to the DC side of each submodule and constructs an independent energy transmission loop via a switching matrix, dual active bridges, and a buffer bus. This allows for the formation of a controllable indirect energy exchange path between the phase submodules, which were originally structurally independent and lacked direct energy interaction channels. This achieves bidirectional energy regulation between submodules without altering the main power circuit topology. Furthermore, by calculating the submodule voltage deviation in real time and selecting the two submodules with the largest deviations for priority equalization, and by adjusting the phase shift angle of the dual active bridges to precisely control the energy transmission direction and amplitude, the voltage of the target submodule gradually converges to a preset equalization range. Compared to traditional voltage equalization methods that rely on main circuit power redistribution, this application significantly improves the voltage equalization capability of the novel series DC-DC link converter under conditions of unbalanced phase-to-phase loads and inconsistent parameters, thereby enhancing system stability and safety.

[0007] Furthermore, the step of selecting the two target sub-modules with the largest voltage deviations when the voltage deviation meets the preset conditions includes: When a first voltage deviation is greater than a preset phase-to-phase voltage imbalance threshold, the duration of the first voltage deviation being greater than the phase-to-phase voltage imbalance threshold is obtained, and the voltage change rate of the two first sub-modules corresponding to the first voltage deviation is calculated. When the duration corresponding to the first voltage deviation is greater than a preset time threshold and both corresponding voltage change rates are less than a preset voltage change rate threshold, it is determined that the first voltage deviation meets the preset condition. The two first sub-modules corresponding to the largest first voltage deviation are designated as the two target sub-modules.

[0008] Compared with the prior art, the above embodiments have the following beneficial effects: by introducing the duration of voltage deviation and the rate of change of voltage as joint criteria when judging the voltage imbalance between sub-modules, phase equalization control is triggered only when the voltage deviation persists and the trend of change is stable, thereby avoiding misjudgment and frequent switching caused by transient disturbances or measurement noise, improving the accuracy and stability of voltage equalization control triggering, and reducing unnecessary energy regulation actions.

[0009] Further, adjusting the phase shift angle of the dual active bridge based on the absolute value of the deviation includes: The target submodule with the higher voltage is designated as the high-voltage phase. If the item with the larger absolute value of the deviation is the high-voltage phase, the phase shift angle of the dual active bridge is adjusted to control the energy transfer from the high-voltage phase to the buffer bus via the dual active bridge. The target submodule with the lower voltage is designated as the low-voltage phase. If the item with the larger absolute value of the deviation is the low-voltage phase, the phase shift angle of the dual active bridge is adjusted to control the energy transfer from the buffer bus to the low-voltage phase via the dual active bridge.

[0010] Compared with the prior art, the above embodiments have the following beneficial effects: by calculating the absolute value of the deviation of the voltage of the two target sub-modules relative to the rated value, and determining the high voltage phase and the low voltage phase accordingly, the energy transmission direction of the dual active bridge is kept consistent with the voltage deviation direction of the sub-modules. This allows energy to be transferred from the sub-module with higher voltage to the sub-module with lower voltage in a targeted manner, avoiding the situation of incorrect energy regulation direction or reduced regulation efficiency, and improving the regulation effectiveness of the inter-phase voltage equalization process.

[0011] Furthermore, adjusting the phase shift angle of the dual active bridge includes: A reference control quantity is generated based on the voltage deviation between the two target sub-modules; The actual transmitted energy of the dual active bridge is collected, and a phase shift control quantity is generated based on the deviation between the reference control quantity and the actual transmitted energy. The phase shift angle of the dual active bridge is adjusted according to the phase shift angle control value.

[0012] Compared with the prior art, the above embodiments have the following beneficial effects: by generating a reference control quantity based on the voltage deviation between sub-modules, and generating a phase shift angle control quantity by combining the deviation between the actual transmitted energy of the dual active bridge and the reference control quantity, closed-loop regulation of the power transmission of the dual active bridge is realized, so that the energy transmission process can dynamically track the voltage equalization demand, avoid the over-adjustment or under-adjustment problems that may occur under open-loop control, and improve the control accuracy and stability of the phase-to-phase voltage equalization process.

[0013] Furthermore, the buffer bus includes: an energy-dissipating branch; the phase-to-phase voltage equalization method further includes: The voltage of the supporting capacitor of the buffer bus is monitored in real time, and the voltage of the supporting capacitor is compared with a preset buffer supporting capacitor voltage threshold. When the voltage of the supporting capacitor exceeds the voltage threshold of the buffer supporting capacitor, the energy dissipation branch is controlled to be turned on, so that the energy stored in the buffer bus can be discharged through the energy dissipation branch. When the voltage of the supporting capacitor recovers to the preset supporting capacitor voltage range, the energy-consuming branch is controlled to disconnect, so that the buffer bus can operate within the preset supporting capacitor voltage range.

[0014] Compared with the prior art, the above embodiments have the following beneficial effects: by setting an energy dissipation branch on the buffer bus and monitoring the voltage of the supporting capacitor in real time, when the voltage of the buffer supporting capacitor exceeds a preset threshold, the stored energy is released through the energy dissipation branch, thereby avoiding the continuous rise of the supporting capacitor voltage when multiple sub-modules transmit energy to the buffer bus at the same time, preventing overvoltage of the buffer bus and the electrical stress it causes to the dual active bridge and sub-modules, and improving the operational safety of the voltage equalization auxiliary circuit.

[0015] Furthermore, the inter-phase voltage equalization method further includes: The abnormal submodule that has experienced transient operating condition abnormality is identified in real time from all the submodules. When the abnormal submodule is identified, the switch matrix is ​​controlled to turn on, so that the isolated energy conversion unit corresponding to the abnormal submodule is connected to the dual active bridge. The other sub-modules besides the abnormal sub-module are used as the second sub-modules. The switch matrix is ​​turned on, and the isolated energy conversion unit corresponding to the second sub-module with the highest voltage amplitude is connected to the dual active bridge to construct an energy transmission loop. By adjusting the phase shift angle of the dual active bridge, the energy stored in the buffer bus is transmitted to the abnormal submodule through the energy transmission circuit to achieve short-term voltage support.

[0016] Compared with the prior art, the above embodiments have the following beneficial effects: by further identifying the sub-modules that have experienced transient operating abnormalities based on the phase-to-phase voltage equalization control, and controlling the switching matrix to construct an energy transmission loop composed of other sub-modules via dual active bridges and a buffer bus, the energy stored in the buffer bus can provide short-term voltage support to the abnormal sub-modules, thereby suppressing further voltage drops when the sub-modules experience voltage drops or power mutations, and improving the converter's shock resistance and operational continuity under transient disturbance conditions.

[0017] Furthermore, the step of identifying abnormal submodules that experience transient operating condition anomalies from all the submodules in real time includes: Calculate the power change rate corresponding to each of the sub-modules; If the voltage amplitude of a submodule is lower than a preset voltage drop threshold, or the power change rate exceeds a preset power mutation threshold, then the submodule is determined to be an abnormal submodule experiencing a transient operating condition.

[0018] Compared with the prior art, the above embodiments have the following beneficial effects: by comprehensively considering the voltage amplitude and power change rate of the submodule to determine transient anomalies, the identification of abnormal submodules not only depends on voltage amplitude changes, but also reflects dynamic anomalies caused by power surges, thereby improving the sensitivity and reliability of transient anomaly detection, providing accurate target submodules for subsequent energy support control, and avoiding the impact of misidentification or omission on voltage equalization and protection control.

[0019] Another embodiment of this application provides a phase-to-phase voltage equalization device for a converter, which includes: multiple phase sub-modules connected in series on the DC side, each sub-module corresponding to an isolated energy conversion unit, each isolated energy conversion unit connected to a switching matrix, the switching matrix connected to one end of a dual active bridge, and the other end of the dual active bridge connected to a buffer bus; the phase-to-phase voltage equalization device includes: a screening module, a first control module, and a second control module; The filtering module is used to collect the voltage amplitude of each sub-module in real time, calculate the voltage deviation between any two sub-modules based on the voltage amplitude, and select the two target sub-modules with the largest voltage deviation when the voltage deviation meets the preset conditions. The first control module is used to control the switch matrix to turn on, so that the isolated energy conversion unit corresponding to each target submodule is connected to the dual active bridge; The second control module is used to calculate the absolute value of the deviation between the voltage amplitude of each target submodule and the preset rated value when the isolated energy conversion unit and the dual active bridge are turned on, and to adjust the phase shift angle of the dual active bridge according to the absolute value of the deviation, so as to perform bidirectional energy transfer between each target submodule and the buffer bus, so that the voltage between the target submodules is restored to the preset balance range.

[0020] Another embodiment of this application also provides a converter, including: multiple phase sub-modules, an isolated energy conversion unit corresponding to each sub-module, a switching matrix, a dual active bridge, and a buffer bus; Each of the sub-modules is connected in series on the DC side, and the DC side outlet of each of the sub-modules is connected to an isolated energy conversion unit. The negative output terminals of each isolated energy conversion unit are interconnected, and the positive output terminals of each isolated energy conversion unit are respectively connected to the switch matrix as inputs. The output terminal of the switch matrix is ​​connected to the high-voltage side of the dual active bridge, and the low-voltage side of the dual active bridge is connected to the buffer bus.

[0021] Another embodiment of this application also provides a computer-readable storage medium item, including: a stored computer program, which, when the computer program is running, controls the device where the computer-readable storage medium is located to perform the steps of the phase-to-phase voltage equalization method of the converter of this application. Attached Figure Description

[0022] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating a phase-to-phase voltage equalization method for a converter provided in some embodiments of this application; Figure 2 This is a structural topology diagram of a converter provided in some embodiments of this application; Figure 3 This is an embodiment of a converter provided in some embodiments of this application; Figure 4 This is a schematic diagram of the structure of a switch matrix provided in some embodiments of this application; Figure 5 This is a schematic diagram of the structure of a buffer bus provided in some embodiments of this application; Figure 6 This is a schematic diagram of the structure of an interphase voltage equalization device for a converter provided in some embodiments of this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0030] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0031] The novel AC / DC converter topology is a core technological solution to address the high cost, large size, and low efficiency of existing DC power transmission systems. However, the DC output port of the aforementioned AC / DC converter topology is composed of three-phase sub-modules (A, B, and C) directly connected in series, lacking energy exchange channels between phases. This makes the voltage of the supporting capacitors in the modules prone to divergence. Voltage divergence affects the AC-DC conversion efficiency, leading to increased harmonic content; it also may cause module overvoltage, posing a risk of device damage. Therefore, ensuring the consistency of the three-phase sub-module capacitor voltages during operation requires an effective method for inter-phase voltage balancing control.

[0032] Existing methods for equalizing phase voltage in converters mostly achieve this by adjusting the DC-side output voltage of each phase or redistributing the three-phase power, which essentially relies on the energy flow path in the main power circuit. In traditional topologies, this type of method can achieve phase-to-phase energy redistribution to a certain extent. However, in the aforementioned novel AC / DC converter structure, since the three-phase modules are connected in series on the DC side and there is no inherent energy path between phases, relying solely on power regulation results in poor phase-to-phase voltage equalization capability.

[0033] Please refer to Figure 1 To address the problem of poor phase-to-phase voltage equalization control capability of the aforementioned novel AC / DC converter in the prior art, this application provides a phase-to-phase voltage equalization method for a converter. The converter includes: multiple phase sub-modules, each sub-module being connected in series on the DC side, each sub-module being connected to an isolated energy conversion unit, each isolated energy conversion unit being connected to a switch matrix, the switch matrix being connected to one end of a dual active bridge, and the other end of the dual active bridge being connected to a buffer bus.

[0034] Please refer to Figure 2 The present application provides a converter in some embodiments, including: multiple phase sub-modules, an isolated energy conversion unit corresponding to each sub-module, a switching matrix, a dual active bridge and a buffer bus; Each of the sub-modules is connected in series on the DC side, and the DC side outlet of each of the sub-modules is connected to an isolated energy conversion unit. The negative output terminals of each isolated energy conversion unit are interconnected, and the positive output terminals of each isolated energy conversion unit are respectively connected to the switch matrix as inputs. The output terminal of the switch matrix is ​​connected to the high-voltage side of the dual active bridge, and the low-voltage side of the dual active bridge is connected to the buffer bus.

[0035] Preferably, in some embodiments of this application, reference is made to Figure 2The multiple phase sub-modules include: phase A sub-module, phase B sub-module, and phase C sub-module; wherein, the phase A sub-module, the phase B sub-module, and the phase C sub-module are connected in series to form the DC output port of the converter.

[0036] Preferably, in some embodiments of this application, reference is made to Figure 2 The topology of the novel AC / DC converter is improved in the following way: An isolated energy conversion unit is connected to the DC-side outlet of the switched capacitor module corresponding to each of the three-phase submodules A, B, and C. This isolated energy conversion unit can be an isolated DC / DC (Direct Current to Direct Current Converter). For the outlet terminals of the isolated energy conversion units connected to the three-phase submodules A, B, and C, the three negative terminals are connected together, and the three positive terminals are connected to a switch matrix as its valve-side input. The buffer side output of the switch matrix has two positive and two negative ports, which are connected to the high-voltage side of the dual active bridge. The low-voltage side of the dual active bridge is connected to the buffer bus.

[0037] Preferably, in some embodiments of this application, the isolated DC / DC converter may be an isolated full-bridge LLC (Inductor–Inductor–Capacitor Resonant Converter) converter, a phase-shifted full-bridge converter, a push-pull isolated DC / DC converter, or a dual active bridge converter built based on a high-frequency transformer.

[0038] Preferably, in some embodiments of this application, Figure 2 The three isolated energy conversion units can be configured to have a high turns ratio on the switch capacitor module chain side and a low turns ratio on the switch matrix side, thereby reducing the voltage level and voltage stress on the switching devices within the switch matrix.

[0039] Preferably, in some embodiments of this application, the DAB (Dual Active Bridge) connecting the switch matrix and the buffer bus module can be a small to medium power converter, because the voltage connected to the high-voltage side of the DAB through the switch matrix is ​​always a differential voltage between two phases, which avoids the DAB being directly connected to the high potential output of the switched capacitor chain and can maintain it at a low voltage level.

[0040] Preferably, in some embodiments of this application, reference is made to Figure 3This is a preferred embodiment of a converter, with an AC port line voltage of 35kV, a DC port voltage of ±15kV, and a device capacity of 50MVA. Each phase has 10 switched capacitor modules, with a rated capacitor voltage of 2.3kV. The DC-side outputs of the switched capacitor modules corresponding to the three-phase sub-modules are each connected to an isolated full-bridge LLC converter to achieve energy isolation and voltage matching between the three-phase DC link and the buffer bus. The isolated full-bridge LLC converter has inherent soft-switching characteristics, low switching losses, suitability for medium-to-high power isolation conversion, and high efficiency. The low-voltage sides of the three isolated full-bridge LLC converters are connected to the high-voltage side of the DAB via a reverse-resistance type IGBT (Insulated Gate Bipolar Transistor) switching matrix. The low-voltage side of the DAB is connected to the buffer bus module. The switching matrix composed of reverse-resistance type IGBT devices can achieve multi-phase addressable connection without changing the main circuit structure, and has the advantages of fast control response and low conduction losses.

[0041] Understandably, in Figure 3 In the preferred embodiment shown, since the switched capacitor modules corresponding to each of the three-phase sub-modules are stacked in series at high potential, directly establishing a Va–Vb channel would cause a hard connection at the high-voltage side and the risk of circulating current. Through the isolation characteristics of the converter, the system only handles the differential voltage between two phases during each voltage equalization process, and energy is transferred via the DAB at the safe voltage level of the switched capacitor module chain and the buffer bus. This method effectively avoids common-mode interference and circulating current problems on the high-voltage side, significantly reduces the electrical stress on the DAB devices and the buffer bus, and can correspondingly reduce the buffer capacitor capacity requirement, thereby improving the system's safety and overall operating efficiency.

[0042] Preferably, in some embodiments of this application, the structure of the switch matrix is ​​as follows: Figure 4 As shown, reverse-resistance IGBT devices are used, and the switching devices connected to the positive and negative terminals of the three phases are arranged symmetrically in a central manner. The unidirectional current flow path is from the valve side to the positive terminal and from the negative terminal to the valve side. , as well as These represent the switching devices that connect the A, B, and C phase submodules to the positive side of the switch matrix, respectively. , as well as These represent the switching devices connecting the A, B, and C phase submodules to the negative side of the switch matrix. By controlling the on and off states of these switching devices, selective connection between any phase submodule and the positive or negative port of the switch matrix can be achieved, thereby constructing energy transfer channels between different phases. For example, only conducting... and By keeping all other switching devices off, the A and B phase submodules can be connected to the positive and negative ports of the switch matrix respectively, and connected to the buffer bus through DAB, thus realizing the current and energy path from the A phase submodule to the B phase submodule.

[0043] Preferably, in some embodiments of this application, the structure of the buffer bus is as follows: Figure 5 As shown, the buffer bus adopts a resistive energy-dissipating branch design, which includes one capacitor, one resistor, and one switching device, namely the buffer bus support capacitor. Energy-consuming resistor and the control switch of the energy-consuming branch .

[0044] Furthermore, in some embodiments of this application, reference is made to... Figure 1 The phase-to-phase voltage equalization method includes the following steps S101 to S103: S101: Real-time acquisition of the voltage amplitude of each sub-module, calculation of the voltage deviation between any two sub-modules based on the voltage amplitude, and selection of the two target sub-modules with the largest voltage deviation when the voltage deviation meets a preset condition.

[0045] Furthermore, in some embodiments of this application, the step of selecting the two target sub-modules with the largest voltage deviation when the voltage deviation meets a preset condition includes: When a first voltage deviation is greater than a preset phase-to-phase voltage imbalance threshold, the duration of the first voltage deviation being greater than the phase-to-phase voltage imbalance threshold is obtained, and the voltage change rate of the two first sub-modules corresponding to the first voltage deviation is calculated. When the duration corresponding to the first voltage deviation is greater than a preset time threshold and both corresponding voltage change rates are less than a preset voltage change rate threshold, it is determined that the first voltage deviation meets the preset condition. The two first sub-modules corresponding to the largest first voltage deviation are designated as the two target sub-modules.

[0046] Preferably, in some embodiments of this application, using Figure 2 Taking the converter topology shown as an example, the voltage difference between each pair of the three-phase switched capacitor modules corresponding to phases A, B, and C at the DC-side outlet is monitored in real time to obtain... , as well as ,in, This represents the voltage deviation between phase A submodule and phase B submodule. This represents the voltage deviation between the B-phase submodule and the C-phase submodule. This represents the voltage deviation between the C-phase submodule and the A-phase submodule.

[0047] Set a threshold for phase-to-phase voltage imbalance, and , as well as Compared with the phase-to-phase voltage imbalance threshold, if , as well as If none of the values ​​exceed the phase-to-phase voltage imbalance threshold, no operation will be performed.

[0048] Preferably, in some embodiments of this application, if , as well as If one or more voltage deviations exceed the phase-to-phase voltage imbalance threshold, the submodules of the two phases with the largest voltage deviations are selected for subsequent adjustment steps. For example, as well as All exceeded the interphase voltage imbalance threshold, but Greater than Then, select phase B and phase C submodules as target submodules.

[0049] Preferably, in some embodiments of this application, in addition to determining the target submodule based on the magnitude of the voltage deviation, the cause of the current voltage deviation can also be determined by combining the trend of the submodule capacitor voltage change. The target submodule is then selected based on this cause and the voltage deviation. The cause includes either transient disturbance or steady-state voltage imbalance. The step of selecting the target submodule based on this cause and the voltage deviation includes: The voltage amplitude of the corresponding three-phase switched capacitor module for each submodule is collected, and the voltage change rate is calculated based on the voltage amplitude. It is assumed that there is a voltage deviation between the X-phase submodule and the Y-phase submodule. The phase-to-phase voltage imbalance threshold has been exceeded, and the voltage change rate corresponding to the current X-phase submodule is [missing information]. The voltage change rate corresponding to the Y-phase submodule is .if and All are less than the preset voltage change rate threshold (in some embodiments of this application, the voltage change rate threshold can be taken as 0.005~0.05 pu / ms), and If the duration of the phase-to-phase voltage imbalance threshold exceeds a preset time threshold, the cause of the current voltage deviation is determined to be steady-state voltage imbalance, and the X-phase submodule and Y-phase submodule are designated as target submodules; otherwise, even if the voltage deviation... If the phase-to-phase voltage imbalance threshold is exceeded, its cause is also classified as transient disturbance.

[0050] This application introduces the duration of voltage deviation and the rate of change of voltage as joint criteria when judging voltage imbalance between submodules. Phase equalization control is triggered only when the voltage deviation persists and the trend of change is stable. This avoids misjudgment and frequent switching caused by transient disturbances or measurement noise, improves the accuracy and stability of voltage equalization control triggering, and reduces unnecessary energy regulation actions.

[0051] S102: Control the switch matrix to turn on, so that the isolated energy conversion unit corresponding to each target submodule is connected to the dual active bridge.

[0052] Preferably, in some embodiments of this application, controlling the switch matrix to turn on so that the isolated energy conversion unit corresponding to each target submodule is connected to the dual active bridge includes: controlling the switching devices in the switch matrix to turn on, so that the target submodule with a higher voltage value is connected to the positive terminal outlet, the target submodule with a lower voltage value is connected to the negative terminal outlet, and the other switching devices are kept off.

[0053] S103: With the isolated energy conversion unit and the dual active bridge in operation, calculate the absolute value of the deviation between the voltage amplitude of each target sub-module and the preset rated value, and adjust the phase shift angle of the dual active bridge according to the absolute value of the deviation to perform bidirectional energy transfer between each target sub-module and the buffer bus, so that the voltage between the target sub-modules is restored to the preset balance range.

[0054] Furthermore, in some embodiments of this application, adjusting the phase shift angle of the dual active bridge based on the absolute value of the deviation includes: The target submodule with the higher voltage is designated as the high-voltage phase. If the item with the larger absolute value of the deviation is the high-voltage phase, the phase shift angle of the dual active bridge is adjusted to control the energy transfer from the high-voltage phase to the buffer bus via the dual active bridge. The target submodule with the lower voltage is designated as the low-voltage phase. If the item with the larger absolute value of the deviation is the low-voltage phase, the phase shift angle of the dual active bridge is adjusted to control the energy transfer from the buffer bus to the low-voltage phase via the dual active bridge.

[0055] Preferably, in some embodiments of this application, when the absolute values ​​of the deviations of the two target sub-modules are both within the threshold range, the DAB phase shift angle is gradually reduced to zero, the DAB power transfer channel is turned off, and then the corresponding branches of the switch matrix are disconnected in sequence.

[0056] This application calculates the absolute value of the voltage deviation of the two target submodules relative to their rated values, and determines the high-voltage phase and low-voltage phase accordingly. This ensures that the energy transmission direction of the dual active bridge is consistent with the voltage deviation direction of the submodules, thereby enabling targeted energy transfer from the higher-voltage submodule to the lower-voltage submodule. This avoids incorrect energy regulation direction or reduced regulation efficiency, and improves the regulation effectiveness of the phase-to-phase voltage balancing process.

[0057] Furthermore, in some embodiments of this application, adjusting the phase shift angle of the dual active bridge includes: A reference control quantity is generated based on the voltage deviation between the two target sub-modules; The actual transmitted energy of the dual active bridge is collected, and a phase shift control quantity is generated based on the deviation between the reference control quantity and the actual transmitted energy. The phase shift angle of the dual active bridge is adjusted according to the phase shift angle control value.

[0058] Preferably, in some embodiments of this application, the DAB achieves operating state switching and energy transfer by adjusting the phase shift angle. This process is implemented through a dual closed-loop control structure, including: a voltage equalization control outer loop, used to calculate the target energy transfer amount based on the corresponding voltage value; and a current regulation control inner loop, used to regulate the power flow between the two ports of the DAB to achieve the energy exchange desired by the outer loop. Specifically, the voltage equalization control outer loop generates a reference current or reference power command based on the detected voltage deviation, and the current regulation control inner loop adjusts the current based on the deviation between the reference current or reference power command and the actual transmission current, and achieves power control by changing the phase shift angle between the two arms of the DAB. When the voltage deviation increases, the controller increases the phase shift angle to increase the energy transfer power; when the voltage deviation decreases, the phase shift angle is gradually decreased until zero, thereby achieving dynamic voltage equalization between phases.

[0059] This application generates a reference control quantity based on the voltage deviation between submodules, and generates a phase shift angle control quantity based on the deviation between the actual transmitted energy of the dual active bridge and the reference control quantity. This enables closed-loop regulation of the power transmission of the dual active bridge, thereby allowing the energy transmission process to dynamically track the voltage equalization demand, avoiding over-adjustment or under-adjustment problems that may occur under open-loop control, and improving the control accuracy and stability of the phase-to-phase voltage equalization process.

[0060] Furthermore, in some embodiments of this application, the phase-to-phase voltage equalization method further includes the following step S104: the buffer bus includes an energy-dissipating branch; when the supporting capacitor voltage exceeds the buffer supporting capacitor voltage threshold, the supporting capacitor voltage is restored to a preset supporting capacitor voltage range. Step S104 includes the following steps S1041 to S1043: S1041: Monitor the support capacitor voltage of the buffer bus in real time and compare the support capacitor voltage with a preset buffer support capacitor voltage threshold. S1042: When the voltage of the supporting capacitor exceeds the voltage threshold of the buffer supporting capacitor, the energy dissipation branch is controlled to be turned on, so that the energy stored in the buffer bus is discharged through the energy dissipation branch. S1043: When the voltage of the supporting capacitor recovers to the preset supporting capacitor voltage range, the energy-consuming branch is disconnected so that the buffer bus can operate within the preset supporting capacitor voltage range.

[0061] Preferably, in some embodiments of this application, step S104 can also be implemented through the following steps: Monitor the voltage of the supporting capacitor of the buffer bus and compare it with the set buffer supporting capacitor voltage threshold. If the supporting capacitor voltage does not exceed the buffer supporting capacitor voltage threshold, no operation is performed. If the supporting capacitor voltage exceeds the buffer supporting capacitor voltage threshold, control the energy dissipation branch switch in the buffer bus to be turned on, so that the excess energy stored in the supporting capacitor of the buffer bus is discharged through the energy dissipation resistor. After the supporting capacitor voltage of the buffer bus returns to the preset supporting capacitor voltage range, the energy dissipation branch switch is turned off.

[0062] Preferably, in some embodiments of this application, the overvoltage release process of the buffer bus support capacitor voltage in S104 and the phase-to-phase voltage equalization operation process corresponding to S101 to S103 are monitored and run alternately, and there is no obvious priority difference between the two; however, when a significant imbalance is detected in one of the two processes, it can be used as an interrupt signal to increase the priority, and the phase-to-phase voltage deviation or the overvoltage of the buffer bus support capacitor voltage can be released first.

[0063] Preferably, in some embodiments of this application, the significant phase-to-phase voltage imbalance corresponding to S101 to S103 can be determined by the voltage deviation amplitude, including: when the voltage deviation... satisfy When a significant imbalance in phase-to-phase voltage is determined, then... The significant imbalance coefficient (can be taken as 1.5 to 3). This is the preset threshold for significant phase-to-phase voltage imbalance.

[0064] Preferably, in some embodiments of this application, the significant overvoltage imbalance of the support capacitor voltage of the buffer bus corresponding to S104 can be determined by the support capacitor voltage of the buffer bus, including: when When it is determined that there is a significant overvoltage in the buffer bus voltage, among which To buffer the rated voltage threshold of the bus, This is the overpressure coefficient (which can be taken as 1.05 to 1.2).

[0065] This application sets up an energy-dissipating branch on the buffer bus and monitors the voltage of the supporting capacitor in real time. When the voltage of the buffer supporting capacitor exceeds a preset threshold, the stored energy is released through the energy-dissipating branch. This prevents the supporting capacitor voltage from continuously rising when multiple submodules transmit energy to the buffer bus at the same time, prevents overvoltage of the buffer bus and the electrical stress it causes to the dual active bridge and submodules, and improves the operational safety of the voltage equalization auxiliary circuit.

[0066] Furthermore, in some embodiments of this application, the phase-to-phase voltage equalization method further includes the following step S105: when there is an abnormal submodule experiencing a transient operating condition anomaly, providing short-term voltage support to the abnormal submodule; step S105 includes the following steps S1051 to S1053: S1051: Identify abnormal sub-modules that have experienced transient operating abnormalities from all the sub-modules in real time. When the abnormal sub-module is identified, control the switch matrix to turn on, so that the isolated energy conversion unit corresponding to the abnormal sub-module is connected to the dual active bridge. S1052: Take the other sub-modules besides the abnormal sub-module as the second sub-module, control the switch matrix to turn on, and connect the isolated energy conversion unit corresponding to the second sub-module with the highest voltage amplitude to the dual active bridge to construct an energy transmission loop; S1053: By adjusting the phase shift angle of the dual active bridge, the energy stored in the buffer bus is transmitted to the abnormal submodule through the energy transmission circuit to achieve short-term voltage support.

[0067] Preferably, in some embodiments of this application, using Figure 2 Taking the illustrated topology as an example, assume that a transient abnormality occurs in the X-phase submodule, while the other two Y-phase and Z-phase submodules do not. At this time, the switch matrix sends a gating signal, causing the voltage drop phase X (i.e., the X-phase submodule) to connect to the negative outlet, while the other switching devices remain open. Further compare the voltage amplitudes of the corresponding Y-phase and Z-phase submodules. If the voltage amplitude of the Y-phase submodule is greater than that of the Z-phase submodule, a gating signal is sent to the switch matrix, causing the Y-phase submodule to connect to the positive outlet. If the voltage amplitude of the Y-phase submodule is less than that of the Z-phase submodule, a gating signal is sent to the switch matrix, causing the Z-phase submodule to connect to the positive outlet. Adjust the DAB phase shift angle to control the energy to be quickly transferred from the support capacitor voltage of the buffer bus to the voltage drop phase X on the high-voltage side via the low-voltage side of the DAB.

[0068] Preferably, in some embodiments of this application, the method for adjusting the phase shift angle of the dual active bridge is the same as the method in step S103, and will not be repeated here.

[0069] This application further identifies sub-modules experiencing transient operating abnormalities based on phase-to-phase voltage equalization control, and controls the switching matrix to construct an energy transmission loop composed of other sub-modules via dual active bridges and a buffer bus. This allows the energy stored in the buffer bus to provide short-term voltage support to the abnormal sub-modules, thereby suppressing further voltage drops when the sub-modules experience voltage drops or power surges, and improving the converter's shock resistance and operational continuity under transient disturbance conditions.

[0070] Furthermore, in some embodiments of this application, the step of identifying the abnormal submodule that has experienced transient operating condition anomalies from all the said submodules in real time includes: Calculate the power change rate corresponding to each of the sub-modules; If the voltage amplitude of a submodule is lower than a preset voltage drop threshold, or the power change rate exceeds a preset power mutation threshold, then the submodule is determined to be an abnormal submodule experiencing a transient operating condition.

[0071] Preferably, in some embodiments of this application, the transient operating condition anomaly includes: single-phase voltage transient drop or power surge; wherein, the identification process of single-phase voltage transient drop includes: determination by the change in the amplitude of AC side phase voltage: for example, assuming the effective values ​​of the three-phase voltages of the AC system are respectively , , Rated voltage is When any phase satisfies When this occurs, it is determined that a transient voltage drop has occurred in the submodule of that phase. , A preset voltage drop threshold (e.g., 0.1–0.2) is set. The power surge identification process includes: assuming the instantaneous power of a certain phase submodule is... When satisfied When a power surge occurs in the system, it is determined that a power surge has occurred. The preset power surge threshold is (e.g., 0.1~0.5 pu / ms).

[0072] This application determines transient anomalies by integrating the voltage amplitude and power change rate of the integrated submodule. This makes the identification of abnormal submodules not only dependent on voltage amplitude changes, but also able to reflect dynamic anomalies caused by power surges. This improves the sensitivity and reliability of transient anomaly detection, provides accurate target submodules for subsequent energy support control, and avoids the impact of misidentification or omission on voltage equalization and protection control.

[0073] In summary, the phase-to-phase voltage equalization method for a converter provided in this application has the following advantages compared to existing technologies: This application connects an isolated energy conversion unit to the DC side of each submodule and constructs an independent energy transmission loop via a switching matrix, dual active bridges, and a buffer bus. This creates a controllable indirect energy exchange path between the phase submodules, which were originally structurally independent and lacked direct energy interaction channels. This achieves bidirectional energy regulation between submodules without altering the main power loop topology. Furthermore, by calculating the submodule voltage deviation in real time and selecting the two submodules with the largest deviations for priority equalization, and by adjusting the phase shift angle of the dual active bridges to precisely control the energy transmission direction and amplitude, the voltage of the target submodule gradually converges to a preset equalization range. Compared to traditional voltage equalization methods that rely on main loop power redistribution, this application significantly improves the voltage equalization capability of the novel series DC-DC link converter under conditions of unbalanced phase-to-phase loads and inconsistent parameters, thereby enhancing system stability and safety.

[0074] like Figure 5 As shown, based on the above-described method embodiments, this application provides an embodiment of a phase-to-phase voltage equalization device for a converter. The converter includes: multiple phase sub-modules, each sub-module being connected in series on the DC side, each sub-module being connected to an isolated energy conversion unit, each isolated energy conversion unit being connected to a switch matrix, the switch matrix being connected to one end of a dual active bridge, and the other end of the dual active bridge being connected to a buffer bus; the phase-to-phase voltage equalization device includes: a screening module 201, a first control module 202, and a second control module 203; The filtering module 201 is used to collect the voltage amplitude of each sub-module in real time, calculate the voltage deviation between any two sub-modules based on the voltage amplitude, and select the two target sub-modules with the largest voltage deviation when the voltage deviation meets the preset conditions. The first control module 202 is used to control the switch matrix to turn on, so that the isolated energy conversion unit corresponding to each target submodule is connected to the dual active bridge; The second control module 203 is used to calculate the absolute value of the deviation between the voltage amplitude of each target sub-module and the preset rated value when the isolated energy conversion unit and the dual active bridge are turned on, and adjust the phase shift angle of the dual active bridge according to the absolute value of the deviation, so as to perform bidirectional energy transfer between each target sub-module and the buffer bus, so that the voltage between the target sub-modules is restored to the preset balance range.

[0075] Further, in some embodiments of this application, the filtering module 201 includes: a first judgment unit, a second judgment unit, and a filtering unit; the filtering module 201 is used to select the two target sub-modules with the largest voltage deviation when the voltage deviation meets a preset condition, including: The first judgment unit is used to obtain the duration of the first voltage deviation being greater than the preset phase-to-phase voltage imbalance threshold when there is a first voltage deviation greater than the preset phase-to-phase voltage imbalance threshold, and to calculate the voltage change rate of the two first sub-modules corresponding to the first voltage deviation. The second judgment unit is used to determine that the first voltage deviation satisfies the preset condition when the duration corresponding to the first voltage deviation is greater than a preset time threshold and both of the corresponding voltage change rates are less than a preset voltage change rate threshold. The filtering unit is used to select the two first sub-modules corresponding to the largest first voltage deviation as the two target sub-modules.

[0076] Further, in some embodiments of this application, the second control module 203 includes: a first execution unit and a second execution unit; the second control module 203 is used to adjust the phase shift angle of the dual active bridge according to the absolute value of the deviation, including: The first execution unit is used to take the target sub-module with a larger voltage as the high voltage phase. If the item with the larger absolute value of the deviation is the high voltage phase, the phase shift angle of the dual active bridge is adjusted to control the energy to be transferred from the high voltage phase to the buffer bus via the dual active bridge. The second execution unit is used to select the target sub-module with the smaller voltage as the low-voltage phase. If the item with the larger absolute value of the deviation is the low-voltage phase, the phase shift angle of the dual active bridge is adjusted to control the energy to be transferred from the buffer bus to the low-voltage phase via the dual active bridge.

[0077] Further, in some embodiments of this application, the second control module 203 includes: a first calculation unit, a second calculation unit, and an adjustment unit; the second control module 203 is used to adjust the phase shift angle of the dual active bridge, including: The first calculation unit is used to generate a reference control quantity based on the voltage deviation between the two target sub-modules; The second calculation unit is used to collect the actual transmission energy of the dual active bridge and generate a phase shift angle control quantity based on the deviation between the reference control quantity and the actual transmission energy. The adjustment unit is used to adjust the phase shift angle of the dual active bridge according to the phase shift angle control amount.

[0078] Furthermore, in some embodiments of this application, the buffer bus includes: an energy-consuming branch; the phase-to-phase voltage equalization device further includes an adjustment module, the adjustment module including: a monitoring unit, a first control unit, and a second control unit; The first monitoring unit is used to monitor the support capacitor voltage of the buffer bus in real time and compare the support capacitor voltage with a preset buffer support capacitor voltage threshold. The first control unit is configured to control the energy dissipation branch to be turned on when the voltage of the supporting capacitor exceeds the voltage threshold of the buffer supporting capacitor, so that the energy stored in the buffer bus is discharged through the energy dissipation branch. The second control unit is used to control the energy-consuming branch to disconnect when the supporting capacitor voltage recovers to a preset supporting capacitor voltage range, so that the buffer bus can operate within the preset supporting capacitor voltage range.

[0079] Furthermore, in some embodiments of this application, the phase-to-phase voltage equalization device further includes a second adjustment module, which includes a second monitoring unit, a third control unit, and a fourth control unit; The second monitoring unit is used to identify abnormal sub-modules that have experienced transient operating abnormalities from all the sub-modules in real time. When the abnormal sub-module is identified, the switch matrix is ​​controlled to turn on, so that the isolated energy conversion unit corresponding to the abnormal sub-module is connected to the dual active bridge. The third control unit is used to designate the other sub-modules besides the abnormal sub-module as second sub-modules, control the switch matrix to turn on, and connect the isolated energy conversion unit corresponding to the second sub-module with the highest voltage amplitude to the dual active bridge to construct an energy transmission loop; The fourth control unit is used to transmit the energy stored in the buffer bus to the abnormal submodule through the energy transmission circuit by adjusting the phase shift angle of the dual active bridge, so as to achieve short-term voltage support.

[0080] Furthermore, in some embodiments of this application, the second monitoring unit is used to identify, in real time, the abnormal sub-modules that have experienced transient operating condition anomalies from all the said sub-modules, including: Calculate the power change rate corresponding to each of the sub-modules; If the voltage amplitude of a submodule is lower than a preset voltage drop threshold, or the power change rate exceeds a preset power mutation threshold, then the submodule is determined to be an abnormal submodule experiencing a transient operating condition.

[0081] It is understood that the above-described device embodiments correspond to the method embodiments of this application, and can implement the phase-to-phase voltage equalization method for converters provided by any of the above-described method embodiments of this application.

[0082] In summary, the phase-to-phase voltage equalization device for a converter provided in this application has the following advantages compared to the prior art: This application connects an isolated energy conversion unit to the DC side of each submodule and constructs an independent energy transmission loop via a switch matrix, dual active bridges, and a buffer bus. This creates a controllable indirect energy exchange path between the phase submodules, which were originally structurally independent and lacked direct energy interaction channels. This achieves bidirectional energy regulation between submodules without altering the main power circuit topology. Furthermore, by calculating the submodule voltage deviation in real time and selecting the two submodules with the largest deviations for priority equalization, and by adjusting the phase shift angle of the dual active bridges to precisely control the energy transmission direction and amplitude, the voltage of the target submodule gradually converges to a preset equalization range. Compared to traditional voltage equalization methods that rely on main circuit power redistribution, this application significantly improves the voltage equalization capability of the novel series DC-DC link converter under conditions of unbalanced phase-to-phase loads and inconsistent parameters, thereby enhancing system stability and safety.

[0083] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided in this application, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0084] Based on the embodiments of the phase-to-phase voltage equalization method for the converter described above, another embodiment of this application provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the phase-to-phase voltage equalization method for the converter of any embodiment of this application.

[0085] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete this application. The one or more module units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0086] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0087] The processor can 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. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0088] Based on the above-described method embodiments, another embodiment of this application provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform the phase-to-phase voltage equalization method of the converter described in any of the above-described method embodiments of this application.

[0089] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

Claims

1. A method for phase-to-phase voltage equalization in a converter, characterized in that, The converter includes: multiple phase sub-modules, each sub-module being connected in series on the DC side, each sub-module being connected to an isolated energy conversion unit, each isolated energy conversion unit being connected to a switching matrix, the switching matrix being connected to one end of a dual active bridge, and the other end of the dual active bridge being connected to a buffer bus; the phase-to-phase voltage equalization method includes: The voltage amplitude of each sub-module is collected in real time. The voltage deviation between any two sub-modules is calculated based on the voltage amplitude. When the voltage deviation meets a preset condition, the two target sub-modules with the largest voltage deviation are selected. The switch matrix is ​​turned on to enable the isolated energy conversion unit corresponding to each target submodule to conduct with the dual active bridge. With the isolated energy conversion unit and the dual active bridge in operation, the absolute value of the deviation between the voltage amplitude of each target submodule and the preset rated value is calculated, and the phase shift angle of the dual active bridge is adjusted according to the absolute value of the deviation to perform bidirectional energy transfer between each target submodule and the buffer bus, so that the voltage between the target submodules is restored to the preset equalization range.

2. The phase-to-phase voltage equalization method for a converter as described in claim 1, characterized in that, When a voltage deviation meets a preset condition, the two target sub-modules with the largest voltage deviations are selected, including: When a first voltage deviation is greater than a preset phase-to-phase voltage imbalance threshold, the duration of the first voltage deviation being greater than the phase-to-phase voltage imbalance threshold is obtained, and the voltage change rate of the two first sub-modules corresponding to the first voltage deviation is calculated. When the duration corresponding to the first voltage deviation is greater than a preset time threshold and both corresponding voltage change rates are less than a preset voltage change rate threshold, it is determined that the first voltage deviation meets the preset condition. The two first sub-modules corresponding to the largest first voltage deviation are designated as the two target sub-modules.

3. The phase-to-phase voltage equalization method for a converter as described in claim 1, characterized in that, The step of adjusting the phase shift angle of the dual active bridge based on the absolute value of the deviation includes: The target submodule with the higher voltage is designated as the high-voltage phase. If the item with the larger absolute value of the deviation is the high-voltage phase, the phase shift angle of the dual active bridge is adjusted to control the energy transfer from the high-voltage phase to the buffer bus via the dual active bridge. The target submodule with the lower voltage is designated as the low-voltage phase. If the item with the larger absolute value of the deviation is the low-voltage phase, the phase shift angle of the dual active bridge is adjusted to control the energy transfer from the buffer bus to the low-voltage phase via the dual active bridge.

4. The phase-to-phase voltage equalization method for a converter as described in claim 3, characterized in that, The adjustment of the phase shift angle of the dual active bridge includes: A reference control quantity is generated based on the voltage deviation between the two target sub-modules; The actual transmitted energy of the dual active bridge is collected, and a phase shift control quantity is generated based on the deviation between the reference control quantity and the actual transmitted energy. The phase shift angle of the dual active bridge is adjusted according to the phase shift angle control value.

5. A method for phase-to-phase voltage equalization of a converter as described in any one of claims 1 to 4, characterized in that, The buffer bus includes: an energy-dissipating branch; the phase-to-phase voltage equalization method further includes: The voltage of the supporting capacitor of the buffer bus is monitored in real time, and the voltage of the supporting capacitor is compared with a preset buffer supporting capacitor voltage threshold. When the voltage of the supporting capacitor exceeds the voltage threshold of the buffer supporting capacitor, the energy dissipation branch is controlled to be turned on, so that the energy stored in the buffer bus can be discharged through the energy dissipation branch. When the voltage of the supporting capacitor recovers to the preset supporting capacitor voltage range, the energy-consuming branch is controlled to disconnect, so that the buffer bus can operate within the preset supporting capacitor voltage range.

6. A method for phase-to-phase voltage equalization of a converter as described in any one of claims 1 to 4, characterized in that, Also includes: The abnormal submodule that has experienced transient operating condition abnormality is identified in real time from all the submodules. When the abnormal submodule is identified, the switch matrix is ​​controlled to turn on, so that the isolated energy conversion unit corresponding to the abnormal submodule is connected to the dual active bridge. The other sub-modules besides the abnormal sub-module are used as the second sub-modules. The switch matrix is ​​turned on, and the isolated energy conversion unit corresponding to the second sub-module with the highest voltage amplitude is connected to the dual active bridge to construct an energy transmission loop. By adjusting the phase shift angle of the dual active bridge, the energy stored in the buffer bus is transmitted to the abnormal submodule through the energy transmission circuit to achieve short-term voltage support.

7. The phase-to-phase voltage equalization method for a converter as described in claim 6, characterized in that, The abnormal submodule that identifies transient operating condition anomalies from all the submodules in real time includes: Calculate the power change rate corresponding to each of the sub-modules; If the voltage amplitude of a submodule is lower than a preset voltage drop threshold, or the power change rate exceeds a preset power mutation threshold, then the submodule is determined to be an abnormal submodule experiencing a transient operating condition.

8. A phase-to-phase voltage equalization device for a converter, characterized in that, The converter includes: multiple phase sub-modules, each sub-module being connected in series on the DC side, each sub-module being connected to an isolated energy conversion unit, each isolated energy conversion unit being connected to a switch matrix, the switch matrix being connected to one end of a dual active bridge, and the other end of the dual active bridge being connected to a buffer bus; the phase-to-phase voltage equalization device includes: a screening module, a first control module, and a second control module. The filtering module is used to collect the voltage amplitude of each sub-module in real time, calculate the voltage deviation between any two sub-modules based on the voltage amplitude, and select the two target sub-modules with the largest voltage deviation when the voltage deviation meets the preset conditions. The first control module is used to control the switch matrix to turn on, so that the isolated energy conversion unit corresponding to each target submodule is connected to the dual active bridge; The second control module is used to calculate the absolute value of the deviation between the voltage amplitude of each target submodule and the preset rated value when the isolated energy conversion unit and the dual active bridge are turned on, and to adjust the phase shift angle of the dual active bridge according to the absolute value of the deviation, so as to perform bidirectional energy transfer between each target submodule and the buffer bus, so that the voltage between the target submodules is restored to the preset balance range.

9. A converter, characterized in that, include: Multiple phase sub-modules, an isolated energy conversion unit corresponding to each sub-module, a switching matrix, a dual active bridge, and a buffer bus; Each of the sub-modules is connected in series on the DC side, and the DC side outlet of each of the sub-modules is connected to an isolated energy conversion unit. The negative output terminals of each isolated energy conversion unit are interconnected, and the positive output terminals of each isolated energy conversion unit are respectively connected to the switch matrix as inputs. The output terminal of the switch matrix is ​​connected to the high-voltage side of the dual active bridge, and the low-voltage side of the dual active bridge is connected to the buffer bus.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed, it controls the device in which the computer-readable storage medium is located to perform an interphase voltage equalization method for a converter as described in any one of claims 1 to 7.

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