Single-stage three-phase bidirectional converter and vehicle-mounted charging device

Abstract

This application provides a single-stage three-phase bidirectional converter and an on-board charging device. The single-stage three-phase bidirectional converter includes a single-stage AC-DC conversion module, which has a first AC input port, a second AC input port, a third AC input port, and a fourth AC input port, as well as a first DC port and a second DC port. According to the technical solution of this application, a single-stage isolated three-phase bidirectional converter can be realized with simplified circuitry.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a single-stage three-phase bidirectional converter. Background Technology

[0002] Currently, resource scarcity and environmental pollution are two major problems hindering human development. To solve the energy problem, it is essential to research and develop new energy sources. Three-phase AC / DC bidirectional converters have become a hot research topic. A single-stage three-phase bidirectional converter is a converter that can convert three-phase AC power to DC power or vice versa. It typically consists of multiple three-phase bridge inverters, each coupled to the others via capacitors or inductors. The advantages of a single-stage three-phase bidirectional converter are its simple structure and low cost, but its disadvantages include low efficiency, low power factor, and the need for large capacitors or inductors for coupling. Compared to back-to-back bidirectional converters, the topology of a three-phase AC / DC bidirectional converter is only half that of a back-to-back bidirectional converter, but it can achieve the same function: bidirectional energy flow. Due to its ability to achieve bidirectional energy transfer, the three-phase AC / DC bidirectional converter has wide applications in motor control, automotive electronics, and new energy power generation.

[0003] Traditional full-bridge circuits operate as three-phase Boost PWM rectifiers in rectification mode, where the bus voltage can only increase and not decrease. Interaction with energy storage systems typically requires two-stage circuitry. In contrast, matrix bidirectional converters operate as three-phase Buck PWM rectifiers in rectification mode. Although matrix converters can achieve single-stage charging, compared to traditional full-bridge topologies, they double the number of switches on the main bridge arm, making control relatively complex.

[0004] Therefore, a technical solution is needed that can simplify the circuit while ensuring power density. Summary of the Invention

[0005] This application aims to provide a single-stage three-phase bidirectional converter. The circuit design of this invention simplifies the circuit and achieves a single-stage isolated three-phase bidirectional converter while ensuring power density.

[0006] According to one aspect of this application, a single-stage three-phase bidirectional converter is provided, comprising:

[0007] A single-stage AC-DC converter module, wherein the single-stage AC-DC converter module has

[0008] Each component corresponds to an independent entity. That is, these functional entities can be implemented in software, or they may have a first AC input port, a second AC input port, a third AC input port, a first DC port, and a second DC port. The single-stage AC-DC conversion module includes:

[0009] A first DC-DC converter, the first DC-DC converter having a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port;

[0010] The second DC-DC converter has a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port.

[0011] A third DC-DC converter, the third DC-DC converter having a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port;

[0012] Wherein, the first polarity input port of the first DC-DC converter is electrically connected to the first AC input port, the first polarity input port of the second DC-DC converter is electrically connected to the second AC input port, and the first polarity input port of the third DC-DC converter is electrically connected to the third AC input port; the second polarity input port of the first DC-DC converter is electrically connected to the second polarity input port of the second DC-DC converter and the second polarity input port of the third DC-DC converter.

[0013] The first polarity output port of the first DC-DC converter, the first polarity output port of the second DC-DC converter, and the first polarity output port of the third DC-DC converter are electrically connected to the first DC port, and the second polarity output port of the first DC-DC converter, the second polarity output port of the second DC-DC converter, and the second polarity output port of the third DC-DC converter are electrically connected to the second DC port.

[0014] According to some embodiments, the single-stage AC-DC converter module further includes a fourth AC input port, and the single-stage AC-DC converter module also includes:

[0015] A fourth DC-DC converter, the fourth DC-DC converter having a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port;

[0016] The first polarity input port of the fourth DC-DC converter is electrically connected to the fourth AC input port, and the second polarity input port of the fourth DC-DC converter is electrically connected to the second polarity input port of the first DC-DC converter, the second polarity input port of the second DC-DC converter, and the second polarity input port of the third DC-DC converter.

[0017] The first polarity output port of the fourth DC-DC converter is electrically connected to the first DC port, and the second polarity output port of the fourth DC-DC converter is electrically connected to the second DC port.

[0018] According to some embodiments, the single-stage three-phase bidirectional converter further includes:

[0019] An AC-side filter module is electrically connected between the AC power supply and the single-stage AC-DC converter module, wherein the AC-side filter module shares the half-bridge capacitor of the single-stage AC-DC converter module.

[0020] According to some embodiments, the single-stage three-phase bidirectional converter further includes:

[0021] A DC-side filter is electrically connected between the first DC port and the second DC port.

[0022] According to some embodiments, the first DC-DC converter includes a first isolation transformer;

[0023] The second DC-DC converter includes a second isolation transformer;

[0024] The third DC-DC converter includes a third isolation transformer;

[0025] The fourth DC-DC converter includes a fourth isolation transformer;

[0026] The first isolation transformer, the second isolation transformer, the third isolation transformer and the fourth isolation transformer share a common secondary side.

[0027] According to some embodiments, the first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer are high-frequency isolation transformers.

[0028] According to some embodiments, when θ = 0, the first DC-DC converter operates in DC-DC mode, the second DC-DC converter operates in DC-DC mode, the third DC-DC converter is in short-circuit mode, and the fourth DC-DC converter operates in DC-DC mode;

[0029] When θ = 120°, the first DC-DC converter is in short-circuit mode, the second DC-DC converter operates in DC-DC mode, the third DC-DC converter operates in DC-DC mode, and the fourth DC-DC converter operates in DC-DC mode.

[0030] When θ = 240°, the first DC-DC converter operates in DC-DC mode, the second DC-DC converter is in short-circuit mode, the third DC-DC converter operates in DC-DC mode, and the fourth DC-DC converter operates in DC-DC mode.

[0031] According to some embodiments, during the period from 0° to 120° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the third DC-DC converter are shorted.

[0032] During the period from 120° to 240° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the first DC-DC converter are short-circuited.

[0033] During the period from 240° to 360° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the second DC-DC converter are shorted.

[0034] According to some embodiments, the first polarity input port is a positive input port or a negative input port, and the second polarity input port is correspondingly a negative input port or a positive input port.

[0035] According to some embodiments, the first DC-DC converter includes a first switching element, a second switching element, a half-bridge circuit consisting of a first capacitor and a second capacitor, and a first isolation transformer, wherein:

[0036] The first switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the first switching element to be turned on or off;

[0037] The second switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the second switching element to be turned on or off;

[0038] The second switching element is connected in series with the first switching element between the first polarity input port and the second polarity input port of the first DC-DC converter, and the first capacitor and the second capacitor are connected in series between the first polarity input port and the second polarity input port of the first DC-DC converter.

[0039] The primary winding of the first isolation transformer is connected between the series node between the second switching element and the first switching element and between the series node between the first capacitor and the second capacitor;

[0040] The second DC-DC converter includes: a third switching element, a fourth switching element, a half-bridge circuit consisting of a third capacitor and a fourth capacitor, and a second isolation transformer, wherein:

[0041] The third switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the third switching element to be turned on or off.

[0042] The fourth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the fourth switching element to be turned on or off.

[0043] The third switching element and the fourth switching element are connected in series between the first polarity input port and the second polarity input port of the second DC-DC converter, and the third capacitor and the fourth capacitor are connected in series between the first polarity input port and the second polarity input port of the second DC-DC converter.

[0044] The primary winding of the second isolation transformer is connected between the series node between the third and fourth switching elements and the series node between the third and fourth capacitors.

[0045] The third DC-DC converter includes: a fifth switching element, a sixth switching element, a half-bridge circuit composed of a fifth capacitor and a sixth capacitor, and a third isolation transformer, wherein:

[0046] The fifth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the fifth switching element to be turned on or off.

[0047] The sixth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the sixth switching element to be turned on or off.

[0048] The fifth switching element and the sixth switching element are connected in series between the first polarity input port and the second polarity input port of the third DC-DC converter, and the fifth capacitor and the sixth capacitor are connected in series between the first polarity input port and the second polarity input port of the third DC-DC converter.

[0049] The primary winding of the third isolation transformer is connected between the series node between the fifth and sixth switching elements and between the series node between the fifth and sixth capacitors.

[0050] The fourth DC-DC converter includes: a half-bridge circuit consisting of a seventh switching element, an eighth switching element, a seventh capacitor, and an eighth capacitor, and a fourth isolation transformer, wherein:

[0051] The seventh switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the seventh switching element to be turned on or off.

[0052] The eighth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the eighth switching element to be turned on or off.

[0053] The seventh switching element and the eighth switching element are connected in series between the first polarity input port and the second polarity input port of the fourth DC-DC converter, and the seventh capacitor and the eighth capacitor are connected in series between the first polarity input port and the second polarity input port of the fourth DC-DC converter.

[0054] The primary winding of the fourth isolation transformer is connected between the series node between the seventh and eighth switching elements and between the series node between the seventh and eighth capacitors.

[0055] The first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer share a secondary winding.

[0056] According to another aspect of this application, an on-board charging device is provided, comprising:

[0057] The on-board charging device uses the aforementioned single-stage three-phase bidirectional converter. According to embodiments of this application, by applying a single-stage circuit structure and sharing a half-bridge capacitor between the AC filter and the single-stage AC-DC conversion module, the circuit structure is simplified and power loss is reduced. The application of a high-frequency isolation transformer not only improves circuit safety but also enhances power quality while reducing noise. Furthermore, two connection methods are available to adapt the circuit to different application scenarios.

[0058] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0060] Figure 1 A schematic diagram of a single-stage isolated three-phase bidirectional converter according to an example embodiment is shown.

[0061] Figure 2A and Figure 2B The diagram shows a primary side common positive connection and a primary side common negative connection of a single-stage isolated three-phase bidirectional converter according to an example embodiment.

[0062] Figure 3 A schematic diagram of the primary-side common-negative connection circuit of a single-stage isolated three-phase bidirectional converter according to an example embodiment is shown.

[0063] Figure 4 The diagram shows the key voltage waveform of the primary side common negative connection of a single-stage isolated three-phase bidirectional converter according to an example embodiment.

[0064] Figure 5 The diagram shows the PFC current injection waveform of a single-stage isolated three-phase bidirectional converter according to an example embodiment.

[0065] Figure 6 An example circuit diagram of a primary-side common-negative connection of a single-stage isolated three-phase bidirectional converter according to an example embodiment is shown.

[0066] Figure 7 An example circuit diagram of a primary-side common-negative connection method for a single-stage isolated three-phase bidirectional converter according to an example embodiment is shown. Detailed Implementation

[0067] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0068] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0069] The block diagrams shown in the attached figures are merely functional entities and do not necessarily have to be physically implemented in one or more hardware modules or integrated circuits, or in different networks and / or processing devices and / or microcontrollers.

[0070] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0071] It should be understood that although the terms first, second, third, etc., may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this application. As used herein, the term "and / or" includes all combinations of any one and more of the associated listed items.

[0072] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily essential for implementing this application, and therefore cannot be used to limit the scope of protection of this application.

[0073] A single-stage three-phase bidirectional converter is a converter that can convert three-phase AC power to DC power or vice versa.

[0074] It typically consists of multiple three-phase bridge inverters, each coupled to the others via capacitors or inductors. The advantages of a single-stage three-phase bidirectional converter are its simple structure and low cost, but its disadvantages include low efficiency, low power factor, and the need for large capacitors or inductors for coupling. Compared to back-to-back bidirectional converters, the three-phase AC / DC bidirectional converter topology is only half the size, but it achieves the same function: bidirectional energy flow. Due to its ability to achieve bidirectional energy transfer, the three-phase AC / DC bidirectional converter has wide applications in motor control, automotive electronics, and new energy power generation.

[0075] Traditional full-bridge circuits operate as three-phase Boost PWM rectifiers in rectification mode, where the bus voltage can only increase and not decrease. Interaction with energy storage systems typically requires two-stage circuitry. In contrast, matrix bidirectional converters operate as three-phase Buck PWM rectifiers in rectification mode. Although matrix converters can achieve single-stage charging, compared to traditional full-bridge topologies, they double the number of switches on the main bridge arm, making control relatively complex.

[0076] To address this, this application proposes a single-stage three-phase bidirectional converter. This design utilizes a single-stage circuit structure, and the AC filter and the single-stage AC-DC conversion module share a half-bridge capacitor, simplifying the circuit structure and reducing power loss. The application of a high-frequency isolation transformer not only improves circuit safety but also enhances power quality while reducing noise. Furthermore, two connection methods are available to adapt the circuit to different application scenarios.

[0077] Before describing the embodiments of this application, some terms or concepts involved in the embodiments of this application will be explained.

[0078] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of this application.

[0079] Figure 1 A schematic diagram of a single-stage isolated three-phase bidirectional converter according to an example embodiment is shown.

[0080] In describing the bidirectional converter of this application, although terms such as input port and output port are used, it is easy to understand that when the bidirectional converter operates in the other direction, the input port becomes the output port, and the output port becomes the input port. Therefore, in this application, for the sake of brevity, the input port can also refer to the output port, and the output port will refer to the input port.

[0081] See Figure 1 The figure shows a single-stage three-phase bidirectional converter, including:

[0082] A single-stage AC-DC converter module 1002 has a first AC input port A, a second AC input port B, a third AC input port C, and a fourth AC input port N, as well as a first DC port X and a second DC port Y.

[0083] According to some embodiments, the single-stage AC-DC converter 1002 is used to convert AC power input into DC output. The single-stage AC-DC converter 1002 has four AC input ports: a first AC input port A, a second AC input port B, a third AC input port C, and a fourth AC input port N. The single-stage AC-DC converter 1002 also has two DC output terminals: a first DC port X and a second DC port Y.

[0084] According to some embodiments, the first AC input port A, the second AC input port B, the third AC input port C, and the fourth AC input port N constitute an AC input terminal for receiving three-phase AC voltage signals. The first DC port X and the second DC port Y constitute a DC port for outputting DC voltage signals.

[0085] See Figure 1 The single-stage AC-DC converter module 1002 includes:

[0086] A first DC-DC converter 100201 has a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port.

[0087] The second DC-DC converter 100202 has a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port.

[0088] The third DC-DC converter 100203 has a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port.

[0089] According to some embodiments, the single-stage AC-DC conversion module 1002 includes four DC-DC converters: a first DC-DC converter 100201, a second DC-DC converter 100202, and a third DC-DC converter 100203. Each DC-DC converter includes a first polarity input port and a second polarity input port for receiving input AC voltage signals. Each DC-DC converter also includes a first polarity output port and a second polarity output port for outputting DC voltage signals.

[0090] See Figure 1 The first polarity input port of the first DC-DC converter 100201 is electrically connected to the first AC input port A, the first polarity input port of the second DC-DC converter 100202 is electrically connected to the second AC input port B, and the first polarity input port of the third DC-DC converter 100203 is electrically connected to the third AC input port C. The second polarity input port of the first DC-DC converter 100201 is electrically connected to the second polarity input port of the second DC-DC converter 100202 and the second polarity input port of the third DC-DC converter 100203.

[0091] According to some embodiments, the first polarity input ports of the three DC-DC converters are respectively connected to the three-phase AC voltage input ports ABC. For example... Figure 1 As shown, the first polarity input port of the first DC-DC converter 100201 is electrically connected to the first AC input port A, the first polarity input port of the second DC-DC converter 100202 is electrically connected to the second AC input port B, and the first polarity input port of the third DC-DC converter 100203 is electrically connected to the third AC input port C.

[0092] According to some embodiments, the second polarity input ports of the three DC-DC converters are electrically connected to point O. See also Figure 1 The second polarity input port of the first DC-DC converter 100201 is electrically connected to the second polarity input port of the second DC-DC converter 100202 and the second polarity input port of the third DC-DC converter 100203, and is marked as point O. Thus, taking a common negative connection as an example, point O is clamped to the lowest potential among the three inputs.

[0093] like Figure 1 As shown, the first polarity output port of the first DC-DC converter 100201, the first polarity output port of the second DC-DC converter 100202, and the first polarity output port of the third DC-DC converter 100203 are electrically connected to the first DC port X, and the second polarity output port of the first DC-DC converter 100201, the second polarity output port of the second DC-DC converter 100202, and the second polarity output port of the third DC-DC converter 100203 are electrically connected to the second DC port Y.

[0094] According to some embodiments, the first polarity output ports of the three DC-DC converters are respectively connected to the first DC port X, that is, the first polarity output ports of the first DC-DC converter 100201, the second DC-DC converter 100202, and the third DC-DC converter 100203 are electrically connected to the first DC port X. The second polarity output ports of the three DC-DC converters are connected to the second DC port Y, that is, the second polarity output ports of the first DC-DC converter 100201, the second DC-DC converter 100202, and the third DC-DC converter 100203 are electrically connected to the second DC port Y.

[0095] According to some embodiments, a DC filter and an output voltage source or load can be connected between the first DC port X and the second DC port Y.

[0096] like Figure 1 As shown, the single-stage three-phase bidirectional converter further includes:

[0097] The fourth DC-DC converter 100204 has a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port.

[0098] The second polarity input port of the fourth DC-DC converter 100204 is electrically connected to the second polarity input port of the first DC-DC converter 100201, the second polarity input port of the second DC-DC converter 100202, and the second polarity input port of the third DC-DC converter 100203.

[0099] The first polarity output port of the fourth DC-DC converter 100204 is electrically connected to the first DC port X, and the second polarity output port of the fourth DC-DC converter 100204 is electrically connected to the second DC port Y.

[0100] According to some embodiments, the first polarity input port of the fourth DC-DC converter 100204 is electrically connected to the fourth AC input port N. For example... Figure 1 As shown, the first polarity input port of the first DC-DC converter 100201 is electrically connected to the first AC input port A, the first polarity input port of the second DC-DC converter 100202 is electrically connected to the second AC input port B, the first polarity input port of the third DC-DC converter 100203 is electrically connected to the third AC input port C, and the first polarity input port of the fourth DC-DC converter 100204 is electrically connected to the fourth AC input port N.

[0101] According to some embodiments, the second polarity input port of the fourth DC-DC converter 100204 is electrically connected to point O. See also Figure 1 The second polarity input port of the fourth DC-DC converter 100204 is electrically connected to the second polarity input ports of the first DC-DC converter 100201, the second polarity input ports of the second DC-DC converter 100202, and the third DC-DC converter 100203, and is marked as point O. Thus, taking a common negative connection as an example, point O is clamped to the lowest potential among the four inputs.

[0102] According to some embodiments, the first polarity output port of the fourth DC-DC converter 100204 is electrically connected to the first DC port X, and the second polarity output port of the fourth DC-DC converter 100204 is electrically connected to the second DC port Y.

[0103] According to some embodiments, the fourth DC-DC converter can be added or omitted by the user according to the needs of the scenario.

[0104] See Figure 1 The single-stage three-phase bidirectional converter further includes:

[0105] The AC-side filter module 1001 is electrically connected between the AC power supply ABC and the single-stage AC-DC converter module 1002, wherein the AC-side filter module 1001 shares the half-bridge capacitor of the single-stage AC-DC converter module 1002.

[0106] According to some embodiments, the single-stage three-phase bidirectional converter further includes an AC-side filter module 1001, electrically connected between the AC power supply ABC and the single-stage AC-DC conversion module 1002. As shown in the figure, the AC filters are connected in series in each branch of the AC power supply output terminal to filter harmonics in the circuit. In actual circuits, the AC-side filter module 1001 can be implemented using an LC filter. In this invention, an inductor coil can be directly used. The inductor coil interacts with the half-bridge capacitor of the single-stage AC-DC conversion module 1002 to achieve the filtering function. This design allows the AC-side filter module 1001 to share the half-bridge capacitor of the single-stage AC-DC conversion module 1002, eliminating the need for capacitors in the filter, simplifying circuit design, and reducing power loss.

[0107] The single-stage three-phase bidirectional converter further includes a DC-side filter 1003, which is electrically connected between the first DC port and the second DC port.

[0108] According to some embodiments, the DC-side filter 1003 is electrically connected between the first DC port and the second DC port for noise suppression of the output DC voltage signal.

[0109] According to some embodiments, a three-phase AC power supply ABC transmits an AC voltage signal. This three-phase AC voltage signal is connected to the AC-side filter module 1001 and then to the single-stage AC-DC converter module 1002. In the single-stage AC-DC converter module 1002, the three-phase AC voltage signal is converted into a DC voltage signal and output to the DC-side filter 1003 via the DC port XY of the single-stage AC-DC converter module. In the DC-side filter 1003, the DC voltage signal undergoes noise filtering by the rectifier bridge circuit, and then serves as a DC voltage source to power external circuits.

[0110] According to some embodiments, the DC power supply can also output AC power through the single-stage three-phase bidirectional converter. The DC power supply passes through the DC-side filter 1003 to remove DC output line interference, and then is input to the single-stage AC-DC conversion module 1002 to convert DC power into AC power. After passing through the AC-side filter module 1001 to remove harmonics from the circuit, a usable AC power supply is finally output.

[0111] The single-stage three-phase bidirectional converter further includes: the first DC-DC converter 100201 includes a first isolation transformer; the second DC-DC converter 100202 includes a second isolation transformer; the third DC-DC converter 100203 includes a third isolation transformer; and the fourth DC-DC converter 100204 includes a fourth isolation transformer; the first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer share a secondary side.

[0112] According to some embodiments, the single-stage three-phase bidirectional converter further includes: the first DC-DC converter 100201 includes a first isolation transformer; the second DC-DC converter 100202 includes a second isolation transformer; the third DC-DC converter 100203 includes a third isolation transformer; and the fourth DC-DC converter 100204 includes a fourth isolation transformer. Each isolation transformer includes an AC side and a DC side, and transmits the output of the single-stage AC-DC conversion module between the AC side and the DC side in an isolated manner. The DC side is electrically connected to the DC side filter 1003.

[0113] According to some embodiments, in actual circuits, the circuit can be simplified so that the first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer share a secondary side.

[0114] The first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer are high-frequency isolation transformers.

[0115] According to some embodiments, high-frequency isolation transformers can prevent contact with live parts in the event of an accident. Like all transformers, a high-frequency isolation transformer is one in which the input and output windings are electrically isolated. However, where transformers typically use electromagnetic induction in the windings to switch current or voltage (AC) from one level to another, the windings on the isolation transformer remain isolated to ensure that a fault does not propagate along the windings. The input and output sides are electrically insulated, and the circuit is also isolated. Additionally, the high-frequency losses in its core are used to suppress the introduction of high-frequency noise into the control loop. Isolation transformers can only be used in applications with small power supply ranges and short lines, where the secondary winding is levitated to ground. In this case, the system's capacitive current to ground is too small to cause personal injury.

[0116] Isolation transformers provide electrical isolation, protecting not only equipment but also personnel. They enhance safety and protect critical equipment used in highly dependent applications. For expensive household appliances, especially medical equipment, where damage is always a risk, isolation transformers prevent further malfunctions and protect workers and patients from electric shock. Isolation transformers are also effective at reducing noise. Their low input-output capacitance coupling suppresses interference from power grid noise caused by lightning strikes, discharges, grid switching, and motor starting, making them effective power supply noise suppressors. For equipment operators, the electromotive force of the isolation transformer is obtained through secondary induction, preventing a circuit with the input side (it forms a circuit with the ground), thus eliminating the risk of electric shock. Furthermore, isolation transformers improve power quality. In practical circuits, the capacity parameters of the high-frequency isolation transformer can be calculated based on the actual load equipment type and starting method for selection.

[0117] According to the foregoing embodiments, multiple converters can operate completely independently and can be connected to unbalanced loads. Furthermore, according to some embodiments, parallel outputs can be employed.

[0118] According to some embodiments, it is readily understood that the fourth AC input port and the fourth DC-DC converter may be omitted.

[0119] Figure 2A and Figure 2B The diagram shows a primary side common positive connection and a primary side common negative connection of a single-stage isolated three-phase bidirectional converter according to an example embodiment.

[0120] According to some embodiments, the single-stage AC-DC converter module has two different connection methods: a primary-side common positive circuit and / or a primary-side common negative circuit.

[0121] According to some embodiments, the primary-side common positive circuit connection method involves shorting the drain input terminals of the four sets of AC-DC conversion unit field-effect transistors. In actual circuit connections, the first, second, third, and fourth DC-DC converters have similar circuit connection methods. The field-effect transistors can be connected in two different ways: with the source connected to the AC input terminal or the drain connected to the input terminal. Shorting the drain input terminals of the field-effect transistors constitutes the single-stage AC-DC conversion module. Correspondingly, the primary-side common negative circuit connection method involves shorting the source input terminals of the four sets of AC-DC conversion unit field-effect transistors.

[0122] Figure 3 A schematic diagram of the operating mode of a single-stage isolated three-phase bidirectional converter with primary side common negative connection θ=0 is shown according to an example embodiment.

[0123] See Figure 3 When θ = 0, the first DC-DC converter operates in DC-DC mode, the second DC-DC converter operates in DC-DC mode, the third DC-DC converter is in short-circuit mode, and the fourth DC-DC converter operates in DC-DC mode.

[0124] According to some embodiments, when θ = 0, the first DC-DC converter operates in DC-DC mode, the second DC-DC converter operates in DC-DC mode, the third DC-DC converter is in short-circuit mode, and the fourth DC-DC converter operates in DC-DC mode, i.e., the third DC / DC converter is short-circuited. The first DC-DC converter operates in DC-DC mode and controls the A-phase current, the second DC-DC converter operates in DC-DC mode and controls the B-phase current, and the fourth DC-DC converter operates in DC-DC mode and controls the N-phase current. IB = -IA - IC + IN.

[0125] According to some embodiments, when θ = 120°, the first DC-DC converter is in short-circuit mode, the second DC-DC converter operates in DC-DC mode, the third DC-DC converter operates in DC-DC mode, and the fourth DC-DC converter operates in DC-DC mode; when θ = 240°, the first DC-DC converter operates in DC-DC mode, the second DC-DC converter is in short-circuit mode, the third DC-DC converter operates in DC-DC mode, and the fourth DC-DC converter operates in DC-DC mode.

[0126] Figure 4 The diagram shows the key voltage waveform of the primary side common negative connection of a single-stage isolated three-phase bidirectional converter according to an example embodiment.

[0127] See Figure 4 For the primary-side common-negative connection, the common point O is connected to the lowest potential point in the input, corresponding to a short circuit on the primary side of the converter. The input voltages of the four converters are shown in the figure. As shown by the dashed line, point O is clamped to the lowest potential.

[0128] According to an embodiment, the converter can transfer energy to the secondary side intermittently, with each DC-DC converter short-circuiting its primary side when the voltage difference between its first polarity input port and its second polarity input port is 0, thus preventing energy transfer to the secondary side.

[0129] See Figure 4 For any DC-DC converter (assuming the input terminal is Z), the primary side is short-circuited and no energy is transferred during the period when the input voltage Uzo = 0. Energy is transferred during the period when Uzo > 0, and the amount of energy transferred is Iz * Uzo. Figure 5The diagram shows the PFC current injection waveform of a single-stage isolated three-phase bidirectional converter according to an example embodiment.

[0130] See Figure 5 The figure shows the corresponding phase currents and the controlled reference currents of each DC / DC converter when the converter is in PFC mode. The dashed lines indicate that the primary side of the DC / DC converter is short-circuited, and the corresponding phase current is not controlled temporarily.

[0131] See Figure 5 In the single-stage three-phase bidirectional converter, the first polarity input port and the second polarity input port of the third DC-DC converter are shorted during the three-phase AC voltage signal cycle from 0° to 120°.

[0132] According to some embodiments, during the period from 0° to 120° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the third DC-DC converter are short-circuited, and the converter is in short-circuit mode, i.e., UCO = 0, ICO = 0 (see 5(d)). Figure 6 (d)

[0133] According to some embodiments, during the period from 0° to 120° of the three-phase AC voltage signal cycle, the first DC-DC converter operates in DC-DC mode, wherein the voltage change is as follows: Figure 5 As shown in Figure b, the current change is as follows Figure 6 As shown in b; the second DC-DC converter operates in DC-DC mode, where the voltage change is as follows. Figure 5 As shown in Figure c, the current change is as follows Figure 6 As shown in Figure c; the fourth DC-DC converter operates in DC-DC mode, and the voltage change across the fourth DC-DC converter is as follows: Figure 5 As shown in e, Figure 6 As shown in Figure e, the current through the fourth DC-DC converter is 0, and the field-effect transistor in the fourth DC-DC converter is in the off state.

[0134] During the period from 120° to 240° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the first DC-DC converter are short-circuited, and the converter is in short-circuit mode, i.e., UAO = 0, IAO = 0 (see 5(b)). Figure 6 (b)

[0135] According to some embodiments, during 120° to 240° of the three-phase AC voltage signal cycle, the second DC-DC converter operates in DC-DC mode, wherein the voltage change is as follows: Figure 5 As shown in Figure c, the current change is as follows Figure 6As shown in c; the third DC-DC converter operates in DC-DC mode, where the voltage changes are as follows. Figure 5 As shown in Figure d, the current change is as follows Figure 6 As shown in d; the fourth DC-DC converter operates in DC-DC mode, wherein the voltage change across the fourth DC-DC converter is as follows Figure 5 As shown in e, Figure 6 As shown in Figure e, the current through the fourth DC-DC converter is 0, and the field-effect transistor in the fourth DC-DC converter is in the off state.

[0136] During the period from 240° to 360° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the second DC-DC converter are shorted.

[0137] According to some embodiments, during the 240° to 360° period of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the second DC-DC converter are short-circuited, and the converter is in short-circuit mode, i.e., UBO = 0, IBO = 0 (see 5(c)). Figure 6 (c)

[0138] According to some embodiments, during the 240° to 360° period of the three-phase AC voltage signal cycle, the first DC-DC converter operates in DC-DC mode, wherein the voltage change is as follows: Figure 5 As shown in Figure b, the current change is as follows Figure 6 As shown in Figure b; the third DC-DC converter operates in DC-DC mode, where the voltage changes are as follows. Figure 5 As shown in Figure d, the current change is as follows Figure 6 As shown in d; the fourth DC-DC converter operates in DC-DC mode, wherein the voltage change across the fourth DC-DC converter is as follows Figure 5 As shown in e, Figure 6 As shown in Figure e, the current through the fourth DC-DC converter is 0, and the field-effect transistor in the fourth DC-DC converter is in the off state.

[0139] According to some embodiments, based on the above analysis, the fourth DC-DC converter remains in the off state throughout the three-phase AC voltage signal cycle. In practical circuits, the fourth DC-DC converter can be omitted depending on the application scenario.

[0140] The first polarity input port is either a positive input port or a negative input port, and the second polarity input port is correspondingly either a negative input port or a positive input port.

[0141] According to some embodiments, the first polarity input port and the second polarity input port in the first DC-DC converter, the second DC-DC converter, the third DC-DC converter and the fourth DC-DC converter constitute an AC input port, wherein the first polarity input port is a positive input port or a negative input port, and the second polarity input port is correspondingly a negative input port or a positive input port.

[0142] Figure 6 An example circuit diagram of a primary-side common-negative connection method for a single-stage isolated three-phase bidirectional converter according to an example embodiment is shown.

[0143] Figure 7 An example circuit diagram of a primary-side common positive connection method for a single-stage isolated three-phase bidirectional converter according to an example embodiment is shown.

[0144] See Figure 6 and Figure 7 The example circuit in the example includes a first switching element, a second switching element, a half-bridge circuit consisting of a first capacitor and a second capacitor, and a first isolation transformer. The first switching element has a first terminal, a second terminal, and a control terminal, and the control terminal controls the first switching element to be turned on or off.

[0145] The second switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the second switching element to be turned on or off;

[0146] The second switching element is connected in series with the first switching element between the first polarity input port and the second polarity input port of the first DC-DC converter, and the first capacitor and the second capacitor are connected in series between the first polarity input port and the second polarity input port of the first DC-DC converter.

[0147] The primary winding of the first isolation transformer is connected between the series node between the second switching element and the first switching element and between the series node between the first capacitor and the second capacitor.

[0148] According to some embodiments, the first and second switching elements are field-effect transistors (FETs). The FETs are connected in series between the first polarity input port and the second polarity input port of the first DC-DC converter. When the first DC-DC converter operates in DC-DC mode, the FETs receive control signals to switch alternately, realizing DC-DC conversion and supplying electrical energy to the first isolation transformer.

[0149] The second DC-DC converter includes: a third switching element, a fourth switching element, a half-bridge circuit consisting of a third capacitor and a fourth capacitor, and a second isolation transformer, wherein:

[0150] The third switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the third switching element to be turned on or off.

[0151] The fourth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the fourth switching element to be turned on or off.

[0152] The third switching element and the fourth switching element are connected in series between the first polarity input port and the second polarity input port of the second DC-DC converter, and the third capacitor and the fourth capacitor are connected in series between the first polarity input port and the second polarity input port of the second DC-DC converter.

[0153] The primary winding of the second isolation transformer is connected between the series node between the third and fourth switching elements and the series node between the third and fourth capacitors.

[0154] According to some embodiments, the third and fourth switching elements are field-effect transistors (FETs). The FETs are connected in series between the first polarity input port and the second polarity input port of the second DC-DC converter. When the second DC-DC converter operates in DC-DC mode, the FETs receive control signals to switch alternately, realize DC-DC conversion, and deliver electrical energy to the second isolation transformer.

[0155] The third DC-DC converter includes: a fifth switching element, a sixth switching element, a half-bridge circuit composed of a fifth capacitor and a sixth capacitor, and a third isolation transformer, wherein:

[0156] The fifth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the fifth switching element to be turned on or off.

[0157] The sixth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the sixth switching element to be turned on or off.

[0158] The fifth switching element and the sixth switching element are connected in series between the first polarity input port and the second polarity input port of the third DC-DC converter, and the fifth capacitor and the sixth capacitor are connected in series between the first polarity input port and the second polarity input port of the third DC-DC converter.

[0159] The primary winding of the third isolation transformer is connected between the series node between the fifth and sixth switching elements and between the series node between the fifth and sixth capacitors.

[0160] According to some embodiments, the fifth and sixth switching elements are field-effect transistors (FETs). The FETs are connected in series between the first polarity input port and the second polarity input port of the third DC-DC converter. When the third DC-DC converter operates in DC-DC mode, the FETs receive control signals to switch alternately, realizing DC-DC conversion and supplying electrical energy to the third isolation transformer.

[0161] The fourth DC-DC converter includes: a half-bridge circuit consisting of a seventh switching element, an eighth switching element, a seventh capacitor, and an eighth capacitor, and a fourth isolation transformer, wherein:

[0162] The seventh switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the seventh switching element to be turned on or off.

[0163] The eighth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the eighth switching element to be turned on or off.

[0164] The seventh switching element and the eighth switching element are connected in series between the first polarity input port and the second polarity input port of the fourth DC-DC converter, and the seventh capacitor and the eighth capacitor are connected in series between the first polarity input port and the second polarity input port of the fourth DC-DC converter.

[0165] The primary winding of the fourth isolation transformer is connected between the series node between the seventh and eighth switching elements and between the series node between the seventh and eighth capacitors.

[0166] According to some embodiments, the seventh and eighth switching elements are field-effect transistors (FETs). The FETs are connected in series between the first polarity input port and the second polarity input port of the fourth DC-DC converter. When the fourth DC-DC converter operates in DC-DC mode, the FETs receive control signals to switch alternately, realizing DC-DC conversion and supplying electrical energy to the fourth isolation transformer.

[0167] The first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer share a secondary winding or have independent secondary windings.

[0168] According to some embodiments, the first isolation transformer, the second isolation transformer, the third isolation transformer and the fourth isolation transformer share a secondary winding, which not only simplifies the physical circuit structure, but also meets the space requirements for circuit application in actual scenarios.

[0169] According to some embodiments, in some special application scenarios, the circuit mode of sharing a secondary winding may not be used. Users can make a judgment based on the specific scenario.

[0170] according to Figure 6 In the example, the single-stage isolated single-phase bidirectional converter can be configured according to... Figure 6 The circuit connection shown in the figure is the primary-side common-negative circuit connection. An LC filter structure is used to implement the AC-side filter module function, and an asymmetrical half-bridge circuit structure and a high-frequency isolation transformer are used to implement the DC-DC converter module. The four sets of high-frequency isolation transformers share a common secondary winding, further simplifying the circuit. The field-effect transistor rectifier bridge circuit is used for filtering and rectification, suppressing noise in the DC circuit.

[0171] according to Figure 7 In the example, the single-stage isolated single-phase bidirectional converter can also be configured according to... Figure 7 The circuit connection shown in the figure is the primary-side common positive circuit connection. An LC filter structure is used to implement the AC-side filter module function, and a symmetrical half-bridge circuit structure and a high-frequency isolation transformer are used to implement the DC-DC converter module. The field-effect transistor rectifier bridge circuit is used for filtering and rectification to suppress noise in the DC circuit.

[0172] according to Figure 6 and Figure 7 In the example above, the AC-side filter module 1001 can utilize an inductor to achieve its function. The inductor interacts with the half-bridge capacitor in the single-stage AC-DC converter module 1002 to form an LC filter structure, removing harmonics from the circuit. In this design, the capacitor in the AC-side filter module is omitted, and a shared half-bridge capacitor is used with the single-stage AC-DC converter module, simplifying the circuit and reducing power loss.

[0173] according to Figure 6 and Figure 7 In the example, the rectifier filter module 1003 is a full-wave rectifier circuit composed of four field-effect transistors, which effectively improves the efficiency of the low-voltage rectifier circuit.

[0174] According to some embodiments of this application, an on-board charging device is also provided, which may include the aforementioned single-stage three-phase bidirectional converter.

[0175] According to some embodiments, compared with conventional rectifier circuits, the use of MOSFETs as rectifier switches and MOSFET rectifier bridges effectively improves the efficiency of low-voltage rectifier circuits due to their low internal resistance during conduction. The application of high-frequency isolation transformers avoids contact with live parts in case of occasional faults, ensuring that faults do not propagate along stages, improving safety and protecting critical equipment used in highly dependent applications. Isolation transformers also improve power quality while reducing noise.

[0176] According to some embodiments, the present invention can be applied to on-board charging equipment, which can utilize the above-described single-stage single-phase bidirectional converter circuit design.

[0177] According to some embodiments, the present invention solves the capacitive coupling problem in multi-stage converters, realizes the sharing of half-bridge capacitors with filters, and realizes a single-stage single-phase converter design, which is simpler than traditional circuits and reduces power loss.

[0178] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0179] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0180] In the several embodiments provided in this application, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some service interface; the indirect coupling or communication connection between apparatuses or units may be electrical or other forms.

[0181] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0182] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0183] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage and includes several instructions to cause a computer device (which may be a personal computer, service, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application.

[0184] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0185] The exemplary embodiments of this application have been specifically shown and described above. It should be understood that this application is not limited to the detailed structures, arrangements, or implementation methods described herein; rather, this application is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended provisions.

Claims

1. A single-stage three-phase bidirectional converter, characterized in that, include: A single-stage AC-DC converter module, comprising a first AC input port, a second AC input port, a third AC input port, a first DC port, and a second DC port, wherein the single-stage AC-DC converter module includes: A first DC-DC converter, the first DC-DC converter having a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port; The second DC-DC converter has a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port. A third DC-DC converter, the third DC-DC converter having a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port; Wherein, the first polarity input port of the first DC-DC converter is electrically connected to the first AC input port, the first polarity input port of the second DC-DC converter is electrically connected to the second AC input port, and the first polarity input port of the third DC-DC converter is electrically connected to the third AC input port; the second polarity input port of the first DC-DC converter is electrically connected to the second polarity input port of the second DC-DC converter and the second polarity input port of the third DC-DC converter. The first polarity output port of the first DC-DC converter, the first polarity output port of the second DC-DC converter, and the first polarity output port of the third DC-DC converter are electrically connected to the first DC port, and the second polarity output port of the first DC-DC converter, the second polarity output port of the second DC-DC converter, and the second polarity output port of the third DC-DC converter are electrically connected to the second DC port.

2. The single-stage three-phase bidirectional converter according to claim 1, characterized in that, The single-stage AC-DC converter module also has a fourth AC input port. The single-stage AC-DC converter module also includes: A fourth DC-DC converter, the fourth DC-DC converter having a first polarity input port and a second polarity input port, as well as a first polarity output port and a second polarity output port; The first polarity input port of the fourth DC-DC converter is electrically connected to the fourth AC input port, and the second polarity input port of the fourth DC-DC converter is electrically connected to the second polarity input port of the first DC-DC converter, the second polarity input port of the second DC-DC converter, and the second polarity input port of the third DC-DC converter. The first polarity output port of the fourth DC-DC converter is electrically connected to the first DC port, and the second polarity output port of the fourth DC-DC converter is electrically connected to the second DC port.

3. The single-stage three-phase bidirectional converter according to claim 1, characterized in that, Also includes: An AC-side filter module is electrically connected between the AC power supply and the single-stage AC-DC converter module, wherein the AC-side filter module shares the half-bridge capacitor of the single-stage AC-DC converter module.

4. The single-stage three-phase bidirectional converter according to claim 1, characterized in that, Also includes: A DC-side filter is electrically connected between the first DC port and the second DC port.

5. The single-stage three-phase bidirectional converter according to claim 2, characterized in that, The first DC-DC converter includes a first isolation transformer; The second DC-DC converter includes a second isolation transformer; The third DC-DC converter includes a third isolation transformer; The fourth DC-DC converter includes a fourth isolation transformer; The first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer share a secondary side or have independent secondary sides.

6. The single-stage three-phase bidirectional converter according to claim 5, characterized in that, The first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer are high-frequency isolation transformers.

7. The single-stage three-phase bidirectional converter according to claim 2, characterized in that, The first DC-DC converter, the second DC-DC converter, the third DC-DC converter, and the fourth DC-DC converter transfer energy to the secondary side in an intermittent manner. When the voltage difference between the first polarity input port and the second polarity input port of each DC-DC converter is 0, the primary side is short-circuited, so that no energy is transferred to the secondary side.

8. The single-stage three-phase bidirectional converter according to claim 2, characterized in that, When θ = 0, the first DC-DC converter operates in DC-DC mode, the second DC-DC converter operates in DC-DC mode, the third DC-DC converter is in short-circuit mode, and the fourth DC-DC converter operates in DC-DC mode; When θ = 120°, the first DC-DC converter is in short-circuit mode, the second DC-DC converter operates in DC-DC mode, the third DC-DC converter operates in DC-DC mode, and the fourth DC-DC converter operates in DC-DC mode. When θ = 240°, the first DC-DC converter operates in DC-DC mode, the second DC-DC converter is in short-circuit mode, the third DC-DC converter operates in DC-DC mode, and the fourth DC-DC converter operates in DC-DC mode.

9. The single-stage three-phase bidirectional converter according to claim 8, characterized in that, During the period from 0° to 120° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the third DC-DC converter are shorted. During the period from 120° to 240° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the first DC-DC converter are short-circuited. During the period from 240° to 360° of the three-phase AC voltage signal cycle, the first polarity input port and the second polarity input port of the second DC-DC converter are shorted.

10. The single-stage three-phase bidirectional converter according to claim 1, characterized in that, The first polarity input port is either a positive input port or a negative input port, and the second polarity input port is correspondingly either a negative input port or a positive input port.

11. The single-stage three-phase bidirectional converter according to claim 2, characterized in that, The first DC-DC converter includes a first switching element, a second switching element, a half-bridge circuit consisting of a first capacitor and a second capacitor, and a first isolation transformer, wherein: The first switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the first switching element to be turned on or off; The second switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the second switching element to be turned on or off; The second switching element is connected in series with the first switching element between the first polarity input port and the second polarity input port of the first DC-DC converter, and the first capacitor and the second capacitor are connected in series between the first polarity input port and the second polarity input port of the first DC-DC converter. The primary winding of the first isolation transformer is connected between the series node between the second switching element and the first switching element and between the series node between the first capacitor and the second capacitor; The second DC-DC converter includes: a third switching element, a fourth switching element, a half-bridge circuit consisting of a third capacitor and a fourth capacitor, and a second isolation transformer, wherein: The third switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the third switching element to be turned on or off. The fourth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the fourth switching element to be turned on or off. The third switching element and the fourth switching element are connected in series between the first polarity input port and the second polarity input port of the second DC-DC converter, and the third capacitor and the fourth capacitor are connected in series between the first polarity input port and the second polarity input port of the second DC-DC converter. The primary winding of the second isolation transformer is connected between the series node between the third and fourth switching elements and the series node between the third and fourth capacitors. The third DC-DC converter includes: a fifth switching element, a sixth switching element, a half-bridge circuit composed of a fifth capacitor and a sixth capacitor, and a third isolation transformer, wherein: The fifth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the fifth switching element to be turned on or off. The sixth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the sixth switching element to be turned on or off. The fifth switching element and the sixth switching element are connected in series between the first polarity input port and the second polarity input port of the third DC-DC converter, and the fifth capacitor and the sixth capacitor are connected in series between the first polarity input port and the second polarity input port of the third DC-DC converter. The primary winding of the third isolation transformer is connected between the series node between the fifth and sixth switching elements and between the series node between the fifth and sixth capacitors. The fourth DC-DC converter includes: a half-bridge circuit consisting of a seventh switching element, an eighth switching element, a seventh capacitor, and an eighth capacitor, and a fourth isolation transformer, wherein: The seventh switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the seventh switching element to be turned on or off. The eighth switching element has a first terminal, a second terminal, and a control terminal, wherein the control terminal controls the eighth switching element to be turned on or off. The seventh switching element and the eighth switching element are connected in series between the first polarity input port and the second polarity input port of the fourth DC-DC converter, and the seventh capacitor and the eighth capacitor are connected in series between the first polarity input port and the second polarity input port of the fourth DC-DC converter. The primary winding of the fourth isolation transformer is connected between the series node between the seventh and eighth switching elements and between the series node between the seventh and eighth capacitors. The first isolation transformer, the second isolation transformer, the third isolation transformer, and the fourth isolation transformer share a secondary winding.

12. A vehicle-mounted charging device, characterized in that, Including the single-stage three-phase bidirectional converter according to any one of claims 1-11.

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