Three-phase single-stage isolated bidirectional converter and control method thereof

Abstract

The application provides a three-phase single-stage isolated bidirectional converter and a control method thereof, wherein the converter comprises a three-phase alternating voltage port, a direct current voltage port, first to third primary circuit units, first to third transformers and a secondary circuit unit, the secondary circuit unit comprising a first fast bridge arm and a second fast bridge arm; the secondary windings of the first to third transformers are connected in parallel and then connected to the bridge arm midpoint of the first fast bridge arm and the second fast bridge arm; wherein the two ends of the primary winding of the first transformer are connected with the first primary circuit unit respectively; the two ends of the primary winding of the second transformer are connected with the second primary circuit unit respectively; and the two ends of the primary winding of the third transformer are connected with the third primary circuit unit respectively. Thus, the number of power tubes and driving circuits is reduced, the cost is lowered, and the power density is improved.

Description

Technical Field

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

[0002] In related technologies, three-phase single-stage isolated bidirectional converters typically include electrolytic capacitors, large filter inductors, and a large number of power transistors and corresponding drive circuits, resulting in high costs. Although three-phase single-stage isolated bidirectional converters also exist, such as the previously filed Chinese patent CN115313878A, which discloses a three-phase single-stage isolated bidirectional converter that does not require electrolytic capacitors and large filter inductors, it still requires a large number of power transistors and corresponding drive circuits, thus resulting in higher costs and lower power density. Summary of the Invention

[0003] To solve the above-mentioned technical problems, this invention provides a three-phase single-stage isolated bidirectional converter, which greatly reduces the number of power transistors and drive circuits, thereby reducing costs and increasing power density.

[0004] The technical solution adopted in this invention is as follows:

[0005] A three-phase single-stage isolated bidirectional converter includes: a three-phase AC voltage port, a DC voltage port, first to third primary circuit units, first to third transformers, and a secondary circuit unit. The three-phase AC port includes a first to a sixth port; the DC voltage port includes a seventh port and an eighth port; the secondary circuit unit includes a first fast bridge arm and a second fast bridge arm, one end of which is connected to the seventh port, and the other end of which is connected to the eighth port; the secondary windings of the first to third transformers are connected in parallel and then connected to the first fast bridge arm and the second fast bridge arm. The bridge arm midpoint; wherein, the two ends of the primary winding of the first transformer are respectively connected to the first primary circuit unit, and the center tap of the primary winding of the first transformer is connected to the first port; the two ends of the primary winding of the second transformer are respectively connected to the second primary circuit unit, and the center tap of the primary winding of the second transformer is connected to the third port; the two ends of the primary winding of the third transformer are respectively connected to the third primary circuit unit, and the center tap of the primary winding of the third transformer is connected to the fifth port; the first primary circuit unit is also connected to the second port; the second primary circuit unit is also connected to the fourth port, and the third primary circuit unit is also connected to the sixth port.

[0006] In one embodiment of the present invention, the first primary-side circuit unit includes a first coupling inductor, a first bus capacitor, a third fast bridge arm, a fourth fast bridge arm, and a first slow bridge arm. The first coupling inductor includes a first winding and a second winding. One end of the first winding is connected to the midpoint of the bridge arm of the third fast bridge arm, and the other end of the first winding is connected to one end of the primary winding of the first transformer. One end of the second winding is connected to the midpoint of the bridge arm of the fourth fast bridge arm, and the other end of the second winding is connected to the other end of the primary winding of the first transformer. The midpoint of the bridge arm of the first slow bridge arm is connected to the second port. The two ends of the first bus capacitor are respectively connected to the two ends of the first slow bridge arm. The second primary-side circuit unit includes a second coupling inductor, a second bus capacitor, a fifth fast bridge arm, a sixth fast bridge arm, and a second slow bridge arm. The second coupling inductor includes a third winding and a fourth winding. One end of the third winding is connected to the midpoint of the bridge arm of the fifth fast bridge arm, and the other end of the third winding is connected to the second... One end of the primary winding of the transformer is connected to the fourth winding, one end of the fourth winding is connected to the midpoint of the sixth fast bridge arm, the other end of the fourth winding is connected to the other end of the primary winding of the second transformer, the midpoint of the second slow bridge arm is connected to the fourth port, and the two ends of the second bus capacitor are respectively connected to the two ends of the second slow bridge arm; the third primary circuit unit includes a third coupling inductor, a third bus capacitor, a seventh fast bridge arm, an eighth fast bridge arm, and a third slow bridge arm. The third coupling inductor includes a fifth winding and a sixth winding. One end of the fifth winding is connected to the midpoint of the seventh fast bridge arm, the other end of the fifth winding is connected to one end of the primary winding of the third transformer, one end of the sixth winding is connected to the midpoint of the eighth fast bridge arm, the other end of the sixth winding is connected to the other end of the primary winding of the third transformer, the midpoint of the third slow bridge arm is connected to the sixth port, and the two ends of the third bus capacitor are respectively connected to the two ends of the third slow bridge arm.

[0007] In one embodiment of the present invention, the first to eighth fast bridge arms all include fast-switching power semiconductor devices.

[0008] In one embodiment of the present invention, the first to third slow bridge arms each include a power semiconductor device that switches slowly.

[0009] A control method for a three-phase single-stage isolated bidirectional converter includes the following steps: controlling the duty cycle of the fast-switching power semiconductor devices on each fast bridge arm in each primary-side circuit unit to be 50%, with the drive signals of the two fast-switching power semiconductor devices on the same fast bridge arm being complementary; controlling the duty cycle of the slow-switching power semiconductor devices on each slow bridge arm in each primary-side circuit unit to be 50%, with the drive signals of the two slow-switching power semiconductor devices on the same slow bridge arm being complementary; controlling the duty cycle of the fast-switching power semiconductor devices on each fast bridge arm in the secondary-side circuit unit to be 50%, with the drive signals of the two fast-switching power semiconductor devices on the same fast bridge arm being complementary; and, according to the operating mode of the three-phase single-stage isolated bidirectional converter, controlling the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit to lead / lag the voltage between the midpoints of the two fast bridge arms in the secondary-side circuit unit.

[0010] In one embodiment of the present invention, when the three-phase single-stage isolated bidirectional converter operates in rectification mode, the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit is controlled to lead the voltage between the midpoints of the two fast bridge arms in the secondary-side circuit by the corresponding outward phase shift; when the three-phase single-stage isolated bidirectional converter operates in inverter mode, the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit is controlled to lag the voltage between the midpoints of the two fast bridge arms in the secondary-side circuit by the corresponding outward phase shift.

[0011] In one embodiment of the present invention, the external phase shift is calculated using the following formula:

[0012] ,

[0013] in, This indicates that at time t, the voltage between the midpoints of the two fast bridge arms in the Kth primary-side circuit unit leads or lags behind the voltage between the midpoints of the two fast bridge arms in the secondary-side circuit. This represents the transmission power corresponding to the Kth primary-side circuit unit at time t. This represents the inductance value of the coupled inductor in the Kth primary-side circuit unit. This indicates the switching frequency of a fast-switching power semiconductor device. This represents the turns ratio of the primary winding to the secondary winding of the Kth transformer. This represents the bus voltage corresponding to the Kth primary circuit unit at time t. This indicates the DC voltage input / output of the DC voltage port.

[0014] In one embodiment of the present invention, the control method of the three-phase single-stage isolated bidirectional converter further includes: injecting harmonics into the bus capacitor voltage of each primary circuit unit to increase the matching degree between the bus capacitor voltage of each primary circuit unit and the DC voltage input / output of the DC voltage port.

[0015] The beneficial effects of this invention are:

[0016] 1. The secondary circuit unit of the present invention consists of two fast bridge arms, which reduces the number of power transistors and drive circuits, thereby saving costs and increasing power density;

[0017] 2. The modulation strategy of the present invention only requires external phase shift to adjust the power, and the modulation strategy is simple;

[0018] 3. This invention injects harmonics into the bus capacitor voltage of each primary circuit unit, making the bus capacitor voltage of each primary circuit unit closer to a trapezoidal wave. This allows the bus capacitor voltage of each primary circuit unit to match the DC voltage input / output of the DC voltage port over a wider range, thereby improving the converter efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a three-phase single-stage isolated bidirectional converter according to an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Figure 1 This is a schematic diagram of the structure of a three-phase single-stage isolated bidirectional converter according to an embodiment of the present invention.

[0022] like Figure 1 As shown, the three-phase single-stage isolated bidirectional converter of this invention may include: a three-phase AC voltage port 100, a DC voltage port 200, first to third primary circuit units 300~500, first to third transformers 600~800, and a secondary circuit unit 900.

[0023] The three-phase AC port 100 includes ports A1 to A6 (first to sixth phases); the DC voltage port 200 includes port A7 (seventh phase) and port A8 (eighth phase). The secondary circuit unit 900 includes a first fast bridge arm 910 and a second fast bridge arm 920. One end of the first fast bridge arm 910 and the second fast bridge arm 920 is connected to port A7 (seventh phase), and the other end of the first fast bridge arm 910 and the second fast bridge arm 920 is connected to port A8 (eighth phase).

[0024] The secondary windings of the first to third transformers 600-800 are connected in parallel and then connected to the midpoint of the first fast bridge arm 910 and the second fast bridge arm 920. Specifically, the two ends of the primary winding of the first transformer 600 are connected to the first primary circuit unit 300, and the center tap of the primary winding of the first transformer 600 is connected to the first port A1. The two ends of the primary winding of the second transformer 700 are connected to the second primary circuit unit 400, and the center tap of the primary winding of the second transformer 700 is connected to the third port A3. The two ends of the primary winding of the third transformer 800 are connected to the third primary circuit unit 500, and the center tap of the primary winding of the third transformer 800 is connected to the fifth port A5.

[0025] The first primary circuit unit 300 is also connected to the second port A2; the second primary circuit unit 400 is also connected to the fourth port A4; and the third primary circuit unit 500 is also connected to the sixth port A6.

[0026] In one embodiment of the present invention, such as Figure 1As shown, the first primary-side circuit unit 300 includes a first coupling inductor 310, a first bus capacitor C1, a third fast bridge arm 320, a fourth fast bridge arm 330, and a first slow bridge arm 340. The first coupling inductor 310 includes a first winding and a second winding. One end of the first winding is connected to the midpoint of the bridge arm of the third fast bridge arm 320, and the other end of the first winding is connected to one end of the primary winding of the first transformer 600. One end of the second winding is connected to the midpoint of the bridge arm of the fourth fast bridge arm 330, and the other end of the second winding is connected to the primary winding of the first transformer 600. The other end of the first primary winding is connected to the second port A2, the midpoint of the first slow bridge arm 340 is connected to the second port A2, and the two ends of the first bus capacitor C1 are respectively connected to the two ends of the first slow bridge arm 340; the second primary circuit unit 400 includes a second coupling inductor 410, a second bus capacitor C2, a fifth fast bridge arm 420, a sixth fast bridge arm 430, and a second slow bridge arm 440. The second coupling inductor 410 includes a third winding and a fourth winding. One end of the third winding is connected to the midpoint of the fifth fast bridge arm 420, and the other end of the third winding is connected to the second primary winding. One end of the primary winding of transformer 700 is connected to the fourth winding, one end of the fourth winding is connected to the midpoint of the sixth fast bridge arm 430, the other end of the fourth winding is connected to the other end of the primary winding of the second transformer 700, the midpoint of the second slow bridge arm 440 is connected to the fourth port A4, and the two ends of the second bus capacitor C2 are respectively connected to the two ends of the second slow bridge arm 440; the third primary circuit unit 500 includes a third coupling inductor 510, a third bus capacitor C3, a seventh fast bridge arm 520, an eighth fast bridge arm 530, and a third slow bridge arm 54. 0. The third coupling inductor 510 includes a fifth winding and a sixth winding. One end of the fifth winding is connected to the midpoint of the seventh fast bridge arm 520, and the other end of the fifth winding is connected to one end of the primary winding of the third transformer 800. One end of the sixth winding is connected to the midpoint of the eighth fast bridge arm 530, and the other end of the sixth winding is connected to the other end of the primary winding of the third transformer 800. The midpoint of the third slow bridge arm 540 is connected to the sixth port A6. The two ends of the third bus capacitor C3 are respectively connected to the two ends of the third slow bridge arm 540.

[0027] In one embodiment of the present invention, the first to eighth fast bridge arms all include fast-switching power semiconductor devices, such as IGBTs and MOSFETs. These fast-switching power semiconductor devices have high switching frequencies (typically above kHz), suitable for high-frequency switching scenarios. In another embodiment of the present invention, the first to third slow bridge arms all include slow-switching power semiconductor devices, such as IGBTs and MOSFETs. These slow-switching power semiconductor devices have low switching frequencies (typically below kHz), suitable for low-frequency switching scenarios.

[0028] Therefore, the secondary circuit unit of the present invention is composed of a first fast bridge arm and a second fast bridge arm, which reduces the number of power transistors and drive circuits, thereby saving costs and increasing power density.

[0029] In summary, the three-phase single-stage isolated bidirectional converter according to an embodiment of the present invention includes: a three-phase AC voltage port, a DC voltage port, first to third primary circuit units, first to third transformers, and a secondary circuit unit. The three-phase AC port includes first to sixth ports; the DC voltage port includes a seventh port and an eighth port; the secondary circuit unit includes a first fast bridge arm and a second fast bridge arm, one end of which is connected to the seventh port, and the other end of which is connected to the eighth port; the secondary windings of the first to third transformers are connected in parallel and then connected to the first fast bridge arm and the second fast bridge arm. The bridge arm of the high-speed bridge has a midpoint; the two ends of the primary winding of the first transformer are connected to the first primary circuit unit, and the center tap of the primary winding of the first transformer is connected to the first port; the two ends of the primary winding of the second transformer are connected to the second primary circuit unit, and the center tap of the primary winding of the second transformer is connected to the third port; the two ends of the primary winding of the third transformer are connected to the third primary circuit unit, and the center tap of the primary winding of the third transformer is connected to the fifth port; the first primary circuit unit is also connected to the second port; the second primary circuit unit is also connected to the fourth port; and the third primary circuit unit is also connected to the sixth port. This significantly reduces the number of power transistors and drive circuits, thereby reducing costs and increasing power density.

[0030] Corresponding to the three-phase single-stage isolated bidirectional converter in the above embodiments, the present invention also proposes a control method for a three-phase single-stage isolated bidirectional converter.

[0031] The control method of the three-phase single-stage isolated bidirectional converter of the present invention may include the following steps: controlling the duty cycle of the fast-switching power semiconductor devices on each fast bridge arm in each primary-side circuit unit to be 50%, the drive signals of the two fast-switching power semiconductor devices on the same fast bridge arm to be complementary, and controlling the duty cycle of the slow-switching power semiconductor devices on each slow bridge arm in each primary-side circuit unit to be 50%, the drive signals of the two slow-switching power semiconductor devices on the same slow bridge arm to be complementary; controlling the duty cycle of the fast-switching power semiconductor devices on each fast bridge arm in the secondary-side circuit unit to be 50%, the drive signals of the two fast-switching power semiconductor devices on the same fast bridge arm to be complementary; and, according to the operating mode of the three-phase single-stage isolated bidirectional converter, controlling the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit to lead / lag the voltage between the midpoints of the two fast bridge arms in the secondary-side circuit.

[0032] Specifically, controlling the complementary drive signals of two fast-switching power semiconductor devices on the same fast bridge arm includes: controlling the drive signal of the first fast-switching power semiconductor device on one fast bridge arm to be the same as the drive signal of the second fast-switching power semiconductor device on the other fast bridge arm, and controlling the drive signal of the second fast-switching power semiconductor device on one fast bridge arm to be the same as the drive signal of the first fast-switching power semiconductor device on the other fast bridge arm; controlling the complementary drive signals of two slow-switching power semiconductor devices on the same slow bridge arm includes: controlling the drive signals of two slow-switching power semiconductor devices on the same slow bridge arm to be complementary based on the three-phase AC voltage control of the three-phase AC port. Two slow-switching power semiconductor devices on the same slow-speed bridge arm are controlled. Specifically, if the AC voltage of a certain phase (the voltage between the first port A1 and the second port A2, or the voltage between the third port A3 and the fourth port A4, or the voltage between the fifth port A5 and the sixth port A6) is greater than 0, the first slow-switching power semiconductor device on the corresponding slow-speed bridge arm is turned off, and the second slow-switching power semiconductor device is turned on; if the AC voltage of a certain phase is less than 0, the first slow-switching power semiconductor device on the corresponding slow-speed bridge arm is turned on, and the second slow-switching power semiconductor device is turned off.

[0033] In one embodiment of the present invention, when the three-phase single-stage isolated bidirectional converter operates in rectification mode, the voltage between the midpoints of the two fast bridge arms in each primary circuit unit is controlled to lead the voltage between the midpoints of the two fast bridge arms in the secondary circuit with a corresponding outward phase shift; when the three-phase single-stage isolated bidirectional converter operates in inverter mode, the voltage between the midpoints of the two fast bridge arms in each primary circuit unit is controlled to lag the voltage between the midpoints of the two fast bridge arms in the secondary circuit with a corresponding outward phase shift.

[0034] In one embodiment of the present invention, the external phase shift can be calculated using the following formula:

[0035] ,

[0036] in, This indicates that at time t, the voltage between the midpoints of the two fast bridge arms in the primary circuit unit (K=1,2,3) leads or lags the voltage between the midpoints of the two fast bridge arms in the secondary circuit, representing an outward phase shift. This represents the transmission power corresponding to the Kth primary-side circuit unit at time t. This represents the inductance value of the coupled inductor in the Kth primary-side circuit unit. This indicates the switching frequency of a fast-switching power semiconductor device. This represents the turns ratio of the primary winding to the secondary winding of the Kth transformer. This represents the bus voltage corresponding to the Kth primary circuit unit at time t. This indicates the DC voltage input / output of the DC voltage port.

[0037] Therefore, the modulation strategy of the present invention only requires external phase shift to adjust the power, and the modulation strategy is simple.

[0038] In one embodiment of the present invention, the control method of the three-phase single-stage isolated bidirectional converter further includes: injecting harmonics into the bus capacitor voltage of each primary circuit unit to increase the matching degree between the bus capacitor voltage of each primary circuit unit and the DC voltage input / output of the DC voltage port.

[0039] Specifically, by injecting third and multiples of the third harmonics into the bus capacitor voltage of each primary circuit unit, the bus capacitor voltage of each primary circuit unit is made closer to a trapezoidal wave. This makes the voltage of the flat segment of the bus capacitor voltage approximately equal to the voltage of the DC voltage input / output port referred to the primary side. This allows the bus capacitor voltage of each primary circuit unit to match the DC voltage input / output port voltage over a wider range, thereby improving the transmission efficiency of the converter.

[0040] In summary, the control method for a three-phase single-stage isolated bidirectional converter according to an embodiment of the present invention controls the duty cycle of the fast-switching power semiconductor devices on each fast bridge arm in each primary-side circuit unit to be 50%, with the drive signals of the two fast-switching power semiconductor devices on the same fast bridge arm being complementary. Similarly, the duty cycle of the slow-switching power semiconductor devices on each slow bridge arm in each primary-side circuit unit is controlled to be 50%, with the drive signals of the two slow-switching power semiconductor devices on the same slow bridge arm being complementary. The same applies to the secondary-side circuit unit. Based on the operating mode of the three-phase single-stage isolated bidirectional converter, the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit is controlled to lead / lag the voltage between the midpoints of the two fast bridge arms in the secondary-side circuit unit. Therefore, the present invention only requires external phase shifting to regulate power, resulting in a simple modulation strategy. Furthermore, it significantly reduces the number of power transistors and drive circuits, thereby lowering costs and increasing power density.

[0041] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., 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. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0044] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0046] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0047] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0048] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments.

[0049] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0050] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A three-phase single-stage isolated bidirectional converter, characterized in that, include: The circuit includes a three-phase AC voltage port, a DC voltage port, first to third primary circuit units, first to third transformers, and a secondary circuit unit. The three-phase AC ports include ports one through six; The DC voltage port includes a seventh port and an eighth port; The secondary circuit unit includes a first fast bridge arm and a second fast bridge arm. One end of the first fast bridge arm and the second fast bridge arm are connected to the seventh port, and the other end of the first fast bridge arm and the second fast bridge arm are connected to the eighth port. The secondary windings of the first to third transformers are connected in parallel and then connected to the midpoints of the first and second fast bridge arms. The two ends of the primary winding of the first transformer are connected to the first primary circuit unit, and the center tap of the primary winding of the first transformer is connected to the first port. The two ends of the primary winding of the second transformer are connected to the second primary circuit unit, and the center tap of the primary winding of the second transformer is connected to the third port. The two ends of the primary winding of the third transformer are connected to the third primary circuit unit, and the center tap of the primary winding of the third transformer is connected to the fifth port. The first primary-side circuit unit is also connected to the second port; the second primary-side circuit unit is also connected to the fourth port; and the third primary-side circuit unit is also connected to the sixth port.

2. The three-phase single-stage isolated bidirectional converter according to claim 1, characterized in that, The first primary-side circuit unit includes a first coupling inductor, a first bus capacitor, a third fast bridge arm, a fourth fast bridge arm, and a first slow bridge arm. The first coupling inductor includes a first winding and a second winding. One end of the first winding is connected to the midpoint of the third fast bridge arm, and the other end of the first winding is connected to one end of the primary winding of the first transformer. One end of the second winding is connected to the midpoint of the fourth fast bridge arm, and the other end of the second winding is connected to the other end of the primary winding of the first transformer. The midpoint of the first slow bridge arm is connected to the second port. The two ends of the first bus capacitor are respectively connected to the two ends of the first slow bridge arm. The second primary-side circuit unit includes a second coupling inductor, a second bus capacitor, a fifth fast bridge arm, a sixth fast bridge arm, and a second slow bridge arm. The second coupling inductor includes a third winding and a fourth winding. One end of the third winding is connected to the midpoint of the fifth fast bridge arm, and the other end of the third winding is connected to one end of the primary winding of the second transformer. One end of the fourth winding is connected to the midpoint of the sixth fast bridge arm, and the other end of the fourth winding is connected to the other end of the primary winding of the second transformer. The midpoint of the second slow bridge arm is connected to the fourth port. The two ends of the second bus capacitor are respectively connected to the two ends of the second slow bridge arm. The third primary-side circuit unit includes a third coupling inductor, a third bus capacitor, a seventh fast bridge arm, an eighth fast bridge arm, and a third slow bridge arm. The third coupling inductor includes a fifth winding and a sixth winding. One end of the fifth winding is connected to the midpoint of the seventh fast bridge arm, and the other end of the fifth winding is connected to one end of the primary winding of the third transformer. One end of the sixth winding is connected to the midpoint of the eighth fast bridge arm, and the other end of the sixth winding is connected to the other end of the primary winding of the third transformer. The midpoint of the third slow bridge arm is connected to the sixth port. The two ends of the third bus capacitor are respectively connected to the two ends of the third slow bridge arm.

3. The three-phase single-stage isolated bidirectional converter according to claim 2, characterized in that, The first through eighth fast bridge arms all include fast-switching power semiconductor devices.

4. The three-phase single-stage isolated bidirectional converter according to claim 3, characterized in that, The first through third slow-speed bridge arms all include power semiconductor devices that switch slowly.

5. A control method for a three-phase single-stage isolated bidirectional converter according to claim 4, characterized in that, The control method includes the following steps: The duty cycle of the fast-switching power semiconductor devices on each fast bridge arm in each primary-side circuit unit is controlled to be 50%, the drive signals of the two fast-switching power semiconductor devices on the same fast bridge arm are complementary, and the duty cycle of the slow-switching power semiconductor devices on each slow bridge arm in each primary-side circuit unit is controlled to be 50%, the drive signals of the two slow-switching power semiconductor devices on the same slow bridge arm are complementary. The duty cycle of the fast-switching power semiconductor devices on each fast bridge arm in the secondary circuit unit is controlled to be 50%, and the drive signals of the two fast-switching power semiconductor devices on the same fast bridge arm are complementary. According to the operating mode of the three-phase single-stage isolated bidirectional converter, the voltage between the midpoints of the two fast bridge arms in each primary circuit unit is controlled to lead / lag the voltage between the midpoints of the two fast bridge arms in the secondary circuit.

6. The control method for a three-phase single-stage isolated bidirectional converter according to claim 5, characterized in that, When the three-phase single-stage isolated bidirectional converter is operating in rectification mode, the voltage between the midpoints of the two fast bridge arms in each primary circuit unit is controlled to lead the voltage between the midpoints of the two fast bridge arms in the secondary circuit by the corresponding outward phase shift. When the three-phase single-stage isolated bidirectional converter operates in inverter mode, the voltage between the midpoints of the two fast bridge arms in each primary circuit unit lags behind the corresponding outward phase shift of the voltage between the midpoints of the two fast bridge arms in the secondary circuit.

7. The control method for a three-phase single-stage isolated bidirectional converter according to claim 6, characterized in that, The external phase is calculated using the following formula: ， in, This indicates that at time t, the voltage between the midpoints of the two fast bridge arms in the Kth primary-side circuit unit leads or lags behind the voltage between the midpoints of the two fast bridge arms in the secondary-side circuit. This represents the transmission power corresponding to the Kth primary-side circuit unit at time t. This represents the inductance value of the coupled inductor in the Kth primary-side circuit unit. This indicates the switching frequency of a fast-switching power semiconductor device. This represents the turns ratio of the primary winding to the secondary winding of the Kth transformer. This represents the bus voltage corresponding to the Kth primary circuit unit at time t. This indicates the DC voltage input / output of the DC voltage port.

8. The control method for a three-phase single-stage isolated bidirectional converter according to claim 5, characterized in that, Also includes: Harmonics are injected into the bus capacitor voltage of each primary circuit unit to increase the matching degree between the bus capacitor voltage of each primary circuit unit and the DC voltage input / output of the DC voltage port.

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