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

Abstract

The invention provides a three-phase single-stage isolated bidirectional converter and a control method thereof.The converter comprises a first primary side circuit unit, a second primary side circuit unit, a third primary side circuit unit, a first transformer, a second transformer, a third transformer and a secondary side circuit unit, the secondary side circuit unit comprises a first fast bridge arm, a second fast bridge arm and a third fast bridge arm, and one ends of the first fast bridge arm, the second fast bridge arm and the third fast bridge arm are connected with a seventh port; the other ends of the first to third quick bridge arms are connected with an eighth port; secondary windings of the first to third transformers are connected to bridge arm midpoints of the first to third fast bridge arms in a star connection or triangular connection mode; wherein two ends of a primary winding of the first transformer are respectively connected with the first primary circuit unit; two ends of the primary winding of the second transformer are respectively connected with the second primary circuit unit; and two ends of the primary winding of the third transformer are respectively connected with the third primary circuit unit. Therefore, the number of the power tubes and the number of the driving circuits are greatly reduced, the cost is reduced, 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, although there are topologies that use three-phase single-stage isolated bidirectional converters to realize three-phase AC-DC power conversion, this topology usually requires a large number of power transistors and a lot of drive circuits, so the cost is high and the power density is low. 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 first to sixth ports; the DC voltage port includes a seventh port and an eighth port; the secondary circuit unit includes first to third fast bridge arms, one end of each fast bridge arm is connected to the seventh port, and the other end of each fast bridge arm is connected to the eighth port; the secondary windings of the first to third transformers are connected to the midpoints of the first to third fast bridge arms in a star or delta configuration. In this configuration, 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.

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

[0007] In one embodiment of the present invention, the first to ninth 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 fast-switching power semiconductor devices on each fast bridge arm in each primary-side circuit unit to be 50%, with the drive signals of two fast-switching power semiconductor devices on the same fast bridge arm being complementary, and controlling the duty cycle of slow-switching power semiconductor devices on each slow bridge arm in each primary-side circuit unit to be 50%, with the drive signals of two slow-switching power semiconductor devices on the same slow bridge arm being complementary; adjusting the switching timing of fast-switching power semiconductor devices on each fast bridge arm in the first to third primary-side circuit units according to the AC voltage; performing vector synthesis on the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit to generate a corresponding bridge arm midpoint voltage synthesis vector; controlling the switching timing of fast-switching power semiconductor devices on each fast bridge arm in the secondary-side circuit unit according to the bridge arm midpoint voltage synthesis vector; wherein, the corresponding transmission power is adjusted by adjusting the phase shift angle between the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit and the corresponding transformer primary winding voltage.

[0010] In one embodiment of the present invention, the corresponding transmission power is adjusted by regulating the phase shift angle between the voltage between the midpoints of the two fast bridge arms in each primary circuit unit and the corresponding transformer primary winding voltage. This includes: when the three-phase single-stage isolated bidirectional converter operates in rectification mode, controlling the voltage between the midpoints of the two fast bridge arms in each primary circuit unit to lead the corresponding transformer primary winding voltage; and when the three-phase single-stage isolated bidirectional converter operates in inverter mode, controlling the voltage between the midpoints of the two fast bridge arms in each primary circuit unit to lag the corresponding transformer primary winding voltage.

[0011] In one embodiment of the present invention, the frequency at which the fast-switching power semiconductor devices on each fast bridge arm of each primary-side circuit unit operate is the switching frequency of the three-phase single-stage isolated bidirectional converter, and the frequency at which the slow-switching power semiconductor devices on each slow bridge arm of each primary-side circuit unit operate is the frequency of the AC voltage.

[0012] The beneficial effects of this invention are:

[0013] 1. The secondary circuit unit of the present invention adopts the first to third fast bridge arms. The secondary windings of the first to third transformers are connected to the midpoint of the bridge arms of the first to third fast bridge arms in a star or delta connection manner, which reduces the power transistors and drive circuits, thereby saving costs and improving power density.

[0014] 2. This invention can adjust the transmitted power by adjusting the phase shift angle between the voltage between the midpoints of the two fast bridge arms of the primary circuit unit and the voltage of the primary winding of the transformer; by adjusting the duration of each mode of the secondary circuit unit in each switching cycle, the effective value of the power transistor and transformer current can be adjusted, the soft switching of the power semiconductor devices of the fast bridge arms of the primary and secondary circuits can be adjusted, efficiency can be optimized, and reactive power transmission and other functions can also be realized. Attached Figure Description

[0015] 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;

[0016] Figure 2 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;

[0017] Figure 3 This is a composite vector sector partitioning diagram corresponding to each switching state of the secondary circuit unit when the three secondary windings of the transformer are connected in a star configuration according to an embodiment of the present invention.

[0018] Figure 4 This is a composite vector sector partitioning diagram corresponding to the switching states of each secondary circuit unit when the three secondary windings of the transformer are connected in a delta configuration according to an embodiment of the present invention. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] like Figure 1 and 2 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.

[0022] The three-phase AC port 100 includes ports A1 to A6 (first to sixth phases); the DC voltage port includes port A7 (seventh phase) and port A8 (eighth phase). It should be noted that, as one possible implementation, the three-phase single-stage isolated bidirectional converter of this invention can adopt a three-phase four-wire wiring method, i.e., ports A1, A3, and A5 are connected, and ports A2, A4, and A6 are connected, as shown below. Figure 1 and 2 As shown; as another possible implementation, the three-phase single-stage isolated bidirectional converter of the present invention can also adopt a three-phase five-wire wiring method (not shown in the figure), that is, the first port A1, the third port A3, the fifth port A5, the second port A2, the fourth port A4, and the sixth port A6 are all connected, and the first to sixth ports A1~A6 are at the same potential. In other words, the three-phase single-stage isolated bidirectional converter of the present invention is suitable for both three-phase four-wire wiring methods and three-phase five-wire wiring methods.

[0023] The secondary circuit unit 900 includes first to third fast bridge arms 910-930, one end of which is connected to the seventh port A7, and the other end of which is connected to the eighth port A8; the secondary windings of the first to third transformers 600-800 are connected to the midpoint of the first to third fast bridge arms 910-930 in a star or delta connection. Figure 1 The diagram shows a star connection. Figure 2 (The diagram shows a triangular connection). 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. 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.

[0024] In one embodiment of the present invention, such as Figure 1 and 2As shown, the first primary-side circuit unit 300 includes a first coupling inductor 310, a fourth fast bridge arm 320, a fifth 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 fourth 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 fifth fast bridge arm 330, and the other end of the second winding is connected to the other end of the primary winding of the first transformer 600. The midpoint of the bridge arm of the first slow bridge arm 340 is connected to the second port A2. The second primary-side circuit unit 400 includes a second coupling inductor 410, a sixth fast bridge arm 420, a seventh 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 bridge arm of the sixth fast bridge arm 420. The other end of the third winding is connected to one end of the primary winding of the second transformer 700. One end of the fourth winding is connected to the midpoint of the seventh 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 bridge arm of the second slow bridge arm 440 is connected to the fourth port A4. The third primary circuit unit 500 includes a third coupling inductor 510, an eighth fast bridge arm 520, a ninth fast bridge arm 530, and a third slow bridge arm 540. 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 bridge arm of the eighth fast bridge arm 520. 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 bridge arm of the ninth fast bridge arm 530. 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 bridge arm of the third slow bridge arm 540 is connected to the sixth port A6.

[0025] In one embodiment of the present invention, the first to ninth fast bridge arms all include fast-switching power semiconductor devices, such as IGBTs and MOSFETs. These fast-switching power semiconductor devices are characterized by high switching frequencies (typically above kHz) and low switching losses (turn-on / turn-off losses), making them 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 are characterized by low switching frequencies (typically below kHz), relatively high switching losses, and low conduction losses (losses during conduction), making them suitable for high-current, low-frequency switching scenarios.

[0026] Therefore, the secondary circuit unit of the present invention adopts the first to third fast bridge arms, and the secondary windings of the first to third transformers are connected to the midpoint of the first to third fast bridge arms in a star or delta connection manner, which reduces the number of power transistors and drive circuits, thereby saving costs and increasing power density.

[0027] 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 first to third fast bridge arms, one end of each fast bridge arm being connected to the seventh port, and the other end being connected to the eighth port; the secondary windings of the first to third transformers are connected to the first to third fast bridge arms in a star or delta configuration. The bridge arm is located at the midpoint of the arm; wherein, 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 lowering costs and increasing power density.

[0028] 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.

[0029] 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 circuit unit to be 50%, the drive signals of the 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 circuit unit to be 50%, the drive signals of the slow-switching power semiconductor devices on the same slow bridge arm to be complementary; adjusting the switching time of the fast-switching power semiconductor devices on each fast bridge arm in the first to third primary circuit units according to the AC voltage; performing vector synthesis on the voltage between the midpoints of the two fast bridge arms in each primary circuit unit to generate a corresponding bridge arm midpoint voltage synthesis vector; controlling the switching time of the fast-switching power semiconductor devices on each fast bridge arm in the secondary circuit unit according to the bridge arm midpoint voltage synthesis vector; wherein, by adjusting the phase shift angle between the voltage between the midpoints of the two fast bridge arms in each primary circuit unit and the corresponding transformer primary winding voltage, the corresponding transmission power is adjusted.

[0030] Here, AC voltage refers to the input / output voltage of the three-phase AC port.

[0031] In one embodiment of the present invention, the frequency of operation of the fast-switching power semiconductor devices on each fast bridge arm in each primary-side circuit unit is the switching frequency of the three-phase single-stage isolated bidirectional converter, and the frequency of operation of the slow-switching power semiconductor devices on each slow bridge arm in each primary-side circuit unit is the frequency of the AC voltage.

[0032] Specifically, since the duty cycle of the fast-switching power semiconductor devices in the fast-bridge arms of the primary-side circuit unit is 50%, and the drive signals of the two fast-switching power semiconductor devices in the same fast-bridge arm are complementary—that is, the drive signal of the first fast-switching power semiconductor device in one fast-bridge arm is the same as the drive signal of the second fast-switching power semiconductor device in another fast-bridge arm, and vice versa—the bus capacitor voltage is twice the absolute value of the AC voltage.

[0033] ,

[0034] in, This represents the bus capacitor voltage of the three corresponding primary circuit units A, B, and C. This represents the AC voltage of the three corresponding primary circuit units A, B, and C.

[0035] Adjusting the switching timing of the fast-switching power semiconductor devices on each fast bridge arm of the first to third primary-side circuit units according to the AC voltage includes: when the AC voltage is greater than 0, adjusting the switching timing of the fast-switching power semiconductor devices on each fast bridge arm of the first to third primary-side circuit units such that, in the first half of the switching cycle, the voltage between the midpoints of the two fast bridge arms of the corresponding primary-side circuit unit is equal to the bus capacitor voltage, and in the second half of the switching cycle, the voltage between the midpoints of the two fast bridge arms of the corresponding primary-side circuit unit is equal to the negative of the bus capacitor voltage; when the AC voltage is less than 0, adjusting the switching timing of the fast-switching power semiconductor devices on each fast bridge arm of the first to third primary-side circuit units such that, in the first half of the switching cycle, the voltage between the midpoints of the two fast bridge arms of the corresponding primary-side circuit unit is equal to the negative of the bus capacitor voltage, and in the second half of the switching cycle, the voltage between the midpoints of the two fast bridge arms of the corresponding primary-side circuit unit is equal to the bus capacitor voltage.

[0036] ,

[0037] in, This represents the voltage between the midpoints of the two fast bridge arms of the three corresponding primary-side circuit units A, B, and C. Indicates the switching cycle.

[0038] In one embodiment of the present invention, the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit is vector-synthesized to generate a corresponding bridge arm midpoint voltage synthesis vector, and the switching timing of the fast-switching power semiconductor devices on each fast bridge arm in the secondary-side circuit unit is controlled according to the bridge arm midpoint voltage synthesis vector, specifically including the following steps:

[0039] Specifically, firstly, since the three-phase AC voltages are balanced, the sum of the voltages between the midpoints of the two fast bridge arms of the primary circuit units corresponding to A, B, and C is equal to 0, that is...

[0040] ,

[0041] The voltage between the midpoints of the two fast bridge arms of the three corresponding primary circuit units A, B, and C. , and Perform vector synthesis, that is

[0042] ,

[0043] Among them, the composite vector of voltages at the midpoint of the bridge arm Equal to the composite vector of AC voltages 2 times, that is

[0044] .

[0045] Secondly, the switching timing of the fast-switching power semiconductor devices on each fast bridge arm in the secondary circuit unit is controlled by the vector synthesis of the bridge arm midpoint voltage.

[0046] Specifically, the switching power semiconductor device above the first fast bridge arm 910 is defined as "S1=1", the switching power semiconductor device below the first fast bridge arm 910 is defined as "S1=0", the switching power semiconductor device above the second fast bridge arm 920 is defined as "S2=1", the switching power semiconductor device below the second fast bridge arm 920 is defined as "S2=0", the switching power semiconductor device above the third fast bridge arm 930 is defined as "S3=1", and the switching power semiconductor device below the third fast bridge arm 930 is defined as "S3=0". Therefore, the switching states of the secondary circuit unit can be represented by (S1 S2 S3), with a total of 8 switching states: (000), (001), (010), (011), (100), (101), (110), and (111).

[0047] For each switching state, the voltages of the corresponding three transformer secondary windings are vector-synthesized, and then multiplied by the ratio n of the number of turns in the transformer primary winding to the number of turns in the secondary winding to obtain the synthesized voltage vector referred to the transformer primary winding. When the three transformer secondary windings are star-connected to the midpoint of the three fast bridge arms of the secondary circuit, the synthesized vector corresponding to each switching state of the secondary circuit unit is:

[0048] ,

[0049] Therefore, as Figure 3 As shown, it can be divided into 6 sectors.

[0050] When the three transformer secondary windings are delta-connected to the midpoints of the three fast bridge arms of the secondary circuit, the composite vector corresponding to each switching state of the secondary circuit unit is:

[0051] ,

[0052] Therefore, as Figure 4 As shown, it can be divided into 6 sectors.

[0053] Based on the AC voltage composite vector The sector it occupies controls the switching state of the secondary circuit unit. When the secondary windings of the three transformers are connected in a star configuration to the midpoint of the three fast bridge arms of the secondary circuit unit, the secondary circuit unit has nine modes in each switching cycle. The switching states and durations of the nine modes are shown in the table below:

[0054]

[0055] When the secondary windings of three transformers are connected in a triangle to the midpoints of the three fast bridge arms of the secondary circuit unit, within each switching period, the secondary circuit unit has nine modes. The switching states and durations of the nine modes are shown in the following table:

[0056]

[0057] Taking improving efficiency or reactive power transmission, etc. as the optimization goal, adjust the durations of the nine modes, but they need to meet the following constraint regulations:

[0058] ,

[0059] Among them, represents the duration of each mode, d is a dimensionless coefficient, Ts is the switching period in seconds, and the range of all d is 0 < d < 1. The sum of all d of the nine modes is equal to 1. Given the synthesized vector V of the voltage at the midpoint of the primary bridge arm pri , through the vector synthesis of the voltages of the primary windings of the transformer, d1 and d2 can be calculated, and thus d0 can be known. According to the first three formulas of the above constraint conditions, there are still three degrees of freedom. By adjusting these three degrees of freedom, the effective value of the inductor current (or transformer current) can be adjusted, as well as the soft switching of the power semiconductor devices of the fast bridge arms of the primary circuit and the secondary circuit.

[0060] By adjusting the phase shift angle between the voltage between the midpoints of the two fast bridge arms of the primary circuit and the voltage of the primary winding of the transformer, the transmitted power can be adjusted. When operating in the rectification mode, the voltage between the midpoints of the two fast bridge arms of the primary circuit leads the voltage of the primary winding of the transformer. When operating in the inversion mode, the voltage between the midpoints of the two fast bridge arms of the primary circuit lags the voltage of the primary winding of the transformer.

[0061] Thus, by adjusting the phase shift angle between the voltage between the midpoints of the two fast bridge arms of the primary circuit unit and the voltage of the primary winding of the transformer, the transmitted power can be adjusted; by adjusting the durations of each mode of the secondary circuit unit within each switching period, the effective values of the power tubes and the transformer current can be adjusted, the efficiency can be optimized, and functions such as reactive power transmission can also be achieved.

[0062] 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%, the drive signals of the two fast-switching power semiconductor devices on the same fast bridge arm to be complementary, and controls 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. The switching times of the fast-switching power semiconductor devices on each fast bridge arm in the first to third primary-side circuit units are adjusted according to the AC voltage. The voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit is vector-synthesized to generate a corresponding bridge arm midpoint voltage synthesis vector. The switching times of the fast-switching power semiconductor devices on each fast bridge arm in the secondary-side circuit unit are controlled according to the bridge arm midpoint voltage synthesis vector. The corresponding transmission power is adjusted by regulating the phase shift angle between the voltage between the midpoints of the two fast bridge arms in each primary-side circuit unit and the corresponding transformer primary winding voltage. Therefore, by adjusting the phase shift angle between the voltage between the midpoints of the two fast bridge arms of the primary circuit unit and the voltage of the primary winding of the transformer, the transmitted power can be adjusted; by adjusting the duration of each mode of the secondary circuit unit within each switching cycle, the effective value of the power transistor and transformer current can be adjusted, efficiency can be optimized, and reactive power transmission function can also be realized.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 by, 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 to a third 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 to the midpoints of the first to third fast bridge arms in a star or delta configuration. The primary winding of the first transformer has both ends connected to the first primary circuit unit, and its center tap is connected to the first port. The primary winding of the second transformer has both ends connected to the second primary circuit unit, and its center tap is connected to the third port. The primary winding of the third transformer has both ends connected to the third primary circuit unit, and its center tap 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 fourth fast bridge arm, a fifth 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 fourth 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 fifth 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 second primary-side circuit unit includes a second coupling inductor, a sixth fast bridge arm, a seventh 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 sixth 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 seventh 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 third primary-side circuit unit includes a third coupling inductor, an eighth fast bridge arm, a ninth 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 eighth 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 ninth 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.

3. The three-phase single-stage isolated bidirectional converter according to claim 2, characterized in that, The first through ninth 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. The control method of the three-phase single-stage isolated bidirectional converter according to claim 4, characterized by, 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 switching timing of the fast-switching power semiconductor devices on each fast bridge arm in the first to third primary-side circuit units is adjusted according to the AC voltage. The voltages between the midpoints of the two fast bridge arms in each primary-side circuit unit are vector synthesized to generate the corresponding bridge arm midpoint voltage synthesis vector. The switching timing of the rapidly switching power semiconductor devices on each fast bridge arm in the secondary circuit unit is controlled based on the synthesized vector of the midpoint voltage of the bridge arm; wherein... The corresponding transmission power is adjusted by regulating the phase shift angle between the voltage between the midpoints of the two fast bridge arms in each primary circuit unit and the corresponding transformer primary winding voltage.

6. The control method of a three-phase single-stage isolated bidirectional converter according to claim 5, characterized by, The corresponding transmission power is adjusted by regulating the phase shift angle between the voltage between the midpoints of the two fast bridge arms in each primary circuit unit and the corresponding transformer primary winding voltage, including: 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 of the corresponding transformer primary winding. 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 transformer primary winding voltage.

7. The control method for a three-phase single-stage isolated bidirectional converter according to claim 6, characterized in that, The frequency at which the fast-switching power semiconductor devices on each fast bridge arm of each primary-side circuit unit operate is the switching frequency of the three-phase single-stage isolated bidirectional converter, and the frequency at which the slow-switching power semiconductor devices on each slow bridge arm of each primary-side circuit unit operate is the frequency of the AC voltage.

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