A three-phase bidirectional dc-dc power converter

Abstract

The three-phase bidirectional DC-DC power converter of the present application comprises a primary side switching network, a resonant network and a secondary side switching network connected in sequence. The resonant network comprises a transformer module, a first primary side resonant unit, a second primary side resonant unit, a first secondary side resonant unit and a second secondary side resonant unit, and any two phases of the three-phase bidirectional DC-DC power converter are provided with resonant units; the other phase is not provided with a resonant unit. When power is transmitted from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the secondary side switching network is used for synchronous rectification control; the primary side switching network can work near the series resonant frequency. The present application greatly reduces the number of resonant devices of the primary and secondary sides, is conducive to reducing the design cost and improving the power density; while realizing bidirectional DC-DC conversion, the transmission efficiency can be greatly improved, and the primary side switching network realizes zero voltage turn-on and the secondary side switching network realizes zero current turn-off.

Description

Technical Field

[0001] This invention relates to the field of electronic power, and more specifically, to a three-phase bidirectional DC-DC power converter. Background Technology

[0002] With the continuous increase in electric vehicle battery capacity and users' urgent demand for fast charging, the power levels of charging modules are constantly expanding. In the context of high-power charging, the topology of charging modules is becoming increasingly complex, and the required design costs are gradually increasing, which undoubtedly increases the R&D costs for companies. To ensure high efficiency, high-power bidirectional power modules often adopt the CLLLC resonant converter topology. However, the primary and secondary sides of this CLLLC resonant converter contain a large number of resonant devices, resulting in a complex topology, large overall size, which is not conducive to improving the power density of high-power power converters and incurs significant design costs. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a three-phase bidirectional DC-DC power converter that can reduce the number of resonant devices on the primary and secondary sides, reduce the overall size, and improve power density and transmission efficiency, in order to address the above-mentioned deficiencies of the prior art.

[0004] The technical solution adopted by the present invention to solve its technical problem is: to construct a three-phase bidirectional DC-DC power converter, including a primary-side switching network, a resonant network and a secondary-side switching network connected in sequence, wherein the resonant network includes a transformer module, a first primary-side resonant unit, a second primary-side resonant unit, a first secondary-side resonant unit and a second secondary-side resonant unit; The input terminal of the primary-side switching network is connected to the first power supply. The first output terminal of the primary-side switching network is connected to the first terminal of the primary winding of the transformer module via the first primary-side resonant unit. The second output terminal of the primary-side switching network is connected to the second terminal of the primary winding of the transformer module. The third output terminal of the primary-side switching network is connected to the third terminal of the primary winding of the transformer module via the second primary-side resonant unit. The first end of the secondary winding of the transformer module is connected to the first input terminal of the secondary-side switching network via the first secondary-side resonant unit; the second end of the secondary winding of the transformer module is connected to the second input terminal of the secondary-side switching network; and the third end of the secondary winding of the transformer module is connected to the third input terminal of the secondary-side switching network via the second secondary-side resonant unit. The output terminal of the secondary-side switching network is connected to a second power supply. When power is transmitted from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the secondary side switching network is used for synchronous rectification control; when power is transmitted from the secondary side to the primary side of the three-phase bidirectional DC-DC power converter, the primary side switching network is used for synchronous rectification control; the primary side switching network can operate near the series resonant frequency, which is the resonant frequency of the resonant unit.

[0005] In the three-phase bidirectional DC-DC power converter of the present invention, the first primary resonant unit, the second primary resonant unit, the first secondary resonant unit and the second secondary resonant unit respectively include a resonant capacitor and a resonant inductor connected in series.

[0006] In the three-phase bidirectional DC-DC power converter of the present invention, the transformer module includes a first transformer, a second transformer, a third transformer, a first magnetizing inductor, a second magnetizing inductor, and a third magnetizing inductor. The same-name terminal of the primary winding of the first transformer is the first terminal of the primary winding of the transformer module, the same-name terminal of the primary winding of the second transformer is the second terminal of the primary winding of the transformer module, and the same-name terminal of the primary winding of the third transformer is the third terminal of the primary winding of the transformer module. The opposite-name terminals of the primary windings of the first transformer, the opposite-name terminals of the primary windings of the second transformer, and the opposite-name terminals of the primary windings of the third transformer are connected to each other. The same-name terminal of the secondary winding of the first transformer is the first terminal of the secondary winding of the transformer module, the same-name terminal of the secondary winding of the second transformer is the second terminal of the secondary winding of the transformer module, and the same-name terminal of the secondary winding of the third transformer is the third terminal of the secondary winding of the transformer module. The opposite-name terminals of the secondary windings of the first transformer, the opposite-name terminals of the secondary windings of the second transformer, and the opposite-name terminals of the secondary windings of the third transformer are connected to each other. The first magnetizing inductance is the inductance between the same-named and opposite-named terminals of the primary winding of the first transformer, the second magnetizing inductance is the inductance between the same-named and opposite-named terminals of the primary winding of the second transformer, and the third magnetizing inductance is the inductance between the same-named and opposite-named terminals of the primary winding of the third transformer.

[0007] In the three-phase bidirectional DC-DC power converter of the present invention, the primary-side switching network includes a first primary-side switch, a second primary-side switch, a third primary-side switch, a fourth primary-side switch, a fifth primary-side switch, and a sixth primary-side switch. The first primary-side switch and the second primary-side switch form a first switch bridge arm, the third primary-side switch and the fourth primary-side switch form a second switch bridge arm, and the fifth primary-side switch and the sixth primary-side switch form a third switch bridge arm. The control signals between the first switch bridge arm, the second switch bridge arm, and the third switch bridge arm are sequentially 120° out of phase.

[0008] In the three-phase bidirectional DC-DC power converter of the present invention, the control terminals of the first primary-side switch, the second primary-side switch, the third primary-side switch, the fourth primary-side switch, the fifth primary-side switch and the sixth primary-side switch receive control signals; The first end of the first primary-side switch is connected to the second end of the second primary-side switch and serves as the first output terminal of the primary-side switching network; the first end of the third primary-side switch is connected to the second end of the fourth primary-side switch and serves as the second output terminal of the primary-side switching network; the first end of the fifth primary-side switch is connected to the second end of the sixth primary-side switch and serves as the third output terminal of the primary-side switching network; the second end of the first primary-side switch is connected to the second ends of the third and fifth primary-side switches and serves as the first input terminal of the primary-side switching network; the first end of the second primary-side switch is connected to the first ends of the fourth and sixth primary-side switches and serves as the second input terminal of the primary-side switching network. The first input terminal of the primary side-side switching network is connected to the positive terminal of the first power supply, and the second input terminal of the primary side-side switching network is connected to the negative terminal of the first power supply. The control signals of the first primary-side switch and the second primary-side switch are complementary; the control signals of the third primary-side switch and the fourth primary-side switch are complementary; and the control signals of the fifth primary-side switch and the sixth primary-side switch are complementary.

[0009] In the three-phase bidirectional DC-DC power converter of the present invention, the secondary-side switching network includes a first secondary-side switch, a second secondary-side switch, a third secondary-side switch, a fourth secondary-side switch, a fifth secondary-side switch, and a sixth secondary-side switch. The first and second secondary-side switching transistors form a first-path switching transistor bridge arm, the third and fourth secondary-side switching transistors form a second-path switching transistor bridge arm, and the fifth and sixth secondary-side switching transistors form a third-path switching transistor bridge arm.

[0010] In the three-phase bidirectional DC-DC power converter of the present invention, the control terminals of the first secondary-side switch, the second secondary-side switch, the third secondary-side switch, the fourth secondary-side switch, the fifth secondary-side switch and the sixth secondary-side switch receive control signals; The first end of the first secondary-side switch is connected to the second end of the second secondary-side switch and serves as the first input terminal of the secondary-side switch network; the first end of the third secondary-side switch is connected to the second end of the fourth secondary-side switch and serves as the second input terminal of the secondary-side switch network; the first end of the fifth secondary-side switch is connected to the second end of the sixth secondary-side switch and serves as the third input terminal of the secondary-side switch network; the second end of the first secondary-side switch is connected to the second ends of the third and fifth secondary-side switches and serves as the first output terminal of the secondary-side switch network; the first end of the second secondary-side switch is connected to the first ends of the fourth and sixth secondary-side switches and serves as the second output terminal of the secondary-side switch network. The first output terminal of the secondary-side switching network is connected to the positive terminal of the second power supply, and the second output terminal of the secondary-side switching network is connected to the negative terminal of the second power supply. When the control signals of the first secondary-side switch, the second secondary-side switch, the third secondary-side switch, the fourth secondary-side switch, the fifth secondary-side switch, and the sixth secondary-side switch are 0, uncontrolled rectification is performed through the body diodes of the first secondary-side switch, the second secondary-side switch, the third secondary-side switch, the fourth secondary-side switch, the fifth secondary-side switch, and the sixth secondary-side switch.

[0011] The three-phase bidirectional DC-DC power converter of the present invention further includes a primary-side filter capacitor and / or a secondary-side filter capacitor. The first end of the primary-side filter capacitor is connected to the positive terminal of the first power supply, and the second end is connected to the negative terminal of the first power supply. The first end of the secondary filter capacitor is connected to the positive terminal of the second power supply, and the second end is connected to the negative terminal of the second power supply.

[0012] In the three-phase bidirectional DC-DC power converter of the present invention, the first primary-side switch, the second primary-side switch, the third primary-side switch, the fourth primary-side switch, the fifth primary-side switch and the sixth primary-side switch respectively include MOSFET, IGBT and transistor.

[0013] In the three-phase bidirectional DC-DC power converter of the present invention, the first secondary-side switch, the second secondary-side switch, the third secondary-side switch, the fourth secondary-side switch, the fifth secondary-side switch and the sixth secondary-side switch respectively include MOSFET, IGBT and transistor.

[0014] The three-phase bidirectional DC-DC power converter of the present invention includes a primary-side switching network, a resonant network, and a secondary-side switching network connected in sequence. The resonant network includes a transformer module, a first primary-side resonant unit, a second primary-side resonant unit, a first secondary-side resonant unit, and a second secondary-side resonant unit. Resonant units are provided in any two phases of the three-phase bidirectional DC-DC power converter; no resonant unit is provided in the other phase. Therefore, compared with the prior art, at least one primary-side resonant unit and one secondary-side resonant unit are reduced, thus significantly reducing the number of resonant devices on the primary and secondary sides. Simultaneously, when power is transmitted from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the secondary-side switching network is used for synchronous rectification control; when power is transmitted from the secondary side to the primary side of the three-phase bidirectional DC-DC power converter, the primary-side switching network is used for synchronous rectification control; the primary-side switching network can operate near the series resonant frequency, which is the resonant frequency of the resonant unit. Therefore, while realizing bidirectional DC-DC conversion, the transmission efficiency can be greatly improved, and zero-voltage conduction of the primary-side switching network and zero-current turn-off of the secondary-side switching network can be achieved. This ensures high efficiency, increases power density, and helps reduce design costs. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a schematic block diagram of a preferred embodiment of the three-phase bidirectional DC-DC power converter of the present invention; Figure 2 This is a circuit diagram of a preferred embodiment of the three-phase bidirectional DC-DC power converter of the present invention; Figure 3 yes Figure 2 The timing diagram shown is for the operation of a three-phase bidirectional DC-DC power converter. Figures 4A-4F yes Figure 2 The equivalent circuit diagram of the three-phase bidirectional DC-DC power converter at different operating times is shown. Figure 5 yes Figure 2 The ZVS waveform diagrams of the upper and lower switches of the same switch bridge arm in the primary-side switching network of the three-phase bidirectional DC-DC power converter are shown. Figure 6 yes Figure 2 The diagram shows the three-phase resonant current waveform on one side of the primary winding of the transformer module of the three-phase bidirectional DC-DC power converter. Figure 7 yes Figure 2 The diagram shows the three-phase resonant current waveform on one side of the secondary winding of the transformer module of the three-phase bidirectional DC-DC power converter. Figure 8 yes Figure 2 The diagram shows the ZCS waveforms of the upper and lower switches of the same switching arm in the secondary-side switching network of a three-phase bidirectional DC-DC power converter. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] Figure 1 This is a schematic block diagram of a preferred embodiment of the three-phase bidirectional DC-DC power converter of the present invention. Figure 1As shown, the three-phase bidirectional DC-DC power converter of the present invention includes a primary-side switching network 100, a resonant network 200, and a secondary-side switching network 300 connected in sequence. The resonant network 200 consists of a transformer module 210, a first primary-side resonant unit 220, a second primary-side resonant unit 230, a first secondary-side resonant unit 240, and a second secondary-side resonant unit 250; any two phases of the three-phase bidirectional DC-DC power converter are provided with resonant units; the other phase of the three-phase bidirectional DC-DC power converter is not provided with a resonant unit. The input terminal of the primary-side switching network 100 is connected to the first power supply V1. The first output terminal A of the primary-side switching network 100 is connected to the first terminal of the primary winding of the transformer module 210 via the first primary-side resonant unit 220. The second output terminal B of the primary-side switching network 100 is connected to the second terminal of the primary winding of the transformer module 210. The third output terminal C of the primary-side switching network 100 is connected to the third terminal of the primary winding of the transformer module 210 via the second primary-side resonant unit 230. The first terminal of the secondary winding of the transformer module 210 is connected to the first input terminal X of the secondary-side switching network 300 via the first secondary-side resonant unit 240. The second terminal of the secondary winding of the transformer module 210 is connected to... The second input terminal Y of the secondary-side switching network 300 is connected to the third input terminal Z of the secondary-side switching network 300 via the second secondary-side resonant unit 250; the output terminal of the secondary-side switching network 300 is connected to the second power supply V2; when power is transmitted from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the secondary-side switching network 300 is used for synchronous rectification control; when power is transmitted from the secondary side to the primary side of the three-phase bidirectional DC-DC power converter, the primary-side switching network 100 is used for synchronous rectification control; the primary-side switching network 100 can operate near the series resonant frequency, which is the resonant frequency of the resonant unit.

[0018] In this invention, the first output terminal A of the primary-side switching network 100 can be any one of the three phases, while the second output terminal B and the third output terminal C can be the other two phases. Similarly, the first input terminal X of the secondary-side switching network 300 can also be any one of the three phases, while the second input terminal Y and the third input terminal Z can be the other two phases. Therefore, it can be understood that the first primary-side resonant unit 220 and the second primary-side resonant unit 230 can be connected to any two phases of the three phases of the primary-side switching network 100, and the first secondary-side resonant unit 240 and the second secondary-side resonant unit 250 can be connected to any two phases of the three phases of the secondary-side switching network 300. The transformer module can be connected to the remaining phase. These connections all fall within the protection scope of this invention. Therefore, it can be understood that in the three-phase bidirectional DC-DC power converter of this invention, primary-side resonant units are provided on the primary side of any two phases, while no primary-side resonant unit is provided on the other phase, and secondary-side resonant units are provided on the secondary side of any two phases, while no secondary-side resonant unit is provided on the other phase.

[0019] The three-phase bidirectional DC-DC power converter of the present invention includes a primary-side switching network, a resonant network, and a secondary-side switching network connected in sequence. The resonant network includes a transformer module, a first primary-side resonant unit, a second primary-side resonant unit, a first secondary-side resonant unit, and a second secondary-side resonant unit. Therefore, compared with the prior art, it reduces at least one primary-side resonant unit and one secondary-side resonant unit, thus greatly reducing the number of resonant devices on the primary and secondary sides, which is beneficial for reducing design costs and improving power density. Simultaneously, when power is transmitted from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the secondary-side switching network is used for synchronous rectification control; when power is transmitted from the secondary side to the primary side of the three-phase bidirectional DC-DC power converter, the primary-side switching network is used for synchronous rectification control. The primary-side switching network can operate near the series resonant frequency, which is the resonant frequency of the resonant unit. Therefore, while realizing bidirectional DC-DC conversion, it can significantly improve transmission efficiency and achieve zero-voltage turn-on of the primary-side switching network and zero-current turn-off of the secondary-side switching network. As those skilled in the art will understand, operating near the series resonant frequency means that the three-phase bidirectional DC-DC power converter operates normally and stably within a certain bandwidth centered on the series resonant frequency.

[0020] Figure 2 This is a circuit diagram of a preferred embodiment of the three-phase bidirectional DC-DC power converter of the present invention. (In conjunction with...) Figures 1-2As can be seen, the three-phase bidirectional DC-DC power converter of the present invention includes a primary-side switching network 100, a resonant network 200, and a secondary-side switching network 300 connected in sequence. The resonant network 200 consists of a transformer module 210, a first primary-side resonant unit 220, a second primary-side resonant unit 230, a first secondary-side resonant unit 240, and a second secondary-side resonant unit 250; the first primary-side resonant unit 220, the second primary-side resonant unit 230, the first secondary-side resonant unit 240, and the second secondary-side resonant unit 250 each include a resonant capacitor Cr and a resonant inductor Lr connected in series. The transformer module 210 includes a first transformer T1, a second transformer T2, a third transformer T3, a first magnetizing inductor Lm1, a second magnetizing inductor Lm2, and a third magnetizing inductor Lm3; the primary-side switching network 100 includes a first primary-side switch S1, a second primary-side switch S2, a third primary-side switch S3, a fourth primary-side switch S4, a fifth primary-side switch S5, and a sixth primary-side switch S6. The secondary-side switch network 300 includes a first secondary-side switch S7, a second secondary-side switch S8, a third secondary-side switch S9, a fourth secondary-side switch S10, a fifth secondary-side switch S11, and a sixth secondary-side switch S12.

[0021] Further as Figure 2 As shown, the same-name terminal of the primary winding of the first transformer T1 is the first terminal of the primary winding of the transformer module 210; the same-name terminal of the primary winding of the second transformer T2 is the second terminal of the primary winding of the transformer module 210; and the same-name terminal of the primary winding of the third transformer T3 is the third terminal of the primary winding of the transformer module 210. The opposite-name terminals of the primary windings of the first transformer T1, the second transformer T2, and the third transformer T3 are connected to each other. The same-name terminal of the secondary winding of the first transformer T1 is the first terminal of the secondary winding of the transformer module 210; and the same-name terminal of the secondary winding of the second transformer T2 is... The second end of the secondary winding of the transformer module 210, the same-name end of the secondary winding of the third transformer T3 is the third end of the secondary winding of the transformer module 210, the opposite-name ends of the secondary windings of the first transformer T1, the opposite-name ends of the secondary windings of the second transformer T2 and the opposite-name ends of the secondary windings of the third transformer T3 are connected to each other; the first magnetizing inductance Lm1 is the inductance between the same-name end and the opposite-name end of the primary winding of the first transformer T1, the second magnetizing inductance Lm2 is the inductance between the same-name end and the opposite-name end of the primary winding of the second transformer T2, and the third magnetizing inductance Lm3 is the inductance between the same-name end and the opposite-name end of the primary winding of the third transformer T3.

[0022] Further as Figure 2As shown, the first primary-side switch S1 and the second primary-side switch S2 constitute the first switch bridge arm, the third primary-side switch S3 and the fourth primary-side switch S4 constitute the second switch bridge arm, and the fifth primary-side switch S5 and the sixth primary-side switch S6 constitute the third switch bridge arm. The control signals between the first switch bridge arm, the second switch bridge arm, and the third switch bridge arm are sequentially phased by 120°. The control terminals of the first primary-side switch S1, the second primary-side switch S2, the third primary-side switch S3, the fourth primary-side switch S4, the fifth primary-side switch S5, and the sixth primary-side switch S6 respectively receive the control signals. The first end of the first primary-side switch S1 is connected to the second end of the second primary-side switch S2 and serves as the first output terminal A of the primary-side switch network 100. The first end of the third primary-side switch S3 is connected to the second end of the fourth primary-side switch S4 and serves as the second output terminal B of the primary-side switch network 100. The first end of the fifth primary-side switch S5 is connected to the second end of the sixth primary-side switch S6 and serves as the third output terminal C of the primary-side switch network 100. The second end of the first primary-side switch S1 is connected to the second ends of the third primary-side switch S3 and the fifth primary-side switch S5 and serves as the first input terminal of the primary-side switch network 100. The first end of the second primary-side switch S2 is connected to the first ends of the fourth primary-side switch S4 and the sixth primary-side switch S6 and serves as the second input terminal of the primary-side switch network 100. The first input terminal of the primary-side switch network 100 is connected to the positive terminal of the first power supply V1, and the second input terminal of the primary-side switch network 100 is connected to the negative terminal of the first power supply V1. A first primary-side resonant unit 220, consisting of a resonant capacitor Cr and a resonant inductor Lr, is connected between the first output terminal A of the primary-side switching network 100 and the corresponding terminal of the primary winding of the first transformer T1. A second primary-side resonant unit 230, consisting of a resonant capacitor Cr and a resonant inductor Lr, is connected between the third output terminal C of the primary-side switching network 100 and the corresponding terminal of the primary winding of the third transformer T3. The second output terminal B of the primary-side switching network 100 is directly connected to the corresponding terminal of the primary winding of the second transformer T2. The control signals of the first primary-side switch S1 and the second primary-side switch S2 are complementary; the control signals of the third primary-side switch S3 and the fourth primary-side switch S4 are complementary; and the control signals of the fifth primary-side switch S5 and the sixth primary-side switch S6 are complementary.

[0023] Further as Figure 2As shown, the first secondary-side switch S7 and the second secondary-side switch S8 form a first switch bridge arm, the third secondary-side switch S9 and the fourth secondary-side switch S10 form a second switch bridge arm, and the fifth secondary-side switch S11 and the sixth secondary-side switch S12 form a third switch bridge arm. The control terminals of the first secondary-side switch S7, the second secondary-side switch S8, the third secondary-side switch S9, the fourth secondary-side switch S10, the fifth secondary-side switch S11, and the sixth secondary-side switch S12 receive control signals. The first terminal of the first secondary-side switch S7 is connected to the second terminal of the second secondary-side switch S8 and serves as the first input terminal X of the secondary-side switch network 300; the first terminal of the third secondary-side switch S9 is connected to the second terminal of the fourth secondary-side switch S10 and serves as the second input terminal Y of the secondary-side switch network 300; and the first terminal of the fifth secondary-side switch S11 is connected to the second terminal of the sixth secondary-side switch S12. The first secondary-side switch S7 is connected to the second terminals of the third secondary-side switch S9 and the fifth secondary-side switch S11, serving as the first output terminal of the secondary-side switch network 300. The first terminal of the second secondary-side switch S8 is connected to the first terminals of the fourth secondary-side switch S10 and the sixth secondary-side switch S12, serving as the second output terminal of the secondary-side switch network 300. The first output terminal of the secondary-side switch network 300 is connected to the positive terminal of the second power supply V2, and the second output terminal of the secondary-side switch network 300 is connected to the negative terminal of the second power supply V2. A first secondary-side resonant unit 240, consisting of a resonant capacitor Cr and a resonant inductor Lr, is connected between the corresponding terminal of the secondary winding of the first transformer T1 and the first input terminal X of the secondary-side switch network 300. A second secondary resonant unit 250, consisting of a resonant capacitor Cr and a resonant inductor Lr, is connected between the corresponding terminal of the secondary winding of the third transformer T3 and the third input terminal Z of the secondary-side switching network 300. The corresponding terminal of the secondary winding of the second transformer T2 is connected to the second input terminal Y of the secondary-side switching network 300.

[0024] When the control signals of the first secondary-side switch S7, the second secondary-side switch S8, the third secondary-side switch S9, the fourth secondary-side switch S10, the fifth secondary-side switch S11, and the sixth secondary-side switch S12 are 0, uncontrolled rectification is performed through the body diodes of the first secondary-side switch S7, the second secondary-side switch S8, the third secondary-side switch S9, the fourth secondary-side switch S10, the fifth secondary-side switch S11, and the sixth secondary-side switch S12.

[0025] exist Figure 2In the preferred embodiment shown, the three-phase bidirectional DC-DC power converter further includes a primary-side filter capacitor C1 and a secondary-side filter capacitor C2; the first end of the primary-side filter capacitor C1 is connected to the positive terminal of the first power supply V1, and the second end is connected to the negative terminal of the first power supply V1; the first end of the secondary-side filter capacitor C2 is connected to the positive terminal of the second power supply V2, and the second end is connected to the negative terminal of the second power supply V2.

[0026] exist Figure 2 In the preferred embodiment shown, the first primary-side switch S1, the second primary-side switch S2, the third primary-side switch S3, the fourth primary-side switch S4, the fifth primary-side switch S5, the sixth primary-side switch S6, the first secondary-side switch S7, the second secondary-side switch S8, the third secondary-side switch S9, the fourth secondary-side switch S10, the fifth secondary-side switch S11, and the sixth secondary-side switch S12 are all MOSFETs, with their control terminal being the gate of the MOSFET, their first terminal being the source of the MOSFET, and their second terminal being the drain of the MOSFET. In other preferred embodiments of the present invention, IGBTs or transistors may be used instead of MOSFETs, and these all fall within the protection scope of the present invention.

[0027] In this invention, four sets of resonant capacitors Cr and resonant inductors Lr are used to form a first primary-side resonant unit, a second primary-side resonant unit, a first secondary-side resonant unit, and a second secondary-side resonant unit, respectively. Therefore, the resonant network of this invention only includes two primary-side resonant units and two secondary-side resonant units, thereby reducing the number of resonant capacitors and resonant inductors in the three-phase resonant network, realizing bidirectional power conversion of the three-phase resonant converter, significantly reducing the topological complexity and design cost of existing technical solutions, and improving overall efficiency and power density. Simultaneously, when power is transmitted from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the secondary-side switching network is used for synchronous rectification control to reduce synchronous rectification losses; when power is transmitted from the secondary side to the primary side of the three-phase bidirectional DC-DC power converter, the primary-side switching network is used for synchronous rectification control to reduce synchronous rectification losses; the primary-side switching network can operate near the series resonant frequency, which is the resonant frequency of the resonant unit (i.e., the self-resonant series resonant frequency of the resonant inductor Lr and the resonant capacitor Cr). Therefore, while realizing bidirectional DC-DC conversion, the transmission efficiency can be greatly improved, and zero-voltage turn-on of the primary-side switching network and zero-current turn-off of the secondary-side switching network can be achieved. Therefore, the three-phase bidirectional DC-DC power converter of the present invention significantly reduces the complexity of the topology of high-power DC-DC power converters, reduces the number of resonant inductors and capacitors on the primary and secondary sides, which helps to reduce design costs and improve the power density of the power system; it can realize bidirectional power conversion and has a wide range of application scenarios; the switching transistors of the primary-side switching network can operate at the resonant frequency point, and the switching transistors of the secondary-side switching network can be used for synchronous rectification control, which greatly improves transmission efficiency; it has the soft-switching characteristics of LLC resonant converters, the switching transistors of the primary-side switching network can achieve zero-voltage conduction, and the switching transistors of the secondary-side switching network (used as rectifiers) can achieve zero-current turn-off, resulting in better EMC performance.

[0028] Figure 3 yes Figure 2 The timing diagram shown is for the operation of a three-phase bidirectional DC-DC power converter. Figures 4A-4F yes Figure 2 The equivalent circuit diagram of the three-phase bidirectional DC-DC power converter at different operating times is shown. Figure 5 yes Figure 2 The ZVS waveform diagrams of the upper and lower switches of the same switch bridge arm in the primary-side switching network of the three-phase bidirectional DC-DC power converter are shown. Figure 6 yes Figure 2 The diagram shows the three-phase resonant current waveform on one side of the primary winding of the transformer module of the three-phase bidirectional DC-DC power converter. Figure 7 yes Figure 2The diagram shows the three-phase resonant current waveform on one side of the secondary winding of the transformer module of the three-phase bidirectional DC-DC power converter. Figure 8 yes Figure 2 The diagram shows the ZCS waveforms of the upper and lower switches of the same switching bridge arm in the secondary-side switching network of a three-phase bidirectional DC-DC power converter. The following will combine... Figures 2-8 The working principle, process, and effects of the three-phase bidirectional DC-DC power converter of the present invention are described in detail below. The three-phase bidirectional DC-DC power converter of the present invention employs a three-phase interleaved 120° control strategy for the primary-side and secondary-side switching networks. When power is transmitted from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the primary-side switching network acts as a three-phase inverter bridge. The phases (i.e., the drive pulse phases) of the control signals of the switching transistors in each bridge arm differ by 120° sequentially. The upper and lower switching transistors of the same bridge arm are complementary in conduction, with duty cycles of 50% (ignoring dead time). That is... Figure 2 As shown, the first primary-side switch S1 and the second primary-side switch S2 form the first switch bridge arm, the third primary-side switch S3 and the fourth primary-side switch S4 form the second switch bridge arm, and the fifth primary-side switch S5 and the sixth primary-side switch S6 form the third switch bridge arm. The control signals between the first, second, and third switch bridge arms are sequentially phased by 120°. The control signals of the first primary-side switch S1 and the second primary-side switch S2 are complementary; the control signals of the third primary-side switch S3 and the fourth primary-side switch S4 are complementary; and the control signals of the fifth primary-side switch S5 and the sixth primary-side switch S6 are complementary. The switches in the secondary-side switching network (i.e., the first secondary-side switch S7, the second secondary-side switch S8, the third secondary-side switch S9, the fourth secondary-side switch S10, the fifth secondary-side switch S11, and the sixth secondary-side switch S12) are synchronously rectified to reduce rectification losses. When the control signal of the switching transistors in the secondary-side switching network is 0 (i.e., no drive signal input) and no control is performed, the current undergoes uncontrolled rectification through the body diodes of the first secondary-side switching transistor S7, the second secondary-side switching transistor S8, the third secondary-side switching transistor S9, the fourth secondary-side switching transistor S10, the fifth secondary-side switching transistor S11, and the sixth secondary-side switching transistor S12. By adopting a complementary drive control strategy with 120° staggered operation, the output current ripple can be effectively reduced, thereby optimizing the design of the filter capacitor and improving reliability and system lifespan.

[0029] The primary-side switching network 100 can operate near the series resonant frequency, which is the resonant frequency of the resonant unit, achieving high-efficiency bidirectional power transmission. At this time, the drive signals of the primary-side switches are essentially the same as the drive signals of the secondary-side synchronous rectifier switches; that is, the control signals of the first primary-side switch S1, the second primary-side switch S2, the third primary-side switch S3, the fourth primary-side switch S4, the fifth primary-side switch S5, and the sixth primary-side switch S6 are the same as the control signals of the first secondary-side switch S7, the second secondary-side switch S8, the third secondary-side switch S9, the fourth secondary-side switch S10, the fifth secondary-side switch S11, and the sixth secondary-side switch S12. The specific operating mode, waveform, and equivalent circuit within one switching cycle are as follows: Figures 3-8 Since the bidirectional power supply structure described in this application is symmetrical, the analysis of the operating mode will be based on forward power transmission as an example.

[0030] exist Figure 3 In the diagram, Vgs1-Vgs12 represent the switching transistors S1-S2. 12 The drive control signal; i Lr1 i Lr2 i Lr3 These represent the three-phase resonant currents on the primary side of the transformer module; i Lr11 i Lr22 i Lr33 These represent the three-phase resonant currents on the secondary side of the transformer module; i s7 -i s12 These represent the secondary-side switching transistors S7-S1 that flow through the secondary-side switching network 300 on the secondary side. 12 The current at this time, the secondary switch S7-S 12 In synchronous rectification mode. iso is the total output current of the secondary rectifier bridge. In one switching cycle (t0-t... 12 In this analysis, since the working modes within the positive and negative half-cycles are symmetrical, only the working mode of the positive half-cycle (t0-t6) is analyzed, while the working mode of the negative half-cycle (t6-t...) is not analyzed. 12 This can be analyzed by analogy.

[0031] Figure 4A The equivalent circuit diagram of a three-phase bidirectional DC-DC power converter in the first operating mode (i.e., operating time t0-t1) is shown. Figure 4AAs shown, at time t0, the first primary-side switch S1 achieves zero-voltage conduction with no turn-on loss. The first secondary-side switch S7 begins to conduct, and current flows through it, reducing rectification losses. After time t0, the first primary-side switch S1, the fourth primary-side switch S4, and the fifth primary-side switch S5 of the three-phase inverter bridge arm are in the conducting state. The resonant capacitor and resonant inductor of the primary-secondary resonant branch in phase A resonate in series, and the resonant capacitor and resonant inductor of the primary-secondary resonant branch in phase C form a series resonance. The resonant current of the primary and secondary sides varies sinusoidally. Since the primary and secondary sides of the three-phase transformer are connected in a star configuration, the resonant current of phase A is... i Lr1 The current direction is positive, the C-phase resonant current direction is positive, the sum of the A-phase and C-phase resonant currents equals the B-phase current, and the B-phase resonant current... i Lr2 The direction is negative. The resonant current of each phase transfers energy to the output side through the transformer. At this time, the secondary side switching network acts as a three-phase rectifier bridge. Its first secondary side switch S7, fourth secondary side switch S10, and fifth secondary side switch S11 are in the conducting state as synchronous rectifier tubes, and the sum of the currents flowing through the first secondary side switch S7 and the fifth secondary side switch S11 is equal to the current flowing through the fourth secondary side switch S10.

[0032] Figure 4B The equivalent circuit diagram of a three-phase bidirectional DC-DC power converter in the second operating mode (i.e., operating time t1-t2) is shown. Figure 4B As shown, at time t1, the fifth primary-side switch S5 is off, and the three-phase bidirectional DC-DC power converter is in the dead time of the fifth primary-side switch S5 and the sixth primary-side switch S6. The fifth secondary-side switch S11 is also off. The C-phase resonant current... i Lr3 The parasitic junction capacitances of the fifth primary-side switch S5 and the sixth primary-side switch S6 are charged and discharged respectively until the drain-source voltage of the fifth primary-side switch S5 rises to the input voltage level, and the drain-source voltage of the sixth primary-side switch S6 drops to 0. At time t2, the sixth primary-side switch S6 achieves zero-voltage turn-on. The resonant current of phase C is equal to the excitation current, and the current flowing through the fifth secondary-side switch S11 naturally decreases to 0, achieving zero-current turn-off. Phases A and B simultaneously transfer energy to the load side, and the secondary-side current flows through the first secondary-side switch S7 and the fourth secondary-side switch S10.

[0033] Figure 4C The equivalent circuit diagram of a three-phase bidirectional DC-DC power converter in the third operating mode (i.e., operating time t2-t3) is shown. Figure 4CAs shown, at time t2, after the sixth primary-side switch S6 turns on, the first primary-side switch S1, the fourth primary-side switch S4, and the sixth primary-side switch S6 are all in the conducting state. The sixth secondary-side switch S12 also begins to conduct. Under the action of series resonance, the resonant currents of phases A and C change sinusoidally. The resonant current of phase C begins to commutate, changing from a positive current to a negative current, while the resonant current of phase A... i Lr1 Resonant current with phase C i Lr3 The difference current is equal to the B-phase resonant current, therefore the B-phase resonant current... i Lr2 It also changes in a sinusoidal form. The first secondary-side switch S7, the fourth secondary-side switch S10, and the sixth secondary-side switch S12 are in the on state, and the sum of the currents flowing through the fourth secondary-side switch S10 and the sixth secondary-side switch S12 is equal to the current flowing through the first secondary-side switch S7. Until time t3, the fourth primary-side switch S4 is turned off.

[0034] Figure 4D The equivalent circuit diagram of a three-phase bidirectional DC-DC power converter in the fourth operating mode (i.e., operating time t3-t4) is shown. Figure 4D As shown, at time t3, the fourth primary-side switch S4 is turned off, and mode 4 is within the dead time of the third primary-side switch S3 and the fourth primary-side switch S4. The fourth secondary-side switch S10 is also in the off mode. The B-phase resonant current... i Lr2 The junction capacitances of the third primary-side switch S3 and the fourth primary-side switch S4 are initially discharged and charged, respectively, causing the source voltage of the fourth primary-side switch S4 to rise to the magnitude of the input voltage, while the drain-source voltage of the third primary-side switch S3 drops to 0. At time t4, the third primary-side switch S3 achieves zero-voltage turn-on. The fourth secondary-side switch S10 naturally drops to 0, achieving zero-current turn-off. The reverse recovery loss of the fourth secondary-side switch S10 is zero, significantly reducing rectification losses.

[0035] Figure 4E The equivalent circuit diagram of a three-phase bidirectional DC-DC power converter in the fifth operating mode (i.e., operating time t4-t5) is shown. Figure 4E As shown, at time t4, the first primary-side switch S1, the third primary-side switch, and the sixth primary-side switch S6 are in the on state, and the B-phase current is... i Lr2 Under the influence of the sinusoidal change, it begins to commutate, changing from a negative current to a positive current, becoming the A-phase resonant current. i Lr1 Resonant current with phase B i Lr2 The sum of the currents equals the C-phase resonant current. i Lr3The resonant current in phase C gradually increases. The resonant devices in the phase A and phase C resonant branches are in a resonant state, causing the current in each phase to change sinusoidally. The transformer module transmits energy to the output terminal through the first secondary switch S7, the third secondary switch S9, and the sixth secondary switch S12. The sum of the currents flowing through the first secondary switch S7 and the third secondary switch S9 is equal to the current flowing through the sixth secondary switch S12.

[0036] Figure 4F The equivalent circuit diagram of a three-phase bidirectional DC-DC power converter in its sixth operating mode (i.e., operating time t5-t6) is shown. Figure 4F As shown, the first primary-side switch S1 is off. The first secondary-side switch S7 is also in the off-mode. Phase A resonant current... i Lr1 The direction is positive, and the current is positive. i Lr1 The junction capacitances of the first primary-side switch S1 and the second primary-side switch S2 are charged and discharged respectively. After the second primary-side switch S2 has finished discharging, the current... i Lr1 Through the freewheeling current of the body diode of the second primary-side switch S2, at time t6, the second primary-side switch S2 achieves zero-voltage turn-on, and the three-phase bidirectional DC-DC power converter begins to enter the negative half-switching cycle. In the sixth mode, the output current of the A-phase transformer drops to 0, and the first secondary-side switch S7 achieves zero-current turn-off.

[0037] Because the dead time is extremely short, it can be almost ignored. It is assumed that during the dead time of the switching transistor, the resonant current of the corresponding phase is equal to the excitation current, and no energy is transferred to the secondary side; therefore, the secondary current of the corresponding phase is zero. For the drive control pulse of synchronous rectification control, its turn-on time is generally slightly delayed compared to the corresponding main switch, and its turn-off time is slightly advanced compared to the corresponding main switch, to achieve better synchronous rectification effect. For simplicity, the drive pulse of the synchronous rectifier transistor is consistent with the drive pulse of the corresponding main switch.

[0038] It can be observed that the first primary-side switch S1 to the sixth primary-side switch S6 of the primary-side bridge arm of the bidirectional DC-DC power converter can all achieve zero-voltage turn-on, and the first secondary-side switch S7 to the sixth secondary-side switch S12 can all achieve zero-current turn-off. This greatly reduces the switching losses of the primary-side switches and the reverse recovery losses of the secondary-side switches, which is beneficial to improving EMI performance and conversion efficiency.

[0039] During one switching cycle, the first primary-side switch S1 to the sixth primary-side switch S6 (used as a three-phase inverter bridge) switch alternately, while the first secondary-side switch S7 to the sixth secondary-side switch S12 (used as a three-phase rectifier bridge) conduct alternately. This balances the losses of each power device, improving the system's safety and stability. In the three-phase interleaved mode, the output current of the secondary-side switching network is the sum of the currents of each secondary-side switch, significantly reducing the output current ripple and increasing the current ripple frequency. This facilitates optimization of the output capacitor size and extends capacitor life. Compared to conventional three-phase bidirectional power converters, the bidirectional converter of this application reduces one phase resonant device (resonant capacitor and resonant inductor) in each of the three phases on the primary and secondary sides, significantly reducing hardware design costs and improving power conversion efficiency and power density.

[0040] like Figure 5 As shown, before the drive control signal for the switching transistor arrives, the voltage across the switching transistor drops to 0, thus enabling the switching transistor to achieve zero-voltage turn-on (ZVS). Both the upper and lower switching transistors in the same bridge arm can achieve zero-voltage turn-on (ZVS), greatly reducing the switching losses of the primary-side switching devices.

[0041] Figure 6 yes Figure 2 The diagram shows the three-phase resonant current waveform on one side of the primary winding of the transformer module of the three-phase bidirectional DC-DC power converter. Figure 7 yes Figure 2 The diagram shows the three-phase resonant current waveform on one side of the secondary winding of the transformer module in the three-phase bidirectional DC-DC power converter. Figures 6-7 As shown, under the star connection of the transformer, the sum of the three-phase currents is zero. The A-phase and C-phase currents, under the action of their respective resonant circuit devices, exhibit sinusoidal resonant current variations; therefore, the B-phase resonant current also varies sinusoidally. Similarly, the three-phase resonant currents on the secondary side of the transformer, under the action of the resonant devices, also exhibit sinusoidal resonant current variations. Since both the primary and secondary three-phase resonant currents transmit energy in a sinusoidal form, the circulating current loss of the power converter is reduced, which helps improve efficiency.

[0042] Figure 8 yes Figure 2The diagram shows the ZCS waveforms of the upper and lower switches on the same switching arm of the secondary-side switching network of the three-phase bidirectional DC-DC power converter. When power is transferred from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the secondary-side switching network is used for synchronous rectification control; the current of the upper and lower switches on the same rectifier bridge arm naturally drops to 0, greatly reducing the reverse recovery loss of the rectifier switches. When power is transferred from the secondary side to the primary side of the three-phase bidirectional DC-DC power converter, the primary-side switching network is used for synchronous rectification control; similarly, it can also reduce the reverse recovery loss of the rectifier switches.

[0043] Although the present invention has been described through specific embodiments, those skilled in the art will understand that various modifications and equivalent substitutions can be made to the invention without departing from its scope. Furthermore, various modifications can be made to the invention for specific situations or materials without departing from its scope. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A three-phase bidirectional DC-DC power converter, comprising a primary-side switching network, a resonant network, and a secondary-side switching network connected in sequence, characterized in that, The resonant network includes a transformer module, a first primary-side resonant unit, a second primary-side resonant unit, a first secondary-side resonant unit, and a second secondary-side resonant unit; The three-phase bidirectional DC-DC power converter is equipped with resonant units in any two phases; the other phase of the three-phase bidirectional DC-DC power converter is not equipped with a resonant unit. The input terminal of the primary-side switching network is connected to the first power supply. The first output terminal of the primary-side switching network is connected to the first terminal of the primary winding of the transformer module via the first primary-side resonant unit. The second output terminal of the primary-side switching network is connected to the second terminal of the primary winding of the transformer module. The third output terminal of the primary-side switching network is connected to the third terminal of the primary winding of the transformer module via the second primary-side resonant unit. The first end of the secondary winding of the transformer module is connected to the first input terminal of the secondary-side switching network via the first secondary-side resonant unit; the second end of the secondary winding of the transformer module is connected to the second input terminal of the secondary-side switching network; and the third end of the secondary winding of the transformer module is connected to the third input terminal of the secondary-side switching network via the second secondary-side resonant unit. The output terminal of the secondary-side switching network is connected to a second power supply. When power is transmitted from the primary side to the secondary side of the three-phase bidirectional DC-DC power converter, the secondary side switching network is used for synchronous rectification control; when power is transmitted from the secondary side to the primary side of the three-phase bidirectional DC-DC power converter, the primary side switching network is used for synchronous rectification control; the primary side switching network can operate near the series resonant frequency, which is the resonant frequency of the resonant unit.

2. The three-phase bidirectional DC-DC power converter according to claim 1, characterized in that, The first primary-side resonant unit, the second primary-side resonant unit, the first secondary-side resonant unit, and the second secondary-side resonant unit each include a resonant capacitor and a resonant inductor connected in series.

3. The three-phase bidirectional DC-DC power converter according to claim 2, characterized in that, The transformer module includes a first transformer, a second transformer, a third transformer, a first magnetizing inductor, a second magnetizing inductor, and a third magnetizing inductor; The same-name terminal of the primary winding of the first transformer is the first terminal of the primary winding of the transformer module, the same-name terminal of the primary winding of the second transformer is the second terminal of the primary winding of the transformer module, and the same-name terminal of the primary winding of the third transformer is the third terminal of the primary winding of the transformer module. The opposite-name terminals of the primary windings of the first transformer, the opposite-name terminals of the primary windings of the second transformer, and the opposite-name terminals of the primary windings of the third transformer are connected to each other. The same-name terminal of the secondary winding of the first transformer is the first terminal of the secondary winding of the transformer module, the same-name terminal of the secondary winding of the second transformer is the second terminal of the secondary winding of the transformer module, and the same-name terminal of the secondary winding of the third transformer is the third terminal of the secondary winding of the transformer module. The opposite-name terminals of the secondary windings of the first transformer, the opposite-name terminals of the secondary windings of the second transformer, and the opposite-name terminals of the secondary windings of the third transformer are connected to each other. The first magnetizing inductance is the inductance between the same-named and opposite-named terminals of the primary winding of the first transformer, the second magnetizing inductance is the inductance between the same-named and opposite-named terminals of the primary winding of the second transformer, and the third magnetizing inductance is the inductance between the same-named and opposite-named terminals of the primary winding of the third transformer.

4. The three-phase bidirectional DC-DC power converter according to claim 3, characterized in that, The primary-side switching network includes a first primary-side switch, a second primary-side switch, a third primary-side switch, a fourth primary-side switch, a fifth primary-side switch, and a sixth primary-side switch. The first primary-side switch and the second primary-side switch form a first switch bridge arm, the third primary-side switch and the fourth primary-side switch form a second switch bridge arm, and the fifth primary-side switch and the sixth primary-side switch form a third switch bridge arm. The control signals between the first switch bridge arm, the second switch bridge arm, and the third switch bridge arm are sequentially 120° out of phase.

5. The three-phase bidirectional DC-DC power converter according to claim 4, characterized in that, The control terminals of the first primary-side switch, the second primary-side switch, the third primary-side switch, the fourth primary-side switch, the fifth primary-side switch, and the sixth primary-side switch receive control signals; The first end of the first primary-side switch is connected to the second end of the second primary-side switch and serves as the first output terminal of the primary-side switching network; the first end of the third primary-side switch is connected to the second end of the fourth primary-side switch and serves as the second output terminal of the primary-side switching network; the first end of the fifth primary-side switch is connected to the second end of the sixth primary-side switch and serves as the third output terminal of the primary-side switching network; the second end of the first primary-side switch is connected to the second ends of the third and fifth primary-side switches and serves as the first input terminal of the primary-side switching network; the first end of the second primary-side switch is connected to the first ends of the fourth and sixth primary-side switches and serves as the second input terminal of the primary-side switching network. The first input terminal of the primary side-side switching network is connected to the positive terminal of the first power supply, and the second input terminal of the primary side-side switching network is connected to the negative terminal of the first power supply. The control signals of the first primary-side switch and the second primary-side switch are complementary; the control signals of the third primary-side switch and the fourth primary-side switch are complementary; and the control signals of the fifth primary-side switch and the sixth primary-side switch are complementary.

6. The three-phase bidirectional DC-DC power converter according to claim 3, characterized in that, The secondary-side switch network includes a first secondary-side switch, a second secondary-side switch, a third secondary-side switch, a fourth secondary-side switch, a fifth secondary-side switch, and a sixth secondary-side switch. The first secondary-side switch and the second secondary-side switch constitute the first switch bridge arm, the third secondary-side switch and the fourth secondary-side switch constitute the second switch bridge arm, and the fifth secondary-side switch and the sixth secondary-side switch constitute the third switch bridge arm.

7. The three-phase bidirectional DC-DC power converter according to claim 6, characterized in that, The control terminals of the first secondary-side switch, the second secondary-side switch, the third secondary-side switch, the fourth secondary-side switch, the fifth secondary-side switch, and the sixth secondary-side switch receive control signals; The first end of the first secondary-side switch is connected to the second end of the second secondary-side switch and serves as the first input terminal of the secondary-side switch network; the first end of the third secondary-side switch is connected to the second end of the fourth secondary-side switch and serves as the second input terminal of the secondary-side switch network; the first end of the fifth secondary-side switch is connected to the second end of the sixth secondary-side switch and serves as the third input terminal of the secondary-side switch network; the second end of the first secondary-side switch is connected to the second ends of the third and fifth secondary-side switches and serves as the first output terminal of the secondary-side switch network; the first end of the second secondary-side switch is connected to the first ends of the fourth and sixth secondary-side switches and serves as the second output terminal of the secondary-side switch network. The first output terminal of the secondary-side switching network is connected to the positive terminal of the second power supply, and the second output terminal of the secondary-side switching network is connected to the negative terminal of the second power supply. When the control signals of the first secondary-side switch, the second secondary-side switch, the third secondary-side switch, the fourth secondary-side switch, the fifth secondary-side switch, and the sixth secondary-side switch are 0, uncontrolled rectification is performed through the body diodes of the first secondary-side switch, the second secondary-side switch, the third secondary-side switch, the fourth secondary-side switch, the fifth secondary-side switch, and the sixth secondary-side switch.

8. The three-phase bidirectional DC-DC power converter according to any one of claims 3 to 7, characterized in that, This further includes primary-side filter capacitors and / or secondary-side filter capacitors; The first end of the primary-side filter capacitor is connected to the positive terminal of the first power supply, and the second end is connected to the negative terminal of the first power supply. The first end of the secondary filter capacitor is connected to the positive terminal of the second power supply, and the second end is connected to the negative terminal of the second power supply.

9. The three-phase bidirectional DC-DC power converter according to claim 4, characterized in that, The first primary-side switch, the second primary-side switch, the third primary-side switch, the fourth primary-side switch, the fifth primary-side switch, and the sixth primary-side switch each include a MOSFET, an IGBT, and a transistor, respectively.

10. The three-phase bidirectional DC-DC power converter according to claim 6, characterized in that, The first secondary-side switch, the second secondary-side switch, the third secondary-side switch, the fourth secondary-side switch, the fifth secondary-side switch, and the sixth secondary-side switch each include a MOSFET, an IGBT, and a transistor, respectively.

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