A direct current transformer

Abstract

The present disclosure relates to a kind of direct current transformer, direct current transformer includes: transformer circuit, inverter circuit, rectifier circuit and resonance circuit;The direct current side of inverter circuit is connected with direct current input port, the alternating current side of inverter circuit is connected with the primary side of transformer circuit;The alternating current side of rectifier circuit is connected with the secondary side of transformer circuit, the direct current side of rectifier circuit is connected with direct current output port;Resonance circuit includes multiple resonance modules, the alternating current side of inverter circuit is connected with the alternating current side of rectifier circuit through multiple resonance modules and transformer circuit;Resonance module includes first capacitor, resonance module is used to control the input or cut-out of first capacitor.The present disclosure can simulate the voltage outputted when direct current transformer adopts different capacitance resonant capacitor, so as to ensure that direct current transformer does not need to set resonant capacitor, can satisfy the realization condition of resonant soft switching in different working condition scene, and then make the switching device in inverter circuit and rectifier circuit can realize soft switching.

Description

Technical Field

[0001] This disclosure relates to the field of transformer technology, and more particularly to a DC transformer. Background Technology

[0002] With the rapid development of new energy power generation technologies, direct current (DC) transmission technology has received widespread attention due to its significant advantages in transmission efficiency, stability, and controllability. The core equipment of DC transmission technology is the DC transformer, a device that integrates power electronics technology and electromagnetic induction principles, possessing both DC voltage transformation and electrical isolation functions.

[0003] DC transformers operate in various scenarios in practical applications. Using resonant capacitors with fixed parameters may prevent the transformer from achieving soft switching of switching devices in some scenarios, increasing losses in these devices. Furthermore, in high-voltage applications, resonant capacitors suffer from difficulties in voltage equalization and lower reliability, thus impacting the overall system reliability. Therefore, ensuring that DC transformers can achieve soft switching of switching devices in different operating scenarios while avoiding the use of high-voltage resonant capacitors is a crucial technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] To solve the above-mentioned technical problems, or at least partially solve them, this disclosure provides a DC transformer that can simulate the output voltage of a DC transformer when using resonant capacitors of different capacitance values. This ensures that the DC transformer can meet the conditions for resonant soft switching under different operating conditions without the need for a resonant capacitor, thereby enabling soft switching of the switching devices in the inverter circuit and rectifier circuit.

[0005] This disclosure provides a DC transformer, including: a transformer circuit, an inverter circuit, a rectifier circuit, and a resonant circuit; The DC side of the inverter circuit is connected to the DC input port, and the AC side of the inverter circuit is connected to the primary side of the transformer circuit. The AC side of the rectifier circuit is connected to the secondary side of the transformer circuit, and the DC side of the rectifier circuit is connected to the DC output port. The resonant circuit includes multiple resonant modules. The AC side of the inverter circuit is connected to the AC side of the rectifier circuit through multiple resonant modules and a transformer circuit. The resonant module includes a first capacitor, which is used to control the connection or disconnection of the first capacitor.

[0006] Optionally, the resonant module may also include a first full-bridge module; The first terminal of the first full-bridge module is connected to the first terminal of the first capacitor, and the second terminal of the first full-bridge module is connected to the second terminal of the first capacitor; the AC side of the inverter circuit is connected to the AC side of the rectifier circuit through the first full-bridge module and the transformer circuit. The first full-bridge module is used to control the connection or disconnection of the first capacitor.

[0007] Optionally, the first full-bridge module includes a first switching element, a second switching element, a third switching element, and a fourth switching element; The first end of the first switching element and the first end of the third switching element are connected to the first end of the first capacitor. The second end of the first switching element and the first end of the second switching element are connected to the first node. The second end of the third switching element and the first end of the fourth switching element are connected to the second node. The second end of the second switching element and the second end of the fourth switching element are connected to the second end of the first capacitor. Multiple first full-bridge modules are connected between the AC side of the inverter circuit and the primary side of the transformer circuit through a first node and a second node, and / or, between the secondary side of the transformer circuit and the AC side of the rectifier circuit.

[0008] Optionally, the DC transformer also includes multiple DC capacitor circuits; the DC side of the inverter circuit and the DC side of the rectifier circuit are both connected to the DC capacitor circuits. The DC capacitor circuit includes multiple DC capacitors and multiple DC capacitor modules connected in series. The DC capacitor module is connected to the DC capacitor in a one-to-one correspondence.

[0009] Optionally, the multiple DC capacitor modules include a first half-bridge module and / or a second full-bridge module.

[0010] Optionally, the inverter circuit includes a first inverter module; the rectifier circuit includes a first rectifier module; and the transformer circuit includes a first transformer. The DC side of the first inverter module is connected to the DC input port, the AC side of the first inverter module is connected to the primary side of the first transformer, the secondary side of the first transformer is connected to the AC side of the first rectifier module, and the DC side of the first rectifier module is connected to the DC output port.

[0011] Optionally, the inverter circuit includes a first inverter module; the rectifier circuit includes multiple first rectifier modules; and the transformer circuit includes multiple first transformers; wherein, each first rectifier module corresponds to a first transformer. The DC side of the first inverter module is connected to the DC input port, the AC side of the first inverter module is connected to the primary side of multiple first transformers, the secondary side of multiple first transformers is connected to the AC side of the corresponding first rectifier module, and the DC side of multiple first rectifier modules is connected to the DC output port.

[0012] Optionally, the first inverter module includes a first switching unit, a second switching unit, a third switching unit, and a fourth switching unit; Multiple DC capacitor circuits include a first DC capacitor circuit; The first end of the first switch unit and the first end of the third switch unit are connected to the first end of the DC input port. The second end of the second switch unit and the second end of the fourth switch unit are connected to the second end of the DC input port. The second end of the first switch unit and the first end of the second switch unit are connected at the midpoint of the first bridge arm. The second end of the third switch unit and the first end of the fourth switch unit are connected at the midpoint of the second bridge arm. The midpoints of the first and second bridge arms are connected to the primary side of the first transformer; the first terminal of the first DC capacitor circuit is connected to the first terminal of the DC input port, and the second terminal of the first DC capacitor circuit is connected to the second terminal of the DC input port.

[0013] Optionally, the first inverter module includes a fifth switching unit and a sixth switching unit; Multiple DC capacitor circuits include a second DC capacitor circuit and a third DC capacitor circuit; The first end of the fifth switching unit and the first end of the second DC capacitor circuit are connected to the first end of the DC input port. The second end of the sixth switching unit and the second end of the third DC capacitor circuit are connected to the second end of the DC input port. The second end of the second DC capacitor circuit and the first end of the third DC capacitor circuit are connected to the midpoint of the third bridge arm. The second end of the fifth switching unit and the first end of the sixth switching unit are connected to the midpoint of the fourth bridge arm. The midpoints of the third and fourth bridge arms are connected to the primary side of the first transformer.

[0014] Optionally, the first rectifier module includes a seventh switching unit, an eighth switching unit, a ninth switching unit, and a tenth switching unit; Multiple DC capacitor circuits include a fourth DC capacitor circuit; The first end of the seventh switch unit and the first end of the ninth switch unit are connected to the first end of the DC output port. The second end of the eighth switch unit and the second end of the tenth switch unit are connected to the second end of the DC output port. The second end of the seventh switch unit and the first end of the eighth switch unit are connected to the midpoint of the fifth bridge arm. The second end of the ninth switch unit and the first end of the tenth switch unit are connected to the midpoint of the sixth bridge arm. The midpoints of the fifth and sixth bridge arms are connected to the secondary side of the first transformer; the first terminal of the fourth DC capacitor circuit is connected to the first terminal of the DC output port, and the second terminal of the fourth DC capacitor circuit is connected to the second terminal of the DC output port.

[0015] Optionally, the DC transformer may also include multiple filter circuits; The DC side of the inverter circuit is connected to the DC input port through a filter circuit, and the DC side of the rectifier circuit is connected to the DC output port through a filter circuit.

[0016] Optionally, the filter circuit includes at least one of a filter inductor, a filter capacitor, and a filter resistor.

[0017] This disclosure provides a DC transformer, which includes: a transformer circuit, an inverter circuit, a rectifier circuit, and a resonant circuit; the DC side of the inverter circuit is connected to a DC input port, and the AC side of the inverter circuit is connected to the primary side of the transformer circuit; the AC side of the rectifier circuit is connected to the secondary side of the transformer circuit, and the DC side of the rectifier circuit is connected to a DC output port; the resonant circuit includes multiple resonant modules, and the AC side of the inverter circuit is connected to the AC side of the rectifier circuit through the multiple resonant modules and the transformer circuit; the resonant module includes a first capacitor, and the resonant module is used to control the connection or disconnection of the first capacitor. Each resonant module is equipped with a first capacitor. Since the resonant module can control the connection or disconnection of the first capacitor, in the actual application of the DC transformer, the external control module can determine the number of resonant modules connected to the first capacitor according to the resonant requirements of the DC transformer under different operating conditions, and control the connection of the first capacitor according to the specific number. Therefore, this disclosure can simulate the output voltage of the DC transformer when using resonant capacitors of different capacitance values, thereby ensuring that the DC transformer can meet the resonant soft switching conditions under different operating conditions without setting a resonant capacitor, and thus enabling the switching devices in the inverter circuit and rectifier circuit to achieve soft switching. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a DC transformer provided in an embodiment of this disclosure.

[0020] Figure 2 This is a schematic diagram of another DC transformer provided in an embodiment of the present disclosure.

[0021] Figure 3 This is a schematic diagram of another DC transformer provided in an embodiment of the present disclosure.

[0022] Figure 4 This is a schematic diagram of another DC transformer provided in an embodiment of the present disclosure.

[0023] Figure 5 This is a schematic diagram of another DC transformer provided in an embodiment of the present disclosure.

[0024] Figure 6 This is a schematic diagram of another DC transformer provided in an embodiment of the present disclosure.

[0025] Figure 7 This is a schematic diagram of another DC transformer provided in an embodiment of the present disclosure.

[0026] Figure 8 This is a schematic diagram of another DC transformer provided in an embodiment of the present disclosure.

[0027] Figure 9 This is a schematic diagram of a DC capacitor circuit provided in an embodiment of the present disclosure.

[0028] Figure 10 This is a schematic diagram of another DC capacitor circuit provided in an embodiment of the present disclosure.

[0029] Figure 11 This is a schematic diagram of another DC capacitor circuit provided in an embodiment of the present disclosure.

[0030] Figure 12 This is a schematic diagram of the structure of a series switch module provided in an embodiment of this disclosure.

[0031] Figure 13 This is a schematic diagram of a diode series valve string provided in an embodiment of the present disclosure.

[0032] Figure 14 This is a schematic diagram of a preferred DC transformer provided in an embodiment of the present disclosure. Detailed Implementation

[0033] The features and exemplary embodiments of various aspects of this application will now be described in detail. Numerous specific details are set forth in the following detailed description in order to provide a comprehensive understanding of this application. However, it will be apparent to those skilled in the art that this application can be implemented without some of these specific details. The following description of embodiments is merely intended to provide a better understanding of this application by illustrating examples thereof.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0035] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0036] It should be understood that when describing the structure of a component, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above the other layer or region, or that it contains other layers or regions between it and the other layer or region. Furthermore, if the component is flipped over, that layer or region will be located "below" or "under" the other layer or region.

[0037] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0038] In the embodiments of this application, the term "electrical connection" can refer to a direct electrical connection between two components, or it can refer to an electrical connection between two components via one or more other components.

[0039] In the embodiments of this application, the first node, the second node, and the third node are defined only for the convenience of describing the circuit structure, and the first node, the second node, and the third node are not actual circuit units.

[0040] Various modifications and variations can be made to this application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the implementation methods provided in the embodiments of this application can be combined with each other without contradiction.

[0041] With the rapid development of new energy power generation technologies, direct current (DC) transmission technology has received widespread attention due to its significant advantages in transmission efficiency, stability, and controllability. The core equipment of DC transmission technology is the DC transformer, a device that integrates power electronics technology and electromagnetic induction principles, possessing both DC voltage transformation and electrical isolation functions.

[0042] In practical applications, DC transformers will operate in different working scenarios. If a DC transformer uses a resonant capacitor with fixed parameters, it may cause the DC transformer to fail to achieve soft switching of the switching devices in some working scenarios, thereby increasing the losses of the switching devices and even affecting the reliability of the entire system.

[0043] Therefore, this disclosure provides a DC transformer. In the actual application of the DC transformer, the external control module can determine the number of resonant modules connected to the first capacitor according to the resonant requirements of the DC transformer under different operating conditions, and control the connection or disconnection of the first capacitor according to the specific number. Therefore, this disclosure can simulate the output voltage of the DC transformer when using resonant capacitors of different capacitance values, thereby ensuring that the DC transformer can meet the realization conditions of resonant soft switching under different operating conditions without setting a resonant capacitor, and thus enabling the switching devices in the inverter circuit and rectifier circuit to achieve soft switching.

[0044] The embodiments will now be described in detail with reference to the accompanying drawings.

[0045] Figure 1 This is a schematic diagram of the structure of a DC transformer provided in an embodiment of the present disclosure, as shown below. Figure 1 As shown, the DC transformer includes: transformer circuit 10, inverter circuit 20, rectifier circuit 30, and resonant circuit 40.

[0046] The DC side of the inverter circuit 20 is connected to the DC input port 51, and the AC side of the inverter circuit 20 is connected to the primary side of the transformer circuit 10.

[0047] For example, the inverter circuit 20 is used to convert the DC voltage signal provided by the DC input port 51 into an AC voltage signal and provide it to the transformer circuit 10, which then boosts or bucks the AC voltage signal.

[0048] The AC side of the rectifier circuit 30 is connected to the secondary side of the transformer circuit 10, and the DC side of the rectifier circuit 30 is connected to the DC output port 52.

[0049] For example, the rectifier circuit 30 is used to convert the AC voltage signal provided by the transformer circuit 10 into a DC voltage signal and provide it to the DC output port 52, which then provides the DC voltage signal to the external load circuit.

[0050] The resonant circuit 40 includes multiple resonant modules 41. The AC side of the inverter circuit 20 is connected to the AC side of the rectifier circuit 30 through the multiple resonant modules 41 and the transformer circuit 10.

[0051] The resonant module 41 includes a first capacitor, which is used to control the connection or disconnection of the first capacitor.

[0052] For example, the resonant module 41 can be disposed between the AC side of the inverter circuit 20 and the primary side of the transformer circuit 10, or between the secondary side of the transformer circuit 10 and the AC side of the rectifier circuit 30, or both between the AC side of the inverter circuit 20 and the primary side of the transformer circuit 10 and between the secondary side of the transformer circuit 10 and the AC side of the rectifier circuit 30.

[0053] The DC transformer also includes a resonant inductor, which can be an additional inductor or the leakage inductance of the transformer circuit 10. When the leakage inductance of the transformer circuit 10 is used as the resonant inductor, the DC transformer does not need to have additional inductors, thus reducing the overall hardware cost and size of the DC transformer to meet the design requirements of low cost and compactness.

[0054] Each resonant module 41 is equipped with a first capacitor. Since the resonant module 41 can control the connection or disconnection of the first capacitor, in the actual application of the DC transformer, the external control module can determine the number of resonant modules 41 connected to the first capacitor according to the resonant requirements of the DC transformer under different operating conditions, and control the connection of the first capacitor according to the specific number. Therefore, this disclosure can simulate the output voltage of the DC transformer when using resonant capacitors of different capacitance values, thereby ensuring that the DC transformer can meet the resonant soft switching conditions under different operating conditions without setting a resonant capacitor, and thus enabling the switching devices in the inverter circuit 20 and the rectifier circuit 30 to achieve soft switching.

[0055] It should be noted that, Figure 1 The resonant module 41 is shown as an example only, positioned between the AC side of the inverter circuit 20 and the primary side of the transformer circuit 10. The resonant module 41 can also be positioned between the secondary side of the transformer circuit 10 and the AC side of the rectifier circuit 30, or both between the AC side of the inverter circuit 20 and the primary side of the transformer circuit 10 and between the secondary side of the transformer circuit 10 and the AC side of the rectifier circuit 30. The specific location of the resonant module 41 is determined according to the actual situation and is not specifically limited here.

[0056] In some embodiments, the resonant module further includes a first full-bridge module.

[0057] The first terminal of the first full-bridge module is connected to the first terminal of the first capacitor, and the second terminal of the first full-bridge module is connected to the second terminal of the first capacitor; the AC side of the inverter circuit is connected to the AC side of the rectifier circuit through the first full-bridge module and the transformer circuit.

[0058] The first full-bridge module is used to control the connection or disconnection of the first capacitor.

[0059] For example, each switching element in the first full-bridge module is connected to an external control module. In the actual application of the DC transformer, the external control module determines the specific operating conditions of the DC transformer and determines the number of first capacitors to be connected based on the operating conditions. This controls the corresponding number of first full-bridge modules to be in the state of first capacitor connection, while the other first full-bridge modules are in the state of first capacitor disconnection. Thus, this disclosure can simulate the output voltage of the DC transformer when using resonant capacitors of different values, thereby ensuring that the DC transformer can meet the conditions for resonant soft switching in different operating conditions without the need to set resonant capacitors. This enables the switching devices in the inverter circuit and rectifier circuit to achieve soft switching.

[0060] In some embodiments, Figure 2 This is a schematic diagram of the structure of another DC transformer provided in an embodiment of this disclosure. Figure 3 This is a schematic diagram of the structure of another DC transformer provided in an embodiment of this disclosure. Figure 4 This is a schematic diagram of the structure of another DC transformer provided in an embodiment of the present disclosure, as shown below. Figure 2 , Figure 3 as well as Figure 4 As shown, the first full-bridge module 410 includes a first switching element 411, a second switching element 412, a third switching element 413, and a fourth switching element 414.

[0061] For example, the first switching element 411, the second switching element 412, the third switching element 413 and the fourth switching element 414 may be semiconductor switching devices such as MOSFETs.

[0062] The first end of the first switching element 411 and the first end of the third switching element 413 are connected to the first end of the first capacitor C1. The second end of the first switching element 411 and the first end of the second switching element 412 are connected to the first node A. The second end of the third switching element 413 and the first end of the fourth switching element 414 are connected to the second node B. The second ends of the second switching element 412 and the second ends of the fourth switching element 414 are connected to the second end of the first capacitor C1.

[0063] Multiple first full-bridge modules 410 are connected between the AC side of the inverter circuit 20 and the primary side of the transformer circuit 10 through a first node A and a second node B, and / or are connected between the secondary side of the transformer circuit 10 and the AC side of the rectifier circuit 30.

[0064] For example, see [link to example]. Figure 2 Multiple first full-bridge modules 410 are connected between the AC side of the inverter circuit 20 and the primary side of the transformer circuit 10 via first node A and second node B. The first node A of the first first full-bridge module 410 is connected to the AC side of the inverter circuit 20, and the second node B of the first first full-bridge module 410 is connected to the first node A of the second first full-bridge module 410. The first node A of the last first full-bridge module 410 is connected to the second node B of the penultimate first full-bridge module 410, and the second node B of the last first full-bridge module 410 is connected to the primary side of the transformer circuit 10. The first node A of other first full-bridge modules 410 is connected to the second node B of the adjacent first full-bridge module 410, and the second node B of other first full-bridge modules 410 is connected to the first node A of the adjacent first full-bridge module 410. That is, multiple first full-bridge modules 410 are connected in series.

[0065] See also Figure 3 Multiple first full-bridge modules 410 are connected between the secondary side of the transformer circuit 10 and the AC side of the rectifier circuit 30 via first node A and second node B. The first node A of the first first full-bridge module 410 is connected to the secondary side of the transformer circuit 10, and the second node B of the first first full-bridge module 410 is connected to the first node A of the second first full-bridge module 410. The first node A of the last first full-bridge module 410 is connected to the second node B of the penultimate first full-bridge module 410, and the second node B of the last first full-bridge module 410 is connected to the AC side of the rectifier circuit 30. The first node A of other first full-bridge modules 410 is connected to the second node B of the adjacent first full-bridge module 410, and the second node B of other first full-bridge modules 410 is connected to the first node A of the adjacent first full-bridge module 410. That is, multiple first full-bridge modules 410 are connected in series.

[0066] See also Figure 4In a plurality of first full-bridge modules 410, some first full-bridge modules 410 are connected between the AC side of inverter circuit 20 and the primary side of transformer circuit 10 via first node A and second node B, while other first full-bridge modules 410 are connected between the secondary side of transformer circuit 10 and the AC side of rectifier circuit 30 via first node A and second node B. On the primary side of transformer circuit 10, the first node A of the first first full-bridge module 410 is connected to the AC side of inverter circuit 20, and the second node B of the first first full-bridge module 410 is connected to the first node A of the second first full-bridge module 410. The first node A of the last first full-bridge module 410 is connected to the second node B of the penultimate first full-bridge module 410, and the second node B of the last first full-bridge module 410 is connected to the primary side of transformer circuit 10. On the secondary side of transformer circuit 10, the first node A of the first first full-bridge module 410 is connected to the secondary side of transformer circuit 10, and the second node B of the first first full-bridge module 410 is connected to the first node A of the second first full-bridge module 410. The first node A of the last first full-bridge module 410 is connected to the second node B of the penultimate first full-bridge module 410, and the second node B of the last first full-bridge module 410 is connected to the AC side of the rectifier circuit 30. The first node A of other first full-bridge modules 410 is connected to the second node B of the adjacent first full-bridge module 410, and the second node B of other first full-bridge modules 410 is connected to the first node A of the adjacent first full-bridge module 410. That is, multiple first full-bridge modules 410 on the primary side of the transformer circuit 10 are connected in series, and multiple first full-bridge modules 410 on the secondary side of the transformer circuit 10 are connected in series.

[0067] In some embodiments, Figure 5 This is a schematic diagram of the structure of another DC transformer provided in an embodiment of this disclosure. Figure 6 This is a schematic diagram of the structure of another DC transformer provided in an embodiment of this disclosure. Figure 7 This is a schematic diagram of the structure of another DC transformer provided in an embodiment of this disclosure. Figure 8 This is a schematic diagram of the structure of another DC transformer provided in an embodiment of the present disclosure, as shown below. Figure 5 , Figure 6 , Figure 7 as well as Figure 8 As shown, the DC transformer also includes multiple DC capacitor circuits 60; the DC side of the inverter circuit 20 and the DC side of the rectifier circuit 30 are both connected to the DC capacitor circuits 60.

[0068] The DC capacitor circuit 60 includes multiple DC capacitors C2 and multiple DC capacitor modules 61 connected in series. Each DC capacitor module 61 is connected to a DC capacitor C2 in a one-to-one correspondence.

[0069] For example, Figure 9 This is a schematic diagram of a DC capacitor circuit provided in an embodiment of the present disclosure, as shown below. Figure 9 As shown, the multiple DC capacitor modules 61 include multiple first half-bridge modules 611 connected in series. The first end of the first half-bridge module 611 is connected to the first end of the corresponding DC capacitor C2, and the second end of the first half-bridge module 611 is connected to the second end of the corresponding DC capacitor C2.

[0070] Figure 10 This is a schematic diagram of another DC capacitor circuit provided in an embodiment of the present disclosure, as shown below. Figure 10 As shown, the multiple DC capacitor modules 61 include multiple second full-bridge modules 612 connected in series. The first end of the second full-bridge module 612 is connected to the first end of the corresponding DC capacitor C2, and the second end of the second full-bridge module 612 is connected to the second end of the corresponding DC capacitor C2.

[0071] Figure 11 This is a schematic diagram of another DC capacitor circuit provided in an embodiment of the present disclosure, as shown below. Figure 11 As shown, the plurality of DC capacitor modules 61 include a plurality of first half-bridge modules 611 and second full-bridge modules 612 connected in series. The first terminal of the first half-bridge module 611 is connected to the first terminal of the corresponding DC capacitor C2, and the second terminal of the first half-bridge module 611 is connected to the second terminal of the corresponding DC capacitor C2. The first terminal of the second full-bridge module 612 is connected to the first terminal of the corresponding DC capacitor C2, and the second terminal of the second full-bridge module 612 is connected to the second terminal of the corresponding DC capacitor C2.

[0072] It should be noted that the multiple series-connected first half-bridge modules 611 and second full-bridge modules 612 can be configured such that multiple first half-bridge modules 611 are connected in series, and then connected in series with multiple series-connected second full-bridge modules 612. Alternatively, the first half-bridge modules 611 and second full-bridge modules 612 can be connected in series alternately. Figure 11 The first half-bridge module 611 and the second full-bridge module 612 are shown in series only as an example, and no specific limitations are made here.

[0073] When a DC transformer operates under high voltage conditions, high-voltage capacitors are required on the DC side of both the inverter circuit 20 and the rectifier circuit 30. However, these high-voltage capacitors are bulky, leading to high costs and hindering compact design. Therefore, this disclosure connects multiple DC capacitors C2 (for low-voltage applications) to the DC side of both the inverter circuit 20 and the rectifier circuit 30 via a DC capacitor module 61. An external control module can control the corresponding number of DC capacitor modules 61 to connect the connected DC capacitors C2 according to their capacitance requirements. After the DC capacitor modules 61 connect the C2s, they are connected in series, thus improving their high-voltage withstand capability. This allows the DC capacitors C2 to withstand the high voltage required for high-voltage operation. Furthermore, since the C2s are designed for low-voltage applications, their size and cost are significantly smaller than those for high-voltage applications, thereby reducing the size and cost of the DC transformer and meeting the requirements for low-cost, compact design.

[0074] In some embodiments, see continue to see Figure 5 and Figure 6 The inverter circuit 20 includes a first inverter module 21; the rectifier circuit 30 includes a first rectifier module 31; and the transformer circuit 10 includes a first transformer 11.

[0075] The DC side of the first inverter module 21 is connected to the DC input port 51, the AC side of the first inverter module 21 is connected to the primary side of the first transformer 11, the secondary side of the first transformer 11 is connected to the AC side of the first rectifier module 31, and the DC side of the first rectifier module 31 is connected to the DC output port 52.

[0076] As an example, see further. Figure 5 The first inverter module 21 includes a first switching unit 211, a second switching unit 212, a third switching unit 213, and a fourth switching unit 214.

[0077] The plurality of DC capacitor circuits 60 include a first DC capacitor circuit 601.

[0078] The first end of the first switch unit 211 and the first end of the third switch unit 213 are connected to the first end of the DC input port 51. The second end of the second switch unit 212 and the second end of the fourth switch unit 214 are connected to the second end of the DC input port 51. The second end of the first switch unit 211 and the first end of the second switch unit 212 are connected to the midpoint C of the first bridge arm. The second end of the third switch unit 213 and the first end of the fourth switch unit 214 are connected to the midpoint D of the second bridge arm.

[0079] The midpoint C of the first bridge arm and the midpoint D of the second bridge arm are connected to the primary side of the first transformer 11; the first end of the first DC capacitor circuit 601 is connected to the first end of the DC input port 51, and the second end of the first DC capacitor circuit 601 is connected to the second end of the DC input port 51.

[0080] The first rectifier module 31 includes a seventh switch unit 311, an eighth switch unit 312, a ninth switch unit 313, and a tenth switch unit 314.

[0081] The multiple DC capacitor circuits 60 include a fourth DC capacitor circuit 604.

[0082] The first end of the seventh switch unit 311 and the first end of the ninth switch unit 313 are connected to the first end of the DC output port 52. The second end of the eighth switch unit 312 and the second end of the tenth switch unit 314 are connected to the second end of the DC output port 52. The second end of the seventh switch unit 311 and the first end of the eighth switch unit 312 are connected to the midpoint G of the fifth bridge arm. The second end of the ninth switch unit 313 and the first end of the tenth switch unit 314 are connected to the midpoint H of the sixth bridge arm.

[0083] The midpoint G of the fifth bridge arm and the midpoint H of the sixth bridge arm are connected to the secondary side of the first transformer 11; the first end of the fourth DC capacitor circuit 604 is connected to the first end of the DC output port 52, and the second end of the fourth DC capacitor circuit 604 is connected to the second end of the DC output port 52.

[0084] Figure 12 This is a schematic diagram of the structure of a series switch module provided in an embodiment of this disclosure, as shown below. Figure 12 As shown, the series switch module 70 includes multiple series switch units 71 connected in series. Each series switch unit 71 includes a first diode D1, a fully controlled switch device T1, a voltage equalizing capacitor C3, and a voltage equalizing resistor R1.

[0085] The positive terminal of the first diode D1 is connected to the first terminal of the fully controlled switch T1. The second terminal of the fully controlled switch T1 is connected to the second terminal of the voltage equalizing capacitor C3. The first terminal of the voltage equalizing capacitor C3 is connected to the negative terminal of the first diode D1. The voltage equalizing capacitor C3 is connected in parallel with the voltage equalizing resistor R1. The control terminal of the fully controlled switch T1 is connected to an external control module (not shown in the figure). The first and second terminals of the fully controlled switch T1 are used to connect to the adjacent series switch unit 71.

[0086] The upper arm of the series switching unit 71 uses the first diode D1, thus eliminating the need for a fully controlled switching device in the upper arm. Furthermore, the first diode D1 serves only as a buffer circuit, acting as a stray inductance freewheeling current source, and its current requirement is far less than that of a power switching device. Therefore, the manufacturing cost of the series switching unit 71 is reduced. Additionally, since the voltage equalizing capacitor C3 only needs to meet the requirements of high-level self-powering and transient voltage equalization during switching, its required capacitance value is significantly reduced, thereby reducing the size and weight of the voltage equalizing capacitor C3.

[0087] Figure 13 This is a schematic diagram of a diode series valve string provided in an embodiment of the present disclosure, as shown below. Figure 13 As shown, the diode series valve string 72 includes multiple second diodes D2 connected in series.

[0088] In a DC transformer suitable for DC step-down operation, the first switching unit 211, the second switching unit 212, the third switching unit 213, and the fourth switching unit 214 are all as follows: Figure 12 The series switch module 70 shown includes the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314, all of which are as follows: Figure 13 The diode series valve string 72 is shown.

[0089] In a DC transformer suitable for DC boost operation, the first switching unit 211, the second switching unit 212, the third switching unit 213, and the fourth switching unit 214 are all as follows: Figure 13 The diode series valve string 72 shown, the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314 are all as follows: Figure 12 The series switch module 70 shown.

[0090] In a DC transformer suitable for both DC boost and buck operation, the first switching unit 211, the second switching unit 212, the third switching unit 213, the fourth switching unit 214, the seventh switching unit 311, the eighth switching unit 312, the ninth switching unit 313, and the tenth switching unit 314 are all as follows: Figure 12 The series switch module 70 shown.

[0091] As yet another example, see [continued] Figure 6 The first inverter module 21 includes a fifth switching unit 215 and a sixth switching unit 216.

[0092] The multiple DC capacitor circuits 60 include a second DC capacitor circuit 602 and a third DC capacitor circuit 603.

[0093] The first end of the fifth switching unit 215 and the first end of the second DC capacitor circuit 602 are connected to the first end of the DC input port 51. The second end of the sixth switching unit 216 and the second end of the third DC capacitor circuit 603 are connected to the second end of the DC input port 51. The second end of the second DC capacitor circuit 602 and the first end of the third DC capacitor circuit 603 are connected to the midpoint E of the third bridge arm. The second end of the fifth switching unit 215 and the first end of the sixth switching unit 216 are connected to the midpoint F of the fourth bridge arm.

[0094] The midpoint E of the third bridge arm and the midpoint F of the fourth bridge arm are connected to the primary side of the first transformer 11.

[0095] The first inverter module 21 adopts, as follows: Figure 6 The structure shown reduces the number of components by changing the primary side of the first transformer 11 from four bridge arms to two bridge arms, and also halves the input voltage of the first transformer 11, thereby reducing the voltage stress on the first transformer 11. Furthermore, the DC side of the first inverter module 21 uses a second DC capacitor circuit 602 and a third DC capacitor circuit 603 connected in series, and the second DC capacitor circuit 602 and the third DC capacitor circuit 603 can be used for grounding. This disclosure provides... Figure 6 The first inverter module 21 shown halves the input voltage of the first transformer 11 and doubles the current, making the DC transformer more suitable for step-down operation scenarios. The high voltage and low current on the primary side of the first transformer 11 ensure that the cost is not affected even though the current is doubled. Furthermore, since the primary side of the first transformer 11 is changed from four bridge arms to two bridge arms, the number of components is halved, which significantly reduces the manufacturing cost of the DC transformer.

[0096] The first rectifier module 31 includes a seventh switch unit 311, an eighth switch unit 312, a ninth switch unit 313, and a tenth switch unit 314.

[0097] The multiple DC capacitor circuits 60 include a fourth DC capacitor circuit 604.

[0098] The first end of the seventh switch unit 311 and the first end of the ninth switch unit 313 are connected to the first end of the DC output port 52. The second end of the eighth switch unit 312 and the second end of the tenth switch unit 314 are connected to the second end of the DC output port 52. The second end of the seventh switch unit 311 and the first end of the eighth switch unit 312 are connected to the midpoint G of the fifth bridge arm. The second end of the ninth switch unit 313 and the first end of the tenth switch unit 314 are connected to the midpoint H of the sixth bridge arm.

[0099] The midpoint G of the fifth bridge arm and the midpoint H of the sixth bridge arm are connected to the secondary side of the first transformer 11; the first end of the fourth DC capacitor circuit 604 is connected to the first end of the DC output port 52, and the second end of the fourth DC capacitor circuit 604 is connected to the second end of the DC output port 52.

[0100] In DC transformers suitable for DC step-down operation, both the fifth switching unit 215 and the sixth switching unit 216 are as follows: Figure 12 The series switch module 70 shown includes the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314, all of which are as follows: Figure 13 The diode series valve string 72 is shown.

[0101] In a DC transformer suitable for DC boost operation, both the fifth switching unit 215 and the sixth switching unit 216 are as follows: Figure 13 The diode series valve string 72 shown, the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314 are all as follows: Figure 12 The series switch module 70 shown.

[0102] In a DC transformer suitable for both DC boost and buck operation, the fifth switch unit 215, the sixth switch unit 216, the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314 are all as follows: Figure 12 The series switch module 70 shown.

[0103] In some embodiments, see continue to see Figure 7 and Figure 8 The inverter circuit 20 includes a first inverter module 21; the rectifier circuit 30 includes multiple first rectifier modules 31; the transformer circuit 10 includes multiple first transformers 11; wherein, the first rectifier module 31 corresponds one-to-one with the first transformer 11.

[0104] The DC side of the first inverter module 21 is connected to the DC input port 51, the AC side of the first inverter module 21 is connected to the primary side of multiple first transformers 11, the secondary side of multiple first transformers 11 is connected to the AC side of the corresponding first rectifier module 31, and the DC side of multiple first rectifier modules 31 is connected to the DC output port 52.

[0105] As an example, see further. Figure 7 The first inverter module 21 includes a first switching unit 211, a second switching unit 212, a third switching unit 213, and a fourth switching unit 214.

[0106] The plurality of DC capacitor circuits 60 include a first DC capacitor circuit 601.

[0107] The first end of the first switch unit 211 and the first end of the third switch unit 213 are connected to the first end of the DC input port 51. The second end of the second switch unit 212 and the second end of the fourth switch unit 214 are connected to the second end of the DC input port 51. The second end of the first switch unit 211 and the first end of the second switch unit 212 are connected to the midpoint C of the first bridge arm. The second end of the third switch unit 213 and the first end of the fourth switch unit 214 are connected to the midpoint D of the second bridge arm.

[0108] The midpoint C of the first bridge arm and the midpoint D of the second bridge arm are connected to the primary side of the first transformer 11; the first end of the first DC capacitor circuit 601 is connected to the first end of the DC input port 51, and the second end of the first DC capacitor circuit 601 is connected to the second end of the DC input port 51.

[0109] The rectifier circuit 30 includes three first rectifier modules 31, and the transformer circuit 10 includes three first transformers 11.

[0110] The first rectifier module 31 includes a seventh switch unit 311, an eighth switch unit 312, a ninth switch unit 313, and a tenth switch unit 314.

[0111] The multiple DC capacitor circuits 60 include a fourth DC capacitor circuit 604.

[0112] The first end of the seventh switch unit 311 and the first end of the ninth switch unit 313 are connected to the first end of the DC output port 52. The second end of the eighth switch unit 312 and the second end of the tenth switch unit 314 are connected to the second end of the DC output port 52. The second end of the seventh switch unit 311 and the first end of the eighth switch unit 312 are connected to the midpoint G of the fifth bridge arm. The second end of the ninth switch unit 313 and the first end of the tenth switch unit 314 are connected to the midpoint H of the sixth bridge arm.

[0113] The midpoint G of the fifth bridge arm and the midpoint H of the sixth bridge arm are connected to the secondary side of the first transformer 11; the first end of the fourth DC capacitor circuit 604 is connected to the first end of the DC output port 52, and the second end of the fourth DC capacitor circuit 604 is connected to the second end of the DC output port 52.

[0114] In a DC transformer suitable for DC step-down operation, the first switching unit 211, the second switching unit 212, the third switching unit 213, and the fourth switching unit 214 are all as follows: Figure 12 The series switch module 70 shown includes the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314, all of which are as follows: Figure 13 The diode series valve string 72 is shown.

[0115] In a DC transformer suitable for DC boost operation, the first switching unit 211, the second switching unit 212, the third switching unit 213, and the fourth switching unit 214 are all as follows: Figure 13 The diode series valve string 72 shown, the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314 are all as follows: Figure 12 The series switch module 70 shown.

[0116] In a DC transformer suitable for both DC boost and buck operation, the first switching unit 211, the second switching unit 212, the third switching unit 213, the fourth switching unit 214, the seventh switching unit 311, the eighth switching unit 312, the ninth switching unit 313, and the tenth switching unit 314 are all as follows: Figure 12 The series switch module 70 shown.

[0117] As yet another example, see [continued] Figure 8 The first inverter module 21 includes a fifth switching unit 215 and a sixth switching unit 216.

[0118] The multiple DC capacitor circuits 60 include a second DC capacitor circuit 602 and a third DC capacitor circuit 603.

[0119] The first end of the fifth switching unit 215 and the first end of the second DC capacitor circuit 602 are connected to the first end of the DC input port 51. The second end of the sixth switching unit 216 and the second end of the third DC capacitor circuit 603 are connected to the second end of the DC input port 51. The second end of the second DC capacitor circuit 602 and the first end of the third DC capacitor circuit 603 are connected to the midpoint E of the third bridge arm. The second end of the fifth switching unit 215 and the first end of the sixth switching unit 216 are connected to the midpoint F of the fourth bridge arm.

[0120] The midpoint E of the third bridge arm and the midpoint F of the fourth bridge arm are connected to the primary side of the first transformer 11.

[0121] The first inverter module 21 adopts, as follows: Figure 8 The structure shown reduces the number of components by changing the primary side of the first transformer 11 from four bridge arms to two bridge arms, and also halves the input voltage of the first transformer 11, thereby reducing the voltage stress on the first transformer 11. Furthermore, the DC side of the first inverter module 21 uses a second DC capacitor circuit 602 and a third DC capacitor circuit 603 connected in series, and the second DC capacitor circuit 602 and the third DC capacitor circuit 603 can be used for grounding. This disclosure provides... Figure 8The first inverter module 21 shown halves the input voltage of the first transformer 11 and doubles the current, making the DC transformer more suitable for step-down operation scenarios. The high voltage and low current on the primary side of the first transformer 11 ensure that the cost is not affected even though the current is doubled. Furthermore, since the primary side of the first transformer 11 is changed from four bridge arms to two bridge arms, the number of components is halved, which significantly reduces the manufacturing cost of the DC transformer.

[0122] The rectifier circuit 30 includes three first rectifier modules 31, and the transformer circuit 10 includes three first transformers 11.

[0123] The first rectifier module 31 includes a seventh switch unit 311, an eighth switch unit 312, a ninth switch unit 313, and a tenth switch unit 314.

[0124] The multiple DC capacitor circuits 60 include a fourth DC capacitor circuit 604.

[0125] The first end of the seventh switch unit 311 and the first end of the ninth switch unit 313 are connected to the first end of the DC output port 52. The second end of the eighth switch unit 312 and the second end of the tenth switch unit 314 are connected to the second end of the DC output port 52. The second end of the seventh switch unit 311 and the first end of the eighth switch unit 312 are connected to the midpoint G of the fifth bridge arm. The second end of the ninth switch unit 313 and the first end of the tenth switch unit 314 are connected to the midpoint H of the sixth bridge arm.

[0126] The midpoint G of the fifth bridge arm and the midpoint H of the sixth bridge arm are connected to the secondary side of the first transformer 11; the first end of the fourth DC capacitor circuit 604 is connected to the first end of the DC output port 52, and the second end of the fourth DC capacitor circuit 604 is connected to the second end of the DC output port 52.

[0127] In DC transformers suitable for DC step-down operation, both the fifth switching unit 215 and the sixth switching unit 216 are as follows: Figure 12 The series switch module 70 shown includes the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314, all of which are as follows: Figure 13 The diode series valve string 72 is shown.

[0128] In a DC transformer suitable for DC boost operation, both the fifth switching unit 215 and the sixth switching unit 216 are as follows: Figure 13 The diode series valve string 72 shown, the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314 are all as follows: Figure 12 The series switch module 70 shown.

[0129] In a DC transformer suitable for both DC boost and buck operation, the fifth switch unit 215, the sixth switch unit 216, the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314 are all as follows: Figure 12 The series switch module 70 shown.

[0130] In some embodiments, see continue to see Figure 5 , Figure 6 , Figure 7 , Figure 8 The DC transformer also includes multiple filter circuits 80.

[0131] The DC side of the inverter circuit 20 is connected to the DC input port 51 through the filter circuit 80, and the DC side of the rectifier circuit 30 is connected to the DC output port 52 through the filter circuit 80.

[0132] For example, the DC transformer includes four filter circuits 80. The positive and negative terminals of the DC side of the inverter circuit 20 are connected to the DC input port 51 through the filter circuits 80, and the positive and negative terminals of the DC side of the rectifier circuit 30 are connected to the DC output port 52 through the filter circuits 80.

[0133] Figure 5 , Figure 6 , Figure 7 , Figure 8 The filter circuit 80 shown here only includes the filter inductor L1 as an example. The filter circuit may also include at least one of the following: a filter inductor, a filter capacitor, and a filter resistor. For example, it may be an RLC filter composed of a filter inductor, a filter capacitor, and a filter resistor, or an LC filter composed of a filter inductor and a filter capacitor. The filter circuit 80 is used to reduce voltage and current harmonics flowing from the DC input port 51 to the DC side of the inverter circuit, and to reduce voltage and current harmonics flowing from the DC side of the rectifier circuit 30 to the DC output port 52.

[0134] In some embodiments, Figure 14 This is a schematic diagram of a preferred DC transformer provided in an embodiment of the present disclosure, as shown below. Figure 14 As shown, the DC transformer includes: four filter circuits 80, a transformer circuit 10, an inverter circuit 20, a rectifier circuit 30, and a resonant circuit 40.

[0135] The filter circuit 80 includes a filter inductor L1. The positive and negative terminals of the DC side of the inverter circuit 20 are connected to the DC input port 51 through the filter inductor L1. The positive and negative terminals of the DC side of the rectifier circuit 30 are connected to the DC output port 52 through the filter inductor L1.

[0136] The inverter circuit 20 includes a first inverter module 21; the rectifier circuit 30 includes three first rectifier modules 31; and the transformer circuit 10 includes three first transformers 11. The resonant circuit 40 includes multiple resonant modules 41 connected in series, which are connected between the primary side of the transformer circuit 10 and the AC side of the inverter circuit 20.

[0137] The first inverter module 21 includes a fifth switching unit 215 and a sixth switching unit 216.

[0138] The first rectifier module 31 includes a seventh switch unit 311, an eighth switch unit 312, a ninth switch unit 313, and a tenth switch unit 314.

[0139] The multiple DC capacitor circuits 60 include a second DC capacitor circuit 602, a third DC capacitor circuit 603, a fourth DC capacitor circuit 604, and a fifth DC capacitor circuit 605.

[0140] The first end of the fifth switching unit 215 and the first end of the second DC capacitor circuit 602 are connected to the first end of the DC input port 51. The second end of the sixth switching unit 216 and the second end of the third DC capacitor circuit 603 are connected to the second end of the DC input port 51. The second end of the second DC capacitor circuit 602 and the first end of the third DC capacitor circuit 603 are connected to the midpoint E of the third bridge arm. The second end of the fifth switching unit 215 and the first end of the sixth switching unit 216 are connected to the midpoint F of the fourth bridge arm.

[0141] The midpoint E of the third bridge arm and the midpoint F of the fourth bridge arm are connected to the primary side of the first transformer 11.

[0142] The first end of the seventh switch unit 311 and the first end of the ninth switch unit 313 are connected to the first end of the DC output port 52. The second end of the eighth switch unit 312 and the second end of the tenth switch unit 314 are connected to the second end of the DC output port 52. The second end of the seventh switch unit 311 and the first end of the eighth switch unit 312 are connected to the midpoint G of the fifth bridge arm. The second end of the ninth switch unit 313 and the first end of the tenth switch unit 314 are connected to the midpoint H of the sixth bridge arm.

[0143] The midpoint G of the fifth bridge arm and the midpoint H of the sixth bridge arm are connected to the secondary side of the first transformer 11; the first end of the fourth DC capacitor circuit 604 is connected to the first end of the DC output port 52, the second end of the fourth DC capacitor circuit 604 is connected to the first end of the fifth DC capacitor circuit 605, and the first end of the fifth DC capacitor circuit 605 is connected to the second end of the DC output port 52.

[0144] The second terminal of the second DC capacitor circuit 602 and the second terminal of the fourth DC capacitor circuit 604 are both grounded.

[0145] Both the fifth switch unit 215 and the sixth switch unit 216 are as follows Figure 12 The series switch module 70 shown includes the seventh switch unit 311, the eighth switch unit 312, the ninth switch unit 313, and the tenth switch unit 314, all of which are as follows: Figure 13 The diode series valve string 72 is shown.

[0146] For example, the first terminal of the DC input port 51 provides a +500kV voltage to the positive terminal of the DC side of the inverter circuit 20, and the second terminal of the DC input port 51 provides a -500kV voltage to the negative terminal of the DC side of the inverter circuit 20. The positive terminal of the DC side of the rectifier circuit 30 provides a +150kV voltage to the first terminal of the DC output port 52, and the negative terminal of the DC side of the rectifier circuit 30 provides a -150kV voltage to the second terminal of the DC output port 52. The first transformer 11 operates at a frequency of 400Hz.

[0147] The voltage-equalizing capacitors of the series-connected switching modules 70 in the fifth switching unit 215 and the sixth switching unit 216 have a capacitance of approximately 100μF, which can meet the high-level self-powering requirements and has a good dynamic voltage equalization effect. Furthermore, since the external control module can determine the number of resonant modules 41 connected to the first capacitor according to the resonant requirements of the DC transformer under different operating conditions, and control the input of the first capacitor according to the specific number, this disclosure can simulate the output voltage of the DC transformer when using resonant capacitors of different capacitance values. This ensures that the DC transformer can meet the conditions for resonant soft switching under different operating conditions without the need for a resonant capacitor, thereby enabling the switching devices in the inverter circuit 20 and the rectifier circuit 30 to achieve soft switching, thus ensuring zero switching losses. Compared with traditional solutions, the capacitor usage in the entire DC transformer system is reduced by 84%, the volume of the DC transformer at the 400Hz intermediate frequency is reduced by more than 50% compared to the 50Hz power frequency, and the number of power semiconductor devices is reduced by more than 35%. Therefore, this disclosure meets the design requirements of low cost and compact design for DC transformers.

[0148] The above are merely specific embodiments of this disclosure, enabling those skilled in the art to understand or implement this disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to these embodiments, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A DC transformer, characterized in that, include: Transformer circuit; An inverter circuit, wherein the DC side of the inverter circuit is connected to the DC input port, and the AC side of the inverter circuit is connected to the primary side of the transformer circuit; A rectifier circuit, wherein the AC side of the rectifier circuit is connected to the secondary side of the transformer circuit, and the DC side of the rectifier circuit is connected to the DC output port; The resonant circuit includes multiple resonant modules, and the AC side of the inverter circuit is connected to the AC side of the rectifier circuit through the multiple resonant modules and the transformer circuit. The resonant module includes a first capacitor, which is used to control the activation or deactivation of the first capacitor.

2. The DC transformer according to claim 1, characterized in that, The resonant module also includes a first full-bridge module; The first terminal of the first full-bridge module is connected to the first terminal of the first capacitor, and the second terminal of the first full-bridge module is connected to the second terminal of the first capacitor; the AC side of the inverter circuit is connected to the AC side of the rectifier circuit through the first full-bridge module and the transformer circuit. The first full-bridge module is used to control the connection or disconnection of the first capacitor.

3. The DC transformer according to claim 2, characterized in that, The first full-bridge module includes a first switching element, a second switching element, a third switching element, and a fourth switching element; The first end of the first switching element and the first end of the third switching element are connected to the first end of the first capacitor. The second end of the first switching element and the first end of the second switching element are connected to the first node. The second end of the third switching element and the first end of the fourth switching element are connected to the second node. The second ends of the second switching element and the second end of the fourth switching element are connected to the second end of the first capacitor. Multiple first full-bridge modules are connected between the AC side of the inverter circuit and the primary side of the transformer circuit through the first node and the second node, and / or connected between the secondary side of the transformer circuit and the AC side of the rectifier circuit.

4. The DC transformer according to claim 1, characterized in that, It also includes multiple DC capacitor circuits; the DC side of the inverter circuit and the DC side of the rectifier circuit are both connected to the DC capacitor circuits. The DC capacitor circuit includes multiple DC capacitors and multiple DC capacitor modules connected in series. The DC capacitor module is connected to the DC capacitor in a one-to-one correspondence.

5. The DC transformer according to claim 4, characterized in that, The plurality of DC capacitor modules include a first half-bridge module and / or a second full-bridge module.

6. The DC transformer according to claim 4, characterized in that, The inverter circuit includes a first inverter module; the rectifier circuit includes a first rectifier module; the transformer circuit includes a first transformer; The DC side of the first inverter module is connected to the DC input port, the AC side of the first inverter module is connected to the primary side of the first transformer, the secondary side of the first transformer is connected to the AC side of the first rectifier module, and the DC side of the first rectifier module is connected to the DC output port.

7. The DC transformer according to claim 4, characterized in that, The inverter circuit includes a first inverter module; the rectifier circuit includes multiple first rectifier modules; the transformer circuit includes multiple first transformers; wherein, the first rectifier module corresponds one-to-one with the first transformer; The DC side of the first inverter module is connected to the DC input port, the AC side of the first inverter module is connected to the primary side of the plurality of first transformers, the secondary side of the plurality of first transformers is connected to the AC side of the corresponding first rectifier module, and the DC side of the plurality of first rectifier modules is connected to the DC output port.

8. The DC transformer according to claim 6 or 7, characterized in that, The first inverter module includes a first switching unit, a second switching unit, a third switching unit, and a fourth switching unit; The plurality of DC capacitor circuits include a first DC capacitor circuit; The first end of the first switch unit and the first end of the third switch unit are connected to the first end of the DC input port, the second end of the second switch unit and the second end of the fourth switch unit are connected to the second end of the DC input port, the second end of the first switch unit and the first end of the second switch unit are connected at the midpoint of the first bridge arm, and the second end of the third switch unit and the first end of the fourth switch unit are connected at the midpoint of the second bridge arm. The midpoints of the first and second bridge arms are connected to the primary side of the first transformer; the first end of the first DC capacitor circuit is connected to the first end of the DC input port, and the second end of the first DC capacitor circuit is connected to the second end of the DC input port.

9. The DC transformer according to claim 6 or 7, characterized in that, The first inverter module includes a fifth switching unit and a sixth switching unit; The plurality of DC capacitor circuits include a second DC capacitor circuit and a third DC capacitor circuit; The first end of the fifth switching unit and the first end of the second DC capacitor circuit are connected to the first end of the DC input port. The second end of the sixth switching unit and the second end of the third DC capacitor circuit are connected to the second end of the DC input port. The second end of the second DC capacitor circuit and the first end of the third DC capacitor circuit are connected at the midpoint of the third bridge arm. The second end of the fifth switching unit and the first end of the sixth switching unit are connected at the midpoint of the fourth bridge arm. The midpoints of the third and fourth bridge arms are connected to the primary side of the first transformer.

10. The DC transformer according to claim 6 or 7, characterized in that, The first rectifier module includes a seventh switching unit, an eighth switching unit, a ninth switching unit, and a tenth switching unit; The plurality of DC capacitor circuits include a fourth DC capacitor circuit; The first end of the seventh switch unit and the first end of the ninth switch unit are connected to the first end of the DC output port. The second end of the eighth switch unit and the second end of the tenth switch unit are connected to the second end of the DC output port. The second end of the seventh switch unit and the first end of the eighth switch unit are connected at the midpoint of the fifth bridge arm. The second end of the ninth switch unit and the first end of the tenth switch unit are connected at the midpoint of the sixth bridge arm. The midpoints of the fifth and sixth bridge arms are connected to the secondary side of the first transformer; the first end of the fourth DC capacitor circuit is connected to the first end of the DC output port, and the second end of the fourth DC capacitor circuit is connected to the second end of the DC output port.

11. The DC transformer according to any one of claims 1-3, characterized in that, It also includes multiple filtering circuits; The DC side of the inverter circuit is connected to the DC input port through the filter circuit, and the DC side of the rectifier circuit is connected to the DC output port through the filter circuit.

12. The DC transformer according to claim 11, characterized in that, The filter circuit includes at least one of a filter inductor, a filter capacitor, and a filter resistor.

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