Flying capacitor converter

Abstract

The invention discloses a flying capacitor converter, which belongs to the field of power electronic power converters and comprises a first direct-current terminal, a second direct-current terminal and a conversion bridge arm connected between the first direct-current terminal and the second direct-current terminal. The conversion bridge arm comprises a first alternating current terminal and a second alternating current terminal; a first potential circuit element connected between the first DC terminal and the first AC terminal; a second potential circuit element connected between the second DC terminal and the second AC terminal; a connector assembly connected between the first potential circuit element and the second potential circuit element and connected between the first AC terminal and the second AC terminal; wherein the conversion bridge arm is provided with a reference surface, and the first potential circuit element and the second potential circuit element are arranged in plane symmetry about the reference surface. The conversion bridge arms of the flying capacitor converter adopt a plane symmetrical structure layout, so that the highest working voltage can be improved, the stray inductance can be reduced, and the performance requirement of high-voltage and high-power application can be met.

Description

Technical Field

[0001] The present application belongs to the field of power electronic power converters, and specifically relates to a flying capacitor converter. Background Art

[0002] Flying capacitor converters have many advantages, such as simple circuit structure, small number of semiconductor power switching devices, and the ability to output multiple levels. They are widely used in low-voltage DC / DC and DC / AC power conversion.

[0003] At present, flying capacitor converters are generally composed of multiple commutation circuit units, each of which contains two power switching devices and two capacitors. When flying capacitor converters are used in high voltage applications, the insulation requirements in the commutation circuit unit are increased, and there is a contradiction between the electrical insulation requirements and the low circuit stray inductance requirements. When the two power switching devices in the commutation circuit unit are too close, there is a risk of insulation failure at high voltage; if the distance between the power switching devices is increased, the stray inductance of the commutation circuit unit will also increase; this makes it impossible to guarantee the performance of flying capacitor converters in high voltage and high power applications. Summary of the invention

[0004] Purpose of the invention: The embodiment of the present application provides a flying capacitor converter, which aims to solve the problem that the performance of existing flying capacitor converters cannot meet the application environment of high voltage and high power.

[0005] Technical solution: A flying capacitor converter according to an embodiment of the present application comprises: a first DC terminal, a second DC terminal, and a conversion bridge arm connected between the first DC terminal and the second DC terminal;

[0006] The transformation bridge arm comprises:

[0007] a first AC terminal and a second AC terminal;

[0008] A first potential circuit element connected between the first DC terminal and the first AC terminal;

[0009] a second potential circuit element connected between the second DC terminal and the second AC terminal;

[0010] A connector assembly connected between the first potential circuit element and the second potential circuit element, and connected between the first AC terminal and the second AC terminal;

[0011] The transformation bridge arm has a reference plane, and the first potential circuit element and the second potential circuit element are arranged in a plane symmetrical relationship with respect to the reference plane.

[0012] In some embodiments, the potential of the first potential circuit element is higher than the potential of the second potential circuit element.

[0013] In some embodiments, the flying capacitor converter further comprises:

[0014] An insulating member is arranged between the first potential circuit element and the second potential circuit element, and the insulating member is extended along the reference plane; the insulating member is provided with an avoidance area, and the connector component is passed through the avoidance area.

[0015] In some embodiments, the flying capacitor converter further comprises:

[0016] A first potential connector, disposed on a side of the insulating member facing the first potential circuit element, the first potential connector being used to electrically connect each circuit element of the first potential circuit element;

[0017] The second potential connector is arranged on a side of the insulating member facing the second potential circuit element, and the second potential connector is used to electrically connect each circuit element of the second potential circuit element.

[0018] In some embodiments, the first potential connector and the second potential connector are arranged in plane symmetry with each other with respect to the reference plane.

[0019] In some embodiments, the insulating member, the first potential connector and the second potential connector are split structures; and / or,

[0020] The insulating member is made of insulating material, and the first potential connector and the second potential connector are respectively made of printed circuit boards or laminated busbars.

[0021] In some embodiments, the insulating member, the first potential connector and the second potential connector are an integrated structure; and / or,

[0022] The insulating member, the first potential connector and the second potential connector are integrally formed in the form of a multi-layer printed circuit board or a multi-layer laminated busbar.

[0023] In some embodiments, the first potential circuit element includes a plurality of first power devices, a first capacitor, and a second capacitor, the plurality of first power devices are connected in series between the first DC terminal and the first AC terminal, the first capacitor is connected to the first DC terminal and is connected in parallel to a side of the first power device away from the first AC terminal, and the second capacitor is connected in parallel between two adjacent first power devices;

[0024] The second potential circuit element comprises a plurality of second power devices, a third capacitor and a fourth capacitor, the plurality of second power devices are connected in series between the second DC terminal and the second AC terminal, the third capacitor is connected to the second DC terminal and connected in parallel to a side of the second power device away from the second AC terminal, and the fourth capacitor is connected in parallel between two adjacent second power devices;

[0025] The connector assembly includes a first connector, a second connector and a third connector, the first connector is connected in series with the first capacitor and the third capacitor, the second connector is connected in series with the second capacitor and the fourth capacitor, and the third connector is connected in series with the first AC terminal and the second AC terminal.

[0026] In some embodiments, the flying capacitor converter further comprises:

[0027] a heat dissipation device, arranged at the first potential circuit element and / or the second potential circuit element, for dissipating heat of the first power device and / or the second power device;

[0028] The heat dissipation device of the first power device and the heat dissipation device of the second power device are respectively located on two sides of the reference plane.

[0029] In some embodiments, the first power devices and the second power devices correspond to each other one by one and are arranged in a plane symmetrical manner with respect to the reference plane, and the number of the first power devices and the number of the second power devices are both N, where N≥2;

[0030] The second capacitors and the fourth capacitors correspond to each other one by one and are arranged in a plane symmetrical manner with respect to the reference plane. The number of the second capacitors and the number of the fourth capacitors are both M, where M=N-1.

[0031] In some embodiments, the first power device and the second power device are selected from one or more of a power diode, a power transistor, and a power module.

[0032] Beneficial effect: Compared with the prior art, the flying capacitor converter of the embodiment of the present application includes: a first DC terminal, a second DC terminal and a conversion bridge arm connected between the first DC terminal and the second DC terminal; the conversion bridge arm includes: a first AC terminal and a second AC terminal; a first potential circuit element, connected between the first DC terminal and the first AC terminal; a second potential circuit element, connected between the second DC terminal and the second AC terminal; a connector assembly, connected between the first potential circuit element and the second potential circuit element, and connected between the first AC terminal and the second AC terminal; wherein the conversion bridge arm has a reference plane, and the first potential circuit element and the second potential circuit element are arranged in a plane symmetrical to each other about the reference plane. The conversion bridge arm of the flying capacitor converter adopts a planar symmetrical structure layout. On the one hand, it reduces the stray inductance of the commutation circuit, which is beneficial to reducing the transient peak voltage of the power switching devices in the converter, reducing the electromagnetic interference level, and improving the reliability of the converter; on the other hand, the symmetrical structure increases the creepage distance between the high and low potential devices in the converter, ensures the insulation performance, and is beneficial to improving the system operating voltage; furthermore, the symmetrical structure makes the voltage difference between adjacent power switching devices only the operating voltage of a single power switching device, reducing the requirements for creepage distance and electrical clearance, which is beneficial to reducing the overall volume of the converter and improving power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 A schematic diagram of the circuit structure of a flying capacitor converter provided in the first embodiment of the present application;

[0035] Figure 2 for Figure 1 Circuit notation diagram of flying capacitor converter;

[0036] Figure 3 This is a schematic diagram of the layout of a flying capacitor converter in the first embodiment of the present application;

[0037] Figure 4 for Figure 3 A schematic diagram of the local structure of the flying capacitor converter viewed from the reference plane AA' toward the first potential circuit element;

[0038] Figure 5 for Figure 3 A schematic diagram of the local structure of the flying capacitor converter viewed from the reference plane AA' toward the second potential circuit element;

[0039] Figure 6 It is a schematic diagram of the cross-sectional structure of the insulating member along the reference plane AA' in the embodiment of the present application;

[0040] Figure 7 A schematic diagram of circuit markings of a flying capacitor converter provided in the second embodiment of the present application;

[0041] Figure 8 This is a schematic diagram of the layout of a flying capacitor converter in the second embodiment of the present application;

[0042] Fig. 9 for Figure 8 A schematic diagram of the local structure of the flying capacitor converter viewed from the reference plane AA' toward the first potential circuit element;

[0043] Fig.10 for Figure 8 A schematic diagram of the local structure of the flying capacitor converter viewed from the reference plane AA' toward the second potential circuit element;

[0044] Figure markings: 100-first DC terminal; 200-second DC terminal; 300-first potential circuit element; 310-first power device; 320-first capacitor; 330-second capacitor; 400-second potential circuit element; 410-second power device; 420-third capacitor; 430-fourth capacitor; 500-connector assembly; 510-first connector; 520-second connector; 530-third connector; 600-first AC terminal; 700-second AC terminal; 810-insulating member; 811-avoidance area; 820-first potential connector; 830-second potential connector; 900-heat dissipation device. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0046] In the description of the present application, it should be understood that the terms "upper", "lower", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In the description of the present application, "multiple" means two or more, and at least one means one, two, or more than two, unless otherwise clearly and specifically defined.

[0047] It should also be noted that in the description of the present application, the reference plane AA' is a virtual plane, and the reference plane AA' is introduced to more clearly illustrate the structure of the components of the flying capacitor converter of the embodiment of the present application and the relative positional relationship between the components. One component and another component are arranged in a plane symmetrical manner with respect to the reference plane AA', which means that the two components are arranged on both sides of the reference plane AA' in a plane symmetrical manner, wherein the so-called "symmetry" can be complete symmetry in geometry (the shapes completely overlap), or it can be rough and relative symmetry (the shapes do not necessarily completely overlap, and the arrangement can have relative deviations).

[0048] The applicant has found that reducing the stray inductance of the commutation circuit unit in the flying capacitor converter is beneficial to reducing the voltage spike of the power switching device and reducing the switching loss. Therefore, it is necessary to shorten the distance between the power switching device and the capacitor in the commutation circuit unit as much as possible to reduce the stray inductance. The voltage difference between the two power switching devices in the commutation circuit unit of the flying capacitor converter can reach the highest converter operating voltage, and the capacitor operating voltage can also reach the highest converter operating voltage. In order to meet the insulation requirements, it is necessary to ensure the device spacing. When the flying capacitor converter is used in high-voltage applications, the insulation requirements in the commutation circuit unit are increased. At this time, there is a contradiction between the electrical insulation requirements and the low loop stray inductance requirements, and the high operating voltage and low loop stray inductance restrict each other. On the other hand, the power switching device generates a lot of heat, and a heat sink needs to be arranged close to the power switching device. The presence of the heat sink further compresses the electrical clearance and creepage distance, exacerbating the above contradiction.

[0049] In view of this, an embodiment of the present application provides a flying capacitor converter to overcome at least one of the above technical problems.

[0050] Please also read Figure 1 and Figure 2 The flying capacitor converter of the first embodiment of the present application mainly includes: a first DC terminal 100, a second DC terminal 200, and a conversion bridge arm connected between the first DC terminal 100 and the second DC terminal 200.

[0051] Among them, the first DC terminal 100 and the second DC terminal 200 are used to connect to the DC power grid. The conversion bridge arm mainly includes: a first AC terminal 600, a second AC terminal 700, a first potential circuit element 300, a second potential circuit element 400 and a connector assembly 500. The first AC terminal 600 and the second AC terminal 700 are used to connect to the AC power grid. The first potential circuit element 300 is connected between the first DC terminal 100 and the first AC terminal 600, and the second potential circuit element 400 is connected between the second DC terminal 200 and the second AC terminal 700. The connector assembly 500 is connected between the first potential circuit element 300 and the second potential circuit element 400 and between the first AC terminal 600 and the second AC terminal 700.

[0052] In the first embodiment, the conversion bridge arm has a reference plane AA', and the first potential circuit element 300 and the second potential circuit element 400 are arranged in a plane symmetrical manner with respect to the reference plane AA'. That is, the first potential circuit element 300 and the second potential circuit element 400 are arranged on both sides of the reference plane AA' in a plane symmetrical manner, and the connector component 500 passes through the reference plane AA'. Preferably, the connector component 500 is arranged in a plane symmetrical manner with respect to the reference plane AA'.

[0053] The conversion bridge arm of the flying capacitor converter adopts a planar symmetrical structure layout, that is, a mirror symmetrical layout, which can effectively reduce the stray inductance of the commutation circuit, which is beneficial to reduce the transient peak voltage of the power switching device, reduce the electromagnetic interference level, and improve the reliability of the converter. The symmetrical structure increases the creepage distance between high and low potential devices in the converter system, which is beneficial to increase the system operating voltage. The voltage difference between adjacent power switching devices and adjacent heat sinks can be made only the operating voltage of a single power switching device, reducing the creepage distance and electrical clearance requirements, which is beneficial to reducing the overall volume of the converter and improving the power density.

[0054] Specifically, in some embodiments, the potential of the first potential circuit element 300 is higher than the potential of the second potential circuit element 400. That is, the first potential circuit element 300 is a high potential circuit element, and the second potential circuit element 400 is a low potential circuit element.

[0055] For details, please refer to Figure 1 and Figure 2In some embodiments, the first potential circuit element 300 includes a plurality of first power devices 310, a first capacitor 320, and a second capacitor 330. The plurality of first power devices 310 are connected in series between the first DC terminal 100 and the first AC terminal 600, the first capacitor 320 is connected to the first DC terminal 100 and connected in parallel to a side of the first power device 310 away from the first AC terminal 600, and the second capacitor 330 is connected in parallel between two adjacent first power devices 310.

[0056] The second potential circuit element 400 includes a plurality of second power devices 410, a third capacitor 420, and a fourth capacitor 430. The plurality of second power devices 410 are connected in series between the second DC terminal 200 and the second AC terminal 700, the third capacitor 420 is connected to the second DC terminal 200 and connected in parallel to a side of the second power device 410 away from the second AC terminal 700, and the fourth capacitor 430 is connected in parallel between two adjacent second power devices 410.

[0057] The connector assembly 500 includes a first connector 510, a second connector 520 and a third connector 530. The first connector 510 is connected in series with the first capacitor 320 and the third capacitor 420, the second connector 520 is connected in series with the second capacitor 330 and the fourth capacitor 430, and the third connector 530 is connected in series with the first AC terminal 600 and the second AC terminal 700.

[0058] Specifically, the first connector 510 includes an N+ connector and an N− connector, the N+ connector is connected to the first capacitor 320, and the N− connector is connected to the third capacitor 420. Thus, the first capacitor 320 and the third capacitor 420 are connected through the first connector 510 to form a DC bus capacitor.

[0059] Specifically, the second connector 520 is set according to the number of flying capacitors required, and the flying capacitor can be one or more according to actual use needs. In this embodiment, taking three flying capacitors as an example, the second connector 520 includes an N1+ connector, an N1- connector, an N2+ connector, an N2- connector, an N3+ connector, and an N3- connector. Among them, the N1+ connector and the N1- connector are respectively used to connect the C1+ second capacitor 330 and the C1- fourth capacitor 430 to form the C1 flying capacitor; the N2+ connector and the N2- connector are respectively used to connect the C2+ second capacitor 330 and the C2- fourth capacitor 430 to form the C2 flying capacitor; the N3+ connector and the N3- connector are respectively used to connect the C3+ second capacitor 330 and the C3- fourth capacitor 430 to form the C3 flying capacitor.

[0060] Specifically, the third connector 530 includes an AC+ connector and an AC- connector, and the AC+ connector and the AC- connector are used to connect the first AC terminal 600 and the second AC terminal 700 respectively.

[0061] In some embodiments, the first power device 310 and the second power device 410 correspond to each other one by one and are arranged in a plane symmetrical to each other about the reference plane AA', and the first power device 310 and the second power device 410 are both N, N ≥ 2; the second capacitor 330 and the fourth capacitor 430 correspond to each other one by one and are arranged in a plane symmetrical to each other about the reference plane AA', and the second capacitor 330 and the fourth capacitor 430 are both M, M = N-1. That is, the first power device 310 and the second power device 410 can be two or more, and the second capacitor 330 and the fourth capacitor 430 are determined according to the specific number of the first power device 310 and the second power device 410.

[0062] Please also read Figure 3 , Figure 4 and Figure 5 In some embodiments of the present application, the flying capacitor converter further includes an insulating member 810, which is disposed between the first potential circuit element 300 and the second potential circuit element 400, and the insulating member 810 is extended along the reference plane AA'. By providing the insulating member 810, the electrical insulation between the non-equipotential electrical positions between the first potential circuit element 300 and the second potential circuit element 400 can be improved, the insulation performance can be further guaranteed, and the voltage can be indirectly promoted.

[0063] Please combine Figure 6 The insulating member 810 is provided with an escape area 811, and the connector assembly 500 is passed through the escape area 811. Therefore, the connection of the connector assembly 500 to the first potential circuit element 300 and the second potential circuit element 400 will not be affected.

[0064] Please refer again Figure 3 , Figure 4 and Figure 5In some embodiments, the flying capacitor converter further includes: a first potential connector 820 and a second potential connector 830. The first potential connector 820 is disposed on the side of the insulating member 810 facing the first potential circuit element 300, and the first potential connector 820 is used to electrically connect the circuit elements of the first potential circuit element 300, that is, the first capacitor 320 and the second capacitors 330 are electrically connected through the first potential connector 820. The second potential connector 830 is disposed on the side of the insulating member 810 facing the second potential circuit element 400, and the second potential connector 830 is used to electrically connect the circuit elements of the second potential circuit element 400, that is, the third capacitor 420 and the fourth capacitors 430 are electrically connected through the second potential connector 830.

[0065] In some embodiments, the first potential connector 820 and the second potential connector 830 are arranged in a plane symmetrical relationship with respect to the reference plane AA′, thereby further facilitating the balance between high operating voltage and low loop stray inductance.

[0066] It should be noted that there are two implementation methods for the insulating member 810 , the first potential connector 820 and the second potential connector 830 : independent implementation and integrated implementation.

[0067] The independent implementation means that the insulating member 810, the first potential connector 820 and the second potential connector 830 are independent components, that is, a split structure. Specifically, the insulating member 810 can be made of insulating materials such as epoxy resin, and the first potential connector 820 and the second potential connector 830 are respectively made of printed circuit boards or laminated busbars.

[0068] The overall implementation means that the insulating member 810, the first potential connector 820 and the second potential connector 830 are an integrated structure. Specifically, the insulating member 810, the first potential connector 820 and the second potential connector 830 are integrally formed by a multi-layer printed circuit board or a multi-layer laminated busbar.

[0069] Please refer again Figure 3 , Figure 4 and Figure 5In some embodiments, the flying capacitor converter further includes a heat sink 900, which is disposed on the first potential circuit element 300 and / or the second potential circuit element 400, and is used to dissipate heat from the first power device 310 and / or the second power device 410. The heat sink 900 for dissipating heat from the first power device 310 and the heat sink 900 for dissipating heat from the second power device 410 are respectively located on both sides of the reference plane AA', that is, the heat sink 900 on both sides can be blocked by the insulating member 810, thereby reducing the requirements for creepage distance and electrical clearance, which is conducive to reducing the overall volume of the flying capacitor converter and improving the power density.

[0070] In some embodiments, the first power device 310 and the second power device 410 are selected from one or more of a power diode, a power transistor, and a power module. Figure 8 The second embodiment is different from the first embodiment in that a board bridge module is used to replace the power switch devices in the first embodiment, wherein a half-bridge module M1 replaces the power switch devices T1 and T2, a half-bridge module M2 replaces the power switch devices T3 and T4, a half-bridge module M3 replaces the power switch devices T5 and T6, and a half-bridge module M4 replaces the power switch devices T7 and T8.

[0071] Please also read Fig. 9 and Fig.10 Preferably, the half-bridge module M1 is mirror-symmetrical to the half-bridge module M4, and the half-bridge module M2 is mirror-symmetrical to the half-bridge module M3.

[0072] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0073] The flying capacitor converter provided in the embodiments of the present application is introduced in detail above, and the principles and implementation methods of the present application are explained by applying specific examples. The description of the above embodiments is only used to help understand the technical solution and core idea of ​​the present application; ordinary technicians in this field should understand that: they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present application.

Claims

1. A flying capacitor converter, characterized in that: include: A first DC terminal (100), a second DC terminal (200), and a conversion bridge arm connected between the first DC terminal (100) and the second DC terminal (200); The transformation bridge arm comprises: A first AC terminal (600) and a second AC terminal (700); A first potential circuit element (300) connected between the first DC terminal (100) and the first AC terminal (600); A second potential circuit element (400) connected between the second DC terminal (200) and the second AC terminal (700); A connector assembly (500) connected between the first potential circuit element (300) and the second potential circuit element (400), and connected between the first AC terminal (600) and the second AC terminal (700); The conversion bridge arm has a reference plane (AA'), and the first potential circuit element (300) and the second potential circuit element (400) are arranged in a plane symmetrical relationship with respect to the reference plane (AA').

2. The flying capacitor converter according to claim 1, characterized in that: The potential of the first potential circuit element (300) is higher than the potential of the second potential circuit element (400).

3. The flying capacitor converter according to claim 1, characterized in that: The flying capacitor converter also includes: An insulating member (810) is arranged between the first potential circuit element (300) and the second potential circuit element (400), and the insulating member (810) is extended along the reference plane (AA'); the insulating member (810) is provided with an avoidance area (811), and the connector assembly (500) is inserted into the avoidance area (811).

4. The flying capacitor converter according to claim 3, characterized in that: The flying capacitor converter also includes: A first potential connector (820), arranged on a side of the insulating member (810) facing the first potential circuit element (300), the first potential connector (820) being used to electrically connect various circuit elements of the first potential circuit element (300); The second potential connector (830) is arranged on the side of the insulating member (810) facing the second potential circuit element (400), and the second potential connector (830) is used to electrically connect the circuit elements of the second potential circuit element (400).

5. The flying capacitor converter according to claim 4, characterized in that: The first potential connector (820) and the second potential connector (830) are arranged in a plane symmetrical relationship with respect to the reference plane (AA').

6. The flying capacitor converter according to claim 4, characterized in that: The insulating member (810), the first potential connecting member (820) and the second potential connecting member (830) are of a split structure; and / or, The insulating member (810) is made of insulating material, and the first potential connector (820) and the second potential connector (830) are respectively made of printed circuit boards or laminated busbars.

7. The flying capacitor converter according to claim 4, characterized in that: The insulating member (810), the first potential connecting member (820) and the second potential connecting member (830) are an integrated structure; and / or, The insulating member (810), the first potential connector (820) and the second potential connector (830) are integrally formed in the form of a multi-layer printed circuit board or a multi-layer laminated busbar.

8. The flying capacitor converter according to any one of claims 1 to 7, characterized in that: The first potential circuit element (300) comprises a plurality of first power devices (310), a first capacitor (320) and a second capacitor (330); the plurality of first power devices (310) are connected in series between the first DC terminal (100) and the first AC terminal (600); the first capacitor (320) is connected to the first DC terminal (100) and is connected in parallel to a side of the first power device (310) away from the first AC terminal (600); and the second capacitor (330) is connected in parallel between two adjacent first power devices (310); The second potential circuit element (400) comprises a plurality of second power devices (410), a third capacitor (420) and a fourth capacitor (430); the plurality of second power devices (410) are connected in series between the second DC terminal (200) and the second AC terminal (700); the third capacitor (420) is connected to the second DC terminal (200) and is connected in parallel to a side of the second power device (410) away from the second AC terminal (700); and the fourth capacitor (430) is connected in parallel between two adjacent second power devices (410); The connector assembly (500) includes a first connector (510), a second connector (520) and a third connector (530), wherein the first connector (510) is connected in series with the first capacitor (320) and the third capacitor (420), the second connector (520) is connected in series with the second capacitor (330) and the fourth capacitor (430), and the third connector (530) is connected in series with the first AC terminal (600) and the second AC terminal (700).

9. The flying capacitor converter according to claim 8, characterized in that: The flying capacitor converter also includes: A heat dissipation device (900), arranged on the first potential circuit element (300) and / or the second potential circuit element (400), for achieving heat dissipation of the first power device (310) and / or the second power device (410); The heat dissipation device (900) of the first power device (310) and the heat dissipation device (900) of the second power device (410) are respectively located on two sides of the reference plane (AA').

10. The flying capacitor converter according to claim 8, characterized in that: The first power device (310) and the second power device (410) correspond to each other one by one and are arranged in a plane symmetrical manner with respect to the reference plane (AA'), and the number of the first power device (310) and the number of the second power device (410) are both N, where N≥2; The second capacitor (330) and the fourth capacitor (430) correspond one to one and are arranged in a plane symmetrical manner with respect to the reference plane (AA'). The number of the second capacitor (330) and the number of the fourth capacitor (430) are both M, where M=N-1.

11. The flying capacitor converter according to claim 8, characterized in that: The first power device (310) and the second power device (410) are selected from one or more of a power diode, a power transistor, and a power module.

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