A power conversion module and cascaded converter

Abstract

The application provides a power conversion module and a cascaded converter. First sides of cascaded units in the power conversion module are respectively connected with corresponding windings in coupling inductors in series, and two branches connected in series or in parallel after the connection are connected between two interfaces in a cascaded side of the power conversion module. When multiple power conversion modules are cascaded through the cascaded side, each winding is connected in series, which is equivalent to decomposing centralized reactance in the prior art into multiple distributed inductors. Each winding does not need to be additionally provided with a spacing meeting the ground insulation requirement, thereby reducing the space requirement for external additional insulation of the inductor and improving the power density. Moreover, by adjusting the connection in the power conversion module, the series-parallel relationship between two cascaded units can be converted, so that the power conversion module can meet the large-current requirement and the high-voltage requirement, and the adaptability is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power converter, in particular to a power conversion module and a cascaded converter. BACKGROUND

[0002] The conventional cascaded converter connects an inductor in series at the end of each phase, such as Figure 1 As shown in the figure, the cascaded unit 1 to the cascaded unit n The inductor is connected in series at the end of the phase. Since the inductor needs to reach the system voltage, such as 35kVac system, the inductor voltage will reach 35kVac, and the installation of the inductor needs special consideration, which will occupy a large space and affect the system power density. SUMMARY

[0003] Therefore, the present application provides a power conversion module and a cascaded converter to reduce the space requirement of the inductor for external additional insulation and improve the power density.

[0004] To achieve the above object, the present application provides the following technical solutions:

[0005] The first aspect of the present application provides a power conversion module, comprising: a coupling inductor and two cascaded units;

[0006] The first side of each cascaded unit is connected in series with the corresponding winding in the coupling inductor, forming a corresponding series branch;

[0007] The two series branches are connected in series or parallel between the two internal interfaces of the cascaded side of the power conversion module;

[0008] The second side of each cascaded unit is used to connect the internal interface of the power supply side of the power conversion module.

[0009] Optionally, the first side of the two cascaded units is connected in series through the coupling inductor, and the two ends of the series branch are connected to the two internal interfaces of the cascaded side of the power conversion module.

[0010] Optionally, one of the cascaded units is connected to the opposite end of the corresponding winding;

[0011] The other cascaded unit is connected to the same end of the other winding;

[0012] The other ends of the two windings are connected.

[0013] Optionally, one end of the first side of the two cascaded units is connected in parallel to one internal interface of the cascaded side of the power conversion module;

[0014] The other end of the first side of the two cascade units is connected to one end of a corresponding winding of the coupling inductor, and the other end of each winding is connected in parallel to another internal interface on the cascade side of the power conversion module.

[0015] Optionally, the two cascade units are connected to the same end of the corresponding winding, respectively.

[0016] The different ends of the two windings are connected.

[0017] Optionally, the cascade unit is an inverter unit.

[0018] The alternating current side of the inverter unit serves as the first side of the cascade unit.

[0019] The direct current side of the inverter unit serves as the second side of the cascade unit.

[0020] Optionally, between the direct current side of the inverter unit and the internal interface corresponding to the power supply side of the power conversion module, a direct current converter or a plurality of direct current converters are further arranged.

[0021] The internal interface of the power supply side of the power conversion module is connected to the direct current side of each inverter unit through a multi-port direct current converter.

[0022] Optionally, the inverter unit is a half-bridge inverter unit or a full-bridge inverter unit.

[0023] The second aspect of the present application further provides a cascade converter, comprising at least one cascade branch, wherein the cascade branch comprises at least one power conversion module as described in any one of the first aspect.

[0024] When the number of power conversion modules in the cascade branch is greater than one, the external interfaces of the cascade side of each power conversion module are connected in series.

[0025] Optionally, the cascade branch further comprises a total inductor for suppressing output fluctuation.

[0026] The total inductor is connected in series to one end of the cascade branch.

[0027] Optionally, when the power conversion module does not comprise a direct current converter, the cascade branch further comprises a plurality of direct current converters arranged outside the power conversion module.

[0028] Each direct current converter is connected to the cascade unit of each power conversion module in the cascade branch in a one-to-one manner, or each cascade unit in the same power conversion module is connected to the same multi-port direct current converter.

[0029] Optionally, the cascaded unit in the power conversion module is an inverter unit, and the number of the cascaded branches is 3, and the three-phase cascaded branches are star-connected or angularly connected at the AC side.

[0030] The power conversion module provided in the application has the first side of each cascaded unit connected in series with the corresponding winding of the coupling inductor, and the cascaded branch is used to connect the internal interface of the cascaded side of the power conversion module; when multiple power conversion modules are cascaded through the cascaded side, each winding is connected in series, which is equivalent to decomposing the centralized reactance in the prior art into multiple distributed inductors; since the potential of each winding is close to the cascaded unit, and the distance between the cascaded unit and the ground meets the insulation requirement, each winding does not need to be additionally provided with a distance meeting the ground insulation requirement, reducing the space requirement of the inductor for external additional insulation and improving the power density. Moreover, by adjusting the internal connection of the power conversion module, the series-parallel relationship between two cascaded units can be converted, so that the power conversion module can meet the large current requirement and the high voltage requirement, further improving its adaptability. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0032] Figure 1 A structural schematic diagram of a cascaded converter provided in the prior art;

[0033] Figures 2 to 4 Three internal structural schematic diagrams of the power conversion module provided in the embodiments of the present application, respectively;

[0034] Figure 5 And Figure 6 Two cascaded schematic diagrams of the power conversion module provided in the embodiments of the present application, respectively;

[0035] Figure 7 And Figure 8 Two topological diagrams of the cascaded unit provided in the embodiments of the present application, respectively;

[0036] Figures 9 to 12 Four structural schematic diagrams of the cascaded branch provided in the embodiments of the present application, respectively;

[0037] Figures 13 to 16 Four topological diagrams of the power conversion module provided in the embodiments of the present application, respectively;

[0038] Figure 17 and Figure 18 are two topological diagrams of the cascaded branch provided by the embodiment of the present application respectively;

[0039] Figure 19 is a structural schematic diagram of the cascaded converter provided by the embodiment of the present application;

[0040] Figure 20 is another structural schematic diagram of the cascaded branch provided by the embodiment of the present application. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application.

[0042] In the present application, the terms "comprising", "containing" or any other variants thereof are intended to cover the non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the sentence "including a…" does not exclude the presence of another same element in the process, method, article or equipment including the element.

[0043] The present application provides a power conversion module to reduce the space requirement of inductance for external additional insulation and improve power density.

[0044] As shown in Figure 2 , the power conversion module 10 includes a coupling inductance 102 and two cascaded units 101; Figure 2 The two cascaded units 101 of the nth power conversion module 10 (referred to as module n) are shown in n1 and n2 ; wherein:

[0045] The first side of each cascaded unit 101 is connected in series with the corresponding winding of the coupling inductance 102, as shown in Figure 2 , the cascaded unit n1 is connected in series with the winding L1, and the cascaded unit n2 is connected in series with the winding L2. The cascaded branch after series connection is used to connect the internal interface of the cascaded side of the power conversion module 10. In actual application, the series connection branch formed by the series connection of each cascaded unit 101 and the corresponding winding can be connected in series (such as Figure 2(as shown) or in parallel (such as) Figure 3 or Figure 4 The interface shown is connected between the two internal interfaces on the cascade side of the power conversion module 10, which can further improve system compatibility. The external interface on the cascade side of the power conversion module 10 is used for series connection with the external interfaces on the cascade side of other power conversion modules 10.

[0046] The second side of each cascade unit 101 is used to connect to the internal power supply interface of the power conversion module 10; the external power supply interface of the power conversion module 10 is used to connect to the corresponding power source, such as photovoltaic modules, photovoltaic strings, battery modules or battery clusters.

[0047] like Figure 2 As shown, when multiple power conversion modules 10 are cascaded through their own cascaded sides, each winding is connected in series, which is equivalent to decomposing the centralized reactance in the prior art into multiple distributed inductors, and arranging them together with the corresponding cascaded units 101 respectively.

[0048] Since the potential of each winding is close to that of the cascaded unit 101 to which it is connected, and the distance between the cascaded unit 101 and the ground meets the insulation requirements, each winding does not need to be additionally set with a distance to meet the insulation requirements to the ground. Therefore, the power conversion module 10 provided in this embodiment can reduce the space requirement for additional external insulation of the inductor and improve the power density.

[0049] Moreover, by adjusting the internal wiring of the power conversion module, the series-parallel relationship between the two cascaded units can be switched, enabling the power conversion module to meet the high current and high voltage requirements respectively, further improving its adaptability.

[0050] In practical applications, when two cascaded units 101 need to be used in series, the first sides of the two cascaded units 101 are connected in series through a coupling inductor 102; the two ends of the resulting branch are respectively connected to the two internal interfaces of the cascaded side of the power conversion module 10. At this time, one cascaded unit 101 is connected to the opposite-named end of the corresponding winding; the other cascaded unit 101 is connected to the same-named end of the other winding; the other ends of the two windings are connected together. Figure 2 Taking module n as an example, the cascaded units above... n1 Its upper output serves as the upper output of the power conversion module 10, and its lower end is connected to the opposite-named terminal of winding L1 in the coupling inductor 102. The same-named terminal of winding L1 in the coupling inductor 102 is connected to the opposite-named terminal of winding L2; and the cascaded unit below n2 Its upper output is connected to the same-name terminal of winding L2 in coupling inductor 102, and its lower output serves as the lower output of the power conversion module 10.

[0051] When two cascade units 101 need to be used in parallel, one end of the first side of the two cascade units 101 is connected in parallel to an interface inside the cascade side of the power conversion module 10; the other end of the first side of the two cascade units 101 is connected to one end of a corresponding winding of the coupling inductor 102, and the other end of each winding is connected in parallel to another interface inside the cascade side of the power conversion module 10. At this time, the two cascade units 101 are connected to the same-named end of the corresponding winding respectively, and the different-named ends of the two windings are connected. Figure 3 The module n is also taken as an example for illustration, in which the cascade unit n1 above is connected to the same-named end of the winding L1 of the coupling inductor 102 at its upper end, and is connected to the lower end of the cascade unit n2 below and serves as the lower output of the module 10; the different-named end of the winding L1 of the coupling inductor 102 is connected to the different-named end of the winding L2 and serves as the upper output of the power conversion module 10, and the upper output of the cascade unit n2 below is connected to the same-named end of the winding L2 of the coupling inductor 102. As shown in Figure 4 , the coupling inductor 102 can also be connected to the lower output of the power conversion module 10, which will not be described again.

[0052] When two cascade units 101 are connected in series through the coupling inductor 102, multiple such power conversion modules 10 can be cascaded to meet the high-voltage requirement of the system; when two cascade units 101 are connected in parallel through the coupling inductor 102, multiple such power conversion modules 10 can be cascaded to meet the large-current requirement of the system; in actual application, Figures 2 to 4 the related elements in the modules are basically the same, and only by adjusting the internal connection of the power conversion module 10, the series-parallel relationship between the two cascade units 101 can be converted, so that the power conversion module 10 can be switched between meeting the large-current requirement and meeting the high / low voltage requirement, thereby improving the application range of the power conversion module 10.

[0053] In addition, by designing the coupling coefficient of the coupling inductor 102, the equivalent differential mode impedance between the two units when the cascade units n1 , n2 run in parallel can also be adjusted, thereby suppressing the problems of current sharing and weak through caused by the inconsistent characteristics of the two cascade units 101, and improving the reliability of the system.

[0054] In practical applications, the cascaded unit 101 in the above embodiments can be a power conversion unit with any conversion function, such as an inverter unit. In this case, the AC side of the inverter unit serves as the first side of the cascaded unit 101, and the DC side of the inverter unit serves as the second side of the cascaded unit 101. It should be noted that if the DC side of the inverter unit is used to connect photovoltaic modules or photovoltaic strings, then the inverter unit is only used to realize the conversion between DC and AC; while if the DC side of the inverter unit is used to connect battery modules or battery clusters, then the inverter unit needs to realize bidirectional conversion between DC and AC. The circuit topology in both cases can be found in the prior art, and will not be repeated here, both of which are within the protection scope of this application.

[0055] In addition, the inverter unit can also be equipped with a corresponding DC-DC converter to realize the first-level DC voltage regulation function of the DC input / output connected to it, or to realize the photovoltaic maximum power point tracking function. In practical applications, the DC-DC converter can be set inside the power conversion module 10, or it can be set outside the power conversion module 10, all of which are within the protection scope of this application.

[0056] When the DC-DC converter is installed inside the power conversion module 10, the DC-DC converter can correspond one-to-one with the cascaded unit 101 (e.g., Figure 5 As shown), it can also be connected to at least two cascaded units 101 via a multi-port DC-DC converter (as shown). Figure 6 (As shown). Specifically:

[0057] See Figure 5 Each inverter unit (as shown in the cascaded unit in the figure) n1 and cascaded units n2 Between the DC side of the power converter module 10 and the power supply side of the power conversion module 10, there is a corresponding DC converter 103.

[0058] See Figure 6 The internal interface on the power supply side of the power conversion module 10 can also be connected to the DC side of each inverter unit through a multi-port DC converter 103. Figure 6 The example shown is a 3-port DC-DC converter 103, in which 2 ports are connected to the DC side of the two inverter units in the power conversion module 10 respectively, and the other port is connected to the internal interface of the power supply side, so that it can be connected to an external power supply as DC input / output.

[0059] In practical applications, this inverter unit can be a half-bridge inverter unit (such as...) Figure 7 (as shown), or it can be a full-bridge inverter unit (such as...) Figure 8The power conversion module 10 can also be other topology units capable of realizing the inverter function in the prior art, as long as it is determined according to the specific application environment, and is within the protection scope of the present application.

[0060] Another embodiment of the present application also provides a cascaded converter, which, as shown in Figures 9 to 18 , comprises at least one phase (one phase is taken as an example for illustration in the figure) cascaded branch, each cascaded branch comprising: at least one power conversion module 10 according to any one of the above embodiments; and the cascaded side external interfaces of the power conversion modules 10 in the cascaded branch are connected in series.

[0061] The structure and principle of the power conversion module 10 can refer to the above embodiments, which will not be repeated here. In the present embodiment, the cascaded converter adopts multiple power conversion modules 10 to form a phase cascaded branch, and further can decompose the common reactance in the prior art into each power conversion module 10 to reduce the insulation requirement. Moreover, when applied to the decomposition into the power conversion module 10, two cascaded units 101 and the coupling inductor 102 are adopted to form a power conversion module 10 (as shown in Figures 2 to 4 ), and the series-parallel conversion of the cascaded units 101 can be realized by changing the connection line in the power conversion module 10, and the switching between the large current and the high voltage requirement can further improve the adaptability of the power conversion module 10. The following further describes the related connection method of the system composed of multiple modules in cascaded when the power conversion module is formed by the coupling inductor.

[0062] As shown in Figure 9 , the internal two cascaded units (such as the cascaded unit 11 and the cascaded unit 12 , the cascaded unit 21 and the cascaded unit 22 , and the cascaded unit n1 and the cascaded unit n2 ) of multiple power conversion modules (such as the module 1 to the module n shown in the figure) 10 are connected in series through the corresponding coupling inductor, and then are connected in series to form a system, that is, a phase cascaded branch.

[0063] As shown in Figure 10 , the internal two cascaded units (such as the cascaded unit 11 and the cascaded unit 12 , the cascaded unit 21 and the cascaded unit 22 , and the cascaded unit n1 and the cascaded unit n2All units are connected in parallel via corresponding coupling inductors (shown as an example of parallel connection with a common lower terminal), and then connected in series to form a system. The parallel connection of two cascaded units with a common upper terminal is similar and will not be illustrated further.

[0064] When the power conversion module (modules 1 to n as shown in the figure) 10 contains a DC-DC converter, such as Figure 11 As shown, each cascade unit (as shown in the figure) 11 and cascaded units 12 Cascaded unit 21 and cascaded units 22 and, cascaded units n1 and cascaded units n2 On the DC side of the power conversion module 10, a corresponding port of a 3-port DC-DC converter is connected to each of the 3-port DC-DC converters. The AC sides of each cascade unit are connected in series and then in series again to form a system. The cases where the DC-DC converter is inside the power conversion module 10 and the AC sides of each cascade unit are connected in parallel, as well as the cases where each cascade unit is equipped with a corresponding DC-DC converter, will not be shown one by one.

[0065] In practical applications, if the power conversion module 10 does not contain a DC-DC converter, the cascaded branch may further include multiple DC-DC converters located outside the power conversion module 10. Each DC-DC converter can be connected one-to-one with a cascaded unit of the power conversion module 10 in the cascaded branch (not shown). Alternatively, each cascaded unit in the same power conversion module 10 can be connected to the same multi-port DC-DC converter; for example... Figure 12 As shown, two cascaded units (as shown in the figure) 11 and cascaded units 12 Cascaded unit 21 and cascaded units 22 and, cascaded units n1 and cascaded units n2 The DC side of each module (as shown in the figure, modules 1 to n) is connected to the DC converter 20 with three external ports. The AC sides of the cascaded units are connected in parallel and then in series to form a system. The parallel connection of two cascaded units sharing the same top end, and the case where the AC sides of two cascaded units are connected in series, will not be shown one by one.

[0066] like Figure 13 As shown, the cascaded unit can be a half-bridge inverter unit, and two half-bridge cascaded units can be connected in series to form a half-bridge series module.

[0067] like Figure 14 As shown, the cascaded unit can be a half-bridge inverter unit. Two half-bridge cascaded units are connected in parallel (taking the parallel connection with the common lower end as an example) to form a half-bridge parallel module.

[0068] As shown in Figure 15 , the cascaded unit can be an inverter unit of full-bridge structure, and two full-bridge cascaded units are connected in series to form a full-bridge series module.

[0069] As shown in Figure 16 , the cascaded unit can be an inverter unit of full-bridge structure, and two full-bridge cascaded units are connected in parallel to form a full-bridge parallel module.

[0070] As shown in Figure 17 , a plurality of Figure 13 As shown in the half-bridge series module, the half-bridge series module is connected in series to form a system.

[0071] As shown in Figure 18 , a plurality of Figure 14 As shown in the half-bridge parallel module, the half-bridge parallel module is connected in series to form a system.

[0072] As shown in Figure 19 , three Figure 13 As shown in the series system, the series system can be connected in three phases to form a three-phase structure. Moreover, the AC side of the three-phase cascaded branch (each cascaded branch is taken as an example of the structure shown in Figure 12 As shown in the three-phase structure, the AC side of the three-phase cascaded branch can be the star connection mode shown in Figure 19 , or can be an angular connection mode (not shown in the figure). Both connection modes are the same as in the prior art, and will not be described one by one here. The specific selection of the connection mode can be determined according to the specific application environment, and is within the protection scope of the present application.

[0073] In the embodiment, the total electric reactance in the prior art is decomposed into each power conversion module, the space requirement of the inductance for external additional insulation is reduced, and the power density is improved. Moreover, when the coupled inductance and the two cascaded unit groups are used in the power conversion module, the series-parallel conversion of the internal cascaded unit can be realized by changing the connection mode, and the problems of the direct parallel connection of the power conversion module output can be solved by the coupling coefficient design of the coupled inductance, and the versatility of the power conversion module is improved.

[0074] It is worth noting that the total electric reactance in the prior art not only can realize the filtering function, but also can realize the function of suppressing the port voltage mutation. Therefore, for the case that the required inductance is large for suppressing the total output fluctuation of the series system, such as zero voltage ride-through of grid demand, in order to keep the design of the power conversion module 10 consistent, only the inductance for suppressing the switching ripple of the cascaded unit can be split into each cascaded unit, and the inductance for suppressing the total output fluctuation of the system is still handled by a total inductance 30.

[0075] At this time, the system structure can be as shown in Figure 20 (when the inductance for suppressing the total output fluctuation of the system is handled by a total inductance 30) Figure 2The cascade branch further comprises a total inductance 30 for suppressing output fluctuation, and the total inductance 30 is connected in series with one end of the cascade branch.

[0076] However, in actual applications, not all application scenarios need to cope with this situation. Therefore, in the case of no system voltage mutation, the equivalent switching frequency of the cascade system is high, and the demand for total reactance is small. The distributed inductance L has more advantages because the additional insulation space of the centralized reactance is saved. In addition, the power conversion module 10 can also be supplemented with an external total inductance 30 in the case of system voltage mutation, further improving the system adaptation range.

[0077] The same or similar parts among the various embodiments in the specification can be referred to each other, and each embodiment mainly describes the difference from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, it is described more simply, and the related parts can be referred to the part of the method embodiment. The above-described system and system embodiment are only illustrative, and the units described as separate components can be or can not be physically separated, and the components displayed as units can be or can not be physical units, that is, they can be located in one place or distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0078] The skilled person can further realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be realized by electronic hardware, computer software or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the components and steps of the examples have been described in the above description in general. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical scheme. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0079] The above description of the disclosed embodiments, the features described in each embodiment in the specification can be replaced or combined with each other, so that those skilled in the art can implement or use the present application. Various modifications of the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power conversion module, characterized by, The power conversion module comprises: a coupling inductor and two cascade units; a first side of each of the cascade units is connected in series with a corresponding winding of the coupling inductor, forming a corresponding series branch; a second side of each of the cascade units is used for connecting an internal interface of a power supply side of the power conversion module; the first sides of the two cascade units are connected in series through the coupling inductor, and the two ends of the series branch are connected to two internal interfaces of a cascade side of the power conversion module; one of the cascade units is connected to a homonymic end of a corresponding winding; the other of the cascade units is connected to a homonymic end of another winding; and the other ends of the two windings are connected; or one end of the first sides of the two cascade units is connected in parallel to one internal interface of the cascade side of the power conversion module; the other end of the first sides of the two cascade units is connected to one end of a corresponding winding of the coupling inductor, and the other ends of the windings are connected in parallel to the other internal interface of the cascade side of the power conversion module; the two cascade units are connected to homonymic ends of corresponding windings; and the homonymic ends of the two windings are connected.

2. The power conversion module of claim 1, wherein, The cascade unit is an inverter unit. An alternating current side of the inverter unit is the first side of the cascade unit. A direct current side of the inverter unit is the second side of the cascade unit.

3. The power conversion module of claim 2, wherein, The direct current side of the inverter unit and a corresponding internal interface of a power supply side of the power conversion module are further provided with a direct current converter; or The internal interfaces of the power supply side of the power conversion module are connected to the direct current sides of the inverter units through a multi-port direct current converter.

4. The power conversion module of claim 2, wherein, The inverter unit is a half-bridge inverter unit or a full-bridge inverter unit.

5. A cascaded converter, characterized by The power conversion module comprises at least one cascade branch, and the cascade branch comprises at least one power conversion module as claimed in any one of claims 1 to 4. When the number of the power conversion modules in the cascade branch is greater than one, the external interfaces of the cascade sides of the power conversion modules are connected in series.

6. The cascaded converter of claim 5, wherein, The cascade branch further comprises a total inductor for suppressing output fluctuation. One end of the total inductor is connected in series to the cascade branch.

7. The cascaded converter of claim 5, wherein, When the power conversion module does not comprise a direct current converter, the cascade branch further comprises a plurality of direct current converters arranged outside the power conversion module. Each direct current converter is connected to the cascade unit of each power conversion module in the cascade branch; or each cascade unit in the same power conversion module is connected to the same multi-port direct current converter.

8. The cascaded converter according to any one of claims 5 to 7, characterized in that, The cascade unit in the power conversion module is an inverter unit, and the number of the cascade branches is three, and the alternating current sides of the three-phase cascade branches are connected in star or delta.

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