AC-DC converter and system thereof

Abstract

The invention relates to an alternating-current and direct-current converter and a system thereof. The alternating-current and direct-current converter comprises at least one alternating-current and direct-current conversion circuit; the AC-DC conversion circuit comprises a switched capacitor module, a first bridge arm and a second bridge arm; the first bridge arm comprises a first switch unit and a second switch unit; the second bridge arm comprises a third switch unit and a fourth switch unit; the first end of the first switch unit and the first end of the third switch unit are connected with the switched capacitor module, the second end of the first switch unit is connected with the first end of the second switch unit, and the second end of the third switch unit is connected with the first end of the fourth switch unit. The second end of the second switch unit and the second end of the fourth switch unit are connected with the switched capacitor module; each switch unit comprises a plurality of first switch devices; the plurality of first switching devices includes at least a half-controlled switching device. According to the invention, the semi-control switching device is used as the first switching device, so that the manufacturing cost of the AC-DC converter is reduced.

Description

Technical Field

[0001] This disclosure relates to the field of converter technology, and more particularly to an AC-DC converter and its system. Background Technology

[0002] With the rapid development of new energy power generation technologies, traditional DC transmission systems can no longer meet the stable operation requirements of new power systems. Therefore, a flexible DC transmission system is needed to provide voltage and frequency support for the power grid. In conventional technologies, DC transmission systems are mainly based on Modular Multilevel Converters (MMCs) as AC-DC converters. MMCs can achieve AC / DC conversion at different voltage and capacity levels, and are characterized by high voltage resistance, large capacity, and high maturity. However, the cost of MMC components is relatively high.

[0003] Therefore, how to reduce the manufacturing cost of AC-DC converters has become a technical problem that urgently 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 an AC-DC converter and system thereof, which reduces the manufacturing cost of the AC-DC converter by using a semi-controlled switching device as the first switching device.

[0005] This disclosure provides an AC-DC converter, including: at least one AC-DC conversion circuit; wherein a first AC terminal and a second AC terminal of the AC-DC conversion circuit are connected to an AC port; when the AC-DC converter includes one AC-DC conversion circuit, the first DC terminal and the second DC terminal of the AC-DC conversion circuit are connected to a DC port; when the AC-DC converter includes multiple AC-DC conversion circuits, the first DC terminal is connected to a DC port or a second DC terminal of an adjacent AC-DC conversion circuit, and the second DC terminal is connected to a DC port or a first DC terminal of an adjacent AC-DC conversion circuit. The AC-DC converter circuit includes a switched capacitor module, a first bridge arm, and a second bridge arm; The first terminal of the switched capacitor module is connected to the first DC terminal, and the second terminal of the switched capacitor module is connected to the second DC terminal. The first bridge arm includes a first switching unit and a second switching unit; the first end of the first switching unit is connected to the first end of the switched capacitor module, the second end of the first switching unit is connected to the first end of the second switching unit at the midpoint of the first bridge arm, the second end of the second switching unit is connected to the second end of the switched capacitor module, and the midpoint of the first bridge arm is connected to the first AC terminal. The second bridge arm includes a third switch unit and a fourth switch unit; the first end of the third switch unit is connected to the first end of the switched capacitor module, 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 second end of the fourth switch unit is connected to the second end of the switched capacitor module, and the midpoint of the second bridge arm is connected to the second AC terminal. The first switch unit, the second switch unit, the third switch unit, and the fourth switch unit each include multiple first switch devices connected in series; the multiple first switch devices include at least a semi-controlled switch device.

[0006] Optionally, the plurality of first switching devices may include a plurality of semi-controlled switching devices; The AC-DC conversion circuit also includes a first auxiliary switching module and / or a second auxiliary switching module; The first terminal of the first auxiliary switch module is connected to the first terminal of the switched capacitor module, and the second terminal of the first auxiliary switch module is connected to the first terminal of the first switch unit and the first terminal of the third switch unit; the first terminal of the second auxiliary switch module is connected to the second terminal of the switched capacitor module, and the second terminal of the second auxiliary switch module is connected to the second terminal of the second switch unit and the second terminal of the fourth switch unit. Both the first auxiliary switch module and the second auxiliary switch module include at least one second switch device; the second switch device includes at least a fully controlled switch device.

[0007] Optionally, the plurality of semi-controlled switching devices include at least one of a unidirectional semi-controlled switching unit and a bidirectional blocking semi-controlled switching unit.

[0008] Optionally, the plurality of first switching devices include at least one fully controlled switching device and at least one semi-controlled switching device.

[0009] Optionally, the plurality of fully controlled switching devices include at least one of a unidirectional fully controlled switching unit, a bidirectional blocking fully controlled switching unit, a unidirectional single-switch unit, and a bidirectional blocking single-switch unit; The plurality of semi-controlled switching devices include at least one of a unidirectional semi-controlled unit and a bidirectional blocking semi-controlled unit.

[0010] Optionally, when the fully controlled switching device includes at least one of a unidirectional fully controlled switching unit and a bidirectional blocking fully controlled switching unit, and / or the semi-controlled switching device includes at least one of a unidirectional semi-controlled switching unit and a bidirectional blocking semi-controlled switching unit, the first switching device further includes a buffer module. The first end of the buffer module is connected to the first end of the first switching device, and the second end of the buffer module is connected to the second end of the first switching device. The buffer module includes multiple buffer units, which are connected in series with each other, and / or, the multiple buffer units are connected in parallel with each other.

[0011] Optionally, the multiple buffer units include at least one of surge arresters, capacitors, resistors, and diodes.

[0012] Optionally, the AC-DC converter may also include a first protection module, a second protection module, a third protection module, and a fourth protection module; The first protection module is connected to the first switch unit, the second protection module is connected to the second switch unit, the third protection module is connected to the third switch unit, and the fourth protection module is connected to the fourth switch unit; The first protection module, the second protection module, the third protection module, and the fourth protection module each include at least one of a surge arrester and an inductor.

[0013] Optionally, the switched capacitor module includes: at least one switched capacitor unit and a fifth protection module.

[0014] The first terminal of the switched capacitor unit is connected to the first pole of the DC port or the second terminal of an adjacent switched capacitor unit, and the second terminal of the switched capacitor unit is connected to the second pole of the DC port or the first terminal of an adjacent switched capacitor unit. The first terminal of the fifth protection module is connected to the first terminal of the switched capacitor module, and the second terminal of the fifth protection module is connected to the second terminal of the switched capacitor module. The switched capacitor unit includes at least one of a full-bridge switching device and a half-bridge switching device.

[0015] This disclosure also provides an AC-DC converter system comprising three arbitrary AC-DC converters as described above; The three AC-DC converters include a first AC-DC converter, a second AC-DC converter, and a third AC-DC converter; The first terminal of the first AC-DC converter is connected to the first pole of the DC port, the second terminal of the first AC-DC converter is connected to the first terminal of the second AC-DC converter, the second terminal of the second AC-DC converter is connected to the first terminal of the third AC-DC converter, and the second terminal of the third AC-DC converter is connected to the second pole of the DC port. The midpoint of the first bridge arm of the first AC-DC converter is connected to the first end of the first phase AC port, and the midpoint of the second bridge arm of the first AC-DC converter is connected to the second end of the first phase AC port; the midpoint of the first bridge arm of the second AC-DC converter is connected to the first end of the second phase AC port, and the midpoint of the second bridge arm of the second AC-DC converter is connected to the second end of the second phase AC port; the midpoint of the first bridge arm of the third AC-DC converter is connected to the first end of the third phase AC port, and the midpoint of the second bridge arm of the third AC-DC converter is connected to the second end of the third phase AC port.

[0016] This disclosure provides an AC-DC converter and system thereof. The AC-DC converter includes: at least one AC-DC conversion circuit; wherein a first AC terminal and a second AC terminal of the AC-DC conversion circuit are connected to an AC port; when the AC-DC converter includes one AC-DC conversion circuit, the first DC terminal and the second DC terminal of the AC-DC conversion circuit are connected to a DC port; when the AC-DC converter includes multiple AC-DC conversion circuits, the first DC terminal is connected to a DC port or a second DC terminal of an adjacent AC-DC conversion circuit, and the second DC terminal is connected to a DC port or a first DC terminal of an adjacent AC-DC conversion circuit; the AC-DC conversion circuit includes a switched capacitor module, a first bridge arm, and a second bridge arm; a first terminal of the switched capacitor module is connected to the first DC terminal, and a second terminal of the switched capacitor module is connected to the second DC terminal; the first bridge arm includes a first... The AC-DC converter includes a first switching unit and a second switching unit. The first terminal of the first switching unit is connected to the first terminal of a switched capacitor module. The second terminal of the first switching unit is connected to the first terminal of the second switching unit at the midpoint of a first bridge arm. The second terminal of the second switching unit is connected to the second terminal of the switched capacitor module. The midpoint of the first bridge arm is connected to a first AC terminal. The second bridge arm includes a third switching unit and a fourth switching unit. The first terminal of the third switching unit is connected to the first terminal of the switched capacitor module. The second terminal of the third switching unit is connected to the first terminal of the fourth switching unit at the midpoint of the second bridge arm. The second terminal of the fourth switching unit is connected to the second terminal of the switched capacitor module. The midpoint of the second bridge arm is connected to a second AC terminal. Each of the first, second, third, and fourth switching units includes multiple first switching devices connected in series. These multiple first switching devices include at least semi-controlled switching devices. This disclosure reduces the manufacturing cost of the AC-DC converter by using partially semi-controlled switching devices, partially fully controlled switching devices, or all semi-controlled switching devices in the first, second, third, and fourth switching units of the AC-DC converter circuit. Attached Figure Description

[0017] 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.

[0018] Figure 1 This is a schematic diagram of an AC-DC converter provided in an embodiment of the present disclosure.

[0019] Figure 2 This is a schematic diagram of another AC-DC converter provided in an embodiment of the present disclosure.

[0020] Figure 3 This is a schematic diagram of another AC-DC converter provided in an embodiment of the present disclosure.

[0021] Figure 4 This is a schematic diagram of another AC-DC converter provided in an embodiment of the present disclosure.

[0022] Figure 5 This is a schematic diagram of another AC-DC converter provided in an embodiment of the present disclosure.

[0023] Figure 6 This is a schematic diagram of the structure of a semi-controlled switching device provided in an embodiment of this disclosure.

[0024] Figure 7 This is a schematic diagram of the structure of the fully controlled switching device provided in the embodiments of this disclosure.

[0025] Figure 8 This is a schematic diagram of the structure of the buffer module provided in an embodiment of this disclosure.

[0026] Figure 9 This is a schematic diagram of a switched capacitor module provided in an embodiment of the present disclosure.

[0027] Figure 10 This is a schematic diagram of another switched capacitor module provided in an embodiment of the present disclosure.

[0028] Figure 11 This is a schematic diagram of a switched capacitor module provided in an embodiment of the present disclosure.

[0029] Figure 12 This is a schematic diagram of an AC-DC converter system provided in an embodiment of the present disclosure.

[0030] Figure 13 This is a schematic diagram of a preferred AC-DC converter system provided in an embodiment of the present disclosure. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] With the rapid development of new energy power generation technologies, traditional DC transmission systems can no longer meet the stable operation requirements of new power systems. Therefore, a flexible DC transmission system is needed to provide voltage and frequency support for the power grid. In conventional technologies, DC transmission systems are mainly based on Modular Multilevel Converters (MMCs) as AC-DC converters. MMCs can achieve AC / DC conversion at different voltage and capacity levels, and are characterized by high voltage resistance, large capacity, and high maturity. However, the cost of MMC components is relatively high.

[0040] Therefore, how to reduce the manufacturing cost of AC-DC converters has become a technical problem that urgently needs to be solved by those skilled in the art.

[0041] Based on the above-mentioned technical problems, this application provides an AC-DC converter and system thereof. The embodiments of this application will be described below with reference to the accompanying drawings.

[0042] This disclosure provides an AC-DC converter, which includes at least one AC-DC conversion circuit.

[0043] Figure 1 This is a schematic diagram of the structure of an AC-DC converter provided in an embodiment of the present disclosure, as shown below. Figure 1 As shown, when the AC-DC converter 1000 includes an AC-DC converter circuit 10, the first DC terminal 101 and the second DC terminal 102 of the AC-DC converter circuit 10 are connected to the DC port 21; the first AC terminal 103 and the second AC terminal 104 of the AC-DC converter circuit 10 are connected to the AC port 22.

[0044] Figure 2 A schematic diagram of another AC-DC converter provided in this disclosure embodiment is shown below. Figure 2 As shown, when the AC-DC converter 1000 includes multiple AC-DC conversion circuits 10, the first DC terminal 101 is connected to the DC port 21 or the second DC terminal 102 of the adjacent AC-DC conversion circuit 10, and the second DC terminal 102 is connected to the DC port 21 or the first DC terminal 101 of the adjacent AC-DC conversion circuit 10.

[0045] See also Figure 1 and Figure 2 The AC-DC converter circuit 10 includes a switched capacitor module 110, a first bridge arm 120, and a second bridge arm 130.

[0046] The first terminal of the switched capacitor module 110 is connected to the first DC terminal 101, and the second terminal of the switched capacitor module 110 is connected to the second DC terminal 102.

[0047] For example, the first terminal of the switched capacitor module 110 is connected to the positive terminal of the DC port 21 via a first DC terminal 101, and the second terminal of the switched capacitor module 110 is connected to the negative terminal of the DC port 21 via a second DC terminal 102. The switched capacitor module 110 includes multiple switched capacitor units (not shown in the figure) connected in series. When the switching device corresponding to the switched capacitor unit activates the capacitor in the switched capacitor unit, the switched capacitor module 110 can filter the DC voltage input to the DC port 21 and prevent damage to the AC-DC converter caused by a sudden large current supplied by the DC port 21. Furthermore, the multiple switched capacitor units included in the switched capacitor module 110 can actively control the number of switched capacitor units activated according to the voltage provided by the DC port 21, thereby enabling voltage division using a corresponding number of switched capacitor units according to different voltage levels at the DC port 21, ensuring the safe operation of the AC-DC converter.

[0048] The first bridge arm 120 includes a first switching unit 121 and a second switching unit 122; the first end of the first switching unit 121 is connected to the first end of the switched capacitor module 110, the second end of the first switching unit 121 and the first end of the second switching unit 122 are connected at the midpoint A of the first bridge arm, the second end of the second switching unit 122 is connected to the second end of the switched capacitor module 110, and the midpoint A of the first bridge arm is connected to the first AC terminal 103.

[0049] The second bridge arm 130 includes a third switch unit 131 and a fourth switch unit 132; the first end of the third switch unit 131 is connected to the first end of the switched capacitor module 110, the second end of the third switch unit 131 and the first end of the fourth switch unit 132 are connected at the midpoint B of the second bridge arm, the second end of the fourth switch unit 132 is connected to the second end of the switched capacitor module 110, and the midpoint B of the second bridge arm is connected to the second AC terminal 104.

[0050] The first switch unit 121, the second switch unit 122, the third switch unit 131 and the fourth switch unit 132 each include a plurality of first switch devices 140 connected in series; the plurality of first switch devices 140 include at least a semi-controlled switch device.

[0051] For example, the multiple first switching devices 140 in the first switching unit 121, the second switching unit 122, the third switching unit 131, and the fourth switching unit 132 can be partially semi-controlled switching devices and partially fully controlled switching devices. Each switching unit controls the fully controlled switching devices and the semi-controlled switching devices to be turned on through a control module (not shown in the figure). When each switching unit needs to be turned off, it controls the fully controlled switching devices to be turned off through the control module, thereby reducing the current in the branch where the fully controlled switching devices and the semi-controlled switching devices are located to 0, and the semi-controlled switching devices are turned off accordingly. Therefore, the semi-controlled switching devices will be turned off along with the fully controlled switching devices, thereby realizing the control of the turn-off of each switching unit.

[0052] The multiple first switching devices 140 in the first switching unit 121, the second switching unit 122, the third switching unit 131, and the fourth switching unit 132 can all be semi-controlled switching devices. In this case, an auxiliary switching device (not shown in the figure) can be set in the AC-DC conversion circuit 10. The auxiliary switching device includes a fully controlled switching device. Therefore, each switching unit controls the semi-controlled switching device to be turned on through the control module. When each switching unit needs to be turned off, the auxiliary switching device is turned off through the control module, thereby providing a reverse voltage to the semi-controlled switching device in each switching unit to turn it off. Therefore, each switching unit can be turned off along with the auxiliary switching device.

[0053] Therefore, this disclosure adopts a combination of partially semi-controlled and partially fully controlled switching devices, or all semi-controlled switching devices, in the first switching unit 121, second switching unit 122, third switching unit 131, and fourth switching unit 132 of the AC-DC converter circuit 10. Since the cost of semi-controlled switching devices is lower than that of fully controlled switching devices, the manufacturing cost of each switching unit can be reduced. Moreover, since semi-controlled switching devices only require the control module to control their conduction and do not need to control their shutdown, the control cost of each switching unit can be reduced compared to the method of using all fully controlled switching devices. Thus, the manufacturing cost and control cost of the AC-DC converter are reduced.

[0054] In some embodiments, the plurality of first switching devices 140 include a plurality of semi-controlled switching devices.

[0055] Figure 3 A schematic diagram of another AC-DC converter provided in this disclosure embodiment is shown below. Figure 3As shown, when the multiple first switching devices 140 in the first switching unit 121, the second switching unit 122, the third switching unit 131 and the fourth switching unit 132 only include multiple semi-controlled switching devices, the AC-DC conversion circuit also includes a first auxiliary switching module 151 and a second auxiliary switching module 152.

[0056] Figure 4 A schematic diagram of another AC-DC converter provided in this disclosure embodiment is shown below. Figure 4 As shown, when the multiple first switching devices 140 in the first switching unit 121 and the fourth switching unit 132 only include multiple semi-controlled switching devices, and the multiple first switching devices 140 in the second switching unit 122 and the third switching unit 131 both include semi-controlled switching devices and fully controlled switching devices, the AC-DC conversion circuit also includes a first auxiliary switching module 151.

[0057] Figure 5 A schematic diagram of another AC-DC converter provided in this disclosure embodiment is shown below. Figure 5 As shown, when the multiple first switching devices 140 in the first switching unit 121 and the fourth switching unit 132 both include semi-controlled switching devices and fully controlled switching devices, and the multiple first switching devices 140 in the second switching unit 122 and the third switching unit 131 only include multiple semi-controlled switching devices, the AC-DC conversion circuit also includes a second auxiliary switching module 152.

[0058] The first terminal of the first auxiliary switch module 151 is connected to the first terminal of the switched capacitor module 110, and the second terminal of the first auxiliary switch module 151 is connected to the first terminal of the first switch unit 121 and the first terminal of the third switch unit 131; the first terminal of the second auxiliary switch module 152 is connected to the second terminal of the switched capacitor module 110, and the second terminal of the second auxiliary switch module 152 is connected to the second terminal of the second switch unit 122 and the second terminal of the fourth switch unit 132.

[0059] The first auxiliary switch module 151 and the second auxiliary switch module 152 each include at least one second switch device; the second switch device includes at least a fully controlled switch device.

[0060] For example, when the multiple first switching devices 140 in the first switching unit 121 and the fourth switching unit 132 only include multiple semi-controlled switching devices, the first switching unit 121 and the fourth switching unit 132 can only be controlled to be turned on by the control module and cannot be controlled to be turned off. Therefore, this disclosure provides a first auxiliary switching module 151 including fully controlled switching devices. By controlling the turn-off of the fully controlled switching devices in the first auxiliary switching module 151, a reverse voltage is provided to the multiple first switching devices 140 in the first switching unit 121 and the fourth switching unit 132 to turn them off. Therefore, the first switching unit 121 and the fourth switching unit 132 can be turned off along with the turn-off of the first auxiliary switching module 151. Furthermore, the first auxiliary switching module 151 can be configured with one or more second switching devices according to the voltage conditions in the AC-DC conversion circuit. By configuring multiple second switching devices, the voltage of the branch where the first auxiliary switching module 151 is located can be divided to achieve protection for the first auxiliary switching module 151. Furthermore, when the first auxiliary switch module 151 includes multiple second switching devices, these devices can be configured as partially fully controlled and partially partially half-controlled switching devices. This allows the half-controlled switching devices in the first auxiliary switch module 151 to be turned off by controlling the turn-off of the fully controlled switching devices. Since the cost of half-controlled switching devices is lower than that of fully controlled switching devices, the manufacturing cost of the first auxiliary switch module 151 can be reduced. Moreover, since the half-controlled switching devices only require the control module to control their conduction and do not need to control their turn-off, the control cost of the first auxiliary switch module 151 can be reduced compared to using all fully controlled switching devices. This, in turn, reduces the manufacturing and control costs of the AC-DC converter.

[0061] When the multiple first switching devices 140 in the second switching unit 122 and the third switching unit 131 only include multiple semi-controlled switching devices, the second switching unit 122 and the third switching unit 131 can only be controlled to be turned on by the control module and cannot be controlled to be turned off. Therefore, this disclosure provides a second auxiliary switching module 152 including fully controlled switching devices. By controlling the turn-off of the fully controlled switching devices in the second auxiliary switching module 152, a reverse voltage is provided to the multiple first switching devices 140 in the second switching unit 122 and the third switching unit 131 to turn them off. Therefore, the second switching unit 122 and the third switching unit 131 can be turned off along with the turn-off of the second auxiliary switching module 152. Furthermore, the second auxiliary switching module 152 can be configured with one or more second switching devices according to the voltage conditions in the AC-DC conversion circuit. By configuring multiple second switching devices, the voltage of the branch where the second auxiliary switching module 152 is located can be divided to achieve protection for the second auxiliary switching module 152. Furthermore, when the second auxiliary switch module 152 includes multiple second switching devices, these devices can be configured as partially fully controlled and partially partially half-controlled switching devices. This allows the half-controlled switching devices in the second auxiliary switch module 152 to be turned off by controlling the turn-off of the fully controlled switching devices. Since the cost of half-controlled switching devices is lower than that of fully controlled switching devices, the manufacturing cost of the second auxiliary switch module 152 can be reduced. Moreover, since the half-controlled switching devices only require the control module to control their conduction and do not need to control their turn-off, the control cost of the second auxiliary switch module 152 can be reduced compared to using all fully controlled switching devices. This, in turn, reduces the manufacturing and control costs of the AC-DC converter.

[0062] In some embodiments, the plurality of semi-controlled switching devices include at least one of a unidirectional semi-controlled switching unit and a bidirectional blocking semi-controlled switching unit.

[0063] For example, multiple semi-controlled switching devices may include only unidirectional semi-controlled switching units, only bidirectional blocking semi-controlled switching units, or a combination of some unidirectional semi-controlled switching units and some bidirectional blocking semi-controlled switching units. Figure 6 This is a schematic diagram of the structure of the semi-controlled switching device provided in the embodiments of this disclosure, as shown below. Figure 6As shown, the semi-controlled switching device can be a unidirectional semi-controlled switching unit 31 or a bidirectional blocking semi-controlled switching unit 32. The unidirectional semi-controlled switching unit 31 includes a thyristor T1, and the bidirectional blocking semi-controlled switching unit 32 includes two thyristors T1 connected in opposite directions. That is, the positive terminal of one thyristor T1 is connected to the negative terminal of the other thyristor T1, and the negative terminal of one thyristor T1 is connected to the positive terminal of the other thyristor T1. The bidirectional blocking semi-controlled switching unit 32 can block the short-circuit current flowing from the AC port 22 to the DC port 21 after a short circuit occurs at the DC port 21.

[0064] In some embodiments, the plurality of first switching devices include at least one fully controlled switching device and at least one semi-controlled switching device.

[0065] For example, each of the first switching unit 121, the second switching unit 122, the third switching unit 131, and the fourth switching unit 132 includes at least one fully controlled switching device and at least one semi-controlled switching device connected in series as the first switching device. The number of fully controlled and semi-controlled switching devices is determined by the voltage division of the bridge arm where each switching unit is located. The fully controlled and semi-controlled switching devices are controlled to turn on according to the control signal provided by the control module, and the fully controlled switching devices are controlled to turn off according to the control signal provided by the control module. After the fully controlled switching device is turned off, the semi-controlled switching device receives a reverse voltage and turns off, thereby realizing the turn-off of each switching unit. Therefore, since the semi-controlled switching device only needs to be controlled to turn on by the control module and does not need to be controlled to turn off, the control cost of each switching unit can be reduced compared to using all fully controlled switching devices. Furthermore, the cost of the semi-controlled switching device is lower than that of the fully controlled switching device, thus reducing the manufacturing cost of each switching unit, thereby reducing the manufacturing cost and control cost of the AC-DC converter.

[0066] In some embodiments, the plurality of fully controlled switching devices include at least one of a unidirectional fully controlled switching unit, a bidirectional blocking fully controlled switching unit, a unidirectional single-switching unit, and a bidirectional blocking single-switching unit.

[0067] For example, multiple fully controlled switching devices may include only one of a fully controlled switching unit, a bidirectional blocking fully controlled switching unit, a unidirectional single-switch unit, and a bidirectional blocking single-switch unit, or they may be a combination of any number of these units. For instance, multiple fully controlled switching devices may be a combination of a fully controlled switching unit and a bidirectional blocking fully controlled switching unit, a combination of a fully controlled switching unit and a unidirectional single-switch unit, a combination of a fully controlled switching unit, a bidirectional blocking fully controlled switching unit, and a unidirectional single-switch unit, or a combination of a fully controlled switching unit, a bidirectional blocking fully controlled switching unit, a unidirectional single-switch unit, and a bidirectional blocking single-switch unit. Multiple fully controlled switching devices may also consist of a half-bridge switching unit and a full-bridge switching unit. The switching devices in the fully controlled switching unit, the bidirectional blocking fully controlled switching unit, the unidirectional single-switching unit, the bidirectional blocking single-switching unit, the half-bridge switching unit, and the full-bridge switching unit can be insulated gate bipolar transistors (IGBTs), integrated gate-commutated thyristors (IGCTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), gate-turn-off thyristors (GTOs), etc. Figure 7 This is a schematic diagram of the structure of the fully controlled switching device provided in the embodiments of this disclosure. Multiple fully controlled switching devices may include, for example: Figure 7 The illustrated fully controlled switch unit 41, bidirectional blocking fully controlled switch unit 42, unidirectional single switch unit 43, bidirectional blocking single switch unit 44, half-bridge switch unit 45, and full-bridge switch unit 46 all include at least one switching device T2. The bidirectional blocking fully controlled switch unit 42 and the bidirectional blocking single switch unit 44 can block the short-circuit current flowing from the AC port 22 to the DC port 21 after a short circuit occurs at the DC port 21.

[0068] The plurality of semi-controlled switching devices include at least one of a unidirectional semi-controlled unit and a bidirectional blocking semi-controlled unit.

[0069] For example, multiple semi-controlled switching devices may include only unidirectional semi-controlled switching units, only bidirectional blocking semi-controlled switching units, or a combination of some unidirectional semi-controlled switching units and some bidirectional blocking semi-controlled switching units. See also... Figure 6The semi-controlled switching device can be a unidirectional semi-controlled switching unit 31 or a bidirectional blocking semi-controlled switching unit 32. The unidirectional semi-controlled switching unit 31 includes a thyristor T1, and the bidirectional blocking semi-controlled switching unit 32 includes two thyristors T1 connected in opposite directions. That is, the positive terminal of one thyristor T1 is connected to the negative terminal of the other thyristor T1, and the negative terminal of one thyristor T1 is connected to the positive terminal of the other thyristor T1. The bidirectional blocking semi-controlled switching unit 32 can block the short-circuit current flowing from the AC port 22 to the DC port 21 after a short circuit occurs at the DC port 21.

[0070] In some embodiments, see continue to see Figure 3 , Figure 4 as well as Figure 5 In the case where the fully controlled switching device includes at least one of a unidirectional fully controlled switching unit and a bidirectional blocking fully controlled switching unit, and / or the semi-controlled switching device includes at least one of a unidirectional semi-controlled switching unit and a bidirectional blocking semi-controlled switching unit, the first switching device 140 further includes a buffer module 141.

[0071] The first end of the buffer module 141 is connected to the first end of the first switching device 140, and the second end of the buffer module 141 is connected to the second end of the first switching device 140.

[0072] The buffer module 141 includes multiple buffer units, which are connected in series with each other, and / or, the multiple buffer units are connected in parallel with each other.

[0073] For example, the buffer module 141 may be multiple buffer units connected in series, multiple buffer units connected in parallel, or some buffer units connected in series, and the series-connected buffer units are also connected in parallel with another part of the buffer units. Figure 8 This is a schematic diagram of the structure of a buffer module provided in an embodiment of the present disclosure. The buffer module 141 includes multiple buffer units, and the multiple buffer units include at least one of a surge arrester 1411, a capacitor 1412, a resistor 1413, and a diode 1414, such as... Figure 8As shown, the buffer module 141 may include only one of the following: surge arrester 1411, capacitor 1412, resistor 1413, and diode 1414. The buffer module 141 may also include surge arrester 1411 and capacitor 1412 connected in parallel; surge arrester 1411 and resistor 1413 connected in parallel; capacitor 1412 and resistor 1413 connected in parallel; surge arrester 1411 connected in parallel with capacitor 1412 and resistor 1413; capacitor 1412 and resistor 1413 connected in series; capacitor 1412 and resistor 1413 connected in series and then in parallel with surge arrester 1411; surge arrester 1411 and resistor 1413 connected in parallel and then in parallel with capacitor 1412; and diode 1414 connected in parallel with resistor 1413 and then in series with capacitor 1412. Diode 1414 is connected in parallel with resistor 1413, then in series with capacitor 1412, and finally in parallel with surge arrester 1411. Diode 1414 is also connected in series with capacitor 1412, then in parallel with resistor 1413, and finally in parallel with surge arrester 1411. Buffer module 141 can absorb excess energy across each of the first switching devices 140, thereby preventing damage to the first switching devices 140 due to overvoltage.

[0074] In some embodiments, see continue to see Figure 3 , Figure 4 as well as Figure 5 The AC-DC converter also includes a first protection module 51, a second protection module 52, a third protection module 53, and a fourth protection module 54.

[0075] The first protection module 51 is connected to the first switch unit 121, the second protection module 52 is connected to the second switch unit 122, the third protection module 53 is connected to the third switch unit 131, and the fourth protection module 54 is connected to the fourth switch unit 132. The first protection module 51, the second protection module 52, the third protection module 53 and the fourth protection module 54 each include at least one of a surge arrester and an inductor.

[0076] For example, Figure 3 , Figure 4 as well as Figure 5 Taking the first protection module 51, the second protection module 52, the third protection module 53, and the fourth protection module 54 as examples, all of which include surge arresters and inductors, the first protection module 51, the second protection module 52, the third protection module 53, and the fourth protection module 54 each include a first surge arrester U1, a first inductor L1, and a second inductor L2.

[0077] The first terminal of the first surge arrester U1 is connected to the first terminal of the corresponding switching unit. The second terminal of the first surge arrester U1 is connected to the first terminal of the first inductor L1. The second terminal of the first inductor L1 is connected to the second terminal of the corresponding switching unit. The second inductor L2 is connected in series with the corresponding switching unit in the corresponding bridge arm. The first surge arrester U1 is used to absorb excess energy in the bridge arm, thereby preventing the switching unit in the bridge arm from being damaged due to overvoltage. The first inductor L1 is used to prevent instantaneous large current in the corresponding bridge arm from causing damage to the switching unit in the bridge arm due to overcurrent in the event of a short circuit fault in the first surge arrester U1. The second inductor L2 is used to limit the rate of current change of the switching unit in the corresponding bridge arm, preventing damage to the switching unit due to instantaneous large current.

[0078] It should be noted that the first protection module 51, the second protection module 52, the third protection module 53 and the fourth protection module 54 may include only the first surge arrester U1, or only the second inductor L2, or the first surge arrester U1 and the first inductor L1 connected in series.

[0079] In some embodiments, see continue to see Figure 3 , Figure 4 as well as Figure 5 The switched capacitor module 110 includes at least one switched capacitor unit 111 and a fifth protection module 112.

[0080] The first end of the switched capacitor unit 111 is connected to the first pole of the DC port 21 or the second end of the adjacent switched capacitor unit 111 through the first DC terminal 101, and the second end of the switched capacitor unit 111 is connected to the second pole of the DC port 21 or the first end of the adjacent switched capacitor unit 111 through the second DC terminal 102.

[0081] The first end of the fifth protection module 112 is connected to the first end of the switched capacitor module 110, and the second end of the fifth protection module 112 is connected to the second end of the switched capacitor module 110.

[0082] The switched capacitor unit 111 includes at least one of a full-bridge switching device and a half-bridge switching device.

[0083] For example, the switched capacitor module 110 includes multiple switched capacitor units 111 connected in series between the first DC terminal 101 and the second DC terminal 102. When the switching device corresponding to the switched capacitor unit 111 engages the capacitor in the switched capacitor unit 111, the switched capacitor module 110 can filter the DC voltage input to the DC port 21 and prevent damage to the AC-DC converter caused by a sudden large current supplied to the DC port 21. Furthermore, the multiple switched capacitor units 111 included in the switched capacitor module 110 can actively control the number of switched capacitor units 111 engaged according to the voltage provided by the DC port 21, thereby enabling voltage division using a corresponding number of switched capacitor units 111 according to different voltage levels at the DC port 21, ensuring the safe operation of the AC-DC converter.

[0084] The fifth protection module 112 includes a second surge arrester U2 and a third inductor L3. The first terminal of the second surge arrester U2 is connected to the first terminal of the switched capacitor module 110, and the second terminal of the second surge arrester U2 is connected to the first terminal of the third inductor L3. The second terminal of the third inductor L3 is connected to the second terminal of the switched capacitor module 110. The second surge arrester U2 is used to absorb excess energy in the switched capacitor module 110, thereby preventing the switched capacitor unit 111 in the switched capacitor module 110 from being damaged due to overvoltage. The third inductor L3 is used to prevent a sudden large current in the switched capacitor module 110 from being damaged due to overcurrent in the switched capacitor unit 111 in the event of a short circuit fault in the second surge arrester U2.

[0085] Figure 9 This is a schematic diagram of the structure of a switched capacitor module provided in an embodiment of the present disclosure, as shown below. Figure 9 As shown, the switched capacitor module 110 includes multiple switched capacitor units 111 connected in series. Each switched capacitor unit 111 includes a first resistor R1, a first capacitor C1, a first half-bridge switching device 1111, and a first switch K1. The first end of the first resistor R1 is connected to the first end of the first capacitor C1 and the first end of the first half-bridge switching device 1111. The second end of the first resistor R1 is connected to the second end of the first capacitor C1 and the second end of the first half-bridge switching device 1111. The third end of the first half-bridge switching device 1111 is connected to the first end of the first switch K1 and the second end of the adjacent switched capacitor unit 111. The fourth end of the first half-bridge switching device 1111 is connected to the second end of the first switch K1 and the first end of the adjacent switched capacitor unit 111. The first switch K1 can be at least one of a mechanical switch, a semiconductor switch, and a thyristor. Controlling the on / off state of the first switch K1 controls the switching on and off state of the corresponding switched capacitor unit 111.

[0086] Figure 10This is a schematic diagram of another switched capacitor module provided in an embodiment of the present disclosure, as shown below. Figure 10 As shown, the switched capacitor module 110 includes multiple switched capacitor units 111 connected in series. Each switched capacitor unit 111 includes a second resistor R2, a second capacitor C2, a first full-bridge switching device 1112, and a second switch K2. The first end of the second resistor R2 is connected to the first end of the second capacitor C2 and the first end of the first full-bridge switching device 1112. The second end of the second resistor R2 is connected to the second end of the second capacitor C2 and the second end of the first full-bridge switching device 1112. The third end of the first full-bridge switching device 1112 is connected to the first end of the second switch K2 and the second end of the adjacent switched capacitor unit 111. The fourth end of the first full-bridge switching device 1112 is connected to the second end of the second switch K2 and the first end of the adjacent switched capacitor unit 111. The second switch K2 can be at least one of a mechanical switch, a semiconductor switch, and a thyristor. Controlling the on / off state of the second switch K2 enables control of the switching on and off state of the corresponding switched capacitor unit 111.

[0087] Figure 11 This is a schematic diagram of the structure of a switched capacitor module provided in an embodiment of the present disclosure, as shown below. Figure 11 As shown, the switched capacitor module 110 includes multiple switched capacitor units 111 connected in series. Each switched capacitor unit 111 includes a third resistor R3, a third capacitor C3, a second half-bridge switching device 1113, a second full-bridge switching device 1114, and a third switch K3. The first end of the third resistor R3 is connected to the first end of the third capacitor C3. The first end of the third resistor R3 is also connected to the first end of either the second half-bridge switching device 1113 or the second full-bridge switching device 1114. The second end of the third resistor R3 is connected to the second end of the third capacitor C3. The second end of the third resistor R3 is also connected to the second end of either the second half-bridge switching device 1113 or the second full-bridge switching device 1114. The third end of either the second half-bridge switching device 1113 or the second full-bridge switching device 1114 is connected to the first end of the third switch K3 and the second end of the adjacent switched capacitor unit 111. The fourth end of either the second half-bridge switching device 1113 or the second full-bridge switching device 1114 is connected to the second end of the third switch K3 and the first end of the adjacent switched capacitor unit 111. The third switch K3 can be at least one of a mechanical switch, a semiconductor switch, and a thyristor. By controlling the on / off state of the third switch K3, the corresponding switched capacitor unit 111 can be controlled to be switched on and off.

[0088] In some embodiments, the switched capacitor module 110 further includes multiple buffer modules, each corresponding to a switched capacitor unit 111, and connected in parallel with the switched capacitor unit 111. The buffer modules can absorb excess energy across each switched capacitor unit 111, thereby preventing the switched capacitor unit 111 from being damaged due to overvoltage.

[0089] This disclosure also provides an AC-DC converter system comprising three AC-DC converters provided in any of the embodiments described above.

[0090] Figure 12 This is a schematic diagram of the structure of an AC-DC converter system provided in an embodiment of the present disclosure, as shown below. Figure 12 As shown, the AC-DC converter system includes three AC-DC converters, namely a first AC-DC converter 1001, a second AC-DC converter 1002, and a third AC-DC converter 1003.

[0091] The first end of the first AC-DC converter 1001 is connected to the first pole of the DC port 21, the second end of the first AC-DC converter 1001 is connected to the first end of the second AC-DC converter 1102, the second end of the second AC-DC converter 1002 is connected to the first end of the third AC-DC converter 1003, and the second end of the third AC-DC converter 1003 is connected to the second pole of the DC port 21.

[0092] The midpoint of the first bridge arm of the first AC-DC converter 1001 is connected to the first end of the first phase AC port 221, and the midpoint of the second bridge arm of the first AC-DC converter 1001 is connected to the second end of the first phase AC port 221; the midpoint of the first bridge arm of the second AC-DC converter 1002 is connected to the first end of the second phase AC port 222, and the midpoint of the second bridge arm of the second AC-DC converter 1002 is connected to the second end of the second phase AC port 222; the midpoint of the first bridge arm of the third AC-DC converter 1003 is connected to the first end of the third phase AC port 223, and the midpoint of the second bridge arm of the third AC-DC converter 1003 is connected to the second end of the third phase AC port 223.

[0093] It is understood that the AC-DC converter system provided in this application embodiment can achieve the corresponding beneficial effects of the AC-DC converter provided in the above embodiments, which will not be elaborated here.

[0094] Figure 13 A schematic diagram of a preferred AC-DC converter system provided in this disclosure is shown below. Figure 13As shown, the AC-DC converter system includes three AC-DC converters, namely a first AC-DC converter 1001, a second AC-DC converter 1002, and a third AC-DC converter 1003.

[0095] The first end of the first AC-DC converter 1001 is connected to the DC port 21, the second end of the first AC-DC converter 1001 is connected to the first end of the second AC-DC converter 1102, the second end of the second AC-DC converter 1002 is connected to the first end of the third AC-DC converter 1003, and the second end of the third AC-DC converter 1003 is connected to the ground electrode 23.

[0096] The midpoint of the first bridge arm of the first AC-DC converter 1001 is connected to the first terminal of the first transformer U3, and the midpoint of the second bridge arm of the first AC-DC converter 1001 is connected to the second terminal of the first transformer U3. The midpoint of the first bridge arm of the second AC-DC converter 1002 is connected to the first terminal of the second transformer U4, and the midpoint of the second bridge arm of the second AC-DC converter 1002 is connected to the second terminal of the second transformer U4. The midpoint of the first bridge arm of the third AC-DC converter 1003 is connected to the first terminal of the third transformer U5, and the midpoint of the second bridge arm of the third AC-DC converter 1003 is connected to the second terminal of the third transformer U5. The third terminal of the first transformer U3 is connected to the first phase AC port 221, the third terminal of the second transformer U4 is connected to the second phase AC port 222, the third terminal of the third transformer U5 is connected to the third phase AC port 223, and the fourth terminal of the first transformer U3 is connected to the fourth terminals of both the second transformer U4 and the third transformer U5.

[0097] For example, since the second terminal of the third AC-DC converter 1003 is directly connected to the ground electrode 23, the switched capacitor module within the third AC-DC converter 1003 does not require a fifth protection module, thus saving on the cost of the AC-DC converter system. The AC sides of the first AC-DC converter 1001, the second AC-DC converter 1002, and the third AC-DC converter 1003 are connected via transformers. These transformers are used to construct a three-phase AC signal on the grid side connected to the first phase AC port 221, the second phase AC port 222, and the third phase AC port 223. Furthermore, since 90% of the switching devices in the first AC-DC converter 1001, the second AC-DC converter 1002, and the third AC-DC converter 1003 are semi-controlled switching devices, the cost of the AC-DC converter system can be significantly reduced.

[0098] 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. An AC-DC converter, characterized in that, include: At least one AC-DC converter circuit; wherein a first AC terminal and a second AC terminal of the AC-DC converter circuit are connected to an AC port; when the AC-DC converter includes one AC-DC converter circuit, the first DC terminal and the second DC terminal of the AC-DC converter circuit are connected to a DC port; when the AC-DC converter includes multiple AC-DC converter circuits, the first DC terminal is connected to a DC port or a second DC terminal of an adjacent AC-DC converter circuit, and the second DC terminal is connected to a DC port or a first DC terminal of an adjacent AC-DC converter circuit. The AC-DC converter circuit includes a switched capacitor module, a first bridge arm, and a second bridge arm. The first terminal of the switched capacitor module is connected to the first DC terminal, and the second terminal of the switched capacitor module is connected to the second DC terminal; The first bridge arm includes a first switching unit and a second switching unit; the first end of the first switching unit is connected to the first end of the switched capacitor module, the second end of the first switching unit and the first end of the second switching unit are connected at the midpoint of the first bridge arm, the second end of the second switching unit is connected to the second end of the switched capacitor module, and the midpoint of the first bridge arm is connected to the first AC terminal; The second bridge arm includes a third switch unit and a fourth switch unit; the first end of the third switch unit is connected to the first end of the switched capacitor module, the second end of the third switch unit is connected to the first end of the fourth switch unit at the midpoint of the second bridge arm, the second end of the fourth switch unit is connected to the second end of the switched capacitor module, and the midpoint of the second bridge arm is connected to the second AC terminal. The first switch unit, the second switch unit, the third switch unit, and the fourth switch unit each include a plurality of first switch devices connected in series; the plurality of first switch devices include at least a semi-controlled switch device.

2. The AC-DC converter according to claim 1, characterized in that, The plurality of first switching devices includes a plurality of semi-controlled switching devices; The AC-DC conversion circuit further includes a first auxiliary switch module and / or a second auxiliary switch module; The first terminal of the first auxiliary switch module is connected to the first terminal of the switched capacitor module, and the second terminal of the first auxiliary switch module is connected to the first terminal of the first switch unit and the first terminal of the third switch unit; the first terminal of the second auxiliary switch module is connected to the second terminal of the switched capacitor module, and the second terminal of the second auxiliary switch module is connected to the second terminal of the second switch unit and the second terminal of the fourth switch unit. The first auxiliary switch module and the second auxiliary switch module each include at least one second switch device; the second switch device includes at least a fully controlled switch device.

3. The AC-DC converter according to claim 2, characterized in that, The plurality of semi-controlled switching devices include at least one of a unidirectional semi-controlled switching unit and a bidirectional blocking semi-controlled switching unit.

4. The AC-DC converter according to claim 1, characterized in that, The plurality of first switching devices includes at least one fully controlled switching device and at least one semi-controlled switching device.

5. The AC-DC converter according to claim 4, characterized in that, The plurality of fully controlled switching devices include at least one of a unidirectional fully controlled switching unit, a bidirectional blocking fully controlled switching unit, a unidirectional single switching unit, and a bidirectional blocking single switching unit. The plurality of semi-controlled switching devices include at least one of a unidirectional semi-controlled unit and a bidirectional blocking semi-controlled unit.

6. The AC-DC converter according to claim 4, characterized in that, In the case where the fully controlled switching device includes at least one of a unidirectional fully controlled switching unit and a bidirectional blocking fully controlled switching unit, and / or the semi-controlled switching device includes at least one of a unidirectional semi-controlled switching unit and a bidirectional blocking semi-controlled switching unit, the first switching device further includes a buffer module. The first end of the buffer module is connected to the first end of the first switching device, and the second end of the buffer module is connected to the second end of the first switching device. The buffer module includes multiple buffer units, which are connected in series or in parallel.

7. The AC-DC converter according to claim 6, characterized in that, The plurality of said buffer units include at least one of surge arresters, capacitors, resistors, and diodes.

8. The AC-DC converter according to any one of claims 1-7, characterized in that, The AC-DC converter also includes a first protection module, a second protection module, a third protection module, and a fourth protection module; The first protection module is connected to the first switch unit, the second protection module is connected to the second switch unit, the third protection module is connected to the third switch unit, and the fourth protection module is connected to the fourth switch unit; The first protection module, the second protection module, the third protection module, and the fourth protection module each include at least one of a surge arrester and an inductor.

9. The AC-DC converter according to claim 1, characterized in that, The switched capacitor module includes: At least one switched capacitor unit, wherein a first terminal of the switched capacitor unit is connected to a first terminal of the DC port or a second terminal of an adjacent switched capacitor unit, and a second terminal of the switched capacitor unit is connected to a second terminal of the DC port or a first terminal of an adjacent switched capacitor unit; The fifth protection module has its first terminal connected to the first terminal of the switched capacitor module, and its second terminal connected to the second terminal of the switched capacitor module. The switched capacitor unit includes at least one of a full-bridge switching device and a half-bridge switching device.

10. An AC-DC converter system, characterized in that, Includes three AC-DC converters as described in any one of claims 1-9; The three AC-DC converters include a first AC-DC converter, a second AC-DC converter, and a third AC-DC converter; The first terminal of the first AC-DC converter is connected to the first pole of the DC port, the second terminal of the first AC-DC converter is connected to the first terminal of the second AC-DC converter, the second terminal of the second AC-DC converter is connected to the first terminal of the third AC-DC converter, and the second terminal of the third AC-DC converter is connected to the second pole of the DC port. The midpoint of the first bridge arm of the first AC-DC converter is connected to the first end of the first phase AC port, and the midpoint of the second bridge arm of the first AC-DC converter is connected to the second end of the first phase AC port; the midpoint of the first bridge arm of the second AC-DC converter is connected to the first end of the second phase AC port, and the midpoint of the second bridge arm of the second AC-DC converter is connected to the second end of the second phase AC port; the midpoint of the first bridge arm of the third AC-DC converter is connected to the first end of the third phase AC port, and the midpoint of the second bridge arm of the third AC-DC converter is connected to the second end of the third phase AC port.

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