An ac-ac converter

Abstract

The application discloses an AC-AC converter, a voltage matching module generates a first AC voltage, the first AC voltage is a half-wave voltage; a frequency conversion module generates a second AC voltage, the second AC voltage is a half-wave voltage, and the first AC voltage and the second AC voltage are of the same polarity; a first frequency voltage generating module reverses the polarity of the first AC voltage according to a first preset frequency and a first preset interval, and generates a first frequency voltage with positive and negative alternation; and a second frequency voltage generating module reverses the polarity of a voltage obtained by adding the first AC voltage and the second AC voltage according to a second preset frequency and a second preset interval, and generates a second frequency voltage with positive and negative alternation. The application utilizes the idea of half-wave frequency conversion, can realize AC-AC frequency conversion by using three bridge arms, reduces the complexity of the converter topology, and greatly reduces the number of modules and the number of devices used.

Description

Technical Field

[0001] This invention relates to the field of power transmission technology, and more specifically to an alternating current exchanger. Background Technology

[0002] The core objective of the current energy transition is to gradually replace fossil fuels with renewable energy and achieve a clean, low-carbon, and efficient energy system composed of renewable energy. Furthermore, the large-scale collection and long-distance transmission of renewable energy presents both a significant challenge and an opportunity for the current and future development of the power sector.

[0003] Flexible low-frequency AC transmission systems leverage power electronics frequency conversion and grid control technologies to enhance the grid's flexible regulation capabilities. By flexibly selecting appropriate frequencies from 0 to 50 Hz, they reduce the impact of line impedance on power transmission, increase grid transmission capacity, and retain the electromagnetic induction transformation and zero-crossing current interruption characteristics of AC transmission. In scenarios such as long cable line transmission, flexible grid interconnection, and large-scale renewable energy aggregation, they serve as a valuable supplement to power frequency AC and DC transmission. The AC-AC converters in flexible low-frequency AC transmission systems often employ a modular multilevel matrix converter (M3C) topology. While achieving frequency conversion, they also provide flexible control of the grid, including power flow regulation and voltage regulation, making them the core equipment of the system.

[0004] However, the M3C AC converter has nine bridge arms, which is complex in structure. Each bridge arm must withstand the peak voltage of the power / low frequency. It has many power modules, low utilization rate, and large losses. Different frequency energy is exchanged in the power modules in a dispersed manner, which makes control difficult. Various complex system operating conditions further increase the difficulty of control. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing M3C AC converter having 9 bridge arms, resulting in a large number of power modules and a complex structure, thereby providing an AC converter.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides an AC converter. Each phase topology of the AC converter includes: a voltage matching module, a frequency conversion module, a first frequency voltage generation module, and a second frequency voltage generation module. The voltage matching module generates a first AC voltage, which is a half-wave voltage. The frequency conversion module, with its first terminal connected to the first terminal of the voltage matching module, generates a second AC voltage, also a half-wave voltage, and the first and second AC voltages have the same polarity. The first frequency voltage generation module, with its first and second terminals connected to the first and second terminals of the voltage matching module respectively, reverses the polarity of the first AC voltage according to a first preset frequency and a first preset gap to generate an alternating positive and negative first frequency voltage. The second frequency voltage generation module, with its first terminal connected to the first terminal of the frequency conversion module and its second terminal connected to the second terminal of the voltage matching module, reverses the polarity of the voltage obtained by adding the first and second AC voltages according to a second preset frequency and a second preset gap to generate an alternating positive and negative second frequency voltage.

[0007] In one embodiment, the voltage matching module includes: a plurality of cascaded first voltage conversion submodules.

[0008] In one embodiment, the first voltage conversion submodule includes either a half-bridge submodule or a full-bridge submodule.

[0009] In one embodiment, the number of first voltage conversion submodules is used to determine the amplitude and frequency of the first AC voltage.

[0010] In one embodiment, the frequency conversion module includes: a plurality of cascaded second voltage conversion sub-modules.

[0011] In one embodiment, the second voltage conversion submodule is a full-bridge submodule.

[0012] In one embodiment, the number of first voltage conversion submodules and the number of second voltage conversion submodules are used to determine the amplitude and frequency of the second frequency voltage.

[0013] In one embodiment, the half-bridge submodule includes: a bridge arm connected in parallel and a first supporting capacitor; the bridge arm is composed of two power electronic switching devices connected in series.

[0014] In one embodiment, the full-bridge submodule includes: two bridge arms connected in parallel and a second supporting capacitor, the second supporting capacitor being connected in parallel with the two bridge arms; each bridge arm is composed of two power electronic switching devices connected in series.

[0015] In one embodiment, when the AC converter is connected in a three-phase configuration, it further includes: multiple transformers; the three phases of the third terminal of the first frequency voltage generation module are connected to a single point, and the three phases of the fourth terminal of the first frequency voltage generation module are respectively connected to the corresponding phases of the first AC system; the third and fourth terminals of the second frequency voltage generation module of each phase topology are respectively connected to the two ends of the primary side of a transformer; the first terminal of the secondary side of each transformer is connected to a single point, and the second terminal of the secondary side of each transformer is correspondingly connected to the second AC system.

[0016] The technical solution of this invention has the following advantages: The AC converter provided by this invention comprises a voltage matching module that generates a first AC voltage, which is a half-wave voltage; a frequency conversion module that generates a second AC voltage, which is also a half-wave voltage, and the first and second AC voltages have the same polarity; a first frequency voltage generation module that reverses the polarity of the first AC voltage according to a first preset frequency and a first preset gap to generate an alternating positive and negative first frequency voltage; and a second frequency voltage generation module that reverses the polarity of the voltage obtained by adding the first and second AC voltages according to a second preset frequency and a second preset gap to generate an alternating positive and negative second frequency voltage. This invention utilizes the concept of half-wave frequency conversion, enabling AC-AC frequency conversion using three bridge arms, reducing the complexity of the converter topology, and significantly reducing the number of modules and components used. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 A composition diagram of a specific example of an AC exchange provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the half-bridge submodule structure provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the full-bridge submodule structure provided in an embodiment of the present invention; Figure 4 A composition diagram of a specific example of an AC exchange provided in an embodiment of the present invention; Figure 5 This is a composition diagram of a specific example of an AC exchanger provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Example This invention provides an alternating current exchange, such as... Figure 1 As shown, each phase topology of the AC converter includes: voltage matching module 1, frequency conversion module 2, first frequency voltage generation module 3, and second frequency voltage generation module 4.

[0024] Specifically, voltage matching module 1 is used to generate a first AC voltage, which is a half-wave voltage. The half-wave voltage can be a positive voltage with a specific amplitude and frequency, and the positive voltage is composed of the positive half-cycle of a sine wave with the specific amplitude and frequency.

[0025] Optionally, the AC converter provided in this embodiment of the invention can be a multilevel converter, wherein the voltage matching module 1 includes: a plurality of cascaded first voltage conversion sub-modules, the number of which is determined by the number of voltage levels. For example, when the number of voltage levels is n, the number of first voltage conversion sub-modules is (n-1) / 2.

[0026] Optionally, the first voltage conversion submodule includes either a half-bridge submodule (HBSM) or a full-bridge submodule (FBSM), but it can also be other voltage conversion submodules. However, it should be noted that the cascaded first voltage conversion submodules can output half-wave voltage.

[0027] Specifically, in this embodiment of the invention, not all of the first voltage conversion submodules are put into operation. Moreover, the amplitude and frequency of the first AC voltage can be determined by controlling the number of first voltage conversion submodules put into operation according to system requirements.

[0028] Specifically, the frequency conversion module 2, whose first terminal is connected to the first terminal of the voltage matching module 1, is used to generate a second AC voltage. The second AC voltage is a half-wave voltage, and the first AC voltage and the second AC voltage have the same polarity. The second AC voltage can be a positive voltage with a specific amplitude and frequency, which is composed of the positive half-cycle of a sine wave with that specific amplitude and frequency.

[0029] Optionally, the frequency conversion module 2 includes: multiple cascaded second voltage conversion sub-modules, wherein the number of circuits connected to the second voltage conversion sub-modules is determined by the number of circuits connected to the first voltage conversion sub-modules.

[0030] Specifically, in this embodiment of the invention, not all of the second voltage conversion submodules are engaged. Moreover, the amplitude and frequency of the second AC voltage can be determined by controlling the number of second voltage conversion submodules engaged according to system requirements.

[0031] Optionally, the second voltage conversion submodule can be a full-bridge submodule, but it can also be other voltage conversion submodules. However, it should be noted that the cascaded second voltage conversion submodules can output half-wave voltage.

[0032] Optionally, such as Figure 2 As shown, the half-bridge submodule includes: a bridge arm connected in parallel and a first supporting capacitor C1; the bridge arm is composed of two power electronic switching devices connected in series, wherein the power electronic switching devices may include IGBTs and diodes, the IGBTs and diodes are connected in reverse parallel, and may also be other controllable switching devices to control the switching on and off of the half-bridge submodule.

[0033] Optionally, such as Figure 3 As shown, the full-bridge submodule includes: two bridge arms connected in parallel and a second supporting capacitor C2, which is connected in parallel with the two bridge arms; each bridge arm is composed of two power electronic switching devices (IGBTs) connected in series, wherein the power electronic switching devices are not limited to IGBTs and diodes, the IGBTs and diodes are connected in reverse parallel, and can also be other controllable switching devices to control the switching on and off of the full-bridge submodule.

[0034] Specifically, the first frequency voltage generation module 3 has its first and second ends connected to the first and second ends of the voltage matching module 1, respectively. It is used to reverse the polarity of the first AC voltage according to the first preset frequency and the first preset gap to generate a first frequency voltage with alternating positive and negative values.

[0035] Optionally, the first frequency voltage can be the power frequency voltage. The first frequency voltage generation module 3 can be composed of cascaded controllable switching devices, and the number of cascaded devices depends on the system requirements.

[0036] Specifically, the second frequency voltage generation module 4 has its first end connected to the first end of the frequency conversion module 2 and its second end connected to the second end of the voltage matching module 1. It is used to generate a second frequency voltage with alternating positive and negative values ​​by adding the first AC voltage and the second AC voltage and reversing the polarity according to the second preset frequency and the second preset gap.

[0037] Optionally, the second frequency voltage can be a low-frequency voltage. The second frequency voltage generation module 4 can be composed of cascaded controllable switching devices, the number of which depends on system requirements.

[0038] For example, this embodiment of the invention uses a first frequency voltage as the power frequency voltage and a second frequency voltage as a low frequency voltage to illustrate the half-wave frequency conversion method. Figure 4 As shown.

[0039] like Figure 4 As shown, in step ①, voltage matching module 1 generates a first AC voltage (Vx) on the x-phase side of the converter. This first AC voltage is a positive voltage with a specific amplitude and frequency, and it consists of the positive half-cycle of a sine wave with that specific amplitude and frequency. In step ②, frequency conversion module 2 generates a second AC voltage. The sum of the first AC voltage and the second AC voltage is denoted as Va. Va is a positive voltage with a specific amplitude and frequency, and it consists of the positive half-cycle of a sine wave with that specific amplitude and frequency. In step ③, first frequency voltage generation module 3 reverses the polarity of the first AC voltage (Vx) at a certain frequency and interval to generate an alternating positive and negative sine wave. In step ④, second frequency voltage generation module 4 reverses the polarity of voltage Va at a certain frequency and interval to generate an alternating positive and negative sine wave. Thus, the AC converter provided in this embodiment of the invention, by utilizing the concept of half-wave frequency conversion, can achieve AC-AC frequency conversion using three bridge arms, reducing the complexity of the converter topology, and significantly reducing the number of modules and devices used.

[0040] In one specific embodiment, such as Figure 5As shown, when the AC converter is connected in a three-phase configuration, it also includes: multiple transformers; the three phases of the third terminal of the first frequency voltage generation module are connected to a single point, and the three phases of the fourth terminal of the first frequency voltage generation module are respectively connected to the corresponding phases of the first AC system; the third and fourth terminals of the second frequency voltage generation module of each phase topology are respectively connected to the two ends of the primary side of a transformer; the first terminal of the secondary side of each transformer is connected to a single point, and the second terminal of the secondary side of each transformer is correspondingly connected to the second AC system.

[0041] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An alternating current exchanger, characterized in that, Each phase topology of the AC converter includes: a voltage matching module, a frequency conversion module, a first frequency voltage generation module, and a second frequency voltage generation module, wherein... A voltage matching module is used to generate a first AC voltage, which is a half-wave voltage. A frequency conversion module, the first terminal of which is connected to the first terminal of the voltage matching module, is used to generate a second AC voltage, the second AC voltage being a half-wave voltage, and the first AC voltage and the second AC voltage having the same polarity. The first frequency voltage generation module has its first and second ends connected to the first and second ends of the voltage matching module, respectively. It is used to reverse the polarity of the first AC voltage according to the first preset frequency and the first preset gap to generate a first frequency voltage with alternating positive and negative values. The second frequency voltage generation module has its first end connected to the first end of the frequency conversion module and its second end connected to the second end of the voltage matching module. It is used to generate a second frequency voltage with alternating positive and negative values ​​by reversing the polarity of the voltage obtained by adding the first AC voltage and the second AC voltage according to the second preset frequency and the second preset gap.

2. The AC converter according to claim 1, characterized in that, The voltage matching module includes: multiple cascaded first voltage transformation sub-modules.

3. The AC converter according to claim 2, characterized in that, The first voltage conversion submodule includes either a half-bridge submodule or a full-bridge submodule.

4. The AC converter according to claim 2, characterized in that, The number of first voltage conversion submodules is used to determine the amplitude and frequency of the first AC voltage.

5. The AC converter according to claim 2, characterized in that, The frequency conversion module includes: multiple cascaded second voltage conversion sub-modules.

6. The AC converter according to claim 5, characterized in that, The second voltage conversion submodule is a full-bridge submodule.

7. The AC converter according to claim 5, characterized in that, The number of first voltage conversion submodules and the number of second voltage conversion submodules are used to determine the amplitude and frequency of the second frequency voltage.

8. The AC converter according to claim 3, characterized in that, The half-bridge submodule includes: The bridge arms and the first supporting capacitor are connected in parallel; The bridge arm is composed of two power electronic switching devices connected in series.

9. The AC exchanger according to any one of claims 3 or 6, characterized in that, The full-bridge submodule includes: Two bridge arms connected in parallel and a second supporting capacitor, wherein the second supporting capacitor is connected in parallel with the two bridge arms; Each bridge arm consists of two power electronic switching devices connected in series.

10. The AC converter according to claim 1, characterized in that, When the AC converter is connected in a three-phase configuration, it further includes: Multiple transformers; The three phases of the third terminal of the first frequency voltage generation module are connected to a single point, and the three phases of the fourth terminal of the first frequency voltage generation module are respectively connected to the corresponding phases of the first AC system. The third and fourth terminals of the second frequency voltage generation module of each phase topology are respectively connected to the two ends of the primary side of a transformer; the first terminal of the secondary side of each transformer is connected to a point, and the second terminal of the secondary side of each transformer is connected to the corresponding second AC system.

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