Alternating-current parallel hybrid converter and direct-current power transmission system
By adopting AC parallel hybrid converters in high-voltage direct current transmission systems and replacing converter transformers with voltage source converters, the cost of equipment has been reduced and the structure simplified, solving the application challenges of high-voltage direct current transmission systems in short-distance, low-voltage scenarios.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NR ELECTRIC CO LTD
- Filing Date
- 2025-03-31
- Publication Date
- 2026-04-21
AI Technical Summary
In high-voltage direct current transmission systems, the existing technology of using converter transformers results in high equipment costs, making it difficult to apply in short-distance, low-voltage transmission scenarios.
An AC parallel hybrid converter is adopted, a voltage source converter is used to replace the converter transformer, the structure is simplified by using a reactor, and a six-pulse bridge circuit is used to filter out the 6k±1 harmonic.
It reduces equipment costs and simplifies the structure of high-voltage direct current transmission systems, making them widely applicable in short-distance, low-voltage transmission scenarios.
Smart Images
Figure CN224153969U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of high voltage direct current transmission technology, and more specifically, to an AC parallel hybrid converter and a DC transmission system. Background Technology
[0002] High-voltage direct current (HVDC) transmission systems can effectively solve transmission problems in scenarios such as limited transmission channels and excessive short-circuit current. They can convert some underutilized AC transmission lines into DC transmission lines to increase transmission capacity, and the short-circuit current is controllable. HVDC transmission systems use grid-commutated converters. Because these converters use thyristor devices, they cannot be controlled to turn off, consuming a large amount of reactive power and generating significant harmonics during operation. Therefore, grid-commutated converters require AC filters and reactive power compensation devices. To improve the flexibility of reactive power control and reduce footprint, static var compensators (SVCs) can be used for reactive power compensation and harmonic suppression, replacing traditional AC filters and reactive power compensation devices.
[0003] However, high-voltage direct current (HVDC) transmission systems still face the problem of high cost. For example, existing technologies still require converter transformers, which account for a large proportion of the cost of HVDC transmission systems, making it difficult for HVDC transmission systems to be applied in short-distance, low-voltage transmission scenarios. Utility Model Content
[0004] To address at least one of the aforementioned problems, this application proposes an AC parallel hybrid converter and a DC transmission system.
[0005] According to a first aspect of this application, at least one embodiment of this application provides an AC parallel hybrid converter, comprising: a current source converter; a voltage source converter, wherein the AC side of the voltage source converter is connected in parallel with the AC side of the current source converter; and a reactor, one end of which is connected to the AC side of the current source converter and the other end of which is connected to an AC system.
[0006] For example, in some embodiments of this application, the current source converter includes: an uncontrolled rectifier circuit, a grid commutation converter, a controlled commutation converter, or a hybrid commutation converter.
[0007] For example, in some embodiments of this application, the uncontrolled rectifier circuit, grid commutation converter, controllable commutation converter or hybrid commutation converter adopts a six-pulse bridge circuit; the voltage source converter adopts a three-phase star connection or delta connection structure.
[0008] For example, in some embodiments of this application, the uncontrolled rectifier circuit includes uncontrolled devices; the grid commutation converter includes semi-controlled devices; and the controllable commutation converter or hybrid commutation converter includes fully controlled devices and / or semi-controlled devices.
[0009] For example, in some embodiments of this application, the voltage source converter includes at least one of the following: modular multilevel structure, hybrid multilevel structure, two-level cascaded structure, and stacked two-level structure.
[0010] For example, in some embodiments of this application, the voltage source converter is used to perform reactive power compensation and harmonic suppression on the current source converter.
[0011] For example, in some embodiments of this application, the AC parallel hybrid converter further includes a DC energy storage unit, one end of which is connected to one end of the DC side of the current source converter, and the other end of which is connected to the other end of the DC side of the current source converter; the DC energy storage unit includes energy storage sub-modules connected in series.
[0012] According to a second aspect of this application, at least one embodiment of this application provides a DC transmission system, comprising: at least two AC parallel hybrid converters as described in any one of the first aspects, the at least two AC parallel hybrid converters including a first AC parallel hybrid converter and a second AC parallel hybrid converter, the DC side of the first AC parallel hybrid converter and the second AC parallel hybrid converter respectively including a first end and a second end, the first end of the first AC parallel hybrid converter being connected to the second end of the second AC parallel hybrid converter, and the second end of the first AC parallel hybrid converter being connected to the first end of the second AC parallel hybrid converter.
[0013] For example, in some embodiments of this application, it further includes: a first AC system connected to the AC side of the first AC parallel hybrid converter; and a second AC system connected to the AC side of the second AC parallel hybrid converter.
[0014] For example, in some embodiments of this application, it further includes: a first smoothing reactor, a second smoothing reactor, a third smoothing reactor, and a fourth smoothing reactor; a first DC line, wherein the first end of the first AC parallel hybrid converter is connected to the second end of the second AC parallel hybrid converter through the first smoothing reactor, the first DC line, and the third smoothing reactor; and a second DC line, wherein the second end of the first AC parallel hybrid converter is connected to the first end of the second AC parallel hybrid converter through the second smoothing reactor, the second DC line, and the fourth smoothing reactor.
[0015] For example, in some embodiments of this application, it further includes: a first DC filter, one end of which is connected to the connection point of the first smoothing reactor and the first DC line, and the other end of which is connected to the connection point of the second smoothing reactor and the second DC line; and a second DC filter, one end of which is connected to the connection point of the third smoothing reactor and the first DC line, and the other end of which is connected to the connection point of the fourth smoothing reactor and the second DC line.
[0016] For example, in some embodiments of this application, it further includes: a fifth smoothing reactor, wherein the first end of the first AC parallel hybrid converter is connected to the second end of the second AC parallel hybrid converter through the fifth smoothing reactor.
[0017] For example, in some embodiments of this application, if the voltage source converter of the first AC parallel hybrid converter and / or the second AC parallel hybrid converter adopts a star connection structure, the neutral point of the voltage source converter of the first AC parallel hybrid converter and / or the second AC parallel hybrid converter is directly grounded, grounded through a resistor, or grounded through a reactor.
[0018] For example, in some embodiments of this application, if the voltage source converter of the first AC parallel hybrid converter adopts a delta connection structure, and the voltage source converter of the second AC parallel hybrid converter adopts a delta connection structure, then the AC side of the current source converter of the first AC parallel hybrid converter and / or the second AC parallel hybrid converter is connected in parallel with a star-connected reactor, and the neutral point of the star-connected reactor is grounded through a resistor.
[0019] Compared with the prior art, this application has the following beneficial effects:
[0020] This application discloses an AC parallel hybrid converter that uses a voltage source converter to filter out the 6k±1 harmonics, directly adopts a six-pulse bridge circuit in the high-voltage direct current transmission system, and replaces the converter transformer with a reactor, thereby simplifying the converter structure of the high-voltage direct current transmission system and reducing equipment costs.
[0021] Accordingly, this application also discloses a DC power transmission system, including an AC parallel hybrid converter, which has a simple structure, low equipment cost, and broad application prospects in short-distance, low-voltage power transmission scenarios.
[0022] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description
[0023] The above and other objects, features, and advantages of this application will become more apparent from the detailed description of exemplary embodiments with reference to the accompanying drawings. The drawings described below are merely some embodiments of this application and are not intended to limit the scope of this application.
[0024] Figure 1 This is a schematic diagram of an AC parallel hybrid converter provided in an embodiment of this application;
[0025] Figure 2 This is a specific structural diagram of an AC parallel hybrid converter provided in an embodiment of this application;
[0026] Figure 3 This application provides a modular multilevel voltage source converter full-bridge sub-module structure.
[0027] Figure 4 This is a specific structural diagram of another AC parallel hybrid converter provided in the embodiments of this application;
[0028] Figure 5 This application provides a DC power transmission system.
[0029] Figure 6 This is another DC power transmission system provided in the embodiments of this application. Detailed Implementation
[0030] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.
[0031] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.
[0032] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.
[0033] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.
[0034] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing this application, and therefore cannot be used to limit the scope of protection of this application.
[0035] Figure 1 This is a schematic diagram of an AC parallel hybrid converter provided in an embodiment of this application.
[0036] like Figure 1 As shown, the AC parallel hybrid converter includes a current source converter, a voltage source converter, and a reactor. The current source converter and the voltage source converter are connected in parallel on the AC side and connected to the AC system via the reactor. The voltage source converter is used for reactive power compensation and harmonic suppression of the current source converter.
[0037] According to some embodiments, current source converters include: uncontrolled rectifier circuits, line-commutated converters (LCCs), controlled line-commutated converters (CLCCs), or hybrid commutated converters (HCCs). Voltage source converters include at least one of the following: modular multilevel structure, hybrid multilevel structure, two-level cascaded structure, and stacked two-level structure. It should be noted that when a current source converter uses an uncontrolled rectifier circuit, it can only operate in rectification mode.
[0038] According to some embodiments, the uncontrolled rectifier circuit, grid-commutated converter, controlled-commutated converter, or hybrid-commutated converter employs a six-pulse bridge circuit. The voltage source converter adopts a three-phase star or delta connection structure.
[0039] According to some embodiments, the uncontrolled rectifier circuit includes uncontrolled devices, the grid-commutated converter includes semi-controlled devices, and the controlled-commutated converter or hybrid-commutated converter includes fully controlled devices and / or semi-controlled devices. Uncontrolled devices include diodes, semi-controlled devices include thyristors, and fully controlled devices include at least one of the following: IGCT (Integrated Gate Commutated Thyristors), IGBT (Insulated Gate Bipolar Transistor), reverse-resistance IGCT, GTO (Gate Turn-Off Thyristor), and MOSFET (Metal Oxide Semiconductor Field Effect Transistor).
[0040] Figure 2 This is a structural diagram of an AC parallel hybrid converter provided in an embodiment of this application.
[0041] like Figure 2 As shown, the AC parallel hybrid converter includes a current source converter 1, a voltage source converter 2, and a reactor 3. The current source converter 1 and the voltage source converter 2 are connected in parallel in phase and connected to the AC system via the reactor 3.
[0042] The current source converter 1 adopts a line commutated converter (LCC), and the voltage source converter 2 adopts a static var generator (SVG) or a static synchronous compensator (STATCOM), and adopts a three-phase star connection structure.
[0043] Current source converter 1 is a six-pulse bridge circuit with six arms, each consisting of valves V1, V2, V3, V4, V5, and V6. Voltage source converter 2 is a three-phase star-connected circuit with three arms, each consisting of valves V7, V8, and V9, and reactor L. SA1 L SB1 L SC1 Optionally, the voltage source converter 2 adopts a three-phase delta-connected circuit.
[0044] Figure 3 This application provides a modular multilevel voltage source converter with a full-bridge sub-module structure.
[0045] like Figure 3As shown, the full-bridge submodule includes four IGBT modules T1, T2, T3, and T4, and one capacitor C1. When T1 and T4 are on and T2 and T3 are off, the submodule presents a positive voltage between X1 and X2; when T1 and T4 are off and T2 and T3 are on, the submodule presents a negative voltage between X1 and X2.
[0046] Figure 4 This is a specific structural diagram of another AC parallel hybrid converter provided in the embodiments of this application.
[0047] The AC parallel hybrid converter also includes a DC energy storage unit 18, one end of which is connected to one end of the DC side of the current source converter 1, and the other end of which is connected to the other end of the DC side of the current source converter 1.
[0048] The DC energy storage unit includes energy storage sub-modules connected in series.
[0049] According to some embodiments, the energy storage submodule includes a half-bridge submodule, and / or a full-bridge submodule, and / or a clamped twin submodule.
[0050] According to some embodiments, the energy storage element of the half-bridge submodule, full-bridge submodule, or clamped twin submodule is a supercapacitor or a battery.
[0051] Figure 5 This is a DC power transmission system provided in the embodiments of this application.
[0052] like Figure 5 As shown, the DC transmission system includes: at least two first AC parallel hybrid converters 10 and second AC parallel hybrid converters 20 as described above, a first AC system 14 and a second AC system 24.
[0053] The first AC system 14 is connected to the AC side of the first AC parallel hybrid converter 10. The second AC system 24 is connected to the AC side of the second AC parallel hybrid converter 20. The DC sides of the first AC parallel hybrid converter 10 and the second AC parallel hybrid converter 20 respectively include a first terminal and a second terminal. The first terminal of the first AC parallel hybrid converter 10 is connected to the second terminal of the second AC parallel hybrid converter 20, and the second terminal of the first AC parallel hybrid converter 10 is connected to the first terminal of the second AC parallel hybrid converter 20.
[0054] The first AC parallel hybrid converter 10 includes a first current source converter 11, a first voltage source converter 12, and a first reactor 13. The second AC parallel hybrid converter 20 includes a second current source converter 21, a second voltage source converter 22, and a second reactor 23.
[0055] This embodiment does not have a DC line and belongs to a back-to-back DC transmission system. Optionally, the first end of the first AC parallel hybrid converter 10 is connected to the second end of the second AC parallel hybrid converter 20 via a reactor; or / and the second end of the first AC parallel hybrid converter 10 is connected to the first end of the second AC parallel hybrid converter 20 via a reactor.
[0056] The AC power from the first AC system 14 is rectified into DC by the first current source converter 11, then sent to the second current source converter 21 and inverted back into AC before being supplied to the second AC system 24. The first voltage source converter 12 performs reactive power compensation for the reactive power consumed by the first current source converter 11 during operation and suppresses the AC harmonics generated by the first current source converter 11 during operation. The second voltage source converter 22 performs reactive power compensation for the reactive power consumed by the second current source converter 21 during operation and suppresses the AC harmonics generated by the second current source converter 21 during operation.
[0057] Optionally, the DC transmission system operates in power reverse transmission mode, with the first current source converter 11 operating in inverter mode and the second current source converter 21 operating in rectifier mode.
[0058] Figure 6 This is another DC power transmission system provided in the embodiments of this application.
[0059] Figure 6 and Figure 4 The circuit structures are basically similar, the difference lies in, Figure 6 The provided DC transmission system also includes: a first smoothing reactor 15, a second smoothing reactor 16, a third smoothing reactor 25, a fourth smoothing reactor 26, a first DC line 31, a second DC line 32, a first DC filter 17, and a second DC filter 27.
[0060] The first end of the first AC parallel hybrid converter 10 is connected to the second end of the second AC parallel hybrid converter 20 via a first smoothing reactor 15, a first DC line 31, and a third smoothing reactor 25. The second end of the first AC parallel hybrid converter 10 is connected to the first end of the second AC parallel hybrid converter 20 via a second smoothing reactor 16, a second DC line 32, and a fourth smoothing reactor 26. One end of the first DC filter 17 is connected to the connection point of the first smoothing reactor 15 and the first DC line 31, and the other end is connected to the connection point of the second smoothing reactor 16 and the second DC line 32. One end of the second DC filter 27 is connected to the connection point of the third smoothing reactor 25 and the first DC line 31, and the other end is connected to the connection point of the fourth smoothing reactor 26 and the second DC line 32.
[0061] This embodiment has a DC line and belongs to an end-to-end DC power transmission system.
[0062] The AC power from the first AC system 14 is rectified into DC by the first current source converter 11, then sent to the second current source converter 21 via the first DC line 31 and the second DC line 32, where it is inverted back into AC and supplied to the second AC system 24. The first voltage source converter 12 compensates for the reactive power consumed by the first current source converter 11 during operation and suppresses the AC harmonics generated by the first current source converter 11 during operation. The second voltage source converter 22 compensates for the reactive power consumed by the second current source converter 21 during operation and suppresses the AC harmonics generated by the second current source converter 21 during operation.
[0063] The first smoothing reactor 15, the second smoothing reactor 16, and the first DC filter 17 suppress the DC harmonics generated during the operation of the first current source converter 11. The third smoothing reactor 25, the fourth smoothing reactor 26, and the second DC filter 27 suppress the DC harmonics generated during the operation of the second current source converter 21.
[0064] Optionally, the DC transmission system operates in power reverse transmission mode, with the first current source converter 11 operating in inverter mode and the second current source converter 21 operating in rectifier mode.
[0065] Optionally, the first end of the first AC parallel hybrid converter 10 and the second end of the second AC parallel hybrid converter 20 are connected through a fifth smoothing reactor.
[0066] According to some embodiments, if the voltage source converter of the first AC parallel hybrid converter 10 and / or the second AC parallel hybrid converter 20 adopts a star connection structure, the neutral point of the voltage source converter of the first AC parallel hybrid converter 10 and / or the second AC parallel hybrid converter 20 is directly grounded, grounded through a resistor, or grounded through a reactor.
[0067] According to some embodiments, if the voltage source converter of the first AC parallel hybrid converter adopts a delta connection structure, and the voltage source converter of the second AC parallel hybrid converter adopts a delta connection structure, then the AC side of the current source converter of the first AC parallel hybrid converter and / or the second AC parallel hybrid converter is connected in parallel with a star-connected reactor, and the neutral point of the star-connected reactor is grounded through a resistor.
[0068] Optionally, the AC parallel hybrid converter in the DC transmission system provided in this application embodiment can be replaced with a voltage source converter.
[0069] In summary, this application provides an AC parallel hybrid converter and a DC transmission system, which uses a voltage source converter to filter out the 6k±1 harmonics, directly adopts a six-pulse bridge circuit in the high-voltage DC transmission system, and replaces the converter transformer with a reactor, thereby simplifying the converter structure of the high-voltage DC transmission system and reducing equipment costs.
[0070] It should be clearly understood that this application describes how specific examples are formed and used, but this application is not limited to any details of these examples. Rather, based on the teachings of the disclosure of this application, these principles can be applied to many other embodiments.
[0071] Furthermore, it should be noted that the above figures are merely illustrative representations of the processes included in the method according to exemplary embodiments of this application, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.
[0072] Exemplary embodiments of this application have been specifically shown and described above. It should be understood that this application is not limited to the detailed structures, arrangements, or implementation methods described herein; rather, this application is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.
Claims
1. An AC parallel hybrid converter, characterized by, include: Current source converter; A voltage source converter, wherein the AC side of the voltage source converter is connected in parallel with the AC side of the current source converter; The reactor is connected at one end to the AC side of the current source converter and at the other end to the AC system.
2. The AC parallel hybrid converter of claim 1, wherein, The current source converter includes: an uncontrolled rectifier circuit, a grid commutation converter, a controlled commutation converter, or a hybrid commutation converter.
3. The AC parallel hybrid converter as described in claim 2, characterized in that, The uncontrolled rectifier circuit, grid commutator, controlled commutator, or hybrid commutator adopts a six-pulse bridge circuit. The voltage source converter adopts a three-phase star or delta connection structure.
4. The AC parallel hybrid converter as described in claim 2, characterized in that, The uncontrolled rectifier circuit includes uncontrolled devices; The grid phase-commutation converter includes semi-controlled devices; The controllable commutated converter or hybrid commutated converter includes fully controlled devices and / or semi-controlled devices.
5. The AC parallel hybrid converter of claim 1, wherein, The voltage source converter includes at least one of the following: modular multilevel structure, hybrid multilevel structure, two-level cascaded structure, and stacked two-level structure.
6. The AC parallel hybrid converter as described in claim 1, characterized in that, The voltage source converter is used to perform reactive power compensation and harmonic suppression for the current source converter.
7. The AC parallel hybrid converter of claim 1, wherein, Also includes: A DC energy storage unit, one end of which is connected to one end of the DC side of the current source converter, and the other end of which is connected to the other end of the DC side of the current source converter; The DC energy storage unit includes energy storage sub-modules connected in series.
8. A direct current power transmission system, characterized by include: At least two AC parallel hybrid converters as described in any one of claims 1-7, wherein the at least two AC parallel hybrid converters include a first AC parallel hybrid converter and a second AC parallel hybrid converter, wherein the DC side of the first AC parallel hybrid converter and the second AC parallel hybrid converter respectively includes a first end and a second end, wherein the first end of the first AC parallel hybrid converter is connected to the second end of the second AC parallel hybrid converter, and the second end of the first AC parallel hybrid converter is connected to the first end of the second AC parallel hybrid converter.
9. The direct current power transmission system of claim 8, wherein, Also includes: The first AC system is connected to the AC side of the first AC parallel hybrid converter; The second AC system is connected to the AC side of the second AC parallel hybrid converter.
10. The direct current power transmission system of claim 8, wherein, Also includes: First smoothing reactor, second smoothing reactor, third smoothing reactor and fourth smoothing reactor; The first DC line, the first end of the first AC parallel hybrid converter is connected to the second end of the second AC parallel hybrid converter through the first smoothing reactor, the first DC line and the third smoothing reactor; The second DC line connects the second end of the first AC parallel hybrid converter to the first end of the second AC parallel hybrid converter via the second smoothing reactor, the second DC line, and the fourth smoothing reactor.
11. The direct current power transmission system of claim 10, wherein, Also includes: The first DC filter has one end connected to the connection point of the first smoothing reactor and the first DC line, and the other end connected to the connection point of the second smoothing reactor and the second DC line. The second DC filter has one end connected to the connection point of the third smoothing reactor and the first DC line, and the other end connected to the connection point of the fourth smoothing reactor and the second DC line.
12. The direct current power transmission system of claim 8, wherein, Also includes: The fifth smoothing reactor connects the first end of the first AC parallel hybrid converter to the second end of the second AC parallel hybrid converter.
13. The DC transmission system as described in claim 8, characterized in that, If the voltage source converter of the first AC parallel hybrid converter and / or the second AC parallel hybrid converter adopts a star connection structure, the neutral point of the voltage source converter of the first AC parallel hybrid converter and / or the second AC parallel hybrid converter is directly grounded, grounded through a resistor, or grounded through a reactor.
14. The DC transmission system as described in claim 8, characterized in that, If the voltage source converter of the first AC parallel hybrid converter adopts a delta connection structure, and the voltage source converter of the second AC parallel hybrid converter adopts a delta connection structure, then the AC side of the current source converter of the first AC parallel hybrid converter and / or the second AC parallel hybrid converter is connected to a star-connected reactor in parallel, and the neutral point of the star-connected reactor is grounded through a resistor.