WO2021147514A1 - 模块化多电平交流-直流变换系统 - Google Patents

模块化多电平交流-直流变换系统 Download PDF

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WO2021147514A1
WO2021147514A1 PCT/CN2020/132722 CN2020132722W WO2021147514A1 WO 2021147514 A1 WO2021147514 A1 WO 2021147514A1 CN 2020132722 W CN2020132722 W CN 2020132722W WO 2021147514 A1 WO2021147514 A1 WO 2021147514A1
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conversion system
level
port
tube
modular multi
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PCT/CN2020/132722
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English (en)
French (fr)
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王新颖
贺之渊
魏晓光
庞辉
李强
吕铮
客金坤
白建成
许航宇
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全球能源互联网研究院有限公司
国家电网有限公司
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Publication of WO2021147514A1 publication Critical patent/WO2021147514A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Definitions

  • This application relates to the field of AC-DC conversion systems, for example, to a modular multi-level AC-DC conversion system.
  • Modular multi-level AC-DC converters are widely used in power conversion fields such as flexible DC transmission systems, DC distribution network systems, and medium voltage motor control.
  • the most widely used is half-bridge modular multi-level converters
  • the electrical topology of Modular Multilevel Converter (MMC) and Cascaded H-bridge Converter (CHC) are shown in Figures 1 and 2.
  • MMC Modular Multilevel Converter
  • CHC Cascaded H-bridge Converter
  • Most of the world's flexible DC transmission projects and DC distribution network projects use MMC converter solutions, such as the TransBay Cable ⁇ 200kV project in the United States, the Xiamen ⁇ 320kV flexible straight project, and the Shanghai 220kV Unified Power Flow Controller (Unified Power Flow Controller, UPFC) project and Suzhou DC distribution network project.
  • Unified Power Flow Controller Unified Power Flow Controller
  • the electrical topology determines the characteristics of the converter, such as electrical characteristics, fault characteristics, and efficiency.
  • the characteristics of MMC First, the number of sub-module capacitors required is large and the capacitance value of each sub-module is relatively large. In high-voltage applications, considering the stability of the capacitor and the requirements for low clutter, polypropylene metal film capacitors are used, which leads to higher cost of the capacitor part. Second, although the modular design is adopted, the integration level in low- and medium-voltage applications is still relatively low and the volume is relatively large. Third, the half-bridge MMC converter cannot effectively suppress the short-circuit fault on the DC side, and the fault current cannot be eliminated by blocking the insulated gate bipolar transistor (IGBT) inside the MMC.
  • IGBT insulated gate bipolar transistor
  • the modular multi-level AC-DC conversion system provided by the present application overcomes the defects of low integration, large volume, and high cost of the AC-DC conversion system in related technologies.
  • the embodiment of the present application provides a modular multi-level AC-DC conversion system, including: a controller, a plurality of sub-module units, a plurality of isolation transformers, and a plurality of DC support capacitors, wherein:
  • each sub-module unit is connected in parallel with one of the plurality of DC support capacitors, and the plurality of DC support capacitors are connected in series or in parallel to form a DC port of the modular multi-level AC-DC conversion system; the AC side of each sub-module unit Connect the first side windings of three isolation transformers.
  • the three isolation transformers correspond to the three-phase one-to-one of the modular multi-level AC-DC conversion system, and are connected in series with the second side windings of each corresponding multiple isolation transformers.
  • each sub-module unit It includes three full-bridge structures and the DC ports of the three full-bridge structures are connected in parallel to form the DC side of each sub-module unit, or each sub-module unit includes three half-bridge structures and the direct current of the three half-bridge structures The ports are connected in parallel to form the DC side of each sub-module unit, or each sub-module unit
  • the DC port of the modular multi-level AC-DC conversion system when the plurality of DC support capacitors are connected in series to form the DC port of the modular multi-level AC-DC conversion system, the DC port of the modular multi-level AC-DC conversion system
  • the number of each DC port is multiple, and the two ends of each DC port are the first end and the second end of one of the multiple DC support capacitors, or the two ends of each DC port are the multiple DC support
  • a plurality of DC support capacitors are connected in series via a half-bridge topology or a full-bridge topology to form a DC port of a modular multi-level AC-DC conversion system.
  • the upper tube of the half-bridge topology uses IGBT
  • the lower tube of the half-bridge topology uses diodes
  • multiple DC support capacitors are connected in series through the half-bridge topology to form the DC port of the modular multi-level AC-DC conversion system, and the modular multi-level
  • the upper tube of the half-bridge topology uses diodes
  • the lower tube of the half-bridge topology uses IGBTs
  • the multiple DC support capacitors are connected in series through the half-bridge topology to form a modular multilevel
  • the upper and lower tubes of the half-bridge topology use IGBTs.
  • the modular multi-level AC-DC conversion system when multiple DC support capacitors are connected in series through a full-bridge topology to form a DC port of a modular multi-level AC-DC conversion system, and the modular multi-level AC-DC conversion system only operates in rectification,
  • the T1 and T4 tubes of the full-bridge topology use IGBTs, and the T2 and T3 tubes of the full-bridge topology use diodes; multiple DC support capacitors are connected in series through the full-bridge topology to form the DC port of the modular multi-level AC-DC conversion system.
  • the T1 and T4 tubes of the full-bridge topology use diodes, and the T2 and T3 tubes of the full-bridge topology use IGBT;
  • the bridge topology is connected in series to form the DC port of the modular multi-level AC-DC conversion system, and the power of the modular multi-level AC-DC conversion system runs in both directions, all the tubes of the full-bridge topology use IGBTs; among them, the T1 tube The first end is connected to the first end of the T3 tube, the second end of the T1 tube is connected to the first end of the T2 tube, the second end of the T2 tube is connected to the first end of the T4 tube, and the second end of the T4 tube is connected to the T3 Connect the second end of the tube.
  • a plurality of DC support capacitors are connected in series, in parallel, or mixed in series and parallel through a DC/DC converter to form a DC port of a modular multi-level AC-DC conversion system.
  • the DC/DC DC/DC converter includes an isolated dual active bridge (DAB) converter or an isolated resonant converter.
  • DAB dual active bridge
  • the isolation transformer adopts a discrete single isolation transformer or a multi-winding isolation transformer integrated with multiple sub-modules.
  • the AC three-phases are connected into a star or delta.
  • the modular multi-level AC-DC conversion system further includes: a fault current suppression unit connected to the DC port of the modular multi-level AC-DC conversion system for limiting the module Analyze the short-circuit fault current of the DC port of the multi-level AC-DC conversion system.
  • Figure 1 is a schematic diagram of the structure of a half-bridge modular multilevel converter in related technologies
  • Figure 2 is a schematic diagram of a cascaded full-bridge converter in related technologies
  • FIG. 3 is a schematic structural diagram of a DC support capacitor directly connected in series to form a DC port in a modular multi-level AC-DC conversion system provided by an embodiment of the application;
  • FIG. 4 is a schematic structural diagram of a DC support capacitor directly connected in parallel to form a DC port according to an embodiment of the application;
  • Figure 5 is a schematic structural diagram of a DC support capacitor connected in series through a half-bridge topology to form a DC port according to an embodiment of the application;
  • FIG. 6 is a schematic structural diagram of a DC support capacitor connected in series through a full-bridge topology to form a DC port according to an embodiment of the application;
  • FIG. 7 is a schematic structural diagram of a DC port formed by connecting a full-bridge topology DC/DC converter in series according to an embodiment of the application;
  • FIG. 8 is a schematic structural diagram of a full-bridge topology DC/DC converter connected in parallel to form a DC port according to an embodiment of the application;
  • FIG. 9 is a schematic structural diagram of a full-bridge topology DC/DC converter connected in series and parallel to form a DC port according to an embodiment of the application.
  • FIG. 10 is a schematic diagram of the connection of a fault current suppression unit provided by an embodiment of the application.
  • FIG. 11 is a schematic structural diagram of a DC support capacitor forming a DC port through a half-bridge topology when the conversion system is only rectifying operation according to an embodiment of the application;
  • FIG. 12 is a schematic structural diagram of a DC support capacitor forming a DC port through a half-bridge topology when the conversion system is only in inverter operation according to an embodiment of the application;
  • FIG. 13 is a schematic structural diagram of a DC support capacitor forming a DC port through a full-bridge topology when the conversion system is only rectifying operation according to an embodiment of the application;
  • FIG. 14 is a schematic structural diagram of a DC support capacitor forming a DC port through a full-bridge topology when the conversion system is only in inverter operation according to an embodiment of the application;
  • 15 is a schematic diagram of the connection of a multi-winding isolation transformer provided by an embodiment of the application.
  • 16 is a schematic diagram of an isolated dual active bridge DAB converter provided by an embodiment of the application.
  • FIG. 17 is a schematic diagram of an isolated resonant converter provided by an embodiment of the application.
  • the modular multi-level AC-DC conversion system provided by the embodiments of the present application can be used for AC voltage transformation of a medium and low voltage distribution network system.
  • the system is shown in Figure 3 and includes: a controller, multiple sub-module units, and multiple Isolation transformer and multiple DC support capacitors.
  • the DC side of each sub-module unit is connected in parallel with one of the multiple DC support capacitors.
  • Each sub-module unit and each DC support capacitor is connected, the controller is set to collect the current of the three-phase AC terminal of the modular multi-level AC-DC conversion system and the voltage of each DC support capacitor, and according to the modular multi-level
  • the current of the three-phase AC terminal of the AC-DC conversion system and the voltage of each DC support capacitor output the trigger signals of the internal power devices of all sub-module units for AC power control, AC output voltage control, DC output
  • the sub-module unit may include three full-bridge structures and the three full-bridge structures are connected in parallel on the DC side, or three half-bridge structures and the three half-bridge structures are connected in parallel on the DC side. Or adopt a three-phase four-arm structure to meet different needs.
  • the DC ports of the three full-bridge structures are connected in parallel to form the DC side of the sub-module unit, and the AC ports of the three full-bridge structures are the AC side of the sub-module unit.
  • FIG. 3 is a schematic structural diagram of a DC support capacitor connected in series to form a DC port in a modular multilevel AC-DC conversion system provided by an embodiment of the application
  • FIG. 4 is a schematic structural diagram of a DC support capacitor connected in parallel to form a DC port according to an embodiment of the application
  • Figure 5 is a schematic structural diagram of the DC support capacitors provided in an embodiment of the application to form a DC port in series through a half-bridge topology
  • Figure 6 is a schematic structural diagram of the DC support capacitors provided in an embodiment of the application to form a DC port in series through a full-bridge topology
  • 7 is a schematic structural diagram of a full-bridge topology DC/DC converter connected in series to form a DC port according to an embodiment of the application
  • FIG. 3 is a schematic structural diagram of a DC support capacitor connected in series to form a DC port in a modular multilevel AC-DC conversion system provided by an embodiment of the application
  • FIG. 4 is a schematic structural diagram of a DC support capacitor connected in parallel
  • FIG. 8 is a structural schematic diagram of a full-bridge topology DC/DC converter connected in parallel to form a DC port according to an embodiment of the application 9 is a schematic diagram of the structure of a DC port formed by a full-bridge topology DC/DC converter serial-parallel hybrid connection provided by an embodiment of the application.
  • the DC support capacitors can be directly connected in series or in parallel to form the DC port required by the conversion system, as shown in Figures 3 and 4; the DC support capacitors can also be connected in series through a half-bridge or full-bridge topology to form a DC Ports, as shown in Figure 5 and Figure 6; DC support capacitors can also be connected in series, parallel or mixed series and parallel through a DC/DC (Direct Current-Direct Current, DC/DC) converter to form a DC port, as shown in Figure 7 , Figure 8 and Figure 9.
  • DC/DC Direct Current-Direct Current, DC/DC
  • FIG. 10 is a schematic diagram of the connection of a fault current suppression unit provided by an embodiment of the application.
  • a fault current suppression unit is added to the DC port of the modular multi-level AC-DC conversion system.
  • the fault current suppression unit can be composed of an IGBT valve and an energy absorption device.
  • the DC support capacitors are connected in series, parallel or mixed series and parallel through the DC/DC converter to form the DC port of the modular multi-level AC-DC conversion system, it can also be used in the modular multi-level AC-DC conversion according to the needs. Add a fault current suppression unit to the DC port of the system to limit the short-circuit fault current of the DC port of the modular multi-level AC-DC conversion system.
  • FIG. 11 is a schematic diagram of the structure of the DC support capacitor forming a DC port through a half-bridge topology when the conversion system is only rectifying operation according to an embodiment of the application
  • FIG. 12 is a diagram of the embodiment of the application when the conversion system is only in inverter operation.
  • the supporting capacitor forms a schematic diagram of the structure of the DC port through the half-bridge topology.
  • the upper tube of the half-bridge topology can use IGBT and the lower tube can use diodes, as shown in Figure 11; if the conversion system only In inverter operation, diodes can be used for the upper tube of the half-bridge topology, and IGBTs can be used for the lower tube, as shown in Figure 12. If the power conversion system operates in both directions, the upper and lower tubes of the half-bridge topology can use IGBTs.
  • FIG. 13 is a schematic diagram of the structure of the DC support capacitor forming a DC port through a full bridge topology when the conversion system is only rectifying operation according to an embodiment of the application;
  • FIG. 14 is a schematic diagram of the DC port when the conversion system is only in inverter operation according to an embodiment of the application.
  • the supporting capacitor forms a schematic diagram of the structure of the DC port through the full-bridge topology.
  • the T1 and T4 tubes of the full-bridge topology can use IGBTs
  • Diodes can be used for T2 and T3 tubes, as shown in Figure 13
  • diodes can be used for T1 and T4 tubes of the full-bridge topology
  • IGBTs can be used for T2 and T3 tubes, as shown in Figure 14
  • the conversion system power runs in both directions, and all tubes in the full-bridge topology can use IGBTs.
  • FIG. 15 is a schematic diagram of the connection of a multi-winding isolation transformer provided by an embodiment of the application.
  • the isolation transformer of the embodiment of the present application adopts a discrete single isolation transformer or a multi-winding isolation transformer integrated with multiple sub-modules, and the connection mode of the multi-winding isolation transformer is shown in FIG. 15. After the second windings of each corresponding plurality of isolation transformers are connected in series, the AC three-phases are connected into a star or delta according to actual requirements.
  • FIG. 16 is a schematic diagram of an isolated dual active bridge DAB converter provided by an embodiment of the application
  • FIG. 17 is a schematic diagram of an isolated resonant converter provided by an embodiment of the application.
  • the DC/DC converter may be an isolated dual active bridge DAB converter, or an isolated resonant converter, as shown in FIG. 16 and FIG. 17.
  • the control system of the modular multi-level AC-DC conversion system provided by the embodiments of the present application has the characteristics of high integration, compactness, and low cost, and is easy to implement in engineering.
  • the conversion system is suitable for high-voltage large-capacity and medium-low-voltage small-capacity applications, and can effectively reduce the number of modular multilevel converter (MMC) sub-modules, large volume, low integration and high cost.
  • MMC modular multilevel converter
  • the controller functions of the control system of the modular multi-level AC-DC conversion system include AC power control, AC output voltage control, DC output voltage control, and sub-module capacitor voltage equalization.

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Abstract

一种模块化多电平交流-直流变换系统，包括：一个控制器、多个子模块单元、多个隔离变压器，以及多个直流支撑电容，每个子模块单元的直流侧与一个直流支撑电容并联，多个直流支撑电容串联或并联形成变换系统的直流端口；每个子模块单元的交流侧连接三个隔离变压器的第一侧绕组，三个隔离变压器与变换系统的三相一一对应，与每一相对应的多个隔离变压器的第二侧绕组串联形成变换系统的所述每一相的交流端；控制器设置为采集三相的交流端的电流和每个直流支撑电容的电压，并根据采集的电流和电压输出所有子模块单元的内部功率器件的触发信号，用于交流功率控制、交流输出电压控制、直流输出电压控制和子模块电容均压控制。

Description

模块化多电平交流-直流变换系统
本申请要求在2020年01月21日提交中国专利局、申请号为202010071325.4的中国专利申请的优先权，该申请的全部内容通过引用结合在本申请中。
技术领域
本申请涉及交流-直流变换系统领域，例如涉及一种模块化多电平交流-直流变换系统。
背景技术
模块化多电平交流-直流变流器广泛应用于柔性直流输电系统、直流配网系统以及中压电机控制等电力变换领域，应用最为广泛的是半桥型模块化多电平换流器(Modular Multilevel Converter，MMC)和级联全桥换流器(Cascaded H-bridge Converter，CHC)，其电气拓扑如图1和2所示。世界范围内的柔性直流输电工程和直流配网工程大多采用MMC换流器方案，例如美国的Trans Bay Cable±200kV工程、厦门±320kV柔直工程、上海220kV统一潮流控制器(Unified Power Flow Controller，UPFC)工程和苏州直流配网工程等。中高压变频器、配网用电力电子变压器以及机车牵引变流器等应用领域中均优先采用级联全桥换流器拓扑。
电气拓扑决定该变换器的特性，如电气特性、故障特性以及效率等多个方面。MMC的特点：一是，所需要的子模块电容个数较多且每个子模块电容容值相对较大。在高压应用场合，考虑电容器的稳定性以及低杂感要求，均是聚丙烯金属膜电容器，导致电容部分的成本较高。二是，虽然采用模块化设计，在中低电压应用场合的集成度仍然较低，体积较大。三是，半桥型MMC变换器对于直流侧的短路故障无法进行有效抑制，无法通过闭锁MMC内部绝缘栅双极型晶体管(Insulated Gate Bipolar Transistor，IGBT)来实现故障电流的清除。级联全桥换流器的特点：一是，没有公共的直流端口，无法直接应用于直流输配电场合；二是，相比于MMC拓扑，所需子模块个数有所减少，但数量依然很多。
发明内容
本申请提供的一种模块化多电平交流-直流变换系统，克服了相关技术中交流-直流变换系统集成度低、体积大、成本高的缺陷。
本申请实施例提供一种模块化多电平交流-直流变换系统，包括：一个控制 器、多个子模块单元、多个隔离变压器、以及多个直流支撑电容，其中，
每个子模块单元的直流侧与多个直流支撑电容中的一个并联，所述多个直流支撑电容串联或并联形成模块化多电平交流-直流变换系统的直流端口；每个子模块单元的交流侧连接三个隔离变压器的第一侧绕组，三个隔离变压器与模块化多电平交流-直流变换系统的三相一一对应，与每一相对应的多个隔离变压器的第二侧绕组串联形成模块化多电平交流-直流变换系统的所述每一相的交流端；控制器与模块化多电平交流-直流变换系统的三相的交流端、每个子模块单元以及每个直流支撑电容连接，控制器设置为采集模块化多电平交流-直流变换系统的三相的交流端的电流和每个直流电容的电压，并根据模块化多电平交流-直流变换系统的三相的交流端的电流和每个直流支撑电容的电压输出所有子模块单元的内部功率器件的触发信号，用于交流功率控制、交流输出电压控制、直流输出电压控制和子模块电容均压控制；其中，每个子模块单元包括三个全桥结构且所述三个全桥结构的直流端口并联形成所述每个子模块单元的直流侧，或者每个子模块单元包括三个半桥结构且所述三个半桥结构的直流端口并联形成每个子模块单元的直流侧，或者每个子模块单元包括三相四桥臂结构。
在一实施例中，在所述多个直流支撑电容串联形成所述模块化多电平交流-直流变换系统的直流端口的情况下，所述模块化多电平交流-直流变换系统的直流端口的数量为多个，每个直流端口的两端为所述多个直流支撑电容中一个直流支撑电容的第一端和第二端，或者每个直流端口的两端为所述多个直流支撑电容中串联连接的至少两个直流支撑电容中首个直流支撑电容的第一端和最后一个直流支撑电容的第二端；在所述多个直流支撑电容并联形成所述模块化多电平交流-直流变换系统的直流端口的情况下，所述模块化多电平交流-直流变换系统的直流端口的数量为1个。
在一实施例中，多个直流支撑电容通过半桥拓扑或全桥拓扑串联形成模块化多电平交流-直流变换系统的直流端口。
在一实施例中，在多个直流支撑电容通过半桥拓扑串联形成模块化多电平交流-直流变换系统的直流端口，且模块化多电平交流-直流变换系统仅整流运行的情况下，半桥拓扑的上管采用IGBT，半桥拓扑的下管采用二极管；在多个直流支撑电容通过半桥拓扑串联形成模块化多电平交流-直流变换系统的直流端口，且模块化多电平交流-直流变换系统仅逆变运行的情况下，半桥拓扑的上管采用二极管，半桥拓扑的下管采用IGBT；在所述多个直流支撑电容通过半桥拓扑串联形成模块化多电平交流-直流变换系统的直流端口，且模块化多电平交流-直流变换系统功率双向运行的情况下，半桥拓扑的上管和下管均采用IGBT。
在一实施例中，在多个直流支撑电容通过全桥拓扑串联形成模块化多电平 交流-直流变换系统的直流端口，且模块化多电平交流-直流变换系统仅整流运行的情况下，全桥拓扑的T1管和T4管采用IGBT，全桥拓扑的T2管和T3管采用二极管；在多个直流支撑电容通过全桥拓扑串联形成模块化多电平交流-直流变换系统的直流端口，且模块化多电平交流-直流变换系统仅逆变运行的情况下，全桥拓扑的T1管和T4管采用二极管，全桥拓扑的T2和T3管采用IGBT；在多个直流支撑电容通过全桥拓扑串联形成模块化多电平交流-直流变换系统的直流端口，且模块化多电平交流-直流变换系统功率双向运行的情况下，全桥拓扑的所有管采用IGBT；其中，T1管的第一端与T3管的第一端连接，T1管的第二端与T2管的第一端连接，T2管的第二端与T4管的第一端连接，T4管的第二端与T3管的第二端连接。
在一实施例中，多个直流支撑电容通过DC/DC变换器串联、并联或串并混合连接后形成模块化多电平交流-直流变换系统的直流端口。
在一实施例中，直流/直流DC/DC变换器包括隔离型双有源桥(Dual Active Bridge，DAB)变换器，或者隔离型谐振式变换器。
在一实施例中，隔离变压器采用分立的单个隔离变压器或多个子模块集成的多绕组隔离变压器。
在一实施例中，在每一相对应的多个隔离变压器的第二侧绕组串联后将交流三相接成星形或三角形。
在一实施例中，所述的模块化多电平交流-直流变换系统，还包括：故障电流抑制单元，与所述模块化多电平交流-直流变换系统的直流端口连接，用于限制模块化多电平交流-直流变换系统的直流端口的短路故障电流。
附图说明
为了说明本申请具体实施方式或相关技术中的技术方案，下面将对实施例或相关技术描述中所需要使用的附图作简单地介绍。
图1为相关技术中半桥型模块化多电平换流器的结构示意图；
图2为相关技术中级联全桥换流器的示意图；
图3为本申请实施例提供的模块化多电平交流-直流变换系统中直流支撑电容直接串联形成直流端口的结构示意图；
图4为本申请实施例提供的直流支撑电容直接并联形成直流端口的结构示意图；
图5为本申请实施例提供的直流支撑电容通过半桥拓扑串联形成直流端口 的结构示意图；
图6为本申请实施例提供的直流支撑电容通过全桥拓扑串联形成直流端口的结构示意图；
图7为本申请实施例提供的通过全桥拓扑DC/DC变换器串联形成直流端口的结构示意图；
图8为本申请实施例提供的通过全桥拓扑DC/DC变换器并联形成直流端口的结构示意图；
图9为本申请实施例提供的通过全桥拓扑DC/DC变换器串并混合连接形成直流端口的结构示意图；
图10为本申请实施例提供的故障电流抑制单元的连接示意图；
图11为本申请实施例提供的在变换系统仅整流运行时，直流支撑电容通过半桥拓扑形成直流端口的结构示意图；
图12为本申请实施例提供的在变换系统仅逆变运行时，直流支撑电容通过半桥拓扑形成直流端口的结构示意图；
图13为本申请实施例提供的在变换系统仅整流运行时，直流支撑电容通过全桥拓扑形成直流端口的结构示意图；
图14为本申请实施例提供的在变换系统仅逆变运行时，直流支撑电容通过全桥拓扑形成直流端口的结构示意图；
图15为本申请实施例提供的多绕组隔离变压器的连接示意图；
图16为本申请实施例提供的隔离型双有源桥DAB变换器的示意图；
图17为本申请实施例提供的隔离型谐振式变换器的示意图。
具体实施方式
下面将结合附图对本申请的技术方案进行描述，所描述的实施例是本申请一部分实施例，而不是全部的实施例。
实施例1
本申请实施例提供的模块化多电平交流-直流变换系统，可以用于中低压配网系统交流变压，该系统如图3所示，包括：一个控制器、多个子模块单元、多个隔离变压器，以及多个直流支撑电容，每个子模块单元的直流侧与多个直流支撑电容中的一个并联，多个直流支撑电容串联或并联形成模块化多电平交流-直流变换系统的直流端口；每个子模块单元的交流侧连接三个隔离变压器的 第一侧绕组，三个隔离变压器与所述模块化多电平交流-直流变换系统的三相一一对应，与每一相对应的多个隔离变压器的第二侧绕组串联形成模块化多电平交流-直流变换系统的所述每一相的交流端；控制器与模块化多电平交流-直流变换系统的三相的交流端、每个子模块单元以及每个直流支撑电容连接，控制器设置为采集模块化多电平交流-直流变换系统的三相的交流端的电流和每个直流支撑电容的电压，并根据模块化多电平交流-直流变换系统的三相的交流端的电流和每个直流支撑电容的电压输出所有子模块单元的内部功率器件的触发信号，用于交流功率控制、交流输出电压控制、直流输出电压控制和子模块电容均压控制。
在本申请实施例中，子模块单元可以包括三个全桥结构且三个全桥结构在直流侧进行并联，也可以采用三个半桥结构，且三个半桥结构在直流侧进行并联，或采用三相四桥臂结构，以满足不同需求。
在子模块单元包括三个全桥结构的情况下，三个全桥结构的直流端口并联形成子模块单元的直流侧，三个全桥结构的交流端口为子模块单元的交流侧。
图3为本申请实施例提供的模块化多电平交流-直流变换系统中直流支撑电容串联形成直流端口的结构示意图，图4为本申请实施例提供的直流支撑电容并联形成直流端口的结构示意图；图5为本申请实施例提供的直流支撑电容通过半桥拓扑串联形成直流端口的结构示意图，图6为本申请实施例提供的直流支撑电容通过全桥拓扑串联形成直流端口的结构示意图；图7为本申请实施例提供的通过全桥拓扑DC/DC变换器串联形成直流端口的结构示意图；图8为本申请实施例提供的通过全桥拓扑DC/DC变换器并联形成直流端口的结构示意图；图9为本申请实施例提供的通过全桥拓扑DC/DC变换器串并混合连接形成直流端口的结构示意图。在本申请实施例中，直流支撑电容可以直接串联或者并联，以形成变换系统所需的直流端口，如图3和图4所示；直流支撑电容也可以通过半桥或全桥拓扑串联形成直流端口，如图5和图6所示；直流支撑电容还可以通过直流/直流(Direct Current-Direct Current，DC/DC)变换器进行串联、并联或串并混合连接后形成直流端口，如图7、图8和图9所示。
图10为本申请实施例提供的故障电流抑制单元的连接示意图。在一实施例中，在直流支撑电容直接串联/并联形成模块化多电平交流-直流变换系统的直流端口时，在模块化多电平交流-直流变换系统的直流端口添加故障电流抑制单元，以限制直流侧短路故障电流，该故障电流抑制单元可以由IGBT阀和能量吸收装置组成。在直流支撑电容通过DC/DC变换器进行串联、并联或串并混合连接后形成模块化多电平交流-直流变换系统的直流端口时，也可以根据需求在模块化多电平交流-直流变换系统的直流端口添加故障电流抑制单元，限制模块化多电 平交流-直流变换系统的直流端口的短路故障电流。
图11为本申请实施例提供的在变换系统仅整流运行时，直流支撑电容通过半桥拓扑形成直流端口的结构示意图；图12为本申请实施例提供的在变换系统仅逆变运行时，直流支撑电容通过半桥拓扑形成直流端口的结构示意图。本申请实施例在直流支撑电容通过半桥拓扑形成直流端口时，若变换系统仅整流运行，半桥拓扑的上管可采用IGBT，下管可采用二极管，如图11所示；若变换系统仅逆变运行，半桥拓扑的上管可采用二极管，下管可采用IGBT，如图12所示；若变换系统功率双向运行，半桥拓扑的上管和下管可采用IGBT。
图13为本申请实施例提供的在变换系统仅整流运行时，直流支撑电容通过全桥拓扑形成直流端口的结构示意图；图14为本申请实施例提供的在变换系统仅逆变运行时，直流支撑电容通过全桥拓扑形成直流端口的结构示意图。本申请实施例提供的模块化多电平交流-直流变换系统，在直流支撑电容通过全桥拓扑形成直流端口时，若变换系统仅整流运行，全桥拓扑的T1管和T4管可采用IGBT，T2和T3管可采用二极管,如图13所示；若变换系统仅逆变运行，全桥拓扑的T1管和T4管可采用二极管，T2和T3管可采用IGBT,如图14所示；若变换系统功率双向运行，全桥拓扑的所有管可采用IGBT。
图15为本申请实施例提供的多绕组隔离变压器的连接示意图。本申请实施例的隔离变压器采用分立的单个隔离变压器或多个子模块集成的多绕组隔离变压器，多绕组隔离变压器的连接方式如图15所示。在每一相对应的多个隔离变压器的第二侧绕组串联后根据实际需求将交流三相接成星形或三角形。
图16为本申请实施例提供的隔离型双有源桥DAB变换器的示意图，图17为本申请实施例提供的隔离型谐振式变换器的示意图。一实施例中，DC/DC变换器可以采用隔离型双有源桥DAB变换器，或者隔离型谐振式变换器，如图16和图17所示。
本申请实施例提供的模块化多电平交流-直流变换系统的控制系统，具备高集成度、紧凑化和低成本等特点，且易于工程实现。该变换系统可适用于高压大容量和中低压小容量应用场合，能够有效降低模块化多电平换流器(MMC)子模块个数多，体积大，集成度低和成本高的问题。模块化多电平交流-直流变换系统的控制系统的控制器功能包括交流功率控制、交流输出电压控制、直流输出电压控制和子模块电容均压等控制。

Claims (10)

  1. 一种模块化多电平交流-直流变换系统，包括：一个控制器、多个子模块单元、多个隔离变压器、以及多个直流支撑电容，其中，
    每个子模块单元的直流侧与所述多个直流支撑电容中的一个并联，所述多个直流支撑电容串联或并联形成所述模块化多电平交流-直流变换系统的直流端口；
    每个子模块单元的交流侧连接三个隔离变压器的第一侧绕组，所述三个隔离变压器与所述模块化多电平交流-直流变换系统的三相一一对应，与每一相对应的多个隔离变压器的第二侧绕组串联形成所述模块化多电平交流-直流变换系统的所述每一相的交流端；
    控制器与所述模块化多电平交流-直流变换系统的三相的交流端、每个子模块单元以及每个直流支撑电容连接，所述控制器设置为采集所述模块化多电平交流-直流变换系统的三相的交流端的电流和每个直流支撑电容的电压，并根据所述模块化多电平交流-直流变换系统的三相的交流端的电流和每个直流支撑电容的电压输出所有子模块单元的内部功率器件的触发信号，用于交流功率控制、交流输出电压控制、直流输出电压控制和子模块电容均压控制；
    其中，每个子模块单元包括三个全桥结构且所述三个全桥结构的直流端口并联形成所述每个子模块单元的直流侧，或者每个子模块单元包括三个半桥结构且所述三个半桥结构的直流端口并联形成所述每个子模块单元的直流侧，或者每个子模块单元包括三相四桥臂结构。
  2. 根据权利要求1所述的系统，其中，在所述多个直流支撑电容串联形成所述模块化多电平交流-直流变换系统的直流端口的情况下，所述模块化多电平交流-直流变换系统的直流端口的数量为多个，每个直流端口的两端为所述多个直流支撑电容中一个直流支撑电容的第一端和第二端，或者每个直流端口的两端为所述多个直流支撑电容中串联连接的至少两个直流支撑电容中首个直流支撑电容的第一端和最后一个直流支撑电容的第二端；
    在所述多个直流支撑电容并联形成所述模块化多电平交流-直流变换系统的直流端口的情况下，所述模块化多电平交流-直流变换系统的直流端口的数量为1个。
  3. 根据权利要求1所述的系统，其中，所述多个直流支撑电容通过半桥拓扑或全桥拓扑串联形成所述模块化多电平交流-直流变换系统的直流端口。
  4. 根据权利要求3所述的系统，其中，在所述多个直流支撑电容通过半桥拓扑串联形成所述模块化多电平交流-直流变换系统的直流端口，且所述模块化多电平交流-直流变换系统仅整流运行的情况下，所述半桥拓扑的上管采用绝缘 栅双极型晶体管IGBT，所述半桥拓扑的下管采用二极管；在所述多个直流支撑电容通过半桥拓扑串联形成所述模块化多电平交流-直流变换系统的直流端口，且所述模块化多电平交流-直流变换系统仅逆变运行的情况下，所述半桥拓扑的上管采用二极管，所述半桥拓扑的下管采用IGBT；在所述多个直流支撑电容通过半桥拓扑串联形成所述模块化多电平交流-直流变换系统的直流端口，且所述模块化多电平交流-直流变换系统功率双向运行的情况下，所述半桥拓扑的上管和下管均采用IGBT。
  5. 根据权利要求3所述的系统，其中，在所述多个直流支撑电容通过全桥拓扑串联形成所述模块化多电平交流-直流变换系统的直流端口，且所述模块化多电平交流-直流变换系统仅整流运行的情况下，所述全桥拓扑的T1管和T4管采用IGBT，所述全桥拓扑的T2管和T3管采用二极管；在所述多个直流支撑电容通过全桥拓扑串联形成所述模块化多电平交流-直流变换系统的直流端口，且所述模块化多电平交流-直流变换系统仅逆变运行的情况下，所述全桥拓扑的T1管和T4管采用二极管，所述全桥拓扑的T2管和T3管采用IGBT；在所述多个直流支撑电容通过全桥拓扑串联形成所述模块化多电平交流-直流变换系统的直流端口，且所述模块化多电平交流-直流变换系统功率双向运行的情况下，所述全桥拓扑的所有管采用IGBT；其中，所述T1管的第一端与所述T3管的第一端连接，所述T1管的第二端与所述T2管的第一端连接，所述T2管的第二端与所述T4管的第一端连接，所述T4管的第二端与所述T3管的第二端连接。
  6. 根据权利要求1所述的模块化多电平交流-直流变换系统，其中，所述多个直流支撑电容通过直流/直流DC/DC变换器串联并联或串并混合连接后形成所述模块化多电平交流-直流变换系统的直流端口。
  7. 根据权利要求6所述的系统，其中，所述DC/DC变换器包括隔离型双有源桥DAB变换器，或者隔离型谐振式变换器。
  8. 根据权利要求1所述的系统，其中，所述隔离变压器采用分立的单个隔离变压器或多个子模块集成的多绕组隔离变压器。
  9. 根据权利要求8所述的系统，其中，在每一相对应的多个隔离变压器的第二侧绕组串联后将交流三相接成星形或三角形。
  10. 根据权利要求6或7所述的系统，还包括：故障电流抑制单元，与所述模块化多电平交流-直流变换系统的直流端口连接，设置为限制所述模块化多电平交流-直流变换系统的直流端口的短路故障电流。
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