WO2023241074A1 - 一种柔性电力变压器 - Google Patents

一种柔性电力变压器 Download PDF

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Publication number
WO2023241074A1
WO2023241074A1 PCT/CN2023/075686 CN2023075686W WO2023241074A1 WO 2023241074 A1 WO2023241074 A1 WO 2023241074A1 CN 2023075686 W CN2023075686 W CN 2023075686W WO 2023241074 A1 WO2023241074 A1 WO 2023241074A1
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WIPO (PCT)
Prior art keywords
voltage
transformer
winding
module
flexible power
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PCT/CN2023/075686
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English (en)
French (fr)
Inventor
赵国亮
乔光尧
李卫国
赵永彬
靳艳娇
孙庆豪
徐云飞
刘海军
李芳义
石秋雨
孙庚�
王丹
李璐
杨志昌
张淆雨
Original Assignee
国网智能电网研究院有限公司
国网辽宁省电力有限公司阜新供电公司
国家电网有限公司
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Publication of WO2023241074A1 publication Critical patent/WO2023241074A1/zh

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Classifications

    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • 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
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • 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
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
    • H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
    • H02M5/10—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers
    • H02M5/12—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers for conversion of voltage or current amplitude 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

Definitions

  • This application relates to but is not limited to the field of electrical equipment in power systems, and specifically relates to a flexible power transformer.
  • Power transformers are the central nodes for power transmission, connecting different voltage levels. By adjusting the voltage of the transformer, the regional voltage can be affected.
  • the conventional power transformer voltage regulation method is mainly mechanical on-load voltage regulation, which can play a regional voltage regulation role in a power grid dominated by traditional synchronous generators. In the new power system, large-scale new energy and power electronic equipment are connected, which puts forward rapid and continuous voltage regulation requirements for the system.
  • the mechanical on-load voltage regulation transformer does not have the ability to continuously regulate voltage, and the mechanical tap changer has a slow regulation speed.
  • this application proposes a flexible power transformer.
  • Embodiments of the present application provide a flexible power transformer.
  • the flexible power transformer at least includes: a main transformer and a commutation device, wherein the main transformer includes a primary side winding and a plurality of secondary side windings; in the main transformer The commutation device is connected in series between the primary side winding end of the transformer and any secondary side winding end, or the commutation device is connected in series between any two secondary side winding ends of the main transformer. Device; the commutation device is used to adjust the voltage of each winding of the main transformer by adjusting the output voltage of the commutation device.
  • the converter device includes a plurality of cascaded sub-units, and the sub-units are used to adjust the output voltage level of the converter device by changing the number of cascaded sub-units.
  • the converter device is used to control the port voltage and power flow of the flexible power transformer by controlling the amplitude and phase of the output voltage on the inverter side of the converter device.
  • the subunit includes a rectifier module, a dual active bridge module with a high-frequency isolation transformer, and an inverter module, wherein the input end of the rectifier module is connected to any secondary side winding, and the The output end of the rectifier module is connected to the input end of the dual active bridge module with high-frequency isolation transformer; the input end of the inverter module is connected to the output end of the dual-active bridge module with high-frequency isolation transformer. , the output end of the inverter module is connected to the end of other windings on the secondary side or the end of the primary side winding;
  • the rectifier module is used to rectify the AC voltage provided by the secondary side winding into a DC voltage, and maintain the stability of the DC voltage of each module in the commutation device;
  • the dual active bridge module with a high-frequency isolation transformer is used to perform DC voltage conversion, transport the converted DC voltage to the inverter module, and at the same time electrically isolate each module in the converter device;
  • the inverter module is also used to change the primary side winding voltage and the secondary side winding voltage of the main transformer by controlling the phase and amplitude of the output voltage of the inverter module.
  • the dual active bridge module with high-frequency isolation transformer has multiple ports, and the multiple ports are used to provide multiple external power switching interfaces.
  • the operating frequency of the high-frequency transformer in the dual active bridge module with a high-frequency isolation transformer is determined by the capacity and area of the converter device and the characteristics of the power device used.
  • the flexible power transformer further includes: a bypass device, which is connected in parallel to both ends of the inverter side of the converter device.
  • the bypass device includes an anti-parallel thyristor and a mechanical switch.
  • the flexible power transformer includes: a main transformer and a converter device, wherein the main transformer includes a primary side winding and multiple secondary side windings; at the end of the primary side winding of the main transformer and any secondary side A commutation device is connected in series between the winding ends, or a commutation device is connected in series between the ends of any two secondary windings of the main transformer; the voltage of each winding of the main transformer is adjusted by adjusting the output voltage of the commutation device.
  • a commutation device is connected in series between the primary winding end of the main transformer and any secondary winding end, or a commutation device is connected in series between any two secondary winding ends of the main transformer.
  • FIG. 2 is a schematic diagram of another specific example of the flexible power transformer in the embodiment of the present application.
  • Figure 3 is a specific wiring diagram of the flexible power transformer in the embodiment of the present application.
  • Figure 5 is a phasor relationship diagram of the voltage regulation of the flexible power transformer in the embodiment of the present application.
  • Figure 6 is an equivalent circuit of the flexible power transformer for power flow regulation in the embodiment of the present application.
  • connection should be understood in a broad sense.
  • connection or integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary; it can also be an internal connection between two components; it can be a wireless connection or a wired connection connect.
  • connection or integral connection
  • connection or integral connection
  • connection can be a mechanical connection or an electrical connection
  • it can be a direct connection or an indirect connection through an intermediary
  • it can also be an internal connection between two components
  • it can be a wireless connection or a wired connection connect.
  • the embodiment of the present application provides a flexible power transformer, including: a main transformer 1 and a converter device 2 .
  • the main transformer 1 includes a primary side winding and a plurality of secondary side windings; a commutation device 2 is connected in series between the end of the primary side winding of the main transformer 1 and the end of any secondary side winding, or between the main side winding and the main side winding.
  • the ends of any two secondary windings of the transformer 1 are connected in series to the commutation device 2; the voltage of each winding of the main transformer 1 is adjusted by adjusting the output voltage of the commutation device 2.
  • the primary winding 11 cooperates with the secondary winding 12 to complete the voltage conversion process, where the secondary winding 12 is responsible for voltage output and supplies energy to the lower-level circuit (ie, the power grid) or the load.
  • the tertiary winding 13 is connected to the input end of the converter device 2 , and the tertiary winding 13 provides active power support for the converter device 2 .
  • a commutation device 2 is connected in series between the end of the primary winding 11 and the tertiary winding 13 of the main transformer 1.
  • the voltage at both ends of the primary winding 11 can be adjusted by adjusting the output voltage of the converter device 2, and at the same time, the output voltage of the secondary winding 12 can be changed synchronously to achieve rapid, continuous and precise adjustment of the voltage amplitude and phase of the main transformer 1.
  • the primary winding 11 and the tertiary winding 13 are both star-connected, and the connection of the secondary winding 12 is not required. It can be flexibly selected according to the wiring method of conventional power transformers according to the application requirements of different scenarios.
  • a commutation device is connected in series between the end of the secondary winding 12 and the tertiary winding 13 of the main transformer 1.
  • the voltage across the secondary winding 12 can be adjusted by adjusting the output voltage of the converter device 2, and at the same time, the voltage across the primary winding 11 can be changed synchronously to achieve rapid, continuous and precise adjustment of the voltage amplitude and phase of the main transformer 1.
  • the secondary winding 12 and the tertiary winding 13 are both star-connected, and the connection method of the primary winding 11 is not required. It can be flexibly selected according to the wiring method of conventional power transformers according to the application requirements of different scenarios.
  • a commutation device 2 with flexible and adjustable voltage amplitude and phase can be connected in series between the winding end of the star connection of the power transformer and the center point (or ground).
  • the converter device 2 By adjusting the converter device 2, the voltage of each winding of the main transformer 1 is changed to replace the traditional mechanical transformer voltage regulation and have a certain phase shifting function.
  • the tertiary windings provide active power support to the converter device 2, realizing the power transformer voltage/ Comprehensive functions such as flexible power flow control, flexible port expansion, and power quality compensation.
  • This application proposes a flexible power transformer in which a commutation device is connected in series between the primary side winding end of the main transformer and any secondary side winding end, or between any two secondary side winding ends of the main transformer.
  • the converter device is connected in series, and the voltage of each winding of the main transformer is adjusted by adjusting the output voltage of the converter device.
  • the voltage adjustment function of each winding of the transformer can be realized without changing the turns ratio of the transformer.
  • the voltage source converter is combined with the power transformer to achieve fast, continuous, precise and flexible adjustment of the transformer's output electrical quantity with a smaller capacity converter.
  • the bypass device bypasses it and the main transformer can continue to work normally.
  • the flexible power transformer has the advantages of arc-free switching, flexible control, fast response, low cost, and high reliability.
  • the inverter device 2 includes multiple cascaded sub-units, and the output voltage level of the inverter device can be adjusted by changing the number of cascaded sub-units.
  • the converter device 2 is implemented by a cascade of multiple sub-units, and the purpose of applying to different voltage levels is achieved by changing the number of cascaded sub-units.
  • the cascading of multiple sub-units can achieve multi-level inversion, reduce the harmonic content injected into the system, and is easy to expand, enabling multi-voltage applications.
  • the sub-unit is based on fully controllable power electronic devices, making the output voltage amplitude and phase flexibly controllable, greatly improving the response speed of on-load voltage regulation, enabling long-term continuous operation, and aiming at the problems caused by the continuous fluctuation of new energy sources. Provides new solutions to the voltage fluctuation problem.
  • the rectifier module 21 is used to rectify the AC voltage provided by the secondary side winding connected to the rectifier module 21 into a DC voltage, and maintain the stability of the DC voltage of each module in the converter device 2; dual active with high-frequency isolation transformer
  • the bridge module 22 is used to perform DC voltage conversion, transport the converted DC voltage to the inverter module 23, and at the same time electrically isolate each module in the converter device 2;
  • the inverter module 23 is used to invert the converted DC voltage. is the AC voltage, and delivers the AC voltage to the ends of other windings on the secondary side or the ends of the windings on the primary side.
  • the commutation device 2 is connected in series between the end of the primary winding 11 and the tertiary winding 13 of the main transformer 1 as an example for explanation.
  • the input end of the rectifier module 21 is connected to the tertiary winding 13
  • the output end of the rectifier module 21 is connected to the input end of the dual active bridge module 22 with a high-frequency isolation transformer
  • the output of the dual-active bridge module 22 with a high-frequency isolation transformer The terminal is connected to the input terminal of the inverter module 23, and the output terminal of the inverter module 23 is connected to the end of the primary winding 11.
  • the dual active bridge module 22 with a high-frequency isolation transformer has a DC voltage conversion function and realizes electrical isolation between modules in the sub-unit, ensuring the scalability of the voltage level and capacity of the flexible power transformer.
  • the dual active bridge module 22 with a high-frequency isolation transformer can adopt a multi-port design and provide multiple external power exchange interfaces to realize energy interaction between distributed photovoltaic, energy storage and other DC power sources and low-voltage AC and DC loads and the main transformer. is the distribution It provides a convenient channel for access to conventional energy and energy supply for low-voltage loads around high-voltage substations, making the operation of the overall equipment more flexible and reliable.
  • the dual active bridge module 22 with high-frequency isolation transformer includes n high-voltage ports and n low-voltage ports, and the number of ports can be flexibly expanded.
  • One of the low-voltage ports is connected to the low-voltage side DC interface circuit, and the other is connected to the low-voltage side AC interface circuit.
  • the low-voltage side AC interface circuit and the low-voltage side DC interface circuit it provides an interface for external AC and DC distributed power supplies and loads, realizing the connection between the external power supply and load and the main engine. Transformer energy exchange, high and low voltage, AC and DC port expansion are easier, and the operation mode is flexible and efficient.
  • a high-frequency isolation transformer is used in the dual active bridge module 22 with a high-frequency isolation transformer, which greatly reduces the size of the converter device 2 and makes it possible to integrate it inside the transformer box, which facilitates engineering applications.
  • the operating frequency of the high-frequency isolation transformer is determined by factors such as the insulation level, capacity, area of the converter device 2 and the characteristics of the power device used.
  • inverter modules 23 are cascaded to output multi-level AC voltages, the amplitude and phase of which can be flexibly adjusted according to a pulse width modulation (Pulse Width Modulation, PMW) modulation strategy.
  • PMW Pulse Width Modulation
  • the output end of the inverter module 23 is connected in series between the end of the winding and the neutral point.
  • the neutral point is the point where the absolute value of the voltage between the external terminals is equal.
  • the power side (transformer or generator) or the load side is star-connected, the common contact where the first ends (or tail ends) of the three-phase coils are connected together is the neutral point, as shown in Figure 3. N of the tertiary winding 13 point.
  • the coupling method of the converter device 2 and the main transformer 1 is to connect the inverter module 23 of the converter device 2 in series between the winding end of the star connection of the main transformer 1 and the center point (or ground).
  • this coupling method is suitable for both high-voltage transmission systems and three-phase four-wire low-voltage distribution systems.
  • the inverter module 23 of the converter device 2 can be connected in series to the end of the high-voltage winding or the end of the low-voltage winding.
  • the inverter module 23 is connected in series between the end of the star-connected winding of the power transformer and the center point (or ground). It has low ground potential and low insulation requirements, which greatly reduces the insulation cost of the converter device.
  • the voltage amplitude and phase of the inverter module 23 are both flexible and adjustable. By controlling the phase and amplitude of the output voltage of the inverter module 23, the voltage of the primary side winding of the main transformer 1 and the voltage of each secondary side are changed. winding voltage.
  • the input end of the inverter device 2 has the function of compensating the reactive power or harmonic current of the system through the tertiary energy-taking winding (ie, the tertiary winding 13) while maintaining a constant DC voltage.
  • the inverter module 23 when the voltage phase of the inverter module 23 is in-phase or anti-phase with its series-connected winding phase, a fast, arc-free, and smooth voltage amplitude adjustment function can be achieved.
  • the phase angle of the voltage on the inlet side of the main transformer 1 can be changed, so that the power flow of the branch where the flexible power transformer is located can be changed, thereby playing the role of power flow control.
  • the inverter module 23 can also have a harmonic voltage compensation function on the basis of realizing voltage amplitude or phase adjustment.
  • Flexible power transformers can adopt voltage control mode and power flow control mode.
  • the port voltage and power flow of the flexible power transformer are controlled by controlling the amplitude and phase of the output voltage on the inverter side of the converter device.
  • the voltage regulation principle and power flow control principle are as follows: a controllable voltage source is connected in series between the winding end of the star connection of the transformer and the center point (or ground), so that the AC system bus voltage is u S , The voltage of the primary winding of the transformer is u 1 and the number of turns is W 1 , the voltage of the secondary winding is u 2 and the number of turns is W 2 , the voltage of the energy-taking winding (i.e. the tertiary winding) of the converter is u 3 and the number of turns is W 3 , the output voltage of the controllable voltage source is u 4 . By adjusting the converter output voltage u 4 , the voltage can be controlled.
  • the power flow adjustment principle is as shown in formulas (3) to (8):
  • the flexible power transformer can also realize power flow control for multiple outgoing lines.
  • the transformer T1 is equivalent to the reactance X (converted to the primary side), and the part where the back-to-back converter is connected in series to the transformer is equivalent to the controlled voltage. source
  • the active power P and reactive power Q delivered by the AC system to the load are respectively:
  • U′ 1 and They are:
  • Figure 5 describes the phasor relationship of the voltage regulation of the flexible power transformer
  • Figure 6 describes the equivalent circuit of the flexible power transformer for power flow regulation.
  • the flexible power transformer further includes: a bypass device 3, which is connected in parallel at both ends of the inverter side of the converter device 2.
  • the bypass device 3 includes: an anti-parallel thyristor and a mechanical switch.
  • the bypass device 3 is composed of an anti-parallel thyristor and a mechanical switch, and is connected in parallel at both ends of the inverter side of the converter device 2.
  • the output end of the bypass device 3 is short-circuited, and the flexible power transformer is used as a conventional The operation of the power transformer ensures the reliability of the equipment.

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  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Ac-Ac Conversion (AREA)

Abstract

本申请实施例提供一种柔性电力变压器，包括：主变压器及换流装置，其中，主变压器包括一个原边侧绕组及多个副边侧绕组；在主变压器的原边侧绕组末端与任意一个副边侧绕组末端之间串联接入换流装置，或在主变压器的任意两个副边侧绕组末端之间串联接入换流装置；所述换流装置用于通过调节换流装置的输出电压调节主变压器各绕组的电压。本申请实施例可以在不改变变压器匝比的情况下实现对压器各绕组电压的调节功能。同时电压源型换流器与电力变压器相结合，以较小容量的换流器来实现变压器输出电气量的快速、连续、精确和灵活调节。

Description

一种柔性电力变压器
相关申请的交叉引用
本公开基于申请号为202210691872.1、申请日为2022年06月17日、申请名称为“一种柔性电力变压器”的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本申请涉及但不限于电力系统电气设备领域，具体涉及一种柔性电力变压器。
背景技术
在“双碳”背景下，我国提出构建以新能源为主体的新型电力系统，电源和电网结构加速清洁化，新能源机组的并网规模逐步攀升，多回特高压交直流工程相继投运。新型电力系统中波动性新能源对常规电源的大规模替代、电网网架结构变化、负荷变化等因素引起的功率和电压快速频繁变化、高/低电压越限等问题突出，限制了电网对高渗透率新能源电网接纳能力和远距离输送，不利于提升供电质量和降低线路损耗，使得电力系统的安全、稳定和经济运行面临巨大压力，亟需提升电网的运行灵活性和调控能力。
电力变压器是电能传输的中枢节点，连接不同电压等级，通过调节变压器电压可影响区域电压。常规电力变压器调压方式主要为机械有载调压，在以传统同步发电机为主体的电网中可以起到区域电压调节作用。在新型电力系统中，大规模新能源和电力电子设备接入，对系统提出了快速、连续的调压需求，但机械有载调压变压器不具备连续调节电压能力、机械分接开关调节速度慢且不具备电压自动调节功能，而且在系统无功功率不足时，通过调整变压器分接头的方式只能调节变压器所在点的电压，而其他区域的电压由于无功的缺额而进一步降低，不能适应于以新能源为主体的新型电力系统调压需求。
为提升新型电力系统对新能源的消纳能力，保持电网电压稳定，提升电网供电的电能质量，亟需开展电力电子有源部分与常规电磁变压器相结合的柔性电力变压器技术研究，以保障以新能源为主题的新能电力系统安全、可靠运行。
发明内容
为实现交流电力变压器电压的快速、连续、精确调节，提升新型电力系统对新能源的消纳能力，保证电网的可靠运行，本申请提出了一种柔性电力变压器。
为达到上述目的，本申请提供如下技术方案：
本申请实施例提供一种柔性电力变压器，所述柔性电力变压器至少包括：主变压器及换流装置，其中，所述主变压器包括一个原边侧绕组及多个副边侧绕组；在所述主变压器的原边侧绕组末端与任意一个副边侧绕组末端之间串联接入所述换流装置，或在所述主变压器的任意两个副边侧绕组末端之间串联接入所述换流装置；所述换流装置用于通过调节所述换流装置的输出电压调节所述主变压器各绕组的电压。
在一些实施例中，所述换流装置包括多个级联的子单元，所述子单元用于通过改变级联的子单元的数量调节所述换流装置输出电压等级。
在一些实施例中，所述换流装置用于通过控制换流装置逆变侧输出电压的幅值和相位，控制所述柔性电力变压器的端口电压和潮流。
在一些实施例中，所述子单元包括整流模块、带高频隔离变压器的双有源桥模块及逆变模块，其中，所述整流模块的输入端与任意一个副边侧绕组连接，所述整流模块的输出端与所述带高频隔离变压器的双有源桥模块的输入端连接；所述逆变模块的输入端与所述带高频隔离变压器的双有源桥模块的输出端连接，所述逆变模块的输出端与副边侧其他绕组末端或原边侧绕组末端连接；
所述整流模块用于将副边侧绕组提供的交流电压整流为直流电压，并维持所述换流装置中各模块的直流电压稳定；
所述带高频隔离变压器的双有源桥模块用于进行直流电压变换，将变换后的直流电压输送至所述逆变模块，同时对所述换流装置中各模块进行电气隔离；
所述逆变模块用于将变换后的直流电压逆变为交流电压，并将所述交流电压输送至所述副边侧其他绕组末端或原边侧绕组末端。
在一些实施例中，所述逆变模块还用于通过控制所述逆变模块输出电压的相位和幅值来改变所述主变压器原边侧绕组电压及各副边侧绕组电压。
在一些实施例中，所述带高频隔离变压器的双有源桥模块具有多个端口，所述多个端口用于对外提供多个功率交换接口。
在一些实施例中，所述带高频隔离变压器的双有源桥模块中高频变压器的工作频率，由换流装置的容量、占地及所采用的功率器件特性确定。
在一些实施例中，所述逆变模块的输出端串联接入绕组末端与中性点之间。
在一些实施例中，所述柔性电力变压器还包括：旁路装置，所述旁路装置并联在所述换流装置逆变侧两端。
在一些实施例中，所述旁路装置包括：反并联晶闸管和机械开关。
本申请技术方案，具有如下优点：
本申请提供的柔性电力变压器，包括：主变压器及换流装置，其中，主变压器包括一个原边侧绕组及多个副边侧绕组；在主变压器的原边侧绕组末端与任意一个副边侧绕组末端之间串联接入换流装置，或在主变压器的任意两个副边侧绕组末端之间串联接入换流装置；通过调节换流装置的输出电压调节主变压器各绕组的电压。在主变压器的原边侧绕组末端与任意一个副边侧绕组末端之间串联接入换流装置，或在主变压器的任意两个副边侧绕组末端之间串联接入换流装置，通过调节换流装置的输出电压调节主变压器各绕组的电压，可以在不改变变压器匝比的情况下实现对压器各绕组电压的调节功能。同时电压源型换流器与电力变压器相结合，以较小容量的换流器来实现变压器输出电气量的快速、连续、精确和灵活调节，具有无弧切换、控制灵活、响应速度快等优势，除了控制电压外，还能辅助控制变压器的潮流。
附图说明
为了更清楚地说明本申请具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本申请实施例中柔性电力变压器的一个具体示例的原理图；
图2为本申请实施例中柔性电力变压器的另一个具体示例的原理图；
图3为本申请实施例中柔性电力变压器具体接线图；
图4为本申请实施例中高频隔离变压器的接线形式；
图5为本申请实施例中柔性电力变压器电压调节的相量关系图；
图6为本申请实施例中柔性电力变压器进行潮流调节的等效电路。
具体实施方式
下面将结合附图对本申请的技术方案进行清楚、完整地描述，显然，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。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
在本申请的描述中，需要说明的是，术语“中心”、“上”、“下”、“左”、“右”、“竖直”、“水平”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。此外，术语“第一”、“第二”、“第三”仅用于描述目的，而不能理解为指示或暗示相对重要性。
在本申请的描述中，需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，还可以是两个元件内部的连通，可以是无线连接，也可以是有线连接。对于本领域的普通技术人员而言，可以具体情况理解上述术语在本申请中的具体含义。
此外，下面所描述的本申请不同实施方式中所涉及的技术特征只要彼此之间未构成冲突就可以相互结合。
本申请实施例提供一种柔性电力变压器，包括：主变压器1及换流装置2。其中，主变压器1包括一个原边侧绕组及多个副边侧绕组；在主变压器1的原边侧绕组末端与任意一个副边侧绕组末端之间串联接入换流装置2，或在主变压器1的任意两个副边侧绕组末端之间串联接入换流装置2；通过调节换流装置2的输出电压调节主变压器1各绕组的电压。
在一些实施例中，如图1或图2所示，以主变压器1包括一次绕组11、二次绕组12及三次绕组13为例进行说明。其中，一次绕组11位于主变压器1的原边侧，二次绕组12和三次绕组13位于主变压器1的副边侧。交流系统与主变压器1的一次绕组11连接，用于为主变压器1提供电源。三次绕组13用于为换流装置2提供电源。
在一些实施例中，一次绕组11与二次绕组12配合，以完成电压变换过程，其中，二次绕组12负责电压输出，为下级线路(即电网)或负载供能。三次绕组13与换流装置2的输入端相连接，三次绕组13为换流装置2提供有功功率支撑。
如图1所示，在主变压器1的一次绕组11末端与三次绕组13之间串联接入换流装置2。这里，可以通过调节换流装置2的输出电压来调节一次绕组11两端的电压，同时同步改变二次绕组12输出电压，实现主变压器1电压幅值和相位的快速、连续、精准调节。此时一次绕组11与三次绕组13均为星型接法，二次绕组12接法不做要求，可根据不同场景应用要求按照常规电力变压器的接线方式进行灵活选择。
如图2所示，在主变压器1的二次绕组12末端与三次绕组13之间串联接入换流装 置2。这里，可以通过调节换流装置2的输出电压来调节二次绕组12两端的电压，同时同步改变一次绕组11两端的电压，实现主变压器1电压幅值和相位的快速、连续、精准调节。此时二次绕组12与三次绕组13均为星型接法，一次绕组11接法不做要求，可根据不同场景应用要求按照常规电力变压器的接线方式进行灵活选择。
在本申请实施例中，如图3所示，可在电力变压器星型接法的绕组末端与中心点(或地)之间串联接入电压幅值、相位灵活可调的换流装置2，通过调节该换流装置2改变主变压器1各绕组的电压，以代替传统机械式变压器调压并兼具一定的移相功能，同时三次绕组给换流装置2提供有功支撑，实现电力变压器电压/潮流灵活控制、端口灵活扩展、电能质量补偿等综合功能。
本申请提出了一种柔性电力变压器，在主变压器的原边侧绕组末端与任意一个副边侧绕组末端之间串联接入换流装置，或在主变压器的任意两个副边侧绕组末端之间串联接入换流装置，通过调节换流装置的输出电压调节主变压器各绕组的电压，可以在不改变变压器匝比的情况下实现对压器各绕组电压的调节功能。同时电压源型换流器与电力变压器相结合，以较小容量的换流器来实现变压器输出电气量的快速、连续、精确和灵活调节。当换流装置故障时，旁路装置对其进行旁路，主变压器能够继续正常工作，柔性电力变压器具有无弧切换、控制灵活、响应速度快、造价低、可靠性高等优势。
在一些实施例中，如图3所示，换流装置2包括多个级联的子单元，可以通过改变级联的子单元的数量来调节换流装置输出电压等级。
在一些实施例中，换流装置2由多个子单元级联实现，通过改变级联子单元的数量来实现应用于不同电压等级的目的。同时多个子单元级联可实现多电平逆变，减小注入系统的谐波含量，且易于扩展，可以实现多电压等级的应用。子单元以全控型电力电子器件为核心，使得输出电压幅值、相位灵活可控，极大提升了有载调压的响应速度，可做到长时间持续运行，针对新能源持续波动引发的电压波动问题，提供了新的解决方案。
在本申请实施例中，子单元包括整流模块21、带高频隔离变压器的双有源桥模块22及逆变模块23，其中，整流模块21的输入端与任意一个副边侧绕组连接，整流模块21的输出端与带高频隔离变压器的双有源桥模块22的输入端连接；逆变模块23的输入端与带高频隔离变压器的双有源桥模块22的输出端连接，逆变模块23的输出端与副边侧其他绕组末端或原边侧绕组末端连接。其中，整流模块21用于将与整流模块21连接的副边侧绕组提供的交流电压整流为直流电压，并维持换流装置2中各模块的直流电压稳定；带高频隔离变压器的双有源桥模块22用于进行直流电压变换，将变换后的直流电压输送至逆变模块23，同时对换流装置2中各模块进行电气隔离；逆变模块23用于将变换后的直流电压逆变为交流电压，并将交流电压输送至副边侧其他绕组末端或原边侧绕组末端。
具体地，如图3所示，在主变压器1的一次绕组11末端与三次绕组13之间串联接入换流装置2为例进行说明。整流模块21的输入端与三次绕组13连接，整流模块21的输出端与带高频隔离变压器的双有源桥模块22的输入端连接，带高频隔离变压器的双有源桥模块22的输出端与逆变模块23的输入端连接，逆变模块23的输出端与一次绕组11末端连接。
其中，三次绕组13通过整流模块21维持子单元中各模块内直流电压稳定。
其中，带高频隔离变压器的双有源桥模块22具备直流电压变换功能，并实现子单元中各模块之间的电气隔离，保证了柔性电力变压器电压等级和容量的可拓展性。带高频隔离变压器的双有源桥模块22可采用多端口设计，对外提供多个功率交换接口，实现分布式光伏、储能等直流电源及低压交直流负载与主变压器之间的能量交互，为分布 式能源的接入及高压变电站周围低压负荷的供能提供了便利渠道，使整体设备的运行更加灵活可靠。如图4所示，带高频隔离变压器的双有源桥模块22包括n个高压端口、n个低压端口，端口数量可灵活扩展。其中一个低压端口连接低压端直流接口电路，一个连接低压端交流接口电路，通过低压端交流接口电路和低压端直流接口电路为外部交直流分布式电源及负载提供接口，实现外部电源和负载与主变压器的能量交换，高低压、交直流的端口扩展更加容易，运行方式灵活高效。
在一些实施例中，带高频隔离变压器的双有源桥模块22中采用高频隔离变压器，大大减小了换流装置2的体积，使得其集成于变压器箱内部成为可能，便于工程化应用。其中，高频隔离变压器的工作频率，由换流装置2的绝缘等级、容量、占地和所采用的功率器件特性等因数确定。
多个逆变模块23级联输出多电平交流电压，其幅值相位可根据脉冲宽度调制(Pulse Width Modulation，PMW)调制策略灵活调整。通过将逆变模块23串联到一次绕组11末端可改变各绕组电压，实现不改变变压器匝比调压的目标。
在一些实施例中，如图3所示，逆变模块23的输出端串联接入绕组末端与中性点之间。这里，中性点为与外部各接线端间电压绝对值相等的点。当电源侧(变压器或发电机)或者负载侧为星型接法时，三相线圈的首端(或尾端)连接在一起的共同接点为中性点，如图3中三次绕组13的N点。
在一些实施例中，换流装置2与主变压器1的耦合方式是将换流装置2的逆变模块23串联接入主变压器1星型接法的绕组末端与中心点(或地)之间，此种耦合方式既适用于高压输电系统，也适用于三相四线制的低压配电系统。换流装置2的逆变模块23可串联接入在高压绕组末端或者低压绕组末端。逆变模块23串联在电力变压器的星型接法绕组末端与中心点(或地)之间，对地电位低，绝缘要求低，大大降低换流装置绝缘成本。
在本申请实施例中，逆变模块23的电压幅值、相位均灵活可调，通过控制逆变模块23输出电压的相位和幅值来改变主变压器1原边侧绕组电压及各副边侧绕组电压。换流装置2输入端具备在维持直流电压恒定的同时，通过三次取能绕组(即三次绕组13)对系统进行无功功率或谐波电流的补偿功能。
在一些实施例中，逆变模块23电压相位与其相串联的绕组相位同相或反相时，可以实现快速、无弧、平滑的电压幅值调节功能。逆变模块23输出的电压相位与其相串联的绕组相位存在角度差时，可以改变主变压器1入口侧电压的相位角，使柔性电力变压器所在支路的潮流发生改变，起到潮流调控的作用。逆变模块23可以在实现电压幅值或相位调节的基础上兼具谐波电压补偿功能。
柔性电力变压器可采用电压控制模式和潮流控制模式。在潮流控制模式时，通过控制换流装置逆变侧输出电压的幅值和相位，控制柔性电力变压器的端口电压和潮流。
在一些实施例中，调压原理及潮流控制原理如下：在变压器星型接法的绕组末端与中心点(或地)之间串联接入可控电压源，令交流系统母线电压为uS，变压器一次侧绕组电压为u1，匝数为W1，二次绕组电压为u2，匝数为W2，换流器取能绕组(即三次绕组)电压为u3，匝数为W3，可控电压源的输出电压为u4。通过换流器输出电压的调节u4，可实现对电压的调控。柔性电力变压器进行潮流调节的等效电路。电压调节原理如公式(1)和(2)所示：
us＝u1+u4            (1)
根据上式(1)可知在不改变绕组匝数的情况下，只对换流器输出电压u4进行调节，即可调整变压器一次绕组的两端电压u1，由式(2)可知感应到二次绕组侧的电压u2也随着一次绕组两端电压u1的改变而同步改变。
在一些实施例中，潮流调节原理如公式(3)至(8)所示：
设送端交流系统侧电压幅值为U1，相角为0，受端交流系统电压幅值为U2，相角为δ2，通过改变换流器逆变侧输出电压的幅值和相角，柔性电力变压器还可实现对多个出线各线路的潮流调控，将变压器T1等效为电抗X(折算到原边)，将背靠背换流器串接入变压器的部分等效为受控电压源
交流系统向负载输送的有功功率P和无功功率Q分别为：

设可控电压源的输出电压幅值为U4，相角为δ4，注入可控电压源之后线路有功功率P′和无功功率Q′分别为：

其中，U′1和分别为：

图5描述了柔性电力变压器电压调节的相量关系，图6描述了柔性电力变压器进行潮流调节的等效电路。
在一些实施例中，如图1或图2所示，柔性电力变压器还包括：旁路装置3，旁路装置3并联在换流装置2逆变侧两端。
在一些实施例中，旁路装置3包括：反并联晶闸管和机械开关。旁路装置3由反并联晶闸管和机械开关等组成，并联在换流装置2逆变侧两端，在换流装置2发生故障时，将旁路装置3的输出端短路，柔性电力变压器作为常规电力变压器运行，保证了设备的可靠性。
显然，上述实施例仅仅是为清楚地说明所作的举例，而并非对实施方式的限定。对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式的变化或变动。这里无需也无法对所有的实施方式予以穷举。而由此所引申出的显而易见的变化或变动仍处于本申请创造的保护范围之中。

Claims (10)

  1. 一种柔性电力变压器，其中，所述柔性电力变压器至少包括：主变压器及换流装置，其中，
    所述主变压器包括一个原边侧绕组及多个副边侧绕组；
    在所述主变压器的原边侧绕组末端与任意一个副边侧绕组末端之间串联接入所述换流装置，或在所述主变压器的任意两个副边侧绕组末端之间串联接入所述换流装置；
    所述换流装置用于通过调节所述换流装置的输出电压，调节所述主变压器各绕组的电压。
  2. 根据权利要求1所述的柔性电力变压器，其中，所述换流装置包括多个级联的子单元，所述子单元用于通过改变级联的子单元的数量，调节所述换流装置输出电压等级。
  3. 根据权利要求2所述的柔性电力变压器，其中，所述换流装置用于通过控制换流装置逆变侧输出电压的幅值和相位，控制所述柔性电力变压器的端口电压和潮流。
  4. 根据权利要求2所述的柔性电力变压器，其中，所述子单元包括整流模块、带高频隔离变压器的双有源桥模块及逆变模块，其中，
    所述整流模块的输入端与任意一个副边侧绕组连接，所述整流模块的输出端与所述带高频隔离变压器的双有源桥模块的输入端连接；
    所述逆变模块的输入端与所述带高频隔离变压器的双有源桥模块的输出端连接，所述逆变模块的输出端与副边侧其他绕组末端或原边侧绕组末端连接；
    所述整流模块用于将副边侧绕组提供的交流电压整流为直流电压，并维持所述换流装置中各模块的直流电压稳定；
    所述带高频隔离变压器的双有源桥模块用于进行直流电压变换，将变换后的直流电压输送至所述逆变模块，同时对所述换流装置中各模块进行电气隔离；
    所述逆变模块用于将变换后的直流电压逆变为交流电压，并将所述交流电压输送至所述副边侧其他绕组末端或原边侧绕组末端。
  5. 根据权利要求4所述的柔性电力变压器，其中，所述逆变模块还用于通过控制所述逆变模块输出电压的相位和幅值来改变所述主变压器原边侧绕组电压及各副边侧绕组电压。
  6. 根据权利要求4所述的柔性电力变压器，其中，所述带高频隔离变压器的双有源桥模块具有多个端口，所述多个端口用于对外提供多个功率交换接口。
  7. 根据权利要求4所述的柔性电力变压器，其中，所述带高频隔离变压器的双有源桥模块中高频变压器的工作频率，由换流装置的容量、占地及所采用的功率器件特性确定。
  8. 根据权利要求4所述的柔性电力变压器，其中，所述逆变模块的输出端串联接入绕组末端与中性点之间。
  9. 根据权利要求1至8任一项所述的柔性电力变压器，其中，所述柔性电力变压器还包括：旁路装置，所述旁路装置并联在所述换流装置逆变侧两端。
  10. 根据权利要求9所述的柔性电力变压器，其中，所述旁路装置包括：反并联晶闸管和机械开关。
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