CN107257206B - Three-terminal direct current transformer - Google Patents

Three-terminal direct current transformer Download PDF

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Publication number
CN107257206B
CN107257206B CN201710339954.9A CN201710339954A CN107257206B CN 107257206 B CN107257206 B CN 107257206B CN 201710339954 A CN201710339954 A CN 201710339954A CN 107257206 B CN107257206 B CN 107257206B
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direct
voltage source
module
current voltage
chain
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CN201710339954.9A
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CN107257206A (en
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蔡旭
游洪程
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Shanghai Jiaotong University
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Shanghai Jiaotong University
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    • 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
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without 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
    • H02M7/537—Conversion of dc power input into ac power output without 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, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without 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, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without 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, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H02M7/53873—Conversion of dc power input into ac power output without 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, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with digital control
    • 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
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without 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
    • H02M7/537—Conversion of dc power input into ac power output without 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, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without 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, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without 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, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation

Abstract

The invention provides a three-terminal direct-current transformer which comprises three chained modules connected in series in sequence, wherein the input end of a first chained module is connected with the anode of a first direct-current voltage source through a bridge arm inductor, the input end of a second chained module is connected with the anode of a second direct-current voltage source through a filter inductor, the input end of a third chained module is connected with the anode of a third direct-current voltage source through a filter inductor, and the output end of the third chained module is respectively connected with the cathode of the first direct-current voltage source, the cathode of the second direct-current voltage source and the cathode of the third direct-current voltage source; each chain module is composed of a plurality of half-bridge submodules and at least one full-bridge submodule which are connected in series.

Description

Three-terminal direct current transformer
Technical Field
The invention relates to the field of electricity, in particular to a three-terminal direct-current transformer.
Background
With the shortage of traditional energy sources and the aggravation of environmental deterioration problems, more and more attention is paid to the utilization and development of renewable clean energy sources such as wind energy, solar energy and the like. The power generation of new energy sources such as wind energy, solar energy and the like has the characteristics of intermittency and randomness, the traditional power grid structure and operation technology cannot adapt to the access of large-scale renewable energy sources, and a conventional direct current and flexible direct current based multi-terminal direct current power transmission system and a direct current power grid technology are effective means for solving the problem. Because a direct-current power grid has no unified standard, most of the existing direct-current lines operate at different voltage levels, and in order to interconnect direct-current transmission systems of different voltage levels to form a direct-current power grid, a direct-current transformer (generally also called a DC-DC converter) needs to be applied. Existing high voltage DC-DC converters can connect two DC transmission systems, and if three DC transmission systems need to be connected simultaneously, multiple DC-DC converters are required, which increases the system cost. Another solution is to use a three-terminal DC transformer (three-terminal DC-DC converter) to directly connect three DC transmission systems to reduce the cost and loss of the system.
The document "quick two-level operation of Modular Multilevel Converter for use in a high-Power dcctransformer with DC fault isolation capability" published in IEEE Transactions on Power Electronics proposes an isolated three-terminal DC-DC Converter topology based on a Modular Multilevel Converter (MMC), which essentially consists of an MMC with three ac buses, and an isolation transformer is used for electrical isolation and voltage transformation. Because the converter needs a power frequency transformer and the number of required submodules is large, the converter has the defects of high cost, large loss and low efficiency.
The document "Multi High-Power LCL DC Hub for Use in DC Transmission Grids" published in IEEE Transactions on Power Delivery proposes a DC transformer topology that uses an LCL circuit for transformation, and therefore does not require an isolation transformer. However, the number of submodules required for the converter is large, and therefore, the cost and the loss are large.
A self-coupling type multi-terminal DC-DC converter topology is proposed in a document "Multi DC-DC Autotransform for Interconnecting Multi High-Voltage DC Systems at Low cost" published in IEEE Transactions on Power Electronics. The capacity of the transformer in the converter is smaller than in the first document mentioned above and the number of sub-modules required is reduced. However, the converter still needs a plurality of power frequency isolation transformers, so the volume and the cost of the system are high.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a three-terminal direct-current transformer which is small in size and low in cost.
The three-terminal direct-current transformer comprises three chained modules which are sequentially connected in series, wherein the input end of the first chained module is connected with the anode of a first direct-current voltage source through a bridge arm inductor, the input end of the second chained module is connected with the anode of a second direct-current voltage source through a filter inductor, the input end of the third chained module is connected with the anode of a third direct-current voltage source through a filter inductor, and the output end of the third chained module is respectively connected with the cathode of the first direct-current voltage source, the cathode of the second direct-current voltage source and the cathode of the third direct-current voltage source;
each chain module is composed of a plurality of half-bridge submodules and at least one full-bridge submodule which are connected in series.
Preferably, the half-bridge sub-module is composed of a capacitor and two power switch tubes, the first power switch tube is connected with the positive electrode of the capacitor, and the second power switch tube is connected with the negative electrode of the capacitor.
Preferably, the full-bridge sub-module is composed of a capacitor and four power switching tubes, the first power switching tube and the third power switching tube are connected with the positive electrode of the capacitor, and the second power switching tube and the fourth power switching tube are connected with the negative electrode of the capacitor.
Preferably, the firstVoltage value U of dc voltage sourcedc1>The voltage value U of the second direct current voltage sourcedc2>The voltage value U of the third direct current voltage sourcedc3。
Preferably, the alternating current component of the output voltage of the chain module is a sine wave, a square wave or a pulse width modulation wave.
Compared with the prior art, the invention has the following beneficial effects:
1) the capacitance value of the sub-module capacitor is greatly reduced, and the size and cost of the converter can be reduced;
2) the ac circulating current is smaller and the switching frequency is lower, thus the efficiency is higher.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a circuit structure diagram of a three-terminal dc transformer according to the present invention;
FIG. 2 is a circuit block diagram of a half-bridge sub-module according to the present invention;
FIG. 3 is a circuit diagram of a full bridge sub-module according to the present invention;
fig. 4 is a schematic diagram of output voltages of three chain modules according to the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1, the three-terminal dc transformer provided by the present invention comprises three chained modules connected in series in sequence, wherein the input end of the chained module 1 passes through the bridge arm inductor LaAnd a DC voltage source Udc1Is connected with the positive pole of the chain module 2, the input end of the chain module 2 passes through the filter inductor Lf1And a DC voltage source Udc2Positive electrode connection, chain typeThe input of the module 3 passes through the filter inductor Lf2And a DC voltage source Udc3Is connected with the positive pole of the chain module 3, the output end of the chain module 3 is respectively connected with a direct current voltage source Udc1Negative electrode, direct current voltage source Udc2And a direct current voltage source Udc3In the negative electrode of (1), wherein Udc1>Udc2>Udc3。
The chained module is formed by connecting a plurality of sub-modules in series, and the sub-modules can be half-bridge sub-modules in fig. 2 or full-bridge sub-modules in fig. 3. The half-bridge sub-module is composed of a capacitor and two power switch tubes, wherein the first power switch tube S1 is connected with the positive electrode of the capacitor, and the second power switch tube S2 is connected with the negative electrode of the capacitor. The full-bridge submodule is composed of a capacitor and four power switch tubes, the first power switch tube S1 and the third power switch tube S3 are connected with the positive electrode of the capacitor, and the second power switch tube S2 and the fourth power switch tube S4 are connected with the negative electrode of the capacitor. When the direct current fault isolation circuit works normally, the submodules are half-bridge submodules, if the direct current fault isolation circuit needs to isolate direct current faults, part of the submodules must be full-bridge submodules, and therefore each chain type module is formed by connecting a plurality of half-bridge submodules and at least one full-bridge submodule in series.
As shown in fig. 4, the output voltages (v) of the chain modules 1, 2 and 3Cl1、vCl2、vCl3) Are all two-level pulse width modulation waveforms with duty ratios d1、d2And d3. The output voltage of the chain module 2 has a phase shift compared with the output voltage of the chain module 1, and the phase shift duty ratio is ds1The output voltage of the chain module 2 has a phase shift compared with the output voltage of the chain module 1, and the phase shift duty ratio is ds2. The DC transformer of the invention adjusts the phase-shifting duty ratio ds1And ds2To maintain all sub-module capacitor voltage balance.
The output voltages of all the chain modules comprise a DC component and an AC component, and the DC components of the output voltages of the chain modules 1, 2 and 3 are respectively (U)dc1-Udc2)、(Udc2-Udc3) And Udc3. Active power transmission between chained modules by AC circulating current to realize sub-module capacitanceAnd (4) charge and discharge balance. The alternating current component of the output voltage of the chain module can be a sine wave, a square wave and a pulse width modulation wave.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (3)

1. The three-terminal direct-current transformer is characterized by comprising three chain-type modules which are sequentially connected in series, wherein the input end of the first chain-type module is connected with the anode of a first direct-current voltage source through a bridge arm inductor, and the input end of the second chain-type module is connected with the anode of a second direct-current voltage source through a filter inductor Lf1The input end of the third chain type module is connected with the anode of the second direct current voltage source through a filter inductor Lf2The output end of the third chained module is respectively connected with the negative electrode of the first direct-current voltage source, the negative electrode of the second direct-current voltage source and the negative electrode of the third direct-current voltage source;
each chain module is composed of a plurality of half-bridge submodules and at least one full-bridge submodule which are connected in series.
2. The three-terminal DC transformer of claim 1, wherein the voltage value U of the first DC voltage sourcedc1>The voltage value U of the second direct current voltage sourcedc2>The voltage value U of the third direct current voltage sourcedc3。
3. The three-terminal dc transformer of claim 1, wherein the ac component of the output voltage of the chain module is a sine wave, a square wave or a pulse width modulated wave.
CN201710339954.9A 2017-05-15 2017-05-15 Three-terminal direct current transformer Active CN107257206B (en)

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CN112583268A (en) * 2020-12-21 2021-03-30 上海交通大学 Modular multilevel DC converter

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CN105375757B (en) * 2014-08-25 2018-07-17 国家电网公司 A kind of DC voltage conversion device and its bridge arm control method
WO2016138949A1 (en) * 2015-03-04 2016-09-09 Siemens Aktiengesellschaft Dc to dc converter
CN105576982B (en) * 2016-02-02 2019-01-25 上海交通大学 Non-isolation type direct-current transformer
CN105978332B (en) * 2016-05-13 2019-04-16 重庆大学 Tetra- level Boost converter of IPOS and its neutral-point-potential balance control
CN105896966B (en) * 2016-05-17 2018-07-06 湖南大学 The modular multilevel DC-DC converter and its control method of a kind of high no-load voltage ratio
CN106505902B (en) * 2016-10-13 2019-08-09 上海交通大学 LCC/VSC direct current interconnects transformer

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