CN103311947B - A kind of three pole DC transmission system topological structures based on modularization multi-level converter - Google Patents

A kind of three pole DC transmission system topological structures based on modularization multi-level converter Download PDF

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CN103311947B
CN103311947B CN201310276517.9A CN201310276517A CN103311947B CN 103311947 B CN103311947 B CN 103311947B CN 201310276517 A CN201310276517 A CN 201310276517A CN 103311947 B CN103311947 B CN 103311947B
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pole
converter
direct current
transmission system
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CN103311947A (en
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胡铭
邵震霞
焦鑫艳
黄志岭
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NR Electric Co Ltd
NR Engineering Co Ltd
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NR Engineering Co Ltd
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention discloses a kind of three pole DC transmission system topological structures based on modularization multi-level converter, it is characterized in that: adopt three pole types of attachment to carry out direct current transportation, each pole comprises rectification side converter transformer, rectification side converter, rectification side smoothing reactor, DC power transmission line, inverter side smoothing reactor, inverter side converter, inverter side converter transformer group; Rectification side converter and inverter side converter adopt modular multilevel structure, and by connection in series-parallel varying number submodule unit to adapt to the needs of different electric pressure and electric current, three transmission lines that three pole direct current systems adopt are cable or overhead transmission line.The three pole DC transmission system topological structures that the present invention proposes have very high reliability, alternating current circuit can be met and be transformed into DC line demand, can not there is commutation failure in inverter side under AC system breaks down situation, both sides AC system voltage can be stablized, without the need to ac filter and reactive power compensator, there is good using value.

Description

A kind of three pole DC transmission system topological structures based on modularization multi-level converter
Technical field
The present invention relates to power transmission and distribution technical field, be specifically related to a kind of three pole DC transmission system existing alternating current circuit being transformed into DC power transmission line.
Background technology
Along with China's sustain economic high speed development, electricity needs contradiction.On the one hand the growth of electric load is beyond the transmittability of original transmission line of alternation current, and limits by land resource, is difficult to the transmission of electricity corridor that acquisition is new; On the other hand, conventional AC transmission of electricity limits by insulation, AC network characteristic, and circuit transmission power seldom reaches the maximum heat power that wire can bear, and therefore needs to employ new technology and excavates the transmission of electricity potentiality of existing line further.
Compared with ac transmission, adopt direct current transportation, line current can reach the maximum heat limit that wire can bear.2004, BartholdLO proposed a kind of employing D.C.current modulation in patent US6714427B1, transmission line of alternation current is converted into three pole HVDC Transmission Technologies of DC power transmission line.Alternating current circuit is being transformed in the various conversion plans of DC power transmission line, because three pole direct current transportation schemes can make full use of original AC three-phase circuit, therefore relative to bipolar and monopolar D. C transmission of electricity modification scheme, three pole direct current transportation schemes in raising ability to transmit electricity, Financial cost and reliability etc. on there is advantage.Utilize three pole HVDC Transmission Technologies alternating current circuit to be transformed into DC power transmission line at present and be in principle conceptual phase, there is no engineering example.
Fig. 1 is the three pole direct current transportation major loop figure based on conventional LCC-HVDC that BartholdLO proposes, shown in figure, pole 1, pole 2 are the bipolar transmission system of conventional LCC-HVDC, and pole 3 is for having the one pole transmission system of two-way admittance ability, and its polarity of voltage and the sense of current can change fast.
LCC-HVDC adopts half control type thyristor, the advantages such as the maturation that possesses skills, transmission power are large, good economy performance, but exists comparatively responsive to AC system intensity, and commutation failure easily occurs inverter side; Passive system can not be accessed; Reactive power consumption is large, and output voltage, output current harmonics content are high, needs to install filter and carrys out the shortcomings such as harmonic carcellation.
In recent years, flexible high pressure direct current transportation (VSC-HVDC) technical development based on voltage source converter is very fast, compared with Traditional DC technology of transmission of electricity, has and does not need line commutation voltage support, can power to passive network; There is not commutation failure; Active power, reactive power can be realized independently control; Without the need to advantages such as reactive power compensators.
The topological structure that VSC-HVDC is conventional comprises two level converters, three-level converter and modularization multi-level converter (MMC) structure.Two level converters, three-level converter due to level number little, need to solve the problems such as device series average-voltage, loss are larger in the application of the high pressure large-power occasions such as direct current transportation, MMC-HVDC has the features such as switching frequency is low, loss is little, easy expansion, preferably resolves an above-mentioned difficult problem.
Owing to adopting conventional LCC-HVDC technology, therefore there is the shortcoming of LCC-HVDC equally in three pole direct current transportation schemes in Fig. 1.As inverter side AC system breaks down causing direct current three poles commutation failure to occur simultaneously, cause DC line transmission power to interrupt, receiving-end system safety and stability is constituted a threat to.In addition, in three pole direct current system runnings, each electrode current size and pole 3 polarity of voltage and the sense of current all need to change fast by some cycles, certainly will produce disturbance to two ends AC system.
In order to solve the problem, make full use of flexible high pressure direct current transportation advantage, a kind of three pole DC transmission system topological structures based on modularization multi-level converter are proposed, modularization multi-level converter quick adjustment is utilized to export idle, l improves the performance of both sides AC system, avoid whole system inverter side generation commutation failure, improve three pole direct current transportation reliabilities, meet alternating current circuit and be transformed into DC power transmission line demand.
Summary of the invention
The object of the invention is to propose a kind of three pole DC transmission system topological structures based on modularization multi-level converter, meet alternating current circuit and be transformed into DC power transmission line needs, solve the shortcoming based on the three pole direct current transportation of LCC-HVDC, ensure whole direct current system stable operation.
Technical scheme of the present invention is, a kind of three pole DC transmission system topological structures based on modularization multi-level converter, adopt three pole types of attachment to carry out direct current transportation, each pole comprises rectification side converter transformer, rectification side converter, rectification side smoothing reactor, DC power transmission line, inverter side smoothing reactor, inverter side converter, inverter side converter transformer group; Rectification side converter and inverter side converter adopt modular multilevel structure, and by connection in series-parallel varying number submodule unit to adapt to the needs of different electric pressure and electric current, three transmission lines that three pole direct current systems adopt both can be cables, also can be overhead transmission lines.
Further, in three pole DC transmission system, adopt the converter of two modularization multi-level converter positive negative bipolars in series, in the middle of the two poles of the earth, draw ground connection branch road, and there is the 3rd the pole earth terminal that two-way admittance ability module multilevel converter forms be connected; The facies unit mid point of three pole rectifier inverters, inverter is connected with converter transformer winding secondary respectively, three pole rectifier inverters, inverter DC side are connected with three transmission lines by smoothing reactor, form the pole 1 of three pole DC transmission system as positive pole respectively, as the pole 2 of negative pole, double as the pole 3 into positive pole/negative pole.
Further, during described three pole DC transmission system are run, two pole DC voltage polarity and direct current direction invariable, current ration is periodic modulation between a minimum value and a maximum value; 3rd pole DC voltage polarity and direct current direction can change fast, its direct current definite value gets the difference of the direct current definite value of two other pole, and direct voltage follows the change of direct current direction, and to present periodically reversion constant to ensure direct current power transmission direction.
Further, DC voltage polarity needs the rectification side converter of the 3rd pole of periodically reversion and inverter side converter to adopt full-bridge submodule, comprises four IGBT, an electric capacity and four diodes.
Further, as adopted cable power transmission, then the converter of two poles that DC voltage polarity is constant adopts half-bridge submodule, comprises two IGBT, an electric capacity and two diodes.
Further, transmit electricity as adopted overhead transmission line, then the rectification side converter of two poles that DC voltage polarity is constant and inverter side converter adopt clamper Shuangzi module, and each clamper Shuangzi module is made up of through the guiding IGBT connection in series-parallel of two clamping diodes and a band anti-paralleled diode equivalent half-bridge cells 1 and equivalent half-bridge cells 2.Comprise two IGBT, an electric capacity and two diodes.
The invention has the beneficial effects as follows: a kind of three pole DC transmission system topological structures based on modularization multi-level converter that the present invention proposes, there is very high reliability, alternating current circuit can be met and be transformed into DC line demand, can not there is commutation failure in inverter side under AC system breaks down situation, both sides AC system voltage can be stablized, without the need to ac filter and reactive power compensator, there is good engineer applied and be worth.
Accompanying drawing explanation
Fig. 1 is the three pole DC transmission system principle assumption diagrams based on LCC-HVDC;
Fig. 2 is typical module multilevel converter system configuration schematic diagram;
Fig. 3 is the three pole DC transmission system structure principle charts based on modularization multi-level converter that the present invention proposes;
Fig. 4 is half-bridge sub modular structure schematic diagram;
Fig. 5 is clamper Shuangzi modular structure schematic diagram;
Fig. 6 is full-bridge sub modular structure schematic diagram.
Embodiment
Below in conjunction with drawings and the specific embodiments, technical scheme of the present invention is described in detail.
As Figure 1-3, three pole direct current system each pole DC voltage polarity are just respectively, and negative, positive/negative, MMC is modularization multi-level converter; The present invention proposes a kind of three pole DC transmission system topological structures based on modularization multi-level converter: comprise rectification converter transformer, rectifier inverter, rectification smoothing reactor, direct current overhead transmission line, inversion smoothing reactor, inverter and inverse transformation convertor transformer, rectifier inverter and inverter are made up of a modularization multi-level converter respectively, three circuits adopted both can be cables, also can be overhead transmission lines.SM in Fig. 2 1-SM nthe Modularized multi-level converter sub-module unit be.
Rectification converter transformer, carries out electric pressure conversion for three-phase alternating current sending end AC system provided.
Rectifier inverter, is converted to direct current for the three-phase alternating current after electric pressure being converted.
Smoothing reactor, for stabilizing the ripple in described direct current.
Inverter, for being converted to three-phase alternating current by the direct current after stabilizing.
Inverse transformation convertor transformer, carries out electric pressure conversion for the three-phase alternating current converted to by multilevel converter, to flow to receiving end AC system.
In Fig. 3, modularization multi-level converter is made up of 6 brachium pontis, and two brachium pontis, one group of facies unit in series, junction is called facies unit mid point, and each brachium pontis is at least in series by a submodule (elementary cell) and a brachium pontis reactor.
Three pole DC transmission system adopt two modularization multi-level converter positive negative bipolars in series, and draw ground connection branch road in the middle of described positive and negative polarities, the earth terminal of the 3rd pole formed with the modularization multi-level converter with two-way admittance ability is connected; The facies unit mid point of three pole rectifier inverters, inverter is connected with converter transformer winding secondary respectively, three pole rectifier inverters, inverter DC side are connected with three transmission lines by smoothing reactor, form the pole 1 of three pole DC transmission system as positive pole respectively, as the pole 2 of negative pole, double as the pole 3 into positive pole/negative pole.The elementary cell of above-mentioned converter adopts modular multilevel structure, and rated voltage and current class are all identical, converter by connection in series-parallel varying number elementary cell to adapt to the needs of different electric pressure and electric current.
In three pole direct current system runnings, two pole DC voltage polarity and direct current direction invariable, current ration is periodic modulation between a minimum value and a maximum value; 3rd pole DC voltage polarity and direct current direction can change fast, its direct current definite value gets the difference of the direct current definite value of two other pole, and direct voltage follows the change of direct current direction, and to present periodically reversion constant to ensure direct current power transmission direction.
Due in three pole direct current system runnings, each electrode current size and the 3rd pole tension polarity and the sense of current all need to change fast by some cycles, disturbance will be produced to two ends AC system, cause ac bus voltage fluctuation, flickering, reduce the quality of power supply of both sides AC system.Three direct current system both sides, pole adopt and determine alternating voltage control or Reactive Power Control for this reason, by the reactive power that quick adjustment modularization multi-level converter exports, suppress ac bus voltage fluctuation, flickering, improve the both sides AC system quality of power supply, improve both sides AC system performance.
Three circuits as adopted are cable, and because cable fault is low, and as broken down, normally permanent fault, removes fault by tripping AC switch, can not affect the availability factor of whole system.The Rectification and Reverse converter submodule (elementary cell) of two poles that therefore DC voltage polarity is constant can adopt half-bridge structure, and concrete structure as shown in Figure 4, comprises the IGBT of two serial connections, an electric capacity and two diodes; The anode of described two diodes connects the source electrode of two IGBT respectively, and the negative electrode of two diodes connects the drain electrode of corresponding IGBT respectively; The drain electrode of a described IGBT connects the source electrode of the 2nd IGBT via electric capacity, and the source electrode of an IGBT connects the drain electrode of the 2nd IGBT, and is in series with brachium pontis reactor.
Three circuits as adopted are overhead transmission line, because the probability of overhead transmission line generation temporary fault is higher, as adopted tripping AC switch, to remove fault, then interruption duration is longer, affect the availability factor of whole system, therefore need the fault being removed DC side by the control of converter self, the converter submodule of two poles that DC voltage polarity is constant adopts the clamper Shuangzi modular structure with the failures removing DC side for this reason.Concrete structure is as shown in Figure 5: comprise two clamper submodules, each clamper submodule by the first equivalent half-bridge cells 1 and the second equivalent half-bridge cells 2 through D6, D7 clamping diode and band anti-paralleled diode D5 with the 5th IGBT(T5) in parallelly to form; First IGBT(T1) collector electrode be connected with one end of first electric capacity (C1), the other end and second IGBT(T2 of first electric capacity) emitter be connected, first half-bridge cells described in formation; 3rd IGBT(T3) collector electrode be connected with one end of second electric capacity (C2), the other end and the 4th IGBT(T4 of second electric capacity) emitter be connected, second half-bridge cells described in formation, IGBT(T1 ~ T5 all in figure) equal inverse parallel fly-wheel diode (D1 ~ D5).
No matter be cable power transmission scheme or overhead transmission line scheme, because three pole DC transmission system the 3rd pole DC voltage polarity needs periodically reversion, therefore the 3rd pole converter submodule adopts the full bridge structure that can realize direct voltage reversed polarity and export, concrete structure is as shown in Figure 6: T1, T2, T3, T4 represent four IGBT in full-bridge submodule respectively, D1, D2, D3, D4 represent the anti-paralleled diode of corresponding IGBT respectively, C represents capacitor in full-bridge submodule, definition U cbe capacitance voltage, then T1 and T4 conducting, submodule exports as U c; T2 and T3 conducting, submodule exports as-U c; T1 and T2 or T3 and T4 conducting, it is 0 that submodule exports.Owing to adopting the modularization multi-level converter of full-bridge submodule to have the ability removing DC side fault, therefore meet the requirement that DC side fault is removed in overhead transmission line scheme the 3rd pole equally.
Above embodiment is only and technological thought of the present invention is described, can not limit protection scope of the present invention with this, and every technological thought proposed according to the present invention, any change that technical scheme basis is done, all falls within scope.

Claims (4)

1. three pole DC transmission system topological structures based on modularization multi-level converter, it is characterized in that: adopt three pole types of attachment to carry out direct current transportation, each pole comprises rectification side converter transformer, rectification side converter, rectification side smoothing reactor, DC power transmission line, inverter side smoothing reactor, inverter side converter, inverter side converter transformer group; Rectification side converter and inverter side converter adopt modular multilevel structure, and by connection in series-parallel varying number submodule unit to adapt to the needs of different electric pressure and electric current, three transmission lines that three pole direct current systems adopt are cables; The converter of two poles that DC voltage polarity is constant adopts half-bridge submodule, and DC voltage polarity needs the converter of the 3rd pole of periodic inversion to adopt full-bridge submodule; Adopt two modularization multi-level converter positive negative bipolars in series in three pole DC transmission system, draw ground connection branch road in the middle of the two poles of the earth, and there is the 3rd the pole earth terminal that two-way admittance ability module multilevel converter forms be connected; The facies unit mid point of three pole rectifier inverters, inverter is connected with converter transformer winding secondary respectively, three pole rectifier inverters, inverter DC side are connected with three transmission lines by smoothing reactor, form the pole 1 of three pole DC transmission system as positive pole, the pole 2 as negative pole respectively, double as pole 3 into positive pole/negative pole.
2. by a kind of three pole DC transmission system topological structures based on modularization multi-level converter according to claim 1, it is characterized in that: during three pole DC transmission system are run, two pole DC voltage polarity and direct current direction invariable, current ration is periodic modulation between a minimum value and a maximum value; 3rd pole DC voltage polarity and direct current direction can change fast, its direct current definite value gets the difference of the direct current definite value of two other pole, and direct voltage follows the change of direct current direction, and to present periodically reversion constant to ensure direct current power transmission direction.
3. a kind of three pole DC transmission system topological structures based on modularization multi-level converter as claimed in claim 1, it is characterized in that: DC voltage polarity needs the converter of the 3rd pole of periodic inversion to adopt full-bridge submodule, comprises four IGBT, an electric capacity and four diodes.
4. a kind of three pole DC transmission system topological structures based on modularization multi-level converter as claimed in claim 1, it is characterized in that: the converter of two poles that DC voltage polarity is constant adopts half-bridge submodule, comprises the IGBT of two serial connections, an electric capacity and two diodes.
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