CN104283233A - Flexible DC power transmission system - Google Patents
Flexible DC power transmission system Download PDFInfo
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- CN104283233A CN104283233A CN201410560372.XA CN201410560372A CN104283233A CN 104283233 A CN104283233 A CN 104283233A CN 201410560372 A CN201410560372 A CN 201410560372A CN 104283233 A CN104283233 A CN 104283233A
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- inverse parallel
- igbt
- parallel unit
- igbt inverse
- inverter
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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
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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
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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- 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]
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
Abstract
The invention provides a flexible DC power transmission system. The flexible DC power transmission system conducts power transmission by means of three-pole connection and comprises a rectifier-side sub-system, a DC circuit and an inverter-side sub-system, wherein the rectifier-side sub-system, the DC circuit and the inverter-side sub-system are connected in sequence; the rectifier-side sub-system comprises a rectifier-side transformer and a smoothing reactor; three-pole connecting lines include a positive pole, a negative pole and a third pole capable of serving as both the positive pole and the negative pole; the DC circuit comprises a rectifier-side smoothing reactor connected with the rectifier-side sub-system and an inverter-side smoothing reactor connected with the inverter-side sub-system; the inverter-side sub-system comprises an inverter-side transformer and a smoothing reactor. A modular multi-level current converter is adopted on the rectifier side and the inverter side, and is small in size, compact in structure and high in modular degree; as a result, filters, the reactors, capacitors and the current converter can all be mounted in a room, and damage to devices and faults caused by influences of various external factors can be reduced; the flexible DC power transmission system has the ability to block a DC-side short-circuit current.
Description
Technical field
The present invention relates to a kind of flexible direct current power transmission system, specifically adopt the flexible direct current power transmission system of modularization multi-level converter.
Background technology
China is electrical energy production and uses big country, but generation assets distribution and demand imbalance, under the condition of population expansion and ecological deterioration and resource requirement, need to develop long-distance and large-capacity power transmission, and when transmission distance is more than 800km, direct current transportation is used to transmit electric energy on cost than adopting ac transmission to transmit electric energy advantageously, therefore, need to pass through high pressure, superhigh pressure, ultra high voltage electric energy transmitting, and adopt direct current transmission electric energy, need to adopt commutation technique, conventional employing LCC-HVDC current conversion station technology carries out the change of current, it has ripe engineering operation experience.But because the LCC-HVDC system of routine needs a large amount of reactive power compensations and filter apparatus, and these device volumes are large, quantity is many, the degree of modularity is lower, usually converter and Control protection system can only be placed in indoor, all the other equipment need to be placed in outdoor field, cause administering and maintaining cost to increase, therefore conventional LCC-HVDC system progressively replace by flexible direct current power transmission system (VSC-HVDC), the small volume of VSC-HVDC system, compact conformation, the degree of modularity is higher, therefore, filter, reactor, capacitor and converter can be arranged on indoor, damage and the fault of device is caused with the impact reducing extraneous various factors.
Patent documentation CN201310276517.9 provides a kind of three pole DC transmission system topological structures based on modularization multi-level converter, it adopts modular multilevel converter system to replace conventional LCC-HVDC system, but modular multilevel structure many employings half-bridge submodule of routine, when DC Line Fault, although can all transistor of locking, but because antiparallel fly-wheel diode can provide path for short circuit current, thus short circuit current can not be blocked, and does not thus possess the locking function of dc-side short-circuit electric current.
Summary of the invention
Based on prior art Problems existing, the invention provides a kind of flexible direct current power transmission system, adopt three poles to connect and carry out power delivery, comprise the rectification side subsystem connected successively, DC line, inverter side subsystem, rectification side subsystem comprises rectification side transformer and smoothing reactor, three pole connecting lines are respectively positive pole, negative pole and the 3rd pole doublely can doing both positive and negative polarity, DC line comprises the inverter side smoothing reactor that the rectification side smoothing reactor that is connected with rectification side subsystem is connected with inverter side subsystem, inverter side subsystem comprises inverter side transformer and smoothing reactor, rectification side and inverter side adopt modularization multi-level converter.
Modularization multi-level converter adopts the structure of upper and lower bridge arm, upper brachium pontis adopts the sub modular structure of cascade, lower brachium pontis adopts full switch structure, the each submodule of upper brachium pontis comprises five IGBT inverse parallel unit, two electric capacity and a diode are formed, IGBT inverse parallel unit comprises an IGBT and and the antiparallel fly-wheel diode of IGBT, DC side input is connected to an IGBT inverse parallel unit first end and the 2nd IGBT inverse parallel unit first end, second end and second end of the 2nd IGBT inverse parallel unit of the one IGBT inverse parallel unit are connected the two ends of the first capacitor respectively, second end of the one IGBT inverse parallel unit also connects the negative electrode of the first diode, second end of the antiparallel unit of the 2nd IGBT also connects the first end of the 3rd IGBT inverse parallel unit, second end of the 3rd IGBT inverse parallel unit is connected with the anode of the first diode and is connected to the first end of the 4th IGBT inverse parallel unit and the first end of the 5th IGBT inverse parallel unit, second end of the 4th IGBT inverse parallel unit and the second end of the 5th IGBT inverse parallel unit are connected respectively to the two ends of the second capacitor, second end of the 5th IGBT inverse parallel unit is also connected to the direct current stream input of next upper brachium pontis submodule, on the next one, brachium pontis submodule adopts identical structure to carry out cascade, upper brachium pontis connects lower bridge arm structure by buffer inductance, lower brachium pontis adopts the parallel IGBT structure that is all-trans, the lower brachium pontis end of buffer inductance is divided into two-way, connect the IGBT inverse parallel unit of two-way series connection respectively, two-way IGBT inverse parallel unit is connected in parallel to each other, the mid point of two-way IGBT inverse parallel unit draws AC output line, the other end of two-way IGBT inverse parallel unit links together and connects DC side output.
The control system of VSC-HVDC can be divided into system-level control, the control of current conversion station level and converter valve level to control three layers by its function height.Wherein, system-levelly control to receive the meritorious class physical quantity (comprising active power, direct voltage, direct current and frequency) that transmits of power-management centre and idle class physical quantity (comprising reactive power and alternating voltage) setting value as its reference input; Current conversion station level controls using the output valve of system-level control as its input reference, through controlling the modulation ratio M and the phase shifting angle δ that obtain SPWM, is supplied to the trigger impulse generation link that valve pole controls; The task that valve level controls receives modulation ratio M and phase shifting angle δ, produces the control of PWM trigger impulse realization to IGBT valve through suitable modulation system.Current conversion station level controls to adopt Direct Current Control, direct current controls to adopt the double-loop control structure that outer shroud controls and inner ring Current Control combines, control system can be divided into outer ring controller, interior ring controller and phase-locked loop three parts substantially, the output of outer ring controller is the reference value of interior ring controller input, the output signal of interior ring controller is after trigger generator, and the gate leve triggering signal producing IGBT controls its work.The effect of phase-locked loop is for coordinate transform provides θ, has reached signal synchronized tracking and the object to voltage vector oriented control.
Outer shroud controls to mainly contain constant DC voltage control, determine active power controller, determine Reactive Power Control, determine FREQUENCY CONTROL and determine alternating voltage control etc.Adopt any control mode, also will be determined on a case-by-case basis.In order to ensure the transmission of active power and maintain system dc voltage constant, one end current conversion station adopts constant DC voltage control, and the other end is then active system or passive system according to contacted system and determines.When the system joined when two ends is active system, one end adopts constant DC voltage control, and one end adopts determines active power controller; When by client link passive system, need adopt by side and determine alternating voltage control with the alternating voltage of stable bus.Surely meritorious class physical quantity controller be input as active power set point Pref, direct voltage set point Udcref or frequency (being usually used in VSC-HVDC in island with power system) set point fref, after the measured value with them compares, through PI link, export the d shaft current reference value idref into inner ring current controller; In like manner, that determines idle class physical quantity controller is input as reactive power set point Qref or alternating voltage set point Uacref, after the measured value with them compares, through PI link, exports the q shaft current reference value iqref into inner ring current controller.
Interior ring controller is current controller, is receiving the d axle that transmits of outer ring controller and q shaft current reference value as its input signal, after linear or Nonlinear Decoupling control, obtains output voltage Ucd and Ucq.Ucd and Ucq, through Park inverse transformation, obtains three-phase voltage U caref, Ucbref and Uccref, finally sends into PWM generator.After adopting suitable modulation system, produce trigger pulse triggers VSC valve break-make.
Phase-locked loop obtains two-phase voltage U a and Ub according to instantaneous value Usa, Usb and Usc of electrical network three-phase voltage through Clark conversion., then divide and be multiplied with sine value with the output phase cosine value of VCO link (VCO), the difference of both products is Ux (i.e. Ki (Uacos θ-Ubsin θ)=Ux).Ux obtains Uf after low-pass filtering link, its again with Proportional coefficient K v, be multiplied and obtain angular frequency error delta w, △ w and system angle frequency w0 sum, after integral element, obtain final input phase θ.
Accompanying drawing explanation
Fig. 1 is modularization multi-level converter of the prior art.
Fig. 2 is the modularization multi-level converter of improvement provided by the invention.
Embodiment
As shown in Figure 2, modularization multi-level converter adopts the structure of upper and lower bridge arm, upper brachium pontis adopts the sub modular structure of cascade, lower brachium pontis adopts full switch structure, the each submodule of upper brachium pontis comprises five IGBT inverse parallel unit, two electric capacity and a diode are formed, IGBT inverse parallel unit comprises an IGBT and and the antiparallel fly-wheel diode of IGBT, DC side input is connected to an IGBT inverse parallel unit first end and the 2nd IGBT inverse parallel unit first end, second end and second end of the 2nd IGBT inverse parallel unit of the one IGBT inverse parallel unit are connected the two ends of the first capacitor respectively, second end of the one IGBT inverse parallel unit also connects the negative electrode of the first diode, second end of the antiparallel unit of the 2nd IGBT also connects the first end of the 3rd IGBT inverse parallel unit, second end of the 3rd IGBT inverse parallel unit is connected with the anode of the first diode and is connected to the first end of the 4th IGBT inverse parallel unit and the first end of the 5th IGBT inverse parallel unit, second end of the 4th IGBT inverse parallel unit and the second end of the 5th IGBT inverse parallel unit are connected respectively to the two ends of the second capacitor, second end of the 5th IGBT inverse parallel unit is also connected to the direct current stream input of next upper brachium pontis submodule, on the next one, brachium pontis submodule adopts identical structure to carry out cascade, upper brachium pontis connects lower bridge arm structure by buffer inductance, lower brachium pontis adopts the parallel IGBT structure that is all-trans, the lower brachium pontis end of buffer inductance is divided into two-way, connect the IGBT inverse parallel unit of two-way series connection respectively, two-way IGBT inverse parallel unit is connected in parallel to each other, the mid point of two-way IGBT inverse parallel unit draws AC output line, the other end of two-way IGBT inverse parallel unit links together and connects DC side output.
The control system of VSC-HVDC can be divided into system-level control, the control of current conversion station level and converter valve level to control three layers by its function height.Wherein, system-levelly control to receive the meritorious class physical quantity (comprising active power, direct voltage, direct current and frequency) that transmits of power-management centre and idle class physical quantity (comprising reactive power and alternating voltage) setting value as its reference input; Current conversion station level controls using the output valve of system-level control as its input reference, through controlling the modulation ratio M and the phase shifting angle δ that obtain SPWM, is supplied to the trigger impulse generation link that valve pole controls; The task that valve level controls receives modulation ratio M and phase shifting angle δ, produces the control of PWM trigger impulse realization to IGBT valve through suitable modulation system.Current conversion station level controls to adopt Direct Current Control, direct current controls to adopt the double-loop control structure that outer shroud controls and inner ring Current Control combines, control system can be divided into outer ring controller, interior ring controller and phase-locked loop three parts substantially, the output of outer ring controller is the reference value of interior ring controller input, the output signal of interior ring controller is after trigger generator, and the gate leve triggering signal producing IGBT controls its work.The effect of phase-locked loop is for coordinate transform provides θ, has reached signal synchronized tracking and the object to voltage vector oriented control.
Outer shroud controls to mainly contain constant DC voltage control, determine active power controller, determine Reactive Power Control, determine FREQUENCY CONTROL and determine alternating voltage control etc.Adopt any control mode, also will be determined on a case-by-case basis.In order to ensure the transmission of active power and maintain system dc voltage constant, one end current conversion station adopts constant DC voltage control, and the other end is then active system or passive system according to contacted system and determines.When the system joined when two ends is active system, one end adopts constant DC voltage control, and one end adopts determines active power controller; When by client link passive system, need adopt by side and determine alternating voltage control with the alternating voltage of stable bus.Surely meritorious class physical quantity controller be input as active power set point Pref, direct voltage set point Udcref or frequency (being usually used in VSC-HVDC in island with power system) set point fref, after the measured value with them compares, through PI link, export the d shaft current reference value idref into inner ring current controller; In like manner, that determines idle class physical quantity controller is input as reactive power set point Qref or alternating voltage set point Uacref, after the measured value with them compares, through PI link, exports the q shaft current reference value iqref into inner ring current controller.
Interior ring controller is current controller, is receiving the d axle that transmits of outer ring controller and q shaft current reference value as its input signal, after linear or Nonlinear Decoupling control, obtains output voltage Ucd and Ucq.Ucd and Ucq, through Park inverse transformation, obtains three-phase voltage U caref, Ucbref and Uccref, finally sends into PWM generator.After adopting suitable modulation system, produce trigger pulse triggers VSC valve break-make.
Phase-locked loop obtains two-phase voltage U a and Ub according to instantaneous value Usa, Usb and Usc of electrical network three-phase voltage through Clark conversion., then divide and be multiplied with sine value with the output phase cosine value of VCO link (VCO), the difference of both products is Ux (i.e. Ki (Uacos θ-Ubsin θ)=Ux).Ux obtains Uf after low-pass filtering link, its again with Proportional coefficient K v, be multiplied and obtain angular frequency error delta w, △ w and system angle frequency w0 sum, after integral element, obtain final input phase θ.
Claims (2)
1. a flexible direct current power transmission system, it is characterized in that, adopt three poles to connect and carry out power delivery, comprise the rectification side subsystem connected successively, DC line, inverter side subsystem, rectification side subsystem comprises rectification side transformer and smoothing reactor, three pole connecting lines are respectively positive pole, negative pole and the 3rd pole doublely can doing both positive and negative polarity, DC line comprises the inverter side smoothing reactor that the rectification side smoothing reactor that is connected with rectification side subsystem is connected with inverter side subsystem, inverter side subsystem comprises inverter side transformer and smoothing reactor, rectification side and inverter side adopt modularization multi-level converter.
2. a kind of flexible direct current power transmission system as claimed in claim 1, it is characterized in that, modularization multi-level converter adopts the structure of upper and lower bridge arm, upper brachium pontis adopts the sub modular structure of cascade, lower brachium pontis adopts full switch structure, the each submodule of upper brachium pontis comprises five IGBT inverse parallel unit, two electric capacity and a diode are formed, IGBT inverse parallel unit comprises an IGBT and and the antiparallel fly-wheel diode of IGBT, DC side input is connected to an IGBT inverse parallel unit first end and the 2nd IGBT inverse parallel unit first end, second end and second end of the 2nd IGBT inverse parallel unit of the one IGBT inverse parallel unit are connected the two ends of the first capacitor respectively, second end of the one IGBT inverse parallel unit also connects the negative electrode of the first diode, second end of the antiparallel unit of the 2nd IGBT also connects the first end of the 3rd IGBT inverse parallel unit, second end of the 3rd IGBT inverse parallel unit is connected with the anode of the first diode and is connected to the first end of the 4th IGBT inverse parallel unit and the first end of the 5th IGBT inverse parallel unit, second end of the 4th IGBT inverse parallel unit and the second end of the 5th IGBT inverse parallel unit are connected respectively to the two ends of the second capacitor, second end of the 5th IGBT inverse parallel unit is also connected to the direct current stream input of next upper brachium pontis submodule, on the next one, brachium pontis submodule adopts identical structure to carry out cascade, upper brachium pontis connects lower bridge arm structure by buffer inductance, lower brachium pontis adopts the parallel IGBT structure that is all-trans, the lower brachium pontis end of buffer inductance is divided into two-way, connect the IGBT inverse parallel unit of two-way series connection respectively, two-way IGBT inverse parallel unit is connected in parallel to each other, the mid point of two-way IGBT inverse parallel unit draws AC output line, the other end of two-way IGBT inverse parallel unit links together and connects DC side output.
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| CN201410560372.XA CN104283233B (en) | 2014-10-18 | 2014-10-18 | A kind of flexible direct current power transmission system |
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| CN201410560372.XA CN104283233B (en) | 2014-10-18 | 2014-10-18 | A kind of flexible direct current power transmission system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107370391A (en) * | 2017-07-05 | 2017-11-21 | 东南大学 | Bridge arm towards mesohigh intelligent distribution network is multiplexed electric power electric transformer |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103311947A (en) * | 2013-07-02 | 2013-09-18 | 南京南瑞继保电气有限公司 | Tri-pole direct current transmission system topology structure based on modular multi-level converter (MMC) |
| WO2013139375A1 (en) * | 2012-03-20 | 2013-09-26 | Abb Technology Ltd | An apparatus for controlling the electric power transmission in an hvdc power transmission system |
| CN103972920A (en) * | 2014-05-14 | 2014-08-06 | 国网上海市电力公司 | Compact modularized multi-level tripolar direct-current power transmission system |
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2014
- 2014-10-18 CN CN201410560372.XA patent/CN104283233B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013139375A1 (en) * | 2012-03-20 | 2013-09-26 | Abb Technology Ltd | An apparatus for controlling the electric power transmission in an hvdc power transmission system |
| CN103311947A (en) * | 2013-07-02 | 2013-09-18 | 南京南瑞继保电气有限公司 | Tri-pole direct current transmission system topology structure based on modular multi-level converter (MMC) |
| CN103972920A (en) * | 2014-05-14 | 2014-08-06 | 国网上海市电力公司 | Compact modularized multi-level tripolar direct-current power transmission system |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107370391A (en) * | 2017-07-05 | 2017-11-21 | 东南大学 | Bridge arm towards mesohigh intelligent distribution network is multiplexed electric power electric transformer |
| CN107370391B (en) * | 2017-07-05 | 2019-05-28 | 东南大学 | Bridge arm towards mesohigh intelligent distribution network is multiplexed electric power electric transformer |
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| CN104283233B (en) | 2016-08-24 |
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