CN108206534A - Closed-loop Control Strategy is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry - Google Patents
Closed-loop Control Strategy is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry Download PDFInfo
- Publication number
- CN108206534A CN108206534A CN201810042267.5A CN201810042267A CN108206534A CN 108206534 A CN108206534 A CN 108206534A CN 201810042267 A CN201810042267 A CN 201810042267A CN 108206534 A CN108206534 A CN 108206534A
- Authority
- CN
- China
- Prior art keywords
- alternate
- mmc
- net side
- losses
- closed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
-
- 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]
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The present invention relates to the alternate losses of MMC in DC grid during a kind of net side asymmetry to divide equally Closed-loop Control Strategy, belongs to high pressure, super high voltage direct current electricity transmission technical field.The program mainly puts into Closed-loop Control Strategy when unbalanced fault occurs for DC grid net side, divides equally the alternate losses of current conversion station MMC, improves the reliability and service life of device.The power that tri- phase elements of MMC occur when mainly for DC grid current conversion station net side unbalanced fault occurs for the control strategy is unevenly distributed problem with loss, it not only realizes dividing equally for alternate loss under unbalanced fault, with more notable, damage effect must drop, and the program only needs change algorithm that can reach drop damage effect well, has good economy.
Description
Technical field
The present invention relates to a kind of MMC current conversion stations coordination control strategies, belong to high pressure, extra-high voltage direct-current transmission field.
Background technology
Flexible DC power transmission is the high voltage dc transmission technology of new generation based on voltage source converter, because with there is no change
The advantages that phase fails, active and idle independent control can be achieved, floor space is small, becomes the research in direct current transportation field in recent years
One of hot spot.And modular multi-level converter is strong because of operational efficiency height, good output, expansibility, it has also become current soft
The preferred option of converter valve in property DC transmission system.
In recent years, being constantly progressive with energy storage technology, the fast development of distributed generation resource, the increasingly increasing of DC load
Add and since with transmission capacity is big, line loss is low, reliability is high etc., advantages, DC grid receive the concern of people.It establishes
DC grid can fully realize the complementation between various energy resources form, Multiple Time Scales, large space span, multiuser types
It is the important development direction of following power grid.
International conference on large HV electric systems（CIGRE）The definition that the technical report of working group B4-52 makees DC grid is:
The DC network that DC grid is made of the transverter of multiple netted and radial connection.However establish DC grid still face
Face several big difficult points, a big key technology therein is shadow of the various AC faults particularly unbalanced fault to DC grid
It rings.After unbalanced fault occurs for AC system, in order to ensure that system failure ride-through capability MMC current conversion stations need continuous service one
Section the time, during which in current conversion station MMC submodules loss and fever cannot ignore.For the reliability for ensureing device and using the longevity
Life, prevents from damaging MMC current conversion stations, needs to add in additional control in the control strategy of normal operation, main at present
Control measure mainly consider the electrical external characteristics and stability of system, to the distribution of current conversion station internal power and MMC submodule situations
Lack consideration.
An important factor for loss and its thermal stress due to power device are influence MMC reliabilities and service life, and change
The fever of stream valve and Wen Sheng constrain the promotion of MMC transimission powers, therefore how to reduce valve loss especially in unbalanced fault
In the case of become research emphasis.However for MMC, the reductions of total losses is it cannot be guaranteed that its reliability and service life
It effectively improves, is lost inside submodule and alternate distribution problem can also impact.
Invention content
In order to supplement the deficiencies in the prior art, considering MMC current conversion stations bulk properties and ensure the reliability of device, the present invention
Closed-loop Control Strategy is divided equally in the alternate losses of MMC in DC grid when providing a kind of net side asymmetry.
It is an object of the invention to the alternate loss of MMC current conversion stations is overcome under net side unbalanced fault to be unevenly distributed to lead to part
Device is damaged when overloading for a long time.The present invention control strategy be：Zero according to needed for negative sequence voltage obtains the alternate power of balance
The amplitude and phase of sequence voltage, active power mean allocation in three phase elements in MMC current conversion stations at this time, but three-phase voltage tune
System is differed than still, and the voltage fluctuation of phase element internal capacitance and two frequency multiplication size of current are still highly asymmetric, this also affects phase
Between loss distribution.In order to make the accurate distribution of alternate loss, the present invention is by calculating each phase power attenuation, and add in PI controls
Device, retrieves the amplitude and phase of residual voltage, this residual voltage is realized alternate in the situation of smaller alternate unbalanced power
Loss evenly distributes, and there is significant drop to damage effect to power device.
Compared with prior art, the present invention have the advantage that for：
When AC system unbalanced fault occurs for DC grid, in the case where ensureing that exporting electrical external characteristics meets the requirements, lead to
It crosses and adds in additional residual voltage to balance alternate loss, which divides equally the operation that closed loop strategy does not influence remaining normal end, and
It only needs change algorithm that can reach drop damage effect well, there is good economy.
Description of the drawings
The present invention is further described below in conjunction with the accompanying drawings.
Fig. 1 shows very bipolar four ends DC grid schematic diagram, and one of current conversion station determines idle control using constant voltage,
Its excess-three current conversion station is using fixed active fixed idle control.Often end current conversion station is divided into positive and negative anodes, and by transformer with exchanging system
System is connected, and A phase earth faults occur at AC1 ends at this time, and for safeguards system fault ride-through capacity, current conversion station needs to put into additional
Control.
Fig. 2 shows MMC in DC grid during net side asymmetry it is alternate loss divide equally Closed-loop Control Strategy schematic diagram, such as
Figure is three-phase symmetrical alternating current, and residual voltage U is calculated between AB phase currentsN, alternate power averaging distribution at this time.It connects
It and controls to obtain new residual voltage U by loss feedback PIN2And alternate accurate distribution is lost.
Fig. 3 shows loss feedback PI control block diagrams, the amplitude that three-phase loss passes through two PI control output residual voltages
Increment Delta U and phase increment, and be added with the original residual voltage being calculated.
Fig. 4 shows the control schematic diagram of MMC current conversion stations totality under unbalanced fault, is calculated including MMC controls under asymmetry
Method module, injected zero-sequence voltage module and alternate loss PI control modules.
Specific embodiment
Below in conjunction with the attached drawing in the embodiment of the present application, the technical solution in the embodiment of the present application is carried out clear, complete
Site preparation describes.
As shown in Figure 1, at AC1 ends A phase earth faults occur for DC grid, since negative-sequence current inhibits, three-phase current is
Symmetrical sine wave, but due to the influence of negative sequence voltage, the power distribution between phase element is uneven, and there are certain phase power devices
Heating loss effectively causes damage.The active power that each phase positive-sequence component generates is steady state value, and DC current distributes in phase element
Depend primarily on the size of each phase element active power of MMC, and projection of each phase negative sequence voltage components on forward-order current not phase
Etc. causing, DC current distribution is uneven.The present invention proposes injection residual voltage such as Fig. 2, i.e., makes to change by injected zero-sequence voltage
Stream device side neutral point potential becomes
(1)
Formula (1) is by adjusting UNWithSize, the power that negative sequence voltage generates in each phase element can be offset.Meet
(2)
It is solved by formula (2)
(3)
It can be seen that according to formula (3), it is only necessary to learn the initial phase of negative sequence voltage amplitude and phase angle and alternating current, it is possible to
The residual voltage of injection is calculated.Residual voltage can be put into immediately when unbalanced fault occurs in MMC, make each phase wattful power
Rate is evenly distributed, and the variation of real-time tracking phase voltage state, so as to prevent power device overload from influencing reliability and using the longevity
Life.
Since the phase element internal capacitance voltage fluctuation of MMC current conversion stations and two frequency multiplication circulation are all related with voltage modulated ratio mj.
And under asymmetrical state, injection residual voltage method can only ensure each phase element active power mean allocations of MMC, it is impossible to do simultaneously
It is more equal than mj to each phase element voltage modulated, and then electric current no longer high degree of symmetry, switching frequency in each phase element is caused also to occur
Variation.Therefore injected zero-sequence voltage method fails that loss is made to evenly distribute alternate, in order to make alternate loss also identical in zero sequence electricity
Be modified on the basis of pressure for
(4)
The corresponding new residual voltage UN2 of Closed-loop Control Strategy is divided equally in loss as shown in Figure 2, and the residual voltage is in original base
Plinth is as obtained by PI control adjustment, and PI is specifically controlled as shown in figure 3, it is each phase device loss of MMC to input, if residual voltage at this time
UN is deviated to A phases direction, the active power in A phase elements increases, and corresponding loss also increases；If the amplitude of UN increases Δ
Active power in U, C phase element is reduced, and corresponding loss is also reduced, and since phase-amplitude offset is little, three phase power is uneven
Weighing apparatus degree very little, within the scope of acceptable.
Closed-loop Control Strategy is divided equally and according to Fig. 4 according to above-mentioned, distributes to calculate with alternate power averaging first herein
The phase and amplitude of the residual voltage injected then as benchmark, three-phase is lost as feedback quantity and passes through PI links
Respectively closed-loop control is carried out, is exported with AB phases differential loss to control, it is lost with C phases and mean difference control is lost with AB phases
System output Δ U.Finally PI outputs result is added in the phase and amplitude of residual voltage, forms new residual voltage to divide equally
Alternate loss.New residual voltage forms three-phase tune after being superimposed with the three-phase voltage reference value that MMC asymmetric controls strategy exports
Wave processed trigger signal the most.
Finally it should be noted that：Described embodiment is only the reality of some embodiments of the present application rather than whole
Apply example.Based on the embodiment in the application, those of ordinary skill in the art are obtained without making creative work
Every other embodiment, shall fall in the protection scope of this application.
Claims (6)
1. Closed-loop Control Strategy is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry, spy is：In net side not
Alternate loss is evenly distributed during symmetric fault, MMC current conversion station fault ride-through capacities has been ensured, has possessed more in flexible direct current power grid
Good prospect.
2. closed-loop control plan is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry according to claim 1
Slightly, it is characterised in that：After unbalanced fault occurs for net side and inhibits negative-sequence current, deposited between negative sequence voltage and forward-order current
It is fluctuated in power cycle, this causes power to be distributed imbalance in three phase elements.
3. closed-loop control plan is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry according to claim 1
Slightly, it is characterised in that：In order to make alternate power distribution uniform, according to negative sequence voltage amplitude and phase calculation obtain residual voltage come
Evenly distribute alternate power.
4. closed-loop control plan is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry according to claim 1
Slightly, it is characterised in that：After input residual voltage, due to the voltage fluctuation of phase element internal capacitance and the height of two frequency multiplication circulation
Asymmetry cause the loss especially switching loss of power device distribute alternately it is still uneven.
5. closed-loop control plan is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry according to claim 1
Slightly, it is characterised in that：On the basis of the residual voltage of calculating, PI controls are mirrored by three phase power device real-time loss value,
The amplitude size of residual voltage is adjusted with this, realizes that the accurate of alternate loss is divided equally.
6. closed-loop control plan is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry according to claim 1
Slightly, it is characterised in that：It is defeated in original asymmetry MMC control algolithms after unbalanced fault occurs for flexible multiterminal element power grid
The sine wave obtained by injected zero-sequence voltage module and alternate loss PI control modules is added on the three-phase sine-wave gone out, finally
Through Overmodulation Method trigger signal is exported to next stage.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810042267.5A CN108206534A (en) | 2018-01-17 | 2018-01-17 | Closed-loop Control Strategy is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810042267.5A CN108206534A (en) | 2018-01-17 | 2018-01-17 | Closed-loop Control Strategy is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN108206534A true CN108206534A (en) | 2018-06-26 |
Family
ID=62605253
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810042267.5A Pending CN108206534A (en) | 2018-01-17 | 2018-01-17 | Closed-loop Control Strategy is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108206534A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109600064A (en) * | 2018-12-05 | 2019-04-09 | 国网重庆市电力公司电力科学研究院 | Modularization multi-level converter exchanges unbalanced fault major loop calculation method, system |
| CN113644677A (en) * | 2020-05-11 | 2021-11-12 | 中国能源建设集团江苏省电力设计院有限公司 | Offshore wind power flexible-direct control method under receiving-end power grid fault |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105119509A (en) * | 2015-07-23 | 2015-12-02 | 上海电力设计院有限公司 | MMC direct circular current inhibition method suitable for asymmetric AC power grid |
-
2018
- 2018-01-17 CN CN201810042267.5A patent/CN108206534A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105119509A (en) * | 2015-07-23 | 2015-12-02 | 上海电力设计院有限公司 | MMC direct circular current inhibition method suitable for asymmetric AC power grid |
Non-Patent Citations (2)
| Title |
|---|
| YINGYU LIANG等: "Arm Current Control Strategy for MMC-HVDC Under Unbalanced Conditions", 《IEEE TRANSACTIONS ON POWER DELIVERY》 * |
| 宋岗平等: "新型牵引供电系统直流侧二次波动分析与抑制", 《电工技术学报》 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109600064A (en) * | 2018-12-05 | 2019-04-09 | 国网重庆市电力公司电力科学研究院 | Modularization multi-level converter exchanges unbalanced fault major loop calculation method, system |
| CN113644677A (en) * | 2020-05-11 | 2021-11-12 | 中国能源建设集团江苏省电力设计院有限公司 | Offshore wind power flexible-direct control method under receiving-end power grid fault |
| CN113644677B (en) * | 2020-05-11 | 2024-04-16 | 中国能源建设集团江苏省电力设计院有限公司 | Offshore wind power flexible direct control method under fault of receiving end power grid |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US9294003B2 (en) | Transformer-less unified power flow controller | |
| CN102522906B (en) | Voltage balance and power balance control method of cascaded H bridge converter | |
| Satyanarayana et al. | A critical evaluation of power quality features using Hybrid Multi-Filter Conditioner topology | |
| CN102723734B (en) | Voltage control method of Y-type connected direct-current bus of serially-connected H bridge multi-level grid-connected inverter | |
| Meral et al. | Mitigation of DC-link voltage oscillations to reduce size of DC-side capacitor and improve lifetime of power converter | |
| CN108206534A (en) | Closed-loop Control Strategy is divided equally in the alternate losses of MMC in DC grid during a kind of net side asymmetry | |
| Xin et al. | AC fault ride-through coordinated control strategy of LCC-MMC hybrid DC transmission system connected to passive networks | |
| Yadav et al. | Scott-tied magnetically linked solar multilevel converter in varying environmental conditions | |
| CN102931864B (en) | Method for voltage balance control of DC (direct current) buses of power units of cascade static var generator | |
| Xiao et al. | Current balancing control for multi-port hybrid AC/DC microgrid | |
| CN107453374A (en) | A kind of control method of 35kV chain H bridges cascade vertical compression | |
| Marzo et al. | Reactive power limits of single-phase and three-phase DC-link VSC STATCOMs under negative-sequence voltage and current | |
| Zhang et al. | FACTS-devices and applications | |
| Hannan et al. | Development of the unified series-shunt compensator for power quality mitigation | |
| Saha et al. | Modelling and control of STATCOM to ensure stable power system operation | |
| CN110011355A (en) | The individual-phase control method of the asymmetric more level mixed energy storage systems of three-phase star cascading | |
| CN105870944B (en) | A kind of alternate Power balance control method of electric power electric transformer | |
| Alabri et al. | Unbalanced modelling of STATCOM and SVC in hybrid load flow method | |
| Kabalci | Reactive power compensation in AC power systems | |
| Wong et al. | Voltage Balance Control of Cascaded H-Bridge Rectifier-Based Solid-State Transformer with Vector Refactoring Technology in αβ Frame | |
| Zhaoming et al. | The Optimized Configuration of Four-terminal Soft Open Point of Active Distribution Network Considering the Influence of Power Supply Capacity | |
| Gao et al. | A method of solving three-phase power unbalance problem with PV inverters connected to the grid in series | |
| CN109921665A (en) | A kind of MMC capacitance voltage balance policy based on average voltage | |
| Raja et al. | Power Quality Enhancement using Dynamic Voltage Restorer in Distributed Networks | |
| Joseph et al. | OPTIMIZING DG FOR DISRUPTIONS IN UNBALANCED SYSTEMS THROUGH GRID-CONNECTED CONVERSION |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WD01 | Invention patent application deemed withdrawn after publication | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20180626 |