CN206023242U - A kind of earthed circuit of the low-voltage direct power distribution network based on flexible direct current networking technology - Google Patents
A kind of earthed circuit of the low-voltage direct power distribution network based on flexible direct current networking technology Download PDFInfo
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- CN206023242U CN206023242U CN201620912700.2U CN201620912700U CN206023242U CN 206023242 U CN206023242 U CN 206023242U CN 201620912700 U CN201620912700 U CN 201620912700U CN 206023242 U CN206023242 U CN 206023242U
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- 238000009826 distribution Methods 0.000 title claims abstract description 70
- 230000006855 networking Effects 0.000 title claims abstract description 21
- 238000005516 engineering process Methods 0.000 title claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims description 17
- 238000003032 molecular docking Methods 0.000 claims description 2
- 230000001052 transient effect Effects 0.000 abstract description 10
- 230000007935 neutral effect Effects 0.000 description 12
- 238000004088 simulation Methods 0.000 description 7
- 238000004458 analytical method Methods 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 4
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- 230000005540 biological transmission Effects 0.000 description 3
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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]
Abstract
The utility model discloses a kind of earthed circuit of the low-voltage direct power distribution network based on flexible direct current networking technology, belongs to electric and electronic technical field.The exchange survey that the earthed circuit of the low-voltage direct power distribution network based on flexible direct current networking technology is set to each VSC voltage source converters is directly grounded by the utility model by alternating current filter and its DC side is earth-free.The utility model lifts stable state and fault transient stability, to improve failover characteristic significant to suppressing the zero sequence earth current of the low-voltage direct power distribution network based on flexible direct current networking technology, keep filter efficiency.
Description
Technical field
The utility model belongs to electric and electronic technical field, and more precisely the utility model is related to a kind of based on flexible straight
The earthed circuit of the low-voltage direct power distribution network of stream networking technology.
Background technology
It is that one kind is based on multi-terminal HVDC transmission (multi based on the low-voltage direct power distribution network of flexible direct current networking technology
Terminal direct current, MTDC), Flexibility Control Technique, the compound technology of distribution energy management, can be used for
Hold the DC loads such as electric automobile battery charger.This distribution network can achieve multiple stage area trend power and mutually supply, and improves charging station and builds
If flexibility, the access capability of electric automobile load can be lifted under existing AC distribution planar network architecture and capacity.
As the busbar voltage of the DC loads such as electric automobile battery charger mostly is 400V or 690V, therefore low-voltage direct distribution
The current conversion station of net is not required to using H bridges or MMC topologys, it is only necessary to using 2 level or 3 level voltage source current transformer (voltage
Sourse converter, VSC) the i.e. achievable conversion by low-voltage distribution voltage to direct current supply voltage of topology.This it is based on
The low pressure Multi-port direct-current distribution system of most ripe topological structure greatly reduces the quantity of switching device in valve, and not only there is unit
The Best Economy of DC bus-bar voltage, also improves the operational reliability of valve group, reduces the loss of valve station.
Earthed circuit has for the temporary steady operation characteristic of the low-voltage direct power distribution network based on flexible direct current networking technology
Material impact.If design of ground system is unreasonable, this TV station area current conversion station can be not only affected, can be also delivered to by DC loop
The current conversion station of other interconnections, affects the temporary steady operation performance at other stations.
The earthing mode of Traditional flexible DC transmission system is most of in current engineering and academic documents to adopt bipolar side
Formula is run, i.e. DC capacitor midpoint is directly grounded, to clamp down on DC side midpoint potential and control dielectric level.Document 1《Two level
VSC-HVDC system dcs side earthing mode is selected》（Guan Minyuan, Xu Zheng,《Automation of Electric Systems》, 2009, 33(5):55-
60）The DC side for proposing back-to-back flexible direct current system is both needed to be grounded, and to limit DC side unbalanced harmonic electric current, but does not carry
Go out the selection of DC side and AC earthing mode.Document 2《Voltage source commutation HVDC transmission system earthing mode is designed》
（Yang Jie, Zheng Jianchao, Tang Guangfu, He Zhiyuan,《Proceedings of the CSEE》, 2010(19):14-19）Propose wave filter midpoint
It is connected with DC capacitor midpoint, then through high resistance ground.Which effectively can suppress, into ground zero-sequence current, to be lifted in DC side
Property point stability, but commutation system in still suffer from still suffering from zero-sequence current point when zero sequence loop, steady-state operation or imbalance fault
Amount, not only increases systematic steady state loss, has also increased the order of severity of transient fault.
Content of the invention
The purpose of this utility model is：For the low-voltage direct power distribution network in prior art based on flexible direct current networking technology
The problem that exists of earthed circuit, there is provided a kind of ground connection electricity of new low-voltage direct power distribution network based on flexible direct current networking technology
Road.
Typically generally comprise AC distribution platform area, distribution based on the low-voltage direct power distribution network of flexible direct current networking technology to change
Stream station and DC power distribution line, AC distribution platform area and distribution current conversion station are multiple, each AC distribution platform area docking one
Distribution current conversion station, wherein AC distribution platform area include AC distribution transformer, are responsible for for the ac high-voltage of AC system being reduced to friendship
Stream low pressure, distribution current conversion station include that VSC voltage source converters, the AC of each VSC voltage source converters are matched somebody with somebody with corresponding exchange
The low-pressure end of the AC distribution transformer of radio area connects, and the DC side of each VSC voltage source converters passes through DC power distribution line
Connected networking.
And the technical solution of the utility model is then：The exchange of each VSC voltage source converters is surveyed straight by alternating current filter
Ground connection, the DC side of each VSC voltage source converters are earth-free.
The beneficial effects of the utility model are as follows：Surveyed due to the exchange of each VSC voltage source converters and pass through alternating current filter
It is directly grounded, neutral harmonic current can be filtered by alternating current filter, it is to avoid Zero-pharse harmonic component flows through transformer circuit simultaneously
Loss is produced, while ensure that the filtration efficiency of alternating current filter.And the earth-free feelings of the DC side of each VSC voltage source converters
Under condition, in earth current, the amplitude of Zero-pharse harmonic greatly reduces, and the steady-state characteristic such as system loss, voltage on line side aberration rate affects
Minimum.Also provable through transient operating mode simulation calculation, selected earthing mode has preferably when AC/DC occurs earth fault
Transient characterisitics.Therefore, the utility model for suppression entered based on the zero sequence of the low-voltage direct power distribution network of flexible direct current networking technology
Earth-current, holding alternating current filter efficiency, lift stable state and fault transient stability, the failover characteristic that improves have important meaning
Justice.
Description of the drawings
Fig. 1 is the low-voltage direct power distribution network canonical system Organization Chart based on flexible direct current networking technology.
Fig. 2 is system earth circuit diagram in low-voltage direct power distribution network separate unit area based on flexible direct current networking technology.
Fig. 3 is the 4 end low-voltage direct power distribution network simulation model figures based on distribution equivalence systematic parameter.
Fig. 4 be wave filter on AC side earth-free when direct current distribution in VSC alternating current filter mid-point voltage situation maps.
Fig. 5 is zero-sequence current amplitude frequency spectrum figure under DC side neutral-point solid ground.
Fig. 6 is zero-sequence current amplitude frequency spectrum figure under DC side neutral point earthed via high resistance.
Fig. 7 is zero-sequence current amplitude frequency spectrum figure under DC side isolated neutral.
Specific embodiment
With reference to the accompanying drawings and with reference to example the utility model is described in further detail.
Embodiment one：
One embodiment of the present utility model, is the low-pressure direct based on flexible direct current networking technology of 4 distributing net platform regions
The earthed circuit of stream distribution network system.
The low-voltage direct power distribution network based on flexible direct current networking technology of 4 distributing net platform region is as shown in figure 1, match somebody with somebody including exchange
Radio area, distribution current conversion station and DC power distribution line, AC distribution platform area and distribution current conversion station are multiple, each AC distribution
A distribution current conversion station is docked in platform area, and wherein AC distribution platform area includes AC distribution transformer, is responsible for the friendship of AC system
Stream high pressure is reduced to AC low-tension, and distribution current conversion station includes prime AC/DC current transformer（Realized by VSC voltage source converters）With rear
Level DC/DC converters, the AC of each prime AC/DC current transformer and the AC distribution transformer in corresponding AC distribution platform area
Low-pressure end connects, and the DC side of each prime AC/DC current transformer is by the connected networking of DC power distribution line.Each prime AC/DC conversion
Device exports DC low-voltage and gives following stage DC/DC converter, then is used for electricity by corresponding rear class DC/DC converter output charging voltage
Electrical automobile charges.
Based on three-phase instantaneous power theory and the sagging Double-loop Control Strategy of optimization, electrical network can be based in PSCAD/EMTDC
Equivalent systematic parameter sets up the simulation model of Fig. 1 distribution network systems, as shown in Figure 3.Platform area 1 can be chosen for canonical analysis object,
Current conversion station adopt 2 level VSC, change of current capacity be 100kVA, switching frequency f=1350Hz, DC voltageU dc=1000V, change of current electricity
Anti- device is 0.7mH（0.158pu.）, DC bus capacitor value is 3800uF, and distribution transformer is 10kV/400V/100kVA, exchange
Wave filter is designed using bivalent high-pass filter.Set stable state to turn for power as 90kVA, reactive compensation power is 40kVA, below
In explanation, AC/DC side generation earth fault sets system operation in the operating mode.
The AC earthed circuit of each VSC voltage source converters of the present embodiment is designed as directly connecing by alternating current filter
Ground, as shown in Figure 2.So that above-mentioned model parameter carries out simulation analysis as an example.Due to AC distribution transformer 400V low pressure in electrical network
Side generally adopts star-like direct grounding way, if alternating current filter is using earth-free mode, the neutral point potential of wave filter is
Impulse level, as shown in Figure 4.The neutral point potential perseverance for comparing alternating current filter direct grounding way is zero, earth-free in the case of
The common-mode oscillation amplitude of neutral point voltage is 477V, which increases the insulation voltage level and manufacturing cost of alternating current filter.With
When, if the DC side of VSC voltage source converters is directly grounded by bipolar fashion, or uneven earth fault occurs, the VSC changes of current
There is zero sequence flow cycle and zero-sequence current in system.As alternating current filter adopts direct grounding way, then can pass through ac filter
Neutral harmonic current is filtered by device, it is to avoid Zero-pharse harmonic component flows through transformer circuit and produces loss, while ensure that exchange
The filtration efficiency of wave filter, and the earth-free mode of alternating current filter cannot then filter neutral harmonic current.Therefore, for low-pressure direct
Stream power distribution network, it is more excellent that the AC earthed circuit of each VSC voltage source converters is designed as being directly grounded by alternating current filter.
The DC side of each VSC voltage source converters of the present embodiment is designed as earth-free mode, as also shown in Figure 2.With above-mentioned
As a example by model carries out simulation analysis.When systematic steady state runs, on the premise of AC is directly grounded, DC side is respectively adopted directly
Ground connection, high resistant (50 Ω) ground connection, under earth-free mode zero sequence earth current spectrum distribution as illustrated in figs. 5-7.Specifically,
Under direct grounding way, 27 zero-sequence currents of switch frequency multiplication are 28.217A, under high grounding, switch 27 zero sequences of frequency multiplication
Electric current is 4.338A, and under earth-free mode, 27 zero-sequence currents of switch frequency multiplication are 0.288A.The off line side line electricity of three kinds of earthing modes
The total harmonic distortion of pressure（Harmonic content）Respectively 1.632%, 1.661% and 1.589%.Therefore, DC side isolated neutral,
Other two kinds of earthing modes are compared, the amplitude of Zero-pharse harmonic greatly reduces in the earth current of earth-free mode, system loss, net
The steady-state characteristics such as side voltage distortion rate affect also minimum.Total harmonic distortion by net side line voltage（Harmonic content）Understand, exchange
When side filter is grounded, no matter which kind of earthing mode DC side is, the filter effect of wave filter on AC side is also in grid-connected permission model
In enclosing, this explanation alternating current filter effectively inhibits neutral harmonic current by Low ESR filter circuit.Therefore, for low-pressure direct
Stream power distribution network, the earth-free mode of direct current side draw is more excellent.
Meanwhile, if DC side takes direct grounding way, can make VSC commutation systems there is zero sequence loop and zero sequence impedance compared with
Little, when AC/DC AC side of converter occurs the imbalance faults such as single-phase earthing, the introducing of its zero-sequence fault electric current makes failure work
Condition compares that DC side is earth-free or the fault condition of high resistant both modes is even more serious.Be directly grounded for AC, direct current
Side is respectively adopted earth-free, high resistance ground and direct grounding way, carries out the fault transient when AC occurs earth fault
Simulation Analysis are obtaining as a result, comparing DC side high resistance ground and being directly grounded, DC side Support Capacitor neutral point is adopted
Earth-free mode is used, in age at failure fault current levels, the direct current voltage across poles range of decrease, and failure during generation singlephase earth fault
In terms of convalescence direct current voltage across poles, phase current level, instantaneous power peak value, there is transient state operation advantage, be therefore preferable
Earthing mode.
Meanwhile, it is directly grounded for AC, DC side is respectively adopted earth-free, high resistance ground and direct grounding way,
The fault transient Simulation Analysis when DC side occurs plus earth failure are carried out, obtaining as a result, DC side is neutral
When point is using earth-free mode, DC side fault current levels, DC Line Fault recover transient overvoltage, compare high resistance ground and straight
Ground connection two ways, in transient fault characteristic there is greater advantage in army, therefore be preferably earthing mode.
Although the utility model is disclosed as above with preferred embodiment, embodiment is not for limiting the utility model
's.In the spirit and scope without departing from the utility model, any equivalence changes that is done or retouching also belong to this practicality new
The protection domain of type.Therefore the content that protection domain of the present utility model should be defined with claims hereof is as mark
Accurate.
Claims (1)
1. a kind of earthed circuit of the low-voltage direct power distribution network based on flexible direct current networking technology, described based on flexible direct current networking
The low-voltage direct power distribution network of technology includes AC distribution platform area, distribution current conversion station and DC power distribution line, AC distribution platform area and
Distribution current conversion station is multiple, each one distribution current conversion station of AC distribution platform area docking, and wherein AC distribution platform area includes handing over
Stream distribution transformer, is responsible for for the ac high-voltage of AC system being reduced to AC low-tension, and distribution current conversion station includes VSC voltage source unsteady flows
Device, the AC of each VSC voltage source converters are connected with the low-pressure end of the AC distribution transformer in corresponding AC distribution platform area,
The DC side of each VSC voltage source converters is by the connected networking of DC power distribution line, it is characterised in that：Each VSC voltage sources unsteady flow
The exchange of device is surveyed and is directly grounded by alternating current filter, and the DC side of each VSC voltage source converters is earth-free.
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| CN201620912700.2U CN206023242U (en) | 2016-08-21 | 2016-08-21 | A kind of earthed circuit of the low-voltage direct power distribution network based on flexible direct current networking technology |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106253319A (en) * | 2016-08-21 | 2016-12-21 | 国家电网公司 | A kind of grounded circuit of low-voltage direct power distribution network based on flexible direct current networking technology |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106253319A (en) * | 2016-08-21 | 2016-12-21 | 国家电网公司 | A kind of grounded circuit of low-voltage direct power distribution network based on flexible direct current networking technology |
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| GR01 | Patent grant | ||
| CP01 | Change in the name or title of a patent holder |
Address after: 100031 Xicheng District West Chang'an Avenue, No. 86, Beijing Co-patentee after: NARI Group Corp. Patentee after: State Grid Corporation of China Co-patentee after: STATE GRID WUHAN HIGH VOLTAGE Research Institute Address before: 100031 Xicheng District West Chang'an Avenue, No. 86, Beijing Co-patentee before: Nanjing Nanrui Group Co. Patentee before: State Grid Corporation of China Co-patentee before: STATE GRID WUHAN HIGH VOLTAGE Research Institute |
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| CP01 | Change in the name or title of a patent holder |