CN109103870A - A kind of distributed generation resource low-voltage direct access system and method containing front end current balancing device - Google Patents
A kind of distributed generation resource low-voltage direct access system and method containing front end current balancing device Download PDFInfo
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- CN109103870A CN109103870A CN201810897310.6A CN201810897310A CN109103870A CN 109103870 A CN109103870 A CN 109103870A CN 201810897310 A CN201810897310 A CN 201810897310A CN 109103870 A CN109103870 A CN 109103870A
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/102—Parallel operation of dc sources being switching converters
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/106—Parallel operation of dc sources for load balancing, symmetrisation, or sharing
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Abstract
The present invention provides a kind of distributed generation resource low-voltage direct access system and method containing front end current balancing device, the system includes a variety of mutually independent distribution type renewable energy power generator, distribution type renewable energy power generator is equally assigned into anode group and cathode group according to each self-capacity, passes through P-type and the side of the positive electrode and negative side of N-type Boost accessing user end DC distribution net；Subscribers' line exit mounts front end current balancing device, realizes that the positive and negative electrode electric current exchanged between user node and external power grid is equal.The present invention effectively stabilizes the positive and negative electrode line current unbalanced phenomena as caused by distributed generation resource and load fluctuation, makes neutral conductor average current zero under stable state；Guarantee that positive and negative electrode electric current, voltage, power are balanced everywhere in bipolarity DC distribution net when stable state, promote power quality under ideal network condition；The present invention realizes that efficient, the flexible direct current of distributed generation resource and load accesses.
Description
Technical field
The present invention relates to distribution type renewable energy power generations and DC distribution technical field, before containing more particularly to one kind
Hold the distributed generation resource low-voltage direct access system and method for current balancing device.
Background technique
Distributed generation grid-connected is to realize the important form of renewable energy development and utilization.In recent years, with photovoltaic, wind-powered electricity generation
Etc. renewable energy develop and use scale rapid growth, in a distributed manner photovoltaic be representative distribution type renewable energy installed capacity
It is constantly improve with the permeability in power distribution network.Distributed generation resource is grid-connected at present, mainly takes exchange connect-in strategy, concrete form
Include: that pressure exchange is grid-connected: renewable generator unit is by pressing AC system in inverter and Industrial Frequency Transformer access；Low pressure is handed over
Flow grid-connected: renewable generator unit is directly accessed low-voltage alternating-current system by Miniature inverter.
It is accessed with scale, high proportion distributed generation resource, conventional AC distribution system faces following technological challenge: system
Trend distribution changes with operational mode；Power distribution network relay protection strategy and way of self-regulation change；A large amount of distribution inversion dresses
Set harmonic pollution and system instability that access causes；Route mistake caused by localized power distribution system interior power total capacity increases
Load problem.Thus the system safety and stability problem and efficiency caused has become and restricts distributed type renewable power supply scale
Change, the critical bottleneck of high permeability access electric system.
Compared to conventional AC power distribution network, direct-flow distribution system has several technical characterstics, comprising: 1. adapts to potential direct current
Load reduces intermediate conversion links, Synergistic and energy-saving；2. transmission capacity is big under identical voltage level (route pressure resistance), coverage area
Extensively；3. line loss is small without kelvin effect；4. not being related to reactive power and frequency issues, network analysis, control are concise clear；5. with
There is inherent compatibility in the renewable power generator of the direct-current-output types such as photovoltaic battery panel, adapt to distributed type renewable power supply Thief zone
Rate access.Therefore, medium/low straightening stream power distribution network, important morphological and high proportion renewable energy point as Future Power System
The ideal carrier of cloth access, has obtained the extensive concern of academia and industry, and in occasions such as data center, communications equipment rooms
Succeed application.
DC distribution net is different according to voltage-to-ground relationship, can be divided into unipolarity and two kinds of standards of bipolarity.It is wherein bipolar
Property DC distribution has following advantages: the optional power supply voltage level of user side is more；Can monopolar operation, power supply reliability is high；It is identical
Under capacity, line-to-earth voltage is low, and insulation stress is small, and safety is good.It is contemplated that bipolarity direct-flow distribution system is as advantage
Technical solution will obtain extensive utilization in the following regional DC distribution net construction.
The mode for constituting the medium/low straightening stream power distribution network of bipolarity can be divided into two kinds: double VSC converter DC side series connection are defeated
Out, " very bipolar " structure of neutral earthing；Take " pseudo- bipolar " structure on ground (also referred to as symmetrical single among single VSC converter DC side
Pole structure).Wherein scheme the features such as progress control method is concise, is widely used in low-voltage direct 2. because having hardware cost low
The building of power distribution network, direct-current micro-grid, basic framework are as shown in Figure 1.
Low-voltage direct power distribution network is as electric system tip link, directly facing user load and distributed generation resource.When adopting
When constructing low-voltage direct distribution system with the symmetrical monopolar standard as shown in Fig. 1 (b), because positive and negative the two poles of the earth institute bringing onto load is uneven,
It is unbalanced to will lead to the two poles of the earth voltage-to-ground, power quality reduces, and influences system normal operation, need to introduce balance of voltage device
(Voltage Balancer, VB) is subject to active control, and structure is as shown in Figure 2.
The technology to generate electricity with distribution type renewable energy is popularized, and the following medium/low pressure direct-flow distribution system, which will become, to be connect
Receive the main carriers of distributed generation resource.High permeability, large-capacity distributing plant-grid connection are " new by the technology for becoming DC distribution net
Normality ".The power output of distributed generation resource has the distinguishing feature that randomness is strong, fluctuating range is big, and a large amount of accesses will be significantly greatly increased
A possibility that direct current distribution positive and negative interpolar power imbalances and potential degree.There are uncompensated loads and uneven distributed generation resource
In the case where, bipolarity DC distribution is unable to ensure using the general bipolarity direct current distribution access scheme based on balance of voltage device
Net positive and negative anodes entirety equilibrium operating, in fact it could happen that: the positive and negative pole tension of user side is unequal；Neutral current is not zero, and over the ground
Current potential deviates；Positive and negative anodes power is not reciprocity under each section of system.And the above problem may cause: user side power quality drop
Low, sensitive load can not work normally；Increase route heating loss；Reduce electrical safety；System positive and negative anodes circuit, equipment are held
It measures and is used less than sufficiently symmetrical, excess loss may be caused or influence the operation of system normal table.
In the prior art, it is mentioned to as a direct-current grid, the document proposes the ambipolar DC micro-electric of low-voltage
Net can provide three line direct currents of high quality according to the control strategy of proposition.But in the document, bipolarity microgrid has been pertained only to
Middle balance of voltage problem, does not refer to power equalization problem.It is not zero for the neutral current being likely to occur in system, system
Under each section positive and negative anodes power not to the problems such as do not propose solution.
In addition, there are also the prior arts to propose the controllable interconnection of gird-connected inverter three-phase output, each phase output power is according to electricity
It presses degree of unbalancedness to carry out the micro-capacitance sensor voltage multimode grading compensation control program of automatic adjusument, it is directly inverse to be able to achieve new energy
Become grid-connected, and micro-capacitance sensor unbalance voltage can be compensated.But of ac is controlled using PI controller, there are certain
Static difference.Meanwhile dynamic property is subject to certain restrictions.Also, on hardware configuration, grid-connected inverters still have volume cost
The disadvantages of big.
To solve the above problems, dedicated interpolar power exchanging device can be introduced in user side, positive and negative anodes circuit electric current is realized
Transfer and secondary Balance route.For this purpose, present invention innovation introduces front end current balancing device concept, and propose,
Summary of the invention
It for the defects in the prior art, is interpolar Balance route and electric energy in the following bipolarity direct-flow distribution system of solution
Quality problems, the distributed generation resource low-voltage direct access system containing front end current balancing device that the object of the present invention is to provide a kind of
And method.The present invention is suitable for the distributed type renewable plant-grid connection bipolarity low-voltage direct power distribution network of low capacity user terminal,
The positive and negative electrode current active balance of access point can be achieved.Also, low pressure distributed generation resource and once-through type load can be achieved in the present invention
High efficiency, flexibility access；It can guarantee that exchanging electric current is equal between any user and distribution positive/negative route, guarantee renewable
Equilibrium operating between DC bipolar under energy high permeability access conditions；The present invention will be interpolar in the following direct-flow distribution system of solution
Balance route and power quality problem provide new technical thought, to effectively facilitate the following direct-flow distribution system construction, operation
It is grid-connected with the direct current of distribution type renewable energy power generation.
The present invention is realized according to following technical scheme:
A kind of distributed generation resource low-voltage direct access system containing front end current balancing device, which is characterized in that including more
The mutually independent distribution type renewable energy power generator of kind, the distribution type renewable energy power generator is according to each self-capacity
It is equally assigned into anode group and cathode group, anode group passes through the anode of P-type Boost accessing user end DC distribution net
Side, cathode group pass through the negative side of N-type Boost accessing user end DC distribution net；Before the mounting of subscribers' line exit
Current balancing device is held, realizes the positive and negative electrode electric current phase exchanged between user node and external power grid.
In above-mentioned technical proposal, the front end converting means is using negative pole structure P-type converter altogether or total anode structure N-
The BOOST converter of type, to realize boosting inverter and MPPT function.
A kind of distributed generation resource low-voltage direct cut-in method containing front end current balancing device of the invention, according to above-mentioned
What access system was realized, which comprises the steps of:
The input terminal of step S1:P- type Boost and the input terminal of N-type Boost respectively with distribution
Renewable energy power generation device connection, wherein the output end positive and negative electrode of P-type Boost respectively with distribution electrode line, in
Property line is connected, and the output end positive and negative electrode of N-type Boost is connected with the neutral conductor, distribution negative line respectively；P-type
The steady state voltage gain of Boost and N-type Boost is equal are as follows:
Wherein, D is switching tube conducting dutycycle, V1For converter DC input voitage, V2For converter direct current output electricity
Pressure.
Step S2: front end current balancing device establishes energy transfer access between positive and negative anodes two sides, realizes that user access point is positive and negative
Pole line current is equal.
In above-mentioned technical proposal, the front end current balancing device, as topological structure, is led to using bridge power transfer circuit
It crosses selection first mode and second mode realizes steady operation；When current balancing device reaches ideal steady-state, then voltage vcKeep steady
Determine and is equal to net side positive and negative anodes total voltage, at this time in switch periods, the average current for flowing through capacitor is zero, that is, have:
ic=0 (2)
As switch S1Or switch S2When conducting, the electric current Δ I for flowing through inductance L will increase, as switch S1Or switch S2Shutdown
When, Δ I will reduce；By changing switch S1Or switch S2Duty ratio d1Or d2The size for adjusting the equivalent transfer current of interpolar, from
And reach stable state.
In above-mentioned technical proposal, the first mode are as follows: switch S2It is held off, switch S1Carry out chop control；
Work as Ip1Greater than In1When, switch S2It is held off, passes through control switch S1Turn-on and turn-off, realize electrode current turn
It moves；As switch S1When conducting, it is formed into a loop S1-L-Ip1With circuit S1-L-In1- C, by capacitor C and positive current source Ip1To inductance L
In be filled with energy；As switch S1When shutdown, switch S2Afterflow will be connected in middle anti-paralleled diode, and then be formed into a loop L-In1-S2Instead
Parallel diode and L-Ip1-C-S2Anti-paralleled diode, to discharge inductance L energy and by positive current source Ip1To capacitor C
Supplement energy；At this point, the port N1/N3 absorbs power from side of the positive electrode always in complete switching cycles；Its port N2/N3 is always
To negative side delivered power, it is achieved in the power transfer from side of the positive electrode to negative side.
In above-mentioned technical proposal, the second mode are as follows: switch S1It is held off, switch S2Carry out chop control；
Work as Ip1Less than In1When, switch S1It is held off, passes through control switch S2Turn-on and turn-off, realize electrode current turn
It moves；As switch S2When conducting, it is formed into a loop S2-In1- L and circuit C-Ip1-L-S2, by capacitor C and cathodal current source In1To inductance L
In be filled with energy；As switch S2When shutdown, switch S1Afterflow will be connected in middle anti-paralleled diode, and then be formed into a loop L-S1Instead simultaneously
Union II pole pipe-Ip1With circuit C-In1-L-S1Anti-paralleled diode, to discharge inductance L energy and by cathodal current source In1To
Capacitor C supplements energy；At this point, the port N1/N3 is always to side of the positive electrode delivered power in complete switching cycles；Its port N2/N3
Always power is absorbed from negative side, is achieved in the power transfer from negative side to side of the positive electrode.
Compared with prior art, the present invention have it is following the utility model has the advantages that
Firstly, the present invention is equipped with front end current balancing device at user and bipolarity DC distribution net points of common connection, it can
The positive and negative electrode line current unbalanced phenomena as caused by distributed generation resource and load fluctuation is effectively stabilized, the neutral conductor under stable state is made
Average current is zero.
Secondly, can control any user node and distribution by being equipped with front end current balancing device in whole user's tie points
Net positive and negative electrode side exchanging electric current is equal；It is positive and negative in bipolarity DC distribution net when to guarantee stable state under ideal network condition
Electrode current, voltage, power are balanced everywhere, promote power quality.
Thirdly, the present invention is cooperated using P-/N- type Boost circuit and bridge power transfer circuit, can be constructed suitable
Renewable energy power generation access system for low voltage dipole direct current distribution；Realize the efficient, clever of distributed generation resource and load
Direct current access living.
Detailed description of the invention
Upon reading the detailed description of non-limiting embodiments with reference to the following drawings, other feature of the invention,
Objects and advantages will become more apparent upon:
Fig. 1 (a) is symmetrical bipolar DC distribution planar network architecture schematic diagram；
Fig. 1 (b) is symmetrical monopolar DC distribution planar network architecture schematic diagram；
Fig. 2 is the three-wire system bipolarity low-voltage direct power distribution network schematic diagram based on balance of voltage device；
Fig. 3 is that the distributed generation resource of the current balancing device containing front end is incorporated to three-wire system bipolarity low-voltage direct distribution network system knot
Structure schematic diagram；
Fig. 4 (a) is P-type Boost circuit topological structure schematic diagram；
Fig. 4 (b) is N-type Boost circuit topological structure schematic diagram
Fig. 5 is front end current balancing device topological structure schematic diagram；
Fig. 6 is front end current balancing device control flow schematic diagram；
Fig. 7 (a) is front and back positive and negative electrode line current waveform figure；
Fig. 7 (b) is neutral current waveform diagram.
Specific embodiment
The present invention is described in detail combined with specific embodiments below.Following embodiment will be helpful to the technology of this field
Personnel further understand the present invention, but the invention is not limited in any way.It should be pointed out that the ordinary skill of this field
For personnel, without departing from the inventive concept of the premise, several changes and improvements can also be made.These belong to the present invention
Protection scope.
The present invention is suitable for the ambipolar low-voltage direct power distribution network of distributed type renewable plant-grid connection of low capacity user terminal,
The positive and negative electrode current active balance of access point can be achieved.
Fig. 3 is that the distributed generation resource of the current balancing device containing front end is incorporated to three-wire system bipolarity low-voltage direct distribution network system knot
Structure schematic diagram；As shown in figure 3, a kind of distributed generation resource low-voltage direct containing front end current balancing device of the invention accesses system
System, which is characterized in that including a variety of mutually independent distribution type renewable energy power generator, the distribution type renewable energy
Power generator is equally assigned into anode group and cathode group according to each self-capacity, and anode group is used by the access of P-type Boost
The side of the positive electrode of family end DC distribution net, cathode group pass through the negative side of N-type Boost accessing user end DC distribution net；
Subscribers' line exit mounts front end current balancing device, realizes the positive and negative electrode electric current phase exchanged between user node and external power grid.
Wherein, the front end converting means is using negative pole structure P-type converter altogether or the BOOST of total anode structure N-type
Converter, to realize boosting inverter and MPPT function.In a specific embodiment of the present invention, renewable energy power generation of the invention
Device can be small-sized fan, photovoltaic panel etc..
A kind of distributed generation resource low-voltage direct cut-in method containing front end current balancing device of the invention, according to above-mentioned
What access system was realized, include the following steps:
The input terminal of step S1:P- type Boost and the input terminal of N-type Boost respectively with distribution
Renewable energy power generation device connection, wherein the output end positive and negative electrode of P-type Boost respectively with distribution electrode line, in
Property line is connected, and the output end positive and negative electrode of N-type Boost is connected with the neutral conductor, distribution negative line respectively；P-type
The steady state voltage gain of Boost and N-type Boost is equal are as follows:
Wherein, D is switching tube conducting dutycycle, V1For converter DC input voitage, V2For converter direct current output electricity
Pressure；
Wherein, P-type Boost topological structure is conventional Boost circuit, as shown in Fig. 4 (a), input-output side
For " cathode altogether " structure.N-type Boost topological structure is that conventional Boost circuit is derived, defeated as shown in Fig. 4 (b)
Enter-outlet side is " altogether anode " structure.It being apparent from by circuit symmetry, the Boost circuit working mechanism of above two structure is similar,
Details are not described herein again.
Step S2: front end current balancing device establishes energy transfer access between positive and negative anodes two sides, realizes that user access point is positive and negative
Pole line current is equal.Its physical essence is consistent with the side VSC balance of voltage device with working mechanism, therefore its specific design can borrow
On the basis of the existing topology of the balance of voltage device that reflects, realized by the Closed-loop Control Strategy for introducing new.
According to concrete application scene described above, considers voltage class and capacity, select bridge as shown in Figure 5 herein
Formula power transfer circuit is as front end current balancing device topological structure.Related physical quantity marking method and reference polarity, direction are such as
As shown in the figure, front end current balancing device is used as topological structure using bridge power transfer circuit, by selecting first mode and the
Two modes realize steady operation；When current balancing device reaches ideal steady-state, then voltage vcIt keeps stablizing and is equal to net side positive and negative anodes
Total voltage, at this time in switch periods, the average current for flowing through capacitor is zero, that is, is had:
ic=0 (2)
As switch S1Or switch S2When conducting, the electric current Δ I for flowing through inductance L will increase, as switch S1Or switch S2Shutdown
When, Δ I will reduce；By changing switch S1Or switch S2Duty ratio d1Or d2The size for adjusting the equivalent transfer current of interpolar, from
And reach stable state (i.e. Ip2=In2, Δ I2=0), specific control block diagram is referring to Fig. 6.
Wherein, the first mode are as follows: switch S2It is held off, switch S1Carry out chop control；
Work as Ip1Greater than In1When, switch S2It is held off, passes through control switch S1Turn-on and turn-off, realize electrode current turn
It moves；As switch S1When conducting, it is formed into a loop S1-L-Ip1With circuit S1-L-In1- C, by capacitor C and positive current source Ip1To inductance L
In be filled with energy；As switch S1When shutdown, switch S2Afterflow will be connected in middle anti-paralleled diode, and then be formed into a loop L-In1-S2Instead
Parallel diode and L-Ip1-C-S2Anti-paralleled diode, to discharge inductance L energy and by positive current source Ip1To capacitor C
Supplement energy；At this point, the port N1/N3 absorbs power from side of the positive electrode always in complete switching cycles；Its port N2/N3 is always
To negative side delivered power, it is achieved in the power transfer from side of the positive electrode to negative side.
Wherein, second mode are as follows: switch S1It is held off, switch S2Carry out chop control；
Work as Ip1Less than In1When, switch S1It is held off, passes through control switch S2Turn-on and turn-off, realize electrode current turn
It moves；As switch S2When conducting, it is formed into a loop S2-In1- L and circuit C-Ip1-L-S2, by capacitor C and cathodal current source In1To inductance L
In be filled with energy；As switch S2When shutdown, switch S1Afterflow will be connected in middle anti-paralleled diode, and then be formed into a loop L-S1Instead simultaneously
Union II pole pipe-Ip1With circuit C-In1-L-S1Anti-paralleled diode, to discharge inductance L energy and by cathodal current source In1To
Capacitor C supplements energy；At this point, the port N1/N3 is always to side of the positive electrode delivered power in complete switching cycles；Its port N2/N3
Always power is absorbed from negative side, is achieved in the power transfer from negative side to side of the positive electrode.
Illustrate technical solution of the present invention below with reference to a specific embodiment of invention:
The system architecture selected in emulation as shown in figure 3, positive and negative electrode group distribution plant-grid connection converter topology respectively such as
Shown in Fig. 4 (a) and Fig. 4 (b), front end current balancing device topology is as shown in Figure 5.
Net side DC voltage ± 375V, positive/negative polar curve, neutral conductor equivalent resistance are 0.1 ' Ω；Front end current balancing device
Inductance 1mH, switching frequency 20kHz；Total equivalent capacity 300uF between positive and negative anodes circuit.
Positive and negative anodes are respectively connected to same size photovoltaic array PV-1 and PV-2, and saturated light shines lower maximum power point voltage
328.2V, maximum power point electric current 33.48A, peak power output 10.99kW；Photovoltaic module is respectively by P-/N- type Boost electricity
Road is connected to positive and negative anodes side.
Simulation time 1.5s, step-length 1us；The illumination condition for changing PV-1 and PV-2 adjusts its output power, and then verifies
Balance route effect under the current balancing device difference operating condition of front end, correlated results are as follows.
PV-1 and PV-2 intensity of illumination numerical value is referring to table 1 under day part.
Table 1
As t=0.5s, front end current balancing device puts into operation；Positive and negative electrode line current I before and after 0.5s and 1.0sp2、In2
With neutral current Δ I2Waveform is respectively as shown in curve I in Fig. 7 (a), (b), curve II, curve III.
Positive line current I before current balancing device starting as seen from Figure 7p2Average value 22.5A, cathode line current In2Average value
16.5A, neutral current Δ I2Average value 6.0A；Current balancing device is put into when t=0.5s, Ip2It is gradually reduced, while In2Gradually
Increase, when t=0.75s reaches balance.As t=1.0s, PV-2 output power step increases, and makes In2It uprushes, Δ I2Less than zero；
Gradually restore under current balancing device control immediately, reaches balance again when t=1.25s.
Above-mentioned simulation result shows that proposed front end current balancing device circuit topology and control strategy are rationally effective,
Corresponding distribution type renewable energy generator unit access bipolarity low-voltage direct distribution system scheme holds water, it can be achieved that pre-
Phase function.
Specific embodiments of the present invention are described above.It is to be appreciated that the invention is not limited to above-mentioned
Particular implementation, those skilled in the art can make a variety of changes or modify within the scope of the claims, this not shadow
Ring substantive content of the invention.In the absence of conflict, the feature in embodiments herein and embodiment can any phase
Mutually combination.
Claims (6)
1. a kind of distributed generation resource low-voltage direct access system containing front end current balancing device, which is characterized in that including a variety of
Mutually independent distribution type renewable energy power generator, the distribution type renewable energy power generator are flat according to each self-capacity
Be positive pole group and cathode group are distributed, anode group passes through the side of the positive electrode of P-type Boost accessing user end DC distribution net,
Cathode group passes through the negative side of N-type Boost accessing user end DC distribution net；Subscribers' line exit mounts front end
Current balancing device realizes the positive and negative electrode electric current phase exchanged between user node and external power grid.
2. a kind of distributed generation resource low-voltage direct access system containing front end current balancing device according to claim 1,
It is characterized in that, the front end converting means is using negative pole structure P-type converter altogether or altogether, the BOOST of anode structure N-type becomes
Parallel operation, to realize boosting inverter and MPPT function.
3. a kind of distributed generation resource low-voltage direct cut-in method containing front end current balancing device, any to 2 according to claim 1
What the access system described in was realized, which comprises the steps of:
The input terminal of step S1:P- type Boost and the input terminal of N-type Boost respectively can be again with distribution
Raw energy source electric generating device connection, wherein the output end positive and negative electrode of P-type Boost respectively with distribution electrode line, the neutral conductor
It is connected, the output end positive and negative electrode of N-type Boost is connected with the neutral conductor, distribution negative line respectively；P-type Boost
The steady state voltage gain of converter and N-type Boost is equal are as follows:
Wherein, D is switching tube conducting dutycycle, V1For converter DC input voitage, V2For converter DC output voltage；
Step S2: front end current balancing device establishes energy transfer access between positive and negative anodes two sides, realizes the positive and negative polar curve of user access point
Road electric current is equal.
4. a kind of distributed generation resource low-voltage direct cut-in method containing front end current balancing device according to claim 3,
It is characterized in that, the front end current balancing device uses bridge power transfer circuit as topological structure, by selecting the first mould
Formula and second mode realize steady operation；When current balancing device reaches ideal steady-state, then voltage vcIt keeps stablizing and is equal to net side
Positive and negative anodes total voltage, at this time in switch periods, the average current for flowing through capacitor is zero, that is, is had:
ic=0 (2)
As switch S1Or switch S2When conducting, the electric current Δ I for flowing through inductance L will increase, as switch S1Or switch S2When shutdown, Δ I
It will reduce；By changing switch S1Or switch S2Duty ratio d1Or d2The size for adjusting the equivalent transfer current of interpolar, to reach
Stable state.
5. a kind of distributed generation resource low-voltage direct cut-in method containing front end current balancing device according to claim 4,
It is characterized in that, the first mode are as follows: switch S2It is held off, switch S1Carry out chop control；
Work as Ip1Greater than In1When, switch S2It is held off, passes through control switch S1Turn-on and turn-off, realize electrode current transfer；
As switch S1When conducting, it is formed into a loop S1-L-Ip1With circuit S1-L-In1- C, by capacitor C and positive current source Ip1Into inductance L
It is filled with energy；As switch S1When shutdown, switch S2Afterflow will be connected in middle anti-paralleled diode, and then be formed into a loop L-In1-S2Instead simultaneously
Union II pole pipe and L-Ip1-C-S2Anti-paralleled diode, to discharge inductance L energy and by positive current source Ip1It is mended to capacitor C
Fill energy；At this point, the port N1/N3 absorbs power from side of the positive electrode always in complete switching cycles；Its port N2/N3 always to
Negative side delivered power is achieved in the power transfer from side of the positive electrode to negative side.
6. a kind of distributed generation resource low-voltage direct cut-in method containing front end current balancing device according to claim 4,
It is characterized in that, the second mode are as follows: switch S1It is held off, switch S2Carry out chop control；
Work as Ip1Less than In1When, switch S1It is held off, passes through control switch S2Turn-on and turn-off, realize electrode current transfer；
As switch S2When conducting, it is formed into a loop S2-In1- L and circuit C-Ip1-L-S2, by capacitor C and cathodal current source In1Into inductance L
It is filled with energy；As switch S2When shutdown, switch S1Afterflow will be connected in middle anti-paralleled diode, and then be formed into a loop L-S1Inverse parallel
Diode-Ip1With circuit C-In1-L-S1Anti-paralleled diode, to discharge inductance L energy and by cathodal current source In1To electricity
Hold C and supplements energy；At this point, the port N1/N3 is always to side of the positive electrode delivered power in complete switching cycles；Begin its port N2/N3
Power is absorbed from negative side eventually, is achieved in the power transfer from negative side to side of the positive electrode.
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