CN110098640A - A kind of low voltage traversing control method and device of photovoltaic parallel in system - Google Patents
A kind of low voltage traversing control method and device of photovoltaic parallel in system Download PDFInfo
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- CN110098640A CN110098640A CN201910549717.4A CN201910549717A CN110098640A CN 110098640 A CN110098640 A CN 110098640A CN 201910549717 A CN201910549717 A CN 201910549717A CN 110098640 A CN110098640 A CN 110098640A
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- H02J3/383—
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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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
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Abstract
This application discloses a kind of low voltage traversing control method of photovoltaic parallel in system and devices, so that photovoltaic parallel in system has low voltage ride-through capability, this method comprises: judging whether that grid voltage sags occur；If so, judging the type of grid voltage sags, and calculate faulted phase voltage drop depth；According to the faulted phase voltage drop depth, it is given to calculate power grid line current positive sequence reactive component；Determine that corresponding power grid line current positive sequence active component is given under different grid voltage sags types；Power grid line current negative sequence active component is given and power grid line current negative phase-sequence reactive component gives and is disposed as zero；Carry out the pulsewidth modulation of the closed-loop current control and inverter module of each order components of power grid line current；When power system restoration is normal, restore conventional Grid-connected Control Strategy.
Description
Technical field
The present invention relates to low voltage crossing technical fields, more specifically to a kind of low-voltage of photovoltaic parallel in system
Traversing control method and device.
Background technique
LVRT (Low voltage ride through, low voltage crossing) ability is to measure photovoltaic parallel in system power grid to fit
One important indicator of answering property.LVRT relevant criterion requires after grid voltage sags, and photovoltaic parallel in system being capable of not off-grid fortune
Row, and centainly idle to support power grid is provided, after power system restoration is normal, photovoltaic parallel in system can quickly recover to routine
It is incorporated into the power networks.
Summary of the invention
In view of this, the present invention provides a kind of low voltage traversing control method of photovoltaic parallel in system and devices, so that
Photovoltaic parallel in system has low voltage ride-through capability.
A kind of low voltage traversing control method of photovoltaic parallel in system, comprising:
Judge whether that grid voltage sags occur；
If so, judging the type of grid voltage sags, and calculate faulted phase voltage drop depth K；
According to the faulted phase voltage drop depth K, calculates power grid line current positive sequence reactive component and give Iqp_LVRT*；Really
Corresponding power grid line current positive sequence active component gives I under fixed different grid voltage sags typesdp_LVRT*；Power grid line current is negative
Sequence active component is given and power grid line current negative phase-sequence reactive component gives and is disposed as zero；
According to the given closed-loop current control for carrying out each order components of power grid line current of each order components of power grid line current and inverse
Become the pulsewidth modulation of module；Wherein, each order components of power grid line current include power grid line current positive sequence is idle, positive sequence is active,
Negative phase-sequence is active and negative phase-sequence reactive component；
When power system restoration is normal, restore conventional Grid-connected Control Strategy.
Optionally, the type of the judgement grid voltage sags, and calculate faulted phase voltage drop depth K；According to described
Faulted phase voltage drop depth K calculates power grid line current positive sequence reactive component and gives Iqp_LVRT*, comprising:
The combination of each order components of type, grid line voltage based on grid voltage sags, faulted phase voltage drop depth K tri-
Mapping table between person is determined under current working by the syntagmatic of each order components of grid line voltage under current working
The type and faulted phase voltage drop depth K of grid voltage sags；Wherein, each order components of grid line voltage include grid line voltage
Positive sequence is idle, positive sequence is active, negative phase-sequence is active and negative phase-sequence reactive component；
Then power grid line current positive sequence reactive component is calculated according to the following formula gives Iqp_LVRT*:
In formula, a is coefficient；Imax=1.05I when grid voltage three-phase symmetrical fallsN, INFor grid line of power grid when normal
Current rating；Imax=0.4I when grid voltage three-phase asymmetry is fallenN。
Optionally, the three-phase output of the photovoltaic parallel in system uses star-like connection, and it is unidirectional that each phase, which all uses prime,
Isolated form DC/DC converter, the two-stage type power conversion architecture that rear class is inverter module；It is corresponding, the different power grids of the determination
Corresponding power grid line current positive sequence active component gives I under voltage sag typedp_LVRT*, comprising:
When network voltage generation three-phase symmetrical falls, power grid line current positive sequence active component gives Idp_LVRT* it is to meet
The arbitrary value united under resistant to flow requirement；
Network voltage occurs single-phase when falling over the ground, and power grid line current positive sequence active component gives Idp_LVRT* value meets
When network voltage generation two is relatively fallen, power grid line current positive sequence active component gives Idp_LVRT* value meets
When two-phase phase fault occurs for network voltage, power grid line current positive sequence active component gives Idp_LVRT* value meets
Optionally, when network voltage generation three-phase symmetrical falls, setting power grid line current positive sequence active component is given
Idp_LVRTIt * is zero；
Network voltage occurs single-phase when falling over the ground, and setting power grid line current positive sequence active component gives Idp_LVRTTaking *
Value meets
When network voltage generation two is relatively fallen, setting power grid line current positive sequence active component gives Idp_LVRTTaking *
Value meets
When two-phase phase fault occurs for network voltage, setting power grid line current positive sequence active component gives Idp_LVRTTaking *
Value meets
It is optionally, described to judge whether that grid voltage sags occur, comprising:
Judge grid line voltage positive sequence active component whether bust, if so, determine occur grid voltage sags.
Optionally, after grid voltage sags and after restoring conventional Grid-connected Control Strategy, further include:
Each inverter module in the photovoltaic parallel in system samples power network current, and reaches in the power network current and set
When fixed current protection threshold value, envelope wave operation is carried out, until when the power network current drops to the current protection threshold value or less, solution
Except envelope wave operation.
A kind of low-voltage crossing controller of photovoltaic parallel in system, comprising:
For judging whether grid voltage sags occur for judging unit；
Component setting unit, for judging the type of grid voltage sags, and calculate failure phase in grid voltage sags
Voltage Drop depth K；According to the faulted phase voltage drop depth K, it is given to calculate power grid line current positive sequence reactive component
Iqp_LVRT*；Determine that corresponding power grid line current positive sequence active component gives I under different grid voltage sags typesdp_LVRT*；Power grid
Line current negative sequence active component is given and power grid line current negative phase-sequence reactive component gives and is disposed as zero；
LVRT control unit, for according to the given electricity for carrying out each order components of power grid line current of each order components of power grid line current
Flow closed-loop control and the pulsewidth modulation of inverter module；Wherein, each order components of power grid line current include power grid line current just
Sequence is idle, positive sequence is active, negative phase-sequence is active and negative phase-sequence reactive component；
Conventional cutting-in control unit, for when power system restoration is normal, running conventional Grid-connected Control Strategy.
Optionally, the component setting unit is specifically used for: each sequence of type, grid line voltage based on grid voltage sags
Mapping table between the combination of component, faulted phase voltage drop depth K three, by each sequence of grid line voltage under current working
The syntagmatic of component determines the type of grid voltage sags and faulted phase voltage drop depth K under current working；Wherein,
Each order components of grid line voltage include that grid line voltage positive sequence is idle, positive sequence is active, negative phase-sequence is active and negative phase-sequence reactive component；
Then power grid line current positive sequence reactive component is calculated according to the following formula gives Iqp_LVRT*:
In formula, a is coefficient；Imax=1.05I when grid voltage three-phase symmetrical fallsN, INFor grid line of power grid when normal
Current rating；Imax=0.4I when grid voltage three-phase asymmetry is fallenN。
Optionally, the three-phase output of the photovoltaic parallel in system uses star-like connection, and it is unidirectional that each phase, which all uses prime,
Isolated form DC/DC converter, the two-stage type power conversion architecture that rear class is inverter module；It is corresponding, the component setting unit
It is specifically used for:
When network voltage generation three-phase symmetrical falls, power grid line current positive sequence active component gives Idp_LVRT* it is to meet
The arbitrary value united under resistant to flow requirement；
Network voltage occurs single-phase when falling over the ground, and power grid line current positive sequence active component gives Idp_LVRT* value meets
When network voltage generation two is relatively fallen, power grid line current positive sequence active component gives Idp_LVRT* value meets
When two-phase phase fault occurs for network voltage, power grid line current positive sequence active component gives Idp_LVRT* value meets
Optionally, the judging unit be specifically used for judge grid line voltage positive sequence active component whether bust, if so, sentencing
Surely grid voltage sags occur.
It can be seen from the above technical scheme that the present invention in grid voltage sags, differentiates the class of grid voltage sags
Type simultaneously calculates faulted phase voltage drop depth K；It calculates power grid line current positive sequence reactive component according to K to give, according to network voltage
Dip type determines that power grid line current positive sequence active component is given, to guarantee that three-phase current is symmetrical, sets power grid line current negative phase-sequence
Given give with power grid line current negative phase-sequence reactive component of active component is zero；The electricity of each order components of power grid line current is carried out with this
The pulsewidth modulation of closed-loop control and inverter module is flowed, until power system restoration is normal.The application gives each order components of power grid line current
Fixed reasonable setting ensure that photovoltaic parallel in system completes safely low voltage crossing.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art without creative efforts, can be with
It obtains other drawings based on these drawings.
Fig. 1 is a kind of photovoltaic parallel in system structural schematic diagram disclosed in the prior art；
Fig. 2 is a kind of two-stage type power conversion unit structural schematic diagram disclosed in the prior art；
Fig. 3 is a kind of low voltage traversing control method flow chart disclosed by the embodiments of the present invention；
Fig. 4 is a kind of conventional cutting-in control block diagram disclosed by the embodiments of the present invention；
Fig. 5 is a kind of LVRT control block diagram disclosed by the embodiments of the present invention；
Fig. 6 is a kind of low-voltage crossing controller structural schematic diagram disclosed by the embodiments of the present invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a kind of low voltage traversing control methods of photovoltaic parallel in system, so that grid-connected system
System has low voltage ride-through capability.
As shown in Figure 1, the basic framework of the photovoltaic parallel in system is as follows: the series-parallel structure of the output end of multiple photovoltaic modulies
At common DC bus；The input terminal of M two-stage type power conversion unit is connected in parallel on the common DC bus, output end
It is together in series and constitutes phase output (M >=1, the output end of this only one two-stage type power conversion unit structure alone as M=1
Cheng Yixiang output)；Three-phase output uses star-like connection mode, is directly accessed exchange transmission and distribution network through net side filter；Such as Fig. 2 institute
Show, the prime of the two-stage type power conversion unit is 1 one-way isolation type DC/DC converter, rear class be N number of input it is in parallel,
Exporting concatenated inverter module, (N >=1, as N=1, the output end of this only one inverter module constitutes alone the two-stage type
The output end of power conversion unit).
Wherein, the one-way isolation type DC/DC converter can be become using LC series resonance current transformer, LLC series resonance
Device or full-bridge DC/DC converter are flowed, but is not limited to.The inverter module can use H bridge structure, but do not do equally and limit to.
As shown in figure 3, the low voltage traversing control method includes:
Step S01: judge whether that grid voltage sags occur, if so, S02 is entered step, if it is not, continuing to run power grid just
Conventional Grid-connected Control Strategy when often, return step S01.
Specifically, the conventional Grid-connected Control Strategy of the photovoltaic parallel in system is as shown in Figure 4:
Sample network voltage usa、usbAnd usc, be sent to software phase-lock loop (DDSRF-SPLL) obtain phase angle θ and
Grid line voltage positive sequence is active, positive sequence is idle, negative phase-sequence is active, negative phase-sequence reactive component usdp、usqp、usdnAnd usqn.Meanwhile sampling electricity
Net electric current isa、isb、isc, it with phase angle θ is sent into grid-connected current component extraction link together obtaining power grid line current positive sequence has
Function, positive sequence are idle, negative phase-sequence is active, negative phase-sequence reactive component Idp、Iqp、IdnAnd Iqn。
Voltage close loop control is carried out to one-way isolation type DC/DC converter, makes its output voltage UdcTrack its input voltage
(output voltage is adjusted according to input voltage and gives Udc*), the output of the voltage close loop is as active point of power grid line current positive sequence
Measure given Idp*；Power grid line current positive sequence reactive component gives Iqp* it is set according to net side power factor command, such as requires net side
It realizes unity power factor operation, then sets power grid line current positive sequence reactive component and give IqpIt * is zero；To realize three-phase current pair
Claim, power grid line current negative sequence active component gives Idn* I is given with power grid line current negative phase-sequence reactive componentqn* it is set as zero；It is right
Each order components I of power grid line currentdp、Iqp、Idn、IqnClosed-loop current control is carried out respectively.Wherein carry out voltage close loop control and electric current
What closed-loop control generallyd use is pi regulator.
By phase angle θ, power grid line current positive sequence active component IdpWith power grid line current positive sequence reactive component IqpIt is sent into Tdq
+/abc link (i.e. 2/3 transform part of positive sequence), while by-θ, power grid line current negative sequence active component IdnIt is negative with power grid line current
Sequence reactive component IqnIt is sent into Tdq-/abc link (i.e. 2/3 transform part of negative phase-sequence), is obtained through Tdq+/abc, Tdq-/abc link
Signal is sent into phase-shifting carrier wave PWM generator and obtains the pulse-width signal of inverter module.
By carrying out above-mentioned each current component closed-loop control and inverter module pulsewidth modulation, to realize to the photovoltaic simultaneously
The conventional cutting-in control of net system.
When network voltage falls, grid line voltage positive sequence active component usdpIt can be fast with falling for network voltage
Speed decline, can identify the generation of grid voltage sags accordingly.Meanwhile by this flashy power grid line current before grid voltage sags
Positive sequence active component gives Idp* current value is recorded as Idp_pre*。
Step S02: judging the type of grid voltage sags, and calculates faulted phase voltage drop depth K；It is mutually electric according to failure
Drop depth K is pressed, power grid line current positive sequence reactive component is calculated and gives Iqp_LVRT*；It determines under different grid voltage sags types
Corresponding power grid line current positive sequence active component gives Idp_LVRT*；Power grid line current negative sequence active component is given and grid line is electric
Stream negative phase-sequence reactive component is given to be disposed as zero.
Specifically, needing to be switched to LVRT control strategy from conventional Grid-connected Control Strategy immediately, at this time when grid voltage sags
It is given given with power grid line current positive sequence reactive component to need to reset power grid line current positive sequence active component, other holdings are not
Become, the LVRT control strategy is as shown in Figure 5.For convenient for distinguish, the power grid line current positive sequence under LVRT control strategy is active
Component is defined as Idp_LVRT*, power grid line current positive sequence reactive component is defined as Iqp_LVRT*, Iqp_LVRT* according to power grid
Drop depth K is by being calculated, Idp_LVRT* be no longer the output of voltage close loop and need to be by being calculated.
Wherein, power grid line current positive sequence reactive component gives Iqp_LVRT* calculating process is as follows:
The grid voltage sags type paid close attention under LVRT control strategy include three-phase symmetrical fall, it is single-phase fall over the ground, two
Relatively fall, four class of two-phase phase fault.Fall in conjunction with the available different network voltage of symmetrical component method and Circuit theory
It falls under type, each order components u of grid line voltagesdp、usdq、usdn、usqnCombination and the corresponding of faulted phase voltage drop depth K close
System, as shown in table 1.
Table 1
In table 1, V is specified power grid phase voltage uN_phPeak value；The value of Q is according to formulaIt is calculated, udNIt is electricity
Grid line voltage positive sequence active component rated value when netting normal, the value for calculating Q can also further calculate out the value of K；D table
What is shown is to fall phase voltage size ufault_phWith specified power grid phase voltage uN_phRatio.
Based on table 1, according to u under current workingsdp、usdq、usdn、usqnSyntagmatic, can determine under current working
The type and faulted phase voltage drop depth K of grid voltage sags.Then it is idle that power grid line current positive sequence is calculated according to the following formula
Component gives Iqp_LVRT*:
In formula (1), a is coefficient；Imax=1.05I when grid voltage three-phase symmetrical fallsN, INFor electricity of power grid when normal
Cable current rating；Grid voltage three-phase asymmetry falls that (i.e. grid voltage sags type is single-phase to fall over the ground, is two opposite
Ground falls or two-phase phase fault) when Imax=0.4IN。
Wherein, power grid line current positive sequence active component gives Idp_LVRT* calculating process is as follows:
Based on symmetrical components and instantaneous power theory, the active of each opposite electrical grid transmission in three-phase system can be derived
The average value expression of power are as follows:
In formula (2), Pa,avg、Pb,avg、Pc,avgIt is the average value of the active power of the opposite electrical grid transmission of A, B, C respectively；Ud p、
Uq p、Ud n、Uq nIt is that power grid phase voltage positive sequence is active, positive sequence is idle, negative phase-sequence is active, negative phase-sequence reactive component respectively；Id p、Iq p、Id n、Iq n
It is that power grid phase current positive sequence is active, positive sequence is idle, negative phase-sequence is active, negative phase-sequence reactive component respectively.
In addition, the power conversion part of the photovoltaic parallel in system is actually by three identical single-phase topology formations, this
The topological structure of sample, which determines, has certain independence between the three-phase of system, from the angle of inverter module DC voltage
It sees, the power transmission of A phase determines the DC voltage of A phases inversion module, and the power transmission of B phase determines B phases inversion module
DC voltage, the power transmission of C phase determines the DC voltage of C phases inversion module.Since one-way isolation type DC/DC becomes
The energy one direction transmission characteristic of parallel operation, when a certain phase absorbs energy from power grid always, the DC voltage meeting of inverter module
Constantly increase.Therefore, it under LVRT control strategy, on the one hand needs to issue certain reactive current according to grid-connected directive/guide；It is another
Aspect needs that any phase is avoided to absorb energy from power grid always, otherwise will lead to the phases inversion module DC voltage and constantly rise
Height, until triggering overvoltage protection, causes fault traversing to fail.Based on this, in order to guarantee that each phase will not under LVRT control strategy
Energy is absorbed from power grid always, needs to meet following formula:
In addition, table 2 is shown under different grid voltage sags types, each order components U of power grid phase voltagedp、Uq p、Ud n、
Uq nCombination and faulted phase voltage drop depth K corresponding relationship.
Table 2
By each order components U of each group of power grid phase voltage in table 2d p、Uq p、Ud n、Uq nIt substitutes into and is made of formula (2), formula (3) respectively
Equation group, solve power grid phase current positive sequence active component Id p, what is obtained at this time is exactly electricity under different grid voltage sags types
The given requirement that need to meet of net phase current positive sequence active component.And since the photovoltaic parallel in system is wye connection, so phase
Electric current is identical with line current, so, the given requirement that need to meet of power grid phase current positive sequence active component at this time namely grid line electricity
It flows positive sequence active component and gives Idp_LVRT* the requirement met is needed, is described in detail below:
1) when network voltage generation three-phase symmetrical falls, the equation group perseverance is set up, so power grid line current positive sequence is active
Component gives Idp_LVRTIt * can with no restriction, as long as value meets the resistant to flow requirement of system；
2) network voltage occurs single-phase when falling over the ground, and power grid line current positive sequence active component gives Idp_LVRT* it needs to meet:
3) when network voltage generation two is relatively fallen, power grid line current positive sequence active component gives Idp_LVRT* it needs to meet:
4) when two-phase phase fault occurs for network voltage, power grid line current positive sequence active component gives Idp_LVRT* it needs to meet:
What needs to be explained here is that lesser watt current facilitates the excessive electric current punching of mitigation grid voltage sags moment
It hits, therefore power grid line current positive sequence active component gives Idp_LVRT* it is preferably met most according to grid voltage sags type
The requirement of small value, the i.e. embodiment of the present invention are recommended: when network voltage generation three-phase symmetrical falls, setting power grid line current positive sequence has
Function component gives Idp_LVRT* minimum value is zero；Network voltage occurs single-phase when falling over the ground, and setting power grid line current positive sequence has
Function component gives Idp_LVRT* value isWhen network voltage generation two is relatively fallen,
It sets power grid line current positive sequence active component and gives Idp_LVRT* value isNetwork voltage
When two-phase phase fault occurs, setting power grid line current positive sequence active component gives Idp_LVRT* value is
Step S03: according to the given current closed-loop control for carrying out each order components of power grid line current of each order components of power grid line current
The pulsewidth modulation of system and inverter module.That is, being controlled according to Fig. 5.Wherein, each order components packet of the power grid line current
Include that power grid line current positive sequence is idle, positive sequence is active, negative phase-sequence is active and negative phase-sequence reactive component.
Step S04: judge whether power grid restores normally, if so, entering step S05；If it is not, return step S02.
Step S05: restore conventional Grid-connected Control Strategy.
Specifically, after network voltage restores normal, usdp=udN, usqp=usdn=usqn=0, it can determine whether network voltage accordingly
Restore normal, and carries out the switching from LVRT control strategy to conventional Grid-connected Control Strategy, such as: firstly, by grid line voltage
Positive sequence reactive component is given by Iqp_LVRT* the value before grid voltage sags is restored to according to certain change rate；Meanwhile by power grid
Line voltage positive sequence active component is given by Idp_LVRT* it changes to before power grid falls according to certain change rate and records in a flash
Idp_pre*, it realizes and smoothly switches conventional Grid-connected Control Strategy；In view of the LVRT time is relatively short, when grid line voltage positive sequence
When active component and grid line voltage positive sequence reactive component are restored to the value before grid voltage sags, inverter module DC bus electricity
Flatten mean value UdcIt can gradually level off to the given value U determined by MPPT algorithmdc*, work as UdcIt is approximately equal to UdcWhen *, cut-in voltage closed loop
Control.Later, system is run according to conventional Grid-connected Control Strategy.In general, when grid voltage sags duration is more than LVRT mark
As defined in standard when length, it is desirable that the protection of photovoltaic parallel in system off-grid.
Optionally, (after being included in grid voltage sags and extensive during the whole service of the photovoltaic parallel in system
After multiple routine Grid-connected Control Strategy), each inverter module detects power network current i every timesa、isbOr iscSampled value reach and set
Fixed current protection threshold value (such as be set as power grid it is normal when 1.2 times of grid line current rating) after, all carry out envelope wave
Operation, that is, the driving pulse for closing all switching tubes in this inverter module are turned off all switching tubes in this inverter module, directly
After dropping to the current protection threshold value or less to the sampled value, envelope wave operation is released, so that power network current isa、isbOr isc
Maximum value be clamped at the current protection Near Threshold without excessive rush of current.
Corresponding to the above method embodiment, the embodiment of the invention also discloses a kind of low-voltages of photovoltaic parallel in system
Control device is passed through, as shown in Figure 6, comprising:
For judging whether grid voltage sags occur for judging unit 10；
Component setting unit 20, for judging the type of grid voltage sags, and calculate failure in grid voltage sags
Phase voltage drop depth K；According to the faulted phase voltage drop depth K, it is given to calculate power grid line current positive sequence reactive component
Iqp_LVRT*；Determine that corresponding power grid line current positive sequence active component gives I under different grid voltage sags typesdp_LVRT*；Power grid
Line current negative sequence active component is given and power grid line current negative phase-sequence reactive component gives and is disposed as zero；
LVRT control unit 30, for according to the given progress each order components of power grid line current of each order components of power grid line current
The pulsewidth modulation of closed-loop current control and inverter module；Wherein, each order components of power grid line current include power grid line current
Positive sequence is idle, positive sequence is active, negative phase-sequence is active and negative phase-sequence reactive component；
Conventional cutting-in control unit 40, for when power system restoration is normal, running conventional Grid-connected Control Strategy.
Optionally, the component setting unit 20 is specifically used for: type, grid line voltage based on grid voltage sags are each
Mapping table between the combinations of order components, faulted phase voltage drop depth K three, it is each by grid line voltage under current working
The syntagmatic of order components determines the type of grid voltage sags and faulted phase voltage drop depth K under current working；Its
In, each order components of grid line voltage include that grid line voltage positive sequence is idle, positive sequence is active, negative phase-sequence is active and negative phase-sequence reactive component；
Then power grid line current positive sequence reactive component is calculated according to the following formula gives Iqp_LVRT*:
In formula, a is coefficient；Imax=1.05I when grid voltage three-phase symmetrical fallsN, INFor grid line of power grid when normal
Current rating；Imax=0.4I when grid voltage three-phase asymmetry is fallenN。
Optionally, the three-phase output of the photovoltaic parallel in system uses star-like connection, and it is unidirectional that each phase, which all uses prime,
Isolated form DC/DC converter, the two-stage type power conversion architecture that rear class is inverter module；It is corresponding, the component setting unit
20 are specifically used for:
When network voltage generation three-phase symmetrical falls, power grid line current positive sequence active component gives Idp_LVRT* power grid is kept
Value before Voltage Drop；
Network voltage occurs single-phase when falling over the ground, and power grid line current positive sequence active component gives Idp_LVRT* value meets
When network voltage generation two is relatively fallen, power grid line current positive sequence active component gives Idp_LVRT* value meets
When two-phase phase fault occurs for network voltage, power grid line current positive sequence active component gives Idp_LVRT* value meets
Optionally, the component setting unit 20 is specifically used for:
When network voltage generation three-phase symmetrical falls, setting power grid line current positive sequence active component gives Idp_LVRTIt * is zero；
Network voltage occurs single-phase when falling over the ground, and setting power grid line current positive sequence active component gives Idp_LVRTTaking *
Value meets
When network voltage generation two is relatively fallen, setting power grid line current positive sequence active component gives Idp_LVRTTaking *
Value meets
When two-phase phase fault occurs for network voltage, setting power grid line current positive sequence active component gives Idp_LVRTTaking *
Value meets
Optionally, judging unit 10 be specifically used for judge grid line voltage positive sequence active component whether bust, if so, judgement
Grid voltage sags occur.
Each embodiment in this specification is described in a progressive manner, the highlights of each of the examples are with other
The difference of embodiment, the same or similar parts in each embodiment may refer to each other.For device disclosed in embodiment
For, since it is corresponded to the methods disclosed in the examples, so being described relatively simple, related place is said referring to method part
It is bright.
The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention.
Various modifications to these embodiments will be readily apparent to those skilled in the art, as defined herein
General Principle can be realized in other embodiments in the case where not departing from the spirit or scope of the embodiment of the present invention.Therefore,
The embodiment of the present invention is not intended to be limited to the embodiments shown herein, and be to fit to principles disclosed herein and
The consistent widest scope of features of novelty.
Claims (10)
1. a kind of low voltage traversing control method of photovoltaic parallel in system characterized by comprising
Judge whether that grid voltage sags occur；
If so, judging the type of grid voltage sags, and calculate faulted phase voltage drop depth K；
According to the faulted phase voltage drop depth K, calculates power grid line current positive sequence reactive component and give Iqp_LVRT*；It determines different
Corresponding power grid line current positive sequence active component gives I under grid voltage sags typedp_LVRT*；Power grid line current negative phase-sequence is active
Component is given and power grid line current negative phase-sequence reactive component gives and is disposed as zero；
According to the given closed-loop current control and inversion mould for carrying out each order components of power grid line current of each order components of power grid line current
The pulsewidth modulation of block；Wherein, each order components of power grid line current include that power grid line current positive sequence is idle, positive sequence is active, negative phase-sequence
Active and negative phase-sequence reactive component；
When power system restoration is normal, restore conventional Grid-connected Control Strategy.
2. low voltage traversing control method according to claim 1, which is characterized in that the judgement grid voltage sags
Type, and calculate faulted phase voltage drop depth K；According to the faulted phase voltage drop depth K, power grid line current positive sequence is calculated
Reactive component gives Iqp_LVRT*, comprising:
The combinations of each order components of type, grid line voltage based on grid voltage sags, faulted phase voltage drop depth K three it
Between mapping table power grid under current working is determined by the syntagmatic of each order components of grid line voltage under current working
The type and faulted phase voltage drop depth K of Voltage Drop；Wherein, each order components of grid line voltage include grid line voltage positive sequence
It is idle, positive sequence is active, negative phase-sequence is active and negative phase-sequence reactive component；
Then power grid line current positive sequence reactive component is calculated according to the following formula gives Iqp_LVRT*:
In formula, a is coefficient；Imax=1.05I when grid voltage three-phase symmetrical fallsN, INThe power grid line current for being power grid when normal
Rated value；Imax=0.4I when grid voltage three-phase asymmetry is fallenN。
3. low voltage traversing control method according to claim 2, which is characterized in that the three-phase of the photovoltaic parallel in system
Output uses star-like connection, and each phase all uses prime for one-way isolation type DC/DC converter, the two-stage that rear class is inverter module
Formula power conversion architecture；Corresponding, corresponding power grid line current positive sequence is active under the different grid voltage sags types of the determination
Component gives Idp_LVRT*, comprising:
When network voltage generation three-phase symmetrical falls, power grid line current positive sequence active component gives Idp_LVRT* resistant to flow to meet system
Arbitrary value under it is required that；
Network voltage occurs single-phase when falling over the ground, and power grid line current positive sequence active component gives Idp_LVRT* value meets
When network voltage generation two is relatively fallen, power grid line current positive sequence active component gives Idp_LVRT* value meets
When two-phase phase fault occurs for network voltage, power grid line current positive sequence active component gives Idp_LVRT* value meets
4. low voltage traversing control method according to claim 3, it is characterised in that:
When network voltage generation three-phase symmetrical falls, setting power grid line current positive sequence active component gives Idp_LVRTIt * is zero；
Network voltage occurs single-phase when falling over the ground, and setting power grid line current positive sequence active component gives Idp_LVRT* value meets
When network voltage generation two is relatively fallen, setting power grid line current positive sequence active component gives Idp_LVRT* value meets
When two-phase phase fault occurs for network voltage, setting power grid line current positive sequence active component gives Idp_LVRT* value meets
5. low voltage traversing control method according to claim 1, which is characterized in that described to judge whether that power grid electricity occurs
Pressure is fallen, comprising:
Judge grid line voltage positive sequence active component whether bust, if so, determine occur grid voltage sags.
6. low voltage traversing control method according to claim 1, which is characterized in that after grid voltage sags and extensive
After multiple routine Grid-connected Control Strategy, further include:
Each inverter module in the photovoltaic parallel in system samples power network current, and reaches setting in the power network current
When current protection threshold value, envelope wave operation is carried out, until releasing envelope when the power network current drops to the current protection threshold value or less
Wave operation.
7. a kind of low-voltage crossing controller of photovoltaic parallel in system characterized by comprising
For judging whether grid voltage sags occur for judging unit；
Component setting unit, for judging the type of grid voltage sags, and calculate faulted phase voltage in grid voltage sags
Drop depth K；According to the faulted phase voltage drop depth K, calculates power grid line current positive sequence reactive component and give Iqp_LVRT*；
Determine that corresponding power grid line current positive sequence active component gives I under different grid voltage sags typesdp_LVRT*；Power grid line current
Negative sequence active component is given and power grid line current negative phase-sequence reactive component gives and is disposed as zero；
LVRT control unit, for being closed according to the given electric current for carrying out each order components of power grid line current of each order components of power grid line current
Ring control and the pulsewidth modulation of inverter module；Wherein, each order components of power grid line current include power grid line current positive sequence without
Function, positive sequence are active, negative phase-sequence is active and negative phase-sequence reactive component；
Conventional cutting-in control unit, for when power system restoration is normal, running conventional Grid-connected Control Strategy.
8. low-voltage crossing controller according to claim 7, which is characterized in that the component setting unit is specifically used
In the combinations of: each order components of type, grid line voltage based on grid voltage sags, faulted phase voltage drop depth K three it
Between mapping table power grid under current working is determined by the syntagmatic of each order components of grid line voltage under current working
The type and faulted phase voltage drop depth K of Voltage Drop；Wherein, each order components of grid line voltage include grid line voltage positive sequence
It is idle, positive sequence is active, negative phase-sequence is active and negative phase-sequence reactive component；
Then power grid line current positive sequence reactive component is calculated according to the following formula gives Iqp_LVRT*:
In formula, a is coefficient；Imax=1.05I when grid voltage three-phase symmetrical fallsN, INThe power grid line current for being power grid when normal
Rated value；Imax=0.4I when grid voltage three-phase asymmetry is fallenN。
9. low-voltage crossing controller according to claim 8, which is characterized in that the three-phase of the photovoltaic parallel in system
Output uses star-like connection, and each phase all uses prime for one-way isolation type DC/DC converter, the two-stage that rear class is inverter module
Formula power conversion architecture；Corresponding, the component setting unit is specifically used for:
When network voltage generation three-phase symmetrical falls, power grid line current positive sequence active component gives Idp_LVRT* resistant to flow to meet system
Arbitrary value under it is required that；
Network voltage occurs single-phase when falling over the ground, and power grid line current positive sequence active component gives Idp_LVRT* value meets
When network voltage generation two is relatively fallen, power grid line current positive sequence active component gives Idp_LVRT* value meets
When two-phase phase fault occurs for network voltage, power grid line current positive sequence active component gives Idp_LVRT* value meets
10. low-voltage crossing controller according to claim 7, which is characterized in that the judging unit is specifically used for
Judge grid line voltage positive sequence active component whether bust, if so, determine occur grid voltage sags.
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