CN106712089A - Multifunctional distributed power supply grid-connection device based on nine-switch-tube inverter - Google Patents
Multifunctional distributed power supply grid-connection device based on nine-switch-tube inverter Download PDFInfo
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- CN106712089A CN106712089A CN201710041343.6A CN201710041343A CN106712089A CN 106712089 A CN106712089 A CN 106712089A CN 201710041343 A CN201710041343 A CN 201710041343A CN 106712089 A CN106712089 A CN 106712089A
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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
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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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
- H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
- H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
Abstract
The invention discloses a multifunctional distributed power supply grid-connection device based on a nine-switch-tube inverter. When a power grid operates normally, one output port of the NSI is connected to a power distribution network through a grid-connection transformer, electric energy generated by a micro-source is inverted into an alternating current meeting grid-connection conditions, and DC bus voltage of a current transformer is kept stable; the other output port of the NSI is connected to a power grid in a parallel manner, and a harmonic current compensation value is added to a current loop to improve power grid electric energy quality; and when the power grid has fault, low-voltage ride through of a distributed power supply is realized through coordinative cooperation between the two output ports of the NSI. Compared with a back-to-back inverter structure, the device not only can save three switch tubes and reduce system cost, but also can carry out compensation on the power quality problem of the power distribution network, thereby realizing LVRT of the distributed power supply under the fault state of the power distribution network and improving operation safety and stability of the power grid after the distributed power supply is accessed.
Description
Technical field
The present invention relates to the configuration of multi-functional distributed power source grid-connecting apparatus of the one kind based on nine switching tube inverters (NSI)
Scheme, it is adaptable to the cutting-in control of distributed power source, the public power caused after being accessed for a large amount of non-linear and impact loads of compensation
Net harmonic pollution problems, realize low voltage crossing of the distributed electrical source inventer under grid failure state, based on nine switching tubes
The topological structure of inverter, and a kind of new distribution type power grid inverter for designing, belong to distributed generation technology neck
Domain.
Background technology
With the exhaustion of earth traditional fossil energy, regenerative resource turns into the new study hotspot in the whole world.Wherein photovoltaic, wind
Electric industry development is rapid, and technology relative maturity has been achieved with scale business development.In grid voltage sags, distributed electrical
The DC side in source is likely to occur a series of transient processes such as overvoltage, overcurrent, and then damages distributed power source grid-connected converter
In power electronic equipment.The generating sets such as the grid-connected directive/guide requirement blower fan of new distributed power source, photovoltaic must possess certain
Low voltage ride-through capability.
At the same time, as the nonlinear-load and distributed generation system using power electronic equipment largely access distribution
Net so that the harmonic content abruptly increase of power network current, above-mentioned harmonic pollution makes the harmonic pollution of utility network be on the rise.Larger
Harmonic current will directly threaten the operation safety of power distribution network.In prior art means, active power filtering (APF) technology is
One of Main Means of harmonic pollution in electric power net are administered, it is in power network, especially distribution and more and more extensive with the application of electrical domain.
To solve the problems, such as low voltage crossing when distributed power source is accessed, domestic and foreign scholars propose numerous distributed power sources
Low voltage crossing scheme, summary gets up to be divided into following 3 class：(1) install electric power generation unloading resistance additional in DC link, disappeared by electric power generation unloading resistance
, can be limited in the fluctuation range of DC bus-bar voltage in 10% rated range by the unnecessary active power of consumption, but system effectiveness
Relatively low, heat dissipation design is difficult；(2) DC bus-bar voltage is controlled by pusher side current transformer, it is impossible to which the energy stores of release are in machine
In group driving-chain, because generator speed is uncontrolled, risk can be brought to system safety operation；(3) will be many using energy storage device
Remaining energy stores are got up, although be capable of achieving power smooth, but can be increased system cost.The present invention is according to Germany's E.ON standard gauges
It is fixed, the low voltage crossing of distributed power source is realized to grid entry point injection reactive power by two net side current transformer ports.
Existing power quality problem shows as harmonic pollution and no-power vacancy, and traditional alternative administering method is main
It is divided into the inactive component as representative with passive power filter, parallel capacitor, and with active filter and static nothing
Work(compensator is the active equipment of representative.Wherein inactive component has that structural principle is simple, operational reliability is high, maintenance cost is low
The advantages of, but also have the potential danger that resonance occurs with electrical network parameter, and when system is run in small mode, easily cause idle
Overcompensation, increases system loss, threatens safe operation of electric network.And active equipment is because having, and the method for operation is flexible, autgmentability is strong, tune
The advantages of section speed is fast, just progressively substitution inactive component turns into the master of power quality controlling device development in Distribution network
Stream.
The content of the invention
Goal of the invention：In order to solve improvement, the distribution of distributed power source grid entry point harmonic wave and the power quality problem such as idle
The problem of formula power supply low voltage crossing control, the present invention devises a kind of multi-functional point based on nine switching tube inverters (NSI)
The allocation plan of cloth power grid device.The two groups of output ports provided using nine switching tube inverters, are respectively constituted point
The main and auxiliary current transformer port of net side of cloth power grid inverter, when power network normally runs, realizes the grid-connected feedback of distributed power source
Harmonics restraint and reactive-load compensation are carried out while energy, to improve the power network quality of power supply；When electric network fault occurs Voltage Drop, lead to
Cross the coordination control between two output ports of NSI to meet the requirement of low voltage crossing, so as to the handle in same set of grid-connecting apparatus
Distributed power source cutting-in control, idle harmonic current compensation, low voltage ride-through function are combined together, reduce system investments into
This, improves the stability and the power network quality of power supply of distributed power source.
Technical scheme：
A kind of multi-functional distributed power source grid-connecting apparatus for being based on nine switching tube inverters, including nine switching tube inverters；
The upper output port of of the nine switching tubes inverter is connected by grid-connected transformer with power network, and another lower output port is simultaneously
Couple into power network；Two output ports of the nine switching tubes inverter form the net side of distributed electrical source grid-connected inverter respectively
Main and auxiliary current transformer port；
When power network normally runs, be reverse into for the electric energy that micro- source produces and meet grid-connected bar by the net side main convertor port
The alternating current of part, and maintain current transformer DC bus-bar voltage stabilization；The auxiliary current transformer port of net side adds humorous in electric current loop
Ripple current offset values；
In electric network fault, using the cooperation between two output ports, realize that the low-voltage of distributed power source is worn
More, the energy that distributed power source is produced smoothly is sent into power network, while sending idle to power network, supports that line voltage recovers.
The nine switching tubes inverter is formed by three bridge arm parallel connections；The bridge arm includes three switches being cascaded
Pipe；
Definition is upper switching tube near dc bus positive switch pipe, is designated as SjH(j=a, b, c)；Born near dc bus
Pole switching tube is lower switching tube, is designated as SjL(j=a, b, c)；It is remaining after the upper and lower switching tube of removing in three switching tubes of each bridge arm
Under switching tube be breaker in middle pipe, be designated as SjM(j=a, b, c)；
By the modulation wave signal U of the upper and lower output port of nine switching tubes inverterrefH、UrefLShared triangular carrier is carried out
Modulation；If UrefHMore than carrier wave, then the switching tube S of phase is corresponded tojH(j=a, b, c) is turned on, otherwise SjHShut-off；If UrefLMore than load
Ripple, then correspond to the switching tube S of phasejL(j=a, b, c) is turned off, otherwise SjLConducting；And per phase intervalve SjMThe drive of (j=a, b, c)
Dynamic signal is correspondence phase SjHWith SjLXOR obtain.
The net side main convertor controls d axles respectively using the feedforward compensation dq decoupling modes based on grid voltage orientation
Watt current and q axle reactive currents；
Net side main convertor is that control is completed in dq coordinate systems, and wherein d axles component is in the same direction with grid entry point voltage vector；
Relation between filter capacitor terminal voltage vector and net side main convertor Injection Current vector is：
Wherein L1It is filter reactance, ed、eqIt is filter capacitor C1D, q axle component of both end voltage, ucd、ucqOpen for described nine
Close d, q axle component of pipe inverter upper port output voltage, id1、iq1It is the nine switching tubes inverter upper port output current
D, q axle component, ωeIt is system angular frequency；
The net side main convertor uses double -loop control, wherein DC bus-bar voltage control outer shroud, by by dc bus
The reference value u of voltagedcrefWith measured value udcCompare after making the difference, d shaft current command values i is produced by PI controllersd1ref, pass through
Given power factor setting q shaft current command values iq1ref；By power network nominal situation current instruction value id1ref、iq1refOr power network
Fault condition current instruction value igd1ref、igq1refThe current inner loop that input decoupling PI controllers are constituted, produces corresponding modulation letter
Number d, q axle component u*gd1And u*gq1, three-phase modulations signal is obtained by Park inverse transformations, further according to PWM algorithm, it is right to complete
The output control of the nine switching tubes inverter upper port.
3rd, multi-functional distributed power source grid-connecting apparatus according to claim 1, it is characterised in that：The net side auxiliary
Current transformer is that control is completed in dq coordinate systems, and wherein d axles component is in the same direction with grid entry point voltage vector；Filter capacitor terminal voltage
Relation between vector and net side main convertor Injection Current vector is：
Wherein L2It is filter reactance, Ugd、UgqIt is filter capacitor C2D, q axle component of both end voltage, uad、uaqIt is NSI upper ends
D, q axle component of mouth output voltage, id2、iq2It is d, q axle component of NSI upper port output currents, ωeIt is system angular frequency；
The net side AuCT uses monocyclic control, the current instruction value i that harmonic detecting link is obtaineddh、iqhOr
Electric network fault operating mode current instruction value igd2ref、igq2refD, q shaft current measured value i corresponding with subordinate inverter port respectivelyd2、
iq2After subtracting each other, the electric current loop that input decoupling PI controllers are constituted produces corresponding modulated signal d, q axle component u*gd2And u*gq2,
Three-phase modulations signal is obtained by Park inverse transformations, further according to PWM algorithm, is completed to the nine switching tubes inverter lower end
The output control of mouth.
When power network normally runs, the reference current value of the net side AuCT is harmonic current compensation value；Institute
The detection for stating harmonic current is as follows：
Digital phase-locked loop PLL tracks power network a phase voltage phases, threephase load electric current ia、ib、icAfter being converted through abc/dq
Active and reactive current component i under to two-phase rotating coordinate systemd、iq, by id、iqBy after low pass filter, obtaining load base
DC component i corresponding to ripple electric currentdb、iqb, then idWith idbDifference be the d axle components i of harmonic current in dq coordinate systemsdh, iq
With iqbDifference be the q axle components i of harmonic current in dq coordinate systemsqh。
When electric network fault and when there is Voltage Drop, the main and auxiliary current transformer of net side switches to LVRT patterns, in reactive power support and
Two aspects of active balance cooperate；
In reactive power support aspect, the reference value of NSI output reactive current controls is respectively set as：
U in formulagIt is line voltage, urefIt is line voltage before failure, igq1refAnd igq2refRespectively main convertor and auxiliary
Current transformer q axles are idle instruction current, all values are perunit value；
System Reactive Power support policy determination after, calculate net side current transformer keep system energy balance on the premise of,
The d axle command current values of the main and auxiliary current transformers of NSI are respectively：
I in formulagd1refAnd igd2refThe respectively main and auxiliary active instruction current of current transformer d axles, PsThere to be system output before failure
Work(power.
When voltage on line side occurs depth to be fallen, auxiliary is controlled and dc bus discharging circuit using DC chopped-wave, straight
Stream side voltage control is in 1.1 times of perunit values.
Beneficial effect：(1) construct the main and auxiliary grid-connected port of distributed power source using two output ports of NSI, can reach with
Tradition leans against back type and controls that inverter identical is grid-connected and compensation effect entirely, but is compared using structure of the present invention and lean against back type
Circuit can but save 3 switching tubes, so as to reduce device volume, reduce cost of investment；(2) using auxiliary port in parallel, in electricity
When net does not break down, active filter function is realized, using the active filter method of operation is flexible, autgmentability strong, regulation speed
The fast advantage of degree, realizes the improvement to the power quality problem such as distributed power source grid entry point harmonic wave, idle, improves power network electric energy matter
Amount；(3) in grid collapses, distributed power source grid-connected converter is realized by two output ports for coordinating control NSI
LVRT strategies, reactive power support is provided according to international relevant criterion to power network, and reduces the radiating pressure of DC side-discharging resistance as far as possible
Power, maintains system capacity balance, realizes the low voltage crossing of distributed power source.The present invention puies forward system, and distributed power source is grid-connected
Control, idle harmonic current compensation, low voltage ride-through function are combined, and improve the stability and the quality of power supply of system, have
Cost performance and system availability higher, therefore with good future in engineering applications.
Brief description of the drawings
Fig. 1 is 12 switching tube inverters and nine switching tube inverter topology graphs of a relation.
Fig. 2 is the multi-functional distributed power source grid-connecting apparatus structure chart based on nine switching tube inverters (NSI).
Fig. 3 is the net side main convertor control block diagram of multi-functional distributed power source grid-connecting apparatus.
Fig. 4 is the net side AuCT control block diagram of multi-functional distributed power source grid-connecting apparatus.
Fig. 5 is multi-functional distributed power source grid-connecting apparatus Harmonic currents detection schematic diagram.
Specific embodiment
The present invention is further described below in conjunction with the accompanying drawings.
The present invention uses nine switching tube inverters as power electronics main circuit, for distributed power source grid-connecting apparatus provide two
Individual independent output port.
Fig. 1 gives the topological relation between 12 switching tube inverters and nine switching tube inverters.Be on the left of Fig. 1 compared with
Frequently with lean against the switching tube inverter of back type 12, the right side of Fig. 1 is new nine switching tubes inverter.It can be seen that nine switching tubes are inverse
Change device is same with 12 switching tube inverters externally to provide two groups of three-phase output ends mouthful, but nine switching tube inverters are than ten
Two switching tube inverters save 3 switching tubes.By comparing, nine switching tube inverters have compact conformation, cost relatively low
Advantage.Therefore, using two output ports of nine switching tube inverters, the master of distributed power source and network interface is formed respectively
Converter part and AuCT part.
Define three switching tubes being cascaded and constitute a bridge arm, then the nine of NSI switching tubes can be divided into three
Bridge arm.In order to avoid by dc bus short circuit, three switching tubes connected on each bridge arm can not be simultaneously turned on.When load contains
When having inductive element, in order to avoid output end is hanging, should control at least while there are two switching tubes to turn on each bridge arm.Definition
It is upper switching tube near dc bus positive switch pipe, is designated as SjH(j=a, b, c)；Under being near dc bus negative switch pipe
Switching tube, is designated as SjL(j=a, b, c)；In three switching tubes of each bridge arm, remaining switching tube is after removing upper and lower switching tube
Breaker in middle pipe, is designated as SjM(j=a, b, c).By the modulation wave signal U of the upper and lower output ports of NSIrefH、UrefLShare triangular carrier
It is modulated.If UrefHMore than carrier wave, then the switching tube S of phase is corresponded tojH(j=a, b, c) is turned on；Otherwise SjHShut-off.If UrefLGreatly
In carrier wave, then the switching tube S of phase is corresponded tojL(j=a, b, c) is turned off；Otherwise SjLConducting.And per phase intervalve SjM(j=a, b, c)
Drive signal be correspondence phase SjHWith SjLXOR obtain.
Fig. 2 gives the multi-functional distributed electrical source grid-connected inverter structure chart based on nine switching tube inverters (NSI).If
A kind of allocation plan of the multi-functional distributed power source grid-connecting apparatus based on nine switching tube inverters (NSI) is counted.Opened using nine
Two groups of output ports that pipe inverter is provided are closed, the main and auxiliary current transformer of net side of distributed electrical source grid-connected inverter is respectively constituted
Port, when power network normally runs, the output port provided using NSI constitutes main output port, it is ensured that system and
Net energy regenerative, while constituting auxiliary output terminal mouthful using another output port that NSI is provided, realizes idle harmonic compensation,
Improve the quality of power supply on grid entry point periphery, realize carrying out harmonics restraint and reactive-load compensation while distributed power source grid-connected energy regenerative,
To improve the power network quality of power supply；When electric network fault occurs Voltage Drop, controlled by the coordination between two output ports of NSI real
The LVRT strategies of existing distributed power source, and reactive power support is provided to power network according to relevant criterion, DC side-discharging electricity is reduced as far as possible
The radiating pressure of resistance, maintains system capacity balance to meet the requirement of low voltage crossing, so as to the handle in same set of grid-connecting apparatus
Distributed power source cutting-in control, idle harmonic current compensation, low voltage ride-through function are combined together, reduce system investments into
This, improves the stability and the power network quality of power supply of distributed power source, there is cost performance and system availability higher.
The DC side parallel of wherein nine switching tube inverters has Equivalent DC bus capacitor C, while being parallel with micro- source control
And DC chopped-wave link is used to control DC bus-bar voltage and micro battery to realize the functions such as MPPT.The one of nine switching tube inverters
Individual output port is by by inductance L1, electric capacity C1The LC filter circuits of composition and grid-connected transformer access power network, and micro- source is produced
Electric energy is reverse into the alternating current for meeting grid-connected conditions, and maintains current transformer DC bus-bar voltage stabilization；Nine switching tube inverters
Another output port is by by inductance L2, electric capacity C2The LC filter circuits of composition are directly accessed the grid side of grid-connected transformer,
Harmonic current compensation value is added in electric current loop, for improving the power network quality of power supply.Grid side includes net side equivalent reactance LgridWith
Three-phase equivalent voltage source Uj(j=a, b, c).Due to that, there may be circulation, can be given between two inverter ports of parallel running
Parallel system brings the adverse effect for increasing switch element burden, increasing system loss, even damage power device.The present invention is logical
Crossing grid-connected transformer will be isolated as the two of main and auxiliary inverter output ports, to eliminate the ring between main and auxiliary current transformer
Stream.
It is illustrated in figure 3 the net side main convertor controller chassis of multi-functional distributed power source grid-connecting apparatus proposed by the invention
Figure, net side main convertor is used to maintain NSI DC side busbar voltages, while adjusting the friendship of reactive power between NSI and bulk power grid
Change, its major control target is that the active power for producing distributed power source injects power network, and adjusts power factor on request.
Net side main convertor controls d axles active respectively using the feedforward compensation dq decoupling modes based on grid voltage orientation
Electric current and q axle reactive currents.
Net side main convertor is that control is completed in dq coordinate systems, and wherein d axles component is in the same direction with grid entry point voltage vector.
Can be by the relationship description between filter capacitor terminal voltage vector and net side main convertor Injection Current vector：
Wherein L1It is filter reactance, ed、eqIt is filter capacitor C1D, q axle component of both end voltage, ucd、ucqIt is NSI upper ports
D, q axle component of output voltage, id1、iq1It is d, q axle component of NSI upper port output currents, ωeIt is system angular frequency.
Net side main convertor in Fig. 3 uses double -loop control, wherein DC bus-bar voltage to control outer shroud, by the way that direct current is female
The reference value u of line voltagedcrefWith the measured value u of DC bus-bar voltagedcCompare after making the difference, d shaft currents are produced by PI controllers
Command value id1ref, q shaft current command values i is set by the power factor for givingq1ref；By power network nominal situation current instruction value
id1ref、iq1refOr electric network fault operating mode current instruction value igd1ref、igq1refThe current inner loop that input decoupling PI controllers are constituted,
Produce corresponding modulated signal d, q axle component u*gd1And u*gq1, three-phase modulations signal is obtained by Park inverse transformations, further according to
PWM algorithm, completes the output control to NSI upper ports.
When power network normally runs, NSI DC bus-bar voltages are stablized by the dual-loop controller of d axle components, so that
The active power for obtaining distributed power source generation can in time inject power network；By the monocyclic controller to q axle components, according to prior
The reactive power of setting exports corresponding reactive current reference value.In electric network fault, d, q axle point of main inverter port current
Amount is determined by low voltage crossing control strategy.
It is illustrated in figure 4 the net side AuCT control of multi-functional distributed power source grid-connecting apparatus proposed by the invention
Block diagram, adds harmonic current compensation value in the electric current loop of net side AuCT, for controlling to produce compensation electric current, improve power network
The quality of power supply.When power network is normal, under APF patterns, its instruction current is harmonic detecting link to AuCT port working
The compensation current of acquisition；When the grid fails, AuCT port is engaged with main convertor port, realizes distributed electrical
The low voltage crossing of source grid-connected inverter.
Net side AuCT port working controls it to power network harmonic and nothing in active filter (APF) pattern
Work(offset, the quality of power supply for improving distributed power source grid entry point.The current reference value source of net side AuCT port
From harmonic current detection, and in d-q coordinate systems, the tracking to instruction current is realized using electric current loop uneoupled control.
Net side AuCT is that control is completed in dq coordinate systems, and wherein d axles component is same with grid entry point voltage vector
To.Can be by the relationship description between filter capacitor terminal voltage vector and net side main convertor Injection Current vector：
Wherein L2It is filter reactance, Ugd、UgqIt is filter capacitor C2D, q axle component of both end voltage, uad、uaqIt is NSI upper ends
D, q axle component of mouth output voltage, id2、iq2It is d, q axle component of NSI upper port output currents, ωeIt is system angular frequency.
Net side AuCT in Fig. 4 uses monocyclic control, the current instruction value i that harmonic detecting link is obtaineddh、
iqhOr electric network fault operating mode current instruction value igd2ref、igq2refD, q shaft current measured value corresponding with subordinate inverter port respectively
id2、iq2After subtracting each other, the electric current loop that input decoupling PI controllers are constituted produces corresponding modulated signal d, q axle component u*gd2With
u*gq2, three-phase modulations signal is obtained by Park inverse transformations, further according to PWM algorithm, complete the output control to NSI lower ports
System.
When power network normally runs, AuCT works in active filter pattern, now the reference of AuCT
Current value is the compensation rate of side harmonics electric current.Therefore harmonic current compensation value is added to electric current loop, is used to improve power network
The quality of power supply.If Fig. 5 is Harmonic currents detection schematic diagram proposed by the present invention.Digital phase-locked loop PLL tracks power network a phase voltage phases
Position, is used to ensure the precision of Harmonic currents detection, threephase load electric current ia、ib、icTwo-phase rotation is obtained after being converted through abc/dq to sit
Active and reactive current component i under mark systemd、iq, by id、iqBy after low pass filter, obtaining corresponding to load fundamental current
DC component idb、iqb, then idWith idbDifference be the d axle components i of harmonic current in dq coordinate systemsdh, iqWith iqbDifference be
The q axle components i of harmonic current in dq coordinate systemsqh。
When electric network fault and when there is Voltage Drop, the power output of net side inverter is restricted.If distributed electrical
The power in source is not adjusted, and unnecessary energy will cause combining inverter DC side overvoltage, jeopardize the operation of distributed power source
Safety.At this point it is possible to make full use of the capacity of main and auxiliary current transformer, two current transformers are switched into LVRT patterns, in reactive power support
Cooperated with two aspects of active balance, so as to the energy that distributed power source is produced smoothly is delivered into power network, while to power network
Reactive power is sent, supports that line voltage recovers.
In reactive power support aspect, specified according to German E.ON company standards：Line voltage often falls 1% rated voltage,
Distributed power source by taking wind generator system as an example need to send the reactive current of 2% rated current size to power network.Therefore, it is distributed
Formula power supply meets the requirement of reactive current first, and the amplitude according to grid voltage sags determines to be conveyed to the reactive current of power network
Size.The reference value of NSI output reactive current controls is respectively set as：
U in formulagIt is line voltage, urefIt is line voltage before failure, igq1refAnd igq2refRespectively main convertor and auxiliary
Current transformer q axles are idle instruction current, all values are perunit value.
System Reactive Power support policy determination after, calculate net side current transformer keep system energy balance on the premise of,
The d axle command current values of the main and auxiliary current transformers of NSI are respectively：
I in formulagd1refAnd igd2refThe respectively main and auxiliary active instruction current of current transformer d axles, PsThere to be system output before failure
Work(power.But due to the limitation of NSI output currents, the control strategy of net side current transformer can only meet and necessarily fall degree
LVRT.When voltage on line side occurs when depth is fallen, it is necessary to aid in using DC chopped-wave to control and dc bus discharging circuit, straight
Stream side voltage control is in 1.1 times of perunit values.
The technology that the present invention is not particularly limited is prior art.
The above is only the preferred embodiment of the present invention, it should be pointed out that：For the ordinary skill people of the art
For member, under the premise without departing from the principles of the invention, some improvements and modifications can also be made, these improvements and modifications also should
It is considered as protection scope of the present invention.
Claims (7)
1. a kind of multi-functional distributed power source grid-connecting apparatus for being based on nine switching tube inverters, it is characterised in that：Including nine switches
Pipe inverter；The upper output port of the nine switching tubes inverter is connected by grid-connected transformer with power network, and lower output port is simultaneously
Couple into power network；Two output ports of the nine switching tubes inverter form the net side of distributed electrical source grid-connected inverter respectively
Main and auxiliary current transformer port；
When power network normally runs, be reverse into for the electric energy that micro- source produces and meet grid-connected conditions by the net side main convertor port
Alternating current, and maintain current transformer DC bus-bar voltage stabilization；The auxiliary current transformer port of net side adds harmonic wave electricity in electric current loop
Stream offset；
In electric network fault, using the cooperation between two output ports, the low voltage crossing of distributed power source is realized, will
The energy that distributed power source is produced smoothly sends into power network, while sending idle to power network, supports that line voltage recovers.
2. multi-functional distributed power source grid-connecting apparatus according to claim 1, it is characterised in that：The nine switching tubes inversion
Device is formed by three bridge arm parallel connections；The bridge arm includes three switching tubes being cascaded；
Definition is upper switching tube near dc bus positive switch pipe, is designated as SjH(j=a, b, c)；Opened near dc bus negative pole
Switching tube under Guan Guanwei, is designated as SjL(j=a, b, c)；It is remaining after the upper and lower switching tube of removing in three switching tubes of each bridge arm
Switching tube is breaker in middle pipe, is designated as SjM(j=a, b, c)；
By the modulation wave signal U of the upper and lower output port of nine switching tubes inverterrefH、UrefLShared triangular carrier is adjusted
System；If UrefHMore than carrier wave, then the switching tube S of phase is corresponded tojH(j=a, b, c) is turned on, otherwise SjHShut-off；If UrefLMore than carrier wave,
Then correspond to the switching tube S of phasejL(j=a, b, c) is turned off, otherwise SjLConducting；And per phase intervalve SjMThe driving letter of (j=a, b, c)
Number it is correspondence phase SjHWith SjLXOR obtain.
3. multi-functional distributed power source grid-connecting apparatus according to claim 1, it is characterised in that：The net side main convertor
D axles watt current and q axle reactive currents are controlled using the feedforward compensation dq decoupling modes based on grid voltage orientation respectively；
Net side main convertor is that control is completed in dq coordinate systems, and wherein d axles component is in the same direction with grid entry point voltage vector；Filtering
Relation between capacitance terminal voltage vector and net side main convertor Injection Current vector is：
Wherein L1It is filter reactance, ed、eqIt is filter capacitor C1D, q axle component of both end voltage, ucd、ucqIt is nine switching tube
D, q axle component of inverter upper port output voltage, id1、iq1It is d, q of the nine switching tubes inverter upper port output current
Axle component, ωeIt is system angular frequency；
The net side main convertor uses double -loop control, wherein DC bus-bar voltage control outer shroud, by by DC bus-bar voltage
Reference value udcrefWith measured value udcCompare after making the difference, d shaft current command values i is produced by PI controllersd1ref, by given
Power factor setting q shaft current command values iq1ref；By power network nominal situation current instruction value id1ref、iq1refOr electric network fault
Operating mode current instruction value igd1ref、igq1refThe current inner loop that input decoupling PI controllers are constituted, produces corresponding modulated signal d, q
Axle component u*gd1And u*gq1, three-phase modulations signal is obtained by Park inverse transformations, further according to PWM algorithm, complete to described
The output control of nine switching tube inverter upper ports.
4. multi-functional distributed power source grid-connecting apparatus according to claim 1, it is characterised in that：The net side auxiliary converter
Device is that control is completed in dq coordinate systems, and wherein d axles component is in the same direction with grid entry point voltage vector；Filter capacitor terminal voltage vector
It is with the relation between net side main convertor Injection Current vector：
Wherein L2It is filter reactance, Ugd、UgqIt is filter capacitor C2D, q axle component of both end voltage, uad、uaqFor NSI upper ports are defeated
Go out d, q axle component of voltage, id2、iq2It is d, q axle component of NSI upper port output currents, ωeIt is system angular frequency；
The net side AuCT uses monocyclic control, the current instruction value i that harmonic detecting link is obtaineddh、iqhOr power network
Fault condition current instruction value igd2ref、igq2refD, q shaft current measured value i corresponding with subordinate inverter port respectivelyd2、iq2Phase
After subtracting, the electric current loop that input decoupling PI controllers are constituted produces corresponding modulated signal d, q axle component u*gd2And u*gq2, pass through
Park inverse transformations obtain three-phase modulations signal, further according to PWM algorithm, complete to the nine switching tubes inverter lower port
Output control.
5. multi-functional distributed power source grid-connecting apparatus according to claim 1, it is characterised in that：Normally run in power network
When, the reference current value of the net side AuCT is harmonic current compensation value；The detection of the harmonic current is as follows：
Digital phase-locked loop PLL tracks power network a phase voltage phases, threephase load electric current ia、ib、icTwo are obtained after being converted through abc/dq
Active and reactive current component i under cordic phase rotator systemd、iq, by id、iqBy after low pass filter, obtaining load fundamental wave electricity
The corresponding DC component i of streamdb、iqb, then idWith idbDifference be the d axle components i of harmonic current in dq coordinate systemsdh, iqWith iqb
Difference be the q axle components i of harmonic current in dq coordinate systemsqh。
6. multi-functional distributed power source grid-connecting apparatus according to claim 1, it is characterised in that：When electric network fault and occur
During Voltage Drop, the main and auxiliary current transformer of net side switches to LVRT patterns, in two aspect collaboration works of reactive power support and active balance
Make；
In reactive power support aspect, the reference value of NSI output reactive current controls is respectively set as：
U in formulagIt is line voltage, urefIt is line voltage before failure, igq1refAnd igq2refRespectively main convertor and auxiliary converter
Device q axles are idle instruction current, all values are perunit value；
System Reactive Power support policy determination after, calculate net side current transformer keep system energy balance on the premise of, NSI
The d axle command current values of main and auxiliary current transformer are respectively：
I in formulagd1refAnd igd2refThe respectively main and auxiliary active instruction current of current transformer d axles, PsIt is system output wattful power before failure
Rate.
7. multi-functional distributed power source grid-connecting apparatus according to claim 6, it is characterised in that：When voltage on line side occurs deeply
When degree falls, auxiliary is controlled and dc bus discharging circuit using DC chopped-wave, DC voltage control in 1.1 times of perunit values
It is interior.
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| CN111313412A (en) * | 2020-03-17 | 2020-06-19 | 浙江华电器材检测研究所有限公司 | Method for analyzing influence of multi-access electric vehicle charging pile on power grid harmonic waves |
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| CN107732921A (en) * | 2017-11-17 | 2018-02-23 | 东南大学 | Quality of power supply composite control apparatus and method of work based on nine switching tube inverters |
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| CN109193755A (en) * | 2018-09-03 | 2019-01-11 | 内蒙古工业大学 | Directly driven wind-powered unit and its control method based on mixed energy storage system |
| CN111313412A (en) * | 2020-03-17 | 2020-06-19 | 浙江华电器材检测研究所有限公司 | Method for analyzing influence of multi-access electric vehicle charging pile on power grid harmonic waves |
| CN111525847A (en) * | 2020-05-21 | 2020-08-11 | 华中科技大学 | Magnetic field modulation driving topology of dual-channel switched reluctance motor and control method thereof |
| CN112072669A (en) * | 2020-09-11 | 2020-12-11 | 西安交通大学 | Variable ratio voltage regulation and current compensation autotransformer and method |
| CN112072669B (en) * | 2020-09-11 | 2022-06-07 | 西安交通大学 | Variable ratio voltage regulation and current compensation autotransformer and method |
| CN112653133A (en) * | 2020-12-09 | 2021-04-13 | 国网湖北省电力有限公司电力科学研究院 | Power grid simulator based on nine-switch converter and application method thereof |
| CN113702766A (en) * | 2021-08-31 | 2021-11-26 | 南通大学 | Motor active short circuit method based on switch tube fault diagnosis |
| CN113702766B (en) * | 2021-08-31 | 2024-03-29 | 南通大学 | Motor active short-circuit method based on switching tube fault diagnosis |
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