CN106712089B - A kind of multi-functional distributed generation resource grid-connecting apparatus based on nine switching tube inverters - Google Patents
A kind of multi-functional distributed generation resource grid-connecting apparatus based on nine switching tube inverters Download PDFInfo
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- CN106712089B CN106712089B CN201710041343.6A CN201710041343A CN106712089B CN 106712089 B CN106712089 B CN 106712089B CN 201710041343 A CN201710041343 A CN 201710041343A CN 106712089 B CN106712089 B CN 106712089B
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Abstract
The invention discloses a kind of multi-functional distributed generation resource grid-connecting apparatus based on nine switching tube inverters, when power grid operates normally, an output port of NSI is accessed into power distribution network via grid-connected transformer, the electric energy that micro- source generates is reverse into the alternating current for meeting grid-connected conditions, and current transformer DC bus-bar voltage is maintained to stablize；The another output mouth of NSI is accessed into power grid by parallel form, harmonic current compensation value is added in electric current loop, for improving grid power quality.When the grid fails, using the cooperation between two output ports provided by NSI, the low voltage crossing of distributed generation resource is realized.Compared to the inverter structure for leaning against back type, the present invention can not only save three switching tubes, reduce system cost, distribution network electric energy quality problem can also be compensated simultaneously, it realizes LVRT of the distributed generation resource under Distribution Network Failure state, improves the security and stability of operation of power networks after distributed generation resource access.
Description
Technical field
The present invention relates to a kind of configurations of multi-functional distributed generation resource grid-connecting apparatus based on nine switching tube inverters (NSI)
Scheme, suitable for the cutting-in control of distributed generation resource, to compensate public power caused by after a large amount of non-linear and impact loads access
Net harmonic pollution problems realize low voltage crossing of the distributed electrical source inventer under grid failure state, are based on nine switching tubes
The topological structure of inverter, and a kind of new distribution type power grid inverter designed, belong to distributed generation technology neck
Domain.
Background technique
With the exhaustion of earth traditional fossil energy, renewable energy becomes the new research 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 generation resource grid-connected converter
In power electronic equipment.It is certain that the grid-connected directive/guide of new distributed generation resource requires the generating sets such as blower, photovoltaic that must have
Low voltage ride-through capability.
At the same time, distribution is largely accessed with using the nonlinear-load and distributed generation system of power electronic equipment
Net, so that the harmonic content abruptly increase of power network current, above-mentioned harmonic pollution make the harmonic pollution of utility network be on the rise.It is biggish
Harmonic current will directly threaten the operational safety of power distribution network.In prior art means, active power filtering (APF) technology is
Administer harmonic pollution in electric power net one of main means, power grid, especially distribution and with electrical domain using more and more extensive.
To solve the problems, such as low voltage crossing when distributed generation resource access, domestic and foreign scholars propose numerous distributed generation resources
Low voltage crossing scheme, to sum up following 3 class can be divided into: (1) installing electric power generation unloading resistance additional in DC link, disappeared by electric power generation unloading resistance
Extra active power is consumed, the fluctuation range of DC bus-bar voltage can be limited in 10% rated range, but system effectiveness
Lower, heat dissipation design is difficult；(2) DC bus-bar voltage is controlled by generator-side converter wear, it is impossible to which the energy stores of release are in machine
In group transmission chain, since generator speed is uncontrolled, risk can be brought to system safety operation；It (3) will be more using energy storage device
Remaining energy stores are got up, although power smooth can be realized, will increase system cost.The present invention is advised according to Germany's E.ON standard
It is fixed, reactive power is injected to realize the low voltage crossing of distributed generation resource to grid entry point by two grid-side converter ports.
Existing power quality problem shows as harmonic pollution and no-power vacancy, and the alternative administering method of tradition is main
It is divided into using passive power filter, parallel capacitor as the inactive component of representative, and with active filter and static nothing
Function compensator is the active equipment of representative.Wherein inactive component is with structural principle is simple, operational reliability is high, maintenance cost is low
The advantages that, but also have the potential danger that resonance occurs with electrical network parameter, and when system is run in a manner of small, be easy to cause idle
Overcompensation increases system loss, threatens safe operation of electric network.And active equipment is because flexible with the method for operation, scalability is strong, adjusts
The advantages that speed is fast is saved, inactive component is just gradually being replaced to become the master of power quality controlling device development in Distribution network
Stream.
Summary of the invention
Goal of the invention: improvement, distribution in order to solve distributed generation resource grid entry point harmonic wave and idle equal power quality problems
The problem of formula power supply low voltage crossing controls, the present invention devise a kind of multi-functional point for being based on nine switching tube inverters (NSI)
The allocation plan of cloth power grid device.Using two groups of output ports provided by nine switching tube inverters, respectively constitute point
The grid-connected feedback of distributed generation resource is realized when power grid operates normally in the main and auxiliary current transformer port of the net side of cloth power grid inverter
Harmonics restraint and reactive compensation are carried out while energy, to improve grid power quality；When Voltage Drop occurs for electric network fault, lead to
The coordinated control crossed between two output ports of NSI meets the requirement of low voltage crossing, thus the handle in same set of grid-connecting apparatus
Distributed generation resource cutting-in control, idle and harmonic current compensation, low voltage ride-through function are combined together, reduce system investments at
This, improves the stability and grid power quality of distributed generation resource.
Technical solution:
A kind of multi-functional distributed generation resource grid-connecting apparatus based on nine switching tube inverters, including nine switching tube inverters；
The upper output port of one of the nine switching tubes inverter is connect by grid-connected transformer with power grid, another lower output port is simultaneously
Couple into power grid；Two output ports of the nine switching tubes inverter are respectively formed the net side of distributed electrical source grid-connected inverter
Main and auxiliary current transformer port；
When power grid operates normally, the electric energy that micro- source generates is reverse by net side main convertor port meets grid-connected item
The alternating current of part, and current transformer DC bus-bar voltage is maintained to stablize；The auxiliary current transformer port of net side is added humorous in electric current loop
Wave current offset values；
In electric network fault, using the cooperation between two output ports, realize that the low-voltage of distributed generation resource is worn
More, the energy that distributed generation resource generates smoothly is sent into power grid, while issues idle, support network voltage recovery to power grid.
The nine switching tubes inverter is formed by three bridge arm parallel connections；The bridge arm includes three switches being cascaded
Pipe；
Defining close to DC bus positive switch pipe is upper switch pipe, is denoted as SjH(j=a, b, c)；It is negative close to DC bus
Pole switching tube is lower switch pipe, is denoted as SjL(j=a, b, c)；In three switching tubes of each bridge arm, remove remaining after upper and lower switching tube
Under switching tube be middle switching tube, be denoted as SjM(j=a, b, c)；
By the modulation wave signal U of the upper and lower output port of nine switching tubes inverterrefH、UrefLTriangular carrier is shared to carry out
Modulation；If UrefHGreater than carrier wave, then the switching tube S of phase is corresponded tojH(j=a, b, c) is connected, otherwise SjHShutdown；If UrefLGreater than load
Wave then corresponds to the switching tube S of phasejL(j=a, b, c) is turned off, otherwise SjLConducting；And every phase intermediate tube SjMThe drive of (j=a, b, c)
Dynamic signal is corresponding phase SjHWith SjLExclusive or obtain.
The net side main convertor controls d axis using the feedforward compensation dq decoupling mode based on grid voltage orientation respectively
Watt current and q axis reactive current；
Net side main convertor is that control is completed in dq coordinate system, and wherein d axis component and grid entry point voltage vector are in the same direction；
Relationship between filter capacitor end voltage vector and net side main convertor Injection Current vector are as follows:
Wherein L1For filter reactance, ed、eqFor filter capacitor C1D, q axis component of both end voltage, ucd、ucqIt is opened for described nine
Close d, q axis component of pipe inverter upper port output voltage, id1、iq1Electric current is exported for the nine switching tubes inverter upper port
D, q axis component, ωeFor system angular frequency；
The net side main convertor uses double -loop control, and wherein DC bus-bar voltage controls outer ring, by by DC bus
The reference value u of voltagedcrefWith measured value udcCompare after making the difference, d shaft current instruction value i is generated by PI controllerd1ref, pass through
Given power factor sets q shaft current instruction value iq1ref；By power grid nominal situation current instruction value id1ref、iq1refOr power grid
Fault condition current instruction value igd1ref、igq1refThe current inner loop that input decoupling PI controller is constituted generates corresponding modulation letter
Number d, q axis component u*gd1And u*gq1, three-phase modulations signal is obtained by Park inverse transformation, further according to PWM modulation algorithm, completion pair
The output of the nine switching tubes inverter upper port controls.
3, multi-functional distributed generation resource 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 system, and wherein d axis component and grid entry point voltage vector are in the same direction；Filter capacitor end voltage
Relationship between vector and net side main convertor Injection Current vector are as follows:
Wherein L2For filter reactance, Ugd、UgqFor filter capacitor C2D, q axis component of both end voltage, uad、uaqFor the upper end NSI
D, q axis component of mouth output voltage, id2、iq2D, q axis component of electric current, ω are exported for NSI upper porteFor system angular frequency；
The net side AuCT is controlled using monocycle, the current instruction value i that harmonic detecting link is obtaineddh、iqhOr
Electric network fault operating condition 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 controller is constituted generates corresponding modulated signal d, q axis component u*gd2And u*gq2,
Three-phase modulations signal is obtained by Park inverse transformation, further according to PWM modulation algorithm, is completed to the nine switching tubes inverter lower end
The output control of mouth.
When power grid operates normally, 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 grid a phase voltage phase, threephase load electric current ia、ib、icAfter abc/dq is converted
Active and reactive current component i under to two-phase rotating coordinate systemd、iq, by id、iqAfter low-pass filter, load base is obtained
DC component i corresponding to wave electric currentdb、iqb, then idWith idbDifference be harmonic current in dq coordinate system d axis component idh, iq
With iqbDifference be harmonic current in dq coordinate system q axis component iqh。
When electric network fault and when Voltage Drop occurs, the main and auxiliary current transformer of net side switches to LVRT mode, in reactive power support and
Two levels of active balance cooperate；
In reactive power support level, the reference value of NSI output reactive current control is set separately are as follows:
U in formulagFor network voltage, urefFor network voltage before failure, igq1refAnd igq2refRespectively main convertor and auxiliary
Current transformer q axis reactive command electric current, all values are per unit value；
After System Reactive Power support policy determines, grid-side converter is calculated under the premise of keeping system capacity balance,
The d axis command current value of the main and auxiliary current transformer of NSI is respectively as follows:
I in formulagd1refAnd igd2refRespectively main and auxiliary current transformer d axis active command electric current, PsHave for system output before failure
Function power.
When depth, which occurs, for voltage on line side falls, auxiliary is using DC chopped-wave control and DC bus discharging circuit, straight
The control of side voltage is flowed in 1.1 times of per unit values.
The utility model has the advantages that (1) constructs main and auxiliary grid-connected port of distributed generation resource using two output ports of NSI, can reach with
Tradition leans against back type and controls that inverter is identical 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, to reduce device volume, reduce cost of investment；(2) using port in parallel is assisted, in electricity
When net does not break down, active filter function is realized, scalability flexible using the active filter method of operation is strong, adjusts speed
Fast advantage is spent, realizes the improvement to the power quality problems such as distributed generation resource grid entry point harmonic wave, idle, improves power grid electric energy matter
Amount；(3) in grid collapses, distributed generation resource grid-connected converter is realized by two output ports of coordinated control NSI
LVRT strategy provides reactive power support to power grid according to international relevant criterion, and minimizes the heat dissipation pressure of DC side-discharging resistance
Power maintains system capacity balance, realizes the low voltage crossing of distributed generation resource.The mentioned system of the present invention is grid-connected by distributed generation resource
Control, idle and harmonic current compensation, low voltage ride-through function combine, and improve the stability and power quality of system, have
Higher cost performance and system availability, therefore there is good future in engineering applications.
Detailed description of the invention
Fig. 1 is 12 switching tube inverters and nine switching tube inverter topology relational graphs.
Fig. 2 is the multi-functional distributed generation resource 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 generation resource grid-connecting apparatus.
Fig. 4 is the net side AuCT control block diagram of multi-functional distributed generation resource grid-connecting apparatus.
Fig. 5 is multi-functional distributed generation resource grid-connecting apparatus Harmonic currents detection schematic diagram.
Specific embodiment
The present invention will be further explained with reference to the accompanying drawing.
The present invention, as power electronics main circuit, provides two using nine switching tube inverters for distributed generation resource grid-connecting apparatus
A independent output port.
Fig. 1 gives the topological relation between 12 switching tube inverters and nine switching tube inverters.The left side of Fig. 1 be compared with
Frequently with lean against 12 switching tube inverter of back type, the right side of Fig. 1 is novel nine switching tubes inverter.It can be seen that nine switching tubes are inverse
Become that device is same as 12 switching tube inverters can externally provide two groups of three-phase output end mouths, but nine switching tube inverters are than ten
Two switching tube inverters save 3 switching tubes.By comparing it is found that nine switching tube inverters have, compact-sized, cost is relatively low
Advantage.Therefore, using two output ports of nine switching tube inverters, it is respectively formed the master of distributed generation resource and network interface
Converter part and AuCT part.
It defines the switching tube that three are cascaded and constitutes a bridge arm, then nine switching tubes of NSI can be divided into three
Bridge arm.In order to avoid DC bus to be shorted, concatenated three switching tubes of institute cannot be simultaneously turned on each bridge arm.When load contains
When having inductive element, in order to avoid output end is hanging, it should control on each bridge arm at least while that there are two switching tubes to be connected.Definition
It is upper switch pipe close to DC bus positive switch pipe, is denoted as SjH(j=a, b, c)；Under close DC bus negative switch pipe is
Switching tube is denoted 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
Middle switching tube, is denoted as SjM(j=a, b, c).By the modulation wave signal U of the upper and lower output port of NSIrefH、UrefLShare triangular carrier
It is modulated.If UrefHGreater than carrier wave, then the switching tube S of phase is corresponded tojH(j=a, b, c) conducting；Otherwise SjHShutdown.If UrefLGreatly
In carrier wave, then the switching tube S of phase is corresponded tojL(j=a, b, c) shutdown；Otherwise SjLConducting.And every phase intermediate tube SjM(j=a, b, c)
Driving signal be corresponding phase SjHWith SjLExclusive or 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 multi-functional distributed generation resource grid-connecting apparatus based on nine switching tube inverters (NSI) is counted.It is opened using nine
Two groups of output ports provided by pipe inverter are closed, the main and auxiliary current transformer of net side of distributed electrical source grid-connected inverter is respectively constituted
Port constitutes main output port using output port provided by NSI when power grid is operated normally, guarantee system and
Net energy regenerative, while auxiliary output terminal mouth is constituted using another output mouth provided by NSI, realize idle and harmonic compensation,
Improve the power quality on grid entry point periphery, carry out harmonics restraint and reactive compensation while realizing distributed generation resource grid-connected energy regenerative,
To improve grid power quality；It is real by the coordinated control between two output ports of NSI when Voltage Drop occurs for electric network fault
The LVRT strategy of existing distributed generation resource, and reactive power support is provided to power grid according to relevant criterion, minimize DC side-discharging electricity
The heat dissipation pressure of resistance maintains system capacity balance, to meet the requirement of low voltage crossing, thus the handle in same set of grid-connecting apparatus
Distributed generation resource cutting-in control, idle and harmonic current compensation, low voltage ride-through function are combined together, reduce system investments at
This, improves the stability and grid power quality of distributed generation resource, there is higher cost performance and system availability.
Wherein the DC side parallel of nine switching tube inverters has Equivalent DC bus capacitor C, while being parallel with micro- source control
And DC chopped-wave link realizes the functions such as MPPT for controlling DC bus-bar voltage and micro battery.The one of nine switching tube inverters
A output port passes through by inductance L1, capacitor C1The LC filter circuit of composition and grid-connected transformer access power grid, and micro- source is generated
Electric energy is reverse into the alternating current for meeting grid-connected conditions, and current transformer DC bus-bar voltage is maintained to stablize；Nine switching tube inverters
Another output mouth passes through by inductance L2, capacitor C2The LC filter circuit of composition is directly accessed the grid side of grid-connected transformer,
Harmonic current compensation value is added in electric current loop, for improving grid power quality.Grid side includes net side equivalent reactance LgridWith
Three-phase equivalent voltage source Uj(j=a, b, c).Since there may be circulation between two inverter ports of parallel running, can give
Parallel system brings the adverse effect for increasing switch element burden, increasing system loss, even damaging 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 generation resource grid-connecting apparatus proposed by the invention
Figure, net side main convertor adjust the friendship of reactive power between NSI and bulk power grid to maintain NSI DC side busbar voltage
It changes, mainly controlling target is that the active power for generating distributed generation resource injects power grid, and regulation power factor as required.
Net side main convertor is active to control d axis respectively using the feedforward compensation dq decoupling mode based on grid voltage orientation
Electric current and q axis reactive current.
Net side main convertor is that control is completed in dq coordinate system, and wherein d axis component and grid entry point voltage vector are in the same direction.
It can be by the relationship description between filter capacitor end voltage vector and net side main convertor Injection Current vector are as follows:
Wherein L1For filter reactance, ed、eqFor filter capacitor C1D, q axis component of both end voltage, ucd、ucqFor NSI upper port
D, q axis component of output voltage, id1、iq1D, q axis component of electric current, ω are exported for NSI upper porteFor system angular frequency.
Net side main convertor in Fig. 3 uses double -loop control, and wherein DC bus-bar voltage controls outer ring, 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 current is generated by PI controller
Instruction value id1ref, q shaft current instruction value i is set by given power factorq1ref；By power grid nominal situation current instruction value
id1ref、iq1refOr electric network fault operating condition current instruction value igd1ref、igq1refThe current inner loop that input decoupling PI controller is constituted,
Generate corresponding modulated signal d, q axis component u*gd1And u*gq1, three-phase modulations signal is obtained by Park inverse transformation, further according to
PWM modulation algorithm is completed the output to NSI upper port and is controlled.
When power grid operates normally, stablize NSI DC bus-bar voltage by the dual-loop controller of d axis component, to make
Power grid can be injected in time by obtaining the active power that distributed generation resource generates；By the monocycle controller to q axis component, according to prior
The reactive power of setting exports corresponding reactive current reference value.In electric network fault, d, q axis 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 generation resource grid-connecting apparatus proposed by the invention
Block diagram adds harmonic current compensation value in the electric current loop of net side AuCT, generates compensation electric current for controlling, improves power grid
Power quality.When power grid is normal, for AuCT port working under APF mode, instruction current is harmonic detecting link
The compensation current of acquisition；When the grid fails, AuCT port is matched 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 grid harmonic and nothing in active filter (APF) mode
Function offset, for improving the power quality of distributed generation resource grid entry point.The current reference value source of net side AuCT port
From harmonic current detection, and in d-q coordinate system, the tracking to instruction current is realized using electric current loop decoupling control.
Net side AuCT is that control is completed in dq coordinate system, and wherein d axis component and grid entry point voltage vector are same
To.It can be by the relationship description between filter capacitor end voltage vector and net side main convertor Injection Current vector are as follows:
Wherein L2For filter reactance, Ugd、UgqFor filter capacitor C2D, q axis component of both end voltage, uad、uaqFor the upper end NSI
D, q axis component of mouth output voltage, id2、iq2D, q axis component of electric current, ω are exported for NSI upper porteFor system angular frequency.
Net side AuCT in Fig. 4 is controlled using monocycle, the current instruction value i that harmonic detecting link is obtaineddh、
iqhOr electric network fault operating condition 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 controller is constituted generates corresponding modulated signal d, q axis component u*gd2With
u*gq2, three-phase modulations signal is obtained by Park inverse transformation, further according to PWM modulation algorithm, completes the output control to NSI lower port
System.
When power grid operates normally, AuCT works in active filter mode, at this time 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, to improve power grid
Power quality.If Fig. 5 is Harmonic currents detection schematic diagram proposed by the present invention.Digital phase-locked loop PLL tracks power grid a phase voltage phase
Position, to guarantee the precision of Harmonic currents detection, threephase load electric current ia、ib、icTwo-phase rotation is obtained after abc/dq is converted to sit
Active and reactive current component i under mark systemd、iq, by id、iqAfter low-pass filter, obtain corresponding to load fundamental current
DC component idb、iqb, then idWith idbDifference be harmonic current in dq coordinate system d axis component idh, iqWith iqbDifference be
The q axis component i of harmonic current in dq coordinate systemqh。
When electric network fault and when Voltage Drop occurs, the power output of net side inverter is restricted.If distributed electrical
The power in source does not adjust, and extra energy will cause gird-connected inverter DC side overvoltage, jeopardizes the operation of distributed generation resource
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 mode, in reactive power support
It cooperates with two levels of active balance, to smoothly sending the energy that distributed generation resource generates to power grid, while to power grid
Reactive power is issued, network voltage is supported to restore.
In reactive power support level, provided according to German E.ON company standard: network voltage often falls 1% voltage rating,
Distributed generation resource by taking wind generator system as an example need to issue the reactive current of 2% rated current size to power grid.Therefore, it is distributed
Formula power supply meets the requirement of reactive current first, and the reactive current for being conveyed to power grid is determined according to the amplitude of grid voltage sags
Size.The reference value of NSI output reactive current control is set separately are as follows:
U in formulagFor network voltage, urefFor network voltage before failure, igq1refAnd igq2refRespectively main convertor and auxiliary
Current transformer q axis reactive command electric current, all values are per unit value.
After System Reactive Power support policy determines, grid-side converter is calculated under the premise of keeping system capacity balance,
The d axis command current value of the main and auxiliary current transformer of NSI is respectively as follows:
I in formulagd1refAnd igd2refRespectively main and auxiliary current transformer d axis active command electric current, PsHave for system output before failure
Function power.But due to the limitation of NSI output electric current, the control strategy of grid-side converter, which can only meet, centainly falls degree
LVRT.When depth, which occurs, for voltage on line side falls, need to assist using DC chopped-wave control and DC bus discharging circuit, straight
The control of side voltage is flowed in 1.1 times of per unit values.
The technology that the present invention is not particularly limited is the prior art.
The above is only a preferred embodiment of the present invention, it should be pointed out that: for the ordinary skill people of the art
For member, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also answered
It is considered as protection scope of the present invention.
Claims (6)
1. a kind of multi-functional distributed generation resource grid-connecting apparatus 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 connect by grid-connected transformer with power grid, and lower output port is simultaneously
Couple into power grid；Two output ports of the nine switching tubes inverter are respectively formed the net side of distributed electrical source grid-connected inverter
Main and auxiliary current transformer port；
When power grid operates normally, the electric energy that micro- source generates is reverse by net side main convertor port meets grid-connected conditions
Alternating current, and current transformer DC bus-bar voltage is maintained to stablize；Harmonic wave electricity is added in the auxiliary current transformer port of net side in electric current loop
Flow offset；
In electric network fault, using the cooperation between two output ports, the low voltage crossing of distributed generation resource is realized, it will
The energy that distributed generation resource generates smoothly is sent into power grid, while idle, support network voltage recovery is issued to power grid；
When electric network fault and when Voltage Drop occurs, the main and auxiliary current transformer of net side switches to LVRT mode, in reactive power support and active
Two levels are balanced to cooperate；
In reactive power support level, the reference value of NSI output reactive current control is set separately are as follows:
U in formulagFor network voltage, urefFor network voltage before failure, igq1refAnd igq2refRespectively main convertor and auxiliary converter
Device q axis reactive command electric current, all values are per unit value；
After System Reactive Power support policy determines, grid-side converter is calculated under the premise of keeping system capacity balance, NSI
The d axis command current value of main and auxiliary current transformer is respectively as follows:
I in formulagd1refAnd igd2refRespectively main and auxiliary current transformer d axis active command electric current, PsWattful power is exported for system before failure
Rate.
2. multi-functional distributed generation resource 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；
Defining close to DC bus positive switch pipe is upper switch pipe, is denoted as SjH(j=a, b, c)；It is opened close to DC bus cathode
Guan Guanwei lower switch pipe, is denoted as SjL(j=a, b, c)；In three switching tubes of each bridge arm, remove remaining after upper and lower switching tube
Switching tube is middle switching tube, is denoted 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 UrefHGreater than carrier wave, then the switching tube S of phase is corresponded tojH(j=a, b, c) is connected, otherwise SjHShutdown；If UrefLGreater than carrier wave,
Then correspond to the switching tube S of phasejL(j=a, b, c) is turned off, otherwise SjLConducting；And every phase intermediate tube SjMThe driving of (j=a, b, c) is believed
Number for corresponding phase SjHWith SjLExclusive or obtain.
3. multi-functional distributed generation resource grid-connecting apparatus according to claim 1, it is characterised in that: the net side main convertor
D axis watt current and q axis reactive current are controlled using the feedforward compensation dq decoupling mode based on grid voltage orientation respectively；
Net side main convertor is that control is completed in dq coordinate system, and wherein d axis component and grid entry point voltage vector are in the same direction；Filtering
Relationship between capacitance terminal voltage vector and net side main convertor Injection Current vector are as follows:
Wherein L1For filter reactance, ed、eqFor filter capacitor C1D, q axis component of both end voltage, ucd、ucqFor nine switching tube
D, q axis component of inverter upper port output voltage, id1、iq1D, q of electric current are exported for the nine switching tubes inverter upper port
Axis component, ωeFor system angular frequency；
The net side main convertor uses double -loop control, and wherein DC bus-bar voltage controls outer ring, by by DC bus-bar voltage
Reference value udcrefWith measured value udcCompare after making the difference, d shaft current instruction value i is generated by PI controllerd1ref, by given
Power factor set q shaft current instruction value iq1ref；By power grid nominal situation current instruction value id1ref、iq1refOr electric network fault
Operating condition current instruction value igd1ref、igq1refThe current inner loop that input decoupling PI controller is constituted, generates corresponding modulated signal d, q
Axis component u*gd1And u*gq1, three-phase modulations signal is obtained by Park inverse transformation, further according to PWM modulation algorithm, is completed to described
The output of nine switching tube inverter upper ports controls.
4. multi-functional distributed generation resource 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 system, and wherein d axis component and grid entry point voltage vector are in the same direction；Filter capacitor end voltage vector
With the relationship between net side main convertor Injection Current vector are as follows:
Wherein L2For filter reactance, Ugd、UgqFor filter capacitor C2D, q axis component of both end voltage, uad、uaqIt is defeated for NSI upper port
D, q axis component of voltage out, id2、iq2D, q axis component of electric current, ω are exported for NSI upper porteFor system angular frequency；
The net side AuCT is controlled using monocycle, the current instruction value i that harmonic detecting link is obtaineddh、iqhOr power grid
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 controller is constituted generates corresponding modulated signal d, q axis component u*gd2And u*gq2, pass through
Park inverse transformation obtains three-phase modulations signal, further according to PWM modulation algorithm, completes to the nine switching tubes inverter lower port
Output control.
5. multi-functional distributed generation resource grid-connecting apparatus according to claim 1, it is characterised in that: operated normally in power grid
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 grid a phase voltage phase, threephase load electric current ia、ib、icTwo are obtained after abc/dq is converted
Active and reactive current component i under cordic phase rotator systemd、iq, by id、iqAfter low-pass filter, load fundamental wave electricity is obtained
The corresponding DC component i of streamdb、iqb, then idWith idbDifference be harmonic current in dq coordinate system d axis component idh, iqWith iqb
Difference be harmonic current in dq coordinate system q axis component iqh。
6. multi-functional distributed generation resource grid-connecting apparatus according to claim 1, it is characterised in that: when voltage on line side occurs deeply
When degree falls, auxiliary is using DC chopped-wave control and DC bus discharging circuit, DC voltage control in 1.1 times of per unit values
It is interior.
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| CN107732921B (en) * | 2017-11-17 | 2020-10-02 | 东南大学 | Electric energy quality composite control device based on nine-switch-tube inverter and working method |
| 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 |
| CN111525847B (en) * | 2020-05-21 | 2022-02-15 | 华中科技大学 | Magnetic field modulation driving topology of dual-channel switched reluctance motor and control method thereof |
| 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 |
| 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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