CN110289635A - Based on the grid-connected current control strategy for improving Repetitive controller - Google Patents
Based on the grid-connected current control strategy for improving Repetitive controller Download PDFInfo
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Classifications
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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- H02J3/382—
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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
- H02M7/53871—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 with automatic control of output voltage or current
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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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/60—Planning or developing urban green infrastructure
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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
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention discloses a kind of based on the grid-connected current control strategy for improving Repetitive controller.Topological structure using the synchronization inverter main circuit of the control strategy includes DC voltage source, three-phase inverter, LC filter, line impedance and power grid.The control strategy carries out differential to capacitance voltage by nonideal Generalized Integrator and obtains capacitance current, bridge arm side inductive current subtracts capacitance current and obtains current on line side, using the difference of current on line side and current on line side fundametal compoment as the error signal of grid-connected current control input, capacitor current feedback is introduced in Repetitive controller, the mode of harmonic signal in current on line side is fed back comprehensively, the rejection ability of harmonic wave is improved, while not increasing cost.
Description
Technical field
The invention belongs to distributed power generation and power electronics fields, more particularly, to one kind based on improvement Repetitive controller
Grid-connected current control strategy.
Background technique
When a large amount of nonlinear-load, load or burden without work and renewable energy by power electronic equipment access power grid in, electricity
The total harmonic distortion factor of net voltage becomes larger, and the harmonic component of network voltage can generate very big shadow to inverter output current
It rings, serious harm is caused to power grid and electrical equipment.Therefore, have ten using control strategy appropriate for grid-connected current
Divide important research significance.
Since the harmonic component in network voltage belongs to periodic disturbing signal, and Repetitive controller is based on inner membrance principle,
There is infinitely great gain to the signal at fundamental frequency integral multiple, it can be with the tracking cycle signal of indifference, therefore to the humorous of power grid
Wave component has good inhibiting effect.But Repetitive controller has lagged a cycle, dynamic property is poor, using being limited
System is broadly divided into two kinds, one is insertions so Repetitive controller is combined to form composite control method with PI control at present
Formula improves the dynamic property and harmonic inhibition capability of system one is parallel.
Currently, having more academic papers for based on the grid-connected current control strategy for improving Repetitive controller and being analyzed
And propose solution, such as:
1, entitled " being controlled using the LCL type gird-connected inverter list closed loop current of Repetitive controller " " Chinese electrical engineering
Report ", the 24th phase article of page 13~21 in 2013.This article devise it is a kind of proportional controller and repetitive controller are combined, draw
Enter voltage feed-forward control to improve dynamic property, and add the combination of trapper to replace phase compensation by first compensation phase device, makes
System obtains higher middle low-frequency harmonics gain, but first compensation phase device is obtained by approximate, and depends on the practical ginseng of filter
Number, working environment have an impact its stability.
2, entitled " the capacitor Split type three-phase four-wire system DSTATCOM control method based on dual-loop controller " " electric power is automatic
Change equipment ", the 8th phase article of page 114~121 in 2014.This article devises a kind of PI controller and repetitive controller is concatenated
Dual-loop controller has taken into account dynamic property and stable state accuracy, but it is fed back to inductive current inner ring, and it is humorous not include capacitance current
Wave component, it is limited to the harmonic inhibition capability of current on line side.
3, Chinese invention patent document (109378862 A of publication number CN) " a kind of base disclosed on December 28th, 2018
In the grid-connected current control method for improving repetitive controller ", the invention proposes a kind of internal model structures for improving Repetitive controller to make
Its delay time shorten to original half, and voltage feed-forward control is added, but the present invention is using current on line side as feedback quantity,
Current sensor is increased, cost is increased.
In summary document, it is existing to be had the disadvantage that based on the grid-connected current control strategy for improving Repetitive controller
1, the research in terms of the existing grid-connected current control strategy based on improvement Repetitive controller, controller parameter design more
Complexity, and depend on filter parameter；
2, the research in terms of the existing grid-connected current control strategy based on improvement Repetitive controller, is fed back to inductive current, no
It is limited to the harmonic inhibition capability of current on line side comprising capacitance current harmonic component；
3, the research in terms of the existing grid-connected current control strategy based on improvement Repetitive controller, is fed back to current on line side, increases
Add current sensor, increases cost.
Summary of the invention
The invention proposes a kind of based on the grid-connected current control strategy for improving Repetitive controller, the system that this method is studied
Include DC voltage source, three-phase inverter, LC filter, line impedance and power grid.Pass through nonideal Generalized Integrator
Differential is carried out to capacitance voltage and obtains capacitance current, bridge arm side inductive current subtracts capacitance current and obtains current on line side, by net side
Error signal of the difference of electric current and current on line side fundametal compoment as grid-connected current control input, introduces in Repetitive controller
Capacitor current feedback, while not needing additional current sensor, has both improved the rejection ability of harmonic wave, also without increase at
This.
The object of the present invention is achieved like this.The present invention proposes a kind of based on the grid-connected current control for improving Repetitive controller
Strategy, the topological structure using the synchronization inverter main circuit of the control strategy include DC voltage source, three-phase inverter, LC
Filter, line impedance and power grid, the DC voltage source and parallel connection of three-phase inverter, three-phase inverter output are filtered by LC
Wave device and line impedance access power grid；
The step of this control strategy, is as follows:
Step 1, sampling three-phase inverter net side capacitance voltage, that is, three-phase inverter exports phase voltage Uoa,Uob,Uoc, and pass through
Three-phase inverter output phase voltage coordinate transformation equation obtains three-phase inverter output phase voltage dq axis component Uod,Uoq, sampling three
Phase inverter leg inductive current ILa,ILb,ILc, and three-phase is obtained through three-phase inverter bridge arm inductive current coordinate transformation equation
Inverter leg inductive current dq axis component ILd,ILq, wherein d axis is active axis, and q axis is idle axis；Electricity is obtained by phaselocked loop
Net frequencies omegag；
Step 2, phase voltage U is exported to the three-phase inverter that step 1 obtains by first-order holderoa,Uob,Uoc, three contraries
Become device and exports phase voltage dq axis component Uod,Uoq, three-phase inverter bridge arm inductive current ILa,ILb,ILcWith three-phase inverter bridge arm
Inductive current dq axis component ILd,ILqCarry out discretization obtain first-order holder it is discrete after three-phase inverter output phase voltage Uoa
(z),Uob(z),Uoc(z), the three-phase inverter after first-order holder is discrete exports phase voltage dq axis component Uod(z),Uoq(z), one
Three-phase inverter bridge arm inductive current I after rank retainer is discreteLa(z),ILb(z),ILc(z) and first-order holder it is discrete after
Three-phase inverter bridge arm inductive current dq axis component ILd(z),ILq(z), then using the non-ideal improper integral in discrete domain
Device GI'(z) obtain discrete domain in three-phase inverter capacitance current ICa(z),ICb(z),ICc(z), it and then obtains in discrete domain
Three-phase inverter current on line side Ioa(z),Iob(z),Ioc(z)；
Three-phase inverter capacitance current I in the discrete domainCa(z),ICb(z),ICc(z) calculation formula are as follows:
ICa(z)=CGI'(z) Uoa(z)
ICb(z)=CGI'(z) Uob(z)
ICc(z)=CGI'(z) Uoc(z)
Wherein, C is the capacitance of LC filter,In formula, ωcFor
Non-ideal Generalized Integrator GI'(z in discrete domain) shearing frequency, ω0For the non-ideal Generalized Integrator GI' in discrete domain
(z) the frequency at unlimited gain, T are the sampling period, and z is discrete domain operator；
Three-phase inverter current on line side I in the discrete domainoa(z),Iob(z),Ioc(z) calculation formula are as follows:
Ioa(z)=ILa(z)-ICa(z)
Iob(z)=ILb(z)-ICb(z)
Ioc(z)=ILc(z)-ICc(z)
Step 3, the three-phase inverter current on line side I in discrete domain obtained according to step 2oa(z),Iob(z),Ioc(z),
First three-phase inverter current on line side dq axis component I is obtained through three-phase inverter current on line side coordinate transformation equationod(z),Ioq(z),
Using acquisition three-phase inverter current on line side fundametal compoment I after low-pass first order filterod_LPF(z),Ioq_LPF(z), then will
Three-phase inverter current on line side dq axis component Iod(z),Ioq(z) with three-phase inverter current on line side fundametal compoment Iod_LPF(z),
Ioq_LPF(z) error signal e of the difference as gird-connected inverter current controld(z) and eq(z)；
The calculation formula of the three-phase inverter current on line side fundametal compoment are as follows:
Wherein, TfFor the time constant of low-pass first order filter；
The error signal e of the gird-connected inverter current controld(z) and eq(z) calculation formula are as follows:
ed(z)=Iod(z)-Iod_LPF(z)
eq(z)=Ioq(z)-Ioq_LPF(z)
Step 4, the error signal e of the gird-connected inverter current control obtained according to step 3d(z) and eq(z), by repeating
Electric current d axis instruction I is obtained after controlcdref(z) and electric current q axis instructs Icqref(z), its calculation formula is:
Wherein, z-NFor cycle delay link, N is per primitive period sampling number, and Q (z) is interior mode filter, takes the Q (z) to be
Constant less than 1, z are discrete domain operator, and C (z) is repetitive control compensator, expression formula are as follows:
C (z)=KrzkS(z)
Wherein, KrFor Repetitive controller gain, zkFor advanced phase shift link, k is positive integer, and S (z) is filtering compensation link
Second-order low-pass filter, expression formula are as follows:
Wherein,For damping ratio, ωnFor natural frequency of oscillation；
Step 5, I is instructed according to the electric current d axis that step 4 obtainscdref(z) and step 2 obtained in three-phase inverter bridge bridge
Arm inductive current d axis component ILd(z), d axis output signal U is obtained by d shaft current closed-loop control equationid(z)；According to step 4
Obtained electric current q axis instruction Icqref(z) and step 2 obtained in three-phase inverter bridge bridge arm inductive current q axis component ILq(z),
Q axis output signal U is obtained by q shaft current closed-loop control equationiq(z), calculation formula is respectively as follows:
Wherein, UidIt (z) is d axis output signal, UiqIt (z) is q axis output signal,For watt current given value,For nothing
Function given value of current value, GPIIt (z) is current closed-loop proportional and integral controller, expression formula are as follows:
Wherein, kpFor three-phase inverter current closed-loop proportional controller coefficient, kiIt integrates and adjusts for three-phase inverter current closed-loop
Save device coefficient；
Step 6, phase voltage d axis component U is exported according to the three-phase inverter that step 2 obtainsod(z) it is exported with three-phase inverter
Phase voltage q axis component Uoq(z) respectively plus d axis output signal U obtained in step 5id(z) and q axis output signal Uiq(z), it obtains
Modulating wave U under to dq coordinate systemmd(z) and Umq(z), expression formula is respectively as follows:
Umd(z)=Uod(z)+Uid(z)
Umq(z)=Uoq(z)+Uiq(z)。
Preferably, output three-phase inverter phase voltage coordinate transformation equation described in claim 1, three-phase inverter bridge arm electricity
The expression formula of inducing current coordinate transformation equation and three-phase inverter current on line side coordinate transformation equation difference is as follows:
The expression formula of the three-phase inverter output phase voltage coordinate transformation equation are as follows:
The expression formula of the three-phase inverter bridge arm inductive current coordinate transformation equation are as follows:
The expression formula of the three-phase inverter current on line side coordinate transformation equation are as follows:
Wherein, θ is the phase difference of d axis and q axis,S is Laplace operator, and θ ' is d axis and q axis in discrete domain
Phase difference, θ '=ωg(1-z-1)。
Compared with the existing technology, the invention has the benefit that
1, of the present invention based on the grid-connected current control strategy for improving Repetitive controller, pass through nonideal Generalized Integrator
Differential is carried out to capacitance voltage and obtains capacitance current, bridge arm side inductive current subtracts capacitance current and obtains current on line side, by net side
Error signal of the difference of electric current and current on line side fundametal compoment as grid-connected current control input, introduces in Repetitive controller
Capacitor current feedback feeds back the mode of harmonic signal in current on line side comprehensively, improves the rejection ability of harmonic wave；
2, the present invention slows down the phase offset for introducing non-ideal Generalized Integrator by first-order holder discretization method, leads to
Advanced phase shift link compensation system Mid Frequency phase offset is crossed, makes system that there is zero gain in middle low frequency by filtering compensation link
The characteristic of zero phase-shift, to improve the stability of system；
3, the grid-connected current control strategy of the present invention based on improvement Repetitive controller can be only to existing power electronics
The control method of changer system improves, and without increasing additional power electronic equipment, reduces power consumption, save the cost.
Detailed description of the invention
Fig. 1 is the synchronization inverter main circuit topology structure chart using the control strategy.
Fig. 2 is the structural block diagram for the grid-connected current control strategy that the embodiment of the present invention improves Repetitive controller.
Fig. 3 is the voltage on line side electric current that the embodiment of the present invention uses the grid-connected current control strategy based on traditional Repetitive controller
Waveform diagram.
Fig. 4 is the embodiment of the present invention using the voltage on line side before and after the grid-connected current control strategy based on traditional Repetitive controller
Total harmonic distortion factor.
Fig. 5 is the embodiment of the present invention using the current on line side before the grid-connected current control strategy based on traditional Repetitive controller
Total harmonic distortion factor.
Fig. 6 is that the embodiment of the present invention is used based on the current on line side after the grid-connected current control strategy for improving Repetitive controller
Total harmonic distortion factor.
Fig. 7 is that the embodiment of the present invention uses the current on line side voltage based on the grid-connected current control strategy for improving Repetitive controller
Waveform diagram.
Fig. 8 is that the embodiment of the present invention is used based on the voltage on line side before and after the grid-connected current control strategy for improving Repetitive controller
Total harmonic distortion factor.
Fig. 9 is that the embodiment of the present invention is used based on the current on line side before the grid-connected current control strategy for improving Repetitive controller
Total harmonic distortion factor.
Figure 10 is that the embodiment of the present invention is used based on the net side electricity after the grid-connected current control strategy for improving Repetitive controller
The total harmonic distortion factor of stream.
Specific embodiment
The present embodiment is specifically described with reference to the accompanying drawing.
Fig. 1 is the topology diagram using synchronization inverter main circuit of the invention, and as seen from the figure, which includes
DC voltage source, three-phase inverter, LC filter, line impedance and power grid.
LC filter and line impedance are passed through in the DC voltage source and parallel connection of three-phase inverter, three-phase inverter output
Access power grid.In addition, in Fig. 1, VinFor DC voltage source, LfFor three-phase inverter bridge arm side inductance, C is three-phase inverter
Filter capacitor, LgFor pure inductive circuit impedance, r is filter capacitor equivalent series resistance.
Design parameter is as follows: inverter rated output line voltage is 380V/50Hz, DC voltage Vin=600V, bridge arm
Side filter inductance Lf=0.56mH exchanges side filter capacitor Cf=270uF, filter capacitor equivalent series resistance r=0.2 Ω, pure sense
Property line impedance Lg=0.1mH.
Fig. 2 is the structural block diagram for the grid-connected current control strategy that embodiment of the embodiment of the present invention improves Repetitive controller.By this
Figure as it can be seen that it is of the present invention based on improve Repetitive controller grid-connected current control strategy the step of it is as follows:
Step 1, sampling three-phase inverter net side capacitance voltage, that is, three-phase inverter exports phase voltage Uoa,Uob,Uoc, and pass through
Three-phase inverter output phase voltage coordinate transformation equation obtains three-phase inverter output phase voltage dq axis component Uod,Uoq, sampling three
Phase inverter leg inductive current ILa,ILb,ILc, and three-phase is obtained through three-phase inverter bridge arm inductive current coordinate transformation equation
Inverter leg inductive current dq axis component ILd,ILq, wherein d axis is active axis, and q axis is idle axis；Electricity is obtained by phaselocked loop
Net frequencies omegag。
The expression formula of the three-phase inverter output phase voltage coordinate transformation equation are as follows:
The expression formula of the three-phase inverter bridge arm inductive current coordinate transformation equation are as follows:
Wherein, θ is the phase difference of d axis and q axis,S is Laplace operator.
Step 2, phase voltage U is exported to the three-phase inverter that step 1 obtains by first-order holderoa,Uob,Uoc, three contraries
Become device and exports phase voltage dq axis component Uod,Uoq, three-phase inverter bridge arm inductive current ILa,ILb,ILcWith three-phase inverter bridge arm
Inductive current dq axis component ILd,ILqCarry out discretization obtain first-order holder it is discrete after three-phase inverter output phase voltage Uoa
(z),Uob(z),Uoc(z), the three-phase inverter after first-order holder is discrete exports phase voltage dq axis component Uod(z),Uoq(z), one
Three-phase inverter bridge arm inductive current I after rank retainer is discreteLa(z),ILb(z),ILc(z) and first-order holder it is discrete after
Three-phase inverter bridge arm inductive current dq axis component ILd(z),ILq(z), then using the non-ideal improper integral in discrete domain
Device GI'(z) obtain discrete domain in three-phase inverter capacitance current ICa(z),ICb(z),ICc(z), it and then obtains in discrete domain
Three-phase inverter current on line side Ioa(z),Iob(z),Ioc(z).The discretization of the first-order holder be emulated by MATLAB it is soft
What part was realized.
Three-phase inverter capacitance current I in the discrete domainCa(z),ICb(z),ICc(z) calculation formula are as follows:
ICa(z)=CGI'(z) Uoa(z)
ICb(z)=CGI'(z) Uob(z)
ICc(z)=CGI'(z) Uoc(z)
Wherein, C is the capacitance of LC filter,In formula, ωcFor
Non-ideal Generalized Integrator GI'(z in discrete domain) shearing frequency, ω0For the non-ideal Generalized Integrator GI' in discrete domain
(z) the frequency at unlimited gain, T are the sampling period, and z is discrete domain operator.In the present embodiment, ω0=2050rad/s, ωc
=950rad/s, C=270uF.
Three-phase inverter current on line side I in the discrete domainoa(z),Iob(z),Ioc(z) calculation formula are as follows:
Ioa(z)=ILa(z)-ICa(z)
Iob(z)=ILb(z)-ICb(z)
Ioc(z)=ILc(z)-ICc(z)
Step 3, the three-phase inverter current on line side I in discrete domain obtained according to step 2oa(z),Iob(z),Ioc(z),
First three-phase inverter current on line side dq axis component I is obtained through three-phase inverter current on line side coordinate transformation equationod(z),Ioq(z),
Using acquisition three-phase inverter current on line side fundametal compoment I after low-pass first order filterod_LPF(z),Ioq_LPF(z), then will
Three-phase inverter current on line side dq axis component Iod(z),Ioq(z) with three-phase inverter current on line side fundametal compoment Iod_LPF(z),
Ioq_LPF(z) error signal e of the difference as gird-connected inverter current controld(z) and eq(z)；
The expression formula of the three-phase inverter current on line side coordinate transformation equation are as follows:
Wherein, θ ' is the phase difference of d axis and q axis in discrete domain, θ '=ωg(1-z-1)。
The calculation formula of the three-phase inverter current on line side fundametal compoment are as follows:
Wherein, TfFor the time constant of low-pass first order filter.In the present embodiment, Tf=0.05.
The error signal e of the gird-connected inverter current controld(z) and eq(z) calculation formula are as follows:
ed(z)=Iod(z)-Iod_LPF(z)
eq(z)=Ioq(z)-Ioq_LPF(z)
Step 4, the error signal e of the gird-connected inverter current control obtained according to step 3d(z) and eq(z), by repeating
Electric current d axis instruction I is obtained after controlcdref(z) and electric current q axis instructs Icqref(z), its calculation formula is:
Wherein, z-NFor cycle delay link, N is per primitive period sampling number, and Q (z) is interior mode filter, takes the Q (z) to be
Constant less than 1, z are discrete domain operator, and C (z) is repetitive control compensator, expression formula are as follows:
C (z)=KrzkS(z)
Wherein, KrFor Repetitive controller gain, zkFor advanced phase shift link, k is positive integer, and S (z) is filtering compensation link
Second-order low-pass filter, expression formula are as follows:
Wherein,For damping ratio, ωnFor natural frequency of oscillation.
In the present embodiment, N is sample frequency fsWith fundamental frequency f0Ratio, fs=5000Hz, f0=50Hz, then N=
100；Q (z)=0.98；Kr=0.05；K=5；ωn=375rad/s.
Step 5, I is instructed according to the electric current d axis that step 4 obtainscdref(z) and step 2 obtained in three-phase inverter bridge bridge
Arm inductive current d axis component ILd(z), d axis output signal U is obtained by d shaft current closed-loop control equationid(z)；According to step 4
Obtained electric current q axis instruction Icqref(z) and step 2 obtained in three-phase inverter bridge bridge arm inductive current q axis component ILq(z),
Q axis output signal U is obtained by q shaft current closed-loop control equationiq(z), calculation formula is respectively as follows:
Wherein, UidIt (z) is d axis output signal, UiqIt (z) is q axis output signal,For watt current given value,For nothing
Function given value of current value, GPIIt (z) is current closed-loop proportional and integral controller, expression formula are as follows:
Wherein, kpFor three-phase inverter current closed-loop proportional controller coefficient, kiIt integrates and adjusts for three-phase inverter current closed-loop
Save device coefficient.In the present embodiment,kp=5, ki=1.
Step 6, phase voltage d axis component U is exported according to the three-phase inverter that step 2 obtainsod(z) it is exported with three-phase inverter
Phase voltage q axis component Uoq(z) respectively plus d axis output signal U obtained in step 5id(z) and q axis output signal Uiq(z), it obtains
Modulating wave U under to dq coordinate systemmd(z) and Umq(z), expression formula is respectively as follows:
Umd(z)=Uod(z)+Uid(z)
Umq(z)=Uoq(z)+Uiq(z)。
Invention is suitable for based on the grid-connected current control strategy for improving Repetitive controller in the present embodiment.It is as shown below for based on
Improve the simulation waveform of the grid-connected current control strategy of Repetitive controller.
Three-phase inverter is using tradition or improves the grid-connected current control strategy of Repetitive controller, and when 0s is incorporated into the power networks.
Fig. 3, Fig. 4, Fig. 5 are respectively the voltage on line side current waveform of the grid-connected current control strategy based on traditional Repetitive controller
Figure, voltage total harmonic distortion factor and current total harmonic distortion rate.By three figures as it can be seen that after grid-connected, the total harmonic distortion of network voltage
Rate is 9.43%, and containing more 5 times and 7 subharmonic, before and after traditional plug-in repetitive conurol, the total harmonic wave of grid-connected current is abnormal
Variability is down to 9.92% from 10.98%, and harmonics restraint rate has reached 9.7%, there is certain inhibition to imitate 5 times and 7 subharmonic
Fruit.
Fig. 6, Fig. 7, Fig. 8 are respectively the voltage on line side current waveform based on the grid-connected current control strategy for improving Repetitive controller
Figure, voltage total harmonic distortion factor and current total harmonic distortion rate.By three figures as it can be seen that after grid-connected, the total harmonic distortion of network voltage
Rate is 9.43%, containing more 5 times and 7 subharmonic, before and after improving Repetitive controller, grid-connected current total harmonic distortion factor from
10.98% is down to 2.00%, and harmonics restraint rate has reached 81.8%, has apparent inhibitory effect to 5 times and 7 subharmonic.
Claims (2)
1. it is a kind of based on the grid-connected current control strategy for improving Repetitive controller, using the synchronization inverter main circuit of the control strategy
Topological structure include DC voltage source, three-phase inverter, LC filter, line impedance and power grid, the DC voltage
Source and parallel connection of three-phase inverter, three-phase inverter output access power grid by LC filter and line impedance；
It is characterized in that, the step of this control strategy, is as follows:
Step 1, sampling three-phase inverter net side capacitance voltage, that is, three-phase inverter exports phase voltage Uoa,Uob,Uoc, and through three-phase
Inverter output phase voltage coordinate transformation equation obtains three-phase inverter output phase voltage dq axis component Uod,Uoq, sampling three-phase is inverse
Become device bridge arm inductive current ILa,ILb,ILc, and three-phase inversion is obtained through three-phase inverter bridge arm inductive current coordinate transformation equation
Device bridge arm inductive current dq axis component ILd,ILq, wherein d axis is active axis, and q axis is idle axis；Power grid frequency is obtained by phaselocked loop
Rate ωg；
Step 2, phase voltage U is exported to the three-phase inverter that step 1 obtains by first-order holderoa,Uob,Uoc, three-phase inverter
Export phase voltage dq axis component Uod,Uoq, three-phase inverter bridge arm inductive current ILa,ILb,ILcWith three-phase inverter bridge arm inductance
Electric current dq axis component ILd,ILqCarry out discretization obtain first-order holder it is discrete after three-phase inverter output phase voltage Uoa(z),
Uob(z),Uoc(z), the three-phase inverter after first-order holder is discrete exports phase voltage dq axis component Uod(z),Uoq(z), single order is protected
Three-phase inverter bridge arm inductive current I after holder is discreteLa(z),ILb(z),ILc(z) three-phase with first-order holder after discrete
Inverter leg inductive current dq axis component ILd(z),ILq(z), then using the non-ideal Generalized Integrator in discrete domain
GI'(z the three-phase inverter capacitance current I in discrete domain) is obtainedCa(z),ICb(z),ICc(z), so obtain discrete domain in three
Phase inverter current on line side Ioa(z),Iob(z),Ioc(z)；
Three-phase inverter capacitance current I in the discrete domainCa(z),ICb(z),ICc(z) calculation formula are as follows:
ICa(z)=CGI'(z) Uoa(z)
ICb(z)=CGI'(z) Uob(z)
ICc(z)=CGI'(z) Uoc(z)
Wherein, C is the capacitance of LC filter,In formula, ωcIt is discrete
Non-ideal Generalized Integrator GI'(z in domain) shearing frequency, ω0For the non-ideal Generalized Integrator GI'(z in discrete domain)
Unlimited gain at frequency, T is the sampling period, and z is discrete domain operator；
Three-phase inverter current on line side I in the discrete domainoa(z),Iob(z),Ioc(z) calculation formula are as follows:
Ioa(z)=ILa(z)-ICa(z)
Iob(z)=ILb(z)-ICb(z)
Ioc(z)=ILc(z)-ICc(z)
Step 3, the three-phase inverter current on line side I in discrete domain obtained according to step 2oa(z),Iob(z),Ioc(z), it first passes through
Three-phase inverter current on line side coordinate transformation equation obtains three-phase inverter current on line side dq axis component Iod(z),Ioq(z), it then passes through
Three-phase inverter current on line side fundametal compoment I is obtained after crossing low-pass first order filterod_LPF(z),Ioq_LPF(z), then by three-phase
Inverter current on line side dq axis component Iod(z),Ioq(z) with three-phase inverter current on line side fundametal compoment Iod_LPF(z),Ioq_LPF
(z) error signal e of the difference as gird-connected inverter current controld(z) and eq(z)；
The calculation formula of the three-phase inverter current on line side fundametal compoment are as follows:
Wherein, TfFor the time constant of low-pass first order filter；
The error signal e of the gird-connected inverter current controld(z) and eq(z) calculation formula are as follows:
ed(z)=Iod(z)-Iod_LPF(z)
eq(z)=Ioq(z)-Ioq_LPF(z)
Step 4, the error signal e of the gird-connected inverter current control obtained according to step 3d(z) and eq(z), by Repetitive controller
After obtain electric current d axis instruction Icdref(z) and electric current q axis instructs Icqref(z), its calculation formula is:
Wherein, z-NFor cycle delay link, N is per primitive period sampling number, and Q (z) is interior mode filter, take Q (z) be less than
1 constant, z are discrete domain operator, and C (z) is repetitive control compensator, expression formula are as follows:
C (z)=KrzkS(z)
Wherein, KrFor Repetitive controller gain, zkFor advanced phase shift link, k is positive integer, and S (z) is the second order of filtering compensation link
Low-pass filter, expression formula are as follows:
Wherein,For damping ratio, ωnFor natural frequency of oscillation；
Step 5, I is instructed according to the electric current d axis that step 4 obtainscdref(z) and three-phase inverter bridge bridge arm obtained in step 2 is electric
Inducing current d axis component ILd(z), d axis output signal U is obtained by d shaft current closed-loop control equationid(z)；It is obtained according to step 4
Electric current q axis instruct Icqref(z) and step 2 obtained in three-phase inverter bridge bridge arm inductive current q axis component ILq(z), pass through
Q shaft current closed-loop control equation obtains q axis output signal Uiq(z), calculation formula is respectively as follows:
Wherein, UidIt (z) is d axis output signal, UiqIt (z) is q axis output signal,For watt current given value,For idle electricity
Flow given value, GPIIt (z) is current closed-loop proportional and integral controller, expression formula are as follows:
Wherein, kpFor three-phase inverter current closed-loop proportional controller coefficient, kiFor three-phase inverter current closed-loop integral controller
Coefficient；
Step 6, phase voltage d axis component U is exported according to the three-phase inverter that step 2 obtainsod(z) and three-phase inverter output phase is electric
Press q axis component Uoq(z) respectively plus d axis output signal U obtained in step 5id(z) and q axis output signal Uiq(z), dq is obtained
Modulating wave U under coordinate systemmd(z) and Umq(z), expression formula is respectively as follows:
Umd(z)=Uod(z)+Uid(z)
Umq(z)=Uoq(z)+Uiq(z)。
2. according to claim 1 based on the grid-connected current control strategy for improving Repetitive controller, which is characterized in that right is wanted
Ask the 1 output three-phase inverter phase voltage coordinate transformation equation, three-phase inverter bridge arm inductive current coordinate transformation equation and
The expression formula difference of three-phase inverter current on line side coordinate transformation equation is as follows:
The expression formula of the three-phase inverter output phase voltage coordinate transformation equation are as follows:
The expression formula of the three-phase inverter bridge arm inductive current coordinate transformation equation are as follows:
The expression formula of the three-phase inverter current on line side coordinate transformation equation are as follows:
Wherein, θ is the phase difference of d axis and q axis,S is Laplace operator, and θ ' is the phase of d axis and q axis in discrete domain
Potential difference, θ '=ωg(1-z-1)。
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