CN101969272A - Grid-connected current control device of photovoltaic inverter - Google Patents
Grid-connected current control device of photovoltaic inverter Download PDFInfo
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- CN101969272A CN101969272A CN201010288712XA CN201010288712A CN101969272A CN 101969272 A CN101969272 A CN 101969272A CN 201010288712X A CN201010288712X A CN 201010288712XA CN 201010288712 A CN201010288712 A CN 201010288712A CN 101969272 A CN101969272 A CN 101969272A
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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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Abstract
The invention discloses a kind of grid-connected current control device of photovoltaic inverter, are sampled by current detection circuit to grid-connected current, and current waveform is divided into M point according to its corresponding phase and carries out PI control respectively, wherein reference value
Also corresponding with the moment phase, the input of PI control is current sampling data and current reference value of the current detection circuit to each phase
It is compared to obtain current error
. Error signal
Through PI controlling unit generate control amount em, control amount em with
The total control amount Em of synthesis passes through pulse width modulating signal generation circuit again and generates the on-off time ratio that generation duty ratio K goes power switch tube in control inversion bridge circuit with the pulse width modulating signal PWM that the total control amount Em of synthesis changes, to reach the control to grid-connected current, make to export grid-connected current with network voltage with the same phase of frequency, while also can control grid-connected current and reaching desired expectation electric current peak I peak.
Description
Technical field
The invention belongs to photovoltaic inversion grid connection electricity generation system technical field, more specifically say, relate to a kind of photovoltaic DC-to-AC converter grid-connected current control device.
Background technology
Photovoltaic inversion electricity generation system is paid close attention to by the many countries in the whole world at present, and photovoltaic DC-to-AC converter has also obtained very big development as the key component of photovoltaic inversion grid connection electricity generation system.Generally, as shown in Figure 1, photovoltaic inversion grid connection electricity generation system all is made up of solar panel array 1, photovoltaic DC-to-AC converter 2.Wherein, photovoltaic DC-to-AC converter 2 comprises MPPT maximum power point tracking (MPPT) module 201, bus circuit 202, inverter bridge circuit 203 and control circuit 204 parts, function with conversion of solar energy be exactly electric energy and with energy delivery to electrical network 3.
Fig. 1 is the basic block diagram of photovoltaic inversion grid connection electricity generation system.The function of solar panel array 1 is an electric energy with conversion of solar energy exactly, MPPT maximum power point tracking (MPPT) module 201 directly links to each other with solar panel array 1, to regulate the operating state of solar panel, solar panel is operated on the maximum power point.Bus circuit 202 links to each other with solar panel array 1 by the booster circuit on the MPPT maximum power point tracking module 201, system begins to carry out power transfer when its busbar voltage is elevated to the value of appointment, and the power delivery that solar panel is transformed is to inverter bridge circuit 203.Inverter bridge circuit 203 is responsible for the direct current that bus circuit 202 transmits is converted to alternating current (normally 50Hz civil power).Control circuit 204 is keys of whole photovoltaic inversion grid connection electricity generation system steady operation, and the realization of maximal power tracing, the balance of busbar voltage are controlled quietly, the tracking Control of inverter bridge circuital current all will rely on control circuit 204 to carry out computing and scheduling.
The grid-connected current tracking Control of photovoltaic DC-to-AC converter 2 is keys that realization is generated electricity by way of merging two or more grid systems, obtains and the same grid-connected current of homophase frequently of line voltage, and guarantees its wave distortion within prescribed limit, and be that photovoltaic DC-to-AC converter is normal, the emphasis and the difficult point of steady operation.Common grid-connected current control method has indirectly and direct two kinds of control modes, and with respect to the indirect current control method, directly control has advantages such as control circuit is simple, low to the dependence of system parameters, the system dynamics response speed is fast.Yet not only precision is not high for direct PI current control method commonly used, and can produce the electric current phase shift, can cause the operating efficiency of whole inverter lower, and problems such as phase error and wave distortion appear in grid-connected current.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art, proposes a kind of photovoltaic DC-to-AC converter grid-connected current control device, and grid-connected current is reached and line voltage frequency homophase together fast and exactly.
For achieving the above object, photovoltaic DC-to-AC converter grid-connected current control device of the present invention is characterized in that, comprising:
One current detection circuit is used for grid-connected current I
NetSample, the sampling period is T, then obtains M current sampling data in the grid-connected current primitive period L
Wherein, M=L/T, m=0,1,2 ..., M-1, current sampling data
0 phase point of corresponding grid-connected current first-harmonic;
One comparator is used for the current sampling data to each phase place
Expectation electric current with corresponding phase
Compare the output current error
Wherein,
One PI controller is used for according to current error
Produce controlled quentity controlled variable e
m
One add circuit is used for controlled quentity controlled variable e
mFeedforward amount with line voltage
Carry out addition, synthetic master control amount E
m
One pulse width modulating signal produces circuit, is used for according to synthetic master control amount E
m, produce duty ratio K with synthetic master control amount E
mThe pulse width modulating signal PWM that changes goes to control the on-off time ratio of power switch pipe in the inverter bridge circuit;
Detect certain some current sampling data of grid-connected current first-harmonic when current detection circuit
Expectation electric current less than corresponding phase
The time, the output current error
For just, the PI controller produces positive controlled quentity controlled variable e
mFeedforward amount with line voltage
Carry out addition, synthetic master control amount E
mIncrease, like this, the duty ratio K of this pulse width modulating signal PWM increases, the grid-connected current of this point
Increase, until with the expectation electric current of corresponding phase
Equate; Otherwise, detect certain some current sampling data of grid-connected current first-harmonic when current detection circuit
Expectation electric current greater than corresponding phase
The time, the output current error
For negative, the PI controller produces negative controlled quentity controlled variable e
mFeedforward amount with line voltage
Carry out addition, synthetic master control amount E
mReduce, like this, the duty ratio K of this pulse width modulating signal PWM reduces, the grid-connected current of this point
Reduce, until with the expectation electric current of corresponding phase
Equate; Like this, M point in the grid-connected current primitive period L all carries out identical control, makes output grid-connected current and line voltage with the frequency homophase, reaches the current peak of expectation simultaneously.
Goal of the invention of the present invention is achieved in that
Photovoltaic DC-to-AC converter grid-connected current control device of the present invention is sampled to grid-connected current by current detection circuit, current waveform is divided into M point according to its corresponding phase place carries out PI control, wherein reference value respectively
Also phase place is corresponding constantly with this, and the input of PI control is current sampling data and the current reference value of current detection circuit to each phase place
Compare and obtain current error
Error signal
Produce controlled quentity controlled variable e through the PI controlling unit
m, controlled quentity controlled variable e
mWith
Synthetic master control amount E
mProduce circuit by pulse width modulating signal again and generate generation duty ratio K with synthetic master control amount E
mThe pulse width modulating signal PWM that changes goes to control the on-off time ratio of power switch pipe in the inverter bridge circuit, thereby reach control to grid-connected current, make output grid-connected current and line voltage with the frequency homophase, also can control the expectation current peak I that grid-connected current reaches expectation simultaneously
Peak
Description of drawings
The basic block diagram of Fig. 1 photovoltaic inversion grid connection electricity generation system;
Fig. 2 is the theory diagram of a kind of embodiment of photovoltaic DC-to-AC converter grid-connected current control device of the present invention;
Fig. 3 postpones the control schematic diagram.
Embodiment
Below in conjunction with accompanying drawing the specific embodiment of the present invention is described, so that those skilled in the art understands the present invention better.What need point out especially is that in the following description, when perhaps the detailed description of known function and design can desalinate main contents of the present invention, these were described in here and will be left in the basket.
Embodiment
Fig. 2 is the theory diagram of a kind of embodiment of photovoltaic DC-to-AC converter grid-connected current control device of the present invention.
In the present embodiment, as shown in Figure 2, photovoltaic DC-to-AC converter grid-connected current control device of the present invention comprises that current detection circuit 2041, comparator 2042, PI controller 2043, add circuit 2044 and pulse width modulating signal produce circuit 2045.
As shown in Figure 2,2041 couples of grid-connected current I of current detection circuit
NetSample, the sampling period is T, then obtains M current sampling data in the grid-connected current primitive period L
Wherein, M=L/T, m=0,1,2 ..., M-1, current sampling data
0 phase point of corresponding grid-connected current first-harmonic.
The current sampling data of 2042 pairs of each phase places of comparator
Expectation electric current with corresponding phase
Compare the output current error
Wherein,
Then in PI controller 2043, according to current error
Produce controlled quentity controlled variable e
mDeliver to add circuit 2044, be used for controlled quentity controlled variable e
mFeedforward amount with line voltage
Carry out addition, synthetic master control amount E
m
Pulse width modulating signal produces circuit 2045 according to synthetic master control amount E
m, produce duty ratio K with synthetic master control amount E
mThe pulse width modulating signal PWM that changes goes to control the on-off time ratio of power switch pipe in the inverter bridge circuit 203.Thereby reach control, make output grid-connected current I grid-connected current
NetWith line voltage frequency homophase together, also can control the expectation current peak I that grid-connected current reaches expectation simultaneously
PeakPhotovoltaic DC-to-AC converter grid-connected current control device of the present invention places photovoltaic DC-to-AC converter, as the part of its control circuit.
Pulse width modulating signal produces circuit 2045 input controlled quentity controlled variables, master control amount E
mBe to be formed by two parts addition: a part is the feedforward amount of line voltage
Another part is the output e of PI controller 2043 among the figure
mThe feedforward amount of line voltage
Account for master control amount E
mMain ratio, it is used to produce stable voltage and the line voltage unlikely line voltage that maintains an equal level and pours in down a chimney photovoltaic DC-to-AC converter.PI controller control output variable is mainly used in and produces and regulate output current wave, and it is less that its numerical value accounts for the ratio of master control amount, and require control precision higher.Therefore, the stability that less value helps improving system is got in the gain of PI controller proportional integral Kp.
The amplitude of grid-connected current is by the decision of the difference of equivalent output voltage of power switch pipe (IGBT) and line voltage, can control its equivalent output voltage by the time of power switch closed and disconnected.Because the control frequency of power switch is far above the frequency of grid-connected current, in the control procedure of integral body, the action of each data sampling, computing and power switch all is incoherent, so controller also is independently to the control of grid-connected current on each phase place.Therefore, can adopt photovoltaic DC-to-AC converter grid-connected current control device of the present invention to grid-connected current I
NetControl, to have eliminated the influence between the out of phase point, make control more accurate, the output waveform better effects if.
As shown in Figure 2, in the process of photovoltaic DC-to-AC converter work, because control system itself is from grid-connected current I
NetSample data are handled, producing pulse width modulating signal PWM again controls power switch pipe and needs the regular hour, and also have delay on the inductance that is incorporated into the power networks, so can not in the same cycle, finish to sampling, computing and the control of some phase point electric currents.At this problem, in the present embodiment, as shown in Figure 2, adopted the method that postpones control: on the basis of general PI control principle, PI controller 2043 is improved, in PI controller 2043, added delayer Z behind the integrator
-N, delayer Z
-NExport one the road and feed back to input; Current sampling data
Process and the expectation electric current of joining corresponding phase
Compare the output current error
2043 pairs of current errors of PI controller then
Do PI control computing, wherein, integration amount postpones N sampled point in delayer, like this, and the controlled quentity controlled variable e of PI controller 2043 outputs
mProlong N sampled point, as the control of the corresponding phase point grid-connected current of following one-period.Kp among Fig. 2 and Ki represent the ratio and the integral parameter of PI controller respectively.
Fig. 3 postpones the control schematic diagram.
Add delay in integral element as shown in Figure 3, offset the controlled quentity controlled variable hysteresis that various time delays cause, reduced owing to the corresponding system mistake that makes mistakes and cause of sampled point with working control point.Among Fig. 2, being a primitive period L between working control point and the sampled point, is the delay that system control itself produces between working control point and the control point.Relevant with the control lag n of each primitive period sampling number M and system itself for choosing of delay sampling points N, the unit of n is a sampled point number, and the grid-connected current primitive period is L, and the sampling period is T, then:
Definite formula of delay sampling points N is:
N＝M-n
Under big inertia environment, export controlled quentity controlled variable in advance and in actual output point sampling, can farthest reduce the problem that lose at sampling and control point.In addition, the proportional component proportion is very small in controlled quentity controlled variable, does not therefore need specially to add to postpone to control.
The present invention is applied in the 5000w solar energy inversion system, can obtain wave distortion THD less than 2% output current, and the cycle of current first harmonics is 0.02s in this system, and the cycle of sampling is 55.5 μ s, and the delay n of control has selected 4, so the size of N is 356.
It is simple that the independent phase PI control method that the present invention adopts has an algorithm, is easy to digitlization and High-speed Control, and robustness is good, reliability height, the advantage that parameter is easily adjusted.Branch PI control simultaneously combines with delay control method, eliminated the problem that traditional PI controls such as phase lag that integral element brings to system and control system easy instability can't overcome, the precise control and the stability of system have been improved, thereby can make the stable tracking Control grid-connected current fast of control system, make it reach requirement fast and accurately.Simultaneously, tracking power network current speed is fast, and the output current wave harmonic distortion is little; This control device is stable, and departure is little, accuracy is high.
Although above the illustrative embodiment of the present invention is described; so that the technical staff of present technique neck understands the present invention; but should be clear; the invention is not restricted to the scope of embodiment; to those skilled in the art; as long as various variations appended claim limit and the spirit and scope of the present invention determined in, these variations are conspicuous, all utilize innovation and creation that the present invention conceives all at the row of protection.
Claims (3)
1. a photovoltaic DC-to-AC converter grid-connected current control device is characterized in that, comprising:
One current detection circuit is used for grid-connected current I
NetSample, the sampling period is T, then obtains M current sampling data in the grid-connected current primitive period L
Wherein, M=L/T, m=0,1,2 ..., M-1, current sampling data
0 phase point of corresponding grid-connected current first-harmonic;
One comparator is used for the current sampling data to each phase place
Expectation electric current with corresponding phase
Compare the output current error
Wherein,
One PI controller is used for according to current error
Produce controlled quentity controlled variable e
m
One add circuit is used for controlled quentity controlled variable e
mFeedforward amount with line voltage
Carry out addition, synthetic master control amount E
m
One pulse width modulating signal produces circuit, is used for according to synthetic master control amount E
m, produce duty ratio K with synthetic master control amount E
mThe pulse width modulating signal PWM that changes goes to control the on-off time ratio of power switch pipe in the inverter bridge circuit;
Detect certain some current sampling data of grid-connected current first-harmonic when current detection circuit
Expectation electric current less than corresponding phase
The time, the output current error
For just, the PI controller produces positive controlled quentity controlled variable e
mFeedforward amount with line voltage
Carry out addition, synthetic master control amount E
mIncrease, like this, the duty ratio K of this pulse width modulating signal PWM increases, the grid-connected current of this point
Increase, until with the expectation electric current of corresponding phase
Equate; Otherwise, detect certain some current sampling data of grid-connected current first-harmonic when current detection circuit
Expectation electric current greater than corresponding phase
The time, the output current error
For negative, the PI controller produces negative controlled quentity controlled variable e
mFeedforward amount with line voltage
Carry out addition, synthetic master control amount E
mReduce, like this, the duty ratio K of this pulse width modulating signal PWM reduces, the grid-connected current of this point
Reduce, until with the expectation electric current of corresponding phase
Equate; Like this, M point in the grid-connected current primitive period L all carries out identical control, makes output grid-connected current and line voltage with the frequency homophase, reaches the current peak of expectation simultaneously.
2. photovoltaic DC-to-AC converter grid-connected current control device according to claim 1 is characterized in that, in the described PI controller, has added delayer Z behind its integrator
-N, delayer Z
-NExport one the road and feed back to input; Current error
When doing PI control computing, integration amount postpones N sampled point in delayer, like this, and the controlled quentity controlled variable e of PI controller output
mProlong N sampled point, as the control of the corresponding phase point grid-connected current of following one-period, wherein, the delay sampling points N is: N=M-n, n are the control lag sampled point number of system itself.
3. photovoltaic DC-to-AC converter grid-connected current control device according to claim 1 is characterized in that, less value is got in the gain of proportional integral Kp in the described PI controller.
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| CN201010288712XA CN101969272B (en) | 2010-09-21 | 2010-09-21 | Grid-connected current control device of photovoltaic inverter |
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| CN201010288712XA CN101969272B (en) | 2010-09-21 | 2010-09-21 | Grid-connected current control device of photovoltaic inverter |
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| CN101969272B CN101969272B (en) | 2013-04-17 |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103795083A (en) * | 2014-02-20 | 2014-05-14 | 新疆希望电子有限公司 | Grid connection current soft start and soft stop method and system for photovoltaic grid-connected inverter |
| CN106849155A (en) * | 2015-12-01 | 2017-06-13 | Det 国际控股有限公司 | For the controller of inverter |
| CN108828933A (en) * | 2018-07-03 | 2018-11-16 | 唐瑭 | Improve the control method and system of grid-connected converter output waveform quality |
| CN112698571A (en) * | 2020-12-09 | 2021-04-23 | 河南知汇电力技术有限公司 | double-PI cooperative control device and method |
| CN114222926A (en) * | 2019-10-04 | 2022-03-22 | 新电元工业株式会社 | Current detection device, motor control device, and current detection method |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103795083A (en) * | 2014-02-20 | 2014-05-14 | 新疆希望电子有限公司 | Grid connection current soft start and soft stop method and system for photovoltaic grid-connected inverter |
| CN103795083B (en) * | 2014-02-20 | 2016-01-13 | 新疆希望电子有限公司 | Photovoltaic combining inverter grid-connected current soft start and soft stop method and system |
| CN106849155A (en) * | 2015-12-01 | 2017-06-13 | Det 国际控股有限公司 | For the controller of inverter |
| CN106849155B (en) * | 2015-12-01 | 2022-02-11 | 泰达电子股份有限公司 | Controller for inverter |
| CN108828933A (en) * | 2018-07-03 | 2018-11-16 | 唐瑭 | Improve the control method and system of grid-connected converter output waveform quality |
| CN108828933B (en) * | 2018-07-03 | 2021-06-11 | 唐瑭 | Control method and system for improving output waveform quality of grid-connected converter |
| CN114222926A (en) * | 2019-10-04 | 2022-03-22 | 新电元工业株式会社 | Current detection device, motor control device, and current detection method |
| CN112698571A (en) * | 2020-12-09 | 2021-04-23 | 河南知汇电力技术有限公司 | double-PI cooperative control device and method |
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