CN104270022A - Photovoltaic grid connected inversion circuit, switch control circuit and control method - Google Patents
Photovoltaic grid connected inversion circuit, switch control circuit and control method Download PDFInfo
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- CN104270022A CN104270022A CN201410523189.2A CN201410523189A CN104270022A CN 104270022 A CN104270022 A CN 104270022A CN 201410523189 A CN201410523189 A CN 201410523189A CN 104270022 A CN104270022 A CN 104270022A
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- 239000000203 mixture Substances 0.000 claims description 10
- 239000010409 thin film Substances 0.000 claims description 3
- 238000005868 electrolysis reaction Methods 0.000 abstract description 3
- 238000010248 power generation Methods 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 6
- 239000010408 film Substances 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
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- 101710156159 50S ribosomal protein L21, chloroplastic Proteins 0.000 description 1
- 102000004895 Lipoproteins Human genes 0.000 description 1
- 108090001030 Lipoproteins Proteins 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 description 1
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Classifications
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- H02J3/383—
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- 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 photovoltaic grid connected inversion circuit, a switch control circuit and a control method and belongs to the technical field of photovoltaic power generation. When the output voltage of a photovoltaic battery pack is larger than the alternating current output voltage of a power grid, a chopped wave switching tube SWc is not switched on, the current flows to an inferior full-bridge inversion unit through a bypass diode Db, and the full-bridge inversion unit works in an SPWM mode; when the output voltage of the photovoltaic battery pack is smaller than or equal to the alternating current output voltage of the power grid, the chopped wave switching tube SWc works in a high-frequency PWM mode, and the full-bridge inversion unit works at the power frequency. Only one level of a converter unit works at the high frequency at any moment so that the efficiency of a whole machine can be improved; due to the fact that a high-capacity electrolysis direct current capacitor set is not used, a solar photovoltaic power generation system which is small in size, light in weight and low in cost can be obtained.
Description
Technical field
The present invention relates to technical field of photovoltaic power generation, more particularly, relate to a kind of photovoltaic grid-connected inversion circuit, ON-OFF control circuit and control method.
Background technology
From the viewpoint of environmental protection, the application of distributed solar energy photovoltaic generating system on residential electric power is more and more welcome on a small scale.For solar photovoltaic generation system, the single-phase sinewave inverter topological structure of non-isolated has advantage in cost, size and efficiency, and this makes non-isolated grid-connected structure have good development prospect.Non-isolated sinewave inverter main circuit mainly comprises two working portions: one is the boosting part for promoting from photovoltaic module array low-voltage; Two is for exchanging the Converting Unit being connected to electrical network or direct load-carrying high-frequency PWM modulation.
The prime of traditional two-stage type combining inverter generally adopts Boost boosting unit to promote input voltage, and rear class inverter is directly converted to alternating current.Prime boosting unit is in high-frequency PWM modulation condition always, later stage inversion unit is then with SPWM (sinusoidal pulse width modulation) mode high frequency modulated, so prime boosting part and rear class Converting Unit are operated in high frequency state simultaneously, the switching loss of switching tube is very large, is unfavorable for the raising of overall efficiency.In addition, in order to keep the voltage after boosting to be constant, the electrolytic capacitor group be connected in DC bus needs sufficiently high electric capacity.Therefore electrolytic capacitor packet size is large, and has the ripple current of higher frequency, due to the existence of equivalent series resistance, can cause power loss, and electrolysis direct current Capacitor banks is heavy, and high to temperature requirement, the life-span is short.
Through retrieval, Chinese Patent Application No. 201110353854.4, the applying date is on November 10th, 2011, invention and created name is: photovoltaic combining inverter inversion of direct current busbar voltage control method and control system, it is in parallel with Boost circuit that the photovoltaic DC-to-AC converter of this application case adds a bypass diode, and at a photovoltaic cell outlet side bulky capacitor in parallel.The voltage control method of this application case comprises the following steps: gather line voltage Vac and input direct voltage Vpv; Judge whether Vpv >=1.6Vac sets up; As being judged as YES, close Boost circuit; As being judged as NO, open Boost circuit; Inversion is carried out to input direct voltage Vpv.This application case, by adjusting busbar voltage in real time, to reduce the operating time of Boost circuit, reduces electromagnetic interference, improves system effectiveness to a certain extent.But the Boost circuit part of this application case photovoltaic DC-to-AC converter comprises two bulky capacitor, the photovoltaic DC-to-AC converter volume because of the introducing of use bulky capacitor analyzed above is large, heavy, not only easy generation high-frequency ripple current and power loss is large etc. that problem is not eased but more serious, photovoltaic DC-to-AC converter manufacturing cost is high and stability is bad; In addition, the Converting Unit of this application case is still operated in high frequency state always, and switching loss is large, and overall efficiency is low.
Summary of the invention
1. invent the technical problem that will solve
The object of the invention is to solve that conventional photovoltaic inverter exists: 1) switching loss is large, overall efficiency is low; 2) owing to using big capacity electrolyte capacitor device group to cause the problems such as photovoltaic DC-to-AC converter volume is large, heavy, and power loss is large; Provide a kind of photovoltaic grid-connected inversion circuit, ON-OFF control circuit and control method.Use technical scheme provided by the invention, determine the mode of operation of 2 stage converter unit according to the magnitude relationship of input voltage and line voltage, any time can be made only to have one-stage transfor-mation device unit high-frequency work, be conducive to the raising of overall efficiency; In addition, owing to not using Large Copacity electrolysis direct current Capacitor banks, little, the lightweight and solar photovoltaic generation system of low cost of size can be realized.
2. technical scheme
For achieving the above object, technical scheme provided by the invention is:
A kind of photovoltaic grid-connected inversion circuit of the present invention, comprises DC boosting unit, full-bridge inverting unit, filter unit, photovoltaic cell group and electrical network, wherein:
Described full-bridge inverting unit is connected with DC boosting unit, and this full-bridge inverting unit is by full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4the inverter bridge of composition;
Described filter unit comprises filter inductance L
fwith filter capacitor C
f, filter inductance L
ffirst end and described full-bridge inverting switching tube SW
1, SW
2the intermediate point of composition brachium pontis connects, this filter inductance L
fthe second end respectively with filter capacitor C
ffirst end, electrical network one end connect, the other end of electrical network and filter capacitor C
fsecond end connect; Filter capacitor C
fthe second end also with full-bridge inverting switching tube SW
3, SW
4the intermediate point of composition brachium pontis connects;
Described DC boosting unit comprises bypass diode D
b, boost inductance L
b, diode Dc, chopping switching tube SWc and intermediate capacitance Cc, the positive pole of photovoltaic cell group respectively with bypass diode D
bpositive pole, boost inductance L
bfirst end connect, bypass diode D
bnegative pole respectively with diode D
cnegative pole, intermediate capacitance Cc first end connect, boost inductance L
bthe second end be connected with the positive pole of diode Dc, the collector electrode of chopping switching tube SWc respectively; The negative pole of described photovoltaic cell group is connected with the emitter of chopping switching tube SWc, second end of intermediate capacitance Cc respectively.
Further, described intermediate capacitance Cc is low capacity thin-film capacitor.
The ON-OFF control circuit of a kind of photovoltaic grid-connected inversion circuit of the present invention, comprises chopping switching tube SWc control circuit and full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4control circuit, wherein:
In described chopping switching tube SWc control circuit, the signal output part of sine-wave generator I is connected with the in-phase input end of comparator I, the input of DSP microprocessor respectively through full-wave rectifier I, the signal output part of signal picker is connected with the inverting input of comparator I, the input of DSP microprocessor respectively, the signal output part of comparator I, DSP microprocessor is connected with the input of multiplier I respectively, and the output signal of multiplier I is as the drive singal of SWc;
Described full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4in control circuit, the signal output part of sine-wave generator II is connected through the in-phase input end of full-wave rectifier II with comparator II, and the signal output part of triangular-wave generator is connected with the inverting input of comparator II; The signal output part of sine-wave generator III is connected with the in-phase input end of comparator III, and the inverting input of comparator III is connected with no-voltage; The signal output part of sine-wave generator IV is connected with the inverting input of comparator IV, and the in-phase input end of comparator IV is connected with no-voltage; The signal output part of comparator II, comparator III is connected with the input of multiplier II, and the output signal of multiplier II is as SW
1drive singal, multiplier II connects the output signal of inverter I as SW
2drive singal; The signal output part of comparator II, comparator IV is connected with the input of multiplier III, and the output signal of multiplier III is as SW
3drive singal, multiplier III connects the output signal of inverter II as SW
4drive singal.
The control method of a kind of photovoltaic grid-connected inversion circuit of the present invention, the steps include:
Step one, judge photovoltaic cell group output voltage V
inwhether be greater than electrical network ac output voltage absolute value | V
out|;
Step 2, controlled the break-make of chopping switching tube SWc by the judged result of step one, if V
in> | V
out|, then control SWc turns off; If V
in≤ | V
out|, then control SWc is operated in high-frequency PWM state;
Step 3, control full-bridge inverting switching tube SW according to the break-make of SWc
1, SW
2, SW
3, SW
4break-make, if SW
cturn off, then control SW
1, SW
2, SW
3, SW
4be operated in SPWM modulating mode, if SW
cbe operated in high-frequency PWM state, then control SW
1, SW
2, SW
3, SW
4work with power frequency modulation system.
Further, the detailed process that step 2 controls chopping switching tube SWc break-make is: sine-wave generator I produces standard AC sine wave, the in-phase input end of input comparator I and the input of DSP microprocessor after full-wave rectifier I rectification, signal picker gathers the output voltage V of photovoltaic cell group
inthe inverting input of input comparator I and the input of DSP microprocessor, compared through comparator I pulse train that obtains and be multiplied by multiplier I through the signal of DSP microprocessor processes, the pulse train control SW that multiplier I exports
cbreak-make.
Further, step 3 controls full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4the detailed process of break-make is: sine-wave generator II produces standard AC sine wave, the in-phase input end of input comparator II after full-wave rectifier II rectification, and it is V that triangular-wave generator produces amplitude
inthe inverting input of triangular wave input comparator II; Sine-wave generator III produces the in-phase input end of the sinusoidal wave input comparator III of standard AC, compares through comparator III with no-voltage; Sine-wave generator IV also produces the inverting input of the sinusoidal wave input comparator IV of standard AC, compares through comparator IV with no-voltage; The output signal of comparator II, comparator III is multiplied by multiplier II, the output signal control SW of multiplier II
1break-make, multiplier II meets the output signal control SW of inverter I
2break-make; The output signal of comparator II, comparator IV is multiplied by multiplier III, the output signal control SW of multiplier III
3break-make, multiplier III meets the output signal control SW of inverter II
4break-make.
Further, the output signal of described DSP microprocessor is pulse regulation duty ratio
3. beneficial effect
Adopt technical scheme provided by the invention, compared with existing known technology, there is following remarkable result:
(1) a kind of photovoltaic grid-connected inversion circuit of the present invention, boost inductance L in its DC boosting unit
ba bypass diode D is parallel with in the series arm of diode Dc
b, when photovoltaic cell group output voltage is higher than line voltage, chopping switching tube SWc not conducting, electric current is by bypass diode D
bflow to full-bridge inverting unit, full-bridge inverting unit High ireguency SPWM works; When photovoltaic cell group output voltage is lower than line voltage, chopping switching tube SWc high frequency modulated, full-bridge inverting unit power frequency works; The mode of operation of 2 stage converter unit is determined according to the magnitude relationship of input voltage and line voltage, can make boost chopper and full-bridge inverting under synchronization only has stage circuit to be operated in high frequency mode, reduce total on-off times, be conducive to the raising of overall efficiency;
(2) control method of a kind of photovoltaic grid-connected inversion circuit of the present invention, it controls prime DC boosting cell operation when PWM mode, for rear class full-bridge inverting unit provides sinusoidal half-wave voltage, rear class full-bridge inverting unit only needs power frequency switch operating can complete sinusoidal current injection electrical network; When prime DC boosting unit leads directly to, rear class full-bridge inverting cell operation is in SPWM mode; This kind of mode of operation, constant voltage is kept without the need to intermediate DC link, the film capacitor of available low capacity, small size replaces jumbo electrolytic capacitor, and achieve miniaturization and the lightness of inverter system, the job stability of inverter have also been obtained raising; In addition, when full-bridge inverting cell S PWM mode works, input current is through bypass diode D
b, and do not flow through boost inductance L
bwith diode Dc, the conduction loss of booster circuit reduces greatly.
Accompanying drawing explanation
Fig. 1 is the structure chart of photovoltaic grid-connected inversion circuit of the present invention;
(a) in Fig. 2 is the fundamental diagram of boost chopper part of the present invention; (b) in Fig. 2 is the fundamental diagram of full-bridge inverting part of the present invention;
Fig. 3 is switching pulse sequence chart of the present invention
(a) in Fig. 4 is for driving the circuit structure diagram of chopping switching tube SWc in ON-OFF control circuit of the present invention; (b) in Fig. 4 is for driving full-bridge inverting switching tube SW in ON-OFF control circuit of the present invention
1, SW
2, SW
3, SW
4circuit structure diagram;
Fig. 5 is intermediate capacitance C in the present invention
cvoltage oscillogram;
Fig. 6 is filter unit input side voltage oscillogram in the present invention;
Fig. 7 is the control flow block diagram of photovoltaic grid-connected inversion circuit of the present invention.
Label declaration in schematic diagram:
1-DC boosting unit; 2-full-bridge inverting unit; 3-filter unit; 4-photovoltaic cell group; 5-electrical network; D
b-bypass diode; L
b-boost inductance; Dc-diode; SWc-chopping switching tube; Cc-intermediate capacitance; SW
1, SW
2, SW
3, SW
4-full-bridge inverting switching tube; L
f-filter inductance; C
f-filter capacitor.
Embodiment
For understanding content of the present invention further, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.
Embodiment 1
Composition graphs 1, a kind of photovoltaic grid-connected inversion circuit of the present embodiment, comprises DC boosting unit 1, full-bridge inverting unit 2, filter unit 3, photovoltaic cell group 4 and electrical network 5, wherein:
Described DC boosting unit 1 comprises bypass diode D
b, boost inductance L
b, diode Dc, chopping switching tube SWc and intermediate capacitance Cc, the positive pole of photovoltaic cell group 4 respectively with bypass diode D
bpositive pole, boost inductance L
bfirst end connect, bypass diode D
bnegative pole respectively with diode D
cnegative pole, intermediate capacitance Cc first end connect, boost inductance L
bthe second end be connected with the positive pole of diode Dc, the collector electrode of chopping switching tube SWc respectively; The negative pole of described photovoltaic cell group 4 is connected with the emitter of chopping switching tube SWc, second end of intermediate capacitance Cc respectively.
Described full-bridge inverting unit 2 is by full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4the inverter bridge of composition, the first end of inverter bridge and intermediate capacitance C
csecond end connect, inverter bridge the second end be connected with the negative pole of photovoltaic cell group 4.
Described filter unit 3 comprises filter inductance L
fwith filter capacitor C
f, filter inductance L
ffirst end and described full-bridge inverting switching tube SW
1, SW
2the intermediate point of composition brachium pontis connects, this filter inductance L
fthe second end respectively with filter capacitor C
ffirst end, electrical network 5 one end connect, the other end of electrical network 5 and filter capacitor C
fsecond end connect; Filter capacitor C
fthe second end also with full-bridge inverting switching tube SW
3, SW
4the intermediate point of composition brachium pontis connects.
Photovoltaic cell group 4 exports the direct current input side that direct current first accesses DC boosting unit 1, DC boosting unit 1 carries out boosting inverter, direct current after boosting accesses the direct current input side of full-bridge inverting unit 2 again, full-bridge inverting unit 2 changes direct current into alternating current, by access electrical network 5 or load after filter unit 3.
Referring to (a) and (b) in Fig. 4, the ON-OFF control circuit of a kind of photovoltaic grid-connected inversion circuit of the present embodiment, comprises chopping switching tube SWc control circuit and full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4control circuit, wherein:
In described chopping switching tube SWc control circuit, the signal output part of sine-wave generator I is connected with the in-phase input end of comparator I, the input of DSP microprocessor respectively through full-wave rectifier I, the signal output part of signal picker is connected with the inverting input of comparator I, the input of DSP microprocessor respectively, the signal output part of comparator I, DSP microprocessor is connected with the input of multiplier I respectively, and the output signal of multiplier I is as the drive singal of SWc.
Described full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4in control circuit, the signal output part of sine-wave generator II is connected through the in-phase input end of full-wave rectifier II with comparator II, and the signal output part of triangular-wave generator is connected with the inverting input of comparator II; The signal output part of sine-wave generator III is connected with the in-phase input end of comparator III, and the inverting input of comparator III is connected with no-voltage; The signal output part of sine-wave generator IV is connected with the inverting input of comparator IV, and the in-phase input end of comparator IV is connected with no-voltage; The signal output part of comparator II, comparator III is connected with the input of multiplier II, and the output signal of multiplier II is as SW
1drive singal, multiplier II connects the output signal of inverter I as SW
2drive singal; The signal output part of comparator II, comparator IV is connected with the input of multiplier III, and the output signal of multiplier III is as SW
3drive singal, multiplier III connects the output signal of inverter II as SW
4drive singal.
Fig. 2 describes the present embodiment and utilizes described ON-OFF control circuit to control the operation principle of photovoltaic grid-connected inversion circuit, and (a) in Fig. 2 is the operation principle of boost chopper part; (b) in Fig. 2 is the operation principle of full-bridge inverting part; As photovoltaic cell group 4 output voltage V
inthan electrical network 5 ac output voltage absolute value | V
out| time large, chopping switching tube SWc is in off state, and input current flows through bypass diode D
b, and do not flow through boost inductance L
bwith diode D
c, the output voltage of DC boosting unit 1 equals input direct voltage V
in, in such cases, full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4be operated in SPWM modulating mode; As photovoltaic cell group 4 output voltage V
inbe less than or equal to electrical network 5 ac output voltage absolute value | V
out| time, chopping switching tube SWc is operated in high-frequency PWM pattern, intermediate capacitance C
cuse low capacity thin-film capacitor, make the output voltage of DC boosting unit 1 produce quasi sine which amplitude modulation waveform.Now, full-bridge inverting switching tube (SW
1~ SW
4) with the work of power frequency modulation system, make output voltage synchronous with electrical network 5 polarity.Due under this kind of mode of operation, constant voltage is kept without the need to intermediate DC link, jumbo electrolytic capacitor is replaced with the film capacitor of low capacity, small size, the film capacitor that the present embodiment adopts is metallized polyimide second membrane of lipoprotein capacitor MEF (CL21), achieve miniaturization and the lightness of inverter system, the job stability of inverter have also been obtained raising.The present embodiment determines the mode of operation of 2 stage converter unit according to the magnitude relationship of input voltage and line voltage, can make boost chopper and full-bridge inverting under synchronization only has stage circuit to be operated in high frequency mode, reduce total on-off times, be conducive to the raising of overall efficiency.
Referring to Fig. 7, the concrete control procedure of the present embodiment is:
Step one, judge photovoltaic cell group 4 output voltage V
inwhether be greater than electrical network 5 ac output voltage absolute value | V
out|.
Step 2, controlled the break-make of chopping switching tube SWc by the judged result of step one, if V
in> | V
out|, then control SWc turns off; If V
in≤ | V
out|, then control SWc is operated in high-frequency PWM state; The detailed process controlling chopping switching tube SWc break-make is: sine-wave generator I produces standard AC sine wave, the in-phase input end of input comparator I and the input of DSP F2812 microprocessor after full-wave rectifier I rectification, signal picker gathers the output voltage V of photovoltaic cell group 4
inthe inverting input of input comparator I and the input of DSP F2812 microprocessor, compare the pulse train obtained and the pulse regulation duty ratio exported after DSP microprocessor processes through comparator I
signal is multiplied by multiplier I, the pulse train control SW that multiplier I exports
cbreak-make.
Step 3, control full-bridge inverting switching tube SW according to the break-make of SWc
1, SW
2, SW
3, SW
4break-make, if SW
cturn off, then control SW
1, SW
2, SW
3, SW
4be operated in SPWM modulating mode, if SW
cbe operated in high-frequency PWM state, then control SW
1, SW
2, SW
3, SW
4work with power frequency modulation system.Control full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4the detailed process of break-make is: sine-wave generator II produces standard AC sine wave, the in-phase input end of input comparator II after full-wave rectifier II rectification, and it is V that triangular-wave generator produces amplitude
inthe inverting input of triangular wave input comparator II; Sine-wave generator III produces the in-phase input end of the sinusoidal wave input comparator III of standard AC, compares through comparator III with no-voltage; Sine-wave generator IV also produces the inverting input of the sinusoidal wave input comparator IV of standard AC, compares through comparator IV with no-voltage; The output signal of comparator II, comparator III is multiplied by multiplier II, the output signal control SW of multiplier II
1break-make, multiplier II meets the output signal control SW of inverter I
2break-make; The output signal of comparator II, comparator IV is multiplied by multiplier III, the output signal control SW of multiplier III
3break-make, multiplier III meets the output signal control SW of inverter II
4break-make.
Fig. 3 describes the pulse train of each switching tube of the present embodiment, at the positive half period of AC sine output voltage, and SW
3not conducting, SW
4straight-through, when photovoltaic cell group 4 output voltage is greater than AC sine output voltage, chopping switching tube SWc not conducting, full-bridge inverting switching tube SW
1, SW
2conducting is modulated through SPWM; When photovoltaic cell group 4 output voltage is less than or equal to AC sine output voltage, chopping switching tube SW
caccording to duty ratio
high frequency modulated, SW
1straight-through, SW
2not conducting.At the negative half-cycle of AC sine output voltage, SW
1not conducting, SW
2straight-through, when the negative value of photovoltaic cell group 4 output voltage is less than AC sine output voltage, chopping switching tube SW
cnot conducting, full-bridge inverting switching tube SW
3, SW
4conducting is modulated through SPWM; When the negative value of photovoltaic cell group 4 output voltage is greater than AC sine output voltage, chopping switching tube SW
caccording to duty ratio
high frequency modulated, full-bridge inverting switching tube SW
3straight-through, SW
4not conducting.
Fig. 5 and 6 is the concrete simulation waveform figure of the present embodiment, and wherein, Fig. 5 is intermediate capacitance C
cvoltage oscillogram, Fig. 6 is filter unit 3 input side voltage oscillogram.Photovoltaic cell group 4 voltage 160V in the present embodiment, electrical network 5 voltage 220Vrms, electrical network 5 frequency f
grid=50Hz, boost inductance L
b=0.9mH, intermediate capacitance C
c=2.2uF, filter inductance L
f=1mH, filter capacitor C
f=10uF, switching frequency f=50kHz.
A kind of photovoltaic grid-connected inversion circuit, ON-OFF control circuit and control method described in embodiment 1, when control prime DC boosting unit 1 is operated in PWM mode, for rear class full-bridge inverting unit provides sinusoidal half-wave voltage, rear class full-bridge inverting unit 2 only needs power frequency switch operating can complete sinusoidal current injection electrical network; When prime DC boosting unit 1 leads directly to, rear class full-bridge inverting unit 2 works in SPWM mode, and only there is one-stage transfor-mation device unit high-frequency work any time; This kind of mode of operation, constant voltage is kept without the need to intermediate DC link, the film capacitor of available low capacity, small size replaces jumbo electrolytic capacitor, and achieve miniaturization and the lightness of inverter system, the job stability of inverter have also been obtained raising; In addition, when full-bridge inverting cell S PWM mode works, input current is through bypass diode D
b, and do not flow through boost inductance L
bwith diode Dc, the conduction loss of booster circuit reduces greatly.
Schematically above be described the present invention and execution mode thereof, this description does not have restricted, and also just one of the embodiments of the present invention shown in accompanying drawing, actual structure is not limited thereto.So, if those of ordinary skill in the art enlightens by it, when not departing from the invention aim, designing the frame mode similar to this technical scheme and embodiment without creationary, all should protection scope of the present invention be belonged to.
Claims (7)
1. a photovoltaic grid-connected inversion circuit, comprises DC boosting unit (1), full-bridge inverting unit (2), filter unit (3), photovoltaic cell group (4) and electrical network (5), wherein:
Described full-bridge inverting unit (2) is connected with DC boosting unit (1), and this full-bridge inverting unit (2) is by full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4the inverter bridge of composition;
Described filter unit (3) comprises filter inductance L
fwith filter capacitor C
f, filter inductance L
ffirst end and described full-bridge inverting switching tube SW
1, SW
2the intermediate point of composition brachium pontis connects, this filter inductance L
fthe second end respectively with filter capacitor C
ffirst end, electrical network (5) one end connect, the other end of electrical network (5) and filter capacitor C
fsecond end connect; Filter capacitor C
fthe second end also with full-bridge inverting switching tube SW
3, SW
4the intermediate point of composition brachium pontis connects; It is characterized in that:
Described DC boosting unit (1) comprises bypass diode D
b, boost inductance L
b, diode Dc, chopping switching tube SWc and intermediate capacitance Cc, the positive pole of photovoltaic cell group (4) respectively with bypass diode D
bpositive pole, boost inductance L
bfirst end connect, bypass diode D
bnegative pole respectively with diode D
cnegative pole, intermediate capacitance Cc first end connect, boost inductance L
bthe second end be connected with the positive pole of diode Dc, the collector electrode of chopping switching tube SWc respectively; The negative pole of described photovoltaic cell group (4) is connected with the emitter of chopping switching tube SWc, second end of intermediate capacitance Cc respectively.
2. a kind of photovoltaic grid-connected inversion circuit according to claim 1, is characterized in that: described intermediate capacitance Cc is low capacity thin-film capacitor.
3. an ON-OFF control circuit for photovoltaic grid-connected inversion circuit, is characterized in that: comprise chopping switching tube SWc control circuit and full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4control circuit, wherein:
In described chopping switching tube SWc control circuit, the signal output part of sine-wave generator I is connected with the in-phase input end of comparator I, the input of DSP microprocessor respectively through full-wave rectifier I, the signal output part of signal picker is connected with the inverting input of comparator I, the input of DSP microprocessor respectively, the signal output part of comparator I, DSP microprocessor is connected with the input of multiplier I respectively, and the output signal of multiplier I is as the drive singal of SWc;
Described full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4in control circuit, the signal output part of sine-wave generator II is connected through the in-phase input end of full-wave rectifier II with comparator II, and the signal output part of triangular-wave generator is connected with the inverting input of comparator II; The signal output part of sine-wave generator III is connected with the in-phase input end of comparator III, and the inverting input of comparator III is connected with no-voltage; The signal output part of sine-wave generator IV is connected with the inverting input of comparator IV, and the in-phase input end of comparator IV is connected with no-voltage; The signal output part of comparator II, comparator III is connected with the input of multiplier II, and the output signal of multiplier II is as SW
1drive singal, multiplier II connects the output signal of inverter I as SW
2drive singal; The signal output part of comparator II, comparator IV is connected with the input of multiplier III, and the output signal of multiplier III is as SW
3drive singal, multiplier III connects the output signal of inverter II as SW
4drive singal.
4. a control method for photovoltaic grid-connected inversion circuit, the steps include:
Step one, judge photovoltaic cell group (4) output voltage V
inwhether be greater than electrical network (5) ac output voltage absolute value | V
out|;
Step 2, controlled the break-make of chopping switching tube SWc by the judged result of step one, if V
in> | V
out|, then control SWc turns off; If V
in≤ | V
out|, then control SWc is operated in high-frequency PWM state;
Step 3, control full-bridge inverting switching tube SW according to the break-make of SWc
1, SW
2, SW
3, SW
4break-make, if SW
cturn off, then control SW
1, SW
2, SW
3, SW
4be operated in SPWM modulating mode, if SW
cbe operated in high-frequency PWM state, then control SW
1, SW
2, SW
3, SW
4work with power frequency modulation system.
5. the control method of a kind of photovoltaic grid-connected inversion circuit according to claim 4, it is characterized in that: the detailed process that step 2 controls chopping switching tube SWc break-make is: sine-wave generator I produces standard AC sine wave, the in-phase input end of input comparator I and the input of DSP microprocessor after full-wave rectifier I rectification, signal picker gathers the output voltage V of photovoltaic cell group (4)
inthe inverting input of input comparator I and the input of DSP microprocessor, compared through comparator I pulse train that obtains and be multiplied by multiplier I through the signal of DSP microprocessor processes, the pulse train control SW that multiplier I exports
cbreak-make.
6. the control method of a kind of photovoltaic grid-connected inversion circuit according to claim 5, is characterized in that: step 3 controls full-bridge inverting switching tube SW
1, SW
2, SW
3, SW
4the detailed process of break-make is: sine-wave generator II produces standard AC sine wave, the in-phase input end of input comparator II after full-wave rectifier II rectification, and it is V that triangular-wave generator produces amplitude
inthe inverting input of triangular wave input comparator II; Sine-wave generator III produces the in-phase input end of the sinusoidal wave input comparator III of standard AC, compares through comparator III with no-voltage; Sine-wave generator IV also produces the inverting input of the sinusoidal wave input comparator IV of standard AC, compares through comparator IV with no-voltage; The output signal of comparator II, comparator III is multiplied by multiplier II, the output signal control SW of multiplier II
1break-make, multiplier II meets the output signal control SW of inverter I
2break-make; The output signal of comparator II, comparator IV is multiplied by multiplier III, the output signal control SW of multiplier III
3break-make, multiplier III meets the output signal control SW of inverter II
4break-make.
7. the control method of a kind of photovoltaic grid-connected inversion circuit according to claim 5 or 6, is characterized in that: the output signal of described DSP microprocessor is pulse regulation duty ratio
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