CN205430162U - Photovoltaic power generation system - Google Patents
Photovoltaic power generation system Download PDFInfo
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- CN205430162U CN205430162U CN201520926751.6U CN201520926751U CN205430162U CN 205430162 U CN205430162 U CN 205430162U CN 201520926751 U CN201520926751 U CN 201520926751U CN 205430162 U CN205430162 U CN 205430162U
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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
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Abstract
The utility model provides a photovoltaic power generation system, organize the cluster including first photovoltaic, a direct -current converter, second photovoltaic group cluster, the 2nd direct -current converter and dc -to -ac converter, the input of dc -to -ac converter includes the first input end, middle input and second input, wherein a first photovoltaic group cluster and a direct -current converter establish ties, second photovoltaic group cluster and the 2nd direct -current converter establish ties, a direct -current converter and the 2nd direct -current converter establish ties and form direct -current converter series connection line, a direct -current converter's output positive pole is connected with the first input end of dc -to -ac converter, direct -current converter series connection line is connected with the middle input of dc -to -ac converter, the 2nd direct -current converter's output negative pole is connected with the second input of dc -to -ac converter, the dc -to -ac converter is to total busbar voltage vb, sub - busbar voltage V1, two arbitrary volumes among the sub - busbar voltage V2 can the independent control, thereby realize the input power of dc -to -ac converter and output's dynamic balance, the stable work of assurance system.
Description
Technical field
This utility model relates to a kind of electricity generation system.Specifically, this utility model relates to a kind of photovoltaic generating system.
Background technology
In the photovoltaic generating system of prior art, after the series connection of n photovoltaic module, form photovoltaic group string, then with enter DC converter and be connected, DC converter is connected with photovoltaic DC-to-AC converter, and the voltage of the output (input of DC converter) of photovoltaic group string is 1000Vdc.If the number connected by photovoltaic module is become 2n from original n, then the output voltage of photovoltaic group string rises to 2000Vdc.After photovoltaic group string output voltage raises, on the one hand can decrease the cable waste of photovoltaic generating system, on the other hand, decrease the cable of photovoltaic generating system, increase the power density of DC converter and photovoltaic DC-to-AC converter, effectively reduce the cost of photovoltaic generating system.nullPhotovoltaic generating system after boosting is as shown in Figure 1，The positive pole of 2n photovoltaic module 1 of series connection is connected to MPPT that (MPPT is the abbreviation of " MaximumPowerPointTracking "，The translation of MPPT is " MPPT maximum power point tracking ") the input positive pole 2a of the DC converter 2 of function，The negative pole of 2n the photovoltaic module 1 of series connection is connected to the input negative pole 2b of the DC converter 2 with MPPT function，The output cathode 2c of DC converter 2 is connected to the input positive pole 3a of inverter 3,The output negative pole 2d of DC converter 2 is connected to the input negative pole 3b of inverter 3,Unidirectional current from DC converter 2 is converted to the three-phase alternating current (3U of exchange by inverter 3,3V,3W)，The output of inverter 3 can feed networking or be connected with load.In an example, inverter 3 can be two-level inversion device.Photovoltaic generating system compared to 1000Vdc, the photovoltaic generating system of 2000Vdc can significantly increase the power density of inverter, the price reduction more than 30% of DC converter and inverter, simultaneously, drastically reduce the area the facilities such as the cable of photovoltaic generating system, header box, reduce photovoltaic generating system cost.
Photovoltaic generating system after the boosting of prior art has the disadvantage that
1) after the voltage of photovoltaic generating system is increased to 2000Vdc, need inside DC converter to use the higher power device of pressure grade, more than 2000Vdc is pressure, and the power device of grade is compared with the power device of 1200Vdc, the power device loss of grade that more than 2000Vdc is pressure is big, reduces the efficiency of photovoltaic generating system.
2) after the voltage of photovoltaic generating system is increased to 2000V, for cost-effective, the power grade of DC converter and inverter is greatly improved, but the quantity of the DC converter containing MPPT function is greatly reduced, and causes the efficiency of photovoltaic module maximal power tracing to reduce.
3), after photovoltaic module series connection, after the inverter output current phase size of photovoltaic group string depends on the assembly that in this photovoltaic group string, inverter output current phase is minimum, i.e. assembly series connection, there is " wooden pail effect " in the inverter output current phase of photovoltaic group string.Therefore, under equal conditions, the group string contrast being in series by n assembly with 2 strings, the group string that 2n assembly is in series, owing to there is current mismatch problem, the power of its output is less, and this will result in the decline of photovoltaic generating system generated energy.
In order to solve the problems referred to above of prior art, the utility model proposes a kind of photovoltaic generating system, which raises efficiency and the efficiency of photovoltaic plant maximal power tracing of DC converter, improve current mismatch problem during 2n assembly series connection, improve the generated energy of photovoltaic generating system.
Utility model content
The utility model proposes a kind of photovoltaic generating system, it is intended to solve photovoltaic generating system in prior art and there is current mismatch and the highest problem of generated energy.
A technical scheme of the present utility model provides a kind of photovoltaic generating system, including the first photovoltaic group string, first DC converter, second photovoltaic group string, second DC converter and inverter, the input of inverter includes first input end, intermediate input end and the second input, wherein the first photovoltaic group string and the series connection of the first DC converter, second photovoltaic group string and the series connection of the second DC converter, first DC converter and the series connection of the second DC converter form DC converter series line, the output cathode of the first DC converter is connected with the first input end of inverter, DC converter series line is connected with the intermediate input end of inverter, the output negative pole of the second DC converter is connected with the second input of inverter.
The photovoltaic generating system provided according to said one technical scheme of the present utility model, wherein inverter is to total busbar voltage Vb, sub-busbar voltage V1, sub-busbar voltage V2In any two amount can independently control.
nullThe photovoltaic generating system provided according to said one technical scheme of the present utility model，Wherein inverter also includes inverter bridge、Wave filter、Control system and outfan，Inverter bridge is connected with wave filter，The wherein control system of inverter and the input of inverter、Outfan and inverter bridge connect，Control system includes total busbar voltage control module、Voltage difference control module、PWM control module and current control module，Wherein，Total busbar voltage control module is for being connected with first input end and the current control module of inverter，Current control module is additionally operable to be connected with PWM control module，PWM control module also inverter bridge with voltage difference control module and inverter is connected，Voltage difference control module is also connected with the intermediate input end of inverter，Wherein control system is by total busbar voltage control module、Voltage difference control module、PWM control module and current control module are to total busbar voltage Vb, sub-busbar voltage V1, sub-busbar voltage V2In any two amount independently control.
The photovoltaic generating system provided according to said one technical scheme of the present utility model, wherein has multiple power switch pipe, will affect sub-busbar voltage V in inverter bridge1Power switch pipe be divided into one group, their dutycycle is the first dutycycle D1；Sub-busbar voltage V will be affected2Power switch pipe be divided into one group, their dutycycle is the second dutycycle D2, control system can be to the first dutycycle D by total busbar voltage control module, voltage difference control module, PWM control module and current control module1With the second dutycycle D2Carry out independent regulation, thus realize busbar voltage V total in inverterb, sub-busbar voltage V1, sub-busbar voltage V2In any two amount independence control.
The photovoltaic generating system provided according to said one technical scheme of the present utility model, wherein control system is by by total busbar voltage Vb, inverter output current phase IgridWith sub-busbar voltage V1Respectively with default total bus reference voltage Vbref, preset reference electric current IrefWith default primary and secondary line reference voltage V1refCompare respectively, according to comparative result to the first dutycycle D1With the second dutycycle D2Carry out independent regulation, thus realize busbar voltage V total in inverterb, sub-busbar voltage V1, sub-busbar voltage V2In any two amount independence control.
The photovoltaic generating system provided according to said one technical scheme of the present utility model, wherein the outfan of inverter includes U outfan, V outfan and W outfan, and the outfan of inverter can be connected with electrical network or load.
The photovoltaic generating system provided according to said one technical scheme of the present utility model, wherein in the first photovoltaic group string and the second photovoltaic group string, the number of components connected is equal or unequal, first photovoltaic group string and the series connection of the second photovoltaic group string form photovoltaic group string series line, and photovoltaic group string series line is connected with the input negative pole of the first DC converter and the input positive pole of the second DC converter.
The photovoltaic generating system provided according to said one technical scheme of the present utility model, wherein inverter is three-level inverter, and DC converter is the DC converter with MPPT maximum power point tracking function.
The photovoltaic generating system provided according to said one technical scheme of the present utility model, wherein inverter is k electrical level inverter, and wherein k is more than 3, and DC converter is the DC converter with MPPT maximum power point tracking function.
Another technical scheme of the present utility model provides a kind of control method for photovoltaic generating system, wherein,
In step 102, to total busbar voltage Vb, inverter output current phase Igrid, sub-busbar voltage V1Carry out real-time sampling；
In step 104, it is judged that total busbar voltage VbWhether more than presetting total bus reference voltage VbrefIf, total busbar voltage VbMore than presetting total bus reference voltage Vbref, then preset reference electric current I is increased in step 106refSo that inverter output current phase IgridIncrease；Otherwise, preset reference electric current I is reduced in step 108refSo that inverter output current phase IgridReduce；
In step 110, it is judged that inverter output current phase IgridWhether more than preset reference electric current IrefIf, inverter output current phase IgridMore than preset reference electric current Iref, then in step 112, the first dutycycle D is reduced1With the second dutycycle D2；Otherwise in step 114, increase the first dutycycle D1With the second dutycycle D2；
In step 116, it is judged that sub-busbar voltage V1Whether more than presetting primary and secondary line reference voltage V1ref.If sub-busbar voltage V1More than presetting primary and secondary line reference voltage V1ref, and judge sub-busbar voltage V in step 1171With default primary and secondary line reference voltage V1refBetween deviation more than preset limit value, then in step 118, increase the first dutycycle D1And reduce the second dutycycle D2；Otherwise program is returned step 102 by step 117；If sub-busbar voltage V1It is not more than and presets primary and secondary line reference voltage V1refAnd judge sub-busbar voltage V in step 1191With default primary and secondary line reference voltage V1refBetween deviation more than preset limit value, then reduce the first dutycycle D in step 1201And increase the second dutycycle D2；Otherwise program is returned step 102 by step 119.
Another technical scheme of the present utility model provides a kind of photovoltaic generating system, including p photovoltaic group string, q photovoltaic group string, p DC converter in parallel, q DC converter in parallel and inverter, p and q is the natural number more than 0, wherein p photovoltaic group string is respectively connected to the input of p DC converter in parallel, q photovoltaic group string is respectively connected to the input of q DC converter in parallel, the output cathode of the DC converter that the output negative pole of p DC converter in parallel is in parallel with q is connected to form DC converter series line, p the output cathode of DC converter in parallel is connected with the first input end of inverter, q the output negative pole of DC converter in parallel is connected with the second input of inverter, DC converter series line is connected with the intermediate input end of inverter.
The photovoltaic generating system provided according to above-mentioned another technical scheme of the present utility model, in the photovoltaic group string that the most each DC converter accesses, the quantity of assembly is equal or unequal.
The photovoltaic generating system provided according to above-mentioned another technical scheme of the present utility model, wherein inverter is three-level inverter, the outfan of inverter includes U outfan, V outfan and W outfan, the outfan of inverter can be connected with electrical network or load, and DC converter is the DC converter with MPPT maximum power point tracking function.
The photovoltaic generating system provided according to above-mentioned another technical scheme of the present utility model, wherein inverter is k electrical level inverter, wherein k is more than 3, the outfan of inverter includes U outfan, V outfan and W outfan, the outfan of inverter can be connected with electrical network or load, and DC converter is the DC converter with MPPT maximum power point tracking function.
Yet another aspect of the present utility model provides a kind of photovoltaic generating system, including (k-1) individual photovoltaic group string, (k-1) individual DC converter and 1 k electrical level inverter, the dc bus of k electrical level inverter input is divided into (k-1) cross-talk bus, (k-1) input of individual photovoltaic group string DC converter individual with (k-1) respectively is connected, (k-1) individual DC converter is sequentially connected in series, and be connected with (k-1) cross-talk bus of inverter input terminal respectively, inverter is to total busbar voltage VbWith sub-busbar voltage ViCan independently control, wherein 1≤i≤(k-1), i is natural number, and k is the natural number more than 3.
A kind of photovoltaic generating system provided according to above-mentioned yet another aspect of the present utility model, wherein
(k-1), in individual photovoltaic group string, the number of components that each group of string is comprised is equal or unequal, and DC converter is the DC converter with MPPT maximum power point tracking function.
1 is had following technical effect that compared to the photovoltaic generating system of prior art according to photovoltaic generating system of the present utility model) DC converter can continue to use the scheme of former 1000V system, and efficiency is high, and technical risk is low；2) MPPT of photovoltaic generating system of the present utility model is in hgher efficiency, thus high according to photovoltaic generating system efficiency of the present utility model；3) sub-busbar voltage can adjust in certain limit, reduces the power mismatch rate between photovoltaic group string, improves the delivery efficiency of each DC converter.
Accompanying drawing explanation
Referring to the drawings, disclosure of the present utility model will be easier to understand.Skilled addressee readily understands that: these accompanying drawings are used only for illustrating the technical solution of the utility model, and are not intended to be construed as limiting protection domain of the present utility model.In figure:
Fig. 1 shows the topology diagram of the photovoltaic generating system of prior art.
Fig. 2 shows the topology diagram of the photovoltaic generating system according to an embodiment of the present utility model.
Fig. 3 shows the topology diagram of the photovoltaic generating system according to another embodiment of the present utility model.
Fig. 4 shows the control block diagram of the photovoltaic generating system according to an embodiment of the present utility model as shown in Figures 2 and 3.
Fig. 5 shows the topology diagram of the photovoltaic generating system according to another embodiment of the present utility model.
Fig. 6 shows the topology diagram of the photovoltaic generating system according to further embodiment of the present utility model.And
Fig. 7 shows the flow chart of the control method for the photovoltaic generating system according to an embodiment of the present utility model as shown in Figure 4.
Parts and label list
| 1 | 2n photovoltaic module |
| 2 | DC converter |
| 2a | Input positive pole |
| 2b | Input negative pole |
| 2c | Output cathode |
| 2d | Output negative pole |
| 3 | Inverter |
| 3a | First input end |
| 3b | Second input |
| 3u | U phase |
| 3v | V phase |
| 3w | W phase |
| 10 | First photovoltaic group string |
| 20 | Second photovoltaic group string |
| 12 | First DC converter |
| 12a | Input positive pole |
| 12b | Input negative pole |
| 12c | Output cathode |
| 12d | Output negative pole 4--> |
| 22 | Second DC converter |
| 22a | Input positive pole |
| 22b | Input negative pole |
| 22c | Output cathode |
| 22d | Output negative pole |
| 30 | Three-level inverter |
| 30a | First input end |
| 30b | Second input |
| 30c | Intermediate input end |
| 30u | U phase |
| 30v | V phase |
| 30w | W phase |
| 50 | Total busbar voltage control module |
| 51 | Voltage difference control module |
| 52 | PWM control module |
| Igrid | Inverter output current phase |
| Iref | Preset reference electric current |
| 53 | Current control module |
| 100 | DC converter series line |
| 101 | Photovoltaic group string series line |
| 300 | Multi-electrical level inverter |
| 300u | U phase |
| 300v | V phase |
| 300w | W phase |
| 300a | The first input end of multi-electrical level inverter |
| 300k | The kth input of multi-electrical level inverter |
Detailed description of the invention
Fig. 2-7 and following description describe how optional embodiment of the present utility model is implemented with teaching those skilled in the art and reproduce this utility model.In order to instruct technical solutions of the utility model, simplify or eliminated some conventional aspects.Those skilled in the art should understand that and be derived from the modification of these embodiments or replace will fall in the range of this utility model.Those skilled in the art should understand that following characteristics can combine to form multiple modification of the present utility model in every way.Thus, this utility model is not limited to following optional embodiment, and is only limited by claim and their equivalent.
Inverter be a kind of be the device of alternating current by DC conversion.The output of inverter, according to grid-connected requirement, can be three-phase and four-line (band N line) system or three-phase three-wire system (without N line).For three-phase and four-line (band N line) is made, output U, V, W of inverter represents U phase, V phase and W phase (live wire), and the output N of inverter is the neutral conductor (zero line).The dc bus of inverter input terminal is by n-1 the bus capacitor C connected1、C2、……、Cn-1Being divided into n-1 section, the voltage of every section of dc bus is respectively V1、V2、……、Vn-1, every section of dc bus can be respectively connected to the DC converter being connected with photovoltaic group string.Such as, in Fig. 2 of the application, the dc bus of three-level inverter input is by the bus capacitor C connected1And C2Being divided into 2 sections, every section of dc bus can access the DC converter with MPPT maximum power point tracking function that the photovoltaic module with n series connection is connected.In k electrical level inverter, by dutycycle D (abbreviation of Duty) of the power switch pipe in regulation inverter bridge, inlet highway voltage and the output current phase of inverter can be controlled.Because there being multiple power switch pipe in inverter bridge, dutycycle D of each power switch pipe can independently control.Here sub-busbar voltage V will be affected1Power switch pipe be divided into one group, their dutycycle is the first dutycycle D1；Sub-busbar voltage V will be affected2Power switch pipe be divided into one group, their dutycycle is the second dutycycle D2；The like, k electrical level inverter has n-1 group dutycycle D1、D2、……、Dk-1, affect sub-busbar voltage V respectively1、V2、……、Vk-1.In this application, photovoltaic group string is formed by the series connection of multiple photovoltaic modulies.
Fig. 2 shows the topology diagram of the photovoltaic generating system according to an embodiment of the present utility model.nullAs shown in Figure 2，Photovoltaic generating system according to an embodiment of the present utility model includes the first photovoltaic group string 10、First DC converter 12、Second photovoltaic group string 20、Second DC converter 22 and inverter 30，The input of inverter includes first input end 30a、Intermediate input end 30c and the second input 30b，Wherein the first photovoltaic group string 10 and the first DC converter 12 are connected，Second photovoltaic group string 20 and the second DC converter 22 are connected，First DC converter 12 and the series connection of the second DC converter 22 form DC converter series line 100，The output cathode 12c of the first DC converter is connected with the first input end 30a of inverter，DC converter series line 100 is connected with the intermediate input end 30c of inverter，The output negative pole 22d of the second DC converter is connected with the second input 30b of inverter，Inverter is to total busbar voltage VbWith sub-busbar voltage V1Can independently control.
First photovoltaic group string 10 and the second photovoltaic group string 20 include n the photovoltaic module connected respectively, first photovoltaic group string 10 and the series connection of the second photovoltaic group string 20 form photovoltaic group string series line 101, and photovoltaic group string series line 101 is connected with the input negative pole 12b of the first DC converter and the input positive pole 22a of the second DC converter.
Specifically, the output negative pole 12d of the first DC converter 12 and the output cathode 22c series connection of the second DC converter 22, form DC converter series line 100, DC converter series line 100 is connected with the intermediate input end 30c of inverter 30.
Specifically, the positive pole of the first photovoltaic group string 10 is connected to the input positive pole 12a of the first DC converter 12, and the negative pole 12b of the first photovoltaic group string 10 is connected to the input negative pole 12b of the first DC converter 12；The positive pole of the second photovoltaic group string 20 is connected to the input positive pole 22a of the second DC converter 22, and the negative pole of the second photovoltaic group string 20 is connected to the input negative pole 22b of the second DC converter 22.
Specifically, as in figure 2 it is shown, inverter is three-level inverter 30, the voltage between the first input end 30a and the intermediate input end 30c of three-level inverter 30 of three-level inverter 30 is referred to as sub-busbar voltage V1, the voltage between the second input 30b and the intermediate input end 30c of three-level inverter 30 of three-level inverter 30 is referred to as sub-busbar voltage V2, total busbar voltage Vb(Vb=V1+V2) refer to the voltage between the first input end 30a of the three-level inverter 30 of Real-time Collection and the second input 30b.At photo-voltaic power generation station, sub-busbar voltage V1With sub-busbar voltage V2Between there may be bigger difference so that three-level inverter 30 there will be overvoltage fault.
Fig. 3 shows the topology diagram of the photovoltaic generating system according to another embodiment of the present utility model.As shown in Figure 3, it is only that with the difference of the photovoltaic generating system in Fig. 2, the negative pole of the first photovoltaic group string 10 and the positive pole of the second photovoltaic group string 20 are connected, forming photovoltaic group string series line 101, photovoltaic group string series line 101 is connected with the input negative pole of the first DC converter 12 and the input positive pole of the second DC converter 22.
In figs. 2 and 3, input power P of inverterin=P1+P2=V1*I1+V2*I2(formula 1), input power P of inverterinOutput P equal to DC converter 12 and DC converter 221And P2Sum, I1And I2Represent DC converter 12 and the output electric current of DC converter 22 respectively.The output P of inverterout=η * Pin=3*Vg*Igrid(formula 2), wherein, η is inverter conversion efficiency, VgPhase voltage, I is exported for invertergridFor inverter output current phase.The function of DC converter is to find the maximum power point of photovoltaic group string, and delivers maximum power to inverter.The most sub-busbar voltage V1And V2By inverter control, by controlling sub-busbar voltage V1And V2, the input power of inverter and the dynamic equilibrium of output can be reached, it is ensured that system stability works.
Input power P when inverterinOutput P more than inverteroutLoss power P with inverterlossAnd time, the unnecessary input power of inverter will be by inverter bus capacitor C1And C2Absorb, cause total busbar voltage VbRise, total busbar voltage VbTotal bus reference voltage V is preset in deviationbref.Now, dutycycle D of power switch pipe in inverter bridge gradually tuned up, then the output of inverter increases, i.e. inverter output current phase Igrid(inverter output power size and inverter output current phase IgridLinear) will increase.As the output P being adjusted to inverteroutLoss power P with inverterlossAnd more than input power P of inverterinTime, total busbar voltage VbThen decline.
While adjusting total busbar voltage, if sub-busbar voltage V1With default primary and secondary line reference voltage V1refDeviation △ V1Beyond preset limit value, adjust the first dutycycle D1, can be with stabistor busbar voltage V1.I.e. △ V1> 0, and beyond preset limit value, then increase the first dutycycle D1, reduce by the second dutycycle D2So that electric capacity C1Release more multi-energy, sub-busbar voltage V1Decline；△V1< 0, and beyond preset limit value, then reduce by the first dutycycle D1, increase the second dutycycle D2So that electric capacity C1Release less energy, sub-busbar voltage V1Rise.And sub-busbar voltage V2(V2=Vb-V1) can also individually adjust.
Thus, it will be seen that total busbar voltage Vb, sub-busbar voltage V1With sub-busbar voltage V2Adjustment be by dutycycle D of power switch pipe in regulation inverter, change inverter output current phase Igrid, thus realizing the input power of inverter and the dynamic equilibrium of output, it is ensured that system stability works.
Fig. 4 shows the control block diagram of the photovoltaic generating system according to an embodiment of the present utility model as shown in Figures 2 and 3.nullAs shown in Figure 4，Inverter 30 includes input、Inverter bridge、Wave filter、Control system and outfan，Inverter bridge is connected with wave filter，The wherein control system of inverter and the input of inverter、Outfan and inverter bridge connect，Control system includes total busbar voltage control module 50、Voltage difference control module 51、PWM control module 52 and current control module 53，Wherein，Total busbar voltage control module is for being connected with first input end 30a and the current control module 53 of inverter，Current control module 53 is additionally operable to be connected with PWM control module 52，PWM control module 52 also inverter bridge with voltage difference control module 51 and inverter is connected，Voltage difference control module 51 is also connected with the intermediate input end 30c of inverter，Wherein control system is by total busbar voltage control module 50、Voltage difference control module 51、PWM control module 52 and current control module 53 can be to total busbar voltages Vb, sub-busbar voltage V1With sub-busbar voltage V2In arbitrarily both are independently controlled.In an example, inverter is three-level inverter 30, and output U, V, W of inverter 30 is connected with electrical network or load.In additional examples, inverter is k electrical level inverter, and wherein n is more than 3.
For inverter, inverter bridge there are multiple power switch pipe, dutycycle D of each power switch pipe can independently control.For three-level inverter 30, sub-busbar voltage V will be affected1Power switch pipe be divided into one group, their dutycycle is the first dutycycle D1；Sub-busbar voltage V will be affected2Power switch pipe be divided into one group, their dutycycle is the second dutycycle D2, control system can be to the first dutycycle D by total busbar voltage control module 50, voltage difference control module 51, PWM control module 52 and current control module 531With the second dutycycle D2Carry out independent regulation so that total busbar voltage Vb, sub-busbar voltage V1With sub-busbar voltage V2In arbitrarily both can be independently controlled.Specifically, control system is by by total busbar voltage Vb, inverter output current phase IgridWith sub-busbar voltage V1Respectively with default total bus reference voltage Vbref, preset reference electric current IrefWith default primary and secondary line reference voltage V1refCompare respectively, according to comparative result to the first dutycycle D1With the second dutycycle D2Carry out independent regulation so that total busbar voltage V of inverterbWith sub-busbar voltage V1Can independently control, thus realize sub-busbar voltage V1With sub-busbar voltage V2Independence control.Due to sub-busbar voltage V1With sub-busbar voltage V2Can independently control, the input power of inverter 30 and the dynamic equilibrium of output can be reached, it is ensured that photovoltaic generating system steady operation.
The most specifically, Fig. 7 shows the flow chart of the control method for the photovoltaic generating system according to an embodiment of the present utility model as shown in Figure 4.As shown in Figure 7:
In step 100, the control method of photovoltaic generating system starts；
In step 102, to total busbar voltage Vb, inverter output current phase Igrid, sub-busbar voltage V1Carry out real-time sampling；
In step 104, it is judged that total busbar voltage VbWhether more than presetting total bus reference voltage Vbref.If total busbar voltage VbMore than presetting total bus reference voltage Vbref, then preset reference electric current I is then increased in step 106refSo that inverter output current phase IgridIncrease；Otherwise, preset reference electric current I is reduced in step 108refSo that inverter output current phase IgridReduce；
In step 110, it is judged that inverter output current phase IgridWhether more than preset reference electric current Iref.If inverter output current phase IgridMore than preset reference electric current Iref, then in step 112, the first dutycycle D is reduced1With the second dutycycle D2；Otherwise in step 114, increase the first dutycycle D1With the second dutycycle D2；
In step 116, it is judged that sub-busbar voltage V1Whether more than presetting primary and secondary line reference voltage V1ref.If sub-busbar voltage V1More than presetting primary and secondary line reference voltage V1ref, and deviation (△ V1Equal to sub-busbar voltage V1Deduct default primary and secondary line reference voltage V1ref) more than preset limit value (step 117), in step 118, increase the first dutycycle D1And reduce the second dutycycle D2；Otherwise program is returned step 102 by step 117；If sub-busbar voltage V1It is not more than and presets primary and secondary line reference voltage V1refAnd deviation is more than preset limit value (step 119), then reduce the first dutycycle D in step 1201And increase the second dutycycle D2；Otherwise program is returned step 102 by step 119.
At step 104, if it should be noted that total busbar voltage VbMore than presetting total bus reference voltage VbrefThen explanation inverter output current phase IgridLess than normal, inverter input power is more than inverter output power and inverter losses power sum, and the unnecessary input power of inverter is to bus capacitor C1And C2Charging, causes virtual voltage VbRise, more than predeterminated voltage Vbref, for this reason, it may be necessary to perform step 106, otherwise perform step 108.
Due to the first dutycycle D1With the second dutycycle D2Can independent regulation, therefore, total busbar voltage V of inverterbWith sub-busbar voltage V1Can independently control, the most sub-busbar voltage V1And V2It is capable of independent control, the input power of inverter 30 and the dynamic equilibrium of output can be reached, it is ensured that photovoltaic generating system steady operation.
Fig. 5 shows the topology diagram of the photovoltaic generating system according to another embodiment of the present utility model.As shown in Figure 5, a kind of photovoltaic generating system, including p photovoltaic group string, q photovoltaic group string, p DC converter in parallel, q DC converter in parallel and an inverter, wherein p photovoltaic group string is respectively connected to the input of p DC converter in parallel, , q photovoltaic group string is respectively connected to the input of q DC converter in parallel, p the output cathode of DC converter in parallel is connected with the first input end 30a of three-level inverter 30, q the output negative pole of DC converter in parallel is connected with the second input 30b of three-level inverter 30, DC converter series line is connected with the intermediate input end 30c of inverter.Unidirectional current is converted to three-phase alternating current (U, V, W) by three-level inverter 30, and the three-phase output of three-level inverter 30 is connected with electrical network or load.In this embodiment, p and q is at least 1.Alternatively, inverter shown in Fig. 5 can be k electrical level inverter, wherein k is more than 3, the outfan of inverter includes U outfan, V outfan and W outfan, the outfan of inverter can be connected with electrical network or load, and DC converter is the DC converter with MPPT maximum power point tracking function.
Fig. 6 shows the topology diagram of the photovoltaic generating system according to further embodiment of the present utility model.As shown in Figure 6, photovoltaic generating system includes (k-1) individual photovoltaic group string, (k-1) individual DC converter and 1 k electrical level inverter, the dc bus of k electrical level inverter input is divided into (k-1) cross-talk bus, (k-1) input of individual photovoltaic group string DC converter individual with (k-1) respectively is connected, (k-1) individual DC converter is sequentially connected in series, and be connected with (k-1) cross-talk bus of inverter input terminal respectively, inverter is to total busbar voltage VbWith sub-busbar voltage ViCan independently control, wherein 1≤i≤(k-1), i is natural number, and k is the natural number more than 3.Specifically, if sub-busbar voltage ViWith predetermined word bus reference voltage VirefThere is deviation, then adjust corresponding dutycycle D according to the regulative mode of Fig. 7i。
nullSpecifically，The output cathode of the first DC converter is connected with the first input end 300a of multi-electrical level inverter 300，The output negative pole of the first DC converter and the input positive pole of the second DC converter are connected，Form the first DC converter series line，First DC converter series line is connected with the second input 300b of multi-electrical level inverter 300，In this manner，(k-2) individual DC converter series line that the output negative pole of (k-2) individual DC converter and the output cathode series connection of (k-1) individual DC converter are formed is connected with (k-1) individual input of multi-electrical level inverter 300，The output negative pole of (k-1) individual DC converter is connected with the kth input of multi-electrical level inverter 300,Multi-electrical level inverter 300 is for being converted to three-phase alternating current (300U by the unidirectional current of input、300V、300W)，The output of multi-electrical level inverter 300 is connected with electrical network or is connected with load.Alternatively, k is at least 3.
1 is had following technical effect that compared to the photovoltaic generating system of prior art according to photovoltaic generating system of the present utility model) DC converter can continue to use the scheme of former 1000V system, and efficiency is high, and technical risk is low；2) MPPT of photovoltaic generating system of the present utility model is in hgher efficiency, thus high according to photovoltaic generating system efficiency of the present utility model；3) sub-busbar voltage can adjust in certain limit, reduces the power mismatch rate between photovoltaic group string, improves the delivery efficiency of each DC converter.
Claims (9)
1. a photovoltaic generating system, including the first photovoltaic group string, first DC converter, second photovoltaic group string, second DC converter and inverter, the input of inverter includes first input end, intermediate input end and the second input, wherein the first photovoltaic group string and the series connection of the first DC converter, second photovoltaic group string and the series connection of the second DC converter, first DC converter and the series connection of the second DC converter form DC converter series line, the output cathode of the first DC converter is connected with the first input end of inverter, DC converter series line is connected with the intermediate input end of inverter, the output negative pole of the second DC converter is connected with the second input of inverter.
2. photovoltaic generating system as claimed in claim 1, it is characterised in that inverter is to total busbar voltage Vb, sub-busbar voltage V1, sub-busbar voltage V2In any two amount can independently control.
null3. photovoltaic generating system as claimed in claim 2，It is characterized in that，Inverter also includes inverter bridge、Wave filter、Control system and outfan，Inverter bridge is connected with wave filter，The wherein control system of inverter and the input of inverter、Outfan and inverter bridge connect，Control system includes total busbar voltage control module、Voltage difference control module、PWM control module and current control module，Wherein，Total busbar voltage control module is for being connected with first input end and the current control module of inverter，Current control module is additionally operable to be connected with PWM control module，PWM control module also inverter bridge with voltage difference control module and inverter is connected，Voltage difference control module is also connected with the intermediate input end of inverter，Wherein control system is by total busbar voltage control module、Voltage difference control module、PWM control module and current control module are to total busbar voltage Vb, sub-busbar voltage V1, sub-busbar voltage V2In any two amount independently control.
4. photovoltaic generating system as claimed in claim 3, it is characterised in that have multiple power switch pipe in inverter bridge, sub-busbar voltage V will be affected1Power switch pipe be divided into one group, their dutycycle is the first dutycycle D1；Sub-busbar voltage V will be affected2Power switch pipe be divided into one group, their dutycycle is the second dutycycle D2, control system can be to the first dutycycle D by total busbar voltage control module, voltage difference control module, PWM control module and current control module1With the second dutycycle D2Carry out independent regulation, thus realize busbar voltage V total in inverterb, sub-busbar voltage V1, sub-busbar voltage V2In any two amount independence control.
5. photovoltaic generating system as claimed in claim 4, it is characterised in that control system is by by total busbar voltage Vb, inverter output current phase IgridWith sub-busbar voltage V1Respectively with default total bus reference voltage Vbref, preset reference electric current IrefWith default primary and secondary line reference voltage V1refCompare respectively, according to comparative result to the first dutycycle D1With the second dutycycle D2Carry out independent regulation, thus realize busbar voltage V total in inverterb, sub-busbar voltage V1, sub-busbar voltage V2In any two amount independence control.
6. photovoltaic generating system as claimed in claim 3, it is characterised in that the outfan of inverter includes U outfan, V outfan and W outfan, the outfan of inverter can be connected with electrical network or load.
7. photovoltaic generating system as claimed in claim 1, it is characterized in that, in first photovoltaic group string and the second photovoltaic group string, the number of components connected is equal or unequal, first photovoltaic group string and the series connection of the second photovoltaic group string form photovoltaic group string series line, and photovoltaic group string series line is connected with the input negative pole of the first DC converter and the input positive pole of the second DC converter.
8. photovoltaic generating system as claimed in claim 1, it is characterised in that inverter is three-level inverter, and DC converter is the DC converter with MPPT maximum power point tracking function.
9. photovoltaic generating system as claimed in claim 1, it is characterised in that inverter is k electrical level inverter, and wherein k is more than 3, and DC converter is the DC converter with MPPT maximum power point tracking function.
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| CN201520926751.6U CN205430162U (en) | 2015-11-19 | 2015-11-19 | Photovoltaic power generation system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105743432A (en) * | 2015-11-19 | 2016-07-06 | 中民新能投资有限公司 | Photovoltaic power generation system and control method thereof |
| WO2022126351A1 (en) * | 2020-12-15 | 2022-06-23 | 华为数字能源技术有限公司 | Photovoltaic system, protection method, and inverter system |
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2015
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105743432A (en) * | 2015-11-19 | 2016-07-06 | 中民新能投资有限公司 | Photovoltaic power generation system and control method thereof |
| CN105743432B (en) * | 2015-11-19 | 2019-04-09 | 中民新能投资集团有限公司 | A kind of photovoltaic generating system and its control method |
| WO2022126351A1 (en) * | 2020-12-15 | 2022-06-23 | 华为数字能源技术有限公司 | Photovoltaic system, protection method, and inverter system |
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