CN105518965B - A kind of grid-connected control method and photovoltaic parallel in system - Google Patents
A kind of grid-connected control method and photovoltaic parallel in system Download PDFInfo
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- CN105518965B CN105518965B CN201480005702.7A CN201480005702A CN105518965B CN 105518965 B CN105518965 B CN 105518965B CN 201480005702 A CN201480005702 A CN 201480005702A CN 105518965 B CN105518965 B CN 105518965B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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Abstract
The application provides a kind of grid-connected control method and photovoltaic parallel in system, including：Judge that the interior environment temperature of the power generator in photovoltaic parallel in system is less than temperature preset value, and judge that one in the first DC DC converters and the 2nd DC DC converters works in first mode, when another works in second mode；The first DC DC converters and the 2nd equal forced working of DC DC converters are controlled in first mode；Wherein, power generator includes：First DC DC converters, the 2nd DC DC converters, inverter and dc bus；The output terminal connection power grid of inverter；The input terminal of first DC DC converters connects the first photovoltaic component apparatus, and the input terminal of the 2nd DC DC converters connects the second photovoltaic component apparatus；The output terminal of first DC DC converters and the 2nd DC DC converters connects the input terminal of inverter by dc bus；First mode is：DC DC converters are booster circuit；Second mode is：DC DC converters, which are bypassed, not to boost.Be not in larger current fluctuation when working in first mode due to two DC DC converters.And DC DC converters are when working in second mode, it may appear that larger current fluctuation.It therefore in this way can be to avoid the larger DC current ripple of appearance all the way for working in second mode.So as to reduce the fault alarm of mistake.
Description
Technical field
The present invention relates to a kind of technical field of photovoltaic power generation more particularly to a kind of grid-connected control methods and grid-connected
System.
Background technology
In short supply with world energy sources, many regions utilize solar power generation, also known as photovoltaic generation now.
In solar power system, photovoltaic component apparatus converts light energy into electric energy.Since photovoltaic component apparatus exports
Electric energy for direct current, therefore, it is necessary to which DC inverter is fed back to power grid for alternating current using inverter, this process is known as simultaneously
Net.
In order to realize that inverter can work under wider input voltage, can generally increase in the input terminal of inverter
DC-DC (DC-DC) converter is added to boost, i.e., will give inversion after the direct current electric boost of photovoltaic component apparatus output
Device.
It is introduced so that the input terminal of inverter connects two DC-DC converters as an example below.As shown in Figure 1, including
One DC-DC converter 100a and the second DC-DC converter 100b.The input terminal of first DC-DC converter 100a connects the first light
The input terminal for lying prostrate assembly apparatus PV1, the second DC-DC converter 100b connects the second photovoltaic component apparatus PV2.First DC-DC becomes
The output terminal of parallel operation 100a and the second DC-DC converter 100b connect the input terminal of inverter 200 by dc bus.
It should be noted that the input terminal of inverter 200 is connected with dc-link capacitance C between dc bus.Inversion
The alternating current of inversion is fed back to power grid by device 200.
It is introduced so that DC-DC converter is by Boost circuit as an example below, referring to Fig. 2, which is of the prior art
Boost circuit.
It should be noted that Boost circuit includes inductance L1, first switch SK1 and the first diode D1；But
In order to the voltage exported in photovoltaic component apparatus it is higher when, without boosting be directly output to inverter, in this way can be by Boost liters
Volt circuit bypasses, i.e., in the input terminal of Boost circuit and the second switch SK2 of output terminal parallel connection.Photovoltaic component apparatus is defeated
SK2 is closed when the voltage gone out is higher, and when SK1 is disconnected, Boost circuit is bypassed, the voltage of photovoltaic component apparatus output
It is directly fed to inverter.
Special SK2 can be switch, can be Relay relays, or diode, when it is diode,
Since busbar voltage is higher than PV voltages, backward voltage is born, therefore is automatically shut down, can not be worked.
It can be obtained with reference to Fig. 1 and Fig. 2, when Vpv voltages are less than preset value Vset, then SK2 is normally opened, and Vpv passes through Boost liters
Volt circuit is boosted so that Vbus voltages are grid-connected higher than the progress of network voltage peak value, this state is known as first mode.
When Vpv voltages are higher than preset value Vset, then SK2 is normally closed, and SK1 is normally opened, and Boost circuit does not work, this state
Referred to as second mode.
Under normal circumstances, PV1 and PV2 is accessed, and do not interfere with each other to be independent.When the voltage of PV1 is higher than network voltage peak value,
The voltage of PV2 is less than network voltage peak value, and the corresponding operating mode of PV1, PV2 is second mode, first mode at this time；Instead
It, when the voltage of PV2 is higher than network voltage peak value, the voltage of PV1 is less than network voltage peak value, and PV1, PV2 are corresponded to respectively at this time
Operating mode for first mode, second mode.
Since photovoltaic parallel in system can be applied to all over the world, the especially more severe area of environment, such as the arctic.North
The outdoor temperature of pole can reach subzero 40 degrees Celsius.And dc-link capacitance generally uses electrolytic capacitor, when temperature is very low,
The capacity of electrolytic capacitor can be greatly lowered, and in this way when DC-DC converter all the way works in first mode, another way DC-DC becomes
When parallel operation works in second mode, then the DC current ripple all the way for working in second mode can be very big, easily goes out in this way
The judgement signal of existing mistake.
Therefore, those skilled in the art need to provide a kind of control method and system, can avoid work in these cases
There is larger DC current ripple all the way in that makees in second mode.
Invention content
In view of this, the present invention provides a kind of grid-connected control method and photovoltaic parallel in system, can be in environment temperature
When relatively low, there is larger DC current ripple all the way in avoid working in second mode.
The embodiment of the present invention provides a kind of grid-connected control method, applied to photovoltaic parallel in system, includes the following steps：
Judge that the interior environment temperature of the power generator in photovoltaic parallel in system is less than temperature preset value, and judge first
One in DC-DC converter and the second DC-DC converter works in first mode, when another works in second mode, control
First DC-DC converter and the equal forced working of the second DC-DC converter are made in the first mode；
Wherein, the power generator includes：First DC-DC converter, second DC-DC converter, inverter
And dc bus；
The output terminal connection power grid of the inverter；The input terminal of first DC-DC converter connects the first photovoltaic group
Part device, the input terminal of second DC-DC converter connect the second photovoltaic component apparatus；First DC-DC converter and
The output terminal of second DC-DC converter connects the input terminal of inverter by dc bus；
The first mode is：DC-DC converter works in pressure-increasning state；
The second mode is：DC-DC converter, which is bypassed, does not boost.
Preferably, one in first DC-DC converter and the second DC-DC converter works in first mode, separately
One works in second mode, including：
First DC-DC converter works in first mode, and second DC-DC converter works in second mode；
Or,
First DC-DC converter works in second mode, and second DC-DC converter works in first mode.
Preferably, it is described to judge that one in the first DC-DC converter and the second DC-DC converter works in the first mould
Formula, another works in second mode, specially：
Judge that the output voltage of first photovoltaic component apparatus is more than the voltage preset value, and judge described second
The output voltage of photovoltaic component apparatus is less than the voltage preset value；
Or,
Judge that the output voltage of first photovoltaic component apparatus is less than the voltage preset value, and judge described second
The output voltage of photovoltaic component apparatus is more than the voltage preset value.
Preferably, the voltage preset value is determined by the output voltage of the inverter, specially：
When the power grid is three phase network or two-phase power grid, the voltage preset value is higher than the line voltage of the inverter
The certain threshold value of peak value；
When the power grid is single-phase power grid, the voltage preset value is higher than the phase voltage of the output voltage of the inverter
The certain threshold value of peak value.
Preferably, it further includes：
When judging that the interior environment temperature of the power generator is greater than or equal to the temperature preset value, and judge described the
The output voltage of one photovoltaic component apparatus is more than voltage preset value, and the output voltage of second photovoltaic component apparatus is less than described
Voltage preset value then controls first DC-DC converter to work in second mode, controls the second DC-DC converter work
Make in first mode；
Or,
When judging that the interior environment temperature of the power generator is greater than or equal to the temperature preset value, and judge described the
The output voltage of one photovoltaic component apparatus is less than voltage preset value, and the output voltage of second photovoltaic component apparatus is more than described
Voltage preset value then controls first DC-DC converter to work in first mode, controls the second DC-DC converter work
Make in second mode.
The embodiment of the present invention also provides a kind of photovoltaic parallel in system, including：Power generator, the first photovoltaic component apparatus,
Two photovoltaic component apparatus, temperature sensor and controller；
The power generator includes：First DC-DC converter, second DC-DC converter, inverter and direct current
Busbar；
The output terminal connection power grid of the inverter；The input terminal of first DC-DC converter connects the first photovoltaic group
Part device, the input terminal of second DC-DC converter connect the second photovoltaic component apparatus；First DC-DC converter and
The output terminal of second DC-DC converter connects the input terminal of inverter by dc bus；
The temperature sensor for detecting the interior environment temperature of the power generator, and the temperature is sent to
The controller；
The controller for judging that the temperature is less than temperature preset value, and judges the first DC-DC converter and the
One in two DC-DC converters works in first mode, when another works in second mode, controls the first DC-DC
Converter and the equal forced working of the second DC-DC converter are in the first mode；
The first mode is：DC-DC converter works in pressure-increasning state；
The second mode is：DC-DC converter, which is bypassed, does not boost.
Preferably, one in first DC-DC converter and the second DC-DC converter works in first mode, separately
One works in second mode, including：
First DC-DC converter works in first mode, and second DC-DC converter works in second mode；
Or,
First DC-DC converter works in second mode, and second DC-DC converter works in first mode.
Preferably, it further includes：Voltage check device；
The voltage check device, for detecting the output voltage of first photovoltaic component apparatus and the second photovoltaic module
The output voltage of device, and the output voltage is sent to the controller；
The controller is additionally operable to judge the first DC-DC converter and the 2nd DC-DC transformation by the output voltage
The operating mode of device judges that in the first DC-DC converter and the second DC-DC converter works in a first mode, another
It is a to work in second mode, specially：
Judge that the output voltage of first photovoltaic component apparatus is more than voltage preset value, and judge second photovoltaic
The output voltage of assembly apparatus is less than the voltage preset value；
Or,
Judge that the output voltage of first photovoltaic component apparatus is less than the voltage preset value, and judge described second
The output voltage of photovoltaic component apparatus is more than the voltage preset value.
Preferably, the voltage preset value is determined by the output voltage of the inverter, specially：
When the power grid is three phase network or two-phase power grid, the voltage preset value is higher than the line voltage of the inverter
The certain threshold value of peak value；
When the power grid is single-phase power grid, the voltage preset value is higher than the phase voltage of the output voltage of the inverter
The certain threshold value of peak value.
Preferably, the controller is additionally operable to judge the interior environment temperature of the power generator more than or equal to described
During temperature preset value, and judge that the output voltage of first photovoltaic component apparatus is more than voltage preset value, second photovoltaic
The output voltage of assembly apparatus is less than the voltage preset value, then first DC-DC converter is controlled to work in second mode,
Second DC-DC converter is controlled to work in first mode；
Or,
When judging that the interior environment temperature of the power generator is greater than or equal to the temperature preset value, and judge described the
The output voltage of one photovoltaic component apparatus is less than voltage preset value, and the output voltage of second photovoltaic component apparatus is more than described
Voltage preset value then controls first DC-DC converter to work in first mode, controls the second DC-DC converter work
Make in second mode.
Compared with prior art, the present invention has the following advantages：
Method provided in this embodiment, it is by detecting the environment temperature inside power generator, environment temperature is pre- with temperature
If value is compared, when judging environment temperature less than temperature preset value, and two DC-DC converters work in different patterns
When, i.e., DC-DC converter the first operating mode ought be in all the way, when in addition DC-DC converter is in the second operating mode all the way,
It detects that DC current ripple at this time is very big, needs that two DC-DC converters of control is forced to work in first mode at this time.
Be not in larger current fluctuation when working in first mode due to two DC-DC converters.And DC-DC converter work
When making in second mode, it may appear that larger current fluctuation.It therefore in this way can be to avoid working in the appearance all the way of second mode
Larger DC current ripple.From the judgement signal without mistake.
Description of the drawings
In order to illustrate more clearly about the embodiment of the present invention or technical scheme of the prior art, to embodiment or will show below
There is attached drawing needed in technology description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention, for those of ordinary skill in the art, without creative efforts, can be with
Other attached drawings are obtained according to these attached drawings.
Fig. 1 is photovoltaic parallel in system schematic diagram of the prior art；
Fig. 2 is the internal structure chart for the DC-DC converter being applied in Fig. 1；
Fig. 3 is grid-connected one flow chart of control method embodiment provided by the invention；
Fig. 3 a are the current direction schematic diagrames of Boost circuit provided by the invention；
Fig. 4 is grid-connected two flow chart of control method embodiment provided by the invention；
Fig. 5 is one schematic diagram of photovoltaic parallel in system embodiment provided by the invention；
Fig. 6 is two schematic diagram of photovoltaic parallel in system embodiment provided by the invention.
Specific embodiment
Below in conjunction with the attached drawing in the embodiment of the present invention, the technical solution in the embodiment of the present invention is carried out clear, complete
Site preparation describes, it is clear that described embodiment is only part of the embodiment of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, those of ordinary skill in the art are obtained every other without making creative work
Embodiment shall fall within the protection scope of the present invention.
In order to make the foregoing objectives, features and advantages of the present invention clearer and more comprehensible, below in conjunction with the accompanying drawings to the present invention
Specific embodiment be described in detail.
Embodiment of the method one：
Referring to Fig. 3, which is grid-connected one flow chart of control method embodiment provided by the invention.
Grid-connected control method provided in this embodiment, applied to photovoltaic parallel in system, includes the following steps：
S301：Detect the interior environment temperature T of the power generator in photovoltaic parallel in system；
Wherein, the power generator includes：First DC-DC converter, second DC-DC converter, inverter
And dc bus；
It should be noted that all devices in power generator, positioned at same enclosure interior, the temperature of detection is
Environment temperature in the housing.
It should be noted that the dc bus is generally the connection in series-parallel of multiple capacitances, in Fig. 1 only by taking a capacitance as an example
Illustrated.Because the capacity of a capacitance and pressure resistance are limited, the connection in series-parallel of multiple capacitances is needed to realize in actual use
High capacity and high pressure resistance.
Since power generator is likely located at the environment temperatures such as the arctic than relatively low area, and dc-link capacitance generally uses
Electrolytic capacitor, electrolytic capacitor is more sensitive to temperature, and when the temperature is low, the capacity of electrolytic capacitor will significantly decline.Due to
Also there are capacitance in PV sides, and in this way when the capacity of dc-link capacitance significantly declines, the electric energy on the capacitance of PV sides will be to direct current
It is shifted on bus capacitor, larger DC current ripple will be will appear by working in this way in the circuit of second mode.
It should be noted that work in first mode also will appear DC current ripple all the way, but ripple is smaller,
Within the acceptable range.
S302：Judge whether the interior environment temperature of the power generator in photovoltaic parallel in system is less than temperature preset value
Tset, if it is, performing S303；
It is understood that temperature preset value is preset value, during less than the temperature, the capacity of electrolytic capacitor will
Have and significantly decline.I.e. the temperature preset value is a sensitive temperature value for electrolytic capacitor.
S303：Judge in the first DC-DC converter and the second DC-DC converter whether one work in first mode, separately
One works in second mode；If it is, perform S304；
The first mode is：DC-DC converter works in pressure-increasning state；
The second mode is：DC-DC converter, which is bypassed, does not boost.
S303 needs to judge that two DC-DC converters work in different patterns.When two DC-DC converters work in phase
With pattern when, even if environment temperature is low again, will not occur larger system being caused the DC current ripple protected occur.
That is, when two DC-DC converters work in identical pattern, the DC current ripple of appearance within the acceptable range, because
This is not in the judgement signal of mistake.
S304：First DC-DC converter and the equal forced working of the second DC-DC converter are controlled in first mould
Formula.
When the interior environment temperature of detection is less than temperature preset value, and two DC-DC converters work in different moulds
During formula, it is necessary to two DC-DC converters be controlled to work in first mode, because two DC-DC converters work in
Two modes also will appear DC current ripple.
It should be noted that the output terminal connection power grid of the inverter；The input terminal of first DC-DC converter connects
The first photovoltaic component apparatus is connect, the input terminal of second DC-DC converter connects the second photovoltaic component apparatus；Described first
DC-DC converter connects the input terminal of inverter with the output terminal of the second DC-DC converter by dc bus.
It is understood that the photovoltaic component apparatus can be the entirety after component, string formation or multiple string formation parallel connections.Its
In, entirety that string formation, that is, multiple photovoltaic modulies are composed in series.
Method provided in this embodiment, it is by detecting the environment temperature inside power generator, environment temperature is pre- with temperature
If value is compared, when judging environment temperature less than temperature preset value, and two DC-DC converters work in different patterns
When, i.e., DC-DC converter the first operating mode ought be in all the way, when in addition DC-DC converter is in the second operating mode all the way,
It detects that DC current ripple is very big, needs that two DC-DC converters of control is forced to work in first mode at this time.Due to two
Be not in larger current fluctuation when a DC-DC converter works in first mode.And DC-DC converter works in
During two modes, it may appear that larger current fluctuation in this way can to avoid work in second mode all the way in there is direct current flow liner
Wave.From the judgement signal without mistake.
It is described below and two DC-DC converters is forced to be operated in first mode rather than control DC-DC transformation why
Device works in second mode.Referring to Fig. 3 a, which is the current direction schematic diagram of Boost circuit provided by the invention.
In order to filter and maintain the effect of voltage stabilization on PV, access PV output terminal all can a capacitance in parallel compare
Small capacitance, C2 as shown in Figure 3a.And in order to control the electric current on L1, take the electric current iL acquired nearby on L1.
When DC-DC converter is in the first operating mode, the voltage above C2 is less than DC bus-bar voltage Vbus, therefore
Capacitance C2 provides energy without normal direction Vbus, can only be provided by L1, however the electric current of L1 is software closed-loop control, therefore the iL lines acquired
Wave electric current will not be very big, is not in the judgement signal of mistake.
However when DC-DC converter is in the second operating mode, SK2 is closed, and not only PV provides energy to dc bus
Amount, C2 also provide energy, and iL=ipv+iC2 to dc bus；Wherein, ipv is the electric current on PV, and iC2 is the electric current on C2.
And dc bus fluctuation at this time is larger, i.e. PV fluctuations are big, cause the voltage fluctuation on C2 big, since the calculating of electric current on capacitance is public
Formula isSince iC2 fluctuations are very big, ipv is substantially stationary, therefore collected electric current iL is caused to have very big high frequency waves
It is dynamic, so as to trigger protection.
It can be seen that it needs that two DC-DC converters is controlled to be operated in first mode.Because work in second mode
When, it may appear that larger current fluctuation ought particularly be in the first operating mode all the way, in addition be in the second operating mode all the way
When, detect current fluctuation bigger.
Embodiment of the method two：
Referring to Fig. 4, which is grid-connected two flow chart of control method embodiment provided by the invention.
The present embodiment and the difference of embodiment of the method one are the increase in S405；
Wherein S401-S404 is identical with the S301-S304 in embodiment of the method one respectively, and details are not described herein.
In S402, if it is determined that the interior environment temperature of the power generator in photovoltaic parallel in system is not less than temperature preset value
Tset, i.e. T are greater than or equal to Tset, then perform S405.I.e. if the interior environment temperature of power generator is greater than or equal to temperature
Preset value, then carry out the work of two converters of control according to normal logic, and S405 is the normal logic.
In S403, if the first DC-DC converter and the second DC-DC converter work in first mode or the first DC-
DC converters and the second DC-DC converter work in second mode, then perform S405.
When the operating mode of i.e. two DC-DC converters is identical, the interior environment temperature of power generator was both made to be less than temperature
Preset value also carries out the work of two converters of control according to normal logic.
S405：Judge that the output voltage Vpv1 of first photovoltaic component apparatus is more than voltage preset value Vset, described second
The output voltage Vpv2 of photovoltaic component apparatus is less than the voltage preset value Vset, then first DC-DC converter is controlled to work
In second mode, second DC-DC converter is controlled to work in first mode；
Or,
Judge that the output voltage Vpv1 of first photovoltaic component apparatus is less than voltage preset value Vset, second photovoltaic
The output voltage Vpv2 of assembly apparatus is more than the voltage preset value Vset, then first DC-DC converter is controlled to work in
One pattern controls second DC-DC converter to work in second mode.
That is, when the output voltage of photovoltaic component apparatus sufficiently high (being more than voltage preset value), then DC-DC transformation is not needed to
Device boosts, and the output voltage of photovoltaic component apparatus is directly fed to inverter.DC-DC converter is bypassed by SK2 at this time,
That is SK2 is closed.Conversely, when the output voltage of photovoltaic component apparatus not high enough (being less than or equal to voltage preset value), then need
DC-DC converter is boosted, at this point, SK2 is disconnected.
It should be noted that the voltage preset value is that the phase voltage exported with inverter is related, it is possible to understand that
It is that the voltage of inverter output is grid-connected on power grid, and power grid electricity can be obtained by the output voltage for measuring inverter
Pressure.
Judge whether the output voltage of photovoltaic component apparatus is less than before voltage preset value, need first to measure current inverter
The phase voltage of output particularly for the different from three phase network system and single-phase network system, is introduced separately below.
The voltage preset value determines by the output voltage of the inverter, specially：
When the power grid is three phase network or two-phase power grid, the voltage preset value is higher than the line voltage of the inverter
The certain threshold value Δ V of peak value；
When the power grid is single-phase power grid, the peak value of the output voltage of the voltage preset value and the inverter is into just
Than.
It should be noted that for two-phase power grid existing for Countries, voltage preset value is also above inverter output
Line voltage the certain threshold value Δ V of peak value.
When the power grid is three phase network, the voltage preset value TsetA kind of computational methods are：For three phase network, V represents the virtual value of the phase voltage of the current inverter measured output；ΔV
For it is preset be more than zero number.
When the power grid is single-phase power grid, the voltage preset value TsetA kind of computational methods are：For single-phase power grid, wherein,VRepresent the virtual value of the current inverter output voltage measured；Δ V is
It is preset be more than zero number.
Δ V is a preset voltage margin, this numerical value is the number more than zero, can be selected according to actual needs.
For three phase network, voltage preset value is above the certain threshold value Δ V's of peak value of line voltage；For single-phase power grid,
Voltage preset value is above the certain threshold value Δ V's of peak value of inverter output voltage；For the two-phase power grid in the U.S., voltage is preset
Value is also above the certain threshold value of peak value of the line voltage of inverter output.Method provided in this embodiment, in normal logic control
Under system, be added to temperature it is relatively low when decision logic, can ensure photovoltaic parallel in system work in the very low environment of temperature in this way
When making, system is not in the judgement signal of mistake, can ensure system worked well in this way, so as to improve generated energy.
Based on a kind of grid-connected control method that above example provides, the present invention also provides a kind of grid-connected systems
System, is discussed in detail its operation principle below in conjunction with the accompanying drawings.
System embodiment one：
Referring to Fig. 5, which is a kind of one schematic diagram of photovoltaic parallel in system embodiment provided by the invention.
Photovoltaic parallel in system provided in this embodiment, including：Power generator 1000, the first photovoltaic component apparatus PV1, second
Photovoltaic component apparatus PV2, temperature sensor 400 and controller 300；
The power generator 1000 includes：The first DC-DC converter 100a, the second DC-DC converter 100b,
Inverter 200 and dc bus C；
The output terminal connection power grid of the inverter 200；
The input terminal of the first DC-DC converter 100a connects the first photovoltaic component apparatus PV1, the 2nd DC-DC
The input terminal of converter 100b connects the second photovoltaic component apparatus；The first DC-DC converter 100a and the 2nd DC-DC transformation
The output terminal of device 100b connects the input terminal of inverter 200 by dc bus；
The temperature sensor 400, for detecting the interior environment temperature of the power generator 1000, and by the temperature
It is sent to the controller 300；
It should be noted that all devices in power generator, positioned at same enclosure interior, the temperature of detection is
Environment temperature in the housing.
It should be noted that the dc bus is generally the connection in series-parallel of multiple capacitances, in Fig. 1 only by taking a capacitance as an example
Illustrated.Because the capacity of a capacitance and pressure resistance are limited, the connection in series-parallel of multiple capacitances is needed to realize in actual use
High capacity and high pressure resistance.
Since power generator is likely located at the environment temperatures such as the arctic than relatively low area, and dc-link capacitance generally uses
Electrolytic capacitor, electrolytic capacitor is more sensitive to temperature, and when the temperature is low, the capacity of electrolytic capacitor will significantly decline.Due to
Also there are capacitance in PV sides, and in this way when the capacity of dc-link capacitance significantly declines, the electric energy on the capacitance of PV sides will be to direct current
It is shifted on bus capacitor, larger DC current ripple will be will appear by working in this way in the circuit of second mode.
It should be noted that work in first mode all the way in also will appear DC current ripple, but ripple compares
It is small, within the acceptable range.
The controller 300, for judging that the temperature is less than temperature preset value, and judges the first DC-DC converter
One in 100a and the second DC-DC converter 100b works in first mode, when another works in second mode, controls institute
The first DC-DC converter 100a and the second equal forced workings of DC-DC converter 100b are stated in the first mode；
The first mode is：DC-DC converter works in pressure-increasning state；
The second mode is：DC-DC converter, which is bypassed, does not boost.
It is understood that temperature preset value is preset value, during less than the temperature, the capacity of electrolytic capacitor will
Have and significantly decline.I.e. the temperature preset value is a sensitive temperature value for electrolytic capacitor.
When the interior environment temperature of detection is less than temperature preset value, and two DC-DC converters work in different moulds
During formula, it is necessary to two DC-DC converters be controlled to work in first mode, because two DC-DC converters work in
Two modes also will appear DC current ripple.
It should be noted that the output terminal connection power grid of the inverter；The input terminal of first DC-DC converter connects
The first photovoltaic component apparatus is connect, the input terminal of second DC-DC converter connects the second photovoltaic component apparatus；Described first
DC-DC converter connects the input terminal of inverter with the output terminal of the second DC-DC converter by dc bus.
System provided in this embodiment detects the environment temperature inside power generator, by the ring by temperature sensor
Border temperature issues controller, and environment temperature and temperature preset value are compared by controller, when judge environment temperature be less than temperature
Preset value, and when two DC-DC converters work in different patterns, two DC-DC converters of control is forced to work in
First mode.Be not in larger current fluctuation when working in first mode due to two DC-DC converters.And DC-DC
When converter works in second mode, it may appear that larger current fluctuation ought particularly be in the first operating mode, in addition all the way
When being in the second operating mode all the way, current fluctuation bigger is detected.In this way can to avoid work in second mode all the way in go out
Existing DC current ripple.From the judgement signal without mistake.
System embodiment two：
Referring to Fig. 6, which is two schematic diagram of photovoltaic parallel in system embodiment provided by the invention.
One in first DC-DC converter and the second DC-DC converter works in first mode, another work
In second mode, including：
First DC-DC converter works in first mode, and second DC-DC converter works in second mode；
Or,
First DC-DC converter works in second mode, and second DC-DC converter works in first mode.
Photovoltaic parallel in system provided in this embodiment, further includes：Voltage check device 500；
The voltage check device 500, for detecting the output voltage and the second light of the first photovoltaic component apparatus PV1
The output voltage of assembly apparatus PV2 is lied prostrate, and the output voltage is sent to the controller 300；
The controller 300 is additionally operable to judge the first DC-DC converter 100a and second by the output voltage
The operating mode of DC-DC converter 100b judges one in the first DC-DC converter 100a and the second DC-DC converter 100b
A to work in first mode, another works in second mode, specially：
Judge that the output voltage of the first photovoltaic component apparatus PV1 is more than voltage preset value, and judge described second
The output voltage of photovoltaic component apparatus PV2 is less than the voltage preset value；
Or,
Judge that the output voltage of the first photovoltaic component apparatus PV1 is less than the voltage preset value, and described in judgement
The output voltage of second photovoltaic component apparatus PV2 is more than the voltage preset value.
The controller 300 is additionally operable to judge the interior environment temperature of the power generator 1000 more than or equal to described
During temperature preset value, and judge that the output voltage of the first photovoltaic component apparatus PV1 is more than voltage preset value, second light
The output voltage for lying prostrate assembly apparatus PV2 is less than the voltage preset value, then the first DC-DC converter 100a is controlled to work in
Second mode controls the second DC-DC converter 100b to work in first mode；
Or,
When judging that the interior environment temperature of the power generator 1000 is greater than or equal to the temperature preset value, and judge institute
The output voltage for stating the first photovoltaic component apparatus PV1 is less than voltage preset value, the output electricity of the second photovoltaic component apparatus PV2
Pressure is more than the voltage preset value, then the first DC-DC converter 100a is controlled to work in first mode, control described second
DC-DC converter 100b works in second mode.
That is, when the output voltage of photovoltaic component apparatus sufficiently high (being more than voltage preset value), then DC-DC transformation is not needed to
Device boost, and the output voltage of photovoltaic component apparatus is directly to inverter.DC-DC converter is other by SK2 at this time
Road, i.e. SK2 are closed.Conversely, when the output voltage of photovoltaic component apparatus not high enough (being less than or equal to voltage preset value), then need
DC-DC converter is wanted to boost, at this point, SK2 is disconnected.
It should be noted that the voltage preset value is that the phase voltage exported with inverter is related, it is possible to understand that
It is that the voltage of inverter output is grid-connected on power grid, and power grid electricity can be obtained by the output voltage for measuring inverter
Pressure.
Judge whether the output voltage of photovoltaic component apparatus is less than before voltage preset value, need first to measure current inverter
The phase voltage of output particularly for the different from three phase network system and single-phase network system, is introduced separately below.
The voltage preset value determines by the output voltage of the inverter, specially：
When the power grid is three phase network or two-phase power grid, the voltage preset value is higher than the line voltage of the inverter
The certain threshold value of peak value；
When the power grid is single-phase power grid, the voltage preset value is higher than the peak value one of the output voltage of the inverter
Determine threshold value.
It should be noted that for two-phase power grid existing for Countries, voltage preset value is also above inverter output
Line voltage peak value certain threshold value.
When the power grid is three phase network, the voltage preset value TsetA kind of computational methods are：For three phase network, V represents the virtual value of the phase voltage of the current inverter measured output；ΔV
For it is preset be more than zero number.
When the power grid is single-phase power grid, the voltage preset value TsetA kind of computational methods are：For single-phase power grid, wherein, V represents the virtual value of the current inverter output voltage measured；Δ V is
It is preset be more than zero number.
Δ V is a preset voltage margin, this numerical value is the number more than zero, can be selected according to actual needs.
For three phase network, voltage preset value is above the certain threshold value of peak value of line voltage；For single-phase power grid, voltage
Preset value is above the certain threshold value of peak value of inverter output voltage；For the two-phase power grid in the U.S., voltage preset value is also
Higher than the certain threshold value of peak value of the line voltage of inverter output.
System provided in this embodiment, normal logic control under, be added to temperature it is relatively low when decision logic, in this way may be used
During ensureing that photovoltaic parallel in system works in the very low environment of temperature, system is not in the judgement signal of mistake, in this way may be used
To ensure system worked well, so as to improve generated energy.
The above described is only a preferred embodiment of the present invention, not make limitation in any form to the present invention.Though
So the present invention is disclosed above with preferred embodiment, however is not limited to the present invention.It is any to be familiar with those skilled in the art
Member, without departing from the scope of the technical proposal of the invention, all using the methods and technical content of the disclosure above to the present invention
Technical solution makes many possible changes and modifications or is revised as the equivalent embodiment of equivalent variations.Therefore, it is every without departing from
The content of technical solution of the present invention, it is any simple modification made to the above embodiment of technical spirit according to the present invention, equivalent
Variation and modification, still fall within technical solution of the present invention protection in the range of.
Claims (10)
1. a kind of grid-connected control method, which is characterized in that applied to photovoltaic parallel in system, include the following steps：
Judge that the interior environment temperature of the power generator in photovoltaic parallel in system is less than temperature preset value, and judge the first DC-
One in DC converters and the second DC-DC converter works in first mode, when another works in second mode, controls institute
The first DC-DC converter and the equal forced working of the second DC-DC converter are stated in the first mode；
Wherein, the power generator includes：First DC-DC converter, second DC-DC converter, inverter and straight
Flow busbar；
The output terminal connection power grid of the inverter；The input terminal of first DC-DC converter connects the first photovoltaic module dress
It puts, the input terminal of second DC-DC converter connects the second photovoltaic component apparatus；First DC-DC converter and second
The output terminal of DC-DC converter connects the input terminal of inverter by dc bus；
The first mode is：DC-DC converter works in pressure-increasning state；
The second mode is：DC-DC converter, which is bypassed, does not boost.
2. grid-connected control method according to claim 1, which is characterized in that first DC-DC converter and
One in two DC-DC converters works in first mode, another works in second mode, including：
First DC-DC converter works in first mode, and second DC-DC converter works in second mode；
Or,
First DC-DC converter works in second mode, and second DC-DC converter works in first mode.
3. grid-connected control method according to claim 2, which is characterized in that the first DC-DC converter of the judgement
First mode is worked in one in the second DC-DC converter, another works in second mode, specially：
Judge that the output voltage of first photovoltaic component apparatus is more than voltage preset value, and judge second photovoltaic module
The output voltage of device is less than the voltage preset value；
Or,
Judge that the output voltage of first photovoltaic component apparatus is less than the voltage preset value, and judge second photovoltaic
The output voltage of assembly apparatus is more than the voltage preset value.
4. grid-connected control method according to claim 3, which is characterized in that the voltage preset value is by the inversion
The output voltage decision of device, specially：
When the power grid is three phase network or two-phase power grid, the voltage preset value is higher than the line voltage peak value of the inverter
Certain threshold value；
When the power grid is single-phase power grid, the voltage preset value is higher than the phase voltage peak value of the output voltage of the inverter
Certain threshold value.
5. grid-connected control method according to claim 4, which is characterized in that further include：
When judging that the interior environment temperature of the power generator is greater than or equal to the temperature preset value, and judge first light
The output voltage for lying prostrate assembly apparatus is more than voltage preset value, and the output voltage of second photovoltaic component apparatus is less than the voltage
Preset value then controls first DC-DC converter to work in second mode, and second DC-DC converter is controlled to work in
First mode；
Or,
When judging that the interior environment temperature of the power generator is greater than or equal to the temperature preset value, and judge first light
The output voltage for lying prostrate assembly apparatus is less than voltage preset value, and the output voltage of second photovoltaic component apparatus is more than the voltage
Preset value then controls first DC-DC converter to work in first mode, and second DC-DC converter is controlled to work in
Second mode.
6. a kind of photovoltaic parallel in system, which is characterized in that including：Power generator, the first photovoltaic component apparatus, the second photovoltaic module
Device, temperature sensor and controller；
The power generator includes：First DC-DC converter, the second DC-DC converter, inverter and dc bus；
The output terminal connection power grid of the inverter；The input terminal of first DC-DC converter connects the first photovoltaic module dress
It puts, the input terminal of second DC-DC converter connects the second photovoltaic component apparatus；First DC-DC converter and second
The output terminal of DC-DC converter connects the input terminal of inverter by dc bus；
The temperature sensor for detecting the interior environment temperature of the power generator, and the temperature is sent to described
Controller；
The controller, for judging that the temperature is less than temperature preset value, and judges the first DC-DC converter and second
One in DC-DC converter works in first mode, when another works in second mode, the first DC-DC is controlled to become
Parallel operation and the equal forced working of the second DC-DC converter are in the first mode；
The first mode is：DC-DC converter works in pressure-increasning state；
The second mode is：DC-DC converter, which is bypassed, does not boost.
7. photovoltaic parallel in system according to claim 6, which is characterized in that first DC-DC converter and the 2nd DC-
One in DC converters works in first mode, another works in second mode, including：
First DC-DC converter works in first mode, and second DC-DC converter works in second mode；
Or,
First DC-DC converter works in second mode, and second DC-DC converter works in first mode.
8. photovoltaic parallel in system according to claim 7, which is characterized in that further include：Voltage check device；
The voltage check device, for detecting the output voltage of first photovoltaic component apparatus and the second photovoltaic component apparatus
Output voltage, and the output voltage is sent to the controller；
The controller is additionally operable to judge the first DC-DC converter and the second DC-DC converter by the output voltage
Operating mode judges that in the first DC-DC converter and the second DC-DC converter works in a first mode, another work
Make in second mode, specially：
Judge that the output voltage of first photovoltaic component apparatus is more than voltage preset value, and judge second photovoltaic module
The output voltage of device is less than the voltage preset value；
Or,
Judge that the output voltage of first photovoltaic component apparatus is less than the voltage preset value, and judge second photovoltaic
The output voltage of assembly apparatus is more than the voltage preset value.
9. photovoltaic parallel in system according to claim 8, which is characterized in that the voltage preset value is by the inverter
Output voltage decision, specially：
When the power grid is three phase network or two-phase power grid, the voltage preset value is higher than the line voltage peak value of the inverter
Certain threshold value；
When the power grid is single-phase power grid, the voltage preset value is higher than the phase voltage peak value of the output voltage of the inverter
Certain threshold value.
10. photovoltaic parallel in system according to claim 9, which is characterized in that the controller is additionally operable to judge the hair
When the interior environment temperature of electric installation is greater than or equal to the temperature preset value, and judge the defeated of first photovoltaic component apparatus
Go out voltage more than voltage preset value, the output voltage of second photovoltaic component apparatus is less than the voltage preset value, then controls
First DC-DC converter works in second mode, and second DC-DC converter is controlled to work in first mode；
Or,
When judging that the interior environment temperature of the power generator is greater than or equal to the temperature preset value, and judge first light
The output voltage for lying prostrate assembly apparatus is less than voltage preset value, and the output voltage of second photovoltaic component apparatus is more than the voltage
Preset value then controls first DC-DC converter to work in first mode, and second DC-DC converter is controlled to work in
Second mode.
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| PCT/CN2014/083300 WO2016015243A1 (en) | 2014-07-30 | 2014-07-30 | Photovoltaic grid connection control method and photovoltaic grid connection system |
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| CN110224381B (en) * | 2019-05-14 | 2022-04-12 | 华为数字能源技术有限公司 | Photovoltaic inverter and photovoltaic power generation system thereof |
| CN113014198B (en) * | 2021-03-31 | 2022-12-13 | 华为数字能源技术有限公司 | Photovoltaic system |
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| WO2011135658A1 (en) * | 2010-04-26 | 2011-11-03 | 三菱電機株式会社 | System interconnection inverter |
| CN202978746U (en) * | 2012-12-21 | 2013-06-05 | 京东方科技集团股份有限公司 | Inverter and grid-connected power generation system |
| CN103294103A (en) * | 2012-12-06 | 2013-09-11 | 许昌学院电气信息工程学院 | Solar controlled change time faze control method based on temperature detection |
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| CN202364144U (en) * | 2011-11-24 | 2012-08-01 | 上海煦达新能源科技有限公司 | Bypass diode and bypass DC/DC converter of dual-stage photovoltaic inverter |
| US8648498B1 (en) * | 2012-11-19 | 2014-02-11 | Renewable Power Conversion, Inc | Photovoltaic power system with distributed photovoltaic string to polyphase AC power converters |
| CN103199724B (en) * | 2013-04-24 | 2015-10-28 | 常熟开关制造有限公司(原常熟开关厂） | A kind of two-stage type photovoltaic DC-to-AC converter |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011135658A1 (en) * | 2010-04-26 | 2011-11-03 | 三菱電機株式会社 | System interconnection inverter |
| CN103294103A (en) * | 2012-12-06 | 2013-09-11 | 许昌学院电气信息工程学院 | Solar controlled change time faze control method based on temperature detection |
| CN202978746U (en) * | 2012-12-21 | 2013-06-05 | 京东方科技集团股份有限公司 | Inverter and grid-connected power generation system |
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