CN104467498B - A kind of five level photovoltaic inverter neutral point voltage control method and system - Google Patents
A kind of five level photovoltaic inverter neutral point voltage control method and system Download PDFInfo
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- CN104467498B CN104467498B CN201410797174.5A CN201410797174A CN104467498B CN 104467498 B CN104467498 B CN 104467498B CN 201410797174 A CN201410797174 A CN 201410797174A CN 104467498 B CN104467498 B CN 104467498B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
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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
This application provides a kind of five level photovoltaic inverter neutral point voltage control method and system，Voltage magnitude by five level of this five level photovoltaic inverter of real-time monitoring output，And calculate voltage magnitude first difference and second difference of corresponding positive negative level，When determine the first difference be more than first threshold and be less than Second Threshold，When second difference is more than the 3rd threshold value and is less than four threshold values，The corresponding switching tube of zero level is made to quit work，And shield neutral balance control algolithm，Even if after midpoint potential no longer changes，Adjust the voltage magnitude of other four level，Make the first difference after adjustment be less than the 5th threshold value and the second difference is less than the 6th threshold value，The corresponding switching tube of zero level is made to resume work，And trigger neutral balance control algolithm and rerun，It can be seen that，The present invention is when Neutral-point Potential Fluctuation is larger，Make five level photovoltaic inverters still in working condition，Avoid generated energy loss，Ensure that the work efficiency of grid-connected photovoltaic system.
Description
Technical field
The invention mainly relates to the control field of grid-connected photovoltaic system, more particularly to a kind of five level light
Volt inverter neutral point voltage control method and system.
Background technology
Photovoltaic DC-to-AC converter is one of grid-connected photovoltaic system vitals, for the direct current generating PV cell panel
Electricity is delivered to electrical network after being converted to alternating current, as shown in figure 1, for a kind of existing photovoltaic based on five level photovoltaic inverters simultaneously
The structural representation of net system, in this photovoltaic parallel in system normal work, five level photovoltaic inverters will export the first positive electricity
This five kinds of level of flat Vp1, the second positive level Vp2, zero level V0, the first negative level Vn1 and the second negative level Vn2, specifically, lead to
Cross first switch pipe SP2 and export the second positive level Vp2, the first positive level Vp1 is exported by second switch pipe SP1, by the 3rd
Switching tube S0 exports zero level V0, exports the first negative level Vn1 by the 4th switching tube SN1, is exported by the 5th switching tube SN2
Second negative level Vn2.
Based on this, in the grid-connected work of five level photovoltaic inverters, the first positive level Vp1 of being exported due to it, second just
Level Vp2, the first negative level Vn1 and the second negative level Vn2, for these level are relative to zero level V0, thus, want
The positive negative level of stability contorting first and the second positive negative level are it is necessary to ensure neutral balance.
In prior art, neutral balance is added to control typically in the control algolithm of system, but, in practical application
In, when Neutral-point Potential Fluctuation and being larger, midpoint potential will exceed certain threshold value, now will trigger protection device control
Five level photovoltaic inverters quit work, and this will cause generated energy to lose, and reduces the work efficiency of grid-connected photovoltaic system.
Content of the invention
In view of this, the invention provides a kind of photovoltaic DC-to-AC converter neutral point voltage control method and system, solve existing
Technology Neutral-point Potential Fluctuation larger and when exceeding certain threshold value, control five level photovoltaic inverters to quit work by direct, from
And cause generated energy loss, and have impact on the technical problem of the work efficiency of grid-connected photovoltaic system.
To achieve these goals, this application provides technical scheme below：
A kind of five level photovoltaic inverter neutral point voltage control methods, in five level photovoltaic inverter normal works, institute
State five level photovoltaic inverters and export the first positive level Vp1, the second positive level Vp2, zero level V0, the first negative level Vn1 and the
Two negative level Vn2, methods described includes：
Monitor the first voltage amplitude of described first positive level Vp1, the second voltage amplitude of described second positive level Vp2,
The tertiary voltage amplitude of described first negative level Vn1 and the 4th voltage magnitude of described second negative level Vn2；
Calculate the first difference of described first voltage amplitude and described tertiary voltage amplitude, and described second voltage amplitude
The second difference with the 4th voltage magnitude；
When described first difference of determination is more than first threshold and is less than Second Threshold, or described second difference is more than the 3rd
Threshold value and during less than four threshold values, controls switching tube corresponding with described zero level V0 in described five level photovoltaic inverters to stop
Work, and shield neutral balance control algolithm；
To the first voltage amplitude of described first positive level Vp1, the second voltage amplitude of described second positive level Vp2, institute
4th voltage magnitude of the tertiary voltage amplitude and described second negative level Vn2 of stating the first negative level Vn1 is adjusted, until
When the second difference that the first difference after adjustment is less than after the 5th threshold value and adjustment is less than six threshold values, control and described zero level
The corresponding switching tube of V0 recovers normal work, and triggers described neutral balance control algolithm and rerun.
Preferably, after being calculated described first difference and described second difference first, methods described also includes：
Described first difference is compared with first threshold and Second Threshold respectively, and by described second difference respectively with
3rd threshold value and the 4th threshold value are compared；
When described first difference of determination is more than described first threshold and is less than described Second Threshold, or described second difference
More than described 3rd threshold value and less than described four threshold value when, execution described control described five level photovoltaic inverters in described
The corresponding switching tube of zero level V0 quits work, and shields neutral balance control algolithm step；
When determining that described first difference is more than described Second Threshold or described second difference more than described four threshold value,
Described five level photovoltaic inverters are controlled to quit work；
When described first difference of determination is less than described first threshold, and when described second difference is less than described three threshold value,
Neutral balance control algolithm is controlled to run.
Preferably, in the second electricity of the first voltage amplitude to described first positive level Vp1, described second positive level Vp2
4th voltage magnitude of pressure amplitude value, the tertiary voltage amplitude of described first negative level Vn1 and described second negative level Vn2 is carried out
During adjustment, also include：
When the second difference that the first difference after adjustment is more than after Second Threshold or adjustment is more than four threshold values, control
Described five level photovoltaic inverters quit work.
Preferably, also include：
When determining that the first difference is more than Second Threshold and/or the second difference more than four threshold values, export warning message.
Preferably, described first threshold is equal to the 3rd threshold value, and Second Threshold is equal to the 4th threshold value, the 5th threshold value is equal to the 6th
Threshold value.
A kind of five level photovoltaic inverter neutral point voltage control systems, in five level photovoltaic inverter normal works, institute
State five level photovoltaic inverters and export the first positive level Vp1, the second positive level Vp2, zero level V0, the first negative level Vn1 and the
Two negative level Vn2, then described system include：
Monitoring modular, for monitoring the first voltage amplitude of described first positive level Vp1, described second positive level Vp2
4th voltage amplitude of second voltage amplitude, the tertiary voltage amplitude of described first negative level Vn1 and described second negative level Vn2
Value；
First computing module, for calculating the first difference of described first voltage amplitude and described tertiary voltage amplitude, with
And the second difference of described second voltage amplitude and the 4th voltage magnitude；
First control module, for being more than first threshold in described first difference of determination and being less than Second Threshold, or institute
State the second difference be more than the 3rd threshold value and less than four threshold values when, control described five level photovoltaic inverters in described zero level
The corresponding switching tube of V0 quits work, and shields neutral balance control algolithm；
Adjusting module, for the first voltage amplitude of described first positive level Vp1, described second positive level Vp2
4th voltage magnitude of two voltage magnitudes, the tertiary voltage amplitude of described first negative level Vn1 and described second negative level Vn2
It is adjusted；
Then described first control module is additionally operable to second after the first difference after the adjustment is less than the 5th threshold value and adjusts
When difference is less than six threshold values, controls switching tube corresponding with described zero level V0 to recover normal work, and trigger described midpoint
Balancing control algorithm reruns.
Preferably, also include：
Comparison module, for will calculated first difference be compared with first threshold and Second Threshold respectively first
Be compared will first calculated second difference respectively relatively, and with the 3rd threshold value and the 4th threshold value；
Second control module, for being more than more than described Second Threshold or described second difference when described first difference of determination
During described four threshold value, described five level photovoltaic inverters are controlled to quit work；
3rd control module, for being less than described first threshold when described first difference of determination, and described second difference is little
When described three threshold value, neutral balance control algolithm is controlled to run.
Preferably, the control process of described second control module also includes：
When the second difference that the first difference after adjustment is more than after Second Threshold or adjustment is more than four threshold values, control
Described five level photovoltaic inverters quit work.
Preferably, also include：
Alarm module, for when determining that the first difference is more than Second Threshold and/or the second difference more than four threshold values, defeated
Go out warning message.
Preferably, described alarm module is specially buzzer, display lamp, voice module or display.
As can be seen here, compared with prior art, this application provides a kind of five level photovoltaic inverter neutral point voltage control
Method and system, by the voltage magnitude of five level of this five level photovoltaic inverter of real-time monitoring output, and calculate correspondence
First difference of voltage magnitude of positive negative level and the second difference, when determining that the first difference is more than first threshold and is less than the second threshold
Value, or when the second difference is more than the 3rd threshold value and is less than four threshold values, control the corresponding switching tube of zero level to quit work, and
Shielding neutral balance control algolithm so that after midpoint potential no longer changes, by adjusting the work of this five level photovoltaic inverter
The voltage magnitude of other four level, the first difference after determining adjustment is less than the 5th threshold value and the second difference is less than the 6th threshold value
When, control the corresponding switching tube of zero level again to resume work, and trigger neutral balance control algolithm and rerun, so that
Five level photovoltaic inverters are restored to five level active patterns it is seen then that leading to just correspond to when Neutral-point Potential Fluctuation is larger
When the voltage magnitude deviation of negative level is larger, in the present invention five level photovoltaic inverters still in working condition, thus avoiding
Generated energy loss is it is ensured that the work efficiency of grid-connected photovoltaic system.
Brief description
In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, below will to embodiment or
In description of the prior art the accompanying drawing of required use be briefly described it should be apparent that, drawings in the following description are only
Embodiments of the invention, for those of ordinary skill in the art, on the premise of not paying creative work, can also root
Obtain other accompanying drawings according to the accompanying drawing providing.
Fig. 1 is a kind of structural representation of existing photovoltaic parallel in system based on five level photovoltaic inverters；
Fig. 2 is a kind of schematic flow sheet of five level photovoltaic inverter neutral point voltage control embodiments of the method for the present invention；
Fig. 3 is the schematic flow sheet of present invention another kind five level photovoltaic inverter neutral point voltage control embodiments of the method；
Fig. 4 is a kind of structural representation of five level photovoltaic inverter neutral point voltage control system embodiments of the present invention.
Specific embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clear, complete
Site preparation description is it is clear that described embodiment is only a part of embodiment of the present invention, rather than whole embodiments.It is based on
Embodiment in the present invention, it is every other that those of ordinary skill in the art are obtained under the premise of not making creative work
Embodiment, broadly falls into the scope of protection of the invention.
This application provides a kind of five level photovoltaic inverter neutral point voltage control method and system, should by real-time monitoring
The voltage magnitude of five level of five level photovoltaic inverters outputs, and calculate corresponding positive negative level voltage magnitude first poor
Value and the second difference, when determine the first difference be more than first threshold and be less than Second Threshold, or the second difference be more than the 3rd threshold
Value and less than four threshold values when, control the corresponding switching tube of zero level quit work, and shield neutral balance control algolithm so that
After midpoint potential no longer changes, by adjusting the voltage magnitude of other four level of this five level photovoltaic inverter work, when true
Set the tone whole after the first difference when being less than the 5th threshold value and the second difference and being less than six threshold values, control the corresponding switching tube of zero level
Again resume work, and trigger neutral balance control algolithm and rerun, so that five level photovoltaic inverters recover again
To five level active patterns it is seen then that leading to the voltage magnitude deviation corresponding to positive negative level larger when Neutral-point Potential Fluctuation is larger
When, in the present invention five level photovoltaic inverters still in working condition, thus avoiding generated energy loss it is ensured that grid-connected
The work efficiency of electricity generation system.
With reference to a kind of flow process of five level photovoltaic inverter neutral point voltage control embodiments of the method for the present invention shown in Fig. 2
Schematic diagram, can export the first positive level Vp1, the second positive level during five level photovoltaic inverter normal work in the present embodiment
Vp2, zero level V0, the first negative level Vn1 and the second negative level Vn2, then the present embodiment this five level photovoltaic inverter is provided
Neutral point voltage control method may comprise steps of：
Step S201：Monitor the first voltage amplitude of the first positive level Vp1, the second voltage amplitude of the second positive level Vp2,
The tertiary voltage amplitude of the first negative level Vn1 and the 4th voltage magnitude of the second negative level Vn2.
Wherein, first voltage amplitude, second voltage amplitude, tertiary voltage amplitude and the 4th voltage magnitude are relative to zero
For level.
Understand in conjunction with Fig. 1, five level inverse conversion modules of five level photovoltaic inverters will be exported by first switch pipe SP2
Second positive level Vp2, exports the first positive level Vp1 by second switch pipe SP1, exports zero level by the 3rd switching tube S0
V0, exports the first negative level Vn1 by the 4th switching tube SN1, exports the second negative level Vn2 by the 5th switching tube SN2, because
And, in the practical application of the present embodiment, system can to first switch pipe SP2, second switch pipe SP1, the 4th switching tube SN1 with
And the 5th the outfan of switching tube SN2 be monitored, thus obtaining the voltage of the first positive negative level and the second positive negative level in real time
Amplitude.
Step S202：Calculate the first difference of first voltage amplitude and tertiary voltage amplitude, and second voltage amplitude with
Second difference of the 4th voltage magnitude.
Step S203：When determining that the first difference is more than first threshold and is less than Second Threshold, or the second difference is more than the
Three threshold values and less than four threshold values when, control five level photovoltaic inverters in switching tube corresponding with zero level V0 quit work,
And shield neutral balance control algolithm.
In the present embodiment practical application, after being calculated above-mentioned first difference and the second difference, can by by this
One difference is compared with default first threshold and Second Threshold respectively, and by the second difference respectively with default 3rd threshold value
It is compared with the 4th threshold value, when determining that the first difference is located between first threshold and Second Threshold, or the second difference is located at
When between the 3rd threshold value and the 4th threshold value, if still will be unable to ensure neutral balance using existing neutral balance control algolithm, with
Unlike existing operation, the present embodiment does not directly control five level photovoltaic inverters to quit work, but controls and zero
The corresponding switching tube of level V0 is that the 3rd switching tube S0 quits work, so that five level photovoltaic inverters only export the first positive electricity
Flat Vp1, the second positive level Vp2, the first negative level Vn1 and the second negative level Vn2, work in four level active patterns,
Avoid generated energy loss.
Understand in conjunction with Fig. 1, controlling the 3rd switching tube S0 to quit work is the equal of by the zero of dc-link capacitance discharge and recharge
Level loop is thoroughly cut off, so that midpoint potential no longer changes.As can be seen here, in the present embodiment, above-mentioned first threshold is permissible
It is to be Second Threshold less than the marginal value of starting protection signal, in the same manner, the 3rd threshold value is less than the 4th threshold value, this first threshold and the
Three threshold values equal but can need both differences within the specific limits it is also possible to be not completely equivalent, and this first threshold and the 3rd
Threshold value is that system cannot realize the marginal value of midpoint point position balance using neutral balance control algolithm, and its concrete numerical value can be according to light
In volt grid-connected system, the design parameter of device determines, here of the present invention is not especially limited.
Wherein, above-mentioned neutral balance control algolithm is to be the conventional control realizing photovoltaic DC-to-AC converter neutral balance in prior art
Algorithm processed, its concrete control process present invention no longer describes in detail.
Step S204：The second electricity to the first voltage amplitude of described first positive level Vp1, described second positive level Vp2
4th voltage magnitude of pressure amplitude value, the tertiary voltage amplitude of described first negative level Vn1 and described second negative level Vn2 is carried out
Adjustment, until adjustment after the first difference be less than the 5th threshold value and adjust after the second difference be less than six threshold values when, control with
The corresponding switching tube of described zero level V0 recovers normal work, and triggers described neutral balance control algolithm and rerun.
Understand, after the 3rd switching tube S0 quits work, five level photovoltaic inverters would operate in four based on above-mentioned analysis
Level mode, to adjust the voltage magnitude of four kinds of level that five level photovoltaic inverters now export, that is, to the first positive level Vp1
First voltage amplitude, the second voltage amplitude of the second positive level Vp2, the tertiary voltage amplitude of the first negative level Vn1 and
4th voltage magnitude of two negative level Vn2 is adjusted, so that the voltage partially falling is pulled back, thus returning to the first positive level
Vp1, the first negative level Vn1 and the second positive level Vp2, the state of second this four balances of power level of negative level Vn2.
Wherein, to the concrete adjustment process of above-mentioned four kinds of level can according to the first positive level Vp1 and the first negative level Vn1,
And second the current voltage amplitude of positive level Vp2 and the second negative level Vn2 be adjusted, as long as enabling to the first positive negative electricity
The voltage magnitude of gentle second positive negative level is partially worth and reduces, and the present invention will not be described in detail herein concrete adjustment process.
In actual applications, system is to the first positive level Vp1 and the first negative level Vn1, and the second positive level Vp2 and
During the adjustment of current voltage amplitude of the second negative level Vn2, can with the voltage magnitude of this four level of real-time detection, once
When determining that the difference after adjustment meets preset requirement, the switching tube S0 turning off is controlled again to resume work in time.
Optionally, after completing step S202, first voltage amplitude and described tertiary voltage amplitude are obtained first
First difference and state second voltage amplitude and the 4th voltage magnitude the second difference when, method proposed by the invention is acceptable
Including：
Described first difference is compared with first threshold and Second Threshold respectively, and by described second difference respectively with
3rd threshold value and the 4th threshold value are compared, and are determining described first difference more than described first threshold and less than described second
Threshold value, or when described second difference is more than described 3rd threshold value and is less than described four threshold value, now original midpoint is described
Balancing control algorithm cannot ensure neutral-point potential balance, need to execute above-mentioned steps S203, and the voltage partially falling is pulled back, thus
Keep neutral-point potential balance；When determining that described first difference is more than described Second Threshold or described second difference and is more than described the
During four threshold values, described five level photovoltaic inverters are controlled to quit work；When described first difference of determination is less than described first threshold,
And described second difference is when being less than described three threshold value, then explanation midpoint potential is in a basic balance, need not adjust other four level
Voltage magnitude, as long as control original neutral balance control algolithm normally to run, you can ensure neutral-point potential balance.
As can be seen here, in five level photovoltaic inverter neutral point voltage control methods disclosed by the invention, as long as the first difference
Less than Second Threshold, and the second difference is less than the 4th threshold value, and five level photovoltaic inverters avoid the need for shutting down, with specific reference to above-mentioned
Content is accordingly controlled, and compared with existing neutral balance control method, reduces generated energy loss, and substantially increases light
The work efficiency of photovoltaic grid-connected system.
The neutral point voltage control method recorded for the clearer explanation present invention, in conjunction with above-mentioned analysis, here provides one
Plant the schematic flow sheet of five level photovoltaic inverter neutral point voltage control method preferred embodiments, such as Fig. 3, wherein, this five level
The composition structure of photovoltaic DC-to-AC converter is same as the previously described embodiments, specifically can refer to Fig. 1, and the present embodiment will not be described in detail herein, then should
The method of preferred embodiment specifically may comprise steps of：
Step S301：Monitor the first voltage amplitude of the first positive level Vp1, the second voltage amplitude of the second positive level Vp2,
The tertiary voltage amplitude of the first negative level Vn1 and the 4th voltage magnitude of the second negative level Vn2.
Step S302：Calculate the first difference of first voltage amplitude and tertiary voltage amplitude, and second voltage amplitude with
Second difference of the 4th voltage magnitude.
Step S303：First difference is compared with first threshold and Second Threshold respectively, and by the second difference respectively
It is compared with the 3rd threshold value and the 4th threshold value, when the first difference is more than first threshold and is less than Second Threshold, or second is poor
When value is more than the 3rd threshold value and is less than four threshold values, execution step S304；When the first difference is poor more than Second Threshold or second
When value is more than four threshold values, execution step S306；When the first difference is less than first threshold, and the second difference is less than the 3rd threshold value,
Execution step S307.
Step S304：Control switching tube corresponding with zero level V0 in five level photovoltaic inverters to quit work, and shield
Neutral balance control algolithm.
Step S305：To the first voltage amplitude of the first positive level Vp1, the second voltage amplitude of the second positive level Vp2,
4th voltage magnitude of the tertiary voltage amplitude of one negative level Vn1 and the second negative level Vn2 is adjusted, until after adjustment
When the second difference that first difference is less than after the 5th threshold value and adjustment is less than six threshold values, control corresponding with described zero level V0
Switching tube recovers normal work, and triggers described neutral balance control algolithm and rerun.
In the present embodiment practical application, determine that the first difference is more than first threshold and is less than Second Threshold, or second is poor
When value is more than the 3rd threshold value and is less than four threshold values, control zero level corresponding switching tube S0 to quit work, treat that midpoint potential is put down
After this switching tube S0 resuming work after weighing apparatus, five level photovoltaic inverters enter normal five level mode work, now again
Only neutral-point-potential balance control algorithm need to be utilized, you can maintain neutral-point potential balance it is ensured that five level photovoltaic inverters are normal simultaneously
Net work.
Step S306：Five level photovoltaic inverters are controlled to quit work.
In order to protect device in five level photovoltaic inverters, when determine the first difference be more than Second Threshold or the second difference
After the 4th threshold value, trigger protection device is made five level photovoltaic inverters shut down, wherein, this Second Threshold can be equal to the
Four threshold values, it is of course also possible to make Second Threshold and the difference of the 4th threshold value be less than predetermined threshold value, the present invention does not specifically limit to this
Fixed.
Step S307：Neutral balance control algolithm is controlled to run.
In actual applications, when the first difference of corresponding positive and negative level voltage amplitude is less than first threshold, and the second difference
During less than three threshold values, control original neutral balance control algolithm normally to run, generally just the voltage partially falling can be retracted
Come so that neutral-point potential balance.
Optionally, it is in operation during a balancing control algorithm, level voltage amplitude can be corresponded to by real-time detection
The whether big first threshold of first difference, the whether big Second Threshold of the second difference, if so, then illustrate that now mid point level is uneven,
Exportable corresponding information, to remind staff to note this situation.
In addition, in embodiments of the present invention, in above-mentioned comparison procedure, can export different for different comparative results
Cue, so that work understands the current state of five level when first five level photovoltaic inverter, wherein, this cue
Concrete manifestation is the form present invention be not especially limited, for example, it may be the flicker of different colours display lamp, or multiple display lamp
According to the flicker of different rules, or the buzzer of different frequency modulations or different time that buzzer sends, or comprise
Voice signal of judged result etc., pays creative work determination so long as not those skilled in the art, belongs to this
Bright protection domain, here of the present invention will not enumerate.
In sum, inventive embodiments are directed to the concrete size of the difference of the correspondence positive and negative level voltage amplitude detecting, and enter
Row is corresponding to be controlled or level adjustment, rather than is determining that the first difference is more than first threshold or the second difference is more than the 3rd threshold value
Afterwards, just directly control five level photovoltaic inverters to shut down, solve in prior art, when midpoint potential is uneven because of shutdown
Guiding discharge amount is lost, and affects the technical problem of the work efficiency of grid-connected photovoltaic system.
With reference to a kind of structural representation of five level photovoltaic inverter neutral point voltage control systems of the present invention shown in Fig. 4,
The concrete composition structure of this five level photovoltaic inverter can refer to shown in Fig. 1, and the present embodiment will not be described in detail herein, wherein, when this
During five level photovoltaic inverter normal works, the second positive level Vp2 will be exported by first switch pipe SP2, by second switch
Pipe SP1 exports the first positive level Vp1, exports zero level V0 by the 3rd switching tube S0, exports first by the 4th switching tube SN1
Negative level Vn1, exports the second negative level Vn2 by the 5th switching tube SN2, then the control system that the present embodiment is provided specifically may be used
To include：
Monitoring modular 401, for monitoring the first voltage amplitude of the first positive level Vp1, second electricity of the second positive level Vp2
4th voltage magnitude of pressure amplitude value, the tertiary voltage amplitude of the first negative level Vn1 and the second negative level Vn2.
First computing module 402, for calculating the first difference of first voltage amplitude and tertiary voltage amplitude, and second
Voltage magnitude and the second difference of the 4th voltage magnitude.
First control module 403, for determining that the first difference is more than first threshold and less than Second Threshold or described
When second difference is more than the 3rd threshold value and is less than four threshold values, control corresponding with zero level V0 in five level photovoltaic inverters opening
Close pipe to quit work, and shield neutral balance control algolithm.
Adjusting module 404, for the second voltage to the first voltage amplitude of the first positive level Vp1, the second positive level Vp2
4th voltage magnitude of amplitude, the tertiary voltage amplitude of the first negative level Vn1 and the second negative level Vn2 is adjusted.
Then this first control module 403 is additionally operable to second after the first difference after the adjustment is less than the 5th threshold value and adjusts
When difference is less than six threshold values, controls switching tube corresponding with described zero level V0 to recover normal work, and trigger described midpoint
Balancing control algorithm reruns.
Optionally, system can also include：
Comparison module, for described first difference is compared with first threshold and Second Threshold respectively, and will be described
Second difference is compared with the 3rd threshold value and the 4th threshold value respectively.
Second control module, for being more than described Second Threshold or described second difference more than described in determination the first difference
During four threshold values, described five level photovoltaic inverters are controlled to quit work.
In the present embodiment practical application, the first difference that this second control module is additionally operable to after adjustment is more than the second threshold
When the second difference after value or adjustment is more than four threshold values, described five level photovoltaic inverters are controlled to quit work.
3rd control module, for being less than described first threshold when described first difference of determination, and described second difference is little
When described three threshold value, neutral balance control algolithm is controlled to run.
Optionally, system can also include
Alarm module, for when determining that the first difference is more than Second Threshold and/or the second difference more than four threshold values, defeated
Go out warning message.
Wherein, this alarm module is specifically as follows buzzer, display lamp, voice module or display etc., the present invention couple
This is not especially limited.
Understood based on above-mentioned analysis, in embodiments of the present invention, when the first of the corresponding positive and negative level voltage amplitude of determination
Difference is more than first threshold and is less than Second Threshold, and when the second difference is more than the 3rd threshold value and is less than four threshold values, system is control
The corresponding switching tube S0 of zero level processed quits work, and shields neutral balance control algolithm, so that midpoint potential no longer becomes
Change, afterwards, then control this five level photovoltaic inverter to be operated in four level modes, and the four kinds of level now exporting are adjusted
Whole, so that midpoint potential restores balance, that is, the first difference after adjusting is less than the 5th threshold value and the second difference is less than the 6th threshold
During value, controlling switch pipe S0 resumes work again so that five level photovoltaic inverters only need to work in five level modes, thus may be used
See, in whole control process, the present invention does not need to control five level photovoltaic inverters to shut down, and decreases generated energy loss,
Improve the work efficiency of grid-connected photovoltaic system.
It should be noted that with regard to, in the various embodiments described above, such as first, second or the like relational terms are used merely to
One is operated or module is made a distinction with another operation or module, and not necessarily require or imply these modules or operation
Between there is any this actual relation or order.
In this specification, each embodiment is described by the way of going forward one by one, and what each embodiment stressed is and other
The difference of embodiment, between each embodiment identical similar portion mutually referring to.For system disclosed in embodiment
For, because it is corresponding with method disclosed in embodiment, so description is fairly simple, referring to method part illustration in place of correlation
?.
Described above to the disclosed embodiments, makes professional and technical personnel in the field be capable of or uses the present invention.
Multiple modifications to these embodiments will be apparent from for those skilled in the art, as defined herein
General Principle can be realized without departing from the spirit or scope of the present invention in other embodiments.Therefore, the present invention
It is not intended to be limited to the embodiments shown herein, and be to fit to and principles disclosed herein and features of novelty phase one
The scope the widest causing.
Claims (10)
1. a kind of five level photovoltaic inverter neutral point voltage control methods are it is characterised in that normal in five level photovoltaic inverters
During work, described five level photovoltaic inverters export the first positive level Vp1, the second positive level Vp2, zero level V0, the first negative electricity
Flat Vn1 and the second negative level Vn2, methods described includes：
Monitor the first voltage amplitude of described first positive level Vp1, the second voltage amplitude of described second positive level Vp2, described
The tertiary voltage amplitude of the first negative level Vn1 and the 4th voltage magnitude of described second negative level Vn2；
Calculate the first difference of described first voltage amplitude and described tertiary voltage amplitude, and described second voltage amplitude and the
Second difference of four voltage magnitudes；
When described first difference of determination is more than first threshold and is less than Second Threshold, or described second difference is more than the 3rd threshold value
And during less than four threshold values, control switching tube corresponding with described zero level V0 in described five level photovoltaic inverters to stop work
Make, and shield neutral balance control algolithm；
To the first voltage amplitude of described first positive level Vp1, the second voltage amplitude of described second positive level Vp2, described
4th voltage magnitude of the tertiary voltage amplitude of one negative level Vn1 and described second negative level Vn2 is adjusted, until adjustment
When the second difference that the first difference afterwards is less than after the 5th threshold value and adjustment is less than six threshold values, control and described zero level V0 pair
The switching tube answered recovers normal work, and triggers described neutral balance control algolithm and rerun.
2. method according to claim 1 is it is characterised in that described first difference and described second ought be calculated first
After difference, methods described also includes：
Described first difference is compared with first threshold and Second Threshold respectively, and by described second difference respectively with the 3rd
Threshold value and the 4th threshold value are compared；
When described first difference of determination is more than described first threshold and is less than described Second Threshold, or described second difference is more than
Described 3rd threshold value and less than described four threshold value when, execution described control described five level photovoltaic inverters in described zero electricity
The corresponding switching tube of flat V0 quits work, and shields neutral balance control algolithm step；
When determining that described first difference is more than described Second Threshold or described second difference more than described four threshold value, control
Described five level photovoltaic inverters quit work；
When described first difference of determination is less than described first threshold, and when described second difference is less than described three threshold value, control
Neutral balance control algolithm is run.
3. method according to claim 2 it is characterised in that the first voltage amplitude to described first positive level Vp1,
The second voltage amplitude of described second positive level Vp2, the tertiary voltage amplitude of described first negative level Vn1 and described second negative
During 4th voltage magnitude of level Vn2 is adjusted, also include：
When the second difference that the first difference after adjustment is more than after Second Threshold or adjustment is more than four threshold values, control described
Five level photovoltaic inverters quit work.
4. method according to claim 3 is it is characterised in that also include：
When determining that the first difference is more than Second Threshold and/or the second difference more than four threshold values, export warning message.
5. the method according to any one of claim 1-4 is it is characterised in that described first threshold is equal to the 3rd threshold value, and the
Two threshold values are equal to the 4th threshold value, the 5th threshold value is equal to the 6th threshold value.
6. a kind of five level photovoltaic inverter neutral point voltage control systems are it is characterised in that normal in five level photovoltaic inverters
During work, described five level photovoltaic inverters export the first positive level Vp1, the second positive level Vp2, zero level V0, the first negative electricity
Flat Vn1 and the second negative level Vn2, then described system include：
Monitoring modular, for monitoring the first voltage amplitude of described first positive level Vp1, the second of described second positive level Vp2
4th voltage magnitude of voltage magnitude, the tertiary voltage amplitude of described first negative level Vn1 and described second negative level Vn2；
First computing module, for calculating the first difference of described first voltage amplitude and described tertiary voltage amplitude, Yi Jisuo
State the second difference of second voltage amplitude and the 4th voltage magnitude；
First control module, for determining that described first difference is more than first threshold and is less than Second Threshold, or described the
When two differences are more than the 3rd threshold value and are less than four threshold values, with described zero level V0 pair in described five level photovoltaic inverters of control
The switching tube answered quits work, and shields neutral balance control algolithm；
Adjusting module, for the second electricity to the first voltage amplitude of described first positive level Vp1, described second positive level Vp2
4th voltage magnitude of pressure amplitude value, the tertiary voltage amplitude of described first negative level Vn1 and described second negative level Vn2 is carried out
Adjustment；
The second difference after the first difference that described first control module is additionally operable to after the adjustment is less than the 5th threshold value and adjusts is little
When six threshold values, control switching tube corresponding with described zero level V0 to recover normal work, and trigger described neutral balance control
Algorithm processed reruns.
7. system according to claim 6 is it is characterised in that also include：
Comparison module, for will calculated first difference be compared with first threshold and Second Threshold respectively first, and
To calculated second difference be compared with the 3rd threshold value and the 4th threshold value respectively first；
Second control module, for described when determining that described first difference is more than more than described Second Threshold or described second difference
During four threshold values, described five level photovoltaic inverters are controlled to quit work；
3rd control module, for being less than described first threshold when described first difference of determination, and described second difference is less than institute
When stating three threshold values, neutral balance control algolithm is controlled to run.
8. system according to claim 7 is it is characterised in that the control process of described second control module also includes：
When the second difference that the first difference after adjustment is more than after Second Threshold or adjustment is more than four threshold values, control described
Five level photovoltaic inverters quit work.
9. the system according to any one of claim 6-8 is it is characterised in that also include：
Alarm module, for when determining that the first difference is more than Second Threshold and/or the second difference more than four threshold values, output is reported
Alarming information.
10. system according to claim 9 is it is characterised in that described alarm module is specially buzzer, display lamp, language
Sound module or display.
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| CN103427695A (en) * | 2013-08-30 | 2013-12-04 | 阳光电源股份有限公司 | Balance controlling method and system for capacitance and level of three-phase five-level converter |
| CN104079197A (en) * | 2014-07-07 | 2014-10-01 | 阳光电源股份有限公司 | Neutral-point potential balance control method and device, multi-level converter and control system |
| CN104218832A (en) * | 2013-05-30 | 2014-12-17 | 阳光电源股份有限公司 | Single-phase five-level topology and inverter |
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| CN104218832A (en) * | 2013-05-30 | 2014-12-17 | 阳光电源股份有限公司 | Single-phase five-level topology and inverter |
| CN103427695A (en) * | 2013-08-30 | 2013-12-04 | 阳光电源股份有限公司 | Balance controlling method and system for capacitance and level of three-phase five-level converter |
| CN104079197A (en) * | 2014-07-07 | 2014-10-01 | 阳光电源股份有限公司 | Neutral-point potential balance control method and device, multi-level converter and control system |
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