CN104467499B - Five-level inverter neutral-point balancing control method and system - Google Patents
Five-level inverter neutral-point balancing control method and system Download PDFInfo
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- CN104467499B CN104467499B CN201510001239.5A CN201510001239A CN104467499B CN 104467499 B CN104467499 B CN 104467499B CN 201510001239 A CN201510001239 A CN 201510001239A CN 104467499 B CN104467499 B CN 104467499B
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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
- H02M7/487—Neutral point clamped inverters
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Abstract
The invention provides a five-level inverter neutral-point balancing control method and system. The method includes the steps of detecting V2Pos and V2Neg; obtaining a two-level neutral-point voltage balancing adjusting result Vout through a difference of the V2Pos and the V2Neg according to a preset adjusting algorithm; obtaining a first total positive and negative bus charging current difference I1 by overlapping a net-side three-phase bridge arm voltage command Vx and the positive zero sequence offset; obtaining a second total positive and negative bus charging current difference I2 by overlapping the Vx and the negative zero sequence offset; obtaining the positive zero sequence offset and the negative zero sequence offset in advance, wherein the Vx is the three-phase bridge arm voltage command before amendment is carried out; determining the overlapped offset V1 according to the Vout, the I1 and the I2, wherein the amended three-phase bridge arm voltage command Vx1 is equal to a sum of V0 and the Vx, and V0=V1*|Vout|; guaranteeing that a positive bus and a negative bus keep symmetrical during working so that risks caused by over-high voltage stress caused by the neutral-point voltage offset in the switching tube motion process can be eliminated.
Description
Technical field
The present invention relates to technical field of photovoltaic power generation, particularly to a kind of five-electrical level inverter neutral balance control method and
System.
Background technology
In photovoltaic generating system, five-electrical level inverter has lower grid-connected with respect to two level and three-level inverter
Current ripples and lower switching loss, therefore, have lower grid-connected current always humorous under same output filter size
Wave distortion (THD, Total Harmonic Distortion) and higher efficiency.
But, five-electrical level inverter is similar with three-level inverter, equally exists the problem of mid-point potential offset, causes out
The voltage stress closing pipe is asymmetric, so that some switching tubes bear too high voltage in some instances it may even be possible to make in switching process
Become demolition.Therefore, in order to ensure the safety of switching tube, need to control five-electrical level inverter neutral balance.
Referring to Fig. 1, this figure is photovoltaic generating system schematic diagram of the prior art.
In photovoltaic generating system, including PV array 100, Boost 200, inverter 300, output filter 400
With transformator 500.
From figure 1 it appears that compare in five-electrical level inverter increased one group of dc bus three-level inverter more：PV
The positive and negative inlet highway of array.Therefore, for five-electrical level inverter, the busbar voltage of balance is needed to have two groups：Always positive and negative direct current is female
Line voltage to neutral V2Pos and V2Neg；PV array positive and negative inlet highway voltage to neutral V1Pos and V1Neg.
The on off state of net side and Boost side and electric current alignment current potential all have an impact, in five-electrical level inverter
Switch combination is more than in three level, and therefore, the neutral balance control method of three-level inverter is not particularly suited for five level inverse conversions
In device.
Therefore, those skilled in the art need to provide a kind of five-electrical level inverter neutral balance control method and system, energy
Enough balance the mid-point voltage of five-electrical level inverter, the safety of protection whole system.
Content of the invention
The technical problem to be solved in the present invention is to provide a kind of five-electrical level inverter neutral balance control method and system, energy
Enough balance the mid-point voltage of five-electrical level inverter, the safety of protection whole system.
The embodiment of the present invention provides a kind of five-electrical level inverter neutral balance control method, is applied to five level photovoltaic inversion
In system, this system includes：PV array, the first Boost circuit, the second Boost circuit, five-electrical level inverter；First electric capacity,
Two electric capacity, the 3rd electric capacity and the 4th electric capacity；+ 1 level that the positive output end of described PV array connects described five-electrical level inverter is defeated
Enter to hold, -1 level input of the negative output terminal described five-electrical level inverter of connection of described PV array, the two of described first electric capacity
End connects the positive output end of described PV array and 0 level input of five-electrical level inverter, the two ends of described second electric capacity respectively
Connect the negative output terminal of described PV array and 0 level input of five-electrical level inverter respectively；Described first Boost circuit defeated
Enter the positive output end that end connects described PV array, the outfan of described first Boost circuit connects+2 electricity of five-electrical level inverter
Flat input, the input of described second Boost circuit connects the negative output terminal of described PV array, described second Boost circuit
Outfan connect five-electrical level inverter -2 level input, the two ends of described 3rd electric capacity connect described first respectively
The outfan of Boost circuit and described 0 level input, the two ends of described 4th electric capacity connect described 2nd Boost electricity respectively
The outfan on road and described 0 level input；The method includes：
Detect -2 level voltage V2Neg on+2 level voltage V2Pos and the 4th electric capacity on described 3rd electric capacity；
Two level neutral point voltage balances are obtained through predetermined adjustment algorithm by the difference of described V2Pos and V2Neg and adjusts result
Vout；
The net side three-phase brachium pontis voltage instruction Vx of described inverter is superimposed positive zero sequence side-play amount respectively and obtains total the
One positive and negative busbar charging current difference I1；The net side three-phase brachium pontis voltage instruction of described inverter is superimposed the skew of negative sense zero sequence respectively
Amount obtains the second total positive and negative busbar charging current difference I2；Described forward direction zero sequence side-play amount and negative sense zero sequence side-play amount obtain in advance
?；Vx is the three-phase brachium pontis voltage instruction before revising；X is a, b and c；
It should be noted that described forward direction zero sequence side-play amount and negative sense zero sequence side-play amount are obtained ahead of time specially：According to Vx
Amplitude choosing positive zero sequence side-play amount and negative sense zero sequence side-play amount, the amplitude maximum of such as Vx is+1, and minima is -1,
If the amplitude of current Vx is 0.8, positive zero sequence side-play amount just takes 0.2, i.e. difference between 0.8 and maximum+1.
Size according to Vout, I1 and I2 determines side-play amount V1 of superposition, revised three-phase brachium pontis voltage instruction Vx1
For：Vx1=V0+Vx, wherein V0=V1* | Vout |；
Judge Vout>0, and I1>During I2, described V1 chooses described forward migration amount；
Judge Vout>0, and I1<During I2, described V1 chooses described negative offset amount；
Judge Vout<0, and I1>During I2, described V1 chooses described negative offset amount；
Judge Vout<0, and I1<During I2, described V1 chooses described forward migration amount.
Preferably, when described inverter is operated in five level modes, described I1=Σ IxPos1-ΣIxNeg1, I2=Σ
IxPos2-ΣIxNeg2；Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative for three-phase
Bus current；
Vx is compared with V1Pos, works as Vx>During V1Pos, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (1)
?；
Wherein, IxFor net side three-phase current；
Work as Vx<During V1Pos, Vx and-V1Neg is compared, works as Vx<When (- V1Neg), described IxPos1、IxPos2With
IxNeg2、IxNeg1Obtained by formula (2)；
Work as Vx<During V1Pos, and Vx>When (- V1Neg), described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (3)；
Preferably, when described inverter is operated in three level modes, described I1=Σ IxPos1-ΣIxNeg1, I2=Σ
IxPos2-ΣIxNeg2；Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative mother for three-phase
Line current；
Vx is compared with 0, works as Vx>When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (4)；
Wherein, IxFor net side three-phase current；
Work as Vx<When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (5)；
Preferably, also include：Detect+1 level voltage V1Pos on described first electric capacity, -1 level on the second electric capacity
Voltage V1Neg；By described V1Pos and V1Neg, all with 1/2nd PV array output voltage instruction be compared, according to than
Relatively result controls positive PV busbar voltage and negative PV busbar voltage respectively.
Preferably, described predetermined adjustment algorithm is following any one：Proportion adjustment algorithm, proportional integral adjust algorithm
Adjust algorithm with PID.
The embodiment of the present invention also provides a kind of five-electrical level inverter neutral balance control device, is applied to five level photovoltaics inverse
In change system, this system includes：PV array, the first Boost circuit, the second Boost circuit, five-electrical level inverter；First electric capacity,
Second electric capacity, the 3rd electric capacity and the 4th electric capacity；The positive output end of described PV array connects+1 level of described five-electrical level inverter
Input, the negative output terminal of described PV array connects -1 level input of described five-electrical level inverter, described first electric capacity
Two ends connect the positive output end of described PV array and 0 level input of five-electrical level inverter respectively, and the two of described second electric capacity
End connects the negative output terminal of described PV array and 0 level input of five-electrical level inverter respectively；Described first Boost circuit
Input connects the positive output end of described PV array, and the outfan of described first Boost circuit connects+the 2 of five-electrical level inverter
Level input, the input of described second Boost circuit connects the negative output terminal of described PV array, described 2nd Boost electricity
The outfan on road connects -2 level input of five-electrical level inverter, and the two ends of described 3rd electric capacity connect described first respectively
The outfan of Boost circuit and described 0 level input, the two ends of described 4th electric capacity connect described 2nd Boost electricity respectively
The outfan on road and described 0 level input；This equipment includes：Positive and negative two level detection module, positive and negative two level modulation modules
With positive and negative two level neutral balance modules；
Described positive and negative two level detection module, for detecting+2 level voltage V2Pos and the 4th on described 3rd electric capacity
- 2 level voltage V2Neg on electric capacity；
Described positive and negative two level modulation modules, obtain two electricity for the difference by described V2Pos and V2Neg through overregulating algorithm
Flat neutral point voltage balance adjusts result Vout；
Described positive and negative two level neutral balance modules, for dividing the net side three-phase brachium pontis voltage instruction Vx of described inverter
Positive zero sequence side-play amount Die Jia not obtain the first total positive and negative busbar charging current difference I1；Net side three-phase bridge by described inverter
Arm voltage instruction is superimposed negative sense zero sequence side-play amount respectively and obtains the second total positive and negative busbar charging current difference I2；Described forward direction zero sequence
Side-play amount and negative sense zero sequence side-play amount are obtained ahead of time；Vx is the three-phase brachium pontis voltage instruction before revising；X is a, b and c；According to
The size of Vout, I1 and I2 determines side-play amount V1 of superposition, and revised three-phase brachium pontis voltage instruction Vx1 is：Vx1=V0+Vx,
Wherein V0=V1* | Vout |；Judge Vout>0, and I1>During I2, described V1 chooses described forward migration amount；Judge Vout>0, and
I1<During I2, described V1 chooses described negative offset amount；Judge Vout<0, and I1>During I2, described V1 chooses described negative offset
Amount；Judge Vout<0, and I1<During I2, described V1 chooses described forward migration amount.
Preferably, described positive and negative two level neutral balance modules include：First electric current obtains submodule；
When described inverter is operated in five level modes, described I1=Σ IxPos1-ΣIxNeg1, I2=Σ IxPos2-Σ
IxNeg2；Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electricity for three-phase
Stream；
Described first electric current obtains submodule, for being compared Vx with V1Pos, works as Vx>During V1Pos, described IxPos1、
IxPos2And IxNeg2、IxNeg1Obtained by formula (1)；
Wherein, IxFor net side three-phase current；
Work as Vx<During V1Pos, Vx and-V1Neg is compared, works as Vx<When (- V1Neg), described IxPos1、IxPos2With
IxNeg2、IxNeg1Obtained by formula (2)；
Work as Vx<During V1Pos, and Vx>When (- V1Neg), described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (3)；
Preferably, described positive and negative two level neutral balance modules include：Second electric current obtains submodule；
When described inverter is operated in three level modes, described I1=Σ IxPos1-ΣIxNeg1, I2=Σ IxPos2-Σ
IxNeg2；Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electricity for three-phase
Stream；
Described second electric current obtains submodule, for being compared Vx with 0, works as Vx>When 0, described IxPos1、IxPos2With
IxNeg2、IxNeg1Obtained by formula (4)；
Wherein, IxFor net side three-phase current；
Work as Vx<When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (5)；
Preferably, also include：Positive negative one level detection module and positive negative one level modulation module；
Described positive negative one level detection module, for detecting+1 level voltage V1Pos on described first electric capacity, the second electricity
- 1 level voltage V1Neg in appearance；
Described positive negative one level modulation module, for by described V1Pos and V1Neg, all defeated with 1/2nd PV array
Go out voltage instruction to be compared, positive PV busbar voltage and negative PV busbar voltage are controlled respectively according to comparative result.
Preferably, described predetermined adjustment algorithm is following any one：Proportion adjustment algorithm, proportional integral adjust algorithm
Adjust algorithm with PID.
Compared with prior art, the present invention has advantages below：
The method that the present embodiment provides, by being modified balancing two level midpoints to net side three-phase brachium pontis voltage instruction
Voltage, detects the voltage on the 3rd electric capacity and the 4th electric capacity first respectively, obtains revising side-play amount according to this two voltage differences
Amplitude, is then judged by being superimposed positive zero sequence side-play amount and negative sense zero sequence side-play amount on net side three-phase brachium pontis voltage instruction
Determine the positive still negative sense zero sequence side-play amount of final superposition.By two can be adjusted to the correction of net side three-phase brachium pontis voltage instruction
Level neutral point voltage balance is it is ensured that positive and negative busbar operationally keeps symmetrical, thus eliminating because of opening that unbalance of neutral-point voltage causes
Close the too high risk of voltage stress in pipe course of action.
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 be to embodiment or existing
Have technology description in required use accompanying drawing be briefly described it should be apparent that, drawings in the following description be only this
Some embodiments of invention, for those of ordinary skill in the art, on the premise of not paying creative work, acceptable
Other accompanying drawings are obtained according to these accompanying drawings.
Fig. 1 is five-electrical level inverter neutral balance control method embodiment one flow chart that the present invention provides；
Fig. 2 is the five level photovoltaic inverting system schematic diagrams that the present invention provides；
Fig. 3 is five-electrical level inverter neutral balance control method embodiment two flow chart that the present invention provides；
Fig. 4 is five-electrical level inverter neutral balance control device embodiment one schematic diagram that the present invention provides；
Fig. 5 is five-electrical level inverter neutral balance control device embodiment two schematic diagram that the present invention provides；
Fig. 6 is five-electrical level inverter neutral balance control device embodiment three schematic diagram that the present invention provides.
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.
Understandable for enabling the above objects, features and advantages of the present invention to become apparent from, 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. 1, this figure is five-electrical level inverter neutral balance control method embodiment one flow chart that the present invention provides.
The five-electrical level inverter neutral balance control method that the present embodiment provides, is applied to five level photovoltaic inverting systems
In, this system schematic may refer to shown in Fig. 2, and five-electrical level inverter therein is three-phase five-level inverter.
This system includes：PV array, the first Boost circuit, the second Boost circuit, five-electrical level inverter；First electric capacity
C1Pos, the second electric capacity C1Neg, the 3rd electric capacity C2Pos and the 4th electric capacity C2Neg；The positive output end of described PV array connects described
+ 1 level input of five-electrical level inverter, -1 level of the negative output terminal described five-electrical level inverter of connection of described PV array is defeated
Enter end, the two ends of described first electric capacity C1Pos connect the positive output end of described PV array and 0 level of five-electrical level inverter respectively
Input, the two ends of described second electric capacity C1Neg connect the negative output terminal of described PV array and 0 electricity of five-electrical level inverter respectively
Flat input；The input of described first Boost circuit connects the positive output end of described PV array, described first Boost circuit
Outfan connect+2 level input of five-electrical level inverter, the input of described second Boost circuit connects described PV battle array
The negative output terminal of row, -2 level input of the outfan connection five-electrical level inverter of described second Boost circuit, the described 3rd
The two ends of electric capacity C2Pos connect the outfan of described first Boost circuit and described 0 level input, described 4th electricity respectively
The two ends holding C2Neg connect the outfan of described second Boost circuit and described 0 level input respectively；The method includes：
S201：Detect -2 electricity on+2 level voltage V2Pos and the 4th electric capacity C2Neg on described 3rd electric capacity C2Pos
Ordinary telegram presses V2Neg；
It is understood that V2Pos and V2Neg is the voltage to negative pole for the positive pole of electric capacity, be all therefore on the occasion of.If two
The neutral-point potential balance of level, then ideally, V2Pos and V2Neg should be equal.
S202：Obtain two level neutral point voltage balances by the difference of described V2Pos and V2Neg through predetermined modulation algorithm to adjust
Result Vout；
The difference of V2Pos and V2Neg can reflect the neutral balance problem of two level.
It should be noted that predetermined adjustment algorithm can adjust algorithm, proportion integral control algorithm and ratio for ratio P
Integral differential PID adjusts any one in algorithm.
S203：The net side three-phase brachium pontis voltage instruction Vx of described inverter is superimposed positive zero sequence side-play amount respectively always obtain
First positive and negative busbar charging current difference I1；The net side three-phase brachium pontis voltage instruction of described inverter is superimposed negative sense zero sequence respectively
Side-play amount obtains the second total positive and negative busbar charging current difference I2；Described forward direction zero sequence side-play amount and negative sense zero sequence side-play amount are in advance
Obtain；Vx is the three-phase brachium pontis voltage instruction before revising；X is a, b and c；
Size according to Vout, I1 and I2 determines side-play amount V1 of superposition, revised three-phase brachium pontis voltage instruction Vx1
For：Vx1=V0+Vx, wherein V0=V1* | Vout |；
Judge Vout>0, and I1>During I2, described V1 chooses described forward migration amount；
Judge Vout>0, and I1<During I2, described V1 chooses described negative offset amount；
Judge Vout<0, and I1>During I2, described V1 chooses described negative offset amount；
Judge Vout<0, and I1<During I2, described V1 chooses described forward migration amount.
The method that the present embodiment provides, by being modified balancing two level midpoints to net side three-phase brachium pontis voltage instruction
Voltage, detects the voltage on the 3rd electric capacity and the 4th electric capacity first respectively, obtains revising side-play amount according to this two voltage differences
Amplitude, is then judged by being superimposed positive zero sequence side-play amount and negative sense zero sequence side-play amount on net side three-phase brachium pontis voltage instruction
The positive still negative sense zero sequence side-play amount of final superposition.By two level can be adjusted to the correction of net side three-phase brachium pontis voltage instruction
Neutral point voltage balance is it is ensured that positive and negative busbar operationally keeps symmetrical, thus eliminating the switching tube causing because of unbalance of neutral-point voltage
The too high risk of voltage stress in course of action.
Embodiment of the method two：
Referring to Fig. 3, this figure is five-electrical level inverter neutral balance control method embodiment two flow chart that the present invention provides.
It should be noted that being positive and negative two level in five-electrical level inverter to be balanced control in embodiment of the method one
Method, in the present embodiment also introduce align negative one level be balanced control method.
In addition, inverter works in and refers to during three level be operated in 0 level and positive and negative two level in the present embodiment.
S301：Detect+1 level voltage V1Pos on described first electric capacity, -1 level voltage V1Neg on the second electric capacity；
S302：By described V1Pos and V1Neg, all it is compared with 1/2nd PV array output voltage instruction, according to
Comparative result controls positive PV busbar voltage and negative PV busbar voltage respectively.
S303-S305 is identical with S101-S103 respectively, will not be described here.
In figure net side inverter needs by five level active pattern switchings in certain special cases to three level active moulds
Formula, i.e. switching tube S2Pos, S2Neg and S0 work output level V2Pos ,-V2Neg and 0.Inverter is described below and is operated in five
For the difference of two level neutral point voltage balances when level mode and three level modes.
When described inverter is operated in five level modes, described I1=Σ IxPos1-ΣIxNeg1, I2=Σ IxPos2-Σ
IxNeg2；Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electricity for three-phase
Stream；
What IxPos1 with IxPos2 characterized is the averaged discharge electricity relative to positive pole line capacitance C2Pos for net side x in a cycle
Stream.Thus Σ IxPos1With Σ IxPos2Characterize is the average discharge current sum to positive bus-bar for the net side three-phase.
The discharge current of the positive pole line capacitance C2Pos that such as IaPos1 is produced by A phase after representing superposition forward migration amount.When
When A phase voltage directive is more than V1Pos, then the switching tube S2Pos that A phase has connection V2Pos in switch periods is open-minded
State, can be obtained by the average discharge current of the corresponding C2Pos of A according to S2Pos service time and A phase current size
IaPos1, calculates B phase and C phase discharge current to C2Pos in a cycle, finally superposition is exactly C2Pos at one in the same manner
In cycle, total average discharge current is produced by net side；If A phase voltage directive VaCmd is less than V1Pos, show switching tube
S2Pos will not open within this cycle, and that is, A phase does not result in C2Pos electric discharge, thus its corresponding C2Pos discharge current is 0.
In the same manner, what negative busbar electric capacity IxNeg1 with IxNeg2 characterized is the average discharge current that net side x is relative to C2Neg, because
And Σ IxNeg1With Σ IxNeg2Characterize is the average discharge current sum to positive bus-bar for the net side three-phase.
What I1 and I2 represented be positive pole line capacitance C2Pos and negative busbar electric capacity C2Neg in switch periods by net side
The average discharge current difference producing；(IbstPos-IbstNeg) it is positive pole line capacitance C2Pos and negative busbar electric capacity C2Neg at one
The mean charging current difference being produced by Boost circuit in switch periods；IbstPosAnd IbstNegBe respectively the first Boost circuit and
Second Boost circuit is input to the electric current of positive and negative busbar；Thus the right of two level mid-point voltage deviations and I1, I2 can be obtained by (7)
Should be related to.In formula (7), y is 1 or 2.
Vx is compared with V1Pos, works as Vx>During V1Pos, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (1)
?；
Wherein, IxFor net side three-phase current；
Work as Vx<During V1Pos, Vx and-V1Neg is compared, works as Vx<When (- V1Neg), described IxPos1、IxPos2With
IxNeg2、IxNeg1Obtained by formula (2)；
Work as Vx<During V1Pos, and Vx>When (- V1Neg), described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (3)；
When described inverter is operated in three level modes, described I1=Σ IxPos1-ΣIxNeg1, I2=Σ IxPos2-Σ
IxNeg2；Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electricity for three-phase
Stream；
Vx is compared with 0, works as Vx>When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (4)；
Wherein, IxFor net side three-phase current；
Work as Vx<When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (5)；
A kind of five-electrical level inverter neutral balance control method being provided based on above example, the embodiment of the present invention also carries
Supply a kind of five-electrical level inverter neutral balance control device, to be explained in detail below in conjunction with the accompanying drawings.
Apparatus embodiments one：
Referring to Fig. 4, this figure is five-electrical level inverter neutral balance control device embodiment one schematic diagram that the present invention provides.
The five-electrical level inverter neutral balance control device that the present embodiment provides, is applied to five level photovoltaic inverting systems
In, system schematic specifically may refer to Fig. 2.This system includes：PV array, the first Boost circuit, the second Boost circuit, five
Electrical level inverter；First electric capacity, the second electric capacity, the 3rd electric capacity and the 4th electric capacity；The positive output end of described PV array connects described
+ 1 level input of five-electrical level inverter, -1 level of the negative output terminal described five-electrical level inverter of connection of described PV array is defeated
Enter end, the two ends of described first electric capacity connect the positive output end of described PV array and 0 level input of five-electrical level inverter respectively
End, the two ends of described second electric capacity connect the negative output terminal of described PV array and 0 level input of five-electrical level inverter respectively；
The input of described first Boost circuit connects the positive output end of described PV array, and the outfan of described first Boost circuit is even
Connect+2 level input of five-electrical level inverter, the input of described second Boost circuit connects the negative output of described PV array
End, the outfan of described second Boost circuit connects -2 level input of five-electrical level inverter, the two ends of described 3rd electric capacity
Connect the outfan of described first Boost circuit and described 0 level input respectively, the two ends of described 4th electric capacity connect respectively
The outfan of described second Boost circuit and described 0 level input；This equipment includes：Positive and negative two level detection module 400,
Positive and negative two level modulation modules 500 and positive and negative two level neutral balance modules 600；
Described positive and negative two level detection module 400, for detecting+2 level voltage V2Pos on described 3rd electric capacity and
- 2 level voltage V2Neg on four electric capacity；
It is understood that V2Pos and V2Neg is the voltage to negative pole for the positive pole of electric capacity, be all therefore on the occasion of.If two
The neutral-point potential balance of level, then ideally, V2Pos and V2Neg should be equal.
Described positive and negative two level modulation modules 500, for the difference by described V2Pos and V2Neg through predetermined adjustment algorithm
Obtain two level neutral point voltage balances and adjust result Vout；
The difference of V2Pos and V2Neg can reflect the neutral balance problem of two level.
It should be noted that predetermined adjustment algorithm can adjust algorithm, proportion integral control algorithm and ratio for ratio P
Integral differential PID adjusts any one in algorithm.
Described positive and negative two level neutral balance modules 600, for by the net side three-phase brachium pontis voltage instruction of described inverter
Vx is superimposed positive zero sequence side-play amount respectively and obtains the first total positive and negative busbar charging current difference I1；Net side three by described inverter
The instruction of phase bridge arm voltage is superimposed negative sense zero sequence side-play amount respectively and obtains the second total positive and negative busbar charging current difference I2；Described forward direction
Zero sequence side-play amount and negative sense zero sequence side-play amount are obtained ahead of time；Vx is the three-phase brachium pontis voltage instruction before revising；X is a, b and c；Root
Size according to Vout, I1 and I2 determines side-play amount V1 of superposition, and revised three-phase brachium pontis voltage instruction Vx1 is：Vx1=V0+
Vx, wherein V0=V1* | Vout |；Judge Vout>0, and I1>During I2, described V1 chooses described forward migration amount；Judge Vout>
0, and I1<During I2, described V1 chooses described negative offset amount；Judge Vout<0, and I1>During I2, described V1 chooses described negative sense
Side-play amount；Judge Vout<0, and I1<During I2, described V1 chooses described forward migration amount.
Vout>0 sign is that C2Pos is more than C2Neg, thus now should select C2Pos and C2Neg discharge current difference I1
The corresponding side-play amount with higher value in I2.
The method that the present embodiment provides, by being modified balancing two level midpoints to net side three-phase brachium pontis voltage instruction
Voltage, detects the voltage on the 3rd electric capacity and the 4th electric capacity first respectively, obtains revising side-play amount according to this two voltage differences
Amplitude, is then judged by being superimposed positive zero sequence side-play amount and negative sense zero sequence side-play amount on net side three-phase brachium pontis voltage instruction
The positive still negative sense zero sequence side-play amount of final superposition.By two level can be adjusted to the correction of net side three-phase brachium pontis voltage instruction
Neutral point voltage balance is it is ensured that positive and negative busbar operationally keeps symmetrical, thus eliminating the switching tube causing because of unbalance of neutral-point voltage
The too high risk of voltage stress in course of action.
Apparatus embodiments two：
Referring to Fig. 5, this figure is five-electrical level inverter neutral balance control device embodiment two schematic diagram that the present invention provides.
In the present embodiment, inverter works in and refers to during three level be operated in 0 level and positive and negative two level.
The five-electrical level inverter neutral balance control device that the present embodiment provides, described positive and negative two level neutral balance modules
Including：First electric current obtains submodule 601；
When described inverter is operated in five level modes, described I1=Σ IxPos1-ΣIxNeg1, I2=Σ IxPos2-Σ
IxNeg2；Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electricity for three-phase
Stream；
Described first electric current obtains submodule 601, for being compared Vx with V1Pos, works as Vx>During V1Pos, described
IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (1)；
Wherein, IxFor net side three-phase current；
Work as Vx<During V1Pos, Vx and-V1Neg is compared, works as Vx<When (- V1Neg), described IxPos1、IxPos2With
IxNeg2、IxNeg1Obtained by formula (2)；
Work as Vx<During V1Pos, and Vx>When (- V1Neg), described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (3)；
Described positive and negative two level neutral balance modules include：Second electric current obtains submodule 602；
When described inverter is operated in three level modes, described I1=Σ IxPos1-ΣIxNeg1, I2=Σ IxPos2-Σ
IxNeg2；Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electricity for three-phase
Stream；
Described second electric current obtains submodule 602, for being compared Vx with 0, works as Vx>When 0, described IxPos1、IxPos2
And IxNeg2、IxNeg1Obtained by formula (4)；
Wherein, IxFor net side three-phase current；
Work as Vx<When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (5)；
Apparatus embodiments three：
Referring to Fig. 6, this figure is apparatus embodiments three schematic diagram that the present invention provides.
The present embodiment is introduced, and when inverter is operated in five level, balances positive negative one level mid-point voltage.
When inverter is operated in five level, also include：Positive negative one level detection module 700 and positive negative one level modulation mould
Block 800；
Described positive negative one level detection module 700, for detect+1 level voltage V1Pos on described first electric capacity,
- 1 level voltage V1Neg on two electric capacity；
Described positive negative one level modulation module 800, for by described V1Pos and V1Neg, the PV array all with 1/2nd
Output voltage instruction is compared, and controls positive PV busbar voltage and negative PV busbar voltage respectively according to comparative result.
The above, be only presently preferred embodiments of the present invention, and not the present invention is made with any pro forma restriction.Though
So the present invention is disclosed above with preferred embodiment, but is not limited to the present invention.Any it is familiar with those skilled in the art
Member, without departing under technical solution of the present invention ambit, can be utilized the methods and techniques content of the disclosure above to the present invention
Technical scheme makes many possible variations and modification, or the Equivalent embodiments being revised as equivalent variations.Therefore, every without departing from
The content of technical solution of the present invention, according to the present invention technical spirit to any simple modification made for any of the above embodiments, equivalent
Change and modification, all still fall within the range of technical solution of the present invention protection.
Claims (10)
1. a kind of five-electrical level inverter neutral balance control method is it is characterised in that be applied in five level photovoltaic inverting systems,
This system includes：PV array, the first Boost circuit, the second Boost circuit, five-electrical level inverter；First electric capacity, the second electric capacity,
3rd electric capacity and the 4th electric capacity；The positive output end of described PV array connects+1 level input of described five-electrical level inverter, institute
The negative output terminal stating PV array connects -1 level input of described five-electrical level inverter, and the two ends of described first electric capacity connect respectively
Connect the positive output end of described PV array and 0 level input of five-electrical level inverter, the two ends of described second electric capacity connect respectively
The negative output terminal of described PV array and 0 level input of five-electrical level inverter；The input of described first Boost circuit connects
The positive output end of described PV array, the outfan of described first Boost circuit connects+2 level input of five-electrical level inverter,
The input of described second Boost circuit connects the negative output terminal of described PV array, and the outfan of described second Boost circuit is even
Connect -2 level input of five-electrical level inverter, the two ends of described 3rd electric capacity connect the defeated of described first Boost circuit respectively
Go out end and described 0 level input, the two ends of described 4th electric capacity connect outfan and the institute of described second Boost circuit respectively
State 0 level input；The method includes：
Detect -2 level voltage V2Neg on+2 level voltage V2Pos and the 4th electric capacity on described 3rd electric capacity；
Two level neutral point voltage balances are obtained through predetermined adjustment algorithm by the difference of described V2Pos and V2Neg and adjusts result Vout；
The net side three-phase brachium pontis voltage instruction Vx of described inverter is superimposed positive zero sequence side-play amount respectively and just obtains total first
Negative busbar charging current difference I1；The net side three-phase brachium pontis voltage instruction of described inverter is superimposed negative sense zero sequence side-play amount respectively obtain
Obtain the second positive and negative busbar charging current difference I2 always；Described forward direction zero sequence side-play amount and negative sense zero sequence side-play amount are obtained ahead of time；Vx
For the three-phase brachium pontis voltage instruction before revising；X is a, b and c；
Size according to Vout, I1 and I2 determines side-play amount V1 of superposition, and revised three-phase brachium pontis voltage instruction Vx1 is：Vx1
=V0+Vx, wherein V0=V1* | Vout |；
Judge Vout>0, and I1>During I2, described V1 chooses described forward migration amount；
Judge Vout>0, and I1<During I2, described V1 chooses described negative offset amount；
Judge Vout<0, and I1>During I2, described V1 chooses described negative offset amount；
Judge Vout<0, and I1<During I2, described V1 chooses described forward migration amount.
2. five-electrical level inverter neutral balance control method according to claim 1 is it is characterised in that work as described inverter
When being operated in five level modes, described I1=∑ IxPos1-∑IxNeg1, I2=∑ IxPos2-∑IxNeg2；Wherein, x is a, b and c；
IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electric current for three-phase；
Vx is compared with V1Pos, works as Vx>During V1Pos, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (1)；
Described V1Pos is+1 level voltage on the first electric capacity；
Wherein, IxFor net side three-phase current；
Work as Vx<During V1Pos, Vx and-V1Neg is compared, works as Vx<During-V1Neg, described IxPos1、IxPos2And IxNeg2、IxNeg1
Obtained by formula (2)；Described V1Neg is -1 level voltage on the second electric capacity；
Work as Vx<During V1Pos, and Vx>During-V1Neg, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (3)；
3. five-electrical level inverter neutral balance control method according to claim 1 is it is characterised in that work as described inverter
When being operated in three level modes, described I1=∑ IxPos1-∑IxNeg1, I2=∑ IxPos2-∑IxNeg2；Wherein, x is a, b and c；
IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electric current for three-phase；
Vx is compared with 0, works as Vx>When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (4)；
Wherein, IxFor net side three-phase current；
Work as Vx<When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (5)；
4. five-electrical level inverter neutral balance control method according to claim 2 is it is characterised in that also include：Detection
- 1 level voltage V1Neg on+1 level voltage V1Pos on described first electric capacity, the second electric capacity；By described V1Pos and
V1Neg is all compared with 1/2nd PV array output voltage instruction, controls positive PV bus electricity respectively according to comparative result
Pressure and negative PV busbar voltage.
5. five-electrical level inverter neutral balance control method according to claim 1 is it is characterised in that described predetermined adjustment
Algorithm is following any one：Proportion adjustment algorithm, proportional integral adjust algorithm and PID adjusts algorithm.
6. a kind of five-electrical level inverter neutral balance control device is it is characterised in that be applied in five level photovoltaic inverting systems,
This system includes：PV array, the first Boost circuit, the second Boost circuit, five-electrical level inverter；First electric capacity, the second electric capacity,
3rd electric capacity and the 4th electric capacity；The positive output end of described PV array connects+1 level input of described five-electrical level inverter, institute
The negative output terminal stating PV array connects -1 level input of described five-electrical level inverter, and the two ends of described first electric capacity connect respectively
Connect the positive output end of described PV array and 0 level input of five-electrical level inverter, the two ends of described second electric capacity connect respectively
The negative output terminal of described PV array and 0 level input of five-electrical level inverter；The input of described first Boost circuit connects
The positive output end of described PV array, the outfan of described first Boost circuit connects+2 level input of five-electrical level inverter,
The input of described second Boost circuit connects the negative output terminal of described PV array, and the outfan of described second Boost circuit is even
Connect -2 level input of five-electrical level inverter, the two ends of described 3rd electric capacity connect the defeated of described first Boost circuit respectively
Go out end and described 0 level input, the two ends of described 4th electric capacity connect outfan and the institute of described second Boost circuit respectively
State 0 level input；This equipment includes：In positive and negative two level detection module, positive and negative two level modulation modules and positive and negative two level
Point balance module；
Described positive and negative two level detection module, for detecting+2 level voltage V2Pos and the 4th electric capacity on described 3rd electric capacity
On -2 level voltage V2Neg；
Described positive and negative two level modulation modules, for obtaining two electricity by the difference of described V2Pos and V2Neg through predetermined adjustment algorithm
Flat neutral point voltage balance adjusts result Vout；
Described positive and negative two level neutral balance modules, for folding the net side three-phase brachium pontis voltage instruction Vx of described inverter respectively
Plus forward direction zero sequence side-play amount obtains the first total positive and negative busbar charging current difference I1；Net side three-phase brachium pontis electricity by described inverter
Pressure instruction is superimposed negative sense zero sequence side-play amount respectively and obtains the second total positive and negative busbar charging current difference I2；Described forward direction zero sequence skew
Amount and negative sense zero sequence side-play amount are obtained ahead of time；Vx is the three-phase brachium pontis voltage instruction before revising；X is a, b and c；According to Vout, I1
Determine side-play amount V1 of superposition with the size of I2, revised three-phase brachium pontis voltage instruction Vx1 is：Vx1=V0+Vx, wherein V0
=V1* | Vout |；Judge Vout>0, and I1>During I2, described V1 chooses described forward migration amount；Judge Vout>0, and I1<I2
When, described V1 chooses described negative offset amount；Judge Vout<0, and I1>During I2, described V1 chooses described negative offset amount；Sentence
Disconnected Vout<0, and I1<During I2, described V1 chooses described forward migration amount.
7. five-electrical level inverter neutral balance control device according to claim 6 is it is characterised in that described positive and negative two is electric
Flat neutral balance module includes：First electric current obtains submodule；
When described inverter is operated in five level modes, described I1=∑ IxPos1-∑IxNeg1, I2=∑ IxPos2-∑IxNeg2；
Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electric current for three-phase；
Described first electric current obtains submodule, for being compared Vx with V1Pos, works as Vx>During V1Pos, described IxPos1、IxPos2
And IxNeg2、IxNeg1Obtained by formula (1)；Described V1Pos is+1 level voltage on the first electric capacity；
Wherein, IxFor net side three-phase current；
Work as Vx<During V1Pos, Vx and-V1Neg is compared, works as Vx<During-V1Neg, described IxPos1、IxPos2And IxNeg2、IxNeg1
Obtained by formula (2)；Described V1Neg is -1 level voltage on the second electric capacity；
Work as Vx<During V1Pos, and Vx>During-V1Neg, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (3)；
8. five-electrical level inverter neutral balance control device according to claim 6 is it is characterised in that described positive and negative two is electric
Flat neutral balance module includes：Second electric current obtains submodule；
When described inverter is operated in three level modes, described I1=∑ IxPos1-∑IxNeg1, I2=∑ IxPos2-∑IxNeg2；
Wherein, x is a, b and c；IxPos1、IxPos2For the positive pole line current of three-phase, IxNeg2、IxNeg1Negative busbar electric current for three-phase；
Described second electric current obtains submodule, for being compared Vx with 0, works as Vx>When 0, described IxPos1、IxPos2And IxNeg2、
IxNeg1Obtained by formula (4)；
Wherein, IxFor net side three-phase current；
Work as Vx<When 0, described IxPos1、IxPos2And IxNeg2、IxNeg1Obtained by formula (5)；
9. five-electrical level inverter neutral balance control device according to claim 7 is it is characterised in that also include：Positive and negative
One level detection module and positive negative one level modulation module；
Described positive negative one level detection module, for detecting+1 level voltage V1Pos on described first electric capacity, the second electric capacity
- 1 level voltage V1Neg；
Described positive negative one level modulation module, for the PV array output voltage all with 1/2nd by described V1Pos and V1Neg
Instruction is compared, and controls positive PV busbar voltage and negative PV busbar voltage respectively according to comparative result.
10. five-electrical level inverter neutral balance control device according to claim 9 is it is characterised in that described pre- set the tone
Section algorithm is following any one：Proportion adjustment algorithm, proportional integral adjust algorithm and PID adjusts algorithm.
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