CN107888101A - A kind of grid-connected NPC three-level inverters modulator approach - Google Patents

A kind of grid-connected NPC three-level inverters modulator approach Download PDF

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CN107888101A
CN107888101A CN201711222802.7A CN201711222802A CN107888101A CN 107888101 A CN107888101 A CN 107888101A CN 201711222802 A CN201711222802 A CN 201711222802A CN 107888101 A CN107888101 A CN 107888101A
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msub
mtd
mtr
mtable
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刘丽娟
杨俊�
董开松
沈渭程
赵炜
张光儒
甄文喜
魏博
同焕珍
闵占奎
刘秀良
李志敏
张赛
朱宏毅
马喜平
姜梅
王斌
杨勇
胡殿刚
李韶瑜
陈明忠
梁有珍
陈柏旭
李炜
李小娟
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State Grid Corp of China SGCC
State Grid Gansu Electric Power Co Ltd
Electric Power Research Institute of State Grid Gansu Electric Power Co Ltd
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State Grid Corp of China SGCC
State Grid Gansu Electric Power Co Ltd
Electric Power Research Institute of State Grid Gansu Electric Power Co Ltd
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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
    • H02J3/383—
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H02M7/53873—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with digital control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H02M7/53875—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output
    • H02M7/53876—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output based on synthesising a desired voltage vector via the selection of appropriate fundamental voltage vectors, and corresponding dwelling times
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The present invention discloses a kind of grid-connected NPC three-level inverters modulator approach, research object is used as using diode-clamped three-level photovoltaic inverter, it is deployed to study using the SVPWM algorithms under 60 ° of coordinate systems, emulation and experimental result show that the correctness of theory and the superperformance of inverter, the application to three-level photovoltaic inverter have reference value.

Description

A kind of grid-connected NPC three-level inverters modulator approach
Technical field
The invention belongs to electricity field, and in particular to a kind of grid-connected NPC three-level inverters modulator approach.
Background technology
With the increasingly depleted of traditional energy reserves, energy field is studied since exploring and tapping a new source of energy as 21 century Focus.Solar energy determines its status for not replacing in energy replacement because of its unique advantage.As a kind of environment friend Good new-generation mode, photovoltaic generation is paid attention to by national governments and business organization favors, grid-connected technology also general As the principal mode of following solar energy development.In grid-connected photovoltaic system, inverter is one of key link, has and connects Connect the function of photovoltaic battery array and power network.The quality of inverter performance directly influences the stability of photovoltaic system, high efficiency And the service life of whole system.According to inverter output voltage form, two level and more level can be divided into.With traditional two Electrical level inverter compares, and multi-electrical level inverter has advantages below：(1) in the case of switching device quantity identical, output Voltage level state increases；(2) output voltage interconversion rate du/dt is reduced, and switching loss reduces；(3) in same switching frequency Under, the harmonic content of output waveform is less.Inverter level number is more, and output waveform and sine wave are closer, but circuit structure More complicated, cost is higher, more unmanageable.Thus in high voltage, large-power occasions, still based on three-level inverter.
The content of the invention
In view of the shortcomings of the prior art, the present invention discloses a kind of grid-connected NPC three-level inverters modulator approach, including Following steps：
S1 selects main circuit of the NPC three-level inverters as combining inverter；Wherein, if DC bus-bar voltage is UDC, By taking A phase bridge arms as an example, as switching tube S1、S2During conducting, A phases output voltage is+UDC/2；As switching tube S2、S3During conducting, A phases Output voltage is 0；As switching tube S3、S4During conducting, A phases output voltage is-UDC/2；Therefore, each phase has three kinds effectively to open Off status, positive level (P), zero point put down (O), negative level (N)；Three combined share 33=27 kinds of on off states；If with SA、SB、SCTo define the on off state of each phase, each phase voltage is represented by：
Wherein,
S2 establishes three level fundamental space vectors；Being marked with quasi- three phase sine voltage transient value expression is：
In order to facilitate analyzing and calculating, three-phase static coordinate system ABC is transformed under two-phase rest frame α β；A is allowed to sit Parameter and α coordinate overlapping of axles, according to Clark transformation for mula：
Obtain synthesized reference voltage vector：
Wherein, ρ is complex coefficient, referred to as twiddle factor, ρ=ej2π/3；
If with the section SA、SB、SCThe on off state of each phase is represented, then fundamental space voltage vector redefinable For：
Wherein, K is basic vector number；It is hereby achieved that fundamental voltage space vector distribution map,
S3 establishes 60 ° of coordinate systems and judges reference vector present position by SVPWM modulation algorithms；Basic vector is calculated to make With the distribution of time and time state；
With 60 ° for a sector, the space vector of voltage of three level can be divided into 6 big regions, it is possible thereby to establish non- 60 ° of orthogonal coordinate systems, are designated as g~h coordinate systems；SVPWM algorithms under 60 ° of coordinate systems realize that step is calculated with traditional SVPWM Method is consistent；
When α axles and g overlapping of axles, 60 ° of rotate counterclockwise is h axles, if UrefCoordinate under α~β coordinate systems is (uα, uβ), the coordinate under g~h coordinate systems is (ug,uh), then the transformation relation of two kinds of coordinate systems is：
With the length U of small vectorDC/ 3 be unit length, then can be by reference vector UrefCoordinate under g~h coordinate systems Being simplified, the coordinate after simplifying is set to (g, h), wherein
S4 carries out simulation analysis；
Further, the calculating basic vector action time method described in step S3 is：
If reference vector is located at the N zonules of the big sectors of N, in unit interval T, basic vector u0Action time For T0, u1Action time be T1, u2Action time be T2, obtain：
The expression of basic vector is substituted into (8) formula to solve：
Further, the distribution of step S3 time states, wherein taking centrosymmetric seven segmentations modulation principle, allow basic Vector keeps symmetrical in each controlling cycle.
The invention has the advantages that using diode-clamped three-level photovoltaic inverter as research object, using 60 ° of coordinates The lower SVPWM algorithms of system deploy to study to it, and emulation and experimental result show the good of theoretical correctness and inverter Performance, the application to three-level photovoltaic inverter have reference value.
Brief description of the drawings
Fig. 1 NPC three-level inverter topology structure charts
Fig. 2 ABC coordinate systems are to α β coordinate system transformation figures
The level SVPWM space vector of voltage of Fig. 3 tri- is distributed
Fig. 4 α~β coordinate systems and g~h coordinate system figures
3 level space vector figure under 60 ° of coordinate systems of Fig. 5
The segmentation SVPWM waveforms of Fig. 6 seven
Fig. 7 three-level photovoltaic inverter system simulation models
Fig. 8 A phase voltage waveforms
Fig. 9 A phase voltage waveform enlarged drawings
Figure 10 AB line voltage oscillograms
Figure 11 AB line voltage waveform enlarged drawings
Figure 12 current waveform figures
The level photovoltaic inverting system structure charts of Figure 13 tri-
Figure 14 phase voltage waveforms
Figure 15 phase voltage waveform enlarged drawings
Figure 16 line voltage waveforms
Figure 17 line voltage waveform enlarged drawings
Embodiment
1NPC three-level inverter topology structures
The present invention selects main circuit of the NPC three-level inverters as combining inverter, and topological structure is as shown in Figure 1.
D in figure1~D2For anti-paralleled diode, S1~S12For switching device IGBT, O is capacitor C1、C2Midpoint, DZ1 ~DZ6For clamp diode (effect is to provide current channel when switching tube turns on to prevent capacitance short-circuit).If DC bus-bar voltage For UDC, by taking A phase bridge arms as an example, as switching tube S1、S2During conducting, A phases output voltage is+UDC/2；As switching tube S2、S3During conducting, A phases output voltage is 0；As switching tube S3、S4During conducting, A phases output voltage is-UDC/2.Therefore, each phase has three kinds effectively On off state, positive level (P), zero point put down (O), negative level (N).Three combined share 33=27 kinds of on off states.If Use SA、SB、SCTo define the on off state of each phase, each phase voltage is represented by：
Wherein,
2SVPWM modulation algorithms
In numerous PWM modulation technologies, space voltage vector (SVPWM) modulation algorithm is due to DC voltage utilization rate Height, control is simple, is easy to the advantages that Digital Realization, more and more be applied.SVPWM is three-phase while modulates, with inverse Become the basic vector that device difference on off state is formed to go to approach the reference vector of synthesis, so that it is determined that switching tube in inverter State, form PWM ripples.
2.1 3 level fundamental space vectors
Being marked with quasi- three phase sine voltage transient value expression is：
In order to facilitate analyzing and calculating, generally three-phase static coordinate system ABC is transformed under two-phase rest frame α β.Allow A reference axis and α coordinate overlapping of axles, vector median filters figure are as shown in Figure 2.
According to Clark transformation for mula：
Obtain synthesized reference voltage vector：
Wherein, ρ is complex coefficient, referred to as twiddle factor, ρ=ej2π/3。
If with the section SA、SB、SCThe on off state of each phase is represented, then fundamental space voltage vector redefinable For：
Wherein, K is basic vector number.It is hereby achieved that fundamental voltage space vector distribution map, as shown in Figure 3.
27 basic vectors in Fig. 3 are sorted out according to size：Long vector 6, size 2UDC/3；Middle vector 6, Size isSmall vector 12, size UDC/3；Zero vector 3.What small vector always occurred in pairs, it is mutually redundant arrow Amount.
To obtain circular rotating magnetic linkage, it is necessary to voltage basic vector is tracked the track of space vector in time.Therefore one In individual controlling cycle, it is thus necessary to determine that basic vector.Generally speaking, the realization of three level SVPWM control algolithms is divided into three steps：
(1) reference vector present position is judged；
(2) three basic vector action times are calculated；
(3) distribution of switching tube action time, that is, the control to power switch pipe is completed.
SVPWM modulation algorithms under 2.2 60 ° of coordinate systems
As seen from Figure 3, if with 60 ° for a sector, the space vector of voltage of three level can be divided into 6 Ge great areas Domain, it is possible thereby to establish non-orthogonal 60 ° of coordinate systems, it is designated as g~h coordinate systems.SVPWM algorithms under 60 ° of coordinate systems realize step Suddenly it is consistent with traditional SVPWM algorithms.
When α axles and g overlapping of axles, 60 ° of rotate counterclockwise is h axles, and the position of α~β coordinate systems and g~h coordinate systems is closed System is as shown in Figure 4.If set UrefCoordinate under α~β coordinate systems is (uα,uβ), the coordinate under g~h coordinate systems is (ug, uh), then the transformation relation of two kinds of coordinate systems is：
If with the length U of small vectorDC/ 3 be unit length, then can be by reference vector UrefSeat under g~h coordinate systems Mark is simplified, and the coordinate after simplifying is set to (g, h), whereinFig. 5 is three level under 60 ° of coordinate systems Three dimensional vector diagram.
2.2.1 judge reference vector present position
As shown in figure 5, for 3 level space vector, separate every 60 ° for a big sector, each big sector is divided again For 4 zonules.Therefore judge to determine by reference to the angle of vector and g axles for big sector；For cell The judgment principle in domain, it can be determined by the linear equation of each vector vertex coordinate formation under g~h coordinate systems, it judges Rule such as table 1, wherein being laterally big sector, longitudinal direction is small sector：
1 60 ° of coordinate system sector judgment rules of table
2.2.2 calculate basic vector action time
When it is determined that behind reference vector present position, then three basic vectors for participating in synthesized reference vector also determine that , and then need to calculate the action time of basic vector.According to voltage-second balance principle, it is assumed that reference vector is located at the first big sector First community domain, in unit interval T, basic vector u0Action time be T0, u1Action time be T1, u2Effect when Between be T2, can be obtained according to voltage-second balance principle：
The expression of basic vector is substituted into (8) formula to solve：
Complicated functional operation is not present in the action time that can be seen that basic vector by (9) formula, and this is under 60 ° of coordinate systems One remarkable advantage of SVPWM algorithms.
Similarly, when can solve proper reference vector and being in other zonules, the action time of basic vector, as shown in table 2：
The basic vector action time of table 2 calculates
2.2.3 the distribution of time state
According to analysis of the prosthomere to tri-level inversion main circuit, N-state is directly jumped to by P-state, it is necessary to two switches Pipe acts, and not only increases the switching frequency of switching tube, and may cause the phase bridge arm direct pass so that switching tube damages.Cause This has to pass through intermediate state O.In order to facilitate controlling and reducing the harmonic content in output voltage, basic vector is generally allowed Keep symmetrical in each controlling cycle, thus take centrosymmetric seven segmentations modulation principle.Assuming that reference vector position In the first big sector, the 3rd zonule, then the action time of basic vector and the corresponding relation of on off state, as shown in Figure 6.
3 simulation analysis
On the basis of theoretical research, the three-level photovoltaic inverter based on MATLAB/Simulink emulation platform buildings Simulation model[7], as shown in Figure 7.Wherein three level DC side voltage is arranged to 720V, frequency 50Hz, SVPWM control Cycle is arranged to 6.2e-5S simulation times are arranged to 2s.
Fig. 8 is A phase voltage simulation waveforms, and Fig. 9 is its waveform amplification figure, it can be seen that it exports three kinds of voltages, It is 360V, 0V, -360V respectively.Figure 10 is AB line voltage simulation waveforms, and Figure 11 is its waveform amplification, it can be seen that its is defeated It is five level staircase waveforms to go out waveform, and closer to sine wave, its output amplitude is DC voltage.Figure 12 is its three-phase current ripple Shape, it can be seen that the sinusoidal waveform for standard.
4 experimental verifications
On the basis of foregoing theoretical research and simulation analysis, the experiment for having built small-power three-level photovoltaic inverter is put down Platform.Figure 13 is the structure chart of the level photovoltaic inverting system of small-power three, mainly includes three level photovoltaic inversion main circuits, driving Circuit, voltage detecting circuit and current detection circuit.
Figure 14 is the inverter outlet side phase voltage waveform drawn in experiment；Figure 15 is phase voltage waveform enlarged drawing.With it is imitative True waveform is compared analysis and understands that experimental waveform and simulation waveform are very identical, and this also demonstrates the effective of SVPWM algorithms Property.
Figure 16 is three-level inverter outlet side line voltage waveform, and Figure 17 is line voltage waveform enlarged drawing.Can be with from figure Find out that experimental waveform and simulation waveform are close, show the correctness of theory and the superperformance of inverter.Can from figure Line voltage waveform is five level staircase waveforms, is compared with two-level inverter, it has the sine of height, waveform and sine wave It is more close, the advantages of this also fully demonstrates three level, show the correctness of theory.
Although an embodiment of the present invention has been shown and described, for the ordinary skill in the art, can be with A variety of changes, modification can be carried out to these embodiments, replace without departing from the principles and spirit of the present invention by understanding And modification, the scope of the present invention is defined by the appended.

Claims (3)

1. a kind of grid-connected NPC three-level inverters modulator approach, it is characterised in that comprise the following steps：
S1 selects main circuit of the NPC three-level inverters as combining inverter；Wherein, if DC bus-bar voltage is UDC, with A phases Exemplified by bridge arm, as switching tube S1、S2During conducting, A phases output voltage is+UDC/2；As switching tube S2、S3During conducting, A phases export electricity Press as 0；As switching tube S3、S4During conducting, A phases output voltage is-UDC/2；Therefore, each phase has three kinds of effective on off states, Positive level (P), zero point put down (O), negative level (N)；Three combined share 33=27 kinds of on off states；If use SA、SB、SC To define the on off state of each phase, each phase voltage is represented by：
<mrow> <mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>U</mi> <mi>A</mi> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <msub> <mi>U</mi> <mrow> <mi>D</mi> <mi>C</mi> </mrow> </msub> <mi>S</mi> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>U</mi> <mi>B</mi> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <msub> <mi>U</mi> <mrow> <mi>D</mi> <mi>C</mi> </mrow> </msub> <mi>S</mi> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>U</mi> <mi>C</mi> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <msub> <mi>U</mi> <mrow> <mi>D</mi> <mi>C</mi> </mrow> </msub> <mi>S</mi> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow>
Wherein,
S2 establishes three level fundamental space vectors；Being marked with quasi- three phase sine voltage transient value expression is：
<mrow> <mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>u</mi> <mi>A</mi> </msub> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>U</mi> <mi>d</mi> </msub> <mi>c</mi> <mi>o</mi> <mi>s</mi> <mrow> <mo>(</mo> <mi>&amp;omega;</mi> <mi>t</mi> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>u</mi> <mi>B</mi> </msub> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>U</mi> <mi>d</mi> </msub> <mi>cos</mi> <mrow> <mo>(</mo> <mi>&amp;omega;</mi> <mi>t</mi> <mo>-</mo> <mn>2</mn> <mi>&amp;pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>u</mi> <mi>C</mi> </msub> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>U</mi> <mi>d</mi> </msub> <mi>c</mi> <mi>o</mi> <mi>s</mi> <mrow> <mo>(</mo> <mi>&amp;omega;</mi> <mi>t</mi> <mo>+</mo> <mn>2</mn> <mi>&amp;pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow>
In order to facilitate analyzing and calculating, three-phase static coordinate system ABC is transformed under two-phase rest frame α β；Allow A reference axis With α coordinate overlapping of axles, according to Clark transformation for mula：
<mrow> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>u</mi> <mi>&amp;alpha;</mi> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>u</mi> <mi>&amp;beta;</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mfrac> <mn>2</mn> <mn>3</mn> </mfrac> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mn>1</mn> </mtd> <mtd> <mrow> <mo>-</mo> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </mtd> <mtd> <mrow> <mo>-</mo> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mrow> <msqrt> <mn>3</mn> </msqrt> <mo>/</mo> <mn>2</mn> </mrow> </mtd> <mtd> <mrow> <mo>-</mo> <msqrt> <mn>3</mn> </msqrt> <mo>/</mo> <mn>2</mn> </mrow> </mtd> </mtr> </mtable> </mfenced> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>u</mi> <mi>A</mi> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>u</mi> <mi>B</mi> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>u</mi> <mi>C</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow>
Obtain synthesized reference voltage vector：
<mrow> <msub> <mi>U</mi> <mrow> <mi>r</mi> <mi>e</mi> <mi>f</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>2</mn> <mn>3</mn> </mfrac> <mo>&amp;lsqb;</mo> <msub> <mi>u</mi> <mi>A</mi> </msub> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>&amp;rho;u</mi> <mi>B</mi> </msub> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>+</mo> <msup> <mi>&amp;rho;</mi> <mn>2</mn> </msup> <msub> <mi>u</mi> <mi>C</mi> </msub> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>&amp;rsqb;</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow>
Wherein, ρ is complex coefficient, referred to as twiddle factor, ρ=ej2π/3；
If with the section SA、SB、SCThe on off state of each phase is represented, then fundamental space voltage vector redefinable is：
<mrow> <mtable> <mtr> <mtd> <mrow> <msub> <mi>u</mi> <mi>K</mi> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mn>3</mn> </mfrac> <msub> <mi>U</mi> <mrow> <mi>D</mi> <mi>C</mi> </mrow> </msub> <mrow> <mo>(</mo> <msub> <mi>S</mi> <mi>A</mi> </msub> <mo>+</mo> <msub> <mi>&amp;rho;S</mi> <mi>B</mi> </msub> <mo>+</mo> <msup> <mi>&amp;rho;</mi> <mn>2</mn> </msup> <msub> <mi>S</mi> <mi>C</mi> </msub> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>6</mn> </mfrac> <msub> <mi>U</mi> <mrow> <mi>D</mi> <mi>C</mi> </mrow> </msub> <mo>&amp;lsqb;</mo> <mrow> <mo>(</mo> <mn>2</mn> <msub> <mi>S</mi> <mi>A</mi> </msub> <mo>-</mo> <msub> <mi>S</mi> <mi>B</mi> </msub> <mo>-</mo> <msub> <mi>S</mi> <mi>C</mi> </msub> <mo>)</mo> </mrow> <mo>+</mo> <mi>j</mi> <msqrt> <mn>3</mn> </msqrt> <mrow> <mo>(</mo> <msub> <mi>S</mi> <mi>B</mi> </msub> <mo>-</mo> <msub> <mi>S</mi> <mi>C</mi> </msub> <mo>)</mo> </mrow> <mo>&amp;rsqb;</mo> </mrow> </mtd> </mtr> </mtable> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow>
Wherein, K is basic vector number；It is hereby achieved that fundamental voltage space vector distribution map,
S3 establishes 60 ° of coordinate systems and judges reference vector present position by SVPWM modulation algorithms；When calculating basic vector effect Between and time state distribution；
With 60 ° for a sector, the space vector of voltage of three level can be divided into 6 big regions, it is possible thereby to establish nonopiate 60 ° of coordinate systems, be designated as g~h coordinate systems；SVPWM algorithms under 60 ° of coordinate systems realize step and traditional SVPWM algorithms one Cause；
When α axles and g overlapping of axles, 60 ° of rotate counterclockwise is h axles, if UrefCoordinate under α~β coordinate systems is (uα,uβ), Coordinate under g~h coordinate systems is (ug,uh), then the transformation relation of two kinds of coordinate systems is：
<mrow> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>u</mi> <mi>g</mi> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>u</mi> <mi>h</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mn>1</mn> </mtd> <mtd> <mrow> <mo>-</mo> <mfrac> <mn>1</mn> <msqrt> <mn>3</mn> </msqrt> </mfrac> </mrow> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mfrac> <mn>2</mn> <msqrt> <mn>3</mn> </msqrt> </mfrac> </mtd> </mtr> </mtable> </mfenced> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>u</mi> <mi>&amp;alpha;</mi> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>u</mi> <mi>&amp;beta;</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <msqrt> <mfrac> <mn>2</mn> <mn>3</mn> </mfrac> </msqrt> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mn>1</mn> </mtd> <mtd> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>1</mn> </mtd> <mtd> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mtd> </mtr> </mtable> </mfenced> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>u</mi> <mi>A</mi> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>u</mi> <mi>B</mi> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>u</mi> <mi>C</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>7</mn> <mo>)</mo> </mrow> </mrow>
With the length U of small vectorDC/ 3 be unit length, then can be by reference vector UrefCoordinate under g~h coordinate systems is carried out Simplifying, the coordinate after simplifying is set to (g, h), wherein
S4 carries out simulation analysis.
A kind of 2. grid-connected NPC three-level inverters modulator approach according to claim 1, it is characterised in that step Calculating basic vector action time method described in S3 is：
If reference vector is located at the N zonules of the big sectors of N, in unit interval T, basic vector u0Action time be T0, u1Action time be T1, u2Action time be T2, obtain：
<mrow> <mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>u</mi> <mn>0</mn> </msub> <msub> <mi>T</mi> <mn>0</mn> </msub> <mo>+</mo> <msub> <mi>u</mi> <mn>1</mn> </msub> <msub> <mi>T</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>u</mi> <mn>2</mn> </msub> <msub> <mi>T</mi> <mn>2</mn> </msub> <mo>=</mo> <msub> <mi>U</mi> <mrow> <mi>r</mi> <mi>e</mi> <mi>f</mi> </mrow> </msub> <mi>T</mi> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>T</mi> <mn>0</mn> </msub> <mo>+</mo> <msub> <mi>T</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>T</mi> <mn>2</mn> </msub> <mo>=</mo> <mi>T</mi> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>8</mn> <mo>)</mo> </mrow> </mrow>
The expression of basic vector is substituted into (8) formula to solve：
<mrow> <mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>T</mi> <mn>0</mn> </msub> <mo>=</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mi>g</mi> <mo>-</mo> <mi>h</mi> <mo>)</mo> </mrow> <mo>&amp;times;</mo> <mi>T</mi> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>T</mi> <mn>1</mn> </msub> <mo>=</mo> <mi>g</mi> <mo>&amp;times;</mo> <mi>T</mi> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>T</mi> <mn>2</mn> </msub> <mo>=</mo> <mi>h</mi> <mo>&amp;times;</mo> <mi>T</mi> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>9</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow>
A kind of 3. grid-connected NPC three-level inverters modulator approach according to claim 1, it is characterised in that step The distribution of S3 time states, wherein taking centrosymmetric seven segmentations modulation principle, basic vector is allowed in each controlling cycle It is middle to keep symmetrical.
CN201711222802.7A 2017-11-29 2017-11-29 A kind of grid-connected NPC three-level inverters modulator approach Pending CN107888101A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109713724A (en) * 2019-02-21 2019-05-03 哈尔滨工业大学 The zero common-mode voltage space vector modulating method of parallel connection three-level converter suitable for grid-connected application
CN111327221A (en) * 2018-12-13 2020-06-23 先控捷联电气股份有限公司 Inverter space vector pulse width modulation method and device
CN112653345A (en) * 2020-11-30 2021-04-13 哈尔滨理工大学 NPC three-level inverter design method based on improved SVPWM algorithm

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111327221A (en) * 2018-12-13 2020-06-23 先控捷联电气股份有限公司 Inverter space vector pulse width modulation method and device
CN109713724A (en) * 2019-02-21 2019-05-03 哈尔滨工业大学 The zero common-mode voltage space vector modulating method of parallel connection three-level converter suitable for grid-connected application
CN109713724B (en) * 2019-02-21 2022-06-07 哈尔滨工业大学 Zero common-mode voltage space vector modulation method suitable for parallel three-level converter in photovoltaic grid-connected application
CN112653345A (en) * 2020-11-30 2021-04-13 哈尔滨理工大学 NPC three-level inverter design method based on improved SVPWM algorithm

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