CN103929082A - Single-phase three-level inverter signal modulation method based on wavelet modulation - Google Patents

Abstract

The invention relates to the field of single-phase three-level inverter signal modulation, in particular to a single-phase three-level inverter signal modulation method based on wavelet modulation. The problems that a traditional single-phase three-level inverter signal modulation method is small in output voltage fundamental amplitude, large in harmonic distortion rate, high in power tube switching frequency and complex in control method are solved. The signal modulation method comprises the following steps that firstly, a linear non-binary synthetic wavelet scaling function is obtained according to a Hall scaling function; secondly, power switch drive pulses of a single-phase three-level inverter are obtained according to the linear non-binary synthetic wavelet scaling function; thirdly, a power switch is driven to move according to the power switch drive pulses, non-even period sampling is carried out on output signals of the single-phase three-level inverter, the value of j is changed after sampling of each period is finished, the second step is executed to obtain the power switch drive pulses of the next period, and single-phase three-level inverter signal modulation is achieved. The method is suitable for single-phase three-level inverter signal modulation.

Description

Single-phase three-level inverter signal modulating method based on wavelet modulation

Technical field

The present invention relates to single-phase three-level inverter field of signal modulation.

Background technology

Three-level inverter is a kind of novel high-voltage large-capacity power inverter, with respect to two-level inverter, there is device voltage stress low, the advantage such as the total percent harmonic distortion of output waveform is low, system electromagnetic interference is little, switching frequency is low and switching loss is little, is generated electricity by way of merging two or more grid systems, the very big concern in new forms of energy, fuel cell and speed regualtion of AC motor field.Due to the extensive use of tri-level inversion circuit, the importance of its control method research is also highlighted day by day.At present, conventional three-level inverter control strategy has sinusoidal pulse width modulation strategy (SPWM) and space vector voltage control (SVPWM).Typical carrier control method for three-level inverter is triangular carrier layered manner.Triangular carrier layered manner is to be divided into upper and lower two-layer laminate by the two class frequencys triangular carrier identical with amplitude, and it is upper and lower that two groups of triangular waves are distributed in transverse axis symmetrically, and modulate with same sine wave.The method is simple, directly perceived, but its shortcoming is that direct voltage utilance is low, and the switching frequency of power tube is high, and switching loss is large.Space voltage vector modulation method (SVPWM) be take circular rotating field and is carried out the work of control inverter as target, forms PWM output voltage waveforms.Compare with carrier Control, its direct voltage utilance of three-level inverter that SVPWM controls is high, and harmonic wave of output voltage aberration rate is low, and the switching frequency of power tube is low.But along with level number increases, this control method is complicated.

Summary of the invention

The problem that traditional single phase three-level inverter signal modulating method fundamental voltage output of voltage amplitude is little in order to solve in the present invention, percent harmonic distortion large, power tube switching frequency is high and control method is complicated, has proposed the single-phase three-level inverter signal modulating method based on wavelet modulation.

Single-phase three-level inverter signal modulating method based on wavelet modulation comprises the following steps:

Step 1, according to Ha Er scaling function ${\mathrm{\φ}}_H\left(t\right)=\begin{array}{c}\left\{\begin{array}{cc}1& t\∈\left[\mathrm{0,1}\right)\\ 0& t\∉\left[\mathrm{0,1}\right)\end{array}\right.\end{array}$ Obtain linear non-two and enter synthetic wavelet scaling function

Step 2, according to linearity non-two, enter synthetic wavelet scaling function obtain the power switch driving pulse of single-phase three-level inverter

Step 3, according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, and the output signal of single-phase three-level inverter is carried out to non-homogeneous periodic sampling, after each periodic sampling finishes, change the value of j, and return to the power switch driving pulse that execution step two obtains next cycle, realize the modulation of single-phase three-level inverter signal.

In step 1 according to Ha Er scaling function obtain non-two and enter synthetic wavelet scaling function process be:

If for cardinal scales function, linear non-two enter to synthesize scaling function and are j is scale parameter, and j is more than or equal to 0 integer.

In step 3, according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, and the modulation signal of single-phase three-level inverter is carried out to non-homogeneous periodic sampling, realizes the modulation of single-phase three-level inverter signal and comprise the following steps:

The initial value j of step 3 A, setting j ₀=1, d _iinitial value d ₀=0;

Step 3 B, calculating sampling point are constantly with t is the sinusoidal period function S of single-phase three-level inverter output _m(t) in cycle, D is the number of sets of sample in each signal period, each group d _irepresent, i ∈ [0, D-1],

Step 3 C, calculating value, S _m(t) the sinusoidal period function of exporting for single-phase three-level inverter, if S ' _m(t _d2) >0, j=j+1, if S ' _m(t _d2) <0, j=j-1;

If step 3 D is t>T _m, j=j ₀and d=d ₀, return to execution step two; If t<T _m, j=j ₀and d=d+1, returns to execution step two, wherein, T _mfor the work period of single-phase three-level inverter.

In step 3, according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, comprise following situation:

Work as t<T _m/ 8 o'clock, power switch driving pulse driving switch pipe V2 action, its complementary pulse signal driving switch pipe V4 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as T _m/ 8≤t<3T _m/ 8 o'clock, power switch driving pulse driving switch pipe V1 action, its complementary pulse signal driving switch pipe V3 action, switching tube V2 conducting, switching tube V4 turn-offs;

Work as 3T _m/ 8≤t<T _m/ 2 o'clock, power switch driving pulse driving switch pipe V2 action, its complementary pulse signal driving switch pipe V4 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as T _m/ 2≤t<5T _m/ 8 o'clock, power switch driving pulse driving switch pipe V3 action, its complementary pulse signal driving switch pipe V1 action, switching tube V2 conducting, switching tube V4 turn-offs;

Work as 5T _m/ 8≤t<7T _m/ 8 o'clock, power switch driving pulse driving switch pipe V4 action, its complementary pulse signal driving switch pipe V2 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as 7T _m/ 8≤t<T _mtime, power switch driving pulse driving switch pipe V3 action, its complementary pulse signal driving switch pipe V1 action, switching tube V2 conducting, switching tube V4 turn-offs.

Beneficial effect: the present invention is applied to wavelet modulation method in single-phase three-level inverter signal modulation, makes that single-phase three-level inverter harmonic wave of output voltage content is little, fundamental voltage amplitude large, power switch frequency is low, percent harmonic distortion is little; And signal modulating method step is simple, be easy to realize, can effectively improve the waveform quality of single-phase three-level inverter output voltage.

Accompanying drawing explanation

Fig. 1 is the topological structure schematic diagram of single-phase three-level inverter;

When Fig. 2 is number of sets of sample D=30, the output voltage waveform of single-phase three-level inverter;

When Fig. 3 is number of sets of sample D=30, the output voltage spectrum waveform figure of single-phase three-level inverter;

When Fig. 4 is number of sets of sample D=35, the output voltage waveform of single-phase three-level inverter;

When Fig. 5 is number of sets of sample D=35, the output voltage spectrum waveform figure of single-phase three-level inverter.

Embodiment

The single-phase three-level inverter signal modulating method based on wavelet modulation described in embodiment one, this embodiment comprises the following steps:

Step 1, according to Ha Er scaling function ${\mathrm{\&phi;}}_H\left(t\right)=\begin{array}{c}\left\{\begin{array}{cc}1& t\&Element;\left[\mathrm{0,1}\right)\\ 0& t\&NotElement;\left[\mathrm{0,1}\right)\end{array}\right.\end{array}$ Obtain linear non-two and enter synthetic wavelet scaling function

Step 2, according to linearity non-two, enter synthetic wavelet scaling function obtain the power switch driving pulse of single-phase three-level inverter

Step 3, according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, and the output signal of single-phase three-level inverter is carried out to non-homogeneous periodic sampling, after each periodic sampling finishes, change the value of j, and return to the power switch driving pulse that execution step two obtains next cycle, realize the modulation of single-phase three-level inverter signal.

The difference of the single-phase three-level inverter signal modulating method based on wavelet modulation described in embodiment two, this embodiment and embodiment one is, in step 1 according to Ha Er scaling function obtain non-two and enter synthetic wavelet scaling function process be:

If for cardinal scales function, linear non-two enter to synthesize scaling function and are j is scale parameter, and j is more than or equal to 0 integer.

The difference of the single-phase three-level inverter signal modulating method based on wavelet modulation described in embodiment three, this embodiment and embodiment one is, in step 3 according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, and the modulation signal of single-phase three-level inverter is carried out to non-homogeneous periodic sampling, realize the modulation of single-phase three-level inverter signal and comprise the following steps:

The initial value j of step 3 A, setting j ₀=1, d _iinitial value d ₀=0;

Step 3 B, calculating sampling point are constantly with t is the sinusoidal period function S of single-phase three-level inverter output _m(t) in cycle, D is the number of sets of sample in each signal period, each group d _irepresent, i ∈ [0, D-1],

Step 3 C, calculating value, S _m(t) the sinusoidal period function of exporting for single-phase three-level inverter, if S ' _m(t _d2) >0, j=j+1, if S ' _m(t _d2) <0, j=j-1;

If step 3 D is t>T _m, j=j ₀and d=d ₀, return to execution step two; If t<T _m, j=j ₀and d=d+1, returns to execution step two, wherein, T _mfor the work period of single-phase three-level inverter.

Embodiment four, in conjunction with Fig. 1, this embodiment is described, the difference of the single-phase three-level inverter signal modulating method based on wavelet modulation described in this embodiment and embodiment one is, in step 3, according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, comprises following situation:

Work as t<T _m/ 8 o'clock, power switch driving pulse driving switch pipe V2 action, its complementary pulse signal driving switch pipe V4 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as T _m/ 8≤t<3T _m/ 8 o'clock, power switch driving pulse driving switch pipe V1 action, its complementary pulse signal driving switch pipe V3 action, switching tube V2 conducting, switching tube V4 turn-offs;

Work as 3T _m/ 8≤t<T _m/ 2 o'clock, power switch driving pulse driving switch pipe V2 action, its complementary pulse signal driving switch pipe V4 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as T _m/ 2≤t<5T _m/ 8 o'clock, power switch driving pulse driving switch pipe V3 action, its complementary pulse signal driving switch pipe V1 action, switching tube V2 conducting, switching tube V4 turn-offs;

Work as 5T _m/ 8≤t<7T _m/ 8 o'clock, power switch driving pulse driving switch pipe V4 action, its complementary pulse signal driving switch pipe V2 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as 7T _m/ 8≤t<T _mtime, power switch driving pulse driving switch pipe V3 action, its complementary pulse signal driving switch pipe V1 action, switching tube V2 conducting, switching tube V4 turn-offs.

Be illustrated in figure 1 the topological structure schematic diagram of single-phase three-level inverter, it is to be combined by three level brachium pontis and two level brachium pontis, and as shown in the figure, the busbar voltage of single-phase three-level inverter is E, and the output voltage between two brachium pontis is U ₀, work as U ₀be output as ± E, ± E/2, ± be defined as respectively 1,1/2,0 level at 0 o'clock, for easy analysis, 0 level is divided into+0 and-0 two kind, work as U ₀=0 and be defined as+0 level while switching between E/2 and 0 level; Work as U ₀=0 and be defined as-0 level while switching between-E/2 and 0 level, inverter output level and each switching tube to open situation as shown in the table:

。

Output voltage waveforms and output voltage frequency spectrum by the single-phase three-level inverter shown in Fig. 2-Fig. 5 can draw, when number of sets of sample D is respectively 30 and 35, single-phase three-level inverter harmonic wave of output voltage content is little, fundamental voltage amplitude is large; And the signal modulating method step that the present invention proposes is simple, be easy to realize, can effectively improve the waveform quality of single-phase three-level inverter output voltage.

Claims (4)

1. the single-phase three-level inverter signal modulating method based on wavelet modulation, is characterized in that, it comprises the following steps:

Step 1, according to Ha Er scaling function ${\mathrm{\&phi;}}_H\left(t\right)=\begin{array}{c}\left\{\begin{array}{cc}1& t\&Element;\left[\mathrm{0,1}\right)\\ 0& t\&NotElement;\left[\mathrm{0,1}\right)\end{array}\right.\end{array}$ Obtain linear non-two and enter synthetic wavelet scaling function

Step 2, according to linearity non-two, enter synthetic wavelet scaling function obtain the power switch driving pulse of single-phase three-level inverter

Step 3, according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, and the output signal of single-phase three-level inverter is carried out to non-homogeneous periodic sampling, after each periodic sampling finishes, change the value of j, and return to the power switch driving pulse that execution step two obtains next cycle, realize the modulation of single-phase three-level inverter signal.

2. the single-phase three-level inverter signal modulating method based on wavelet modulation according to claim 1, is characterized in that, in step 1 according to Ha Er scaling function obtain non-two and enter synthetic wavelet scaling function process be:

If for cardinal scales function, linear non-two enter to synthesize scaling function and are j is scale parameter, and j is more than or equal to 0 integer.

3. the single-phase three-level inverter signal modulating method based on wavelet modulation according to claim 1, it is characterized in that, in step 3 according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, and the modulation signal of single-phase three-level inverter is carried out to non-homogeneous periodic sampling, realize the modulation of single-phase three-level inverter signal and comprise the following steps:

The initial value j of step 3 A, setting j ₀=1, d _iinitial value d ₀=0;

Step 3 B, calculating sampling point are constantly with t is the sinusoidal period function S of single-phase three-level inverter output _m(t) in cycle, D is the number of sets of sample in each signal period, each group d _irepresent, i ∈ [0, D-1],

Step 3 C, calculating value, S _m(t) the sinusoidal period function of exporting for single-phase three-level inverter, if S ' _m(t _d2) >0, j=j+1, if S ' _m(t _d2) <0, j=j-1;

If step 3 D is t>T _m, j=j ₀and d=d ₀, return to execution step two; If t<T _m, j=j ₀and d=d+1, returns to execution step two, wherein, T _mfor the work period of single-phase three-level inverter.

4. the single-phase three-level inverter signal modulating method based on wavelet modulation according to claim 1, is characterized in that, in step 3, according to the action of the power switch driving pulse driving power switch of single-phase three-level inverter, comprises following situation:

Work as t<T _m/ 8 o'clock, power switch driving pulse driving switch pipe V2 action, its complementary pulse signal driving switch pipe V4 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as T _m/ 8≤t<3T _m/ 8 o'clock, power switch driving pulse driving switch pipe V1 action, its complementary pulse signal driving switch pipe V3 action, switching tube V2 conducting, switching tube V4 turn-offs;

Work as 3T _m/ 8≤t<T _m/ 2 o'clock, power switch driving pulse driving switch pipe V2 action, its complementary pulse signal driving switch pipe V4 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as T _m/ 2≤t<5T _m/ 8 o'clock, power switch driving pulse driving switch pipe V3 action, its complementary pulse signal driving switch pipe V1 action, switching tube V2 conducting, switching tube V4 turn-offs;

Work as 5T _m/ 8≤t<7T _m/ 8 o'clock, power switch driving pulse driving switch pipe V4 action, its complementary pulse signal driving switch pipe V2 action, switching tube V3 conducting, switching tube V1 turn-offs;

Work as 7T _m/ 8≤t<T _mtime, power switch driving pulse driving switch pipe V3 action, its complementary pulse signal driving switch pipe V1 action, switching tube V2 conducting, switching tube V4 turn-offs.