CN204481711U - A kind of Z source three-level PWM rectifier - Google Patents

Abstract

The utility model relates to a kind of Z source three-level PWM rectifier, comprises three-phase brachium pontis in parallel, and every phase brachium pontis comprises the switching tube of four series connection, and the mid point of each phase brachium pontis is connected as the input source of this rectifier through inductance with electrical network or alternating current source; Each brachium pontis output in parallel is connected with the input of Z source network; The output of Z source network is connected in series switching tube S up and down respectively _w1and S _w2; Thereafter output and electric capacity C ₁with electric capacity C ₂series arm be connected in parallel, electric capacity C ₁with electric capacity C ₂series arm be connected with DC load; Topology of the present utility model not only can realize reduced output voltage, and allows upper and lower bridge arm direct pass, and reliability obviously increases, and the deadband eliminating time, prevents wave distortion; Z source three-level rectifier while raising voltage withstand class, can reduce AC harmonic voltages and electric current, improves the quality of its net side waveform under identical switching frequency and control mode, reduce distortion effectively.

Description

A kind of Z source three-level PWM rectifier

Technical field

The utility model relates to a kind of Z source three-level PWM rectifier.

Background technology

The advantages such as compare with phase control rectifier with traditional uncontrollable rectifier, PWM rectifier achieves the sine of current on line side, and can run on unity power factor, and therefore have power factor high, output voltage ripple is little, and dynamic response is good.PWM rectifier is divided into voltage-source recitifier (VSR) and current source rectifier (CSR) two kinds, and wherein voltage-source recitifier has electric energy transmitted in both directions, power factor correction, reduces the advantages such as input harmonics, applies comparatively extensive.Although current source rectifier has the advantage of circuit protection and very fast current response, its AC electric capacity and the huge volume of DC side inductance need the application limiting it.Common voltage-source recitifier only possesses the function of boosting rectification, is less than the occasion of AC input voltage, needs to add DC/DC boost module, add cost and design difficulty at DC side output voltage.In addition the electromagnetic interference that pass-through state is brought can cause damage to it, reduces its antijamming capability and operation stability.

In order to improve the deficiency of traditional electrical die mould rectifier, someone proposes a kind of Z source two level PWM rectifier.This rectifier overcomes voltage type PWM rectifier can not the defect of step-down, can realize the function of buck, thus be one-level formula structure by two-stage type designs simplification.And this structure allows two pipes conducting simultaneously of each brachium pontis, improves the fail safe of system.

The weak point of two level PWM rectifiers is, when it is applied to the occasion of high-power, need use the power switch pipe of high back-pressure, or multiple power switch pipe series connection is used.In addition because this structure rectifying device AC output voltage always switches on two level, when switching frequency is not high, harmonic content will be caused relatively large.Than two level, three-level rectifier, while raising voltage withstand class, effectively reduces AC harmonic voltages and electric current, significantly can improve its net side waveform quality under identical switching frequency and control mode, reduces distortion.

Utility model content

The purpose of this utility model is exactly that propose a kind of Z source three-level PWM rectifier, this structure adds Z source network between three-level rectifier and load, and adds switching tube S on the right side of Z source in order to solve the problem _w1and S _w2dC side loop is controlled.Use the Z source three-level rectifier of this control method, the direct voltage being less than input voltage amplitude can be exported, and allow each way switch pipe of main circuit to lead directly to, improve the antijamming capability of rectifier.

For achieving the above object, the utility model adopts following technical scheme:

A kind of Z source three-level PWM rectifier, is characterized in that, comprises three-phase brachium pontis in parallel, and every phase brachium pontis comprises the switching tube of four series connection, and the mid point of each phase brachium pontis is connected as the input source of this rectifier through inductance with electrical network or alternating current source; Each brachium pontis output in parallel is connected with the input of Z source network; The output of Z source network is connected in series switching tube S up and down respectively _w1and S _w2; Thereafter output and electric capacity C ₁with electric capacity C ₂series arm be connected in parallel, electric capacity C ₁with electric capacity C ₂series arm be connected with DC load;

The switching tube S on the right side of the switching tube of rectifier three-phase brachium pontis and Z source network is controlled by control circuit _w1and S _w2conducting and shutoff, make Z source three-level PWM rectifier run on non-straight-through, complete straight-through, upper straight-through and lower straight-through four kinds of operational modes respectively.

In described three-phase brachium pontis, the first switching tube respectively in each phase brachium pontis and be connected in series pair of diodes between the 4th switching tube, the simultaneously mid point of diode and electric capacity C ₁with electric capacity C ₂the mid point of series arm is connected.

Described Z source network is made up of two electric capacity and two inductance being connected into class X-type, this network is a symmetrical structure, two capacitance values are identical, and two inductance inductance values are identical, connect the output of rectifier, right side exports as the input of DC load on the left of described Z source network.

Described switching tube S _w1and S _w2all combined by IGBT and diode inverse parallel; Switching tube S _w1and S _w2cut-off and depend on which kind of pattern rectifier runs under:

When rectifier is in non-direct mode operation, switching tube S _w1and S _w2iGBT all receive and open signal; When rectifier is in full direct mode operation, switching tube S _w1and S _w2iGBT all receive cut-off signals; When rectifier is in upper direct mode operation, switching tube S _w1iGBT receive open signal, switching tube S _w2iGBT receive cut-off signals; When rectifier is in lower pass-through state, switching tube S _w1iGBT receive cut-off signals, switching tube S _w2iGBT receive open signal.

Described control circuit comprises protective circuit, drive circuit, sampling modulate circuit and DSP module; sampling modulate circuit connects DSP module; DSP module and protective circuit two-way communication, DSP module connects drive circuit, and in drive circuit output pwm signal driving brachium pontis, IGBT pipe opens and shutoff.

The magnitude of voltage size that the amplitude of described sampling modulate circuit Gather and input three-phase alternating voltage and three-phase current and phase place, Z source network capacitance voltage and DC side export.

The beneficial effects of the utility model are:

1, for three-level rectifier, Z source three-level rectifier not only can realize reduced output voltage, and due to the straight-through damage that can not cause power device, reliability obviously increases, and the deadband eliminating time, prevents wave distortion;

Although 2, Z source two level PWM rectifier can realize step-down rectifier and bridge arm direct pass protection, when it is applied to powerful occasion, the power switch pipe of high back-pressure need be used or multiple power switch pipe series connection is used; In addition this structure rectifying device AC output voltage switches on two level, when switching frequency is not high, harmonic content will be caused relatively large.And Z source three-level rectifier while raising voltage withstand class, can reduce AC harmonic voltages and electric current effectively, under identical switching frequency and control mode, improve the quality of its net side waveform, reduce distortion.

3, the utility model Z source three-level PWM rectifier has the advantages such as high power, waveform quality be good, extensive in field of renewable energy prospects such as photovoltaic generating system, wind generator system, fuel cells.

Accompanying drawing explanation

Fig. 1 is the topology diagram of the utility model system;

Fig. 2 (a) is the current circuit figure under the full direct mode operation of Z source three-level PWM rectifier;

Fig. 2 (b) is the current circuit figure under direct mode operation in the three-level PWM rectifier of Z source;

Fig. 2 (c) is the current circuit figure under direct mode operation under the three-level PWM rectifier of Z source;

Fig. 3 is the equivalent current circuit diagram of Z source three-level PWM rectifier;

The non-straight-through simple equivalent circuit figure that Fig. 4 (a) is Z source three-level PWM rectifier;

Fig. 4 (b) is the simple equivalent circuit figure of the full pass-through state of Z source three-level PWM rectifier;

Fig. 4 (c) is the simple equivalent circuit figure of the upper pass-through state of Z source three-level PWM rectifier;

Fig. 4 (d) is the simple equivalent circuit figure of the lower pass-through state of Z source three-level PWM rectifier;

Fig. 5 (a) adds straight-through modulator approach for carrier wave is anti-phase;

Fig. 5 (b) is for carrier wave is with being added straight-through modulator approach;

Fig. 6 is Z source three-level PWM rectifier control block diagram;

Fig. 7 (a) does not add straight-through Z source capacitance voltage waveform and DC side load waveform for using carrier wave in-phase modulation method;

Fig. 7 (b) does not add straight-through voltage on line side and three-phase current waveform for using carrier wave in-phase modulation method;

Fig. 7 (c) does not add straight-through interchange side line voltage waveform for using carrier wave in-phase modulation method;

Fig. 7 (d) detects for using carrier wave in-phase modulation method not add straight-through interchange side line voltage harmonic;

The harmonic detecting of Fig. 7 (e) for using carrier wave in-phase modulation method not add straight-through AC three-phase current;

Fig. 8 (a) does not add straight-through Z source capacitance voltage and DC side load waveform for using the anti-phase modulator approach of carrier wave;

Fig. 8 (b) does not add straight-through voltage on line side and three-phase current waveform for using the anti-phase modulator approach of carrier wave;

Fig. 8 (c) does not add straight-through interchange side line voltage waveform for using the anti-phase modulator approach of carrier wave;

Fig. 8 (d) detects for using the anti-phase modulator approach of carrier wave not add straight-through interchange side line voltage harmonic;

Fig. 8 (e) does not add straight-through AC three-phase current harmonic detecting for using the anti-phase modulator approach of carrier wave;

Fig. 9 (a) leads directly to duty ratio d for using carrier wave in-phase modulation method _u=d _lz source capacitance voltage and DC side load waveform when=0.1;

Fig. 9 (b) leads directly to duty ratio d for using carrier wave in-phase modulation method _u=d _lz source input side V when=0.1 _iwaveform;

Fig. 9 (c) leads directly to duty ratio d for using carrier wave in-phase modulation method _u=d _lz source outlet side V when=0.1 _owaveform;

Figure 10 (a) leads directly to duty ratio d for using carrier wave in-phase modulation method _u=d _lz source capacitance voltage and DC side load waveform when=0.25;

Figure 10 (b) leads directly to duty ratio d for using carrier wave in-phase modulation method _u=d _lz source input side V when=0.25 _iwaveform;

Figure 10 (c) leads directly to duty ratio d for using carrier wave in-phase modulation method _u=d _lz source outlet side V when=0.25 _owaveform.

Embodiment

Below in conjunction with accompanying drawing and embodiment, the utility model is described further.

Fig. 1 is the structure chart of utility model Z source three-level rectifier, U _a, U _b, U _cfor ideal voltage source: R _sfor net side equivalent resistance, L _sfor net side inductance, C ₁and C ₂for DC bus capacitor and the equal (C of capacitance ₁=C ₂), the voltage of the two correspondence is V respectively _d1and V _d2, o is mid point; Z source network is by two the electric capacity C being connected into class X-shaped _z1, C _z2with two inductance L ₁and L ₂form.S _w1and S _w2two switching tubes, respectively with two diode D ₁and D ₂inverse parallel, they are normally under non-pass-through state, can selectivity turn off under specific pass-through state.

The introducing of Z source network, makes each phase bridge arm direct pass of rectifier become possibility.Therefore, compared with traditional electrical die mould PWM rectifier, Z source PWM rectifier, except having effective vector zero vector, also add shoot-through zero vector.And compared with the PWM rectifier of Z source, Z source three-level PWM rectifier turn increases the pass-through state of several uniqueness, the introducing of these pass-through states makes Z source three-level rectifier be provided with the characteristic of step-down rectifier just.For Z source three-level PWM rectifier, following table lists on off state under the different operational mode of C phase brachium pontis and corresponding output voltage.Z source three-level rectifier has four kinds of operational modes as can be seen from Table 1: non-direct mode operation, full direct mode operation, upper direct mode operation and lower direct mode operation.When Z source three-level rectifier is operated in non-direct mode operation, its running status and common voltage-type three-level rectifier do not have any difference.And when it operates under direct mode operation, the operating characteristic of Z source network just displays.

Table 1 Z source three-level rectifier on off state

Fig. 2 (a) is the current circuit figure under the full direct mode operation of Z source three-level PWM rectifier.As seen from the figure, complete straight-through operational mode is exactly four switching tubes conducting simultaneously of a certain phase in three-phase brachium pontis (or a few phase).Now circuit switching pipe S _w1and S _w2disconnect, diode D simultaneously ₁and D ₂be in reverse blocking state, Z source network and DC side circuit disconnect completely.

Fig. 2 (b) is the current circuit figure under direct mode operation in the three-level PWM rectifier of Z source.As seen from the figure, under Z source three-level rectifier is in upper straight-through operational mode, three switching tube conducting, now circuit switching pipe S simultaneously above of a certain phase (or a few phase) in its three-phase brachium pontis _w2disconnect, with S _w1antiparallel diode D ₁conducting, with the derided capacitors C of DC side ₁together form a current circuit.

Fig. 2 (c) is the current circuit figure under direct mode operation under the three-level PWM rectifier of Z source.As seen from the figure, under Z source three-level rectifier is in lower straight-through operational mode, three switching tube conducting, now circuit switching pipe S simultaneously below a certain phase (or a few phase) in its three-phase brachium pontis _w1disconnect, with S _w2antiparallel diode D ₂conducting, with the derided capacitors C of DC side ₂together form a current circuit.

Fig. 3 is the equivalent current circuit diagram of Z source three-level PWM rectifier.Wherein Vi is the input voltage of Z source network, and Vo is the output voltage of Z source network, and Z source electric capacity both end voltage is V respectively _c1and V _c2, the voltage at inductance two ends, Z source is V respectively _l1and V _l2, DC side load voltage is Vdc, and the voltage of two derided capacitors is V respectively _d1and V _d2the reference direction of ,+-representative voltage.Easy for analyzing, suppose that the capacitance of two electric capacity in Z source is equal, the inductance value of two inductance is identical, is denoted as C _z1=C _z2, L ₁=L ₂.Now can be drawn by the symmetry of Z source network:

V _C1＝V _C2＝V _CV _L1＝V _L2＝V _L(1)

Suppose that the capacitance of two derided capacitors is identical again, and the current potential of its mid point 0 is zero, then have:

$V_{d1}=V_{d2}=\frac{V_{dc}}{2}---\left(2\right)$

The non-straight-through simple equivalent circuit figure that Fig. 4 (a) is Z source three-level PWM rectifier.Now S _w1and S _w2all be in conducting state, its Z source network voltage V _land V _c, Z source input side voltage V _iand corresponding three independent voltage V (+N), V _n, V (-N), Z source output voltage V _owith DC side load voltage V _dcrelational expression respectively as follows:

V _L＝V _i-V _C(3)

$\begin{array}{ccc}V(+N)=+\frac{V_i}{2}& V_N=0V& V(-N)\end{array}=-\frac{V_i}{2}---\left(4\right)$

V _o＝V _dc＝V _C-V _L＝2V _C-V _i(5)

Fig. 4 (b) is the simple equivalent circuit figure of the full pass-through state of Z source three-level PWM rectifier.Now S _w1and S _w2all be in off-state, its Z source network voltage V _land V _c, Z source input side voltage V _iand corresponding three independent voltage V (+N), V _n, V (-N), Z source output voltage V _orelational expression respectively as follows:

V _L＝-V _C(6)

V _i＝0V V(+N)＝V _N＝V(-N)＝0V (7)

V _o＝V _C-V _L＝2V _C(8)

Suppose in a switch periods T, the time that rectifier bridge is operated in non-pass-through state is T ₁, the time being operated in pass-through state is T ₀, straight-through duty ratio is d, then have T=T ₀+ T ₁, d=T ₀/ T.In a switch periods T, must be 0 under the average voltage stable state at inductance two ends, can be obtained by formula (3) (6):

$\stackrel{\‾}{V_L}=\[T_0\·(-V_C)+T_1\·(V_i-V_C)\]/T=0---\left(9\right)$

Abbreviation obtains: $\frac{V_C}{V_i}=\frac{T_1}{T}=1-d---\left(10\right)$

Obtained by formula (5) (6):

$\stackrel{\‾}{V_L}=\[T_0\·(-V_C)+T_1\·(V_C-V_O)\]/T=0---\left(11\right)$

Abbreviation obtains: $\frac{V_C}{V_O}=\frac{T_1}{T_1-T_0}=\frac{1-d}{1-2d}---\left(12\right)$

In like manner, the mean value expression formula of the direct voltage of Z source output is as follows:

$\stackrel{\‾}{V_O}=\[T_0\·\left(2V_C\right)+T_1\·(2V_C-V_i)\]/T=V_C---\left(13\right)$

From formula (5) (10), the relation of load-side VD and Z source capacitance voltage and Z source input voltage peak value is as follows:

$V_{dc}=2V_C-V_i=\frac{1-2d}{1-d}\·V_C---\left(14\right)$

$V_{dc}=2V_C-{\hat{V}}_i=(1-2d)\·{\hat{V}}_i---\left(15\right)$

If B=1-2d meets 0<B<=1, call it as the Hypotensive factor of Z source rectifier, can find out when straight-through duty ratio d=0 time, B=1, under Z source three-level rectifier operates in normal rectification pattern, when d>0 time, B<1, under now Z source three-level rectifier operates in step-down rectifier pattern.

From upper surface analysis, the full direct-passing mode of Z source two level rectifier is equally applicable to Z source three-level rectifier.Although Z source three-level rectifier switches back and forth between non-pass-through state and full pass-through state just can realize step-down rectifier, three-level rectifier is not brought into play than the advantage that two level rectifier wave form output quality are higher.In fact due to the existence of midpoint potential o, the two kinds of new direct mode operations that made Z source three-level rectifier many again: upper direct mode operation and lower direct mode operation.Different from full direct mode operation, these two kinds of direct mode operations do not need S _w1and Sw ₂whole shutoff, only needs to turn off one of them.

Fig. 4 (c) is the simple equivalent circuit figure of the upper pass-through state of Z source three-level PWM rectifier.When brachium pontis is in 0 state time, add upper through connect signal, make 3 switching tube conductings simultaneously above of brachium pontis, now Z source three-level PWM rectifier just runs on direct mode operation.Now only has S _w2be in off-state.Its Z source network voltage V _land V _c, Z source input side voltage V _iand corresponding three independent voltage V (+N), V _n, V (-N), Z source output voltage V _orelational expression respectively as follows:

$V_L=-V_{d1}=-\frac{V_{dc}}{2}---\left(16\right)$

V(+N)＝V _N＝0V (17)

$V(-N)=-V_L-V_C=\frac{V_{dc}}{2}-V_C---\left(18\right)$

$V_i=V(+N)-V(-N)=V_C-V_{d1}=V_C-\frac{V_{dc}}{2}---\left(19\right)$

$V_o=V_C-V_L=V_C+V_{d1}=V_C+\frac{V_{dc}}{2}---\left(20\right)$

Fig. 4 (d) is the simple equivalent circuit figure of the lower pass-through state of Z source three-level PWM rectifier.When brachium pontis is in 0 state time, add lower through connect signal, make 3 switching tube conductings simultaneously below brachium pontis, now Z source three-level PWM rectifier just runs on lower direct mode operation.Now only has S _w1be in off-state.Its Z source network voltage V _land V _c, Z source input side voltage V _iand corresponding three independent voltage V (+N), V _n, V (-N), Z source output voltage V _orelational expression respectively as follows:

$V_L=-V_{d2}=-\frac{V_{dc}}{2}---\left(21\right)$

$V(+N)=V_C+V_L=V_C-\frac{V_{dc}}{2}---\left(22\right)$

V _N＝V(-N)＝0V (23)

$V_i=V(+N)-V(-N)=V_C-V_{dc}=V_C-\frac{V_{dc}}{2}---\left(24\right)$

$V_o=V_C-V_L=V_C+V_{d2}=V_C+\frac{V_{dc}}{2}---\left(25\right)$

Suppose in a switch periods T, the time that rectifier bridge is operated in non-pass-through state is T ₁, the time being operated in pass-through state is T _u, being operated in the lower straight-through time is T _l, total straight-through time T ₀=T _u+ T _ltotal duty ratio is d ', then have T=T ₀+ T ₁, d _u=T _u/ T, d _l=T _l/ T, d _u+ d _l=d '.In a switch periods T, must be 0 under the average voltage stable state at inductance two ends, can be obtained by formula (5) (16) (21):

$\begin{array}{c}\stackrel{\&OverBar;}{V_L}=\&lsqb;T_1\&CenterDot;(V_C-V_{dc})+(T_U+T_L)\&CenterDot;(-\frac{V_{dc}}{2})\&rsqb;/T\\ =\&lsqb;T_1\&CenterDot;(V_c-V_{dc})+T_0\&CenterDot;(-\frac{V_{dc}}{2})\&rsqb;/T=0\end{array}---\left(26\right)$

Abbreviation obtains:

$V_C=V_{dc}\frac{2T-T_0}{2(T-T_0)}=V_{dc}\&CenterDot;\frac{1-\frac{d^{\&prime;}}{2}}{1-d^{\&prime;}}---\left(27\right)$

In like manner, the mean value expression formula of the direct voltage of Z source output is as follows:

$\stackrel{\&OverBar;}{V_O}=\&lsqb;T_0\&CenterDot;\left(2V_C\right)+T_1\&CenterDot;(2V_C-V_i)\&rsqb;/T=V_C---\left(28\right)$

From formula (5) (27), the relation of load-side VD and Z source input voltage peak value is as follows:

$V_{dc}=2V_c-{\hat{V}}_i=(1-d^{\&prime;})\&CenterDot;{\hat{V}}_i---\left(29\right)$

Because upper direct mode operation is derided capacitors C ₁there is provided discharge loop, lower direct mode operation is derided capacitors C ₂there is provided discharge loop, in order to ensure C ₁with C ₂dividing potential drop is identical as far as possible, up and down straight-through time T _uand T _l, straight-through duty ratio d up and down _uand d _lt should be met _u=T _l, d _u=d _l.

Fig. 5 (a) adds straight-through modulator approach for carrier wave is anti-phase.Wherein upper straight-through comparison signal C+ amplitude is identical with lower straight-through comparison signal C-absolute value, with lower straight-through comparison signal C ₁-absolute value is different.Upper straight-through comparison signal and upper carrier wave ratio comparatively produce through connect signal, lower straight-through comparison signal and lower carrier wave ratio comparatively add the lower through connect signal of generation, 1 is made when upper and lower through connect signal overlap time, 4 switching tubes are conducting simultaneously when output 0 state, thus make the conducting simultaneously of 4 switching tubes, namely entirely lead directly to.As seen from the figure, when upper and lower two straight-through comparison signal absolute values are equal, straight-through region could be completely overlapping up and down, realize completely straight-through, when straight-through comparison signal absolute value is not identical up and down, straight-through region only overlaps up and down, will produce straight-through or lower pass-through state.

Fig. 5 (b) is that the SPWM modulator approach of carrier wave homophase adds straight-through mode.As can be seen from the figure, upper straight-through comparison signal and upper carrier wave ratio comparatively produce through connect signal, lower straight-through comparison signal and lower carrier wave ratio comparatively produce lower through connect signal, and the position that upper through connect signal and lower through connect signal add misses one another in a switch periods, complete straight-through state would not be there is like this.Upper and lower pass-through state is also add when brachium pontis is in 0 state, and upper through connect signal makes three pipe conductings simultaneously above brachium pontis, and now this brachium pontis is in pass-through state.Lower through connect signal makes three pipe conductings simultaneously below brachium pontis, and now this brachium pontis is in lower pass-through state.

Fig. 6 is Z source three-level PWM rectifier control block diagram.As seen from the figure, on the basis of two close cycles, the closed loop adding again load-side direct voltage makes DC side export can be any given.For Z source three-level rectifier, the reference value V of given Z source electric capacity _c* with load-side direct voltage reference value U _dc*, substitute into formula (14) (17) respectively according to straight-through type and draw initial duty cycle d ₀.U _dc* with U _dcmake difference and obtain straight-through side-play amount d* through PI adjustment, finally obtain actual duty cycle d and meet d=d ₀+ d*.Then regulate the reference signal generated signal d and two close cycles to SPWM controller, thus realize the constant output of load-side direct voltage.

Fig. 7 (a)-(e) does not add straight-through Z source three-level PWM rectifier output waveform for using carrier wave in-phase modulation method.When not adding through connect signal as seen from the figure, the output of Z source three-level rectifier DC side is identical with common three-level rectifier, does not have the effect of step-down.The total harmonic distortion now exchanging side line voltage and phase current is 42.52% and 1.29% respectively.

Fig. 8 (a)-(e) does not add straight-through Z source three-level PWM rectifier output waveform for using the anti-phase modulator approach of carrier wave.When not adding through connect signal as seen from the figure, the output of Z source three-level rectifier DC side is identical with common three-level rectifier, does not have the effect of step-down.The total harmonic distortion now exchanging side line voltage and phase current is 75.31% and 3.02% respectively.Can obtain thus, when capacitance voltage given identical, carrier wave in-phase modulation method is compared with the anti-phase modulator approach of carrier wave, DC side exports not large difference, but exchange the distortion of side line voltage harmonic and be reduced to 42.52% by 75.31%, total harmonic distortion of AC phase current has been reduced to 1.29% by 3.02%, illustrate that the modulator approach of carrier wave homophase is more suitable for Z source three-level PWM rectifier, therefore through connect signal is joined in the modulator approach of carrier wave homophase, in the hope of reaching best operational effect.

Fig. 9 (a)-(c) leads directly to duty ratio d for using carrier wave in-phase modulation method _u=d _lz source three-level PWM rectifier output waveform when=0.1.Get V _c*=600V, U _dc*=533V, therefore has d _u=d _l=0.1, d ₀=d _u+ d _l=0.2.Now Z source input voltage V _iwith Z source output voltage V _ocalculated value be respectively:

Non-straight-through time: V _i=2V _c-V _dc=1200-533=667V; V _o=V _dc=533V

Upper and lower straight-through time: V _i=Vc-V _dc/ 2=600-400/2=333.5V; V _o=V _c+ V _dc/ 2=600+400/2=866.5V

Calculated value is above consistent with oscillogram shown in Fig. 9.

Figure 10 (a)-(c) leads directly to duty ratio d for using carrier wave in-phase modulation method _u=d _lz source three-level PWM rectifier output waveform when=0.25.Get V _c*=600V, U _dc*=400V, therefore has d _u=d _l=0.25, d ₀=d _u+ d _l=0.5.Now Z source input voltage V _iwith Z source output voltage V _ocalculated value be respectively:

Non-straight-through time: V _i=2V _c-V _dc=1200-400=800V; V _o=V _dc=400V

Upper and lower straight-through time: V _i=Vc-V _dc/ 2=600-400/2=400V; V _o=V _c+ V _dc/ 2=600+400/2=800V

Calculated value is above consistent with oscillogram shown in Figure 10.

By reference to the accompanying drawings embodiment of the present utility model is described although above-mentioned; but the restriction not to the utility model protection range; one of ordinary skill in the art should be understood that; on the basis of the technical solution of the utility model, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection range of the present utility model.

Claims (6)

1. a Z source three-level PWM rectifier, is characterized in that, comprises three-phase brachium pontis in parallel, and every phase brachium pontis comprises the switching tube of four series connection, and the mid point of each phase brachium pontis is connected as the input source of this rectifier through inductance with electrical network or alternating current source; Each brachium pontis output in parallel is connected with the input of Z source network; The output of Z source network is connected in series switching tube S up and down respectively _w1and S _w2; Thereafter output and electric capacity C ₁with electric capacity C ₂series arm be connected in parallel, electric capacity C ₁with electric capacity C ₂series arm be connected with DC load;

Switching tube and the Z source right-side switch pipe S of rectifier three-phase brachium pontis is controlled by control circuit _w1and S _w2conducting and shutoff, make Z source three-level PWM rectifier run on non-straight-through, complete straight-through, upper straight-through and lower straight-through four kinds of operational modes respectively.

2. a kind of Z source as claimed in claim 1 three-level PWM rectifier, is characterized in that, in described three-phase brachium pontis, and the first switching tube respectively in each phase brachium pontis and be connected in series pair of diodes between the 4th switching tube, the simultaneously mid point of diode and electric capacity C ₁with electric capacity C ₂the mid point of series arm is connected.

3. a kind of Z source as claimed in claim 1 three-level PWM rectifier, it is characterized in that, described Z source network is made up of two electric capacity and two inductance being connected into class X-type, this network is a symmetrical structure, two capacitance values are identical, two inductance inductance values are identical, connect the output of rectifier, right side exports as the input of DC load on the left of described Z source network.

4. a kind of Z source as claimed in claim 1 three-level PWM rectifier, is characterized in that, described switching tube S _w1and S _w2all combined by IGBT and diode inverse parallel; Switching tube S _w1and S _w2cut-off and depend on which kind of pattern rectifier runs under:

When rectifier is in non-direct mode operation, switching tube S _w1and S _w2iGBT all receive and open signal; When rectifier is in full direct mode operation, switching tube S _w1and S _w2iGBT all receive cut-off signals; When rectifier is in upper direct mode operation, switching tube S _w1iGBT receive open signal, switching tube S _w2iGBT receive cut-off signals; When rectifier is in lower pass-through state, switching tube S _w1iGBT receive cut-off signals, switching tube S _w2iGBT receive open signal.

5. a kind of Z source as claimed in claim 1 three-level PWM rectifier; it is characterized in that; described control circuit comprises protective circuit, drive circuit, sampling modulate circuit and DSP module; sampling modulate circuit connects DSP module; DSP module and protective circuit two-way communication; DSP module connects drive circuit, and in drive circuit output pwm signal driving brachium pontis, IGBT pipe opens and shutoff.

6. a kind of Z source as claimed in claim 5 three-level PWM rectifier, is characterized in that, the magnitude of voltage size that the amplitude of described sampling modulate circuit Gather and input three-phase alternating voltage and three-phase current and phase place, Z source network capacitance voltage and DC side export.