CN106100413A - A kind of drain current suppressing method being applied to cascaded H-bridges five-electrical level inverter - Google Patents

Abstract

The present invention discloses a kind of drain current suppressing method being applied to cascaded H-bridges five-electrical level inverter, including: when the DC input voitage of said two H bridge module is identical, respectively obtain, with turning off, 16 on off states that said two H bridge module comprises according to the conducting of the switching tube on four brachium pontis of said two H bridge module；Calculate the parasitic capacitor voltage of each H bridge module that each on off state is corresponding in described 16 on off states and the parasitic capacitor voltage sum that said two H bridge module is total；Select to form two kinds of Switch State Combination in Power Systems from all on off states that the parasitic capacitor voltage sum that said two H bridge module is total is identical；According to the two Switch State Combination in Power Systems, compared with carrier wave by modulating wave, generate PWM drive signal and the switching tube of said two H bridge module is controlled, be effectively increased the inhibition of photovoltaic combining inverter leakage current.

Description

A kind of drain current suppressing method being applied to cascaded H-bridges five-electrical level inverter

Technical field

The invention belongs to active inverter technical field, relate to a kind of drain current suppressing side being applied to photovoltaic DC-to-AC converter Method, particularly relates to a kind of drain current suppressing method being applied to cascaded H-bridges five-electrical level inverter, and it is applicable to photovoltaic power generation grid-connecting Field.

Background technology

Non-isolation type H bridge photovoltaic DC-to-AC converter, because lacking the buffer action of transformator, makes to exist between photovoltaic panel and electrical network Directly electrical connection, causes the parasitic capacitance between photovoltaic panel and the earth to form loop, when the circuit is operating, high in parasitic capacitance The voltage of frequency change will produce leakage current, have a strong impact on efficiency and the reliability of system, even threaten personal safety.Therefore, leakage Current problems is urgently to be resolved hurrily.

At present, traditional drain current suppressing method can be classified as following three kinds, and the first is for using modified model topology, as H5 opens up Flutter, H6 topology, Heric topological sum mixing bridge arm topological etc., the second is for using the filter of passive filter, such as common mode inductance and EMI Ripple devices etc., the third is to use new modulation strategy.

From above-mentioned three kinds of angles, scholars have carried out substantial amounts of research respectively, such as document " High-efficiency single-phase transformerless PV H6inverterwith hybrid modulation method” BaojianJi, JianhuaWang, Jianfeng Zhao, " IEEE Transactions on Indu strial Electronics ", 2013,60 (5), 2,104 2115 (" hybrid modulation method of high-efficiency single-phase non-isolation type H6 inverter ", " IEEE journal-industrial electronic periodical ", volume 60 the 5th phase page 2,104 2115 in 2013) use Cascade H 6 topology, although one Determine to inhibit in degree leakage current, but compared with traditional H4 topology, its modulation strategy is complicated, and autgmentability is poor, relatively costly.

Document " Eliminating Ground Current in a Transformerless Photovoltaic Appli-cation”Freijedo,Alejandro G.Yepes,JanoMalvar,et al.《IEEETransacionson Energy Conversion ", 2010,25 (1), 140-147 (" eliminating the leakage current of non-isolation type photovoltaic application occasion ", " IEEE journal-energy conversion periodical ", volume 25 the 1st phase page 140 147 in 2010) propose to be added by the outlet side at H bridge Passive filter suppresses the scheme of leakage current, although the program can suppress leakage current effectively, but along with H bridge cascades quantity Increase, the volume of inverter is consequently increased with cost, and the parameter designing of wave filter is relative complex.

Document " Hybrid Multicarrier Modulation to Reduce Leakage Current in a Tran-sformerless Cascaded Multilevel Inverter for Photovoltaic Systems” Rajasekar Selvamuthukumaran,AbhishekGarg,and Rajesh Gupta.《IEEE Transactions On Power Electronics ", 2015,30 (4): 1779-1783 (" for non-isolation type cascaded multilevel inverter photovoltaic The mixing multi-carrier modulation strategy of system ", " IEEE journal-power electronics periodical ", the 4th phase 1,779 1783 of volume 30 in 2015 Page) POD (the Phase Opposite Disposition) modulation strategy of a kind of correction is proposed, use common-mode voltage to cut at switch The principle that when changing, amplitude change is minimum is to suppress leakage current, but the common-mode voltage obtained by this modulation strategy still suffers from high frequency division Amount, and not operatively killer stage joins the leakage current of H bridge photovoltaic DC-to-AC converter.

Summary of the invention

In order to solve above-mentioned leakage problem, the present invention, by the angle from the third drain current suppressing method, carries Go out a kind of new modulation strategy, parasitic capacitor voltage sum can be made to keep constant or low frequency variation, effectively suppress cascaded H-bridges Leakage current.

The embodiment provides a kind of drain current suppressing method being applied to cascaded H-bridges five-electrical level inverter, should For non-isolation type tandem photovoltaic combining inverter, described non-isolation type tandem photovoltaic combining inverter includes two-stage photovoltaic cell Plate and two H bridge modules, described H bridge module includes four switching tubes being arranged on the brachium pontis of left and right, wherein, described suppressing method Including:

When the DC input voitage of said two H bridge module is identical, according on four brachium pontis of said two H bridge module The conducting of switching tube respectively obtains, with turning off, 16 on off states that said two H bridge module comprises；

Calculate parasitic capacitor voltage and the institute of each H bridge module that each on off state is corresponding in described 16 on off states State two total parasitic capacitor voltage sums of H bridge module；

Select to form two kinds from all on off states that the parasitic capacitor voltage sum that said two H bridge module is total is identical Switch State Combination in Power Systems；

According to the two Switch State Combination in Power Systems, compared with carrier wave by modulating wave, generate PWM drive signal to institute The switching tube stating two H bridge modules is controlled, thus realizes the suppression of leakage current.

In one embodiment of the invention, when the DC input voitage of said two H bridge module is identical, according to described The conducting of the switching tube on four brachium pontis of two H bridge modules and turn off and respectively obtain 16 that said two H bridge module comprises and open Off status, including:

Definition S_a1/S_b1/S_a2/S_b2It is the switch function of switching tube on four brachium pontis of two H bridge modules, respectively by numeral 0,1 shutoff representing the described each switching tube of H bridge module and opening state, the switch function of the most described four brachium pontis switching tubes S_a1/S_b1/S_a2/S_b216 on off states are produced as follows in different conditions combination:

0101,0100,0111,0110,0001,1101,0000,1111,0011,1100,0010,1110,1001, 1000,1011,1010。

In one embodiment of the invention, if the DC input voitage of two H bridge modules is identical and be v_pv, the most each H Bridge output-v_pv、0、v_pvThree kinds of level, the total-2v of photovoltaic DC-to-AC converter of two H bridge cascades_pv、-v_pv、0、v_pv、2v_pvFive kinds of outputs Level；Described 16 on off states ultimately form the-2v of the photovoltaic DC-to-AC converter of two H bridge cascades_pv、-v_pv、0、v_pv、2v_pvFive kinds Output level.

In one embodiment of the invention, from the institute that the parasitic capacitor voltage sum that said two H bridge module is total is identical Have on off state and select to form two kinds of Switch State Combination in Power Systems, including:

Selection said two H bridge module total parasitic capacitor voltage sum of sening as an envoy to is v_pvAll on off states；And according to electricity When truncation is changed, principle composition the following two kinds Switch State Combination in Power Systems: the 1010-1000-1100-that switching tube action frequency is minimum 0011-0001-0101 and 1010-1110-1100-0011-0111-0101.

In one embodiment of the invention, each H that in described 16 on off states, each on off state is corresponding is calculated The parasitic capacitor voltage of bridge module, including:

$v_{cpv1}=\frac{v_{a1n1}+v_{b1n1}}{2}-\frac{v_{a2n2}-v_{b2n2}}{2}-\frac{v_g}{2}$

$v_{cpv2}=\frac{v_{a1n1}-v_{b1n1}}{2}+\frac{v_{a2n2}+v_{b2n2}}{2}-\frac{v_g}{2}$

Wherein, v_cpv1And v_cpv2It is respectively the parasitic capacitor voltage value of two H bridge modules, v_a1n1、v_b1n1、v_a2n2And v_b2n2Point Wei four brachium pontis outfan a of said two H bridge module₁、b₁、a₂And b₂To common point n₁And n₂Voltage；v_gFor line voltage.

In one embodiment of the invention, when generating PWM drive signal, described carrier wave uses two homophase triangular carriers Signal tri1, tri2, wherein tri1 > tri2；Described modulating wave v_refModulation degree is 0.9, and first half cycle is positioned at axis of ordinates 1 On, the later half cycle is positioned at axis of ordinates less than 1.

In one embodiment of the invention, when PWM drive signal generates, said two carrier signal tri1, tri2 Meet: as described modulating wave v_refDuring more than 1,1.5 < tri1 < 2,1 < tri2 < 1.5；As described modulating wave v_refDuring less than 1,0.5 < Tri1 < 1,0 < tri2 < 0.5.

In one embodiment of the invention, according to the two Switch State Combination in Power Systems, carried out with carrier wave by modulating wave Relatively, generate PWM drive signal and the switching tube of said two H bridge module is controlled, including:

The PWM drive signal of the first described Switch State Combination in Power Systems 1010-1000-1100-0011-0001-0101 generates Mode includes:

As modulating wave v_refWhen >=1, S_a1=1, S_b2=0；S_b1Compared with carrier wave tri2 by modulating wave and obtain, if v_ref> Tri2, S_b1=0, otherwise S_b1=1；S_a2Compared with carrier wave tri1 by modulating wave and obtain, if v_ref> tri1, S_a2=1, otherwise S_a2= 0；

As modulating wave v_ref< when 1, then S_a1=0, S_b2=1；S_b1By modulating wave v_refCompare with carrier wave tri2 and obtain, if v_ref> Tri2, S_b1=0, otherwise S_b1=1；S_a2By modulating wave v_refCompare with carrier wave tri1 and obtain, if v_ref> tri1, S_a2=1, otherwise S_a2=0；

The PWM drive signal of Switch State Combination in Power Systems 1010-1110-1100-0011-0111-0101 described in the second generates Mode includes:

As modulating wave v_refWhen >=1, S_a1=1, S_b2=0；S_b1Compared with carrier wave tri1 by modulating wave and obtain, if v_ref> Tri1, S_b1=0, otherwise S_b1=1；S_a2Compared with carrier wave tri2 by modulating wave and obtain, if v_ref> tri2, S_a2=1, otherwise S_a2= 0；

As modulating wave v_ref< when 1, then S_a1=0, S_b2=1；S_b1By modulating wave v_refCompare with carrier wave tri1 and obtain, if v_ref> Tri1, S_b1=0, otherwise S_b1=1；S_a2By modulating wave v_refCompare with carrier wave tri2 and obtain, if v_ref> tri2, S_a2=1, otherwise S_a2=0.

Compared with prior art, the invention have the benefit that

Without passive filtering inductance and in the case of not changing existing topological structure, by new modulation plan Slightly, while output voltage can be made to be five level, it is ensured that parasitic capacitor voltage sum is constant or low frequency variation, restrained effectively The leakage current of cascaded H-bridges.

Accompanying drawing explanation

In order to understand the explanation embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing skill In art description, the required accompanying drawing used is briefly described.Accompanying drawing in describing below is some embodiments of the present invention, right In those of ordinary skill in the art, on the premise of not paying creative work, it is also possible to obtain other according to these accompanying drawings Accompanying drawing.

The schematic flow diagram of a kind of drain current suppressing method that Fig. 1 provides for the embodiment of the present invention.

The schematic flow diagram of the another kind of drain current suppressing method that Fig. 2 provides for the embodiment of the present invention.

The schematic diagram of two module-cascade H bridge photovoltaic DC-to-AC converters that Fig. 3 provides for the embodiment of the present invention.

Two module-cascade H bridge photovoltaic DC-to-AC converter equivalent models that Fig. 4 provides for the embodiment of the present invention.

The first Switch State Combination in Power Systems that Fig. 5 provides for the embodiment of the present invention realize schematic diagram.

The second Switch State Combination in Power Systems that Fig. 6 provides for the embodiment of the present invention realize schematic diagram.

Detailed description of the invention

For making those skilled in the art be more fully understood that technical scheme, below in conjunction with the accompanying drawings and specific embodiment party The case drain current suppressing method that be applied to cascaded H-bridges five-electrical level inverter a kind of to the present invention is described in further detail.Example Only represent possible change.Unless explicitly requested, otherwise individually components and functionality is optional, and the order operated is permissible Change.The part of some embodiments and feature can be included in or replace the forehead of other embodiments and divide and feature.This The scope of the embodiment of invention includes the gamut of claims, and all obtainable equivalent of claims Thing

Below in conjunction with the accompanying drawings the present invention is described in further details.

Embodiment one

Referring to Fig. 1, Fig. 1 is a kind of electric leakage being applied to cascaded H-bridges five-electrical level inverter that the embodiment of the present invention provides Stream suppressing method schematic flow sheet, the method is applied to non-isolation type tandem photovoltaic combining inverter, described non-isolation type Tandem photovoltaic combining inverter includes two-stage photovoltaic battery panel and two H bridge modules, and described H bridge module includes being arranged at left and right bridge Four switching tubes on arm, wherein, described suppressing method includes:

When the DC input voitage of said two H bridge module is identical, according on four brachium pontis of said two H bridge module The conducting of switching tube respectively obtains, with turning off, 16 on off states that said two H bridge module comprises；

Calculate parasitic capacitor voltage and the institute of each H bridge module that each on off state is corresponding in described 16 on off states State two total parasitic capacitor voltage sums of H bridge module；

Select to form two kinds from all on off states that the parasitic capacitor voltage sum that said two H bridge module is total is identical Switch State Combination in Power Systems；

According to the two Switch State Combination in Power Systems, compared with carrier wave by modulating wave, generate PWM drive signal to institute The switching tube stating two H bridge modules is controlled, thus realizes the suppression of leakage current.

Wherein, when the DC input voitage of said two H bridge module is identical, according to four bridges of said two H bridge module The conducting of the switching tube on arm respectively obtains, with turning off, 16 on off states that said two H bridge module comprises, including:

Definition S_a1/S_b1/S_a2/S_b2It is the switch function of switching tube on four brachium pontis of two H bridge modules, respectively by numeral 0,1 shutoff representing the described each switching tube of H bridge module and opening state, the switch function of the most described four brachium pontis switching tubes S_a1/S_b1/S_a2/S_b216 on off states are produced as follows: 0101,0100,0111,0110,0001,1101 in different conditions combination, 0000,1111,0011,1100,0010,1110,1001,1000,1011,1010。

If the DC input voitage of two H bridge modules is identical and be v_pv, the most each H bridge output-v_pv、0、v_pvThree kinds of level, Total-the 2v of photovoltaic DC-to-AC converter of two H bridge cascades_pv、-v_pv、0、v_pv、2v_pvFive kinds of output levels；Described 16 on off states are End form becomes the-2v of the photovoltaic DC-to-AC converter of two H bridge cascades_pv、-v_pv、0、v_pv、2v_pvFive kinds of output levels.

Wherein, from all on off states that the parasitic capacitor voltage sum that said two H bridge module is total is identical, shape is selected Become two kinds of Switch State Combination in Power Systems, including:

Selection said two H bridge module total parasitic capacitor voltage sum of sening as an envoy to is v_pvAll on off states；And according to electricity When truncation is changed, principle composition the following two kinds Switch State Combination in Power Systems: the 1010-1000-1100-that switching tube action frequency is minimum 0011-0001-0101 and 1010-1110-1100-0011-0111-0101.

Calculate the parasitic capacitor voltage of each H bridge module that each on off state is corresponding in described 16 on off states, bag Include:

$v_{cpv1}=\frac{v_{a1n1}+v_{b1n1}}{2}-\frac{v_{a2n2}-v_{b2n2}}{2}-\frac{v_g}{2}$

$v_{cpv2}=\frac{v_{a1n1}-v_{b1n1}}{2}+\frac{v_{a2n2}+v_{b2n2}}{2}-\frac{v_g}{2}$

Wherein, v_cpv1And v_cpv2It is respectively the parasitic capacitor voltage value of two H bridge modules, v_a1n1、v_b1n1、v_a2n2And v_b2n2Point Wei four brachium pontis outfan a of said two H bridge module₁、b₁、a₂And b₂To common point n₁And n₂Voltage；v_gFor line voltage.

Wherein, when generating PWM drive signal, described carrier wave uses two homophases triangle carrier signal tri1, tri2, wherein tri1>tri2；Described modulating wave v_refModulation degree is 0.9, and first half cycle is positioned on axis of ordinates 1, and the later half cycle is positioned at vertical Coordinate axes less than 1.

When PWM drive signal generates, said two carrier signal tri1, tri2 meet: as described modulating wave v_refIt is more than When 1,1.5 < tri1 < 2,1 < tri2 < 1.5；As described modulating wave v_refDuring less than 1,0.5 < tri1 < 1,0 < tri2 < 0.5.

Wherein, according to the two Switch State Combination in Power Systems, compared with carrier wave by modulating wave, generate PWM and drive letter Number the switching tube of said two H bridge module is controlled, including:

The PWM drive signal of the first described Switch State Combination in Power Systems 1010-1000-1100-0011-0001-0101 generates Mode includes:

As modulating wave v_refWhen >=1, S_a1=1, S_b2=0；S_b1Compared with carrier wave tri2 by modulating wave and obtain, if v_ref> Tri2, S_b1=0, otherwise S_b1=1；S_a2Compared with carrier wave tri1 by modulating wave and obtain, if v_ref> tri1, S_a2=1, otherwise S_a2= 0；

As modulating wave v_ref< when 1, then S_a1=0, S_b2=1；S_b1By modulating wave v_refCompare with carrier wave tri2 and obtain, if v_ref> Tri2, S_b1=0, otherwise S_b1=1；S_a2By modulating wave v_refCompare with carrier wave tri1 and obtain, if v_ref> tri1, S_a2=1, otherwise S_a2=0；

The PWM drive signal of Switch State Combination in Power Systems 1010-1110-1100-0011-0111-0101 described in the second generates Mode includes:

As modulating wave v_refWhen >=1, S_a1=1, S_b2=0；S_b1Compared with carrier wave tri1 by modulating wave and obtain, if v_ref> Tri1, S_b1=0, otherwise S_b1=1；S_a2Compared with carrier wave tri2 by modulating wave and obtain, if v_ref> tri2, S_a2=1, otherwise S_a2= 0；

As modulating wave v_ref< when 1, then S_a1=0, S_b2=1；S_b1By modulating wave v_refCompare with carrier wave tri1 and obtain, if v_ref> Tri1, S_b1=0, otherwise S_b1=1；S_a2By modulating wave v_refCompare with carrier wave tri2 and obtain, if v_ref> tri2, S_a2=1, otherwise S_a2=0.

The present embodiment, by new modulation strategy, while output voltage can be made to be five level, it is ensured that parasitic capacitor voltage Sum is constant or low frequency variation, restrained effectively the leakage current of cascaded H-bridges, solves non-isolation type Cascade H in prior art Bridge photovoltaic combining inverter can not effectively suppress the problem of leakage current, has reached preferably to suppress non-isolation type cascaded H-bridges photovoltaic The effect of combining inverter leakage current.

Embodiment two

The schematic diagram of two module-cascade H bridge photovoltaic DC-to-AC converters that Fig. 3 provides for the embodiment of the present invention.In figure, C_pv1With C_pv2For the parasitic capacitance between photovoltaic array and the earth, v_pv1And v_pv2It is the DC input voitage of two modules, C_in1And C_in2For DC side input capacitance, L₁And L₂For grid side filter inductance, R₁And R₂For the dead resistance of grid side filter inductance, v_gFor electrical network Voltage.

See Fig. 2, be embodied as step as follows:

Step a, if the DC input voitage of two H bridge modules is equal, and is v_pv, it is all that row write out that two modules comprise 16 on off state (S_a1/S_b1/S_a2/S_b2), and calculate the parasitic capacitor voltage of each module corresponding to each on off state and total Parasitic capacitor voltage sum.

Wherein, S_a1The switch function of pipe, S on the left brachium pontis of representation module 1_b1The switch letter of pipe on the right brachium pontis of representation module 1 Number, S_a2The switch function of pipe, S on the left brachium pontis of representation module 2_b2The switch function of pipe on the right brachium pontis of representation module 2.It addition, it is each Switch function can take 0 or 1,1 representation switch pipe conducting, and 0 representation switch pipe turns off, the complementation work of switching tube up and down of each brachium pontis Make.

Fig. 4 is the cascaded H-bridges photovoltaic DC-to-AC converter equivalent model of two modules.Wherein, v_a1n1、v_b1n1、v_a2n2And v_b2n2Respectively For each brachium pontis outfan a₁、b₁、a₂And b₂To common point n₁And n₂Voltage.As a example by the positive half period of power network current, it is assumed that net Side filter inductance L₁=L₂, owing to leakage current is the least, therefore L₁And L₂The voltage approximately equal of upper generation and be v_L, meanwhile, the filter of net side The voltage of ripple inductance parasitic resistance is v_R；

According to Fig. 4, Kirchhoff's law can obtain formula:

$\left\{\begin{array}{c}-v_{a1n1}+v_L+v_R+v_g+v_{cpv1}=0\\ -v_{b2n2}-v_L-v_R+v_{cpv2}=0\\ -v_{b1n1}+v_{a2n2}-v_{cpv2}+v_{cpv1}=0\end{array}\right.$

Can be obtained by above three formulas:

$v_{cpv1}=\frac{v_{a1n1}+v_{b1n1}}{2}-\frac{v_{a2n2}-v_{b2n2}}{2}-\frac{v_g}{2}$

$v_{cpv2}=\frac{v_{a1n1}-v_{b1n1}}{2}+\frac{v_{a2n2}+v_{b2n2}}{2}-\frac{v_g}{2}$

Due to line voltage v_gPredominantly power frequency component, the least to the influence of leakage current in parasitic capacitance, analysis hereafter Do not consider further that, therefore parasitic capacitance C_pv1And C_pv2Voltage v_cpv1And v_cpv2Can be expressed as:

$v_{cpv1}^{\&prime;}=\frac{v_{a1n1}+v_{b1n1}}{2}-\frac{v_{a2n2}-v_{b2n2}}{2}$

$v_{cpv2}^{\&prime;}=\frac{v_{a1n1}-v_{b1n1}}{2}+\frac{v_{a2n2}+v_{b2n2}}{2}$

Table 1 is on off state and the parasitic capacitor voltage of two H bridge modules, wherein v_abFor total output voltage, v_cpv1For H The parasitic capacitor voltage of bridge module 1, v_cpv2For the parasitic capacitor voltage of H bridge module 2, v_cpv1+v_cpv2It is posting of two H bridge modules Raw capacitance voltage sum.It can be seen that two H bridge modules has five level outputs, it is respectively as follows: 2v_pv、v_pv、0、-v_pvWith- 2v_pv.Different switch function S_a1/S_b1/S_a2/S_b2When controlling switching tube, make the parasitic capacitor voltage sum of two H bridge modules v_cpv1+v_cpv20～2v_pvBetween there is high frequency change, thus produce leakage current.

The on off state of 1 two H bridge modules of table and parasitic capacitor voltage

Step b, the result calculated according to step 1, selecting parasitic capacitor voltage sum of sening as an envoy to is v_pvAll switch shapes State, and when switching according to level, the principle composition the following two kinds Switch State Combination in Power Systems that switching tube action frequency is minimum, it is respectively as follows: 1010-1000-1100-0011-0001-0101 and 1010-1110-1100-0011-0111-0101.

Step c: the Switch State Combination in Power Systems selected according to step 2, generates PWM drive signal switch tube and is controlled, its Implementation is modulating wave and two synchronous carrier waves compare and obtain pwm signal.

Wherein, wherein T is modulating wave v_refIn the cycle, two carrier signals are tri1, tri2, meet: work as v_refDuring more than 1, 1.5 < tri1 < 2,1 < tri2 < 1.5；Work as v_refDuring less than 1,0.5 < tri1 < 1,0 < tri2 < 0.5.Modulating wave v_refModulation degree is 0.9, and first half cycle is positioned on axis of ordinates 1, the later half cycle is positioned at axis of ordinates less than 1.

Realizing the first Switch State Combination in Power Systems of embodiment as shown in Figure 5, concrete manner of comparison is as follows:

(1) as modulating wave v_refWhen >=1, S_a1=1, S_b2=0；S_b1Compared with carrier wave tri2 by modulating wave and obtain, if v_ref> Tri2, S_b1=0, otherwise S_b1=1；S_a2Compared with carrier wave tri1 by modulating wave and obtain, if v_ref> tri1, S_a2=1, otherwise S_a2= 0；

(2) as modulating wave v_ref< when 1, then S_a1=0, S_b2=1；S_b1By modulating wave v_refCompare with carrier wave tri2 and obtain, if v_ref> tri2, S_b1=0, otherwise S_b1=1；S_a2By modulating wave v_refCompare with carrier wave tri1 and obtain, if v_ref> tri1, S_a2=1, no Then S_a2=0；

Realizing the second Switch State Combination in Power Systems of embodiment as shown in Figure 6, concrete manner of comparison is as follows:

(1) as modulating wave v_refWhen >=1, S_a1=1, S_b2=0；S_b1Compared with carrier wave tri1 by modulating wave and obtain, if v_ref> Tri1, S_b1=0, otherwise S_b1=1；S_a2Compared with carrier wave tri2 by modulating wave and obtain, if v_ref> tri2, S_a2=1, otherwise S_a2= 0；

(2) as modulating wave v_ref< when 1, then S_a1=0, S_b2=1；S_b1By modulating wave v_refCompare with carrier wave tri1 and obtain, if v_ref> tri1, S_b1=0, otherwise S_b1=1；S_a2By modulating wave v_refCompare with carrier wave tri2 and obtain, if v_ref> tri2, S_a2=1, no Then S_a2=0；

The method is used to pass through new modulation strategy, while output voltage can be made to be five level, it is ensured that parasitic capacitance electricity Press sum constant or low frequency variation, restrained effectively the leakage current of cascaded H-bridges.

Above content is to combine concrete preferred implementation further description made for the present invention, it is impossible to assert Being embodied as of the present invention is confined to these explanations.For general technical staff of the technical field of the invention, On the premise of present inventive concept, it is also possible to make some simple deduction or replace, all should be considered as belonging to the present invention's Protection domain.

Claims (8)

1. it is applied to a drain current suppressing method for cascaded H-bridges five-electrical level inverter, is applied to non-isolation type tandem photovoltaic also Net inverter, described non-isolation type tandem photovoltaic combining inverter includes two-stage photovoltaic battery panel and two H bridge modules, described H Bridge module includes four switching tubes being arranged on the brachium pontis of left and right, it is characterised in that described suppressing method includes:

When the DC input voitage of said two H bridge module is identical, according to the switch on four brachium pontis of said two H bridge module The conducting of pipe respectively obtains, with turning off, 16 on off states that said two H bridge module comprises；

Calculate the parasitic capacitor voltage and described two of each H bridge module that each on off state is corresponding in described 16 on off states The parasitic capacitor voltage sum that individual H bridge module is total；

Select to form two kinds of switches from all on off states that the parasitic capacitor voltage sum that said two H bridge module is total is identical Combinations of states；

According to the two Switch State Combination in Power Systems, compared with carrier wave by modulating wave, generate PWM drive signal to described two The switching tube of individual H bridge module is controlled, thus realizes the suppression of leakage current.

Suppressing method the most according to claim 1, it is characterised in that at the DC input voitage of said two H bridge module Time identical, conducting and shutoff according to the switching tube on four brachium pontis of said two H bridge module respectively obtain said two H bridge mould 16 on off states that block comprises, including:

Definition S_a1/S_b1/S_a2/S_b2It is the switch function of switching tube on four brachium pontis of two H bridge modules, respectively with 0,1 generation of numeral The shutoff of each switching tube of H bridge module described in table and opening state, the switch function S of the most described four brachium pontis switching tubes_a1/S_b1/ S_a2/S_b216 on off states are produced as follows in different conditions combination:

0101,0100,0111,0110,0001,1101,0000,1111,0011,1100,0010,1110,1001,1000, 1011,1010。

Suppressing method the most according to claim 2, it is characterised in that if the DC input voitage of two H bridge modules is identical And be v_pv, the most each H bridge output-v_pv、0、v_pvThree kinds of level, the total-2v of photovoltaic DC-to-AC converter of two H bridge cascades_pv、-v_pv、0、 v_pv、2v_pvFive kinds of output levels；Described 16 on off states ultimately form the-2v of the photovoltaic DC-to-AC converter of two H bridge cascades_pv、- v_pv、0、v_pv、2v_pvFive kinds of output levels.

Suppressing method the most according to claim 3, it is characterised in that from the parasitic capacitance electricity that said two H bridge module is total All on off states that pressure sum is identical select form two kinds of Switch State Combination in Power Systems, including:

Selection said two H bridge module total parasitic capacitor voltage sum of sening as an envoy to is v_pvAll on off states；And cut according to level When changing, principle composition the following two kinds Switch State Combination in Power Systems: the 1010-1000-1100-0011-that switching tube action frequency is minimum 0001-0101 and 1010-1110-1100-0011-0111-0101.

Suppressing method the most according to claim 4, it is characterised in that calculate each switch shape in described 16 on off states The parasitic capacitor voltage of each H bridge module that state is corresponding, including:

$v_{cpv1}=\frac{v_{a1n1}+v_{b1n1}}{2}-\frac{v_{a2n2}-v_{b2n2}}{2}-\frac{v_g}{2}$

$v_{cpv2}=\frac{v_{a1n1}+v_{b1n1}}{2}+\frac{v_{a2n2}+v_{b2n2}}{2}-\frac{v_g}{2}$

Wherein, v_cpv1And v_cpv2It is respectively the parasitic capacitor voltage value of two H bridge modules, v_a1n1、v_b1n1、v_a2n2And v_b2n2It is respectively Four brachium pontis outfan a of said two H bridge module₁、b₁、a₂And b₂To common point n₁And n₂Voltage；v_gFor line voltage.

Suppressing method the most according to claim 5, it is characterised in that when generating PWM drive signal, described carrier wave uses two Individual homophase triangle carrier signal tri1, tri2, wherein tri1 > tri2；Described modulating wave v_refModulation degree is 0.9, and first half cycle Being positioned on axis of ordinates 1, the later half cycle is positioned at axis of ordinates less than 1.

Suppressing method the most according to claim 6, it is characterised in that when PWM drive signal generates, said two carrier wave Signal tri1, tri2 meet: as described modulating wave v_refDuring more than 1,1.5 < tri1 < 2,1 < tri2 < 1.5；When described modulating wave v_refDuring less than 1,0.5 < tri1 < 1,0 < tri2 < 0.5.

Suppressing method the most according to claim 7, it is characterised in that according to the two Switch State Combination in Power Systems, by adjusting Ripple processed compares with carrier wave, generates PWM drive signal and is controlled the switching tube of said two H bridge module, including:

The PWM drive signal generating mode of the first described Switch State Combination in Power Systems 1010-1000-1100-0011-0001-0101 Including:

As modulating wave v_refWhen >=1, S_a1=1, S_b2=0；S_b1Compared with carrier wave tri2 by modulating wave and obtain, if v_ref> tri2, S_b1 =0, otherwise S_b1=1；S_a2Compared with carrier wave tri1 by modulating wave and obtain, if v_ref> tri1, S_a2=1, otherwise S_a2=0；

As modulating wave v_ref< when 1, then S_a1=0, S_b2=1；S_b1By modulating wave v_refCompare with carrier wave tri2 and obtain, if v_ref> Tri2, S_b1=0, otherwise S_b1=1；S_a2By modulating wave v_refCompare with carrier wave tri1 and obtain, if v_ref> tri1, S_a2=1, otherwise S_a2=0；

The PWM drive signal generating mode of Switch State Combination in Power Systems 1010-1110-1100-0011-0111-0101 described in the second Including:

As modulating wave v_refWhen >=1, S_a1=1, S_b2=0；S_b1Compared with carrier wave tri1 by modulating wave and obtain, if v_ref> tri1, S_b1 =0, otherwise S_b1=1；S_a2Compared with carrier wave tri2 by modulating wave and obtain, if v_ref> tri2, S_a2=1, otherwise S_a2=0；

As modulating wave v_ref< when 1, then S_a1=0, S_b2=1；S_b1By modulating wave v_refCompare with carrier wave tri1 and obtain, if v_ref> Tri1, S_b1=0, otherwise S_b1=1；S_a2By modulating wave v_refCompare with carrier wave tri2 and obtain, if v_ref> tri2, S_a2=1, otherwise S_a2=0.