CN103929052A - Output filter of grid-connected inverter - Google Patents

Abstract

The embodiment of the invention discloses an output filter of a grid-connected inverter. The output filter comprises a passive filter, damping resistors and LC series resonance circuits. The passive filter comprises N filter capacitor branches which are connected in parallel, and the damping resistors are connected to each of M filter capacitor branches which are connected in parallel in series, wherein N and M are positive integers and M is equal to or larger than 1 but smaller than or equal to N. The LC series resonance circuits are connected to the damping resistors in parallel. The impedance of the LC series resonance circuits at the switching frequency points is lower than the resistance value of the damping resistors, and the purpose of reducing the power loss on the damping resistors on the premise of guaranteeing the damping effect is achieved.

Description

A kind of combining inverter output filter

Technical field

The present invention relates to electric and electronic technical field, more particularly, relate to a kind of combining inverter output filter.

Background technology

For the combining inverter that adopts pulse modulation technology, in its output waveform, must contain the harmonic component relevant with carrier wave, and then cause harmonic pollution, therefore be necessary to set up filter with this part harmonic component of filtering at the outlet side of combining inverter, LCL filter and LC filter are widely used two kinds of passive filters wherein.

Consider that resonance problems all easily appears in LCL filter and LC filter, therefore need to each filter capacitor in its filter-capacitor circuit when practical application on respectively series damping resistor to avoid resonance.

Yet the negative issue that the introducing of damping resistance produces is but to have brought extra power loss thereupon, therefore, how guaranteeing, under the prerequisite of damping, to reduce the power loss on damping resistance, become those skilled in the art's problem demanding prompt solution.

Summary of the invention

In view of this, the invention provides a kind of combining inverter output filter, to realize, guaranteeing, under the prerequisite of damping, to reduce the power loss on damping resistance.

A combining inverter output filter, comprising:

Passive filter, described passive filter comprises N filter capacitor branch road parallel with one another;

Be connected on M the damping resistance on each filter capacitor in described filter capacitor branch road parallel with one another, wherein N and M are positive integer and 1≤M≤N;

And be connected in parallel on the LC series resonant circuit on damping resistance described in each; Wherein, described LC series resonant circuit is the resistance lower than described damping resistance in the impedance of switching frequency point, and in the impedance of the resonant frequency point of described combining inverter output filter the resistance higher than described damping resistance.

Wherein, the resonance frequency of described LC series resonant circuit equals described switching frequency.

Wherein, the inductance parameters of described LC series resonant circuit meets

$\begin{array}{cc}{C}_n=(1-\frac{1}{k^2})\frac{1}{{\mathrm{\ω}}_{\mathrm{res}}{k}_d{R}_d},& L_n=\frac{1}{{\mathrm{\ω}}_{\mathrm{chop}}^2{C}_n}\end{array}$

In formula, C_ncapacitance for electric capacity in described LC series resonant circuit; L_ninductance value for inductance in described LC series resonant circuit; ω_resresonance frequency for described combining inverter output filter; R_dresistance for described damping resistance; K=ω_chop/ ω_res, ω_chopfor angular frequency corresponding to the switching frequency of described combining inverter; k_d=Z_lC/ R_d, Z_lCfor the impedance of described LC series resonant circuit at the resonant frequency point of described combining inverter, R_dresistance for described damping resistance.

Wherein, described k_d>2.

Alternatively, also comprise: be connected in parallel on the by-pass inductor on damping resistance described in each.

Wherein, described passive filter is LC filter.

Wherein, described passive filter is LCL filter.

Wherein, described N=1.

Wherein, described N=2, described M=1.

Wherein, described N filter capacitor branch road parallel with one another is delta connection circuit or is star connection, Y connection circuit.

From above-mentioned technical scheme, can find out, the present invention is after being filter capacitor series damping resistor in passive filter, it is also each damping resistance LC series resonant circuit in parallel, due to this LC series resonant circuit in the impedance of switching frequency point the resistance lower than damping resistance, therefore high frequency ripple electric current that can by-pass overdamp resistance, reduces the loss of damping resistance; Meanwhile, due to this LC series resonant circuit in the impedance of the resonant frequency point of combining inverter output filter the resistance higher than damping resistance, therefore can when reducing damping resistance loss, still ensure the damping characteristic that it is good.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the disclosed a kind of LCL filter construction schematic diagram of prior art;

Fig. 2 is the disclosed a kind of LC filter construction schematic diagram of prior art;

Fig. 3 is the disclosed a kind of combining inverter output filter structural representation of the embodiment of the present invention one;

Fig. 4 is the disclosed a kind of combining inverter output filter structural representation of the embodiment of the present invention two;

Fig. 5 is the disclosed a kind of combining inverter output filter structural representation of the embodiment of the present invention three;

Fig. 6 is the disclosed a kind of combining inverter output filter structural representation of the embodiment of the present invention four;

Fig. 7 is the impedance contrast figure of the disclosed a kind of LC series resonant circuit of the embodiment of the present invention four and damping resistance;

Fig. 8 is the disclosed a kind of brachium pontis electric current Bode diagram while having or not LC series resonant circuit of the embodiment of the present invention four;

Fig. 9 is the disclosed a kind of grid-connected current Bode diagram while having or not LC series resonant circuit of the embodiment of the present invention four;

Figure 10 is the disclosed a kind of simulation waveform figure of the embodiment of the present invention four;

Figure 11 flows through near the high frequency ripple current amplitude comparison diagram of switching frequency of damping resistance while being the disclosed a kind of LC of the having or not series resonant circuit of the embodiment of the present invention four;

Figure 12 is near disclosed a kind of grid-connected current ripple amplitude comparison diagram switching frequency while having or not LC series resonant circuit of the embodiment of the present invention four.

Embodiment

In existing combining inverter output filter, these two kinds of passive filters of LCL filter and LC filter have stronger damping capacity to the high frequency ripple in combining inverter output waveform (being higher harmonic components), its good filter effect significantly reduces the high frequency ripple amplitude in grid-connected current, therefore enjoys favor.

Concrete, the circuit structure of LCL filter as shown in Figure 1, comprising: the inverter side reactor 11 between access grid-connected inverter 20 and electrical network 30, filter-capacitor circuit 13 and grid side reactor 12 in turn.The circuit structure of LC filter as shown in Figure 2, comprising: the inverter side reactor 11 between access grid-connected inverter 20 and electrical network 30 and filter-capacitor circuit 13 in turn.

The difference of LC filter and LCL filter is just: LC filter has been cast out grid side reactor 12, thereby it has formed equivalent LCL filter as an alternative by existing transformer leakage reactance and electric network impedance 31 in electrical network 20, and then reduced cost and improved the efficiency of combining inverter 20.But no matter be that LCL filter or LC filter all may occur resonance problems, and LC filter is owing to having saved grid side reactor 12, makes its resonance frequency affected by electric network impedance and becomes large, therefore more easily occurs resonance compared to LCL filter.

Solving resonance problems will increase the system damping of filter, although the mode of series damping resistor can reach good damping on employing each filter capacitor in filter-capacitor circuit 13, but when the electric current of combining inverter 20 outputs simultaneously flows through this damping resistance, will inevitably produce extra damping resistance loss, cause the significant wastage of electric energy.Therefore, the present invention is devoted in the ohmically power loss of prerequisite decline low resistance that guarantees the damping of damping resistance, by the filter-capacitor circuit 13 of LC filter or LCL filter is improved, following a plurality of combining inverter output filter with novel filter-capacitor circuit is disclosed.

Below in conjunction with the accompanying drawing in various embodiments of the present invention, the technical scheme in various embodiments of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Embodiment based in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.

Embodiment mono-:

Referring to Fig. 3, the disclosed combining inverter output filter of the present embodiment one, comprising:

LCL filter, comprises inverter side reactor 11, grid side reactor 12 and filter-capacitor circuit 13;

Be connected on each the filter capacitor C in filter-capacitor circuit 13_fon damping resistance R_d;

And be connected in parallel on each damping resistance R_don LC series resonant circuit, described LC series resonant circuit in the impedance of switching frequency point lower than damping resistance R_dresistance, and in the impedance of the resonant frequency point of described combining inverter output filter higher than damping resistance R_dresistance.

The present embodiment one is by being each filter capacitor C_fseries and parallel has the damping resistance R of LC series resonant circuit_dthereby, build and obtained a kind of combining inverter output filter with novel filter-capacitor circuit 103, realized and guaranteed damping resistance R_dthe prerequisite of damping under, reduce damping resistance R_don power loss, be analyzed as follows:

Known LC series resonant circuit is a kind of inductance L by being in series_nand capacitor C_nthe resonant circuit forming, its impedance magnitude at each Frequency point can be by regulating inductance L_nand capacitor C_nparameter value determine;

For each filter capacitor C in filter-capacitor circuit 13 only_fupper series damping resistor R_dfilter-capacitor circuit, flow through damping resistance R_delectric current comprise the fundamental current that high frequency ripple electric current and line voltage produce on filter capacitor, and be each damping resistance R_dafter LC series resonant circuit in parallel, by inductance L is set_nand capacitor C_nparameter value, can make this LC series resonant circuit in the impedance of high band lower than damping resistance R_dresistance, so now, this LC series resonant circuit just can play by-pass through damping resistance R_dthe effect of high frequency ripple electric current, thereby reduced the described high frequency ripple electric current damping resistance R that flows through_dtime the power loss that produces, realized damping resistance R_dlow-loss;

In addition, for guaranteeing, realizing damping resistance R_dlow-loss while, can be to damping resistance R_ddamping cause too large impact, the present embodiment also arrange this LC series resonant circuit in the impedance at the resonance frequency place of described combining inverter output filter higher than damping resistance R_dresistance, damping resistance R when solving resonance problems like this_dmany the going of can trying one's best consumes and is enough to cause the energy of described combining inverter output filter generation resonance, thereby makes the introducing of this LC series resonant circuit can be to damping resistance R_dexisting damping causes too large impact.

Preferably, consider the disclosed LC series resonant circuit of the present embodiment at the impedance phase of high band to damping resistance R_dresistance lower, damping resistance R_dloss just less; And described LC series resonant circuit at the impedance phase of high band to damping resistance R_dresistance higher, damping resistance R_ddamping just better, so the present embodiment is by arranging most preferred inductance L for described LC series resonant circuit_nparameter and capacitor C_nparameter, makes described LC series resonant circuit relative damping resistance R_dresistance can reach minimum at described switching frequency place, and make the described LC series resonant circuit can be far above damping resistance R in the impedance at the resonance frequency place of described combining inverter output filter simultaneously_dresistance.Concrete, determine described most preferred inductance L_nparameter and capacitor C_nthe process of parameter is as follows:

First, known LC series resonant circuit has in the characteristic in resonance frequency place impedance minimum, and in the frequency spectrum of described high frequency ripple electric current, amplitude is the highest, and what have the greatest impact is that frequency is the high frequency ripple electric current of switching frequency, therefore the resonance frequency that the present embodiment arranges described LC series resonant circuit equals described switching frequency, to realize maximum reduction damping resistance R_dloss.The resonance frequency f of wherein said LC series resonant circuit_chopexpression formula is as follows

$f_{\mathrm{chop}}=1/\left(2\mathrm{\π}\sqrt{L_n{C}_n}\right)$

In formula, L_nand C_nbe respectively inductance L_nparameter (being inductance value) and capacitor C_nparameter (being capacitance), is meeting f_chopreach in the situation of described switching frequency inductance L_nand capacitor C_nthere are many group parameter values optional, not unique definite.

Then, according to the impedance expression of described LC series resonant circuit (being designated as expression formula 1), and angular frequency expression formula (being designated as expression formula 2) corresponding to the resonance frequency of described LC series resonant circuit, derive and obtain described LC series resonant circuit at the impedance expression (being designated as expression formula 3) at the resonance frequency place of described combining inverter output filter;

Wherein, described expression formula 1 is$Z_{\mathrm{LC}}\left(s\right)=\frac{s^2{L}_n{C}_n+s{C}_n{R}_n+1}{s{C}_n},$

Described expression formula 2 is

Described expression formula 3 is Z$|_{\mathrm{\ω}={\mathrm{\ω}}_{\mathrm{res}}}^{\mathrm{LC}}=(1-\frac{1}{k^2})\frac{1}{{\mathrm{\ω}}_{\mathrm{res}}{C}_n},$

In above-mentioned expression formula, L_nfor inductance L_ninductance value, C_nfor capacitor C_ncapacitance, R_nfor inductance L_ninternal resistance, ω_resfor angular frequency corresponding to the resonance frequency of described combining inverter output filter, ω_chopfor angular frequency corresponding to the resonance frequency of described LC series resonant circuit, k=ω_chop/ ω_res.

Then, according to expression formula 2 and expression formula 3, calculate inductance L_nand capacitor C_nparameter value,

$\begin{array}{cc}{C}_n=(1-\frac{1}{k^2})\frac{1}{{\mathrm{\ω}}_{\mathrm{res}}{k}_d{R}_d},& L_n=\frac{1}{{\mathrm{\ω}}_{\mathrm{chop}}^2{C}_n},\end{array}$

In above-mentioned expression formula, k_d=Z_lC|_{ω=ω res}/ R_d, R_dfor damping resistance R_dresistance.

Wherein about k_dvalue be analyzed as follows, on the one hand, enough wide at the trap frequency band of the switching frequency point of described combining inverter for guaranteeing described LC series resonant circuit, thus make described LC series resonant circuit by-pass switch frequency and near the high frequency ripple electric current of switching frequency, so k simultaneously_dvalue should choose enough little; On the other hand, for the introducing that guarantees described LC series resonant circuit is to damping resistance R_dthe impact of damping as far as possible little, k so_dvalue should choose enough large, comprehensively this two aspect is considered, finally can set k_d>2, but do not limit to.

Seen from the above description, the present embodiment one is after being filter capacitor series damping resistor in passive filter, it is also each damping resistance LC series resonant circuit in parallel, due to this LC series resonant circuit in the impedance of switching frequency point the resistance lower than damping resistance, therefore high frequency ripple electric current that can by-pass overdamp resistance, reduces the loss of damping resistance; Meanwhile, due to this LC series resonant circuit in the impedance of the resonant frequency point of combining inverter output filter the resistance higher than damping resistance, therefore can when reducing damping resistance loss, still ensure the damping characteristic that it is good.

Embodiment bis-:

Text description based on embodiment mono-and accompanying drawing thereof, the present embodiment two discloses another combining inverter output filter, referring to Fig. 4, also comprises: be connected in parallel on each damping resistance R_don by-pass inductor L_d.

Due to by-pass inductor L_din the impedance of first-harmonic frequency range compared to damping resistance R_dresistance less, therefore can by-pass overdamp resistance R_dfundamental current, thereby the present embodiment two has reached and has utilized described LC series resonant circuit by-pass overdamp resistance R_dhigh frequency ripple electric current time, also utilize by-pass inductor L_dby-pass overdamp resistance R_dthe object of fundamental current, compared to embodiment mono-, the present embodiment two has further reduced damping resistance R_don power loss.

Embodiment tri-:

Referring to Fig. 5, the present embodiment three discloses another combining inverter output filter, comprising:

LCL filter, comprises inverter side reactor 11, grid side reactor 12 and filter-capacitor circuit 13, and wherein filter-capacitor circuit 13 comprises 2 filter capacitor branch roads parallel with one another;

Be connected on each the filter capacitor C in 1 described filter capacitor branch road_f1on damping resistance R_d;

And be connected in parallel on each damping resistance R_don LC series resonant circuit, wherein said LC series resonant circuit in the impedance of switching frequency point lower than damping resistance R_dresistance, and in the impedance of the resonant frequency point of described combining inverter output filter higher than damping resistance R_dresistance.

The present embodiment three with the difference part of embodiment mono-is, first the present embodiment is equivalent to filter-capacitor circuit 13 2 branch roads that are in parallel, and therein on each filter capacitor of 1 branch road series and parallel have the damping resistance R of LC series resonant circuit_dthereby, obtained a kind of preferred novel filter-capacitor circuit 103, be analyzed as follows:

For described LCL filter, damping resistance R_dintroducing will inevitably increase its filter-capacitor circuit in the impedance of high band, cause described filter-capacitor circuit to weaken the inhibition of high frequency ripple electric current; And after the filter-capacitor circuit of described LCL filter is equivalent to 2 parallel branches, due to the damping resistance R that connected on 1 branch road therein only_d, introduce and have damping resistance R so_dbranch road have damping resistance R with not introducing_dbranch circuit parallel connection after equiva lent impedance will inevitably reduce, thereby effectively reduce filter-capacitor circuit in the impedance of high band, improved the filter effect of filter;

So, follow-up by being each damping resistance R_ddescribed LC series resonant circuit in parallel, can guarantee, under the prerequisite of damping, to reduce damping resistance R_don power loss.

Seen from the above description, the present embodiment three is by filter-capacitor circuit 13 being equivalent to 2 branch roads that are in parallel, and therein on each filter capacitor of 1 branch road series and parallel have the damping resistance R of LC series resonant circuit_dthereby, guaranteeing, under the prerequisite of the good filter effect of damping, to have reduced damping resistance R_don power loss.Wherein it should be noted that, for the scheme of expanding according to the present embodiment, as filter-capacitor circuit 13 equivalences being split as to N filter capacitor branch road parallel with one another, and series and parallel has the damping resistance R of LC series resonant circuit on M described filter capacitor branch road parallel with one another_dscheme (wherein N and M are positive integer and 1≤M≤N), its principle is consistent with the present embodiment three principles, repeats no longer one by one herein.In addition consider that branch road in parallel too much can increase damping resistance R_dthe weakening intensity of damping characteristic, therefore using N=2 as preferred embodiment.

Embodiment tetra-:

Text description based on embodiment tri-and accompanying drawing thereof, the present embodiment four discloses another combining inverter output filter, referring to Fig. 6, also comprises: be connected in parallel on each damping resistance R_don by-pass inductor L_d.

Consistent with the present embodiment two, by-pass inductor L_deffect be by-pass overdamp resistance R_dfundamental current, to reduce described fundamental current, flow through damping resistance R_dtime the power loss that produces, compare embodiment tri-, the present embodiment four has further reduced damping resistance R_dloss.

Figure below 7-12 shows the practical application effect of product described in the present embodiment four, so that those skilled in the art can get more information about the superiority of this product, wherein:

Fig. 7 is described LC series resonant circuit and damping resistance R_dimpedance contrast figure (curve 1 represents the impedance frequency characteristics curve of described LC series resonant circuit, and curve 1 represents damping resistance R_dimpedance frequency characteristics curve), can find out, at the resonant frequency point of described combining inverter output filter, the impedance of described LC series resonant circuit is at least damping resistance R_d2 times of resistance, and at described switching frequency point, the impedance of described LC series resonant circuit is far below damping resistance R_dresistance.Explanation thus, described LC series resonant circuit is guaranteeing damping resistance R_din the time of damping characteristic as far as possible many bypass the frequency high frequency ripple electric current that is switching frequency, reduced damping resistance R_dloss.

Fig. 8 is brachium pontis electric current (output current of the inverter side reactor 11) Bode diagram while having or not described LC series resonant circuit, can find out, compare the brachium pontis electric current of removing after described LC series resonant circuit, after increasing described LC series resonant circuit, resonance peak just increases a little, thereby the introducing of described LC series resonant circuit is to damping resistance R_ddamping impact less.

Fig. 9 is grid-connected current (input current of the net side inverter 12) Bode diagram while having or not described LC series resonant circuit, can find out, and due near the low impedance characteristic of described LC series resonant circuit described switching frequency, itself and damping resistance R_dafter parallel connection, strengthened near the filter effect of switching frequency.

Figure 10 is the simulation waveform figure of this product, can find out, the bypass of described LC series resonant circuit the most high frequency ripple electric current (referring to curve 1) of opening frequent rate place, by-pass inductor L_dbypass most fundamental current (referring to curve 2), flow through damping resistance R_dbe mainly the resonance frequency place of described combining inverter output filter and near the high frequency ripple electric currents (referring to curve 3) 2 times of switching frequencies.

Figure 11 flows through damping resistance R when having or not described LC series resonant circuit_dswitching frequency near high frequency ripple current amplitude comparison diagram, can find out, after introducing described LC series resonant circuit, near the high frequency ripple current amplitude 3000 hertz of switching frequencies significantly reduces, and has greatly reduced damping resistance R_dloss.

Figure 12 is near grid-connected current ripple amplitude comparison diagram switching frequency while having or not described LC series resonant circuit, can find out, compared to only introducing and have damping resistance R_dscheme, after introducing described LC series resonant circuit in corresponding grid-connected current (i.e. the input current of net side inverter 12), near the high frequency ripple current amplitude 3000 hertz of switching frequencies significantly reduces, and has strengthened filter effect.

In sum, the present invention is after being filter capacitor series damping resistor in passive filter, it is also each damping resistance LC series resonant circuit in parallel, due to this LC series resonant circuit in the impedance of switching frequency point the resistance lower than damping resistance, therefore high frequency ripple electric current that can by-pass overdamp resistance, reduces the loss of damping resistance; Meanwhile, due to this LC series resonant circuit in the impedance of the resonant frequency point of combining inverter output filter the resistance higher than damping resistance, therefore can when reducing damping resistance loss, still ensure the damping characteristic that it is good.

Finally it should be noted that, because LCL filter is to be obtained in conjunction with transformer leakage reactance and electric network impedance 31 equivalences by LC filter, therefore above-mentionedly for usining the analytic process of LCL filter as the combining inverter output filter of passive filter, be equally applicable to using LC filter as the combining inverter output filter of passive filter, repeat no more herein.In addition, the circuit connecting structure of the filter capacitor branch road in various embodiments of the present invention does not limit to, and can be delta connection, can be star connection, Y connection yet, and various embodiments of the present invention respective figure is only that described delta connection structure is schematically provided.

In this specification, each embodiment adopts the mode of going forward one by one to describe, and each embodiment stresses is the difference with other embodiment, between each embodiment identical similar part mutually referring to.

Above-mentioned explanation to the disclosed embodiments, makes professional and technical personnel in the field can realize or use the present invention.To the multiple modification of these embodiment, will be apparent for those skilled in the art, General Principle as defined herein can be in the situation that do not depart from the spirit or scope of the embodiment of the present invention, realization in other embodiments.Therefore, the embodiment of the present invention will can not be restricted to these embodiment shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.

Claims (10)

1. a combining inverter output filter, is characterized in that, comprising:

Passive filter, described passive filter comprises N filter capacitor branch road parallel with one another;

Be connected on M the damping resistance on each filter capacitor in described filter capacitor branch road parallel with one another, wherein N and M are positive integer and 1≤M≤N;

And be connected in parallel on the LC series resonant circuit on damping resistance described in each; Wherein, described LC series resonant circuit is the resistance lower than described damping resistance in the impedance of switching frequency point, and in the impedance of the resonant frequency point of described combining inverter output filter the resistance higher than described damping resistance.

2. combining inverter output filter according to claim 1, is characterized in that, the resonance frequency of described LC series resonant circuit equals described switching frequency.

3. combining inverter output filter according to claim 2, is characterized in that, the inductance parameters of described LC series resonant circuit meets

$\begin{array}{cc}{C}_n=(1-\frac{1}{k^2})\frac{1}{{\mathrm{\ω}}_{\mathrm{res}}{k}_d{R}_d},& L_n=\frac{1}{{\mathrm{\ω}}_{\mathrm{chop}}^2{C}_n}\end{array}$

In formula, C_ncapacitance for electric capacity in described LC series resonant circuit; L_ninductance value for inductance in described LC series resonant circuit; ω_resresonance frequency for described combining inverter output filter; R_dresistance for described damping resistance; K=ω_chop/ ω_res, ω_chopfor angular frequency corresponding to the switching frequency of described combining inverter; k_d=Z_lC/ R_d, Z_lCfor the impedance of described LC series resonant circuit at the resonant frequency point of described combining inverter, R_dresistance for described damping resistance.

4. combining inverter output filter according to claim 3, is characterized in that k_d>2.

5. according to the combining inverter output filter described in any one in claim 1-4, it is characterized in that, also comprise: be connected in parallel on the by-pass inductor on damping resistance described in each.

6. according to the combining inverter output filter described in any one in claim 1-4, it is characterized in that, described passive filter is LC filter.

7. according to the combining inverter output filter described in any one in claim 1-4, it is characterized in that, described passive filter is LCL filter.

8. according to the combining inverter output filter described in any one in claim 1-4, it is characterized in that described N=1.

9. according to the combining inverter output filter described in any one in claim 1-4, it is characterized in that described N=2, described M=1.

10. according to the combining inverter output filter described in any one in claim 1-4, it is characterized in that, described N filter capacitor branch road parallel with one another is delta connection circuit or is star connection, Y connection circuit.