CN103929052B - A kind of combining inverter output filter - Google Patents

Abstract

The embodiment of the invention discloses a kind of combining inverter output filter, including: passive filter, described passive filter includes N number of filter capacitor branch road parallel with one another；The damping resistance being connected on each filter capacitor in M described filter capacitor branch road parallel with one another, wherein N and M is positive integer and 1≤M≤N；And it is connected in parallel on the LC series resonant circuit on each described damping resistance, wherein said LC series resonant circuit in the impedance of switching frequency point less than the resistance of described damping resistance, achieve on the premise of ensureing damping, reduce the power attenuation on damping resistance.

Description

A kind of combining inverter output filter

Technical field

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

Background technology

For using the combining inverter of pulse modulation technology, its output waveform necessarily contains and loadThe harmonic component that ripple is relevant, and then cause harmonic pollution, it is therefore necessary at the outlet side of combining inverterSetting up wave filter to filter this fractional harmonic component, LCL filter and LC wave filter is that wherein application is wideTwo kinds of general passive filters.

In view of LCL filter and LC wave filter, resonance problems the most easily occurs, therefore when reality is appliedNeed on each filter capacitor in its filter-capacitor circuit respectively series damping resistor to avoid resonance.

But, the negative issue that the introducing of damping resistance produces therewith is but to bring extra power attenuation,The most how on the premise of ensureing damping, reduce the power attenuation on damping resistance, become abilityField technique personnel's problem demanding prompt solution.

Summary of the invention

In view of this, the present invention provides a kind of combining inverter output filter, to realize ensureing dampingOn the premise of effect, reduce the power attenuation on damping resistance.

A kind of combining inverter output filter, including:

Passive filter, described passive filter includes N number of filter capacitor branch road parallel with one another；

The damping being connected on each filter capacitor in M described filter capacitor branch road parallel with one anotherResistance, wherein N and M is positive integer and 1≤M≤N；

And it is connected in parallel on the LC series resonant circuit on each described damping resistance；Wherein, described LC stringConnection resonance circuit in the impedance of switching frequency point less than the resistance of described damping resistance, and described grid-connected inverseThe impedance of the resonant frequency point becoming device output filter is higher than the resistance of described damping resistance.

Wherein, the resonant frequency of described LC series resonant circuit is equal to 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_nFor the capacitance of electric capacity in described LC series resonant circuit；L_nHumorous for described LC series connectionShake the inductance value of inductance in circuit；ω_resResonant frequency for described combining inverter output filter；R_dForThe resistance of described damping resistance；K=ω_chop/ω_res, ω_chopSwitching frequency for described combining inverter is correspondingAngular frequency；k_d=Z_LC/R_d, Z_LCFor described LC series resonant circuit described combining inverter resonance frequencyThe impedance of rate point, R_dResistance for described damping resistance.

Wherein, described k_d>2。

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

Wherein, described passive filter is LC wave filter.

Wherein, described passive filter is LCL filter.

Wherein, described N=1.

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

Wherein, described N number of filter capacitor branch road parallel with one another is triangle junction circuit or is starShape connection circuit.

From above-mentioned technical scheme it can be seen that the present invention is connecting for the filter capacitor passive filterAfter damping resistance, it is also each damping resistance parallel connection LC series resonant circuit, due to this LC series resonanceCircuit in the impedance of switching frequency point less than the resistance of damping resistance, therefore can by-pass overdamp resistanceHigh frequency ripple current, reduces the loss of damping resistance；Simultaneously as this LC series resonant circuit is grid-connectedThe impedance of the resonant frequency point of inverter output filter, higher than the resistance of damping resistance, therefore can reduceIts good damping characteristic is still ensured while damping resistance loss.

Accompanying drawing explanation

In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, below will be to realityExecute the required accompanying drawing used in example or description of the prior art to be briefly described, it should be apparent that below,Accompanying drawing in description is only some embodiments of the present invention, for those of ordinary skill in the art,On the premise of not paying creative work, it is also possible to obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is a kind of LCL filter structural representation disclosed in prior art；

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

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

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

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

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

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

Fig. 8 is a kind of with or without bridge arm current ripple during LC series resonant circuit disclosed in the embodiment of the present invention fourSpecial figure；

Fig. 9 is a kind of with or without grid-connected current ripple during LC series resonant circuit disclosed in the embodiment of the present invention fourSpecial figure；

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

Figure 11 be disclosed in the embodiment of the present invention four a kind of with or without LC series resonant circuit time flow through damping electricityHigh frequency ripple current amplitude comparison diagram near the switching frequency of resistance；

Figure 12 be disclosed in the embodiment of the present invention four a kind of with or without during LC series resonant circuit at switching frequencyNeighbouring grid-connected current ripple amplitude comparison diagram.

Detailed description of the invention

In existing combining inverter output filter, LCL filter and LC wave filter both are passiveHigh frequency ripple (i.e. higher harmonic components) in combining inverter output waveform is had higher by wave filterDamping capacity, its good filter effect makes the high frequency ripple amplitude in grid-connected current be greatly lowered,Therefore favor is enjoyed.

Concrete, the circuit structure of LCL filter is as it is shown in figure 1, include: sequentially access grid-connected inverterInverter side reactor 11, filter-capacitor circuit 13 and grid side reactor 12 between 20 and electrical network 30.The circuit structure of LC wave filter is as in figure 2 it is shown, include: sequentially access grid-connected inverter 20 and electrical network 30Between inverter side reactor 11 and filter-capacitor circuit 13.

With the difference of LCL filter, LC wave filter is that grid side reactor cast out by LC wave filter12, it as an alternative thus constitutes by transformator leakage reactance existing in electrical network 20 and electric network impedance 31The LCL filter of equivalence, and then reduce cost and improve the efficiency of combining inverter 20.But,Whether LCL filter or LC wave filter is all likely to occur resonance problems, and LC wave filter is owing to savingGrid side reactor 12 so that it is big that its resonant frequency is affected change by electric network impedance, therefore filters compared to LCLRipple device is easier to resonance occur.

Resonance problems to be solved will increase the system damping of wave filter, use in filter-capacitor circuit 13Although each filter capacitor on the mode of series damping resistor can reach good damping, but simultaneouslyWhen the electric current of combining inverter 20 output flows through this damping resistance, extra damping resistance will necessarily be produced and damageConsumption, causes the significant wastage of electric energy.Therefore, this invention address that at the damping ensureing damping resistanceOn the premise of reduce the power attenuation on damping resistance, by the filtering to LC wave filter or LCL filterCondenser network 13 improves, and discloses following multiple combining inverter with novel filter-capacitor circuitOutput filter.

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 enteredRow clearly and completely describes, it is clear that described embodiment is only a part of embodiment of the present invention,Rather than whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art are not havingMake the every other embodiment obtained under creative work premise, broadly fall into the scope of protection of the invention.

Embodiment one:

See Fig. 3, combining inverter output filter disclosed in the present embodiment one, including:

LCL filter, including inverter side reactor 11, grid side reactor 12 and filter-capacitor circuit13；

Each filter capacitor C being connected in filter-capacitor circuit 13_fOn damping resistance R_d；

And it is connected in parallel on each damping resistance R_dOn LC series resonant circuit, described LC series resonanceCircuit is less than damping resistance R in the impedance of switching frequency point_dResistance, and export at described combining inverterThe impedance of the resonant frequency point of wave filter is higher than damping resistance R_dResistance.

The present embodiment one is by for each filter capacitor C_fSeries and parallel has the damping of LC series resonant circuitResistance R_d, thus build and obtained a kind of combining inverter output with novel filter-capacitor circuit 103Wave filter, it is achieved that ensureing damping resistance R_dDamping on the premise of, reduce damping resistance R_dOnPower attenuation, be analyzed as follows:

Known LC series resonant circuit is a kind of by the inductance L being in series_nWith electric capacity C_nThe resonance electricity of compositionRoad, it can be by regulation inductance L in the impedance magnitude of each Frequency point_nWith electric capacity C_nParameter value determine；

For only each filter capacitor C in filter-capacitor circuit 13_fUpper series damping resistor R_d'sFor filter-capacitor circuit, flow through damping resistance R_dElectric current include high frequency ripple current and line voltageThe fundamental current produced on filter capacitor, and for each damping resistance R_dLC series resonance electricity in parallelLu Hou, by arranging inductance L_nWith electric capacity C_nParameter value, this LC series resonant circuit can be made at high frequencyThe impedance of section is less than damping resistance R_dResistance, then now, this LC series resonant circuit just can play sideRoad flows through damping resistance R_dThe effect of high frequency ripple current, thus reduce described high frequency ripple current streamThrough damping resistance R_dTime produce power attenuation, it is achieved that damping resistance R_dLow-loss；

Additionally, for ensureing realizing damping resistance R_dThe while of low-loss, will not be to damping resistance R_dResistanceBuddhist nun's effect influences too much, and the present embodiment also sets up this LC series resonant circuit at described combining inverterImpedance at the resonant frequency of output filter is higher than damping resistance R_dResistance, so solve resonance askDamping resistance R during topic_dMany consumption of going of can trying one's best be enough to cause described combining inverter output filterThere is the energy of resonance, so that the introducing of this LC series resonant circuit will not be to damping resistance R_dExistingDamping influence too much.

Preferably, it is contemplated that disclosed in the present embodiment, LC series resonant circuit hinders relatively in the impedance of high bandBuffer resistance R_dResistance the lowest, damping resistance R_dLoss the least；And described LC series resonant circuit existsThe impedance relative damping resistance R of high band_dResistance the highest, damping resistance R_dDamping the best,Therefore the present embodiment is by arranging most preferred inductance L for described LC series resonant circuit_nParameter and electric capacityC_nParameter so that described LC series resonant circuit relative damping resistance R_dResistance can be at described switch lockReach minimum at rate, and make described LC series resonant circuit in the output filtering of described combining inverter simultaneouslyImpedance at the resonant frequency of device can be far above damping resistance R_dResistance.Concrete, determine described inPreferably inductance L_nParameter and electric capacity C_nThe process of parameter is as follows:

First, it is known that LC series resonant circuit has in the minimum characteristic of impedance at resonant frequency, andIn the frequency spectrum of described high frequency ripple current, what the highest impact of amplitude was maximum is, and frequency is the height of switching frequencyFrequently ripple current, therefore the present embodiment arrange the resonant frequency of described LC series resonant circuit be equal to described in openClose frequency, to realize farthest reducing damping resistance R_dLoss.Wherein said LC series resonance electricityResonant frequency f on road_chopExpression formula is as follows

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

In formula, L_nAnd C_nIt is respectively inductance L_nParameter (i.e. inductance value) and electric capacity C_nParameter (i.e. capacitance),Meeting f_chopIn the case of reaching described switching frequency, inductance L_nWith electric capacity C_nHaving many group parameter values canChoosing, the most uniquely determines.

Then, according to the impedance expression (being designated as expression formula 1) of described LC series resonant circuit, andThe angular frequency expression formula (being designated as expression formula 2) that the resonant frequency of described LC series resonant circuit is corresponding, pushes awayLead the resistance obtaining described LC series resonant circuit at the resonant frequency of described combining inverter output filterAnti-expression formula (is designated as expression formula 3)；

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 electric capacity C_nCapacitance, R_nFor inductanceL_nInternal resistance, ω_resFor the angular frequency that the resonant frequency of described combining inverter output filter is corresponding, ω_chopForThe angular frequency that the resonant frequency of described LC series resonant circuit is corresponding, k=ω_chop/ω_res。

Then, it is calculated inductance L according to expression formula 2 and expression formula 3_nWith electric capacity 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, for ensure described LC series resonant circuit in instituteThe notch band of the switching frequency point stating combining inverter is sufficiently wide, so that described LC series resonance is electricRoad can simultaneously high frequency ripple current near by-pass switch frequency and switching frequency thereof, then k_dValue shouldThat chooses is sufficiently small；On the other hand, for ensureing that the introducing of described LC series resonant circuit is to damping resistance R_dThe impact of damping the least, then k_dValue should choose sufficiently large, comprehensive these two aspects consider,Finally can set k_d> 2, but do not limit to.

Seen from the above description, the present embodiment one is electric for the filter capacitor series damped in passive filterAfter resistance, it is also each damping resistance parallel connection LC series resonant circuit, owing to this LC series resonant circuit existsThe impedance of switching frequency point, therefore can the high frequency stricture of vagina of by-pass overdamp resistance less than the resistance of damping resistanceRipple electric current, reduces the loss of damping resistance；Simultaneously as this LC series resonant circuit is at combining inverterThe impedance of the resonant frequency point of output filter, higher than the resistance of damping resistance, therefore can reduce damping electricityIts good damping characteristic is still ensured while resistance loss.

Embodiment two:

Word based on embodiment one describes and accompanying drawing, and the present embodiment two discloses another parallel network reverseDevice output filter, sees Fig. 4, also includes: 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, thereforeCan by-pass overdamp resistance R_dFundamental current, thus, the present embodiment two has reached utilizing described LCSeries resonant circuit by-pass overdamp resistance R_dHigh frequency ripple current while, also utilize by-pass inductorL_dBy-pass overdamp resistance R_dThe purpose of fundamental current, compared to embodiment one, the present embodiment two is moreCreate a further reduction damping resistance R_dOn power attenuation.

Embodiment three:

Seeing Fig. 5, the present embodiment three discloses another combining inverter output filter, including:

LCL filter, including inverter side reactor 11, grid side reactor 12 and filter-capacitor circuit13, wherein filter-capacitor circuit 13 includes 2 filter capacitor branch roads parallel with one another；

Each filter capacitor C being connected in 1 described filter capacitor branch road_f1On damping resistance R_d；

And it is connected in parallel on each damping resistance R_dOn LC series resonant circuit, wherein said LC connectResonance circuit is less than damping resistance R in the impedance of switching frequency point_dResistance, and at described combining inverterThe impedance of the resonant frequency point of output filter is higher than damping resistance R_dResistance.

It is that the present embodiment is first by filter-capacitor circuit 13 in place of the present embodiment three and the difference of embodiment oneIt is equivalent to 2 branch roads being in parallel, and on each filter capacitor of 1 branch road wherein, series and parallel has LCThe damping resistance R of series resonant circuit_d, thus obtained a kind of preferred novel filter-capacitor circuit103, it is analyzed as follows:

For described LCL filter, damping resistance R_dIntroducing will necessarily increase its filter capacitor electricityRoad, in the impedance of high band, causes described filter-capacitor circuit to weaken the inhibition of high frequency ripple current；And after the filter-capacitor circuit of described LCL filter is equivalent to 2 parallel branches, due to only at itIn 1 branch road on connected damping resistance R_d, then introduce and have damping resistance R_dBranch road be not introduced intoThere is damping resistance R_dBranch circuit parallel connection after equiva lent impedance will necessarily reduce, thus effectively reduce filtered electricalCapacitive circuit, in the impedance of high band, improves the filter effect of wave filter；

So, subsequently through for each damping resistance R_dDescribed LC series resonant circuit in parallel, Ji KeOn the premise of ensureing damping, reduce damping resistance R_dOn power attenuation.

Seen from the above description, the present embodiment three is in parallel by filter-capacitor circuit 13 is equivalent to 2Branch road, and on each filter capacitor of 1 branch road wherein, series and parallel has LC series resonant circuitDamping resistance R_d, thus on the premise of ensureing the good filter effect of damping, reduce damping resistance R_dOn power attenuation.Wherein it should be noted that for the scheme expanded according to the present embodiment, filter as incited somebody to actionRipple condenser network 13 equivalence is split as N number of filter capacitor branch road parallel with one another, and M described mutuallyOn filter capacitor branch road in parallel, series and parallel has the damping resistance R of LC series resonant circuit_dScheme (itsMiddle N and M is positive integer and 1≤M≤N), its principle is consistent, the most no longer with the present embodiment three principleRepeat one by one.In addition too much can increase damping resistance R in view of branch road in parallel_dThe cutting of damping characteristicWeak intensity, therefore with N=2 preferably.

Embodiment four:

Word based on embodiment three describes and accompanying drawing, and the present embodiment four discloses another parallel network reverseDevice output filter, sees Fig. 6, also includes: 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_dFirst-harmonicElectric current, flows through damping resistance R reducing described fundamental current_dTime produce power attenuation, compare embodimentThree, the present embodiment four further reduces damping resistance R_dLoss.

Figure below 7-12 shows the practical application effect of product described in the present embodiment four, in order to this area skillArt personnel 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 instituteStating the impedance frequency characteristics curve of LC series resonant circuit, curve 1 represents damping resistance R_dImpedance-frequentlyRate characteristic curve), it can be seen that in the resonant frequency point of described combining inverter output filter, instituteThe impedance stating LC series resonant circuit is at least damping resistance R_d2 times of resistance, and at described switching frequencyPoint, the impedance of described LC series resonant circuit is far below damping resistance R_dResistance.Thus illustrate, described LCSeries resonant circuit is ensureing damping resistance R_dThe frequencies that bypassed the most while damping characteristic is switchThe high frequency ripple current of frequency, reduces damping resistance R_dLoss.

Fig. 8 is with or without bridge arm current (the inverter side reactor 11 during described LC series resonant circuitOutput electric current) Bode diagram, it can be seen that compare and remove the electricity of the brachium pontis after described LC series resonant circuitStream, after increasing described LC series resonant circuit, resonance peak simply somewhat increases, thus described LC series resonanceThe introducing of circuit is to damping resistance R_dDamping impact less.

Fig. 9 is with or without the grid-connected current (input of net side inverter 12 during described LC series resonant circuitElectric current) Bode diagram, it can be seen that owing to described LC series resonant circuit is near described switching frequencyLow impedance characteristic, itself and damping resistance R_dThe filter effect near switching frequency is enhanced after parallel connection.

Figure 10 is the simulation waveform figure of this product, it can be seen that described LC series resonant circuit has bypassed greatlyThe high frequency ripple current (seeing curve 1) opened at frequent rate of part, by-pass inductor L_dBypass major partFundamental current (seeing curve 2), flow through damping resistance R_dThe output of mainly described combining inverterHigh frequency ripple current (seeing curve 3) at the resonant frequency of wave filter and near 2 times of switching frequencies.

Figure 11 is for flowing through damping resistance R during with or without described LC series resonant circuit_dSwitching frequency nearHigh frequency ripple current amplitude comparison diagram, it can be seen that after introducing described LC series resonant circuit, switchThe neighbouring high frequency ripple current amplitude of frequency 3000 hertz significantly reduces, and substantially reduces damping resistance R_d'sLoss.

Figure 12 is with or without grid-connected current ripple width near switching frequency during described LC series resonant circuitValue comparison diagram, it can be seen that have damping resistance R compared to only introducing_dScheme, introduce described LC stringIn grid-connected current (i.e. the input current of net side inverter 12) corresponding after connection resonance circuit, switching frequencyThe high frequency ripple current amplitude of 3000 hertz neighbouring significantly reduces, and enhances filter effect.

In sum, the present invention, after for the filter capacitor series damping resistor in passive filter, is alsoEach damping resistance parallel connection LC series resonant circuit, owing to this LC series resonant circuit is at switching frequency pointImpedance less than the resistance of damping resistance, therefore can the high frequency ripple current of by-pass overdamp resistance, fallThe loss of low resistance resistance；Simultaneously as this LC series resonant circuit is at combining inverter output filterThe impedance of resonant frequency point higher than the resistance of damping resistance, therefore can reduce the same of damping resistance lossTime still ensure its good damping characteristic.

Last it should be noted that owing to LCL filter is to be combined transformator leakage reactance and electricity by LC wave filterNet impedance 31 equivalence obtains, the most above-mentioned for the parallel network reverse using LCL filter as passive filterThe analysis process of device output filter is equally applicable to the parallel network reverse using LC wave filter as passive filterDevice output filter, here is omitted.Additionally, filter capacitor branch road in various embodiments of the present inventionCircuit couples structure is not limited to, and can be triangle junction, it is possible to be star connection, and the present invention is eachEmbodiment respective figure is only illustrative and provides described triangle junction structure.

In this specification, each embodiment uses the mode gone forward one by one to describe, and each embodiment stressesBeing the difference with other embodiments, between each embodiment, identical similar portion sees mutually.

Described above to the disclosed embodiments, makes professional and technical personnel in the field be capable of or usesThe present invention.Multiple amendment to these embodiments will be aobvious and easy for those skilled in the artSeeing, generic principles defined herein can be in the spirit or scope without departing from the embodiment of the present inventionIn the case of, realize in other embodiments.Therefore, the embodiment of the present invention is not intended to be limited to institute hereinThese embodiments shown, and it is to fit to consistent with principles disclosed herein and features of novelty the widestScope.

Claims (10)

1. a combining inverter output filter, it is characterised in that including:

Passive filter, described passive filter includes N number of filter capacitor branch road parallel with one another；

The damping being connected on each filter capacitor in M described filter capacitor branch road parallel with one anotherResistance, wherein N and M is positive integer and 1≤M≤N；

And it is connected in parallel on the LC series resonant circuit on each described damping resistance；Wherein, described LC stringConnection resonance circuit in the impedance of switching frequency point less than the resistance of described damping resistance, and described grid-connected inverseThe impedance of the resonant frequency point becoming device output filter is higher than the resistance of described damping resistance.

Combining inverter output filter the most according to claim 1, it is characterised in that described LCThe resonant frequency of series resonant circuit is equal to described switching frequency.

Combining inverter output filter the most according to claim 2, it is characterised in that described LCThe inductance parameters of 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_nFor the capacitance of electric capacity in described LC series resonant circuit；L_nHumorous for described LC series connectionShake the inductance value of inductance in circuit；ω_resResonant frequency for described combining inverter output filter；R_dForThe resistance of described damping resistance；K=ω_chop/ω_res, ω_chopSwitching frequency for described combining inverter is correspondingAngular frequency；k_d=Z_LC/R_d, Z_LCFor described LC series resonant circuit described combining inverter resonance frequencyThe impedance of rate point, R_dResistance for described damping resistance.

Combining inverter output filter the most according to claim 3, it is characterised in that k_d>2。

5., according to the combining inverter output filter according to any one of claim 1-4, its feature existsIn, also include: be connected in parallel on the by-pass inductor on each described damping resistance.

6., according to the combining inverter output filter according to any one of claim 1-4, its feature existsIn, described passive filter is LC wave filter.

7., according to the combining inverter output filter according to any one of claim 1-4, its feature existsIn, described passive filter is LCL filter.

8., according to the combining inverter output filter according to any one of claim 1-4, its feature existsIn, described N=1.

9., according to the combining inverter output filter according to any one of claim 1-4, its feature existsIn, described N=2, described M=1.

10., according to the combining inverter output filter according to any one of claim 1-4, its feature existsIn, described N number of filter capacitor branch road parallel with one another is triangle junction circuit or is star connectionCircuit.