CN109033699A - A kind of Parameters design of gird-connected inverter LCLCL filter - Google Patents
A kind of Parameters design of gird-connected inverter LCLCL filter Download PDFInfo
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- CN109033699A CN109033699A CN201810957283.7A CN201810957283A CN109033699A CN 109033699 A CN109033699 A CN 109033699A CN 201810957283 A CN201810957283 A CN 201810957283A CN 109033699 A CN109033699 A CN 109033699A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a kind of gird-connected inverter Parameters designs of LCLCL filter, belong to gird-connected inverter technical field.To the effect that: by the parameter decomposition of LCLCL filter at parameter designing two parts of LCL filter parameter designing and two inductance.Include the following steps: step 1: according to traditional LCL filter Parameters design, designing the inverter side inductance of LCL filter, the value of net side inductance and filter capacitor；Step 2: the inverter side inductance and two capacitances of LCLCL filter are calculated by the parameter that step 1 obtains；Step 3: parameter is verified.The high-frequency harmonic that Parameters design of the present invention had not only considered filter inhibits to require, but also has reserved sufficiently large closed-loop control bandwidth；This method step is illustrated, convenient and easy.
Description
Technical field
The invention belongs to gird-connected inverter technical fields, are a kind of gird-connected inverter LCLCL filters more particularly
And its Parameters design.
Background technique
With ever-increasing photovoltaic combining inverter, power grid is experienced by huge test, the technology of photovoltaic DC-to-AC converter
Index directly determines the quality of inverter output electric energy, and wherein influence of the harmonic wave to power grid is especially very important.Therefore, the world
Each state all sets a series of grid-connected harmonic standard to grid-connected inverting system, for example China can define inverter in mark standard
In rated power operation, the harmonic current THDi of power grid must not exceed 5%, and also set limit value to each harmonic content.
To make grid-connected inverting system meet the requirement of grid-connected harmonic wave, passive filter is often accessed after gird-connected inverter in engineering
Wave device, to inhibit the harmonic wave at harmonic wave, especially switching frequency.The structure of L filter is simple, but its ability to harmonics restraint
It is weaker, in order to guarantee the harmonic requirement of grid-connected system, it usually needs the inductance value for increasing L filter will increase grid-connected inverse in this way
Become the volume and cost of device.LCL filter is compared with L filter, when the two realizes identical filter effect, LCL filter
Total inductance amount ratio L filter small more of total inductance amount, such LCL filter reduces the volume of gird-connected inverter.But
LCL filter often only considers the size of networking current total harmonic distortion rate in actual design process, and has ignored switch frequency
The harmonic wave of rate and its integer multiple frequency electric current.LLCL filter is one inductance of series connection, shape in the capacitive branch of LCL filter
At a series resonance branch, switch frequency harmonics electric current can be bypassed using this series resonance branch, energy
Enough significantly attenuator switch frequency harmonics.It is often abnormal according to current harmonics at switching frequency when designing LLCL filter
Variability is calculated less than 0.3%.The networking requirement that can be good at guaranteeing higher hamonic wave is designed in this way, but often total harmonic wave is abnormal
Variability does not reach requirement.LCLCL filter is a five rank filters, and high-frequency harmonic damping capacity will be substantially better than other filtering
Device rationally designs its parameter, and the performance of entire grid-connected system can be improved.
Higher order filter is due to there is natural resonance characteristic, during parameter designing, generally require to resonance frequency into
Row selection.Resonance frequency selects higher, and system closed-loop bandwidth is bigger, is more advantageous to the design of control system, while will improve
Rejection ability of the system to low-frequency range current harmonics.On the other hand, resonance frequency selection is excessively high may result in high-band currents
Index of correlation requirement is not achieved in the inhibitory effect of harmonic wave.Therefore, the selection of filter resonance frequency should be both humorous in view of low frequency
The inhibition requirement of high-frequency harmonic is taken into account in the requirement of conformance control bandwidth again.
Summary of the invention
The purpose of the present invention: for the defect of above-mentioned wave filter technology, a kind of parameter designing side of LCLCL filter is proposed
Method, making filter, there are enough control bandwidths, while meeting corresponding grid-connected requirement, and design method is simple and effective.
Technical solution: a kind of the LCLCL filter and its Parameters design of gird-connected inverter include the following steps:
Step 1: the relevant parameter of LCL filter is calculated.
Determine the structure and inverter switching frequency f of inverter and filters；
Inverter side inductance L is determined according to the design method of LCL filter1With net side inductance L2Value；
Requirement according to system to reactive power selects the size of LCL filter capacitor C.
Step 2: the parameter of LCLCL filter is calculated.
The inverter side inductance of LCLCL filter is identical as LCL filter inverter side inductance value；
The first capacitor of LCLCL filter and the second capacitor take identical value, are the half of LCL filter capacitor；
The inductance L of LCLCL filter2With L3The sum of net side inductance L with LCL filter2It is equal；
Enable α=L2/L3, in high-frequency resonant frequency fr2With low-frequency resonant frequency fr1The difference place of being minimized can obtain αmin；
According to determining αminValue, available (L2,L3) valued combinations.
Step 3: parameter is verified.
Harmonic inhibition capability verification is carried out to obtained parameter value；If this group of parameter value meets grid-connected requirement, this is chosen
Group parameter is the final argument of LCLCL filter；
If being not up to grid-connected requirement by the filter of this group of parameter designing, α range is expanded as into [αmin-1,αmin+ 1],
Compare newly-increased data as a result, choose the strongest one group of parameter of harmonic inhibition capability as final argument.
The beneficial effects of the present invention are:
The high-frequency harmonic that design method of the present invention had not only considered filter inhibits to require, but also has reserved sufficiently large
Closed-loop control bandwidth.
LCLCL filter is simplified to two parts, including three steps, step by Parameters design of the present invention
It is illustrated, method can be promoted the use of in the design process of five ranks and higher order filter.
Detailed description of the invention
Fig. 1 is the circuit diagram of LCLCL filter used in the present invention；
Fig. 2 is LCL filter circuit diagram；
Fig. 3 is the Bode diagram of three kinds of filters；
Fig. 4 is the relationship of resonant frequency difference value and inductance ratio in specific example；
Fig. 5 is the Bode diagram that transmission function between electric current and input voltage is exported in specific example；
Specific embodiment
This implementation is explained further the design of LCLCL filter by taking the grid-connected inverter system of 3KW as an example.It is wherein electric
The virtual value of net side line voltage is 100V, and gird-connected inverter DC side busbar voltage is 150V, and inverter switching frequency is
10KHz, power grid fundamental frequency 50Hz.
LCLCL filter circuit figure is as shown in Figure 1, L1Indicate inverter side inductance, L2Indicate middle inductor, L3Indicate net side
Inductance, C1For the first filter capacitor, C2For the second filter capacitor.
From LCLCL filter circuit figure, the transmission function of available inverter output voltage to current on line side are as follows:
Two resonance frequencies point of LCLCL filter can be derived by the transmission function of inverter side voltage to current on line side
Not are as follows:
Traditional LCL filter circuit diagram is as shown in Figure 2.
Step 1: the relevant parameter of LCL filter is calculated.
According to the ripple size requirements of input current, inductance L is selected1LCLParameter value, formula is as follows:
Inverter rated current peak IrefAre as follows:
When using SPWM modulation, L1LCLCalculation formula is as follows:
Wherein, m is current ripples coefficient, and general value range is 0 < m < 40%, takes m=20% here.
According to the limitation of grid-connected system reactive power, the value of filter capacitor is selected, formula is as follows:
Wherein λ is power system reactive power factor, and power system reactive power generally requires 5% less than rated power, and λ takes herein
5%.
According to the resonance frequency of desired LCL filter, the value of net side inductance is selected, is calculated according to following formula:
Wherein, ω is resonance angular frequency, ω=15700rad.
Step 2: the relevant parameter of LCLCL filter is calculated.
The inverter side inductance of LCLCL filter is identical as LCL filter inverter side inductance value.
L1LCLCL=L1LCL=0.2mH formula (8)
In order to facilitate engineer application, the first capacitor of LCLCL filter and the second capacitor take identical value, are LCL filtering
The half of device capacitor.
The difference for making two resonance frequencies, is shown below:
F=fr2-fr1Formula (10)
It enables
The sum of middle inductor value and net side inductance value of LCLCL filter are equal to LCL filter net side inductance value.Such as following formula
It is shown:
L2LCL=L2LCLCL+L3LCLCL=0.2mH formula (12)
Use L2LCLL is respectively indicated with α2LCLCLAnd L3LCLCL, it is shown below:
The two expression formulas are substituted into the relational expression of resonant frequency difference value, obtains resonant frequency difference value and inductance ratio cc
Relational expression.
For the ease of practical engineering application, α value is not answered excessive.
It enables
The formula of 1≤α≤10 (15)
Image of the F about α is made, as shown in Figure 4.
Corresponding α when being minimized from F available in the figure of F and αmin。
αmin=2 formulas (16)
Two inductance parameters can be obtained to be respectively as follows:
| α | L2LCLCL | L3LCLCL |
| 2 | 0.13mH | 0.067mH |
Resonance frequency is obtained by this group of parameter are as follows:
| α | fr1 | fr2 |
| 2 | 2.995kHz | 5.319kHz |
Step 3: parameter is verified.
Fft analysis is carried out to current on line side, carries out the verification of harmonic inhibition capability.
Judge whether 35 times or more individual harmonic currents meet the requirement less than 0.3%.Judge that total harmonic distortion verifies THD
Whether requirement less than 5% is met.
Verification discovery, α=2 meet the requirement of current harmonics inhibition.
Meanwhile from Fig. 5 Bode diagram, it can be found that the difference of two resonance frequencies is smaller, sufficiently large control is remained
Bandwidth.
Claims (2)
1. a kind of gird-connected inverter LCLCL filter and its Parameters design, it is characterised in that by the ginseng of LCLCL filter
Number design method resolves into parameter designing two parts of traditional LC L filter parameter design and two inductance, and its step are as follows:
Step 1: according to traditional LCL filter Parameters design, the inverter side inductance of LCL filter, net side inductance are designed
With the value of filter capacitor.
Step 2: the parameter obtained by step 1 calculate LCLCL filter inverter side inductance and two capacitances, formula it is as follows
It is shown:
L1LCLCL=L1LCL
The middle inductor of corresponding LCLCL filter and the ratio of net side inductance are determined by the minimum value of two resonance frequency differences
αmin。
By αminDetermine the value of middle inductor and net side inductance.
Step 3: verifying parameter, if this group of parameter value meets grid-connected requirement, choosing this group of parameter is filter
Parameter；
If this group of parameter is not up to grid-connected requirement, α range is expanded as into [αmin-1,αmin+ 1], the harmonic wave of relatively more newly-increased parameter
Inhibitory effect chooses the strongest one group of parameter of harmonic inhibition capability as optimized parameter.
2. the LCLCL filter and its Parameters design, feature of a kind of gird-connected inverter according to claim 1 exist
It include inverter side inductance, middle inductor and net side inductance in three inductance of the LCLCL filter, two capacitors are the first electricity
Hold and the second capacitor.In the step 2, when choosing resonance frequency difference minimum value, first by software for mathematical computing such as MATLAB
Image of the resonant frequency difference value about inductance ratio is drawn, selects the corresponding α of minimum value in the picturemin。
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113328439A (en) * | 2021-05-31 | 2021-08-31 | 国网河南省电力公司经济技术研究院 | LCLLC parallel active filter and control method thereof |
| CN113922641A (en) * | 2021-06-22 | 2022-01-11 | 北方工业大学 | LCL-LC type filter design method based on graphical method |
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| US20090303753A1 (en) * | 2008-06-10 | 2009-12-10 | Dianbo Fu | Multi-Element Resonant Converters |
| CN103414325A (en) * | 2013-07-19 | 2013-11-27 | 合肥工业大学 | Parameter design method of grid-connected inverter LLCL filter |
| CN104242617A (en) * | 2014-07-25 | 2014-12-24 | 南京航空航天大学 | Parameter designing method of LCL filter of grid-connected inverter |
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2018
- 2018-08-22 CN CN201810957283.7A patent/CN109033699A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US20090303753A1 (en) * | 2008-06-10 | 2009-12-10 | Dianbo Fu | Multi-Element Resonant Converters |
| CN103414325A (en) * | 2013-07-19 | 2013-11-27 | 合肥工业大学 | Parameter design method of grid-connected inverter LLCL filter |
| CN104242617A (en) * | 2014-07-25 | 2014-12-24 | 南京航空航天大学 | Parameter designing method of LCL filter of grid-connected inverter |
Non-Patent Citations (3)
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113328439A (en) * | 2021-05-31 | 2021-08-31 | 国网河南省电力公司经济技术研究院 | LCLLC parallel active filter and control method thereof |
| CN113922641A (en) * | 2021-06-22 | 2022-01-11 | 北方工业大学 | LCL-LC type filter design method based on graphical method |
| CN113922641B (en) * | 2021-06-22 | 2023-07-04 | 北方工业大学 | LCL-LC filter design method based on graphic method |
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Application publication date: 20181218 |