Research On Conducted Electromagnetic Intefrerence In Three Phase Grid-Connected Inverter

With high frequency switches widely used in the production of life, such as IGBT,MOSFET, these components has greatly improved the various converter responseperformance, also produced a very powerful electromagnetic interference, theinterference of the device is due to high frequency movement caused a lot of and form.The interference of frequency distribution is very wide, the seriously influence inverteroutput performance and various indexes.This paper mainly content that is about three-phase photovoltaic inverterconduction EMI research, mainly three aspects: to three-phase grid inverter conductedinterference analysis and completion of the common-mode current modeling, based onLCL filter which filter out of the electromagnetic interference’s research and itssimulation results, using random modulation of inverter technology to improve outputharmonic frequency spectrum.This paper first introduces the high frequency model and high frequencycharacteristics of passive components in the three-phase inverter, puts forward somebasic measures to improve their parasitic parameters estimation some equipmentexpression, the second is the analysis of three-phase inverter differential-modeinterference with the electrical current and common-mode current interference reasons,and with buck circuit analysis the equivalent circuit model is derived for single phaseinverter common-mode current, and eventually expanded to single-phase three-phasecircuit simulation verify their existence and evolution law and parasitic.Passive EMI filter structure is simple, affordable and widely used, and thebasic good attenuation of conducted interference of the inverter circuit output,so do mode ling research on the three-phase inverter output LCL filter is givenattenuation harmonic LCL filter design, and verified by simulation, and to concludethat the LCL filter to inhibition Conducted EMI.Analyzes of three-phase grid-connected inverter commonly used control strategies,studies show that the inverter output harmonic regularity, a specific sub-harmonic of theamplitude of these harmonic spectrum is widely distributed, it is difficult through the setthe bandwidth of the passive EMI filter attenuation completely, For this reason, throughresearch and analysis SPWM control strategy for suppression of common modeinterference at the same time, the use of random number of SPWM control strategyproposed to improve the random SPWM control method for an improved verificationobtained in the case of many requirements to meet and network, which can very goodsmooth output harmonic power spectrum, suppressing conduction and radiationelectromagnetic interference of electromagnetic interference purpose.