Research And Analyse On The DCM Of The Interleaved High Gain DC-DC Converter With Coupled-Inductor And VMC

With the increase usage of renewable energy sources such as wind,solar and fuel cells,the energy structure of the world is changing substantially.Renewable energy sources have been widely used in power-grid systems,industrial power systems,onboard power supply systems and sophisticated aerospace power supply systems.The DC-DC converter is an important part in the application of renewable energy,which is widely utilized in low voltage DC output applications such as photovoltaics and fuel cells.In practice,according to the continuous or not of the inductance current of DCDC converter,the converter’s operating mode can be divided into Continuous Current Mode or Discontinuous Current Mode.The DC steady-state characteristics of the converter are discrepant in CCM and DCM.The research on DC-DC converter with high voltage gain and analysis on the DC steady-state characteristics under different operating mods are significant,which promoting the use of DC-DC converter in the application of renewable energy.In view of this research direction,this paper has carried out the following research:In this paper,the research status of high voltage gain technology for DC-DC converter is summarized,and several kinds of classical technologies for improving voltage gain and their pros and cons are briefly described.In this paper,an interleaved DC-DC converter with coupled inductor and voltage multiplier cell is studied.The DC steady-state characteristics of the converter under DCM are analyzed by two methods.The analysis results are obtained,compared and verified by simulation and experiment.The results show that in the case of limit duty cycle,the conclusions of the two methods are quite different,which means that the results obtained by the non-simplified analysis method are more suitable for the occasions with higher requirements for voltage gain accuracy.By discussing the discharge time of the coupled inductor,a new discontinuous current mode is proposed in the converter,which called DCM II.The DC steady-state characteristics of the converter under DCM II and the division of DCM and DCM II operational domain are discussed in this paper.And the results are verified by simulation and experiment.The results show that the converter can achieve 10-14 times voltage gain when the duty cycle is 0.5-0.6,which is obviously different from the DC characteristic of the converter operated in DCM.However,the voltage gain of the two modes is superior to that of the basic converter.In the case of high frequency and heavy load,the converter operates in DCM and in the case of low frequency and light load,the converter operates in DCM II.