High Step-up DC-DC Converter Of Two-stage Grid-Tied PV System

At present,every contry in the world increasingly dependent on energy,the consumption of Primary energy increased year by year,result in energy shortage and environmental problems which hampered the development of modern society seriously.To solve the above problems,many contries in the world has increased the investment in renewable energy as an alternative to the traditional fuels.Solar energy,as an important member of the renewable energy,it has renewable ans environmental advantages which other members of renewable energy also have.Besides,it has no geographical restrictions,and inexhaustible reserves.C urrently,many countries have put his heart into the research and envelopments of the photovoltaic industry.Grid-tried PV system has become a hot research field because of its efficient photoelectric conversion and the ability of putting the power back to the grid.In the two-stage grid-connected PV systems,the DC-DC converter is an important part.Due to the low output voltage of the single photovoltaic cell which can not meet the requirements,it is necessary to elevate the voltage level of the PV cell with the high step-up DC-DC converter.A novel single-switch high step-up DC-DC converter with coupled-inductor and switched-capacitor techniques is proposed in this paper.The proposed converter can achieve high voltage gain when the value of the duty ratio is close to 0.5(0.56);there is only one switch in the main circuit which is easy to be controlled;Lower voltage stress on the power devices that could effect ively reduce the conduction losses.Moreover,the energy stored in leakage inductance of coupled inductor is efficiently recycled to the output.The operating principles and the steady state analyses of the proposed converter are discussed in detail.In the paper,a simulation model of the new converter is built,and make a detailed analysis of the working principle and steady performance of the converter.Finally,a 150 W prototype with 30V-input and 300V-output was implemented and the experim ental results verify the correction of the theoretical analysis.