Research And Design Of A Novel Nonisolated High-Step-Up DC/DC Converter

In recent years,in order to solve the energy problem,photovoltaic power generation has become the world's general development and focus on the strategic industry.However the output voltage of the photovoltaic panel is very low,so it's necessary to boost the low voltage through a high-step-up converter to meet the inverter's voltage level need.And a novel nonisolated high-step-up converter is reasearched in this paper.The first chapter of this paper reviews the study of high-step-up converters,introduce the basic operating principles of isolated high-step-up converters,classify and analyze the nonisolated high-step-up converters.Then,introduce the research status of soft switching technology and the advantages and disadvantages of those methods.In chapter two,introducing the derivation of the high-step-up converter based on Boost/Buck-Boost firstly,obtaining its steady state model and know its boost ratio is twice of the traditional boost converter.Then,using equivalent circuit method to analyze its working process and find there exists spike current that affect system normal operation,and put forward connecting an inductor with the output diode to suppress the spike current.This forms the novel high-step-up converter.At last,simulation and experiment results vertify that the method could suppress spike current very well.In the third chapter,three DC/DC converter control modes is introduced and choose peak current control mode to control the novel high-step-up converter.Then take the 200W prototype as an example,design the passive devices in the main circuit,determain the steady operating point and get the frequency response curve.Design the voltage compensator based on the frequency response curve,ensure the converter can work in the full input range.Experiment vertify the theoretical analysis.The fourth chapter focus on the soft switching of high-step-up converter.First,introduce the classification of GaN HEMT and the characteristics of each category,determine using cascade GaN HEMT as the main power switch,and it's necessary to make it work in the zero voltage open state.Then adding auxiliary circuit to the novel high-step-up converter and get ZVT high-step-up converter,detailed analyze its working principle and design controller to achieve ZVT high-step-up converter normal operation.The fifth chapter introduces the high step up boost converter prototype building work and the key problems,including device selection,circuit design,PCB drawing,introduction of the prototype,gives some key waveforms in the debugging process.Finally,introduce the ZVT high-step-up converter of the control program,circuit and its prototype building work.