Research On High Efficiency And High Step-up DC/DC Converter

In recent centuries,the massive development and adoption of non-renewable resources on the earth have made it difficult to avoid causing incalculable damage to the ecological environment.With the improvement of people's environmental awareness and the gradual depletion of fossil fuels,the development and utilization of new energy has received more and more attention.Many specialist and researcher have joined in the development and research of new energy.As one of the renewable energy sources to solve the fossil energy crisis,solar energy has been greatly developed in recent years,due to the advantages of convenience,cleanliness and safety.But for photovoltaic power generation,limited by the characteristics of a single photovoltaic power generation module,the output voltage is usually below 50V,in the process of grid-connected,the lower output voltage needs to rise to 380V-760V.Because of parasitic parameters,traditional boost converter has been difficult to meet its high boost requirement.In addition,considering with the actual application of the system economy and other factors,also requires a high efficiency converter.As an important index parameter of power electronic converter,switching frequency has a great influence on the performance of the converter,In the increasingly pursuit of lower cost and higher power density of the converter,it is necessary to improve the switching frequency of converter switch,however,the increase of switching frequency will make the switching loss increase,while,the efficiency of the converter will reduce,furthermore the volume and weight of the radiator will increase.In order to solve the above problems,soft switching technology which can theoretically reduce the switching loss was proposed by experts and scholars in the 1970s.Under the realistic demand of photovoltaic power generation,it is of great value and significance to study the high gain and high-efficiency DC/DC converters,which has become a hotspot in the field of power electronics.The article summarized various existing soft-switching schemes and proposed a high-efficiency high-gain DC/DC converter suitable for photovoltaic power generation systems.With the help of the passive snubber circuit,all power switches realize zero voltage turn-off,the switch turn-off loss is reduced effectively,and the whole efficiency of the converter is become higher.At the same time,the high ste^IVp-up is realized by the converter with the help of the voltage multiple cells,and the input/output gain ratio can be adjusted according to the number of the voltage multiple cells.Theoretical analysis and experimental verification show that the proposed converter has the advantages of high conversion efficiency,low voltage stress of switch,high input and output gain.The main contents of this paper are as follows:Firstly,this paper introduces the research background and significance of the thesis and analyzes the current research status of the high gain DC converter and the current research status of the soft-switching snubber circuit.Secondly,operation principle and performance characteristics analysis of the proposed converter with two voltage multiple cells is performed,the working waveform is drawn,the working state of the converter is analyzed in detail.The parameters of the converter are deduced and calculated.Then,the parameters of the topology containing n voltage multiplier are calculated and the general formula of the parameters is obtained.Thirdly,the mathematical model of the program was analyzed and a closed-loop control system was designed.First of all,the equivalent equation of inductance and capacitance in each working mode is calculated,then the equivalent small signal exchange model is obtained by averaging in a switching period,then the transfer function is deduced,and the control system is designed,then the validity and correctness of the control system are verified by the closed loop experiment.Fourth,simulations and hardware experiments were performed to verify that the main parameters of the converter were first calculated,including the selection of inductors,switches,diodes,and capacitors.Then,in combination with hardware experimental circuits,simulation prototypes and hardware prototypes were obtained.Then the hardware experiment was conducted and the experimental waveform results were compared with the theoretical analysis results.Lastly,several different passive buffer circuit schemes are selected to compare the performance and analyze the economic benefits.At the same time,in order to quantitatively analyze the operating losses and working efficiency of the proposed converter,more accurate analysis results are obtained,and the operating losses of the components including the passive buffer circuit and the passive buffer circuit converter are calculated.