Study On High Efficiency High Voltage Gain Quadratic DC-DC Converter

With the increasingly serious energy and environmental problems in recent years,the development and utilization of new energy have become the focus of research.Because of the low output voltage,large voltage fluctuation of photovoltaic and fuel cell,DC-DC switching converters with high voltage gain and wide input characteristics are required.Conventional quadratic DC-DC converters use only a single switch to achieve the cascade of two converters,which have a high voltage gain,but the efficiency is low and transmission loss is large with all converter power transmitted through two stages.The power flow types of integrated quadratic DC-DC converters which are composed of’ two basic DC-DC converters are analyzed in this thesis.From the efficiency analysis,it can be seen that the efficiency of the direct cascade converter is the lowest.The non-cascading structures can reduce redundant power processing(R2P2)by avoiding the double processing of power.A series of integrated quadratic DC-DC converters with R2P2 principle can be obtained by the combination of basic DC-DC switching converters.The combination principle of basic DC-DC switching converters is studied.The quadratic Boost converter with R2P2 is taken as an example to analyze the integration process of the converter and its working mode and steady state characteristics in continuous current mode(CCM).Combining coupled inductor technique and the quadratic Boost converter with R2P2,a R2P2 high voltage gain quadratic Boost converter based on coupled inductor is presented in this thesis.Steady state and operating characteristics of the proposed converter are analyzed in detail and the design principle of circuit parameters is given.The analysis results indicate that this converter can achieve a higher voltage gain through proper design of coupled inductor ratio without extreme duty cycle.Passive snubber cell is utilized to recycle the leakage energy and suppress voltage spike stress of the switch,which can reduce the power loss and cost.The simulation and experimental results are presented to verify the theoretical analysis of the proposed converter.For the quadratic Boost converter with R2P2 suffers from hard-switched working,a soft switching R2P2 high voltage gain quadratic Boost converter based on auxiliary circuit is proposed.The operating characteristics of steady-state,requirement of the zero-voltage switching(ZVS)of active switches and the duty ratio loss of the proposed converter are analyzed in detail.The analysis results show that the proposed converter can achieve ZVS of active switches and zero-current switching(ZCS)of output diodes,which can reduce the power loss.The voltage gain is improved owing to the output-series of the auxiliary circuit and quadratic converter,and the voltage stress of the switch is low,so low voltage level MOSFET can be utilized.Simulation and experimental results verify the correctness of theoretical analysis.