Research On High-gain Sepic Converter With Zero Input Current Ripple

A high-gain DC-DC converter is needed to improve the DC output voltage of photovoltaic power generation system,for DC output voltage of PV system is low and it is difficult to meet the higher voltage requirements of grid-connected photovoltaic inverter.At the same time,the input current ripple of the converter affects the power generation efficiency and shortens the battery life.Therefore,the input current ripple is also an important factor to be considered in the research of DC-DC converters.Firstly,compared with frequently used methods of reducing current ripple,the passive ripple current injection method was determined through comprehensive comparison,which has the advantages of simple parameter design,easy realization of zero current ripple,and no additional loss.Coupled inductor DC-DC converters can easily achieve high voltage gain and have been widely concerned.There are many topology structures of the converters,which lack systematic comparison and summary.This article is based on the basic coupled inductor converter,in view of the shortcomings,combined with the existing literature for deduction and improvement,and systematically summarizes the deduction rules,combination constraints,and internal connections.The performance of the deduced topology was compared,and the topology with better performance was selected after comprehensive consideration.Secondly,the converter with better performance in the derivation was analyzed in detail,The topology of the two converters is similar,only one diode and one voltage doubling capacitor are different in the coupling inductor voltage doubling unit.Both converters have the characteristics of high gain and low voltage stress,which can greatly increase the output voltage by increasing the coupling turns ratio,and avoid excessive duty cycle value.At the same time,the switch tube can realize zero current conduction,and the reverse recovery of the output diode is relieved.And did the following work,modal analysis,gain and voltage stress formula derivation,performance comparison,leakage inductance on the voltage gain.And build a simulation circuit to verify the theoretical analysis.Finally,in order to eliminate the input current ripple,the determined passive ripple current injection unit was parallel at the pre-stage position of the selected first converter under the condition of maintaining high gain and low loss,so as to form a new topology satisfying both high gain and zero current ripple.The introduction of the filter unit does not change the working mode of the original converter and does not add too much loss.The device parameters in the filter unit are simple to design,easy to achieve zero current ripple and retain the characteristics of the original converter.The switch tube can conduct zero current,the voltage at both ends of each device is lower,and the diode reverse recovery is alleviated.This article analyzed the working principle in detail,derived the voltage stress and current stress of each device,and compared various performances with other converters.The correctness of the theoretical analysis was verified by simulation.In order to ensure the reliable operation of the converter and improve the selection standard of the device,the minimum critical input inductance and excitation inductance values were deduced according to the working mode of the converter under DCM state.The maximum voltage stress and current stress of switch tube and diode were derived,and the relevant parameters of transformer were designed.A 100 W experimental prototype was built to verify the correctness of the theoretical analysis and meet the characteristics of high voltage gain and zero ripple in input current.The paper has 70 pictures,9 tables,and 66 references.