Research On High Gain Sepic Converter With Coupled Inductors

In the photovoltaic power generation system,the output voltage of the photovoltaic cell module is low DC voltage,and the bus voltage required by the grid-connected inverter is high.In order to raise the DC voltage of the lower photovoltaic cell module to about 10 times to meet the bus voltage,a high-gain dc-dc converter is needed.Conventional dc-dc converters need to operate at high duty ratio to achieve high gain,which leads to increased switching losses and serious diode reverse recovery problems.How to mention gain and efficiency is the focus of converter research.In this paper,based on the traditional Sepic converter,two coupled inductance voltage doubler unit are introduced respectively,and two topology structures of ccoupled inductance voltage doubler unit Sepic converter are proposed.These two converters have high voltage gain,and the gain of the converters can be changed by adjusting the turn ratio of the coupling inductance to avoid the converters working in the limit duty cycle state.he voltage stress of the switching device is reduced by using the leakage energy.Zero current turn-off of the diodes and zero current turn-on of the switches are achieved,and the reverse recovery problem of diode is alleviated,thus,the loss of these switches is reduced and the efficiency of the converter is improved.The working principle of these two converters is analyzed in detail,the expression of voltage gain and voltage stress are derived,and the influence of the duty cycle loss on the converter caused by the leakage inductance is studied.Comparison of performance analysis with other converter topologies are made on several aspects such as voltage gain and voltage stress on switches.The simulation platform is built to verify the correctness of the theoretical analysis.In order to further improve the gain of the converter and reduce the voltage stress of the switching tube,an active switching inductor unit is introduced on the basis of coupled inductor voltage doubler unit Sepic converter topologies,and two double-switch coupled inductor voltage doubler unit Sepic converter topologies are proposed.On the premise of retaining the advantages of the coupled inductor voltage doubler unit Sepic converter,the voltage gain is doubled,and the voltage gain increases significantly with the same duty cycle and turn ratio.The stress of the switch tube becomes half of the original,so the MOS tube with low voltage level and low conduction loss can be selected.The working principle of these two converters is analyzed in detail,the expression of voltage gain and voltage stress are derived,and the influence of the dutycycle loss on the converter caused by the leakage inductance is studied.Comparison of performance analysis with other converter topologies are made on several aspects such as voltage gain and voltage stress on switches.The simulation platform is built to verify the correctness of the theoretical analysis.