Research On High Frequency High Voltage Gain SEPIC Converter Based On Switched Inductor

In recent years,new renewable energy is becoming the main means of grid connected power generation technology instead of traditional fossil fuels.At the same time,as an indispensable part of the new renewable energy grid connected power generation system,high efficiency,miniaturization and stability of high voltage gain DC-DC converter have become the key and difficult points of continuous breakthrough.Based on the above background,a novel high step-up DC-DC converter based on the single ended primary inductor converter is proposed in this paper.In the structure,two boost cells and a resonant capacitor are added with the characteristics of low voltage stress and soft switching.The proposed converter has significant application advantages compared with most traditional high step-up converters.Compared with Si,the third generation wide band gap semiconductor GaN stands out in high-frequency and high-voltage applications due to its low parasitic parameters,fast switching rate and high voltage characteristics.However,switching loss is the main disadvantage to limit the high frequency converters application.Therefore,this paper is based on GaN,combining soft switching technology,a resonant link is added in the proposed converter,which can achieve zero voltage on of the switch while maintaining simple topology structure,reducing the switching loss in high frequency applications significantly.The design of magnetic components is of vital importance for the whole performance of converter.The planar magnetic structure with a flat profile,good heat dissipation effect and excellent repeatability of windings is more suitable for the high frequency converter proposed in this paper.On the other hand,the combination of magnetic integration technology realizes the integration of three discrete inductors,which improves the power density of the system furtherly.At the same time,the Maxwell finite element simulation software is used for simulation analysis,and the lowest loss magnetic integration scheme EIE structure is selected from the perspective of magnetic loss.On the basis of steady state analysis of the system,in order to improve the dynamic performance of the converter furtherly,the generalized state space average modeling method is used to model and analyze the proposed converter with resonant link.According to the obtained small signal model,the open-loop transfer function from the output to the control variable is calculated,and the Bode diagram is drawn.The type Ⅲ high-order compensator is designed to improve the dynamic performance of the system furtherly.At the same time,the digital control scheme of the closed-loop system is given,so that the system can achieve the constant voltage output while maintaining the soft switching characteristics in the process of dynamic regulation.This paper presents the experimental results of a 200 W rated power test prototype,which can achieve 36V～400V voltage conversion and the soft switching characteristics under rated condition,the switching frequency is 1MHz.The working waveforms of each components tested under rated conditions are consistent with the theoretical analysis.At the same time,the dynamic performance of system under the fluctuation of the input voltage is verified.Finally,the loss of each part of the system is given,and the working efficiency can reach 91.57% under rated conditions.