Research On Series Capacitor High-Gain Bidirectional DC-DC Converter

With the increasingly serious climate warming and energy crisis,the development and research of new energy have continuously increased.Electric vehicles,micro grid,photovoltaic,wind power and other new energy have been greatly developed.Bidirectional DC-DC converter has been widely concerned as the important device to realize DC power conversion and bidirectional transmission in the development and utilization of new energy.The voltage difference between battery pack and DC bus may be very large in electric vehicles,micro grid and other applications.Traditional non-isolated bidirectional DC-DC converter is difficult to achieve high voltage gain and can not match the battery pack and DC bus.Although the isolated bidirectional DC-DC converter can achieve high voltage gain by adjusting the turn ratio of high-frequency transformer,its leakage inductance is large and its efficiency is low.Therefore,it is of great significance to study the non-isolated high-gain bidirectional DC-DC converter.In this paper,the research status of non-isolated high-gain converter is analyzed and summarized,and the series capacitor high-gain bidirectional DC-DC converter using interleaved technology and switched capacitor technology is analyzed and studied in depth.In the traditional interleaved control method of the converter,the duty cycle has range limitation.Although it can achieve high voltage gain,its adjustable range of input-output ratio is very narrow,so it can not be applied in wide input or wide output occasions.In order to solve this issue,this paper proposed a 180° interleaved control method without duty cycle limitation.The improved control method not only make the input-output ratio of the converter can be adjustment started from 1,but also broaden the current sharing range of the converter.Furthermore,the operating principle,voltage gain,current distribution characteristics and switches stress of the 3-phase series capacitor high-gain bidirectional DC-DC converter with the proposed control method are analyzed in detail.Some conclusions are extended to n-phase.In order to make the converter suitable for wide input or wide output applications,the small signal modeling is carried out according to the operating principle of the proposed control method,and the closed-loop design is carried out.In this paper,PSIM are used to simulate,and the correctness of the theoretical analysis is preliminarily verified.Through the corresponding hardware and software design,a wide input test prototype with TMS320F28335 as the core,with input voltage of 12～36V and output voltage of 120V is built.The converter under different control methods are compared and analyzed,and the effectiveness and practicability of the proposed control method are further verified.