Research On A Novel High Step-Up Current-Fed Push-Pull Converter With A Resonant Output-Voltage-Tripler

As the worldwide energy crisis and environmental pollution become more and more serious,renewable energy such as photovoltaic,fuel cells,wind energy,etc.,have drawn much attention all over the world.Due to lower production cost,fuel cell becomes a promising one.The current-fed type converter stands out for its merits of the low input current ripple and high voltage gain for fuel cell applications.However,high voltage spike and hard-switching are two essential challenges associated with current-fed type converters which are common in current-fed topologies.In order to solve the problems,a novel high step-up current-fed push-pull dc-dc converter with a resonant output-voltage-tripler is proposed in this paper.Based on the traditional current-fed push-pull converter,an active clamp circuit is added and a resonant output-voltage-tripler is utilized as a rectifier.The proposed converter conserves inherent advantages of low input-current stress and high voltage conversion ratio of the conventional current-fed converter.Besides,the voltage spike can be suppressed,and all power devices achieve ZVS turn-on at light load condition which helps to improve the overall efficiency.What's more,the two resonant capacitors of the tripler are parallel charged and series discharged via the leakage inductor,which can further improve the voltage gain and achieve the ZCS of all secondary-side diodes in the full range of load and input voltage,thus to remove their reverse-recovery current spike issues.The capacitor connected to the input source not only helps to improve the voltage gain but also helps to recycle the energy stored in the clamp capacitor and serve to the load when the capacitor operates in the mode of being series connected with the input voltage.At first,the topology structure is proposed and the operating process of the proposed converter is presented in details.Secondly,the characteristics of the converter,such as the voltage convertion ratio,input current ripple,soft-switching range,voltage stress,etc,are analyzed,and all these works are the theoretical foundation for the selection of the system parameters,the optimization of efficiency and the design of circuit.In order to further improve the efficiency,the power losses analysis and modeling,in which power losses P_loss are used as an objective function whereas the switching frequency f_s and the maximum flux density B_max are chosen as optimization variables,are carried out and the optimization methods are presented.Finally,the principles and suggestions needing to be paid attation of the device selection,the design of the magnetic components and the PCB drawing are given in this paper.Four 500W prototypes with input voltage range of 30V-50V are implemented to verify the performance of the proposed converter.The efficiency of different optimization methods are tested and compared to prove the correctness of the theoretical analysis.