Research On Bi-directional Current-fed Push-pull DC-DC Converter

At present,due to the global energy shortage and the increasingly serious problems for environmental pollution,the replacement of fossil fuels by new energy has become a trend.Among new energy sources such as photovoltaics,wind energy,water energy,fuel cells,etc.,fuel cells have become one of the most promising energy sources due to their high efficiency,no pollution,and a wide range of using.At the same time,the rapidly developing electric vehicle is also increasing demand for fuel cell systems.Compared with other electric vehicle power batteries,fuel cells have the advantages of high energy conversion efficiency and fast hydrogenation speed.However,in the process of energy conversion,fuel cells usually have large current and voltage fluctuations,which cannot meet the power requirements of the output motor and the voltage requirements of the DC bus.A common solution is to connect a supercapacitor or high-voltage battery in parallel to the fuel cell to stabilize the output voltage.Using supercapacitors as auxiliary energy storage modules and connecting to the DC bus through a bidirectional DC/DC converter can effectively improve the output characteristics of the fuel cell.The bidirectional DC/DC converter is an important component of the fuel cell system.Under this background,a new bidirectional high-gain push-pull triple voltage converter is proposed.First,the low-voltage side is a current source type push-pull structure,and the high-voltage side is a triple voltage structure,which is used to increase the voltage gain.The advantages for the converter are low current ripple and high voltage gain.Secondly,the article proposes to put the active clamping circuit on the low voltage side to improve the hard switching and turn-off voltage spikes.The final bidirectional high-gain push-pull resonant triple voltage converter implements full-switch soft switching in boost mode and partial switch soft switching in buck mode,which improves converter efficiency.In addition,the inverter reuses the energy of the clamping part,improving energy efficiency.First,this paper analyzes the working principle waveform of the bidirectional push-pull triple voltage converter.Then,the focus of this article,the working principle of the converter with active clamping principle is analyzed in detail,including the boost mode and the buck mode.In addition,the voltage gain in the boost mode and the buck mode,the voltage stress analysis of the switching device,and the input current ripple are all described in detail.Finally,combined with the above working principle analysis and switch stress analysis,this article describes the application principles and design methods of device selection,resonance capacitor selection,PCB design,etc.,and builds an experimental platform for simulation and actual experiments.Comparing the results of simulation and experiment with the above working principle verifies the correctness of the theoretical analysis.