Research Of A Novel Current-fed Bidirectional Isolated DC-DC Converter With Full-operating-range ZVS

The renewable energies,such as wind,solar and hydrogen energy,are widely applied in power generation system,hybrid electric vehicles and so on.However,the solar and wind energies are always influenced by the climate,season,geographical environment,etc.And the output power of these energies fluctuates.Therefore,the energy storage system is essential to ensure the quality and reliability of the power supply.The energy storage system demands low input current ripple and has wide output voltage range,and the current-fed bidirectional DC-DC converter can statisfy these requirements.Hence,the current-fed bidirectional isolated DC-DC converter is used to transfer power.A novel current-fed bidirectional isolated DC-DC converter is proposed in this paper.The low voltage(LV)side of the proposed converter is similar to that of the traditional Boost half bridge bidirectional isolated DC-DC converter.The Boost inductor at the input port means the low input current ripple,and the Boost circuit at the LV side is designed to high voltage gain.What is more,the voltage spike of the LV side switches is lower than that in the traditional current-fed bidirectional isolated DC-DC converter.The high voltage(HV)side of the proposed converter parallels two active half bridges,and these two half bridges share the same capacitor bridge.The midpoints of the switch bridges are all in series with inductors and connected to the transformer,respectively,which is of great benefit to the zero-voltage switching(ZVS)of the HV side switches.The hybrid phase shift plus pulse width modulation(PWM)control is adopted.The PWM control can match the bus voltages between both sides,and the current stress,the root mean square(RMS)of the current flowing through switches and the conduction losses are all decreased.The hybrid phase-shift control can make ensure the HV side switches achieve practical ZVS with full operating range and wide input voltage range.Therefore,the switching losses are decreased and the efficiency of the proposed converter can be improved.The converter topology is proposed firstly.In order to facilitate the analysis,the T-type and ?-type primary-referred equivalent circuits of the proposed converter are derived.Combined with the operating principles of the proposed converter,the power and total RMS current characteristics are derived.And then,the theoretical and practical ZVS restrained conditions of all switches are analyzed in detail.After that,the closed-loop control scheme is acquired with the help of the to tal RMS current characteristics and restrained conditions of the practical ZVS of the HV side switches.Then,an experimental prototype with 30-60 V input and 400V/2.5A output is built and the design of the transformer,inductors,switches and digital contr ol is recommended.Finally,the experiment results verify the feasibility of the control scheme and the correctness of theoretical analysis.