| Bidirectional DC/DC converters are key devices to reach high-efficiency power transmission between energy storage devices and high voltage DC-bus,and are widely used in EV?microgrid and energy storage systems.As the voltage of battery varies in a wide range and battery is sensitive to current ripple,the bidirectional DC/DC converters are required to have a wide range voltage regulation ability and low current ripple of battery side.In addition,high efficiency should be guaranteed within a wide voltage and load range.Therefore,the realization of high-performance bidirectional DC/DC converter in energy storage system faces with significant challenges.Firstly,a bidirectional isolated resonant converter with low current ripple is proposed in this paper.This proposed converter is derived based on integration of a bidirectional Boost/Buck converter and a dual-active-bridge series-resonant converter.The operatingal principles and characteristics of this converter are analyzed in detail,and a 1600 W prototype is built to verify the feasibility of the proposed converter.Furthermore,since the control method of the proposed converter is complicated and suffers from narrow range of soft switching,a modified PWM controlled bidirectional isolated resonant converter is obtained by adding an auxiliary inductor La in primary-side.This modified converter can realized ZVS in whole voltage and load range and wide voltage bidirectional power transmission by simple PWM control.Detailed analysis is given to show that its voltage gain is only determined by the duty cycle of primary-side switches and has nothing to do with the transferred power.Therefore,the design,control and realization of the converter can be simplified.In addition,with the help of an auxiliary inductor,zero voltage switching can be achieved for all the active switches on both primary and secondary sides within the entire operation range,and the efficiency can be increased at the same time.The operational principles and characteristics of this modified PWM controlled bidirectional isolated resonant converter are analyzed in detail.The feasibility and effectiveness of the proposed converter is fully verified by the experimental results from a 1600 W prototype. |
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