Research On A Current-fed High Gain Bidirectional DC-DC Converter

With the rapid growth of economy and the improvement of industrial level,a large number of fossil energy consumption has made China fall into the predicament of energy crisis and environmental pollution.In order to solve these problems,China has vigorously carried out the development and use of renewable energy,among which new energy vehicles and distributed generation systems are highly prevalent.As a link between energy storage unit and DC bus,high gain bidirectional DC-DC converter plays a vital role in new energy vehicles and distributed generation system.Firstly,on the basis of high gain bidirectional DC-DC converter proposed by predecessors,the PWM control strategy when the converter is operating in the forward Boost mode is changed to PWM + PFM control strategy.The converter controls the output voltage by changing the duty cycle and adjusts the switching frequency to realize the ZCS of the high-side switches.At the same time,the forward and backward control strategy of the converter is unified,which reduces the complexity of the converter closed loop system design compared with that before the improvement.In addition,the forward Boost mode and reverse Buck mode of the converter are analyzed in detail,and the characteristics of the converter are analyzed from th ree aspects: voltage gain,soft-switching and current ripple.However,the high gain bidirectional DC-DC converter still has the hard-switching problem of some low-voltage side switches.Secondly,in order to realize the ZVS of all switches in the low voltage side of the converter,and to further improve the voltage gain of the converter,a new high gain LLC bidirectional DC-DC converter is proposed in this paper by adding the LLC resonant network at the low voltage side of the converter.In addition,the circuit structure of the converter is introduced,the main waveform of the converter’s forward and reverse work is given.Then the forward Boost mode and the reverse Buck mode of the converter are analyzed in detail,the voltage gain and the soft-switching of the converter are analyzed.Finally,the high gain bidirectional DC-DC converter and the new high gain LLC bidirectional DC-DC converter proposed in this paper are simulated respectively.The results are in agreement with the theoretical analysis.In addition,an experimental prototype is built to verify the correctness and feasibility of the converter.