Research On Three-phase LLCL Bidirectional Resonant Converter With Wide Gain Range

The excessive use of fossil energy by human beings has caused serious environmental pollution and energy shortage,and countries around the world are looking for the way to solve the problem,and the development of new energy storage systems has become a important solution.At present,the electric vehicles are widely promoted around the world,with the improvement of battery energy,customer requirements and other reasons,more and more applications require electric vehicles transfer energy in bidirection,battery charging and discharging power is also increasing.Batteries are used by electric vehicles as the main power supply unit,and used as the main energy storage unit in various new energy generation systems.Therefore,the study of a bidirectional DC/DC converter with high power capacity,wide gain range,high efficiency and high power density applied to electric vehicle charging is of great significance to the development and application of electric vehicles.Firstly,the research status of bidirectional resonant converter and three-phase resonant converter is analyzed.LLC resonant converter is widely used in the DC/DC field due to its high frequency,high efficiency and natural soft switching characteristics.However,LLC resonant converter has a limited gain range,large output current ripple,and asymmetric forward and reverse gain,making it unsuitable for bidirectional,high-power applications.Therefore,by combining the LLCL resonant network with the three-phase interleaved parallel structure,a three-phase LLCL bidirectional resonant converter with wide gain range is studied,the forward and reverse gain characteristics are relatively symmetrical,the frequency modulation is adopted,the three-phase drive signal is 120° apart,the output current ripple is small,and it can be applied to the applications of high current,high power and bidirectional power transmission.Secondly,the working principle of the three-phase LLCL bidirectional resonant converter is analyzed in detail,and the forward and reverse gain characteristics of the converter are obtained by fundamental analysis.The influence of resonant element parameters on gain is analyzed,the resonant element design method of the three-phase LLCL bidirectional resonant converter is proposed,and the experimental prototype of3.3k W three-phase LLCL bidirectional resonant converter is completed.Finally,the PSIM simulation software is used to simulate the awakening simulation of the three-phase LLCL bidirectional resonant converter,and the key simulation waveforms are presented.The 3.3k W experimental prototype is verified by experiments,and the key experimental waveforms are presented.According to the experimental results,the efficiency curves of the converter in forward mode and reverse mode were drawn,and the peak efficiency is 97.8% in forward mode and 98.0% in reverse mode.