Research On Three-phase LLC Resonant Converter With High Power And Wide Output Range

At present,the shortage of energy and environmental pollution has led to the rapid development of the pure electric vehicle industry,which has become a new industrial hotspot,and a number of new electric vehicle manufacturers have emerged in China.However,the charging needs of various electric vehicle manufacturers are not uniform,and a large number of charging equipments will bring new impact to the power grid.Therefore,the charging equipment of electric vehicles requires high power,wide range,high efficiency,and high power factor.This is also one of the bottlenecks for the mass popularization of electric vehicles.Research on charging piles for electric vehicles have great significance.This paper mainly studies the DC/DC module of high-power DC charging pile,and adopts two-way star three-phase LLC resonant converter as the main topology.In this paper,the equivalent circuit of star three-phase LLC resonant converter is established by using the Fundamental Harmonic Approximation.The working mode and DC voltage gain are studied.The influence of various parameters of the resonant converter on the voltage gain is studied.The conditions for the soft switching of the switch tube are studied,and the quantitative demand for the dead time of the switch tube is obtained.In this paper,the effect of multi-phase parallel connection of LLC resonant converters on reducing current ripple is studied,and the influence of the parameters of the resonant cavity of three-phase LLC resonant converters on the current sharing effect between phases is obtained.This paper studies the phase shielding technology of the star three-phase LLC converter,solves the problem of low efficiency under light load conditions,and obtains the changes in cavity parameters and voltage gain after single-phase and two-phase shielding,respectively.In order to solve the problem that the DC charging pile of electric vehicle needs a wide range of output,a two modules star three-phase LLC resonant converter is proposed in which the primary side is connected in series and the secondary side is serial/parallel.The model is built in Matlab/Simulink and the simulation is verified.A hardware experimental platform with a maximum power of 15 kW was built.The performance and working mode of the test module were tested.The experimental results were analyzed and the feasibility of the design was verified.