Isolation Control Of Three Port Full Bridge Converter

With the destruction of the ecological environmental,people begin to notice the importance of protecting the environment.The electric vehicles(EVs)gradually replace fossil vehicles because of the advantages of zero emissions and zero pollution.EVs electrical equipment shall meet the requirements of miniaturization and lightweight to increase battery quantity and size suitcase for the purpose of improve the endurance mileage.The three-port full-bridge DC/DC converter can be used in electric vehicles as a combined charger that consists of a battery charger and a DC-DC converter.This paper focused on idling port isolation between the DC-DC converter and the on-board charger,i.e.,where the DC-DC converter is isolated during the charging state and the on-board charger is isolated during the DC-DC operation state.Idling port isolation means the average power is zero,which is achieved by control the RMS current equal to zero.Phase shift control has been used in three-port full-bridge DC/DC converter to achieve idling port isolation.The current implementation is to give three-port full-bridge DC/DC converter modeling,and get an equivalent delta circuit and the equivalent ? circuit.The isolation equivalent is deduced by KCL and KVL.Even phase shift control has the advantage of simpleness,but it has the drawbacks of high RMS,high peak current,which lead to large state loss and device stress.In order to solve aboved problem,this paper propose phase shift plus PWM control.Through the Floruier analysis,peak current and ZVS range mathmetical model is constructed.The optimal phase shift angles can be deduced by lagrange equation.Based on the analysis,a consulation is given that phase shift plus PWM control have less RMS current,peak curren,return power and large ZVS region than phase shift control.Finally the simulation and experiment platform is given to verify the effectness of idling port isolation control,and the advantages of phase shift plus PWM control compared to phase shift control.This article has made theory and the technical support for the electric vehicle integration research and its application.