Design And Implementation Of 3kW On-board Charger In Electric Vehicle

With the increase of energy shortage and environmental pollution,the development of new energy electric vehicles has become the first choice of countries.As its core supporting facilities,on-board chargers have become a research hotspot in this field.The on-board charger with excellent performance can not only reduce the harmonic pollution of the power grid,prolong the service life of the vehicle’s power battery,but also improve the energy utilization rate and reduce the environmental pollution.This paper mainly takes the vehicle charger as the research object,and starts from the key technical indicators such as power factor,harmonic distortion rate,efficiency and output ripple,and fully analyzes and studies the topology and control strategy of the vehicle charger.The main research contents of this paper are as follows:The main circuit solution for the on-board charger has been designed.According to the demand of power battery,the key technical indicators of the on-board charger has been determined.Via Comparing with the topology of the existing on-board charger.a two-stage topology based on the staggered parallel totem-pole bridgeless PFC and ZVS phase-shifted full-bridge converter has been proposed.The pre-staggered parallel totem-pole bridgeless PFC is used to eliminate the grid side harmonics and improve the power factor;the latter stage ZVS phase shift full bridge converter is used for lithium battery energy management,providing efficient and reliable charging current and voltage to the lithium battery at all times.The interleaved parallel totem-pole bridgeless PFC has been designed.Based on the structure and working principle of the totem-pole bridgeless PFC,the technical difficulties in the actual working process are deeply analyzed,and a new inductor current zero-crossing signal detection circuit is proposed.The software algorithm is used to realize current sharing control in the critical-conduction mode.A constant voltage mode control strategy with fixed on-time is studied.The components of the pre-stage power circuit are calculated and selected.Through building the pre-stage circuit simulation model,the circuit performance on the simulation platform has been verified.The ZVS phase-shifted full-bridge converter has been designed.Based on the structure and working mode of the phase-shifted full-bridge converter,the contradiction between the soft-switch implementation of Lagging bridge arm and the loss of duty cycle has been balanced via the research and design of the resonant inductor.By establishing a small-signal model,the theoretical optimal loop parameters have been determined,and the constant voltage-constant current-floating charge three-stage charging control strategy based on the charging characteristics of lithium battery has been applied.Same as the pre-stage circuit,the paper also has analyzed parameter design and device selection of the latter circuit.Finally,the simulation model of the latter circuit verifies the correctness of the proposed theory.A 3kW vehicle charger experimental platform has been built.Combined with the control function requirements of the on-board charger,this paper has completed the software and hardware design based on the DSP control system,and verified the overall performance indicators of the on-board charger on the experimental platform.Experimental platform test results show that the on-board charger designed in this paper can not only achieve the basic functions required for work,but also possessed excellent performances with high power factor,high efficiency and low ripple.