Research On Topology And Control Strategy Of Bidirectional Single-Stage On-board Charger System

Bidirectional single-stage charger system has a simple structure,fewer components,less components losses,it is applicable to a high performance on-board charger system limited by volume,weight,cost.But the inherent double-line frequency ripple of the DC bus may cause overheating and shortening lifetime of batteries.Therefore,it's meaningful to research single-stage on-board charger system with double-line frequency ripple suppression function.Firstly,the appropriate bidirectional AC/DC converter is selected,and it's working principle described by steady operation phasor diagram.Then,the AC/DC converter mathematic model is established.In order to realize energy interaction between vehicle and grid,the control strategy of the AC/DC converter is analyzed.In this paper,the generation mechanism and influence of the DC side ripple are analyzed in detail,because the inherent double-line frequency ripple degrades system performance.Addressing this issue,the solutions are mainly divided into passive power decoupling method and active power decoupling(APD)method.After discussing various APD circuits,the symmetrical half-bridge APD circuit is picked as the ripple processing module of single-stage on-board charger system.Due to the fact that the capacitance bridge arm is hard to be complete symmetry,the impact of system that will inject ripple at the grid frequency to the DC bus is studied when the capacitance bridge arm is asymmetrical.In view of this,the asymmetrical half-bridge APD circuit is researched and an improved control strategy is proposed.Owing to the half-bridge inductance was not considered,the half-bridge APD circuit,designed by the existing parameters design method,may not meet the design requirements.Further study on parameters design method is carried out.Finally,to verify the improved control strategy and the parameters design method of the half-bridge APD circuit,the simulation model of single-stage on-board charger system with half-bridge APD circuit is established by Matlab/Simulink.For further verification,the hardware experiment system of single-stage on-board charger system is carried out in dSPACE DS1005 platform.The validity of the proposed control strategy and the feaibility of the parameters design method are verified by simulation results and experiment results.