Design and analysis of isolated integrated charger for PHEV

Abstract

The operation and efficiency of HEV (hybrid electrical vehicle) greatly depends on its charging system. The HEV uses grid power to charge the battery. The traction circuit components are not normally engaged during the charging time, so there is a possibility to use them in the charger circuit to have an on-board integrated charger. Most charges are non isolated type having low charging power capacity. Therefore on board isolated high power charger is required for PHEV (plug in hybrid electrical vehicle) which may improve the charging efficiency of the battery. The size and price are important considerations for such integrated charger. In this paper, an integrated on board charger is proposed which provides high charging power and unity power factor operation. In the proposed design, asynchronous machine and bi directional converter are used so that the machine can act as motor during traction and isolated transformer during charging. The boost converter topology is used for the bidirectional converter which can be used as inverter during traction. The proper operation of integrated charger greatly depends on grid synchronization and controlling mechanism of converter and asynchronous machine. The Park transformation is used for mathematical electromechanical model of the asynchronous machine. A controller scheme is designed by using the concepts of conventional controlling scheme of IPM (induction permanent magnet) motor/generator set and decoupled current control method of boost converter. The whole system is simulated in Matlab/Simulink based model in order to verify the system operation of the proposed charger. The simulation results show good performance of the charger leading to machine speed stability and smooth grid synchronization.