An Isolated Integrated Charger for Electric or Plug-in Hybrid Vehicles

Abstract

For electric and hybrid vehicles using grid power to charge the battery, 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. In this Licentiate thesis, an isolated high power integrated charger is proposed, designed and constructed based on a special ac machine with a double set of stator windings called motor/generator. The charger is capable of unit power factor operation as well as bi-directional power operation for grid to vehicle application. The mathematical electromechanical model of the motor/generator is derived and presented. Based on the developed model, new controller schemes are developed and designed for the grid synchronization and charge control. The machine windings are re-arranged for the traction and charging by a controllable relay-based switching device that is designed for this purpose. A laboratory system is designed and implemented based on a $4$ pole $25~kW$ interior permanent magnet synchronous motor and a frequency converter considering the integrated charging features for winding re-configuration. The practical results will be added in the next step of the project. The charging power is limited to $12.5~kW$ due to the machine thermal limit (half of the motor full power in the traction mode) for this system. The whole system is simulated in Matlab/Simulink based on the developed model and controllers to verify the system operation for the charge control. Simulation results show that the system has good performance during the charging time for a load step change. The simulation results show also a good performance of the controllers leading to machine speed stability and smooth grid synchronization. Moreover, the unit power factor operation is achieved for battery charging in the simulations