On-board integrated battery chargers for electric vehicles using nine-phase machines

The paper considers on-board battery charging of electrical vehicles (EV) using a three-phase voltage source and a nine-phase propulsion motor. The nine-phase inverter and induction machine are fully integrated into the charging process. The proposed integrated on-board battery charger has an advantage of unity power factor operation with no torque production in the machine during the charging mode. Moreover, there is no need for any hardware reconfiguration between the charging and propulsion mode. The principle of the charging mode operation is based on the additional degrees of freedom that exist in nine-phase machines and that can be conveniently utilized to achieve charging through the machine´s stator windings with zero electromagnetic torque. Detailed theoretical analysis is reported for asymmetrical and symmetrical nine-phase systems. For both systems control in the charging mode is discussed, and the theoretical considerations are validated by simulations.