Multiphase integrated on-board battery chargers for electrical vehicles

The paper considers on-board battery charging of electrical vehicles (EVs) using a multiphase voltage source and a multiphase propulsion motor. The multiphase inverter and the multiphase 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. The principle of the charging mode operation is based on the additional degrees of freedom that exist in multiphase machines. It is shown that they can be conveniently utilised to achieve charging through the machine's stator winding with zero electromagnetic torque. Detailed theoretical analysis is reported for a five-phase system, with a subsequent generalization to other multiphase systems with other higher odd numbers of phases. A mathematical model of a multiphase voltage source rectifier (VSR) is developed, its control in the charging mode is discussed, and the concept is validated by simulation.