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Abstract-Using the vector space decomposition (VSD) approach, the currents in a multiphase machine with distributed winding can be decoupled into the flux and torque producing α-β components, and the loss-producing x-y and zero-sequence components. While the control of α-β currents is crucial for flux and torque regulation, control of x-y currents is important for machine/converter asymmetry and dead-time effect compensation. In this paper, an attempt is made to provide a physically meaningful insight into current control of a six-phase machine, by showing that the fictitious x-y currents can be physically interpreted as the circulating currents between the two three-phase windings. Using this interpretation, the characteristics of x-y currents due to the machine/converter asymmetry can be analysed. The use of different types of x-y current controllers for asymmetry compensation and suppression of dead time induced harmonics is then discussed. Experimental results are provided throughout the paper, to underpin the theoretical considerations, using tests on a prototype asymmetrical six-phase induction machine.

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AbstractThe paper considers an integrated on-board charger for electric vehicles (EVs) that incorporates an asymmetrical nine-phase machine and an inverter into the charging process. The charging is from three-phase mains, and it employs exclusively the power electronic components that already exist on-board the vehicle, and that are mandatory for the propulsion. No new elements are introduced. Moreover, the charging is achieved without any hardware reconfiguration since the existing elements and their connections are not altered during the transfer from propulsion to the charging mode. Instead, the operating principle is based on additional degrees of freedom that exist in nine-phase machines. These degrees of freedom are employed to avoid electromagnetic torque production in the machine during the charging process, although currents flow through its stator windings. The configuration operates with a unity power factor and is capable of vehicle-to-grid (V2G) operation as well. A detailed theoretical analysis is given, and the control for the charging/V2G and propulsion modes is discussed. Theoretical analysis is validated by experiments for charging, V2G and propulsion operating regimes.