Current Control for Multi-phase Machine Under Multiple Open-Faults Condition Using Gram-Schmidt Orthonormalization

This paper proposes a current control method for multi-phase machines, which supports multiple open faults in windings and inverters. For the asymmetrical machine condition caused by the faults, this paper proposes to apply Gram-Schmidt orthogonalization to an extended Clarke transformation. This method gives an orthonormal transformation even for fault conditions and allows to control of the rotating magnetic field in asymmetric conditions by DC signals in rotational reference frames. Experimental verification was conducted to compare the proposed current control with a conventional method with a nine-phase open-winding induction machine under a four-phase fault condition. The experimental results demonstrated significant suppression of instantaneous power oscillation under the multiple faults condition.