Harmonic subspace and sequence mapping in a series-connected six-phase two-motor drive

The torque and flux of sinusoidally distributed multiphase machines can be controlled by using only two stator d-q components. Thus, in these machines there exist additional degrees of freedom, which in multimotor drive systems are used to independently control a group of series-connected multiphase machines. Series connected machines share stator currents, therefore it is interesting to study how harmonics produced by non-linearities, faults or imbalance of the feeding system are distributed in the two-motor system, in terms of subspaces and sequences. This paper analyzes low-order harmonic distribution and its effects in a series-connected six-phase two-motor drive through experimental results collected from a laboratory setup.