A five-phase series-connected two-motor drive with current control in the rotating frame

It has been shown recently that a number of multiphase machines can be controlled independently, with the supply coming from a single multiphase inverter, provided that the stator windings are connected in series in an appropriate manner. The concept has been developed under the assumption that the inverter currents are controlled in the stationary reference frame. This paper examines for the first time the possibility of using the current control in the rotating reference frame for decoupled vector control of a multiphase series-connected multimotor drive system. The considerations of the paper, although restricted to the series-connected two-motor five-phase drive system, can be extended to any other number of phases. It is shown that in contrast to the situation that arises when current control is performed in the stationary reference frame, current control in the rotating reference frame requires appropriate modifications of the vector control scheme. The need for these modifications is explained using physical reasoning and two methods of realising completely independent vector control of the two machines are proposed. Verification of the novel control schemes is provided by simulation.