Independent Voltage Control for Series-Connected Six- and Three-Phase Induction Machines

Many relevant concepts related to series connection and independent control of multiphase machines supplied from a single current-controlled voltage-source inverter (VSI) have recently been demonstrated by several researchers. These previous evaluations give great contribution to further improvements of multimachine series-connected devices and reduced count VSI applications. Following the initial proposition, which includes an evaluation based on the general theory of electrical machines, this paper evaluates pulsewidth modulation schemes for two-motor series-connected motor drives. The goal of this paper is to show how to achieve independent feedforward voltage control and to evaluate the switched voltage profile in the motors' windings and their behavior. Scalar and vector approaches are addressed, and simulation and experimental results are shown to illustrate the details discussed in this paper.