Stability analysis of a series-connected five-phase induction motor drive system using flux-linkage model

An additional topology, opened up by the use of multiphase machines, is independent control of two series connected motors, when being fed from a single VSI. The vector control of two machines connected in series when fed by a multiphase inverter lead to additional degree of freedom which lead to independent control of the two machines. To do so, it is necessary to connect in series stator windings of all the multi-phase machines, with an appropriate phase transposition. This paper deals with stability analysis of five phase series connected two motor drive system being fed by a single VSI. The linearized model used to evaluate the control characteristics of the multiphase machine is based on voltage flux linkage relationship rather than conventional model based on current voltage relationship. The presented model offers several advantages and some more meaningful information. The major contribution of this paper work is the derivation and application of this linearized model to the above mentioned drive to evaluate control characteristics of the drive system. The stability analysis of the drive system has been carried out using conventional techniques like Bode plot, Nyquist plot etc. Analytical and simulation approach used in the paper has been carried out with help of Matlab/ Simulink software.