Nonlinear Decoupled Control for a Six-Phase Series-Connected Two Induction Motor Drive Using the Sliding-Mode Technique

In this paper a nonlinear decoupled control is designed for a series connected two six-phase squirrel induction motor (IM) drive which is supplied by a six-phase space vector pulse width modulation voltage source inverter (SVPWM VSI). By using a well known phase transposition in the series connection, the independent control of two machines can be realized completely. The nonlinear controller is developed in a stationary (alpha, beta) reference frame with rotor fluxes (lambda_alphatau, lambda_betatau) and stator currents (i_alphas, i_betas) as state variables. At the first, an ideal feedback linearization control (IFLC) system is adopted in order to decouple the torque and rotor flux amplitude of each IM. Then to enhance the performance of the drive system against uncertainties of the plant, such as electrical and mechanical parameter variation, external torque disturbance and unmodelled system dynamics, a sliding- mode feedback linearization control (SMFLC) system is applied, that comprises a SM flux controller and a SM speed controller. Moreover a two level SVPWM is used to supply the two motors drive system. Finally, the effectiveness and capability of the proposed control strategy is verified by computer simulation.