A nonlinear controller for current source inverter induction motor drive systems

A new approach is presented for the speed control of PWM current source inverter-induction motor (CSI-IM) drive systems. This approach is conceptually based on the well-known feedback linearization technique in nonlinear control theory. Here, the commanded DC link current is generated as a specific nonlinear function of speed in the control algorithm so that the torque-speed characteristic of the CSI-IM system is forced to emulate the torque-speed characteristic of a separately excited DC motor. This is augmented by a feedback controller that slides the torque-speed characteristic along the speed axis in the torque-speed plain, in order to adjust the operating point to any desired value of speed. Meanwhile, it is shown that the proposed controller is highly robust in the presence of external disturbances.