induction motor drive; field oriented control; vector control; speed control; inverter fed motor drive
This paper presents the analysis of the dynamic performance of a closed-loop hysteresis current controlled voltage source inverter (VSI) fed cage induction motor drive. The control scheme employs the principle of field orientation which is also known as the vector control. This essentially transforms the dynamic structure of the induction motor into that of a separately excited DC motor. The induction motor drive is modelled and simulated with a view to studying its dynamic behaviour in the closed loop. The dynamic response of the system for conditions such as starting, speed reversal and load perturbations has been investigated in detail. The speed loop with IP (integral plus proportional) controller maintains the desired level of speed irrespective of the load variation to which the machine is subjected. The design aspects of the IP based speed controller are also discussed. Simulated results showing the behaviour of the cage motor drive in field coordinates are given to demonstrate the effectiveness of this type of control.