Four-quadrant operation of sensorless FOC induction machine in field weakening region using MRAS-sliding mode observer

In high speed induction machine drive such as elevator system, 50% to 200% of the torque of the steady state torque is needed to get the required acceleration and deceleration for a short period. Also the machine should generate positive torque as well as negative torque at either direction. Thus the four-quadrant operation in torque-speed plane is necessary in such applications. In a sensorless field oriented controlled (FOC) induction machine, the speed estimation in Field Weakening (FW) region and the sensitivity to parameter error of the motor is a major problem. Model Reference Adaptive System (MRAS) approach is one of the best techniques to estimate the rotor speed due to its straight forward stability approach. Space vector pulse width modulated (SVM) voltage source inverter is preferred to feed the FOC induction machine rather than the traditional sinusoidal pulse width modulated (SPWM) inverter due to the full utilization of voltage and current rating of the inverter. In this paper, a sensorless FOC induction motor drive with MRAS scheme based on sliding mode (SM) technique to estimate the rotor speed in the FW region for four-quadrant operation using SVM fed inverter is modeled. The drive system is simulated by MATLAB/Simulink and the performance of the technique is evaluated.