ABSTRACT
The paper describes a new technique for sensorless rotor flux estimation of vector control induction motor at low speed operation. The sensorless rotor flux estimation at low speed region is difficult mainly due to the terminal voltage acquisition problem and parameter variation effect. The estimation technique proposed here, estimates rotor fluxes without the motor terminal voltages signal. Thus, the problems associated with the estimation of rotor fluxes at low-speed due to terminal voltage measurement can be eliminated. To achieve this feature, the rotor flux is estimated during null or zero space vector (state 8 or 7) periods of Space Vector PWM Inverter. The terminal voltages are zero during null or zero space vector period as motor terminals are shorted through the upper or lower switching devices of the inverter. Thus, the rotor position estimation can be performed using the zero vector period stator currents considering terminal voltages are zero. Theoretically the proposed estimator can estimate the position signal just after the first sampling period of the inverter. The method is simple and easy for implementation. Extensive computer Simulation results are presented in this work to validate the performance of the proposed estimator scheme.
