Current sensorless field-oriented control of induction motors

A new method for controlling a current sensorless induction motor is presented. It uses a partial state estimator to estimate the torquecurrent and a voltage predictor to predict the voltage vector of voltage source inverter (VSI). In the system, a speed controller, a torque-current estimator, a voltage-predictive voltage-source inverter (VPVSI) and a slip calculator are included. Fast response and adaptive field weakening above the base speed of the induction motor are achieved through a direct software control system based on field orientation with recursive operation between partial state estimation and voltage prediction. Besides low cost, the simplicity of the system hardware yields high reliability and good maintainability.