Stator flux controlled V/f PWM inverter with identification of IM parameters [induction motors]

A V/f PWM inverter control algorithm based on controlling the stator flux vector of an induction motor is presented. The algorithm permits an automatic boost of inverter voltage in such a way that the stator flux magnitude is kept constant. The voltage autoboost method is based on knowledge of the IM equivalent circuit parameters and given load characteristics. An offline auto measurement of the equivalent circuit parameters using a PWM inverter is described. The technique consists of performing the no-load and single-phase tests when the motor is connected to the inverter. The complete control system has been constructed and tested and the experimental results have been found satisfactory. The proposed method has achieved a considerable improvement of IM torque-speed characteristics under optimal slip frequency operation