Rotor time constant identification in vector controlled induction motor applied flux model reference adaptive system (MRAS)

The indirect field-oriented control (IFOC) technique brought on a renaissance in modern high-performance control of PWM inverter fed induction motor drives. This method requires the actual value of the rotor time constant which is used to calculate the magnitude and the position of the rotor flux. This value varies widely with rotor temperature and flux level of the machine. So, the quality of the drive system decreases if no means for compensation or identification is applied. This paper describes a rotor time constant identification method in order to update control gains of a vector controlled induction motor. A flux model reference adaptive system (MRAS) is used to estimate the inverse rotor time constant by only using measurements of the stator voltages and currents and rotor speed of an induction motor. The estimated rotor time constant is used as feedback in a vector speed control system for voltage-controlled pulse width modulation (PWM) inverter fed induction motor. The proposed method identifies the inverse rotor time constant with a good accuracy at any load and speed references. Simulation results point out the validity of the proposed method