Stator Resistance and Speed Estimation for Induction Motor Drives As Influenced by Saturation

In this paper, stator resistance and speed estimation for a vector controlled induction motor drive taking saturation into account is presented. A mathematical dynamic model of an induction motor as influenced by magnetic circuit saturation is presented. Moreover, a modified structure of indirect vector controller scheme is proposed which involves the saturated value of the magnetizing inductance. Parallel stator resistance and rotor speed estimation based on model reference adaptive system (MRAS) has been used to obtain accurate estimation for rotor speed. On-line magnetizing inductance estimation has been used within the speed estimator. Digital simulations have been carried out in order to evaluate the effectiveness of the proposed sensorless drive system. The results prove excellent steady-state and dynamic performances of the drive system in a wide speed range, which confirms validity of the proposed scheme. KeywordsInduction Machines, Vector control, Speed Sensorless, Saturation, Stator Resistance, Parameters Estimation. List of symbols m L Magnetizing inductance (H) m L̂ Estimated Magnetizing inductance (H) r L Rotor self leakage inductance (H) s L Stator self leakage inductance (H) ls L Stator leakage inductance (H) lr L Rotor leakage inductance (H)  Leakage coefficient       − r s m L L L 2 1 l T Load torque (Nm), e T Electromagnetic torque (Nm) s R Stator resistance (Ω) , r R Rotor resistance (Ω) s R̂ Estimated stator resistance (Ω) e  Synchronous speed (rad/sec), sl  Slip speed (rad/sec) * e  Command synchronous speed (rad/sec) * sl  Command slip speed (rad/sec) r  Actual Rotor speed (rad/sec) * r  Reference Rotor speed (rad/sec) r ̂ Estimated Rotor speed (rad/sec) r T Rotor time constant r r r R L T =