Induction machine rotor time constant identification using bisection search method

In order to achieve high performance field oriented control of induction motors, it is important that the rotor time constant be accurately known for slip speed and synchronous speed calculation. However the rotor time constant may vary during operation. In this paper, a novel rotor time constant identification method is presented. With the flux command disturbance, the current command produced by the speed regulator has different behavior under different sign of the rotor time constant error. A bisection method is then applied with the sign of the rotor time constant error to quickly find the real value of the rotor time constant. This method can be used as an online rotor time constant identification method because the disturbance in the flux command will generate smaller speed oscillation if the rotor time constant is close to the real one. Simulation results are given to verify the effectiveness of the proposed method.