Estimation of state variables of inductions motors by using block-pulse functions

In this study, an estimation algorithm is proposed to estimate the state variables of a squirrel-cage three phase induction motor using only stator voltage and rotor angular speed measurements. The proposed recursive algorithm, which is based on 4th degree state model that composes stator current and rotor flux components uses block-pulse functions. In order to accept mentioned model linear in interval nTt(n+1)T integration step as T is sampling interval, it is assumed that rotor angular speed is constant for this interval. In order to specify the feedback gain matrix G used in proposed algorithm, observer poles was chosen arbitrary. As poles of the observer that determines observer error dynamic move to the left in the left half s-plane, the estimation curves are illustrated converge to the true solution in a shorter time.A squirrel-cage induction motor is fed from sinusoidal, six-steps and, PWM sources at different times in order to observe the performance of the proposed estimator for different operation conditions. When the number of samples for BPF is sufficiently large, the estimation results illustrate the fact that simulation and estimation values of the state variables are in good agreement.