A reduced order extended Kalman filter in induction motor drives

Estimating the rotor flux components and rotor resistance in induction motor drives is central to the implementation of field-oriented control strategy. The aim of this paper is to show a reduced order filter, based on the extended Kalman filter theory, for estimating these quantities. Starting from full order continuous-time and discrete-time models of the induction motor, this paper proposes a suitable reduced order model, which, with only the unmeasurable rotor fluxes as state variables, is characterized by an output equation which allows a current estimator to be derived. By augmenting the previous state vector with the rotor resistance, a non-linear model is obtained. Then, through successive extension to a stochastic model, the basis of the proposed reduced order extended Kalman filter is provided. Simulations have been carried out to verify the feasibility of estimating the rotor flux components and the rotor resistance by the proposed filter