This paper proposes a programmable low pass

filter (LPF) to estimate stator flux for speed sensorless stator

flux orientation control of induction motors. The programmable

LPF is developed to solve the dc drift problem associated with a

pure integrator and a LPF. The pole of the programmable LPF is

located far from the origin in order to decrease the time constant

with the increasing speed. In addition, the programmable LPF

has the phase/gain compensator to estimate exactly stator flux

in a wide speed range. Consequently, the drift problem is much

improved and the stator flux is exactly estimated in the wide speed

range. The validity of the proposed programmable LPF is verified

by speed sensorless vector control of a 2.2 [kW] three-phase

induction motor.