Direct Torque Control of Induction Motor with Stator
Flux Estimation Based on an Improved Voltage Model
Abdelkarim Belbali, Salim Makhloufi
Using sensors to measure the stator flux for induc-
tion motor presents many drawbacks such as far less reliability,
noisy signals, vibration, and additional cost. Thus, it is essential
to synthesize an estimator (also called a software sensor) allowing
to replace the hardware sensor, for the flux estimation. In general,
this estimation is done by integrating the back electromotive force
(EMF) of the stator. However, the presence of the pure integrator
presents problems due to the inevitable DC component and the ini-
tial condition error in the back EMF. To overcome these problems,
a low pass filter has been used in the literature. Nevertheless, this
solution does not solve the problem of undesirable high-frequency
noise, especially at low speed. In this paper, we present a solution
to improve the stator flux estimator by proposing a fractional or-
der integrator to estimate the flux at low speed. This solution does
not require any hardware device; it involves low calculation time
and provides accurate practical results. The proposed solution has
been implemented using the dSPACE 1104 platform.