Inductor Selection, Improved Active Damping, and Speed Sensorless Operation Without Voltage Sensors in IM Drive With LC Filter

Owing to the phase delay and resonance oscillations introduced by the
LC
filter connected in-between the voltage-source inverter (VSI) and the induction motor (IM), the “
L
” and “
C
” design methodology is critical. Also, the closed-loop control and the speed sensorless operation of such drives are complex without stator voltage sensors. This article addresses these issues by proposing a simple filter inductor (
$L_{f}$
) selection criterion for an
LC
filter equipped IM drive, which allows retaining the designed dc-bus capacitor, heat-sink, and power devices of VSI upon
LC
filter insertion in-between the VSI and IM. Furthermore, an existing filter capacitor selection criterion is improved adhering to the constraint on voltage drop (
$V_{f}$
) across
$L_{f}$
. In addition, this article also examines the existing active damping (AD) techniques to perform the speed sensorless operation on the IM +
LC
(IMLC) filter drive without stator voltage sensors and improves one of them to achieve the same. Summarily, through the filter selection criteria and improved active damping technique, this article proposes to retrofit the
LC
filter into the IM drive and performs speed and voltage-sensorless operation. The simulation and experimental results obtained from a 5-hp IM drive are presented to validate the proposed work.