Limitations in Inner-Loop PI Controllers in IM Drive With an $LC$ Filter and Its Remedies

This article presents the proportional–integral (PI) controller design, its limitation, and remedies for
$dq$
-axis currents in a vector-controlled voltage-source-inverter-fed induction motor (IM) drive with an inverter output
$LC$
filter. The idea of designing PI controllers by incorporating the
$LC$
filter dynamics into the IM dynamics is applied for the vector-controlled IM +
$LC$
filter drive. This article shows that the PI controller, a first-order controller, has limitations of stability margins and performance criteria for an IM +
$LC$
filter system. These limitations in the PI controller are demonstrated by deriving the complete range of stabilizing PI gains (
$K_{p}$
and
$K_{i}$
) for the IM +
$LC$
filter system and segregating them to satisfy the desired frequency-domain specifications. As a remedy to the limitations, this article proposes to use a second-order controller instead of a PI controller to provide better stability margins, attenuation at the resonance frequency, and more robustness. The controller design and resulting closed-loop stability are thoroughly analyzed, and the experimental results are presented to validate the same.