EMI Filter Volume Minimization of a Three-Phase, Three-Level T-Type PWM Converter System

In this study, the power density of a two-stage, i.e., LCLCL, electromagnetic interference (EMI) filter for a 10 kW three-phase, T-type three-level, boost-type PWM rectifier system is optimized concerning construction volume. It is found that reasonable boundary conditions limit or define most component values and only few degrees of freedom are remaining. In this context, the ratio of the first filter stage's common to differential mode inductance, k
_L
= L
_cm,1
/L
_dm,1
, is identified to particularly affect the total filter volume. For given switching frequency and DC-link voltage of f
_s
= 48 kHz and V
_dc
= 700 V, a flat minimum of the overall filter volume results for 10 <; k
_L
<; 40. The boxed volume of the filter realized for k
_L
= 18 is 763 cm
³
(46.6 in
³
), which corresponds to a filter power density of 13.1 kW / dm
³
(215 W / in
³
). Measurements of conducted EMI confirm that the rectifier system complies with the considered limits of conducted EMI (CISPR 11, class A).