Measurement-Based Equivalent Circuit Model for Time-Domain Simulation of EMI Filters

In this paper, a methodology to derive equivalent circuits of EMI filters from S-parameters is introduced and discussed. Starting from measured S-parameters and with no need for information on the internal structure of the filter, a rational approximation of the measured frequency responses is derived and equivalent circuits are directly synthesized. The proposed black-box filter models are compatible with SPICE solvers and can be used, in combination with component-level representations of power-electronic equipment, for the prediction of conducted emissions through time-domain simulation. As an example of usage, a CISPR-25 test setup where the EMI filter operates in the presence of an inverter is discussed.