Computer-assisted modeling of traction drive converter impedance

To avoid interference of traction drive circuits on signalling systems, the power converter input impedance must overcome assigned thresholds at the signal frequencies. Such impedance is usually modelled on the basis of time invariant open loop equivalent circuits. In fact, the influence of feedback in the power converter may have a significant effect, as is shown in the paper, that provides the impedance model with the control loops closed. A computer assisted modeling technique, well suited for DC to DC power converters, has been extended to DC to AC schemes, through Park transformation. On the base of an averaged sampled data approach, the converter-input impedance is expressed in the Z-transform domain and plotted against frequency. Reference is made to a practical case