Fast accurate computation of the DC-side harmonics in a traction VSI drive

The authors identify the inverter voltage-distortion mechanisms that are present in large VLSI drives due to inverter delay and turn-off times as well as snubber circuit operation. A fast-frequency domain model for computing the DC-input harmonics of such a drive is also presented. They show that this model may be extended to include the distortion mechanisms discussed. The accuracy of the model is confirmed by comparing the computed and measured input-current harmonics for a range of invertor delay times commonly used in traction VSI drives