IGBT phase leg non-idealities in active du/dt output filtering

Active du/dt output filtering is a previously presented method to reduce the variable-speed AC drive cable reflection overvoltages. It uses a passive LC low-pass filter and a pulse pattern from IGBT phase leg to control the filter output voltage slopes. The pulse pattern has to be formed in accordance to the LC filter resonant frequency, and timing errors will show up as additional overshoot at the filter output voltage, eventually reaching motor as well. IGBT phase leg output voltage distortion versus the logic-level command timing affects the active du/dt filtering performance. This paper evaluates the most relevant error sources in an experimental setup for 22 kW motor with a filter for 200 m cable length. Analysis of the filter under timing errors based on measurement results is shown. The timing distortions have an effect, but in this particular case, the practical implications are not severe as the average overshoot due to timing errors was found to be in range on 10%.