FREQUENCY CONVERTER WITH LCL LINE AND COMMON MODE FILTER

摘要

A filtering method and arrangement for a system comprising a regenerative frequency converter and a motor, which regenerative frequency converter has an intermediate DC circuit comprising positive and negative pole and which regenerative frequency converter is connected to a supplying 3-phase mains network via a line filter unit comprising in serial connection a first 3-phase inductor unit with mains side terminals and motor side terminals and a second 3-phase inductor unit, and a 3-phase capacitor unit which comprises phase-specific capacitors which are connected in star connection between the motor side terminals of the first 3-phase inductor unit and a star point, which star point is connected to ground via a fourth capacitor. The filtering arrangement further comprises a common mode inductor unit and a filtering capacitor unit. Filtering capacitor unit comprises two capacitors in serial connection between the poles of the intermediate DC circuit such that the common point of the capacitors is connected to the star point of the capacitor unit in the line filter unit. The filter arrangement is configured to determine the control pattern of the controllable power switches by using a 60° bus clamp modulation or a softened 60° bus clamp modulation.