In single phase fed traction systems the supplied single phase AC is converted to DC, using AC/DC converters, and then to three phase AC using DC/AC PWM inverters for driving AC motors. In this conversion process, however, the DC voltage contains a ripple with a frequency equal to twice that of the single phase AC supply frequency. This fluctuation introduces disturbances in the PWM inverter output current supplied to the AC motor and causes other negative effects. In this paper, these negative effects are discussed and a new DC active filter is proposed to reduce the ripple in the DC voltage of the motor drive. The proposed filter's control is of the feed forward type. In this control, the ripple power of the smoothing capacitor voltage is calculated and used to generate a compensating current to minimize the ripple power. Simulation results for a 1,500kVA model and experimental results for a 1OkVA mini-model system which confirm the operation of the active filter will also be presented.

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