Three-phase flyback/current-fed push-pull dc-dc converter with y-Δ connected transformer

This paper presents the three-phase dc-dc flyback/current-fed push-pull converter. The main features of the proposed converter are: flyback operation for a duty cycle less than 1/3; boost operation for a duty cycle range from 1/3 to 1; input and output ripple current cancellation for a duty cycle of 1/3 or 2/3; reduced inrush current in flyback mode operation; the voltage and current frequencies in the output filter are three times higher than the switching frequency; The Y-Δ connection allows a reduction of reactive power processed by transformer. Typical applications include charging stations for electric vehicles, installations fed by battery units, photovoltaic arrays or fuel cell systems. This paper gives theoretical analysis, simulation and experimental result data for a 2 kW; 150 Vdc input; output from 100 Vdc to 540 Vdc and, 40 kHz switching frequency.