An Average Current-mode Controlled Three-phase Step-up DC-DC Converter with a Three-phase High Frequency Transformer

This paper presents a new three-phase step-up DC-DC converter with a three-phase high frequency isolation transformer in an average current-mode controlled closed loop. This converter was developed for industrial applications where the dc input voltage is lower than the output voltage, for instance in, installations fed by battery units, photovoltaic arrays or fuel cell systems. The converter´s main characteristics are: reduced input ripple current, step-up voltage, high frequency isolating transformer, reduced output voltage ripple due to three pulsed output current and the presence of only three actives switches connected at the same reference, this being a main advantage of this converter. By means of a specific switch modulation, the converter allows two operational regions. An average current-mode control strategy is applied to input-current and output-voltage regulation. Theoretical expressions and experimental results are presented for a 6.8 kW prototype, operating in region R₂ and for a 3.4 kW prototype operating in region R3, both in continuous conduction mode