A Single-Switch High-Gain PV Microconverter With Low-Switch-Voltage-to-High-Voltage-Bus Ratio

Abstract

A new soft-switched, single-switch electrolytic capacitor-less step-up dc/dc microconverter for photovoltaic applications is presented in this article. The proposed circuit is an improved coupled-magnetics based single-switch topology that has low-voltage stress across the switch compared to the high voltage dc bus level (380–400 V). The proposed circuit is able to achieve zero voltage switching turn- on and zero current switching turn- off for the switch. Since the input inductor in the proposed circuit operates in continuous conduction mode, the required input filter capacitance is reduced and hence, allows for the small-size nonelectrolytic capacitor to be used. The main advantage of the proposed circuit is that it is able to achieve high voltage gain while the ratio between the peak switch voltage and the output dc-bus voltage is reduced compared to other coupled-inductor based topologies. In addition, the proposed converter is able to achieve maximum power point tracking through variable switching frequency control. Results are provided on a 40-V/380-V, 200-W system to highlight the merits of the proposed circuit.