Bidirectional single stage isolated DC-AC converter

Abstract

A topology of bidirectional AC-DC single stage converter with galvanic isolation is proposed. The conversion is performed in one stage by using an original topology derived from LLC dual active bridge converters. By combining PWM and frequency control, it is possible to control conversion ratio and equivalent output impedance of the converter. The proposed converter can be used as off-line uninterruptible power supply with pure sinewave output, enabling both DC-AC conversion in battery backup mode and AC-DC conversion for battery charging with mains present. It can also be used as a bidirectional grid-tie inverter capable of transferring power between mains and DC voltage source (e.g. supercapacitor, battery, fuel cell, photovoltaic panels, wind generator, etc.).