A Single-Stage Bidirectional AC–DC Converter Feasible for Onboard Battery Chargers

Abstract

This article proposes a novel topology of a single-stage single-phase bidirectional ac–dc converter with high-frequency isolation feasible for onboard chargers. Its structure uses the interleaving concept associated with an autotransformer that is responsible for sharing the current stresses and increasing the current ripple frequency, as well as obtaining a five-level voltage waveform. A theoretical study of the structure, the operation principle, and a detailed loss analysis are performed. The mathematical analysis and control strategy are validated through simulations and a 1-kW small-scale experimental prototype. The topology is also redesigned to 6.6 kW and a comparison with a traditional two-stage solution usually employed in onboard chargers is presented, thus demonstrating that the proposed structure is competitive with other similar counterparts. Despite the proposed converter presents higher capacitive losses, when operating at 200 kHz, it has reduced volume of magnetics, resulting in an efficiency of 95.71%. If the proposed converter is designed for the operation at 80 kHz, a similar magnetic volume results when compared with the two-stage solution, but with a higher efficiency of 96.36% and avoiding the volume of resonant capacitors.