A Boost-Inductorless Electrolytic-Capacitorless Single-Stage Bidirectional Isolated AC–DC Converter

Abstract

With the development of wide-bandgap devices, bidirectional isolated ac–dc converter becomes an attractive solution to realize highly compact, highly efficient power conversion for electric vehicle (EV) chargers and energy storage applications. However, in the existing literature, regardless of two-stage or single-stage isolated ac–dc converters, the circulating current in boost inductors is inversely proportional to the inductance value, resulting in large volume and high loss of the converter. In this article, a boost-inductorless electrolytic-capacitorless single-stage bidirectional ac–dc converter with high-frequency isolation is proposed. With the introduction of a center-tapped transformer, the proposed converter can achieve nearly zero circulating current without any boost inductor, thus overcoming the drawbacks mentioned above. Equivalent circuit analysis is applied to illustrate the operation principle and advantages of the proposed topology. A detailed comparison between the proposed topology and the state-of-the-art is also provided. The experimental results obtained from a 3.6 kW, 140 kHz single-phase EV charger prototype are given as the proof-of-the-concept. It is demonstrated that the proposed converter prototype realizes a peak efficiency of 96.4% with only 38 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> H total inductance and 6.33 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> F total capacitance.