Assessment of a DAB Converter with a Variable Transformer by Means of Orthogonal Premagnetization for Wide Voltage Operation and Enhanced Efficiency at Light-Load Conditions

This paper presents the implementation of a dual active bridge (DAB) converter with a variable transformer (VT) controlled through orthogonal premagnetization for wide voltage operation and improved efficiency under light-load conditions. The main feature of this topology is its ability to regulate the primary-referred voltage of the transformer across a wide range of output voltages, expanding the zero-voltage switching region and reducing the effective currents. The primary objective of this study is to evaluate whether the distinctive features of the DAB+ VT converter using parallel premagnetization can be extrapolated when orthogonally biasing is used. Furthermore, the study aims to assess the influence of the control winding configuration and its impact on the control current and frequency response. A 1 kW rated power prototype undergoes testing at a frequency of 200 kHz to validate the functionality of the proposed VT implementation.