A 6.6 kW Highly Efficient Reconfigurable Dual Active Bridge Converter Designed Using Planar Transformer, SiC-FETs and Monolithic Bidirectional Devices

Efficient performance of a standard dual active bridge (DAB) converter with symmetric full bridges in primary and secondary sides of a galvanic transformer and within a limited range of voltage conversion gain has been extensively proven in both industry and academia. However, when a battery charger system for energy storage or automotive applications operates at a lower power rating, or whenever a wider voltage conversion range is required (200 V to 800 V), such efficient performance is compromised due to the loss of zero voltage switching (ZVS). The concept of reconfigurable DAB converter is developed in this work to alleviate such problem. The proposed topology consists of a T-cell branch and a half-bridge cell in both the primary and secondary sides, which can be reconfigured as a full- or half-bridge circuit. By incorporation of SiC-FETs and a recently developed monolithic bidirectional GaN device in the proposed reconfigurable DAB converter, four different configurations are extracted aiming to preserve the ZVS operation with a high overall efficiency for a wide range of input/output voltage regulation. A planar transformer (PT) design using Pareto-Front optimization is also carried out for the galvanic isolation. Working principle of the proposed concept is discussed, while the design guidance of the PT, and the ZVS range analysis are given in details. A 6.6 kW/50 kHz prototype with a 98% peak efficiency for 200 V to 800 V input voltage and 400 V output voltage is fabricated and its detailed experimental results in each of the operation modes are presented.