A 15-kW Wide-Input Reconfigurable Three-Level DAB Converter for On-Board Charging of 1.25-kV Electric Vehicle Powertrains

Abstract

The demand to reduce charging times and run-time losses in electric vehicles has created a push to increase battery pack’s voltage level. 800 V class vehicles in production are approaching the 1 kV voltage limit of the Combined Charging System (CCS) connector. New fast charging standards such as ChaoJi (CHAdeMO 3.0) and Megawatt Charging System (MCS) have voltages defined up to 1.5 kV and 1.25 kV, respectively. The SAE J3068 standard, focused on 3-Φ AC charging, recommends compatibility from 208/120Y to 600/347Y, resulting in a wide voltage variation of the power factor correction (PFC) stage’s DC link. This paper proposes a reconfiguration method of a neutral-point clamped (NPC) converter in a three-level dual active bridge (DAB) converter to accommodate the wide voltage swing. The reconfigurable three-level DAB converter (R3L-DAB) topology is introduced, and its modes of operation are presented. The steady-state analysis and its soft-switching criterion are discussed. A power loss model and design methodology are established to choose the switching frequency ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_sw</i> ), turns ratio ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> ), and leakage inductance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L_k</i> ). Finally, the experimental results of a 15 kW R3L-DAB converter, with a power density of 3.25 kW/L and peak efficiency of 97.32% are presented.