Onboard Charger for 800 V Electric Vehicles with Low Component Count

Abstract

Ultrafast charging is essential for promoting battery electric vehicles (BEVs) as it effectively addresses critical issues like range anxiety and extended charging times. Traditional 400 V battery systems face challenges when dealing with high charging currents due to cable limitations and thermal concerns. Transitioning to 800 V battery systems allows for greater charging power capacity at lower current levels, thereby enhancing ultrafast charging capability. The advancement of 800 V passenger BEVs has made rapid charging a reality. This shift to 800 V requires careful design of onboard chargers (OBCs), as most BEV charging will still occur overnight in residential settings. It is particularly important to design single-phase OBC topologies, since most residential charging systems are single-phase. Thus, the objective of this thesis is to propose a novel, compact, and efficient 800 V OBC with high voltage gain from 120 V or 240 V AC inputs including flexible charging capabilities. Firstly, this work performs a comprehensive review of state-of-the-art 800 V passenger BEV OBC topologies, control and challenges, focusing primarily on single-phase topologies. Then, a novel single-stage isolated Cuk-derived converter for 800 V electric vehicle onboard charging is proposed, aiming to reduce component count, improve power density, and manage costs due to the necessity for higher voltage components. Finally, this thesis presents a straightforward technique of vehicle-to-vehicle (V2V) charge transfer using the proposed topology for battery charging enabling flexible charging opportunities such as DC charging.