A Novel Control Scheme of Four Switch Buck-Boost Converter for Super Capacitor Pre-Charger

This paper presents the novel control method of the Four-Switch Buck-Boost (FSBB) converter for Super Capacitor Pre-Charger (SCPC) in hydrogen electric vehicles. The method is proposed to improve voltage regulation characteristic during super capacitor pre-charging, and is able to maintain continuity of duty ratio and voltage conversion ratio. The novel control scheme uses two independent duty ratio, and one varies while the other is fixed in whole operation. The duty ratio of changing the value changes at the transition point. Even though operation mode changes for achieving unity voltage gain, the additional switch state diminishes voltage fluctuation at transition point compared to conventional method. Also, the size of passive components can be reduced. The feasibility of the proposed control method is substantiated through simulation and experiment with 10kW prototype.