Abstract
To date hybrid-electric vehicles (HEV) make use of high-power density ac propulsion systems to provide comparable performance with vehicles using internal combustion engine (ICE) technology. Electric motor, inverter, and associated control technology has made substantial progress during the past decade and it is not the limiting factor to either vehicle performance or the large-scale production of hybrid vehicles. The search for a compact, lightweight, and efficient energy storage system that is both affordable and has acceptable cycle life remains the major roadblock to large-scale production of HEVs.
This paper deals with an original HEV propulsion system that includes fuel cell generator and storage energy system combining ultracapacitor tank and battery. The three on-board power sources supply the vehicle traction drive through a multi-input dc-to-dc power converter which provides the desired management of the power flows. In particular, in the proposed arrangement the ultracapacitor tank is used for leveling the battery load current during transients resulting from either acceleration or braking operation of the vehicle. The paper outlines the features of the dc-to-dc power converter being used in the proposed propulsion system and describes the main characteristics of a 35 kW prototype of the propulsion system ENEA and University ROMA TRE jointly developed to conduct laboratory experiments and validate the control strategy.