TABLE OF CONTENTS In contrast to ICE-based and battery-electric vehicles, hybrid vehicles are characterized by two or more prime movers and power sources. Usually, the term "hybrid vehicle" is used for a vehicle combining an engine and an electric motor. More appropriately, such a combination should be called a hybrid-electric vehicle (HEV), since other, different "hybrid" configurations have been proposed (see Chap. 5 for mechanical and hydraulic hybrids and Chap. 6 for fuel cell vehicles).
In general, an HEV includes an engine (see Chap. 3) as a fuel converter or irreversible prime mover (fuel cells are treated in Chap. 6; gas turbines or Stirling engines are not considered here [1]). As electric prime movers, different types of motors (standard DC, induction AC, brushless DC, etc.) are used. In some configurations, a second electric machine is required, which acts primarily as a generator. The electric energy storage system is usually an electrochemical battery, though supercapacitors may be used in some prototypes. Sections 4.3 4.6 describe motor, battery, and supercapacitor models, respectively.
One of the main motivations for developing HEVs is the possibility to combine the advantages of the purely electric vehicles, in particular zero local emissions, with the advantages of the ICE-based vehicles, namely high energy and power density. HEVs can profit from various possibilities for improving the fuel economy with respect to ICE-based vehicles. In principle, it is possible to:
downsize the engine and still fulfill the maximum power requirements of the vehicle;
recover some energy during deceleration instead...
