Modeling and Simulation of Vehicular Power Systems - webfiles its ...

Figure 2-4: Generic traction system structureThere are different topologies of hybrid vehicles but series and parallel topologies are themost commonly used ones [9]. Hybrid electric systems can be broadly classified as seriesor parallel hybrid systems [4], [5]. In series hybrid systems, all the torque required topropel the vehicle is provided by an electric motor. On the other hand, in parallel hybridsystems, the torque obtained from the heat engine is mechanically coupled to the torqueproduced by an electric motor. In an electric vehicle, the electric motor behaves exactlyin the same manner as in a series hybrid. Therefore, the torque and power requirements ofthe electric motor are roughly equal for an electric vehicle and a series hybrid, while theyare lower for a parallel hybrid [8].Each topology has its own drive train and components. It also has its own advantagesand disadvantages and uses different control strategies. In the following, the principle andmain components of each topology will be explained.2.4.1 Series Hybrid VehiclesIn this topology the primary energy converter is the internal combustion engine (ICE)which has been connected to an electric motor working as a generator. The out-put of thegenerator through power electronic converters is connected to the secondary energystorage which is a battery. The battery via power electronic converters is connected to an7