Considering an extreme increase in both energy price and consumption, in the recent years, the researchers have focused their studies on fossil fuels consumption optimization as well as renewable energies. Today, fossil fuel sources are the first choise in traortation systems, therefore energy consumption optimization is considered as a significant issue, and hybrid electric vehicles (HEV) play an outstanding role in this regard which even could be considered as a long term solution in fuel consumption optimization. There are two basic topologies for the HEVs are named “Series” and “Parallel” topology. Each of them has its particular applications. In this thesis features of Conventional Series Hybrid Electric Vehicle (SHEV) have been discussed in details first, and then application of doubly fed generator has been analyzed in a SHEV to enhance the efficiency. The opportunity obtained by use of doubly fed induction generator in a SHEV provides it to have torque and speed coupling separately and electrically. In this structure the speed control of internal combustion engine is feasible independently of traction motor speed in a specific region by rotor power control of the machine through sleep control. Here to achieve this aim, a stator flux vector control has been applied to use doubly fed induction generator as a speed coupling unit. Also the oscillation of traction motor torque can be compensated by inserting a DC to AC converter between AC bus and energy storage system to inject the appropriate current to AC bus. This Converter is only used to inject the current in phase with the phase voltage and not to produce reactive power. Utilization of doubly fed generator in a SHEV leads to loss reduction arisen by the power conversion and then to efficiency enhancement of whole system. However, an appropriate control method should be used considering the operation of all parts of system. There are two basic methods used in a conventional SHEV to control the operation of the system that are “ON-OFF” and “Power Follower”. In this thesis first, these two methods are applied to a SHEV benefiting from doubly fed induction generator,. The simulation results for the first control confirm the fact that because of low average load power, the efficiency of the system does not improve. In the second method, the circulating power among some parts of the system makes the efficiency not to enhance dramatically. To solve these problems, in this thesis, a new method so called “Operating Point Follower” is introduced for the SHEV benefiting from doubly fed induction generator in which the traction motor operating point is followed by Internal Combustion . Keywords: 1- Hybrid Electric Vehicle (HEV), 2- Series Hybrid(SHEV), 3- Doubly Fed Induction Generator(DFIG), 4- Power Follower Control, 5- Operating Point Follower Control.
