Modelling and simulation of vehicular power systems

Abstract

Regarding limitation of fossil fuels and the high consumption rate of this energy for transportation, inclination of vehicle industry toward other sources of energy is inevitable. Electric vehicles and hybrid vehicles could be a good solution. Thanks to the state of art electric motors, power electronics, embedded power train controller, energy storage systems like batteries and ultra capacitors, the performance of the vehicle could become more and more energy efficient. Since the integrating of all these components in a drive train configuration could be a challenge for the manufacturer, computer simulation and modeling before prototyping could be really beneficial in terms of cost, safety and design performance. In this thesis some of the principles of modeling and simulation are discussed. The main components in hybrid vehicles are modeled and different methods of modeling are discussed. As battery plays a significant role in electric and hybrid vehicles, modeling of it is of importance. In this thesis some of the methods to model Lead-acid and Lithium-ion battery are introduced. Some tests in order to find the internal parameters of the battery are explained and based on the data from the tests a Lithium-ion battery is modeled in Simulink/Matlab. The dynamics of the vehicle in terms of longitudinal and lateral forces are discussed and a model representing the phenomenon of wheel slip is developed in Simulink. Modeling of engine and electric motors is explained. Having models in Matlab/Simulink, a series hybrid drive train including batteries, motor, generator, vehicle dynamics and control system is simulated. Given the data from the test data from a series hybrid bus manufactured by the New Flyer Company, the performance of the vehicle in terms of fuel economy, acceleration and maximum cruise speed is analyzed. The behavior of different components is also discussed. Finally, comparing the simulation results with test data, it is shown that modeling and simulation could be really helpful in design process. The battery model was verified with measurements and is proved to have a good accuracy.