Computerized modelling of an electrical power system for a fuel cell based hybrid locomotive

The objective of this thesis is to create a computerized model for a fuel cell based hybrid switcher and pusher locomotives. These locomotives are powered by three power sources namely solid oxide fuel cell, lead acid batteries and ultra-capacitors connected to a common DC bus via unidirectional and bidirectional converters. A real time power demand for the locomotives is considered, to determine the ratings of each power source. Fuel cell supplies average power as it has a large time constant and the dynamics in the power demand are handled by a combination of batteries and ultra-capacitors. Discharging and charging current of the battery are controlled depending on the state of charge of the VRLA battery. A series and parallel combination of VRLA batteries and ultra-capacitors are used as auxiliary power sources for supplying the power demand. Voltage variations of each power source are obtained from simulation results. Power supplied by the sources supplies the power demand at the DC bus and also compensates for the losses in the system.