Design and Development of An Ultra-capacitor based Peak Power Management System for Electrified Metro Transit Powertrains

Hybridization of the metro traction systems has been the research focus during the last few years. Research has been done on various technologies that combine, in addition to its main energy source (DC rail), reversible energy storage devices like fly-wheels, ultra-capacitors, and batteries. Among these technologies, ultra-capacitors are promising because of their high power density and the fact that their lifespan is about ten years longer than that of batteries. The idea is to store the regenerative braking energy in an ultra-capacitor module. This energy will be used during the acceleration. As such, the grid will be protected from the over-currents related to start-up of the metro car. Moreover, the traction system efficiency will increase since the braking energy which is dissipated in resistors in the current system, will be recovered. In this thesis the Montreal Metro Traction system is studied. The main energy source (MES) is the DC rail in Metro. The metro system is first analysed and model. Ultra-capacitor sizing is done for the system. For the purpose of simulation, the initial system is scaled down. A 2 Hp machine is used as the traction motor. A bidirectional buck-boost DC/DC converter is designed to drive the motor. The ultra-capacitor interfaced bidirectional DC/DC converter and the ultra-capacitor bank are modeled and simulated. A unidirectional boost DC/DC converter is designed and simulated along with PI controllers, to control the flow of power from the DC rail (MES). Moreover, two efficient supervisory control strategies are developed for two possible ultra-capacitor bank sizes of the Montreal metro system. The novel control strategies enables superior regulation capability and ease of control