Fuel cell-battery hybrid system integrating two DC/DC converters for transport applications

This paper presents the arrangement, modeling and control of a hybrid system for a tramway. In order to supply the power consumption of the tramway (due to the auxiliary services and four traction induction motor drives), the hybrid system presents two power sources: 1) a Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) as primary energy source; and 2) a Ni-MH battery as secondary energy source, which serves as a supplement to the FC for tramway acceleration or for energy recovery during braking. In addition, a braking chopper is required to absorb the regenerative energy produced by motors deceleration when it cannot be absorbed by the battery due to its limitations. Both FC and battery are coupled to a dc/dc power converter, which enables an active control of the two power sources. An energy management system (EMS) is responsible for: 1) the appropriate distribution of the power demanded by the tramway between the power sources; and 2) the braking chopper operation when required during regenerative braking. The simulation results show the hybrid system capability to allow the tramway to properly follow the driving cycle.