Hybrid Train Power with Diesel Locomotive and Slug Car–Based Flywheels for NOx and Fuel Reduction

Abstract

An energy-storage flywheel consists of a large inertia wheel sharing a common shaft with a motor generator (MG) set and with magnetic bearings to support the entire rotating assembly. Flywheels mounted on a special slug car are charged from the local utility grid and from regenerative-braking events. Usage of these power sources reduces fuel consumption and the related NOx emission by the locomotive-mounted Diesel generator sets (DGS). The flywheel-supplied power can replace the DGS-supplied power in one or more of the eight fixed power settings (notches), plus idle and reverse, which are common to most locomotives either for line-haul or switchyard service. The slug cars have separate traction motors to be driven by the flywheel systems so that the flywheel power and DGS power are electrically and physically decoupled. A system model is presented that includes the train dynamics coupled with the electromechanical models for the flywheels and traction motors. The modified Davis equation is employed in the train model to account for windage and other losses. A novel, feedback-based flux-weakening control of the flywheel’s motor generator current-torque and speed-back electromotive force (emf) gain is employed to increase the charge capacity, depth of discharge, and regenerative-braking efficiency for the flywheels. The simulation results show significant cost- and emissions-reduction potential for the proposed hybrid DGS–flywheel locomotive power system in line-haul and switcher service.