Optimization control for the efficiency of an on-board hybrid energy storage system in tramway based on fuzzy control

The rapid development of rail transit brings a great increment of electricity, in order to reduce the energy consumption and the operating cost, energy storage technology has become a hot focus in the field of rail transit. In this paper, the power loss model of hybrid energy storage system (HESS) is established from the point of efficiency improving, which includes the loss of lithium-ion battery, ultracapacitor and bi-directional DC/DC converter. In order to make the best use of HESS, an optimal equation with two objectives including the minimization of power loss and the stable operation of energy storage elements, is derived. Moreover, an efficiency optimization method with adaptive adjustment of weight coefficients is proposed after fuzzy processing. Simulation results carried out on Matlab show that compared with the threshold power management strategy, the total power loss of the HESS can be effectively reduced and the energy efficiency in a single scale tramway can be increased by the proposed control strategy.