Implementation of a modular power and energy management structure for battery-ultracapacitor powered electric vehicles

Abstract

The primary design challenges in electric vehicles having multiple energy storage systems lies in controlling the net energy expenditure, determining the proportional power split and establishing methods to interface between the energy systems so as to meet the demands of the vehicle propulsion and auxiliary load requirements. This paper presents a structured and modular approach to the design and implementation a power and energy management system (PEMS) for electric vehicles (EV). The physical model EV developed for this work is powered by dual energy sources, consisting of batteries and ultracapacitors. Operation of the PEMS has been structured into modular hierarchical process shells. The energy management shell (EMS) handles the longer-term decisions of energy usage in relation to the longitudinal dynamics of the vehicle. The process within the power management shell (PMS) however handles the fast decisions to generate power split ratios between the batteries and ultracapacitors. Finally the power electronics shell (PES) handles the ultra fast switching functions that facilitate the active power sharing between the two sources. Design procedures, simulations as well as preliminary experimental results are presented to exemplify the function the structure. The modular structure approach is design-implementation oriented, with the objective of contributing towards a more unified description of the EV power and energy management problem.