Hybrid Optimal Energy Management for HTE Vehicles

Abstract

This paper aims to optimize the energy cost for Hybrid Thermal Electric Vehicle (HTEV). The considered HTEV combines an irreversible source fuel tank with two electrical sources, namely a lithium-ion battery and a supercapacitor. The complementarity of these energy sources improves the overall performance of the traction system. More precisely, the main objective of this article is to minimize the cost of the vehicle's mission, by exploiting the on-board energy mix. To establish a compromise between the simplicity of the real time implementation and the optimality of the solution, this paper develops a strategy that combines an optimization technique with a deterministic method. The proposed approach consists firstly in distributing the traction power between the thermal engine and the electric motor.  This sharing is treated as an optimization problem under constraints. The corresponding objective function includes the on-board sources operating costs as well as penalty cost on CO2 emissions. This problem is solved using the Bellman algorithm through the dynamic programming. Thereafter, the adopted energy for supplying the electric motor is shared between the battery and the supercapacitor using a deterministic rule, namely frequency separation. To achieve optimum performances from on-board electrical sources, a judicious choice of the sharing filter cut-off frequency is made based on several criteria, namely: the effective power, the state of charge variation, and the storage devices charge and discharge cycle number. The effectiveness of the proposed energy management system is illustrated with various simulations carried out under the Matlab environment. Its supremacy is highlighted by comparing its performance with that of a conventional management strategy.