Optimisation of hybrid vehicles operation with ON/OFF strategy

In the last years, many papers already addressed the analysis of techniques for optimizing energy management on-board hybrid vehicles. However, the large majority of them focused on detailed analyses for specific architectures, suggesting algorithms valid only for them. This paper, on the contrary, performs a basic analysis and tries to find general rules, adequate for a large variety of hybrid vehicles. In particular, strategies to minimize fuel consumption using ON/OFF technique to manage the ICE have been analysed, investigating whether these last are effectively useful, considering also the costs associated to each engine start-up. At the end, some practical case studies have been considered, to verify the validity of the general proposed approach.

I. Introduction

Nowadays hybrid vehicles are more and more considered, as their diffusion is actually increasing on the market. These vehicles are equipped with both a rechargeable energy storage system (RESS) and a fuelled power source for propulsion [1]. Different architectures can be identified. In this regard, in a series-hybrid vehicle the powers coming from the two sources are summed in an electric form, while in a parallel-hybrid scheme such power sum takes place in mechanical form. Series-parallel combinations are also possible. These aspects make hybrid vehicles very different from ordinary vehicles, in which there is a unique energy path from the reservoir to the wheels. The double path opens to an energy optimisation problem: how to continuously choose at each instant the share of the useful power between the two sourcesƒ