Development of Energy Optimization Strategies for Catenary-Free Tramways

The current development trend in the railway field has led to an ever-increasing interest for the energetic optimization of railway systems. A strong attention is paid to the mutual interactions between the loads presented by railway vehicles and the electrical infrastructure, including all the sub-systems related to distribution and smart energy management, such as energy storage systems. The use of regenerative braking, already widespread in tramway field, may represent one of the most promising methods to increase energy efficiency, combined with regenerative braking with storage systems of various types (Energy Storage Systems - ESS), placed on the vehicle or along the line. With the aim of correctly estimating energy performances, it is necessary to develop predictive models of entire railway systems. The objective of the present research activity was to develop an energy optimization strategy for a tram system, considering a city line in Florence. Particularly, a model of the tramway line and of the vehicle were developed with the use of simulation tools such as MATLAB-Simulink and MATLAB-Simscape. An optimization was carried out to determine the correct energy management and the use of regenerative braking, as well as the possibility to run the entire line (or portions of it) without the over-head line. The results show that recovered energy produced in the braking phase and a correct energy management can reduce the emissions produced, saving energy about 40% for each line configuration and obtain architectural improvement.