Energy storage solutions toward future trolleybus networks for increasing public transport electrification

In the future, the infrastructure of trolleybus networks will tend to suffer a significant increase in power demand due to the trend of increasing the electrification of public transport. The increase of conventional trolleybuses and the emergence of new vehicle fleets moved by on-board batteries, including ones capable of In-Motion-Charging (IMC) technology are responsible for this increase in power demand. This PhD dissertation presents solutions to modernize trolleygrids in view of this future condition, without the need to perform major modifications in the infrastructure such as, but not limited to, the construction of new traction substations (TSs) or the replacement of current overhead contact lines (OCLs) by ones with larger gauges. Modeling trolleybus systems is a crucial step for designing purposes of trolleygrid infrastructures, especially when considering the operation of new fleet technologies (e.g., IMC). In this context, the first topic discussed in this work involves presenting the procedure for simulating trolleybus systems within the scope of this dissertation. The second discussed topic is the grid congestion in AC distribution networks that the rising electrification of urban transportation systems can cause. The proposed solution involves adopting Energy Storage Systems (ESSs) to reduce power demand at TSs. Different types of Lithium-Ion batteries are compared, focusing on the types of Lithium Titanate Oxide and Lithium Iron Phosphate, as well as their second-life versions. The third discussed topic proposes solutions to mitigate high voltage drops at vulnerable OCL points, which could jeopardize trolleybus vehicle operation and increase Joule loss in the system. As the deployment of second-life batteries in stationary applications tends to be prevalent, their integration into the OCL infrastructure is explored. Investigations were performed to determine the conditions under which the operation of an ESS in the middle of a section does not affect the overall efficiency of the trolleybus system.