Storage in electrified transport systems

Today electrified transport systems such as underground systems, light railways, trolley bus systems and cable car railways will quickly see the development of electric vehicles with onboard energy storage to be recharged through various kind of charging stations.These systems are usually connected to the grid through a static AC/DC conversion system, which can either be a line com-mutated converter or a force commutated one, the latter enabling the interface to work on the whole PQ plane. With a proper operation and the help of some storage devices, these systems can provide useful functions in the framework of demand response. A very useful characteristic which eases the possible switch towards a new operation strategy is that a transport system is usually operated by a single entity. The paper describes the functions the transport systems can perform and then focuses on the example of the Bergamo “San Vigilio” cable car, where a new drive has been installed. The refurbishment of the plant includes the installation of a 100kW, 18kWh lithium battery storage system which helps controlling the demand from the grid, provides the needed reactive power as well as acts as an active filter. Some economical evaluations complete the analysis.