Experimentation with a ZEBRA plus EDLC based hybrid storage system for urban means of transport

This paper presents an experimental evaluation phase carried out on ZEBRA batteries and Electrical Double Layer Capacitors (EDLCs) based storage system, which is able to power electric urban mini-busses. The particular analyzed case study is focused on a power train, specifically designed for electric urban road applications, composed by a fixed ratio gear box connected to an asynchronous 70 kW electric drive, which is supplied by the electric parallel of two 20 kWh Zebra batteries and a 63 F super-capacitors bank. The power train is studied by means of a laboratory 100 kW regenerative electric brake, provided with speed and torque controls, in order to experimentally measure the performance of the vehicle under study, on both steady state and dynamic operative conditions. The energy flux management of the hybrid storage system is preliminarily evaluated and tested in a simulation environment and then directly embedded in the power converters, interposed between storage systems and traction electric motor, to run experiments on the whole vehicle power train. In this way the combination of the two technologies of storage systems are tested in laboratory under various working conditions and with a different contribution of each storage device, in terms of electric energy and power. The obtained experimental results shows, on one side the effectiveness of the control strategies, evaluated to balance energy and power coming from the storage system to supply the traction electric drive, and on the other side the identification of a methodology to evaluate the performance of innovative hybrid storage systems, when powering road urban transportation vehicles.