Flywheel-Based Distributed Bus Signalling Strategy for the Public Fast Charging Station

Fast charging stations (FCS) are able to recharge plug-in hybrid electric vehicles (pHEVs) in less than half an hour, thus representing an appealing concept to vehicle owners since the off-road time is similar as for refuelling at conventional public gas stations. However, since these FCS plugs have power ratings of up to 100 kW, they may expose the utility mains to intolerable stresses in the near future scenario where there will be a large number of public FCS spread across the network. This paper proposes an internal power balancing strategy for FCS based on flywheel energy storage system (ESS) which is able to mitigate those impacts by ramping the initial power peak. The balancing strategy was implemented in a distributed manner to grid and flywheel interfacing converters by means of distributed bus signaling (DBS) method. Since the parameters in the proposed upper hierarchical control layer affect the stability features of the system, a reduced order small-signal model has been assembled and parameters have been selected accordingly. Finally, real-time simulation results performed on a full scale model have been reported in order to verify the validity of proposed approach.