The main goal of smart grids via ICT infrastructure is to limit the peak power with less required capacity of energy storages or to maximally supply power for the local loads from the renewable energy sources, if there is a certain percent of time shift-table power sources and loads. However, the response time of these sources and loads might be significant. Moreover, the impact of large scale integration of renewable energy sources and plug-in hybrid electric vehicles in smart grids cannot be ignored. In order to ensure the stability and reliability, power difference must be limited in the different time scales. In this paper, a test platform of smart grids with super capacitor based peak power unit and plug-in hybrid electric vehicles is presented. And the enhanced strategies of power management are evaluated in islanding mode as well as in grid connected mode. The evaluation results prove that seamless grid connection/disconnection can be realised by using the presented control principles in this paper.