Energy storage has become a key issue for achieving goals connected with increasing the efficiency of both producers and users. In particular, supercapacitors currently seem to be interesting devices for many applications because they can supply high power for a significant amount of time and can be recharged more quickly than electrochemical batteries. In different applications, a combination of the two devices, batteries and supercapacitors, could be used to develop a high-efficiency storage system with a high dynamic performance. Because of the diffusion of supercapacitors, a good model is needed to represent their behavior in different applications. Some models have been proposed that characterize supercapacitors working at either low or high frequencies. In this paper, the authors present a full-frequency-range model that can be used to represent all of the phenomena that involve supercapacitors. Moreover, to realize a simple and useful tool, the authors present a simple procedure to identify the parameters of the model that can be used to characterize a supercapacitor before use

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The advantages arising from dc distribution networks are related to the possibilities of achieving higher quality supply and easier reconfigurability of the system. This paper presents the concept of introducing some dc islands interconnected with the ac distribution network. This will make it easier to connect storage systems, electrical drives, power converters, and renewable sources (i.e., photovoltaic panels). In order to realize the aforementioned goals, a methodology for designing the control strategy of different power converters connected to a dc bus without a centralized system management control unit is proposed. In this way, a plug-and-play functionality for connecting new power converter interfaced elements in the dc network able to stabilize the voltage under different working conditions is realized. In order to prove the advantages obtainable with such a network, a 100-kW dc test facility has been realized at the laboratories of RSE. Different working conditions were tested by means both of numerical and experimental results, proving the effectiveness of the proposed strategy for voltage regulation, continuity of service, and the smart use of storage devices

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