A multi-source hybrid system with Li-Ion storage

To support future requirements in terms of efficiency, availability and flexibility of access, the European electricity transmission networks will undergo substantial changes in the near future that require the development of new architectures of plant and equipments which will enhance the flexibility and the ability to manage an increasing number of generators by changing the current grid scheme (from purely "distribution" to "distributed") with a considerable reduction in size of generation plants. However, although this view has been adopted by major European operators, today the end user provides only a passive contribution to the system. One of the main requirement provided in the Strategic Research Agenda of the European Technology Platform "Smart Grids" is the ability to make the end user an actor of the future energy scenario allowing him to exchange with the network both "packets" of information and "packets" of energy. The presented work is based on the development of a Multi-source Hybrid Renewable Energy System and it is a part of the results of a National Program between the Italian Ministry of Economic Development and the National Research Council (CNR). The system has been sized, designed and built and currently it is under evaluation at CNR-ITAE of Messina. Summary: The aim of the research activities was the development of a pilot plant based on PV/Wind/FC that, through a power management system and a Li-Ion battery, allowing the study and evaluation of different technologies in scenarios that each time can be modified. Ad hoc control system was implemented to manage energy and grid integration. However, when the request is scheduled for disconnection, or in case of disconnection for failure or maintenance of the network, it is capable of operating in stand-alone mode. The system was able to communicate with the user trough a graphic interface built for the control and monitoring of all signals. The plant consist of (Fig.1): a PV System (Amorphous silicon) of 1.8 kWp; a Wind turbine (Vertical axis) of 1.5 kW; a Fuel Cell (PEM) of 1.2 kW; a Li-Ion battery of 2.3 kWh. The systems are connected to the same bus voltage (230V-50Hz) and feeding an AC electronic load. The plant allows: To set different load cycles in the range 0-5kW; To enable / disable the operation of generators from renewable sources; The characterization of other electrochemical storage systems; To regulate the current from the storage system and fuel cell to the AC bus; To switch configuration grid-connected/stand alone and vice versa; To collect all the significant parameters for data analysis. The whole system, that was built in an electrical cabinet, is divided into three sections: power conditioning, protection and interfaces and control and management section (Figs. 2 and 3). Power conditioning devices have been designed to ensure that all devices maintaining high levels of safety in relation to their possible applicability in a residential installation. To supervise the management and safety of battery during charging, as well as electronics on board, was installed a rectifier governed by a programmable controller. The rectifier and the inverter allows the conditioning of input power and output, interfacing 48Vdc bus to 230Vac bus. The Electronic Management System allows to change the storage policy control (power quality, bridging power, energy management) and to monitor all electrical characteristics. The software allows also a complete data acquisition. The pilot plant has developed a double function, first to check the technical feasibility of a management and storage system of energy produced from renewable sources, on the other side to test and validate technologies in the field of electrochemical storage operating under the modality of the distributed generation.