SMART-SQUARE: Smart recharging station for EVs with energy-flow management and grid stabilization capabilities Concettina Buccella, Carlo Cecati, Maria Gabriella Cimoroni, Paolo Giammatteo, Hassan A. Khalid, Hamed Latafat, Kaveh Razi, Azhar Ul-Haq University of L’Aquila & DigiPower s.r.l. - L’Aquila - Italy Our Vision of Distributed Generation and Smart Grid Paradigm A convenient, reliable, clean and the greener system involving ICT for coordination and cooperation among various nodes of the system with market-based energy flow management where SMART-SQUARE represents a key element in sustainable energy production, power system stabilization and electro-mobility. Basic Concepts It is widely accepted that new paradigms in en- ergy systems are: • use of renewables • penetration of distributed generation • diffusion of smart grids and smart loads. Moreover, it is well known that society is going fast toward electro-mobility. In distributed generation and smart grids, sig- nificant problems are, among others: • quality of energy • its immediate and long term availability • complexity of energy exchanges among mi- crogrids. In renewable energy systems significant prob- lems may arise due to the fluctuating availabil- ity of energy caused by changes in metheorogi- cal conditions. Auxiliary generators with quick start-up (e.g. biomass, turbogas ...) and energy storage systems capable of immediate reaction to instantaneous load changes are needed, in or- der to limit the influence of voltage sags and other disturbances. Grid stabilization systems are also mandatory due to actual situation. In the meanwhile, the incoming electro-mobility imposes a significant re-thinking of electric grid, due to huge amount of energy necessary for fast recharging of electric vehicles, but on the other side makes available a potentially huge number of energy storage systems which, when fully or only partially charged might integrate energy available on the grid during peak demands. Therefore, an alternative solution, fully exploit- ing renewables, and fully integrating electric ve- hicles with the grid represents a viable solution, where the energy necessary for fast recharge of vehicles (Level 3, i.e. half hour at most) is lo- cally generated by photovoltaic generators and only exceptionally supplied by the grid at higher hierarchical level, while the surplus of local en- ergy could be injected on the grid. What’s SMART-SQUARE SMART-SQUARE is a new concept of smart recharge station. Distinctive features are: • main energy source is the sun • PV system consists of separate fields (eventually the single panel) each with an embedded DC/DC resonant converter providing maximum extraction of energy (MPPT) at highest efficiency • full bi-directional power conversion: the energy can flow from grid/to vehicle or viceversa i.e. it might accumulate PV en- ergy in EVs batteries, then inject it in the grid when needed (V2G operation) Smart Grid with SMART-SQUARE What’s SMART-SQUARE - Cont.d • in normal operation EVs are supplied by PV, only when PV energy is unsufficient, EVs are supplied by grid • when EVs are fully charged and,or PV pro- duce a surplus of electric energy, the latter is injected on the grid • when PV energy is not enough, grid sup- plies EVs • the whole system is governed by a sophisti- cated ICT-based energy-demand manage- ment system interacting with the main players: utility, SMART-SQUARE, users (i,e, EVs’owners) Distinctive Operational Features In order to offer high operational capabilities and the highest efficiency, SMART-SQUARE imple- ments several new features: • the whole system operates as DC micro- grid interconnected with higher hierarchi- cal level AC grid • sources are: PV panels, existing AC grid, EVs. The latest two (grid and EVs) oper- ate either absorbing or injecting energy on the grid (prosumer nodes) • each panel, or group of few panels has its own DC/DC LLC resonant converter, thus it is operating as ideal voltage source, elim- inating shadowing effects and optimizing interconnection between PV panels and the DC link. These features greatly in- crease PV generation efficiency • during standard operation EVs are sup- plied by PV. Only when PV energy is un- sufficient, EVs are supplied by grid • the whole system consists of a number of DC links (supplied by PV arrays) and a multilevel converter as bidirectional inter- face with the grid Distinctive Op. Features - Cont.d • interface between EV and SMART-SQUARE can be either a bidirectional DC/DC LLC resonant converter or a back-to-back mul- tilevel converter (depends on the EV speci- fication about input source). They operate at high power, thus ensuring fast recharge (1/2 hour at most) and full exploitation of EV energy storage operation • when EVs are fully charged and,or PV pro- duce a surplus of electric energy, the latter is injected on the grid • when PV energy is not enough, grid sup- plies EVs • power converters implement State-of-the- Art technologies: Silicon Carbide devices, Non linear control, Selective Harmonics Elimination algorithm for multilevel con- verter • the whole system is governed by a sophisti- cated ICT-based energy-demand manage- ment system interacting with the main players: utility, SMART-SQUARE, users (i,e, EVs’owners) What’s current status • the whole architecture has been drawn • the single elements have been fully speci- fied and deeply analized • a 2 kW prototype of the DC/DC LLC res- onant converter has been realized and suc- cessful tested • a 5 kW-single phase modular Cascaded H-bridge converter and a 20 kW three- phase Active Neutral Point Clamped (A- NPC) converter prototype have been real- ized and successful tested in the lab • new generation power devices are under study and a detailed Simulink model of a Silicon Carbide MOSFET has been devel- oped and successful tested • detailed studies about control and mod- ulation techniques for DC/DC LLC res- onant converters and for multilevel con- verters have been done and original algo- rithms (fuzzy logic, extended describing functions, flatness theory, selective har- monics elimination and others) have been developed obtaining original results Conclusion Our research group is dealing with some im- portant issues related to development of dis- tributed generation, smart grids and electro- mobility. The proposed architecture could sig- nificantly contribute to sustainable development of cities. View publication stats View publication stats