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This paper presents a control strategy for the power flow management of a wayside energy storage system based on a supercapacitor technology installed in a tramway network. The control is based on the management in real time of voltage levels at catenary point connections in order to optimize the energy flow among the running tramcars and substations with the goals of improving the energy saving and reducing the voltage drops in the supply network. The suggested control algorithm was experimentally validated using a laboratory-scale model to verify the effectiveness of the strategy. A lithium-ion capacitor module with 72 series-connected laminated cells of the JSR Micro ULTIMO type was used. Thus, an emulation of a real tramway network in the city of Naples (ANM) was implemented to evaluate the potential impact in terms of costs/benefits of the next installation on the ANM network.

DC power distribution systems for building application are gaining interest both in academic and industrial world, due to potential benefits in terms of energy efficiency and capital savings. These benefits are more evident were the end-use loads are natively DC (e.g., computers, solid-state lighting or variable speed drives for electric motors), like in data centers and commercial buildings, but also in houses. When considering the presence of onsite renewable generation, e.g. PV or micro-wind generators, storage systems and electric vehicles, DC-based building microgrids can bring additional benefits, allowing direct coupling of DC loads and DC Distributed energy Resources (DERs). A number of demonstrating installations have been built and operated around the world, and an effort is being made both in USA and Europe to study different aspects involved in the implementation of a DC distribution system (e.g. safety, protection, control) and to develop standards for DC building application. This paper discusses on the planning of an experimental DC microgrid with power hardware in the loop features at the University of Naples Federico II, Dept. of Electr. Engineering and Inf. Technologies. The microgrid consists of a 3-wire DC bus, with positive, negative and neutral poles, with a voltage range of +/-0÷400 V. The system integrates a number of DERs, like PV, Wind and Fuel Cell generators, battery and super capacitor based storage systems, EV chargers, standard loads and smart loads. It will include also a power-hardware-in-the-loop platform with the aim to enable the real time emulation of single components or parts of the microgrid, or of systems and sub-systems interacting with the microgrid, thus realizing a virtual extension of the scale of the system. Technical features and specifications of the power amplifier to be used as power interface of the PHIL platform will be discussed in detail.

Nowadays, in several European Railway networks, the old DC supply systems are severely limited by line-voltage drops. In some sectors, it is not possible to increase traffic or to operate locomotives at their nominal ratings. To increase the capacity of a DC supply system, without additional substations, the authors propose a new three-wire supply system which restores the overhead line voltage with multilevel DC choppers operating as voltage boosters. Circuits using a third wire with a negative or a positive polarity are considered and compared. Case studies are presented for the French and Italian rail networks. Finally, experimental results performed on a test platform of the French railways, are presented in the case of a double 1.5 kV supply system.

This paper focuses on three alternative railway systems (i.e., railway, urban metro and city tram). An approach to assess the size of an on-board energy storage unit is proposed. The unit is designed to supply the three trains along a catenary-free track. The equations of motion are formulated in a common case. The approach solves the system of equations by means of an optimization procedure where a set of constraints on the representative variables is assigned. Service duty cycle and energy requirements are characteristics of the three alternative systems. The results of the numerical simulations focus on the design of a battery-based storage unit to be equipped in the rolling stock vehicles. Specifically, the performance required to the storage units in the three alternative configurations are investigated and compared. Some final notes pointed out the impact of the design constraints on the unit sizing.

This paper is aimed to present an experimental criterion that allows researchers and designers to evaluate the performance of DC micro-grids dedicated to charging operations of full EV. The laboratory methodology is explained through tests on a demonstrator of power architecture, specifically designed as simplified case study of a DC charging station for fully-electrified low-power two-wheeler, such as: electric scooters and bikes. This experimental prototype is composed by a 20. kW AC/DC bidirectional grid-tied converter, which realizes the DC conversion stage, and two DC/DC power converters, interconnected with the micro-grid through a DC bus. The power architecture provides on one hand the charging operations of electric two-wheeler battery packs and on the other hand the integration of the micro-grid with an ES buffer, which has the main function of supporting the main grid while an electric vehicle is on charge. The performance of the considered architecture is characterized and analyzed in different operative conditions, through a specific management of the energy fluxes. The laboratory tests evaluate efficiency, charging times and impact on the main grid, with specific reference to the DC charging operations of electric scooters. The obtained experimental results show the advantages of adopting the DC buffer architecture, compared with an AC commercial battery charger, considered as reference in this work. Finally, the numerical data of this paper, related to the single power components and to the experimental results evaluated for the whole demonstrator, effectively support the lack of knowledge in the literature about charging stations for EVs. In fact, these pieces of information, based on experimental tests, are expected to support the building of simulation models and the identification of the best energy management and control strategies to be adopted in a smart-grid scenario, characterized by distributed generation systems including renewable energy sources.

The paper proposes an energy efficiency analysis for an Ultra-Fast Charging Station (UFCS). The UFCS, realized at the DIETI Lab of the University of Naples Federico II, is equipped with two charging slots of 160 kW rated power, a grid-tied power converter of 50 kW and a Battery Energy Storage System (BESS). It is operated in Grid to Vehicle (G2V) mode using a peak-shaving strategy. The infrastructure uses two DC/DC power converters based on H-bridge, a medium frequency transformer, and diode rectifier architecture. The infrastructure is able to operate the two converters as a single or twin EV charging configuration, respectively. This paper focuses on the operating behavior of the power converters during the phases of EV fast charging. Analyses of energy efficiency have been carried out taking into account the switching and thermal behavior of the power converters. The validation of the analyses is performed through comparison with the numerical results obtained in PLECS environment. The proposed methodology is a viable tool to give support in designing UFCSs in terms of components and subsystems sizing.

The paper deals with a single-phase photovoltaic (PV) inverter based on the Cascaded H-Bridge (CHB) topology for Low Voltage (LV) grid. A distributed architecture of PV sources integrated with battery energy storage systems (BESS) is proposed with the particularity of avoiding the use of dc-dc converters. A method of compensating for the short-term daily variability of PV energy is also presented. The control implements power scheduling to ensure that constant active power is fed into the grid at every predetermined time interval (e.g., every quarter of an hour). Furthermore, a dedicated hybrid modulation scheme based on a sorting algorithm for balancing the state of charge (SOC) of the single cells is proposed. Numerical investigations are carried out on a 19-level CHB inverter implemented in a PLECS®(i.e., the simulation platform for power electronic systems from Plexim) environment to validate the feasibility and effectiveness of the proposed control strategy.

Worldwide expectancy of larger fleets of PEVs requires an increasing number of available fast and ultra-fast charging stations. In order to reduce the impact on the distribution grid of the power demand of large fleets of PEVs, the coordination of charging in stations equipped with multiple charging slots is mandatory. The paper suggests a smart charging profile of electrical vehicles based on an optimization problem in order to minimize the charging time. Constraints in term of limits on the power supplied by DSO, the available state of charge (SOC) of the BESS and the energy requested by the PEVs are taken into account. Some simulations are presented to validate the suggested charging strategy.