• Energy Research

In the 2000s, the liberalization of the rail markets for freight and passenger travel opened up the competition. Nowadays, local, regional, and long-distance passenger rail are gradually following suit. As a consequence of the paradigm of realizing smart and sustainable cities, the operators of local railway infrastructures (i.e., metro, light railway, and commuter) are studying strategies to improve the energy efficiency of the overall system. The operators are thus involved in renewing technological infrastructures and examining new operation models for coordinating the motion of the trains fleet. With this regard, the present work proposes a timetable adjustment approach to reduce energy consumption in metro rail transit systems. In addition, a centralized control strategy to manage the output voltage of Traction Power Substations (TPSs), train regenerative power, and charge/discharge power profiles of off-board Energy Storage Systems (ESSs) is proposed. The approach is based on a two-step procedure aimed at optimally allocating the layover time among the train stops. This approach is formulated as an optimization problem, which consider the adopted control strategy, because of the correlation between control actions and timetable. Numerical examples have been carried out based on the real data from metro line 1 of Naples, (Italy). The results highlight the capability of the strategy to achieve relevant results in terms of energy saving. In addition, the advantages introduced by the proposed centralized control strategy are emphasized through a comparison with the conventional local control strategy.

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.

High Voltage (HV) overhead power lines are systems of interconnected elements that deliver massive amounts of electrical energy over long distances. Electrical conductors, used as energy carriers, are designed according voltage, current, and temperature rated value. Monitoring the power line's state variables is emerging as a crucial topic aiming at both determining the optimal real-time capability and defining a suitable model for Health Index assessment. A Wireless Sensor Network (WSN), consisting of many distributed sensor nodes that communicate with each other, can be a suitable tool to improve line ampacity by maintaining the operating variables in respect of their rated values. This paper investigates the design of an Energy Management System (EMS) for a wireless sensor for HV power line application and proposes a maximum power point tracker (MPPT). The behavior of the MPPT is discussed in terms of electromagnetic field laws and properties of magnetic materials. Ordinary and extraordinary operating conditions are investigated. The theoretical results are validated through a series of experimental tests. A prototype has been realized and tested for real operating currents. The tests are also used to verify the sensor's resilience in the presence of harsh fault conditions.

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.

This paper examines the management of ship power systems equipped by energy storage systems. Energy storage in the on-board power system can increase the efficiency of prime movers in order to reduce fuel consumption and pollutant emissions. In this paper, a management strategy for the on-board electrical network is proposed. The strategy optimally balances the charge/discharge of the storage device, the power of the generation system, the loads’ demand of hotels, auxiliaries, and electrical machineries used for propulsion and maneuvering purposes. The optimal approach aims at minimizing the fuel consumption, while technical constraints of the on-board system are considered in terms of both generation system and energy storage system. A case study of a real off-shore supply vessel is proposed. The results of the numerical application are discussed showing the effectiveness of the proposed strategy.

Abstract This paper deals with the modelling of the 2 × 25 kV – 50 Hz high speed railway supply system. The proposed approach extends the traditional multi-conductor transmission line approach typically used for high speed railway systems, which is based on the assumption of overhead conductors. More specifically, this approach models the system by considering the presence of both overhead and buried conductors. Analytical formulations to calculate self and mutual line parameters are used. A numerical simulation allows evidencing the different results when the simplified and the detailed modelling approaches are adopted. A sensitivity analysis to point out the influence of the finitely conductive ground is also proposed.

Electrified railway systems are stimulating worldwide a growing interest in innovative models, technologies and operating measures to increase energy efficiency and sustainable development, while satisfying customer requirements. Railway System Operators (RSOs) are widely studying how technologically renewing infrastructures and vehicles or applying eco-driving techniques. Any measure applied to railway systems impacts also on the primary grid, which supplies the system in terms of power and energy. Modes of impact do not depend only on the type of the measure, but also on the technological characteristics of the railway system and its modalities of operating. Aiming at verifying the interaction between a real metro system and its primary distribution grid, this paper proposes a methodology to model the interaction between the systems in terms of power flow exchanges. The model is used to verify how eco-driving techniques applied on the railway system can affect the main state variables of the primary grid, modifying the operating values of the instantaneous power and net energy. In this paper, primary grid, traction substations and railway system are modelled according to real data. The observed case study is the line 1 metro system operating in the city of Naples. Numerical simulations are carried out by means of a two-step procedure: 1) the OpenTrack software is used to determine the power requirements of the railway system as a function of the imposed operating constraints; 2) the power flow approach assesses the operating state of the distribution grid.

Proper management of railway systems is currently mandatory in order to reach energy saving objectives that positively impact on both the internal railway system and its supplying power system. In such a context, the railway system has to be analyzed in terms of both structure renewal and energy efficiency strategies, including measures ranging from the eco-driving techniques to the energy recovery. The choice of the more appropriate measures to be implemented depends on the type of system under study, because diverse responses can be obtained for different system as a function of the technological characteristics and the imposed operating assignments. Therefore, the availability of tools able to accurately describe the behavior of a system characterized by high level of complexity phenomena becomes a fundamental instrument to assess the impact of alternative measures. Railway are complex systems, which depend of logistics, mechanical and electrical elements. These aspects are all together integrated in order to meet the expected requirements of customers. Motivated by above, this paper proposes a novel train-simulator developed in Simulink-MatLab framework. The proposed simulator calculates train dynamics and energy absorption for an assigned observation time. It performs the resolution of the motion equation for a rolling stock moving on assigned track and operating conditions. One of the advantages of the proposed simulator is its ability to be easily update to different type of railway systems as well as eco-driving techniques. In this paper, the simulator was tested on an urban metro system operating in the North of Italy.