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This article reports an overview of main issues related to hosting capacity and harmonic disturbances caused by electric vehicle (EV) penetration in a smart grid, taking into account renewable energy sources and energy storage systems as well as nonlinear loads. A new mixed deterministic and probabilistic method based on algorithms and new control strategies, able to perform EVs charging controls, is presented. The methodology shows that it is possible to achieve high levels of power quality, thanks to a pre-evaluation of harmonic disturbance. Studies on real networks are reported in order to carry out indices able to define a preliminary assessment of the network hosting capacity. Suggestions and guidelines about the management of EVs charging stations are proposed and discussed in order to properly integrate them in a smart grid concept.

This study illustrates how selected instrument voltage transformers (VTs-I) behave in a transitory state. Some laboratory tests are conducted on medium voltage (MV) inductive voltage types to evaluate the voltage transferred from primary to secondary windings when a fast voltage impulse (1.2/50 μs) excites three machines constructively in different ways. Possible effects of metal parts present in the laboratory on the VTs-I behavior are analyzed, and other tests are conducted to determine a suitable shielding for the VTs-I. In order to interpret the experimental results, a theoretical study is performed using a simplified model of the instrument transformer. Finally, characteristic parameters are assigned values that were derived from experimental tests.

The paper proposes a novel approach to modelling time-varying non-linear loads in power systems, based on demand conditions. The model allows a pre-evaluation of harmonic disturbances under variable conditions using normal and uniform distribution to randomize the electrical values of the non-linear loads and the related harmonic spectra. A measurement campaign conducted on an industrial area, a deposit/maintenance and repair site utilized for trains in operation on the metro line B of Rome, has been taken into account to verify the model performance. The methodology allows estimating the voltage total harmonic distortion at the point of common coupling. Through a statistical analysis, the harmonic distortion distribution via common normality tests was evaluated. The procedure has been used also to a harmonic disturbance pre-evaluation due to a future introduction of electric vehicles charging stations in the area.

This paper proposes a methodology that is based on mixed-integer linear programming (MILP) to calculate the optimal sizing of a hybrid wind-photovoltaic power plant in an industrial area. The proposed methodology considers the: i) load requirements; ii) physical and geometric constraints for the renewable plants installation; iii) operating and maintenance costs of both wind and PV power plants; and the iv) electric energy absorbed by the public network. The power demand variation associated with the production cycles is considered by using a stochastic simulation tool. To consider both the load and seasonality variability, and to adapt the methodology to the actual operational use of the power plant, the optimization is performed separately for each month of the year. Then, an integrated economic analysis is discussed. The methodology is adopted to analyze an industrial plant in the Rome area used as a train depot and for maintenance purposes. The results, which combine the needs of the plant activity with the availability of renewable energy, enabled the determination of optimal solutions and the relevant savings achievable.

The paper presents a preliminary technical-economic comparison between a 3 kV DC railway and the use of trains with on-board storage systems. Numerical simulations have been carried out on a real railway line, which presents an electrified section at 3 kV DC and a non-electrified section, currently covered by diesel-powered trains. Different types of ESS have been analyzed, implementing the models in Matlab/Simulink environment. A preparatory economic investigation has been carried out.

The paper proposes a generic Matlab-Simulink model to represent quasi-static time-varying non-linear loads in power systems. The methodology presented allows to combine both deterministic and a probabilistic approaches. The procedure is able to evaluate voltage and current harmonic spectra under uncertainty scenarios in a power system allowing a preevaluation of harmonic disturbances. The methodology allows to simulate load variability taking into account power consumption and harmonic profile changes in time and to evaluate the introduction of new non-linear loads and renewable sources in a generic electrical power system.

The paper reports a methodology to analyze the voltage unbalance induced by a railway line electrified at 2×25 kV 50 Hz on the main high voltage network.Starting from the knowledge of maximum power consumption by trains, carrying out a train performance, a Simulink model of a real railway line electrified at 2×25 k-50 Hz has been carried out in order to calculate the voltage unbalance.Taken into account CEI EN 50160 and IEEE Std. 1159-1995, some technical solution have been proposed in order to mitigate the voltage unbalance under threshold limit imposed by standard.

The paper proposes an optimal siting and sizing methodology to design an energy storage system (ESS) for railway lines. The scope is to maximize the economic benefits. The problem of the optimal siting and sizing of an ESS is addressed and solved by a software developed by the authors using the particle swarm algorithm, whose objective function is based on the net present value (NPV). The railway line, using a standard working day timetable, has been simulated in order to estimate the power flow between the trains finding the siting and sizing of electrical substations and storage systems suitable for the railway network. Numerical simulations have been performed to test the methodology by assuming a new-generation of high-performance trains on a 3 kV direct current (d.c.) railway line. The solution found represents the best choice from an economic point of view and which allows less energy to be taken from the primary network.

The paper describes and analyzes the electrical system of a long tunnel placed along the “Naples-Bari” High-Speed railway line. In particular, a critical situation, due to a blackout event has been investigated. A generator set must guarantee the service continuity to supply safety and signaling system, emergency lighting and auxiliary equipment of electrical substations. A shunt reactor has been installed to compensate the reactive power produced by the long feeding cable and to respect the capability curve of the generator. The dynamic model of the generator set takes into account the speed governor and the automatic voltage regulator, in order to study the behaviour during the line cables energization transient. MATLAB/Simulink has been used to represent the electrical system. The results obtained by Simulink have been compared with the simulations performed by ATP software.

The paper focuses on evaluation of stray current distribution and rail potential for “Albate-Chiasso” DC railway line, that connects Italy and Switzerland. A model has been developed to calculate stray current and rail potential taking into account the European Standard, in order to avoid electrolytic corrosion and electrical safety problems. A real case study has been presented and simulated using Simulink software. A measurement campaign has been used to validate the model proposed.

Electrified guided vehicles typically face routes having a large number of acceleration and braking phases. The braking energy, since the feeding line presents nonreversible electrical feeding substations, can be recovered in the presence of other nearby vehicles. To improve braking energy recovery, one or more storage systems can be positioned along the track. Analysis of effectiveness for the considered solution requires time-domain simulation models, to be created through suitable simulation general-purpose languages or specialised languages/software. In this paper, three different tools for the considered existing tramway were developed, and the main examined characteristics have been compared to each other. Then, analysis of output results was also performed, demonstrating the real cost-effectiveness of introducing one storage device on the considered tramline in operation.

The paper reports a complete study of electrical power system on a metro line under construction in Buenos Aires supplied at 2x25 kV-50 HZ. The metro line, is at the forefront from the technological point of view, because of it represents one of the very few examples of a metro line with a 2x25 kV alternating current electrification system.The results of traffic and electrical simulations of the proposed 2x25 kV-50 Hz electrical system are presented, including energy performance due to the braking recovery, considering time shifting of departures.Different network operations, have been taken into account considering the out of service of main electrical substation. Electrical standard requirements have been taken into account to verified the results performed.Overloads of electrical machines, voltage values on the pantograph, step and touch voltages and voltage unbalances have been calculated.

The study reports the evaluations of energy recovery through the train braking. The simulations were carried out on an Italian 3 kV d.c. railway line used for high frequency transport. Several cases of braking phases were studied and the energy returned into the system, used by other trains, was reported. The energy dissipated on the on-board rheostat are also highlighted, considering the possibility of reintroducing the recovered energy into the primary power supply through reversible ESSs or storage in ESSs.

The paper describes four optimization solutions that can be used to support the transmission system planning. The problems are focused on the identification of the primary transmission system operations that optimize the power flows on the transmission lines. The approaches are based on a DC model of the transmission system and the optimization problems can be solved recurring at LP and MILP. The mathematical model and the optimization problems have been described in detail, reporting a list of applications that can be handled by the proposed methodology to evaluate the effects on transmission and generation expansion. A 9 bus test grid has been used to support the methodology explanation.

The transmission expansion planning has to guarantee the increase of competitiveness of market participants ensuring high standards of reliability and the safety of system operation. The congestion occurrences limit the competitiveness and cause an increase of costs for the final users. In the present paper a new deterministic methodology is proposed in order to support the static transmission system planning in deregulated electricity markets, which are characterized by high levels of uncertainties. The concept of criticality in transmission system planning is introduced: congestion cases and bottlenecks represent critical cases of the transmission system from a point of view of planners. The proposed approach allows individuating these critical states by solving specific optimization problems and performing reliability analyses based on the N − 1 criterion. A comparison of different transmission expansion plans is performed assessing the indices of criticality, whose evaluation is based on measuring the exploitation of the margin capabilities of transmission lines. The indices have been used to measure the reduction of criticality associated to expansion plans. The proposed approaches have been applied on two different test systems in order to demonstrate the effectiveness of the methodology in transmission system planning applications.

The paper reports a methodologic approach to define the capacity of railway junctions. The railway traffic increase, together with the improvement of passenger comfort, has produced a greater need for electricity. Consequently, solutions to augment the railway system capacity, including railway junctions, have to be achieved. In order to design new plants and to improve or certificate the existing ones, simulation of the overall railway system is necessary. In this paper the Authors propose a guideline with a theoretical approach to study the capacity of railway junctions.

The commercial routes interconnection in maritime world transport requires common criteria for the standardization of shore connection's rules in port areas. A brief focus on the part 1: High Voltage Shore Connection (HVSC) Systems (IEC-ISO-IEEE 80005–1) has been presented that is an example of global harmonization. This paper reports the cold ironing system issues due to the grounding systems. Several aspects must be taken into account as transferred touch potentials according to the workers safety for interferences due to the ground loops. The same standard 80005–1 highlights the problem about the ship's integrity related to galvanic corrosion. The goal of this paper is to show the current TN-system multiple grounding solutions adopted and to discuss the introduction of a TN-island system for HVSC, showing the decrease of the risks for corrosion of the ships and the transfer of touch potentials.

The paper reports a measurement campaign and a simulation validation for the “Roma-Giardinetti” tram line in Rome, that provides urban service from the main train station of Rome “Roma Termini” towards a suburban neighborhood of the city. A digital oscilloscope recorder Yokogawa OR100 has been used for the measurements. A monitoring on voltage and current profiles along the line, as well as on power consumptions of the tramline during the daily service, has been performed. Simulations have been carried out to compare the obtained results with measurements, in order to highlight differences. Driving style management has been applied in train performance to quantify the energy used with or without the coasting phase. Simulation results show differences between simulated and measured power and energy consumptions, due to two types of braking phase.

Auxiliary-battery-based substations (ABSs) can enhance conventional railway feeder systems. In particular, ABSs make dc feeders located in areas far from the ac grid able to power high-performance passenger and freight trains and store their braking energy. This paper proposes a techno-economic method to define size, position along the track, and control parameters of an ABS, with the goal to minimize the annual cost of energy. Our approach takes into account the replacements of battery modules within the ABS’s expected lifetime in order to reduce costs. Numerical simulations are carried out assuming a new-generation high-performance train on a real Italian 3-kV dc railway system equipped with one ABS. Although, in some cases, ABSs are already cheaper solutions compared to new traditional substations, the proposed sizing method allows obtaining a further reduction in the ABS cost.

In European Union (EU), buildings are the larger consumers of energy. To save energy, use of energy in buildings must be effectively controlled on the basis of accurate field information, acquired from indoor and outdoor sensors. In this work an all-round management approach is proposed to simultaneously control in a building all types of load, both thermal and electrical. To this aim, a load simulator implementing a novel analysis and simulation method of customer’s electric energy usage is illustrated. The model provides an estimated daily load profile by following a bottom-up approach through procedures each focused on simulating a specific energy usage in the building. The paper reports some of the main flow charts of the simulation model, as well as possible applications of the program for the prediction of the response of buildings to different demand management strategies. The suggested on-line management system was also validated through field experimental tests and a case study, whose results are reported and discussed.

This paper presents a statistical analysis about domestic PV prosumers in Terni (Italy). Data of energy produced by domestic photovoltaic systems (PVs) and of energy injected into the grid are collected for years 2015 and 2016. Statistical distributions of self-consumption and self-sufficiency rates per prosumer are reported. The analyses show low values of both self-consumption and self-sufficiency rates with respect to expected ones, as well as a reduction of such indexes from 2015 to 2016, prompting the need to increase such values (by means of storage systems and/or demand side management) in order to attain a higher penetration of PVs in low voltage distribution networks.

This paper presents the second phase of the Naval Smart Grid (NaSG) research project. In particular, it regards the study of an Integrated Power System (IPS) for an Italian Navy electric propelled ship, endowed with improved control and reliability characteristics. Aim of the project is to develop guidelines useful for designing a new ship, capable of exploiting innovative features: modular power system, subsystem’s flexible integration, improved efficiency, enable new weapon systems’ installation, improved survivability. In this regard, this paper presents the aims and the most significant technology research results of the NaSG project second phase.

The paper proposes a methodological approach to manage the electric vehicles recharging in an isolated power system characterized by low short circuit power. Focusing on harmonic disturbances, current harmonics injected in the network depend on the specific EV power converter. The model carried out allows for the evaluation of harmonic disturbances under variable conditions for non-linear loads and their harmonic spectra. The methodology allows estimating both current and voltage total harmonic distortion (THDV, THDI) at the point of common coupling (PCC). An algorithm able to manage and control the EV charging in a parking area has been developed in order to keep the THDV under a threshold limit.

The paper proposes a computational procedure able to control in real-time the harmonic disturbance injected by nonlinear loads in an islanded MV/LV Smart Grid, characterized by low short circuit power. Aim of the proposed procedure is to keep automatically under acceptable values the penetration of harmonic disturbances caused by different loads, by means of a control algorithm suitable to a Smart Grid context. The control logic has been developed to perform detachments/controls in realtime in function of non-linear loads and their harmonic injection, starting from the assessment of voltage total harmonic distortion (THDv). In order to not exceed the harmonic disturbance thresholds, imposed by the Standard, the smart grid loads are scheduled by means of delayed activations over time, also using energy storage systems. The procedure is able to simulate load variability taking into account power consumption and harmonic profile changes in time. Electrical network, linear and non-linear loads and control algorithm have been implemented in a Simulink model. A case study representing a typical smart grid with residential and tertiary users, electric vehicle charging points and renewable sources is presented.

This paper presents an innovative proposal for the selection of electrical loads in intelligent networks when main power sources are limited or totally absent (in the following: in emergency conditions). The control strategy is based on the mathematical approach of the basis 0–1 Knapsack Problem. Results from three different algorithms are compared: Tabu Search, Greedy heuristic and dynamic programming. To verify correctness and accuracy in the solutions, a MatLab software have been developed. To evaluate the achieved results, a case study is shown in a true-life environment.

Advanced guidelines have to support the design of every electric power systems in hunting performances of safety, dependability and costs saving. Particularly, power systems, critical for the mission of their loads and/or equalized to mission critical for the vulnerability of their supplying network, need a “partition system”, local fortified structure, interface between network and utilization, designed as a service continuity “castle” and managed to guarantee an adequate response to every emergency. The paper emphasizes the importance of a Business Continuity Management (BCM), qualified to a comprehensive design of the system throughout its life cycle complying with the criteria of the ‘Plan-Do-Check-Act’ (PDCA) that is taking care of all the exigencies with both the approaches of the installer and of the operator (In-Op design). This operational management must ensure the efficacy of the partition system in maintaining dependability and functional safety against the loss service continuity during fault events, maintenance demands and emergencies for external stresses. In fault events, the protection system contemplates the starting of a countdown time for a prompt response of a qualified team must in solving the problem before the system collapses causing the automatic disconnection of supply.

The paper reports a methodologie approach to analyze a new layout of 3 kV DC railway substation. An evaluation about the substations' (ESSs) filter, in order to reduce the reactor encumbrance has been carried out. By means of simulations with different filter configurations, the proposed approach allows to verify that the harmonic content of the released current in the return circuit is compatible with the safety and signalling devices and to evaluate the effect of new configurations on the fault current.

The AC power supply systems represent one of the most considered technical solutions for high-speed railway lines. This paper analyses these systems by utilization of numerical simulation models, to determine current voltage and power flows under realistic operating conditions. The proposed models are implemented in two ways: as a model for the well-known Electro-magnetics transient program ATP, and as a model written in the standard modelling language Modelica, and used inside a Modelica-capable simulation tool.

The paper shows the typical architecture of a 2×25 kV–50 Hz traction system, and the details that need to be considered and approximations that can safely be done, for power frequency studies. Power frequency models are important to allow simulations of long timespans, such as those needed when evaluation of trains acceleration/braking, for instance to analyse active and reactive power flows, voltages and currents. The proposed models are implemented in two ways: as data to be inputted to the well-known ATP Program, and as specific models written in the standard Modelica language. The latter can be virtually used for simulations using any of the available Modelica-capable simulation tools; moreover, the power of Modelica allows flexibility, expandability, scalability. A comparison between the two tools is proposed.

This paper presents an experimental application of LiFePO4 battery energy storage systems (BESSs) to primary frequency control, currently being performed by Terna, the Italian transmission system operator (TSO). BESS performance in the primary frequency control role was evaluated by means of a simplified electrical-thermal circuit model, taking into account also the BESS auxiliary consumptions, coupled with a cycle-life model, in order to assess the expected life of the BESS. Numerical simulations have been carried out considering the system response to real frequency measurements taken in Italy, spanning a whole year; a parametric study taking into account different values of governor droop and of BESS charge/discharge rates (C-rates) was also performed. Simulations, fully validated by experimental results obtained thus far, evidenced a severe trade-off between expected lifetime and overall efficiency, which significantly restricts the choice of operating parameters for frequency control.

In the last years, high penetration of distributed generation (DG) has strongly affected public MV networks. In order to improve their reliability and availability, loop operation is being tested. This solution requires the installation of new line protection devices and the identification of appropriate settings against phase-to-phase and ground faults. This study refers to an experimental loop line operated by ENEL Distribuzione, the largest Italian Distribution System Operator (DSO). The paper deals with the behavior of the currently installed line protection during cross-country faults (CCFs), occurring both in radial and loop lines. MV network response has been preliminary evaluated by approximated formula (which allow a fast check of line protection performances), and then verified by accurate simulations based on a detailed Simulink network model. CCFs occurring inside and outside the loop line have been analyzed. Obtained results show that the zero-sequence and phase directional overcurrent (Blocking-Scheme supported) are generally able to selectively identify and clear CCFs. Nevertheless, if CCFs occur in the same overhead stretch of the loop line, the adopted protection scheme may fail.

Aim of the paper is to underline harmonic disturbance issues about the penetration of electric vehicle (EV) charging stations in real MV/LV distribution networks. The presence of various non-linear loads, due to the high penetration of electronic converters on the LV side, highlights the need to assess the state of the network also on MV side. A sensitivity analysis about the composition of harmonic disturbances due to AC/DC converters installed on-board in EVs has been developed, based on experimental data obtained from laboratory measurements on five commercial EVs. Harmonic resonance evaluation is essential to know the effect of non-linear loads penetration, or when one or more portions of the network are not connected to MV busbars. In particular, harmonic disturbances for two scenarios with different slow charging point penetration and different MV network configurations are presented.

Reliability and quality analyses play an important role in defining the structural and operative characteristics of the system and in setting reliability and maintainability specifications, which could assure that service quality requirements will be met. The paper illustrates a methodology for the prediction of service quality of a high-speed railway system as a function of reliability and maintainability of subsystems forming transit system, failure recovery policy of failed subsystems and degraded conditions traffic management policy, quantifying delay trip acceptable by passengers. A specific model to evaluate System Service Dependability for each transit system has been developed for different values of acceptable delay. The Rome-Naples line of Italian high-speed Railway System and its features have been analysed. The proposed methodology can be useful also for the management of maintenance optimization in railway power systems.

Instrument Voltage Transformers (VT) are well known for their critical behavior when subjected to fast impulse voltages. Furthermore, the accuracy of VT is defined by IEC Standards only at power frequency and doesn't consider fast impulse response. Under these conditions the VT may introduce errors in voltage measurements and the transmitted signals may create overvoltages in correspondence of the secondary circuitry and by nominal withstand. The paper reports experimental analysis on Instrument Voltage Transformers response, in time domain, to a fast voltage impulse (1.2/50 µs). The main experimental results on three commercial Instrument Voltage Transformers, having similar features but manufactured by different Producers, are presented and discussed. Also some considerations are reported considering the shielding effects of such components.

The study presents a railway system simulation model aimed to evaluate the safety requirements about touch voltage in the railway lines fed by 3 kV DC. In particular, the model analyses the transient period during a fault and the dynamic behavior of the DC circuit breaker. The graphical preprocessor ATP Draw of the ATP version of the Electromagnetic Transients Program (EMTP) has been used to develop the model.

The proximity between two different railway supply systems, ac and dc power systems, could bring about to the propagation of interferences from one system to the other. Furthermore, unexpected overvoltages and overcurrents could appear due to the breakdown of equipments installed in the interconnection point. The protection system considered is placed in the Chiasso station, where there are several constraints, among which a limited space available to realize a traditional separation section. The present paper proposes a new protection system from faults between the Italian d.c. railway line and the Switzerland a.c. one. The innovative system will be in operation in a short time. In order to simulate several phenomena, a specific Matlab-Simulink model has been implemented and used to simulate the system proposed.