• Energy Research

The goal of the paper is the comparison between two guidelines for harmonic analysis evaluation given by international standards on quality of power: the IEEE 519, mainly related to the American market, and the IEC 1000, mainly adopted in the European market. The comparison is made considering an industrial plant where nonlinear loads and large motors are present. Comments and discussion are made on the suggested models and harmonic summation methods.

AbstractThis paper describes an efficient and reliable algorithm that modifies the Fast Decoupled Load Flow (FDLF) in order to overcome non‐convergence troubles in solving strongly stressed power systems. The Hartkopf's algorithm for improving the Newton‐Raphson method's convergence features in ill‐conditioned cases is taken as a basis. The proposed changes to FDLF consist fundamentally in minimizing the squared power mismatches with a second order interpolation technique. The simple modification makes it possible to establish for sure whether a case of non‐convergence is owing to numerical or to physical problems, and lets the operator evaluate the system condition correctly. Several numerical examples show the remarkable behaviour of the algorithm proposed.

This paper deals with the selectivity problems highlighted on the considered hospital system, presented in the first paper. The paper presents a possible solution to this problem, supported by a correct application of the Italian standard CEI 0–16 and a deeply selectivity study.

Wireless charging systems for electric vehicles have some advantages respect the wired ones, not obliging the user to connect physically the vehicle to the electric charging station. However, at the same time, they have disadvantages linked to issues of electromagnetic compatibility and low efficiency. This study considers some scenarios for which both wired and wireless recharging systems can be adopted, with the aim of estimate the efficiency that must be guaranteed by wireless systems, so that its realization could be more favorable with respect to wired one. The estimation is developed by means of classical economic indexes, in the framework of Italian end European markets. Results report the possible advantages and the disadvantages linked with the use of the two technologies.

A sustainable public transportation system is crucial to reduce air pollution and the environmental impacts of the sector. This is pursued not only in big cities and metropolitan areas, but also small citizen context are interested in this environmental commitment. This paper wants to analyse the renewal process of Local Public Transport (LPT) applied to a small city. A focus on the city centre of Cremona is set and the goal of reproducibility of each step is assessed as results. The implementation of two new bus lines planned to adapt the service currently available to the potentially evolving demand is discussed as result. Electric-powered buses were selected as the best alternative to accomplish the purpose of this research and a particular attention was paid to the energy supply chain. The economic aspects were then explored to evaluate the different scenarios given by the adoption of supply chain chosen.

A comparison is presented between two of the most significant international standards for short-circuit calculation: the IEC 909 Standard and the ANSI/IEEE C37.010-1979. The ANSI standard is more oriented toward breaker selection while the IEC standard gives general guidelines for short-circuit current computation. A set of short-circuit currents, directly extracted from the standards or obtainable after some elaborations, were determined as values useful for the comparison. A detailed dynamic analysis performed by using a well-known program for electromagnetic simulation was used as reference for the comparison between the two standards. The comparison shows that the IEC 909 is somewhat more ponderous than the ANSI standard. Hypothesis and assumptions are more numerous and more detailed in the IEC 909 than in the ANSI standard. In the former standard, more information and more formulas about the possibility of neglecting motor contributions are presented, as well as the basis for determining whether short-circuit is to be considered near or far from generators. The results of calculations confirm that both standards give satisfactory approximations of the short-circuit currents, which are mostly on the safety side. >

This paper evaluates the trend of fast dc charging systems (combining the trends of the infrastructure and of the vehicles) to verify the feasibility of the development of an infrastructure of transnational corridors that can guarantee the accessibility for all vehicles. This paper starts with the real-life situation characterized by multiple disjointed projects in many countries to verify whether, in spite of the different solutions employed, it is possible to find a common trend that can become a guideline for future projects. A predictive model for the e-mobility trend is developed to understand the market and the development of the infrastructure over the next few years. The results are used to identify how to equip European transnational corridors with fast dc charging stations, and a study case is presented.

This paper describes an improved model of rotating loads in complex load areas. The first section of the paper concentrates on the theoretical aspects of load modeling in harmonic penetration studies with a particular reference to the rotating part of the load. The second section illustrates the results achieved from the experimental surveys conducted both in the laboratory and at a major industrial customer, in order to validate the model proposed in the field. The third section describes the calibration stage of the proposed model based on results from a statistical survey conducted at manufacturers on parameter variation vs. frequency with a large sample of both LV and MV induction motors. Finally, some guidelines are also provided for a correct use of the proposed model in system studies concerning harmonic penetration within electric distribution networks.

This paper presents a detailed model of the AC 2 × 25 kV High Speed/High Capacity (HS/HC) railway lines in order to dynamically analyze the electric systems. The power quality analysis reported here is important considering that these lines are directly connected to the high voltage (HV) transmission grid and also that the control and auxiliary devices are directly connected to the feeder wire. The accuracy of the results, obtained by carrying out numerous simulations, was confirmed via comparison with dedicated experimental surveys on the lines during their operation.