This paper presents an analysis and comparison of Phase Locked Loop techniques used in grid utility applications to find the voltage vector angle generated from the supply voltages. The Phase Locked Loop (PLL) has a wide range of applications as Distributed Generation (DG), Flexible AC Transmission Systems (FACTS), static VAR compensators, cycloconverters, Active Power Filters (APF's) and others systems connected to the utility. The performance of these systems in grid connected applications is strongly influenced by the adopted PLL strategy. For this reason, the goal of the proposed paper is to present a comparison of different PLL-based techniques for utility applications to indicate the appropriate solution dedicated to a specific application. The criteria to compare the Phase Locked Loops techniques is the performance under distorted and unbalanced supply voltages.

In the case of adjustable drives systems with an induction motor (IM), a harmonic regime is manifested, whose knowledge and analysis are always necessary. However, most studies are focused on specific drive systems, the results of these works being valid only for drive systems of the same type. The objective of the present paper was to determine the harmonics consequences not only on the technical characteristics of the IM but also on the power supply as well as on the mechanical drive system. Thus, by initiating a methodology for estimating the consequences of each voltage harmonic separately, the aim was to substantiate a generally applicable method, which allows the evaluation, for any application, of the overall effects of the harmonics. The main feature of the method used in this paper was the consideration of the presence of voltage harmonics in the stator voltage of the IM, of certain frequencies and with certain levels, and the determination of all the electrical and mechanical consequences on the model of the drive system. It has been found that the harmonics of the IM affects the power quality (PQ) of the power supply, having significant influences also on the mechanical part of the drive system.

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There are numerous and different ways to design an energy efficient street lighting system, but not always the best technical solution is the optimal economic solution as well. In this paper, we used two distinct software tools in order to obtain the optimal technical and economic solution for selecting street lighting technology. The first software used was DIALux, which is frequently applied in this field, assisting designers in choosing the most appropriate electrical installations and evaluating the technical performance of the chosen solutions. This tool determined the street lighting system variants for which there are predetermined configurations, so that the lighting parameters obtained are in accordance with the normative requirements of the lighting classes in which the roadways are included. Different ways of locating the luminaires and other parameters were changed to reach the best version that meets the qualitative requirements of the lighting technology. The second software used was the one developed by the authors, based on ELECTRE III method, which evaluated the technical solutions returned by DIALux against several criteria, taking into account the designer's preferences and constraints. The optimal technical and economic solution was obtained after ranking the variants by their performance at each criterion. The simulation experiment and the results returned suggested that the combination of the two software tools is comprehensive and effective and it can be used in this type of decisions at large scale.

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