TECHNOLOGIES AND METRICS FOR METROLOGICAL CHARACTERISTICS IMPROVEMENT OF LOW-COST DEVICES FOR SMART GRIDS MEASUREMENTS

In recent years, rapid changes have occurred in electric grids. This includes the significant integration of renewable energy sources into the grid, alongside the liberalization of the electricity market. Additionally, there has been a rise in the number of "prosumers" – users who transit from passive consumers to active producers, generating their own energy, primarily through domestic photovoltaic systems. Although mini and micro wind generators are less common, they also contribute to this trend. These transformations have not only altered the traditional concept of the grid, which previously involved a unidirectional power flow from generation sites to users, but have also transformed it from a passive into an active and intelligent network – known as a smart grid.In smart grids, the measurement of voltage and current parameters, as well as the amount of energy exchanged between users and producers, takes on a fundamental role. For example, the load flow problem, that needs to know the active and reactive power in the different nodes of the network, for a correct application of dispatching, or the frequency and voltage regulation, key features to provide an efficient energy service. The increased complexity of the electricity grid, combined with the new needs related to remote control, communication and interconnection, has made it necessary to use distributed measurement systems, which require a greater number of instruments capable of carrying out different activities. For this reason, the possibility of using low-cost devices for measurements, and in particular for power quality measurements, has become increasingly important. The use of programmable devices also allows great flexibility in adapting to the required measures. One of the main aspects taken into account in the management of the network is “power quality”, a term that includes the main characteristics of voltage and current, and that requires continuous and different measurement techniques. Among the various aspects related to power quality, the evaluation of the harmonic content of the voltage is one of those that attracts the greatest interest both from users, who are increasingly informed and attentive to the management and economic aspects of domestic utilities, that by energy producers and managers, in order to maximize profits. The Ph.D. project involved the participation and financial support of the University of Palermo, the National Research Council (CNR) and the company STMicroelectronics. The goal of this thesis is to investigate the feasibility of the development of a measuring instrument, based on a low-cost microcontroller and AFE device, able to perform a harmonic analysis of the power system voltage respecting the requirements of the standard (to reach the highest accuracy class).Specifically, the project started with standard review to establish the requirements from current legislation, for a device within the highest accuracy class. Different technological solutions and metrics have been developed and compared in order to ensure compliance with the standard while using low-level hardware, optimizing the software component. For the validation, different tests have been conducted using an existing microcontroller board, with typical specifications of a low-cost device.This thesis is the conclusion of this project, in which this possibility was evaluated defining which specifications this device should have.The thesis consists of five chapters: in the first one, an in-depth analysis of power quality measurements for smart grids is reported, with a focus on current standards (in particular the IEC 61000-4-7 and 61000-4-30). In the second chapter the studies concerning the techniques of harmonic analysis and the aspects related to the possibility of realizing a harmonics measurement instrument using a low-cost device, with all the consequent difficulties, are reported. The third chapter includes simulation tests to assess the feasibility of implementing the necessary metrics, in order to narrow the field to workable solutions and to be able to define some minimum specifications. The simulated metrics were then implemented on a real device, which was appropriately characterized, and tested under different conditions, described in chapter four. The last chapter contains the conclusions.