VOLTAGE CONTROL SYSTEMS FOR TRANSMISSION AND DISTRIBUTION GRIDS

The research activities carried out for the present PhD dissertation concerns the increasingly evident and widespread set of problems related to the remarkable levels of distributed generation (DG) connected to electric networks. It has also included the proposal of applicable and performing control techniques, suitable to allow new connection of Renewable Energy Sources (RES) generators, able to assure adequate reliability and quality of service through the integration of electric networks with Information and Communication Technology (ICT) (process also known with the term “Smart Grid”). The focus of the research activity was directed to voltage control of DG units based on RES, both connected to low voltage (LV) and medium voltage (MV) distribution networks and the ones directly connected to high voltage (HV) transmission system. A short summary of the different chapters provides an overview of the present work: - Chapter 1 describes the architecture of the national electric system, the on-going change from the traditional paradigm of energy production towards the DG model and the problems deriving from such change. To provide an idea of the dimension of the phenomenon some data about DG installed in the latest years both at international and national level are given, together with the results of studies on the economic and energetic advantage of photovoltaic technology carried out in view of a possible assessment of future impacts on energy distribution systems. - Chapter 2 outlines the features of a Smart Grid apt to receive RES generation, at the same time guaranteeing suitable levels of reliability and quality service. The chapter summarizes the European and Italian Regulatory Environment for the connection of DG to distribution networks and electric transmission. - Chapter 3 concentrates on voltage control for DG plants based on RES. The chapter reports a review of the control techniques proposed by literature and by recent connection rules, together with the control techniques collected and proposed by our research group. - Chapter 4 presents the results of the studies carried out on some test electric networks presented in scientific literature and some really existing ones. - Chapter 5 reports some final considerations. - Appendix A1 provides a description of the software tools used to carry out the simulations. More specifically tests have been conducted with the aid of Matlab@ software, the toolbox open source PSAT and DOME software for steady state and dynamic simulations.