Ancillary Services in Hybrid AC/DC Low Voltage Distribution Networks

In the last decade, distribution systems are experiencing a drastic transformation with the advent of new technologies. In fact, distribution networks are no longer passive systems, considering the current integration rates of new agents such as distributed generation, electrical vehicles and energy storage, which are greatly influencing the way these systems are operated. In addition, the intrinsic DC nature of these components, interfaced to the AC system through power electronics converters, is unlocking the possibility for new distribution topologies based on AC/DC networks. This paper analyzes the evolution of AC distribution systems, the advantages of AC/DC hybrid arrangements and the active role that the new distributed agents may play in the upcoming decarbonized paradigm by providing different ancillary services.Ministerio de Economía y Competitividad ENE2017-84813-RUnión Europea (Programa Horizonte 2020) 76409

The Impact of Large-Scale Renewable Energy on Grid Small-Signal and Frequency Stability: Modelling, Analysis, and Control

This thesis intends to discuss the influence of renewable energy sources (RES) on the stability of power system. Although integration of renewable brings incalculable optimistic aspects, the variability of RES concerning fluctuation of active power may exhibit adverse influence on stability issues regarding small-signal and frequency stability point of views. Thus, this thesis discusses those two stability aspects. From small-signal stability perspectives, the agenda is divided into three parts. First small signal research investigates the influence of time-varying RES on low frequency oscillation, which triggers weak frequency band of vulnerable modes on remote area. Second study of small signal is to observe the influence of high penetration change on interarea oscillation. Third research of small signal is to investigate the influence of solar irradiation and wind velocity with stochastic characteristics on small signal stability due to the change of the generation quantity of photovoltaics (PV) and wind turbine generators (WTG). From frequency stability perspectives, the future grid might be operated under reduced inertia and high penetration, resulting in deterioration of frequency stability. Against this backdrop, ESS emerges as a countermeasure for the implications of large fleet of RES. First chapter of frequency stability aspects introduces ESS methodology enabling ESS to coordinate ancillary service among existing equipment with proposed method: droop control and State-of-Charge feedback (DaSOF). The last chapter suggests a method for EV application, based on Smart Charging method and DaSOF method. The efficacy of large group of EV application with this method against variability of RES is investigated and proved on the Jeju island system in Korea

Methodologies for Frequency Stability Assessment in Low Inertia Power Systems

L'abstract è presente nell'allegato / the abstract is in the attachmen