Wind Turbine and Electrochemical Based Storage Modeling and Integrated Control Strategies to Improve Renewable Energy Integration in the Grid

The aim of this thesis is to study and to describe the main dynamics that characterizes a wind farm composed by five full converter wind turbines and two different electrochemical storage technologies and to develop models, in the Matlab-Simulink simulation environment, for implementing integrated control strategies of the whole resulting system in order to evaluate the benefits that storage can provide. Chapter 1 provides an analysis of the future drives in power systems and highlights the interest for the integration of the non-dispatchable renewable sources, as the wind energy. The presence of storage systems, in fact, could allow a better management of the electric system granting the full exploitation of renewable energy sources. The first step is therefore to study the single models to gain a better comprehension of the different dynamics implemented. The models are characterized from an electro-mechanical and an electrochemical perspective and the time horizon of the studies ranges from minutes to hours in order to appreciate both the quickly changing wind dynamics and the slowly variability typical of the battery thermal dynamics. Thus, in Chapter 2, the proposed wind turbine model is analyzed. It provides: an analysis of the aerodynamic behaviour of the rotor including the pitch control system, the shaft dynamic and the maximum power tracking control. Moreover an analysis of the wind speed profiles, one for each machine, used to feed the turbines is done and the turbine models are tested by means of these turbulent wind speed profiles. Chapter 3 presents the developed storage models. These models are suited for electrical studies and they include: the state-of-charge behaviour, the electrochemical equivalent circuit, the thermal characterization and the protection and limitation systems. Two different storage technologies are chosen: one belonging to the Redox Flow group, the Vanadium Redox Flow Battery (also known as VRBTM) and the other one belonging to the high temperature batteries, the Sodium Nickel Chloride (also known as ZEBRATM). The storage systems are tested by means of charge/discharge cycles, with different degree of intensity, to characterize their performances. Hence, the main idea is to control the battery charging and discharging phases in order to control the whole plant output. Therefore, in Chapter 4, different control strategies are analyzed. Different tasks are
performed, the duties analyzed range from short-term fluctuation levelling and power quality improvement to generation shifting. At last Chapter 5 reports the conclusions and the future research perspective. The bibliography and the list of works published during the PhD are reported at the end of the
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