Modern power systems are characterized by an increasing penetration of renewable energy generating units. These aim to reduce the carbon emissions in the environment by replacing conventional energy generating units which rely on fossil fuels. In this new power systems composition, wind generators (WGs) dominate, being one of the largest and fastest-growing sources of renewable energy production. Nevertheless, their unpredictable and highly volatile power output hinders their efficient and secure large-scale deployment, and poses challenges for the transient stability of power systems. Given that, we identify two challenges in the operation of modern power systems: rendering WGs capable of reguating their power output while securing transient stabilization of conventional synchronous generators (SGs). This dissertation makes several contributions for effectively dealing with these major challenges by introducing new distributed control techniques for SGs, storage devices and state-of-the-art (SoA) WGs. Initially, this dissertation introduces a novel nonlinear control design which is able to coordinate a storage device and a SG to attain transient stabilization and concurrent voltage regulation on their terminal bus. Thereafter, it proposes control designs that SoA WGs can adopt to effectively regulate their power out- put to meet local or group objectives. In this context, the rst control design is a decentralized nonlinear energy-based control design, that can be employed by a wind double-fed induction generator (DFIG) with an incorporated energy storage device (namely a SoA WG) to regulate its power output by harnessing stored energy, with guaranteed performance for a wide-range of operating conditions. Recognizing that, today, albeit wind farms (WFs) are comprised of numerous WGs which are sparsely located in large geographical areas, they are required to respond rapidly and provide services to the grid in an efficient, reliable and timely fashion. To this end, this dissertation proposes distributed control methods for power output regulation of WFs comprised of SoA WGs. In particular, a novel distributed control design is proposed, which can be adopted by SoA WGs to continuously, dynamically and distributively self-organize and control their power outputs by leveraging limited peer-to-peer communication. By employing the proposed control design, WGs can exploit their storage devices in a fair load-sharing manner so that their total power output tracks a total power reference under highly dynamical conditions. Finally, this dissertation proposes a distributed control design for wind DFIGs without a storage device, the most common type of WGs deployed today. With this control design, wind DFIGs can dynamically, distributively and fairly self-dispatch and adjust the power they extract from the wind for the purpose of their total power tracking a dynamic reference. The effectiveness of the control designs proposed in this dissertation is illustrated through several case studies on a 3-bus power system and the IEEE 24-bus Reliability Test System.

Spacecraft formation flying refers to the coordinated operation of a group of spacecraft with a common objective. While the concept has been in existence for a long time, practical fruition of the ideas was not possible earlier due to technological limitations. The topic has received widespread attention in the last decade, with the development of autonomous control, improved computational facilities and better communication technology. It allows a number of small, lightweight, economical spacecraft to work together to execute the function of a larger, heavier, more complex and expensive spacecraft. The primary advantage of such systems is that they are flexible, modular, and cost-effective.<div><br></div><div>The flexibility of formation flying and other derived concepts comes from the fact that the units are not physically attached, allowing them to change position or orientation when the need arises. To fully realize this possibility, it is important to develop methods for spatial reorganization. This thesis is an attempt to contribute to this development. </div><div><br></div><div>In this thesis, the reconfiguration problem has been formulated as a single system with multiple inputs and multiple outputs, while preserving the individuality of the agents to a certain degree. The agents are able to communicate with their neighbors by sharing information. In this framework, a distributed closed-loop stabilizing controller has been developed, that would drive the spacecraft formation to a target shape. An expression for the controller gain as a function of the graph Laplacian eigenvalues has also been derived. The practical applications of this work have been demonstrated through simulations</div>