Abstract
The main objective of this paper is to present the development of microsource modelling and the definition of control strategies to be adopted to evaluate the feasibility of operation of a microgrid when it becomes isolated. Normally, the microgrid operates in interconnected mode with the MV network, however scheduled or forced isolation can take place. In such conditions, the microgrid must have the ability to operate stably and autonomously. An evaluation of the need of storage devices and load-shedding strategies is included in the paper.

Abstract
MicroGrids comprise low voltage distribution systems with distributed energy sources, storage devices and controllable loads, operated connected to the main power network or autonomously, in a controlled coordinated way. In case of MicroGrids autonomous operation, management of instantaneous active power balance imposes unique challenges. Traditionally, power grids are supplied by sources having rotating masses and these are regarded as essential for the inherent stability of the system. In contrast, MicroGrids are dominated by inverter interfaced sources that are inertia-less, but do offer the possibility of a more flexible operation. When a forced or scheduled islanding takes place in a MicroGrid, it must have the ability to operate stably and autonomously, requiring the use of suitable control strategies. The MicroGrid power sources can also be exploited in order to locally promote a service restoration strategy following a general blackout. A sequence of actions for the black start procedure is also presented and it is expected to be an advantage in terms of reliability as a result from the presence of very large amounts of dispersed generation in distribution grids. © Springer-Verlag Berlin Heidelberg 2012.

Abstract
The Smart Vehicle-to-Grid Project at INESC TEC is currently studying the application of matrix converters to implement an isolated bidirectional AC-DC power converter using a single power conversion stage to provide a high-frequency link between the grid and vehicle. The single-stage structure and bidirectional power flow make the matrix converter an attractive solution for the charging applications of electric vehicles. A very brief overview of the matrix converter and its modulation strategy is presented, followed by detailed analysis. The power conversion system performance is investigated in terms of the switching commutation, input filter and input power factor. Simulations and experimental results of a prototype are also presented to further validate the proposed topology and operating principle.

Abstract
MicroGrids comprise low voltage distribution systems with distributed energy sources, storage devices and controllable loads, operated interconnected with the main power grid or autonomously, in a controlled coordinated way. Storage devices are absolutely essential for MicroGrid autonomous operation. However, depending on the operating conditions, their limited storage capacity is a major drawback and might compromise successful MicroGrid islanded operation. In this paper is proposed an index to evaluate MicroGrids security regarding an unplanned transition to islanded operation due to disturbances in the upstream Medium Voltage network. An Artificial Neural Network tool is proposed to forecast the security index for a credible range of operating scenarios. The usage of Artificial Neural Networks is emphasized due to its computational speed for on-line performance and its flexibility for providing corrective actions for insecure operating conditions in order to achieve a seamless transition from interconnected to islanded operation. © 2007 IEEE.

Abstract
From the studies developed so far, it is a general consensus that Electric Vehicles (EV), when properly managed, can provide many benefits to the grid operation. In the power systems of islands the potential benefits may be even larger. The case of S. Miguel Island, in the Azorean archipelago, may be one of such cases. This island achieves typically an annual peak power of 75 MW and a valley slightly higher than 30 MW. Currently, around 75% of its installed capacity is formed by fuel units, 22% by geothermal units and the rest by small hydro units. Yet, there are numerous unexplored endogenous resources in this place, especially geothermal and wind power, which cannot be used due to technical restrictions. Geothermal is limited by the valley load as the involved technology is not suited for load following, even with very small ramp rates. Wind power requires sufficient conventional spinning reserve to be safely integrated due to the variability of the wind resource. High EV integration, with an adequate charging management, would then increase base load allowing further geothermal and a reduced need for conventional spinning reserves. This paper evaluates the benefits of the presence of EV as controllable loads performing frequency control in a scenario with abundant wind resource availability, where a sudden loss of wind power production over a short period of time occurs. Ultimately, this work will show that S. Miguel power system would benefit from the presence of EV. A comparison with the conventional approach considering EV as regular loads will also be performed for benchmarking purposes.

Abstract
The massive interconnection of offshore Wind Farms (WF) brings challenges for the operation of electric grids. The predicted amount of offshore wind power will lead to a smaller ratio of conventional units operating in the system. Thus, the power system will have less capability to provide fast dynamic regulation. Despite of offshore WF being able to inject power on the AC grid through High Voltage Direct Current (HVDC) convertors, they cannot participate on frequency support by the intrinsic decoupling that DC adoption brings. This paper proposes a control methodology, based on local controllers, to enable the participation of offshore WF in primary frequency control. Additionally, enhancements were made on the Wind Energy Converters (WEC) controller to make them capable of emulating inertial behaviour. Tests were performed in a multi-terminal DC network with two off shore wind farms to assess the feasibility and effectiveness of the concept in a communication-free framework.