Abstract
This paper presents a new hierarchical approach to deal with the problem of controlling frequency and active power generation of a medium voltage network comprising several microgrids and distributed generation sources operated in islanded mode. The hierarchical approach described here should be cost effective and capable of dealing with large numbers of distributed microsources and performing tasks related to coordinated frequency control.

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
This paper proposes the utilization of water storage ability to improve wind park operational economic gains and to attenuate the active power output variations due to the intermittence of the wind-energy resource. An hourly-discretized optimization algorithm is proposed to identify the optimum daily operational strategy to be followed by the wind turbines and the hydro generation pumping equipments, provided that a wind-power forecasting is available. The stochastic characteristics of the wind power are exploited in the approach developed in order to identify an envelope of recommended operational conditions. Three operational conditions were analyzed and the obtained results are presented and discussed.

Abstract

Abstract
This paper describes a new approach for the dimensioning and location of STATCOMs in Grids with large scale integration of wind energy. The approach developed uses as criterion the reduction of the loss of wind generation due to the operation of under voltage relays following a grid disturbance. The methodology adopted exploits Simulated Annealing in the identification of the problem solution. The approach has been tested in Iberian electrical system and results obtained show also its effectiveness regarding the global dynamic behaviour of the system.