Abstract
Restructuring of power markets has helped in the penetration of Distributed Generation (DG) in the electricity networks. Microgrids are Low Voltage distribution networks comprising various distributed generators (DG), storage devices and controllable loads that can operate interconnected or isolated from the main distribution grid, as a controlled entity. This paper describes the main functions of the Microgrid Central Controller required for the optimization of Microgrid operation its interconnected operation. This is achieved by maximizing its value, i.e. optimizing production of the local DGs and power exchanges with the main distribution grid.

Abstract
In the present paper an advanced control system for the optimal operation and management of medium size power systems with large penetration from renewable power sources is presented. This control system is aimed to assist the power system operators in their managing task, by proposing them optimal actions for the economic and secure management of the power system. The control system is composed of various modules performing functions like short-term forecasting of the load and of the renewable sources, economic dispatch of the power units and on-line dynamic security assessment. The pilot control system is being installed and evaluated in the Greek island of Lemnos.

Abstract
A new type of bus for load flow analysis is proposed in this paper; this type of bus, named PX, is particularly suited for modelling elements like static compensators or asynchronous generators. The inclusion of this PX bus in the Fast Decoupled Load Flow method is presented and discussed. Numerical results are reported when applying this approach to solve load flow problems in two standard systems.

Abstract
Operation problems that result from MV distribution networks with local asynchronous generation sources connected are examined. In order to analyze steady-state operating situations, a load-flow calculation must be performed. The presence of asynchronous generators imposes the adoption of a consistent bus modelization using a new bus type, the PX bus, where P is the active generated power and X is a nonlinear magnetizing reactance. This approach introduces some modifications in the conventional load-flow algorithms, thereby increasing the total number of iterations.

Abstract
The authors present a novel automatic transient stability classification approach, based on a two-stage hierarchical classifier obtained through the combination of two different pattern recognition structures. The first-level classifier uses low-cost computational variables evaluated at the fault occurrence moment. The classification structure used in this first level is a linear one and is obtained through the combination of a Fisher discriminant transformation and a Bayesian probabilistic approach for the independent term determination. The second-level classifier uses a new set of transient variables, directly related to kinetic and potential energies at the fault clearance moment. The classification structure in this second level is based on a weighted K nearest-neighbor rule, using a Euclidian metric defined in an optimum discriminant plane, where all data have been previously projected. Results obtained in the CIGRE test system are presented, showing that this method provides an efficient tool for online transient stability assessment of electric power systems.

Abstract
A candidate methodology for online transient stability assessment in power systems is presented. The method uses dynamic system variables as primary features. Linear security functions are derived by applying Fisher discriminant transformations and probabilistic considerations. Test results obtained on the CIGRE system are presented and discussed.