Abstract
This paper presents a characterization of the wind energy in Portugal in what regards: the installed power capacity, the capacity under construction, and the geographical location of wind turbines. The Portuguese Lightning Location System (LLS) is described, and new experimental and analytical results are presented. Analysis about geographical and time distribution of cloud-to-ground (CG) strikes and accumulative probability of peak current are carried out. Also, new ground flash density (GFD) maps are presented. Hence, the paper improves the knowledge about the lightning activity in Portugal, allowing the enhancement of risk analysis studies.

Abstract
This paper is concerned with modeling and Simulation of a wind energy system with different topologies for the power converters, namely a matrix converter and a multilevel converter. We use pulse modulation by space vector modulation associated with sliding mode for controlling the converters, and we introduce power factor control at the output of the converters. Finally, we present the electric behavior for the power and the current at the output of the converters.

Abstract
This paper is concerned with modeling and simulation of a wind energy system with different topologies for the power converters, namely a two-level converter and a multilevel converter. Pulse modulation by space vector modulation associated with sliding mode is used for controlling the converters, and power factor control is introduced at the output of the converters. Finally, a case study is presented, showing the electric behavior of the power and the current at the output of the converters and the direct voltage at the multilevel converter.

Abstract
This paper is concerned with the transient stability of variable-speed wind turbines with permanent magnet synchronous machines at a pitch control malfunction. As wind power generation undergoes rapid growth, new technical challenges emerge: dynamic stability and power quality. We study the influence of a pitch control malfunction on the quality of the energy injected into the electrical grid, analyzing the transient stability with different topologies for the power-electronic converters. Computer simulations obtained by using Matlab/Simulink are presented, and conclusions are duly drawn.

Abstract
This paper is on the problem of short-term hydro scheduling, particularly concerning a head-dependent hydro chain. We propose a novel mixed-integer nonlinear programming approach for optimizing power generation efficiency. The proposed approach considers not only the nonlinear dependence between power generation, water discharge and head, but also discontinuous operating regions, in order to obtain more realistic and feasible results. Numerical results, based on one of the Portuguese cascaded hydro systems, illustrate the proficiency of the proposed approach. Finally, conclusions are duly drawn.

Abstract
This paper is on the problem of short-term hydro scheduling, particularly concerning a head-sensitive hydro chain. A new mixed-integer nonlinear method is proposed for optimizing power generation efficiency. The proposed method considers not only the nonlinear dependence between power generation, water discharge and head, but also start-up costs for the hydro units and discontinuous operating regions, in order to obtain more realistic and feasible results. Numerical results, based on one of the main Portuguese cascaded hydro systems, illustrate the proficiency of the proposed method. Finally, conclusions are duly drawn.