Abstract
The continuous growth of wind energy integration on electrical networks has led many utilities to impose fault ride-through capability to wind farms. This means that wind turbines must remain connected to the system during severe fault occurrence. Regarding the existing wind farms equipped with fixed speed induction generators directly connected to the grid, fault ride-through capability is commonly assisted with dynamic compensation devices, such as DSTATCOM units. These power electronic devices are controlled for voltage regulation purposes and behave like a balanced three-phase voltage source converter since commonly used control techniques are based only on the positive sequence of both voltage and current measured at its connection point. These control techniques are suitable only when compensation devices are operated under balanced conditions and therefore its performance when facing unbalanced faults needs to be evaluated. This paper tackles with this subject and the results obtained through numerical simulations demonstrate that over voltages can arise on non faulty phases leading to the wind farm disconnection.

Abstract
Large scale integration of distributed generation of both medium and low voltage (LV) networks can be achieved by exploiting the Multi-MicroGrid (MMG) concept, a new distribution system architecture comprising a hierarchical control system, which allows the coordination among distributed generation units and MicroGrids (MGs) and therefore the operation of such a system in islanded mode. After a general blackout the MMG capabilities can also be used to provide service restoration in distribution systems. A new procedure for MMGs black start is then addressed in this paper. A sequence of control actions is defined and evaluated through numerical simulations. Fully automation of the entire MMG black start procedure is discussed along the paper. The results obtained demonstrate the feasibility of the proposed sequence of control actions and highlight some accomplishments that should be considered in order to successfully restore the MMG service, ensuring system stability and power quality. Copyright (C) 2010 John Wiley & Sons, Ltd.

Abstract
In general, distributed generation is not subject to a centralized dispatch and reactive power generation is usually restricted by operation rules defined by the distribution system operators. With the growth of distributed generation and microgrids in distribution networks, the development of voltage control functionalities for these units needs to be investigated. This requires a new operation philosophy to exploit reactive power generation capability of distributed generation and microgeneration with the objective of optimizing network operation: minimize active power losses and maintain voltage profiles within adequate margins. This implies that distributed generation should adjust their reactive power generation, i.e. supply an ancillary service of voltage and reactive power control. In addition to the growth in distributed generation penetration, microgeneration is expected to develop considerably and contribute to the implementation of efficient voltage control schemes. For this new scenario, a hierarchical voltage control scheme must be implemented, using communication and control possibilities that will be made available for microgrid operation. Technical advantages and feasibility of this operation philosophy are investigated in this chapter by analyzing the impact of the proposed control procedures on distribution networks. In addition, the identification of control action needs is assessed by solving an optimization problem, where voltage profiles are improved and active power losses minimized, subject to a set of technical constraints. The solution for this problem is obtained using an Evolutionary Particle Swarm Optimization algorithm. The control algorithm implemented will enable dealing even with extreme situations, where reactive power control is not sufficient to maintain system operation and therefore generation shedding actions must be performed.

Abstract
This paper presents a methodology to make EV able to contribute to secondary frequency regulation, by participating in Automatic Generation Control (AGC). The aggregator entity is used in this methodology to act as intermediate between the AGC and the EV controllers. The case-study used is an approximation of the Portuguese transmission/generation network, including existing tie lines with Spain, to which a solid three-phase short circuit was applied. After the disturbance, the impact of EV in the AGC operation was studied for two different situations: EV contributing to secondary frequency regulation and EV behaving as uncontrollable loads. The results obtained for both situations were then compared, in terms of interconnection active power flows in the existing tie-lines and its re-establishment time. ©2010 IEEE.

Abstract
An advanced control system for the optimal operation and management of autonomous wind-diesel systems is presented. This system minimises the production costs through an on-line optimal scheduling of the power units, which takes into account the technical constraints of the diesel units, as well as short-term forecasts of the load and renewable resources. The power system security is maximised through on-line security assessment modules, which enable the power system to withstand sudden changes in the production of the renewable sources. The control system was evaluated using data from the island of Lemnos, where it has been installed and operated since January 1995. © 1997 Elsevier Science Ltd.

Abstract
This paper presents a new approach to perform on-line dynamic security assessment and monitoring of electric power systems exploiting a statistical hybrid learning technique - the Kernel Regression Trees This technique, besides producing fast;security classification, can still quantify, hi real-time, the security degree of the system, by emulating continuos security indices that translate the power system dynamic behavior. Moreover it can provide interpretable security structures. The feasibility of this approach was demonstrated in the dynamic security assessment of isolated systems with large amounts of wind power production, like In the Crete island electric network (Greece) Comparative results regarding performances of Decision Trees and Neural Networks are also presented and discussed. From the obtained results, the proposed approach showed to provide good predicting structures whose performance stands up to the performance of the two other existent methods.