Abstract
This paper presents a general overview about the system operation, management and control following a large scale integration of renewable energy sources, focusing in particular the wind generation, both onshore and offshore. Regarding the operation of distribution networks, the integration of renewable energy sources and other distributed generation systems requires the adoption of active control and management structures. These structures will contribute to extend intelligence from the transmission to the distribution networks, aiming to change the operation paradigm from passive towards the smart grids vision for European networks of energy. The MicroGrid concept plays a key role in this context and has been exploited in order to support the progressive integration of electric vehicles, trying to avoid grid reinforcements. © 2011 IEEE.

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
This paper addresses the problematic of operating isolated networks with large penetration of intermittent renewable power sources, as well as the benefits that electric vehicles might bring to these systems. A small island's network was used as case study and a 100% renewable dispatch for a valley period, only with hydro and wind generation, was tested in a dynamic simulation platform developed in Eurostag. Two distinct wind speed disturbances were simulated and, for both, the impact in the network's frequency was evaluated considering two different situations: electric vehicles only in charging mode and electric vehicles participating in primary frequency control. It was assumed the existence of 575 electric vehicles in the island. The impact of having electric vehicles performing primary frequency control in the expected batteries state of charge was also evaluated. © 2011 IEEE.

Abstract
This paper addresses the extension of the microgrid concept, following a massive integration of these active cells in power distribution networks, by adopting a coordinated management strategy together with distributed generation units directly connected to the medium voltage distribution network. In order to achieve this, a technical and commercial management scheme must be developed for coordinated control of a distribution system with multi-microgrids, which should take into account the specific technical capabilities and characteristics of each type of generating source. In particular, tools for coordinated voltage support and frequency control, as well as for state estimation have been developed for this type of network. Concerning voltage support, a new methodology exploiting an optimization tool based on a meta-heuristic approach was developed. For state estimation, two approaches were considered: multi-microgrid state estimation and fuzzy state estimation. Regarding frequency control, the hierarchical structure of the multi-microgrid is exploited to deal with the transition to islanded operation and load following in islanded operation. All these tools have proved to be efficient in managing the multi-microgrid system in normal interconnected mode and, in case of the frequency control, in islanded operation. Copyright (C) 2010 John Wiley & Sons, Ltd.

Abstract
The expected growth of Distributed Generation (DG) penetration in distribution systems will fundamentally alter both planning and operating procedures of Distribution Network Operators (DNO). This means that distribution networks can no longer be considered as a passive appendage to the transmission network and should be explored actively to take full advantage of the capabilities of DG units available and avoid technical problems (such as line overloading or poor voltage profiles) resulting from massive integration of this type of sources. Presently, when the capacity of the generation, transmission and distribution systems is exceeded, the traditional utility response is expanding or reinforcing existing circuits through large investments in power transformers, substations or distribution feeders. However, in some situations such as in congested metropolitan areas these actions can have prohibitive costs or simply be impossible due to space restrictions, for instance. Although current investment costs of many solutions for energy storage remain extremely high, recent developments and advances in both energy storage technologies and power electronic interfaces are opening new doors to the inclusion of Energy Storage Systems (ESS) as a potentially viable solution for modern power applications, including their use in distribution network planning and operation. This paper presents a heuristic approach for siting and sizing of ESS in distribution networks in order to maximize the capacity of DG that can be integrated in the grid without bringing technical problems to network operation. The proposed methodology enables a technical and economical comparison between a strategy based on ESS deployment and exploitation and typical traditional DNO grid reinforcement strategies. Several technologies for ESS were considered, each one with different costs and technical characteristics. The proposed methodology was validated using a real Portuguese Medium Voltage (MV) distribution network.

Abstract
The implementation of innovative network solutions to allow for an increase of micro-generation and demand side integration are highly dependent on building scale and cost effective infrastructures, where sharing of responsibilities among different stakeholders is the basis for a proper implementation of an active distribution network concept. In order to integrate large amounts of small and micro-generation (µG) units that exploit different power sources (with high or no intermittency) together with controllable loads and storage devices it is necessary to develop flexible management and control solutions where responsibilities for the system operation are shared between Distribution System Operators (DSO), customers and Distributed Generation (DG) units according to a regulatory environment. The incentives provided to the different parties (stakeholders) may have a major impact on their decision to adopt Micro-grid and Multi Micro-grid concepts. Therefore, an identification of the benefits and costs associated with these concepts adoption is needed in order to recognize the real value of their deployment. Moreover, only by proper allocation of these costs and benefits, each stakeholder affected may receive the right incentive to opt for Micro-grid and Multi Micro-grid solutions. The DSO is interested in maximizing profits, by minimizing the capital and operational costs related to the distribution service (for instance, loss reduction and reinforcement costs) and at the same time achieving the performance goals imposed by the regulators [1]. Micro-generation developers make decision considering capital and operational expenditures, the connection costs, and use of system charges. Incomes from energy selling (which may include RES incentives) are the main goals (benefits) for the µG investors. Therefore, one of the priorities of regulators is to ensure that these benefits are perceived by µG developers. Finally, customers may be asked to share with the DSO the responsibility for an increased reliable system and for having the possibility to reduce their bills when exploiting the best market options offered by different traders. This paper presents a detailed identification and characterization of the different benefits and costs for each stakeholder involved. Some of these benefits can be identified and allocated directly to a certain stakeholder, while others need to be shared among a large group of players, involving the society in general (for example CO2 emissions reduction, job creation).