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 massive interconnection of offshore Wind Farms (WF) brings challenges for the operation of electric grids. The predicted amount of offshore wind power will lead to a smaller ratio of conventional units operating in the system. Thus, the power system will have less capability to provide fast dynamic regulation. Despite of offshore WF being able to inject power on the AC grid through High Voltage Direct Current (HVDC) convertors, they cannot participate on frequency support by the intrinsic decoupling that DC adoption brings. This paper proposes a control methodology, based on local controllers, to enable the participation of offshore WF in primary frequency control. Additionally, enhancements were made on the Wind Energy Converters (WEC) controller to make them capable of emulating inertial behaviour. Tests were performed in a multi-terminal DC network with two off shore wind farms to assess the feasibility and effectiveness of the concept in a communication-free framework.

Abstract
In this paper, a new operational strategy regarding islanding operation is presented exploiting Distributed Generation for islanding; purposes. The presence of DG may be used to enhance reliability to final consumers by providing an alternative power source when there is an interruption in the upstream network. The feasibility of this type of operation in distribution networks is analyzed in a case study by analyzing the behavior of different generating units and protection settings.