Abstract
Increasing penetration of distributed generation (DG), may be interesting from several points of view, but it raises important challenges about distribution system operation and planning practices. To optimal allocation of DG, which play an important role in construction of microgrids, the benefits and risks should be qualified and quantified. This paper introduces several probabilistic indices to evaluate the potential operational effects of increasing penetration of renewable DG units such as wind power and photovoltaic on rural distribution network with the aid of evaluating technical benefits and risks tradeoffs. A probabilistic generation-load model is suggested to calculate these indices which combine a large number of possible operating conditions of renewable DG units with their probabilities. Temporal and annual indices of voltage profile and line flow-related attributes such as interest voltage rise, risky voltage rise, risky voltage down, line loss reduction, line loss increment, and line overload flow are introduced using probability and expected values of their occurrence. Also, to measure the overall interests and risks of installing DG, composite indices are presented. The implementation of the proposed framework in a 4-bus and IEEE 33-bus radial distribution systems shows the effectiveness of the benefits and risks assessment technique with the proposed metrics.

Abstract
In this paper an analysis is made of the impact of emergency loading made by several inductive loads on the thermal ageing of a distribution transformer belonging to a private industrial client. The analyzed system is a fragment of an isolated electric grid in a Portuguese Island. A transformer thermal model is used to estimate the hot-spot temperature and top-oil temperature given the load ratio. Real data are used for the main inputs of the model, i.e., private industrial client load, transformer parameters and the characteristics of the factory. Finally, a smart transformer protection method is proposed by the authors with the aim of monitoring and protecting it from similar upcoming challenges.

Abstract
This paper presents an overview of the different methodologies and mathematical optimization models developed in the framework of the EU-funded project SiNGULAR towards the optimal exploitation and efficient short-term operation of RES production in insular electricity networks. Specifically, the algorithms employed for the creation of system load and RES production scenarios that capture the spatial and temporal correlations of the corresponding variables as well as the procedure followed for the creation of units' availability scenarios using Monte Carlo simulation are discussed. In addition, the advanced unit commitment and economic dispatch models, that have been developed for the short-term scheduling of the conventional and RES generating units in different short-term time-scales (day-ahead, intra-day, and real-time) are presented. Indicative test results from the implementation of all models in the pilot system of the island of Crete, Greece, are illustrated and valuable conclusions are drawn.

Abstract
This paper describes a novel control strategy of voltage source converters (VSC) in large-scale wind farm applications, in order to achieve a constant DC voltage for connecting to the long transmission system based on multi-terminal high voltage direct current (HVDC) technology. The control strategy is based on a multi-loop current and voltage control for tracking the predetermined value of the DC link voltage in the rectifier side station to achieve proper performance in the irregular circumstances of wind farm operation. In addition, the control strategy is able to transmit the maximum input power to the consumption side in different situations in grid side converter. Grid connection of the HVDC system is analysed under two conditions: balanced AC grid, and connection of unbalanced nonlinear load into the AC grid. The control strategy guarantees injection of minimum harmonic current components from the grid to the loads. MATLAB simulation results are presented to demonstrate the effectiveness of the proposed strategy for different types of variations in AC voltage amplitude and frequency of wind turbines output voltage.

Abstract
Because of the development of enabling technologies such as appropriate metering infrastructures and communication possibilities, the smart-grid vision has started to be implemented. Smart appliances and Plug-in Electric Vehicles (PEV) at the residential end-user premises constitute a typical example. Nevertheless, a distribution system (DS) that has been designed and operated by a distribution system operator (DSO) for decades considering only inflexible consumers has to be equipped with appropriate operating strategies and technological upgrades in order to adapt to the new conditions. This study examines the case in which PEV have penetrated in the DS without any supportive operational strategy. Next, a coordination strategy employed from the DSO for EV charging together with the scheduling of smart-appliances is proposed. In both cases, the selection of the daily optimal radial configuration of the DS is considered in order to facilitate the operational goals of the DSO. The optimality criterion is the minimization of the active power losses and both cases are compared by means of operational performance.

Abstract
In recent years, in addition to the traditional aspects concerning efficiency and profitability, the energy sector is facing new challenges given by environmental issues, security of supply, and the increasing role of the local demand. Therefore, the researchers have developed new decision-making frameworks enabling higher local integration of distributed energy resources (DER). In this context, new energy players appeared in the retail markets, increasing the level of competition on the demand side. In this paper, a multienergy player (MEP) is defined, which behaves as a DER aggregator between the wholesale energy market and a number of local energy systems (LES). The MEP and the LES have to find a long-term equilibrium in the multienergy retail market, in which they are interrelated through the price signals. To achieve this goal, in this paper the decision-making conflict between the market players is represented through a bilevel model, in which the decision variables of the MEP at the upper level are parameters for the decision-making problem at the lower level (for the individual LES). The problem is transformed into a mathematical program with equilibrium constraints by implementing duality theory, which is solved with the CPLEX 12 solver. The numerical results show the different MEP behavior in various conditions that impact on the total flexibility of the energy system.