Abstract
Design and hierarchical control of three phase parallel Voltage Source Inverters are developed in this paper. The control scheme is based on synchronous reference frame and consists of primary and secondary control levels. The primary control consists of the droop control and the virtual output impedance loops. This control level is designed to share the active and reactive power correctly between the connected VSIs in order to avoid the undesired circulating current and overload of the connected VSIs. The secondary control is designed to clear the magnitude and the frequency deviations caused by the primary control. The control structure is validated through dynamics simulations. The obtained results demonstrate the effectiveness of the control structure.

Abstract

Abstract
While renewable energy generation from time variable sources keeps increasing, end-user interactions through smart grid development and the adoption of smart appliances lead to significant changes in consumer behavior. Hence, renewable energy generation must be curtailed more frequently when the expected demand is surpassed. Likewise, demand side measures should be considered more thoroughly so that appropriate capacity limits for new generation units can be defined. An analysis of load shifting is performed for Sao Miguel Island, Azores, and indicates that through defined rules of load shifts the base load limit can be elevated and new limits for the maximum installed capacity can be set. The effects of load shifts are crucial for decision makers since investments in additional renewable energy capacities can be limited and back-up capacities can be reduced. (C) 2016 The Authors. Published by Elsevier Ltd.

Abstract
The EU megagrid is foreseen to exploit the very large resource of solar energy in southern Europe and of wind power in northern Europe. Microgrids with enhanced control capabilities can integrate and coordinate local distributed resources enhancing the resilience of the EU megagrid and providing local restoration capabilities. The future modeling challenges of microgrids and in particular the shift to distributed control, enhancing further the microgrids resilience, are highlighted. © 2015 IEEE.

Abstract
Several control schemes specifically designed to operate inverter-based industrial microgrids during voltage sags have been recently proposed. This paper first classifies these control schemes in three categories and then performs a comparative analysis of them. Representative control schemes of each category are selected, described and used to identify the main features and performance of the considered category. The comparison is based on the evaluation of several indexes, which measure the power quality of the installation and utility grid during voltage sags, including voltage regulation, reactive current injection and transient response. The paper includes selected simulation results from a 500 kVA industrial microgrid to validate the expected features of the considered control schemes. Finally, in view of the obtained results, the paper proposes an alternative solution to cope with voltage sags, which includes the use of a static compensator in parallel with the microgrid. The novelty of this proposal is the suitable selection of the control schemes for both the microgrid and the static compensator. The superior performance of the proposal is confirmed by the analysis of the quality indexes. Its practical limitations are also revealed, showing that the topic studied in this paper is still open for further research.

Abstract
This article addresses the developments ongoing in SENSIBLE, an H2020 funded project focused on energy storage and energy management, which demonstration occurs in Évora-Portugal, Nottingham, UK and Nuremberg, Germany. Currently, the presented work focuses on the developments necessary to make possible islanding operation in low-voltage grids, where new assets like storage and new automation and protection schemes are necessary to guaranty safety and reliability of low-voltage grids. These developments are a result of the ongoing works under one of SENSIBLE use cases which demonstrations occurs in a small village in Évora district in Portugal.