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.

Abstract

Abstract
MicroGrid (MG) is becoming an important system for a massive and reliable integration of renewable energy sources. Hence, due to its benefits, photovoltaic (PV) systems are the most suitable and widely used in MGs. However, for a reliable integration of PV panels, they must be interfaced by smart power electronics devices that allow the implementation of advanced control solutions. In addition to operating as active power generator with maximum power point tracking (MPPT), the new PV systems (PVS) should behave as ancillary services providers by participating to the grid regulation, such as frequency stabilization, voltage profile control, harmonics compensation and so forth. This paper aims at reviewing the control and operation of PVS in AC MG. Control structures, active power control, MPPT and inner loops are presented and discussed. Design, analysis and control of single-stage three phase PVS in AC MG that is able to operate at MPP or as a dispatchable source are made. The control structure is validated through dynamic simulations. © 2016 IEEE.

Abstract
Photovoltaic systems (PVS) based MicroGrid (MG) should be able to operate at the maximum power point (MPP) in order to extract the maximum available power during atmospheric conditions changes. In addition to this, the PVSs should be able also to operate below the MPP in order to participate to the MG regulation such as grid frequency stabilization, voltage profile control and grid management support. This paper discusses the state of the art of operation and control of PVS in MG. Design and control of a single stage single phase PVS connected to a low voltage AC MG are presented and analyzed. A comparison between two current control methods, Proportional integral with grid voltage feed forward (PI+FF) and proportional resonant with selective harmonics compensation (PR+HC) is also made. The control structures are validated through dynamic simulation. © 2016 IEEE.

Abstract
The deployment of smart grids and renewable energy dispatch centers motivates the development of forecasting techniques that take advantage of near real-time measurements collected from geographically distributed sensors. This paper describes a forecasting methodology that explores a set of different sparse structures for the vector autoregression (VAR) model using the least absolute shrinkage and selection operator (LASSO) framework. The alternating direction method of multipliers is applied to fit the different LASSO-VAR variants and create a scalable forecasting method supported by parallel computing and fast convergence, which can be used by system operators and renewable power plant operators. A test case with 66 wind power plants is used to show the improvement in forecasting skill from exploring distributed sparse structures. The proposed solution outperformed the conventional autoregressive and vector autoregressive models, as well as a sparse VAR model from the state of the art. Copyright (c) 2016 John Wiley & Sons, Ltd.