Abstract
A microgrid embraces a low-voltage (LV) distribution grid with distributed energy resources (DER) and controllable loads. In the last years, there has been a growing awareness in exploiting microgrids to facilitate DER integration in electric power systems as well as to improve reliability and power quality in distribution grids. A microgrid can operate connected to the upstream medium voltage (MV) grid-utility grid-or islanded (disconnected from the MV grid) in a controlled and coordinated way. A major challenge associated with the implementation of microgrids is to design a suitable protection system scheme for different operating conditions. To overcome this challenge, different approaches have been proposed in the literature. The protection systems applied at microgrids must work both in utility grid faults and microgrid faults. Faults on the utility grid could lead to a protection response that isolates the microgrid from the utility grid as fast as required to keep the microgrid safety. On the other hand, faults in the own microgrid require the smallest sector removal of the microgrid to isolate the fault. Due to the presence of several DER in microgrids, the protection systems are also needed to cope with the bidirectional energy flows. Thus, the traditional protection devices (fuses and electromechanical switches) and standard solid-state relays are designed for selectivity purposes, making them inapt to ensure the protection of microgrids. These protection devices do not provide flexibility for setting the tripping characteristics neither the current direction sensitivity feature. Some problems related to protections sensitivity and selectivity arises when a microgrid is in islanded operation (DER generation). Thus, this new paradigm of distribution facilities requires a protection system based on microprocessor relaying and communications. Protecting microgrids in both modes (grid-connected and islanded) can be achieved by using different communication architectures associated with protections. Using centralized or distributed architectures means that the relay protection settings are modified centrally or locally regarding microgrid operating conditions. This chapter aims to provide the key highlights of the available protection schemes used to address microgrid protection issues.

Abstract
Over the last few years, the need for electricity has increased in households as new and different appliances are progressively introduced. This increased demand for electricity raises a concern to many developed and developing countries since it is a human's responsibility to assure a sustainable future. Energy demand management can be an effective approach to reduce the energy consumption; this approach requires final consumers to be empowered with more information for improving their decision-making and actions on the energy usage through increased awareness. Therefore, metering and behind the meter monitoring systems have a crucial role in the exploitation of this potential in the customer side. A significant disadvantage of traditional meters is the fact that they do not provide detailed information to the customers, which is achieved with the help of smart meters. A smart meter allows the customers to have access to the information about electricity consumption of the appliances in their houses. The acceptance of smart meters by customers is the fundamental step to achieve the potential carbon emission reductions that are provided by the use of advanced metering infrastructures. The smart meter is an advanced energy meter that measures consumption of electrical energy such as a traditional meter but also provides additional information in real time, making it the key element of the new energy demand management system. Integration of smart meters into electricity grids implies the implementation of several technologies, depending on the features that each situation request. The design of a smart meter has been in constant development since it is increasingly necessary to satisfy both the requirements of the utility company and those of the customer. Therefore, smart metering provides benefits to the energy utilities optimizing their business, and beyond that it can provide advantages to the final customers. All over the world many smart metering projects have been developed. However, it is still not entirely clear which are the associated costs, the characteristics, and the mechanisms internal to projects that bring advantages and benefits for the different concerned parties. The smart metering methods and the communication technologies used in smart grid are being substantially studied due to widespread applications of smart grid. The monitoring and control processes are largely used in industrial systems. Nevertheless, the energy management requirements at service supplier and customer promoted the evolution of smart grid and consequently the development of microgrids. This chapter discusses various characteristics and technologies that can be integrated with a smart meter for smart grids and microgrids uses. In fact, placement of smart meters needs proper selection and implementation of a communication network fulfilling the security standards of smart grid/microgrid communication. This chapter outlines various issues and challenges involved in design, deployment, utilization, and maintenance of the smart metering infrastructure.

Abstract
Smart Transformers (ST) are power-electronic based apparatuses that bring new opportunities for defining innovative operating strategies for Medium Voltage (MV) and Low Voltage (LV) distribution grids in future scenarios with increased shares of small-scale generation units. A distinctive advantage of ST is the possibility of connecting a storage device in the DC link when considering a three-stage configuration (AC/DC/AC). In this paper, ST is exploited within the context of Multi-Microgrids (MMG) in order to enhance the possibility of islanding operation through the identification of new control functionalities. The identification of robust control strategies to coordinate the flexibility of all the available resources (distributed resources at the LV and MV grids and storage units connected to the ST) is required to guarantee the successful operation of the MMG in the islanded mode. In order to address the need of specific control requirements, two different configurations are considered, being the proposed control strategies properly described: (1) ST with an energy storage unit in the DC link which fully decouples all the control possibilities for the MV and LV grid sides; (2) ST without an energy storage unit, requiring proper coordination between the MV and LV grid levels.

Abstract
This work consists in assessing a real islanded power system from a dynamic security point of view, to support the planned installation, in the near future, of a hydro power plant with pumped storage, aiming to increase the integration of renewable energy. The analysed hydro power plant will include a Pelton turbine as it is a high-head hydro facility. Due to economic reasons, the adopted water pumping technology consists in fixed speed pumps coupled to induction motors with direct grid connection. It was possible to verify through detailed simulations of this power system's time domain behaviour that, even though the expected installation of this new power plant will bring additional frequency stability constraints, a robust technical solution may be found dealing with the new constraints without increasing the complexity of operation in this islanded power system. The conclusions obtained from this specific case are also valid for similar isolated power systems, namely when hydro pumping stations are being considered to increase time-variable renewable generation penetration.

Abstract
In this work, the evaluation of the performance of a small-size photovoltaic plant, with 15 kWp of capacity, is made and some proposals for its optimization are presented. The plant consists of a grid-connected centralized system, where the output power is consumed in the same building. The PV plant production data of the last couple of years are analysed, filtering the periods of inoperation. To obtain an accurate prediction of the efficiency and power output, the characteristics of all plant components were introduced in SAM software. The results obtained through the simulations and the measured output power values were compared. (C) 2018 The Authors. Published by Elsevier Ltd.

Abstract