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About this book

This book constitutes the refereed post-conference proceedings of the 5th EAI International Conference on Green Energy and Networking, GreeNets 2018, held in Guimarães, Portugal, in November 2018. The 15 full papers were selected form 26 submissions and cover a wide spectrum of ideas to reduce the impact of the climate change, while maintaining social prosperity. In this context, growing global concern leads to the adoption of the new technological paradigms, especially for the operation of future smart cities.

Table of Contents


Improved Voltage Control of the Electric Vehicle Operating as UPS in Smart Homes

As a contribution for sustainability, electric vehicles (EVs) are seen as one of the most effective influences in the transport sector. As complement to the challenges that entails the EVs integration into the grid considering the bidirectional operation (grid-to-vehicle and vehicle-to-grid), there are new concepts associated with the EV operation integrating various benefits for smart homes. In this sense, this paper proposes an improved voltage control of the EV operating as uninterruptible power supply (UPS) in smart homes. With the EV plugged-in into the smart home, it can act as an off-line UPS protecting the electrical appliances from power grid outages. Throughout the paper, the foremost advantages of the proposed voltage control strategy are comprehensively emphasized, establishing a comparison with the classical approach. Aiming to offer a sinusoidal voltage for linear and nonlinear electrical appliances, a pulse-width modulation with a multi-loop control scheme is used. A Kalman filter is used for decreasing significantly the time of detecting power outages and, consequently, the transition for the UPS mode. The experimental validation was executed with a bidirectional charger containing a double stage power conversion (an ac-dc interfacing the grid-side and a dc-dc interfacing the batteries-side) and a digital stage. The computer simulations and the acquired experimental results validate the proposed strategy in different conditions of operation.
Vítor Monteiro, Joao P. S. Catalão, Tiago J. C. Sousa, J. G. Pinto, Marcello Mezaroba, João L. Afonso

Energy End-Use Flexibility of the Next Generation of Decision-Makers in a Smart Grid Setting: An Exploratory Study

Demand Response (DR) mechanisms have been developed to reshape consumption patterns in face of price signals, enabling to deal with the increasing penetration of intermittent renewable resources and balance electricity demand and supply. Although DR mechanisms have been in place for some time, it is still unclear to what extent end-users are ready, or willing, to embrace DR programs that can be complex and imply adjustments of daily routines. This work aims to understand how the next generation of Portuguese decision makers, namely young adults in higher education, are prepared to deal with energy decisions in the context of the challenges brought by the smart grids. Results demonstrate that cost savings and the contribution to environmental protection are found to be important motivating factors to enroll into DR programs, which should be further exploited in future actions for the promotion of end-user engagement. Moreover, DR solutions are well-accepted by higher education students, although with limited flexibility levels. In addition, there is room to exploit the willingness to adopt time-differentiated tariffs, yet savings should be clearer and more attractive to end-users. Also, the framing effect should be considered when promoting this type of time-differentiated tariffs.
Inês F. G. Reis, Marta A. R. Lopes, Paula F. V. Ferreira, Carlos Henggeler Antunes, Madalena Araújo

Optimizing the Train-Catenary Electrical Interface Through Control Reconfiguration

Electric railway vehicles are supplied by substations and catenaries at increasingly high power levels being the interface between the traction motors and the overhead contact line based on power electronics converters. A large part of these are AC-DC four quadrant converters operating in parallel at relatively small switching frequencies but using the interleaving principle to reach a low harmonic distortion of the catenary current and imposing specific harmonic ranges in this current. However, the current is not a pure sinusoidal wave and its harmonics can excite unwanted resonances due to the combined effect of the catenary distributed parameters, the substation equivalent impedance and the current spectrum that can vary according to normal and abnormal operating conditions. This paper analyses this phenomenon and proposes a control strategy capable of minimizing the resonance effects.
António Martins, Vítor Morais, Carlos Ramos, Adriano Carvalho, João L. Afonso

Home Energy Monitoring System Towards Smart Control of Energy Consumption

The need to manage, control and reduce energy consumption has led researchers to propose reliable solutions based on new technologies to achieve this goal. Our contribution in this subject is presented in this paper and consists of the design, implementation and testing of a home energy monitoring system. The presented system is dedicated for residential customers and allows the monitoring and control of the energy consumption, based on distributed and central processing. The system includes distributed monitoring devices, a gateway and a graphical user interface (GUI). To connect the all parts we use a hybrid wireless solution based on the Wi-Fi and Bluetooth Low Energy standards. We present the design and the implementation of the monitoring device hardware as well as the embedded software used to calculate the electrical quantities. We also present the calibration methodology used to eliminate gain and offset errors. In terms of performance test results, we have achieved voltage measurement accuracy below 0.2% and current measurement accuracy below 0.5%. A GUI was also developed for the user to visualize and control remotely the household appliances.
Zakariae Jebroni, Jose A. Afonso, Belkassem Tidhaf

Performance Comparison of a Typical Nonlinear Load Connected to Ac and Dc Power Grids

This paper presents a performance comparison of a typical nonlinear load used in domestic appliances (electronic load), when supplied by an ac and a dc voltage of the same rms value. The performance of the nonlinear load towards its connection to ac and dc power grids is accomplished in terms of the waveforms which are registered in the consumed current, internal dc-link voltage and output voltage. A simulation model was developed using realistic database models of the power semiconductors comprising a nonlinear load with input ac-dc converter, so that the efficiency can be calculated and compared for three distinct cases: (1) load supplied by an ac voltage; (2) load supplied by a dc voltage; (3) load without the input ac-dc converter supplied by a dc voltage. Thus, besides the comparison between the ac and dc power grids supplying the same nonlinear load (cases 1 and 2), a third case is considered, which consists of removing the input ac-dc converter (eliminating needless components of the nonlinear load when supplied by a dc voltage). The obtained results show that supplying nonlinear loads with dc power grids is advantageous in relation to the ac power grid, and therefore it can be beneficial to adapt nonlinear loads to be powered by dc power grids.
Tiago J. C. Sousa, Vítor Monteiro, J. G. Pinto, João L. Afonso

How Much are Portuguese Residential Consumers Willing to Invest in Photovoltaic Systems?

This paper presents the main results of a survey conducted aiming at analysing and evaluating the citizen’s perceptions and willingness to invest in the installation of residential photovoltaic systems. Data has been collected in Coimbra, an urban municipality of Portugal, through a questionnaire involving three groups of questions related to socio-economic characterization of the household and building characteristics, ownership of any type of renewable energy system and willingness to invest in residential photovoltaic systems. Regarding the investment cost of the different photovoltaic systems considered, and according to the type of housing, an individual technical and economic evaluation was performed. Most of the 88 respondents have a positive attitude towards the integration of renewable energy systems in the residential sector and some of them have good knowledge of these systems. However, only a few of the respondents own a solar system and about two-thirds of respondents expressed no interest in investing in PV systems. The study served as a starting point for the assessment of the integration of renewable energies in an urban context and the obtained results will serve as the basis for the definition of scenarios related to the penetration of solar photovoltaic systems in the residential sector. This type of results can also be considered by Policy-makers in defining future measures to support the installation of residential renewable energy systems.
Joana Figueira, Dulce Coelho, Fernando Lopes

Sustainability Assessment of High Voltage Transmission Lines

This work aims to contribute to the proposal of a multi-criteria based methodology for sustainability evaluation of impacts from high voltage transmission lines integrating indicators reflecting environmental and socio-economic criteria. The proposed methodology was applied to a transmission grid project in Manaus/Amazonas, Brazil, evaluating its sustainability. From the analysis, it can be observed that the implementation of the project tends to have a significant impact during the construction phase. The most important indexes come from the environmental dimension resulting from a proximity to environmental protected areas and reduction of vegetation both during implementation and operation phases, which is particularly important for the case of Amazonia forest. As for the socio-economic index, this reflects an optimistic expectation of the population towards the arrival of electricity to communities that can lead to the creation of more jobs and improvement of cities infrastructures along with the low expected impact on local protected communities, given the previous studies addressing these concerns during the design phase. Based on the results achieved, avenues for future research are proposed.
Paula Ferreira, Glaucivan da Cunha, Madalena Araújo

Voltage Distortion Minimization in Cascaded H-Bridge Inverters

Multilevel inverters based on the series connection of H-bridges are the most modular multilevel inverter family. The use of a large number of these devices connected in series, controlled by modulation based on the fundamental frequency, allows to obtain an output voltage of the inverter with low harmonic distortion and low losses in the inverter. This paper analyses the main characteristics of a fundamental frequency modulation method applied to multilevel inverters based on cascaded H-bridges (CHB). Particular emphasis is given to the harmonic distortion of the output voltage and the range of variation of the amplitude of the fundamental component in static and dynamic conditions. It is also discussed the implementation of the algorithm in real-time and in an FPGA platform. Simulation and experimental results are presented with a different number of H-bridges.
António Martins, João Faria, Abel Ferreira

A Selective Harmonic Compensation with Current Limiting Algorithm

This paper addresses a control algorithm to determine the reference currents indirectly from the grid voltages, taking into account the limited capacity of the power converter for compensating, entirely, the selected harmonic current. In previous works, the reference current was indirectly determined based on an average component correlated with the selected harmonic current. Thus, when the selected harmonic current was entirely compensated, that average value was decreased to zero. Now, this paper introduces a novel control algorithm considering the limited capacity of the power converter for producing the selected harmonic current. In this novel condition, the phase-angle of the reference current is dynamically modified while the minimum point of the cost function is not reached. The remaining parameters of the reference currents correspond to the harmonic frequency and amplitude as well. The harmonic frequency was identified through a PLL (Phase-Locked-Loop) circuit whereas the amplitude corresponds to a specific value of 10A to all of the developed test cases. Other aspects of the simulated power circuit, control algorithms, including the optimization methods, are described throughout the paper. Simulation results involving different test cases were implemented to verify the performance of the proposed algorithm compensating of the fifth-harmonic component under transient -and steady-state conditions.
Nayara V. Oliveira, Cleiton M. Freitas, Luis F. C. Monteiro

Power Electronics Converters for an Electric Vehicle Fast Charging Station with Storage Capability

Fast charging stations are a key element for the wide spreading of Electric Vehicles (EVs) by reducing the charging time to a range between 20 to 40 min. However, the integration of fast charging stations causes some adverse impacts on the Power Grid (PG), namely by the huge increase in the peak demand during short periods of time. This paper addresses the design of the power electronics converters for an EV DC fast charging station with local storage capability and easy interface of renewables. In the proposed topology, the energy storage capability is used to smooth the peak power demand, inherent to fast charging systems, and contributes to the stability of the PG. When integrated in a Smart Grid, the proposed topology may even return some of the stored energy back to the power grid, when necessary. The accomplishment of the aforementioned objectives requires a set of different power electronics converters that are described and discussed in this paper.
J. G. Pinto, Vítor Monteiro, Bruno Exposto, Luis A. M. Barros, Tiago J. C. Sousa, Luis F. C. Monteiro, João L. Afonso

Experimental Evaluation of Magnetostrictive Strain of Electrical Steel

Environmental noise pollution has gained increasing importance, over the past few years. Due to population growth along with a rapid urbanization and the increasing power supply needs, more and more electrical power transformers are set near or inside of urban agglomerations. This fact has generated several complaints regarding the noise produced by this equipment, forcing manufacturers to develop low noise solutions. As it is known, magnetostriction is one of the main sources of electrical machines noise. This research presents an experimental study in which magnetostriction properties of electrical steel are evaluated and analyzed. The magnetic flux density influence on the hysteretic strain behavior of magnetostriction was addressed, as well as the effect of a clamping load on the core joints. This study was addressed by means of an Epstein frame and a data acquisition system, where strain, current and voltage data is obtained and then processed in a data logging software. These measurements gave essential inputs for numerical models which simulate the power transformer core behavior, allowing a faster evaluation of noise mitigation solutions.
António Vieira, João Espírito Santo, Cristiano P. Coutinho, Sérgio M. O. Tavares, Marta Pinto, Cassiano C. Linhares, Hélder Mendes

Design of Compact LoRa Devices for Smart Building Applications

The use of smart devices in buildings is many times compromised by its form and size. Smart devices are composed of several components including sensors, boards, batteries, processing units, and antennas. However, the form and size of the smart devices are usually limited due to antenna restrictions. In this paper, we propose the architecture of a compact low-cost LoRa smart device designed for easy deployment in smart building applications. The proposed device architecture features a reduced size embedded antenna and an ultra-low-power microcontroller to interface several sensors and actuators. The results obtained have shown that the proposed design can be used for communication, between two compact LoRa devices, in line-of-sight for up to 4.2 km, in urban environments for up to 1.2 km and also for in-building communications for up to 152 m, without compromising the low-power features that LoRa supports.
Sérgio I. Lopes, Felisberto Pereira, José M. N. Vieira, Nuno B. Carvalho, António Curado

Electro-Optical System for Evaluation of Dynamic Inductive Wireless Power Transfer to Electric Vehicles

Inductive lanes that can wirelessly transfer power to moving electric vehicles is a research theme of worldwide interest. The goal is to provide on-the-road recharging, thus extending vehicle’s autonomy and reducing battery capacity requirements. These lanes share, however, a common limitation: the power transfer is affected by the lateral displacement of the vehicle, with respect to the center of the lane. In the case of two-wheeled vehicles, such as electric scooters and bicycles, lateral inclination can also be pronounced enough as to interfere with power coupling. In order to experimentally evaluate the characteristics of such vehicular dynamic power transfer schemes, it is then necessary to synchronously log the vehicle’s electric data, lateral displacement and attitude. In this paper, the design and implementation of an electro-optical measuring system with these capabilities, based on Light Detection and Ranging (LIDAR) technology and inertial sensors, is reported. A testing range with specific reference geometry, consisting of a corridor of parallel walls, is used to simplify the continuous and accurate estimation of lateral displacement. The design was validated by statistical characterization of the measurement errors, using simulated trajectories. A prototype was built and mounted on a non-electric bicycle, with the first tests confirming its positioning measurement qualities.
Luiz A. Lisboa Cardoso, Dehann Fourie, John J. Leonard, Andrés A. Nogueiras Meléndez, João L. Afonso

On the Effects of Parameter Adjustment on the Performance of PSO-Based MPPT of a PV-Energy Generation System

The growing concern on environmental issues caused by fossil fuels and, indeed, on the availability of such energy resources in a long-run basis have settled the ground for the spreading of the so called green energy sources. Among them, photovoltaic energy stands out due to the possibility of turning practically any household into a micro power plant. One important aspect about this source of energy is that practical photovoltaic generators are equipped with maximum power point tracking (MPPT) systems. Currently, researchers are focused on developing MPPT algorithms for partial shaded panels, among which, particle swarm optimization (PSO) MPPT stands out. PSO is an artificial intelligence method based on the behavior of flock of birds and it works arranging a group of mathematical entities named particles to deal with an optimization problem. Thus, this work focus on analyzing the performance of this algorithm under different design conditions, which means different amount of particles and different set points for the constants. Besides that, the article presents a brief guideline on how to implement PSO-MPPT. Simulations of an array with three photovoltaic panels, boost-converter driven, were carried out in order to back the analyzes.
André Luiz Marques Leopoldino, Cleiton Magalhães Freitas, Luís Fernando Corrêa Monteiro

Multi-temporal Active Power Scheduling and Voltage/var Control in Autonomous Microgrids

This paper presents a multi-temporal approach for the energy scheduling and voltage/var control problem in a microgrid (MG) system with photovoltaic (PV) generation and energy storage devices (PV-battery MG) during islanded operation conditions. A MG is often defined as a low voltage (LV) distribution grid that encompasses distributed energy resources and loads that operate in a coordinated way, either connected to the upstream distribution grid or autonomously (islanded from the main grid). Considering the islanded operation of the MG during a given period, it is necessary to develop proper tools that allow the effective coordination of the existing resources. Such tools should be incorporated in the MG control system hierarchy in order to assure proper conditions for the operation of the autonomous MG in terms of active power, voltage and reactive power management. Energy storage devices are essential components for the successful operation of islanded MG. These devices have a very fast response and are able to absorb/inject the right amount of power. For the operation of the MG in islanding conditions during a longer period, it is necessary to integrate information related to the forecasting of loads and PV-based generation for the upcoming hours for which is intended to maintain MG in islanded operation. Therefore, this paper presents a tool to be integrated in the Microgrid Central Controller (MGCC) that is responsible to perform a multi-temporal optimal power flow (OPF) in order to schedule the active and reactive power within the MG for the next time intervals.
Manuel V. Castro, Carlos L. Moreira


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