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In this paper, a protection method with two cascaded algorithms is proposed to face fault events in Electrical Distribution Systems (EDSs). The first algorithm uses the Total Harmonic Distortion (THD), the estimates of the amplitude voltages, and the zero-sequence component of the grid voltages for defining an adaptive algorithm that provides a secure detection and identification process for the faults in the grid network. The second algorithm uses the behavior of the positive and negative-sequence components of the grid voltages during the fault events to locate and isolate the faults. Its main merit is that it doesn’t need to employ communication lines for transmitting trip signals between the protective devices (PDs) of the system. A Second Order Generalized Integrator (SOGI) is used for obtaining the estimated variables and sequence components, which allows fast detection with a low computational burden. The harmonic content existing prior to the fault is taken into consideration for not affecting the detection of the fault. The performance of the protection method’s is evaluated experimentally and by using simulations in MATLAB/Simulink and employing the IEEE 9-bus standard ring system. The proposed method shows the capability for detecting, identifying, and isolating different fault types with different DG penetrations and fault resistances in different locations of the proposed network and even when the grid configuration is changed. The method is robust to the possible harmonic distortion of the network., Peer Reviewed, Postprint (published version)

The main objective of this work is to evaluate the energy efficiency improvement obtained in grid-connected photovoltaic systems based on a dynamic reconfiguration strategy. The MIX and team reconfigurable photovoltaic system topologies have been considered since both minimize the operation of the inverters in low-load conditions. A numerical method is used to analyze the energy flows within the photovoltaic system, with a specific focus on the plant-oriented configuration. In this work, MIX systems are only presented briefly, while team reconfigurable photovoltaic Systems are analyzed in more detail. This is because team systems can be implemented using conventional commercial inverters, electromechanical switches to redirect power flows, and a simple digital controller (as based on the Arduino platforms). The energy supplied to the grid by two gridconnected photovoltaic systems will be evaluated: one based on a classic non-reconfigurable strategy and another based on the team strategy. The measurement of the energy generated by these two systems, tested under various irradiance levels (emulating different climatic conditions), shows that reconfigurable systems always exhibit greater energy efficiency. However, this energy improvement can only be considered substantial in certain situations., Peer Reviewed, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Postprint (published version)

Earlier protection methods mainly focused on using communication channels to transmit trip signals between the protective devices (PDs), with no solutions provided in the case of communication failure. Therefore, this paper introduces a dual-layer protection system to ensure secure protection against fault events in the Distribution Systems (DSs), particularly in light of communication failures. The initial layer uses the Total Harmonic Distortion (THD), the estimates of the amplitude voltages, and the zero-sequence grid voltage components, functioning as a fault sensor, to formulate an adaptive algorithm based on a Finite State Machine (FSM) for the detection and isolation of faults within the grid. This layer primarily relies on communication protocols for effective coordination. A Second-Order Generalized Integrator (SOGI) expedites the derivation of the estimated variables, ensuring fast detection with minimal computational overhead. The second layer uses the behavior of the positive- and negative-sequence components of the grid voltages during fault events to locate and isolate these faults. In the event that the first layer exposes a communication failure, the second layer will automatically be activated to ensure secure protection as it operates, using the local information of the Protective devices (PDs), without the need for communication channels to transmit trip signals between the PDs. The proposed protection system has been assessed using simulations with MATLAB/Simulink and providing experimental results considering an IEEE 9-bus standard radial system. The obtained results confirm the capability of the system for identifying and isolating different types of faults, varying conditions, and modifications to the grid configuration. The results show good behavior of the initial THD-based layer, with fast time responses ranging from 6 to 8.5 ms in all the examined scenarios. In contrast, the sequence-based layer exhibits a protection time response of appro, Peer Reviewed, Postprint (published version)

© 2024 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, Nowadays, the increase in electric power coverage worldwide is a priority scope of the study, where Microgrids (MG) emerge as feasible solutions to supply electricity. The use of MG to provide energy to isolated communities, especially its use as Isolated Multi-Microgrid (IMMG) systems, has become an object of study worldwide. Different control techniques have been developed to improve and optimize the energy management system (EMS) associated with an isolated MG and new alternatives for energy exchange between IMMGs. However, the geographical location of a possible implementation of an MG directly affects the optimal dimensioning, the operating cost, and the environmental impact, among others. In this context, this work proposes a novel design of an EMS based on a fuzzy logic controller focusing on power exchange between IMMG systems. The proposed EMS aims to minimize the consumption of fossil fuels, reduce the total energy wasted by the power generation units, and keep the state-of-charge of the energy storage system (ESS) at safe levels to extend its useful life. Moreover, an ESS state of health analysis is presented to determine its degradation over time when applying the proposed EMS. In addition, the proposed EMS considers the uncertainties in the disconnection of any MG, ensuring the independent operation of each one. Simulation results are performed for a case study of an isolated community in the Amazon region of Ecuador. For this purpose, a group of microgrids is considered in three different scenarios. In the first scenario, there is no power exchange between the microgrids. In the second scenario, the microgrids exchange power using a simple EMS based on a set of analytical rules, and in the third scenario, the microgrids exchange power using the proposed EMS. The results show an improvement in the overall performance of the third scenario compared to the first two, both in reducing the energy wasted by the PV system and in the cost of fossil fuel. Final, Peer Reviewed, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.1 - Per a 2030, garantir l’accés universal a serveis d’energia assequibles, confiables i moderns, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles, Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.1 - Per a 2030, assegurar l’accés de totes les persones a habitatges i a serveis bàsics adequats, segurs i assequibles, i millorar els barris marginal, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.1 - Per a 2030, garantir l’accés universal a serveis d’energia assequibles, confiables i moderns, Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.1 - Per a 2030, assegurar l’accés de totes les persones a habitatges i a serveis bàsics adequats, segurs i assequibles, i millorar els barris marginal, Postprint (author's final draft)

Climate change is an important research topic due to the catastrophic impact that may have in human societies. We evaluate the entropy flows generated by cars to estimate the most efficient car transport and its impact in the framework. We characterize the entropy flows, applying Gouy-Stodola theorem and constructal law. We find that environment entropy is higher than both combustion or energy transformation entropies., Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Postprint (published version)

A microgrid is defined as the link of consumer loads and decentralized energy assets with the ability to control the entire system as a whole. The modeling of an electromagnetic microgrid is discussed in this work to analyze energy effectiveness and entropy balance. The method computes the associated losses and simulates the electrical behavior of the components. The model is built and tested by using the MATLAB Simulink application. The system is made up of several blocks consisting of solar panels, batteries, consumer loads, and the inverter needed to connect them all. Their energy efficiency is assessed using the findings from each of these components. The system's entropy generation is also calculated to study how it relates to performance., Peer Reviewed, Postprint (published version)

Li-ion batteries are crucial for the forthcoming energy transition. They are complex systems that show heterogeneous current distribution patterns and degradation. The development of valid methods to determine their internal state as well as for performance optimization and life cycle extension are vital for battery full deployment.We study the entropy production in the cells in the presence of temperature gradients.We observe that entropy is produced faster in the regions with larger temperatures which are generally associated with faster degradation patterns., Postprint (author's final draft)

This work presents a literature review about control techniques for parallel connected power inverters under microgrid applications. Some control strategies, based on droop control for parallel inverters of distributed generation units in an ac distribution system will be presented in this work. Finally, an important method called Virtual Oscillating Control (VOC) is suggested for connecting voltage source inverters. Inverters are able to work in parallel with a constant-voltage constant frequency system, as well as with other inverters and also in standalone operation. The different power sources can share the load also under unbalanced conditions. Throughout this work several simulation results are presented in order to demonstrate the behaviour the behavior of the different control strategies tested., Peer Reviewed, Postprint (published version)

© 2023 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, This paper proposes a cooperative strategy for the flexible integration of stand-alone AC microgrids using an intermediate multiterminal DC link based on voltage source converters. The strategy manages cooperative power exchange between microgrids through a knowledge-based fuzzy inference system that relies on the current operating conditions of the microgrids. By determining the amount of power to be exchanged between microgrids to improve global reliability, the cooperative strategy achieves an overall reduction in load loss and an increase in the use of available renewable energy. Additionally, the multiterminal DC link provides complete isolation between microgrids, allowing for independent AC bus voltage regulation and management. The effectiveness and expandability of the proposed cooperative energy exchange strategy for enhancing the overall operation of multiple integrated microgrids have been fully verified by simulation and experimental validation., Peer Reviewed, Postprint (published version)

The integration of Distributed Generators (DGs) into distribution systems (DSs) leads to more reliable and efficient power delivery for customers. However, the possibility of bi-directional power flow creates new technical problems for protection schemes. This poses a threat to conventional strategies because the relay settings have to be adjusted depending on the network topology and operational mode. As a solution, it is important to develop novel fault protection techniques to ensure reliable protection and avoid unnecessary tripping. In this regard, Total Harmonic Distortion (THD) can be used as a key parameter for evaluating the grid’s waveform quality during fault events. This paper presents a comparison between two DS protection strategies that employ THD levels, estimated amplitude voltages, and zero-sequence components as instantaneous indicators during the faults that function as a kind of fault sensor to detect, identify, and isolate faults. The first method uses a Multiple Second Order Generalized Integrator (MSOGI) to obtain the estimated variables, whereas the second method uses a single SOGI for the same purpose (SOGI-THD). Both methods rely on communication lines between protective devices (PDs) to facilitate coordinated protection. The effectiveness of these methods is assessed by using simulations in MATLAB/Simulink considering various factors such as different types of faults and DG penetrations, different fault resistances and fault locations in the proposed network. Moreover, the performance of these methods is compared with conventional overcurrent and differential protections. The results show that the SOGI-THD method is highly effective in detecting and isolating faults with a time interval of 6–8.5 ms using only three SOGIs while requiring only 447 processor cycles for execution. In comparison to other protection methods, the SOGI-THD method exhibits a faster response time and a lower computational burden. Furthermore, the SOGI-THD method is, Peer Reviewed, Postprint (published version)

Hydropower systems are the basis of electricity power generation in Ecuador. However, some isolated areas in the Amazon and Galapagos Islands are not connected to the National Interconnected System. Therefore, isolated generation systems based on renewable energy sources (RES) emerge as a solution to increase electricity coverage in these areas. An extraordinary case occurs in the Galapagos Islands due to their biodiversity in flora and fauna, where the primary energy source comes from fossil fuels despite their significant amount of solar resources. Therefore, RES use, especially photovoltaic (PV) and wind power, is essential to cover the required load demand without negatively affecting the islands’ biodiversity. In this regard, the design and installation planning of PV systems require perfect knowledge of the amount of energy available at a given location, where power forecasting plays a fundamental role. Therefore, this paper presents the design and comparison of different deep learning techniques: long-short-term memory (LSTM), LSTM Projected, Bidirectional LSTM, Gated Recurrent Units, Convolutional Neural Networks, and hybrid models to forecast photovoltaic power generation in the Galapagos Islands of Ecuador. The proposed approach uses an optimized hyperparameter-based Bayesian optimization algorithm to reduce the forecast error and training time. The results demonstrate the accurate performance of all the methods by achieving a low-error short-term prediction, an excellent correlation of over 99%, and minimizing the training time., Peer Reviewed, Postprint (published version)

Motors that work with high voltage and consume a lot of power, specifically those of 6 kV and 650 kW, generate harmonics of voltage and current harmful to the electro-energy system, causing problems in its correct operation. In this study, the quality of the electrical energy of a motor having those characteristics is analyzed by measuring voltage, current intensity, power factor, active power, reactive power, as well as voltage and current harmonics. Results show that the main problem lies in the fact that the total current harmonic distortion reached a value of 17.1%, which is above the maximum value permissible according to the standard for the motor object of study. However, the total voltage harmonic distortion resulted within the allowable values, reaching a maximum of 3.3%. To mitigate the harmful effects of the total current harmonic distortion, passive and active filters were designed and simulated to improve the motor's operation and solve the problems. For the design and simulation of the filters, MATLAB R2015a software and LabView 2014 software were used., Peer Reviewed, Postprint (author's final draft)

This paper proposes the use of linear-assisted switching power converters in the context of single-inductor dual-output (SIDO) for microgrids (MG) applications. By combining a DC/DC ripple-controlled switching power converter with the respective voltage linear regulators at each output, improved performance in terms of load and line regulations is obtained. To achieve that aim, a current-steering switching policy is proposed, together with a resource-aware circuit implementation. The ripple-based hysteretic control results in variable switching frequency to guarantee critical conduction mode (boundary of CCM and DCM)., Peer Reviewed, Postprint (published version)

In modern trends, the voltage profile has become increasingly critical when incorporating wind turbine energy sources because of changes in fault ride-through capabilities throughout voltage reaction. Ripple, voltage magnitude changes, and injected harmonics due to conversion switches are power quality issues for grid-integrated doubly fed induction generators (DFIG) wind sources. In this study, FACTS (flexible alternating current transmission system) devices like the static VAR compensator (SVC), thyristor controlled series compensator (TCSC), unified power flow controllers (UPFC), and static synchronous compensators (STATCOM) are used to stabilise wind energy with DFIGs. The simulation test cases using MATLAB also analyse three lines to ground fault (LLL-G) of fault measures, which showed a 9 MW that transferred to utility grid. Therefore, it is suggested to inject or absorb reactive power to stabilise the system using moth flame optimization with firebug swarm optimization (MFO-FSO). The simulation results clearly demonstrate that the proposed MFOFSO based STATCOM devices outperform the current nonlinear generalized predictive control based STATCOM, which only achieves 0.9815 per unit voltage stability, by achieving a higher voltage profile of 0.9925 per unit voltage stability with a reactive power injection of 1.82 MVAR., Peer Reviewed, Postprint (published version)

The Second Order Generalized Integrator–Frequency Locked Loop (SOGI-FLL) is a widely used and popular adaptive filter for estimating grid voltage parameters with minimal computational burden. However, it is vulnerable to voltage sag and swell faults, especially voltage sags that can significantly distort the estimated frequency. In this paper, we propose an error-and-hold algorithm for the SOGI-FLL that can quickly detect faults and hold the estimated frequency during these perturbations. The algorithm uses the absolute value of the SOGI's error, its average, and the average of the FLL's estimated frequency to operate. It reduces induced errors in the SOGI-FLL's quadrature outputs, improves the FLL's transient response, holds the estimated frequency, and restores the phase to its previous value before the fault. The proposed algorithm is a straightforward and low computational burden algorithm that can be executed on a low-cost processor. We validate the effectiveness of the proposed error-and-hold algorithm through simulations and experimental results., Peer Reviewed, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Postprint (published version)

Motor imagery-based brain–computer interfaces (MI-BCIs) are a promise to revolutionize the way humans interact with machinery or software, performing actions by just thinking about them. Patients suffering from critical movement disabilities, such as amyotrophic lateral sclerosis (ALS) or tetraplegia, could use this technology to interact more independently with their surroundings. This paper aims to aid communities affected by these disorders with the development of a method that is capable of detecting the intention to execute movements in the upper extremities of the body. This will be done through signals acquired with an electroencephalogram (EEG), their conditioning and processing, and their subsequent classification with artificial intelligence models. In addition, a digital signal filter will be designed to keep the most characteristic frequency bands of each individual and increase accuracy significantly. After extracting discriminative statistical, frequential, and spatial features, it was possible to obtain an 88% accuracy on validation data with a random forest (RF) model when it came to detecting whether a participant was imagining a left-hand or a right-hand movement. Furthermore, a convolutional neural network (CNN) was used to distinguish if the participant was imagining a movement or not, which achieved 78% accuracy and 90% precision. These results will be verified by implementing a real-time simulation with the usage of a robotic arm., Peer Reviewed, Postprint (author's final draft)

Best Paper Award in the 2023 International Conference on Predictive Control of Electrical Drives and Power Electronics (PRECEDE 2023), The increasing development of 5G technology has focused attention on the energy consumption of its base stations. As a result, it is crucial to establish energy-efficient 5G networks and reduce the operating costs associated with 5G base stations. In this paper, a multi-time-scale energy management strategy based on model predictive control (MPC) is proposed to achieve this aim. Firstly, a 5G base station model that takes into account several factors is established, including backup energy storage, inverter air conditioning scheduling potential, photovoltaic output fluctuations, load, and temperature. Secondly, a day-ahead optimal economic dispatch model for minimizing operational costs is developed. Thirdly, an intraday rolling optimization strategy based on MPC to dynamically adjust the day-ahead operation scheme is proposed. Finally, comprehensive case studies are carried out, which indicate that the proposed strategy can effectively improve the robustness and economy of the system., Peer Reviewed, Award-winning, Postprint (published version)

Pulsed power load (PPL) is a special load type in shipboard microgrids (SMGs), which consists of the generation module, energy storage system, and various types of loads. Having a reliable power supply to shipboard loads is a challenge as the SMG operates in islanded mode in most cases. Particularly, the PPLs require high transient power transfer with fast dynamics and strong robustness. Conventional solution to supply for the PPL is based on proportional-integral (PI) control, which can be used by linearizing the system around the equilibrium operation point. However, for a pulsed power supply (PPS) system, the load demand drastically changes in a short time, usually in millisecond level, making the operating point changes when the pulsed power is triggered or terminated. To supply the PPL with fast dynamics and robustness, an improved PPS control method is presented in this paper. By adopting a nonlinear sliding mode control (SMC) method, fast voltage regulation and robust pulse power tracking can be achieved. In the PPS, the PPL power demand is divided into two terms: one is the average power that is supplied by the SMG and the other is the fast pulsed power that is supplied by the storage capacitor. The size and cost of the storage capacitor are reduced as it is intentionally driven to a deep discharge. The PPS system configuration and coordination principle, SMC controllers, and sizing of passive elements in the PPS are analyzed in detail. The effectiveness of the presented PPS is verified by simulation results., Peer Reviewed, Postprint (published version)

A microgrid is defined as the link of consumer loads and decentralized energy assets with the ability to control the entire system as a whole. The modeling of an electromagnetic microgrid is discussed in this work to analyze energy effectiveness and entropy balance. The method computes the associated losses and simulates the electrical behavior of the components. The model is built and tested by using the MATLAB Simulink application. The system is made up of several blocks consisting of solar panels, batteries, consumer loads, and the inverter needed to connect them all. Their energy efficiency is assessed using the findings from each of these components. The system's entropy generation is also calculated to study how it relates to performance., Peer Reviewed, Postprint (published version)

The rapid growth of the distributed generators (DGs) integration into the distribution systems (DSs) creates new technical issues; conventional relay settings need to be updated depending on the network topology and operational mode as fault protection is a major challenge. This emphasizes the need for new fault protection methods to ensure secure protection and prevent undesirable tripping. Total harmonic distortion (THD) is an important indicator for assessing the quality of the grid. Here, a new protection system based on the THD of the grid voltages is proposed to address fault events in the electrical distribution network. The proposed protection system combines the THD with the estimates of the amplitude voltages and the zero-sequence component for defining an algorithm based on a finite state machine (FSM) for the detection, identification, and isolation of faults in the grid. The algorithm employs communication lines between all the protective devices (PDs) of the system to transmit tripping signals, allowing PDs to be coordinated. A second order generalized integrator (SOGI) and multiple SOGI (MSOGI) are used to obtain the THDs, estimated amplitude voltages, and zero-sequence component, which allows for fast detection with a low computational burden. The protection algorithm performance is evaluated through simulations in MATLAB/Simulink and a comparative study is developed between the proposed protection method and a differential relay (DR) protection system. The proposed method shows its capability to detect and isolate faults during different fault types with different fault resistances in different locations in the proposed network. In all the tested scenarios, the detection time of the faults has been between 7–10 ms. Moreover, this method gave the best solution as it has a higher accuracy and faster response than the conventional DR protection system., Peer Reviewed, Postprint (published version)

El sonambulismo es un trastorno del sueño que afecta principalmente a niños y adolescentes; sin embargo, se considera que aproximadamente el 2 % de la población adulta lo padece. Se desconocen las causas de su aparición; no obstante, las consecuencias resultantes pueden ser peligrosas puesto que el individuo puede realizar acciones como caminar, ducharse o salir de casa, mientras duerme; por lo tanto, de manera inconsciente. Este artículo no sólo presenta un sistema cuyo objetivo es evitar aquellas situaciones inseguras para el sonámbulo, sino que se distingue de los métodos empleados actualmente en donde se detectan este tipo de eventos empleando cámaras y sensores de movimiento, sino que procura ir un paso más allá; evitar que la persona se levante de la cama mediante señales electroencefalográficas que permiten detectar el sonambulismo des de su inicio, siendo capaces de pararlo usando una pulsera vibratoria., Postprint (published version)

In University environment, it is common to use multiple-choice objective tests with three or four possible answers, of which only one is correct and the rest are erroneous. In this type of tests, usually the wrong answers are penalized in order to avoid the effect of the random answers. However, there are questions that hardly students answer since their difficulty is high. On the other hand, there are also questions that answer virtually all students since their difficulty is simple. While sometimes the course professor chooses to suppress these questions, it is also common to leave them as part of the calculation of the overall score. This communication proposes a way of, without suppressing any question, making a readjustment of the grades based on fuzzy logic techniques. To do this, it is considered, on the one hand, the initial grade obtained by each student and, on the other, the total difficulty index of the test. With these two variables, an approximation can be made to a system of linguistic variables that allows correcting the final grades of each student based on the objective difficulty of the test and a set of rules established by the professor. This will revert to greater “justice” in students’ mark system, since it will be a function of the difficulty of the test., Postprint (published version)

In University environment, it is common to use multiple-choice objective tests with three or four possible answers, of which only one is correct and the rest are erroneous. In this type of tests, usually the wrong answers are penalized in order to avoid the effect of the random answers. However, there are questions that hardly students answer since their difficulty is high. On the other hand, there are also questions that answer virtually all students since their difficulty is simple. While sometimes the course professor chooses to suppress these questions, it is also common to leave them as part of the calculation of the overall score. This communication proposes a way of, without suppressing any question, making a readjustment of the grades based on fuzzy logic techniques. To do this, it is considered, on the one hand, the initial grade obtained by each student and, on the other, the total difficulty index of the test. With these two variables, an approximation can be made to a system of linguistic variables that allows correcting the final grades of each student based on the objective difficulty of the test and a set of rules established by the professor. This will revert to greater “justice” in students’ mark system, since it will be a function of the difficulty of the test., Postprint (published version)

Micro hydro power plants (µHPP) are typically used to supply electric energy to microgrids outside the national power grids taking care of the frequency control of the isolated system. A conventional way to maintain the load balance in the system is to use thyristor switched AC-AC converters controlled dump loads. A disadvantage of the AC-AC converters is their reactive power consumption decreasing the power factor at the generator output. To avoid this problem the authors have earlier proposed two converter topologies utilizing symmetrical switching scheme resulting to zero reactive power consumption. The objective of this paper is to evaluate the frequency regulation loop performance of the dump load controlled single generator system by using the symmetrically switched converter structures. Evaluation is carried out by analyzing the performances of different converter structures in a simulator representing the operation of a Cuban µHPP “Los Gallegos”. The results showed that the frequency regulation loop performance using each proposed converter structure satisfied the Cuban standard of frequency regulation, but with the symmetrically switched structures reactive power consumption was reduced resulting to reduced losses and improved effective current delivery capacity of the generator., Postprint (published version)

In University environment, it is common to use multiple-choice objective tests with three or four possible answers, of which only one is correct and the rest are erroneous. In this type of tests, usually the wrong answers are penalized in order to avoid the effect of the random answers. However, there are questions that hardly students answer since their difficulty is high. On the other hand, there are also questions that answer virtually all students since their difficulty is simple. While sometimes the course professor chooses to suppress these questions, it is also common to leave them as part of the calculation of the overall score. This communication proposes a way of, without suppressing any question, making a readjustment of the grades based on fuzzy logic techniques. To do this, it is considered, on the one hand, the initial grade obtained by each student and, on the other, the total difficulty index of the test. With these two variables, an approximation can be made to a system of linguistic variables that allows correcting the final grades of each student based on the objective difficulty of the test and a set of rules established by the professor. This will revert to greater “justice” in students’ mark system, since it will be a function of the difficulty of the test., Postprint (published version)

Renewable Energy Sources (RES) are currently being used on a much larger scale to support and satisfy the higher energy demands caused by industrialization and population growth. Due to this rise in the number of consumers of power systems and the unpredictable nature of the electric load, the vast power demand proves to be a tough challenge for electric utilities and system operators. So, power demands have occurred over many periods and become a threat to the system's functionality. Therefore, an effective Energy Management System (EMS) name called Golden Eagle Optimization with Incremental Conductance (GEO-INC) is proposed to meet the load demand. Three different systems, namely: RES Photovoltaic (PV) module, wind turbine, and battery create an effective EMS. The proposed method extracts more power from the PV panel and effectively controls the switching between the wind turbine and the battery storage system. The proposed method achieves 1.98 % distortion from the results, which is less than the existing methods., The authors would like to thank the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN)-Agencia Estatal de Investigación (AEI) and the European Regional Development Funds (ERDF), by grant PGC2018-098946-B-I00 funded by MCIN/ AEI/10.13039/501100011033/ and by ERDF ERDF A way of making Europe., Peer Reviewed, Postprint (published version)

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., In Ecuador, electricity generation is mainly covered by renewable energy sources that feed the National Interconnected System (NIS). Its economical price means that the installation of systems based on non-conventional renewable energy sources does not represent a benefit for the user. However, rural communities isolated from the NIS do not have electricity services. Due to this, isolated systems become an effective option to supply electricity to these communities. In this regard, the Galapagos Islands have unique biodiversity in the world. Since they are not connected to the NIS, their primary energy sources are based on biogas obtained from fossil fuels, with their negative consequences despite the great potential of solar resources. Hence the need to use non-conventional renewable energy sources that covers the energy demand and do not affect the biodiversity there. Photovoltaic energy forecasting is an essential step in the installation of photovoltaic systems. Prediction models based on deep learning (DL) techniques can obtain a high degree of accuracy in energy prediction tasks. For this reason, this work presents the development of long short-term memory (LSTM) and gated recurrent unit (GRU) models to predict photovoltaic energy in an isolated area of Ecuador. The results highlight the performance of both methods through the achieved short-term prediction., Peer Reviewed, Postprint (published version)

This paper presents a neural network-generalized predictive control (NN-GPC) for a single-phase grid-connected z-source inverter. The NN forecasts the predictive horizon, and the conventional GPC algorithm calculates the control horizon. The results verify the proposed NN-GPC effectively enhances the dynamic operation of z-source inverter regarding the non-minimum phase characteristics of these converters., Postprint (published version)

El sonambulismo es un trastorno del sueño que afecta principalmente a niños y adolescentes; sin embargo, se considera que aproximadamente el 2 % de la población adulta lo padece. Se desconocen las causas de su aparición; no obstante, las consecuencias resultantes pueden ser peligrosas puesto que el individuo puede realizar acciones como caminar, ducharse o salir de casa, mientras duerme; por lo tanto, de manera inconsciente. Este artículo no sólo presenta un sistema cuyo objetivo es evitar aquellas situaciones inseguras para el sonámbulo, sino que se distingue de los métodos empleados actualmente en donde se detectan este tipo de eventos empleando cámaras y sensores de movimiento, sino que procura ir un paso más allá; evitar que la persona se levante de la cama mediante señales electroencefalográficas que permiten detectar el sonambulismo des de su inicio, siendo capaces de pararlo usando una pulsera vibratoria., Postprint (published version)

This paper describes the experience carried out within the Bachelor's Degree in Industrial Electronics and Automation Engineering taught at the Eastern Barcelona School of Engineering (EEBE) of the Technical University of Catalonia–BarcelonaTech (UPC). Specifically, the experience is based on the realization of a cross project that is under the framework of the degree intensification named Application Design in Electronics Engineering (ADEE). This intensification, consisting of a block of two courses, taught in the Fall and Spring semesters, and offered for students in their final year, allows the fulfillment, for two semesters, of the aforementioned project. This includes the design, simulation, implementation (assembly), testing and experimental results (corroboration) of an electronic system or equipment within the field of Electronic Engineering., Postprint (published version)

Within the offer of core courses of the Bachelor’s Degree in Industrial Electronics and Automation Engineering of the Technical University of Catalonia (UPC), which appeared as a result of the current undergraduate study program, within the European Higher Education Area (EHEA), there is a course, Analog Electronics (EAEIA), which allows the Electronic Engineering student to delve into the knowledge of this content. This paper exposes the philosophy of this course, in such a way that it analyzes the orientation that is intended to be given, especially within the new framework of courses offered at the EEBE where, in addition to the hours of lectures and laboratory sessions, there must be room for to the guided activities (GAs) that the current syllabus contemplates., Postprint (published version)

Within the offer of core courses of the Bachelor’s Degree in Industrial Electronics and Automation Engineering of the Technical University of Catalonia (UPC), which appeared as a result of the current undergraduate study program, within the European Higher Education Area (EHEA), there is a course, Analog Electronics (EAEIA), which allows the Electronic Engineering student to delve into the knowledge of this content. This paper exposes the philosophy of this course, in such a way that it analyzes the orientation that is intended to be given, especially within the new framework of courses offered at the EEBE where, in addition to the hours of lectures and laboratory sessions, there must be room for to the guided activities (GAs) that the current syllabus contemplates., Postprint (published version)

El presente trabajo tiene como objetivo el análisis de diferentes escenarios con microrredes domésticas con colaboración entre prosumidores domésticos. Se persigue encontrar estrategias que permiten una optimización de la colaboración entre los prosumidores que conforman los casos estudiados considerados en el artículo. El sistema de gestión de energía diseñado distribuye los flujos energéticos teniendo en cuenta una serie de parámetros y siguiendo una colaboración entre pares o peer-to-peer (P2P), específicamente el método store-then-cooperate (STC)., Postprint (published version)

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., This paper presents a neural network-generalized predictive control (NN-GPC) for a single-phase grid-connected z-source inverter. The NN forecasts the predictive horizon, and the conventional GPC algorithm calculates the control horizon. The results verify the proposed NN-GPC effectively enhances the dynamic operation of z-source inverter regarding the non-minimum phase characteristics of these converters., The authors would like to thank the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN)-Agencia Estatal de Investigación (AEI) and the European Regional Development Funds (ERDF), by grant PGC2018-098946-B-I00 funded by MCIN/AEI/10.13039/501100011033/ and by ERDF A way of making Europe., Peer Reviewed, Postprint (published version)

Load Frequency Control (LFC) is an issue of top importance to ensure microgrids (MGs) safe and reliable operation in AC MGs. Primary frequency control of each energy source can be guaranteed in AC MGs in order to integrate other energy sources. This paper proposes a micro-hydro frequency control scheme, combining the control of a reduced dump load and the nozzle flow control of Pelton turbines operating in isolated from electricity grid. Some researchs have reported the integration of dump load and flow control methods, but they did not reduce the dump load value and adjust the nozzle flow linearly to the power value demanded by users, causing the inefficient use of water. Simulation results were obtained in Matlab®/Simulink® using models obtained from previous research and proven by means of experimental studies. The simulation of the proposed scheme shows that instantaneous frequency variation is about 2 % even for perturbations magnitude up to 12 %. The validation result shows a 60 % reduction in overshoot and settling time of frequency temporal behaviour operating the micro-hydro autonomously., Peer Reviewed, Postprint (published version)

The aim of this paper is to demonstrate that collaboration between microgrids should be varied and global in order to optimize the collaboration and therefore, decrease the dependence on the electrical grid. In the article, different scenarios will be defined where the prosumers will collaborate by selling or buying their electricity generation through an energy management system. The designed energy management system distributes the energy flows of each prosumer considering a series of constraints, following a peer-to-peer (P2P) collaboration, specifically the store-then-cooperate (STC) method., Peer Reviewed, Postprint (published version)

Networked microgrid (NMG) is a novel conceptual paradigm that can bring multiple advantages to the distributed system. Increasing renewable energy utilization, reliability and efficiency of system operation and flexibility of energy sharing amongst several microgrids (MGs) are some specific privileges of NMG. In this paper, residential MGs, commercial MGs, and industrial MGs are considered as a community of NMG. The loads’ profiles are split into multiple sections to evaluate the maximum load demand (MLD). Based on the optimal operation of each MG, the operating reserve (OR) of the MGs is calculated for each section. Then, the self-organizing map as a supervised and a k-means algorithm as an unsupervised learning clustering method is utilized to cluster the MGs and effective energy-sharing. The clustering is based on the maximum load demand of MGs and the operating reserve of dispatchable energy sources, and the goal is to provide a more efficient system with high reliability. Eventually, the performance of this energy management and its benefits to the whole system is surveyed effectively. The proposed energy management system offers a more reliable system due to the possibility of reserved energy for MGs in case of power outage variation or shortage of power., Peer Reviewed, Postprint (published version)

Electrical impedance tomography (EIT) is based on the physical principle of bioimpedance defined as the opposition that biological tissues exhibit to the flow of a rotating alternating electrical current. Consequently, here, we propose studying the characterization and classification of bioimpedance patterns based on EIT by measuring, on the forearm with eight electrodes in a non-invasive way, the potential drops resulting from the execution of six hand gestures. The starting point was the acquisition of bioimpedance patterns studied by means of principal component analysis (PCA), validated through the cross-validation technique, and classified using the k-nearest neighbor (kNN) classification algorithm. As a result, it is concluded that reduction and classification is feasible, with a sensitivity of 0.89 in the worst case, for each of the reduced bioimpedance patterns, leading to the following direct advantage: a reduction in the numbers of electrodes and electronics required. In this work, bioimpedance patterns were investigated for monitoring subjects’ mobility, where, generally, these solutions are based on a sensor system with moving parts that suffer from significant problems of wear, lack of adaptability to the patient, and lack of resolution. Whereas, the proposal implemented in this prototype, based on the so-called electrical impedance tomography, does not have these problems., Peer Reviewed, Postprint (published version)

This paper addresses the attainment of a methodology aimed at obtaining simplified models embedding the regulatory constraints imposed by the country-specific remuneration mechanisms in the energy management system of long operating life renewable assets under a high degree of uncertainty. This methodology, composed of different steps in which sensitivity analysis as well as Monte Carlo simulation play a key role, is focused on a significant case study that has implemented two of the most widely used worldwide remuneration mechanisms in the promotion of renewable energies, i.e., feed-in tariffs and auctions. The earnings before interest, tax, depreciation and amortization have been used as the output variable of the energy management model, as it is essential to take into account both revenues and operating costs of these renewable assets to manage them optimally. Some valid simplified models have been achieved by applying the proposed methodology to the case study with generalized errors below 5%. Specifically, one simplified energy management system model has been obtained under the feed-in tariff scheme, which involves acting on almost 40% of the equations of the original model and reducing the initial input parameters by 22%. Meanwhile, two simplified energy management system models have been obtained under the auction scheme. The most conservative simplified model involves acting on almost 50% of the equations of the original model and reducing the initial input parameters by 35%, while in the less conservative case it involves acting on more than 50% of the equations of the original model and reducing the initial input parameters by 42%. In short, although the uncertainty on the energy assets cannot be completely eliminated, it can be considerably reduced by facilitating the assessment of its prospective financial results. The validity of the achieved simplified models demonstrates the suitability and usefulness of the proposed simplifying methodology, providi, Peer Reviewed, Postprint (author's final draft)

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., Community Microgrid offers effective energy harvesting from distributed energy resources and efficient energy consumption by employing an energy management system (EMS). Therefore, the collaborative microgrids are essentially required to apply an EMS, underlying an operative control strategy in order to provide an efficient system. An EMS is apt to optimize the operation of microgrids from several points of view. Optimal production planning, optimal demand-side management, fuel and emission constraints, the revenue of trading spinning and non-spinning reserve capacity can effectively be managed by EMS. Consequently, the importance of optimization is explicit in microgrid applications. In this paper, the most common control strategies in the microgrid community with potential pros and cons are analyzed. Moreover, a comprehensive review of single objective and multi-objective optimization methods is performed by considering the practical and technical constraints, uncertainty, and intermittency of renewable energies sources. The Pareto-optimal solution as the most popular multi-objective optimization approach is investigated for the advanced optimization algorithms. Eventually, feature selection and neural network-based clustering algorithms in order to analyze the Pareto-optimal set are introduced., This work was supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN)–Agencia Estatal de Investigación (AEI), and by the European Regional Development Funds (ERDF), a way of making Europe, under Grant PGC2018-098946-B-I00 funded by MCIN/AEI/10.13039/501100011033/., Peer Reviewed, Postprint (published version)

© 2022 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, This paper proposes an all-pass filter-based true time delay (TTD) element covering a 3–5-GHz ultra-wideband (UWB) frequency. The proposed TTD element designed in a standard 0.18-µm CMOS technology achieves a tunable delay range of 385–540 ps with 6-ps delay steps and maximum 11% absolute delay error over a 3–5-GHz frequency band. It exhibits an average 3.6–4.6-dB noise figure (NF) within the whole bandwidth. A four-channel beamforming receiver realized by the proposed TTD element is designed and examined in this paper, as well. With the maximum delay of 540 ps and 6-ps average delay resolution, a maximum steering angle of ±45¿ with 5¿ (18 steps) steering resolution is demonstrated for the beamforming receiver with 2-cm antenna spacing., Peer Reviewed, Postprint (author's final draft)

The energy performance of a building located in La Roca del Vallès, close to Barcelona in Spain designed under the near Zero Energy Building (nZEB) and Net Zero Energy Building (NZEB) criteria was investigated. The aim was to introduce entropy generation rate as a magnitude to describe energy efficiency in buildings. This was achieved by studying the energy and entropy balances using a commercial energy performance simulation software for different scenarios proposing different efficiency conditions. The annual energy and entropy flow balances cancel. Entropy generation was due to heat losses through the envelope, sun irradiance, appliances, lighting and occupation of the building. The building designed following nZEB criteria was compared with the same building with poorer energy performance. The first one generated 45,834 kJ K-1 while the second one generated 79,985 kJ K-1. This is an important result because with a single magnitude, entropy generation, we combine the impact of all energy transformations taking place in the building. Sun irradiance is found to be the most important entropy generation source: a building with sun irradiance can generate nearly 3.4 times more entropy than a shadowed building. Finally, we evaluated the generated entropy ratio between the transferred entropy to the environment in terms of Gouy-Stodola theorem and the cumulated entropy that contributes to building degradation. Although cumulated degradation entropy is well below the threshold of building collapse, practical degradation effects in the building were shown., Peer Reviewed, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Postprint (author's final draft)

Stand-alone Microgrids (MGs) can effectively be utilized to provide the energy demand for different purposes, such as reducing the burden of the main grid. Paying attention to harvesting renewable energies in MGs resulted in coming up with networked MG (NMG) in recent years. Unlike individual MGs, there is no prominent study on component sizing in NMG. In this paper, a novel component sizing procedure is proposed for NMG. The proposed procedure is based on the optimal operation of each individual MGs. The proposed reduced factor (RF) determines the size reduction of each component in NMG. In order to validate the proposed method, the NMG's operation is evaluated according to the calculated component's size. The results show, in NMG, the capital cost can reduce significantly due to the possibility of power-sharing amongst MGs., Postprint (published version)

El presente trabajo tiene como objetivo el análisis de diferentes escenarios con microrredes domésticas con colaboración entre prosumidores domésticos. Se persigue encontrar estrategias que permiten una optimización de la colaboración entre los prosumidores que conforman los casos estudiados considerados en el artículo. El sistema de gestión de energía diseñado distribuye los flujos energéticos teniendo en cuenta una serie de parámetros y siguiendo una colaboración entre pares o peer-to-peer (P2P), específicamente el método store-then-cooperate (STC)., Postprint (published version)

This paper describes the experience carried out within the Bachelor's Degree in Industrial Electronics and Automation Engineering taught at the Eastern Barcelona School of Engineering (EEBE) of the Technical University of Catalonia–BarcelonaTech (UPC). Specifically, the experience is based on the realization of a cross project that is under the framework of the degree intensification named Application Design in Electronics Engineering (ADEE). This intensification, consisting of a block of two courses, taught in the Fall and Spring semesters, and offered for students in their final year, allows the fulfillment, for two semesters, of the aforementioned project. This includes the design, simulation, implementation (assembly), testing and experimental results (corroboration) of an electronic system or equipment within the field of Electronic Engineering., Postprint (published version)

Entropy is a valuable magnitude to monitor degradation processes and energy efficiency. Since no commercial equipment is available to measure entropy, this paper proposes a new contactless entropy measurement system based on infrared sensors. Infrared radiation of a black body, such an electric resistor, is measured with four different types of commercial sensors. Transport thermodynamics in terms of entropy is experimentally inferred from temperature and radiated power. Entropy flow rate from the black body, entropy flow rate received by the sensor and entropy generation rate during the transport process are evaluated. A simple and inexpensive electronic set-up is used to measure degradation in the resistor, which was powered above its power rating. A relationship between entropy flow rate and resistor degradation is found. The degradation modes, i.e., fatigue and failure, in the resistor can be distinguished using contactless entropy flow measurements., Peer Reviewed, Postprint (author's final draft)

The power calculation is an indispensable element in droop-controlled inverters because the bandwidth of the measured power has a direct impact on the controller performance. This paper proposes a fast and accurate power calculation algorithm based on the combined Second Order Generalized Integrator (SOGI) filters in stationary coordinates for a three-phase system, which takes into consideration the use of nonlinear loads. The power calculation scheme is formed by the two-stage SOGI filters that are employed for obtaining the active and reactive powers required to perform a droop-based inverter operation, respectively. From the two-stage structure, the first SOGI is used as a band-pass filter (BPF) for filtering harmonics and obtaining the fundamental current of the nonlinear load; The second SOGI is used as a low-pass filter (LPF) for extracting the DC-component, which corresponds with the average power. A small-signal model of a two droop-controlled inverters system is built to obtain the dynamical response and stability margin of the system. And compared it with the dynamical behaviour of a standard droop-control method. Next, the proposed power calculation system is designed in order to achieve the same ripple amplitude voltage as that obtained with the standard droop-control method by adjusting the bandwidth gains. Through simulation and hardware in the loop (HIL) validation, the proposed approach presents a faster and more accurate performance when sharing nonlinear loads, and also drives the inverters’ output voltage with lower distortion., Peer Reviewed, Postprint (published version)

The next generation of wireless networks is expected to tap into the terahertz (THz) band (0.1–10 THz) to satisfy the extreme latency and bandwidth density requirements of future applications. However, the development of systems in this band is challenging as THz waves confront severe spreading and penetration losses, as well as molecular absorption, which leads to strong line-of-sight requirements through highly directive antennas. Recently, reconfigurable intelligent surfaces (RISs) have been proposed to address issues derived from non-line-of-sight (non-LoS) propagation, among other impairments, by redirecting the incident wave toward the receiver and implementing virtual-line-of-sight communications. However, the benefits provided by a RIS may be lost if the network operates at multiple bands. In this article, the suitability of the RIS paradigm in indoor THz scenarios for 6G is assessed grounded on the analysis of a tunable graphene-based RIS that can operate in multiple wideband transparency windows. A possible implementation of such a RIS is provided and numerically evaluated at 0.65/0.85/1.05 THz separately, demonstrating that beam steering and other relevant functionalities are realizable with excellent performance. Finally, the challenges associated with the design and fabrication of multiwideband graphene-based RISs are discussed, paving the way to the concurrent control of multiple THz bands in the context of 6G networks., Peer Reviewed, Postprint (author's final draft)

The increasing demands of reducing fuel consumption for marine transportation have motivated the use of high fuel efficiency power plants and the development of power management systems (PMS). Current studies on shipboard PMS are mostly categorized as centralized, which are easy to be implemented and able to converge to the global optimum solutions. However, centralized techniques may suffer from the high computational burden and single-point failures. Considering the future trends of marine vessels toward zonal electrical distribution (ZED), distributed PMS are becoming an alternative choice. To achieve the ship high fuel-efficiency operation under high fluctuated propulsion loads, a real-time distributed PMS is developed in this paper that can acquire as good fuel economy as centralized PMS, but with faster computing speed. With a combination of filter-based, rule-based, and optimization-based approaches in a highly computationally efficient manner, the distributed PMS is constructed based on three layers that guarantees not only high fuel efficiency, but also sufficient energy reservation in different sailing modes and even in faulty conditions. Convergence tests and multiple case studies are conducted to prove the effectiveness of the proposed PMS in terms of fast convergence speed, improved fuel efficiency, and enhanced resilience., Peer Reviewed, Postprint (published version)

The power-sharing possibility amongst microgrids (MGs) in networked microgrids (NMGs) offers multiple profits to the NMG by employing an applicable energy management system. An efficient energy management system can provide an adequate compromise in terms of the component sizing of NMGs through MG collaboration. This paper proposes a procedure to size the component for an isolated networked hybrid microgrid. The proposed design procedure relies on the optimum operation of individual MGs. The defined Reduced Factor (RF) identifies the possible size reduction for the dispatchable components, such as diesel generators and the energy storage system of each MG. The introduced RF is based on the operating reserve evaluation obtained from the optimal operation of individual MGs and the correlation between load profiles. Eventually, the simulation and practical results of a networked hybrid MG consisting of three MGs are presented to verify the proposed component sizing procedure. The practical results verify the theoretical expectations. The results show that NPC and capital costs are reduced up to 13% and 17%, respectively., The authors would like to thank the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN)—Agencia Estatal de Investigación (AEI) and the European Regional Development Funds (ERDF) by grant PGC2018-098946-B-I00 funded by MCIN/AEI/10.13039/501100011033/ and by ERDF A way of making Europe., Peer Reviewed, Postprint (published version)