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En este artículo se ha llevado a cabo una revisión de literatura científica con respecto al tema de resiliencia estableciéndose una línea de tiempo desde el año 2000 hasta 2020 abordando diferentes temas de los recursos energéticos distribuidos (DER) y su influencia en la resiliencia energética. A partir de dicha revisión, se ha realizado un análisis estadístico y una proyección probabilística de las tendencias de desarrollo a futuro sobre el tema. Este trabajo de investigación, enfoca en el desarrollo de una estrategia para fortalecer la gestión una red eléctrica de distribución de manera dinámica que se ajuste a los requerimientos funcionales como calidad de la energía eléctrica suministrada y la máxima cobertura posible a cargas de alta prioridad como hospitales y centros de atención, en periodos durante y después de la ocurrencia de un desastre natural como un movimiento telúrico. Con el fin de apoyar y afrontar la situación de un desastre, se propone utilizar recursos energéticos distribuidos apoyados en elementos de Generación Distribuida (GD), sistemas de almacenamiento y recursos de Respuesta de la Demanda generada que son gestionados mediante sistemas de control automatizado.

Introducción− Las redes eléctricas tradicionales están migrando a nuevas configuraciones de redes inteligentes, que traen retos operacionales y de planeación. Con miras a avanzar en estos retos se propone resolver un problema de optimización usando programación en elementos de redes distribuidas inteligentes. Objetivo− El problema de optimización consiste en adminis-trar el despacho energético de una red inteligente para opti-mizar los recursos disponibles, considerando la incertidum-bre de energías renovables, viajes planeados de vehículos eléctricos, el pronóstico de carga y los precios del mercado. Metodología− Se propuso utilizar un ensamble entre dos métodos heurísticos. El algoritmo VNS (Variable Neigh-borhood Search) y el DEEPSO (Differential Evolutionary Particle Swarm).Resultados− El algoritmo VNS-DEEPSO fue evaluado en una competencia de “Smart Grids” con otros algoritmos con un valor de 18.21, siendo 7 % mejor que el segundo algoritmo clasificado en la competencia.Conclusiones− El algoritmo VNS-DEEPSO fue ganador entre 9 algoritmos metaheurísticos que solucionaron el prob-lema, este problema tenía un mayor incremento de dificultad debida a la incertidumbre generada por factores ambien-tales, pronóstico de carga, viajes en vehículos eléctricos y el mercado de precios. Acorde a los resultados, el algoritmo VNS-DEEPSO demostró ser el más eficiente en minimizar los costos operacionales y maximizar los ingresos de la red inteligente. Introduction− Traditional electric networks are mi-grating to new configurations of intelligent networks, which bring operational and planning challenges. In order to advance in these challenges, an optimization problem is proposed to solve in the programming of intelligent network elements.Objective− The optimization problem consists of man-aging the energy dispatch of an intelligent network to optimize the available resources, considering the uncer-tainty of renewable energies, planned trips of electric vehicles, cargo forecast and market prices.Methodology− It was proposed to use an assembly between two heuristic methods. The VNS algorithm (Variable Neighborhood Search) and the DEEPSO (Dif-ferential Evolutionary Particle Swarm).Results− The value obtained by the VNS-DEEPSO algorithm was 18.21, being 7 % better than the second algorithm classified in the competition. Conclusions− The VNS-DEEPSO algorithm was the winner among 9 metaheuristic algorithms that solved the problem. This problem has a greater increase in difficulty due to the uncertainty generated by weather conditions, load forecast, planned EV ́s trips, and mar-ket prices. According to the results, the VNS-DEEPSO algorithm proved to be the most efficient in minimizing operational costs and maximizing the revenues of the intelligent network.

Microgrids have presented themselves as an effective concept to guarantee a reliable, efficient and sustainable electricity delivery during the current transition era from passive to active distribution networks. Moreover, microgrids could offer effective ancillary services (AS) to the power utility, although this will not be possible before the traditional planning and operation methodologies are updated. Hence, a probabilistic multi-objective microgrid planning (POMMP) methodology is proposed in this paper to contemplate the large number of variables, multiple objectives, and different constraints and uncertainties involved in the microgrid planning. The planning methodology is based on the optimal size and location of energy distributed resources with the goal of minimizing the mismatch power in islanded mode, while the residual power for AS provision and the investment and operation costs of the microgrid in grid-connected mode are maximized and minimized, respectively. For that purpose, probabilistic models and a true multi-objective optimization problem are implemented in the methodology. The methodology is tested in an adapted PG&E 69-bus distribution system and the non-dominated sorting genetic algorithm II (NSGA-II) optimization method and an analytic hierarchy process for decision-making are used to solve the optimization problem.

Microgrids have been introduced as powerful concepts to tackle the transition toward a decentralized power supplying. For this reason, complex methodologies for their planning have been proposed, and the selection of effective algorithms for its solution has become a transcendental task. In this work, the Multiobjective Evolutionary Algorithm Based On Decomposition (MOEA/D) is tested in the PG&E 69-bus. Optimization planning and results show the performance and advantages of their implementation for solving this practical problem.

This paper studies the electric field parameters of negative cloud-to-ground (CG) lightning flashes in the Bogota savanna (a large plateau located in central Colombia), and its comparison with other regions. This work is the first of its kind in the country where the parameters of lightning-generated electric fields are analyzed in detail. A total of 329 CG lightning flashes had been examined. These flashes were recorded within 4–250 km from the measuring station during the period August–November 2016. From observations, negative CG flashes comprised 93% of total events registered. It has been found that negative lightning discharges occurred along the plateau (4250 km2 at 2550 m altitude) exhibit some different characteristics compared with measurements carried out in several regions (tropical, subtropical and temperate latitudes). In this study, it was found that 64.7% of the negative CG flashes are multiple strokes with an average multiplicity of 2.58 strokes per flash. In addition, the mean interval between 789 negative return strokes (306 first- and 483 subsequent strokes) was 61.3 ± 51.9 ms, while the arithmetic mean of the total duration for 198 multiple-stroke flashes was 149.5 ms. Other lightning flash features such as relation between the interstroke interval and the return stroke order, the ratio of the subsequent stroke peak field to the corresponding first one and the maximum multiplicity are also analyzed.

This paper presents the statistical analysis of several parameters associated with the electric field generated by negative cloud-to-ground (CG) lightning flashes recorded in the Bogota savannah (central province of Colombia), including a comparison with other regions. In this way, this is the first study in Colombia where nine parameters of the electric field and two more related to the electric field derivative are analyzed in detail. From a measuring campaign carried out during the second semester of 2016, 306 negative cloud-to-ground lightning flashes containing the same number of first return strokes (FRS) and 483 subsequent return strokes (SRS) had been analyzed. These 789 return strokes occurred in the range from 3 to 250 km from the measuring station, in such a way that the waveforms analyzed have static components, radiated components or a combination of both. At first, a total of 64.7% of negative CG flashes were categorized as multiple-stroke flashes, the multiplicity reached up to 13 strokes/flash with an average of 2.6. For the first and subsequent return strokes analyzed in Colombia, the arithmetic mean (AM) of the initial electric field peak normalized to 100 km ( E P _ N ) were 27.6 V/m and 12.4 V/m, respectively. On the other hand, the average of the peak value of the electric field derivative ( d E / d t ) P was 5.9 V/m/μs for FRS and 3.6 V/m/μs for SRS. These results are similar to those observed in Florida, Germany, Sweden, Japan, Sri Lanka and Malaysia, where the E P _ N and the ( d E / d t ) P for FRS are larger than those for SRS. Furthermore, as reported in Malaysia and other tropical regions, several electric field parameters in Colombia are affected by the geographical location, the distance with respect to the measuring system and the propagation medium. The above was more evident for some temporal parameters such as zero-to-peak rise time, the 10–90% transition duration, the slow front duration and the fast front duration. Additional differences after comparing with previous data related to natural and rocket-triggered lightnings measured in different regions (tropical, subtropical and temperate latitudes) were also observed.

Loop-based microgrids are signified by their high reliability in islanded and grid-connected operations. This paper proposes an iterative procedure for the optimal design of a microgrid topology in active distribution networks, which applies graph partitioning, integer programming, and performance index for the optimal design. The proposed approach avoids infeasible and non-optimal designs of microgrid structures and provides remedial solutions for enhancing our previous topology design method. The numerical results for a microgrid test system show that the proposed designated steps can optimize a loop-based microgrid structure in an active distribution network.

© The Institution of Engineering and Technology 2018. Reconfiguration, sizing and downsizing of the storage unit, in electrically propelled vehicles, are techniques that have been reported effective to improve the shelf life and performance of the storage cells. However, these solutions might decrease the rated voltage of the storage unit and therefore DC-DC converters with high voltage gain are suitable solutions to connect these low-voltage units to the motor drive, keeping a good performance of the vehicle. Moreover, parasitic resistances presented in the components of these converters have proved to influence the efficiency and the voltage gain of the converter. The ideal voltage gain of four high step-up converters is analysed, derived, and compared. These converters were selected because of their potential to be applied in electric mobility and their similarity in the techniques that use to achieve high voltage gain: interleaving phases and magnetic integration. One of the analysed topologies is proposed by the authors. Afterwards, the parasitic resistance effect is analysed to obtain the non-ideal voltage gain and the efficiency of these four topologies. Finally, the topology that presents the best trade-off between the non-ideal voltage gain and the efficiency is experimentally tested with a 100 W prototype. ispartof: Iet Power Electronics vol:11 issue:10 status: published

The e-cooking feasibility was evaluated for two of the main staple foods across rural Sub-Saharan Africa (rice and maize porridge) considering basic solar home systems (SHS) of 100–150 W and using inexpensive market available low-power DC cooking devices (rice cooker and slow cooker). The coverage of e-cooking necessities was spatially evaluated for the African continent considering households of two, five, and eight people. While households of two people were able to be covered &gt, 95% of the days, the increase in e-cooking necessities implied that only larger PV generators (150 W) located in high irradiation sites (&gt, 2400 kWh/m2/year) were able to fulfill e-cooking, even in scenarios of households of five and eight people. Furthermore, the economic cost and the greenhouse gases emission factor (GHG) of e-cooking via small SHS were evaluated and benchmarked against traditional technologies with wood and charcoal considering three-stone and improved stoves and liquefied petroleum gas (LPG) cookers. The GHG for e-cooking was 0.027–0.052 kgCO2eq/kg.meal, which was strikingly lower than the other technologies (0.502–2.42 kgCO2eq/kg.meal). The e-cooking cost was in the range of EUR 0.022–0.078 person/day, which was clearly lower than LPG and within the range of the cost of cooking with wood and charcoal (EUR 0.02–0.48 person/day). The results provided a novel insight regarding market available technologies with a potential of changing cooking conditions in this region.

This study seeks to determine a suitable arbitrage strategy that allows a battery energy storage system (BESS) owner to obtain the maximum economic benefits when participating in the Colombian electricity market. A comparison of different arbitration strategies from the literature, such as seasonal, statistical, and neural networks-based models, is performed. To determine BESS’s optimal operation, a Mixed Integer Linear Programming (MILP) optimization problem is formulated, including a battery degradation model based on an upper piecewise linear approximation method. A financial evaluation of the different arbitrage strategies is carried out, resulting, for all the analyzed cases, in a negative net present value (NPV), thus, the results show that the income obtained from BESS when only performing energy arbitrage in the Colombian market do not compensate the investment costs. Results have also shown that strategies based on statistical and prediction models have a better performance than seasonal strategies, especially in atypical circumstances such as COVID-19.

One of the main problems in electric vehicles is the volume of their electrical systems because their bulky components carry additional mass and high cost to the total system. On this topic, interleaving-phases and magnetic coupling techniques have been reported as effective methods for increasing the power density of the DC–DC converters that work between the storage unit and the motor inverter. In that sense, a volume assessment of these topologies would provide a better understanding of the problems to be faced when an electric power train is designed. In this paper, a volume modelling methodology is introduced with the purpose of comparing four different DC–DC converters: Single-Phase Boost, Two-Phase Interleaved with non-coupled inductors, Loosely Coupled Inductor (LCI), and Integrated Winding Coupled Inductor (IWCI). The analysis considers the volume of magnetic components, power devices (conventional and next-generation), cooling devices and capacitors. The methodology can be used as a part of an optimization procedure to minimize the volume of DC–DC converters. Conclusively, LCI and IWCI were found effective to miniaturize power converters with a power density of 8.4 W/cc and 9.66 W/cc, respectively. Moreover, a maximum efficiency of 98.04% and 97.61% was obtained for a 1kW LCI and IWCI prototypes, respectively. ispartof: IET Power Electronics vol:10 issue:14 pages:2010-2020 status: published

In this paper, important features of electric fields produced by cloud-to-ground (CG) lightning flashes in the central region of Colombia are analyzed. This study is the first conducted in the country where more than 100 CG lightning flash signatures are analyzed. The measurements were conducted at Bogotá, Colombia between August-September 2016. A total of 138 electric field waveforms obtained from 7 thunderstorms events with an average duration of 2.7 hours were included. The distance of the electric field signatures with respect to the measuring system was in the range between 40 and 249 km. The statistical analysis showed that 38% of the recorded negative CG flashes were single-strokes, which is a high percentage in comparison with other tropical and sub-tropical regions. The maximum multiplicity during the season was 9 strokes per flash and the average duration of the multiple-stroke flashes was 165 ms. In addition, although electric field signatures present a signal-to-noise ratio (SNR) with a medium level, the preliminary breakdown pulse train was identified in 22.8% of the recorded flashes. The minimum and maximum duration of preliminary breakdown for the examined negative flashes were 800 ns and 22 ms, respectively.

In this paper, an electric powertrain for a bus of rapid transit (BRT) is designed, which includes the driving behavior, road infrastructure, orography, and traffic system as a fundamental part of the design. An electric hybrid power source is proposed to efficiently recover the braking energy and for fast charging at bus stations. Since the local traffic parameters have direct influence over the BRT energy consumption, an energy methodology to obtain a characteristic and energy representative synthetic driving cycle is proposed and then experimentally tested in a real BRT system. The Transmilenio BRT system of Bogota, Colombia, was chosen as a case study. This BRT system is selected due to its particular orography that increases the energy consumption. Additionally, a BRT dynamic model is proposed to analyze the energy requirements prior to designing the electric powertrain and the two energy storage systems. As a result, and as the main contribution, an innovative general methodology to BRT powertrain design is established using the BRT dynamic model and local traffic parameters.

The design of efficient three-phase induction motors is a challenge for engineering; therefore, new design techniques are continually being proposed. For example, efficiency is in conflict with manufacturing cost, which leads to the use of multi-objective optimisation techniques to solve this engineering problem. Nevertheless, this study shows that the way of accurately modelling the behaviour of the motor is as important as the optimisation method itself. Thus, the study discusses fundamental considerations in the motor model as part of a proposed methodology for the design of highly efficient three-phase squirrel cage induction motors. For this purpose, the motor is modelled in two ways: an analytical equivalent circuit and the finite element method, which are validated with data obtained from laboratory tests. The main contribution of this study is to show for the first time the required characteristics of the analytical model used as part of a multi-objective optimisation problem to have a suitable accuracy with a competitive runtime. Moreover, the problem is solved using three bio-inspired optimisation algorithms: non-dominated sorting genetic algorithms II, non-dominated sorting particle swarm optimisation and bacterial chemotaxis multi-objective optimisation algorithm. The methodology is tested in the optimal redesign of a two-pole, 3.7 kW, IE2 efficiency motor, for which the efficiency and cost were improved.

Partial discharges (PD) are one of the most important factors that affect the insulation of power and distribution transformers. Because their repeated occurrence can produce isolation failures, the identification and analysis of PD pulses are important to guarantee the correct operation of equipment. In the last two decades, some processing tools based on time domain, frequency domain or hybrid domains have been developed to detect and analyze PD signals. Fourier transform, short-time Fourier transform, wavelet transform and Gabor transform are some examples of techniques used to provide information about the amplitude levels in time-frequency bands and identify the power spectrum of off-line/on-site PD waveforms. However, there are currently no proposed techniques to evaluate the performance of the instantaneous frequency (IF) of PD signals and its variation with respect to time. This paper presents the application of the local polynomial Fourier transform (LPFT) and the computation of local polynomial periodogram (LPP) for time-frequency analysis of PD pulses generated in distribution transformers. PD signals were acquired from an experimental setup specially designed and built for the research purposes. To acquire electrical signals, a fast current transformer is used to measure directly the transient current pulses generated by PD. Simulation results show that power spectrum of practical PD signals, computed with LPFT, reveals a low and medium frequency content related to secondary peaks and other high frequency components produced by noise and interferences, which are not detected when the STFT is used.

High step-up converters have been widely used in renewable energy systems and, recently, in automotive applications, owing to their high voltage gain capability. In these applications, power losses, mass, and volume are quite restrictive, because they affect the system operation and cost. However, it is difficult to optimize these characteristics simultaneously. Consequently, multi-objective optimization through the design automation of power electronics is useful to meet the efficiency and power density requirements. This paper presents a procedure to optimize the efficiency and power density of a coupled inductor used in a high step-up converter. In this procedure, a complete modelling of power losses and size is evaluated by comparing different materials and dimensions. In addition, 3D and 2D finite element modelling simulations are used to validate the magnetic core shapes and sizes. The results of this modelling stage are introduced into a multi-objective optimization algorithm to obtain a Pareto front. Finally, the optimization methodology is experimentally validated. ispartof: IEEJ Journal of Industry Applications vol:8 issue:6 pages:984-990 status: published

Increased use of renewable energies in smart microgrids (SMGs) present new technical challenges to system operation. SMGs must be self-sufficient and operate independently; however, when more elements are integrated into SMGs, as distributed energy resources (DER), traditional explicit mathematical formulations will demand too much data from the network and become intractable. In contrast, tools based on optimization with metaheuristics can provide near optimal solutions in acceptable times. Considering this, this paper presents the variable neighborhood search differential evolutionary particle swarm optimization (VNS-DEEPSO) algorithm to solve multi-objective stochastic control models, as SMGs system operation. The goal is to control DER while maximizing profit. In this work, DER considered the bidirectional communication between energy storage systems (ESS) and electric vehicles (EVs). They can charge/discharge power and buy/sell energy in the electricity markets. Also, they have elements such as traditional generators (e.g., reciprocating engines) and loads, with demand response/control capability. Sources of uncertainty are associated with weather conditions, planned EV trips, load forecasting and the market prices. The VNS-DEEPSO algorithm was the winner of the IEEE Congress on Evolutionary Computation/The Genetic and Evolutionary Computation Conference (IEEE-CEC/GECCO 2019) smart grid competition (with encrypted code) and also won the IEEE World Congress on Computational Intelligence (IEEE-WCCI) 2018 smart grid competition (these competitions were developed by the group GECAD, based at the Polytechnic Institute of Porto, in collaboration with Delft University and Adelaide University). In the IEEE-CEC/GECCO 2019, the relative error improved between 32% and 152% in comparison with other algorithms.

The development and implementation of Microgrids have expanded the integration of distributed energy resources for economically and efficiently providing electricity and ancillary services to the main grid. This paper proposes a multi-objective mathematical model in order to optimally plan a Microgrid with ancillary services supplying capacity and positive revenue streams. The model is based on the size and location of distributed energy resources and the results show how the market influences the optimal design of the Microgrid, as well as the advantages of a multi-objective formulation.

English Abstract: En el marco del Bicentenario de la independencia de Colombia, el Centro de Investigaciones para el Desarrollo (CID), en alianza con el periodico Portafolio, ha presentado una serie de reflexiones sobre la trayectoria economica que ha atravesado el pais, en aras de entender los retos del futuro y las lecciones aprendidas del pasado. El contenido es muy amplio incluyendo temas que han jugado un rol clave en la historia del pais, como el cafe, la violencia, la tierra, hasta temas que son menos conocidos pero deberian formar parte de la reflexion colectiva, como el papel de la mujer, los estudios sectoriales, o el desarrollo de largo plazo. El lector no tiene que esperarse una narracion univoca, ni un recorrido lineal: estos escritos son reflexiones que vienen de investigadores con enfoques teoricos y metodologicos muy diferentes, como tradicion en la Universidad Nacional. Asi, ensayos de analisis economico de las instituciones son acompanados por reflexiones de analisis marxiano aplicado, y la cliometria se entrelaza a la finanza publica. Por la misma razon, decidimos no proponer una estructura interpretativa o una organizacion del contenido, prefiriendo reportar los escritos en el orden cronologico en el cual aparecieron en el portal del periodico. English Abstract: In the framework of the Bicentennial of the independence of Colombia, the Centro de Investigaciones para el Desarrollo (CID), in alliance with the newpaper Portafolio, has gathered a series of reflections about the economic trajectory that the country has gone through, for the sake of understanding the challenges of the future and the lessons learned from the past. The content is very broad including issues that have played a key role in the history of the country, such as coffee, violence, land, and issues that are less known but should be part of collective reflection, such as the role of women, sectoral studies, or long-term development. The reader should not expect a univocal narrative, nor a linear perspective: these texts are reflections that come from researchers with very different theoretical and methodological approaches, as a tradition at the Universidad Nacional. As a result, economic analysis of the institutions goes hand by hand with applied Marxian analysis, and the cliometry is intertwined with public finance. For the same reason, we decided not to propose an interpretative structure or an organization of the content, opting for an order of presentation that follows the chronological order in which they appeared in the newspaper's portal.

Microgrids have attracted the attention of researchers and stakeholders because of their well-known impacts and related benefits. Especially the provision of ancillary services has drawn attention. However, traditional planning should be re-defined to optimally achieve such promising advantages, which leads to a complex decision-making problem that should be progressively addressed with a more modern and comprehensive holistic approach. Hence, this paper proposes an enhanced version of the probabilistic multi-objective microgrid planning methodology (POMMP2) that includes a novel strategy to apply graph partitioning and metaheuristic optimization to consider simultaneously the planning of a cluster-based topology with the size and location of distributed energy resources under the paradigm of a microgrid with capacity for providing ancillary services. POMMP2 is tested in an adapted IEEE-37 node system, and NSGAII and AHP are used as optimization and decision-making algorithms, respectively. Results show the benefits of a planning methodology viewed as a comprehensive problem and not a set of independent tasks.

Wavelet Transform (WT) is a powerful technique of signal processing, its applications in power systems have been increasing to evaluate power system conditions, such as faults, switching transients, power quality issues, among others. Electromagnetic transients in power systems are due to changes in the network configuration, producing non-periodic signals, which have to be identified to avoid power outages in normal operation or transient conditions. In this paper a methodology to develop a new adaptive mother wavelet for electromagnetic transient analysis is proposed. Classification is carried out with an innovative technique based on adaptive wavelets, where filter bank coefficients will be adapted until a discriminant criterion is optimized. Then, its corresponding filter coefficients will be used to get the new mother wavelet, named wavelet ET, which allowed to identify and to distinguish the high frequency information produced by different electromagnetic transients.

The implementation of the microgrid concept is expected to bring multiple advantages on the sustainability and reliability of electric power systems. In this paper, the performance of a modified Cuckoo's Search (CS) algorithm with parameter control is evaluated for solving a planning optimization problem which considers uncertainties of non dispatchable energy resources and both operations modes of a microgrid. The results show that the Cuckoo's Search algorithm offers advantages in terms of exploration of the search space.

Microgrids have become an attractive strategy to guaranty a reliable, efficient and sustainable electricity delivery to the distribution network, as well as to offer effectively ancillary services to the power utility. Therefore, special features have to be introduced to the planning methodology, while the optimization problem has also to be re-evaluated to contemplate the large number of variables, multiple objectives, and different constraints and uncertainties. Hence, a probabilistic multi-objective microgrid planning methodology based on the optimal size and location of distributed generation is proposed. In this methodology, the mismatch power in islanded mode and the annual energy losses in grid-connected mode are minimized, while the residual power for reserve provision is maximized. For that purpose, probabilistic models, distributed storage units, and constructive constraints are contemplated in the methodology. The methodology is tested in an adapted PG&E 69-bus distribution system and the NSGAII optimization method is used to solve the optimization problem.

Lightning electric field (LEF) measurements are aperiodic signals characterized by inherent noise of different sources, i.e., it is not possible to register a noise-free signal. In the last decade, the denoising of LEF measurements has been achieved using some time-frequency representations such as short-time Fourier transform (STFT), wavelet transform (WT) and fractional Fourier transform (FRFT) without definitive results. In this paper, a denoising process applied on LEF measurements using the Local Polynomial Approximation (LPA) is proposed. The window size selection is made by combining the LPA with the intersection of confidence intervals (ICI) algorithm. Furthermore, a cross-validation criterion is used to select the optimal value of the threshold parameter in the LPA-ICI denoising method. It is shown that for different signal-to-noise ratio (SNR) values, the proposed method significantly reduces the noise present in the recorded signals. Finally, a discussion about the processed signatures in terms of some lightning electric field temporal features is performed. Resumen Las mediciones de campo eléctrico producido por rayos (LEF) son señales aperiódicas caracterizadas por ruido inherente de diferentes fuentes, es decir, no es posible registrar una señal libre de ruido. En la última década, se ha logrado filtrar mediciones de LEF utilizando algunas representaciones tiempo-frecuencia tales como la transformación de Fourier de corto tiempo (STFT), la transformación wavelet (WT) y la transformación de Fourier fraccionaria (FRFT) sin resultados definitivos. En este trabajo, se propone un proceso de eliminación de ruido aplicado a mediciones de LEF usando la aproximación polinomial local (LPA). La selección del tamaño de la ventana se realiza combinando la LPA con el algoritmo de intersección de intervalos de confianza (ICI). Además, un criterio de validación cruzada se utiliza para seleccionar el valor óptimo del umbral en el método de reducción de ruido LPA-ICI. Se muestra que para diferentes valores de relación señal-a-ruido (SNR), el método propuesto reduce significativamente el ruido presente en las señales registradas. Finalmente, se realiza una discusión sobre las señales procesadas en términos de algunas características temporales del campo eléctrico.

This paper presents a study by simulation of the performance of a Hybrid Energy Storage System (HESS) integrated to a residential microgrid. The storage system is composed of li-ion battery units and supercapacitors connected in a parallel active topology. An optimization-based real-time frequency-decoupling control strategy is used for the power split and for the assignation of the high-frequency and low-frequency energy components to the storage mediums. The simulation system emulates a photovoltaic generation source with typical intermittence of the injected power, the typical loads of a residential electric grid, and a HESS.

High step-up converters have been widely used in renewable energy systems and, recently, in automotive applications, due to their high voltage gain capability. In these applications, efficiency and high-power density are usually required, although these characteristics are commonly opposite objectives. Therefore, a multi-objective optimization is quite useful in order to comply with both requirements of high efficiency and small size. In that sense, the Finite Element Method can be effective to complement optimization methods. This paper presents a procedure to optimize the efficiency and the volume of a high step-up converter that utilizes a coupled inductor with three windings installed in only one core. This optimization procedure is carried out using 3D and 2D Finite Element Method simulations. In this procedure, a complete modeling of power losses, size, and flux density is evaluated by comparing different materials and dimensions. The results of this modeling stage are introduced into a multi-objective optimization algorithm to obtain a Pareto front. Finally, the optimization methodology is validated by experimental tests.

In many studies of lightning flash characterization, the lightning generated electric field measuring system uses a circuit based on the buffer-amplifier LH0033. This circuit was proposed 35 years ago and there is no doubt of its excellent performance to measure the lightning electric field intensity. However, LH0033 is no longer manufactured, making it necessary to find a replacement. This paper proposes an improvement of the electric field measuring system, which consists of a new electronic circuit that uses the buffer-amplifier BUF602. This circuit presents a similar performance of the classic circuit, but has a lower energy consumption and allows its implementation in surface mount technology, which reduces the space required for the circuit. The field tests were performed in Bogota, Colombia during a complete thunderstorm season and their results show that new circuit is a good alternative for measuring electric field signals with a bandwidth up to 11 MHz.

In current automotive applications, novel and robust communication technologies have been used to optimize some features related to security, fuel consumption and user interface. However, the automotive communication protocols present two problems: 1. the connections between devices are very complex and their maintenance is difficult, and 2. most of the commercial devices, specialized to send data between devices, use proprietary software to perform operations inside the vehicle. In this work, a novel embedded platform was designed to measure and control the speed and torque of electric motors of a 200 kW electric vehicle. It is a versatile, modular and open-source design, which exchanges data with each motor using the CAN Bus protocol to control their speed. Also, the implementation and maintenance of the proposed platform becomes simpler. The proposed platform was built and tested with the devices that are used inside the car.

A non-isolated high step-up DC-DC converter with coupled inductor is developed for large voltage gain applications such as electric mobility and renewable energies. This converter combines the concepts of magnetic integration and interleaving phases that are effective for downsizing of power converters. The developed converter offers a good performance of voltage gain vs. converter size, because, compared with the conventional two-phase interleaved boost converter, it only needs the addition of two diodes and one winding. Nevertheless, in order to describe the design method of the developed high step-up converter, the coupled inductor characterization is required. Therefore, the current ripple characterization of the coupled inductor is analyzed and evaluated in this paper. A 100W prototype is constructed and experimental results are provided to verify the characterization analysis.

The interleaved boost converter with magnetic coupling is a recent DC-DC converter topology that has drawn attention for its reduced size and good voltage gain. However, for its proper functioning, a real converter has to be controlled to deal with the unavoidable imbalance of the currents. This paper compares two control techniques applied on an interleaved boost converter with magnetic coupling. Therefore, the characteristics of the selected converter, the average current control and predictive control techniques are presented. As a result, it was found that the average current controller has the characteristic of zero steady state error, in contrast, the predictive controller allows an error in the estimated variables which causes the output voltage not to be equal to the reference value. The predictive controller considers and uses the discontinuous mode of operation, but controller has a higher computational cost than the average current controller.

This paper presents a study by simulation of the performance of two of the current topologies for the interconnection of batteries and supercapacitors in a Hybrid Energy Storage System with potential application in electric microgrids. Converters selection is made taking into account the most used topologies documented in the literature for the integration of storage technologies. Control strategies are implemented pursuing the goal of prolonging the lifetime of batteries, using the supercapacitor for reducing the dynamic component of the current from a pulsed current load to the batteries.

In this paper, adaptive filters are applied (in the fractional Fourier transform domain – FRFd) for denoising lightning electric-field signals, both in high and low signal-to-noise-ratio (SNR) environments. These filters are based on the concentration energy property of the fractional Fourier transform (FRFT). The proposed method integrates the advantages of leakage least mean square (LLMS) and normalized least mean square (NLMS) algorithms, including a leakage factor γ and a normalized step-size μ, in order to reduce the memory effect when tracking a non-stationary signal and also to reduce the effect of the input signal power on the algorithm performance, respectively. Parameter estimation of adaptive filters is analyzed in several case studies for various lightning-generated electric field signals. The adaptive algorithm is shown to provide better performance in low SNR environments. Finally, some analyses (in terms of temporal parameters of lightning electric-field signals) are included to demonstrate the validity of the method.

Este artículo presenta una introducción a la transformada fraccional de Fourier (FRFT) y describe el proceso para implementar la transformada fraccional de Fourier Discreta (DFRFT) basada en la descomposición espectral del operador matricial de la transformada discreta de Fourier (DFT). En la última década, la FRFT ha sido considerada como una herramienta útil para el procesamiento y tratamiento de señales. En el desarrollo teórico de la FRFT, se han presentado varias definiciones de su versión discreta (DFRFT). Sin embargo, pocas definiciones de la DFRFT entregan resultados similares a los que presenta la FRFT sin perder sus propiedades más importantes. Por lo tanto, en este trabajo se hacen algunas aclaraciones teóricas con respecto a trabajos previos, y se muestra la relación existente entre la FRFT y la DFRFT. Finalmente, con el fin de promover el uso de esta transformación dentro de la comunidad de procesamiento de señales, se describen algunos algoritmos de la DFRFT con bajos costos computacionales.

Efficiency is one of the most important aspects to consider in the design of electric systems for mobility applications. In this study, the interface between the storage system and the inverter is considered. This interface is a step-up DC-DC converter aimed to boost the energy storage voltage to the inverter voltage. This paper introduces the analysis, design, and comparison of four topologies of the interleaved boost DC-DC converter evaluating the effect of magnetic coupling in multi-phase and modular circuits. Additionally, a novel idea of a four-phase coupled inductor is presented. These power DC-DC converters are designed in order to find the suitable arrangement with the best efficiency.

In the last two decades, various lightning events have been analyzed using mathematical and signal processing techniques. In this paper, electric field waveforms radiated by negative first and subsequent strokes were analyzed using the Local Polynomial Fourier Transform (LPFT). The analysis provided by LPFT shows the instantaneous frequency (IF) of the signals and its first derivative. The electric field signatures came from a thunderstorm occurred in Bogota, Colombia. In addition, the return stroke energy concentration is presented in the form of the Local Polinomial Periodogram (LPP). The LPP shows that the return stroke spectrum is distributed in a frequency range with the peak value spread in a specific part of this range. Form the time-frequency analysis provided by LPFT, the energy radiated by negative first return strokes remains in the average frequency range from low frequency (lower than 1 kHz) up to 36 kHz, while the energy radiated by subsequent strokes ranges between 0.5–42 kHz. In addition, for the initial stage and the overshoot region of the transient pulse, the first return stroke signatures present a frequency range slightly higher than those of the subsequent return strokes.

Although three-phase squirrel cage induction motors are commonly considered a mature technology, their design has always been a challenge for engineering; therefore, new techniques and methodologies are continually being proposed. The growth in the relevance of efficiency has set it as part of the design objectives. However, increased efficiency is in conflict with the manufacturing cost, not only because of the cost of improved materials, but also because of the dimensional modifications. Therefore, a true multi-objective optimization methodology turns out to be attractive for this engineering problem. On the other hand, bio-inspired methods have become an important tool for induction motor optimal design because this involves many variables and parameters, and it is in general a complex optimization problem by nature. Thus, a methodology for the design of highly efficient three-phase squirrel cage induction motors, based on the non-dominated sorting genetic algorithm II (NSGA-II) and the non-dominated sorting particle swarm optimization (NSPSO), together with a true multi-objective optimization problem of manufacturing cost and operation efficiency, is proposed in this paper. The methods are evaluated and compared in order to be used with this type of engineering problems.

Power losses and their consequences in the addition of storage cells have the negative effect of decreasing the power density and the efficiency in Electric Vehicles. For this reason, an efficiency optimization methodology is required to help reduce that problem. Specifically, in the power converters that interface the storage unit with the electric motors and their inverters, an efficiency optimization is essential to reduce the power losses and thereby downsize the cooling components and the storage unit. In this work, the topology under evaluation is the two-phase interleaved boost converter using different magnetic components such as coupled and non-coupled inductors, which are topologies known as effective for high power density applications. This paper presents a methodology that optimizes the efficiency of the chosen topologies through a complete power loss modeling of each component. Next generation components such as Super Junction Mosfets, GaN and SiC diodes and Mosfets are compared to obtain the most efficient and suitable material to be implemented to the topologies, especially to the converter with coupled-inductor. Moreover, a design procedure is proposed to integrate the loss model and the characteristics of the selected components as the base to obtain the objective function, which is later solved using analytical calculations. Finally, the optimization methodology is validated by experimental tests.

El presente estudio tiene un enfoque cualitativo de modelo hermenéutico con un alcance descriptivo. El objetivo de la investigación es identificar los factores que posibilitan el proceso de resocialización y la reducción del consumo en los habitantes de calle. Los participantes fueron 12 personas mayores de 18 años en proceso de resocialización, a quienes se les realizó una entrevista semiestructurada que indagaba por aspectos de la esfera personal, familiar y psicosocial. Entre los principales hallazgos se encuentran: elementos motivacionales, valores, actitudes, aptitudes y redes de apoyo que incluyen a la familia, amigos e instituciones. Además, los resultados muestran que los factores espirituales, religiosos y las expectativas frente al consumo, son igualmente importantes para el proceso.

Efficient signal processing techniques are necessary for assessing the exposure to broadband magnetic fields. The use of flat-top windows along with the DFT is a simple and fast method that reduces the characteristic leakage errors and picket fence effects when using the classical DFT for the exposure assessment. This paper proposes a new class of flat-top windows, making a trade-off between the sidelobe fall-off and the maximum sidelobe height, called fast-decaying minimum-sidelobe (FDMS) flat-top windows. Moreover, the procedure used to find the coefficients of the optimal flat-top windows is reviewed, and a new procedure is proposed in order to find the flat-top window coefficients that uses multi-objective optimization and an appropriate selection of constraints. Using this procedure, a new minimum sidelobe (MS) flat-top window with four terms is also found, having better characteristics than a previously proposed 4-term MS flat-top window. In addition, a new MS flat-top window with five terms is proposed having a maximum sidelobe level of -95.15dB. These windows are used to propose a method for assessing the exposure to broadband magnetic fields using flat-top windows and the DFT.