Publicaciones académicas

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Esta colección incluye artículos de profesores de la Pontificia Universidad Católica de Chile, publicados en revistas nacionales y extranjeras.

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23-Level Inverter for Electric Vehicles Using a Single Battery Pack and Series Active Filters
(IEEE, 2012) Pereda Torres, Javier Eduardo; Dixon, Juan
Cascaded H-bridge (CHB) multilevel inverters have been conceived as an alternative to reduce total harmonic distortion (THD) in medium-voltage drives. The reduced THD makes them useful for electric vehicle (EV) applications, but the main problem with the CHB is the large amount of isolated power sources required to feed each of the H-bridges. An improved variant known as the asymmetrical CHB (ACHB) inverter uses H-bridges of different sizes and then needs fewer isolated power sources than the CHB. However, in battery-powered EVs, only one power supply (fuel cell or battery pack) is desirable. This work presents a solution to solve the problem, operating some of the small H-bridges (Aux-bridges) as series active filters and using a small high-frequency link (HFL). With this solution, only one dc source is required to feed the inverter, and if the control is adjusted to work at particular switching points, more than 98% of power is transferred through the larger H-bridges (MAIN bridges). The proposed ACHB topology can produce any number of levels, and the M AIN bridges always commutate at fundamental frequency. As the number of levels must remain constant for all output voltages, a variable dc source is required to control the amplitude of the motor voltage. This work shows some simulations and experiments on a 2-kW 27-level ACHB working with only 23 levels. The concept is being implemented in a small EV with an ACHB drive of 18 kW.
3D Microstructured Inorganic Perovskite Materials for Thermal Neutron Detection
(2022) Caraveo-Frescas, Jesus A.; Reyes-Banda, Martin G.; Fernandez-Izquierdo, Leunam; Quevedo-Lopez, Manuel A.
A combination of novel techniques such as a solvent-free thin-film deposition, perovskite patterning, and B-10 back-fill technique enables the high neutron detection efficiency in a perovskite-based microstructured thermal neutron detector. High-efficiency cesium lead bromide (CsPbBr3) perovskite-based microstructured detectors are demonstrated here. Trenches up to 10 mu m deep are etched into the CsPbBr3 thin films using a novel dry etching process involving a combination of HBr and Ar plasma. The microstructured diodes are then backfilled with isotopically enriched boron as neutron conversion material via a sedimentation process to preserve the perovskite integrity. The fabricated microstructured CsPbBr3 thermal neutron detectors show an efficiency of 4.3%. This represents >1.2x efficiency improvement over planar silicon (3.5%) and >2x efficiency improvement over planar CsPbBr3 (2.1%) detectors, respectively. More importantly, gamma-ray discrimination of 10(7) is measured in CsPbBr3-based microstructured neutron detectors.
A compact ultrafast capillary plasma discharge as an intense XUV source
(2014) Valenzuela, J. C.; Wyndham, Edmund
A convex chance-constrained model for reactive power planning
(2015) Lopez, Julio; Pozo, David; Contreras, Javier; Mantovani, J. R. S.
A Design Methodology of Multiresonant Controllers for High Performance 400 Hz Ground Power Units
(2019) Rojas, Félix; Cárdenas, Roberto; Clare, Jon; Díaz, Matías; Pereda Torres, Javier Eduardo; Kennel, Ralph
A general architecture for electric power management of small scale NCRE converters: Design methodology and validation
(2017) Hernández, Franco; Chiang Sánchez, Luciano Eduardo; Corbalán Campos, Patricio Alejandro
A long panel survey to elicit variation in preferences and attitudes in the choice of electric vehicles
(2014) Jensen, A.; Cherchi, E.; Ortúzar Salas, Juan de Dios; CEDEUS (Chile)
A method to estimate the robustness of the secondary refined copper supply function
(2023) Rivera, Nilza; Ignacio Guzman, Juan; Lagos, Gustavo
Knowing the factors that influence the secondary refined copper supply behavior has been fundamental in generating a copper market model and developing public and corporate policies. When analyzing the explanatory variables used in the existing models in the literature, it is possible to observe high variability in estimating the parameters when modifying the availability of information or changing the observation period. Based on this, we argue that only some explanatory variables will have robust estimated parameters, which means that they are unbiased, stable (i.e., they do not vary significantly when the specification of the equation or the number of observations changes), and with asymptotic convergence over time. This work defines and validates a method to select robust explanatory variables capable of quantifying the refined secondary supply of copper (or any other variable) in a given period. Using a database with 23 explanatory variables in the period 1960-2017, we characterize the estimated parameters with high and low robustness, thus supporting the proposed hypothesis. The results obtained allowed identifying those variables with low uncertainty in estimating their parameters, with a high statistical significance, and with a low standard deviation. This allows to obtain a robust function for the secondary refined copper supply in the long term, capturing essential elements of reality.
A Modified Multi-Winding DC-DC Flyback Converter for Photovoltaic Applications
(2021) Pesce, Cristian; Riedemann, Javier; Pena, Ruben; Degano, Michele; Pereda Torres, Javier; Villalobos, Rodrigo; Maury, Camilo; Young, Hector; Andrade, Ivan
A NEW POPULATION OF ULTRA-LONG DURATION GAMMA-RAY BURSTS
(IOP PUBLISHING LTD, 2014) Levan, A. J.; Tanvir, N. R.; Starling, R. L. C.; Wiersema, K.; Page, K. L.; Perley, D. A.; Schulze, S.; Wynn, G. A.; Chornock, R.; Hjorth, J.; Cenko, S. B.; Fruchter, A. S.; O'Brien, P. T.; Brown, G. C.; Tunnicliffe, R. L.; Malesani, D.; Jakobsson, P.; Watson, D.; Berger, E.; Bersier, D.; Cobb, B. E.; Covino, S.; Cucchiara, A.; de Ugarte Postigo, A.; Fox, D. B.; Gal Yam, A.; Goldoni, P.; Gorosabel, J.; Kaper, L.; Kruehler, T.; Karjalainen, R.; Osborne, J. P.; Pian, E.; Sanchez Ramirez, R.; Schmidt, B.; Skillen, I.; Tagliaferri, G.; Thoene, C.; Vaduvescu, O.; Wijers, R. A. M. J.; Zauderer, B. A.
We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations of several thousand seconds. We demonstrate that these events are extragalactic transients; in particular, we resolve the long-standing conundrum of the distance of GRB 101225A (the "Christmas-day burst"), finding it to have a redshift z = 0.847 and showing that two apparently similar events (GRB 111209A and GRB 121027A) lie at z = 0.677 and z = 1.773, respectively. The systems show extremely unusual X-ray and optical light curves, very different from classical GRBs, with long-lasting, highly variable X-ray emission and optical light curves that exhibit little correlation with the behavior seen in the X-ray. Their host galaxies are faint, compact, and highly star-forming dwarf galaxies, typical of "blue compact galaxies." We propose that these bursts are the prototypes of a hitherto largely unrecognized population of ultra-long GRBs, which while observationally difficult to detect may be astrophysically relatively common. The long durations may naturally be explained by the engine-driven explosions of stars of much larger radii than normally considered for GRB progenitors, which are thought to have compact Wolf-Rayet progenitor stars. However, we cannot unambiguously identify supernova signatures within their light curves or spectra. We also consider the alternative possibility that they arise from the tidal disruption of stars by massive black holes and conclude that the associated timescales are only consistent with the disruption of compact stars (e. g., white dwarfs) by black holes of relatively low mass (<10(5) M-circle dot).
A new zero-dimensional (0D) hybrid bismuth (III) halide: Synthesis, crystal structure, thermal analysis, photophysical properties and DFT calculations
(2024) Msaoura, Selma; Benito, Monica; Molins, Elies; Khirouni, Kamel; Zarate, Ximena; Saavedra-Torres, Mario; Schott, Eduardo; Houas, Ammar; Rayes, Ali
Low-dimensional organic-inorganic hybrid Bi(III) halides, with organic N, O-heterocycles, are promising solid -state photoluminescent materials, but are underexplored. In this work, we present the synthesis and charac-terization of a novel bismuth (III) hybrid salt, namely (C8H12NO)(4)[Bi2Cl10] (referred as (1)). (1) was synthesized using a solvent-evaporation method and extensively characterized using various techniques. The crystal structure of (1) was determined to be zero-dimensional (0D). In this structure, the individual bioctahedral [Bi2Cl10](4-) dimers, which share edges, are completely isolated from each other. These dimers are separated by large 4-methoxybenzylammonium cations (C8H12NO)(+). The latter are crucial for the crystal structural stability by balancing [Bi2Cl10](4-) dimer charges and maintaining overall integrity. Solid-state diffuse reflectance UV-Vis spectrum demonstrates that (1) is a semiconductor with a band gap of 3.32 eV. Its photoluminescence spectrum exhibits intense blue emission when exposed to UV light, with CIE chromaticity coordinates of (0.22, 0.21). Theoretical calculations suggest that the emission with multiple centers originates both from a charge transition between (C8H12NO)(+) and Bi2Cl104- ions and from excited-state proton transfer (ESPT) processes related to fluo-rescence properties. These ESPT processes occur through C-H center dot center dot center dot pi and C-H center dot center dot center dot O intermolecular hydrogen bonding between the organic cations.
A note on environmental policy and innovation when governments cannot commit
(2011) Montero Ayala, Juan Pablo
A novel inclusion of intermittent generation resources in long term energy auctions
(2017) Marambio, R; Rudnick Van de Wyngard, Henry
A novel stomatal resistance equation for modeling heat and mass transfer of extensive vegetative roofs
(Elsevier GMBH, 2024) Rojas Mondaca, Aldo Nicolás; Steinfort Needham, Úrsula Carla; Vera Araya, Sergio Eduardo
The cooling potential of vegetated roofs depends on the stomatal resistance (rs), leaf area index, and other factors. Sailor (2008) and Tabares-Velasco and Srebric (2012) are among the most cited heat and mass transfer vegetative roof models. They include different equations to estimate rs, which show large differences, and significantly overestimate rs under certain conditions. Therefore, their models offer particular opportunities for improvement to reflect the actual vegetation cooling potential. This is necessary to predict the impact of vegetative roofs more accurately on the building energy performance and the urban heat island effect. The rs of both vegetative roof heat and mass transfer models have been developed based on studies with species that are not commonly planted on vegetative roofs. It was found that both models overestimate the rs under certain conditions that could turn into the underestimation of the transpiration rates and the cooling potential. Consequently, this paper aims to develop a novel equation for rs based on field measurements in a semiarid climate. The species tested were Glandularia berterii (C3), Selliera radicans (C3), Phyla reptans (C3), Aptenia cor-difolia (CAM), Sedum palmeri (CAM), and Sedum spurium (CAM). A New Linear Model (NLM) was formulated to estimate rs. The regressors of NLM are minimum stomatal resistance (rs,min), incident solar radiation (Rsh), leaf area index (LAI), substrate volumetric water content (VWC), and vapor pressure difference (VPD). The results show that rs,min and Rsh reflect 64 % of rs; the species with higher cooling potential were Selliera radicans, Sedum palmeri, and Sedum spurium due to higher LAI and lower/moderate rs,min; and, the NLM showed a better agree-ment with the measured rs, correcting points where Sailor (2008) and Tabares-Velasco and Srebric (2012) equations significantly overestimated rs. Finally, it was demonstrated that the developed NLM better represents the stomatal behavior and distinguishes the responses between C3 and CAM species.
A Novel Three-Port NPC Converter for Grid-Tied Photovoltaic Systems with Integrated Battery Energy Storage
(IEEE, 2020) Neira Castillo, Sebastian Felipe; Lizana Gajardo, Alonso Javier; Pereda Torres, Javier Eduardo
The variable behaviour of the photovoltaic (PV) generation arises as the main drawback of this technology. Therefore, Battery Energy Storage (BES) units appear as a promising solution to overcome the inherent intermittent generation profile of PV systems. BES can be implemented separated from the PV generation units or integrated within a single power system. The latter option gives a better dynamic response, as the variable generation can be directly complemented with the BES, controlling the power flow between both elements with the grid. Thus, there is a need for power converters with capability of interface both PV and BES with the grid in a reliable and efficient way. This paper proposes a Three-Port NPC converter to connect a PV array and a BES unit with the ac grid using a single power processing stage. The converter is based in the H-NPC inverter and allows the connection of a low voltage battery to act as a power buffer ensuring a firm energy dispatch to the grid. Furthermore, simulation results show that the proposed topology maintains the good performance of the H-NPC in terms of efficiency, voltage harmonic distortion and reduced leakage current.
A robust decision-support method based on optimization and simulation for wildfire resilience in highly renewable power systems
(2021) Tapia, Tomas; Lorca, Alvaro; Olivares, Daniel; Negrete-Pincetic, Matias; Lamadrid L, Alberto J.
Wildfires can pose a major threat to the secure operation of power networks. Chile, California, and Australia have suffered from recent wildfires that have induced considerable power supply cuts. Further, as power systems move to a significant integration of variable renewable energy sources, successfully managing the impact of wildfires on the power supply can become even more challenging due to the joint uncertainty in wildfire trajectories and the power injections from wind and solar farms. Motivated by this, this paper develops a practical decision-support approach that concatenates a stochastic wildfire simulation method with an attacker-defender model that aims to find a worst-case realization for (i) transmission line and generator contingencies, out of those that can potentially be affected by a given wildfire scenario, and for (ii) wind and solar power trajectories, based on a max-min structure where the inner min problem represents a best adaptive response on generator dispatch actions. Further, this paper proposes an evaluation framework to assess the power supply security of various power system topology configurations, under the assumption of limited transmission switching capabilities, and based on the simulation of several wildfire evolution scenarios. Extensive computational experiments are carried out on two representations of the Chilean power network with up to 278 buses, showing the practical effectiveness of the proposed approach for enhancing wildfire resilience in highly renewable power systems.
A Robust optimization approach to assess the effect of delays in the connection-to-the-grid time of new generation power plants over transmission expansion planning
(2015) Sauma Santis, Enzo Enrique; Traub, Fernando; Vera Andreo, Jorge
A Trisheteroleptic Cyclometalated Ru-II Sensitizer that Enables High Power Output in a Dye-Sensitized Solar Cell
(2011) Bomben, Paolo G.; Gordon, Terry J.; Schott Verdugo, Eduardo Enrique; Berlinguette, Curtis P.
Ablation dynamics in wire array Z-pinches under modifications on global magnetic field topology
(2015) Veloso Espinosa, Felipe Eduardo; Munoz Cordovez, Gonzalo; Donoso Tapia, Luis; Valenzuela Villaseca, Vicente; Suzuki-Vidal, Francisco; Swadling, George; Chittenden, Jeremy; Favre Domínguez, Mario; Wyndham, Edmund
Acetyl xylan esterase II from Penicillium purpurogenum is similar to an esterase from Trichoderma ressei but lacks a cellulose binding domain
(1998) Gutiérrez, R; Cederlund, E; Hjelmqvist, L; Peirano, A; Herrera, F; Ghosh, D; Duax, W; Jörnvall, H; Eyzaguirre, J
Penicillium purpurogenum produces at least two acetyl xylan esterases (AXE I and LI). The AXE II cDNA, genomic DNA and mature protein sequences were determined and show that the axe 2 gene contains two introns, that the primary translation product has a signal peptide of 27 residues, and that the mature protein has 207 residues, The sequence is similar to the catalytic domain of AXE I from Trichoderma reesei (67% residue identity) and putative active site residues are conserved, but the Penicillium enzyme lacks the linker and cellulose binding domain, thus explaining why it does not bind cellulose in contrast to the Tricoderma enzyme. These results point to a possible common ancestor gene for the active site domain, while the linker and the binding domain may have been added to the Trichoderma esterase by gene fusion. (C) 1998 Federation of European Biochemical Societies.

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