Ingeniería eléctrica

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https://hdl.handle.net/10669/264

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2D SLAM Algorithms Characterization, Calibration, and Comparison Considering Pose Error, Map Accuracy, CPU Usage, and Memory Usage
(2022) Trejos Vargas, Kevin Francisco; Rincón Riveros, Laura Camila; Bolaños Torres, Miguel Eduardo; Fallas Pizarro, José Ariel; Marín Paniagua, Leonardo José
The present work proposes a method to characterize, calibrate, and compare, any 2D SLAM algorithm, providing strong statistical evidence, based on descriptive and inferential statistics to bring confidence levels about overall behavior of the algorithms and their comparisons. This work focuses on characterize, calibrate, and compare Cartographer, Gmapping, HECTOR-SLAM, KARTO-SLAM, and RTAB-Map SLAM algorithms, there were four metrics in place, these are pose error, map accuracy, CPU usage, and memory usage, from these four metrics, to characterize them, Plackett-Burman and factorial experiments were performed, and enhancement after characterization and calibration was granted by using hypothesis tests besides central limit theorem.
A Comparative Study on Denoising Algorithms for Footsteps Sounds as Biometric in Noisy Environments
(2022-08-03) Caravaca Mora, Ronald; Brenes Jiménez, Carlos; Coto Jiménez, Marvin
Biometrics is the automated identification of a person based on distinctive characteristics, such as fingerprints, face, voice, or the sound of footsteps. This last characteristic has significant challenges considering the background noise present in any real-life application, where microphones would record footsteps sounds and different types of noise. For this reason, it is crucial to consider not only the capacity of classification algorithms for recognizing a person using foostetps sounds, but also at least one stage of denoising algorithms that can reduce the background sounds before the classification. In this paper we study the possibilities of a two-stage approach for this problem: a denoising stage followed by a classification process. The work focuses on discovering the proper strategy for applying combinations of both stages for specific noise types and levels. Results vary according to the type and level of noise, e.g., for White noise at signal-to-noise ratio level, accuracy can increase from 0.96 to 1.00 by applying deep learning based-filters, but the same option does not benefit the cases of signals with low level natural noises, where Wiener filtering can increase accuracy from 0.6 to 0.77 at the highest level of noise. The results represent a baseline for developing real-life implementations of footstep biometrics.
A comparison of bio-inspired optimization methodologies applied to the tuning of industrial controllers
(2016-11-09) Céspedes, Macarena; Contreras, Mónica; Cordero, Joaquín; Montoya, Gustavo; Valverde, Karen; Rojas Fernández, José David
A comparison of different bio-inspired methods is presented for the problem of tuning the parameters of a PID industrial controller for second order plus time delay plants. The compared algorithms are representative of three different kind of methodologies (evolutionary, swarm-based and ecology-based). Al methods are briefly explained and are fully implemented to solve the control problem at hand. It was found that all methods are well suited to solve the problem, but they differ in its computational cost. However in all cases, the different methodologies tested were able to find similar minimum values for different families of plants
A DMC implementation for a binary distillation column: a MIMO approach
(2022-11) Villalobos Herra, Elena; Chacón Vásquez, Mercedes
Distillation columns are essential equipment for many industries, they are in charge of separating liquid mixtures based on the volatility differences of their components. Traditional PID control techniques have proven not to be the best fit for operating distillation columns when trying to obtain pure components, since they are a very complex process. In order to test MPC control with distillation columns, a real pilot-scale model is chosen and a multiple-input multiple-output DMC algorithm is developed in MATLAB®. Additionally, a fuzzy logic controller is created based on previous work, in order to compare the distillation column control performance. Simulation results show good performance of the MPC.
A first approach to acoustic characterization of Costa Rican children’s speech
(2020-03-27) Coto Jiménez, Marvin; Morales Rodríguez, Maribel; Vargas Díaz, Daniel Alfredo
As human interaction with computers becomes more pervasive, the value of developing automatic speech recognition, text-to-speech synthesis, and related speech technologies become more important for people of all ages, accents, and conditions. One of the groups that represent bigger challenges is children, due to the difficulties in recording enough speech, and the lack of characterization of their speech, which is particular of every language and accent. This paper presents the first approach to acoustic analyses of Costa Rican children aged from six to twelve years. These analyses aimed to achieve a better understanding of the characteristics of speech produced by this group, in terms of providing future development and enhancement of automatic speech recognizers and speaker identification systems. For this purpose, we record the speech consisting of isolated words of three children, and compare the results with three adults, in terms of the vowel’s formants. The formants give information about the vocal track of the speaker, and it is an important method to provide the first analysis of these signals. Results show noticeable differences between the children and adults and may provide useful information about future trends to adapt and develop the current speech technologies for this population.
A modeling methodology to evaluate the impact of temperature on Solar Home Systems for rural electrification
(2018) Narayan, Nishant; Vega Garita, Víctor; Qin, Zian; Popovic Gerber, Jelena; Bauer, Pavol; Zeman, Miroslav
Solar Home Systems (SHS) have recently gained prominence as the most promising solution for increasing energy access in remote, off-grid communities. However, the higher than standard testing conditions (STC) temperatures have a significant impact on the SHS components like PhotoVoltaic (PV) module and battery. A modeling methodology is described in this study for quantifying the temperature impact on SHS. For a particular location with high irradiation and temperatures and a given load profile, an SHS model was simulated, and the temperature-impact was analyzed on the performance and lifetime of the SHS components. Different PV module temperature estimation models were applied, and the corresponding dynamic PV outputs were compared. The nominal operating cell temperature (NOCT) model was found inadequate for estimating PV module temperatures under high irradiance conditions. The PV yield was found to be affected by almost 10% due to thermally induced losses. When different levels of temperature variations were considered, the battery lifetime was seen to be up to 33% less than that at 25°C. The modeling methodology presented in this paper can be used to include the thermal losses in SHS for rural electrification, which can further help accordingly in system sizing.
A novel control strategy for modular multilevel-based drives considering the system operating point
(2018-11-01) Espinoza Bolaños, Mauricio; Donoso Urrutia, Felipe Ignacio; Espina González, Enrique; Díaz Díaz, Matías; Cárdenas Dobson, Jesús Roberto Pedro Alejandro
Modular Multilevel Converters (MMC) are considered an attractive solution for high-power mediumvoltage drives. However, in drive applications, the influence of the loading conditions leads to more complex control systems than the required ones for constant frequency applications. To solve this issue, a novel control methodology for the MMC-based drive is presented in this paper. The proposed scheme defines the best control structure to balance the voltage of the converter capacitors considering the drive operating point (e.g. the loading conditions and the machine frequency). The design of the converter parameters considering the desired behaviour of the converter is also discussed in this paper. Experimental results with an 18-power cells MMC are used to validate the proposed control strategy.
A Novel Control System for Medium-Voltage Hexverter-Based Drives
(2020-09-23) Espinoza Bolaños, Mauricio; Donoso M., Felipe; Díaz D., Matías; Urrutia O., Matías; Cárdenas Dobson, Roberto
In this paper, a novel control system for the Hexverter-based drive is proposed and analysed. Unlike previously proposed control schemes, the proposed one does not require the information of the machine variables to regulate the converter floating capacitors, as required in high-performance drive applications. The feasibility of the proposed control system is demonstrated by using simulation results of an Hexverter-based drive driving a medium-voltage machine, including the whole frequency range and high starting torque loads.
A novel distributed secondary control strategy applied to hybrid ac/dc microgrids
(2019-11-28) Espina González, Enrique; Cárdenas Dobson, Jesús Roberto Pedro Alejandro; Donoso Urrutia, Felipe Ignacio; Urrutia Ortiz, Matías Alonso; Espinoza Bolaños, Mauricio
In this paper, a distributed secondary control strategy for hybrid ac/dc-microgrids is proposed. The control strategy restores the variables modified by the primary control loop, i.e. voltage on the DC-side and voltage amplitude and frequency of the AC-side, to their nominal values while maintaining a good power-sharing capability between AC- and DC-units, A distributed communication network among the generation units is needed for the proper performance of the control strategy, however, a high bandwidth communication network is not needed to ensure a good behaviour of the proposed control scheme. The effectiveness of the control scheme is validated through simulation of a 9.0kW hybrid ac/dc-microgrid.
A novel LVRT control strategy for Modular Multilevel Matrix Converter based high-power Wind Energy Conversion Systems
(2015-06-01) Díaz Díaz, Matías; Cárdenas Dobson, Jesús Roberto Pedro Alejandro; Espinoza Bolaños, Mauricio; Mora Castro, Andrés Felipe; Rojas Lobos, Félix Eduardo
The trend of multimegawatt wind turbines has positioning multilevel converters as a promising solution for high-power Wind Energy Conversion Systems (WECSs). Furthermore, due to the high penetration of wind energy into the electrical network, some rather strict grid regulations have been development in case of fault into the grid power. Mainly, grid codes set Low Voltage Ride Through (LVRT) requirements for grid connected WECS. In this scenario, this paper presents a novel modelation and control strategy to fulfil Low Voltage Ride Through requirements using a Modular Multilevel Matrix Converter for interfacing a high power wind turbine.
A novel topology and control system for Interconnected Wave Energy converters (IWECS)
(2019-11-28) Rodríguez Vindas, Mauricio; Espinoza Bolaños, Mauricio; Cárdenas Dobson, Jesús Roberto Pedro Alejandro; McDonald, Stephen P.; Baker, Nick J.
Recently, the extraction of energy from the incoming waves has taken more importance in the energy generation based on renewable resources. However, most of the attention has been directed towards the Power-Take-Off systems more than in the interaction between several generating units. Consequently, in this work, there are presented and carefully analysed a novel topology of Interconnected Wave-Energy Converters (IWECs) and its associated control system. A representative set of data of a real wave frequency and height variation from the South Uist island, in Scotland, and a proof-of-concept simulation show that the energy requirements of the proposed IWEC are lower than those required for individual WECs.
A performance evaluation of several artificial neural networks for mapping speech spectrum parameters
(2020) Yeom Song, Victor; Zeledón Córdoba, Marisol; Coto Jiménez, Marvin
In this work, we compare different neural network architectures, for the task of mapping spectral coefficients of noisy speech signals with those corresponding to natural speech. In previous works on the subject, fully-connected multilayer perception (MLP) networks and recurrent neural networks (LSTM & BLSTM) have been used. Several references report some initial trial and error processes to determine which architecture to use. Finding the best network type and size is of great importance due to the considerable training time required by some models of recurrent networks. In our work, we conducted extensive tests training more than five hundred networks, with several architectures to determine which cases present significant differences. The results show that for this application of neural networks, the architectures with more layers or the greater number of neurons are not the most convenient, both for the time required in their training and for the adjustment achieved. These results depend on the complexity of the task (the signal-to-noise ratio or SNR) and the amount of data available. This exploration can guide the most efficient use of these types of neural networks in future mapping applications, and can help to optimize resources in future studies by reducing computational time and complexity.
A practical method for considering shading on photovoltaics systems energy yield
(2023-10-01) Vega Garita, Víctor; Alpízar Gutiérrez, Verónica; Alpízar Castillo, Joel
Along with the widespread adoption of solar energy, it is fundamental to develop methods and tools that help practitioners during the design phase of photovoltaic (PV) systems. Currently, multiple commercial software can quantify a particular location’s annual energy yield while including the horizon’s shading effect (e.g., mountains, buildings, and trees). To do so, precise information about the PV system’s surroundings is necessary. This information is gathered by specialized equipment or by having access to satellite imagery. Therefore, to offer a more practical approach, we propose a method that requires only a cellphone camera, a fixed point for taking a panoramic photograph, and a compass. Once the panoramic image is taken, the obstacles’ width, height, and altitude are calculated, and the skyline is built. With this information, the method correlates the position of the sun with meteorological data to include the effect of shading on direct irradiation. The method was tested using one–year meteorological data to determine the best orientation of a PV system. The image processing method and the general method were validated by getting PV power generation data and aerial images and comparing them to the method’s predictions. Therefore, we introduce a method that, with low computational complexity, facilitates the study of shading on the performance of PV systems.
A risk-based methodology for defining the time of intentional controlled islanding
(2015-10-05) Fernández Porras, Pablo; Panteli, Mathaios; Quirós Tortós, Jairo
Power systems are operated close to their stability limits and this increases the probability of cascading outages leading to large-area blackouts. To mitigate these phenomena, intentional controlled islanding (ICI) has been suggested as an effective corrective strategy that splits the system into sustainable subsystems (islands). There are two primary aspects associated with ICI: i) where to island, and ii) when to island? This work focuses on the latter and proposes a risk-based methodology that compares in a real-time fashion (i.e., quickly enough) the overall risk of the system without and with islanding (i.e., when an ICI scheme is activated) in order to define a suitable time for system splitting. Simulation results on the IEEE 9-bus system demonstrate the effectiveness of the methodology in determining a suitable time for the creation of islands, which in turn corresponds to the crossing point between the risks of the system without and with islanding.
A simple methodology for estimating battery lifetimes in Solar Home System design
(2017) Narayan, Nishant; Papakosta, Thekla; Vega Garita, Víctor; Popovic Gerber, Jelena; Bauer, Pavol; Zeman, Miroslav
The proliferation of Solar Home Systems (SHS) in recent times hopes to provide an alleviating solution to the global problem of energy poverty. Battery is usually the most expensive but important part of an SHS; it is also normally the first part to fail. Estimating the battery lifetime can help make informed system design choices, and it is therefore an important exercise for an SHS designer. Battery lifetime modelling is often a complex task requiring empirical data or reliance on modelling cell level electrochemical phenomena. This paper presents a simple battery lifetime estimation method specific to the application and candidate battery choices at hand. An SHS application specific simulation is carried out for a year and the effect of microcycles on the battery activity is analyzed. The concept of active Depth-of-Discharge (DOD) is introduced. Cyclic ageing of the battery is thus quantified and relative cycle lives of 2 battery technologies are compared. A delicate trade-off is demonstrated between battery sizing and lifetime. The described methodology is also compared with an empirical model and the lifetime results are found to be within 3.85%. The methodology described in this paper can potentially help SHS designers in making quick, reasonable estimations of battery lifetimes based on the intended application and battery manufacturer's data.
A solid state transformer based on a three-phase to single-phase modular multilevel converter for power distribution networks
(2018-04-09) Espinoza Bolaños, Mauricio; Díaz Díaz, Matías; Rojas Lobos, Félix Eduardo; Cárdenas Dobson, Jesús Roberto Pedro Alejandro
To properly integrate electric vehicles and distributed generation systems in a massive scale, new revolutionary features and unprecedented transformations has to be implemented in power distribution networks, such as: access to LV DC interconnection point, reconfiguration capability for power flow management, disturbance isolation, low power-losses, high reliability, high power-quality, smart protection and low failure rate. In this paper, an innovative topology for a Solid State Transformer based on AC/AC Modular Multilevel Converter (MMC) is proposed. The proposed topology uses only one centralized singlephase Medium Frequency Transformer (MFT), which reduces the footprint of the SST. Furthermore, it provides three-phase balanced low-voltage system under unbalanced and non-linear loads. Simulation results validate the proposed topology and the control of the MMC to modulate a medium frequency mediumvoltage to provide a desired power flow.
A survey on 3D Perception for robot object manipulation tasks
(2019) Peralta Sáenz, Javier Ignacio; Ruiz Ugalde, Federico
Un sistema confiable de manipulación de objetos requiere de percepción sofisticada. Aspectos importantes de este sistema es ser capaz de detectar la forma, tamaño y pose de los objetos a manipular. Estas capacidades se han mostrado antes en la literatura pero sin demostrar altos grados de confiabilidad en ambientes no controlados. Las soluciones actuales tienen muchas limitaciones para lograr un manejo adecuado de los objetos. El objetivo principal de este estudio es revisar las técnicas de percepción más relevantes al problema, sus características y limitaciones. Esto será de utilidad para dirigir el trabajo futuro a los aspectos que un robot (como el desarrollado en el ARCOS-Lab) necesita para manipular objetos en ambientes humanos no controlados cotidianos, como las cocinas
A system-level design for a public transportation information system in Costa Rica
(2024) Abarca Calderón, Fabián; Murillo Rodríguez, José David; Segura Cruz, Joser David; Vargas Céspedes, Eddy Josué; Cordero Méndez, Adrián; Murillo Mamani, Edson Joao; Núñez Segura, Gustavo; Coto Jiménez, Marvin
Service information for passengers is a major factor in promoting the use of public transportation and enhancing user satisfaction. Implementing a comprehensive digital information system for travelers is a complex task that requires expertise in Intelligent Public Transportation Systems and, more broadly, in developing Enterprise Architectures. Costa Rica currently lacks diagnoses or plans for a large-scale implementation of such systems. In this paper the contributions are, first, an overview of the application of digital technologies in the transit system in Costa Rica, and second, a set of design principles and architectural decisions that are relevant to transit information systems and are specifically tailored for deployment in Costa Rica. For this purpose, this work adopts the Architecture Development Method (ADM) cycle, as proposed by The Open Group Architecture Framework (TOGAF), along with reference architectures and data specifications like the Architecture Reference for Cooperative and Intelligent Transportation (ARC-IT), the General Transit Feed Specification (GTFS), and the Smart Data Models framework, among others.
A vector control strategy to eliminate active power oscillations in four-leg grid-connected converters under unbalanced voltages
(2020-06) Mora Castro, Andrés Felipe; Cárdenas Dobson, Jesús Roberto Pedro Alejandro; Urrutia O., Matías; Espinoza Bolaños, Mauricio; Díaz Díaz, Matías
The problems associated with active power oscillations (APOs) in grid-connected converters are well-known. Imbalances in the grid usually produce double-frequency oscillations in the dc-link voltage and current which could reduce the useful life of solar panels, batteries, and capacitors connected to this point. Moreover, as reported in the literature, double-frequency reactive power oscillations (RPOs) also produce adverse effects in distribution systems, and it is desirable to eliminate or mitigate them. When a four-leg power converter is connected to an unbalanced grid, the zero-sequence current provides extra degrees of freedom to compensate or even eliminate the power oscillations at the converter dc-link side. In this paper, a new methodology to regulate these double-frequency power components is proposed. It is based on a closed-loop vector control approach, where the active power oscillations (APOs) at converter side are transformed into a synchronous frame rotating at twice the grid frequency and regulated using the zero-sequence current. To avoid overcurrent produced by the circulation of positive-, negative-, and zero-sequence components a current limiter is also proposed in this paper. Experimental results obtained with a 4-kW four-leg power converter prototype are presented and discussed in this paper.
Active power angle droop control per phase for unbalanced 4-wire microgrids
(2018-04-09) Espina González, Enrique; Espinoza Bolaños, Mauricio; Cárdenas Dobson, Jesús Roberto Pedro Alejandro
Most low voltage microgrids have four wires and operate mainly unbalanced. This paper considers a new droop control per phase of a four-wire microgrid to solve the problems associated to unbalanced operation (e.g. high neutral current). Unlike the conventional approaches, in this work, the active power per phase of each converter is shared varying the output voltage angle of each inverter phase. The proposed control system is based on a hierarchical control structure. The inner control loop of the inverter output voltage is implemented using resonant controllers, applying an active damping strategy to improve the system response. On the primary control loop, the angle droop control strategy is applied to share the active power per phase, according to the nominal ratings of the generation units. Then, a secondary control loop is utilised to restore the unbalance of the voltages to the nominal values. Experimental results obtained with a 3 kW four-wire microgrid prototype are presented and discussed to validate the proposed control system.

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