### Examinando por Autor "López-Santos, Oswaldo"

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- PublicaciónSólo datosA Unified Approach for the Control of Power Electronics Converters. Part I—Stabilization and Regulation(Applied Sciences, 2021-01-11) García, Germain; López-Santos, OswaldoThis work deals with the control of power electronics converters. In that context, the majority of the problems of interest can be translated into two main problems: stabilization control problems and tracking control problems. Numerous methods exist in the literature to propose solutions which are based on several ways of handling them in a more appropriate context: linear, nonlinear, switching, and hybrid control, to cite the most important. In recent years, a considerable effort has been made to derive control design methods taking into account the specificities and properties of the complex behavior of these systems, going beyond the numerous techniques based on approximated models or focused on the specific converter topology under study and, in that way, making a step towards a desirable genericity level. It is the objective of this work to go a step further trying to tackle the control of power converters in a unified way. The idea is to avoid, as much as possible, the use of approximations and exploit all the mathematical properties of the associated switched models. Writing them in a specific way, it is possible to deal with a lot of problems of interest whose solutions are based on assumptions which are the expressions of some kind of practical feasibility, and then closely related to the existence of solutions to the studied problems. In some cases, the resulting controls have an inevitable complexity level which reflects one of the problems under study. For such situations, the implementation issues are important and are not discussed in details in this paper. The proposed methods are illustrated by numerical simulations conducted with the help of PSIM software. This research work is decomposed into two parts, the first one focused on stabilization problems is developed in this paper. The other one concerning the tracking problems will be developed in a future paper.
- PublicaciónSólo datosA Unified Multimode Control of a DC–DC Interlinking Converter Integrated into a Hybrid Microgrid(Electronics, 2019-11-08) López-Santos, Oswaldo; Aldana-Rodríguez, Yeison Alejandro; García, Germain; Martínez-Salamero, LuisDC–DC interlinking converters (ILCs) allow bidirectional energy exchange between DC buses of different voltage levels in microgrids. This paper introduces a multimode control approach of a half-bridge DC–DC converter interlinking an extra-low-voltage DC (ELVDC) bus of 48 VDC and a low-voltage DC (LVDC) bus of 240 VDC within a hybrid microgrid. By using the proposed control, the converter can transfer power between the buses when the other converters regulate them, or it can ensure the voltage regulation of one of the buses, this originating from its three operation modes. The proposed control scheme is very simple and provides a uniform system response despite the dependence of the converter dynamic on the operating point and the selected mode. Simulation and experimental results validated the theoretical development and demonstrated the usefulness of the proposed scheme
- PublicaciónSólo datosAdaptive Sampling Frequency Synchronized Reference Generator for Grid Connected Power Converters(Communications in Computer and Information Science, 2018-09-13) López-Santos, Oswaldo; Tilaguy-Lezama, Sebastián; García, GermainThis paper introduces a simplified method for digital generation of high-quality references required for control of single-phase grid-connected (GC) power converters, which can generate synchronized sinusoidal waveforms at the same frequency of the input signal or its harmonics. Therefore, its application can be useful for active power filtering, high power factor rectification, and grid integration of renewable energy sources. A hybrid analog-digital implementation is proposed integrating an Adaptive Sampling Frequency Moving Average Filter (ASF-MAF) and a discrete-time Proportional-Integral (PI) controller into a Digital Signal Processor (DSP) operating with a sampling frequency defined by an external hardware-based Voltage Controlled Oscillator (VCO). The main advantages attributed to the method are immunity to harmonic content, accuracy in computations despite of frequency changes, flexibility to produce phase displacements and reduced computational cost. Performance of the proposal was verified by means of simulation and experimental results.
- PublicaciónSólo datosAnalysis, Design and Implementation of a Static Conductance-Based MPPT Method(IEEE, 2018-05-15) López-Santos, Oswaldo; García, Germain; Martinez-Salamero, Luis; Giral, Roberto; Vidal-Idiarte, Enric; Merchán-Riveros, María C.; Moreno-Guzman, YamelThis paper introduces a maximum power point tracking (MPPT) method based on a power (P) versus static conductance (G) curve of a photovoltaic (PV) array. The maximum power point (MPP) is tracked by comparing the PV array instantaneous power to a varying power reference generated by the MPPT algorithm. The comparison error is used to reduce or increase the conductance at which the PV array is forced to operate until the MPP is reached. Simultaneously, the error is used to change the power reference until the trajectory of this reference in the P-G curve enters a limit cycle around the MPP. The P-G curve is derived from a piecewise linear approximation of the current versus voltage (I-V) curve, which facilitates the analytical description of the tracking operation. The technique reported can also be implemented by means of simple analog or digital circuitry and requires two sensors to measure the instantaneous PV array current and voltage. It uses only four tuning parameters, which are selected depending on the maximum value of the derivative of the power with respect to the conductance. The theoretical predictions are verified with simulations and experimental results. The latter show that the procedure performs well enough to be favorably compared with the most efficient MPPT methods.
- PublicaciónSólo datosAutomatic Fault Detection in a Cascaded Transformer Multilevel Inverter Using Pattern Recognition Techniques(Lecture notes in Computer Science, 2019-10-01) Salazar-D’antonio, Diego; Meneses-Casas, Nohora; Forero, Manuel G.; López-Santos, OswaldoCascade transformer multilevel inverters (CT-MLI) are DC–AC converters used in medium and high power applications to provide standardized AC output. Despite their numerous advantages and robustness, these devices are highly susceptible to fault events because of their high amount of components. Therefore, early failure detection enables turning off the power system avoiding the propagation of the fault to the connected loads. Beyond that, converter operation can be reconfigured to tolerate the fault and activate a fail flag facilitating the subsequent corrective maintenance. The techniques proposed so far required several sensors, which is not practical. Therefore, in this study, we propose an automatic fault detection algorithm for cascade multilevel inverters based on pattern recognition, that only requires a sensor located at the output of the inverter. Naive Bayes, decision tree, nearest neighbor, and support vector machine were tested as classifiers using cross validation. The proposed method showed high detection accuracy when all the obtained descriptors were employed, being the K-NN the classifier showing superior performance. Furthermore, an evaluation was developed to determine the minimum number of descriptors required for the effective operation of the detection system, reducing the computational cost and simplifying its implementation. The method was validated by using simulation results obtained from a multilevel inverter circuit model.
- PublicaciónSólo datosCiencia con conciencia: apagando el piloto automático y activando el piloto intencional en la cultura investigativa en América Latina(Research strategy, culture development and Doctoral Support: Tools and Techniques for Latin American Universities, 2018-12-03) Hernández, Iván; López-Santos, Oswaldo; Bernal, Estrella; Jiménez, Édgar; Mazorco, Julio; Sánchez, Frank
- PublicaciónSólo datosComputational Tool for Simulation and Automatic Testing of a Single-Phase Cascaded Multilevel Inverter(Applied Computer Sciences in Engineering, 2018-09-13) López-Santos, Oswaldo; Corredor, Julián R.; Salazar, Diego F.This work describes in detail a computational tool designed to study performance indicators of a four-stage transformer-based single-phase cascaded multilevel inverter. The proposed system integrates simulation, on-line measurement, control and signal processing providing automating testing functionality to optimize the performance of the inverter with base on indicators such as Total Harmonic Distortion (THD), partial and global efficiency and power balance between the stages. The computational component of the tool was developed in LabVIEW providing not only didactic interactivity with the user through the Human-Machine Interface (HMI) but also a reliable interconnection with the power converter and the instruments of the experimental setup. The hardware component was developed integrating the power converter prototype, an acquisition card and electronic circuits providing measurement, conditioning, digital control and gate driving functions. Experimental results obtained from automatic tests are presented showing potentiality of the tool to support research activities related with this type of power converters.
- PublicaciónSólo datosContinuous Simulation of the Power Flow in AC–DC Hybrid Microgrids Using Simplified Modelling(Computation, 2022-03-29) López-Santos, Oswaldo; Salas-Castaño, María C.; Salazar-Dantonio, Diego F.This paper reports the development of a model for continuous simulation of the power flow into AC–DC hybrid microgrids operating for different generation–consumption scenarios. The proposed application was assembled using a multiple-input multiple-output model which was built using blocks containing simplified models of photovoltaic (PV) modules, wind turbines (WT), battery arrays (energy storage units, ESU), and power loads. The average power was used as the input/output variable of the blocks, allowing flexibility for easy reconfiguration of the microgrid and its control. By defining a generation profile, PV and WT were modeled considering environmental conditions and efficiency profiles of the maximum power point tracking (MPPT) algorithms. ESUs were modeled from intrinsic characteristics of the batteries, considering a constant power charge regime and using the State of Energy (SoE) approach to compute autonomy. To define a consumption profile, DC and AC loads were modeled as a constant real power. As an innovative characteristic, unidirectional and bidirectional power conversion stages were modeled using efficiency profiles, which can be obtained from experiments applied to the real converters. The outputs of the models of generation, consumption, and storage units were integrated as inputs of the mathematical expressions computing the power balance of the buses of the microgrid. The proposed model is suitable to analyze efficiency for different configurations of the same microgrid architecture, and can be extended by integrating additional elements. The model was implemented in LabVIEW software and three examples were developed to test its correct operation.
- PublicaciónSólo datosControl of a Bidirectional Cûk Converter Providing Charge/Discharge of a Battery Array Integrated in DC Buses of Microgrids(Applied Computer Sciences in Engineering, 2017-10-01) López-Santos, Oswaldo; Zambrano-Prada, David; Aldana-Rodríguez, Yeison A.; Esquivel-Cabeza, Harold A.This paper presents a proposal to charge and discharge valve-regulated lead-acid (VRLA) battery arrays integrated into microgrids by using the bidirectional Cûk converter with a multi-mode multi-loop control scheme based on sliding-mode control. The proposed control integrates the constant current - constant voltage - constant voltage charge method (CC-CV-CV) which is implemented using an inner current loop based on the sliding mode control of the input current of the converter and two nested outer loops based on the voltage and current of the battery. Conversely, the discharge is studied using two operational modes, one using a current reference given by a high level on a hierarchical structure and other using a current reference given by an outer Proportional-Integral (PI) controller regulating the voltage of the DC bus. The modelling of the bidirectional Cûk converter in these applications and its operational modes besides the analysis of the inner loop and the design criteria used in the synthesis of the outer loops are addressed. Simulation results are presented validating the control proposal.
- PublicaciónSólo datosControl of the bidirectional buck-boost converter operating in boundary conduction mode to provide hold-up time extension(Energies, 2018-09-26) López-Santos, Oswaldo; Urrego-Aponte, Jose O; Tilaguy-Lezama, Sebastián; Almansa-López, José DavidA hold-up time extension circuit (HTEC) is used to charge and discharge an auxiliary capacitor. This capacitor stores the energy required to extend the operation time of critical loads experiencing short duration failures (SDF) at the DC bus to which they are connected. This paper presents complete modeling and a control-wise approach to a parallel HTEC based on the bidirectional buck-boost converter, which operates in Boundary Conduction Mode (BCM) with a variable switching frequency. The circuit permanently regulates the voltage of the auxiliary capacitor as well as the voltage of the DC bus during SDF, which is uncommon in industrial versions of HTEC. Enforcing the operation in BCM allows a reduction in the size of the inductor in the converter without requiring additional control circuitry. The entire behavior of the proposed HTEC, in all its operation modes, was analyzed theoretically and validated using simulation and experimental results, showing the potential of the circuit to be used in real applications.
- PublicaciónSólo datosDetailed Modeling of the Low Energy Storage Quadratic Boost Converter(IEEE Transactions on Power Electronics, 2021-10-17) López-Santos, Oswaldo; López Varón, Nicolás; Rosas-Caro, Julio C.; Mayo-Maldonado, Jonathan C.; Valdez-Resé, Jesús E.The low energy storage quadratic boost converter (LES-QBC) was recently proposed as an advantageous topology in terms of reduced output voltage ripple and fast dynamic response, besides high power density and reduced energy storage. The topological configuration can be exploited mainly through a 180° phase shift between the controlled switch gate signals. Nevertheless, this feature imposes a relevant challenge in terms of modeling, since traditional averaging an ripple estimation techniques cannot provide an accurate approximation to the actual switching dynamics of the converter. Motivated by this issue, in this article, we provide a complete quantitative analysis of both the steady-state and dynamic behavior of the LES-QBC, giving a fine understanding of their operation in continuous conduction mode when a pulse width modulator is used. The voltage gain, ripple factor, and dynamic behavior are modeled considering parasitic resistances and a wide operation range for the input voltage and the load. The demonstrated performance corroborates the high value of the converter for several applications in the industry. Every theoretical prediction is fully validated via simulations and experimental results.
- PublicaciónSólo datosDevelopment of a Low-Cost UV-Vis Spectrophotometer and Its Application for the Detection of Mercuric Ions Assisted by Chemosensors(Sensors, 2020-02-08) González-Morales, David; Valencia, Asmilly; Díaz-Núñez, Astrid; Fuentes-Estrada, Marcial; López-Santos, Oswaldo; García-Beltrán, OlimpoDetection of an environmental contaminant requires the use of expensive measurement equipment, which limits the realization of in situ tests because of their high cost, their limited portability, or the extended time duration of the tests. This paper presents in detail the development of a portable low-cost spectrophotometer which, by using a specialized chemosensor, allows detection of mercuric ions (Hg2+), providing effective and accurate results. Design specifications for all the stages assembling the spectrophotometer and the elements selected to build them are presented along with the process to synthesize the chemosensor and the tests developed to validate its performance in comparison with a high-precision commercial laboratory spectrophotometer.
- PublicaciónSólo datosDiscrete Time Nested-Loop Controller for the Output Stage of a Photovoltaic Microinverter(Communications in Computer and Information Science, 2017-01-01) López-Santos, Oswaldo; Cortes-Torres, Luis; Tilaguy-Lezama, SebastiánThis paper presents a comprehensive study of the digital implementation of the control requirements of the output stage of a two-stage solar microinverter. This approach uses a synchronized nested-loop controller which ensures the tracking of an internally generated high-quality current reference, the estimation and cancelation of the effect of the DC-link voltage ripple in the control loops and the regulation of the average value of the DC-link voltage. The proposed control architecture is validated by means of simulation results comparing operation of the inverter using continuous time, quasi-discrete time and discrete time implementations.
- PublicaciónSólo datosDouble Sliding-Surface Multiloop Control Reducing Semiconductor Voltage Stress on the Boost Inverter(Applied sciences, 2020-07-17) López-Santos, Oswaldo; García, GermainSliding-mode control (SMC) has been successfully applied to boost inverters, which solves the tracking problem of imposing sinusoidal behavior to the output voltage despite the coupled or decoupled operation of both boost cells in the converter. Most of the results reported in the literature were obtained using the conventional cascade-control structure involving outer loops that generate references for one or two sliding surfaces defined using linear combinations of inductor currents and capacitor voltages. As expected, all proposed methods share the inherent robustness and insensitivity to the uncertainties of SMC, which are the reasons why one of the few comparison criteria between them is the simplicity of their implementation that is evaluated according to the required measurements and mathematical operations. Furthermore, the slight differences between the obtained dynamic performances do not allow a clear distinction of the best solution. This study presents a new SMC approach applied to a boost inverter in which two boost cells are independently commutated. Each of these boost cells integrates an outer loop, enforcing the tracking of harmonic-enriched waveforms to the capacitor voltage. Although this approach increases by two the number of measurements and requires multiloop controllers, it allows effective alleviation of the semiconductor voltage stress by reducing the required voltage gain. A complete analytical study using harmonic balance technique allows deducing a simplified model allowing to obtain a PI controller valid into to the whole set of operation conditions. The several simulation results completely verified the potential of the control proposal and the accuracy of the employed methods.
- PublicaciónSólo datosEmulation of a Photovoltaic Module Using a Wiener-Type Nonlinear Impedance Controller for Tracking of the Operation Point(Applied Computer Sciences in Engineering, 2017-10-01) López-Santos, Oswaldo; Merchán-Riveros, María C.; Salas-Castaño, Maria C.; Londoño, William; García, GermainThis paper proposes a control method to provide the function of Solar Panel Emulation (SPE) to a low-cost programmable DC source. The proposed control operates with base on the error between measurement of the conductance connected at the output of the SPE and the conductance obtained evaluating the I-V characteristic of the panel model. The principle of operation is that the output of the controller modifies the value of the voltage introduced into the W-Lambert function to obtain the corresponding current enforcing the regulation of the measured conductance. In this paper, a controller composed by a nonlinear static gain and a conventional PI controller is proposed. The controller architecture configures a Wiener system structure which ensures the stable convergence of the real SPE variables to the values defined by the model. Simulation results are presented evaluating the dynamic performance of the system for irradiance and load variations. SPE method is implemented using simple measurement and conditioning circuits interacting with an application developed in LabVIEW through a data acquisition card. This implementation provides a complete solution highly applicable in research and industrial development.
- PublicaciónSólo datosEvent-Triggered Digital Implementation of MPPT for Integration of PV Generators in DC Buses of Microgrids(Applied Computer Sciences in Engineering, 2018-09-13) López-Santos, Oswaldo; Merchán-Riveros, María C.; García, GermainThis paper presents an event-triggered approach to optimally implement a Maximum Power Point Tracking (MPPT) algorithm into a Digital Signal Processor (DSP). The proposed method allows improving the amount and distribution of time required for executing control tasks. The used nested loop control architecture has an outer loop of MPPT generating the conductance reference used by an inner loop which regulates the input conductance of a DC-DC converter. This last loop enforces a sliding-mode loss-free-resistor behavior for the power converter by means of a simple hysteresis comparator. Computations required by the MPPT algorithm are synchronously executed by the two possible commutation events produced by the inner loop during a switching period. Then, the acquisition of signals must be activated only at an instant before each one of the switching events, releasing the most of the time to implement other tasks. This last characteristic and the use of a nested loop control architecture facilitate the integration of the other essential control functions for photovoltaic (PV) generators in microgrids. Simulation and experimental results confirm the high potetialities of this implementation approach.
- PublicaciónSólo datosExperimental Modelling of DC Motor for Position Control Systems Involving Nonlinear Phenomena(Communications in Computer and Information Science, 2020-10-08) González-Morales, David; García-Beltrán, Olimpo; Aldana-Rodríguez, Yeison Alejandro; López-Santos, OswaldoNonlinear phenomena in the dynamic behavior of DC motors are commonly disregarded in speed regulation systems because it has a constant operation point or a reduced range of variation. Therefore, in the majority of applications, a second order linear model is enough to design the required controllers. However, in angle positioning systems involving DC-motor based actuators, deviation of linear models becomes unacceptable because the impact of non-linearities accentuates. This paper presents a method for experimental modelling of DC motor bidirectional dynamic following three main steps: i) obtaining input-output measurements from multiple experiments using chirp signals as input stimulus; ii) to produce a family of Hammerstein-Wiener type models using software tools for parametric system identification, and iii) to synthesize a unique model from superposition analysis of both the nonlinear gains and the root loci of the linear part. Validity of the obtained model is demonstrated using simulation results showing its potential application in engineering practice.
- PublicaciónSólo datosHybrid control scheme for a half-bridge inverter(IFAC-PapersOnLine, 2017-10-01) Albea Sanchez, Carolina; López-Santos, Oswaldo; Zambrano-Prada, David; Gordillo, Francisco; García, GermainThis paper presents a control law based on Hybrid Dynamical Systems (HDS) theory for electronic inverters. This kind of systems are very suited for the use of such theory since they combine both kind of signals: continuous (voltages and currents) and discrete (on-off state of switches). Unlike previous applications of HDS to power converters, the studied problem can be considered as a tracking problem since the objective is to generate a desired ac voltage from a dc source. The effectiveness of the resultant control law is validated by means of simulations and experiments.
- PublicaciónSólo datosLow-Cost Spectrophotometer for In-Situ Detection of Mercury in Water(2018 IEEE SENSORS, 2018-10-28) González-Morales, David F.; López-Santos, Oswaldo; García-Beltrán, OlimpoThis paper presents the design and implementation of a low-cost spectrophotometer (LCSPM) for in-situ detection of mercury in water. The proposed device is composed of a white light emitting diode (LED), a diffraction grating (DG), a rotational positioning system, two photodiodes and a low-cost microcontroller. High-resolution angle displacement of DG allows obtaining a selective projection of the visible spectrum on the studied water and the reference during the same test. All required algorithms are embedded into the microcontroller allowing the transfer of the resulting data to a computer. The capability of the proposed LCSPM for detection of mercuric ions (Hg 2 +) in water was tested with the help of a synthesized coumarin and then validated by comparison with a standard device.
- PublicaciónAcceso abiertoMódulo de automatización eléctrica(Universidad de Ibagué, 2018-10-04) Henao Castaño, Angélica; López-Santos, Oswaldo