Estudio de técnicas de control de rectificadores Boost Trifásicos con filtro LCL para reducción de la distorsión armónica en corriente, aplicadas al procesado eficiente de energía en aerogeneradores síncronos de imanes permanentes operando a velocidad variable

La tesis se plantea como objetivo principal el estudio y la aplicación de técnicas de corrección de armónicos a sistemas de generación eólica de pequeña potencia, enfocando el problema desde el punto de vista del aerogenerador, esto es, centrando los objetivos en la etapa de entrada del convertidor de potencia utilizado, el cual está constituido por un rectificador trifásico pasivo, un convertidor dc-dc tipo boost y un inversor de conexión a red. Para reducir el factor THDi de las corrientes de salida del aerogenerador (lo que a su vez repercute en menores vibraciones provocadas por armónicos de par) y elevar el factor de potencia del mismo, el convertidor dc-dc opera en conducción discontinua, siguiendo un principio conocido y aplicado a rectificadores trifásicos con corrección del factor de potencia actuando como front-end de sistemas de alimentación con conexión a una red eléctrica de amplitud y frecuencia nominal fijas. La tesis propone como novedad destacada la extensión de este principio a aerogeneradores operando a velocidad variable, de manera que el rectificador trifásico opera con tensiones de amplitud y frecuencia variables en un rango muy extenso. Para operar en conducción discontinua se requiere añadir un filtro LCL resonante en la salida del aerogenerador, por lo que el estudio riguroso de la estabilidad de los controles de corriente utilizados es crítico. Adicionalmente, se tienen en consideración otras cuestiones de relevancia en el contexto estudiado, como son una comparativa de algoritmos estimadores de la velocidad del aerogenerador en condiciones ruidosas de sensado (debido a la conducción discontinua), y el estudio de una estructura de control que permite implementar los algoritmos de búsqueda de la máxima potencia del aerogenerador sin degradar significativamente las prestaciones alcanzadas mediante las técnicas propuestas. Los resultados analíticos han sido validados experimentalmente mediante un prototipo de sistema de generación eólica de 2kCarranza Castillo, O. (2012). Estudio de técnicas de control de rectificadores Boost Trifásicos con filtro LCL para reducción de la distorsión armónica en corriente, aplicadas al procesado eficiente de energía en aerogeneradores síncronos de imanes permanentes operando a velocidad variable [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14575Palanci

Analysis of the control structure of wind energy generation systems based on a permanent magnet synchronous generator

This paper presents the analysis of the two usual control structures for variable speed and fixed pitch wind energy generation systems, namely speed and torque control, to determine the most appropriate structure to improve both robustness and reliability of this kind of distributed generators. The study considers all the elements of a typical wind power generation system and it has been carried out in a general way, so that conclusions are independent of the kind of the AC/DC converter that it is used to process the energy at the output of the generator. Particular emphasis was placed on developing a model of the turbine where the mechanical torque is considered as a system variable and not an exogenous disturbance for the system, as in other previous studies. After showing that speed control presents several advantages in terms of stability and reliability, an experimental study of this technique was carried out by using a grid connected wind generation system, which is composed by a three-phase boost rectifier feeding the grid connected inverter. Other practical issues for the design of high efficient wind generation systems, like the use of a Kalman speed estimator to avoid the need of mechanical sensors, are also implemented in the prototype and discussed in the paper. (c) 2012 Elsevier Ltd. All rights reserved.The first author thanks the support of the Instituto Politecnico Nacional (IPN) and of the Comision de Operacion y Fomento de Actividades Academicas (COFAA). This work was supported by the Spanish Ministry of Science and Innovation under Grant ENE2009-13998-C02-02.Carranza Castillo, O.; Figueres Amorós, E.; Garcerá Sanfeliú, G.; González Medina, R. (2013). Analysis of the control structure of wind energy generation systems based on a permanent magnet synchronous generator. Applied Energy. 103:522-538. https://doi.org/10.1016/j.apenergy.2012.10.015S52253810

Comparative study of speed estimators with highly noisymeasurement signals for Wind Energy Generation Systems

This paper presents a comparative study of several speed estimators to implement a sensorless speed control loop in Wind Energy Generation Systems driven by power factor correction three-phase boost rectifiers. This rectifier topology reduces the low frequency harmonics contents of the generator currents and, consequently, the generator power factor approaches unity whereas undesired vibrations of the mechanical system decrease. For implementation of the speed estimators, the compared techniques start from the measurement of electrical variables like currents and voltages, which contain low frequency harmonics of the fundamental frequency of the wind generator, as well as switching frequency components due to the boost rectifier. In this noisy environment it has been analyzed the performance of the following estimation techniques: Synchronous Reference Frame Phase Locked Loop, speed reconstruction by measuring the dc current and voltage of the rectifier and speed estimation by means of both an Extended Kalman Filter and a Linear Kalman Filter. © 2010 Elsevier Ltd.The first author thanks the support of the Instituto Politecnico Nacional (IPN) to finance his stay at the Universidad Politecnica de Valencia (UPV). This work was supported by the Spanish Ministry of Science and Innovation under Grant ENE2009-13998-C02-02.Carranza Castillo, O.; Figueres Amorós, E.; Garcerá Sanfeliú, G.; González Morales, LG. (2011). Comparative study of speed estimators with highly noisymeasurement signals for Wind Energy Generation Systems. Applied Energy. 88(3):805-813. https://doi.org/10.1016/j.apenergy.2010.07.039S80581388

Estudio comparativo del coeficiente de potencia y de torque presentados en diversas turbinas eólicas

Este artículo presenta un estudio comparativo del coeficiente de potencia y de torque presentado en diversas turbinas eólicas; que se emplean para realizar el análisis de una turbina eólica, estableciendo los conceptos que permiten encontrar la relación de la energía cinética del viento entre la energía mecánica. En este estudio se presentan tres modelos generales que expresan el coeficiente de potencia y de torque, los cuales se agrupan en exponencial, sinusoidal y polinomial. Cabe destacar que los modelos exponenciales y sinusoidales incluyen variaciones en relación a la velocidad específica y del ángulo de ataque; y los modelos polinomiales solo dependen de la velocidad específica. Los modelos son obtenidos considerando características reales de las turbinas eólicas. El propósito de este estudio es analizar el comportamiento de coeficiente de potencia y de torque para establecer todas las consideraciones a tomar en cuenta para el desarrollo e implementación de un emulador de turbinas eólicas.Palabra(s) Clave(s): Coeficiente de Potencia, Coeficiente de Torque, Turbina Eólica

Anxiety and depression as predictors of life satisfaction during pre-professional health internships in COVID-19 times: the mediating role of psychological well-being

Due to the emotional impact of COVID-19 on university students, the goal was to explore the relationship between anxiety, depression, psychological well-being, and life satisfaction among pre-professional interns. The research was carried out using an explanatory cross-sectional design, with the participation of 1011 pre-professional interns of 13 health networks from the department of Puno (Peru). Data were collected using the Satisfaction with Life Scale, Generalized Anxiety Disorder Scale-2, Patient Health Questionnaire 2, and the Psychological Wellbeing Scale. The main data analysis was carried out using the R statistical software, and implementing the confirmatory factor analysis technique, which evidenced that the explanatory model provides an acceptable value. Based on the above, a negative relationship between depression and life satisfaction, (β ¼ .60, p < .001) and a positive relationship between anxiety and life satisfaction (β ¼ .28, p < .001) was shown, in addition to a mediating effect of the psychological wellbeing related to depression and life satisfaction (p < .001). In conclusion, life satisfaction is explained concerning the degree of depression and anxiety, as well as the moderating effect of psychological well-being. Despite that, there is an urgent need to take preventive actions to strengthen the mental health of the pre-professional health interns, who have also been providing support during the COVID-19 pandemic.Campus Arequip

CONTROL DEL FLUJO DE POTENCIA HACIA LA RED ELÉCTRICA DE UN SISTEMA DE GENERACIÓN EÓLICA EMPLEANDO UN GENERADOR DE INDUCCIÓN DE DOBLE ALIMENTACIÓN

ResumenEn este trabajo se presenta el control del flujo de potencia hacia la red eléctrica, a través del Convertidor del Lado de la Red (CLR) de un Sistema de Generación Eólica (SGE), con el objetivo de ser utilizado en un Convertidor Back to Back (CBB) que se requiere conectar a un Generador de Inducción de Doble Alimentación (GIDA). Se diseñan los controladores Proporcionales-Integrales requeridos para controlar la tensión del bus de CD, así como, la Potencia Activa y Potencia Reactiva del SGE. Se simula el CLR en el programa Simulink de Matlab®, donde se valida el funcionamiento del convertidor en los dos modos de operación: como rectificador y como inversor. Aplicando la técnica del control vectorial se obtiene control total en el intercambio de potencias entre el SGE y la red eléctrica.Palabras Claves: Control Vectorial, control proporcional-integral, convertidor del lado de la red, flujo de potencia. CONTROL OF THE POWER FLOW TO THE ELECTRICAL NETWORK OF A WIND GENERATION SYSTEM USING A DOUBLE-FEED INDUCTION GENERATORAbstractIn this paper is presented the control of the power flow to the electrical network, through the Grid-Side Converter (GSC) of a Wind Generation System (WGS) with the objective of being used in a Back to Back Converter that is required to be connected to a Doubly Fed Induction Generator (DFIG). The Proportional-Integral controls are designed in order to control the voltage on the DC Link, as well as, the Active and Reactive Power of the WGS. The GSC is simulated in the program Simulink of Matlab®, where the operation of the converter is validated in the two modes of operation: as a rectifier and as an inverter. Applying the vector control technique is obtained the total control in the power exchange between the WGS and the electrical network.Keywords: Grid side converter, power flow, proportional-integral control, vector control

OBSERVADOR HÍBRIDO DE MODOS DESLIZANTES PARA EL CONTROL SENSORLESS DE UN MOTOR SÍNCRONO DE IMANES PERMANENTES (HYBRID SLIDING MODE OBSERVER FOR SENSORLESS CONTROL OF A PERMANENT-MAGNET SYNCHRONOUS MOTOR)

En este artículo se propone un observador híbrido, el cual está constituido por un observador de Luenberger y un observador de modos deslizantes, ambos funcionando en paralelo para combinar las ventajas de ambas técnicas de observación. Debido a su naturaleza no lineal, este observador es usado para estimar la fuerza electromotriz de un motor síncrono de imanes permanentes, la cual contiene la información de la posición y velocidad. Esta fuerza electromotriz estimada es procesada digitalmente por un algoritmo PLL para estimar la posición y la velocidad del motor. Estas estimaciones son realimentadas en un esquema de control vectorial, con lo cual se elimina la necesidad del sensor mecánico de posición/velocidad (control sensorless). Simulaciones en MATLAB/Simulink son llevadas a cabo, donde se demuestra el correcto funcionamiento del observador propuesto. Finalmente, los resultados obtenidos son analizados y discutidos.In this paper, a hybrid observer is proposed, which is constituted by a Luenberger observer and a sliding mode observer, both working in parallel, so to obtain the advantages of both observation techniques. Due to its nonlinear nature, this observer is used to estimate the back-electromotive force of a permanent magnet synchronous motor, which contains the rotor position and speed information. This estimated back-electromotive force is digitally processed by a PLL algorithm to estimate the motor position and speed. These estimates are feedback into a vector control scheme, where the need for the mechanical position/speed sensor (sensorless control) is eliminated. Simulations in MATLAB/Simulink are carried out, where the performance of the proposed observer is demonstrated. Finally, the results obtained are analyzed and discussed

Validez y confiabilidad de una escala de procrastinación académica en estudiantes cubanos de Estomatología

Introduction: Academic procrastination can have a negative impact on student education and professional performance, hence the need for valid and reliable instruments for its study. Objective: To analyze the evidence of validity and reliability of an academic procrastination scale in Cuban dental students. Methods: Instrumental, cross-sectional and multicenter study, which included students from seven Cuban universities. Using an instrument in Spanish validated in Peruvian students, a confirmatory factor analysis was performed, structural equation modeling was used, and internal consistency was calculated with Cronbach's α coefficient. Results: 684 participants were included, of which 63,45 % were women and the mean age was 22,0 ± 1,71 years. From the initial scale of 12 items distributed in 2 factors, the factor analysis suggested eliminating item 5. The final model was made up of 11 items, 8 for factor 1 (Academic self-regulation) and 3 for factor 2 (Postponement of activities). A Cronbach's α coefficient of 0,786 (95 % CI = 0,75 – 0,81) was obtained, which indicates that the internal consistency of the instrument is good. Conclusions: An 11-item academic procrastination scale was validated (EPA-11-Odonto), which has evidence of validity and adequate reliability to evaluate the construct in Cuban dental students.Introducción: La procrastinación académica puede repercutir negativamente en la formación estudiantil y el desempeño profesional, de allí la necesidad de contar con instrumentos válidos y confiables para su estudio. Objetivo: Analizar las evidencias de validez y confiabilidad de una escala de procrastinación académica en estudiantes cubanos de Estomatología. Métodos: Estudio instrumental, transversal y multicéntrico, que incluyó estudiantes de siete universidades cubanas. A partir de un instrumento en español validado en estudiantes peruanos, se realizó un análisis factorial confirmatorio, se utilizó el modelamiento de ecuaciones estructurales y se calculó la consistencia interna con el coeficiente α de&nbsp;Cronbach. Resultados: Se incluyó a 684 participantes, de los cuales el 63,45 % fueron mujeres y la media de la edad fue 22,0 ± 1,71 años. De la escala inicial de 12 ítems distribuidos en 2 factores, el análisis factorial sugirió eliminar el ítem 5. El modelo final quedó conformado por 11 ítems, 8 para el factor 1 (Autorregulación académica) y 3 para el factor 2 (Postergación de actividades). Se obtuvo un coeficiente α de Cronbach de 0,786 (IC 95 % = 0,75 – 0,81), lo cual indica que la consistencia interna del instrumento es buena. Conclusiones: Se validó una escala de procrastinación académica de 11 ítems (EPA-11-Odonto), la cual posee evidencias de validez y confiabilidad adecuadas para evaluar el constructo en estudiantes cubanos de Estomatología

The influence of self-esteem, depression, and life satisfaction on the future expectations of Peruvian university students

IntroductionStrengthening the self-confidence of future professionals can help them achieve professional goals with a likelihood of being able to achieve them in the future. The objective was to determine whether self-esteem, depression, and life satisfaction influence the future expectations of Peruvian university students.MethodsA total of 708 university students participated (64.8% were female, mean age = 21.49; SD = 4.83). The Rosenberg Self-Esteem Scale, the Patient Health Questionnaire-2, the Life Satisfaction Scale, and the Adolescent Future Expectations Scale were used. Structural equation modeling was employed to test the impact of selfesteem, depression, and life satisfaction on future expectations.ResultsThe model relating the study variables demonstrated an adequate fit (p &lt; 0.001, CFI = 0.940, RMSEA = 0.073), confirming the relationship between self-esteem (β = 0.33, p &lt; 0.001), life satisfaction (β = 0.28, p &lt; 0.001), and depression (β =  −0.14, p &lt; 0.010.) with future expectations. This model explained 36% of future expectations.DiscussionIn conclusion, future expectations may be affected by low levels of self-esteem and life satisfaction and high levels of depression

Emotional fatigue, academic engagement, and satisfaction with studies during the return to post-pandemic university attendance

IntroductionThe COVID-19 pandemic has significantly transformed various sectors, including higher education, exposing structural weaknesses and fostering the adoption of innovative teaching methods. This situation has created the need to understand how these changes have affected the academic satisfaction, academic engagement, and mental well-being of university students during the return to in-person education at universities.MethodsIn this explanatory study, 1,321 Peruvian university students (52.1% women) aged between 18 and 35 years old (M = 20.16, SD = 3.04) participated. Participants were selected through a non-probabilistic convenience sampling method, recruited from the 3 regions of Peru (88.7% from the highlands, 76.2% from private universities), from faculties such as business sciences, humanities and education, engineering, and health sciences. Data were collected using the Emotional Exhaustion Scale (EES), the Brief Scale of Satisfaction with Studies (BSSS), and the Academic Engagement Scale (UWES S9).ResultsThe model relating the study variables showed an adequate fit: χ2(4) = 31.5, p &lt; 0.001, CFI = 0.986, RMSEA = 0.072, SRMR = 0.017. The hypotheses were supported, showing the effect on satisfaction with studies both from emotional exhaustion, β = −0.11, p &lt; 0.001, and from academic engagement, β = 0.61, p &lt; 0.001. Additionally, a 43% variance was explained in satisfaction with studies.ConclusionThis study evidence that, in the post-pandemic context, emotional exhaustion is a negative predictor of academic satisfaction, while academic engagement is positively associated with it. These findings suggest the need for educational strategies that mitigate emotional exhaustion and promote academic engagement to improve student satisfaction and well-being in the new educational normality