Nicolás Muñoz

Fault diagnosis in induction motors fed by PWM inverters

Motors have become critical components for many industries. A motor failure can result in the shutdown of a production line, or require that redundant equipment be utilised to circumvent the problem. By this way, the early detection of motor deterioration can increase plant availability and safety in an economical way. Many publications have investigated the detection of rotor and stator winding failures in electrical machines; however, there is more limited research on fault diagnosis in induction motors fed by PWM converters. This paper proposes a method, based on spectral estimation to diagnosis stator winding faults in induction motors fed by PWM converters. Simulation and experimental results are employed to validate the method. Further, a 5 hp and 3 hp, 230V induction motors with internal tapings from the stator windings are specially constructed. The motors are powered by a PWM converter and different fault conditions are investigated.

Modeling, analysis and design procedure of LCL filter for grid connected converters

This paper presents the mathematical deduction of models for LCL filters with and without the damping resistor, the criteria for designing LCL filter, a systematic procedure for designing LCL filter and experimental tests with an isolated load. Experimental tests demonstrate the relevance of propose procedure for the design of LCL filter. Usually, power inverter is the interface between renewable energy sources such as wind, solar and hydrogen fuel cells, and utility grid. However, high frequency PWM modulation generated in power inverter causes harmonic injection to the utility grid and reduces quality of the injected energy. LCL filter can reduce harmonic injection to the utility grid. Inappropriate design of LCL filter can cause excessive voltage attenuation at the output of the power inverter, resonances and oscillations that can increase total harmonic distortion, instability in power system and slow dynamic response.

Aplicación de las Redes Neuronales al Pronóstico de Precios en el Mercado de Valores

Resumen Este trabajo propone un modelo basado en redes neuronales artificiales para el pronostico de los precios de dos de las principales acciones transadas en mercado de valores colombiano. El modelo propuesto se aplica al estudio de las acciones de Ecopetrol y Preferencial Bancolombia, empresas que negocian en las bolsas de valores de Colombia y Nueva York. Se utilizan dos estructuras de redes incluyendo como entradas la serie de precios diarios en la primera y la serie de precios mas el indice del dolar estadounidense DXY en la segunda. Se prueban diferentes configuraciones de redes neuronales utilizando una serie de seis meses, donde los datos de los primeros cinco se utilizan para entrenamiento dejando el ultimo mes para verificar la capacidad predictiva de la red. Los resultados muestran un buen comportamiento de las redes neuronales con bajos errores en su desempeno tanto en aprendizaje como en prediccion. Palabras clave: mercado de valores, redes neuronales artificiales, pronostico de precios

Design methodologies and programmable devices used in power electronic converters — A survey

This paper presents a review of the state of the art of the design methodologies for Hardware (HW) and Software (SW) for design of the digital control system in power electronic converters. This paper presents also a review of programmable electronic devices used in applications including power converters: Microcontroller (μC), Digital Signal Controllers (DSC), Digital Signal Processors (DSP) and Field Programmable Gate Array (FPGA). This paper presents relevant concepts for electronic power converters developers. However, concepts and information presented can also be used in other applications that require the design of embedded systems. Finally, this paper also presents the case study of the development of the control system of a three-phase inverter, using the system-level design methodology.

Metaheuristics Applied to the Optimal Location and Sizing of Distributed Generation in Power Distribution Systems

Resumen En este articulo se presenta una evaluacion de la ubicacion y dimensionamiento optimo de generacion distribuida en sistemas de distribucion de energia electrica. Para tal evaluacion se han considerado las siguientes tecnicas de busqueda: i) recocido simulado, ii) busqueda de entorno variable iii) algoritmo genetico y iv) algoritmo genetico hibrido. En el problema de ubicacion y dimensionamiento optimo se han considerado dos objetivos: la minimizacion de perdidas activas y el mejoramiento del perfil de tensiones. Para comparar la efectividad de los metodos implementados se utiliza un sistema de distribucion de prueba de 34 barras. La correcta ubicacion y dimensionamiento de la generacion distribuida permitio mejorar sustancialmente el perfil de tension de la red y reducir en un 80% las perdidas para el sistema de prueba. Palabras clave: generacion distribuida, algoritmos geneticos, entorno variable, recocido simulado Metaheuristics Applied to the Optimal Location and Sizing of Distributed Generation in Power Distribution Systems

Análisis de Vulnerabilidad de Sistemas de Potencia Mediante Programación Binivel

This paper presents a new technique for vulnerability analysis in power systems under multiple contingencies. The model under study is known as the “Terrorist Problem”. The main contribution of this work is the formulation and solution of the AC version of this problem, which allows identifying the most critical elements of the power system and gives early signals to the system operator regarding the vulnerability of the system. Furthermore, the AC version of the model allows obtaining more realistic results than the traditional DC model, due to the fact that such version considers the effect of reactive power and voltage magnitudes in the system buses. The proposed model is solved by means of a hybrid metaheuristic technique that combines genetic algorithms with local search. The results obtained using the IEEE RTS – 24 bus test system show the relevance and applicability of the proposed methodology.

Reducción Selectiva de las Corrientes de Neutro en Instalaciones Eléctricas Mediante el Uso de Compensadores Activos Paralelo

Resumen Se usa un compensador activo de potencia paralelo para la reduccion de las corrientes que circulan por el neutro en instalaciones electricas trifasicas a cuatro hilos. Las corrientes que debe inyectar el compensador activo a la carga son deducidas obteniendose expresiones para reducir de forma global y selectiva las corrientes del neutro. Se diferencian las corrientes provocadas por cargas lineales desequilibradas y las corrientes provocadas por cargas no lineales. Las corrientes que circulan por el neutro causan diversos problemas en los sistemas electricos de acuerdo a su naturaleza u origen. La reduccion selectiva de la corriente del neutro permite abordar estos problemas, de acuerdo a la causa que los producen, de tal manera que es posible maximizar la eficiencia y confiabilidad de los sistemas electricos. Palabras clave: compensador de potencia paralelo, corrientes de compensacion, cargas desequilibradas, cargas no lineales Selective Reduction of Neutral Currents in Electrical Installations by means of Shunt Active Compensators

Análisis de los Flujos de Potencia de Sistemas Eléctricos y su Interpretación Física

In this paper, the instantaneous power theory of the Institute of Electrical and Electronics Engineers (IEEE, Std. 1459 of 2010) used for single-phase electric systems is expanded to threephase electric systems. A general instantaneous power expression is obtained through instantaneous voltages and currents. This expression is useful to explain the phenomena in electrical systems. This expression is also verified through experimental tests relating power flow and its causes. There are numerous instantaneous power expression reported in the literature, but these expressions do not relate physically and mathematically the electrical phenomena and its causes. For this reason, it is proposed to use the instantaneous power theory to explain physical phenomena in electrical systems contributing with a power theory that can be simultaneity used for measuring or monitoring to revenue purposes, for evaluating the power quality, for designing active filters, and for detecting sources of harmonic distortion.

Redes Neuronales Artificiales aplicadas a la Predicción del Precio del Oro

espanolEn este trabajo se predice el comportamiento del precio del oro mediante un modelo basado en redes neuronales artificiales (RNA). El objetivo del modelo es predecir los precios de cierre diarios del mercado de Londres, los cuales son tomados como referencia por el Banco central de Colombia. Se estudian varias configuraciones de RNA tipo propagacion hacia adelante tomando como variables de entrada las series diarias del indice del dolar estadounidense DXY, el indice SP500, los precios del petroleo y los precios del oro. Se entrenan diferentes estructuras de RNA utilizando la serie historica de datos, donde una parte de los mismos se utiliza para entrenamiento y la restante para la prediccion. Los resultados obtenidos muestran un buen desempeno del modelo tanto en el periodo historico analizado como en la prediccion, encontrando como mejor estructura aquella que utiliza las series de precios diarias del oro, el indice DXY y el indice SP500. EnglishGold price prediction using an artificial neural network model (ANN) is proposed in this work. The objective of the model is to predict the daily closing prices in the London market, which are taken as reference prices for the Central Bank of Colombia. Different configurations of type feed-forward Aaa are considered using the dollar index DXY, the SP500 index, the daily oil price series, and the daily gold price series, as inputs to the Aaa model. A set of ANN structures are trained using the historical series of data, where one portion is used for training and the other portion is used for testing (prediction). The results show good performance of the model both in the analyzed historical period and the predictions, where the best structure includes the daily price series of gold, the DXY index and the SP500 index.

Procedimiento Novedoso para el Diseño del Circuito Amortiguador RCD (Snubber RCD) y Deducción Matemática de las Ecuaciones

espanolEste articulo propone un procedimiento novedoso para el diseno del amortiguador RCD (Snubber RCD) en circuitos electronicos de potencia con el objetivo de reducir el voltaje maximo (peak) transitorio en el apagado de los interruptores de potencia. El procedimiento incluye un metodo para la determinacion de los elementos parasitos en el circuito de conmutacion y la deduccion matematica de las ecuaciones de diseno. El procedimiento propuesto se constituye en una herramienta util para el analisis y el diseno del amortiguador RCD, aplicados en la mayoria de los circuitos electronicos de potencia. Las ecuaciones de diseno deducidas permiten calcular teoricamente el valor del condensador y de la resistencia del amortiguador RCD en funcion de las reactancias parasitas del circuito implementado y del voltaje maximo de operacion del interruptor, haciendo posible verificar mediante simulacion el desempeno dinamico del circuito antes de la implementacion experimental. El procedimiento y las ecuaciones de diseno son verificados en el laboratorio, corroborando la coherencia del analisis teorico con los resultados experimentales. EnglishThis paper proposes a new procedure for the design of snubber RCD in power electronic circuits to reduce the peak transient voltage when the power switch is turned off. The procedure involves a method for the determination of parasitic elements in the switching circuit and the mathematical deduction of design equations. The proposed procedure is a useful tool for the analysis and design of snubber RCD circuits, used in the majority of power electronic circuits. The design equations obtained in this work allow the theoretical calculation of the value of the capacitor and of the resistance of the snubber RCD based on the parasitic reactances of the implemented circuit and the maximum operating voltage of the switch, allowing the verification through simulation of the dynamic performance of the circuit before the experimental implementation. The procedure and the design equations are verified in the laboratory, corroborating the consistency of the theoretical analysis with the experimental results.