Browsing by Author "Dixon Rojas, Juan"

Now showing 1 - 20 of 44
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    27-level converter for electric vehicles using only one power supply
    (IEEE, 2010) Dixon Rojas, Juan; Pereda Torres, Javier Eduardo
    The main advantage of asymmetrical multilevel inverters is the optimization of levels with a minimum number of power supplies. However, this optimized multilevel system still needs a large number of isolated and floating DC supplies, which makes these converters complicated to implement in electric vehicles (EVs), because the system will require many independent battery packs. In this paper, a very simple scheme, based on a small and cheap high frequency link (HFL), allows the utilization of only one power supply for the complete multilevel inverter drive, with an inherent regulation of the voltages supplied among the H-bridges. It also allows voltage control with full number of levels if the DC power supply is of variable voltage characteristic. This work is focused on a 27-level asymmetric inverter but the strategy, using only one power supply, can be applied to converters with any number of levels. In particular, an asymmetrical 27-level converter needs nine isolated power supplies and the proposed system reduces these nine sources to only one: the battery car. The topology also permits full regenerative braking working as a three-level converter. The proposed system is intended for application in electric vehicles from power ratings up to 150 kW. Simulations and experimental results show the feasibility to implement this “one-source†multilevel system.
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    A fuzzy-controlled active front-end rectifier with current harmonic filtering characteristics and minimum sensing variables
    (1999) Dixon Rojas, Juan; Contardo, J. M.; Morán, L. A.
    A control strategy which allows conventional voltage-source current-controlled (VSCC) pulsewidth modulation (PWM) rectifiers to work simultaneously as active power filters is presented. The proposed control strategy also allows compensating the system power factor and compensating unbalanced loads. The measurement and/or calculation of the harmonics and reactive power are not required, making the proposed control scheme very simple. The active front-end rectifier acts directly on the mains line currents, forcing them to be sinusoidal and in phase with the mains voltage supply. To improve the dynamic of the system, the amplitude of the current is controlled by a fuzzy system, which adjusts the DC-link voltage of the PWM rectifier. The strategy is based on connecting all the polluting loads between the PWM rectifier and their input current sensors. The main advantages of this approach are the following: (1) there is no need to install a specially dedicated active power filter; (2) it also works simultaneously as a power factor compensator; and (3) no special and complicated calculations are required for harmonic elimination. The viability of the proposed active front-end rectifier is proved by simulation and with experimental results obtained from a 2 kVA PWM prototype.
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    A New Compensation Method for High Current Non-Linear Loads
    (IEEE, 2006) Ruminot, P.; Moran, L.; Aeloiza, E.; Enjeti, P.; Dixon Rojas, Juan
    A new active compensation scheme to eliminate current harmonic components and compensate reactive power for high current non-linear loads is presented and analyzed. The new active compensation technique is based in a series active filter that employs a unique power circuit topology (two single phase inverters) with a simple control scheme, and is suitable for current harmonics and reactive power compensation. It is address to compensate highly polluted electric feeders such as the ones connected to high current rectifiers. The proposed approach allows for low cost and part count reduction in comparison with previous compensation solutions (passive and active). The paper analyzes the new active power compensation technique in terms of principles of operation, power topology, control design and implementation. Experimental results obtained in a laboratory DSP based controlled prototype are presented validating the simulated waveforms and confirming the viability of the proposed compensation technique
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    A New Hybrid Filter Topology for Sub and Inter-Harmonic Attenuation in Cycloconverter-Fed Drives Applications
    (IEEE, 2009) Aravena, P.; Moran, L.; Dixon Rojas, Juan; Espinoza, J.; Godoy, O.
    This paper presents a filter scheme composed by passive and series active power filters specially designed to compensate fundamental reactive power (with passive filters) and current harmonics (combination of passive and active). Low frequency current sub and inter-harmonics generated by cycloconverters are eliminated with an active power filter connected in series to a C type passive filter. Current frequency harmonics associated with cycloconverter topology are eliminated with passive filter units. With the proposed filter topology compensation effectiveness is significantly improved and allows the elimination of passive filter units, reducing cost and space required as compared with traditional passive schemes. This paper presents the principles of operation and design requirements of the proposed hybrid filter scheme. Simulated results based in the compensation of a real grinding mill plant prove the effectiveness and advantages of the proposed scheme.
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    A Novel Noninvasive Failure-Detection System for High-Power Converters Based on SCRs
    (2013) Guerrero, Victor; Pontt, Jorge; Dixon Rojas, Juan; Rebolledo, Jaime
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    A series active power filter based on a sinusoidal current controlled voltage source inverter
    (IEEE, 1995) Dixon Rojas, Juan; Venegas Castro, Gustavo Adolfo; Morán, L.
    A series active power filter, working as a sinusoidal current source, in phase with the mains voltage, has been developed and tested. The amplitude of the fundamental current in the series filter is controlled through the error signal generated between the load voltage and a pre-established reference. The control allows an effective correction of power factor, harmonic distortion, and load voltage regulation.
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    Análisis técnico-económico de producción y almacenamiento de hidrógeno
    (2017) Rodríguez Machuca, Pablo Andrés; Dixon Rojas, Juan; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Los problemas de capacidad en las líneas de trasmisión de energía, producto del exceso de oferta de energía, en ciertas horas del día, proveniente principalmente de generadoras fotovoltaicas del norte de Chile, producen vertimientos de energía o desacoples del sistema. Este vertimiento, es literalmente "botar energía", pues no pueden ser inyectados a las líneas de transmisión. Para poder cuantificar este vertimiento, se realizó un análisis de las centrales fotovoltaicas, por un periodo de 3 meses, registrando vertimientos de energía que van desde 101 a 2 848 MWh. Para las centrales analizadas, se definieron ciertos escenarios conducentes a determinar la energía que podría ser almacenable y estimar aIgún precio de energía. Resulta clave destacar, que sobre un 90% de los costos marginales en horas de desacople, proporcionaron valores inferiores a 1 USD/MWh. En la búsqueda de como almacenar la energía vertida en los momentos de desacople, se realizó una revisión del estado del arte de diferentes sistemas de almacenamiento de energía, y en particular los sistemas basados en hidrógeno. El estudio presenta diversas aplicaciones del hidrógeno, formas de producirlo, sistemas para almacenarlo, además de-las tecnologías de celdas de combustible. Con lo anterior, se realizaron dos análisis, el primero utiliza la energía de vertimientos solo para producir hidrógeno y otro, además de producir hidrógeno, lo inyecta en celdas de combustible, para transformarlo nuevamente en energía eléctrica. Para ambos casos, se efectuó un dimensionamiento de planta, donde se esquematizan los distintos equipos y diversas configuraciones, y su respectivo análisis económico. Para las distintas configuraciones, técnicamente ambos análisis son viables. No obstante, los análisis económicos, no favorecen a los sistemas en los cuales el hidrógeno se trasforma en energía eléctrica mediante una celda de combustible, pero sí muestra interesantes indicadores en plantas que están diseñadas solo para producir hidrógeno.
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    Aplicación de control predictivo a filtro activo paralelo multinivel.
    (2013) Saldías Molina, Hernaldo Enrique; Dixon Rojas, Juan; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    El objetivo de este documento es mostrar el diseño e implementación de un filtro activo de nueve niveles controlado por medio de un esquema de control llamado Control Predictivo con Estados Finitos. Este método de control se basa en escoger la mejor combinación de variables (manipuladas) con el fin de optimizar una función de costos (la que depende de variables de desempeño del sistema), aprovechando la naturaleza discreta del inversor. Las ventajas de este método de control radican en su simplicidad, dado que es muy fácil de entender, es fácil de ajustar y también es fácil cambiar los objetivos de control e imponer restricciones. Como contraparte, la principal desventaja es que requiere de un sistema de muestreo y control muy rápido para lograr resolver el problema de optimización en tiempo real.
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    Asymmetrical Multilevel Inverter for Traction Drives Using Only One DC Supply
    (2010) Dixon Rojas, Juan; Pereda Torres, Javier Eduardo; Castillo Tamayo, Carlos Ignacio; Bosch Castro, Sebastián Andrés
    The main advantage of asymmetrical multilevel inverters is the optimization of levels with a minimum number of power supplies. However, this optimized multilevel system still needs a large number of isolated and floating dc supplies, which makes these converters complicated to implement in electric vehicles (EVs), because the system will require many independent battery packs. In this paper, a very simple scheme, based on a small and cheap high-frequency link (HFL), allows the utilization of only one power supply for the complete multilevel inverter drive, with an inherent regulation of the voltages supplied among the H-bridges. It also allows voltage control with the full number of levels if the dc source is of a variable voltage characteristic. This paper is focused on a 27-level asymmetric inverter, but the strategy, using only one power supply, can be applied to converters with any number of levels. In particular, an asymmetrical 27-level converter needs nine isolated power supplies, and the proposed system reduces these nine sources to only one: the battery car. The topology also permits full regenerative braking working as a three-level converter. The proposed system is intended for application in EVs from power ratings up to 150 kW. Simulations and experimental results show the feasibility to implement this “one-source†multilevel system.
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    Binary position sensor for synchronous machines based on a serial n-bit sequential code
    (IEEE, 2013) Dixon Rojas, Juan; Garcés Guajardo, Cristian Andrés
    This work presents the design of an absolute position encoder with n-bit resolution based on a serial sequential code to measure rotor position in synchronous machines. The encoder is capable of define 2n positions minimizing the sensor disc size compared to conventional gray encoders and using the same hardware. Besides, a new approach to single-track code generation is proposed with the development of a code generation program. This design is going to be installed into an experimental hybrid vehicle helping in startup synchronization between the generator and combustion engine.
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    Cascaded converters for EVs with single power source and increased power quality
    (2013) Pereda Torres, Javier Eduardo; Dixon Rojas, Juan
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    Cascaded Nine-Level Inverter for Hybrid-Series Active Power Filter, Using Industrial Controller
    (2010) Varschavsky Páez, Alexander; Dixon Rojas, Juan; Rotella Macchiavello, Mauricio Humberto; Morán, L.
    An industrial controller, specifically designed for two- and three-level converters, was adapted to work on an asymmetrical nine-level active power filter (APF). The controller is now able to make all required tasks for the correct operation of the APF, such as current-harmonic elimination and removal of high-frequency noise. The low switching-frequency operation of the nine-level converter was an important advantage in the application of the industrial controller. In addition, with the nine-level filter, switching losses were significantly reduced. The filter was designed to work as voltage source and operates as harmonic isolator, improving the filtering characteristics of the passive filter. The control strategy for detecting current harmonics is based on the “ p-q theory †and the phase-tracking system in a synchronous reference frame phase-locked loop. The dc-link voltage control is analyzed together with the effect of controller gain and delay time in the system's stability. Simulations for this application are displayed and experiments in a 1-kVA prototype, using the aforementioned industrial controller, were tested, validating the effectiveness of this new application.
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    CED: a new method for high speed stepping motor driving
    (IEEE, 1997) Vadell Rivera, Jaime Ernesto; Lira Canguilhem, Ignacio; Dixon Rojas, Juan
    Stepper motors are indexing devices widely used today in microcomputer controlled machines because of their low cost, simplicity, accuracy and repeatability. Even though their speed is presently adequate for many purposes, there is still some room for improving this parameter. In this article, the authors propose a new electrical driving method especially designed for small stepper motors, fed with unidirectional currents. The method is called "controlled energy discharge" (CED) and is based on changing the time response constant of the current due to winding inductance by the addition of a charged capacitor. The theory of the method, its implementation and performance comparisons with traditional control schemes are presented. From these comparisons, the authors' proposal appears to be an excellent alternative for driving stepping motors.
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    Compensador multinivel activo, reactivo y armónico respaldado por paneles fotovoltaicos.
    (2008) Flores Lara, Patricio Armando; Dixon Rojas, Juan; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    El presente trabajo de Tesis describe la implementación de un filtro activo y compensador estático de reactivos con capacidad de inyección de potencia activa, utilizando un inversor multietapa de 27 niveles. Cada fase del inversor está compuesta por tres puentes \201CH\201D, todos los cuales están conectados a la misma barra DC, mientras que sus salidas están conectadas a transformadores escalados en potencias de tres. El filtro puede compensar corrientes de carga con alto contenido armónico y bajo factor de potencia, lo que resulta en entrega de corrientes sinusoidales desde la red. Para tomar mayor ventaja de este compensador, la barra DC, en vez de un condensador, utiliza un banco de baterías, el que es cargado a través de un arreglo fotovoltaico conectado a las baterías a través de un MPPT (Maximum Power Point Tracker). Esta topología combinada hace posible la producción de potencia activa, e incluso la alimentación de las cargas durante apagones prolongados. Se muestran resultados de simulaciones de esta aplicación, así como algunos experimentos realizados con un prototipo de inversor de 3 kVA.
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    Control de torque para motor BLDC de vehículo eléctrico impulsado por ultracapacitores
    (2009) Mura Jornet, Maximiliano; Dixon Rojas, Juan; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    En este trabajo se presenta el análisis, diseño e implementación de un control de torque para un motor síncrono tipo Brushless DC (BLDC) de 5 kW de potencia, con el objeto de ser utilizado en un vehículo eléctrico. El inversor a utilizar es de 9 niveles, construyéndose con 2 puentes H en cascada por fase y utilizando como única fuente de energía un módulo ultracapacitor de 48 Vdc por cada puente. A diferencia de los vehículos eléctricos convencionales que existen hoy en día, los cuales usan como fuente primaria de almacenamiento energético baterías de distintos tipos, el vehículo en el cual se implementará el controlador tendrá una capacidad de potencia mucho más elevada; permitiendo cargar el vehículo en el transcurso de segundos o minutos, dependiendo de la capacidad del cargador. Por otro lado, como los ultracapacitores actuales disponen de una baja densidad energética, la eficiencia del sistema de tracción y la capacidad de frenado regenerativo son puntos importantes en la implementación. La estrategia de control utilizada en este trabajo fue el control de corriente por medio de múltiples bandas de histéresis, el cual fue primero probado en simulaciones utilizando MATLAB/Simulink. El vehículo dispondrá en total de aproximadamente 280 Wh de energía, lo que le permitirá tener una autonomía cercana a 3 km., demostrando así que en cuanto los ultracapacitores basados en nanotubos de carbono salgan al mercado (con 20 o 30 veces más capacidad de almacenamiento que los utilizados en esta investigación), será perfectamente viable construir vehículos eléctricos que permitan su uso en ciudad, tengan un tiempo de carga muy reducido y no requieran ser cambiados en toda su vida útil.
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    Design, construction and performance of a buck-boost converter for an ultracapacitor-based auxiliary energy system for electric vehicles
    (IEEE, 2003) Ortuzar Dworsky, Micah Etan; Dixon Rojas, Juan; Moreno de la Carrera, Jorge Alejandro
    This paper describes step by step the process of designing, constructing and testing a bidirectional buck-boost converter. This converter is conceiving to be used as a controlled energy-transfer-equipment between the main energy source of an electric vehicle (a battery pack in this case) and an auxiliary energy system based on ultracapacitors. The converter is able to transfer energy in both directions, at rates of more than 40 kW. The battery pack's nominal voltage is 330 V, while the ultracapacitor's voltage depends on their state of charge (SOC), ranging from 100 V to 300 V. Equations governing current transfer and current ripple are analyzed. These equations will be used as guidelines for the control system design and smoothing inductor size requirement. The topology used is a buck-boost configuration. Special care had to be taken in designing the smoothing inductor and managing thermal loses, for these are critical to the overall performance. The inductor constructed, rating l.5 mH, is capable of transferring 200 A for several minutes with low loses and no core saturation (air core was used). A special water-cooled heatsink was designed and constructed, with a very low volume of less than 900 cc and a thermal resistance of less than 0.011/spl deg/C/W. The control system was implemented on a TMS320F241 DSP from Texas Instruments, which consists in two control loops. The first one controls the converter's current, using as a reference the value obtained from the second loop, which controls the ultracapacitors state of charge (SOC). Criteria ruling this second loop are not discussed in this paper. Finally, some experimental results of the overall system are displayed.
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    Direct Torque Control for sensorless induction motor drives using an improved H-Bridge multilevel inverter
    (IEEE, 2009) Pereda Torres, Javier Eduardo; Dixon Rojas, Juan; Rotella, M.
    This paper presents the application of a sensorless direct torque control (DTC) for an induction motor, using an improved H-Bridge multilevel inverter with 27-Levels. The inverter topology reduces the power sources from nine to only four active sources and three ultracapacitors. The power sources are unidirectional and non-redundant; scaled in power of three to optimize the number of voltage levels with a minimum of semiconductors and power sources. For the improved inverter topology, two additional control strategies are introduced; 1) an inhibit negative currents (INC) controller, which solves the regeneration problem when unidirectional sources are used; and a 2) proportional-integral (PI) controller, which keeps the ultracapacitor voltages at the reference value. Both controls work on a pulse width modulation (PWM) signal, where the INC control decides the levels among the PWM operates, and the PI controller changes the duty-cycle. A closed-loop estimator called model reference adaptive system (MRAS) was used for the speed estimation, with the advantage of using the stator voltages and currents already obtained for the DTC. The application of the system was simulated and implemented in Matlab®/Simulink® software using the industrial controller AC800PEC from ABB, obtaining satisfactory results. The multilevel inverter was specially designed and built for this application.
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    Diseño de un nuevo sistema de control sin sensor de posición para un generador de reluctancia conmutada, en aplicaciones de generación eólica
    (2008) Echenique Subiabre, Estanislao Juan Pablo; Dixon Rojas, Juan; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    En este trabajo se presenta el análisis, diseño e implementación de un nuevo estimador de posición para el control de generadores de reluctancia conmutada (SRGs), de velocidad variable. La estimación de posición se obtiene a partir de la información contenida en la inductancia insaturada instantánea. Ésta es estimada calculando, en tiempo real, la pendiente de la corriente de fase y utilizando una red neuronal (NN) cuyas entradas son la corriente promedio y la inductancia saturada. El estimador propuesto requiere menos esfuerzo computacional que los métodos tradicionales de estimación de posición, y puede ser implementado en un DSP de bajo costo, con un mínimo de componentes adicionales. El método de control propuesto puede ser aplicado a un sistema de conversión de energía eólica, donde el SRG es utilizado como generador de velocidad variable. Esta aplicación ha sido desarrollada puesto que el SRG tiene conocidas ventajas como su robustez, bajo costo de fabricación y buena relación de tamaño-potencia. Las simulaciones y resultados experimentales presentados en este trabajo, se han realizado en un prototipo de 8/6 polos, de 2.5kW de potencia.
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    Diseño e implementación de un filtro activo híbrido-serie multietapa de 9 niveles
    (2008) Varschavsky Páez, Alexander; Dixon Rojas, Juan; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    La presente tesis describe el diseño y la implementación de un filtro activo híbrido-serie basado en un inversor multietapa de 9 niveles de baja potencia nominal y en filtros pasivos paralelos sintonizados a la 5ª y 7ª armónica. Cada fase del inversor está compuesta por dos puentes H conectados al mismo condensador en la barra dc y a su vez conectados en serie a través de transformadores de salida escalados en potencias de tres. A través de la topología multinivel utilizada, el filtro es capaz de eliminar el contenido armónico de la corriente de línea producida por cargas no lineales sin introducir ruido de alta frecuencia ni perdidas por conmutación como lo hacen los inversores de dos niveles tipo PWM típicamente utilizados en aplicaciones de este tipo. Los filtros pasivos compensan las armónicas de corriente principales de la carga, mientras que el filtro activo actúa como un aislador de armónicas, mejorando las características de filtrado de los filtros pasivos y mitigando sus conocidas desventajas. La estrategia de control utilizada se basó en la teoría de la Potencia Reactiva Instantánea p-q y el mecanismo de sincronización con la red trifásica en un PLL en el marco de referencia síncrono. Se analizan el lazo de control de voltaje del condensador de la barra dc y el efecto de la ganancia del controlador y de los retardos introducidos por los sistemas de control en la estabilidad del sistema. Simulaciones del sistema en el programa MATLAB/Simulink, así como también pruebas experimentales para una carga de 1 kVA utilizando el controlador industrial ABB AC800 PEC, corroboran el correcto funcionamiento del sistema propuesto.
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    Electric Vehicle Using a Combination of Ultracapacitors and ZEBRA Battery
    (2010) Dixon Rojas, Juan; Nakashima Dueñas, Ian; Arcos Fuentes, Eduardo Fabián; Ortúzar Dworsky, Micah Etan
    The sodium-nickel chloride battery, commonly known as ZEBRA, has been used for an experimental electric vehicle (EV). These batteries are cheaper than Li-ion cells and have a comparable specific energy (in watt-hours per kilogram), but one important limitation is their poor specific power (in watts per kilogram). The main objective of this paper is to demonstrate experimentally that the combination of ZEBRA batteries and ultracapacitors (UCAPs) can solve the lack of specific power, allowing an excellent performance in both acceleration and regenerative braking in an EV. The UCAP system was connected to the ZEBRA battery and to the traction inverter through a buck-boost-type dc-dc converter, which manages the energy flow with the help of DSP controllers. The vehicle uses a brushless dc motor with a nominal power of 32 kW and a peak power of 53 kW. The control system measures and stores the following parameters: battery voltage, car speed to adjust the energy stored in the UCAPs, instantaneous currents in both terminals (battery and UCAPs), and present voltage of the UCAP. The increase in range with UCAPs results in more than 16% in city tests, where the application of this type of vehicle is being oriented. The results also show that this alternative is cheaper than Li-ion powered electric cars.