Browsing by Author "Dixon Rojas, Juan, 1948-"

Now showing 1 - 9 of 9
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    A full compensating system for general loads, based on a combination of thyristor binary compensator, and a PWM-IGBT active power filter
    (IEEE, 2001) Dixon Rojas, Juan, 1948-; Del Valle, Yamille; Orchard, Marcos; Ortúzar Dworsky, Micah Etan; Morán, Luis; Maffrand, Carlos
    A full compensating system for distribution networks which is able to eliminate harmonics, correct unbalanced loads and generate or absorb reactive power is presented. The system is based on a combination of a thyristor binary compensator (TBC), and a PWM-IGBT active power filter (APF) connected in cascade. The TBC compensates the fundamental reactive power and balances the load connected to the system. The APF eliminates the harmonics and compensates the small amounts of load unbalances or power factor that the TBC cannot eliminate due to its binary condition. The TBC is based on a chain of binary-scaled capacitors and one inductor per phase. This topology allows, with an adequate number of capacitors, a soft variation of reactive power compensation and a negligible generation of harmonics. The capacitors are switched on when the line voltage reaches its peak value, avoiding inrush currents generation. The inductor helps to balance the load, and absorbs reactive power when required. The APF works by measuring the source currents, forcing them to be sinusoidal. The two converters (TBC and APF) work independently, making the control of the system simpler and more reliable. The system is able to respond to many kinds of transient perturbations in no more than a couple of cycles. The paper analyzes the circuit proposed, the way it works and the results obtained under operation with different types of loads.
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    An active power filter using single-phase NPC converters and predictive control for medium voltage distribution systems
    (IEEE, 2013) Acuña, P.; Morán, L.; Rivera Inalaf, Marco Antonio; Dixon Rojas, Juan, 1948-; Burgos, Rolando
    An active power filter implemented with three single-phase Neutral Point Clamped (NPC) converters is presented and analyzed. The proposed active power filter is aimed to compensate current harmonics and reactive power in three-phase medium voltage power distribution systems. A predictive control algorithm provides the switching states that ensure fast current tracking capability. To take advantage of the predictive control implementation simplicity, this paper includes useful information to replicate this implementation on similar topologies of multilevel converters. The proposed scheme presents lower line to line voltage harmonic distortion as well as an independent control in each phase, compared with the conventional three-phase NPC topology. Simulated results confirm the implementation viability of the proposed active power filter topology and associated control strategy.
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    DC link fuzzy control for an active power filter, sensing the line current only
    (IEEE, 1997) Dixon Rojas, Juan, 1948-; Contardo Guevara, Jaime; L. Moran
    A different approach for controlling a shunt active power filter is presented. The DC link is controlled with fuzzy logic, and the current generated for the filter to compensate harmonics and power factor is not sensed. The sensors acts directly on the mains line currents, forcing them to be sinusoidal, and in phase with the mains voltage supply. The amplitude of the current is controlled by the fuzzy system, which operates through the error between the DC link voltage of the PWM modulator (active power filter), and a pre-established reference voltage, Vref. The main advantages of this approach are the following: (a) the control block becomes simpler because there is no need to evaluate the current template for the filter currents; (b) the DC link fuzzy control has better dynamic behavior than conventional PI control; and (c) the filter can operate simultaneously as a power factor compensator, and as a four quadrant rectifier-inverter system.
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    Fault-Tolerant Reconfiguration System for Asymmetric Multilevel Converters Using Bidirectional Power Switches
    (IEEE, 2009) Barriuso, Pablo; Dixon Rojas, Juan, 1948-; Flores Lara, Patricio Armando; Moran, Luis
    Asymmetric multilevel converters can optimize the number of levels by using H-bridges scaled in the power of three. The shortcoming of this topology is that the H-bridges are not interchangeable, and then, under certain faulty conditions, the converter cannot operate. A reconfiguration system based on bidirectional electronic valves has been designed for three-phase cascaded H-bridge inverters. Once a fault is detected in any of the insulated gate bipolar transistors of any H-bridge, the control is capable to reconfigure the hardware keeping the higher power bridges in operation. In this way, the faulty phase can continue working at the same voltage level by adjusting its gating signals. Some simulations and experiments with a 27-level inverter, to show the operation of the system under a faulty condition, are displayed.
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    High-Frequency Link: A Solution for Using Only One DC Source in Asymmetric Cascaded Multilevel Inverters
    (IEEE, 2011) Pereda Torres, Javier Eduardo; Dixon Rojas, Juan, 1948-
    Multilevel inverters are in state-of-the-art power conversion systems due to their improved voltage and current waveforms. Cascaded H-bridge (CHB) multilevel inverters have been considered as an alternative in the medium-voltage converter market and experimental electric vehicles. Their variant, the asymmetrical CHB (ACHB) inverter, optimizes the number of voltage levels by using dc supplies with different voltages. However, the CHB and ACHB inverters require a large number of bidirectional and isolated dc supplies that must be balanced, and as any multilevel inverter, they reduce the power quality with the voltage amplitude. This paper presents a solution to improve the already mentioned drawbacks of ACHB inverters by using a high-frequency link using only one dc power source. This single power source can be selected according to the application (regenerative, nonregenerative, and with variable or permanent voltage amplitude). This paper shows the experimental results of a 27-level ACHB inverter with a variable and single dc source, but the strategy can be applied to any ACHB inverter with any single dc source. As a result, the reduction of active semiconductors, transformers, and total harmonic distortion was achieved using only one dc power source.
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    Multilevel inverter, based on multi-stage connection of three-level converters scaled in power of three
    (IEEE, 2002) Dixon Rojas, Juan, 1948-; Morán, L
    A multi-stage inverter using three-state converters is being analyzed for multipurpose applications, such as active power filters, static VAr compensators and machine drives for sinusoidal and trapezoidal current applications. The great advantage of this kind of converter is the minimum harmonic distortion obtained. The drawbacks are the isolated power supplies required for each one of the stages of the multiconverter. In this paper this problem has been overcome by using isolated, bidirectional DC power supplies, which are fed from a common power source. This solution becomes practical because only one converter of the chain, called Master, takes more than 80% of the total active power required by the system. The rest of the converters, called "Slaves", need very low power, and then those DC supplies are small. Another configuration with common DC supply and output transformers is displayed, and simulation results for different applications are shown and compared with similar results obtained with conventional PWM converters. The control of this multi-converter is being implemented using DSP controllers, which give flexibility to the system.
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    Passive Filters for High Power Cycloconverter Grinding Mill Drives
    (IEEE, 2009) Aravena, Pablo; Vallebuona, Giovanni; Moran, Luis; Dixon Rojas, Juan, 1948-; Godoy, Orlando
    This paper presents a design method for passive filters used to compensate power factor and current harmonics generated by high power cycloconverter drives. The paper includes the analysis of different passive filter topologies effectiveness (band-pass, high-pass and C type), a procedure to calculate filter parameters, tuning frequency selection, and reactive power distribution. The passive filters are designed to compensate high power grinding mill drives energized from cycloconverters. Simulated results based on a real grinding mill plant prove the effectiveness of the proposed method.
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    PWM regenerative rectifiers: state of the art
    (IEEE, 2005) Rodriguez, J.R.; Dixon Rojas, Juan, 1948-; Espinoza, J.R.; Pontt, J.; Lezana, P.
    New regulations impose more stringent limits on current harmonics injected by power converters that are achieved with pulsewidth-modulated (PWM) rectifiers. In addition, several applications demand the capability of power regeneration to the power supply. This work presents the state of the art in the field of regenerative rectifiers with reduced input harmonics and improved power factor. Regenerative rectifiers are able to deliver energy back from the dc side to the ac power supply. Topologies for single- and three-phase power supplies are considered with their corresponding control strategies. Special attention is given to the application of voltage- and current-source PWM rectifiers in different processes with a power range from a few kilowatts up to several megawatts. This paper shows that PWM regenerative rectifiers are a highly developed and mature technology with a wide industrial acceptance.
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    Static Var Compensator and Active Power Filter With Power Injection Capability, Using 27-Level Inverters and Photovoltaic Cells
    (IEEE, 2009) Flores Lara, Patricio Armando; Dixon Rojas, Juan, 1948-; Ortuzar, Micah; Carmi, Rodrigo; Barriuso, Pablo; Moran, Luis
    An active power filter and static var compensator with active power generation capability has been implemented using a 27-level inverter. Each phase of this inverter is composed of three ldquoHrdquo bridges, all of them connected to the same dc link and their outputs connected through output transformers scaled in the power of three. The filter can compensate load currents with a high harmonic content and a low power factor, resulting in sinusoidal currents from the source. To take advantage of this compensator, the dc link, instead of a capacitor, uses a battery pack, which is charged from a photovoltaic array connected to the batteries through a maximum power point tracker. This combined topology make it possible to produce active power and even to feed the loads during prolonged voltage outages. Simulation results for this application are shown, and some experiments with a 3-kVA device are displayed.