Showing papers by "Instituto Tecnológico de Morelia published in 2012"

Modelling of a wind turbine with permanent magnet synchronous generator

Abstract: This investigation presents the implementation and simulation of a Simulink-based controlled permanent magnet synchronous generator (PMSG) wind turbine in the dq0 reference frame. The model consists of a current control subsystem, a PMSG model, a mechanical subsystem, a pitch angle controller and a wind turbine model. The current control subsystem makes use of PI controllers governing the wind turbine speed, the direct and quadrature stator currents and the pitch angle of the turbine blades. The pitch angle controller measures the speed and the active power from the generator limiting both in case of high-speed wind conditions. In order to verify the functioning and the effectiveness of the proposed controllers, simulations- for different operation conditions- are presented and discussed.

A bibliographic analysis of transformer literature 2001-2010

Abstract: This paper analyzes the bibliography on transformer research covering the period of 2001-2010. Due to the large number of publications in peer review journals, conferences and symposia contributions were not included. That is why 22 peer review journals were investigated, in which 933 papers including the word “transformer” in their title have been published in the decade 2001-2010. The most productive and high-impact authors and countries are identified. The four most productive countries are Japan, USA, China, and Canada. More than 75 citations were received by each one of the five most cited papers. The bibliographic research presented in this paper is important because it includes and analyzes the best research papers on transformers coming from many countries all over the world and published in top rated scientific electrical engineering journals. (6 pages)

Scaling the virtual air-gap principle to high voltage large power applications

Abstract: Fixed or variable reactors are required in modern high voltage transmission systems. The virtual air-gap principle offers an alternative avenue for the development of controllable compensation devices to overcome voltage regulation problems in high voltage transmission systems. In this paper the scaling of the virtual air-gap principle to high voltage and large power devices is considered. A novel conceptual design of a Virtual Gap Reactor (VGR) is developed, and its configuration and essential working principle are discussed in order to clarify the design possibilities and manufacturing constraints of such a device.

State of the art, modeling and simulation of an advanced power electronics transformer

Abstract: This paper presents a state of the art on electronic transformer, whose structure is based on power electronic devices and high-frequency electromagnetic induction It has the capability to handle bidirectional flow of active and reactive power for different input-output voltage ratios and mitigate voltage disturbances and harmonic voltage and / or current These features overcome the current limitations of distribution transformers, thus improving power quality and preserving the characteristics of voltage conditioning This paper describes the evolution of electronic transformers as a generational change in the traditional distribution transformers, with the advantage of control added capacity for the benefit of users and the electric network

Asymptotic methods for calculating electric arc model parameters

Abstract: A new method for calculating the parameters of electric arc models for power circuit breaker is developed. The methodology consists in the optimization of the theoretical arc voltage curve, as a function of a set of parameters, with respect to experimental data. Since the solution of the equation for the electric arc model cannot be obtained in general form, then, the theoretical arc voltage is an asymptotic solution obtained for one or several time-ranges. A case of the irregular behavior of the electric arc is analyzed. The developed methods are applied to obtain an improved arc model for a SF6 power circuit breaker previously published in the literature. The new model has a compact form and exhibits a good correlation between the measured and calculated voltage curves.

Experimental validation of a new methodology to reduce hot spots on the screws of power transformer tanks

Abstract: In power transformers, the presence of stray currents in the structural elements near to the high current bushings can be considerable and this usually leads to hot spots. This work presents the analysis of the overheating of the screws that join the tank and the cover; these screws are near to the low voltage bushings of the transformer. Overheating results are analyzed and discussed for the case of a 420 MVA, 20/230 kV, OA/FOA transformer. The hot spots in the screws are discovered by thermal maps (thermography) that are obtained during the power transformer operation as part of the preventive maintenance program. This paper proposes the use of copper sill to ensure the connection of both the cover and the tank body because this solution significantly reduces the overheating of the screws. The proposed solution, which has been validated by measurements, significantly reduces the hot spots on the screws of power transformer tank.

Isolation, molecular and fermentative characterization of a yeast used in ethanol production during mezcal elaboration

Abstract: Numerous ecological studies have been conducted over the years to understand the dynamics, quantification, and composition of the microflora responsible for ...

Modeling and Analysis of Three-phase Diode Bridge Rectifiers as Linear Complementarity Systems

Abstract: This article presents the use of complementarity formalism to derive compact representations of models for electrical circuits that contain resistors, capacitors, sources, and diodes. As an important application, models will be developed in order to describe the behavior of an important class of electric power components: the diode bridge rectifiers. There are two important advantages of complementarity models. First, the theory of the complementarity systems aims at providing a compact representation of many such systems, especially in comparison with conventionally used switched models. Second, complementarity modeling offers powerful methods for analysis. For instance, by using the well-developed theory of the linear complementarity problem from the optimization theory, one may prove strong results such as the existence and uniqueness of solutions. The article shows also that the steady state of diode bridge rectifiers can be computed directly by means of non-iterative methods, and its existen...

Generation companies' adaptive bidding strategies using finite-state automata in a single-sided electricity market

Abstract: SUMMARY This paper explores the use of genetic algorithms (GAs) in the development of the bidding strategies used by generation companies under two different market clearing mechanisms, uniform pricing and pay-as-bid pricing. The bidding strategies are represented by two modifications of a classical data processing structure known as finite-state automata. Semi-fixed fitness function and co-evolutionary fitness function were incorporated in our GA. A third simple representation to obtain a comparison baseline for the other two representations, showing how their behaviors compare with a “standard” solution, was also incorporated. The strategies developed by our method were adaptive, and all GA types were based on maximizing profit in a competitive bidding situation. Copyright © 2011 John Wiley & Sons, Ltd.

A Control System for Static VAr Compensator Based on a Digitally Controlled Oscillator

Abstract: This article deals with the design, construction, and testing of a new control system for a static VAr compensator. The new control system is based on monitoring reactive power, which is used as the only feedback variable for a digitally controlled oscillator. In addition to synchronizing the static VAr compensator with the AC system, the digitally controlled oscillator also schedules the firing of converter valves in order to achieve the reactive power compensation level required in the AC connection bus. The control system design was initially developed in MATLAB® and Simulink® (The MathWorks, Natick, Massachusetts, USA), and then a ±1-KVAr static VAr compensator experimental prototype was built. The static VAr compensator control system was implemented in a PIC16F877 microcontroller (Microchip Technology Inc., Chandler, Arizona, USA). Computer simulations and experimental results for the static VAr compensator and its control system are presented in the article. Finally, the performance of the...

Mathematical Model of Thermal and Microstructural Evolution during Austempering of Ductile Iron

Abstract: Austempering of ductile iron is a heat treating process designed to improve the mechanical properties of ductile iron: Increasing its strength and wear resistance while maintaining the tenacity and ductility associated with the untreated condition. This task is achieved by rapidly cooling the part from the austenitizing temperature to the austempering temperature and holding it during a specific time. Austempering promotes the formation of an ausferrite matrix, i.e., a mixture of bainitic ferrite and retained austenite, along with graphite nodules. In order to achieve the required microstructural control, a detailed knowledge of the phase transformation evolution coupled with a heat transfer analysis is required. Thus a thermostructural model has been developed to simulate the phase transformations during austempering of a ductile iron cylindrical probe. The thermal and microstructural submodels were coupled within the Abaqus software. The predictions were validated by austempering ductile iron probes from an austenitizing temperature of 920°C to an austempering temperature of 300°C in a molten salt bath and comparing predictions versus experimental data. It was concluded that the model is suitable to predict the thermal behavior and the final microstructure of the austempered ductile iron.

Computational Fluid Dynamics in the Carbon Nanotubes Synthesis by Chemical Vapor Deposition

Abstract: In this paper, an experimental study aimed at achieving better control of the deposition patterns of carbon nanotubes (CNTs) is presented. CNTs were grown on a long of reactor by the catalytic chemical vapor deposition (CVD) of a benzene/ferrocene solution at 1073 K. The deposition patterns on the substrate were controlled for process times and carrier gas flow rates. In order to investigate the reaction mechanism and production rate for the growth of CNTs in catalyst CVD, computational fluid dynamics (CFD) model was developed in this study. Then the computational model was integrated with the dynamic model to optimize the process parameters formulating a correlation between turbulence, deposition rate for the growth of carbon nanotubes and parameters as process time and carrier gas flow rate. Scanning electron microscopes (SEM) are used to characterize carbon nanotubes products.

Effect of Water Temperature on Wetting Front Kinematics during Forced Convective Quenching

Abstract: The kinematics of the wetting front, i.e., the history of the locus of the boundary between the vapor blanket and the nucleate boiling area is of outmost importance in quenching operations. In this investigation, the effect of water temperature on the wetting front kinematics was studied in forced convective quenching experiments of conical-end cylindrical probes. Three values of water temperature (30, 45 and 60 °C) were studied for a free-stream water velocity of 0.2 m/s. The wetting front kinematics was characterized from: 1) the measured thermal response at three longitudinal positions inside the probe, near the probe surface, and 2) high-speed video-recordings of the events that took place at the probe surface upon quenching. From the video-recordings, the position of the wetting front as a function of time was determined to estimate the wetting front velocity from a linear regression. The wetting front velocity was constant for a given experiment and increased as the water temperature decreased. The bubble size decreased and the frequency of bubble formation increased as the water temperature decreased. Using the measured thermal responses, the surface heat flux history was estimated, solving the corresponding inverse heat conduction problem. A regression analysis was applied to relate the maximum (critical) surface heat flux and the water temperature as a first step towards modeling the surface heat flux history as a function of water temperature.

Single DC multilevel hybrid topology

Abstract: This paper proposes a new structure of DC-AC multilevel converters which is developed by combining a modification of a DC-DC buck converter and a DC-AC hybrid multilevel converter with cascade configuration and a ratio of 1∶1.5. The buck converter is used to obtain two independent voltage sources from a single power supply without using transformer. The advantages of this configuration are: it does not require isolated power supplies and has a high power density because it does not use transformers.

Study of parameters influencing the performance of connectors used for load and temperature tests on transformers

Abstract: This paper emphasizes the factors to be considered when designing power connectors used in the load and temperature tests of power transformers. External conductors used to perform load and temperature tests in transformers are referred as power connectors in this contribution. Electrical and thermal investigations of a single-phase shell-type, 300 MVA, 400 kV–21.5 kV power transformer connector were performed. To analyze the behavior of the connector, a harmonic analysis to calculate losses by Joule effect generated in the electrical connector was first performed, followed by a thermal, finite element based analysis to determine temperature distribution. As heat sources, harmonic losses analyses were performed. Temperature distribution obtained by the finite element simulation was compared with measurements recorded by an infrared camera during the tests.

Switched reluctance motor control in two-quadrants with electric vehicle applications

Abstract: This paper presents a three-phase switched reluctance motor control with a 6/4 configuration in two operation quadrants of the machine torque-angular speed. The switched reluctance motor plays an important role in the electric vehicle propulsion system; the aim of the control system is to achieve a speed trajectory tracking commanded by an urban driving cycle. A control scheme is proposed involving the Direct Instantaneous Torque Control technique and a current hysteresis control for the two operation quadrants C I and C IV respectively. Simulation results are presented with a satisfactory torque, speed and current tracking.

Effect of Slag on Mixing Time in Gas-Stirred Ladles Assisted with a Physical Model

Abstract: A 1/6th water physical model of a 140 tons gas-stirred steel ladle is used to evaluate mixing times (τm at 95% of chemical uniformity) in a two phase system without slag (air-water) and in a more realistic three phase system (air-water-oil) to simulate the argon-steel-slag system and quantify the effect of the slag layer on the mixing time. Slag layer is kept constant at 0.004 m. Mixing times are estimated through measured changes in pH due to the addition of a tracer (NaOH 1 M). The effect of the following variables on the mixing time is evaluated for a single injector: gas flow rate (7, 17 y 37 l/min) and the injector position (R/r= 0, 1/3, ½, 2/3 and 4/5). Experimental results obtained in this work show good agreement when compared against mixing time correlations reported by Mazumdar for the two phase air-water case (no slag considered). Another comparison is done using the new concept called “effective bath height” proposed by Barati, where the mixing time is a function of the size of the slag layer since this layer dissipates part of the total amount of stirring energy introduced into the ladle by the injection of gas. Agreement is not good in this case. Finally, an estimation of the percentage of the stirring energy dissipated by the slag is computed, including other factors that govern the dissipation of stirring energy. Percentage of energy dissipated by the slag is found to be between 2.7 to 12 % depending on the process conditions.

Photoplethysmographic augmentation index using the signal fourth derivative

Abstract: This work aimed to provide, that using the derivatives of photoplethysmographic signal enhance the location of inflection points. Furthermore, using the signal fourth derivative, it is possible to locate inflections points as photoplethysmographic augmentation index (PAI). A computing photoplethysmographic analyzer was developed. The first, second, third and fourth derivatives were obtained by the mean square error interpolation method. The PAI was quantified by fourth derivative. PAI was calculated similar to augmentation index for pressure (AIx). The AIx is obtained as the difference between late and early systolic inflections expressed as a percentage of the pulse pressure. A study with 36 people, 18 healthy volunteers and 18 subjects with previously diagnosed cardiovascular disease was carried out. A t-tested distribution between healthy volunteers and patients showed a significant differences in calculated PAI (0.0231 vs 0.4678, p < 0.0001). In conclusion, PAI has shown to be a noninvasive indicator for vascular assessments. Using the fourth derivative, inflection point identification on the photoplethysmographic signal is more accurate mainly in subjects with previously diagnosed cardiovascular disease.

Influence of pore hERG mutation on dofetilide proarrhythmic risk

Abstract: The aim of this work was to study the influence of pore KCNH2 mutation on the effects of dofetilide Markovian models of G604S/WT mutation and dofetilide have been introduced in guinea pig ventricular cellular model The effects of this pore mutation affecting this channel were analyzed The G604S/WT mutation accelerates the inactivation and recovery from inactivation Using this mutated cellular model we have studied the effects of dofetilide concentrations (I Kr blocker) The results showed that the reduction of G Kr is the main factor in the APD prolongation in the case of G604S/WT mutation The shift of the inactivation curve and the recovery from inactivation to the left accelerates the transition between the open and inactivated states The action of dofetilide prolongs the APD in the G604S/WT epicardial and endocardial cells and even provokes EADs development in endocardial cells In addition, exposure of G604S/WT to this drug amplifies the amplitude of the EADs generated in midmyocardial cells by the mutation alone In conclusion, the heterozygous G604S hERG mutation increases the proarrhythmic risk of dofetilide prolonging the APD and enhancing the dispersion of repolarization