Capelli, F.; Riba, J.; Gonzalez, D. International Conference on Power Engineering, Energy and Electrical Drives p. 104-109 DOI: 10.1109/CPE.2016.7544167 Presentation's date: 2016-06-29 Presentation of work at congresses
The contact resistance is the key variable that characterizes the stable performance and long-term service of an electrical connection. It is worth noting that the contact resistance in substation connectors can be several times that of the connector's resistance. To reduce connection losses and thus decrease connector's operating temperature, it is important to minimize contact resistance. The aim of this work is to characterize the relationship between the surface preparation, the resulting contact resistance and the thermal performance of substation connectors. First, the thermal behavior of substation connectors assembled with the traditional and a new installation method proposed by the authors has been characterized. It has been done by means of experimental temperature rise test and current cycle test. Thanks to these results, it has been proved that the new installation procedure allows reducing connector's temperature in operating conditions as well as the variability of the electrical resistance among different samples due to thermal stress. Moreover, by means of experimental measurements, the temperature dependence of the contact resistance has been analyzed, with the objective to characterize the performance of an electrical contact under different operating temperatures. To determine the temperature coefficient of the contact resistance, an experimental resistance measurement has been continuously performed during the cooling of a contact interface, previously heated at 200 °C. This value can be very useful for an optimal design of the substation connectors.
En l'actual situació de l'energia, amb un pronosticat augment del consum energètic en un context d'esgotament dels combustibles fòssils, s'està posant més atenció en les fonts d'energia renovable per generació elèctrica. Per millorar el seu desplegament arreu, els sistemes híbrids d'energia renovable són una alternativa en puixança, donat que aquests poden aprofitar l'escalabilitat i flexibilitat de les fonts d'energia renovable donat que la combinació de dues o més fonts permet contrarrestar les debilitats d'una font d'energia no controlable amb les fortaleses d'una altra o amb la controlabilitat d'una font d'energia no renovable.Aquest treall presenta una metodologia d'optimització que ha estat desenvolupada per a optimització del cost de cicle de vida i per la optimització multi-objectiu de cost i impacte ambiental (IA) de cicle vida d'un sistema híbrid d'energia renovable connectat a la xarxa elèctrica i basat en l'ús de les energies solar fotovoltaica (FV), eòlica i de la biomassa. En aquest sistema l'ús de la biomassa busca l'aprofitament del recurs forestal autòcton en forma de 'wood chips' per proporcionar energia en aquells períodes en els què les energies FV i eòlica no són suficients per a subministrar la demanda existent i, addicionalment, produïr energia tèrmica adoptant un esquema de cogeneració. El model desenvolupat ha estat testat i validat en un municipi rural situat a la Catalunya central i utilitzant dades reals de velocitat de vent, irradiació solar i demanda elèctrica amb una precisió horària.Per a evaluar diferents situacions i disposicions del sistema, s'han dut a terme 4 casos d'estudi, i el model ha estat adaptat a cada una de les situacions analitzades. També s'han dut a terme anàlisis de sensibilitat que permeten detectar a quines variables és més sensible el model i el sistema de producció elèctrica. En tots els casos, el model respon adequadament als canvis implementats en les dades d'entrada, a la vegada que proporciona resultats del dimensionat òptim del sistema.Fixant-nos en un sistema FV - eòlic, els resultats de la seva optimització de cost mostren que seria econòmicament viable la seva instal·lació en la localització evaluada, amb un període de retorn de la inversió de 18 anys dels 25 anys de vida útil del sistema.Si ens fixem en un sistema FV - eòlic - biomassa, els resulstats mostren que el sistema requereix de menys inversió inicial que l'anterior, avantatge contrarrestat per un cost de cicle de vida major. No obstant, aquest sistema aportaria beneficis en termes d'autonomia energètica, millora de qualitat ambiental i en creació de llocs de treball derivats del processat de la biomassa forestal, una font intensiva en demanda de llocs de treball.El mateix sistema també s'ha analitzat des d'una perspectiva multi-criteri, considerant també l'IA. En aquest cas, els resultats mostren que cost i impacte ambiental són criteris contradictoris: sistemes de baix IA tenen costs més elevats que aquells que se sustenten en l'energia de la xarxa elèctrica, que presenta un elevat IA. Els resultats també mostren que la millora de la taxa de retorn de la inversió seria una mesura molt beneficiosa per fomentar l'ús de les energies renovables per a la generació d'electricitat degut al seus retorns positius en termes de reducció de cost i IA.La darrera hipòtesi analitzada ha estat l'adopció d'un esquema de cogeneració. En aquest cas, el sistema mostra menors períodes de retorn de la inversió, fent-lo rentable a partir dels 10 anys. Això es deu a la utilització de l'energia tèrmica produïda en la valorització energètica de la biomassa, que té efectes en la millora de l'eficiència al aprofitar energia que d'altra manera es malbarata. Els balanços entre cost i impacte ambiental mostren de nou que petites inversions en energia renovable tenen grans retorns en termes de reducció de l'IA, en especial partint d'un sistema elèctric on més d'un 50% de fonts energètiques són combustibles fòssils amb elevat IA.
Power devices intended for high-voltage systems must be tested according to international standards, which includes the short-time withstand current test and peak withstand current test. However, these tests require very special facilities which consume huge amounts of electrical power. Therefore, mathematical tools to simulate such tests are highly appealing since they allow reproducing the electromagnetic and thermal behavior of the test object in a fast and economical manner. In this paper, a three-dimensional finite element method (3D-FEM) approach to simulate the transient thermal behavior of substation connectors is presented and validated against experimental data. To this end, a multiphysics 3D-FEM method is proposed, which considers both the connector and the reference power conductors. The transient and steady-state temperature profiles of both the conductors and connector provided by the 3D-FEM method prove its suitability and accuracy as compared to experimental data provided by short-circuit tests conducted in two high-current laboratories. The proposed simulation tool, which was proven to be accurate and realistic, may be particularly useful during the design and optimization phases of substation connectors since it allows anticipating the results of mandatory laboratory tests.
Several factors including fossil fuels scarcity, prices volatility, greenhouse gas emissions or current pollution levels in metropolitan areas are forcing the development of greener transportation systems based on more efficient electric and hybrid vehicles. Most of the current hybrid electric vehicles use electric motors containing powerful rare-earth permanent magnets. However, both private companies and estates are aware of possible future shortages, price uncertainty and geographical concentration of some critical rare-earth elements needed to manufacture such magnets. Therefore, there is a growing interest in developing electric motors for vehicular propulsion systems without rare-earth permanent magnets. In this paper this problematic is addressed and the state-of-the-art of the electric motor technologies for vehicular propulsion systems is reviewed, where the features required, design considerations and restrictions are addressed.
Natural rubber matrix, reinforced with several conventional stabilizer additives, was further charged with perovskite nanoparticles. Although the addition of BaTiO3 ceramic particles usually transforms a non-conducting pristine polymer into a more conductive polymer composite, in this case we use the addition of a few percent of BaTiO3 (less than 1 wt.%) to decrease the effective electrical conductivity of natural rubber (NR). This reduction has been attributed to the synergistic effect between ceramic particles and the amorphous phase of the polymer matrix, which allowed decreasing the interfacial polarisation among the NR/oxide particles interfaces. Electrical tests clearly indicate that the breakdown voltage increases and the leakage current decreases, whereas the mechanical and hydrophobicity properties of solid films improve after accurate sonication of all solid particles before pre-vulcanization process. Therefore, the dielectric elastomer becomes more insulating with the addition of nanometric oxide particles.
Giacometto, Francisco javier; Capelli, F.; Sala, E.; Riba, J.; Romeral, L. Annual Conference of the IEEE Industrial Electronics Society p. 003957-003962 DOI: 10.1109/IECON.2015.7392717 Presentation's date: 2015-11-11 Presentation of work at congresses
A wide study regarding the suitability of data-driven modelling applied to the prediction of thermal convection responses on substation connectors is presented in this paper. The study starts with the compilation of a database with thermal profiles obtained from a finite element method simulation (FEM). Afterwards, we applied partitioning methods in order to increase the number of data sets used for modelling and later evaluate the stability of the learning algorithms. After the modeling process, the accuracy of the model per each data set is measured and the statistics about the errors are analyzed. Normality test are applied to measure the error variance. They bring us information about the error distribution and the stability of the learning algorithms. The study finish when it probes that any data-driven model is computationally less time expensive than any FEM simulation running on this study. Experimental work also confirms that the accuracy of the data-driven models: cascade feed forward neural network and feed forward neural network, can replace the FEM simulations; providing a high accuracy and a low error variance while speeding up the simulation time.
The contact resistance is the main variable that defines the energy efficiency of an electrical connection, its stable performance and long term service. It is worth noting that according to the measurements performed in this work, the contact resistance in substation connectors can be several times that of the connector’s resistance. To reduce connection losses and thus increase connector’s efficiency, it is important to minimize contact resistance, to ensure an efficient connection. The aim of this work is to find out, by means of experimental measurements, the relationship between the different components of contact resistance in substation connectors and the main related variables such as material properties, applied bolts torque, true contact area, or surface’s conditions among others. Furthermore, this study proposes a novel surface treatment for substation connectors, which allows reducing the contact resistance. Experimental measurements demonstrate the effectiveness of the novel chemical treatment in improving energy efficiency in substation connectors.
Skin and proximity effects in single- or multi-conductor systems can notoriously affect the AC resistance in conductors intended for electrical power transmission and distribution systems and for electronic devices. This increase of the AC resistance raises power loss and limits the conductors' current-carrying capacity, being an important design parameter. There are some internationally recognized exact and approximated formulas to calculate the AC resistance of conductors, whose accuracy and applicability is evaluated in this paper. However, since these formulas can be applied under a wide range of configurations and operating conditions, it is necessary to evaluate the applicability of these models. This is done by comparing the results that they provide with experimental data and finite element method (FEM) simulation results. The results provided show that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied to a wide range of conductors' configurations and electrical frequencies
Skin and proximity effects in single- or multi-conductor systems can notoriously affect the AC
resistance in conductors intended for electrical power transmission and distribution systems and for
electronic devices. This increase of the AC resistance raises power loss and limits the conductors’ currentcarrying
capacity, being an important design parameter. There are some internationally recognized exact
and approximated formulas to calculate the AC resistance of conductors, whose accuracy and applicability
is evaluated in this paper. However, since these formulas can be applied under a wide range of
configurations and operating conditions, it is necessary to evaluate the applicability of these models. This is
done by comparing the results that they provide with experimental data and finite element method (FEM)
simulation results. The results provided show that FEM results are very accurate and more general than
those provided by the formulas, since FEM models can be applied to a wide range of conductors’
configurations and electrical frequencies
This paper presents a design tool for Induction
Machines, Permanent Magnet Synchronous Machines,
Externally Excited Synchronous Machines and
Switched Reluctance Machines. This software, based
on Modelica language, is able to provide full
dimensioning (cross and axial section measures) and
operation characteristics according to mechanical and
electrical requirements set as inputs. The tool is able to
perform error handling, which informs a designer about
unfeasible designs and gives clues about the possible
errors. Both aspects of the tool GUI and scripts provide
help files and code explanation in order to re-use the
tool and improve library’s functionalities.
Hybrid renewable energy systems (HRES) are a trendy alternative to enhance the renewable energy deployment worldwide. They effectively take advantage of scalability and flexibility of these energy sources, since combining two or more allows counteracting the weaknesses of a stochastic renewable energy source with the strengths of another or with the predictability of a non-renewable energy source. This work presents an optimization methodology for minimum life cycle cost of a HRES based on solar photovoltaic, wind and biomass power. Biomass power seeks to take advantage of locally
available forest wood biomass in the form of wood chips to provide energy in periods when the PV and wind power generated are not enough to match the existing demand. The results show that a HRES combining the selected three sources of renewable energy could
be installed in a rural township of about 1300 dwellings with an up-front investment of US $7.4 million, with a total life cycle cost of slightly more than US $30 million. Such a system would have benefits in terms of energy autonomy and environment quality
improvement, as well as in term of job opportunity creation
Hybrid renewable energy systems (HRES) have been widely identified as an efficient mechanism to generate electrical power based on renewable energy sources (RES). This kind of energy generation systems are based on the combination of one or more RES allowing to complement the weaknesses of one with strengths of another and, therefore, reducing installation costs with an optimized installation. To do so, optimization methodologies are a trendy mechanism because they allow attaining optimal solutions given a certain set of input parameters and variables. This work is focused on the optimal sizing of hybrid grid-connected photovoltaic-wind power systems from real hourly wind and solar irradiation data and electricity demand from a certain location. The proposed methodology is capable of finding the sizing that leads to a minimum life cycle cost of the system while matching the electricity supply with the local demand. In the present article, the methodology is tested by means of a case study in which the actual hourly electricity retail and market prices have been implemented to obtain realistic estimations of life cycle costs and benefits. A sensitivity analysis that allows detecting to which variables the system is more sensitive has also been performed. Results presented show that the model responds well to changes in the input parameters and variables while providing trustworthy sizing solutions. According to these results, a grid-connected HRES consisting of photovoltaic (PV) and wind power technologies would be economically profitable in the studied rural township in the Mediterranean climate region of central Catalonia (Spain), being the system paid off after 18 years of operation out of 25 years of system lifetime. Although the annual costs of the system are notably lower compared with the cost of electricity purchase, which is the current alternative, a significant upfront investment of over $10 M - roughly two thirds of total system lifetime cost - would be required to install such system. (C) 2015 Elsevier Ltd. All rights reserved.
This paper analyzes the skin and proximity effects in different conductive nonmagnetic straight conductor configurations subjected to applied alternating currents and voltages. These effects have important consequences, including a rise of the ac resistance, which in turn increases power loss, thus limiting the rating for the conductor. Alternating current (ac) resistance is important in power conductors and bus bars for line frequency applications, as well as in smaller conductors for high frequency applications. Despite the importance of this topic, it is not usually analyzed in detail in undergraduate and even in graduate studies. To address this, this paper compares the results provided by available exact formulas for simple geometries with those obtained by means of two-dimensional finite element method (FEM) simulations and experimental results. The paper also shows that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied in a wide range of electrical frequencies and configurations.
This paper analyzes the skin and proximity effects in different conductive nonmagnetic straight conductors’ configurations subjected to applied alternating currents and voltages. These effects have important consequences, including a rise of the ac resistance, which in turn increases power loss, thus limiting the rating for the conductor. The alternating current (ac) resistance is important in power conductors and bus bars for line frequency applications as well as in smaller conductors for high frequency applications. Despite the importance of this topic, it is usually not analyzed in detail in undergraduate and even in graduate studies. For this purpose, this paper compares the results provided by available exact formulas for simple geometries with those obtained by means of two-dimensional finite element method (FEM) simulations and experimental results. The paper also shows that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied in a wide range of electrical frequencies and configurations
Paperboard is widely used in different applications, such as packaging and graphic printing, among others. Consumption of recycled paper is growing, which has led the paper-mill packaging industry to apply strict quality controls. This means that it is very important to develop methods to test the quality of recycled products. In this article, we focus on determining the recoveredfiber content of paperboard samples by applying Fourier transform mid-infrared (FT-MIR) spectroscopy in combination with multivariate statistical methods. To this end, two very fast, nondestructive approaches were applied: classification and quantification. The first approach is based on classifying unknown paperboard samples into two groups: high and low recovered-fiber content. Conversely, under the quantification approach, the content of recovered fiber in the incoming paperboard samples is determined. The experimental results presented in this article show that the classification approach, which classifies unknown incoming paperboard samples, is highly accurate and that the quantification approach has a root mean square error of prediction of about 4.1
Capelli, F.; Riba, J.; González, D. IEEE International Conference on Industrial Technology p. 1368-1374 DOI: 10.1109/ICIT.2015.7125288 Presentation's date: 2015-03-19 Presentation of work at congresses
One of the main problems that arises when
performing short-circuit tests to large loops involving substation
connectors is the inductive component of the loop impedance.
Transformers used to perform short-circuit tests have a
secondary winding with very few turns, producing a very low
output voltage. The increase in the reactive component of the
impedance, which is related to loop size, limits the current output
capacity, because the reactive component tends to saturate the
output of the transformer and absorbs large amounts of reactive
power. This paper analyzes a simple method to minimize the
power requirements when conducting short-circuit tests, based
on the reduction of reactive power consumption during the test.
It is based on placing a wired conductor forming a closed inner
loop concentric with the testing loop. The decrease of reactive
power is related to the effect of the mutual inductance between
the inner and outer loops. Three-dimensional finite element
method (3D-FEM) simulations are used to optimize the problem,
allowing changing the geometric and material properties of the
inner loop. Experimental results validate the simulation method
applied in this work to optimize the short-circuit tests
This work analyzes the behavior of surface-mounted permanent magnet synchronous motors (SPMSMs) operating under stator faults. The studied faults are resistive unbalance and winding inter-turn short circuits, which may lead to unbalanced conditions of the motor. Both faults may reduce motor efficiency and performance and produce premature ageing. This work develops an analytical model of the motor when operating under stator faults. By this way, the theoretical basis to understand the effects of resistive unbalance and stator winding inter-turn faults in SPMSMs is settied. This work also compares two methods for detecting and discriminating both faults. For this purpose, a method based on the analysis of the zero-sequence voltage component is presented, which is compared to the traditional method, i.e. the analysis of the stator currents harmonics. Both simulation and experimental results presented in this work show the potential of the zero-sequence voltage component method to provide helpful and reliable data to carry out a simultaneous diagnosis of resistive unbalance and stator winding inter-turn faults.
La publicación final está disponible en Springer a través de 10.1007/s00202-014-0316-z
Debido a las nuevas políticas de conservación medio ambiental, los vehículos eléctricos toman una posición más importante en la sociedad actual. Los motores eléctricos constituyen el corazón de la cadena de tracción de un EV, por esta razón se debe encaminar la investigación hacia el diseño de motores de mayor eficiencia y fiabilidad. Este trabajo se enfoca en el análisis y diseño óptimo de un motor de flujo axial con tolerancia a fallos. Como base, se parte de la investigación de los procedimientos analíticos de diseño de motores eléctricos y del estudio de los efectos de los fallos eléctricos en elcomportamiento de estos, de acuerdo a la configuración específica de cada máquina. Para desarrollar esta tesis se hará uso de herramientas analíticas y de métodos de simulación basados en métodos finitos (FEM). En primera parte se hace un estudio del estado del arte del diseño de motores eléctricos tolerantes a fallos, en el cual se identifican las posibles configuraciones a usar y las principales reglas de diseño de estos motores. Debido a que las consecuencias de un cortocircuito entre espiras pueden ser catastróficas para el motor de imanes permanentes, en el siguiente capítulo se analiza su efecto en dependencia de la configuración de los devanados del motor, además de su posible detección. Ladetección del cortocircuito se basa en el análisis del espectro de frecuencias de las corrientes del estator y la componente homopolar de voltaje (ZSVC). Para este estudio se seleccionan los 5 tipos de bobinados generalmente usados en motores eléctricos. Tomando en cuenta las tendencias de sistemas tolerantes a fallos de utilizar la redundancia de elementos, el estudio del cortocircuito se extiende al motor de 5 fases, para esto se desarrolla un modelo paramétrico del motor, el cual es utilizado para seleccionar los armónicos de frecuencias que permitan la detección del cortocircuito entre espiras en su fase más temprana. De la misma manera estos armónicos son analizados en modelos de simulación por elementosfinitos, probando su potencial para el desarrollo de algoritmo de detección de fallos, característica deseable en los sistemas tolerantes a fallos. En última parte de este capítulo se estudia el efecto de la desmagnetización en el comportamiento de motores, en particular la influencia de la forma de los imanes cuando el motor funciona en régimen de fallo, como conclusión de este estudio se selecciona la forma de imán que mejor se comporta ante este tipo de fallos. Una vez analizado los posibles fallos eléctricos en el motor, el trabajo se centra en el diseño electromagnético óptimo de una máquina de flujo axial. El diseño optimo se apoya en el uso de ecuaciones analíticas del motor (AFPMM) y se valida por medio de simulaciones FEM. Para lograr el diseño óptimo de hace uso de algoritmo de optimización heurísticos, enparticular los algoritmos genéticos. A estos algoritmos se les aplica las restricciones anteriormente encontradas en los estudios de fallos y en el estado de arte de motores tolerantes a fallos. Finalmente aplicando una serie de ecuaciones analíticas y teniendo en cuenta las restricciones de un diseño tolerante a fallos previamente seleccionadas se obtiene el diseño electromagnético óptimo de un motor de flujo axial tolerante a fallos. Para el proceso de optimización se utilizan algoritmos genéticos multi-objetivos en donde se busca maximizar la densidad de potencia y la eficiencia. Por último, el modelo del motor pentafásico de flujo axial es verificado por medio de simulaciones en elementos finitos.
Electric vehicles (EVs) are attractive comparted to internal combustion engine powered vehicles due to several benefits, including low emissions, higher efficiency, less maintenance costs, stronger acceleration or lower fuel price, among others. EVs require traction motors with especial features, including high efficiency, high power and torque density, compactness, precise torque control, extended speed range. This work focuses on the analysis and optimal electromagnetic design of fault tolerant permanent magnet synchronous motors. The study is mainly based on the research of analytical design procedures and the effect of electrical faults in the motor behavior, according to the configurations of each machine. The study will be developed by using analytical tools, and validated by applying 2-D and 3-D finite element methods (FEM). A brief study about the main achievements regarding the design of fault tolerant machines is made, identifying the possible improvements and main rules of design in this kind of machines. Then a study focused on the requirements of a fault tolerant design is made, in order to select the appropriate motor configuration. Since the consequences of inter-turn faults can be catastrophic in PMSMs, chapter 3 studies the influence of the winding configuration on the detection of such faults. This detection is based on the analysis of the stator currents and the (zero-sequence voltage component) ZSVC spectra. Several types of winding configurations are selected for analysis i.e. fractional- and integral-slot windings, overlapping- and non-overlappingwindings, single- and double-layer, full- and short-pitch, constant- and variable-pitch windings. Taking into the fault tolerant tendencies about the redundancy of the system, the study of the effect of inter turn fault is extended to the five phase machine, thus a parametric model of the five-phase PMSM is developed, this model accounts for the effects of inter-turn faults. This parametric model is used to select the harmonic frequencies to be studied to detect such faults. Likewise, the amplitudes of these harmonic frequencies are further analyzed by means of FEM simulations, therefore showing the potential of the proposed system to detect inter-turn faults in their early stage, which is a desirable characteristic for a fault tolerant system. The demagnetization effect on AFPMM torque is also analyzed. The main objective was to study the influence of the magnet shape in the performance of an AFPMM working under faulty condition, in order to select the most suitable type of magnet for the design of a fault tolerant machine. After an exhaustive analysis of the main electromagnetic faults on PMSMs, the work is focused on the optimal electromagnetic design of an AFPMM. The optimal design is based on a set of analytical equations whose accuracy is validated by means of FEM simulations. Next, to find the optimal solution, the huge set of possible motor solutions is explored by means of computationally efficient optimization algorithms leading to an optimum solution while minimizing the computational burden. The set of analytical equations are solved to obtain the geometrical, electric and mechanical parameters of the optimized AFPMM and several design restrictions are applied to ensure fault tolerance capability, along with the recommended features that have been drawn from the fault analysis study. Finally, a dual outer rotor AFPMM with NN configuration for automotive applications is optimized by applying accurate analytical sizing equations and
taking into account fault tolerant constraints. For optimization purpose, a multi-objective design strategy is applied, in which the optimization variables are the motor efficiency and power density and ten input geometric and electric parameters are considered, with their respective bounds and constraints. At last the model is verified by applying 3D-FEM simulations and the main performance characteristics are compared.
Debido a las nuevas políticas de conservación medio ambiental, los vehículos eléctricos toman una posición más importante en la sociedad actual. Los motores eléctricos constituyen el corazón de la cadena de tracción de un EV, por esta razón se debe encaminar la investigación hacia el diseño de motores de mayor eficiencia y fiabilidad. Este trabajo se enfoca en el análisis y diseño óptimo de un motor de flujo axial con tolerancia a fallos. Como base, se parte de la investigación de los procedimientos analíticos de diseño de motores eléctricos y del estudio de los efectos de los fallos eléctricos en el comportamiento de estos, de acuerdo a la configuración específica de cada máquina. Para desarrollar esta tesis se hará uso de herramientas analíticas y de métodos de simulación basados en métodos finitos (FEM). En primera parte se hace un estudio del estado del arte del diseño de motores eléctricos tolerantes a fallos, en el cual se identifican las posibles configuraciones a usar y las principales reglas de diseño de estos motores. Debido a que las consecuencias de un cortocircuito entre espiras pueden ser catastróficas para el motor de imanes permanentes, en el siguiente capítulo se analiza su efecto en dependencia de la configuración de los devanados del motor, además de su posible detección. La detección del cortocircuito se basa en el análisis del espectro de frecuencias de las corrientes del estator y la componente homopolar de voltaje (ZSVC). Para este estudio se seleccionan los 5 tipos de bobinados generalmente usados en motores eléctricos. Tomando en cuenta las tendencias de sistemas tolerantes a fallos de utilizar la redundancia de elementos, el estudio del cortocircuito se extiende al motor de 5 fases, para esto se desarrolla un modelo paramétrico del motor, el cual es utilizado para seleccionar los armónicos de frecuencias que permitan la detección del cortocircuito entre espiras en su fase más temprana. De la misma manera estos armónicos son analizados en modelos de simulación por elementos finitos, probando su potencial para el desarrollo de algoritmo de detección de fallos, característica deseable en los sistemas tolerantes a fallos. En última parte de este capítulo se estudia el efecto de la desmagnetización en el comportamiento de motores, en particular la influencia de la forma de los imanes cuando el motor funciona en régimen de fallo, como conclusión de este estudio se selecciona la forma de imán que mejor se comporta ante este tipo de fallos. Una vez analizado los posibles fallos eléctricos en el motor, el trabajo se centra en el diseño electromagnético óptimo de una máquina de flujo axial. El diseño optimo se apoya en el uso de ecuaciones analíticas del motor (AFPMM) y se valida por medio de simulaciones FEM. Para lograr el diseño óptimo de hace uso de algoritmo de optimización heurísticos, en particular los algoritmos genéticos. A estos algoritmos se les aplica las restricciones anteriormente encontradas en los estudios de fallos y en el estado de arte de motores tolerantes a fallos. Finalmente aplicando una serie de ecuaciones analíticas y teniendo en cuenta las restricciones de un diseño tolerante a fallos previamente seleccionadas se obtiene el diseño electromagnético óptimo de un motor de flujo axial tolerante a fallos. Para el proceso de optimización se utilizan algoritmos genéticos multi-objetivos en donde se busca maximizar la densidad de potencia y la eficiencia. Por último, el modelo del motor pentafásico de flujo axial es verificado por medio de simulaciones en elementos finitos.
Electric motors used for traction purposes in electric vehicles (EVs) must meet several requirements, including high efficiency, high power density and faulttolerance. Among them, permanent magnet synchronous motors (PMSMs) highlight. Especially, five-phase axial flux permanent magnet (AFPM) synchronous motors are particularly suitable for in-wheel applications with enhanced fault-tolerant capabilities. This paper is devoted to optimally design an AFPM for in-wheel applications. The main geometric, electric and mechanical parameters of the designed AFPM are calculated by applying an iterative method based on a set of analytical equations, which is assisted by means of a reduced number of three-dimensional finite element method (3D-FEM) simulations to limit the computational burden. To optimally design the AFPM, a constrained multi-objective optimization process based on a genetic algorithm is applied, in which two objective functions are considered, i.e. the power density and the efficiency. Several fault-tolerance constraints are settled during the optimization process to ensure enhanced fault-tolerance in the resulting motor design. The accuracy of the best solution attained is validated by means of 3D-FEM simulations.
Sinusoidally fed permanent magnet synchronous motors (PMSM) fulfill the special features required for traction
motors to be applied in electric vehicles (EV). Among them, axial flux permanent magnet (AFPM) synchronous motors are
especially suited for in-wheel applications. Electric motors used
in such applications must meet two main requirements, i.e. high power density and fault tolerance. This paper deals with the
optimal design of an AFPM for in-wheel applications used to drive an electrical scooter. The single-objective optimization
process carried out in this paper is based on designing the AFPM to obtain an optimized power density while ensuring appropriate fault tolerance requirements. For this purpose a set of analytical
equations are applied to obtain the geometrical, electric and mechanical parameters of the optimized AFPM and several design restrictions are applied to ensure fault tolerance capability. The optimization process is based on a genetic
algorithm and two more constrained nonlinear optimization algorithms in which the objective function is the power density.
Comparisons with available data found in the technical bibliography show the appropriateness of the approach
developed in this work.
Five-phase permanent magnet synchronous motors (PMSMs) have inherent fault-tolerant capabilities. This paper analyzes the detection of inter-turn short circuit faults in five-phase PMSMs in their early stage, i.e. with only one turn in short circuit by means of the analysis of the stator currents and the zero-sequence voltage component (ZSVC) spectra. For this purpose, a parametric model of five-phase PMSMs which accounts for the effects of inter-turn short circuits is developed to determine the most suitable harmonic frequencies to be analyzed to detect such faults. The amplitudes of these fault harmonic are analyzed in detail by means of finite-elements method (FEM) simulations, which corroborate the predictions of the parametric model. A low-speed five-phase PMSM for in-wheel applications is studied and modeled. This paper shows that the ZSVC-based method provides better sensitivity to diagnose inter-turn faults in the analyzed low-speed application. Results presented under a wide speed range and different load levels show that it is feasible to diagnose such faults in their early stage, thus allowing applying a post-fault strategy to minimize their effects while ensuring a safe operation.
In the current energy conjunction, with an expected growth of energy consumption in a context of fossil fuel depletion, more focus is being placed on renewable energy sources (RES) for electricity generation. One of the most appealing alternatives is biomass, which can be efficiently used to generate electricity as well as heat with the application of cogeneration technologies that enhance the efficiency of the entire energy conversion process. The Mediterranean basin is a region with a recognized potential for electricity and heat production using primary forest biomass and sub-products from sawmills, among which highlight wood chips for their easiness to be obtained, processed and dried as well as for their good and stable burning or gasification behavior. However, in order to efficiently use the available resources, that is, minimizing logistical requirements to reduce the energy necessary for the electricity generation process, the biomass found in Mediterranean forests can only be used at micro- and small-scale levels to be compatible with sustainable forestry practices. This article is aimed to describe the different technological alternatives to convert wood chips into electricity and heat and it also reviews and compares the current performances in terms of efficiency of these technologies at the micro- and small-scale levels.
Melo-Espinosa, E.; Sánchez-Borroto, Y.; Errasti, M.; Piloto-Rodríguez, R.; Sierens, R.; Riba, J.; Christopher-Hansen, A. Energy procedia Vol. 57, p. 886-895 DOI: 10.1016/j.egypro.2014.10.298 Date of publication: 2014-10-10 Journal article
The surface tension is one of the main properties for character
ization of the quality of the fuel atomization process for its use in a diesel engine. There is a lack of published information about the values of surface tension of vegetable oils. The aim of this research is to obtain a mathematical model based on physical properties that establishes a relationship between the surface tensions of different vegetable oils and their fatty acid composition. For this reason,
from literature reports, experimental data of oils related to the surface tensions was collected. Knowing that surface tension as a function of temperature, a total amount of 15 oils from different feedstocks at 20
°C was selected. The obtained models were developed based in the use of artificial neural networks and multiple linear regressions fits,
based on the experimental data available in the literatur
e. Also, the obtained models present a good correlation
between surface tension and the fatty acid composition, with a 95 % of confidence interval and coefficient of correlation higher than 0,9
5. The coefficient of correlation obtained shown a high correlation between the analyzed variables. According to the obtained results, the proposed models are a useful tool for the surface tension estimation
from the oils fatty acid composition
The study of the dynamic behaviour of electric vehicles is being incorporated in the syllabuses of an increasing number of graduate and undergraduate courses. This paper analyses the basic mechanical and electric concepts of electric traction applied to automobiles. For this purpose, in this work the switched reluctance motor is analysed. A model based on MATLAB/Simulink to simulate the behaviour of both the electric motor and the vehicle dynamics is described. It allows students to gain a better understanding of the fundamental mechanical and electrical concepts by simulating the system behavior in an interactive and flexible manner.
'The Multi Layer Cable Model MultiCaB project proposal aims to research and develop advanced parametric power cable models for aeronautical applications, specifically, thermo electric Wing Ice Protection Systems, WIPS.
Apart from basic voltage and current analysis, models must allow to simulate and study high frequency effects, such as skin and proximity effects, standing waves and resonances, conductive and isolation losses and temperature effects. Two different layers of the model, which are related to result accuracy and computational burden, are considered in the project.
To implement the model it is proposed a lumped parameters based model, which are frequency dependents, that must replicate the frequency response of the full cable for all the frequencies of interest. It means that not only the fundamental frequency have be taken into account in the model simulation, but also harmonics, switching frequency and high frequencies due to trise and tfall at the power converter must be considered for the complete results.
A specific research in cable models and high frequency effects, a powerful methodology based on experimental measurements and if proceed, FEM simulations, and experimental validation of developed models and methodologies will be performed in the project.
A proper management, a well-defined topic manager relationship and an adequate consideration of intellectual property rights and exploitation are included in the proposal.
The project is presented by researches and technicians from the MCIA Research Center of Universitat Politècnica de Catalunya (www.mcia.upc.edu), with probed experience in high frequency modeling of electric and electronics components and power electronics applications and control, as well as in European projects' management and execution.'
Moreno-Eguilaz, J.M.; Garcia, A.; Riba, J.; Ortega, J.A.; Romeral, L.; Hernandez, E. Congrés Internacional de Docència Universitària i Innovació Presentation's date: 2014-07-02 Presentation of work at congresses
Se describe una experiencia docente pionera basada en el clásico concepto“learning-by-doing”, en la que diseño e ingeniería se unen para obtener un producto de mercado. En concreto, se describen los retos planteados así como las dificultades encontradas por el equipo ETSEIB-ELISAVA, procedentes de la Universidad Politécnica de Cataluña y de la Universidad Pompeu Fabra, respectivamente, que consiguió el premio al diseño en la primera edición de la competición Barcelona Smart Moto Challenge.
In many countries worldwide, the energy demand is growing faster than the transmission capacity. However, due to environmental constrains, social concerns and financial costs, the construction of new power transmission lines is an arduous task. In addition, power transmission systems are often loaded close to their nominal values. Therefore, improving power transmission system efficiency and reliability is a matter of concern. This work deals with a 400 kV, 3000 A, 50 Hz extra-high-voltage expansion substation connector used to connect two substation bus bars of 150 mm diameter each. This substation connector has four aluminum wires which provide the conductive path between both bus bars. Preliminary tests showed an unequal current distribution through the wires which was mainly attributed to the proximity effect. A three-dimensional finite elements method approach was applied to improve the design and evaluate the electromagnetic and thermal behavior of both the original and improved versions of the connector. Experimental tests made under laboratory conditions have validated the accuracy of the simulation method presented in this paper, which may be a valuable tool to assist the design process of substation connectors, therefore allowing improving both the thermal performance and reliability of the redesigned connectors.
Les investigacions realitzades en aquesta tesi es va realitzar en el marc d'un acord empresa - universitat . L'objectiu d'aquesta investigació és determinar la tensió d'inici de l'efecte corona en geometries no uniformes per evitar la seva aparició, i així poder incidir en la fase de disseny del connectors de subestació de EHV i UHV i equipmanet auxiliar de línia instal·lats en condicions de funcionament, d'acord amb les normes internacionals . Per tant , s'ha prestat una consideració especial a l'estudi i el modelatge de l'efecte corona per assegurar que els connectors dissenyats es trobin gairebé lliures d'aquest efecte indesitjable . Degut a de la natura d'aquest acord marc, la investigació científica s'ha vist delimitada a l'aplicabilitat en un entorn industrial a fi d'obtenir la accreditació, segons les normatives internacionals, dels productes analitzats.Per tant , els temes tractats en aquesta investigació inclouen l'anàlisi de camps electromagnètics i els càlculs de l'efecte corona , sent aquest últim de gran importància en el disseny dels connectors de subestació per EHV i UHV . És objectiu d'aquesta tesi proporcionar augmentar el coneixement i aportar mètodes matemàtics apropiats per avaluar el comportament dielèctric de connectors de subestació per a sistemes de transmissió de EHV i UHV . En concret , s'ha destinat un capítol a la introducció a l'estat de la tècnica en connectors de la subestació i l'efecte corona, seguit d'un capítol adreçat a l'estudi dels camps elèctrics i magnètics creats pels connectors de la subestació i les equacions empíriques per al càlcul de l'effecte corona. A continuació, s'introdueix una descripció macroscòpica del corona a través de la descripció matemàtica del procés de ionització, tant des del cas estacionari com el transitori. Seguit de la descripció microscòpica a través de funcions de distribució estadístiques utilitzdes per descriure i calcular els paràmetres d'ionització del corona en l'aire . Finalment, es troba el capítol de tancament amb les principals aportacions de la investigació realitzada.
This paper shows the capabilities of applying the three-dimensional finite element method (3D-FEM) for designing complex-shaped substation connectors to operate at 765 kVRMS AC. To check this methodology, it was analyzed the feasibility of upgrading a 400 kVRMS substation connector to operate at 765 kVRMS. However, both experimental and simulation results conducted according to the ANSI/NEMA CC 1-2009 standard concluded that although it passed the visual corona test, to ensure a wide safety margin it was desirable an improvement of the electrical behavior of such connector. It was shown that FEM results allowed detecting the peak stress points of the connector regarding the electrical stress thus allowing applying a corrective action. Then, two possible solutions were analyzed, i.e. the use of corona shields and the redesign of the connector assisted by 3D-FEM simulations. Results presented in this work show that both approaches have an excellent behavior in reducing the electric field strength on the connector surface. However, to make the final decision, the production cost of both alternatives was analyzed, thus favoring the redesign option. Next, the redesigned version of the substation connector was manufactured and tested. Experimental results conducted in a high voltage laboratory verified the effectiveness of the methodology and the potential of the proposed system to act as an advanced design tool for optimizing the behavior of complex-shaped substation connectors. Thus, this system allows assisting efficiently the design process while permitting constraining the economic costs
Interturn faults in permanent magnet synchronous motors (PMSMs) may develop fast into more severe faults such as coil-to-coil, phase-to-phase and phase-to-ground short circuits. These faults are very destructive and may irreversibly damage the PMSM. Therefore, it is highly desirable to develop suitable methods for the early detection of such faults. The effects of interturn faults are visible in both the stator currents and the zero-sequence voltage component (ZSVC) spectra. By designing appropriate fault diagnosis schemes based on the analysis of the harmonic content of such electric variables it is possible to detect short circuit faults in its early stage. However, the stator winding configuration of the PMSM deeply impacts the harmonic content of both spectra. This paper studies the effects of different stator winding configurations in both the stator currents and the ZSVC spectra of healthy and faulty machines. Results presented may help to develop fault diagnosis schemes based on the acquisition and further analysis of the stator currents and/or the ZSVC harmonic components.
This work performs a comparative life cycle assessment (LCA) of two fuels for heating boilers, namely wood chips and oil. The LCA methodology allows comparing the environmental impacts of the two analyzed fuels, thus assessing which is environmentally more advantageous. The study is focused on Mediterranean forests located in the Argençola region (Catalonia, northeastern Spain) by applying forest management practices focused to ensure a sustainable exploitation. The direct use of wood chips as a fuel for boilers simplifies notably the number of processes involved in producing such a fuel. The results presented clearly show the environmental benefits of using small-scale produced wood chips instead of fossil oil by analyzing representative impact categories defined by the CML and EDIP methods, even when considering the changes in the carbon stock in the forests under analysis due to the management approach adopted. A sensitivity analysis has also been conducted to assess the impact of the data with higher uncertainty on the final LCA results.
Life cycle thinking is a good approach to be used for environmental decision-support, although the complexity of the Life Cycle Assessment (LCA) studies sometimes prevents their wide use. The purpose of this paper is to show how LCA methodology can be simplified to be more useful for certain applications. In order to improve waste management in Catalonia (Spain), a Cumulative Energy Demand indicator (LCA-based) has been used to obtain four mathematical models to help the government in the decision of preventing or allowing a specific waste from going out of the borders. The conceptual equations and all the subsequent developments and assumptions made to obtain the simplified models are presented. One of the four models is discussed in detail, presenting the final simplified equation to be subsequently used by the government in decision making. The resulting model has been found to be scientifically robust, simple to implement and, above all, fulfilling its purpose: the limitation of waste transport out of Catalonia unless the waste recovery operations are significantly better and justify this transport.
In this paper the effect of the magnets shape on the AFPMM performance under a demagnetization fault has been analyzed by means of 3D-FEM simulations. Demagnetization
faults in permanent magnet synchronous motors (PMSMs) may generate specific fault harmonic frequencies in the stator currents, output torque and the zero-sequence voltage component (ZSVC) spectra the ones can affect motor behavior, and so these parameters have been studied and compared, for each magnet
configuration in each condition. These analyses are carried out to find out the more suitable geometry for an operation under
healthy and faulty condition.
Hernandez-Guiteras, J.; Riba, J.; Casals, P.; Bosch, R. IEEE Transactions on dielectrics and electrical insulation Vol. 20, num. 5, p. 1590-1597 DOI: 10.1109/TDEI.2013.6633688 Date of publication: 2013-10 Journal article
Breakdown and corona extra-and ultra-high voltage tests are expensive, timeconsuming and require large and extremely costly high-voltage halls, of which there are very few worldwide. Some of these limiting requirements may be minimized by using test cages and by applying reduced-scale tests. In this work the feasibility of performing breakdown reduced-scale tests combined with the use of test cages is analyzed. For this purpose a three-dimensional finite elements based methodology is introduced to determine the geometric dimensions of the test cage in order to adjust the test voltage according to the allowable output voltage of a conventional high-voltage laboratory. To validate the findings of this work, breakdown tests of a full-scale 500 kVRMS substation connector and a 1:3 reduced-scale model using test cages are conducted in a highvoltage laboratory, which maximum allowable output voltage is of 125 kVRMS. Results from this work show that by using appropriately designed test cages and scaled versions of the test samples the results may be scaled with high accuracy.
'The project intends to develop a new Electric Machine Modelica Library with improving functionalities for an accurate design and simulation of motors and generators.
New Externally Excited Synchronous Machines, Permanent Magnet Synchronous Machines (PMSM and BLDC) and Asynchronous Induction Machines (IM) models in Modelica language including spatial harmonics and nonlinear saturation behavior, as well as improved thermal model for the thermal evaluation of the machine, are the main objectives of the proposed project, together new software tools with GUIs for guided model design from geometric motor considerations and torque and power demand profiles.
Generalized space phasor theory to m phases with arbitrary spatial angle of the coils, and arbitrary number of windings and winding factor of the coils will be considered for the new Library. Constructive harmonics and distortions of flux couplings are taken into account as well.
Also, non-linearity due to saturation and skin-effect on the resistances are considered in updated libraries. Moreover, thermal models able to calculate hotspots and asymmetric windings temperature distribution from the thermal losses into the machine are included in the Library.
A graphical guided Interface for directing the modeling of machines is included in the project.'
This paper deals with the effects of inter-turn short circuit faults in five-phase permanent magnet synchronous motors (PMSMs). For this purpose a finiteelements model (FEM) of a faulty machine with 1, 2 and 4 inter-turns in short circuit is analyzed. From the results of this
model the effects of these fault severities in the stator currents and zero-sequence voltage components (ZSVC) harmonics is
analyzed and the possibility of developing a fault diagnosis scheme based on the changes in their spectral content is exposed. Moreover, the effect of the fault severity on the total power losses in the machine is presented. Inter-turn faults generate large circulating currents which may lead to
catastrophic failures. Therefore it is very important to know the increase in power losses in the machine due to the occurrence of such faults for applying corrective actions at the precise time once the fault has been diagnosed.
Demagnetization faults have a negative impact on the behavior of permanent-magnet synchronous machines, thus reducing their efficiency, generating torque ripple, mechanical vibrations, and acoustic noise, among others. In this paper, the displacement of the shaft trajectory induced by demagnetization faults is studied. It is proved that such faults may increase considerably the amplitude of the rotor displacement. The direct measure of the shaft trajectory is performed by means of a noncontact self-mixing interferometric sensor. In addition, the new harmonics in the back electromotive force (EMF) and the stator current spectrum arising from the shaft displacement are analyzed by means of finite-element method (FEM) simulations and experimental tests. Since conventional finite-element electromagnetic models are unable to predict the harmonics arising from the shaft trajectory displacement, an improved finite-element model which takes into account the measured trajectory has been developed...
Abstract—Demagnetization faults have a negative impact on the behavior of permanent-magnet synchronous machines, thus
reducing their efficiency, generating torque ripple, mechanical vibrations, and acoustic noise, among others. In this paper, the
displacement of the shaft trajectory induced by demagnetization faults is studied. It is proved that such faults may increase considerably the amplitude of the rotor displacement. The direct measure of the shaft trajectory is performed by means of a noncontact self-mixing interferometric sensor. In addition, the new harmonics
in the back electromotive force (EMF) and the stator current spectrum arising from the shaft displacement are analyzed by means
of finite-element method (FEM) simulations and experimental tests. Since conventional finite-element electromagnetic models are
unable to predict the harmonics arising from the shaft trajectory displacement, an improved finite-element model which takes into account the measured trajectory has been developed. It is shown that this improved model allows obtaining more accurate back EMF and stator current spectra than those obtained by means of
conventional models. This work presents a comprehensive analysis of the effects generated by demagnetization faults, which may be useful to develop improved fault diagnosis schemes
Demagnetization faults in permanent magnet synchronous motors may generate specific fault harmonic frequencies in the stator currents and the zero-sequence voltage component (ZSVC) spectra. Hence, by analyzing the stator currents or/and the ZSVC spectra it is possible to develop fault diagnosis schemes to detect such faults. In order to have a broad view of such effects, a representative set of stator windings configurations must be considered. By analyzing different stator windings configurations this paper shows that the amplitude of the harmonic frequencies of both the stator currents and the ZSVC spectrato be analyzed are significantly influenced by the stator windings configuration. It is also proved that depending on the winding configuration, new harmonic components may emerge in both spectra. The results presented in this paper may help to develop fault diagnosis schemes based on the acquisition and further analysis of the stator currents and the ZSVC harmonic components.