Joaquin Mur | University of Zaragoza (original) (raw)
Papers by Joaquin Mur
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
ABSTRACT The classification of states can be based on power output, "unperturbed wind sp... more ABSTRACT The classification of states can be based on power output, "unperturbed wind speed" and wind speed prediction, depending on available data and aim of the wind farm model. The performance matrix in Standard IEC 61400-12-3 can be used as emission matrix to relate wind and power in a wind farm using a hidden Markov model. The wind farm model can be used also as time interpolation between horizons of wind prediction or to account switching events such as sudden disconnection of the farm. The basic workflow to compute a stochastic power flow based in Markov model is presented. A simplified, steady state, quadratic model of the wind farm is shown for justifying the approximation of networks to PQ nodes and the interpolation between states. This quadratic model can be used also to estimate the reactive power for steady state.
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
In this article, the model described in the first part of the series is applied to a system with ... more In this article, the model described in the first part of the series is applied to a system with three wind farms. The model is adjusted from one year data and some measures of the goodness of the fit are shown. In particular, the exponential distribution of the permanence time in states is contrasted with real data. The uncertainty of the transition probabilities and the estimation of uncommon events are also studied. Some theoretical properties obtained from the model are also checked with experimental data.
Energia Eolica 2008 Isbn 978 84 92521 21 0 Pags 175 211, 2008
This paper reports an example of state-of-the-art technology applied to academic training of elec... more This paper reports an example of state-of-the-art technology applied to academic training of electrical engineers. An updated commercial Finite Element Method Software package is used to calculate electrical fields and power dissipation in a resistor with a complex geometry. These results are compared with theoretical solutions of a simplified model which can be obtained by the students with basic mathematics. Using a powerful tool to calculate electromagnetic fields very accurately let them to acknowledge the limitations of their theoretical solutions. The aim of this activity is the presentation of Electromagnetics theory in a more engaging manner, using a breakthrough technology as a bridge between the classical theoretical approach and industrial applications. Analytical solutions of resistors with non-uniform distributions of current and power density are restricted to simplified geometries which are rough representations of the real model. These resistors present engineering p...
1. RESUMEN El presente documento es una reflexión sobre la conveniencia de incorporar experimento... more 1. RESUMEN El presente documento es una reflexión sobre la conveniencia de incorporar experimentos de forma regular durante el desarrollo de las clases magistrales de teoría en un curso básico de Electromagnetismo. Estos experimentos, conocidos como "experimentos de cátedra", ayudan a comprender mejor los contenidos teóricos y su aplicación práctica. Contrariamente a lo ocurrido en otros países, durante los últimos años del siglo XX han sido escasamente utilizados en la universidad española, relegándose, caso de realizarse, a las sesiones de prácticas de laboratorio junto con otras actividades típicas de dicha sala. Los autores comenzaron a incorporar, de forma regular y sistemática, experimentos en clase en el curso 2000-01, coincidiendo con la renovación del plan de estudio de una de las especialidades en las que impartían docencia. Aunque la mayor parte de los materiales necesarios fueron adquiridos con fondos asignados a la renovación del plan de estudios, otros han si...
This is the second part of a study on Power Quality (PQ) analysis of Wind Turbines (WT) installed... more This is the second part of a study on Power Quality (PQ) analysis of Wind Turbines (WT) installed in wind farms. A specifically designed measurement system has been installed in three wind farms with three different types of asynchronous generators of 600 kW and 700 kW classes. This part is focused on the analysis of transient events, connections and disconnections and power fluctuations. A new method to study power fluctuations based in joint time-frequency analysis is proposed. Transient events such as connection of capacitor banks are studied with the waveforms. The firing of thyristors during soft start is also studied through waveforms. The whole evolution during the connection of the generator is analyzed through the RMS value of each cycle of the grid because it is a longer transient. Power fluctuations are also studied through values of current and power each cycle or half-cycle.
This paper presents a combined system of a capacitor, a thyristor controlled reactor (TCR) and a ... more This paper presents a combined system of a capacitor, a thyristor controlled reactor (TCR) and a small-rated active filter (PWM-VSI) whose goal is to obtain a regulation of reactive power with a generation of harmonic currents very reduced. The electrical analysis and filtering characteristics (and size of the active unit) are discussed theoretically and several situations are simulated.
A combined system that permits a wise control of reactive power in WECS (Wind Energy Conversion S... more A combined system that permits a wise control of reactive power in WECS (Wind Energy Conversion Systems) without harmonic generation is presented. In the case of asynchronous generator, it uses the thyristors of the usual soft-starting system to connect a TCR (thyristor controlled reactor) and a small-rated active filter (PWM-VSI) so its implementation is very economical.
This paper presents an algorithm to optimal location of small generators that allows to consider ... more This paper presents an algorithm to optimal location of small generators that allows to consider the optimal operation of the distribution network. Una operación adecuada de las redes débiles permite mejorar la penetración de generadores distribuidos en dichas redes y mejorar los beneficios de su instalación. An optimal operation of the weak netwoks allows to improve the penetration of distributed generators in the above mentioned netwoks and to improve the benefits of its installation. The used algorithm is based on the heuristic technique of Tabu Search. The obtained results allow to check the efficiency of the utilised search technique and the benefits that supposes for the location of new generators the optimal operation of the network.
Resumen Un importante número de personas que deciden estudiar carreras experimentales, fundamenta... more Resumen Un importante número de personas que deciden estudiar carreras experimentales, fundamentalmente Ingenierías y Física, lo hacen atraídos por los fenómenos físicos que han observado y han visto aplicados tecnológicamente en máquinas e instrumentos de uso diario. La ausencia de experimentos reales, insertados en el desarrollo de los contenidos teóricos de asignaturas, de primer curso, de Física (o electromagnetismo en el caso que nos ocupa), provoca en parte de los estudiantes una impresión de pérdida de tiempo, inutilidad del esfuerzo exigido y frustración. Hace varios cursos, los autores comenzaron a insertar en sus explicaciones teóricas pequeñas demostraciones o experimentos que podían transportarse fácilmente al aula y eran, de alguna manera, "espectaculares". La reacción de los estudiantes fue muy positiva, constatándose incluso casos de fuerte motivación como consecuencia de la observación de estos fenómenos. En los párrafos siguientes se describen tres de esto...
Resumen En el presente artículo se presenta un sistema híbrido compuesto por un condensador, una ... more Resumen En el presente artículo se presenta un sistema híbrido compuesto por un condensador, una bobina controlada por tiristores (TCR) y un filtro activo de pequeña potencia. Con él se logra una regulación suave de reactiva, sin generación elevada de armónicos y sin tener que instalar filtros pasivos, con la problemática que ello conlleva. Palabras Clave: Potencia Reactiva, distorsión armónica, filtros activos.
This work studies reactive power strategies for wind turbines and wind farms. Previous Spanish re... more This work studies reactive power strategies for wind turbines and wind farms. Previous Spanish regulation stated unity power factor (P.F.) as target. New regulation introduced in RD 436/2004 rewarded up to 8% with P.F. < 0,95 inductive (on low-load hours) and P.F. < 0,95 capacitive (on peak hours). A better utilization of the infrastructure can be attained considering the reactive power generation availability even in calm periods -depending on the reactive power compensation scheme implemented in the wind farm-. This can lead to a voltage support strategy in a nearby node, especially if the voltage at that node can be estimated despite tap changing transformers. The effect of some control strategies in nearby nodes are quantified statistically regarding the stochastic nature of wind power.
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, 2014
ABSTRACT In this paper, it presented a device intended to reproduce magnetic fields of differents... more ABSTRACT In this paper, it presented a device intended to reproduce magnetic fields of differents shapes to help the test or calibration of current measuring instruments based on Ampere's Law (current transformers, current clamps, and Rogowsky probes). In particular, this device can reproduce the effect of uncentered currents without requiring any mechanical displacement of the conductor or the device under test during its operation. Any uncentered or distributed current is approximated by a linear combination of currents flowing along a specific set of conductors. First, the theoretical vectorial analysis is presented, and second, a specific arrangement of conductors is used to illustrate the method. A number of measurements have been taken to check the results. Copyright © 2014 John Wiley & Sons, Ltd.
IEEE Transactions on Magnetics, 2014
ABSTRACT publications/rights/index.html for more information. The document shows a generalization... more ABSTRACT publications/rights/index.html for more information. The document shows a generalization and further development of a previous work of the authors already published. We describe and analyze a kind of devices intended to create a prescribed magnetic field by using a set of conductors. More precisely, it is capable to shape the tangential component of the magnetic field along a specific path by controlling the current applied to each conductor. An orthogonal function decomposition is used to determinate the magnitude of each current. The system performance depends on the number of conductors and their location, so we introduce a set of quality parameters and some common geometries are evaluated upon them. These devices are intended for calibration purposes of current measuring instruments based on Ampere's Integral, although the metrological aspects are out of the scope of this document.
European Grid Codes has been reviewed due to the increasing levels of wind-turbine generation in ... more European Grid Codes has been reviewed due to the increasing levels of wind-turbine generation in modern power systems. The main requirements concern the fault ride through capabilities. Since simultaneous loss of several thousand MW wind generation in system fault would lead to stability problems. The wind turbine fault ride-through capabilities can be analyzed by means of dynamic simulation. The aim
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
ABSTRACT The classification of states can be based on power output, "unperturbed wind sp... more ABSTRACT The classification of states can be based on power output, "unperturbed wind speed" and wind speed prediction, depending on available data and aim of the wind farm model. The performance matrix in Standard IEC 61400-12-3 can be used as emission matrix to relate wind and power in a wind farm using a hidden Markov model. The wind farm model can be used also as time interpolation between horizons of wind prediction or to account switching events such as sudden disconnection of the farm. The basic workflow to compute a stochastic power flow based in Markov model is presented. A simplified, steady state, quadratic model of the wind farm is shown for justifying the approximation of networks to PQ nodes and the interpolation between states. This quadratic model can be used also to estimate the reactive power for steady state.
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
In this article, the model described in the first part of the series is applied to a system with ... more In this article, the model described in the first part of the series is applied to a system with three wind farms. The model is adjusted from one year data and some measures of the goodness of the fit are shown. In particular, the exponential distribution of the permanence time in states is contrasted with real data. The uncertainty of the transition probabilities and the estimation of uncommon events are also studied. Some theoretical properties obtained from the model are also checked with experimental data.
Energia Eolica 2008 Isbn 978 84 92521 21 0 Pags 175 211, 2008
This paper reports an example of state-of-the-art technology applied to academic training of elec... more This paper reports an example of state-of-the-art technology applied to academic training of electrical engineers. An updated commercial Finite Element Method Software package is used to calculate electrical fields and power dissipation in a resistor with a complex geometry. These results are compared with theoretical solutions of a simplified model which can be obtained by the students with basic mathematics. Using a powerful tool to calculate electromagnetic fields very accurately let them to acknowledge the limitations of their theoretical solutions. The aim of this activity is the presentation of Electromagnetics theory in a more engaging manner, using a breakthrough technology as a bridge between the classical theoretical approach and industrial applications. Analytical solutions of resistors with non-uniform distributions of current and power density are restricted to simplified geometries which are rough representations of the real model. These resistors present engineering p...
1. RESUMEN El presente documento es una reflexión sobre la conveniencia de incorporar experimento... more 1. RESUMEN El presente documento es una reflexión sobre la conveniencia de incorporar experimentos de forma regular durante el desarrollo de las clases magistrales de teoría en un curso básico de Electromagnetismo. Estos experimentos, conocidos como "experimentos de cátedra", ayudan a comprender mejor los contenidos teóricos y su aplicación práctica. Contrariamente a lo ocurrido en otros países, durante los últimos años del siglo XX han sido escasamente utilizados en la universidad española, relegándose, caso de realizarse, a las sesiones de prácticas de laboratorio junto con otras actividades típicas de dicha sala. Los autores comenzaron a incorporar, de forma regular y sistemática, experimentos en clase en el curso 2000-01, coincidiendo con la renovación del plan de estudio de una de las especialidades en las que impartían docencia. Aunque la mayor parte de los materiales necesarios fueron adquiridos con fondos asignados a la renovación del plan de estudios, otros han si...
This is the second part of a study on Power Quality (PQ) analysis of Wind Turbines (WT) installed... more This is the second part of a study on Power Quality (PQ) analysis of Wind Turbines (WT) installed in wind farms. A specifically designed measurement system has been installed in three wind farms with three different types of asynchronous generators of 600 kW and 700 kW classes. This part is focused on the analysis of transient events, connections and disconnections and power fluctuations. A new method to study power fluctuations based in joint time-frequency analysis is proposed. Transient events such as connection of capacitor banks are studied with the waveforms. The firing of thyristors during soft start is also studied through waveforms. The whole evolution during the connection of the generator is analyzed through the RMS value of each cycle of the grid because it is a longer transient. Power fluctuations are also studied through values of current and power each cycle or half-cycle.
This paper presents a combined system of a capacitor, a thyristor controlled reactor (TCR) and a ... more This paper presents a combined system of a capacitor, a thyristor controlled reactor (TCR) and a small-rated active filter (PWM-VSI) whose goal is to obtain a regulation of reactive power with a generation of harmonic currents very reduced. The electrical analysis and filtering characteristics (and size of the active unit) are discussed theoretically and several situations are simulated.
A combined system that permits a wise control of reactive power in WECS (Wind Energy Conversion S... more A combined system that permits a wise control of reactive power in WECS (Wind Energy Conversion Systems) without harmonic generation is presented. In the case of asynchronous generator, it uses the thyristors of the usual soft-starting system to connect a TCR (thyristor controlled reactor) and a small-rated active filter (PWM-VSI) so its implementation is very economical.
This paper presents an algorithm to optimal location of small generators that allows to consider ... more This paper presents an algorithm to optimal location of small generators that allows to consider the optimal operation of the distribution network. Una operación adecuada de las redes débiles permite mejorar la penetración de generadores distribuidos en dichas redes y mejorar los beneficios de su instalación. An optimal operation of the weak netwoks allows to improve the penetration of distributed generators in the above mentioned netwoks and to improve the benefits of its installation. The used algorithm is based on the heuristic technique of Tabu Search. The obtained results allow to check the efficiency of the utilised search technique and the benefits that supposes for the location of new generators the optimal operation of the network.
Resumen Un importante número de personas que deciden estudiar carreras experimentales, fundamenta... more Resumen Un importante número de personas que deciden estudiar carreras experimentales, fundamentalmente Ingenierías y Física, lo hacen atraídos por los fenómenos físicos que han observado y han visto aplicados tecnológicamente en máquinas e instrumentos de uso diario. La ausencia de experimentos reales, insertados en el desarrollo de los contenidos teóricos de asignaturas, de primer curso, de Física (o electromagnetismo en el caso que nos ocupa), provoca en parte de los estudiantes una impresión de pérdida de tiempo, inutilidad del esfuerzo exigido y frustración. Hace varios cursos, los autores comenzaron a insertar en sus explicaciones teóricas pequeñas demostraciones o experimentos que podían transportarse fácilmente al aula y eran, de alguna manera, "espectaculares". La reacción de los estudiantes fue muy positiva, constatándose incluso casos de fuerte motivación como consecuencia de la observación de estos fenómenos. En los párrafos siguientes se describen tres de esto...
Resumen En el presente artículo se presenta un sistema híbrido compuesto por un condensador, una ... more Resumen En el presente artículo se presenta un sistema híbrido compuesto por un condensador, una bobina controlada por tiristores (TCR) y un filtro activo de pequeña potencia. Con él se logra una regulación suave de reactiva, sin generación elevada de armónicos y sin tener que instalar filtros pasivos, con la problemática que ello conlleva. Palabras Clave: Potencia Reactiva, distorsión armónica, filtros activos.
This work studies reactive power strategies for wind turbines and wind farms. Previous Spanish re... more This work studies reactive power strategies for wind turbines and wind farms. Previous Spanish regulation stated unity power factor (P.F.) as target. New regulation introduced in RD 436/2004 rewarded up to 8% with P.F. < 0,95 inductive (on low-load hours) and P.F. < 0,95 capacitive (on peak hours). A better utilization of the infrastructure can be attained considering the reactive power generation availability even in calm periods -depending on the reactive power compensation scheme implemented in the wind farm-. This can lead to a voltage support strategy in a nearby node, especially if the voltage at that node can be estimated despite tap changing transformers. The effect of some control strategies in nearby nodes are quantified statistically regarding the stochastic nature of wind power.
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, 2014
ABSTRACT In this paper, it presented a device intended to reproduce magnetic fields of differents... more ABSTRACT In this paper, it presented a device intended to reproduce magnetic fields of differents shapes to help the test or calibration of current measuring instruments based on Ampere's Law (current transformers, current clamps, and Rogowsky probes). In particular, this device can reproduce the effect of uncentered currents without requiring any mechanical displacement of the conductor or the device under test during its operation. Any uncentered or distributed current is approximated by a linear combination of currents flowing along a specific set of conductors. First, the theoretical vectorial analysis is presented, and second, a specific arrangement of conductors is used to illustrate the method. A number of measurements have been taken to check the results. Copyright © 2014 John Wiley & Sons, Ltd.
IEEE Transactions on Magnetics, 2014
ABSTRACT publications/rights/index.html for more information. The document shows a generalization... more ABSTRACT publications/rights/index.html for more information. The document shows a generalization and further development of a previous work of the authors already published. We describe and analyze a kind of devices intended to create a prescribed magnetic field by using a set of conductors. More precisely, it is capable to shape the tangential component of the magnetic field along a specific path by controlling the current applied to each conductor. An orthogonal function decomposition is used to determinate the magnitude of each current. The system performance depends on the number of conductors and their location, so we introduce a set of quality parameters and some common geometries are evaluated upon them. These devices are intended for calibration purposes of current measuring instruments based on Ampere's Integral, although the metrological aspects are out of the scope of this document.
European Grid Codes has been reviewed due to the increasing levels of wind-turbine generation in ... more European Grid Codes has been reviewed due to the increasing levels of wind-turbine generation in modern power systems. The main requirements concern the fault ride through capabilities. Since simultaneous loss of several thousand MW wind generation in system fault would lead to stability problems. The wind turbine fault ride-through capabilities can be analyzed by means of dynamic simulation. The aim