Articles de revista
http://hdl.handle.net/2117/3651
2015-10-09T18:06:28ZIluminación pública con energia eólica y solar
http://hdl.handle.net/2117/76341
Iluminación pública con energia eólica y solar
Bargalló Perpiñá, Ramón
2015-04-01T00:00:00ZPSpice model of discharge lamps with saturated magnetic ballast and non-square arc voltage
http://hdl.handle.net/2117/25222
PSpice model of discharge lamps with saturated magnetic ballast and non-square arc voltage
Molina, Julio; Sainz Sapera, Luis
High intensity discharge lamps with magnetic ballast are energy-efficient lighting devices commonly used in industrial and public installations. These lamps can be important pollution loads, and their harmonic modeling has been extensively studied considering linear magnetic ballast and square arc voltage waveform. Previous assumptions can be far from describing actual lamp behavior, affecting the accuracy of the model. This paper proposes a PSpice model of high intensity discharge lamps considering both the non-linear behavior of the magnetic ballast and the non-square waveform of the arc voltage. The PSpice model is successfully validated with lab experimental measurements. (C) 2014 Elsevier B.V. All rights reserved.
2014-09-01T00:00:00ZDetailed study of DFIG-based wind turbines to overcome the most severe grid faults
http://hdl.handle.net/2117/25218
Detailed study of DFIG-based wind turbines to overcome the most severe grid faults
Rolán Blanco, Alejandro; Pedra Durán, Joaquim; Córcoles López, Felipe
This paper studies the effects of voltage sags caused by faults on doubly-fed induction generators to overcome grid faults. A wide range of sag duration and depth values is considered. It is observed that sag duration influence is periodical. Sag effects depend on duration and depth and on the fault-clearing process as well. Two approaches of the model are compared: the most accurate approach, discrete sag, considers that the fault is cleared in the successive natural fault-current zeros of affected phases, leading to a voltage recovery in several steps; the least accurate approach, abrupt sag, considers that the fault is cleared instantaneously in all affected phases, leading to a one-step voltage recovery. Comparison between both sag models reveals that the fault-clearing process smoothes sag effects. The study assumes that the rotor-side converter can keep constant the transformed rotor current in the synchronous reference frame, thus providing insights into wind turbine fault ride-through capability. The voltage limit of the rotor-side converter is considered to show the situations where the rotor current can be controlled. Finally, a table and a 3D figure summarizing the effects of the most severe grid faults on the rotor-side converter to overcome the most severe faults are provided. (C) 2014 Elsevier Ltd. All rights reserved.
2014-11-01T00:00:00ZComparison of simplified models for voltage-source-inverter-fed adjustable-speed drive during voltage sags when the during-event continue mode of operation is active
http://hdl.handle.net/2117/24746
Comparison of simplified models for voltage-source-inverter-fed adjustable-speed drive during voltage sags when the during-event continue mode of operation is active
Bogarra Rodríguez, Santiago; Monjo Mur, Lluís; Saura Perisé, Jaime; Córcoles López, Felipe; Pedra Durán, Joaquim
Three simplified models for adjustable-speed drives are compared with measurements on an actual drive where the
inverter control strategy remains unaltered during the event (also known as continue mode of operation) to assess drive
behaviour prediction during balanced and unbalanced sags. In particular, the models calculate the dc-link voltage and ac line
current dynamic evolution, assuming that neither the drive nor the system protection will trip. The comparison reveals minor
differences in behaviour between the three models and the actual drive, although the constant current model exhibits slightly
a better agreement. To verify whether differences in the simplified models remain small, extensive ranges of sags are
simulated, and drive sensitivity to sag type and depth is illustrated. As the straightforward models studied predict the
measured drive dynamic behaviour in severe network conditions with similar accuracy to other unnecessarily complicated
models, they are very useful to reduce computational burden and overall complexity for sag immunity as well as dynamic and
steady-state network studies. On the other hand, laboratory measurements on the actual drive when the inertia ride-through
mode of operation is active illustrate that the simplified models are not valid when the inverter control strategy is modified
during the sag.
2014-11-13T00:00:00ZModel of electronic ballast compact fluorescent lamps
http://hdl.handle.net/2117/23636
Model of electronic ballast compact fluorescent lamps
Molina, Julio; Sainz Sapera, Luis
The use of compact fluorescent lamps (CFLs) in utility distribution systems is spreading due to energy consumption concerns. This can damage system power quality because CFLs are nonlinear harmonic injecting loads. For this reason, CFL modeling must be studied to predict their harmonic current emissions into networks. This paper presents a CFL model for calculating these emissions, as well as a simple estimation algorithm for determining the model parameters from experimental measurements. They are both validated with laboratory tests.
2014-06-01T00:00:00ZParameter estimation of wound-rotor induction motors from transient measurements
http://hdl.handle.net/2117/23163
Parameter estimation of wound-rotor induction motors from transient measurements
Kojooyan, Hengameh; Monjo Mur, Lluís; Córcoles López, Felipe; Pedra Durán, Joaquim
A new method for determination of the steady-state equivalent circuit parameters of wound-rotor induction motors using experimental data from starting transient measurements is presented. The algorithm data are the stator currents and voltages
andmechanical speed. The algorithm uses the least-square method and motor dynamic equations in the synchronous reference frame.
Moreover, an approximation of the rotor flux that improves the accuracy of the estimation method, as well as a detailed study of
errors, is included. The estimation method is applied to starting transient measurement data of a 2 kW wound rotor induction
motor, and the accuracy of the obtained parameters is verified by comparing steady-state torque- and current-slip curves calculated with the estimated parameters and those measured in the laboratory
2014-06-01T00:00:00ZModel of discharge lamps with saturated magnetic ballast and non-square arc voltage
http://hdl.handle.net/2117/20690
Model of discharge lamps with saturated magnetic ballast and non-square arc voltage
Molina, Julio; Sainz Sapera, Luis; Monjo Mur, Lluís
Harmonic modeling of high intensity discharge lamps with magnetic ballast has been extensively studied
because they are energy-efficient lighting devices commonly used in industrial and public installations,
and can be an important source of harmonics. This kind of modeling usually considers the linear saturation
curve of the magnetic ballast and represents the arc voltage by a square waveform. However,
both assumptions can be far from describing actual lamp behavior, affecting the accuracy of the model.
This paper proposes a novel characterization of high intensity discharge lamps considering both the nonlinear
behavior of the magnetic ballast and the non-square waveform of the arc voltage. The accuracy
of the new model is validated with experimental measurements and compared to that of the traditional
models.
2013-11-01T00:00:00ZStatistical study of resonance in AC traction systems equipped with Steinmetz circuit
http://hdl.handle.net/2117/19911
Statistical study of resonance in AC traction systems equipped with Steinmetz circuit
Monjo Mur, Lluís; Sainz Sapera, Luis; Rull Duran, Joan
AC traction systems can be 25 kV/50 Hz single-phase, non-linear, time-varying loads of random naturecausing unbalance and distortion of the supply voltages. To reduce voltage unbalance, thyristor controlledreactances are usually delta-connected with traction systems. This setup, called Steinmetz circuit, canadapt reactance values to traction load fluctuations in order to balance consumed currents. To avoidvoltage distortion problems due to harmonic currents injected by traction loads, resonances betweenthe Steinmetz and supply system reactances “observed” from the traction system must be analyzed. Thispaper characterizes stochastic behavior of these resonances, which is caused by random variations intraction power consumption. The study used simulations of an AC traction system with intercity servicesand measurements of a French railway traction substation.
2013-10-01T00:00:00ZModel of discharge lamps with magnetic ballast
http://hdl.handle.net/2117/17783
Model of discharge lamps with magnetic ballast
Molina, Julio; Sainz Sapera, Luis; Mesas García, Juan José; Bergas Jané, Joan Gabriel
Magnetic ballast discharge lamp modeling has been extensively studied because these lamps can be an important source of harmonics. Discharge lamp models usually represent the arc voltage by a square waveform. However, this waveform can be far from actual arc voltages, which affects the accuracy of the lamp models. This paper investigates the actual arc voltage behavior of discharge lamps from laboratory measurements and proposes a novel characterization of these voltages to reformulate the conventional models. The accuracy of the new model is validated with experimental measurements.
2013-02-01T00:00:00ZSaturation effects on torque- and current–slip curves of squirrel-cage induction motors
http://hdl.handle.net/2117/17751
Saturation effects on torque- and current–slip curves of squirrel-cage induction motors
Monjo Mur, Lluís; Córcoles López, Felipe; Pedra Durán, Joaquim
This paper measures and analyzes the saturation
effects on torque- and current–slip curves of three squirrel-cage induction
motors.Motor saturation is illustrated by three sets of measurements:
I) torque and current for each slip measured at three
voltage levels; II) short-circuit impedance measured at different
current levels; and III) no-load impedance measured at different
voltage levels. In test I, torque and current measured at reduced
voltage are prorated to full voltage for comparison purposes. A
double-cage model is used to model the motors, and the nonlinearity
of their reactances is examined. In order to evaluate the individual
weight of every nonlinear reactance on the observed saturated
behavior, we try to fit the measurements considering that only one
reactance of the double-cage model is nonlinear. Good agreement is
obtained only when the stator leakage reactance is considered nonlinear.
On the contrary, when magnetizing or remaining leakage
reactances are considered nonlinear, they predict machine behaviors
inconsistent with measurements. In otherwords, the saturation
of the stator leakage reactance is the main contributor to torque
and current behavior, while the saturation of the remaining reactances
has a negligible influence. Consequently, when all voltage
levels are considered, the squirrel-cage induction motors can be
accurately modeled (with reasonable accuracy) with a double-cage
modelwhere only the stator leakage reactance is considered nonlinear.
When only a constant voltage level is considered, the paper also
proves that a linear double-cage model (all reactances are linear)
accurately predicts machine behavior at such voltage level.
2012-12-24T00:00:00Z