Articles de revista
http://hdl.handle.net/2117/3651
Sat, 30 Apr 2016 01:31:50 GMT2016-04-30T01:31:50ZStatistical study of personal computer cluster harmonic currents from experimental measurements
http://hdl.handle.net/2117/83447
Statistical study of personal computer cluster harmonic currents from experimental measurements
Mesas García, Juan José; Sainz Sapera, Luis; Sala Pérez, Pau
The net harmonic currents generated by a cluster of desktop personal computers are studied statistically. Personal computers (PCs) are single-phase non-linear loads with low individual consumption but significant collective distortion effects, as many of them can be connected to the same bus (personal computer cluster). This article reports experimental measurements of harmonic currents injected by single-phase rectifiers and seven personal computer types during four operating modes. The probability density functions (pdfs) of the harmonic currents (magnitude and phase angle) are investigated from the measurements. An analytical procedure to obtain these probability density functions for any typical personal computer working session is described and experimentally validated. The obtained probability density functions are found to be applicable to large-scale harmonic penetration statistical studies. Furthermore, attenuation and diversity effects are analyzed from the previous probability density functions, and the harmonic current cancellation effect on personal computer clusters is investigated with Monte Carlo simulations.
Thu, 25 Feb 2016 14:32:56 GMThttp://hdl.handle.net/2117/834472016-02-25T14:32:56ZMesas García, Juan JoséSainz Sapera, LuisSala Pérez, PauThe net harmonic currents generated by a cluster of desktop personal computers are studied statistically. Personal computers (PCs) are single-phase non-linear loads with low individual consumption but significant collective distortion effects, as many of them can be connected to the same bus (personal computer cluster). This article reports experimental measurements of harmonic currents injected by single-phase rectifiers and seven personal computer types during four operating modes. The probability density functions (pdfs) of the harmonic currents (magnitude and phase angle) are investigated from the measurements. An analytical procedure to obtain these probability density functions for any typical personal computer working session is described and experimentally validated. The obtained probability density functions are found to be applicable to large-scale harmonic penetration statistical studies. Furthermore, attenuation and diversity effects are analyzed from the previous probability density functions, and the harmonic current cancellation effect on personal computer clusters is investigated with Monte Carlo simulations.Lessons learned in the use of WIRIS quizzes to upgrade Moodle to solve electrical circuits
http://hdl.handle.net/2117/81933
Lessons learned in the use of WIRIS quizzes to upgrade Moodle to solve electrical circuits
Bogarra Rodríguez, Santiago; Corbalán Fuertes, Montserrat; Font Piera, Antonio; Plaza, Inma; Arcega Solsona, Francisco Javier
WIRIS quizzes is an online mathematics tool for educational purposes that
upgrades Moodle quizzes, and allows the development of personalized quizzes using
random data and conditional instructions. WIRIS quizzes can be used in any mathematics
or science degree; its complex operators allow it to be used to solve electrical circuits.
This tool promotes autonomous student learning and enables teachers to monitor that
learning and make adjustments if necessary. Therefore, this tool improves teaching
quality. It can also be used as an assessment tool by both the teacher and the student.
This paper shows how WIRIS quizzes has been integrated into the virtual campus of the
Polytechnic University of Catalonia (UPC), Spain to teach electrical circuits. Lessons
learned in performing and using WIRIS quizzes with second year students at the UPC are
shown.
Mon, 25 Jan 2016 09:05:18 GMThttp://hdl.handle.net/2117/819332016-01-25T09:05:18ZBogarra Rodríguez, SantiagoCorbalán Fuertes, MontserratFont Piera, AntonioPlaza, InmaArcega Solsona, Francisco JavierWIRIS quizzes is an online mathematics tool for educational purposes that
upgrades Moodle quizzes, and allows the development of personalized quizzes using
random data and conditional instructions. WIRIS quizzes can be used in any mathematics
or science degree; its complex operators allow it to be used to solve electrical circuits.
This tool promotes autonomous student learning and enables teachers to monitor that
learning and make adjustments if necessary. Therefore, this tool improves teaching
quality. It can also be used as an assessment tool by both the teacher and the student.
This paper shows how WIRIS quizzes has been integrated into the virtual campus of the
Polytechnic University of Catalonia (UPC), Spain to teach electrical circuits. Lessons
learned in performing and using WIRIS quizzes with second year students at the UPC are
shown.Using the instantaneous power of a free acceleration test for squirrel-cage motor parameters estimation
http://hdl.handle.net/2117/79352
Using the instantaneous power of a free acceleration test for squirrel-cage motor parameters estimation
Kojooyan, Hengameh; Monjo Mur, Lluís; Córcoles López, Felipe; Pedra Durán, Joaquim
A new parameters determination method for squirrel-cage induction motors is presented. As a main contribution, the method uses the instantaneous electrical power and the mechanical speed measured in a free acceleration test to estimate the double-cage model parameters. The parameters are estimated from the machine impedance calculated at several points. At speed points where the double-cage effect is significant, i.e., between the zero speed point and the maximum torque point, the machine impedance is evaluated by the instantaneous power method, and at speed points where the double-cage effect is not significant, i.e., between the maximum torque point and synchronism, the machine impedance is evaluated by a dynamic-model-based linear least-square method. The proposed method has been applied to obtain the parameters of three motors tested in the laboratory. To check the method accuracy, the steady-state torque and current-slip curves predicted by the estimated parameters are successfully compared with those measured in the laboratory.
Tue, 17 Nov 2015 11:16:19 GMThttp://hdl.handle.net/2117/793522015-11-17T11:16:19ZKojooyan, HengamehMonjo Mur, LluísCórcoles López, FelipePedra Durán, JoaquimA new parameters determination method for squirrel-cage induction motors is presented. As a main contribution, the method uses the instantaneous electrical power and the mechanical speed measured in a free acceleration test to estimate the double-cage model parameters. The parameters are estimated from the machine impedance calculated at several points. At speed points where the double-cage effect is significant, i.e., between the zero speed point and the maximum torque point, the machine impedance is evaluated by the instantaneous power method, and at speed points where the double-cage effect is not significant, i.e., between the maximum torque point and synchronism, the machine impedance is evaluated by a dynamic-model-based linear least-square method. The proposed method has been applied to obtain the parameters of three motors tested in the laboratory. To check the method accuracy, the steady-state torque and current-slip curves predicted by the estimated parameters are successfully compared with those measured in the laboratory.Study of resonances in 1 x 25 kV AC traction systems
http://hdl.handle.net/2117/79350
Study of resonances in 1 x 25 kV AC traction systems
Monjo Mur, Lluís; Sainz Sapera, Luis
AC traction systems are 1 x 25 or 2 x 25 kV 50-Hz single-phase, non-linear, time-varying loads that can cause power quality problems. One of the main concerns about these systems is voltage distortion, because adjustable-speed drives for trains may inject harmonic currents of frequencies below 2kHz. Since the presence of parallel resonances in the contact feeder section of the traction circuit worsens the scenario, traction system resonance phenomena should be analyzed to prevent problems. Several works addressed these phenomena, but they only drew weak numerical conclusions based on the frequency scan method. This article studies 1 x 25 kV traction system resonances at pantograph terminals and provides more effective analytical expressions to locate them and determine the impact of traction system parameters on them. These expressions are validated from several traction systems in the literature.
Tue, 17 Nov 2015 10:34:12 GMThttp://hdl.handle.net/2117/793502015-11-17T10:34:12ZMonjo Mur, LluísSainz Sapera, LuisAC traction systems are 1 x 25 or 2 x 25 kV 50-Hz single-phase, non-linear, time-varying loads that can cause power quality problems. One of the main concerns about these systems is voltage distortion, because adjustable-speed drives for trains may inject harmonic currents of frequencies below 2kHz. Since the presence of parallel resonances in the contact feeder section of the traction circuit worsens the scenario, traction system resonance phenomena should be analyzed to prevent problems. Several works addressed these phenomena, but they only drew weak numerical conclusions based on the frequency scan method. This article studies 1 x 25 kV traction system resonances at pantograph terminals and provides more effective analytical expressions to locate them and determine the impact of traction system parameters on them. These expressions are validated from several traction systems in the literature.Study of resonance in wind parks
http://hdl.handle.net/2117/79320
Study of resonance in wind parks
Monjo Mur, Lluís; Sainz Sapera, Luis; Liang, Jun; Pedra Durán, Joaquim
Wind turbine harmonic current emissions are a well-known power quality problem. These emissions flow through wind park impedances, leading to grid voltage distortion. Parallel resonance may worsen the problem because it increases voltage distortion around the resonance frequency. Hence, it is interesting to analyze the parallel resonance phenomenon. The paper explores this phenomenon in wind parks and provides analytical expressions to determine parallel resonances. (C) 2015 The Authors. Published by Elsevier B.V.
Mon, 16 Nov 2015 15:09:28 GMThttp://hdl.handle.net/2117/793202015-11-16T15:09:28ZMonjo Mur, LluísSainz Sapera, LuisLiang, JunPedra Durán, JoaquimWind turbine harmonic current emissions are a well-known power quality problem. These emissions flow through wind park impedances, leading to grid voltage distortion. Parallel resonance may worsen the problem because it increases voltage distortion around the resonance frequency. Hence, it is interesting to analyze the parallel resonance phenomenon. The paper explores this phenomenon in wind parks and provides analytical expressions to determine parallel resonances. (C) 2015 The Authors. Published by Elsevier B.V.Parameter estimation of squirrel-cage motors with parasitic torques in the torque–slip curve
http://hdl.handle.net/2117/79316
Parameter estimation of squirrel-cage motors with parasitic torques in the torque–slip curve
Monjo Mur, Lluís; Córcoles López, Felipe; Pedra Durán, Joaquim
This paper studies parasitic torques in steady-state torque–slip curves of squirrel-cage induction motors. The
curves of nine motors (small, medium and large size units), three of which were measured in the range s = 2 to 0, are
analysed. The torque–slip curves of eight of these nine motors differ significantly from the smooth curves predicted by the
classical single- and double-cage models: a torque dip at large slips in the motoring regime and a notable torque increase
in the braking regime occur. As parasitic torques have been traditionally associated with space harmonics, two singlecage
chain models (which consider the space harmonics) are tested to fit the measured torque and current of the three
measured motors: one neglects the skin effect, leading to the wrong torque prediction, whereas the other (the chain
model proposed in the early 60s in the literature) considers the skin effect, leading to an accurate torque prediction.
Mon, 16 Nov 2015 14:04:52 GMThttp://hdl.handle.net/2117/793162015-11-16T14:04:52ZMonjo Mur, LluísCórcoles López, FelipePedra Durán, JoaquimThis paper studies parasitic torques in steady-state torque–slip curves of squirrel-cage induction motors. The
curves of nine motors (small, medium and large size units), three of which were measured in the range s = 2 to 0, are
analysed. The torque–slip curves of eight of these nine motors differ significantly from the smooth curves predicted by the
classical single- and double-cage models: a torque dip at large slips in the motoring regime and a notable torque increase
in the braking regime occur. As parasitic torques have been traditionally associated with space harmonics, two singlecage
chain models (which consider the space harmonics) are tested to fit the measured torque and current of the three
measured motors: one neglects the skin effect, leading to the wrong torque prediction, whereas the other (the chain
model proposed in the early 60s in the literature) considers the skin effect, leading to an accurate torque prediction.Testing of three-phase equipment under voltage sags
http://hdl.handle.net/2117/79313
Testing of three-phase equipment under voltage sags
Rolán Blanco, Alejandro; Córcoles López, Felipe; Pedra Durán, Joaquim; Monjo Mur, Lluís; Bogarra Rodríguez, Santiago
This paper provides insight into the testing of three-phase equipment exposed to voltage sags caused by faults.
The voltage sag recovers at the fault-current zeros, leading to a ‘discrete’ voltage recovery, that is, the fault is cleared in
different steps. In the literature, the most widespread classification divides ‘discrete’ sags into 14 types. The authors study shows that it is generally sufficient to consider only five sag types for three-phase equipment, here called ‘time-invariant
(TI)’ equipment. As the remaining nine sag types cause identical equipment behaviour in Park or Ku variables, the number of laboratory tests (or of extensive simulations) on equipment under sags is reduced by a ratio of 14/5. The study is validated by simulation of a three-phase induction generator and a three-phase inverter, which are ‘TI’, and a threephase
diode bridge rectifier, which is not ‘TI’. Both analytical study and simulation results are validated by testing a three-phase induction motor and a three-phase diode bridge rectifier.
Mon, 16 Nov 2015 13:24:24 GMThttp://hdl.handle.net/2117/793132015-11-16T13:24:24ZRolán Blanco, AlejandroCórcoles López, FelipePedra Durán, JoaquimMonjo Mur, LluísBogarra Rodríguez, SantiagoThis paper provides insight into the testing of three-phase equipment exposed to voltage sags caused by faults.
The voltage sag recovers at the fault-current zeros, leading to a ‘discrete’ voltage recovery, that is, the fault is cleared in
different steps. In the literature, the most widespread classification divides ‘discrete’ sags into 14 types. The authors study shows that it is generally sufficient to consider only five sag types for three-phase equipment, here called ‘time-invariant
(TI)’ equipment. As the remaining nine sag types cause identical equipment behaviour in Park or Ku variables, the number of laboratory tests (or of extensive simulations) on equipment under sags is reduced by a ratio of 14/5. The study is validated by simulation of a three-phase induction generator and a three-phase inverter, which are ‘TI’, and a threephase
diode bridge rectifier, which is not ‘TI’. Both analytical study and simulation results are validated by testing a three-phase induction motor and a three-phase diode bridge rectifier.Model of aeronautical ground lighting system transformers
http://hdl.handle.net/2117/79229
Model of aeronautical ground lighting system transformers
lomvarte, daniel; Monjo Mur, Lluís; Sainz Sapera, Luis; Pedra Durán, Joaquim
Airport ground lighting (AGL) systems provide visual reference to aircrafts during
airport operations. In AGL systems, constant current regulators feed a beacon circuit supplied
through isolation transformers. Component modeling is necessary to simulate AGL systems, and
thus characterize and predict their behavior. This paper presents an isolation transformer model
including transformer core saturation. Moreover, a procedure to estimate transformer model
parameters is proposed. Both the model and the estimation method are validated with extensive
measurements on more than 20 isolation transformers of different power ratings and trade names.
Fri, 13 Nov 2015 12:15:36 GMThttp://hdl.handle.net/2117/792292015-11-13T12:15:36Zlomvarte, danielMonjo Mur, LluísSainz Sapera, LuisPedra Durán, JoaquimAirport ground lighting (AGL) systems provide visual reference to aircrafts during
airport operations. In AGL systems, constant current regulators feed a beacon circuit supplied
through isolation transformers. Component modeling is necessary to simulate AGL systems, and
thus characterize and predict their behavior. This paper presents an isolation transformer model
including transformer core saturation. Moreover, a procedure to estimate transformer model
parameters is proposed. Both the model and the estimation method are validated with extensive
measurements on more than 20 isolation transformers of different power ratings and trade names.Squirrel-cage induction motor parameter estimation using a variable frequency test
http://hdl.handle.net/2117/78507
Squirrel-cage induction motor parameter estimation using a variable frequency test
Monjo Mur, Lluís; Kojooyan, Hengameh; Córcoles López, Felipe; Pedra Durán, Joaquim
This paper presents amethod for squirrel-cage induction motor parameter estimation using a phase-to-phase standstill variable frequency test. The measured resistance and reactance at different frequencies are the data of the minimization error function to be minimized for single-and double-cage model parameters estimation. It is observed that the single-cage model is unable to fit the measured data for frequencies above several tenths of Hertz, whereas the double-cage model fits the measured data accurately in all the frequency ranges (from 0 to 150 Hz). The single-and double-cage estimated parameters are validated by comparison with data from two additional tests: 1) steady-state torque and current measurement test at different speeds; and 2) dynamic free-acceleration test. Again, the agreement between measured and predicted torque (in the first test) and current (in both tests) is satisfactory only for the double-cage model.
Thu, 29 Oct 2015 13:46:17 GMThttp://hdl.handle.net/2117/785072015-10-29T13:46:17ZMonjo Mur, LluísKojooyan, HengamehCórcoles López, FelipePedra Durán, JoaquimThis paper presents amethod for squirrel-cage induction motor parameter estimation using a phase-to-phase standstill variable frequency test. The measured resistance and reactance at different frequencies are the data of the minimization error function to be minimized for single-and double-cage model parameters estimation. It is observed that the single-cage model is unable to fit the measured data for frequencies above several tenths of Hertz, whereas the double-cage model fits the measured data accurately in all the frequency ranges (from 0 to 150 Hz). The single-and double-cage estimated parameters are validated by comparison with data from two additional tests: 1) steady-state torque and current measurement test at different speeds; and 2) dynamic free-acceleration test. Again, the agreement between measured and predicted torque (in the first test) and current (in both tests) is satisfactory only for the double-cage model.Iluminación pública con energia eólica y solar
http://hdl.handle.net/2117/76341
Iluminación pública con energia eólica y solar
Bargalló Perpiñá, Ramón
Mon, 27 Jul 2015 11:55:26 GMThttp://hdl.handle.net/2117/763412015-07-27T11:55:26ZBargalló Perpiñá, Ramón