Articles de revista
http://hdl.handle.net/2117/3651
Sat, 21 Jan 2017 02:35:35 GMT
20170121T02:35:35Z

Study of resonances in 1 x 25 kV AC traction systems with external balancing equipment
http://hdl.handle.net/2117/99309
Study of resonances in 1 x 25 kV AC traction systems with external balancing equipment
Mesbahi, Nadhir; Monjo Mur, Lluís; Sainz Sapera, Luis
AC traction systems are 1 × 25 or 2 × 25 kV/50 Hz singlephase, nonlinear, timevarying loads that can cause powerquality problems, such as unbalanced or distorted voltages. To reduce unbalance, external balancing equipment is usually connected to these systems, forming the Steinmetz circuit. Parallel resonances can occur in these types of circuits, exciting the harmonic emissions (below 2 kHz) of railwayadjustable speed drives. This paper studies these resonances at pantograph terminals and provides analytical expressions to determine their harmonic frequencies. The expressions are validated from several traction systems in the literature and PSCAD simulations.
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Mon, 16 Jan 2017 12:37:05 GMT
http://hdl.handle.net/2117/99309
20170116T12:37:05Z
Mesbahi, Nadhir
Monjo Mur, Lluís
Sainz Sapera, Luis
AC traction systems are 1 × 25 or 2 × 25 kV/50 Hz singlephase, nonlinear, timevarying loads that can cause powerquality problems, such as unbalanced or distorted voltages. To reduce unbalance, external balancing equipment is usually connected to these systems, forming the Steinmetz circuit. Parallel resonances can occur in these types of circuits, exciting the harmonic emissions (below 2 kHz) of railwayadjustable speed drives. This paper studies these resonances at pantograph terminals and provides analytical expressions to determine their harmonic frequencies. The expressions are validated from several traction systems in the literature and PSCAD simulations.

Aeronautical ground lighting system study: field measurements and simulations
http://hdl.handle.net/2117/99215
Aeronautical ground lighting system study: field measurements and simulations
Vidal, Daniel; Monjo Mur, Lluís; Sainz Sapera, Luis
Aeronautical ground lighting (AGL) systems are singlephase series circuits where constant current regulators supply transformers and luminaires. These systems provide visual reference to aircraft during airport operations. There is a lack of AGL system models and measurements in the literature to study AGL system behaviour and predict their response to electrical events and future technological changes. The study contributes to AGL system modelling with an equivalent circuit useful to study AGL system concerns by Matlab/Simulink simulations. It also presents field measurements taken at Reus airport (Catalonia, Spain) for the validation of the proposed model and understanding of AGL system behaviour in the event of luminaire failure.
Fri, 13 Jan 2017 11:28:58 GMT
http://hdl.handle.net/2117/99215
20170113T11:28:58Z
Vidal, Daniel
Monjo Mur, Lluís
Sainz Sapera, Luis
Aeronautical ground lighting (AGL) systems are singlephase series circuits where constant current regulators supply transformers and luminaires. These systems provide visual reference to aircraft during airport operations. There is a lack of AGL system models and measurements in the literature to study AGL system behaviour and predict their response to electrical events and future technological changes. The study contributes to AGL system modelling with an equivalent circuit useful to study AGL system concerns by Matlab/Simulink simulations. It also presents field measurements taken at Reus airport (Catalonia, Spain) for the validation of the proposed model and understanding of AGL system behaviour in the event of luminaire failure.

Optimal fitting of highfrequency cable model parameters by applying evolutionary algorithms
http://hdl.handle.net/2117/98430
Optimal fitting of highfrequency cable model parameters by applying evolutionary algorithms
Bogarra Rodríguez, Santiago; Riba Ruiz, JordiRoger; Sala Caselles, Vicenç; García Espinosa, Antonio
Due to the widespread use of electronic power converters, lowvoltage highfrequency cable models are being increasingly applied in industry, automobile or aeronautics applications among others. It is known that depending on switching frequency, cable configuration and length, transient overvoltage effects comprising a wide frequency range from dc up to several tens of MHz can appear. However, to accurately reproduce the wideband frequency response, such models often require the use of ladder networks, thus being necessary to adjust the values of a relatively large number of R, L and C components, which is a complex task. This paper is focused to solve this problem, which is done by applying an iterative genetic algorithm (IGA) optimization approach. From a set of experimental short circuit and open circuit tests the highfrequency cable model of a given cable configuration is obtained, whose parameters are fitted by means of the proposed IGAbased method. Finally, the accuracy of the model obtained is validated experimentally by comparing the frequencydomain and timedomain responses through overvoltage predictions of different samples of the analyzed cable.
Fri, 16 Dec 2016 09:38:19 GMT
http://hdl.handle.net/2117/98430
20161216T09:38:19Z
Bogarra Rodríguez, Santiago
Riba Ruiz, JordiRoger
Sala Caselles, Vicenç
García Espinosa, Antonio
Due to the widespread use of electronic power converters, lowvoltage highfrequency cable models are being increasingly applied in industry, automobile or aeronautics applications among others. It is known that depending on switching frequency, cable configuration and length, transient overvoltage effects comprising a wide frequency range from dc up to several tens of MHz can appear. However, to accurately reproduce the wideband frequency response, such models often require the use of ladder networks, thus being necessary to adjust the values of a relatively large number of R, L and C components, which is a complex task. This paper is focused to solve this problem, which is done by applying an iterative genetic algorithm (IGA) optimization approach. From a set of experimental short circuit and open circuit tests the highfrequency cable model of a given cable configuration is obtained, whose parameters are fitted by means of the proposed IGAbased method. Finally, the accuracy of the model obtained is validated experimentally by comparing the frequencydomain and timedomain responses through overvoltage predictions of different samples of the analyzed cable.

Statistical 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 singlephase nonlinear 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 singlephase 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 largescale 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 GMT
http://hdl.handle.net/2117/83447
20160225T14:32:56Z
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 singlephase nonlinear 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 singlephase 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 largescale 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 GMT
http://hdl.handle.net/2117/81933
20160125T09:05:18Z
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.

Using the instantaneous power of a free acceleration test for squirrelcage motor parameters estimation
http://hdl.handle.net/2117/79352
Using the instantaneous power of a free acceleration test for squirrelcage motor parameters estimation
Kojooyan, Hengameh; Monjo Mur, Lluís; Córcoles López, Felipe; Pedra Durán, Joaquim
A new parameters determination method for squirrelcage 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 doublecage model parameters. The parameters are estimated from the machine impedance calculated at several points. At speed points where the doublecage 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 doublecage effect is not significant, i.e., between the maximum torque point and synchronism, the machine impedance is evaluated by a dynamicmodelbased linear leastsquare method. The proposed method has been applied to obtain the parameters of three motors tested in the laboratory. To check the method accuracy, the steadystate torque and currentslip curves predicted by the estimated parameters are successfully compared with those measured in the laboratory.
Tue, 17 Nov 2015 11:16:19 GMT
http://hdl.handle.net/2117/79352
20151117T11:16:19Z
Kojooyan, Hengameh
Monjo Mur, Lluís
Córcoles López, Felipe
Pedra Durán, Joaquim
A new parameters determination method for squirrelcage 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 doublecage model parameters. The parameters are estimated from the machine impedance calculated at several points. At speed points where the doublecage 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 doublecage effect is not significant, i.e., between the maximum torque point and synchronism, the machine impedance is evaluated by a dynamicmodelbased linear leastsquare method. The proposed method has been applied to obtain the parameters of three motors tested in the laboratory. To check the method accuracy, the steadystate torque and currentslip 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 50Hz singlephase, nonlinear, timevarying loads that can cause power quality problems. One of the main concerns about these systems is voltage distortion, because adjustablespeed 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 GMT
http://hdl.handle.net/2117/79350
20151117T10:34:12Z
Monjo Mur, Lluís
Sainz Sapera, Luis
AC traction systems are 1 x 25 or 2 x 25 kV 50Hz singlephase, nonlinear, timevarying loads that can cause power quality problems. One of the main concerns about these systems is voltage distortion, because adjustablespeed 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 wellknown 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 GMT
http://hdl.handle.net/2117/79320
20151116T15:09:28Z
Monjo Mur, Lluís
Sainz Sapera, Luis
Liang, Jun
Pedra Durán, Joaquim
Wind turbine harmonic current emissions are a wellknown 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 squirrelcage motors with parasitic torques in the torque–slip curve
http://hdl.handle.net/2117/79316
Parameter estimation of squirrelcage motors with parasitic torques in the torque–slip curve
Monjo Mur, Lluís; Córcoles López, Felipe; Pedra Durán, Joaquim
This paper studies parasitic torques in steadystate torque–slip curves of squirrelcage 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 doublecage 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 GMT
http://hdl.handle.net/2117/79316
20151116T14:04:52Z
Monjo Mur, Lluís
Córcoles López, Felipe
Pedra Durán, Joaquim
This paper studies parasitic torques in steadystate torque–slip curves of squirrelcage 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 doublecage 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 threephase equipment under voltage sags
http://hdl.handle.net/2117/79313
Testing of threephase 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 threephase equipment exposed to voltage sags caused by faults.
The voltage sag recovers at the faultcurrent 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 threephase equipment, here called ‘timeinvariant
(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 threephase induction generator and a threephase 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 threephase induction motor and a threephase diode bridge rectifier.
Mon, 16 Nov 2015 13:24:24 GMT
http://hdl.handle.net/2117/79313
20151116T13:24:24Z
Rolán Blanco, Alejandro
Córcoles López, Felipe
Pedra Durán, Joaquim
Monjo Mur, Lluís
Bogarra Rodríguez, Santiago
This paper provides insight into the testing of threephase equipment exposed to voltage sags caused by faults.
The voltage sag recovers at the faultcurrent 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 threephase equipment, here called ‘timeinvariant
(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 threephase induction generator and a threephase 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 threephase induction motor and a threephase diode bridge rectifier.