Departament d'Enginyeria Elèctrica
http://hdl.handle.net/2117/4007
20171214T19:19:15Z

Detection of eccentricity faults in fivephase ferritePM assisted synchronous reluctance machines
http://hdl.handle.net/2117/111545
Detection of eccentricity faults in fivephase ferritePM assisted synchronous reluctance machines
López Torres, Carlos; Riba Ruiz, JordiRoger; García Espinosa, Antonio; Romeral Martínez, José Luis
Air gap eccentricity faults in fivephase ferriteassisted synchronous reluctance motors (fPMaSynRMs) tend to distort the magnetic flux in the air gap, which in turn affects the spectral content of both the stator currents and the ZSVC (zerosequence voltage component). However, there is a lack of research works dealing with the topic of fault diagnosis in multiphase PMaSynRMs, and in particular, focused to detect eccentricity faults. The analysis of the spectral components of the line currents and the ZSVC, allows developing fault diagnosis algorithms to detect eccentricity faults. The effect of the operating conditions is also analyzed, since this paper shows that it has a nonnegligible impact on the effectivity and sensitivity of the diagnosis based on the analysis of the stator currents and the ZSVC. To this end, different operating conditions are analyzed. The paper also evaluates the influence of the operating conditions on the harmonic content of the line currents and the ZSVC, and determines the most suitable operating conditions to enhance the sensitivity of the analyzed methods. Finally, fault indicators to detect eccentricity faults, which are based on the spectral content of the stator currents and the ZSVC are derived, and their performance is assessed. The approach presented in this work may be useful to develop fault diagnosis strategies based on the acquisition and subsequent analysis and interpretation of the spectral content of the line currents and the ZSVC.
20171205T08:40:14Z
López Torres, Carlos
Riba Ruiz, JordiRoger
García Espinosa, Antonio
Romeral Martínez, José Luis
Air gap eccentricity faults in fivephase ferriteassisted synchronous reluctance motors (fPMaSynRMs) tend to distort the magnetic flux in the air gap, which in turn affects the spectral content of both the stator currents and the ZSVC (zerosequence voltage component). However, there is a lack of research works dealing with the topic of fault diagnosis in multiphase PMaSynRMs, and in particular, focused to detect eccentricity faults. The analysis of the spectral components of the line currents and the ZSVC, allows developing fault diagnosis algorithms to detect eccentricity faults. The effect of the operating conditions is also analyzed, since this paper shows that it has a nonnegligible impact on the effectivity and sensitivity of the diagnosis based on the analysis of the stator currents and the ZSVC. To this end, different operating conditions are analyzed. The paper also evaluates the influence of the operating conditions on the harmonic content of the line currents and the ZSVC, and determines the most suitable operating conditions to enhance the sensitivity of the analyzed methods. Finally, fault indicators to detect eccentricity faults, which are based on the spectral content of the stator currents and the ZSVC are derived, and their performance is assessed. The approach presented in this work may be useful to develop fault diagnosis strategies based on the acquisition and subsequent analysis and interpretation of the spectral content of the line currents and the ZSVC.

Dancing sprites: detailed analysis of two case studies
http://hdl.handle.net/2117/111417
Dancing sprites: detailed analysis of two case studies
Soula, Serge; Mlynarczyk, Janusz; Fullekrug, Martin; Pineda Rüegg, Nicolau; Georgis, J.F.; Van der Velde, Oscar Arnoud; Montañá Puig, Juan; Fabró Tàpia, Ferran
On 29–30 October 2013, a lowlight video camera installed at Pic du Midi (2877¿m), recorded transient luminous events above a very active storm over the Mediterranean Sea. The minimum cloud top temperature reached 73°C, while its cloud to ground (CG) flash rate exceeded 30¿fl¿min1. Some sprite events have long duration and resemble to dancing sprites. We analyze in detail the temporal evolution and estimated location of two series of sprite sequences, as well as the cloud structure, the lightning activity, the electric field radiated in a broad range of low frequencies, and the current moment waveform of the lightning strokes. (i) In each series, successive sprite sequences reflect time and location of corresponding positive lightning strokes across the stratiform region. (ii) The longer timedelayed (>20¿ms) sprite elements correspond to the lower impulsive charge moment changes (iCMC) of the parent strokes (<200¿C¿km), and they are shifted few tens of kilometers from their SP¿+¿CG stroke. However, both short and long timedelayed sprite elements also occur after strokes that produce a large iCMC and that are followed by a continuing current. (iii) The long timedelayed sprite elements during the continuing current correspond to surges in the current moment waveform. They occur sometimes at an altitude apparently lower than the previous short timedelayed sprite elements, possibly because of changes in the local conductivity. (iv) The largest and brightest sprite elements produce significant current signatures, visible when their delay is not too short (~3–5¿ms).
20171201T09:58:43Z
Soula, Serge
Mlynarczyk, Janusz
Fullekrug, Martin
Pineda Rüegg, Nicolau
Georgis, J.F.
Van der Velde, Oscar Arnoud
Montañá Puig, Juan
Fabró Tàpia, Ferran
On 29–30 October 2013, a lowlight video camera installed at Pic du Midi (2877¿m), recorded transient luminous events above a very active storm over the Mediterranean Sea. The minimum cloud top temperature reached 73°C, while its cloud to ground (CG) flash rate exceeded 30¿fl¿min1. Some sprite events have long duration and resemble to dancing sprites. We analyze in detail the temporal evolution and estimated location of two series of sprite sequences, as well as the cloud structure, the lightning activity, the electric field radiated in a broad range of low frequencies, and the current moment waveform of the lightning strokes. (i) In each series, successive sprite sequences reflect time and location of corresponding positive lightning strokes across the stratiform region. (ii) The longer timedelayed (>20¿ms) sprite elements correspond to the lower impulsive charge moment changes (iCMC) of the parent strokes (<200¿C¿km), and they are shifted few tens of kilometers from their SP¿+¿CG stroke. However, both short and long timedelayed sprite elements also occur after strokes that produce a large iCMC and that are followed by a continuing current. (iii) The long timedelayed sprite elements during the continuing current correspond to surges in the current moment waveform. They occur sometimes at an altitude apparently lower than the previous short timedelayed sprite elements, possibly because of changes in the local conductivity. (iv) The largest and brightest sprite elements produce significant current signatures, visible when their delay is not too short (~3–5¿ms).

Criterion for the electrical resonance stability of offshore wind power plants connected through HVDC links
http://hdl.handle.net/2117/111326
Criterion for the electrical resonance stability of offshore wind power plants connected through HVDC links
Cheah Mañé, Marc; Sainz Sapera, Luis; Liang, Jun; Jenkins, Nicholas; Ugalde Loo, Carlos E.
Electrical resonances may compromise the stability of HVDCconnected offshore wind power plants (OWPPs). In particular, an offshore HVDC converter can reduce the damping of an OWPP at lowfrequency series resonances, leading to the system instability. The interaction between offshore HVDC converter control and electrical resonances of offshore grids is analyzed in this paper. An impedancebased representation of an OWPP is used to analyze the effect that offshore converters have on the resonant frequency of the offshore grid and on system stability. The positivenetdamping criterion, originally proposed for subsynchronous analysis, has been adapted to determine the stability of the HVDCconnected OWPP. The reformulated criterion enables the net damping of the electrical series resonance to be evaluated and establishes a clear relationship between electrical resonances of the HVDCconnected OWPPs and stability. The criterion is theoretically justified, with analytical expressions for lowfrequency series resonances being obtained and stability conditions defined based on the total damping of the OWPP. Examples are used to show the influence that HVDC converter control parameters and the OWPP configuration have on stability. A root locus analysis and timedomain simulations in PSCAD/EMTDC are presented to verify the stability conditions.
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20171129T11:57:48Z
Cheah Mañé, Marc
Sainz Sapera, Luis
Liang, Jun
Jenkins, Nicholas
Ugalde Loo, Carlos E.
Electrical resonances may compromise the stability of HVDCconnected offshore wind power plants (OWPPs). In particular, an offshore HVDC converter can reduce the damping of an OWPP at lowfrequency series resonances, leading to the system instability. The interaction between offshore HVDC converter control and electrical resonances of offshore grids is analyzed in this paper. An impedancebased representation of an OWPP is used to analyze the effect that offshore converters have on the resonant frequency of the offshore grid and on system stability. The positivenetdamping criterion, originally proposed for subsynchronous analysis, has been adapted to determine the stability of the HVDCconnected OWPP. The reformulated criterion enables the net damping of the electrical series resonance to be evaluated and establishes a clear relationship between electrical resonances of the HVDCconnected OWPPs and stability. The criterion is theoretically justified, with analytical expressions for lowfrequency series resonances being obtained and stability conditions defined based on the total damping of the OWPP. Examples are used to show the influence that HVDC converter control parameters and the OWPP configuration have on stability. A root locus analysis and timedomain simulations in PSCAD/EMTDC are presented to verify the stability conditions.

A new approach for flux and rotor resistance estimation of induction motors
http://hdl.handle.net/2117/111323
A new approach for flux and rotor resistance estimation of induction motors
Bazylev, Dmitry; Dòria Cerezo, Arnau; Pyrkin, Anton A.; Bobstov, Alexey A.; Ortega, Romeo
In this paper we address the problems of flux and rotor resistance estimation of induction motors. We propose a radically new approach that combines the recently introduced techniques of parameter estimation based observers (PEBO) with the dynamic regression extension and mixing (DREM) parameter adaptation. The PEBO framework is used to recast the flux observation task as a parameter estimation problem, for which the DREM technique is utilised. The resulting flux observer is then combined with a standard gradient estimator for the rotor resistance. Simulation results of an adaptive implementation of the classical field oriented controller demonstrate the effectiveness of the proposed flux observer and rotor resistance estimator even in closedloop operation.
20171129T10:47:16Z
Bazylev, Dmitry
Dòria Cerezo, Arnau
Pyrkin, Anton A.
Bobstov, Alexey A.
Ortega, Romeo
In this paper we address the problems of flux and rotor resistance estimation of induction motors. We propose a radically new approach that combines the recently introduced techniques of parameter estimation based observers (PEBO) with the dynamic regression extension and mixing (DREM) parameter adaptation. The PEBO framework is used to recast the flux observation task as a parameter estimation problem, for which the DREM technique is utilised. The resulting flux observer is then combined with a standard gradient estimator for the rotor resistance. Simulation results of an adaptive implementation of the classical field oriented controller demonstrate the effectiveness of the proposed flux observer and rotor resistance estimator even in closedloop operation.

Aliasing of the Schumann resonance background signal by spriteassociated Qbursts
http://hdl.handle.net/2117/111322
Aliasing of the Schumann resonance background signal by spriteassociated Qbursts
Guha, Anirban; Williams, Earle R.; Boldi, Robert; Satori, Gabriella; Nagy, Tamás; Bór, József; Montañá Puig, Juan; Ortega, Pascal
The Earth's naturally occurring Schumann resonances (SR) are composed of a quasicontinuous background component and a largeramplitude, shortduration transient component, otherwise called ‘Qburst’ (Ogawa et al., 1967). Sprites in the mesosphere are also known to accompany the energetic positive ground flashes that launch the Qbursts (Boccippio et al., 1995). Spectra of the background Schumann Resonances (SR) require a natural stabilization period of ~10–12 min for the three conspicuous modal parameters to be derived from Lorentzian fitting. Before the spectra are computed and the fitting process is initiated, the raw time series data need to be properly filtered for local cultural noise, narrow band interference as well as for large transients in the form of global Qbursts. Mushtak and Williams (2009) describe an effective technique called Isolated Lorentzian (ILOR), in which, the contributions from local cultural and various other noises are minimized to a great extent. An automated technique based on median filtering of time series data has been developed. These special lightning flashes are known to have greater contribution in the ELF range (below 1 kHz) compared to general negative CG strikes (Huang et al., 1999; Cummer et al., 2006). The global distributions of these Qbursts have been studied by Huang et al. (1999) Rhode Island, USA by wave impedance methods from single station ELF measurements at Rhode Island, USA and from Japan Hobara et al. (2006). The present work aims to demonstrate the effect of Q bursts on SR background spectra using GPS timestamped observation of TLEs. It is observed that the Qbursts selected for the present work do alias the background spectra over a 5s period, though the amplitudes of these Q bursts are far below the background threshold of 16 Core Standard Deviation (CSD) so that they do not strongly alias the background spectra of 10–12 min duration. The examination of one exceptional Qburst shows that appreciable spectral aliasing can occur even when 12min spectral integrations are considered. The statistical result shows that for a 12min spectrum, events above 16 CSD are capable of producing significant frequency aliasing of the modal frequencies, although the intensity aliasing might have a negligible effect unless the events are exceptionally large (~200 CSD). The spectral CSD methodology may be used to extract the time of arrival of the Qburst transients. This methodology may be combined with a hyperbolic ranging, thus becoming an effective tool to detect TLEs globally with a modest number of networked observational stations.
20171129T10:24:57Z
Guha, Anirban
Williams, Earle R.
Boldi, Robert
Satori, Gabriella
Nagy, Tamás
Bór, József
Montañá Puig, Juan
Ortega, Pascal
The Earth's naturally occurring Schumann resonances (SR) are composed of a quasicontinuous background component and a largeramplitude, shortduration transient component, otherwise called ‘Qburst’ (Ogawa et al., 1967). Sprites in the mesosphere are also known to accompany the energetic positive ground flashes that launch the Qbursts (Boccippio et al., 1995). Spectra of the background Schumann Resonances (SR) require a natural stabilization period of ~10–12 min for the three conspicuous modal parameters to be derived from Lorentzian fitting. Before the spectra are computed and the fitting process is initiated, the raw time series data need to be properly filtered for local cultural noise, narrow band interference as well as for large transients in the form of global Qbursts. Mushtak and Williams (2009) describe an effective technique called Isolated Lorentzian (ILOR), in which, the contributions from local cultural and various other noises are minimized to a great extent. An automated technique based on median filtering of time series data has been developed. These special lightning flashes are known to have greater contribution in the ELF range (below 1 kHz) compared to general negative CG strikes (Huang et al., 1999; Cummer et al., 2006). The global distributions of these Qbursts have been studied by Huang et al. (1999) Rhode Island, USA by wave impedance methods from single station ELF measurements at Rhode Island, USA and from Japan Hobara et al. (2006). The present work aims to demonstrate the effect of Q bursts on SR background spectra using GPS timestamped observation of TLEs. It is observed that the Qbursts selected for the present work do alias the background spectra over a 5s period, though the amplitudes of these Q bursts are far below the background threshold of 16 Core Standard Deviation (CSD) so that they do not strongly alias the background spectra of 10–12 min duration. The examination of one exceptional Qburst shows that appreciable spectral aliasing can occur even when 12min spectral integrations are considered. The statistical result shows that for a 12min spectrum, events above 16 CSD are capable of producing significant frequency aliasing of the modal frequencies, although the intensity aliasing might have a negligible effect unless the events are exceptionally large (~200 CSD). The spectral CSD methodology may be used to extract the time of arrival of the Qburst transients. This methodology may be combined with a hyperbolic ranging, thus becoming an effective tool to detect TLEs globally with a modest number of networked observational stations.

Load identification of different Halbacharray topologies on permanent magnet synchronous generators using the coupled fieldcircuit FE methodology
http://hdl.handle.net/2117/111237
Load identification of different Halbacharray topologies on permanent magnet synchronous generators using the coupled fieldcircuit FE methodology
Asef, Pedram; Bargalló Perpiñá, Ramón; Barzegaran, M.R.; lapthorn, andrew; Mewes, Daniela
In this paper, the influence of gap consideration on load identification under various Halbacharraybased topologies (HABOs) is investigated while the system is onduty. The load characteristics of a radial flux generator with closedslots and the exterior rotor topology is discussed, where the effect of eddycurrents are observed. This comparative study deals with the consideration of the combined moment of inertia calculation that demonstrates how electromagneticbased post processing calculations are estimated without the aid of nominal machine parameter values. The analysis was performed using a 2D finiteelement simulation of different HABOs with the gap consideration between the segments. Additionally, a comprehensive comparison with no gap is considered. Also, the dynamic analysis using an uncontrolled conventional rectifier model is used to derive effected key output parameters such as torque, output power, power factor, and linetoline voltage. The major objective of the study is to determine corresponding load results in order to employ the most suitable and capable magnetization topology from the load perspective in the PM synchronous generator (PMSGs). Accordingly, the maximum power (MP) point was carried out to maximize the output DC power. With respect to the combined moment of inertia estimation, the load parameter estimation is verified experimentally on a surfacemounted PMSG using different magnetization topologies. Furthermore, commercial and environmental issues of the project are considered to reduce CO2 emissions as part of green power generation development.
20171127T09:41:30Z
Asef, Pedram
Bargalló Perpiñá, Ramón
Barzegaran, M.R.
lapthorn, andrew
Mewes, Daniela
In this paper, the influence of gap consideration on load identification under various Halbacharraybased topologies (HABOs) is investigated while the system is onduty. The load characteristics of a radial flux generator with closedslots and the exterior rotor topology is discussed, where the effect of eddycurrents are observed. This comparative study deals with the consideration of the combined moment of inertia calculation that demonstrates how electromagneticbased post processing calculations are estimated without the aid of nominal machine parameter values. The analysis was performed using a 2D finiteelement simulation of different HABOs with the gap consideration between the segments. Additionally, a comprehensive comparison with no gap is considered. Also, the dynamic analysis using an uncontrolled conventional rectifier model is used to derive effected key output parameters such as torque, output power, power factor, and linetoline voltage. The major objective of the study is to determine corresponding load results in order to employ the most suitable and capable magnetization topology from the load perspective in the PM synchronous generator (PMSGs). Accordingly, the maximum power (MP) point was carried out to maximize the output DC power. With respect to the combined moment of inertia estimation, the load parameter estimation is verified experimentally on a surfacemounted PMSG using different magnetization topologies. Furthermore, commercial and environmental issues of the project are considered to reduce CO2 emissions as part of green power generation development.

A family of gradient descent grid frequency estimators for the SOGI filter
http://hdl.handle.net/2117/111151
A family of gradient descent grid frequency estimators for the SOGI filter
Matas Alcalá, José; Martín Cañadas, María Elena; Hoz Casas, Jordi de la; Abusorrah, A.; AlTurki, Y.A.; AlHindawi, M.
This paper applies the adaptive gradient descent method to the secondorder generalized integrator (SOGI) filter in order to find an online estimation algorithm for the grid frequency, which leads to the proposal of three possible estimators. One of them is identical to the FLL algorithm reported in literature, which proves that it should be understood as a gradient descent estimation algorithm and not as a "frequency locked loop". The proposed gradient descent estimators are simple and suitable to be implemented into a digital processor with small computational burden. However, due to the SOGI characteristics, the estimators show to be especially sensitive to subharmonic and dcoffset voltage distortion. These problems are removed adopting a cascaded double SOGI approach, which strongly increases the rejection capability to harmonics and enhances the response to voltage sags. Simulation and experimental results are provided to validate the proposed contribution.
20171124T10:14:29Z
Matas Alcalá, José
Martín Cañadas, María Elena
Hoz Casas, Jordi de la
Abusorrah, A.
AlTurki, Y.A.
AlHindawi, M.
This paper applies the adaptive gradient descent method to the secondorder generalized integrator (SOGI) filter in order to find an online estimation algorithm for the grid frequency, which leads to the proposal of three possible estimators. One of them is identical to the FLL algorithm reported in literature, which proves that it should be understood as a gradient descent estimation algorithm and not as a "frequency locked loop". The proposed gradient descent estimators are simple and suitable to be implemented into a digital processor with small computational burden. However, due to the SOGI characteristics, the estimators show to be especially sensitive to subharmonic and dcoffset voltage distortion. These problems are removed adopting a cascaded double SOGI approach, which strongly increases the rejection capability to harmonics and enhances the response to voltage sags. Simulation and experimental results are provided to validate the proposed contribution.

Design and optimization for vehicle driving cycle of rareearthfree SynRM based on coupled lumped thermal and magnetic networks
http://hdl.handle.net/2117/111149
Design and optimization for vehicle driving cycle of rareearthfree SynRM based on coupled lumped thermal and magnetic networks
López Torres, Carlos; García Espinosa, Antonio; Riba Ruiz, JordiRoger; Romeral Martínez, José Luis
This work presents a range optimization of a SynRM (synchronous reluctance motor) and a PMaSynRM (permanentmagnetassisted synchronous reluctance motor) according to a standard driving cycle, and the solutions obtained are compared. The proposed approach avoids the use of finite element analysis (FEA) during the optimization process, thus greatly reducing the time required to obtain the optimal solution. The paper validates the optimal motors obtained in different domains, since the methodology takes into account a multiphysics design. Using two coupled reluctance and thermal networks, all possible working points in the torquespeed plane are obtained taking into account thermal effects, magnetic saturation, iron losses as well as voltage and current constraints imposed by the inverter. The proposed approach allows a fast comparison of the solutions attained. The design and optimization methodology presented in this work can be applied to any driving cycle.
20171124T09:53:02Z
López Torres, Carlos
García Espinosa, Antonio
Riba Ruiz, JordiRoger
Romeral Martínez, José Luis
This work presents a range optimization of a SynRM (synchronous reluctance motor) and a PMaSynRM (permanentmagnetassisted synchronous reluctance motor) according to a standard driving cycle, and the solutions obtained are compared. The proposed approach avoids the use of finite element analysis (FEA) during the optimization process, thus greatly reducing the time required to obtain the optimal solution. The paper validates the optimal motors obtained in different domains, since the methodology takes into account a multiphysics design. Using two coupled reluctance and thermal networks, all possible working points in the torquespeed plane are obtained taking into account thermal effects, magnetic saturation, iron losses as well as voltage and current constraints imposed by the inverter. The proposed approach allows a fast comparison of the solutions attained. The design and optimization methodology presented in this work can be applied to any driving cycle.

Series interline DC/DC current flow controller for meshed HVDC grids
http://hdl.handle.net/2117/111145
Series interline DC/DC current flow controller for meshed HVDC grids
Sau Bassols, Joan; Prieto Araujo, Eduardo; Gomis Bellmunt, Oriol; Hassan, Fainan
This paper proposes a DC/DC Current Flow Controller (CFC) for meshed High Voltage Direct Current (HVDC) grids. The CFC has the advantage of a simplified structure that allows to use minimum number of switches when unidirectional current flows through the DC lines are expected. An extended CFC topology able to operate with all the possible current flows is also presented. Then, the operating principle of the CFC is discussed and its structure is compared with a dual Hbridge analysing advantages and disadvantages. The work also details the applied modulation strategy and the control methodology. Finally, a 5terminal meshed HVDC grid is used to validate the CFC by means of simulations.
20171124T08:46:32Z
Sau Bassols, Joan
Prieto Araujo, Eduardo
Gomis Bellmunt, Oriol
Hassan, Fainan
This paper proposes a DC/DC Current Flow Controller (CFC) for meshed High Voltage Direct Current (HVDC) grids. The CFC has the advantage of a simplified structure that allows to use minimum number of switches when unidirectional current flows through the DC lines are expected. An extended CFC topology able to operate with all the possible current flows is also presented. Then, the operating principle of the CFC is discussed and its structure is compared with a dual Hbridge analysing advantages and disadvantages. The work also details the applied modulation strategy and the control methodology. Finally, a 5terminal meshed HVDC grid is used to validate the CFC by means of simulations.

Regenerative braking in electric scooters
http://hdl.handle.net/2117/111144
Regenerative braking in electric scooters
Montesinos Miracle, Daniel; Ruiz Bassols, Toni
Electric urban vehicles are in the spotlight of society since its autonomy dependence is not that high. Electric motorcycles and scooters are actually already reliable urban vehicles for short journeys. These vehicles can have different configurations for their powertrains. In this paper an electric scooter model is developed using Energetic Macroscopic Representation in order to analyze its braking and traction systems and determine by simulations, which is the best configuration for its powertrain from energy consumption point of view.
20171124T08:34:09Z
Montesinos Miracle, Daniel
Ruiz Bassols, Toni
Electric urban vehicles are in the spotlight of society since its autonomy dependence is not that high. Electric motorcycles and scooters are actually already reliable urban vehicles for short journeys. These vehicles can have different configurations for their powertrains. In this paper an electric scooter model is developed using Energetic Macroscopic Representation in order to analyze its braking and traction systems and determine by simulations, which is the best configuration for its powertrain from energy consumption point of view.