Articles de revista
http://hdl.handle.net/2117/3832
2019-08-24T00:53:18ZSingle-carrier phase-disposition PWM techniques for multiple interleaved voltage-source converter legs
http://hdl.handle.net/2117/114230
Single-carrier phase-disposition PWM techniques for multiple interleaved voltage-source converter legs
Konstantinou, Georgios; Capellá Frau, Gabriel José; Pou, Josep; Ceballos Recio, Salvador
Interleaved converter legs are typically modulated with individual carriers per leg and phase-shifted PWM (PS-PWM) as it facilitates current balancing amongst the legs. Phase-disposition PWM (PD-PWM), despite the better harmonic performance, cannot be directly used due to the resulting current imbalance that may damage the converter. This paper addresses the current sharing issue and proposes a single-carrier PD-PWM technique for multiple leg two-level converters based on a hierarchy scheme derived from current sorting algorithms. An extension of the proposed algorithm through a switching state feedback loop, limiting the average switching frequency, is also developed. In both cases, the load current is shared amongst the legs and the high-quality of the output voltages and currents is maintained while the circulating currents amongst the converter legs are kept to a minimum. Simulation results demonstrate the method for multiple interleaved legs as well as its current sharing capabilities for high-power applications. Experimental results from a low-power laboratory prototype validate the operation of the proposed approach.
2018-02-19T09:32:31ZKonstantinou, GeorgiosCapellá Frau, Gabriel JoséPou, JosepCeballos Recio, SalvadorInterleaved converter legs are typically modulated with individual carriers per leg and phase-shifted PWM (PS-PWM) as it facilitates current balancing amongst the legs. Phase-disposition PWM (PD-PWM), despite the better harmonic performance, cannot be directly used due to the resulting current imbalance that may damage the converter. This paper addresses the current sharing issue and proposes a single-carrier PD-PWM technique for multiple leg two-level converters based on a hierarchy scheme derived from current sorting algorithms. An extension of the proposed algorithm through a switching state feedback loop, limiting the average switching frequency, is also developed. In both cases, the load current is shared amongst the legs and the high-quality of the output voltages and currents is maintained while the circulating currents amongst the converter legs are kept to a minimum. Simulation results demonstrate the method for multiple interleaved legs as well as its current sharing capabilities for high-power applications. Experimental results from a low-power laboratory prototype validate the operation of the proposed approach.Nonlinear loads model for harmonics flow prediction, using multivariate regression
http://hdl.handle.net/2117/108748
Nonlinear loads model for harmonics flow prediction, using multivariate regression
Lamich Arocas, Manuel; Balcells Sendra, Josep; Corbalán Fuertes, Montserrat; Griful Ponsati, Eulàlia
This paper describes a method for obtaining a model of a single or a set of nonlinear loads (NLL) connected to a certain point of an electrical network. The basic assumption is that the network supplying the NLL has significant series impedances and is disturbed by other parallel, random, and unknown neighbor loads, sharing part of the supply system with the NLL. The main interest for obtaining the model is its further use to predict the amount and flow of harmonic currents generated by the NLL, in the case of adding a filter to reduce the harmonics distortion. The modeling technique used in the paper is based on multivariate multiple outputs regression and leads to a set of equations giving the NLL behavior (one for each of the harmonic currents). The model is obtained from data taken at measuring point and is only valid to predict the NLL behavior when new loads are connected at this point. The modeling method was first tested with V, I data coming from simulations using a MATLAB-Simulink SimPowerSystems toolbox. Finally, the method has been validated using V, I data taken in a real installation with different neighbor loads and under different load conditions.
2017-10-17T12:00:15ZLamich Arocas, ManuelBalcells Sendra, JosepCorbalán Fuertes, MontserratGriful Ponsati, EulàliaThis paper describes a method for obtaining a model of a single or a set of nonlinear loads (NLL) connected to a certain point of an electrical network. The basic assumption is that the network supplying the NLL has significant series impedances and is disturbed by other parallel, random, and unknown neighbor loads, sharing part of the supply system with the NLL. The main interest for obtaining the model is its further use to predict the amount and flow of harmonic currents generated by the NLL, in the case of adding a filter to reduce the harmonics distortion. The modeling technique used in the paper is based on multivariate multiple outputs regression and leads to a set of equations giving the NLL behavior (one for each of the harmonic currents). The model is obtained from data taken at measuring point and is only valid to predict the NLL behavior when new loads are connected at this point. The modeling method was first tested with V, I data coming from simulations using a MATLAB-Simulink SimPowerSystems toolbox. Finally, the method has been validated using V, I data taken in a real installation with different neighbor loads and under different load conditions.Influence of data resolution in nonlinear loads model for harmonics prediction
http://hdl.handle.net/2117/106333
Influence of data resolution in nonlinear loads model for harmonics prediction
Balcells Sendra, Josep; Lamich Arocas, Manuel; Griful Ponsati, Eulàlia; Corbalán Fuertes, Montserrat
This paper describes the influence of data resolution in the agreement of models to predict harmonics generated by nonlinear loads (NLL), basically formed by single phase and three phase rectifiers, eventually combined with linear loads. We assume that the network supplying the NLL has significant impedances and that it is disturbed by other parallel, random and unknown neighbor loads, sharing part of the supply system. The aim of building NLL models is to make predictions on the amount and flow paths of harmonic currents generated by such NLL in case of using parallel filters. In this paper, the models are obtained from sets of (V,I) data taken at a certain point, called measuring point (MP) and are valid to predict the NLL behavior when random known or unknown parallel loads are connected upstream of this point. The technique used to obtain the models studied here is based on Multivariate Multiple Outputs Regression (MMOR) and will not be described in detail in this paper. This method allows obtaining a set of equations giving the current harmonics as a function of voltage harmonics observed at the measuring point (MP). The accordance between model and the experimental results is very dependent on the resolution and accuracy of V and I measurements at the MP and is the core matter of this paper.
2017-07-11T07:59:53ZBalcells Sendra, JosepLamich Arocas, ManuelGriful Ponsati, EulàliaCorbalán Fuertes, MontserratThis paper describes the influence of data resolution in the agreement of models to predict harmonics generated by nonlinear loads (NLL), basically formed by single phase and three phase rectifiers, eventually combined with linear loads. We assume that the network supplying the NLL has significant impedances and that it is disturbed by other parallel, random and unknown neighbor loads, sharing part of the supply system. The aim of building NLL models is to make predictions on the amount and flow paths of harmonic currents generated by such NLL in case of using parallel filters. In this paper, the models are obtained from sets of (V,I) data taken at a certain point, called measuring point (MP) and are valid to predict the NLL behavior when random known or unknown parallel loads are connected upstream of this point. The technique used to obtain the models studied here is based on Multivariate Multiple Outputs Regression (MMOR) and will not be described in detail in this paper. This method allows obtaining a set of equations giving the current harmonics as a function of voltage harmonics observed at the measuring point (MP). The accordance between model and the experimental results is very dependent on the resolution and accuracy of V and I measurements at the MP and is the core matter of this paper.Generalized PWM-based method for multiphase neutral-point-clamped converters with capacitor voltage balance capability
http://hdl.handle.net/2117/102266
Generalized PWM-based method for multiphase neutral-point-clamped converters with capacitor voltage balance capability
López, Iraide; Ceballos Recio, Salvador; Pou, Josep; Zaragoza Bertomeu, Jordi; Andreu, Jon; Ibarra Basabe, Edorta; Konstantinou, Georgios
This paper presents a generalized pulse width modulation (PWM)-based control algorithm for multiphase neutral-point-clamped (NPC) converters. The proposed algorithm provides a zero sequence to be added to the reference voltages that contributes to improve the performance of the converter by: 1) Regulating the neutral-point (NP) current to eliminate/attenuate the low-frequency NP voltage ripples; 2) reducing the switching losses of the power semiconductors; and 3) maximizing the range of modulation indices for linear operation mode. The control method is formulated following a carrier-based PWM approach. Hence, dealing with complex space-vector diagrams to solve the modulation problem for multiphase converters is avoided. The recursive approach means that it can be easily extended to n-phase converters without increasing the complexity and computational burden, making it especially attractive for digital implementation. The proposed method allows regulating the NP voltage without the need for external controllers; therefore, no parameter tuning is required. The algorithm has been tested in a four-leg NPC converter prototype performing as a three- and four-phase system and operating with balanced and unbalanced loads.
2017-03-10T09:39:54ZLópez, IraideCeballos Recio, SalvadorPou, JosepZaragoza Bertomeu, JordiAndreu, JonIbarra Basabe, EdortaKonstantinou, GeorgiosThis paper presents a generalized pulse width modulation (PWM)-based control algorithm for multiphase neutral-point-clamped (NPC) converters. The proposed algorithm provides a zero sequence to be added to the reference voltages that contributes to improve the performance of the converter by: 1) Regulating the neutral-point (NP) current to eliminate/attenuate the low-frequency NP voltage ripples; 2) reducing the switching losses of the power semiconductors; and 3) maximizing the range of modulation indices for linear operation mode. The control method is formulated following a carrier-based PWM approach. Hence, dealing with complex space-vector diagrams to solve the modulation problem for multiphase converters is avoided. The recursive approach means that it can be easily extended to n-phase converters without increasing the complexity and computational burden, making it especially attractive for digital implementation. The proposed method allows regulating the NP voltage without the need for external controllers; therefore, no parameter tuning is required. The algorithm has been tested in a four-leg NPC converter prototype performing as a three- and four-phase system and operating with balanced and unbalanced loads.Harmonic interaction influence due to current source shunt filters in networks supplying nonlinear loads
http://hdl.handle.net/2117/99846
Harmonic interaction influence due to current source shunt filters in networks supplying nonlinear loads
Sainz Sapera, Luis; Balcells Sendra, Josep
2017-01-23T12:01:42ZSainz Sapera, LuisBalcells Sendra, JosepControl of Circulating Currents in Modular Multilevel Converters Through Redundant Voltage Levels
http://hdl.handle.net/2117/99708
Control of Circulating Currents in Modular Multilevel Converters Through Redundant Voltage Levels
Konstantinou, Georgios; Pou Félix, Josep; Ceballos Recio, Salvador; Picas Prat, Ricard; Zaragoza Bertomeu, Jordi; Agelidis, Vassilios
Among the main control targets in a modular multilevel converter (MMC) is the control of the circulating currents within the phase legs of the topology. This paper presents a controller for the circulating current of the MMC that utilizes the available redundancies of the multilevel waveform in 2N + 1 modulated MMCs in order to regulate the circulating current to its reference. The main advantages of the approach are the elimination of control loops that generate the reference voltages for the control of the circulating current, simple implementation and very fast dynamic performance. The controller is implemented at the modulation stage and its operation is independent of the circulating current reference. An extension of the controller to track large deviations in the circulating current is also demonstrated. The simplicity and effectiveness of the proposed controller is illustrated through detailed simulations and experimental results from a single-phase laboratory prototype.
2017-01-19T14:27:05ZKonstantinou, GeorgiosPou Félix, JosepCeballos Recio, SalvadorPicas Prat, RicardZaragoza Bertomeu, JordiAgelidis, VassiliosAmong the main control targets in a modular multilevel converter (MMC) is the control of the circulating currents within the phase legs of the topology. This paper presents a controller for the circulating current of the MMC that utilizes the available redundancies of the multilevel waveform in 2N + 1 modulated MMCs in order to regulate the circulating current to its reference. The main advantages of the approach are the elimination of control loops that generate the reference voltages for the control of the circulating current, simple implementation and very fast dynamic performance. The controller is implemented at the modulation stage and its operation is independent of the circulating current reference. An extension of the controller to track large deviations in the circulating current is also demonstrated. The simplicity and effectiveness of the proposed controller is illustrated through detailed simulations and experimental results from a single-phase laboratory prototype.Reliable modular multilevel converter fault detection with redundant voltage sensor
http://hdl.handle.net/2117/98870
Reliable modular multilevel converter fault detection with redundant voltage sensor
Picas Prat, Ricard; Zaragoza Bertomeu, Jordi; Pou Félix, Josep; Ceballos Recio, Salvador
This paper presents a fault-tolerant configuration for the modular multilevel converter (MMC). The procedure is able to detect faults in voltage sensors and semiconductor switching devices, and it can reconfigure the system so that it can keep on operating. Both switch and sensor faults can be detected by comparing the output voltage of a set of submodules (SMs), which is measured by a so-called supervisory sensor, with two calculated reference voltages. Faults in the supervisory sensors are also considered. Sensor faults are overcome by using a measuring technique based on estimates that are periodically updated with the voltage measurements of the supervisory sensors. Additional SMs are included in the arms so that the MMC can bypass a faulty SM and continue operating without affecting the output voltage of the phase-leg. Experimental results obtained from a low-power MMC prototype are presented in order to demonstrate the effectiveness of the proposed techniques.
2017-01-09T11:54:06ZPicas Prat, RicardZaragoza Bertomeu, JordiPou Félix, JosepCeballos Recio, SalvadorThis paper presents a fault-tolerant configuration for the modular multilevel converter (MMC). The procedure is able to detect faults in voltage sensors and semiconductor switching devices, and it can reconfigure the system so that it can keep on operating. Both switch and sensor faults can be detected by comparing the output voltage of a set of submodules (SMs), which is measured by a so-called supervisory sensor, with two calculated reference voltages. Faults in the supervisory sensors are also considered. Sensor faults are overcome by using a measuring technique based on estimates that are periodically updated with the voltage measurements of the supervisory sensors. Additional SMs are included in the arms so that the MMC can bypass a faulty SM and continue operating without affecting the output voltage of the phase-leg. Experimental results obtained from a low-power MMC prototype are presented in order to demonstrate the effectiveness of the proposed techniques.Interleaved operation of three-level neutral point clamped converter legs and reduction of circulating currents under SHE-PWM
http://hdl.handle.net/2117/90948
Interleaved operation of three-level neutral point clamped converter legs and reduction of circulating currents under SHE-PWM
Capellá Frau, Gabriel José; Pou Félix, Josep; Konstantinou, Georgios
Interleaving of voltage-source converter
(VSC) legs enables higher output currents per phase,
effectively increasing the power rating without increasing
semiconductor ratings. However, the interleaved operation
results in circulating currents between each phase converter
legs as well as a zero-sequence circulating current
(ZSCC), which become quite prominent when the converters
operate with low switching frequencies. This paper
demonstrates the interleaved operation of three-level converters
under selective harmonic elimination pulsewidth
modulation (SHE-PWM). A controller for the circulating
current within the legs of each phase is also proposed. The
controller is used in combination with optimally selected
SHE-PWM patterns to generate the maximum number of
voltage levels and minimize the peak value of the circulating
current. Simulation and experimental results show the
interleaved operation and the effect of SHE-PWM pattern
selection in the overall system.
2016-10-21T10:41:31ZCapellá Frau, Gabriel JoséPou Félix, JosepKonstantinou, GeorgiosInterleaving of voltage-source converter
(VSC) legs enables higher output currents per phase,
effectively increasing the power rating without increasing
semiconductor ratings. However, the interleaved operation
results in circulating currents between each phase converter
legs as well as a zero-sequence circulating current
(ZSCC), which become quite prominent when the converters
operate with low switching frequencies. This paper
demonstrates the interleaved operation of three-level converters
under selective harmonic elimination pulsewidth
modulation (SHE-PWM). A controller for the circulating
current within the legs of each phase is also proposed. The
controller is used in combination with optimally selected
SHE-PWM patterns to generate the maximum number of
voltage levels and minimize the peak value of the circulating
current. Simulation and experimental results show the
interleaved operation and the effect of SHE-PWM pattern
selection in the overall system.Closed-Loop discontinuous modulation technique for capacitor voltage ripples and switching losses reduction in modular multilevel converters
http://hdl.handle.net/2117/87604
Closed-Loop discontinuous modulation technique for capacitor voltage ripples and switching losses reduction in modular multilevel converters
Picas Prat, Ricard; Ceballos Recio, Salvador; Pou Félix, Josep; Zaragoza Bertomeu, Jordi; Konstantinou, Georgios; Agelidis, Vassilios
2016-06-01T14:04:47ZPicas Prat, RicardCeballos Recio, SalvadorPou Félix, JosepZaragoza Bertomeu, JordiKonstantinou, GeorgiosAgelidis, VassiliosOn improving phase-shifted PWM for flying capacitor multilevel converters
http://hdl.handle.net/2117/87482
On improving phase-shifted PWM for flying capacitor multilevel converters
Ghias, Amer M. Y. M.; Pou Félix, Josep; Capellá Frau, Gabriel José; Acuna, Pablo; Agelidis, Vassilios
This letter proposes a phase-shifted pulse-width modulation (PS-PWM) technique for the flying capacitor (FC) multilevel converter that improves the quality of the line-to-line voltages. In traditional PS-PWM, the line-to-line voltages include intervals that switch between nonadjacent voltage levels, which deteriorates the harmonic performance. The proposed PS-PWM constantly achieves line-to-line voltages with switching transitions between two adjacent levels. The proposed modulation technique is implemented using two sets of n evenly phase-shifted carriers that are alternatively applied depending on the instantaneous value of the reference signal of each phase-leg. Furthermore, it can be implemented in FC multilevel converters with any number of levels while maintaining natural capacitor voltage balance. Experimental results from a four-level FC converter prototype are presented.
2016-05-30T10:34:39ZGhias, Amer M. Y. M.Pou Félix, JosepCapellá Frau, Gabriel JoséAcuna, PabloAgelidis, VassiliosThis letter proposes a phase-shifted pulse-width modulation (PS-PWM) technique for the flying capacitor (FC) multilevel converter that improves the quality of the line-to-line voltages. In traditional PS-PWM, the line-to-line voltages include intervals that switch between nonadjacent voltage levels, which deteriorates the harmonic performance. The proposed PS-PWM constantly achieves line-to-line voltages with switching transitions between two adjacent levels. The proposed modulation technique is implemented using two sets of n evenly phase-shifted carriers that are alternatively applied depending on the instantaneous value of the reference signal of each phase-leg. Furthermore, it can be implemented in FC multilevel converters with any number of levels while maintaining natural capacitor voltage balance. Experimental results from a four-level FC converter prototype are presented.