Articles de revista
http://hdl.handle.net/2117/3669
2017-10-23T17:32:24ZFinite control set model predictive control for a three-phase shunt active power filter with a kalman filter-based estimation
http://hdl.handle.net/2117/108982
Finite control set model predictive control for a three-phase shunt active power filter with a kalman filter-based estimation
Guzmán Solà, Ramon; García de Vicuña Muñoz de la Nava, José Luis; Castilla Fernández, Miguel; Miret Tomàs, Jaume; Camacho Santiago, Antonio
In this paper, the finite control set model predictive control is combined with the vector operation technique to be applied in the control of a three-phase active power filter. Typically, in the finite control set technique applied to three-phase power converters, eight different vectors are considered in order to obtain the optimum control signal by minimizing a cost function. On the other hand, the vector operation technique is based on dividing the grid voltage period into six different regions. The main advantage of combining both techniques is that for each region the number of possible voltage vectors to be considered can be reduced to a half, thus reducing the computational load employed by the control algorithm. Besides, in each region, only two phase-legs are switching at high frequency while the remaining phase-leg is maintained to a constant dc-voltage value during this interval. Accordingly, a reduction of the switching losses is obtained. Unlike the typical model predictive control methods which make use of the discrete differential equations of the converter, this method considers a Kalman filter in order to improve the behavior of the closed-loop system in noisy environments. Selected experimental results are exposed in order the demonstrate the validity of the control proposal
2017-10-23T15:59:55ZGuzmán Solà, RamonGarcía de Vicuña Muñoz de la Nava, José LuisCastilla Fernández, MiguelMiret Tomàs, JaumeCamacho Santiago, AntonioIn this paper, the finite control set model predictive control is combined with the vector operation technique to be applied in the control of a three-phase active power filter. Typically, in the finite control set technique applied to three-phase power converters, eight different vectors are considered in order to obtain the optimum control signal by minimizing a cost function. On the other hand, the vector operation technique is based on dividing the grid voltage period into six different regions. The main advantage of combining both techniques is that for each region the number of possible voltage vectors to be considered can be reduced to a half, thus reducing the computational load employed by the control algorithm. Besides, in each region, only two phase-legs are switching at high frequency while the remaining phase-leg is maintained to a constant dc-voltage value during this interval. Accordingly, a reduction of the switching losses is obtained. Unlike the typical model predictive control methods which make use of the discrete differential equations of the converter, this method considers a Kalman filter in order to improve the behavior of the closed-loop system in noisy environments. Selected experimental results are exposed in order the demonstrate the validity of the control proposalControl Strategies for Improving Energy Efficiency and Reliability in Autonomous Microgrids with Communication Constraints
http://hdl.handle.net/2117/108979
Control Strategies for Improving Energy Efficiency and Reliability in Autonomous Microgrids with Communication Constraints
Portelinha Júnior, Francisco Martins; Zambroni de Sousa, Antonio Carlos; Castilla Fernández, Miguel; Queiroz Oliveira, Denisson; Ribeiro, Paulo Fernando
Microgrids are a feasible path to deploy smart grids, an intelligent and highly automated power system. Their operation demands a dedicated communication infrastructure to manage, control and monitor the intermittent sources of energy and loads. Therefore, smart devices will be connected to support the growth of grid smartness increasing the dependency on communication networks, which consumes a high amount of power. In an energy-limited scenario, one of the main issues is to enhance the power supply time. Therefore, this paper proposes a hybrid methodology for microgrid energy management, integrated with a communication infrastructure to improve and to optimize islanded microgrid operation at maximum energy efficiency. The hybrid methodology applies some control management rules, such as intentional load shedding, priority load management, and communication energy saving. These energy saving rules establish a trade-off between increasing microgrid energy availability and communication system reliability. To achieve a compromised solution, a continuous time Markov chain model describes the impact of energy saving policies into system reliability. The proposed methodology is simulated and tested with the help of the modified IEEE 34 node test-system.
2017-10-23T14:31:32ZPortelinha Júnior, Francisco MartinsZambroni de Sousa, Antonio CarlosCastilla Fernández, MiguelQueiroz Oliveira, DenissonRibeiro, Paulo FernandoMicrogrids are a feasible path to deploy smart grids, an intelligent and highly automated power system. Their operation demands a dedicated communication infrastructure to manage, control and monitor the intermittent sources of energy and loads. Therefore, smart devices will be connected to support the growth of grid smartness increasing the dependency on communication networks, which consumes a high amount of power. In an energy-limited scenario, one of the main issues is to enhance the power supply time. Therefore, this paper proposes a hybrid methodology for microgrid energy management, integrated with a communication infrastructure to improve and to optimize islanded microgrid operation at maximum energy efficiency. The hybrid methodology applies some control management rules, such as intentional load shedding, priority load management, and communication energy saving. These energy saving rules establish a trade-off between increasing microgrid energy availability and communication system reliability. To achieve a compromised solution, a continuous time Markov chain model describes the impact of energy saving policies into system reliability. The proposed methodology is simulated and tested with the help of the modified IEEE 34 node test-system.Computing and communications for the software-defined metamaterial paradigm: a context analysis
http://hdl.handle.net/2117/107462
Computing and communications for the software-defined metamaterial paradigm: a context analysis
Abadal Cavallé, Sergi; Liaskos, Christos; Tsioliaridou, Ageliki; Ioannidis, Sotiris; Pitsillides, Andreas; Solé Pareta, Josep; Alarcón Gallo, Eduardo; Cabellos Aparicio, Alberto
Metamaterials are artificial structures that have recently enabled the realization of novel electromagnetic components with engineered and even unnatural functionalities. Existing metamaterials are specifically designed for a single application working under preset conditions (e.g., electromagnetic cloaking for a fixed angle of incidence) and cannot be reused. Software-defined metamaterials (SDMs) are a much sought-after paradigm shift, exhibiting electromagnetic properties that can be reconfigured at runtime using a set of software primitives. To enable this new technology, SDMs require the integration of a network of controllers within the structure of the metamaterial, where each controller interacts locally and communicates globally to obtain the programmed behavior. The design approach for such controllers and the interconnection network, however, remains unclear due to the unique combination of constraints and requirements of the scenario. To bridge this gap, this paper aims to provide a context analysis from the computation and communication perspectives. Then, analogies are drawn between the SDM scenario and other applications both at the micro and nano scales, identifying possible candidates for the implementation of the controllers and the intra-SDM network. Finally, the main challenges of SDMs related to computing and communications are outlined.
2017-09-06T14:09:24ZAbadal Cavallé, SergiLiaskos, ChristosTsioliaridou, AgelikiIoannidis, SotirisPitsillides, AndreasSolé Pareta, JosepAlarcón Gallo, EduardoCabellos Aparicio, AlbertoMetamaterials are artificial structures that have recently enabled the realization of novel electromagnetic components with engineered and even unnatural functionalities. Existing metamaterials are specifically designed for a single application working under preset conditions (e.g., electromagnetic cloaking for a fixed angle of incidence) and cannot be reused. Software-defined metamaterials (SDMs) are a much sought-after paradigm shift, exhibiting electromagnetic properties that can be reconfigured at runtime using a set of software primitives. To enable this new technology, SDMs require the integration of a network of controllers within the structure of the metamaterial, where each controller interacts locally and communicates globally to obtain the programmed behavior. The design approach for such controllers and the interconnection network, however, remains unclear due to the unique combination of constraints and requirements of the scenario. To bridge this gap, this paper aims to provide a context analysis from the computation and communication perspectives. Then, analogies are drawn between the SDM scenario and other applications both at the micro and nano scales, identifying possible candidates for the implementation of the controllers and the intra-SDM network. Finally, the main challenges of SDMs related to computing and communications are outlined.Analysis, design and implementation of a residential inductive contactless energy transfer system with multiple mobile clamps
http://hdl.handle.net/2117/107353
Analysis, design and implementation of a residential inductive contactless energy transfer system with multiple mobile clamps
Momeneh, Arash; Castilla Fernández, Miguel; Moradi Ghahderijani, Mohammad; Miret Tomàs, Jaume; García de Vicuña Muñoz de la Nava, José Luis
This study presents the analysis, design and implementation of a simple and cost-effective residential inductive contactless energy transfer system with multiple mobile clamps. The topology is based on the cascaded connection of a buck converter and a high-frequency resonant inverter loaded by several output passive rectifiers. The proposed system includes a sliding transformer to supply the mobile loads, leading to a safe and flexible location of loads. The theoretical analysis and design of the proposed system is based on a mathematical model derived using the first harmonic approximation. Selected experimental results are included to verify the system features. In comparison with conventional topology, the proposed system significantly improves efficiency, complexity and cost.
2017-09-04T10:21:43ZMomeneh, ArashCastilla Fernández, MiguelMoradi Ghahderijani, MohammadMiret Tomàs, JaumeGarcía de Vicuña Muñoz de la Nava, José LuisThis study presents the analysis, design and implementation of a simple and cost-effective residential inductive contactless energy transfer system with multiple mobile clamps. The topology is based on the cascaded connection of a buck converter and a high-frequency resonant inverter loaded by several output passive rectifiers. The proposed system includes a sliding transformer to supply the mobile loads, leading to a safe and flexible location of loads. The theoretical analysis and design of the proposed system is based on a mathematical model derived using the first harmonic approximation. Selected experimental results are included to verify the system features. In comparison with conventional topology, the proposed system significantly improves efficiency, complexity and cost.Secondary switched control with no communications for islanded microgrids
http://hdl.handle.net/2117/106354
Secondary switched control with no communications for islanded microgrids
Rey, Juan M; Martí Colom, Pau; Velasco García, Manel; Miret Tomàs, Jaume; Castilla Fernández, Miguel
Flexibility and reliability of AC microgrids are enhanced by reducing the dependence on communications in multi-layer hierarchical control. In this sense, this paper presents a secondary control with no communications for islanded microgrids. It is based on a control scheme that switches between two configurations according to a time-dependent protocol. With this proposal, an excellent performance in terms of transient response and frequency restoration in steady-state is achieved. The paper also presents design considerations for the control parameters. In addition, the theoretical predictions are validated by experimental results from a laboratory microgrid.
2017-07-12T10:30:02ZRey, Juan MMartí Colom, PauVelasco García, ManelMiret Tomàs, JaumeCastilla Fernández, MiguelFlexibility and reliability of AC microgrids are enhanced by reducing the dependence on communications in multi-layer hierarchical control. In this sense, this paper presents a secondary control with no communications for islanded microgrids. It is based on a control scheme that switches between two configurations according to a time-dependent protocol. With this proposal, an excellent performance in terms of transient response and frequency restoration in steady-state is achieved. The paper also presents design considerations for the control parameters. In addition, the theoretical predictions are validated by experimental results from a laboratory microgrid.Frequency-modulation control of a DC/DC current-source parallel-resonant converter
http://hdl.handle.net/2117/106352
Frequency-modulation control of a DC/DC current-source parallel-resonant converter
Moradi Ghahderijani, Mohammad; Castilla Fernández, Miguel; Momeneh, Arash; Tomas Miret, Jaume; García de Vicuña Muñoz de la Nava, José Luis
This paper proposes a frequency-modulation control scheme for a dc/dc current-source parallel-resonant converter with two possible configurations. The basic configuration comprises an external voltage loop, an internal current loop, and a frequency modulator: the voltage loop is responsible for regulating the output voltage, the current loop makes the system controllable and limits the input current, and the modulator provides robustness against variations in resonant component values. The enhanced configuration introduces the output inductor current as a feed-forward term and clearly improves the transient response to fast load changes. The theoretical design of these control schemes is performed systematically by first deriving their small-signal models and second using Bode diagram analysis. The actual performance of the proposed control schemes is experimentally validated by testing on a laboratory prototype.
2017-07-12T10:05:42ZMoradi Ghahderijani, MohammadCastilla Fernández, MiguelMomeneh, ArashTomas Miret, JaumeGarcía de Vicuña Muñoz de la Nava, José LuisThis paper proposes a frequency-modulation control scheme for a dc/dc current-source parallel-resonant converter with two possible configurations. The basic configuration comprises an external voltage loop, an internal current loop, and a frequency modulator: the voltage loop is responsible for regulating the output voltage, the current loop makes the system controllable and limits the input current, and the modulator provides robustness against variations in resonant component values. The enhanced configuration introduces the output inductor current as a feed-forward term and clearly improves the transient response to fast load changes. The theoretical design of these control schemes is performed systematically by first deriving their small-signal models and second using Bode diagram analysis. The actual performance of the proposed control schemes is experimentally validated by testing on a laboratory prototype.Variable structure control for three-phase LCL-filtered inverters using a reduced converter model
http://hdl.handle.net/2117/106253
Variable structure control for three-phase LCL-filtered inverters using a reduced converter model
Guzmán Solà, Ramon; García de Vicuña Muñoz de la Nava, José Luis; Castilla Fernández, Miguel; Miret Tomàs, Jaume; Hoz Casas, Jordi de la
This paper presents a new concept in active damping techniques using a reduced model of a LCL-filtered grid connected inverter. The presence of the LCL filter complicates the design of the inverter control scheme, particularly when uncertainties in the system parameters, especially in the grid inductance, are considered. The proposed control algorithm is addressed to overcome such difficulties using a reduced model of the inverter in a state observer. In this proposal, two of the three state variables of the system are obviated from the physical inverter model and only the inverter side current is considered. Therefore, the inverter side current can be estimated emulating the case of an inverter with only one inductor, thus eliminating the resonance problem produced by the LCL filter. Besides, in the case of a distorted grid, the method allows to estimate the voltages at the point of common coupling free of noise and distortion without using any PLL-based synchronization. To complete the control scheme, a theoretical stability analysis is developed considering the effect of the observer, the system discretization and the system parameters deviation. Experimental and comparative evaluation results are presented to validate the effectiveness of the proposed control scheme
2017-07-07T11:15:48ZGuzmán Solà, RamonGarcía de Vicuña Muñoz de la Nava, José LuisCastilla Fernández, MiguelMiret Tomàs, JaumeHoz Casas, Jordi de laThis paper presents a new concept in active damping techniques using a reduced model of a LCL-filtered grid connected inverter. The presence of the LCL filter complicates the design of the inverter control scheme, particularly when uncertainties in the system parameters, especially in the grid inductance, are considered. The proposed control algorithm is addressed to overcome such difficulties using a reduced model of the inverter in a state observer. In this proposal, two of the three state variables of the system are obviated from the physical inverter model and only the inverter side current is considered. Therefore, the inverter side current can be estimated emulating the case of an inverter with only one inductor, thus eliminating the resonance problem produced by the LCL filter. Besides, in the case of a distorted grid, the method allows to estimate the voltages at the point of common coupling free of noise and distortion without using any PLL-based synchronization. To complete the control scheme, a theoretical stability analysis is developed considering the effect of the observer, the system discretization and the system parameters deviation. Experimental and comparative evaluation results are presented to validate the effectiveness of the proposed control schemeVariable structure control in natural frame for three-phase grid-connected inverters with LCL filter
http://hdl.handle.net/2117/106247
Variable structure control in natural frame for three-phase grid-connected inverters with LCL filter
Guzmán Solà, Ramon; García de Vicuña Muñoz de la Nava, José Luis; Castilla Fernández, Miguel; Miret Tomàs, Jaume; Martín Cañadas, María Elena
This paper presents a variable structure control in natural frame for a three-phase voltage source inverter. The proposed control method is based on modifying the converter model in natural reference frame, preserving the low frequency state space variables dynamics. Using this model in a Kalman filter, the system state-space variables are estimated allowing to design three robust current sliding-mode controllers in natural frame. The main closed-loop features of the proposed method are: 1) robustness against grid inductance variations because the proposed model is independent of the grid inductance, 2) the power losses are reduced since physical damping resistors are avoided, and 3) the control bandwidth can be increased due to the combination of a variable hysteresis controller with a Kalman filter. To complete the control scheme, a theoretical stability analysis is developed. Finally, selected experimental results validate the proposed control strategy and permit illustrating all its appealing features.
2017-07-07T10:48:30ZGuzmán Solà, RamonGarcía de Vicuña Muñoz de la Nava, José LuisCastilla Fernández, MiguelMiret Tomàs, JaumeMartín Cañadas, María ElenaThis paper presents a variable structure control in natural frame for a three-phase voltage source inverter. The proposed control method is based on modifying the converter model in natural reference frame, preserving the low frequency state space variables dynamics. Using this model in a Kalman filter, the system state-space variables are estimated allowing to design three robust current sliding-mode controllers in natural frame. The main closed-loop features of the proposed method are: 1) robustness against grid inductance variations because the proposed model is independent of the grid inductance, 2) the power losses are reduced since physical damping resistors are avoided, and 3) the control bandwidth can be increased due to the combination of a variable hysteresis controller with a Kalman filter. To complete the control scheme, a theoretical stability analysis is developed. Finally, selected experimental results validate the proposed control strategy and permit illustrating all its appealing features.Energy dissipation in the presence of sub-harmonic excitation in dynamic atomic force microscopy
http://hdl.handle.net/2117/103298
Energy dissipation in the presence of sub-harmonic excitation in dynamic atomic force microscopy
Chiesa, Matteo; Gadelrab, Karim Raafat; Verdaguer, Albert; Segura, Juan José; Barcons Xixons, Víctor; Thomson, Neil H.; Phillips, M.A.; Stefancich, M.; Santos Hernández, Sergio
Amplitude modulation atomic force microscopy allows quantifying energy dissipation in the nanoscale with great accuracy with the use of analytical expressions that account for the fundamental frequency and higher harmonics. Here, we focus on the effects of sub-harmonic excitation on energy dissipation and its quantification. While there might be several mechanisms inducing sub-harmonics, a general analytical expression to quantify energy dissipation whenever sub-harmonics are excited is provided. The expression is a generalization of previous findings. We validate the expression via numerical integration by considering capillary forces and provide experimental evidence of sub-harmonic excitation for a range of operational parameters.
2017-04-04T14:10:15ZChiesa, MatteoGadelrab, Karim RaafatVerdaguer, AlbertSegura, Juan JoséBarcons Xixons, VíctorThomson, Neil H.Phillips, M.A.Stefancich, M.Santos Hernández, SergioAmplitude modulation atomic force microscopy allows quantifying energy dissipation in the nanoscale with great accuracy with the use of analytical expressions that account for the fundamental frequency and higher harmonics. Here, we focus on the effects of sub-harmonic excitation on energy dissipation and its quantification. While there might be several mechanisms inducing sub-harmonics, a general analytical expression to quantify energy dissipation whenever sub-harmonics are excited is provided. The expression is a generalization of previous findings. We validate the expression via numerical integration by considering capillary forces and provide experimental evidence of sub-harmonic excitation for a range of operational parameters.Cantilever dynamics in amplitude modulation AFM: continuous and discontinuous transitions
http://hdl.handle.net/2117/102923
Cantilever dynamics in amplitude modulation AFM: continuous and discontinuous transitions
Santos Hernandez, Sergio; Barcons Xixons, Víctor; Font Teixidó, Josep; Thomson, Neil H.
Transitions between the attractive and the repulsive force regimes for amplitude modulation atomic force microscopy (AFM) can be either discontinuous, with a corresponding jump in amplitude and phase, or continuous and smooth. During the transitions, peak repulsive and average forces can be up to an order of magnitude higher when these are discrete. Under certain circumstances, for example, when the tip radius is relatively large (e.g. R > 20–30 nm) and for high cantilever free amplitudes (e.g. A0 > 40–50 nm), the L state can be reached with relatively low set-points only (e.g. Asp/A0 < 0.30). We find that these cases do not generally lead to higher resolution but increase the background noise instead. This is despite the fact that the imaging can be non-contact under these conditions. The appearance of background noise is linked to increasing cantilever mean deflection and tip–surface proximity with increasing free amplitude in the L state.
Cantilever dynamics in amplitude modulation AFM: Continuous and discontinuous transitions (PDF Download Available). Available from: https://www.researchgate.net/publication/231025693_Cantilever_dynamics_in_amplitude_modulation_AFM_Continuous_and_discontinuous_transitions [accessed Mar 27, 2017].
2017-03-27T15:56:43ZSantos Hernandez, SergioBarcons Xixons, VíctorFont Teixidó, JosepThomson, Neil H.Transitions between the attractive and the repulsive force regimes for amplitude modulation atomic force microscopy (AFM) can be either discontinuous, with a corresponding jump in amplitude and phase, or continuous and smooth. During the transitions, peak repulsive and average forces can be up to an order of magnitude higher when these are discrete. Under certain circumstances, for example, when the tip radius is relatively large (e.g. R > 20–30 nm) and for high cantilever free amplitudes (e.g. A0 > 40–50 nm), the L state can be reached with relatively low set-points only (e.g. Asp/A0 < 0.30). We find that these cases do not generally lead to higher resolution but increase the background noise instead. This is despite the fact that the imaging can be non-contact under these conditions. The appearance of background noise is linked to increasing cantilever mean deflection and tip–surface proximity with increasing free amplitude in the L state.
Cantilever dynamics in amplitude modulation AFM: Continuous and discontinuous transitions (PDF Download Available). Available from: https://www.researchgate.net/publication/231025693_Cantilever_dynamics_in_amplitude_modulation_AFM_Continuous_and_discontinuous_transitions [accessed Mar 27, 2017].