Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3671
20170124T05:27:11Z

Reactive power control for loss minimization in lowvoltage distributed generation systems
http://hdl.handle.net/2117/98467
Reactive power control for loss minimization in lowvoltage distributed generation systems
Martí Colom, Pau; Velasco García, Manel; Torres Martínez, Javier; Miret Tomàs, Jaume; Castilla Fernández, Miguel
Dispersed small distributed generation (DG) systems in lowvoltage (LV) grids pose diverse challenges for
successful grid operation. The main one is to guarantee power quality by ensuring that voltages along all the feeders in
the network are within the permissible bounds. In addition, voltage regulation by means of reactive power control can
be used to achieve side benefits such as power loss minimization. The contribution of this paper is to analyze optimal
control settings for solar inverters in such a way that reactive power control keeps local voltages within the statutory
limits while overall losses are minimized. The expected output of a simulated realistic case study is a set of simple but
practical control design guidelines for future LV grids deployment. © 2016 IEEE.
20161216T13:03:50Z
Martí Colom, Pau
Velasco García, Manel
Torres Martínez, Javier
Miret Tomàs, Jaume
Castilla Fernández, Miguel
Dispersed small distributed generation (DG) systems in lowvoltage (LV) grids pose diverse challenges for
successful grid operation. The main one is to guarantee power quality by ensuring that voltages along all the feeders in
the network are within the permissible bounds. In addition, voltage regulation by means of reactive power control can
be used to achieve side benefits such as power loss minimization. The contribution of this paper is to analyze optimal
control settings for solar inverters in such a way that reactive power control keeps local voltages within the statutory
limits while overall losses are minimized. The expected output of a simulated realistic case study is a set of simple but
practical control design guidelines for future LV grids deployment. © 2016 IEEE.

A general MILP model for the sizing of islanded/gridconnected microgrids
http://hdl.handle.net/2117/87310
A general MILP model for the sizing of islanded/gridconnected microgrids
Alabert Aldana, Aniol; Somoza Tornos, Ana; Hoz Casas, Jordi de la; Graells Sobré, Moisès
Recently, energy systems have experienced a change of paradigm, from a largescale centr alized approach to the insitu exploitation of renewabl e sources. Special atte ntion has been paid to microgrids, a particular case of distributed generation where consumer nodes include generation and can be either grid connected or isolated. This work aims to develop a general model to determine the optimal sizing of an energy system under fixed conditions and to analyze the eff ect of considering different cycle patterns on the solution. The mi xed integer linear programming (MILP) formulation proposes allows determining the best combination of available technologi es that satisfies the demand of a given set of scenarios at minimum total cost. The model has been implemented using AIMMS and applied to a case study consisting of a fivemember Mediterranean house. The results obtained reveal the need to select the most convenient time cycles for defining the scenarios of the sizing model
20160525T10:14:14Z
Alabert Aldana, Aniol
Somoza Tornos, Ana
Hoz Casas, Jordi de la
Graells Sobré, Moisès
Recently, energy systems have experienced a change of paradigm, from a largescale centr alized approach to the insitu exploitation of renewabl e sources. Special atte ntion has been paid to microgrids, a particular case of distributed generation where consumer nodes include generation and can be either grid connected or isolated. This work aims to develop a general model to determine the optimal sizing of an energy system under fixed conditions and to analyze the eff ect of considering different cycle patterns on the solution. The mi xed integer linear programming (MILP) formulation proposes allows determining the best combination of available technologi es that satisfies the demand of a given set of scenarios at minimum total cost. The model has been implemented using AIMMS and applied to a case study consisting of a fivemember Mediterranean house. The results obtained reveal the need to select the most convenient time cycles for defining the scenarios of the sizing model

On the optimal reactive power control for gridconnected photovoltaic distributed generation systems
http://hdl.handle.net/2117/85169
On the optimal reactive power control for gridconnected photovoltaic distributed generation systems
Velasco García, Manel; Martí Colom, Pau; Torres Martínez, Javier; Miret Tomàs, Jaume; Castilla Fernández, Miguel
The increasing deployment of distributed generation (DG) such as photovoltaic panels (PV) connected to lowvoltage (LV) grids is becoming a common trend in urban areas. The advances of information and communication technology (ICT) facilitates the collaborative operation of DG systems to achieve collective benefits. The fusion of these two trends creates a new scenario where reactive power control methods can offer
additional features and benefits beyond the conventional voltage regulation provided by the droop method. Taking advantage of this new scenario, this paper formulates the application of reactive power control as an optimization problem where simple and ideal settings are imposed by design in order to facilitate the exploration search as well as to avoid overconstraining the optimization space. By appropriately using the reactive power capacity of inverters, the desired collective benefit is to minimize
power losses while individual voltages at each inverter should be kept within the statutory limits. The simulated solution of the optimization problem is applied to a realinspired PVLV grid subject to an overvoltage situation, which may typically occur during periods of high production but low consumption.
Simulation results reveal unexpected optimal settings for reactive power control setpoints at each inverter, which calls for a final discussion to review the applicability of the optimization approach.
20160405T08:23:21Z
Velasco García, Manel
Martí Colom, Pau
Torres Martínez, Javier
Miret Tomàs, Jaume
Castilla Fernández, Miguel
The increasing deployment of distributed generation (DG) such as photovoltaic panels (PV) connected to lowvoltage (LV) grids is becoming a common trend in urban areas. The advances of information and communication technology (ICT) facilitates the collaborative operation of DG systems to achieve collective benefits. The fusion of these two trends creates a new scenario where reactive power control methods can offer
additional features and benefits beyond the conventional voltage regulation provided by the droop method. Taking advantage of this new scenario, this paper formulates the application of reactive power control as an optimization problem where simple and ideal settings are imposed by design in order to facilitate the exploration search as well as to avoid overconstraining the optimization space. By appropriately using the reactive power capacity of inverters, the desired collective benefit is to minimize
power losses while individual voltages at each inverter should be kept within the statutory limits. The simulated solution of the optimization problem is applied to a realinspired PVLV grid subject to an overvoltage situation, which may typically occur during periods of high production but low consumption.
Simulation results reveal unexpected optimal settings for reactive power control setpoints at each inverter, which calls for a final discussion to review the applicability of the optimization approach.

Performance analysis of frequency restoration for parallel voltage source inverters connected with a realistic communication channel
http://hdl.handle.net/2117/83934
Performance analysis of frequency restoration for parallel voltage source inverters connected with a realistic communication channel
Martí Colom, Pau; Velasco García, Manel; Martín Rull, Enric Xavier; Castilla Fernández, Miguel; Miret Tomàs, Jaume; Torres Martínez, Javier
A topic of interest within the microgrid (MG) community is to achieve accurate sharing of active and reactive power among voltage source inverters (VSI) working in parallel while keeping the voltage frequency and amplitude stable, and close to a given reference. This problem has been mainly solved by the socalled frequency and voltage droop controllers that are local control loops implemented in each VSI. However, since they introduce a frequency and amplitude deviation, a secondary integrallike control loop using a communication system is usually deployed to enable each VSI to cancel the deviations. This paper evaluates two secondary control implementations of the frequency restoration with respect to properties of the communication system. Networked control applications are subject to known problems that are inherent to the use of a communication system such as message losses or varying sampling/transmission intervals, to name a few. The performance analysis reveals that control policies should be designed accounting also for the properties of the communication system. Otherwise, unexpected results violating the control specifications may appear.
20160308T08:00:42Z
Martí Colom, Pau
Velasco García, Manel
Martín Rull, Enric Xavier
Castilla Fernández, Miguel
Miret Tomàs, Jaume
Torres Martínez, Javier
A topic of interest within the microgrid (MG) community is to achieve accurate sharing of active and reactive power among voltage source inverters (VSI) working in parallel while keeping the voltage frequency and amplitude stable, and close to a given reference. This problem has been mainly solved by the socalled frequency and voltage droop controllers that are local control loops implemented in each VSI. However, since they introduce a frequency and amplitude deviation, a secondary integrallike control loop using a communication system is usually deployed to enable each VSI to cancel the deviations. This paper evaluates two secondary control implementations of the frequency restoration with respect to properties of the communication system. Networked control applications are subject to known problems that are inherent to the use of a communication system such as message losses or varying sampling/transmission intervals, to name a few. The performance analysis reveals that control policies should be designed accounting also for the properties of the communication system. Otherwise, unexpected results violating the control specifications may appear.

Active damping based on Ackermann's formula for a threephase voltage source inverter with LCL filter
http://hdl.handle.net/2117/82498
Active damping based on Ackermann's formula for a threephase voltage source inverter with LCL filter
Guzmán Solà, Ramon; García de Vicuña Muñoz de la Nava, José Luis; Morales López, Javier; Momeneh, Arash; Miret Tomàs, Jaume; Torres Martínez, Javier
This paper presents an active damping method in natural frame for a threephase voltage source inverter with LCL filter. The proposed method is based on the pole placement technique via Ackermann's formula. This approach is used to obtain the proper sliding surface vector coefficients to emulate a virtual resistor in series with the capacitor filter. Besides a wellknown method in the literature have been used to obtain three decoupled controllers in natural frame. The stability is theoretically studied and experimental results shows the validity of this proposal.
20160203T13:13:36Z
Guzmán Solà, Ramon
García de Vicuña Muñoz de la Nava, José Luis
Morales López, Javier
Momeneh, Arash
Miret Tomàs, Jaume
Torres Martínez, Javier
This paper presents an active damping method in natural frame for a threephase voltage source inverter with LCL filter. The proposed method is based on the pole placement technique via Ackermann's formula. This approach is used to obtain the proper sliding surface vector coefficients to emulate a virtual resistor in series with the capacitor filter. Besides a wellknown method in the literature have been used to obtain three decoupled controllers in natural frame. The stability is theoretically studied and experimental results shows the validity of this proposal.

Slidingmode control for a threephase shunt active power filter in natural frame
http://hdl.handle.net/2117/82494
Slidingmode control for a threephase shunt active power filter in natural frame
Guzmán Solà, Ramon; García de Vicuña Muñoz de la Nava, José Luis; Morales López, Javier; Castilla Fernández, Miguel; Miret Tomàs, Jaume; Torres Martínez, Javier
This paper presents an improved variable hysteresisband currentcontrol in natural frame for a threephase shunt active power filter. The proposed control algorithm is based on three decoupled slidingmode controllers combined with three independent Kalman filters. The use of Kalman filters instead of a nonadaptive state observer improves the quality of the estimated signals in presence of noise, increasing the immunity of the control loop in noisy environments and also reducing the THD of the current delivered to the grid. The overall control proposal has been fully integrated into a digital signal processor. Selected experimental results are introduced to validate the theoretical contributions of this paper.
20160203T13:02:35Z
Guzmán Solà, Ramon
García de Vicuña Muñoz de la Nava, José Luis
Morales López, Javier
Castilla Fernández, Miguel
Miret Tomàs, Jaume
Torres Martínez, Javier
This paper presents an improved variable hysteresisband currentcontrol in natural frame for a threephase shunt active power filter. The proposed control algorithm is based on three decoupled slidingmode controllers combined with three independent Kalman filters. The use of Kalman filters instead of a nonadaptive state observer improves the quality of the estimated signals in presence of noise, increasing the immunity of the control loop in noisy environments and also reducing the THD of the current delivered to the grid. The overall control proposal has been fully integrated into a digital signal processor. Selected experimental results are introduced to validate the theoretical contributions of this paper.

Architecture and design of an inductive contactless energy transfer system with two mobile loads for residential applications
http://hdl.handle.net/2117/80559
Architecture and design of an inductive contactless energy transfer system with two mobile loads for residential applications
Momeneh, Arash; Castilla Fernández, Miguel; van der Pijl, Fredrik F.A.; Guzmán Solà, Ramon; Morales López, Javier
Inductive contactless energy transfer systems with multiple mobile loads are very complex systems. Main
challenges of these systems are to propose a suitable architecture and to design their power components.
These challenges are particularly more noticeable in residential areas where various types of consumers
(loads) are expected. This paper introduces a new architecture and design guidelines for a highfrequency
resonant transformer operating with frequency modulation. The design process includes the effects of 1)
the resonant frequency, 2) the magnetizing inductance, and 3) the characteristic impedance. The excellent
performance of the designed system is validated by simulation results.
20151215T11:51:31Z
Momeneh, Arash
Castilla Fernández, Miguel
van der Pijl, Fredrik F.A.
Guzmán Solà, Ramon
Morales López, Javier
Inductive contactless energy transfer systems with multiple mobile loads are very complex systems. Main
challenges of these systems are to propose a suitable architecture and to design their power components.
These challenges are particularly more noticeable in residential areas where various types of consumers
(loads) are expected. This paper introduces a new architecture and design guidelines for a highfrequency
resonant transformer operating with frequency modulation. The design process includes the effects of 1)
the resonant frequency, 2) the magnetizing inductance, and 3) the characteristic impedance. The excellent
performance of the designed system is validated by simulation results.

On the modeling of switched capacitor converters with multiple outputs
http://hdl.handle.net/2117/24780
On the modeling of switched capacitor converters with multiple outputs
Delos, Julia; Lopez, Toni; Alarcón Gallo, Eduardo; Hendrix, Marcel A.M.
The internal nodes of switched capacitor converters can be used to provide multiple pulsed width modulated voltages that, in combination with filter inductors, can extend the available dc outputs. Such converter architecture requires models that accurately predict the behaviour of switched capacitor converters operated in current output mode. Based on the wellknown output impedance model, a new circuit representation is proposed for converters with multiple currentloaded outputs. A characterization methodology is developed to determine the parameters of said model. Predictions of the new model compare favorably to circuit simulations and experimental measurements
20141119T17:12:36Z
Delos, Julia
Lopez, Toni
Alarcón Gallo, Eduardo
Hendrix, Marcel A.M.
The internal nodes of switched capacitor converters can be used to provide multiple pulsed width modulated voltages that, in combination with filter inductors, can extend the available dc outputs. Such converter architecture requires models that accurately predict the behaviour of switched capacitor converters operated in current output mode. Based on the wellknown output impedance model, a new circuit representation is proposed for converters with multiple currentloaded outputs. A characterization methodology is developed to determine the parameters of said model. Predictions of the new model compare favorably to circuit simulations and experimental measurements

Nonlinear dynamics in a graphene nanostructured device for energy harvesting
http://hdl.handle.net/2117/24772
Nonlinear dynamics in a graphene nanostructured device for energy harvesting
El Aroudi, Abdelali; Lopez Suarez, Miquel; Alarcón Gallo, Eduardo; Rurali, Riccardo; Abadal, Gabriel
Nonlinearities have been shown to play an important role in increasing the extracted energy of energy harvesting devices at the macro and micro scales. Vibrationbased energy harvesting on the nano scale has also received attention. In this paper, we characterize the nonlinear dynamical behavior of a strained nanostructured graphene for its potential use in energy harvesting applications. A compressed vibrating membrane graphene sheet free from any external excitation is first studied. We present a continuous time dynamical model of the system in the form of a doublewell single degree of freedom system. Equilibrium points are obtained and their stability analysis is carried out. Then, random vibrations are considered as the main ambient energy source for the system and its performances in terms of the well occupation zones, RMS value of the position, and the corresponding energy harvested are presented in the steady state nonequilibrium regime when the noise level is considered as a control parameter. From this model, nonlinear analysis is carried out by computing state space trajectories, probability density and FFT spectra under a deterministic excitation. The ultimate goal of this parameter space exploration based upon a behavioral model is to provide designoriented guidelines for engineering graphenebased mechanical harvesters
20141119T15:54:42Z
El Aroudi, Abdelali
Lopez Suarez, Miquel
Alarcón Gallo, Eduardo
Rurali, Riccardo
Abadal, Gabriel
Nonlinearities have been shown to play an important role in increasing the extracted energy of energy harvesting devices at the macro and micro scales. Vibrationbased energy harvesting on the nano scale has also received attention. In this paper, we characterize the nonlinear dynamical behavior of a strained nanostructured graphene for its potential use in energy harvesting applications. A compressed vibrating membrane graphene sheet free from any external excitation is first studied. We present a continuous time dynamical model of the system in the form of a doublewell single degree of freedom system. Equilibrium points are obtained and their stability analysis is carried out. Then, random vibrations are considered as the main ambient energy source for the system and its performances in terms of the well occupation zones, RMS value of the position, and the corresponding energy harvested are presented in the steady state nonequilibrium regime when the noise level is considered as a control parameter. From this model, nonlinear analysis is carried out by computing state space trajectories, probability density and FFT spectra under a deterministic excitation. The ultimate goal of this parameter space exploration based upon a behavioral model is to provide designoriented guidelines for engineering graphenebased mechanical harvesters

Mixing local and distributed reactive power control for balancing inverters' effort in gridconnected photovoltaic systems
http://hdl.handle.net/2117/24370
Mixing local and distributed reactive power control for balancing inverters' effort in gridconnected photovoltaic systems
Velasco García, Manel; Martí Colom, Pau; Camacho Santiago, Antonio; Miret Tomàs, Jaume; Castilla Fernández, Miguel
Reactive power control methods have been proven to be a successful technique for maintaining voltages of photovoltaic (PV) distributed generators (DG) within the admissible limits without enforcing to reduce the production of active power. Usually the control goal is achieved at the expenses of stressing PV inverters unequally. As a consequence, inverters deteriorate at different velocities. This paper presents a mixed local and distributed control strategy that aims at balancing the effort posed by each inverter while achieving the control goal. The local control is a droplike method that locates inverters' voltages within the permissible voltage levels. Simultaneously, the distributed control, making use of a communication infrastructure, is in charge of driving the DG system to the point where all connected inverters inject the same current, thus balancing the stress between them.
20141015T08:37:53Z
Velasco García, Manel
Martí Colom, Pau
Camacho Santiago, Antonio
Miret Tomàs, Jaume
Castilla Fernández, Miguel
Reactive power control methods have been proven to be a successful technique for maintaining voltages of photovoltaic (PV) distributed generators (DG) within the admissible limits without enforcing to reduce the production of active power. Usually the control goal is achieved at the expenses of stressing PV inverters unequally. As a consequence, inverters deteriorate at different velocities. This paper presents a mixed local and distributed control strategy that aims at balancing the effort posed by each inverter while achieving the control goal. The local control is a droplike method that locates inverters' voltages within the permissible voltage levels. Simultaneously, the distributed control, making use of a communication infrastructure, is in charge of driving the DG system to the point where all connected inverters inject the same current, thus balancing the stress between them.