ACES  Control Avançat de Sistemes d'Energia
http://hdl.handle.net/2117/114
20170625T13:55:42Z

Observation of the electrochemically active surface area in a proton exchange membrane fuel cell
http://hdl.handle.net/2117/105337
Observation of the electrochemically active surface area in a proton exchange membrane fuel cell
Luna Pacho, Julio Alberto; Usai, Elio; Husar, Attila Peter; Serra, Maria
In this paper a methodology for the estimation of the Electrochemically active Surface Area (ECSA) of a Proton Exchange Membrane Fuel Cell (PEMFC) is developed. Specifically, the ECSA in the Cathode Catalyst Layer (CCL) is estimated, which makes it possible to quantify the amount of active platinum (Pt) in the CCL. In order to estimate the ECSA, the internal conditions of the PEMFC have to be known. A modelbased observer for the distributed parameter dynamics is designed. From the observation of the distributed states, the ECSA can be estimated as well. With the aim of representing the most relevant phenomena that affects the PEMFC voltage, the simulation model includes a twophase water model and the effects of liquid water on the CCL. The results of the methodology are discussed in a simulation environment using the New European Driving Cycle (NEDC) as a case study.
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20170612T08:55:15Z
Luna Pacho, Julio Alberto
Usai, Elio
Husar, Attila Peter
Serra, Maria
In this paper a methodology for the estimation of the Electrochemically active Surface Area (ECSA) of a Proton Exchange Membrane Fuel Cell (PEMFC) is developed. Specifically, the ECSA in the Cathode Catalyst Layer (CCL) is estimated, which makes it possible to quantify the amount of active platinum (Pt) in the CCL. In order to estimate the ECSA, the internal conditions of the PEMFC have to be known. A modelbased observer for the distributed parameter dynamics is designed. From the observation of the distributed states, the ECSA can be estimated as well. With the aim of representing the most relevant phenomena that affects the PEMFC voltage, the simulation model includes a twophase water model and the effects of liquid water on the CCL. The results of the methodology are discussed in a simulation environment using the New European Driving Cycle (NEDC) as a case study.

Tachyons in the Galilean limit
http://hdl.handle.net/2117/105012
Tachyons in the Galilean limit
Batlle Arnau, Carles; Gomis Torné, Joaquin; Mezincescu, Luca; Townsend, Paul K.
The Souriau massless Galilean particle of “colour” k and spin s is shown to be the Galilean limit of the Souriau tachyon of mass m = ik and spin s. We compare and contrast this result with the Galilean limit of the NambuGoto string and GreenSchwarz superstring.
20170530T10:09:05Z
Batlle Arnau, Carles
Gomis Torné, Joaquin
Mezincescu, Luca
Townsend, Paul K.
The Souriau massless Galilean particle of “colour” k and spin s is shown to be the Galilean limit of the Souriau tachyon of mass m = ik and spin s. We compare and contrast this result with the Galilean limit of the NambuGoto string and GreenSchwarz superstring.

Nonlinear predictive control for durability enhancement and efficiency improvement in a fuel cell power system
http://hdl.handle.net/2117/104411
Nonlinear predictive control for durability enhancement and efficiency improvement in a fuel cell power system
Luna Pacho, Julio Alberto; Jemei, Samir; YousfiSteiner, Nadia; Husar, Attila Peter; Serra, Maria; Hissel, Daniel
In this work, a nonlinear model predictive control (NMPC) strategy is proposed to improve the efficiency and enhance the durability of a proton exchange membrane fuel cell (PEMFC) power system. The PEMFC controller is based on a distributed parameters model that describes the nonlinear dynamics of the system, considering spatial variations along the gas channels. Parasitic power from different system auxiliaries is considered, including the main parasitic losses which are those of the compressor. A nonlinear observer is implemented, based on the discretised model of the PEMFC, to estimate the internal states. This information is included in the cost function of the controller to enhance the durability of the system by means of avoiding local starvation and inappropriate water vapour concentrations. Simulation results are presented to show the performance of the proposed controller over a given case study in an automotive application (New European Driving Cycle). With the aim of representing the most relevant phenomena that affects the PEMFC voltage, the simulation model includes a twophase water model and the effects of liquid water on the catalyst active area. The control model is a simplified version that does not consider twophase water dynamics.
© <year>. This manuscript version is made available under the CCBYNCND 4.0 license http://creativecommons.org/licenses/byncnd/4.0/
20170515T10:12:22Z
Luna Pacho, Julio Alberto
Jemei, Samir
YousfiSteiner, Nadia
Husar, Attila Peter
Serra, Maria
Hissel, Daniel
In this work, a nonlinear model predictive control (NMPC) strategy is proposed to improve the efficiency and enhance the durability of a proton exchange membrane fuel cell (PEMFC) power system. The PEMFC controller is based on a distributed parameters model that describes the nonlinear dynamics of the system, considering spatial variations along the gas channels. Parasitic power from different system auxiliaries is considered, including the main parasitic losses which are those of the compressor. A nonlinear observer is implemented, based on the discretised model of the PEMFC, to estimate the internal states. This information is included in the cost function of the controller to enhance the durability of the system by means of avoiding local starvation and inappropriate water vapour concentrations. Simulation results are presented to show the performance of the proposed controller over a given case study in an automotive application (New European Driving Cycle). With the aim of representing the most relevant phenomena that affects the PEMFC voltage, the simulation model includes a twophase water model and the effects of liquid water on the catalyst active area. The control model is a simplified version that does not consider twophase water dynamics.

Extended Galilean symmetries of nonrelativistic strings
http://hdl.handle.net/2117/104368
Extended Galilean symmetries of nonrelativistic strings
Batlle Arnau, Carles; Gomis Torné, Joaquin; Not, Daniel
We consider two nonrelativistic strings and their Galilean symmetries. These strings are obtained as the two possible nonrelativistic (NR) limits of a relativistic string. One of them is nonvibrating and represents a continuum of nonrelativistic massless particles, and the other one is a nonrelativistic vibrating string. For both cases we write the generator of the most general point transformation and impose the condition of Noether symmetry. As a result we obtain two sets of nonrelativistic Killing equations for the vector fields that generate the symmetry transformations. Solving these equations shows that NR strings exhibit two extended, infinite dimensional spacetime symmetries which contain, as a subset, the Galilean symmetries. For each case, we compute the associated conserved charges and discuss the existence of noncentral extensions.
20170512T12:18:09Z
Batlle Arnau, Carles
Gomis Torné, Joaquin
Not, Daniel
We consider two nonrelativistic strings and their Galilean symmetries. These strings are obtained as the two possible nonrelativistic (NR) limits of a relativistic string. One of them is nonvibrating and represents a continuum of nonrelativistic massless particles, and the other one is a nonrelativistic vibrating string. For both cases we write the generator of the most general point transformation and impose the condition of Noether symmetry. As a result we obtain two sets of nonrelativistic Killing equations for the vector fields that generate the symmetry transformations. Solving these equations shows that NR strings exhibit two extended, infinite dimensional spacetime symmetries which contain, as a subset, the Galilean symmetries. For each case, we compute the associated conserved charges and discuss the existence of noncentral extensions.

Nonlinear model predictive control methodology for efficiency and durability improvement in a fuel cell power system
http://hdl.handle.net/2117/104199
Nonlinear model predictive control methodology for efficiency and durability improvement in a fuel cell power system
Luna Pacho, Julio Alberto; Jemei, Samir; YousfiSteiner, Nadia; Husar, Attila Peter; Serra, Maria
The main contribution of this work is the improvement of the efficiency of a PEMFC power system while guaranteeing conditions that also improve its durability. Adopting the NMPC scheme with the distributed parameter model and the nonlinear observer, the efficiency of the PEMFCbased system can be maximized guaranteeing at the same time the appropriate internal gas concentration profiles to avoid global and local hydrogen and oxygen starvation and proper membrane humidification.
20170508T12:53:55Z
Luna Pacho, Julio Alberto
Jemei, Samir
YousfiSteiner, Nadia
Husar, Attila Peter
Serra, Maria
The main contribution of this work is the improvement of the efficiency of a PEMFC power system while guaranteeing conditions that also improve its durability. Adopting the NMPC scheme with the distributed parameter model and the nonlinear observer, the efficiency of the PEMFCbased system can be maximized guaranteeing at the same time the appropriate internal gas concentration profiles to avoid global and local hydrogen and oxygen starvation and proper membrane humidification.

Rejection of periodic disturbances using MRAC with minimal controller synthesis
http://hdl.handle.net/2117/104158
Rejection of periodic disturbances using MRAC with minimal controller synthesis
Larco Barros, Ciro Mauricio; Olm Miras, Josep Maria; Costa Castelló, Ramon
The tracking/rejection of periodic disturbances in linear systems is achievable via internal model principlebased techniques, such as repetitive control. However, when the frequency of the signal to track/reject is uncertain or timevarying, the performance of these controllers decays dramatically. This article discusses the basics of Model Reference Adaptive Control with Minimal Controller Synthesis, and assesses its applicability to this problem from a comparative study of the performance of this type of controllers and a repetitive controller, both designed to regulate the speed of a DC motor subject to periodic disturbances. The study is supported by experimental results.
20170508T09:52:19Z
Larco Barros, Ciro Mauricio
Olm Miras, Josep Maria
Costa Castelló, Ramon
The tracking/rejection of periodic disturbances in linear systems is achievable via internal model principlebased techniques, such as repetitive control. However, when the frequency of the signal to track/reject is uncertain or timevarying, the performance of these controllers decays dramatically. This article discusses the basics of Model Reference Adaptive Control with Minimal Controller Synthesis, and assesses its applicability to this problem from a comparative study of the performance of this type of controllers and a repetitive controller, both designed to regulate the speed of a DC motor subject to periodic disturbances. The study is supported by experimental results.

Integral MRAC with Minimal Controller Synthesis and bounded adaptive gains: The continuoustime case
http://hdl.handle.net/2117/104084
Integral MRAC with Minimal Controller Synthesis and bounded adaptive gains: The continuoustime case
Montanaro, Umberto; Olm Miras, Josep Maria
Model reference adaptive controllers designed via the Minimal Control Synthesis (MCS) approach are a viable solution to control plants affected by parameter uncertainty, unmodelled dynamics, and disturbances. Despite its effectiveness to impose the required reference dynamics, an apparent drift of the adaptive gains, which can eventually lead to closedloop instability or alter tracking performance, may occasionally be induced by external disturbances. This problem has been recently addressed for this class of adaptive algorithms in the discretetime case and for squareintegrable perturbations by using a parameter projection strategy [1]. In this paper we tackle systematically this issue for MCS continuoustime adaptive systems with integral action by enhancing the adaptive mechanism not only with a parameter projection method, but also embedding a smodification strategy. The former is used to preserve convergence to zero of the tracking error when the disturbance is bounded and L2, while the latter guarantees global uniform ultimate boundedness under continuous L8 disturbances. In both cases, the proposed control schemes ensure boundedness of all the closedloop signals. The strategies are numerically validated by considering systems subject to different kinds of disturbances. In addition, an electrical power circuit is used to show the applicability of the algorithms to engineering problems requiring a precise tracking of a reference profile over a long time range despite disturbances, unmodelled dynamics, and parameter uncertainty.
20170505T09:41:33Z
Montanaro, Umberto
Olm Miras, Josep Maria
Model reference adaptive controllers designed via the Minimal Control Synthesis (MCS) approach are a viable solution to control plants affected by parameter uncertainty, unmodelled dynamics, and disturbances. Despite its effectiveness to impose the required reference dynamics, an apparent drift of the adaptive gains, which can eventually lead to closedloop instability or alter tracking performance, may occasionally be induced by external disturbances. This problem has been recently addressed for this class of adaptive algorithms in the discretetime case and for squareintegrable perturbations by using a parameter projection strategy [1]. In this paper we tackle systematically this issue for MCS continuoustime adaptive systems with integral action by enhancing the adaptive mechanism not only with a parameter projection method, but also embedding a smodification strategy. The former is used to preserve convergence to zero of the tracking error when the disturbance is bounded and L2, while the latter guarantees global uniform ultimate boundedness under continuous L8 disturbances. In both cases, the proposed control schemes ensure boundedness of all the closedloop signals. The strategies are numerically validated by considering systems subject to different kinds of disturbances. In addition, an electrical power circuit is used to show the applicability of the algorithms to engineering problems requiring a precise tracking of a reference profile over a long time range despite disturbances, unmodelled dynamics, and parameter uncertainty.

Passivitybased control of active and reactive power in singlephase PV inverters
http://hdl.handle.net/2117/103939
Passivitybased control of active and reactive power in singlephase PV inverters
Biel Solé, Domingo; Scherpen, Jacquelien
This work presents the control design guidelines of a passivitybased control of the active and the reactive power in singlephase PV inverters. The control ensures global asymptotic convergence of the tracking error to zero and the PV inverter shows robust current tracking with fast dynamics. The control is particularized in the cases of strong and weak grid operation. In the last case, the knowledge of the grid impedance and the injected active power allows to calculate the value of the required reactive power in order to set the amplitude of the voltage at the connection point to the ideal grid amplitude. The control is validated by means of numerical simulations when the power references are changed and when the PV irradiance varies.
20170503T08:50:08Z
Biel Solé, Domingo
Scherpen, Jacquelien
This work presents the control design guidelines of a passivitybased control of the active and the reactive power in singlephase PV inverters. The control ensures global asymptotic convergence of the tracking error to zero and the PV inverter shows robust current tracking with fast dynamics. The control is particularized in the cases of strong and weak grid operation. In the last case, the knowledge of the grid impedance and the injected active power allows to calculate the value of the required reactive power in order to set the amplitude of the voltage at the connection point to the ideal grid amplitude. The control is validated by means of numerical simulations when the power references are changed and when the PV irradiance varies.

A unified approach to explain contrary effects of hysteresis and smoothing in nonsmooth systems
http://hdl.handle.net/2117/103747
A unified approach to explain contrary effects of hysteresis and smoothing in nonsmooth systems
Bonet Revés, Carles; MartínezSeara Alonso, M. Teresa; Fossas Colet, Enric; Jeffrey, Mike R.
Piecewise smooth dynamical systems make use of discontinuities to model switching between regions of smooth evolution. This introduces an ambiguity in prescribing dynamics at the discontinuity: should the dynamics be given by a limiting value on one side or other of the discontinuity, or a member of some set containing those values? One way to remove the ambiguity is to regularize the discontinuity, the most common being either to smooth it out, or to introduce a hysteresis between switching in one direction or the other across it. Here we show that the two can in general lead to qualitatively different dynamical outcomes. We then define a higher dimensional model with both smoothing and hysteresis, and study the competing limits in which hysteretic or smoothing effects dominate the behaviour, only the former of which correspond to Filippov’s standard ‘sliding modes’.
20170426T09:23:33Z
Bonet Revés, Carles
MartínezSeara Alonso, M. Teresa
Fossas Colet, Enric
Jeffrey, Mike R.
Piecewise smooth dynamical systems make use of discontinuities to model switching between regions of smooth evolution. This introduces an ambiguity in prescribing dynamics at the discontinuity: should the dynamics be given by a limiting value on one side or other of the discontinuity, or a member of some set containing those values? One way to remove the ambiguity is to regularize the discontinuity, the most common being either to smooth it out, or to introduce a hysteresis between switching in one direction or the other across it. Here we show that the two can in general lead to qualitatively different dynamical outcomes. We then define a higher dimensional model with both smoothing and hysteresis, and study the competing limits in which hysteretic or smoothing effects dominate the behaviour, only the former of which correspond to Filippov’s standard ‘sliding modes’.

Nonlinear observation in fuel cell systems: a comparison between disturbance estimation and HighOrder SlidingMode techniques
http://hdl.handle.net/2117/103673
Nonlinear observation in fuel cell systems: a comparison between disturbance estimation and HighOrder SlidingMode techniques
Luna Pacho, Julio Alberto; Usai, Elio; Husar, Attila Peter; Serra, Maria
This paper compares two Nonlinear Distributed Parameter Observers (NDPO) for the observation of a Proton Exchange Membrane Fuel Cell (PEMFC). Both NDPOs are based on the discretisation of distributed parameters models and they are used to estimate the state profile of gas concentrations in the anode and cathode gas channels of the PEMFC, giving detailed information about the internal conditions of the system. The reaction and water transport flow rates from the membrane to the channels are uncertainties of the observation problem and they are estimated throughout all the length of the PEMFC without the use of additional sensors. The first observation approach is a Nonlinear Disturbance Observer (NDOB) for the estimation of the disturbances in the NDPO. In the second approach, a novel implementation of a HighOrder SlidingMode (HOSM) observer is developed to estimate the true value of the states as well as the reaction terms. The proposed observers are tested and compared through a simulation example at different operating points and their performance and robustness is analysed over a given case study, the New European Driving Cycle.
© <year>. This manuscript version is made available under the CCBYNCND 4.0 license http://creativecommons.org/licenses/byncnd/4.0/
20170424T11:50:09Z
Luna Pacho, Julio Alberto
Usai, Elio
Husar, Attila Peter
Serra, Maria
This paper compares two Nonlinear Distributed Parameter Observers (NDPO) for the observation of a Proton Exchange Membrane Fuel Cell (PEMFC). Both NDPOs are based on the discretisation of distributed parameters models and they are used to estimate the state profile of gas concentrations in the anode and cathode gas channels of the PEMFC, giving detailed information about the internal conditions of the system. The reaction and water transport flow rates from the membrane to the channels are uncertainties of the observation problem and they are estimated throughout all the length of the PEMFC without the use of additional sensors. The first observation approach is a Nonlinear Disturbance Observer (NDOB) for the estimation of the disturbances in the NDPO. In the second approach, a novel implementation of a HighOrder SlidingMode (HOSM) observer is developed to estimate the true value of the states as well as the reaction terms. The proposed observers are tested and compared through a simulation example at different operating points and their performance and robustness is analysed over a given case study, the New European Driving Cycle.