Doria-Cerezo, A.; Olm, Josep M.; Scherpen, J.M.A. IFAC Workshop on Lagrangian and Hamiltonian Methods for Non Linear Control p. 135-140 Presentation's date: 2015-07-06 Presentation of work at congresses
This paper proposes a decentralized, passivity-based cont
rol design for power stations in a multi-terminal High Voltage Direct Current transmissi on system. The control algorithm
is shown to asymptotically stabilize the closed-loop syste
m when the voltage set points are appropriately selected. The analysis is carried out taking into account actual power, current and voltage saturations that affect power stations and, consequ ently, the control action. Numerical results illustrate the performance of the obtained control lers.
Network frequency variations cause a dramatic performance decay in repetitive controller-based shunt active power filters. This problem may be solved by adapting the sampling period in order to keep the ratio between the network period and the sampling period at a constant value. However, these changes may yield closed-loop instability. The introduction of a precompensator that forces the plant to remain invariant despite sampling rate changes allows the use of standard LTI methods in control design and stability analysis as well. Moreover, in order to improve robustness in the face of network frequency estimation uncertainty and sampling time quantization, the regular repetitive controller is replaced by a high order one. Experimental results show the validity of the proposal.
Doria-Cerezo, A.; Olm, Josep M.; di Bernardo, M.; Quaglia, M.; Nuño, E. IEEE Conference on Decision and Control p. 3677-3682 DOI: 10.1109/CDC.2014.7039961 Presentation's date: 2014-12 Presentation of work at congresses
Multi-terminal VSC-HVDC transmission is a promising solution to transport energy from the generating plants to the distribution stations, and the number and size of the corresponding power grids is expected to increase in the next years. Such a system presents challenging control problems that, so far, have been approached with classical control techniques.
However, large scale systems of interconnected nodes
fall within the framework of the emerging field of complex
networks. This paper analyzes the stability of multi-terminal
VSC-HVDC systems from a complex dynamical network perspective, and provides sufficient conditions to ensure bounded
synchronization of its trajectories. The obtained results are
validated via numerical simulations.
The substitution of the original switches by a full bridge in a Non-Inverting Buck-Boost converter results in an inverter capable of carrying out step-down and step-up tasks as well under sliding mode control. The control law is implemented by means of the Zero Average Dynamics algorithm, which provides a fixed frequency operation and guarantees null error in each switching period, thus achieving a highly accurate tracking of periodic reference profiles. Furthermore, semi-infinite programming techniques are used to reduce power losses and, at the same time, prevent undesirable effects of control action saturation. The performance of the inverter is ensured to be robust in the face of bounded nonlinear and resistive loads. Realistic simulation results obtained with PSIMR software validate the proposed schemes.
The rejection of the undesirable effects of sudden
load changes undergone by power inverters requires control
techniques able to recover regular operation with a low transient
error, in a short number of periods and being robust
to unmodelled dynamics and parametric uncertainties. The
possibilities are explored in this paper of controlling a fullbridge
buck inverter via the discrete-time version of a model
reference adaptive algorithm with minimal controller synthesis
recently proposed by some of the authors. Besides confirming
the theoretically predicted stability and robustness properties
in the face of large load jumps, numerical results show that
acceptable performance is still guaranteed when the control
signal is injected through a PWM generator switching at a
Spinetti, M. de J.; Olm, Josep M.; Biel, D.; Fossas, E. Communications in nonlinear science and numerical simulation Vol. 18, num. 11, p. 3108-3125 DOI: 10.1016/j.cnsns.2013.03.018 Date of publication: 2013-11 Journal article
Lyapunov-based controlled boost converters have a unique equilibrium point, which is globally asymptotically stable, for known resistive loads. This article investigates the dynamic behaviors that appear in the system when the nominal load differs from the actual one and no action is taken by the controller to compensate for the mismatch. Exploiting the fact that the closed-loop system is, in fact, planar and quadratic, one may provide not only local but also global stability results: specifically, it is proved that the number of equilibria of the converter may grow up to three and that, in any case, the system trajectories are always bounded, i.e. it is a bounded quadratic system. The possible phase portraits of the closed-loop system are also characterized in terms of the selected bifurcation parameters, namely, the actual load value and the gain of the control law. Accordingly, the analysis allows the numerical illustration of many bifurcation phenomena that appear in bounded quadratic systems through a physical example borrowed from power electronics.
di Bernardo, M.; di Gaeta, A.; Montanaro, U.; Olm, Josep M.; Santini, S. Control engineering practice Vol. 21, num. 6, p. 847-859 DOI: 10.1016/j.conengprac.2012.12.004 Date of publication: 2013-06 Journal article
This paper is concerned with the implementation and experimental validation of a discrete-time model reference adaptive control strategy, known as Minimal Control Synthesis (MCS) algorithm. After discussing
the proof of stability of the algorithm when applied to discretized models of continuous-timeplants, the problem of controlling a highly nonlinear electro-mechanical device is taken as a representative case
of study. It is shown that the discrete-time MCS is an effective strategy to solve the problem while guaranteeing robustness to unmodeled nonlinear dynamics over a wide range of test manoeuvres
This paper is concerned with the implementation and experimental validation of a discrete-time model reference adaptive control strategy, known as Minimal Control Synthesis(MCS)algorithm. After discussing the proof of stability of the algorithm when applied to discretized models of continuous-time plants, the problem of controlling a highly nonlinear electro-mechanical device is taken as a representative case of study. It is shown that the discrete-time MCS is an effective strategy to solve the problem while
guaranteeing robustness to unmodeled nonlinear dynamics over a wide range of test manoeuvres
di Bernardo, M.; Montanaro, U.; Olm, Josep M.; Santini, S. International journal of robust and nonlinear control Vol. 23, num. 7, p. 709-730 DOI: 10.1002/rnc.2786 Date of publication: 2013-06-01 Journal article
This article presents a switched model reference adaptive controller for discrete-time piecewise linear systems.
In the spirit of the work by Landau in the late seventies, proof of asymptotic stability of the closed-loop error system is obtained, recasting its dynamics as a feedback system and showing the feedforward and the feedback paths are both passive. The challenge is that both paths can be piecewise linear. Numerical results
show excellent performance of the proposed controller even in the face of sudden variations of the plant parameters.
This article provides sufficient conditions for the existence of periodic solutions with nonconstant sign in a family of polynomial, non-auto-nomous, firrst-order diferential equations that arise as a generalization of the Abel equation of the second kind.
Costa-Castelló, R.; Olm, Josep M.; Vargas, H.; Ramos, G. A. International journal of innovative computing information and control Vol. 8, num. 8, p. 5591-5606 Date of publication: 2012-08 Journal article
This article presents an educational approach to resonant control and repet-
itive control, which are Internal Model Principle-based control techniques speci cally de-
signed for the tracking/rejection of periodic signals. The analytical formulation is com-
pleted by a set of simulations and physical experiments on a mechatronic educational
plant integrated in a virtual/remote laboratory. The laboratory features are oriented to
realize the limited performance of classic PID control to reject non-constant disturbances
and, at the same time, to show the effectiveness of the Internal Model Principle for the
rejection of periodic disturbances by means of resonators and repetitive control. Assess-
ment based on students' perception reveals it as a useful distance learning tool. The
laboratory is integrated in Automatl@bs, a Spanish interuniversity network of web-based
laboratories devoted to distance learning of control engineering.
Olm, Josep M.; Biel, D.; Spinetti, M. de J.; Fossas, E. International journal of circuit theory and applications Vol. 40, num. 8, p. 777-792 DOI: 10.1002/cta.755 Date of publication: 2012-08 Journal article
The achievement of step-up inversion with a boost DC/AC converter requires appropriate periodic references for inductor currents, which have to satisfy ordinary differential equations (ODE) of the Abel type. These are equations with highly unstable solutions for which the existence of periodic solutions remains unproved. Hence, the studies reported so far in this subject obtain periodic output voltages that approximately track the expected profile using different periodic current references that do not exactly satisfy the Abel ODE. However, neither an explanation of why are periodic output voltages still obtained, nor an assessment of the output voltage error is provided. This paper analyzes the effect of using periodic current references in a Lyapunov-based controlled boost DC/AC converter performing step-up inversion tasks. It is shown that, for sufficiently accurate current references, the system exhibits asymptotically stable periodic solutions with bounded error. Moreover, the paper propounds the use of Harmonic Balance (HB)-based techniques to obtain such current references. Simulation and experimental results confirm that this choice yields periodic output voltages with an error that may be lowered using higher HB approximations.
Costa-Castelló, R.; Ramos, G.A.; Olm, Josep M. Revista iberoamericana de automática e informática industrial Vol. 9, num. 3, p. 219-230 DOI: 10.1016/j.riai.2012.05.012 Date of publication: 2012-07-01 Journal article
El control repetitivo digital es una t´ecnica basada en el principio del modelo interno que permite seguir y/o rechazar se˜nales
peri´odicas. Una hip´otesis clave en los dise˜nos tradicionales de control repetitivo es que la frecuencia de tales se˜nales es constante y
conocida, siendo su principal desventaja la elevada degradaci´on de prestaciones que aparece cuando dicha frecuencia es incierta o
var´ıa con el tiempo. En este trabajo se presenta una revisi´on de las principales estrategias introducidas hasta la fecha para resolver este problema.
En este trabajo se revisa la técnica de control adaptativo por modelo de referencia con síntesis de controlador mínima y se
relacionan las diferentes extensiones del método que se encuentran en la literatura especializada.
Ramos, G.A.; Olm, Josep M.; Costa-Castelló, R. IEEE Latin American Conference on Automatic Control and Industry Applications p. 1-5 DOI: 10.1109/LARC.2011.6086827 Presentation's date: 2011-11-28 Presentation of work at congresses
The study of periodic solutions with constant sign in the Abel equation of the second kind can be made through the equation of the first kind. This is because the situation is equivalent under the transformation xmaps tox−1, and there are many results available in the literature for the first kind equation. However, the equivalence breaks down when one seeks for solutions with nonconstant sign. This note is devoted to periodic solutions with nonconstant sign in Abel equations of the second kind. Specifically, we obtain sufficient conditions to ensure the existence of a periodic solution that shares the zeros of the leading coefficient of the Abel equation. Uniqueness and stability features of such solutions are also studied.
di Bernardo, M.; di Gaeta, A.; Montanaro, U.; Olm, Josep M.; Santini, S. World Congress of the International Federation of Automatic Control p. 5064-5069 DOI: 10.3182/20110828-6-IT-1002.01052 Presentation's date: 2011-08-31 Presentation of work at congresses
Digital repetitive control is a strategy that allows tracking/
rejecting periodic signals. Repetitive controllers are designed
assuming that the exogenous signal period is constant
and known, its main drawback being the dramatic
loss of performance when signal frequency varies. This
paper reviews the most relevant proposals advanced for
overcoming this problem.El control repetitivo digital es una técnica que permite el
seguimiento y rechazo de señales periódicas. Los controladores
repetitivos son diseñados asumiendo que las señales
a seguir/rechazar tienen una frecuencia fija y conocida,
siendo su principal desventaja la degradación de
desempeño cuando esta frecuencia varía. Este artículo
presenta una revisión de las diferentes estrategias utilizadas
con el fin de solventar dicha problemática.
Digital repetitive control is a technique which allows tracking periodic references and/or rejecting
periodic disturbances. Repetitive controllers are usually designed assuming a fixed fundamental
frequency for the signals to be tracked/rejected and its main drawback being a dramatic
performance decay when this frequency varies. A usual approach to overcome the problem
consists of an adaptive change of the sampling period according to the reference/disturbance
period variation. This paper presents a stability analysis of a digital repetitive controller working
under time-varying sampling period by means of an LMI gridding approach. Theoretical
developments are illustrated with experimental results, which are preceded by a detailed
description of fundamental issues related to the implementation procedure.
The study of periodic solutions with constant sign in the Abel equation of the second kind can be made through
the equation of the first kind. This is because the situation is equivalent under the transformation x 7¡æ x.1, and
are many results available in the literature for the first kind equation. However, the equivalence breaks down when
one seeks for solutions with nonconstant sign. This note is devoted to periodic solutions with nonconstant sign in
Abel equations of the second kind. Specifically, we obtain sufficient conditions to ensure the existence of a periodic
solution that shares the zeros of the leading coefficient of the Abel equation. Uniqueness and stability features of
solutions are also studied
di Bernardo, M.; di Gennaro, F.; Olm, Josep M.; Santini, S. International journal of control Vol. 83, num. 12, p. 2641-2657 DOI: 10.1080/00207179.2010.536916 Date of publication: 2010-12-12 Journal article
Ramos, G. A.; Costa-Castelló, R.; Olm, Josep M. IEEE International Conference on Emerging Technologies and Factory Automation DOI: 10.1109/ETFA.2010.5641241 Presentation's date: 2010-09-13 Presentation of work at congresses
Costa-Castelló, R.; Olm, Josep M.; Ramos, G. A.; Cardoner, R. 2010 IEEE Multi-Conference on Systems and Control p. 398-403 DOI: 10.1109/CCA.2010.5611211 Presentation's date: 2010-09-08 Presentation of work at congresses
This work deals with the design and analysis of a controller for a shunt active power filter. The design is based on combined feedforward and feedback actions, the last using oddharmonic repetitive control, and aims at obtaining good closedloop
performance in spite of the possible frequency variations that may occur in the electrical network. As these changes
affect the performance of the controller, the proposal includes a compensation technique consisting of an adaptive change of the sampling time of the digital controller according to the network frequency variation. However, this implies structural changes in the closed-loop system that may eventually destabilize it.
Hence, this article is also concerned with closed-loop stability of the resulting system, which is analyzed using a robust control approach that takes advantage of the small gain theorem. Experimental results reporting good performance of the closedloop
system are provided.
This article addresses the robust output regulation problem for a class of nonlinear switched power converters after its linearization by means of a change of the control vector variable. The methodology employs a dynamic state feedback control law and considers parametric uncertainty due to unknown values of resistive loads. Restrictions arising from the fact that the control gains exhibit fixed values are taken into account. The proposed technique is exemplified with the output voltage regulation of a Noninverting Buck-Boost converter and tested through realistic numerical simulations.
Ramos, G.A.; Costa-Castelló, R.; Olm, Josep M.; Cardoner, R. Annual Conference of the IEEE Industrial Electronics Society p. 1040-1045 Presentation's date: 2010-07-07 Presentation of work at congresses
Shunt active power filters have proven to be an
efficient means to compensate for the negative effects of nonlinear
and reactive loads on the power quality of the electrical distribution
network. In this context, the control objective is to achieve
a power factor close to 1, as well as load current harmonics
and reactive power compensation. A useful control strategy for
this purpose is repetitive control. However, the performance of
repetitive controllers is strongly affected by frequency variations
of the involved signals. This work analyzes the effect of such
variations and describes the architecture of an odd-harmonic,
high-order repetitive controller specifically designed to obtain
robust closed-loop performance against frequency variations that
may occur in the electrical network.
Best Presentation in Session Award, que atorga la 2010 American Control Conference
This work deals with the design and analysis of a controller for a shunt active power filter. The design is based on combined feedforward and feedback actions, the last using repetitive control, and aims at the obtention of a good closedloop performance in spite of the possible frequency variations that may occur in the electrical network. As these changes affect the performance of the controller, the proposal includes a compensation technique consisting of an adaptive change of the digital controller’s sampling time according to the network frequency variation. However, this implies structural changes in the closed-loop system that may destabilize the overall system. Hence, this article is also concerned with closed-loop stability of the resulting system, which is analyzed using a robust control approach through the small gain theorem. Experimental results that indicate good performance of the closed-loop system are provided.
Roqueiro, N.; Muñoz-Aguilar, R. S.; Griño, R.; Fossas, E.; Doria-Cerezo, A.; Batlle, C.; Riera, J.; Olm, Josep M.; Pagano, D.; Valencia, M.; Oliveira, A.; Nicolazzi, L.; de Souza , R.; Gaudenzi, M.; de Lima, S.; de Souza, D. Competitive project
This article studies the robust tracking control
problem in nonminimum phase DC-DC nonlinear switched
power converters. The proposed procedure introduces a stable
inversion-based iterative technique that, taking advantage of
Banach’s fixed point theorem, provides closed-form analytic
expressions uniformly convergent to the exact solution of the
corresponding inverse problem. Then, piecewise constant load
disturbances belonging to an a priori known compact set
are successfully rejected by means of dynamic compensation.
Simulation results validate the proposal.
Costa-Castelló, R.; Olm, Josep M.; Ramos, G.A. IEEE Conference on Decision and Control and Chinese Control Conference. Symposium on Learning Control p. 1-6 Presentation's date: 2009-12-14 Presentation of work at congresses
This article introduces and analyzes the performance
features of different design schemes for digital repetitive
control systems subject to references/disturbances that exhibit
non-uniform frequency. Aiming for the maintenance of a
constant value for the ratio Tp/Ts, where Tp is the period of
the reference/disturbance signal and Ts is the sampling period,
two approaches are proposed. The first one deals with the realtime
adaptation of Ts to the actual changes of Tp; the stability
issue is studied by means of an LMI gridding method and also
using robust control techniques. The second one propounds the
introduction of an additional compensator that annihilates the
effect of the time-varying sampling in the closed-loop system
and forces its behavior to coincide with the one corresponding
to an a priori selected nominal sampling period; the procedure
needs the internal stability of the compensator-plant subsystem,
which is checked by means of LMI gridding. The theoretical
results are experimentally tested and compared through a
mechatronic plant model.
Digital repetitive control is a technique which al-
lows to track periodic references and/or reject peri-
odic disturbances. Repetitive controllers are usually de-
signed assuming a fixed frequency for the signals to be
tracked/rejected, its main drawback being a dramatic per-
formance decay when this frequency varies. A usual ap-
proach to overcome the problem consists of an adap-
tive change of the sampling time according to the refer-
ence/disturbance period variation. However, this sam-
pling period adaptation implies parametric changes af-
fecting the closed-loop system behavior, that may compro-
mise the system stability. This article presents a design
strategy which allows to compensate for the parametric
changes caused by sampling period adjustment. Stabil-
ity of the digital repetitive controller working under time-
varying sampling period is analyzed. Theoretical devel-
opments are illustrated with experimental results.