L’activitat científica del grup es centra en l’estudi de les propietats elèctriques i electròniques de materials i dispositius, de cara a les seves aplicacions. S’incideix en aspectes que van des de la caracterització i millora dels materials actius fins a la optimització de dispositius i sistemes. La recerca esta dotada de un fort contingut interdisciplinari; requereix coneixements de química (síntesi de materials micro i nanoestructurats) i física de estat sòlid (propietats de dielèctrics i ferroelèctrics, processos de conducció en nous materials, etc.), així com de electrònica i de eines matemàtiques complexes. L’objectiu bàsic de l’activitat científica del grup és contribuir al coneixement de la relació processament-estructura-propietats de materials funcionals avançats amb noves i millors propietats, amb potencial ús en aplicacions diverses. Per altra banda, contribuir a la optimització de sistemes, mitjançant una adequada simulació de les seves propietats no lineals.
Del Barrio, M.; Levit, R.; Lloveras, P.; Aznar, A.; Negrier, P.; Mondieig, D.; Tamarit, J. Ll. Fluid phase equilibria Vol. 459, p. 219-229 DOI: 10.1016/j.fluid.2017.07.020 Data de publicació: 2018-03-15 Article en revista
The temperature-composition phase diagram of the two-component system 1-Br-adamantane and 1-Cl-adamantane has been determined by means of thermal analysis techniques and X-ray powder diffraction from the low-temperature phase to the liquid state.
The crossed isopolymorphism formalism has been applied to the two-component system to infer the normal pressure properties of the orthorhombic metastable phase of 1-Cl-adamantane at normal pressure. The experimental pressure-temperature phase diagrams for the involved compounds are related to the two-phase equilibria determined at normal pressure and inferences about the monotropic behavior of the aforementioned orthorhombic phase are discussed.
The dynamics of a DC-AC self-oscillating LC resonant inverter with a zero current switching strategy is considered in this paper. A model that includes both the series and the parallel topologies and accounts for parasitic resistances in the energy storage components is used. It is found that only two reduced parameters are needed to unfold the bifurcation set of this extended system: one is related to the quality factor of the LC resonant tank, and the other accounts for the balance between serial and parallel losses. Through a rigorous mathematical study, a complete description of the bifurcation set is obtained and the parameter regions where the inverter can work properly is emphasized.
Rubio-Marcos, F.; Ochoa, D. A.; Del Campo, A.; García, M. A.; Castro, G. R.; Fernández, J.F; Garcia, J. E. Nature photonics Vol. 12, num. 1, p. 29-32 DOI: 10.1038/s41566-017-0068-1 Data de publicació: 2018-01-01 Article en revista
The optical control of ferroic properties is a subject of fascination for the scientific community, because it involves the establishment of new paradigms for technology. Domains and domain walls are known to have a great impact on the properties of ferroic materials. Progress is currently being made in understanding the behaviour of the ferroelectric domain wall, especially regarding its dynamic control. New research is being conducted to find effective methodologies capable of modulating ferroelectric domain motion for future electronics. However, the practical use of ferroelectric domain wall motion should be both stable and reversible (rewritable) and, in particular, be able to produce a macroscopic response that can be monitored easily. Here, we show that it is possible to achieve a reversible optical change of ferroelectric domains configuration. This effect leads to the tuning of macroscopic polarization and its related properties by means of polarized light, a non-contact external control. Although this is only the first step, it nevertheless constitutes the most crucial one in the long and complex process of developing the next generation of photo-stimulated ferroelectric devices.
Aquest llibre és un conjunt de problemes de física quàntica ordenats temàticament i pensats per a estudiants de grau, de ciències o d’enginyeria. Cada tema conté una breu introducció teòrica seguida d’un recull de problemes. Des de la quantització i la dualitat ona-partícula fins a l’oscil·lador harmònic quàntic i el moment angular intrínsec, passant per l’equació de Schrödinger i el principi d’indeterminació de Heisenberg, en l’obra es treballa especialment l’efecte túnel i les seves conseqüències, com les bandes d’energia prohibides per a electrons i per a fotons. L’obra introdueix els aspectes fonamentals de la física quàntica que ja són essencials en el currículum de ciències aplicades o d’un enginyer.
The temperature dependence of the dielectric response of ordinary ferroelectric materials exhibits a frequency-independent anomalous peak as a manifestation of the ferroelectric to paraelectric phase transition. A second anomaly in the permittivity has been reported in different ferroelectric perovskite-type systems at low temperatures, often at cryogenic temperatures. This anomaly manifests as a frequency-dependent local maximum, which exhibits similar characteristics to that observed in relaxor ferroelectrics around their phase transition. The origin of this unexpected behavior is still controversial. In order to clarify this phenomenon, a model-free route solution is developed in this work. Our findings reveal the same critical linear pattern/glass-like freezing behavior previously observed for glass-forming systems. Contrary to current thought, our results suggest that a critical-like dynamic parameterization could provide a more appropriate solution than the conventional Vogel–Fulcher–Tammann equation. The implemented methodology may open a new pathway for analyzing relaxation phenomena in other functional materials like relaxor ferroics.
The outcome of the collision between two liquid jets depends on the liquid properties, jet velocity, and impact angle. So far studies on liquid jet impingement have been carried out in normal gravity conditions. In microgravity, jets are not accelerated and can show a different behavior than on ground. We perform an experimental analysis of the injection of liquid jets in microgravity, focusing in the jet impingement at different velocities and impact angles at low Weber numbers. Several regimes are obtained, some of which are not observable on ground. Other regimes take place at different parameter ranges than in normal gravity. A map of the observed regimes is proposed in terms of the Weber number and the impact angle.
Rubio-Marcos, F.; Fernández, J.F; Ochoa, D. A.; Garcia, J. E.; Rojas-Hernandez, R. E.; Castro, M.; Ramajo, L. Journal of the european ceramic society Vol. 37, num. 11, p. 3501-3509 DOI: 10.1016/j.jeurceramsoc.2017.04.045 Data de publicació: 2017-09 Article en revista
Lead zirconate titanate (PZT) based ceramics are currently enjoying a wide use in piezoelectric devices despite lead toxicity. Due to growing environmental concerns, the attention on piezoelectric ceramics has been moving to lead-free materials, in particular to (K,Na)NbO3-based ceramics. Here we report a systematic evaluation of the effects of the compositional modifications on [(K0.44Na0.52Li0.04)[(Nb0.86Ta0.10Sb0.04)1-xZr5x/4]O3 lead–free piezoceramics. We show that an interrelationship between the intrinsic and extrinsic factors is the linchpin for the development of good piezoelectric properties. Hence, the stabilization of the tetragonal symmetry on the orthorhombic-tetragonal polymorphic phase boundary facilities the poling process of the system, thereby enhancing the piezoelectric response. Additionally, the microstructure appears to be related to the piezoelectric properties; i.e., the improved piezoelectric properties correlate to the increase in grain size. The results of this work could help to understand the origin of piezoelectricity in potassium–sodium niobate-based ceramics.
This paper deals with the global dynamical analysis
of a self-oscillating resonant inverter which is based on switching
between two symmetrical circuit configurations. The analysis
predicts coexisting steady-state solutions, which are increasingly
relevant for low values of the quality factor of the resonant circuit,
thus likely driving to an improper system operation. A repelling
sliding region is found to be connected with the two unstable limit
cycles that split the phase plane in three basins of attraction. To
avoid the presence of multiple steady-state solutions, a viable
solution consisting of a modification of the control is proposed
and validated by numerical simulations.
Ochoa, D. A.; Levit, R.; Fancher, C.M.; Esteves, G.; Jones, J.L.; Garcia, J. E. Journal of Physics D: Applied Physics Vol. 50, num. 20, p. 205305-1-205305-14 DOI: 10.1088/1361-6463/aa6b9e Data de publicació: 2017-04-26 Article en revista
Ordinary ferroelectrics exhibit a second order phase transition that is characterized by a sharp peak in the dielectric permittivity at a frequency-independent temperature. Furthermore, these materials show a low temperature dielectric relaxation that appears to be a common behavior of perovskite systems. Tetragonal lead zirconate titanate is used here as a model system in order to explore the origin of such an anomaly, since there is no consensus about the physical phenomenon involved in it. Crystallographic and domain structure studies are performed from temperature dependent synchrotron x-ray diffraction measurement. Results indicate that the dielectric relaxation cannot be associated with crystallographic or domain configuration changes. The relaxation process is then parameterized by using the Vogel–Fulcher–Tammann phenomenological equation. Results allow us to hypothesize that the observed phenomenon is due to changes in the dynamic behavior of the ferroelectric domains related to the fluctuation of the local polarization.
In this paper, the dynamics of a dc-ac resonant self-oscillating LC series inverter is analyzed
from the point of view of piecewise smooth dynamical systems. Our system is defined by two
symmetric configurations and its bifurcation analysis can be given in a one dimensional param-
eter space, thus finding a non smooth transition between two strongly different dynamics. The
oscillating regime, which is the one useful for applications and involves a repetitive switching
action between those configurations, is given whenever their open loop equilibrium is a fo-
cus. Otherwise, the only attractors are equilibrium points of node type whose stable manifolds
preclude the appearance of oscillations.
In this paper, the switching dynamics of a dc-ac
resonant self-oscillating inverter is considered. Using bifurcation
analysis coexisting steady-state solutions are predicted, which
are increasingly relevant for low values of the quality factor
of the resonant circuit. A repelling sliding region is found to be
connected with the two unstable limit cycles that split the phase
plane in three basins of attraction. Simulation results obtained
from the switched model confirm the theoretical derivations.
Ferrer-Anglada, N.; Arcos, D.; D. Gabriel; Bernat Sempere; Colominas, C. International Winterschool on the Electronic Properties of Novel Materials-Molecular Nanostructures p. 58 Data de presentació: 2017-03-06 Presentació treball a congrés
Machado, R.; dos Santos, V.B.; Ochoa, D. A.; Cerdeiras, E.; Mestres, L.; Garcia, J. E. Journal of alloys and compounds Vol. 690, p. 568-574 DOI: 10.1016/j.jallcom.2016.08.116 Data de publicació: 2017-01-05 Article en revista
A systematic study of the functional properties of the (1-x)(Bi0.5Na0.5)TiO3–xBaTiO3 (BNT-xBT) piezoceramic system for 0.05 = x = 0.07 is performed. The samples are obtained through the conventional solid-state route. The expected microstructure for these compounds, with no significant dependence on the composition, is verified by field-emission scanning electron microscopy. The morphotropic phase boundary (MPB) is detected for x = 0.06–0.07 by means of the Rietveld analysis of X-ray diffraction data. The dielectric spectra show a frequency-independent, completely diffuse phase transition with a composition-dependent diffusivity coefficient. The depolarization temperature is effectively evaluated from pyroelectric measurements, the value being strongly dependent on the composition. A significant contribution of the extrinsic effect to elastic, dielectric and electromechanical properties is revealed for MPB BNT-xBT. The Bi3+ substitution by Ba2+ leads to the formation of A-site vacancies, which give rise to the enhancement of domain wall motion, as occurs in other perovskite-type piezoelectrics. Good functional properties are achieved for x = 0.07 (d33 = 180 pC/N), which are similar or even better than those obtained by complex synthesis routes. This system exhibits a remarkable stability in the permittivity that has hitherto not been reported. This fact may open the way for BNT-BT compositions to be used in specific applications in which lead-free piezoceramics have previously been employed with little success, e.g. in high power devices.
Arcos, D.; Gabriel, D.; Dumcenco, D.; kis, A.; Ferrer-Anglada, N. Physica status solidi B. Basic solid state physics Vol. 253, num. 12, p. 2499-2504 DOI: 10.1002/pssb.201600281 Data de publicació: 2016-12-09 Article en revista
In the increasing research field of 2D materials such as graphene, molybdenum disulfide MoS2 has attracted great interest due to the existence of a direct bandgap in monolayer MoS2, which gives the possibility of achieving MoS2 field-effect transistors or optoelectronic devices. We analyzed by THz time-domain spectroscopy (THz-TDS) up to 2 THz and infrared (IR) spectroscopy, CVD-obtained MoS2 using either S or H2S gas as a sulfur precursor, grown on a sapphire substrate. From THz-TDS we obtained the transmittance, conductivity, and attenuation. From IR spectroscopy on the same samples, we deduced the transmittance in the IR frequency range. We observed the coherence of both spectroscopic methods. The advantage of the THz-TDS method is that we can get significant parameters related to the sample quality without the need for depositing any electrical contact or sample preparation. Our results show that at high frequencies MoS2 is even better than graphene as a material for optoelectronic devices.
Machado, R.; Ochoa, D. A.; dos Santos, V.B.; Cerdeiras, E.; Mestres, L.; Garcia, J. E. Materials letters Vol. 183, p. 73-76 DOI: 10.1016/j.matlet.2016.07.045 Data de publicació: 2016-11-15 Article en revista
The (1-x)Bi0.5Na0.5TiO3–xBaTiO3 (BNT-xBT) system with composition at its morphotropic phase boundary (MPB) has received significant attention because of their attractive properties as lead-free piezoceramics. Although the basic properties of this system are well-established, reports about the stability of the functional properties of these piezoelectric materials are still lacking. A study on the dielectric and piezoelectric properties of BNT-xBT close to their MPB, with emphasis on material response under high electric field or mechanical stress, is performed in this work. The results indicate that the BNT-BT system exhibits a high stability of dielectric and piezoelectric properties, making it potentially interesting for specific applications. A direct correlation between piezoelectric properties and nonlinear response is evidenced for a wide number of piezoceramics, which is expected due to the extrinsic nature of the piezoelectric response. Finding compositions that show high electromechanical properties and low nonlinear behavior is a challenge in the search for competitive lead-free piezoceramics.
Vendrell, X.; Garcia, J. E.; Cerdeiras, E.; Ochoa, D. A.; Rubio-Marcos, F.; Fernández, J.F; Mestres, L. Ceramics international Vol. 42, num. 15, p. 17530-17538 DOI: 10.1016/j.ceramint.2016.08.066 Data de publicació: 2016-11-15 Article en revista
Lanthanides-doped K0.5Na0.5NbO3(KNN) lead-free piezoelectric ceramics are prepared by conventional solid-state reaction. The effects of lanthanum concentration and the lanthanide type on the structure, microstructure and ferro-piezoelectric properties are evaluated. Ln3+ doping has a slight effect on the structure, but greatly inhibits the grain growth. Moreover, a decrease in the Curie temperature and an increase in the dielectric constant values are observed when doping. Large amounts of lanthanum induce a diffuse phase transition and an increase of the dielectric losses. The piezoelectric properties are greatly improved when doping with small amounts of dopants. As the ionic radii of the lanthanide is reduced, the piezoelectric properties of the ceramics are increased, the Eu3+-doped ceramics show an increase of 29% of the piezoelectric coefficient d33 with respect to pure KNN. The results show that low concentrations of lanthanides improve significantly the functional properties of KNN lead-free piezoceramics. Doping with lanthanides should be taken into consideration in some other compositions based on KNN.
Pérez-Madrigal, Maria M.; Ochoa, D. A.; Garcia, J. E.; Armelin, E.; Aleman, C. Journal of polymer science. Part B, polymer physics Vol. 54, num. 18, p. 1896-1905 DOI: 10.1002/polb.24095 Data de publicació: 2016-09-15 Article en revista
Dielectric elastomer actuators (DEAs) transform electrical energy into mechanical work. However, despite displaying exceptional features, the low permittivity of elastomers restricts their application. Hence, to overcome this limitation, DEAs are fabricated by dispersing poly(3-methylthiophene acetate) (P3TMA), a polarizable conducting polymer, into poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), a thermoplastic elastomer with excellent mechanical properties. Although high-quality SEBS:P3TMA films are obtained for all compositions (between 0.5 and 20 wt % P3TMA), their thickness and surface roughness increase with the nano-sized filler content. Moreover, the conducting particles are well integrated into the SEBS network with no evidence of aggregation or significant change in the mechanical properties of the composites. P3TMA, which forms encapsulated conductive domains within the polymeric matrix, improves the dielectric behavior of SEBS:P3TMA by increasing their dielectric constant with low dielectric losses and no current leakage. Thus, indicating the potential future application of these nanocomposites as elastomer actuators or high energy density capacitors.
Ochoa, D. A.; Esteves, G.; Iamsasri, T.; Rubio-Marcos, F.; Fernández, J.F; Garcia, J. E.; Jones, J.L. Journal of the european ceramic society Vol. 36, num. 10, p. 2489-2494 DOI: 10.1016/j.jeurceramsoc.2016.03.022 Data de publicació: 2016-08 Article en revista
The origins of high piezoelectric properties in the lead-free (K,Na)NbO3-based tetragonal composition (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 (KNL-NTS) is investigated by quantifying the intrinsic and extrinsic contributions from high energy X-ray diffraction measurements. The applied methodology, which allows discerning between the intrinsic contribution, related to the field induced lattice distortion, and the extrinsic contributions, related to non-180° domain wall motion, is widely described in this work. The non-180° domain reorientation of the KNL-NTS piezoceramic is quantify from the integrated intensities of the 002 and 200 reflections obtained from line profile, while the shifts in peak position versus the applied electric field is used to obtain the lattice strain contribution. Large non-180° domain wall contribution to the electric field induced macroscopic strain (80% of the macroscopic strain) is verified in KNL-NTS.
Cerdeiras, E.; Ochoa, D. A.; Garcia, J. E.; Mestres, L. Reunión Científico Plenaria de Química Inorgánica y Reunión Científico Plenaria de Química del Estado Sólido Data de presentació: 2016-06 Presentació treball a congrés
Amaral, T. M.; Antonelli, E.; Ochoa, D. A.; Garcia, J. E.; Hernandes, A. Ceramics international Vol. 42, num. 7, p. 8488-8494 DOI: 10.1016/j.ceramint.2016.02.071 Data de publicació: 2016-05-15 Article en revista
The dielectric, pyroelectric and ferroelectric properties of bilayered BaTiO3/BaTi0.8Zr0.2O3 ceramics are described and correlated with their microstructure. Different sintering times are employed to change the microstructure and promote interdiffusion between the layers. The effects of constrained sintering on both compositions are analyzed and their properties are compared to that of single phase BaTiO3 and BaTi0.8Zr0.2O3 ceramics. The results show that, at sintering times until 2 hours, the bilayer properties are predominantly affected by the presence of residual stresses. Only after 4 hours sintering, the properties are predominantly affected by interdiffusion between the layers.
Ochoa, D. A.; Esteves, G.; Jones, J.L.; Rubio-Marcos, F.; Fernández, J.F; Garcia, J. E. Applied physics letters Vol. 108, num. 14, p. 142901-1-142901-5 DOI: 10.1063/1.4945593 Data de publicació: 2016-04-04 Article en revista
Polymorphic phase boundaries (PPBs) in piezoelectric materials have attracted significant interest in recent years, in particular because of the unique properties that can be found in their vicinity. However, to fully harness their potential as micro-nanoscale functional entities, it is essential to achieve reliable and precise control of their piezoelectric response, which is due to two contributions known as intrinsic and extrinsic. In this work we have used a (K,Na)NbO3-based lead-free piezoceramic as a model system to investigate the evolution of the extrinsic contribution around a PPB. X-ray diffraction measurements are performed over a wide range of temperatures in order to determine the structures and transitions. The relevance of the extrinsic contribution at the PPB region is evaluated by means of nonlinear dielectric response measurements. Though it is widely appreciated that certain intrinsic properties of ferroelectric materials increase as PPBs are approached, our results demonstrate that the extrinsic contribution also maximizes. An enhancement of the extrinsic contribution is therefore also responsible for improving the functional properties at the PPB region. Rayleigh’s law is used to quantitatively analyze the nonlinear response. As a result, an evolution of the domain wall motion dynamics through the PPB region is detected. This work demonstrates that the extrinsic contribution at a PPB may have a dynamic role in lead-free piezoelectric materials, thereby exerting a far greater influence on their functional properties than that considered to date.
The Preisach model is a classical method for describing nonlinear behavior in hysteretic systems. According to this model, a hysteretic system contains a collection of simple bistable units which are characterized by an internal field and a coercive field. This set of
bistable units exhibits a statistical distribution that depends on these fields as parameters. Thus, nonlinear response depends on the specific distribution function associated with the material. This model is satisfactorily used in this work to describe the temperature-dependent ferroelectric response in PZT- and KNN-based piezoceramics. A distribution function expanded in Maclaurin series considering
only the first terms in the internal field and the coercive field is proposed. Changes in coefficient relations of a single distribution function allow us to explain the complex temperature dependence of hard piezoceramic behavior. A similar analysis based on the same form of the distribution function shows that the KNL–NTS properties soften
around its orthorhombic to tetragonal phase transition.
Cristiano, R.; Pagano, D.; Benadero, L.; Ponce, E. International journal of bifurcation and chaos Vol. 26, num. 4, p. 1630010-1-1630010-18 DOI: 10.1142/S021812741630010X Data de publicació: 2016-04 Article en revista
Direct current (DC) microgrids (MGs) are an emergent option to satisfy new demands for power quality and integration of renewable resources in electrical distribution systems. This work addresses the large-signal stability analysis of a DC–DC bidirectional converter (DBC) connected to a storage device in an islanding MG. This converter is responsible for controlling the balance of power (load demand and generation) under constant power loads (CPLs). In order to control the DC bus voltage through a DBC, we propose a robust sliding mode control (SMC) based on a washout filter. Dynamical systems techniques are exploited to assess the quality of this switching control strategy. In this sense, a bifurcation analysis is performed to study the nonlinear stability of a reduced model of this system. The appearance of different bifurcations when load parameters and control gains are changed is studied in detail. In the specific case of Teixeira Singularity (TS) bifurcation, some experimental results are provided, confirming the mathematical predictions. Both a deeper insight in the dynamic behavior of the controlled system and valuable design criteria are obtained.
Piezoceramic materials generally exhibit a notable instability of their functional properties when they work under real external conditions. This undesirable effect, known as nonlinear behavior, is mostly associated with the extrinsic contribution to material response. In this article, the role of the ferroelectric domain walls' motion in the nonlinear response in the most workable lead-based and lead-free piezoceramics is reviewed. Initially, the extrinsic origin of the nonlinear response is discussed in terms of the temperature dependence of material response. The influence of the crystallographic phase and of the phase boundaries on the material response are then reviewed. Subsequently, the impact of the defects created by doping in order to control the extrinsic contribution is discussed as a way of tuning material properties. Finally, some aspects related to the grain-size effect on the nonlinear response of piezoceramics are surveyed.
Gabriel, D.; Bernat Sempere; Colominas, C.; Ferrer-Anglada, N. Physica status solidi B. Basic solid state physics Vol. 252, num. 11, p. 2423-2428 DOI: 10.1002/pssb.201552248 Data de publicació: 2015-10-23 Article en revista
Optoelectronic properties of CVD graphene are charac-terized over a wide frequency range: THz, IR, visible and near-UV. We used Raman spectroscopy to characterize the synthesized graphene films. All graphene layers were deposited on various substrates, some ones transparent or flexible, such as polyethylene terephthalate (PET), poly-ethylene naphthalate (PEN), quartz and silicon. Trans-mission Terahertz time-domain spectroscopy (THz-TDS) method, in the range from 100 GHz to 3 THz, is used to analyze the transmittance, sheet conductivity and attenua-tion of graphene and the complex refractive index of sub-strates. From IR, near-UV and visible spectroscopy we obtained the transmittance of the substrate and the sam-ple at those frequency ranges, and we deduced the gra-phene transmittance on each substrate. We found that it is close to 97% in most cases.
Optoelectronic properties of CVD graphene are charac-terized over a wide frequency range: THz, IR, visible and near-UV. We used Raman spectroscopy to characterize the synthesized graphene films. All graphene layers were deposited on various substrates, some ones transparent or flexible, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), quartz and silicon. Transmission Terahertz time-domain spectroscopy (THz-TDS) method, in the range from 100 GHz to 3 THz, is used to analyze the transmittance, sheet conductivity and attenuation of graphene and the complex refractive index of substrates. From IR, near-UV and visible spectroscopy we obtained the transmittance of the substrate and the sample at those frequency ranges, and we deduced the graphene transmittance on each substrate. We found that it is close to 97% in most cases.
Benadero, L.; Cristiano, R.; Pagano, D.; Ponce, E. IEEE Journal on Emerging and Selected Topics in Circuits and Systems Vol. 5, num. 3, p. 326-335 DOI: 10.1109/JETCAS.2015.2462017 Data de publicació: 2015-09-01 Article en revista
In this paper the nonlinear dynamics of interconnected power converters in an islanded direct current (DC) microgrid is analyzed. By using a simplified scheme based on two cascaded converters we analyze the dynamical behavior that can arise from the interconnection of these devices on a common DC bus. Furthermore, in order to address the bus voltage control problem, we propose a Sliding Mode Controller for a DC-DC bidirectional power converter to control the DC bus voltage under instantaneous constant power loads. This class of loads introduces a destabilizing nonlinear effect on the converter through an inverse voltage term that can lead to significant oscillations in the DC bus voltage. Simulation results are shown to illustrate the nonlinear analysis.