Germline mutations of breast cancer susceptibility genes through expanded genetic analysis in unselected Colombian patients.

BACKGROUND: In Colombia and worldwide, breast cancer (BC) is the most frequently diagnosed neoplasia and the leading cause of death from cancer among women. Studies predominantly involve hereditary and familial cases, demonstrating a gap in the literature regarding the identification of germline mutations in unselected patients from Latin-America. Identification of pathogenic/likely pathogenic (P/LP) variants is important for shaping national genetic analysis policies, genetic counseling, and early detection strategies. The present study included 400 women with unselected breast cancer (BC), in whom we analyzed ten genes, using Whole Exome Sequencing (WES), know to confer risk for BC, with the aim of determining the genomic profile of previously unreported P/LP variants in the affected population. Additionally, Multiplex Ligation-dependent Probe Amplification (MLPA) was performed to identify Large Genomic Rearrangements (LGRs) in the BRCA1/2 genes. To ascertain the functional impact of a recurrent intronic variant (ATM c.5496 + 2_5496 + 5delTAAG), a minigene assay was conducted. RESULTS: We ascertained the frequency of P/LP germline variants in BRCA2 (2.5%), ATM (1.25%), BRCA1 (0.75%), PALB2 (0.50%), CHEK2 (0.50%), BARD1 (0.25%), and RAD51D (0.25%) genes in the population of study. P/LP variants account for 6% of the total population analyzed. No LGRs were detected in our study. We identified 1.75% of recurrent variants in BRCA2 and ATM genes. One of them corresponds to the ATM c.5496 + 2_5496 + 5delTAAG. Functional validation of this variant demonstrated a splicing alteration probably modifying the Pincer domain and subsequent protein structure. CONCLUSION: This study described for the first time the genomic profile of ten risk genes in Colombian women with unselected BC. Our findings underscore the significance of population-based research, advocating the consideration of molecular testing in all women with cancer.

The value of additional electrodes when stereo-electroencephalography is inconclusive.

OBJECTIVE: Stereo-electroencephalography (SEEG) is the preferred method for intracranial localization of the seizure-onset zone (SOZ) in drug-resistant focal epilepsy. Occasionally SEEG evaluation fails to confirm the pre-implantation hypothesis. This leads to a decision tree regarding whether the addition of SEEG electrodes (two-step SEEG - 2sSEEG) or placement of subdural electrodes (SDEs) after SEEG (SEEG2SDE) would help. There is a dearth of literature encompassing this scenario, and here we aimed to characterize outcomes following unplanned two-step intracranial EEG (iEEG). METHODS: All 225 adult SEEG cases over 8 years at our institution were reviewed to extract patient data and outcomes following a two-step evaluation. Three raters independently quantified benefits of additional intracranial electrodes. The relationship between two-step iEEG benefit and clinical outcome was then analyzed. RESULTS: Fourteen patients underwent 2sSEEG and nine underwent SEEG2SDE. In the former cohort, the second SEEG procedure was performed for these reasons-precise localization of the SOZ (36%); defining margins of eloquent cortex (21%); and broadening coverage in the setting of non-localizable seizure onsets (43% of cases). Sixty-four percent of 2sSEEG cases were consistently deemed beneficial (Light's κ = 0.80). 2sSEEG performed for the first two indications was much more beneficial than when onsets were not localizable (100% vs 17%, p = .02). In the SEEG2SDE cohort, SDEs identified the SOZ and enabled delineation of margins relative to eloquent cortex in all cases. SIGNIFICANCE: The two-step iEEG is useful if the initial evaluation is broadly concordant with the original electroclinical hypothesis, where it can clarify onset zones or delineate safe surgical margins; however, it provides minimal benefit when the implantation hypothesis is erroneous, and we recommend that 2sSEEG not be generally utilized in such cases. SDE implantation after SEEG minimizes the need for SDEs and is helpful in delineating surgical boundaries relative to ictal-onset zones and eloquent cortex.

Effects of Aquatic Exercise on Physical Performance in Older Adults: A Systematic Review and Meta-Analysis.

This systematic review aimed to evaluate the effects of aquatic exercise on physical performance in older adults. Databases were searched up to July 2021. Randomized controlled trials were screened by two reviewers, who extracted data and assessed study quality. Ten randomized controlled trials (603 participants) were included. Compared with nonexercising controls, aquatic exercise probably improved lower limb muscle power (30-s Chair Stand Test; mean difference 4.75 repetitions; 95% confidence interval [0.07, 9.42]; I2 = 99%; 251 participants; very low-quality evidence). When comparing aquatic exercise with land exercise, there is probably no superiority in favor of either intervention on dynamic balance (Timed Up and Go Test; mean difference -0.12 s; 95% confidence interval [-0.37, 0.12]; I2 = 3%; 244 participants; very low-quality evidence).

Genetic evaluations of dairy goats with few pedigree data: different approaches to use molecular information.

One of the limitations of implementing animal breeding programs in small-scale or extensive production systems is the lack of production records and genealogical records. In this context, molecular markers could help to gain information for the breeding program. This study addresses the inclusion of molecular data into traditional genetic evaluation models as a random effect by molecular pedigree reconstruction and as a fixed effect by Bayesian clustering. The methods were tested for lactation curve traits in 14 dairy goat herds with incomplete phenotypic data and pedigree information. The results showed an increment of 37.3% of the relationships regarding the originals with MOLCOAN and clustering into five genetic groups. Data leads to estimating additive variance, error variance, and heritability with four different models, including pedigree and molecular information. Deviance Information Criterion (DIC) values demonstrate a greater fitting of the models that include molecular information either as fixed (genetic clusters) or as random (molecular matrix) effects. The molecular information of simple markers can complement genetic improvement strategies in populations with little information.

Role of the arts in the life and mental health of young people that participate in artistic organizations in Colombia: a qualitative study.

BACKGROUND: Adolescents and young adults are vulnerable to developing mental distress. However, evidence suggests that more than half of the young people with symptoms of depression and anxiety overcome their distress within a year. However, there is little research on the exact resources that young people use and help them to recover. The aim of this study was to explore how arts activities can support the recovery of young people engaged with arts organizations in Bogota. METHODS: We recruited 38 participants from two arts organizations in Bogotá and conducted six focus groups embedded within artistic workshops. The type of activities in the workshops varied reflecting the different teaching methods of the two organizations. The focus group discussions were recorded and analyzed using thematic analysis. RESULTS: Five themes explained how arts activities can help young people participating in artistic organizations to overcome mental distress: i) allowing the expression of emotions; ii) helping to manage and transform emotions; iii) distracting from problems; iv) facilitating social support and relationships; and v) contributing to the identity of young people. CONCLUSIONS: For young people who participate in artistic organizations, the arts are a resource for overcoming negative emotions such as anxiety, depression, and sadness. The beneficial role of arts activities includes different process of managing, expressing, and distracting from distress, and it differs depending on whether arts are perceived as a professional vocation or a hobby.

Static coded illumination strategies for low-dose x-ray material decomposition.

Static coded aperture x-ray tomography was introduced recently where a static illumination pattern is used to interrogate an object with a low radiation dose, from which an accurate 3D reconstruction of the object can be attained computationally. Rather than continuously switching the pattern of illumination with each view angle, as traditionally done, static code computed tomography (CT) places a single pattern for all views. The advantages are many, including the feasibility of practical implementation. This paper generalizes this powerful framework to develop single-scan dual-energy coded aperture spectral tomography that enables material characterization at a significantly reduced exposure level. Two sensing strategies are explored: rapid kV switching with a single-static block/unblock coded aperture, and coded apertures with non-uniform thickness. Both systems rely on coded illumination with a plurality of x-ray spectra created by kV switching or 3D coded apertures. The structured x-ray illumination is projected through the objects of interest and measured with standard x-ray energy integrating detectors. Then, based on the tensor representation of projection data, we develop an algorithm to estimate a full set of synthesized measurements that can be used with standard reconstruction algorithms to accurately recover the object in each energy channel. Simulation and experimental results demonstrate the effectiveness of the proposed cost-effective solution to attain material characterization in low-dose dual-energy CT.

A Composite DC-DC Converter Based on the Versatile Buck-Boost Topology for Electric Vehicle Applications.

The composite converter allows integrating the high-efficiency converter modules to achieve superior efficiency performance, becoming a prominent solution for electric transport power conversion. In this work, the versatile buck-boost dc-dc converter is proposed to be integrated into an electric vehicle composite architecture that requires a wide voltage range in the dc link to improve the electric motor efficiency. The inductor core of this versatile buck-boost converter has been redesigned for high voltage applications. The versatile buck-boost converter module of the composite architecture is in charge of the control stage. It provides a dc bus voltage regulation at a wide voltage operation range, which requires step-up (boost) and step-down (buck) operating modes. The PLECS thermal simulation of the composite architecture shows a superior power conversion efficiency of the proposed topology over the well-known classical noninverting buck-boost converter under the same operating conditions. The obtained results have been validated via experimental efficiency measures and experimental transient responses of the versatile buck-boost converter. Finally, a hardware-in-the-loop (HIL) real-time simulation system of a 4.4 kW powertrain is presented using a PLECS RT Box 1 device. The HIL simulation results verified the accuracy of the theoretical analysis and the effectiveness of the proposed architecture.

StaticCodeCT: single coded aperture tensorial X-ray CT.

Coded aperture X-ray CT (CAXCT) is a new low-dose imaging technology that promises far-reaching benefits in industrial and clinical applications. It places various coded apertures (CA) at a time in front of the X-ray source to partially block the radiation. The ill-posed inverse reconstruction problem is then solved using l1-norm-based iterative reconstruction methods. Unfortunately, to attain high-quality reconstructions, the CA patterns must change in concert with the view-angles making the implementation impractical. This paper proposes a simple yet radically different approach to CAXCT, which is coined StaticCodeCT, that uses a single-static CA in the CT gantry, thus making the imaging system amenable for practical implementations. Rather than using conventional compressed sensing algorithms for recovery, we introduce a new reconstruction framework for StaticCodeCT. Namely, we synthesize the missing measurements using low-rank tensor completion principles that exploit the multi-dimensional data correlation and low-rank nature of a 3-way tensor formed by stacking the 2D coded CT projections. Then, we use the FDK algorithm to recover the 3D object. Computational experiments using experimental projection measurements exhibit up to 10% gains in the normalized root mean square distance of the reconstruction using the proposed method compared with those attained by alternative low-dose systems.

Outcomes and complications of hospitalised patients with HIV-TB co-infection.

BACKGROUND: Tuberculosis is one of the most common causes of hospitalisation in patients with HIV. Despite this, hospital outcomes of patients with this co-infection have rarely been described since antiretroviral therapy became widely available. METHODS: Prospective cohort study of HIV-infected adult patients hospitalised with TB in six referral hospitals in Medellin, Colombia, from August 2014 to July 2015. RESULTS: Among 128 HIV-infected patients hospitalised with tuberculosis, the mean age was 38.4 years; 79.7% were men. HIV was diagnosed on admission in 28.9% of patients. The median CD4 + T-cell count was 125 (±158 SD) cells/µL. Only 47.3% of patients with a known diagnosis of HIV upon admission were on antiretroviral therapy, and only 11.1% had a tuberculin skin test in the previous year. Drug toxicity due to tuberculosis medications occurred in 11.7% of patients. Mean length of stay was 23.2 days, and 10.7% of patients were readmitted. Mortality was 5.5%. CONCLUSIONS: Hospital mortality attributable to tuberculosis in patients with HIV is low in reference hospitals in Colombia. Cases of tuberculosis in HIV-infected patients occur mainly in patients with advanced HIV, or not on antiretroviral therapy, despite a known diagnosis of HIV. Only one of every 10 patients in this cohort had active screening for latent tuberculosis, possibly reflecting missed treatment opportunities.

CONTEXTE: La tuberculose (TB) est l'une des causes les plus courantes d'hospitalisation chez les patients VIH positifs. Malgré cela, les résultats hospitaliers des patients atteints de cette coinfection ont rarement été décrits depuis que le traitement antirétroviral est devenu largement disponible. MÉTHODES: Etude de cohorte prospective de patients adultes infectés par le VIH hospitalisés pour TB dans six hôpitaux de référence à Medellin, en Colombie, d'août 2014 à juillet 2015. RÉSULTATS: Sur 128 patients infectés par le VIH hospitalisés pour TB, l'âge moyen était de 38,4 ans; 79,7% étaient des hommes. Le VIH a été diagnostiqué à l'admission chez 28,9% des patients. Le nombre médian de lymphocytes T CD4+ était de 125 (±158 SD) cellules/µL. Seuls 47,3% des patients dont le diagnostic de VIH était connu lors de leur admission étaient sous traitement antirétroviral et 11,1% seulement avaient subi un test cutané à la tuberculine l'année précédente. Une toxicité médicamenteuse due aux médicaments antituberculeux est survenue chez 11,7% des patients. La durée moyenne de séjour était de 23,2 jours et 10,7% des patients ont été réadmis. La mortalité était de 5,5%. CONCLUSIONS: La mortalité hospitalière attribuable à la TB chez les patients VIH positifs est faible dans les hôpitaux de référence en Colombie. Les cas de TB chez les patients infectés par le VIH surviennent principalement chez les patients à un stade avancé du VIH, ou qui ne sont pas sous traitement antirétroviral, malgré un diagnostic connu de VIH. Seul un patient sur 10 de cette cohorte a subi un dépistage actif de la TB latente, ce qui reflète peut-être des opportunités de traitement manquées.

Experiences and outcomes of group volunteer befriending with patients with severe mental illness: an exploratory mixed-methods study in Colombia.

BACKGROUND: Improving care for patients with severe mental illness in Latin America requires effective strategies that are low-cost. One such strategy is a volunteering scheme, referred to as befriending, which seeks to support the social integration of patients. Despite positive reports in other world regions, this intervention has not been studied in Latin America. Whilst befriending programmes commonly form patient-volunteer dyads, group arrangements may be an alternative with some benefits. Here, we aim to explore the feasibility, experiences and outcomes of a group volunteer befriending intervention for patients with severe mental illness in Colombia. METHODS: In this exploratory non-controlled study, 10 groups of five individuals were formed, each consisting of three individuals with schizophrenia or bipolar disorder and two volunteers from the community in Bogotá, Colombia. Each group was encouraged to participate together in social activities within their community over a 6-month period. Patients' quality of life, objective social outcomes, symptom levels and internalised stigma were assessed before and after the intervention. Patients' and volunteers' experiences were explored in semi-structured interviews which were analysed using inductive content analysis. RESULTS: Outcomes were available for 23 patients. Whilst their objective social situation had significantly improved at the end of the intervention, other outcomes did not show statistically significant differences. The interviews with participants revealed positive experiences which fell into five categories: 1) stigma reduction; 2) personal growth; 3) formation of relationships; 4) continuity and sustainability of befriending; 5) acceptability and feasibility of befriending. CONCLUSIONS: A volunteer befriending programme in small groups of two volunteers and three patients is feasible and associated with positive experiences of participants. Such programmes may also improve the objective social situation of patients. This low-cost intervention may be useful for patients with severe mental illnesses in Latin America. TRIAL REGISTRATION: ISRCTN72241383 (Date of Registration: 04/03/2019, retrospectively registered).

Thoracic Cardiovascular Complications of Tuberculosis.

ABSTRACT: Mycobacterium infection remains a leading cause of morbidity and mortality worldwide. Although rare, thoracic cardiovascular complications are associated with devastating consequences if not promptly diagnosed using computed tomography. Intrapulmonary complications include tuberculous aortitis, Rasmussen aneurysms, involvement of bronchial and nonbronchial systemic arteries, and thromboembolic events. Extrapulmonary complications include pericarditis, myocarditis, endocarditis, involvement of coronary arteries, annular-subvalvular left ventricle aneurysms and mediastinal fibrosis. This article will review these complications and their computed tomography features.

Blue noise coding for a coherent x-ray diffraction imaging system.

Coded x-ray diffraction imaging (CXRDI) is an emerging computational imaging approach that aims to solve the phase retrieval problem in x-ray crystallography based on the intensity measurements of encoded diffraction patterns. Boolean coding masks (BCMs) with complementary structures have been used to modulate the diffraction pattern in CXRDI. However, the optimal spatial distribution of BCMs still remains an open problem to be studied in depth. Based on the spectral initialization criterion, we provide a theoretical proof for the premise that the optimal complementary BCMs should obey the blue noise distribution in the sense of mathematical expectation. In addition, the benefits of the blue noise coding strategy are assessed by a set of simulations, where better reconstruction quality is observed compared to the random BCMs and other complementary BCMs.

Multi-objective optimization for structured illumination in dynamic x-ray tomosynthesis.

Dynamic coded x-ray tomosynthesis (CXT) uses a set of encoded x-ray sources to interrogate objects lying on a moving conveyor mechanism. The object is reconstructed from the encoded measurements received by the uniform linear array detectors. We propose a multi-objective optimization (MO) method for structured illuminations to balance the reconstruction quality and radiation dose in a dynamic CXT system. The MO framework is established based on a dynamic sensing geometry with binary coding masks. The Strength Pareto Evolutionary Algorithm 2 is used to solve the MO problem by jointly optimizing the coding masks, locations of x-ray sources, and exposure moments. Computational experiments are implemented to assess the proposed MO method. They show that the proposed strategy can obtain a set of Pareto optimal solutions with different levels of radiation dose and better reconstruction quality than the initial setting.

Healthcare access barriers for FARC ex-combatants in Colombia: qualitative perspectives from healthcare providers and FARC health promoters.

BACKGROUND: Following the 2016 Peace Agreement with the Fuerzas Armadas Revolucionarias de Colombia (FARC), Colombia promised to reincorporate more than 13,000 guerrilla fighters into its healthcare system. Despite a subsidized healthcare insurance program and the establishment of 24 Espacios Territoriales de Capacitación y Reincorporación (ETCRs-Territorial Spaces for Training and Reintegration) to facilitate this transition, data has shown that FARC ex-combatants access care at disproportionately lower rates, and face barriers to healthcare services. METHODS: Semi-structured interviews were conducted with FARC health promoters and healthcare providers working in ETCRs to determine healthcare access barriers for FARC ex-combatants. Analysis was completed with a qualitative team-based coding method and barriers were categorized according to Julio Frenk's Domains of Healthcare Access framework. RESULTS: Among 32 participants, 25 were healthcare providers and 7 self-identified as FARC health promoters. The sample was majority female (71.9%) and worked with the FARC for an average of 12 months in hospital, health center, medical brigade, and ETCR settings. Our sample had experiences with FARC across 16 ETCRs in 13 Departments of Colombia. Participants identified a total of 141 healthcare access barriers affecting FARC ex-combatants, which affected healthcare needs, desires, seeking, initiation and continuation. Significant barriers were related to a lack of resources in rural areas, limited knowledge of the Colombian health system, the health insurance program, perceived stigma, and transition process from the FARC health system. CONCLUSIONS: FARC ex-combatants face significant healthcare access barriers, some of which are unique from other low-resource populations in Colombia. Potential solutions to these barriers included health insurance provider partnerships with health centers close to ETCRs, and training and contracting FARC health promoters to be primary healthcare providers in ETCRs. Future studies are needed to quantify the healthcare barriers affecting FARC ex-combatants, in order to implement targeted interventions to improve healthcare access.

Decision making in the end-of-life care of patients who are terminally ill with cancer - a qualitative descriptive study with a phenomenological approach from the experience of healthcare workers.

BACKGROUND: In Colombia, recent legislation regarding end-of-life decisions includes palliative sedation, advance directives and euthanasia. We analysed which aspects influence health professionals´ decisions regarding end-of-life medical decisions and care for cancer patients. METHODS: Qualitative descriptive-exploratory study based on phenomenology using semi-structured interviews. We interviewed 28 oncologists, palliative care specialists, general practitioners and nurses from three major Colombian institutions, all involved in end-of-life care of cancer patients: Hospital Universitario San Ignacio and Instituto Nacional de Cancerología in Bogotá and Hospital Universitario San José in Popayan. RESULTS: When making decisions regarding end-of-life care, professionals consider: 1. Patient's clinical condition, cultural and social context, in particular treating indigenous patients requires special skills. 2. Professional skills and expertise: training in palliative care and experience in discussing end-of-life options and fear of legal consequences. Physicians indicate that many patients deny their imminent death which hampers shared decision-making and conversations. They mention frequent ambiguity regarding who initiates conversations regarding end-of-life decisions with patients and who finally takes decisions. Patients rarely initiate such conversations and the professionals normally do not ask patients directly for their preferences. Fear of confrontation with family members and lawsuits leads healthcare workers to carry out interventions such as initiating artificial feeding techniques and cardiopulmonary resuscitation, even in the absence of expected benefits. The opinions regarding the acceptability of palliative sedation, euthanasia and use of medications to accelerate death without the patients´ explicit request vary greatly. 3. Conditions of the insurance system: limitations exist in the offer of oncology and palliative care services for important proportions of the Colombian population. Colombians have access to opioid medications, barriers to their application are largely in delivery by the health system, the requirement of trained personnel for intravenous administration and ambulatory and home care plans which in Colombia are rare. CONCLUSIONS: To improve end-of-life decision making, Colombian healthcare workers and patients need to openly discuss wishes, needs and care options and prepare caregivers. Promotion of palliative care education and development of palliative care centres and home care plans is necessary to facilitate access to end-of-life care. Patients and caregivers' perspectives are needed to complement physicians' perceptions and practices.

Validation of 3D fluoroscopy for image-guidance registration in depth electrode implantation for medically refractory epilepsy.

BACKGROUND: Frame registration is a critical step to ensure accurate electrode placement in stereotactic procedures such as stereoelectroencephalography (SEEG) and is routinely done by merging a computed tomography (CT) scan with the preoperative magnetic resonance (MR) examination. Three-dimensional fluoroscopy (XT) has emerged as a method for intraoperative electrode verification following electrode implantation and more recently has been proposed as a registration method with several advantages. METHODS: We compared the accuracy of SEEG electrode placement by frame registration with CT and XT imaging by analyzing the Euclidean distance between planned and post-implantation trajectories of the SEEG electrodes to calculate the error in both the entry (EP) and target (TP) points. Other variables included radiation dose, efficiency, and complications. RESULTS: Twenty-seven patients (13 CT and 14 XT) underwent placement of SEEG electrodes (319 in total). The mean EP and TP errors for the CT group were 2.3 mm and 3.3 mm, respectively, and 1.9 mm and 2.9 mm for the XT group, with no statistical difference (p = 0.75 and p = 0.246). The time to first electrode placement was similar (XT, 82 ± 10 min; CT, 84 ± 22 min; p = 0.858) and the average radiation exposure with XT (234 ± 55 mGy*cm) was significantly lower than CT (1245 ± 123 mGy*cm) (p < 0.0001). Four complications were documented with equal incidence in both groups. CONCLUSIONS: The use of XT as a method for registration resulted in similar implantation accuracy compared with CT. Advantages of XT are the substantial reduction in radiation dose and the elimination of the need to transfer the patient out of the room which may have an impact on patient safety and OR efficiency.

Sensorless Adaptive Voltage Control for Classical DC-DC Converters Feeding Unknown Loads: A Generalized PI Passivity-Based Approach.

The problem of voltage regulation in unknown constant resistive loads is addressed in this paper from the nonlinear control point of view for second-order DC-DC converters. The converters' topologies analyzed are: (i) buck converter, (ii) boost converter, (iii) buck-boost converter, and (iv) non-inverting buck-boost converter. The averaging modeling method is used to model these converters, representing all these converter topologies with a generalized port-Controlled Hamiltonian (PCH) representation. The PCH representation shows that the second-order DC-DC converters exhibit a general bilinear structure which permits to design of a passivity-based controller with PI actions that ensures the asymptotic stability in the sense of Lyapunov. A linear estimator based on an integral estimator that allows reducing the number of current sensors required in the control implementation stage is used to determine the value of the unknown resistive load. The main advantage of this load estimator is that it ensures exponential convergence to the estimated variable. Numerical simulations and experimental validations show that the PI passivity-based control allows voltage regulation with first-order behavior, while the classical PI controller produces oscillations in the controlled variable, significantly when the load varies.

Modelling of SEPIC, Cuk and Zeta Converters in Discontinuous Conduction Mode and Performance Evaluation.

High-order switched DC-DC converters, such as SEPIC, Cuk and Zeta, are classic energy processing elements, which can be used in a wide variety of applications due to their capacity to step-up and/or step-down voltage characteristic. In this paper, a novel methodology for analyzing the previous converters operating in discontinuous conduction mode (DCM) is applied to obtain full-order dynamic models. The analysis is based on the fact that inductor currents have three differentiated operating sub-intervals characterized by a third one in which both currents become equal, which implies that the current flowing through the diode is zero (DCM). Under a small voltage ripple hypothesis, the currents of all three converters have similar current piecewise linear shapes that allow us to use a graphical method based on the triangular shape of the diode current to obtain the respective non-linear average models. The models' linearization around their steady-state operating points yields full-order small-signal models that reproduce accurately the dynamic behavior of the corresponding switched model. The proposed methodology is applicable to the proposed converters and has also been extended to more complex topologies with magnetic coupling between inductors and/or an RC damping network in parallel with the intermediate capacitor. Several tests were carried out using simulation, hardware-in-the-loop, and using an experimental prototype. All the results validate the theoretical models.

DC Voltage Sensorless Predictive Control of a High-Efficiency PFC Single-Phase Rectifier Based on the Versatile Buck-Boost Converter.

Many electronic power distribution systems have strong needs for highly efficient AC-DC conversion that can be satisfied by using a buck-boost converter at the core of the power factor correction (PFC) stage. These converters can regulate the input voltage in a wide range with reduced efforts compared to other solutions. As a result, buck-boost converters could potentially improve the efficiency in applications requiring DC voltages lower than the peak grid voltage. This paper compares SEPIC, noninverting, and versatile buck-boost converters as PFC single-phase rectifiers. The converters are designed for an output voltage of 200 V and an rms input voltage of 220 V at 3.2 kW. The PFC uses an inner discrete-time predictive current control loop with an output voltage regulator based on a sensorless strategy. A PLECS thermal simulation is performed to obtain the power conversion efficiency results for the buck-boost converters considered. Thermal simulations show that the versatile buck-boost (VBB) converter, currently unexplored for this application, can provide higher power conversion efficiency than SEPIC and non-inverting buck-boost converters. Finally, a hardware-in-the-loop (HIL) real-time simulation for the VBB converter is performed using a PLECS RT Box 1 device. At the same time, the proposed controller is built and then flashed to a low-cost digital signal controller (DSC), which corresponds to the Texas Instruments LAUNCHXL-F28069M evaluation board. The HIL real-time results verify the correctness of the theoretical analysis and the effectiveness of the proposed architecture to operate with high power conversion efficiency and to regulate the DC output voltage without sensing it while the sinusoidal input current is perfectly in-phase with the grid voltage.

A Bidirectional Versatile Buck-Boost Converter Driver for Electric Vehicle Applications.

This work presents a novel dc-dc bidirectional buck-boost converter between a battery pack and the inverter to regulate the dc-bus in an electric vehicle (EV) powertrain. The converter is based on the versatile buck-boost converter, which has shown an excellent performance in different fuel cell systems operating in low-voltage and hard-switching applications. Therefore, extending this converter to higher voltage applications such as the EV is a challenging task reported in this work. A high-efficiency step-up/step-down versatile converter can improve the EV powertrain efficiency for an extended range of electric motor (EM) speeds, comprising urban and highway driving cycles while allowing the operation under motoring and regeneration (regenerative brake) conditions. DC-bus voltage regulation is implemented using a digital two-loop control strategy. The inner feedback loop is based on the discrete-time sliding-mode current control (DSMCC) strategy, and for the outer feedback loop, a proportional-integral (PI) control is employed. Both digital control loops and the necessary transition mode strategy are implemented using a digital signal controller TMS320F28377S. The theoretical analysis has been validated on a 400 V 1.6 kW prototype and tested through simulation and an EV powertrain system testing.