A Grid-Connected Multilevel Converter for Interfacing PV Arrays and Energy Storage Devices

This paper presents a design procedure and a \ud control strategy for a grid-connected single-phase multilevel \ud converter. The proposed system uses two series connected H-bridge modules, one fed by photovoltaic panels, the other by \ud energy storage devices. The former switches at line frequency, \ud while the latter operates in PWM. The system is designed to \ud minimize the voltage stress on the switches, while the control \ud strategy is such that a constant active power is delivered to the \ud grid with high power factor, even if the energy produced by the \ud photovoltaic panels is variable. The paper illustrates the power \ud converter design procedure, the hybrid PWM method and the \ud small signal modeling used to design the controllers of each \ud inverter. In addition, the performance of the multilevel converter \ud is verified by means of simulation and experimental results, \ud which show the system ability to operate as expectedFAPES

Repetitive-Based Control for Selective Active Filters Using Discrete Cosine Transform

This paper proposes selective harmonic current compensation using a closed-loop repetitive controller. The controller is based on measuring the line currents. It performs the compensation of specific harmonics selected by a DCT (Discrete Cosine Transform) digital filter, which is self-adjusted to track utility frequency deviations by means of a Phase Locked Loop (PLL) system. Compared to conventional solutions, this approach allows full compensation of selected harmonics, even if the active filter has limited bandwidth. This method also requires a simpler algorithm than, e.g., the synchronous frame harmonic regulators and its complexity is independent of the number of compensated harmonics. Moreover, it is more appropriate for DSP implementation and less sensitive to rounding and quantization errors when finite word length or fixed-point implementation is required. Simulations and experimental results confirm the theoretical expectations

An electronic solution for the direct connection of a three-phase induction generator to a single-phase feeder

This paper proposes a solution for the direct connection of a three-phase induction generator to a single-phase feeder. This high power quality system is intended to be used in micro-hydro power plants applications with control of the water flow. It is employed to maintain the speed of the induction generator greater than its synchronous value. The difference between the generated power and the power consumed by the local load flows through the single-phase feeder. The power flow control is provided by a three-phase PWM inverter that additionally guarantees the local power quality. A system with good power quality must have sinusoidal and constant amplitude voltages, fixed frequency operation, balanced induction generator voltages and currents, harmonics and reactive power compensation. The paper describes the inverter control strategy, presents design criteria of the controllers, and shows experimental results

Output Capacitance Minimization for Converters in DC Microgrids via Multi-Objective Tuning of Droop-Based Controllers

This paper proposes a controller tuning methodology for voltage-current droop-based DC-DC converters in DC microgrids to reduce the output capacitance. This minimization is cost saving and implies lower fault currents. However, it leads to higher DC voltage variability during load transients, which requires an output impedance shaping by control means to reduce over or undershoot. The proposed control structure and problem definition simultaneously takes into account that the solution must achieve the impedance shaping, performance and stand-alone stability objectives. This comprises a multi-objective problem which is effectively formulated here and, then, solved by a non-smooth $\mathcal {H}_\infty$ optimization technique that tunes all free parameters. For comparison purposes, this tuning methodology is applied to several droop proposals, and the proposed droop is able to reduce the output capacitance of bidirectional buck-type and boost-type half-bridge converters by 37.5% and 23.08%, respectively, with respect to previous proposals. The designs are validated in time and frequency domains by means of theoretical analysis and experimental results on DC microgrid prototypes with bidirectional buck-type or boost-type half-bridge converters

Perfil dos pacientes diagnosticados com glomus timpânico: uma revisão sistemática da literatura / Profile of patients diagnosed with tympanic glomus: a systematic review of the literature

Introdução:  Glomus timpânico são tumores benignos da orelha média originados de células paraganglionares do plexo timpânico. Além do exame físico, a tomografia computadorizada auxilia no diagnóstico. Entre os sitomas mais comuns estão o zumbido pulsátil e a perda auditiva condutiva. Objetivo: Demonstrar o perfil dos pacientes acomentidos por glomus timpânico. Materiais e Métodos: Trata-se de uma revisão sistmática da literatura realizada no mês de maio de 2020. Resultados e Discussão: Predominância de casos no sexo feminino, com média de idade de 58 anos. O zumbido pulsátil, a perda auditiva condutiva, foram os sintomas mais recorrentes, e 72,7% dos pacientes apresentaram estadiamento do Tipo I. Conclusão: Logo, a revisão permitiu identificar uma predominância de glomus timpânico no sexo feminino, sendo o zumbido pulsátil, perda auditiva condutiva e neurossensorial, os sintomas mais recorrentes. Ademais, detectou-se a importância da tomografia computadorizada no diagnóstico e grande aplicabilidade e bons resultadso da terapêutica cirúrgica

Esercizi per il corso di Fondamenti di Elettronica

Dispensa di supporto per i corsi di base di Elettronica analogica. Esercizi risolti e da risolvere

Design of a robust voltage controller for a buck-boost converter using mu-synthesis

This paper proposes the structured singular value (mu) approach to the problem of designing an output voltage regulator for a Buck-Boost converter with current-mode control. This approach allows a quantitative description of the effects of reactive components\u2019 tolerances and operating point variations, which strongly affect the converter dynamics. At first, a suitable linear converter model is derived, whose parameter variations are described in terms of perturbations of the linear fractional transformation (LFT) class. Then, mu-analysis is used to evaluate the robustness of a conventional PI voltage regulator with respect to the modeled perturbations. Finally, the approximate mu-synthesis procedure known as D-K iteration is used to design a robustly performing regulator. Simulation results are presented, describing the small and large signal behavior of a reduced order approximation of the mu-synthesized controller