Yales Rômulo de Novaes

Isolated DC/DC Structure Based on Modular Multilevel Converter

In the future, new aspects from decentralized generation using different dc voltage levels are expected to influence the general concept of power exchange. Converter are needed to adapt the voltage between low voltage (LV), medium voltage (MV), and high voltage (HV). In this paper, a galvanic isolated bidirectional dc/dc converter based on the modular multilevel converter is studied, with a large potential for secure and flexible dc power flow control. The use of medium frequency transformation allows savings in copper and iron. A fundamental frequency modulation method is introduced for the presented converter, that enables variable stepup or step-down between primary and secondary dc voltage in discrete steps. The balancing mechanism of the internal power storage components is explained and verified by simulation and experiment.

Parameters design for modular multilevel converter (MMC)

The modular multilevel converter is one of the most interesting transformerless multilevel converter topology intended for medium and high-voltage power conversion. Thus, as a new topology, a fewer design guidelines are presented in the literature, on the other hand there are many restrictions. This paper presents aims to be a design guide lines to project a MMC system. The minimum submodule capacitor requirement is presented as the capacitance related to the load displacement angle, operating frequency and output power. The arm inductor design include three parameters: current ripple, fault condition and circulating current. Semiconductor current stress are calculated using average quasi-instantaneous values and rms quasi-instantaneous values will be used. From the performed analysis some normalized abacus are derived and can be used as start point for a new MMC design. The results were validated using MATLAB simulation. Furthermore, experimental results based on 2.2 kW, 5 kHz switching frequency prototype are also include and analyzed.

A new high gain non-isolated DC-DC boost converter for photovoltaic application

This paper introduces a new topology of the high gain non-isolated DC-DC boost converter with central point on its output. The proposed converter is derived from the quadratic single switch boost converter and the three level boost converter. The static gain of this converter is bigger than the one from the conventional boost converter and the maximum voltage on both switches is half of the output voltage. Qualitative and quantitative analysis of the operation stages, the main waveforms and the experimental results of a 520 W prototype are presented. The converter is aimed for modular photovoltaic application.

A non-insulated resonant boost converter

In this paper, a resonant boost converter is analyzed and verified through experimentation. Switching losses are reduced since the converter operates at ZCS (Zero Current Switching). The analysis presented here covers its operation with variable switching frequency but only below the resonant frequency. The range of its voltage gain goes from 1 to 2 and the energy conversion efficiency (including filtering at input) is around 97% for the lowest input voltage. Its envisioned that it could be applied as a front-end converter when a backend inverter is needed, for instance with batteries, photovoltaic converters or fuel cells, perform partial output voltage regulation only.

A Voltage Regulator for Power Quality Improvement in Low-Voltage Distribution Grids

This paper presents a voltage-controlled distribution static synchronous compensator (DSTATCOM)-based voltage regulator for low-voltage distribution grids. The voltage regulator is designed to temporarily meet the grid code, postponing unplanned investments while a definitive solution could be planned to solve regulation issues. The power stage is composed of a three-phase four-wire voltage-source inverter and a second-order low-pass filter. The control strategy has three output voltage loops with active damping and two dc bus voltage loops. In addition, two loops are included to the proposed control strategy: the concept of minimum power point tracking (mPPT) and the frequency loop. The mPPT allows the voltage regulator to operate at the minimum power point, avoiding the circulation of unnecessary reactive compensation. The frequency loop allows the voltage regulator to be independent of the grid voltage information, especially the grid angle, using only the information available at the point-of-common coupling. Experimental results show the regulation capacity, the features of the mPPT algorithm for linear and nonlinear loads, and the frequency stability.

Analysis of a snubber for the T-type NPC converter

The study of a totally passive snubber applied to the T-type NPC converter is presented in this paper. The snubber circuit aids all commutations in all the switches. The voltage across the switches is clamped in a value close to half of the total input voltage. The description of the operation is presented in this paper.

Three-phase flyback/current-fed push-pull dc-dc converter with y-Δ connected transformer

This paper presents the three-phase dc-dc flyback/current-fed push-pull converter. The main features of the proposed converter are: flyback operation for a duty cycle less than 1/3; boost operation for a duty cycle range from 1/3 to 1; input and output ripple current cancellation for a duty cycle of 1/3 or 2/3; reduced inrush current in flyback mode operation; the voltage and current frequencies in the output filter are three times higher than the switching frequency; The Y-Δ connection allows a reduction of reactive power processed by transformer. Typical applications include charging stations for electric vehicles, installations fed by battery units, photovoltaic arrays or fuel cell systems. This paper gives theoretical analysis, simulation and experimental result data for a 2 kW; 150 Vdc input; output from 100 Vdc to 540 Vdc and, 40 kHz switching frequency.

Frequency compensation for stand alone voltage-controlled DSTATCOM

This paper presents a simple control loop for voltage-controlled DSTATCOMs able to mitigate the effects of grid frequency deviation, greatly increasing the voltage regulation autonomy. The DSTATCOM consists of a three-phase four-wire Voltage Source Inverter (VSI) connected to the grid through a second order low pass filter. The control structure is composed of the conventional loops: three for the output voltage with active damping, and two for dc bus voltages, along to the frequency loop. The inclusion of the frequency loop makes the grid voltage phase information no longer needed. In other words, only the PCC voltage information is needed for the DSTATCOM operation. Experimental results prove its features and the effectiveness of the new loop.

ZVS PWM buck-boost converter applied to regenerate the energy of a three level NPC voltage-fed inverter with modified Undeland snubber

This paper analyses the utilization of an energy regeneration circuit in a three-level NPC (Neutral-Point Clamped) voltage-fed inverter using a modified Undeland snubber. The regeneration circuit uses a QSC (Quasi-Square wave Converter) ZVS (Zero Voltage Switching) dc-dc auxiliary converter to restore the energy from the snubber capacitor to the dc bus. The regenerative circuit uses a single active switch and operates independently of the inverter. Operation stages, theoretical waveforms and a design methodology are presented. Experimental results of a 1.5 kVA prototype are included to validate the proposed topology.

Attractiveness of light-emitting diodes (LEDs) of different wavelengths to the South American rice water weevil

Arq. Inst. Biol., v.85, 1-6, e0382016, 2018 RESUMO: Uma das pragas‐chave do arroz irrigado é a bicheira‐da‐ raiz, denominação comum atribuída às larvas do gorgulho aquático Oryzophagus oryzae (Costa Lima) (Coleoptera: Curculionidae). A utilização de armadilhas luminosas poderia ser uma alternativa viável no manejo integrado, pois esse gorgulho apresenta elevado fototropismo positivo. Assim, objetivou‐se determinar a atratividade de diodos emissores de luz (LEDs) de diferentes comprimentos de onda ao O. oryzae e definir o seu melhor arranjo para compor a lâmpada de armadilhas luminosas fotovoltaicas. LEDs de diferentes comprimentos de onda foram testados em sala escura, em uma arena hexagonal com saídas para as fontes de luz. Grupos de 200 indivíduos foram liberados no centro da arena e capturados em sacos plásticos nas saídas ao fim do tempo de exposição. Os LEDs da faixa do espectro luminoso de ondas curtas (365 e 460 nm) e LEDs brancos, bem como as misturas de luzes de LEDs 365 com 460 nm ou branco, foram atrativos ao O. oryzae. Entre os LEDs com espectro ultravioleta, os mais atrativos foram aqueles acima de 380 nm, devendo estes compor, prioritariamente, lâmpadas de LED para uso nas armadilhas luminosas fotovoltaicas.