Sergio Pires Pimentel

Control of Power Electronic Interface for renewable energy sources under distorted grid voltage

In this paper a Power Electronic Interface (PEI) to integrate up to two renewable energy sources is presented. Through the control of the DC link terminal voltage and the AC terminal voltage of the voltage source converter (VSC) the generation of the different distributed sources can be adapted to the grid, supplying the local load and exporting energy to the grid. The system was analyzed under distorted grid voltage, where the quality of the grid current is affected. Solutions based on the use of resonant passive filters and injection of harmonics to compensate the distortion of the grid voltage is presented.

Mitigation of harmonic distortion by power electronic interface connecting distributed generation sources to a weak grid

In this paper a Power Electronic Interface (PEI) that integrates up to two renewable energy sources is presented. The generation of the different distributed sources is controlled through the DC link terminal voltage and the AC terminal voltage of the voltage source converter (VSC). The renewable source can be controlled to supply electricity to the local load and export the exceeding energy to the grid. The system is analyzed under distorted grid voltage, where the quality of the grid current is affected. Solutions based on resonant passive filters and on the injection of harmonics to compensate the voltage grid distortion are presented.

Single-phase distributed generation system based on asymmetrical cascaded multilevel inverter

A single-phase distributed generation system (DGS) is proposed for residential power generation. It is based on an utility-interactive asymmetrical cascaded multilevel inverter with 19 levels, which is supplied by asynchronous voltage sources. It is possible to operate continuously the proposed DGS during the grid-connected or the stand-alone modes. Details about its operation modes are presented. A prototype has been implemented on a fixed-point DSP TMS320F2812. An injection of only active power into the grid utility and an uninterrupted load supply have been pursued. Simulation and experimental results presents the performance of the proposed DGS operating under normal and abnormal conditions.

The impact of different torques for the insertion of immediately loaded implants on the peri-implant levels of angiogenesis- and bone-related markers

The aim of this split-mouth, randomized, double-blind, controlled clinical trial was to evaluate the influence of different insertion torque values for dental implants on bone- and angiogenesis-related marker profiles. Eighteen edentulous patients received dental implants and fixed complete-arch mandibular prostheses. The implants (n=36) were assigned randomly to two groups: reduced torque (n=18), with insertion torque <30Ncm; and conventional torque (n=18), with insertion torque ≥30Ncm. Levels of vascular endothelial growth factor (VEGF), placental growth factor, bone morphogenetic protein 9 (BMP-9), periostin, osteoprotegerin (OPG), and tartrate-resistant acid phosphatase (TRAP) in the peri-implant fluid were quantified at 7, 14, 30, and 120days after implant placement. Inter-group comparisons showed that VEGF and OPG levels were higher in the low-level torque group than in the conventional torque group on days 7 and 30, respectively (P<0.05). BMP-9 and periostin levels were higher in the conventional group than in the low-level torque group on day 120, and TRAP was up-regulated around implants inserted with conventional torque when compared to those inserted with lower-level torque at all time points evaluated (P<0.05). In conclusion, the use of different levels of torque for implantation of immediately loaded implants significantly influenced the levels of bone- and angiogenesis-related markers during early peri-implant repair.

Wavelet Transform analysis for grid-connected photovoltaic systems

This paper aims to present some applications of Wavelet Transform (WT) in grid-connected photovoltaic (PV) systems, main differences among Wavelet transform and Fourier transforms and also some aspects related to power quality (PQ) and islanding detection methods in a grid-connected PV system. An example of Discrete Wavelet Transform (DWT) applied to detect disturbs on electrical signals is also presented. Wavelet analysis is an important addition to time-frequency methods with practical applications in PV systems. The wavelet transform has more advantages than techniques such as Fourier transform and Short-Time Fourier Transform. Therefore, wavelet transform can be applied for detection and classification of disturbances in grid-connected PV systems. And also, a wavelet-based anti-islanding method can be applied for a reliable island condition detection. Simulation results are presented and discussed in order to describe the proposal of applying WT in grid-connected PV system analysis.