New Algorithms for Computing a Single Component of the Discrete Fourier Transform

This paper introduces the theory and hardware implementation of two new algorithms for computing a single component of the discrete Fourier transform. In terms of multiplicative complexity, both algorithms are more efficient, in general, than the well known Goertzel Algorithm.Comment: 4 pages, 3 figures, 1 table. In: 10th International Symposium on Communication Theory and Applications, Ambleside, U

Desenvolvimento de um sistema de monitoramento remoto de umidade do solo.

Este trabalho tem por objetivo apresentar o protótipo de um sistema autônomo de monitoramento de umidade do solo. O sistema consiste de três sensores de umidade de solo conectados a um microcontrolador Arduino, alimentado por uma bateria carregada por uma célula fotovoltaica. O propósito desse sistema é realizar a transmissão por módulo Xbee® de sinal analógico referente ao teor de umidade do solo. O sinal transmitido é captado por outro módulo Xbee® ligado a um programa servidor capaz de armazenar continuamente as informações captadas

A discussion about a start-up procedure of a doubly-fed induction generator system

The present work proposes a start-up procedure for a doubly-fed induction generator (DFIG) driven by a wind turbine. In the DFIG topology the stator is connected direct to the grid while the rotor is connected to a back-to-back converter. This structure requires some care during grid synchronization to avoid undesired overloads. The main goal of a start-up procedure is to reduce the stresses on the electrical and mechanical components during synchronization. In this work, it is achieved by equalization among the induced stator voltage, the voltage over the filter capacitor and the grid voltage. A phase-locked-loop (PLL) computes the grid voltage phase displacement required for the system control orientation and synchronization procedures. Previous to the starting-up, the output currents set-points of the grid-side converter and rotor-side converter are computed in order to produce the same grid voltage over the filter capacitors and on the stator terminals. The whole procedure is summarized in seven different steps: turbine acceleration by the pitch control, DC-link pre-charge; initialization of the filter current controllers; filter synchronization; DC-Link voltage adjust; rotor current controllers' initialization and stator synchronization. The proposed start-up procedure was tested in a 4 kW test bench and the description of each step as well as simulation and experimental results are presented throughout the paper.reviewe