Tadeusz Lobos

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Abstract — Modern frequency power converters generate a wide spectrum of harmonics components. Standard tools of harmonic analysis based on the Fourier transform assume that only harmonics are present and the periodicity intervals are fixed, while periodicity intervals in the presence of interharmonics are variable and very long. A novel approach to(More)
Modern power frequency converters generate not only a wide spectrum of characteristic harmonics but also non-characteristic harmonics and interharmonics. Interharmonics are considered more damaging than ordinary harmonic components of the distorted signals. Usual tools of the harmonic analysis based on Fourier transform assume that only harmonics are(More)
The diagnosis of cryptococcal infection was established in 3 patients with AIDS. Infection was meningo-encephalic in all and presented a violent outset. The chemical characteristics of the CSF were normal. Detection of cryptococcal antigen, presence of encapsulated yeast forms revealed by india-ink staining and positive cultures allowed a definitive(More)
The International Electrotechnical Commission (IEC) standards characterize the waveform distortions in power systems with the amplitudes of harmonic and interharmonic groups and subgroups. These groups/subgroups utilize the waveform spectral components obtained from a fixed frequencyresolution discrete Fourier transform (DFT). Using the IEC standards allows(More)
This paper considers applying nonparametric and parametric methods for the calculation of the time–frequency representation of nonstationary signals in power electronics. A space phasor is proposed as a complex representation of a three-phase signal to calculate the spectrum of positiveand negative-sequence components. The developed methods are tested with(More)
Purpose – The purpose of this paper is to compare the accuracy of tracking the amplitude and frequency changes of non-stationary electric signals. Design/methodology/approach – Short-time fourier transform (STFT) and S-transform algorithms were applied to analyze non-stationary signals originating from switching of capacitor banks in a power system.(More)
In this paper time-frequency methods have been investigated for complex investigations of transient states in wind power plants. Application of parallel processing in time and frequency domain brought new findings in description of wind power plants working under transient conditions. Proposed algorithms represents standard Short-Time Fourier Transform(More)