Search results for "Z source"
showing 9 items of 9 documents
A Novel Symmetrical Boost Modulation Method for qZS-based CHB Inverters
2020
Quasi-Z-source cascaded H-bridge (qZS-CHB) inverters are arising as an innovation in the field of the electrical conversion for PV applications. This type of converters inherit the advantages of multilevel inverters and single-stage configuration. In this context, this paper proposes a novel symmetrical boost modulation strategy for qZS CHB multilevel inverters to increase the performance in terms of voltage stresses and power quality. The novelty lies in the adoption of a different concept to generate the shoot-through states compared to the traditional methods. Simulation analysis in a grid connected application to evaluate the benefits of this boost method is performed in the MATLAB/PLEC…
Modified Modulation Techniques for Quasi-Z-Source Cascaded H-Bridge Inverters
2018
Quasi-Z-source cascaded H-bridge (q Z S - C H B) inverters are one promising solution for high power photovoltaic (PV) systems. This type of topologies inherits the advantages of cascaded converters (i.e., multilevel outputs) and impedance-source inverters (i.e., high conversion ratios). In addition, it allows increasing the inverter reliability (with high redundancy). However, the modulation and control of qZS-CHB inverters are challenging to a certain extent. Thus, this paper proposes modified modulation techniques to increase the performances of qZS-CHB converters in terms of voltage gains and stresses. The novelty lies in the use of the switching frequency optimal as reference signals i…
Wideband THz time domain spectroscopy based on optical rectification and electro-optic sampling
2013
We present an analytical model describing the full electromagnetic propagation in a THz time-domain spectroscopy (THz-TDS) system, from the THz pulses via Optical Rectification to the detection via Electro Optic-Sampling. While several investigations deal singularly with the many elements that constitute a THz-TDS, in our work we pay particular attention to the modelling of the time-frequency behaviour of all the stages which compose the experimental set-up. Therefore, our model considers the following main aspects: (i) pump beam focusing into the generation crystal; (ii) phase-matching inside both the generation and detection crystals; (iii) chromatic dispersion and absorption inside the c…
5th EOS Topical Meeting on Optical Microsystems, Poster OμS13_1569798553: Analytical Model for wideband THz sources and detectors based on Optical Re…
2013
Analytical Model for wideband THz sources and detectors based on Optical Rectification and Electro-Optic Sampling
2013
An analytical model describing a laser based set-up for wideband THz generation and detection is presented. Particular attention is focused on the main broadband phenomena, which occur when THz radiations have to be handled.
Spatial and spectral properties of small area THz generation for sub-wavelength microscopy
2010
A highly localized THz source is a promising candidate for sub-wavelength microscopy, due to its superior radiation power throughput with respect to others near-field techniques. Here, we report on the spatial and the spectral near-field properties of our highly localized THz source.
A new BeppoSAX observation of the Z Source GX 349+2
2004
Abstract We report on the results from two BeppoSAX observations of the Z source GX 349+2 performed in February 2001 and covering the broad energy range 0.12–200 keV. The average spectrum is well described by a soft blackbody (kTBB∼0.5 keV) and a Comptonized component having a seed-photon temperature of kT0∼1 keV, an electron temperature of kTe∼2.7 keV, and optical depth τ∼11. To well fit the energy spectrum three gaussian lines are needed at 1.2 keV, 2.6 keV, and 6.7 keV with corresponding equivalent widths of 13 eV, 10 eV, and 39 eV, probably associated to L-shell emission of Fe XXIV, Lyα S XVI, and Fe XXV, respectively. These lines may be produced at different distances from the neutron …
A relativistically smeared line profile in the spectrum of the bright Z-source GX 340+0
2009
We present preliminary results of a 50 ks long XMM-Newton observation of the bright Z-source GX 340+0. We study the temporal and spectral variability of the source, performing a time resolved analysis. In the energy spectra, a broad asymmetric emission line in the Fe Ka energy band is always present. Its shape is compatible with a relativistically smeared profile arising from reflection on a hot accretion disk extending close to the central accreting neutron star. Despite a significant change in the continuum emission and luminosity, the line profile remains substantially unchanged. The line is produced by recombination of highly ionized iron (Fe XXV), the reflecting disk has an inner radiu…
Numerical Model of THz sources and detectors based on Optical Rectification and Electro-Optic Sampling
2013
A model describing a laser based set-up for wideband THz generation and detection is presented. Particular attention is focused on the main broadband phenomena, which occur when THz radiations have to be handled.