A Phase-Angle Tracking Method for Synchronization of Single- and Three-Phase Grid-Connected Converters

This thesis proposes a phase-angle tracking method, i.e., based on discrete Fourier transform for synchronization of three-phase and single-phase power-electronic converters under distorted and variable-frequency conditions. The proposed methods are designed based on fixed sampling rate and, thus, they can simply be employed for control applications. For three-phase applications, first, analytical analysis are presented to determine the errors associated with the phasor estimation using standard full-cycle discrete Fourier transform in a variable-frequency environment. Then, a robust phase-angle estimation technique is proposed, which is based on a combination of estimated positive and negative sequences, tracked frequency, and two proposed compensation coefficients. The proposed method has one cycle transient response and is immune to harmonics, noises, voltage imbalances, and grid frequency variations. An effective approximation technique is proposed to simplify the computation of the compensation coefficients. The effectiveness of the proposed method is verified through a comprehensive set of simulations in Matlab software. Simulation results show the robust and accurate performance of the proposed method in various abnormal operating conditions. For single-phase applications, an accurate phasor-estimation method is proposed to track the phase-angle of fundamental frequency component of voltage or current signals. This method can be used in three-phase applications as well. The proposed method is based on a fixed sampling frequency and, thus, it can simply be integrated in control applications of the grid-connected converters. Full-cycle discrete Fourier transform (DFT) is adopted as a base for phasor estimation. Two procedures are taken to effectiveness reduce the phasor estimation error using DFT during o - nominal frequency operation. First, adaptive window length (AWL) is applied to match the window-length of the DFT with respect to the input signal frequency. As AWL can partially reduce the error if sampling rate is not high, phasor compensation is employed to compensate the remaining error in the estimated phasor. Both procedures require system frequency, thus, an effective frequency-estimation technique is proposed to obtain fast and accurate performance. The proposed method has one cycle transient response and is immune to harmonics, noises, and grid frequency variations. The effectiveness of the proposed method is verified through a comprehensive set of simulations in Matlab and hardware implementation test using real-time digital signal processor data acquisition system

7-Chloro-2-[1-(4-methoxy­phen­yl)pyrazol-4-yl]-3,3-dimethyl-3H-indole

In the title compound, C20H18ClN3O, the dihedral angle between the pyrazole and the 3H-indole components is only 13.28 (6)°, indicating that there is conjugation between the two heterocyclic subunits. The N-methoxy­phenyl unit makes a dihedral angle of 25.10 (7)° with the pyrazole ring

Vilsmeier-Haack reagent: A facile synthesis of 2-(4-chloro-3,3-dimethyl-7-phenoxyindolin-2-ylidene)malonaldehyde and transformation into different heterocyclic compounds

2-(5-Chloro-2-phenoxyphenyl)hydrazine was converted to corresponding 3H-indole by Fischer method utilizing the isopropyl methyl ketone in acetic acid. The reaction of 3H-indole with Vilsmeier-Haack reagent furnished aminomethylene malonaldehyde in excellent yield while the reactions of malonaldehyde with hydrazine, arylhydrazines, amines, cyanoacetamide and hydroxylamine hydrochloride, led to the corresponding pyrazole derivatives, enamines, cyanopyridone, and cyanoacetamide derivatives respectively

Design and Analysis of A New Illumination Invariant Human Face Recognition System

In this dissertation we propose the design and analysis of a new illumination invariant face recognition system. We show that the multiscale analysis of facial structure and features of face images leads to superior recognition rates for images under varying illumination. We assume that an image I ( x,y ) is a black box consisting of a combination of illumination and reflectance. A new approximation is proposed to enhance the illumination removal phase. As illumination resides in the low-frequency part of images, a high-performance multiresolution transformation is employed to accurately separate the frequency contents of input images. The procedure is followed by a fine-tuning process. After extracting a mask, feature vector is formed and the principal component analysis (PCA) is used for dimensionality reduction which is then proceeded by the extreme learning machine (ELM) as a classifier. We then analyze the effect of the frequency selectivity of subbands of the transformation on the performance of the proposed face recognition system. In fact, we first propose a method to tune the characteristics of a multiresolution transformation, and then analyze how these specifications may affect the recognition rate. In addition, we show that the proposed face recognition system can be further improved in terms of the computational time and accuracy. The motivation for this progress is related to the fact that although illumination mostly lies in the low-frequency part of images, these low-frequency components may have low- or high-resonance nature. Therefore, for the first time, we introduce the resonance based analysis of face images rather than the traditional frequency domain approaches. We found that energy selectivity of the subbands of the resonance based decomposition can lead to superior results with less computational complexity. The method is free of any prior information about the face shape. It is systematic and can be applied separately on each image. Several experiments are performed employing the well known databases such as the Yale B, Extended-Yale B, CMU-PIE, FERET, AT&T, and LFW. Illustrative examples are given and the results confirm the effectiveness of the method compared to the current results in the literature

3-(1-Methyl­pyrrolidin-2-yl­idene)-3H-indole sesquihydrate

The asymmetric unit of the title compound, C13H14N2·1.5H2O, contains two similar mol­ecules of 3-(1-methyl­pyrrolidin-2-yl­idene)-3H-indole, (I), and three water mol­ecules. (I) is the product of reacting indole with 1-methyl­pyrrolidin-2-one in the presence of phospho­rus oxychloride. Both organic molecules are almost completely planar; the maximum distances above and below the least-squares plane through all the atoms of mol­ecule 1 are 0.050 (8) and −0.045 (8) Å, respectively, and the deviations for mol­ecule 2 are 0.096 (8) and −0.059 (8) Å, respectively. In the crystal, the two crystallographically different mol­ecules alternate in π-stacked columns [centroid–centroid distances = 3.729 (5) and 3.858 (5) Å], which are linked by O—H⋯N hydrogen bonds to a network of hydrogen-bonded water mol­ecules. O—H⋯O inter­actions are also present

Six-membered ring systems: with O and/or S atoms

A large variety of publications involving O- and S-6-membered ring systems have appeared in 2017. The importance of these heterocyclic compounds is highlighted by the huge number of publications on the total synthesis of natural oxygen derivatives and of other communications dedicated to synthetic derivatives. Reviews on stereoselective organocatalytic synthesis of tetrahydropyrans (17EJO4666), of tetrahydropyrans and their application in total synthesis of natural products (17CSR1661), on the synthesis of the less thermodynamically stable 2,6-trans-tetrahydropyrans (17S4899), on enantioselective synthesis of polyfunctionalized pyran and chromene derivatives (17TA1462), and on enantioselective and racemic total synthesis of camptothecins, including the formation of their pyran-2-one ring (17SL1134), have appeared. Advances in the transition metal-catalyzed synthesis of pyran-2/4-ones (17TL263), N-heterocyclic carbene (NHC)-catalyzed achiral synthesis of pyran-2-one, coumarin and (thio)chromone derivatives (17OBC4731), on the synthesis and transformation of 2H-pyran-2-ones (17T2529) and 2-styrylchromones (17EJO3115) into other heterocyclic compounds, have been surveyed. The strategies to build up the tetrahydropyranyl core of brevisamide (17H(95)81) and the reactions of ketyl radicals, generated from carbonyl derivatives under transition-metal photoredox-catalyzed conditions, leading to isochromen- and chroman-type compounds (17CC13093) were disclosed. Developments in the synthesis of pentafluorosulfanyl(chromene and coumarin) derivatives (17TL4803), photoswitchable D9-tetrahydrocannabinol derivatives (17JA18206), and aminobenzopyranoxanthenes with nitrogen-containing rings (17JOC13626) have been studied.info:eu-repo/semantics/publishedVersio